Search PubMed⌕ Search

Biomedical subjects

N Yamaguchi

Publications and source records attributed to N Yamaguchi.

At least 901 records · Page 50Linked to original sources
PubMed1977

Glycopeptides from epithelial cell mutants: temperature sensitive for the transformation phenotype.

Fucose-labelled glycopeptides obtained from the cell surfaces of normal and transformed epithelial cells were compared by co-chromatography on Sephadex G-50. The material obtained from epithelial cells transformed in vitro or from hepatoma cells in culture elutes earlier than the fucose-containing glycopeptides obtained from normal rat epithelial cells. A mutant (TS 223) of a transformed epithelial cell that is temperature-sensitive for maintenance of the transformed phenotype, varies in its Sephadex G-50 profile of cell surface glycopeptides when grown at the permissive (36 degrees C) or the non-permissive temperature (40 degrees C). When grown and labelled at 36 degrees C the gel filtration profile of the glycopeptides resembles that of transformed cells. At 40 degrees C there is an enrichment of later eluting glycopeptides. These differences are more striking in confluent-phase cultures than in log-phase culture. The differences are reversible following upward or downward shifts in growth temperature although there appears to be a lag of at least 6 h before the alteration can be demonstrated by these procedures.

Animals↗
PubMed1977

Simian virus 40 gene A regulates the association between a highly phosphorylated protein and chromatin and ribosomes in simian virus 40-transformed cells.

The species of proteins associated with chromatin and ribosomes of simian virus 40 (SV40)-transformed and untransformed monkey, mouse, and rat cells have been compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis after phosphorylation of these proteins either in vivo or in vitro. In vitro phosphorylation was carried out by protein kinase associated with these organelles and [gamma-(32) P]ATP as the phosphoryl donor. The reaction products contained both phosphoserine and phosphothreonine in approximately equal amounts. The electrophoretic analysis of the phosphorylated proteins revealed that the highly phosphorylated protein with a molecular weight of approximately 90,000 (90K protein) was associated with chromatin and ribosomes from transformed cells but not from untransformed cells. The 90K protein could be extracted from chromatin and ribosomes with 0.5 to 1.0 M NaCl or KCl. The 90K protein was still associated with the runoff ribosomes prepared by the puromycin reaction of the post-mitochondrial supernatant in the protein-synthesizing system. In vitro phosphorylation of chromatin and ribosomes from SV40 tsA-transformed mouse and rat cells indicated that the amounts of 90K protein associated with these organelles decreased greatly when the cells were cultivated at the restrictive temperature. A similar temperature-dependent decrease in the amount of (32)P-labeled 90K protein was observed in nonhistone chromosomal and ribosome-associated protein fractions prepared from SV40 tsA-transformed cells labeled with [(3)H]leucine and [(32)P]orthophosphate in vivo. In vitro phosphorylated 90K protein in nonhistone chromosomal and ribosome-associated proteins extracted with high salt was not immunoprecipitated with anti-SV40 T sera.

Adenosine Triphosphate↗
PubMed1977

Regulation of norepinephrine release from cardiac sympathetic fibers in the dog by presynaptic alpha- and beta-receptors.

The effect of phenoxybenzamine (PBA), desmethylimipramine (DMI), clonidine (CLND), sotalol (STL), and isoproterenol (ISPR) on the release of endogenous norepinephrine (NE) from the heart on right cardioaccelerator nerve stimulation was studied in anesthetized dogs. Under control conditions, the catecholamine levels in coronary sinus blood increased linearly with increasing frequencies of stimulation up to 10 Hz and did not increase further at 30 Hz. The release of NE was markedly enhanced after PBA (1 mg/kg, iv) and DMI (1 mg/kg, iv). The enhanced release of NE after DMI, but not after PBA, was associated with a prolonged response in heart rate. In contrast, NE release was reduced after CLND (15 microgram/kg, iv) at stimulation frequencies of 1 and 2 Hz and this was associated with reduced responses in heart rate and left ventricular dtp/dt. STL (5 mg/kg, iv) reduced significantly the release of NE at stimulation frequencies of 1-5 Hz, whereas ISPR enhanced NE outflow at frequencies of 1-4 Hz. These results support the existence of both negative and positive feedback mechanisms on the release of norepinephrine by cardiac sympathetic fibers mediated through presynaptic alpha- and beta-adrenoreceptors, respectively. The functional significance of these mechanisms is also suggested by the correlation found between changes in NE release and variations in cardiac responses under the various drug treatements.

Adrenergic Fibers↗
PubMed1976

Alterations in surface glycoproteins and level of sialyltransferase of cells transformed by a temperature-sensitive mutant of simian virus 40.

Mouse cells transformed by a temperature-sensitive mutant of simian virus 40 belonging to complementation group A lost their ability to regulate cell growth when grown at the permissive temperature (35 degrees) but showed the low saturation density of cell growth at the restrictive temperature (39.5 degrees) that is characteristic of normal cells in vitro. Biochemical analysis of the membranes of cells grown under the restrictive and the permissive conditions demonstrated no qualitative temperature-dependent differences either in neutral glycolipids or in acidic glycolipids of the cells. Plasma membrane glycoproteins labeled with radioactive glucosamine showed significantly different patterns on both polyacrylamide gel electrophoresis and electrofocusing. When the levels of glycoprotein glycosyltransferases of the cells were examined, the level of sialyltransferase (CMP-N-acetylneuraminytransferase,EC 2.4.99.1) of the cells grown at the restrictive temperature was low compared with that of cells grown at the permissive temperature. Our results indicate that the level of sialyltransferase is under the control of the gene A function of simian virus 40 and consequently is related to alterations in the cell surface glycoproteins.

Cell Transformation, Neoplastic↗