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81.
Multiple transduction mechanisms are likely involved in calcium-mediated exocrine secretory events in rat parotid cells 总被引:1,自引:0,他引:1
L Bodner M T Hoopes M Gee H Ito G S Roth B J Baum 《The Journal of biological chemistry》1983,258(5):2774-2777
The parotid gland of the aged rat provides an example of an altered alpha 1-adrenergic physiologic response (K+ efflux) resulting from a postreceptor perturbation in signal transduction mechanisms (Ito, H., Baum, B. J., Uchida, T., Hoopes, M. T., Bodner, L. & Roth, G. S. (1982) J. Biol. Chem. 257, 9532-9538). This alteration in gland function can be completely circumvented by eliciting K+ efflux via the Ca2+-ionophore, A23187, at several Ca2+ concentrations (ibid.). Since Ca2+ is purported to mediate other secretory events in the rat parotid, we have probed neurotransmitter regulated Ca2+ mobilization and secretory mechanisms in this tissue by employing an aging paradigm. The responses studied were alpha-adrenergic- and muscarinic-cholinergic-mediated K+ efflux, 45Ca2+ release, and amylase secretion. No differences were detected between young (3 months) and old (24 months) cell preparations for any muscarinic-cholinergic agonist-induced response studied. Following alpha-adrenergic stimulation, K+ efflux and 45Ca2+ release from old cell preparations were reduced markedly, while no changes were found for the amylase secretion response. These results suggest that 1) alpha-adrenergic and cholinergic signal transduction mechanisms for K+ efflux and 45Ca2+ release are dissociated in cells of the rat parotid gland, and 2) following alpha 1-adrenergic stimulation, signal transduction likely proceeds by at least two pathways, one which is apparently involved in protein excytosis (intact in cells from old rats) and the other which is apparently involved in K+ efflux and 45Ca2+ release (perturbed in old cells). 相似文献
82.
Antibodies against a nonapeptide of polyomavirus middle T antigen: cross-reaction with a cellular protein(s). 总被引:4,自引:3,他引:1 下载免费PDF全文
Y Ito Y Hamagishi K Segawa T Dalianis E Appella M Willingham 《Journal of virology》1983,48(3):709-720
Antibodies were raised against the sequence Glu-Glu-Glu-Glu-Tyr-Met-Pro-Met -Glu, which represents a part of the middle T antigen of polyomavirus that is considered to be important in inducing the phenotype of transformed cells. The antibodies reacted with native as well as denatured middle T antigens. In addition, the antibodies immunoprecipitated a cellular protein with an apparent molecular weight of 130,000 (130K) from mouse and rat cells. In some cases, a 33K protein was also immunoprecipitated. Immunoprecipitation of middle T antigen as well as 130K and 33K proteins was blocked by the peptide. The antibodies labeled microfilaments of untransformed mouse, rat, human, and chicken cells by immunofluorescence. This labeling was also blocked by the peptide. The labeling pattern and distribution under a variety of conditions were indistinguishable from those of anti-actin antibodies, although no evidence has been obtained to indicate that the anti-peptide antibodies react with actin. The 130K protein migrated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis slightly slower than chicken gizzard vinculin (130K) and slightly faster than myosin light-chain kinase of chicken smooth muscle (130K). Neither of these proteins absorbed the anti-peptide antibodies. The 33K protein does not seem to be tropomyosin (32K to 40K). 相似文献
83.
A temperature-sensitive mutant of E. coli exhibiting slow processing of exported proteins 总被引:53,自引:0,他引:53
A temperature-sensitive E. coli mutant with a mutation in the spc ribosomal protein operon was found to have a conditional defect in the processing of precursor proteins destined for the periplasmic space or the outer membrane. At high temperatures, significant amounts of precursor proteins having unprocessed signal sequences are detected in the mutant cell by pulse-labeling. The precursors are processed at very slow rates during a subsequent chase. Genetic analysis indicates that the mutation impairs the function of a gene, termed secY, located at the promoter-distal part of the spc operon. The secY gene is distinct from those genes previously known to specify ribosomal proteins, yet it is within the spc operon. It is suggested that the product of the secY gene is a component of the cellular apparatus that is essential for protein secretion across the cytoplasmic membrane. The gene secY is probably identical with prlA, previously identified as a suppressor of signal sequence mutations. 相似文献
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Nitrate and ammonium were shown to alter the growth ofRhodotorula glutinis var.salinaria in saline and non-saline media. In saline medium in which ammonium was the sole nitrogen source, ammonium inhibited growth
in the presence of molybdate ions. Detailed comparisons of the growth in saline and non-saline media when nitrate was supplemented
in the presence of molybdate ions showed that differences in utilizability of purine bases of nucleic acid were responsible
for the differences in growth,i.e. adenine increased the growth in such saline medium, but decreased it in non-saline medium. There was not such a specific
requirement for adenine in saline medium in the presence of molybdate ions when nitrate was substituted for ammonium as the
sole nitrogen source. It was suggested that adenine might provide the necessary skeleton of nucleic acid for serving nitrate
reduction in saline medium. 相似文献
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