Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.36 (hyaluronidase)
 4,606 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Insectivora are of special interest as the most primitive of the eutherian mammals, but essentially nothing is known of their gamete function. In this respect, the Asian musk shrew (Suncus murinus), investigated in the present study, displays many idiosyncrasies. In the epididymis, the giant acrosome undergoes further stabilization, its unusual resilience being especially evident in a "rim" created by a persistent close alignment of the outer acrosomal and overlying plasma membranes. However, until spermatozoa reached a gland on the vas deferens, no post-testicular change was demonstrable in the sperm head surface, the unusual nature of which was indicated by a dorso-ventral differentiation, by an inability to auto-agglutinate or to bind to the homologous zona pellucida, and by an insensitivity to anti-sperm immunoglobulin IgG in fresh serum. At mating, only about 1 x 10(6) spermatozoa are inseminated as far as the anterior vagina with plug formation. Within the small (6 mm) fallopian tube, the isthmus and ampulla are sharply delineated by their contractile activity and epithelial character; there is evidence of some sperm entry into isthmic crypts and a tendency for ipsilateral ovarian control of sperm transport to the tubal ampulla. The cumulus oophorus does not undergo preovulatory mucification and expansion, is characterized by persistent intercellular gap junctions, and is insensitive to hyaluronidase and trypsin. It is unclear how the compact cumulus is penetrated at fertilization. The giant acrosome contains acrosin and an unusually temperature-dependent cumulytic activity; it is intact in motile ampullary spermatozoa but appears to be discharged before reaching the zona pellucida. Since eggs were not penetrated in the presence of ampullary spermatozoa until 4-10 h after ovulation, Suncus spermatozoa spend a long period in the female before they can fertilize. The determinants of sperm function, including capacitation and the acrosome reaction (AR), may depend on a different set of controls in Suncus, perhaps as a legacy of the resilient giant acrosome. This possibility could be examined in other Crociduran and Soricine shrews selected according to acrosome size.
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PMID:Distinctive features of the gametes and reproductive tracts of the Asian musk shrew, Suncus murinus. 819 63

The gametes of the least shrew, Cryptotis parva, were studied in regard to their maturation and structure, and with particular emphasis on their behavior in the fallopian tube, from the time of ovulation until the appearance of two-cell embryos beginning some 9 h after ovulation. Cryptotis spermatozoa are organized according to the conventional eutherian mold, with the exception of a barbed perforatorium and an unusual plasma membrane density lent by a bristly coat where it overlies the acrosome rim. In the epididymis they undergo a maturation of the capacity for motility and an -S-S-related stabilization of the nucleus and tail organelles, with the cauda housing only approximately 4-5 million spermatozoa. Mating involves penile locking and also the deposition of a modest vaginal plug that covers the cervix. The short (4-5 mm) fallopian tube has three regions-a simple isthmus, a relatively narrow ampulla populated throughout by ciliated crypts, and a crypt-free terminal infundibulum-the fertilization site. Unlike the situation in most mammals, the tubal isthmus was devoid of spermatozoa in mated females before and after ovulation, which occurred approximately 13 h post-hCG and produced a mean of 5.7 ova. However, the ampulla then housed approximately 1500 active cells in groups within the ciliated crypts, sometimes together with leukocytes but with few spermatozoa above in the infundibulum. Within about 1 h after their ovulation from approximately 400-microm follicles, eggs were penetrated while in the infundibulum despite the nonexpanded hyaluronidase-resistant state of the cumulus oophorus. However, on moving down to the ampulla by 2-4 h after ovulation, the dense cumulus around fertilized eggs appeared to proliferate and began to disperse coincidentally with secretion of a hyaluronidase-sensitive matrix in which hundreds of motile spermatozoa often became enmeshed. This cumulus change also occurred around unfertilized eggs, though more slowly, but not around fertilized or unfertilized eggs cultured in vitro. Thus, cumulus matrix production appeared to be stimulated to an important degree by factors in the oviduct, not by preovulatory gonadotropins as in many mammals. Although cumulus-invested eggs were fertilized readily in vitro, cumulus-free eggs of the same age were never fertilized, and spermatozoa bound to the zona pellucida had intact acrosomes. This and related evidence from other shrews makes it seem likely that the soricid cumulus has an essential role in fertilization and may induce the acrosome reaction.
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PMID:Unusual ampullary sperm crypts, and behavior and role of the cumulus oophorus, in the oviduct of the least shrew, Cryptotis parva. 916 Jul 26