| Abstract: | During maturation in the epididymis, mouse sperm nuclei become difficult to stain with Giemsa and its component basic dyes. Mature sperm from the cauda epididymis can be stained only after DTT treatment. Stainable sperm such as those from the testis accumulate 3H NEM when examined by autoradiography, while unstainable sperm do not, indicating a close correlation between the basic dye binding capacity and SH levels in the sperm nuclei. During insemination of zonafree ovarian oocytes with a germinal vesicle (GV), mature sperm nuclei become stainable and capable of binding with 3H NEM. At the same time, sperm have established pronase-resistant contact with the oocyte. Similarly, sperm nuclei become stainable during fertilization when the sperm attachment to the egg becomes pronase resistant. However, these changes occur before sperm chromatin decondensation begins. Therefore, it is suggested that S-S bonds in sperm nucleoproteins are reduced when the sperm establish a stable contact with the egg plasma membrane, thus reversing sperm maturational changes. The reduction of S-S bonds may be a prerequisite for sperm chromatin decondensation. |
