Identification of human male meiotic chromosomes

The study is based on examinations of surgical testicular biopsies performed in eleven men aged from 19-79 years (300 cells at leptotent stage, 19 at zygotene, 300 cells at pachytene, 490 spermatocytes at diakinesis/first metaphase and 23 cells at the second metaphase of meiotic division), as well as post-mortem necropsies taken from six men aged from 19-51 years (6,000 cells at the first meiotic prophage). Identification of chromosomes at leptotene and zygotene stages is limited to the determination of X and Y chromosomes enclosed in the sex vesicle. At the pachytene stage, identification of chromosomes can make use of the differences in their length and number of chromomeres, but is feasible only in figures with good chromosome spreading. Identification of chromosomes at diakinesis/first metaphase in preparations stained by classical methods rests on the size and shape of the bivalents. Application of centromeric heterochromatin staining technique enables us to differentiate among bivalents Nos. 1, 2, and 3, to recognize bivalents belonging to the B group, to identify bivalents Nos. 9, 16, 17-18, and to distinguish between bivalent No. 21 and 22. It further permits the modality of pairing of the X and Y chromosomes to be determined by their short arms. Chromosomes of secondary spermatocytes at metaphase show typical morphological characteristics essential for karyotyping, so that it is possible to arrange them into the haploid karyotype, analogous to the karyotype of somatic cells. Male germinal cells undergo very rapid autolytic changes. No spermatocytes at diakinesis/first metaphase stage could be detected in specimens taken as early as 2 hours after death. The morphology of chromosomes of cells at earlier stages of the first meiotic prophase was markedly altered. Post-mortem testicular material was found unsuitable for an analysis of meiotic chromosomes.