[en] Letter to the editor. (author)

[en] Both kidneys in mature female pigs, ca. 45 weeks old were irradiated with single doses of 7.8-14.0 Gy of ⁶⁰Co γ-rays. Two weeks after irradiation effective renal plasma flow (ERPF) and in particular the glomerular filtration rate (GFR) was increased, followed by a pronounced, dose-dependent decline in renal haemodynamics. Minimal functional levels were observed 8-12 weeks after irradiation. Function then somewhat recovered. There was a significant inverse relationship between mean values of GFR and ERPF, determined at 4-24 weeks after irradiation, and radiation dose. After a dose of 7.8 Gy reduction in ERPF was greater than that for GFR. However, at higher doses both parameters were reduced to an equal extent. The resulting slope of the dose-effect curve for impaired renal function versus dose was significantly steeper for GFR than that for ERPF (p<0.001). There was a significant reduction in erythrocyte count, haematocrit and haemoglobin levels within 6-8 weeks of irradiation, characterized as a normochromic normocytic anaemia. There were no marked changes in plasma renin levels. (author)

[en] Radiation-resistant L5178Y-R(LY-R) and radiation-sensitive L5178Y-S(LY-S) murine lymphoma cells were X-irradiated and their free Ca²⁺ concentration examined with Fura-2 in Ca²⁺-free salt solution. The release of free Ca²⁺ from intracellular stores was linear between 10 and 60 min after irradiation (1-5 Gy X-rays) and higher in LY-S than in LY-R cells. Pre-treatment with 2mM benzamide (Bz) further increased the concentration of free Ca²⁺ in LY-S cells but not in LY-R cells. In contrast, LY-S cells had previously been found to be radiosensitized by continuous 2mM Bz treatment (Szumiel et al. 1948b). Thus, there was a parallel effect of Bz on survival and on the increase in free Ca²⁺ concentration in LY cells. The rates of Ca²⁺ release after irradiation with 1-5 Gy of X-rays with or without Bz treatment were inversely related to the respective surviving fractions of LY cells. (author)

[en] Split-dose studies were performed on four human tumour cell lines of widely differing radiosensitivity to characterize the relationship between cellular recovery and irradiation dose. Cellular recovery at any given dose was greatest in the most radiosensitive cell line, suggesting that increased radiosensitivity does not result from decreased recovery capacity. The results suggest that cells with steep acute radiation survival curves and which show little split-dose recovery may not be recovery deficient. Using such cells in attempts to correlate recovery with the underlying molecular processes of radiation damage repair could lead to misleading results. (Author)

[en] Single crystals of guanine hydrochloride dihydrate, in which the guanine base is protonated at N7, were X-irradiated at 20K, 65K and 150K. Study with K-band ESR and ENDOR techniques indicated at least four radical species to appear in the temperature range 20-300K. The data indicated this product to be trapped in four different conformations which coalesced into the most stable form as the sample temperature was raised to ca. 180K. From these results, and those from two other systems containing N7-protonated guanine bases, reaction mechanisms are proposed to account for formation of the products. (Author)

[en] The authors evaluated the relationship between the repair of DNA single- and double-strand breaks and cellular radiosensitivity in proliferating vs. quiescent cells of the mouse mammary tumor lines 66 and 67 in vitro, using the technique of filter elution at pH 12.2, pH 7.2 and pH 9.6 In these lines, quiescent (Q; unfed plateau-phase) cells are more radiosensitive than are proliferating(P) cells. At doses of 4-6 Gy, both 66 and 67 Q cells repair single-strand breaks (ssb) with kinetics similar to those of P cells. (author)

[en] The time-resolved light-scattering changes of aqueous, aerated solutions of poly-C, poly-U and poly-A at pH 7.8, following pulse irradiation, have been studied as indices of strand break formation. With doses of 4-24 Gy/pulse a number of kinetically distinct components have been detected. These observations support a proposal that the rate-limiting step of major strand breakage for these polynucleotides, in the presence of oxygen, is a base peroxyl radical-mediated abstraction of a H-atom from an adjacent sugar moiety (Bothe et al. 1986), with the resulting sugar peroxyl radicals then leading to strand break formation at a rate equivalent to that for loss of the initial, fast LSI components. These latter processes are attributed to strand breaks arising from the direct interaction of OH radical with the polynucleotide sugar phosphate backbone. (author)

[en] Induction and repair of DNA strand breaks was studied in X-irradiated proliferating and quiescent CHO cells using the alkaline unwinding technique. The results showed that induction of strand breaks is identical for both states of proliferation, whereas repair is different. (author)

[en] A single dose of 8 or 20 Gy ⁶⁰Co γ-rays was given to C3H male mice at 4 months of age. Degenerative changes in the cardiac muscle due to brain irradiation were observed first at 6 months after irradiation, and became progressively more severe at 12-24 months. The changes seen at the ultrastructural level included myofibrillolysis, the presence of lysosomal-like bodies and interstitial fibrosis. (author)

[en] After exposure to radiation in the presence of different oxygen concentrations, the OER values were determined for human fibroblast cell strains with differing intrinsic GSH content, and cells depleted of GSH to different extent by treatment with BSO. The yield of DNA single-strand breaks was used as the measure of radiosensitivity. The K values were found to be related specifically to the GSH concentration in the cell nuclei. A good agreement was found between the experimental observations and the prediction of a variant of the competition model in which a second type of damage, not influenced by oxygen, was included. (author)