No abstract available

[en] Application of diethyl sulphate onto G₁ cells of barley seeds resulted preferentially in chromatid-type aberrations in the root tips (193 chromatid vs 4 chromosome types). Artificially prolonging the G₁ phase by a 1-4 week storage of the treated seeds at 20% seed-water content led both to a manifold increase in the frequency of aberrant metaphases in the first mitosis and to a clear-cut change in the ratio of induced aberrations (7 chromatid versus 4052 chromosome types). Exposure of barley seeds to X-rays resulted in chromosome-type aberrations, and neither the number nor the spectrum of aberrations was changed by prolonging the G₁ phase

[en] Data are summarized proving the occurrence of photoreactivation of UV-induced pyrimidine dimers in cells of Nicotiana tabucum, Gingko and carrot, the excision of dimers in cells of Nicotiana tabacum, Gingko and carrot, the excision of dimers in protoplasts of carrot and in embryos of Lathyrus sativus, and the repair of DNA single-strand breaks induced in carrot protoplasts and barley embryonic cells by ionizing radiation. In irradiated barley embryos the unscheduled DNA synthesis and higher accessibility of induced primers to DNA polymerase I of E. coli were observed preferentially in G₁ cells with diffused chromatin. These reactions were inhibited by caffeine and EDTA. Unscheduled DNA synthesis was also observed in synchronized irradiated root cuttings of Vicia faba and in barley embryos treated with 4-nitroquinoline oxide, the latter being inhibited by caffeine and hydroxyurea. Repair synthesis was also established in barley embryos treated with mutagenic N-methyl-N-nitrosourea under conditions that postponed the onset of germination after the treatment. The same conditions enhanced the repair of DNA single-strand breaks induced by this mutagen and several other monofunctional alkylating compounds. From tissues of barley and of Phaseolus multiflorus, endonucleases for apurinic sites were isolated and characterized. Some of them are located in chromatin, others in chloroplasts. The relation between DNA repair and genetic effects of mutagens in higher plants is also discussed. (Auth.)

No abstract available

No abstract available

[en] Ethyl methanesulfonate (EMS)-treated barley seeds stored at 30% water content for 1 to 4 weeks are capable of recovering from the mutagen induced injury. The level and speed of the recovery depends on the EMS dose and storage period. Seeds treated with extremely severe EMS doses reducing the % of germination to 5 to 10% cannot recover from the induced injury. Due to a 1 to 6 weeks storage of EMS-treated seeds with 20% water content the amount of induced injury increases in dependence on the applied EMS dose and storage period. Doses of EMS, reducing the seedling height in the M₁ generation to 90 to 95% of the control reveal no storage after-effects. Storage of X-ray exposed seeds at 20% or 30% water content did not result in any significant changes in the yield of induced genetic damage. (author)

[en] A simple radioimmunoassay (RIA) for thyroxine (T₄) in saliva has been described. Fifty euthyroid control subjects, 14 euthyroid pregnant women, 23 thyreotoxic and 10 hypothyroid patients were examined. Serum T₃, T₄, thyroxine binding globulin (TBG) and TSH were measured simultaneously. The mean level of T₄ in saliva in controls was 1.10 +- 0.07 nmol/l. There was a good correlation between the saliva and serum T₄ concentrations (r = 0.74) and between saliva T₄ values and the T₄/TBG ratio (r = 0.83). The saliva T₄ levels, like serum free T₄, were not dependent on fluctuations of serum TBG concentrations. In euthyroid pregnant women, saliva T₄ levels were within the normal range while the serum T₄ and TBG were increased. There was a good agreement of saliva T₄ values with the functional state of the thyroid. Thus, the RIA of saliva T₄ could replace the laborious determination of serum free T₄. It can especially be useful in instances with abnormal values of TBG, as it is in pregnancy, in congenital deficiency of serum TBG or in subjects with hereditary elevated TBG levels. (author)

No abstract available

No abstract available

[en] A method of plasma and urine aldosterone radioimmunoassay is described and evaluated. Highly specific antisera were obtained through rabbit immunization using partly aldosterone-18,21-dihemisuccinate-BSA, partly aldosterone-3-carboxymethyl-oxime-BSA, free of the 18-derivative. The use of a more specific antiserum against the 3-derivative permitted the determination to be performed immediately from the biological specimen extract. Hydrolysis with sulphuric acid in the presence of dichloromethane proved the most appropriate of the different techniques of releasing aldosterone-glucuronoside for the determination of the total urine hormone. The normal values (average +- 2 S. D.) of plasma aldosterone were 0.19 +- 0.067 nmol/l, those of the free urine hormone 0.918 +- 0.458 nmol/day, and the total urine aldosterone 15.3 +- 5.8 nmol/day. (author)