bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of collateral ventilation in ventilation-perfusion balance
Authors: Kuriyama T. , Latham L. P. , Horwitz L. D. , Reeves J. T. , Wagner W. W.
Published: December 2017

Species with collateral ventilation have an auxiliary respiratory mechanism that could protect them, under certain circumstances, from regional alveolar hypoxia. Species without collateral ventilation may have a greater potential for routinely experiencing regional hypoxia; to maintain ventilation-perfusion balance they would have to rely on pulmonary vasoconstriction. We tested these ideas by ventilating a sublobar region of pig lung (no collateral ventilation) with 13% O2 while the rest of the lung was ventilated with 30% O2. Blood flow, as measured by radioactive microsphere distribution to the sublobar region, was reduced 50% during hypoxia. The hypoxia-induced vasoconstriction effectively defended arterial PO2. When a vasodilator was infused, regional blood flow increased to control levels; shunt fraction rose, and arterial PO2 fell. In dogs (collateral ventilation present) the same experimental maneuvers had no significant effect on regional end-tidal gases or on microsphere distribution, indicating that collateral ventilation was able to maintain ventilation-perfusion balance. When regional hypoxia was created in dogs by overcoming collateral ventilation with slightly positive airway pressure in the sublobar region, the dog acted like the pig and used hypoxic vasoconstriction to shift approximately 30% of the blood flow away from the hypoxic alveoli.
Performance of hypothermic isolated rat heart at various levels of blood acid-base status
Authors: Sinet M. , Muffat-Joly M. , Henzel D. , Renault G. , Pocidalo J. J.
Published: December 2017

The effects of respiratory-induced pH variation on mechanical function and myocardial oxygenation of isolated, blood-perfused working rat hearts were studied in hypothermia (26 degrees C) and compared with control values (37 degrees C). In these experiments, the change of plasma pH during hypothermia was parallel to the change in pH of neutral water. At 37 degrees C, pH was varied from 7.15 to 7.62; heart rate increased with pH, both cardiac output and external work remaining unaltered. An increase in pH induced a decrease in coronary flow and an increase in the O2 arteriovenous difference. In hypothermia, hemodynamic performance and myocardial O2 consumption decreased proportionately with no change in cardiac efficiency. At 26 degrees C, the cardiac capacity to react to acid-base variations (pH from 7.34 to 7.86) was preserved, i.e., heart rate increased with pH. As at 37 degrees C, regulation of both coronary flow and myocardial oxygenation was maintained. The present data suggest that the myocardial function of a working isolated rat heart undergoing hypothermia was also preserved. Moderate variations in extracellular acid-base status during hypothermia did not impair either myocardial function or the O2 supply-to-demand ratio.
Role of vagal C-fiber afferents in respiratory response to hypercapnia
Authors: Russell N. J. , Raybould H. E. , Trenchard D.
Published: December 2017

The respiratory response to hypercapnia has been investigated in 10 anesthetized rabbits by use of a rebreathing technique. The responses were obtained in three situations: with one intact vagus nerve (control), during differential block of conduction, and after vagotomy. Differential block was achieved using anodal hyperpolarization by application of a direct current to the cervical vagus nerve. Great care was taken during the differential block to establish that all impulse conduction in myelinated fibers of the cervical vagus nerve was abolished but that the nonmyelinated fibers conducted normally. Additionally, in five more rabbits the nature of the differential block was confirmed from single-fiber recordings of activity in both myelinated and nonmyelinated fibers. The same increase in tidal volume in response to hypercapnia was present in all three experimental situations, indicating that it was not vagally mediated. The increase in frequency in response to hypercapnia in the control state was abolished by vagotomy but preserved when only the nonmyelinated fibers were functioning during the differential block. This increased frequency response, attributable to decreases in both inspiratory and expiratory durations, was usually enhanced during the differential block, despite the slower deeper pattern of breathing attributed to loss of activity in myelinated fibers. The implications of this reflex increase in frequency in response to hypercapnia, mediated by nonmyelinated vagal endings in the lung, are discussed.
Potentiation of surfactant release in fetal lung by thyroid hormone action
Authors: Das D. K. , Ayromlooi J. , Bandyopadhyay D. , Bandyopadhyay S. , Neogi A. , Steinberg H.
Published: December 2017

Thyroid hormone has been shown to accelerate fetal lung development, but the mechanisms by which this hormone acts are yet unknown. Since this hormone may act indirectly by potentiating the action of endogenous catecholamines, we studied this mechanism by measuring beta-adrenergic receptors in fetal lung. Fetal rabbits at 27 days of gestation were treated with triiodothyronine (T3), 100 micrograms/100 g, in the presence and absence of propranolol, 200 micrograms/100 g, or actinomycin D, 20 micrograms/100 g. Fetuses were killed by decapitation either after 4 or 24 h of T3 treatment. The beta-adrenergic antagonist l-[3H]dihydroalprenolol was used to directly estimate the number and affinity of beta-adrenergic receptor in lung membranes. T3 increased the number of beta-adrenergic receptors in fetal lung, but the affinity of binding did not change. The enhancement of binding capacity after 4 h of T3 treatment was not inhibited by actinomycin D. However, 24-h T3-mediated stimulation was partially blocked by actinomycin D. In addition, T3 stimulated the catecholamine content, adenylate cyclase activity, and adenosine 3′,5′-cyclic monophosphate content of lung. T3 increased the lecithin-to-sphingomyelin ratio, phosphatidylglycerol, and disaturated phosphatidylcholine content of the pulmonary lavage fluid. These parameters were completely inhibited by propranolol after 4 h and partially inhibited by actinomycin D after 24 h. Thus thyroid hormone enhances lung maturation by increasing the number of beta-adrenergic receptors in fetal lung.
Role of interstitium in clearance of alveolar fluid in normal and injured lungs
Authors: Havill A. M. , Gee M. H.
Published: December 2017

We investigated the contribution of the pulmonary interstitial space to the removal of alveolar fluid and solute. We prepared anesthetized sheep for the collection of lung lymph. A balloon-tipped catheter was advanced into a lower lung lobe, and 20 ml Ringer lactate solution (RL) were instilled in one group. Other groups received 20 ml RL with 4 mg/ml Evans blue dye (EB) or 10 micrograms/kg phorbolmyristate acetate (PMA) or both. Instillation of 20 ml RL and EB resulted in an increase in lymph flow over RL alone, presumably by an osmotic mechanism. After 4 h, small perivascular fluid cuffs, whichcontained little EB, were present, and 1.9% of the instilled EB was removed by the lymphatics. An average of 9.2 ml of excess water remained in the lung. Instillation of RL, EB, and PMA resulted in an increase in lymph flow and large perivascular fluid cuffs, which contained large amounts of EB. Lymphatic removal of the instilled EB accounted for 1.2% of the total amount instilled. An average of 19.1 ml water was present in the lung after 4 h. We conclude that alveolar instillation of PMA results in epithelial and endothelial membrane injury and that when lung injury is present interstitial fluid reservoirs may be important sites of alveolar fluid accumulation and important routes of fluid removal from the air space.
Cardiac hypertrophy and function in master endurance runners and sprinters
Authors: Child J. S. , Barnard R. J. , Taw R. L.
Published: December 2017

Cardiac enlargement with increased left ventricular mass is a recognized adaptive response to intensive physical conditioning. There have been few reports regarding cardiac hypertrophy and function in the middle-aged or older athlete. Accordingly, we studied 9 male Masters Track endurance distance runners (E) (mean age 54 yr) and 13 male Masters Track sprinters (S) (mean age 47 yr) by M-mode echocardiography, systolic time intervals, and maximal treadmill stress testing with direct measurement of maximal O2 consumption (VO2max). Left ventricular mass (LVM) index for E (154.0 +/- 27.4 g/m2; mean +/- SD) was greater than for S (127.1 +/- 15.9 g/m2) (P less than 0.05). LVM index was greater for both groups compared with age-range matched controls (N = 111.7 +/- 23.8 g/m2) (P less than 0.02). VO2max was greater in E (54 +/- 12 ml X kg-1 X min-1) than S (47 +/- 7 ml X kg-1 X min-1) (P less than 0.05) despite the younger age of S (P less than 0.05); both E and S had greater VO2max than predicted for nonathletic males of equivalent age. There was no significant linear relationship for LVM index and VO2max in the athletes. Left ventricular function at rest was normal. Thus, in well-trained older (greater than or equal to 40 yr) male distance runners and sprinters VO2max and LVM index are greater in E than S, and each greater than in controls, resting left ventricular function is normal, as judged by fractional shortening and systolic time intervals, and the degree of hypertrophy (LVM index) does not directly correlate with aerobic capacity (VO2max).
Effects of vascular pressure on the pulmonary microvasculature in isolated dog lungs
Authors: Rippe B. , Townsley M. , Thigpen J. , Parker J. C. , Korthuis R. J. , Taylor A. E.
Published: December 2017

The effects of short periods of high pulmonary vascular pressures on the filtration characteristics of the lung's microcirculation have been studied in isolated dog lungs. When left atrial pressures (Pla) were less than 30 cmH2O, the capillary filtration coefficient (Kf,c) was not different from that of controls (0.192 +/- 0.009 ml X min-1 X cmH2O–1 X 100 g-1). In 17 of 23 observations, where Pla exceeded 55 cmH2O, Kf,c was at least 1.5 times control. In 10 of 13 lungs, Kf,c returned to control values within 2 h after the Pla increase. However, in the other three experiments, Kf,c did not return to control values. These findings indicate that the filtration coefficient of pulmonary microvessels increases at high left atrial pressures (greater than 55 cmH2O) and may represent either a “stretching” of existing pores or opening of a few large pores.
Changes in lung, airway, and chest wall function in boys and girls between 8 and 12 yr
Authors: Hibbert M. E. , Couriel J. M. , Landau L. I.
Published: December 2017

Maximum expiratory flows, maximum inspiratory and expiratory pressures, and lung volumes were measured in 248 8-yr-old and 215 12-yr-old healthy school children. Eight-year-old girls had smaller total lung capacity but higher volume-corrected expiratory flows than boys. Maximum expiratory flow and total lung capacity increased more in girls than in boys between 8 and 12 yr. Girls had a greater increase in residual volume (0.23 liter for girls, 0.16 liter for boys) as well as lower maximum expiratory and inspiratory pressures (P less than 0.001). Girls have smaller lung volumes than boys, so one would expect smaller airways in girls, but girls generate greater flows, indicating that their airways are possibly wider than those of boys. There is also evidence of unequal growth of the airways and air spaces between 8 and 12 yr. Chest wall development appears less in girls than boys and the difference becomes more marked at 12 yr.
Coronary vascular response to adrenergic stimulation in exercise-conditioned dogs
Authors: Gwirtz P. A. , Stone H. L.
Published: December 2017

The present study was designed to determine whether daily exercise alters adrenergic and muscarinic neural control of coronary blood flow during resting and exercising conditions in the conscious dog. Mean left circumflex artery blood flow (CBF), mean coronary blood pressure, and heart rate were measured during resting conditions (55 +/- 9 ml/min, 108 +/- 6 mmHg, and 93 +/- 2 beats/min, respectively) and during submaximal exercise (85 +/- 9 ml/min, 108 +/- 7 mmHg, and 210 +/- 15 beats/min). Injection of phentolamine into the left circumflex coronary artery during treadmill exercise resulted in a 10 +/- 1% increase in CBF before training (untrained, UT) and a 21 +/- 6% increase after 4–5 wk of daily exercise (partially trained, PT) (P less than 0.02 UT vs. PT). Intracoronary atenolol or propranolol caused a 15 +/- 6% reduction in CBF during exercise in dogs before and after PT. While the dogs were lying quietly at rest intracoronary injections of norepinephrine initially increased CBF 85%, followed by a prolonged 19 +/- 9% decrease in CBF. CBF decreased 16 +/- 3% after intracoronary injection of phenylephrine. After PT the coronary vasoconstriction following norepinephrine and phenylephrine injections was significantly potentiated (31 +/- 6 and 35 +/- 4%, respectively). These data suggest that exercise training caused significant changes in the coronary vascular response to alpha-receptor stimulation so that an alteration in the neural control of the coronary circulation occurred.
Effects of addition of nitrogen during rapid compression of baboons
Authors: Rostain J. C. , Dumas J. C. , Gardette B. , Imbert J. P. , Lemaire C.
Published: December 2017

A series of dives was carried out to depths of 600 and 800 m seawater (msw) using baboons (Papio papio). Experiments were designed to study the effects of compression and the use of a He-N2–O2 gas mixture on high-pressure nervous syndrome (HPNS). When N2 was added to the He-O2 mixture at the beginning of a linear compression (200 msw/h), the symptoms associated with HPNS were still seen; in addition, the electroencephalogram (EEG) changes were more severe than those seen without N2. By use of an identical mixture, a 2-h exponential compression to 600 msw produced less severe signs of HPNS than the nonexponential profile. By use of a 2-h exponential compression to 600 msw and with addition of N2 at the end of compression, the HPNS that had been started under the He-O2 mixture decreased. Progressive addition of N2 during compression reduced the behavioral signs of HPNS without further EEG changes. These results show that the action of N2 is more complex than can be explained by a simple narcotic pressure antagonism and that the HPNS differed according to the gas mixture used.
Heat acclimation in cystic fibrosis
Authors: Orenstein D. M. , Henke K. G. , Green C. G.
Published: December 2017

Cystic fibrosis (CF) patients may be at risk for heat illness because of their high sweat chloride and sodium concentrations ([Cl-], [Na+]), but it is not known if they can heat acclimate. We studied 10 CF patients and 10 normal controls on 8 consecutive days of cycle exercise in the heat (37 degrees C dry bulb, 24–29 degrees C wet bulb). Both groups acclimated. CF peak rectal temperature (Tre) was 38.2 +/- 0.3 degrees C on day 1 and 37.8 +/- 0.4 degrees C on day 8 (P less than .005), and peak heart rates (HR) were 151 +/- 24 beats/min on day 1 and 136 +/- 22 beats/min on day 8 (P less than 0.025). Control temperature (T) and HR were similar. Controls decreased sweat [Cl-] from 37.2 +/- 14.6 meq/l on day 1 and to 24.9 +/- 10.6 meq/l on day 8 (P less than 0.005). CF sweat [Cl-] was significantly higher and did not change with acclimation (day 1, 71.1 +/- 20.9 meq/l; day 8, 72.6 +/- 21.6 meq/l, NS). Before and after acclimation, exercise-heat sessions resulted in significant decreases in serum [Cl-] in CF patients (104.5 +/- 4.6 to 101.3 +/- 4.4 meq/l on day 1, P less than 0.05; 103.5 +/- 5.1 to 99.7 +/- 4.2 meq/l on day 8, P less than 0.025) but not in controls. Serum [Cl-] was significantly lower in CF than control subjects at every measurement. Both groups had significant renal Na+ conservation after exercise on both days.(ABSTRACT TRUNCATED AT 250 WORDS)
Acute increase in anastomotic bronchial blood flow after pulmonary arterial obstruction
Authors: Jindal S. K. , Lakshminarayan S. , Kirk W. , Butler J.
Published: December 2017

We examined the acute changes in anastomotic bronchial blood flow (Qbr) serially for the 1st h after pulmonary arterial obstruction and subsequent reperfusion. We isolated and perfused the pulmonary circulation of the otherwise intact left lower lobe (LLL) with autologous blood in the widely opened chest of anesthetized dogs. Qbr was measured from the amount of blood overflowing from the closed pulmonary vascular circuit and the changes in the lobe weight. The right lung and the test lobe (LLL) were ventilated independently. The LLL, which was in zone 2 (mean pulmonary arterial pressure = 14.8 cm H2O, pulmonary venous pressure = 0, alveolar pressure = 5–15 cmH2O), was weighed continuously. The systemic blood pressure, gases, and acid-base status were kept constant. In control dogs without pulmonary arterial obstruction, the Qbr did not change for 2 h. Five minutes after pulmonary arterial obstruction, there was already a marked increase in Qbr, which then continued to increase for 1 h. After reperfusion, Qbr decreased. The increase in Qbr was greater after complete lobar than sublobar pulmonary arterial obstruction. It was unaltered when the downstream pulmonary venous pressure was increased to match the preobstruction pulmonary microvascular pressure. Thus, in zone 2, reduction in downstream pressure was not responsible for the increase in Qbr; neither was the decrease in alveolar PCO2, since ventilating the lobe with 10% CO2 instead of air did not change the Qbr. These findings suggest that there is an acute increase in Qbr after pulmonary arterial obstruction and that is not due to downstream pressure or local PCO2 changes.
Exercise-thermoregulatory stress and increased plasma beta-endorphin/beta-lipotropin in humans
Authors: Kelso T. B. , Herbert W. G. , Gwazdauskas F. C. , Goss F. L. , Hess J. L.
Published: December 2017

Six adult male volunteers of similar body composition and physical fitness were tested to determine plasma immunoreactive beta-endorphin/beta-lipotropin (beta-EN/beta-LPH) response under three exercise-thermoregulatory stress conditions. The experimental protocol consisted of 120 min of stationary upright cycling at 50% VO2max under neutral (24 degrees C, 50% rh)-euhydration (NE), hot (35 degrees C, 50% RH)-euhydration (HE), and hot-dehydration (HD) environmental conditions. beta-EN/beta-LPH was calculated by radioimmunoassay at -30-min, 0-min, and 15-min intervals thereafter. Change in plasma volume (delta PV) was measured to determine its effect on beta-EN/beta-LPH concentration. Preexercise beta-EN/beta-LPH levels averaged 23.7 +/- 2.6 pg X ml-1 in all conditions. The greatest beta-EN/beta-LPH response occurred at 105 min in HD conditions when levels rose to 43.2 +/- 6.9 pg X ml-1. Exercise in HD and HE conditions resulted in significantly (P less than 0.05) elevated beta-EN/beta-LPH above levels observed in NE. delta PV did not account for more than 10% of beta-EN/beta-LPH changes at any time interval. The beta-EN/beta-LPH response pattern closely paralleled rectal temperature changes in all conditions. These data suggest that conditions of increasing exercise thermoregulatory stress are associated with increasing peripheral beta-endorphin concentration.
Effect of respiratory apparatus on respiration
Authors: Weissman C. , Askanazi J. , Milic-Emili J. , Kinney J. M.
Published: December 2017

A mouthpiece plus noseclip (MP & NC) is frequently used in performing measurements of breathing patterns. Although the effects the apparatus exerts on breathing patterns have been studied, the mechanism of the changes it causes remains unclear. The current study examines the effects on respiratory patterns of a standard (17-mm-diam) MP & NC during room air (RA) breathing and the administration of 2 and 4% CO2 in normal volunteers and in patients 2–4 days after abdominal operation. When compared with values obtained with a noninvasive canopy system, the MP & NC induced increases in minute ventilation (VE), tidal volume (VT), and mean inspiratory flow (VT/TI), but not frequency (f) or inspiratory duty cycle, during both RA and CO2 administration. The percentage increase in VE, VT, and VT/TI caused by the MP & NC decreased as the concentration of CO2 increased. During RA breathing, the application of noseclip alone resulted in a decrease in f and an increase in VT, but VE and VT/TI were unchanged. The changes were attenuated during the administration of 2 and 4% CO2. Reducing the diameter of the mouthpiece to 9 mm abolished the alterations in breathing pattern observed with the larger (17-mm) diameter MP.
Effect of varied lactate levels on bicycle ergometer performance
Authors: Hogan M. C. , Welch H. G.
Published: December 2017

Six subjects exercised on the bicycle ergometer on three separate occasions. Each of the three tests that each subject performed consisted of a 5-min work period [95% maximal O2 uptake (VO2max)], followed by a 4-min rest period, and then a performance task to exhaustion (90% VO2max). Each test varied only in the inspired O2 fraction (FIO2) (16, 21, or 60% O2 in N2) that was breathed during the initial 5-min work period. The remainder of each test was carried out with 21% O2. Total power output was the same for each subject during the initial 5-min work bout. However, the varied FIO2 breathed during this initial work period resulted in significantly different mean blood lactate (and H+) concentrations at the start of the performance task (P less than 0.05). Mean performance time was significantly greater (P = 0.04) after the hyperoxic treatment (14.8 min) when compared with the hypoxic (9.1 min). Mean blood lactate and H+ levels at exhaustion were not significantly different. These data demonstrate that when various blood (or muscle) lactate and H+ levels were induced on different occasions by leg muscles, the subsequent performance of those muscles was significantly affected.
Glucocorticoid-induced cardiac hypertrophy: additive effects of exercise
Authors: Kurowski T. T. , Chatterton R. T. , Hickson R. C.
Published: December 2017

Female rats were divided into a sedentary control and an exercise group that was trained by treadmill running 100 min/day for 13–15 wk. During the last 12 days of training, they were further subdivided into trained and sedentary groups that received either daily subcutaneous injections of cortisone acetate (CA) (100 mg/kg body wt) or the vehicle, 1% (wt/vol) carboxymethylcellulose. As a result of the exercise program, ventricular weights were 15% (P less than 0.01) heavier in the vehicle-treated runners than in the vehicle-treated controls, but there were no changes in cardiac androgen (methyltrienolone, R1881) or glucocorticoid (dexamethasone, DEX) cytosol-specific binding concentrations. Body weights were decreased by 11–12% in both CA-treated groups. Ventricular weights of the CA-treated controls were 11% (P less than 0.01) heavier than the weights of the vehicle-treated controls. The combination of exercise and glucocorticoid treatments resulted in ventricular weights that were 21% heavier than those in the vehicle-treated controls and 8 and 5% (P less than 0.05) greater than those resulting from CA and endurance training individually. Both R1881 and DEX binding were decreased in hearts of CA-treated animals from those of vehicle-treated animals, and exercise did not modify this response. These results show that glucocorticoid treatment can induce cardiac enlargement, and the combination of glucocorticoids and exercise can have additive effects on the growth, yet their mechanisms appear different.
Oxygen consumption and hemodynamic responses during graded treadmill exercise in the dog
Authors: Ordway G. A. , Floyd D. L. , Longhurst J. C. , Mitchell J. H.
Published: December 2017

A description is given of a technique that provides a relatively simple means by which O2 consumption and hemodynamic variables can be measured in exercising dogs. We used a multistage submaximal treadmill test to study the responses of 10 foxhounds to dynamic exercise. They were also studied during maximal treadmill exercise. O2 consumption increased from 16.3 +/- 1.7 ml O2 X min-1 X kg-1 at rest to 92.9 +/- 9.7 ml O2 X min-1 X kg-1 at a work load of 6.4 km/h, 20% grade and to 111.9 +/- 9.6 ml O2 X min-1 X kg-1 during maximal exercise. Cardiac output (CO) increased from 6.11 +/- 0.45 l/min at rest to 16.91 +/- 1.46 and 17.66 +/- 0.60 l/min at 6.4 km/h, 20% grade and maximal exercise, respectively. Arteriovenous O2 difference increased from 5.8 +/- 0.3 vol% at rest to 12.0 +/- 0.4 and 13.2 +/- 0.7 vol% at 6.4 km/h, 20% grade and maximal exercise, respectively. Heart rate (HR) increased from 116 +/- 7 beats/min at rest to 250 +/- 8 beats/min at 6.4 km/h, 20% grade and to 278 +/- 6 beats/min during maximal exercise. O2 uptake, CO, and arteriovenous O2 difference increased with the onset of exercise, appeared to level at lower work intensities (6.4 km/h, 4 and 8% grade), and increased significantly at each of the higher work intensities (6.4 km/h, 12, 16, and 20% grade). Additionally, we observed linear relationships between O2 consumption and HR (HR = 1.35 X VO2 + 120.5; r = 0.87; P less than 0.001) and between O2 consumption and CO (CO = 5.91 X VO2 + 216.6; r = 0.96; P less than 0.001). Further, the linear relationship between O2 consumption and CO demonstrated in the present study is similar to that observed in humans.
Physiological responses to prolonged bed rest and fluid immersion in humans
Authors: Greenleaf J. E.
Published: December 2017

Rest in bed and immersion in water have been used for centuries by physicians and healers in treating injury and disease. The qualitative similarity of acute and chronic responses to bed rest, immersion, and weightlessness has sparked renewed interest in and a resultant greater understanding of the mechanisms of disuse deconditioning. Some combination of changes in hydrostatic pressure, reduced total metabolism (exercise), compression force on weight-bearing bones, as well as psychological factors associated with prolonged confinement in a new environment probably comprise the major input stimuli for the adaptive responses. Virtually every physiological system is affected. Early responses involve the fluid, electrolyte, and blood pressure control systems with significant muscular atrophy and decreases in bone density occurring over weeks and months. Much effort has been expended to describe the various responses to bed rest and immersion with understandably less effort devoted to research during weightlessness. Future research should be directed mainly toward an understanding of the mechanisms of these adaptive responses. Additional work is especially needed to elucidate the effects of deconditioning on drug metabolism, functioning of the immune system, carbohydrate metabolism, protein and peptide metabolism in muscle, and calcium metabolism as it affects integrity of bone.
Soft palate and oronasal breathing in humans
Authors: Rodenstein D. O. , Stanescu D. C.
Published: December 2017

In 20 naive patients without respiratory impairment, we investigated the ability of the soft palate to direct airflow during breathing. Patients were connected to a spirometer, without noseclip. No instructions were given on the breathing route. During quiet respiration, 15 patients breathed solely through the nose, despite an open mouth. During forced vital capacity (FVC) maneuvers, 19 patients expired exclusively through the mouth. When specifically asked to breathe quietly through the mouth, pure nasal breathing was no longer observed. Tidal volume (VT) or FVC were comparable when patients were asked to breathe through the mouth, with or without noseclip: 0.67 +/- 0.46 vs. 0.60 +/- 0.21 liter for VT (mean +/- SD); 4.05 +/- 0.65 vs. 4.18 +/- 0.70 liters for FVC. In eight separate healthy volunteers, the soft palate was shown by fluoroscopy to close the oropharyngeal isthmus during quiet breathing (resulting in pure nasal breathing) and to close the nasopharynx during FVC efforts (resulting in mouth breathing). During oronasal breathing, the soft palate lay in between the tongue and the posterior pharyngeal wall. These data suggest that when both mouth and nose are open, the soft palate is responsible for the partitioning of oronasal flow.
Factors affecting massive postmortem bronchoconstriction in guinea pig lungs
Authors: Lai Y. L. , Lamm W. J. , Hildebrandt J.
Published: December 2017

To examine endogenous factors affecting the development of the massive bronchoconstriction in the postmortem guinea pig lung, 58 anesthetized open-chest animals were divided into three groups: 1) exsanguination only (n = 13), 2) pulmonary perfusion with 5% dextran and 1% bovine serum albumin (BSA) in Tyrode's solution (Ca2+ perfusate) (n = 21), and 3) pulmonary perfusion with 5% dextran and 1% BSA in saline (Ca2+-free perfusate) (n = 24). These groups were further divided into several subgroups according to treatments: 1) substance P depletion by chronic administration of capsaicin, 2) acute capsaicin treatment to release substance P, 3) dazoxiben treatment to block endogenous synthesis of thromboxane A2, 4) diethylcarbamazine treatment to eliminate leukotriene (LT) synthesis, and 5) FPL 55712 treatment to antagonize actions of LT. Vital capacity from the deflation pressure-volume (PV) curve of the lung was used as the indicator of bronchoconstriction. Most PV curves were performed for 30 min following exsanguination or artificial perfusion. Ca2+-free perfusate enhanced the airway spasm at 5–10 min, but the spasm disappeared gradually after 10 min. Substance P depletion significantly decreased (P less than 0.01) the bronchial constriction at 20–30 min, whereas substance P release induced severe airway spasm (P less than 0.01) during the entire study. In addition, FPL 55712 reduced the bronchospasm (P less than 0.05) in Ca2+ perfusate at 30 min. Thus Ca2+ and several endogenous mediators may be involved with the airway spasm of the postmortem guinea pig lung.
Scaling of added loads to breathing: magnitude estimation vs. handgrip matching
Authors: Muza S. R. , Zechman F. W.
Published: December 2017

Six healthy male adults were studied at five levels of suprathreshold added resistance (delta R) applied three times to inspiration in a random sequence. Subjects squeezed an isometric handgrip dynamometer coincident with the breath to express the perceived magnitude of the load and also gave a numerical estimate after completing the loaded inspiration. Peak mouth pressure, grip deflection, and numerical estimate were analyzed to derive the exponents for Stevens' power law. The mean exponent and correlation coefficient obtained from numerical estimates were 1.11 +/- 0.16 and 0.94 +/- 0.04, respectively, while the exponent and correlation coefficient simultaneously obtained from handgrip matching was 0.73 +/- 0.10 and 0.91 +/- 0.05, respectively. Multiplying each subject's exponent obtained from handgrip matching by 1.7 yields a mean equated exponent of 1.23 +/- 0.17. The equated exponents were not statistically different (P greater than 0.05) from the exponents derived from numerical estimates. These results suggest that the use of cross-modality (handgrip) matching provides a reliable method for obtaining psychophysical magnitude functions of respiratory sensations and that exponents obtained using either technique can be equated for comparison.
Effects of sleep state on ventilatory acclimatization to hypoxia in humans
Authors: Berssenbrugge A. D. , Dempsey J. A. , Skatrud J. B.
Published: December 2017

We assessed the influence of sleep state on ventilatory acclimatization to hypoxia. Ventilation, arterial O2 saturation (SaO2), and arterial acid-base status were monitored in healthy adult males during wakefulness, nonrapid-eye-movement (NREM) sleep, and rapid-eye-movement (REM) sleep in normoxia [barometric pressure (PB) = 740 Torr] and over 4 continuous days of hypobaric hypoxia (PB = 455 Torr). The relative hypoventilation observed during sleep compared with wakefulness in normoxia was also observed during all stages of hypoxic acclimatization. The characteristic time-dependent changes associated with acclimatization to chronic hypoxia were similar during wakefulness and all sleep states: 1) arterial CO2 partial pressure (PaCO2) decreased 27–31% by night 4 with approximately half of this fall occurring acutely (0.3–3 h hypoxia); 2) minute ventilation increased progressively with duration of hypoxic exposure including increased levels of hyperventilation throughout the initial night of sleep in hypoxia; 3) SaO2 was lowest acutely and gradually increased coincident with the progressive hyperventilation; and 4) pHa increased acutely and remained unchanged despite additional hyperventilation due to a compensatory reduction in [HCO3-]a. In addition, in the acclimatized subject hyperventilation persisted following acute restoration of normoxia, and this continued hyperventilation was similar in magnitude during both wakefulness and NREM sleep. These results indicate that suprapontine influences on ventilatory control associated with the state of wakefulness are not required in the process of ventilatory acclimatization to chronic hypoxia.
ECoG and breathing activity in fetal lambs after undercut of cerebral cortex
Authors: Ioffe S. , Jansen A. H. , Chernick V.
Published: December 2017

Reduction of cortical inhibition has been suggested as a possible mechanism for the transition from episodic fetal to continuous postnatal breathing. Twelve fetal lambs were chronically decorticated at 112–115 days gestation. Lateral rectus, neck, and diaphragmatic electromyogram (EMG), electrocorticogram (ECoG), and tracheal and arterial blood pressure were monitored after allowing 3 days for recovery. The fetal lambs were studied for 4–28 days in 2- to 4-h sessions/day. There were no episodes of low-voltage high-frequency ECoG activity. The mean duration (+/- SD) of rapid eye movements (REM) measured by lateral rectus EMG [11 +/- 7.9 min and periods of tonic activity or silence [non-REM (NREM)], 14 +/- 7.4 min] in decorticated fetuses were not statistically different from REM (12 +/- 5.1 min) and NREM (15 +/- 6.8 min) sleep periods in intact fetuses. After decortication, the percentage of time (+/- SD) occupied by different states were phasic diaphragmatic EMG activity 36 +/- 7.8%, tonic diaphragmatic EMG 21 +/- 8.6%, and diaphragmatic silence 43 +/- 14.2%. Phasic diaphragmatic EMG activity occurred together with REM, the latter being present 45 +/- 3.7% of the time. Despite decortication, between 115 and 125 days gestation ECoG changed from a trace alternans to a high-voltage low-frequency pattern. We conclude that the cerebral cortex is not responsible for apnea during fetal life. In addition, these data suggest that the cerebral cortex may normally be the source of ECoG synchrony.
Mechanism of substance P-induced bronchoconstriction in maturing rabbit
Authors: Grunstein M. M. , Tanaka D. T. , Grunstein J. S.
Published: December 2017

The maturational effects of substance P (SP) on airway function were quantitatively assessed in 30 anesthetized tracheotomized rabbits ranging in age from 2 to 29 days. Following paralysis, during mechanical ventilation with 100% O2 in a body plethysmograph, respiratory resistance (Rrs) and dynamic compliance (Cdyn) were continuously monitored. Noncumulative systemic infusions of SP (0.001–5.0 micrograms/g) produced dose-dependent decreases in pulmonary conductance (Grs), i.e., 1/Rrs, and Cdyn. The dose of SP producing a 50% decrease in Cdyn (PD50-Cdyn) significantly increased as a function of age indicating a diminution in airway sensitivity to SP. Bilateral cervical vagotomy and ganglionic blockade with hexamethonium had no effect on the airway response to SP. On the other hand, the response was significantly reduced following atropine sulfate infusion (2 mg/kg), suggesting a peripheral cholinergic contribution located distal to the airway parasympathetic ganglia. The magnitude of this cholinergic contribution increased as a function of age. Unlike atropine, antagonists to histamine and 5-hydroxytryptamine had no effect on the airway response to SP, however, the response was inhibited following infusion of the SP antagonist, D-Pro2,D-Trp7,9-SP. These findings indicate that the airway response to SP is age-related and mediated by binding of the agonist to airway smooth muscle coupled with an accelerated release of acetylcholine at the airway neuromuscular junction.
Cigarette smoke-induced bronchoconstriction in dogs: vagal and extravagal mechanisms
Authors: Hartiala J. , Mapp C. , Mitchell R. A. , Shields R. L. , Gold W. M.
Published: December 2017

We reassessed the severity of cigarette smoke-induced bronchoconstriction and the mechanisms involved in anesthetized dogs. To evaluate the severity of smoke-induced bronchoconstriction, we measured airway pressure and airflow resistance (Rrs, forced oscillation method). We studied the mechanisms in other dogs by measuring airway pressure, central airway smooth muscle tone in tracheal segments in situ, and respiratory center drive by monitoring phrenic motor nerve output, including the role of vagal and extravagal nerves vs. the role of blood-borne materials during inhalation of cigarette smoke. Rrs increased more than fourfold with smoke from one cigarette delivered in two tidal volumes. About half the airway response was due to local effects of smoke in the lungs. The remainder was due to stimulation of the respiratory center, which activated vagal motor efferents to the airway smooth muscle. Of this central stimulation, about half was due to blood-borne materials and the rest to vagal pulmonary afferents from the lungs. We conclude that inhalation of cigarette smoke in dogs causes severe bronchoconstriction which is mediated mainly by extravagal mechanisms.
Estimation of rat thermoregulatory ability based on body temperature response to heat
Authors: Furuyama F. , Ohara K. , Ota A.
Published: December 2017

A new simple but general estimation method for survival time in a hot environment is presented in this study. Even in heat-tolerant rats showing a triphasic heat response, an accurate estimation of survival time (ST) is possible. Rat groups, which included some heat-tolerant individuals, were exposed to 42.5 degrees C, 40% rh. Colonic temperature (Tco) was measured continuously by copper-constantan thermocouple. The ST (Y) of male and female rats were expressed as a linear function of time (X) until the Tco of 42.5 degrees C was reached: Y = 0.976X + 30.6 and Y = 0.968X + 31.6, respectively. A Tco of 42.5 degrees C at rest was just below the maximum survivable body temperature and above the steady-state equilibrium Tco levels during the second phase of the triphasic heat-response curve. Heat-tolerant individuals showed lower equilibrium temperatures than heat-intolerant rats. All 140 rats survived the Tco of 42.5 degrees C and lived for more than 8 wk, thus enabling them to be used for future experiments on thermoregulation. The heat survivors were able to reproduce, and their genetically controlled offspring could be used for thermoregulatory experiments.
Evaluation of a microprocessor-controlled exercise testing system
Authors: Jones N. L.
Published: December 2017

We evaluated a new exercise-testing system (Beckman Horizon MMC), incorporating a microprocessor that controls the acquisition of data, corrects for time delays, applies calibration factors, ensures quality control, and presents results in a variety of formats. Precision of measurements of ventilation (VE) and mixed expired gas concentrations was high. In steady-state exercise (n = 100) VO2 was measured with a precision (+/- SD) of 66 ml/min (4.3%), (r = 0.991); there was a small (4.62%) systematic underestimation of VCO2, but precision was comparable with VO2, with SD being 67 ml/min (4.55%) (r = 0.993). Good agreement was obtained between measurements made in progressive incremental exercise in healthy subjects with correlation coefficients of 0.997 for VE, 0.995 for VO2, and 0.994 for VCO2. Agreement in patients with cardiorespiratory disorders (n = 10) was similar, except in three patients in whom a variable pattern of breathing limited strict comparisons. Comparison with a breath-by-breath analysis system (n = 5) showed that rapid changes in VE, VCO2, and VO2 were followed accurately; the half time for a change in VO2 was not systematically different between the two systems (SD, 3.34 s, r = 0.951). The incorporation of microprocessor-controlled calibration procedures, which are simple to carry out frequently, was judged to be an important feature of this system.
Decrease in functional residual capacity during sleep in normal humans
Authors: Hudgel D. W. , Devadatta P.
Published: December 2017

A decrease in functional residual capacity (FRC) during sleep could result in worsening of ventilation distribution contributing to sleep hypoxemia. Therefore the purpose of this study was to determine whether FRC does decrease and to what extent it decreases in normal humans during sleep. Using helium dilution in a closed system we measured FRC in 10 healthy males during wakefulness, stage 2, stages 3–4, and rapid-eye-movement (REM) sleep. Mean FRC decreased from 3.14 +/- 0.01 (SE) liters during wakefulness to 2.95 +/- 0.01 liters in stage 2 sleep. Lowest sleep values were 2.86 +/- 0.01 liters in stages 3–4 and 2.83 +/- 0.01 liters in REM sleep (P less than 0.05 from wakefulness). Although the amount of the decrease in FRC identified during sleep was surely not large enough to impair ventilation distribution in normal humans, this degree of decrease might contribute to the hypoxemia seen in patients with severe airflow limitation.
Blood-gas equilibration of CO2 and O2 in lungs of awake dogs during prolonged rebreathing
Authors: Scotto P. , Rieke H. , Schmitt H. J. , Meyer M. , Piiper J.
Published: December 2017

To reinvestigate the blood-gas CO2 equilibrium in lungs, rebreathing experiments were performed in five unanesthetized dogs prepared with a chronic tracheostomy and an exteriorized carotid loop. The rebreathing bag was initially filled with a gas mixture containing 6–8% CO2, 12, 21, or 39% O2, and 1% He in N2. During 4–6 min of rebreathing PO2 in the bag was kept constant by a controlled supply of O2 while PCO2 rose steadily from approximately 40 to 75 Torr. Spot samples of arterial blood were taken from the carotid loop; their PCO2 and PO2 were measured by electrodes and compared with the simultaneous values of end-tidal gas read from a mass spectrometer record. The mean end-tidal-to-arterial PO2 differences averaging 16, 4, and 0 Torr with bag PO2 about 260, 130, and 75 Torr, respectively, were in accordance with a venous admixture of about 1%. No substantial PCO2 differences between arterial blood and end-tidal gas (PaCO2 - PE'CO2) were found. The mean PaCO2 - PE'CO2 of 266 measurements in 70 rebreathing periods was -0.4 +/- 1.4 (SD) Torr. There was no correlation between PaCO2 - PE'CO2 and the level of arterial PCO2 or PO2. The mean PaCO2 - PE'CO2 became +0.1 Torr when the blood transit time from lungs to carotid artery (estimated at 6 s) and the rate of rise of bag PCO2 (4.5 Torr/min) were taken into account. These experimental results do not confirm the presence of significant PCO2 differences between arterial blood and alveolar gas in rebreathing equilibrium.
Dynamic lung function in dogs with compensatory lung growth
Authors: Arnup M. E. , Greville H. W. , Oppenheimer L. , Mink S. N. , Anthonisen N. R.
Published: December 2017

Nine puppies underwent left pneumonectomy at 10 wk of age while nine sex-matched littermates had a sham operation, and all animals were studied at 25 wk of age. Postpneumonectomy dogs demonstrated compensatory growth in that lung weight and total lung capacity (TLC) were the same as those of control animals when normalized for body weight. In postpneumonectomy dogs all lobes of the remaining right lung increased in weight, but this was most notable in the cardiac lobe which grew across the mediastinum. Subdivisions of lung volume were normal in postpneumonectomy animals except for residual volume (RV): RV/TLC was increased when compared with control animals. In intact dogs static pressure-volume curves of the lung and respiratory system did not differ between groups, and the static pressure-volume curves of excised lungs were closely similar. Maximum expiratory flow was sharply reduced in postpneumonectomy dogs, averaging 40% of flow in control dogs over the lower 50% of the vital capacity. In both groups the fractional increase in maximal expiratory flow during HeO2 breathing was substantial and similar. Regional compliances, resistances, and perfusion distribution were examined using 133Xe. Regional compliance and perfusion were reduced in the left hemithorax of postpneumonectomy dogs while regional resistances were increased.
A technique to locate the pacemaker in smooth muscles
Authors: Publicover N. G. , Sanders K. M.
Published: December 2017

A technique was developed to locate the site of slow-wave origin (pacemaker) in a sheet of smooth muscle tissue. Evoked slow waves were used to measure conduction velocities in the two dimensions of sheets of smooth muscle. These conduction velocities were used to "triangulate" to the pacemaker site by an iterative minimization process. The model was tested by triangulating to events evoked from known regions within sheets of canine gastric muscle. The technique was used to determine the sites of origin of spontaneous slow waves and the shift in the spontaneous pacemaker caused by localized injury. This technique will be useful in locating pacemaker regions and to study the factors that affect the origin and frequency of slow waves in syncytial tissues. The triangulation technique should be applicable to intact organs as well as isolated sheets of muscle.
Spacelab--the coming of age of space physiology research
Authors: West J. B.
Published: December 2017

Spacelab is a cylindrical pressurized laboratory (approximately 7 m long and 4 m in diameter) that is part of the payload of the Space Shuttle. It provides an orbiting "shirtsleeves" environment for laboratory experiments on the physiological effects of weightlessness. The first Spacelab flew in November 1983 with great success. Of special interest to physiologists is Spacelab 4, which is scheduled for early 1986 and will be the first dedicated to life sciences. It will contain 24 experiments covering the area of vestibular, cardiovascular, pulmonary, renal, endocrine, blood, bone, and muscle physiology, with additional experiments in gravitational biology. Opportunities for research on subsequent life science Spacelabs have recently been announced, and this is therefore an opportune time to review progress to date in the field of space physiology and to point to some of the challenges of this emerging discipline.
Effects of pulmonary congestion on airway reactivity to histamine aerosol in dogs
Authors: Kikuchi R. , Sekizawa K. , Sasaki H. , Hirose Y. , Matsumoto N. , Takishima T. , Hildebrandt J.
Published: December 2017

We examined the effect of acute pulmonary vascular congestion on bronchial reactivity in dogs in a standard challenge protocol. Airway responsiveness to histamine whose concentration was varied in a stepwise incremental fashion was assessed from changes in pulmonary resistance (RL) and dynamic compliance (Cdyn) in 10 anesthetized dogs. Brief acute pulmonary congestion was created by inflating a balloon placed in the left atrium to raise left atrial pressure to 20-30 cmH2O for 1 min. Pulmonary congestion did not change RL in the control condition. However, after histamine inhalation, RL was further increased by pulmonary congestion, making the two effects synergistic. This phenomenon could not be observed with vagi cut. Pulmonary congestion decreased Cdyn in all dogs regardless of histamine concentration, with or without vagotomy. We conclude that pulmonary vascular congestion makes the bronchi hyperreactive through vagal reflexes. The reduction in Cdyn caused by pulmonary congestion appears to stem mainly from the narrowing of peripheral airways by adjacent vascular engorgement.