Immunoelectron microscopy on lysis of the oocyte vitelline coat induced by a protein from spermatozoa in a marine mollusk, Tegula pfeifferi

Abstract

A protein responsible for lysis of the oocyte vitelline coat (VC), that is, a VC lysin, has been isolated from spermatozoa of the mollusk, Tegula pfeifferi. Biochemical studies using purified VC lysin and isolated VCs have revealed that the action of this VC lysin is stoichiometric rather than enzymatic. The present immunoelectron microscopic study was undertaken to obtain morphological evidence for this uncommon lytic mechanism using antibodies against the lysin and the soluble product (SP) released from the VC upon lysin treatment.Oocytes isolated from dissected ovaries were treated with the lysin (1 mg/ml) at 25°C for 10 min until their VCs were elevated high from the oocyte surface. The lysin-treated oocytes were prefixed with either 1% glutaraldehyde (GA) for cytochemical study or 2.5% GA plus tannic acid (TA) for morphological study. To localize the lysin and the SP in the VCs, prefixed oocytes were treated with ovalbumin followed by one of the antisera or preimmune serum (control).