bluuebunny/crossref_metadata_2025 huggingface dataset:
Endurance exercise with and without a thermal clamp: effects on leukocytes and leukocyte subsets
Authors: Cross M. C. , Radomski M. W. , VanHelder W. P. , Rhind S. G. , Shephard R. J.
Published: December 2017

To test how leukocyte responses to endurance exercise were modified by clamping body temperature, nine men (27.3 +/- 6.0 yr) completed four 80-min immersions to midchest at water temperatures of 23 or 39 degrees C; two tests included 40-min of cycle ergometer exercise at 65% of aerobic power. When the subjects were exercising, rectal temperature peaked at 39.1 +/- 0.4 degrees C in the warm water and 37.8 +/- 0.3 degrees C in the cool water. When the subjects were sitting in warm water, rectal temperature closely matched the core temperature during exercise in cool water, whereas when they were sitting in cool water, rectal temperatures decreased to 36.4 +/- 0.6 degrees C. Total and differential white cell counts were determined by using a Coulter counter, and cortisol and growth hormone concentrations were determined by radioimmunoassay; all data were adjusted for changes of blood and plasma volumes. Heat clamping during exercise substantially reduced the rise in white cell, lymphocyte, and granulocyte counts but not the increase in monocyte count. Clamping also abolished previously observed associations between cell counts and cortisol and weakened associations with growth hormone concentrations (D. A. McCarthy and M. M. Dale. Sports Med. 6: 333–363, 1988). We conclude that both exercise and a rise of core temperature contribute to the changes in white cell and subset counts during and immediately after moderate exercise. Both cortisol and growth hormone concentrations appear to be mediators of these responses.
Pulmonary hemodynamic response to exercise in subjects with prior high-altitude pulmonary edema
Authors: Eldridge M. W. , Podolsky A. , Richardson R. S. , Johnson D. H. , Knight D. R. , Johnson E. C. , Hopkins S. R. , Michimata H. , Grassi B. , Feiner J. , Kurdak S. S. , Bickler P. E. , Wagner P. D. , Severinghaus J. W.
Published: December 2017

Individuals with a prior history of (susceptible to high altitude pulmonary edema (HAPE-S) have high resting pulmonary arterial pressures, but little data are available on their vascular response to exercise. We studied the pulmonary vascular response to exercise in seven HAPE-S and nine control subjects at sea level and at 3,810 m altitude. At each location, both normoxic (inspired PO2 = 148 Torr) and hypoxic (inspired PO2 = 91 Torr) studies were conducted. Pulmonary hemodynamic measurements included pulmonary arterial and pulmonary arterial occlusion pressures. A multiple regression analysis demonstrated that the pulmonary arterial pressure reactivity to exercise was significantly greater in the HAPE-S group. This reactivity was not influenced by altitude or oxygenation, implying that the response was intrinsic to the pulmonary circulation. Pulmonary arterial occlusion pressure reactivity to exercise was also greater in the HAPE-S group, increasing with altitude but independent of oxygenation. These findings suggest an augmented flow-dependent pulmonary vasoconstriction and/or a reduced vascular cross-sectional area in HAPE-S subjects.
Minimal redistribution of pulmonary blood flow with exercise in racehorses
Authors: Bernard S. L. , Glenny R. W. , Erickson H. H. , Fedde M. R. , Polissar N. , Basaraba R. J. , Hlastala M. P.
Published: December 2017

We determined the spatial distribution of pulmonary blood flow at rest and during increasing levels of exercise (34, 59, and 90% of maximal oxygen consumption) in Thoroughbred racehorses (n = 4) using 15-microns fluorescent microspheres. After the horses were killed, the lungs were flushed free of blood, removed, air-dried at total lung capacity, and sliced into isogravitational planes, which were sampled in a systematic fashion for three-dimensional reconstruction. The fluorescence was measured for quantification of blood flow. Mean pulmonary blood flow heterogeneity (expressed as a coefficient of variation) did not change with increasing exercise levels [36.2 +/- 16.4 (rest) to 26.9 +/- 6.8% (gallop); P = not significant]. Greater than 70% of pulmonary blood flow variation across rest to high-exercise states is determined by a fixed spatial pattern. Thirty percent of the variation in pulmonary blood flow seen in horses over rest and exercising states is due to redistribution. The majority of flow redistribution was due to flow increasing to the dorsal region of the lung during exercise at 90% of maximal oxygen consumption (a flow gradient of 0.20 ml. min-1.cm-1 up the lung; P = 0.04).
Effects of carbon monoxide on the brain may be mediated by nitric oxide
Authors: Meilin S. , Rogatsky G. G. , Thom S. R. , Zarchin N. , Guggenheimer-Furman E. , Mayevsky A.
Published: December 2017

Carbon monoxide (CO) is known to be a toxic molecule due to the high affinity of hemoglobin for it. However, it has recently been shown that low doses of CO may play a physiological role. The aim of the present study was to examine processes occurring in the brain during exposure to 1,000 parts per million CO that result in an increase in cerebral blood flow (CBF) but are not accompanied by changes in oxidation metabolism. This study was carried out in awake rats with the multiprobe assembly developed in this laboratory for the simultaneous continuous measurement of CBF, intramitochondrial NADH redox levels, direct current potential, and extracellular concentrations of K+, Ca2+, and H+ as well as the electrocorticogram. Exposure to 1,000 parts per million CO in air resulted in an increased CBF without any concomitant changes in any of the other metabolic or ionic parameters measured. This indicates that tissue hypoxia was not the trigger for this vasodilation. Injection of N omega-nitro-L-arginine (L-NNA), a nitric oxide synthase inhibitor, before exposure to CO effectively blocked the increase in CBF that was observed when the animal was exposed to CO without prior injection of L-NNA. Furthermore, electrocorticographic depression was observed after the combined treatment of L-NNA and CO. In conclusion, exposure to relatively low doses of CO apparently does not have a deleterious effect on oxidative metabolism because the increase in CBF after this exposure is sufficient to prevent changes in oxidative metabolism, as indicated by the fact that NADH levels remained constant. This protective autoregulatory effect may be mediated by nitric oxide.
Dynamics of the cerebral blood flow response to step changes in end-tidal PCO2 and PO2 in humans
Authors: Poulin M. J. , Liang P. J. , Robbins P. A.
Published: December 2017

This study examined the dynamics of the cerebral blood flow response to hypoxia and hypercapnia in humans. Middle cerebral artery blood flow (MCAF) was assessed continuously using transcranial Doppler ultrasound. MCAF was calculated on a beat-by-beat basis as the product of the intensity-weighted mean velocity and the total power of the reflected signal. End-tidal PCO2 (PETCO2) and PO2 (PETO2) were controlled using a dynamic end-tidal forcing system. Six repeats of each of four protocols were administered to six subjects. The first was a control protocol with PETO2 held at 100 Torr and PETCO2 held 1-2 Torr above eucapnia throughout. The second was a hypoxic step protocol with PETO2 lowered from control values to 50 Torr for 20 min. The third was a hypercapnic step protocol with PETCO2 elevated from control by 7.5 Torr for 20 min. The fourth was a hypoxic-and-hypercapnic step protocol lasting 20 min. The total power of the Doppler signal remained relatively constant, suggesting that the cross-sectional area of the vessel changed little. After the initial transient in MCAF at the onset of the stimulus, no adaptation or progressive increase was observed over the remaining 20 min. A simple model consisting of a single pure delay, gain terms, time constants, and offsets for the on and off transients was fitted to the hypoxic and hypercapnic protocols. For hypercapnia, all the parameters for the onset were significantly different from the relief of the stimulus. The asymmetry was characterized by a slower on transient than off transient and also by a degree of undershoot after the relief of hypercapnia. Finally, the results from this study show that the cerebral blood flow response to hypoxia and hypercapnia in humans is much faster than has previously been thought.
Changes in breath 13CO2/12CO2 during exercise of different intensities
Authors: Gautier J. F. , Pirnay F. , Lacroix M. , Mosora F. , Scheen A. J. , Cathelineau G. , Lefebvre P. J.
Published: December 2017

The measurement of breath 13CO2/12CO2 is commonly used during exercise to evaluate the oxidation rate of exogenous carbohydrates enriched in 13C. The aim of this study was to investigate whether exercise itself affects the 13C/12C ratio in expired air CO2 in relation to exercise intensity. The relative abundance of 13C and 12C in expired air CO2 was determined by isotoperatio mass spectrometry and expressed as delta 13C (in %o) by using Craig's formula and calibrated standards. Five healthy young men exercised on a treadmill after an overnight fast during > or = 105 min on four occasions and in a randomized order. Work rates were performed at approximately 30, 45, 60, and 75% of their maximal O2 uptake (VO2max). Delta 13C in expired air CO2 and respiratory exchange ratio (RER) were determined every 15 or 30 min during exercise. At 30 and 45% VO2max, a slight and not statistically significant increase in delta 13C was observed at 30 min. In contrast, at 60 75% VO2max, the rise was statistically significant and averaged 0.83 and 0.99%o, respectively. Average delta 13C (between 0 and 105 min) progressively increased with the intensity of exercise. Individual values of delta 13C and RER were positively correlated (r = 0.653, P = 0.002) as were values of delta 13C and endogenous carbohydrates utilized (r = 0.752, P < 0.001). Factitious or "pseudooxidation" of a 13C-enriched exogenous glucose load (indeed noningested) was calculated from the changes in expired air delta 13C. Over the whole period of exercise it was not statistically significant at 30 and 40% VO2max. However, over the first 60 min of exercise, such pseudooxidation of exogenous glucose was significant at 30 and 45% VO2max. In conclusion, by modifying the mix of endogenous substrates oxidized, exercise at 60% VO2max and above significantly increases the 13C/12C ratio in expired air CO2. At these intensities, this could lead to overestimation of the oxidation of 13C-labeled substrates given orally. At lower intensities of exercise, such overestimation is much smaller an affects mainly the values recorded during the initial part of the exercise bout.
Heart rate recording method validated by whole body indirect calorimetry in 10-yr-old children
Authors: Bitar A. , Vermorel M. , Fellmann N. , Bedu M. , Chamoux A. , Coudert J.
Published: December 2017

The aim of the study was to validate the heart rate (HR) recording method against whole body indirect calorimetry in prepubertal children. Nineteen 10.5-yr-old healthy children (10 boys, 9 girls) participated in this study. HR and energy expenditure (EE) were recorded through laboratory tests. Individual relationships between HR and EE were computed (equation established in laboratory). Several models were tested and validated from 24-h measurements of EE and HR by whole body indirect calorimetry. The best fit was obtained with individual polynomial relationships. Mean differences between predicted (equation established in laboratory) and measured total daily EE averaged 7.6 +/- 20.1%. The causes of the differences and the means of improving the accuracy of the prediction equation are discussed.
Reactive oxygen species modify reflex cardiovascular responses to static contraction
Authors: Bonigut S. , Stebbins C. L. , Longhurst J. C.
Published: December 2017

Reactive oxygen species can reflexly activate the cardiovascular system through stimulation of abdominal visceral afferents. The mechanism appears to involve hydroxyl radicals. We tested the hypothesis that reactive oxygen species contribute to the reflex cardiovascular response to static muscle contraction (i.e., the exercise pressor reflex). Thus blood pressure and heart rate responses to 5 min of intermittent electrically stimulated static contraction of the triceps surae muscles (15 s on, 15 s off) in anesthetized cats were compared before and after intravenous administration of the free radical scavengers dimethylthiourea (DMTU; 10 mg/kg; n = 8) or deferoxamine (Def; 10 mg/kg; n = 15). The contraction-induced pressor response was augmented from 51 +/- 6 to 61 +/- 7 mmHg after treatment with DMTU (P < 0.05) and from 44 +/- 8 to 58 +/- 8 mmHg after administration of Def (P < 0.05). Corresponding heart rate responses were not affected by either drug. Because this DMTU- or Def-induced augmentation of the exercise pressor reflex may have been due to a reduction in free radical-evoked vasodilation in the contracting skeletal muscle, popliteal artery blood velocity was measured with a Doppler flow transducer before and during contraction in the absence and presence of Def (n = 8). Blood velocity during contraction was not altered by Def (16 +/- 5 vs. 24 +/- 6 cm/s). These data suggest that reactive oxygen species exert an inhibitory effect on the exercise pressor reflex that is not associated with their local vasodilator properties. This response is opposite to that observed during stimulation of visceral afferents by reactive oxygen species.
Eosinophilia-induced vascular and airway remodeling and hyperresponsiveness in rat lungs
Authors: Yoshikawa S. , Kayes S. G. , Martin S. L. , Parker J. C.
Published: December 2017

We evaluated the effects of pulmonary infiltration of eosinophils without exogenous activators on airway and vascular hyperresponsiveness to muscarinic challenge in the lungs of rats infected with Toxocara [correction of Toxicara] canis, the canine round worm. Bronchoalveolar lavage of infected lungs produced 4.26 x 10(7) cells with 85% eosinophils, 15% mononuclear cells, and essentially no neutrophils. Eosinophils were present in the air spaces and interstitial spaces surrounding airways and vessels. The smooth muscle thickness increased about fourfold in large airways and vessels, and medium and small vessels were muscularized in infected lungs. In the T. canis-infected lungs, baseline airway resistance increased 288%, total vascular resistance (RT) increased 202%, and capillary filtration coefficient increased 208% compared with uninfected control lungs. Lung compliance was 56% of control. The concentration of acetylcholine that produced 50% of maximal response was 18.4 times greater for airway resistance and 18.7 times greater for RT in uninfected controls than in infected lungs. Isoproterenol (10(-4) M) decreased RT and peak airway pressure by 21% in infected lungs but had no significant effect on controls. We conclude that pulmonary interstitial infiltrates of eosinophils cause airway and vascular remodeling and increase baseline resistances and muscarinic reactivities of airways and vessels in rat lungs infected with T. canis.
Influence of pregnancy on the febrile response to intracerebroventricular administration of PGE1 in rats
Authors: Stobie-Hayes K. M. , Fewell J. E.
Published: December 2017

Rats have an attenuated or absent febrile response to exogenous pyrogen (e.g., bacterial endotoxin) and endogenous pyrogen (e.g., interleukin-1 beta) near term of pregnancy. The present experiments have been carried out on 19 nonpregnant and 18 time-bred pregnant Long-Evans rats to investigate the febrile response to intracerebroventricular (ICV) administration of prostaglandin E1 (PGE1). Each rat was anesthetized, a biotelemetry device was placed in the peritoneal cavity for measurement of body core temperature (Tbc), and guide cannulas were placed above the lateral cerebral ventricles for ICV injection of PGE1. At least 6 days were allowed to lapse between surgery and the experiments. ICV injection of 0.2 micrograms PGE1 produced significant increases in Tbc in both nonpregnant and pregnant animals (day 19 of gestation). The increase in Tbc as well as the fever index, however, were significantly attenuated in the pregnant compared with the nonpregnant rats. Vehicle had no effect on Tbc or fever index in either group of animals. The attenuated febrile response to PGE1 in the pregnant rats may have resulted from a pregnancy-related activation of endogenous antipyretics and/or impaired thermoregulatory effector mechanisms.
Cardiorespiratory kinetics during exercise of different muscle groups and mass in old and young
Authors: Chilibeck P. D. , Paterson D. H. , Smith W. D. , Cunningham D. A.
Published: December 2017

The purpose was to compare cardiorespiratory kinetics during exercise of different muscle groups (double-leg cycling vs treadmill walking and single-leg ankle plantar flexion) in old and young subjects. Oxygen uptake (VO2) during exercise transitions was measured breath by breath, and the phase 2 portion of the response was fit by a monoexponential for determination of the time constant (tau) of VO2. Two separate studies were performed: in study 1, 12 old (age 66.7 yr) and 16 young (aged 26.3 yr) subjects were compared during cycling and ankle plantar flexion exercise, and in the study 2, five old (aged 69.6 yr) and five young (24.4 yr) subjects were compared during cycling and treadmill walking. VO2 transients during square-wave cycling exercise were significantly slower in the old compared with the young groups. In contrast, VO2 kinetics did not differ between old and young groups during plantar flexion exercise. Heart rate (HR) kinetics followed the same pattern, with tau HR being significantly slower in the old vs young groups during transitions to cycling but not to plantar flexion. In study 2 tau VO2 and tau HR during on-transients to treadmill square-wave exercise were significantly slower in the old group compared with the young group, but tau VO2 was significantly faster during treadmill exercise than during cycling in the old group. The differences with aging between the modes of exercise may be related to the muscle mass involved and the circulatory demands. On the other hand, slowed VO2 kinetics with age appear to occur in a mode (cycling) in which the muscles are not accustomed to the activity, whereas in a mode of normal activity (walking) and with the muscle groups (plantar flexors) accustomed to the activity, VO2 kinetics are not slowed to the same degree with age.
Tendinous movement of a human muscle during voluntary contractions determined by real-time ultrasonography
Authors: Fukunaga T. , Ito M. , Ichinose Y. , Kuno S. , Kawakami Y. , Fukashiro S.
Published: December 2017

The degree of shortening or lengthening of muscles during joint actions has not been clarified in humans, although such information is essential in understanding human muscle functions. In this study, the tendinous movement of a muscle was determined by real-time ultrasonography during voluntary contractions. The tibialis anterior muscle (TA) was tested in five healthy men who performed dorsi- and plantar flexion movements (shortening and lengthening of TA) at two frequencies (0.1 and 1.5 Hz). The insertion point (eta) of fascicles onto the aponeurosis was clearly visualized on the ultrasonogram, and its position relative to a fixed marker moved proximally and distally according to dorsi- and plantar flexion of ankle joint. The movement of eta occurred in phase with the angular change of ankle joint, giving high correlations (r = 0.93 to 0.97) between the displacement of eta and the angle. The displacement of eta for one radian of joint angle change, 46.5 +/- 1.7 (SD) mm, was comparable to the reported moment arm of TA. The present method has many potential applications in the field of muscle physiology and biomechanics in humans.
Pulmonary clearance of circulating endothelin-1 in dogs in vivo: exclusive role of ETBreceptors
Authors: Dupuis Jocelyn , Goresky Carl A. , Fournier Alain
Published: December 2017

Dupuis, Jocelyn, Carl A. Goresky, and Alain Fournier.Pulmonary clearance of circulating endothelin-1 in dogs in vivo: exclusive role of ETB receptors. J. Appl. Physiol. 81(4): 1510–1515, 1996.—The pulmonary circulation plays an important role in the removal of circulating endothelin-1 (ET-1). Plasma ET-1 levels are increased in pulmonary hypertensive states of various etiologies (e.g., idiopathic, heart failure, and congenital anomalies) in proportion to the severity of pulmonary hypertension. It is possible that reduced pulmonary clearance of this peptide contributes to the hyperendothelinemia of those pathologies. The ETA and ETB receptors are abundant in lung tissues: on the vascular endothelium, the ETB receptor is predominant and may contribute to ET-1 extraction through receptor-mediated endocytosis. We designed experiments to determine and quantify the importance of the ETA and ETB receptors in the pulmonary extraction of circulating ET-1 in anesthetized dogs. The single-pass cumulative tracer ET-1 extraction by the lung was measured with the indicator-dilution technique before and 5 min after intrapulmonary injection of the specific ETAantagonist BQ-123 ( n = 5, 120–960 nmol) and the specific ETBantagonist BQ-788 ( n = 6, 1,000 nmol). The inhibitors had no significant effect on pulmonary and systemic hemodynamics. Mean cumulative pulmonary ET-1 extraction was not modified by BQ-123 [control (C): 36 ± 4%, antagonist (A): 34 ± 6%] but was completely abolished by BQ-788 (C: 34 ± 6%, A: 0 ± 2%, P < 0.001). The pulmonary rate constant ( K) for ET-1 removal was also unaffected by BQ-123 (C: 0.050 ± 0.0085 s−1, A: 0.047 ± 0.012 s−1) but significantly decreased and became close to zero after BQ-788 (C: 0.058 ± 0.014 s−1, A: 0.009 ± 0.007 s−1, P < 0.001). We conclude that the ETB receptor is completely and exclusively responsible for pulmonary ET-1 removal in vivo. Future studies are needed to show whether desensitization or downregulation of the ETB receptor may contribute to the increase in circulating ET-1 levels in conditions associated with pulmonary hypertension. This novel pulmonary endothelial cell function may play a protective role by modulating circulating ET-1 levels in the systemic circulation.
Effects of N2O narcosis on breathing and effort sensations during exercise and inspiratory resistive loading
Authors: Fothergill D. M. , Carlson N. A.
Published: December 2017

Fothergill, D. M., and N. A. Carlson. Effects of N2O narcosis on breathing and effort sensations during exercise and inspiratory resistive loading. J. Appl. Physiol. 81(4): 1562–1571, 1996.—The influence of nitrous oxide (N2O) narcosis on the responses to exercise and inspiratory resistive loading was studied in thirteen male US Navy divers. Each diver performed an incremental bicycle exercise test at 1 ATA to volitional exhaustion while breathing a 23% N2O gas mixture and a nonnarcotic gas of the same [Formula: see text], density, and viscosity. The same gas mixtures were used during four subsequent 30-min steady-state submaximal exercise trials in which the subjects breathed the mixtures both with and without an inspiratory resistance (5.5 vs. 1.1 cmH2O ⋅ s ⋅ l−1at 1 l/s). Throughout each test, subjective ratings of respiratory effort (RE), leg exertion, and narcosis were obtained with a category-ratio scale. The level of narcosis was rated between slight and moderate for the N2O mixture but showed great individual variation. Perceived leg exertion and the time to exhaustion were not significantly different with the two breathing mixtures. Heart rate was unaffected by the gas mixture and inspiratory resistance at rest and during steady-state exercise but was significantly lower with the N2O mixture during incremental exercise ( P< 0.05). Despite significant increases in inspiratory occlusion pressure (13%; P < 0.05), esophageal pressure (12%; P < 0.001), expired minute ventilation (4%; P < 0.01), and the work rate of breathing (15%; P < 0.001) when the subjects breathed the N2O mixture, RE during both steady-state and incremental exercise was 25% lower with the narcotic gas than with the nonnarcotic mixture ( P < 0.05). We conclude that the narcotic-mediated changes in ventilation, heart rate, and RE induced by 23% N2O are not of sufficient magnitude to influence exercise tolerance at surface pressure. Furthermore, the load-compensating respiratory reflexes responsible for maintaining ventilation during resistive breathing are not depressed by N2O narcosis.
Alveolar P CO 2 and P O 2 of high-altitude natives living at sea level
Authors: León-Velarde Fabiola , Vargas Manuel , Monge-C. Carlos , Torrance Robert W. , Robbins Peter A.
Published: December 2017

León-Velarde, Fabiola, Manuel Vargas, Carlos Monge-C., Robert W. Torrance, and Peter A. Robbins. Alveolar[Formula: see text] and[Formula: see text] of high-altitude natives living at sea level. J. Appl. Physiol. 81(4): 1605–1609, 1996.—This study was designed to determine whether subjects born at high altitude (HA; 2,000 m or above) who subsequently move to near sea level (SL) develop end-tidal [Formula: see text]([Formula: see text]) and[Formula: see text]([Formula: see text]) values that equal those of SL natives living near SL. A total of 108 male HA natives living near SL were identified by survey of a district in Lima, Peru, and a further 108 male SL natives from the same district were identified as control subjects. Of these subjects, satisfactory data for inclusion in the study were obtained from 93 HA and 82 SL subjects. Mean [Formula: see text] and[Formula: see text] values were 37.7 ± 2.5 (SD) and 104.7 ± 3.2 Torr, respectively, in HA subjects and 37.7 ± 2.2 and 104.8 ± 3.0 Torr, respectively, in SL subjects. The average difference between SL natives and HA natives for[Formula: see text] was 0.07 Torr (−0.64 to 0.78; 95% confidence interval) and for[Formula: see text] was 0.05 Torr (−0.89 to 0.99, 95% confidence interval). The average age and weight of the SL and HA subjects did not differ, but the HA subjects were shorter and tended to have larger vital capacities, consistent with their origin at HA. We conclude that the[Formula: see text] and[Formula: see text] near SL of SL natives and HA natives do not differ.
Changes in bronchial and pulmonary arterial blood flow with progressive tension pneumothorax
Authors: Carvalho Paula , Hildebrandt Jacob , Charan Nirmal B.
Published: December 2017

Carvalho, Paula, Jacob Hildebrandt, and Nirmal B. Charan.Changes in bronchial and pulmonary arterial blood flow with progressive tension pneumothorax. J. Appl. Physiol. 81(4): 1664–1669, 1996.—We studied the effects of unilateral tension pneumothorax and its release on bronchial and pulmonary arterial blood flow and gas exchange in 10 adult anesthetized and mechanically ventilated sheep with chronically implanted ultrasonic flow probes. Right pleural pressure (Ppl) was increased in two steps from −5 to 10 and 25 cmH2O and then decreased to 10 and −5 cmH2O. Each level of Ppl was maintained for 5 min. Bronchial blood flow, right and left pulmonary arterial flows, cardiac output (Q˙t), hemodynamic measurements, and arterial blood gases were obtained at the end of each period. Pneumothorax resulted in a 66% decrease inQ˙t, bronchial blood flow decreased by 84%, and right pulmonary arterial flow decreased by 80% at Ppl of 25 cmH2O ( P < 0.001). At peak Ppl, the majority ofQ˙t was due to blood flow through the left pulmonary artery. With resolution of pneumothorax, hemodynamic parameters normalized, although abnormalities in gas exchange persisted for 60–90 min after recovery and were associated with a decrease in total respiratory compliance.
Greater initial adaptations to submaximal muscle lengthening than maximal shortening
Authors: Hortobágyi Tibor , Barrier Jason , Beard David , Braspennincx John , Koens Peter , Devita Paul , Dempsey Line , Lambert Jean
Published: December 2017

Hortobágyi, Tibor, Jason Barrier, David Beard, John Braspennincx, Peter Koens, Paul Devita, Line Dempsey, and Jean Lambert.Greater initial adaptations to submaximal muscle lengthening than maximal shortening. J. Appl. Physiol.81(4): 1677–1682, 1996.—The purpose of this study was to compare the short-term strength and neural adaptations to eccentric and concentric training at equal force levels. Forty-two sedentary women (age = 21.5 yr) were ranked based on the initial quadriceps strength score, and trios of subjects were randomly assigned to either an eccentric ( n = 14), a concentric ( n = 14), or a nonexercising control group ( n = 14). Training involved a total of 824 eccentric or concentric quadriceps actions at 1.05 rad ⋅ s−1administered in four sets of 6–10 repetitions, four times per week for 6 wk. Before and after training, all subjects were tested for unilateral maximal isometric and eccentric and concentric actions at 1.05 rad ⋅ s−1and for a 40-repetition eccentric and concentric fatigue series of the left and right quadriceps. Surface electromyographic activity of the vastus lateralis and medialis was monitored during testing. Concentric training increased concentric (36%, P< 0.05), isometric (18%, P < 0.05), and eccentric strength (13%), and eccentric training increased eccentric (42%, P < 0.05), isometric (30%, P < 0.05), and concentric (13%) strength. Eccentric training improved eccentric and isometric strength more ( P < 0.05) than did concentric training. The electromyographic adaptations were greater with eccentric training. Cross-education was 6%, and neither training mode modified fatigability. The data suggest that training of the quadriceps muscle with submaximal eccentric actions brings about greater strength adaptations faster than does training with maximal-level concentric actions in women. This greater adaptation is likely to be mediated by both mechanical and neural factors.
Maturational changes in responses of tissue and airway resistance to histamine
Authors: Dreshaj Ismail A. , Haxhiu Musa A. , Potter Charles F. , Agani Faton H. , Martin Richard J.
Published: December 2017

Dreshaj, Ismail A., Musa A. Haxhiu, Charles F. Potter, Faton H. Agani, and Richard J. Martin. Maturational changes in responses of tissue and airway resistance to histamine. J. Appl. Physiol. 81(4): 1785–1791, 1996.—We determined how postnatal maturation affects the relative contributions of airways and lung parenchyma to pulmonary resistance (Rl) and whether there are developmental differences in their respective responses to constrictive agents. We studied open-chest ventilated anesthetized piglets of three ages: 2–4 days, 2–3 wk, and 10 wk. Rl was partitioned into tissue (Rti) and airway (Raw) resistance by means of alveolar capsules under baseline conditions and after intravenous histamine. Postnatal maturation was associated with a progressive decline in Rl, Rti, and Raw and with an increase in the contribution of Rti to Rl from 38 ± 8% at 2–4 days to 72 ± 2% at both 2–3 and 10 wk. Histamine caused Rl to increase at all ages. When partitioned into Rti and Raw, the percent increase in Rti significantly exceeded that of Raw at both 2–4 days and 2–3 wk. In contrast, the percent increase in Raw significantly exceeded that of Rti at 10 wk. Administration of atropine before histamine in piglets aged 10 wk reduced the response of Rti and Raw to histamine. Histamine-induced responses of Rl were blocked by prior H1-receptor blockade with pyrilamine (2 mg/kg). These results indicate that 1) the contribution of Rti and Raw to Rl changes during maturation and that 2) contractile responses to exogenous histamine are manifest predominantly in most distal airways and lung parenchyma during early postnatal life; with advancing maturation there is greater contribution of airways to the increase in Rl induced by histamine.
Mechanisms regulating regional cerebral activation during dynamic handgrip in humans
Authors: Williamson J. W. , Friedman D. B. , Mitchell J. H. , Secher N. H. , Friberg L.
Published: December 2017

Williamson, J. W., D. B. Friedman, J. H. Mitchell, N. H. Secher, and L. Friberg. Mechanisms regulating regional cerebral activation during dynamic handgrip in humans. J. Appl. Physiol. 81(5): 1884–1890, 1996.—Dynamic hand movement increases regional cerebral blood flow (rCBF) of the contralateral motor sensory cortex (MS1). This increase is eliminated by regional anesthesia of the working arm, indicating the importance of afferent neural input. The purpose of this study was to determine the specific type of afferent input required for this cerebral activation. The rCBF was measured at +5.0 and +9.0 cm above the orbitomeatal (OM) plane in 13 subjects during 1) rest; 2) dynamic left-hand contractions; 3) postcontraction ischemia (metaboreceptor afferents); and 4) biceps brachii tendon vibration (muscle spindles). The rCBF increased only during dynamic hand contraction; contralateral MS1 (OM +9) by 15% to 64 ± 8.6 ml ⋅ 100 g−1⋅ min−1( P < 0.05); supplementary motor area (OM +9) by 11% to 69 ± 9.8 ml ⋅ 100 g−1⋅ min−1( P < 0.05); and there were also bilateral increases at MS2 (OM +5) [by 16% to 64 ± 8.6 ml ⋅ 100 g−1⋅ min−1( P < 0.05)]. These findings suggest that the rCBF increase during dynamic hand contraction does not require neural input from muscle spindles or metabolically sensitive nerve fibers, although the involvement of mechanoreceptors (group III or Ib) cannot be excluded.
Decreased insulin action on muscle glucose transport after eccentric contractions in rats
Authors: Asp Sven , Richter Erik A.
Published: December 2017

Asp, Sven, and Erik A. Richter. Decreased insulin action on muscle glucose transport after eccentric contractions in rats. J. Appl. Physiol. 81(5): 1924–1928, 1996.—We have recently shown that eccentric contractions (Ecc) of rat calf muscles cause muscle damage and decreased glycogen and glucose transporter GLUT-4 protein content in the white (WG) and red gastrocnemius (RG) but not in the soleus (S) (S. Asp, S. Kristiansen, and E. A. Richter. J. Appl. Physiol. 79: 1338–1345, 1995). To study whether these changes affect insulin action, hindlimbs were perfused at three different insulin concentrations (0, 200, and 20,000 μU/ml) 2 days after one-legged eccentric contractions of the calf muscles. Compared with control, basal glucose transport was slightly higher ( P < 0.05) in Ecc-WG and -RG, whereas it was lower ( P < 0.05) at both submaximal and maximal insulin concentrations in the Ecc-WG and at maximal concentrations in the Ecc-RG. In the Ecc-S, the glucose transport was unchanged in hindquarters perfused in the absence or presence of a submaximal stimulating concentration of insulin, whereas it was slightly ( P < 0.05) higher during maximal insulin stimulation compared with control S. At the end of perfusion the glycogen concentrations were lower in both Ecc-gastrocnemius muscles compared with control muscles at all insulin concentrations. Fractional velocity of glycogen synthase increased similarly with increasing insulin concentrations in Ecc- and control WG and RG. We conclude that insulin action on glucose transport but not glycogen synthase activity is impaired in perfused muscle exposed to prior eccentric contractions.
Utilization of glycogen but not plasma glucose is reduced in individuals with NIDDM during mild-intensity exercise
Authors: Colberg Sheri R. , Hagberg James M. , McCole Steve D. , Zmuda Joseph M. , Thompson Paul D. , Kelley David E.
Published: December 2017

Colberg, Sheri R., James M. Hagberg, Steve D. McCole, Joseph M. Zmuda, Paul D. Thompson, and David E. Kelley. Utilization of glycogen but not plasma glucose is reduced in individuals with NIDDM during mild-intensity exercise. J. Appl. Physiol. 81(4): 2027–2033, 1996.—To test the hypothesis that substrate utilization during mild-intensity exercise differs in non-insulin-dependent diabetes mellitus (NIDDM) compared with nondiabetic subjects, seven lean healthy subjects (L), seven obese healthy subjects (O), and seven individuals with NIDDM were studied during 40 min of mild-intensity cycling (40% of peak O2 uptake). Systemic utilization of plasma glucose (Glc Rd) was determined by using isotope dilution methods. Gas exchange was measured to determine rates of carbohydrate (CHO) and lipid oxidation. During exercise, when CHO oxidation was greater than Glc Rd, the net oxidation of glycogen was calculated as the difference: CHO oxidation − Glc Rd. During mild-intensity cycling, the respiratory exchange ratio was similar across groups (0.87 ± 0.02, 0.85 ± 0.02, and 0.86 ± 0.01 in L, O, and NIDDM subjects, respectively), and CHO oxidation accounted for one-half of total energy expenditure during exercise. Glc Rd increased during exercise and was greatest in subjects with NIDDM (3.0 ± 0.2, 2.9 ± 0.2, and 4.5 ± 0.4 ml ⋅ kg−1 ⋅ min−1in L, O, and NIDDM subjects, respectively, P < 0.05), yet Glc Rd was less than CHO oxidation during exercise, indicating net oxidation of glycogen. Glycogen oxidation was greater in L and O than in NIDDM subjects (3.4 ± 1.0, 2.5 ± 0.9, and 1.7 ± 0.8 ml ⋅ kg−1 ⋅ min−1; P < 0.05). In summary, during mild-intensity exercise, NIDDM subjects have an increased Glc Rd and a decreased oxidation of muscle glycogen.
Effects of concentric and eccentric training on muscle strength, cross-sectional area, and neural activation
Authors: Higbie Elizabeth J. , Cureton Kirk J. , Warren Gordon L. , Prior Barry M.
Published: December 2017

Higbie, Elizabeth J., Kirk J. Cureton, Gordon L. Warren III, and Barry M. Prior. Effects of concentric and eccentric training on muscle strength, cross-sectional area, and neural activation. J. Appl. Physiol. 81(5): 2173–2181, 1996.—We compared the effects of concentric (Con) and eccentric (Ecc) isokinetic training on quadriceps muscle strength, cross-sectional area, and neural activation. Women (age 20.0 ± 0.5 yr) randomly assigned to Con training (CTG; n = 16), Ecc training (ETG; n = 19), and control (CG; n = 19) groups were tested before and after 10 wk of unilateral Con or Ecc knee-extension training. Average torque measured during Con and Ecc maximal voluntary knee extensions increased 18.4 and 12.8% for CTG, 6.8 and 36.2% for ETG, and 4.7 and −1.7% for CG, respectively. Increases by CTG and ETG were greater than for CG ( P < 0.05). For CTG, the increase was greater when measured with Con than with Ecc testing. For ETG, the increase was greater when measured with Ecc than with Con testing. The increase by ETG with Ecc testing was greater than the increase by CTG with Con testing. Corresponding changes in the integrated voltage from an electromyogram measured during strength testing were 21.7 and 20.0% for CTG, 7.1 and 16.7% for ETG, and −8.0 and −9.1% for CG. Quadriceps cross-sectional area measured by magnetic resonance imaging (sum of 7 slices) increased more in ETG (6.6%) than in CTG (5.0%) ( P< 0.05). We conclude that Ecc is more effective than Con isokinetic training for developing strength in Ecc isokinetic muscle actions and that Con is more effective than Ecc isokinetic training for developing strength in Con isokinetic muscle actions. Gains in strength consequent to Con and Ecc training are highly dependent on the muscle action used for training and testing. Muscle hypertrophy and neural adaptations contribute to strength increases consequent to both Con and Ecc training.
Interaction of chemical and state effects on ventilation during sleep onset
Authors: Dunai Judith , Wilkinson Mal , Trinder John
Published: December 2017

Dunai, Judith, Mal Wilkinson, and John Trinder.Interaction of chemical and state effects on ventilation during sleep onset. J. Appl. Physiol. 81(5): 2235–2243, 1996.—Ventilation varies as a function of state, being higher during wakefulness (as indicated by alpha electroencephalogram activity) than during sleep (theta activity). A recent experiment observed a progressive increase in the magnitude of these state-related fluctuations in ventilation over the sleep-onset period (28). The aim of the present experiment was to test the hypothesis that this effect resulted from chemical (feedback-related) amplification of state effects on ventilation. A hyperoxic condition was used to eliminate peripheral chemoreceptor activity. It was hypothesized that hyperoxia would reduce the amplification of changes in ventilation associated with electroencephalogram state transitions. Ventilation was measured over the sleep-onset period under both hyperoxic and normoxic conditions in 10 young healthy male subjects. Sleep onsets were divided into three phases. Phase 1 corresponded to presleep wakefulness; and phases 2 and 3 corresponded to early and late sleep onset, respectively. The magnitudes of state-related changes in ventilation during phases 2 and 3, and under hyperoxic and normoxic conditions were compared using a phase by condition analysis of variance. Results revealed a significant phase by condition interaction, confirming that hyperoxia reduced the amplification of state-related changes in ventilation by selectively decreasing the magnitude of phase 3 state changes in ventilation. However, some degree of amplification was evident during hyperoxia, thus the results demonstrated that peripheral chemoreceptor activity contributed to the amplification of state-related changes in ventilation but that additional factors may also be involved.
Changes in maximum oxygen uptake during prolonged training, overtraining, and detraining in horses
Authors: Tyler Catherine M. , Golland Lorraine C. , Evans David L. , Hodgson David R. , Rose Reuben J.
Published: December 2017

Tyler, Catherine M., Lorraine C. Golland, David L. Evans, David R. Hodgson, and Reuben J. Rose. Changes in maximum oxygen uptake during prolonged training, overtraining, and detraining in horses. J. Appl. Physiol. 81(5): 2244–2249, 1996.—Thirteen standardbred horses were trained as follows: phase 1 (endurance training, 7 wk), phase 2 (high-intensity training, 9 wk), phase 3 (overload training, 18 wk), and phase 4 (detraining, 12 wk). In phase 3, the horses were divided into two groups: overload training (OLT) and control (C). The OLT group exercised at greater intensities, frequencies, and durations than group C. Overtraining occurred after 31 wk of training and was defined as a significant decrease in treadmill run time in response to a standardized exercise test. In the OLT group, there was a significant decrease in body weight ( P < 0.05). From pretraining values of 117 ± 2 (SE) ml ⋅ kg−1⋅ min−1, maximal O2uptake (V˙o2 max) increased by 15% at the end of phase 1, and when signs of overtraining were first seen in the OLT group,V˙o2 maxwas 29% higher (151 ± 2 ml ⋅ kg−1⋅ min−1in both C and OLT groups) than pretraining values. There was no significant reduction inV˙o2 maxuntil after 6 wk detraining whenV˙o2 maxwas 137 ± 2 ml ⋅ kg−1⋅ min−1. By 12 wk detraining, meanV˙o2 maxwas 134 ± 2 ml ⋅ kg−1⋅ min−1, still 15% above pretraining values. When overtraining developed,V˙o2 maxwas not different between C and OLT groups, but maximal values for CO2production (147 vs. 159 ml ⋅ kg−1⋅ min−1) and respiratory exchange ratio (1.04 vs. 1.11) were lower in the OLT group. Overtraining was not associated with a decrease inV˙o2 maxand, after prolonged training, decreases inV˙o2 maxoccurred slowly during detraining.
Distribution of myosin heavy chain isoforms in non-weight-bearing rat soleus muscle fibers
Authors: Talmadge Robert J. , Roy Roland R. , Edgerton V. Reggie
Published: December 2017

Talmadge, Robert J., Roland R. Roy, and V. Reggie Edgerton.Distribution of myosin heavy chain isoforms in non-weight-bearing rat soleus muscle fibers. J. Appl. Physiol. 81(6): 2540–2546, 1996.—The effects of 14 days of spaceflight (SF) or hindlimb suspension (HS) (Cosmos 2044) on myosin heavy chain (MHC) isoform content of the rat soleus muscle and single muscle fibers were determined. On the basis of electrophoretic analyses, there was a de novo synthesis of type IIx MHC but no change in either type I or IIa MHC isoform proportions after either SF or HS compared with controls. The percentage of fibers containing only type I MHC decreased by 26 and 23%, and the percentage of fibers with multiple MHCs increased from 6% in controls to 32% in HS and 34% in SF rats. Type IIx MHC was always found in combination with another MHC or combination of MHCs; i.e., no fibers contained type IIx MHC exclusively. These data suggest that the expression of the normal complement of MHC isoforms in the adult rat soleus muscle is dependent, in part, on normal weight bearing and that the absence of weight bearing induces a shift toward type IIx MHC protein expression in the preexisting type I and IIa fibers of the soleus.
Effect of Diazinon PLUS on rapidly adapting receptors in the rabbit
Authors: Campbell Hillary , Ravi Krishnan , Bravo Emigdio , Kappagoda C. Tissa
Published: December 2017

Campbell, Hillary, Krishnan Ravi, Emigdio Bravo, and C. Tissa Kappagoda. Effect of Diazinon PLUS on rapidly adapting receptors in the rabbit. J. Appl. Physiol. 81(6): 2604–2610, 1996.—The effects of Diazinon PLUS aerosol on the activities of rapidly adapting receptors (RARs) and slowly adapting receptors (SAR) of the airways were investigated in anesthetized rabbits. The effects on both the baseline activity and the responses to stimulation by increasing mean left atrial pressure were examined. Action potentials were recorded from the left cervical vagus nerve. Aerosols (particle size 3 μm) were generated by a Mini-HEART nebulizer. We observed that an aerosol of Diazinon PLUS (1:10 vol/vol dilution in normal saline) decreased the baseline RAR activity ( n= 10) significantly ( P < 0.05) from 209 ± 77 to 120 ± 40 impulses/min. In the post-Diazinon PLUS control period, the RAR activity recovered partially to 185 ± 75 impulses/min and decreased significantly to 131 ± 52 impulses/min ( P < 0.05) after a second exposure of Diazinon PLUS (undiluted) aerosol. Aerosols of normal saline in the control state did not produce a significant change in the RAR activity. A group of SAR ( n = 8) were examined under similar conditions, and it was found that only the exposure to Diazinon PLUS (undiluted) aerosol decreased the activity significantly ( P < 0.05) from 1,536 ± 206 to 1,367 ± 182 impulses/min. The effect of Diazinon PLUS on the response to increasing mean left atrial pressure was examined in seven RARs. In the control state, RAR activity increased significantly ( P < 0.05) during elevation of mean left atrial pressure. This response was abolished after exposure to Diazinon PLUS. These findings suggest that diazinon may interfere with airway defense mechanisms by reducing the activity of RARs.
Gender-specific effects of dexamethasone treatment on rat diaphragm structure and function
Authors: Prezant D. J. , Karwa M. L. , Richner B. , Maggiore D. , Gentry E. I. , Cahill J.
Published: December 2017

Prezant, D. J., M. L. Karwa, B. Richner, D. Maggiore, E. I. Gentry, and J. Cahill. Gender-specific effects of dexamethasone treatment on rat diaphragm structure and function. J. Appl. Physiol. 82(1): 125–133, 1997.—The effects of long-term dexamethasone treatment on diaphragm muscle were studied in female and male rats. Compared with pair-fed control animals, dexamethasone treatment did not significantly affect estrous cycling or peak serum estradiol levels; however, testosterone levels were significantly increased in females and decreased in males. Dexamethasone significantly reduced body and costal diaphragm weights, but to a lesser extent in females than in males. Reductions in diaphragm weight were proportional to reductions in body weight. In females and males, dexamethasone treatment significantly decreased diaphragm fiber (types I and II) cross-sectional area and the relative expression of myosin heavy chain isoform 2B. With the exception of type I fiber atrophy, these changes occurred to a lesser extent in females. Dexamethasone did not significantly affect specific forces. Dexamethasone significantly increased twitch one-half relaxation time and fatigue resistance indexes in males but not in females. In conclusion, the effects of long-term dexamethasone treatment were gender specific, with significantly fewer effects in females, and changes in serum testosterone levels were associated with these findings.