The meiotic chromosomes of man.

Abstract

Information was obtained on the chromosome number, and the behavior of autosomes as well as of the sex chromosomes in meiosis in human male germ cells derived from 25 Japanese patients, 4 to 79 years in age, who were hospitalized mostly due to epididymitis, prostate cancer, undescended testes or infertility. In 16 out of the 25 specimens, the chromosome numbers, 46 in 2n and 23 in n, were consistently established together with an XY sex-determining mechanism based on spermatogonial and spermatocyte divisions. No reliable counts were obtained from the remaining 9 cases, because of that they provided no cells for precise investigation. The X and Y chromosomes during the leptotene stage were observed as two separate heteropycnotic bodies lying along the inner wall of the nucleus, while at pachytene they formed a sex-vesicle after homologous pairing. At the diplotene, diakinesis and first metaphase the X and the Y appeared as an isopycnotic bivalent showing an end-to-end association, though there were some cells in which they remained as two separate entities free from contact. Evidence was presented that the X and the Y seemed to associate with each other at the distal end of the short arm of each element. One or sometimes two smallest autosomal bivalents tended to show rather precociously a chiasma-terminalization at the first metaphase. The metaphase chromosomes of the second spermatocytes were evident by the haploid number as well as by their widely diverged chromatids with a characteristic spiral configuration. The testicular materials under study contained in most cases polyploid cells with a considerable frequency in spermatogonia as well as in first and second spermatocytes. Giant sperm heads were observed not infrequently, mostly being abnormal in shape. No significant correlation was obtained between the frequency of polyploid cells and the age of patients so far studied.