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PubMed1999

Naproxen does not alter indices of muscle damage in resistance-exercise trained men.

PURPOSE: Unaccustomed exercise is associated with an elevated plasma creatine kinase (CK), myofibrillar inflammation, and delayed onset muscle soreness (DOMS). Nonsteroidal antiinflammatory drugs (NSAID) may attenuate DOMS and indirect indices of inflammation in humans. METHODS: We studied the effects of an NSAID (naproxen sodium (500 mg, 2 times a day for 48 h)) taken before and after resistance exercise in eight healthy, moderately trained men in a randomized, double-blind trial. The exercise consisted of unilateral knee concentric/eccentric weight lifting with 6 sets x 10 repetitions at 80-85% of the 1 repetition maximal contraction. Muscle biopsies of each vastus lateralis (EX = exercised/REST = control) were taken 24 h after exercise for immunohistochemical staining of inflammatory cells (leukocyte common antigen). At 24 and 48 h postexercise, we also determined DOMS, plasma CK activity, and knee extensor muscle torque. RESULTS: Exercise resulted in an increased CK activity at +24 and +48 h (vs preexercise: P < 0.01), with no treatment effect. There were no treatment effects for any of the measured variables except for a return of voluntary knee extension torque to baseline by +48 h postexercise for NSAID treatment (P < 0.05). CONCLUSIONS: NSAID administration did not alter CK rise, muscle force deficit at 24 h postexercise, nor perceived muscle pain. In addition, the increased CK at 24 h postexercise was not associated with an acute myofibrillar inflammatory cell infiltrate in moderately trained men after resistance exercise.

Administration, Oral↗

PubMed1998

A randomized controlled trial of the effect of naproxen on delayed onset muscle soreness and muscle strength.

OBJECTIVE: To determine the effect of naproxen in attenuating the symptoms (muscle soreness level) and signs (plasma creatine kinase [CK] activity and muscular strength decrement) of delayed onset muscle soreness (DOMS) induced by repeated bouts of eccentric exercise. DESIGN: The design was a randomized, double-blind, placebo-controlled, crossover trial with two testing phases of 8 days' duration that were separated by a "washout" period of 7 days. SETTING: University-based sports science center. PARTICIPANTS: Twenty healthy male volunteers who responded to a notice in the university's athletic complex. INTERVENTIONS: Eccentric single-leg exercises were performed on days 1, 3, and 4 to induce DOMS in the quadriceps muscles. Naproxen or placebo tablets (500 mg) were taken orally twice per day beginning on day 2 and continuing until the end of the testing phase. MAIN OUTCOME MEASURES: Perception of muscle soreness and knee extensor torque were evaluated daily throughout each phase. Plasma CK levels were evaluated on days 1, 3, 6, and 8 of each phase. RESULTS: After the eccentric exercise, plasma CK levels were similarly elevated in both naproxen and placebo conditions (F=1.42; p=0.25). After DOMS developed, naproxen reduced the perception of soreness on day 3, when muscle soreness was highest (F=2.20; p=0.04). After treatments with naproxen, peak quadriceps torque during leg extension at 60 degrees/s was higher than that after treatment with the placebo (F=4.77; p=0.04). There were no significant differences between the naproxen and placebo conditions for leg extension at 180 degrees/s (F= 1.66; p=0.21) and 300 degrees/s (F=0.71; p=0.41). CONCLUSION: The data indicate that therapeutic doses of naproxen do not prevent CK release into the plasma but decrease the perception of muscle soreness and positively influence quadriceps peak torque.

Adult↗

PubMed2000

The efficacy of Farabloc, an electromagnetic shield, in attenuating delayed-onset muscle soreness.

OBJECTIVE: To assess the hypothesis that Farabloc, a fabric with electromagnetic shielding properties, would attenuate the symptoms, signs, and muscular strength deficit secondary to delayed-onset muscle soreness (DOMS) induced by two exposures to eccentric exercise in humans. DESIGN: Randomized, single-blind, placebo-controlled, crossover trial with two testing stages of 5 days duration separated by a washout period of more than 8 weeks. SETTING: University-based sports medicine center. PARTICIPANTS: Twenty volunteers equally representing untrained male and female subjects. INTERVENTIONS: 20 sets of 10 repetitions of single-leg eccentric knee extensions for 37 minutes with the Biodex dynamometer set at 30 degrees per second were performed on the first day of stage one and stage two to induce DOMS in the quadriceps muscle. Double layers of fabric, either Farabloc or placebo, were wrapped around the thigh of each participant during each stage for 5 days. MAIN OUTCOME MEASURES: Perception of muscle pain, as measured by a visual analog scale (VAS), and strength, as measured by knee extensor torque (EST) with the Biodex dynamometer, were evaluated at 0, 24, 48, 72, and 96 hours. Serum inflammatory markers of muscle damage, including malondialdehyde. creatine phosphokinase, myoglobin, leukocytes, and neutrophils, were assayed at 0, 2, 6, 24, and 48 hours. RESULTS: Repeated-measures analysis of variance was carried out for each of the seven variables to assess differences for fabric, order of treatment, time, and all combinations. Results of VAS and EST and levels of malondialdehyde, creatine phosphokinase, myoglobin, leukocytes, and neutrophils all showed a highly significant effect of Farabloc compared with placebo. This analysis shows that the order of Farabloc or placebo fabric use in stage I and 2 produces different results. This may be caused by a learning effect, but did not alter the overall influence of Farabloc. CONCLUSION: The data indicate that double layers of Farabloc fabric wrapped around the thigh reduces pain and strength loss and serum levels of malondialdehyde, creatine phosphokinase, myoglobin, leukocytes, and neutrophils when untrained human subjects are exposed to eccentric exercise to produce DOMS in the quadriceps. Farabloc shields high-frequency electromagnetic fields, although the results do not indicate how these changes are mediated. Further research is needed to determine the mechanism.

Adult↗

PubMed2001

Seasonal changes in the character and nitrogen content of dissolved organic matter in an alpine/subalpine headwater catchment.

We are studying the chemical quality of dissolved organic nitrogen (DON) in a high-elevation watershed in the Colorado Front Range. Samples were collected over the 2000 snowmelt runoff season at two sites across an alpine/subalpine ecotone to understand how the transition between the lightly vegetated alpine and forested reaches of the catchment influences the chemical character of DON. Samples were analyzed approximately weekly for dissolved organic material (DOM) content and chemical character. A subset of samples was analyzed for the elemental content of fulvic and hydrophilic acids. Concentrations of DON at both sites were highest in the spring at the initiation of snowmelt, decreased during snowmelt, and increased again during the late summer and fall. In contrast, concentrations of dissolved organic carbon (DOC) peaked on the ascending limb of the hydrograph and declined to seasonal minima on the descending limb of the hydrograph. The ratio of DOC:DON showed a seasonal shift at both sites with high values (40 to 55) during peak runoff in early summer and lower values (15 to 25) during low flows late in the runoff season. These results indicate that there was a seasonal change in the relative N content of DOM at both sites. Chemical fractionation of DOC showed that there were temporal and longitudinal changes in the chemical character of DOC. At the alpine site, the fulvic acid content of DOC decreased from 57% in June to 35% in September. The change in fulvic acid was less pronounced at the forested site, from 66% in June to 54% in September. Elemental analysis of fulvic and hydrophilic acids indicated that hydrophilic acids were N rich compared to fulvic acids. Additionally, fulvic and hydrophilic acids isolated at the alpine site had a lower C:N ratio than those isolated at the forested site. Similarly, the C:N ratio of organic acids at both sites was lower in September than in June during peak runoff. These differences appear to be a result of changes in both DOM precursor material and hydrologic flowpaths. Using C:N ratios of fulvic and hydrophilic acids, we estimate that nonhumic material carried between 54 to 73% of the organic N in surface water at the alpine site and 44 to 58% of the organic N in surface water at the subalpine site.

Benzopyrans↗

PubMed1999

Administration of a nonpeptidyl growth hormone secretagogue, L-163, 255, changes somatostatin pattern, but has no effect on patterns of growth hormone-releasing factor in the hypophyseal-portal circulation of the conscious pig.

The activity of the growth hormone secretagog, L-163,255, on growth hormone (GH), growth hormone-releasing factor (GRF), and somatostatin (SRIF) levels was evaluated in a porcine model of hypophyseal portal blood (HPB) collection. Young, castrated pigs had HPB and jugular blood collected for approximately 300 min. The blood collection was divided into discrete periods: baseline (BL) approximately 180 min; GH response period (RSP) approximately 90 min; and positive control period following a GRF bolus, 30 min. RSP was divided into a dominant response period (DOM) and a tail (TL). The spontaneous relationship between HPB GRF and SRIF and peripheral GH during BL has been reported (Proc Soc Exp Biol Med 217:188-196, 1998). The apex of the GH pulse resulting from L-163,255 administration was nonrandomly associated (P < 0.05) with descending periods of SRIF troughs. Frequency and amplitude of GRF and SRIF pulses, and frequency and depth of SRIF troughs were not different between BL and the beginning of DOM (the 20-30 min of GH increase). GH AUC was significantly greater (P < 0.05) for DOM compared to BL and TL, and for TL compared to BL. GRF AUC tended to be greater (P < 0.1) for RSP compared to BL, but the majority of the increase was in the TL period. There were no significant differences in the SRIF AUCs between the sampling periods. Furthermore, in a separate experiment, fos activity (a marker of neuronal activation) in the hypothalamus of pigs was examined after either L-163,255 (1x or 4x), isotonic saline (control), or hypertonic saline (positive control) administration. There were no differences in fos activity in the GRF, SRIF, or CRH immunopositive neurons between L-163,255 treatment and control. The pituitaries of the L-163,255-treated pigs showed marked fos activation compared to the controls. In conclusion, L-163,255 in pigs has its primary effect at the level of the anterior pituitary.

Animals↗

PubMedDate not supplied

Fluorescence of dissolved organic matter as a natural tracer of ground water.

The fluorescence properties of dissolved organic matter (DOM) in ground water in the Permian limestone of northeast England is determined from six monitoring boreholes, a private water supply well and from a natural resurgence in a flooded collapse doline in the environs of Darlington, County Durham, northeast England. Measurements of both protein and "fulvic-like" fluorescence was undertaken from January to December 1999. The wavelengths of fulvic-like fluorescence excitation and emission and of protein fluorescence emission were all determined to be sensitive fingerprints of organic matter fluxes through the ground water, with water within the till and within both gypsum and limestone strata deep inside the Magnesian Limestone being differentiated by these parameters. Previous research has suggested that proteins in waters are "young" in age, hence our seasonal variations suggest that we are sampling recently formed DOM. The rapid response of all deep borehole samples suggests relatively rapid ground water flow, probably through karstic cave systems developed in the gypsum and solution widened features in the dolomitic limestone. Our results suggest that use of both protein and fulvic-like fluorescence wavelength variations provides a DOM signature that can be used as a natural tracer.

Benzopyrans↗

PubMed2005

Supplementation with beta-hydroxy-beta-methylbutyrate (HMB) and alpha-ketoisocaproic acid (KIC) reduces signs and symptoms of exercise-induced muscle damage in man.

This study examined the effects of beta-hydroxyl-beta-methylbutyrate (HMB) and alpha-ketoisocaproic acid (KIC) supplementation on signs and symptoms of exercise-induced muscle damage following a single bout of eccentrically biased resistance exercise. Six non-resistance trained male subjects performed an exercise protocol designed to induce muscle damage on two separate occasions, performed on the dominant or non-dominant arm in a counter-balanced crossover design. Subjects were assigned to an HMB/KIC (3 g HMB and 0.3 g alpha-ketoisocaproic acid, daily) or placebo treatment for 14 d prior to exercise in the counter-balanced crossover design. One repetition maximum (1RM), plasma creatine kinase activity (CK), delayed onset muscle soreness (DOMS), limb girth, and range of motion (ROM) were determined pre-exercise, at 1h, 24 h, 48 h, and 72 h post-exercise. DOMS and the percentage changes in 1RM, limb girth, and ROM all changed over the 72 h period (P < 0.05). HMB//IC supplementation attenuated the CK response, the percentage decrement in 1RM, and the percentage increase in limb girth (P < 0.05). In addition, DOMS was reduced at 24 h post-exercise (P < 0.05) in the HMB/KIC treatment. In conclusion, 14 d of HMB and KIC supplementation reduced signs and symptoms of exercise-induced muscle damage in non-resistance trained males following a single bout of eccentrically biased resistance exercise.

Adult↗

PubMed1993

Aminopeptidase activity in marine chroococcoid cyanobacteria.

Synechococci are important primary producers in the ocean and can also utilize some components of the dissolved organic matter (DOM). The readily utilizable DOM in seawater is mainly polymeric (e.g., protein, polysaccharide) or phosphorylated and requires hydrolysis prior to uptake. We examined whether synechococci express ectoenzymes to hydrolyze DOM components and considered the possible significance of ectohydrolases for Synechococcus ecology and organic matter cycling in the sea. Five strains of non-nitrogen-fixing synechococci in axenic cultures were tested for enzyme activities with fluorogenic substrates. All strains show ectocellular aminopeptidase activity, but other enzymes were undetectable. The aminopeptidase level was in the range determined for five marine heterotrophic bacterial isolates tested for comparison. Aminopeptidase was not secreted into the medium; the majority (74%; tested in WH 7803) was cell surface bound, and a small fraction was periplasmic. The periplasmic activity was not released by cold osmotic shock of WH 7803. Phenylmethylsulfonyl fluoride and EDTA, inhibitors of serine and metalloproteases, strongly or completely inhibited WH 7803 aminopeptidase. The enzyme seemed constitutive; per-cell activity did not change during incubations in unenriched seawater, bovine serum albumin, or nitrate-replete mineral medium. In natural planktonic assemblages in the Southern California Bight, aminopeptidase activity was correlated with Synechococcus abundance as well as the abundance of other bacteria. Ectocellular aminopeptidase may be common in marine synechococci and play roles in their nitrogen nutrition, particularly in low-nitrate and low-light environments. Since synechococci are much less abundant than heterotrophic bacteria in seawater, the impact of Synechococcus aminopeptidase on proteolysis in the sea is likely to be episodic and restricted to specialized microenvironments.

Journal Article↗

PubMed1998

Significance of viral lysis and flagellate grazing as factors controlling bacterioplankton production in a eutrophic lake.

The effects of viral lysis and heterotrophic nanoflagellate (HNF) grazing on bacterial mortality were estimated in a eutrophic lake (Lake Plusssee in northern Germany) which was separated by a steep temperature and oxygen gradient into a warm and oxic epilimnion and a cold and anoxic hypolimnion. Two transmission electron microscopy-based methods (whole-cell examination and thin sections) were used to determine the frequency of visibly infected cells, and a model was used to estimate bacterial mortality due to viral lysis. Examination of thin sections also showed that between 20.2 and 29.2% (average, 26.1%) of the bacterial cells were empty (ghosts) and thus could not contribute to viral production. The most important finding was that the mechanism for regulating bacterial production shifted with depth from grazing control in the epilimnion to control due to viral lysis in the hypolimnion. We estimated that in the epilimnion viral lysis accounted on average for 8.4 to 41.8% of the summed mortality (calculated by determining the sum of the mortalities due to lysis and grazing), compared to 51.3 to 91.0% of the summed mortality in the metalimninon and 88.5 to 94.2% of the summed mortality in the hypolimnion. Estimates of summed mortality values indicated that bacterial production was controlled completely or almost completely in the epilimnion (summed mortality, 66.6 to 128.5%) and the hypolimnion (summed mortality, 43.4 to 103.3%), whereas in the metalimnion viral lysis and HNF grazing were not sufficient to control bacterial production (summed mortality, 22.4 to 56.7%). The estimated contribution of organic matter released by viral lysis of cells into the pool of dissolved organic matter (DOM) was low; however, since cell lysis products are very likely labile compared to the bulk DOM, they might stimulate bacterial production. The high mortality of bacterioplankton due to viral lysis in anoxic water indicates that a significant portion of bacterial production in the metalimnion and hypolimnion is cycled in the bacterium-virus-DOM loop. This finding has major implications for the fate and cycling of organic nutrients in lakes.

Journal Article↗

PubMed1997

Homoeopathy for delayed onset muscle soreness: a randomised double blind placebo controlled trial.

OBJECTIVE: To pilot a model for determining whether a homoeopathic medicine is superior to placebo for delayed onset muscle soreness (DOMS). DESIGN: Randomised double blind placebo controlled trial. SETTING: Physiotherapy department of a homoeopathic hospital. SUBJECTS: Sixty eight healthy volunteers (average age 30; 41% men) undertook a 10 minute period of bench stepping carrying a small weight and were randomised to a homoeopathic medicine or placebo. OUTCOME MEASURES: Mean muscle soreness in the five day period after the exercise test, symptom free days, maximum soreness score, days to no soreness, days on medication. RESULTS: The difference between group means was 0.17 in favour of placebo with 95% confidence intervals +/- 0.50. Similar results were found for other outcome measures. CONCLUSION: The study did not find benefit of the homoeopathic remedy in DOMS. Bench stepping may not be an appropriate model to evaluate the effects of a treatment on DOMS because of wide variation between subject soreness scores.

Adolescent↗

PubMed2005

Rofecoxib and tramadol do not attenuate delayed-onset muscle soreness or ischaemic pain in human volunteers.

We assessed the effect of rofecoxib, a cyclo-oxygenase-2 inhibitor, and tramadol, a centrally acting analgesic, on both delayed-onset muscle soreness (DOMS) and experimentally induced ischaemic pain. We induced DOMS in 10 male and 5 female healthy volunteers by downhill running for 30 min at a 12% decline and a speed of 9 km x h(-1). We also induced ischaemic pain by finger movements with an arterial tourniquet around the arm. In a randomized, double-blind crossover format, we administered rofecoxib (50 mg, daily), tramadol (50 mg, 3 times per day), and a placebo (orally for 3 days), starting immediately after exercise. A 100 mm visual analogue scale (VAS) and McGill pain questionnaire were used to describe muscle soreness and ischaemic forearm pain 24 h after the exercise. The pressure pain threshold (PPT) in the thigh and ischaemic pain tolerance in the forearm were measured before exercise and 24 and 72 h after exercise. PPT decreased 24 h after exercise, compared with pre-exercise values (ANOVA, p < 0.05), but neither drug had any significant effect on the PPT. Neither rofecoxib nor tramadol had any effect on time of ischaemia tolerated or amount of finger activity during ischaemia. The VAS and pain-rating index, for both muscle soreness and experimental ischaemic pain, were not affected significantly by either drug. Both DOMS and ischaemic pain share peripheral and central mechanisms, yet neither are attenuated by rofecoxib or tramadol.

Adult↗

PubMed1992

MR imaging-guided muscle biopsy for correlation of increased signal intensity with ultrastructural change and delayed-onset muscle soreness after exercise.

To determine if there is a correlation between the degree of delayed increase in signal intensity (SI) of muscle after exercise on magnetic resonance (MR) images and the amount of ultrastructural (ULS) injury and delayed-onset muscle soreness (DOMS), MR imaging-guided muscle biopsy was performed to obtain tissue from the legs of nine sedentary subjects 48 hours after downhill running on a treadmill. The degree of soreness was subjectively graded. T1-weighted, spin-density, T2-weighted, and short inversion time inversion-recovery images were obtained before and after biopsy, at 48 and 96 hours after exercise, respectively. The delayed SI increase of muscle on images obtained before biopsy was subjectively graded and measured. The degree of ULS injury was determined with electron micrographs. Serum creatine kinase levels were obtained before and up to 144 hours after exercise at 24-hour intervals. The measured SI, SI grades, and DOMS grades were correlated with the degree of ULS injury. Linear regression analysis revealed poor correlation between the DOMS grades and the degree of ULS injury and good correlation between the SI grade and the degree of ULS injury.

Adult↗

PubMed1992

Effect of downhill running on motoneuron pool excitability.

The purpose of this study was to compare alterations in motoneuron pool excitability after eccentric-biased (ECC-B) downhill running exercise with non-biased (NO-B) level running exercise. Six male subjects (25-34 yr) participated in the study, which included ECC-B exercise (-10% grade) and NO-B exercise (0% grade) at 50% of maximal O2 uptake for 20 min. The control trial consisted of 20 min of quiet rest with all subjects participating in all conditions (repeated measures). Motoneuron pool excitability was measured by the Hoffman reflex (H-wave), which was expressed as a ratio (H/M ratio) of the maximal electrically stimulated muscle action potential (M-wave). NO-B exercise resulted in a 9.3 +/- 2.7% (SE) reduction in the H/M ratio. ECC-B exercise resulted in a 24.6 +/- 5.7% reduction in the ratio (P less than 0.05 for both). The two exercise treatment conditions were also significantly different from one another (P less than 0.05). Twenty-four-hour postexercise H/M ratios were similar to baseline (P greater than 0.05). Postexercise subjective muscle soreness assessment (DOMS) produced significant increases in DOMS of 36 and 166% immediately and 24 h after exercise, respectively, for the ECC-B trial only (P less than 0.001). The data show that ECC-B exercise results in greater postexercise H/M ratio reductions than NO-B exercise and that H/M ratio changes post-ECC-B exercise are not solely associated with DOMS.

Action Potentials↗

PubMed1993

Effect of training on eccentric exercise-induced muscle damage.

Eccentric muscle contractions generate delayed onset muscle soreness (DOMS), possibly as a result of the high tensions involved causing muscle damage. Muscle function, serum indicators of muscle damage, and DOMS were investigated throughout a training regimen that involved a 40-min eccentric walk down a 25% gradient on a treadmill at 6.4 km/h once a week for 8 wk. Serum creatine kinase and myoglobin concentrations were used as indicators of muscle damage, and both demonstrated a delayed increase after the exercise protocol. The muscles that contracted eccentrically exhibited low-frequency fatigue, as well as decreases in muscle fatigability and maximal voluntary contraction force, which were greatest immediately postexercise. Although the results show that training reduces DOMS, the serum muscle protein response, and muscle function impairment, the time courses of these adaptations are different. It is suggested that the function of the muscle can be impaired without apparent muscle damage.

Adaptation, Physiological↗

PubMed1996

Presence of WBC, decreased strength, and delayed soreness in muscle after eccentric exercise.

The purposes of this study were to assess the presence of 99mTc-labeled white blood cells (WBC) in exercised muscle compared with nonexercised muscle over time and to determine the time course of delayed onset muscle soreness (DOMS) and eccentric torque in 10 female subjects. A pretest was followed by 300 eccentric repetitions of the right quadriceps. DOMS and eccentric torque were measured at 2, 4, 20, 24, 48, and 72 h postexercise. Eccentric torque was also tested at 0 h. Radionuclide images of both quadriceps were taken at 2, 4, 20, and 24 h postexercise. The presence of 99mTc-WBC in the exercised muscle was significantly greater (P < 0.001) than in the nonexercised muscle. Eccentric torque declined at 0 and 24 h postexercise. DOMS peaked at 24 h postexercise. The presence of 99mTc-WBC in the exercised muscle in the first 24 h suggests that acute inflammation occurs as a result of exercise-induced muscle injury. The bimodal pattern of eccentric torque supports the hypothesis that more than one mechanism is involved.

Adult↗

PubMed2005

Augmented mechanical response of muscle thin-fiber sensory receptors recorded from rat muscle-nerve preparations in vitro after eccentric contraction.

Unaccustomed strenuous exercise, especially that from eccentric muscular work, often causes muscle tenderness, which is a kind of mechanical hyperalgesia. We developed an animal model of delayed-onset muscle soreness (DOMS) from eccentric muscular contraction (ECC) in rats and demonstrated the existence of muscle tenderness by means of behavioral pain tests and c-Fos protein expression in the spinal dorsal horn. The purpose of the present study was to examine whether the sensitivities of muscle thin-fiber sensory receptors to mechanical, chemical, and thermal stimuli were altered after repetitive ECC in a rat model of DOMS. ECC was caused in the animals by electrical stimulation of the common peroneal nerve innervating the extensor digitorum longus muscle (EDL) while the muscle was being stretched. Activities of single thin-fiber receptors (sensitive to pressure but insensitive to stretch, with conduction velocity slower than 2.0 m/s) were recorded from muscle (EDL)-nerve preparations in vitro 2 days after ECC when mechanical hyperalgesia was at its peak. The mechanical threshold of thin-fiber receptors was found to be very much lower in the ECC preparations than in the nontreated control (CTR) [median 65.4 mN (interquartile range [IQR]; 46.6-122.0 mN) in the CTR preparation vs. 38.2 mN (IQR; 26.8-55.8 mN) in the ECC, P < 0.001]. In addition, the total number of evoked discharges during a ramp mechanical stimulus, taken as an index of the magnitude of the mechanical response, nearly doubled in the ECC preparations compared with the CTR [24.7 spikes (IQR; 14.2-37.1 spikes) in the CTR preparation vs. 54.2 spikes (IQR; 24.3-89.0 spikes) in the ECC, P < 0.001]. In contrast, the numbers of discharges induced by chemical (pH 5.5, lactic acid, adenosine triphosphate, and bradykinin) and thermal (cold and heat) stimuli were not different between the two preparations. These results suggest that augmentation of the mechanical response in muscle thin-fiber sensory receptors might be related to the muscle tenderness in DOMS after ECC.

Action Potentials↗

PubMed1994

Persisting functional connection in growth-hormone-deficient patients with a transected stalk.

Prolactin response after domperidone (DOM) stimulus was used to investigate the functional status of the hypothalamo-hypophyseal axis in 57 congenital growth-hormone-deficient (GHD) children with and without magnetic resonance imaging (MRI) abnormalities. Response to DOM was significantly lower in the GHD children compared with controls, using maximum peak (p < 0.0001), increase (p < 0.0001) or percentage increase (p < 0.05). The lowest values were observed in patients with hypophyseal stalk transection. Thus, the DOM test revealed reduced dopaminergic transmission in GHD subjects, more severe in the transected group, in whom, however, a response to the stimulus was still present. Therefore, it seems that a residual hypothalamo-hypophyseal connection is preserved even if it is not detectable with MRI.

Adolescent↗

PubMed1994

Effect of dopamine2 blockade on renal function under varied sodium intake.

This study explored the role of the dopamine-2 receptor (DA2) in the control of renal blood flow (RBF) and the influence of variations in sodium intake. These relationships have not been previously defined in man. Seven normotensive male subjects underwent a low dose dopamine (DA) infusion (1 microgram/kg.min) for 3 h, known to activate both DA1 and DA2 receptors. The effect of DA2 receptor on renal hemodynamics was studied using a relatively specific DA2 blocker [domperidone (DOM); 60 mg, orally] alone and with a DA infusion. Systemic and renal hemodynamics parameters were measured noninvasively. Urinary prostacyclin was measured in 3-h urine specimens, obtained during the DA infusion. The DA infusion increased RBF and prostacyclin during both normal and high salt diets, but this effect was attenuated on a low salt diet. DOM alone significantly reduced basal RBF during normal (1304 +/- 48 vs. 1175 +/- 45 mL/min.1.73 m2; P < 0.01) and low salt diets (1402 +/- 80 vs. 1220 +/- 101 mL/min.1.73 m2; P < 0.02), but was without effect during high sodium intake. DOM had no effect on prostacyclin excretion at any level of salt intake. These results suggest that both DA1 and DA2 are activated in renal vessels by DA, and that DA2 receptors play a role in the renal vasodilating action of DA. Changes in sodium balance alter the actions of the two receptors (DA1 and DA2) in a coordinated fashion in the regulation of RBF.

Adult↗