bluuebunny/crossref_metadata_2025 huggingface dataset:
Acute response of the lung mechanics of the rabbit to hypoxia
Authors: Sakai H. , Fukui M. , Nakano Y. , Endo K. , Hirai T. , Oku Y. , Mishima M.
Published: December 2017

We measured the change in total lung resistance (Rl) and that in total lung elastance (El) induced by hypoxia ( n = 7) and compared the results with those by intravenous histamine bolus ( n = 5) at three different positive end-expiratory pressure (PEEP) levels (2, 5, and 8 hPa) in open-chest and vagotomized rabbits. The percent increase ratio of Rl(PIRR) and El(PIRE) was defined as the change in Rl and El, respectively, induced by hypoxia compared with that in the normoxic condition, expressed as a percentage. PIR values for the change in Rl and El induced by bolus injection of histamine were also calculated. The PIRR and PIRE induced by hypoxia and by histamine were positive by a statistically significant amount at every PEEP level, except for the PIREvalue at 8-hPa PEEP in the hypoxic challenge. The PIRE-to-PIRRratio values in the hypoxic challenge at 2-hPa PEEP were significantly larger than those in the histamine challenge (hypoxia: 0.91 ± 0.23%; histamine: 0.37 ± 0.065%, P < 0.05). The increase in El induced by histamine in the acute phase has been reported to be mainly derived from tissue distortion secondary to bronchial constriction. Thus our results suggest that a part of the increase in El by hypoxia was originated in different parenchymal responses from histamine and imply that this hypoxic response of lung parenchyma is sensitive to the increase in parenchymal tethering at high PEEP levels.
Effects of eccentric exercise on the immune system in men
Authors: Malm Christer , Lenkei Rodica , Sjödin Bertil
Published: December 2017

The effects of eccentric exercise on changes in numbers of circulating leukocytes, cell activation, cell adhesion, and cellular memory function were investigated in 12 men, aged 22–35 yr. The immunologic effects of postexercise epidermal treatment with monochromatic, infrared light were also evaluated. Blood was drawn before and 6, 24, and 48 h after exercise for phenotyping and analysis of creatine kinase activity. There was an increase in leukocyte, monocyte, and neutrophil number, no change in the number of basophils, eosinophils, B cells, and T cells, and a decrease in natural killer cell number postexercise. Some markers of lymphocyte and monocyte activation remained unchanged or decreased, whereas the expression of adhesion molecules 62L and 11b increased on monocytes. It is concluded that eccentric exercise induced decreased activation, and increased cell adhesion capacity, of monocytes. Altered trafficking of cells between lymphoid tissue and blood, selective apoptosis, or attachment/detachment from the endothelial wall can explain the observed phenotypic changes. Treatment with monochromatic, infrared light did not significantly affect any of the investigated variables. Correlations between immunologic and physiological parameters indicate a role of the immune system in adaptation to physical exercise.
Interferon-γ has immunomodulatory effects with minor endocrine and metabolic effects in humans
Authors: de Metz J. , Sprangers F. , Endert E. , Ackermans M. T. , ten Berge I. J. M. , Sauerwein H. P. , Romijn J. A.
Published: December 2017

To evaluate whether interferon-γ (IFN-γ) is involved in the interaction between the immune and endocrine systems in vivo, we studied six healthy subjects twice in a placebo-controlled trial: once after administration of recombinant human IFN-γ and, on another occasion, after administration of saline. The rate of appearance of glucose was determined by infusion of [6,6-2H2]glucose and resting energy expenditure by indirect calorimetry. Human leukocyte antigen-DR gene expression on monocytes and serum neopterin increased after administration of IFN-γ ( P < 0.05 vs. control). IFN-γ increased serum interleukin-6 levels significantly. Levels of tumor necrosis factor-α remained below detection limits. IFN-γ increased plasma concentrations of ACTH and cortisol ( P < 0.05 vs. control), IFN-γ did not alter concentrations of growth hormone, (nor)epinephrine, insulin, C peptide, glucagon, or insulin-like growth factor I. IFN-γ did not alter plasma concentrations of glucose and free fatty acids nor the rate of appearance of glucose. IFN-γ increased resting energy expenditure significantly. We conclude that IFN-γ is a minor stimulator of the endocrine and metabolic pathways. Therefore, IFN-γ by itself is probably not a major mediator in the interaction between the immune and the endocrine and metabolic systems.
Effect of concentric and eccentric muscle actions on muscle sympathetic nerve activity
Authors: Carrasco Dario I. , Delp Michael D. , Ray Chester A.
Published: December 2017

The purpose of this study was to determine the effects of concentric (Con) and eccentric (Ecc) muscle actions on leg muscle sympathetic nerve activity (MSNA). Two protocols were utilized. In protocol 1, eight subjects performed Con and Ecc arm curls for 2 min, with a resistance representing 50% of one-repetition maximum for Con curls. Heart rate (HR) and mean arterial pressure (MAP) were greater ( P < 0.05) during Con than during Ecc curls. Similarly, the MSNA was greater ( P < 0.05) during Con than during Ecc curls. In protocol 2, eight different subjects performed Con and Ecc arm curls to fatigue, followed by postexercise muscle ischemia, by using the same resistance as in protocol 1. Endurance time was significantly greater for Ecc than for Con curls. The increase in HR, MAP, and MSNA was greater ( P < 0.05) during Con than during Ecc curls. However, when the data were normalized as a function of endurance time, the differences in HR, MAP, and MSNA between Con and Ecc curls were no longer present. HR, MAP, and MSNA responses during postexercise muscle ischemia were similar for Con and Ecc curls. Con curls elicited greater increase ( P < 0.05) in blood lactate concentration than did Ecc curls. In summary, Con actions contribute significantly more to the increase in cardiovascular and MSNA responses during brief, submaximal exercise than do Ecc actions. However, when performed to a similar level of effort (i.e., fatigue), Con and Ecc muscle actions elicit similar cardiovascular and MSNA responses. These results indicate that the increase in MSNA during a typical bout of submaximal dynamic exercise is primarily mediated by the muscle metaboreflex, which is stimulated by metabolites produced predominantly during Con muscle action.
Maturation of gait dynamics: stride-to-stride variability and its temporal organization in children
Authors: Hausdorff J. M. , Zemany L. , Peng C.-K. , Goldberger A. L.
Published: December 2017

In very young children, immature control of posture and gait results in unsteady locomotion. In children of ∼3 yr of age, gait appears relatively mature; however, it is unknown whether the dynamics of walking change beyond this age. Because stride dynamics depend on neural control, we hypothesized that motor control would continue to develop beyond age 3. To test this hypothesis, we measured the gait cycle duration on a stride-by-stride basis in 50 healthy 3- to 14-yr-old children (25 girls). Measurements of stride-to-stride variability were significantly larger both in the 3- and 4-yr-old children, compared with the 6- and 7-yr-old children, and in the 6- and 7-yr-old children, compared with the 11- to 14-yr-old children. Measurements of the temporal organization of gait also revealed significant age-dependent changes. The effects of age persisted even after adjusting for height. These findings indicate that mature stride dynamics may not be completely developed even in healthy 7-yr-old children and that different aspects of stride dynamics mature at different ages.
Barometric pressures on Mt. Everest: new data and physiological significance
Authors: West John B.
Published: December 2017

Barometric pressures (Pb) near the summit of Mt. Everest (altitude 8,848 m) are of great physiological interest because the partial pressure of oxygen is very near the limit for human survival. Until recently, the only direct measurement on the summit was 253 Torr, which was obtained in October 1981, but, despite being only one data point, this value has been used by several investigators. Recently, two new studies were carried out. In May 1997, another direct measurement on the summit was within ∼1 Torr of 253 Torr, and meteorologic data recorded at the same time from weather balloons also agreed closely. In the summer of 1998, over 2,000 measurements were transmitted from a barometer placed on the South Col (altitude 7,986 m). The mean Pbvalues during May, June, July, and August were 284, 285, 286, and 287 Torr, respectively, and there was close agreement with the Pb-altitude (h) relationship determined from the 1981 data. The Pb values are well predicted from the equation Pb = exp (6.63268 − 0.1112 h − 0.00149 h2), where h is in kilometers. The conclusion is that on days when the mountain is usually climbed, during May and October, the summit pressure is 251–253 Torr.
Physiological variability of fluid-regulation hormones in young women
Authors: Stachenfeld Nina S. , DiPietro Loretta , Kokoszka Cheryl A. , Silva Celso , Keefe David L. , Nadel Ethan R.
Published: December 2017

We tested the physiological reliability of plasma renin activity (PRA) and plasma concentrations of arginine vasopressin (P[AVP]), aldosterone (P[ALD]), and atrial natriuretic peptide (P[ANP]) in the early follicular phase and midluteal phases over the course of two menstrual cycles ( n = 9 women, ages 25 ± 1 yr). The reliability (Cronbach’s α ≥0.80) of these hormones within a given phase of the cycle was tested 1) at rest, 2) after 2.5 h of dehydrating exercise, and 3) during a rehydration period. The mean hormone concentrations were similar within both the early follicular and midluteal phase tests; and the mean concentrations of P[ALD] and PRA for the three test conditions were significantly greater during the midluteal compared with the early follicular phase. Although Cronbach’s α for resting and recovery P[ANP] were high (0.80 and 0.87, respectively), the resting and rehydration values for P[AVP], P[ALD], and PRA were variable between trials for the follicular (α from 0.49 to 0.55) and the luteal phase (α from 0.25 to 0.66). Physiological reliability was better after dehydration for P[AVP] and PRA but remained low for P[ALD]. Although resting and recovery P[AVP], P[ALD], and PRA were not consistent within a given menstrual phase, the differences in the concentrations of these hormones between the different menstrual phases far exceeded the variability within the phases, indicating that the low within-phase reliability does not prevent the detection of menstrual phase-related differences in these hormonal variables.
Heart rate during exercise with leg vascular occlusion in spinal cord-injured humans
Authors: Kjær M. , Pott F. , Mohr T. , Linkis P. , Tornøe P. , Secher N. H.
Published: December 2017

Feed-forward and feedback mechanisms are both important for control of the heart rate response to muscular exercise, but their origin and relative importance remain inadequately understood. To evaluate whether humoral mechanisms are of importance, the heart rate response to electrically induced cycling was studied in participants with spinal cord injury (SCI) and compared with that elicited during volitional cycling in able-bodied persons (C). During voluntary exercise at an oxygen uptake of ∼1 l/min, heart rate increased from 66 ± 4 to 86 ± 4 (SE) beats/min in seven C, and during electrically induced exercise at a similar oxygen uptake in SCI it increased from 73 ± 3 to 110 ± 8 beats/min. In contrast, blood pressure increased only in C (from 88 ± 3 to 99 ± 4 mmHg), confirming that, during exercise, blood pressure control is dominated by peripheral neural feedback mechanisms. With vascular occlusion of the legs, the exercise-induced increase in heart rate was reduced or even eliminated in the electrically stimulated SCI. For C, heart rate tended to be lower than during exercise with free circulation to the legs. Release of the cuff elevated heart rate only in SCI. These data suggest that humoral feedback is of importance for the heart rate response to exercise and especially so when influence from the central nervous system and peripheral neural feedback from the working muscles are impaired or eliminated during electrically induced exercise in individuals with SCI.
Age-related changes in contractile properties of single skeletal fibers from the soleus muscle
Authors: Thompson LaDora V. , Brown Marybeth
Published: December 2017

Peak absolute force, specific tension (peak absolute force per cross-sectional area), cross-sectional area, maximal unloaded shortening velocity ( Vo; determined by the slack test), and myosin heavy chain (MHC) isoform compositions were determined in 124 single skeletal fibers from the soleus muscle of 12-, 24-, 30-, 36-, and 37-mo-old Fischer 344 Brown Norway F1 Hybrid rats. All fibers expressed the type I MHC isoform. The mean Voremained unchanged from 12 to 24 mo but did decrease significantly from the 24- to 30-mo time period (from 1.71 ± 0.13 to 0.85 ± 0.09 fiber lengths/s). Fiber cross-sectional area remained constant until 36 mo of age, at which time there was a 20% decrease from the values at 12 mo of age (from 5,558 ± 232 to 4,339 ± 280 μm2). A significant decrease in peak absolute force of single fibers occurred between 12 and 24 mo of age (from 51 ± 2 × 10−5to 35 ± 2 × 10−5N) and then remained constant until 36 mo, when another 43% decrease occurred. Like peak absolute force, the specific tension decreased significantly between 12 and 24 mo by 20%, and another 32% decline was observed at 37 mo. Thus, by 24 mo, there was a dissociation between the loss of fiber cross-sectional area and force. The results suggest time-specific changes of the contractile properties with aging that are independent of each other. Underlying mechanisms responsible for the time-dependent and contractile property-specific changes are unknown. Age-related changes in the molecular dynamics of myosin may be the underlying mechanism for altered force production. The presence of more than one β/slow MHC isoform may be the mechanism for the altered Vowith age.
Modulation of temperature-induced tone by vasoconstrictor agents
Authors: Massett Michael P. , Lewis Stephen J. , Bates James N. , Kregel Kevin C.
Published: December 2017

One of the primary cardiovascular adjustments to hyperthermia is a sympathetically mediated increase in vascular resistance in the viscera. Nonneural factors such as a change in vascular tone or reactivity may also contribute to this response. Therefore, the aim of this study was to determine whether vascular smooth muscle tone is altered during heating to physiologically relevant temperatures >37°C. Gradually increasing bath temperature from 37°C (normothermia) to 43°C (severe hyperthermia) produced graded contractions in vascular ring segments from rat mesenteric arteries and thoracic aortae. In untreated rings these contractions were relatively small, whereas hyperthermia elicited near-maximal increases in tension when rings were constricted with phenylephrine or KCl before heating. In phenylephrine-treated mesenteric arterial rings, the contractile responses to heating were markedly attenuated by the Ca2+channel antagonists nifedipine and diltiazem. Diltiazem also blocked the contractile responses to heating in thoracic aortic rings. These results demonstrate that hyperthermia has a limited effect on tension generation in rat vascular smooth muscle in the absence of vascular tone. However, in the presence of agonist-induced tone, tension generation during heating is markedly enhanced and dependent on extracellular Ca2+. In conclusion, these data suggest that local regulation of vascular tone can contribute to the hemodynamic adjustments to hyperthermia.
Expression of the cell adhesion molecules on leukocytes that demarginate during acute maximal exercise
Authors: van Eeden Stephan F. , Granton John , Hards Jennifer M. , Moore Barbara , Hogg James C.
Published: December 2017

The pulmonary vascular bed is an important reservoir for the marginated pool of leukocytes that can be mobilized by exercise or catecholamines. This study was designed to determine the phenotypic characteristics of leukocytes that are mobilized into the circulation during exercise. Twenty healthy volunteers performed incremental exercise to exhaustion [maximal O2consumption (V˙o2 max)] on a cycle ergometer. Blood was collected at baseline, at 3-min intervals during exercise, atV˙o2 max, and 30 min after exercise. Total white cell, polymorphonuclear leukocyte (PMN), and lymphocyte counts increased with exercise toV˙o2 max( P < 0.05). Flow cytometric analysis showed that the mean fluorescence intensity of L-selectin on PMN (from 14.9 ± 1 at baseline to 9.5 ± 1.6 atV˙o2 max, P < 0.05) and lymphocytes (from 11.7 ± 1.2 at baseline to 8 ± 0.8 atV˙o2 max, P < 0.05) decreased with exercise. Mean fluorescence intensity of CD11b on PMN increased with exercise (from 10.2 ± 0.6 at baseline to 25 ± 2.5 atV˙o2 max, P < 0.002) but remained unchanged on lymphocytes. Myeloperoxidase levels in PMN did not change with exercise. In vitro studies showed that neither catecholamines nor plasma collected atV˙o2 maxduring exercise changed leukocyte L-selectin or CD11b levels. We conclude that PMN released from the marginated pool during exercise express low levels of L-selectin and high levels of CD11b.
Interaction of factors determining oxygen uptake at the onset of exercise
Authors: Tschakovsky M. E. , Hughson R. L.
Published: December 2017

Considerable debate surrounds the issue of whether the rate of adaptation of skeletal muscle O2consumption (Q˙o2) at the onset of exercise is limited by 1) the inertia of intrinsic cellular metabolic signals and enzyme activation or 2) the availability of O2to the mitochondria, as determined by an extrinsic inertia of convective and diffusive O2transport mechanisms. This review critically examines evidence for both hypotheses and clarifies important limitations in the experimental and theoretical approaches to this issue. A review of biochemical evidence suggests that a given respiratory rate is a function of the net drive of phosphorylation potential and redox potential and cellular mitochondrial[Formula: see text](Pmitoo2). Changes in both phosphorylation and redox potential are determined by intrinsic metabolic inertia. Pmitoo2is determined by the extrinsic inertia of both convective and diffusive O2transport mechanisms during the adaptation to exercise and the rate of mitochondrial O2utilization. In a number of exercise conditions, Pmitoo2appears to be within a range capable of modulating muscle metabolism. Within this context, adjustments in the phosphate energy state of the cell would serve as a cytosolic “transducer,” linking ATP consumption with mitochondrial ATP production and, therefore, O2consumption. The availability of reducing equivalents and O2would modulate the rate of adaptation ofQ˙o2.
External thoracic restriction, respiratory sensation, and ventilation during exercise in men
Authors: Harty Helen R. , Corfield Douglas R. , Schwartzstein Richard M. , Adams Lewis
Published: December 2017

Multiple factors may contribute to the dyspnea associated with restrictive ventilatory disease (RVD). Simple models that examine specific features of this problem are likely to provide insight into the mechanisms. Previous models of RVD utilizing elastic loads may not represent completely the impact on pulmonary and chest wall receptors derived from breathing at low thoracic volumes. The purpose of this study was to investigate the sensory consequences of breathing at low lung volumes induced by external thoracic restriction in an attempt to further elucidate the etiology of dyspnea in this setting. Ten men were studied, with and without an inelastic corset applied at residual volume (restriction resulted in mean reductions in vital capacity, functional residual capacity, residual volume, and forced expired volume in 1 s of 44, 31, 12.5, and 42%, respectively). During 10-min steady-state exercise tests (at a workload set to achieve ∼65% maximum heart rate), restriction resulted in significant increases, compared with control, in minute ventilation (61 vs. 49 l/min), respiratory frequency (43 vs. 23 breaths/min), and visual analog scale measurements of respiratory discomfort (65 vs. 20 mm). Alveolar hyperventilation (end-tidal [Formula: see text] = 39 vs. 44 Torr for control) and mild O2desaturation (arterial blood O2saturation = 93 vs. 95% for control) occurred. Hypoxemia, atelectasis, increased work and effort of breathing, or a decrease in the volume-related feedback from chest wall and/or lungs could be responsible for the increased dyspnea reported. External thoracic restriction provides a useful model to study mechanisms of dyspnea in RVD.
Compensatory alveolar growth normalizes gas-exchange function in immature dogs after pneumonectomy
Authors: Takeda Shin-Ichi , Hsia Connie C. W. , Wagner Eva , Ramanathan Murugappan , Estrera Aaron S. , Weibel Ewald R.
Published: December 2017

To determine the extent and sources of adaptive response in gas-exchange to major lung resection during somatic maturation, immature male foxhounds underwent right pneumonectomy (R-Pnx, n = 5) or right thoracotomy without pneumonectomy (Sham, n = 6) at 2 mo of age. One year after surgery, exercise capacity and pulmonary gas-exchange were determined during treadmill exercise. Lung diffusing capacity (Dl) and cardiac output were measured by a rebreathing technique. In animals after R-Pnx, maximal O2 uptake, lung volume, arterial blood gases, and Dl during exercise were completely normal. Postmortem morphometric analysis 18 mo after R-Pnx ( n = 3) showed a vigorous compensatory increase in alveolar septal tissue volume involving all cellular compartments of the septum compared with the control lung; as a result, alveolar-capillary surface areas and Dl estimated by morphometry were restored to normal. In both groups, estimates of Dl by the morphometric method agreed closely with estimates obtained by the physiological method during peak exercise. These data show that extensive lung resection in immature dogs stimulates a vigorous compensatory growth of alveolar tissue in excess of maturational lung growth, resulting in complete normalization of aerobic capacity and gas-exchange function at maturity.
Tomographical description of tennis-loaded radius: reciprocal relation between bone size and volumetric BMD
Authors: Ashizawa Noriko , Nonaka Kiichi , Michikami Sizuka , Mizuki Tomoe , Amagai Hitoshi , Tokuyama Kumpei , Suzuki Masashige
Published: December 2017

Effects of long-term tennis loading on volumetric bone mineral density (vBMD) and geometric properties of playing-arm radius were examined. Paired forearms of 16 tennis players (10 women) and 12 healthy controls (7 women), aged 18–24 yr, were scanned at mid and distal site by using peripheral quantitative computerized tomography. Tomographic data at midradius showed that tennis playing led to a slight decrease in cortical vBMD (−0.8% vs. nonplaying arm, P< 0.05) and increase both in periosteal and endocoritcal bone area (+15.2% for periosteal bone, P < 0.001; and +18.8% for endocortical bone, P < 0.001). These data suggest that, together with an increase in cortical thickness (+6.4%, P < 0.01), cortical drift toward periosteal direction resulted in improvement of mechanical characteristics of the playing-arm midradius. Enlargement of periosteal bone area was also observed at distal radius (+6.8%, P < 0.01), and the relative side-to-side difference in periosteal bone area was inversely related to that in trabecular vBMD ( r = −0.53, P < 0.05). We conclude that an improvement of mechanical properties of young adult bone in response to long-term exercise is related to geometric adaptation but less to changes in vBMD.
Peripheral chemoreceptor function after carbonic anhydrase inhibition during moderate-intensity exercise
Authors: Scheuermann Barry W. , Kowalchuk John M. , Paterson Donald H. , Cunningham David A.
Published: December 2017

The effect of carbonic anhydrase inhibition with acetazolamide (Acz, 10 mg/kg) on the ventilatory response to an abrupt switch into hyperoxia (end-tidal [Formula: see text]= 450 Torr) and hypoxia (end-tidal[Formula: see text] = 50 Torr) was examined in five male subjects [30 ± 3 (SE) yr]. Subjects exercised at a work rate chosen to elicit an O2 uptake equivalent to 80% of the ventilatory threshold. Ventilation (V˙e) was measured breath by breath. Arterial oxyhemoglobin saturation (%[Formula: see text]) was determined by ear oximetry. After the switch into hyperoxia, V˙eremained unchanged from the steady-state exercise prehyperoxic value (60.6 ± 6.5 l/min) during Acz. During control studies (Con),V˙e decreased from the prehyperoxic value (52.4 ± 5.5 l/min) by ∼20% (V˙enadir = 42.4 ± 6.3 l/min) within 20 s after the switch into hyperoxia. V˙e increased during Acz and Con after the switch into hypoxia; the hypoxic ventilatory response was significantly lower after Acz compared with Con [Acz, change (Δ) inV˙e/[Formula: see text]= 1.54 ± 0.10 l ⋅ min−1 ⋅ [Formula: see text] −1; Con, ΔV˙e/[Formula: see text]= 2.22 ± 0.28 l ⋅ min−1 ⋅ [Formula: see text] −1]. The peripheral chemoreceptor contribution to the ventilatory drive after acute Acz-induced carbonic anhydrase inhibition is not apparent in the steady state of moderate-intensity exercise. However, Acz administration did not completely attenuate the peripheral chemoreceptor response to hypoxia.
Vagal afferents and active upper airway closure during pulmonary edema in lambs
Authors: Diaz Véronique , Dorion Dominique , Kianicka Irenej , Létourneau Patrick , Praud Jean-Paul ,   (With the Technical Assistance of Bruno Gagné)
Published: December 2017

The present study was undertaken to gain further insight into the mechanisms responsible for the sustained active expiratory upper airway closure previously observed during high-permeability pulmonary edema in lambs. The experiments were conducted in nonsedated lambs, in which airflow and thyroarytenoid and inferior pharyngeal constrictor muscle electromyographic activity were recorded. We first studied the consequences of hemodynamic pulmonary edema (induced by impeding pulmonary venous return) on upper airway dynamics in five lambs; under this condition, a sustained expiratory upper airway closure consistently appeared. We then tested whether expiratory upper airway closure was related to vagal afferent activity from bronchopulmonary receptors. Five bivagotomized lambs underwent high-permeability pulmonary edema: no sustained expiratory upper airway closure was observed. Finally, we studied whether a sustained decrease in lung volume induced a sustained expiratory upper airway closure. Five lambs underwent a 250-ml pleural infusion: no sustained expiratory upper airway closure was observed. We conclude that 1) the sustained expiratory upper airway closure observed during pulmonary edema in nonsedated lambs is related to stimulation of vagal afferents by an increase in lung water and 2) a decrease in lung volume does not seem to be the causal factor.
Effects of capsaicin pretreatment on expiratory laryngeal closure during pulmonary edema in lambs
Authors: Diaz Véronique , Dorion Dominique , Renolleau Sylvain , Létourneau Patrick , Kianicka Irenej , Praud Jean-Paul ,   (With the Technical Assistance of Bruno Gagné)
Published: December 2017

The present study, performed in nonsedated, conscious lambs, consisted of two parts. In the first part, we 1) examined for the first time whether a respiratory response to pulmonary C-fiber stimulation could be elicited in nonsedated newborns and 2) determined whether this response could be abolished by capsaicin pretreatment. Then, by using capsaicin-desensitized lambs, we studied whether pulmonary C fibers were involved in the sustained, active expiratory upper airway closure previously observed during pulmonary edema. Airflow and thyroarytenoid and inferior pharyngeal constrictor muscle electromyographic activities were recorded. In the first set of experiments, a 5–10 μg/kg capsaicin bolus intravenous injection in seven intact lambs consistently led to a typical pulmonary chemoreflex, showing that C fibers are functionally mature in newborn lambs. In the second series of experiments, eight lambs pretreated with 25–50 mg/kg subcutaneous capsaicin did not exhibit any respiratory response to 10–50 μg/kg intravenous capsaicin injection, implicating C fibers in the response. Finally, in the above capsaicin-desensitized lambs, we observed that halothane-induced high-permeability pulmonary edema did not cause the typical response of sustained expiratory upper airway closure seen in the intact lamb. We conclude that functionally mature C fibers are present and responsible for a pulmonary chemoreflex in response to capsaicin intravenous injection in nonsedated lambs. Capsaicin pretreatment abolishes this reflex. Furthermore, the sustained expiratory upper airway closure observed during halothane-induced pulmonary edema in intact nonsedated lambs appears to be related to a reflex involving stimulation of pulmonary C fibers.
Acid-base disturbance during hemorrhage in rats: significant role of strong inorganic ions
Authors: Alfaro V. , Pesquero J. , Palacios L.
Published: December 2017

The present study tests the hypothesis that changes in the strong inorganic ion concentrations contribute significantly to the acid-base disturbance that develops during hemorrhage in the arterial plasma of rats in addition to lactate concentration ([Lac−]) increase. The physicochemical origins for this acid-base disorder were studied during acute, graded hemorrhage (10, 20, and 30% loss of blood volume) in three groups of rats: conscious, anesthetized with ketamine, and anesthetized with urethan. The results support the hypothesis examined: strong-ion difference (SID) decreased in the arterial plasma of all groups studied because of an early imbalance in the main strong inorganic ions during initial hemorrhagic phase. Moreover, changes in plasma [Lac−] contributed to SID decrease in a later hemorrhagic phase (after 10% hemorrhage in urethan-anesthetized, after 20% hemorrhage in ketamine-anesthetized, and after 30% hemorrhage in conscious group). Inorganic ion changes were due to both dilution of the vascular compartment and ion exchange with extravascular space and red blood cells, as compensation for blood volume depletion and hypocapnia. Nevertheless, anesthetized rats were less able than conscious rats to preserve normal arterial pH during hemorrhage, mainly because of an impaired peripheral tissue condition and incomplete ventilatory compensation.
Neuromechanical interaction in human snoring and upper airway obstruction
Authors: Huang Lixi , Williams John E. Ffowcs
Published: December 2017

The fact that snoring and obstructive apnea only occur during sleep means that effective neuromuscular functioning of the upper airway during sleep is vital for the maintenance of unimpeded breathing. Recent clinical studies in humans have obtained evidence demonstrating that upper airway neural receptors sense the negative pressure generated by inspiration and “trigger,” with a certain delay, reflex muscle activation to sustain the airway that might otherwise collapse. These findings have enabled us to propose a model in which the mechanics is coupled to the neuromuscular physiology through the generation of reflex wall stiffening proportional to the retarded fluid pressure. Preliminary results on this model exhibit three kinds of behavior typical of unimpeded breathing, snoring, and obstructive sleep apnea, respectively. We suggest that the increased latency of the reflex muscle activation in sleep, together with the reduced strength of the reflex, have important clinical consequences.
Respiratory energetics during exercise at high altitude
Authors: Cibella Fabio , Cuttitta Giuseppina , Romano Salvatore , Grassi Bruno , Bonsignore Giovanni , Milic-Emili Joseph
Published: December 2017

The purpose of this study was to assess the effect of high altitude (HA) on work of breathing and external work capacity. On the basis of simultaneous records of esophageal pressure and lung volume, the mechanical power of breathing (W˙rs) was measured in four normal subjects during exercise at sea level (SL) and after a 1-mo sojourn at 5,050 m. Maximal exercise ventilation (V˙e max) and maximal W˙rs were higher at HA than at SL (mean 185 vs. 101 l/min and 129 vs. 40 cal/min, respectively), whereas maximal O2 uptake averaged 2.07 and 3.03 l/min, respectively. In three subjects, the relationship ofW˙rs to minute ventilation (V˙e) was the same at SL and HA, whereas, in one individual, W˙rs for any givenV˙e was consistently lower at HA. Assuming a mechanical efficiency (E) of 5%, the O2 cost of breathing at HA and SL should amount to 26 and 5.5% of maximal O2 uptake, whereas for E of 20% the corresponding values were 6.5 and 1.4%, respectively. Thus, at HA, W˙rs may substantially limit external work unless E is high. Although at SLV˙e max did not exceed the critical V˙e, at which any increase inV˙e is not useful in terms of body energetics even for E of 5%, at HAV˙e maxexceeded critical V˙e even for E of 20%.
Lack of antilipolytic effect of lactate in subcutaneous abdominal adipose tissue during exercise
Authors: Trudeau François , Bernier Sylvain , de Glisezinski Isabelle , Crampes François , Dulac François , Rivière Daniel
Published: December 2017

The purpose of our study was to evaluate the potential inhibition of adipose tissue mobilization by lactate. Eight male subjects (age, 26.25 ± 1.75 yr) in good physical condition (maximal oxygen uptake, 59.87 ± 2.77 ml ⋅ kg−1⋅ min−1; %body fat, 10.15 ± 0.89%) participated in this study. For each subject, two microdialysis probes were inserted into abdominal subcutaneous tissue. Lactate (16 mM) was perfused via one of the probes while physiological saline only was perfused via the other, both at a flow rate of 2.5 μl/min. In both probes, ethanol was also perfused for adipose tissue blood flow estimation. Dialysates were collected every 10 min during rest (30 min), exercise at 50% maximal oxygen consumption (120 min), and recovery (30 min) for the measurement of glycerol concentration. During exercise, glycerol increased significantly in both probes. However, no differences in glycerol level and ethanol extraction were observed between the lactate and control probes. These findings suggest that lactate does not impair subcutaneous abdominal adipose tissue mobilization during exercise.
Intrathymic and intrasplenic oxidative stress mediates thymocyte and splenocyte damage in acutely exercised mice
Authors: Azenabor A. A. , Hoffman-Goetz L.
Published: December 2017

Reactive oxygen species may contribute to apoptosis in lymphoid tissues observed after exercise. Thymic and splenic tissues excised from control mice (C) or mice immediately after ( t 0) or 24 h after ( t 24) a run to exhaustion (RTE) were assayed for biochemical indexes of oxidative stress [thymic and splenic membrane lipid peroxides, superoxide dismutase, catalase, plasma uric acid (UA), and ascorbic acid (AA)]. There were significant increases in membrane lipid peroxides in thymus ( P < 0.001) and spleen ( P < 0.001) in acutely exercised mice relative to controls (thymus: C = 2.74 ± 0.80 μM; t 0 = 7.45 ± 0.48 μM; t 24 = 9.44 ±1.41 μM; spleen: C = 0.48 ± 0.22 μM; t 0 = 1.78 ± 0.28 μM; t 24 = 2.81 ± 0.34 μM). The thymic and splenic tissue antioxidant enzymes concentrations of superoxide dismutase and catalase were significantly lower in samples collected at t 0 relative to C and t 24 mice ( P < 0.001). Plasma UA and AA levels were used to assess the impact of the RTE on the peripheral antioxidant pool. There was no significant change in UA levels and a significant reduction in plasma AA concentrations ( P < 0.001); the reduction in plasma AA occurred at t 24 (6.53 ± 1.64 μM) relative to t 0 (13.11 ± 0.71 μM) and C (13.26 ± 1.2 μM). These results suggest that oxidative damage occurs in lymphoid tissues after RTE exercise and that such damage may contribute to lymphocyte damage observed after acute exercise.
Impact of hyperinsulinemia on myosin heavy chain gene regulation
Authors: Houmard Joseph A. , O’Neill D. Sean , Zheng Donghai , Hickey Matthew S. , Dohm G. Lynis
Published: December 2017

The purpose of this study was to determine whether hyperinsulinemia alters myosin heavy chain (MHC) gene expression in human skeletal muscle. A biopsy from the vastus lateralis was obtained in young, lean [age 24.6 ± 1.0 (SE) yr, body fat 11.9 ± 1.9%, body mass index 26.1 ± 1.1 kg/m2; n = 10] men before and after 3 h of hyperinsulinemia (hyperinsulinemic-euglycemic clamp). Muscle was analyzed for mRNA of type I, IIa, and IIx MHC isoforms. Hyperinsulinemia (mean of 1,065.7 ± 9.8 pmol/l during minutes 20 to 180) did not change ( P > 0.05) the mRNA concentration of either the type I MHC or type IIA MHC isoforms. In contrast, type IIX MHC mRNA increased ( P < 0.05) with hyperinsulinemia compared with the fasted condition. These data indicate that hyperinsulinemia rapidly increases type IIx MHC mRNA in human skeletal muscle.
Acute hypoxic pulmonary vasoconstriction in conscious dogs decreases renin and is unaffected by losartan
Authors: Krebs Martin O. , Boemke Willehad , Simon Stephan , Wenz Maieli , Kaczmarczyk Gabriele
Published: December 2017

Acute hypoxic pulmonary vasoconstriction (HPV) may be mediated by vasoactive peptides. We studied eight conscious, chronically tracheostomized dogs kept on a standardized dietary sodium intake. Normoxia (40 min) was followed by hypoxia (40 min, breathing 10% oxygen, arterial oxygen pressures 36 ± 1 Torr) during both control (Con) and losartan experiments (Los; iv infusion of 100 μg ⋅ min−1 ⋅ kg−1losartan). During hypoxia, minute ventilation (by 0.9 l/min in Con, by 1.3 l/min in Los), cardiac output (by 0.36 l/min in Con, by 0.30 l/min in Los), heart rate (by 11 beats/min in Con, by 30 beats/min in Los), pulmonary artery pressure (by 9 mmHg in both protocols), and pulmonary vascular resistance (by 280 and 254 dyn ⋅ s ⋅ cm−5in Con and Los, respectively) increased. Mean arterial pressure and systemic vascular resistance did not change. In Con, PRA decreased from 4.2 ± 0.7 to 2.5 ± 0.5 ng ANG I ⋅ ml−1 ⋅ h−1, and plasma ANG II decreased from 11.9 ± 3.0 to 8.2 ± 2.1 pg/ml. The renin-angiotensin system is inhibited during acute hypoxia despite sympathetic activation. Under these conditions, ANG II AT1-receptor antagonism does not attenuate HPV.
Age and renal prostaglandin inhibition during exercise and heat stress
Authors: Farquhar W. B. , Kenney W. L.
Published: December 2017

Aging is associated with a number of physiological changes that may cause the kidney to rely to a greater extent on vasodilatory PGs for normal functioning. Acute exercise has been shown to cause renal vasoconstriction that may be partially buffered by vasodilatory PGs. To determine the relative importance of renal PGs during exercise in older adults, we compared the renal effects of the PG inhibitor ibuprofen (1.2 g/day for 3 days) vs. a placebo control in a cohort of eight younger (24 ± 2 yr) and eight older (64 ± 2 yr) women during treadmill exercise (∼57% maximal oxygen consumption) in the heat (36°C). This over-the-counter dose of ibuprofen reduced renal PG (i.e., PGE2) excretion by 47% ( P < 0.05). Acute exercise in the heat caused dramatic decreases in glomerular filtration rate, renal blood flow, and sodium excretion in both age groups. PG inhibition was associated with greater decreases in urine production and free water clearance ( P < 0.05). There were no drug-related declines in glomerular filtration rate or renal blood flow. We conclude that PG inhibition has only modest effects on renal function during exercise. Also, the lack of hemodynamic changes with PG inhibition indicates that healthy well-hydrated older women are not in a renal PG-dependent state.
Nitric oxide does not modulate whole body oxygen consumption in anesthetized dogs
Authors: Crystal George J. , Zhou Xiping , Halim Ayman A. , Alam Syed , El-Orbany Mohammad , Salem M. Ramez
Published: December 2017

The effects of the NO synthase inhibitor NG-nitro-l-arginine methyl ester (l-NAME) and the NO donor sodium nitroprusside (SNP) on whole body O2consumption (V˙o2) were assessed in 16 dogs anesthetized with fentanyl or isoflurane. Cardiac output (CO) and mean arterial pressure (MAP) were measured with standard methods and were used to calculate V˙o2and systemic vascular resistance (SVR). Data were obtained in each dog under the following conditions: 1) Control 1, 2) SNP (30 μg ⋅ kg−1⋅ min−1iv) 3) Control 2, 4)l-NAME (10 mg/kg iv), and 5) SNP and adenosine (30 and 600 μg ⋅ kg−1⋅ min−1iv, respectively) after l-NAME. SNP reduced MAP by 29 ± 3% and SVR by 47 ± 3%, while it increased CO by 39 ± 9%.l-NAME had opposite effects; it increased MAP and SVR by 24 ± 4% and 103 ± 11%, respectively, and it decreased CO by 37 ± 3%. Neither agent changedV˙o2from the baseline value of 4.3 ± 0.2 ml ⋅ min−1⋅ kg−1, since the changes in CO were offset by changes in the arteriovenous O2difference. Both SNP and adenosine returned CO to pre-l-NAME values, butV˙o2was unaffected. We conclude that 1) basally released endogenous NO had a tonic systemic vasodilator effect, but it had no influence on V˙o2; 2) SNP did not alterV˙o2before or after inhibition of endogenous NO production; 3) the inability ofl-NAME to increaseV˙o2was not because CO, i.e., O2supply, was reduced below the critical level.
Effects of spaceflight and PEG-IL-2 on rat physiological and immunological responses
Authors: Chapes Stephen K. , Simske Steven J. , Sonnenfeld Gerald , Miller Edwin S. , Zimmerman Robert J.
Published: December 2017

Sprague-Dawley rats were subjected to two 8-day spaceflights on the space shuttle. Rats housed in the National Aeronautics and Space Administration’s animal enclosure were injected (iv or sc) with pegylated interleukin-2 (PEG-IL-2) or a placebo. We tested the hypothesis that PEG-IL-2 would ameliorate some of the effects of spaceflight. We measured body and organ weights; blood cell differentials; plasma corticosterone; colony-forming units (macrophage and granulocyte macrophage); lymphocyte mitogenic, superantigenic, and interferon-γ responses; bone marrow cell and peritoneal macrophage cytokine secretion; and bone strength and mass. Few immunological parameters were affected by spaceflight. However, some spaceflight effects were observed in each flight. Specifically, peritoneal macrophage spontaneous secretion of tumor necrosis factor-α occurred in the first but not in the second flight. A significant monocytopenia and lymphocytopenia were detected in the second but not in the first flight. The second mission produced bone changes more consistent with past spaceflight investigations. PEG-IL-2 did not appear to be beneficial; however, this was mostly due to the lack of spaceflight effects. These studies reflect the difficulty in reproducing experimental models by using current space shuttle conditions.
Assessment of physical activity in older individuals: a doubly labeled water study
Authors: Starling Raymond D. , Matthews Dwight E. , Ades Philip A. , Poehlman Eric T.
Published: December 2017

We compared the accuracy of two physical activity recall questionnaires and a motion detector in 45- to 84-yr-old women ( n = 35) and men ( n = 32), using doubly labeled water (DLW) in conjunction with indirect calorimetry as the criterion measure. Subjects were administered the Yale Physical Activity Survey (YPAS) and Minnesota Leisure Time Physical Activity Questionnaire (LTA). Physical activity energy expenditure was determined over a 10-day period by using a Caltrac uniaxial accelerometer and DLW in conjunction with indirect calorimetry. In older women, Minnesota LTA (386 ± 228 kcal/day) and Caltrac (379 ± 162 kcal/day) underestimated physical activity by ∼55% compared with DLW (873 ± 244 kcal/day). No difference was observed between daily physical activity measured by the YPAS (863 ± 447 kcal/day) and DLW in older women. In older men, Minnesota LTA (459 ± 288 kcal/day) and Caltrac (554 ± 242 kcal/day) underestimated daily physical activity by ∼50–60% compared with DLW (1,211 ± 429 kcal/day). No difference was found between physical activity measured by the YPAS (1,107 ± 612 kcal/day) and DLW in older men. Despite no difference in mean physical activity levels between YPAS and DLW in women and men, Bland and Altman ( Lancet 1: 307–310, 1986) analyses demonstrated poor concordance between DLW and YPAS (i.e., limits of agreement = −1,310–1,518 kcal/day). Our data suggest that the Minnesota LTA recall and Caltrac uniaxial accelerometer may significantly underestimate free-living daily physical activity energy expenditure in older women and men. Although the YPAS compares favorably with DLW on a group basis, its use as a proxy measure of individual daily physical activity energy expenditure may be limited in older women and men.
Increased levels of circulating ICAM-1, VCAM-1, and L-selectin in obstructive sleep apnea syndrome
Authors: Ohga Eijiro , Nagase Takahide , Tomita Tetsuji , Teramoto Shinji , Matsuse Takeshi , Katayama Hirofumi , Ouchi Yasuyoshi
Published: December 2017

Obstructive sleep apnea syndrome (OSAS) may be one of the most important risk factors of cardiovascular disorders, although the exact mechanism remains to be elucidated. In the present study, we hypothesized that OSAS-induced hypoxic stress might be involved in the etiology of cardiovascular disorders by activating adhesion molecules, including intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and L-selectin. To examine this hypothesis, we measured circulating ICAM-1, VCAM-1, and L-selectin levels before and after sleep in OSAS patients and age-matched controls. The circulating ICAM-1, VCAM-1, and L-selectin levels increased in the OSAS patients before sleep compared with the normal subjects (ICAM-1: 392.9 ± 48.5 vs. 201.2 ± 55.0 ng/ml, P < 0.05; VCAM-1: 811.0 ± 87.8 vs. 574.2 ± 42.7 ng/ml, P < 0.05; L-selectin: 1,386.6 ± 77.9 vs. 1,038.8 ± 78.6 ng/ml, P< 0.01, respectively). After sleep, significantly greater levels of ICAM-1 and L-selectin, but not VCAM-1, were observed in the OSAS group. These observations suggest that OSAS-induced hypoxia activates adhesion molecules, resulting in the important risk factor of cardiovascular disorders. Treatment of OSAS can be, therefore, a potential approach to prevention of cardiovascular events.
Influence of nitric oxide on vascular resistance and muscle mechanics during tetanic contractions in situ
Authors: Ameredes Bill T. , Provenzano Mark A.
Published: December 2017

Studies of the effect of nitric oxide (NO) synthesis inhibition were performed in the isometrically contracting blood-perfused canine gastrocnemius-plantaris muscle group. Muscle blood flow (Q˙) was controlled with a pump during continuous NO blockade produced with either 1 mMl-argininosuccinic acid (l-ArgSA) or N G-nitro-l-arginine methyl ester (l-NAME) during repetitive tetanic contractions (50-Hz trains, 200-ms duration, 1/s). PumpQ˙ was set to match maximal spontaneousQ˙ (1.3–1.4 ml ⋅ min−1 ⋅ g−1) measured in prior, brief (3–5 min) control contraction trials in each muscle. Active tension and oxygen uptake were 500–600 g/g and 200–230 μl ⋅ min−1 ⋅ g−1, respectively, under these conditions. Within 3 min ofl-ArgSA infusion, vascular resistance across the muscle (Rv) increased significantly (from ∼100 to 300 peripheral resistance units; P < 0.05), whereas Rv increased to a lesser extent with l-NAME (from ∼100 to 175 peripheral resistance units; P < 0.05). The increase in Rv withl-ArgSA was unchanged by simultaneous infusion of 0.5–10 mMl-arginine but was reduced with 1–3 μg/ml sodium nitroprusside (41–54%). The increase in Rv withl-NAME was reversed with 1 mM ofl-arginine. Increased fatigue occurred with infusion ofl-ArgSA; active tension and intramuscular pressure decreased by 62 and 66%, whereas passive tension and baseline intramuscular pressure increased by 80 and 30%, respectively. These data indicate a possible role for NO in the control of Rv and contractility within the canine gastrocnemius-plantaris muscle during repetitive tetanic contractions.