Über die Ursachen der Osmotoleranz bei Hefen

Zusammenfassung Mit Untersuchungen über die Abhängigkeit des Zellvolumens vom osmotischen Wert und über die Konzentration der Zellinhaltsstoffe wird versucht, zur Kenntnis der Ursachen der Osmotoleranz bei Hefen beizutragen. In konzentrierten Lösungen verringern alle untersuchten Hefen ihr Volumen, die osmotoleranten Hefen aber weniger als die nichtosmotoleranten. Der Beginn einer meßbaren Volumenverringerung tritt bei osmotoleranten Hefen bei höheren Konzentrationen ein als bei nichtosmotoleranten. Eine Abhängigkeit der Zellgröße vom osmotischen Wert kann nur in einem bestimmten Konzentrationsbereich (zwischen 0,7–2% und 10% NaCl) festgestellt werden. Darunter fehlt eine osmotische Reaktion, und darüber bleibt die Zellgröße gleich. In Nährlösungen mit erhöhtem osmotischen Wert vermehren sich Zellen beider Typen in ihrer normalen Größe. Der osmotische Wert ihres Zellinhaltes ist annähernd gleich groß. Eine veränderte Struktur des Zellplasmas bzw. ein dadurch bedingter höherer Gehalt an fest gebundenem Hydratationswasser wird als Ursache der Osmotoleranz bei Hefen angesehen.

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About the causes of osmotolerance in yeasts

Summary The question, if the yeast cell volume depends on the osmotic pressure and on the solutes of the cell, has been investigated. In concentrated solutions all yeasts investigated reduced their volume. A smaller reduction was found in osmotolerant yeasts. Osmotolerant yeasts begin to reduce their volume at higher osmotic pressures than non-osmotolerant ones. In concentrated nutrient media the cells of osmotolerant and non-osmotolerant yeasts grow in their normal size. The cell size depends only in the range between 0.7 to 2% and 10% NaCl approximately on the osmotic pressure of the surrounding medium. Beneath 2% there is no osmotic reaction and above 10% the cell size remains unchanged. The osmotic value in the cells of both yeast types is about the same. Causes of osmotolerance in yeasts may be a modified structure of cytoplasm and an increased content of bound water.

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(Prof. Dr. S. Windisch)     

Isoleucine and Valine Metabolism in Escherichia coli XVIII. Induction of Acetohydroxy Acid Isomeroreductase

The regulation by substrate induction of the acetohydroxy acid isomeroreductase was studied in Escherichia coli. Induction was inhibited by chloramphenicol and rifampin. The addition of rifampin resulted in a decay of the capacity to form isomeroreductase. This was attributed to the breakdown of the isomeroreductase messenger, which had a half-life of about 45 sec at 37 C. Induction of isomeroreductase was enhanced by including glucose in the medium. This effect was shown to be due in part to the lowering of the pH of the medium, which presumably made inducer entry more rapid.     

GABA UPTAKE IN RAT BRAIN SLICES: INHIBITION BY GABA ANALOGUES AND BY VARIOUS DRUGS

Abstract— 2-Hydroxy-, 2-chloro-, 2- and Cmethyl-GABA are linear competitive inhibitors of GABA uptake in rat brain slices. These analogues are thus potential substrates for the GABA transport system and possible'false transmitters'. 2-Hydroxy-GABA is the most potent inhibitor of GABA uptake yet described. No specific inhibitor of GABA uptake was revealed amongst the drugs tested.     

Localization of alkaline phosphatase and NADH diaphorase in the principal cells of the guinea pig epididymis

The activities of alkaline phosphatase and reduced nicotinamide adenine dinucleotide (NADH) diaphorase in the principal cells of the guinea pig epididymis were studied histochemically. Alkaline phosphatase activity was absent from the principal cells but was present in the basement membrane of the epididymal epithelium. NADH diaphorase activity was distributed throughout the cytoplasm of the principal cells in each epididymal segment. There was a gradual increase in NADH diaphorase activity from segments 1 through 7. Possible functions of alkaline phosphatase and NADH diaphorase in the epididymis are discussed.