Differences of morphometrical parameters in hind limb muscle fibres between ovarectomized and sexually intact female dogs.

Slow and fast twitch fibres of the Mm. tibialis cranialis, semitendinosus and sartorius of seven sexually intact and seven ovarectomized female beagles were histochemically and morphometrically analysed. Along with type I and type IIA fibres, another main type II fibre (IIS), which seems to be peculiar to the dog, was found in the Mm. semitendinosus and tibialis cranialis. Type I fibers comprised 26% and type II fibres 74% of all recorded muscle fibres in the M. tibialis cranialis, 29% (type I) and 71% (type II) in the M. semitendinosus and 51% (type I) and 49% (type II) in the M. sartorius, respectively. The average single profile area and the corresponding mean diameter of fibre types I and II in the investigated hind limb muscles were generally larger in ovarectomized than in sexually intact animals. This was more evident in type II than in type I fibres. However only the type II fibres of the M. tibialis cranialis and sartorius exhibited a statistically significant increase in diameter (p < 0.01 and p < 0.05, respectively). Accordingly, the mean density (number of fibres/mm2) of both fibre types in the hind limb muscles of spayed dogs was generally reduced. Again, this reduction attained statistical relevance in the type I and II fibres of the tibialis cranialis. In addition, the fibre densities of type I in the semitendinosus and type II in the sartorius muscles were also significantly reduced in ovarectomized dogs. In conclusion, ovarectomized beagles showed a generally increased mean diameter of the investigated type I and II hind limb muscle fibres and a concomitant decreased average fibre density of the respective types when compared to sexually intact animals.     

Coexistence of slow and fast isoforms of contractile and regulatory proteins in human skeletal muscle fibres induced by endurance raining

The distribution of fast and slow isoforms of troponin C, I, and T components and myosin heavy chains was investigated in histochemically typed myofibrillar ATPase intermediate (IM) fibres, that is, fibres that stain after both acid and alkaline pre-incubation in stainings for myofibrillar ATPase. In addition to the previously described IM fibres of types II C and I B, fibres that displayed staining characteristics between types II C and I B were observed and termed type II C–I B. The IM fibres constitute less than 1% of the fibres in normal human limb and abdominal muscles. The IM fibres studied here resulted from extensive endurance training of human triceps brachii muscle (n= 6) and were induced by conversion of a proportion (130) of type II fibres. The immunohistochemical stains of serial sections with antibodies to slow isoforms of troponin I, T, C and myosin heavy chain showed no staining of type II fibres but intense staining of types I and I B fibres, whereas type II C fibres stained with intermediate intensity. The antibodies to fast isoforms of the troponin components and myosin heavy chain did not give rise to staining of type I fibres but dark staining of type II fibres. Type I B fibres stained with intermediate intensity and type II C was either as dark as type II or slightly lighter. Type II C-I B fibres showed staining intensities intermediate between those observed for types I B and IIC in the immunohistochemical stains. It is therefore concluded that training-induced myofibrillar ATPase intermediate human skeletal muscle fibres are characterized by the coexistence of slow and fast isoforms of contractile and regulatory proteins. Changes in the distribution of fast and slow isoforms of several of the myofibrillar proteins appeared to be induced in a co-ordinated manner.     

Enzyme levels in pools of microdissected human muscle fibres of identified type. Adaptive response to exercise

Enzyme activities were determined in pools of type I (slow twitch) and II A and II B (fast twitch) fibres of the thigh muscle from individuals engaged to a high degree in physical training of an endurance character and from non-endurance-trained controls. The endurance-trained (ET) group had significantly higher activity levels of the mitochondrial enzymes citrate synthase, malate dehydrogenase, and 3-OH-acylCoA dehydrogenase both in type I (2.1X, 1.7X, 1.4X) and in type II A (2.3X, 1.8X, 1.4X) and II B fibres (2.0X, 1.5X, 1.5X) than the non-endurance-trained (NET) group. Of the glycolytic enzymes, phosphofructokinase (PFK) in type I fibres was significantly higher (1.8X) in the ET than in the NET group whereas glyceraldehydephosphate dehydrogenase (GAPDH) in type I fibres was similar in the two groups. In type II fibres both PFK and GAPDH levels tended to be higher in the ET group. Lactate dehydrogenase (LDH) of both fibre types were not different in the two groups. Type I fibres differed significantly from type II fibres for all the six enzymes measured in both groups. However, no significant difference between fibres of types II A and II B was found. The results indicate that fibres of types I, II A and II B in human skeletal muscle all possess great adaptability with regard to their oxidative capacity. Furthermore, the data suggest that extensive endurance training may enhance the glycolytic capacity in both type I and type II fibres although the glycolytic capacity of the muscle as a whole generally is low in endurance trained subjects owing to a predominance of type I fibres. It is concluded that further studies are needed to determine whether there is a metabolic distinction between fibres of types II A and II B.     

Glycogen depletion of different fibre types in human skeletal muscle during intermittent and continuous exercise

Muscle biopsies from the vastus lateralis were obtained from thirteen healthy subjects at rest and at intervals during continuous and intermittent exercise. After freeze-drying of the muscle sample, fragments of single fibres were dissected out and stained for myofibrillar ATPase with preincubation at pH 10.3, 4.6 or 4.3 to identify type 1, II A and II B fibres respectively. The remaining part of each fragment was used for quantitative glycogen analyses. At rest, mean glycogen content was significantly higher in type II fibres (402 mmol/kg dry weight) than in type 1 (344 mmol/kg dry weight). After 60 min continuous exercise at moderate work load a more pronounced glycogen depletion had occurred in type I (277 mmol/kg dry weight) than in type II (A-r B) fibres (113 mmol/kg dry weight). With 60 min intense intermittent exercise a significant and similar depletion occurred in both type I (213 mmol/kg dry weight) and type II (A + B) fibres (203 mmol/kg dry weight). With continuous intense exercise to exhaustion (4–6 min), glycogen depletion was more marked in type II (A- B) (1 !8 mmol/kg dry weight) than type I fibres (74 mmol/kg dry weight). These data imply that the glycogen depletion pattern in muscle fibres is determined mainly by the work intensity but the lower glycogen depletion per unit time in intermittent compared with continuous intense exercise indicates that the mode and duration of exercise is important, too.     

Enzyme activities in type I and II muscle fibres of human skeletal muscle in relation to age and torque development

The quadriceps muscles from 20- 30- and 70-year-old clinically healthy men and women were studied regarding maximal isometric and isokinetic muscle torque in Newton metres (Nm), morphology and enzyme activity. Biopsy specimens were taken from the vastus lateralis muscle and freeze-dried, and individual fibres were dissected out and identified as type I or type II. The activities of citrate synthase (CS), 3-OHacyl-coA dehydrogenase (HAD), lactate dehydrogenase (LDH), myokinase (MK) and creatine phosphokinase (CPK) were determined in pools of type I and type II fibres. In both age groups a higher oxidative (CS, HAD, 1.3-1.5 x) and a lower glycolytic (LDH, 0.7 x) capacity was found in type I than in type II fibres. The myokinase activity was higher in type II (2 x) than in type I, whereas CPK activity was similar. The young men showed higher CS activity in both type I and type II fibres (1.5 x) and higher CPK activity in type I fibres (1.4 x) than the young women. There were only minor changes in oxidative or glycolytic capacities in relation to age. Myokinase was the only enzyme that decreased markedly with age in both pools of fibre types. Type II fibre area and mean fibre area correlated significantly to muscle torque in both sexes. In men, myokinase activity in type II fibres was significantly correlated to type II fibre area and to maximal muscle torque.     

Enzyme levels of the NADH shuttle systems: measurements in isolated muscle fibres from humans of differing physical activity

The aim of the present study was to investigate enzyme levels of the malate-aspartate and alpha-glycerophosphate shuttles in type I (slow-twitch) and type II (fast-twitch) fibres of human skeletal muscle. The influence of endurance training on these levels was also elucidated. Biopsy specimens were obtained from the lateral part of the quadriceps femoris muscle of six untrained and six endurance-trained subjects. Type I vs. type II. In both groups the type I fibres exhibited higher levels of the TCA cycle marker enzyme citrate synthase (CS), as well as of the malate-aspartate shuttle enzymes (cytoplasmic and mitochondrial malate dehydrogenase (cMDH, mMDH), and aspartate aminotransferase (cASAT, mASAT]. A more pronounced difference between type I and type II fibres was noted for cMDH (58%) than for mMDH (16%), cASAT (20%), mASAT (18%) and CS (25%). In contrast to these enzymes, the levels of cytoplasmic glycerol-3-phosphate dehydrogenase (cGPDH), the enzyme representative of the alpha-glycerophosphate shuttle, were higher (25%) in the type II fibres. Endurance-trained vs. untrained. In the endurance-trained group, both fibre types were characterized by higher levels of CS (mean for both fibre types: 48%) as well as of mitochondrial malate-aspartate shuttle enzymes (mMDH: 47%, mASAT: 48%) than in the corresponding fibre types in the untrained group, while the differences in the levels of cytoplasmic malate-aspartate shuttle enzymes (cMDH: 13%, cASAT: 16%) were not statistically significant. Nor were the differences in cGPDH levels (8%) between the untrained and endurance-trained groups statistically significant. It is concluded that in human skeletal muscle, malate-aspartate shuttle enzymes are expressed to a higher degree in type I (slow) fibres than in type II (fast) fibres, with cMDH exhibiting the most marked difference. The single fibre analysis indicated that the muscle's activity level might exert a greater influence on the mitochondrial isoenzymes than on the cytoplasmic ones. In contrast to the malate-aspartate shuttle enzymes, the alpha-glycerophosphate shuttle is expressed to a higher degree in type II fibres and its capacity appears to not be influenced by endurance training. The present studies demanded considerable methodological investigations which also are presented in this paper.     

Ca2+-activated force-generating properties of mammalian skeletal muscle fibres: histochemically identified single peeled rabbit fibres

Summary Single peeled (sarcolemma removed) rabbit skeletal muscle fibres, identified histochemically from their myofibrillar ATPase and oxidative staining pattterns, were characterized according to their Ca²⁺-activated steady-state force-generating properties at normal intracellular pH (7.0) and under acidotic (pH 6.5) conditions. Maximum force-generating capacity of each fibre was assessed by measuring steady-state isometric force generation at saturating Ca²⁺ concentration at both pH values. The Ca²⁺ sensitivity of each fibre was ascertained by determining the percentage of maximum force generated at each of several subsaturating Ca²⁺ concentrations at both pH values. Fibres were selected from soleus, tibialis anterior and adductor magnus muscles. At subsaturating Ca²⁺ concentrations only two functional groups of fibres were distinguishable, corresponding to the histochemical classifications type I and type II. Type I fibres were more sensitive to Ca²⁺ and less depressed by acidosis than type II fibres in the subsaturating range of Ca²⁺ concentrations. At saturating Ca²⁺ concentrations, the acidotic depression of maximum force was significantly less for type I fibres than type II nonoxidative fibres regardless of their muscle of origin. Type II oxidative fibre maximum force properties depended upon the muscle of origin and demonstrated subgroups of these fibres that were different from type II nonoxidative fibres and similar to type I fibres.     

Enzyme levels in pools of microdissected human muscle fibres of identified type: Adaptive response to exercise

Enzyme activities were determined in pools of type I (slow twitch) and IIA and II B (fast twitch) fibres of the thigh muscle from individuals engaged to a high degree in physical training of an endurance character and from non-endurance-trained controls. The endurance-trained (ET) group had significantly higher activity levels of the mitochondrial enzymes citrate synthase, malate dehydrogenase, and 3-OH-acylCoA dehydrogenase both in type I (2.1×, 1.7×, 1.4×) and in type IIA (2.3×, 1.8×, 1.4×) and IIB fibres (2.0×, 1.5 ×, 1.5×) than the non-endurance-trained (NET) group. Of the glycolytic enzymes, phosphofructokinase (PFK) in type I fibres was significantly higher (I.8×) in the ET than in the NET group whereas glyceraldehydephosphate dehydrogenase (GAPDH) in type I fibres was similar in the two groups. In type II fibres both PFK and GAPDH levels tended to be higher in the ET group. Lactate dehydrogenase (LDH) of both fibre types were not different in the two groups. Type 1 fibres differed significantly from type II fibres for all the six enzymes measured in both groups. However, no significant difference between fibres of types IIA and IIB was found. The results indicate that fibres of types I, IIA and IIB in human skeletal muscle all possess great adaptability with regard to their oxidative capacity. Furthermore, the data suggest that extensive endurance training may enhance the glycolytic capacity in both type I and type II fibres although the glycolytic capacity of the muscle as a whole generally is low in endurance trained subjects owing to a predominance of type I fibres. It is concluded that further studies are needed to determine whether there is a metabolic distinction between fibres of types IIA and IIB.     

Baboon (<Emphasis Type="Italic">Papio ursinus</Emphasis>) single fibre contractile properties are similar to that of trained humans

This study investigated the contractile properties of single skeletal muscle fibres from the Vastus lateralis (VL) of two male adult chachma baboons (Papio ursinus) and compared it to that from five male human cyclists. Species comparisons are observational and statistical analyses were not performed due to the low sample size. The histological analyses revealed that the baboon muscles contained more type II fibres than their human counterparts. Cross-sectional areas of type I and type II fibres from human VL were similar in size, whereas baboon type I and type II fibres appeared smaller and larger compared to humans, respectively. On average, type II fibres from baboons and type IIAX fibres from humans produced the highest specific force (88?±?41 and 155?±?4 kN/m², respectively), compared to 57?±?27 and 68?±?5 kN/m² for baboon and human type I fibres. Maximum shortening velocity appeared highest in human type IIAX fibres, but fairly similar between human and baboon type I and II fibres. Baboon and human type I (2.2?±?0.4 vs. 1.5?±?0.5 kN/m² Fl/s) and type II (6.0?±?2.8 vs. 7.7?±?1.0 kN/m² Fl/s) fibres appeared similar in maximum power output. From these observations, it seems that baboon and human muscle fibre contractile properties appear similar to one another, and that fibre type composition itself may play a determining role in muscle strength between these two species.     

Effect of exercise on concentrations of free amino acids in pools of type I and type II fibres in human muscle with reduced glycogen stores

A few animal studies have shown that some amino acid concentrations vary between different muscle fibre types. In the present study, amino acid concentrations were measured in separate pools of different fibre types in human skeletal muscle, with reduced glycogen stores, before and after sustained exercise. Five subjects exercised at a submaximal work rate for 60 min and then at a maximal rate for 20 min. Biopsy samples were taken from the vastus lateralis muscle before and after exercise; they were freeze-dried and individual fibres were dissected out. Fragments of these fibres were stained for myosin-adenosine triphosphatase (ATPase) and identified as type I or type II fibres. The concentrations of free amino acids were measured by high performance liquid chromatography (HPLC) in perchloric acid (PCA) extracts containing pools of either type of fibre. After exercise, glycogen was decreased in type I fibres (53%) and in four subjects also in type II fibres. The concentrations of most amino acids were similar in the two fibre types before exercise, but the glutamate, aspartate and arginine levels were 10% higher in type II than in type I fibres. After exercise, the glutamate concentration was decreased by 45% in both fibre types and the branched-chain amino acids (BCAA) were decreased in type II fibres (14%). Exercise caused an increase by 25-30% in tyrosine concentration in both type I and type II fibres. The results show that amino acids can be measured in pools of fibre fragments and suggest that amino acid metabolism play an important role in both type I and type II fibres during exercise.     

Creatine kinase MB and citrate synthase in type I and type II muscle fibres in trained and untrained men

Summary Total creatine kinase (CK), creatine kinase MB (CK-MB) and citrate synthase (CS) were determined in isolated and pooled type I and type II skeletal muscle fibres. Determinations were made on biopsies from 3 sedentary men, 3 junior cyclists and 2 elite cyclists. CS and CK-MB activities were higher in the trained groups in both fibre types. The total CK activity was not related to training status, although it was lower in type I fibres than in type II fibres (p<0.05). The reverse relation was observed for CS and CK-MB activities (p<0.01). The ratio of type I/type II for CS was not related to training status, while the corresponding ratio for CK-MB increased with a greater degree of endurance training. For a given increase in CS activity, the increase in CK-MB activity was greater in type I fibres than in type II fibres (p<0.01). Thus, with endurance training there seems to be a specific adaptation for CK-MB, particularly in type I fibres.     

Growth-related alterations in motor endplates of type-identified diaphragm muscle fibres

Summary Using a double-labelling technique, and dual-channel confocal microscopy, we examined the three-dimensional and two-dimensional morphologies of motor endplates on type I and II muscle fibres of 21-day-old and adult rat diaphragms. Motor endplates were visualized with fluorescein-conjugated -bungarotoxin, and muscle fibre type was immunocytochemically determined using an anti-fast (type II) myosin antibody with a Cy5-conjugated label. Surface (three-dimensional) and planar (two-dimensional) areas were obtained from three-dimensional reconstructions of confocal optical sections of labelled endplates. Muscle fibre diameters were also measured. Total branch lengths were measured from projection images of the three dimensional reconstructions. The surface and planar areas of endplates on type I fibres at day 21 were larger than those on type II fibres, and this difference increased with maturation. In adults, the surface area of endplates was positively correlated to muscle fibre size, but such a correlation was not found at day 21. When normalized for fibre diameter, the surface areas of endplates on type I fibres were still significantly larger than those on type II fibres in both age groups. The normalized endplate surface area for type II fibres remained constant with maturation, whereas for type I fibres, the increase in endplate surface area was disproportionate to fibre growth.     

Coexistence of slow and fast isoforms of contractile and regulatory proteins in human skeletal muscle fibres induced by endurance training

The distribution of fast and slow isoforms of troponin C, I, and T components and myosin heavy chains was investigated in histochemically typed myofibrillar ATPase intermediate (IM) fibres, that is, fibres that stain after both acid and alkaline preincubation in stainings for myofibrillar ATPase. In addition to the previously described IM fibres of types IIC and IB, fibres that displayed staining characteristics between types IIC and IB were observed and termed type IIC-IB. The IM fibres constitute less than 1% of the fibres in normal human limb and abdominal muscles. The IM fibres studied here resulted from extensive endurance training of human triceps brachii muscle (n = 6) and were induced by conversion of a proportion (13%) of type II fibres. The immunohistochemical stains of serial sections with antibodies to slow isoforms of troponin I, T, C and myosin heavy chain showed no staining of type II fibres but intense staining of types I and IB fibres, whereas type IIC fibres stained with intermediate intensity. The antibodies to fast isoforms of the troponin components and myosin heavy chain did not give rise to staining of type I fibres but dark staining of type II fibres. Type IB fibres stained with intermediate intensity and type IIC was either as dark as type II or slightly lighter. Type IIC-IB fibres showed staining intensities intermediate between those observed for types IB and IIC in the immunohistochemical stains. It is therefore concluded that training-induced myofibrillar ATPase intermediate human skeletal muscle fibres are characterized by the coexistence of slow and fast isoforms of contractile and regulatory proteins.(ABSTRACT TRUNCATED AT 250 WORDS)     

Glycogen breakdown in different human muscle fibre types during exhaustive exercise of short duration.

The rates of glycogen breakdown during exhaustive intense exercise of three different intensities were determined in type I and subgroups of type II fibres. The exercise intensity corresponded to 122 +/- 2, 150 +/- 7 and 194 +/- 7% of VO2max. Muscle biopsies were taken from both legs before and immediately after exhaustion. Muscle lactate concentration increased by 27 +/- 1, 27 +/- 1 and 20 +/- 2 mmol kg-1 wet wt during the exercise at 122, 150 and 194% VO2max, respectively. The rates of glycogen depletion increased in all fibre types with increasing intensity, and the decline in type I fibres was 30-35% less than in type II fibres at all intensities. No differences were observed between the glycogen depletion rates in subgroups of type II fibres (IIA, IIAB and IIB). During the exercise at 194% VO2max, the rates of glycogen breakdown were 0.35 +/- 0.03 and 0.52 +/- 0.05 mmol s-1 kg-1 wet wt in type I and type II fibres, respectively. For both fibre types, the rates were 32 and 69% lower during the exercise at 150 and 122% VO2max. These data indicate that the glycolytic capacity of type I fibres is 30-35% lower than the capacity of type II fibres, in good agreement with the differences in phosphorylase and phosphofructokinase activities (Essén et al. 1975, Harris et al. 1976). The data also indicate that both fibre types contribute significantly to the anaerobic energy release at powers up till almost 200% VO2max.     

Muscle glycogen depletion patterns in type I and subgroups of type II fibres during prolonged severe exercise in man

Glycogen depletion of muscle fibre types I, II A, II AB and II B was studied using a histochemical method to quantify glycogen content in individual fibres. The reliability was examined in 29 muscle biopsies, in which total glycogen content was compared to average periodic acid Schiff (PAS) stain intensity in sections from the same samples. Over a wide range of glycogen content (1-252 mmole glucosyl units . kg-1 wet weight) a linear relationship (r = 0.93) was found between the two methods for quantification of muscle glycogen. Glycogen depletion patterns in type I, II A, II AB and II B fibres were studied in 5 subjects during exhaustive bicycle exercise at 75% of VO2 max. At rest before exercise glycogen content was 16% higher in type II subgroups than in type I (p less than 0.05). From start of exercise the same glycogen depletion rate was observed in type I and II A. Glycogen content of Type II AB and II B was unchanged during the first part of exercise. Later a decrease was observed, first in type II AB and finally in II B, suggesting a decrease in threshold force of these fibre types. The results indicate physiological differences between the 3 subgroups of type II fibres in man, whereas at the present exercise intensity type I and II A fibres were recruited simultaneously from start.     

Energy metabolism in type I and type II human muscle fibres during short term electrical stimulation at different frequencies.

The degradation of adenosine triphosphate, phosphocreatine and glycogen was determined in type I and type II fibres of the human quadriceps femoris muscle during intermittent electrical stimulation at 20 and 50 Hz, (1.6 seconds stimulation, 1.6 seconds rest). Seven healthy volunteers took part in the study. Muscle biopsy samples were obtained at rest and after 10 and 20 seconds of stimulation (six and 12 contractions, respectively). The resting contents of adenosine triphosphate, phosphocreatine and glycogen were all higher (P less than 0.05) in type II fibres compared to type I fibres. By the end of stimulation, whole muscle force production had declined to 84 and 77% of the initial force at 20 and 50 Hz, respectively. The phosphocreatine degradation rate for 10 and 20 seconds of stimulation was greater in type II fibres (P less than 0.05) compared to type I fibers at both 20 and 50 Hz. The rates of glycogenolysis after 20 seconds stimulation in type II fibres were 3.18 +/- 1.1 and 6.31 +/- 1.39 mmol glycosyl units kg-1 s-1. The corresponding rates in type I fibres were 0.46 +/- 0.73 and 0.60 +/- 0.39 mmol glycosyl units kg-1 s-1, which were not significantly different from zero. It is hypothesized that the decline in whole muscle force observed during electrical stimulation may be a consequence of the rapid loss of PCr stores in type II fibres.     

Muscle fibre size and type distribution in thoracic and lumbar regions of erector spinae in healthy subjects without low back pain: normal values and sex differences

This study sought to investigate the normal muscle fibre size and type distribution of the human erector spinae, both in thoracic and lumbar regions, in a group of 31 young healthy male (n=17) and female (n=14) volunteers. Two percutaneous muscle biopsy samples were obtained under local anaesthesia, from the belly of the left erector spinae, at the levels of the 10th thoracic and 3rd lumbar vertebrae. Samples were prepared for routine histochemistry for the identification of fibre types. Fibre size (cross-sectional area (CSA) and narrow diameter (ND)) was quantified using computerised image analysis. The mean CSA/ND for each fibre type was greater in the thoracic than the lumbar region, but there was no difference between the 2 regions either for percentage type I (i.e. percentage distribution by number), percentage type I area (i.e. relative area of the muscle occupied by type I fibres) or the ratio describing the size of the type I fibre relative to that of the type II. Men had larger fibres than women, for each fibre type and at both sampling sites. In the men, each fibre type was of a similar mean size, whereas in the women the type I fibres were considerably larger than both the type II A and type II B fibres, with no difference between the latter two. In both regions of the erector spinae there was no difference between men and women for the proportion (%) of a given fibre type, but the percentage type I fibre area was significantly higher in the women. The erector spinae display muscle fibre characteristics which are clearly very different from those of other skeletal muscles, and which, with their predominance of relatively large type I (slow twitch) fibres, befit their function as postural muscles. Differences between thoracic and lumbar fascicles of the muscle, and between the muscles of men and women, may reflect adaptive responses to differences in function. In assessing the degree of any pathological change in the muscle of patients with low back pain, it seems clear that (1) sex cannot be disregarded and (2) ‘atrophied’ (using the criteria from other muscles) type II fibres are not necessarily abnormal for the erector spinae, particularly in women.     

Investigation of the organelle pathology of skeletal muscle in chronic alcoholism.

The muscle abnormalities associated with chronic alcohol consumption were studied by applying histological and biochemical techniques to tissue obtained by percutaneous needle biopsy from the quadriceps muscles of 41 patients. Measurement of the fibre size showed atrophy of both type I (p less than 0.05) and type II (p less than 0.001) fibres. The degree of atrophy was more severe for type II fibres (33% reduction in median diameter) than type I (17%). Marker enzyme activities for the principal organelles were assayed. Compared with biopsy specimens from non-alcoholic controls, no differences were found in the activities of lysosomal, mitochondrial, peroxisomal, cytosolic, sarcolemmal, or sarcoplasmic reticulum enzymes, expressed per microgram DNA. A reduction in the protein to DNA ratio was evident in severely atrophic biopsies, and this was associated with a significant reduction of myofibrillary Ca2+-ATPase activity. These results suggest a selective loss of type II fibre myofibrillary protein and do not confirm earlier suggestions of specific mitochondrial damage.     

ATP content in single fibres from human skeletal muscle after electrical stimulation and during recovery

The ATP content was measured in type I and type II fibres from human vastus lateralis muscle at rest, after electrical stimulation and during recovery. At rest the mean values were 25.2 ± 4.02 and 25.9 ± 3.62 mmol kg^-1 dry muscle (mean ± SD) for type I and type II fibres respectively. Normal distribution curves were found for both types I and II fibres. After intermittent electrical stimulation for 83 s (1.6 s Stimulation, 1.6 s pause) with occluded blood flow, the force generation decreased to 22± of the initial value and the muscle tissue showed a mean decrease in ATP to 14.8 and in phosphocreatine to 5.44 mmol kg^-1 dry muscle; lactate increased to 128.9 mmol kg^-1 dry muscle. The ATP content in isolated fibres was equally decreased in both fibre types to 16 mmol kg^-1 dry muscle. In 11± of the fibres the ATP content was lower than 10 mmol kg^-1 dry muscle. After 15 min rest with intact blood circulation ATP was completely resynthesized in type I fibres and to 91± in type II fibres.     

Histochemical and biochemical changes in human skeletal muscle with age in sedentary males, age 22--65 years.

Biopsies for histochemical and biochemical analyses were taken from the vastus lateralis muscle of 55 untrained, healthy male subjects from 22 to 65 years of age. Fibre type distribution changed towards a decrease in the percentage of type II fibres, both in type IIA and type IIB fibres, whereas type IIB/IIA fibre ratio and type IIC percentage did not change with increasing age. It was found that the type IIB/IIA fibre ratio was inversely related to type I fibres, i.e. subjects rich in type I fibres had a relatively smaller proportion of type IIB fibres. Fibre area determinations revealed a selective decrease in type II fibre area. Consequently, the type II/I fibre area ratio and relative type II fibre area decreased. No changes in the specific activities of Mg2+ stimulated ATPase and myokinase were observed, while the activity of lactate dehydrogenase (LDH) was higher in the youngest groups than in the oldest. LDH isozyme pattern shifted towards a decrease in percentage distribution of the muscle specific isozymes and a corresponding decrease in muscle specific activity while the activity of the heart specific isozymes did not change.