The APS Journal Legacy Content is the corpus of 100 years of historical scientific research from the American Physiological Society research journals. This package goes back to the first issue of each of the APS journals including the American Journal of Physiology, first published in 1898. The full text scanned images of the printed pages are easily searchable. Downloads quickly in PDF format.
A new inherited variant of glucose-6-phosphate dehydrogenase having both a lowered enzyme activity and an altered electrophoretic mobility was discovered in two unrelated American families, one of Irish and the other of German ancestry. Family studies of the trait indicate that it is due to a sexlinked gene.
Studies have been conducted on eight sets of monozygous and nine sets of dizygous female Negro twins, both members of whom were heterozygous for G-6-PD deficiency. Twins were studied both by assay of erythrocytic G-6-PD activity and by the methemoglobin elution test (MET). The M E T is a procedure which identifies histochemieally cells with appreciable G-6-PD activity and permits accurate determination of the percentage of such cells in heterozygotes. Monozygous twins showed significantly less "within-pair" variation than dizygous twins with both the M E T and G-6-PD assay. Concerning the significantly greater agreement in M E T results in monozygous twins than dizygous twins, our present working hypothesis is that X-chromosomal inactivation in the Negro female is genetically controlled, rather than random. However, certain alternate hypotheses allowing for random X-inactivation have not been excluded; these include somatic cell selection after random X-inactivation, and cell exchange between identical twins in utero. Studies in nontwin related heterozygotes now underway should help differentiate among these various possibilities. In addition to the studies on 17pairs of female twins heterozygous for G-6-PD deficiency, 26pairs of nondefieient female Negro twins have been studied by G-6-PD assay. Within-pair variation in monozygous twins was significantly less than within-pair variation in dizygous twins in all cases. The genetic influences detected with the G-6-PD assay in the female twins eouM theoretically be due to nonrandom X-inactivation, to genetically determined quantitative differences in enzyme activity (e.g., isoalleles),
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