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871.
Résumé Les effets de l'ypérite nitrée sur le cerveau et yeux de l'embryon du rat blanc ont été analysés. Seulement les embryons présentant un aspect normal ont été coupés et colorés. De larges centres de nécrose ont été trouvés sur les coupes tandis que les «rosettes» n'ont pas pu être décelées.Bien que connue comme radiomimétique, l'yperite nitrée ne mime pas les rayons X en ce qui concerne la formation des «rosettes» dans le cerveau. 相似文献
872.
Adenosine-induced slow ionic currents in the Xenopus oocyte 总被引:11,自引:0,他引:11
Adenosine and its 5'-phosphorylated congeners evoke specific membrane-mediated responses in excitable tissues. Available data suggest that inhibition of the target cell occurs due to hyperpolarization, and in some preparations a compound effect of ATP (excitation and inhibition) has been found. However, the ionic mechanism of the purinergic-mediated response has not been studied by standard intracellular voltage-clamping techniques. Recently, we have discovered purinergic receptors in the Xenopus oocyte, a well defined giant cell amenable to rigorous electrophysiological and biochemical studies. We report here that in these cells, adenosine-induced slow membrane responses consisted of an early depolarizing (D) transient current carried by Cl ions, followed by a steady hyperpolarizing (H) current involving K+ ions. The relative potency sequence for the D current was ATP congruent to ADP greater than AMP congruent to adenosine; this order was reversed for the H current. 相似文献
873.
874.
875.
876.
S. N. Hegde 《Cellular and molecular life sciences : CMLS》1972,28(12):1451-1452
Zusammenfassung Taubenmilch ist lipidhaltig und enthält zwei wesentliche Fettsäuren: Linol- und Linolensäure. Ein nicht identifizierter Faktor zusammen mit einer fett- und aminosäurehaltigen Diät ist imstande, auf Jungvögel wachstumfördernd zu wirken. 相似文献
877.
Schödel R Ott T Genzel R Hofmann R Lehnert M Eckart A Mouawad N Alexander T Reid MJ Lenzen R Hartung M Lacombe F Rouan D Gendron E Rousset G Lagrange AM Brandner W Ageorges N Lidman C Moorwood AF Spyromilio J Hubin N Menten KM 《Nature》2002,419(6908):694-696
Many galaxies are thought to have supermassive black holes at their centres-more than a million times the mass of the Sun. Measurements of stellar velocities and the discovery of variable X-ray emission have provided strong evidence in favour of such a black hole at the centre of the Milky Way, but have hitherto been unable to rule out conclusively the presence of alternative concentrations of mass. Here we report ten years of high-resolution astrometric imaging that allows us to trace two-thirds of the orbit of the star currently closest to the compact radio source (and massive black-hole candidate) Sagittarius A*. The observations, which include both pericentre and apocentre passages, show that the star is on a bound, highly elliptical keplerian orbit around Sgr A*, with an orbital period of 15.2 years and a pericentre distance of only 17 light hours. The orbit with the best fit to the observations requires a central point mass of (3.7 +/- 1.5) x 10(6) solar masses (M(*)). The data no longer allow for a central mass composed of a dense cluster of dark stellar objects or a ball of massive, degenerate fermions. 相似文献
878.
Christlieb N Bessell MS Beers TC Gustafsson B Korn A Barklem PS Karlsson T Mizuno-Wiedner M Rossi S 《Nature》2002,419(6910):904-906
The chemical composition of the most metal-deficient stars largely reflects the composition of the gas from which they formed. These old stars provide crucial clues to the star formation history and the synthesis of chemical elements in the early Universe. They are the local relics of epochs otherwise observable only at very high redshifts; if totally metal-free ('population III') stars could be found, this would allow the direct study of the pristine gas from the Big Bang. Earlier searches for such stars found none with an iron abundance less than 1/10,000 that of the Sun, leading to the suggestion that low-mass stars could form from clouds above a critical iron abundance. Here we report the discovery of a low-mass star with an iron abundance as low as 1/200,000 of the solar value. This discovery suggests that population III stars could still exist--that is, that the first generation of stars also contained long-lived low-mass objects. The previous failure to find them may be an observational selection effect. 相似文献
879.
Statins: the new aspirin? 总被引:10,自引:0,他引:10
3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, or statins, have been described as the principal and
the most effective class of drug to reduce serum cholesterol levels. Statin therapies have been shown to reduce cardiovascular
events, including myocardial infarction, stroke, and death, significantly, by altering vascular atherosclerosis development
in patients with or without coronary artery disease symptoms. Extensive use of statins has led to the increase of some undesirable
effects that are heavily counterbalanced by the benefits. Indeed, pleiotropic effects extend far beyond cholesterol reduction
and involve non-lipid-related mechanisms that modify endothelial functions, immunoinflammatory responses, smooth muscle cell
activation, proliferation and migration, atherosclerotic plaque stability, and thrombus formation. In this review, we describe
in detail the targets and mechanisms of action of statins.
Received 6 June 2002; received after revision 6 September 2002; accepted 6 September 2002
RID="*"
ID="*"Corresponding author. 相似文献
880.
Axonal transport of neurofilaments in normal and disease states 总被引:5,自引:0,他引:5
Miller CC Ackerley S Brownlees J Grierson AJ Jacobsen NJ Thornhill P 《Cellular and molecular life sciences : CMLS》2002,59(2):323-330
Neurofilaments are among the most abundant organelles in neurones. They are synthesised in cell bodies and then transported
into and through axons by a process termed 'slow axonal transport' at a rate that is distinct from that driven by conventional
fast motors. Several recent studies have now demonstrated that this slow rate of transport is actually the consequence of
conventional fast rates of movement that are interrupted by extended pausing. At any one time, most neurofilaments are thus
stationary. Accumulations of neurofilaments are a pathological feature of several human neurodegenerative diseases suggesting
that neurofilament transport is disrupted in disease states. Here, we review recent advances in our understanding of neurofilament
transport in both normal and disease states. Increasing evidence suggests that phosphorylation of neurofilaments is a mechanism
for regulating their transport properties, possibly by promoting their detachment from the motor(s). In some neurodegenerative
diseases, signal transduction mechanisms involving neurofilament kinases and phosphatases may be perturbed leading to disruption
of transport.
Received 11 July 2001; received after revision 30 August 2001; accepted 31 August 2001 相似文献