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)
A progress report of the Marshall Islands nationwide thyroid study: an international cooperative scientific study.
The objective of this report is to present a summary of progress of the Marshall Islands Nationwide Thyroid Study. As well known, the US atomic weapons testing program in the Pacific was conducted primarily between 1946 and 1958 in the Marshall Islands. The nuclear tests resulted in radioactive contamination of a number of atolls and resulted in exposure of Marshallese to undefined levels before our study. Little information has been paid to health consequences among residents of the nearly twenty inhibited atolls except for some information about nodular thyroid disease which was reported on by an US group. In a cooperative agreement with the Government of the Marshall Islands, between 1993 and 1997 we studied the prevalence of both thyroid nodules and thyroid cancer among 4766 Marshallese potentially exposed to radioiodines from bomb test fallout. That group represents more than 65% of the population at risk. We diagnosed 45 thyroid cancers and 1398 benign thyroid nodules. In addition, 23 study participants had been operated on prior to our study for thyroid cancer. Presently, we are developing a database of information to estimate radiation doses and planning a statistical analysis to determine if a dose-response relationship exists. These data will be important for the health promotion of exposed people all over the world including Hiroshima, Nagasaki, Semipalatinsk, Chernobyl and other locations. A timely completion is important for purpose of assisting Marshallese as well as to add the global understanding of radiation induced thyroid cancer. (+info)
Salivary gland cancer in the United States.
The risk of salivary gland cancer (SGC) is increased in atomic bomb survivors and after radiotherapy, but other risk factors are not well established. Some studies have suggested an association of SGC with breast cancer and with exposure to various viruses or UVB radiation. Corroborating evidence of these associations was sought by using population-based registries to examine the demographic distribution of SGC, patterns of secondary primary cancers after SGC, and risk of SGC with AIDS. SGC incidence per 100,000 persons did not change between 1973 and 1992, averaging 1.2 in males and 0.8 in females, with a steep age gradient. To examine the relationship between UVB exposure and SGC, population-based, age-adjusted incidence rates of SGC were plotted against the UVB insolation of each registry site. Regression analysis suggested no correlation between SGC incidence and increasing UVB insolation (beta = 0.10, R2 = 0.08). SGC also did not appear to be associated with second cancers that have been linked to herpes or papilloma viruses or with AIDS [observed/expected (O/E) ratio, <2.8], but all of these conditions are so uncommon that only very large relative risks would have been statistically significant. Women with SGC before age 35 had a statistically nonsignificant elevation in breast cancer risk [O/E, 3.30; 95% confidence interval (CI), 0.66-9.65], and older women had no increased risk of breast cancer. SGC patients were at increased risk for nonsalivary, second-primary oropharyngeal cancers (O/E, 3.27; 95% CI, 2.00-5.05), thyroid cancer (O/E, 3.31; 95% CI, 1.07-7.73), and lung cancer (O/E, 1.86; 95% CI, 1.45-2.35), particularly in patients whose SGC was treated with radiotherapy (O/E, 2.83; 95% CI, 2.06-3.80). In summary, SGC remains rare and does not appear to be associated with AIDS, virally related malignancies, or UVB. Patients who have had SGC, however, should be monitored for subsequent oropharyngeal, thyroid, and lung cancers. (+info)
Two cases of thyroid cancer in a small workforce.
In 1994, in a large parcel depot in the north of England employing 600 staff and 24 electrical and mechanical engineers, two engineers developed papillary cell carcinoma of the thyroid in the same year. A comprehensive review of the literature revealed that ionizing radiation is the only known direct cause of this disease. There was speculation that air filter changing undertaken by the two men affected, shortly after the Chernobyl accident in 1986, may have exposed them to concentrated radioactive fallout. A radiation survey of the parcel depot was undertaken and revealed no evidence of abnormal radioactivity. A total of 27 past and present engineering staff were screened for thyroid cancer. No cases of thyroid cancer were found. Investigation of clusters of rare disease in the occupational setting is indicated mainly in order to address the concerns of the workforce. Nevertheless, investigation is warranted, especially when the aetiology of a disease is poorly understood. It would be prudent for doctors, in whatever speciality, to take an occupational history from individuals who develop thyroid cancer. (+info)
Thyroid abnormality trend over time in northeastern regions of Kazakstan, adjacent to the Semipalatinsk nuclear test site: a case review of pathological findings for 7271 patients.
From 1949 through 1989 nuclear weapons testing carried out by the former Soviet Union at the Semipalatinsk Nuclear Test Site (SNTS) resulted in local fallout affecting the residents of Semipalatinsk, Ust-Kamenogorsk and Pavlodar regions of Kazakstan. To investigate the possible relationship between radiation exposure and thyroid gland abnormalities, we conducted a case review of pathological findings of 7271 urban and rural patients who underwent surgery from 1966-96. Of the 7271 patients, 761 (10.5%) were men, and 6510 (89.5%) were women. The age of the patients varied from 15 to 90 years. Overall, a diagnosis of adenomatous goiter (most frequently multinodular) was found in 1683 patients (63.4%) of Semipalatinsk region, in 2032 patients (68.6%) of Ust-Kamenogorsk region and in 1142 patients (69.0%) of Pavlodar region. In the period 1982-96, as compared before, there was a noticeable increase in the number of cases of Hashimoto's thyroiditis and thyroid cancer. Among histological forms of thyroid cancer, papillary (48.1%) and follicular (33.1%) predominated in the Semipalatinsk region. In later periods (1987-96), an increased frequency of abnormal cases occurred among patients less than 40 years of age, with the highest proportion among patients below 20 in Semipalatinsk and Ust-Kamenogorsk regions of Kazakstan. Given the positive findings of a significant cancer-period interaction, and a significant trend for the proportion of cancer to increase over time, we recommend more detailed and etiologic studies of thyroid disease among populations exposed to radiation fallout from the SNTS in comparison to non-exposed population. (+info)
High incidence of micronuclei in lymphocytes from residents of the area near the Semipalatinsk nuclear explosion test site.
The Semipalatinsk area is highly contaminated with radioactive fallout from 40 years of continuous nuclear testing. The biological effects on human health in this area have not been studied. Significant remaining radioactivities include long-lived radioisotopes of 238,239,400Pu, 137Cs and 90Sr. To evaluate the long-term biological effects of the radioactive fallout, the incidence of micronuclei in lymphocytes from residents of the area was observed. Blood was obtained from 10 residents (5 females and 5 males, aged 47 to 55 years old) from each of the 3 areas of Znamenka, Dolon and Semipalatinsk, which are about 50-150 km from the nuclear explosion test site. For micronucleus assay, PHA-stimulated lymphocytes were cultured for 72 h and cytochalasin B was added at 44 h for detecting binuclear lymphocytes. Five thousand binuclear lymphocytes in each resident were scored. The means of micronucleus counts in 1,000 lymphocytes in residents of Semipalatinsk, Dolon and Znamenka were 16.3, 12.6, and 7.80, respectively, which were higher than those of the normal Japanese persons (4.66). These values were equivalent to the results obtained from 0.187-0.47 Gy of chronic exposure to gamma-rays at a dose rate of 0.02 cGy/min. The high incidence of micronuclei in residents of the Semipalatinsk nuclear test site area was mainly caused by internal exposure rather than external exposure received for the past 40 years. (+info)
A novel syndrome of radiation-associated acute myeloid leukemia involving AML1 gene translocations.
AML1 is a transcriptional activator that is essential for normal hematopoietic development. It is the most frequent target for translocations in acute leukemia. We recently identified 3 patients in whom pancytopenia developed almost 50 years after high-level radiation exposure from nuclear explosions during or after World War II. In all 3 patients, acute myeloid leukemia (AML) eventually developed that had similar characteristics and clinical courses. Cytogenetics from the 3 patients revealed a t(1;21)(p36;q22), a t(18;21)(q21;q22), and a t(19;21)(q13.4;q22). By fluorescent in situ hybridization (FISH), all 3 translocations disrupted the AML1 gene. Two of these AML1 translocations, the t(18;21) and the t(19;21), have not been reported previously. It is possible that the AML1 gene is a target for radiation-induced AML. (Blood. 2000;95:4011-4013) (+info)
Chernobyl fallout and outcome of pregnancy in Finland.
Possible effects of Chernobyl fallout on outcome of pregnancy in Finland were evaluated in a nationwide follow-up study. The outcomes were the rate of live births and stillbirths, pregnancy loss, and induced abortions by municipality. Exposure was assessed based on nationwide surveys of radiation dose rate from the Chernobyl fallout, from both external and internal exposures. Using these measurements, we estimated the monthly dose rate for each of the 455 Finnish municipalities. On average, the dose rate from Chernobyl fallout reached 50 microSv per month in May 1986--a doubling of the natural background radiation. In the most heavily affected area, 4 times the normal background dose rates were recorded. Given the underlying regional differences in live birth, stillbirth, and abortion rates, we used longitudinal analysis comparing changes over time within municipalities. A temporary decline in the live birth rate had already begun before 1986, with no clear relationship to the level of fallout. A statistically significant increase in spontaneous abortions with dose of radiation was observed. No marked changes in induced abortions or stillbirths were observed. The decrease in the live birth rate is probably not a biological effect of radiation, but more likely related to public concerns of the fallout. The effect on spontaneous abortions should be interpreted with caution, because of potential bias or confounding. Further, there is little support in the epidemiologic literature on effects of very low doses of radiation on pregnancy outcome. (+info)