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Biomedical subjects

R K Kulkarni

Publications and source records attributed to R K Kulkarni.

16 recordsLinked to original sources
PubMed1990

Mannitol Metabolism in Lentinus edodes, the Shiitake Mushroom.

Mannitol metabolism was evaluated in fruiting bodies of Lentinus edodes. Cell extracts were prepared from fruiting bodies, and key enzymes involved in mannitol metabolism were assayed, including hexokinase, mannitol dehydrogenase, mannitol-1-phosphate dehydrogenase, mannitol-1-phosphatase, and fructose-6-phosphatase. Mannitol dehydrogenase, fructose-6-phosphatase, mannitol-1-phosphatase, and hexokinase activities were found in extracts of fruiting bodies. However, mannitol-1-phosphate dehydrogenase activity was not detected. Mycelial cultures were grown in an enriched liquid medium, and enzymes of the mannitol cycle were assayed in cell extracts of rapidly growing cells. Mannitol-1-phosphate dehydrogenase activity was also not found in mycelial extracts. Hence, evidence for a complete mannitol cycle both in vegetative mycelia and during mushroom development was lacking. The pathway of mannitol synthesis in L. edodes appears to utilize fructose as an intermediate.

Journal Article↗
PubMed1985

Calmodulin levels in the yeast and mycelial phases of Ceratocystis ulmi.

The calmodulin content of the yeast and mycelial phases of Ceratocystis ulmi was determined by radioimmunoassay. Calmodulin levels increased at the G1-S boundary of the cell cycle, coinciding with the first visible appearance of buds or germ tubes. However, in both phases the cellular calmodulin levels were equivalent. No differential synthesis was observed.

Ascomycota↗
PubMed1984

Tumor-promoting phorbol esters stimulate the phosphorylation of ribosomal protein S6 in quiescent Reuber H35 hepatoma cells.

The addition of the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA) to serum-starved quiescent Reuber H35 hepatoma cells results in a rapid 5- to 11-fold increase in the incorporation of 32Pi into a Mr = 32,000 ribosomal protein. The Mr = 32,000 protein was the major phosphorylated protein extracted from isolated 80 S ribosomes and was identified as the 40 S ribosomal protein S6 based upon its migration in two-dimensional gels. Insulin, which has been demonstrated to increase the phosphorylation of S6 in a number of cell lines, caused a 10- to 20-fold increase in the incorporation of 32Pi into this Mr = 32,000 ribosomal protein. S6 phosphorylation was dose- and time-dependent being detected as early as 5 min following the addition of 1.6 microM TPA. Maximal phosphorylation of ribosomal protein S6 was achieved by 60 min and remained elevated for at least 90 min in the presence of TPA. The 50% effective dose for TPA was estimated to be 0.14 microM. Based upon the altered migration of S6 in pH 8.5 urea-polyacrylamide gels, it was demonstrated that the increased 32Pi labeling of S6 by TPA was due to a net increase in the incorporation of phosphates into the S6 molecule. Non-tumor-promoting phorbol esters were ineffective in increasing the phosphorylation of S6. In whole cells, exogenously added 1 mM 8-bromoadenosine 3':5'-monophosphate failed to substantially increase phosphorylation of S6 suggesting that the TPA-induced phosphorylation of S6 occurs via a cyclic AMP-independent mechanism. The S6 amino acid residue phosphorylated in response to TPA was phosphoserine. A possible role for protein kinase C in the phosphorylation of ribosomal protein S6 is discussed.

Animals↗
PubMed1983

Insulin-mediated phosphorylation of ribosomal protein S6 in mouse melanoma cells and melanoma x fibroblast hybrid cells in relation to cell proliferation.

The possible role of insulin-mediated phosphorylation of ribosomal protein S6 in the control of cell proliferation was examined in insulin-unresponsive mouse melanoma calls (PG19) and insulin-responsive melanoma x fibroblast clone 100A. In the hybrid cells, under conditions of growth arrest in medium with low serum, ribosomal protein S6 was rapidly phosphorylated in response to insulin or serum. The phosphorylation of the S6 protein increased over a wide range of insulin concentrations, suggesting that insulin stimulated the phosphorylation by interacting with both high- and low-affinity receptors. In contrast, in growth-arrested melanoma cells, an intermediate level of S6 phosphorylation was observed. Insulin caused only a marginal increase and serum caused a small but consistent increase in the level of S6 phosphorylation in the melanoma cells. Cell cycle analysis revealed that both cell lines arrested growth to a similar degree in the G1 phase of the cell cycle; thus, the higher baseline level of S6 phosphorylation observed in the melanoma cells was not attributable to less complete growth arrest of these cells in medium with low serum. The S6 phosphorylation results correlate well with previous results suggesting that the hybrid cells, but not the parental melanoma cells, can become growth-limited for processes regulated by insulin.

Animals↗
PubMed1978

Biocompatibility testing of polymers: in vitro studies with in vivo correlation.

An in vitro method has been developed for screening of candidate biomaterials in an early phase of their development. The test is based on L-929 mouse fibroblast cultures and their response to powdered polymer samples. It applies microscopic observation for the detection of morphological changes, uses dye exclusion testing for cell viability determination, and utilizes estimation of population doublings as an end point. The test is shown to be reliable and reproducible and is compared to in vivo implantation studies in rats, previously reported.

Animals↗
PubMed1978

Biocompatibility testing of polymers: in vivo implantation studies.

An in vivo method is described for screening polymeric materials for biocompatibility. The test is based on grading acute and subacute tissue reactions at 7 and 28 days, respectively, following implantation in rats. The methods is reproducible and reliable. It is designed to provide uniform test criteria for biocompatibility assessment in the early phases of the development of surgical implant materials.

Animals↗