Loading...
(1/256) Genome reduction in a hemiclonal frog Rana esculenta from radioactively contaminated areas.

A decrease in genome size was found in the hemiclonal hybridogenetic frog Rana esculenta (R. ridibunda x R. lessonae) from areas of radioactive contamination that resulted from the Chernobyl fallout. This genome reduction was of up to 4% and correlated with the background level of gamma-radiation (linear regression corresponded on average to -0.4% per doubling of radiation level). No change in genome size was observed in the coexisting parental species R. lessonae. There was no correlation between genome size and body mass in R. esculenta froglets, which have metamorphosed in the year of the study. The hemiclonal forms may become a suitable object for study on biological significance of individual DNA sequences (and of genome size as a whole) because mutant animals with deletions in a specified genome can arise after a low radiation dose. The proneness to genetic damage makes such forms also a prospective bioindicator of radioactive (and possibly other mutagenic) pollution with the effects of genetic damage conveniently and rapidly monitored by DNA flow cytometry.  (+info)

(2/256) Prostatic intraepithelial neoplasia and apoptosis in benign prostatic hyperplasia before and after the Chernobyl accident in Ukraine.

The prevalence of prostatic intraepithelial neoplasia (PIN) in men who underwent surgery for benign prostatic hyperplasia (BPH) before and after the Chernobyl nuclear accident was studied. BPH samples were obtained by adenomectomy from 45 patients operated in 1984 before the accident (Group I), and 47 patients from the low contaminated Kiev City (Group II) and 76 from high contaminated area (Group III) operated between 1996 and 1998. Their BPH samples were examined histologically and immunohistochemically. The incidences of prostatic intraepithelial neoplasia (PIN) and high grade PIN (HGPIN) were 15.5 and 11.1% in Group I, 29.8 and 14.9% in Grpoup II, and 35. 5 and 19.7% in Group III. The difference between the incidences of PIN in Group I and III is significant (p<0.02). There was increased apoptosis in areas of PIN in Group II and III as compared to Group I (p<0.001). Since apoptosis has been shown to be associated with ionizing radiation and it is now found to be associated with PIN in patients diagnosed after the Chernobyl nuclear accident, this suggests that long-term low dose internal ionizing radiation potentially may cause prostate cancer.  (+info)

(3/256) Juvenile hypothyroidism among two populations exposed to radioiodine.

We found an epidemic of juvenile hypothyroidism among a population of self-defined "downwinders" living near the Hanford nuclear facility located in southeast Washington State. The episode followed massive releases of 131I. Self-reported data on 60 cases of juvenile hypothyroidism (<20 years of age) among a group of 801 Hanford downwinders are presented, as well as data concerning the thyroid status of approximately 160,000 children exposed to radioiodine before 10 years of age as a result of the 26 April 1986 Chernobyl explosion in the former Soviet Union. These children were residents of five regions near Chernobyl. They were examined by standardized screening protocols over a period of 5 years from 1991 to 1996. They are a well-defined group of 10 samples. Fifty-six cases of hypothyroidism were found among boys and 92 among girls. Body burdens of 137Cs have been correlated with hypothyroidism prevalence rates. On the other hand, the group of juvenile (<20 years of age) Hanford downwinders is not a representative sample. Most of the 77 cases of juvenile hypothyroidism in the Hanford group were diagnosed from 1945 to 1970. However, the ratio of reported cases to the county population under 20 years of age is roughly correlated with officially estimated mean levels of cumulative thyroid 131I uptake in these counties, providing evidence that juvenile hypothyroidism was associated with radioiodine exposures. Because even subtle hypothyroidism may be of clinical significance in childhood and can be treated, it may be useful to screen for the condition in populations exposed to radioiodine fallout. Although radiation exposure is associated with hypothyroidism, its excess among fallout-exposed children has not been previously quantified.  (+info)

(4/256) Carotenoids, sexual signals and immune function in barn swallows from Chernobyl.

Carotenoids have been hypothesized to facilitate immune function and act as free-radical scavengers, thereby minimizing the frequency of mutations. Populations of animals exposed to higher levels of free radicals are thus expected to demonstrate reduced sexual coloration if use of carotenoids for free-radical scavenging is traded against use for sexual signals. The intensity of carotenoid-based sexual coloration was compared among three populations of barn swallows Hirundo rustica differing in exposure to radioactive contamination. Lymphocyte and immunoglobulin concentrations were depressed, whereas the heterophil:lymphocyte ratio, an index of stress, was enhanced in Chernobyl swallows compared to controls. Spleen size was reduced in Chernobyl compared to that of two control populations. Sexual coloration varied significantly among populations, with the size of a secondary sexual character (the length of the outermost tail feathers) being positively related to coloration in the two control populations, but not in the Chernobyl population. Thus the positive covariation between coloration and sexual signalling disappeared in the population subject to intense radioactive contamination. These findings suggest that the reliable signalling function of secondary sexual characters breaks down under extreme environmental conditions, no longer providing reliable information about the health status of males.  (+info)

(5/256) Childhood exposure due to the Chernobyl accident and thyroid cancer risk in contaminated areas of Belarus and Russia.

The thyroid dose due to 131I releases during the Chernobyl accident was reconstructed for children and adolescents in two cities and 2122 settlements in Belarus, and in one city and 607 settlements in the Bryansk district of the Russian Federation. In this area, which covers the two high contamination spots in the two countries following the accident, data on thyroid cancer incidence during the period 1991-1995 were analysed in the light of possible increased thyroid surveillance. Two methods of risk analysis were applied: Poisson regression with results for the single settlements and Monte Carlo (MC) calculations for results in larger areas or sub-populations. Best estimates of both methods agreed well. Poisson regression estimates of 95% confidence intervals (CIs) were considerably smaller than the MC results, which allow for extra-Poisson uncertainties due to reconstructed doses and the background thyroid cancer incidence. The excess absolute risk per unit thyroid dose (EARPD) for the birth cohort 1971-1985 by the MC analysis was 2.1 (95% CI 1.0-4.5) cases per 10(4) person-year Gy. The point estimate is lower by a factor of two than that observed in a pooled study of thyroid cancer risk after external exposures. The excess relative risk per unit thyroid dose was 23 (95% CI 8.6-82) Gy(-1). No significant differences between countries or cities and rural areas were found. In the lowest dose group of the settlements with an average thyroid dose of 0.05 Gy the risk was statistically significantly elevated. Dependencies of risks on age-at-exposure and on gender are consistent with findings after external exposures.  (+info)

(6/256) The transcription coactivator HTIF1 and a related protein are fused to the RET receptor tyrosine kinase in childhood papillary thyroid carcinomas.

Children exposed to radioactive iodine as a consequence of the Chernobyl reactor accident have an increased risk of papillary thyroid carcinomas (PTC). The predominant molecular lesions in these tumors are rearrangements of the RET receptor tyrosine kinase (tk). Here we report on two novel types of RET rearrangement, PTC6 and 7, and describe the fusion products and the ret fused gene (rfg) proteins. Like the other rfg proteins identified so far they are ubiquitously expressed, not membrane-bound and contain coiled coil domains required for constitutive activation of the ret tk domain. In the PTC6 rearrangement the ret tk domain is fused to the aminoterminal part of the human transcription intermediary factor htif 1. In the PTC7 rearrangement the ret tk domain is fused to a novel protein that is strongly related to htif1. Like htif1 it contains a RBCC motif (ring finger, B boxes, coiled coil domain) located in the aminoterminal part and a phd finger and a bromodomain in the carboxyterminal part. Htif1 and related proteins are transcription coactivators for nuclear receptors, thus participating in controlling cellular development, differentiation and homeostasis. This is the first report on their involvement in human thyroid carcinogenesis.  (+info)

(7/256) Specific p53 gene mutations in urinary bladder epithelium after the Chernobyl accident.

After the Chernobyl accident, the incidence of urinary bladder cancers in the Ukraine population increased gradually from 26.2 to 36.1 per 100,000 between 1986 and 1996. Urinary bladder epithelium biopsied from 45 male patients with benign prostatic hyperplasia living in radiocontaminated areas of Ukraine demonstrated frequent severe urothelial dysplasia, carcinoma in situ, and a single invasive transitional cell carcinoma, combined with irradiation cystitis in 42 cases (93%). No neoplastic changes (carcinoma in situ or transitional cell carcinoma) were found in 10 patients from clean areas (areas without radiocontamination). DNA was extracted from the altered urothelium of selected paraffin-embedded specimens that showed obviously abnormal histology (3 cases) or intense p53 immunoreactivity (15 cases), and mutational analysis of exons 5-8 of the p53 gene was performed by PCR-single-strand conformational polymorphism analysis followed by DNA sequencing. Nine of 17 patients (53%) had one or more mutations in the altered urothelium. Urine sediment samples were also collected from the patients at 4-27 months after biopsy and analyzed by PCR-single-strand conformational polymorphism analysis or yeast functional assay, and identical or additional p53 mutations were found in four of five cases. Interestingly, a relative hot spot at codon 245 was found in five of nine (56%) cases with mutations, and 11 of the 13 mutations determined (73%) were G:C to A:T transitions at CpG dinucleotides, reported to be relatively infrequent (approximately 18%) in human urinary bladder cancers. Therefore, the frequent and specific p53 mutations found in these male patients may alert us to a future elevated occurrence of urinary bladder cancers in the radiocontaminated areas.  (+info)

(8/256) Biodosimetry results obtained by various cytogenetic methods and electron spin resonance spectrometry among inhabitants of a radionuclide contaminated area around the siberian chemical plant (Tomsk-7).

On April 6, 1993, near the town of Tomsk (Russia) there was an accident at the Siberian Chemical Plant (SCP) which resulted in extensive contamination of an area of 250 km(2) to the north of SCP with long-lived radionuclides such as (239)Pu, (137)Cs and (90)Sr. Cytogenetic methods and electron spin resonance (ESR) spectrometry of tooth enamel were used to estimate the radiation doses received by the population. The ESR signal intensity and the chromosomal aberration frequency in lymphocytes of the tooth donors showed a good correlation. The data showed that 15% of the inhabitants of the Samus settlement received a radiation dose >90 cGy. The exceptions were results of an examination of fishermen, where ESR gave high values (80-210 cGy) but both the chromosome assay and the cytokinesis block micronucleus method gave lower ones (8-52 cGy). A large increase in chromosome damage was observed in people born between 1961 and 1969. It was found that during these years several serious accidents at the Siberian Chemical Plant had occurred causing radiation pollution of the area. The number of cells with chromosome aberrations was significantly less among the people arriving in Samus after 1980. We found good correlations between the level of carotene consumption and a decrease in frequency of both micronuclei in binucleated lymphocytes (r = 0.68, P < 0.01) and chromatid aberrations (r = 0.61, P < 0.01) among the inhabitants. We also examined the inhabitants of Samus for opisthorchis infection, which was present in 30% of the population. The Samus inhabitants affected by Opisthorchis felineus showed significantly increased levels of micronuclei in binucleated lymphocytes and chromatid aberrations as compared with the controls.  (+info)