Experimental induction of rheumatoid arthritis in temporomandibular joint of the guinea pig: a clinical and radiographic study.

OBJECTIVE: To correlate the clinical and radiographic changes at different stages of experimentally-induced rheumatoid arthritis (RA) of the TMJ. METHODS: Forty eight adult male guinea pigs, aged 4-6 months, were divided into two groups. Arthritis was induced in the experimental animals by intraperitoneal injection of heat-inactivated group A Streptococcus pyogenes. Four animals from each group were sacrificed and examined clinically and radiographically at intervals of 48 h and 1, 2, 4, 6 and 8 weeks. RESULTS: The main clinical findings were stiffness, crepitation and reduction in mouth opening. Radiographically, the main features were condylar erosion, flattening and sclerosis subcortical cyst formation. CONCLUSION: RA passes through stages that can be correlated clinically and radiographically. Both the clinical and radiographic manifestations in this experimental model are comparable with those previously reported in the small joints of humans.

A scanning electron microscopic study of tooth surface changes induced by tannic acid.

STATEMENT OF PROBLEM: Exposing the tooth structure to chemicals used in displacing the gingival tissue is inevitable. PURPOSE: This study was undertaken to microscopically examine the effect of tannic acid on the prepared dentin surface. MATERIAL AND METHODS: Forty recently extracted intact human teeth were mounted for buccal surface preparation. Teeth were equally divided into 10 groups. One group was kept as a control and the other teeth received a topical application of 15%, 20%, and 25% aqueous tannic acid solutions each for 5, 10, and 15 minutes at room temperature. All samples were washed, air-dried, then prepared for scanning electron microscopic examination. Two different areas in the cervical region were randomly selected and examined under magnifications of x1000 and x2000, then photographed. The assessment of the changes was performed qualitatively. RESULTS: The results showed an incomplete removal of the smear layer in all experimental samples. The astringent action of the tannic acid solution on both the smear layer and the surface peritubular dentin around the orifices of dentinal tubules had contributed to their constriction. The degree of constriction of the orifices of dentinal tubules increased as higher concentrations of tannic acid solutions were used and as the application time was further increased at each concentration. CONCLUSION: The tannic acid had an incomplete action on the removal of the smear layer. It also seemed to have an astringent action on both the smear layer and the peritubular dentin.

Immunohistochemical and fluorescent microscopic study of histogenesis of salivary mucoepidermoid carcinoma.

The purpose of the present investigation was to study the histogenesis of the mucoepidermoid carcinoma of the salivary glands. Eleven cases of mucoepidermoid carcinoma of the minor salivary glands and five of the major glands were extensively studied employing immunohistochemical and fluorescent microscopic techniques. Both the intermediate cells and the duct cells showed a rather similar pattern of reactivity for vimentin, actin and EMA. Also, the intermediate cells and the myoepithelial cells showed a similar reaction pattern for keratin and UGA-1. The intermediate, myoepithelial and duct cells shared a similar reaction pattern for desmin, myosin, CEA, and S-100 protein. However, the rest of the tumor markers studied (AFP, PNA and WGA) were found to be non contributary. We also found that the intermediate and to some extent the epidermoid tumor cells showed a positive reaction with Azophloxine GA, which is a selective stain for myoepithelial cells in the normal glands. Based on these findings, the duct cells, the myoepithelial cell in the normal glands and the intermediate cells of the mucoepidermoid carcinoma share certain similar characteristics. The intermediate cells may actually be a mixed population, some having characteristics of the myopithelial cells and others of duct cells. These findings are relevant to the possible role of the intermediate cell in the histogenesis of the mucoepidermoid carcinoma.

Comparative light, scanning, and transmission electron microscopic study of chemically induced premalignant lesions in hamster's cheek pouch.

The early chemically induced epithelial dysplastic changes in the hamster's cheek pouch were studied using light, scanning, and transmission electron microscopy. Epithelial dysplasia was noticed on the light microscopic level by the sixth week of the experiment and became marked by the eighth week. At the scanning electron microscopic level, surface alterations with features previously reported in early epithelial dysplasis in human and oral mucosa were seen by the second week of the experiment and progressed over time. These early changes were also confirmed at the ultrastructural level. The usefulness of scanning and transmission microscopy in detecting early oral epithelial dysplastic changes in this animal model is discussed.

Surface ultrastructural changes in chemically induced premalignant lesions in the hamster cheek pouch.

The histopathological and topographical alterations occurring during the early stages of chemical carcinogenesis in the hamster cheek pouch using 7,12-dimethylbenz (alpha) anthracene (DMBA) were studied by light and scanning electron microscopy. At the scanning electron microscopic level, cellular overlapping and mild disturbance of intercellular bridges were noticed as early as the second week of DMBA application; these changes progressed with time. Clear epithelial dysplastic changes at the light microscopic level were detected by the sixth week of the experiment. The results of this investigation demonstrate the usefulness of scanning electron microscopy as an adjunct tool to study early alterations in cell morphology which occur in the stratified squamous epithelium of the hamster cheek pounch in response to a chemical carcinogen.