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  • 1
    ISSN: 1432-0428
    Keywords: Type 2 (non-insulin-dependent) diabetes mellitus ; glucokinase ; gestational diabetes ; American Blacks ; single-strand conformation polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Mutations of the glucokinase gene result in early-onset familial Type 2 (non-insulin-dependent) diabetes mellitus, and several members of the mutant glucokinase kindreds were originally diagnosed as having gestational diabetes. This study examined the glucokinase gene in 270 American Black women, including 94 with gestational diabetes whose diabetes resolved after pregnancy (gestational diabetes only), 77 with gestational diabetes who developed Type 2 diabetes after pregnancy (overt diabetes), and 99 normal control subjects who were recruited during the peripartum period. Two simple sequence repeat polymorphisms flanking either end of the glucokinase gene were evaluated. No association was found between glucokinase alleles and gestational diabetes only or overt diabetes, after adjustment for multiple comparisons. To detect single base changes, all 11 exons and proximal islet and liver promoter regions were examined by polymerase chain reaction plus single-stranded conformational polymorphism analysis in 45 gestational diabetes only patients who had not yet developed Type 2 diabetes. Nine coding region variants were identified: Ala11 (GCC) to Thr11 (ACC) in islet exon 1, and 8 variants either in untranslated regions or in the third base of a codon. Four variant sites were found in introns, but none in splicing consensus sequences. Analysis of the promoter regions revealed two common variants, G→A at islet −30 (24%), and G→A at liver −258 (42%). The frequencies of the promoter variants, determined by allele specific polymerase chain reaction analysis, did not differ among the three groups. Thus, no significant coding sequence glucokinase mutations were found in 90 alleles from 45 patients with gestational diabetes. Further studies will be required to rule out a minor role of the newly-described promoter region variants as susceptibility factors in this disorder.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 95 (1993), S. 122-133 
    ISSN: 1432-1939
    Keywords: Sargassum patens ; Halichoeres tenuispinus ; Competition ; Predation ; Macrofauna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The possibility that resource limits constrain the growth of mobile epifaunal populations associated withSargassum patens plants was investigated by placing plants and associated animals into field microcosms which excluded fish predators, and then comparing faunal abundance and size-structure changes in different microcosm treatments with field populations. Four different micrososm treatments were set up: two treatments containing defaunated plants inoculated with caprellid amphipods, and two control treatments with natural faunas. The estimated secondary production of faunas enclosed in all microcosm treatments rapidly settled on a constant value (5 mg/day) which was similar to that determined in experiments conducted in Western Australia using the same microcosms but for faunas associated with a seagrass rather than a macroalga. These results support the hypothesis that the secondary production of epifaunal communities associated with macrophytes is constrained by quantifiable food resource ceilings. Predation by the most common fish species in the area, the wrasseHalichoeres tenuispinis, did not appear to alter macrofaunal production in theS. patens bed; however, it did greatly affect the faunal size-structure by eliminating most of the larger animals. The majority of epifaunal animals ≥ 2.0 mm sieve-size were consumed byH. tenuispinis, while negligible numbers of 0.5-mm sieve-size animals were captured. We postulate that food resource ceilings and predatory size-selectivity are widespread phenomena, affecting epifaunal populations at a variety of locations. Predation is predicted to generally increase rather than decrease faunal abundance because the consumption of each large invertebrate by a predator frees sufficient resources to feed several smaller individuals.
    Type of Medium: Electronic Resource
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