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  • 1
    Electronic Resource
    Electronic Resource
    Effects of different patterns of long-term stimulation on blood flow, fuel uptake and enzyme activities in rabbit fast skeletal muscles (1984)
    Springer
    Pflügers Archiv 402 (1984), S. 306-311 
    Details
    ISSN: 1432-2013
    Keywords: Stimulated fast muscle ; Enzyme activities ; Oxygen consumption ; Blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Long-term electrical stimulation (14–28 days) of rabbit fast muscles (tibialis anterior, TA and extensor digitorum longus, EDL) using intermittent high frequency (3 trains per min of 5 s duration at 40 Hz, for 8 h per day) produced changes in enzyme activities similar to those found with continuous stimulaton at a frequency occuring in nerves to slow muscles (10 Hz). The activity of citrate synthetase, 3-hydroxyacyl-CoA dehydrogenase and succinate dehydrogenase increased two to 3-fold within 28 days. There was a 4-fold increase in hexokinase whereas phosphofructokinase, pyruvate kinase, lactate dehydrogenase and fructose-1,6-diphosphatase decreased to about 60% of the activity levels in the contralateral unstimulated muscles. Blood flow and oxygen consumption at rest were not changed even after 28 days of stimulation, but were increased during contractions in muscles stimulated at either frequency, the level being twice as high as in control muscles. Glucose uptake was similar to that in control muscles both at rest and during contractions and the output of lactate was similar to that found in control muscles in muscles stimulated at 40 Hz. Muscles stimulated at 10 Hz had smaller lactate output. Thus intermittent stimulation at high frequency (40 Hz) and continuous low frequency (10 Hz) produced similar changes in aerobic metabolism and fuel uptake provided that the total number of stimuli was comparable and that the stimulation was carried out for sufficiently long period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585514
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  • 2
    Electronic Resource
    Electronic Resource
    Species-specific effects of chronic nerve stimulation upon tibialis anterior muscle in mouse, rat, guinea pig, and rabbit (1988)
    Springer
    Pflügers Archiv 412 (1988), S. 86-92 
    Details
    ISSN: 1432-2013
    Keywords: Chronic, low-frequency nerve stimulation ; Enzyme activities ; Energy metabolism ; Fast-twitch skeletal muscle ; Species differences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Tibialis anterior (TA) muscle of mouse, rat, guinea pig, and rabbit was indirectly stimulated for 10 h/day at 10 Hz up to 28 days. Changes in the activity levels of hexokinase (HK), phosphofructokinase (PFK) glyceraldehydephosphate dehydrogenase (GAPDH), lactate dehydrogenase (LDH), creatine kinase (CK), citrate synthase (CS), malate dehydrogenase (MDH), 3-hydroxyacyl-CoA dehydrogenase (HADH), and β-hydroxybutyrate dehydrogenase (HBDH) were compared. Although the direction of changes in the enzyme activity pattern was in accordance with previous findings on rabbit TA, the magnitude of the responses varied markedly between themammals under study. Mouse TA was almost unaffected. A major effect of chronic stimulation in rat, guinea pig and rabbit was an increase in enzyme activities of aerobic-oxidative metabolism. According to intrinsic differences of the muscles under study, the increases varied among the species and appeared to be inversely related to the basal levels of these enzymes in the unstimulated muscles. Conversely, glycolytic enzyme activities (PFK, GAPDH, LDH) markedly decreased in rat, guinea pig, and rabbit, and were only slightly reduced in mouse. Changes in HK and HBDH activities displayed the largest variations in the induced change between species. These results indicate species-specific patterns of metabolic adaptation to increased contractile activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00583735
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Fibre type specific transformations in the enzyme activity pattern of rat vastus lateralis muscle by prolonged endurance training (1983)
    Springer
    Pflügers Archiv 399 (1983), S. 216-222 
    Details
    ISSN: 1432-2013
    Keywords: Enzyme activities ; Energy metabolism ; Fast glycolytic (FG) fibres ; Fast oxidative glycolytic (FOG) fibres ; Metabolic fibre transformation ; Prolonged endurance training ; Vastus lateralis muscle (rat)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The alterations in activity patterns of representative enzymes in energy metabolism were investigated in the superficial (white) and deep (red) portions of the fast vastus lateralis muscle of the adult rat in response to prolonged endurance training. It was found that following 15 weeks of extreme training (final running duration: 210 min per day, 27 m/min at 15 degree grade), increases in the activities of marker enzymes of the citric acid cycle (citrate synthase), β-oxidation (3-hydroxyacyl CoA dehydrogenase), and ketone body utilization (3-ketoacid CoA transferase) as well as of glutamate pyruvate transaminase occurred in both regions of the muscle, with the geatest increase being observed in the superficial portion (2.6–4.2-fold). Pronounced increases were also seen for hexokinase which showed highest activities after 7 weeks of training. Conversely, decreases were noted for various glycogenolytic, glycolytic and gluconeogenic enzymes (phosphorylase, glyceraldehydephosphate dehydrogenase, pyruvate kinase, lactate dehydrogenase and fructose-1,6-diphosphatase). Reduction in the activities of these enzymes was most pronounced in the deep portion of the muscle. These results demonstrate a fundamental rearrangement of the energy metabolism of the muscle in response to prolonged, high intensity training. In the case of the deep portion of the vastus lateralis muscle, which has been shown to be composed of a large percentage of fast oxidative-glycolytic fibres (FOG), the enzyme profile becomes similar to the slow oxidative (SO) fibre. In the superficial portion which contains predominantly fast glycolytic fibres (FG), the enzyme profile becomes similar to FOG fibres. The magnitude of the observed changes in enzyme activities was greater than in previous animal studies. This suggests that there might be no limit to the metabolic adaptability of skeletal muscle to increased contractile activity. In this context, the adaptations observed here qualitatively resemble the metabolic transformations reported for chronic low frequency electrical stimulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656718
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  • 4
    Electronic Resource
    Electronic Resource
    Responses of fatigable and fatigue-resistant fibres of rabbit muscle to low-frequency stimulation (1993)
    Springer
    Pflügers Archiv 424 (1993), S. 529-537 
    Details
    ISSN: 1432-2013
    Keywords: Energy metabolism ; Enzyme activities ; Fatigue ; Fibre types ; Force generation ; Fructose 2,6-bisphosphate ; Low-frequency stimulation ; Metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study investigates early adaptive responses of fast-twitch muscle to increased contractile activity by low-frequency stimulation. Changes in metabolite levels and activities of regulatory enzymes of carbohydrate metabolism were investigated in rabbit tibialis anterior muscle after 24 h of stimulation. In addition, changes elicited during a 5-min lasting acute stimulation experiment were compared between 24-hprestimulated and contralateral control muscles. Stimulation for 5 min reduced energy-rich phosphates and glycogen, and increased lactate in the control muscle. A transient elevation of fructose 2,6-bisphosphate demonstrated that activation of phosphofructokinase 2 was an immediate response to contractile activity. Prestimulated muscles displayed nearly normal values for ATP, phosphocreatine and glycogen, and did not augment lactate. Increased activities of hexokinase and phosphofructokinase 2 and permanently elevated levels of fructose 2,6-bisphosphate pointed to enhanced glycolysis with glucose as the main fuel in the prestimulated muscle. Isometric tension of the control muscle decreased rapidly a few minutes after the onset of stimulation. In the prestimulated muscles, tension was almost stable, but amounted to only 30%–40% of the initial tension of the control muscle. In view of the fibre type distribution of rabbit tibialis anterior, these findings suggested that a large fibre fraction of the prestimulated muscle, possibly the glycolytic type IID fibres, did not contract. Therefore, the possibility must be considered that the metabolite pattern of the 24-h-stimulated muscle primarily reflected metabolic activities of the contracting, less fatigable fibres, most likely type IIA and type I fibres. The suggestion that a large fibre fraction did not produce force, in spite of metabolic recovery, points to factors responsible of their refractoriness to low-frequency stimulation other than metabolic exhaustion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374918
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Biochemical and ultrastructural changes of skeletal muscle mitochondria after chronic electrical stimulation in rabbits (1985)
    Springer
    Pflügers Archiv 404 (1985), S. 1-9 
    Details
    ISSN: 1432-2013
    Keywords: Energy metabolism ; Muscle transformation ; Morphometry ; Glycolysis ; Citric acid cycle ; Ketone body utilisation ; Enzyme activities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of the present investigation was to follow and correlate changes of structural and biochemical markers of energy metabolism during chronic electrical stimulation of tibialis anterior muscle in rabbits. In the superficial portion of the muscle, 5 to 6-fold increases occurred in enzyme activities of the citric acid cycle and of fatty acid oxidation after 28 days of stimulation. Enzyme activity changes in the deep, more oxidative part of the muscle were relatively smaller. Consequently, levels of the citric acid cycle enzymes became similar in superficial and deep parts of the muscle after the longest stimulation periods. With the exception of hexokinase, which increased in parallel with the citric acid cycle enzymes, glycolytic enzymes decreased 2 to 3-fold. Muscle mass and fibre size remained unchanged, while capillary density and capillary to fiber ratio increased 2-fold. The volume density of total mitochondria increased in a fashion similar to the changes of the enzymes of the citric acid cycle (7-fold in superficial and 3.5-fold in deep parts of the muscle) and, thus, approached values found in heart muscle. Disproportionate changes in enzyme activities of ketone body utilisation and of mitochondrial glycerolphosphate oxidase indicated qualitative changes within the mitochondrial population. However, the proportion of subsarcolemmal to interfibrillar mitochondria, as well as the area of inner mitochondrial membrane per unit volume of mitochondrion remained unchanged. Similarly, intracellular lipid deposits remained unchanged with stimulation. It is concluded that there is an excellent agreement between morphometric and biochemical measurements of tissue oxidative capacity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581484
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    Paper (German National Licenses)
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