Haematoporphyrin derivative photosensitization and gamma-radiation damage interaction in Chinese hamster ovary fibroblasts

The interaction of haematoporphyrin derivative (HPD) photosensitization and gamma-irradiation was studied with regard to clonogenicity of Chinese hamster ovary (CHO) fibroblasts. Exposure to either treatment alone resulted in shouldered response curves. Exposure to 4.2 Gy gamma-radiation immediately before graded doses of visible light had no effect on the shape of the visible-light survival curve; similarly, exposure to 8.75 kJ/m2 light immediately before graded doses of gamma-radiation had no effect on the shape of the gamma-radiation response curve. These data indicate that damage due to gamma-radiation and HPD photosensitization did not interact, suggesting that the mechanisms of cell killing are different.     

p53-Independent ceramide formation in human glioma cells during gamma-radiation-induced apoptosis

Although the p53 tumor-suppressor gene product plays a critical role in apoptotic cell death induced by DNA-damaging chemotherapeutic agents, human glioma cells with functional p53 were more resistant to gamma-radiation than those with mutant p53. U-87 MG cells with wild-type p53 were resistant to gamma-radiation. U87-W E6 cells that lost functional p53, by the expression of type 16 human papillomavirus E6 oncoprotein, became susceptible to radiation-induced apoptosis. The formation of ceramide by acid sphingomyelinase (A-SMase), but not by neutral sphingomyelinase, was associated with p53-independent apoptosis. SR33557 (2-isopropyl-1-(4-[3-N-methyl-N-(3,4-dimethoxybphenethyl)amino]propyloxy)benzene-sulfonyl) indolizine, an inhibitor of A-SMase, suppressed radiation-induced apoptotic cell death. In contrast, radiation-induced A-SMase activation was blocked in glioma cells with endogenous functional p53. The expression of acid ceramidase was induced by gamma-radiation, and was more evident in cells with functional p53. N-oleoylethanolamine, which is known to inhibit ceramidase activity, unexpectedly downregulated acid ceramidase and accelerated radiation-induced apoptosis in U87-W E6 cells. Moreover, cells with functional p53 could be sensitized to gamma-radiation by N-oleoylethanolamine, which suppressed radiation-induced acid ceramidase expression and then enhanced ceramide formation. Sensitization to gamma-radiation was also observed in U87-MG cells depleted of functional p53 by retroviral expression of small interfering RNA. These results indicate that ceramide may function as a mediator of p53-independent apoptosis in human glioma cells in response to gamma-radiation, and suggest that p53-dependent expression of acid ceramidase and blockage of A-SMase activation play pivotal roles in protection from gamma-radiation of cells with endogenous functional p53.     

The effect of gamma-radiation and desiccation on the viability of the soil bacteria isolated from the alienated zone around the Chernobyl Nuclear Power Plant

Methylobacterium extorquens, M. mesophilicum, and Bacillus subtilis strains were found to be resistant to gamma-radiation, irrespective of whether they were isolated from the alienated zone around the Chernobyl Nuclear Power Plant or outside this zone. The LD90 of Methylobacterium and B. subtilis strains with respect to gamma-radiation was 2.0-3.4 and 3.7-4.4 kGy, respectively, whereas their LD99.99 values were 4.5-6.9 and more than 10 kGy, respectively. The high threshold levels of gamma-radiation for Methylobacterium and B. subtilis imply the efficient functioning of DNA repair systems in these bacteria. Unlike Bacillus polymyxa cells, the cells of M. extorquens, M. mesophilicum, and B. subtilis were also resistant to desiccation. Pseudomonas sp., Nocardia sp., and nocardioform actinomycetes were sensitive to both gamma-radiation and desiccation. Similar results were obtained when the bacteria studied were exposed to hydrogen peroxide and ultraviolet radiation. The results obtained indicate that the bacteria that are resistant to gamma-radiation are also resistant to desiccation, UV radiation, and hydrogen peroxide. The possibility of using simple laboratory tests (such as the determination of bacterial resistance to UV light and desiccation) for the evaluation of bacterial resistance to gamma-radiation is discussed.     

Cytogenetic effects in follicular epithelium of thyroid gland under prolonged exposure to gamma-radiation at low-doses

The forming processes of micronucleated follicular thyrocytes in thyroid gland of mature Wistar rats under exposure to the prolonged low-intensity gamma-radiation with 5 and 50 cGy (dose rates: 25, 400 microGy/h; duration: 55, 80 days) were investigated. The chronic exposure to low-intensity gamma-radiation in both doses invokes the frequency of micronuclated thyrocytes three times higher in comparison with control animals. As a result of the small-sized micronuclei formation prevalence in irradiated group, the average size of micronuclei was 1.4-2 times lower than control values. This phenomenon can be reproduced in model experiments with hemithyroidectomized animals exposured to acute gamma-radiation with 2-4 Gy. The obtained results show high sensitivity of micronucleus test to the early determination of radiation-induced genetic damages in follicular epithelium of thyroid gland.     

Nickel(II) affects poly(ADP-ribose) polymerase-mediated DNA repair in normal and cancer cells

Nickel(II) can be genotoxic, but the mechanism of its genotoxicity is not fully understood and the process of DNA repair may be considered as its potential target. We studied the effect of nickel chloride on the poly(ADP-ribose) polymerase (PARP)-mediated repair of DNA damaged by gamma-radiation and idarubicin with the alkaline comet assay in normal and cancer cells. Our results indicate that nickel chloride at very low, non-cytotoxic concentration of 1 microM can affect PARP-mediated DNA repair of lesions evoked by idarubicin and gamma-radiation. We also suggest that in the quiescent lymphocytes treated with gamma-radiation, nickel(II) could interfere with DNA repair process independent of PARP.     

Cytogenetic effect of 238Pu alpha radiation on the germ cells of male mice

A study was made of the yield of reciprocal translocations in stem spermatogonia of mice exposed to alpha-radiation (238Pu) and whole-body acute and chronic gamma-radiation within a wide range of doses and dose-rates. The frequency of reciprocal translocations induced by a single intraperitoneal administration of plutonium nitrate was relatively low and independent of the dose 1.5-18 months after the effect. The yield of the reciprocal translocations induced by chronic effect of gamma-radiation was appreciably lower than that observed after acute irradiation with the same dose and grew linearly with dose. The RBE of alpha-radiation was 10-20 with respect to chronic effect of gamma-radiation.     

The effect of thioredoxin on the radiosensitivity of bacteria

The ability of Escherichia coli thioredoxin to protect cells from lethal amounts of gamma radiation was tested using bacterial strains engineered to contain different amounts of thioredoxin per cell. Cells grown to late stationary phase demonstrated a decreasing sensitivity to gamma-radiation with increasing amounts of thioredoxin per cell. Exponentially growing cells were equally sensitive to the gamma-radiation regardless of the intracellular concentration of thioredoxin. Cells exhibiting the radiation-resistant phenotype in the stationary phase reverted to the radiation-sensitive phenotype when diluted into fresh growth medium. These results suggest that thioredoxin can protect cells from gamma-radiation under certain metabolic conditions.     

DNA damage in thymocytes of mice under combined acute whole body exposure to cadmium ions and gamma-radiation

The effect of the combined acute whole body exposure to cadmium chloride (0.5 mg Cd2+ per kg body weight of animals) and gamma-radiation (1 Gy) on the DNA damage induction in thymocytes and thymic cellularity of mice was studied. It has been shown that CdCl2 solution injection 0.5 h before irradiation reduces the quantity of single-strand DNA breaks and alkali-labile sites in thymocytes 48 h after injection compared to gamma-radiation action only. The observed effect is accompanied by a sharp decrease of the thymic cellularity compared with the separate effects of both cadmium ions and irradiation, which masks the overall genotoxic effect of combined exposure and gives an illusion of cadmiumL ions radioprotective action. Cadmium chloride injection 24 h before irradiation leads to a significant additive increase in the single-strand DNA breaks and alkali-labile sites number as compared to the separate effects of cadmium ions and irradiation alone. At the same time the decrease in the percentage of DNA tightly bound to proteins (DNA-protein cross-links) was noted in comparison with the action of gamma-radiation only. Statistically significant changes in thymic cellularity compared with separate effects of cadmium ions and irradiation were not found. Thus, our research has shown that under a combined action of cadmium ions and gamma-radiation on thymocytes in mice at the applied doses and exposure schemes the additive effects, rather than antagonism or radioprotective effects are observed.     

Exposure to ionizing radiation decreases hemoglobin binding to erythrocyte membrane

The influence of gamma-radiation at doses 10, 10(2) and 10(3) Gy on binding of hemoglobin to the erythrocyte membrane by inductive--resonance energy transfer in the donor-acceptor pair anthracene-hemoglobin was studied. It was found that binding of hemoglobin to the erythrocyte membrane decreases with increasing dose of gamma-radiation.     

Modifying action of gamma-radiation in mutagenesis of E. coli WU36-10 induced by ethylene oxide, ethyl methanesulfonate and methyl methanesulfonate

The influence of gamma-radiation pre-exposure on ethylene oxide, ethyl methanesulfonate and methyl methanesulfonate mutagenesis in Escherichia coli WU36-10 was studied. Pretreatment with gamma-radiation resulted, in the case of subsequent treatment with ethylene oxide and ethyl methanesulfonate, in a decrease of the frequency of leu+ revertants, and in the case of subsequent treatment with methyl methanesulfonate, in an increase of this mutation frequency.     

Structure-activity studies of quinuclidinone analogs as anti-proliferative agents in lung cancer cell lines

We have synthesized and tested novel quinuclidinone analogs to assay the effects on H1299 lung cancer cell lines alone or with gamma-radiation. We have found two series of quinuclidinone analogs that act as anti-cancer agents. Of these, four interesting analogs significantly decreased cell viability in H1299 lung cancer cell lines. Two derivatives decreased cell proliferation in a dose-dependent fashion alone or in the presence of gamma-radiation. Radiosensitization increased when derivative treatment preceded radiation treatment for both derivatives. These preliminary studies show an evidence for both additive and synergistic cytotoxicity for treatment of lung cancer by these novel quinuclidinone analogs.     

Quantitative characteristics of radiation injury of the spermatogenic epithelium and the rate of its recovery after exposure to fast neutrons and gamma-radiation

The paper submits the results of studies on the kinetics of spermatogenous epithelium cell number after exposure to fast neutrons (60-300 cGy) and gamma-radiation (200-600 cGy). It was shown that a relative decrease in the quantity of spermatocytes is determined by an exponential dose-response curve with D0 of 35 and 120 cGy for neutrons and gamma-radiation respectively. For spermatides and spermatozoa a single D0 value of 20 and 55 cGy was obtained for neutrons and gamma-radiation respectively. As the radiation dose increases the recovery process in the epithelium is substantially decelerated. The equation T1/2 = T1/2(0)e0.0009D well describes the dependence of the half-recovery period T1/2 upon the equivalent dose.     

The diagnostic of membranes' state after exposure of gamma-radiation of small doses

There are the results of experimental research of the change of membranes' conditions under the action of gamma-radiation using the method of following membranes' electroporation of the accurate impulse of the electrical field for the analysis of defects after the action of gamma-radiation. As of the research material the suspension of erythrocytes was used. It was shown that the velocity of decreasing of the erythrocytes in the case of combined action of gamma-radiation and the impulse of the electrical field is more than the sum of such velocities in the case of the action of the factors separately. The method of the electroporation of the accurate impulse of the electircal field is obvious for the practicaland the analytical research of membranes' defects.     

Somatic aberration induction in Tradescantia occidentalis by neutrons, x- and gamma-radiations. I. Dosimetry.

The dosimetry is described for an investigation of the induction of somatic aberrations in Tradescantia occidentalis by substantially mono-energetic neutrons in the energy range 100 keV to 15 MeV, by 200 keV X-rays and cobalt-60 gamma-radiation. Spectrometry was carried out for both neutrons and X-rays. Neutron fluence was measured by uranium fission chambers. Two types of ionization chamber were employed for dose measurement. One chamber was manufactured of CH-plastic and filled with acetylene and the other of graphite and filled with carbon dioxide. Dosimetry for X- and gamma-radiation was by means of lithium fluoride thermoluminescent dosemeters calibrated against a Victoreen ionization chamber.     

Comparative od adaptive response to gamma-radiation and nickel sulfate treatment in human cells

Increased viability of human cells (line rhabdomyosarcoma) to challenge doses of NiSO4 (10(-5)-10(-3) M) was formed when cells were preirradiated with low doses of gamma-radiation (10-14 cGy). Observed adaptive response was similar to radioadaptive response in human fibroblasts, pretreated with low doses of gamma-radiation and challenge dose of the same mutagen. Pretreatment with low concentration of NiSO4 induced in human fibroblasts increased resistance of DNA to the treatment with challenge doses of gamma-radiation and stimulated DNA repair synthesis after treatment with NiSO4 and 4-nitroquinoline-1-oxide. These data confirm the existence of cross-adaptation in the experiments with NiSO4.     

Radiation-induced gastric epithelial apoptosis occurs in the proliferative zone and is regulated by p53, bak, bax, and bcl-2

Unlike the small intestine and colon where gamma-radiation-induced apoptosis has previously been well characterized, the response of murine gastric epithelium to gamma-radiation has not been investigated in detail. Apoptosis was therefore assessed on a cell positional basis in gastric antral and corpus glands from adult male mice following gamma-radiation. Maximum numbers of apoptotic cells were observed in both antrum and corpus at 48 h and at radiation doses greater than 12 Gy. However, the number of apoptotic cells observed in the gastric epithelium was much lower than observed in the small intestine or colon after similar doses of radiation. Hematoxylin and eosin, caspase 3 immunohistochemistry, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling detected similar numbers and cell positional distributions of apoptotic cells, hence hematoxylin and eosin was used for subsequent studies. The highest numbers of apoptotic cells were observed at cell positions 5-6 in the antrum and cell positions 15-18 in the corpus. These distributions coincided with the distributions of PCNA-labeled proliferating cells, but not with the distributions of H(+)-K(+)-ATPase-labeled parietal cells or TFF2-labeled mucous neck cells. Decreased numbers of apoptotic gastric epithelial cells were observed in p53-null, bak-null, and bax-null mice compared with wild-type counterparts 6 and 48 h after 12 Gy gamma-radiation. Significantly increased numbers of apoptotic gastric epithelial cells were observed in bcl-2-null mice compared with wild-type littermates 6 h after 12 Gy gamma-radiation. Radiation therefore induces apoptosis in the proliferative zone of mouse gastric epithelium. This response is regulated by the expression of p53, bak, bax, and bcl-2.     

The level of lymphocytes in the peripheral blood as a criterion of the degree of severity of acute radiation sickness (based on materials from the accident at the Chernobyl Nuclear Power Station)

A study was made of the peripheral blood lymphocyte level as a function of gamma-radiation dose after single gamma-radiation attack resulted from Chernobyl disaster. After the initial drop an average level of lymphocytes was stabilized by day 2 after exposure and no further systematic decrease in the number of lymphocytes occurred. The accuracy of prognostication of the severity of acute radiation sickness, determined by the average lymphocyte level on days 3-6 amounted to as low as 50%. However, when the neighbouring, by the severity, groups of patients were taken into account, the accuracy was 88%.     

Combined action of gamma irradiation and 5-bromodeoxyuridine on human chromosomes

A combined effect has been studied of 5-bromo-deoxyuridine (BDU) and gamma-radiation on human lymphocytes at the G0 stage. BDU is shown to induce chromatid aberrations irrespective of its radiation. The frequency of chromatid aberrations rises with the BDU concentration. BDU modifies the effect of gamma-radiation on human lymphocytes at the G0 stage, increasing the number of chromosome aberrations. BDU slows down the lymphocyte cell cycle.