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J Thorner

Publications and source records attributed to J Thorner.

114 records · Page 7Linked to original sources
PubMed1978

Cell-cell recognition in Saccharomyces cerevisiae: regulation of mating-specific adhesion.

Mating-specific adhesion between haploid yeast cells of opposite mating type (a and alpha) was studied by using a quantitative agar plate assay. Washed a and alpha cells that had not previously been exposed to their respective opposite mating type ("naive" cells) adhered relatively weakly. In water, only 5 to 10% of the a cells stuck tightly enough to alpha cells to give rise subsequently to diploid clones on the assay plates. Under optimum conditions (pH 6 to 7, at least 0.1 M Nacl or 0.01 M Mg(2+)), there was about 20% adhesion. Nevertheless, this weak binding defined a mating type-specific interaction because, even under optimum conditions, the homologous interactions (a with a and alpha with alpha) yielded only 3 to 5% cohesion. In contrast to these results, washed cells that had been preincubated in the cell-free culture medium of their opposite mating type ("preconditioned" cells) adhered quite strongly. The degree of adhesion between preconditioned cells (40 to 50%) was essentially unaffected by extremes of ionic strength, pH, and temperature and by the absence of divalent cation. This strong interaction was also mating type specific since cohesion between preconditioned cells of like mating type was only about 5%. The increase in agglutinability was obtained if only the a cells were preconditioned and could be induced by highly purified preparations of natural or synthetically prepared alpha-factor, an oligopeptide pheromone released by the alpha cells. The appearance of increased adhesiveness was blocked by an inhibitor of RNA synthesis and by an inhibitor of protein synthesis, but not by an inhibitor of polysaccharide synthesis. Adhesion between preconditioned cells could be inhibited by pretreatment with functionally univalent succinylated concanavalin A or with extracts from preconditioned cells of the opposite mating type. These results confirm in a quantitative manner that the recognition between conjugating cells of S. cerevisiae is a developmentally regulated event that is under the control of the mating type locus.

Adhesiveness↗
PubMed1977

Thymidine 5'-monophosphate-requiring mutants of Saccharomyces cerevisiae are deficient in thymidylate synthetase.

Thymidylate synthetase activity was measured in crude extracts of the yeast Saccharomyces cerevisiae by a sensitive radiochemical assay. Spontaneous non-conditional mutants auxotrophic for thymidine 5'-monophosphate (tmp1) lacked detectable thymidylate synthetase activity in cell-free extracts. In contrast, the parent strains (tup1, -2, or -4), which were permeable to thymidine 5'-monophosphate, contained levels of activity similar to those found in wild-type cells. Specific activity of thymidylate synthetase in crude extracts of normal cells or of cells carrying tup mutations was essentially unaffected by the ploidy or mating type of the cells, by the medium used for growth, by the respiratory capacity of the cells, by concentrations of exogenous thymidine 5'-monophosphate as high as 50 mug/ml, or by subsequent removal of thymidine 5'-monophosphate from the medium. Extracts of a strain bearing the temperature-sensitive cell division cycle mutation cdc21 lacked detectable thymidylate synthetase activity under all conditions tested. Its parent and another mutant (cdc8), which arrests with the same terminal phenotype under restrictive conditions, had normal levels of the enzyme. Cells of a temperature-sensitive thymidine 5'-monophosphate auxotroph arrested with a morphology identical to the cdc21 strain at the nonpermissive temperature and contained demonstrably thermolabile thymidylate synthetase activity. Tetrad analysis and the properties of revertants showed that the thymidylate synthetase defects were a consequence of the same mutation causing, in the auxotrophs, a requirement for thymidine 5'-monophosphate and, in the conditional mutants, temperature sensitivity. Complementation tests indicated that tmp1 and cdc21 are the same locus. These results identify tmp1 as the structural gene for yeast thymidylate synthetase.

Cell-Free System↗
PubMed1975

Metabolic and cardiovascular abnormalities in patients with peripheral arterial disease.

Twenty-eight consecutive patients of an average age of 63 years with intermittent claudication secondary to underlying peripheral arterial disease were studied for evidence of metabolic or other cardiovascular abnormalities and the results obtained were compared with those of 28 matched control subjects free of vascular disease. Patients with peripheral arterial disease had significantly higher levels of systolic and diastolic blood pressure, a greater incidence of ECG abnormalities, lipoprotein abnormalities, elevated serum triglycerides, and serum copper. The incidence of smoking and abnormal glucose tolerance, while higher in peripheral arterial disease patients, was not statistically significant. Hematocrit and serum cholesterol levels were nearly indentical in both groups of patients. Twenty-six of the 28 patiens with peripheral arterial disease had either a cardiovascular or a metabolic abnormality, indicating the high incidence of multisystem illness in this disorder. The epidemiologic data in peripheral arterial disease are similar to those in coronary artery disease but some measurements contrast sharply, such as the apparent normal level of serum cholesterol in patients with peripheral arterial diseases.

Adult↗