Charge interactions in sperm-egg recognition

Glycoconjugate histochemistry of the secretory epithelium lining the seminal vesicles of the miniature pig

The present study thoroughly examined the localization and characterization of glycoconjugates in the secretory epithelium lining the seminal vesicles of the miniature pig, employing light and electron microscopic histochemical procedures, including lectin methods. The present results showed the epithelial cells and luminal secretions to contain glycoconjugates with abundant neutral saccharides and a small amount of acidic saccharides, containing varying types of terminal sugar residues. At ultrastructural levels, the free surface coat of the plasma membrane was rich in alpha-D-Man, alpha-D-Glc, beta-D-Gal, GlcNAc, and sialic acid. The flocculent contents of the secretory vesicles indicated the localization of alpha-D-Man, alpha-D-Glc, alpha-L-Fuc, beta-D-Gal, GlcNAc, and sialic acid; such sugar residues were also seen in the elements of the Golgi apparatus. The present results have characterized the seminal vesicles of the miniature pig as having a high secretory activity and copiously producing glycoconjugates with various sugar residues. Such glycoconjugates appear to be indispensable substances for porcine reproduction, possibly influencing the fertilizing capacity of spermatozoa within the female genital tract.

The charged milieu: a major player in fertilization reactions

In previous studies, we have found that negatively charged, but not uncharged, amino acids and sugars block sea urchin fertilization. These studies were developed from modeling work in non-living systems using derivatized agarose beads that suggested that charge-charge bonding may control at least some adhesive interactions. In the present study, the effects of positively charged, negatively charged and uncharged molecules were examined in the sea urchin sperm-egg system in over 300 individual trials. The results indicate that depending on the specific molecules utilized, both sperm and egg are exquisitely sensitive to charged but not uncharged molecules and to pH changes in sea water caused by some of the charged molecules. It is shown that egg activation, as well as sperm motility and sperm-egg interactions, can be affected by charged molecules. One compound, fructose-1-phosphate blocked fertilization in S. purpuratus sea urchins but not in Lytechinus pictus sea urchins. These findings indicate that charge alone cannot explain all the results. In this case, the presence of a ketone instead of an aldehyde group indicates that species-specific components may control fertilization reactions. The present study is a comprehensive survey of the effects of charge, pH and molecular structure on the fertilization activation continuum in a model system of sea urchins.