Semiautomatic morphometric analysis of the nucleolar development in the nucl. n. oculomotorii of Tupaia belangeri during ontogenesis.

The development during ontogenesis of the nuclear and nucleolar diameters and of the numbers of nucleoli per nucleus in the nucl. n. oculomotorii of 32 male Tupaia belangeri are described. The measurements of the nucleolar diameters were done automatically using the Micro-Videomat (Zeiss, Oberkochen). Increase of the nuclear and nucleolar diameters yielded a nearly sigmoid-shaped curve, which was fitted using the logistic growth function. The "ideal" value of the nucleolar diameter is 3.7 mum with a half value time of 22 days of ontogenesis and an enlargement factor of 1.53. The respective parameters for the nucleus are 12.2 mum, 28 days and 1.27. The ratio of the nuclear to nucleolar diameters decreases exponentially during ontogenesis to a value of 3.3. The validity of these easily determinable morphologic parameters for the RNA-synthesis is discussed. The number of nuclei with 2 or 3 nucleoli decreases during ontogenesis. The relevance of this fact for cell counting is also discussed.