Biomedical subjects

S Herlick

Publications and source records attributed to S Herlick.

2 recordsLinked to original sources

PubMed1989

UTP/CTP ratio, an important regulatory parameter for ATCase expression.

Intracellular nucleotides of Salmonella typhimurium were separated and quantified by high performance liquid chromatography (HPLC). Wild type and specially constructed strains of S. typhimurium, in which uridine and cytidine nucleotides could be manipulated independently, were used in this study. By varying growth conditions it was possible to create different concentrations of uridine and cytidine nucleotides in the cell. The specific activity of ATCase was determined for each condition. Generally, a direct correlation was found: at high nucleotide (UTP) concentrations, maximal repression of ATCase was usually seen; at low nucleotide (UTP) concentrations ATCase was derepressed. However, it was the ratio of the concentrations of UTP-to-CTP rather than either the concentration of UTP or CTP alone that best determined the extent of ATCase expression. This applied to all conditions in the present work as well as to all conditions in work hitherto reported by others. The ratio of UTP/CTP is proposed as a key regulatory parameter for pyr enzyme expression.

Aspartate Carbamoyltransferase↗

PubMed1985

Cell-cell proximity is a parameter affecting the transfer of mutagenic polycyclic aromatic hydrocarbons between cells.

A keratinocyte cell-mediated mutation assay was used to examine the importance of cellular proximity to the transfer of mutagenic and cytotoxic polycyclic aromatic hydrocarbon (PAH) metabolites between cells. The PAHs 7,12-dimethylbenz[a]anthracene (DMBA) and benzo[a]pyrene (BP) were both mutagenic and cytotoxic to V-79 fibroblasts co-cultured on the surface of a keratinocyte feeder layer. However, neither PAH was mutagenic to the V-79 cells when the V-79 cells were co-incubated with the cultured keratinocytes under conditions in which the two cell types were separated by 0.5-1.5 mm but continually shared a common medium. Similarly, DMBA cytotoxicity was eliminated and BP-dependent cytotoxicity was greatly reduced in co-incubation protocols. These results suggest that cells must either be in contact or very close to facilitate the transfer of mutagenic PAH metabolites between cells.

9,10-Dimethyl-1,2-benzanthracene↗