bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of chronic exercise and deconditioning on platelet function in women
Authors: Wang Jong-Shyan , Jen Chauying J. , Chen Hsiun-Ing
Published: December 2017

Wang, Jong-Shyan, Chauying J. Jen, and Hsiun-Ing Chen.Effects of chronic exercise and deconditioning on platelet function in women. J. Appl. Physiol.83(6): 2080–2085, 1997.—To investigate the effects of chronic exercise and deconditioning on platelet function in women, 16 healthy sedentary women were divided into control and exercise groups. The exercise group cycled on an ergometer at 50% maximal oxygen consumption for 30 min/day, 5 days/wk, for two consecutive menstrual cycles and then were deconditioned for three menstrual cycles. During this period, platelet adhesiveness on a fibrinogen-coated surface, ADP-induced platelet aggregation and intracellular calcium concentration elevation, guanosine 3′,5′-cyclic monophosphate (cGMP) content in platelets, and plasma nitric oxide metabolite levels were measured before and immediately after a progressive exercise test in the midfollicular phase. Our results indicated that, after exercise training, 1) resting heart rates and blood pressures were reduced, and exercise performance was improved; 2) resting platelet function was decreased, whereas plasma nitrite and nitrate levels and platelet cGMP contents were enhanced; and 3) the potentiation of platelet function by acute strenuous exercise was decreased, whereas the increases in plasma nitrite and nitrate levels and platelet cGMP contents were enhanced by acute exercise. Furthermore, deconditioning reversed these training effects. This implies that training-induced platelet functional changes in women in the midfollicular phase may be mediated by nitric oxide.
Bed rest suppresses bioassayable growth hormone release in response to muscle activity
Authors: McCall G. E. , Goulet C. , Grindeland R. E. , Hodgson J. A. , Bigbee A. J. , Edgerton V. R.
Published: December 2017

McCall, G. E., C. Goulet, R. E. Grindeland, J. A. Hodgson, A. J. Bigbee, and V. R. Edgerton. Bed rest suppresses bioassayable growth hormone release in response to muscle activity. J. Appl. Physiol. 83(6): 2086–2090, 1997.—Hormonal responses to muscle activity were studied in eight men before (−13 or −12 and −8 or −7 days), during (2 or 3, 8 or 9, and 13 or 14 days) and after (+2 or +3 and +10 or +11 days) 17 days of bed rest. Muscle activity consisted of a series of unilateral isometric plantar flexions, including 4 maximal voluntary contractions (MVCs), 48 contractions at 30% MVC, and 12 contractions at 80% MVC, all performed at a 4:1-s work-to-rest ratio. Blood was collected before and immediately after muscle activity to measure plasma growth hormone by radioimmunoassay (IGH) and by bioassay (BGH) of tibia epiphyseal cartilage growth in hypophysectomized rats. Plasma IGH was unchanged by muscle activity before, during, or after bed rest. Before bed rest, muscle activity increased ( P < 0.05) BGH by 66% at −13 or −12 days (2,146 ± 192 to 3,565 ± 197 μg/l) and by 92% at −8 or −7 days (2,162 ± 159 to 4,161 ± 204 μg/l). After 2 or 3 days of bed rest, there was no response of BGH to the muscle activity, a pattern that persisted through 8 or 9 days of bed rest. However, after 13 or 14 days of bed rest, plasma concentration of BGH was significantly lower after than before muscle activity (2,594 ± 211 to 2,085 ± 109 μg/l). After completion of bed rest, muscle activity increased BGH by 31% at 2 or 3 days (1,807 ± 117 to 2,379 ± 473 μg/l; P < 0.05), and by 10 or 11 days the BGH response was similar to that before bed rest (1,881 ± 75 to 4,160 ± 315 μg/l; P < 0.05). These data demonstrate that the ambulatory state of an individual can have a major impact on the release of BGH, but not IGH, in response to a single bout of muscle activity.
Impact of resistance exercise during bed rest on skeletal muscle sarcopenia and myosin isoform distribution
Authors: Bamman Marcas M. , Clarke Mark S. F. , Feeback Daniel L. , Talmadge Robert J. , Stevens Bruce R. , Lieberman Steven A. , Greenisen Michael C.
Published: December 2017

Bamman, Marcas M., Mark S. F. Clarke, Daniel L. Feeback, Robert J. Talmadge, Bruce R. Stevens, Steven A. Lieberman, and Michael C. Greenisen. Impact of resistance exercise during bed rest on skeletal muscle sarcopenia and myosin isoform distribution. J. Appl. Physiol. 84(1): 157–163, 1998.—Because resistance exercise (REx) and bed-rest unloading (BRU) are associated with opposing adaptations, our purpose was to test the efficacy of REx against the effects of 14 days of BRU on the knee-extensor muscle group. Sixteen healthy men were randomly assigned to no exercise (NoEx; n = 8) or REx ( n = 8). REx performed five sets of leg press exercise with 80–85% of one repetition maximum (1 RM) every other day during BRU. Muscle samples were removed from the vastus lateralis muscle by percutaneous needle biopsy. Myofiber distribution was determined immunohistochemically with three monoclonal antibodies against myosin heavy chain (MHC) isoforms (I, IIa, IIx). MHC distribution was further assessed by quantitative gel electrophoresis. Dynamic 1-RM leg press and unilateral maximum voluntary isometric contraction (MVC) were determined. Maximal neural activation (root mean squared electromyogram) and rate of torque development (RTD) were measured during MVC. Reductions ( P < 0.05) in type I (15%) and type II (17%) myofiber cross-sectional areas were found in NoEx but not in REx. Electrophoresis revealed no changes in MHC isoform distribution. The percentage of type IIx myofibers decreased ( P < 0.05) in REx from 9 to 2% and did not change in NoEx. 1 RM was reduced ( P < 0.05) by 9% in NoEx but was unchanged in REx. MVC fell by 15 and 13% in NoEx and REx, respectively. The agonist-to-antagonist root mean squared electromyogram ratio decreased ( P < 0.05) 19% in REx. RTD slowed ( P < 0.05) by 54% in NoEx only. Results indicate that REx prevented BRU-induced myofiber atrophy and also maintained training-specific strength. Unlike spaceflight, BRU did not induce shifts in myosin phenotype. The reported benefits of REx may prove useful in prescribing exercise for astronauts in microgravity.
Hypohydration and thermoregulation in cold air
Authors: O’Brien Catherine , Young Andrew J. , Sawka Michael N.
Published: December 2017

O’Brien, Catherine, Andrew J. Young, and Michael N. Sawka.Hypohydration and thermoregulation in cold air. J. Appl. Physiol. 84(1): 185–189, 1998.—This study examined the effects of hypohydration on thermoregulation during cold exposure. In addition, the independent influences of hypohydration-associated hypertonicity and hypovolemia were investigated. Nine male volunteers were monitored for 30 min at 25°C, then for 120 min at 7°C, under three counterbalanced conditions: euhydration (Eu), hypertonic hypohydration (HH), and isotonic hypohydration (IH). Hypohydration was achieved 12 h before cold exposure by inducing sweating (HH) or by ingestion of furosemide (IH). Body weight decrease (4.1 ± 0.2%) caused by hypohydration was similar for HH and IH, but differences ( P < 0.05) were found between HH and IH in plasma osmolality (292 ± 1 vs. 284 ± 1 mosmol/kgH2O) and plasma volume reduction (−8 ± 2 vs. −18 ± 3%). Heat debt (349 ± 14 among) did not differ ( P > 0.05) among trials. Mean skin temperature decreased throughout cold exposure during Eu but plateaued after 90 min during HH and IH. Forearm-finger temperature gradient tended ( P = 0.06) to be greater during Eu (10.0 ± 0.7°C) than during HH or IH (8.9 ± 0.7°C). This suggests weaker vasoconstrictor tone during hypohydration than during Eu. Final mean skin temperature was higher for HH than for Eu or IH (23.5 ± 0.3, 22.6 ± 0.4, and 22.9 ± 0.3°C, respectively), and insulation was lower on HH than on IH (0.13 ± 0.01 vs. 0.15 ± 0.01°C ⋅ W−1 ⋅ m−2, respectively), but not with Eu (0.14 ± 0.01°C ⋅ W−1 ⋅ m−2). This provides some evidence that hypertonicity impairs the vasoconstrictor response to cold. Although mild hypohydration did not affect body heat balance during 2-h whole body exposure to moderate cold, hypohydration-associated hypertonicity may have subtle effects on vasoconstriction that could become important during a more severe cold exposure.
Forearm training reduces the exercise pressor reflex during ischemic rhythmic handgrip
Authors: Mostoufi-Moab Sogol , Widmaier Eric J. , Cornett Jacob A. , Gray Kristen , Sinoway Lawrence I.
Published: December 2017

Mostoufi-Moab, Sogol, Eric J. Widmaier, Jacob A. Cornett, Kristen Gray, and Lawrence I. Sinoway. Forearm training reduces the exercise pressor reflex during ischemic rhythmic handgrip. J. Appl. Physiol. 84(1): 277–283, 1998.—We examined the effects of unilateral, nondominant forearm training (4 wk) on blood pressure and forearm metabolites during ischemic and nonischemic rhythmic handgrip (30 1-s contractions/min at 25% maximal voluntary contraction). Contractions were performed by 10 subjects with the forearm enclosed in a pressurized Plexiglas tank to induce ischemic conditions. Training increased the endurance time in the nondominant arm by 102% ( protocol 1). In protocol 2, tank pressure was increased in increments of 10 mmHg/min to +50 mmHg. Training raised the positive-pressure threshold necessary to engage the pressor response. In protocol 3, handgrip was performed at +50 mmHg and venous blood samples were analyzed. Training attenuated mean arterial pressure (109 ± 5 and 98 ± 4 mmHg pre- and posttraining, respectively, P < 0.01), venous lactate (2.9 ± 0.4 and 1.8 ± 0.3 mmol/l pre- and posttraining, respectively, P < 0.01), and the pH response (7.21 ± 0.02 and 7.25 ± 0.01, pre- and posttraining, respectively, P < 0.01). However, deep venous O2saturation was unchanged. Training increased the positive-pressure threshold for metaboreceptor engagement, reduced metabolite concentrations, and reduced mean arterial pressure during ischemic exercise.
Muscle fiber architecture of the dog diaphragm
Authors: Boriek Aladin M. , Miller Charles C. , Rodarte Joseph R.
Published: December 2017

Boriek, Aladin M., Charles C. Miller III, and Joseph R. Rodarte. Muscle fiber architecture of the dog diaphragm. J. Appl. Physiol. 84(1): 318–326, 1998.—Previous measurements of muscle thickness and length ratio of costal diaphragm insertions in the dog (A. M. Boriek and J. R. Rodarte. J. Appl. Physiol. 77: 2065–2070, 1994) suggested, but did not prove, discontinuous muscle fiber architecture. We examined diaphragmatic muscle fiber architecture using morphological and histochemical methods. In 15 mongrel dogs, transverse sections along the length of the muscle fibers were analyzed morphometrically at ×20, by using the BioQuant System IV software. We measured fiber diameters, cross-sectional fiber shapes, and cross-sectional area distributions of fibers. We also determined numbers of muscle fibers per cross-sectional area and ratio of connective tissue to muscle fibers along a course of the muscle from near the chest wall (CW) to near the central tendon (CT) for midcostal left and right hemidiaphragms, as well as ventral, middle, and dorsal regions of the left costal hemidiaphragm. In six other mongrel dogs, the macroscopic distribution of neuromuscular junctions (NMJ) on thoracic and abdominal diaphragm surfaces was determined by staining the intact diaphragmatic muscle for acetylcholinesterase activity. The average major diameter of muscle fibers was significantly smaller, and the number of fibers was significantly larger midspan between CT and CW than near the insertions. The ratio of connective tissues to muscle fibers was largest at CW compared with other regions along the length of the muscle. The diaphragm is transversely crossed by multiple scattered NMJ bands with fairly regular intervals offset in adjacent strips. Muscle fascicles traverse two to five NMJ, consistent with fibers that do not span the entire fascicle from CT to CW. These results suggest that the diaphragm has a discontinuous fiber architecture in which contractile forces may be transmitted among the muscle fibers through the connective tissue adjacent to the fibers.
Effect of oxygen tension and rate of pressure reduction during decompression on central gas bubbles
Authors: Reinertsen R. E. , Flook V. , Koteng S. , Brubakk A. O.
Published: December 2017

Reinertsen, R. E., V. Flook, S. Koteng, and A. O. Brubakk.Effect of oxygen tension and rate of pressure reduction during decompression on central gas bubbles. J. Appl. Physiol. 84(1): 351–356, 1998.—Reduction in ascent speed and an increase in the O2 tension in the inspired air have been used to reduce the risk for decompression sickness. It has previously been reported that decompression speed and O2 partial pressure are linearly related for human decompressions from saturation hyperbaric exposures. The constant of proportionality K( K = rate/partial pressure of inspired O2) indicates the incidence of decompression sickness. The present study investigated the relationship among decompression rate, partial pressure of inspired O2, and the number of central gas bubbles after a 3-h dive to 500 kPa while breathing nitrox with an O2 content of 35 kPa. We used transesophageal ultrasonic scanning to determine the number of bubbles in the pulmonary artery of pigs. The results show that, for a given level of decompression stress, decompression rate and O2 tension in the inspired air can be traded off against each other by using pulmonary artery bubbles as an end point. The results also seem to confirm that decompressions that have a high K value are more stressful.
Relationship between airway microvascular leakage, edema, and baseline airway functions
Authors: Matheson Melissa , Rynell Ann-Christine , McClean Melissa , Berend Norbert
Published: December 2017

Matheson, Melissa, Ann-Christine Rynell, Melissa McClean, and Norbert Berend. Relationship between airway microvascular leakage, edema, and baseline airway functions. J. Appl. Physiol. 84(1): 77–81, 1998.—This study was designed to examine the relationship among microvascular leakage, edema, and baseline airway function. Microvascular leakage was induced in the airways of anesthetized, tracheostomized New Zealand White rabbits ( n = 22) by using nebulized N-formyl-methionyl-leucyl-phenylalanine (10 mg) and was measured in the trachea by using the Evans blue dye technique. Airway wall thickness was assessed morphometrically in the right main bronchus after Formalin fixation at a pressure of 25 cmH2O. Areas calculated included the mucosal wall area, the adventitial wall area, the total wall area, and the percentage of total wall area consisting of blood vessels. A neutrophil count was also performed by analyzing numbers of cells in both the mucosal wall area and the adventitial wall area. Airway function was assessed before and 30 min after challenge with N-formyl-methionyl-leucyl-phenylalanine by determining airway resistance, functional residual capacity, specific airway resistance, and flow-volume and pressure-volume curves (after paralysis of the animals with suxamethonium). The concentration of Evans blue dye in tracheal tissue ranged from 31.3 to 131.2 μg. There was a significant correlation between this concentration and both the adventitial wall area ( P < 0.01) and mucosal neutrophil numbers ( P < 0.005). There was no correlation between Evans blue concentration and either blood vessel area or changes in respiratory physiology parameters before and after challenge. There was no significant difference between any respiratory physiology measurements before and after challenge. We conclude that an increase in microvascular leakage correlates with airway edema in the adventitia; however, these airway changes have no significant effect on airway elastic or resistive properties.
Effect of resistance exercise training on cortical and cancellous bone in mature male rats
Authors: Westerlind Kim C. , Fluckey James D. , Gordon Scott E. , Kraemer William J. , Farrell Peter A. , Turner Russell T.
Published: December 2017

Westerlind, Kim C., James D. Fluckey, Scott E. Gordon, William J. Kraemer, Peter A. Farrell, and Russell T. Turner.Effect of resistance exercise training on cortical and cancellous bone in mature male rats. J. Appl. Physiol. 84(2): 459–464, 1998.—The effect of resistance training on tibial cancellous and cortical bone was evaluated in rats by using static histomorphometry and Northern analysis. Five-month-old male Sprague-Dawley rats were randomly assigned to exercise (Ex; n = 8) or control (Con; n = 4) groups. Animals were operantly conditioned to press two levers, facilitating full extension and flexion of the hindlimbs (“squats”), while wearing an unweighted vest. After an 8-wk familiarization period, Ex animals performed 3 sessions/wk for 17–19 sessions with progressively increased amounts of weight applied to the vest. Con rats completed the same exercise protocol without applied resistance. No difference in cross-sectional, medullary, or cortical bone area was observed between Ex and Con rats in the tibial diaphysis. In contrast, the cancellous bone area in the proximal tibial metaphysis was significantly larger in trained rats. Trabecular number, trabecular thickness, and the percentage of cancellous bone covered by osteoid were significantly greater in the Ex animals compared with Con animals. In addition, steady-state mRNA levels for osteocalcin for the Ex group were 456% those expressed in the Con group. The data demonstrate that resistance training increases cancellous bone area in sexually mature male rats and suggest that it does so, in part, by stimulating bone formation.
Effects of 4 wk of hindlimb suspension on skeletal muscle mitochondrial respiration in rats
Authors: Yajid Fatima , Mercier Jacques G. , Mercier Béatrice M. , Dubouchaud Hervé , Préfaut Christian
Published: December 2017

Yajid, Fatima, Jacques G. Mercier, Béatrice M. Mercier, Hervé Dubouchaud, and Christian Préfaut.Effects of 4 wk of hindlimb suspension on skeletal muscle mitochondrial respiration in rats. J. Appl. Physiol. 84(2): 479–485, 1998.—We investigated in rats the effect of 4 wk of hypodynamia on the respiration of mitochondria isolated from four distinct muscles [soleus, extensor digitorum longus, tibial anterior, and gastrocnemius (Gas)] and from subsarcolemmal (SS) and intermyofibrillar (IMF) regions of mixed hindlimb muscles that mainly contained the four cited muscles. With pyruvate plus malate as respiratory substrate, 4 wk of hindlimb suspension produced an 18% decrease in state 3 respiration for IMF mitochondria compared with those in the control group ( P < 0.05). The SS mitochondria state 3 were not significantly changed. Concerning the four single muscles, the mitochondrial respiration was significantly decreased in the Gas muscle, which showed a 59% decrease in state 3 with pyruvate + malate ( P < 0.05). The other muscles presented no significant decrease in respiratory rate in comparison with the control group. With succinate + rotenone, there was no significant difference in the respiratory rate compared with the respective control group, whatever the mitochondrial origin (SS, or IMF, or from single muscle). We conclude that 4 wk of hindlimb suspension alters the respiration of IMF mitochondria in hindlimb skeletal muscles and seems to act negatively on complex I of the electron-transport chain or prior sites. The muscle mitochondria most affected are those isolated from the Gas muscle.
Sprint training attenuates myocyte hypertrophy and improves Ca2+homeostasis in postinfarction myocytes
Authors: Zhang Xue-Qian , Ng Yuk-Chow , Musch Timothy I. , Moore Russell L. , Zelis R. , Cheung Joseph Y.
Published: December 2017

Zhang, Xue-Qian, Yuk-Chow Ng, Timothy I. Musch, Russell L. Moore, R. Zelis, and Joseph Y. Cheung. Sprint training attenuates myocyte hypertrophy and improves Ca2+homeostasis in postinfarction myocytes. J. Appl. Physiol. 84(2): 544–552, 1998.—Myocytes isolated from rat hearts 3 wk after myocardial infarction (MI) had decreased Na+/Ca2+exchange currents ( INa/Ca; 3 Na+out:1 Ca2+in) and sarcoplasmic reticulum (SR)-releasable Ca2+contents. These defects in Ca2+regulation may contribute to abnormal contractility in MI myocytes. Because exercise training elicits positive adaptations in cardiac contractile function and myocardial Ca2+regulation, the present study examined whether 6–8 wk of high-intensity sprint training (HIST) would ameliorate some of the cellular maladaptations observed in post-MI rats with limited exercise activity (Sed). In MI rats, HIST did not affect citrate synthase activities of plantaris muscles but significantly increased the percentage of cardiac α-myosin heavy chain (MHC) isoforms (57.2 ± 1.9 vs. 49.3 ± 3.5 in MI-HIST vs. MI-Sed, respectively; P ≤ 0.05). At the single myocyte level, HIST attenuated cellular hypertrophy observed post-MI, as evidenced by reductions in cell lengths (112 ± 4 vs. 130 ± 5 μm in MI-HIST vs. MI-Sed, respectively; P ≤ 0.005) and cell capacitances (212 ± 8 vs. 242 ± 9 pF in MI-HIST vs. MI-Sed, respectively; P ≤ 0.015). Reverse INa/Cawas significantly lower ( P ≤ 0.0001) in myocytes from MI-Sed rats compared with those from rats that were sham operated and sedentary. HIST significantly increased reverse INa/Ca( P ≤ 0.05) without affecting the amount of Na+/Ca2+exchangers (detected by immunoblotting) in MI myocytes. SR-releasable Ca2+content, as estimated by integrating forward INa/Caduring caffeine-induced SR Ca2+release, was also significantly increased ( P ≤ 0.02) by HIST in MI myocytes. We conclude that the enhanced cardiac output and stroke volume in post-MI rats subjected to HIST are mediated, at least in part, by reversal of cellular maladaptations post-MI.
Effect of microgravity on the expression of mitochondrial enzymes in rat cardiac and skeletal muscles
Authors: Connor Michael K. , Hood David A.
Published: December 2017

Connor, Michael K., and David A. Hood. Effect of microgravity on the expression of mitochondrial enzymes in rat cardiac and skeletal muscles. J. Appl. Physiol. 84(2): 593–598, 1998.—The purpose of this study was to examine the expression of nuclear and mitochondrial genes in cardiac and skeletal muscle (triceps brachii) in response to short-duration microgravity exposure. Six adult male rats were exposed to microgravity for 6 days and were compared with six ground-based control animals. We observed a significant 32% increase in heart malate dehydrogenase (MDH) enzyme activity, which was accompanied by a 62% elevation in heart MDH mRNA levels after microgravity exposure. Despite modest elevations in the mRNAs encoding subunits III, IV, and VIc as well as a 2.2-fold higher subunit IV protein content after exposure to microgravity, heart cytochrome c oxidase (CytOx) enzyme activity remained unchanged. In skeletal muscle, MDH expression was unaffected by microgravity, but CytOx activity was significantly reduced 41% by microgravity, whereas subunit III, IV, and VIc mRNA levels and subunit IV protein levels were unaltered. Thus tissue-specific (i.e., heart vs. skeletal muscle) differences exist in the regulation of nuclear-encoded mitochondrial proteins in response to microgravity. In addition, the expression of nuclear-encoded proteins such as CytOx subunit IV and expression of MDH are differentially regulated within a tissue. Our data also illustrate that the heart undergoes previously unidentified mitochondrial adaptations in response to short-term microgravity conditions more dramatic than those evident in skeletal muscle. Further studies evaluating the functional consequences of these adaptations in the heart, as well as those designed to measure protein turnover, are warranted in response to microgravity.
Pulmonary diffusing capacities for oxygen-labeled CO2and nitric oxide in rabbits
Authors: Heller Hartmut , Fuchs Gabi , Schuster Klaus-Dieter
Published: December 2017

Heller, Hartmut, Gabi Fuchs, and Klaus-Dieter Schuster. Pulmonary diffusing capacities for oxygen-labeled CO2and nitric oxide in rabbits. J. Appl. Physiol. 84(2): 606–611, 1998.—We determined the pulmonary diffusing capacity (Dl) for18O-labeled CO2(C18O2) and nitric oxide (NO) to estimate the membrane component of the respective gas conductances. Six anesthetized paralyzed rabbits were ventilated by a computerized ventilatory servo system. Single-breath maneuvers were automatically performed by inflating the lungs with gas mixtures containing 0.9% C18O2or 0.05% NO in nitrogen, with breath-holding periods ranging from 0 to 1 s for C18O2and from 2 to 8 s for NO. The alveolar partial pressures of C18O2and NO were determined by using respiratory mass spectrometry. Dl was calculated from gas exchange during inflation, breath hold, and deflation. We obtained values of 14.0 ± 1.1 and 2.2 ± 0.1 (mean value ± SD) ml ⋅ mmHg−1⋅ min−1for[Formula: see text]and DlNO, respectively. The measured[Formula: see text]/DlNOratio was one-half that of the theoretically predicted value according to Graham’s law (6.3 ± 0.5 vs. 12, respectively). Analyses of the several mechanisms influencing the determination of[Formula: see text]and DlNOand their ratio are discussed. An underestimation of the membrane diffusing component for CO2is considered the likely reason for the low[Formula: see text]/DlNOratio obtained.
Effect of neuropeptide Y on hemodynamics of the rabbit lung
Authors: Lang Sally A. , Maron Michael B.
Published: December 2017

Lang, Sally A., and Michael B. Maron.Effect of neuropeptide Y on hemodynamics of the rabbit lung. J. Appl. Physiol. 84(2): 618–623, 1998.—We evaluated the effect of neuropeptide Y (NPY) on the hemodynamics of the isolated rabbit lung perfused at constant flow and outflow pressure. Doses of 10−8 and 10− 7 M NPY increased pulmonary arterial pressure (Ppa) from 11.5 ± 1.0 (SE) mmHg to, respectively, 16.4 ± 1.5 and 26.0 ± 3.8 mmHg ( P < 0.05, n = 5 mmHg lungs), with 78 ± 4% of the increase at 10−7 M resulting from an increased arterial resistance. At the latter dose, pulmonary capillary pressure increased from 5.8 ± 0.9 to 9.4 ± 1.0 mmHg ( P < 0.05). When administered in the presence of norepinephrine, 10−8 and 10−7 M NPY ( n = 6) produced extreme increases in Ppa to 66.1 ± 20.5 and 114.7 ± 25.5 mmHg, respectively, that were due primarily to an increased arterial resistance. To determine the significance of circulating NPY as a pulmonary vasoactive agent, we measured plasma NPY-like immunoreactivity in anesthetized rabbits after massively activating the sympathetic nervous system with veratrine. NPY-like immunoreactivity increased from 74 ± 10 to 111 ± 10 (SE) pM ( P < 0.05). Thus, although NPY is a potent vasoconstrictor in the rabbit lung, it is not likely that plasma NPY concentrations rise sufficiently, even after massive sympathetic nervous system activation, to produce pulmonary vasoconstriction in the intact rabbit.
Perfluorochemical rescue after surfactant treatment: effect of perflubron dose and ventilatory frequency
Authors: Wolfson Marla R. , Kechner Nancy E. , Roache Robert F. , Dechadarevian Jean-Pierre , Friss Helena E. , Rubenstein S. David , Shaffer Thomas H.
Published: December 2017

Wolfson, Marla R., Nancy E. Kechner, Robert F. Roache, Jean-Pierre DeChadarevian, Helena E. Friss, S. David Rubenstein, and Thomas H. Shaffer. Perfluorochemical rescue after surfactant treatment: effect of perflubron dose and ventilatory frequency. J. Appl. Physiol. 84(2): 624–640, 1998.—To test the hypotheses that perfluorochemical (PFC) liquid rescue after natural surfactant (SF) treatment would improve pulmonary function and histology and that this profile would be influenced by PFC dose or ventilator strategy, anesthetized preterm lambs ( n = 31) with respiratory distress were studied using nonpreoxygenated perflubron. All animals received SF at 1 h and were randomized at 2 h as follows and studied to 4 h postnatal age: 1) conventional mechanical gas ventilation ( n = 8), 2) 30 ml/kg perflubron with gas ventilation [partial liquid ventilation (PLV)] at 60 breaths/min ( n = 8), 3) 10 ml/kg perflubron with PLV at 60 breaths/min ( n = 7), and 4) 10 ml/kg perflubron with PLV at 30 breaths/min ( n = 8). All animals tolerated instillation without additional cardiopulmonary instability. All perflubron-rescued groups demonstrated sustained improvement in gas exchange, respiratory compliance, and reduction in pressure requirements relative to animals receiving SF alone. Improvement was directly related to perflubron dose and breathing frequency; peak inspiratory pressure required to achieve physiological gas exchange was lower in the higher-dose and -frequency groups, and mean airway pressure was lower in the lower-frequency group. Lung expansion was greater and evidence of barotrauma was less in the higher-dose and -frequency group; regional differences in expansion were not different as a function of dose but were greater in the lower-frequency group. Regional differences in lung perflubron content were reduced in the higher-dose and -frequency groups and greatest in the lower-dose and -frequency group. The results suggest that, whereas PLV of the SF-treated lung improves gas exchange and lung mechanics, the protective benefits of perflubron in the lung may depend on dose and ventilator strategy to optimize PFC distribution and minimize exposure of the alveolar-capillary membrane to a gas-liquid interface.
Arginine in burn injury improves cardiac performance and prevents bacterial translocation
Authors: Horton Jureta W. , White Jean , Maass David , Sanders Billy
Published: December 2017

Horton, Jureta W., Jean White, David Maass, and Billy Sanders. Arginine in burn injury improves cardiac performance and prevents bacterial translocation. J. Appl. Physiol. 84(2): 695–702, 1998.—This study examined the effects of arginine supplement of fluid resuscitation from burn injury on cardiac contractile performance and bacterial translocation after a third-degree burn comprising 43% of the total body surface area in adult rats. Before burn injury, rats were instrumented to measure blood pressure; after burn (or sham injury), paired groups of sham-burned and burned rats were given vehicle (saline), l-arginine,d-arginine, or N-methyl-l-arginine (300 mg/kg in 0.3 ml of saline 30 min, 6 h, and 23 h postburn) plus fluid resuscitation; sham-burned rats received drug only. Twenty-four hours after burn trauma, hemodynamics were measured; the animals were then killed and randomly assigned to Langendorff heart studies or to studies examining translocation of gut bacteria. Burn rats treated with vehicle,d-arginine, or N-methyl-l-arginine had well-defined cardiocirculatory responses that included hypotension, tachycardia, respiratory compensation for metabolic acidosis, hypocalcemia, cardiac contractile depression, and significant bacterial translocation. Compared with values measured in vehicle-treated burn rats, l-arginine given after burn improved blood pressure, prevented tachycardia, reduced serum lactate levels, improved cardiac performance, and significantly reduced bacterial translocation, confirming thatl-arginine administration after burn injury provided significant cardiac and gastrointestinal protection. Circulating neutrophil counts fell after burn trauma and serum glucagon levels rose, but these changes were not altered by pharmacological intervention. Our finding of significantly higher coronary perfusate guanosine 3′,5′-cyclic monophosphate concentration inl-arginine-treated burn rats suggests that the beneficial effects ofl-arginine were mediated by nitric oxide production.
Blood flow vs. venous pressure effects on filtration coefficient in oleic acid-injured lung
Authors: Anglade Daniel , Corboz Michel , Menaouar Ahmed , Parker James C. , Sanou Sagazaga , Bayat Sam , Benchetrit Gila , Grimbert Francis A.
Published: December 2017

On the basis of changes in capillary filtration coefficient ( K fc) in 24 rabbit lungs, we determined whether elevations in pulmonary venous pressure (Ppv) or blood flow (BF) produced differences in filtration surface area in oleic acid-injured (OA) or control (Con) lungs. Lungs were cyclically ventilated and perfused under zone 3 conditions by using blood and 5% albumin with no pharmacological modulation of vascular tone. Pulmonary arterial, venous, and capillary pressures were measured by using arterial, venous, and double occlusion. Before and during each K fc-measurement maneuver, microvascular/total vascular compliance was measured by using venous occlusion. K fc was measured before and 30 min after injury, by using a Ppv elevation of 7 cmH2O or a BF elevation from 1 to 2 l ⋅ min−1 ⋅ 100 g−1 to obtain a similar double occlusion pressure. Pulmonary arterial pressure increased more with BF than with Ppv in both Con and OA lungs [29 ± 2 vs. 19 ± 0.7 (means ± SE) cmH2O; P < 0.001]. In OA lungs compared with Con lungs, values of K fc (200 ± 40 vs. 83 ± 14%, respectively; P < 0.01) and microvascular/total vascular compliance ratio (86 ± 4 vs. 68 ± 5%, respectively; P < 0.01) increased more with BF than with Ppv. In conclusion, for a given OA-induced increase in hydraulic conductivity, BF elevation increased filtration surface area more than did Ppv elevation. The steep pulmonary pressure profile induced by increased BF could result in the recruitment of injured capillaries and could also shift downstream the compression point of blind (zone 1) and open injured vessels (zone 2).
Effect of standing on neurohumoral responses and plasma volume in healthy subjects
Authors: Jacob Giris , Ertl Andrew C. , Shannon John R. , Furlan Raffaello , Robertson Rose Marie , Robertson David
Published: December 2017

Upright posture leads to rapid pooling of blood in the lower extremities and shifts plasma fluid into surrounding tissues. This results in a decrease in plasma volume (PV) and in hemoconcentration. There has been no integrative evaluation of concomitant neurohumoral and PV shifts with upright posture in normal subjects. We studied 10 healthy subjects after 3 days of stable Na+ and K+ intake. PV was assessed by the Evans blue dye method and by changes in hematocrit. Norepinephrine (NE), NE spillover, epinephrine (Epi), vasopressin, plasma renin activity, aldosterone, osmolarity, and kidney response expressed by urine osmolality and by Na+ and K+ excretion of the subjects in the supine and standing postures were all measured. We found that PV fell by 13% (375 ± 35 ml plasma) over ∼14 min, after which time it remained relatively stable. There was a concomitant decrease in systolic blood pressure and an increase in heart rate that peaked at the time of maximal decrease in PV. Plasma Epi and NE increased rapidly to this point. Epi approached baseline by 20 min of standing. NE spillover increased 80% and clearance decreased 30% with 30 min of standing. The increase in plasma renin activity correlated with an increase in aldosterone. Vasopressin increased progressively, but there was no change in plasma osmolarity. The kidney response showed a significant decrease in Na+ and an increase in K+ excretion with upright posture. We conclude that a cascade of neurohumoral events occurs with upright posture, some of which particularly coincide with the decrease in PV. Plasma Epi levels may contribute to the increment in heart rate with maintained upright posture.
Effect of muscle glycogen content on exercise-induced changes in muscle T2 times
Authors: Price Thomas B. , Gore John C.
Published: December 2017

Effects of gastrocnemius glycogen (Gly) concentration on changes in transverse relaxation time (T2; ms) were studied after 5-min plantar flexion at 25% of maximum voluntary contraction (MVC). Gastrocnemius Gly, phosphorus metabolites, and T2 were measured in seven subjects by using interleaved13C/31P magnetic resonance spectroscopy (MRS) at 4.7 T and magnetic resonance imaging (MRI; 1.5 T). After baseline MRS/MRI, subjects exercised for 5 min at 25% of MVC and were reexamined (MRS/MRI). Subjects then performed ∼15 min of single-leg toe raises (50 ± 2% of MVC), depleting gastrocnemius Gly by 43%. After a 1-h rest (for T2 return to baseline), subjects repeated the 5-min protocol, followed by a final MRI/MRS. After the initial 5-min protocol, T2 values increased by 5.9 ± 0.8 ms (29.9 ± 0.4 to 35.8 ± 0.6 ms), whereas Gly did not change significantly (70.5 ± 6.8 to 67.6 ± 7.4 mM). After 15 min of toe raises, gastrocnemius Gly was reduced to 40.4 ± 5.3 mM ( P ≤ 0.01), recovering to 45.8 ± 5.3 mM ( P ≤ 0.05) during a 1-h rest. After the second 5-min bout of plantar flexion (reduced Gly at 25% of MVC), T2 values increased by 5.0 ± 0.8 ms (30.4 to 35.4 ms), whereas muscle Gly rose to 57.6 ± 5.3 mM. We conclude that muscle Gly concentration per se does not affect exercise-induced T2 increases in the human gastrocnemius.
Time course of sympathovagal imbalance and left ventricular dysfunction in conscious dogs with heart failure
Authors: Ishise Hisanari , Asanoi Hidetsugu , Ishizaka Shinji , Joho Shuji , Kameyama Tomoki , Umeno Katsumi , Inoue Hiroshi
Published: December 2017

To elucidate the time course of sympathovagal balance and its relationship to left ventricular function in heart failure, we serially evaluated left ventricular contractility and relaxation and autonomic tone in 11 conscious dogs with tachycardia-induced heart failure. We determined a dynamic map of sympathetic and parasympathetic modulation by power spectral analysis of heart rate variability. The left ventricular peak +dP/d t substantially fell from 3,364 ± 338 to 1,959 ± 318 mmHg/s ( P< 0.05) on the third day and declined gradually to 1,783 ± 312 mmHg/s at 2 wk of rapid ventricular pacing. In contrast, the time constant of left ventricular pressure decay and end-diastolic pressure increased gradually from 25 ± 4 to 47 ± 5 ms ( P < 0.05) and from 10 ± 2 to 21 ± 3 mmHg ( P < 0.05), respectively, at 2 wk of pacing. The high-frequency component (0.15–1.0 Hz), a marker of parasympathetic modulation, decreased from 1,928 ± 1,914 to 62 ± 68 × 103ms2( P < 0.05) on the third day and further to 9 ± 12 × 103ms2( P < 0.05) at 2 wk. Similar to the time course of left ventricular diastolic dysfunction, plasma norepinephrine levels and the ratio of low (0.05- to 0.15-Hz)- to high-frequency component increased progressively from 135 ± 50 to 532 ± 186 pg/ml ( P< 0.05) and from 0.06 ± 0.06 to 1.12 ± 1.01 ( P < 0.05), respectively, at 2 wk of pacing. These cardiac and autonomic dysfunctions recovered gradually toward the normal values at 2 wk after cessation of pacing. Thus a parallel decline in left ventricular contractility with parasympathetic influence and a parallel progression in left ventricular diastolic dysfunction with sympathoexcitation suggest a close relationship between cardiac dysfunction and autonomic dysregulation during development of heart failure.
Energy metabolism in sedentary and active 49- to 70-yr-old women
Authors: Withers R. T. , Smith D. A. , Tucker R. C. , Brinkman M. , Clark D. G.
Published: December 2017

This study examined differences between long-term exercising (LE) and long-term nonexercising (LNE) women [ n = 24; age 56.4 ± 6.2 (SD) yr] for resting metabolic rate (RMR) and energy expenditure in the free-living state by using doubly labeled water (DLW). There was a statistically significant difference ( P = 0.0002) between the 12 LE (94.85 ± 8.44 kJ ⋅ kg−1 ⋅ day−1) and 12 LNE (81.16 ± 6.62 kJ ⋅ kg−1 ⋅ day−1) for RMR, but this difference was only marginally significant ( P = 0.06) when the data (MJ/day) were subjected to an analysis of covariance with fat-free mass as the covariate. The DLW data indicated that the eight most active LE (12.99 ± 3.58 MJ/day) expended significantly ( P = 0.01) more energy than did the eight least active LNE (9.30 ± 1.15 MJ/day). Energy expenditures ranged from 7.64 to 18.15 MJ/day, but there was no difference ( P = 0.96) between the LE and LNE in energy expenditure during activity that was not designed to either improve or maintain fitness. These cross-sectional data on 49- to 70-yr-old women therefore suggest that 1) aerobic-type training results in a greater RMR per unit of body mass and also when statistical control is exerted for the effect of the metabolically active fat-free mass, 2) there is a large range in the energy intake necessary to maintain energy balance, and 3) aerobic training does not result in a compensatory reduction in energy expenditure during the remainder of the day.
Airway mechanics, gas exchange, and blood flow in a nonlinear model of the normal human lung
Authors: Liu C. H. , Niranjan S. C. , Clark J. W. , San K. Y. , Zwischenberger J. B. , Bidani A. ,   (With the Technical Assistance of H. B. Winnike, C. Vanouye, and J. B. Olansen)
Published: December 2017

A model integrating airway/lung mechanics, pulmonary blood flow, and gas exchange for a normal human subject executing the forced vital capacity (FVC) maneuver is presented. It requires as input the intrapleural pressure measured during the maneuver. Selected model-generated output variables are compared against measured data (flow at the mouth, change in lung volume, and expired O2 and CO2concentrations at the mouth). A nonlinear parameter-estimation algorithm is employed to vary selected sensitive model parameters to obtain reasonable least squares fits to the data. This study indicates that 1) all three components of the respiratory model are necessary to characterize the FVC maneuver; 2) changes in pulmonary blood flow rate are associated with changes in alveolar and intrapleural pressures and affect gas exchange and the time course of expired gas concentrations; and 3) a collapsible midairway segment must be included to match airflow during a forced expiration. Model simulations suggest that the resistances to airflow offered by the collapsible segment and the small airways are significant throughout forced expiration; their combined effect is needed to adequately match the inspiratory and expiratory flow-volume loops. Despite the limitations of this lumped single-compartment model, a remarkable agreement with airflow and expired gas concentration measurements is obtained for normal subjects. Furthermore, the model provides insight into the important dynamic interactions between ventilation and perfusion during the FVC maneuver.
Developmental change in isoproterenol-mediated relaxation of pulmonary veins of fetal and newborn lambs
Authors: Gao Yuansheng , Tolsa Jean-Francois , Botello Michael , Raj J. Usha
Published: December 2017

β-Adrenergic agonists are important regulators of perinatal pulmonary circulation. They cause vasodilation primarily via the adenyl cyclase-adenosine 3′,5′-cyclic monophosphate (cAMP) pathway. We examined the responses of isolated fourth-generation pulmonary veins of term fetal (145 ± 2 days gestation) and newborn (10 ± 1 days) lambs to isoproterenol, a β-adrenergic agonist. In vessels preconstricted with U-46619 (a thromboxane A2analog), isoproterenol induced greater relaxation in pulmonary veins of newborn lambs than in those of fetal lambs. The relaxation was eliminated by propranolol, a β-adrenergic antagonist. Forskolin, an activator of adenyl cyclase, also caused greater relaxation of veins of newborn than those of fetal lambs. 8-Bromoadenosine 3′,5′-cyclic monophosphate, a cell membrane-permeable analog of cAMP, induced a similar relaxation of all vessels. Biochemical studies show that isoproterenol and forskolin induced a greater increase in cAMP content and in adenyl cyclase activity of pulmonary veins in the newborn than in the fetal lamb. These results demonstrate that β-adrenergic-agonist-mediated relaxation of pulmonary veins increases with maturation. An increase in the activity of adenyl cyclase may contribute to the change.
Effect of carbohydrate ingestion on adipose tissue lipolysis during long-lasting exercise in trained men
Authors: De Glisezinski I. , Harant I. , Crampes F. , Trudeau F. , Felez A. , Cottet-Émard J. M. , Garrigues M. , Riviere D.
Published: December 2017

To study whether sucrose administration acts on lipid mobilization during prolonged exercise, we used subcutaneous abdominal adipose tissue microdialysis in eight well-trained subjects submitted at random to two 100-min exercises (50% maximal aerobic power) on separate days. After 50 min of exercise, the subjects ingested either a sucrose solution (0.75 g/kg body wt) or water. By using a microdialysis probe, dialysate was obtained every 10 min from the subjects at rest, during exercise, and during a 30-min recovery period. During exercise without sucrose, plasma and dialysate glycerol increased significantly. With sucrose, the response was significantly lower for dialysate glycerol ( P < 0.05). Plasma free fatty acid level was lower after sucrose than after water ingestion ( P < 0.05). With water ingestion, plasma catecholamines increased significantly, whereas insulin fell ( P < 0.05). With sucrose ingestion, the epinephrine response was blunted, whereas the insulin level was significantly increased. In conclusion, the use of adipose tissue microdialysis directly supports a lower lipid mobilization during exercise when sucrose is supplied, which confirms that the availability of carbohydrate influences lipid mobilization.
Cervical magnetic stimulation as a method to discriminate between diaphragm and rib cage muscle fatigue
Authors: Similowski Thomas , Straus Christian , Attali Valérie , Duguet Alexandre , Derenne Jean-Philippe
Published: December 2017

Inspiratory muscle fatigue can probably determine hypercapnic respiratory failure. Diaphragm fatigue is detected by electrical phrenic stimulation (ELS), but there is no simple tool to assess rib cage muscle (RCM) fatigue. Cervical magnetic stimulation (CMS) costimulates the phrenic nerves and RCM. We reasoned that changes in transdiaphragmatic pressure twitch (Pdi,tw) with CMS and ELS should be different after selective diaphragm vs. RCM fatigue. Five volunteers performed inspiratory resistive tasks while voluntarily uncoupling diaphragm and RCM. Baseline Pdi,twELS and Pdi,twCMS were 28.57 ± 1.68 and 32.83 ± 2.92 cmH2O. After selective diaphragm loading, Pdi,twELS and Pdi,twCMS were reduced by 39 and 26%, with comparable decreases in gastric pressure twitch (Pga,tw). Esophageal pressure twitch (Pes,tw) was better preserved with CMS. Therefore Pes,tw/Pga,tw was lower with ELS than CMS (−1.24 ± 0.16 vs. −1.73 ± 0.11, P = 0.05). After selective RCM loading, there was no diaphragm fatigue, but Pes,twCMS was significantly reduced (−30%). These findings support the role of rib cage stiffening by CMS-related RCM contraction in the ELS-CMS differences and suggest that CMS can be used to assess RCM fatigue.
Abdominal motor unit activity during respiratory and nonrespiratory tasks
Authors: Puckree Threethambal , Cerny Frank , Bishop Beverly
Published: December 2017

Abdominal muscles serve multiple roles, but the functional organization of their motoneurons remains unclear. To gain insight, we recorded single motor unit potentials from the internal oblique (IO) and transversus abdominis (TA) muscles of three standing subjects during quiet breathing, a leg lift, and an expiratory threshold load. Inspiratory airflow, recorded from a pneumotachometer, provided tidal volumes and respiratory cycle timing. Fine wires, implanted under ultrasonic imaging, detected single motor unit potentials that were visually distinguished by their spike morphology. From the number of spikes, firing profiles, times of occurrence in the respiratory cycle, and their onset, instantaneous, mean, and peak firing frequencies we deduced that 1) breathing patterns varied across tasks, 2) different motor units were recruited for each task with essentially no overlap, 3) their firing displayed prominent expiratory activity during each task, and 4) the recruitment levels and discharge patterns of IO and TA were different. We conclude that the IO and TA motor pools receive a strong central respiratory drive, yet each pool receives its own distinct, task-dependent synaptic input.