Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.3.5.1 (succinate dehydrogenase)
 8,177 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Spaceflight or hindlimb suspension results in a loss of mass and alterations of the metabolic and contractile protein profiles of skeletal muscles toward that resembling faster muscles. Given the influence of motoneurons on muscle properties, ventral horn cells of the lumbosacral enlargement of the spinal cord were studied to determine whether similar adaptations were present. Three groups of rats (5 per group) were studied: control, 14-day spaceflight, and 14-day hindlimb suspension. Spinal cords were quick-frozen, and the succinate dehydrogenase (SDH) activity and cross-sectional area of the soma of ventral horn cells were measured using a computer-enhanced image-processing system. Briefly, the optical density for SDH activity was determined after 8 min of incubation in a medium that gave a steady-state enzymatic reaction. Soma sizes were determined in cells with a visible nucleus. Although there were no significant differences among the three groups in mean cross-sectional area and SDH activity, the population distributions of both variables shifted significantly. In the flight rats, there was a shift toward smaller cells. Compared with control, the population distribution of SDH activities in the flight rats shifted toward higher activities, whereas the distribution shifted toward lower activities in the suspended rats. When considering the interactive effects within individual cells, there was a higher percentage of small cells with high SDH activities in the flight than in the control or suspended rats. These contrasting effects of spaceflight and hindlimb suspension suggest that the changes observed in ventral horn cells were due to factors other than simply the absence of weight support.
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PMID:Ventral horn cell responses to spaceflight and hindlimb suspension. 152 37

Previous studies have demonstrated that a chronic change in neuronal activation can produce a change in soma oxidative capacity, suggesting that: (i) these 2 variables are directly related in neurons and (ii) ion pumping is an important energy requiring activity of a neuron. Most of these studies, however, have focused on reduced activation levels of sensory systems. In the present study the effect of a chronic increase or decrease in motoneuronal activity on motoneuron oxidative capacity and soma size was studied. In addition, the effect of chronic axotomy was studied as an indicator of whether cytoplasmic volume may also be related to the oxidative capacity of motoneurons. A quantitative histochemical assay for succinate dehydrogenase activity was used as a measure of motoneuron oxidative capacity in experimental models in which chronic electromyography has been used to verify neuronal activity levels. Spinal transection reduced, and spinal isolation virtually eliminated lumbar motoneuron electrical activity. Functional overload of the plantaris by removal of its major synergists was used to chronically increase neural activity of the plantaris motor pool. No change in oxidative capacity or soma size resulted from either a chronic increase or decrease in neuronal activity level. These data indicate that the chronic modulation of ionic transport and neurotransmitter turnover associated with action potentials do not induce compensatory metabolic responses in the metabolic capacity of the soma of lumbar motoneurons. Soma oxidative capacity was reduced in the axotomized motoneurons, suggesting that a combination of axoplasmic transport, intracellular biosynthesis and perhaps neurotransmitter turnover represent the major energy demands on a motoneuron. While soma oxidative capacity may be closely related to neural activity in some neural systems, e.g. visual and auditory, lumbar motoneurons appear to be much less sensitive to modulations in chronic activity levels.
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PMID:Adaptability of the oxidative capacity of motoneurons. 161 1