A 'dry' condensation origin for circumstellar carbonates

The signature of carbonate minerals has long been suspected in the mid-infrared spectra of various astrophysical environments such as protostars. Abiogenic carbonates are considered as indicators of aqueous mineral alteration in the presence of CO2-rich liquid water. The recent claimed detection of calcite associated with amorphous silicates in two planetary nebulae and protostars devoid of planetary bodies questions the relevance of this indicator; but in the absence of an alternative mode of formation under circumstellar conditions, this detection remains controversial. The main dust component observed in circumstellar envelopes is amorphous silicates, which are thought to have formed by non-equilibrium condensation. Here we report experiments demonstrating that carbonates can be formed with amorphous silicates during the non-equilibrium condensation of a silicate gas in a H2O-CO2-rich vapour. We propose that the observed astrophysical carbonates have condensed in H2O(g)-CO2(g)-rich, high-temperature and high-density regions such as evolved stellar winds, or those induced by grain sputtering upon shocks in protostellar outflows.     

Mutations in genes in the renin-angiotensin system are associated with autosomal recessive renal tubular dysgenesis

Autosomal recessive renal tubular dysgenesis is a severe disorder of renal tubular development characterized by persistent fetal anuria and perinatal death, probably due to pulmonary hypoplasia from early-onset oligohydramnios (Potter phenotype). Absence or paucity of differentiated proximal tubules is the histopathological hallmark of the disease and may be associated with skull ossification defects. We studied 11 individuals with renal tubular dysgenesis, belonging to nine families, and found that they had homozygous or compound heterozygous mutations in the genes encoding renin, angiotensinogen, angiotensin converting enzyme or angiotensin II receptor type 1. We propose that renal lesions and early anuria result from chronic low perfusion pressure of the fetal kidney, a consequence of renin-angiotensin system inactivity. This is the first identification to our knowledge of a renal mendelian disorder linked to genetic defects in the renin-angiotensin system, highlighting the crucial role of the renin-angiotensin system in human kidney development.     

Low dose oral cannabinoid therapy reduces progression of atherosclerosis in mice

Atherosclerosis is a chronic inflammatory disease, and is the primary cause of heart disease and stroke in Western countries. Derivatives of cannabinoids such as delta-9-tetrahydrocannabinol (THC) modulate immune functions and therefore have potential for the treatment of inflammatory diseases. We investigated the effects of THC in a murine model of established atherosclerosis. Oral administration of THC (1 mg kg(-1) per day) resulted in significant inhibition of disease progression. This effective dose is lower than the dose usually associated with psychotropic effects of THC. Furthermore, we detected the CB2 receptor (the main cannabinoid receptor expressed on immune cells) in both human and mouse atherosclerotic plaques. Lymphoid cells isolated from THC-treated mice showed diminished proliferation capacity and decreased interferon-gamma secretion. Macrophage chemotaxis, which is a crucial step for the development of atherosclerosis, was also inhibited in vitro by THC. All these effects were completely blocked by a specific CB2 receptor antagonist. Our data demonstrate that oral treatment with a low dose of THC inhibits atherosclerosis progression in the apolipoprotein E knockout mouse model, through pleiotropic immunomodulatory effects on lymphoid and myeloid cells. Thus, THC or cannabinoids with activity at the CB2 receptor may be valuable targets for treating atherosclerosis.     

A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization

Changes in iron supply to oceanic plankton are thought to have a significant effect on concentrations of atmospheric carbon dioxide by altering rates of carbon sequestration, a theory known as the 'iron hypothesis'. For this reason, it is important to understand the response of pelagic biota to increased iron supply. Here we report the results of a mesoscale iron fertilization experiment in the polar Southern Ocean, where the potential to sequester iron-elevated algal carbon is probably greatest. Increased iron supply led to elevated phytoplankton biomass and rates of photosynthesis in surface waters, causing a large drawdown of carbon dioxide and macronutrients, and elevated dimethyl sulphide levels after 13 days. This drawdown was mostly due to the proliferation of diatom stocks. But downward export of biogenic carbon was not increased. Moreover, satellite observations of this massive bloom 30 days later, suggest that a sufficient proportion of the added iron was retained in surface waters. Our findings demonstrate that iron supply controls phytoplankton growth and community composition during summer in these polar Southern Ocean waters, but the fate of algal carbon remains unknown and depends on the interplay between the processes controlling export, remineralisation and timescales of water mass subduction.     

Effect of glucagon on ethanol oxidation in isolated rat liver cells

Summary Addition of glucagon 5 min after ethanol was found to stimulate the rate of ethanol oxidation in hepatocytes isolated from starved rats. This stimulation is of the same order of magnitude as that mediated by asparagine. The glucagon effect is suppressed by antiproteolytic agents such as insulin or NH₄Cl. The stimulatingeffect of glucagon on ethanol oxidation is probably liked to enhanced proteolysis andan elevated glutamate level in the hepatocytes.Acknowledgments. this investigation was supported by grants from the Institut de la Santé de la Recherche Médicale, the Scientific Council of the Faculté de Médecine Paris-Ouest and the Ecole Pratique des Hautes Etudes (3rd section).     

A diploid population of the polyploid amphibianOdontophrynus americanus and an artificial intraspecific triploid hybrid

Resumen La ocurrencia de poliploidia ha sido relatada en anuros de la familia Ceratophrydidae incluyendo la especie tetraploideO. americanus (4n=44). En una área geográfica distinta, sin embargo, fue observada una población diploide deO. americanus (2n=22). Fueron obtenidos híbridos intraespecíficos triploides (3n=33) por cruzamiento de ejemplares diploides y tetraploides deO. americanus.     

W-Sex chromatin fluorescence in snakes

Resumen En los ofídios, las hembras presentan, en los núcleos interfásicos teñidos por la quinacrina, un corpúsculo fluorescente brillante. Este coincide con él condensado heteropicnótico de preparaciones comunes y corresponde al cromosoma W. Sin enbargo, él W no presenta fluorescencia intensa en las metafases somaticas.

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This work was supported by the Brazilian CNPq, FAPESP and FPIB.     

Interspecific variability of DNA content in Amphibia

Resumen Fueron determinados por citofotometría los valores de DNA en 33 especies de Amphibia, en las que estaban incluidas 30 especies de Salientia, 1 de Gymnophiona y 2 de Caudata, y fueron comparadas con sus constituciones cromosomicas. Las variaciones encontradas sugieren que hubo aumento de DNA, independientemente, en las diferentes familias estudiadas y que en general, las especies más primitivas filogeneticamente, poseen menor cantidad de DNA, cuando comparadas a los valores encontrados para las más evoluidas.

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This work was supported by PHS Grant No. GM-14577-03-NIGMS, by the CNPq and by the FPIB. Our thanks to Dr. L. D.Vizotto for collecting and classifying several specimens used in this work, as well as for the phylogenetical approach.