The incidence of spontaneous cytogenetic aberrations in lymphocytes cultured from normal humans for 48 and 72 h.

Spontaneously occurring cytogenetic aberrations were compared in 48- and 72-h human lymphocyte cultures from a group of 20 normal male volunteers. Mitotic indices for both cultures times were also evaluated. BUdR (5-bromo, 2-deoxyuridine) labelled metaphases from three men were utilized to determine the cell cycle kinetics in the medium used. There was no statistically significant difference between 48- and 72-h cultures among the majority of aberration categories considered. Possibly, the lymphocyte populations at the two different culture times maintained a consistent yield level. Mitotic indices in 72-h cultures were invariably higher than those in 48-h cultures. An overwhelming number of first division metaphases were observed at 48 h of incubation; however, approximately 22% of the lymphocytes did not enter into mitosis until 72 h in culture. A number of difficulties with regard to utilizing BUdR-labelled first division metaphases for cytogenetic analyses are discussed.