Observations on nuclear differentiation in Ascaris

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Abstract
A microdensitometric survey of the DNA content of adult Ascaris nuclei was undertaken to determine the relationship between these values and those expected as a consequence of somatic chromatin diminution. The species diploid value was derived from measurements of Feulgen stained sperm nuclei and unreduced primary oocytes. The somatic DNA values, expected to be hypodiploid if unaltered following diminution, fall into three groups. The first, the intestinal nuclei, are closest of all positively staining nuclei to the anticipated values but are nevertheless in the tetraploid range. A second group of somatic cells, constituting the uterine epithelium, pharyngeal glands and excretory cell present nuclei with quantities of DNA suggestive of high degrees of polyploidy. A “polyploid” gradient exists within the nuclei of the uterine epithelium. Values equivalent to 150‐ploid are found in the posterior half of the uterus, becoming progressively lower toward both ends. The gradient corresponds closely to the known protein synthetic activity of the epithelium. Nuclei of the pharyngeal glands and excretory cell, among the largest nuclei reported, stain distinctly with the Feulgen reaction but their degree of “polyloidy” has not been estimated. On occasion, the excretory nucleus has been noted to be Feulgen negative.The third group of nuclei include those of the somatic muscle and ganglia. By all of the cytological tests for DNA applied (Feulgen staining with standard and fluorescent Schiff reagent, acridine orange and methyl green staining) the muscle nuclei are negative; however, they contain considerable amounts of RNA. Some of the neuron nuclei are negative while others show a faint membrane‐associated staining. The Feulgen‐negative nuclei of the adult most likely represent those which remain in the originally diminished condition.