Influence Of Gossypol On Chromosome Pairing In Spermatocytes Of Male Mice

Synaptonemal complex (SC) is a transient structure which happened in eukaryotic nuclei during the first meiotic division when homologous chromosomes are pairing. The structure is closely related with homologous chromosomes synapsis, recombination and segregation. The studies on SC may not only contribute to the knowledge of submicroscopic structure in meiosis but also has been widely used in the studies on eukaryotic chromosome rearrangement, medical cytogenetics and genetic toxicology. Gossypol was reported male antifertility agent by Chinese scientists at first. It has not been systematically studied if the gossypol resulted in the aberration of SC. The conventional methods were applied in preparing chromosomes from marrow cell and sex cell. The SCs were prepared by surface spreading-silvers staining transmission electron microscope (TEM) technique. The structure and pairing of chromosomes and SCs from control male mice (untreated by gossypol) and experiment mice (treated by gossypol) were observed by light microscope (LM) and TEM. The results are reported as follows: (1) The SC karyotype was constructed in spermatocytes of untreated mice agreed closely with that of mitotic chromosomes (related coefficient of mean relative lengths was 0.9754). It showed that SCs karyotype analysis was important to recognition chromosomal aberrations in spermatogenesis. It was one of the most important methods in study male infertility. (2) Mitotic metaphase chromosomes in untreated mouse were identified by a new chromosomal fluorescence banding technique combining 4', 6-diamidino-2-phenylindole (DAPI) staining with image analysis. Clear DAPI multiple bands like G-bands could be produced. Based on the results, the clear and accurate DAPI banding karyotype of mouse metaphase chromosomes was established. The technique was considered as a new method in cytogenetics studies of mouse. (3) The autosomal and sex SCs developments in spermatocytes of control male mice were observed by TEM. It could not only supply some evidence for pairing behaviour of homology and deepen the comprehension of meiosis, but also offer references to visible SCs damage examples after treatment by gossypol. (4) SC aberrations in spermatocyte of treated male mice could be induced by gossypol. SC abnormalities were classified as various forms of breakage and synapsis errors. It included various forms as follows: ① breakage of the SC; ② lateral element break; ③ asynapsis; ④ multi-axial configuration(MAC); ⑤ non-homologous synapsis; ⑥ XY-mispairing; ⑦ XY separation (X and Y in separate areas of the nucleus when they should be paired); ⑧ synapsis irregularity. The chromosomes abnormalities in MI stage were showed as follows: ① univalents of autosomes; ② isochromatid break of autosomes; ③ multivalent; ④ univalent of XY. (5) It is obvious that more serious damages could be observed as the increased dosage or prolonged treated time of gossypol, but no special aberration forms were produced in high dosage gossypol. (6) It is concluded that we can evaluate the genetic risk induced by gossypol in males by SC analysis. The relationship between the behavior of SC and the mechanism of infertility was discussed. Our results are considered as a reliable evidence for cytological studies of gossypol-induced infertility.