bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaction between serotonin and efferent vagus nerves in dog lungs
Authors: Hahn H. L. , Wilson A. G. , Graf P. D. , Fischer S. P. , Nadel J. A.
Published: December 2017

We anesthetized, paralyzed, and ventilated 32 dogs. In 16 dogs we measured total pulmonary resistance (RL) during inhalation of acetylcholine (ACh), serotonin (5-HT), and histamine (Hist) aerosols. Cooling both cervical vagi reduced the bronchoconstriction caused by 5-HT 64% (P = 0.001), reduced Hist-induced bronchoconstriction 17% (P = 0.003), and did not significantly reduce bronchoconstriction due to ACh. In seven dogs, we ventilated both lungs separately through a double-lumen catheter. Application of 5-HT to one lung increased the transpulmonary pressure amplitude in the homolateral but not in the contralateral lung. Cooling the homolateral vagus reduced this response 32% (P = 0.02). In nine dogs, we stimulated the peripheral ends of both cut cervical vagi before and during aerosol application of ACh, 5-HT, and Hist. ACh and Hist increased baseline RL 97 and 134%, respectively, without increasing the effect of vagal stimulation. 5-HT increased baseline RL only 27% but greatly augmented the effect of vagal stimulation (mean increase, 271%, P = 0.001). We conclude that 5-HT acts to potentiate vagal effects on airway smooth muscle via the efferent vagal pathway.
Effects of age on regional residual volume
Authors: Jones R. L. , Overton T. R. , Hammerlindl D. M. , Srpoule B. J.
Published: December 2017

Forty-one normal non-smokers between the ages of 20 and 80 were studied to determine if the increased residual volume, known to occur with aging, results from increased residual volume throughout, or only in specific regions of the lung. The subjects were dividied into groups consisting of 20–29, 30–39, 40–49, 50–69, and 70+ yr. Measurements of regional residual volume to regional total lung capacity ratio (RVr/TLCr) were made using zenon-133 and a multidetector analysis system in which five zones (from top to bottom) were analyzed in each lung. Closing volume was also measured. The subjects were in the sitting position for all studies. The results showed regardless of age, the RVr/TLCr was higher at the top than at the bottom of the lung. In addition, the ratio of upper to lower RVr/TLCr was not significantly different between any of the age groups. The results can be explained if airways throughout the lung close at higher volumes as age increases, or if altered emptying sequences within regions occur due to retarded emptying of highly compliant lung regions.
Maturation of respiratory control in unanesthetized newborn rabbits
Authors: Wyszogrodski I. , Thach B. T. , Milic-Emili J.
Published: December 2017

The maturation of control of breathing was studied in unanesthetized rabbit pups breathing room air in a body plethysmograph during the first 8 postnatal days. Measurements include pulmonary ventilation (VE), tidal volume (VT), inspiratory (TI) and total breathing cycle (Ttot) durations, TI/Ttot, mean inspiratory flow (VT/TI), and tracheal pressure developed by the inspiratory muscles 0.1 and 0.2 s after the onset of inspirations with airways occluded at functional residual capacity (P0.1 and P0.2). All of the above variables increased progressively from the 1st to the 8th day, except for P0.1, P0.2, and TI/Ttot which remained constant. The constancy of TI/Ttot implies that the increase in VE with age was due entirely to increased VT/TI. The constancy of P0.1 and P0.2 implies that the increase in VT/TI with age was due to decreased “effective” impedance of the respiratory system. The latter probably mainly reflects increased compliance and decreased flow resistance with growth. The results also show that during the first 8 days of life there is a progressive shift to the right in the VT vs. TI relationship.
Control of ventilation during intravenous CO2 loading in the awake dog
Authors: Stremel R. W. , Huntsman D. J. , Casaburi R. , Whipp B. J. , Wasserman K.
Published: December 2017

The ventilatory response to venous CO2 loading and its effect on arterial CO2 tension was determined in five awake dogs. Blood, 200–500 ml/min, was diverted from a catheter in the right common carotid artery through a membrane gas exchanger and returned to the right jugular vein. CO2 loading was accomplished by changing the gas ventilating the gas exchanger from a mixture of 5% CO2 in air to 100% CO2. The ventilatory responses to this procedure were compared with those resulting from increased inspired CO2 concentrations (during which ventilation of the gas exchanger with the air and 5% CO2 mixture continued). The ventilatory response to each form of CO2 loading was computed as deltaVE/deltaPaco9. The mean ventilatory response to airway CO2 loading was 1.61 1/min per Torr PaCO2. The mean response for the venous CO2 loading was significantly higher and not significantly different from “infinite” CO2 sensitivity (i.e., isocapnic response). The results provide further evidence for a CO2-linked hyperpnea, not mediated by significant changes in mean arterial PCO2.
Solute permeability of the alveolar epithelium in alloxan edema in dogs
Authors: Nelson R. M. , McIntyre B. R. , Egan E. A.
Published: December 2017

The permeability of the alveolar epithelium following alloxan challenge was studied in dogs by determining transfer of radiolabeled solutes between alveolus and blood. Two days after injection of 131-Ialbumin into the blood, anesthetized dogs had the air space of part of one lung isolated by a balloon catheter lodged in a bronchus. We infused the atelectatis-isolated area with normal saline containing trace amounts of Blue Dextran, 125Ialbumin, and 57Co-cyanocobalamin; challenged six animals with intravenous alloxan, and six animals with alloxan added to the alveolar saline. During the pulmonary edema, 57Co-cyanocabalamin and 125I-albumin appeared in the blood and 131I-albumin entered the alveolar saline. The animals challenged by alveolar instillation showed a greater permeability change (P less than 0.05). The bidirectional transfer of macromolecules indicates that alloxan produces a change in the permeability of the alveolar epithelium, allowing diffusional exchange of macromolecules. Since alveolar flooding in hemodynamic edema does not show a similar change in the permeability of the epithelial lining, alveolar flooding in alloxan edema is not due solely to an effect on the endothelial membrane, but also to a direct effect on the epithelial membrane.
Emptying patterns of the lung studied by multiple-breath N2 washout
Authors: Lewis S. M.
Published: December 2017

Changes in the nitrogen concentration seen during the single-breath nitrogen washout reflect changes in relative flow (V) from units with differing ventilation/volume ratios (V/V0). The multiple-breath washout provides sufficient data for the V for units with varying V/V0 to be plotted as a function of the volume expired. Flow from the dead space may also be determined. In young normals the emptying patterns are narrow and unimodal throughout the alveolar plateau with little or no flow from the dead space at the end of the breath. Older normals show more flow from the dead space, particularly toward the end of the breath, and some show a high V/V0 mode early in the breath. Patients with obstructive lung disease have a high flow from the dead space which is present throughout the breath. A well ventilated mode at the end of the breath is seen in some obstructed subjects. Patients with cystic fibrosis showed a poorly ventilated mode appearing at the end of the breath as well as a very high dead space.
Temperature and corticosterone relationships in microwave-exposed rats
Authors: Lotz W. G. , Michaelson S. M.
Published: December 2017

Plasma corticosterone and colonic temperature were measured in unanesthetized male rats exposed to 2,450-MHz continuous wave (cw) radiation to characterize the response of the pituitary-adrenal axis to microwave exposure. The rats were exposed in the far field of a horn antenna for 30 or 60 min at power densities of 0, 13, 20, 30, 40, 50, or 60 mW/cm2, or for 120 min at 0, 13, 20, 30, or 40 mW/cm2. The average energy absorption rate of the rats was 0.16 W/kg absorbed per mW/cm2 incident. Plasma from individual rats decapitated immediately after exposure was collected for analysis. Colonic temperature was significantly elevataed after exposures to power densities of 13 mW/cm2 or greater, with progressively larger increases after high intensity exposures. Plasma corticosterone was significantly elevated above control levels only after exposures at 50 or 60 mW/cm2 for 30- or 60-min exposures, and at 20, 30, and 40 mW/cm2 for 120-min exposures. The relationship between the increased levels of circulating corticosterone and colonic temperature suggested that the increases in corticosterone levels may reflect a level of physiological response to the body temperature elevations caused by microwave exposure.
Familial aspects of decreased hypoxic drive in endurance athletes
Authors: Scoggin C. H. , Doekel R. D. , Kryger M. H. , Zwillich C. W. , Weil J. V.
Published: December 2017

One difference between endurance athletes and nonathletes is decreased ventilatory responsiveness to hypoxia and hypercapnia. It has never been clear whether these decreased responses are a consequence of conditioning or precede participation in endurance athletics. Recent studies demonstrating clusters of decreased ventilatory responses to hypoxia in families of patients with unexplained respiratory failure suggest that decreased responses in endurance athletes might be familial. To investigate this possibility, ventilatory response to hypoxia and hypercapnia were measured in 16 nonathletic, healthy parents and siblings of five successful long-distance runners. Response were compared to 34 nonathletic controls. As measured by the shape parameter A, hypoxic response was decreased to a similar extent in runners 74 +/- 6.4 (mean +/- SE) (P less than 0.05) and their relatives 69 +/- 15.2 (P less than 0.01) compared to control 128 +/- 11.3. Hypercapnic responses were slightly, but not significantly, decreased in runners and their families. We conclude familial influences made a major contribution to the decreased hypoxic ventilatory response seen in long-distance runners.
Ventilatory and waking responses to hypoxia in sleeping dogs
Authors: Phillipson E. A. , Sullivan C. E. , Read D. J. , Murphy E. , Kozar L. F.
Published: December 2017

We examined waking and ventilatory responses to acute hypoxia in four dogs during natural sleep. Progressive hypoxia was induced by a rebreathing technique in which alveolar CO2 pressure (PACO2) was held at the eucapnic level. Arterial O2 saturation (SaO2) was measured with an ear oximeter, and sleep stage was determined by electroencephalographic and behavioral criteria. Arousal from eucapnic hypoxia occurred at a SaO2 of 87.5 +/- 2.6% (mean +/- SE) during slow-wave sleep (SWS), and at a SaO2 of 70.5 +/- 3.4% during rapid-eye-movement (REM) sleep (P less than 0.005). The irregular pattern of breathing typical of REM sleep persisted during hypoxia. However linear regression analysis of breath-by-breath instantaneous minute volume of ventilation (VI) against SaO2 revealed regression coefficients in REM sleep that were similar to those found in SWS and wakefulness. This finding contrasts with earlier observations of a decreased response of VI to CO2 during REM sleep. The results indicate that although waking responses to hypoxia are delayed in REM sleep, ventilatory responses remain intact and therefore may be of importance in maintaining adequate ventilation during this stage of sleep.
Effects of severe prior exercise on assessment of maximal oxygen uptake
Authors: Stamford B. A. , Rowland R. , Moffatt R. J.
Published: December 2017

Five moderately fit males (50.8 ml.kg-1.min-1) performed 14 continuous type VO2 max tests on a motor-driven treadmill. Randomly assigned experimental sessions, consisting of three tests each and separated by 10 (tests 1, 2, 3), 20 (tests 4, 5, 6), 30 (tests 7, 8, 9), or 40 (tests 10, 11, 12) min, were conducted at a consistent hour for each subject every 4th day. Two separately performed tests were also included in the random assignment with the test eliciting the highest VO2 max value designated as the standard reference (SR). VO2 max values for tests 1 through 12 were not significantly different from the SR in spite of elevated pretest blood lactate concentrations ranging from 5 mM to 16 mM. Performance time was reduced for all tests other than tests 1, 4, 7, and 10, reaching the level of statistical significance (P less than 0.05) in tests 2, 3, 5, 6, and 9. It was concluded that valid and reliable assessment of VO2 max is possible even though testing is initiated with subjects in varying stages of exhaustion.
Effect of five human anesthetics on respiratory control in cats
Authors: Younes M. , Youssef M.
Published: December 2017

The effect of halothane, fentanyl, Innovar, thiopental, and ketamine on inspiratory output, vagal influence, and chest wall reflex was assessed in seven cats lightly anesthetized with pentobarbital, using the method of airway occlusion with and without rapid vagal cooling. All anesthetics depressed inspiratory output, as expressed by deltaP/deltat, of the first occluded inspiration. However, only halothane depressed peak inspiratory output (Pmax). Phasic vagal influence was markedly depressed by 2% halothane but was preserved under other anesthetics. The ability to induce tonic vagal influence (expiratory muscle recruitment) was lost under halothane. Inspiratory inhibitory chest wall reflex was evident in two cats during airway occlusion. Addition of any test anesthetic abolished the reflex. It is concluded that halothane should be avoided in studies dealing with assessment of vagal influence.
A roentgenographic method for measuring nasal mucous velocity
Authors: Yergin B. M. , Saketkhoo K. , Michaelson E. D. , Serafini S. M. , Kovitz K. , Sackner M. A.
Published: December 2017

Nasal mucous velocity was estimated by following the motion of radiopaque discs of Teflon by means of a fluoroscopic image intensifier. From 5 to 10 discs were deposited on the superior surface of the inferior turbinate with a forceps. No local anesthesia was employed and the subjects experienced no discomfort. The linear velocity of the discs was obtained by playing the videotape onto a television monitor, measuring distance with a ruler, and dividing by elapsed time. Duplicate runs of 1–2 min, 15 min apart were very reproducible but runs at 4-h intervals or daily over a 5-day period had a coefficient of variation of 30%. Average nasal velocity for individual ranged from 0 to 22.5 mm/min and group means ranged from 6. 8 to 10.8 mm/min. There was no statistically significant difference in nasal mucous velocity between young and elderly subjects nor was there a sexual difference. The saccharin test of nasal mucous transport was unsatisfactory because of inability to repeat the test more often than 1–2 h and its propensity to produce mild discomfort in a significant number of subjects. Saccharin times did not correlate significantly with values of nasal mucous velocity.
Body mass, composition, and food intake in rabbits during altered acceleration fields
Authors: Katovich M. J. , Smith A. H.
Published: December 2017

The effects of gravitational loading and unloading on body mass, body composition, and food intake were investigated in chronically accelerated adult male rabbits. The intensity of the acceleration field was increased by 0.25-G increments at intervals that permitted stabilization of body mass and food intake to a maximal field of 2.5 G. Control rabbits of the same age were maintained at Earth gravity under the same conditions of light and temperature. A negative rectilinear relationship was observed between body mass and the intensity of acceleration field. In spite of this, the decreased body mass appeared to be regulated, since centrifuged animals readily regained their lost body mass upon realimentation after a 3-day fast. At acceleration intensities above 1.75 G, ad libitum food intakes as well as maintenance food requirements increased with increasing acceleration fields despite a corresponding reduction in body mass. Analysis of body composition indicated a significant decrease in body fat and an increase in body water in animals adapted to a 2.5-G environment. Within 6 wk after the animals were returned from 2.5 G to Earth gravity, body mass and food intakes returned to the precentrifuged levels of corresponding control animals.
An organ culture model for study of biochemical development of fetal rat lung
Authors: Gross I. , Smith G. J. , Maniscalco W. M. , Czajka M. R. , Wilson C. M. , Rooney S. A.
Published: December 2017

We have developed a short-term organ culture model for the study of the biochemical and morphological development of late gestation fetal rat lung. Explants (1 mm3) of 19-day lung were cultured in an oxygen enriched environment in the presence of synthetic serum-free medium for 3 days. Morphological maturation continued in culture. The rate of incorporation of choline into disaturated phosphatidylcholine and the content of this phospholipid in the explants increased in vitro in a pattern very similar to that which occurs in vivo. The activities of choline kinase and cholinephosphotransferase were also similar in cultured lung and in vivo. Studies of glucose oxidation to CO2 provided additional evidence that the explants remained viable in culture. The explants retained the sensitivity of fetal lung to hormonal action. This was demonstrated by the stimulation of choline incorporation into phospholipid by cyclic AMP and an increase in the glycogen content after exposure to insulin.
Volume, flow, and timing of each breath during positive-pressure breathing in man
Authors: Bishop B. , Hirsch J. , Thursby M.
Published: December 2017

This study is a breath-by-breath analysis of the effects of 5, 10, and 15 cmH2O positive-pressure breathing (PPB) on man's steady-state breathing pattern. Inspiratory (TI), expiratory (TE), and cycle (TT) durations, tidal volumes (VT), minute ventilation (VE), mean inspiratory flow rate (VT/TI), and mean expiratory flow rate (VT/TE) were determined from pneumotachograph and Wedge spirometer recordings before and during steady states on PPB. End-tidal CO2 was continuously recorded. Seventeen adults, seated in a full body-box, breathed quietly for 8 min through a mouthpiece on a bag-in-box. Pressure in the body-box was lowered to the desired level prior to 4 min of stress. On all pressure levels, end-expiratory volume, VT, VE, VT/TI, and VT/TE increased; end-tidal CO2, TE, and TT decreased with no consistent change in TI. Calculated alveolar ventilations indicated that the increases in VE were true hyperventilations. Each individual increased VE by using a unique combination of VT, TI, and TE. End-expiratory volume increased less and expiratory flow increased more than would occur passively. Hence, it is concluded that active reflexes account for the resistance of the systems to the passive distention, the facilitation of expiratory flow, and the shortening of TE.
A radiotelemetry transmitter for transmitting temperatures from small animals
Authors: Riley J. L. , Thurston J. R. , Egemo C. L. , Elliott H. L.
Published: December 2017

A small, reliable temperature-telemetry transmitter was designed and tested for use in small laboratory animals. It transmits a continuous signal that makes it very reliable. It can be constructed of standard small parts and contains and electric watch battery as a source of power. Two models were developed. One transmits at 100 MHz and its signal can be received on a standard FM tuner. The other model transmits at 40 MHz and provides a longer battery life.
Phosphorylase a in human skeletal muscle during exercise and electrical stimulation
Authors: Gollnick P. D. , Karlsson J. , Piehl K. , Saltin B.
Published: December 2017

Experiments were conducted to examine the conversions of phosphorylase b to phosphorylase a in human skeletal muscle during bicycle exercise or isometric contractions. Muscle biopsies were obtained from the vastus lateralis with the needle technique at rest and either during or immediately after activity and frozen in liquid nitrogen within 2--4 s. Total phosphorylase and phosphorylase a activities were differentiated by measurement in the presence and absence of AMP, respectively. At rest 8.5% of the total phosphorylase activity existed in the a form. Little or no change in the percent of phosphorylase in the a form occurred during voluntary dynamic or static muscular activity that produced muscle lactate concentrations in excess of 18 mmol.kg-1 wet muscle. Electrical stimulation of the vastus lateralis muscle also failed to produce an increase in the percentage of phosphorylase a. These data suggest that during exercise the conversion of phosphorylase to the a form is of minor importance. An increased activity of phosphorylase b due to changes in muscle concentrations of ATP, AMP, and inorganic phosphate may regulate glycogenolysis during voluntary exercise in man.
Mean alveolar gases and alveolar-arterial gradients in pulmonary patients
Authors: Luft U. C. , Loeppky J. A. , Mostyn E. Mary
Published: December 2017

Page 534: U. C. Luft, J. A. Loeppky, and E. Mary Mostyn. "Mean alveolar gases and alveolar-arterial gradients in pulmonary patients." Page 536: Eq. 4 should read
Vascular and extravascular compartments of the isolated perfused rabbit lung
Authors: Chang R. S. , Silverman P. , Effros R. M.
Published: December 2017

The vascular, interstitial, and cellular compartments of 15 isolated, perfused and ventilated rabbit lungs determined by a steady-state indicator-dilution procedure. Five lungs were perfused with constant pulmonary artery flow and zero left atrial pressure for more than 1 h. Edema formation was continuous and pulmonary vascular volume (PVV) decreased initially at a time when pulmonary vascular resistance (PVR) was falling. Increases in PVR were not seen until edema formation had become severe. In 10 other lungs, increases in pulmonary artery or left atrial pressure resulted in elevation of PVV and accelerated edema formation. The initially abrupt increase in PVV was followed by a more gradual increase over a 10-min period. Return of fluid to the vasculature was never observed in these studies. Labeled albumin readily entered the extravascular space but a relatively constant fraction of the interstitium remained inaccessible to albumin. No changes were found in the cellular volume during edema formation.
Responses of pial arterioles after prolonged hypercapnia and hypoxia in the awake rabbit
Authors: Levasseur J. E. , Wei E. P. , Kontos H. A. , Patterson J. L.
Published: December 2017

The changes in the responsiveness of pial arterioles to CO2 and in the composition of cortical cerebrospinal fluid bathing these vessels were studied in the awake rabbit before and after 6 days exposure to hypercapnia (7% CO2) or hypoxia (10% O2). The vasodilator response of pial arterioles to inhalation of 3--10% CO2 was diminished after prolonged hypercapnia and enhanced after prolonged hypoxia. After both hypoxia and hypercapnia, pial arteriolar responsiveness to CO2 was immediately returned toward control levels by washing the brain surface with normal artificial cerebrospinal fluid. The bicarbonate concentration of cerebrospinal fluid bathing the pial vasculature showed a significant decrease after hypoxia and a significant increase after hypercapnia, whereas CSF pH remained unaltered. We conclude that the alteration in responsiveness of pial arterioles to CO2 is due to a change in the chemical composition of the CSF bathing these vessels, involving an adjustment in the concentration of bicarbonate ions.
PGA1 and PGF2 alpha metabolism by pig pulmonary endothelium, smooth muscle, and fibroblasts
Authors: Ody C. , Dieterle Y. , Wand I. , Stalder H. , Junod A. F.
Published: December 2017

To determine the cellular site for uptake and degradation of circulating prostaglandins (PGs) by the lung, the metabolism of PGA1 and PGF2 alpha was studied in pig lung slices, smooth muscle preparations, and pulmonary valves, as well as in isolated and cultured endothelial cells and cultured fibroblasts. Formation of 15-keto metabolites of both PGA1 and PGF2 alpha by lung slices was confirmed. No evidence of PGF2 alpha degradation could be found in any of the remaining preparations. For PGA1, however, 15-hydroxyprostaglandin dehydrogenase activity was detected in the three smooth muscle preparations studied (trachea, aorta, pulmonary artery) and found to be similar to that measured in lung slices. But the inhibitory effect of diphloretin phosphate and bromcresol green was much more marked in smooth muscle tissues than in lung slices, which suggested that PGA1 metabolism by the lung was not due to smooth muscle cells. Endothelial cells, freshly isolated and cultured, originating from the pulmonary artery and from the aorta, formed a PGA1-glutathione adduct, poorly extractable in ethyl acetate. This reaction, also present in cultured fibroblasts, was inhibited by ethacrynic acid. The cellular site responsible for the pulmonary degradation of circulating PGs remains undetermined.
A system for rapid measurement of lung function in small animals
Authors: Holub D. , Frank R.
Published: December 2017

A semiautomated system has been developed to facilitate the rapid measurement of a variety of pulmonary functional parameters in small animals. They include lung volumes, mechanics, flow-volume curves, nitrogen washout curves, and diffusing capacity. The animals are anesthetized, intubated, and ventilated mechanically. The construction of the system is described in detail and the results obtained on rats are compared with those published by other investigators.
Breath-by-breath variation of FRC: effect on VO2 and VCO2 measured at the mouth
Authors: Wessel H. U. , Stout R. L. , Bastanier C. K. , Paul M. H.
Published: December 2017

We examined breath-by-breath (B-B) variations of FRC (delta FRC) and their effect on measured O2 and CO2 gas exchange in 52 2- to 4-min segments of continuous air breathing obtained in 29 patients (age range 6--50 yr). Respiratory frequency ranged from 13 to 43 breaths/min, VE from 6.7 to 22.5 l/min (BTPS), and expired VT from 234 to 1,370 ml (BTPS). Computer analysis was based on the following source data measured at the mouth: inspired (VI) and expired (VE) gas flow, FN2, FO2 and FCO2. The analysis provides B-B evaluation of VI, VE, delta FRC in terms of VN2, and VO2 and VCO2 at the mouth and at the alveolar level, i.e., after correction for delta FRC. Significant B-B variations of FRC were found in all studies. delta FRC ranged from +360 to -360 ml (BTPS). For single respiratory cycles VI - VE is primarily a function of N2 exchange at the mouth (VMN2). VO2 and VCO2, uncorrected for delta FRC, are significantly more dispersed about mean values than the corrected gas uptakes (P less than 0.0005). The data support the view that the assumption of VIN2 = VEN2 is invalid for single respiratory cycles. Determination of breath-by-breath VO2 and VCO2 should therefore, not be based on steady-state gas uptake equations. It requires measurement of both inspired and expired breath volumes and evaluation of N2 gas exchange.
Denervated and intact kidney responses to exercise in the dog
Authors: Sadowski J. , Gellert R. , Kurkus J. , Portalaska E.
Published: December 2017

In conscious female dogs exercise-induced changes in the function of the innervated and denervated kidney were studied by clearance techniques. The animals were prepared for experiments by chronic unilateral renal denervation and surgical division of the urinary bladder to enable separate urine collection from each kidney. A 20-min run on a treadmill at a speed of 2.6 m/s significantly decreased urine flow, osmolar clearance, sodium excretion, as well as clearances of exogenous creatinine and p-aminohippurate in the denervated kidney only. In dogs running at 3.6 m/s renal hemodynamics decreased significantly and similarly for both kidneys, whereas the fall in renal excretion was virtually limited to the denervated kidney. As glomerular filtration rate (GFR) was falling during exercise, sodium excretion per 100 ml GFR tended to increase in the innervated kidney, in contrast to an expected slight fall on the denervated side. This indicated a defect of tubular sodium reabsorption of the innervated kidney. On the whole, the data do not support an important mediatory role of renal nerves in the mechanism of renal function changes during exercise.
Effect of elastase or histamine on single-breath N2 washouts in the rat
Authors: Likens S. A. , Mauderly J. L.
Published: December 2017

A method for performing single-breath N2 washouts (SBNW) in rats was developed and the test's usefulness was studied using two experimentally induced models of lung disease. Rats were anesthetized, intubated with oral tracheal and esophageal catheters, and tested by plethysmography. The SBNW expirogram was recorded during exhalation after inhaling 100% O2 from residual volume. The slope of phase III (slope III), closing volume (CV), and closing capacity (CC) were calculated. Changes in the SBNW expirogram were compared with changes in breathing pattern, dynamic and quasistatic lung mechanics, lung volumes, and forced expiratory indices. Pre- and postinstillation tests were performed on rats treated with elastase or histamine and on untreated controls. The SBNW indices were altered at significant levels equal to those of other indices of lung function, and different patterns of change were induced by the two disease models. Elastase increased CV and CC, but slope III was unchanged. Other tests suggested loss of elastic recoil and expiratory flow limitation. Histamine increased slope III, but CV and CC were unchanged. Other tests suggested large airway constriction. These results suggested the usefulness of the SBNW in rats, but the relationships between SBNW changes and underlying physiological phenomena remain to be defined.
Nonlinear increases in diffusing capacity during exercise by seated and supine subjects
Authors: Stokes D. L. , MacIntyre N. R. , Nadel J. R.
Published: December 2017

Page 858: D. L. Stokes, N. R. MacIntyre, and J. R. Nadel. “Nonlinear increases in diffusing capacity during exercise by seated and supine subjects.” Page 859: equation should read

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Muscle surface pH: measurement technique and responses to acidosis and alkalosis
Authors: Kost G. J.
Published: December 2017

The technique of muscle surface pH measurement used clinically was refined for application in animal experimentation. Guidelines for electrode utilization were developed, and sources of error were investigated. In pentobarbital sodium-anesthetized rabbits, during steady-state conditions, the surface pH of the medial gastrocnemius [7.39 +/- 0.05 (SD)] was equal to that of the soleus, and both were lower than femoral venous outflow pH (7.42 +/- 0.04, P less than 0.001), which was lower than arterial pH (7.46 +/- 0.05, P less than 0.001). With acid-base infusions, the same relationship found during steady-state control conditions (arterial greater than venous outflow greater than muscle surface pH) was observed despite large fluctuations in blood pH. Only during forced hypoventilation, when CO2 transiently moved into muscle, did the relationship reverse. In all experiments, muscle surface pH followed venous outflow pH more closely than it followed arterial pH, the soleus more rapidly than the medial gastrocnemius. Results were consistent with the physiological characteristics of the two muscles and demonstrated that muscle surface pH reflects the local pH of the interstitial compartment under the site of electrode placement.
Perivascular interstitial fluid pressure measured by micropipettes in isolated dog lung
Authors: Lai-Fook S. J.
Published: December 2017

Micropipettes in conjunction with a servo-nulling system were used to measure fluid pressure (Pf) in the interstitium around the partially exposed vein near the hilus of the right upper lung lobes of the dog. Lobes were studied at constant transpulmonary pressure (Ptp). In the absence of extravascular water accumulation, Pf was -1.5 cmH2O relative to pleural pressure at Ptp of 6 cmH2O and vascular pressure (Pv) of 0 cmH2O and was more negative in lobes tested at higher Ptp values. In five lobes made edematous with plasma at Ptp of 6 cmH2O and Pv of 15 cmH2O, mean Pf increased from -1 to 4.4 cmH2O as lung weight increased up to 400% of the initial excised weight. In four other lobes, at Ptp of 15 cmH2O and Pv of 20 cmH2O, Pf increased from -2.4 to 8.8 for a similar increase in weight. In lobes degassed and filled with saline or plasma, Pf always equilibrated to alveolar pressure (PA). Results suggest that alveolar surface tension (tau) in air-filled lobes with gross edema prevented Pf from reaching PA. Reduction in Pf below PA was larger at higher Ptp, consistent with increased tau with lung inflation.
Maturation of ventilatory response to hypoxia in puppies during sleep
Authors: Haddad G. G. , Gandhi M. R. , Mellins R. B.
Published: December 2017

Using the barometric method, we studied the maturation of the ventilatory response to steady-level hypoxia (FIO2 = 15%O2) during sleep in 37 beagle puppies. In rapid-eye-movement (REM) sleep, instantaneous minute ventilation (VT/Ttot) and mean inspiratory time (VT/TI) increased, and inspiratory time (TI) and expiratory time (TE) were shortened in response to hypoxia at all the ages studied (14, 19, 24, 29 days). In quiet sleep, however, VT/Ttot decreased, and TE and Ttot were prolonged at 14 days in response to the same hypoxic stimulus. There was no change in VT/Ttot at 19 and 24 days of age, but VI/Ttot and VT/TI increased, and TI and TE were shortened at 29 days of age in response to hypoxia in the same sleep state. The mean arterial O2 tension (PaO2) dropped during hypoxia to about 45 Torr, and the mean arterial CO2 tension (PaCO2) decreased, and the mean pH increased at all ages in both REM and quiet sleep. We conclude that in beagles puppies 1) the ventilatory response to hypoxia matures at a slower rate in quiet than in REM sleep and depends primarily on timing rather than volume mechanisms: and 2) in response to hypoxia, the regulation of blood gases in REM sleep may be achieved differently from that in quiet sleep in early life.
Measurement of pleural pressure in neonates
Authors: Asher M. I. , Coates A. L. , Collinge J. M. , Milic-Emili J.
Published: December 2017

The indirect measurement of pleural pressure in neonates is obtained from measurements of esophageal pressure (Pes) with either a liquid-filled catheter or an esophageal balloon-catheter system. The purpose of this investigation was to assess the validity of the water-filled esophageal catheter by comparing the simultaneous changes in Pes and airway opening pressure (Pao) during occluded respiratory efforts. Equal changes in Pes and Pao under this condition indicate that Pes is a valid measurement of pleural pressure. In six healthy unsedated term neonates (aged 2–3 days) we measured Pes in the lower third of the esophagus with a water-filled catheter of eight French gage (FC), which has a 2-mm internal diameter. During occlusions, changes in Pes and Pao were almost identical in magnitude and timing in each body position studied (right lateral, prone, and supine). We conclude that the water-filled 8-FG esophageal catheter gives an accurate measurement of pleural pressure changes in healthy neonates.
Nonpurinergic nature and efficacy of nonadrenergic bronchodilation
Authors: Irvin C. G. , Martin R. R. , Macklem P. T.
Published: December 2017

The nonadrenergic inhibition of airway smooth muscle was investigated in vivo in the anesthetized cat. We examined 1) the bronchodilatating nature of the selective purinergic agonists [adenosine (AD) and adenosine triphosphate (ATP)], 2) antagonistic nature of aminophylline and quinidine, and 3) the comparative efficacy of nonadrenergic and sympathetic inhibition in reversing bronchoconstriction induced with serotonin. Alterations in smooth muscle tone were studied via electrical stimulation of the vagus nerves and measurements of pulmonary resistance. We found that neither AD nor ATP, aerosolized or injected, altered the tonic bronchoconstriction. Dipyridamole, an AD reuptake inhibitor, did not alter the response to AD, ATP, or electrical stimulation. Both aminophylline and quinidine block nonadrenergic dilatation at high dose levels (69 and 29 mg/kg, respectively); further, both reputed antagonists impair cholinergic excitation. Nonadrenergic inhibition is equipotent to sympathetic inhibition in reversing bronchoconstriction; however, nonadrenergic inhibition is more prolonged (4.0 +/- 1.8 min). We conclude that probably neither ATP nor AD is the neurotransmitter for nonadrenergic bronchodilatation in the cat, and that nonadrenergic inhibition is both potent and long lasting.
Abdominal muscle use during quiet breathing and hyperpnea in uninformed subjects
Authors: Loring S. H. , Mead J.
Published: December 2017

Although there is electromyographic evidence for abdominal muscle activity during quiet breathing in standing subjects, several studies have shown, or assumed, that subjects normally breathe on their relaxation characteristics. This latter observation would by itself suggest that abdominal muscles do not contract during quiet breathing. To test this assumption we observed abdominal and rib cage displacements with magnetometers in 17 uninformed subjects. During quiet breathing most subjects showed evidence of tonic or phasic abdominal muscle contraction while standing and sitting but not supine. Subjects studied during hyperpnea immediately following exercise-showed evidence of greater abdominal muscle contraction than at rest. We conclude that most subjects standing at rest normally contract their abdominal muscles.
Pulmonary impedance in dogs measured by forced random noise with a retrograde catheter
Authors: Fullton J. M. , Hayes D. A. , Pimmel R. L.
Published: December 2017

Retrograde catheter and forced random noise techniques were combined to study the distribution of resistance and compliance in dogs following the inhalation of aerosols containing 2.5 and 5.0 mg/ml of histamine. Mean base-line peripheral resistance was 0.367 cmH2O . l'1 . s, agreeing with previous estimates. After correction for the endotracheal tube, the mean central airway resistance was 0.040 cmH2O . l'1 . s, considerably lower than previous estimates. This discrepancy was attributed to an overcorrection for the endotracheal tube resistance. The lower histamine dose caused a substantial increase in peripheral resistance, a relatively small increase in central resistance, and substantial decreases in total and peripheral compliance. After the higher histamine dose, changes in peripheral resistance and both compliances were similar to those obtained with the lower dose; however, the increase in central resistance was much larger than at the lower dose. The difference between total and peripheral compliance yielded estimates of airway compliance of 0.00306 l/cmH2O before and 0.00104 l/cmH2O after 2.5 mg/ml of histamine.
Role of ciliary motility in acute allergic mucociliary dysfunction
Authors: Maurer D. R. , Sielczak M. , Oliver W. , Abraham W. M. , Wanner A.
Published: December 2017

The purpose of this investigation was to determine if abnormal ciliary function contributes to allergic mucociliary dysfunction. In conscious sheep with Ascaris suum hypersensitivity, ciliated cells were obtained with a cytology brush and tracheal mucous velocity (TMV) was determined before and serially for 2 h following antigen inhalation. The recovered cells (also containing mast cells) were suspended in a chamber, and ciliary activity was viewed microscopically and recorded on videotape for subsequent slow-motion analysis of ciliary beat frequency (CBF). One hour after A. suum challenge mean CBF (+/- SE) showed a slight increase from a base-line value of 630 +/- 16 to 716 +/- 30 beats/min (P less than 0.05) when mean TMV was decreased to 57% of base line (P less than 0.05). After 2 h, both mean CBF and TMV returned toward base line. Since possible in vivo actions of chemical mediators liberated by antigen challenge may have been lost after suspension of the brushed cells, we also assessed the effects of antigen on CBF in vitro. A. suum caused a dose-dependent increase in CBF that was blocked by cromolyn sodium. We conclude that 1) allergic mucociliary dysfunction is not caused by a decrease in CBF and 2) antigen-induced release of chemical mediators increases CBF.
Parameter estimation of transpulmonary mechanics by a nonlinear inertive model
Authors: Hantos Z. , Daroczy B. , Klebniczki J. , Dombos K. , Nagy S.
Published: December 2017

Transpulmonary mechanics of anesthetized intubated dogs were studied during control breathing and hemorrhage-induced hyperventilation by least-mean-squares parameter estimation using several model versions. The classical elastance-resistance model was modified to include nonlinear elastic and viscous pressure terms with and without a linear inertive pressure component. Inclusion of the nonlinear terms decreased the root-mean-square error of fitting (q) of the classical model on the average to 67% in the control period and to 58% during hyperventilation. An additional decrease due to inertance was 4% (control) and 22% (hyperventilation) and was associated with acceptable estimates of inertance [0.056 +/- 0.02 (SD) and 0.063 +/- 0.008 cmH2O . l'1 . s2, respectively]. When inertance alone was added to the classical model, negligible improvement in q and unrealistic values of inertance were obtained. Conventional measures (Edyn and midvolume resistance) were close to the corresponding least-mean-squares estimates (E and R) of all model versions, except that in hyperventilation neglecting the inertance caused Edyn to markedly overestimate E of nonlinear inertive model.
Interactions between lung stretch and PaCO2 in modulating ventilatory activity in dogs
Authors: Mitchell G. S. , Cross B. A. , Hiramoto T. , Scheid P.
Published: December 2017

The effects of changes in airway pressure (Paw) and arterial PCO2 (PaCO2) on ventilatory activity were studied in anesthetized thoracotomized dogs in which both lungs were ventilated separately. Pulmonary artery occlusion on one side and contralateral vagotomy allowed the reflex effects on ventilation of changes in Paw and PaCO2 to be elicited independently of each other. Ventilatory activity was assessed from integrated efferent phrenic activity, analyzed with respect to burst amplitude (Phr), burst frequency (f), and inspiratory TI) and expiratory duration (TE). While Phr increased linearly with PaCO2, it was independent of Paw. Both PaCO2 and Paw affected f in a complex nonadditive way; this response was entirely mediated by effects on TE, TI being unaffected by either stimulus. The analog of ventilation, estimated as Phr x f, increased linearly with PaCO2 and decreased linearly with Paw, but the effects of both stimuli appeared to be additive. It is concluded that the apparently simple effect of Paw and PaCO2 on ventilation results from more complex effects these stimuli exert on its components.
Biochemical and physiological development of fetal rhesus lung
Authors: Perelman R. H. , Engle M. J. , Kemnitz J. W. , Kotas R. V. , Farrell P. M.
Published: December 2017

Study of 17 fetal rhesus monkeys (Macaca mulatta) revealed a sequential rise in lung phosphatidylcholine (PC) concentration due to elevations in both disaturated (DSPC) and unsaturated constituents. The % DSPC in lung tissue clinical abruptly at 145 days of gestation prior to significant increases in PC or DSPC concentration but in association with improved lung deflation stability (% V10). This suggests that the DSPC-to-PC ratio may be a sensitive biochemical indicator of surfactant phospholipid production in lung parenchyma. Phosphatidyl-glycerol content did not increase significantly until after 155 days gestation, which was coincident with maximizing pulmonary distensibility (V max). Declining levels of phosphatidylethanolamine and sphingomyelin in lung tissue at 162 days support the hypothesis that preferential synthesis of PC occurs during late gestation. A serial decline in lung glycogen content with advancing gestation may reflect glycogen utilization as a substrate for lung phospholipid production. Comparison of biochemical and physiological data confirms the impression that discordances occur among lung maturational events. Lastly, a relationship between rising fetal blood cortisol levels and indices of fetal lung development was not demonstrated.
Brain extracellular fluid pH and blood flow during isocapnic and hypocapnic hypoxia
Authors: Nolan W. P. , Davies D. G.
Published: December 2017

Cerebrovascular responses to 30 min of isocapnic hypoxia [arterial O2 partial pressure (PaO2) = 33 +/- 1 Torr; means +/- SE] were examined in eight chloralose-urethan-anesthetized, paralyzed, and artificially ventilated New Zealand White rabbits. Cerebral blood flow (Q) was measured using the radioactive microsphere technique. Vascular resistance (R) was calculated from arterial pressure and Q. Brain extracellular fluid (ECF) pH was measured continuously in the same animals using pH microelectrodes (1- to 2-micrometers tip diameter) placed stereotaxically in the diencephalon. Diencephalon Q increased from 40 +/- 2 to 69 +/- 4 ml . 100 g-1 . min-1 (P less than 0.05) as R decreased (P less than 0.05) after 413;6 min of isocapnic hypoxia. Total brain Q and R changes resembled those of the diencephalon. The ECF pH of the diencephalon increased by 0.016 +/- 0.006 (P less than 0.05) after 1 min of isocapnic hypoxia and remained significantly elevated through the first 20 min of hypoxia. Ten minutes after the return of normoxia Q and R were at control levels, whereas diencephalon ECF pH was 0.043 +/- 0.006 below control (P less than 0.05). Five additional rabbits were prepared as described above then made hypocapnic [arterial CO2 partial pressure (PaCO2) = 21 +/- 0.3 Torr] for 18 min. Diencephalon and total brain Q and R remained at control levels through 12–14 min of hyperventilation, whereas diencephalon ECF pH was elevated by 0.03 +/- 0.006 (P less than 0.05). Hyperventilation was then continued with hypoxic gas to lower PaO2 to 35 +/- 4 Torr for 30 min. Both diencephalon and total brain R decreased (P less than 0.05), with no change in Q after 4–6 min of hypocapnic hypoxia. Diencephalon ECF pH was not significantly different from control throughout the hypocapnic-hypoxic period. We conclude that the early cerebral vasodilation during hypoxia is not mediated by increased brain ECF acidity.
Pulmonary stretch receptor discharge patterns in eupnea, hypercapnia, and hypoxia
Authors: Iscoe S.
Published: December 2017

The discharge properties of pulmonary stretch receptors (PSR) were studied in spontaneously breathing, pentobarbital sodium-anesthetized cats. During eupneic breathing, 105 of 116 PSR (both tonically and phasically active) were recruited in the first third of inspiration; none were recruited in the last third. Linear equations adequately expressed the relation between instantaneous discharge frequency and inspired volume in eupnea. During CO2 rebreathing, both tidal volume and peak PSR discharge frequency were inversely related to inspiratory duration. At fixed volumes less than 40 ml above functional residual capacity, instantaneous PSR discharge frequency either did not change or decreased with increases in flow. Above 40 ml, increases in discharge frequency accompanied increases in flow (0.033 spikes/s per ml/s). During progressive hypocapnic hypoxia, discharge frequency increased, on average, at all volumes with increases in flow (0.206 spikes/s per ml/s). During both conditions, as with eupnea, increases in frequency were linearly related to increments in tidal volume. Therefore, tidal volume alone can be used to estimate PSR feedback to the respiratory centers, provided that its instantaneous value is appropriately scaled to account for the different effects of CO2 and hypocapnic hypoxia on PSR discharge.