bluuebunny/crossref_metadata_2025 huggingface dataset:
Lack of electrical interaction between proximal bundle branches and subjacent muscle
Authors: Lathrop D. A. , Bailey J. C.
Published: December 2017

Microelectrode techniques were used to assess the importance of subthreshold electrotonic interactions between the canine proximal bundle branches and adjacent septal myocardium, and vice versa. Bundle branch action potential duration, maximal rising velocity of phase O, current threshold requirements for all-or-none depolarization, transmembrane voltage, and spontaneous frequency were not altered by adjacent septal muscle activation. Activation of the proximal bundle branches did not change the transmembrane voltage of immediately subjacent muscle cells; likewise, all-or-none activation of ventricular septal muscle did not effect a voltage change in the overlying proximal bundle branches. We conclude that a high ohmic resistance barrier between proximal bundle branch and subjacent muscle precludes significant electrotonic interactions between these neighboring structures.
Pulmonary vascular response to increase in intracranial pressure: role of sympathetic mechanisms
Authors: Malik A. B.
Published: December 2017

The pulmonary vascular response to intracranial hypertension was studied in anesthetized controlled ventilated dogs in which intracranial pressure (ICP) was elevated to 20 Torr below the mean arterial pressure for a 20-min period, and regulated at this level. Pulmonary vascular resistance (PVR) increased from control value of 2.7 +/- 0.30 to 8.3 +/- 0.51 Torr-l-1-min at the end of 20-min increase in ICP. The increase in PVR was associated with marked increase (P less than 0.001) in pulmonary arterial pressure from 14.4 +/- 1.3 to 35.4 +/- 4.0 Torr, small increase in left atrial pressure from 5.4 +/- 1.2 to 7.9 +/- 1.9 Torr, and no significant change in pulmonary blood flow. The increase in PVR occurred independently of changes in the arterial pressure. The increase in PVR induced by elevated ICP was correlated with increases in lung water, physiological shunt (Qs/Qt), alveolar dead space (VD), and with hypoxemia. Pretreatment with propranolol (1.5 mg-kg-1) attenuated the increase in PVR during elevation in ICP; the smaller increase in PVR was associated with a marked increase in left atrial pressure and a smaller increase in pulmonary perfusion pressure than in the control group. The propranolol-treated dogs also developed increases in lung water, Qs/Qt, VD, and hypoxemia. In contrast, pretreatment with phenoxybenzamine (1.5 mg-kg-1) inhibited the increases in pulmonary perfusion pressure and PVR induced by ICP elevation as well as the associated increases in lung water, Qs/Qt, VD, and hypoxemia. Therefore, a sustained elevation in ICP at a level below the mean arterial pressure in the intact dog evokes pulmonary vasoconstriction which is mediated by alpha-adrenergic mechanisms. The neurogenic pulmonary vasoconstriction results in the increases in lung water, Qs/Qt, VD, and in the hypoxemia.
Myocardial Feulgen-DNA levels and capillary vascularization in hypoxia-exposed rats
Authors: Stere A. J. , Anthony A.
Published: December 2017

Male abino rats were exposed to simulated altitude of 18,000 ft (380 Torr) for 1 day to 8 wk. Histological sections of heart ventricles were stained by the Feulgen technique and amounts of Feulgen-DNA were determined cytophotometrically. Heart weights, relative to body weights, increased over controls at all exposure periods, as did myocardial capillary vascularization. Ninety percent of cardiac muscle nuclei were found to contain tetraploid amounts of DNA. All nuclei exhibited a high degree of chromatin dispersion in exposed and unexposed rats, which reflects a highly reactive metabolic state of cardiac cells in both groups. There was no evidence of increased ploidy or increased DNA synthesis associated with hypertrophy after acute or chronic hypoxia exposure. The data suggest that an initial event which could facilitate augmented protein synthesis during hypoxia acclimation appears to be an increased availability of oxygen and/or nutrients brought about by an expansion of the capillary bed and vascular proliferation.
Effect of acute hypoxia on the hormonal response to exercise
Authors: Sutton J. R.
Published: December 2017

The hormonal responses to submaximal exercise under normoxic and hypoxic conditions were studied in eight fit males, aged 22--28 yr, with mean maximal oxygen uptake of 4.4 +/- 0.7 l/min. Studies were performed in a hypobaric chamber, decompressed to a simulated altitude of 4,550 m (PIO2 = 83 Torr). The subjects exercised for 20 min at 750 kpm/min on a cycle ergometer. Venous blood samples were obtained at rest, during exercise and for 60 min after exercise. Plasma glucose, free fatty acids, lactate, cortisol, and serum growth hormone concentrations all increased more during hypoxic exercise than under normoxic conditions. Serum insulin concentration showed a small decrease under normoxic conditions, but decreased by 50% during hypoxic exercise, and was followed by marked rebound when exercise stopped. These changes suggest that energy substrate-hormone interrelationships are altered by hypoxic exercise, resulting in increased fat mobilization and increased gluconeogenesis.
Extravascular lung water after extracellular fluid volume expansion in dogs
Authors: Snashall P. D. , Weidner W. J. , Staub N. C.
Published: December 2017

We have compared extravascular lung water after extracellular fluid volume expansion with that predicted from lung sucrose space measured in control dogs. In control lungs mean extravascular water:dry weight ratio was 3.81 +/- 0.16 (SD) (n = 5) and extravascular sucrose space/dry weight was 1.79 +/- 0.45 (n = 4). After acute expansion of extracellular fluid volume by 10% of body weight mean extravascular water:dry lung weight was 4.17 +/- 0.27 (m = 5), less than half the predicted increase to 4.63 +/- 0.19, suggesting some degree of protection. After 20% (n = 4), 30% (n = 2), and 40% (n = 1) expansion, no protection was demonstrated and there was considerable scatter of lung water at each infusion volume. When volume expansion increased pulmonary capillary intravascular forces (due to decreased protein osmotic pressure and increased hydrostatic pressure) by more than 20 cmH2O there was a linear increase in extravascular lung water with increasing intravascular forces. Three dogs did not conform to this relationship and had disproportionately large increases in lung water, possibly due to alveolar flooding.
Total body water and lean body mass estimated by ethanol dilution
Authors: Loeppky J. A. , Myhre L. G. , Venters M. D. , Luft U. C.
Published: December 2017

Total body water (TBW) was determined on 35 subjects with a tritium (HTO) and an ethanol (ETH) dilution method, the latter using breath analyses for blood ethanol content. Lean body mass (LBM) was estimated by hydrostatic weighing. Mean values for water fraction (TBW/wt) were 0.618 +/- 0.05 with HTO and 0.603 +/- 0.06 with ETH. The difference was not significant. The correlation between the two methods was highly significant (r = 0.90, SEE = 3.5 liters, P less than 0.0001). High correlations were also found between TBW and LBM with either method for TBW (r = 0.94 with HTO, r = 0.91 with ETH). Mean values for TBW/LBM were 0.735 with HTO and 0.717 with ETH. The ETH method compares favorably with the HTO, it has the advantage that it is nonradioactive and can be repeated daily if necessary.
Effects of growth, diving history, and high altitude on blood oxygen capacity in harbor seals
Authors: Kodama A. M. , Elsner R. , Pace N.
Published: December 2017

Blood volume and body composition measurements were carried out on diving and nondiving harbor seals, Phoca vitulina. There were small, statistically significant differences in several red blood cell parameters between diving and nondiving seals, but the effect was superimposed on uniformly large blood volumes ranging from 11 to 12% of body weight found in all the animals. It is suggested that the large blood oxygen transport and storage capacity is not so much a direct result of the apneic diving experience, but an expression of phylogenetic control. The development of blood volume during early growth was closely related to the increase in lean body mass. In spite of the inherently large blood volume, this marine mammal when exposed to high altitude for 85 days at an elevation of 3.1 km above sea level appeared to exhibit typical mammalian erythropoietic and ventilatory responses to long-term, mild hypoxia. Thus, it probably cannot be considered to be preacclimatized to high altitude.
Cardiac autonomic blockade in exercising dogs
Authors: Atkins J. M. , Horwitz L. D.
Published: December 2017

Pharmacological blockade of autonomic control of the heart was studied in dogs performing mild, moderate, and severe running exercise on a level treadmill. The dogs were studied without drugs, after atropine, after propranolol, and after both atropine and propranolol. As compared with results without drugs, cardiac denervation resulted in elevated resting heart rate (+45 beats/min) but reduced heart rate during moderate (-17 beats/min) and severe exercise (-47 beats/min); no change in cardiac output at rest or during mild exercise but decreases (-23% and -25%) during moderate and severe exercise; and reduced first derivatives of left ventricular pressure at rest (-24%) and during exercise (-35, -41, and -52% for mild, moderate, and severe loads, respectively). Cardiac denervation did not alter end-diastolic left ventricular diameter but significantly increased end-systolic diameter during exercise. It is concluded that blockade of autonomic control of the heart diminishes cardiac output during exercise by reducing heart rate and myocardial contractile force but does not alter cardiac output at rest.
Canine pulmonary response to aerosol histamine: direct versus vagal effects
Authors: Loring S. H. , Drazen J. M. , Ingram R. H.
Published: December 2017

Histamine, a potent bronchoconstrictor, has been shown to produce bronchoconstriction both directly and by a vagal reflex. To define the relative roles of direct and reflex effects, we studied the pulmonary response of dogs exposed to increasing doses of aerosol histamine before and after vagal blockade or vagotomy. In addition, the relative contributions of aerodynamically large and small airways to the overall response were determined by the measurement of pulmonary resistance on sulfur hexafluoride-oxygen and helium-oxygen mixtures. Histamine aerosol caused a similar dose-dependent increase in resistance of aerodynamically large and small airways and fall in dynamic compliance. The dose-response relationships were not consistently altered by either vagal blockade or vagotomy. The following variables were found not to alter the experimental results: anesthesia, type of aerosol generator, control of breathing during aerosol exposure, spontaneous breathing vs. controlled ventilation after aerosol exposure, cold block of vagi vs. vagotomy. We conclude that 1) histamine aerosol in dogs causes a local dose-dependent constriction of bronchial smooth muscle, and 2) the vagus nerve played a relatively minor role in the pulmonary response to aerosol histamine in these experiments.
Ventilatory and cholinergic control of pulmonary surfactant in the rabbit
Authors: Oyarzun M. J. , Clements J. A.
Published: December 2017

Four sets of experiments on surfactant secretion were performed using New Zealand rabbits under light pentobarbital anesthesia. Pa02, Paco2, and pHa remained normal during all experiments. In controls lung lavage yielded 1.62 +/- 0.26 (SD) mg of alveolar phospholipid (PL)/g lung; disaturated phosphatidylcholine comprised 55.5% of total PL. a) Acetylcholine infusion into the left pulmonary artery for 1–4 h caused a 13% increase in alveolar PL of left as compared to right lung. b) Efferent left vagus stimulation for 1 h increased alveolar PL of right and left lungs 31% as compared to controls (P = 0.012). c) Increasing minute ventilation by 100% by augmenting dead space for periods of 1, 2, and 4 h, increased alveolar PL 45% (P = 0.001), 54%, (P = 0.002), and 25% (P = 0.004), respectively, compared to controls. d) Administration of atropine prevented the increase in alveolar PL caused by increased ventilation. These findings show that increased ventilation can stimulate surfactant release through a cholinergically mediated mechanism but do not rule out the participation of other mechanisms.
Glycogen, lactate, and alanine changes in muscle fiber types during graded exercise
Authors: Baldwin K. M. , Campbell P. J. , Cooke D. A.
Published: December 2017

The effect of different speeds of incline running (16–48 m/min) on changes in glycogen, lactate, and alanine concentrations in different skeletal muscle fiber types and in blood were investigated in nontrained adult female rats during 5-min bouts of exercise. Glycogen depletion occurred extensively (25–86%) in fast-oxidative-glycogenolytic (FOG) and in slow-oxidative (SO) fibers over the range of speeds studied, whereas it occurred primarily (76%) at 48 m/min in the fast-glycogenolytic (FG) fiber type. No marked increases in lactate over resting control levels occurred in the FOG fibers. However, compared to resting levels, lactate increased over fourfold in FG muscle during running at 48 m/min and blood lactate concentrations paralleled these changes. No changes occurred in alanine concentration in FOG muscle and in blood under these experimental conditions, whereas there were approximately 70% increases in FG and SO fibers during moderate-to-heavy exercise. These findings suggest that elevations in blood lactate of rodents primarily result from lactate production in the FG fiber type.
Effect of ozone on bronchomotor response to inhaled histamine aerosol in dogs
Authors: Lee L. Y. , Bleecker E. R. , Nadel J. A.
Published: December 2017

To study the effect of ozone on bronchial reactivity to inhaled histamine diphosphate aerosol, we performed 14 experiments on 5 dogs anesthetized with pentobarbital sodium (25–30 mg/kg, iv) and ventilated with a Harvard respirator. Prior to ozone exposure, inhalation of histamine aerosol (2% solution; 5 breaths) increased total pulmonary resistance (RL) 5.1 +/- 0.5 cmH2O/1 per s (mean +/- SE). One day after ozone exposure (0.7-1.2 ppm; 2 h), the base-line RL was not significantly changed (P greater than 0.05), but the increase of RL caused by histamine (10.7 +/- 1.1 cmH2O/1 per s) was greater than in the control state (P less than 0.01). When the dogs were pretreated with atropine sulfate aerosol (1.5% solution; 10 breaths), the increase of RL after histamine was decreased to 3.8 +/- 0.3 cmH2O/1 per s before ozone, and this was not significantly different after ozone (4.5 +/- 1.1 cmH2O/1 per s; P greater than 0.5). Cooling blockade of conduction in the vagus nerves diminished the increase of RL after histamine to 3.9 +/- 0.5 cmH2O/1 per s before ozone, and this was not significantly different after ozone (4.4 +/- 0.6 cmH2O/1 per s; P less than 0.5). Since both atropine and vagal cooling abolished the ozone-induced bronchial hyperirritability, we conclude that it is mediated via vagal cholinergic pathways.
Bronchial reactivity: interaction between vagal stimulation and inhaled histamine
Authors: Benson M. K. , Graf P. D.
Published: December 2017

The interaction between the effects of vagal stimulation and inhaled histamine on the bronchi was studied in anesthetized dogs. Reactivity was assessed by measuring changes in bronchial caliber visualized with tantalum bronchograms. In seven vagotomized dogs the bronchoconstrictor response to a combination of electrical stimulation of the vagus nerves and inhaled histamine solution produced a mean reduction in airway diameter (Daw) of 2.21 mm which was significantly greater than the additive results of the two stimuli applied separately (mean decrease in Daw 0.29 +/- 0.91 mm). In three dogs the effect of vagal stimulation was to produce a shift in the dose-response curve to inhaled histamine. These results indicate that the effect of the base-line bronchomotor tone must be considered in the evaluation of the effect of vagal blockade on airway reactivity. An increase in the resting degree of bronchomotor tone may contribute to the hyperreactivity observed in patients with asthma.
Mechanism of respiratory responses to intravenous NaHCO3, HCl, and KCN
Authors: Gonzalez F. , Fordyce W. E. , Grodins F. S.
Published: December 2017

We studied the mechanism by which respiratory responses are produced by rapid injection of NaHCO3, HCl, or KCN into the superior vena cava of lightly anesthetized dogs. To estimate independently circulatory transit time to receptor sites, the solutions were injected at 0 degrees C and their arrival time at the ascending aorta and carotid sinus was detected by thermocouples. All of the ventilatory responses were observed to begin after the substances had reached the ascending aorta and 94% began after the carotid sinus had been reached. The injections were repeated following bilateral vagotomy and/or carotid body resection. Vagotomy produced no significant changes in ventilatory responses, but carotid body resection considerably reduced them. Following both procedures, few ventilatory responses were observed, and the time lag to the onset of the response increased greatly. We conclude that all of the observed ventilatory responses can be accounted for by the known arterial and central chemoreceptors, and that no evidence for pulmonary chemoreceptors was obtained.
Relationship between maximal oxygen uptake and left ventricular function in exercise
Authors: Wolfe L. A. , Cunningham D. A. , Davis G. M. , Rosenfeld H.
Published: December 2017

Left ventricular systolic time intervals (STI's), cardiac output, and arterial blood pressures were measured during bicycle ergometer work in three groups of 10 young men (aged 20–33 yr) who represented average (VO2max = 42–45 ml.kg-1.min-1), moderate (VO2max = 50–56 ml.kg-1.min-1), and high (VO2max = 59–72 ml.kg-1.min-1) levels of cardiovascular fitness. The subjects were studied using noninvasive procedures at steady-state heart rate of approximately 110, 130, and 150 beats.min-1. At all exercise levels, the fitter subjects displayed slightly shorter values for the preejection period (PEP) compared with less fit groups. Significantly (P less than 0.05) larger stroke volumes, longer left ventricular ejection times (LVET), faster mean systolic ejection rates and lower PEP/LVET ratios were found in the group with the highest aerobic capacity. Although these observations appear to indicate a superior mean level of left ventricular performance in groups who represent high levels of cardiovascular fitness, it was concluded that the use of STI values by themselves to describe the cardiovascular fitness of an individual would not be warranted.
Fluid leaks from extra-alveolar vessels in living dog lungs
Authors: Albert R. K. , Lakshminarayan S. , Huang T. W. , Butler J.
Published: December 2017

Edema transudation from extra-alveolar vessels was investigated in anesthetized, open-chested dogs. Fluid accumulation at different alveolar and extra-alveolar vascular pressures was assessed by continuous lung weighing and microscopy. The left (experimental) lung was distended with 6% CO2 and air while normal arterial blood gases were maintained by separately ventilating the right lung. Extra-alveolar vessels were isolated by compressing alveolar vessels with alveolar pressures high enough to stop blood flow. Weight increased steadily (edemogenesis) when pulmonary arterial and/or pulmonary venous pressure was 1 cmH2O below this pressure. Because some alveolar vessels at the lung base could have remained open and leaked, extra-alveolar vessels were also separated from alveolar vessels by glass bead embolization sufficient to stop perfusion. Lung weight gains followed selective pulmonary arterial or venous pressure elevations. Electron microscopy demonstrated edema in experimental lobes which was not present in control lobes with undistended extra-alveolar vessels at the same alveolar pressure. Thus pulmonary edema can be caused by fluid leaking from extra-alveolar vessels.
Effect of calcium on ion transport and electrical properties of tracheal epithelium
Authors: Marin M. G. , Zaremba M. M.
Published: December 2017

Active transport of Cl- toward the tracheal lumen and Na+ away from the lumen creates an electrical potential difference across dog tracheal epithelium. This study examined in vitro the effect of varying calcium concentration in the bathing media on the ion transport and electrical properties of dog tracheal epithelium. In six pairs of epithelia, changing calcium concentration from 1.9 to 0 mM resulted in a significant decrease in electrical resistance, from 318 +/- 36 to 214 +/- 24 omega.cm2. Short-circuit current and net Cl- and Na+ fluxes measured under short-circuit conditions were not changed significantly. Changing calcium concentration from 1.9 to 10 mM resulted in no significant change from control in the electrical properties nor in net Cl- and Na+ fluxes (short-circuit conditions). Histamine (10(-4) M) produced a significantly smaller increase in short-circuit current in 0 than in 1.9 mM Ca2+ (+5 +/- 2 vs. +12 +/- 2 microamperemeter/cm2). However, electrical changes were not significantly different in 1 or 10 mM Ca2+. These results indicate that calcium lack increased permeability of tracheal epithelium and that the increase in short-circuit current due to histamine depended in part on calcium.
Sensitivity of the carotid body to within-breath changes in arterial PCO2
Authors: Band D. M. , McClelland M. , Phillips D. L. , Saunders K. B. , Wolff C. B.
Published: December 2017

Respiration, sinus nerve chemoreceptor discharge, and carotid arterial pH were monitored in cats. Chemoreceptor discharge frequency showed oscillations that had a respiratory period when averaged over many respiratory cycles. These oscillations disappeared when pH oscillations of respiratory period were eliminated from the carotid arterial blood. The maximum sinus nerve discharge was associated with the most acid point of the recorded pH oscillation. Briefly increasing PCO2 by giving CO2-rich saline into the aortic root resulted in brief reduction in carotid arterial pH, and when this reduction occurred during inspiration tidal volume increased, even with a pH change no larger than the pH oscillations. However, increased chemoreceptor discharge could only be demonstrated when each pH change had twice the amplitude of the pH oscillations. Injections of fixed acid mixed with free carbonic anhydrase transiently increased chemoreceptor frequency, whereas injections of fixed acid alone had no effect. The carotid body is therefore sensitive to small rapid changes in arterial PCO2, and the pH electrode record indicates the size of the stimulus except when fixed acid changes are produced too closely upstream.
Growth of pulmonary circulation in normal pig--structural analysis and cardiopulmonary function
Authors: Rendas A. , Branthwaite M. , Reid L.
Published: December 2017

Morphometric analysis of the postnatal development of the pig lung, with emphasis on alveoli and vessels, shows features of growth similar to man, but occurring at a much faster rate in the pig, which telescopes in the first 3 mo the changes seen in human childhood and adolescence. During the first weeks, arteries (birth to 2 wk) and alveoli (1––12 wk) increase in number, whereas increase in size continues until adulthood. Wall thickness decreases soon after birth in arteries 15––200 micrometer, and by 8 wk in those 200–1,000 micrometer. At this age the adult left ventricular predominance in weight is already present. Throughout growth the venous wall thickness does not change. Cardiopulmonary function studies in pigs, from 2 to 16 wk, show that, during the period of rapid postnatal lung growth, there is no change in tidal volume, dynamic compliance, and thoracic gas volume as related to body weight; right ventricular and pulmonary arterial pressures also remain unchanged, whereas pulmonary vascular resistance decreases during the 1st mo.
A model of the effects of respiration on left ventricular performance
Authors: Robotham J. L. , Mintzner W.
Published: December 2017

We have investigated the interaction of left ventricular afterload and right-heart volume on left ventricular performance. By utilizing a right-heart bypassed heart-lung preparation, we have been able to control independently each factor. We have previously suggested that the major influences of the inspiratory decrease in pleural pressure in decreasing left ventricular stroke volume (LVSV) may be via the inspiratory increases in left-heart afterload and right-heart volume (RHV). Thus, our preparation serves as a model to study in detail the specific effects on the left ventricle of changes that are induced by respiration. Our results show that increases in transmural (relative to pleural pressure) aortic pressure (Pao) caused an increased left ventricular end-diastolic pressure (LVEDP), and that the effect of equivalent increases in Pao was greater when RHV was greater. Increase in RHV had minimal effects at low volume, but resulted in large increases in LVEDP at large RHV. These effects were markedly attenuated after pericardiectomy. Rapid increases in either RHV or Pao produced transient falls in LVSV. Our results are consistent with the hypothesis that increases in both right-heart volume and LV afterload contribute to the inspiratory decrease in LVSV and increase in LVEDP.
Reversal of 2-deoxyglucose inhibition of serotonin uptake in isolated guinea pig lung
Authors: Fisher A. B. , Steinberg H. , Dodia C.
Published: December 2017

The effect of various substrates on the rate of uptake of 5-hydroxytryptamine (serotonin) from the pulmonary circulation was studied with isolated guinea pig lungs. Lungs were ventilated and were perfused with an electrolyte solution in a recirculating system. Uptake of serotonin was calculated from the rate of disappearance of [14C]serotonin from the perfusate. Serotonin uptake was inhibited by approximately 40% when 5 mM 2-deoxyglucose was substituted for glucose in the pulmonary perfusate. The inhibition due to 2-deoxyglucose was reversed by addition to the perfusate of pyruvate, lactate, acetate, alanine, beta-hydroxybutyrate, palmitate, or glycerol. Fructose ans succinate were less efficient substrates while no significant effect was noted with L-glycerol 1-phosphate or L-phenylalanine. These results indicate that a wide variety of metabolizable substrates can be utilized by the pulmonary endothelium to support uptake of serotonin.
Esophageal temperature during exercise in asthmatic and nonasthmatic subjects
Authors: Deal E. C. , McFadden E. R. , Ingram R. H. , Jaeger J. J.
Published: December 2017

We measured the temperature in the rectum and two esophageal sites (retrocardiac and retrotracheal) during exercise in eight asthmatic and six normal subjects while they breathed air at subfreezing, ambient, and body conditions. Various aspects of pulmonary mechanics were recorded before and after exercise. The asthmatic subjects developed the greatest airway obstruction following exercise with cold air and no response at body conditions. There were no changes in pulmonary mechanics in the postexercise period in the normal individuals with any of the inspired air conditions. Despite these divergent mechanical responses retrotracheal temperatures fell by the same magnitude below core values in both groups of subjects, indicating that identical degrees of airway cooling occurred. We conclude that rather than having a defect in the ability to condition inspired air, asthmatic subjects are more responsive to the effects of incompletely conditioned air.
Sex and age differences in intrathoracic airways mechanics in normal man
Authors: Yernault J. C. , De Troyer A. , Rodenstein D.
Published: December 2017

Expiratory pressure-volume curves and maximal expiratory flow-volume curves were obtained in 74 healthy subjects (49 males 25 females) aged between 20 and 64. Maximal expiratory flowstatic recoil (MEFSR) curves were then constructed. Aging was associated with loss of lung recoil and reduction in maximal expiratory flow measured between 80 and 50% total lung capacity (TLC), in both males and females, with the slope of the MEFSR curve becoming steeper. In subjects less than 40 yr old the conductance of the upstream segment increased from 80 to 50% TLC, whereas in older subjects it decreased. We also studied the effects of alveolar gas compression artifacts on MEFSR curves in 12 additional subjects and 10 patients with chronic obstructive lung disease; consistent changes were found, but the subsequent shift of the MEFSR curve toward the left was only mild. These changes are interpreted as reflecting the net effects of an increase in the unstressed dimensions of the airways together with a decrease in intraparenchymal airways diameter, probably due to loss of parenchymal airways diameter, probably due to loss of parenchymal support. It was also concluded that the analysis of the MEFSR curve did not allow a quantitative estimate of the chantes in airways compressibility with aging.
Breathing pattern and ventilatory response to carbon dioxide in divers
Authors: Florio J. T. , Morrison J. B. , Butt W. S.
Published: December 2017

The breathing pattern and ventilatory response to carbon dioxide of 10 experienced divers was compared with that of 10 nondivers of similar age and build. Breathing pattern was described by the equation VE = M (VT - K) and the response to carbon dioxide by VE = S(PCO2 - B). The divers exhibited a value form 27% lower than the nondivers; S was 33% lower. The difference was significant (P less than 0.05) in both cases. B was significantly higher (P less than 0.05) in the divers than nondivers. These differences are not attributable to age, build, or vital capacity. S was well correlated with M when all subjects were considered a single group. Within the diving group no correlation of S and M with diving experience was found.
Myocardial intracellular pH regulation during chloride depletion
Authors: Gonzalez N. C. , Clancy R. L.
Published: December 2017

The possible role of a HCO-3/Cl- transmembrane exchange as a mechanism of alkalinization in the myocardial cell was studied in isolated rabbit hearts perfused with Ringer solution. Cl- depletion was produced by replacing Cl- of the perfusate by SO2(-4) or glucuronate. Intracellular pH (pHi) was calculated both in Cl--free and Cl--containing hearts from the distribution of 14C-labeled 5′,5′-dimethyloxazolidine-2,4-dione. Acid-base alterations were produced by changing perfusate HCO-3 concentration and/or CO2 partial pressure (PCO2). Depletion of Cl- resulted in an increase in pHi for any given level of extracellular pH. Increasing PCO2 at constant perfusate HCO-3 resulted in changes in pHi and cell HCO-3 (HCO-3i) that were similar in both Cl--free and Cl--containing hearts. Increasing perfusate HCO-3 at constant PCO2 resulted in increases in pHi and HCO-3i in both Cl--free and Cl--containing preparations. When the increases in HCO-3i secondary to an increase in extracellular HCO-3 were plotted as a function of the initial HCO-3i, a significant negative correlation was observed, suggesting that the elevation of HCO-3i was influenced by the initial HCo-3i and not by the presence or absence of Cl-. It is concluded that even though HCO-3 may enter the myocardial cells in exchange for Cl- during Cl-depletion, lack of Cl- does not alter the ability of the myocardial cell to regulate its pHi. This argues against a HCO-3/Cl- exchange as a mechanism of regulation of myocardial pHi.
Effect of cardiovascular variables on hyperpnea during recovery from diving in ducks
Authors: Lillo R. S. , Jones D. R.
Published: December 2017

Control of hyperpnea during recovery from diving in unanesthetized White Pekin ducks, Anas platyrhynchos, was examined. Postdive minute ventilation (VE) increased five times regardless of the length of the preceding dive (1–4 min), although longer dives resulted in slower return of VE towards predive levels. Manipulation of arterial blood gases showed that both hypoxia and hypercapnia contributed to hyperpnea on emergence. Although chronic bilateral carotid body denervation depressed VE before and after diving, VE still increased four times after 1-min dives. Postdive hyperpnea was accompanied by dramatic elevations in heart rate, cardiac output, and the ventilation/perfusion ratio. However, artificially maintaining heart rate at abnormally low levels did not affect the postdive hyperpnea. In addition, postdive hyperpnea was unaffected by systemic arterial baroreceptor denervation. Postdive hyperpnea in ducks depends on blood gas changes occurring during a dive, yet a substantial part of the response is independent of input from carotid body chemoreceptors and the accompanying rises in heart rate and cardiac output.
Ventilatory control during experimental maldistribution of VA/Q in the dog
Authors: Juratsch C. E. , Whipp B. J. , Huntsman D. J. , Laks M. M. , Wasserman K.
Published: December 2017

To determine the role of the peripheral chemoreceptors in mediating the hyperpnea associated with acute, nonocclusive inflation of a balloon in the main pulmonary artery of the conscious dog, we performed balloon inflations in awake and lightly anesthetized (chloralose-urethan) dogs before and after a) bilateral carotid body resection (CBR), b) cervical vagotomy (V), and c) after both CBR and V. In the intact awake state, balloon inflation increased VE from a mean of 4.91 to 7.16 1/min, usually within 1.5–2.0 min. Mean arterial PO2 decreased from 82 to 71 Torr and end-tidal PCO2 was reduced by 6 Torr. Arterial PCO2 and pH were unchanged in the steady state (as evidenced by discrete blood samples), even in those dogs in which VE increased up to 7.5 1/min. However, an indwelling PCO2 electrode in the femoral artery demonstrated a consistent transient elevation of arterial PCO2 prior to the steady state regulation. Vagotomy alone did not impair the ability to regulate PCO2 during balloon inflation. In some cases with CBR alone, arterial PCO2 was regulated at control levels in the steady state, but the transient increase during the early phase of balloon inflation was more marked (mean increase, 2 Torr). We conclude that the peripheral chemoreceptors are responsible for a significant component of the dynamic ventilatory behavior during this early phase (1.5–2.0 min) of acute maldistribution of VA/Q.
Free and conjugated catecholamines and metabolites in cat urine after hypoxia
Authors: Claustre J. , Peyrin L.
Published: December 2017

Catecholamine and metabolite excretion was studied in the cat after 6 h of 7.5% O2 hypoxia. Norepinephrine (NE) release from sympathetic nervous endings was strongly activated, whereas epinephrine (E) excretion was only slightly increased. A noteworthy result was the increase of dopamine (DA) and its metabolites [3-methoxytyramine (MT); 3,4-dihydroxyphenylacetic acid (DOPAC)] in urine samples. This increased release does not seem to originate from the central nervous system, but rather from peripheral dopaminergic structures; available knowledge on peripheral DA suggests that the hypoxia-induced DA release might be partly related to chemosensory or renal function. Indeed, in addition to enhanced DA and NE excretion, we observed an increase in sodium excretion that correlated with both DA and NE. Analysis of free and conjugated urinary metabolites showed that only free NE and both free and conjugated normetanephrine were increased in urine after hypoxic stress. Among DA metabolites, conjugated DOPAC was the main DA metabolite in the basal state and after hypoxia. Both the free and the conjugated forms of DA, MT, and DOPAC were increased by hypoxia.
Acclimatization to dry heat: active men vs. active women
Authors: Horstman D. H. , Christensen E.
Published: December 2017

Physiological responses to exercise in dry heat were compared between six active men [maximum O2 consumption (VO2max), 51.4 +/- 1.2 ml . kg-1 . min-1] and four active women (VO2max, 47.2 +/- 1.3 ml . kg-1 . min-1) before, during, and after heat acclimatization. Subjects cycled a maximum of 2 h at 40% VO2max at 45 degrees C dry-bulb temperature, 23 degrees C wet-bulb temperature for 11 days. Prior to acclimatization there were no sexual differences for performance time, rate of increase of rectal temperature (delta Tre), or sweat rate per degree C increase of rectal temperature (msw/delta Tre). Sweat rate (msw) was greater for the men than for the women. Although there was no difference in the rate of increase of heart rate (delta HR), HR for the women was maintained 15–20 beats . min-1 higher than for the men. Acclimatization occurred for both sexes as indicated by reduced Tre and HR and increased msw and performance time. With acclimatization the women had longer performance times than the men. Even though the men still had greater msw, delta Tre was also greater; therefore msw/delta Tre for the men was less than for the women. Neither HR nor delta HR was different between the sexes. Throughout, resting hematocrit for the women was less than for the men; no changes in hematocrit were observed during exercise or with acclimatization. Plasma protein concentration increased during exercise on all days; no changes in plasma osmolality were observed. It is concluded that active women perform exercise of equal relative intensity in dry heat as well as active men. Moreover active women acclimatized to heat at a faster rate or to a greater extent than did active men.
Tracheal contraction and relaxation initiated by lung and somatic afferents in dogs
Authors: Coleridge J. C. , Coleridge H. M. , Roberts A. M. , Kaufman M. P. , Baker D. G.
Published: December 2017

Capsaicin injected into the right heart of dogs causes reflex bronchoconstriction by stimulating pulmonary C-fibers, but injected into the left heart it is said to have little effect even though it stimulates bronchial C-fibers, which are known to cause contraction of airway smooth muscle. Attempting to resolve this apparent contradiction, we recorded smooth muscle tension in an innervated tracheal segment in anesthetized dogs and examined the reflex effects of injecting capsaicin intravascularly at different sites. Right atrial injection of capsaicin (10 micrograms/kg) caused tracheal contraction, as did bronchial arterial injection (0.15–5.0 micrograms); left atrial injection (10 micrograms/kg), however, caused relaxation or slight contraction, or a combination of the two. Contraction but not relaxation was abolished by cutting or cooling (0 degree C) the cervical vagus nerves. Femoral arterial injection (10–100 micrograms) caused tracheal relaxation, which was abolished by cutting hindlimb nerves. We conclude that both pulmonary and bronchial C-fibers evoke tracheal contraction, but when capsaicin is injected into the left atrium any effects of stimulating bronchial C-fibers are masked by the reflex action of somatic afferents, which cause tracheal relaxation.
Effect of pH on sensation and vastus lateralis electromyogram during cycling exercise
Authors: Kostka C. E. , Cafarelli E.
Published: December 2017

Six male subjects performed 30 min of cycling exercise: 15 min at 50% of maximum oxygen consumption (VO2 max) and 15 min at 80% VO2 max. On random days subjects ingested 300 mg/kg body wt of NH4Cl to induce acidosis, NaHCO3 to induce alkalosis, or CaCO3 as a placebo during a 3-h preexercise period. Blood pH at the onset of exercise was 7.238 in acidosis, 7.435 in alkalosis, and 7.394 in the placebo control. A direct ratio scaling technique was employed to measure the sensation of how hard exercise felt. Sensory intensity increased twofold after 15 min at 50% VO2max (P less than 0.01). There was no effect of pH on how hard exercise felt during 50% VO2max bouts. Sensory intensity at the end of heavy exercise increased 20% more in acidosis but was not different in alkalosis compared with placebo (P less than 0.05). There was no difference in integrated electromyogram (EMG) between conditions, but there was an average 13% integrated EMG increase by the end of exercise (P less than 0.05). Plasma lactate was lower in acidosis and higher in alkalosis than placebo at 80% VO2max. These data indicate that during heavy exercise acidotic pH accelerates the change in sensory intensity, but this phenomenon is not necessarily associated with changes in the integrated surface EMG.
PAO2 and PVO2 interaction on hypoxic pulmonary vasoconstriction
Authors: Pease R. D. , Benumof J. L. , Trousdale F. R.
Published: December 2017

We sought to determine why large lung compartment hypoxic pulmonary vasoconstriction fails to redistribute blood flow at a low fraction of inspired oxygen (FIO2) level (0.06) when the remaining small lung compartment is ventilated with room air. In 10 pentobarbital-anesthetized dogs, we decreased large compartment FIO2 from 1.0 to 0.06 while the small compartment FIO2 was constant at 0.21, 0.3, 0.5, or 1.0. When small compartment FIO2 was 0.21 and 0.3, large compartment FIO2 decreases from 1.0 to 0.15–0.10 caused a disproportionate increase in large compartment pulmonary vascular resistance (PVR) and further large compartment FIO2 decreases from 0.15–0.10 to 0.06 caused a decrease in large compartment PVR while small compartment PVR continued to increase. When small compartment FIO2 was 0.5, large compartment FIO2 decreases caused an increase and then no change in large compartment PVR, while small compartment PVR remained constant. When small compartment FIO2 was 1.0, all large compartment FIO2 decreases caused increases in large compartment PVR, while small compartment PVR remained constant. When small compartment FIO2 was 0.21 and 0.3, small compartment alveolar oxygen tension (PAO2) and PVR were always inversely related. When small compartment FIO2 was 0.21, 0.3, and 0.5, large compartment PVR either decreased or remained constant whenever mixed venous oxygen tension (PVO2) was less than 30–32 Torr and large compartment PAO2 was less than 50–60 Torr. We conclude that both small compartment hypoxic pulmonary vasoconstriction and primarily failure of large compartment hypoxic pulmonary vasoconstriction occurred when large compartment FIO2 was low (0.06) and small compartment FIO2 was 0.21 or 0.3.
Cardiac output and stroke volume in exercising ducks and pigeons
Authors: Grubb B. R.
Published: December 2017

The purpose of this study was to determine the relationship between oxygen consumption (VO2) and cardiac output, stroke volume, and arteriovenous O2 content differences in resting and exercising birds. Pigeons and ducks showed a linear relationship between oxygen consumption and cardiac output and appeared to have a greater cardiac output for a given oxygen consumption than do mammals of the same body mass. In these birds the arteriovenous O2 content difference was hyperbolically related to oxygen consumption. The cardiac output was relatively high, implying a smaller arteriovenous O2 content difference than found in mammals. Resting stroke volume, relative to body mass, was greater in these birds than in mammals. However, as birds have disproportionately larger hearts for their body mass, these birds showed almost the same stroke volume per gram of heart as do mammals.
Perfusion fixation of lungs for structure-function analysis: credits and limitations
Authors: Bachofen H. , Ammann A. , Wangensteen D. , Weibel E. R.
Published: December 2017

The quality of tissue preservation in lungs fixed by vascular perfusion has been reevaluated. Excised rabbit lungs inflated to 60% of total lung capacity were perfused (zone III conditions) with different but widely used fixatives. The effects of the perfusates on pertinent physiological variables have been assessed by a continuous monitoring, the effects on the pulmonary microstructure by qualitative and morphometric analysis of electron micrographs. Important results include the following. 1) Perfusions with isotonic glutaraldehyde at flow rates within the physiological range produce large increases of perfusion pressure and lung weight that reflect intracellular, interstitial, and intra-alveolar edema. 2) No edema occurs if glutaraldehyde is added to isotonic buffer solutions (total osmolarity 510 mosM). 3) Glutaraldehyde as sole perfusate does not fully eliminate the retractive force of lung tissue. Upon release of transpulmonary pressure the lungs retract by an indeterminable amount. 4) Satisfactory results can be obtained by sequential perfusion with osmium tetroxide and uranyl acetate or glutaraldehyde (510 mosM) followed by osmium tetroxide and uranyl acetate. The latter combination yields optimal preparations to study the alveolar and capillary architecture but causes a hyperosmotic volume loss of lung cells (cell shrinkage).
Action of the diaphragm on the rib cage inferred from a force-balance analysis
Authors: Loring S. H. , Mead J.
Published: December 2017

Displacements of the rib cage are determined by the intrinsic passive properties of the rib cage, rib cage musculature, pleural and abdominal pressures, and the diaphragm. The diaphragm's mechanical actions on the rib cage are inferred from a force-balance analysis in which the diaphragm is seen to cause expansion of the rib cage by pulling cephalad at its insertions on the lower ribs (insertional component) and by raising intra-abdominal pressure, which pushes outward on the diaphragm's zone of apposition to the rib cage (appositional component). Goldman and Mead suggested that the diaphragm, acting alone, could drive both the rib cage and abdomen on their passive characteristics. The force-balance analysis shows that the diaphragm's inspiratory action on the rib cage is less than predicted by Goldman and Mead, but that in the special circumstances of their experiment (low lung volumes), the appositional component is large and the rib cage can be driven close to its passive characteristics. The force-balance analysis is consistent with recent observations by other investigations and is incompatible with the model proposed by Macklem and colleagues and with the Goldman-Mead hypothesis. Experiments on three subjects produced data consistent with the force-balance analysis, showing that the inspiratory action of the diaphragm on the rib cage is greatest at low lung volumes.
Structural changes in the canine lung and pulmonary arteries after pneumonectomy
Authors: Davies P. , McBride J. , Murray G. F. , Wilcox B. R. , Shallal J. A. , Reid L.
Published: December 2017

The study set out to describe the structural changes in the remaining lung of beagle dogs after left-sided pneumonectomy, performed at 6–10 wk or 1 yr of age. After a 5-yr postoperative recovery, lung volume and weight had increased in the operated groups, though only the latter was significant in comparison with 5-yr-old controls. In both operated groups, total alveolar number in the right lung was normal. The total volume of alveolar ducts, mean linear intercept, and (in the young operated group) mean alveolar volume were increased, indicating a compensatory enlargement of distal air spaces. Lobar differences reinforced these conclusions. In the 1-yr operated group, medial hypertrophy was present in preacinar arteries, with a similar trend in intra-acinar arteries where peripheral extension of medial smooth muscle was also present. Despite the lack of structural change in their pulmonary arterial system, the young operated group had right ventricular hypertrophy. Previously reported evidence of alveolar proliferation shortly after pneumonectomy probably represents a speeding up of normal developmental patterns, but after prolonged recovery the final alveolar number is no greater than normal.