We investigated the effects of different frequencies of treadmill running on immobilization-induced soleus and gastrocnemius muscle atrophy and ankle joint contracture in rats using morphology and histochemistry. The right ankle joint of rat was immobilized for 2 weeks. Thereafter, the rats were randomly assigned to four groups for 6 weeks of exercise under different conditions: free cage activity and free remobilization (FR), once-a-week treadmill running (lowfrequency running program (LFR)), three-time-a-week running (middle-frequency running program (MFR)), and six-time-a-week running (high-frequency running program (HFR)) groups. Two weeks of immobilization significantly reduced the cross-sectional area of soleus type I (62%, Po0.05) and type II muscle fibers (66%, Po0.05), gastrocnemius type I (78%, Po0.05) and type II muscle fibers (68%, Po0.05), and the range of ankle joint movement (46%, Po0.05). Immobilization also increased the ratio of type II to total fiber numbers in the soleus (Po0.05), and gastrocnemius (Po0.05), and induced pathological changes in muscle fibers. Some of these changes could not be corrected by free remobilization; however, the LFR, MFR, and HFR groups clearly recovered toward normal levels with exercise frequency, the effect on muscle recovery being more beneficial in the MFR and HFR groups. In addition, the range of ankle joint contracture was improved in LFR, MFR, and HFR groups in comparison with that in the FR group. These findings indicate that treadmill running exercise improved the immobilization-induced muscle fiber histochemical alterations and the range of the ankle motion in rats. Running three times and six times a week was more beneficial for recovery of immobilization-induced muscle atrophy and joint contracture compared with no running or once-a-week running.

Thrombomodulin (TM) is a newly described endothelial cell-associated protein that functions as a potent natural anticoagulant by converting thrombin from a procoagulant protease to an anticoagulant. Various vascular tumors were characterized with immunoperoxidase staining with the use of a polyclonal anti-TM serum. The staining patterns of TM were compared with those of Factor VIII-related antigen (FVIII-RAG) and Ulex europaeus agglutinin-I (UEA-I), which have been used as markers for endothelial cells. The results showed that TM is a specific and a highly sensitive marker for angiosarcomas in comparison with FVIII-RAG or UEA-I. In contrast, UEA-I is more sensitive for benign vascular tumors than TM or FVIII-RAG. The other mesenchymal tumors of nonvascular origin showed negative staining for three endothelial markers. These results indicate that TM is a new specific and sensitive tool for the diagnosis of angiosarcomas.

Abstract.To investigate the effect of denervation and subsequent reinnervation on skeletal muscle, a histochemical study was performed on the soleus muscles of rats. Partial denervation was carried out by freezing the sciatic nerve locally, and the change in the nerve and the soleus muscles was examined for 5 weeks. The muscle fiber cross-sectional area of the denervated soleus muscles progressively declined to a minimum 2 weeks after the injury (type I fibers, 1209.1 ± 248.3 µm 2 ; type II fibers, 802.4 ± 126.8 µm 2 ) and began to reverse the decline at 3 weeks. The type II fiber ratios to total fiber of the denervated sides were consistently higher than the control levels, and muscle fibers stained in both acid preincubation and alkaline preincubation were observed. The proportion of type II fibers in the soleus muscles showed an increase and consequently a decrease with a short delay in response to denervation and consequent reinnervation. These data suggest that denervation elicits an alteration in fiber type composition and a reduction in fiber size. The increase of type II fibers seemed to occur in hybrid fibers containing both myosin heavy chains I and II at varying ratios in the same fibers. The reinnervation took the crucial role of recovering from atrophy and composing the integrity of the soleus muscles. However, the ability to generate muscle tension needs a much longer time to recover. This suggests a need to investigate interventions to facilitate the functional recovery of partially-denervated muscle.

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