The segmenting mammalian ovum represents a unique object for the study of the first differentiation processes of the embryo, reflected in the changes in the morphology, biochemistry, physiology, and other properties of the ovum. The basis of this study are more than 2500 rat ova (Rattus norvegicus var. alba) obtained after fertilization and during cleavage at the one-, two-, four-, and eight-cell stages, the morula, and the early and the late blastocysts. The ova flushed from the tuba uterina or the uterus were processed especially for electron microscopy, part of them were subjected to ultracytochemical or cytochemical studies. In particular, the location of enzymes — alkaline and acid phosphatases, nonspecific esterase, Cholinesterase, succinate dehydrogenase, α-glucan Phosphorylase, glycogen synthetase, and endogenous peroxidase — was studied. Further more, the occurrence of polysaccharides, particularly glycogen, and the glycocalyx were investigated. The ingestion of exogenous proteins (e.g., horseradish peroxidase and microperoxidase) was also studied ultracytochemically. Besides the qualitative analysis of the ultrastructural pattern of changes during the cleavage of the rat ovum, the quantitative analysis of the changes in the occurrence of cytoplasmic structures was also carried out by the morphometric method. Comprehensive information is also supplied concerning the functional aspects of morphologic changes during cleavage with respect to data in the literature.
KeywordsPolysaccharide Succinate Alba Cholinesterase Dehy
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