bluuebunny/crossref_metadata_2025 huggingface dataset:
Physician Gender and Patient-Centered Communication: A Critical Review of Empirical Research
Authors: Roter Debra L. , Hall Judith A.
Published: March 2004

Physician gender has stimulated a good deal of interest as a possible source of variation in the interpersonal aspects of medical practice, with speculation that female physicians are more patient-centered in their communication with patients. Our objective is to synthesize the results of two meta-analytic reviews the effects of physician gender on communication in medical visits within a communication framework that reflects patient-centeredness and the functions of the medical visit. We performed online database searches of English-language abstracts for the years 1967 to 2001 (MEDLINE, AIDSLINE, PsycINFO, and BIOETHICS), and a hand search was conducted of reprint files and the reference sections of review articles and other publications. Studies using a communication data source such as audiotape, videotape, or direct observation were identified through bibliographic and computerized searches. Medical visits with female physicians were, on average, two minutes (10%) longer than those of male physicians. During this time, female physicians engaged in significantly more communication that can be considered patient-centered. They engaged in more active partnership behaviors, positive talk, psychosocial counseling, psychosocial question asking, and emotionally focused talk. Moreover, the patients of female physicians spoke more overall, disclosed more biomedical and psychosocial information, and made more positive statements to their physicians than did the patients of male physicians. Obstetrics and gynecology may present a pattern different from that of primary care: Male physicians demonstrated higher levels of emotionally focused talk than their female colleagues. Female primary care physicians and their patients engaged in more communication that can be considered patient-centered and had longer visits than did their male colleagues. Limited studies exist outside of primary care, and gender-related practice patterns might differ in some subspecialties from those evident in primary care.
Time-Series Studies of Particulate Matter
Authors: Bell Michelle L. , Samet Jonathan M. , Dominici Francesca
Published: March 2004

Studies of air pollution and human health have evolved from descriptive studies of the early phenomena of large increases in adverse health effects following extreme air pollution episodes to time-series analyses based on the use of sophisticated regression models. In fact, advanced statistical methods are necessary to address the challenges inherent in the detection of a relatively small pollution risk in the presence of potential confounders. This paper reviews the history, methods, and findings of the time-series studies estimating health risks associated with short-term exposure to particulate matter (PM), though much of the discussion is applicable to epidemiological studies of air pollution in general. We review the critical role of epidemiological studies in setting regulatory standards and the history of PM epidemiology and time-series analysis. We also summarize recent time-series results and conclude with a discussion of current and future directions of time-series analysis of particulates, including research on mortality displacement and the resolution of results from cohort and time-series studies.
The Direct Care Worker: The Third Rail of Home Care Policy
Authors: Stone Robyn I.
Published: March 2004

Home health aides, home care workers, and personal care attendants form the core of the paid home care system, providing assistance with activities of daily living and the personal interaction that is essential to quality of life and quality of care for their clients. High turnover and long vacancy periods are costly for providers, consumers, their families, and workers themselves. In 2002, 37 states identified worker recruitment and retention as major priority issues. Demographic and economic trends do not augur well for the future availability of quality home care workers. Policymakers in the areas of health, long-term care, labor, welfare, and immigration must partner with providers, worker organizations, and researchers to identify and implement the most successful interventions for developing and sustaining this workforce at both policy and practice levels. The future of home care will depend, in large part, on this “third rail” of long-term care policy.
Elaboration of Transparent Polymeric Films Trapping Copper Ions by Complexation
Authors: Pagani Lakard Sophie , Herlem Guillaume , Lakard Boris , Herlem Michel , Gharbi Tijani , Fahys Bernard
Published: March 2004

The aim of this work was to elaborate on a thin polymeric film for coating transparent fluorine-doped tin oxide (FTO) electrode supported on a glass substrate for trapping

Cu

2
+

ions. Possible applications are the easier detection of

Cu

2
+

ions due to complexation on the FTO surface or could be the making up of electrochromic devices using copper(I)-salt based electrolytes to avoid diffusion of

Cu

2
+

ions formed at the anode toward Cu(0) deposited on the cathode. These thin polymeric films proposed here as complexing material candidates toward copper ions belong to polyalkyleneimine polymers. They were obtained by anodic electropolymerization of aliphatic polyamines (with at least two primary amino groups) such as ethylenediamine, 1,3-diaminopropane, or diethylenetriamine on FTO electrode surfaces and characterized by IR attenuated total reflectance spectroscopy. Moreover, we have shown that polyalkyleneimine-type polymers used here present good chelating properties towards

Cu

2
+

ions due to the amino groups they contain. © 2004 The Electrochemical Society. All rights reserved.
Lateral-Type Field Emission-Based Magnetic Sensor Fabricated by Electron-Beam Lithography
Authors: Lee Keekeun , Holbert Keith E.
Published: March 2004

A deflected edge emission field effect transistor (DEEFET), a hybrid solid-state and vacuum microelectronics device, was constructed with electron-beam lithography to measure magnetic fields. The fabricated DEEFET device employs an extremely sharp emitter tip, a pair of gate electrodes, and a pair of split anodes. Field emission currents were observed around an anode bias of 40 V without gate bias. As the gate potential was increased, a lower turn-on voltage (around 25 V) and a higher field emission current were observed. A comparison of the anode and gate currents showed that most of the emitted electrons are collected by the anode, and only a few electrons are lost to the gate electrode. When forward and reverse magnetic fields were applied, an emission current imbalance was measured due to electron deflection by the Lorentz force. The calculated magnetic sensitivity was 98%/tesla for a forward magnetic field of 0.5 T and 92%/tesla for the reverse magnetic field. These magnetic sensitivities are up to six or seven times higher than those from a conventional silicon-based magnetic sensor with a split drain. © 2004 The Electrochemical Society. All rights reserved.
Electrochemical Characterization of Carbon Nanotube/Nanohoneycomb Diamond Composite Electrodes for a Hybrid Anode of Li-Ion Battery and Super Capacitor
Authors: Honda K. , Yoshimura M. , Kawakita K. , Fujishima A. , Sakamoto Y. , Yasui K. , Nishio N. , Masuda H.
Published: March 2004

Carbon nanotube/nanohoneycomb diamond (CNT-NANO) composite electrodes were fabricated by introducing multiwalled carbon nanotubes into the pores of nanohoneycomb diamond of 400 nm diam using the chemical vapor deposition method. The electrochemical behavior of these electrodes was examined with cyclic voltammetry, electrochemical impedance, and galvanostatic measurements in

LiClO

4

/
propylene

carbonate electrolyte. The behavior of

Li

+

insertion into CNTs was observed in the cathodic sweep at −3.3 V (vs.

Ag
/

Ag

+

)

in CV. AC impedance measurements have indicated that at the nanohoneycomb diamond densely deposited CNTs (HD CNT-NANO), only the

Li

+

intercalation process was observed. In contrast, the nanohoneycomb diamond modified with CNTs in low-density (LD CNT-NANO) exhibited the combination behavior of

Li

+

intercalation at CNTs and the electrochemical double-layer discharging on the diamond surface. In galvanostatic measurements, HD CNT-NANO behaved as a pure

Li

+

ion battery anode, and the specific capacity (per 1 g of activated material) was found to be 894 mAh g−1, which is higher than that obtained for mesophase carbon materials. For LD CNT-NANO, in the initial time following the start of discharging, the behavior of the double-layer discharging was observed in addition to

Li

+

deintercalation. Suppression of the potential drops associated with

Li

+

deintercalation by rapid discharging from the electrical double-layer could increase the specific power for LD CNT-NANO. The combination function of the super capacitor and the

Li

+

­
ion

battery that work simultaneously supporting each other in one electrochemical cell suggests the possible realization of a hybrid electrode material with high energy density and high specific power. © 2004 The Electrochemical Society. All rights reserved.
Microneurography: how the technique developed and its role in the investigation of the sympathetic nervous system
Authors: Vallbo Åke B. , Hagbarth Karl-Erik , Wallin B. Gunnar
Published: March 2004

A historical review is given of the development of microneurography and its application for studies of sympathetic nerve activity in humans.
Hypercapnia increases core temperature cooling rate during snow burial
Authors: Grissom Colin K. , Radwin Martin I. , Scholand Mary Beth , Harmston Chris H. , Muetterties Mark C. , Bywater Tim J.
Published: March 2004

Previous retrospective studies report a core body temperature cooling rate of 3°C/h during avalanche burial. Hypercapnia occurs during avalanche burial secondary to rebreathing expired air, and the effect of hypercapnia on hypothermia during avalanche burial is unknown. The objective of this study was to determine the core temperature cooling rate during snow burial under normocapnic and hypercapnic conditions. We measured rectal core body temperature (Tre) in 12 subjects buried in compacted snow dressed in a lightweight clothing insulation system during two different study burials. In one burial, subjects breathed with a device (AvaLung 2, Black Diamond Equipment) that resulted in hypercapnia over 30-60 min. In a control burial, subjects were buried under identical conditions with a modified breathing device that maintained normocapnia. Mean snow temperature was -2.5 ± 2.0°C. Burial time was 49 ± 14 min in the hypercapnic study and 60 min in the normocapnic study ( P = 0.02). Rate of decrease in Tre was greater with hypercapnia (1.2°C/h by multiple regression analysis, 95% confidence limits of 1.1-1.3°C/h) than with normocapnia (0.7°C/h, 95% confidence limit of 0.6-0.8°C/h). In the hypercapnic study, the fraction of inspired carbon dioxide increased from 1.4 ± 1.0 to 7.0 ± 1.4%, minute ventilation increased from 15 ± 7 to 40 ± 12 l/min, and oxygen saturation decreased from 97 ± 1 to 90 ± 6% ( P < 0.01). During the normocapnic study, these parameters remained unchanged. In this study, Tre cooling rate during snow burial was less than previously reported and was increased by hypercapnia. This may have important implications for prehospital treatment of avalanche burial victims.
Diurnal variation of aldosterone and plasma renin activity: timing relation to melatonin and cortisol and consistency after prolonged bed rest
Authors: Hurwitz Shelley , Cohen Richard J. , Williams Gordon H.
Published: March 2004

Exposure to prolonged bed rest is known to induce changes in the renin-angiotensin-aldosterone system (RAAS) by way of posture, sodium and potassium balance, and stress, which may have serious consequences for patients. We focused on the diurnal variation of the RAAS by investigating changes in the levels of plasma renin activity (PRA) and aldosterone; for comparison to markers of the intrinsic pacemaker and to stress, we measured melatonin and cortisol. PRA, aldosterone, melatonin, and cortisol were measured hourly in 10 normal subjects with standardized sleep patterns, posture, and diet at baseline and after 11 days of prolonged bed rest conducted under a light-dark cycle. Circadian characteristics of hormone secretion patterns were estimated by multiple harmonic regression with excellent goodness-of-fit measures. Variability in the melatonin and cortisol patterns across subjects was minimal. Even for pulsatile hormones, this technique successfully estimated the acrophase, which was the salient feature. Baseline hormone peak times started with melatonin near the middle of the sleep period, followed by PRA, then aldosterone, and then cortisol around wake time. Prolonged bed rest did not induce significant changes in any timing characteristic of the secretion patterns. Baseline and prolonged bed rest peak times for melatonin and cortisol and amplitude characteristics for all hormones were highly correlated, indicating consistency within individuals. These data provide strong evidence that prolonged bed rest of 11 days' duration does not disrupt either the timing characteristics of the RAAS or the intrinsic pacemaker.
Effects of hypergravity on the distributions of lung ventilation and perfusion in sitting humans assessed with a simple two-step maneuver
Authors: Rohdin Malin , Sundblad Patrik , Linnarsson Dag
Published: March 2004

Increased gravity impairs pulmonary distributions of ventilation and perfusion. We sought to develop a method for rapid, simultaneous, and noninvasive assessments of ventilation and perfusion distributions during a short-duration hypergravity exposure. Nine sitting subjects were exposed to one, two, and three times normal gravity (1, 2, and 3 G) in the head-to-feet direction and performed a rebreathing and a single-breath washout maneuver with a gas mixture containing C2H2, O2, and Ar. Expirograms were analyzed for cardiogenic oscillations (COS) and for phase IV amplitude to analyze inhomogeneities in ventilation (Ar) and perfusion [CO2-to-Ar ratio (CO2/Ar)] distribution, respectively. COS were normalized for changes in stroke volume. COS for Ar increased from 1-G control to 128 ± 6% (mean ± SE) at 2 G ( P = 0.02 for 1 vs. 2 G) and 165 ± 13% at 3 G ( P = 0.002 for 2 vs. 3 G). Corresponding values for CO2/Ar were 135 ± 12% ( P = 0.04) and 146 ± 13%. Phase IV amplitude for Ar increased to 193 ± 39% ( P = 0.008) at 2 G and 229 ± 51% at 3 G compared with 1 G. Corresponding values for CO2/Ar were 188 ± 29% ( P = 0.02) and 219 ± 18%. We conclude that not only large-scale ventilation and perfusion inhomogeneities, as reflected by phase IV amplitude, but also smaller-scale inhomogeneities, as reflected by the ratio of COS to stroke volume, increase with hypergravity. Except for small-scale ventilation distribution, most of the impairments observed at 3 G had been attained at 2 G. For some of the parameters and gravity levels, previous comparable data support the present simplified method.
Pathophysiological significance of peroxidative stress, neuronal damage, and membrane permeability in acute mountain sickness
Authors: Bailey Damian M. , Kleger Gian-Reto , Holzgraefe Manfred , Ballmer Peter E. , Bärtsch Peter
Published: March 2004

Free radical-mediated changes in vascular permeability and subsequent inflammatory response may be a contributory pathogenetic cofactor responsible for the development of neurological sequelae associated with acute mountain sickness (AMS). To investigate this, 49 subjects were examined at sea level and serially after rapid ascent to 4,559 m. Although the venous concentration of total creatine phosphokinase activity was measured in all subjects, a complementary examination of lipid peroxidation (F2-isoprostanes), inflammatory (TNF-α, IL-1β, IL-2, IL-6, IL-8, C-reactive protein), and cerebrovascular tissue damage (neuron-specific enolase) biomarkers was confined to a subcohort of 24 subjects. A selective increase ( P < 0.05) in total creatine phosphokinase was observed in subjects diagnosed with AMS at high altitude ( n = 25) compared with apparently healthy controls ( n = 24). However, despite a marked increase in IL-6 and C-reactive protein attributable primarily to subjects developing high-altitude pulmonary edema, subcohort analyses demonstrated no selective differences in F2-isoprostanes, neuron-specific enolase, or remaining proinflammatory cytokines due to AMS ( n = 14). The present findings are the first to demonstrate that free radical-mediated neuronal damage of sufficient degree to be detected in the peripheral circulation does not occur and is, therefore, unlikely to be an important, initiating event that is critical for the development of AMS. The pathophysiological significance of increased sarcolemmal membrane permeability and inflammatory response, either as a cause or epiphenomenon of AMS and/or high-altitude pulmonary edema, remains to be elucidated.
Effects of voluntary exercise and genetic selection for high activity levels on HSP72 expression in house mice
Authors: Belter Jason G. , Carey Hannah V. , Garland Theodore
Published: March 2004

We studied expression of heat shock protein 72 (HSP72) in female mice from four replicate lines that had been selectively bred for high voluntary wheel running (S) and from four random-bred control lines (C). Mice from generation 23 were sampled after 6 days of wheel access, and those from generation 14 were sampled after 8 wk of access to wheels either free to rotate or locked. Mice from S lines ran ∼2.6 times as many revolutions per day as did those from C lines. Western blotting of tissues from generation 23 mice indicated that S mice had elevated HSP72 expression in triceps surae muscle, but levels in spleen, kidney, heart, and lung were similar in S and C mice. HSP72 expression in triceps surae from generation 14 mice was measured by ELISA and analyzed with a two-way analysis of covariance. The interaction between wheel type and line type (S vs. C) was statistically significant, and subsequent analyses indicated that S mice had significantly elevated HSP72 expression only when housed with free wheels. Mice with the previously described mini-muscle phenotype (Houle-Leroy P, Guderley H, Swallow JG, and Garland T Jr. Am J Physiol Regul Integr Comp Physiol 284: R433-R443, 2003) occurred in both generations and had elevated HSP72 expression in triceps surae. For the generation 23 sample, wheel running as a covariate had a significant negative association with HSP72 expression, and the effect of line type was still statistically significant. Therefore, the increased HSP72 expression of S mice is not a simple proximate effect of their increased wheel running.
Strength training reduces force fluctuations during anisometric contractions of the quadriceps femoris muscles in old adults
Authors: Tracy Brian L. , Byrnes William C. , Enoka Roger M.
Published: March 2004

The greater fluctuations in motor output that are often exhibited by old adults can be reduced with strength training. The purpose of the study was to determine the effect of strength and steadiness training by old adults on fluctuations in force and position during voluntary contractions with the quadriceps femoris muscle. Healthy old adults (65-80 yr) completed 16 wk of heavy-load (80% of maximum, n = 11) strength training, heavy-load steadiness training ( n = 6), or no training ( n = 9). Steadiness training required subjects to match the angular displacement about the knee joint to a constant-velocity template. The Heavy-Load group experienced a 5.5% increase in muscle volume, a 25% increase in maximal voluntary contraction force, and a 26% increase in the one-repetition (1-RM) load. The Heavy-Load Steady group experienced increases of 11.5, 31, and 36%, respectively. The maximal electromyogram signal of quadriceps femoris increased by 51% in the two training groups. The coefficient of variation (CV) for force during submaximal isometric contractions did not change with training for any group. Although both training groups also experienced a reduction in CV for force during anisometric contractions with a 50% 1-RM load, the standard deviation of position did not change with time for any group. The Heavy-Load Steady group also experienced a reduction in CV for force during the training contractions performed with the 80% 1-RM load. Thus strength training reduced the force fluctuations of the quadriceps femoris muscles during anisometric contractions but not during isometric contractions.
Influence of body composition on physical activity validation studies using doubly labeled water
Authors: Mâsse Louise C. , Fulton Janet E. , Watson Kathleen L. , Mahar Matthew T. , Meyers Michael C. , Wong William W.
Published: March 2004

This study investigated the influence of two approaches (mathematical transformation and statistical procedures), used to account for body composition [body mass or fat-free mass (FFM)], on associations between two measures of physical activity and energy expenditure determined by doubly labeled water (DLW). Complete data for these analyses were available for 136 African American (44.1%) and Hispanic (55.9%) women (mean age 50 ± 7.3 yr). Total energy expenditure (TEE) by DLW was measured over 14 days. Physical activity energy expenditure (PAEE) was computed as 0.90 × TEE - resting metabolic rate. During week 2, participants wore an accelerometer for 7 consecutive days and completed a 7-day diary. Pearson's product-moment correlations and three statistical procedures (multiple regressions, partial correlations, and allometric scaling) were used to assess the effect of body composition on associations. The methods-comparison analysis was used to study the effect of body composition on agreement. The statistical procedures demonstrated that associations improved when body composition was included in the model. The accelerometer explained a small but meaningful portion of the variance in TEE and PAEE after body mass was accounted for. The methods-comparison analysis confirmed that agreement with DLW was affected by the transformation. Agreement between the diary (transformed with body mass) and TEE reflected the association that exists between body mass and TEE. These results suggest that the accelerometer and diary accounted for a small portion of TEE and PAEE. Most of the variance in DLW-measured energy expenditure was explained by body mass or FFM.
Higher dietary carbohydrate content during intensified running training results in better maintenance of performance and mood state
Authors: Achten J. , Halson S. L. , Moseley L. , Rayson M. P. , Casey A. , Jeukendrup A. E.
Published: March 2004

The aim of this study was to determine whether consumption of a diet containing 8.5 g carbohydrate (CHO)·kg-1·day-1(high CHO; HCHO) compared with 5.4 g CHO·kg-1·day-1(control; Con) during a period of intensified training (IT) would result in better maintenance of physical performance and mood state. In a randomized cross-over design, seven trained runners [maximal O2uptake (V̇o2 max) 64.7 ± 2.6 ml·kg-1·min-1] performed two 11-day trials consuming either the Con or the HCHO diet. The last week of both trials consisted of IT. Performance was measured with a preloaded 8-km all-out run on the treadmill and 16-km all-out runs outdoors. Substrate utilization was measured using indirect calorimetry and continuous [U-13C]glucose infusion during 30 min of running at 58 and 77% V̇o2 max. Time to complete 8 km was negatively affected by the IT: time significantly increased by 61 ± 23 and 155 ± 38 s in the HCHO and Con trials, respectively. The 16-km times were significantly increased (by 8.2 ± 2.1%) during the Con trial only. The Daily Analysis of Life Demands of Athletes questionnaire showed significant deterioration in mood states in both trials, whereas deterioration in global mood scores, as assessed with the Profile of Mood States, was more pronounced in the Con trial. Scores for fatigue were significantly higher in the Con compared with the HCHO trial. CHO oxidation decreased significantly from 1.7 ± 0.2 to 1.2 ± 0.2 g/min over the course of the Con trial, which was completely accounted for by a decrease in muscle glycogen oxidation. These findings indicate that an increase in dietary CHO content from 5.4 to 8.5 g CHO·kg-1·day-1(41 vs. 65% total energy intake, respectively) allowed better maintenance of physical performance and mood state over the course of training, thereby reducing the symptoms of overreaching.
Historical analysis of the neural control of movement from the bedrock of animal experimentation to human studies
Authors: Matthews Peter B. C.
Published: March 2004

The history of the investigation of the sensorimotor control of movement is outlined from its inception at the beginning of the 19th century. Particular emphasis is placed on the opening up of new possibilities by the development of new techniques, from chronophotography to magnetic brain stimulation, all of which have exploited developments in technology. Extrapolating from history, future advance in physiological understanding can be guaranteed to require seizing the new tools provided by the physical sciences and refining these to our particular need. The ever-present danger is that these are then deployed with triumphal optimism rather than critical doubt and earlier methods either jettisoned prematurely or used incautiously. The new techniques have enabled experimentation to become ever less intrusive, permitting a progressive shift from animal to human work, thereby offering the prospect of an increasing clinical reward.
No α-adrenoreceptor-induced C-fiber activation in healthy human skin
Authors: Zahn Sebastian , Leis Stefan , Schick Christoph , Schmelz Martin , Birklein Frank
Published: March 2004

In healthy volunteers, flare responses induced by norepinephrine (NE) iontophoresis have been observed. However, as NE iontophoresis is a combined electrical and chemical stimulus axon, reflexes cannot be directly linked to pharmocological activity of NE. Different concentrations of NE, clonidine (CL), and phenylephrine (PE) (NE: 10-10-10-3 M; CL and PE: 10-8-10-3 M) were applied via intradermal microdialysis fibers into the skin of healthy volunteers. Simultaneously, skin blood flow was visualized by laser-Doppler imaging scans and quantified in a vasoconstriction skin area directly above the membranes to control drug effects and in expected axon reflex vasodilation areas that were 0.75 cm apart. NE, PE, and CL caused dose-dependent vasoconstriction. However, neither in the presumed axon reflex areas (quantitative analysis) nor on laser-Doppler imaging pictures (qualitative analysis) were any vasodilation observed. Even at concentrations causing maximum vasoconstriction (10-3 M for any drug), no vasodilation was induced. Our results indicate that, in healthy human skin, exogenously supplied α-adrenoreceptor agonists alone do not activate nociceptors sufficiently to induce axon reflex flare.
RhoA expression during recovery from skeletal muscle disuse
Authors: McClung J. M. , Thompson R. W. , Lowe L. L. , Carson J. A.
Published: March 2004

Functional overload and anabolic steroid administration induce signaling pathways that regulate skeletal muscle RhoA expression. The purpose of this study was to determine RhoA and associated protein expression at the onset of disuse and after a brief period of reloading. Male Sprague-Dawley rats were randomly assigned to cage control (Con), 3 days of hindlimb suspension (Sus), or 3 days of hindlimb suspension with 12 h of reloading (12-h Reload). The reloading stimuli consisted of 12 h of resumed normal locomotion after 3 days of hindlimb suspension. Plantaris muscle-to-body weight (mg/g) ratio decreased 17% from Con with Sus but returned to Con with 12-h Reload, increasing 13% from Sus. Sus decreased RhoA protein concentration 46%, whereas 12-h Reload induced a 24% increase compared with Sus. The ratio of cytosolic- to membrane-associated RhoA protein was not changed with either Sus or 12-h Reload. RhoA mRNA concentration was decreased 48% by Sus, and 12-h Reload induced a 170% increase from Sus. β1-Integrin protein, a transmembrane protein associated with RhoA activation, was not altered by Sus but increased 155% with 12-h Reload. Although β1-integrin mRNA was not altered by Sus, it increased 70% from Con with 12-h Reload. Rho family member Cdc42 protein associated with the muscle membrane was decreased 60% with Sus, and 12-h Reload induced a 172% increase compared with Sus. In conclusion, decreased RhoA protein expression and mRNA abundance are early adaptations to disuse but recover rapidly after normal locomotion is resumed.
Oxidation of exogenous glucose, sucrose, and maltose during prolonged cycling exercise
Authors: Jentjens Roy L. P. G. , Venables Michelle C. , Jeukendrup Asker E.
Published: March 2004

The purpose of the present study was to investigate whether combined ingestion of two carbohydrates (CHO) that are absorbed by different intestinal transport mechanisms would lead to exogenous CHO oxidation rates of >1.0 g/min. Nine trained male cyclists (maximal O2consumption: 64 ± 2 ml·kg body wt-1·min-1) performed four exercise trials, which were randomly assigned and separated by at least 1 wk. Each trial consisted of 150 min of cycling at 50% of maximal power output (60 ± 1% maximal O2consumption), while subjects received a solution providing either 1.8 g/min of glucose (Glu), 1.2 g/min of glucose + 0.6 g/min of sucrose (Glu+Suc), 1.2 g/min of glucose + 0.6 g/min of maltose (Glu+Mal), or water. Peak exogenous CHO oxidation rates were significantly higher ( P < 0.05) in the Glu+Suc trial (1.25 ± 0.07 g/min) compared with the Glu and Glu+Mal trials (1.06 ± 0.08 and 1.06 ± 0.06 g/min, respectively). No difference was found in (peak) exogenous CHO oxidation rates between Glu and Glu+Mal. These results demonstrate that, when a mixture of glucose and sucrose is ingested at high rates (1.8 g/min) during cycling exercise, exogenous CHO oxidation rates reach peak values of ∼1.25 g/min.
Circulating plasma VEGF response to exercise in sedentary and endurance-trained men
Authors: Kraus Raymond M. , Stallings Howard W. , Yeager Robert C. , Gavin Timothy P.
Published: March 2004

The skeletal muscle capillary supply is an important determinant of maximum exercise capacity, and it is well known that endurance exercise training increases the muscle capillary supply. The muscle capillary supply and exercise-induced angiogenesis are regulated in part by vascular endothelial growth factor (VEGF). VEGF is produced by skeletal muscle cells and can be secreted into the circulation. We investigated whether there are differences in circulating plasma VEGF between sedentary individuals (Sed) and well-trained endurance athletes (ET) at rest or in response to acute exercise. Eight ET men (maximal oxygen consumption: 63.8 ± 2.3 ml·kg-1·min-1; maximum power output: 409.4 ± 13.3 W) and eight Sed men (maximal oxygen consumption: 36.3 ± 2.1 ml·kg-1·min-1; maximum power output: 234.4 ± 13.3 W) exercised for 1 h at 50% of maximum power output. Antecubital vein plasma was collected at rest and at 0, 2, and 4 h postexercise. Plasma VEGF was measured by ELISA analysis. Acute exercise significantly increased VEGF at 0 and 2 h postexercise in ET subjects but did not increase VEGF at any time point in Sed individuals. There was no difference in VEGF between ET and Sed subjects at any time point. When individual peak postexercise VEGF was analyzed, exercise did increase VEGF independent of training status. In conclusion, exercise can increase plasma VEGF in both ET athletes and Sed men; however, there is considerable variation in the individual time of the peak VEGF response.
Temperature regulation during rest and exercise in the cold in premenarcheal and menarcheal girls
Authors: Klentrou Panagiota , Cunliffe Melora , Slack Jill , Wilk Boguslaw , Bar-Or Oded , De Souza Mary Jane , Plyley Michael
Published: March 2004

Temperature regulation during exercise in the cold was examined in 13 adolescent female individuals, aged 13-18 yr. Six girls with established menstrual cycles comprised the eumenorrheic menarcheal (EM) group, and seven nonmenstruating girls comprised the premenarcheal (PM) group. During the first visit, maximal oxygen consumption (V̇o2 max), height, weight, and percent body fat were measured. The second visit included a determination of metabolic rate in thermoneutrality (21°C), consisting of a 10-min rest period and 20 min of cycling (30% of V̇o2 max), and a cold test (5°C, 40% humidity, <0.3 m/s air velocity) involving a 20-min rest period and 40 min of cycling (30% of V̇o2 max). Subjects in the EM group were tested twice in the chamber: once during the follicular and once during the luteal phase. Heat production per kilogram in thermoneutrality and in the cold was significantly ( P < 0.05) higher in the PM compared with the EM girls. However, the PM girls had a significantly ( P < 0.05) lower core temperature in the cold than the EM group. PM girls also had a significantly higher body surface area-to-mass ratio compared with the EM girls. Although percent body fat between groups was not significantly different, within the PM group percent body fat explained 79% ( P < 0.01) of the variance in the decrease of core temperature. There were no menstrual phase-related differences in temperature regulation in either the thermoneutral or cold environment. In conclusion, menstrual phase does not influence temperature regulation in female individuals during adolescence. EM girls had lower metabolic heat production but maintained their core temperature more effectively in the cold than did the PM girls. This thermoregulatory difference between PM and EM girls is mainly a function of geometric differences with maturation-related peripheral vasoconstrictive differences maybe limiting the effectiveness of the mechanism of increased heat storage in younger female individuals.
Noninvasive assessment of sympathetic vasoconstriction in human and rodent skeletal muscle using near-infrared spectroscopy and Doppler ultrasound
Authors: Fadel Paul J. , Keller David M. , Watanabe Hitoshi , Raven Peter B. , Thomas Gail D.
Published: March 2004

The precise role of the sympathetic nervous system in the regulation of skeletal muscle blood flow during exercise has been challenging to define in humans, partly because of the limited techniques available for measuring blood flow in active muscle. Recent studies using near-infrared (NIR) spectroscopy to measure changes in tissue oxygenation have provided an alternative method to evaluate vasomotor responses in exercising muscle, but this approach has not been fully validated. In this study, we tested the hypothesis that sympathetic activation would evoke parallel changes in tissue oxygenation and blood flow in resting and exercising muscle. We simultaneously measured tissue oxygenation with NIR spectroscopy and blood flow with Doppler ultrasound in skeletal muscle of conscious humans ( n = 13) and anesthetized rats ( n = 9). In resting forearm of humans, reflex activation of sympathetic nerves with the use of lower body negative pressure produced graded decreases in tissue oxygenation and blood flow that were highly correlated ( r = 0.80, P < 0.0001). Similarly, in resting hindlimb of rats, electrical stimulation of sympathetic nerves produced graded decreases in tissue oxygenation and blood flow velocity that were highly correlated ( r = 0.93, P < 0.0001). During rhythmic muscle contraction, the decreases in tissue oxygenation and blood flow evoked by sympathetic activation were significantly attenuated ( P < 0.05 vs. rest) but remained highly correlated in both humans ( r = 0.80, P < 0.006) and rats ( r = 0.92, P < 0.0001). These data indicate that, during steady-state metabolic conditions, changes in tissue oxygenation can be used to reliably assess sympathetic vasoconstriction in both resting and exercising skeletal muscle.
Low-threshold motor unit membrane properties vary with contraction intensity during sustained activation with surface EMG visual feedback
Authors: Farina Dario , Gazzoni Marco , Camelia Federico
Published: March 2004

Single-motor unit (MU) activities were detected from the abductor pollicis and abductor digiti minimi muscles providing the subjects with visual feedback of multichannel surface electromyogram (EMG) signals. The subjects could modulate the force to observe on the surface recordings a single dominant MU and modulate its firing rate for contractions of 300 s with a noninvasive EMG feedback. The firing rate was maintained at ∼8 pulses per second [low-frequency (LF) contraction] and at ∼12 pulses per second [high-frequency (HF) contraction]. Single-MU conduction velocity (CV) decreased slightly but significantly over time, and it was possible to identify a significantly larger rate of decrease of CV during the HF with respect to the LF contractions. CV initial value significantly increased with the average firing rate, and CV values were significantly correlated to the instantaneous firing rate ( R ranging from 0.21 to 0.39). Both additional MU recruitment and substitution were observed during the contractions. The study provides evidence that 1) it is possible to follow the same MU in a hand muscle at two different intensities (HF and LF) for 300-s durations by using visual feedback of surface EMG, 2) low-threshold single-MU CV changes over time since the beginning of the contraction, and 3) it is possible to distinguish between CV changes of the same MU at slightly different firing rates. The technique provides a practical method for the noninvasive assessment of both control and membrane properties of single MUs.
Hypertrophy of chronically unloaded muscle subjected to resistance exercise
Authors: Tesch P. A. , Trieschmann J. T. , Ekberg A.
Published: March 2004

In an effort to simulate the compromised function and atrophy of lower limb muscles experienced by astronauts after spaceflight, 21 men and women age 30-56 yr were subjected to unilateral lower limb unloading for 5 wk. Whereas 10 of these subjects performed unilateral knee extensor resistance exercise (ULRE) two or three times weekly, 11 subjects (UL) refrained from training. The exercise regimen consisted of four sets of seven maximal actions, using an apparatus that offers concentric and eccentric resistance by utilizing the inertia of rotating flywheel(s). Knee extensor muscle strength was measured before and after UL and ULRE, and knee extensor and ankle plantar flexor muscle volumes were determined by means of magnetic resonance imaging. Surface electromyographic activity measured after UL inferred increased muscle use to perform a given motor task. UL induced an 8.8% decrease ( P < 0.05) in knee extensor muscle volume. After ULRE and as a result of only ∼16 min of maximal contractile activity over the 5-wk course, muscle volume increased 7.7% ( P < 0.05). Muscle strength decreased 24-32% ( P < 0.05) in response to UL. Group ULRE showed maintained ( P > 0.05) strength. Ankle plantar flexor muscle volume of the unloaded limb decreased ( P < 0.05) in both groups (UL 10.5%; ULRE 11.1%). In neither group did the right weight-bearing limb show any change ( P > 0.05) in muscle volume or strength. The results of this study provide evidence that resistance exercise not only may offset muscle atrophy but is in fact capable of promoting marked hypertrophy of chronically unloaded muscle.
Influence of carbohydrate ingestion on immune changes after 2 h of intensive resistance training
Authors: Nieman D. C. , Davis J. M. , Brown V. A. , Henson D. A. , Dumke C. L. , Utter A. C. , Vinci D. M. , Downs M. F. , Smith J. C. , Carson J. , Brown A. , McAnulty S. R. , McAnulty L. S.
Published: March 2004

Thirty strength-trained subjects were randomized to carbohydrate (CHO) or placebo (Pla) groups and lifted weights for 2 h (10 exercises, 4 sets each, 10 repetitions, with 2- to 3-min rest intervals). Subjects received 10 ml·kg-1·h-1 CHO (6%) or Pla beverages during the weight training bout. Blood, saliva, and vastus lateralis muscle biopsy samples were collected before and after exercise. Blood cell counts were determined, and plasma was analyzed for IL-6, IL-10, IL-1 receptor antagonist (IL-1ra), IL-8, and cortisol. Muscle was analyzed for glycogen content and relative gene expression of 13 cytokines (IL-1α, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12p35, IL-12p40, IL-15, IFN-γ, TNF-α) by use of real-time quantitative RT-PCR. Significant but modest increases were measured for plasma IL-6, IL-10, IL-1ra, and IL-8, but the pattern of increase did not differ between CHO and Pla groups. The rate of decrease in muscle glycogen content did not differ between CHO and Pla ( P = 0.463). Muscle cytokine mRNA was detected preexercise for IL-1β, IL-6, IL-15, IL-8, and TNF-α, and of these, IL-1β, IL-6, IL-8, and TNF-α were significantly increased after the 2-h weight training bout. The increase in mRNA (fold difference from preexercise) did not differ between CHO and Pla groups. In summary, CHO vs. Pla ingestion did not alter modest increases measured for plasma IL-6, IL-10, IL-1ra, and IL-8, and muscle gene expression for IL-1β, IL-6, IL-8, and TNF-α in strength-trained subjects lifting weights intensively for 2 h.
The extraction of neural strategies from the surface EMG
Authors: Farina Dario , Merletti Roberto , Enoka Roger M.
Published: March 2004

This brief review examines some of the methods used to infer central control strategies from surface electromyogram (EMG) recordings. Among the many uses of the surface EMG in studying the neural control of movement, the review critically evaluates only some of the applications. The focus is on the relations between global features of the surface EMG and the underlying physiological processes. Because direct measurements of motor unit activation are not available and many factors can influence the signal, these relations are frequently misinterpreted. These errors are compounded by the counterintuitive effects that some system parameters can have on the EMG signal. The phenomenon of crosstalk is used as an example of these problems. The review describes the limitations of techniques used to infer the level of muscle activation, the type of motor unit recruited, the upper limit of motor unit recruitment, the average discharge rate, and the degree of synchronization between motor units. Although the global surface EMG is a useful measure of muscle activation and assessment, there are limits to the information that can be extracted from this signal.
β2-Adrenoceptor agonist fenoterol enhances functional repair of regenerating rat skeletal muscle after injury
Authors: Beitzel Felice , Gregorevic Paul , Ryall James G. , Plant David R. , Sillence Martin N. , Lynch Gordon S.
Published: March 2004

β2-Adrenoceptor agonists such as fenoterol are anabolic in skeletal muscle, and because they promote hypertrophy and improve force-producing capacity, they have potential application for enhancing muscle repair after injury. No previous studies have measured the β2-adrenoceptor population in regenerating skeletal muscle or determined whether fenoterol can improve functional recovery in regenerating muscle after myotoxic injury. In the present study, the extensor digitorum longus (EDL) muscle of the right hindlimb of deeply anesthetized rats was injected with bupivacaine hydrochloride, which caused complete degeneration of all muscle fibers. The EDL muscle of the left hindlimb served as the uninjured control. Rats received either fenoterol (1.4 mg·kg-1·day-1) or an equal volume of saline for 2, 7, 14, or 21 days. Radioligand binding assays identified a ∼3.5-fold increase in β2-adrenoceptor density in regenerating muscle at 2 days postinjury. Isometric contractile properties of rat EDL muscles were measured in vitro. At 14 and 21 days postinjury, maximum force production (Po) of injured muscles from fenoterol-treated rats was 19 and 18% greater than from saline-treated rats, respectively, indicating more rapid restoration of function after injury. The increase in Poin fenoterol-treated rats was due to increases in muscle mass, fiber cross-sectional area, and protein content. These findings suggest a physiological role for β2-adrenoceptor-mediated mechanisms in muscle regeneration and show clearly that fenoterol hastens recovery after injury, indicating its potential therapeutic application.
Noninvasive stimulation of the human corticospinal tract
Authors: Taylor J. L. , Gandevia S. C.
Published: March 2004

Spinal tracts can be stimulated noninvasively in human subjects by passing a high-voltage stimulus between the mastoids or by magnetic stimulation over the back of the head. The stimulus probably activates the corticospinal tract at the cervicomedullary junction (pyramidal decussation) and evokes large, short-latency motor responses in the arm muscles. These responses have a large monosynaptic component. Responses in leg muscles can be elicited by cervicomedullary junction stimulation or by stimulation over the cervical or thoracic spine. Because nerve roots are more easily activated than spinal tracts, stimulus spread to motor axons can occur. Facilitation of responses by voluntary activity confirms that the responses are evoked synaptically. Stimulation of the corticospinal tract is useful in studies of central conduction and studies of the behavior of motoneurons during different tasks. It also provides an important comparison to allow interpretation of changes in responses to stimulation of the motor cortex. The major drawback to the use of electrical stimulation of the corticospinal tract is that each stimulus is transiently painful.
Continuous tracheal gas insufflation during partial liquid ventilation in juvenile rabbits with acute lung injury
Authors: Zhu Guangfa , Shaffer Thomas H. , Wolfson Marla R.
Published: March 2004

To examine the hypothesis that combined treatment with tracheal gas insufflation (TGI) and partial liquid ventilation (PLV) may improve pulmonary outcome relative to either treatment alone in acute lung injury (ALI), saline lavage lung injury was induced in 24 anesthetized, ventilated juvenile rabbits that were then randomly assigned to receive ( n = 6/group) 1) conventional mechanical ventilation (CMV) alone, 2) continuous TGI at 0.5 l/min, 3) PLV with perfluorochemical liquid, and 4) combined TGI and PLV (TGI + PLV), and subsequently ventilated with minimized pressures and tidal volume (Vt) to keep arterial Po2 (PaO2) >100 Torr and arterial Pco2 (PaCO2) at 45-60 Torr for 4 h. Gas exchange, lung mechanics, myeloperoxidase, IL-8, and histomorphometry [including expansion index (EI)] were assessed. The CMV group showed no improvement in lung mechanics and gas exchange; all treated groups had significant increases in compliance, PaO2, ventilation efficacy index (VEI), and EI, and decreases in PaCO2, oxygenation index, physiological dead space-to-Vt ratio (Vd/Vt), myeloperoxidase, and IL-8, relative to the CMV group. TGI resulted in lower peak inspiratory pressure, Vt, Vd/Vt, and greater VEI vs. PLV group; PLV resulted in greater compliance, PaO2, and EI vs. TGI. TGI + PLV resulted in decreased peak inspiratory pressure, Vt, Vd/Vt, and increased VEI compared with TGI, improved compliance and EI compared with PLV, and a further increase in PaO2 and oxygenation index and a decrease in PaCO2 vs. either treatment alone. These results indicate that combined treatment of TGI and PLV results in improved pulmonary outcome than either treatment alone in this animal model of ALI.