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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The reaction kinetics of blue tetrazolium with selected arylhydrazines were investigated under pseudo-first-order conditions. The reaction rate constants were obtained at various temperatures, and the enthalpy (8.4-11.2 kcal/mole) and entropy (-38--45 eu) of activations were calculated. A Hammett plot yielded a straight line with a slope of 0.52. The reaction was inhibited by atmospheric oxygen and iodine. A free radical mechanism is presented.
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PMID:Kinetic and mechanistic studies of blue tetrazolium reaction with phenylhydrazines. 66 May 10

1. Changes in the water and ion contents of rabbit renal cortical slices, which had been bathed, immediately after slicing, in air-equilibrated media at room temperature ('freshly prepared slices'), were followed during subsequent incubation at 25 degrees C in oxygenated media of the same composition as the initial bathing medium. 2. In comparison with conventional 'equilibrated' slices (slices incubated at 25 degrees C in oxygenated ordinary medium immediately after slicing) these 'freshly prepared' slices had increased tissue water, sodium and chloride contents and low tissue potassium contents. 3. Control freshly prepared slices incubated at 25 degrees C in oxygenated ordinary medium recovered within 4 min to the tissue water content that is usual for rabbit renal cortical slices incubated in oxygenated ordinary medium at 25 degrees C. Freshly prepared slices incubated at 25 degrees C in oxygenated media containing 1 mM-oubain took 75 min or more to recover to this usual tissue water content. Thus the presence of 1 mM-oubain in both bathing and incubation media produced a marked inhibition of the volume recovery observed when freshly prepared slices are incubated in oxygenated media at 25 degrees C. 4. Reduction of the ouabain concentration reduced the inhibition of cell volume recovery. 5. Replacement of medium glucose by 3-O-methylglucose did not inhibit cell volume recovery in the absence of ouabain. 6. The oxygen consumptions of slices that were bathed and incubated in 1 mM-ouabain media were similar to those of slices initially bathed and incubated in ouabain-free media and then incubated in ouabain media. Thus the effect of ouabain in inhibiting cell volume recovery was unlikely to be secondary to inhibition of cellular energy production. 7. The tissue potassium content of slices incubated aerobically in 1 or 10 mM ouabin fell to an apparently stable value of approximately 100 m-mole/kg dry wt., which corresponds to a calculated concentration ratio of 10:1 across the cellular membrane, suggesting that some residual potassium uptake may still have been occurring. 8. These results indicate that in freshly prepared rabbit renal cortical slices ouabain-sensitive mechanisms play a major role in cell volume recovery. They are not in accord with the postulate that renal cortical cells possess a separate ouabain-insensitive mechanism regulating cell volume.
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PMID:Ouabain and regulation of cellular volume in freshly prepared slices of rabbit renal cortex. 67 54

The binding to neutrophil leukoyctes of human serum albumin (HSA), which is chemokinetic for leukocytes, i.e. influences their rate of locomotion, and of alkali-denatured HSA, which is chemotactic for leukocytes, i.e. influences their direction of locomotion, was studied. Native serum albumin showed low affinity binding to the neutrophil surface. Denatured serum albumin showed saturable binding with a Ka of approximately 1-(6) litres per mole to about 10(6) binding sites per cell. Another protein chemotactic factor, alpha5-casein, gave similar binding. These results exclude that chemotactic reactions to denatured proteins are mediated in a completely non-specific manner and suggest the presence on the cell of a restricted number of defined recognition sites. Binding was reduced following treatment of the cells with either of two lipid-specific bacterial toxins, perfringolysin, the theta-toxin of Clostridium perfringens, an oxygen-labile cholesterol-specific toxin, and Staphylococcus aureus Sphingomyelinase C. Both have previously been shown to reduce chemotactic reactions and both were used at doses which did not reduce cell viability. These results suggest an important, and possiblly direct, role for membrane lipid in the binding sites for chemotactic factors. Visual analysis of the behaviour of perfringolysin-treated neutrophils showed that these cells were still capable of chemotactic locomotion. The cells appeared to be less efficient than normal in detecting chemotactic gradients only when at a distance from the gradient source, a finding which is consistent with reduced binding of the chemotactic factor to the cell surface.
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PMID:Binding of protein chemotactic factors to the surfaces of neutrophil leukocytes and its modification with lipid-specific bacterial toxins. 67 3

1. The circulatory and metabolic effects of temperature reduction were studied in autoperfused canine subcutaneous adipose tissue in situ. 2. Cooling the adipose tissue sufficiently to reduce venous effluent temperature by 5--6 degrees C decreased blood flow from an average of 6.4--4.1 ml. min-1 . 100g-1. 3. Vasoconstrictor responses to sympathetic nerve stimulation (4 HZ) and injected noradrenaline (5 n-mole) were potentiated by cooling while vasodilator components of the vascular responses, such as autoregulatory escape and post-stimulatory hyperaemia, were virtually abolished by this treatment. 4. Oxygen uptake was reduced by cooling without signs of tissue hypoxia. This reduced oxygen demand may partly cause the decrease in adipose tissue blood flow. 5. Cooling inhibited glycerol mobilization from the adipose tissue during sympathetic nerve stimulation. Post-stimulatory lipolysis was, however, not inhibited. In vitro studies with 'perifused' rat fat cells suggest that this may be due to impaired inactivation of the lipolytic process, rather than to changes in transmitter removal, following stimulation at low temperature. 6. Cooling inhibited the mobilization of fatty acids more than that of glycerol, suggesting increased re-esterification of fatty acids within the tissue at low temperature. 7. It is concluded that cooling increases the sensitivity to vasoconstrictor stimuli and that inhibition of metabolic vasodilator mechanisms play a role for this effect. The stimultaneous inhibition of activating and inactivating mechanisms could explain the unchanged vascular and lipolytic responses to brief stimuli. Some possible implications of the present findings for the physiology of adipose tissue during cooling are discussed.
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PMID:Vascular and metabolic responses to adrenergic stimulation in isolated canine subcutaneous adipose tissue at normal and reduced temperature. 70 88

The effects of growth temperature on the aerobic growth yield with respect to oxygen consumption (Y0-grams [dry weight] per gram-atom of O) and the rate of maintenance respiration (m0-milligram-atoms of O/gram [dry weight] per hour) are reported for Escherichia coli B cultivated continuously in the presence of oxygen with limiting glucose. During anaerobic continuous culture, YATP(max) (grams [dry weight] per mole of ATP corrected for maintenance) increases from 10.3 to 12.7 as the growth temperature is lowered from 37 to 25 C. Over this same range, Y0(max) (Y0 corrected for maintenance respiration) rises from 12.5 to 28.8 and remains at the higher value down to 17.5 C. From 37 to 32 C, m0 increases from 0.9 to 4.4 but then falls to 1.5 as the temperature is lowered to 17.5 C. The value of m0 sharply rises some 13-fold as the temperature is raised to 42 C without a significant change in the value of Y0(max). Changes of Y0(max) are consistent with a temperature-sensitive doubling of the efficiency of oxidative phosphorylation, but the reasons for the changes of the rate of maintenance respiration are not known.
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PMID:Effects of growth temperature on yield and maintenance during glucose-limited continuous culture of Escherichia coli. 77 Apr 23

1. The respiratory chain energy conservation systems of Bacillus megaterium strains D440 and M have been investigated following growth in batch and continuous culture. Respiratory membranes from these strains contained cytochromes b, aa3, o and b, c, a, o, respecitvely; both readily oxidised NADH but neither showed any pyridine nucleotide transhydrogenase activity. 2. Whole cells of both strains exhibited endogenous leads to H+/O ratios of approximately 4; when loaded with specific substrates the resultant leads to H+/O ratios indicated that proton translocating loops 1 and 2 were present in strain D440 and that loops 2 and 3 were present in strain M. 3. In situ respiratory activities were measured as a function of dilution rate during growth in continuous culture. True molar growth yields with respect to oxygen (Y02) of approximately 50 g cells-mole oxygen-1 were obtained for most of the nutrient limitations employed. Average values for YATP of 12.7 and 10.8 g cells-mole ATP equivalent-1 were subsequently calculated for strains D440 and M respectively. 4. Energy requirements for maintenance purposes were low in energy-limited cultures but were substantially increased when growth was limited by nitrogen source (NH+/4). Under the latter conditions there is probably a partial uncoupling of energy-conserving and energy-utilising processes leading to energy wastage.
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PMID:Energy conservation in Bacillus megaterium. 81 45

We have clarified the use of Wyman's differential equation for the facilitated oxygen flux through a slab of solution of myoglobin or hemoglobin by showing that there is a unique choice of boundary condition on the carrier concentration to be employed in conjunction with it. The singular perturbation solution of Wyman's equation, due to Murrayand Mitchell and Murray, has been extended. By means of it, the paradox of Wittenberg, that the facilitated oxygen flux per mole of heme is apparently independent of the protein carrier, has been resolved.
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PMID:The facilitated diffusion of oxygen by hemoglobin and myoglobin. 85 16

The effect of ethanol on hepatic respiration and glycolysis was studied in perfused rat livers. 1. Ethanol increased the rate of oxygen uptake in livers from fed rats, but decreased the rate in livers from fasted animals perfused in the absence of added substrates. 2. Addition of ethanol decreased the rate of lactate + pyruvate production reflecting an inhibition of glycolysis irrespective of whether glycogen or added glucose was the substrate. 3. Half-maximal stimulation of respiration and inhibition of glycolysis were observed at ethanol concentrations between 0.2 and 0.4 mM. 4. A stoichiometric relationship of one mole of stimulated oxygen uptake to 3.6 mol of decreased lactate + pyruvate production was observed under a variety of experimental conditions. 5. The effects of ethanol on oxygen uptake and lactate + pyruvate production were abolished by the addition of 4-methylpyrazole, an inhibitor of alcohol dehydrogenase, but were unaffected by aminooxyacetate, an inhibitor of hydrogen transport across the mitochondrial membrane. 6. Carboxyatractyloside, an inhibitor of adenine nucleotide translocase, largely abolished the increase in oxygen uptake due to ethnol, but had little effect on the inhibitory action of ethanol on glycolysis. These data indicate that the ethanol-stimulated oxygen uptake is due to an increased flux through the mitochondrial respiratory chain and that it involves the NAD+-dependent oxidation of ethanol by alcohol dehydrogenase. The data are consistent with the hypothesis that the ethanol-stimulated respiration results from an increased demand for mitochondrial oxidative phosphorylation as a consequence of the decreased extramitochondrial ATP generation following inhibition of glycolysis by ethanol.
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PMID:Interaction of glycolysis and respiration in perfused rat liver. Changes in oxygen uptake following the addition of ethanol. 86 14

UV-irradiation (lambda = 254 nm) of liquid aqueous solutions of deoxyguanosine in the presence of oxygen at pH less than 7 causes an intensive degradation of nucleoside. The quantum yield estimated from A254 decrease for the reaction mixture was found to be 1.5X10(-4) at doses to 150 E/mole. The rate of A254 decrease was found to grow with increasing doses. The structures of the products isolated from the reaction mixture after irradiation suggest that one of the ways of deoxyguanosine degradation is a breakdown of a purine cycle without splitting of N-glycoside bond. Simultaneously another type of photoinduced modification of guanine nucleus takes place, which is followed by appearance of free 2-deoxyribose. Deoxyguanosine degradation in both directions is kinetically one-step process proceeding with comparable quantum yields of approximately 1X10(-4).
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PMID:The photochemistry of purine components of nucleic acids. II. Photolysis of deoxyguanosine. 86

Mitochondrial monoamine oxidase isolated from bovine brain stem and purified to electrophoretic homogeneity contained 15 SH groups per mole (100000) of protein. The enzyme deaminated tyramine, p-nitro-beta-phenylethylamine, dopamine, 5-hydroxytryptamine, tryptamine but did not deaminate histamine, GABA or spermidine. Oxidation of 9-II SH groups in the MAO by air oxygen was accompanied by appearance of the properties to deaminate histamine or GABA. This qualitative alteration (transformation) in catalytic properties of the enzyme was readily reversed by treatment with reducing agents (dithiothreitol or GSH). No structural alterations detectable by electrophoresis in polyacrylamide gel were observed in course of the qualitative reversible modifications in catalytic activity of MAO. The qualitative alterations in substrate specificity were also initiated by treatment with H2O2 of the monoamine oxidases tightly bound with membrane structures of mitochondria from bovine brain stem.
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PMID:[Changes in substrate specificity of brain mitochondrial monoamine oxidase]. 88 99


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