Potassium translocation in yeast mitochondria and its relationship to ergostrol biosynthesis.

The energy-dependent transport and accumulation of K+ in respiring mitochondria has been found to inhibit the S-adenosylmethionine: delta-24-sterol methyltransferase enzyme of Saccharomyces cerevisiae. Potassium cation translocation is discussed as a possible regulatory mechanism over the biosynthesis of ergosterol.

Effect of altered sterol composition on growth characteristics of Saccharomyces cerevisiae.

The function of sterols in mitochondrial structures of yeast was examined. Sterol mutant strains were employed to examine the effects of altered sterolic content on optimal and permissive growth temperatures in respiring and fermenting cultures. Although fermentative growth was unaffected by sterol composition, a definite decrease in both the optimal and the permissive growth temperatures of respiring cultures was observed when ergosterol was replaced by Delta(8(9), 22)-ergostadiene-3beta-ol.

Alpha Fetoprotein: An index of progression or regression of hepatoma, and a target for immunotherapy.

CLINICAL AND LABORATORY STUDIES OF AFP PRODUCING HEPATOMAS DEMONSTRATED THAT: 1) serum AFP levels correlated directly with tumor growth; 2) circulating AFP could be cleared by passive administration of an. excess of anti-AFP; and 3) highly specific anti-AFP functioned as a carrier to localize diagnostic and possibly therapeutic amounts of radioactivity in hepatoma tissue. These studies helped elucidate certain criteria which should be fulfilled before attempts to initiate passive humoral immunotherapy of cancer are undertaken.

Cell division and deoxyribonucleic acid synthesis after a nutritional shift-up of Saccharomyces cerevisiae.

Rates of cell division and deoxyribonucleic acid synthesis after shift-up with grande and mitchondrial deoxyribonucleic-acid-less petite yeasts were studied. The results indicate that simple eukaryotes behave as prokaryotes.

Response of the intracellular adenosine triphosphate pool of Saccharomyces cerevisiae to growth inhibition induced by excess L-methionine.

Yeast cells accumulate S-adenosyl-l-methionine (S-AM) when cultivated in the presence of l-methionine. Cell growth is inhibited by the addition of high concentrations of l-methionine. A number of investigators have attributed this to the depletion of adenosine triphosphate (ATP) as a consequence of the utilization of that mucleotide for S-AM formation.

8(9),22 -Ergostadiene-3 -ol, an ergosterol precursor accumulated in wild-type and mutants of yeast.

Whereas wild-type strains of Saccharomyces cerevisiae can synthesize up to 7% dry weight of ergosterol, a polyene-resistant mutant has been obtained which produces no ergosterol. Instead, a C-28 methyl sterol is produced, and it has been identified as Delta(8(9),22)-ergostadiene-3beta-ol. This sterol is converted to ergosterol by wild-type yeasts and is observed transiently in cells during aerobic adaption of anaerobically grown wild-type yeasts.

Transmethylation of sterols in aerobically adapting Saccharomyces cerevisiae.

The transmethylation of methyl-(14)C-methionine and methyl-(14)C-adenosylmethionine into the nonsaponifiable lipids of anaerobically grown yeast during adaptation to aerobic conditions was investigated. The rate and extent of methyl transfer increased with aeration time and was dependent upon the presence of a fermentable carbon source and O(2). Methionine and adenosylmethionine uptake rates increased in adaptation buffer but did not seem to be the rate-limiting factor for transmethylation under the conditions studied.