Changes in sarcomere length following tenotomy in the rat

Abstract

The medial belly of the gastrocnemius and the extensor digitorum longus muscles of rats were tenotomized. One day following tenotomy, the mean sarcomere length of the fast medial gastrocnemius was 1.8 microns, a value comparable to that of tenotomized slow soleus. The mean sarcomere length of the tenotomized extensor digitorum longus, however, was 2.0 microns, a figure which differed significantly from the values obtained for both the soleus and the gastrocnemius. Histological preparations showed the presence of central core degeneration in slow fatigue-resistant fibers of the tenotomized gastrocnemius comparable to that seen in the soleus. No changes were found in the fibers of the tenotomized extensor digitorum longus. The fact that central core lesions were produced in the fibers of soleus and medial gastrocnemius but not in the extensor digitorum longus may be related to the lesser reduction in sarcomere length following tenotomy of the latter muscle.

Muscle Force and Power Following Tendon Repair at Altered Tendon Length

“…As a result, the adjacent muscles may have "splinted" the EDL at or near its optimum resting length. Prior study shows that, at 1 day post tenotomy, the EDL sarcomere length is only slightly shorter than control muscle, while both the soleus and gastrocnemius sarcomere lengths are significantly decreased following tenotomy [8,46]. Additionally, simply acutely dissecting extra-muscular connective tissue results in reduced muscle force output [47].…”

“…When muscle length is permanently changed, sarcomere number alters to accommodate an absolute optimal sarcomere length [6][7][8][9][10][11]. Loading or stretching a muscle to increase passive tension up-regulates slow myosin mRNA production [12,13].…”

Development of Fatty Atrophy After Neurologic and Rotator Cuff Injuries in an Animal Model of Rotator Cuff Pathology

“…Disuse of the unloaded muscle results in a significant loss of muscle mass (approximately 60%) with a decrease in muscle fiber crosssectional area and an increase in fat content [3][4][5] . Furthermore, chronically detached muscles become stiffer and shorter than normal tendon-muscle units, and the passive load required to reduce and repair the tendon becomes excessive 6,7 . Denervation of a muscle is also known to reproducibly create architectural changes such as a decrease in cross-sectional area and fatty atrophy in a muscle group 8 .…”

Passive stretch inhibits central corelike lesion formation in the soleus muscles of hindlimb-suspended unloaded rats

“…CCLs occur in other conditions of chronic shortening, such as tenotomy and immobilization by casting in a shortened position (4,8,19). The degeneration of myofibrils after tenotomy correlates with the hypershortened state of the sarcomeres (3). The formation of CCLs in tenotomy is inhibited by denervation, suggesting that contractile activity is essential for lesion generation (1,34).…”