The effects of zinc chloride on the RNP structures in HEp-2 cells: accumulation of perichromatin granules

Nucleus structure and transcriptional activity in relation to oocyte diameter in cattle

Bovine abattoir ovaries were sliced, and recovered oocytes were washed and incubated in medium enriched with 3H-uridine for 30 min. Uridine incorporation was stopped by washing at 4 degrees C in PBS supplemented with cold uridine. The oocytes were grouped according to their inside diameter- < 100, 100- < 110, 110- < 120, and > or = 120 microns-and processed for autoradiography and transmission electron microscopy. Oocytes < 110 microns in diameter typically presented fibrillogranular nucleoli and were actively transcribing; in contrast, most oocytes > 110 microns displayed electron-dense fibrillar nucleoli and lacked transcriptional activity, as measured by the present means. Based on morphological and transcriptional information, a dynamic model of nucleolus inactivation is proposed. The degree of chromatin condensation varied among oocytes. Fibrillogranular nucleoli were most frequently accompanied by lightly condensed chromatin. The dense fibrillar nucleoli were usually encapsulated by heavily condensed chromatin. The oocyte nuclei underwent a peripheral translocation as the oocyte diameter increased from < 100 to 110 microns. In conclusion, RNA synthesis appeared to cease as the oocyte diameter exceeded 110 microns, and concomitantly the nucleoli restructured from fibrillogranular to dense fibrillar.

Fine structure of EBV-infected keratinocytes in oral hairy leukoplakia

We evaluated biopsy specimens of 42 cases of clinically suspected oral hairy leukoplakia for the pattern and frequency of ultrastructural alterations specific to epithelial cells infected with Epstein-Barr virus. Some structures could clearly be identified as Epstein-Barr virus at different stages of assembly, but other intranuclear and cytoplasmic alterations were not conclusively identifiable as any known structure. Keratinocytes producing Epstein-Barr virus contained intranuclear particles of different size and shape; some of them were arranged in a monodispersed pattern and others formed arrays. In contrast, both lesional keratinocytes not producing virus and keratinocytes in uninvolved mucosa contained intranuclear particles reminiscent of perichromatin granules. The nuclei of productive cells also contained marginated chromatin, tubular structures, and, occasionally, crystalline and fibrillar formations as well as enveloped virus. Formations of electron-dense bilayers were seen on both sides of the nuclear membrane. In the cytoplasm of productive cells we observed aggregates of parallel tubules and enveloped electron-dense bodies. Although many of these observations are of diagnostic and pathobiological significance, the morphogenesis, composition, and function of alterations with uncertain morphological identification remain unclear.