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Kinetic studies of copper-induced LDL peroxidation commonly assume that the availability of molecular oxygen in the reaction media is not a limiting factor. The present study reveals that this assumption is valid only at low LDL concentrations. At high LDL concentrations, accumulation of oxidation products, as monitored spectroscopically under conditions of various oxygen concentrations in the medium, comes to a halt when the oxygen concentration in the solution, as measured by an oxygen electrode, decreases to near zero levels. Bubbling of the oxygen into the solution results in resumption of peroxidation. These results are important with respect to the ex vivo assaying of lipoprotein peroxidation because many previous studies have been conducted with LDL concentrations that corresponded to polyunsaturated fatty acid concentrations in access of the concentration of molecular oxygen. The possible pathophysiological significance of the results of this study has yet to be evaluated. 相似文献
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Glutamate receptor trafficking into dendritic spines is a pivotal step in synaptic plasticity, yet the relevance of plasticity-producing rise of [Ca2+]i and of spine morphology to subsequent delivery of glutamate receptors into dendritic spine heads are still not well understood. Following chemical induction of LTP, an increase in eGFP-GluR1 fluorescence in short but not long dendritic spines of cultured hippocampal neurons was found. Repeated flash photolysis of caged calcium, which produced a transient rise of [Ca2+]i inside spine heads caused a selective, actin and protein synthesis dependent increase of eGFP-GluR1 in these spines. Strikingly, GluR1 increase was correlated with the ability of a calcium transient generated in the spine head to diffuse into the parent dendrite, and inversely correlated with the length of the spine: short spines were more likely to raise GluR1 than long ones. These observations link, for the first time, calcium transients in dendritic spines with spine morphology and its ability to undergo synaptic plasticity. 相似文献
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The effect of angiotensin II on myosin heavy chain expression in cultured myocardial cells 总被引:1,自引:0,他引:1
Noa Shalitin Menahem Friedman Hadassa Schlesinger Yael Barhum Maurice J. Levy Wolfgang Schaper Gania Kessler-Icekson 《In vitro cellular & developmental biology. Animal》1996,32(9):573-578
Summary Angiotensin II (AII), the principal mediator of the renin-angiotensin system, is an important regulator of vascular and cardiac
homeostasis. AII has also been shown to be a regulator of cardiac hypertrophy and of the corresponding changes in amount and
composition of certain tissue proteins. We examined the trophic effects of AII on cultured myocytes derived from neonatal
rat ventricles and followed, by Northern blot analysis and polyacrylamide gel electrophoresis, the expression of α- and β-myosin
heavy chain iso-mRNAs and isoproteins. Our findings show that a single administration of AII is sufficient to induce a trophic
response in cultured beating myocytes and to enhance the expression of β-myosin heavy chain iso-mRNA and isoprotein, having
no effect on α-myosin heavy chain. Induction of α-myosin heavy chain expression by thyroid hormone before AII was administered
showed that AII could not potentiate a shift from α- to β-myosin heavy chain predominance. We suggest that the potency of
AII to regulate the expression of myosin heavy chain isogenes is restricted to the β isoform and is overridden by thyroid
hormone. 相似文献