Alteration of cholesterol synthesis in rat liver as induced by 4-methyl-5-hydroxy valeric acid

Summary The rate of cholesterogenesis in rat liver, measured by the incorporation of labelled acetate or mevalonate into cholesterol, was significantly supressed by the use of 4-methyl-5-hydroxy valeric acid sodium salt. This effect cannot be explained by changes in HMG CoA reductase activity.     

Effect of mecloqualone on the oxygen and glucose uptake by brain tissue in vitro

Resumen La mecloqualona inhibe in vitro, la respiración de cortes y homogenizados de cerebro, incrementando el consumo de glucosa; este último efecto no se produce cuando al medio de incubación se añaden 100 mM de potasio.     

Adaptation to intermittent fasting as a factor modifying the radiation resistance of mice

Summary Mice adapted to intermittent food intake (24 h fasting:24 h feeding) for 2–3 weeks exhibit a higher resistance to whole-body gamma irradiation. This is manifested by increased survival of animals and a more effective recovery of blood leukocyte counts.     

Effects of sphingolipids on erythroblastic maturation in the mouse

Summary The changes effected by injection of an extract of phospholipids obtained from the plasma of normal human donors (PLE) or an emulsion of commercially available sphingolipids on erythropoiesis in the mouse were studied. The parameters followed were⁵⁹Fe uptake by the erythroid tissue and the number of circulating reticulocytes. It was found that in the 12–24-h period following administration of PLE or purified sphingomyelin a significant increase in⁵⁹Fe uptake by circulating RBC and by their hemic fraction takes place. This change was associated with a higher⁵⁹Fe utilization by the bone marrow and with an increase in the number of circulating reticulocytes.Acknowledgments. This work was supported by a grant from the Consejo Nacional de Investigaciones científícas y Técnicas de la República Argentina. We thank Isabel Zingariello and Maria Amalia Nicastro for excellent technical assistance.     

Effect of streptozotocin diabetes on adenosine-5′-triphosphate,oxygen consumption and steroidogenesis in testis mitochondria from rats

Summary The activity of the enzyme cleaving the side-chain of cholesterol (rate limiting step in steroidogenesis) was considerably reduced in experimentally induced diabetes. This result was accompained by both an increase in oxygen consumption and an increase in ATP synthesis. Insulin treatment prevented them.     

Studies on the structure of collagen V. The site of binding of trivalent iron on collagen

Zusammenfassung Die Reaktion zwischen Kollagen und Fe^III wurde studiert. Es zeigte sich, dass das Eisen an die Sequenzen des Typs Ala-Asp-Gly gebunden wird. Weiter wurde gefunden, dass 1 mol Ratten-Tropokollagen 1 mol Cystein als Sequenz Cys-Ala-Asp-Gly enthält.

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S. Bump, Z. Deyl andJ. Rosmus, Communication IV, Experientia23, 518 (1967).     

Dynamics of singularities in a constrained elastic plate

Large deformations of thin elastic plates usually lead to the formation of singular structures which are either linear (ridges) or pointlike (developable cones). These structures are thought to be generic for crumpled plates, although they have been investigated quantitatively only in simplified geometries. Previous studies have also shown that a large number of singularities are generated by successive instabilities. Here we study, experimentally and numerically, a generic situation in which a plate is initially bent in one direction into a cylindrical arch, then deformed in the other direction by a load applied at its centre. This induces the generation of pairs of singularities; we study their position, their dynamics and the corresponding resistance of the plate to deformation. We solve numerically the equations describing large deformations of plates; developable cones are predicted, in quantitative agreement with the experiments. We use geometrical arguments to predict the observed patterns, assuming that the energy of the plate is given by the energy of the singularities.     

Southern Ocean dust-climate coupling over the past four million years

Dust has the potential to modify global climate by influencing the radiative balance of the atmosphere and by supplying iron and other essential limiting micronutrients to the ocean. Indeed, dust supply to the Southern Ocean increases during ice ages, and 'iron fertilization' of the subantarctic zone may have contributed up to 40?parts per million by volume (p.p.m.v.) of the decrease (80-100 p.p.m.v.) in atmospheric carbon dioxide observed during late Pleistocene glacial cycles. So far, however, the magnitude of Southern Ocean dust deposition in earlier times and its role in the development and evolution of Pleistocene glacial cycles have remained unclear. Here we report a high-resolution record of dust and iron supply to the Southern Ocean over the past four million years, derived from the analysis of marine sediments from ODP Site 1090, located in the Atlantic sector of the subantarctic zone. The close correspondence of our dust and iron deposition records with Antarctic ice core reconstructions of dust flux covering the past 800,000 years (refs 8, 9) indicates that both of these archives record large-scale deposition changes that should apply to most of the Southern Ocean, validating previous interpretations of the ice core data. The extension of the record beyond the interval covered by the Antarctic ice cores reveals that, in contrast to the relatively gradual intensification of glacial cycles over the past three million years, Southern Ocean dust and iron flux rose sharply at the Mid-Pleistocene climatic transition around 1.25 million years ago. This finding complements previous observations over late Pleistocene glacial cycles, providing new evidence of a tight connection between high dust input to the Southern Ocean and the emergence of the deep glaciations that characterize the past one million years of Earth history.