Muscle Fiber Changes of the Vastus Medialis in Rheumatoid Patients

To study the pathology of muscle atrophy in rheumatoid arthritis (RA), we examined the vastus medialis in rheumatoid patients histologically. The relationship of the findings to their ambulatory ability and long-term steroid therapy was investigated. The muscles of the RA patients were also compared with those of patients with osteoarthritis (OA). Specimens of the vastus medialis were collected from 29 knees of 23 patients with RA and 16 knees of 13 patients with OA during total knee arthroplasty. Muscle fibers were classified according to their type, and the ratio between the area of single type I and type II fibers as well as the ratio between the total area of these fibers was calculated. The total area of type II fibers in the RA group was significantly greater than in the OA group (P &#60; 0.05). In the RA group, the mean proportion of the type II fibers relative to the total muscle fiber area tended to increase with the decline of ambulatory ability, while there was no such increase in the OA group. The proportion of type II fibers was increased significantly in RA patients on long-term steroid therapy when compared to those without therapy. In the ratio of the area of a single fiber, there was no clear relationship to ambulatory ability and long-term steroid therapy. It is considered that muscle atrophy in RA is not solely disuse atrophy, but also has a close relationship to steroid therapy and the pathology of the disease itself.</p

Influence of exercise on muscle fibers in rats with steroid myopathy.

The influence of mild exercise on skeletal muscle fibers was investigated histochemically to assess the effects of exercise on steroid myopathy and its efficacy for preventing this disease. Twenty male Wistar rats were divided into 4 groups of 5 each: group T, which received exercise alone; group S which received steroid alone; group ST which received both exercise and steroid; and group C, the control group. In groups S and ST, hydrocortisone was administered subcutaneously at a dose of 10 mg/kg/day for 4 weeks. In the exercise groups, the animals were made to run at a speed of 15 m/min for about 1 h/day for 5 days a week on a treadmill. After the completion of treadmill exercise and steroid administration for 4 weeks, the rats were anesthetized with Nembutal, the soleus muscle (SOL) and the extensor digitorum longus muscle (EDL) were removed and prepared for examinations. The area of type I fibers in the SOL was significantly larger in group ST than in group S. The area of type IIa fibers in the EDL was significantly larger in group ST than in group S. In group S, the proportion of type I fibers in the SOL was significantly lower than in the other three groups. There was little difference in fiber type distribution between groups ST and C. These results suggest that steroid myopathy can be prevented by even mild exercise.</p