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Scaling of metabolic rate with body mass and temperature in teleost fish 总被引:27,自引:0,他引:27
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A species of DNA polymerase alpha that is active in the ATP(GTP)-dependent conversion of MVM parvovirus single-stranded linear DNA to the duplex replicative form has been purified 4300-fold from Ehrlich ascites mouse tumour cells. The single-stranded----replicative form activity is maintained throughout ammonium sulfate precipitation, DEAE-cellulose, phosphocellulose and hydroxyapatite column chromatography and glycerol gradient sedimentation. Polypeptides with Mr = 230 000, 220 000, 183 000, 157 000, 125 000, 70 000, 65 000, 62 000, 57 000, 53 000 and 48 000 copurify with the single-stranded----replicative form activity, which sediments at approx. 10 S. The Mr = 183 000, 157 000 and 125 000 polypeptides exhibit catalytic activity when assayed in situ following SDS-polyacrylamide gel electrophoresis. The 10 S form of DNA polymerase alpha is functionally distinguishable from an 8.4 S form of the enzyme obtained from the same cells on the basis of single-stranded----replicative form activity. The single-stranded----replicative form activity of the 10 S enzyme is stable at 22 degrees C for up to 3 h, but exhibits a half life of only 5 min at 45 degrees C. 相似文献
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Conditions of formation of the heparin-fibronectin-collagen complex and the effect of plasmin 总被引:2,自引:0,他引:2
The formation and composition of the insoluble heparin-fibronectin-collagen complex and its degradation by proteolysis was investigated. At fixed concentrations of the other molecular components of the complex, the maximal rate of complex formation, measured turbidimetrically, was reached at a concentration of 4 microM heparin and 0.9 microM collagen, while the rate of complex formation was linearly related to concentrations of fibronectin as high as 3 microM. Heparin was incorporated into the complex in a saturable manner, and was released in active anticoagulant form by plasmin but not by urokinase. The complex formation was inhibited by 5 mM calcium or 250 mM NaCl as well as by polybrene or spermin. It is suggested that fibronectin binds both heparin and collagen cooperatively to form an insoluble ternary complex of the extracellular matrix. 相似文献
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The characteristics of HSV type-1 infection following subcutaneous inoculation in the dorsum of one hind paw of Sprague-Dawley rats were studied to determine whether infection in rats might more closely parallel the infection in man than is seen in other animals. The serologic and virologic characteristics of acute and latent ganglion infection conformed to those of human infection. Immunohistochemical studies suggested that sensory ganglion infection arose via centripetal axonal migration of virus as is hypothesized in man. In rat, small type B neuronal cell bodies appeared central to the maintenance of latent infection and reactivation observed during cocultivation of lumbar ganglia. Acute and latent lumbar sensory ganglion infection in rats after subcutaneous hind paw injection of HSV-1 appears to be another suitable model of this infection in man. 相似文献
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Effect of diabetic ketosis on jejunal glutaminase 总被引:2,自引:0,他引:2
The intestine is capable of shifting its major fuel source from glutamine in the fed animal to ketone bodies in the fasted animal. Glutaminase (EC 3.5.1.2), the entry enzyme of glutamine oxidation, was examined for its function as a determinant in the utilization of jejunal fuel during diabetes and fasting. Male Sprague-Dawley rats were made ketotic to varied degrees by either fasting or the induction of diabetes with graded doses of streptozotocin (SZ). Specific activity of glutaminase was decreased in the diabetic animals to 64% (p less than 0.05) of controls in the group receiving 110 mg/kg SZ and 82% of controls in the group receiving 65 mg/kg SZ and to 78% (p less than 0.05) of controls in the fasted animals. The activity of glutaminase in the small intestine was negatively correlated to the concentration of beta-hydroxybutyrate in the plasma (r = -0.97, p less than 0.025) and jejunum (r = -0.92, p less than 0.05) for the four groups of animals. Specific activity of glutaminase was decreased in all cell types isolated along the villus-crypt axis of the small intestine from diabetic and fasted rats compared with control rats. The quantity of glutaminase-protein was determined by a dot immunobinding assay using an antibody to purified glutaminase. The activity of glutaminase relative to immunoreactive glutaminase-protein was significantly decreased (p less than 0.05) to 53% of control values in the 110 mg/kg SZ group, 77% in the 65 mg/kg SZ group, and 70% in the fasted group. These data indicate that an inactivation of glutaminase-protein may play a role in the ability of the intestine to shift its fuel source from glutamine to ketone bodies during diabetes and fasting. 相似文献