The imbalance of masticatory muscle activity affects the asymmetric growth of condylar cartilage and subchondral bone in rats.

OBJECTIVE: To examine the effects of imbalance of masticatory muscle activity of the rat mandible on the condylar cartilage and subchondral bone during the growth period. DESIGN: Forty 5-week-old male Wistar rats were randomly divided into experimental (n=20) and control (n=20) groups. In the experimental group, the left masseter muscles were resected. The rats were sacrificed at 7 or 9 weeks of age in both groups. Microcomputed tomography was used to determine the three-dimensional morphology and cancellous bone structure. For histological and histochemical examination, 5-µm-thick serial frontal sections of the condyle were stained with toluidine blue and immunostained with asporin and TGF-ß1 to evaluate the promotion and inhibition of chondrogenesis. RESULTS: In the experimental group, microcomputed tomography analysis showed asymmetric growth; the resected side condyles showed degenerative changes. Histological analysis showed that the total cartilage in the central region of the resected side was significantly thinner than in the non-resected side in the experimental group, as well as in the control group. Compared with the control group, the expression of asporin was significantly higher in the resected side, and significantly lower in the non-resected side. In contrast, the expression of TGF-ß1-immunopositive cells in the non-resected side was significantly higher than in the resected side and the control group. CONCLUSIONS: These findings imply that lateral imbalance of masseter muscle activity lead to inhibition of chondrogenesis and induce asymmetric formation of the condyle during the growth period.

Identification of regions of alpha-catenin required for desmosome organization in epithelial cells.

Alpha-catenin, a cadherin-associated protein, links cadherin/beta-catenin and cadherin/plakoglobin complexes to the actin cytoskeleton. This protein is required for the function of cadherins, cell adhesion molecules. We transfected an alpha-catenin-deficient colon carcinoma line, which cannot organize desmosomes, with a series of alpha-catenin mutant constructs. We examined the formation of desmosomes in these cells by immunofluorescence staining using anti-desmoglein and anti-desmoplakin antibodies. The results demonstrated that either the middle or the carboxy-terminal region of alpha-catenin was required for desmosome formation. Immunoblot analysis revealed that the amounts of desmoglein and desmoplakin did not differ significantly between cells that were capable of forming desmosomes and those that failed to form desmosomes. Cell surface biotinylation revealed that desmoglein was retained intracellularly in cells that could not organize desmosomes. The internal domain binds vinculin and alpha-actinin, actin-binding proteins, while the carboxy-terminal domain has the ability to bind and bundle actin filaments. These results indicate that the interaction of alpha-catenin and actin functions in the assembly of desmosomes in epithelial cells.

IgG responses to intranasal immunization with cholera-toxin-immobilized polymeric nanospheres in mice.

IgG responses to antigen-nanosphere hybrids were studied in mice. Cholera toxin (CT) was covalently immobilized onto the surface of polymeric nanospheres (NS) with a nanophase-separated structure consisting of a polystyrene core and a poly(methacrylic acid) graft corona. Reaction conditions favoring the dehydroxide condensation reaction of the amino group of the CT with the carboxyl group of NS effectively immobilized CT onto their surface. When CT-immobilized nanospheres (CT-NS) were suspended in aqueous solution and administrated to mice either intranasally or intramuscularly, serum IgG titers elevated with increasing time and reached a maximum level at 8 weeks after immunization. On the other hand, intranasal administration of CT alone induced an even higher serum IgG titer than that of CT-NS at 4 weeks. However, the titer gradually decreased thereafter. Thus, polymeric NS may be an effective substrate to covalently immobilize antigen on their surface, steadily inducing a high level of IgG production in response to the intranasal administration.