title: A cell surface block to polyspermy occurs in golden hamster eggs.
abstract: We have examined the frequency and fate of supernumerary sperm in the perivitelline space (PVS) of in vitro fertilized hamster eggs to determine if there is a cell surface block to polyspermy. The zona pellucida block to polyspermy is very effective since only one sperm penetrated the zona pellucida in 72.8% of the 876 fertilized eggs examined. Of the polypenetrated eggs, 41.6% had a supernumerary sperm within the PVS. The proportion of polypenetrated eggs with PVS sperm did not change when the duration of coincubation was increased from 3 to 6 hr. PVS sperm were found in 67% of the inseminations. From these data we conclude that there is a cell surface block to polyspermy in the hamster. To investigate the mechanism of the cell surface block, we used the Hoechst-transfer technique (R. Hinkley, B. Wright, and J. Lynn, 1986, Dev. Biol. 118, 148-154) to monitor sperm-egg fusion. We first demonstrated that dye transfer from zona pellucida-free eggs to sperm only occurred when fusion was possible, i.e., in the presence of calcium, and that dye was transferred to all fused sperm. When cumulus-free, zona-intact eggs were preloaded with Hoechst dye and viewed 3 hr postinsemination, three classes of eggs with supernumerary sperm in the PVS were observed: eggs with only Hoechst-positive sperm (62%), eggs with only Hoechst-negative sperm (27%), and eggs with both a Hoechst-positive and a Hoechst-negative sperm (11%). Because of the limited time resolution of the Hoechst-transfer technique, the cell surface block could operate by preventing sperm fusion (Hoechst-negative), by the failure of the eggs to incorporate fused sperm (Hoechst-positive), and/or by the "unfusing" of fused sperm (Hoechst-positive and Hoechst-negative). We are unable at this time to differentiate between these mechanisms.
authors: Department of Veterinary Science, University of Wisconsin-Madison 53706.
authors: J
authors: J
authors: Stewart-Savage
authors: B D
authors: BD
authors: Bavister
mesh_terms: D000818:Animals; D001562:Benzimidazoles; D006224:Cricetinae; D005260:Female; D005306:Fertilization; D005456:Fluorescent Dyes; D008297:Male; D008647:Mesocricetus; D008856:Microscopy, Fluorescence; D010063:Ovum / Q000502:physiology*; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000166:cytology / Q000502:physiology; D013194:Staining and Labeling; D015044:Zona Pellucida / Q000502:physiology*
chemical_list: D001562:Benzimidazoles; D005456:Fluorescent Dyes; C017807:bisbenzimide ethoxide trihydrochloride