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K Weiser

Publications and source records attributed to K Weiser.

5 recordsLinked to original sources
PubMed1979

Response of specific transfer-ribonucleic-acid levels to amino-acid deprivation in Friend leukemia cells.

In eukaryotes, the levels of specific tRNAs are closely correlated with the demands for their cognate amino acids in protein synthesis. To account for this phenomenon, we have proposed that the extent of aminoacylation of a given tRNA species in vivo controls the relative rate of synthesis or turnover of that species. Previously, we reported that Friend leukemia cells respond to histidine deprivation by increasing their relative level of tRNAHis by as much as two-fold, with no change in the relative level of tRNALeu. In this paper, we show that deprivation of leucine or tryptophan also causes a specific increase in the relative level of tRNAs cognate to the deprived amino acid. At least in the case of tRNATrp, the increases in relative tRNA levels are preceded by extensive declines in the steady-state extent of aminoacylation of the tRNA in vitro. We also find that different isoacceptors may respond differently to amino acid deprivation. These results suggest that decreased extents of aminoacylation of a given tRNA species in vivo cause increases in the relative rate of synthesis or decreases in the relative rate of degradation of that species.

Amino Acids↗
PubMed1978

Histidine transfer RNA levels in Friend leukemia cells: stimulation by histidine deprivation.

Friend leukemia cells incubated with sublethal concentrations of histidinol for 5 to 6 days show up to twofold increases in their relative concentrations of histidine transfer RNA and no change in the relative concentrations of leucine transfer RNA. A similar effect is seen when cells are grown to stationary phase in the presence of 0.2 times the amount of histidine in Eagle's minimum essential medium. These observations support the theory that the concentrations of specific transfer RNA's are regulated by a mechanism that is sensitive to the extent of their aminoacylation.

Cell Division↗
PubMed1975

[The influence of adrenalectomy on DNA-synthesis in the liver after partial hepatectomy and on corticosterone concentration of the serum in rats (author's transl)].

UNLABELLED: Problemacy: In an earlier paper we have reported the influence of adrenalectomy on DNA-synthesis in rat liver and found that during the first 2 days the incorporation of H3 thymidine is elevated). (DESSER-WIEST 1974). Therefore we have examined the DNA-synthesis in regenerating live of rats with and without adrenals. MATERIAL AND METHODS: 300 g male rats were adrenalectomized and 14 days later 2/3 hepatectomized. One group of animals were bled and the concentration of corticosterone in serum was determined by a radioprotein-binding method (SPATH and JOZAN 1972). The other group of animals were injected with H3thymidine at 9 a.m. All animals were killed between 10:00 a.m. and 10:15 a.m. The incorporation of H3thymidine was determined by the method of BURTON (1969). In adrenalectomized animals, the onset of liver regeneration was found to be retarded for 18 hours, the maximum of DNA-synthesis was depressed. RESULTS: The corticosterone concentration of the serum was 17,8 mug/100 ml serum in contro animals and was undetectable in animals during the first and second day after adrenalectomy, thereafter the steroid level increased. A third of the amount found in control animals was found 14 days after operation. Partial hepatectomy, caused an increase of the corticosterone level in serum of animals with and without adrenals. In castrated and adrenalectomized animals no corticosterone in serum was found. The importance of corticosterone for liver regeneration is discussed.

Adrenalectomy↗