Changes in neural modulation and motor control during voluntary movement of older individuals

BACKGROUND: Changes in the modulation of soleus alpha motoneuron excitability, as assessed by H reflexes, and temporal sequencing of the soleus and tibialis anterior muscles during voluntary ankle dorsiflexions and plantar flexions of young (24.7 +/- 11.5; n = 13) and older (68.7 +/- 5.4; n = 13) subjects were assessed to determine potential neural mechanisms that might contribute to motor control changes associated with aging. METHODS: A repetitive stimulation (5 Hz) soleus H-reflex testing protocol and surface electromyography (EMG) were used to assess the latencies of soleus H-reflex changes in relation to tibialis anterior and soleus EMG activations of standing subjects during voluntary ankle dorsiflexions and plantar flexions at self-selected speeds. The pattern and latency of H-reflex changes in relation to EMG activity were compared between young and old subjects. RESULTS: There were no differences in the relative amount of antagonist muscle (soleus) inhibition during voluntary ankle dorsiflexions between young and old subjects (26.4% and 27.2% decrease from resting H-reflex values, respectively). Older subjects, however, required additional time to achieve these levels of inhibition. Delays in the activation of soleus H reflexes during the plantar flexion task were also observed in older subjects. Older subjects also had considerable intra- and intersubject variability in muscle temporal sequencing patterns during ankle plantar flexions. CONCLUSIONS: Although older subjects exhibited similar relative levels of alpha motoneuron inhibition and excitation during voluntary movements, this modulation was delayed when compared to younger subjects. Temporal sequencing of distal muscle activations also appears to undergo change with aging.     

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.     

Experimental muscle pain increases the human stretch reflex

In this study we investigated the effect of human experimental muscle pain on H- and stretch reflexes as indicators of changes in muscle spindle sensitivity. Fourteen healthy, male volunteers participated in the study. Muscle pain was produced by infusion of 5% hypertonic saline over a period of 10-15 min in m. soleus and in m. tibialis anterior. Reflexes were elicited in the relaxed and active soleus muscle (10-15 Nm ankle torque) before, during and after muscle pain. Control measurements were made with infusions of 0.9% isotonic saline. Surface electromyograms (EMG) were measured from the soleus muscle, and torque was measured from the ankle joint. With pain in the soleus muscle the mechanical stretch reflex response (ankle torque) increased significantly (P = 0.0007) as compared to before pain. With pain in the tibialis anterior muscle both the mechanical and EMG responses increased significantly (P = 0.001; P = 0.0003) as compared to before pain. The H-reflex showed no significant changes during the infusions in either muscles. This study has demonstrated a muscle pain-related increase in the amplitude of the stretch reflex without a corresponding increase in the H-reflex amplitude. One explanation could be an increased dynamic sensitivity of the muscle spindles during muscle pain caused by an increased firing rate in the dynamic gamma-motoneurones. However, the data could not support the vicious cycle model because the excitability of the alpha-motoneurone pool was unchanged.     

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.     

Mapping of somato-sensory evoked potentials (SEP): new findings suggesting the role of brain waves as a "temporal analyzer of the stimulus"

Patients with multiple sclerosis (MS) show a poor exercise tolerance. A reduction in respiratory muscle strength has also been reported. The purpose of this study was to evaluate whether reduction in exercise tolerance was related to respiratory muscle dysfunction. Twenty four multiple sclerosis patients (mean +/- SD age: 48 +/- 9 yrs, duration of illness 12.2 +/- 6 yrs, severity of illness as assessed by Expanded Disability Scale Score (EDSS) 5.3 +/- 2), underwent detailed evaluation of lung function tests, arterial blood gas analysis, respiratory muscle strength and endurance, and exercise test on an arm ergometer. Sixteen of the 24 patients were able to perform the exercise test (Group I), whilst the other eight were not (group II). Arterial blood gases and lung function tests were normal for both groups. Respiratory muscle strength as assessed both by maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) was significantly reduced (MIP 18-76 cmH2O; MEP 16-82 cmH2O) compared to predicted values. Inspiratory muscle endurance time was significantly reduced in Group II in comparison to Group I (247 +/- 148 vs 397 +/- 154 s, respectively). Both MIP and MEP were significantly related to inspiratory muscle endurance time. Endurance time, MIP and MEP were inversely significantly related to duration of illness, whilst only endurance time was significantly related to Expanded Disability Scale Score.(ABSTRACT TRUNCATED AT 250 WORDS)     

Size and myosin heavy chain profiles of rat hindlimb extensor muscle fibers after 2 weeks at 2G

METHOD: The effects of 14 d of continuous centrifugation at approximately 2G on the hindlimb extensor musculature of male rats were studied. RESULTS: The mean body mass of centrifuged rats was 17% smaller than age-matched controls. In centrifuged rats, the mean absolute masses of the soleus and medial gastrocnemius (MG) were similar to control, while the mean relative masses (expressed as milligram muscle mass/gram of body mass) were larger than control. Based on a battery of monoclonal antibodies for specific myosin heavy chains (MHC), the soleus of centrifuged rats had a lower percentage (68 vs. 74%) of fibers expressing type I MHC only and a higher percentage (15 vs. 10%) that co-expressed type I and IIa MHC's. The MHC composition of fibers from the deep portion of the MG was unaffected by centrifugation. The MHC compositions based on SDS-PAGE gel electrophoresis for each muscle were similar in the two groups. Mean fiber size of each fiber type in the soleus was unaffected by centrifugation. In the MG, the fibers, expressing only type IIb MHC were smaller in the centrifuge compared to control rats. CONCLUSION: Although 2 weeks of chronic centrifugation at 2G resulted in a cessation of body growth, there was essentially no effect on the muscle masses or fiber size in either a slow or fast extensor muscle. These data suggest that periods of centrifugation may be beneficial in maintaining extensor muscle mass in an animal that is not growing at a normal rate e.g., during chronic unloading.     

Region- and age-dependent variations of muscle fibre properties

The cytophotometric-morphometrical analysis of extensor digitorum longus and soleus muscles of 2.5 and 18 months old rats revealed regional and age-dependent differences in fibre type distribution, fibre area and fibre type related-enzyme activities which characterize contractility and metabolic profile. Variations along the longitudinal axis from the origin to the insertion and along three transversal axes from superficial to deep were found dependent on the muscle investigated. For example, the fibres of extensor digitorum longus muscle showed increased contractile and glycolytic capacities near insertion and the fibres of soleus muscle increased oxidative capacity in its middle part. Furthermore, the contribution of the fibre type that is dominant in a muscle (fast-glycolytic fibre type in extensor digitorum longus and slow-oxidative fibre type in soleus muscle) to the total number of fibres increased from origin to insertion by 15 and 30%, respectively. Along the superficial-deep axes the oxidative capacity of all fibres increased, the most in fast fibres of the soleus muscle by approximately 50%. In soleus muscle, a decrease of cross areas of all fibre types from superficial to deep was found, correlating negatively with the succinate dehydrogenase activity of the fibres. In extensor digitorum longus muscle the change in cross areas of slow-oxidative and fast-oxidative glycolytic fibres was dependent on the position of the transversal axis in the muscle. The results suggest that distribution patterns of fibre types and the metabolic make up of individual muscle fibres are adapted on the basis of local functional demands. In both muscles, higher numbers and increased oxidative capacity of fast-glycolytic fibres were found during ageing, but variations from superficial to deeper regions were irrespective of age.     

Variety of muscle responses to tactile stimuli

Influences exerted by tactile stimuli on the muscle activity were investigated with two methods: (1) analysis of kinematics and electromyographic (EMG) activity of eight forelimb muscles during contact placing (CP) reactions elicited by tactile stimuli applied to the dorsal, medial or lateral sides of the paw in cats, and (2) the Hoffmann (H)-reflex technique to quantify the effects of the tactile stimuli on the excitability of the alpha motoneurones of the soleus muscle in awake rats. The first group of the data showed that the tactile stimuli applied to dorsal, medial or lateral aspects of the paw led to different strategies of the forelimb movements during CP reactions. These differences arose from various patterns of activation of the elbow flexor and extensor muscles at the beginning of CP reactions and a various involvement of the medio-lateral components of movements, depending on the site of the tactile stimulus application. With the H-reflex technique it was found that the tactile stimulus diminished the excitability of alpha motoneurones of the soleus muscle when applied to the skin overlying the lateral side of the ankle joint. This effect was in line with the observation that the tactile stimulus applied to the lateral side of the paw activated the elbow flexor muscles but not their antagonists to initiate CP reaction.     

Electromyographic and neuromuscular variables in post-polio subjects

OBJECTIVE: Post-polio subjects experience functional deterioration many years after developing acute poliomyelitis and have been shown previously to have a deficit in strength recovery after isometric activity. This study characterized the size and stability of the motor units in a group of post-polio subjects with macro and single fiber electromyography (EMG) and correlated these variables with isometric strength, endurance, "work capacity," and strength recovery after fatiguing isometric exercise. DESIGN: A cohort of 12 post-polio subjects was tested for neuromuscular function. Electromyographic variables were determined on a separate day. SETTING: Volunteers were recruited from the community and tested in our neuromuscular research laboratory. SUBJECTS: A volunteer sample was obtained from advertisements. All subjects acknowledged post-polio syndrome symptoms. MAIN OUTCOME MEASURES: Neuromuscular variables were isometric knee extension peak torque, endurance (time to exhaustion) at 40% of maximal torque, tension time index, and recovery of torque at 10 minutes. Electromyographic variables were macro EMG and single fiber EMG (percent blocking and jitter). RESULTS: Macro EMG amplitude was ninefold the control value, and both jitter and blocking were greatly increased in comparison to control values. Isometric strength significantly (p < .05) correlated negatively with macro EMG amplitude. CONCLUSIONS: The weakest subjects had the greatest number of muscle fibers within the motor unit (as measured by macro EMG amplitude). Jitter and blocking did not correlate with neuromuscular function.     

The relationship between electromyography and work intensity revisited: a brief review with references to lacticacidosis and hyperammonia

The aim of this investigation was to re-evaluate the relationship between electromyography and work intensity during incremental work in light of highly discrepant literature. Trained male subjects participated in the study (n = 14). Each subject completed a VO2max test on a cycle ergometer. Tests started at a power output of 60 Watts with a 30 Watt.4 min-1 work increment. Each test was terminated at exhaustion. Blood was collected at the end of each work intensity for lactate and ammonia analysis. EMG were recorded from the vastus lateralis, rectus femoris and vastus medialis using pre-amplified surface electrodes. EMG were collected at each intensity over a period of 60 cycle revolutions. EMG signals were analyzed using integration and EMG spectral analysis. Gas exchange variables were recorded on-line for each test (15 second interval). Ammonia and lactate threshold points were surpassed at the same absolute work intensity (200 Watts) which was equivalent to 64-69% VO2max. When a linear model was applied to the iEMG data, coefficients of determination achieved were greater than those obtained when an exponential model was used for the vastus lateralis and medialis. Gradients of regression lines fitted to iEMG data at pre- and post-lactate/ammonia threshold work intensities were not different. Alternatively, the iEMG-work intensity relationship for the rectus femoris muscle tended to be curvilinear. Significant increases in iEMG were observed at post-lactate/ammonia threshold work intensities for the rectus femoris reflecting increases in fatigue and type II motor unit recruitment at these intensities. In general, median frequency of the EMG power spectrum function were unchanged during incremental work, although highly individualistic results were observed between some subjects and muscles. Grouped median frequency values were insensitive to changes in recruitment, metabolite accumulation and fatigue associated with the increases in work intensity. Consequently, the usefulness of EMG spectral analysis during incremental work was questioned.     

Measurement of respiratory muscle performance in patients with chronic obstructive pulmonary disease

Respiratory muscle performance is measured in terms of strength and endurance. A RMSE-1 type measuring system for evaluation of respiratory muscle strength (RMS) and endurance (RME) has been developed and tested in normal subjects and patients with stable chronic obstructive pulmonary disease (COPD). The results showed that there was no significant difference between normal subjects and stable COPD patients in RMS measured as maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP). The maximum load (Load(m)), mean mouth pressure at maximum load (Pmean), and the maximum sustainable inspiratory pressure (SIP(m)) as % MIP (SIP(m)/MIP) were taken as measure of RME. All measures of RME in COPD group were much lower than those in the normal. The measurement of RME can be used to evaluate the effect of respiratory muscle training and direct the respiratory rehabilitation in COPD patients.     

Experimental muscle pain does not cause long-lasting increases in resting electromyographic activity

The mutual links between muscle pain and resting electromyographic (EMG) activity are still controversial. This study described effects of experimental muscle pain on resting EMG activity in a jaw-closing muscle and a leg muscle. Pain was induced by injections of hypertonic saline into the muscles in 10 subjects. Injections of isotonic saline served as a control. The pain intensity was scored on visual analog scales (VAS) and surface and intramuscular wire EMGs were obtained from the resting muscles before, during, and after saline injections. EMG activity was analyzed in 30-s intervals and demonstrated, in both muscles, significant increases 30-60 s after injection of hypertonic saline, but not after injection of isotonic saline. In contrast to the transient increase in EMG activity, the pain sensation lasted up to 600 s after injection of hypertonic saline. It was concluded that acute muscle pain is unable to maintain longer-lasting resting muscle hyperactivity.     

Coenzyme Q10 in pregnancy

BACKGROUND: When H-reflexes are recorded during movement in human subjects, the stimulator current output is not a good indicator of sensory stimulation efficacy because of unavoidable nerve movement relative to the stimulus electrodes. Therefore, the M-wave amplitude has been used by researchers as an indicator of the efficacy of the stimulus. In this study we have examined the general validity of the hypothesis that the M-wave amplitude is directly proportional to the group I sensory afferent volley evoked by the stimulus. METHODS: A nerve recording cuff, stimulating electrodes, and EMG recording electrodes were implanted in cats. Nerve cuff recordings of centrally propagating volleys evoked by electrical stimuli were directly compared to M-waves produced by the same stimuli. Compound action potentials (CAPs) recorded in the sciatic nerve were compared with soleus M-waves during either tibial nerve or soleus muscle nerve stimulation. CAPs in the ulnar nerve were correlated with flexor carpi ulnaris M-waves during ulnar nerve stimulation. RESULTS AND CONCLUSIONS: Our findings indicate that for mixed nerve stimulation (e.g., tibial or ulnar nerve) the M-wave can be a reliable indicator of the centrally propagating sensory volley. Due to the high correlation between CAP and M-wave amplitude in these nerves, a small number of M-waves can give a good estimate of the size of the group I sensory volley. On the other hand, when nerves with only partially overlapping fibre diameter populations are stimulated (e.g., the soleus muscle nerve), the M-wave is not well correlated with the group I sensory volley and thus may not be used as a measure of the size of the input volley for H-reflex studies.     

Xenobiotic-enhanced expression of cytochromes P450 2E1 and 2B in primary cultured rat hepatocytes

The purpose of this investigation was to determine whether long-term, heavy resistance training would cause adaptations in rat skeletal muscle structure and function. Ten male Wistar rats (3 weeks old) were trained to climb a 40-cm vertical ladder (4 days/week) while carrying progressively heavier loads secured to their tails. After 26 weeks of training the rats were capable of lifting up to 800 g or 140% of their individual body mass for four sets of 12-15 repetitions per session. No difference in body mass was observed between the trained rats and age-matched sedentary control rats. Absolute and relative heart mass were greater in trained rats than control rats. When expressed relative to body mass, the mass of the extensor digitorum longus (EDL) and soleus muscles was greater in trained rats than control rats. No difference in absolute muscle mass or maximum force-producing capacity was evident in either the EDL or soleus muscles after training, although both muscles exhibited an increased resistance to fatigue. Individual fibre hypertrophy was evident in all four skeletal muscles investigated, i.e. EDL, soleus, plantaris and rectus femoris muscles of trained rats, but muscle fibre type proportions within each of the muscles tested remained unchanged. Despite an increased ability of the rats to lift progressively heavier loads, this heavy resistance training model did not induce gross muscle hypertrophy nor did it increase the force-producing capacity of the EDL or soleus muscles.     

Reduced stretch-reflex sensitivity after exhausting stretch-shortening cycle exercise

The stretch-shortening cycle (SSC) is an effective and natural form of muscle function but, when repeated with sufficient intensity or duration, it may lead to muscle damage and functional defects. A reduced tolerance to impact has been reported, which may be partly attributed to a reduced stretch-reflex potentiation. The aim of the present study was to examine the influence of SSC-induced metabolic fatigue and muscle damage on the efficacy of stretch reflexes, as judged by the electromyograph (EMG) response of two shank muscles (lateral gastrocnemius LG, soleus SOL) to controlled ramp stretches. These EMG responses were recorded before and immediately after exhausting SSC-type leg exercise and 2 h, 2 days and 4 days later. Serum concentrations of creatine kinase ([CK]), myoglobin and lactate were measured repetitively along the protocol. Two maximal vertical drop jumps and counter-movement jumps were performed after each reflex test. The exhausting SSC-type exercise induced an immediate reduction (P < 0.05) with a delayed short-term recovery of the LG peak-to-peak reflex amplitude. This was not accompanied by significant changes in the reflex latency. The drop jump performance remained slightly but significantly reduced (P < 0.05) until the 2nd day postexercise. Peak [CK] appeared for all the subjects on the 2nd day, suggesting the presence of muscle damage. The increase in [CK] between the 2nd h and the 2nd day postexercise was found to be negatively related (P < 0.001) to the relative changes in the drop jump height. Furthermore, a significant relationship (P < 0.05) was found between recovery of the stretch reflex in LG and the decrease of [CK] between the 2nd and the 4th day. These findings support the hypothesis of a reduced stretch-reflex sensitivity. While the exact mechanisms of the reflex inhibition remain unclear, it is emphasized that the delayed recovery of the reflex sensitivity could have resulted from the progressive inflammation that develops in cases of muscle damage.     

The need for more efficacy and relevance in medical education

To study quantitatively the effect of breathing exercises on the prevention of progression in chronic obstructive pulmonary disease (COPD), 324 patients with stable COPD were randomly assigned to either breathing exercises (BE) or placebo medicine as control. The maximum respiratory pressure (320 cases) and transdiaphragmatic pressure (129 cases) were monitored with RMS-1 and Type-2 gastrointestinal pressure measuring instrument. BE were taught and checked by experienced specialists periodically. Patients in BE group were compared with those in the control group by measuring MIP, MEP, Pdi, and Pdimax after one to 20 months. In BE group MIP increased by 30.42%, MEP 32.10%, Pdi 30.94%, and Pdimax 65.59% (P < 0.001). No significant change was observed in the control group. MIP, MEP, Pdi, and Pdimax increased by 6.95%, 2.92%, 14.63% and 9.05% respectively (P < 0.05) in the control group. It is shown preliminarily that BE had potent and lasting effect on respiratory muscle contraction after studying large number of cases. The methods mentioned above can be used as quantitative indices for the contractile properties of respiratory muscle.     

The role of the lateral pterygoid muscles in TMJ disorders during static conditions

Intramuscular EMG of the lateral pterygoid muscles (LPM), surface EMG of the temporalis and masseter muscles and force measurements of the temporomandibular joint (TMJ) were synchronously used to investigate the biomechanical role of the two heads of the LPM in relation to internal derangement (ID) of the TMJ. EMG and kinetic analysis of five static conditions (resting, protraction, opening, molar and incisor clenching) and three maximum isometric masticatory forces (opening, molar and incisor clenching) were done to compare forces and muscular activity between TMJ ID and control subjects. The analysis of variance results of the integrated linear envelope (LE) EMG showed no significant differences between the two groups for the masseter and temporalis muscles. Therefore, there is no apparent reason to believe that these muscles are hyperactive in TMJ ID. The integrated LE EMG of the SLP was significantly lower in the TMJ group during molar clenching (104 microV + 60.0 over 159 microV + 68.8 for a p = .020). The superior head of the lateral pterygoid muscle (SLP) seemed to have lost its diskal stabilizing function. The integrated LE EMG signals of the ILP were significantly higher in the TMJ ID group during rest, resisted protraction and incisor clenching (p = .029, p = .046, p = .031 respectively). The ILP muscle has probably adapted to control the inner joint instability while continuing its own actions. The ILP muscle seemed to have lost its functional specificity. The results of the isometric forces showed that TMJ ID subjects exhibited significantly lower molar bite forces (297.1N over 419N, p = .042) confirming that they have less muscle strength and tissue tolerance than subjects with healthy masticatory muscle systems. A neuromuscular adaptation could be occurring in the TMJ ID masticatory system affecting muscular actions and forces.     

Use of serotonin for treatment of patients with diabetic angiopathies

In 26 patients (female 11, males--15) with diabetic angiopathy (necrosis of the foot or toes) local measurement of pO2 by transcutaneous mode was carried out before and during introduction of serotonine adipinate. Simultaneously with evaluation of pO2 in 14 patients electromyography (EMG) was made. Serotonine adipinate was introduced intravenously with a speed of 5.0-10.0 mg per hour. In this group mean age of the patients made up 57.4 years, mean values of initial pO2 25.6 mm Hg, and mean indices of pO2 at the moment of serotonine treatment 38.5 mm Hg. Average increase of pO2 during serotonine infusion was registered as 50.4% in comparison with mean initial data. In all 14 patients, who underwent simultaneous measurement of pO2 and registration of EMG, reinforcement of electrical activity of smooth muscles (SM) of various intensity and increase in tissue pO2 were detected. Improvement of microcirculation (increase of transcutaneous pO2, reinforcement of electrical activity of SM as a result of serotonine introduction) evidences that functional and morphological changes of serotonine receptors of SM are involead in genesis of diabetic angiopathy. The data obtained showed that in diabetes mellitus, besides insulin deficiency, insufficiency of such an endogenous factor as serotonine duclops. Thus, serotonin should be used for prophylaxis and treatment of diabetic angiopathies.     

Management of caustic esophagitis in adults

We investigated whether a cortical potential exists, that is similar to the Bereitschaftspotential, preceding postural adjustment followed by voluntary ballistic rising on tiptoe in 10 healthy subjects. On the basis of the electromyogram (EMG) activities of the soleus muscle, the onsets of the premotion silent period (PMSP) and EMG discharge were determined. The negative potentials associated with a voluntary rise-on-tiptoe movement with respect to EMG onset were similar to the readiness potential associated with voluntary foot movement. The slopes of the slow negative potential associated with the PMSP onset were significantly more negative than those of the potential associated with rise-on-tiptoe movement, particularly over the frontal electrode positions. The results suggest that a cortical potential precedes postural adjustment that is followed by voluntary rising on tiptoe.     

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.