The antibody-producing cell count of rats exposed to polymeric 239Pu

In experiments with Wistar rats a study was made of the content of antibody-forming cells (AFC) in the spleen at remote times (3 to 12 months) after intravenous injection of 239Pu(IV) in doses of 166, 55, and 18 kBq/kg body mass. The doses absorbed in the central and peripheral immunity organs were defined. Pronounced spleen hypoplasia and profound inhibition of humoral immunity were displayed 1 year after the injection of a small amount of the radionuclide. AFC deficiency in animals was amounted to 11-32 per cent throughout the entire period of observation.     

Efficacy of polymeric 239Pu removal by liposome-encapsulated pentacin

Liposome-incapsulated pentacine (DTPA) removes intracellular polimeric 239Pu and colloidal hydroxide of polymeric 239Pu from a rat body in the amounts 2- and 4 times, respectively, exceeding those eliminated by free DTPA. However the amount of 239Pu removed decreases sharply with increasing 239Pu hydrolysation and polymerization. It is concluded that the effectiveness of 239Pu removal depends on the physico-chemical status of the radionuclide and its interaction with the biosubstrate rather than on the amount of DTPA entering the cells.     

The subcellular distribution of 238Pu and 239Pu in primary cultures of rat hepatocytes

The subcellular distribution of 238Pu and 239Pu after incubation of primary cultures of rat hepatocytes with the citrate complex of these metals was studied, and the results were compared with data from in vivo experiments. As in vivo, the lysosomes are the principal organelles in which 238Pu and 239Pu are accumulated. In contrast to in vivo studies, 239Pu is also detectable on the pericellular membranes and in the cell nuclei, where it is predominantly bound to a high-molecular-weight component. The percentage of the total cellular 239Pu which can be recovered in the cell nuclei increased with incubation time from 10% at 1 h to nearly 30% at 5 h. Plutonium-238, an isotope with 270-fold higher specific activity than 239Pu, showed no association with the nuclei. The membrane-bound fraction of 239Pu, as determined using the exogenous chelator diethylenetriaminepentaacetic acid decreased from 30% at shorter incubation times to 15% at longer incubation periods. After incubation with 238Pu the membrane fraction and the cytosolic fraction contained higher concentrations of the radionuclide than after incubation with 239Pu.     

Frequency and distribution of mitomycin C-induced structural chromosome aberrations in lymphocytes from non-Hodgkin lymphoma patients

Lymphocytes from 15 untreated patients with non-Hodgkin lymphoma (NHL) and 15 controls were exposed to 0.08 micrograms/ml mitomycin C, and the frequency and distribution of structural chromosome aberrations (chromatid and chromosome gaps, breaks, and exchanges) were analyzed in 100 mitoses per subject. The mean frequencies of aberrant cells, and gap, break, and gap + break events were 8.7, 0.9, 9.7, and 10.6 in the NHL group and 11.6, 1.1, 12.7, and 13.8 in the control group. None of the differences between the two groups was significant (P greater than 0.05). The distribution of breakpoints was nonrandom (P less than 0.001) in both groups, with a particularly marked excess of breaks in 9q11. The other breakage-prone bands were 1q11 and 1q21 in the NHL group and 1p11, 1q11, 2q31, and 16q11 in the control group. None of these hot spots coincided with any of the 60 bands known to be involved in primary chromosome abnormalities in NHL.     

Differences in the uptake of transferrin bound 239Pu and 59Fe into multicellular spheroids of hepatocytes from adult male rats

Hepatocytes were cultured as monolayers and multicellular spheroids, respectively. The uptake of both transferrin-bound metals, iron and plutonium, differed significantly between these two culture systems. The uptake into the multicellular spheroids for plutonium was about 30 times greater, and for iron about 4 times greater, than in monolayer-cultured hepatocytes, which is not a consequence of proliferation and/or de-differentiation of the hepatocytes in the multicellular spheroid culture system. A comparison of the iron and plutonium uptake showed that plutonium was delivered to the cells to an 8-fold greater extent than iron if the hepatocytes were cultured as spheroids. Additionally, the binding of plutonium was not inhibited by preincubation of the spheroids with the iron-transferrin complex. Therefore, we propose that there are two different binding sites for iron and plutonium on hepatocyte membranes.     

mFISH analysis of chromosome aberrations in workers occupationally exposed to mixed radiation

We performed a study on the presence of chromosome aberrations in a cohort of plutonium workers of the Mayak production association (PA) with a mean age of 73.3 ± 7.2 years to see whether by multi-color fluorescence in situ hybridization (mFISH) translocation analysis can discriminate individuals who underwent occupational exposure with internal and/or external exposure to ionizing radiation 40 years ago. All Mayak PA workers were occupationally exposed to chronic internal alpha-radiation due to incorporated plutonium-239 and/or to external gamma-rays. First, we obtained the translocation yield in control individuals by mFISH to chromosome spreads of age-matched individuals and obtained background values that are similar to previously published values of an international study (Sigurdson et al. in Mutat Res 652:112–121, 2008). Workers who had absorbed a total dose of >0.5 Gy external gamma-rays to the red bone marrow (RBM) displayed a significantly higher frequency of stable chromosome aberrations relative to a group of workers exposed to <0.5 Gy gamma-rays total absorbed RBM dose. Thus, the translocation frequency may be considered to be a biological marker of external radiation exposure even years after the exposure. In a group of workers who were internally exposed and had incorporated plutonium-239 at a body burden >1.48 kBq, mFISH revealed a considerable number of cells with complex chromosomal rearrangements. Linear associations were observed for translocation yield with the absorbed RBM dose from external gamma-rays as well as for complex chromosomal rearrangements with the plutonium-239 body burden.     

Enhanced frequency of chromosome aberrations in workers occupationally exposed to diagnostic X-rays

To estimate the level of radiation exposure of personnel handling diagnostic X-ray machines, the yield of chromosomal aberrations was analysed in peripheral blood lymphocyte cultures. These occupationally exposed individuals showed higher frequencies of dicentrics as well as acentrics than normal controls. Absorbed radiation doses calculated by extrapolating reference in vitro dose-response curve for dicentrics ranged between 0.13 and 0.17 Gy. This implies exposure beyond the permissible limit of 0.05 Gy/year for the whole body. However, no obvious trend of increased aberrations as a function of either duration of employment or age was noticed. The increase in the aberration yields in this personnel underscores the need of adopting measures to avoid or minimise such overexposure.     

Frequency of chromosome aberrations in residents of the Semipalatinsk Oblast]

Cytogenetic analysis of the population of the Beskaragai district of the Semipalatinsk oblast adjacent to the territory of the nuclear test site was conducted by means of an ecological genetic questionnaire and cytogenetic examination of metaphase chromosomes. An increase in the total mutation level in the region was observed. The frequency of chromosome aberrations among the population of the Beskaragai district (3.2%) was statistically significantly (about 1.5 times) higher than the background levels in the clear regions (from 1 to 2%). Furthermore, the frequency of aberrations in adolescents was comparable with that in the adults. The spectrum of chromosome aberrations pointed to a significant contribution of radiation component to the mutagenesis.     

Significance of structural chromosome aberrations in human sperm: analysis of induced aberrations

Summary A significant increase in the incidence of structural chromosome anomalies has been observed in the sperm of patients treated with radio and/or chemotherapy for different types of cancer when analyzed by the interspecific fertilization of hamster eggs. The analysis of these aberrations shows that while in controls only 9.4% of structural abnormalities are of the stable type, in treated patients this figure increases to 39.3%, thus indicating that the anomalies have not been produced during the fertilization of the hamster egg. However, it is possible that part, or even most, of the breaks appear as a result of a reduced repair capacity of sperm chromosomes in the cytoplasm of the hamster egg.     

A twin study of structural chromosome aberrations in lymphocytes

Structural chromosome aberrations were analyzed in peripheral lymphocytes of eight monozygotic (MZ) and seven dizygotic (DZ) pairs of male twins. There was no significant intrapair difference in the variance of aberration frequencies among the MZ and DZ twins. Thus, there was no evidence of a major genetic influence on the development of structural chromosome aberrations. Although a genetic component could not be excluded, it was concluded that any chromosome aberrations observed were probably due mainly to environmental influences.     

Detection of structural chromosome aberrations in immunophenotyped mitoses.

The recently developed MAC (morphology-antibody-chromosome) method allows simultaneous immunophenotype and karyotype analysis in the same cell. To date, application of this new method has been hampered by the poor quality of chromosome banding. In this paper, we describe a modified simultaneous immunofluorescence and Q-banding technique, as well as a new combination of immunohistochemical and fluorescent R-banding methods. By further modifying the MAC method, we were able not only to achieve unequivocal results with weakly expressed antigens but also to improve the quality of the banding techniques, so that even structural chromosome abnormalities were well defined.     

Importance of detecting numerical versus structural chromosome aberrations

The aim is to review briefly the key questions related to aneuploidy/polyploidy and to compare the advantages and disadvantages of the in vitro micronucleus test to assess aneuploidy/polyploidy in vitro. The key questions that will be addressed, concern the importance of polyploidy for health, and cancer in particular, the mechanisms leading to aneuploidy and polyploidy, and the survival of aneuploid/polyploid cells.The recently recognised contribution of numerical chromosome changes to carcinogenesis triggered the development and the implementation of tests specifically aiming at the detection of aneugens in the test battery for mutagenicity and carcinogenicity. The validation of the in vitro micronucleus test in combination with the identification of in vitro divided cells with the cytokinesis-block methodology and of centromeres with pancentromeric or chromosome specific centromeric probes fluorescence in situ hybridisation (FISH) provides a sensitive, easy to score and powerful test which allows assessment of cell proliferation, the discrimination between chromosome breaks, chromosome loss and chromosome non-disjunction and polyploidy. Moreover, classic histology permits the estimation of necrosis and apoptosis on the same slide. The cytokinesis-blocked micronucleus assay could be considered as a multi-endpoint test for genotoxic responses to clastogens/aneugens. This methodology has also shown to be capable of identifying threshold values for the induction of chromosome loss and/or non-disjunction by microtubule inhibitors, data which are particularly important for risk calculations. Similar approaches were conducted in vivo on bone marrow in mice and rats (except for identification of chromosome non-disjunction), and are in development for gut in mice.     

Radiation- and chemical-induced structural chromosome aberrations in human spermatozoa

An apoptotic phenotype induced by oxygen radicals or Bax expression has been observed in Saccharomyces cerevisiae yeast cells by electron and fluorescence microscopy. In this work, we analyzed DNA content and cellular morphology of S. cerevisiae after H(2)O(2) or UV treatment by TdT-mediated dUTP nick end labeling (TUNEL)-test and flow cytofluorimetry. A TUNEL-positive phenotype was observed in both cases, on the same samples a dose-dependent increase in the sub-G(1) population was pointed out by flow cytometry. Sub-G(1) cells were isolated by flow sorting and analyzed by electron microscopy. This population showed condensed chromatin in the nucleus and cell shrinking. This paper reports the first evidence of apoptosis in yeast cells induced by DNA damage after UV irradiation.     

Persistence of chromosome aberrations in mice acutely exposed to 56Fe+26 ions

Space exploration has the potential to yield exciting and significant discoveries, but it also brings with it many risks for flight crews. Among the less well studied of these are health effects from space radiation, which includes the highly charged, energetic particles of elements with high atomic numbers that constitute the galactic cosmic rays. In this study, we demonstrated that 1 Gy iron ions acutely administered to mice in vivo resulted in highly complex chromosome damage. We found that all types of aberrations, including dicentrics as well as translocations, insertions and acentric fragments, disappear rapidly with time after exposure, probably as a result of the death of heavily damaged cells, i.e. cells with multiple and/or complex aberrations. In addition, numerous cells have apparently simple exchanges as their only aberrations, and these cells appear to survive longer than heavily damaged cells. Eight weeks after exposure, the frequency of cells showing cytogenetic damage was reduced to less than 20% of the levels evident at 1 week, with little further decline apparent over an additional 8 weeks. These results indicate that exposure to 1 Gy iron ions produces heavily damaged cells, a small fraction of which appear to be capable of surviving for relatively long periods. The health effects of exposure to high-LET radiation in humans on prolonged space flights should remain a matter of concern.     

Spontaneous chromosome aberrations in the oogenesis of laboratory rats]

Cytological preparations were made by Tarkovsky's method from 2335 rat oocytes obtained after an induced superodulation. The chromosomes could be counted exactly in 861 oocytes. In 797 oocytes (92.7%) euploidy (metaphase II with 21 chromosomes) and in 64 oocytes (7.5%) aneuploidy was found. 60 oocytes were hypoploid, but only 4 oocytes (0.4%) were hyperploid (with 22 chromosomes). Hypoploidy can often be due to the presence of artefacts. Probably the rate of spontaneous aneuploidy in rat oogenesis is about 0.8%, this being significantly lower than the rate of spontaneous aneuploidy in mice oogenesis.     

No increase in chromosome aberrations in lymphocytes from workers exposed to nitrogen fertilisers.

The putative genetic risk of people occupationally exposed to nitrogen fertilisers was studied using the structural chromosome aberration assay in peripheral blood lymphocytes. The exposed group included 23 subjects working at complex and mixed fertiliser plants. The percent of aberrant cells (Ab.C %) and break to cell ratio (B/C) were 0.95% and 0.01 respectively. The matched control group (20 subjects) was found to have 0.80% Ab.C and a B/C ratio of 0.0085. The results show a lack of detectable genetic damage in exposed people using this cytogenetic approach.     

Cytogenetic effects of alpha-irradiation due to incorporated 239Pu

Intravenous injection of plutonium dioxide with 1-2 microns particle sizes in amount of 92.5, 46.3 and 23.2 kBq/kg of body mass increased the yield of chromosome aberrations in bone marrow cells of rats by 3.7, 2.3 and 1.7 times, correspondingly, in comparison with the spontaneous level. The model of chromosome aberration dependence on dose of radionuclide was developed based on the experimental results.