| 1. |
- Hultén, B, et al.
(författare)
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Relationship between isometric endurance and fibre types in human leg muscles.
- 1975
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 93:1, s. 135-8
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Tidskriftsartikel (refereegranskat)abstract
- Relationship between isometric endurance performance at 50% of maximal voluntary isometric contraction (MCV) and skeletal muscle fibre composition has been elucidated in 19 physical education students. This was found to be linear and the equation corresponded to: y=9.35 + 1.093x; r=0.70 (endurance time expressed in seconds and fibre composition as percent slow twitch muscle fibres (ST) of the vastus lateralis muscle). As it is assumed from previous studies that similar isometric tensions preferentially recruit fast twitch muscle fibres (FT) and that the muscle at the point of exhaustion exhibits maximal values for lactate accumulation, it is suggested that lactate formed in FT fibres is released and stored in nonrecruited ST fibres. The ability to sustain similar isometric tension would then be depending on how large the fraction of ST fibres is that can serve as a lactaterecipient for lactate producing FT fibres.
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| 2. |
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| 3. |
- Karlsson, J, et al.
(författare)
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LDH isozymes in skeletal muscles of endurance and strength trained athletes.
- 1975
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 93:2, s. 150-6
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Tidskriftsartikel (refereegranskat)abstract
- Muscle biopsy samples were obtained from arm and leg muscles of endurance and strength trained athletes, respectively. Total LDH activity as well as occurrence and activity of LDH isozymes were determined. Comparing the results from the athletes with those from non-trained subjects with corresponding fibre compositions, it was found that the endurance athletes had a lower total LDH activity, a higher relative activity of the most heart-specific isozymes. LDH (1 + 2), and, on electrophoretic separation, a complete absence of LDH (4 + 5) in both arm and leg muscles. As compared to the untrained material the strength trained athletes tended to have a higher total LDH activity, a similar distribution of relative isozyme activities, and, in the leg muscles, a strong electrophoretic band corresponding to LDH 5, the most skeletal muscle specific isozyme.
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| 4. |
- Komi, P V, et al.
(författare)
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Skeletal muscle fibres and muscle enzyme activities in monozygous and dizygous twins of both sexes.
- 1977
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 100:4, s. 385-92
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Tidskriftsartikel (refereegranskat)abstract
- Significance of the genetic component in determining the interindividual variation observed in skeletal muscle fibre composition and enzyme activities was investigated in 31 pairs of male and female monozygous (MZ) and dizygous (DZ) twins, whose ages ranged in all but one pair (11 years) from 15 to 24 years. Percent distribution of slow twitch muscle fibres and activities of Ca2+ and Ng2+ stimulated ATPases, creatine phosphokinase, myokinase, phosphorylase, lactate dehydrogenase (LDH) and distribution of its isozyme LDH-1 were all analyzed in biopsy samples taken from the vastus lateralis muscle. The data disclosed that in contrast to DZ twins the MZ twins of both sexes had an essentially identical muscle fibre composition. Calculation of the heritability estimate for this parameter gave the values of 99.5% and 92.8%, respectively for males and females. In contrast to the fibre composition presence of a significant genetic component was not observed in any of the enzyme activities studied. It was concluded that there is a predominant genetic influence on the skeletal muscle fibre composition in man, and thus also on the potential capacity of the muscles to perform work.
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| 5. |
- Sjödin, B, et al.
(författare)
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Effect of physical training on LDH activity and LDH isozyme pattern in human skeletal muscle.
- 1976
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 97:2, s. 150-7
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Tidskriftsartikel (refereegranskat)abstract
- Total lactate dehydrogenase (LDH) activity and LDH isozyme pattern were studied in muscle biopsies obtained from m. vastus lateralis after 1) "aerobic" training performed as interval and extreme distance running, respectively (3 subjects); and 2) "anaerobic" training for two months, carried out as repeated maximal bursts of approximately 1 min running (6 subjects). After the "anaerobic training" no changes in LDH properties could be detected, although running performance improved. The extreme distance running resulted in a decrease in total LDH activity and an increase in relative activity of the heart specific isozymes. A relationship was also shown between the relative activity of these isozymes and the training distance covered. The relatively more aerobic prevailing during distance running as compared to "anaerobic training" were proposed to decrease muscle specific subunits and/or increase synthesis of heart specific subunits in both muscle fiber types. This suggestion was supported by isozyme analysis of lyophilized and dissected single muscle fibres.
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| 6. |
- Støen, R., et al.
(författare)
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Relative significance of the nitric oxide (NO)/cGMP pathway and K+ channel activation in endothelium-dependent vasodilation in the femoral artery of developing piglets
- 2001
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 171:1, s. 29-35
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Tidskriftsartikel (refereegranskat)abstract
- Mechanisms mediating endothelium-dependent vasodilation were investigated in femoral artery rings from <2-day-old (newborn) and 2-week-old piglets. Based on previous results we hypothesized an age difference in the relative contribution of nitric oxide(NO)-cyclic 3′,5′-guanosine monophosphate (cGMP) and K+ channel-activation to acetylcholine (ACh)-induced vasodilation. Changes in vascular tone were studied in organ baths in the absence or presence of NO synthase(NOS) inhibition or K+ channel blockade and the intra-arterial accumulation of cGMP in response to ACh was measured with radioimmunoassay (RIA). In control experiments, relaxant responses to ACh were equal in the two age groups. In the presence of the NOS-inhibitors N G-monomethyl-L-arginine acetate (L-NMMA; 100 μM) or NG-nitro-L-arginine (L-NOARG; 1–100 μM), however, relaxation was significantly more reduced in femoral artery rings from 2-week-old than from newborn, with lower pD2 values in the older age group. Inhibition of large (BKCa) conductance calcium-sensitive K+ channels with tetraethylammonium chloride (TEA; 1 mM), gave a significant rightward shift in the concentration-response curves to ACh which was of the same magnitude in both age groups. The ACh-induced vasodilation was abolished in both age groups by high K+ (20 mM) in combination with L-NOARG (100 μM). The relative increase in cGMP levels after addition of ACh (10 nM) was significantly larger in rings from newborn compared with 2-week-old piglets (12- vs. four-fold). In summary, sensitivity to NOS inhibition increased with age while the effect of K+ channel blockade with TEA was the same in femoral artery rings from newborn to 2-week-old piglets. Lower sensitivity to NOS inhibition and a larger increase in cGMP in response to ACh could indicate a higher efficacy of the NO/cGMP pathway in this vessel in the newborn piglet.
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Tesch, P, et al.
(författare)
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Muscle fatigue and its relation to lactate accumulation and LDH activity in man.
- 1978
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 103:4, s. 413-20
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Tidskriftsartikel (refereegranskat)abstract
- The lactate concentration in different muscle fibre types was determined in biopsy specimens from human vastus lateralis muscle after 30 and 60 s of maximal dynamic leg exercise. In addition, muscle fibre type distribution, total lactate dehydrogenase (LDH) activity, and isozymes of LDH were determined. In accordance with previous studies (Thorstensson and Karlsson 1976, Nilsson et al. 1977) it was found that an increasing proportion of slow twitch (ST) fibres corresponded to better sustained muscle force. Lactate was found preferentially in fast twitch (FT) fibres after 30 s, but after 60 s this difference was abolished. Differences between the two main muscle fibre types in muscle lactate, total LDH activity, and M-LDH activity were correlated to muscle fatigue. It was concluded that lactate or associated pH changes primarily in FT fibres could be one factor responsible for the impaired muscle function.
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