NOVEL NUCLEAR RIBONUCLEOPROTEIN STRUCTURAL COMPONENTS IN THE DORMOUSEADRENAL-CORTEX DURING HIBERNATION

Adrenocortical cell nuclei of the dormouse Muscardinus avellanarius we re investigated by electron microscopic immunocytochemistry in hiberna ting, arousing and euthermic individuals. While the basic structural c onstituents of the cell nucleus did not significantly modify in the th ree groups, novel structural components were found in nuclei of hibern ating dormice. Lattice-like bodies (LBs), clustered granules (CGs), fi brogranular material (FGM) and granules associated with bundles of nuc leoplasmic fibrils (NF) all contained ribonucleoproteins (RNPs), as sh own by labeling with anti-snRNP (small nuclear RNP), anti-m(3)G-capped RNA and anti-hnRNP (heterogeneous nuclear RNP) antibodies. Moreover, the FGM also showed immunoreactivity for the proliferation associated nuclear antigen (PANA) and the non-snRNP splicing factor SC-35. All th ese nuclear structural components disappeared early during arousal and were not found in euthermic animals. These novel RNP-containing struc tures, which have not been observed in other tissues investigated so f ar in the same animal mo-del, could represent storage and/or processin g sites for pre-mRNA during the extreme metabolic condition of hiberna tion, to be quickly released upon arousal. NFs, which had been sometim es found devoid of associated granules in nuclei of brown adipose tiss ue from hibernating dormice, were present in much higher amounts in ad renocortical cell nuclei; they do not contain RNPs and their role rema ins to be elucidated. The possible roles of these structures are discu ssed in the frame of current knowledge of morpho-functional relationsh ips in the cell nucleus.