DENSE GRANULAR BODIES - A NOVEL NUCLEOPLASMIC STRUCTURE IN HIBERNATING DORMICE

Dense granular bodies (DGB) are particular structural constituents obs erved in cell nuclei of different tissues - liver, pancreas, brown adi pose tissue, adrenal cortex - of hibernating dormice. They appear as s trongly electron-dense clusters of closely packed granules, with thin fibrils spreading out at their periphery. DGB always occur in the nucl eoplasm, sometimes making contact with other nuclear structural consti tuents typical of the hibernating state, such as coiled bodies, amorph ous bodies and nucleoplasmic fibrils. DGB are present only during deep hibernation and rapidly disappear upon arousal from hibernation. Cyto chemical and immunocytochemical analyses showed that DGB contain ribon ucleoproteins and several nucleoplasmic RNA processing factors, sugges ting that DGB can represent accumulation sites of splicing factors whi ch are provided to splicing sites when normal metabolic activity is ra pidly restored during arousal.