Sister-chromatid exchanges induced in swine lymphocytes by chronic oral doses of dimethylbenzanthracene

Immune response impairment, genotoxicity and morphological transformation induced by Taenia solium metacestode

In chronic helminthic infections such as cysticercosis, where the parasites live for years, profound modulation of the host immune response has been reported. To evaluate the genotoxicity of a drug used to treat cysticercosis, we observed the occurrence of genetic damage in cultured lymphocytes from cysticercotic swine and patients who had not been exposed to the drug. The human lymphocytes also showed a slower proliferation. These data suggested that the disease itself was promoting genetic damage in host lymphocytes which, in part, could explain the retardation of the lymphocyte proliferation observed in cysticercotic patients. Pigs infected with Taenia solium cysticerci showed an increased lymphocyte proliferation for 6-8 weeks post infection, followed by an impaired proliferation after this period. Significant induction of sister-chromatid exchanges was also observed in lymphocytes from infected pigs after the 6th week post infection. Additionally, it was found that a factor secreted by the cysticerci morphologically transformed primary fibroblasts in culture. The results strongly suggest that the parasite produces genetic instability in the host cells, which could result in immunosuppression and malignant transformation of target cells.

Sister-chromatid exchange: second report of the Gene-Tox Program

This paper reviews the ability of a number of chemicals to induce sister-chromatid exchanges (SCEs). The SCE data for animal cells in vivo and in vitro, and human cells in vitro are presented in 6 tables according to their relative effectiveness. A seventh table summarizes what is known about the effects of specific chemicals on SCEs for humans exposed in vivo. The data support the concept that SCEs provide a useful indication of exposure, although the mechanism and biological significance of SCE formation still remain to be elucidated.

Individual and strain differences in patterns of long-term persistence of urethane-induced sister chromatid exchanges (SCEs) in mouse lymphocytes and their relation to carcinogen susceptibility

Using an improved microculture method, we investigated how the patterns of persistence of urethane-induced SCEs in lymphocytes differ among individuals and strains of mice (the ddY and C57BL strains), and we attempted to speculate on their relationship to carcinogen susceptibility. After a single intraperitoneal (i.p.) injection of 900 mg/kg of body weight of urethane into ten female mice each for the two strains, blood samples for the SCE analysis were collected from the tail vein at ten times during the 180 posttreatment days for each individual. Immediately after the treatment, SCE values increased to about three to four times the spontaneous values in all of the animals tested and then fell gradually. (The difference from spontaneous values was statistically significant until 120 days after the treatment.) Even after 180 days, however, some "outlier" cells with exceptionally high SCEs (greater than 20) persisted. Although there was some difference in average SCEs between the ddY and C57BL strains, the magnitude of the difference was too small to account for the difference between the strains in the incidence of urethane-induced malignancy. Also, when autopsy data at the 200th posttreatment day were matched individually with the data of SCE values within each strain, it was difficult to predict the individual risk of the occurrence of lung adenoma or other tumors from the relative difference in SCE values.

Chromosomal aberrations and sister-chromatid exchanges in swine

Frequencies of chromosomal aberrations and sister-chromatid exchanges (SCEs) in peripheral blood lymphocytes were investigated in 56 swine from 3 herds (I, breeding sows; II and III, fattening pigs). The mean frequencies of aberrant cells (AB.C.) were 3.58 +/- 1.59%, 2.10 +/- 1.52% and 6.20 +/- 3.21%, respectively. The mean numbers of SCEs per cell were 7.73 +/- 0.86, 6.51 +/- 0.89 and 7.06 +/- 1.47, respectively. A significant difference was found between the herds under study with regard to the number of aberrant cells but not the SCE frequency. In a parallel study, the presence of aflatoxin B1, polychlorinated biphenyls (PCB), dichlorodiphenyltrichloromethylmethane (DDT), lindane, mercury, lead and cadmium in the environment of fattening pigs was investigated. The total exposure to mutagens of pigs from herd III with a mean frequency of 6.2% AB.C., was markedly higher than that of herd II with the mean frequency of 2.1% AB.C.

Accumulation of SCEs in lymphocytes during chronic ingestion of a mutagen

Studies in 2 large-animal species have shown that continued ingestion of a mutagen increases sister chromatid exchanges (SCE) in circulating lymphocytes at rates directly related to the accumulated dose but differing between species. Groups of 3 pigs received daily oral doses of 0, 1.25, or 2.50 mg/kg body weight of 7,12-dimethylbenzanthracene (DMBA) for 160 consecutive da; similar groups of sheep received 0, 0.625, or 1.25 mg/kg daily for up to 114 da. Lymphocytes taken at 3-wk intervals from pigs and every 2 wk from sheep were cultured, and 25 randomly selected second-division metaphases from each culture were scored for SCE. Swine lymphocytes had elevated numbers of SCE at the earliest sampling times after DMBA feeding was begun. Sister chromatid exchanges continued to increase gradually among pigs consuming 1.25 mg/kg/da for 160 da whereas those on 2.5 mg/kg tended to plateau at approximately 2.5 times their pretreatment level after some 80 da. Sheep treated with comparable levels of DMBA (1.25 mg/kg) exhibited a much more rapid rise in SCE than pigs; within 40 da their SCEs were at 4 times the control level and animals were exhibiting toxicity symptoms. Low-dose sheep also showed a rapid initial increase but plateaued at about 2.5 times the control level beyond 40 da.