Studies of frog oviducal jelly secretion. I. Chemical analysis of secretory product.

The jelly secreted by the oviduct of Rana pipiens has been analyzed histochemically and biochemically. Histochemical techniques show that the jelly contains neutral carbohydrates and a protein moiety. Colorimetric estimation reveals that the jelly contains protein and also appreciable quantities of hexose and hexosamine. Sialic acid is present. Chromatographic methods were employed to identify the simple sugars, galactose, fucose, mannose, xylose and glucose, and the hexosamines, glucosamine and galactosamine. Frog ova become coated with three layers of jelly as they traverse the oviduct. Eggs taken from the body cavity, which have not passed through the oviduct or received a coat of jelly, cannot be fertilized (Bataillon, '19). Artificially covering coelomic eggs with jelly capsules dissected from eggs expressed from the cloaca markedly improves the percentage of normal development induced when blastula nuclei are implanted into the eggs (Subtelny and Bradt, '61). The jelly may affect maturation of the egg; somehow interacts with sperm in fertilization; and appears to have mechanical and possibly nutritive significance during cleavage (Humphries, '66). An understanding of the chemical nature of this secretion product of the oviduct is meaningful in the interpretation of the events of early development. Amphibian egg jelly harvested from egg masses collected in ponds contains galactosamine (Schulz and Ditthorn, '00) ; glucosamine, glucose, and galactose (Schulz and Becker, '35); fucose (Bray and James, '49); mannose and xylose (Folkes, Grant and Jones, '50). Concentrations calculated for the various carbohydrates include : total hexosamines, 40.4% ; fucose, 10.4% ; galactose and mannose, 11.4% (Minganti, '55). The present study is concerned with the chemical analysis of jelly dissected from eggs in distilled water immediately after spawning, and with a histochemical analysis of sections of frog oviducts. Samples were analyzed histochemically and biochemically, with greatest emphasis on J. EXP. ZOOL., 166: 99-106. carbohydrates. In a subsequent paper (part II), the morphological details of synthesis of secretory granules of oviducal cells will be described. MATERIALS AND METHODS Histochemical analyses Histochemical analyses were performed on oviducts of females of Rana pipiens collected by the author in the vicinity of Ann Arbor, Michigan, or the University of Michigan Biological Station during the summer months of 1962 and 1963 as well as upon animals purchased from a commercial supplier in Wisconsin. Biochemical studies were made with jelly collected from eggs obtained directly from oviducts or after stripping them. Tests for protein. Mercury bromphenol blue (Pearse, '60) was used as a general protein stain. Special tests for reactive components of proteins included the ninhydrin-Schiff method for protein-bound amino groups (Pearse, 'SO), Millon's reaction for tyrosine (Pearse, '60), and Barrnett and Seligman's ('56) method for sulfydryl and disulfide protein. Tests for carbohydrate. The periodic acid-Schiff reaction was used to identify 1-2 glycol linkages (Lillie, '54), if staining was abolished by acetylating sections with 1 This work was supported in part by a grant from the University of Michigan Cancer Research Institute and a training grant from the National Institutes of Health (USPHS Grant no. GM989). 2 Part 'of a dissertation submitted at the University of Michigan in partial fulfillment of the requirements for the degree of Doctor of Philosophy.