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231.
1. The distribution of thiol:protein-disulphide oxidoreductase (disulphide interchange enzyme) in 17 bovine tissue extracts was determined by rocket immunoelectrophoresis and by measuring the reductive cleavage of insulin. 2. The relative concentration (per mg total protein) was found to be in the order: Pancreas greater than liver greater than lymph node greater than testes, fat tissue greater than parotid gland, brain, spleen, lung greater than small intestine, spinal cord, large intestine, kidney greater than paunch, aorta greater than skeletal muscle greater than heart. 3. The distribution of specific activity showed a similar pattern, irrespectively of whether glutathione or L-cysteine was used as cosubstrate. 4. The concentration varied 200-fold and the specific activity 400-fold between pancreas and heart muscle, respectively. 5. Crossed immunoelectrophoresis demonstrated that a fast-migrating form of the enzyme was the only one present in almost all tissues, but 15% of the enzyme in liver was a slow-migrating form and 50% in heart muscle a medium-migrating form. 6. The lung contains a species having partial immunological identity to the enzyme. 7. Purified enzyme from bovine liver has a somewhat lower mobility than the fast-migrating form in extract. 8. The results seem to support the general view that the enzyme is involved in synthesis of disulphide-bonded extracellular proteins, although the presence of the enzyme in tissues like fat, brain, spinal cord, skeletal muscle and heart indicates other cellular functions as well.  相似文献   
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Introduction of valinomycin into erythrocyte incubation medium increased the cell stability to water-induced hemolysis. In these conditions the erythrocytes of spontaneously hypertensive and normotensive (control) rats release 63.2 +/- 1.5% and 80.9 +/- 1.6%, respectively, of the total hemoglobin content. Valinomycin effect is completely abolished with K+ substitution for Na+ and is independent of extracellular Ca2+ concentration. Valinomycin had no effect on human erythrocyte osmotic stability. It has been shown that valinomycin-induced kinetics of Na+ and K+ redistribution was different in human and rat erythrocytes. The distinctions are thought to be related to specific anion transport mediated by the third band protein--the main component of membrane cytoskeleton.  相似文献   
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In the experiments on the anesthesized cats sodium hydroxybutyrate and piracetam, in contrast to glyo-6, have been shown to slow down the growth rate of creatine phosphokinase activity in the blood of the coronary sinus during 60-min occlusion of the coronary artery. At the same time, in the experiments on rats with 3-day myocardial infarction GABA derivatives like glyo-6 failed to influence the final size of cardiac necrosis. It may be concluded that anti-ischemic action of some drugs may be expressed only in the reduction of the rate of ischemic lesion development in the heart, but not in the limitation of the infarction size.  相似文献   
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The mechanism of the binding of 2-(4'-hydroxyphenylazo)benzoic acid (HABA) to bovine serum albumin was studied by relaxation methods as well as the binding isotherm using gel chromatography. A single relaxation was observed over a wide range of HABA concentration except at the extremes of high concentration where another slow process was observed. The concentration dependence of the reciprocal relaxation time of the fast process decreased monotonically with increase in concentration of HABA at constant polymer concentration. The data were analyzed on the basis of Brown's domain structure model and were found to be consistent with a sequential binding mechanism. The azohydrazon tautomerism of HABA was identified with the intramolecular step of the complex. The activation parameters of the step, determined from the temperature dependence of the relaxation time of the fast process, showed that this step is rate limited by an enthalpy barrier in both forward and backward directions. Comparison of the activation parameters with those of other serum albumin-ligand systems suggests that there is an enthalpy-entropy compensation in the activation process of the intramolecular step with the compensation temperature at about 270 K; the enthalpy-entropy compensation is thought to be related to the hydrophobic nature of the ligand.  相似文献   
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Summary Madin-Darby canine kidney (MDCK) cells kept in suspension culture for 12–15 hr displayed high-affinity binding sites for125I-lathyritic (soluble) collagen (120,000/cell,K D =30nm) and preferred collagens types I and IV over laminin or fibronectin as substrates during the first hour of attachment. On the other hand, after 4 hr, attachment to all four substrates was equally efficient. Upon challenge with a collagen substrate, the high-affinity sites were rapidly recruited on it (T1/2=6 min). Their occupancy by soluble collagen triggered the exocytosis of a second large population of low-affinity collagen binding sites that included laminin and seems to be involved in a second cell-attachment mechanism. These results are compatible with a twostep model of MDCK cell attachment to the substrate: first, via high-affinity collagen binding sites, and second, via laminin of cellular origin.  相似文献   
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