Inheritance of quantitative expression of erythrocyte glucose-6-phosphate dehydrogenase activity in the Negro—a twin study

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 MET is a procedure which identifies histochemically 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 MET and G-6-PD assay.Concerning the significantly greater agreement in MET 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/it. Studies in nontwin related heterozygotes now underway should help differentiate among these various possibilities.In addition to the studies on 17 pairs of female twins heterozygous for G-6-PD deficiency, 26 pairs of nondeficient 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 could theoretically be due to nonrandom X-inactivation, to genetically determined quantitative differences in enzyme activity (e.g., isoalleles), or to both. By appropriate calculations, based on the MET results, we have factored out the effects of X-inactivation on overall enzyme activity in the heterozygous deficient twins. After removal of the effect of X-inactivation, monozygous twins heterozygous for enzyme deficiency continue to show significantly less within-pair variation than dizygous twins. This finding indicates significant genetic influences on quantitative G-6-PD activity other than X-inactivation and other than the deficiency allele. This conclusion has been strengthened by studies on male twins where X-inactivation is not present.Supported by USPHS research grants AM-09381, HE-17544, AM-09919, and HE-03341, by USPHS Career Development Award 1-K3-AM-7959 (Dr. Brewer) and by U.S.A.E.C. Contract (11-1)-1552.     

Blood Viscosity in Healthy Subjects and Patients with Coronary Heart Disease

Viscosity of whole blood and plasma was measured in 258 apparently healthy subjects of both sexes from 5 to 60 years of age, and in 86 patients with unequivocal evidence of chronic coronary heart disease. Children and young healthy females had the lowest viscosity readings. Healthy young and middle-aged males had significantly higher blood viscosity than females. Patients with coronary heart disease had significantly higher blood viscosity values than healthy groups of the same sex. It is suggested that the higher viscosity of whole blood and of plasma is a contributory factor in development of clinical manifestations of coronary heart disease and possibly of the basic vascular lesion itself.     

Absorption and long distance transport by isolated stele of maize roots in relation to the dual mechanisms of ion absorption

Summary Ion absorption and transport by intact roots, isolated cortex and isolated stele were compared shortly after tissue isolation and after aging. Absorption isotherms in the low and in the high concentration range show that in stripped-stele, which absorbs at a very low rate immediately after isolation, the capacity of system 1 but not system 2 is built up with aging. In agreement with this result analysis of individual fluxes across plasmamembrane and tonoplast reveals that only the influx from the medium into the cytoplasm increases considerably with aging of stele. Changes observed in aging excised roots and in isolated cortex are much less significant. In spite of the increase of absorption with aging by isolated stele, long distance transport, which is essentially passive through freshly stripped stele, decreases with aging. The reported results reflect the marked permeability of the plasmamembrane of fresh isolated stele, and demonstrate the importance of the cortex as a tissue collecting ions for long distance transport. New evidence for the theory of symplasmatic transport of ions into the xylem vessels is thus provided.

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Zusammenfassung Die Ionenaufnahme durch intakte Wurzeln, isolierte Rinde und isolierte Zentralzylinder und der Ferntransport durch intakte und entrind ete Wurzeln wurden verglichen, und zwar kurz nach der Isolierung und nach Altern der Gewebe. Frisch isolierte Zentralzylinder akkumulieren Io nen nur in ganz geringem Maße oder überhaupt nicht. Von den beiden Systemen der metabolischen Ionenaufnahme, die in einem niedrigen (System 1: bis 0,5 meq/l) und in einem hohen Konzentrationsbereich (System 2: 1-50 meq/l) die Geschwindigkeit der Ionenaufnahme durch intakte Wurzeln und isolierte Wurzelrinde bestimmen, entwickelt sich während des Alterungsprozesses in isolierten Zentralzylindern System 1, nicht aber System 2.In Übereinstimmung mit diesem Befund zeigt die Analyse der Einzelfluxe am Plasmalemma und am Tonoplasten, daß nur der Influx aus der Außenlösung in das Cytoplasma beim Altern der Zentralzylinder beträchtlich ansteigt. Veränderungen beim Altern von abgeschnittenen, intakten Wurzeln und isolierter Rinde sind viel weniger ausgeprägt.Obwohl die Ionenaufnahme beim Altern isolierter Zentralzylinder steigt, verringert sich der Ferntransport, der bei frisch isolierten Zentralzylindern rein passiv ist. Die mitgeteilten Ergebnisse zeigen die ausgeprägte Permeabilität frisch isolierter Zentralzylinder und demonstrieren die Bedeutung der Wurzelrinde als ein Gewebe, das Ionen für den Ferntransport sammelt. Auf diese Weise werden neue Anhaltspunkte für die Theorie des symplasmatischen Transportes der Ionen in die Gefäße gewonnen.

     

Simian Virus 40 Transformation and the Period of Cellular Deoxyribonucleic Acid Synthesis

The antiviral agents interferon and statolon protected cells of the mouse line 3T3 against the transforming effect of simian virus 40. Loss of ability of these agents to protect when added some time after infection indicated that the transformation was already fixed. The cells of exponentially growing cultures became resistant to the protective effect of interferon at a linear rate after infection; after one cell generation, the whole population was resistant. By use of synchronous cultures, it was shown that, in cells passing though the G-1 period of the growth cycle, the transformation did not pass the interferon-sensitive stage, whereas cells in S [the period of cellular deoxyribonucleic acid (DNA) synthesis] readily passed this stage (i.e., became interferon-resistant). An irreversible step in transformation appeared to occur in cells synthesizing DNA, and it seems likely that replicating cellular DNA was the target of the viral action.     

Factors in the Testing and Application of Algicides

A review is presented of some of the factors affecting the laboratory testing and practical applications of chemicals toxic to algae. The basic factor demonstrated is that the amount of chemical required to inhibit the growth of algae is dependent on the amount of algae present and not on the volume of water in which the algae are dispersed. It is shown how a chemical can be tested for algistatic or algicidal properties, thus enabling one to decide how best to apply a particular chemical. The selectivity of chemicals and the development of resistance in algae towards certain chemicals is demonstrated. Also, it is shown how certain algae can appear to be resistant to chemical treatments because of their growth habit or their production of extracellular products which affect the toxicity of added chemicals. With a better understanding of how various factors can influence the effectiveness of toxic chemicals, it is hoped that the selection of a chemical and method of application to a particular problem will be more successful.