The effect of tenotomy and immobilisation on intramuscular connective tissue. A morphometric and microscopic study in rat calf muscles.

The effect of tenotomy and of immobilisation in lengthened and shortened positions on the intramuscular connective tissue of the calf muscles of the rat was studied morphometrically and with a scanning electron microscope. Both tenotomy and immobilisation produced a marked increase in both the endomysial and the perimysial collagen networks, with a simultaneous decrease in intramuscular capillary density. The increase in connective tissue volume was more pronounced and occurred more rapidly in the soleus, which consists mainly of type I, slow-twitch fibres than in the gastrocnemius, which is mainly of type II, fast-twitch fibres. The relative volume of connective tissue increased in parallel with the duration of immobilisation or after tenotomy. There was slightly more increase after immobilisation in a shortened rather than in a lengthened position.

Quantitative alterations of intramuscular connective tissue in calf muscles of the rat during combined hypoxia and hypokinesia.

The investigations were designed to study the long-term effect of hypoxia, hypokinesia and of combined hypokinesia and hypoxia on the skeletal muscle in the rat. In the muscles of the hypoxic and hypokinetic animals serious degenerative changes were found and the fibre-type ratio was altered. In the hypoxic animals moderate fibrosis was revealed. In the hypokinetic, and hypokinetic + hypoxic animals the amount of connective tissue was 5 to 10-fold greater in the calf muscles as compared to the control.

Quantitative alterations in intramuscular connective tissue following immobilization: an experimental study in the rat calf muscles.

The purpose of the present investigation was to study the effect of immobilization in two different positions, shortened or lengthened, on the connective tissue and capillarization of the rat calf muscles. In 18 rats the left hind limb was immobilized so that the soleus and gastrocnemius muscles were in a lengthened position and tibialis anterior was in a shortened position, and in 18 rats vice versa. The right hind limbs were kept free to serve as controls. After 1, 2, and 3 weeks of immobilization, an equal number of rats were killed and the muscles were analyzed. The connective tissue muscle ratio was measured from histological sections by automatic image analyzer and the number of capillaries per 1000 muscle fibers was also recorded. In the intact muscles the proportions of intramuscular connective tissue in the soleus, gastrocnemius, and tibialis anterior were 2, 3, and 5%, respectively. During the immobilization period of 3 weeks the proportion of connective tissue increased significantly in all muscles, but the only significant difference between the positions was in the soleus muscle in which more connective tissue was found in the lengthened position, 54% vs 30% in the shortened position. The amount of capillaries decreased significantly during immobilization in all muscles to about 65% of normal capillar density, but the position of immobilization seemed to have no effect on this phenomenon. The increase in intramuscular connective tissue during immobilization seems to occur simultaneously with muscle atrophy and loss of muscle capillarity. The stretched position of immobilization seems to have an additional fibrotic effect if the immobilized muscle, such as soleus, consists mainly of type I fibers generally known to be more vulnerable to disuse atrophy than type II fibers.

Fine structural alterations of the palmar aponeurosis in Dupuytren's contracture. A combined scanning and transmission electronmicroscopic examination.

The authors examined the fine structural alterations of palmar aponeurosis in Dupuytren's contracture. Two types of the fibroblasts can be identified: classic fibroblasts and myofibroblasts. In the Dupuytren's tissue one fourth of all non-inflammatory cells were regarded as myofibroblasts. In the Dupuytren's aponeurosis the orientation of the thin and thick collagen fibers varied. The Paccini corpuscles were hypertrophised and around them compact collagen tissue was increased.