bluuebunny/crossref_metadata_2025 huggingface dataset:
Variable-frequency train stimulation of canine latissimus dorsi muscle during shortening contractions
Authors: George David T. , Binder-Macleod Stuart A. , Delosso Thomas N. , Santamore William P.
Published: December 2017

George, David T., Stuart A. Binder-Macleod, Thomas N. Delosso, and William P. Santamore. Variable-frequency train stimulation of canine latissimus dorsi muscle during shortening contractions. J. Appl. Physiol. 83(3): 994–1001, 1997.—In cardiomyoplasty, the latissimus dorsi muscle (LDM) is wrapped around the heart ventricles and electrically activated with a constant-frequency train (CFT). This study tested the hypotheses that increased mechanical performance from the LDM could be achieved by activating the muscle with variable-frequency trains (VFTs) of shorter duration or containing fewer stimulus pulses than the CFT now used. The mechanical performance of the canine LDM ( n = 7) during shortening contractions was measured while the muscle was stimulated with 5- and 6-pulse CFTs (of duration 132 and 165 ms, respectively) and 5- and 6-pulse VFTs (of duration 104 and 143 ms, respectively) that were designed to take advantage of the catchlike property of skeletal muscle. Measurements were made from fresh and fatigued muscles. For the fresh muscles, the VFTs elicited significantly greater peak power than did the 6-pulse CFT. When the muscles were fatigued, VFT stimulation significantly improved both the peak and mean power produced compared with stimulation by CFTs. These results show that stimulation of the LDM with shorter duration VFTs is potentially useful for application in cardiomyoplasty.
Tidal volume effects on surfactant treatment responses with the initiation of ventilation in preterm lambs
Authors: Wada Kazuko , Jobe Alan H. , Ikegami Machiko
Published: December 2017

Wada, Kazuko, Alan H. Jobe, and Machiko Ikegami. Tidal volume effects on surfactant treatment responses with the initiation of ventilation in preterm lambs. J. Appl. Physiol. 83(4): 1054–1061, 1997.—We hypothesized that initiation of ventilation in preterm lambs with high volumes would cause lung injury and decrease the subsequent response to surfactant treatment. Preterm lambs were randomized to ventilation for 30 min after birth with 5 ml/kg (Vt5), 10 ml/kg (Vt10), or 20 ml/kg (Vt20) tidal volumes and then ventilated with ∼10 ml/kg tidal volumes to achieve arterial[Formula: see text] values of ∼50 Torr to 6 h of age. Vt20 lambs had lower compliances, lower ventilatory efficiencies, higher recoveries of protein, and lower recoveries of surfactant in alveolar lavages and in surfactant that had decreased compliances when tested in preterm rabbits than Vt5 or Vt10 lambs. Other lambs randomized to treatment with surfactant at birth and ventilation with 6, 12, or 20 ml/kg tidal volumes for 30 min had no indicators of lung injury. An initial tidal volume of 20 ml/kg decreased the subsequent response to surfactant treatment, an effect that was prevented with surfactant treatment at birth.
Corticosteroid effects on isotonic contractile properties of rat diaphragm muscle
Authors: Van Balkom Roland H. H. , Zhan Wen-Zhi , Prakash Y. S. , Dekhuijzen P. N. Richard , Sieck Gary C.
Published: December 2017

Van Balkom, Roland H. H., Wen-Zhi Zhan, Y. S. Prakash, P. N. Richard Dekhuijzen, and Gary C. Sieck. Corticosteroid effects on isotonic contractile properties of rat diaphragm muscle. J. Appl. Physiol. 83(4): 1062–1067, 1997.—The effects of corticosteroids (CS) on diaphragm muscle (Diam) fiber morphology and contractile properties were evaluated in three groups of rats: controls (Ctl), surgical sham and weight-matched controls (Sham), and CS-treated (6 mg ⋅ kg−1 ⋅ day−1prednisolone at 2.5 ml/h for 3 wk). In the CS-treated Diam, there was a selective atrophy of type IIx and IIb fibers, compared with a generalized atrophy of all fibers in the Sham group. Maximum isometric force was reduced by 20% in the CS group compared with both Ctl and Sham. Maximum shortening velocity in the CS Diamwas slowed by ∼20% compared with Ctl and Sham. Peak power output of the CS Diam was only 60% of Ctl and 70% of Sham. Endurance to repeated isotonic contractions improved in the CS-treated Diam compared with Ctl. We conclude that the atrophy of type IIx and IIb fibers in the Diam can only partially account for the CS-induced changes in isotonic contractile properties. Other factors such as reduced myofibrillar density or altered cross-bridge cycling kinetics are also likely to contribute to the effects of CS treatment.
Trauma-induced changes of skeletal muscle membrane: decreased K+ and increased Na+ permeability
Authors: Hong S. J. , Chang C. C.
Published: December 2017

Hong, S. J., and C. C. Chang.Trauma-induced changes of skeletal muscle membrane: decreased K+ and increased Na+ permeability. J. Appl. Physiol. 83(4): 1096–1103, 1997.—Trauma of skeletal muscle causes membrane depolarization and reduces membrane resistance. The underlying mechanisms were studied in isolated mouse phrenic nerve diaphragms subject to sharp transections of muscle. Depolarization was most marked at the vicinity (∼1 mm) of trauma, where the membrane potential dropped rapidly from about −80 mV to zero and repolarized to about −25 mV. At the end-plate region (located ∼3 mm away from the cut end), the membrane gradually attained a plateau potential around −45 mV. The magnitude of depolarization was not reduced by inhibition of Na+, Ca2+, or Cl− channel, whereas the progress of depolarization was delayed in low-Na+ medium. Activation of the K+ channel with lemakalim induced some hyperpolarization at damaged site but produced a glybenclamide-sensitive outward current and hyperpolarization of end-plate region to the levels before trauma, as if there was no diminution of transmembrane K+gradient in this area. Appropriate elevation of extracellular K+ to stimulate K+ conductance also hyperpolarized the end-plate region. The results suggest that depolarization at regions remote from trauma is related to decreased K+ and increased Na+ permeability. The cytoplasma compartmentalization and permeability changes may protect muscle fiber from trauma.
Passive sensitization of human airways induces myogenic contractile responses in vitro
Authors: Mitchell R. W. , Rabe K. F. , Magnussen H. , Leff A. R.
Published: December 2017

Mitchell, R. W., K. F. Rabe, H. Magnussen, and A. R. Leff.Passive sensitization of human airways induces myogenic contractile responses in vitro. J. Appl. Physiol. 83(4): 1276–1281, 1997.—We assessed effects of passive sensitization on human bronchial smooth muscle (BSM) response to mechanical stretching in vitro. Bronchial rings were sham (control) or passively sensitized overnight by using sera from donors demonstrating sensitivity to Dermatophagoides farinae and having immunoglobulin E (IgE) concentrations of 2,600 ± 200 U/ml. Tissues were fixed isometrically to force transducers to measure responses to electrical field stimulation (EFS) and quick stretch (QS). The myogenic response to QS was normalized to the maximal response to EFS (%EFS). The myogenic response of sensitized BSM was 47.9 ± 10.9 %EFS to a QS of ∼6.5% optimal length ( L o); sham-sensitized tissues had a myogenic response of 13.5 ± 6.4 %EFS ( P = 0.012 vs. passively sensitized). A QS of ∼13% L o in sensitized BSM caused a response of 82.8 ± 20.9 %EFS; sham-sensitized tissues developed a response of 38.2 ± 17.3 %EFS ( P = 0.004). BSM incubated with serum from nonallergic donors did not demonstrate increased QS response (4.6 ± 1.4 %EFS, P = not significant vs. tissue exposed to atopic sera). However, tissues incubated in sera from nonatopic donors supplemented with hapten-specific chimeric IgE (JW8) demonstrated augmented myogenic response to QS of ∼6.5% L o (21.9 ± 6.2 %EFS, P = 0.027 vs. nonatopic sera alone). We demonstrate that passive sensitization of human BSM preparations causes induction and augmentation of myogenic contractions to QS; this hyperresponsiveness corresponds to the IgE concentration in sensitizing sera.
Skeletal muscle force and actomyosin ATPase activity reduced by nitric oxide donor
Authors: Perkins William J. , Han Young-Soo , Sieck Gary C.
Published: December 2017

Perkins, William J., Young-Soo Han, and Gary C. Sieck.Skeletal muscle force and actomyosin ATPase activity reduced by nitric oxide donor. J. Appl. Physiol.83(4): 1326–1332, 1997.—Nitric oxide (NO) may exert direct effects on actin-myosin cross-bridge cycling by modulating critical thiols on the myosin head. In the present study, the effects of the NO donor sodium nitroprusside (SNP; 100 μM to 10 mM) on mechanical properties and actomyosin adenosinetriphosphatase (ATPase) activity of single permeabilized muscle fibers from the rabbit psoas muscle were determined. The effects of N-ethylmaleimide (NEM; 5–250 μM), a thiol-specific alkylating reagent, on mechanical properties of single fibers were also evaluated. Both NEM (≥25 μM) and SNP (≥1 mM) significantly inhibited isometric force and actomyosin ATPase activity. The unloaded shortening velocity of SNP-treated single fibers was decreased, but to a lesser extent, suggesting that SNP effects on isometric force and actomyosin ATPase were largely due to decreased cross-bridge recruitment. The calcium sensitivity of SNP-treated single fibers was also decreased. The effects of SNP, but not NEM, on force and actomyosin ATPase activity were reversed by treatment with 10 mMdl-dithiothreitol, a thiol-reducing agent. We conclude that the NO donor SNP inhibits contractile function caused by reversible oxidation of contractile protein thiols.
Heat shock proteins and heat adaptation of the whole organism
Authors: Moseley Pope L.
Published: December 2017

Moseley, Pope L. Heat shock proteins and heat adaptation of the whole organism. J. Appl. Physiol. 83(5): 1413–1417, 1997.—Adaptation to heat may occur through acclimatization or thermotolerance; however, the linkage of these phenomena is poorly understood. The importance of heat shock proteins (HSPs) in thermotolerance and differences in their accumulation in organisms adapted to the heat suggest a role for HSPs in acclimatization as well. The role of HSPs in heat adaptation of the whole organism and the interrelationships among heat adaptation, endotoxin tolerance, and cytokine resistance through HSPs are reviewed.
Cerebral areas associated with motor control of speech in humans
Authors: Murphy K. , Corfield D. R. , Guz A. , Fink G. R. , Wise R. J. S. , Harrison J. , Adams L.
Published: December 2017

Murphy, K., D. R. Corfield, A. Guz, G. R. Fink, R. J. S. Wise, J. Harrison, and L. Adams. Cerebral areas associated with motor control of speech in humans. J. Appl. Physiol. 83(5): 1438–1447, 1997.—We have defined areas in the brain activated during speaking, utilizing positron emission tomography. Six normal subjects continuously repeated the phrase “Buy Bobby a poppy” (requiring minimal language processing) in four ways: A) spoken aloud, B) mouthed silently, C) without articulation, and D) thought silently. Statistical comparison of images from conditions Awith C and B with D highlighted areas associated with articulation alone, because control of breathing for speech was controlled for; we found bilateral activations in sensorimotor cortex and cerebellum with right-sided activation in the thalamus/caudate nucleus. Contrasting images from conditions A with B and C with D highlighted areas associated with the control of breathing for speech, vocalization, and hearing, because articulation was controlled for; we found bilateral activations in sensorimotor and motor cortex, close to but distinct from the activations in the preceding contrast, together with activations in thalamus, cerebellum, and supplementary motor area. In neither subtraction was there activation in Broca’s area. These results emphasize the bilaterality of the cerebral control of “speaking” without language processing.
Protoveratrines A and B increase sleep apnea index in Sprague-Dawley rats
Authors: Trbovic Sinisa M. , Radulovacki Miodrag , Carley David W.
Published: December 2017

Trbovic, Sinisa M., Miodrag Radulovacki, and David W. Carley. Protoveratrines A and B increase sleep apnea index in Sprague-Dawley rats. J. Appl. Physiol. 83(5): 1602–1606, 1997.—The action of protovertarines A and B, which stimulate carotid sinus baroreceptors and vagal sensory endings in the heart as well as pulmonary bed, were assessed on spontaneous and postsigh central sleep apneas in freely moving Sprague-Dawley rats. During the 6-h recording period, animals were simultaneously monitored for sleep by using electroencephalogram and electromyogram recordings, for respiration by single-chamber plethysmography, and for blood pressure and heart period by using radiotelemetry. After administration of 0.2, 0.5, or 1 mg/kg sc of protoveratrines, cardiopulmonary changes lasting at least 6 h were observed in all three behavioral states [heart period increased up to 23% in wakefulness, 21% in non-rapid-eye-movement (non-REM) sleep, and 20% in REM sleep; P < 0.005 for each]. At the same time, there was a substantial increase in the number of spontaneous (375% increase; P = 0.04) and postsigh (268% increase, P = 0.0002) apneas. Minute ventilation decreased by up to 24% in wakefulness, 25% in non-REM, and 35% in REM sleep ( P < 0.05 for each). We conclude that pharmacological stimulation of baroreflexes promotes apnea expression in the sleeping rat.
Inhibition of shivering increases core temperature afterdrop and attenuates rewarming in hypothermic humans
Authors: Giesbrecht Gordon G. , Goheen M. S. L. , Johnston C. E. , Kenny G. P. , Bristow Gerald K. , Hayward John S.
Published: December 2017

Giesbrecht, Gordon G., M. S. L. Goheen, C. E. Johnston, G. P. Kenny, Gerald K. Bristow, and John S. Hayward. Inhibition of shivering increases core temperature afterdrop and attenuates rewarming in hypothermic humans. J. Appl. Physiol. 83(5): 1630–1634, 1997.—During severe hypothermia, shivering is absent. To simulate severe hypothermia, shivering in eight mildly hypothermic subjects was inhibited with meperidine (1.5 mg/kg). Subjects were cooled twice (meperidine and control trials) in 8°C water to a core temperature of 35.9 ± 0.5 (SD) °C, dried, and then placed in sleeping bags. Meperidine caused a 3.2-fold increase in core temperature afterdrop (1.1 ± 0.6 vs. 0.4 ± 0.2°C), a 4.3-fold increase in afterdrop duration (89.4 ± 31.4 vs. 20.9 ± 5.7 min), and a 37% decrease in rewarming rate (1.2 ± 0.5 vs. 1.9 ± 0.9°C/h). Meperidine inhibited overt shivering. Oxygen consumption, minute ventilation, and heart rate decreased after meperidine injection but subsequently returned toward preinjection values after 45 min postimmersion. This was likely due to the increased thermoregulatory drive with the greater afterdrop and the short half-life of meperidine. These results demonstrate the effectiveness of shivering heat production in attenuating the postcooling afterdrop of core temperature and potentiating core rewarming. The meperidine protocol may be valuable for comparing the efficacy of various hypothermia rewarming methods in the absence of shivering.
Ultrasound evaluation of piglet diaphragm function before and after fatigue
Authors: Kocis Keith C. , Radell Peter J. , Sternberger Wayne I. , Benson Jane E. , Traystman Richard J. , Nichols David G.
Published: December 2017

Kocis, Keith C., Peter J. Radell, Wayne I. Sternberger, Jane E. Benson, Richard J. Traystman, and David G. Nichols. Ultrasound evaluation of piglet diaphragm function before and after fatigue. J. Appl. Physiol. 83(5): 1654–1659, 1997.—Clinically, a noninvasive measure of diaphragm function is needed. The purpose of this study is to determine whether ultrasonography can be used to 1) quantify diaphragm function and 2) identify fatigue in a piglet model. Five piglets were anesthetized with pentobarbital sodium and halothane and studied during the following conditions: 1) baseline (spontaneous breathing); 2) baseline + CO2[inhaled CO2to increase arterial[Formula: see text] to 50–60 Torr (6.6–8 kPa)]; 3) fatigue + CO2(fatigue induced with 30 min of phrenic nerve pacing); and 4) recovery + CO2(recovery after 1 h of mechanical ventilation). Ultrasound measurements of the posterior diaphragm were made (inspiratory mean velocity) in the transverse plane. Images were obtained from the midline, just inferior to the xiphoid process, and perpendicular to the abdomen. M-mode measures were made of the right posterior hemidiaphragm in the plane just lateral to the inferior vena cava. Abdominal and esophageal pressures were measured and transdiaphragmatic pressure (Pdi) was calculated during spontaneous (Sp) and paced (Pace) breaths. Arterial blood gases were also measured. Pdi(Sp) and Pdi(Pace) during baseline + CO2were 8 ± 0.7 and 49 ± 11 cmH2O, respectively, and decreased to 6 ± 1.0 and 27 ± 7 cmH2O, respectively, during fatigue + CO2. Mean inspiratory velocity also decreased from 13 ± 2 to 8 ± 1 cm/s during these conditions. All variables returned to baseline during recovery + CO2. Ultrasonography can be used to quantify diaphragm function and identify piglet diaphragm fatigue.
Monitoring changes in lung air and liquid volumes with electrical impedance tomography
Authors: Adler A. , Amyot R. , Guardo R. , Bates J. H. T. , Berthiaume Y.
Published: December 2017

Adler, A., R. Amyot, R. Guardo, J. H. T. Bates, and Y. Berthiaume. Monitoring changes in lung air and liquid volumes with electrical impedance tomography. J. Appl. Physiol. 83(5): 1762–1767, 1997.—Electrical impedance tomography (EIT) uses electrical measurements at electrodes placed around the thorax to image changes in the conductivity distribution within the thorax. This technique is well suited to studying pulmonary function because the movement of air, blood, and extravascular fluid induces significant conductivity changes within the thorax. We conducted three experimental protocols in a total of 19 dogs to assess the accuracy with which EIT can quantify changes in the volumes of both gas and fluid in the lungs. In the first protocol, lung volume increments from 50 to 1,000 ml were applied with a large syringe. EIT measured these volume changes with an average error of 27 ± 6 ml. In the second protocol, EIT measurements were made at end expiration and end inspiration during regular ventilation with tidal volume ranging from 100 to 1,000 ml. The average error in the EIT estimates of tidal volume was 90 ± 43 ml. In the third protocol, lung liquid volume was measured by instilling 5% albumin solution into a lung lobe in increments ranging from 10 to 100 ml. EIT measured these volume changes with an average error of 10 ± 10 ml and was also able to detect into which lobe the fluid had been instilled. These results indicate that EIT can noninvasively measure changes in the volumes of both gas and fluid in the lungs with clinically useful accuracy.
A servo-controlled respiration system for inhalation studies in anesthetized animals
Authors: Rosenthal Frank S. , Li Changhong
Published: December 2017

Rosenthal, Frank S., and Changhong Li. A servo-controlled respiration system for inhalation studies in anesthetized animals. J. Appl. Physiol. 83(5): 1768–1774, 1997.—To facilitate aerosol deposition experiments and aerosol exposures in anesthetized animals, a servo-controlled respiration system was developed and tested. The system induces ventilation by varying extrathoracic pressure in a whole body respirator in which an intubated animal is placed. The pressure inside the whole body respirator is varied with a three-way servo-controlled spool valve connected to sources of positive and negative pressure. A computer-based system detects respiratory flow and computes the controlling signal for the valve by using a proportional-integral-derivative algorithm, to achieve desired patterns of flow and volume vs. time. The system was used with dogs and found to accurately induce various single-breath breathing patterns involving constant-flow inspirations and expirations as well as breath-hold periods. A similar system was used to induced repeated breaths with desired parameters for continuous exposure to particles and for ventilation of animals between experiments.
Nitric oxide and vasodilation in human limbs
Authors: Joyner Michael J. , Dietz Niki M.
Published: December 2017

Joyner, Michael J., and Niki M. Dietz.Nitric oxide and vasodilation in human limbs. J. Appl. Physiol. 83(6): 1785–1796, 1997.—Both the skeletal muscle and skin of humans possess remarkable abilities to vasodilate. Marked vasodilation can be seen in these vascular beds in response to a variety of common physiological stimuli. These stimuli include reactive hyperemia (skin and muscle), exercise hyperemia (muscle), mental stress (muscle), and whole body heating (skin). The physiological mechanisms that cause vasodilation in response to these stimuli are poorly understood, and the substance(s) responsible for it remain unclear. In this context, recent attention has been focused on the possible contribution of nitric oxide (NO) to the regulation of hyperemic responses in human skin and skeletal muscle. The emerging picture is that NO is not an essential component of the dilator response seen during reactive hyperemia. However, it does appear that NO may play a modest role in exercise hyperemia. NO appears to play a major role in the skeletal muscle vasodilation seen in response to mental stress in humans. Preliminary evidence also indicates that NO is not essential for the normal dilator responses observed in the cutaneous circulation during body heating in humans, but this issue needs further study. There are a number of possible mechanisms that might mediate NO release in humans, and the role of these mechanisms in the various hyperemic responses is also poorly understood. The role of altered NO-mediated vasodilation in some disease states is also discussed. Whereas NO is a potent vasodilating substance, the actions of NO alone do not explain a variety of poorly understood vasodilator mechanisms in conscious humans. Much work remains for those interested in the role of NO in the regulation of blood flow to the skin and skeletal muscle of humans.
Hormonal and metabolic responses to exercise across time of day and menstrual cycle phase
Authors: Galliven E. A. , Singh A. , Michelson D. , Bina S. , Gold P. W. , Deuster P. A.
Published: December 2017

Galliven, E. A., A. Singh, D. Michelson, S. Bina, P. W. Gold, and P. A. Deuster. Hormonal and metabolic responses to exercise across time of day and menstrual cycle phase. J. Appl. Physiol. 83(6): 1822–1831, 1997.—Two studies, each utilizing short-term treadmill exercise of a different intensity, assessed the metabolic and hormonal responses of women to exercise in the morning (AM) and late afternoon (PM). In study 1, plasma concentrations of growth hormone, arginine vasopressin, catecholamines, adrenocorticotropic hormone, cortisol, lactate, and glucose were measured before, during, and after high-intensity exercise (90% maximal O2 uptake) in the AM and PM. In study 2, plasma concentrations of adrenocorticotropic hormone, cortisol, lactate, and glucose were measured before, during, and after moderate-intensity exercise (70% maximal O2 uptake) in the AM and PM in the follicular ( days 3–9), midcycle ( days 10–16), and luteal ( days 18–26) phases of the menstrual cycle. The results of studies 1 and 2 revealed no significant diurnal differences in the magnitude of responses for any measured variable. In addition, study 2 revealed a significant time-by-phase interaction for glucose ( P = 0.014). However, net integrated responses were similar across cycle phases. These data suggest that metabolic and hormonal responses to short-term, high-intensity exercise can be assessed with equal reliability in the AM and PM and that there are subtle differences in blood glucose responses to moderate-intensity exercise across menstrual cycle phase.
Endurance training attenuates the decrease in skeletal muscle malonyl-CoA with exercise
Authors: Hutber C. Adrian , Rasmussen B. B. , Winder W. W.
Published: December 2017

Hutber, C. Adrian, B. B. Rasmussen, and W. W. Winder.Endurance training attenuates the decrease in skeletal muscle malonyl-CoA with exercise. J. Appl. Physiol. 83(6): 1917–1922, 1997.—Muscle malonyl-CoA has been postulated to regulate fatty acid metabolism by inhibiting carnitine palmitoyltransferase 1. In nontrained rats, malonyl-CoA decreases in working muscle during exercise. Endurance training is known to increase a muscle’s reliance on fatty acids as a substrate. This study was designed to investigate whether the decline in malonyl-CoA with exercise would be greater in trained than in nontrained muscle, thereby allowing increased fatty acid oxidation. After 6–10 wk of endurance training (2 h/day) or treadmill habituation (5–10 min/day), rats were killed at rest or after running up a 15% grade at 21 m/min for 5, 20, or 60 min. Training attenuated the exercise-induced drop in malonyl-CoA and prevented the exercise-induced increase in the constant for citrate activation of acetyl-CoA carboxylase in the red quadriceps muscle of rats run for 20 and 60 min. Hence, contrary to expectations, the decrease in malonyl-CoA was less in trained than in nontrained muscle during a single bout of prolonged submaximal exercise.
Cardiopulmonary control in sleeping Sprague-Dawley rats treated with hydralazine
Authors: Carley David W. , Trbovic Sinisa M. , Bozanich Alex , Radulovacki Miodrag
Published: December 2017

Carley, David W., Sinisa M. Trbovic, Alex Bozanich, and Miodrag Radulovacki. Cardiopulmonary control in sleeping Sprague-Dawley rats treated with hydralazine. J. Appl. Physiol. 83(6): 1954–1961, 1997.—To test the hypothesis that hydralazine can suppress spontaneous sleep-related central apnea, respiratory pattern, blood pressure, and heart period were monitored in Sprague-Dawley rats. In random order and on separate days, rats were recorded after intraperitoneal injection of 1) saline or 2) 2 mg/kg hydralazine. Normalized minute ventilation (NV˙i) declined significantly with transitions from wake to non-rapid-eye-movement (NREM) sleep (−5.1%; P = 0.01) and rapid-eye-movement (REM) sleep (−4.2%; P = 0.022). Hydralazine stimulated respiration (NV˙iincreased by 21%; P < 0.03) and eliminated the effect of state on NV˙i. Blood pressure decreased by 17% after hydralazine, and the correlation between fluctuations in mean blood pressure and NV˙i changed from strongly positive during control recordings to weakly negative after hydralazine ( P < 0.0001 for each). Postsigh and spontaneous apneas were reduced during NREM and REM sleep after hydralazine ( P < 0.05 for each). This suppression was strongly correlated with the reduction in blood pressure and with the degree of respiratory stimulation. We conclude that mild hydralazine-induced hypotension leads to respiratory stimulation and apnea suppression.
A dual-respiration chamber system with automated calibration
Authors: Schoffelen Paul F. M. , Westerterp Klaas R. , Saris Wim H. M. , Ten Hoor Foppe
Published: December 2017

Schoffelen, Paul F. M., Klaas R. Westerterp, Wim H. M. Saris, and Foppe Ten Hoor. A dual-respiration chamber system with automated calibration. J. Appl. Physiol. 83(6): 2064–2072, 1997.—This study characterizes respiration chambers with fully automated calibration. The system consists of two 14-m3pull-type chambers. Care was taken to provide a friendly environment for the subjects, with the possibility of social contact during the experiment. Gas analysis was automated to correct for analyzer drift and barometric pressure variations and to provide ease of use. Methods used for checking the system’s performance are described. The gas-analysis repeatability was within 0.002%. Results of alcohol combustion (50–350 ml/min CO2) show an accuracy of 0.5 ± 2.0 (SD) % for O2consumption and −0.3 ± 1.6% for CO2 production for 2- to 24-h experiments. It is concluded that response time is not the main factor with respect to the smallest practical measurement interval (duration); volume, mixing, gas-analysis accuracy, and levels of O2 consumption and CO2 production are at least equally important. The smallest practical interval was 15–25 min, as also found with most chamber systems described in the literature. We chose to standardize 0.5 h as the minimum measurement interval.
Posttetanic potentiation of human dorsiflexors
Authors: O’Leary Deborah D. , Hope Karen , Sale Digby G.
Published: December 2017

O’Leary, Deborah D., Karen Hope, and Digby G. Sale.Posttetanic potentiation of human dorsiflexors. J. Appl. Physiol. 83(6): 2131–2138, 1997.—Twitch contractions of the ankle dorsiflexors were evoked before and after applied 7-s tetanic stimulation at 100 Hz in 20 young adults. Torque decreased 15% during the tetanus. At 5 s after tetanus, twitch peak torque had potentiated 45%. Potentiation declined to 28% after 1 min, rose slightly to 33% at 2 min, and declined slowly with potentiation still 25% after 5 min. There was large intersubject variation in the amount of potentiation (5–140%) and its persistence (5 to ≥20 min). The muscle compound action potential (M wave) did not change significantly (from pretetanic value) at 5 s after tetanus but increased sharply (26%) at 2 min and then subsided. Twitch half relaxation time (23%) decreased significantly more than twitch rise time (13%) 5 s after tetanus and recovered more slowly. Twitch rates of torque development (75%) and relaxation (71%) increased similarly 5 s after tetanus and were still elevated (∼25%) at 5 min. The extent of twitch torque potentiation was significantly inversely correlated with pretetanic twitch rise time ( r = −0.69), half relaxation time ( r = −0.61), and twitch-to-tetanus ratio ( r = −0.66). The data indicate that posttetanic potentiation has a greater effect on twitch half relaxation time than on time to peak torque and is more prominent in muscles with a short twitch time course and small twitch-to-tetanus ratio.
Effects of gender on resting leg blood flow: implications for measurement of regional substrate oxidation
Authors: Jensen Michael D. , Nguyen Tu T. , Mijares A. Hernández , Johnson C. Michael , Murray Michael J.
Published: December 2017

Jensen, Michael D., Tu T. Nguyen, A. Hernández Mijares, C. Michael Johnson, and Michael J. Murray. Effects of gender on resting leg blood flow: implications for measurement of regional substrate oxidation. J. Appl. Physiol. 84(1): 141–145, 1998.—These studies were designed to examine whether the respiratory quotient (RQ) of leg tissue (primarily skeletal muscle) would increase to a greater degree in women than in men during meal ingestion. We found that mean leg and systemic RQ values were similar in men under both basal and fed conditions, whereas the agreement was poor in women. In women, leg RQ values tended to be greater than the systemic RQ, whereas splanchnic RQ values tended to be lower than the systemic RQ. The possibility that measurement imprecision accounted for the different findings in women could not be excluded because the arteriovenous blood O2 differences were almost twice as great in men as in women (53.7 ± 5.4 vs. 28.6 ± 2.9 ml of O2/l, respectively; P < 0.01), as were venoarterial blood CO2 differences. The smaller arteriovenous differences in women appeared to limit our ability to accurately measure their leg RQ values. O2 uptake relative to leg fat-free mass (FFM) was not different between men and women, whereas leg blood flow relative to leg FFM was greater in women than in men (55 ± 3 vs. 39 ± 2 ml ⋅ kg FFM−1 ⋅ min−1, respectively; P < 0.001). These findings were confirmed by examining data from other studies conducted in our laboratory to create a larger data set. We conclude that resting leg blood flow in women is greater (relative to FFM) than in men, making it more difficult to accurately measure leg RQ in women.
Supercritical fluid-aerosolized vitamin E pretreatment decreases leak in isolated oxidant-perfused rat lungs
Authors: Hybertson Brooks M. , Kitlowski Roger P. , Jepson Eric K. , Repine John E.
Published: December 2017

Hybertson, Brooks M., Roger P. Kitlowski, Eric K. Jepson, and John E. Repine. Supercritical fluid-aerosolized vitamin E pretreatment decreases leak in isolated oxidant-perfused rat lungs. J. Appl. Physiol. 84(1): 263–268, 1998.—We hypothesized that direct pulmonary administration of supercritical fluid-aerosolized (SFA) vitamin E would decrease acute oxidative lung injury. We previously reported that rapid expansion of supercritical CO2formed respirable particles of vitamin E and that administering SFA vitamin E to rats increased lung vitamin E levels and decreased neutrophil-mediated lung leak. In the present investigation, we found that pretreatment with SFA vitamin E protected isolated rat lungs against the oxidant-induced lung leak caused by perfusion with xanthine oxidase (XO) and purine, an enzyme system that generates superoxide anion ([Formula: see text]) and hydrogen peroxide. SFA vitamin E droplets were 0.7–3 μm in diameter, and inhalation of the airborne droplets for 30 min deposited ∼55 μg of vitamin E in rat lungs. Isolated rat lungs perfused with XO (0.02 U/ml) and purine (10 mM) gained more weight (1.75 ± 0.12 g, n = 8), retained more Ficoll (11.5 ± 1.2 mg/left lung, n = 7), and accumulated more Ficoll in their lung lavages (700 ± 146 μg/ml, n = 8) than control lungs [0.25 ± 0.06 g ( n = 10), 6.2 ± 1.2 mg/left lung ( n = 9), and 141 ± 31 μg/ml ( n = 8), respectively, P < 0.05]. In contrast, isolated lungs from rats that were pretreated with SFA vitamin E had decreased ( P < 0.05) weight gains (0.32 ± 0.06 g, n = 7), Ficoll retentions (3.3 ± 1.1 mg/left lung, n = 7), and lung lavage Ficoll concentrations (91 ± 26 μg/ml, n = 6) after perfusion with XO and purine compared with isolated lungs from control rats perfused with XO and purine. This protective effect was not observed in rat lungs given sham treatments (CO2alone or vitamin E acetate aerosolized with supercritical CO2). Our results suggest that direct pulmonary supplementation of vitamin E decreases susceptibility to vascular leakage caused by XO-derived oxidants.
An induced blood pressure rise does not alter upper airway resistance in sleeping humans
Authors: Wilson Christine R. , Manchanda Shalini , Crabtree David , Skatrud James B. , Dempsey Jerome A.
Published: December 2017

Wilson, Christine R., Shalini Manchanda, David Crabtree, James B. Skatrud, and Jerome A. Dempsey. An induced blood pressure rise does not alter upper airway resistance in sleeping humans. J. Appl. Physiol. 84(1): 269–276, 1998.—Sleep apnea is associated with episodic increases in systemic blood pressure. We investigated whether transient increases in arterial pressure altered upper airway resistance and/or breathing pattern in nine sleeping humans (snorers and nonsnorers). A pressure-tipped catheter was placed below the base of the tongue, and flow was measured from a nose or face mask. During non-rapid-eye-movement sleep, we injected 40- to 200-μg iv boluses of phenylephrine. Parasympathetic blockade was used if bradycardia was excessive. Mean arterial pressure (MAP) rose by 20 ± 5 (mean ± SD) mmHg (range 12–37 mmHg) within 12 s and remained elevated for 105 s. There were no significant changes in inspiratory or expiratory pharyngeal resistance (measured at peak flow, peak pressure, 0.2 l/s or by evaluating the dynamic pressure-flow relationship). At peak MAP, end-tidal CO2 pressure fell by 1.5 Torr and remained low for 20–25 s. At 26 s after peak MAP, tidal volume fell by 19%, consistent with hypocapnic ventilatory inhibition. We conclude that transient increases in MAP of a magnitude commonly observed during non-rapid-eye-movement sleep-disordered breathing do not increase upper airway resistance and, therefore, will not perpetuate subsequent obstructive events.
Prediction of hemorrhagic blood loss with a genetic algorithm neural network
Authors: Jefferson M. F. , Pendleton N. , Mohamed S. , Kirkman E. , Little R. A. , Lucas S. B. , Horan M. A.
Published: December 2017

Jefferson, M. F., N. Pendleton, S. Mohamed, E. Kirkman, R. A. Little, S. B. Lucas, and M. A. Horan. Prediction of hemorrhagic blood loss with a genetic algorithm neural network. J. Appl. Physiol. 84(1): 357–361, 1998.—There is no established method for accurately predicting how much blood loss has occurred during hemorrhage. In the present study, we examine whether a genetic algorithm neural network (GANN) can predict volume of hemorrhage in an experimental model in rats and we compare its accuracy to stepwise linear regression (SLR). Serial measurements of heart period; diastolic, systolic, and mean blood pressures; hemoglobin; pH; arterial[Formula: see text]; arterial[Formula: see text]; bicarbonate; base deficit; and blood loss as percent of total estimated blood volume were made in 33 male Wistar rats during a stepwise hemorrhage. The GANN and SLR used a randomly assigned training set to predict actual volume of hemorrhage in a test set. Diastolic blood pressure, arterial[Formula: see text], and base deficit were selected by the GANN as the optimal predictors set. Root mean square error in prediction of estimated blood volume by GANN was significantly lower than by SLR (2.63%, SD 1.44, and 4.22%, SD 3.48, respectively; P < 0.001). A GANN can predict highly accurately and significantly better than SLR volume of hemorrhage without knowledge of prehemorrhage status, rate of blood loss, or trend in physiological variables.
Pulmonary vasodilation by nitric oxide gas and prodrug aerosols in acute pulmonary hypertension
Authors: Adrie Christophe , Ichinose Fumito , Holzmann Alexandra , Keefer Larry , Hurford William E. , Zapol Warren M.
Published: December 2017

Adrie, Christophe, Fumito Ichinose, Alexandra Holzmann, Larry Keefer, William E. Hurford, and Warren M. Zapol. Pulmonary vasodilation by nitric oxide gas and prodrug aerosols in acute pulmonary hypertension. J. Appl. Physiol. 84(2): 435–441, 1998.—Sodium 1-( N, N-diethylamino)diazen-1-ium-1,2-diolate {DEA/NO; Et2N[N(O)NO]Na} is a compound that spontaneously generates nitric oxide (NO). Because of its short half-life (2.1 min), we hypothesized that inhaling DEA/NO aerosol would selectively dilate the pulmonary circulation without decreasing systemic arterial pressure. We compared the pulmonary selectivity of this new NO donor with two other reference drugs: inhaled NO and inhaled sodium nitroprusside (SNP). In seven awake sheep with pulmonary hypertension induced by the infusion of U-46619, we compared the hemodynamic effects of DEA/NO with those of incremental doses of inhaled NO gas. In seven additional awake sheep, we examined the hemodynamic effects of incremental doses of inhaled nitroprusside (i.e., SNP). Inhaled NO gas selectively dilated the pulmonary vasculature. Inhaled DEA/NO produced nonselective vasodilation; both systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR) were reduced. Inhaled SNP selectively dilated the pulmonary circulation at low concentrations (≤10−2M), inducing a decrease of PVR of up to 42% without any significant decrease of SVR (−5%), but nonselectively dilated the systemic circulation at larger doses (>10−2M). In conclusion, despite its short half-life, DEA/NO is not a selective pulmonary vasodilator compared with inhaled NO. Inhaled SNP appears to be selective to the pulmonary circulation at low doses but not at higher levels.
Removal of a dimeric form of surfactant protein C from mouse lungs: its acceleration by reduction
Authors: Li Zhong-Yuan , Suzuki Yasuhiro , Kurozumi Mafumi , Shen Hui-Qing , Duan Chen-Xia
Published: December 2017

Li, Zhong-Yuan, Yasuhiro Suzuki, Mafumi Kurozumi, Hui-Qing Shen, and Chen-Xia Duan. Removal of a dimeric form of surfactant protein C from mouse lungs: its acceleration by reduction. J. Appl. Physiol. 84(2): 471–478, 1998.—Clearance of hydrophobic surfactant-associated protein C (SP-C) and its dimeric form ([SP-C]2) was investigated. SP-C and [SP-C]2obtained from proteinosis patients were fluorescently labeled and were instilled into mouse lungs as lipid-protein complexes. [SP-C]2was removed more slowly than SP-C, with apparent half-lives of 30 and 18 h, respectively. A significant amount of [SP-C]2was removed as SP-C, and the conversion rate was 0.22 μg ⋅ h−1⋅ mouse−1. By correcting the removal as SP-C, we obtained 38 h for a possible half-life of [SP-C]2. Conversion from SP-C to [SP-C]2seemed very slow. Decrease in glutathione (GSH) in the lung inhibited the conversion of [SP-C]2to SP-C and GSH-treatment of liposomes accelerated clearance of [SP-C]2. These results suggest that the removal of [SP-C]2from lung is accelerated by reduction and that GSH acts as a reducing agent in the lung.
Effects of meals on objective and subjective measures of daytime sleepiness
Authors: Wells Anita S. , Read Nicholas W. , Idzikowski Chris , Jones Jane
Published: December 2017

Wells, Anita S., Nicholas W. Read, Chris Idzikowski, and Jane Jones. Effects of meals on objective and subjective measures of daytime sleepiness. J. Appl. Physiol. 84(2): 507–515, 1998.—Effects of recent food ingestion on daytime sleepiness were assessed in 16 subjects (8 men and 8 women) who were each studied on two occasions, 28 days apart. On each occasion, subjects ate a high-fat low-carbohydrate (CHO) (fat/CHO energy ratio 54:41) meal and an isoenergetic low-fat high-CHO meal (fat/CHO energy ratio 7:88) 4 h apart in a counterbalanced order. Sleepiness was measured at 2-h intervals by using the Multiple Sleep Latency Test and the Akerstedt electroencephalograph sleepiness test. To control for circadian factors, one group (4 men, 4 women) ate the meals 2 h later than did the other group of subjects. There were no differences in sleepiness according to the composition of the meal. Sleepiness in the Multiple Sleep Latency Test was significantly greater 1.5 h after the meals were eaten than before ( F 11.37; df 1,15; P = 0.004). Sleepiness was also enhanced in the Akerstedt sleepiness test 3 h 20 min after the meals. The results suggest that the meals induced an enhancement in sleepiness that was not solely due to circadian rhythms.
Sleep apnea in obese miniature pigs
Authors: Lonergan Robert P. , Ware J. Catsby , Atkinson Richard L. , Winter W. Christopher , Suratt Paul M.
Published: December 2017

Lonergan, Robert P., III, J. Catsby Ware, Richard L. Atkinson, W. Christopher Winter, and Paul M. Suratt. Sleep apnea in obese miniature pigs. J. Appl. Physiol. 84(2): 531–536, 1998.—We postulated that three extremely obese Yucatan miniature pigs would have more sleep apnea than three nonobese Yucatan miniature pigs. Pigs were studied with the use of electroencephalograms, inductance plethysmography, oximetry, expired nasal CO2, or thermistors. All of the obese pigs, but none of the nonobese pigs, had both sleep apnea (8.5, 10.3, and 97.0 in obese pigs vs. 0 apnea + hypopnea/h in all nonobese pigs; P < 0.05) and oxyhemoglobin desaturation episodes during sleep [9.4 ± 3.0 vs. 0 + 0.53 (SD) mean desaturation episodes/h in obese pigs vs. nonobese pigs, respectively; P < 0.05]. Two of the extremely obese pigs had obstructive sleep apnea, whereas the third obese pig had central sleep apnea. We conclude that sleep apnea occurs in extremely obese Yucatan minipigs and suggest that this animal can be used as a model for sleep apnea in obesity.
Hypoxia, temperature, and pH/CO2effects on respiratory discharge from a turtle brain stem preparation
Authors: Johnson Stephen M. , Johnson Rebecca A. , Mitchell Gordon S.
Published: December 2017

Johnson, Stephen M., Rebecca A. Johnson, and Gordon S. Mitchell. Hypoxia, temperature, and pH/CO2effects on respiratory discharge from a turtle brain stem preparation. J. Appl. Physiol. 84(2): 649–660, 1998.—An in vitro brain stem preparation from adult turtles ( Chrysemys picta) was used to examine the effects of anoxia and increased temperature and pH/CO2on respiration-related motor output. At pH ∼7.45, hypoglossal (XII) nerve roots produced patterns of rhythmic bursts (peaks) of discharge (0.74 ± 0.07 peaks/min, 10.0 ± 0.6 s duration) that were quantitatively similar to literature reports of respiratory activity in conscious, vagotomized turtles. Respiratory discharge was stable for 6 h at 22°C; at 32°C, peak amplitude and frequency progressively and reversibly decreased with time. Two hours of hypoxia had no effect on respiratory discharge. Acutely increasing bath temperature from 22 to 32°C decreased episode and peak duration and increased peak frequency. Changes in pH/CO2increased peak frequency from zero at pH 8.00–8.10 to maxima of 0.81 ± 0.01 and 1.44 ± 0.02 peaks/min at 22°C (pH 7.32) and 32°C (pH 7.46), respectively; pH/CO2sensitivity was similar at both temperatures. We conclude that 1) insensitivity to hypoxia indicates that rhythmic discharge does not reflect gasping behavior, 2) increased temperature alters respiratory discharge, and 3) central pH/CO2sensitivity is unaffected by temperature in this preparation (i.e., Q10∼1.0).
α-Adrenoreceptor influences on liquid movements by in vitro lungs from fetal guinea pigs
Authors: Doe S. , Perks A. M.
Published: December 2017

Doe, S., and A. M. Perks. α-Adrenoreceptor influences on liquid movements by in vitro lungs from fetal guinea pigs. J. Appl. Physiol. 84(2): 746–753, 1998.—Lungs from near-term fetal guinea pigs (60 ± 2 days of gestation) were supported in vitro for 3 h; lung liquid production was monitored by a dye-dilution method. Studies of 30 fetuses showed that untreated preparations produced fluid at 1.34 ± 0.21 ml ⋅ h−1 ⋅ kg body wt−1, but epinephrine at concentrations known at delivery (10−8 and 10−7 M) produced significant reductions or fluid reabsorption (analysis of variance, regression analysis); at high levels (10−6 and 10−5 M), epinephrine had no effect. Maximal responses from 10−7 M epinephrine involved α-adrenoreceptors, since they were abolished by 10−6 M phentolamine (α-antagonist) but were unaffected by 10−6 M propranolol (β-antagonist; n = 36). Activation was through α2-adrenoreceptors, since responses were abolished by 10−4 M yohimbine (α2-antagonist; n = 24) but were resistant to 10−5 M prazosin (α1-antagonist; n = 24). At high levels of epinephrine (10−5 M), where responses did not normally occur, reductions in lung liquid production were large if prazosin was also present ( n = 24), and increases were significant if yohimbine was included ( n = 24). In guinea pigs, epinephrine appears to activate lung fluid reabsorption through α2-adrenoreceptors; at high concentrations only, it can also increase production through α1-adrenoreceptors. Therefore, species differences appear to exist.
Upper airway muscle activity in normal women: influence of hormonal status
Authors: Popovic Rainer M. , White David P.
Published: December 2017

Obstructive sleep apnea is a disorder with a strong male predominance. One possible explanation could be an effect of female hormones on pharyngeal dilator muscle activity. Therefore, we determined the level of awake genioglossus electromyogram (EMGgg) and upper airway resistance in 12 pre- and 12 postmenopausal women under basal conditions and during the application of an inspiratory resistive load (25 cmH2O ⋅ l−1 ⋅ s). In addition, a subgroup of eight postmenopausal women were studied a second time after 2 wk of combined estrogen and progesterone replacement in standard doses. Peak phasic and tonic genioglossus activity, expressed as a percentage of maximum, were highest in the luteal phase of the menstrual cycle (phasic 23.9 ± 3.8%, tonic 10.2 ± 1.0%), followed by the follicular phase (phasic 15.5 ± 2.2%, tonic 7.3 ± 0.8%), and were lowest in the postmenopausal group (phasic 11.3 ± 1.6%, tonic of 5.0 ± 0.6), whereas upper airway resistance did not differ. There was a weak but significant positive correlation between progesterone levels and both peak phasic ( P < 0.05) and tonic ( P < 0.01) EMGgg. Finally, there was a significant increase in EMGgg in the postmenopausal group restudied after hormone therapy. In conclusion, female hormones (possibly progesterone) have a substantial impact on upper airway dilator muscle activity.