Difference in thiamine metabolism between extensor digitorum longus and soleus muscles

1. Thiamine diphosphate level was higher in soleus muscle than in extensor digitorum longus muscle in various animals, whereas thiamine triphosphate level was less in the former muscle than in the latter except for mouse. 2. 2-Oxoglutarate dehydrogenase, transketolase and thiamine pyrophosphokinase activities were higher in soleus muscle than in extensor digitorum longus in rat and guinea pig. 3. The differences between rat two muscle phenotypes in thiamine diphosphate, but not thiamine triphosphate, level and the thiamine-related enzyme activities disappeared after denervation. 4. Tenotomy had little effect on thiamine phosphate levels and the thiamine-related enzyme activities in rat skeletal muscles.     

Maximal peak torque as a predictor of angle-specific torques of hamstring and quadriceps muscles in man.

This study assessed the relationship between the isokinetic peak torque (PT) (speed of movement 1.05 and 3.14 rads-1) and the angle-specific torques (ASTs) at 0.26 and 1.31 rad of knee flexion in multiple contractions of the quadriceps and hamstrings in 70 individuals with a chronic anterior cruciate ligament (ACL) insufficiency and 78 individuals with a chronic medial collateral ligament (MCL) insufficiency in one knee. At every test speed, the Pearson product moment correlation coefficients (r) between the PT and ASTs were highly significant (P less than 0.001) in the uninjured knees (r = 0.61-0.93) as well as in the knees with ACL (r = 0.61-0.87) and MCL (r = 0.74-0.91) insufficiency. In addition, in both groups the majority of the correlation coefficients exceeded 0.80, which is generally regarded as the threshold for the relationship to be considered clinically significant. Furthermore, using regression analysis, both extremities showed completely non-systematic distribution of the residuals. It is concluded that in healthy knees or knees with ACL or MCL insufficiency, the predictability of ASTs from PT was good, and, therefore, that AST analyses may offer little additional information about thigh muscle function to that obtained from a simpler and more commonly used measurement, the PT analysis.     

Myofascial force transmission between the human soleus and gastrocnemius muscles during passive knee motion

The plantarflexors of the lower limb are often assumed to act as independent actuators, but the validity of this assumption is the subject of considerable debate. This study aims to determine the degree to which passive changes in gastrocnemius muscle length, induced by knee motion, affect the tension in the adjacent soleus muscle. A second aim is to quantify the magnitude of myofascial passive force transmission between gastrocnemius and adjacent soleus. Fifteen healthy volunteers participated. Simultaneous ultrasound images of the gastrocnemius and soleus muscles were obtained during passive knee flexion (0-90°), while keeping the ankle angle fixed at either 70° or 115°. Image correlation analysis was used to quantify muscle fascicle lengths in both muscles. The data show that the soleus muscle fascicles elongate significantly during gastrocnemius shortening. The approximate change in passive soleus force as a result of the observed change in fascicle length was estimated and appears to be <5 N, but this estimate is sensitive to the assumed slack length of soleus.     

Contraction level-related modulation of corticomuscular coherence differs between the tibialis anterior and soleus muscles in humans

The sensorimotor cortex activity measured by scalp EEG shows coherence with electromyogram (EMG) activity within the 15- to 35-Hz frequency band (β-band) during weak to moderate intensity of isometric voluntary contraction. This coupling is known to change its frequency band to the 35- to 60-Hz band (γ-band) during strong contraction. This study aimed to examine whether such contraction level-related modulation of corticomuscular coupling differs between muscles with different muscle compositions and functions. In 11 healthy young adults, we quantified the coherence between EEG over the sensorimotor cortex and rectified EMG during tonic isometric voluntary contraction at 10-70% of maximal voluntary contraction of the tibialis anterior (TA) and soleus (SOL) muscles, respectively. In the TA, the EEG-EMG coherence shifted from the β-band to the γ-band with increasing contraction level. Indeed, the magnitude of β-band EEG-EMG coherence was significantly decreased, whereas that of γ-band coherence was significantly increased, when the contraction level was above 60% of maximal voluntary contraction. In contrast to the TA, the SOL showed no such frequency changes of EEG-EMG coherence with alterations in the contraction levels. In other words, the maximal peak of EEG-EMG coherence in the SOL existed within the β-band, irrespective of the contraction levels. These findings suggest that the central nervous system regulates the frequency of corticomuscular coupling to exert the desired levels of muscle force and, notably, that the applicable rhythmicity of the coupling for performing strong contractions differs between muscles, depending on the physiological muscle compositions and functions of the contracting muscle.     

The relationship between muscle deoxygenation and activation in different muscles of the quadriceps during cycle ramp exercise

The relationship between muscle deoxygenation and activation was examined in three different muscles of the quadriceps during cycling ramp exercise. Seven young male adults (24 ± 3 yr; mean ± SD) pedaled at 60 rpm to exhaustion, with a work rate (WR) increase of 20 W/min. Pulmonary oxygen uptake was measured breath-by-breath, while muscle deoxygenation (HHb) and activity were measured by time-resolved near-infrared spectroscopy (NIRS) and surface electromyography (EMG), respectively, at the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM). Muscle deoxygenation was corrected for adipose tissue thickness and normalized to the amplitude of the HHb response, while EMG signals were integrated (iEMG) and normalized to the maximum iEMG determined from maximal voluntary contractions. Muscle deoxygenation and activation were then plotted as a percentage of maximal work rate (%WR(max)). The HHb response for all three muscle groups was fitted by a sigmoid function, which was determined as the best fitting model. The c/d parameter for the sigmoid fit (representing the %WR(max) at 50% of the total amplitude of the HHb response) was similar between VL (47 ± 12% WR(max)) and VM (43 ± 11% WR(max)), yet greater (P < 0.05) for RF (65 ± 13% WR(max)), demonstrating a "right shift" of the HHb response compared with VL and VM. The iEMG also showed that muscle activation of the RF muscle was lower (P < 0.05) compared with VL and VM throughout the majority of the ramp exercise, which may explain the different HHb response in RF. Therefore, these data suggest that the sigmoid function can be used to model the HHb response in different muscles of the quadriceps; however, simultaneous measures of muscle activation are also needed for the HHb response to be properly interpreted during cycle ramp exercise.     

Corticospinal control of soleus motoneurons in man

Electrical or magnetic stimulation of the human motor cortex causes a strong, short latency facilitation of tibialis anterior (TA) motoneurons but only weak, longer latency changes in the excitability of soleus (SOL) motoneurons. The facilitation of TA motoneurons has been attributed to the monosynaptic action of the "fast" corticospinal pathway. The present study further investigates the cortical control of soleus motoneurons in man. In tests of reaction time to auditory stimuli, normal subjects took significantly longer to activate soleus motoneurons than tibialis anterior motoneurons. Thus we could not demonstrate the existence of a "fast" pathway from the brain to SOL motoneurons that, for some reason, is not activated by magnetic stimulation. The hypothesis that the cortex might control soleus motoneurons indirectly by modulation of the Ia input from muscle spindles was tested. Magnetic stimulation of the cortex was used to condition the facilitation of soleus motoneurons resulting from the stimulation of group I fibres in the tibial nerve. There were no consistent changes in Ia facilitation. We conclude (i) that there is no evidence so far that SOL motoneurons are excited by a direct pathway from the cortex (similar to that projecting to TA motoneurons) and (ii) that the observed changes in firing probability of soleus motoneurons produced by magnetic stimulation over the motor cortex do not result from modulation of presynaptic inhibition of Ia afferents.     

Eccentric and concentric torque-velocity characteristics of the quadriceps femoris in man

The primary purpose of this investigation was to study the eccentric and concentric torque-velocity characteristics of the quadriceps femoris in man using a recently developed combined isometric, concentric and eccentric controlled velocity dynamometer (the SPARK System). A secondary purpose was to compare the method error associated with maximal voluntary concentric and eccentric torque output over a range of testing velocities. 21 males (21-32 years) performed on two separate days maximal voluntary isometric, concentric and eccentric contractions of the quadriceps femoris at 4 isokinetic lever arm velocities of 0 degree.s-1 (isometric), 30 degrees.s-1, 120 degrees.s-1 and 270 degrees.s-1. Eccentric peak torque and angle-specific torques (measured every 10 degrees from 30 degrees to 70 degrees) did not significantly change from 0 degrees.s-1 to 270 degrees.s-1 (p greater than 0.005) with the exception of angle-specific 40 degrees torque, which significantly increased; p less than 0.05). The mean method error was significantly higher for the eccentric tests (10.6% +/- 1.6%) than for the concentric tests (8.1% +/- 1.7%) (p less than 0.05). The mean method error decreased slightly with increasing concentric velocity (p greater than 0.05), and increased slightly with increasing eccentric velocity (p greater than 0.05). A tension restricting neural mechanism, if active during maximal eccentric contractions, could possibly account for the large difference seen between the present eccentric torque-velocity results and the classic results obtained from isolated animal muscle.     

Development of various types of muscle fibers in the quadriceps femoris and the soleus during human ontogenesis

By means of histological methods for revealing adenosine triphosphatase of myosin (pH 4.6) and succinate dehydrogenase activity, using postmortem material, development of various muscle fibers of the femoral m. quadriceps and m. soleus has been studied in human ontogenesis. The first stage of rearrangements lasts from the 5th-6th month of the uterine development up to 2 years of age and is characterized by formation (from non-differentiated) of oxidative, glycolytic and oxidative-glycolytic fibers. During the period from 2 up to 7-8 years of age the ratio in the types changes slightly, but transversal section size of the muscle fiber increases intensively. Then from 11 up to 17 years of age, together with maximal increment of the fibers transversal section, there is an essential change in the type relation. By the 17th years of age, in the femoral m. quadriceps the part of the fibers with glycolytic type of energy supply increases, while in the m. soleus the oxidative fibers become more numerous. By the 70th years of age in the femoral m. quadriceps relative amount of intermediate fibers increases.     

Peroxisomes of the rat cardiac and soleus muscles increase after starvation

Summary We have investigated the change of catalase activity in the homogenates of rat cardiac and skeletal muscles. After 7 days' starvation, the catalase activity of heart increased about 3-fold and that of soleus muscle enhanced 2-fold higher than that of control rats. Immunoblot analysis of catalase showed a single band in the homogenates of cardiac and soleus muscles and increase of catalase antigen after starvation. Light microscopic immunoenzyme staining showed that after starvation catalase positive granules markedly increased in both the cardiac and soleus muscle. Quantitative analysis of the staining showed that number of the granules per 100 m² of tissue section was about 1.4-fold in the soleus muscle and 1.7-fold in the cardiac muscle after starvation. By electron microscopy of alkaline DAB staining, we confirmed that the granules were peroxisomes, which increased in both number and size. Furthermore, we stained the peroxisomes for catalase by a protein A-gold technique. Labeling density (gold particles/m²) of the cardiac and soleus muscles from the starved rat increased approximately 1.4 times as much as that of normal animal. When the numerical density is multiplied by the labeling density, the values are largely consistent with the enhancement of catalase activity. These results show that increase in the catalase activity of the muscle tissue after starvation is caused by increase in number and size of peroxisomes.     

Gluteus maximus and soleus compensate for simulated quadriceps atrophy and activation failure during walking

Important activities of daily living, like walking and stair climbing, may be impaired by muscle weakness. In particular, quadriceps weakness is common in populations such as those with knee osteoarthritis (OA) and following ACL injury and may be a result of muscle atrophy or reduced voluntary muscle activation. While weak quadriceps have been strongly correlated with functional limitations in these populations, the important cause–effect relationships between abnormal lower extremity muscle function and patient function remain unknown. As a first step towards determining those relationships, the purpose of this study was to estimate changes in muscle forces and contributions to support and progression to maintain normal gait in response to two sources of quadriceps weakness: atrophy and activation failure. We used muscle-driven simulations to track normal gait kinematics in healthy subjects and applied simulated quadriceps weakness as atrophy and activation failure to evaluate compensation patterns associated with the individual sources of weakness. We found that the gluteus maximus and soleus muscles display the greatest ability to compensate for simulated quadriceps weakness. Also, by simulating two different causes of muscle weakness, this model suggested different compensation strategies by the lower extremity musculature in response to atrophy and activation deficits. Estimating the compensation strategies that are necessary to maintain normal gait will enable investigations of the role of muscle weakness in abnormal gait and inform potential rehabilitation strategies to improve such conditions.     

Satellite DNA relationships in man and the primates

We have investigated the genomes of a series of primates to identify the presence of sequences related to human satellite DNAs I, II and III by restriction enzyme digestion and hybridisation with probes of these satellite DNAs. Where we have found such related sequences we have examined the extent to which they have diverged by measuring the stability of the hybrids. DNA satellite III is the oldest sequence being common to species which have diverged some 24 million years ago. In contrast DNA satellites I and II are of much more recent origin. Our results permit us to draw conclusions about the way these sequences have evolved, and how the evolution of repeated DNA sequences may be related to the evolution of the primate lineage.     

A comparison of the contractile properties of the human gastrocnemius and soleus muscles

Twitch speeds and potentiating capacities have been determined for human medial and lateral gastrocnemius and soleus muscles. The experiments involved and application of submaximal stimuli to the respective muscle bellies, with monitoring of the evoked compound action potentials (M-waves) during repetitive stimulation. Contrary to an earlier report, the lateral gastrocnemius was found to have a significantly shorter mean contraction time (100.0 +/- 10.8 ms) than the soleus (156.5 +/- 14.7 ms) and this value was also significantly different from that of the medial gastrocnemius (113.7 +/- 19.6 ms). The mean half-relaxation time for each muscle also differed significantly from those for the other two muscles. A further contrast between the muscles was that potentiation of the twitch, following a 3-s tetanus at 50 Hz, was significantly greater in the lateral gastrocnemius than in soleus (mean values 60.4 +/- 43.1% and 2.6 +/- 3.3% respectively.     

Interaction between Visual and Proprioceptive Analyzers in Vertical Posture Control

The CNS can precisely assess the spatial position of the human body only by simultaneously processing and integrating the visual, proprioceptive, and vestibular inputs. Postural stability data make it possible to estimate changes taking place in the function of analyzers involved in the maintenance of the upright posture. The vertical posture stability was assessed in healthy children and children with spastic diplegic cerebral palsy from their postural responses to the presentation of single optokinetic or somatosensory stimuli. The visual analyzer was found to play a significant role in maintaining the upright position under natural gravity conditions in healthy children. A single exposure of the proprioceptive system to variable forces directed with the gravity of the earth (vertical) decreased the contribution of the visual analyzer. Healthy children maintained the upright position relying on the direction of movement of the optokinetic stimuli, which, however, produced no effect on the maintenance of posture in the patients. A hypothesis is proposed that prenatal or early postnatal CNS lesions decrease the contribution of phylogenetically newer brain structures to the regulation of upright posture.