bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic elastance and tissue resistance of isolated liquid-filled rat lungs
Authors: Navajas D. , Moretto A. , Rotger M. , Nagase T. , Dallaire M. J. , Ludwig M. S.
Published: December 2017

The effect of the surface forces of the alveolar air-liquid interface on the dynamic behavior of lung tissue was investigated in five isolated liquid-filled rat lungs. The lungs were subjected to 0.04-Hz sinusoidal oscillation (1.5-ml tidal volume) at lung volume (VL) levels ranging from volume at zero pressure (V0) + 4 ml to V0 + 10 ml. Oscillations were performed at each VL after inflation of the lungs from V0. Alveolar pressure (PA) was measured with an alveolar capsule attached to the visceral pleura. Dynamic elastance (Edyn), tissue resistance (Rti), and hysteresivity [eta = Rti omega/Edyn, where omega is angular frequency (2 pi x frequency)] were computed from PA and VL changes. Edyn was 59.6 +/- 4.3 Pa/ml at V0 + 4 ml and varied little up to V0 + 7 ml. Thereafter, Edyn increased markedly with VL, reaching 102 +/- 16 Pa/ml at V0 + 10 ml. No significant difference was found between elastance computed from PA and that computed from pressure recorded at the airway opening. Rti was 35.2 +/- 3.6 Pa.s.ml-1 and exhibited a VL dependence similar to that of Edyn. As a result, eta was 0.16 and did not vary significantly in the explored VL range. We conclude that PA can be reliably measured in the liquid-filled lung by means of alveolar capsules. In the liquid-filled lung, Edyn was smaller than and eta was similar to values reported for air-filled lungs. Hence, surface tension accounts for a considerable part of elastance and Rti of the air-filled lung within the volume range of normal breathing.
Role of vasoconstrictors in the systemic hypertension of rats acclimatized to hypoxia
Authors: Moue Y. , Smith P. G. , Clancy R. L. , Gonzalez N. C.
Published: December 2017

Exposure to hypoxia (2–5 wk) results in systemic hypertension in rats and in humans. The possible mechanism(s) was investigated in rats acclimatized for 3 wk to barometric pressure of approximately 370 Torr (A) and in nonacclimatized littermates (NA) by administration of alpha-adrenergic [phentolamine (PHLM)], angiotensin II (ANG II), and arginine vasopressin (AVP V1) receptor antagonists. Both A and NA rats were studied in hypoxia (inspiratory O2 fraction = 0.10). Baseline mean arterial blood pressure (MABP) was higher in A than in NA rats: 126 +/- 4 vs. 101 +/- 2 mmHg (P < 0.05). Neither ANG II nor AVP V1 receptor antagonist influenced baseline MABP; however, both contributed to MABP recovery after PHLM. After simultaneous blockade of ANG II and AVP V1, PHLM lowered MABP by 65 +/- 2 and 45 +/- 3 mmHg in A and NA rats, respectively (P < 0.05). After combined blockade of the three systems, the smooth muscle relaxant sodium nitroprusside did not further modify MABP, which remained higher in A rats. It is concluded that 1) the hypertension in A rats is partly due to a higher alpha-adrenergic tone, 2) neither ANG II nor AVP contributes to the hypertension, but ANG II and AVP participate in MABP control after PHLM, 3) no other vasoconstrictor agents operate in either group, and 4) the higher MABP in A rats after sodium nitroprusside may reflect additional hypertensive mechanisms.
Measurement of three-dimensional lung tree structures by using computed tomography
Authors: Wood S. A. , Zerhouni E. A. , Hoford J. D. , Hoffman E. A. , Mitzner W.
Published: December 2017

A method was devised to computationally segment and measure three-dimensional pulmonary trees in situ. Bronchi and pulmonary vessels were computationally extracted from volumetric computed tomography data based on radiopacity differences between airway wall and airway lumen and between blood and parenchyma, respectively. The tree was reduced to a central axis to facilitate measurement of branch segment length and angle. Cross-sectional area was measured on a reconstructed computed tomography slice perpendicular to this central axis. The method was validated by scanning two Plexiglas phantoms and an intact lung. Reconstructed diameters in the phantoms were accurate for branches > 2 mm. In the lung airway branches between 1 and 2 mm in diameter were often unresolved when their angle of orientation with respect to the axis of the scanner was > 45 degrees. However, if a branch was resolved, its reconstructed diameter was little affected by orientation. This method represents a significant improvement in the analysis of complex pulmonary structures in three dimensions.
Interaction between airway lining fluid forces and parenchymal tethering during pulmonary airway reopening
Authors: Perun M. L. , Gaver D. P.
Published: December 2017

In this study, our goal is to identify the interaction between airway lining fluid viscous and surface forces and parenchymal tethering forces during pulmonary airway reopening. The type of closure we modeled occurs when the airway walls and surrounding parenchyma collapse and are held in apposition by the lining fluid. We mimicked this system with a polyethylene tube coated with a Newtonian lining fluid supported by open-cell foam. Reopening occurs when a finger of air travels through the collapsed region. We measured the airway pressure (Paw) required to open the airway at a constant velocity (U). Increasing the foam stiffness (K), lining fluid viscosity (mu), and surface tension (gamma) results in an increase in Paw. Furthermore, increasing the downstream suction pressure (Pds), through tethering, causes an equivalent reduction in Paw. The upstream radius is the primary length scale, and fluid forces are represented by the capillary number: Ca = microU/gamma. On the basis of these results, we predicted the likelihood that tethering would begin to reopen collapsed airways in various disease states. This analysis showed that the ratio of tethering to fluid forces determines airway patency, which is defined as follows: lambda = PTrans/(gamma/R), where PTrans = Paw-Pds and R is airway radius. Finally, lung volume-dependent surface tension appears to be necessary to stabilize the lung.
Venous mechanics of contracting gastrocnemius muscle and the muscle pump theory
Authors: Magder S.
Published: December 2017

The time constant of venous drainage (tau v) is an important determinant of the return of blood to the heart. The lower the tau v, the higher the flow for a given volume. To determine whether the tau v of muscle decreases during muscle contraction, we anesthetized dogs with pentobarbital sodium and mechanically ventilated them. We isolated the vasculature of the gastrocnemius muscle and attached the muscle to a force transducer. The muscle was pump perfused, and flows were measured with electromagnetic flow probes on the artery and vein. Pressure in the venous compliant region (Pel) was obtained by simultaneously occluding the artery and vein. Changes in volume (delta V) were produced by changing inflow and obtaining the integral of the difference between inflow and outflow. The tau v was obtained from delta V divided by change in flow. Compliance was calculated from delta V divided by change in Pel from before to after a change in flow. The venous resistance was calculated from tau v divided by venous compliance. The muscle was set at the optimal length, and contractions were produced by stimulating the nerve to the muscle with supramaximal voltage at either 1- or 5-Hz trains with stimulations at 20 Hz, 0.2-ms duration, and duty cycle of 0.25. The tau v at rest was 4.06 +/- 2.16 s and decreased to 2.44 +/- 1.07 s (P < 0.05) at 1 Hz and to 1.81 +/- 0.4 s at 5 Hz. There were no significant changes in venous compliance or venous resistance. In conclusion, muscle contractions can reduce the time constant of venous drainage of muscle and could thereby contribute to the increased venous return and cardiac output during exercise.
Evaluation of voluntary and elicited dorsiflexor torque-angle relationships
Authors: Koh T. J. , Herzog W.
Published: December 2017

The purposes of this study were to determine the relative influence of mechanical (muscle force and moment arm) and neural (activation) factors on the shape of dorsiflexor torque-angle relationships and to determine the interday reliability of measurements of such relationships. Dorsiflexor torque-angle relationships produced with maximal voluntary contractions (MVCs) and with electrically elicited contractions (twitch, 20-Hz tetanic, 40-Hz tetanic) were obtained for seven male subjects on 2 separate days. MVC torque-angle relationships were reproducible between days. Elicited relationships were less reproducible than the MVC relationships, with the 40-Hz relationship the most reproducible of the elicited relationships. The shapes of the MVC and elicited twitch torque-angle relationships were significantly different. The shapes of the MVC, 20-, and 40-Hz elicited relationships were similar. The simplest explanation for this latter finding is that the shape the MVC relationship is determined primarily by mechanical factors and is not strongly dependent on neural factors. The results of this study may affect the interpretation of comparisons of torque-angle relationships between subject groups or pre- and posttraining.
Methacholine-induced pulmonary gas trapping in guinea pigs, hamsters, mice, and rats
Authors: Stengel P. W. , Yiamouyiannis C. A. , Obenchain R. L. , Cockerham S. L. , Silbaugh S. A.
Published: December 2017

Postmortem pulmonary gas trapping was investigated as an index of in vivo airway obstruction following methacholine inhalation in four different rodent species. Male guinea pigs (Hartley), hamsters (golden Syrian), mice (A/J, BALB/c, and ICR), and rats (Brown-Norway, Fischer 344, Lewis, and Sprague-Dawley) were exposed to aerosols of methacholine or sodium chloride. Maximum excised lung gas volumes (ELGV) of methacholine-exposed guinea pigs, hamsters, mice, and rats were 2.3–8.7 times those of sodium chloride-treated animals. Mean ELGV values of sodium chloride-exposed animals ranged from 1.50 +/- 0.20 ml/kg for guinea pigs to 2.75 +/- 0.20 ml/kg for Brown-Norway rats. Although all species responded to methacholine, guinea pigs were the most responsive, with approximately 1.6 microgram/kg of inhaled methacholine needed to increase ELGV to 200% of control. Compared with guinea pigs, hamsters, mice, and rats were 11- to 1,395-fold less responsive. Although hamsters, mice, and rats are less sensitive than guinea pigs to the airway-obstructive effects of methacholine, pulmonary gas trapping appears useful as a measure of airway responses in these species.
Experimental hypothermia and rewarming: changes in mechanical function and metabolism of rat hearts
Authors: Tveita T. , Skandfer M. , Refsum H. , Ytrehus K.
Published: December 2017

Rewarming from accidental hypothermia is associated with fatal circulatory derangements. To investigate potential pathophysiological mechanisms involved, we examined heart function and metabolism in a rat model rewarmed after 4 h at 15-13 degrees C. Hypothermia resulted in a significant reduction of left ventricular (LV) systolic pressure, cardiac output, and heart rate, whereas stroke volume increased. The maximum rate of LV pressure rise decreased to 191 +/- 28 mmHg/s from a control value of 9,060 +/- 500 mmHg/s. Myocardial tissue content of ATP, ADP, and glycogen was significantly reduced, whereas lactate content remained unchanged. After rewarming, heart rate returned to control value, whereas LV systolic pressure, cardiac output, and stroke volume all remained significantly depressed. The posthypothermic maximum rate of LV pressure rise was 5,966 +/- 1.643 mmHg/s. The posthypothermic myocardial lactate content was significantly increased (to 13.3 +/- 3.2 nmol/mg from control value of 5.7 +/- 1.9 nmol/mg), and ATP and glycogen remained significantly lowered. Creatine phosphate or energy charge did not change significantly during the experiment. The finding of deteriorated myocardial mechanical function and a shift in energy metabolism shows that the heart could be an important target during hypothermia and rewarming in vivo, thus contributing to the development of a posthypothermic circulatory collapse.
Age-dependent vulnerability to carotid chemodenervation in piglets
Authors: Cote A. , Porras H. , Meehan B.
Published: December 2017

We sought to determine the age of greatest vulnerability in piglets to the loss of carotid chemoreceptor function. We studied four groups of carotid body-denervated (CBD) piglets whose carotid bodies were surgically removed at 4-5, 9-10, 12-15, and 21-22 days and who are herein referred to, respectively, as the CBD5, CBD10, CBD15, and CBD20 groups. Four intact groups, at corresponding ages, underwent a sham surgical procedure. After a postsurgery recovery of at least 7 days, we studied all animals to detect the presence of apnea and the consequences of it, if any. Two days before the experiments, we implanted in all animals a fiber-optic arterial catheter for continuous monitoring of arterial O2 saturation, and electroencephalographic electrodes for the recording of sleep states. During quiet sleep in the CBD15 group, we found numerous prolonged central apneic events accompanied by a profound desaturation, tachycardia, a rise in blood pressure, and, eventually, a flattening of the electroencephalogram. No prolonged apneic events occurred, however, in the other CBD groups nor in the intact animals. During active sleep, no prolonged apneic events occurred at all. We thus conclude that, in piglets, the absence of normally functioning carotid chemoreceptors at approximately 2 wk of age can lead to life-threatening apneic events with severe hypoxemia, events that are state specific.
Effect of inhaled and intravenous acetylcholine on bronchial blood flow in anesthetized sheep
Authors: Scuri M. , McCaskill V. , Chediak A. D. , Abraham W. M. , Wanner A.
Published: December 2017

The reported effects of cholinergic agonists on bronchial blood flow (Qbr) have been inconsistent. The aim of the present study was to determine whether the inconsistency could be due to the mode of agonist administration (systemic vs. aerosol) or the anatomic site of blood flow in the bronchus (mucosal vs. deep wall). In 10 anesthetized mechanically ventilated adult sheep, we measured Qbr in main bronchi by color-coded microspheres, systemic and pulmonary arterial pressures, cardiac output, and lung resistance (RL) before and after acetylcholine (ACh) administered either as an aerosol (nebulized dose 100 micrograms) or as an intravenous bolus (2 micrograms/kg). Before drug administration, 72% of mean Qbr was distributed to the bronchial mucosa and the remainder was distributed to the deep bronchial wall. For a comparable increase in mean RL (150% for intravenous ACh and 205% for aerosol ACh), mean total Qbr normalized for systemic arterial pressure increased by 291% after intravenous ACh (P < 0.05) and decreased by 9% after aerosol ACh (not significant). Mucosal and deep wall Qbr increased proportionally. Atropine (0.2 microgram/kg) prevented the changes in Qbr and RL after intravenous ACh. Thus intravenous but not aerosol ACh increased blood flow in the mucosa and deep wall of extrapulmonary bronchi. This suggests that the muscarinic receptors mediating vasodilation are more accessible to intravascular than intrabronchial ACh.
Evidence for contribution of effector organ cellular responses to the biphasic dynamics of heat acclimation
Authors: Horowitz M. , Kaspler P. , Marmary Y. , Oron Y.
Published: December 2017

The involvement of cellular processes in the biphasic dynamics of heat acclimation was studied. Key steps in the cholinergic signal transduction pathway for water secretion were measured in the submaxillary gland of acclimating [2-day short-term heat acclimation (STHA) and 30-day long-term heat acclimation (LTHA) at 34 degrees C] or acute heat-stressed (2 h at 40 degrees C) rats in vitro. Both the carbamylcholine (CCh)-induced maximal fractional rate and the total 86Rb+ efflux, reflecting K+ efflux and water transport, transiently decreased in STHA (P < 0.001). In LTHA, the total K+ efflux increased (P < 0.001), whereas the maximal fractional rate of efflux increased only slightly. During STHA, the density of the high-affinity binding site of the muscarinic receptors (MRs) increased by 50% and their affinity for the muscarinic antagonist [3H]-N-methylscopolamine decreased transiently by 87%. Basal cytosolic Ca2+ concentration ([Ca2+]i) decreased (P < 0.05), but the peak CCh-induced [Ca2+]i increase resembled the control values. In LTHA, MR density continued to increase (100%; P < 0.05), whereas affinity resumed control values. Basal and CCh-induced [Ca2+]i increases returned to control levels. We conclude that glandular cellular processes follow a biphasic pattern with major apparent changes attributable to events distal to the [Ca2+]i rise. This was further validated by employing heat stress, which produced qualitatively different effects on the MR profile with a decrease in 86Rb+ efflux comparable to STHA. Hence, although heat-induced changes in the proximal components of the signal transduction pathway may contribute to altered regulatory span, the predominant apparent cellular effect is on the distal part of the pathway.
Caffeine counteracts the ergogenic action of muscle creatine loading
Authors: Vandenberghe K. , Gillis N. , Van Leemputte M. , Van Hecke P. , Vanstapel F. , Hespel P.
Published: December 2017

This study aimed to compare the effects of oral creatine (Cr) supplementation with creatine supplementation in combination with caffeine (Cr+C) on muscle phosphocreatine (PCr) level and performance in healthy male volunteers (n = 9). Before and after 6 days of placebo, Cr (0.5 g x kg-1 x day-1), or Cr (0.5 g x kg-1 x day-1) + C (5 mg x kg-1 x day-1) supplementation, 31P-nuclear magnetic resonance spectroscopy of the gastrocnemius muscle and a maximal intermittent exercise fatigue test of the knee extensors on an isokinetic dynamometer were performed. The exercise consisted of three consecutive maximal isometric contractions and three interval series of 90, 80, and 50 maximal voluntary contractions performed with a rest interval of 2 min between the series. Muscle ATP concentration remained constant over the three experimental conditions. Cr and Cr+C increased (P < 0.05) muscle PCr concentration by 4-6%. Dynamic torque production, however, was increased by 10-23% (P < 0.05) by Cr but was not changed by Cr+C. Torque improvement during Cr was most prominent immediately after the 2-min rest between the exercise bouts. The data show that Cr supplementation elevates muscle PCr concentration and markedly improves performance during intense intermittent exercise. This ergogenic effect, however, is completely eliminated by caffeine intake.
Effects of coca chewing on metabolic and hormonal changes during graded incremental exercise to maximum
Authors: Spielvogel H. , Caceres E. , Koubi H. , Sempore B. , Sauvain M. , Favier R.
Published: December 2017

We examined the effects of 1 h of coca chewing on metabolic and hormonal responses during incremental exercise to exhaustion in traditional coca chewers (C; n = 8), and the results were compared with a group of nonchewers (n = 13). For 1 h, C chewed approximately 12 g of coca leaves that resulted in the apparition of cocaine in blood that reached 72 +/- 9 ng/ml. In resting conditions, even though sympathoadrenergic activity (as assessed by norepinephrine and epinephrine plasma levels) was similar in both groups, C displayed a higher level of plasma free fatty acids. Oxygen uptake measured at exhaustion and delta work efficiency during exercise were similar in both groups. During the incremental exercise, C displayed a significantly lower arterial oxygen saturation that cannot be explained by a reduced ventilatory response after coca chewing. In fact, even at maximal exercise, both ventilatory output and ventilatory equivalent were higher in C compared with nonchewers. It is concluded that the beneficial effects of coca chewing on exercise tolerance reported frequently by traditional coca users is not related to either an improved maximal exercise capacity or an increased work efficiency. However, during incremental exercise, coca chewing appeared to result in an increased free fatty acid availability that could be beneficial for prolonged submaximal exercise.
Influence of global inspiratory muscle fatigue on breathing during exercise
Authors: Sliwinski P. , Yan S. , Gauthier A. P. , Macklem P. T.
Published: December 2017

We evaluated the effect of global inspiratory muscle fatigue (GF) on respiratory muscle control during exercise at 30, 60, and 90% of maximal power output in normal subjects. Fatigue was induced by breathing against a high inspiratory resistance until exhaustion. Esophageal and gastric pressures, anteroposterior displacement of the rib cage and abdomen, breathing pattern, and perceived breathlessness were measured. Induction of GF had no effect on the ventilatory parameters during mild and moderate exercise. It altered, however, ventilatory response to heavy exercise by increasing breathing frequency and minute ventilation, with minor changes in tidal volume. This was accompanied by an increase in perceived breathlessness. GF significantly increased both the tonic and phasic activities of abdominal muscles that allowed 1) the diaphragm to maintain its function while developing less pressure, 2) the same tidal volume with lesser shortening of the rib cage inspiratory muscles, and 3) relaxation of the abdominal muscles to contribute to lung inflation. The increased work performed by the abdominal muscles may, however, lead to a reduction in their strength. GF may impair exercise performance in some healthy subjects that is probably not related to excessive breathlessness or other ventilatory factors. We conclude that the respiratory system is remarkably adaptable in maintaining ventilation during exercise even with impaired inspiratory muscle contractility.
Near-infrared estimation of O2 supply and consumption in forearm muscles working at varying intensity
Authors: Homma S. , Eda H. , Ogasawara S. , Kagaya A.
Published: December 2017

We estimated a blood flow index, O2 supply index, and O2 consumption index from near-infrared (NIR) signals during venous occlusion imposed at rest and immediately after handgrip exercise with loads equal to 5, 10, 15, 20, 25, and 30% of the maximum voluntary contraction. We also estimated forearm blood flow (BFfa) by strain-gauge plethysmography and forearm O2 consumption (VO2fa) by the invasive method. There was a significant correlation between the rate of increase in total hemoglobin during venous occlusion obtained from NIR signals and BFfa in each subject (r = 0.853 approximately 0.981, P < 0.001). There was also a significant correlation (r = 0.854 approximately 0.944, P < 0.001) between the O2 consumption index estimated from NIR signals and VO2fa. The mean values for O2 supply index in five subjects increased with exercise intensity, while the O2 consumption index showed no further increase about 25% of maximum voluntary contraction. We found significant positive correlations between the O2 supply index and BFfa (r = 0.986, P < 0.001) and the O2 consumption index and VO2fa (r = 0.976, P < 0.001) during exercise at 5-30% of maximum voluntary contraction. These results demonstrate that analysis of NIR signals during venous occlusion provides an advantageous method of estimation of O2 supply and consumption in working muscles during exercise of varying intensity.
Effects of pursed-lips breathing and expiratory resistive loading in healthy subjects
Authors: Spahija J. A. , Grassino A.
Published: December 2017

To examine the effect of pursed-lips breathing (PLB) on breathing pattern and respiratory mechanics, we studied 11 healthy subjects breathing with and without PLB at rest and during steady-state bicycle exercise. Six of these subjects took part in a second study, which compared the effects of PLB to expiratory resistive loading (ERL). PLB was found to prolong expiratory and total breath durations and to promote a slower and deeper breathing pattern. During exercise, the compensatory increase that occurred in tidal volume was not sufficient to counter the reduction in breathing frequency, causing minute ventilation to be reduced. Although ERL similarly caused minute ventilation and breathing frequency to be decreased, unlike PLB, it produced no change in tidal volume and prolonged expiratory and total breath durations to a lesser extent. PLB and ERL increased the expiratory resistance to a comparable degree, also increasing the expiratory resistive work of breathing and promoting greater expiratory rib cage and abdominal muscle recruitment in response to the expiratory loads. End-expiratory lung volume, which was determined from inspiratory capacity maneuvers, was not altered by PLB; however, with ERL it was increased by 0.20 and 0.24 liter during rest and exercise, respectively. Inspiratory muscle recruitment patterns were not altered by PLB at rest, although small increases in the relative contribution of the rib cage/accessory muscles in conjunction with abdominal muscle relaxation occurred during exercise. Similar trends were observed with ERL. We conclude that, although ERL and PLB induce comparable respiratory muscle recruitment responses, they are not equivalent with respect to breathing pattern changes and effect on end-expiratory lung volume.
Contribution of LFA-1 and Mac-1 to CD18-dependent neutrophil emigration in a neonatal rabbit model
Authors: Graf J. M. , Smith C. W. , Mariscalco M. M.
Published: December 2017

Human neonatal polymorphonuclear leukocytes (PMNs) exhibit decreased mobility, adherence, and transendothelial migration in vitro compared with adult PMNs. These deficits, in part, are due to functional and quantitative defects in neonatal Mac-1 (CD11b/CD18), whereas LFA-1 (CD11a/CD18) function is similar to that found in adults (D.C.Anderson, O.Abbassi, T.K.Kishimoto, J.M.Koenig, L.V.McIntire, and C.W.Smith, J.Immunol. 146: 3372-3379, 1991; C. W. Smith, T. K. Kishimoto, O. Abbassi, B.J.Hughes, R.Rothlein, L.V.McIntire, E.Butcher, and D.C. Anderson, J. Clin. Invest. 87: 609-618, 1991). We tested the hypothesis that the primary mechanism for the neonatal PMN CD18-dependent emigration in vivo is due to LFA-1. Neutrophils from 1-day-old rabbit pups had 32 and 60% of adult rabbit levels of CD11a and CD11b, respectively. Rabbit pups or adult rabbits received the monoclonal antibody (MAb) R7.1 (anti-CD11a) or R15.7 (anti-CD18) or the vehicle phosphate-buffered saline (PBS) before the instillation of intraperitoneal thioglycollate. Six hours later peritoneal exudate was collected. The administration of MAbs R7.1 and R15.7 in adult animals resulted in 60 and 83% inhibition of leukocyte emigration, respectively, compared with PBS-treated animals (P < 0.01). In neonatal animals, R7.1 and R15.7 inhibited leukocyte peritoneal accumulation to the same extent (50 and 60%, respectively) compared with PBS-treated animals (P < 0.01). Adult animals were also treated with the anti-CD11b MAb 198. MAb 198 decreased emigration by 25%, although this was not significant compared with PBS-treated animals. We conclude that although neonatal animals have significantly less neutrophil CD11a, the diminished levels did not contribute to a reduced ability to emigrate to the peritoneum and, like adult animals, neonatal animals primarily utilize LFA-1 for accumulation in this model. The contribution of Mac-1 to neonatal leukocyte emigration remains uncertain.
Hormonal and metabolic responses to electrically induced cycling during epidural anesthesia in humans
Authors: Kjaer M. , Secher N. H. , Bangsbo J. , Perko G. , Horn A. , Mohr T. , Galbo H.
Published: December 2017

Hormonal and metabolic responses to electrically induced dynamic exercise were investigated in eight healthy young men with afferent neural influence from the legs blocked by epidural anesthesia (25 ml of 2% lidocaine) at L3-L4. This caused cutaneous sensory anesthesia below T8-T9 and complete paralysis of the legs. Cycling increased oxygen uptake to 1.90 +/- 0.13 (SE) l/min, and fatigue developed after 22.7 +/- 2.7 min. Compared with voluntary exercise at the same oxygen uptake and heart rate, concentrations of blood and muscle lactate (musculus vastus lateralis) as well as plasma potassium increased more while muscle glycogen decreased more during electrically induced exercise. Hepatic glucose production always rose during exercise. However, during involuntary exercise with sensory blockade, it did not match the rise in peripheral glucose uptake and plasma glucose decreased (P < 0.05). Plasma glycerol increased less in electrically induced vs. voluntary exercise, and free fatty acids and beta-hydroxybutyrate decreased only during electrically induced exercise. Epinephrine, growth hormone, adrenocorticotropic hormone, and cortisol levels were higher during involuntary vs. voluntary exercise (P < 0.05). In conclusion, neural and humoral mechanisms exert redundant control with regard to responses of catecholamines and pituitary hormones (growth hormone and adrenocorticotropic hormone). In contrast, neural input from motor centers and feedback from working muscle are important for glucose production and lipolysis during exercise in humans. Humoral feedback is apparently not sufficient to trigger normal mobilization of extramuscular fuel stores.
Effect of tracheal and tongue displacement on upper airway airflow dynamics
Authors: Rowley J. A. , Permutt S. , Willey S. , Smith P. L. , Schwartz A. R.
Published: December 2017

We have previously shown that caudal tracheal displacement alters the airflow dynamics of the upper airway. In the present study, we specifically examined the effects of tongue and tracheal displacement on upper airway airflow dynamics. To determine how tongue and tracheal displacement modulate maximal inspiratory airflow (VImax), we analyzed the pressure-flow relationships obtained in the isolated upper airway of paralyzed cats. VImax and its determinants, the pharyngeal critical pressure (Pcrit) and the nasal resistance (Rn) upstream to the flow-limiting site, were measured as tongue displacement and tracheal displacement were systematically varied. Four results were obtained: 1) there was no independent effect of tongue displacement on VImax, Pcrit, or Rn; 2) there was an increase in VImax with 2 cm of tracheal displacement, which was associated with a decrease in Pcrit and an increase in Rn; 3) there was an interactive effect of tongue and tracheal displacement on VImax and Pcrit but not on Rn; and 4) there was a large increase in VImax with tongue displacement > 2.5 cm with the trachea nondisplaced, which was associated with a large decrease in Pcrit and a large increase in Rn. We conclude that tongue and tracheal displacement exert differing influences on airflow dynamics and present a mechanical model of the upper airway that explains these results.
Carotid artery blood flow and middle cerebral artery blood flow velocity during physical exercise
Authors: Hellstrom G. , Fischer-Colbrie W. , Wahlgren N. G. , Jogestrand T.
Published: December 2017

Factors controlling cerebral blood flow (CBF) during exercise are complex and incompletely known. Different techniques have shown partly contradictory results of changes in regional and global cerebral perfusion during dynamic exercise in healthy subjects. To elucidate the global CBF response to supine stepwise increasing physical exercise, we measured blood flow in the left common carotid artery (QCCA) and the left internal carotid artery (QICA) simultaneously with the blood flow velocity in the ipsilateral middle cerebral artery (VMCA) using duplex ultrasonography and transcranial Doppler ultrasonography. During moderate exercise intensity (60-67% of maximal capacity), the VMCA increased 14% (P < 0.001), the QICA 17% (P < 0.01), and the QCCA 33% (P < 0.001) compared with baseline values. High physical exercise intensity (80-90% of maximal capacity) tended to reduce VMCA and QICA compared with moderate exercise, in contrast to a continued increase in QCCA. The results indicate an increased global CBF during exercise. This increase was reduced during hard exercise due to a decrease of the arterial PCO2 secondary to hyperventilation.
Horizontal angular VOR changes in orbital and parabolic flight: human neurovestibular studies on SLS-2
Authors: Oman C. M. , Pouliot C. F. , Natapoff A.
Published: December 2017

Further evidence was found for adaptive changes in the vestibular "velocity storage" (VS) component of the vestibuloocular reflex in four shuttle astronauts tested in parabolic flight and before, during, and after a 14-day mission. Nystagmus was recorded during and after 1 min of 120 degrees/s rotation. Gains and time constants were determined by computer analysis. Responses correlated with experience. Two subjects were making their first spaceflight. In parabolic flight, their time constants shortened to an average of 60% of 1 G values, presumably because unfamiliar otolith cues reduced VS. However, after 4-10 days in orbit, their time constants were similar or greater than those preflight, indicating VS recovery. The other two subjects had previously flown in space. Their time constants shortened in orbit to an average of 69% of 1 G values, indicating a persisting reduction of VS. This correlation with spaceflight experience has been seen in 9 of 11 subjects on 3 missions. Head pitch did not significantly "dump" nystagmus as it does on Earth.
Interactions among metabolic rate, hypoxia, and control of breathing
Authors: Gautier H.
Published: December 2017

This review attempts to emphasize the fact that the interpretation of the ventilatory response to hypoxia may be complicated by the reduction in metabolic rate that is often associated with hypoxia. The hypoxic hypometabolism is more apparent when oxygen consumption is relatively high, either in small or young mammals at subnormal ambient temperatures or in larger mammals exposed to cold. This hypometabolism is not mediated by an activation of the arterial chemoreceptors and, furthermore, may result from a decrease in arterial oxygen content independent of the arterial PO2. Substantial experimental evidence supports the hypothesis of a lowering of the thermoregulatory set point during hypoxia through a direct action on central neural structures. The ventilatory response to hypoxia, which may appear blunted or depressed, especially in small animals exposed to cold, should in fact be reevaluated by taking into account the hypometabolism and hypothermia associated with hypoxia. Finally, it is emphasized that the mechanisms involved in control of body temperature and those that account for the interactions with hypoxia are located in the hypothalamus. This suggests that common integrative structures are probably involved in the metabolic and ventilatory responses to hypoxia.
Mediators of contraction-evoked skeletal muscle depressor response in anesthetized rats
Authors: Toney G. M. , Mifflin S. W.
Published: December 2017

In the present study, mediators of muscle contraction-evoked cardiovascular responses were examined in anesthetized rats. Rhythmic contractions of the hindlimb triceps surae muscle were produced by stimulating the tibial nerve (motor threshold 22.7 +/- 2.3 microA; n = 10) by using a 1 s on-1 s off pattern. Mean arterial pressure (MAP) and heart rate (HR) responses were recorded before and after 1) muscarinic receptor blockade (atropine sulfate; 2.0 mg/kg i.v., n = 5); 2) nitric oxide synthase inhibition with N omega-nitro-L-arginine methyl ester (L-NAME; 300 microM/kg i.v., n = 7); 3) beta-adrenoceptor blockade (propranolol; 2.0 mg/kg i.v., n = 10); and 4) bilateral adrenalectomy (n = 4). Rhythmic stimulation (10-s) significantly reduced MAP (P < 0.05) and elicited small decreases in HR that were abolished by neuromuscular blockade (n = 4). Atropine had no effect on MAP or HR responses to contraction. L-NAME increased baseline MAP (112.2 +/- 2.2 to 137.1 +/- 4.6 mmHg, P < 0.05) and attenuated contraction-evoked reductions of MAP (P < 0.05) without affecting HR. L-NAME-induced response deficits were mimicked in four separate rats by elevating MAP with phenylephrine (7–10 micrograms.kg-1.h-1 iv) to a level not different from that produced by L-NAME. Bilateral adrenalectomy and propranolol did not significantly affect HR responses but reduced contraction-evoked decreases in MAP from 14.3 +/- 2.9 to 7.7 +/- 2.2 mmHg and from 13.4 +/- 1.3 to 6.3 +/- 3.1 mmHg, respectively (P < 0.05). Baseline MAP was unchanged. We conclude that adrenal catecholamines, acting at beta-adrenoceptors, contribute significantly to the contraction-evoked depressor response in rats. No role for muscarinic receptors is evident in this response. Furthermore, attenuation of depressor responses to contraction after nitric oxide inhibition could result from an indirect effect of the pressor actions of L-NAME.
Determination of regional pulmonary blood flow with systemically injected nonentrapped microspheres
Authors: Kleen M. , Zwissler B. , Schosser R. , Messmer K.
Published: December 2017

Radioactive microspheres (MS) injected into the systemic circulation shunt to the venous side of the circulation and are trapped in the lung vasculature. We hypothesized that regional pulmonary perfusion could be determined by using systemically injected shunted MS. In seven anesthetized mechanically ventilated foxhounds, regional pulmonary perfusion was measured at baseline and during experimental acute respiratory distress syndrome with MS injected into both the right and left atrium (protocol 1). Methodological error of the MS technique was assessed by simultaneous injection of two different batches of MS into the right atrium (protocol 2). Measurement of perfusion during baseline and during experimental acute respiratory distress syndrome with shunted MS had a mean bias of 0.8 and 5.6% and mean precision of 19.2 and 34.7% (r = 0.94 and r = 0.95), respectively, compared with data from nonshunted MS. Simultaneous perfusion measurements displayed bias of -2.7 and 6% and precision of 8.2 and 5.3% (r = 0.98 and r = 0.99), respectively. Systemic shunt should be high for this method to prevent bronchial circulation from imposing significant error. We conclude that systemically injected MS can be used for simultaneous measurement of regional systemic and regional pulmonary perfusion, provided that MS that shunted in the first pass are measured in lung tissue.
Peak ventilatory responses during cycling and swimming in pregnant and nonpregnant women
Authors: Spinnewijn W. E. , Wallenburg H. C. , Struijk P. C. , Lotgering F. K.
Published: December 2017

This study was designed to determine whether pregnancy affects peak O2 uptake (VO2peak) during swimming compared with cycling. We studied 11 women at 30–34 wk gestation and 8–12 wk postpartum. We measured heart rate (HR), O2 uptake (VO2), CO2 output (VCO2), minute ventilation (VE), and lactic acid concentration. Peak HR was not significantly affected by the type of exercise or by pregnancy. VO2peak was 9% lower during swimming than during cycling but was not affected by pregnancy, with values for pregnancy cycling, pregnancy swimming, postpartum cycling, and postpartum swimming of 2.36 +/- 0.12, 2.11 +/- 0.11, 2.29 +/- 0.10, and 2.12 +/- 0.07 l/min, respectively. Peak VCO2 (VCO2peak) and peak VE were significantly lower during swimming than during cycling by 18–25%, but only VCO2peak during swimming was affected by pregnancy (-10%). Lactic acid concentrations were 12–17% lower after swimming than after cycling and 17–31% lower during pregnancy than postpartum. We conclude that perceived maximal exertion is reached at a lower percent maximal VO2 in swimming than in cycling and that the reduced energy expenditure is reflected by lower VO2peak, VCO2peak, and peak VE. Pregnancy, however, does not affect VO2peak in cycling or swimming.
In vivo IIX and IIB fiber recruitment in gastrocnemius muscle of the rat is compartment related
Authors: De Ruiter C. J. , Habets P. E. , de Haan A. , Sargeant A. J.
Published: December 2017

The purpose of the present study was to investigate to what extent fast-twitch IIX and IIB fiber recruitment was related to the natural existing muscle compartments (subvolumes of muscle innervated by different primary nerve branches) in rat medial gastrocnemius. Three groups (n = 6) of rats trotted on a motor-driven treadmill (20 degrees incline) at different speeds. A fourth group served as controls, and a fifth group received in situ electrical stimulation of all medial gastrocnemius muscle fibers. Postexercise glycogen levels (periodic acid-Schiff staining intensities) were made. Running caused more and in situ stimulation caused less glycogen breakdown in the proximal IIX and IIB fibers compared with the fibers of the same type in the most distal compartment. Furthermore, the boundaries of the most distal compartment could often be recognized in the periodic acid-Schiff-stained cross sections. It was concluded that during running the proximal IIX and IIB fibers were recruited to a greater extent (and at lower treadmill speeds) compared with the distal IIX and IIB fibers, respectively.
Regulation of ventilatory muscle blood flow
Authors: Hussain Sabah N. A.
Published: December 2017

Hussain, Sabah N. A. Regulation of ventilatory muscle blood flow. J. Appl. Physiol. 81(4): 1455–1468, 1996.—The ventilatory muscles perform various functions such as ventilation of the lungs, postural stabilization, and expulsive maneuvers (e.g., coughing). They are classified in functional terms as inspiratory muscles, which include the diaphragm, parasternal intercostal, external intercostal, scalene, and sternocleidomastoid muscles; and expiratory muscles, which include the abdominal muscles, internal intercostal, and triangularis sterni. The ventilatory muscles require high-energy phosphate compounds such as ATP to fuel the biochemical and physical processes of contraction and relaxation. Maintaining adequate intracellular concentrations of these compounds depends on adequate intracellular substrate levels and delivery of these substrates by arterial blood flow. In addition to the delivery of substrates, blood flow influences muscle function through the removal of metabolic by-products, which, if accumulated, could exert negative effects on several excitatory and contractile processes. Skeletal muscle substrate utilization is also dependent on the ability to extract substrates from arterial blood, which, in turn, is accomplished by increasing the total number of perfused capillaries. It follows that matching perfusion to metabolic demands is critical for the maintenance of normal muscle contractile function. In this article, I review the factors that influence ventilatory muscle blood flow. Major emphasis is placed on the diaphragm because a large number of published reports deal with diaphragmatic blood flow. The second reason for focusing on the diaphragm is because it is the largest and most important inspiratory muscle.
Effects of hypoxic pulmonary vasoconstriction on pulmonary gas exchange
Authors: Brimioulle Serge , Lejeune Philippe , Naeije Robert
Published: December 2017

Brimioulle, Serge, Philippe Lejeune, and Robert Naeije.Effects of hypoxic pulmonary vasoconstriction on pulmonary gas exchange. J. Appl. Physiol. 81(4): 1535–1543, 1996.—Several reports have suggested that hypoxic pulmonary vasoconstriction (HPV) might result in deterioration of pulmonary gas exchange in severe hypoxia. We therefore investigated the effects of HPV on gas exchange in normal and diseased lungs. We incorporated a biphasic HPV stimulus-response curve observed in intact dogs (S. Brimioulle, P. Lejeune, J. L. Vachièry, M. Delcroix, R. Hallemans, and R. Naeije, J. Appl. Physiol. 77: 476–480, 1994) into a 50-compartment lung model (J. B. West, Respir. Physiol. 7: 88–110, 1969) to control the amount of blood flow directed to each lung compartment according to the local hypoxic stimulus. The resulting model accurately reproduced the blood gas modifications caused by HPV changes in dogs with acute lung injury. In single lung units, HPV had a moderate protective effect on alveolar oxygenation, which was maximal at near-normal alveolar[Formula: see text] (75–80 Torr), mixed venous[Formula: see text] (35 Torr), and[Formula: see text] at which hemoglobin is 50% saturated (24 Torr). In simulated diseased lungs associated with 40–60 Torr arterial [Formula: see text], however, HPV increased arterial [Formula: see text]by 15–20 Torr. We conclude that HPV can improve arterial oxygenation substantially in respiratory failure.
Rate of uptake of CO by hemoglobin in pig erythrocytes as a function of P O 2
Authors: Te Nijenhuis Francis C. A. M. , Lin Lydia , Moens Gerko H. , Versprille Adrian , Forster Robert E.
Published: December 2017

Te Nijenhuis, Francis C. A. M., Lydia Lin, Gerko H. Moens, Adrian Versprille, and Robert E. Forster. Rate of uptake of CO by hemoglobin in pig erythrocytes as a function of[Formula: see text]. J. Appl. Physiol. 81(4): 1544–1549, 1996.—This study was initiated to obtain data on the rate of carbon monoxide (CO) uptake (ΘCO) by hemoglobin in pig erythrocytes to derive, in a later study, the pulmonary capillary blood volume (Qc) in pigs from the Roughton-Forster relationship. Blood from five different female pigs was used. The ΘCO, the milliliters of CO taken up by 1 ml of whole blood per minute per Torr CO tension, was determined on each blood sample with a continuous-flow rapid-mixing apparatus and double-beam spectrophotometry at 37°C and pH 7.4 at four or five different [Formula: see text] values. Because the individual regression lines of ΘCOvs.[Formula: see text] were not significantly different, a common regression equation was calculated: 1/ΘCO= 0.0084[Formula: see text] + 0.63. The slope of this regression line is significantly steeper than the reported slopes of the regression lines for human and dog erythrocytes measured under the same conditions. Our results revealed that calculation of Qc in pigs by using ΘCOvalues for human or dog erythrocytes would result in an underestimation of 51 and 50%, respectively.
Effect of prior O2 breathing on ventilatory response to sustained isocapnic hypoxia in adult humans
Authors: Honda Y. , Tani H. , Masuda A. , Kobayashi T. , Nishino T. , Kimura H. , Masuyama S. , Kuriyama T.
Published: December 2017

Honda, Y., H. Tani, A. Masuda, T. Kobayashi, T. Nishino, H. Kimura, S. Masuyama, and T. Kuriyama. Effect of prior O2 breathing on ventilatory response to sustained isocapnic hypoxia in adult humans. J. Appl. Physiol. 81(4): 1627–1632, 1996.—Sixteen healthy volunteers breathed 100% O2 or room air for 10 min in random order, then their ventilatory response to sustained normocapnic hypoxia (80% arterial O2saturation, as measured with a pulse oximeter) was studied for 20 min. In addition, to detect agents possibly responsible for the respiratory changes, blood plasma of 10 of the 16 subjects was chemically analyzed. 1) Preliminary O2 breathing uniformly and substantially augmented hypoxic ventilatory responses. 2) However, the profile of ventilatory response in terms of relative magnitude, i.e., biphasic hypoxic ventilatory depression, remained nearly unchanged. 3) Augmented ventilatory increment by prior O2 breathing was significantly correlated with increment in the plasma glutamine level. We conclude that preliminary O2administration enhances hypoxic ventilatory response without affecting the biphasic response pattern and speculate that the excitatory amino acid neurotransmitter glutamate, possibly derived from augmented glutamine, may, at least in part, play a role in this ventilatory enhancement.