Calsequestrin (CS) is the protein responsible for the high-capacity, moderate affinity binding of Ca2+within the terminal cisternae of the sarcoplasmic reticulum, believed up to now to be specific for striated muscle. The cells of two nonmuscle lines (HL-60 and PC12) and of two rat tissues (liver and pancreas) are shown here to express a protein that resembles CS in many respects (apparent mass and pH-dependent migration in NaDodSO4/PAGE; blue staining with StainsAll dye; Ca2`binding ability) and is specifically recognized by afflinity-purified antibodies against skeletal muscle CS. In these cells, the CS-like protein is shown by immunofluorescence and immunogold procedures to be localized within peculiar, heretofore unrecognized structures distributed throughout the cytoplasm. These structures appear to be discrete organelles, which we propose to be named "calciosomes." By cell fractionation (Percoll gradient and free-flow electrophoresis), the CS-like protein of HL-60 cells is shown to copurify with the markers of the inositol 1,4,5-trisphosphate (Ins-P3)-sensitive Ca2+ store, whereas the markers of other organelles (endoplasmic reticulum, Golgi complex, mitochondria, endosomes) and of the plasma membrane do not. Calciosome might thus be the intracellular target of Ins-P--i.e., the source of the Ca2" redistributed to the cytosol following receptor-triggered generation of the messenger.

The periodontal ligament, located between the cementum and the alveolar bone, has a width ranging from 0.15 to 0.38 mm. Regeneration and homeostasis of the periodontal ligament are highly significant functions in relation to periodontal therapy, tooth transplantation or replantation, and orthodontic tooth movement. The purpose of this review is to discuss the regulatory mechanisms of regenerative and homeostatic functions in the periodontal ligament based on currently published studies and also on our own experimental data. We consider the capability of the ligament tissue to promote or to suppress calcification in connection with bone and cementum formation and the maintenance of the periodontal ligament space. Also discussed are the involvement of the periodontal ligament tissue in the regenerative ability, cell proliferation, growth and differentiation factors, extracellular matrix proteins, homeostatic phenomena, function of Malassez epithelial rests, tooth movement, or occlusal loading. Regulatory mechanisms for regeneration and homeostasis of the periodontal ligament are hypothetically proposed.

The subcellular distribution of the lysosomal enzymes cathepsin B and D in the pancreas was evaluated in rats infused with saline (control) or a maximal (0.25 microgram . kg-1 . h-1) or a supramaximally stimulating dose (5 micrograms . kg-1 . h-1) of the secretagogue caerulein. The latter results in acute edematous pancreatitis, inhibition of digestive enzyme secretion, and the localization of digestive zymogens in organelles whose fragility has been increased by caerulein infusion [A. Saluja et al. Am. J. Physiol. 249 (gastrointest. Liver Physiol. 12): G702-G710, 1985]. Samples from control animals were found to have 29.9 +/- 1.8% of the cathepsin B activity in the pellet centrifuged at 1,300 g for 15 min (containing primarily zymogen granules) and 54.7 +/- 2.5% in the pellet centrifuged at 12,000 g for 12 min (containing primarily lysosomes and mitochondria). After supramaximal stimulation with caerulein for 3.5 h the pellet centrifuged at 1,300 g for 15 min had 55.1 +/- 2.5%, and the pellet centrifuged at 12,000 g for 12 min had 30.6 +/- 2.0% of cathepsin B activity. This redistribution was time dependent, noted within 1 h of starting caerulein infusion, and maximal after 2.5 h of infusion. Electron microscopic immunolabeling studies revealed localization of cathepsin D in discrete organelles that, in the samples from animals infused with a supramaximally stimulating dose of caerulein, were larger, more abundant, and more concentrated in the pellet centrifuged at 1,300 g for 15 min than in the controls. During infusion with supramaximal doses of caerulein, the cathepsin B-containing organelles were found to become progressively more fragile.(ABSTRACT TRUNCATED AT 250 WORDS)

These results suggest that cellular proliferation and death is regulated in association with apoptosis-related proteins in the lining epithelia of OKCs, and subsequently those cysts are seen as cystic lesions but not as tumor masses.

This review summarizes the biological properties of the junctional epithelium, focusing on its developmental aspects, wide intercellular spaces and desmosomes, dense granules, permeability barrier, phagocytotic activity, adhesive structures and nerve terminals. It also discusses the morphology and functions of long junctional epithelium and peri-implant epithelium. Junctional epithelium is derived from the reduced enamel epithelium during tooth development. Apoptosis occurs in the border between oral and reduced enamel epithelia during tooth eruption. Junctional epithelium expresses a cytokeratin-19 immunoreaction, suggesting that this protein is a consistent differentiation marker. Wide intercellular spaces, which contain neutrophils and nerve endings, are formed as there are fewer desmosomes than in the oral epithelium. Dense, membrane-bound granules in the epithelium might correspond with membrane-coating granules, as revealed by their shape, components and freeze-fracture images. Junctional epithelium with high permeability contains exogenously expressed alpha-defensins, while stratified epithelia contain endogenously expressed beta-defensins. The phagocytotic activity in this epithelium remains unclear. Integrin-alpha6beta4 and laminin-5 form a complex in the tooth surface internal basal lamina. Long junctional epithelium created experimentally attaches to the cementum surface by hemidesmosomes and basal lamina. The peri-implant epithelium differs in proliferation and in adhesive structure from the normal junctional epithelium. In conclusion, wide intercellular spaces and poorly developed desmosomes are closely correlated with a permeable nature. There is still uncertainty over the phagocytotic activity of the epithelium. Integrin-alpha6beta4 and laminin-5 form a significant complex in the internal basal lamina. Junctional epithelium receives a rich sensory nerve and has a high rate of cell turnover. Long junctional epithelium can be produced rapidly during wound healing, due to high proliferative activity. Peri-implant epithelium might be a poorly adhered and permeable epithelium.