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  • 1
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Cotton-top tamarins (Saguinus oedipus) in captivity are unusual in that they exhibit low levels of polymorphism and allelic diversity at the major histocompatibility complex (Mhc) class I loci. Since the polymorphism has previously only been examined in captive tamarins, we analyzed the Mhc class I alleles of a population of wild tamarins. These wild tamarins, like their captive counterparts, exhibited limited class I polymorphism. We also assessed the levels of polymorphism and allelic diversity at the Mhc class II DQA1, DQB1, DQB2, and the DRB loci in captive populations of cotton-top tamarins. In contrast to the extensive polymorphism in Old World monkeys, only two alleles were detected at each of DQA1 and DQB1. Also, the DQB2 locus was monomorphic and conserved between New and Old World monkeys. Sequences derived from four putative DRB loci were obtained, and extensive polymorphism was found at all four loci. Phylogenetic analysis did not indicate that any of the tamarin DRB loci, with the possible exception of Saoe-DRB3, were orthologous to the human DRB loci. At three of the DRB loci (Saoe-DRB11, Saoe-DRB * W12, Saoe-DRB * W22), the number of nonsynonymous changes was higher than the number of synonymous changes in the putative antigen recognition sites, indicative of positive selection. We found no support for a restriction on the polymorphism at the cotton-top tamarin class II loci. However, the allelic diversity at some of the Saoe-DRB loci is more limited than for the HLA-DRB1, consistent with a restriction imposed by the bone marrow-chimerical lifestyle.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 411 (1999), S. 139-143 
    ISSN: 1573-5117
    Keywords: fluctuating asymmetry ; temperature stress ; Asellus aquaticus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study examines Fluctuating Asymmetry (FA) in the isopod Crustacean Asellus aquaticus (Linn.). FA occurs in bilaterally symmetrical traits not closely related to survival or fecundity and is the presence of small random deviations from perfect symmetry caused by environmental or genetic stress. These stresses perturb the developmental programme of the organism involved, resulting in asymmetry. FA was induced in the laboratory with temperature stress. Increasing levels of FA were found with increasing environmental temperature, but alteration between extremes of temperature was not found to be as stressful as simple increases in temperature. Extreme temperatures are, therefore, inferred to be an environmental stress for A. aquaticus.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0730-2312
    Keywords: amylin ; adenylate cyclase ; kinetics ; mnemonical ; negative co-operativity ; cyclic AMP ; hepatocytes ; CGRP ; G-protein ; Gi-2 ; guanine nucleotide regulatory protein ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Challenge of intact hepatocytes with amylin only succeeded in elevating intracellular cyclic AMP levels and activating phosphorylase in the presence of the cAMP phosphodiesterase inhibitor IBMX. Both amylin and CGRP similarly activated adenylate cyclase, around 5-fold, although ∼ 400-fold higher levels of amylin were required to elicit half maximal activation. Amylin activated adenylate cyclase though apparently simple Michaelin kinetics whereas CGRP elicited activation by kinetics indicative of apparent negative co-operativity. Use of the antagonist CGPP(8-37) showed that both CGRP and amylin activated hepatocyte adenylate cyclase through a common receptor by a mnemonical mechanism where it was proposed that the receptor co-existed in interconvertible high and low affinity states for CGRP. It is suggested that this model may serve as a paradigm for G-protein linked receptors in general. Amylin failed to both stimulate inositol phospholipid metabolism in hepatocytes and to elicit the desensitization of glucagon-stimulated adenylate cyclase. Amylin did, however, elicit the phosphorylation of the inhibitory guanine nucleotide regulatory protein Gi-2 in hepatocytes and prevented the action of insulin in reducing the level of phosphorylation of this G-protein. © 1994 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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