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Properties of rat lens phosphofructokinase.
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Two interconvertible forms of phosphofructokinase (PFK) have been eluted from a DEAE-cellulose column from the supernatant fraction of rat lens homogenates centrifuged at 96,000 x g for 1 hour at 0 to 4 degrees C. The interconversion can be manipulated by a change in the pH of the extracting and eluting buffers. PFK-I is the dominant form at pH between 7.4 to 7.05, while PFK-II dominates at pH 7.4 to 8.2. PFK-II is believed to be the functional form; it is inhibited by high concentrations of ATP and the inhibitory effect is enhanced by more acidic pH. Fructose-6-phosphate counteracts ATP inhibition, but the most potent de-inhibitors are ADP and AMP. Among the inorganic ions tested, sulfate, phosphate, ammonium, and potassium also de-inhibit, whereas calcium further inhibits the enzyme. The behavior of PFK under physiologic conditions and the significance of the presence of two forms of PFK in the lens are discussed.
| 4,411
|
Control of inositol biosynthesis in Saccharomyces cerevisiae: properties of a repressible enzyme system in extracts of wild-type (Ino+) cells.
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Inositol biosynthesis was studied in soluble, cell extracts of a wild-type (Ino) strain of Saccharomyces cerevisiae. Two reactions were detected: (i) conversion of D-glucose-6-phosphate to a phosphorylated form of inositol, presumably inositol-1-phosphate (IP synthethase, EC5.5.1.4), and (ii) conversion of phosphorylated inositol to inositol (IP phosphatase, EC3.1.3.25). The in vitro rate of conversion of glucose-6-phosphate to inositol was proportional to incubaion time and enzyme concentration. The pH optimum was 7.0. The synthesis of inositol required oxidized nicotinamide adenine dinucleotide (NAD) and was stimulated byNH4C1 and MgC12. NADP substituted poorly for NAD, and NADH inhibitedthe reaction. Phosphorylated inositol accumulated in the absence of MgC12, suggesting that inositol-phosphate is an intermediate in the pathway and that Mg ions stimulate the dephosphorylation of inositol-phosphate. IP synthetase was inhibited approximately 20% in the presence of inositol in the reaction mixture at concentrations exceeding 1 mM. The enzyme was repressed approximately 50-fold when inositol was present in the growth medium at concentrations exceeding 50 muM. IP synthetase reached the fully repressed level approximately 10 h after the addition of inositol to logarithmic cultures grown in the absence of inositol. The specific activity of the enzyme increased with time in logarithmically growing cultures lacking inositol andapproached the fully depressed level as the cells entered stationary phase.
| 4,423
|
[Acute amebic abscess of the liver followed by colonic ulcers. Report of 2 cases].
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Two unusual cases of ruptured acute amebic liver abcess are presented one with inferior vena caval compression. Surgical drainage was followed by the development of colonic complications (haemorrhage and perforation) although the patients were under specific therapy. After a new surgical operation both cases were cured. The relation with amebiasis is discussed. The possibility of such an association must always be kept in mind. The value of immunofluorescence test in the diagnosis is emphasised.
| 4,462
|
Glucagon-sensitive adenylate cyclase in human renal medulla.
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In cell-free preparations (washed 600 x g pellets) of human renal medulla, glucagon produced a dose-dependent stimulation of adenylate cyclase. The stimulation of renal medullary adenylate cyclase by saturating concentrations of glucagon was additive to the saturating doses of vasopressin. Furthermore, L-isoproterenol stimulated renal medullary adenylate cyclase in a dose-dependent manner, and this stimulation was blocked by DL-propranolol. Stimulation of the renal medullary adenylate cyclase by maximal doses of glucagon and L-isoproterenol was additive. DL-Propranolol did not inhibit stimulation of glucagon. Thus, the results indicate the existence of a specific adenylate cyclase that is responsive to glucagon--distinct from the isoproterenol-sensitive adenylate cyclase and the previously described vasopressin-sensitive adenylate cyclase in human renal medulla. We suggest that the renal tubular effect of glucagon may be mediated by glucagon-dependent cyclic-AMP production in renal tissue.
| 4,466
|
A kinetic concepto of lipid transport in ruminants.
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Summarization of the literature shows a strong correlation between dietary fatty acid intake and total lipid concentration in plasma in lactating cows whereas total milk fat secreted is related to neither of these. In the process of plasma triglyceride removal, chylomicra and very low density lipoproteins are converted to low density lipoproteins. Limited kinetic data indicate that the fractional removal rates for chulomicra and very low density lipoproteins are rapid in lactating cows whereas fractional removal of low density lipoproteins is slower, resulting in accumulation of the latter in plasma. Under such conditions, low density lipoprotein concentrations of plasma would not be expected to reflect quantitatively the transfer of plasma triglyceride fatty acids to milk fat. Quantitative analysis or triglyceride fatty acid turnover in density less than 1.006 lipoproteins should delineate the role of plasma lipid transport in milk fat synthesis. High fat diets protected from rumen biohydrogenation have proven to be a useful approach in studying ruminant fat metabolism and may be used more extensively to elucidate the role of cholesterol in plasma lipid transport and the metabolism of essential fatty acids in ruminants.
| 4,477
|
Nonimmunologic aspects of caries resistance.
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A variety of components provide salivary secretions with an array of potentially effective means of combating cariogenic challenges. These defense factors range from a laissez-faire mechanical cleansing to exquisitely controlled production of highly specific antibodies. In between the two extremes are antibacterial systems whose operating characteristics are only beginning to be understood. These systems are well worth our attention. They may be the key to our understanding of variations in individual susceptibility, and could provide valuable leads for development of anticaries agents.
| 4,481
|
Morphologic and biochemical changes in autolysing dog heart muscle.
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The progressive changes in pH, lactate content, and light and electron microscopic appearances were studied in dog myocardium undergoing a 6-hour period of autolysis in vitro at 37 degrees C. and at room temperature. At 37 degrees C. there was a rapid cumulative fall in pH during the 1st hour after excision of the heart and a corresponding increase in lactate content, but little additional change in either subsequently. The nature and sequence of the morphologic alterations at this temperature were generally similar to those which occur in ischemic myocardium in vivo. At room temperature, a much slower cumulative decrease in pH and increase in lactate content took place throughout the whole period of investigation and was paralleled by a slower rate of development of morphologic change.
| 4,649
|
The relationship between alcohol dosage and performance decrement in humans.
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The effects of alcohol on human perceptual, cognitive and motor performance was assessed in a battery of tests, and the dose-response relationships for alcohol, important for the study of drug-alcohol interactions, established.
| 4,663
|
[Cerebral palsy--early diagnosis and treatment (author's transl)].
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The main aim of the present Conference has been to debate that early diagnosis and treatment of cerebral palsy. The Conference was attended by specialists taking care of the child with cerebral palsy (C.P.): child neurologists, surgeons--orthopedists, psychologists, rehabilitants, pediatricians. In connection with the fact that the Conference was devoted to the early diagnosis and therapy of C.P., problems concerning the lower age groups of children were debated. The Conference discussed the definitions of "cerebral palsy" used in the literature, the clinical forms, the auxiliary diagnostic methods and their significance in the diagnosing of this pathological syndrome. Early clinical symptoms, enabling to establish the diagnosis of cerebral palsy were particularly extensively debated. In the latter problem particular attention was paid to the diagnostic value of kinetic automatisms of the group of tonic posture reflexes and dysfunctions of the kinetic pattern in children. It was underlined in the debate the C.P. was no separate clinical disease, but a pathological syndrome arisen as a result of the negative influence of different factors and yielding very diverse clinical and neurolopathologic symptoms, according to the kind of noxious factors and the period and degree of maturity of the nervous system in which they acted. The participants in the debate also sressed that, as the child develops and is observed for a longer period it is fairly often necessary to check this diagnosis, as C.P. may prove, as the time passes, to be a degenerative syndrome, a pressure syndrome etc. The psychologists participating in the Conference discussed the psychological problems of the child with C.P. and also the early diagnosis of the pathological syndrome debated. The diversity of the symptoms of the C.N.S. in children suffering from C.P. was underscored, as--apart from dysfunctions within the kinetic area, there can be present sight, hearing and speech dysfunctions, those of sensory perceptions and mental development. These children require multispecialist care, as everyone of dysfunctions mentioned may present a complicated diagnostic problem. Plenty of place was devoted to the discussion of problems connected with epilepsy in children with C.P. Also extensively debated were the general principles of the medical procedure in children with C.P. As a result of the discussion it was decided that children with severer forms of C.P. and those from poor social conditions should be subjected to long-lasting sanatorium rehabilitation. Keeping the child in its family environment should, however, be the generally adopted principle of the rehabilitation of a little child. The parents of the child should be trained in the proper rearing of the child under household conditions, a manner to secure all the needs resulting from the then stage of its development. In connection with this problem the project of the programme of sensoric-and-kinetic rehabilitation was debated, as presented by psychologists and rehabilitants (kinesitherapeuts).
| 4,786
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A 15-hydroxyprostaglandin dehydrogenase specific for prostaglandin A in rabbit kidney.
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Examination of a soluble fraction derived from homogenates of rabbit kidney papilla revealed the existence of a 15-hydroxyprostaglandin dehydrogenase specific for A-type prostaglandins. Prostaglandins of the E- and F-series were not substrates for this enzyme. In agreement with published data, the 15-hydroxyprostaglandin dehydrogenase(s) derived from the kidney cortex were found to degrade all prostaglandins examined (PGE, PGF, PGA) in the presence of added cofactor NAD. Thus it is evident that in this species the kidney 15-hydroxyprostaglandin dehydrogenases are anatomically compartmentalized so that the papilla is able to metabpable of degrading E-, F-, and A-type prostaglandins by this metabolic pathway.
| 4,794
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Chemical reactivities of tetrapyrrole pigments: a comparison of experimentalbehaviour with the results of s.c.f.-pi-m.o. calculations.
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Porphyrins are highly sigma-electron donating bases and very weak pi-acids. Hence they increase the electron density on central metal ions, e.g. iron, which leads to the specific reactivity of haem cytochromes, haemoglobin and oxidizing enzymes. The macrocyclic chlorin ligand behaves similarly but to a lesser degree which explains the comparably low oxidation potential of chlorophyll. Phlorins, oxophlorins, oxa- and aza-orphyrins, tetradehydrocorrins, corrins and biliverdins all produce metal complexes which have a similar geometry to that of metalloporphyrins, but their reactivity patterns are different. In contrast to the metalloporphyrins which undergo many fully reversible reactions, these compounds tend to irreversible addition and cleavage reactions. The tetrapyrrole ligands are stronger pi-acids than porphyrins. Results of some recent experimental work and pi-electron s.c.f. calculations are presented in support of these generalizations.
| 4,842
|
Assessment of antipsychotic activity of an unique agent: SU-23397.
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SU-23397 is a unique new hybrid molecule, the animal profile being characteristic of neuroleptic activity. Although the trial was uncontrolled, there appears to be no doubt that SU-23397 exerts antipsychotic activity between 20 mg and 250 mg daily in severely ill schizophrenic patients. Seven of the ten subjects required at least transient antiparkinson medication. Two patients demonstrated premature ventricular contractions. One patient had infrequent PVCs at baseline which increased in frequency with rising dosage. The other patient developed frequent premature ventricular contractions only after active and medication was initiated and was subsequently withdrawn from the study.
| 4,858
|
The search for the dopamine receptor: tribulations.
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In an attempt to identify specific binding to dopamine receptors the binding of 3H-pimozide to preparations of brain and to an artificial cellulose membrane was examined. Binding occurred rapidly, was pH and temperature dependent, and was displaceable by other neuroleptics. Displaceable binding was saturable at 5 X 10(-8) M pimozide. A weak correlation between IC50's for displacement of binding by drugs and their clinical potencies was observed. Displaceable binding of 3H-pimozide in different brain areas did not correlate with dopamine levels. The similarity of binding properties to brain and to artificial membrane suggests that these effects are a function of the physical-chemical properties of these drugs, and that these properties may be related to their clinical effect.
| 4,861
|
Irreversible protein binding of norethisterone (norethindrone) epoxide.
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14,15-3H-Norethisterone-4 beta, 5 beta-epoxide, a metabolite of norethisterone, was incubated with several proteins and nucleic acids. After 30 min incubation 0.19 nmol of the epoxide were irreversibly bound per mg albumin which contains free sulfhydryl groups; proteins without SH-groups, such as concanavalin A, gamma-globulin, DNA and RNA, did not irreversibly bind norethisterone epoxide. A superoxide (O2) generating enzyme system comprised of xanthine oxidase and hypoxanthine was capable of catalyzing the irreversible binding of the parent compound, norethisterone, to albumin, indicating that an oxidation product was formed which reacted with the protein. When norethisterone epoxide was incubated for 60 min with hepatic microsomes of rats in absence of NADPH, about 2.0 nmol of the epoxide were irreversibly incorporated per mg microsomal protein. This binding was increased to 5.2 nmol by addition of a NADPH regenerating system. Addition of glutathione and cytosol decreased only the NADPH-dependent protein binding; phenobarbital pretreatment of rats induced this NADPH-dependent binding of norethisterone epoxide to microsomal protein by a factor of 2. In presence of NADPH, binding of the epoxide to microsomal protein depended on substrate concentration used. The results indicate that norethisterone epoxide is able to chemically react with proteins. In addition, hepatic microsomal enzymes convert the epoxide to another metabolite which also can react with proteins.
| 4,905
|
A comparison of the cardiovascular effects of enflurane, halothane, methoxyflurane and fluroxene during open cardiac surgery.
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During open heart surgery hemodynamic changes due to 1.5% enflurane, 0.75% halothane, 0.18% methoxyflurane and 3.4% fluroxene have been compared. The following parameters have been measured: arterial pressure, heart rate, cardiac output, right and left atrial pressure, left ventricular pressure and dp/dt. The strongest effects were found with enflurane and halothane. Marked reduction in cardiac index, stroke index, left ventricular dp/dt as well as reduction of peripheral resistance caused severe systemic hypotension. Because of its slow uptake methoxyflurane was followed by small hemodynamic changes in this study. The rapid acting fluroxene had caused only minor reductions of cardiac output, stroke volume and dp/dt. There was no decrease in peripheral resistance.
| 4,951
|
Internal mammary artery bypass graft in reoperative myocardioal revascularization.
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Thirty-two consecutive patients who earlier received indirect or direct myocardial revascularization underwent reoperation with one or more internal mammary artery grafts either alone or in combination with saphenous vein grafts. The main indication for reoperation was graft closure or progression of coronary atherosclerosis in nongrafted vessels, or both. Graft construction was performed under normothermic perfusion and anoxic arrest with interrupted suture technique. No intraoperative infarctions or hospital deaths occurred. All patients are alive after an average follow-up period of 20 months, and two thirds are asymptomatic. Arteriography after reoperation in nine patients revealed patency of eight of nine internal mammary artery and five of five secondary vein grafts. When angiographic and symptomatic indications for reoperation exist, the internal mammary artery bypass graft has become a valuable alternative, particularly for patients with small coronary vessels or previous vein graft failure.
| 4,970
|
Experiments on the role of virus infections in the pathogenesis of bronchial asthma. The role of innate or acquired insufficiency or ergotropic adaptation in the mechanism of genesis of bronchial asthma.
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The wide mosaic of congruent clinical and experimental observations led to the postulation that the cause of the pharmacological abnormality of the asthmatic patient, i.e. the immensely increased reactivity of the bronchial smooth muscles, is to be sought in an insufficiency of the beta-adrenergic receptor system. It is to be assumed that the so-called asthma diatheses is based inter alia on a genetically determined defect of the adenyl cyclase system. The role of previous infections of the respiratory tract in asthmagenesis should lie--following this working theory--not in a sensitization in the sense of an allergic reaction of the immediate type, but in the formation of a defective beta-adrenergic substance or in a blockade of the beta-receptor. A genetically determined innate defect of the beta-adrenergic receptors, or a defect acquired through infections of the respiratory tract, is hence likely to be the cause of the pathologically potentiated reactivity of the bronchia. It is likely that the infective stimuli--quite apart from this preparatory role--are later capable of triggering asthmatic paroxysms when the vegetative homeostasis is impaired. We know from the experiments of many authors that a blockade of the beta-receptors produced by chemical blocker substances, or by pertussis vaccine or various bacterial substances, results in a significant increase in bronchial reactivity towards histamine, serotonin, acetylcholine and other stimuli. We have shown in our experiments that heat-inactivated adeno viruses and influenza viruses also increase the anaphylactic shock reactivity and the histamine reactivity of the organism. On the basis of this working hypothesis, the pathomechanism of the asthmatic process is as follows in individual asthma forms: 1) In the 'purely" allergic asthma form, the antigen-antibody reaction that occurs after sensitization (i.e. formation of skin-sensitizing allergic antibodies of the class IgE) results in re-formation and release of slow-reacting-substances. spasm of the bronchial muscles, asthmatic paroxysm. The expulsion of catecholamines that follows the release of slow-reacting-substances makes a decisive contribution to the reestablishment of the impaired homeostatic balance. It is to be assumed that this form of asthma both symptomatically and causally--using specific desensitization--can be influenced more easily than other forms of asthma with a more complicated pathogenic background. 2) In the second allergically determined form of asthma, we are confronted by the genetically fixed or acquired insufficiency of the beta-receptors in addition to the immunological mechanism. As a result of the innate or acquired blockade of the beta-receptive substance, or the relative dominance of the alpha-receptors, the catecholamines (that physiologically serve to maintain homeostasis) contribute to a protraction, intensification and perpetuation of the bronchial obstruction. In this way the asthmatic circulus vitiosus is complete...
| 4,969
|
Cardiovascular effects of cerebroventricular ouabain perfusion in the adult dog.
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Cerebroventricular perfusion with artificial cerebrospinal fluid containing 10(-5) M ouabain was performed in adult dogs in order to describe the time course of the cardiovascular effect of intraventricular ouabain and to evaluate treatments to eliminate the cardiovascular effect. The central effect of ouabain caused a 56% increase in blood pressure above control values and a 35% increase in heart rate with various cardiac arrhythmias. Both alpha- and beta-adrenergic blocking drugs given intravenously.altered the pressure and rate effects ou ouabain, whereas vagotomy attenuated the effect.
| 4,981
|
Biliary secretion in elasmobranchs. I. Bile collection and composition.
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Bile composition and secretion were studied in tow elasmobranch species, Squalus acanthias (spiny dogfish shark) and Raja erinacea (small skate), after ligation of the common duct and insertion of cannulas into the gallbladder lumen. Fish were then allowed to swim freely in large pools and bile was collected in balloons attached to the externalized cannulas. Both species secreted bile for periods of 4-7 days at a maximum rate of 1.77 +/- .89 ml/kg per 24 h in Squalus acanthias and 2.66 +/- .89 ml/kg per 24 h in Raja erinacea. Comparison of the composition of cannula and gallbladder bile indicated that hepatic bile could be collected by this technique in both species without effective contact with gallbladder epithelium. The low concentrations of HCO3- and CL- and the gigh bile salt levels in dogfish gallbladder bile indicate that mechanisms for concentration and acidification of bile in the gallbladder developed early in vertebrate evolution. These results indicate that gallbladder cannulation in free-swimming elasmobranchs is a useful technique for the study of bile secretory and excretory function in marine species.
| 4,983
|
[The influence of PaCO2 on oxygen consumption during extracorporeal circulation in hypothermia (author's transl)].
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Hypocapnia during extracorporeal circulation in hypothermia increases oxygen consumption. Po2 in mixed venous blood decreases. This probably reflects a decrease in tissue oxygen tension. Hyperventilation will therefore increase the risk of hypoxia in critically perfused tissues. Therefore we recommend to keep PaCO2 (T) constant at 40 mm Hg during hypothermia.
| 4,989
|
[Accidental peroperative hypothermia during rapid transfusion].
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Six cases of grave hypothermias are reported, having arisen during surgical interventions which necessitated a rapid and abundant transfusion of badly warmed blood. The role of favouring factors, surrounding cold due to the air-conditioning, anaesthesia, extent of the area of operation, seems important. The symptomatology permits the individualization of a hypothermic syndrom neighbouring the picture described in toxic accidental hypothermias. Accidents during the warming process associate collapse and disturbances in coagulation. It is therefore necessary to consider certain signs of alarm as important and generalize the conditions for prevention of thermolysis in the operating theatre.
| 5,005
|
[Iskedyl and general anesthesia. Measurement of the systolic ejection volume and peripheral resistance using the arterial pressure curves].
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ISKEDYL (PF 50), which is sold as a vasoregulator of cerebral irrigation, consists of a mixture of dihydroergocristine and raubasine. This work aims at determining possible interactions between this product and certain drugs used in anesthesia from the cardiovascular point of view. ISKEDYL does not seem to be a contraindication to anesthesia of the "neuroleptic" type, when injected in pre-, per- or post-operative period. A slight temporary and spontaneously reversible fall in arterial blood pressure, affecting both maximum and minimum pressure, together with a decrease in stroke volume and peripheral resistances, estimated by the study of the arterial blood pressure curve, seem to indicate that this product has peripheral vaso-dilatory properties.
| 5,007
|
[Postoperative circulatory arrest (apropos of 37 cases)].
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Within five years, the authors received 37 patients who had presented a post-operative cardiac arrest. Most of them came from the Bordeaux district (from the hospital as well as the public sector) although they did not represent the totality of such accidents. The study bears first of all upon the data concerning the patients, then upon the surgical intervention, the mode of anaesthesia and ventilation, the posture and finally the treatment. In 10 cases. it was noted, as early as the admission, that the blood volume feel short of the theoretical total blood volume by one liter or more. The authors take into account how traces of previous affections, the localization in O.R.L., and, in ophthalmology, an important number of mistakes in anaesthesia, favour the progress of the genesis of the accident.
| 5,017
|
[Comparative study of nitrogen savings during enteral and parenteral feeding (Trive 1000)].
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Through a study of Nitrogen balances, the authors compare the effectiveness of a proteinic intake carried out per os or by intravenous route. The study involved 22 different carcinoma carriers and lasted for 9 days during which the Nitrogen intake was effected either by the digestive tract or by intravenous route supplemented by a sufficient caloric ration. In the latter case, the aminoacid intake was supplied by Trive 1000 combined with glucides and lipids which were then quantitatively deducted from the enteral intake. A study of the results showed that the assimilation of the Nitrogen injected intravenously was very similar to the one obtained by enteral route.
| 5,021
|
[The use of dopamine during postoperative cardiogenic shock in children. Preliminary results].
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Dopamine was used in a dose of 5 mug/kg/min in ten infants with congenital cardiopathy and presenting in the immediate postoperative period a syndrome of low cardiac output. The output was not measured but, based on the evolution of the clinical signs, six favourable results, with correction of the syndrome, can be reported.
| 5,030
|
Susceptibility of pneumococci and Haemophilus influenzae to antibacterial agents.
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Strains of Diplococcus pneumoniae and Haemophilus influenzae were tested for susceptibility to numerous antibiotics by a twofold agar dilution method using an inocula replicator. Undiluted, fully grown broth cultures were used as inocula for both species, and cultures of pneumococci diluted 1:1,000 were also tested. The antibiotics included most of those in common use in the United States as well as some chemical modifications recently approved and others that are under investigation. The most striking aspect of the results was the marked susceptibility of the pneumococci to all the antibiotics tested except the polymyxins and most of the aminoglycoside antibiotics, although some new aminoglycosides were active in quite low concentrations. Some of the strains of pneumococci were of decreased susceptibility to penicillin G (minimal inhibitory concentrations, 0.2 to 0.4 mug/ml), but none were tetracycline resistant, although such strains had been reported previously from this laboratory. The strains of H. influenzae, which were all serologically nontypable, exhibited different patterns of susceptibility to the groups of antibiotics and to the individual chemically related ones. None of these strains (isolated early in 1972) were ampicillin resistant. The most active agents against H. influenzae were: carbenicillin and ampicillin, analogues related to each of them, rifampin, chloramphenicol, and the polymyxins. However, the tetracycline analogues other than tetracycline, some aminoglycosides, notably tobramycin, kanamycin, gentamicin, and verdamicin, erythromycin, and some new lincomycin analogues were also active in low concentrations. Trimethoprim alone was highly active, and in combination with sulfamethoxazole it was even more active and synergistic against strains of both D. pneumoniae and H. influenzae.
| 5,052
|
Acute toxicity of selenium dioxide to freshwater fishes.
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Acute toxicity tests of selenium dioxide were conducted for 96 to 336 hr in intermittent-flow bioassay systems using six species of freshwater fish. The decreasing order of species sensitivity was: fathead minnow, flagfish, brook trout, channel catfish, goldfish, and bluegil. Curves relating median lethal concentration to exposure time for each species exposed for more than 168 hr were sigmoid in shape and were characterized by a change in slope indicating a more rapid mortality rate after 96 to 168 hr toxicant exposure. The 96-hr LC50 estimates ranged from 2.9 mg/L SeO2 for fathead minnow fry to 40.0 mg/L for bluegill juveniles. Effects of brief toxicant exposure (24 hr) on fathead minnow and flagfish juveniles included limited delayed mortality and no effects on growth over a 28-day period.
| 5,060
|
Effect of alpha and beta adrenergic blockade on epinephrine induced pulmonary insufficiency.
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Recent studies demonstrated that epinephrine causes significant pulmonary A-V shunting. This study reports the effect of alpha and beta adrenergic blockade on this shunting. Sixty-three anesthetized mongrel dogs were ventilated with a mechanical respirator. Measurements of (1) the pulmonary shunt, (2) cardiac output, (3) mean pulmonary artery, pulmonary capillary wedge and systemic pressures, and (4) pulmonary and systemic vascular resistances were obtained at 5, 15 and 30 minute intervals during the first hour and hourly for 5 hours. Fifteen dogs received no treatment. All others received epinephrine hydrochloride, 2 mug/kg/min for 5 hours. Ten received epinephrine only. Ten were pretreated with propranolol hydrochloride, 250 mug/kg, 12 with phenoxybenzamine, 1 mg/kg, and 16 with phenoxybenzamine and propranolol. Propranolol significantly decreased the epinephrine induced pulmonary shunt at all times and was the most effective drug. Phenoxybenzamine decreased the early shunting, but less than propranolol, and did not decrease the late shunting. Blockade with propranolol and phenoxybenzamine was less effective than propranolol alone. Based on the observed hemodynamic changes it was suggested that beta blockade is effective in reducing epinephrine induced pulmonary insufficiency by favorably altering the flow and distribution of pulmonary blood flow which in turn decreases epinephrine induced ventilation-perfusion inequalities and capillary hypertension both of which result in shunting. Conversely phenoxybenzamine has an unfavorable effect on the pulmonary flow. These studies support previous work in animals and man which showed that beta adrenergic stimulation is important in the pathogenesis of pulmonary insufficiency. Because the amounts of epinephrine used produce blood levels observed in critical illness, these studies add support to a relationship between the increased catecholamine stimulation of critical illness and the associated and often unexplained pulmonary insufficiency.
| 5,061
|
Mechanistic studies of glutamine synthetase from Escherichia coli: kinetics of ADP and orthophosphate binding to the unadenylylated enzyme.
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The kinetics of protein fluorescence change exhibited by ADP or orthophosphate addition to the Mg2+-or Mn2+-activated unadenylylated glutamine synthetase from Escherichia coli were studied. The kinetic patterns of these reactions are incompatible with a simple bimolecular binding process and a mechanism which required protein isomerization prior to substrate binding. They are consistent with a mechanism in which direct substrate binding is followed by a substrate-induced conformational change step, ES in equilibrium ES. At pH 7.0 and 15 degrees C, the association constants for the direct binding (K1) of ADP to MnE1.0 and of Pi to MnE1.0ADP are 3.9 X 10(4) and 2.28 X 10(2) M(-1), respectively. The association constant for the direct binding of ADP to MnE1.0Pi is 2.3 X 10(4) M(-1) at pH 7.0 and 19 degrees C. The deltaG degrees for the substrate-induced conformational step are -3.5 and -1.3 kcal mol(-1) due to ADP binding to MnE1.0Pi and MnE1.0, respectively, and -1.4 kcal mol(-1) due to Pi binding to MnE1.0ADP. Rate constants, k2 and k(-2), for the isomerization step are: 90 and 9.5 s(-1) for ADP binding to MnE1.0, 440 and 0.36 s(-1) for ADP binding to MnE1.0Pi, and 216 and 1.8 s(-1) for Pi binding to MnE1.0ADP. Due to low substrate affinity, the association constant for direct Pi binding to MnE1.0 was roughly estimated to be 230 M(-1) and k2 = 750 s(-1), k(-2) = 250 s(-1). At 9 degrees C and pH 7.0, the estimated association constants for the direct ADP binding to MgE1.0 and MgE1.0 Pi are 1.8 X 10(4) and 1.6 X 10(4) M(-1), respectively; and the rate constants for the isomerization step associated with the corresponding reaction are k2 = 550 s(-1), k(-2) = 500 s(-1), and k2 = 210 s(-1), k(-2) = 100 s(-1). From the kinetic analysis it is evident that the inability of Mn2+ to support biosynthetic activity of the unadenylylated enzyme is due to the slow rate of ADP release from the MnE1.0PiADP complex. In contrast the large k(-2) obtained for ADP release from the MgE1.0ADP or MgE1.0PiADP complex indicates that this step is not rate limiting in the biosynthesis of glutamine since the k catalysis obtained under the same conditions is 7.2 s(-1).
| 5,113
|
Isolation and partial characterization of a protease from Agave americana variegata.
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A new protease was isolated from an extract of leaves of Agave americana variegata. The protease (EC 3.4.-) was purified 565-fold with a yield of 39.5%. The 43.8 mg enzyme had a specific activity of 0.44 units/mg. According to electrophoretic, ultracentrifugal and other physical characterizations the enzyme was homogeneous. The enzyme had a MR of 57000, a S20,W-value of 4.37 S, a D20, W-value of 6.8-7.0 - 10(-7) cm2sec-1, a Stokes radius of 3.18 nm, a partial specific volume of 0.735 cm3g-1, a frictional ration of 1.25, a molecular absorbancy index at 280 nm of 5.773-10(4), an isoelectric point of 5.25 and contained 8-10% carbohydrate. The enzyme contained no cysteine. Agave protease could hydrolyze a variety of protein substrates although it did have a restricted specificity. It is not a sulphhydryl protease but seems to be an alkaline "serine" protease with an optimum pH of 7.8-8.0 Agave protease had marked esterolytic activity and with Cbz-Tyr-ONp had an apparent Michaelis constant of 0.0345 -10(-3) M and a V of 1.24 mol substrate/mol enzyme per sec. The enzyme did not need metal ions for optimal activity, monovalent cations did not influence its kinetic parameters, but it was inhibited by cobalt, pC1HgBzO- and TosPheCH2C1. With respect to its primary specificity, as well as its pH-dependence there was a resemblance with chymotrypsin, although the rate of hydrolysis of Agave protease is much lower.
| 5,146
|
Intrinsic resistance to methotrexate of cultured mammalian cells in relation to the inhibition kinetics of their dihydrololate reductases.
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Four cultured mammalian cell lines, differing in intrinsic resistance to methotrexate over a 70-fold range, have been compared with respect to several biochemical factors that might influence response to the drug. Cellular activity of the enzymes dihydrofolate reductase and thymidylate synthetase and the total levels of folate cofactors did not vary by more than a factor of 2 among the cell lines. All the cell types were able to transport extracellular methotrexate efficiently across the cell membrane, and at comparable rates. A kinetic study of highly purified dihydrofolate reductases from the four sources revealed small differences in the Km values for dihydrofolate and reduced nicotinamide adenine dinucleotide phosphate. A study was made of the inhibition of the four dihydrofolate reductases by methotrexate, and Ki values were obtained by fitting the Zone B equation of Goldstein (Goldstein, A., J. Gen. Physiol., 27: 529-580, 1944) to the resulting data. Values Ki determined by this method correlated with intrinsic resistance of the cell lines and showed a 25-fold range from the most sensitive to the most resistant line. It is concluded that the response of a cell to methotrexate is significantly influenced by the dissociation constant of its dihydrofolate reductase-methotrexate complex.
| 5,189
|
Binding of radioactivity from (14C)thiourea to rat lung protein.
|
Binding of radioactivity from [14C]thiourea (TU) to rat lung protein was found to occur in vitro. Two binding sites are present. One possesses low affinity/high capacity while the other is characterized by high affinity/low capacity. In vitro binding of [14C]TU to lung protein can be antagonized by the presence of either unlabeled congeners (alpha-napthylthiourea or phenylthiourea) or thiol-containing compounds (cysteine, reduced glutathione). Conversely, depletion of lung-reduced glutathione by means of diethyl maleate administration results in elevated protein binding. Prior administration (24 hr) of a sublethal dose of TU (which renders tolerance to a subsequent lethal dose in vivo) results in a decrease in in vitro binding of radioactivity from [14C)TU to lung protein. In addition, immature rats, which are less sensitive to the edematogenic effect of TU, bind less radioactivity from [14C]TU to lung protein when the drug is administered in vivo. These results suggest a correlation between [14C]TU binding to lung protein and the pathophysiological effect of the drug in the lung.
| 5,255
|
Oxisuran metabolism in pigs.
|
The fate of oxisuran in the pig was studied with 14C-labeled drug to quantify its biotransformation and disposition. Despite interanimal differences, it was clear that the compound absorbed rapidly and biotransformed extensively to metabolites which were excreted principally in urine rather than in feces. Direct attacks upon oxisuran involved reduction to diastereo-isomeric oxisuran alcohol sulfoxides and oxidation to oxisuran sulfone. Subsequently, the oxisuran alcohol sulfoxides were reduced to a sulfide and oxidized to a sulfone. Phase II reactions appeared to be limited to sulfation of oxisuran alcohol sulfoxides and oxisuran alcohol sulfone. Pharmacokinetics were investigated for oxisuran and its metabolites.
| 5,259
|
Differential dependence on NADPH concentrations of two microsomal corticosteroid 21-hydroxylation reactions.
|
The dependency on NADPH concentrations of the bovine adrenal cortex microsomal 21-hydroxylation of progesterone and of 17-hydroxyprogesterone was investigated. The average Km for NADPH in the 21-hydroxylation of progesterone is 10.4 muM while that for the 21-hydroxylation of 17-hydroxyprogesterone is 0.6 muM. The optimal NADPH concentrations for these two hydroxylations are, in average, one order of magnitude apart. The different affinities of the two 21-hydroxylating activities with respect to NADPH may indicate the presence of independent 21-hydroxylation reactions for these two steroid substrates. This evidence is consistent with the observed genetic data in human congenital adrenal hyperplasia.
| 5,267
|
Reconstituted liver microsomal enzyme system that hydroxylates drugs, other foreign compounds, and endogenous substrates. IX. The formation of a 455-nm metabolite-cytochrome P-450 complex.
|
The reconstituted liver microsomal hydroxylation system was used to study the formation of a metabolite-cytochrome P-450 complex absorbing maximally at 455 nm, with benzphetamine and N-hydroxyamphetamine as substrates. Complex formation required the presence of NADPH, substrate, NADPH-cytochrome c reductase, lipid, and cytochrome P-450, indicating that metabolism of the substrate is essential. In the presence of fixed amounts of lipid and NADPH-cytochrome c reductase, the rate of complex formation with cytochrome P-450 isolated from phenobarbital-treated rats was much greater than that observed with cytochrome P-48 from 3-methylcholanthrene-treated rats or rabbits. These results are consistent with recent studies indicating that different forms of cytochrome P-450 with distinct spectral, catalytic, and immunological properties exist in liver microsomes.
| 5,265
|
Isolation, purification and properties of aortic elastase.
|
An elastase from pig aorta has been partially purified and characterised; it exhibits immunological cross reaction with pig pancreatic elastase. Its proteolytic (k-elastin gel and polymeric elastin substrates) and esterolytic (N-succinoyl-trialanine paranitroanilide) activities as well as its degree of inhibition by serum protease inhibitors (alpha1-antitrypsin and alpha2-macro-globulin) differ sensibly from those of pancreatic elastase [14,16].
| 5,303
|
Oral lesions caused by habits.
|
Oral lesions caused by habits can be of teeth only, of teeth and the soft tissues of the mouth or may be only of the soft tissues. Lesions of teeth are permanent and may remain even when there has been total destruction of soft tissues. Recognition of lesions due to habits such as betel chewing, snuff dipping, pipe smoking and certain sexual practices may help towards establishing the sex, the ethnic grouping or even the place of origin of a person or their remains. Certain dental and gingival changes may indicate a person's working circumstances and even the type of treatment received.
| 5,345
|
Partial purification and properties of Enterobacter cloacae heat-stable enterotoxin.
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Cell free preparations of the whole-cell lysate and ultrafiltration (UF) fractions of broth cultures of a strain of Enterobacter cloacae, isolated from a Puerto Rican with tropical sprue, were assayed for their ability to induce in vivo net water secretion in the rat jejunum. The whole-cell lysate and UM-10 retentate of broth cultures were inactive. The UM-2 retentate and filtrate were active at a concentration of 100 mug/ml or more; the toxigenic activity was entirely retained, and increased to 1 mug/ml, by a UM-05 membrane; washing this retentate yielded a fraction with an activity of 10 ng/ml. Stationary aerobic culture conditions yielded the most active UF fractions when ammonium sulfate was used as the precipitating agent, whereas anaerobic culture conditions produced the most active fractions in broth cultures precipitated by acetone. Passage of the active acetone-precipitated UF fractions through a Sephadex G-25 column yielded eluate pools with enhanced toxigenic activity in, or adjacent to, the void volume, but maximum activity of the ammonium sulfate-precipitated UM-05 retentate eluated at a Kav of 0.38 to 0.52. Neither of the most active gel filtration elution fractions of the UM-05 retentates contained detectable carbohydrate, suggesting that the toxin is not associated with endotoxin. Toxigenic activity was unaltered by exposure to a temperature of 100C for 30 min, lowering the pH to 1, or incubation with either Pronase or trypsin. These observations indicate that the strain of E. cloacae under study elaborates a heat-stable enterotoxin htat has approximately the same molecular weight and shares many of the characteristics of the heat-stable enterotoxin produced by some strains of Escherichia coli and Klebsiella pneumoniae.
| 5,376
|
Further studies of the physical and metabolic properties of foot-and-mouth disease virus temperature-sensitive mutants.
|
Three temperature-sensitive (ts) mutants of foot-and-mouth disease virus were classified as ribonucleic acid negative and as belonging to the same complementation group when measured by virus yields and [3H] uridine incorporation in paired, mixed infections at the nonpermissive temperature (38.5C). Mutant ts-22, the only mutant able to produce plaques at 38.5 C, was more sensitive to acid than were the parental wild-type or other mutant viruses. Diethylaminoethyl-dextran did not enhance the plaque-forming ability of the mutant viruses at 38.5C. All of the viruses inhibited host cell protein syntehsis at both permissive (33C) and nonpermissive (38.5C) temperatures.
| 5,377
|
Luminescence and respiratory activities of Photobacterium phosphoreum. Competition for cellular reducing power.
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Changes in the in vivo luminescence, respiratory activities, contents of cytochromes, extractable luciferase and NAD(P)H-FMN reductase during growth of the wild (bright) strain of Photobacterium phosphoreum and its dim mutant were determined. The intensity of the in vivo luminescence per cell increased 10 times in the wild strain and 750 times in the dim strain during logarithmic growth, while the contents of luciferase and NAD(P)H-FMN reductase remained almost constant. It is suggested that a characteristic change in the mode of competition of the luminescence reaction system with another electron transfer chain involving cytochromes for NAD(P)H take place during the growth of this bacterium.
| 5,397
|
Purification and properties of two ribonucleases in different intracellular compartments in pea root tissue.
|
Two RNases in bound forms associated with the microsomal membrane and with the ribosomes or unknown particles in pea root tissue were solubilized by subjecting the membrane to sonic oscillation in the presence of EDTA and KC1 and by treating the particles with EDTA, respectively. The RNases were than purified by DEAE-cellulose and Sephadex G-75 column chromatographies. The elution profiles of RNases from the columns were very similar. No significant differences were observed in their electrophoretic mobilities in polyacrylamide gels, in molecular weight, in activation by inorganic ions, urea or phospholipid micelles or in the dependence of their activities upon pH. The purified RNASES were not different from the bound enzymes as regards activation by inorganic ions and urea and the dependence of the activity upon pH. Triton X-100 stimulated the activity only if RNase was in a bound form associated with the microsomal membrane. We propose that the two RNases may be the same molecular species and differ only in the form of association with intracellular structures.
| 5,408
|
Purification and properties of an exo-cellulase component of novel type from Trichoderma miride.
|
An enzyme extract from Cellulase-Onozuka, a commercial product of Trichoderma viride, was fractionated by Amberlite CG-50 column chromatography into three cellulase [EC 3.2.1.4] groups, peaks I to III. A noval enzyme, which has both beta-glucosidase [EC 3.2.1.21] and exo-carboxymethyl-cellulase (exo-CMCase) properties was obtained from peak III by extensive purification throuh consecutive column chromatography. The enzyme was homogeneous on ultracentrifugation, SDS-gel and cellulose acetate film electrophoreses and molecular sieve chromatography on Bio-Gel P-150. The molecular weight of this enzyme was estimated to be 53,000. The enzyme appeared to release cellobiose residues one by one from the nonreducing end of higher cellooligosaccharides and CM-cellulose (CMC), but to release glucosyl residues from reduced cellotriose and beta-cellobioside, resembling a beta-glucosidase in this respect. Furthermore, this exo-CMCase also attacked xylan exo-wise to produce xylobiose moleculaes one by one, but it scarcely attacked insoluble cellulose, except for a cellodextrin apparently rich in amorphous structure.
| 5,409
|
Titration study of acetylated lysozyme.
|
To study the interaction between carboxyl groups and amino groups in native lysozyme [EC 3.2.1.17], and to identify the positions and the pK values of the abnormal carboxyl groups, N-acetylated lysozyme was prepared. The acetylation did not affect the molecular shape of the enzyme, but changed six amino groups to a non-ionizable form, leaving one amino group free; this was determined to be Lys 33. In addition, pH titration of the acetylated lysozyme in 0.2 or 0.02 M KCl aqueous solution indicated fewer titratable groups with pK(int) of 7.8 or 10.4 compared with the native protein, though the number of titratable carboxyl groups was not affected by the acetylation. From the pH titration results and structural considerations, the unititratable carboxyl groups were suggested to be Asp 48, Asp 66, and Asp 87. On the other hand, spectrophotometric titration in 0.2 M KCl showed that all three tyrosine residues are titratable in the acetylated protein, although an abnormal tyrosine residue exists in the native state. Tyr 20 was suggested to be untitratable in the pH range of 8-12.6.
| 5,421
|
Isolation of a low molecular weight active fragment of potato proteinase inhibitor IIb.
|
A low molecular weight active fragment of potato proteinase inhibitor IIPB was obtained by incubating the inhibitor with an equimolar amount of trypsin [EC 3.4.21.4] at pH 8 and 30 degrees for 16 hr, followed by gel filtration through Sephadex G-50, treatment with trichloroacetic acid, and CM-cellulose chromatography. The purified active fragment consisted of a single peptide chain with a molecular weight of 4,300, comprising 39 amino acid residues. It retained very strong inhibitory activity against chymotrypsin [EC 3.4.21.1] and subtilisin [EC 3.4.21.14]. However, the yield of this active fragment was rather low and was variable. On further incubation with trypsin, it was converted into smaller inactive peptides.
| 5,422
|
Regulation of steady state level of phosphoenzyme and ATP synthesis in sarcoplasmic reticulum vesicles during reversal of the Ca2+ pump.
|
The role of the Ca2+ concentration gradient in ATP synthesis and membrane phosphorylation by Pi was investigated in sarcoplasmic reticulum vesicles isolated from rabbit skeletal muscle. The Pi concentration required to attain 50% of the maximal membrane phosphorylation varies significantly in the pH range of 5.5 to 4.5, the optimal being at pH 6.0. In the pH range of 6.0 to 7.0, this concentration of Pi was 4- to 10-fold higher in empty vesicles than in vesicles loaded with calcium phosphate, i.e. having transmembrane Ca2+ concentration gradient. ATP, ADP, and Ca2+ inhibit the membrane phosphorylation by Pi, the inhibition being greater at pH 7.0 than at pH 6.0. The pH profile for ATP synthesis shows a higher optimum than for membrane phosphorylation. The optimum pH for synthesis, but not for phosphorylation depends on whether the vesicles were previously loaded with calcium phosphate or with calcium oxalate. Addition of Ca2+ to the assay medium inhibits the extent of membrane phosphorylation and the rate of ATP synthesis to different extents. Evidence is presented that the rate of membrane phosphorylation by Pi is higher than the rate by which the phosphoprotein transfers its pohsphate to ADP for the ATP synthesis.
| 5,437
|
Studies on tyrosine residues in porcine muscle adenylate kinase. Circular dichroism spectra and chemical modification with tetranitromethane.
|
Substrate-induced conformational change of porcine muscle adenylate kinase (EC 2.7.4.3) is evidenced by a change in circular dichroism spectra in the near ultraviolet. In the absence of tryptophan in porcine muscle adenylate kinase, the spectral change may be assigned to a perturbation of tyrosine chromophore(s). The spectral change was specific for adenine nucleotide binding and was greater with ATP than with AMP. In the x-ray model, Tyr153 and Tyr154 are located at a hinge region of two domains which form a deep active site cleft and are therefore susceptible to conformational change on substrate binding. Adenylate kinase was treated with equimolar tetranitromethane. The yellow-colored product, separated from unmodified enzyme by substrate gradient elution on a phosphocellulose column, had about 1 mol of nitrotyrosine per mol of the enzyme by amino acid analysis and showed a slightly higher Km value than native enzyme for ADP (Km = 0.50 mM compared with 0.25 mM for native adenylate kinase). Spectrophotometric titration of nitroadenylate kinase gave pKa 8.4 for the dissociation constant of the nitrotyrosyl hydroxyl group. On binding ATP the pKa value increased to 9.0 while AMP binding caused very little change. By peptide mapping of the carboxypeptidase digestion product, 0.70 mol of nitro group per mol of adenylate kinase was detected on Tyr153 and a small amount of nitro group was also found on Tyr95. From these results it is proposed that Tyr153 is directly or indirectly involved in the binding of ATP.
| 5,449
|
Association of gylcogenolysis with cardiac sarcoplasmic reticulum.
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Sarcoplasmic reticulum fragments isolated from dog cardiac muscle possess a calcium-accumulating system associated with a series of enzymes linked to glycogenolysis. These enzymes include: adenylate cyclase, cyclic AMP-dependent protein kinase, phosphorylase b kinase, phosphorylase (b/a, 30/1),"debrancher" enzyme, and glycogen (0.3 to 0.7 mg/mg of protein). The sarcoplasmic reticulum preparation produced glucose 1-phosphate and glucose from either endogenous or exogenous glycogen. Both the calcium-accumulating and glycogenolytic enzymes sediment in a single peak at 33% sucrose on a linear continous sucrose density gradient, and the complex remains intact throughout repeated washing. Glycogen particles appear to be associated with the sarcoplasmic reticulum in situ as well as in the isolated microsomal fraction. The sarcoplasmic reticulum-glycogenolytic complex, monitored by a linked enzyme spectrophotometric assay, shows several features: (a) activation of phosphorylase activity to peak rate occurs over a very rapid time course which cannot be duplicated using combinations of purified enzymes; (b) activation is inhibited by protein kinase inhibitor; (c) phosphorylase b functions as in the purified form with respect to AMP (Km, 0.3 mM); (d) in the presence of limiting amounts of glycogen, optimal phosphorylase b activity in the sarcoplasmic reticulum requires the presence of debrancher, and the activity is sensitive to inhibitors of that enzyme such as Tris, which suggests the possiblity that the enzymes bear a specific structual relationship to the glycogen present. Phosphorylase b leads to a activation in the sarcoplasmic reticulum was completely resistant to ethylene glycol bis(beta-aminoethyl either)-N,N'-tetraacetic acid (EGTA). Inhibition of calcium accumulation by or release of bound calcium from sarcoplasmic reticulum by X537A (RO 2-2985) did not alter the EGTA resistance. These results suggest that cardiac sarcoplasmic reticulum is a complex organelle containing functions that may be related to excitation-contraction coupling and intermediary metabolism.
| 5,455
|
A reversed-phase thin-layer chromotographic method for the determination of relative partition coefficients of very lipophilic compounds.
|
A reversed-phase thin-layer chromatographic method has been developed for the determination of partition coefficients. A support phase has been chosen, following investigation of the lack of adsorptive properties, which has a minimal effect on the pH of the buffer system. A stationary phase has been chosen to give deltaRm values of the same magnitude as Hansch pi values for a series of phenothiazines. The method can be applied to molecules of a wide range of lipophilicity following preliminary investigations of suitable phase-volume ratios and of the pH and composition of the binary mobile phase, providing adsorption on the support phase is excluded.
| 5,460
|
Purification of canine prolactin by preparative isotachophoresis.
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Preparative isotachophoresis in polyacrylamide gel using carrier ampholytes as 'spacers' has been used to purify prolactin from canine pituitary extracts. Using Ampholine pH 5-8 as spacers, a prolactin fraction was obtained which was essentially homogeneous as judged by the criteria of disc electrophoresis and isoelectric focusing. Amino acid analysis indicated a close similarity between canine and ovine prolactin. A growth hormone fraction, identified by its electrophoretic mobility, was also obtained although this was heterogeneous in disc electrophoresis at alkaline pH.
| 5,569
|
Mannosidosis: phenotype of a severely affected child and characterization of alpha-mannosidase activity in cultured fibroblasts from the patient and his parents.
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A three-year-old boy has coarse facial features, upper respiratory congestion, profound mental retardation, hepatosplenomegaly, increased height and head circumference, cataracts, a gibbus deformity, radiographic changes of dysostosis multiplex, and vacuolized peripheral lymphocytes. These findings are the most commonly reported clinical features in the previously described patients with mannosidosis. Our patient has a severe deficiency, and his parents have intermediate levels, of the acidic component of alpha-mannosidase in their cultured fibroblasts.
| 5,584
|
Rapid GLC determination of fusaric acid in biological fluids.
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A simple, sensitive GLC assay was developed for fusaric acid, the active metabolite of bupicomide, to follow the disposition of this investigational antihypertensive agent in patients undergoing therapy. Fusaric acid is efficiently extracted from biological samples, derivatized by on-column methylation, and chromatographed using flame-ionization detection. An internal standard is utilized to quantitate results. The procedure is rapid and specific for fusaric acid, and has a lower limit of sensitivity of 0.1 mug/ml. The method is suitable for supporting pharmacokinetic studies of bupicomide following therapeutic doses in animals and humans.
| 5,590
|
Conformational populations for antihistamines and antihypertensives in solution.
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The conformations in aqueous solution were determined for the XCH2CH2N systems of some antihistamines (H1-receptor antagonists) and some adrenergic neuron blocking agents, including the antihypertensive drugs guanethidine and guanoclor. The rotameric species thought to be the pharmacologically active one is often not the only rotamer present in solution.
| 5,591
|
Aminopyridines and sparteine as inhibitors of membrane potassium conductance: effects on Myxicola giant axons and the lobster neuromuscular junction.
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The effects of the compounds 2-, 3- and 4-aminopyridine and sparteine on membrane conductance changes were examined using both voltage-clamped Myxicola axons and the lobster neuromuscular junction. In Myxicola axons, the aminopyridines very specifically inhibited the potassium conductance when applied at concentrations of 0.1 mM to 5 mM without any apparent effect of resting membrane potential. Concentrations in excess of 5 mM were needed to inhibit noticeably the sodium conductance. Potassium conductance-voltage curves were shifted in the depolarized direction along the voltage axis with no significant change in shape. There were only minor changes in the kinetics of potassium activation. In high potassium solutions, both inward and outward potassium currents were equally sensitive to the aminopyridines. Sparteine was, in general, found to be a more potent, but somewhat less specific, inhibitor of the potassium conductance. In contrast to the aminopyridines, sparteine was more effective when applied at basic pH and in addition tended to produce a noticeable degree of potassium inactivation. When applied to the lobster neuromuscular junction, 2-aminopyridine and sparteine dramatically increased the amplitude of both excitatory and inhibitory postjunctional potentials, with little or no change in resting potential, resting input conductance, reversal potential, or miniature end plate potential amplitude or frequency. Quantal content per fiber was increased by approximately a factor of 3 for the excitatory responses.
| 5,600
|
Changes in contractility and calcium binding of guinea pig taenia coli by treatment with enzymes which hydrolyze sialic acid.
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The effects of neuraminidase and phospholipase C on the contractility and the Ca++ -binding of guinea pig taenia coli were investigated. Potassium contracture or histamine-induced contracture of taenia coli was inhibited by treatment with neuraminidase, though acetylcholine-induced contracture was not. Treatment with phospholipase C markedly inhibited the contracture induced by isotonic potassium, histamine or acetylcholine. By treatment with neuraminidase for 4 hr, about 40 mumol/100 mg wer wt of sialic acid was released from taenia coli. This corresponded to two-fifths of total content of sialic acid. By treatment with phospholipase C for 2 hr, a similar amount of sialic acid to that produced by neuraminidase treatment was released. The Scarchard plot of Ca++-binding was a biphasic pattern indicating the presence of two types ofthe Ca++ -binding site with different affinity constants. Neuraminidase produced a 57% decrease in the amount of bound Ca++. The Scatchard plot of Ca++ -binding changed to a monophasic pattern indicating the disapperance of thel ow affinity Ca++ -binding site. Phospholipase C caused a 59% decrease of bound Ca++. The Scatchard plot also indicated the disappearance of the low affinity Ca++ -binding site. From these results, we speculated that sialicacid residue of surface membrane of the muscle cell was first site in the Ca++ -influx mechanism.
| 5,622
|
The effects of nalorphine and naloxone on maternal and fetal blood gas and pH.
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In the control trials on near-term pregnant women before the onset of labour, nalorphine was found to cause a mild respiratory acidosis in the mother and metabolic acidosis in the fetus. These effects were not apparent when naloxone was administered.
| 5,649
|
[Investigations of the lipase activity of a pancreatin compound (author's transl)].
|
In connection with the physiologic process of digestion, the requirements for an enzyme-based drug are stated. Quick release of highly active enzymes in the duodenum is a prerequisite of physiological stimulation of the pancreatic excretory function. Digestive potency is regarded as a suitable gauge for comparing of results in large-scale in vitro scanning. Our own in vitro and in vivo studies have borne out the possibility of transferring in vitro findings to the therapeutic value of this compound. As shown by our investigations, quick release of highly active enzymes in vitro is coupled with a high degree of bioavailability in Fermento duodenal. As a result, normalization or reduction of the lipid content of faeces--as a sign of therapeutic efficacy--is seen in patients with pancreatic excretory insufficiency. Statistical evaluation resulted in the following: 1 A statistically significant (p less than 0.1%) increase in lipase activity in the duodenal juice in vitro after addition of one capsule of Fermento duodenal. 2. Lipase activity in vivo after 15 minutes is significantly different from all other values. 3. A statistically significant (p less than 1%) drop in the amount and lipid content of faeces following the treatment with Fermento duodenal.
| 5,651
|
[Interaction between proteins and acid polysaccharides].
|
The intereaction between proteins and acid polysaccharides is electrostatic in nature and leads to the formation of soluble charged and insoluble neutral complexes. The complex formation in the system casein-dextran sulphate is followed by means of turbidimetric titration. It depends on the pH value and the electrolyte concentration. On free electrophoresis, complexes formed below the isoelectric point of the protein exhibit anodic mobility, whereas pure casein migrates to the cathode. The protein in the complex is not able to bind amido black. Consequently, it cannot be detected electrophoretically by dyebinding. The results from viscosity and diffusion measurements are indicative of an increased hydrodynamic volume of the complexes.
| 5,677
|
[Mass transfer in production of milk protein coprecipitates].
|
During the last twenty years heat coagulation has become a more important technical procedure for the isolation of milk proteins because of its very efficient utilization of raw material. Experiments are reported to get approximation equations for the mass transfer in the production of milk protein coprecipitates from skim milk and mixtures of skim milk with rennet and acid whey by means of statistical planning and interpreting of experiments. Good exactness was reached. The coagula consist of casein fractions, whey protein fractions, calcium, and phosphates. The products are thermically rather stable, sensorically indifferent and contain water insoluble protein. They are suitable to improve the fat: protein ration of sausages, but also for the protein enrichment of other foods and for dietetic purposes.
| 5,680
|
Oxygen transport in congenital heart disease: influence of fetal hemoglobin, red cell pH, and 2,3-diphosphoglycerate.
|
In 48 individuals (age 1 day to 13 years) with congenital heart disease, blood oxygen transport function was studied in order to evaluate adaptive changes in shunt hypoxemia and to investigate the in vivo regulation of erythrocyte 2, 3-diphosphoglycerate concentration (RBC 2, 3-DPG) in the presence of fetal hemoglobin (HbF). Arterial pO2 and oxygen content, oxygen capacity, acid base status, oxygen affinity, HbF fraction, plasma pH, red cell pH, and RBC 2, 3-DPG were determined. During the first 50 days of life values of standard P50 (stdP50) (37, pH 7.4), actual in vivo P50 (actP50), RBC 2, 3-DPG, O2 capacity, arterial plasma pH, and red cell pH were scattered around the normal range, although tending to low values for stdP50 and arterial plasma pH and to high values for O2 capacity. After the third month, stdP50 actP50, RBC 2, 3-DPG, O2 capacity, and red cell pH were found to be elevated. Plasma pH and actP50 were scattered around the normal range (Figs. 1 and 2). Intraerythrocytic pH in hypoxemic infants was increased compared with normal children when related to plasma pH (Fig. 3). A close to normal intraerythrocytic pH was therefore found in the hypoxemic infants with low plasma pH, and an increased intraerythrocytic pH in the hypoxemic children with normal plasma pH (Fig. 1). A significant negative correlation exists between erythrocyte H+ ion and 2, 3-DPG concentration (Fig. 5); regression constants derived from data at high (mean 47%) and low (mean 9%) fractions of HbF are not significantly different (Regression Equations 8 and 11 in Table 1). Thus, the known difference in 2, 3-DPG binding to fetal or adult deoxyhemoglobin does not measurably influence the erythrocyte 2, 3-DPG concentration, indicating that in vivo the 2, 3-DPG synthesis in hypoxia is virtually regulated by the erythrocyte pH, which in turn is determined by plasma pH and the oxygenation state of hemoglobin.
| 5,699
|
Effect of excision of the Y-base on the interaction of tRNAPhe (yeast) with phenylalanyl-tRNA synthetase (yeast).
|
The interaction between tRNAPhe (yeast), from which the Y-base has been removed by acid treatment, and phenylalanyl-tRNA synthetase (yeast) has been investigated by fluorescence competition titrations and sedimentation velocity runs. The binding parameters are given under various ionic conditions. The tRNAPhe-Y still can occupy the specific binding sites on the enzyme. Compared to unmodified tRNAPhe, the binding constant is lowered by more than one order of magnitude. It can be concluded that the Y-base is not necessary for specific recognition of tRNAPhe by the cognate synthetase, it rather may represent a point of attachment for the synthetase.
| 5,707
|
Desensitization of beta-adrenergic receptors by beta-adrenergic agonists in a cell-free system: resensitization by guanosine 5'-(beta, gamma-imino)triphosphate and other purine nucleotides.
|
Incubation of purified frog erythrocyte membranes with beta-adrenergic agonists at 25 degrees produces relatively rapid (half-time about 10 min) desensitization (inactivation) of about 60% of the beta-adrenergic receptor binding sites. The desensitized receptors no longer bind the specific beta-adrenergic ligand (-)[3H]dihydroalprenolol. The decrease in the number of functional beta-adrenergic receptors is also manifest as a decreased ability of isoproterenol to stimulate the membrane-bound adenylate cyclase.
| 5,723
|
A comparison of beating parameters in larval and post-larval locomotor systems of the lobster Homarus gammarus (L.).
|
A study has been made of the interrelations between rhythmical exopodite beating in different larval stages and swimmeret beating in poast-larval stages of the lobster Homarus gammarus. Data on exopodite beat cycle durations have been used for statistical comparisons of exopodite performance within one larva, and also between different stages of larval development. Inter-exopodite comparisons reveal clear bilateral differences (table 1), although there is no consistently favoured relationship (tables 2 and 3). There are significant differences in cycle duration between the first three developmental stages, with a slight increase at the first moult, and a marked decrease at the second (table 4). However, within each stage the repeat frequency exhibits little change (table 5). Therefore it appears that changes in swimming behaviour occur discontinuously in development, and are associated with the larval moults. It is suggested that changes in beat frequency, and especially the faster beating in stage III, may represent responses to changed loading conditions (table 7). Measurements of swimmeret beating in post-larval lobsters have been analysed in terms of cycle durations, and inter- and intra-segmental phase relations. Swimmeret beating patterns are very regular (figure 1), but not restricted to a narrow range of frequencies (table 6a). Intersegmental phase lag remains constant around 0.2 (figure 3) independent of beat frequency (figure 4). Similarly the powerstroke/returnstroke ratio of approximately 0.5 (figure 5) shows no significant correlation with cycle duration (figure 6). Differences emerge in the performance of larval exopodites and post-larval swimmerets (table 6b), although the possibility cannot be excluded that the larval exopodite oscillator in some way influences the developing action of the post-larval swimmeret system.
| 5,739
|
Reduced myocardial ATP and creatine phosphate in diabetes: role of 2,3-diphosphoglycerate.
|
Observations are presented which suggest that myocardial cellular hypoxia may account for the reduction in myocardial ATP and CP in the ketoacidotic diabetic state. It is suggested that reduced 2,3-diphosphoglycerate adversely affects oxygen release from the red blood cell, thereby leading to myocardial cellular hypoxia.
| 5,754
|
Muscarinic stimulation of cardiac guanylate cyclase.
|
Right ventricular kitten papillary muscles were incubated with dibutyryl adenosine 3',5'-monophosphate (db-cAMP) at varying concentrations from 1 X 10(-4) M to 1 X 10(-3) M. A positive inotropic effect was observed with all concentrations of db-cAMP. Concomitant administration of 5 X 10(-4) M monobutyryl guanosine 3',5'-monophosphate and 1--2 X 10(-4) M db-cAMP did not produce an inotropic response. At the biochemical level cardiac guanyl cyclase activity is enhanced 2--3 times with acetylcholine and this enhancement is completely blocked by atropine. This increased activity appears to be the result of a decrease in the Michaelis constant (Km) for GTP. Calcium also produces a significant activation of guanyl cyclase activity.
| 5,759
|
Some properties of rat myocardial ornithine decarboxylase and the in vitro effects of nucleotides.
|
Myocardial ornithine decarboxylase appears to have characteristics similar to those of enzymes isolated from other tissues. Ornithine decarboxylase activity decreased very rapidly after the death of the animal. Storage of the cell sap fraction at 0 degrees C or -15 degrees C, however, led to only a small decrease in the enzyme activity up to 3 days after preparation. Pyridoxal phosphate at an optimum of 50 muM was essential for full enzyme activity. Thiol compounds did not increase the myocardial ornithine decarboxylase enzyme activity. The subcellular distribution of the enzyme in the myocardium was found to be different from that reported in other tissues. A partial purification of the enzyme was possible using the proteins precipitated at pH 5 from a cell-soluble fraction or by passing a soluble fraction through a Sephadex G 100 gel column. ATP, ADP, and AMP inhibited ornithine decarboxylase at high concentrations (5 mM), but GTP, CTP, and ITP inhibited at a 1 mM concentration and above.
| 5,762
|
Response to jejunal acidification in man. I. Changes in composition of perfusate.
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The jejunal disposal of perfused acid was studied in 11 control subjects and 12 patients with duodenal ulcer. It was found that the capacity to dispose of acid was saturable and was less than control in patients with duodenal ulcer. When the load of acid was small, all the acid disappeared from the jejunum and sodium bicarbonate could be aspirated. During acid perfusion there was secretion of water and electrolytes into the jejunum if the load of acid exceeded the dissipative capacity. Superimposed intravenous infusion of secretin and cholecystokinin increased acid disposal, particularly in patients with duodenal ulcer, and increased the associated rate of secretion of water and electrolytes or changed net absorption to net secretion. We conclude, firstly, that acid is removed from the jejunum by secreted bicarbonate, and secondly that the whole of the upper small intestine of patients with duodenal ulcer is functionally abnormal.
| 5,770
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[Bacteriological examinations of bronchial secretion in children with non-specific bronchopulmonary disease (author's transl)].
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One thousand specimens of bronchial secretion from children with non-specific respiratory diseases have been examined bacteriologically. In spite of the complex nature of acute and especially of chronic respiratory disease the role of bacterial infection should not be underestimated. Thirty per cent of the specimens were sterile. More than 20 per cent of the bacterial species isolated from bronchial secretion were pathogenic. Relatively frequent was the isolation of E. coli and of pathogenic staphylococci. Nearly 40 per cent of all isolated bacteria were alpha-haemolytic streptococci. The latter have been found more frequently in children with, than in children without bronchological alterations. The pathogenicity of alpha-haemolytic streptococci in the bronchial tree is discussed.
| 5,823
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Some factors influencing the haemolysis of Bordetella bronchiseptica.
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Strain-dependent variations in the ability of Bordetella bronchiseptica to produce haemolysis on solid media exist. Haemolysis is strongest at an acid reaction and will not take place if the reaction is too alkaline. Peptone and glutamine inhibit haemolysis and favour growth. The vigorous growth rapidly produced an alkaline reaction which inhibits the haemolysis.
| 5,844
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Oxygen uptake and tissue oxygen tension during adrenergic stimulation in canine subcutaneous adipose tissue.
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The effect of sympathetic nerve stimulation (NS) and injected noradenaline (NA) or isoprenaline (Iso) on PVO2, VO2 and PtO2 was studied in isolated canine subcutaneous adipose tissue. These effects were compared to those produced by mechanical blood flow reduction (clamping). Resting VO2 measured 13.0+/- 2.3 mumol X min-1 X 100 g-1. When blood flow was reduced by 20% or less there was no significant change of VO2. Reducing blood flow to 50% of control or less by NS caused a parallel reduction in VO2, while clamping reduced VO2 significantly less. NA gave effects similar to those of NS. After NS or NA there was a period of hyperemia and increased oxygen extraction which more than compensated for the decrease in VO2 during vasoconstriction. Such a net increase in VO2 was not produced by clamping. Control PtO2 averaged 29+/-2 mmHg. NA reduced it by 70% and clamping to the same blood flow level only by 14% (p less than 0.01). Thus, a mere reduction in blood flow has little effect on PtO2, while blood flow reduction combined with redistribution of blood flow and an increased oxygen deman can lead to tissue hypoxia.
| 5,850
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Properties of hydroxysteroid oxidoreductase isolated from yeast.
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Yeasts can advantageously be utilized for the production of the 17beta-hydroxy-derivative, from 3-methoxy-8,14-seco-1,3,5(10),9(11)-estratetraene-14,17-dione (14,17-dione) while 14alpha-hydroxy and 14alpha,17beta-dihydroxy-derivatives are also formed. The biochemical properties of yeasts' enzymes responsible for the formation of the two monohydroxy-derivatives have been studied in detail. In the cell-free extract of Saccharomyces the presence of two hydroxysteroid oxidoreductases could be detected. The first enzyme forms 3beta,17beta-dihydroxy-derivative from 5alpha-androstane-317-dione. This enzyme is responsible for the formation of 17beta-hydroxy-derivative from 14,17-dione. The second enzyme forms 3alpha-hydroxy-derivative from 5beta-androstanedione as well as 14alpha-hydroxy-derivative from its 14,17-dione. The cofactor of both enzymes is pyridine nucleotide. The two enzymes possessing different properties can selectively be inhibited.
| 5,855
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Inhibition of Newcastle disease virus replication by 6-azauridine. II. Combination of 6-azauridine and adenine derivatives.
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Twenty-five metabolites (purines, pyrimidines, nucleosides and nucleosides) were tested for their simultaneous action with 6-azauridine (AzUrd) in inhibition of Newcastle disease virus (NDV) replication. With the exception of deoxyadenosine and cyclic AMP all natural adenine derivatives exerted a synergic effect with AzUrd like ATP. Glutamine in combination with AzUrd did not inhibit NDV replication. The inhibitory effect of the combination of AzUrd and adenine derivatives was reversible by guanosine, uridine and cytidine but not by orotic acid or orotidylic acid.
| 5,863
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Levels of immunoglobulins and antibodies to haemaglutinin and neuraminidase of influenza virus in nasal secretions after natural infection.
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Nasal washings (NW) from 16 influenza patients in the course of an epidemic in November and December, 1974 were examined for the presence of influenza virus, immunoglobulins (Ig) and titres of haemagglutination inhibiting (HI) and neuraminidase inhibiting (NI) antibodies. Influenza virus identical with A/Port Chalmers/1/73 (H3N2), increased levels of IgA and occasionally IgG, and specific antibodies were detected in the NW. The dynamics of HI and NI antibody formation did not differ substantially, but there were individual differences in titres and persistence of antibodies. Convalescent sera always contained increased levels of HI and NI antibodies. In some cases, the titres of antibody to viral ribonucleoprotein did not increase.
| 5,867
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Histidine decarboxylase-mediated histamine synthesis in glomeruli from rat kidneys.
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Enzymatic histamine synthesis by renal glomeruli of the rat has been examined. Assays of the partially purified enzyme demonstrated a pH optimum of 6.2, a Michaelis-Menten constant of 2.4 X 10(-4) histidine, and lack of potentiation by benzene. These data thus indicate that renal glomeruli contain the histidine-specific histidine decarboxylase.
| 5,898
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Premedicant drugs and gastric juice pH and volume in pediatric patients.
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The effects of premedication on gastric juice volume and pH were evaluated in five groups of 206 pediatric patients undergoing elective surgical procedures: Group 1 (Control) received no premedication; Group 2 was given morphine sulfate and pentobarbital as premedicants. The other groups received, in addition to morphine and pentobarbital, atropine (Group 3), scopolamine (Group 4), or glycopyrrolate (Group 5). After endotracheal intubation, gastric aspirates were examined for volume, pH and color. Neither premedication with morphine and pentobarbital nor addition of atropine or scopolamine to the premedication significantly altered volume. In patients treated with glycopyrrolate, volume was reduced to less than a third of that of patients in Group 1 (P less than 0.001), and the percentage of pH's higher than 2.5 was significantly greater than in other groups. The incidences of unobtainable samples and samples with pH's higher than 2.5 were greatest with atropine (32.0 per cent, P less than 0.05) and glycopyrrolate (58.1 per cent, P less than 0.01). In 60 per cent of the bile-stained specimens, pH's were below 2.5. It is concluded that because of its selective inhibitory effect on gastric acid secretions, glycopyrrolate appears superior to other anticholinergic drugs. The reduction of gastric juice volume and acidity produced by glycopyrrolate would have important clinical implications in case of accidental aspiration. It is also concluded that bile staining of gastric contents is not a reliable indicator of gastric juice pH.
| 5,924
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Arterial hypoxemia caused by intravenous ketamine.
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Ketamine given IV in a dose of 2 mg/kg caused a significant reduction in Pao2 in 7 patients spontaneously breathing with an unassisted airway. Under the same conditions, in 7 patients, ketamine (2 mg/kg IV) preceded by diazepam (0.2 mg/kg IV) also caused a reduction in Pao2 not significantly different from that caused by ketamine. In some patients, alarmingly low levels of Pao2 ( less than or equal to 40 torr) were seen following ketamine administration. Based on these findings, the authors recommend that O2 and ventilatory assistance accompany ketamine given IV for anesthesia.
| 5,920
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Clinical investigation of a new intravenous anesthetic--etoxadrol hydrochloride (CL-1848; U-37862A).
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Twenty-eight patients were anesthetized with etoxadrol as primary agent. The anesthesia produced was characterized by profound analgesia and amnesia, while pharyngeal and laryngeal reflexes, as well as swallowing and lid reflexes, remained active. Systolic, diastolic, and pulse pressure were slightly increased, with associated tachycardia and tachypnea. A dose of 0.75 mg/kg produced anesthesia for an average of 26 (14 to 53) minutes. Alternating nystagmus was present for several hours and associated with dreams and/or visions that were pleasing to most patients. Six patients, however, had unpleasant dreams for up to 24 hours. One patient given an excessive dose (4.65 mg/kg) was cataleptic, amnesic, and analgesic for 6 days. The occurrence of unpleasant dreams and aberrations in over 20% of the patients suggests that the drug probably has little usefulness in anesthesia. However, the extreme safety of the drug (an LD50 equal to some 20 to 40 times the ED50) and the prolonged analgesia justified clinical testing. There was no evidence of metabolic or systemic organ system change from any of the clinical laboratory studies.
| 5,921
|
[Study of the penicillin amidase from E. coli. An ultrasonic method of studying the ph- and temperature-conformational transitions in the active center of the enzyme].
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pH and temperature conformation transitions in the active center of penicillin amidase i.e. penicillinamidohydrolase E.C. 3.5.I.II were investigated by means of the kinetic method and a new ultrasonic method. It was shown that the catalytic activity of the enzyme was controlled by 2 ionogenic groups with pK 6.1 and 10.2. The study of penicillinamidase by means of the ultrasonic method showed that the ionogenic group with pK 10 was responsible for maintaining the catalytically active conformation of the enzyme active center. Investigation of the temperature relation between the kinetic parameters of the enzymatic hydrolysis of benzylpenicillin catalyzed by penicillin amidase and the data on the effect of ultrasound on the enzyme showed that the enzyme was subjected to the temperature conformation transiton. The temperature and thermodynamic parameters of the conformation transition were determinded (T=318 degrees K, delta H=81 kcal/mole and delta S=255 e.u.). The structure of the active center of the enzyme is discussed on the basis of the data obtained.
| 5,943
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Nitrogen fixation by hydrogen-utilizing bacteria.
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Seventeen strains of nitrogen-fixing bacteria, isolated from different habitats on hydrogen and carbon dioxide as well as on other substrates, morphologically resembled each other. All strains, including Mycobacterium flavum 301, grew autotrophically with hydrogen. The isolate strain 6 was sensitive to oxygen when dependent on N2 as nitrogen source, a consequence of the sensitivity of its nitrogenase towards oxygen. At the same time, strain 6 was sensitive to hydrogen when growing autotrophically on N2 as nitrogen source, but hydrogen did not affect acetylene reduction by these cells.
| 5,978
|
Glycogenolysis in the heart and skeletal muscle during stimulation and blocking of cholinergic receptors. III. Action of acetylcholine under conditions of sympathicolysis.
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Changes in enzymatic activities in phosphorolytic and hydrolytic glycogenolysis in the working heart and in resting skeletal muscle after intravenous injection of sympathicolytic compounds were studied in vitro. Reserpine, alderline and ligation of the adrenals inhibited the influence of acetylcholine on phosphorylase, Reserpine alone or ligation of the adrenals caused an increase in hydrolytic activity similar to that produced by compounds acting on the ganglia. This confirms the concept according to which the adrenergic system (beta-receptor) inhibits hydrolytic activity during glycogenolysis.
| 5,985
|
Biomedical aspects of oxygen regulator performance: I. Static characteristics.
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Static performance characteristics of current-inventory USAF oxygen regulators were evaluated with the use of a specialized regulator test stand. Outlet suction pressures, flows, positive pressures, and delivered oxygen dilutions were monitored and recorded as functions of operational altitudes. General findings indicated that: 1) excessive oxygen addition occurs in all models, especially at low cabin altitudes; 2) positive pressure schedules generally conform to specifications; 3) negative suction pressures for most regulators are less than -2.54 cm H2O. The validity of static evaluation is discussed and data interpretation is considered with respect to biomedical compatibility emphasizing maintenance of crewmember physiological sufficiency.
| 5,993
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Gamma-glutamyltransferase of rat kidney. Simultaneous assay of the hydrolysis and transfer reactions with (glutamate-14C)glutathione.
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1. The hydrolytic and transfer reactions catalysed by rat kidney-gamma-glutamyltransferase (EC 2.3.2.2) were studied in vitro with substrates [U-14C]glutamic acid-labelled glutathione and methionine. Initial-velocity patterns, isotope-exchange and binding studies were consistent with a branched non-sequential mechanism in which a gamma-glutamyl-enzyme intermediate may react either with water (hydrolysis) or with methionine (gamma-glutamyl transfer). 2. The Michaelis constant for glutathione in hydrolysis was 13.9 +/- 1.4 mum, for glutathione in transfer it was 113 +/- 15 muM and for methionine as substrate it was 4.7 +/- 0.7 mM. At substrate concentrations in the ranges of their respective Michaelis constants, the rate of transfer was about ten times higher than that of hydrolysis, but at concentrations of methionine approximating to the physiological (64 muM in rat plasma) the transfer is negligible. 3. The enzyme is reported to lie on the luminal surface of the proximal straight kidney tubule. In this situation, if the kinetic results obtained with the detergent-solubilized enzyme are relevant to the behavior of the enzyme in vivo, it appears likely that the main function of renal gamma-glutamyltransferase is not in amino acid transport, but rather to hydrolyse glutathione in the renal filtrate.
| 6,004
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Light-induced membrane potential and pH gradient in Halobacterium halobium envelope vesicles.
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Illumination of envelope vesicles prepared from Halobacterium halobium cells causes translocation of protons from inside to outside, due to the light-induced cycling of bacteriorhodopsin. This process results in a pH gradient across the membranes, an electrical potential, and the movements of K+ and Na+. The electrical potential was estimated by following the fluorescence of a cyanine dye, 3,3'-dipentyloxadicarbocyanine. Illumination of H. halobium vesicles resulted in a rapid, reversible decrease of the dye fluorescence, by as much as 35%. This effect was not seen in nonvesicular patches of purple membrane. Observation of maximal fluorescence decreases upon ilumination of vesicles required an optimal dye/membrane protein ratio. The pH optimum for the lightinduced fluorescence decrease was 6.0. The decrease was linear with actinic light intensity up to about 4 X 10(5) ergs cn-2 s-1. Valinomycin, gramicidin, and triphenylmethylphosphonium ion all abolished the fluorescence changes. However, the light-induced pH change was enhanced by these agents. Conversely, buffered vesicles showed no pH change but gave the same or larger fluorescence changes. Thus, we have identified the fluorescence decrease with a light-induced membrane potential, inside negative. By using valinomycin-K+-induced membrane potentials, we calibrated the fluorescence decrease with calculated Nernst diffusion potentials. We found a linear dependence between potential and fluorescence decrease of 3 mV/%, up to 90 mV. When the envelope vesicles were illuminated, the total proton-motive force generated was dependent on the presence of Na+ and K+ and their concentration gradients across the membrane. In general, K+ appeared to be more permeable than Na+ and, thus, permitted development of greater pH gradients and lower electrical potentials. By calculating the total proton-motive force from the sum of the pH and potential terms, we found that the vesicles can produce proton-motive forces near--200 mV.
| 6,040
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[Immobilized phospholipase D].
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Conditions of phospholipase D adsorption on silica gels have been studied. The immobilized phospholipase D is shown to differ from the soluble form in thermostability, pH optima and activation conditions. A question is discussed as to the connection of the use of activators and the adsorption immobilization. It is assumed that phospholipase D belongs to enzymes, functioning only in the immobilized state.
| 6,081
|
Regulation of acetyl-CoA synthetase of Saccharomyces cerevisiae.
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Acetyl-coenzyme A synthetase (EC 6.2.1.1) activity of Saccharomyces cerevisiae was determined by a radioactive assay procedure. The activity in vitro was inhibited significantly by NADPH, NADH, or AMP and to a lesser extent by NADP, NAD, or ADP. Glutamic acid and alpha-ketoglutaric acid were not inhibitory. The enzyme level was repressed when the cells were grown in a complex nutrient medium as opposed to the minimal medium. However, a glutamic acid auxotroph glul, when grown in excess glutamic acid, demonstrated a fivefold increase of acetyl-CoA synthetase.
| 6,141
|
Transient inhibition of cell proliferation in rat glioma monolayer cultures by cortisol.
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The effect of 3 muM cortisol on cell proliferation in rat glioma (strain C6) monolayer cultures was investigated. Cell density measurements showed that cortisol-treated C6 cells continued to proliferate at maximum log phase rates for 1 to 2 days. Then cell proliferation ceased as growth in control cultures continued into stationary phase. A 2-day period of growth inhibition followed during which cell densities were 30 to 50% lower relative to controls. Growth resumed subsequently, and final cell densities were similar to those of controls. The presence of epicortisol (the biologically inactive isomer of cortisol) in the culture medium did not alter the rate of log phase growth relative to controls. During the initial period of continued growth after exposure to cortisol, the pH of the medium decreased at the same rate in control and treated cultures. During the growth-inhibitory period, erythrosin B dye was excluded equally well (greater than 94%) by control and treated cells, and no morphological differences were detected by phase contrast microscopy. When the culture medium was replaced daily, the control cells at elevated densities continued to proliferate at a reduced rate. In cortisol-treated cultures, the period of growth inhibition commenced 3 days after the cells were exposed initially to cortisol. A 2-day period of growth inhibition followed during which the pH of the 1-day-old media from both control and treated cultures decreased from 7.4 to 6.9. Growth resumed subsequently in the treated cultures to produce elevated cell densities similar to those of controls. These results demonstrate that cortisol at concentrations considered chemotherapeutic in vivo exerts a transient inhibitory effect on C6 glioma cell proliferation.
| 6,144
|
Diazepam abuse: incidence, rapid screening, and confirming methods.
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We studied 2500 patients suspected to be drug-overdose victims. Blood samples were quantitatively screened for the most commonly abused drugs, including diazepam. Of these, 61% had positive findings, including diazepam in about one of every four. A new rapid, simple, and quantitative gas-chromatographic method for simultaneous analysis of diazepam and sedatives (in two instruments) is described. A single extraction at low pH is used, preserving the balance of the sample to be used for confirming methods via ultraviolet spectrophotometry and thin-layer chromatography. Prevalance of other positive findings is also listed, and findings for diazepam are categorized by age.
| 6,164
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Alkaline phosphatase. I. Kinetics and inhibition by levamisole of purified isoenzymes from humans.
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I studied the kinetics and sensitivity toward inhibition by levamisole and R 8231 of the most important human alkaline phosphatase isoenzymes. N-Ethylaminoethanol proved superior to the now widely used diethanolamine buffer, especially for the enzymes from the intestine and placenta, behaving as an uncompetitive activator. The optimum pH largely depends on the substrate concentration. The addition of Mg2+ has no effect on the activities. The meaning of Km-values for alkaline phosphatases is questioned. Isoenzymes from human liver, bone, kidney, and spleen are strongly inhibited by levamisole or R 8231 at concentrations that barely affect the enzymes from intestine or placenta. The inhibition is stereospecific, uncompetitive, and not changed by Mg2+. Inhibition is counteracted by increasing concentrations of N-ethylaminoethanol. The mechanism of inhibition is suggested to be formation of a complex with the phosphoenzyme.
| 6,169
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Determination of erythrocyte folate by competitive protein binding assay preceded by extraction.
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Determination of the concentration of erythrocyte folate by means of competitive protein binding assay critically depends on the extraction procedure applied. Results will be influenced by variable factors such as the in vitro age of the blood samples, the degree of hemolysis, the presence of ascorbic acid, and the pH during extraction and elimination of proteins. The radioassay is strongly influenced by the pH of the final reaction mixture, the method used to separate free and protein-bound molecules, and the molecular configuration of the folates present. Based on experimental results presented, I describe a method for the determination of erythrocyte folate.
| 6,170
|
Central nervous system salicylate.
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The poor correlation between clinical salicylate toxicity and serum blood levels is reapproached in light of recent evidence linking clinical severity with initial volume of distribution (Vd). It is recognized that two variables alter salicylate Vd in such manner that serum salicylate levels are misleading (thus, the change in Vd is not detected by present methods). These variables are serum protein binding and the pH-dependent ionized/un-ionized ratio in the unbound salicylate fraction. Measurements of salicylate concentration in the cerebro spinal fluid (CSF) would circumvent these variables, but would be clinically impractical. Thus, an alternative is sought to the inexact total serum salicylate levels and the impractical CSF salicylate levels for assessment of the severity of salicylate poisoning. This study indicates that, in dogs, serum unbound salicylate levels closely reflect CSF salicylate levels, even as a decrease in serum protein binding is in progress. However, serum unbound salicylate concentration does not reflect CSF salicylate concentration as a decrease in serum pH is elicited (CSF salicylate actually increased as serum unbound salicylate decreased). On the other hand, serum unbound salicylate measurement would seem preferable to total serum salicylate measurements now used in that the total value decreased markedly as either protein binding change or acidosis produced a change in distribution and the resultant increase in CSF salicylate.
| 6,188
|
Mirex kinetics in the rhesus monkey. II. Pharmacokinetic model.
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14C-Mirex was given iv and po to female rhesus monkeys (Macaca mulatta) and radioactivity was measured in plasma, urine, and feces at intervals after dosing and in tissues when animals were killed. Graphical analysis of plots of the logarithm of plasma concentration vs. time was used to provide estimates of the values of the first-order rate constants required by the proposed pharmacokinetic models. A BASIC-language program, FITKIN, was used to obtain numerical solutions to the differential equations for each model and to adjust the estimates to obtain a normalized, least squares fit. Of several models postulated, a mammillary, four-compartment, open-system model, providing for the urinary excretion of Mirex from a "central" compartment and for the fecal excretion of Mirex from a "fast" tissue compartment, yielded theoretical data in agreement with observed values. This model predicted that the accumulation of Mirex into fat would be retarded by the presence of a "slow" tissue compartment so that distribution equilibrium would take about half a year. From that time to the end of a 5-year projection, little decline in the quantities of Mirex was predicted for any compartment. Sequestration in fat and a lack of metabolism were responsible for the long biological half-life of Mirex in the rhesus monkey.
| 6,235
|
Some aspects of the pharmacology of beta-adrenorecptor blockers.
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The pharmacodynamic properties of a beta-blocker are mainly determined by its affinity to beta1 and beta2-receptors respectively and by its intrinsic activity. It is suggested that there is no absolute organ separation of the two receptor sub-types. Instead both beta1 and beta2-receptors are involved in the mediation of the same effect. The frequency distribution ratio of beta1/beta2-receptors varied markedly among various effector responses. A non-selective and a beta1-selective blocker may have different haemodynamic effects when the levels of circulating adrenaline are high, because of their markedly different potency in inhibiting the beta2-mediated vasodilator effect of adrenaline. Data are presented which suggest the existence of a presynaptic beta1-receptor mediating a positive feedback mechanism on neuronal release of noradrenaline.
| 6,242
|
Experience with beta-adrenoreceptor blockers in hypertension.
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At the Dunedin Hypertension Clinic beta-blockers are the drugs of choice for most hypertensive patients, usually in combination with diuretics (especially in older subjects) and often with other drugs in the more severe cases. All beta-blockers have an antihypertensive effect, regardless of other characteristics (e.g. cardio-selectivity, instrinsic sympathomimetic effect, or membrane activity). d-Propranolol has no significant effect on blood pressure. Beta-blockers do not prevent stress-induced (mental arithmetic) rises in blood pressure in hypertensive subjects through the level of blood pressure reached during stress tends to be lower because the base line is lower. Twice-daily dosage of beta-blockers is usually satisfactory.
| 6,249
|
Uptake of bromosulfophthalein by isolated liver cells.
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Uptake of the hepatodiagnostic dye bromosulfophthalein into isolated hepatocytes was studied with special regard to the kinetics of transport. The following results were obtained. 1. The uptake of bromosulfophthalein follows Michaelis-Menten kinetics only at low substrate concentrations with an apparent Km=7 +/- 2 muM and V=2.6 +/- 1.7 nmol X mg protein -1 X min -1. At higher bromosulfophthalein concentrations a second mechanism of uptake is observed as indicated by the deviation from linearity in the Lineweaver-Burk plot. 2. The activation energy of uptake was found to be 11 kcal/mol at 10 muM bromosulfophtalein. 3. Uptake is independent of metabolic energy and of the Na+ gradient across the membrane. 4. Taurocholate does not inhibit uptake while indocyanine green inhibits competitively at low bromosulfophthalein concentrations and activates uptake at high bromosulfophthalein concentrations (greater than 20 muM). 5. Amino acid reagents, such as dinitrofluorobenzene, mersalyl, N-ethylmaleimide, and dithionitrobenzene, which modify specific functional groups, did not affect uptake at a concentration of 100 muM. 6. No pH optimum for bromosulfophthalein uptake was observed in the physiological pH range. 7. Adsorption of bromosulfophthalein to the liver cell membrane has two distinguishable sites with affinities K1=5.7 X 10(-6) M and K2=7 X 10(-5) M and binding capacities n1=1.2 nmol/mg protein and n2=7 nmol/mg protein. Adsorption is inhibited by indocyanine green. The results do not indicate the mediation of bromosulfophthalein uptake by a carrier protein and are consistent with the hypothesis that bromosulfophthalein is bound in an energy-consuming process to a translocating site, possibly in the undissociated form or as ion pair. The consecutive transfer across the membrane appears to require little additional energy.
| 6,268
|
Purification and properties of D-glyceraldehyde-3-phosphate dehydrogenase from an extreme thermophile, Thermus thermophilus strain HB 8.
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1. D-Glyceraldehyde-3-phosphate dehydrogenase from an extreme thermophile, T. thermophilus strain HB8, was purified and crystallized. 2. The enzyme was found to possess remarkable heat stability, being slowly inactivated at 90 degrees C. 3. Basic kinetic constants and pH profile are reported. The enzyme was activated 25-fold by 90 mM NH4Cl, and also by ethanol up to 5-fold at 30 degrees C. 4. The enzyme was found to be far more resistant to urea or sodium dodecylsulfate than the rabbit enzyme. 5. The enzyme was shown to be a tetramer of molecular weight 130000--135000. Amino acid composition analysis revealed no unusual features. Circular dichroic spectra suggested that the contents of the ordered structure of the thermophile enzyme are similar to those of the rabbit enzyme. 6. The other catalytic properties of the thermophile enzyme are discussed in comparison with those of the enzymes from other sources.
| 6,270
|
Some adrenergic beta-blocking agents affecting lipolysis in human adipose tissue in vitro.
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Antagonistic actions of beta-blocking drugs on isoproterenol-induced lipolysis were studied in human omental adipose tissue. Competitive interaciton characterized by the following pA2 values was found: propranolol 8.7; trimepranol 8.7; practolol 7.1; H 35/25 6.0. The plot of pA2 values of these drugs for human versus rat adipose tissue is linear with slope 2.0 indicating a higher differentiation of beta-antagonist actions in human than in rat adipose tissue.
| 6,293
|
Role of fat maldigestion in pathogenesis of steatorrhea in ileal resection. Fat digestion after two sequential test meals with and without cholestyramine.
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To clarify the role of fat maldigestion in the pathogenesis of steatorrhea in patients with ileal resection the total and aqueous phase concentrations of bile acid and fatty acid were characterized in 8 such patients (5 patients with small ileal resection, bile acid diarrhea, and steatorrhea less than 20 g per day; 3 patients with large ileal resection, fatty acid diarrhea, and steatorrhea greater than 20 g per day) as well as 4 healthy control subjects after a morning and an afternoon liquid test meal. The study was then repeated with cholestyramine, 4 g being administered before each meal to induce fat maldigestion. After a conventional test meal, patients with large resections and severe steatorrhea had significantly lower aqueous phase concentrations of bile acids (and fatty acids) than patients with smaller resections or control subjects, explained in part by intraluminal precipitation of about one-half of the bile acids during digestion. When cholestyramine was administered before the meal, aqueous phase bile acid concentrations decreased in all patients, including the normal control subjects; the degree of fat maldigestion induced in the patients with small resections (and the control subjects) became similar to that present after the conventional test meal in the patients with large resections. Because steatorrhea increased little in the patients with small resections when cholestyramine was administered continuously, the data suggest that fat maldigestion per se does not induce severe fat malabsorption in patients with sufficient anatomical reserve, because such patients can absorb fat efficiently by utilizing the distal small intestine. In patients with large ileal resections, severe steatorrhea is explained in part by the combination of fat maldigestion and decreased surface area. It is also speculated that the steatorrhea occurring in patients with small resections and relatively normal fat digestion during two test meals may be explained by impaired fat digestion which occurs during the final meal of the day, which is often the largest meal.
| 6,360
|
Kinetic studies of the alkaline mesentericopeptidase. Study on the active centre topography of alkaline mesentericopeptidase by means of bifunctional reversible inhibition.
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The inhibitory effect of alkylboronic acids H(CH2)nB(OH)2(n=2-8) and Ph(CH2)n-B(OH)2, (n=0-4), on the alkaline mesentericopeptidase-catalysed hydrolysis of synthetic substrates was studied. It was shown that alkylboronic acids act as bifunctional reversible inhibitors. The borate group interacts with an ionogenic group of the enzyme with a pKa of about 6.9-7.0. The latter is probably the catalytically active imidazole of the active centre. The hydrocarbon part of the molecule also takes part in the formation of the enzyme-inhibitor complex. The dependence of the degree of the enzyme-inhibitor complex formation upon the length of the side-chain of the inhibitor indicates the presence of two binding sites on the enzyme molecule.
| 6,394
|
pH-dependent temperature sensitivity of rat lens phosphofructokinase.
|
Rat lens phosphofructokinase (PFK) has been found to be cold-labile at acidic pH, even in the presence of sulfate and inorganic phosphate, two known positive effectors. The inactivation appears to be an irreversible process, but can be prevented by including ATP in the incubating media. The enzyme is relatively stable at pH 8.2 incubated at 0 to 4 degrees, 25 degrees, or 37 degrees C. in the absence of the effectors, but is extremely thermolabile if the pH is lowered to 7.30 or lower. The thermolability is counteracted by many effectors, among them sulfate and ATP are the most effective. The physiologic significance of PFK instability and effector protection in the lens are discussed.
| 6,404
|
The fetal renin-angiotensin system in normal and hypertensive pregnancy.
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Plasma angiotensin II was measured in the umbilical cord arterial and/or venous blood of 54 babies delivered vaginally and in 12 delivered by elective lower segment cesarean section. Angiotensin II was also measured in the peripheral venous blood of 51 of the mothers. Mean angiotensin II levels at delivery were higher in the cord venous blood of infants born to hypertensive than to normotensive mothers. Cord venous angiotensin II levels were always higher than those of the mother and there was a strongly positive relationship between maternal and fetal angiotensin II. The duration of the second stage of labor was found significantly to affect fetal angiotensin II levels, prolonged labor being associated with high levels. When this was taken into account, there was a highly significant positive relationship between the body weight of the infants and cord venous angiotensin II levels. There was an inverse relationship between cord venous pH and angiotensin II levels. Babies delivered by lower segment cesarean section had much lower angiotensin II levels than those delivered vaginally. The levels were, however, twice as high as those in the nonpregnant adult.
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Role of polyadenylic acid in a deoxyribonucleic acid-membrane fraction extracted from pneumococci.
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After the addition of radioactive polyadenylic acid to cell suspensions of pneumocci, part of the radioactivity becomes associated with a deoxyribonucleic acid (DNA)-membrane fraction extracted from the cells. A variety of techniques show that a portion of this associated radioactivity may represent oligoadenylates complexed to DNA, probaby as part of a ribonucleic acid (RNA) component. Polyadenylic acid, which had previously been shown to enhance DNA synthesis in cell suspensions (Firshein and Benson, 1968), also enhances the extent of DNA synthesis by the DNA-membrane fraction in vitro under specific conditions of concentration and conformation. The mechanism of action of this enhancement may be related to the ability of oligoadenylates to increase the number of initiation sites for DNA replication by stimulating the production of an RNA primer, thus providing additional 3'-OH groups with which DNA polymerase can react.
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