Menstrual cycle effects on sympathetic neural burst amplitude distribution during orthostasis in young women

Purpose

Fluctuations in ovarian hormones during the menstrual cycle impact muscle sympathetic nerve activity burst frequency and burst incidence at rest. The purpose of this study was to investigate menstrual cycle effects on sympathetic neural burst amplitude distribution during an orthostatic challenge in young women.

Methods

This study included 11 healthy women (33 ± 10 years [mean ± standard deviation]). Muscle sympathetic nerve activity was measured in the supine position as baseline measurement and during 5 min of 60° upright tilting, during the early follicular phase (low estrogen and progesterone) and mid-luteal phase (high estrogen and progesterone) of the menstrual cycle. Relative burst amplitude distribution of muscle sympathetic nerve activity was characterized by the mean, median, skewness, and kurtosis.

Results

From the supine to upright position, mean and median values of relative burst amplitude increased (both P?<?0.05), regardless of phases of the menstrual cycle (P = 0.5 and P = 0.7, respectively). In comparison, during the early follicular phase, skewness and kurtosis remained unchanged (P = ?0.6 and P = ? 0.3, respectively) and kurtosis decreased (1.25?±?1.11 supine vs. ? 0.03?±?0.73 upright; P?=?0.02); there was no change in skewness during the mid-luteal phase (P?=?0.4).

Conclusions

In response to orthostasis, while the symmetry and tailedness/peakness of burst amplitude distribution do not change during the early follicular phase, the distribution during the mid-luteal phase becomes flatter with a lower but broader peak. The latter result suggests that the firing probability of large axon action potentials in response to orthostatic challenge is higher when estrogen and progesterone levels are elevated. The role of changes in sympathetic neural burst amplitude distribution in orthostatic tolerance remains to be determined.

     

Resistance training and aerobic training improve muscle strength and aerobic capacity in chronic inflammatory demyelinating polyneuropathy

Introduction: We investigated the effects of aerobic and resistance exercise in patients with chronic inflammatory demyelinating polyneuropathy (CIDP). Methods: Eighteen CIDP patients treated with subcutaneous immunoglobulin performed 12 weeks of aerobic exercise and 12 weeks of resistance exercise after a run‐in period of 12 weeks without exercise. Three times weekly the participants performed aerobic exercise on an ergometer bike or resistance exercise with unilateral training of knee and elbow flexion/extension. Primary outcomes were maximal oxygen consumption velocity (VO₂‐max) and maximal combined isokinetic muscle strength (cIKS) of knee and elbow flexion/extension. Results: VO₂‐max and muscle strength were unchanged during run‐in (?4.9% ± 10.3%, P = 0.80 and ?3.7% ± 10.1%, P = 0.17, respectively). Aerobic exercise increased VO₂‐max by 11.0% ± 14.7% (P = 0.02). Resistance exercise resulted in an increase of 13.8% ± 16.0% (P = 0.0004) in cIKS. Discussion: Aerobic exercise training and resistance exercise training improve fitness and strength in CIDP patients. Muscle Nerve 57 : 70–76, 2018     

Electrical and mechanical properties of skeletal muscle underlying increased fatigue in patients with amyotrophic lateral sclerosis

To investigate the mechanical efficiency of surviving motor units of anterior tibial muscle in patients with amyotrophic lateral sclerosis (ALS), we studied motor unit action potentials, muscle force, and muscle fatigability in patients with ALS and controls using 25 min of low to moderate intensity voluntary isometric exercise. During exercise, tetanic force (TF) and maximum voluntary contraction declined more in patients than in controls. The mean motor unit action potential duration, amplitude, and polyphasia were increased in patients compared to controls but did not change during 9 months of disease progression. The enlarged motor units in patients were negatively correlated to the muscle force and positively correlated to muscle fatigability. Furthermore, after a mean follow-up period of 9 months, the decline in force-generating capacity of the anterior tibial muscle in patients (twitch tension by 37.5 ± 11.2%, TF by 30.6 ± 7.4%) was greater than the decline in the amplitude of the compound muscle action potential (21.1 ± 8.8%, P < 0.05), suggesting a relative dissociation between electrical and mechanical properties. In conclusion, the enlarged motor units in patients with ALS are mechanically less efficient and fatigue relatively more than in healthy muscles, possibly due to an abnormality that is primarily distal to the muscle membrane. © 1996 John Wiley & Sons, Inc.     

Effect of dimenhydrinate on autonomic activity in humans

The purpose of this study was to examine the effect of dimenhydrinate on resting muscle sympathetic nerve activity (MSNA), the vestibulosympathetic reflex, and the baroreflexes. Sixteen subjects participated in two double-blinded studies that measured mean arterial pressure (MAP), heart rate (HR), and MSNA responses before and after oral administration of dimenhydrinate (100 mg) or a placebo. In study one, 3 min of head-down rotation (HDR) was performed to engage the otolith organs. Dimenhydrinate (n = 10) did not alter resting MSNA, MAP, or HR. HDR increased MSNA before (Δ5 ± 1 bursts/min; P < 0.01) and after (Δ4 ± 1 bursts/min; P < 0.01) drug administration, but these responses were not different from the placebo (n = 6). In study two, 4 min of lower body negative pressure (LBNP) at −30 mmHg was performed. During the third min of LBNP, HDR was performed. MSNA increased during the first 2 min of LBNP before (Δ13 ± 2 bursts/min; P < 0.01) and after (Δ14 ± 2 bursts/min; P < 0.01) dimenhydrinate. HDR combined with LBNP increased MSNA further during the third min of LBNP (Δ18 ± 2 bursts/min before and Δ17 ± 2 bursts/min after dimenhydrinate; P < 0.01). These responses were not significantly different from the placebo. In contrast, HR responses to LBNP during the dimenhydrinate trial were increased when compared to all other trials (Δ5 ± 1 beats/min; P < 0.01). These results indicate that dimenhydrinate augments heart rate responses to baroreceptor unloading, but does not alter resting MSNA, the sympathetic baroreflexes, or the vestibulosympathetic reflex.     

Impairment of muscle mitochondrial oxidative metabolism in McArdle's disease

Impairment of muscle glycogenolysis in McArdle's disease (myophosphorylase deficiency) leads to exercise intolerance and exercise-induced myalgia. The pathophysiology of these symptoms is not entirely clear. We used phosphorus magnetic resonance spectroscopy to measure muscle phosphate metabolite concentrations and intracellular pH during brief ischemic exercise and in the period of aerobic metabolic recovery after exercise, with special attention to cytoplasmic adenosine 5′-diphosphate (ADP). In 5 patients with McArdle's disease, calculated muscle intracellular ADP concentrations at the beginning of recovery were higher than in normal control subjects (70–425 mmol/L, control mean: 73 ± 40 mmol/L, P < 0.05). The half-time for intracellular ADP recovery after exercise, an index of maximal mitochondrial oxidative phosphorylation, was 0.16 ± 0.07 in normal controls and was independent of metabolic state or intracellular pH. ADP recoveries were abnormally slow in all patients with McArdle's disease (range: 0.32–0.83 min, mean = 0.2 min, P < 0.0001). These results are indicative of a limitation in the rate of oxidative phosphorylation in muscle of patients with McArdle's disease, most likely due to impaired substrate delivery to mitochondria. This impairment of mitochondrial function may contribute to the exercise-related symptoms in McArdle's disease. © 1996 John Wiley & Sons, Inc.     

Autonomic control of the heart and renal vascular bed during autonomic dysreflexia in high spinal cord injury

Autonomic function and hemodynamics were studied in nine spinal cord injured (SCI) subjects, at rest and during peripheral afferent stimulation, bladder percussion. Nine able-bodied subjects were studied for comparison during unstimulated conditions. Spontaneous baroreceptor reflex sensitivity was calculated from recordings of ECG and intraarterial blood pressure. An index of sympathetic activity was provided by measuring total body noradrenaline (NA) spillover by isotope dilution technique. Renal vascular resistance was calculated from PAH-clearance. SCI subjects had lower total body NA spillover (1011 ± 193 vs 2261 ± 328 pmol/min, P < 0.01), but similar baroreceptor reflex sensitivity and hemodynamics compared to able-bodied subjects at rest. In SCI group, during bladder percussion, mean arterial pressure increased (79 ± 5 vs 113 ± 8 mm Hg, P < 0.01), whereas heart rate was reduced during the first minute of the manoeuvre (62 ± 2 vs 56 ± 2 bpm, P < 0.05). Baroreceptor reflex sensitivity remained unchanged. Total body NA spillover and renal vascular resistance increased by 332 % (from 1004 ± 218 pmol/min, P < 0.05) and 55 % (from 0.078 ± 0.011 mmHg/ml/min, P < 0.05), respectively. SCI subjects demonstrated lower total body sympathetic outflow but normal baroreceptor reflex sensitivity at rest, suggesting a balanced autonomic output to the heart. Bladder percussion caused a substantial increase in renal vascular resistance and blood pressure, which was partly due to marked generalised sympathetic activation. This activation was counterbalanced by an increased vagal activity as evidenced by reduction of the heart rate. Received: 6 March 2002, Accepted: 28 August 2002 Correspondence to Sinsia A. Gao, MD     

Global and regional brain mean diffusivity changes in patients with heart failure

Heart failure (HF) patients show gray and white matter changes in multiple brain sites, including autonomic and motor coordination areas. It is unclear whether the changes represent acute or chronic tissue pathology, a distinction necessary for understanding pathological processes that can be resolved with diffusion tensor imaging (DTI)‐based mean diffusivity (MD) procedures. We collected four DTI series from 16 HF (age 55.1 ± 7.8 years, 12 male) and 26 control (49.7 ± 10.8 years, 17 male) subjects with a 3.0‐Tesla magnetic resonance imaging scanner. MD maps were realigned, averaged, normalized, and smoothed. Global and regional MD values from autonomic and motor coordination sites were calculated by using normalized MD maps and brain masks; group MD values and whole‐brain smoothed MD maps were compared by analysis of covariance (covariates; age and gender). Global brain MD (HF vs. controls, units × 10⁻⁶ mm²/sec, 1103.8 ± 76.6 vs. 1035.9 ± 69.4, P = 0.038) and regional autonomic and motor control site values (left insula, 1,085.4 ± 95.7 vs. 975.7 ± 65.4, P = 0.001; right insula, 1,050.2 ± 100.6 vs. 965.7 ± 58.4, P = 0.004; left hypothalamus, 1,419.6 ± 165.2 vs. 1,234.9 ± 136.3, P = 0.002; right hypothalamus, 1,446.5 ± 178.8 vs. 1,273.3 ± 136.9, P = 0.004; left cerebellar cortex, 889.1 ± 81.9 vs. 796.6 ± 46.8, P < 0.001; right cerebellar cortex, 797.8 ± 50.8 vs. 750.3 ± 27.5, P = 0.001; cerebellar deep nuclei, 1,236.1 ± 193.8 vs. 1,071.7 ± 107.1, P = 0.002) were significantly higher in HF vs. control subjects, indicating chronic tissue changes. Whole‐brain comparisons showed increased MD values in HF subjects, including limbic, basal‐ganglia, thalamic, solitary tract nucleus, frontal, and cerebellar regions. Brain injury occurs in autonomic and motor control areas, which may contribute to deficient function in HF patients. The chronic tissue changes likely result from processes that develop over a prolonged period. © 2014 Wiley Periodicals, Inc.     

Subthalamic nucleus stimulation restores corticospinal facilitation in Parkinson's disease

We have previously shown that in patients with Parkinson's disease (PD), high‐frequency stimulation (HFS) of the subthalamic nucleus (STN) modifies spinal excitability via subcortical reticulospinal routes. To investigate whether STN‐HFS also modifies spinal excitability via transcortical routes in PD, 10 patients with PD (9 men, 1 woman; 58.3 ± 8.3 years) were investigated in the medical OFF‐state with or without STN‐HFS. The H‐reflex of the right soleus muscle was recorded during slight plantar flexion at 20% of maximum force. A conditioning transcranial stimulus was applied at 95% of active motor threshold to the contralateral primary motor leg area (M1) 0–5 ms after eliciting the H‐reflex. The same paradigm was applied to 8 healthy individuals (5 men, 3 women; 50.8 ± 3.0 years). Transcranial magnetic stimulation (TMS) facilitated the H‐reflex amplitude in healthy controls. A facilitatory effect of the corticospinal input on the H‐reflex was also found in patients with PD, but only with STN‐HFS switched on. When STN‐HFS was discontinued, the H‐reflex was no longer facilitated by the TMS pulse. Accordingly, analysis of variance showed a main effect of stimulation (F = 11.15; P = 0.005), ISI (F = 6.1; P = 0.003), and an interaction between stimulation and group (PD vs. control) (F = 8.9; P = 0.01). STN‐HFS restores the normal facilitatory drive of a transcranially evoked motor cortical response to the spinal motoneuron pool. In addition to subcortical routes, STN‐DBS also alters spinal excitability via transcortical pathways. © 2008 Movement Disorder Society.     

Effect of pulmonary vein isolation on the relationship between left atrial reverse remodeling and sympathetic nerve activity in patients with atrial fibrillation

Purpose

Catheter ablation (CA) to isolate the pulmonary vein, which is an established treatment for atrial fibrillation (AF), is associated with left atrium reverse remodeling (LARR). The intrinsic cardiac autonomic nervous system includes the ganglion plexi adjacent to the pulmonary vein in the left atrium (LA). However, little is known about the effect of CA on the relationship between LARR and sympathetic nerve activity in patients with AF.

Methods

This study enrolled 22 AF patients with a normal left ventricular ejection fraction (LVEF) aged 64.6?±?12.9 years who were scheduled for CA. Sympathetic nerve activity was evaluated by direct recording of muscle sympathetic nerve activity (MSNA) before and 12 weeks after CA. Blood pressure, heart rate (HR), HR variability, and echocardiography were also measured.

Results

The heart rate increased significantly after CA (63?±?10.9 vs. 70.6?±?7.7 beats/min, p?<?0.01), but blood pressure did not change. A high frequency (HF) and low frequency (LF) of HR variability decreased significantly after ablation, but no significant change in LF/HF was observed. CA significantly decreased MSNA (38.9?±?9.9 vs. 28?±?9.1 bursts/min, p?<?0.01). Moreover, regression analysis revealed a positive correlation between the percentage change in MSNA and the LA volume index (r?=?0.442, p?<?0.05).

Conclusions

Our results show that CA for AF reduced MSNA and the decrease was associated with the LA volume index in AF patients with a normal LVEF. These findings suggest that LARR induced by CA for AF decrease sympathetic nerve activity.

     

Autonomic function in patients with chronic fatigue syndrome

Subtle signs of autonomic dysfunction and orthostatic intolerance have been reported in patients with chronic fatigue syndrome (CFS). To assess cardiovascular autonomic function noninvasively in an unselected group of patients with CFS, we examined responsiveness to several cardiovascular reflex tests in 37 CFS patients and 38 healthy control subjects. Blood pressure and heart rate (HR) were recorded continuously by a Finapres device before and during forced breathing, standing up, Valsalva maneuver, and sustained handgrip exercise (HG). In addition, a mental arithmetic test was carried out and questionnaires to assess the severity of CFS symptoms were completed. At rest, there were no significant differences in blood pressure or in HR between the two groups. The in- and expiratory difference in HR tended to be lower in CFS patients (28.4±10.5 beats) than in healthy controls (32.2±9.5) (p=0.11). The maximal increase in HR during standing up was not significantly different between the CFS group (37.6±8.9 beats) and the control group (40.2±8.9 beats). There were no significant differences between both groups with regard to the Valsalva ratio, but the systolic and diastolic blood pressure responses were significantly larger in CFS patients, despite the fact that many CFS patients were not able to sustain the Valsalva maneuver. The HR response to MA was significantly less in the CFS group (22.6±9.9) than in the control group (29.5±16.7) (p<0.05), suggesting impaired cardiac sympathetic responsiveness to mental stress. The lower HR responses could not be explained by the level of concentration in the CFS group. During HG exercise, the hemodynamic responses were lower in the CFS group than in the control group, but this might be attributed to the lower level of muscle exertion in CFS patients. There were no significant differences between CFS patients with and without symptoms of autonomic dysfunction regarding the hemodynamic responses to the cardiovascular reflex tests. The findings of the study suggest that there are no gross alterations in cardiovascular autonomic function in patients with CFS.     

Subtle involvement of the parasympathetic nervous system in patients with irritable bowel syndrome

Abstract This study comprises assessment of autonomic function in irritable bowel syndrome (IBS) patients, focusing on meal-related changes. In 18 IBS patients (4 males, mean age 45±3.0 [SEM] years) and 19 healthy volunteers (6 males, mean age 41±3.5 years) blood pressure, heart rate, heart rate variability and muscle sympathetic nerve activity (MSNA) were assessed before, during and after consumption of a standardized meal. In pre- and postprandial phase Valsalva maneuver, cold pressor test (CPT) and deep breathing test were carried out and Visual Analog Scale (VAS) scores for nausea, bloating and pain were obtained. In the IBS group, the meal induced significantly higher VAS scores for pain (P=0.002) and bloating (P=0.02). During food intake, the increase in blood pressure, heart rate and MSNA was equal in patients and controls, but the increase of LF/HF ratio of heart rate variability was significantly higher in the IBS group (median [quartiles] 2.29 [1.14–3.00] versus 0.77 [0.25–1.81]; P=0.03). IBS patients scored lower on pre- and postprandial RRmax/RRmin ratio during deep breathing (DB ratio, P=0.03). The increase in MSNA (burst frequency) in response to CPT tended to be higher in the IBS patients (P=0.07). We conclude that reactivity to food intake, measured as muscle sympathetic nerve activity, is normal in IBS patients. The lower DB ratio and higher LF/HF ratio during food intake in IBS patients is an indication of a reduced parasympathetic reactivity. These results suggest that reduced baseline activity as well as responsiveness of the parasympathetic system could play a role in the pathogenesis of IBS.     

Subclinical pulmonary dysfunction in spinocerebellar ataxias 1, 2 and 3

Sriranjini SJ, Pal PK, Krishna N, Sathyaprabha TN. Subclinical pulmonary dysfunction in spinocerebellar ataxias 1, 2 and 3. Acta Neurol Scand: 2010: 122: 323–328. © 2009 The Authors Journal compilation © 2009 Blackwell Munksgaard. Objectives – Evaluation of pulmonary function in patients with spinocerebellar ataxias (SCA) 1, 2 and 3 without clinical evidence of pulmonary dysfunction. Methods – Thirty patients (F:M = 7:23; age: 35 ± 11.3 years; SCA1 – 13, SCA2 – 9 and SCA3 – 8) without clinical manifestations of respiratory dysfunction and 30 controls underwent pulmonary function tests. The percentage predicted values of forced vital capacity (FVC), volume of air exhaled during first second of FVC (FEV1), peak expiratory flow rate (PEFR) and maximal voluntary ventilation (MVV), actual values of maximal inspiratory and expiratory pressures (MIP and MEP in mmHg), and ratios of actual values of FEV1/FVC (%) and FEV1/PEFR (ml/l/min) were analyzed. Results – Compared with controls SCA patients had significant reductions of FVC (71.1 ± 17.5 vs 85.5 ± 18.7; P < 0.01), PEFR (51.5 ± 20.7 vs 77.1 ± 24.9; P < 0.001), MVV (64.4 ± 21.6 vs 97.2 ± 22.7; P < 0.001), MIP (27.7 ± 16.8 vs 50.1 ± 15.1; P < 0.001) and MEP (38.1 ± 18.7 vs 74.7 ± 16.0; P < 0.001), elevation of FEV1/PEFR (10.5 ± 2.8 vs 7.4 ± 2.1; P < 0.001), but no significant change of FEV1 and FEV1/FVC. FEV1/PEFR correlated positively with illness duration and MVV negatively with severity of illness. Conclusions – The present study showed subclinical restrictive type of pulmonary dysfunction in SCA, and possible presence of upper airway obstruction. Chest physiotherapy and breathing exercises should be introduced early in management of SCA.     

The effect of intraduodenal glucose on muscle sympathetic nerve activity in healthy young and older subjects

Objective The cardiovascular response to a meal is modulated by gastric distension and the interaction of nutrients, particularly carbohydrate, within the small intestine. We tested the hypothesis that the depressor effect of small intestinal glucose is greater in older than in young subjects, because the reflex increase in muscle sympathetic nerve activity (MSNA) is blunted by age. Methods The effects of intraduodenal glucose infusion (IDGI) on blood pressure, heart rate and MSNA were evaluated in eight healthy young subjects (4 women; mean age ± SEM: 28.8 ± 3.4 years), eight healthy elderly (4 women; 75.3 ± 1.6 years) and in two patients with symptomatic postprandial hypotension (PPH), one young (21 years), and one old (90 years). Results In both young and elderly healthy subjects, IDGI decreased blood pressure (P < 0.05), but the fall in systolic blood pressure was greater in the older subjects (−17.0 ± 4.1 vs. −6.5 ± 1.6 mmHg, P < 0.03). MSNA increased similarly, after infusion in both young (9.0 ± 3.4 bursts/min) and elderly (7.8 ± 1.0 bursts/min) subjects. Baroreflex sensitivity for number of sympathetic bursts was attenuated in the elderly (P < 0.03). The increase in burst area in the young patient with PPH was attenuated (18 vs. 63% in the healthy young group). Interpretation The fall in BP induced by IDGI was greater in healthy elderly compared to healthy young subjects. The reason for this is unclear, as they have similar increases in MSNA.     

Cardiac stress test is normal in pre‐motor Parkinson's disease

Cardiac sympathetic denervation is an early nonmotor feature of Parkinson's disease (PD). The aim of the current study was to trace evidence for cardiac dysfunction abnormalities in the premotor phase of PD. We retrospectively reviewed treadmill ergometric tests of a large cohort (n = 16,841) between 2000 and 2012, that attended the Executive Screening Survey (ESS) at Sheba Medical Center. Heart rate and blood pressure profiles as well as exercise capacity were compared between subjects who later developed PD and age‐ and sex‐matched subjects (ratio 1:2) who did not. We identified 28 subjects (24 males) who developed PD at follow‐up. The PD group was older than the group of subjects who did not develop PD on first ergometric test (64.82 ± 8.82 vs. 48.91 ± 10.60 years, P < 0.001). The time between the first ergometric test and motor symptoms onset was 4.64 ± 2.86 years. Patients who later developed PD had lower maximal heart rate (P < 0.001) and lower heart rate reserve than healthy controls (P < 0.001); however, compared with age‐ and sex‐matched subjects, subjects who developed PD had similar exercise capacity and heart rate profile during rest, exercise, and recovery, even 1 year before diagnosis. In this study, we did not detect significant signs of sympathetic dysfunction during the premotor phase of PD. © 2014 International Parkinson and Movement Disorder Society     

Cardiovascular autonomic dysfunction in multiple sclerosis: correlation with orthostatic intolerance

Autonomic dysfunction is frequently observed in patients with multiple sclerosis (MS), but clinical studies disagree on the frequency and type of abnormalities in autonomic function tests. Orthostatic dizziness (OD) has been reported in up to 49% of patients, but the pathophysiological mechanisms are poorly understood. This study investigated cardiovascular reflex tests and their association with OD in patients with MS in order to examine the hypothesis that the sympathetic nervous system is specifically involved in these patients. Forty patients with clinically active relapsing-remitting (n = 27) and secondary progressive MS (n = 13), aged 35.0 ± 8.5 years, were studied by parasympathetic (heart rate responses to the Valsalva maneuver, deep breathing, and active change in posture) and sympathetic function tests (blood pressure responses to active change in posture and sustained handgrip), and by spectral analysis of heart rate variability during rest and during standing. Results were compared to those obtained in 24 healthy volunteers, aged 29.4 ± 7.2 years. A standardized questionnaire was used to evaluate symptoms of orthostatic intolerance. Abnormal responses on at least one cardiovascular reflex test were observed in 40% of MS patients, compared to 17% of the control group, with a statistically significant involvement of the sympathetic vasomotor system. Orthostatic intolerance was reported in 50% of patients (controls: 14%, P < 0.006). Subgroup comparison of patients with and without OD suggests that orthostatic intolerance results from impaired sympathetic vasoconstriction. These results provide further evidence that the sympathetic nervous system is involved in patients with MS. Received: 18 September 1998 Received in revised form: 28 December 1998 Accepted: 3 January 1999     

Postexercise phosphocreatine resynthesis is slowed in multiple sclerosis

To determine whether skeletal muscle oxidative metabolism is impaired in multiple sclerosis (MS), ³¹ phosphorus magnetic resonance spectroscopy was used to measure the rate of intramuscular phosphocreatine (PCr) resynthesis following exercise in MS and controls. Thirteen MS patients underwent intermittent isometric tetanic contractions of the dorsiflexor muscles elicited by stimulation of the peroneal nerve. Eight healthy control subjects performed voluntary isometric exercise of the same muscles. During exercise, there were no differences between groups in the fall of either PCr or pH. However, the half-time (T-_1/2) of PCr recovery following exercise was significantly longer in MS (2.3 ± 0.3 min) compared to controls (1.2 ± 0.1 min, P < 0.02). These data provide evidence of slowed PCr resynthesis following exercise in MS, which indicates impaired oxidative capacity in the skeletal muscle of this group. This finding suggests that intramuscular changes consistent with deconditioning may be important in the altered muscle function of persons with MS. © 1994 John Wiley & Sons, Inc.     

Increased severity of dyspeptic symptoms related to mental stress is associated with sympathetic hyperactivity and enhanced endocrine response in patients with postprandial distress syndrome

Background Mental stress (MS) may alter gastric sensory‐motor function. The aim of the study was to assess postprandial autonomic nervous system activity and stress hormones in response to acute mental stress in dyspeptic patients. Methods A total of 25 patients with postprandial distress syndrome (PDS; 11 mol L^?1, age 35.9 ± 9.3 years) and 12 healthy controls (5 mol L^?1, age 25.8 ± 4.6 years) underwent electrogastrography and ¹³C‐octanoate gastric emptying study using a 480 kcal solid meal. Heart rate variability (LF/HF ratio) and corticotrophin‐releasing factor, adrenocorticotropic hormone (ACTH), and cortisol serum levels were also evaluated. Dyspeptic symptoms were scored by analogue visual scale and expressed as symptoms total score (TS). The protocol was repeated twice in each subject, with and without a mental stress test before the meal. Key Results Mental stress significantly increased postprandial symptoms severity in patients (TS: stress 111 ± 18 vs basal 50 ± 10; P < 0.05). Low‐/high‐frequency component ratio was significantly higher in patients after MS at 120 min (stress 5.46 ± 0.41 vs basal 3.41 ± 0.64; P < 0.01) and 180 min (stress 5.29 ± 0.2 vs basal 3.58 ± 0.19; P < 0.05). During stress session, in patients we found a significantly higher ACTH level than baseline at 30, 60, 90, 150, 210, 240, and 270 min and a significantly higher cortisol level at 30, 60, 90, 120, 210, and 270 min. Gastric emptying rate and electrical activity were not influenced by MS. Conclusions & Inferences In PDS patients, administration of MS before meal increases symptoms severity by inducing sympathetic hyperactivity and increased stress hormones levels. As the gastric emptying looks not altered, we conclude that these neurohormonal responses mainly affect sensitive function.     

Low‐volume resistance exercise attenuates the decline in strength and muscle mass associated with immobilization

We determined the effectiveness of low‐volume resistance exercise (EX) for the attenuation of loss of muscle mass and strength during leg immobilization. Men (N = 5) and women (N = 12, age 24 ± 5 years, body mass index 25.4 ± 3.6 kg/m²) were divided into two groups: exercise (EX; n = 12) and control (CON; n = 5). Subjects wore a knee brace on one leg that prevented weight bearing for 14 days. Resistance exercise (EX; 80% of maximal) was performed by the immobilized limb every other day. Immobilization induced a significant reduction (P < 0.05) in muscle fiber and thigh cross‐sectional area (CSA), isometric knee extensor, and plantarflexor strength in the CON (P < 0.01) but not in the EX group. There were significant losses in triceps surae CSA in the CON and EX groups (P < 0.05), but the losses were greater in CON subjects (P < 0.01). A minimal volume (140 contractions in 14 days) of resistive exercise is an effective countermeasure against immobilization‐induced atrophy of the quadriceps femoris but is only partially effective for the triceps surae. Muscle Nerve, 2010     

Sympathetic hyperactivity in patients with ulcerative colitis

Hypo and hyperactivity of the autonomic nervous system have been associated with chronic bowel inflammation diseases. We investigated the autonomic function in 11 patients with chronic ulcerative colitis (UC) and 17 healthy controls by means of cardiovascular autonomic tests and heart rate variability. Autonomic responses were normal in patients and controls. At rest, LF/HF ratios were significantly (P < 0.05) higher in chronic UC patients (2.4 ± 1.6) compared to controls (1.2 ± 1.0). Our results suggest a higher sympathetic tone at rest in patients with chronic UC.     

Blunted heart rate response to vagal withdrawal in persons with tetraplegia

Cardiovascular autonomic mechanisms control heart rate (HR) and determination of heart rate variability (HRV) permits the quantitative assessment of relative shifts in autonomic cardiac control during head-up tilt (HUT). The study herein used HRV techniques to determine the vagal and sympathetic contribution to the change in HR during HUT in persons with tetraplegia (T; n = 7) paraplegia (P; n = 7) and a non-spinal cord injured (non-SCI; n = 8) control group. Heart rate (HR) was continuously monitored and cardiovascular autonomic responses were assessed for 5-minutes at supine and at 45° HUT. Change associated with tilt from supine to 45° HUT was calculated for HR (deltaHR), high & low frequency HRV (HF & LF) and the LF/HF ratio. HR and LF power were lower in the T compared to the P and non-SCI groups at 45° HUT, whereas there were no group differences for HF at 45° HUT. The LF/HF ratio was lower in the T compared to the non-SCI group at 45° HUT. The relationship between delta HR and delta HF response differed between groups (significant group × delta HF interaction) such that the slope of this relationship was reduced in the T (−1.026: 95% CI: −2.623 to 0.571) compared with the non-SCI (−6.985: 95% CI: −11.25 to 2.72) and P (−5.218: 95% CI: −8.197 to −2.239) groups. There was no significant interaction effect for the relationships between deltaHR and deltaLF or deltaLF/HF. In summary, although the magnitude of vagal withdrawal was comparable among the groups, the increase in HR was attenuated in the group with tetraplegia, which may reflect reduced sympathetic cardiac modulation or altered SA node responsiveness to vagal withdrawal.