1,720,976 research outputs found
Amiloride inhibition of Na+/Ca2+ exchange in cardiac sarcolemmal vesicles at different temperatures.
No full textTemperature dependence of Na+/Ca2+ exchange activity in beef-heart sarcolemmal vesicles and proteoliposomes.
No full textTemperature dependence of Na+/Ca2+ exchange activity was studied in beef cardiac sarcolemmal vesicles in the absence and presence of the inhibitor amiloride and in proteoliposomes reconstituted with different lipid mixtures. Arrhenius plots for Na+/Ca2+ exchange activity in both control and amiloride-treated vesicles revealed an apparent energy of activation of 9665 +/- 585 (SE, n = 4) cal/mol, corresponding to a temperature coefficient (Q10) value of 1.70 +/- 0.05 (SE, n = 4) over the range 25-37 degrees C. When Na+/Ca2+ exchange was reconstituted into phosphatidylcholine (PC):phosphatidylserine (PS) (52:48, mol/mol), PC:PS:cholesterol (25:39:36, mol/mol), and PC:PS:distearoylphosphatidylcholine (DSPC) (31:48:21, mol/mol) proteoliposomes, the highest activity was found in PC:PS:cholesterol proteoliposomes. Arrhenius plots of Na+/Ca2+ exchange activity exhibited breakpoints at 23 degrees C (PC:PS), 33 degrees C (PC:PS:cholesterol), and 23 degrees C (PC:PS:DSPC). The increase in the thermotropic transition temperature with cholesterol could result from the condensing effect of this sterol, whereas the breaks observed with PC:PS and PC:PS:DSPC could be caused by a non-lipid-mediated membrane protein conformational change. These results indicate that the lipid microenvironment around the Na+/Ca2+ exchanger and the nature of the specific lipid-protein interactions influence the activity of this antiporter. Further evidence supporting the hypothesis that cholesterol behaves as a specific positive effector for the exchanger is also given
Cholesterylphosphoserine as inhibitor of cell adhesion and actin polymerization in human T cells.
No full textAbstractTo further investigate the immunosuppressive activity of cholesterylphosphoserine (CPHS), we examined a variety of human T cell responses including proliferation, adhesion and cytoskeletal organization. The CPHS-induced inhibition of T cell response is greater in the integrin-dependent mixed lymphocyte reaction than in the integrin-independent proliferation elicited by anti-TCR-CD3 or anti-CD28 antibodies in the presence of tetradecanoylphorbol acetate. Consistently, CPHS inhibits the homotypic T cell adhesion involving the integrin αLβ2 (LFA-1) and the cell adhesion to fibronectin and rVCAM-1 involving the integrins of the β1 family. Since CPHS does not change integrin expression but inhibits post-receptor events such as cell spreading and pseudopodal projections, it seems likely that the site of CPHS influence is distal to the adhesion receptors. In agreement, the steroid prevents the reorganization of actin cytoskeleton occurring when T cells are allowed to spread on immobilized anti-CD3 in the absence of integrin activation. We suggest that CPHS acts on the metabolic pathway in which signals from integrin and growth factor receptors converge to induce the reorganization of the actin cytoskeleton. Selectivity in the action of CPHS is indicated by its ineffectiveness in the integrin-mediated adhesion of the monocytic cell line U-937 to fibronectin
SIGNALING PATHWAYS INVOLVED IN THE APOPTOTIC ACTION OF OUABAIN IN TWO DIFFERENT CANCER CELL LINES
No full textRole of reactive oxygen species (ROS) in the antiapoptotic effect of oxysterols on human umbilical vein endothelial cells (HUVEC)
No full textEffect of oxysterols on cell survival and proliferation pathways in human endothelial cells
No full textα-Glucosidase and advanced glycation end products inhibition with Vernonia amygdalina root and leaf extracts: new data supporting the antidiabetic properties
No full textOBJECTIVE: This study aims to investigate antidiabetic activity of several Vernonia amygdalina extracts to study their potential use in medicine. METHODS: Aqueous and ethanol extracts were obtained by maceration and Soxhlet extraction from roots and leaves of V. amygdalina. The extracts were tested as inhibitors of α-glucosidase activity and of advanced glycation end products (AGEs) formation. Further, radical scavenging activity was examined detecting the oxygen radical absorbance capacity, while the potential cytotoxicity of extracts was estimated with MTT assay. KEY FINDINGS: In aqueous and ethanol extracts, several polyphenolic compounds were identified; in detail, (-)-catechin and luteolin were found in leaf extracts, while caffeic acid, chlorogenic acid and the terpenoid vernodalol were recognized in root extracts. Regarding antidiabetic activity, the aqueous root extracts efficiently inhibited α-glucosidase activity in a concentration-dependent manner (IC50 = 5.6 μg/ml and 39.8 μg/ml, respectively of macerated and Soxhlet extracts), whereas those obtained from leaves exhibited lower potency. Furthermore, AGEs formation was reduced by all V. amygdalina extracts starting from 10 μg/ml. CONCLUSIONS: The aqueous extracts of V. amygdalina roots obtained by maceration and Soxhlet extraction show remarkable anti-α-glucosidase activity, and all extracts have favourable antiglycation and antioxidant activities
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