Baseline Frequencies of Spontaneous Chromosome Aberrations, Sister Chromatid Exchanges and Micronuclei in Human Newborns.

Abstract

A cytogenetic monitoring programme on human new borns carried out from 1983-1987 to find out the incidence of constitutional chromosome anomalies also included studies to obtain baseline data on spontaneous chromosomal aberrations (CA), sister chromatid exchanges (SCEs) and micronuclei (MN) from cord blood samples in limited number of human neonates. The results are compared with data obtained in our laboratory on these cytogenetic end points from adult peripheral blood lymphocytes. The micronuclei data was obtained from adult lymphocytes by the cytokinesis blocked lymphocyte assay, by Cytochalasin B. 120 cord blood samples analysed gave a mean frequency of 0.0052 chromatid breaks/metaphase and 0.0059 chromatid gaps/metaphase. Only one dicentric chromosome was noticed in the 12, 000 cells analysed. No statistically significant difference was noticed between male and female new borns in the spontaneous CA frequency. 20 adult blood samples analysed after 48 hr culture and 10 adult blood samples analysed after 72 hr culture gave mean frequency of 0.0085, 0.013 chromatid breaks/metaphase and 0.01414, 0.019 chromatid gaps/metaphase respectively. A large statistically significant elevation in SCE/cell was found when adult blood samples were compared to cord blood samples (the difference 1.94 SCE/cell, P<0.001 by simple ‘t’ test) the mean frequency of SCEs observed in cord blood samples and adult samples being 5.56±0.21 and 7.496±0.21 SCE/cell respectively. The frequency of micronuclei in cord blood lymphocytes was found to be 0-1.5/1000 cells, 1-3/1000 cells, 2-5/1000 cells in 48, 72 and 96 hr cultures respectively. Adult blood lymphocytes exhibited a micronuclei frequency of 0.0123±0.001 MN/CB cell. The low incidence reported here of all three cytogenetic end points may possibly reflect the influence of high folate levels in cord bloods on spontaneous chromosomal damage.