Na(+)-K+ ATPase concentration in different adult rat skeletal muscles is related to oxidative potential

To investigate the relationship among fibre type, oxidative potential, and Na(+)-K+ ATPase concentration in skeletal muscle, adult male Wistar rats weighing 259 +/- 8 g (mean +/- SE) were sacrificed and the soleus (SOL), extensor digitorum longus (EDL), red vastus lateralis (RV), and white vastus lateralis (WV) removed. These muscles were chosen as being representative of the two major fibre type populations: slow twitch (SOL) and fast twitch (EDL, RV, WV) and exhibiting either a high (SOL, EDL, RV) or low (WV) oxidative potential. Na(+)-K+ ATPase concentration (pmol.g-1 wet weight), measured by the [3H]ouabain binding technique, differed (p < 0.01) only between the WV (238 +/- 7.9) and the SOL (359 +/- 9.6), EDL (365 +/- 10), and RV (403 +/- 12). Similarly, muscle oxidative potential as measured by the maximal activity of citrate synthase was different (p < 0.01) only between the WV and the other three muscles. Citrate synthase activity (mumol.min-1.g-1 wet weight) was 4.0 +/- 0.7, 12.3 +/- 0.9, 9.1 +/- 0.7, and 11.3 +/- 1.0 in the WV, SOL, EDL, and RV, respectively. These results indicate that Na(+)-K+ ATPase concentration is not related to the speed of contraction but to the oxidative potential of the muscle. Since chronic activity is a primary determinant of oxidative potential, it would be expected that increases in Na(+)-K+ ATPase would accompany increases in muscle utilization.     

Murine endodermal F9E cells, derived from the teratocarcinoma line F9, contain high basal levels of retinoic acid receptors (RARs and RXRs) but are not sensitive to the actions of retinoic acid

We observed differences in the capillary architecture of the skeletal muscles that have different fiber metabolism. The soleus, the vastus intermedius and the tibialis anterior muscles of adult Wistar rats were prepared using two different techniques. Samples for adenosine triphosphatase (ATPase) staining were prepared following Dubovitz's method, and the distributions of fiber type, Types 1, 2A and 2B, were analyzed. Then, corrosion casts of capillary architecture of these muscles prepared following Murakami's method were observed with a scanning electron microscope (SEM) and compared with the fiber distribution. The fiber type composition of the soleus muscle showed Type 1 (slow-twitch) dominance and that of the vastus intermedius and the tibialis anterior muscle showed Type 2 (fast-twitch) dominance. The capillaries of the soleus muscle were tortuous, and this was thought to be advantageous for blood supply. In contrast, the capillaries of the vastus intermedius and tibialis anterior muscles had a relatively parallel pattern. Additionally, two different patterns of capillary architecture that appeared to correspond to certain metabolic characteristic of different muscle fiber types were preserved with corrosion casting. In conclusion, comparative studies on capillary architecture of the skeletal muscles are useful for analyses of its function.     

Muscle creatine kinase-deficient mice. II. Cardiac and skeletal muscles exhibit tissue-specific adaptation of the mitochondrial function

Functional properties of in situ mitochondria and of mitochondrial creatine kinase were studied in saponin-skinned fibers taken from normal and M-creatine kinase-deficient mice. In control animals, apparent Km values of mitochondrial respiration for ADP in cardiac (ventricular) and slow-twitch (soleus) muscles (137 +/- 16 microM and 209 +/- 10 microM, respectively) were manyfold higher than that in fast-twitch (gastrocnemius) muscle (7.5 +/- 0.5 microM). Creatine substantially decreased the Km values only in cardiac and slow-twitch muscles (73 +/- 11 microM and 131 +/- 21 microM, respectively). As compared to control, in situ mitochondria in transgenic ventricular and slow-twitch muscles showed two times lower Km values for ADP, and the presence of creatine only slightly decreased the Km values. In mutant fast-twitch muscle, a decrease rather than increase in mitochondrial sensitivity to ADP occurred, but creatine still had no effect. Furthermore, in these muscles, relatively low oxidative capacity was considerably elevated. It is suggested that in the mutant mice, impairment of energy transport function in ventricular and slow-twitch muscles is compensated by a facilitation of adenine nucleotide transportation between mitochondria and cellular ATPases; in fast-twitch muscle, mainly energy buffering function is depressed, and that is overcome by an increase in energy-producing potential.     

Interorgan signaling between adipose tissue metabolism and skeletal muscle uncoupling protein homologs: is there a role for circulating free fatty acids?

Uncoupling proteins 3 and 2 (UCP3 and UCP2) are two newly cloned genes that have been implicated in the regulation of lipids as fuel substrate in skeletal muscle on the basis that their mRNA expressions are upregulated during starvation (when fat stores are being rapidly mobilized) and downregulated during the early phase of refeeding (when fat stores are being rapidly replenished). To test the hypothesis that circulating free fatty acids (FFAs) may have a physiological role as an interorgan signal linking these dynamic changes in the fat stores to skeletal muscle expression of UCP3 and UCP2, the mRNA levels of these UCP homologs were examined in fed and fasted rats treated with the antilipolytic agent nicotinic acid. In 46-h fasted rats, we observed a threefold increase in serum FFA levels and increases in UCP3 and UCP2 mRNA levels that were more marked in the gastrocnemius and tibialis anterior muscles (predominantly fast-twitch fibers) than in the soleus muscle (predominantly slow-twitch fibers). Treatment with nicotinic acid blunted the fasting-induced increase in serum FFA levels and prevented the increase in mRNA levels of UCP3 and UCP2 in the soleus muscle, but had little or no effect on the elevated mRNA levels of these UCP homologs in the gastrocnemius and tibialis anterior muscles. Furthermore, treatment of ad libitum-fed animals with nicotinic acid resulted in a twofold reduction in serum FFA levels (i.e., by a magnitude similar to that observed during early refeeding) and significant reductions in UCP3 and UCP2 mRNA levels in the soleus muscle, but not in the gastrocnemius or tibialis anterior muscles. These results revealed a muscle-type dependency in the way UCP2 and UCP3 gene expression in skeletal muscle is regulated, and suggest that the hypothesis that circulating FFAs function as an interorgan signal between fat stores and skeletal muscle UCP3 and UCP2 gene expression is adequate only for slow-twitch (oxidative) muscles. Consequently, a signal(s) other than circulating FFAs must be implicated in the link between dynamic changes in body fat stores and UCP expression in predominantly fast-twitch (glycolytic/oxidative-glycolytic) muscles, which constitute the major fiber type of the total skeletal muscle mass and which have high susceptibility to developing insulin resistance and impairment in substrate utilization in metabolic diseases.     

Muscle unloading induces slow to fast transitions in myofibrillar but not mitochondrial properties. Relevance to skeletal muscle abnormalities in heart failure

Muscle deconditioning is a common observation in patients with congestive heart failure (CHF), chronic obstructive pulmonary disease, neuromuscular diseases or prolonged bed rest. To gain further insight into metabolic and mechanical properties of deconditioned slow-twitch (soleus) or fast-twitch (EDL) skeletal muscles, we induced experimental muscle deconditioning by hindlimb suspension (HS) in rats for 3 weeks. Cardiac muscle was also studied. Besides profound muscle atrophy, increased proportion of fast type II fibers as well as fast myosin isoenzymes, we found decreased calcium sensitivity of Triton X-100 skinned fiber bundles of soleus muscle directed towards the fast muscle phenotype. Glycolytic enzymes such as hexokinase and pyruvate kinase were increased, and the LDH isoenzyme pattern was clearly shifted from an oxidative to an anaerobic profile. Creatine kinase (CK) and myokinase activities were increased in HS soleus towards EDL values. Moreover, the M-CK mRNA level was greatly increased in soleus, with no change in EDL. However, oxygen consumption rate assessed in situ in saponin skinned fibers (12.5 +/- 0.8 in C and 15.1 +/- 0.9 micromol O2/min/g dw in HS soleus compared to 7.3 +/- 1.3 micromol O2/min/g dw in control EDL), as well as mitochondrial CK (mi-CK) and citrate synthase activities, were preserved in HS soleus. Following deconditioning no change in Km for ADP of mitochondrial respiration, either in the absence (511 +/- 92 in C and 511 +/- 111 microM in HS soleus compared to 9 +/- 4 microM in control EDL) or presence of creatine (88 +/- 10 in C and 95 +/- 16 microM in HS soleus compared to 32 +/- 9 microM in control EDL), was found. The results show that muscle deconditioning induces a biochemical and functional slow to fast phenotype transition in myofibrillar and cytosolic compartments of postural muscle, but not in the mitochondrial compartment, suggesting that these compartments are differently regulated under conditions of decreased activity.     

Fiber architecture of the extensors of the hindlimb in semiterrestrial and arboreal guenons

Fiber architecture of the extensor musculature of the knee and ankle is examined in two African gueon species--the semiterrestrial Cercopithecus aethiops, and the arboreal C. ascanius. Using histologic and microscopic techniques to measure lengths of sarcomeres, the original lengths of muscle fasciculi and angles of pinnation in quadriceps femoris and triceps surae are reconstructed from direct measurements on cadavers. Calculations of reduced physiological cross-sectional area, mass/predicted effective tetanic tension, maximum excursion, and tendon length/fasciculus+tendon lengths are correlated to preferred locomotor modalities in the wild. For both species, greater morphological differences occur among the bellies of quadriceps femoris--rectus femoris, vastus intermedius, v. lateralis, and v. medialis--than among the bellies of triceps surae--gastrocnemius lateralis, g. medialis, plantaris, and soleus. With regard to quadriceps femoris, few differences occur between species. Interspecific differences in the triceps surae indicate (1) redirection of muscle force to accommodate arboreality in which the substrate is less than body width; (2) muscles more suited for velocity in the semiterrestrial vervets; and (3) muscles used more isotonically in vervets and more isometrically in red-tailed monkeys. The inherent flexibility of muscles may be preadaptive to a primary species shift in locomotor modality until the bony morphology is able to adapt through natural selection.     

Features of the organization of the cytochrome systems and oxygen regimen in skeletal muscles of marine fishes

The organization of cytochrome systems in pelagic (Mugil so-iuy) and benthic (Platichthys flesus luscus) species of sea fishes were investigated. The total cytochrome content was 3.6-3.7 times higher (p < 0.001) in muscles of active M. so-iuy and made 67.5 +/- 5.3 nM g-1 for red and 5.91 +/- 0.58 nM g-1 for white muscle tissue. Cytochrome stechiometry had non-compensation character in benthic P. flesus luscus. Cytochrome ratio-b/aa3, was less than one and was equivalent 0.80-0.83 for both muscle groups. On the contrary it was higher than one--1.47-1.66 (p < 0.001) in M. so-iuy. Differences in cytochrome organization were connected with oxygen state of muscle tissue of these fishes. Mean oxygen tension in P. flesus luscus muscles was lower for 20.1-22.5% (p < 0.001). A number of anoxic and hypoxic zones (less than 6 mm Hg) in muscle tissue of this fish made 70 and 4-6% for white and red muscles accordingly. This value was 1.7-2.5 times lower in M. so-iuy muscles.     

Neuromuscular blocking effects of aminoglycoside antibiotics on fast- and slow-contracting muscles of the cat

The neuromuscular-blocking effects of neomycin, streptomycin, and gentamicin were examined in fast- and slow-twitch muscles of pentobarbital-anesthetized cats. These antibiotics were more effective in reducing indirectly stimulated contractions of the gastrocnemius muscle than of the ipsilateral soleus muscle in adult cats. Respiratory-depressant effects of these antibiotics were more closely associated temporally with effects on soleus than on gastrocnemius twitch. Neomycin was a more potent neuromuscular blocking agent in kittens greater than 7 weeks old than in kittens less than 6 weeks old. Calcium ions were more effective in antagonizing the effects of neomycin on gastrocnemius than on soleus twitch; however, neostigmine was more effective in antagonizing the effects of neomycin on soleus than on gastrocnemius twitch. These data indicate a difference in responsiveness of fast- and slow-twitch muscles (fast greater than slow) to the neuromuscular-blocking effects of aminoglycoside antibiotics, and suggest that this may be related to a difference in the predominance of pre- and postjunctional inhibitory actions of these agents in the 2 muscle types.     

Double-positive thymocytes resistant to antigen-MHC-induced negative selection lack active caspase

The aim of the current study was to elucidate the synergism of dietary calcium restriction and exhaustive exercise in the antioxidant enzyme system of rat soleus muscle, and to investigate the involvement of neutrophils in exercise-induced muscle damage. Forty-eight male Wistar rats were assigned to the following groups: control (C) or calcium-restricted [1 month (1 M) or 3 months (3 M)]. Each group was subdivided into acutely exercised or non-exercised groups. Soleus muscle from each rat was analysed to determine the levels of antioxidant enzymes [Mn-superoxide dismutase (SOD), Cu, Zn-SOD, glutathione peroxidase (GPX), and catalase (CAT)]. Dietary calcium restriction resulted in calcium deficiency and upregulated the antioxidant enzymes examined except GPX. Conversely, exhaustive exercise significantly decreased GPX and CAT, but not SODs activities in the calcium-restricted (1 M and/or 3 M) rats. Contents of immunoreactive Mn-SOD and Cu,Zn-SOD were only increased in the 3 M rats. During calcium restriction, the mRNA expression of both forms of SOD showed initial upregulation, followed by downregulation. Exhaustive exercise significantly increased the mRNA expressions only in the 3 M rats. Moreover, exhaustive exercise markedly increased myeloperoxidase activity in soleus muscles from the 1 M and 3 M rats compared with the C rats, and significantly enhanced the ability of neutrophils to generate superoxide in the 3 M rats. The results demonstrate that dietary calcium restriction upregulates certain antioxidant enzyme activities in rat soleus muscle, indicating an enhanced resistance to potential increases in intracellular reactive oxygen species. The results also suggest that exhaustive exercise may cause oxidative damage in soleus muscle of calcium-deficient rats through the activation of neutrophils.     

Role of thyroid hormones in early postnatal development of skeletal muscle and its implications for undernutrition

Energy intake profoundly influences many endocrine axes which in turn play a central role in development. The specific influence of a short period of mild hypothyroidism, similar to that induced by undernutrition, in regulating muscle development has been assessed in a large mammal during early postnatal life. Hypothyroidism was induced by providing methimazole and iopanoic acid in the feed of piglets between 4 and 14 d of age, and controls were pair-fed to the energy intake of their hypothyroid littermates. Thyroid status was evaluated, and myofibre differentiation and cation pump concentrations were then assessed in the following functionally distinct muscles: longissimus dorsi (l. dorsi), soleus and rhomboideus. Reductions in plasma concentrations of thyroxine (T4; 32%, P < 0.01), triiodothyronine (T3; 48%, P < 0.001), free T3 (58%, P < 0.001) and hepatic 5'-monodeiodinase (EC 1.11.1.8) activity (74%, P < 0.001) occurred with treatment. Small, although significant, increases in the proportion of type I slow-twitch oxidative fibres occurred with mild hypothyroidism, in l. dorsi (2%, P < 0.01) and soleus (7%, P < 0.01). Nuclear T3-receptor concentration in l. dorsi of hypothyroid animals compared with controls increased by 46% (P < 0.001), a response that may represent a homeostatic mechanism making muscle more sensitive to low levels of circulating thyroid hormones. Nevertheless, Na+, K(+)-ATPase (EC 3.6.1.37) concentration was reduced by 15-16% in all muscles (l. dorsi P < 0.05, soleus P < 0.001, rhomboideus P < 0.05), and Ca(2+)-ATPase (EC 3.6.1.38) concentration was significantly reduced in the two slow-twitch muscles: by 22% in rhomboideus (P < 0.001) and 23% in soleus (P < 0.05). It is concluded that during early postnatal development of large mammals a period of mild hypothyroidism, comparable with that found during undernutrition, induces changes in myofibre differentiation and a down-regulation of cation pumps in skeletal muscle. Such changes would result in slowness of movement and muscle weakness, and also reduce ATP hydrolysis with a concomitant improvement in energetic efficiency.     

A comparison of the electrophysiological effects of two organophosphates, mipafox and ecothiopate, on mouse limb muscles

Adult male albino mice were given single subcutaneous injections of either mipafox (110 mumol/kg) or ecothiopate (0.5 mumol/kg), two organophosphorus compounds (OPs). Acetylcholinesterase activity was measured in the soleus (slow-twitch) and extensor digitorum longus (EDL; fast-twitch) muscles. At 7 and 28 days after dosing, in vitro electrophysiological measurements were carried out in the soleus and EDL. Action potentials and end-plate potentials were evoked at 30 Hz and recorded intracellularly from single muscle fibers. The amplitudes, time course, and latencies of these potentials were measured and the variability (jitter) of latencies was calculated. Recordings after mipafox were also made with 3-Hz stimulation. Acetylcholinesterase activity was inhibited by mipafox (65% in the soleus; 76% in the EDL) and ecothiopate (59% in the soleus; 42% in the EDL). Mipafox and ecothiopate both increased postjunctional (muscle action potential) jitter in the soleus and EDL at 7 days after dosing. Organophosphates caused an increase in end-plate potential amplitudes in the soleus. Mipafox caused an increase in prejunctional (end-plate potential) jitter at 28 days after dosing in both muscles. A single dose of ecothiopate also caused an increase in prejunctional jitter at 28 days in the soleus. The OP-induced increase in jitter was different at different frequencies of stimulation. The results show that there are electrophysiological changes in both muscles after administration of organophosphorus compounds. The slow-twitch soleus appears more sensitive to prejunctional changes caused by OPs than the fast-twitch EDL.     

Overexpression of IGF-1 exclusively in skeletal muscle prevents age-related decline in the number of dihydropyridine receptors

Excitation-contraction uncoupling has been identified as a mechanism underlying skeletal muscle weakness in aging mammals (sarcopenia). The basic mechanism for excitation-contraction uncoupling is a larger number of ryanodine receptors (RyR1) uncoupled to dihydropyridine receptors (DHPRs) (Delbono, O., O'Rourke, K. S., and Ettinger, W. H. (1995) J. Membr. Biol. 148, 211-222). In the present study, we used transgenic mice overexpressing human insulin-like growth factor-1 exclusively in skeletal muscle to test the hypothesis that a high concentration of IGF-1 prevents age-related decreases in DHPR number and in muscle force. Transgenic mice express 10-20-fold higher IGF-1 concentrations than nontransgenic mice at all ages (1-24 months). The number of DHPRs is 50-100% higher, and the DHPR/RyR1 ratio is 40% higher in transgenic soleus (predominantly type I fiber muscles), extensor digitorum longus (predominantly type II fiber muscles), and the pool of type I and type II fiber muscles than in nontransgenic young (6 months), adult (12 months), and old (24 months) mice. Furthermore, no age-related changes in DHPRs and the DHPR/RyR1 ratio were observed in transgenic muscles. The specific single twitch and tetanic muscle force in old transgenic soleus and extensor digitorum longus muscles are 50% higher than in old nontransgenic muscles. Taken together, these results support the concept that IGF-1- dependent prevention of age-related decline in DHPR expression is associated with stronger muscle contraction in older transgenic mice.     

Interaction of hyperthyroidism and hindlimb suspension on skeletal myosin heavy chain expression

We examined the novel interaction of hyperthyroidism and hindlimb suspension on the pattern of myosin heavy chain (MHC) expression (mRNA and protein) in skeletal muscles. Female Sprague-Dawley rats were assigned to four groups: 1) normal control (Con); 2) thyroid hormone treated [150 micrograms 3,5,3'-triiodothyronine (T3). kg-1. day-1] (T3); 3) hindlimb suspension (HS); or 4) T3-treated and HS (T3 + HS). Results show for the first time the novel observation that the combination T3 + HS induces a rapid and sustained, marked (80-90%) downregulation of type I MHC gene expression that is mirrored temporally by concomitant marked upregulation of type IIb MHC gene expression, as evidenced by the de novo synthesis of type IIb MHC protein in the soleus. The fast type IIx MHC isoform showed a differential response among the experimental groups, generally increasing with the separate and combined treatments in both the soleus and vastus intermedius muscles while decreasing in the plantaris muscles. The fast type IIa MHC was the least responsive to suspension of the MHCs and reflected its greatest responsiveness to T3 treatment while also undergoing differential adaptations in slow vs. fast muscle (increases vs. decreases, respectively). These results confirm previous findings that all four adult MHC genes are sensitive to T3 and suspension in a muscle-specific manner. In addition, we show that T3 + HS can interact synergistically to create novel adaptations in MHC expression that could not be observed when each factor was imposed separately.     

Cocontraction and phasic activity during GAIT in children with cerebral palsy

Simultaneous activity of agonist and antagonistic muscles during a task is known as cocontraction. The primary aim of the present study was to use a cocontraction index (CI) to quantify differences in EMG activity between a group of CP and control children at two different walking speeds. The secondary aim was to compare the amount of time the muscles were activated ("on" thresholds) between the groups. Seventeen subjects volunteered for the study. One group consisted of 9 (7M, 2F) children with CP (age 12.7 +/- 2.8 years, mean +/- SD). The second group consisted of 8 able-bodied controls (7M, 1F). The discontinuous submaximal treadmill walking protocol had two 4min stages at 0% gradient. Speeds selected were 3 km.h-1 and 90% of the pre-determined fastest walking speed (FWS). Two sites of CI were measured from the EMGs of tibialis anterior and soleus (leg) and vastus lateralis and hamstrings (thigh). Significantly (p < 0.05) higher CI values were noted for the CP subjects compared to the controls, irrespective of speed or cocontraction site and there was a significant (p < 0.05) increase in CI values with increased walking speed for both CP and control subjects. Phasic analyses for 5% max EMG and 10% max EMG "on" thresholds demonstrated significant (p < 0.05) main effects for group (CP subjects had a longer time period of muscle activation than controls) and speed (muscles were active longer at 90% FWS than 3 km.h-1). The precise mechanisms by which cocontraction contributes toward abnormal gait and wasted mechanical energy require further research incorporating both electromyographic and kinematic analysis.     

The whey proteins of the milk of red deer (Cervus elaphus L.). A homologue of bovine beta-lactoglobulin

Increasing plasma free fatty acids decreased the degree of glycogen depletion, and increased the citrate concentration, in slow-red (soleus) and fast-red (deep portion of vastus lateralis) muscle during exercise (approx. 50% depletion of glycogen, as against 75% in control animals). There was no effect in fast-white muscle (superficial portion of vastus lateralis). Glycogen concentration in the liver decreased by 83% in controls, but only by 23% in animals with increased free fatty acids during exercise. The decreased glycogen depletion may be partly explained by the findings that (a) plasma-insulin concentration was two- to three-fold higher in animals with increased plasma free fatty acids and (b) the exercise-induced increase in plasma glucagon was lessened by increased free fatty acids. Blood glucose was higher in the animals with increased free fatty acids after the exercise. The rats with increased plasma free fatty acids utilized approx. 50% as much carbohydrate as did the controls during the exercise.     

Cross-bridge movement in rat slow skeletal muscle as a function of calcium concentration

A single fibre bundle from rat soleus muscle was chemically skinned with saponin and the transfer of myosin heads from the thick filaments to the thin filaments at a sarcomere length of 2.4 microm was measured as a function of Ca2+ concentration using an x-ray diffraction method at 4-7 degrees C. In the relaxed state, the 1,0 spacing was 42.08 nm. The spacing showed no significant decrease when the Ca2+ concentration was below the threshold (-log10 [Ca2+] or pCa 5.8). No significant transfer of the myosin heads occurred when the Ca2+concentration was below the threshold (pCa 5.8). When the muscle was maximally activated at pCa 4.4, the spacing decreased to 40.35 nm. During the maximum isometric contraction at pCa 4.4, 54. 9 +/- 6.5% (+/-SE of the mean) of the myosin heads were transferred to the thin filaments. The transfer of the myosin heads was approximately proportional to relative tension. These results suggest that myosin heads of both fast-twitch and slow-twitch skeletal muscles transferred on the common movement as a function of Ca2+ concentration.     

Fluorometric studies of recovery metabolism of rat fast- and slow-twitch muscles

Recovery metabolism of fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (SOL) muscles of the rat has been investigated using fluorometric monitoring of reduction of nicotinamide adenine dinucleotide (NAD). In both EDL and SOL, groups of twitch contractions produced a decrease in fluorescence (oxidation of NADH) which returned to the resting base line after contraction ceased. These responses proceeded more quickly in EDL than SOL and were abolished by anoxia. A 1-s tetanus of SOL produced an initial reduction which could be abolished with iodoacetate followed by a prolonged oxidation which could be blocked by anoxia. The fluorescence of EDL was decreased immediately following a 1-s tetanus but then rapidly increased well beyond the resting level of reduction and persisted throughout the recovery period. This reduction was largely depressed by iodoacetate. The results indicate marked differences in the recovery metabolism of these muscles, consistent with predominantly mitochondrial oxidative activity in the slow-twitch muscles and predominantly glycolytic activity in the fast-twitch muscles.     

Comparing the behavior of children treated using general anesthesia with those treated using conscious sedation

The histopathologic study was performed to elucidate whether the fiber type atrophy of the vastus lateralis muscle in patients with hip or knee joint disorders is related to the activities of daily living (ADL) or habitual physical activity. Subjects were 16 female patients, 52.4 +/- 16.0 yr of age (mean +/- standard deviation), who underwent a vastus lateralis muscle biopsy at the time of total hip or knee replacement. At the time of referral to the rehabilitation center, the Functional Independence Measure (FIM) motor score and habitual physical activity at home were evaluated, and the diameter and atrophy factor for each muscle fiber type were measured on the histopathologic preparations of the biopsied muscles. The data were analyzed using ttest, one-way analysis of variance (ANOVA), Kruskal-Wallis one-way ANOVA, Spearman's correlation coefficient, and partial correlation coefficient. The patients showed muscle fiber atrophy and small angular fibers, and the atrophy factor was significantly increased in type 1, 2A, and 2B fibers, in that order (one-way ANOVA, P < 0.05). The patterns of the fiber type atrophy, consisting of normal, type 2B atrophy, type 2AB atrophy, and type 1 and 2AB atrophy, had a significant relationship with the fiber type atrophy (Spearman's correlation coefficient; rho = 0.834, P < 0.001). The FIM motor score showed a significant correlation with the atrophy factor (r = -0.584, P < 0.05), and significant differences were recognized among the four patterns of the fiber type atrophy (Kruskal-Wallis one-way ANOVA, P < 0.05). In conclusion, the muscle atrophy and patterns of the fiber type atrophy of the vastus lateralis muscle in patients with joint disorders may be related to changes in the FIM motor score.