bluuebunny/crossref_metadata_2025 huggingface dataset:
Metabolism of rat granular pneumocytes isolated in primary culture
Authors: Fisher A. B. , Furia L. , Berman H.
Published: December 2017

Granular pneumocytes (GP) were isolated by trysinization of minced rat lungs followed by short-term primary culture. The yield from the lungs of one rat was approximately 3.5 X 10(6) GP representing 25 micrograms DNA and 0.5 mg protein. Depending on the method to remove cells from attachment to plastic, the purity was 82--92% GP of which > 90% excluded erythrosin B. Resting O2 consumption (37 degrees C) of cells was 202 +/- 29 (mean +/- SE, n = 3) nmol.h-1.(10(6) cells)-1 with a 2.5 times increase in the presence of an uncoupler of oxidative phosphorylation. ATP content of resting pneumocytes was 4.1 +/- 0.18 nmol.(10(6) cells)-1 and was markedly depressed by the "uncoupling" agent. During incubation with [U-14C]glucose, production of metabolites in nmol.h-1.(10(6) cells)-1 was lactate 58.0 +/- 7.9, pyruvate 25.8 +/- 3.2, and 14CO2 56.4 +/- 2.1, and glucose utilization was 104 +/- 38.5. Sonicated GP had higher activities of both lactate and succinate dehydrogenases compared with alveolar macrophages. Alkaline phosphatase activity was localized predominantly to GP, whereas macrophages contained predominantly acid phosphatase. The intracellular water space for granular pneumocytes was 0.55 +/- 0.05 ml.(10(6) cells)-1 and was 71% greater for alveolar macrophage. The presence of active glycolytic and oxidative pathways and appropriate responses to metabolic inhibitors and substrates suggest the presence of intact cell membranes and the retention of metabolic control mechanisms in this isolated lung epithelial cell preparation.
CSF bicarbonate regulation in metabolic acidosis: role of HCO3- formation in CNS
Authors: Herrera L. , Kazemi H.
Published: December 2017

In metabolic acidosis, cerebrospinal fluid bicarbonate content (CSF [HCO3-]) falls in parallel with reductions in CSF CO2 tension (PCO2), and the fall is minimal with isocapnia. Regulation of CSF HCO3- was therefore investigated during 6 h of isocapnic metabolic acidosis in dogs. One group received intraventricular injections of acetazolamide to inhibit the centrally located carbonic anhydrase, essential in central nervous system (CNS) HCO3- formation, while the control group received intraventricular saline. Plasma [HCO3-] was reduced by 10 meq/l with iv infusion of 0.2 N HCl. CSF [HCO3-] fell in the control group from 22.8 to 17.7 meq/l at 6 h, whereas in the acetazolamide group it fell from 22.9 to 13.0 meq/l. Brain ammonia content was 1,286 +/- 153 microgram/100 g in the controls and 666.2 +/- 103 microgram/100 g in the acetazolamide-treated group at 6 h. Therefore, some reduction in CSF [HCO3-] occurred during 6 h of isocapnic metabolic acidosis along the chemical concentration gradient between CSF and blood, but further falls, in CSF [HCO3-] were minimized by de novo, carbonic anhydrase-dependent HCO3- formation within the CNS. Some of H+ formed were buffered by the increase in brain ammonia. These central mechanisms contribute to local CNS H+ homeostasis in metabolic acidosis.
Exercise capacity and cardiac function in trained and untrained thyroid-deficient rats
Authors: Baldwin K. M. , Ernst S. B. , Herrick R. E. , Hooker A. M. , Mullin W. J.
Published: December 2017

This study was undertaken to ascertain the extent that impairments in a) the oxidative capacity of skeletal muscle, b) cardiac functional and biochemical correlates of contractile capacity, and c) maximal oxygen consumption (VO2 max) can be reversed in thyroid-deficient (TD) female rats subjected to an 8-wk physical training (running) program. Compared with a normal control (NC) group, thyroid deficiency caused reductions in the following: VO2 max (-32%), skeletal muscle homogenate respiratory capacity (-50%), cardiac myosin ATPase (-58%), and in situ-derived ventricular dP/dt max (-58%) (P < 0.001). The training program restored to within normal limits skeletal muscle oxidative capacity and VO2 max, but it did not improve cardiac myosin ATPase, Ca2+ regulation of myofibril ATPase, and dP/dt max relative to TD sedentary rats. However, the heart weight-to-body weight ratio was highest among the three groups in the TD trained group. These findings suggest that maximal oxygen utilization capacity of TD rats can be normalized by physical training, even though intrinsic contractile capacity of the heart could not.
Adrenergic and cholinergic nerves mediate fluid secretion from tracheal glands of ferrets
Authors: Borson D. B. , Chin R. A. , Davis B. , Nadel J. A.
Published: December 2017

Our aim was to determine whether adrenergic as well as cholinergic nerves mediate secretion of fluids from tracheal submucosal glands and, if so, via which receptors. To do this, we studied the secretory responses of tracheal segments to electrical and pharmacologic stimulation in vitro in the presence and absence of a specific nerve blocker and autonomic antagonists. Stimulation caused small elevations, or "hillocks," the size of which we estimated by measuring their diameters. We found that electrical stimulation, acetylcholine, and phenylephrine each caused secretion but that terbutaline did not. Tetrodotoxin prevented the secretory response to electrical stimulation but did not prevent the responses to acetylcholine or phenylephrine. Neither atropine nor phentolamine alone prevented the response to electrical stimulation, but both drugs together did, and propranolol did not inhibit the adrenergic component of the response to electrical stimulation. Atropine blocked the response to acetylcholine, and phentolamine blocked the response to phenylephrine. We conclude that adrenergic and cholinergic nerves mediate secretion from the tracheal glands of ferrets via alpha-adrenergic and muscarinic receptors, respectively.
Effects of repeated heat exposure on hypothalamic sensitivity to norepinephrine
Authors: Christman J. V. , Gisolfi C. V.
Published: December 2017

Bilateral stainless steel guide tubes were stereotaxically implanted above the anterior hypothalamus (AH) of 12 male Sprague-Dawley rats (300-360 g). Beginning 3 days postsurgery, norepinephrine (NE) was injected into the AH each day at increasing depths below the guide tube until colonic temperature fell at least 0.8 degrees C. Subsequently, the effects of treadmill exercise at 21.5 m/min for 3 wk at 22 degrees C (n = 6) or 35 degrees C (n = 6) on the magnitude of the NE-induced hypothermia were investigated. Training duration ranged from 12 to 50 min/day, depending on the time required for colonic temperature of the heated rats to rise to a predetermined level: 40.4 degrees C on day 1, increasing 0.1 degree C/day to 41.5 degrees C on day 12 and thereafter. Before and after training, bilateral injections of NE (10 micrograms) at 22 degrees C at rest and just before exercise (21.5 m/min) caused the following mean +/- SE reductions in colonic temperature (degree C). (Formula: See Text). These reductions in colonic temperature were associated with sharp elevations in tail-skin temperature, but there were no significant differences in the response between the two groups. We conclude that repeated heat exposure increased the sensitivity of the AH to exogenous NE.
Thermal control of respiratory evaporative heat loss in exercising dogs
Authors: Mercer J. B. , Jessen C.
Published: December 2017

Experiments were carried out to determine whether respiratory evaporative heat loss (REHL) in exercising dogs is entirely under thermal control or whether a nonthermal input is additionally involved. To determine body core thermosensitivity, hypothalamic perfusion thermodes and intravascular heat exchanges were chronically implanted in the animals. This allowed the temperature of these two areas to be independently manipulated. At 30 degrees C air temperature, REHL was measured in three dogs during rest or while running on a treadmill (6 km . h-1, 0 degree gradient). During exercise, the threshold temperature was lowered by 9 degrees C, and the slope of the heat-loss response was reduced to one-third as compared with rest when hypothalamic temperature alone was clamped at various levels between 30 degrees and 42 degrees C. However, when extrahypothalamic body core temperature was additionally clamped, the decrease in threshold during exercise was reduced to 0.43 degrees C, while the slope of the response was identical to that during rest. The results suggest that by taking account of total body core thermosensitivity, instead of hypothalamic thermosensitivity, the alleged role of a nonthermal input is greatly reduced. In addition, the results showed that the major pat of central thermosensitivity must be attributed to the extrahypothalamic body core.
Gas transport capacity and echocardiographically determined cardiac size in children
Authors: Blimkie C. J. , Cunningham D. A. , Nichol P. M.
Published: December 2017

One hundred and seventeen boys (10, 12, and 14 yr of age) were studied to determine the relation between maximal gas transport capacity (VO2 max) and cardiac size and the interaction of growth and physical activity on this relation. VO2 max was measured during treadmill exercise and heart size was obtained during supine rest by M-mode echocardiography. Left ventricular end-diastolic diameter (LVIDd), resting stroke volume (SV), and calculated left ventricular mass (LVM) were highly correlated (0.75 < r < 0.84) with VO2 max within all age categories. Subjects with high VO2 max had significantly (P < 0.05) larger LVIDd, end-diastolic volumes, resting SV, calculated LVM, and, with the exception of the 12 yr olds, larger left ventricular end-systolic diameters and volumes than subjects with lower VO2 max. Multiple linear regression analysis revealed that fat-free weight accounted for most of the variance in VO2 max and that cardiac dimensions were only of minimal importance in determining maximal gas transport capacity in this study. The seemingly good relationship between cardiac dimensions and VO2 max was mainly attributable to the shared influence of body size on both these factors.
Effect of chest wall vibration on ventilation in patients with spinal cord lesion
Authors: Homma I. , Nagai T. , Sakai T. , Ohashi M. , Beppu M. , Yonemoto K.
Published: December 2017

Changes of respiration caused by chest wall vibration were studied in 13 patients with cervical cord lesions. Vibrators applied on the chest wall were intermittently triggered by the patient's respiratory movements. The vibrators were triggered to be applied in three ways. 1) Upper vibrations were bilaterally applied during inspiration on the 2nd or 3rd parasternal intercostal spaces (insp "in-phase" vibration). 2) Lower vibrations were bilaterally applied during expiration on the 7th-to 10th intercostal spaces anterior to midaxillary lines (exp "in-phase" vibration). 3) Inspiratory and expiratory vibrations were combined to produce alternating in phase vibration. Both inspiratory and expiratory vibrations increased tidal volume (VT), but the alternating in-phase vibration increased it to significantly higher values (P less than 0.05). Minute volume of ventilation (VE l/min) also increased with insp or exp in-phase vibration. The alternating in-phase vibration increased VE l/min to even higher values (P less than 0.05). The responses described probably depend on segmental vibration reflexes arising in the inspiratory and expiratory intercostal muscles underlying the vibrators. The alternating in-phase vibration may well be useful to improve the breathing in patients with respiratory insufficiency.
Diffusing capacity of the lung during hypoxia: role of capillary recruitment
Authors: Capen R. L. , Latham L. P. , Wagner W. W.
Published: December 2017

We have used in vivo microscopy to show that airway hypoxia caused pulmonary capillary recruitment. To determine whether the recruited capillaries add to the surface area for gas exchange, we measured the diffusing capacity of the lung for carbon monoxide before and after inducing recruitment with hypoxia. Diffusing capacity increased during hypoxia. However, some increase in diffusing capacity was expected, since there were fewer oxygen molecules to compete with carbon monoxide for hemoglobin-binding sites. To determine the effect of capillary recruitment alone on diffusing capacity, we held hypoxia constant while infusing a vasodilator to diminish recruitment. Diffusing capacity decreased concomitantly as recruitment diminished. These results indicate that our microscopic observations reflect a widespread recruitment that increases the gas exchange surface area.
Effect of methysergide on the acute lung mechanics response to endotoxin
Authors: Allison R. C. , Murphy T. L. , Weisman I. M. , McCaffree D. R. , Gray B. A.
Published: December 2017

The effect of the serotonin antagonist methysergide on the acute lung mechanics response to endotoxin in anesthetized, paralyzed, mechanically ventilated dogs was investigated. In five dogs given 0.25 mg/kg Escherichia coli endotoxin only, the pulmonary nonelastic resistance (RL) increased to 238% of control and dynamic compliance (CL) decreased to 50% of control. In a second group of five dogs, methysergide (0.25 mg/kg) was shown to markedly attenuate the lung mechanics response to serotonin (0.04 mg/kg), which alone had produced changes in lung mechanics greater than endotoxin. In these same dogs endotoxin administered after injection of methysergide produced an increase in RL to 377% and a decrease in CL to 33% of control. In a third group of five dogs whose lung mechanics response to serotonin was also greater than to endotoxin alone, endotoxin administered after injection of saline produced an increase in RL to 168% and a decrease in CL to 58% of control. Since the response to endotoxin after injection of methysergide exceeded the response after saline, we conclude that serotonin is not a mediator of the acute lung mechanics response to endotoxin.
Thoracic resistivity for stroke volume calculation in impedance cardiography
Authors: Quail A. W. , Traugott F. M. , Porges W. L. , White S. W.
Published: December 2017

Blood resistivity (rho) values used in the Kubicek formula for stroke volume (SV) calculation by impedance cardiography are bench derived and do not take into account complex blood velocity movements and dynamic hematocrit changes in systole. In this study, the relevance of rho has been questioned. Thoracic resistivity (rho tau) has been calculated in dogs from the rearranged Kubicek formula: rho tau = (SV . ZO2)/(L2 dZ/dtmax.T), where SV was measured by the electromagnetic flowmeter (EM). Hematocrit (Hct) in the dog was varied by hemorrhage and infusion. In contrast to the direct and exponential bench rho-Hct relationship, rho tau varies inversely with Hct, but by no more than +6.3 omega . cm (at Hct 26%) and -11.8 omega . cm (at Hct 66%) about a mean rho tau of 135 +/- 1.0 omega . cm (at Hct 40%). Impedance SV calculated using rho tau over a wide range of SV bears a linear relationship to EM values with a 95% prediction limit for a single SV estimate of +/- 0.84 about a mean value of 26.9 ml. The findings suggest that rho tau is virtually constant during a variety of physiological disturbances.
Evaluation using dogs of a method for estimating mixed venous and arterial PCO2 from a single breath
Authors: Mohammed M. M. , Hainsworth R.
Published: December 2017

Estimates of arterial and true mixed venous carbon dioxide tension (PCO2) were made from the continuous records of the changes in carbon dioxide and oxygen tensions in the expired gas during a single prolonged expiration, as described by Kim, Rahn, and Fahri (J. Appl. Physiol. 21: 1338, 1966). The results were compared with the results of direct analyses of systemic arterial and pulmonary arterial blood. There was no systemic error of the arterial estimates over a range of 32-48 Torr or of the venous estimates over a range of 33-59 Torr. The random errors of the arterial and venous estimates were +/- 1.5 and 1.2 Torr (2 SD) respectively. These results are better than those obtained by other noninvasive methods.
Evaluation using dogs of a method for estimating cardiac output from a single breath
Authors: Mohammed M. M. , Wood L. M. , Hainsworth R.
Published: December 2017

We have evaluated the single-breath method of Kim, Rahn, and Fahri (J. Appl. Physiol. 21: 1338, 1966) using anesthetized dogs (avg wt 26 kg). The systematic error was determined by comparing the single-breath estimates of cardiac output with values obtained by the dye-dilution method. In some dogs the effects of moderate exercise were stimulated by joining the circulations of two dogs. From paired estimates, the random error of the single-breath method was +/- 12% (95% tolerance limits; 23 pairs) over a range of outputs 1.1-5.0 l/min. There was no significant difference between values of cardiac output by the single-breath method and by dye dilution, and in four dogs the dye-dilution values were not significantly different from values of pulmonary blood flow controlled by perfusion. These results indicate that under carefully controlled conditions the single-breath method is capable of providing reliable estimates of cardiac output.
Influence of exercise on free amino acid concentrations in rat tissues
Authors: Dohm G. L. , Beecher G. R. , Warren R. Q. , Williams R. T.
Published: December 2017

Levels of free amino acids in muscle, liver, and plasma were measured in rats that had either swum (1 or 2 h) or run (until exhausted). Exercise lowered alanine levels in all three tissues except for liver of exhausted rats. Exercise decreased the plasma levels of the acidic amino acids and their amides. Glutamate and glutamine levels were depressed in muscle, and the glutamine level was lowered in liver by exercise. Aspartate concentration was lowered by exercise in liver but elevated in muscle. The branched-chain amino acids were generally elevated by exercise as were tyrosine, phenylalanine, methionine, and lysine. Plasma 3-methylhistidine concentration was also elevated by an exercise bout. The changes observed in the amino acid contents of muscle, liver, and plasma are consistent with the increase in protein degradation during exercise that we previously reported. The lowered levels of some amino acids (e.g., alanine, glutamine, glutamate) seem to suggest that amino acid catabolism and/or gluconeogenesis is increased by exercise.
Plasma C-peptide and insulin in trained and untrained subjects
Authors: Wirth A. , Diehm C. , Mayer H. , Morl H. , Vogel I. , Bjorntorp P. , Schlierf G.
Published: December 2017

Plasma insulin and C-peptide were simultaneously determined under various conditions in 11 endurance-trained athletes and 12 nonathletes. Both groups performed an exhaustive ergometer test and an endurance test with 38% of the maximal achieved work load for 45 min. An intravenous glucose tolerance test was also performed. In the basal state, athletes had low plasma insulin and C-peptide concentrations. During exercise, insulin and C-peptide decreased similarly in both groups. In the recovery period, insulin and C-peptide rose within a few minutes. There were differences between the extent as well as the time course of this "rebound" effect after exhaustive or endurance exercise that might be related to glucose alterations. The insulin response but not the C-peptide response after glucose injection was blunted in trained subjects. Results indicate that basal plasma insulin concentrations are lower in athletes due to reduced insulin secretion. During exercise, insulin secretion is diminished independent of the training state. The blunted response of insulin after glucose administration in athletes is due to an enhanced plasma clearance.
Perception of changes in breathing in normal human subjects
Authors: Wolkove N. , Altose M. D. , Kelsen S. G. , Kondapalli P. G. , Cherniack N. S.
Published: December 2017

Respiratory sensation was evaluated in normal subjects from their ability to quantitate changes in tidal volume. Subjects attempted to duplicate or double tidal volumes of different sizes while breathing freely or against a resistive or elastic load. When the mechanical conditions during control and test breaths were constant, tidal volume duplication was accomplished with an error of approximately 100 ml, regardless of the control volume. The error in doubling, however, increased progressively with increasing control tidal volume. There was a greater error in both volume duplication and doubling when the mechanical conditions between control and test breaths were changed. When test breaths against a load followed unloaded control breaths, tidal volume failed to double, but intrathoracic pressure changes twice exceeded control values. Conversely, when unloaded test breaths followed loaded control breaths, pressure changes underwent less than a twofold increase while tidal volume more than doubled. The results indicate that tidal volume changes are normally sensed with considerable accuracy and suggest that both tidal volume per se, as well as the forces generated by the respiratory muscles, are used in the estimation of tidal volume changes.
Effects of hyperoxia on transtracheal chloramphenicol influx
Authors: Cloutier M. M. , Block E. R.
Published: December 2017

Effects of exposure to high partial pressures of oxygen on transtracheal influx of chloramphenicol (Chlor) were examined using in vitro perfusion of the rat trachea. Net Chlor influx decreased with increasing duration of exposure to 100% O2 from control levels of 37.0 +/- 2.4 ng.min-1.trachea-1 to 30.0 +/- 1.0 ng.min-1.trachea-1 after 36 h of exposure to 100% O2 and was further depressed after 48 h of exposure to 100% O2 60 23.0 +/- 0.9 ng.min-1.trachea-1. Examination of the O2-exposed tracheas by light microscopy showed normal morphology. In contrast, net Chlor influx was not affected by exposure to 50% O2 for 48 h. In a separate group of rats recovery from the effects of hyperoxia was studied. Within 24 h after removal from the hyperoxic environment, net Chlor influx had returned to control levels. We conclude that high partial pressures of oxygen inhibit net Chlor influx in the rat trachea at a time when tracheal histology is normal. This inhibition is a function of the partial pressure of oxygen and the duration of exposure and it is reversible after removal from the hyperoxic environment.
Pharmacologic study of respiratory afterdischarge
Authors: Millhorn D. E. , Eldridge F. L. , Waldrop T. G.
Published: December 2017

Respiratory afterdischarge, an increased but slowly declining respiratory output lasting some minutes after cessation of a stimulus, is generated by a bulbopontine mechanism whose precise anatomic locus and neurophysiological mechanism are unknown. To determine if the mechanism responsible for the afterdischarge was due to one of the major long-acting central neurotransmitters, we studied a control group of animals and groups of animals that were pretreated with the antiserotonin agents, methysergide, parachlorophenylalanine, and 5,7-dihydroxytryptamine, the dopamine-norepinephrine antagonists alpha-methytyrosine and haloperidol, and the endorphin antagonist, naloxone. Anesthetized, paralyzed, vagotomized, and glomectomized cats were used. We measured phrenic activity before, during, and after carotid sinus nerve and calf muscle stimulation. None of the antagonists had an effect on the response to stimulation, on the magnitude of the afterdischarge, or on its time course during recovery. We conclude that these central neurotransmitters do not participate in the genesis of the respiratory afterdischarge.
Fibrinolytic activity without fibrinogenolysis during long-distance racing in horses
Authors: Ferguson E. W. , Bernier L. L. , Shaughness G. P. , Boucher J. H.
Published: December 2017

Fourteen horses were studied during a 157-km endurance ride. Two humans who ran the 157 km were also evaluated at the finish. Fibrin monomer samples were examined by two-dimensional gel electrophoresis and sodium dodecyl sulfate polyacrylamide gel electrophoresis. Two major species of horse Beta-chain with higher molecular weights and different isoelectric mobilities than human beta-chain were observed. Horse alpha-chains had higher molecular weights than human alpha-chains but similar alpha-chain heterogeneities. Mean euglobulin lysis time (ELT) in the horses was accelerated to similar levels throughout the ride (52% of control at 44 km, P less than 0.01), but mean plasma clot lysis time (PCLT) decreased progressively during the ride (30% of control at finish, P less than 0.005). Similar values for ELTs and PCLTs were noted in the runners and horses at the finish. Although fibrinolytic activity was accelerated for an extended period by the strenuous activity of this long-distance race, no evidence of increased carboxyl terminal degradation of the A alpha-chain was observed. This study suggests that prolonged physiological stimulation of the fibrinolytic enzyme (plasmin) system is not responsible for fibrinogen A alpha-chain heterogeneities observed in horses and humans. It further demonstrates the usefulness of horses as models for the study of exercise-induced fibrinolysis.
Hypoxemia and pulmonary gas exchange during hemodialysis
Authors: Patterson R. W. , Nissenson A. R. , Miller J. , Smith R. T. , Narins R. G. , Sullivan S. F.
Published: December 2017

With measured values of arterial blood gas tensions, of expired respiratory gas fractions, and volume of the expired ventilation, the determinants of alveolar oxygen tension (PAO2) were used to evaluate their influence on the development of the arterial hypoxemia that occurs in spontaneously breathing patients undergoing hemodialysis using an acetate dialysate. Dialysis produced no significant changes in the alveolar-arterial O2 tension gradient (AaDO2). The extracorporeal dialyzer removed an average of 30 ml.m-2.min-1 of CO2. Accordingly the pulmonary gas exchange ratio (R) dropped from a mean predialysis value of 0.81 to 0.62 (P less than 0.001). The arterial CO2 tension remained constant throughout, whereas the minute ventilation, both total (P less than 0.01) and alveolar (P less than 0.01), decreased during dialysis. This decrease in ventilation accounts for more than 80% of the fall in PAO2. During dialysis there was a decrease (P less than 0.001) in arterial oxygen tension (PaO2), which varied among the individuals from 9 to 23% of control. During the postdialysis hour PaO2 returns to control values concomitant with increase in ventilation. The quantitative gas exchange relationships among R, alveolar ventilation, and AaDO2 predict the PaO2 values actually measured.
Correlation studies of individual variation in susceptibility to various components of HPNS in mice
Authors: Brauer R. W. , Beaver R. W. , Gillen H. W.
Published: December 2017

Individual convulsion threshold pressures were determined in mice exposed successively to type I and type II convulsions of the high-pressure neurological syndrome (HPNS), as well as in others exposed, in successive compressions, to type I convulsions under diverse conditions of replication of compression rate. Correlation analyses of the results showed the following degrees of correlation of individual convulsion-threshold pressures: type I with type II-negligible (r2 less than equal to 0.2); type I with type I at the same compression rate-closely correlated (r2 greater than or equal to 0.8); type I with type I at a different compression rate-negligible (r2 less than or equal to 0.2). Individual susceptibility to HPNS (type I) convulsions thus is a stable characteristic of individual seizures vary independently of one another. Likewise, the magnitude of the individual compression rate effect varies independently of intrinsic individual susceptibility to type I HPNS seizures. The results support the view that the HPNS is a composite entity, define constraints on personnel selection, and provide a basis for estimating the efficacy of various selection strategies.
Effect of acute alterations of blood volume on circulatory performance in humans
Authors: Fortney S. M. , Nadel E. R. , Wenger C. B. , Bove J. R.
Published: December 2017

We produced left lower lobe (LLL) pneumococcal pneumonia in seven dogs and measured lung volumes and pulmonary mechanics before (day 1) and 48 h after (day 3) development of the infection. Compared with seven control dogs, total lung capacity (TLC) and functional residual capacity (FRC) decreased 550 and 140 ml, respectively, representing a 15% reduction from the initial value in both cases. Compliance measured during tidal breathing decreased by 30%, and even when corrected for the smaller FRC on day 3, specific compliance (CLsp) was reduced. At autopsy, the infected LLL had an excess weight of 89 g, and its 50% reduction in gas volume accounted for the decrease in TLC from day 1 to day 3. Compared with control dogs, there were no changes in the deflation pressure-volume curves of the noninfected lung of the pneumonia dogs. These results indicate that the reduction in TLC in bacterial lobar pneumonia was small and resulted from the reduced gas volume of the infected lobe. Assuming that the increased weight gain in the LLL represented 89 ml of exudate that filled alveoli, we propose that bacterial pneumonia reduced gas volume at FRC by filling alveoli with inflammatory exudate and further decreased TLC by preventing these alveoli from inflating. The reduced CLsp suggested nonventilation of air spaces in addition to those that were liquid filled and was consistent with nonventilation of the entire LLL.
Spectral characteristics of normal breath sounds
Authors: Gavriely N. , Palti Y. , Alroy G.
Published: December 2017

An objective and accurate measurement and characterization of breath sounds was carried out by a fast-Fourier-transform frequency-domain analysis. Normal vesicular breath sounds, picked up over the chest wall of 10 healthy subjects showed a characteristic pattern: the power of the signal decreased exponentially as frequency increased. Since the log amplitude vs. log frequency relationships were linear, they could be characterized by the values of the slope and the maximal frequency. The average slope of the power spectrum curves was found to be (in dB/oct +/- SD) 13.0 +/- 1.4 over the base of the right lung, 12.6 +/- 2.4 over the base of the left lung, 9.8 +/- 1.4 over the interscapular region, and 14.4 +/- 4.3 over the right anterior chest. The maximal frequencies of inspiratory and expiratory breath sounds, picked up over the base of the right lung, were (in Hz +/- SD) 446 +/- 143 and 286 +/- 53 (P less than 0.01), over the base of the left lung 475 +/- 115 and 284 +/- 47 (P less than 0.01), over the interscapular region 434 +/- 130 and 338 +/- 77 (P less than 0.05), and over the right anterior chest 604 +/- 302 and 406 +/- 205 (P less than 0.05). Breath sounds picked up over the trachea were characterized by power spectra typical to a broad spectrum sound with a sharp decrease of power at a cut-off frequency that varied between 850 and 1,600 Hz among the 10 healthy subjects studied.
Ventilation-perfusion relationships with high cardiac output in lobar atelectasis
Authors: Schumacker P. T. , Newell J. C. , Saba T. M. , Powers S. R.
Published: December 2017

Pulmonary gas exchange was evaluated in 10 anesthetized mechanically ventilated dogs. Cardiac output (QT) was increased approximately 50% by opening peripheral arteriovenous fistulas. With both lungs ventilated, increasing QT increased mixed venous O2 both pressure (PO2) and pulmonary arterial pressure, but neither shunt fraction nor the distribution of ventilation-perfusion was consistently altered. During left lung atelectasis, increasing QT again increased mixed venous PO2 and pulmonary arterial pressure, but two different responses in shunt-like perfusion were measured. In four dogs, left lung atelectasis caused a shunt fraction of 46 +/- 6% that was not changed by high QT (P greater than 0.05). In six dogs, atelectasis caused a shunt fraction of 24 +/- 3% during normal QT that increased to 42 +/- 2% during high QT (P less than 0.001). Dogs whose shunt fraction during atelectasis was high and unchanged by QT had lower arterial pH (7.24 +/- 0.03) than dogs whose shunt fraction was initially lower and was increased with QT (7.36 +/- 0.02) (P less than 0.01). We conclude that increased QT can worsen shunt flow during lobar atelectasis when hypoxic vasoconstriction has been effective in limiting perfusion to the collapsed region at normal levels of QT.
Effect of peripheral chemoreceptor denervation on acclimatization of goats during hypoxia
Authors: Forster H. V. , Bisgard G. E. , Klein J. P.
Published: December 2017

The purpose of this study was to determine the effect of peripheral chemoreceptor denervation on ventilatory acclimatization of goats during chronic hypoxia. After 1 h of stimulated altitude (PB 450 Torr), arterial O2 tension (PaO2) in seven normal goats averaged 42 Torr, and arterial CO2 tension (PaCO2) was 1.3 Torr below control (P less than 0.001). In these goats nearly 66% of the increase in alveolar ventilation (VA) associated with acclimatization occurred between 1.5 and 4 h of hypoxia. Acclimatization was complete by the 3rd day of hypoxia, and it caused 1) a 23% increase in VA/CO2 output (P less than 0.001); 2) a 5-Torr increase in PaO2 (P less than 0.001); and 3) a 6.5-Torr decrease in PaCO2 (P less than 0.001). Denervation of the carotid chemoreceptors in seven goats caused hypoventilation during eupnea at sea level (PaCO2 change from control +7 Torr, P less than 0.001). Denervation also attenuated but did not eliminate peripheral chemoreceptor responsiveness. No additional changes were observed following attempted denervation of the aortic chemoreceptors. After 1 h of simulated altitude (PB 530 Torr), PaO2 in the denervated goats averaged 46 Torr, and PaCO2 was increased 1.1 Torr above control (P less than 0.001). In these goats VA did not change significantly during the subsequent 3 days of hypoxia. Accordingly, we conclude that the peripheral chemoreceptors are essential for ventilatory acclimatization of goats during chronic hypoxia.
Efficiency of trained subjects differing in maximal oxygen uptake and type of training
Authors: Stuart M. K. , Howley E. T. , Gladden L. B. , Cox R. H.
Published: December 2017

This study was undertaken to examine the relationship between energy expenditure and work rate on a bicycle ergometer in five sprinters and five distance runners who differed in maximal oxygen uptake (VO2max) and type of training. Each subject performed at work rates of 30, 60, 90, 120, and 150 watts (W). The relationship between energy expenditure and work rates was most accurately described by a quadratic curve for both groups: for sprinters, energy expenditure (kJ) = 11.57 + 0.1812 (W) + 0.00046 (W)2; for distance runners, energy expenditure (kJ) = 11.74 + 0.1386 (W) + 0.00060 (W)2. Delta efficiency (delta work accomplished divided by delta energy expended X 100%) decreased as work rate increased. Statistical analyses revealed no significant differences between groups in delta efficiency at the same work rate (P greater than 0.25) or at the same relative work rate (P greater than 0.75). These results suggest that differences in VO2max and/or type of training have little or no causal effect on the decrease in delta efficiency with increasing work rate. The observed decrease in delta efficiency may be due to increases in metabolism not directly related to the performance of the external work or to an increasing amount of unmeasured work as work rate increases on a bicycle ergometer.
Effect of severe hypoxia on the pulmonary vascular response to vasoconstrictor agents
Authors: Harabin A. L. , Peake M. D. , Sylvester J. T.
Published: December 2017

When isolated blood-perfused pig lungs are exposed to inspired O2 tensions (PIO2) below 30 Torr, hypoxic pulmonary vasoconstriction is transient. To determine whether this transience is caused by a decrease in the amount of ATP available for maintenance of smooth muscle contraction, we compared normoxic (PIO2 = 100 Torr) and hypoxic (PIO2 = 10 Torr) dose-response curves to infusions of prostaglandin F2 alpha (PGF2 alpha), angiotensin II (AII), and potassium chloride (KCl). Hypoxia caused reversible depression of the responses to PGF2 alpha and AII but had no effect on the response to KCl. Because during hypoxia the lung was capable of an undiminished vasoconstrictor response to at least one agent, it seems unlikely that the supply of ATP available for contraction was limiting. The mechanism for the transience of the vasoconstrictor response to low PO2 values and the depression of the response to AII and PGF2 alpha remains unknown, but could involve depression of ATP production sufficient to limit some energy-requiring process other than contraction or release of a vasodilator.
CSF acid-base regulation and ventilation during acute hypercapnia in the newborn dog
Authors: Nattie E. E. , Edwards W. H.
Published: December 2017

We studied the response of blood, cerebrospinal fluid (CSF), and brain ionic composition and acid-base status as well as ventilation to acute respiratory acidosis (FICO2 0.08) in lightly anesthetized newborn puppies. Control puppy plasma ions and CSF-plasma ionic distribution ratios were essentially adultlike while in blood a mild, compensated respiratory acidosis was present, and in CSF, PCO2 and [HCO3-] were slightly higher than in adults. Brain tissue water content was higher in puppy vs. adult; the Cl- space was greater; the content of [Na+], [Cl-], and [HCO3-] were higher and [K+] lower. During respiratory acidosis, CSF [HCO3-] increased 2.0 mmol/l by 15 min and 6.2 mmol/l by 3 h, a response quantitatively like that observed in the adult. The quantity, CSF [Na+] -- [Cl-], increased stoichiometrically with CSF [HCO3-], indicating the mechanistic involvement of these ions in the CSF [HCO3-] response. In brain tissue, water content, [Cl-], and the [Cl-] space were unchanged, but by 3 h [Na+] and [HCO3-] were increased. Ventilation was stimulated but the response expressed as ml.min-1.Torr-1.body wt-1 was less in puppy than in adult.
Breathing at low lung volumes and chest strapping: a comparison of lung mechanics
Authors: Douglas N. J. , Drummond G. B. , Sudlow M. F.
Published: December 2017

In six normal subjects forced expiratory flow rates increased progressively with increasing degrees of chest strapping. In nine normal subjects forced expiratory flow rates increased with the time spent breathing with expiratory reserve volume 0.5 liters above residual volume, the increase being significant by 30 s (P less than 0.01), and flow rates were still increasing at 2 min, the longest time the subjects could breathe at this lung volume. The increase in flow after low lung volume breathing (LLVB) was similar to that produced by strapping. The effect of LLVB was diminished by the inhalation of the atropinelike drug ipratropium. Quasistatic recoil pressures were higher following strapping and LLVB than on partial or maximal expiration, but the rise in recoil pressure was insufficient to account for all the observed increased in maximum flow. We suggest that the effects of chest strapping are due to LLVB and that both cause bronchodilatation.
A new method for computer-assisted determination of airways resistance
Authors: Chowienczyk P. J. , Rees P. J. , Payne J. , Clark T. J.
Published: December 2017

Conventional methods for determining airways resistance, based on the recording of pressure and flow as X-Y displays, may yield inconsistent results because airways resistance is only one of a number of factors determining the shape of such displays. The temporal behavior of alveolar pressure and flow during panting suggests that the relationship between pressure and flow should be formulated in terms of differential equations. An equation is postulated to include terms characterizing resistance, gas inertance, and the behavior of the lungs as a number of parallel compartments with time constants that may be different. A simple algorithm allows these terms to be deduced from measured pressure and flow signals. Measurements obtained using the new method correlate well with those obtained using conventional methods. Variation of specific airways conductance is significantly reduced when compared with values obtained by conventional methods. Measured values for inertance agree well with theoretically predicted values.
Modification of the Monark bicycle ergometer for underwater exercise
Authors: Shapiro Y. , Avellini B. A. , Toner M. M. , Pandolf K. B.
Published: December 2017

A standard Monark bicycle ergometer was modified for underwater exercise by removal of the friction belt and attachment of one to six metal fins to the flywheel. Three fins could be fastened to either side of the flywheel. The fins used on the left side of the wheel were made of standard perforated angle iron with the perpendicular side measuring 38 mm; those on the right side were made from the same length of nonperforated angle iron but with a perpendicular side of only 26 mm. Net surface area of the two types of fins (excluding area of perforation) was the same. Oxygen uptake (VO2) was found to be: VO2 = a(rpm)b + 0.25, 1.min-1, with a = 0.00164 -- 0.00104n + 0.000266n2 -- 0.00002n3; b = 1.64 + 0.506n -- 0.104n2 + 0.00667n3, when n is the number of fins. The correlation coefficient (r) between measured and predicted VO2 was r = 0.98. The preferable range of pedaling speeds was 29-40 rpm to maintain a constant speed for up to 1 h. Major advantages of this modified ergometer for underwater exercise are 1) the modification is simple and the same ergometer can be used for land exercise, 2) the ergometer can be biologically calibrated and used for a wide range of exercise oxygen uptakes, and 3) subjects can perform for a proportionally longer time period than other modifications of the same ergometer.
Effect of naloxone on ventilation in newborn rabbits
Authors: Hazinski T. A. , Grunstein M. M. , Schlueter M. A. , Tooley W. H.
Published: December 2017

Endorphins have been isolated from amniotic fluid and cord blood of mammals. To determine if these agents influence ventilation after birth, we measured ventilation (VE), tidal volume, inspiratory time, and respiratory frequency (f) in 19 rabbit pups before and after administration of naloxone (NLX), an endorphin antagonist. Tracheostomy and carotid artery cannulation were performed under light ether anesthesia. After 30-90 min for recovery the pups were placed in a body plethysmograph. Rectal temperature was kept at 37 +/- 0.5 degrees C. After 15 min of control measurements we infused saline, which had no respiratory effect. NLX (4 microgram/g) was then infused and measurements continued for 30 min. In 6 of 7 pups less than or equal to 4 days old, VE increased to 140-180% of control values and remained elevated for the remainder of the study period. Increased VE was due solely to increased f. By contrast, only 1 of 12 pups greater than or equal to 5 days old responded in this fashion. This difference was significant (P less than 0.005). Arterial blood gases were measured before and after NLX in 10 pups. In those pups who increased their ventilation after NLX, arterial CO2 tension fell and pH rose above pre-NLX values (P less than 0.05) for both variables). Blood gases of the group whose ventilation was uneffected remained unchanged. These results indicate that early in postnatal life endorphins probably modulate central respiratory drive in rabbits but that these agents become less important with maturation.
Acid-base regulation during heating and cooling in the lizard, Varanus exanthematicus
Authors: Wood S. C. , Johansen K. , Glass M. L. , Hoyt R. W.
Published: December 2017

Current concepts of acid-base balance in ectothermic animals require that arterial pH vary inversely with body temperature in order to maintain a constant OH-/H+ and constant net charge on proteins. The present study evaluates acid-base regulation in Varanus exanthematicus under various regimes of heating and cooling between 15 and 38 degrees C. Arterial blood was sampled during heating and cooling at various rates, using restrained and unrestrained animals with and without face masks. Arterial pH was found to have a small temperature dependence, i.e., pH = 7.66--0.005 (T). The slope (dpH/dT = -0.005), while significantly greater than zero (P less than 0.05), is much less than that required for a constant OH-/H+ or a constant imidazole alphastat (dpH/dT congruent to 0.018). The physiological mechanism that distinguishes this species from most other ectotherms is the presence of a ventilatory response to temperature-induced changes in CO2 production and O2 uptake, i.e., VE/VO2 is constant. This results in a constant O2 extraction and arterial saturation (approx. 90%), which is adaptive to the high aerobic requirements of this species.
Wheelchair exercise performance of the young, middle-aged, and elderly
Authors: Sawka M. N. , Glaser R. M. , Laubach L. L. , Al-Samkari O. , Suryaprasad A. G.
Published: December 2017

The purpose of this study was to quantitate the maximal power output (POmax), peak oxygen uptake (peak VO2), and maximal heart rate (HRmax) for wheelchair ergometer (WERG) exercise performed by three groups of disabled males: young adult (20-30 yr), middle-aged (50-60 yr), and elderly (80-90 yr). These subjects, who were confined to wheelchairs for similar time periods (mean = 11.7 yr), participated in progressive-intensity discontinuous test protocols on a WERG. Lower (P less than 0.01) mean POmax, peak VO2, and HRmax values were found with advancing age groups. In relationship to age, decreases in POmax and HRmax values were best described by parabolic models, whereas decreases in peak VO2 values were best described by a linear model. In comparison with young adults (83 W, 27 ml . kg-1 . min-1), surprisingly low POmax and peak VO2 values were found for the middle-aged (16 W, 10 ml . kg-1 . min-1) and elderly (7 W, 8 ml . kg-1 . min-1). When our peak VO2 data were combined with other data in the literature for upper body exercise by male disabled individuals, a decrease of 0.19 1 . min-1 or 2.9 ml . kg-1 . min-1 per decade of life was found.
Metabolic response to respiratory heat loss-induced core cooling
Authors: Piantadosi C. A. , Thalmann E. D. , Spaur W. H.
Published: December 2017

To study the phenomenon of isolated core cooling, four resting men breathed cooled helium-oxygen (T in = 14 +/- 2 degrees C, 40-60% relative humidity) in a warm hyperbaric chamber at pressures equivalent to 640, 1,000, and 1,400, and 1,800 ft seawater (fsw). Rectal temperature (T re) fell by 0.43 +/- 0.13 degrees C at 640 fsw to 0.98 +/- 0.15 degrees C at 1,800 fsw after 60 min. The rate at which T re fell was linearly related to the product of inspired gas density times specific heat. The metabolic response (VO2) to this isolated core cooling was more closely related to the rate of fall in T re than to the magnitude of this fall. A distinct threshold temperature, below which a rise in VO2 would occur, was not demonstrable. However, when the rate of fall of T re exceeded 0.70 degrees C . h-1, VO2 increased above base line, in spite of high skin temperatures that may have blunted the VO2 response. When VO2 did increase, its net benefit on thermal homeostasis was negated by the associated rise in pulmonary ventilation and its attendant increase in respiratory heat loss. Breathing cool helium-oxygen under hyperbaric conditions can rapidly lower deep body temperature, even in the presence of a warm body surface.