CHROMATIN PATTERNS IN VARIOUS RODENTS, WITH SPECIAL REFERENCE TO SEXUAL DIMORPHISM IN INTERPHASE NUCLEI

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Abstract
Chromatin patterns have been studied in cells of both sexes from 6 regions of the nervous system and in various cell types of several other tissues and organs of the beaver, pocket gopher, muskrat, flying squirrel and striped ground squirrel. Various cells, other than nerve cells, were also examined for sexual dimorphism of nuclei in the ground hog, guinea pig, hamster and rat. Clear-cut sexual dimorphism of nuclei was not recognized in any nerve cells of the species examined. Similarly, no sex differences could be detected in chromatin patterns of cells in other tissues and organs of the beaver, pocket gopher, ground hog, guinea pig, muskrat, striped ground squirrel and flying squirrel. The nuclei of both sexes contain multiple coarse chromatin particles and such sexual dimorphism as may be present is obscured. The parenchymal cells of the liver of the hamster exhibit sexual dimorphism, but the sex chromatin is not easy to recognize. Sexual dimorphism of nuclei is also present in the following tissues of the newborn rat: ameloblasts, epithelial cells of the stomach and cheek, epidermal cells, especially in the tip of the ear and foot, cartilage, smooth, skeletal, and cardiac muscle and kidney. It was observed that the sexual dimorphism of nuclei was not distinct in adult rats and that, in practice, it was absent from all nuclei except those in parenchymal cells of the liver and in cells of renal convoluted tubules. Sexual dimorphism of nuclei is present in cells of whole amounts of rat amnion, but could not be detected in cells of smears prepared from amniotic fluid.