Title: Oogenesis in Xenopus laevis (Daudin). III. Localization of negative charges on the surface of developing oocytes
Abstract: Developing oocytes and coelomic eggs of mature HCG-stimulated Xenopus females were dissected from the ovary, fixed in glutaraldehyde, and treated with a positively charged solution of colloidal iron. Electron micrographs reveal anionic sites preferentially localized in or on the plasmalemma covering the distal portions of the numerous microvilli of Stage IV oocytes. Both prior to and subsequent to Stage IV (the peak of vitellogenic activity), the anionic sites on the oolemma are more randomly distributed. No iron particles appear in endocytotic pits of the oolemma at any stage of development, but endocytotic pits of follicle cells are labeled. There are few if any anionic sites in the vitelline envelope. The assumption that the negative charges are due to sialic acid moieties of surface mucopolysaccharides was borne out by treatment with neuraminidase. Oocytes subjected to the enzyme and subsequently fixed and treated with colloidal iron show a marked reduction in the amount of labeling. These results are discussed in the light of earlier evidence regarding the endocytosis of vitellogenin, a negatively charged molecule.
Publication Year: 1976
Publication Date: 1976-04-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
Access and Citation
Cited By Count: 25
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