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Immunohistochemical and neurochemical study on the aged mouse cerebellum
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1 Ageing AGE-RELATED CHANGES IN THE FAST AND SLOW TWITCH MOTOR UNITS IN THE RAT MEDIAL GASTROCNEMIUS.
KENRO KANDA, KEN HASHIZUME* AND EMI NOMOTO*. Department of Physiology, Tokyo Metropolitan Institute of Gerontology, 35-2, Sakae-cho, Itabashi-ku, Tokyo 173, Japan.
W-hen compared with a motor unit sample of younger animals, there was a large increase in the population and mean tetanic tension for type S motor units in old animals, whereas there was a slight decrease for type F motor units. There was no alteration of twitch contraction times in any unit type. (Kanda et al., Jpn. J. Physiol., 1985; Kanda et al., Neuroscience Abstr., 11, 729, 1985) The present experiment was directed at the study of mechanisms causing this age-related change. Experiments were performed on five middle-aged (11-14 months) and five old (24-29 months) male rats which were anesthetized with urethane (500 mg/kg) and chloralose (50 mg/kg). Single medial gastrocnemius motor-units (type S) were isolated by the stimulation of dissected ventral root filaments. After looking at various physiological properties, the unit was subjected to long stimulation in order to deplete glycogen in the muscle fibers. Then, the MG muscle was excised for later histochemical study. The mean cross-sectional area of muscle fibers in the type S units of the old rats did not alter. However, the innervatlon ratio of type S units in old rats increased, and muscle fibers grouped with more than two together were frequently found. Most of the muscle fibers belonging to the same unit were isolated in the middle-aged rats. These findings suggest that the type S units in the old rats adopted denervated fibers by axon-collaterals. The number of MG muscle-fibers was estimated in two middle-aged and two old muscles. The number of type I muscle fibers increased by about 70%, whereas type II muscle fibers decreased. Consequently, the total number of muscle fibers consisting of the MG muscle was decreased slightly in the old rats. Strongly atrophied fibers were also noted among type II muscle fibers. These findings together with our previous findings that there is no alteration of twitch contraction time, and that there is a more marked decrease in the conduction velocity of axons belonging to type F units, suggest the preferential degeneration of type F motor units and the adoption of denervated fibers by type S units.
IMMUNOHISTOCHEMICAL AND NEUROCHEMICAL STUDY ON THE AGED MOUSE CEREBELLUM
KUNIHIKO OBATA and NOBUHIKO KOJIMA , Department of Pharmacology, Medicine, Maebashi 371
Gunma University School of
Indirect immunofluorescence histochemistry was performed on the cerebellar cortex of aged mice (ddY strain) with the nervous system-specific monoclonal antibodies (MAbs) produced in our laboratory. MAb 159A9 stained the Purklnje cells and their processes. MAb 8C5 stained all cell nuclei (Fujita et al., 1983). MAb 171B5 stained the synaptic vesicle protein (Obata et al., 1986) and disclosed the presynaptic terminals in the molecular and granular layers. Among the young adult (3-6 months old) and aged animals (14-16 and 22-24 months old), there was no difference in the number of Purkinje cells and granular layer-cells, and in the density of Purkinje dendritic spines, molecular layer synapses and mossy fiber terminals. MAb 82EI0 stained the basket cell axons (Obata and Fujita, 1984). In the aged mice the more numerous 82E10-positive fibers surrounded the axon hillock of Purkinje cells. MAb 23CI0 stained a proportion of parallel fibers in the deep molecular layer. MAb 23ClO-positive parallel fibers increased enormously in number in the aged animals. MAb 23CI0 stained also the basket axons in the young adults but this staining disappeared in the aged animals. Auto-fluorescent lipofuscin accumulated with age within Purkinje cells. Some neurochemical analyses were performed on the cerebellum. Two-dimensional gel electrophoresis demonstrated that there was no quantitative difference in protein spots except for acidic protein with a molecular weight of 25,000 which disappeared in the aged cerebellum. Concentration of glutamic acid and gan~a-aminobutyric acid was within a normal range in the young and old cerebellum. Thus the present study indicated several differences in chemical composition in the aged central nervous system.
1 Ageing AGE-RELATED CHANGES IN THE FAST AND SLOW TWITCH MOTOR UNITS IN THE RAT MEDIAL GASTROCNEMIUS.
KENRO KANDA, KEN HASHIZUME* AND EMI NOMOTO*. Department of Physiology, Tokyo Metropolitan Institute of Gerontology, 35-2, Sakae-cho, Itabashi-ku, Tokyo 173, Japan.
W-hen compared with a motor unit sample of younger animals, there was a large increase in the population and mean tetanic tension for type S motor units in old animals, whereas there was a slight decrease for type F motor units. There was no alteration of twitch contraction times in any unit type. (Kanda et al., Jpn. J. Physiol., 1985; Kanda et al., Neuroscience Abstr., 11, 729, 1985) The present experiment was directed at the study of mechanisms causing this age-related change. Experiments were performed on five middle-aged (11-14 months) and five old (24-29 months) male rats which were anesthetized with urethane (500 mg/kg) and chloralose (50 mg/kg). Single medial gastrocnemius motor-units (type S) were isolated by the stimulation of dissected ventral root filaments. After looking at various physiological properties, the unit was subjected to long stimulation in order to deplete glycogen in the muscle fibers. Then, the MG muscle was excised for later histochemical study. The mean cross-sectional area of muscle fibers in the type S units of the old rats did not alter. However, the innervatlon ratio of type S units in old rats increased, and muscle fibers grouped with more than two together were frequently found. Most of the muscle fibers belonging to the same unit were isolated in the middle-aged rats. These findings suggest that the type S units in the old rats adopted denervated fibers by axon-collaterals. The number of MG muscle-fibers was estimated in two middle-aged and two old muscles. The number of type I muscle fibers increased by about 70%, whereas type II muscle fibers decreased. Consequently, the total number of muscle fibers consisting of the MG muscle was decreased slightly in the old rats. Strongly atrophied fibers were also noted among type II muscle fibers. These findings together with our previous findings that there is no alteration of twitch contraction time, and that there is a more marked decrease in the conduction velocity of axons belonging to type F units, suggest the preferential degeneration of type F motor units and the adoption of denervated fibers by type S units.
IMMUNOHISTOCHEMICAL AND NEUROCHEMICAL STUDY ON THE AGED MOUSE CEREBELLUM
KUNIHIKO OBATA and NOBUHIKO KOJIMA , Department of Pharmacology, Medicine, Maebashi 371
Gunma University School of
Indirect immunofluorescence histochemistry was performed on the cerebellar cortex of aged mice (ddY strain) with the nervous system-specific monoclonal antibodies (MAbs) produced in our laboratory. MAb 159A9 stained the Purklnje cells and their processes. MAb 8C5 stained all cell nuclei (Fujita et al., 1983). MAb 171B5 stained the synaptic vesicle protein (Obata et al., 1986) and disclosed the presynaptic terminals in the molecular and granular layers. Among the young adult (3-6 months old) and aged animals (14-16 and 22-24 months old), there was no difference in the number of Purkinje cells and granular layer-cells, and in the density of Purkinje dendritic spines, molecular layer synapses and mossy fiber terminals. MAb 82EI0 stained the basket cell axons (Obata and Fujita, 1984). In the aged mice the more numerous 82E10-positive fibers surrounded the axon hillock of Purkinje cells. MAb 23CI0 stained a proportion of parallel fibers in the deep molecular layer. MAb 23ClO-positive parallel fibers increased enormously in number in the aged animals. MAb 23CI0 stained also the basket axons in the young adults but this staining disappeared in the aged animals. Auto-fluorescent lipofuscin accumulated with age within Purkinje cells. Some neurochemical analyses were performed on the cerebellum. Two-dimensional gel electrophoresis demonstrated that there was no quantitative difference in protein spots except for acidic protein with a molecular weight of 25,000 which disappeared in the aged cerebellum. Concentration of glutamic acid and gan~a-aminobutyric acid was within a normal range in the young and old cerebellum. Thus the present study indicated several differences in chemical composition in the aged central nervous system.