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891.
Resumen Los distintos cationes alcalinos monovalentes (145 mM) y divalentes (100 mM) modifican marcadamente el grado de hemólisis de eritrocitos humanos provocado por Triton X-100 y por desoxicolato de Na (DOC). La serie de actividad con cationes monovalentes en hemólisis por Triton es K>Rb=Cs>NaLi, y por DOC es Li>Rb=Cs>K>Na. Por el contrario, el grado de solubilización de membranas eritrocitarias producido por Triton o DOC es independiente de los distintos cationes alcalinos. 相似文献
892.
893.
894.
P. La Colla O. Zuffardi C. de Giuli A. M. Cioglia B. Loddo 《Cellular and molecular life sciences : CMLS》1971,27(4):479-481
Riassunto La scarsa incorporazione di precursori dello ARN in cellule infette da poliovirus ed incubate a 41,5°C è dovuta ad una inibizione della sintesi dello ARN virale più che non ad una sua digestione ad opera di nucleasi.
Work supported by a Grant of Consiglio Nazionale delle Ricerche, Rome. 相似文献
Work supported by a Grant of Consiglio Nazionale delle Ricerche, Rome. 相似文献
895.
896.
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898.
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
899.
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
900.
Chemical investigation of hassium (element 108) 总被引:5,自引:0,他引:5
Düllmann ChE Brüchle W Dressler R Eberhardt K Eichler B Eichler R Gäggeler HW Ginter TN Glaus F Gregorich KE Hoffman DC Jäger E Jost DT Kirbach UW Lee DM Nitsche H Patin JB Pershina V Piguet D Qin Z Schädel M Schausten B Schimpf E Schött HJ Soverna S Sudowe R Thörle P Timokhin SN Trautmann N Türler A Vahle A Wirth G Yakushev AB Zielinski PM 《Nature》2002,418(6900):859-862
The periodic table provides a classification of the chemical properties of the elements. But for the heaviest elements, the transactinides, this role of the periodic table reaches its limits because increasingly strong relativistic effects on the valence electron shells can induce deviations from known trends in chemical properties. In the case of the first two transactinides, elements 104 and 105, relativistic effects do indeed influence their chemical properties, whereas elements 106 and 107 both behave as expected from their position within the periodic table. Here we report the chemical separation and characterization of only seven detected atoms of element 108 (hassium, Hs), which were generated as isotopes (269)Hs (refs 8, 9) and (270)Hs (ref. 10) in the fusion reaction between (26)Mg and (248)Cm. The hassium atoms are immediately oxidized to a highly volatile oxide, presumably HsO(4), for which we determine an enthalpy of adsorption on our detector surface that is comparable to the adsorption enthalpy determined under identical conditions for the osmium oxide OsO(4). These results provide evidence that the chemical properties of hassium and its lighter homologue osmium are similar, thus confirming that hassium exhibits properties as expected from its position in group 8 of the periodic table. 相似文献