bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of muscle fiber type and pedal frequency on oxygen uptake kinetics of heavy exercise
Authors: Barstow Thomas J. , Jones Andrew M. , Nguyen Paul H. , Casaburi Richard
Published: December 2017

Barstow, Thomas J., Andrew M. Jones, Paul H. Nguyen, and Richard Casaburi. Influence of muscle fiber type and pedal frequency on oxygen uptake kinetics of heavy exercise. J. Appl. Physiol. 81(4): 1642–1650, 1996.—We tested the hypothesis that the amplitude of the additional slow component of O2 uptake (V˙o 2) during heavy exercise is correlated with the percentage of type II (fast-twitch) fibers in the contracting muscles. Ten subjects performed transitions to a work rate calculated to require aV˙o 2 equal to 50% between the estimated lactate (Lac) threshold and maximalV˙o 2 (50%Δ). Nine subjects consented to a muscle biopsy of the vastus lateralis. To enhance the influence of differences in fiber type among subjects, transitions were made while subjects were pedaling at 45, 60, 75, and 90 rpm in different trials. BaselineV˙o 2 was designed to be similar at the different pedal rates by adjusting baseline work rate while the absolute increase in work rate above the baseline was the same. The V˙o 2 response after the onset of exercise was described by a three-exponential model. The relative magnitude of the slow component at the end of 8-min exercise was significantly negatively correlated with %type I fibers at every pedal rate ( r = 0.64 to 0.83, P < 0.05–0.01). Furthermore, the gain of the fast component forV˙o 2 (as ml ⋅ min−1 ⋅ W−1) was positively correlated with the %type I fibers across pedal rates ( r = 0.69–0.83). Increase in pedal rate was associated with decreased relative stress of the exercise but did not affect the relationships between %fiber type and V˙o 2parameters. The relative contribution of the slow component was also significantly negatively correlated with maximalV˙o 2( r = −0.65), whereas the gain for the fast component was positively associated ( r = 0.68–0.71 across rpm). The amplitude of the slow component was significantly correlated with net end-exercise Lac at all four pedal rates ( r = 0.64–0.84), but Lac was not correlated with %type I ( P > 0.05). We conclude that fiber type distribution significantly affects both the fast and slow components ofV˙o 2 during heavy exercise and that fiber type and fitness may have both codependent and independent influences on the metabolic and gas-exchange responses to heavy exercise.
V˙/Q˙ distribution and correlation to atelectasis in anesthetized paralyzed humans
Authors: Tokics Leif , Hedenstierna Göran , Svensson Leif , Brismar Bo , Cederlund Torsten , Lundquist Hans , Strandberg Åke
Published: December 2017

Tokics, Leif, Göran Hedenstierna, Leif Svensson, Bo Brismar, Torsten Cederlund, Hans Lundquist, and Åke Strandberg. V˙/Q˙ distribution and correlation to atelectasis in anesthetized paralyzed humans. J. Appl. Physiol. 81(4): 1822–1833, 1996.—Regional ventilation and perfusion were studied in 10 anesthetized paralyzed supine patients by single-photon emission computerized tomography. Atelectasis was estimated from two transaxial computerized tomography scans. The ventilation-perfusion (V˙/Q˙) distribution was also evaluated by multiple inert gas elimination. While the patients were awake, inert gas V˙/Q˙ ratio was normal, and shunt did not exceed 1% in any patient. Computerized tomography showed no atelectasis. During anesthesia, shunt ranged from 0.4 to 12.2%. Nine patients displayed atelectasis (0.6–7.2% of the intrathoracic area), and shunt correlated with the atelectasis ( r = 0.91, P < 0.001). Shunt was located in dependent lung regions corresponding to the atelectatic area. There was considerable V˙/Q˙ mismatch, with ventilation mainly of ventral lung regions and perfusion of dorsal regions. Little perfusion was seen in the most ventral parts (zone 1) of caudal (diaphragmatic) lung regions. In summary, shunt during anesthesia is due to atelectasis in dependent lung regions. TheV˙/Q˙ distributions differ from those shown earlier in awake subjects.
Medullary regions for neurogenesis of gasping: noeud vital or noeuds vitals?
Authors: St. John Walter M.
Published: December 2017

St. John, Walter M. Medullary regions for neurogenesis of gasping: noeud vital or noeuds vitals? J. Appl. Physiol. 81(5): 1865–1877, 1996.—Gasping is a critical mechanism for survival in that it serves as a mechanism for autoresuscitation when eupnea fails. Eupnea and gasping are separable patterns of automatic ventilatory activity in all mammalian species from the day of birth. The neurogenesis of the gasp is dependent on the discharge of neurons in the rostroventral medulla. This gasping center overlaps a region termed “the pre-Bötzinger complex.” Neuronal activities of this complex, characterized in an in vitro brain stem spinal cord preparation of the neonatal rat, have been hypothesized to underlie respiratory rhythm generation. Yet, the rhythmic activity of this in vitro preparation is markedly different from eupnea but identical with gasping in vivo. In eupnea, medullary neuronal activities generating the gasp and the identical rhythm of the in vitro preparation are incorporated into a portion of the pontomedullary circuit defining eupneic ventilatory activity. However, these medullary neuronal activities do not appear critical for the neurogenesis of eupnea, per se.
Zone of apposition in the passive diaphragm of the dog
Authors: Boriek Aladin M. , Rodarte Joseph R. , Margulies Susan S.
Published: December 2017

Boriek, Aladin M., Joseph R. Rodarte, and Susan S. Margulies. Zone of apposition in the passive diaphragm of the dog. J. Appl. Physiol. 81(5): 1929–1940, 1996.—We determined the regional area of the diaphragmatic zone of apposition (ZAP) as well as the regional craniocaudal extent of the ZAP (ZAPht) of the passive diaphragm in six paralyzed anesthetized beagle dogs (8–12 kg) at residual lung volume (RV), functional residual capacity (FRC), FRC + 0.25 and FRC + 0.5 inspiratory capacity, and total lung capacity (TLC) in prone and supine postures. To identify the caudal boundary of the ZAP, 17 lead markers (1 mm) were sutured to the abdominal side of the costal and crural diaphragms around the diaphragm insertion on the chest wall. Two weeks later, the dogs’ caudal thoraces were scanned by the use of the dynamic spatial reconstructor (DSR), a prototype fast volumetric X-ray computer tomographic scanner, developed at the Mayo Clinic. The three-dimensional spatial coordinates of the markers were identified (±1.4 mm), and the cranial boundary of the ZAP was determined from 30–40 1.4-mm-thick sagittal and coronal slices in each DSR image. We interpolated the DSR data to find the position of the cranial and caudal boundaries of the ZAP every 5° around the thorax and computed the distribution of regional variation of area of the ZAP and ZAPht as well as the total area of ZAP. The ZAPht and area of ZAP increased as lung volume decreased and were largest near the lateral extremes of the rib cage. We measured the surface area of the rib cage cephaled to the ZAP ( A L) in both postures in another six beagle dogs (12–16 kg) of similar stature, scanned previously in the DSR. We estimated the entire rib cage surface area ( A rc =  A ZAP + A L). The A ZAP as a percentage of A rc increased more than threefold as lung volume decreased from TLC to RV, from ∼9 to 29% of A rc.
Muscle protein metabolism in female swimmers after a combination of resistance and endurance exercise
Authors: Tipton Kevin D. , Ferrando Arny A. , Williams Bradley D. , Wolfe Robert R.
Published: December 2017

Tipton, Kevin D., Arny A. Ferrando, Bradley D. Williams, and Robert R. Wolfe. Muscle protein metabolism in female swimmers after a combination of resistance and endurance exercise. J. Appl. Physiol. 81(5): 2034–2038, 1996.—There is little known about the responses of muscle protein metabolism in women to exercise. Furthermore, the effect of adding resistance training to an endurance training regimen on net protein anabolism has not been established in either men or women. The purpose of this study was to quantify the acute effects of combined swimming and resistance training on protein metabolism in female swimmers by the direct measurement of muscle protein synthesis and whole body protein degradation. Seven collegiate female swimmers were each studied on four separate occasions with a primed constant infusion of ring-[13C6]phenylalanine (Phe) to measure the fractional synthetic rate (FSR) of the posterior deltoid and whole body protein breakdown. Measurements were made over a 5-h period at rest and after each of three randomly ordered workouts: 1) 4,600 m of intense interval swimming (SW); 2) a whole body resistance-training workout with no swimming on that day (RW); and 3) swimming and resistance training combined (SR). Whole body protein breakdown was similar for all treatments (0.75 ± 0.04, 0.69 ± 0.03, 0.69 ± 0.02, and 0.71 ± 0.04 μmol ⋅ min−1⋅ kg−1for rest, RW, SW, and SR, respectively). The FSR of the posterior deltoid was significantly greater ( P< 0.05) after SR (0.082 ± 0.015%/h) than at rest (0.045 ± 0.006%/h). There was no significant difference in the FSR after RW (0.048 ± 0.004%/h) or SW (0.064 ± 0.008%/h) from rest or from SR. These data indicate that the combination of swimming and resistance exercise stimulates net muscle protein synthesis above resting levels in female swimmers.
Effect of nitric oxide synthase inhibition on cardiorespiratory responses in the conscious rat
Authors: Gozal David , Torres José E. , Gozal Yair M. , Littwin Sanford M.
Published: December 2017

Gozal, David, José E. Torres, Yair M. Gozal, and Sanford M. Littwin. Effect of nitric oxide synthase inhibition on cardiorespiratory responses in the conscious rat. J. Appl. Physiol. 81(5): 2068–2077, 1996.—Nitric oxide synthase (NOS) blockade was used to test the cardioventilatory responses to hypercapnia and hypoxia in freely behaving animals. Chronically instrumented adult Sprague-Dawley rats were studied before and after intravenous administration of either 100 mg/kg of NG-nitro-l-arginine methyl ester (l-NAME), a nonspecific NOS blocker, or 10 mg/kg of S-methyl-l-thiocitrulline (SMTC), a selective neural NOS inhibitor.l-NAME injection induced sustained blood pressure (BP) elevation with transient tachycardia and increased minute ventilation (V˙e), which returned to baseline within minutes. SMTC elicited similar, although transient, BP increases; however, heart rate andV˙e decreased.l-NAME and SMTC did not modify overall steady-state hypercapnic responses. In control conditions, hypoxia induced early V˙eincreases with further V˙e enhancements at 30 min. l-NAME increased the early V˙e response to 10% O2but induced lateV˙e reductions in hypoxia. SMTC did not change early V˙e responses but induced marked reductions in the later V˙ehypoxic responses. In control animals, hypoxia induced a significant heart rate increase. This increase was absent during the early response after SMTC and was followed in bothl-NAME- and SMTC-treated animals by significant heart rate reductions to values below room air. Similarly, the sustained BP response to hypoxia in control animals was absent after administration of NOS inhibitors. These findings suggest that NOS activity exerts excitatory influences on respiration and cardiac chronotropy and sustained vasomotor tone during hypoxia. We speculate that NOS-mediated mechanisms may play an important role in hypoxia-induced ventilatory roll-off during wakefulness.
Effect of leucine metabolite β-hydroxy-β-methylbutyrate on muscle metabolism during resistance-exercise training
Authors: Nissen S. , Sharp R. , Ray M. , Rathmacher J. A. , Rice D. , Fuller J. C. , Connelly A. S. , Abumrad N.
Published: December 2017

Nissen, S., R. Sharp, M. Ray, J. A. Rathmacher, D. Rice, J. C. Fuller, Jr., A. S. Connelly, and N. Abumrad. Effect of leucine metabolite β-hydroxy-β-methylbutyrate on muscle metabolism during resistance-exercise training. J. Appl. Physiol. 81(5): 2095–2104, 1996.—The effects of dietary supplementation with the leucine metabolite β-hydroxy-β-methylbutyrate (HMB) were studied in two experiments. In study 1, subjects ( n = 41) were randomized among three levels of HMB supplementation (0, 1.5 or 3.0 g HMB/day) and two protein levels (normal, 117 g/day, or high, 175 g/day) and weight lifted for 1.5 h 3 days/wk for 3 wk. In study 2, subjects ( n = 28) were fed either 0 or 3.0 g HMB/day and weight lifted for 2–3 h 6 days/wk for 7 wk. In study 1, HMB significantly decreased the exercise-induced rise in muscle proteolysis as measured by urine 3-methylhistidine during the first 2 wk of exercise (linear decrease, P < 0.04). Plasma creatine phosphokinase was also decreased with HMB supplementation ( week 3, linear decrease, P < 0.05). Weight lifted was increased by HMB supplementation when compared with the unsupplemented subjects during each week of the study (linear increase, P < 0.02). In study 2, fat-free mass was significantly increased in HMB-supplemented subjects compared with the unsupplemented group at 2 and 4–6 wk of the study ( P < 0.05). In conclusion, supplementation with either 1.5 or 3 g HMB/day can partly prevent exercise-induced proteolysis and/or muscle damage and result in larger gains in muscle function associated with resistance training.
Endothelial cell dilatory pathways link flow and wall shear stress in an intact arteriolar network
Authors: Frame Mary D. S. , Sarelius Ingrid H.
Published: December 2017

Frame, Mary D. S., and Ingrid H. Sarelius. Endothelial cell dilatory pathways link flow and wall shear stress in an intact arteriolar network. J. Appl. Physiol.81(5): 2105–2114, 1996.—Our purpose was to determine whether the endothelial cell-dependent dilatory pathways contribute to the regulation of flow distribution in an intact arteriolar network. Cell flow, wall shear stress (Tω), diameter, and bifurcation angle were determined for four sequential branches of a transverse arteriole in the superfused cremaster muscle of pentobaribtal sodium (Nembutal, 70 mg/kg)-anesthetized hamsters ( n = 51). Control cell flow was significantly greater into upstream than into downstream branches [1,561 ± 315 vs. 971 ± 200 (SE) cells/s, n = 12]. Tissue exposure to 50 μM N ω-nitro-l-arginine + 50 μM indomethacin (l-NNA + Indo) produced arteriolar constriction of 14 ± 4% and decreased flow into the transverse arteriole. More of the available cell flow was diverted to downstream branches, yet flow distribution remained unequal. Control Tω was higher upstream than downstream (31.3 ± 6.8 vs. 9.8 ± 1.5 dyn/cm2).l-NNA + Indo decreased Tω upstream and increased Tω downstream to become equal in all branches, in contrast to flow. To determine whether constriction in general induced the same changes, 5% O2 (8 ± 4% constriction) or 10−9 M norepinephrine (NE; 4 ± 3% constriction) was added to the tissue ( n = 7). With O2, flow was redistributed to become equal into each branch. With NE, flow decreased progressively more into the first three branches. The changes in flow distribution were thus predictable and dependent on the agonist. With O2 or NE, the spatial changes in flow were mirrored by spatial changes in Tω. Changes in diameter and in cell flux were not related forl-NNA + Indo ( r = 0.45), O2( r = 0.07), or NE ( r = 0.36). For all agonists, when the bifurcation angle increased, cell flow to the branch decreased significantly, whereas if the angle decreased, flow was relatively preserved; thus active changes in bifurcation angle may influence red cell distribution at arteriolar bifurcations. Thus, when the endothelial cell dilatory pathways were blocked, the changes in flow and in Tω were uncoupled; yet when they were intact, flow and Tω changed together.
Aerobic fitness effects on exercise-induced low-frequency diaphragm fatigue
Authors: Babcock Mark A. , Pegelow David F. , Johnson Bruce D. , Dempsey Jerome A.
Published: December 2017

Babcock, Mark A., David F. Pegelow, Bruce D. Johnson, and Jerome A. Dempsey. Aerobic fitness effects on exercise-induced low-frequency diaphragm fatigue. J. Appl. Physiol. 81(5): 2156–2164, 1996.—We used bilateral phrenic nerve stimulation (BPNS; at 1, 10, and 20 Hz at functional residual capacity) to compare the amount of exercise-induced diaphragm fatigue between two groups of healthy subjects, a high-fit group [maximal O2consumption (V˙o 2 max) = 69.0 ± 1.8 ml ⋅ kg−1 ⋅ min−1, n = 11] and a fit group (V˙o 2 max = 50.4 ± 1.7 ml ⋅ kg−1 ⋅ min−1, n = 13). Both groups exercised at 88–92% V˙o 2 maxfor about the same duration (15.2 ± 1.7 and 17.9 ± 2.6 min for high-fit and fit subjects, respectively, P > 0.05). The supramaximal BPNS test showed a significant reduction ( P< 0.01) in the BPNS transdiaphragmatic pressure (Pdi) immediately after exercise of −23.1 ± 3.1% for the high-fit group and −23.1 ± 3.8% ( P > 0.05) for the fit group. Recovery of the BPNS Pdi took 60 min in both groups. The high-fit group exercised at a higher absolute workload, which resulted in a higher CO2production (+26%), a greater ventilatory demand (+16%) throughout the exercise, and an increased diaphragm force output (+28%) over the initial 60% of the exercise period. Thereafter, diaphragm force output declined, despite a rising minute ventilation, and it was not different between most of the high-fit and fit subjects. In summary, the high-fit subjects showed diaphragm fatigue as a result of heavy endurance exercise but were also partially protected from excessive fatigue, despite high ventilatory requirements, because their hyperventilatory response to endurance exercise was reduced, their diaphragm was utilized less in providing the total ventilatory response, and possibly their diaphragm aerobic capacity was greater.
Interactive effects of denervation and malnutrition on diaphragm structure and function
Authors: Lewis Michael I. , Lorusso Thomas J. , Zhan Wen-Zhi , Sieck Gary C.
Published: December 2017

Lewis, Michael I., Thomas J. Lorusso, Wen-Zhi Zhan, and Gary C. Sieck. Interactive effects of denervation and malnutrition on diaphragm structure and function. J. Appl. Physiol. 81(5): 2165–2172, 1996.—The purpose of this study was to examine the interactive effects of unilateral denervation (DN) and prolonged malnutrition (MN) on the structure and function of the diaphragm muscle (Dia). Four groups of rats were studied: control (Con), MN, DN, and DN-MN. MN began 2 wk after DN and lasted 4 wk. In both the DN and DN-MN groups, the relative loss in Dia weight exceeded the relative change in body weight. Compared with the Con group, Dia specific force was reduced by ∼40% in both the DN and DN-MN groups but was unaffected in the MN group. Dia fatigue resistance improved in all experimental groups but to a greater extent in the DN and DN-MN groups. In both the DN and DN-MN groups, ∼50% of Dia fibers were classified as type IIc, whereas fiber type proportions did not change in the MN group. In the DN group, only type IIb/x fibers atrophied, whereas all fiber types atrophied in the MN and DN-MN groups. We conclude that in the DN-MN group the reduction in specific force combined with the reduction in total cross-sectional area of the muscle significantly curtails Dia force-generating capacity.
Effects of training duration on substrate turnover and oxidation during exercise
Authors: Phillips S. M. , Green H. J. , Tarnopolsky M. A. , Heigenhauser G. J. F. , Hill R. E. , Grant S. M.
Published: December 2017

Phillips, S. M., H. J. Green, M. A. Tarnopolsky, G. J. F. Heigenhauser, R. E. Hill, and S. M. Grant. Effects of training duration on substrate turnover and oxidation during exercise. J. Appl. Physiol. 81(5): 2182–2191, 1996.—Adaptations in fat and carbohydrate metabolism after a prolonged endurance training program were examined using stable isotope tracers of glucose ([6,6-2H2]glucose), glycerol ([2H5]glycerol), and palmitate ([2H2]palmitate). Active, but untrained, males exercised on a cycle for 2 h/day [60% pretraining peak O2consumption (V˙o 2 peak) = 44.3 ± 2.4 ml ⋅ kg−1 ⋅ min−1] for a total of 31 days. Three cycle tests (90 min at 60% pretrainingV˙o 2 peak) were administered before training (PRE) and after 5 (5D) and 31 (31D) days of training. Exercise increased the rate of glucose production (Ra) and utilization (Rd) as well as the rate of lipolysis (glycerol Ra) and free fatty acid turnover (FFA Ra/Rd). At 5D, training induced a 10% ( P < 0.05) increase in total fat oxidation because of an increase in intramuscular triglyceride oxidation (+63%, P < 0.05) and a decreased glycogen oxidation (−16%, P < 0.05). At 31D, total fat oxidation during exercise increased a further 58% ( P < 0.01). The pattern of fat utilization during exercise at 31D showed a reduced reliance on plasma FFA oxidation (FFA Rd) and a greater dependence on oxidation of intramuscular triglyceride, which increased more than twofold ( P < 0.001). In addition, glucose Raand Rd were reduced at all time points during exercise at 31D compared with PRE and 5D. We conclude that long-term training induces a progressive increase in fat utilization mediated by a greater oxidation of fats from intramuscular sources and a reduction in glucose oxidation. Initial changes are present as early as 5D and occur before increases in muscle maximal mitochondrial enzyme activity [S. M. Phillips, H. J. Green, M. A. Tarnopolsky, G. J. F. Heigenhauser, and S. M. Grant. Am. J. Physiol. 270 ( Endocrinol. Metab. 33): E265–E272, 1996].
Hypoxia- and normoxia-induced reversibility of autonomic control in Andean guinea pig heart
Authors: León-Velarde Fabiola , Richalet Jean-Paul , Chavez Juan-Carlos , Kacimi Rachid , Rivera-Chira Maria , Palacios José-Antonio , Clark Daniel
Published: December 2017

León-Velarde, Fabiola, Jean-Paul Richalet, Juan-Carlos Chavez, Rachid Kacimi, Maria Rivera-Chira, José-Antonio Palacios, and Daniel Clark. Hypoxia- and normoxia-induced reversibility of autonomic control in Andean guinea pig heart. J. Appl. Physiol. 81(5): 2229–2234, 1996.—We herein describe the regulation of cardiac receptors in a typical high-altitude native animal. Heart rate response to isoproterenol (HRIso) (beats ⋅ min−1⋅ mg Iso ⋅ kg−1) and atropine, the density of β-adrenergic (βAR) and muscarinic (M2) receptors, and the ventricular content of norepinephrine (NE) and dopamine (DA) were studied in guinea pigs ( Cavia porcellus). Animals native to Lima, Peru (150 m) were studied at sea level (SL) and after 5 wk at 4,300-m altitude (SL-HA). Animals native to Rancas [Pasco, Peru (4,300 m)] were studied at high altitude (HA) and after 5 wk at SL (HA-SL). HA animals had a lower HRIso, maximum number of βARbinding sites (Bmax), βARdissociation constant ( Kd), NE, and DA ( P < 0.05) and a higher M2Bmax( P < 0.001) when compared with the SL group. HA-SL showed an increase of the HRIso, βARKd, and NE ( P < 0.05) and a decrease of the M2Bmaxand Kd( P < 0.0001) when compared with the HA group. The present study demonstrates the differential regulation and reversibility of the autonomic control in the guinea pig heart.
Pulmonary chemoreflexes elicited by intravenous injection of lactic acid in anesthetized rats
Authors: Lee Lu-Yuan , Morton Robert F. , Lundberg Jan M.
Published: December 2017

Lee, Lu-Yuan, Robert F. Morton, and Jan M. Lundberg.Pulmonary chemoreflexes elicited by intravenous injection of lactic acid in anesthetized rats. J. Appl. Physiol. 81(6): 2349–2357, 1996.—Experiments were carried out to characterize the cardiorespiratory reflex responses to intravenous injection of lactic acid and to determine the involvement of vagal bronchopulmonary C-fiber afferents in eliciting these responses in anesthetized rats. Bolus injection of lactic acid (0.2 mmol/kg iv) immediately elicited apnea, bradycardia, and hypotension, which were then followed by a sustained hyperpnea. The immediate apneic and bradycardiac responses to lactic acid were completely abolished by bilateral vagotomy and were absent when the same dose of lactic acid was injected into the left ventricle. The subsequent hyperpneic response was substantially attenuated by denervation of carotid body chemoreceptors. After a perineural capsaicin treatment of both vagus nerves to block the conduction of C fibers, lactic acid no longer evoked the immediate apnea and bradycardia, whereas the hyperpneic response became more pronounced and sustained, presumably because of the removal of the inhibitory effect on breathing mediated by pulmonary C-fiber activation. Single-unit electrophysiological recording showed that intravenous injection of lactic acid consistently evoked an abrupt and intense burst of discharge from the vagal C-fiber afferent endings in the lungs. In conclusion, the cardiorespiratory depressor responses induced by lactic acid are predominantly elicited by activation of vagal pulmonary C fibers.
Suppressive action of endogenous adenosine on ovine fetal nonshivering thermogenesis
Authors: Ball Karen T. , Gunn Tania R. , Gluckman Peter D. , Power Gordon G.
Published: December 2017

Ball, Karen T., Tania R. Gunn, Peter D. Gluckman, and Gordon G. Power. Suppressive action of endogenous adenosine on ovine fetal nonshivering thermogenesis. J. Appl. Physiol. 81(6): 2393–2398, 1996.—Nonshivering thermogenesis is not initiated when the fetal sheep is cooled in utero but appears to require the removal of an inhibitor of placental origin at birth. To test whether adenosine is such an inhibitor, we examined the effect of the adenosine antagonist theophylline on the initiation of nonshivering thermogenesis during sequential cooling, ventilation, and umbilical cord occlusion in utero. Theophylline (18 mg/kg bolus and 0.6 mg ⋅ kg−1 ⋅ min−1thereafter) was infused for 90 min before and 90 min after cord occlusion. Theophylline enhanced the nonshivering thermogenic free fatty acid (FFA) and glycerol responses before cord occlusion, raising FFA concentrations 99% to 415 ± 60 μeq/l ( P < 0.01) and glycerol levels 87% to 526 ± 135 μmol/l ( P < 0.05). These FFA ( P < 0.001) and glycerol ( P < 0.05) concentrations were significantly greater than the corresponding period during the birth-simulation control. Umbilical cord occlusion did not alter FFA levels but induced a 41% rise in glycerol concentrations to 774 ± 203 μmol/l ( P < 0.05). The increases in nonshivering thermogenic indexes after the administration of the adenosine-receptor antagonist suggest that the quiescent state of ovine fetal brown adipose tissue may result, in part, from the tonic inhibitory actions of adenosine and that a decrease in adenosine concentrations enhances nonshivering thermogenesis. However, the further rise after umbilical cord occlusion suggests that at least one other inhibitor of placental origin inhibits nonshivering thermogenesis before birth.
Functional role and structure of the scalene: an accessory inspiratory muscle in hamster
Authors: Fournier Mario , Lewis Michael I.
Published: December 2017

Fournier, Mario, and Michael I. Lewis. Functional role and structure of the scalene: an accessory inspiratory muscle in hamster. J. Appl. Physiol. 81(6): 2436–2444, 1996.—Although the scalene muscle (Sca) is a primary inspiratory muscle in humans, its respiratory function in other species is less clear. The electromyographic (EMG) activity of the Sca was studied during resting ventilation (eupnea) in both the awake and anesthetized hamster and after a variety of respiratory challenges in the anesthetized animal. The EMG activities of the medial Sca and the costal diaphragm were compared. The medial Sca, the major component of the Sca, originates from cervical transverse processes 2 to 5 and inserts primarily onto rib 4, with a small segment onto rib 3. In both the anesthetized and awake animal, the Sca was always silent during quiet breathing. With CO2-stimulated hyperpnea, the Sca was always recruited during inspiration in phase with the diaphragm. Active recruitment of the Sca was also observed after resistive loading and total airway occlusion. After ipsilateral phrenicotomy, the Sca was persistently recruited during eupnea. The specificity of the EMG signals was tested both by excluding cross contamination from other rib cage muscles and by selective denervation studies. Muscle spindles were identified in the medial Sca histochemically, suggesting that the respiratory activity of the Sca can also be modulated by changes in muscle length and/or load. These results indicate that the Sca functions as an accessory inspiratory muscle in the hamster and may play an important role in conditions of chronic load.
Nitric oxide decreases lung injury after intestinal ischemia
Authors: Terada Lance S. , Mahr Nancy N. , Jacobson Eugene D.
Published: December 2017

Terada, Lance S., Nancy N. Mahr, and Eugene D. Jacobson.Nitric oxide decreases lung injury after intestinal ischemia. J. Appl. Physiol. 81(6): 2456–2460, 1996.—After injury to a primary organ, mediators are released into the circulation and may initiate inflammation of remote organs. We hypothesized that the local production of nitric oxide (NO) may act to limit the spread of inflammation to secondarily targeted organs. In anesthetized rats, 30 min of intestinal ischemia followed by 2 h of reperfusion (I/R) did not increase lung albumin leak. However, after treatment with NG-nitro-l-arginine methyl ester (l-NAME), intestinal I/R led to increased lung leak, suggesting a protective effect of endogenous NO. The site of action of NO appeared to be the lung and not the gut because 1) after treatment withl-NAME, local delivery of NO to the lung by inhalation abolished the increase in intestinal I/R-induced lung leak; 2)l-NAME had no effect on epithelial permeability (51Cr-labeled EDTA clearance) of reperfused small bowel; and 3) after treatment with l-NAME, local delivery of NO to the gut by luminal perfusion did not improve epithelial permeability of reperfused intestines. Furthermore,l-NAME increased, and inhaled NO de- creased, the density of lung neutrophils in rats subjected to intestinal I/R, and treatment with the selectin antagonist fucoidan abolished l-NAME-induced lung leak in rats subjected to intestinal I/R. We conclude that endogenous lung NO limits secondary lung injury after intestinal I/R by decreasing pulmonary neutrophil retention.
Effects of hypoxic hypoxia on O2uptake and heart rate kinetics during heavy exercise
Authors: Engelen Marielle , Porszasz Janos , Riley Marshall , Wasserman Karlman , Maehara Kazuhira , Barstow Thomas J.
Published: December 2017

Engelen, Marielle, Janos Porszasz, Marshall Riley, Karlman Wasserman, Kazuhira Maehara, and Thomas J. Barstow. Effects of hypoxic hypoxia on O2uptake and heart rate kinetics during heavy exercise. J. Appl. Physiol. 81(6): 2500–2508, 1996.—It is unclear whether hypoxia alters the kinetics of O2uptake (V˙o2) during heavy exercise [above the lactic acidosis threshold (LAT)] and how these alterations might be linked to the rise in blood lactate. Eight healthy volunteers performed transitions from unloaded cycling to the same absolute heavy work rate for 8 min while breathing one of three inspired O2concentrations: 21% (room air), 15% (mild hypoxia), and 12% (moderate hypoxia). Breathing 12% O2slowed the time constant but did not affect the amplitude of the primary rise inV˙o2(period of first 2–3 min of exercise) and had no significant effect on either the time constant or the amplitude of the slowV˙o2component (beginning 2–3 min into exercise). Baseline heart rate was elevated in proportion to the severity of the hypoxia, but the amplitude and kinetics of increase during exercise and in recovery were unaffected by level of inspired O2. We conclude that the predominant effect of hypoxia during heavy exercise is on the early energetics as a slowed time constant forV˙o2and an additional anaerobic contribution. However, the sum total of the processes representing the slow component ofV˙o2is unaffected.
Surfactant inhibition by plasma: gestational age and surfactant treatment effects in preterm lambs
Authors: Ikegami Machiko , Rebello Celso M. , Jobe Alan H.
Published: December 2017

Ikegami, Machiko, Celso M. Rebello, and Alan H. Jobe.Surfactant inhibition by plasma: gestational age and surfactant treatment effects in preterm lambs. J. Appl. Physiol. 81(6): 2517–2522, 1996.—The preterm infant with respiratory distress syndrome has edematous lungs and small amounts of surfactant that do not function normally. We reported that surfactant recovered from preterm lambs after surfactant treatment can have decreased sensitivity to inhibition of surface tension by plasma. We asked whether this augmented resistance to inhibition was dependent on lung development (gestational age) by testing sensitivity to plasma inhibition of 1) endogenous surfactant from preterm lambs and 2) surfactant from preterm lambs after treatment with an organic solvent-extracted natural sheep surfactant. Surfactant recovered after surfactant treatment of 121- or 128-days-gestation lambs had the same sensitivity to plasma inhibition as did the surfactant used to treat the lambs. Surfactant recovered from 134-days-gestation lambs had decreased sensitivity to inhibition. Lung maturation is a variable influencing surfactant inhibition by plasma.
Segmental body composition assessed by bioelectrical impedance analysis and DEXA in humans
Authors: Bracco David , Thiébaud Daniel , Chioléro René L. , Landry Michel , Burckhardt Peter , Schutz Yves
Published: December 2017

Bracco, David, Daniel Thiébaud, René L. Chioléro, Michel Landry, Peter Burckhardt, and Yves Schutz.Segmental body composition assessed by bioelectrical impedance analysis and DEXA in humans. J. Appl. Physiol. 81(6): 2580–2587, 1996.—The present study assessed the relative contribution of each body segment to whole body fat-free mass (FFM) and impedance and explored the use of segmental bioelectrical impedance analysis to estimate segmental tissue composition. Multiple frequencies of whole body and segmental impedances were measured in 51 normal and overweight women. Segmental tissue composition was independently assessed by dual-energy X-ray absorptiometry. The sum of the segmental impedance values corresponded to the whole body value (100.5 ± 1.9% at 50 kHz). The arms and legs contributed to 47.6 and 43.0%, respectively, of whole body impedance at 50 kHz, whereas they represented only 10.6 and 34.8% of total FFM, as determined by dual-energy X-ray absorptiometry. The trunk averaged 10.0% of total impedance but represented 48.2% of FFM. For each segment, there was an excellent correlation between the specific impedance index (length2/impedance) and FFM ( r = 0.55, 0.62, and 0.64 for arm, trunk, and leg, respectively). The specific resistivity was in a similar range for the limbs (159 ± 23 cm for the arm and 193 ± 39 cm for the leg at 50 kHz) but was higher for the trunk (457 ± 71 cm). This study shows the potential interest of segmental body composition by bioelectrical impedance analysis and provides specific segmental body composition equations for use in normal and overweight women.
Ovine fetal adaptations to chronically reduced urine flow: preservation of amniotic fluid volume
Authors: Mann Stephanie E. , Nijland Mark J. M. , Ross Michael G.
Published: December 2017

Mann, Stephanie E., Mark J. M. Nijland, and Michael G. Ross.Ovine fetal adaptations to chronically reduced urine flow: preservation of amniotic fluid volume. J. Appl. Physiol. 81(6): 2588–2594, 1996.—Adequate amniotic fluid (AF) volume is maintained by a balance of fetal fluid production (lung liquid and urine) and resorption (swallowing and intramembranous flow). Because fetal urine is the principle source of AF, alterations in urine flow and composition directly impact AF dynamics. Intra-amniotic 1-desamino-8-d-arginine vasopressin (DDAVP) is rapidly absorbed into fetal plasma and induces a marked fetal urinary antidiuresis. To examine the effect of intra-amniotic- DDAVP-induced fetal urinary responses on AF volume and composition, six chronically prepared ewes with singleton fetuses (gestation 128 ± 2 days) were studied for 72 h after a single intra-amniotic DDAVP (50-μg) injection. After DDAVP, fetal urine osmolality significantly increased at 2 h (157 ± 13 to 253 ± 21 mosmol/kg) and remained elevated at 72 h (400 ± 13 mosmol/kg). Urinary sodium (33.0 ± 4.5 to 117.2 ± 9.7 meq/l) and chloride (26.0 ± 2.8 to 92.4 ± 8.1 meq/l) concentrations similarly increased. AF osmolality increased (285 ± 3 to 299 ± 4 mosmol/kgH2O), although there was no change in fetal plasma osmolality (294 ± 2 mosmol/kg). Despite a 50% reduction in fetal urine flow (0.12 ± 0.03 to 0.05 ± 0.02 ml ⋅ kg−1 ⋅ min−1at 2 h and 0.06 ± 0.01 ml ⋅ kg−1 ⋅ min−1after 72 h), AF volume did not change (693 ± 226 to 679 ± 214 ml). There were no changes in fetal arterial blood pressures, pH,[Formula: see text], or[Formula: see text] after DDAVP. We conclude the following. 1) Intra-amniotic DDAVP injection induces a prolonged decrease in fetal urine flow and increases in urine and AF osmolalities. 2) Despite decreased urine flow, AF volume does not change. We speculate that, in response to DDAVP-induced fetal oliguria, reversed intramembranous flow (from isotonic fetal plasma to hypertonic AF) preserves AF volume.
Effect of topical upper airway anesthesia on apnea duration through the night in obstructive sleep apnea
Authors: Cala S. J. , Sliwinski P. , Cosio M. G. , Kimoff R. J.
Published: December 2017

Cala, S. J., P. Sliwinski, M. G. Cosio, and R. J. Kimoff.Effect of topical upper airway anesthesia on apnea duration through the night in obstructive sleep apnea. J. Appl. Physiol. 81(6): 2618–2626, 1996.—It has previously been reported that the duration of obstructive apneas increases from the beginning to the end of the night (M. Charbonneau, J. M. Marin, A. Olha, R. J. Kimoff, R. D. Levy, and M. Cosio. Chest 106: 1695–1701, 1994). The purpose of this study was to test the hypothesis that stimulation of upper airway (UA) sensory receptors during obstructed inspiratory efforts contributes to arousal and apnea termination and that a progressive attenuation of this mechanism through the night contributes to apnea lengthening. We studied seven patients (six men, one woman) with severe obstructive sleep apnea (apnea-hypopnea index = 93 ± 26 events/h) during two consecutive nights of polysomnographic monitoring. On one night (random order), we performed topical UA anesthesia with 0.2% tetracaine and on the control night, sham anesthesia. We measured apnea duration, esophageal pressure (Pes) during apneas, and apneic O2 desaturation. Consistent with previous findings, apnea duration, number of efforts per apnea, and peak Pes at end apnea increased from the beginning to the end of the control nights. UA anesthesia produced a significant increase in apnea duration at the beginning of the night but no change in apnea length at the end of the night. Peak Pes and the rate of increase in Pes during the anesthesia nights were greater than during control nights, but the rate of increase in Pes was similar for the beginning and end of the control and anesthesia nights. These findings suggest that UA sensory receptors play a role in mediating apnea termination at the beginning of the night but that the contribution of these receptors diminishes as the night progresses such that greater inspiratory efforts are required to trigger arousal, leading to apnea prolongation.
Ring distraction technique for measuring surface tension of sputum: relationship to sputum clearability
Authors: Albers G. M. , Tomkiewicz R. P. , May M. K. , Ramirez O. E. , Rubin B. K.
Published: December 2017

Albers, G. M., R. P. Tomkiewicz, M. K. May, O. E. Ramirez, and B. K. Rubin. Ring distraction technique for measuring surface tension of sputum: relationship to sputum clearability. J. Appl. Physiol. 81(6): 2690–2695, 1996.—Poor sputum clearance has been related to sputum adhesion tension. In this study, we describe a modified du Noüy ring method for measuring the surface tension (γ) of small samples of sputum and for comparinge the calculated work of adhesion (Wad) for sputum specimens with the measured mucociliary transportability (MCTR) and cough transportability (CTR). The γ, as measured by this method, correlates with γ measured by sputum contact angle on a low-surface-energy solid ( R2= 0.368, P = 0.03). There is a small but significant difference in measurements made by these two methods ( P = 0.03). Wadcalculated from the surface tension ring method is inversely correlated with CTR ( R2= 0.181, P = 0.004) but has no correlation with MCTR in this study. The miniaturized ring method gives accurate and reproducible measurements of the surface tension of small amounts of respiratory secretions. Because sputum behaves enough like a liquid that the assumptions made in using the Young equation to calculate Wadappear valid, we also showed that the Neumann equation can be used to determine the surface tension of sputum by its contact angle on tetrafluoroethylene (Teflon).
Comparison of techniques for measuring pulse-wave velocity in the rat
Authors: Mitchell Gary F. , Pfeffer Marc A. , Finn Peter V. , Pfeffer Janice M.
Published: December 2017

Mitchell, Gary F., Marc A. Pfeffer, Peter V. Finn, and Janice M. Pfeffer. Comparison of techniques for measuring pulse-wave velocity in the rat. J. Appl. Physiol. 82(1): 203–210, 1997.—We evaluated methods for measuring average and regional pulse-wave velocity along the full length of the aorta in 18-mo-old ether-anesthetized male spontaneously hypertensive rats. Catheter-tip manometers were placed in the ascending and descending thoracic aorta via the right carotid and left femoral arteries, respectively. As the distal catheter was withdrawn at 1-cm intervals, the relationship between distal catheter insertion distance and distance between transducers was determined from the intercept of the insertion distance vs. transmission delay regression line. Methods that assessed the foot-to-foot time delay between pressures accurately predicted the separation between catheters (measured distance of 14.3 cm; intercept of 14.0 ± 0.5 cm; P = not significant) were highly reproducible (coefficient of variation of 2.3% for repeated measurements) and showed minimal variability (range 509 ± 30 to 600 ± 29 cm/s) along the full length of the aorta. Methods that made use of the pressure-pressure transfer function were spatially (range of values along the aorta 367 ± 17 to 722 ± 39 cm/s) and temporally more variable, especially during vasoconstriction with methoxamine, due to the effects of reflected waves.
Glucose administration before exercise modulates catecholaminergic responses in glycogen-depleted subjects
Authors: Gozal David , Thiriet Patrice , Cottet-Emard Jean Marie , Wouassi Dieudonné , Bitanga Emmanuel , Geyssant André , Pequignot Jean Marc , Sagnol Marcel
Published: December 2017

Gozal, David, Patrice Thiriet, Jean Marie Cottet-Emard, Dieudonné Wouassi, Emmanuel Bitanga, André Geyssant, Jean Marc Pequignot, and Marcel Sagnol. Glucose administration before exercise modulates catecholaminergic responses in glycogen-depleted subjects. J. Appl. Physiol. 82(1): 248–256, 1997.—In glycogen-depleted subjects (GD) a nonlinear increase in epinephrine (Epi) and norepinephrine (NE) parallels blood lactate (La) during graded exercise. The effect of glucose (Glc) supplementation and route of administration on these relationships was studied in 26 GD athletes who were randomly assigned to receive 1.3 g/kg Glc by slow intravenous infusion (IV; n = 9), oral administration (PO; n = 9), or artificially sweetened placebo in 1 liter of water (Asp; n = 8) in the 2 h preceding a graded maximal exercise. Performance and La were similar among the three groups in normal glycogen (NG) or GD conditions. However, slightly improved performances were observed in GD compared with NG and were associated with a shift to the right in La curves. Blood Glc concentrations were higher in IV and PO before exercise, but they rapidly decreased to lowest levels in IV, gradually decreased over time in PO, and remained stable in Asp or NG. Insulin concentrations were highest in IV and lowest in Asp and NG at onset of exercise, rapidly decreasing in IV and PO although remaining at higher levels than in Asp or NG. In contrast, higher serum levels of free fatty acids were measured during exercise in Asp with no significant differences in glucagon or glycerol among the three groups. Free and sulfated NE increases were smaller in IV than in PO and Asp on exhaustion. In contrast, free and conjugated Epi were most increased in IV, with smallest increases in Asp. Dopamine levels were most increased in IV at exhaustion. We conclude that the changes of Epi and NE concentrations, associated with the activation of glucoregulatory mechanisms, including hyperinsulinemia, display different magnitude and time courses during exercise in GD subjects who receive oral vs. intravenous load of Glc before exercise. We speculate that the magnitude of insulin surge after acutely increased Glc before exercise in GD subjects may exert dissociative effects on adrenal-dependent glycogenolysis and on sympathetic responses.
Skeletal muscle mass and exercise performance in stable ambulatory patients with heart failure
Authors: Lang Chim C. , Chomsky Don B. , Rayos Glenn , Yeoh T. K. , Wilson John R.
Published: December 2017

Lang, Chim C., Don B. Chomsky, Glenn Rayos, T. K. Yeoh, and John R. Wilson. Skeletal muscle mass and exercise performance in stable ambulatory patients with heart failure. J. Appl. Physiol. 82(1): 257–261, 1997.—The purpose of this study was to determine whether skeletal muscle atrophy limits the maximal exercise capacity of stable ambulatory patients with heart failure. Body composition and maximal exercise capacity were measured in 100 stable ambulatory patients with heart failure. Body composition was assessed by using dual-energy X-ray absorption. Peak exercise oxygen consumption (V˙o 2 peak) and the anaerobic threshold were measured by using a Naughton treadmill protocol and a Medical Graphics CardioO2 System.V˙o 2 peak averaged 13.4 ± 3.3 ml ⋅ min−1 ⋅ kg−1or 43 ± 12% of normal. Lean body mass averaged 52.9 ± 10.5 kg and leg lean mass 16.5 ± 3.6 kg. Leg lean mass correlated linearly with V˙o 2 peak( r= 0.68, P < 0.01), suggesting that exercise performance is influenced by skeletal muscle mass. However, lean body mass was comparable to levels noted in 1,584 normal control subjects, suggesting no decrease in muscle mass. Leg muscle mass was comparable to levels noted in 34 normal control subjects, further supporting this conclusion. These findings suggest that exercise intolerance in stable ambulatory patients with heart failure is not due to skeletal muscle atrophy.