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991.
Summary The changes in short-circuit current occurring when one or both solutions bathing the intestine of rat or guinea-pig mounted in flux chambers were recorded. The results with the guinea-pig can be explained in terms of diffusion potentials arising from the ionic replacements, and an electrogenic sodium pump, sensitive to ouabain, in the contraluminal membrane of the cell. In the rat, the situation is more complicated, and the enterocyte probably possesses an electrogenic sodium pump in the brush-border membrane. 相似文献
992.
Summary Melatonin, in concentrations up to 10–3
M, showed no effect on mitosis in cultures of HeLa or KB cells. However, when melatonin at 10–4
M was preincubated with HeLa cells prior to addition of 10–7
M colchicine, a reduction in the mitotic index, in comparison to colchicine alone, was observed.This work was supported by PHS Grant No. CA 16425. 相似文献
993.
J. M. Gelles 《Cellular and molecular life sciences : CMLS》1976,32(7):906-907
Summary Using classical microelectrode techniques in canine cardiac Purkinje fibres, calcium ionophore X-537A was shown to shorten the action potential, hyperpolarizing the membrane and lowering the plateau, suggesting that intracellular calcium controls membrane permeability to potassium in this preparation.This work was supported by grant No. HL 05726 from the U.S. Public Health Service, National Heart Institute, Bethesda, Md.I thank Dr.N. Krasnow for his valuable advice in carrying out this work. 相似文献
994.
995.
Effect of conditioned media on nerve cell differentiation 总被引:2,自引:0,他引:2
M. Sensenbrenner G. G. Jaros G. Moonen B. J. Meyer 《Cellular and molecular life sciences : CMLS》1980,36(6):660-662
Summary Glial conditioned medium strongly stimulates the morphological maturation of cultured neuronal cells, while fibroblast and meningeal conditioned media have weaker effects.Acknowledgment. We acknowledge the expert technical assistance of Mrs M.F. Knoetgen. 相似文献
996.
G. H. Rossmanith J. Unsworth R. D. Bell 《Cellular and molecular life sciences : CMLS》1980,36(1):51-53
Summary Small-amplitude sinusoidal displacements, in the frequency rang 4–100 Hz, were applied to intact whole frog sartorius muscle whilst in a state of tetanus. At low frequencies the muscle, was observed to do oscillatory work, while at higher frequencies it tended towards elastic behaviour. Frequency-response plots obtained were compared with those from other muscle preparations. Results were interpreted in terms of mechano-chemical transduction properties of muscle.The authors wish to thank the Australian Research Grants Commission for provision of the laser, and L. I. Patterson for construction of the mechanical apparatus. 相似文献
997.
Retroviral antigens on gs- chf- leukocytes 总被引:1,自引:0,他引:1
It has recently been suggested that the endogenous retroviruses present in many different species might be involved during stimulation of the immune system of their hosts. We have now studied the expression of two avian retroviral antigens p27 and gp85 in chicken lymphoid cells by indirect immunofluorescence (IIF) and by complement-dependent microcytotoxicity (CDM). We have now found that these viral antigens are expressed in peripheral blood leukocytes of adults and embryos and in splenic and bursal lymphocytes of Spafas gs- chf- chickens but they are not expressed in fibroblasts cultured from the feather follicles of the same individual adult birds nor in fibroblasts cultured from embryos of the same flock. The differential expression of viral antigens in leukocytes may be related to a specific property or function of these cells. 相似文献
998.
A relationship between the amount of available estradiol receptors in uteri of inbred mice and their H-2 genotype is suggested by study in congenic animals. 相似文献
999.
Regulation of non-muscle myosin assembly by calmodulin-dependent light chain kinase 总被引:33,自引:0,他引:33
The presence of actin and myosin in non-muscle cells suggests that they may be involved in a wide range of cellular contractile activities. The generally accepted view is that interaction between actin and myosin in these cells and in vertebrate smooth muscle, is regulated by the level of phosphorylation of the 20,000-molecular weight (MW) light chain. In the absence of calcium, this light chain is not phosphorylated and the myosin cannot interact with actin. Calcium activates a specific calmodulin-dependent kinase which phosphorylates the light chain, initiating actin-myosin interaction. Although most studies on the role of phosphorylation have concentration on the regulation of actin-activated myosin Mg-ATPase activity, phosphorylation of the light chain also seems to control the assembly of smooth muscle myosin into filaments. Using purified smooth muscle light chain kinase, we have confirmed this observation. We report here studies of myosins isolated from the two non-muscle sources, thymus cells and platelets. We observed that these myosins are assembled into filaments at physiological ionic strength and Mg-ATP concentrations, only when the 20,000-MW light chain is phosphorylated. 相似文献
1000.
Summary Genic activity in tetraploid members of the amphibian speciesOdontophrymus americanus is reduced to that of diploid ones. Loss of ribosomal genes, a mechanism suggested by others as a means of decreasing genetic activity, could be ruled out. The diploids and the tetraploids have almost identical proportions of their genomes complementary to (28s+18s) ribosomal RNA. 相似文献