We studied the effects of stimulation frequency on the energy metabolism of rat skeletal muscles during electrical low-frequency stimulation by in vivo Phosphorus-31 Magnetic Resonance Spectroscopy (³¹P-MRS). For this, the sciatic nerve of Wistar-Kyoto rats (WKY) was stimulated electrically at 30Hz and 100Hz as tetanizing frequency. The initial tension at 30Hz was 201.1±21.0 dynes and that at 100Hz was 518.0±5.6 dynes, which was significantly different (p<0.01). Later, the tension produced at 30Hz and 100Hz decreased with time and was not significantly different. The phosphocreatine (PCr)/{inorganic phosphate (Pi)+sugar phosphate (SP)} indicates the energy level of skeletal muscles. In the first 2min of stimulation, the ratios at 30Hz and 100Hz were 0.3±0.1 and 0.5±0.1, respectively. Later, the ratios at 30Hz were maintained at lower values than those at 100Hz. In ³¹P-MRS spectra, SP peaks at 30Hz were higher than those at 100Hz. The intracellular pH at 30Hz and 100Hz in the first 2min of stimulation was 6.28±0.02 and 6.77±0.02, respectively. From 2min to 12min of stimulation, the intracellular pH at 30Hz was maintained at lower values than that at 100Hz.
The results showed that 30Hz-stimulation maintained lower levels of both energy and intracellular pH of skeletal muscles and facilitated aerobic glycolysis to produce ATP during stimulation, and suggest that 30Hz may be a more effective frequency of electrical low-stimulation than 100Hz to improve muscle atrophy and muscle weakness.

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We performed muscle biopsies to know whether the muscular atrophy in hemiplegia on the involved side derived from disuse. Specimens that were taken from M. vastus lateralis of 9 hemiplegic patients, M. flexor hallucis longus of 4 hemiplegic patients and M. vastus lateralis of 11 patients with bone and joint disorders were analyzed qualitatively by enzyme histochemistry. Pathological findings of M. vastus lateralis did not show any statistical differences between hemiplegia and bone and joint disorders, but the muscle fiber atrophy was more prominent in hemiplegia than in bone and joint disorders. Though the muscular fiber atrophy in bone and joint disorders was related to the daily activities, the muscular fiber atrophy in hemiplegia had less relation to these activities, and the two active hemiplegic patients had moderate type 1 and 2 fiber atrophy. A characteristic feature of the muscle fiber type and diameter of M. vastus lateralis was “type 1 fiber≥type 2A fiber≥type 2B fiber”. The muscle fiber type and diameter of M. flexor hallucis longus in hemiplegia consisted of type 1 and 2 fiber atrophy or type 1 and 2B fiber atrophy accompanied by type 2 fiber hypertrophy that was possibly induced by gait. As the hemiplegic muscular atrophy had enzyme histochemical features similar to disuse due to bone and joint disorders and was only a little improved by the daily activities, we thought that the muscular atrophy in hemiplegia on the involved side was caused by unknown central trophic effects with disuse atrophy.

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The purpose of this research was to study the clinical impression that the firing rates of fibrillation potential (FP) are different according to muscle type, being higher in denervated white muscles than in denervated red muscles of rats. A needle electromyographic study was carried out in white muscles (m. extensor digitorum longus, m. tibialis anterior and m. gastrocnemius) and a red muscle (m. soleus) of the right hind limbs, 1-4 weeks after sciatic section of 69 adult male rats. The left hind limbs were not denervated and served as controls. The firing rates of FP (>100μV) were measured in each muscle. An enzyme-histochemical study (ATPase stain) was done simultaneously in 19 rats two weeks after denervation in order to determine the proportion of 1, 2a+2b, and 2c muscle fiber types in each muscle.
The findings are as follows: (1)the firing rates of FP were different in each type of muscle, and they were higher in white muscle than in red muscle (p<0.01), and (2) white muscle contained a higher percentage of type 2a and 2b muscle fibers than red muscle (p<0.01).
It is concluded that the FPs originate more from type 2a and 2b muscle fibers than type 1 and type 2c muscle fibers.

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We measured the passive range of motion (P-ROM) in mentally retarded children using the eye measurement method and obtained the following results:
The P-ROM of a group of children showing mental retardation of unknown etiology but with not-retarded initial walking was not different from that of the normally developed control group. The P-ROM of children showing both mental retardation and retarded initial walking was larger (p<0.01) than that of the control group and also bigger than the not-retarded initial walking group with mental retardation (p<0.01). The P-ROM of the Down's syndrome group was larger than the mentally retarded-retarded initial walking group (p<0.01) and also their joint laxity was significantly higher (p<0.01). The Down's syndrome group, in contrast to the mentally retarded-retarded initial walking group, whose P-ROM approached normal levels with increasing age and growth, did not show such a tendency. The P-POM in the upper half of the body of children showing both mental retardation and autism was larger than that of the control group (p<0.01).

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[in Japanese]

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