bluuebunny/crossref_metadata_2025 huggingface dataset:
Esophageal P CO 2 as a monitor of perfusion failure during hemorrhagic shock
Authors: Sato Yoji , Weil Max Harry , Tang Wanchun , Sun Shijie , Xie Jianlin , Bisera Joe , Hosaka Hidehiro
Published: December 2017

Sato, Yoji, Max Harry Weil, Wanchun Tang, Shijie Sun, Jianlin Xie, Joe Bisera, and Hidehiro Hosaka. Esophageal[Formula: see text] as a monitor of perfusion failure during hemorrhagic shock. J. Appl. Physiol. 82(2): 558–562, 1997.—Measurement of gastric wall [Formula: see text]([Formula: see text]) by tonometric method has emerged as an attractive option for estimating visceral perfusion during circulatory shock. However, gastric acid secretion obfuscates the tonometric measurement. We, therefore, investigated the option of measuring[Formula: see text] in the esophagus to minimize these restraints. Hemorrhagic shock was induced in five Sprague-Dawley rats, and five rats served as sham controls.[Formula: see text] was measured with an ion-sensitive field effect transistor that was surgically implanted into the gastric wall. Esophageal luminal[Formula: see text]([Formula: see text]) was measured by a second ion-sensitive field effect transistor sensor. During hemorrhagic shock, mean aortic pressure declined from 150 to 50 mmHg. Gastric blood flow decreased from 58 to 12 ml ⋅ min−1 ⋅ 100 g−1 (21% of preshock) and esophageal blood flow from 44 to 7 ml ⋅ min−1 ⋅ 100 g−1 (16% of preshock).[Formula: see text]simultaneously increased from 47 to 116 Torr and[Formula: see text] from 47 to 127 Torr. The increases in[Formula: see text] were highly correlated with increases in[Formula: see text]( r = 0.90). Esophageal tonometry may, therefore, serve as a practical alternative to gastric tonometry.
Mechanism of lobar alveolar pressure decline during forced deflation in canine regional emphysema
Authors: Mink S. N.
Published: December 2017

Mink, S. N. Mechanism of lobar alveolar pressure decline during forced deflation in canine regional emphysema. J. Appl. Physiol. 82(2): 632–643, 1997.—A canine model of unilobar papain-induced emphysema was used to examine the extent to which differences in alveolar pressures (Pa) would develop between an emphysematous right lower lobe (RLL) and normal left lower lobe (LLL) during forced vital capacity (FVC) deflation. RLL and LLL Pa(Pa RLL and Pa LLL, respectively) were measured by the alveolar capsule technique. During forced deflation, Pa and lobar flows were determined between 95 and 20% FVC. A choke point common to both lower lobes was observed at >40% FVC. The results showed that deflation compliance (C) was altered for the RLL such that <90% lobar vital capacity, CRLL > CLLL, whereas >90% lobar vital capacity, CRLL < CLLL. At 95 and 90% FVC, the initial RLL Pa decline was greater than that for the LLL ( P < 0.05). However, large differences in Pa were prevented because of the effect of interdependence of regional expiratory flow (IREF). IREF caused a relative decrease in RLL flows and increase in LLL flows that limited Pa differences. Between 80 and 50% FVC, as CRLL became greater than CLLL, and because of the initial effect of IREF, Pa RLL was ∼Pa LLL. At ≤40% FVC, without IREF, lobar differences in Pa widened. These findings indicate that IREF may affect the dynamics of flow limitation in regional lung disease.
Extended models of the ventilatory response to sustained isocapnic hypoxia in humans
Authors: Liang Pei-Ji , Bascom Daphne A. , Robbins Peter A.
Published: December 2017

Liang, Pei-Ji, Daphne A. Bascom, and Peter A. Robbins.Extended models of the ventilatory response to sustained isocapnic hypoxia in humans. J. Appl. Physiol. 82(2): 667–677, 1997.—The purpose of this study was to examine extensions of a model of hypoxic ventilatory decline (HVD) in humans. In the original model ( model I) devised by R. Painter, S. Khamnei, and P. Robbins ( J. Appl. Physiol. 74: 2007–2015, 1993), HVD is modeled entirely by a modulation of peripheral chemoreflex sensitivity. In the first extension ( model II), a more complicated dynamic is used for the change in peripheral chemoreflex sensitivity. In the second extension ( model III), HVD is modeled as a combination of both the mechanism of Painter et al. and a component that is independent of peripheral chemoreflex sensitivity. In all cases, a parallel noise structure was incorporated to describe the stochastic properties of the ventilatory behavior to remove the correlation of the residuals. Data came from six subjects from a study by D. A. Bascom, J. J. Pandit, I. D. Clement, and P. A. Robbins ( Respir. Physiol.88: 299–312, 1992). For model II, there was a significant improvement in fit for two out of six subjects. The reasons for this were not entirely clear. For model III, the fit was again significantly improved in two subjects, but in this case the subjects were those who had the most marked undershoot and recovery of ventilation at the relief of hypoxia. In these two subjects, the chemoreflex-independent component contributed ∼50% to total HVD. In the other four subjects, the chemoreflex-independent component contributed ∼10% to total HVD. It is concluded that in some subjects, but not in others, there may be a component of HVD that is independent of peripheral chemoreflex sensitivity.
Assessing total body and extracellular water from bioelectrical response spectroscopy
Authors: Siconolfi Steven F. , Gretebeck Randal J. , Wong William W. , Pietrzyk Robert A. , Suire Sheril S.
Published: December 2017

Siconolfi, Steven F., Randal J. Gretebeck, William W. Wong, Robert A. Pietrzyk, and Sheril S. Suire. Assessing total body and extracellular water from bioelectrical response spectroscopy. J. Appl. Physiol. 82(2): 704–710, 1997.—We developed and validated assessments for total body water (TBW) and extracellular water (ECW) by using two resistance values of a new electric circuit model (CM) (two resistors: a capacitor and an inductor) with or without body mass. Fluid shifts occurring after 40 min of supine rest did not decrease the validity of either estimate. CM estimates were valid; r = 0.941 to 0.969, low SE of estimates of 1.15–2.28 kg, nonsignificant mean differences (CM − dilution; %Δ = −0.4 to 1.3%) that were close to the expected measurement errors for TBW (±1%) and ECW (±5%), and Bland-Altman pairwise comparisons that showed equivalence between methods. The CM estimates of TBW and ECW had marginally better validity than the previously published bioimpedance models. The advantage of the CM model is its assessments of multiple fluid spaces and that it does not require gender-specific equations. We conclude that CM estimate of TBW is acceptable, whereas further validation is needed before the ECW estimate should be used in a clinical or research setting.
Detection of expiratory flow limitation during exercise in COPD patients
Authors: Koulouris Nickolaos G. , Dimopoulou Ioanna , Valta Päivi , Finkelstein Richard , Cosio Manuel G. , Milic-Emili J.
Published: December 2017

Koulouris, Nickolaos G., Ioanna Dimopoulou, Päivi Valta, Richard Finkelstein, Manuel G. Cosio, and J. Milic-Emili.Detection of expiratory flow limitation during exercise in COPD patients. J. Appl. Physiol. 82(3): 723–731, 1997.—The negative expiratory pressure (NEP) method was used to detect expiratory flow limitation at rest and at different exercise levels in 4 normal subjects and 14 patients with chronic obstructive pulmonary disease (COPD). This method does not require performance of forced expirations, nor does it require use of body plethysmography. It consists in applying negative pressure (−5 cmH2O) at the mouth during early expiration and comparing the flow-volume curve of the ensuing expiration with that of the preceding control breath. Subjects in whom application of NEP does not elicit an increase in flow during part or all of the tidal expiration are considered flow limited. The four normal subjects were not flow limited up to 90% of maximal exercise power output (W˙max). Five COPD patients were flow limited at rest, 9 were flow limited at one-third W˙max, and 12 were flow limited at two-thirdsW˙max. Whereas in all patients who were flow limited at rest the maximal O2uptake was below the normal limits, this was not the case in most of the other patients. In conclusion, NEP provides a rapid and reliable method to detect expiratory flow limitation at rest and during exercise.
Spatial pattern of pulmonary blood flow distribution is stable over days
Authors: Glenny Robb W. , McKinney Steven , Robertson H. Thomas
Published: December 2017

Glenny, Robb W., Steven McKinney, and H. Thomas Robertson.Spatial pattern of pulmonary blood flow distribution is stable over days. J. Appl. Physiol. 82(3): 902–907, 1997.—Despite the heterogeneous distribution of regional pulmonary perfusion over space, local perfusion remains stable over short time periods (20–100 min). The purpose of this study was to determine whether the spatial distribution of pulmonary perfusion remains stable over longer time periods (1–5 days). Regional blood flow was measured each day for 5 days in five awake standing dogs. Fluorescent microspheres of different colors were injected into a limb vein over 30 s on each day. After the last microsphere injection, the dogs were killed, and lungs were flushed free of blood, excised, dried at total lung capacity, and diced into ∼2-cm3 pieces ( n = 1,296–1,487 per dog). Relative blood flow to each piece on each day was determined by extracting the fluorescent dyes and determining the concentrations of each color. We established that blood flow is spatially heterogeneous with a coefficient of variation of 29.5 ± 2%. Blood flow to each piece is highly correlated with flow to the same piece on all days ( r = 0.930 ± 0.006). The temporal heterogeneity of regional perfusion as measured by the coefficient of variation is 6.9 ± 0.7% over the 5 days and is nonrandom. The magnitude of spatial and temporal variation is significantly less than previously reported in a study in which anesthetized and mechanically ventilated dogs were used. We conclude that spatial distribution of pulmonary blood flow remains stable over days and we speculate that in the normal awake dog regional perfusion is determined primarily by a fixed structure such as the geometry of the pulmonary vascular tree rather than by local vasoactive regulators. Anesthesia and/or mechanical ventilation may increase the temporal variability in regional perfusion.
Acute blood pressure elevation during repetitive hypocapnic and eucapnic hypoxia in rats
Authors: Bao Gang , Randhawa Preet M. , Fletcher Eugene C.
Published: December 2017

Bao, Gang, Preet M. Randhawa, and Eugene C. Fletcher.Acute blood pressure elevation during repetitive hypocapnic and eucapnic hypoxia in rats. J. Appl. Physiol. 82(4): 1071–1078, 1997.—Using a rat model, we investigated whether episodic eucapnic hypoxia was a more potent stimulus to acute blood pressure (BP) elevation and bradycardia than episodic hypocapnic hypoxia. We also investigated the role of sympathetic and parasympathetic nervous system in this cardiovascular response. Sprague-Dawley (SD) and Wistar Kyoto (WKY) rats were exposed to repetitive 30-s cycles of hypocapnic or eucapnic hypoxia before and after intravenous injection of the α1-adrenergic blocker prazosin, α2-adrenergic blocker yohimbine, or atropine. Eucapnic hypoxia caused a threefold elevation in systolic BP from baseline (83.5 ± 3.5 mmHg in WKY, 70.6 ± 4.6 mmHg in SD) and greater bradycardia (−178 ± 20 beats/min in WKY, −178 ± 21 beats/min in SD) compared with hypocapnic hypoxia (29.8 ± 3.6 mmHg and −43 ± 15 beats/min in WKY, 19.0 ± 4.1 mmHg and −45 ± 12 beats/min in SD). After prazosin, the BP increase from eucapnic hypoxia was blunted, yohimbine showed no effect, and atropine blocked the bradycardia. Direct measurement of sympathetic nerve activity confirmed that adding CO2to the hypoxic gas mixture caused a 61% increase in sympathetic nerve activity. WKY rats seem more vulnerable than SD rats to both hypoxia exposures in terms of the elevation in BP. We conclude that, in the rat, eucapnic hypoxia is a more potent stimulus to acute BP elevation and bradycardia than is hypocapnic hypoxia. An increased sympathetic tone appears to be involved in the BP response to acute episodic hypoxia.
Effect of luteal phase elevation in core temperature on forearm blood flow during exercise
Authors: Kolka Margaret A. , Stephenson Lou A.
Published: December 2017

Kolka, Margaret A., and Lou A. Stephenson. Effect of luteal phase elevation in core temperature on forearm blood flow during exercise. J. Appl. Physiol. 82(4): 1079–1083, 1997.—Forearm blood flow (FBF) as an index of skin blood flow in the forearm was measured in five healthy women by venous occlusion plethysmography during leg exercise at 80% peak aerobic power and ambient temperature of 35°C (relative humidity 22%; dew-point temperature 10°C). Resting esophageal temperature (Tes) was 0.3 ± 0.1°C higher in the midluteal than in the early follicular phase of the menstrual cycle ( P < 0.05). Resting FBF was not different between menstrual cycle phases. The Tes threshold for onset of skin vasodilation was higher (37.4 ± 0.2°C) in midluteal than in early follicular phase (37.0 ± 0.1°C; P < 0.05). The slope of the FBF to Tes relationship was not different between menstrual cycle phases (14.0 ± 4.2 ml ⋅ 100 ml−1 ⋅ min−1 ⋅ °C−1for early follicular and 16.3 ± 3.2 ml ⋅ 100 ml−1 ⋅ min−1 ⋅ °C−1for midluteal phase). Plateau FBF was higher during exercise in midluteal (14.6 ± 2.2 ml ⋅ 100 ml−1 ⋅ min−1 ⋅ °C−1) compared with early follicular phase (10.9 ± 2.4 ml ⋅ 100 ml−1 ⋅ min−1 ⋅ °C−1; P < 0.05). The attenuation of the increase in FBF to Tes occurred when Tes was 0.6°C higher and at higher FBF in midluteal than in early follicular experiments ( P < 0.05). In summary, the FBF response is different during exercise in the two menstrual cycle phases studied. After the attenuation of the increase in FBF and while Tes was still increasing, the greater FBF in the midluteal phase may have been due to the effects of increased endogenous reproductive endocrines on the cutaneous vasculature.
Pulmonary diffusing capacity and pulmonary capillary blood volume during parabolic flights
Authors: Vaïda Pierre , Kays Christian , Rivière Daniel , Téchoueyres Pierre , Lachaud Jean-Luc
Published: December 2017

Vaı̈da, Pierre, Christian Kays, Daniel Rivière, Pierre Téchoueyres, and Jean-Luc Lachaud.Pulmonary diffusing capacity and pulmonary capillary blood volume during parabolic flights. J. Appl. Physiol. 82(4): 1091–1097, 1997.—Data from the Spacelab Life Sciences-1 (SLS-1) mission have shown sustained but moderate increase in pulmonary diffusing capacity (Dl). Because of the occupational constraints of the mission, data were only obtained after 24 h of exposure to microgravity. Parabolic flights are often used to study some effects of microgravity, and we measured changes in Dl occurring at the very onset of weightlessness. Measurements of Dl, membrane diffusing capacity, and pulmonary capillary blood volume were made in 10 male subjects during the 20-s 0-G phases of parabolic flights performed by the “zero-G” Caravelle aircraft. Using the standardized single-breath technique, we measured Dl for CO and nitric oxide simultaneously. We found significant increases indl for CO (62%), in membrane diffusing capacity for CO (47%), in Dl for nitric oxide (47%), and in pulmonary capillary blood volume (71%). We conclude that major changes in the alveolar membrane gas transfers and in the pulmonary capillary bed occur at the very onset of microgravity. Because these changes are much greater than those reported during sustained microgravity, the effects of rapid transition from hypergravity to microgravity during parabolic flights remain questionable.
Body composition analysis by DEXA by using dynamically changing samarium filtration
Authors: Gotfredsen Anders , Bæksgaard Lene , Hilsted And Jannik
Published: December 2017

Gotfredsen, Anders, Lene Bæksgaard, and Jannik Hilsted.Body composition analysis by DEXA by using dynamically changing samarium filtration. J. Appl. Physiol.82(4): 1200–1209, 1997.—Dual-energy X-ray absorptiometry (DEXA) has a high accuracy for body composition analysis but is influenced by beam hardening and other error sources in the extremes of measurement. To compensate for beam hardening, the Norland XR-36 introduces a dynamically changing samarium filtration system, which depends on the current-absorber thickness. With this system we found a good agreement ( r = 0.99) between reference and measured amounts of tissue or fat percentages in a plastic phantom and in smaller (∼0.5–4 kg) and larger (∼5–20 kg) piles of tissue (ox muscle and lard). Scans of six healthy volunteers covered with combinations of beef and lard (∼5–15 kg) showed a good agreement ( r = 0.99) between reference and DEXA values of added soft tissue mass and fat percentage. We conclude that the DEXA method (and, in particular, the Norland XR-36 using dynamic filtration) has a high accuracy for body composition analysis. It has a potential for gaining status as a reference method in the future and may presently be used as a supplement to the traditional methods for body composition analysis.
Intracranial pressure dynamics in patients with acute brain damage
Authors: Ursino M. , Lodi C. A. , Rossi S. , Stocchetti N.
Published: December 2017

Ursino, M., C. A. Lodi, S. Rossi, and N. Stocchetti.Intracranial pressure dynamics in patients with acute brain damage. J. Appl. Physiol. 82(4): 1270–1282, 1997.—The time pattern of intracranial pressure (ICP) during pressure-volume index (PVI) tests was analyzed in 20 patients with severe acute brain damage by means of a simple mathematical model. In most cases, a satisfactory fitting between model response and patient data was achieved by adjusting only four parameters: the cerebrospinal fluid (CSF) outflow resistance, the intracranial elastance coefficient, and the gain and time constant of cerebral autoregulation. The correlation between the parameter estimates was also analyzed to elucidate the main mechanisms responsible for ICP changes in each patient. Starting from information on the estimated parameter values and their correlation, the patients were classified into two main classes: those with weak autoregulation (8 of 20 patients) and those with strong autoregulation (12 of 20 patients). In the first group of patients, ICP mainly reflects CSF circulation and passive cerebral blood volume changes. In the second group, ICP exhibits paradoxical responses attributable to active changes in cerebral blood volume. Moreover, in two patients of the second group, the time constant of autoregulation is significantly increased (>40 s). The correlation between the parameter estimates was significantly different in the two groups of patients, suggesting the existence of different mechanisms responsible for ICP changes. Moreover, analysis of the correlation between the parameter estimates might give information on the directions of parameter changes that have a greater impact on ICP.
Response of compressed skinned skeletal muscle fibers to conditions that simulate fatigue
Authors: Myburgh Kathryn H. , Cooke Roger
Published: December 2017

Myburgh, Kathryn H., and Roger Cooke. Response of compressed skinned skeletal muscle fibers to conditions that simulate fatigue. J. Appl. Physiol. 82(4): 1297–1304, 1997.—During fatigue, muscles become weaker, slower, and more economical at producing tension. Studies of skinned muscle fibers can explain some but not all of these effects, and, in particular, they are less economical in conditions that simulate fatigue. We investigated three factors that may contribute to the different behavior of skinned fibers. 1) Skinned fibers have increased myofilament lattice spacing, which is reversible by osmotic compression. 2) A myosin subunit becomes phosphorylated during fatigue. 3) Inosine 5′-monophosphate (IMP) accumulates during fatigue. We tested the response of phosphorylated and unphosphorylated single skinned fibers (isometric tension, contraction velocity, and adenosinetriphosphatase activity) to changes in lattice spacing (0–5% dextran) and IMP (0–5 mM) in the presence of altered concentrations of Pi(3–25 mM), H+(pH 7–6.2), and ADP (0–5 mM). The response of maximally activated skinned fibers to the direct metabolites of ATP hydrolysis is not altered by osmotic compression, phosphorylating myosin subunits, or increasing IMP concentration. These factors, therefore, do not explain the discrepancy between intact and skinned fibers during fatigue.
Prior eccentric contractions impair maximal insulin action on muscle glucose uptake in the conscious rat
Authors: Asp Sven , Watkinson Allan , Oakes Nicholas D. , Kraegen Edward W.
Published: December 2017

Asp, Sven, Allan Watkinson, Nicholas D. Oakes, and Edward W. Kraegen. Prior eccentric contractions impair maximal insulin action on muscle glucose uptake in the conscious rat. J. Appl. Physiol. 82(4): 1327–1332, 1997.—Our aim was to examine the effect of prior eccentric contractions on insulin action locally in muscle in the intact conscious rat. Anesthetized rats performed one-leg eccentric contractions through the use of calf muscle electrical stimulation followed by stretch of the active muscles. Two days later, basal and euglycemic clamp studies were conducted with the rats in the awake fasted state. Muscle glucose metabolism was estimated from 2-[14C(U)]deoxy-d-glucose andd-[3-3H] glucose administration, and comparisons were made between the eccentrically stimulated and nonstimulated (control) calf muscles. At midphysiological insulin levels, effects of prior eccentric exercise on muscle glucose uptake were not statistically significant. Maximal insulin stimulation revealed reduced incremental glucose uptake above basal ( P < 0.05 in the red gastrocnemius; P < 0.1 in the white gastrocnemius and soleus) and impaired net glycogen synthesis in all eccentrically stimulated muscles ( P < 0.05). We conclude that prior eccentric contractions impair maximal insulin action (responsiveness) on local muscle glucose uptake and glycogen synthesis in the conscious rat.
Enhancement of signal quality in esophageal recordings of diaphragm EMG
Authors: Sinderby Christer A. , Beck Jennifer C. , Lindström Lars H. , Grassino Alejandro E.
Published: December 2017

Sinderby, Christer A., Jennifer C. Beck, Lars H. Lindström, and Alejandro E. Grassino. Enhancement of signal quality in esophageal recordings of diaphragm EMG. J. Appl. Physiol. 82(4): 1370–1377, 1997.—The crural diaphragm electromyogram (EMGdi) is recorded from a sheet of muscle, the fiber direction of which is mostly perpendicular to an esophageal bipolar electrode. The region from which the action potentials are elicited, the electrically active region of the diaphragm (EARdi) and the center of this region (EARdi ctr) may vary during voluntary contractions in terms of their position with respect to an esophageal electrode. Depending on the bipolar electrode’s position with respect to the EARdi ctr, the EMGdi is filtered to different degrees. The objectives of the present study were to reduce these filtering effects on the EMGdi by developing an analysis algorithm referred to as the “double-subtraction technique.” The results showed that changes in the position of the EARdi ctr by ±5 mm with respect to the electrode pairs located 10 mm caudal and 10 mm cephalad provided a systematic variation in the EMG power spectrum center-frequency values by ±10%. The double-subtraction technique reduced the influence of movement of the EARdi ctr relative to the electrode array on EMG power spectrum center frequency and root mean square values, increased the signal-to-noise ratio by 2 dB, and increased the number of EMG samples that were accepted by the signal quality indexes by 50%.
Skeletal muscle mass and the reduction ofV˙o 2 max in trained older subjects
Authors: Proctor David N. , Joyner Michael J.
Published: December 2017

Proctor, David N., and Michael J. Joyner. Skeletal muscle mass and the reduction ofV˙o 2 max in trained older subjects. J. Appl. Physiol.82(5): 1411–1415, 1997.—The role of skeletal muscle mass in the age-associated decline in maximal O2 uptake (V˙o 2 max) is poorly defined because of confounding changes in muscle oxidative capacity and in body fat and the difficulty of quantifying active muscle mass during exercise. We attempted to clarify these issues by examining the relationship between several indexes of muscle mass, as estimated by using dual-energy X-ray absorptiometry and treadmillV˙o 2 max in 32 chronically endurance-trained subjects from four groups ( n = 8/group): young men (20–30 yr), older men (56–72 yr), young women (19–31 yr), and older women (51–72 yr).V˙o 2 max per kilogram body mass was 26 and 22% lower in the older men (45.9 vs. 62.0 ml ⋅ kg−1 ⋅ min−1) and older women (40.0 vs. 51.5 ml ⋅ kg−1 ⋅ min−1). These age differences were reduced to 14 and 13%, respectively, whenV˙o 2 max was expressed per kilogram of appendicular muscle. When appropriately adjusted for age and gender differences in appendicular muscle mass by analysis of covariance, whole bodyV˙o 2 max was 0.50 ± 0.09 l/min less ( P < 0.001) in the older subjects. This effect was similar in both genders. These findings suggest that the reducedV˙o 2 max seen in highly trained older men and women relative to their younger counterparts is due, in part, to a reduced aerobic capacity per kilogram of active muscle independent of age-associated changes in body composition, i.e., replacement of muscle tissue by fat. Because skeletal muscle adaptations to endurance training can be well maintained in older subjects, the reduced aerobic capacity per kilogram of muscle likely results from age-associated reductions in maximal O2 delivery (cardiac output and/or muscle blood flow).
Role of inhibition of nitric oxide production in monocrotaline-induced pulmonary hypertension
Authors: Mathew Rajamma , Gloster Elizabeth S. , Sundararajan T. , Thompson Carl I. , Zeballos Guillermo A. , Gewitz Michael H.
Published: December 2017

Mathew, Rajamma, Elizabeth S. Gloster, T. Sundararajan, Carl I. Thompson, Guillermo A. Zeballos, and Michael H. Gewitz. Role of inhibition of nitric oxide production in monocrotaline-induced pulmonary hypertension. J. Appl. Physiol. 82(5): 1493–1498, 1997.—Monocrotaline (MCT)-induced pulmonary hypertension (PH) is associated with impaired endothelium-dependent nitric oxide (NO)-mediated relaxation. To examine the role of NO in PH, Sprague-Dawley rats were given a single subcutaneous injection of normal saline [control (C)], 80 mg/kg MCT, or the same dose of MCT and a continuous subcutaneous infusion of 2 mg ⋅ kg−1 ⋅ day−1of molsidomine, a NO prodrug (MCT+MD). Two weeks later, plasma[Formula: see text] levels, pulmonary arterial pressure (Ppa), ratio of right-to-left ventricular weights (RV/LV) to assess right ventricular hypertrophy, and pulmonary histology were evaluated. The plasma [Formula: see text] level in the MCT group was reduced to 9.2 ± 1.5 μM ( n = 12) vs. C level of 17.7 ± 1.8 μM ( n = 8; P < 0.02). In the MCT+MD group, plasma [Formula: see text] level was 12.3 ± 2.0 μM ( n = 8). Ppa and RV/LV in the MCT group were increased compared with C [Ppa, 34 ± 3.4 mmHg ( n = 6) vs. 19 ± 0.8 mmHg ( n = 8) and 0.41 ± 0.01 ( n = 9) vs. 0.25 ± 0.008 ( n = 8), respectively; P < 0.001]. In the MCT+MD group, Ppa and RV/LV were not different when compared with C [19 ± 0.5 mmHg ( n = 5) and 0.27 ± 0.01 ( n = 9), respectively; P < 0.001 vs. MCT]. Medial wall thickness of lung vessels in the MCT group was increased compared with C [31 ± 1.5% ( n = 9) vs. 13 ± 0.66% ( n = 9); P < 0.001], and MD partially prevented MCT-induced pulmonary vascular remodeling [22 ± 1.2% ( n = 11); P < 0.001 vs. MCT and C]. These results indicate that a defect in the availability of bioactive NO may play an important role in the pathogenesis of MCT-induced PH.
Thermal and metabolic responses to cold-water immersion at knee, hip, and shoulder levels
Authors: Lee Dae T. , Toner Michael M. , McArdle William D. , Vrabas Ioannis S. , Pandolf Kent B.
Published: December 2017

Lee, Dae T., Michael M. Toner, William D. McArdle, Ioannis S. Vrabas, and Kent B. Pandolf. Thermal and metabolic responses to cold-water immersion at knee, hip, and shoulder levels. J. Appl. Physiol. 82(5): 1523–1530, 1997.—To examine the effect of cold-water immersion at different depths on thermal and metabolic responses, eight men (25 yr old, 16% body fat) attempted 12 tests: immersed to the knee (K), hip (H), and shoulder (Sh) in 15 and 25°C water during both rest (R) or leg cycling [35% peak oxygen uptake; (E)] for up to 135 min. At 15°C, rectal (Tre) and esophageal temperatures (Tes) between R and E were not different in Sh and H groups ( P > 0.05), whereas both in K group were higher during E than R ( P < 0.05). At 25°C, Tre was higher ( P < 0.05) during E than R at all depths, whereas Tes during E was higher than during R in H and K groups. Tre remained at control levels in K-E at 15°C, K-E at 25°C, and in H-E groups at 25°C, whereas Tes remained unchanged in K-E at 15°C, in K-R at 15°C, and in all 25°C conditions ( P > 0.05). During R and E, the magnitude of Tre change was greater ( P < 0.05) than the magnitude of Tes change in Sh and H groups, whereas it was not different in the K group ( P > 0.05). Total heat flow was progressive with water depth. During R at 15 and 25°C, heat production was not increased in K and H groups from control level ( P > 0.05) but it did increase in Sh group ( P < 0.05). The increase in heat production during E compared with R was smaller ( P < 0.05) in Sh (121 ± 7 W/m2 at 15°C and 97 ± 6 W/m2 at 25°C) than in H (156 ± 6 and 126 ± 5 W/m2, respectively) and K groups (155 ± 4 and 165 ± 6 W/m2, respectively). These data suggest that Tre and Tes respond differently during partial cold-water immersion. In addition, water levels above knee in 15°C and above hip in 25°C cause depression of internal temperatures mainly due to insufficient heat production offsetting heat loss even during light exercise.
Predicting body cell mass with bioimpedance by using theoretical methods: a technological review
Authors: De Lorenzo A. , Andreoli A. , Matthie J. , Withers P.
Published: December 2017

De Lorenzo, A., A. Andreoli, J. Matthie, and P. Withers.Predicting body cell mass with bioimpedance by using theoretical methods: a technological review. J. Appl. Physiol. 82(5): 1542–1558, 1997.—The body cell mass (BCM), defined as intracellular water (ICW), was estimated in 73 healthy men and women by total body potassium (TBK) and by bioimpedance spectroscopy (BIS). In 14 other subjects, extracellular water (ECW) and total body water (TBW) were measured by bromide dilution and deuterium oxide dilution, respectively. For all subjects, impedance spectral data were fit to the Cole model, and ECW and ICW volumes were predicted by using model electrical resistance terms REand RIin an equation derived from Hanai mixture theory, respectively. The BIS ECW prediction bromide dilution was r = 0.91, standard error of the estimate (SEE) 0.90 liter. The BIS TBW prediction of deuterium space was r = 0.95, SEE 1.33 liters. The BIS ICW prediction of the dilution-determined ICW was r = 0.87, SEE 1.69 liters. The BIS ICW prediction of the TBK-determined ICW for the 73 subjects was r = 0.85, SEE = 2.22 liters. These results add further support to the validity of the Hanai theory, the equation used, and the conclusion that ECW and ICW volume can be predicted by an approach based solely on fundamental principles.
Respiratory muscle work compromises leg blood flow during maximal exercise
Authors: Harms Craig A. , Babcock Mark A. , McClaran Steven R. , Pegelow David F. , Nickele Glenn A. , Nelson William B. , Dempsey Jerome A.
Published: December 2017

Harms, Craig A., Mark A. Babcock, Steven R. McClaran, David F. Pegelow, Glenn A. Nickele, William B. Nelson, and Jerome A. Dempsey.Respiratory muscle work compromises leg blood flow during maximal exercise. J. Appl. Physiol.82(5): 1573–1583, 1997.—We hypothesized that during exercise at maximal O2 consumption (V˙o 2 max), high demand for respiratory muscle blood flow (Q˙) would elicit locomotor muscle vasoconstriction and compromise limb Q˙. Seven male cyclists (V˙o 2 max 64 ± 6 ml ⋅ kg−1 ⋅ min−1) each completed 14 exercise bouts of 2.5-min duration atV˙o 2 max on a cycle ergometer during two testing sessions. Inspiratory muscle work was either 1) reduced via a proportional-assist ventilator, 2) increased via graded resistive loads, or 3) was not manipulated (control). Arterial (brachial) and venous (femoral) blood samples, arterial blood pressure, leg Q˙ (Q˙legs; thermodilution), esophageal pressure, and O2 consumption (V˙o 2) were measured. Within each subject and across all subjects, at constant maximal work rate, significant correlations existed ( r = 0.74–0.90; P < 0.05) between work of breathing (Wb) and Q˙legs (inverse), leg vascular resistance (LVR), and leg V˙o 2(V˙o 2 legs; inverse), and between LVR and norepinephrine spillover. Mean arterial pressure did not change with changes in Wb nor did tidal volume or minute ventilation. For a ±50% change from control in Wb,Q˙legs changed 2 l/min or 11% of control, LVR changed 13% of control, and O2extraction did not change; thusV˙o 2 legschanged 0.4 l/min or 10% of control. TotalV˙o 2 max was unchanged with loading but fell 9.3% with unloading; thusV˙o 2 legsas a percentage of totalV˙o 2 max was 81% in control, increased to 89% with respiratory muscle unloading, and decreased to 71% with respiratory muscle loading. We conclude that Wb normally incurred during maximal exercise causes vasoconstriction in locomotor muscles and compromises locomotor muscle perfusion andV˙o 2.
Modeling of adaptations to physical training by using a recursive least squares algorithm
Authors: Busso Thierry , Denis Christian , Bonnefoy Régis , Geyssant André , Lacour Jean-René
Published: December 2017

Busso, Thierry, Christian Denis, Régis Bonnefoy, André Geyssant, and Jean-René Lacour. Modeling of adaptations to physical training by using a recursive least squares algorithm. J. Appl. Physiol. 82(5): 1685–1693, 1997.—The present study assesses the usefulness of a systems model with time-varying parameters for describing the responses of physical performance to training. Data for two subjects who undertook a 14-wk training on a cycle ergometer were used to test the proposed model, and the results were compared with a model with time-invariant parameters. Two 4-wk periods of intensive training were separated by a 2-wk period of reduced training and followed by a 4-wk period of reduced training. The systems input ascribed to the training doses was made up of interval exercises and computed in arbitrary units. The systems output was evaluated one to five times per week by using the endurance time at a constant workload. The time-invariant parameters were fitted from actual performances by using the least squares method. The time-varying parameters were fitted by using a recursive least squares algorithm. The coefficients of determination r 2 were 0.875 and 0.879 for the two subjects using the time-varying model, higher than the values of 0.682 and 0.666, respectively, obtained with the time-invariant model. The variations over time in the model parameters resulting from the expected reduction in the residuals appeared generally to account for changes in responses to training. Such a model would be useful for investigating the underlying mechanisms of adaptation and fatigue.
Exercise-induced changes in β-adrenergic-receptor mRNA level measured by competitive RT-PCR
Authors: Fujii Nobuharu , Shibata Takeshi , Homma Sachiko , Ikegami Haruo , Murakami Kazuo , Miyazaki Hitoshi
Published: December 2017

Fujii, Nobuharu, Takeshi Shibata, Sachiko Homma, Haruo Ikegami, Kazuo Murakami, and Hitoshi Miyazaki. Exercise-induced changes in β-adrenergic-receptor mRNA level measured by competitive RT-PCR. J. Appl. Physiol. 82(6): 1926–1931, 1997.—Competitive reverse transcription-polymerase chain reaction (RT-PCR) analysis was used to clarify whether dynamic exercise-induced increases in β-adrenergic-receptor (β-AR) number in human lymphocytes are accompanied by increases in the β-AR mRNA level. Sixteen healthy subjects performed cycle ergometry until exhaustion. Before and immediately after exercise, peripheral blood was drawn from a forearm vein for preparation of lymphocytes. Both the β-AR mRNA level and the β-AR number were significantly increased by exercise. The changes in β-AR mRNA level and β-AR number were significantly correlated ( r = 0.63, P < 0.01). This finding suggests that a rapid increase in β-AR mRNA level might be an early adaptive response of the sympathetic nervous system to dynamic exercise. In vitro incubation of lymphocytes with epinephrine had no effect on β-AR mRNA levels, nor did adenosine 3′,5′-cyclic monophosphate, protein kinase C, or intracellular Ca2+increase the β-AR mRNA level in vitro. Therefore, it appears that other mechanisms underlie the exercise-induced elevation of β-AR mRNA levels in human lymphocytes.
Volume capacity and contraction control of the seal spleen
Authors: Cabanac Arnaud , Folkow Lars P. , Blix Arnoldus Schytte
Published: December 2017

Cabanac, Arnaud, Lars P. Folkow, and Arnoldus Schytte Blix.Volume capacity and contraction control of the seal spleen. J. Appl. Physiol. 82(6): 1989–1994, 1997.—Volume changes in the spleens of hooded seals ( Cystophora cristata) and harp seals ( Phoca groenlandica) were measured plethysmographically in vitro in response to epinephrine, norepinephrine, isoprenaline, phentolamine, and acetylcholine. Dilated spleens contracted forcefully within 1–3 min of α-adrenoceptor activation with 1.0–5.0 μg epinephrine/kg body mass, whereas stimulation of β-adrenoceptors and cholinergic receptors had little effect. The mass of dilated hooded seal spleens corresponded to 2–4% ( n = 7) of body mass, with volume (V; ml) relating to body mass (M; kg) as follows: V = 12.0M + 910 ( r2= 0.96, n = 4). Thus the spleen of a 250-kg hooded seal maximally expels 3.9 liters, or 13%, of its estimated total blood volume. Average hematocrit in splenic venous outflow from dilated spleens was 90 ± 3% ( n = 3) in hooded seals and 85% ( n = 2) in harp seals. From these data we have estimated that the aerobic diving limit of a 250-kg hooded seal increases only 105 s, at the most, if complete emptying of the spleen occurs during diving, while the corresponding estimate for a 112-kg harp seal is 80 s.
Restricted postexercise pulmonary diffusion capacity and central blood volume depletion
Authors: Hanel Birgitte , Teunissen Inge , Rabøl Alan , Warberg Jørgen , Secher Niels H.
Published: December 2017

Hanel, Birgitte, Inge Teunissen, Alan Rabøl, Jørgen Warberg, and Niels H. Secher. Restricted postexercise pulmonary diffusion capacity and central blood volume depletion. J. Appl. Physiol. 83(1): 11–17, 1997.—Pulmonary diffusion capacity for carbon monoxide (Dl CO), regional electrical impedance (Z0), and the distribution of technetium-99m-labeled erythrocytes together with concentration of plasma atrial natriuretic peptide (ANP) were determined before and after a 6-min “all-out” row in nine oarsmen and in six control subjects. Two and one-half hours after exercise in the upright seated position, Dl CO was reduced by 6 (−2 to 21; median and range) %, the thoracic-to-thigh electrical impedance ratio (Z0 thorax/Z0 thigh) rose by 14 (−1 to 29) %, paralleled by a 7 (−3 to 11) % decrease and a 3 (−5 to 12) % increase in the thoracic and thigh blood volume, respectively. These responses were associated with a decrease in the plasma ANP concentration from 15 (13–31) to 12 (9–27) pmol/l ( P < 0.05). Similarly, in the supine position, Z0 thorax/Z0 thighincreased by 10 (−5 to 28) % when Dl CO was reduced 12 (6–26) % ( P < 0.05), whereas Dl COremained stable in the control group. The increase in Z0 thorax/Z0 thighand the corresponding redistribution of the blood volume in both body positions show that approximately one-half of the postexercise reduction of Dl CO is explained by a decrease in the pulmonary blood volume. The role of a reduced postexercise central blood volume is underscored by the lower plasma ANP, which aids in upregulating the blood volume after exercise in athletes.
A simplified strong ion model for acid-base equilibria: application to horse plasma
Authors: Constable Peter D.
Published: December 2017

Constable, Peter D. A simplified strong ion model for acid-base equilibria: application to horse plasma. J. Appl. Physiol. 83(1): 297–311, 1997.—The Henderson-Hasselbalch equation and Stewart’s strong ion model are currently used to describe mammalian acid-base equilibria. Anomalies exist when the Henderson-Hasselbalch equation is applied to plasma, whereas the strong ion model does not provide a practical method for determining the total plasma concentration of nonvolatile weak acids ([Atot]) and the effective dissociation constant for plasma weak acids ( Ka). A simplified strong ion model, which was developed from the assumption that plasma ions act as strong ions, volatile buffer ions ([Formula: see text]), or nonvolatile buffer ions, indicates that plasma pH is determined by five independent variables:[Formula: see text], strong ion difference, concentration of individual nonvolatile plasma buffers (albumin, globulin, and phosphate), ionic strength, and temperature. The simplified strong ion model conveys on a fundamental level the mechanism for change in acid-base status, explains many of the anomalies when the Henderson-Hasselbalch equation is applied to plasma, is conceptually and algebraically simpler than Stewart’s strong ion model, and provides a practical in vitro method for determining [Atot] and Kaof plasma. Application of the simplified strong ion model to CO2-tonometered horse plasma produced values for [Atot] (15.0 ± 3.1 meq/l) and Ka(2.22 ± 0.32 × 10−7eq/l) that were significantly different from the values commonly assumed for human plasma ([Atot] = 20.0 meq/l, Ka= 3.0 × 10−7eq/l). Moreover, application of the experimentally determined values for [Atot] and Kato published data for the horse (known [Formula: see text], strong ion difference, and plasma protein concentration) predicted plasma pH more accurately than the values for [Atot] and Kacommonly assumed for human plasma. Species-specific values for [Atot] and Kashould be experimentally determined when the simplified strong ion model (or strong ion model) is used to describe acid-base equilibria.
Vasomotor instability preceding tilt-induced syncope: does respiration play a role?
Authors: Lipsitz Lewis A. , Morin Raymond , Gagnon Margaret , Kiely Dan , Medina Aharon
Published: December 2017

Lipsitz, Lewis A., Raymond Morin, Margaret Gagnon, Dan Kiely, and Aharon Medina. Vasomotor instability preceding tilt-induced syncope: does respiration play a role? J. Appl. Physiol. 83(2): 383–390, 1997.—This study aimed to determine whether alterations in cardiovascular dynamics before syncope are related to changes in spontaneous respiration. Fifty-two healthy subjects underwent continuous heart rate (HR), arterial blood pressure (BP), and respiratory measurements during 10-min periods of spontaneous and paced breathing (0.25 Hz) in the supine and 60° head-up tilt positions. Data were evaluated by power spectrum and transfer function analyses. During tilt, 27 subjects developed syncope or presyncope and 25 remained asymptomatic. Subjects with tilt-induced syncope had significantly greater increases in low-frequency (0.04–0.15 Hz) systolic BP, diastolic BP, and HR power during tilt than the asymptomatic subjects ( P ≤ 0.01). This difference was present during spontaneous but not paced breathing. However, average tidal volume, respiratory rate, minute ventilation, proportion of breaths below 0.15 Hz, and low-frequency respiratory power during tilt did not differ between syncopal and nonsyncopal subjects. Transfer magnitudes between low-frequency respiration and BP, and between BP and interbeat interval, were also similar between groups. Thus vasomotor instability before syncope is not related to alterations in respiration or the cardiovagal baroreflex but may reflect oscillating central sympathetic outflow to the vasculature.
Mechanical properties of rabbit latissimus dorsi muscle after stretch and/or electrical stimulation
Authors: James R. S. , Cox V. M. , Young I. S. , Altringham J. D. , Goldspink D. F.
Published: December 2017

James, R. S., V. M. Cox, I. S. Young, J. D. Altringham, and D. F. Goldspink Mechanical properties of rabbit latissimus dorsi muscle after stretch and/or electrical stimulation. J. Appl. Physiol. 83(2): 398–406, 1997.—The work loop technique was used to measure the mechanical performance in situ of the latissimus dorsi (LD) muscles of rabbits maintained under fentanyl anesthesia. After 3 wk of incrementally applied stretch the LD muscles were 36% heavier, but absolute power output (195 mW/muscle) was not significantly changed relative to that of external control muscle (206 mW). In contrast, continuous 10-Hz electrical stimulation reduced power output per kilogram of muscle >75% after 3 or 6 wk and muscle mass by 32% after 6 wk. When combined, stretch and 10-Hz electrical stimulation preserved or increased the mass of the treated muscles but failed to prevent an 80% loss in maximum muscle power. However, this combined treatment increased fatigue resistance to a greater degree than electrical stimulation alone. These stretched/stimulated muscles, therefore, are more suitable for cardiomyoplasty. Nonetheless, further work will be necessary to find an ideal training program for this surgical procedure.
Flow-induced vasodilation in the ferret lung
Authors: Chammas Joseph H. , Rickaby David. A. , Guarin Margarita , Linehan John H. , Hanger Christopher C. , Dawson Christopher A.
Published: December 2017

Chammas, Joseph H., David. A. Rickaby, Margarita Guarin, John H. Linehan, Christopher C. Hanger, and Christopher A. Dawson.Flow-induced vasodilation in the ferret lung. J. Appl. Physiol. 83(2): 495–502, 1997.—To examine the possibility that shear stress may be a pulmonary vasodilator stimulus, we studied the effect of changing blood flow on the diameters of small pulmonary arteries in isolated perfused ferret lung lobes. The arteries studied were in the ∼0.3- to 1.3-mm-diameter range, and the diameters were measured by using microfocal X-ray imaging. The diameters were measured at two flow rates, 10 and 40 ml/min, with the intravascular pressure in the measured vessels the same at the two flow rates as the result of venous pressure adjustment. The response to a change in flow was studied under both normoxic and hypoxic conditions. Hypoxia was used to elevate pulmonary arterial tone to increase the likelihood of detecting a vasodilator response. Under normoxic conditions, changing flow had little effect on the arterial diameters, but under hypoxic conditions the arteries were consistently larger at the higher flow than at the lower flow, even though the distending pressure was the same at the two flow rates. The results are consistent with the hypothesis that shear stress is a pulmonary vasodilator stimulus.