Oxidative phosphorylation of guinea-pig aorta

Zusammenfassung Bei der Untersuchung von Aorta-Homogenaten von Meerschweinchen wurde ein hoher P/O Quotient für die oxydative Phosphorylierung gefunden.

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This work was supported by Public Health Service Grand No. HE-00891.     

Transmission of the ‘lymphoid tumour’ ofXenopus laevis by injection of cell-free extracts

Résumé La «tumeur lymphoïde» deXenopus laevis est transmissible par des filtrats acellulaires ainsi que par injection des surnageants de centrifugation des extraits de tissus cancéreux à des vitesses qui sédimentent les virus connus jusqu'à présent.

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This investigation was supported by the Fonds National Suisse pour la Recherche Scientifique No. 4411.

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I wish to thank Professor M.Fischberg for his interest in this work and the facilities he provided     

Photostimulation of ATP production,in cell-free extracts of insect integument

Summary Cell free extracts ofPieris brassicae integument or its 220,000×g sonicated supernatant exhibit a light-dependent ATP production system (LAPS). ADP and Pi seem to be the substrates of the reaction. LAPS cannot be located in intact mitochondria.     

Specificity of anti-RH serum inhibition by lipid extracts as determined by quantitative nitrogen assays

Zusammenfassung Eine Reihe der Lipidfraktionen von Rh-positiv und Rh-negativ (D-positiv und D-negativ) roten Zellen menschlichen Blutes wurde der Wirkung von anti-Rho Serum (anti-D) ausgesetzt. Die dabei adsorbierte Menge von Stickstoff wurde quantitativ bestimmt. In jedem Fall adsorbierten die Lipide von Rh-positiv roten Zellen mehr Antikörperstickstoff als die aus Rh-negativ roten Zellen extrahierten Lipide. Man darf wohl daraus schliessen, dass der höhere Grad der Adsorption von Antikörperstickstoff auf Lipiden von Rh positiv roten Zellen ein spezifischer Effekt ist.     

Action of alkylating agents on nitrogen fixation by clones of Anabaena doliolum Bharadwaja

Summary The physiological and mutagenic actions of three alkylating agents have been studied on the process of nitrogen fixation byAnabaena doliolum Bharadwaja. The results show that these chemicals presumably switch off the activity of nitrogenase, resulting in the inhibition of fixation.     

Biosynthesis of aflatoxins by cell-free preparations fromAspergillus flavus

Résumé Incorporation d'acétate-1-¹⁴C, de leucine-U-¹⁴C et de mévalonate-2-¹⁴C sous forme d'aflatoxine dans les extraits libres des cellulesd'Aspergillus flavus. Dans le cas du mévalonate, l'incorporation de l'ordre de 0,4 pour 100 et les activités spécifiques sont 13 000 à 40 000 cpm/mg d'aflatoxine. La capacité d'incorporation des substrats en aflatoxine s'observe, en particulier, dans les mitochondries.     

The purine nucleoside cycle in cell-free extracts of rat brain: evidence for the occurrence of an inosine and a guanosine cycle with distinct metabolic roles

The purine nucleoside cycle is a cyclic pathway composed of three cytosolic enzymes, hypoxanthine-guanine phosphoribosyltransferase, IMP-GMP specific 5'-nucleotidase, and purine-nucleoside phosphorylase. It may be considered a 'futile cycle', whose net reaction is the hydrolysis of 5-phosphoribosyl-1-pyrophosphate to inorganic pyrophosphate and ribose 1-phosphate. The availability of a highly purified preparation of cytosolic 5'-nucleotidase prompted us to reconstitute the purine nucleoside cycle. Its kinetics were strikingly similar to those observed when dialyzed extracts of rat brain were used. Thus, when the cycle is started by addition of inorganic phospate (Pi) and hypoxanthine or inosine (the 'inosine cycle'), steady-state levels of the intermediates are observed and the cycle 'turns over' as far as 5-phosphoribosyl-1-pyrophosphate is being consumed. In the presence of ATP, which acts both as an activator of IMP-GMP-specific 5'-nucleotidase and as substrate of nucleoside mono- and di-phosphokinases, no IDP and ITP are formed. The inosine cycle is further favored by the extremely low xanthine oxidase activity. Evidence is presented that ribose 1-phosphate needed to salvage pyrimidine bases in rat brain may arise, at least in part, from the 5-phosphoribosyl-1-pyrophosphate hydrolysis as catalyzed by the inosine cycle, showing that it may function as a link between purine and pyrimidine salvage. When the cycle is started by addition of Pi and guanine (the 'guanosine cycle'), xanthine and xanthosine are formed, in addition to GMP and guanosine, showing that the guanosine cycle 'turns over' in conjunction with the recycling of ribose 1-phosphate for nucleoside interconversion. In the presence of ATP, GDP and GTP are also formed, and the velocity of the cycle is drastically reduced, suggesting that it might metabolically modulate the salvage synthesis of guanyl nucleotides.     

Inactivation of catalase by phospholipide extracts

Riassunto L'autore, analogamente a quanto ha già dimostrato avvenire per il citocromoc, mette in evidenza una potente azione inattivante la catalasi da parte dei fosfolipidi estratti da tessuti e dal lievito.