bluuebunny/crossref_metadata_2025 huggingface dataset:
Stretch-induced enhancement of mechanical power output in human multijoint exercise with countermovement
Authors: Takarada Yudai , Hirano Yuichi , Ishige Yusuke , Ishii Naokata
Published: December 2017

Takarada, Yudai, Yuichi Hirano, Yusuke Ishige, and Naokata Ishii. Stretch-induced enhancement of mechanical power output in human multijoint exercise with countermovement. J. Appl. Physiol. 83(5): 1749–1755, 1997.—The relation between the eccentric force developed during a countermovement and the mechanical power output was studied in squatting exercises under nominally isotonic load (50% of 1-repetition maximum). The subjects ( n = 5) performed squatting exercises with a countermovement at varied deceleration rates before lifting the load. The ground reaction force and video images were recorded to obtain the power output of the body. Net muscle moments acting at hip, knee, and ankle joints were calculated from video recordings by using inverse dynamics. When an intense deceleration was taken at the end of downward movement, large eccentric force was developed, and the mechanical power subsequently produced during the lifting movement was consistently larger than that produced without the countermovement. Both maximal and mean power outputs during concentric actions increased initially with the eccentric force, whereas they began to decline when the eccentric force exceeded ∼1.4 times the sum of load and body weight. Video-image analysis showed that this characteristic relation was predominantly determined by the torque around the knee joint. Electromyographic analyses showed no consistent increase in time-averaged integrated electromyograph from vastus lateralis with the power output, suggesting that the enhancement of power output is primarily caused by the prestretch-induced improvement of an intrinsic force-generating capability of the agonist muscle.
Synchronous direct gradient layer and indirect room calorimetry
Authors: Seale James L. , Rumpler William V.
Published: December 2017

Rumpler, James L., and William V. Seale. Synchronous direct gradient layer and indirect room calorimetry. J. Appl. Physiol. 83(5): 1775–1781, 1997.—A dual direct/indirect room-sized calorimeter is used at the Beltsville Human Nutrition Research Center to measure heat emission and energy expenditure in humans. Because the response times of a gradient layer direct calorimeter and an indirect calorimeter are not equivalent, the respective rate of heat emission and energy expenditure cannot be directly compared. A system of equations has been developed and tested that can correct the respective outputs of the direct gradient layer calorimeter and indirect calorimeter for delays due to the response times of the measurement systems. Performance tests using alcohol combustion to simulate a human subject indicate accurate measurements of heat production from indirect (99.9 ± 0.4%), indirect corrected for response time (99.9 ± 0.5%), direct (99.9 ± 0.8%), and direct corrected for response time (99.9 ± 0.8%) calorimetry systems. Results from 24-h measurements in 10 subjects indicate that corrected heat emission is equivalent to (99.8 ± 2.0%) corrected energy expenditure. However, heat emission measured during sleep was significantly greater (14%) than energy expenditure, suggesting a change in the energy stored as heat in the body. This difference was reversed during the day. These results illustrate how the simultaneous measurement of heat emission and energy expenditure provides insights into heat regulation.
Intensity and frequency dependence of laryngeal afferent inputs to respiratory hypoglossal motoneurons
Authors: Mifflin Steven W.
Published: December 2017

Mifflin, Steven W. Intensity and frequency dependence of laryngeal afferent inputs to respiratory hypoglossal motoneurons. J. Appl. Physiol. 83(6): 1890–1899, 1997.—Inspiratory hypoglossal motoneurons (IHMs) mediate contraction of the genioglossus muscle and contribute to the regulation of upper airway patency. Intracellular recordings were obtained from antidromically identified IHMs in anesthetized, vagotomized cats, and IHM responses to electrical activation of superior laryngeal nerve (SLN) afferent fibers at various frequencies and intensities were examined. SLN stimulus frequencies <2 Hz evoked an excitatory-inhibitory postsynaptic potential (EPSP-IPSP) sequence or only an IPSP in most IHMs that did not change in amplitude as the stimulus was maintained. During sustained stimulus frequencies of 5–10 Hz, there was a reduction in the amplitude of SLN-evoked IPSPs with time with variable changes in the EPSP. At stimulus frequencies >25 Hz, the amplitude of EPSPs and IPSPs was reduced over time. At a given stimulus frequency, increasing stimulus intensity enhanced the decay of the SLN-evoked postsynaptic potentials (PSPs). Frequency-dependent attenuation of SLN inputs to IHMs also occurred in newborn kittens. These results suggest that activation of SLN afferents evokes different PSP responses in IHMs depending on the stimulus frequency. At intermediate frequencies, inhibitory inputs are selectively filtered so that excitatory inputs predominate. At higher frequencies there was no discernible SLN-evoked PSP temporally locked to the SLN stimuli. Alterations in SLN-evoked PSPs could play a role in the coordination of genioglossal contraction during respiration, swallowing, and other complex motor acts where laryngeal afferents are activated.
Intratracheal instillation of a novel NO/nucleophile adduct selectively reduces pulmonary hypertension
Authors: Brilli Richard J. , Krafte-Jacobs Brian , Smith Daniel J. , Roselle Dominick , Passerini Daniel , Vromen Amos , Moore Lori , Szabó Csaba , Salzman Andrew L.
Published: December 2017

Brilli, Richard J., Brian Krafte-Jacobs, Daniel J. Smith, Dominick Roselle, Daniel Passerini, Amos Vromen, Lori Moore, Csaba Szabó, and Andrew L. Salzman. Intratracheal instillation of a novel NO/nucleophile adduct selectively reduces pulmonary hypertension. J. Appl. Physiol. 83(6): 1968–1975, 1997.—We examined the pulmonary and systemic hemodynamic effects of administering soluble nitric oxide (NO) donor compounds (NO/nucleophile adducts, i.e., NONOates) directly into the trachea of animals with experimentally induced pulmonary hypertension. Steady-state pulmonary hypertension was created by using the thromboxane agonist U-46619. Yorkshire pigs were randomly assigned to one of four groups: group 1, intratracheal saline (control; n = 8); group 2, intratracheal sodium nitroprusside ( n = 6); group 3, intratracheal ethylputreanine NONOate ( n = 6); and group 4, intratracheal 2-(dimethylamino)-ethylputreanine NONOate (DMAEP/NO; n = 6). Pulmonary and systemic hemodynamics were monitored after drug instillation. Group 4 had significant reductions in pulmonary vascular resistance index (PVRI) at all time points compared with steady state and compared with group 1 ( P < 0.05), whereas systemic vascular resistance index did not change. The mean change in mean pulmonary arterial pressure in group 4 was −33.1 ± 1.2% compared with +6.4 ± 1.3% in group 1( P < 0.001), and the mean change in mean arterial pressure was −9.3 ± 0.7% compared with a control value of −0.9 ± 0.5% ( P < 0.05). Groups 2 and 3 had significant decreases in both PVRI and systemic vascular resistance index compared with steady state and with group 1. In conclusion, intratracheal instillation of a polar-charged tertiary amine NONOate DMAEP/NO results in the selective reduction of PVRI. Intermittent intratracheal instillation of selective NONOates may be an alternative to continuously inhaled NO in the treatment of pulmonary hypertension.
Autonomic control of skeletal muscle vasodilation during exercise
Authors: Buckwalter John B. , Mueller Patrick J. , Clifford Philip S.
Published: December 2017

Buckwalter, John B., Patrick J. Mueller, and Philip S. Clifford. Autonomic control of skeletal muscle vasodilation during exercise. J. Appl. Physiol. 83(6): 2037–2042, 1997.—Despite extensive investigation, the control of blood flow during dynamic exercise is not fully understood. The purpose of this study was to determine whether β-adrenergic or muscarinic receptors are involved in the vasodilation in exercising skeletal muscle. Six mongrel dogs were instrumented with ultrasonic flow probes on both external iliac arteries and with a catheter in a branch of one femoral artery. The dogs exercised on a treadmill at 6 miles/h while drugs were injected intra-arterially into one hindlimb. Isoproterenol (0.2 μg) or acetylcholine (1 μg) elicited increases in iliac blood flow of 89.8 ± 14.4 and 95.6 ± 17.4%, respectively, without affecting systemic blood pressure or blood flow in the contralateral iliac artery. Intra-arterial propranolol (1 mg) or atropine (500 μg) had no effect on iliac blood flow, although they abolished the isoproterenol and acetylcholine-induced increases in iliac blood flow. These data indicate that exogenous activation of β-adrenergic or muscarinic receptors in the hindlimb vasculature increases blood flow to dynamically exercising muscle. More importantly, because neither propranolol nor atropine affected iliac blood flow, we conclude that β-adrenergic and muscarinic receptors are not involved in the control of blood flow to skeletal muscle during moderate steady-state dynamic exercise in dogs.
Modulation of pulmonary arterial input impedance during transition from inspiration to expiration
Authors: Castiglioni P. , Tommasini R. , Morpurgo M. , Di Rienzo M.
Published: December 2017

Castiglioni, P., R. Tommasini, M. Morpurgo, and M. Di Rienzo. Modulation of pulmonary arterial input impedance during transition from inspiration to expiration. J. Appl. Physiol. 83(6): 2123–2130, 1997.—We investigated whether respiration influences pulmonary arterial input impedance during transition from inspiration to expiration in five anesthetized, spontaneously breathing dogs. Impedance (Z) was separately assessed for heart beats occurring in inspiration, in expiration, and during the transition from inspiration to expiration (transitional beat). Transitional beats were scored by the ratio between the fraction of beat falling in expiration and the total beat duration [expiratory fraction (Efr)] to quantify their position within the transition. In transitional beats, input resistance linearly increased with Efr; Z modulus at the heart-rate frequency (fHR) decreased up to −50% for Efr = 50%. Z phase at fHR was greater than in inspiration for Efr<40% and lower for Efr >50%. Unlike blood flow velocity, mean value and first harmonic of pulmonary arterial pressure were correlated to Efr and paralleled the changes of input resistance and Z at fHR. This indicates that respiration influences Z through modifications in arterial pressure. The evidence of important respiratory influences on Z function may help the pathophysiological interpretation of dysfunctions of the right heart pumping action, such as the so-called cor pulmonale.
An improved statistical methodology to estimate and analyze impedances and transfer functions
Authors: Curran-Everett Douglas , Zhang Yiming , Jones M. Douglas , Jones Richard H.
Published: December 2017

Curran-Everett, Douglas, Yiming Zhang, M. Douglas Jones, Jr., and Richard H. Jones. An improved statistical methodology to estimate and analyze impedances and transfer functions. J. Appl. Physiol. 83: 2146–2157, 1997.—Estimating the mathematical relationship between pulsatile time series (e.g., pressure and flow) is an effective technique for studying dynamic systems. The frequency-domain relationship between time series, often calculated as an impedance (pressure/flow), is known more generally as a frequency-response or transfer function (output/input). Current statistical methods for transfer function analysis 1) assume erroneously that repeated observations on a subject are independent, 2) have limited statistical value and power, or 3) are restricted to use in single subjects rather than in an entire sample. This paper develops a regression model for transfer function analysis that corrects each of these deficiencies. Spectral densities of the input and output time series and the cross-spectral density between them are first estimated from discrete Fourier transforms and then used to obtain regression estimates of the transfer function. Statistical comparisons of the transfer function estimates use a test statistic that is distributed as χ2. Confidence intervals for amplitude and phase can also be calculated. By correctly modeling repeated observations on each subject, this improved statistical approach to transfer function estimation and analysis permits the simultaneous analysis of data from all subjects in a sample, improves the power of the transfer function model, and has broad relevance to the study of dynamic physiological systems.
Letters to the Editor
Authors: Meyer Ronald A. , Wiseman Robert W.
Published: December 2017

The following is the abstract of the article discussed in the subsequent letter:

Nevill, Alan M., David A. Jones, David McIntyre, Gregory C. Bogdanis, and Mary E. Nevill. A model for phosphocreatine resynthesis. J. Appl. Physiol. 82(1): 329–335, 1997.—A model for phosphocreatine (PCr) resynthesis is proposed based on a simple electric circuit, where the PCr store in muscle is likened to the stored charge on the capacitor. The solution to the second-order differential equation that describes the potential around the circuit suggests the model for PCr resynthesis is given by PCr( t) = R − [ d 1 ⋅ exp(− k 1 ⋅ t) ± d 2 ⋅ exp(− k 2 ⋅ t)], where R is PCr concentration at rest, d 1, d 2, k 1, and k 2 are constants, and t is time. By using nonlinear least squares regression, this double-exponential model was shown to fit the PCr recovery data taken from two studies involving maximal exercise accurately. In study 1, when the muscle was electrically stimulated while occluded, PCr concentrations rose during the recovery phase to a level above that observed at rest. In study 2, after intensive dynamic exercise, PCr recovered monotonically to resting concentrations. The second exponential term in the double-exponential model was found to make a significant additional contribution to the quality of fit in both study 1( P < 0.05) and study 2 ( P < 0.01).
Design and calibration of unicapillary pneumotachographs
Authors: Giannella-Neto A. , Bellido C. , Barbosa R. B. , Melo M. F. Vidal
Published: December 2017

Giannella-Neto, A., C. Bellido, R. B. Barbosa, and M. F. Vidal Melo. Design and calibration of unicapillary pneumotachographs. J. Appl. Physiol.84(1): 335–343, 1998.—This study presents a method for design and calibration of unicapillary pneumotachographs for small-animal experiments. The design, based on Poiseuille’s law, defines a set of internal radius and length values that allows for laminar flow, measurable pressure differences, and minimal interference with animal’s respiratory mechanics and gas exchange. A third-order polynomial calibration (Pol) of the pressure-flow relationship was employed and compared with linear calibration (Lin). Tests were done for conditions of ambient pressure (Pam) and positive pressure (Ppos) ventilation at different flow ranges. A physical model designed to match normal and low compliance in rats was used. At normal compliance, Pol provided lower errors than Lin for mixed (1–12 ml/s), mean (4–10 ml/s), and high (8–12 ml/s) flow rate calibrations for both Pam and Ppos inspiratory tests (P < 0.001 for all conditions) and expiratory tests ( P < 0.001 for all conditions). At low compliance, they differed significantly with 8.6 ± 4.1% underestimation when Lin at Pam was used in Ppos tests. Ppos calibration, preferably in combination with Pol, should be used in this case to minimize errors (Pol = 0.8 ± 0.5%, Lin = 6.5 ± 4.0%, P < 0.0005). Nonlinear calibration may be useful for improvement of flow and volume measurements in small animals during both Pam and Ppos ventilation.
Human ventilatory response to 8 h of euoxic hypercapnia
Authors: Tansley John G. , Pedersen Michala E. F. , Clar Christine , Robbins Peter A.
Published: December 2017

Tansley, John G., Michala E. F. Pedersen, Christine Clar, and Peter A. Robbins. Human ventilatory response to 8 h of euoxic hypercapnia. J. Appl. Physiol. 84(2): 431–434, 1998.—Ventilation (V˙e) rises throughout 40 min of constant elevated end-tidal[Formula: see text] without reaching steady state (S. Khamnei and P. A. Robbins. Respir. Physiol. 81: 117–134, 1990). The present study investigates 8 h of euoxic hypercapnia to determine whetherV˙e reaches steady state within this time. Two protocols were employed: 1) 8-h euoxic hypercapnia (end-tidal[Formula: see text] = 6.5 Torr above prestudy value, end-tidal [Formula: see text] = 100 Torr) followed by 8-h poikilocapnic euoxia; and 2) control, where the inspired gas was air. V˙ewas measured over a 5-min period before the experiment and then hourly over a 16-h period. In the hypercapnia protocol,V˙e had not reached a steady state by the first hour ( P < 0.001, analysis of variance), but there were no further significant differences inV˙eover hours 2–8 (analysis of variance). V˙efell promptly on return to eucapnic conditions. We conclude that, whereas there is a component of theV˙e response to hypercapnia that is slow, there is no progressive rise inV˙e throughout the 8-h period.
Cardiorespiratory responses to systemic administration of a protein kinase C inhibitor in conscious rats
Authors: Gozal David , Graff Gavin R. , Torres José E. , Khicha Sanjay G. , Nayak Gautam S. , Simakajornboon Narong , Gozal Evelyne
Published: December 2017

Gozal, David, Gavin R. Graff, José E. Torres, Sanjay G. Khicha, Gautam S. Nayak, Narong Simakajornboon, and Evelyne Gozal.Cardiorespiratory responses to systemic administration of a protein kinase C inhibitor in conscious rats. J. Appl. Physiol. 84(2): 641–648, 1998.—Although protein kinase C (PKC) is an essential component of multiple neurally mediated events, its role in respiratory control remains undefined. The ventilatory effects of a systemically active PKC inhibitor (Ro-32-0432; 100 mg/kg ip) were assessed by whole body plethysmography during normoxia, hypoxia (10% O2), and hyperoxia (100% O2) in unrestrained Sprague-Dawley rats. A sustained expiratory time increase occurred within 8–10 min of injection in room air [mean 44.8 ± 5.2 (SE) % ], was similar to expiratory time prolongations after Ro-32-0432 administration during 100% O2(45.5 ± 8.1%; not significant), and was associated with mild minute ventilation (V˙e) decreases. Hypercapnic ventilatory responses (5% CO2) remained unchanged after Ro-32-0432. During 10% O2,V˙e increased from 122.6 ± 15.6 to 195.7 ± 10.1 ml/min in vehicle-treated rats ( P < 0.001). In contrast, marked attenuation of V˙e hypoxic responses occurred after Ro-32-0432 [86.2 ± 6.2 ml/min in room air to 104.1 ± 7.1 ml/min in 10% O2; pre- vs. post-Ro32–0432, P < 0.001 (analysis of variance)]. Overall, PKC activity was reduced and increases with hypoxia were abolished in the particulate subcellular fraction of brain tissue after Ro-32-0432 treatment, indicating that this compound readily crosses the blood-brain barrier. We conclude that systemic PKC inhibition elicits significant centrally mediated expiratory prolongations and ventilatory reductions as well as blunted ventilatory responses to hypoxia but not to hypercapnia. We postulate that PKC plays an important role in signal transduction pathways within brain regions underlying respiratory control.
Skeletal muscle chemoreflex and pHiin exercise ventilatory control
Authors: Oelberg David A. , Evans Allison B. , Hrovat Mirko I. , Pappagianopoulos Paul P. , Patz Samuel , Systrom David M.
Published: December 2017

Oelberg, David A., Allison B. Evans, Mirko I. Hrovat, Paul P. Pappagianopoulos, Samuel Patz, and David M. Systrom. Skeletal muscle chemoreflex and pHiin exercise ventilatory control. J. Appl. Physiol. 84(2): 676–682, 1998.—To determine whether skeletal muscle hydrogen ion mediates ventilatory drive in humans during exercise, 12 healthy subjects performed three bouts of isotonic submaximal quadriceps exercise on each of 2 days in a 1.5-T magnet for31P-magnetic resonance spectroscopy (31P-MRS). Bilateral lower extremity positive pressure cuffs were inflated to 45 Torr during exercise (BLPPex) or recovery (BLPPrec) in a randomized order to accentuate a muscle chemoreflex. Simultaneous measurements were made of breath-by-breath expired gases and minute ventilation, arterialized venous blood, and by31P-MRS of the vastus medialis, acquired from the average of 12 radio-frequency pulses at a repetition time of 2.5 s. With BLPPex, end-exercise minute ventilation was higher (53.3 ± 3.8 vs. 37.3 ± 2.2 l/min; P < 0.0001), arterialized[Formula: see text] lower (33 ± 1 vs. 36 ± 1 Torr; P = 0.0009), and quadriceps intracellular pH (pHi) more acid (6.44 ± 0.07 vs. 6.62 ± 0.07; P = 0.004), compared with BLPPrec. Blood lactate was modestly increased with BLPPexbut without a change in arterialized pH. For each subject, pHiwas linearly related to minute ventilation during exercise but not to arterialized pH. These data suggest that skeletal muscle hydrogen ion contributes to the exercise ventilatory response.
Effects of hormone replacement on growth hormone and prolactin exercise responses in postmenopausal women
Authors: Kraemer R. R. , Johnson L. G. , Haltom R. , Kraemer G. R. , Gaines H. , Drapcho M. , Gimple T. , Castracane V. Daniel
Published: December 2017

Kraemer, R. R., L. G. Johnson, R. Haltom, G. R. Kraemer, H. Gaines, M. Drapcho, T. Gimple, and V. Daniel Castracane. Effects of hormone replacement on growth hormone and prolactin exercise responses in postmenopausal women. J. Appl. Physiol. 84(2): 703–708, 1998.—Exercise elevates growth hormone (GH) and prolactin (PRL) blood concentrations in premenopausal women. Postmenopausal women taking hormone replacement therapy (HRT) maintain higher estrogen levels that could affect GH and PRL. The purpose of the study was to determine the effects of HRT on GH and PRL responses to treadmill exercise. Seventeen healthy women who were postmenopausal (naturally or surgically) [8 on HRT; 9 not on HRT (NHRT)], completed 30 min of treadmill exercise at 79.16 ± 1.2% maximal O2 consumption (HRT group) and 80.19 ± 0.91% maximal O2 consumption (NHRT group). Blood samples were collected from an intravenous catheter during an exercise session and during a control session without exercise. GH and PRL concentrations were significantly higher in the exercise trial than in the nonexercise trial, whereas resting concentrations were similar for both trials. GH and PRL peaked at 10.8 ± 1.60 and 12.67 ± 2.58 ng/ml, respectively, for HRT subjects and at 4.90 ± 1.18 and 9.04 ± 2.17 ng/ml, respectively, for NHRT subjects. GH concentrations in the exercise trial were significantly higher for HRT than for NHRT subjects. This is the first study to demonstrate that HRT enhances treadmill-exercise-induced GH release and that similar PRL responses to treadmill exercise occur in postmenopausal women regardless of HRT status.
Forearm blood flow responses to handgripping after local neuromuscular blockade
Authors: Dyke Christopher K. , Dietz Niki M. , Lennon Robert L. , Warner David O. , Joyner Michael J.
Published: December 2017

Dyke, Christopher K., Niki M. Dietz, Robert L. Lennon, David O. Warner, and Michael J. Joyner. Forearm blood flow responses to handgripping after local neuromuscular blockade. J. Appl. Physiol. 84(2): 754–758, 1998.—To test the hypothesis that acetylcholine “spillover” from motor nerves contributes significantly to skeletal muscle vasodilation during exercise, we measured the forearm blood flow responses during attempted handgripping after local paralysis of the forearm with the neuromuscular-blocking drug pipecuronium. This compound blocks postsynaptic nicotinic receptors but has no impact on acetylcholine release from motor nerves. The drug was administered selectively to one forearm by using regional intravenous drug administration techniques in five subjects. Pipecuronium reduced maximum forearm grip strength from 40.0 ± 3.2 kg before treatment to 0.0 kg after treatment. By contrast, drug administration had no effect on maximum voluntary contraction in the untreated forearm (41.3 ± 3.3 vs. 41.4 ± 2.7 kg). During 2 min of attempted maximal contraction of the paralyzed forearm, the forearm blood flow increased from only 3.4 ± 0.8 to 4.8 ± 1.2 ml ⋅ 100 ml−1 ⋅ min−1( P < 0.05). Heart rate increased from 63 ± 3 to 73 ± 8 beats/min ( P > 0.05) during attempted contraction, and only three of five subjects showed obvious increases in heart rate. Mean arterial pressure increased significantly ( P < 0.05) from 102 ± 6 to 109 ± 9 mmHg during attempted contractions. When these increases in flow are considered in the context of the marked (10-fold or greater) increases in flow seen in contracting forearm skeletal muscle, it appears that acetylcholine spillover from motor nerves has, at most, a minimal impact on the hyperemic responses to contraction in humans.
Capillary and arteriolar responses to local vasodilators are impaired in a rat model of sepsis
Authors: Tyml Karel , Yu Jingcheng , McCormack David G.
Published: December 2017

Although sepsis is known to affect vascular function, little is known about changes at the capillary level. We hypothesized that sepsis attenuates the “upstream” arteriolar response to vasoactive agents applied locally to capillaries. Sepsis in rats was induced by cecal ligation and perforation. After 24 h, extensor digitorum longus muscle was prepared for intravital microscopy. Phenylephrine (PE, 10 mM) and acetylcholine (ACh, 10 mM) were applied iontophoretically on terminal arterioles and on their downstream daughter capillaries (300 μm from arteriole). There was no significant difference between control and septic rats in baseline arteriolar diameters [8.0 ± 0.6 vs. 9.8 ± 0.8 (SE) μm] or baseline red blood cell velocity ( V RBC) in perfused daughter capillaries (255 ± 10 vs. 264 ± 13 μm/s). Application of PE onto arterioles resulted in comparable constrictions (i.e., −22% diameter change) and V RBC reductions (−100%) in control and septic rats. In contrast, arteriolar diameter and V RBCincreases after application of ACh were attenuated in sepsis (diameter: from 41 to 14%; V RBC: from 67 to 24%). Application of PE onto the capillary reduced V RBC to the same level (−100%) in both groups, whereas application of ACh increased V RBCless in septic than in control rats (20 vs. 73%). On the basis of arteriolar-capillary pair stimulations, sepsis affected V RBC responses to ACh more in the capillary than in the arteriole. When the adenosine analog 5′- N-ethylcarboxamidoadenosine (0.1 mM) was used instead of ACh, similar effects of sepsis were seen. To test for a possible involvement of inducible NO synthase (iNOS) in sepsis-induced attenuated ACh responses, arterioles and capillaries in septic animals were locally pretreated with the iNOS blocker aminoguanidine (10 mM). In both microvessels, aminoguanidine restored the ACh response to the control level. We conclude that impaired capillary V RBCand arteriolar diameter responses to vasodilators applied to capillaries in septic rat skeletal muscle were due to dysfunction at arteriolar and capillary levels. The study underscores the significant role iNOS/NO may play in sepsis-induced alteration of vascular reactivity in vivo.
Vasoconstrictor responses of coronary resistance arteries in exercise-trained pigs
Authors: Laughlin M. Harold , Muller Judy M.
Published: December 2017

Coronary resistance arteries isolated from exercise-trained pigs have been shown to exhibit enhanced myogenic reactivity (J. M. Muller, P. R. Myers, and M. Harold Laughlin. J. Appl. Physiol.75: 2677–2682, 1993). The purpose of this study was to test the hypothesis that exercise training results in enhanced vasoconstrictor responses of these arteries to all vasoconstrictor stimuli [specifically acetylcholine (ACh), endothelin-1 (ET-1), KCl, and the Ca2+ channel-agonist Bay K 8644]. Female Yucatan miniature swine were trained (Trn) on a motor-driven treadmill ( n = 16) or remained sedentary (Sed, n = 15) for 16–20 wk. Arteries 50–120 μm in diameter were isolated and cannulated with micropipettes, and intraluminal pressure was set at 60 cmH2O throughout experiments. Vasoreactivity was evaluated by examining constrictor responses to increasing concentrations of ACh (10−9 to 10−4 M), ET-1 (10−10 to 10−8 M), KCl (bath replacement with isotonic physiological saline solution containing 30 or 80 mM), and Bay K 8644 (10−9 to 10−6 M). Constricted diameters are expressed relative to the passive diameter observed after 100 μM SNP. All four constrictors produced similar decreases in diameter in arteries from both groups [ACh: 0.52 ± 0.07 (Trn) and 0.54 ± 0,06 (Sed); ET-1: 0.66 ± 0.05 (Trn) and 0.70 ± 0.07 (Sed); KCl: 0.66 ± 0.05 (Trn) and 0.70 ± 0.07 (Sed); Bay K 8644: 0.86 ± 0.05 (Trn) and 0.76 ± 0.05 (Sed)]. Present results combined with previous observations indicate that exercise training does not alter vasoconstrictor responses of porcine coronary resistance arteries but specifically increases myogenic reactivity. Thus the underlying cellular mechanisms for myogenic tone are altered by training but not receptor-mediated mechanisms (ACh and ET-1) nor voltage-gated Ca2+ channels (KCl and Bay K 8644) in coronary resistance arteries.
Respiratory muscle activity in the assessment of bronchial responsiveness in asthmatic children
Authors: Sprikkelman Aline B. , Van Eykern Leo A. , Lourens Marlies S. , Heymans Hugo S. A. , Van Aalderen Wim M. C.
Published: December 2017

We investigated whether an increase in transcutaneous electromyographic (EMG) activity of the diaphragm and intercostal muscles corresponds with the concentration of histamine that induces a 20% fall in the forced expiratory volume in one second (FEV1; PC20). Eleven asthmatic children (mean age 11.9 yr) were studied after they were given histamine challenge. EMG activity at PC20 or at the highest histamine concentration was compared with activity at baseline by calculating the ratio of the mean peak-to-peak excursion at the highest histamine dose to that at baseline [EMG activity ratio (EMGAR)]. In all children reaching PC20, an increase in diaphragmatic and intercostal EMGAR was observed. No increase was found at the dose step before PC20 was reached. In six challenges, no fall in FEV1 was induced, and no increase in EMGAR was seen. In two challenges, no fall in FEV1 was induced, but increase in diaphragmatic or intercostal EMGAR was observed. Increase in the electrical activity of the diaphragm and intercostal muscles in asthmatic children corresponds closely to a 20% fall in FEV1 induced by histamine challenge.
High-frequency oscillatory ventilation in neonatal RDS: initial volume optimization and respiratory mechanics
Authors: Kalenga Masendu , Battisti Oreste , François Anne , Langhendries Jean-Paul , Gerstmann Dale R. , Bertrand Jean-Marie
Published: December 2017

To determine whether initial lung volume optimization influences respiratory mechanics, which could indicate the achievement of optimal volume, we studied 17 premature infants with respiratory distress syndrome (RDS) assisted by high-frequency oscillatory ventilation. The continuous distending pressure (CDP) was increased stepwise from 6–8 cmH2O up to optimal CDP (OCDP), i.e., that allowing good oxygenation with the lowest inspired O2fraction. Respiratory system compliance (Crs) and resistance were concomitantly measured. Mean OCDP was 16.5 ± 1.2 cmH2O. Inspired O2fraction could be reduced from an initial level of 0.73 ± 0.17 to 0.33 ± 0.07. However, Crs (0.45 ± 0.14 ml ⋅ cmH2O−1⋅ kg−1at starting CDP point) remained unchanged through lung volume optimization but appeared inversely related to OCDP. Similarly, respiratory system resistance was not affected. We conclude that there is a marked dissociation between oxygenation improvement and Crs profile during the initial phase of lung recruitment by early high-frequency oscillatory ventilation in infants with RDS. Thus optimal lung volume cannot be defined by serial Crs measurement. At the most, low initial Crs suggests that higher CDP will be needed.
Exposing guinea pigs to ozone for 1 wk enhances responsiveness of rapidly adapting receptors
Authors: Joad J. P. , Kott K. S. , Bonham A. C.
Published: December 2017

Acute exposure to ozone causes changes in breathing pattern and lung function which may be caused in part by stimulation of rapidly adapting receptors (RARs). The consequences of repeated daily ozone exposure on RAR responsiveness are unknown, although ozone-induced changes in pulmonary function diminish with repeated exposure. Accordingly, we investigated whether repeated daily ozone exposure diminishes the general responsiveness of RARs. Guinea pigs ( n = 30) were exposed to 0.5 parts/million ozone or filtered air (8 h/day for 7 days). The animals were then anesthetized, and RAR impulse activity, dynamic compliance (Cdyn), and lung resistance were recorded at baseline and in response to four stimuli: substance P, methacholine, hyperinflation, and removal of positive end-expiratory pressure. Repeated daily ozone exposure exaggerated RAR responses to substance P, methacholine, and hyperinflation without causing physiologically relevant effects on baseline or substance P- and methacholine-induced changes in Cdyn and lung resistance. Because agonist-evoked changes in RAR activity preceded Cdyn changes, the data suggest that repeated daily ozone exposure enhances RAR responsiveness via a mechanism other than changes in Cdyn.
The Hering-Breuer reflex in anesthetized infants: end-inspiratory vs. end-expiratory occlusion technique
Authors: Brown K. , Stocks J. , Aun C. , Rabbette P. S.
Published: December 2017

Both end-inspiratory (EIO) and end-expiratory (EEO) occlusions have been used to measure the strength of the Hering-Breuer inflation reflex (HBIR) in infants. The purpose of this study was to compare both techniques in anesthetized infants. In each infant, HBIR activity was calculated as the relative prolongation of expiratory and inspiratory time during EIO and EEO, respectively. Respiratory drive was assessed from the change in airway pressure during inspiratory effort against the occlusion, both at a fixed time interval of 100 ms (P0.1) and a fixed proportion (10%) of the occluded inspiratory time (P10%). Twenty-two infants [age 14.3 ± 6.4 (SD) mo] were studied. No HBIR activity was present during EIO [−11.8 ± 15.9 (SD) %]. By contrast, there was significant, albeit weak, reflex activity during EEO [HBIR: 27.2 ± 17.4%]. A strong HBIR (up to 310%) was elicited in six of seven infants in whom EIO was repeated after lung inflation. P0.1 was similar during both types of occlusions, whereas mean ± SD P10% was lower during EEO than during EIO: 0.198 ± 0.09 vs. 0.367 ± 0.15 kPa, respectively ( P < 0.01). These data suggest a difference in the central integration of stretch receptor activity in infants during anesthesia compared with during sleep.
Use of nonlinear methods to assess effects of clonidine on blood pressure in spontaneously hypertensive rats
Authors: Mestivier Denis , Dabiré Hubert , Safar Michel , Chau Nguyen Phong
Published: December 2017

In spontaneously hypertensive rats (SHR), chronic infusion of clonidine failed to decrease blood pressure and blood pressure variability. We used nonlinear methods to get a deeper insight on the effects of clonidine on blood pressure dynamics. For 24 h and 4 wk, clonidine (0.1 mg ⋅ kg−1 ⋅ day−1sc) was infused by minipumps in the conscious SHRs, and, for comparison, a vehicle was infused in SHRs and in Wistar-Kyoto rats. Blood pressure was recorded for 30 min before and after treatments. We used the Lyapunov exponent, approximated by the inverse of the l max index derived from the recurrence plot method, to characterize nonlinear dynamics. Before treatment, l max index of blood pressure was lower ( P < 0.01) in the SHRs than in the Wistar-Kyoto rats. Clonidine significantly increased l max( P < 0.01) to the level observed in normotensive rats, at 24 h and up to 4 wk after infusion. We conclude that clonidine has a significant chronic effect on blood pressure dynamics, as evidenced by nonlinear methods. Our study also suggests that the mechanisms governing blood pressure variations are nonlinear.
Recovery of muscle transfers replacing the total plantar flexor muscle group in rats
Authors: Miller Stephanie W. , Hassett Cheryl A. , Faulkner John A.
Published: December 2017

In rats, combinations of plantar flexor muscles representing ∼20, 40, 60, and 80% of the mass of the total plantar flexor group were transferred orthotopically in the absence of synergistic muscles and allowed to recover for 120 days. We hypothesized that, compared with their individual control values for structural and functional variables, the transfers would display a hierarchical array of deficits, proportional to their initial mass and, consequently, inversely proportional to the relative load on the transfers. Surprisingly, compared with their individual control values, each muscle transfer displayed deficits of 30–40% in muscle mass, total fiber cross-sectional area, and maximum isometric force, with the exception of the smallest transfer, the plantaris (PLN) muscle, which recovered 100% of its control value for each of these variables. Therefore, except for the PLN transfer, the muscle transfers studied displayed deficits similar in magnitude to those reported for muscles transferred in the presence of synergistic muscles. The greater recovery of the PLN transfer was attributed to the relatively large requirement for force production imposed on this transfer due to the average force requirements of the total plantar flexor group.
Developmentally regulated expression of cytochrome-coxidase isoforms in regenerating rat skeletal muscle
Authors: Ongvarrasopone Chalermporn , Kennedy John M.
Published: December 2017

The developmental expression of tissue-specific isoforms of cytochrome- c oxidase (COX) subunit VIII [heart (COX VIII-H) and liver (COX VIII-L)] and the influence of innervation were examined in regenerating fast [extensor digitorum longus (EDL)] and slow (soleus) muscles. In adult muscles, COX VIII-H was the predominant isoform. The COX VIII-L mRNA was expressed 3 days after induction of regeneration, and it progressively decreased after 7, 10, 14, and 30 days of regeneration in both muscles. In contrast, the expression of COX VIII-H mRNA accumulated as myogenesis proceeded to the myotube stage between 7 and 10 days of regeneration and progressively increased to near control levels by 30 days. The influence of innervation on the expression of COX VIII and α-actin isoforms was examined in control, innervated, and denervated regenerating muscles at 3 and 10 days. The relative expression of COX VIII-L mRNA in denervated regenerating EDL muscles was significantly greater, while that of COX VIII-H was significantly less than in innervated regenerating EDL muscles after 10 days of regeneration. Similarly, cardiac α-actin mRNA levels were elevated in denervated regenerating EDL muscles after 10 days of regeneration. In conclusion, motor innervation influences the transition from the COX VIII-L to COX VIII-H isoform during myogenesis in regenerating muscles.
Thermal drive contributes to hyperventilation during exercise in sheep
Authors: Entin Pauline L. , Robertshaw David , Rawson Richard E.
Published: December 2017

The etiology of exercise hypocapnia is unknown. The contributions of exercise intensity (ExInt), lactic acid, environmental temperature, rectal temperature (Tre), and physical conditioning to the variance in arterial CO2tension ([Formula: see text]) in the exercising sheep were quantified. We hypothesized that thermal drive contributes to hyperventilation. Four unshorn sheep were exercised at ∼30, 50, and 70% of maximal O2consumption for 30 min, or until exhaustion, both before and after 5 wk of physical conditioning. In addition, two of the sheep were shorn and exercised at each intensity in a cold (<15°C) environment. Treand O2consumption were measured continuously. Lactic acid and [Formula: see text] were measured at 5- to 10-min intervals. Data were analyzed by multiple regression on[Formula: see text]. During exercise, Trerose and[Formula: see text] fell, except at the lowest ExInt in the cold environment. Treexplained 77% of the variance in [Formula: see text], and ExInt explained 5%. All other variables were insignificant. We conclude that, in sheep, thermal drive contributes to hyperventilation during exercise.
NF-κB induction during in vivo hypoxia in dorsocaudal brain stem of rat: effect of MK-801 andl-NAME
Authors: Gozal Evelyne , Simakajornboon Narong , Gozal David
Published: December 2017

In the nucleus of the solitary tract, NMDA receptors are critical for the hypoxic ventilatory response while neuronal nitric oxide synthase (NOS) modulates the late component of this response. Nuclear factor (NF)-κB is a ubiquitous transcription factor that increases the expression of multiple stress-activated genes. We sought to examine temporal changes in expression of NF-κB within the dorsocaudal brain stem of conscious rats after exposures to 10% O2. Time-dependent increases in NF-κB occurred with hypoxia and peaked at 60 min. Pretreatment with the N-methyl-d-aspartate (NMDA)-receptor channel antagonist dizocilpine maleate (MK-801) markedly attenuated NF-κB complexes during hypoxia. In contrast, after NOS inhibition with N G-nitro-l-arginine methyl ester (l-NAME), although NF-κB was diminished in normoxia, increased NF-κB expression still occurred with hypoxia. Increased phosphorylation of the NF-κB regulatory unit [inhibitory (I)κB] was detected by immunoblotting and also peaked at 60 min. Phosphorylation of Iκ-B during hypoxia was attenuated by MK-801 but not byl-NAME. Thus NMDA-receptor activation in the dorsocaudal brain stem during hypoxia elicits in NF-κB activity marked enhancements that are unaffected after NOS blockade.
Low nitric oxide concentrations in exhaled gas and nasal airways of mammals without paranasal sinuses
Authors: Lewandowski Klaus , Busch Thilo , Lohbrunner Hansjörg , Rensing Susanne , Keske Uwe , Gerlach Herwig , Falke Konrad J.
Published: December 2017

To investigate whether relevant levels of nasal nitric oxide (NO) are produced in the absence of paranasal sinuses, we studied 17 healthy baboons, mammals without any paranasal sinuses. The animals were anesthetized with ketamine hydrochloride and breathed spontaneously. While the baboons breathed through a face mask (mouths closed) connected to a respirator, NO concentrations in exhaled gas were sampled from the expiratory limb and analyzed by chemiluminescence. While the animals were breathing ambient air, nasal gas was sampled via a thin plastic tube and analyzed for NO concentrations by chemiluminescence. Mean NO concentration in the exhaled gas was 1.00 ± 0.59 parts/billion, and NO release was 4.28 ± 2.72 nl/min. A NO concentration of 4.79 ± 2.08 parts/billion was found in the nasal gas (NO release: 7.18 ± 3.13 nl/min). An age-dependent increase in nasal NO levels was not observed. Exhaled and nasal NO concentrations in baboons were markedly lower than in mammals with paranasal sinuses, suggesting that paranasal sinuses might be an anatomic requirement for production of relevant nasal NO levels.
Micropuncture measurements of interstitial fluid pressure in rat nasal mucosa during early inflammatory reactions
Authors: Berg Ansgar , Kirkebø Arne , Heyeraas Karin J.
Published: December 2017

Interstitial fluid pressure (Pif) has been studied in rat nasal mucosa during early inflammatory reactions induced by dextran anaphylaxis and local application of histamine. Pif was measured by using sharpened micropipettes connected to a servo-controlled counterpressure system. Access to the nasal mucosa was obtained from the facial side of the head through a small cavity drilled in the nasal bone. During dextran anaphylaxis, Pif increased significantly from control values of 2.2 ± 0.4 to 3.8 ± 0.21 mmHg ( P < 0.05) within 1 h. Corresponding Pif values for histamine were 1.6 ± 0.9 and 2.9 ± 0.9 mmHg ( P < 0.05), respectively. These measurements support the hypothesis that a major driving force for the rapid exudation across inflamed respiratory mucosa is a hydrostatic pressure gradient created by increased mucosa Pif. When the transvascular fluid shifts accompanying the inflammatory reactions are prevented by circulatory arrest, Pif decreased significantly to subatmospheric values, −0.8 ± 0.8 and −3.3 ± 1.2 mmHg in the dextran and histamine group, respectively ( P < 0.05). The decrease in Pif in the nasal mucosa after inflammatory stimuli, during circulatory arrest, provides further evidence for “active” modulation of Pif through changes in mechanical properties of the interstitial matrix. The decrease in Pif seen under these circumstances reveals a possible mechanism participating in the rapid and initial edema formation after inflammatory provocations.
Salbutamol enhances isotonic contractile properties of rat diaphragm muscle
Authors: Van Der Heijden H. F. M. , Zhan W. Z. , Prakash Y. S. , Dekhuijzen P. N. R. , Sieck G. C.
Published: December 2017

The effects of the β2-adrenoceptor agonist salbutamol (Slb) on isometric and isotonic contractile properties of the rat diaphragm muscle (Diamus) were examined. A loading dose of 25 μg/kg Slb was administered intracardially before Diamusexcision to ensure adequate diffusion. Studies were then performed with 0.05 μM Slb in the in vitro tissue chamber. cAMP levels were determined by radioimmunoassay. Compared with controls (Ctl), cAMP levels were elevated after Slb treatment. In Slb-treated rats, isometric twitch and maximum tetanic force were increased by ∼40 and ∼20%, respectively. Maximum shortening velocity increased by ∼15% after Slb treatment, and maximum power output increased by ∼25%. During repeated isotonic activation, the rate of fatigue was faster in the Slb-treated Diamus, but both Slb-treated and Ctl Diamusfatigued to the same maximum power output. Still, endurance time during repetitive isotonic contractions was ∼10% shorter in the Slb-treated Diamus. These results are consistent with the hypothesis that β-adrenoceptor stimulation by Slb enhances Diamuscontractility and that these effects of Slb are likely mediated, at least in part, by elevated cAMP.
Functional aspects of skeletal muscle contractile apparatus and sarcoplasmic reticulum after fatigue
Authors: Williams Jay H. , Ward Christopher W. , Spangenburg Espen E. , Nelson Reagan M.
Published: December 2017

This study examined the effects of fatigue on the functional aspects of the contractile apparatus and sarcoplasmic reticulum (SR). Frog semitendinosus muscles were stimulated to fatigue, and skinned fibers or a homogenate fraction was prepared from both fatigued and rested contralateral muscles. In fatigued fibers, maximal Ca2+-activated force of the contractile apparatus was unaltered, whereas maximal actomyosin-ATPase activity was depressed by 20%. The Ca2+sensitivity of force was increased, whereas that of actomyosin-ATPase was not altered. Also, the rate constant for tension redevelopment was decreased at submaximal Ca2+concentration. These latter findings suggest that fatigue slows the dissociation of force-generating myosin cross bridges. Ca2+uptake and Ca2+-ATPase activity of the SR were depressed by 46 and 21%, respectively, in the fatigued muscles. Fatigue also reduced the rates of SR Ca2+release evoked by AgNO3and 4-chloro- m-cresol by 38 and 45%, respectively. During fatigue, the contractile apparatus and SR undergo intrinsic functional alterations. These changes likely result in altered force production and energy consumption by the intact muscle.