Rapid repair of titanium particle-induced osteolysis is dramatically reduced in aged mice.

Aseptic loosening is the most common cause of orthopaedic implant failure. This process is thought to be due to osteolysis induced by implant-derived wear particles. Teitelbaum and colleagues have recently developed a promising murine calvarial model of wear particle-induced osteolysis. However, prior to this study, this model had only been assessed qualitatively. We now report a reproducible, quantitative version of the calvarial model of wear particle-induced osteolysis, in which the extent of osteolysis (and repair) of entire parietal bones is assessed by histomorphometry of contact microradiographs. Using this model, we found that the osteolytic response is transient and rapidly repaired in one month old mice. The extent of osteolysis peaks 7 days after particle implantation and returns to baseline levels by 13 days. A similar amount of osteolysis and even more extensive repair is observed when particles are implanted repeatedly. In contrast, aged mice develop progressive osteolysis with no detectable repair. As a result, 26 month old mice have approximately 17-fold more osteolysis than one month old mice 21 days after particle implantation. Skeletally mature, adult mice (4-16 months old) show an intermediate pattern of response. Osteolysis in these mice peaks at 7 days after particle implantation but it is repaired more slowly than in the one month old mice. Taken together, these results underscore the role of an imbalance between bone resorption and bone formation in the development of aseptic loosening and suggest that agents that stimulate bone formation maybe useful in prevention or treatment of aseptic loosening.

Role of nitric oxide in hypoxia-induced changes in newborn rats.

In order to investigate the role of nitric oxide (NO) in hypoxic tissue damage in newborns, we studied the effects of systemic administration of an inhibitor of NO synthase, N(G)-nitro-L-arginine (L-NNA), and the precursor for the synthesis of NO, L-arginine (L-ARG), on the biochemical and histological changes in brain, heart, lung, liver, kidney, intestine, and skeletal muscle tissues. Four groups of 1-day-old Wistar rat pups were used: control, hypoxic, L-ARG, and L-NNA groups. L-ARG 100 mg/kg or L-NNA 2 mg/kg was administered as a bolus intraperitoneally 1.5 h before hypoxia. Hypoxia increased lipid peroxidation in all tissues except muscle; this increase was prevented by L-NNA and L-ARG in brain, heart, lung, kidney, and liver tissues. L-NNA in intestine and L-ARG in muscle tissue increased lipid peroxidation. The tissue-associated myeloperoxidase activity was decreased in the liver by L-NNA and L-ARG. Histopathological changes in intestines were villous epithelial separation and hyperemia in hypoxic and L-NNA groups which were not observed in control and L-ARG groups. In lungs, pulmonary hemorrhage was observed only in the hypoxic group. These data suggest that NO acts both as a destructive and a protective agent in the pathogenesis of hypoxia-reoxygenation injuries.

Effects of intra-articular vitamin E and corticosteroid injection in experimental hemarthrosis in rabbits.

The effects of intra-articular injections of vitamin E and corticosteroid were investigated in skeletally mature New Zealand white rabbits in which experimental hemarthrosis was induced for 14 days. The rabbits were divided into three groups composed of eight rabbits each: the first group comprised of animals with hemarthrosis, the second group animals with hemarthrosis and intra-articular injections of 20 mg vitamin E, and the third group animals with hemarthrosis and intra-articular injections of 10 mg of triamcinolone acetonide (TCA). Proteoglycan levels in the joint cartilage of the hemarthrosis group were found to be increased significantly compared with the controls (P < .01), whereas in the vitamin E-injected group they were significantly decreased (P < .05). In the TCA-injected group, proteoglycan levels were not found to be significantly different from those in the hemarthrosis group (P > .05). Histopathological evaluation showed that the cartilage structure in the joint of the control limbs was identical to that in the vitamin E- and TCA-injected limbs. In the hemarthrosis group, in comparison with the controls, the joint surface was roughened and fibrillated. In the superficial areas of the cartilage tissue, chondrocytes were decreased in number. These findings suggest that in this model, vitamin E and TCA may be helpful in preventing the joint cartilage changes seen in hemarthrosis.

Camptodactyly, myopia, and fibrosis of the medial rectus of the eye in two sibs born to consanguineous parents: autosomal recessive entity?

Unaffected but consanguineous parents suggest autosomal recessive inheritance of a previously apparently undescribed syndrome of camptodactyly, fibrosis of the medial rectus muscle of the eye, severe myopia, facial anomalies, joint contractures, and mild scoliosis in a 13-year-old Turkish girl and her 11-year-old brother. The girl also had ptosis.