Rearrangement of nuclear ribonucleoproteins and extrusion of nucleolus-like bodies during apoptosis induced by hypertonic stress

Short-term hypertonic (HT) stress induces apoptotic cell death in human EUE cells in culture, as observed by electron microscopy, agarose-gel electrop horesis of low-molecular-weight DNA, DNA flow cytometry and annexin-V-propi dium iodide double-staining. During MT-induced apoptosis, nuclear ribonucle oprotein (RNP)-containing structures undergo rearrangement, with the format ion of Heterogeneous Ectopic RNP-Derived Structures (HERDS) which pass into the cytoplasm, as already reported for other examples of spontaneous and d rug-induced apoptosis. Of special interest was the observation that nucleol us-like bodies (NLBs) which resemble morphologically nuclear functional nuc leoli may be extruded into the cytoplasm of apoptotic cells and are observe d inside the cytoplasmic fragments blebbing-out at the cell surface; these NLBs still contain immunodetectable nucleolar proteins (such as fibrillarin ). This is an additional example of RNP-containing structures of nuclear or igin which are extruded from the nucleus, in an almost "native" form, durin g apoptosis.