Muscle Contraction In Patients Research Articles

Cardiovascular responses to static handgrip exercise and postexercise ischemia in heart failure with preserved ejection fraction.

Heart failure with preserved ejection fraction (HFpEF) is characterized by reduced ability to sustain physical activity that may be due partly to disease-related changes in autonomic function that contribute to dysregulated cardiovascular control during muscular contraction. Thus, we used a combination of static handgrip exercise (HG) and postexercise ischemia (PEI) to examine the pressor response to exercise and isolate the skeletal muscle metaboreflex, respectively. Mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), and total peripheral resistance (TPR) were assessed during 2-min of static HG at 30 and 40% of maximum voluntary contraction (MVC) and subsequent PEI in 16 patients with HFpEF and 17 healthy, similarly aged controls. Changes in MAP were lower in patients with HFpEF compared with controls during both 30%MVC (Δ11 ± 7 vs. Δ15 ± 8 mmHg) and 40%MVC (Δ19 ± 14 vs. Δ30 ± 8 mmHg), and a similar pattern of response was evident during PEI (30%MVC: Δ8 ± 5 vs. Δ12 ± 8 mmHg; 40%MVC: Δ13 ± 10 vs. Δ18 ± 9 mmHg) (group effect: P = 0.078 and P = 0.017 at 30% and 40% MVC, respectively). Changes in HR, CO, and TPR did not differ between groups during HG or PEI (P > 0.05). Taken together, these data suggest a reduced pressor response to static muscle contractions in patients with HFpEF compared with similarly aged controls that may be mediated partly by a blunted muscle metaboreflex. These findings support a disease-related dysregulation in neural cardiovascular control that may reduce an ability to sustain physical activity in HFpEF.NEW & NOTEWORTHY The current investigation has identified a diminution in the exercise-induced rise in arterial blood pressure (BP) that persisted during postexercise ischemia (PEI) in an intensity-dependent manner in patients with heart failure with preserved ejection fraction (HFpEF) compared with older, healthy controls. These findings suggest that the pressor response to exercise is reduced in patients with HFpEF, and this deficit may be mediated, in part, by a blunted muscle metaboreflex, highlighting the consequences of impaired neural cardiovascular control during exercise in this patient group.

Does training to sustain the paretic upper limb on an unstable surface provoke contraction of muscles around the shoulder in patients with hemiplegia? A pilot randomized controlled trial

IntroductionActivities with unstable supports provoke greater muscle contractions than those with stable surfaces. Using unstable surfaces to provoke upper limb muscle contraction after hemiplegia has not been explored. Hence, this study tested the effect of efforts to maintain the hemiparetic hand on an unstable surface on proximal muscle contractions of upper limb in patients with acute stroke.MethodsFirst-time stroke patients in the acute phase were randomly allocated into 2 groups. The control group (<i>n</i> = 18) received conventional physiotherapy, whilst the experimental group (<i>n</i> = 19) was given activities to maintain their hemiparetic side hand on an unstable surface in 5 different positions, in addition to conventional physiotherapy. Surface electromyogram was recorded from deltoid and upper trapezius on the hemiparetic side before and after 10 sessions of training.ResultsOverall, 14 patients (aged 57.71 ± 10.70 years) in the control group and 14 (55.78 ± 7.52 years) in the experimental group completed the training. Non-parametric tests for between-group analysis showed that the average electromyography output in the deltoid and trapezius muscles was higher in the experimental group compared with the control group (<i>p</i> < 0.05).ConclusionsTraining involving efforts to maintain the hemiparetic side hand on an unstable surface can be used to provoke activity in upper limb proximal muscles. This could be a simple training with minimal equipment and minimal manual assistance required, added to routine physiotherapy to facilitate proximal muscle contraction in patients with stroke during the acute phase.

Evaluation of Lateral Pterygoid Muscle Contraction in Patients with Temporomandibular Disorders Based on 3D-T2 Weighted Imaging

Objective To evaluate lateral pterygoid muscle(LPM)contraction in the patients with temporomandibular disorders(TMD)based on 3D-T2 weighted imaging(3D-T2WI).Multiplanar reconstruction(MPR)was employed to measure the length of LPM in the images taken in closed-and open-mouth positions. Methods Seventeen TMD patients [age of(29.82±10.70)years,males/females=8/9] and 13 normal volunteers [control,age of(23.54±3.31)years,males/females=6/7] received 3D-T2WI of the temporomandibular joints in closed-and open-mouth positions from November 2019 to April 2020 in Department of Radiology,Hainan Hospital of Chinese PLA General Hospital.According to the position of the discs,the subjects were classified into the following groups:TMD with disc displacement without reduction(TMD-DDwoR),TMD with disc displacement with reduction(TMD-DDwR),TMD without disc displacement(TMDwoDD),and normal control without disc displacement(NCwoDD).MPR was employed to measure the maximal length of the superior belly of LPM.One-way analysis of variance,receiver operating characteristic curve,and permutation test were employed for the statistical analyses. Results The contraction of LPM was significantly shorter in TMD-DDwoR group [(3.36±1.96)mm] than in TMDwoDD group [(7.90±3.95)mm],NCwoDD group [(8.77±3.13)mm](F=12.891,P=0.000),and TMD-DDwR group[(7.12±3.69)mm](χ2=5.314,P=0.031). Conclusion This study confirmed that the contraction of LPM decreased in patients with TMD-DDwoR,which provided imaging evidence for the study of disc displacement mechanism in TMD patients.

Reduction of muscle contraction and pain in electroporation-based treatments: An overview.

BACKGROUNDIn the first studies of electrochemotherapy (ECT), small cutaneous metastases were treated and only mild or moderate pain was observed; therefore, pain was not considered a significant issue. As the procedure began to be applied to larger cutaneous metastases, pain was reported more frequently. For that reason, reduction of both muscle contractions and pain have been investigated over the years.AIMTo present an overview of different protocols described in literature that aim to reduce muscle contractions and pain caused by the electroporation (EP) effect in both ECT and irreversible EP treatments.METHODSThirty-three studies published between January 1999 and November 2020 were included. Different protocol designs and electrode geometries that reduce patient pain and the number of muscle contractions and their intensity were analysed.RESULTSThe analysis showed that both high frequency and bipolar/biphasic pulses can be used to reduce pain and muscle contractions in patients who undergo EP treatments. Moreover, adequate electrode design can decrease EP-related morbidity. Particularly, needle length, diameter and configuration of the distance between the needles can be optimised so that the muscle volume crossed by the current is reduced as much as possible. Bipolar/biphasic pulses with an inadequate pulse length seem to have a less evident effect on the membrane permeability compared with the standard pulse protocol. For that reason, the number of pulses and the voltage amplitude, as well as the pulse duration and frequency, must be chosen so that the dose of delivered energy guarantees EP efficacy.CONCLUSIONPain reduction in EP-based treatments can be achieved by appropriately defining the protocol parameters and electrode design. Most results can be achieved with high frequency and/or bipolar/biphasic pulses. However, the efficacy of these alternative protocols remains a crucial point to be assessed further.

Structural and functional indicators of the heart of patients with ischemic heart disease and type 2 diabetes mellitus. Rhythmoinotropic response isolated myocardium at different levels of glycated hemoglobin

BACKGROUND: Adequate glycemic control can significantly reduce the risk of developing cardiovascular events. However, until now, glycaemic targets in aged patients remain a subject of discussion, especially in the conditions of the combined development of Type 2 Diabetes Mellitus (T2DM) and ischemic heart disease (IHD).AIMS: To examine the structural and functional heart parameters in patients with IHD associated with T2DM and the rhythmoinotropic responses of their isolated myocardium depending on glycated hemoglobin level.MATERIALS AND METHODS: The study included 44 patients with a diagnosis of "chronic IHD associated with T2DM", of which 2 groups were formed. Patients with glycated hemoglobin level (HbA1c) <8% were included in the 1st group, and patients with HbA1c ≥8% were included in the 2nd group. The structural and functional heart parameters obtained with ultrasonography, and the rhythmoinotropic responses of myocardium in patients ex vivo were analyzed using the right atrial appendage fragments obtained during elective coronary artery bypass graft. The inotropic response of muscle strips at a basic stimulation frequency of 0,5 Hz to testing influences was assessed. An extrasystolic test and post-rest test were performed.RESULTS: It was found that extrasystolic contractions of isolated myocardial strips in patients of the 2nd group appeared at shorter extrasystolic intervals, which indicates a greater excitability of the myocardium in patients of this group. Postextrasystolic muscle contractions in patients of the 2nd group had significant potentiation. The amplitude of the muscle strips contractions in patients of both groups was potentiative after short rest periods. However, with an increase in the rest duration, potentiation of contractions was observed only in the group with a higher HbA1c level. According to the ultrasonography data, it was found that the values of the endsystolic and diastolic volumes, the interventricular septum thickness and the left ventricular (LV) myocardium mass were significantly lower in the patients of the 1st group compared with the corresponding indicators in the patients of the 2nd group. The early LV filling velocity (peak E) was significantly lower in the patients of the 1st group, which indicates a slower LV relaxation. At the same time, the rapid LV filling velocity did not have a significant intergroup difference, but this indicator exceeded the reference values in both groups.CONCLUSIONS: With a moderately increased glycemic level (9,2 [8,0; 10,3]%), the structural and functional heart parameters are preserved both at the level of the isolated myocardial tissue and at the level of the whole heart.

Структурно-функциональные показатели сердца пациентов с ишемической болезнью сердца и сахарным диабетом 2 типа. Ритмоинотропная реакция изолированного миокарда при разном уровне гликированного гемоглобина

BACKGROUND : Adequate glycemic control can significantly reduce the risk of developing cardiovascular events. However, until now, glycaemic targets in aged patients remain a subject of discussion, especially in the conditions of the combined development of Type 2 Diabetes Mellitus (T2DM) and ischemic heart disease (IHD). AIMS : To examine the structural and functional heart parameters in patients with IHD associated with T2DM and the rhythmoinotropic responses of their isolated myocardium depending on glycated hemoglobin level. MATERIALS AND METHODS : The study included 44 patients with a diagnosis of chronic IHD associated with T2DM, of which 2 groups were formed. Patients with glycated hemoglobin level (HbA 1c ) <8% were included in the 1 st group, and patients with HbA 1c ≥8% were included in the 2 nd group. The structural and functional heart parameters obtained with ultrasonography, and the rhythmoinotropic responses of myocardium in patients ex vivo were analyzed using the right atrial appendage fragments obtained during elective coronary artery bypass graft. The inotropic response of muscle strips at a basic stimulation frequency of 0,5 Hz to testing influences was assessed. An extrasystolic test and post-rest test were performed. RESULTS : It was found that extrasystolic contractions of isolated myocardial strips in patients of the 2 nd group appeared at shorter extrasystolic intervals, which indicates a greater excitability of the myocardium in patients of this group. Postextrasystolic muscle contractions in patients of the 2 nd group had significant potentiation. The amplitude of the muscle strips contractions in patients of both groups was potentiative after short rest periods. However, with an increase in the rest duration, potentiation of contractions was observed only in the group with a higher HbA 1c level. According to the ultrasonography data, it was found that the values of the endsystolic and diastolic volumes, the interventricular septum thickness and the left ventricular (LV) myocardium mass were significantly lower in the patients of the 1 st group compared with the corresponding indicators in the patients of the 2 nd group. The early LV filling velocity (peak E) was significantly lower in the patients of the 1 st group, which indicates a slower LV relaxation. At the same time, the rapid LV filling velocity did not have a significant intergroup difference, but this indicator exceeded the reference values in both groups. CONCLUSIONS : With a moderately increased glycemic level (9,2 [8,0; 10,3]%), the structural and functional heart parameters are preserved both at the level of the isolated myocardial tissue and at the level of the whole heart.

PULMONARY REHABILITATION IMPROVES QUADRICEPS MUSCLE STRENGTH IN PATIENTS WITH CHRONIC RESPIRATORY DISORDERS

SESSION TITLE: Pulmonary Rehabilitation Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: October 18-21, 2020 PURPOSE: Skeletal muscle dysfunction is an important factor in reduced exercise capacity, impaired quality of life and higher health-care utilization in COPD. Reduced quadriceps function is associated with decreased survival, functional status, and quality of life. Relating quadriceps peak torque (Tq) to its peak electromyographic (EMG) signal (Eq) is an index that may predict fatigue during active contraction. It has not been investigated in patients with chronic respiratory disorders. The objective of this study is to assess changes in skeletal muscle function in patients undergoing a standard 8-week outpatient pulmonary rehabilitation (PR) program. We hypothesized that the ratio Eq/Tq in such patients should be increased in comparison to healthy control subjects. METHODS: Peak Tq as measured by dynamometry and its corresponding peak Eq were recorded using surface sensors and electrodes placed over the vastus lateralis in stable patients undergoing PR. Signals were averaged for a train of 5 knee extensions from the knee bent at 90 degrees to the horizontal plane against a graded resistance adjusted on the dynamometer (isokinetic contractions). Maneuvers were performed at beginning, midway through, and at completion of PR. The ratio Eq/Tq was used as an index of muscle fatigue. Results were compared to those of healthy control subjects who had previously tested the equipment for accuracy and reproducibility. RESULTS: Nine patients (F6/M3, mean age 52 y; diagnoses: 5 interstitial lung disease, 2 bronchiectasis, 2 COPD) were tested and their results compared to 8 healthy individuals (F6/M2, mean age 45 y). Their mean Eq/Tq ratio was 3.1 times as high as that of the control subjects (p <0.01). Six patients who underwent testing mid-way through their PR and 3 who were tested at completion of PR have shown variable responses to physical therapy with decrease in Eq/Tq so far. Mean Eq/Tq in patients decreased from baseline by 35% midway through PR, and by 23% at the end of PR. CONCLUSIONS: Baseline skeletal muscle contraction in patients with chronic respiratory disorders shows greater neural stimulation required to generate a force equivalent to that in healthy individuals, as shown by increase in Eq/Tq. The ratio decreases with PR, indicating improvement in skeletal muscle strength. Use of Eq/Tq has the potential to assess skeletal muscle fatigue and its reversal in patients undergoing PR. CLINICAL IMPLICATIONS: Non-invasive measurement of quadriceps muscle fatigue during a pulmonary rehabilitation program can be used as a tool to assess a patient's progress throughout the program. This can be used in conjunction with validated tools to assess a patient's respiratory symptoms to determine how the pulmonary rehabilitation program is helping a patient. DISCLOSURES: No relevant relationships by Ahmet Baydur, source=Admin input No relevant relationships by Spencer Briglio, source=Web Response No relevant relationships by Juan Cortez, source=Web Response No relevant relationships by Gregory Grandio, source=Web Response No relevant relationships by Guadalupe Yetter, source=Web Response

Basal ganglia and cerebellar circuits have distinct roles in blepharospasm

IntroductionTo identify areas of brain activity associated with involuntary muscle contractions in patients with blepharospasm using functional MRI. Methods15 patients with blepharospasm underwent 8-min resting state scans with spontaneous orbicularis oculi muscle contractions simultaneously recorded using MRI-compatible surface electromyography. Spasm severity and spasm onset/offset were modeled using the amplitude of the electromyography signal (EMG-Amp) and its first temporal derivative (EMG-Onset), respectively, and included in a multiple regression functional MRI analysis using SPM12. Primary outcome was within-group blood-oxygen-level dependent activations that co-varied with EMG-Amp and EMG-Onset following correction for multiple comparisons for an overall cluster corrected p < 0.05. Secondary analyses included testing for correlations between imaging findings and symptom severity, as measured by clinical dystonia rating scales, using an uncorrected voxel-level threshold of p < 0.001. ResultsImaging data from one subject were excluded due to excessive movement. EMG-Amp co-activated within the left sensorimotor cortex and cerebellum, as well as right lingual gyrus and superior temporal gyrus. EMG-Onset co-activated within the left posterior putamen/pallidum and a frontal eye field region in the left superior frontal gyrus. Symptom severity and EMG-Amp significantly co-varied in a small cluster within the left cerebellum. ConclusionOur preliminary findings here suggest that cerebello-cortical circuits in blepharospasm could drive the intensity of eyelid spasms while basal ganglia circuits are associated with the triggering of spasms. This supports the network model for dystonia and identifies specific areas of involvement consistent with known brain regions responsible for control of movement.

Tolerability of facial electrostimulation in healthy adults and patients with facial synkinesis

PurposeTo evaluate optimal stimulation parameters with regard to discomfort and tolerability for transcutaneous electrostimulation of facial muscles in healthy participants and patients with postparetic facial synkinesis.MethodsTwo prospective studies were performed. First, single pulse monophasic stimulation with rectangular pulses was compared to triangular pulses in 48 healthy controls. Second, 30 healthy controls were compared to 30 patients with postparetic facial synkinesis with rectangular pulse form. Motor twitch threshold, tolerability threshold, and discomfort were assessed using a numeric rating scale at both thresholds.ResultsDiscomfort at motor threshold was significantly lower for rectangular than for triangular pulses. Average motor and tolerability thresholds were higher for patients than for healthy participants. Discomfort at motor threshold was significantly lower for healthy controls compared to patients. Major side effects were not seen.ConclusionsSurface electrostimulation for selective functional and tolerable facial muscle contractions in patients with postparetic facial synkinesis is feasible.

Investigation of the mechanisms of cyclooxygenase-mediated mechanoreflex sensitization in a rat model of simulated peripheral artery disease.

Mechanical and metabolic stimuli within contracting skeletal muscles reflexly increase sympathetic nervous system activity and blood pressure. That reflex, termed the exercise pressor reflex, is exaggerated in patients with peripheral artery disease (PAD) and in a rat PAD model with a chronically ligated femoral artery. The cyclooxygenase (COX) pathway contributes to the exaggerated pressor response during rhythmic skeletal muscle contractions in patients with PAD, but the specific mechanism(s) of the COX-mediated exaggeration are not known. In decerebrate, unanesthetized rats with a chronically ligated femoral artery ("ligated" rats), we hypothesized that hindlimb arterial injection of the COX inhibitor indomethacin would reduce the pressor response during 1-Hz dynamic hindlimb skeletal muscle stretch; a model of the activation of the mechanical component of the exercise pressor reflex (i.e., the mechanoreflex). In ligated rats (n = 7), indomethacin reduced the pressor response during stretch (control: 30 ± 4; indomethacin: 12 ± 3 mmHg; P < 0.01), whereas there was no effect in rats with "freely perfused" femoral arteries (n = 6, control: 18 ± 5; indomethacin: 17 ± 5 mmHg; P = 0.87). In ligated rats (n = 4), systemic indomethacin injection had no effect on the pressor response during stretch. Femoral artery ligation had no effect on skeletal muscle COX protein expression or activity or concentration of the COX metabolite prostaglandin E2. Conversely, femoral artery ligation increased expression of the COX metabolite receptors endoperoxide 4 and thromboxane A2-R in dorsal root ganglia tissue. We conclude that, in ligated rats, the COX pathway sensitizes the peripheral endings of mechanoreflex afferents, which occurs principally as a result of increased expression of COX metabolite receptors.NEW & NOTEWORTHY We demonstrate that the mechanoreflex is sensitized by the cyclooxygenase (COX) pathway within hindlimb skeletal muscles in the rat chronic femoral artery ligation model of simulated peripheral artery disease (PAD). The mechanism of sensitization appears attributable to increased receptors for COX metabolites on sensory neurons and not increased concentration of COX metabolites. Our data may carry important clinical implications for patients with PAD who demonstrate exaggerated increases in blood pressure during exercise compared with healthy counterparts.

Analysis of Skeletal Muscle Torque Capacity and Circulating Ceramides in Patients with Advanced Heart Failure

BackgroundHeart failure (HF)-related exercise intolerance is thought to be perpetuated by peripheral skeletal muscle functional, structural, and metabolic abnormalities. We analyzed specific dynamics of muscle contraction in patients with HF compared with healthy, sedentary controls. MethodsIsometric and isokinetic muscle parameters were measured in the dominant upper and lower limbs of 45 HF patients and 15 healthy age-matched controls. Measurements included peak torque normalized to body weight, work normalized to body weight, power, time to peak torque, and acceleration and deceleration to maximum strength times. Body morphometry (dual energy X-ray absorptiometry scan) and circulating fatty acids and ceramides (lipodomics) were analyzed in a subset of subjects (18 HF and 9 controls). ResultsExtension and flexion time-to-peak torque was longer in the lower limbs of HF patients. Furthermore, acceleration and deceleration times in the lower limbs were also prolonged in HF subjects. HF subjects had increased adiposity and decreased lean muscle mass compared with controls. Decreased circulating unsaturated fatty acids and increased ceramides were found in subjects with HF. ConclusionsDelayed torque development suggests skeletal muscle impairments that may reflect abnormal neuromuscular functional coupling. These impairments may be further compounded by increased adiposity and inflammation associated with increased ceramides.

초음파 영상을 통한 뇌졸중 환자의 외측복부근 근수축의 비대칭성 연구

Purpose : This study aimed to identify the asymmetry observed in the rehabilitative ultrasound imaging of lateral abdominal muscle thickness and performance between the affected and unaffected side during the abdominal drawing-in maneuver (ADIM), an exercise used to facilitate activation of selectively TrA to stabilize the trunk prior to limb movement. Methods : The Participants were twenty one patients with post-stroke hemiplegia in this study. Ultrasound imaging was used to measure amount of changes in thickness of the external oblique (EO), internal oblique (IO), transversus abdominis (TrA). A Paired t-test was used to compare relaxed muscle thickness to contracted muscle thickness of all 3 muscles between the affected and unaffected sides. Results : The outcome measures included side to side differences of absolute thickness, contraction ratio among the lateral abdominal muscles. There was no significantly difference in between the affected and unaffected side at rest. But, there was a significantly difference in absolute muscle thickness between the affected and unaffected side of only TrA muscle. Also contraction ratio was a significantly difference between the affected and unaffected TrA muscle. Conclusion : These findings support the asymmetrical activation of TrA muscle during abdominal muscle contraction in patients with post-stroke hemiplegia. Further studies are warranted for confirming this outcome.

Cardiovascular Responses to Static Muscle Contraction in Patients with Brachial Plexus Injury Treated with Intercostal Nerve Transfer

Pressor response is carried in afferent fibers of somatic nerves to increase blood pressure (BP) and heart rate (HR) during static exercise in humans. However, there is no information that peripheral responses restore muscle contraction with nerve transfer operation. In this study, we aimed to assess isometric exercise-induced pressor responses in patients with brachial plexus injury (BPI) after intercostal nerve transfer (ICNT) to restore elbow flexor muscles. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and HR during 2-min sustained isometric muscle contraction of elbow flexors at 20% and 35% of maximal voluntary contraction (MVC) on the unaffected side and the ICNT side, were measured in seven subjects with BPI treated with ICNT. SBP, DBP, and HR during 2-min sustained isometric muscle contraction of elbow flexors at 20% of MVC on the unaffected side were similar to those recorded before and after the exercise. However, the same variables increased significantly (p<0.001) during a similar type of exercise at 35% MVC on the unaffected side. On the ICNT side, no significant differences were noted in elbow flexors at 20% and 35% MVC. Isometric static exercise at 35% of MVC did not induce pressor and HR changes on the ICNT side. The difference in the responses between the two sides could have been caused by incomplete recovery of afferent nerve function following nerve repair, despite the restoration of efferent nerve function. Alternatively, the HR and BP responses to static contraction may depend upon the active muscle mass.

T1880 Esophageal Emptying and Longitudinal Muscle Contraction in Patients With Achalasia as Defined by High Resolution Manometry, High Frequency Ultrasound (Hfus) and Impedance

T1880 Esophageal Emptying and Longitudinal Muscle Contraction in Patients With Achalasia as Defined by High Resolution Manometry, High Frequency Ultrasound (Hfus) and Impedance

Comparison between gentamycin and exon skipping treatments to restore ryanodine receptor subtype 2 functions in mdx mouse duodenum myocytes

In Duchenne muscular dystrophy, a stop-codon mutation in the dystrophin gene induces an impairment of skeletal and smooth muscles contraction. In duodenum from mdx mouse, the disease model, the decrease of contractility was linked with the decrease of calcium signals encoded by ryanodine receptor subtype 2. Aminoglycoside and antisense oligonucleotide strategies were investigated to restore calcium signalling in the mdx mouse. Mdx mice were treated by intraperitoneal injection of gentamycin or 2-O-methyl antisense ribonucleotide directed against exon 23 of dystrophin for 2 weeks. The efficiency of both therapeutic strategies was determined by the level of dystrophin protein expression. The physiological effects of both treatments on ryanodine receptor expression and function were followed by RT-PCR, western blot and calcium measurements. Fourteen days after injection of gentamycin or anti-dystrophin antisense, the expression of dystrophin was recovered in skeletal muscle from treated mdx mice. In duodenum cells, RT-PCR and western blot indicated that the expression of ryanodine receptor subtype 2 was similar in treated mice than in control mice in association with the recovery of caffeine-induced Ca 2+ response. No significant difference was observed in the ryanodine subtype 3-dependent spontaneous Ca 2+ oscillations in untreated and treated mice. Conclusions — these results may help to explain the efficiency of aminoglycoside and anti-dystrophin antisense treatments in smooth muscle. Both treatments could be an interesting therapeutic option to restore smooth muscle contraction in patients with Duchenne muscular dystrophy.

Post-exercise facilitation and depression of motor evoked potentials to transcranial magnetic stimulation: a study in multiple sclerosis

Objective: To evaluate motor cortex excitability changes by transcranial magnetic stimulation (TMS) following repetitive muscle contractions in patients with multiple sclerosis (MS); to state whether a typical pattern of post-exercise motor evoked potentials (MEPs) is related to clinical fatigue in MS. Methods: In 41 patients with definite MS (32 with fatigue and 9 without fatigue according to Fatigue Severity Scale) and 13 controls, MEPs were recorded at rest: at baseline condition, following repetitive contractions until fatigue, and after fatigue, to evaluate post-exercise MEP facilitation (PEF) and depression (PED). Results: After exercise, MEP amplitude significantly increased both in patients and controls (PEF). When fatigue set in, MEP amplitude was significantly reduced in normal subjects (PED), but not in patients. Post-exercise MEP findings were similar both in patients with and without fatigue. Conclusions: Our findings suggest an intracortical motor dysfunction following a voluntary contraction in MS patients, possibly due to failure of depression of facilitatory cortical circuits, or alternatively of inhibitory mechanisms.

Esophageal striated muscle contractions in patients with Chagas' disease and idiopathic achalasia.

Chagas' disease causes degeneration and reduction of the number of intrinsic neurons of the esophageal myenteric plexus, with consequent absent or partial lower esophageal sphincter relaxation and loss of peristalsis in the esophageal body. The impairment of esophageal motility is seen mainly in the distal smooth muscle region. There is no study about esophageal striated muscle contractions in the disease. In 81 patients with heartburn (44 with esophagitis) taken as controls, 51 patients with Chagas' disease (21 with esophageal dilatation) and 18 patients with idiopathic achalasia (11 with esophageal dilatation) we studied the amplitude, duration and area under the curve of esophageal proximal contractions. Using the manometric method and a continuous perfusion system we measured the esophageal striated muscle contractions 2 to 3 cm below the upper esophageal sphincter after swallows of a 5-ml bolus of water. There was no significant difference in striated muscle contractions between patients with heartburn and esophagitis and patients with heartburn without esophagitis. There was also no significant difference between patients with heartburn younger or older than 50 years or between men and women or in esophageal striated muscle contractions between patients with heartburn and Chagas' disease. The esophageal proximal amplitude of contractions was lower in patients with idiopathic achalasia than in patients with heartburn. In patients with Chagas' disease there was no significant difference between patients with esophageal dilatation and patients with normal esophageal diameter. Esophageal striated muscle contractions in patients with Chagas' disease have the same amplitude and duration as seen in patients with heartburn. Patients with idiopathic achalasia have a lower amplitude of contraction than patients with heartburn.

Esophageal striated muscle contractions in patients with gastroesophageal reflux symptoms.

Although there are studies showing that the amplitude of contraction in the distal esophageal body may be lower in gastroesophageal reflux (GER) disease than in asymptomatic subjects, there are no data about proximal striated muscle contraction in this disease. We studied the esophageal contraction 2 or 3 cm below the upper esophageal sphincter in response to swallowing a 5-ml bolus of water in 122 consecutive patients submitted to esophageal manometry who complained of heartburn and acid regurgitation. Sixty-nine had esophagitis seen at endoscopy. Thirty-three also complained of dysphagia. No patients had esophageal stenosis, esophageal motility abnormalities in distal esophagus, chest pain, or extraesophageal manifestations of GER. We also studied 20 patients with systemic sclerosis (SSc), a disease with no involvement of striated muscle. When we measured the amplitude, duration, and area under the curve (AUC) of the proximal esophageal contraction, we did not find any differences (P > 0.05) between patients with esophagitis (N = 69) or without esophagitis (N = 53), with dysphagia (N = 33) or without dysphagia (N = 89), with mild (N = 55) or severe (N = 14) esophagitis, or younger than 40 years (N = 45) or older than 60 years (N = 19). There was also no difference between patients with GER symptoms and patients with SSc (P > 0.05). We conclude that patients with GER symptoms with or without esophagitis and with or without dysphagia have similar esophageal striated muscle contractions.

A Decreased Ability to Relax Between Repetitive Muscle Contractions in Patients with Chronic Symptoms After Whiplash Trauma of the Neck

Objectives: The aim was to investigate if patients with common chronic symptoms after whiplash trauma had an inability to relax certain neck and shoulder muscles in pauses between repetitive shoulder forward flexions.Methods: The control group [27 clinically healthy females] and the patient group [22 female patients with chronic symptoms after whiplash trauma] performed maximum isokinetic shoulder flexions [100 contractions scheduled]. Surface-electromyography [EMG] was obtained from four neck/shoulder muscles. Peak torque and the signal amplitude ratio [SAR] of each contraction were determined. The SAR was calculated as the ratio [%] between root mean square [RMS] of the EMG of the passive extension and the RMS of the active flexion. The subjects rated their perceived fatigue of the shoulder flexors throughout the test.Results: The majority of the patient group was not able to perform the number of contractions scheduled. Significantly higher SAR of trapezius two portions and infraspinatus for the patien...

Studies on maximal voluntary muscle contraction in patients with fibromyalgia.

In view of clinical experience of a low-force output in testing situations in patients with fibromyalgia syndrome (FS), this study evaluated the possibility of reaching a higher muscular performance by use of superimposed electrical stimulation: the tests mainly involved knee-extension in a Kin Com dynamometer. Twenty-five patients fulfilling the criteria of FS were compared with 22 healthy subjects. The patients showed a markedly reduced maximal voluntary contraction, but superimposed electrical stimulation revealed submaximal values. The electromyographic activity during stool climbing exceeded that recorded during maximum voluntary contraction during the dynamometric test. The cause of the reduced voluntary maximal performance is discussed. An impaired control mechanism at a supraspinal level is suggested. This has to be considered when measuring muscle strength in FS patients. Tests related to functional activities are recommended as measures of muscular performance in this patient group.