Effects of donor age and contamination level of dioxins and related chemicals on frequency of sister chromatid exchanges in human lymphocytes cultured in vitro

The relationship between dioxin congeners in the breast milk of Vietnamese women and sister chromatid exchange

The aim of this study was to clarify the relationship between dioxin concentrations in breast milk and the sister chromatid exchange (SCE) frequency in women from herbicide-sprayed and non sprayed areas. Blood samples were taken from 21 women with high TCDD (tetrachlorodibenzo-p-dioxin) levels from sprayed areas, 23 women with moderate TCDD levels from sprayed areas, and 19 women from non sprayed areas to determine their SCE frequency. The SCE frequencies for the high and moderate TCDD groups from the sprayed area and for the non sprayed area group were 2.40, 2.19, and 1.48 per cell, respectively. Multiple regression analysis showed that the standardized β values for 1,2,3,6,7,8-hexaCDD (β = 0.60), 1,2,3,4,6,7,8-heptaCDD (β = 0.64), and octaCDD (β = 0.65) were higher than those for TCDD (β = 0.34) and 1,2,3,7,8-pentaCDD (β = 0.42). The adjusted R² value for polyCDDs (R² = 0.38) was higher than that for polyCDD toxic equivalents (TEQ (toxic equivalents); R² = 0.23). This study therefore shows that levels of hexa-, hepta-, and octaCDD, which were previously regarded as being less toxic than TCDD, are closely related to SCE frequency and that the level of dioxin (pg/g lipid) is potentially more useful as an indicator than TEQ value for explaining SCE frequency.

Age-related changes in genomic stability of horses

Recently, the old horse has been proposed as a model to study telomere-dependent senescence, immunosenescence and inflamm-aging. In the present paper, we used 80 Hucul and Anglo-Arabian horses divided into 3 age groups (juvenile, adult, old) to evaluate age-dependent changes at the genomic and DNA level and in cell proliferative potential. The level of positive TUNEL cells (both apoptotic and with DNA fragmentation), oxidative DNA damage (8-oxoG immunostaining), sister chromatid exchange and bleomycin-induced chromatid breaks were significantly increased in the combined old group compared to the combined adult group. We observed a negative correlation between micronuclei formation and age, which may be associated with damaged cells undergoing apoptosis, rather than expressing micronuclei. We were unable to show any significant changes in the nuclear division index value, which reflects the proliferative status of the viable cell fraction during aging. Here, we show that breed-independent and age-associated changes in genomic stability may contribute, at least in part, to the aging process in the horse.

Sex chromosome loss, micronuclei, sister chromatid exchange and aging: a study including 16 centenarians

In the present study we analysed the possible effect of age, sex and smoking on the mean values of micronucleus (MN) and sister chromatid exchange (SCE) frequencies on peripheral blood obtained from 38 subjects ranging in age from 16 to 63 years and 16 centenarians. The mean number of binucleated cells with micronuclei varied in function of age and sex (as demonstrated by the analysis of covariance (F=13.13; P<0.001), particularly evident was the increment observed in women with increasing age (interaction age/sex: F=5.53; P<0.05). Smoking habits had no effects on MN frequency (F=0.36; P>0.05). Sex (F=4.18; P<0.05) and smoking habits (F=14.64; P<0.001) influenced significantly SCE per cell frequencies, but age had no effects on them (F=2.45; P>0.05). The age-associated increase of sex chromosome loss was studied using fluorescence in situ hybridisation (FISH) on interphase nuclei. The loss of Y signals was observed in approximately 10% of interphase cells from the centenarians males, that is six times more often than in the younger control men (approximately 1.6%). The frequency of X signal loss (approximately 1.7%) in young women was similar to that observed in male controls of the same age but the incidence of the X chromosome aneuploidy in centenarian females was appreciably higher (approximately 22%) than that found for the Y chromosome in males. These results were correlated with the data on MN formation and a positive correlation between the percentage of aneuploid cells (FISH) and MN values was observed (r=0.50; P<0.05).

Comparison between "Yusho" patients and healthy Japanese in contamination level of dioxins and related chemicals and frequency of sister chromatid exchanges

Highly toxic organochlorine chemicals such as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (CoPCBs) were determined in the peripheral blood and sebum from the face of 16 "Yusho" patients of about 27 yr after the outbreak of Yusho accident, and 39 healthy Japanese people. The mean total toxic equivalent (TEQ) levels of PCDDs, PCDFs and CoPCBs in the blood were still about seven times higher in Yusho patients than in healthy Japanese at the age of 45 yr and more. The sebum excretion of these chemicals seemed proportional to their blood levels in Yusho patients. These toxic chemicals, however, did not enhance frequencies of sister chromatid exchanges (SCEs) in the control and 7,8-benzoflavone (ANF) treated cultures in Yusho patients. Hence, no significant difference was observed in the mean SCE rates between the Yusho patients and general Japanese people of more than 45 yr of age. In this study, the number of Yusho patients examined is limited, so further large-scale investigations are needed to get more conclusive results concerning the genotoxic potency such as SCE induction.