Radiation and Environmental Biophysics

Steinsträßer, A.

doi: 10.1007/BF01324260pmid: 7220794

Thorotrast is a X-ray contrast medium which has been used in the ears 1930–1950. It is hardly ever eliminated from the body and is stored in the organs of the reticulohistiocytic system (RHS). Since Thorotrast contains all radionuclides of the thorium decay chain, the effect of internal irradiation by these radionuclides can be investigated in the so called “Thorotrast patients”. It is the purpose of this study to determine the radiation dose absorbed by the lymphocytes of the peripheral blood of these persons, and to correlate it with their chromosome aberration rate.

Steinsträßer, A.; Kemmer, W.

doi: 10.1007/BF01324261pmid: 7220795

The biological effect ofα-radiation, which has been examined in this investigation, is the occurence of chromosome aberrations in lymphocytes from the peripheral blood of Thorotrast patients. To set up a dose-effect relationship, it is necessary to estimate the absorbed dose of a single lymphocyte found in a blood sample. Then it would be possible to use chromosome aberrations of lymphocytes from peripheral blood as an indicator for estimating the effective radiation dose. The physical aspects of this investigation have been described in part I of this paper.

Virsik, R.; Harder, D.

doi: 10.1007/BF01324262pmid: 7220796

Acentric fragments induced by low and medium LET radiations and observed in the first mitosis after stimulation were evaluated in the total collective of cells and in the sub-collectives of cells with and without dicentric chromosomes. For 13 MeV electrons and 150 kV X-rays the dose-yield relationships of all acentrics and of excess acentrics (acentrics not associated to dicentrics) were best fitted by linear-quadratic functions. For soft X-rays (10 kV) the dose-yield relationship of excess acentrics was linear. LET-independent proportions of, on the average, 1.03 ± 0.07 acentric fragments associated with 1 dicentric chromosome and of approximately 0.5 acentrics associated with other aberrations of the binary interaction type have been observed. The linear yield components of the excess acentrics are relatively large, and an LET-dependent proportion, decreasing with increasing LET, exists between the linear components of excess acentrics and dicentrics. This may be taken to indicate the presence of acentrics resulting from single “primary lesions”, a result questioning Revell's exchange hypothesis. The evaluated distributions of excess acentrics show overdispersion, which can be explained by the simultaneous formation of two acentrics in certain incomplete exchange aberrations or interstitial deletions.

Langendorff, M.; Stevenson, A.

doi: 10.1007/BF01324263pmid: 7220797

The long-term regeneration of the semeniferous epithelium after irradiation with 15 MeV neutrons was studied in the mouse on a comparative basis; 150 kV X-rays were used as reference-radiation. The mice received total-body exposures at matched doses. The spermatogonial Regeneration Index (RI) was scored from stained paraffin-sections of testes which were obtained after periodic sacrifice. A biphasic pattern of regeneration was recorded. Dose-independent and dose-dependent effects have been indicated. The radiobiological implications are discussed on a cellular basis.

Attri, Arun; Mookerjee, Anjali

doi: 10.1007/BF01324264pmid: 7220798

Y-peak is found to be a function of ionic strength and concentrations of DNA. The Y-peak reveals close dynamic interaction between DNA and solvent system. Electronic transitions responsible for Y-peak are not the same transitions that are responsible for X-peak. Y-peak's electronic transitions are indicative of charge transfer complex formation between DNA and solvent system.γ-irradiation induces hyperchromicity due to strand separation at lower doses. A-T base pairs are first to undergo coiled state as shown byΔTm spread. Strand chopping and saturation of double bonds of the exposed bases by free radicals (H° and OH°) give rise to hypochromic regions at X-peak. Rise in ionic strength and the concentration of DNA has protective effect againstγ-damage. Y-peak is found to be a function of solvent, whereas, X-peak is independent of solvent nature.

Kohlmaier, Gundolf

doi: 10.1007/BF01324265pmid: 6784148