Mechanics of sperm-egg interaction at the zona pellucida

Mammalian sperm traverse several layers of egg vestments before fertilization can occur. The innermost vestment, the zona pellucida, is a glycoprotein shell, which captures and tethers the sperm before they penetrate it. We report here direct measurements of the force required to tether a motile human sperm as well as independent calculations of this force using flagellar beat parameters observed for sperm of several species on their homologous zonae. We have compared these sperm-generated forces with the calculated tensile strength of sperm-zona bonds, and found that a motile sperm can be tethered, at least temporarily, by a single bond. Therefore, sperm can be captured by the first bond formed and tethered permanently by a few. The sperm cannot subsequently penetrate the zona unless the bonds are first eliminated. However, premature elimination would simply allow the sperm to escape. Therefore, not only must the bonds be eliminated, but the timing of this must be regulated so that the sperm is already oriented toward the egg and beginning to penetrate as the bonds are broken

Chemicals identified in feral and food animals: a data base. First annual report, October 1981. Volume I. Records 1-532

This data file is a companion to Chemicals Identified in Human Biological Media, A Data Base, and follows basically the same format. The data base on human burden is in its third year of publication. This is the first annual report for the feral and food animal file. Data were obtained primarily from the open literature through manual searches (retrospective to 1979) of the journals listed in Appendix A. The data base now contains information on 60 different substances. Chemicals are listed by Chemical Abstracts Service (CAS) registry numbers and preferred names in Appendix B. For the user's convenience, cross-referenced chemical lists of CAS preferred and common names are provided in Appendix C. The animals, tissues, and body fluids found to be contaminated by these chemicals are listed in Appendix D. The data base is published annually in tabular format with indices and chemical listings that allow specific searching. A limited number of custom computer searches of the data base are available in special cases when the published format does not allow for retrieval of needed information