The cytogenetic indication of irradiation in persons exposed to the action of the factors in the Chernobyl accident]

363 men who have been working under conditions of additional irradiation in terms from few hours to some months were cytogenetically examined to define individual irradiation. In 111 men with the known dose of irradiation (5-140 cGy), the results of cytogenetic evaluation indicated, as a rule, a less intensive irradiation than physical dosimetry. This could be caused by elimination of chromosome aberrations, individual sensitivity, peculiar irradiation situation, or in some cases by incorrect evaluation of dose. In 252 men with the unknown dose of irradiation a tentative level was determined as based on frequency of metaphases with chromosome type aberrations. According to the study the absorbed dose was below 25 cGy in 209 cases, 26-50 cGy in 39 cases, and reached 51-90 cGy in 4 cases.     

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     

Effect of acyclovir on the radiation-induced micronuclei and cell death

Treatment of HeLa cells with 0.1 microM Acyclovir [9-(2-hydroxyethoxymethyl)guanine] (ACV) before exposure to 0, 0.25, 0.5, 1, 2 and 3 Gy of gamma-radiation resulted in a dose-dependent decline in the growth kinetics and cell proliferation indices at 20, 30 and 40 h post-irradiation when compared with the PBS+irradiation group. These results were reflected in the cell survival, which declined in a dose-dependent manner and the surviving fraction of cells was significantly lower in ACV+irradiation group than that of PBS+irradiation group. The effect of ACV+1 Gy irradiation was almost similar to PBS+3 Gy irradiation suggesting an enhancement of the radiation effect by ACV pretreatment. The frequency of micronuclei increased in a dose-dependent manner at all the post-irradiation time periods in both PBS+irradiation and ACV+irradiation group and it was significantly elevated in the latter when compared with the former group. The dose-response for both groups was linear. The surviving fraction of HeLa cells declined with the increasing MN frequency and a close linear quadratic correlation between cell survival and micronuclei-induction was observed.     

Effect of the helium-neon laser on cell ultrastructure and proliferation of the epithelium of the duodenal mucosa

Irradiation of the rat duodenal wall with helium-neon laser at a wave length of 0.63 microns for 1,3 and 5 min and irradiation energy density of 6.78, 20.34 and 33.9 J/cm2, respectively, produced ultrastructural changes in enterocytes and connective tissues. These changes consisted in intracellular edema and occurrence of cellular branches in basal portions and vesicles in apical portions of enterocytes. The changes increased as the irradiation energy was raised. Laser irradiation caused a significant rise of proliferative activity.     

Role of the competitive microbial flora in the radiation-induced enhancement of ochratoxin production by Aspergillus alutaceus var. alutaceus NRRL 3174.

The radiation sensitivity and the toxigenic potential of conidiospores of the fungus Aspergillus alutaceus var. alutaceus were determined after irradiation with 60Co gamma rays and high-energy electrons. Over the pH range of 3.6 to 8.8, the doses required for a 1 log10 reduction in viability based on the exponential portion of the survival curve ranged from 0.21 to 0.22 kGy, with extrapolation numbers (extrapolation of the exponential portion of the survival curve to zero dose) of 1.01 to 1.33, for electron irradiation, and from 0.24 to 0.27 kGy, with extrapolation numbers of 2.26 to 5.13, for gamma irradiation. Nonsterile barley that was inoculated with conidia of the fungus and then irradiated with either electrons or gamma rays and incubated for prolonged periods at 28 degrees C and at a moisture content of 25% produced less ochratoxin A with increasing doses of radiation. Inoculation of barley following irradiation resulted in enhanced ochratoxin levels compared with unirradiated controls. In these experiments, inoculation with 10(2) spores per g produced greater radiation-induced enhancement than inoculation with 10(5) spores per g. There was no radiation-induced enhancement when the barley was surface sterilized by chemical means prior to irradiation. These results are consistent with the hypothesis that a reduction in the competing microbial flora by irradiation is responsible for the enhanced mycotoxin production observed when nonsterile barley is inoculated with the toxigenic fungus A. alutaceus var. alutaceus after irradiation.     

Effects of electrons and neutrons on the synthesis of RNA in resistant and sensitive strains of the slime-mould Dictyostelium discoideum and the modifying effect of caffeine.

RNA synthesis was investigated after irradiation in resistant and sensitive lines of the slime-mould Dictyostelium discoideum. When 3H adenine was used as a precursor to RNA, incorporation increased after irradiation in the resistant WT line but not in the sensitive line (gammas-13). The extent of RNA synthesis after irradiation was correlated with the shoulder width on the survival curve of the resistant line. When this was reduced by irradiating with neutrons, or treatment with caffeine RNA synthesis was also reduced. No preferential synthesis of one RNA species occurred; there was increased labelling in all RNA species after irradiation. Sucrose gradient analysis of ribosomal RNA extracted from irradiated cells and free of messenger RNA revealed no apparent difference in composition from that extracted from unirradiated cells. Increased RNA synthesis after irradiation may form part of the recovery processin the resistant cells.     

The dynamics of cytogenetic anomalies output in seedling merysteme at the chronic irradiation of seeds

The dynamics of chromosomal aberrations in seedling root merysteme is explored in various terms of irradiation of two genotype corn dry seeds. The effects of chronic irradiation with low rate dose, with acute and with combined irradiation are explored in the different terms of seed storage. It is shown that the output of chromosomal aberrations and of the efficiency of irradiation (1/Gy) change depending on the accumulated dose of chronic irradiation and for both genotypes are described by unmonotonous functions. Efficiency of acute irradiation changes the dependence on the terms of seed storage. The efficiency of chronic irradiation considerably exceeds the efficiency of acute irradiation. Antagonistic effect of combined irradiation dry seeds of one of genotypes is marked.     

Role of the competitive microbial flora in the radiation-induced enhancement of ochratoxin production by Aspergillus alutaceus var. alutaceus NRRL 3174.

The radiation sensitivity and the toxigenic potential of conidiospores of the fungus Aspergillus alutaceus var. alutaceus were determined after irradiation with 60Co gamma rays and high-energy electrons. Over the pH range of 3.6 to 8.8, the doses required for a 1 log10 reduction in viability based on the exponential portion of the survival curve ranged from 0.21 to 0.22 kGy, with extrapolation numbers (extrapolation of the exponential portion of the survival curve to zero dose) of 1.01 to 1.33, for electron irradiation, and from 0.24 to 0.27 kGy, with extrapolation numbers of 2.26 to 5.13, for gamma irradiation. Nonsterile barley that was inoculated with conidia of the fungus and then irradiated with either electrons or gamma rays and incubated for prolonged periods at 28 degrees C and at a moisture content of 25% produced less ochratoxin A with increasing doses of radiation. Inoculation of barley following irradiation resulted in enhanced ochratoxin levels compared with unirradiated controls. In these experiments, inoculation with 10(2) spores per g produced greater radiation-induced enhancement than inoculation with 10(5) spores per g. There was no radiation-induced enhancement when the barley was surface sterilized by chemical means prior to irradiation. These results are consistent with the hypothesis that a reduction in the competing microbial flora by irradiation is responsible for the enhanced mycotoxin production observed when nonsterile barley is inoculated with the toxigenic fungus A. alutaceus var. alutaceus after irradiation.     

Teniposide (VM-26) treatment enhances the radiation-induced micronuclei in the bone marrow of mouse

The effect of Teniposide (VM-26) pretreatment was studied on the micronuclei induction in the bone marrow of mice exposed to 0, 0.5, 1, 2 and 3 Gy of gamma radiation at 12, 24 and 36 h post-irradiation. Administration of 0.05 mg/kg body weight of VM-26 to mice before irradiation resulted in the significant enhancement of micronucleated polychromatic erythrocytes (MPCE) at 12, 24 and 36 h post-irradiation. Highest elevation in the frequency of MPCE was observed in VM-26+irradiation group after exposure to 0.5 Gy when compared to concurrent DDW+irradiation group. This increase was two fold higher in VM-26+irradiation group at 12 and 24 h, while it was 3 fold higher at 36 h post-irradiation compared to DDW+irradiation group. The peak frequency of MPCE was observed at 24 h post-irradiation in both groups, which declined thereafter. The frequency of micronucleated normochromatic erythrocytes (MNCE) increased in a dose dependent manner in both DDW+irradiation and VM-26+irradiation groups. However, the frequency of MNCE was significantly higher in the latter when compared to the former group. The frequency of MNCE exhibited a continuous elevation up to 36 h post-irradiation in both DDW+irradiation and VM-26+irradiation groups. Treatment of mice with teniposide before irradiation resulted in a significant decline in the PCE/NCE ratio compared to DDW+irradiation group. The PCE/NCE ratio continued to decline up to 36 h post-irradiation in both the groups. The dose response for MPCE and PCE/NCE ratio was linear quadratic, while it was linear for MNCE.     

Regulation of lipid oxidation and structural state of the nuclear membrane after the irradiation of tumor-bearing animals

Changes of antioxidative activity (AOA), lipid composition and microviscosity of different membrane regions in tumor cell nuclei and in the liver of tumor-host with Ehrlich ascite carcinoma (EAC) after irradiation were studied. On the basis of the obtained data the analysis of the control system of lipid oxidation in the membrane was carried out. This control system involves a relationship between AOA changes, lipid composition, their oxidative ability and the nuclear membrane structure. It was shown that after irradiation the control system in the nuclei of tumor cells had the same state as before irradiation and was different from the normal one. The control system in the nuclei of tumor-host liver after irradiation starts to work in a regime which is characteristic of irradiated cells. It was shown that the principle difference in the control system functioning in tumor and tumor-host nuclei disappeared after irradiation.     

Effect of gamma-irradiation on the molecular properties of myoglobin

To elucidate the effect of gamma-irradiation on the molecular properties of myoglobin, the secondary and tertiary structures, as well as the molecular weight size of the protein, were examined after irradiation at various irradiation doses. Gamma-irradiation of myoglobin solutions caused the disruption of the ordered structure of the protein molecules, as well as degradation, crosslinking, and aggregation of the polypeptide chains. A SDSPAGE study indicated that irradiation caused initial fragmentation of the proteins and subsequent aggregation, due to cross-linking of the protein molecules. The effect of irradiation on the protein was more significant at lower protein concentrations. Ascorbic acid protected against the degradation and aggregation of proteins by scavenging oxygen radicals that are produced by irradiation. A circular dichroism study showed that an increase of the irradiation decreased the alpha-helical content of myoglobin with a concurrent increase of the aperiodic structure content. Fluorescence spectroscopy indicated that irradiation increased the emission intensity that was excited at 280 nm.     

The genome instability in the descendants of the Chinese hamster of the cells, irradiated by the low dose and by various intensities of gamma-radiation

The V-79 Chinese hamster cells were irradiated by gamma-rays in dose of 0.5 Gy at powers of doses 0.48 Gy/min (an acute irradiation) and 0.0485 MGy/min (a prolonged irradiation). The acute and prolonged irradiation in a dose of 0.5 Gy enlarges frequency of the appearance of micronucleus (MN). Subsequent cultivation of the irradiated cells during 20 generations enlarges frequency of MN, and for prolonged an irradiation the boosted frequency of MN, is saved during 40-60 generations. After an acute irradiation the number of MN starts to reduce after 20 doublings.     

Impact of Pulsed Nd:YAG Laser Irradiation on the Growth and Mortality of the Biofilm Forming Marine Bacterium Pseudoalteromonas carrageenovora

The impact of pulsed laser irradiation on the marine biofilm forming bacterium Pseudoalteromonas carrageenovora was investigated in the laboratory by monitoring mortality and the post-irradiation growth pattern. The impact of laser irradiation on bacterial mortality increased with the duration of irradiation. Laser irradiation at 532 nm (0.1 J cm m 2 ) for 15 min resulted in a 53% cell mortality immediately after irradiation. However, the impact after a period of 5 h (delayed impact) was more severe. The growth pattern of irradiated samples showed a prolonged lag phase compared to the reference, due to a reduction in total viable counts (TVC) in the irradiated samples. Nucleic acid staining is suggested to be a promising technique for monitoring laser inflicted bacterial mortality. Thus, the results suggest that laser irradiation could be considered as an alternative technique to reduce the number of biofilm forming bacteria and thereby biofilm formation on hard surfaces.     

Effect of gemcitabine on the tolerance of the lung to single-dose irradiation in C3H mice.

In an early phase II trial combining gemcitabine (dFdC) and radiotherapy for lung carcinomas, severe pulmonary toxicity was observed. In this framework, the objective of this study was to investigate the effect of dFdC on the tolerance of the lungs of C3H mice to single-dose irradiation. The thoraxes of C3H mice were irradiated with a graded single dose of 8 MV photons; dFdC (150 mg/kg) or saline (control animals) was administered i.p. 3 or 48 h prior to irradiation. Lung tolerance was assessed by the LD50 at 7-180 days after irradiation. For irradiation alone, the LD50 reached 14.45 Gy (95% CI 13.33-15.66 Gy). With a 3-h interval between administration of dFdC and irradiation, the LD50 reached 13.29 (95% CI 12.26-14.44 Gy); the corresponding value with a 48-h interval reached 13.01 Gy (95% CI 11.92-14.20 Gy). Our data also suggested a possible effect of dFdC on radiation-induced esophageal toxicity. dFdC has a minimal effect on lung tolerance after single-dose irradiation. However, a proper phase I-II trial should be designed before any routine use of combined dFdC and radiotherapy in the thoracic region.     

Short- and long-term effects of whole-body irradiation with fission neutrons or X rays on the thymus in CBA mice

Young adult (6 weeks old) female CBA mice were exposed to whole-body irradiation with either 2.5-Gy fast fission neutrons of 1 MeV mean energy or 6.0-Gy 300 kVp X rays at centerline dose rates of 0.1 and 0.3 Gy/min, respectively. The weight of spleen and animal and the weight, cellularity, and histological structure of the thymus were studied at different times after irradiation. Thymic recovery after whole-body irradiation showed a biphasic pattern with minima at 5 and 21 days after irradiation and peaks of regeneration at Days 14 and 42 after X irradiation or at Days 14 and 70 after neutron irradiation. After the second phase of recovery, a marked decrease in relative thymus weight and cellularity was observed, which lasted up to at least 250 days after irradiation. Splenic recovery showed a monophasic pattern with an overshoot on Day 21 after irradiation. After neutron irradiation a late decrease in relative spleen and animal weight was observed. The observed late effects on thymus and spleen weight and thymus cellularity are discussed in terms of a persistent defect in the bone marrow.     

Radiation-induced developmental abnormalities of the brain ventricles in the golden hamster

The dysontogenesis of the brain ventricle system of golden hamster fetuses was studied after X-ray irradiation of the mother at different stages of pregnancy. Groups of gravid hamsters were irradiated with a single dose (200 R) on either the 6th, 8th, 10th or 12th day of gestation. The fetuses were removed 1 day before birth. The most prominent finding in all stages of development was the dilatation of the brain ventricles. In addition to hydrocephalus, hematocephaly was also found in some cases. Furthermore, a widening of the central canal of the spinal cord with hemorrhagic content could sometimes be observed. Ependymal ectopies and subependymal rosettes occurred more frequently when irradiation was given in the late fetal period. The experimental findings demonstrate that after irradiation of the mother animal, malformation of the brain may be produced during the whole intrauterine period of development. The pattern and extent of malformation depend not only upon the dose of irradiation but also upon the stage of development at which irradiation was given.     

Synergetic effect of freeze-drying and gamma irradiation on the mechanical properties of human cancellous bone

Freeze-drying and irradiation are common process used by tissue banks to preserve and sterilize bone allografts. Freeze dried irradiated bone is known to be more brittle. Whether bone brittleness is due to irradiation alone, temperature during irradiation or to a synergetic effect of the freeze-drying-irradiation process was not yet assessed. Using a left–right femoral head symmetry model, 822 compression tests were performed to assess the influence of sequences of a 25 kGy irradiation with and without freeze-drying compared to the unprocessed counterpart. Irradiation of frozen bone did not cause any significant reduction in ultimate strength, stiffness and work to failure. The addition of the freeze-drying process before or after irradiation resulted in a mean drop of 35 and 31% in ultimate strength, 14 and 37% in stiffness and 46 and 37% in work to failure. Unlike irradiation at room temperature, irradiation under dry ice of solvent–detergent treated bone seemed to have no detrimental effect on mechanical properties of cancellous bone. Freeze-drying bone without irradiation had no influence on mechanical parameters, but the addition of irradiation to the freeze-drying step or the reverse sequence showed a detrimental effect and supports the idea of a negative synergetic effect of both procedures. These findings may have important implications for bone banking.     

Reaction of a population of HeLa tumor cells in the stationary stage of growth to irradiation at different rates

The early stages of a repopulation process of HeLa cells under the action of irradiation 5 Gy dose and an influence of a preliminary 0.1 Gy dose irradiation at that process were investigated. As it was shown the fraction of cells with a great proliferation potential appeared in one day after lethal 5 Gy dose irradiation of the resting HeLa cells. If the other irradiation regime was used: 0.1 Gy dose plus 4.9 Gy dose in 3 min after the first action, the part of cells with a great proliferation potential became considerably less.     

Effects of irradiation on the reproductive ability of Zonitoides arboreus, a snail pest of orchid roots

The effect of irradiation on the reproductive ability of the orchid snail, Zonitoides arboreus, a serious pest of potted orchids in Hawaii, was investigated. Weekly egg production averaged between 0.8 and 1.9 over a 9–wk period for snails not exposed to irradiation, and egg hatch averaged 61%. In comparison to untreated controls, irradiation of snails at the lowest dose tested (34–37 Gy) reduced egg production and egg hatch by 63% and 94%, respectively over a 9–wk period. None of the snails treated with levels of irradiation ≥ 69 Gy produced viable eggs. This is the first study measuring the effect of ionising irradiation on a terrestrial snail or slug species using sterilising doses. Overall, the results show that the reproductive ability of this snail species is affected by irradiation in a similar manner as for Biomphalaria glabrata, an aquatic snail for which the effects of irradiation have been studied in detail.     

Characterization of altered absorptive and secretory functions in the rat colon after abdominal irradiation: comparison with the effects of total-body irradiation.

The aim of this work was to determine the alterations in the absorptive and secretory functions of the rat colon after abdominal irradiation and to compare the effects of abdominal and whole-body irradiation. Rats received an abdominal irradiation with 8 to 12 Gy and were studied at 1, 4 and 7 days after exposure. Water and electrolyte absorption was measured in vivo by insertion of an agarose cylinder into the colons of anesthetized rats. In vitro measurements of potential difference, short-circuit current and tissue conductance were performed in Ussing chambers under basal and agonist-stimulated conditions. Most of the changes appeared at 4 days after abdominal irradiation. At this time, a decrease in water and electrolyte absorption in the colon was observed for radiation doses > or = 9 Gy. The response to secretagogues (VIP, 5-HT and forskolin) was attenuated after 10 and 12 Gy. Epithelial integrity, estimated by potential difference and tissue conductance, was altered from 1 to 7 days after 12 Gy abdominal irradiation. These results show that the function of the colon was affected by abdominal irradiation. Comparison with earlier results for total-body irradiation demonstrated a difference of 2 Gy in the radiation dose needed to induce changes in the function of the colon.