We examine the muscle fiber population and metabolic properties of skeletal muscles from the whole body in Thoroughbred horses. Postmortem samples were taken from 46 sites in six Thoroughbred horses aged between 3 and 6 years. Fiber type population was determined on muscle fibers stained with monoclonal antibody to each myosin heavy chain isoform and metabolic enzyme activities were determined spectrophotometrically. Histochemical analysis demonstrated that most of the muscles had a high percentage of Type IIa fibers. In terms of the muscle characteristic in several parts of the horse body, the forelimb muscles had a higher percentage of Type IIa fiber and a significantly lower percentage of Type IIx fiber than the hindlimb muscles. The muscle fiber type populations in the thoracic and trunk portion were similar to those in the hindlimb portion. Biochemical analysis indicated high succinate dehydrogenase activity in respiratory-related muscle and high phosphofructokinase activity in hindlimbs. We suggested that the higher percentage of Type IIa fibers in Thoroughbred racehorses is attributed to training effects. To consider further the physiological significance of each part of the body, data for the recruitment pattern of each muscle fiber type during exercise are needed. The muscle fiber properties in this study combined with the recruitment data would provide fundamental information for physiological and pathological studies in Thoroughbred horses.
1We examine the muscle fiber population of skeletal muscles from whole body in 2 the cheetah (Acinonyx jubatus). In the present experiments, we showed the 3 characteristics of fiber composition in the cheetah by comparative studies among the 4 cheetah, domestic cat, and the beagle dog. Fiber population was determined on muscle 5 fibers stained with monoclonal antibody to each myosin heavy chain isoform. 6Histochemical analysis demonstrated that many muscles in the cheetah and domestic cat muscle fibers in the cheetah, corresponded to its ability to perform high-speed running.
Frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17T) can show various clinical phenotypes. 1 We describe Japanese siblings with the intronic 10 ϩ 14 splice site mutation of the microtubule-associated protein tau (MAPT) gene, showing parkinsonism, depression, weight loss, and central hypoventilation with reduced serotonin concentration suggested by low 5-hydroxyindole acetic acid (5-HIAA) in CSF. These clinical and biochemical features are just shared by Perry syndrome, 2-4 although neither DCTN1 gene mutation nor TDP-43 proteinopathy was found.Case reports. A Japanese woman (III-5) (figure, A) developed clumsiness, tremor of the upper limbs, appetite loss, and apathy at age 44. She had lost 14 kilograms of body weight during 10 months. Masklike face, hypophonic voice, bradykinesia, and muscle rigidity with predominance on the right side were observed. Deep tendon reflexes were hyperactive, especially in the right extremities with the Babinski sign. Despite levodopa treatment, her parkinsonism progressed and memory loss, disorientation, and cyanosis became apparent. Blood tests, EKG, and chest X-ray were not remarkable. Arterial blood gases showed reduced oxygen (60.3 Torr) and increased carbon dioxide (55.5 Torr). CSF analysis showed reduced 5-HIAA (5.6 ng/mL [normal 28.5 Ϯ 7.2 ng/ mL]). Brain MRI demonstrated mild atrophy in the brainstem tegmentum. Polysomnography revealed central hypoventilation with hypoxia. Although memory loss, disorientation, and apathy improved under ventilation assistance, she died due to sudden apnea, 22 months after the onset. Autopsy examination showed severe neuronal loss with gliosis in the globus pallidus, dentate nucleus, subthalamic nucleus, substantia nigra, locus ceruleus, and brainstem tegmentum including the dorsal raphe. Phosphorylated-tau-positive globose-type neurofibrillary tangles, neuropil threads, and oligodendroglial inclusions were seen in the above lesions. These structures were positive for 4 repeat (4R) tau, but negative for TDP-43. In addition to these typical progressive supranuclear palsy (PSP) pathologies,
Satellite cell activation and proliferation could be enhanced after a run to exhaustion without detectable injury as assessed by the histochemical analysis. Understanding the response of satellite cell activation to running exercise provides fundamental information about the skeletal muscle adaptation in Thoroughbred horses.
We compared the time-course of satellite cell (SC) activation between eccentric and concentric contractions in the vastus lateralis (VL) muscle after step exercise. Young adults participated in a 30-min step up/down exercise which mainly involved concentric contractions with the right VL muscle and eccentric contractions with the left VL muscle. The concentric and eccentric contraction phases of the VL muscles were identified by changes in the electromyogram (EMG) and knee joint angle. Biopsy samples were taken from both VL muscles at three time periods: before the exercise and 2 and 5 days after the exercise. We found that the numbers of SCs were significantly increased in the type IIa fibers of the left VL at 2 and 5 days after the exercise. The expression of both hepatocyte growth factor (HGF) and myogenic differentiation 1 (MyoD) mRNA had significantly increased in the left VL at 2 and 5 days after the exercise and in the right VL at 5 days after the exercise. The expression of transient receptor potential canonical (TRPC) 1 mRNA also increased in the left VL at 2 days after exercise. These results indicate that eccentric contraction can effectively activate SC proliferation for up to 5 days after exercise. Similar changes in HGF, MyoD and TRPC1 mRNA expression suggest that HGF/c-Met signal activation through cation influx has a major impact on skeletal muscle SC activation in response to eccentric exercise.
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