Dry Mass, Lipid Content and Protein Content of the Intact and Zona-free Mouse Ovum.

MAMMALIAN ova have not been studied as thoroughly as the eggs of lower vertebrates. Increasing interest in the physiology and biochemistry of mammalian embryogenesis in recent years has been met with little quantitative information. Up to now there have been no direct chemical analyses of mammalian ova published. Reported here are the dry mass and protein and lipid contents of the single cell fertilized mouse ovum. The mouse was chosen because of its frequent use as an experimental animal for the study of developmental genetics and because large numbers of mouse ova can be obtained with relative ease. Single cell stage ova from mated females were chosen as the starting point from which to follow these parameters through cleavage and blastocyst formation, although it must be realized that a proportion of such ova would not be fertilized. Besides being of general interest to embryologists, information such as this is necessary for the interpretation of respiratory studies (Boell & Nicholas, 1948; Fridhandler, Hafez & Pincus, 1956, 1957; Fridhandler, 1961) and for the comparison of respiratory rates of ova with the respiratory rates of other tissues. When enzymes assays are undertaken it will be necessary to know the protein content in order to quantify enzyme specific activity. The techniques demonstrated in this study can be applied to the study of fertility and sterility and to the investigation of the effects of maternal nutritional status and genetic background on development.