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Type II Fibres (type + ii_fibre)
Selected AbstractsAlcoholic skeletal muscle myopathy: definitions, features, contribution of neuropathy, impact and diagnosisEUROPEAN JOURNAL OF NEUROLOGY, Issue 6 2001V. R. Preedy Alcohol misusers frequently have difficulties in gait, and various muscle symptoms such as cramps, local pain and reduced muscle mass. These symptoms are common in alcoholic patients and have previously been ascribed as neuropathological in origin. However, biochemical lesions and/or the presence of a defined myopathy occur in alcoholics as a direct consequence of alcohol misuse. The myopathy occurs independently of peripheral neuropathy, malnutrition and overt liver disease. Chronic alcoholic myopathy is characterized by selective atrophy of Type II fibres and the entire muscle mass may be reduced by up to 30%. This myopathy is arguably the most prevalent skeletal muscle disorder in the Western Hemisphere and occurs in approximately 50% of alcohol misusers. Alcohol and acetaldehyde are potent inhibitors of muscle protein synthesis, and both contractile and non-contractile proteins are affected by acute and chronic alcohol dosage. Muscle RNA is also reduced by mechanisms involving increased RNase activities. In general, muscle protease activities are either reduced or unaltered, although markers of muscle membrane damage are increased which may be related to injury by reactive oxygen species. This supposition is supported by the observation that in the UK, , -tocopherol status is poor in myopathic alcoholics. Reduced , -tocopherol may pre-dispose the muscle to metabolic injury. However, experimental , -tocopherol supplementation is ineffective in preventing ethanol-induced lesions in muscle as defined by reduced rates of protein synthesis and in Spanish alcoholics with myopathy, there is no evidence of impaired , -tocopherol status. In conclusion, by a complex series of mechanisms, alcohol adversely affects skeletal muscle. In addition to the mechanical changes to muscle, there are important metabolic consequences, by virtue of the fact that skeletal muscle is 40% of body mass and an important contributor to whole-body protein turnover. [source] Muscle fibre size and capillarity in Korean diving womenACTA PHYSIOLOGICA, Issue 2 2003K. A. Bae Abstract Aim:, Effects of prolonged habitual cold-water immersion on fibre size and capillarity in vastus lateralis muscle were studied in human beings. The hypothesis tested in the present study was that cold acclimatized human skeletal muscle would have reduced muscle fibre size and higher capillarity, favouring the idea of efficacy of recruitment under cold environment. Methods:, Ten women breath-hold divers (BHDs) and 10 active women (controls CONs) participated in this study. Muscle biopsy was obtained from vastus lateralis and determined fibre type composition and capillary density. Results: A major finding was that all BHDs revealed a markedly smaller cross-sectional area (CSA) in all fibre types than the CONs, or even than any other morphological data reported in previous investigations. Furthermore, mean CSA of type II fibre (range 1205,2766 ,m2) was much smaller than type I fibre (2343,4327 ,m2). The number of capillaries per fibre in different fibre types in the BHDs was higher than in the CONs (P < 0.001), and diffusional area was smaller in type II fibres than in type I fibres (P < 0.001). The BHDs and the CONs have similarity in the percentage of type I fibres, but type II fibre was predominant in both groups. Interestingly the proportion of type IIx fibre in the BHDs was higher (31%) than in the CONs (22%). No significant difference was found in the thigh circumference between the groups. Conclusion:, The present study demonstrates that prolonged habitual cold-water immersion may induce a decrease in fibre size and an increase in capillarity in human skeletal muscle. [source] EMG and Oxygen Uptake Responses During Slow and Fast Ramp Exercise in HumansEXPERIMENTAL PHYSIOLOGY, Issue 1 2002Barry W. Scheuermann This study examined the relationship between muscle recruitment patterns using surface electromyography (EMG) and the excess O2 uptake (ExV,O2) that accompanies slow (SR, 8 W min,1) but not fast (FR, 64 W min,1) ramp increases in work rate (WR) during exercise on a cycle ergometer. Nine subjects (2 females) participated in this study (25 ± 2 years, ± S.E.M.). EMG was obtained from the vastus lateralis and medialis and analysed in the time (root mean square, RMS) and frequency (median power frequency, MDPF) domain. Results for each muscle were averaged to provide an overall response and expressed relative to a maximal voluntary contraction (%MVC). ,V,O2/,WR was calculated for exercise below (S1) and above (S2) the lactate threshold (LT) using linear regression. The increase in RMS relative to the increase in WR for exercise below the LT (,RMS/,WR-S1) was determined using linear regression. Due to non-linearities in RMS above the LT, ,RMS/,WR-S2 is reported as the difference in RMS (,RMS) and the difference in WR (,WR) at end-exercise and the LT. SR was associated with a higher (P < 0.05) ,V,O2/,WR (S1, 9.3 ± 0.3 ml min,1 W,1; S2, 12.5 ± 0.6 ml min,1 W,1) than FR (S1, 8.5 ± 0.4 ml min,1 W,1; S2, 7.9 ± 0.4 ml min,1 W,1) but a similar ,RMS/,WR-S1 (SR, 0.11 ± 0.01% W,1; FR, 0.10 ± 0.01% W,1). ExV,O2 was greater (P < 0.05) in SR (3.6 ± 0.7 l) than FR (-0.7 ± 0.4 l) but was not associated with a difference in either ,RMS/,WR-S2 (SR, 0.14 ± 0.01% W,1; FR, 15 ± 0.02% W,1) or MDPF (SR, 2.6 ± 5.9%; FR, -15.4 ± 4.5%). The close matching between power output and RMS during SR and FR suggests that the ExV,O2 of heavy exercise is not associated with the recruitment of additional motor units since ExV,O2 was observed during SR only. Compared to the progressive decrease in MDPF observed during FR, the MDPF remained relatively constant during SR suggesting that either (i) there was no appreciable recruitment of the less efficient type II muscle fibres, at least in addition to those recruited initially at the onset of exercise, or (ii) the decrease in MDPF associated with fatigue was offset by the addition of a higher frequency of type II fibres recruited to replace the fatigued motor units. [source] Characterisation of human soft palate muscles with respect to fibre types, myosins and capillary supplyJOURNAL OF ANATOMY, Issue 2 2000PER S. STĹL Four human soft palate muscles, and palatopharyngeus, the uvula, the levator and tensor veli palatini were examined using enzyme-histochemical, immunohistochemical and biochemical methods and compared with human limb and facial muscles. Our results showed that each palate muscle had a distinct morphological identity and that they generally shared more similarities with facial than limb muscles. The palatopharyngeus and uvula muscles contained 2 of the highest proportions of type II fibres ever reported for human muscles. In contrast, the levator and tensor veli palatini muscles contained predominantly type I fibres. A fetal myosin heavy chain isoform (MyHC), not usually found in normal adult limb muscles, was present in a small number of fibres in all palate muscles. The mean muscle fibre diameter was smaller than in limb muscles and the individual and intramuscular variability in diameter and shape was considerable. All palate muscles had a high capillary density and an unusually high mitochondrial enzyme activity in the type II fibres, in comparison with limb muscles. No ordinary muscle spindles were observed. The fibre type and MyHC composition indicate that the palatopharyngeus and uvula muscles are functionally involved in quick movements whereas the levator and tensor veli palatini muscles perform slower and more continuous contractions. The high aerobic capacity and the rich capillarisation suggest that the palate muscles are relatively fatigue resistant. Absence of ordinary muscle spindles indicates a special proprioceptive control system. The special morphology of the palate muscles may be partly related to the unique anatomy with only one skeletal insertion, a feature consistent with muscle work at low load and tension and which may influence the cytoarchitecture of these muscles. Other important factors determining the special morphological characteristics might be specific functional requirements, distinct embryological origin and phylogenetic factors. [source] Phosphocreatine degradation in type I and type II muscle fibres during submaximal exercise in man: effect of carbohydrate ingestionTHE JOURNAL OF PHYSIOLOGY, Issue 1 2001Kostas Tsintzas 1The aim of this study was to examine the effect of carbohydrate (CHO) ingestion on changes in ATP and phosphocreatine (PCr) concentrations in different muscle fibre types during prolonged running and relate those changes to the degree of glycogen depletion. 2Five male subjects performed two runs at 70 % maximum oxygen uptake (V,O2,max), 1 week apart. Each subject ingested 8 ml (kg body mass (BM)),1 of either a placebo (Con trial) or a 5.5 % CHO solution (CHO trial) immediately before each run and 2 ml (kg BM),1 every 20 min thereafter. In the Con trial, the subjects ran to exhaustion (97.0 ± 6.7 min). In the CHO trial, the run was terminated at the time coinciding with exhaustion in the Con trial. Muscle samples were obtained from the vastus lateralis before and after each trial. 3Carbohydrate ingestion did not affect ATP concentrations. However, it attenuated the decline in PCr concentration by 46 % in type I fibres (CHO: 20 ± 8 mmol (kg dry matter (DM)),1; Con: 34 ± 6 mmol (kg DM),1; P < 0.05) and by 36 % in type II fibres (CHO: 30 ± 5 mmol (kg DM),1; Con: 48 ± 6 mmol (kg DM),1; P < 0.05). 4A 56 % reduction in glycogen utilisation in type I fibres was observed in CHO compared with Con (117 ± 39 vs. 240 ± 32 mmol glucosyl units (kg DM),1, respectively; P < 0.01), but no difference was observed in type II fibres. 5It is proposed that CHO ingestion during exhaustive running attenuates the decline in oxidative ATP resynthesis in type I fibres, as indicated by sparing of both PCr and glycogen breakdown. The CHO-induced sparing of PCr, but not glycogen, in type II fibres may reflect differential recruitment and/or role of PCr between fibre types. [source] Relationship of Birth Weight with the Size, Number and Proportion of Fibres in the Pig Semitendinosus MuscleANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 4 2009F. Tristán Summary The objective of this study was to determine the relationship between body weight and the size, number and proportion of muscle fibre types in the pig semitendinosus muscle at birth. Based on weight at birth, 68 specimens selected from 21 different litters from the same farm were allotted in two equal groups (G1 and G2). G1 included 34 piglets ,1.1 kg and G2 34 pigs ,2 kg. Fifteen piglets per group were killed at birth and the remaining 19 piglets in each group were reared until weaning (21 days) and post-weaning (67 days). The weight and total cross-sectional area of the semitendinosus muscle were recorded at birth. Then, type I and type II fibres from the superficial portion of the muscle were identified according to histochemistry and immunohistochemistry techniques and percentages, average size of each fibre type, and the total number of muscle fibres were estimated by morphometry. Birth weight in G1 was 54.74% lower than that in G2. Correspondingly, the total cross-sectional area of the semitendinosus, as well as the size and number of muscle fibres, was significantly lower in G1 (P < 0.001). Weight at birth still influenced weights at weaning and post-weaning, hence it was 43.17% and 28.38% lower respectively in G1. It is concluded that pig weight at birth is associated with muscle cellularity of the semitendinosus muscle of pig, which may influence the postnatal muscle growth and final size of muscle fibres and meat quality. [source] The Effect of Testosterone on Gastrocnemius Muscle Fibres in Growing and Adult Male and Female Rats: A Histochemical, Morphometric and Ultrastructural Study,ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2 2003. Üstünel Summary In this study, the effect of testosterone on gastrocnemius muscle fibres in growing and adult rats (male and female) was examined using histochemical, morphometric and ultrastructural techniques. After physiological saline (PS), olive oil (OvO) or olive oil + testosterone (OvOT) injections on 72 rats (growing and mature, 36 male and 36 female), the sample tissues of fibre types of the gastrocnemius muscle taken were examined by histochemical [alkaline adenosine triphosphatase (alk-ATPase), acid ATPase (ac-ATPase)], morphometric and ultrastructural techniques. In PS-injected control groups, the gastrocnemius muscle of both sexes contained all the fibre types studied [slow-oxidative muscle fibres (type I), fast-oxidative glycolytic muscle fibres (type IIA) and fast-glycolytic muscle fibres (type IIB)]. The type I fibres had the smallest diameter, type IIA had a medium diameter and type IIB fibres had the largest diameter. In OvO-injected groups, it was observed that the OvO had little effect on the gastrocnemius muscles of either sex, although there was significant enlargement of type IIB fibres. After the injection of OvOT, hypertrophy of muscle fibres was determined by morphometric study. The biggest increase in diameter was on type I fibres. In addition, degenerations on some mitochondria, accumulation of lipid droplets on type I and type II fibres, an increase in glycogen particles, bifurcation of myofibrils, an increase in the number and diameter of units resembling T tubules and an increase in ribosomal content were also observed in the same group by transmission electron microscope. Consequently, it was determined that testosterone can induce protein synthesis in gastrocnemius muscle fibres, and induces changes in shape and size, and also can change the appearance and the number of fibres. [source] Acetazolamide prevents vacuolar myopathy in skeletal muscle of K+ -depleted ratsBRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2008D Tricarico Background and purpose: Acetazolamide and dichlorphenamide are carbonic anhydrase (CA) inhibitors effective in the clinical condition of hypokalemic periodic paralysis (hypoPP). Whether these drugs prevent vacuolar myopathy, which is a pathogenic factor in hypoPP, is unknown. The effects of these drugs on the efflux of lactate from skeletal muscle were also investigated. Experimental approach: For 10 days, K+ -depleted rats, a model of hypoPP, were administered 5.6 mg kg,1 day,1 of acetazolamide, dichlorphenamide or bendroflumethiazide (the last is not an inhibitor of CA). Histological analysis of vacuolar myopathy and in vitro lactate efflux measurements were performed in skeletal muscles from treated and untreated K+ -depleted rats, and also from normokalemic rats. Key results: About three times as many vacuoles were found in the type II fibres of tibialis anterioris muscle sections from K+ -depleted rats as were found in the same muscle from normokalemic rats. In ex vivo experiments, a higher efflux of lactate on in vitro incubation was found in muscles of K+ -depleted rats compared with that found in muscles from normokalemic rats. After treatment of K+ -depleted rats with acetazolamide, the numbers of vacuoles in tibialis anterioris muscle decreased to near normal values. Incubation with acetazolamide in vitro inhibited efflux of lactate from muscles of K+ -depleted rats. In contrast, bendroflumethiazide and dichlorphenamide failed to prevent vacuolar myopathy after treatment in vivo and failed to inhibit lactate efflux in vitro. Conclusions and implications: Acetazolamide prevents vacuolar myopathy in K+ -depleted rats. This effect was associated with inhibition of lactate transport, rather than inhibition of CA. [source] | |||||||||||||