The effect of a chemically induced oxygen‐derived free radical flux has been studied on extracted porcine gingival hyaluronic acid and proteoglycans as well as on cryostat sections of porcine gingivae. The result of the free radical producing system on hyaluronic acid and the proteoglycans was one of reduction of specific viscosity and molecular size. When frozen sections were subjected to the same oxygen‐derived free radical flux and subsequently stained with Alcian blue, a noticeable decrease in staining intensity was observed when compared to control sections. These results are considered to reflect the in vitro capacity of oxygen‐derived free radicals to depolymerize the two major non‐fibrous extracellular macromolecules of gingivae. It is postulated that such a mechanism may be responsible, at least in part, for the destruction of gingival proteoglycans and hyaluronic acid observed in inflammatory periodontal disease.

Defects in growth plates due to trauma, infection, or genetic causes can result in bone formation across the defect, bridging the epiphysis and metaphysis, resulting in growth arrest and limb deformation. We have investigated the capacity of implanted chondrocyte cultures to prevent this process. Sheep growth plate chondrocytes were isolated, and after culture at high density produced easily manipulated cartilaginous discs. The tissue was implanted into growth plate defects produced in lambs and the response was assessed histologically. Following implantation, cultures continued to proliferate and maintain a cartilage-like matrix. After 8 to 12 weeks, hypertrophic maturation chondrocyte columnation, and associated endochondral calcification were observed. Culture implantation was always associated with local immune inflammatory reaction, which continued throughout the course of investigation. Cellular survival was variable and resulted in the presence of viable implants as well as residual cartilage matrix devoid of chondrocytes; however, implanted chondrocyte discs always prevented bone bridge formation. These findings encourage the expectation that cultured chondrocytes may provide a useful replacement for the inert interpositional materials currently used in the treatment of growth arrest. The potential of this technique for growth plate replacement, however, requires a more predictable rate of implant survival. The likely reasons for implant loss are discussed.

Overall CM, Wiebkin O W, and Thonard JC: Demonstration of tissue collagenase activity in vivo and its relationship to inflammation severity in human gingiva. Journal of Periodontal Research; 1987: 22: 81-88. To directly demonstrate both the presence and in vivo activity of tissue collagenase (EC 3.4.24.7) during gingival inflammation, tissue extracts from 54 specimens of variously inflamed human gingiva were analyzed individually for: a) collagenasespecific collagen degradation products, and b) collagen-bound collagenase. The TC"^ collagen degradation product, identified using SDS-PAGE, was shown in 13/19 (68.4%) of insoluble tissue-residue fractions extracted from moderate-toseverely inflamed gingiva, but in only 2/21 (9.6%) slight-to-mildly inflamed gingival specimens, suggesting differences in the in vivo collagenase activity between the two groups. Using in vitro collagenase assays, gingival collagenase (as bound to insoluble collagen) was demonstrated in 92.8% of the moderate-toseverely inflamed gingival specimens and in 50% of the slight-to-mildly inflamed gingival specimens. A relationship was established between the active and latent forms of the enzyme and the degree of inflammation. Active enzyme was present in 78% of the moderate-to-severely inflamed specimens and in 14% of the slightto-mildly inflamed gingiva. In contrast, latent collagenase was predominant in the slight-to-mildly inflamed group (86% of coliagenase-positive samples) compared with 46% of coliagenase-positive moderate-to-severely inflamed gingival samples. The collagen-bound gingival collagenase was inhibited by metal ion chelators, sulphydryl reagents and 10% FBS, but not by serine-nor thiol-proteinase inhibitors and is therefore a neutral metalloproteinase.

SUMMARY Preparative chromatographic fractions of human umbilical cord hyaluronic acid (HA) of a molecular weight of 106 were subjected to graded oxygen-derived free radical (oxy radical) fluxes produced by: (a) the autoxidation of ferrous ions; (b) the action of xanthine oxidase (XO) on hypoxanthine (HX); and (c) by peripheral blood polymorphonuclear leucocytes that had been stimulated by phorbol myristate acetate (PMA). Analysis by gel chromatography of the products obtained with each of the oxy radical generating systems showed polydispersity in size. The smallest molecules detected had a molecular weight of i04. This limiting size was not reduced further by exposure to a second oxy radical flux. The relative proportions of large, medium, and small degradation products were established for various levels of oxy radical flux. Consistently a relatively rapid transition from large to small material was seen on Sepharose 2B chromatography, suggesting an ordered element to the breakdown process. Although the decrease in molecular weight after oxy radical exposure was confirmed by analytical ultracentrifugation, this procedure showed that those samples of lowest viscosity did not

Invasive growth of cancer cells is a complex process involving specific interactions between tumour cells and the orderly, integrated complexes of the extracellular matrix. Basement membranes have been proposed as one constituent of extracellular matrix which carries responsibility for regulating invasion and metastasis. Using a chemically induced rat tongue carcinoma model, it has been shown that components of the basement membrane and its overall structure are altered during tumour invasion, and methods have been developed to quantitate some of these differences. Since the basement membrane can be specifically characterized by its fibrous protein network of Type IV collagen and laminin, which is embedded in a heparan sulphate-rich proteoglycan matrix, these components have been targeted. In particular, the current paper presents results in the context of current concepts of early changes in neoplastic invasion of underlying connective tissues. In consequence, further elaboration of the underlying mechanisms of epithelial migration in oral cancer may allow an exploration of the use of alterations in expression of basement membrane components as prognostic indicators.