This study has analyzed variations in the number of nucleoli and nuclear bodies, as well as in their ultrastructural and cytochemical organization, after the osmotically induced activation of supraoptic nucleus (SON) neurons of the rat. The number of nucleoli and nuclear bodies and also the nucleolar size were determined on smear preparations of previously block-impregnated SON. The mean number of nucleoli per cell was 1.35 +/- 0.6 (mean +/- SDM) in control rats. No significant variations in this value were registered either in dehydrated or rehydrated rats. The mean nucleolar volume and the total nucleolar volume per cell showed a significant increase in dehydrated rats with respect to the controls, whereas these two parameters tended to return to control values in rats rehydrated after dehydration. The mean number of nuclear bodies per cell increased significantly from 0.56 +/- 0.50 (mean +/- SDM) in control rats to 1.54 +/- 1.1 after 6 days of dehydration. By electron microscopy, SON neurons displayed a reticulated nucleolar configuration. After the osmotically induced neuronal activation, there was an increase in the proportion of the total nucleolar area occupied by the granular component, and also a reduction in the mean fibrillar-center area. The most characteristic nucleolar features in rehydrated rats were the tendency for the granular component to be segregated and the occurrence of intranucleolar vacuoles. Ultrastructural cytochemistry with a specific silver method revealed a selective silver reaction on the coiled threads of the nuclear bodies--identified as "coiled bodies"--and on the nucleolar fibrillar components in all animal groups studied. Since nucleoli play a major role in ribosome biogenesis, a relationship between these nucleolar changes and the level of cellular activity of SON neurons is proposed. Furthermore, the response of nuclear "coiled bodies" to neuronal activation suggests their participation in the processing and transport of rRNA precursors.

Animals↗

PubMed1991

Influence of age on nuclear bodies and nuclear volume in pituicytes of the rat neurohypophysis.

This study has analyzed age-related changes in the nuclear organization of pituicytes of the rat. The cytological study of the cell nucleus and the quantitative analysis of nuclear bodies (NBs) were performed on ultrathin sections. Nuclear diameter, perimeter, and area were measured on semithin sections, and nuclear volume was estimated from these data. The nucleolus was mainly composed of a few large fibrillar centers with their associated dense fibrillar component, whereas the granular component tended to form large masses at the nucleolar periphery. The most frequent configuration of NBs was a globular inclusion composed of a fibrillar capsule with a core that contained a few electron-dense granules. Intranuclear glycogen was detected on rare occasions and only in old rats. The proportion of nuclear sections containing NBs increased significantly from 1.5% in 3-month-old rats to 8.6% in 18-month-old rats. A significant increase in the nuclear volume was detected in older rats with respect to the younger ones (157 +/- 69 vs. 98 +/- 43 microns 3, mean +/- S.D.). Our results suggest an age-related activation of nuclear metabolism in pituicytes resulting in a nuclear expansion and an increase in the frequency of appearance of NBs. This activation might be a reactive cellular event induced by the degenerative changes in neurosecretory nerve endings naturally occurring in older animals.

Aging↗