Fractionator studies on Purkinje cells in the human cerebellum: numbers in right and left halves of male and female brains.

Direct estimates of the numbers of Purkinje cell nucleoli in 22 aged human cerebella of known weight were obtained from paraffin-embedded sections using the fractionator. The nucleoli were counted in single sections. The estimates are unbiased by fixation, section thickness or sampling errors and are free from any assumptions about shape, size or spatial orientation. Left and right sides of the cerebellum were analysed in ten subjects whilst sex differences were examined in eleven subjects. No significant lateral differences in fixed weight or nucleolar number were observed. The group means (coefficients of variation) per side were 45 g (18%) and 7.8 millions (26%) respectively. The average complement of nucleoli in 22 cerebella amounted to 15.6 millions (22%). Estimated numbers did not show any significant correlation with cerebellar weights and, in a subsample of these brains (five male and six female), apparent sex differences were not significant.