A degenerative medial meniscus retains some protective effect against osteoarthritis-induced subchondral bone changes.

OBJECTIVES: The objective was to estimate the impact of the meniscus on cartilage and subchondral bone in knee osteoarthritis (OA). METHODS: In a sample of 46 knee specimens (26 females), 13 (7 females) were classified as OA according to the Kellgren-Lawrence classification. Outerbridge and meniscal grading were performed. Using micro-computed tomography images, we analyzed the cartilage thickness, subchondral plate thickness and micro-architecture of trabecular subchondral bone at different depths and in two different locations of the medial tibial plateau: one peripheral (PER) covered by the meniscus and one central (CENT) uncovered by the meniscus. RESULTS: Uncoverage by the meniscus was associated with bone sclerosis, defined as higher bone volume to total volume (BV/TV), higher trabecular number, thicker trabeculae with lower spacing, and anisotropy and a more plate-like architecture. The protective effect of meniscal coverage was observed in the uppermost 5 to 6 mm of the subchondral bone. As compared with normal knees, knees with OA showed significantly higher bone sclerosis (P <0.05­0.001) at the PER location, but only BV/TV (P=0.03) and trabecular number (P=0.02) differed between OA and non-OA knees at the CENT location uncovered by meniscus. CONCLUSIONS: OA results showed a partial dedifferentiation of the subchondral bone micro-architecture between PER and CENT locations probably due to menisci that still retain some of their protective effects on the subchondral bone.

Changes in smooth muscle contractility of rainbow trout (Oncorhynchus mykiss Walbaum) intestine during acclimation to altered temperature.

The effects of altered water temperature in vivo on in vitro smooth muscle contractility of rainbow trout intestine were investigated. Temperature has a significant effect on receptor-mediated intestinal smooth muscle contractility in the rainbow trout. The efficacy of 5-HT, carbachol, and transmural stimulation increased with temperatures above 10°C, with an optimal increase at 15°C. There was also a modest increase in the potency of 5-HT and carbachol within 2 days of establishing trout at 20°C. By day 8, most of these changes had either stabilized or were returning to control values, suggesting that acclimation changes in membranes and enzyme activities were taking effect. However, the contractile responses to carbachol and transmural stimulation were still increasing at this time. This may imply that the muscarinic receptors are more resistant to membrane acclimation changes and may take longer to adapt. Because these experiments were controlled for handling stress and seasonal changes that affect contractility, we have been able to demonstrate some early changes in smooth muscle contractility that occur during acclimation to altered temperature.

Evaluation of the instantaneous centers of rotation of the stifle before and after repair of torn cruciate ligament by use of the over-the-top technique in dogs.

Seven dogs with torn cruciate ligament were used to evaluate the "over-the-top" repair procedure, using instantaneous center of rotation (ICR). Normal and cruciate-torn stifles of dogs were radiographed before surgery, using an image intensifier videotape system. The injured stifle was reradiographed 6 weeks after surgery. Images of the stifles were photographed from video monitor. Photographs were analyzed by a digitizer hooked to a computer to find the ICR at various angles. Data were analyzed, using multivariate analysis of variance. Relative to those of normal stifles, ICR of the damaged stifles were located significantly (P less than 0.05) proximal and caudal. After surgery, the ICR were still proximal and caudal, but not significantly so. We conclude that the cruciate-torn stifle deviates significantly from normal and that such deviation is restored to normal limits by use of the over-the-top procedure.