Sister-chromatid exchanges in lymphocytes from infants with Down's syndrome

Sister-chromatid exchange (SCE) frequencies were studied in blood lymphocytes from 12 patients (3 females and 9 males) with Down's syndrome (DS). The mean frequency of SCE per metaphase for the patients (both sexes) was 9.2 +/- 0.8 which was significantly higher (P less than 0.01) than the mean SCE value (5.1 +/- 0.2) scored for 16 healthy infants (8 females and 8 males). A significant increase in the mean frequency of SCE in 12 parents of infants with DS (8.7 +/- 0.9 SCE/cell) was noticeable when compared with 20 parents of normal infants (6.3 +/- 0.1 SCE/cell). Increases in cellular division with reduction in their replication were also observed in patients with DS. Treatment with mitomycin C (0.05 micrograms/ml), hycanthone (0.1 micrograms/ml) and gamma-radiation (0.1 Gy) revealed a significant (P less than 0.01) increase in frequencies of SCE in DS lymphocytes and in those of their parents as compared to controls. These data may reveal a familial hypersensitivity reaction to these agents. The results indicate a genomic instability and deranged DNA-repair mechanisms which are accentuated by exposure to mutagenic agents, the underlying causal factor for which might be genetic.

Radiation-induced changes in liver and kidney alkaline phosphatase and esterase of mice

Whole-body exposure of mice to 2 Gy gamma radiation results in an increase in the specific and total activities of esterase and alkaline phosphatase found in the supernatant of liver and kidney. This increase developed at 1 h, reached a maximum at 24 h, and then declined at 48 h after irradiation. The increase in the activity of these enzymes was not accompanied by an increase in protein content. Electrophoretic analysis on acrylamide gel confirmed the results obtained by the quantitative biochemical analysis. An increase in the level and/or number of bands was observed postirradiation.