Aging rate after continual low dose irradiation of drosophila strains with apoptosis deregulation

In this article the results of investigations of interrelation between radio-induced apoptosis in larvae nervous system and aging in imago are presented. It was shown that the apoptosis level of larvae nervous ganglion 2.5 folds increased after exposure to ionizing radiation (54 cGy). Irradiation of stocks with higher apoptosis induction sensitivity, bearing mutations of inhibitor apoptosis protein th (allele th1 and th4) and wild type strain Berlin leaded to elevation of activity at all ages and accordingly to decreasing of aging speed. Whereas in stocks with lower apoptosis induction sensitivity (with mutations of genes rpr, grim, hid, dArk and Dcp-1) this effect was not observed. The obtained results suggested that radiation-induced apoptosis could be one of the mechanisms preventing aging.     

Survival of human normal thyroid cells after X-ray irradiation

Normal thyroid cells from 25 individuals treated surgically for malignant or benign thyroid tumour were cultured in vitro and radiation induced cytotoxicity was studied. The mean lethal dose (Do), quasi-threshold (Dq), and extrapolation number (n) of survival curves of actively dividing thyroid cells assayed by colony formation were estimated to be 92.9 +/- 2.8 cGy (rad), 58.1 +/- 6.9 cGy and 2.0 +/- 0.1, respectively (average for 25 individuals +/- standard error). These results suggest that proliferating human thyroid cells are more sensitive to X-rays than most other nonhaematologic mammalian cells in similar assays. Cell survival was not significantly affected by sex, age, disease or exposure to atomic bomb radiation of the cell donor. However, the number of samples currently available is too small for definite conclusions in this regard.     

Membrane fluidity of microsomal and thymocyte membranes after X-ray and UV irradiation

A brief literature review shows that ionizing radiation in biological membranes and in pure lipid membranes causes malondialdehyde formation, indicating lipid peroxidation processes. With respect to membrane fluidization by ionizing radiation, in pure lipid membranes rigidization effects are always reported, whereas contradictory results exist for biological membranes. Starting from the assumption that membrane proteins at least partly compensate for radiation effects leading to a rigidization of membrane lipid regions, pig liver microsomes, as a representative protein-rich intracellular membrane system, were irradiated with X-rays or UV-C with doses up to 120 Gy at a dose rate of 0.67 Gy min^–1 and up to 0.73 J cm^–2 at an exposure rate of 16.2 mJ cm^–2 min^–1, respectively. For both irradiation types a weak but significant positive correlation between malondialdehyde formation and membrane fluidity is revealed throughout the applied dose ranges. We conclude that the membraneous protein lipid interface increases its fluidity under radiation conditions. Also, thymocyte ghosts showed an increased fluidity after X-ray irradiation. Fluidity measurements were performed by the pyrene excimer method.     

Changes in the mitochondrial ATPase activity of liver cells after X-ray irradiation

24 h following total-body X-irradiation of rats with a dose of 7 Gy the growth of the ATPase activity diminished, with the addition of bicarbonate, by 2 times in the preparations of mitochondria and submitochondrial particles, and by 1.5 times, in preparations of a soluble enzyme. No changes were noted in the electrophoretic motility of soluble ATPase.     

On the relationship between the frequency of two types of lethal-mutation and X-ray doses in drosophila

The dose-frequency relationship for each of 2 types of lethal mutations, fractional- and whole-lethal, was obtained using X-rays on Drosophila melanogaster. The results show that fractional-lethal mutations are induced by X-rays, and also that the proportion of fractional-lethal mutations in the total of mutations tends to decrease with increasing doses, namely, 61% at 0 R, 47% at 500 R, 37% at 1000 R and 20% at 2000 R. The same tendency is observed with visible mutations.In order to consider the problems related to the above results, the relationship between the true frequency and the observed frequency of the induced lethal mutations is discussed, taking into consideration the existence of the ontensible whole-lethal and the ontensible normal.     

Changes of SOD-like substances in mouse organs after low-dose X-ray irradiation.

We demonstrated that low-dose irradiation with 50 cGy of X-ray induces in vivo production of superoxide dismutase (SOD)-like substances and accelerates antioxidant activity. To elucidate the defense mechanism against X-ray radiation, we examined which components among these SOD-like substances, such as SOD, vitamin C and celuroplasmin, are produced by low-dose irradiation. Our study revealed that SOD-like specific activity hardly involved SOD-like substances other than SOD. Moreover, it is suggested that low-dose irradiation induced synthesis and production of SOD itself, leading to elevation of SOD-specific activity.     

Reactions of the intracellular NADpool in the yeastS. cerevisiae after UV-C- or X-ray irradiation

Summary The reaction of the intracellular NADpool after irradiation of cells either with UV-C light or with X-rays was studied in four different strains of the yeastS. cerevisiae. We found neither in wildtype strains nor in radiation sensitive mutants remarkable changes in the NADpool within 2 h after irradiation. Preculture of cells in medium enriched with nicotinic acid, a precursor of NAD, influenced the intracellular NAD concentration only to a small extend in all strains, but enhanced the radiation resistance against UV-C significantly in one rad6 mutant strain. The uptake of NAD and NAC by all strains before and after irradiation with UV-C and X-ray was tested also. NAD generally is taken up by the cells to a very low extent before and after irradiation without irradiation-dose dependency. NAC is taken up by all strains before and after irradiation. Only the rad6 mutant exhibited an irradiation-dose dependent NAC-uptake after UV-C irradiation.Abbreviations ADPRT ADPribosyltransferase - NAC nicotinic acid - YEPG yeast extract-peptone-glucose medium     

Development of rat embryos after prolonged irradiation of ovocytes at the stage of immature follicles

It was shown that the prolonged low-dose irradiation (up to 0.6 Gy) of the immature ovocytes of young rats (21-28 days old) caused delay of development of preimplantation embryos after fertilization of ovicells.     

Behavioral reactions of rats and the contents of neurospecific proteins in their brain after single X-ray irradiation

We studied the behavior of rats in an open-field test and the contents of neurospecific proteins [neural cell adhesion molecule (NCAM) and glial fibrillary acidic protein (GFAP)] in the brain cortex, hippocampus, striatum, midbrain, cerebellum, andpons Varolii 1, 12, 24, 120, and 168 h after a single X-ray irradiation session (dose of 0.25 Gy). Within the postirradiation period, manifestations of the behavioral activity of the animals were mostly suppressed, and the parameters related to the emotional state of the animals were influenced to a greater extent. The dynamics of the NCAM and GFAP contents were complex and dissimilar in the brain structures under study, but it was possible to observe some general regularities. Within early periods of time, 12 h after irradiation, the NCAM content increased in the cortex, hippocampus, and cerebellum. In these structures, it reached approximately 220, 170, and 150%, respectively, as compared with the control, while it dropped to about 40% in thepons Varolii. Changes in the GFAP content reached their maximum 24 h after irradiation; this index dropped to 29, 44, 34, and 67% in the striatum,pons Varolii, midbrain, and cerebellum, respectively, while it increased to 380% in the hippocampus. Later time intervals were characterized by smoother changes in the contents of the above neurospecific proteins. Seven days after irradiation, the NCAM content did not differ from initial values in the striatum and cerebellum and was higher than the control in the neocortex, hippocampus, and midbrain. Within this period, the GFAP level in the cerebellum and midbrain was relatively normalized, but it increased in the hippocampus and decreased in the pons and striatum. Therefore, the greatest postirradiation shifts in the NCAM and GFAP levels were observed in the structures of the limbic system, and this can be correlated with the data on testing the rats in an open field.     

Lipids of neocortex after X-ray irradiation of the rat head at a dose of 200 Gy

X-ray irradiation at a dose of 200 Gy with local exposure of the rat head induced the change of the lipid content in the neocortex tissue. The amount of phosphatidylinositol was decreased, the amount of free fatty acids, diglycerols, sphingomyelin was increased, and the amount of cholesterol had a growth trend in 2 h after X-ray exposition. The results testify in favor of participation of phosphatidylinositol- and sphingomyelin-relating signal systems and cholesterol in early stages of the cerebral radiation syndrome. We suggest that the change of the lipid content in early periods after the effect of a super-high dose of X-ray irradiation indicates the lipid dependence in the elimination of motion damages and the restoration of the functions of nerve cells. Effects on the lipid metabolism in the nerve tissue are promising for correcting the cerebral radiation syndrome.     

Leupeptin-sensitive proteases involved in cell survival after X-ray irradiation in human RSa cells

Proteases have received attention as important cellular components responsible for stress response in human cells. However, little is known about the role of proteases in the early steps of cell response after X-ray irradiation. In the present study, we first searched for proteases whose activity levels are changed soon after X-ray irradiation in human RSa cells with a high sensitivity to X-ray cell-killing. RSa cells showed an increased level of fibrinolytic protease activity within 10 min after irradiation with X-ray (up to 3 Gy). The induced protease activity was proved to be inhibited by leupeptin. We next examined whether this protease inducibility is related to the X-ray susceptibility of cells. Treatment of RSa cells with leupeptin prior to X-ray irradiation resulted in lowered colony survival and an increased ratio of G(2)/M-arrested cells and apoptotic cells. These results suggest that leupeptin-sensitive proteases are involved in the resistance of human RSa cells to X-ray cell-killing.     

Changes in the transaldolase activity in the liver, spleen and bone marrow of rats after total X-ray irradiation

The paper deals with changes in the activity of transaldolase in tissues of the liver, spleen and bone marrow of rats 4.24 h and on the 3 d, 7th, 18th, 30th, 45th, and 60th day after total X-ray irradiation in a dose of 600 R. The ionizing irradiation causes a stable inhibition of the enzyme activity in All tissues. The observed changes are homogeneous in their direction but have their own peculiarities for each tissue. Differences in the degree and extent of the enzyme activity changes at various stages of the X-ray lesion development in the tissues under study may be explained by their different sensitivity to the penetrating radiation.     

Lack of synergistic effect between X-ray and UV irradiation on the frequency of chromosome aberrations in PHA-stimulated human lymphocytes in the G1 stage.

PHA-stimulated human lymphocytes in the G1 stage were irradiated with UV radiation and X-rays, and the cells were analyzed for chromosomal aberrations in the first mitotic division. The frequency of dicentric chromosomes after single X-irradiation in the G1 stage was about twice the yield in the G0 stage. No increase in the yield of dicentrics was observed after combined irradiation with UV and X-rays. This is contrary to the finding for G0 lymphocytes, where a 2-fold increase of chromosome aberrations was observed. UV irradiation of G1 lymphocytes induced chromatid-type aberrations whereas no significant yield of dicentric chromosomes was observed. This is in agreement with previous findings in Chinese hamster cells in the G1 stage [7]. Irradiation of G0 lymphocytes with UV radiation induce a low frequency of dicentric chromosomes. Thus, the present data indicate that the ratio between chromosome-type and chromatid-type aberrations is different in the G1 and G0 stages in human lymphocytes irradiated with UV radiation.     

Changes in the ultraviolet fluorescence and the size of Ehrlich ascites carcinoma cells in the 1st hours after X-ray irradiation

Using the Ehrlich ascite carcinoma cells, a decrease in ultraviolet fluorescence (UVF) was demonstrated one hour following a 10 Gy X-irradiation, and an increase in UVF 5 hours following the same irradiation. The same changes were demonstrated for cell turbidity. Association between the optical changes and those in cell radius and membrane protein state is discussed.