Desoxyribose nucleic acid from isolated chromosome threads in experimental epidermal methylcholanthrene carcinogenesis in mice

This article does not have an abstract

Cytochemical studies of nuclear metabolism in biological systems

This article does not have an abstract

Adenine complexes of thymine and uracil: electron spin resonance and thermoluminescence investigations

Electron spin resonance (E.S.R.) and thermoluminescence (T1) studies following irradiation with high-energy electrons and 60Co λ-rays have been carried out at room temperature and at low (77°Κ) temperature. Adenine, thymine and uracil and their two equimolecular complexes, adenine-thymine and adenine-uracil, have been used in these investigations. E.S.R. measurements at room temperature showed that the complexes were more resistant to radiation, and the differences in the free-radical yields of the complexes on the one hand, and their constituents on the other, follow dose-response patterns that are specific to the complexes. Low-temperature E.S.R. measurements carried out before and after T1 have indicated that the E.S.R. signal originates in at least two groups of electrons, probably only one of which is active for T1. These studies also show that the modes of transfer of radiation damage in the two complexes are different. These results are further substantiated by quantitative measurements on the photo-bleaching characteristics of thermoluminescence of the samples

Formation of thymyl radicals in gamma-irradiated frozen aqueous systems: an E.S.R. study

This article does not have an abstract

Possibility of anion formation in irradiated frozen solutions of nucleic acid bases

From E.S.R. spectroscopy it is suggested that purine and pyrimidine anions are formed after gamma-irradiation of their alkaline solutions at - 196°c. On warming to higher temperatures, the anions usually became hydrolysed, giving rise to secondary radicals formed by hydrogen addition. A direct relation was obtained between the yields of anions and radicals, which increased with the alkalinity of the solution. On exposure to visible light, anions decayed following second-order kinetics

On the biological effects of high background radioactivity: studies on Tradescantia grown in radioactive monazite sand

Tradescantia, clone 02, plants were grown in garden soil and were exposed to low level external radiations ranging from 0.08 mR/hr to 1.3 mR/hr or were raised in radioactive monazite sand cultures. In the experiment on external exposure alone, one group of plants was irradiated from transplanting while another group was irradiated from flowering. The occurrence of somatic mutations in the staminal hairs was recorded from flowering, for a period of over sixty days. After the specified period of growth, the plants from the monazite cultures and control were sacrificed and assayed for the absorbed radionuclides, especially for the alpha emitters. The radionuclide content in the plant body did not show a direct relation with the amount of monazite in the cultures. It appears that the contribution from the absorbed radionuclides is much more important in the production of biological damage than external irradiation alone

Correlation between EMS uptake by barley embryos under different treatment conditions and mutation frequency

Uptake of ethyl methanesulphonate and its alkylation in the TCA-insoluble fraction of embryo cell lysates was followed after hull-less barley seeds (karyopses) had been treated with 3H-labelled EMS. The effects of modifying factors such as pre-soaking of seeds in water before mutagen treatment, post-soaking and drying back after treatment were investigated. The effects of the same factors on M1 parameters and chlorophyll mutation frequencies in the M2 were studied in parallel experiments with "cold" EMS. The uptake of EMS on the dry matter basis was greater in the embryo than in the rest of the karyopses. Movement of the mutagen or its hydrolytic products into the embryo from seed endosperm was noted during germination. Enhanced mutation frequencies in M2, when pre-soaked seeds were treated, was partly due to greater uptake of mutagen. The mutagen and its hydrolytic products were leached out of the treated seeds during the post-soaking. This leaching out decreased the effect on M1 parameters but had no significant effect on mutation frequencies in the M2. Drying of seeds after treatment with the mutagen and storage for seven days increased alkylation in the TCA-insoluble fraction and enhanced mutagenic and also the deleterious effects. It is concluded that at least some of th differences in mutation frequencies after various treatment procedures were due to variation in the actual dose of the mutagen ultimately received by the target cells

Iodine incorporated in cell constituents during sensitization to radiation by iodoacetic acid

Iodine atoms are incorporated in bacterial membrane proteins when cells are irradiated in the presence of iodoacetic acid labeled with iodine-131. Such atoms are produced on reaction of iodoacetic acid with the gamma ray-induced hydroxyl radicals in the surrounding medium

Modification of mutagenic efficiency of ethyl methanesulfonate with ethidium bromide, iodoacetamide and sodium fluoride in barley

In order to modify the cellular sieves through which a pre-mutational lesion must pass before it can be realized as a phenotypic change, barley seeds were treated with ethyl methanesulfonate (EMS) in combination with non-toxic concentrations of ethidium bromide (EB), iodoacetamide (IA) and sodium fluoride (NaF). Treatments with EMS, EB, IA and NaF alone served as controls. Pre- and post-treatments with the modifying chemicals were also investigated. Seeds treated with EMS and three different modifiers served as the various controls. The parameters considered were germination, seedling injury, plants with chlorophyll chimeras, mitotic and meiotic aberrations, pollen sterility and seed set in M1 and the frequency of chlorophyll mutations in M2. None of the modifiers at the concentrations used, induced chlorophyll mutations in M2. However, the presence of EB, IA and NaF at the same concentration during treatments with EMS, significantly enhanced the mutagenic effect of the latter. Pre- and post-treatment with IA also significantly enhanced the mutation frequency in M2 seedlings. Pre- and post-treatments of EB and NaF did not bring about significant alterations in the mutation rates