Occurrence of 1st division metaphases in human lymphocyte cultures.

Human lymphocytes were cultured for 40, 42 and 44 h and analysed for the number of 1st and 2nd division metaphases using the Brd U-Giemsa technique. The most suitable time to obtain the majority of cells in their 1st division concommittant with an adequate mitotic index was 42 h. It is recommended that laboratories use sister chromatid differential staining to determine the most suitable culture time for the analysis of 1st division metaphases. This will permit accurate comparisons between individuals and laboratories to be made.