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  • 1
    Electronic Resource
    Electronic Resource
    Phentolamine and hypoxia: modulation of contractility and α1-adrenoceptors in isolated rat atria (1994)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 350 (1994), S. 563-568 
    Details
    ISSN: 1432-1912
    Keywords: α1-Adrenoceptors ; \-Adrenoceptors ; Hypoxia ; Phentolamine ; Atrial function ; Yoshida rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The hypoxia-induced effects on the binding sites and affinity constant of adrenoceptors, in the presence and absence of phentolamine, were determined for atrial membranes of hearts from normal and genetically hyperlipidaemic Yoshida (YOS) rats. Atrial function was also measured during normoxia and hypoxia, in the presence and absence of phentolamine. Hypoxia increased a1-adrenoceptor density in atrial membranes of normal rats (Bmax 10.6 to 26.7 fmoles/mg protein). Phentolamine prevented the increase in the Bmax of α1-adrenoceptors and increased the equilibrium dissociation constant of these receptors (K D 0.17 to 0.53 nmol/l). Beta-adrenoceptors did not change during hypoxia, but the Bmax was slightly increased (26%) in the presence of phentolamine. Thus, the α1/\ ratio increased from 0.40 in normoxia to 1.06 in hypoxia. In normoxic atria from YOS rats, the α1/\ ratio was already elevated (0.86) in comparison to control rats (mainly due to a higher density of at-adrenoceptors in atrial membranes from YOS rats). This ratio was not modified by hypoxia (0.84), but decreased when phentolamine was present (0.30). Hypoxia reduced the force of contraction and increased diastolic tension of atria of normal rats, while the sinus rate was not significantly modified. Phentolamine abolished the increase in diastolic tension and reduced the negative effect of hypoxia on contractile force. In YOS rat atria, functional parameters were modified by hypoxia in a qualitatively similar way to that of normal rat atria. The observed increase in α1-adrenoceptor density during hypoxia is in accordance with the results of experiments with animal models of the ischaemic heart and with findings in human heart failure. The possible therapeutic significance of these data is considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00173027
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Synthetic fragments and analogues of elastin. I. The synthesis (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 845-854 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of some repetitive sequences of elastin and their simplified analogues, all comprising the structural unit Gly-X-Gly (X = Val, Leu, Ala), is described. In particular, the following peptides and polypeptides were synthesized and characterized: Boc-Gly-Val-Gly-Gly-Leu-OMe, Boc-Gly-Leu-Gly-Gly-Val-OMe, Boc-(Gly-Val-Gly-Gly-Leu)2-OMe, Boc-(Gly-Val-Gly-Gly-Leu)3-OMe, Boc-Gly-Val-Gly-Gly-OEt, Boc-Leu-Gly-Gly-Leu-OMe, Boc-Val-Gly-Gly-Val-OMe, poly(Ala-Gly-Gly), poly(Val-Gly-Gly), and poly (Leu-Gly-Gly).In every case, the synthesis was accomplished by classical procedures in solution, by using the p-nitrophenyl ester method for the polycondensation step, and the mixed anhydride or the azide methods for the coupling steps.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290418
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  • 3
    Electronic Resource
    Electronic Resource
    Synthetic fragments and analogues of elastin. II. Conformational studies (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 855-870 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational studies on synthetic repetitive sequences and analogues of elastin are described.CD and nmr measurements gave evidence of flexible β-turns as the dominant structural feature whose stability was found to decrease by increasing the number of repetitive units. The sequences comprised the structural unit Gly-X-Gly (X = Val, Leu, Ala), with X-Gly or Gly-Gly located at the corners of the bend.Based on that, it is proposed that these regions of elastin, unlike the proline-containing sequences, contribute to the elasticity of the protein through a classical mechanism in terms of the rotational isomeric state theory.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290419
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    Paper (German National Licenses)
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