bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of ventilatory responsiveness to progressive hypoxia and hypercapnia in low-birth-weight lambs
Authors: Moss T. J. , Davey M. G. , McCrabb G. J. , Harding R.
Published: December 2017

Moss, T. J., M. G. Davey, G. J. McCrabb, and R. Harding.Development of ventilatory responsiveness to progressive hypoxia and hypercapnia in low-birth-weight lambs. J. Appl. Physiol. 81(4): 1555–1561, 1996.—Our aim was to determine the effects of low birth weight on ventilatory responses to progressive hypoxia and hypercapnia during early postnatal life. Seven low-birth-weight (2.7 ± 0.3 kg) and five normal-birth-weight (4.8 ± 0.2 kg) lambs, all born at term, underwent weekly rebreathing tests during wakefulness while arterial[Formula: see text],[Formula: see text], and pH were measured. Hypoxic ventilatory responsiveness (HOVR; percent increase in ventilation when arterial [Formula: see text] fell to 60% of resting values) increased in normal lambs from 86.6 ± 7.1% at week 1 to 227.4 ± 24.9% at week 6. In low-birth-weight lambs, HOVR was not significantly different at week 1 (60.1 ± 18.7%) from that of normal lambs but did not increase with postnatal age (56.6 ± 19.3% at week 6). HOVR of all lambs at 6 wk was significantly correlated with birth weight ( r2= 0.8). Hypercapnic ventilatory responsiveness (gradient of ventilation vs. arterial [Formula: see text]) did not change with age and was not significantly different between groups [84.7 ± 7.5 (low-birth-weight lambs) vs. 89.4 ± 6.6 ml ⋅ min−1⋅ kg−1⋅ mmHg−1(normal lambs)]. We conclude that intrauterine conditions that impair fetal growth lead to the failure of HOVR to increase with age.
Airway wall dimensions during carbachol-induced bronchoconstriction in rabbits
Authors: Sasaki F. , Saitoh Y. , Verburgt L. , Okazawa M.
Published: December 2017

Sasaki, F., Y. Saitoh, L. Verburgt, and M. Okazawa.Airway wall dimensions during carbachol-induced bronchoconstriction in rabbits. J. Appl. Physiol. 81(4): 1578–1583, 1996.—Airway wall area is an important determinant of airway narrowing. We hypothesized that in cross-sectioned peripheral airways, the wall area internal to the outer smooth muscle border (inner wall area) would decrease and the airway wall area external to the outer smooth the muscle layer (adventitial area) would increase during bronchoconstriction because of the relocation of blood and/or fluid between these compartments. To test this hypothesis, we used anesthetized open-chest rabbits and measured airway wall dimensions and smooth muscle shortening of membranous airways after carbachol-induced bronchoconstriction using morphometric techniques. Acute (3-min) and sustained (40-min) bronchoconstriction was induced by aerosol nebulization of carbachol and compared with saline treatment. After physiological measurements, the heart base was snared, and the lung and heart were excised en bloc and frozen by using liquid nitrogen while a transpulmonary pressure of 2 cmH2O was maintained. The lung was processed for light-microscopic examination by using a freeze substitution technique. Results show that adventitial area was significantly decreased after sustained but not acute bronchoconstriction. The mechanism of this change, which contradicts our hypothesis, is unclear. However, the decrease of adventitial area could increase rather than decrease the effect of lung parenchymal tethering and attenuate airway narrowing.
Effect of inhibition of nitric oxide synthesis on the diaphragmatic microvascular response to hypoxia
Authors: Ward Michael E.
Published: December 2017

Ward, Michael E. Effect of inhibition of nitric oxide synthesis on the diaphragmatic microvascular response to hypoxia. J. Appl. Physiol. 81(4): 1633–1641, 1996.—The purpose of this study was to determine the effect of inhibition of nitric oxide (NO) release on the diaphragmatic microvascular responses to hypoxia. In α-chloralose-anesthetized mongrel dogs, the microcirculation of the vascularly isolated ex vivo left hemidiaphragm was studied by intravital microscopy. The diaphragm was pump perfused with blood diverted from the femoral artery through a series of membrane oxygenators. The responses to supramaximal concentrations of sodium nitroprusside, moderate hypoxia (phrenic venous [Formula: see text] 27 Torr), and severe hypoxia (phrenic venous [Formula: see text] 15 Torr) were recorded before and after an infusion of N G-nitro-l-arginine (l-NNA; 6 × 10−4 M) into the phrenic circulation for 20 min. Under control conditions, diaphragmatic blood flow was 12.4 ± 1.1 ml ⋅ min−1 ⋅ 100 g−1. Diaphragmatic blood flows recorded during moderate and severe hypoxia were 15.6 ± 1.2 and 24.3 ± 1.5 ml ⋅ min−1 ⋅ 100 g−1, respectively ( P < 0.05 for both compared with control values). Treatment withl-NNA reduced diaphragmatic blood flow to 9.6 ± 0.8 ml ⋅ min−1 ⋅ 100 g−1 under control conditions ( P < 0.05) and caused arteriolar vasoconstriction to a degree that was dependent on vessel size (i.e., larger vessels constricted more than smaller vessels).l-NNA eliminated the increase in blood flow during moderate hypoxia and inhibited arteriolar dilation by an amount that was related to vessel size (i.e., dilation of larger vessels was inhibited more than that of smaller vessels). Inhibition of NO synthesis had no effect on the increase in diaphragmatic blood flow (23.6 ± 1.9 ml ⋅ min−1 ⋅ 100 g−1; P > 0.05 compared with that during severe hypoxia before treatment withl-NNA) or arteriolar diameters during severe hypoxia. NO release plays a role in the diaphragmatic vascular response to hypoxia, but this role is limited to dilation of larger arterioles during hypoxia of moderate severity.
Metabolic, catecholamine, and endurance responses to caffeine during intense exercise
Authors: Jackman M. , Wendling P. , Friars D. , Graham T. E.
Published: December 2017

Jackman, M., P. Wendling, D. Friars, and T. E. Graham.Metabolic, catecholamine, and endurance responses to caffeine during intense exercise. J. Appl. Physiol. 81(4): 1658–1663, 1996.—This study examined the possible effects of caffeine ingestion on muscle metabolism and endurance during brief intense exercise. We tested 14 subjects after they ingested placebo or caffeine (6 mg/kg) with an exercise protocol in which they cycled for 2 min, rested 6 min, cycled 2 min, rested 6 min, and then cycled to voluntary exhaustion. In each exercise the intensity required the subject’s maximal O2consumption. Eight subjects had muscle and venous blood samples taken before and after each exercise period. The caffeine ingestion resulted in a significant increase in endurance (4.12 ± 0.36 and 4.93 ± 0.60 min for placebo and caffeine, respectively) and resulted in a significant increase in plasma epinephrine concentration throughout the protocol but not in norepinephrine concentration. During the first two exercise bouts, the power and work output were not different; blood lactate concentrations were not affected significantly by caffeine ingestion, but during the exercise bouts muscle lactate concentration was significantly increased by caffeine. The net decrease in muscle glycogen was not different between treatments at any point in the protocol, and even at the time of fatigue there was at least 50% of the original glycogen concentration remaining. The data demonstrated that caffeine ingestion can be an effective ergogenic aid for exercise that is as brief as 4–6 min. However, the mechanism is not associated with muscle glycogen sparing. It is possible that caffeine is exerting actions directly on the active muscle and/or the neural processes that are involved in the activity.
Coordination of breathing and swallowing: effects of bolus consistency and presentation in normal adults
Authors: Preiksaitis Harold G. , Mills Catherine A.
Published: December 2017

Preiksaitis, Harold G., and Catherine A. Mills.Coordination of breathing and swallowing: effects of bolus consistency and presentation in normal adults. J. Appl. Physiol. 81(4): 1707–1714, 1996.—Respiration and swallowing were recorded simultaneously by inductance plethysmography, submental electromyography, and a throat microphone in 10 normal subjects during eating and drinking tasks that included single boluses of varying volume (5–20 ml) and consistency presented with a syringe and cup, a 200-ml drink taken with and without the use of a straw, and a sandwich meal. Swallows were associated with a brief swallow apnea (SA) lasting ∼1 s. Swallow effects on the duration or tidal volume of the preswallow, postswallow and swallow-associated breathing cycles varied depending on bolus characteristics and presentation. Expiration before and after the SA was the preferred pattern with all drinking and eating tasks. Inspiration followed SA in <5% of single-bolus swallows, but this pattern increased significantly with a 200-ml drink administered by cup or by straw and during a sandwich meal (23.8 ± 5.2, 27.0 ± 2.6, and 16.3 ± 2.7%, respectively). Hence, the swallow-associated breathing pattern seen with single-bolus swallows may not reflect that associated with regular eating and drinking behavior. This finding implies that the risk of aspiration may be reduced by teaching patients prone to aspiration to simplify the complex behavior of eating and drinking to a series of single-bolus swallows.
Sidestream smoke exposure enhances rapidly adapting receptor responses to substance P in young guinea pigs
Authors: Bonham A. C. , Kott K. S. , Joad J. P.
Published: December 2017

Bonham, A. C., K. S. Kott, and J. P. Joad. Sidestream smoke exposure enhances rapidly adapting receptor responses to substance P in young guinea pigs. J. Appl. Physiol. 81(4): 1715–1722, 1996.—We determined the effect of sidestream tobacco smoke (SS) exposure on responses of lung rapidly adapting receptors (RARs), peak tracheal pressure (Ptr), and arterial blood pressure (ABP) to substance P in young guinea pigs. Guinea pigs were exposed to SS or filtered air from day 8 to days 41–45 of life. They were then anesthetized and given three doses of intravenous substance P (1.56–4.94 nmol/kg). SS exposure augmented substance P-evoked increases in RAR activity ( P = 0.029 by analysis of variance) but not substance P-evoked increases in peak Ptr or decreases in ABP. Neurokinin 1-receptor blockade (CP-96345, 400 nmol/kg) attenuated substance P-evoked increases in RAR activity ( P = 0.001) and ABP ( P = 0.009) but not in peak Ptr ( P = 0.06). Thus chronic exposure to SS in young guinea pigs exaggerates RAR responsiveness to substance P. The findings may help explain the increased incidence of airway hyperresponsiveness and cough in children chronically exposed to environmental tobacco smoke.
Forearm training attenuates sympathetic responses to prolonged rhythmic forearm exercise
Authors: Sinoway Lawrence , Shenberger Jeffrey , Leaman Gretchen , Zelis Robert , Gray Kristen , Baily Robert , Leuenberger Urs
Published: December 2017

Sinoway, Lawrence, Jeffrey Shenberger, Gretchen Leaman, Robert Zelis, Kristen Gray, Robert Baily, and Urs Leuenberger.Forearm training attenuates sympathetic responses to prolonged rhythmic forearm exercise. J. Appl. Physiol. 81(4): 1778–1784, 1996.—We previously demonstrated that nonfatiguing rhythmic forearm exercise at 25% maximal voluntary contraction (12 2-s contractions/min) evokes sympathoexcitation without significant engagement of metabolite-sensitive muscle afferents (B. A. Batman, J. C. Hardy, U. A. Leuenberger, M. B. Smith, Q. X. Yang, and L. I. Sinoway. J. Appl. Physiol. 76: 1077–1081, 1994). This is in contrast to the sympathetic nervous system responses observed during fatiguing static forearm exercise where metabolite-sensitive afferents are the key determinants of sympathetic activation. In this report we examined whether forearm exercise training would attenuate sympathetic nervous system responses to rhythmic forearm exercise. We measured heart rate, mean arterial blood pressure (MAP), muscle sympathetic nerve activity (microneurography), plasma norepinephrine (NE), and NE spillover and clearance (tritiated NE kinetics) during nonfatiguing rhythmic forearm exercise before and after a 4-wk unilateral forearm training paradigm. Training had no effect on forearm mass, maximal voluntary contraction, or heart rate but did attenuate the increase in MAP (increase in MAP: from 15.2 ± 1.8 before training to 11.4 ± 1.4 mmHg after training; P < 0.017), muscle sympathetic nerve activity (increase in bursts: from 10.8 ± 1.4 before training to 6.2 ± 1.1 bursts/min after training; P < 0.030), and the NE spillover (increase in arterial spillover: from 1.3 ± 0.2 before training to 0.6 ± 0.2 nmol ⋅ min−1 ⋅ m−2after training, P < 0.014; increase in venous spillover: from 2.0 ± 0.6 before training to 1.0 ± 0.5 nmol ⋅ min−1 ⋅ m−2after training, P < 0.037) seen in response to exercise performed by the trained forearm. Thus forearm training reduces sympathetic responses during a nonfatiguing rhythmic handgrip paradigm that does not engage muscle metaboreceptors. We speculate that this effect is due to a conditioning-induced reduction in mechanically sensitive muscle afferent discharge.
Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training
Authors: McCall G. E. , Byrnes W. C. , Dickinson A. , Pattany P. M. , Fleck S. J.
Published: December 2017

McCall, G. E., W. C. Byrnes, A. Dickinson, P. M. Pattany, and S. J. Fleck. Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training. J. Appl. Physiol. 81(5): 2004–2012, 1996.—Twelve male subjects with recreational resistance training backgrounds completed 12 wk of intensified resistance training (3 sessions/wk; 8 exercises/session; 3 sets/exercise; 10 repetitions maximum/set). All major muscle groups were trained, with four exercises emphasizing the forearm flexors. After training, strength (1-repetition maximum preacher curl) increased by 25% ( P < 0.05). Magnetic resonance imaging scans revealed an increase in the biceps brachii muscle cross-sectional area (CSA) (from 11.8 ± 2.7 to 13.3 ± 2.6 cm2; n = 8; P < 0.05). Muscle biopsies of the biceps brachii revealed increases ( P < 0.05) in fiber areas for type I (from 4,196 ± 859 to 4,617 ± 1,116 μm2; n = 11) and II fibers (from 6,378 ± 1,552 to 7,474 ± 2,017 μm2; n = 11). Fiber number estimated from the above measurements did not change after training (293.2 ± 61.5 × 103 pretraining; 297.5 ± 69.5 × 103 posttraining; n = 8). However, the magnitude of muscle fiber hypertrophy may influence this response because those subjects with less relative muscle fiber hypertrophy, but similar increases in muscle CSA, showed evidence of an increase in fiber number. Capillaries per fiber increased significantly ( P < 0.05) for both type I (from 4.9 ± 0.6 to 5.5 ± 0.7; n = 10) and II fibers (from 5.1 ± 0.8 to 6.2 ± 0.7; n = 10). No changes occurred in capillaries per fiber area or muscle area. In conclusion, resistance training resulted in hypertrophy of the total muscle CSA and fiber areas with no change in estimated fiber number, whereas capillary changes were proportional to muscle fiber growth.
Cigarette smoke-induced bronchoconstriction: causative agents and role of thromboxane receptors
Authors: Hong Ju-Lun , Lee Lu-Yuan
Published: December 2017

Hong, Ju-Lun, and Lu-Yuan Lee. Cigarette smoke-induced bronchoconstriction: causative agents and role of thromboxane receptors. J. Appl. Physiol. 81(5): 2053–2059, 1996.—Inhalation of cigarette smoke induces a biphasic bronchoconstriction in guinea pigs: the first phase is induced by a combination of cholinergic reflex and tachykinins, whereas the second phase involves cyclooxygenase metabolites (J.-L. Hong, I. W. Rodger, and L.-Y. Lee. J. Appl. Physiol. 78: 2260–2266, 1995). This study was carried out to further determine the causative agents in the smoke and the types of prostanoid receptors and endogenous prostanoids mediating the bronchoconstriction. Inhalation of 10 ml of high-nicotine cigarette smoke consistently elicited the biphasic bronchoconstriction in anesthetized and artificially ventilated guinea pigs. Pretreatment with hexamethonium (10 mg/kg iv) significantly reduced the first-phase bronchoconstriction but did not have any measurable effect on the second-phase response. In sharp contrast, gas-phase smoke did not elicit any bronchoconstrictive effect. Furthermore, when the animals were challenged with low-nicotine cigarette smoke, only a single second-phase response was evoked, accompanied by increases in thromboxane (Tx) B2(a stable metabolite of TxA2), prostaglandin (PG) D2, PGF2αin the bronchoalveolar lavage fluid. The bronchoconstrictive response induced by low-nicotine smoke was completely prevented by pretreatment with SQ-29548 (0.3 mg/kg iv), a TxA2-receptor antagonist. These results indicate that 1) nicotine is the primary causative agent responsible for the first-phase bronchoconstriction and 2) nonnicotine smoke particulates evoke the release of TxA2, PGD2, and PGF2α, which act on TxA2receptors on airway smooth muscles and induce the second-phase response to cigarette smoke.
Morphometry of the human pulmonary vasculature
Authors: Huang W. , Yen R. T. , McLaurine M. , Bledsoe G.
Published: December 2017

Huang, W., R. T. Yen, M. McLaurine, and G. Bledsoe.Morphometry of the human pulmonary vasculature. J. Appl. Physiol. 81(5): 2123–2133, 1996.—The morphometric data on the branching pattern and vascular geometry of the human pulmonary arterial and venous trees are presented. Arterial and venous casts were prepared by the silicone elastomer casting method. Three recent innovations are used to describe the vascular geometry: the diameter-defined Strahler ordering model is used to assign branching orders, the connectivity matrix is used to describe the connection of blood vessels from one order to another, and a distinction between vessel segments and vessel elements is used to express the series-parallel feature of the pulmonary vessels. A total of 15 orders of arteries were found between the main pulmonary artery and the capillaries in the left lung and a total of 15 orders of veins between the capillaries and the left atrium in the right lung. The elemental and segmental data are presented. The morphometric data are then used to compute the total cross-sectional areas, blood volumes, and fractal dimensions in the pulmonary arterial and venous trees.
Alterations in structure of elastic laminae of rat pulmonary arteries in hypoxic hypertension
Authors: Liu S. Q.
Published: December 2017

Liu, S. Q. Alterations in structure of elastic laminae of rat pulmonary arteries in hypoxic hypertension. J. Appl. Physiol. 81(5): 2147–2155, 1996.—The effect of hypoxic hypertension on the remodeling process of the elastic laminae of the rat hilar pulmonary arteries (PAs) was studied by electron microscopy. Rats were exposed to hypoxia (10% O2) for periods of 0.5, 2, 6, 12, 48, 96, 144, and 240 h. Changes in the structure of the PA elastic laminae were examined and analyzed with respect to changes in the PA wall tensile stress. The PA blood pressure increased rapidly within the first several hours of hypoxia and reached a stable level within 2 days, whereas the PA wall tensile stress increased initially due to elevated blood pressure and then decreased after 48 h due to vessel wall thickening and returned to the control level after 4 days. In association with these changes, the elastic laminae, which appeared homogeneous in normal control rats, changed into structures composed of randomly oriented filaments and edematous contents with an increase in the volume during the early period of hypoxia and regained their homogeneous appearance and normal volume after 4 days. The changes in the elastic laminae were correlated with changes in the tensile stress. These changes were associated with a transient decrease in the stiffness of the PAs. In hypoxic rats given nifedipine, no change was found in the blood pressure, the tensile stress, or the structure of the elastic laminae of the PAs despite continuous exposure to hypoxia. These results suggested that altered tensile stress in the PA wall played a critical role in the initiation and regulation of structural changes in the elastic laminae and that these changes might contribute to alterations in the mechanical properties of the PA in hypoxic hypertension.
Baroreceptor control of the cutaneous active vasodilator system
Authors: Crandall C. G. , Johnson J. M. , Kosiba W. A. , Kellogg D. L.
Published: December 2017

Crandall, C. G., J. M. Johnson, W. A. Kosiba, and D. L. Kellogg, Jr. Baroreceptor control of the cutaneous active vasodilator system. J. Appl. Physiol.81(5): 2192–2198, 1996.—We sought to identify whether reductions in cutaneous active vasodilation during simulated orthostasis could be assigned solely to cardiopulmonary or to carotid baroreflexes by unloading cardiopulmonary baroreceptors with low levels of lower body negative pressure (LBNP) or unloading carotid baroreceptors with external pressure applied over the carotid sinus area [carotid pressure (CP)]. Skin blood flow was measured at a site at which adrenergic function was blocked via bretylium tosylate iontophoresis and at an unblocked site. During LBNP of −5 and −10 mmHg in hyperthermia, neither heart rate (HR) nor cutaneous vascular conductance (CVC) at either site changed ( P > 0.05 for both), whereas forearm vascular conductance (FVC) was reduced (−5 mmHg: from 21.6 ± 4.8 to 19.8 ± 4.1 FVC units, P = 0.05; −10 mmHg: from 22.3 ± 4.0 to 19.3 ± 3.7 FVC units, P = 0.002). LBNP of −30 mmHg in hyperthermia reduced CVC at both sites (untreated: from 51.9 ± 5.7 to 43.2 ± 5.1% maximum, P = 0.02; bretylium tosylate: from 60.9 ± 5.4 to 53.2 ± 4.4% maximum, P = 0.02), reduced FVC (from 23.2 ± 3.6 to 18.1 ± 3.3 FVC units; P = 0.002), and increased HR (from 83 ± 4 to 101 ± 3 beats/min; P = 0.003). Pulsatile CP (45 mmHg) did not affect FVC or CVC during normothermia or hyperthermia ( P > 0.05). However, HR and mean arterial pressure were elevated during CP in both thermal conditions (both P < 0.05). These results suggest that neither selective low levels of cardiopulmonary baroreceptor unloading nor selective carotid baroreceptor unloading can account for the inhibition of cutaneous active vasodilator activity seen with simulated orthostasis.
Effect of vitamin E deprivation and exercise training on induction of HSP70
Authors: Kelly D. A. , Tiidus P. M. , Houston M. E. , Noble E. G.
Published: December 2017

Kelly, D. A., P. M. Tiidus, M. E. Houston, and E. G. Noble.Effect of vitamin E deprivation and exercise training on induction of HSP70. J. Appl. Physiol. 81(6): 2379–2385, 1996.—To investigate the effects of dietary vitamin E deprivation and chronic exercise on the relative content of selected isoforms of the heat-shock protein 70 (HSP70) family in rat hindlimb muscle, vitamin E was withheld for 16 wk from female rats that underwent treadmill run training during the final 8 wk. As indicated by increased ( P < 0.05) content of the stress-inducible isoform (HSP72), training did stress the exercising muscles. However, vitamin E deficiency did not alter HSP72 content in nontrained rats and was associated with a lesser induction ( P < 0.01) in some muscles of trained animals. The constitutive isoform, which exhibited similar levels in muscles of varying fiber types, was demonstrated to be largely refractory to exercise, with an equivocal response to vitamin E deprivation. HSP72 content was correlated to type I myosin heavy chain (MHC-I) content but only in muscles of sedentary normal-diet rats. After training, HSP72 content in a muscle essentially devoid of MHC-I (superficial vastus lateralis) reached levels comparable to those in a muscle high in MHC-I (soleus).
The relationships among IGF-1, DNA content, and protein accumulation during skeletal muscle hypertrophy
Authors: Adams G. R. , Haddad F.
Published: December 2017

Adams, G. R., and F. Haddad. The relationships among IGF-1, DNA content, and protein accumulation during skeletal muscle hypertrophy. J. Appl. Physiol. 81(6): 2509–2516, 1996.—Insulin-like growth factor-1 (IGF-1) is known to have anabolic effects on skeletal muscle cells. This study examined the time course of muscle hypertrophy and associated IGF-1 peptide and mRNA expression. Data were collected at 3, 7, 14, and 28 days after surgical removal of synergistic muscles of both normal and hypophysectomized (HX) animals. Overloading increased the plantaris (Plant) mass, myofiber size, and protein-to-body weight ratio in both groups (normal and HX; P < 0.05). Muscle IGF-1 peptide levels peaked at 3 (normal) and 7 (HX) days of overloading with maximum 4.1-fold (normal) and 6.2-fold (HX) increases. Increases in muscle IGF-1 preceded the hypertrophic response. Total DNA content of the overloaded Plant increased in both groups. There was a strong positive relationship between IGF-1 peptide and DNA content in the overloaded Plant from both groups. These results indicate that 1) the muscles from rats with both normal and severely depressed systemic levels of IGF-1 respond to functional overload with an increase in local IGF-1 expression and 2) this elevated IGF-1 may be contributing to the hypertrophy response, possibly via the mobilization of satellite cells to provide increases in muscle DNA.
Enhancement of intestinal water absorption and sodium transport by glycerol in rats
Authors: Wapnir Raul A. , Sia Maria C. , Fisher Stanley E.
Published: December 2017

Wapnir, Raul A., Maria C. Sia, and Stanley E. Fisher.Enhancement of intestinal water absorption and sodium transport by glycerol in rats. J. Appl. Physiol.81(6): 2523–2527, 1996.—Glycerol (Gly) is a hydrophilic, absorbable, and energy-rich solute that could make water absorption more efficient. We investigated the use of Gly in a high-energy beverage containing corn syrup (CS) by using a small intestine perfusion procedure in the rat, an approach shown earlier to provide good preclinical information. The effectiveness of several formulations with Gly and CS was compared with commercial products and to experimental formulas where Gly substituted for glucose (Glc). The CS-Gly combination was more effective than preparations on the market containing sucrose and Glc-fructose syrups (G-P and G-L, respectively) in maintaining a net water absorption balance in the test jejunal segment [CS-Gly = 0.021 ± 0.226, G-L = −1.516 ± 0.467, and G-P = −0.299 ± 0.106 (SE) μl ⋅ min−1⋅ cm−1( P = 0.0113)] and in reducing sodium release into the lumen [CS-Gly = −133.2 ± 16.2, G-L = −226.7 ± 25.2, and G-P = −245.6 ± 23.4 nmol ⋅ min−1⋅ cm−1( P = 0.0022)]. In other preparations, at equal CS concentrations (60 and 80 g/l, respectively), Gly clearly improved net water absorption over a comparable Glc-containing product [CS60-Gly = 0.422 ± 0.136 and CS80-Gly = 0.666 ± 0.378 vs. CS60-Glc = −0.282 ± 0.200 and CS80-Glc = −1.046 ± 0.480 μl ⋅ min−1⋅ cm−1( P = 0.0019)]. On the basis of the data of this rat intestine perfusion model, Gly could be a useful ingredient in energy-rich beverages and might enhance fluid absorption in humans.
Decreased contraction economy in mouse EDL muscle injured by eccentric contractions
Authors: Warren Gordon L. , Williams Jay H. , Ward Christopher W. , Matoba Hideki , Ingalls Christopher P. , Hermann Karl M. , Armstrong R. B.
Published: December 2017

Warren III, Gordon L., Jay H. Williams, Christopher W. Ward, Hideki Matoba, Christopher P. Ingalls, Karl M. Hermann, and R. B. Armstrong. Decreased contraction economy in mouse EDL muscle injured by eccentric contractions. J. Appl. Physiol. 81(6): 2555–2564, 1996.—The objective of this study was to find out whether basal and/or active energy metabolism are altered in isolated mouse extensor digitorum longus muscle injured by eccentric (Ecc) contractions. Measurements of basal O2 consumption and isometric tetanus O2 recovery cost were made at 25°C on muscles that had done either 10 Ecc, 10 isometric (Iso), or no contractions (No). In parallel experiments, rates of lactate and pyruvate production were measured to estimate the anaerobic contribution. Basal O2 consumption was unaffected by the type of protocol performed ( P = 0.07). However, the tetanus O2 cost per force-time integral was elevated by 30–36% for the Ecc protocol muscles over that for the Iso and No protocol muscles. When including the increased lactate production by the Ecc protocol muscles, the total energetic cost per force-time integral was 53% higher than that for the Iso protocol muscles [2.35 ± 0.17 vs. 1.54 ± 0.18 μmol O2/(N ⋅ m ⋅ s)]. The decreased economy was attributed to two factors. First, in skinned fibers isolated from the injured muscles, the ratio of maximal actomyosin adenosinetriphosphatase activity to force production was up by 37.5%, suggesting uncoupling of ATP hydrolysis from force production. Second, increased reliance on anaerobic metabolism along with the fluorescent microscopic study of mitochondrial membrane potential and histochemical study of ATP synthase suggested an uncoupling of oxidative phosphorylation in the injured muscles.
Reproductive function in male endurance athletes: sperm analysis and hormonal profile
Authors: Lucía Alejandro , Chicharro José L. , Pérez Margarita , Serratosa Luis , Bandrés Fernando , Legido. Julio C.
Published: December 2017

Lucı́a, Alejandro, José L. Chicharro, Margarita Pérez, Luis Serratosa, Fernando Bandrés, and Julio C. Legido. Reproductive function in male endurance athletes: sperm analysis and hormonal profile. J. Appl. Physiol. 81(6): 2627–2636, 1996.—The purpose of this investigation was to study the effects of endurance exercise on male reproductive function (sex hormones and seminograms). Professional cyclists [ n = 12; mean age 24 ± 2 (SD) yr], elite triathletes ( n = 9; 26 ± 3 yr), recreational marathon runners ( n = 10; 32 ± 6 yr), and sedentary subjects (control group; n = 9; 30 ± 4 yr) were selected as subjects. For each group, the following parameters were measured three times during the sports season (training period: winter; competition period: spring; resting period: fall): percentage of body fat, hormonal profile (resting levels of follicle-stimulating hormone, luteinizing hormone, total and free testosterone, and cortisol), and seminograms (quantitative parameters: sperm volume and sperm count; qualitative parameters: sperm motility and morphology). The following comparisons were made in the measured parameters: 1) within groups (longitudinal design) and 2) between groups in each of the three periods (cross-sectional design) and over time (mixed design). In addition, both the volume and the intensity of training of each subject during the season (except for the control group) were quantified. Despite significant differences in training characteristics and in body fat percent, in general no significant differences ( P > 0.05) were found in hormonal profiles or in semen characteristics between or within groups. A lower sperm motility (46.2 ± 19.5%), however, was observed in the cyclists during the competition period when compared either with the other groups during this same period ( P < 0.05) or with themselves during the other two periods of study ( P < 0.01). In any case, the later phenomenon was attributed to physical factors associated with cycling, such as mechanical trauma to the testis and/or increased gonadal temperature. In conclusion, our findings suggest that endurance exercise does not adversely affect the hypothalamic-pituitary-testis axis.
Greater airway narrowing in immature than in mature rabbits during methacholine challenge
Authors: Shen X. , Bhargava V. , Wodicka G. R. , Doerschuk C. M. , Gunst S. J. , Tepper R. S.
Published: December 2017

Shen, X., V. Bhargava, G. R. Wodicka, C. M. Doerschuk, S. J. Gunst, and R. S. Tepper. Greater airway narrowing in immature than in mature rabbits during methacholine challenge. J. Appl. Physiol. 81(6): 2637–2643, 1996.—It has been demonstrated that methacholine (MCh) challenge produces a greater increase in lung resistance in immature than in mature rabbits (R. S. Tepper, X. Shen, E. Bakan, and S. J. Gunst. J. Appl. Physiol. 79: 1190–1198, 1995). To determine whether this maturational difference in the response to MCh was primarily related to changes in airway resistance (Raw) or changes in tissue resistance, we assessed airway narrowing in 1-, 2-, and 6-mo-old rabbits during intravenous MCh challenge (0.01–5.0 mg/kg). Airway narrowing was determined from measurements of Raw in vivo and from morphometric measurements on lung sections obtained after rapidly freezing the lung after the MCh challenge. The fold increase in Raw was significantly greater for 1- and 2-mo-old animals than for 6-mo-old animals. Similarly, the degree of airway narrowing assessed morphometrically was significantly greater for 1- and 2-mo-old animals than for 6-mo-old animals. The fold increase in Raw was highly correlated with the degree of airway narrowing assessed morphometrically ( r 2 = 0.82, P < 0.001). We conclude that the maturational difference in the effect of MCh on lung resistance is primarily caused by greater airway narrowing in the immature rabbits.
Chest wall and lung volume estimation by optical reflectance motion analysis
Authors: Cala S. J. , Kenyon C. M. , Ferrigno G. , Carnevali P. , Aliverti A. , Pedotti A. , Macklem P. T. , Rochester D. F.
Published: December 2017

Cala, S. J., C. M. Kenyon, G. Ferrigno, P. Carnevali, A. Aliverti, A. Pedotti, P. T. Macklem, and D. F. Rochester. Chest wall and lung volume estimation by optical reflectance motion analysis. J. Appl. Physiol. 81(6): 2680–2689, 1996.—Estimation of chest wall motion by surface measurements only allows one-dimensional measurements of the chest wall. We have assessed an optical reflectance system (OR), which tracks reflective markers in three dimensions (3-D) for respiratory use. We used 86 (6-mm-diameter) hemispherical reflective markers arranged circumferentially on the chest wall in seven rows between the sternal notch and the anterior superior iliac crest in two normal standing subjects. We calculated the volume of the entire chest wall and compared inspired and expired volumes with volumes obtained by spirometry. Marker positions were recorded by four TV cameras; two were 4 m in front of and two were 4 m behind the subject. The TV signals were sampled at 100 Hz and combined with grid calibration parameters on a personal computer to obtain the 3-D coordinates of the markers. Chest wall surfaces were reconstructed by triangulation through the point data, and chest wall volume was calculated. During tidal breathing and vital capacity maneuvers and during CO2-stimulated hyperpnea, there was a very close correlation of the lung volumes (Vl) estimated by spirometry [Vl(SP)] and OR [Vl(OR)]. Regression equations of Vl(OR) ( y) vs. Vl(SP) ( x,btps in liters) for the two subjects were given by y = 1.01 x − 0.01 ( r = 0.996) and y = 0.96 x + 0.03 ( r = 0.997), and by y = 1.04 x + 0.25 ( r = 0.97) and y = 0.98 x + 0.14 ( r = 0.95) for the two maneuvers, respectively. We conclude spirometric volumes can be estimated very accurately and directly from chest wall surface markers, and we speculate that OR may be usefully applied to calculations of chest wall shape, regional volumes, and motion analysis.
Nature and site of action of endogenous nitric oxide in vasculature of isolated pig lungs
Authors: Cremona George , Higenbottam Tim , Takao Motoshi , Bower Edward A. , Hall Leslie W.
Published: December 2017

Cremona, George, Tim Higenbottam, Motoshi Takao, Edward A. Bower, and Leslie W. Hall. Nature and site of action of endogenous nitric oxide in vasculature of isolated pig lungs. J. Appl. Physiol. 82(1): 23–31, 1997.—The site of action of endogenous and exogenous nitric oxide (NO) in isolated pig lungs was investigated by using arterial, double, and venous occlusion, which allowed precapillary, postcapillary, and venous segments to be partitioned into arterial, precapillary, postcapillary, and venous segments. N G-nitro-l-arginine (l-NNA; 10−5 M) increased resistance in the arterial (35 ± 6.6%, P = 0.003), precapillary (39.3 ± 5.1%, P = 0.001), and venous (18.3 ± 4.8%, P = 0.01) segments, respectively. Sodium nitroprusside (10−5 M) and NO (80 parts/million) reversed the effects ofl-NNA. Total pulmonary vascular resistance fell with increasing flow, due to a fall in precapillary resistance and dynamic resistance, and was significantly lower than mean total resistance.l-NNA increased the resistances but did not alter the pattern of the pressure-flow relationships. It is concluded that, in isolated pig lungs, the effect of endogenous NO seems to be dependent on flow in the arterial segment and independent of flow in the precapillary segment, but variation of its release does not appear to be fundamental to accommodation to changes in steady flow.
Effects of surface tension and intraluminal fluid on mechanics of small airways
Authors: Hill Mark J. , Wilson Theodore A. , Lambert Rodney K.
Published: December 2017

Hill, Mark J., Theodore A. Wilson, and Rodney K. Lambert.Effects of surface tension and intraluminal fluid on the mechanics of small airways. J. Appl. Physiol.82(1): 233–239, 1997.—Airway constriction is accompanied by folding of the mucosa to form ridges that run axially along the inner surface of the airways. The muscosa has been modeled (R. K. Lambert. J. Appl. Physiol. 71: 666–673, 1991) as a thin elastic layer with a finite bending stiffness, and the contribution of its bending stiffness to airway elastance has been computed. In this study, we extend that work by including surface tension and intraluminal fluid in the model. With surface tension, the pressure on the inner surface of the elastic mucosa is modified by the pressure difference across the air-liquid interface. As folds form in the mucosa, intraluminal fluid collects in pools in the depressions formed by the folds, and the curvature of the air-liquid interface becomes nonuniform. If the amount of intraluminal fluid is small, <2% of luminal volume, the pools of intraluminal fluid are small, the air-liquid interface nearly coincides with the surface of the mucosa, and the area of the air-liquid interface remains constant as airway cross-sectional area decreases. In that case, surface energy is independent of airway area, and surface tension has no effect on airway mechanics. If the amount of intraluminal fluid is >2%, the area of the air-liquid interface decreases as airway cross-sectional area decreases, and surface tension contributes to airway compression. The model predicts that surface tension plus intraluminal fluid can cause an instability in the area-pressure curve of small airways. This instability provides a mechanism for abrupt airway closure and abrupt reopening at a higher opening pressure.
Effects of acute hyperoxic exposure on solute fluxes across the blood-gas barrier in rat lungs
Authors: Zheng Lu P. , Du Rui Sheng , Goodman Barbara E.
Published: December 2017

Zheng, Lu P., Rui Sheng Du, and Barbara E. Goodman.Effects of acute hyperoxic exposure on solute fluxes across the blood-gas barrier in rat lungs. J. Appl. Physiol. 82(1): 240–247, 1997.—We investigated effects of acute hyperoxia on solute transport from air space to vascular space in isolated rat lungs. Air spaces were filled with Krebs-Ringer bicarbonate solution containing fluorescein isothiocyanate-labeled dextran (FD-20; mol wt 20,000) and either22Na+and [14C]sucrose, ord-[14C]glucose andl-[3H]glucose. Apparent permeability-surface area products for tracers over time (up to 120 min) were calculated for isolated perfused lungs from control rats (room air) and rats exposed to >95% O2for 48 or 60 h immediately postexposure. After O2exposures, mean fluxes for [14C]sucrose and FD-20 were significantly higher than in room-air control lungs. However, amiloride-sensitive Na+and actived-glucose fluxes were unchanged after hyperoxic exposure. Therefore, it is unlikely that decreases in net solute transport in this lung-injury model contributed to pulmonary edema resulting from O2toxicity. Increased net solute transport shown to help resolve pulmonary edema after acute hyperoxic exposure must therefore begin during the recovery period. In summary, our data show increases in passive solute fluxes but no changes in active solute fluxes immediately after acute hyperoxic lung injury.
Airway and alveolar permeability and surface liquid thickness: theory
Authors: Widdicombe John
Published: December 2017

Widdicombe, John. Airway and alveolar permeability and surface liquid thickness: theory. J. Appl. Physiol. 82(1): 3–12, 1997.—The thickness of airway surface liquid (ASL) can be calculated as the ratio of the permeability coefficient of an absorbed inert tracer to the percentage rate in which it decreases in content in the airway lumen. The percentage clearance of radiolabeled diethylenetriaminepentaacetic acid (DTPA) from human airways or lungs has been measured many times, with a mean value of 1.04 ± 0.25 (SD) %/min. Rates of clearance from animal lungs of most species give values of the same order, although they are lower in the sheep and higher in the dog. Permeability coefficients have not been measured simultaneously with percentage clearances and not at all for human tissues. Values for mannitol and sucrose, of which the former gives a permeability coefficient ∼25% greater than that for sucrose and DTPA in airway tubes and isolated mucosal sheets from experimental animals, give a mean of ∼7.1 × 10−7cm/s. This corresponds to thicknesses of ASL of ∼20–150 μm for various species. The assumptions underlying this estimate are discussed. It is concluded that ASL thickness in vivo may be considerably greater than in vitro measurements involving rapid freezing of the airway wall. Estimates of alveolar permeability suggest that either it is very considerably lower than that of the airway epithelium, that methods to measure alveolar permeability mainly reflect airway permeability, or both.
Mortality rate and longevity of food-restricted exercising male rats: a reevaluation
Authors: Holloszy John O.
Published: December 2017

Holloszy, John O. Mortality rate and longevity of food-restricted exercising male rats: a reevaluation. J. Appl. Physiol. 82(2): 399–403, 1997.—Food restriction increases the maximal longevity of rats. Male rats do not increase their food intake to compensate for the increase in energy expenditure in response to exercise. However, a decrease in the availability of energy for growth and cell proliferation that induces an increase in maximal longevity in sedentary rats only results in an improvement in average survival, with no extension of maximal life span, when caused by exercise. In a previous study (J. O. Holloszy and K. B. Schechtman. J. Appl. Physiol. 70: 1529–1535, 1991), to test the possibility that exercise prevents the extension of life span by food restriction, wheel running and food restriction were combined. The food-restricted runners showed the same increase in maximal life span as food-restricted sedentary rats but had an increased mortality rate during the first one-half of their mortality curve. The purpose of the present study was to determine the pathological cause of this increased early mortality. However, in contrast to our previous results, the food-restricted wheel-running rats in this study showed no increase in early mortality, and their survival curves were virtually identical to those of sedentary animals that were food restricted so as to keep their body weights the same as those of the runners. Thus it is possible that the rats in the previous study had a health problem that had no effect on longevity except when both food restriction and exercise were superimposed on it. Possibly of interest in this regard, the rats in this study did considerably more voluntary running than those in the previous study. It is concluded that 1) moderate caloric restriction combined with exercise does not normally increase the early mortality rate in male rats, 2) exercise does not interfere with the extension of maximal life span by food restriction, and 3) the beneficial effects of food restriction and exercise on survival are not additive or synergistic.
Innervation pattern of guinea pig pulmonary vasculature depends on vascular diameter
Authors: Haberberger Rainer , Schemann Michael , Sann Holger , Kummer Wolfgang
Published: December 2017

Haberberger, Rainer, Michael Schemann, Holger Sann, and Wolfgang Kummer. Innervation pattern of guinea pig pulmonary vasculature depends on vascular diameter. J. Appl. Physiol. 82(2): 426–434, 1997.—The pulmonary vasculature is supplied by various neurochemically distinct types of nerve fibers, including sensory substance P-containing and autonomic noradrenergic, nitrergic, and cholinergic axons. Pharmacological experiments have suggested that various segments of the pulmonary vascular tree respond differently to the respective neuromediators. We, therefore, aimed to determine histochemically and immunohistochemically for each of these neurochemically distinct perivascular axons their quantitative distribution along the vascular tree from the extrapulmonary trunks to the smallest intraparenchymal ramifications in control guinea pigs ( n = 5). Generally, arterial innervation was more developed than that of veins. Along the arterial tree, noradrenergic and substance P-containing axons were ubiquitous from the pulmonary trunk to smallest intraparenchymal vessels, whereas nitrergic axons were practically restricted to large (>700-μm) extrapulmonary arteries. Cholinergic axons were regularly present at arteries down to 100 μm in diameter and innervated two-thirds of small arteries (50–100 μm). The results demonstrate that the noradrenergic vasoconstrictor innervation extends throughout the pulmonary vascular system whereas the innervation pattern with various types of vasodilator fibers changes with vascular diameter, parallel to known pharmacological differences in cholinergic and nitrergic vasodilator effects.
Left ventricular mass, geometry, and filling in endurance athletes: association with exercise blood pressure
Authors: Karjalainen Jouko , Mäntysaari Matti , Viitasalo Matti , Kujala Urho
Published: December 2017

Karjalainen, Jouko, Matti Mäntysaari, Matti Viitasalo, and Urho Kujala. Left ventricular mass, geometry, and filling in endurance athletes: association with exercise blood pressure. J. Appl. Physiol. 82(2): 531–537, 1997.—We studied whether left ventricular (LV) mass and concentricity [relative myocardial volume (RMV)] are associated with exercise blood pressure (BP) in athletes. LV structure and filling were evaluated by Doppler echocardiography and BP in maximal bicycle ergometry and isometric handgrip tests on 32 male endurance athletes and 15 age-matched controls. Indexed LV mass was 145 ± 14 (SD) g/m in athletes and 93 ± 20 g/m in controls. Mass was not associated with BP at rest or in low-grade exercise, but with heavier exercise loads this association strengthened in athletes, being maximal at peak exercise ( r = 0.65 for mass and 0.58 for indexed mass; P < 0.001). Multivariate analysis indicated that BP at peak exercise accounted for 34% and the amount of training for an additional 11% of the variance in indexed LV mass. RMV was 21% larger in athletes. Only the increase in systolic BP during handgrip explained significantly (19%) the variance in RMV. LV filling velocities were not associated with mass, RMV, or BP. We conclude that in endurance athletes LV mass is associated with BP in heavy dynamic exercise and LV concentricity with BP response in static exercise.