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1.
Neuroreport ; 11(4): 823-8, 2000 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-10757527

RESUMO

Succinate dehydrogenase (SDH) activities and cross-sectional areas (CSAs) of tibialis anterior motoneurons and muscle fibers were determined in 20-, 40-, and 60-week-old male senescence-accelerated mice (SAMP6), and compared with those in age-matched accelerated-senescence resistant mice (SAMR1). The mean CSA of motoneurons in SAMP6 decreased at 60 weeks, primarily due to a selective loss of large (>400 microm2) motoneurons. The mean SDH activity of motoneurons with CSAs between 100 and 400 microm2 decreased in SAMP6, but not SAMR1, at 60 weeks. The mean muscle fiber SDH activities and CSAs in SAMP6 decreased at 60 weeks. There were no differences in the mean SDH activity or CSA of motoneurons or muscle fibers among 20-, 40-, and 60-week-old SAMR1. These results demonstrate that mice which have been shown to have a variety of accelerated-senescent features also have an earlier onset of age-related changes in motoneurons and the muscle fibers that they innervate when compared with age-matched accelerated-senescence resistant mice.


Assuntos
Tamanho Celular/fisiologia , Perna (Membro)/anatomia & histologia , Perna (Membro)/fisiologia , Neurônios Motores/enzimologia , Fibras Musculares Esqueléticas/enzimologia , Músculo Esquelético/enzimologia , Succinato Desidrogenase/metabolismo , Fatores Etários , Animais , Peso Corporal , Modelos Animais de Doenças , Masculino , Camundongos , Camundongos Mutantes , Neurônios Motores/citologia , Fibras Musculares Esqueléticas/citologia , Músculo Esquelético/citologia , Atrofia Muscular/enzimologia
2.
Acta Histochem ; 96(1): 74-80, 1994 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-8030383

RESUMO

Hypoxia-acclimatized rats had a higher percentage of fast-twitch oxidative glycolytic fibers and a lower percentage of slow-twitch oxidative fibers in the soleus muscle than age-matched normoxic-rats. However, there was no difference in the fiber type composition of the soleus muscle between hypoxic- and normoxic-male rats after hypoxic-rats were bred at the sea level atmospheric pressure for 5 weeks. Therefore, it is suggested that a higher percentage of fast-twitch oxidative glycolytic fibers in the muscle is found only under hypoxic conditions and is due to an acute response to hypoxia.


Assuntos
Pressão Atmosférica , Hipóxia/patologia , Músculos/química , Animais , Peso Corporal , Feminino , Histocitoquímica , Masculino , Músculos/metabolismo , Músculos/patologia , Ratos , Ratos Sprague-Dawley , Caracteres Sexuais
3.
Jpn J Physiol ; 50(6): 561-8, 2000 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-11173551

RESUMO

Mammalian skeletal muscle fibers are classified into three basic types based on their enzyme histochemical profiles: fast-twitch glycolytic (FG), fast-twitch oxidative glycolytic (FOG), and slow-twitch oxidative (SO) types. The type-shift of fibers from FOG to SO in the slow soleus muscle of rats occurs during postnatal growth. Our previous studies have demonstrated that hypoxic exposure inhibits a growth-related type-shift of fibers from FOG to SO in the rat soleus muscle, irrespective of the duration and age at which the animals are exposed to hypoxia. Our previous studies have also revealed that a high percentage of FOG fibers in the soleus muscle of the hypoxia-adapted rats is found only under hypoxic conditions. Furthermore, we have found that these adaptations in fibers of the rat soleus muscle correspond well with those in motoneurons at the ventral horn of the spinal cord that innervate the muscle fibers.


Assuntos
Hipóxia/fisiopatologia , Neurônios Motores/fisiologia , Músculo Esquelético/fisiologia , Adaptação Fisiológica , Animais , Músculo Esquelético/inervação , Ratos
4.
Jpn J Physiol ; 50(4): 413-8, 2000 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-11082539

RESUMO

The cross-sectional areas and succinate dehydrogenase activities of different types of fibers in different regions of the plantaris and tibialis anterior muscles in 10-week-old male rats were determined using quantitative histochemistry. The muscle fibers were classified as type I, type IIA, or type IIB according to their adenosine triphosphatase activities. There were no regional differences in either the mean cross-sectional area or the mean succinate dehydrogenase activity of type IIA fibers in both muscles. In contrast, type IIB fibers in the deep region of both muscles had smaller cross-sectional areas and higher succinate dehydrogenase activities than those in the superficial and middle regions. These data suggest the presence of regional differences in the cross-sectional area and succinate dehydrogenase activity of type IIB fibers in the muscle.


Assuntos
Fibras Musculares de Contração Rápida/enzimologia , Fibras Musculares de Contração Lenta/enzimologia , Músculo Esquelético/citologia , Músculo Esquelético/metabolismo , Succinato Desidrogenase/metabolismo , Adenosina Trifosfatases/metabolismo , Animais , Tamanho Celular/fisiologia , Masculino , Fibras Musculares de Contração Rápida/química , Fibras Musculares de Contração Rápida/citologia , Fibras Musculares de Contração Lenta/química , Fibras Musculares de Contração Lenta/citologia , Músculo Esquelético/química , Miosinas/análise , Oxirredução , Ratos , Ratos Wistar
5.
Aviat Space Environ Med ; 63(7): 583-7, 1992 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-1616433

RESUMO

The fiber type composition of the soleus muscle was investigated in male Sprague-Dawley rats exposed to hypobaric hypoxia of 460 mm Hg from 5 to 12 weeks of age. The muscle fibers were classified as fast-twitch oxidative (FO) and slow-twitch (S) on the basis of adenosine triphosphatase (ATPase) and succinate dehydrogenase (SDH) reactions. Intermediate fibers (INT) with intermediate ATPase and high SDH reaction intensities were also examined. A type shift of muscle fibers from FO to INT and S was found in the control group during development. After exposure to hypoxia, the hypoxia group had a significantly greater percentage of FO fibers than the age-matched control group. There was no significant change in the total number of fibers in the muscle during development and after exposure to hypoxia. These results indicate that the increased percentage of FO fibers found in the developing rat under hypoxic conditions is due to a hypoxia-induced inhibition of the type shift of muscle fibers from FO to S during development.


Assuntos
Hipóxia/patologia , Músculos/patologia , Animais , Câmaras de Exposição Atmosférica , Masculino , Desenvolvimento Muscular , Ratos , Ratos Endogâmicos
6.
Can J Physiol Pharmacol ; 70(11): 1522-4, 1992 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-1296867

RESUMO

The effect of chronic hypoxia on the whole-body insulin action in rats was investigated. Rats were kept in a hypobaric hypoxia chamber maintained at a simulated altitude of 4000 m for 10 weeks. At the end of the experimental period, the mean body weight of the hypoxic rats was significantly lower than that of the control rats. The muscle weight to body ratio of the quadriceps muscle in hypoxic rats was larger than that in control rats, but those of the gastrocnemius, soleus, and extensor digitorum longus muscles did not differ between the control and hypoxic rats. On the other hand, the epididymal fat pads of hypoxic rats were markedly smaller than those of the control rats. The results of a euglycemic clamp experiment with infusions of 14 and 3.6 mU insulin.kg-1.min-1 indicated that the steady-state glucose infusion rate was not statistically different between hypoxic and control rats. It is suggested that chronic hypoxia did not influence the whole-body insulin action on glucose transport activity.


Assuntos
Glicemia/metabolismo , Hipóxia/metabolismo , Insulina/farmacologia , Tecido Adiposo/patologia , Animais , Peso Corporal , Contagem de Eritrócitos , Hipóxia/patologia , Insulina/sangue , Masculino , Músculos/patologia , Ratos , Ratos Sprague-Dawley
7.
J Anat ; 181 ( Pt 2): 327-33, 1992 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-1295870

RESUMO

Fibre type composition in the soleus muscle was studied in second generation male and female Sprague-Dawley rats bred at 460 Torr (hypobaric hypoxia). In control male and female rats (bred at sea level atmospheric pressure) the percentage of slow twitch oxidative (SO) fibres increased, and the percentage of fast twitch oxidative glycolytic (FOG) fibres decreased over time. In male hypoxic rats fibre type composition did not change. However, in female hypoxic rats the percentage of SO fibres increased, and that of FOG fibres decreased over time. The female hypoxic rats had a higher percentage of FOG fibres and a lower percentage of SO fibres than age-matched control rats. These findings indicate that hypoxia-acclimatised rats have a relatively high percentage of FOG fibres, and that this is due to inhibition of the fibre type shift from FOG to SO, which occurs during normal development. Furthermore, there is a sex-related difference in the change in fibre type composition in hypoxia-acclimatised rats.


Assuntos
Hipóxia/patologia , Músculos/patologia , Aclimatação , Animais , Peso Corporal/fisiologia , Feminino , Masculino , Músculos/anatomia & histologia , Ratos , Ratos Sprague-Dawley , Caracteres Sexuais
8.
Artigo em Inglês | MEDLINE | ID: mdl-2369905

RESUMO

Twelve male Sprague-Dawley rats (21 days old) were randomly assigned into two experimental groups: sea level control (CONT) and hypobaric hypoxia (HYPO). The HYPO rats were kept in an hypobaric chamber maintaining a simulated altitude of 4000 m (61.1 kPa). After 10 weeks of treatment, the rat hindlimb muscles [soleus (SOL) and extensor digitorum longus (EDL)] were subjected to histochemical and electro-mechanical analyses. Results indicated that compared to CONT the HYPO SOL muscle had a significantly greater relative distribution of fast-twitch-oxidative-glycolytic (FOG) fibres (28.9% SEM 2.0 vs 18.3% SEM 1.8, P less than 0.01) with a significant decrease in slow twitch oxidative fibre distribution (69.5% SEM 2.4 vs 82.9% SEM 3.1, P less than 0.01). Compared to CONT the HYPO EDL muscle also manifested a significant increase in FOG fibre distribution (51.6% SEM 0.8 vs 46.6% SEM 1.1, P less than 0.01), but this was accompanied by a significant decrease in fast twitch glucolytic fibres (44.3% SEM 0.9 vs 49.2% SEM 1.7, P less than 0.05). These histochemical fibre type transformations accompanied significant and expected changes in the electro-mechanical parameters tested in situ, e.g. maximal twitch force, maximal rate of force development, contraction time, half relaxation time, force: frequency curve, and fatigability. It was concluded that chronic hypobaric hypoxia could have a potent influence upon the phenotype expression of muscle fibres.


Assuntos
Hipóxia/fisiopatologia , Músculos/fisiopatologia , Animais , Pressão Atmosférica , Fenômenos Biomecânicos , Eletrofisiologia , Membro Posterior , Histocitoquímica , Hipóxia/etiologia , Masculino , Ratos , Ratos Endogâmicos
9.
Acta Neuropathol ; 89(3): 204-8, 1995.
Artigo em Inglês | MEDLINE | ID: mdl-7754741

RESUMO

The fiber type distribution of the soleus muscle in male and female rats was investigated 4 weeks after hypophysectomy. Oxidative enzyme activity of the soleus motoneurons in the spinal cord was also examined by enzyme histochemical assay. In male rats, the total number of fibers in the soleus muscle was not changed after hypophysectomy, but the percentage of intermediate (INT) fibers (with intermediate adenosine triphosphatase activity following alkaline preincubation, and high succinate dehydrogenase and alpha-glycerophosphate dehydrogenase activities) was increased. All types of fibers in the soleus muscle of hypophysectomized rats showed high adenosine triphosphatase activity following acid preincubation. Oxidative enzyme activity of the motoneurons innervating the soleus muscle was not changed after hypophysectomy. Similar results were obtained in female rats. It is suggested that the increased percentage of INT fibers in the rat soleus muscle after hypophysectomy is due to a lack or reduced levels of growth hormones, and that the metabolic capacities of the muscle fibers and of the innervating motoneurons are affected independently by hypophysectomy.


Assuntos
Hipofisectomia , Neurônios Motores/enzimologia , Fibras Musculares Esqueléticas/enzimologia , Músculos/inervação , Medula Espinal/enzimologia , Animais , Feminino , Membro Posterior , Masculino , Oxirredução , Ratos , Ratos Wistar , Valores de Referência
10.
Pflugers Arch ; 429(5): 601-6, 1995 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-7792137

RESUMO

Histochemical fibre-type composition and myosin heavy chain isoform component in the soleus muscle were studied in normoxic rats at postnatal ages of 5, 10, 15, and 20 weeks and in rats exposed to hypobaric hypoxia (460 torr) for 5 weeks from postnatal ages of 5, 10, and 15 weeks. The increase in the percentage of type I fibres and the concomitant decrease in that of type IIa fibres in the soleus muscle of normoxic rats were observed until 15 weeks of age. On the other hand, no change in the fibre-type composition of the muscle during postnatal development was observed in hypoxic rats, irrespective of the age at which they were exposed to hypoxia. The changes in the myosin heavy chain isoform component (MHC I and MHC IIa) of the muscle during postnatal development and by hypoxia corresponded well with those in the muscle fibre-type composition. It is concluded that hypobaric hypoxia inhibits the growth-related shift of muscle fibre-types from type IIa to type I and of myosin heavy chain isoforms from MHC IIa to MHC I in the rat soleus muscle, and that there are no changes in the muscle fibre-type composition or the myosin heavy chain isoform component caused by hypoxia after the shifts in these parameters which occur during postnatal development are completed.


Assuntos
Hipóxia/metabolismo , Hipóxia/patologia , Fibras Musculares Esqueléticas/fisiologia , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Subfragmentos de Miosina/metabolismo , Envelhecimento/metabolismo , Envelhecimento/fisiologia , Animais , Pressão Atmosférica , Peso Corporal/fisiologia , Histocitoquímica , Isomerismo , Masculino , Fibras Musculares Esqueléticas/metabolismo , Fibras Musculares Esqueléticas/ultraestrutura , Tamanho do Órgão/fisiologia , Ratos , Ratos Sprague-Dawley
11.
Arch Histol Cytol ; 62(4): 393-9, 1999 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-10596950

RESUMO

Succinate dehydrogenase (SDH) activities and cross-sectional areas (CSAs) of different types of fibers in the superficial (EDLs) and deep (EDLd) regions of the extensor digitorum longus and soleus (SOL) muscles and the left ventricular muscle of the heart (HEART) of 10-week-old male rats were determined using quantitative histochemistry and a computer-assisted image processing system. The fibers were classified as type I, type IIA, type IIB, or type IIC according to their histochemically assessed adenosine triphosphatase activities. The mean SDH activity was higher and the mean CSA was smaller in type IIA fibers than in type IIB fibers in both the EDLs and EDLd. The mean SDH activity of type IIA fibers in the SOL was higher than that of type I fibers. Fibers in the HEART showed the highest mean SDH activity and the smallest mean CSA among all fiber types in the muscles examined. There was an inverse correlation between CSA and SDH activity for the different fiber types in different muscles. These data suggest that the SDH activity of fibers in muscle is fiber type- and size-specific, and that the highest SDH activity of fibers in the left ventricular muscle of the heart contributes to their functional properties, i.e., high fatigue resistance.


Assuntos
Fibras Musculares de Contração Rápida/enzimologia , Fibras Musculares de Contração Lenta/enzimologia , Músculo Esquelético/enzimologia , Miocárdio/enzimologia , Succinato Desidrogenase/metabolismo , Animais , Histocitoquímica , Processamento de Imagem Assistida por Computador , Masculino , Ratos , Ratos Wistar
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