bluuebunny/crossref_metadata_2025 huggingface dataset:
Exercise causes blood glutathione oxidation in chronic obstructive pulmonary disease: prevention by O2 therapy
Authors: Viña José , Servera Emilio , Asensi Miguel , Sastre Juan , Pallardó Federico V. , Ferrero José A. , García-De-La-Asunción José , Antón Vicente , Marín Julio
Published: December 2017

Viña, José, Emilio Servera, Miguel Asensi, Juan Sastre, Federico V. Pallardó, José A. Ferrero, JoséGarcı́a-de-la-Asunción, Vicente Antón, and Julio Marı́n. Exercise causes blood glutathione oxidation in chronic obstructive pulmonary disease: prevention by O2therapy. J. Appl. Physiol. 81(5): 2199–2202, 1996.—The aim of the present study was to determine whether glutathione oxidation occurs in chronic obstructive pulmonary disease (COPD) patients who perform exercise and whether this could be prevented. Blood glutathione red-ox ratio [oxidized-to-reduced glutathione (GSSG/GSH)] was significantly increased when patients performed exercise for a short period of time until exhaustion. Their resting blood GSSG/GSH was 0.039 ± 0.008 (SD) ( n = 5), whereas after exercise it increased to 0.085 ± 0.019, P < 0.01. Glutathione oxidation associated with exercise was partially prevented by oxygen therapy (resting value: 0.037 ± 0.014, n = 5; after exercise: 0.047 ± 0.016, n = 5, P < 0.01). We conclude that light exercise causes an oxidation of glutathione in COPD patients, which can be partially prevented by oxygen therapy.
Chest wall muscle cross talk in canine costal diaphragm electromyogram
Authors: Sinderby C. , Friberg S. , Comtois N. , Grassino A.
Published: December 2017

Sinderby, C., S. Friberg, N. Comtois, and A. Grassino.Chest wall muscle cross talk in the canine costal diaphragm electromyogram. J. Appl. Physiol.81(5): 2312–2327, 1996.—The present paper describes the influence of cross talk from the abdominal and intercostal muscles on the canine diaphragm electromyogram (EMG). The diaphragm EMG was recorded with bipolar surface electrodes placed on the costal portion of the diaphragm (abdominal side), aligned in the fiber direction, and positioned in a region with a relatively low density of motor end plates. The results indicated that cross talk may occur in the diaphragm EMG, especially during conditions of loaded breathing and light general anesthesia. The cross-talk signals showed characteristics that were entirely different from the diaphragm EMG. Although the diaphragm EMG was typical for signals recorded with electrodes aligned in the fiber direction, the cross-talk signals were characteristic of those obtained with electrode pairs not aligned in the direction of the muscle fibers. Alterations in electrode positioning, interelectrode distance, and/or electrode surface area cannot guarantee the elimination of cross-talk signals, whereas spinal anesthesia at a high thoracic level will paralyze the sources of the cross talk and hence eliminate the cross-talk signals. By taking advantage of the differences in EMG signal characteristics for the diaphragm EMG and cross-talk signals, an index that has the capability to detect cross talk was developed.
Noxious stimuli do not determine reflex cardiorespiratory effects in anesthetized rabbits
Authors: Raimondi G. , Legramante J. M. , Iellamo F. , Frisardi G. , Cassarino S. , Peruzzi G.
Published: December 2017

Raimondi, G., J. M. Legramante, F. Iellamo, G. Frisardi, S. Cassarino, and G. Peruzzi. Noxious stimuli do not determine reflex cardiorespiratory effects in anesthetized rabbits. J. Appl. Physiol. 81(6): 2421–2427, 1996.—The main purpose of this study is to examine whether the stimulation of an exclusively pain-sensing receptive field (dental pulp) could determine cardiorespiratory effects in animals in which the cortical integration of the peripheral information is abolished by deep anesthesia. In 15 anesthetized (α-chloralose and urethan) rabbits, low (3-Hz)- and high-frequency (100-Hz) electrical dental pulp stimulation was performed. Because this stimulation caused dynamic and static reflex contractions of the digastric muscles leading to jaw opening [jaw-opening reflex (JOR); an indirect sign of algoceptive fiber activation], experimentally induced direct dynamic and static contractions of the digastric muscle were also performed. The low- and high-frequency stimulation of the dental pulp determined cardiovascular [systolic arterial pressure (SAP): −21.7 ± 4.6 and 10.8 ± 4.7 mmHg, respectively] and respiratory [pulmonary ventilation (V˙e): 145.1 ± 44.9 and 109.3 ± 28.4 ml /min, respectively] reflex responses similar to those observed during experimentally induced dynamic (SAP: −17.5 ± 4.2 mmHg;V˙e: 228.0 ± 58.5 ml /min) and static (SAP: 5.8 ± 1.5 mmHg;V˙e: 148.0 ± 75.3 ml /min) muscular contractions. The elimination of digastric muscular contraction (JOR) obtained by muscular paralysis did away with the cardiovascular changes induced by dental pulp stimulation, the effectiveness of which in stimulating dental pulp receptors has been shown by recording trigeminal-evoked potentials in six additional rabbits. The main conclusion was that, in deeply anesthetized animals, an algesic stimulus is unable to determine cardiorespiratory effects, which appear to be exclusively linked to the stimulation of ergoreceptors induced by muscular contraction.
Effect of furosemide on hyperpnea-induced airway obstruction, injury, and microvascular leakage
Authors: Freed Arthur N. , Taskar Varsha , Schofield Brian , Omori Chiharu
Published: December 2017

Freed, Arthur N., Varsha Taskar, Brian Schofield, and Chiharu Omori. Effect of furosemide on hyperpnea-induced airway obstruction, injury, and microvascular leakage. J. Appl. Physiol. 81(6): 2461–2467, 1996.—Furosemide attenuates hyperpnea-induced airway obstruction (HIAO) in asthmatic subjects via unknown mechanism(s). We studied the effect of furosemide on dry air-induced bronchoconstriction, mucosal injury, and bronchovascular hyperpermeability in a canine model of exercise-induced asthma. Peripheral airway resistance (Rp) was recorded before and after a 2-min dry-air challenge (DAC) at 2,000 ml/min. After pretreatment with aerosolized saline containing 0.75% dimethyl sulfoxide, DAC increased Rp 72 ± 11% (SE, n = 7) above baseline; aerosolized furosemide (10−3M) reduced this response by ∼50 ± 6% ( P < 0.01). To assess bronchovascular permeability, colloidal carbon was injected (1 ml/kg iv) 1 min before DAC, and after 1 h, the vehicle- and furosemide-treated airways were prepared for morphometric analysis. Light microscopy confirmed previous studies showing that DAC damaged the airway epithelium and enhanced bronchovascular permeability. Furosemide did not inhibit dry air-induced mucosal injury or bronchovascular hyperpermeability and in fact tended to increase airway damage and vascular leakage. This positive trend toward enhanced bronchovascular permeability in DAC canine peripheral airways is consistent with the hypothesis that furosemide inhibits HIAO in part by enhancing microvascular leakage and thus counterbalancing the evaporative water loss that occurs during hyperpnea.
Muscular blood flow response to submaximal leg exercise in normal subjects and in patients with heart failure
Authors: Isnard Richard , Lechat Philippe , Kalotka Hanna , Chikr Hafida , Fitoussi Serge , Salloum Joseph , Golmard Jean-Louis , Thomas Daniel , Komajda Michel
Published: December 2017

Isnard, Richard, Philippe Lechat, Hanna Kalotka, Hafida Chikr, Serge Fitoussi, Joseph Salloum, Jean-Louis Golmard, Daniel Thomas, and Michel Komajda. Muscular blood flow response to submaximal leg exercise in normal subjects and in patients with heart failure. J. Appl. Physiol. 81(6): 2571–2579, 1996.—Blood flow to working skeletal muscle is usually reduced during exercise in patients with congestive heart failure. An intrinsic impairment of skeletal muscle vasodilatory capacity has been suspected as a mechanism of this muscle underperfusion during maximal exercise, but its role during submaximal exercise remains unclear. Therefore, we studied by transcutaneous Doppler ultrasonography the arterial blood flow in the common femoral artery at rest and during a submaximal bicycle exercise in 12 normal subjects and in 30 patients with heart failure. Leg blood flow was lower in patients than in control subjects at rest [0.29 ± 0.14 (SD) vs. 0.45 ± 0.14 l/min, P < 0.01], at absolute powers and at the same relative power (2.17 ± 1.06 vs. 4.39 ± 1.4 l/min, P< 0.001). Because mean arterial pressure was maintained, leg vascular resistance was higher in patients than in control subjects at rest (407 ± 187 vs. 247 ± 71 mmHg ⋅ l−1 ⋅ min, P < 0.01) and at the same relative power (73 ± 49 vs. 31 ± 13 mmHg ⋅ l−1 ⋅ min, P < 0.01) but not at absolute powers. Although the magnitude of increase in leg blood flow corrected for power was similar in both groups (31 ± 10 vs. 34 ± 10 ml ⋅ min−1 ⋅ W−1), the magnitude of decrease of leg vascular resistance corrected for power was higher in patients than in control subjects (5.9 ± 3.3 vs. 1.9 ± 0.94 mmHg ⋅ l−1 ⋅ min ⋅ W−1, P < 0.001). These results suggest that the ability of skeletal muscle vascular resistance to decrease is not impaired and that intrinsic vascular abnormalities do not limit vasodilator response to submaximal exercise in patients with heart failure.
Arousal pattern following central and obstructive breathing abnormalities in infants and children
Authors: McNamara Frances , Issa Faiq G. , Sullivan Colin E.
Published: December 2017

McNamara, Frances, Faiq G. Issa, and Colin E. Sullivan.Arousal pattern following central and obstructive breathing abnormalities in infants and children. J. Appl. Physiol. 81(6): 2651–2657, 1996.—We analyzed the polysomnographic records of 15 children and 20 infants with obstructive sleep apnea (OSA) to examine the interaction between central and obstructive breathing abnormalities and arousal from sleep. Each patient was matched for age with an infant or child who had no OSA. We found that the majority of respiratory events in infants and children was not terminated with arousal. In children, arousals terminated 39.3 ± 7.2% of respiratory events during quiet sleep and 37.8 ± 7.2% of events during active (rapid-eye-movement) sleep. In infants, arousals terminated 7.9 ± 1.0% of events during quiet sleep and 7.9 ± 1.2% of events during active sleep. In both infants and children, however, respiratory-related arousals occurred more frequently after obstructive apneas and hypopneas than after central events. Spontaneous arousals occurred in all patients with OSA during quiet and active sleep. The frequency of spontaneous arousals was not different between children with OSA and their matched controls. During active sleep, however, infants with OSA had significantly fewer spontaneous arousals than did control infants. We conclude that arousal is not an important mechanism in the termination of respiratory events in infants and children and that electroencephalographic criteria are not essential to determine the clinical severity of OSA in the pediatric population.
Sodium alterations in isolated rat heart during cardioplegic arrest
Authors: Schepkin V. D. , Choy I. O. , Budinger T. F.
Published: December 2017

Schepkin, V. D., I. O. Choy, and T. F. Budinger. Sodium alterations in isolated rat heart during cardioplegic arrest. J. Appl. Physiol. 81(6): 2696–2702, 1996.—Triple-quantum-filtered (TQF) Na nuclear magnetic resonance (NMR) without chemical shift reagent is used to investigate Na derangement in isolated crystalloid perfused rat hearts during St. Thomas cardioplegic (CP) arrest. The extracellular Na contribution to the NMR TQF signal of a rat heart is found to be 73 ± 5%, as determined by wash-out experiments at different moments of ischemia and reperfusion. With the use of this contribution factor, the estimated intracellular Na ([Na+]i) TQF signal is 222 ± 13% of preischemic level after 40 min of CP arrest and 30 min of reperfusion, and the heart rate pressure product recovery is 71 ± 8%. These parameters are significantly better than for stop-flow ischemia: 340 ± 20% and 6 ± 3%, respectively. At 37°C, the initial delay of 15 min in [Na+]igrowth occurs during CP arrest along with reduced growth later (∼4.0%/min) in comparison with stop-flow ischemia (∼6.7%/min). The hypothermia (21°C, 40 min) for the stop-flow ischemia and CP dramatically decreases the [Na+]igain with the highest heart recovery for CP (∼100%). These studies confirm the enhanced sensitivity of TQF NMR to [Na+]iand demonstrate the potential of NMR without chemical shift reagent to monitor [Na+]iderangements.
Whole body sweat collection in humans: an improved method with preliminary data on electrolyte content
Authors: Shirreffs S. M. , Maughan R. J.
Published: December 2017

Shirreffs, S. M., and R. J. Maughan. Whole body sweat collection in humans: an improved method with preliminary data on electrolyte content. J. Appl. Physiol.82(1): 336–341, 1997.—Previous methods used to collect human sweat for electrolyte analysis have been criticized because they involve only regional sampling or because of methodological problems associated with whole body-washdown techniques. An improved method for collection of whole body sweat from exercising subjects is described. It involved construction of a plastic frame that supports a large plastic bag within which the subject exercises. The subject and the equipment are washed with distilled, deionized water before exercise begins. After exercise is completed, the subject and equipment are again washed with water containing a marker not present in sweat (ammonium sulfate). Total sweat loss is calculated from the change in body mass, and the volume of sweat not evaporated is calculated from dilution of the added marker. Recovery of added water was 102 ± 2% (SD) of the added volume, and recovery of added electrolytes was 99 ± 2% for sodium, 98 ± 9% for potassium, and 101 ± 4% for chloride. Repeated trials ( n = 4) on five subjects to establish the reproducibility of the method gave a coefficient of variation of 17 ± 5% for sodium, 23 ± 6% for potassium, and 15 ± 6% for chloride. These values include the biological variability between trials as well as the error within the method. The biological variability thus appears to be far greater than the methodological error. Normal values for the composition of sweat induced by exercise in a hot, humid environment in healthy young men and women were (in mM) 50.8 ± 16.5 sodium, 4.8 ± 1.6 potassium, 1.3 ± 0.9 calcium, 0.5 ± 0.5 magnesium, and 46.6 ± 13.1 chloride.
Muscle capillarization, O2diffusion distance, and V˙o 2kinetics in old and young individuals
Authors: Chilibeck P. D. , Paterson D. H. , Cunningham D. A. , Taylor A. W. , Noble E. G.
Published: December 2017

Chilibeck, P. D., D. H. Paterson, D. A. Cunningham, A. W. Taylor, and E. G. Noble. Muscle capillarization, O2 diffusion distance, andV˙o 2 kinetics in old and young individuals. J. Appl. Physiol.82(1): 63–69, 1997.—The relationships between muscle capillarization, estimated O2diffusion distance from capillary to mitochondria, and O2 uptake (V˙o 2) kinetics were studied in 11 young (mean age, 25.9 yr) and 9 old (mean age, 66.0 yr) adults. V˙o 2kinetics were determined by calculating the time constants (τ) for the phase 2V˙o 2 adjustment to and recovery from the average of 12 repeats of a 6-min, moderate-intensity plantar flexion exercise. Muscle capillarization was determined from cross sections of biopsy material taken from lateral gastrocnemius. Young and old groups had similarV˙o 2 kinetics (τV˙o 2-on = 44 vs. 48 s; τV˙o 2-off = 33 vs. 44 s, for young and old, respectively), muscle capillarization, and estimated O2 diffusion distances. Muscle capillarization, expressed as capillary density or average number of capillary contacts per fiber/average fiber area, and the estimates of diffusion distance were significantly correlated toV˙o 2-off kinetics in the young ( r = −0.68 to −0.83; P < 0.05). We conclude that 1) capillarization andV˙o 2 kinetics during exercise of a muscle group accustomed to everyday activity (e.g., walking) are well maintained in old individuals, and 2) in the young, recovery ofV˙o 2 after exercise is faster, with a greater capillary supply over a given muscle fiber area or shorter O2 diffusion distances.
Diaphragm interference pattern EMG and compound muscle action potentials: effects of chest wall configuration
Authors: Beck Jennifer , Sinderby Christer , Lindström Lars , Grassino Alex
Published: December 2017

Beck, Jennifer, Christer Sinderby, Lars Lindström, and Alex Grassino. Diaphragm interference pattern EMG and compound muscle action potentials: effects of chest wall configuration. J. Appl. Physiol. 82(2): 520–530, 1997.—The effect of chest wall configuration on the diaphragm electromyogram (EMGdi) was evaluated in five healthy subjects with an esophageal electrode for both interference pattern EMGdi (voluntary contractions) and electrically evoked diaphragm compound muscle action potentials (CMAPs). Diaphragm CMAPs (both unilateral and bilateral) were evaluated for the baseline-to-peak amplitude (Ampl), the time from the onset of the CMAP to first peak (T1), root mean square (RMS), and center frequency (CF) values of the CMAP power spectrum. CF values from the interference pattern EMGdi power spectrum were also calculated. For CMAPs obtained at an electrode position least influenced by variations induced by electrode positioning, Ampl increased with diaphragm shortening from functional residual capacity (FRC) to total lung capacity (TLC) by 101 and 98% (unilateral and bilateral, respectively). Bilateral CMAP RMS values increased 116% from FRC to TLC. CMAP T1 values decreased with diaphragm shortening from FRC to TLC by 1.1 and 2.1 ms for the unilateral and bilateral stimulations, respectively, and CF increased for the bilateral diaphragm CMAPs with diaphragm shortening. CF values from the interference pattern EMGdi did not show any consistent change with chest wall configuration. Thus CF values of the interference pattern EMGdi obtained with an esophageal electrode can be considered reliable for physiological interpretation, at any diaphragm length (if electrode positioning and signal contamination are controlled for), contrary to the diaphragm CMAPs, which are sensitive to changes in chest wall configuration. It is speculated that the different results (over the effects of chest wall configuration on interference pattern EMGdi and diaphragm CMAPs) may be because of summation properties of the signals and how these influence the EMG power spectrum.
Quantitative analysis of transpleural flux in the isolated lung
Authors: Li M. H. , Hildebrandt J. , Hlastala M. P.
Published: December 2017

Li, M. H., J. Hildebrandt, and M. P. Hlastala.Quantitative analysis of transpleural flux in the isolated lung. J. Appl. Physiol. 82(2): 545–551, 1997.—In this study, the loss of inert gas through the pleura of an isolated ventilated and perfused rabbit lung was assessed theoretically and experimentally. A mathematical model was used to represent an ideal homogeneous lung placed within a box with gas flow (V˙box) surrounding the lung. The alveoli are assumed to be ventilated with room air (V˙a) and perfused at constant flow (Q˙) containing inert gases ( x) with various perfusate-air partition coefficients (λp, x ). The ratio of transpleural flux of gas (V˙pl x ) to its total delivery to the lung via pulmonary artery (V˙ v), representing fractional losses across the pleura, can be shown to depend on four dimensionless ratios: 1) λp, x , 2) the ratio of alveolar ventilation to perfusion (V˙a/Q˙), 3) the ratio of the pleural diffusing capacity (Dpl x ) to the conductance of the alveolar ventilation (Dpl x /V˙aβg, where βg is the capacitance coefficient of gas), and 4) the ratio of extrapleural (box) ventilation to alveolar ventilation (V˙box/V˙a). Experiments were performed in isolated perfused and ventilated rabbit lungs. The perfusate was a buffer solution containing six dissolved inert gases covering the entire 105-fold range of λp, x used in the multiple inert gas elimination technique. Steady-state inert gas concentrations were measured in the pulmonary arterial perfusate, pulmonary venous effluent, exhaled gas, and box effluent gas. The experimental data could be described satisfactorily by the single-compartment model. It is concluded that a simple theoretical model is a useful tool for predicting transpleural flux from isolated lung preparations, with known ventilation and perfusion, for inert gases within a wide range of λ.
Effect of running intensity on intestinal permeability
Authors: Pals Kay L. , Chang Ray-Tai , Ryan Alan J. , Gisolfi Carl V.
Published: December 2017

Pals, Kay L., Ray-Tai Chang, Alan J. Ryan, and Carl V. Gisolfi. Effect of running intensity on intestinal permeability. J. Appl. Physiol. 82(2): 571–576, 1997.—Enhanced intestinal permeability has been associated with gastrointestinal disorders in long-distance runners. The primary purpose of this study was to evaluate the effect of running intensity on small intestinal permeability by using the lactulose and rhamnose differential urinary excretion test. Secondary purposes included assessing the relationship between small intestinal permeability and gastrointestinal symptoms and evaluating gastric damage by using sucrose as a probe. Six healthy volunteers [5 men, 1 woman; age = 30 ± 2 yr; peak O2 uptake (V˙o 2 peak) = 57.7 ± 2.1 ml ⋅ kg−1 ⋅ min−1] rested or performed treadmill exercise at 40, 60, or 80%V˙o 2 peakfor 60 min in a moderate environment (22°C, 50% relative humidity). At 30 min into rest or exercise, the permeability test solution (5 g sucrose, 5 g lactulose, 2 g rhamnose in 50 ml water; ∼800 mosM) was ingested. Urinary excretion rates (6 h) of the lactulose-to-rhamnose ratio were used to assess small intestinal permeability, and concentrations of each probe were determined by using high-performance liquid chromatography. Running at 80%V˙o 2 peakincreased ( P < 0.05) small intestinal permeability compared with rest, 40, and 60%V˙o 2 peakwith mean values expressed as percent recovery of ingested dose of 0.107 ± 0.021 (SE), 0.048 ± 0.009, 0.056 ± 0.005, and 0.064 ± 0.010%, respectively. Increases in small intestinal permeability did not result in a higher prevalence of gastrointestinal symptoms, and urinary recovery of sucrose did not reflect increased gastric permeability. The significance and mechanisms involved in increased small intestinal permeability after high-intensity running merit further investigation.
Muscle chemoreflex alters carotid sinus baroreflex response in humans
Authors: Papelier Y. , Escourrou P. , Helloco F. , Rowell L. B.
Published: December 2017

Papelier, Y., P. Escourrou, F. Helloco, and L. B. Rowell.Muscle chemoreflex alters carotid sinus baroreflex response in humans. J. Appl. Physiol. 82(2): 577–583, 1997.—The arterial baroreflex opposes pressor responses to muscle ischemia (muscle chemoreflex). Our experiments sought to quantify the unknown effects of muscle chemoreflex on carotid sinus baroreflex (CSB) sensitivity. We generated CSB stimulus-response (S-R) curves by pulsatile application (triggered by each electrocardiogram R wave) of positive and negative neck pressure (from 60 to −80 mmHg in 20-mmHg steps of 20 s each) in seven normal young men. S-R curves were obtained at rest (upright), during the last 3 min of upright cycle ergometer exercise (150 W), and at the first minute of postexercise recovery with leg circulation free (control). A second study repeated the same procedures, except that leg circulation was occluded 20 s before the end of exercise to elicit muscle chemoreflex, and occlusion was maintained during recovery measurements (∼3- to 4-min duration). S-R curves for CSB were shifted upward and rightward (25 mmHg) to higher arterial blood pressure (BP) by exercise and less so (10 mmHg) in recovery (free leg flow). Postexercise occlusion (muscle chemoreflex) raised BP and shifted S-R curves above exercise curves. CSB gain rose from −0.26 ± 0.06 (control) to −0.44 ± 0.08 (occlusion) during positive neck pressure application and was reduced from −0.14 ± 0.04 to zero (−0.04 ± 0.03) during negative neck pressure. Heart rate responses during postexercise muscle chemoreflex were not significantly different from control. Results reveal a nonlinear summation of CSB and muscle chemoreflex effects on BP. BP-raising capability of muscle chemoreflex enhances CSB responses to hypotension but overpowers baroreflex opposition to hypertension.
Pulmonary blood flow distribution has a hilar-to-peripheral gradient in awake, prone sheep
Authors: Walther Sten M. , Domino Karen B. , Glenny Robb W. , Polissar Nayak L. , Hlastala Michael P.
Published: December 2017

Walther, Sten M., Karen B. Domino, Robb W. Glenny, Nayak L. Polissar, and Michael P. Hlastala. Pulmonary blood flow distribution has a hilar-to-peripheral gradient in awake, prone sheep. J. Appl. Physiol. 82(2): 678–685, 1997.—We examined the pulmonary blood flow distribution with intravenous fluorescent microspheres (15 μm) in nine prone, unanesthetized, lambs. Lungs flushed free of blood were air-dried at total lung capacity and sectioned into ∼2-cm3 pieces. The pieces were weighed, identified by lobe, and assigned spatial coordinates. Fluorescence was read on a spectrophotometer, and signals were corrected for piece weight and normalized to mean flow. Pulmonary blood flow heterogeneity was assessed by using the coefficient of variation of the flow data. The number of pieces (±SD) analyzed were 1,249 ± 150/animal. Heterogeneity of blood flow was 29.5 ± 6.5% (coefficient of variation = SD/mean). Pulmonary blood flow decreased with distance from hilus ( P < 0.002) but did not change significantly with vertical height. Distance from the hilus was the best predictor of pulmonary blood flow ( R 2 = 0.201) and, together with spatial coordinates and lobe, accounted for 33.7 ± 12.0% of blood flow variability. We conclude that pulmonary blood flow in the awake, prone sheep is distributed with a hilar-to-peripheral gradient but no significant vertical gradient.
Mechanomyographic responses to maximal eccentric isokinetic muscle actions
Authors: Smith Douglas B. , Housh , Terry J. , Stout Jeffrey R. , Johnson Glen O. , Evetovich Tammy K. , Ebersole Kyle T.
Published: December 2017

Smith, Douglas B., Terry J. Housh, Jeffrey R. Stout, Glen O. Johnson, Tammy K. Evetovich, and Kyle T. Ebersole.Mechanomyographic responses to maximal eccentric isokinetic muscle actions. J. Appl. Physiol. 82(3): 1003–1007, 1997.—The purpose of the present investigation was to examine the mechanomyographic (MMG) responses to maximal eccentric isokinetic muscle actions. Eight adult male volunteers [age 22 ± 2 (SD) yr] performed maximal eccentric muscle actions of the leg extensors at 60, 90, 120, and 180°/s on a Cybex 6000 isokinetic dynamometer. MMG was detected by a piezoelectric crystal contact sensor placed over the vastus lateralis muscle. Test-retest intraclass correlations ranged from R= 0.88 to 0.97 for peak torque and from R = 0.97 to 0.98 for root mean square MMG amplitude values. There was no significant ( P > 0.05) velocity-related change in eccentric peak torque; however, there was a significant ( P < 0.05) increase in MMG between 60 [119 ± 44 (SE) mV] and 180°/s (302 ± 128 mV). These findings indicated a velocity-related dissociation between MMG and peak torque for maximal eccentric isokinetic muscle actions.
Human respiratory input impedance between 32 and 800 Hz, measured by interrupter technique and forced oscillations
Authors: Frey Urs , Suki Bela , Kraemer Richard , Jackson Andrew C.
Published: December 2017

Frey, Urs, Bela Suki, Richard Kraemer, and Andrew C. Jackson. Human respiratory input impedance between 32 and 800 Hz, measured by interrupter technique and forced oscillations. J. Appl. Physiol. 82(3): 1018–1023, 1997.—Respiratory input impedance (Zin) over a wide range of frequencies ( f) has been shown to be useful in determining airway resistance (Raw) and tissue resistance in dogs or airway wall properties in human adults. Zin measurements are noninvasive and, therefore, potentially useful in investigation of airway mechanics in infants. However, accurate measurements of Zin at these f values with the use of forced oscillatory techniques (FOT) in infants are difficult because of their relatively high Raw and large compliance of the face mask. If pseudorandom noise pressure oscillations generated by a loudspeaker are applied at the airway opening (FOT), the power of the resulting flow decreases inversely with f because of capacitive shunting into the volume of the gas in the speaker chamber and in the face mask. We studied whether high-frequency respiratory Zin can be measured by using rapid flow interruption [high-speed interrupter technique (HIT)], in which we expect the flow amplitude in the respiratory system to be higher than in the FOT. We compared Zin measured by HIT with Zin measured by FOT in a dried dog lung and in five healthy adult subjects. The impedance was calculated from two pressure signals measured between the mouth and the HIT valve. The impedance could be assessed from 32 to 800 Hz. Its real part at low f as well as the f and amplitude of the first and second acoustic resonance, measured by FOT and by HIT, were not significantly different. The power spectrum of oscillatory flow when the HIT was used showed amplitudes that were at least 100 times greater than those when FOT was used, increasing at f > 400 Hz. In conclusion, the HIT enables the measurement of high-frequency Zin data ranging from 32 to 800 Hz with particularly high flow amplitudes and, therefore, possibly better signal-to-noise ratio. This is particularly important in systems with high Raw, e.g., in infants, when measurements have to be performed through a face mask.
Ventilatory response to exercise in subjects breathing CO2 or HeO2
Authors: Babb T. G.
Published: December 2017

Babb, T. G. Ventilatory response to exercise in subjects breathing CO2 or HeO2. J. Appl. Physiol. 82(3): 746–754, 1997.—To investigate the effects of mechanical ventilatory limitation on the ventilatory response to exercise, eight older subjects with normal lung function were studied. Each subject performed graded cycle ergometry to exhaustion once while breathing room air; once while breathing 3% CO2-21% O2-balance N2; and once while breathing HeO2 (79% He and 21% O2). Minute ventilation (V˙e) and respiratory mechanics were measured continuously during each 1-min increment in work rate (10 or 20 W). Data were analyzed at rest, at ventilatory threshold (VTh), and at maximal exercise. When the subjects were breathing 3% CO2, there was an increase ( P < 0.001) inV˙e at rest and at VTh but not during maximal exercise. When the subjects were breathing HeO2,V˙e was increased ( P < 0.05) only during maximal exercise (24 ± 11%). The ventilatory response to exercise below VTh was greater only when the subjects were breathing 3% CO2( P < 0.05). Above VTh, the ventilatory response when the subjects were breathing HeO2 was greater than when breathing 3% CO2( P < 0.01). Flow limitation, as percent of tidal volume, during maximal exercise was greater ( P < 0.01) when the subjects were breathing CO2 (22 ± 12%) than when breathing room air (12 ± 9%) or when breathing HeO2 (10 ± 7%) ( n = 7). End-expiratory lung volume during maximal exercise was lower when the subjects were breathing HeO2 than when breathing room air or when breathing CO2( P < 0.01). These data indicate that older subjects have little reserve for accommodating an increase in ventilatory demand and suggest that mechanical ventilatory constraints influence both the magnitude of V˙eduring maximal exercise and the regulation ofV˙e and respiratory mechanics during heavy-to-maximal exercise.
High-resolution maps of regional ventilation utilizing inhaled fluorescent microspheres
Authors: Robertson H. Thomas , Glenny Robb W. , Stanford Derek , McInnes Lynn M. , Luchtel Daniel L. , Covert David
Published: December 2017

Robertson, H. Thomas, Robb W. Glenny, Derek Stanford, Lynn M. McInnes, Daniel L. Luchtel, and David Covert. High-resolution maps of regional ventilation utilizing inhaled fluorescent microspheres. J. Appl. Physiol. 82(3): 943–953, 1997.—The regional deposition of an inhaled aerosol of 1.0-μm diameter fluorescent microspheres (FMS) was used to produce high-resolution maps of regional ventilation. Five anesthetized, prone, mechanically ventilated pigs received two 10-min inhalations of pairs of different FMS labels, accompanied by intravenous injection of 15.0-μm radioactive microspheres. The lungs were air dried and cut into 1.9-cm3pieces, with notation of the spatial coordinates for each piece. After measurement of radioactive energy peaks, the tissue samples were soaked in 2-ethoxyethyl acetate, and fluorescent emission peaks were recorded for the wavelengths specific to each fluorescence label. The correlation of fluorescence activity between simultaneously administered inhaled FMS ranged from 0.98 to 0.99. The mean coefficient of variation for ventilation for all 10 trials (47.9 ± 8.1%) was similar to that for perfusion (46.2 ± 6.3%). No physiologically significant gravitational gradient of ventilation or perfusion was present in the prone animals. The strongest predictor of the magnitude of regional ventilation among all animals was regional perfusion ( r = 0.77 ± 0.13).
Multivariate genetic analysis of maximal isometric muscle force at different elbow angles
Authors: Thomis Martine A. , Van Leemputte Marc , Maes Hermine H. , Blimkie Cameron J. R. , Claessens Albrecht L. , Marchal Guy , Willems Eustachius , Vlietinck Robert F. , Beunen Gaston P.
Published: December 2017

Thomis, Martine A., Marc Van Leemputte, Hermine H. Maes, Cameron J. R. Blimkie, Albrecht L. Claessens, Guy Marchal, Eustachius Willems, Robert F. Vlietinck, and Gaston P. Beunen. Multivariate genetic analysis of maximal isometric muscle force at different elbow angles. J. Appl. Physiol. 82(3): 959–967, 1997.—The maximal isometric moment at five different elbow joint angles was measured in 25 monozygotic and 16 dizygotic male adult twin pairs (22.4 ± 3.7 yr). Genetic model fitting was used to quantify the genetic and environmental contributions to individual differences in isometric strength. Additive genetic factors explained 66–78% of the variance in maximal torque at 170–140–110 and 80° flexion (extension = 180°). At 50° flexion, common and subject-specific environmental factors contributed equally to the variation. The contribution of unique environmental factors concurs with the level of variability in muscle activation and (dis)-comfort of torque production in the specific angle. The relative contribution of lever arm and force-length relationship in torque varies according to the angle. Because these factors might be genetic, this variability is reflected in the genetic contribution at the extreme angles of 170 and 50°. Multivariate analyses suggested a general set of genes that control muscle area and isometric strength, together with a more specific strength factor. Genetic correlations were high (0.82–0.99). Genes responsible for arm-segment lengths did not contribute to muscle area nor to isometric strength.
Effect of insulin-like growth factor I and/or growth hormone on diaphragm of malnourished adolescent rats
Authors: Lewis Michael I. , Lorusso Thomas J. , Fournier Mario
Published: December 2017

Lewis, Michael I., Thomas J. LoRusso, and Mario Fournier.Effect of insulin-like growth factor I and/or growth hormone on diaphragm of malnourished adolescent rats. J. Appl. Physiol. 82(4): 1064–1070, 1997.—Young growing animals appear to have significantly reduced “nutritional reserve” to short periods of unstressed starvation compared with adults, with resultant growth arrest and/or atrophy of diaphragm (Dia) muscle fibers. The aim of this study was to assess in an adolescent rat model of acute nutritional deprivation (ND; 72 h) the impact of insulin-like growth factor I (IGF-I), with or without added growth hormone (GH), on the cross-sectional areas (CSA) of individual Dia muscle fibers. Five groups were studied: 1) control (Ctr); 2) ND; 3) ND given IGF-I (ND/IGF-I); 4) ND given GH (ND/GH); and 5) ND given a combination of IGF-I and GH (ND/IGF-I/GH). IGF-I was given by a subcutaneously implanted osmotic minipump (200 μg/day), whereas GH was administered twice daily by a subcutaneous injection (250 μg every 12 h). Isometric contractile and fatigue properties of the Dia were determined in vitro. Forces were normalized for muscle CSA (i.e., specific force). Dia fiber type proportions were determined histochemically, and fiber CSA was quantified by using a computer-based image-processing system. Total serum IGF-I concentrations were significantly reduced in ND and ND/GH animals, compared with Ctr, and elevated in the groups receiving IGF-I. The provision of growth factors did not alter the contractile or fatigue properties of ND animals. Dia fiber type proportions were similar among the groups. In ND animals, there was a significant reduction in the CSA of types I, IIa, IIx, and IIc Dia fibers compared with Ctr. The administration of IGF-I alone or in combination with GH to ND animals significantly diminished the reduction in Dia fiber size. GH alone had no effect on Dia fiber size in ND animals. We conclude that with acute ND the peripheral resistance to the action of GH appears to be bypassed by the administration of IGF-I alone or in combination with GH.
Respiratory tissue properties derived from flow transfer function in healthy humans
Authors: Tomalak W. , Peslin R. , Duvivier C.
Published: December 2017

Tomalak, W., R. Peslin, and C. Duvivier. Respiratory tissue properties derived from flow transfer function in healthy humans. J. Appl. Physiol. 82(4): 1098–1106, 1997.—Assuming homogeneity of alveolar pressure, the relationship between airway flow and flow at the chest during forced oscillation at the airway opening [flow transfer function (FTF)] is related to lung and chest wall tissue impedance (Zti): FTF = 1 + Zti/Zg, where Zg is alveolar gas impedance, which is inversely proportional to thoracic gas volume. By using a flow-type body plethysmograph to obtain flow rate at body surface, FTF has been measured at oscillation frequencies ( fos) of 10, 20, 30 and 40 Hz in eight healthy subjects during both quiet and deep breathing. The data were corrected for the flow shunted through upper airway walls and analyzed in terms of tissue resistance (Rti) and effective elastance (Eti,eff) by using plethysmographically measured thoracic gas volume values. In most subjects, Rti was seen to decrease with increasing fosand Eti,eff to vary curvilinearly with fos2, which is suggestive of mechanical inhomogeneity. Rti presented a weak volume dependence during breathing, variable in sign according to fosand among subjects. In contrast, Eti,eff usually exhibited a U-shaped pattern with a minimum located a little above or below functional residual capacity and a steep increase with decreasing or increasing volume (30–80 hPa/l2) on either side. These variations are in excess of those expected from the sigmoid shape of the static pressure-volume curve and may reflect the effect of respiratory muscle activity. We conclude that FTF measurement is an interesting tool to study Rti and Eti,eff and that these parameters have probably different physiological determinants.
Effects of nandrolone decanoate on respiratory and peripheral muscles in male and female rats
Authors: Bisschop Anja , Gayan-Ramirez Ghislaine , Rollier Hélène , Dekhuijzen P. N. Richard , Dom René , De Bock Vera , Decramer Marc
Published: December 2017

Bisschop, Anja, Ghislaine Gayan-Ramirez, Hélène Rollier, P. N. Richard Dekhuijzen, René Dom, Vera de Bock, and Marc Decramer. Effects of nandrolone decanoate on respiratory and peripheral muscles in male and female rats. J. Appl. Physiol. 82(4): 1112–1118, 1997.—Thirty male and 18 female adult rats received weekly an intramuscular injection of either saline (control; C), 1.5 mg/kg (low-dose; LD) nandrolone decanoate or 7.5 mg/kg (high-dose; HD) nandrolone decanoate during 5 wk. Compared with respective C, growth rate was stunted in male HD rats from 2 wk of treatment on, whereas it was enhanced in female LD and HD rats after 1 wk. Mass of all muscles studied varied proportionally to body weight, except for the gastrocnemius (males: 0.49 ± 0.04 vs. C: 0.52 ± 0.03%, not significant; females: 0.17 ± 0.01 vs. C: 0.15 ± 0.01%, P < 0.05). In vitro contractile and fatigue properties of the diaphragm remained unchanged, except for a decrease in twitch kinetics (time to peak tension: C, 21 ± 2; LD, 19 ± 1; HD, 19 ± 2 ms, P < 0.05; half-relaxation time: C, 26 ± 5, LD, 25 ± 5, HD, 23 ± 3 ms, P < 0.01). Histochemistry of the diaphragm and the gastrocnemius revealed a significant increase in type IIx/b dimensions. In the gastrocnemius, type I fiber dimensions also increased. A pair-fed study, including another 24 female rats, showed that the changes in oral food intake only partly accounted for the observed anabolic effects.
Effects of lung motion and tracer kinetics corrections on PET imaging of pulmonary function
Authors: Mijailovich Srboljub M. , Treppo Steven , Venegas José G.
Published: December 2017

Mijailovich, Srboljub, Steven Treppo, and José G. Venegas. Effects of lung motion and tracer kinetics corrections on PET imaging of pulmonary function. J. Appl. Physiol. 82(4): 1154–1162, 1997.—A method to assess the three-dimensional distribution of alveolar ventilation-perfusion ratio (V˙a/Q˙) by imaging the lungs with positron emission tomography (PET) during a constant-rate intravenous infusion of 13NN-labeled saline solution was developed by C. G. Rhodes, S. O. Valind, L. H. Brudin, P. E. Wollmer, T. Jones, P. D. Buckingham, and J. M. B. Hughes ( J. Appl. Physiol. 66: 1896–1904 and 1905–1913, 1989). We have modified this methodology to obtain high-resolution, low-noise PET images of local V˙a/Q˙where lung motion artifact was eliminated by respiratory gating of image collection. In addition, we have refined and implemented the methods to assess local alveolar ventilation by imaging the washout of equilibrated 13NN and local perfusion by imaging the distribution of an intravenous bolus of13NN-labeled saline solution during apnea. This paper experimentally evaluates the effect of the implemented modifications in mechanically ventilated and anesthetized dogs. We found that the lack of gating had no significant effect on the average recoveredV˙a/Q˙, but the spatial heterogeneity [pixel-by-pixel coefficient of variation squared (CV2) = SD2/mean2] was underestimated by 14%. The lack of gating during the washout underestimated the average specific ventilation by 11% and decreased the corresponding CV2 by 50%.
Comparison of magnetic and electrical phrenic nerve stimulation in assessment of phrenic nerve conduction time
Authors: Similowski Thomas , Mehiri Selma , Duguet Alexandre , Attali Valérie , Straus Christian , Derenne Jean-Philippe
Published: December 2017

Similowski, Thomas, Selma Mehiri, Alexandre Duguet, Valérie Attali, Christian Straus, and Jean-Philippe Derenne.Comparison of magnetic and electrical phrenic nerve stimulation in assessment of phrenic nerve conduction time. J. Appl. Physiol. 82(4): 1190–1199, 1997.—Cervical magnetic stimulation (CMS), a nonvolitional test of diaphragm function, is an easy means for measuring the latency of the diaphragm motor response to phrenic nerve stimulation, namely, phrenic nerve conduction time (PNCT). In this application, CMS has some practical advantages over electrical stimulation of the phrenic nerve in the neck (ES). Although normal ES-PNCTs have been consistently reported between 7 and 8 ms, data are less homogeneous for CMS-PNCTs, with some reports suggesting lower values. This study systematically compares ES- and CMS-PNCTs for the same subjects. Surface recordings of diaphragmatic electromyographic activity were obtained for seven healthy volunteers during ES and CMS of varying intensities. On average, ES-PNCTs amounted to 6.41 ± 0.84 ms and were little influenced by stimulation intensity. With CMS, PNCTs were significantly lower (average difference 1.05 ms), showing a marked increase as CMS intensity lessened. ES and CMS values became comparable for a CMS intensity 65% of the maximal possible intensity of 2.5 Tesla. These findings may be the result of phrenic nerve depolarization occurring more distally than expected with CMS, which may have clinical implications regarding the diagnosis and follow-up of phrenic nerve lesions.
Dehydration markedly impairs cardiovascular function in hyperthermic endurance athletes during exercise
Authors: José González-Alonso, , Mora-Rodríguez Ricardo , Below Paul R. , Coyle Edward F.
Published: December 2017

González-Alonso, José, Ricardo Mora-Rodrı́guez, Paul R. Below, and Edward F. Coyle.Dehydration markedly impairs cardiovascular function in hyperthermic endurance athletes during exercise. J. Appl. Physiol. 82(4): 1229–1236, 1997.—We identified the cardiovascular stress encountered by superimposing dehydration on hyperthermia during exercise in the heat and the mechanisms contributing to the dehydration-mediated stroke volume (SV) reduction. Fifteen endurance-trained cyclists [maximal O2consumption (V˙o2 max) = 4.5 l/min] exercised in the heat for 100–120 min and either became dehydrated by 4% body weight or remained euhydrated by drinking fluids. Measurements were made after they continued exercise at 71%V˙o2 maxfor 30 min while 1) euhydrated with an esophageal temperature (Tes) of 38.1–38.3°C (control); 2) euhydrated and hyperthermic (39.3°C); 3) dehydrated and hyperthermic with skin temperature (Tsk) of 34°C; 4) dehydrated with Tesof 38.1°C and Tskof 21°C; and 5) condition 4 followed by restored blood volume. Compared with control, hyperthermia (1°C Tesincrease) and dehydration (4% body weight loss) each separately lowered SV 7–8% (11 ± 3 ml/beat; P < 0.05) and increased heart rate sufficiently to prevent significant declines in cardiac output. However, when dehydration was superimposed on hyperthermia, the reductions in SV were significantly ( P< 0.05) greater (26 ± 3 ml/beat), and cardiac output declined 13% (2.8 ± 0.3 l/min). Furthermore, mean arterial pressure declined 5 ± 2%, and systemic vascular resistance increased 10 ± 3% (both P < 0.05). When hyperthermia was prevented, all of the decline in SV with dehydration was due to reduced blood volume (∼200 ml). These results demonstrate that the superimposition of dehydration on hyperthermia during exercise in the heat causes an inability to maintain cardiac output and blood pressure that makes the dehydrated athlete less able to cope with hyperthermia.