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  • 1
    Electronic Resource
    Electronic Resource
    Heterogeneity of human red blood cell membrane: Co-existence of heavy and light membranes (1999)
    Springer
    Molecular and cellular biochemistry 196 (1999), S. 141-149 
    Details
    ISSN: 1573-4919
    Keywords: antioxidant enzymes ; ATPases ; spectrin ; cell membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The exact chemical composition of the red blood cell (RBC) membrane may vary depending on the methods used to isolate the membrane. We provide evidence here that RBC membrane can be fractionated by differential centrifugation and/or density gradient centrifugation into two distinct types, designated as ‘heavy membrane’ (HM) and ‘light membrane’ (LM). The amount of LM is twice that of HM on a per cell basis. HM and LM differ in some biochemical and electrophoretic properties. The total activities of Na+, K+ - and Ca2+- ATPases, superoxide dismutase, glutathione peroxidase, catalase and glucose-6-phosphate and 6-phosphogluconate dehydrogenase are significantly higher in LM than HM on a per cell basis. While there is no significant difference in the specific activity of other enzymes between the two membranes, the specific activity of Ca2+-ATPase is significantly higher in HM, whereas Na+, K+-ATPase activity is higher in LM. There is a remarkable difference in the distribution of major ghost polypeptides between these two membranes. Component I of spectrin, component III and a protein with mol. wt. of 165 KDa are present in smaller amounts, whereas component II of spectrin and proteins with mol. wt. of 145, 84 and 76 KDa, respectively, are present in higher amounts in HM than LM. Some proteins such as band 4.1, 48 and 46 KDa are present only in LM, whereas some proteins with mol. wt. of 96, 78 and 43 KDa, respectively are present only in HM. It has been confirmed that these two membranes are not representatives of either (a) right side-out vs. inside out vesicles, or (b) open vs. sealed membranes. Thus HM and LM are two distinct membrane fractions. It is suggested that some part of the membrane is denser than other parts, and during hemolysis of RBCs, the rbc membrane is spliced resulting in two populations, dense and light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006932010565
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  • 2
    Electronic Resource
    Electronic Resource
    β-Adrenoreceptors of multiple affinities in a clonal capillary endothelial cell line and its functional implication (1994)
    Springer
    Molecular and cellular biochemistry 140 (1994), S. 49-54 
    Details
    ISSN: 1573-4919
    Keywords: capillary endothelial cells ; β-adrenoreceptor ; cell proliferation ; endothelial cell culture ; angiogenesis ; adenylate cyclase-cAMP system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract β-Adrenoreceptor has been studied in a clonal capillary endothelial cell line established from the vascular bed of the bovine adrenal medulla. [3H]Dihydroalprenolol ([3H]DHA) binding to the isolated plasma membranes from these cells has demonstrated the presence of β-adrenoreceptors with two different affinities. the dissociation constants (Kd) have been found to be 0.27±0.09×10−9 M and 2.96±0.31×10−9 M, respectively with the corresponding Bmax of 5.1±0.05 and 70.0±0.2 pmol/mg protein, respectively. Inhibition of [3H]DHA binding to the β-receptor by atenolol (a β1-antagonist) and ICI 118,551 (a β1-antagonist) has suggested that the IC50cor (=Ki) for atenolol and ICI 118,551 for high affinity site are 0.08±0.03×10−12 M and 0.25±0.08×10−12 M, respectively. This, therefore, indicates that both atenolol and ICI 118,551 are able to displace the bound ligand effectively but the β1-selective antagonist atenolol is 3 times more potent than its β2 counterpart, ICI 118,551. Displacement of [3H]DHA binding to the endothelial cell plasma membrane by the agonists isoproterenol, epinephrine and norephinephrine has established a relative order of Ki for these agents as isoproterenol (0.56±0.19×10−9 M)〈epinephrine (0.77±0.26−9 M)〉-norepinephrine (0.71±0.24×10−9 M) for the high affinity site. The corresponding values for the low affinity site, however, are 4.62±0.64×10−9 M, 6.21±0.86×10−9 M and 5.90±0.82×10−9 M, respectively for the same agonists. Increased intracellular cAMP accompanied with cellular proliferation in the presence of isoproterenol has suggested not only the coupling of β-adrenoreceptors to the adenylate cyclase system but also its involvement in endothelial cell proliferation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00928365
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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