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PubMed1996

Terminal maturation of resting B cells induced by macrophage factors.

Mouse splenic macrophages from BALB/c nude mice (purified by plastic adherence) or cloned macrophage hybridomas stimulated with jacalin (12.5 micrograms/ml), a D-Gal binding lectin, produce one or more B-cell stimulatory factors which cause splenic B cells from BALB/c or C3H/HeJ mice to secrete immunoglobulin in a polyclonal manner as detected by reverse protein A plaque assays. Jacalin-stimulated macrophage supernatants (JacSup) activate both normal and Percoll gradient-purified small high-density (resting) B cells. Supernatants from total or resting BALB/c spleen cells cultured for 7 days in the presence of JacSup (derived from splenic BALB/c nude mice macrophages) were assayed for immunoglobulin isotypes by ELISA. Resting B cells produce only IgG3 and IgM, whereas total B cells secrete IgG3 and IgM as well as IgG1, IgG2a, IgG2b and IgA. Resting and total B cells from BALB/c nude mice are also stimulated by macrophage supernatants to secrete immunoglobulin, thus indicating that this activity is likely to be T cell independent. Moreover, jacalin-stimulated macrophage supernatants did not induce spleen cells or purified B cells to proliferate. Fractionation of factor-rich supernatants on a Sephacryl S-200 column revealed that the factor activity is located in fractions corresponding to a molecular mass of 25-27 kDa. Taken together, these results suggest that upon the action of a macrophage factor(s) resting B cells undergo terminal differentiation without proliferation in the absence of T cells.

Animals↗
PubMed1996

Superficial sarcoplasmic reticulum calcium buffering of resting, voltage-dependent Ca++ influx in rat femoral arterial smooth muscle.

To determine the Ca(+2)-buffering function of sarcoplasmic reticulum (SR) in the resting state of arterial smooth muscle, the effects of cyclopiazonic acid (CPA) and thapsigargin, which inhibit the Ca(+20-ATPase of SR, on tension and cytosolic Ca+2 level ¿[Ca+2]¿ were examined in endothelium-denuded strips of rat femoral artery. In resting strips preloaded with fura-PE3, the addition of CPA (10 microM) or thapsigargin (100 nM) caused an elevation of [Ca+2]i and a contraction. These responses were inhibited by blockers of L-type voltage-dependent Ca+2 channels (verapamil, nifedipine and diltiazem). The inhibition by verapamil was much greater for contraction than for [Ca+2]i Verapamil itself decreased the resting [Ca+2]i without affecting the resting tone. In a Ca(+2)-free solution, CPA caused a small elevation of [Ca+2]i that was not accompanied by a contraction. In the presence of CPA or thapsigargin, the effects of caffeine (20 mM) on [Ca+2]i and tension were greatly inhibited. In strips where the SR Ca+2 was depleted by the addition of caffeine and a Ca(+2)-free solution, the Ca+2 influx from the extracellular space was completely taken up into the SR. This process was inhibited by CPA or thapsigargin, which resulted in a contraction. This contraction was also inhibited by verapamil. However, the basal Ca+2 influx measured by a 5-min incubation of the artery with 45Ca+2 was not increased by CPA or thapsigargin. The net Ca+2 entry measured in a 30-min incubation of the artery with 45Ca+2 was decreased by CPA or thapsigargin. The basal 45Ca+2 efflux from the artery was increased during the addition of CPA. These results suggested that the basal Ca+2 influx was completely buffered by Ca+2 uptake into the SR in the resting state of rat femoral artery and therefore the inhibition of SR Ca+2 uptake by CPA or thapsigargin caused an elevation of [Ca+2]i and a contraction. During this process, the basal Ca+2 influx via L-type voltage-dependent Ca+2 channels mainly contributed to the contraction. The present study also showed the existence of a relatively large compartment of cytosolic Ca+2 that does not contribute to contraction during the addition of CPA or thapsigargin.

Animals↗
PubMed1997

The cardiac effects of pimobendan (but not amrinone) are preserved at rest and during exercise in conscious dogs with pacing-induced heart failure.

We compared the effects of pimobendan (0.25 mg/kg i.v.), a Ca++ sensitizer, with some phosphodiesterase-III inhibition effects, and amrinone (1 mg/kg plus 10 microg/kg/min i.v.), a PDE-III inhibitor, on left ventricular (LV) systolic and diastolic performance, both at rest and during exercise, in seven conscious dogs before and after pacing-induced congestive heart failure (CHF). Before CHF, under resting conditions, both pimobendan and amrinone caused a similar significant decrease in left ventricle size and end-systolic pressure, arterial elastance, and the time constant of LV relaxation. Similar results were obtained during exercise. Both agents also produced a similar increase in E(ES), the slope of the LV end-systolic pressure-volume relation (3.4 +/- 1.5 vs. 4.2 +/- 1.1 mm Hg/ml; amrinone vs. pimobendan). After CHF, the vasodilatory effects of amrinone and pimobendan were preserved both at rest and during exercise; however, the inotropic actions were different. After CHF, pimobendan increased E(ES) (3.9 +/- 0.5 vs. 5.7 +/- 0.4 mm Hg/ml, P < .05), decreased the time constant of LV relaxation, increased the maximum rate of LV filling (37 +/- 19 ml/sec) (P < .05) and produced a downward shift of the early diastolic portion of LV pressure-volume loop. Pimobendan also augmented LV contractile performance during CHF exercise. In contrast, after CHF, amrinone no longer produced a positive inotropic effect. Amrinone improved LV relaxation and filling, both at rest and during exercise after CHF, but significantly less than pimobendan. We conclude that after CHF, the cardiac response to a PDE-III inhibitor is attenuated, but the response to Ca++ sensitizer is preserved. Thus, after CHF, pimobendan is more effective than amrinone in enhancing LV contractile state, LV relaxation and LV filling both at rest and during exercise.

Amrinone↗
PubMed1997

Partial activation of naive CD4 T cells and tolerance induction in response to peptide presented by resting B cells.

Tolerance is thought to occur when Ag is presented to T cells in the absence of costimulatory interactions from APC accessory molecules. Of the professional APC, the resting B cell may be the main tolerizing cell in vivo. We have analyzed several aspects of activation of naive transgenic CD4 cells stimulated with resting or activated B cells presenting peptide Ag. Similar results were obtained with stimulation from peptide presenting fibroblast APC lacking or expressing B7-1 with intracellular adhesion molecule-1. TCR ligation with little or no accessory molecule coreceptor engagement induced efficient blastogenesis; up-regulation of CD25, CD44, CD69, CD95 and CD71; and down-regulation of CD62L over a 48-h period. Accessory molecule help enhanced the expression of CD25, CD44, CD69, and CD71, but to very modest degrees. Only two molecules, CD40 ligand and IL-2, were found to be extremely dependent on accessory molecule help, with little or no expression evident with peptide presented on resting B cells or class II-positive fibroblasts. T cells induced on resting B cells expanded minimally over 3 days, and this was followed by extensive cell death and hyporesponsiveness of the resulting cells. These studies suggest that under tolerizing conditions, such as Ag presentation by resting B cells, much of the naive CD4 response is induced efficiently. Partial activation, however, may be the overall result due to the lack of CD40 ligand expression, which may regulate costimulatory activity in APC and, in turn, may contribute to limiting the production of IL-2 required for T cell expansion and survival.

Abatacept↗
PubMed1998

Gender differences in fat oxidation and sympathetic nervous system activity at rest and during submaximal exercise in older individuals.

1. Gender differences in fat oxidation at rest and during exercise may contribute to higher body fat in women. We examined gender differences in fat oxidation at rest and during submaximal exercise and their relationship to sympathetic nervous system activity, free fatty acid availability, body composition and aerobic capacity in older volunteers. 2. We measured free fatty acid kinetics using [14C]palmitate, absolute (micromol/min) and relative (respiratory quotient) rates of fat oxidation by indirect calorimetry and sympathetic nervous system activity from noradrenaline kinetics using [3H]noradrenaline in 12 older men (70+/-4 years) and 12 older women (66+/-4 years) at rest and during 30 min of submaximal exercise (45% of peak oxygen consumption). 3. At rest, men oxidized more fat than women on both an absolute (88+/-19 versus 51+/-15 micromol/min; P<0.01) and relative (respiratory quotient: 0.80+/-0. 04 versus 0.85+/-0.04; P<0.01) basis. These differences were not related to noradrenaline appearance rate, free fatty acid concentration, body composition or aerobic capacity. During exercise, fat oxidation was higher (P<0.05 to P<0.01) in men on an absolute level, but respiratory quotient did not differ. Higher absolute fat oxidation in men during exercise was explained by their higher absolute workload. Plasma free fatty acids and free fatty acid rate of appearance did not differ between men and women during exercise despite higher (P<0.05 to P<0.01) plasma noradrenaline concentrations in men. 4. We conclude that: (i) resting fat oxidation is higher in older men compared with older women independent of differences in noradrenaline appearance rate, free fatty acid availability, body composition or aerobic capacity, and (ii) despite higher plasma noradrenaline concentrations during submaximal exercise, no gender differences in free fatty acid appearance rate or fat oxidation were found. These results suggest a sex dimorphism in post-absorptive fat metabolism in the elderly.

Aged↗
PubMed1998

Induction of resting microglia in culture medium devoid of glycine and serine.

Cultured microglial cells usually exhibit ameboid morphology and peripheral macrophage-like properties, which are distinct from those observed in the normal mature brain. This might be caused by the inappropriate culture of microglial cells in high concentrations (approximately 200-400 microM) of Gly and Ser, although the concentrations of the amino acids in extracellular spaces of the brain parenchyma are quite low (approximately 5 microM). In the present study, we focused on the concentration-dependent effects of glycine (Gly) and serine (Ser) on microglial morphology and function. Under Gly/Ser-free and serum-free condition, the majority of rat microglial cells displayed round morphology, whereas in the presence of 5 microM Gly and 25 microM Ser, which correspond to the concentrations of Gly and Ser in the cerebrospinal fluid, they extended multiple branched processes and formed clusters of rough endoplasmic reticulum. On the other hand, Gly and Ser did not affect morphology of astrocytes. The viability of microglia was not affected by the changes in the concentrations of Gly and Ser. Metabolic activity, activities of acid phosphatase and inducible nitric oxide synthase, and superoxide anion (O2-) generation were all strongly suppressed in Gly/Ser-free medium or in medium containing physiological concentrations of both amino acids. Such activities were all enhanced in harmony with increases in the concentrations of Gly and Ser. Thus, microglial cells cultured in Gly/Ser-free medium, even though exhibiting ameboid morphology, appears to be in the functionally resting state. Furthermore, once the resting state was achieved, the microglial cells remained inactive even after the subsequent 24 h culture in serum-supplemented medium containing 400 microM of both amino acids. The medium conditioned by microglial cells that were cultured in the presence of 400 microM of Gly and Ser was toxic to cortical neurons, whereas the microglia-conditioned medium obtained in the absence of both amino acids facilitated the survival of cortical neurons. Therefore, microglial cells in the resting state, which was induced in the Gly/Ser-free condition, are likely to support neurons. Microglial cells could ramify on glass coverslips coated with astrocyte-derived extracellular matrix or on coverslips coated thinly with fibronectin and/or laminin even under the Gly/Ser-free condition. The ramified cells as induced in this way kept suppressed O2- generating activity. These findings suggest that resting ramified microglial cells with a neurotrophic activity can be induced with the combination of Gly/Ser-free medium and small amounts of extracellular matrix proteins, and that the resting state is rather stable.

Acid Phosphatase↗
PubMed1998

Identification of viable myocardium in patients with chronic coronary artery disease using rest-redistribution thallium-201 tomography: optimal image analysis.

UNLABELLED: With the widely used 50% threshold, sensitivity is high, but specificity is low in detecting viable myocardium on 201Tl SPECT. In this study, we sought to identify the best threshold for semiquantitative 201Tl analysis. METHODS: Rest-redistribution 201Tl SPECT was performed in 46 patients with chronic coronary artery disease before and after myocardial revascularization. Regional function was evaluated by two-dimensional echocardiography before and after myocardial revascularization using a 3-point scale (1 = normal, 2 = hypokinetic, 3 = a/dyskinetic). Myocardial segments with abnormal systolic function were defined as viable if the systolic function score decreased > or = 1 after myocardial revascularization. A second group of 12 patients with chronic coronary artery disease constituted the validation population. Sensitivity-specificity curves, as well as receiver operating characteristic curves, for rest and redistribution mages were generated by varying the 201Tl uptake threshold. RESULTS: A 65% threshold uptake using resting images was found to be the best for detecting a/dyskinetic segments that improve after myocardial revascularization from those that do not improve. Sensitivity was lower with a 65% threshold (75%) than with a 50% threshold (90%, p < 0.05), but specificity was higher (76% versus 26%, p < 0.05) resulting in better accuracy (76% versus 57%, p < 0.05) and positive predictive value (77% versus 55%), while the negative predictive value was not different (69% versus 75%, p not significant). The area under the receiver operating characteristic curve was significantly (p < 005) larger for rest (0.80 +/- 0.05) as opposed to redistribution (0.72 +/- 0.05) images. Similar results were obtained in a subgroup of patients with low ejection fraction. Significant correlations between the percentage of revascularized viable segments and both the change in ejection fraction and in postrevascularization ejection fraction were found. When these findings were applied in the validation group, a gain in specificity, accuracy and positive predictive value was obtained with the 65% threshold compared with the 50% threshold. CONCLUSION: This study demonstrated that analysis of resting images and use of the 65% 201Tl uptake threshold is preferable for separating viable from not viable dyssynergic myocardial segments in patients with chronic coronary artery disease.

Case-Control Studies↗
PubMed1995

Blood volume regulating hormones response during two space related simulation protocols: four-week confinement and head-down bed-rest.

The volume of regulating hormones (renin, aldosterone, arginine vasopressin and atrial natriuretic factor), electrolytes and creatinine concentrations, and blood pressure were measured in two different four-week experimental protocols: respectively -6 degrees head-down bed-rest (5 subjects) and confinement (6 subjects). We observed a significant increase (P < 0.01 at D2 vs D-5) of systolic blood pressure during confinement and a different level of response for some hormones, especially for arginine vasopressin (300% increase during confinement instead of 50% during bed-rest). The renin-angiotensin-aldosterone system was enhanced during confinement and head-down bed-rest. In both conditions, we obtained a similar pattern of response for blood volume regulating hormones. During confinement, two main factors were inactivity and stress activation of the sympathetic nervous system. In the bed-rest study the response is principally due to the fluid shift and blood volume adaptation but it is not possible to exclude the role of inactivity and stress.

Adult↗
PubMed2005

Modulation of endothelial and smooth muscle function by bed rest and hypoenergetic, low-fat nutrition.

Prolonged microgravity alters the regulation of the peripheral vasculature. The influence of reduced food intake, as often observed in astronauts, on vascular function is unclear. In a randomized, four-phase, crossover study, the effect of simulated microgravity (13 days of bed rest), energetic restriction (-25%, fat reduced), and their combination on endothelium-dependent and -independent vasodilation was compared with ambulatory control conditions. Using venous occlusion plethysmography, cumulative intra-arterial dose-response curves to endothelium-dependent (acetylcholine) and -independent (sodium nitroprusside) vasodilators were constructed in 10 healthy male volunteers before and on day 13 of each of the four intervention periods. Bed rest combined with normoenergetic nutrition impaired the dose-response to acetylcholine (ANOVA, P = 0.004) but not to sodium nitroprusside, whereas hypoenergetic diet under ambulatory conditions improved responses to acetylcholine (P = 0.044) and sodium nitroprusside (P < 0.001). When bed rest was combined with hypoenergetic diet, acetylcholine responses did not change. Similarly, under control conditions, no change was observed. Individual changes in the total cholesterol-to-HDL ratio were correlated with changes in endothelial and vascular smooth muscle relaxation. In conclusion, short-term bed rest impairs endothelium-dependent arterial relaxation in humans. A hypoenergetic, low-fat diet modulates serum lipids, improves endothelium-dependent and -independent relaxation, and may antagonize the unfavorable effects of simulated microgravity on endothelial function.

Adaptation, Physiological↗
PubMed1999

A positron emission tomographic study of subthalamic nucleus stimulation in Parkinson disease: enhanced movement-related activity of motor-association cortex and decreased motor cortex resting activity.

BACKGROUND: Long-term high-frequency stimulation of the subthalamic nucleus (STN) improves akinesia in Parkinson disease. The neural correlates of STN stimulation are not well understood. Positron emission tomography can be applied to the in vivo study of the mechanisms of deep brain stimulation. OBJECTIVE: To study changes in regional cerebral blood flow as an index of synaptic activity in patients with Parkinson disease with effective STN stimulation on and off during rest and movement. METHODS: Eight patients with Parkinson disease who had electrodes implanted in the STN underwent 12 measurements of regional cerebral blood flow with water O 15 positron emission tomography at rest and during performance of paced freely selected joystick movements, both with and without STN stimulation (3 scans per experimental condition). Motor performance and reaction and movement times were monitored. Statistical parametric mapping was used to compare changes in regional cerebral blood flow between conditions and differences in activation. RESULTS: All patients showed improvement in reaction and movement times during scans with the stimulator on. As predicted, increases in activation of rostral supplementary motor area and premotor cortex ipsilateral to stimulation were observed when stimulation was on during contralateral movement (P<.001). Unpredicted observations included decreases in regional cerebral blood flow in primary motor cortex at rest induced by STN stimulation. CONCLUSION: Stimulation of the STN reduces the movement-related impairment of frontal motor association areas and the inappropriate motor cortex resting activity in Parkinson disease.

Adult↗
PubMed1999

T1 measurements of 31P metabolites in resting and exercising human gastrocnemius/soleus muscle at 1.5 Tesla.

This study has measured the apparent 31P T1 times at 1.5 T in human gastrocnemius/soleus muscle groups at rest, during exercise, and during recovery from a 90-sec submaximal plantar flexion exercise. T1 times were measured with a 10-sec time resolution in 11 normally active volunteers using a surface coil with a nine-point progressive saturation technique. A two-point short repetition time technique was also used. Both techniques showed similar trends in the apparent T11 times of all the 31P metabolites at rest, during exercise, and during recovery. For the nine-point progressive saturation technique, the apparent T1 of PCr and beta-ATP decreased approximately 20% to a steadystate value (P = 0.027 and P = 0.004, respectively). The two-point short repetition time technique demonstrated a 10% reduction in the apparent T1 of PCr and beta-ATP Both techniques demonstrated an apparent T1 increase of 58% for inorganic phosphate at the beginning of exercise (P<0.0001) and a return to resting value during the 90-sec submaximal isometric contraction. Neither technique showed any significant differences between resting and exercising T1 times of the alpha-ATP and gamma-ATP resonances (P = 0.06 and P>0.40, respectively).

Exercise↗
PubMed2000

Objective quantification of resting and activated parkinsonian rigidity: a comparison of angular impulse and work scores.

The clinical assessment of rigidity is influenced by a number of variables which limit the reproducibility of rating scores and the usefulness of comparisons between subjects. We evaluated an objective measure of rigidity which uses unpredictable but reproducible limb perturbations mimicking the waveform, rate, and amplitude of those used in the clinical examination; and evaluates total resistive force, thus avoiding assumptions about the relative influence of elastic, viscous, or inertial components of the measured resistive forces on the genesis of rigidity. We then used this measure to quantify the effects of an activation procedure on parkinsonian rigidity, because this forms an important but poorly understood part of the routine clinical examination. We studied 20 patients with a clinical diagnosis of Parkinson's disease and 10 age-matched control subjects. A torque motor was used to deliver reproducible, transient, sinusoidal perturbations varying between 1.0 and 1.5 Hz. To quantify rigidity, we calculated angular impulse scores, which reflect the relationship between change in total resistive torque and time. Angular impulse scores were compared with work scores, which have previously been found to correlate with clinical assessments of rigidity. All subjects were studied at rest and with activation. Angular impulse scores were more consistently correlated with rigidity and more clearly differentiated between patients and control subjects than work scores. Activation increased both clinical and objective rigidity scores; activated angular impulse scores ranged from approximately 100%-200% of resting values. When plotted against clinical rigidity scores, activated angular impulse scores lay on a continuum with resting values. We conclude that angular impulse is a valid objective measure of parkinsonian rigidity. Activation increases rigidity, but to varying degrees in different patients. To improve the sensitivity and reproducibility of clinical rigidity assessments, parkinsonian rating scales should include separate resting and activated scores.

Aged↗
PubMed1981

Hemodynamic effects of disopyramide at rest and during exercise in normal subjects.

The hemodynamic effects of disopyramide phosphate, 2.0 mg/kg body weight, given intravenously over a period of five minutes were studied at rest and during exercise in ten patients without clinical or angiographic evidence of heart disease. Following disopyramide, the resting cardiac index was lower (4.0 +/- 0.6 vs 4.3 +/- 0.6 liters/min/m2, mean +/- 1 SD,P less than 0.05), while left ventricular end-diastolic pressure (16 +/- 4 vs 11 +/- 4 mm Hg, P less than 0.001), pulmonary arterial (PA) mean pressure (20 +/- 5 vs 17 +/- 5 mm Hg, P less than 0.05), and brachial arterial (BA) mean pressure (105 +/- 8 vs 96 +/- 7 mm Hg, P less than 0.05), were higher than the pre-infusion resting values. During exercise, there was no change in left ventricular end-diastolic pressure while cardiac index rose from 4.0 +/- 0.6 to 6.5 +/- 0.6 liters/min/m2 (P less than 0.001) and left ventricular stroke work index increased from 62 +/- 19 to 84 +/- 22 gm/beat/m2 (P less than 0.001). The normal hemodynamic response during exercise after disopyramide despite the apparent depression of left ventricular function at rest probably reflects the positive inotropic effect of enhanced sympathoadrenergic activity.

Adult↗
PubMed2005

Effect of timed bright light treatment for rest-activity disruption in institutionalized patients with Alzheimer's disease.

BACKGROUND: Disturbances in rest-activity rhythm are prominent and disabling symptoms in Alzheimer's disease (AD). Nighttime sleep is severely fragmented and daytime activity is disrupted by multiple napping episodes. In most institutional environments, light levels are very low and may not be sufficient to entrain the circadian clock to the 24-hour day. METHOD: The purpose of this randomized clinical trial was to test the effectiveness of timed bright light therapy in reducing rest-activity (circadian) disruption in institutionalized patients with AD. The experimental groups received either morning (9.30-10.30 am) or afternoon (3.30-4.30 pm) bright light exposure ( > or = 2500 lux in gaze direction) Monday through Friday for 10 weeks. The control group received usual indoor light (150-200 lux). Nighttime sleep, daytime wake, and rest-activity parameters were determined by actigraphy. Repeated measures analysis of variance was employed to test the primary study hypotheses. RESULTS: Seventy institutionalized subjects with AD (mean age 84) completed the study. No significant differences in actigraphy-based measures of nighttime sleep or daytime wake were found between groups. Subjects in either experimental light condition evidenced a significantly (p < 0.01) more stable rest-activity rhythm acrophase over the 10-week treatment period compared to the control subjects whose rhythm phase delayed by over two hours. CONCLUSIONS: One hour of bright light, administered to subjects with AD either in the morning or afternoon, did not improve nighttime sleep or daytime wake compared to a control group of similar subjects. However, exposure to one-hour of bright light in either the morning or afternoon may provide sufficient additional input to the circadian pacemaker to facilitate entrainment to the 24-hour day.

Aged↗
PubMed2004

Modulation of functional connectivity during the resting state and the motor task.

Quite a few studies in functional magnetic resonance imaging (fMRI) have tested that, even in a resting state, motor cortices constitute a network. It has never been investigated how the network modulates from the resting state to the motor task state. In this report, by a newly developed approach taking into account n-to-1 connectivity using 1-to-1 connectivity measures instead of conventional pairwise connectivity, we show the existence of a large organized functional connectivity network related to motor function in the resting brain with fMRI. More importantly, we found that such a network can be modulated from a conscious resting state to planning, initiation, coordination, guidance, and termination of voluntary movement state, exhibited by significant changes of functional connectivity of some brain regions in different brain activity. Moreover, a quantitative description of such a functional modulation has also been presented.

Adult↗
PubMed1993

Use of lower body negative pressure to counter symptoms of orthostatic intolerance in patients, bed rest subjects, and astronauts.

This report briefly discusses some aspects of autonomic cardiovascular dysfunction as related to changes in orthostatic function in patients, bed rest subjects, and astronauts. This relationship is described in normal individuals to provide the basis for discussion of parameters that may be altered in patients, bed rest subjects, and astronauts. The relationships between disease states, age, periods of weightlessness during space flight, and autonomic dysfunction, and their contribution to changes in orthostatic tolerance are presented. The physiologic effects of lower body negative pressure are illustrated by presenting data obtained in bed rest subjects and in astronauts. Finally, the usefulness of lower body negative pressure to counter symptoms of orthostatic intolerance in patients, bed rest subjects, and astronauts is discussed.

Autonomic Nervous System Diseases↗
PubMed2001

Walking and resting blood pressure in adults: a meta-analysis.

BACKGROUND: The purpose of this study was to examine the effects of walking on resting systolic and diastolic blood pressure in adults. METHODS: A total of 24 primary outcomes from 16 studies and 650 subjects (410 exercise, 240 control) met the criteria for inclusion: (1) randomized and nonrandomized controlled trials, (2) walking as the only intervention, (3) subjects apparently sedentary, (4) adult humans > or =18 years of age, (5) English-language studies published between January 1966 and December 1998, (6) resting blood pressure assessed, (7) training studies > or =4 weeks. RESULTS: Using a random effects model, statistically significant decreases of approximately 2% were found for both resting systolic and diastolic blood pressure (systolic, mean +/- SEM = -3 +/- 1 mm Hg, 95% confidence interval: -5 to -2 mm Hg; diastolic, mean +/- SEM = -2 +/- 1 mm Hg, 95% confidence interval: -3 to -1 mm Hg). CONCLUSION: Walking exercise programs reduce resting blood pressure in adults.

Adult↗
PubMed1992

Enalapril versus combined enalapril and nadolol treatment: effects on blood pressure, heart rate, humoral variables, and plasma potassium at rest and during exercise in hypertensive patients.

The effect of enalapril alone and in combination with nadolol on resting and exercising blood pressure, heart rate, plasma renin activity, aldosterone, noradrenaline, and potassium levels was studied in 10 hypertensive patients (diastolic blood pressure between 95 and 114 mmHg). Patients received placebo for 4 weeks, enalapril (mean daily dose 24.5 mg) for 8 weeks, and nadolol, 40 mg once daily, was added for the remaining 8 weeks of the study. Exercise testing (modified Bruce, treadmill) was conducted at the end of the placebo run-in phase and at the end of each treatment period. Enalapril reduced resting and exercising blood pressure independent of any change in heart rate: This effect was increased with combination treatment. Plasma renin activity at rest and during exercise was increased by enalapril. Combination treatment attenuated this response and significantly reduced plasma aldosterone. Neither treatment had any effect on plasma noradrenaline levels. Resting plasma potassium levels were increased with combination treatment, whereas both treatment regimens increased plasma potassium levels during exercise. There were no clinically relevant episodes of hyperkalemia. Further investigation is required to qualify the nature of the blood pressure and plasma potassium response with combination treatment.

Adult↗