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51.
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53.
Human erythrocytes were incubated in isotonic solutions of different monovalent cations. The apparent size of the red cells
measured on scanning electron microscopic pictures decreases in the order Li+>Na+=K+>Rb+. These differences in size are abolished after pretreatment with trypsin, which removes a large part of the charges associated
with membrane glycoproteins. Shape alterations are also observed. Normal biconcave shapes are visible after Na+ or K+ incubation, whereas Li+ leads to flabby, flattened cells with a certain tendency to crenation, and Rb+ causes more pronounced biconcavity with a certain tendency to cupping. The overall effects of pretreatment with trypsin are
similar to those of Li+. Our results provide evidence that the electrostatic repulsion of glycoproteins and other charged membrane components may
play an essential role in maintaining red cell shape. 相似文献
54.
Koji Yamada Masumi Ohtsu Genki Kimura 《In vitro cellular & developmental biology. Plant》1985,21(8):428-432
Summary Sodium butyrate causes proliferation arrest with a G2 (4C) DNA content and induces formation of tetraploid cells upon removal
of the inhibitor, in rat 3Y1 diploid fibroblasts. We isolated tetraploid clones from the butyrate-treated 3Y1 cells with high
efficiency; among 21 clones randomly isolated, 5 were pure diploid, 7 were mainly tetraploid with a small contaminating diploid
population, and 7 were pure tetraploid. Among the pure tetraploid clones, two showed doubled chromosome numbers with slightly
broader distributions than that seen in parental 3Y1 cells. Butyrate further induced polyploid formation in the tetraploid
cells thus produced, but octaploid cells that resulted could not be maintained for prolongeed, cultivation. We found no difference
between the tetraploid and the (parental and parallel isolated) diploid clones in terms of colony-forming ability, proliferation
rate, and sensitivity to density-dependent inhibition of proliferation. These results suggest that doubling of chromosome
number by itself does not cause a change in proliferation property. The tetraploid clones had lower average saturation densities
possibly due to enlargement of cell size represented by higher cellular protein content. 相似文献
55.
Karla J. Matteson Bon-chu Chung Walter L. Miller 《Biochemical and biophysical research communications》1984,120(1):264-270
P450scc is the rate-limiting hormonally regulated enzyme that cleaves the cholesterol side chain. Translation of bovine adrenocortical mRNA and immunoprecipitation with rabbit anti-bovine P450scc indicates P450scc mRNA represents 1% of the total. DNA complementary to bovine adrenocortical mRNA was cloned in the site of pBR322 by dC·dG tailing and high-efficiency transformation. A clone containing sequences complementary to P450scc mRNA was identified by hybrid-selected translation only when plasmid DNA was first purified by CsCl gradient centrifugation. As is often the case with hybrid-selected translation, the clone identified contains a small insert. 相似文献
56.
C. Lal Kapoor Gerald J. Chader 《Biochemical and biophysical research communications》1984,122(3):1397-1403
A calcium phospholipid-dependent protein kinase (C-kinase) activity was detected in the soluble fraction of rod outer segments (ROS) of the bovine retina. The enzyme required calcium, phosphatidylserine (PS) and diacylglycerol for maximal activity. In the presence of calcium and PS, C-kinase endogenously phosphorylated proteins with molecular weights of 95,000, 91,000, 31,000, 21,000, 19,000, 18,000, 16,000, 14,000 and 11,000. Addition of diolein in the reaction mixture further enhanced the endogenous phosphorylation of these proteins. Retinal was found to inhibit the phosphorylation of endogenous proteins by C-kinase in a concentration dependent manner. Half-maximal inhibition of enzyme activity was obtained at a retinal concentration of about 12μM. These results suggest that calcium, phospholipids and the C-kinase enzyme may play an important role in the functional regulation of rod photoreceptors and, with retinal, perhaps in the visual process as well. 相似文献
57.
P Midoux J P Grivet F Delmotte M Monsigny 《Biochemical and biophysical research communications》1984,119(2):603-611
The synthesis of N-acetyl- and N-trifluoroacetyl-glucosaminides was reported. The interaction of these compounds with wheat germ agglutinin, a plant lectin specific for N-acetyl-glucosamine and sialic acid, was investigated by two complementary approaches: 1H and 19F NMR, and fluorescence spectroscopy. This last technique relies on the existence of a competitive equilibrium involving the protein, the ligand and O-(methylumbelliferyl)-N-acetyl-glucosaminide, a fluorescent saccharide. The binding constants and the chemical shifts in the complex were determined and were related to the protein structure. 相似文献
58.
Y Gache F Landon H Touitou A Olomucki 《Biochemical and biophysical research communications》1984,124(3):877-881
Purified alpha-actinin from human platelets was digested with Ca2+-activated protease from muscle. The alpha subunit (Mr = 100 kDa) was degraded into a unique polypeptide b of slightly lower molecular mass. In fresh platelets, only the a subunit was detected by immunoblotting techniques, while in out-dated platelets, both a and b polypeptides were present. Since a similar conversion of a to b occurs in vitro as in whole platelets, it can be assumed that, in platelets, alpha-actinin is cleaved by the endogenous Ca2+-activated protease. 相似文献
59.
SODIUM TRANSPORT IN ENTEROMORPHA INTESTINALIS (L.) LINK 总被引:1,自引:1,他引:0
60.
Electrophoretic analysis of polyphenoloxidase isoenzymes from a variety of angiosperms and from mushroom revealed that the enzymes remain active in the presence of 0.1 % sodium dodecylsulfate. Electrophoresis in the presence of sodium dodecylsulfate allows the detection of latent enzyme forms of polyphenoloxidase, and can also convert slower migrating enzyme forms to faster migrating forms. Electrophoresis in the absence of sodium dodecylsulfate followed by incubation in the presence of sodium dodecylsulfate can also be used to detect latent forms of polyphenoloxidase. Together, these approaches provide a method for screening latent enzymes and give some insight into the mechanism of activation by sodium dodecylsulfate. 相似文献