bluuebunny/crossref_metadata_2025 huggingface dataset:
Dose-dependent inhibition of cold air-induced bronchoconstriction by atropine
Authors: Sheppard D. , Epstein J. , Holtzman M. J. , Nadel J. A. , Boushey H. A.
Published: December 2017

We undertook a study to demonstrate whether inhalation of atropine could inhibit cold air-induced bronchoconstriction in a dose-dependent fashion. In seven subjects with asthma we assessed the effects of placebo and of various doses of inhaled atropine (0.1313;2.08 mg) on a base-line specific airway resistance (sRaw) and on the increase in sRaw produced by 5 min of voluntary eucapnic hyperventilation with subfreezing air at -17 degrees C. We also assessed the effect of the lowest doses of atropine on the increase in sRaw produced by five breaths of 1.0% metacholine. Atropine in doses of 0.13 or 0.26 mg caused a maximal reduction in base-line sRaw and completely inhibited the effect of 1.0% methacholine on sRaw, but it did not inhibit the bronchomotor response to cold air. Higher doses of atropine did inhibit the effect of cold air on sRaw in a dose-dependent fashion. The dose of atropine required to inhibit this effect of cold air varied with the increase in sRaw produced by cold air after placebo. These results suggest that cold air causes bronchoconstriction through vagal pathways and that higher doses of antimuscarinic agents are required to inhibit vagally mediated bronchoconstriction than those required to reduce base-line airway tone or to inhibit the effects of a large dose of an inhaled muscarinic agonist.
Sympathetic inhibition of histamine-induced contraction of canine trachealis in vivo
Authors: Leff A. R. , Munoz N. M. , Hendrix S. G.
Published: December 2017

The effect of sympathetic stimulation on histamine-induced tracheal contraction was studied in 42 dogs in situ. After cholinergic blockade with atropine, dose-response curves to intra-arterial (ia) histamine (10(-10)-10(-6) mol) were performed in 11 adrenal-intact (ADi) and 5 adrenalectomized (ADx) dogs receiving steady-state sympathetic stimulation from continuous intravenous infusion (62.513;312 micrograms . kg-1 . min-1) of 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP). In ADi dogs receiving maximal sympathetic prestimulation (312 micrograms . kg-1 . min-1 DMPP), tracheal tension barely exceeded base-line resting tension after 10(-6) mol ia histamine. In five dogs, tracheal tension after maximal sympathetic prestimulation exceeded base line for greater than or equal to 10(-8) mol ia histamine. In 12 other dogs, reversal of histamine-induced contraction by maximal sympathetic prestimulation was studied. Tracheal tension decreased 45.6 +/- 4.4 g/cm in four ADi dogs (P less than 0.001), 12.4 +/- 2.8 g/cm in four ADx dogs (P less than 0.02), and 2.2 +/- 2.5 g/cm in four control dogs receiving sham infusions (P greater than 0.90). No evidence was found for nonadrenergic relaxation of canine airway smooth muscle. We conclude that tracheal sympathetic nerves cause significant antagonism of histamine-induced contraction, which is augmented by adrenal secretion. We also report a pharmacological method for dose-related steady-state sympathetic stimulation of canine airways.
An electromagnetic valve for rebreathing exercise studies
Authors: Kiers A. , van der Mark T. W. , Folkerts F. J. , Blankena H. J. , Woldring M. G. , Peset R.
Published: December 2017

An electromagnetic valve for use in exercise rebreathing studies is described. This valve enables the investigator to connect a rebreathing system immediately after the onset of inspiration even at high breathing frequencies. The rapid switching causes minimal leakage; the rebreathing bag can be washed out and refilled without disconnection during exercise testing. For one year this valve has been used in measurements of functional residual capacity and diffusing capacity during exercise in volunteers as well as in patients.
Comparison of human vocal cord movements during isocapnic hypoxia and hypercapnia
Authors: England S. J. , Bartlett D. , Knuth S. L.
Published: December 2017

Respiratory vocal cord movements were analyzed in healthy human subjects during air breathing and in isocapnic hypoxia and hypercapnia. In the majority of experiments, expiratory glottic narrowing was substantially greater during hypoxia than during hypercapnia. Because ventilations were carefully matched under these two conditions, it is concluded that hypoxic stimulation of peripheral chemoreceptors favors expiratory glottic narrowing and leads to a relatively high laryngeal airflow resistance. In contrast, hypercapnia is accompanied by low expiratory laryngeal resistance. Similar rates of expiratory airflow with these two stimuli must be achieved by different balances of the factors that determine this flow.
Oxygen affinity and Bohr coefficients of dog blood
Authors: Reeves R. B. , Park J. S. , Lapennas G. N. , Olszowka A. J.
Published: December 2017

Complete dynamic oxygen equilibrium curves (O2EC) on dog whole blood were measured at 25 and 39 degrees C using a spectrophotometric micro blood film technique. O2EC were run at three CO2 levels (2, 4, and 8%) for each of three base excess levels (-10, 0, +10 meq/l). The standard curve (ph 7.4) was determined for saturations 013;0.98. At 39 degrees C the standard curve O2 pressure at half-saturation (P50) was 31.5 Torr; fixed-acid Bohr factor, -0.488; CO2 Bohr factor, -0.498; delta log P50/delta log PCO2, -0.0045. CO2 Bohr slope was linear over the pH range of 7–8. Bohr factors were not significantly saturation dependent. At 25 degrees C P50 was 15.4 Torr and CO2 Bohr factor, -0.647. The temperature coefficient (delta log P50/delta T) equaled 0.022. Dog O2EC were shown with curve-fitting techniques to be isomorphic with human blood O2EC. The absence of significant oxylabile carbamate formation in dog red blood cells (RBC) was attributed to high 2,3-diphosphoglycerate (DPG) concentrations, 6.23 mM/l RBC, equal to a DPG/Hb4 ratio of 1.12. A simple two-constant equation S = [(37,900)/(P3 + 205P) + 1]-1, where S is saturation and P is oxygen tension, was found to fit the dog 39 degrees C standard curve.
Chest wall mechanics in dogs with acute diaphragm paralysis
Authors: De Troyer A. , Kelly S.
Published: December 2017

To investigate the action of the inspiratory intercostals, we studied the patterns of rib cage and abdominal motion during tidal breathing in eight dogs before and after bilateral phrenicotomy. Hooks screwed into the sternum and the ribs were used to monitor the anteroposterior and transverse diameters of the rib cage and the axial displacements of the sternum and the ribs. In all animals, we found that during tidal inspirations performed with the inspiratory intercostals alone, 1) the rib cage moved outward while the abdomen moved inward; 2) the rib cage was displaced near its relaxation curve (defined by a plot of its transverse vs. anteroposterior diameter) but expanded more in its transverse than in its anteroposterior dimension; and 3) the ribs in the midaxillary line moved cephalad, whereas the sternum was displaced caudally. Additional experiments performed on four dogs demonstrated that contraction of the parasternal intercostals was responsible for the inspiratory caudal displacement of the sternum. These findings indicate that in the dog, 1) the inspiratory intercostals act essentially on the lateral walls of the rib cage, and 2) those of the parasternal area produce a caudal displacement of the sternum. In addition, they suggest strongly that the axial displacement of the sternum constitutes an additional degree of freedom of motion of the rib cage and that contraction of the neck accessory muscles is mandatory for the sternum to be displaced in a cephalad direction during inspiration.
Effect of warm-up on left ventricular response to sudden strenuous exercise
Authors: Foster C. , Dymond D. S. , Carpenter J. , Schmidt D. H.
Published: December 2017

Sudden strenuous exercise (SSE) has been shown to produce ischemic electrocardiographic (ECG) responses, abnormalities of myocardial blood flow, and decreases in left ventricular ejection fraction. Prior exercise taken as warm-up has been shown to ameliorate the ECG and myocardial blood flow abnormalities induced by SSE. The purpose of this study was to determine whether warm-up would normalize the responses of the left ventricular ejection fraction to SSE. Twenty healthy male volunteers performed SSE (400-W bicycle exercise) either with (group A, n = 10) or without (group B, n = 10) warm-up. Ejection fraction was measured using first-pass radionuclide angiography under control conditions and during SSE. During SSE ejection fraction decreased from control values in both group A (70.5 +/- 6.3 to 64.8 +/- 8.2%) and group B (70.3 +/- 10.1 to 57.7 +/- 7.7%), although ejection fraction was significantly higher during SSE in group A. The results are consistent with the hypothesis that the abnormal responses to SSE are attributable to subendocardial ischemia secondary to a delay in autoregulation of myocardial blood flow. However, the decrease in ejection fraction during SSE even following warm-up suggests that the mechanism for the abnormal response to SSE is more complicated than previously hypothesized.
Estimation of transmural cardiac pressures during ventilation with PEEP
Authors: Marini J. J. , O'Quin R. , Culver B. H. , Butler J.
Published: December 2017

Assessment of ventricular performance during positive end-expiratory pressure (PEEP) requires accurate measurement of transmural cardiac pressures. We investigated the influence of PEEP on the atrial and juxtacardiac pressures estimated by different methods in eight dogs. Left atrial pressure was measured by hydraulic and transducer-tipped catheter systems. Juxtacardiac pressure was estimated by an esophageal balloon and by air- and fluid-filled mediastinal wafer sensors. The supine canine heart was observed radiographically to lift and tilt during PEEP subjecting the left atrial catheters and the fluid-filled mediastinal wafer to a hydrostatic pressure increase. The esophageal balloon seriously underestimated the pressure increment occurring during the application of PEEP in the supine (but not prone) position, perhaps because mediastinal weight was lifted from the esophagus during lung distension. Similar phenomena were also observed in three human subjects. We conclude that lung distension lifts and tilts the heart in a supine preparation causing a hydrostatic increase of intracavitary pressure and attenuation of the esophageal pressure increment. These effects help to account for the apparent alterations of ventricular compliance and performance previously attributed to PEEP.
Analysis of the effects of hematocrit on pulmonary CO2 transfer
Authors: Bidani A. , Crandall E. D.
Published: December 2017

A mathematical model of the chemical and transport events in blood during and after gas exchange has been used to examine the rates of CO2 excretion (Vco2) and O2 uptake (Vo2) in the lung at different levels of hematocrit (Hct), assuming fixed mixed venous blood O2 and CO2 contents and alveolar gases and constant cardiac output. The results show that a reduction in Hct from 45 to 30% leads to approximately 25% reduction in Vco2 compared with approximately 30% reduction in Vo2. Reduction of Hct from 45 to 15% results in approximately 50% reduction in Vco2 and approximately 63% reduction in Vo2. An increase in Hct from 45 to 60% results in approximately 25% increase in Vco2, accompanied by approximately 30% increase in Vo2. These fractional changes in gas exchange are only slightly affected by the extent of catalysis of the plasma CO2-H2CO3 hydration-dehydration reactions in the pulmonary vasculature. The reduction in Vco2 with reductions in Hct are due to 1) decrease in the total quantity of Bohr protons released during diminution of Vo2, 2) decrease in the size of the high buffer capacity intraerythrocytic pool, and 3) decrease in the total surface area available for HCO-3/Cl- exchange across the red cell membrane. We conclude that hitherto unrecognized changes in Vco2 (in addition to the well-known changes in Vo2) may occur as a consequence of alterations in Hct.
Neuromuscular adaptation in human thenar muscles following strength training and immobilization
Authors: Sale D. G. , McComas A. J. , MacDougall J. D. , Upton A. R.
Published: December 2017

The effects of strength training and limb immobilization on the human thenar muscles were investigated in 11 healthy subjects. One group (n = 6) trained prior to immobilization and a second group (n = 5) underwent immobilization prior to training. Measurements made in the control condition and following the two experimental conditions included voluntary isometric strength, motor-unit counts, motor nerve conduction velocity, reflex potentiation, and isometric twitch-contraction properties. When the results of both groups were combined an average of 5 wk of immobilization was found to cause a significant decrease in voluntary strength (42%, P less than 0.05) and reflex potentiation (37%, P less than 0.01) in relation to the control condition. Training caused an increase (40%, P less than 0.05) in voluntary strength and a decrease in twitch tension (25%, P less than 0.01) and contraction time (8%, P less than 0.05). Training prior to immobilization provided a reserve of neuromuscular function, which attenuated the effect of immobilization in relation to the control condition. It was concluded that neural as well as muscular adaptation occurred in response to immobilization.
Chemical specificity of a laryngeal apneic reflex in puppies
Authors: Boggs D. F. , Bartlett D.
Published: December 2017

In neonatal mammals the introduction of water and some other fluids into the larynx causes prolonged reflex apnea by stimulation of afferents in the superior laryngeal nerve (SLN). We have studied the chemical specificity of this reflex in 1- to 9-day-old anesthetized puppies. The laryngeal lumen was perfused with a variety of substances while ventilation through a tracheal cannula was recorded. Water consistently elicited apnea, which was terminated by 150 mM NaCl. Sucrose and urea solutions (100–500 mM) also elicited apnea, suggesting that osmolarity is not a critical factor. Phosphate buffer solutions containing NaCl and ranging in pH from 4.5 to 8.7 did not elicit apnea nor did cation substitutions in 150 mM chloride salts, with the exception of K+. Anion substitutions in 150 mM sodium salts indicated that anions of relatively large hydrated size (F-, acetate, formate, gluconate, tartrate, SO2–4, diatrizoate, IO-3, BrO-3, H2PO-4, HCO-3, borate, CO2–3) do induce apnea, whereas small anions (NO-3, ClO-3, SCN-, I-, Br-) similar to Cl- in size do not. Large anion salts and the nonelectrolytes sucrose, urea, and milk ceased to be effective stimuli in the presence of Cl- in concentrations of 80 or more meq/l. The principal stimulus for this apneic reflex is thus the absence or reduced concentration of Cl- (or small anions that can functionally replace Cl-) in the laryngeal fluid. Single fibers in the SLN were responsive to all the substances found capable of eliciting apnea and unresponsive to those not capable of doing so.
CO concentration-dependent changes in pulmonary diffusing capacity in humans
Authors: Sybert A. , Ayash R. , Chatham M. , Gurtner G. H.
Published: December 2017

Steady-state CO pulmonary diffusing capacity (DLCO) was measured at different inspired CO concentrations in seven males and one female during light treadmill exercise. As the CO level is increased. DLCO increases, reaches a maximum at an end-tidal CO concentration of approximately 100 ppm, and then decreases. The maximum DLCO is up to twice as large as the DLCO measured at an inspired CO concentration of approximately 1,780 ppm. These results are consistent with the presence of saturation kinetics, one of the basic properties of carrier-mediated transport systems. A similar relationship between DLCO and CO concentration was found in previous studies of mechanically ventilated dogs. Thus there is evidence for carrier-mediated transport of CO in the lungs of both humans and dogs.
Effect of pulmonary arterial occlusion on lung fluid and protein exchange
Authors: Barie P. S. , Malik A. B.
Published: December 2017

We examined the effects of left pulmonary arterial occlusion and reperfusion on pulmonary transvascular fluid and protein exchange in the sheep lung lymph fistula preparation. Pulmonary lymph flow (Qlym) increased from the base-line value of 5.0 +/- 0.8 to 10.0 +/- 2.1 ml/h after occlusion (P less than 0.05); the steady-state value of 11.9 +/- 2.2 ml/h during reperfusion was not significantly different from the value during occlusion. The lymph-to-plasma protein concentration ratio (L/P) did not change significantly during either occlusion or reperfusion. Transvascular protein clearance (Qlym X L/P) increased from 3.7 +/- 0.6 to 8.4 +/- 2.1 ml/h during occlusion (P less than 0.05) and remained elevated at 8.6 +/- 1.7 ml/h during reperfusion. The sustained increases in Qlym and protein clearance could not be explained by the 3-Torr increase in mean pulmonary arterial pressure during the occlusion period or by an increase in the interstitial protein concentration caused by a period of decreased filtration during occlusion. The increases in protein clearance that occurred with increased Qlym during occlusion and reperfusion were greater than the increases in protein clearance with comparably increased Qlym during left atrial hypertension. The results suggest that occlusion of a pulmonary artery increases vascular permeability to plasma proteins in the lung.
Factors inducing periodic breathing in humans: a general model
Authors: Khoo M. C. , Kronauer R. E. , Strohl K. P. , Slutsky A. S.
Published: December 2017

A general model is developed to account for all kinds of periodic breathing (PB) resulting from instability in respiratory control: in normals during sleep and on acute exposure to high altitude, in sleeping infants, and in patients with cardiovascular or neurologic lesions. It is found that in almost every case the ventilatory oscillation is mediated predominantly by the peripheral controller. System stability is decreased by hypoxia, hypercapnia, increased lung washout times, prolonged lung-chemoreceptor delays, and high controller sensitivity. Stability is enhanced by large lung CO2 and O2 storage volumes but little affected by body tissue stores. Using our own measurements of lung-ear delays, the model predicts that the mean cycle time of PB decreases from about 30 s at sea level to 20 s at 14,000 ft, in excellent agreement with data from other studies. Allometric scaling of the relevant parameters also shows close agreement between model predictions and data obtained on infants.
Breathing patterns influence aerosol deposition sites in excised dog lungs
Authors: Valberg P. A. , Brain J. D. , Sneddon S. L. , LeMott S. R.
Published: December 2017

Particles' suspended in inhaled air can deposit on lung surfaces. The amount deposited in different lung regions is determined by distribution of ventilation and local efficiency of particle collection. We examined how the pattern of ventilation influences sites of aerosol deposition in excised dog lungs. The lungs breathed a 99mTc-labeled aerosol according to one of three patterns: slow-deep (f less than 25/min, VT greater than 0.35 TLC); rapid-shallow (f greater than 65/min, VT less than 0.26 TLC); and slow-shallow (f = 8.4/min, VT = 0.1 TLC). After exposure, lungs were inflated, dried, and sliced transversely at 1-cm intervals. Distribution of deposited aerosol in each slice was measured by 1) gamma camera, 2) autoradiography, and 3) dissection of each slice into pieces whose activity, weight, and airway content were recorded. Our results indicate that a) total deposition decreases as f increases, b) slow-deep breathing produces uniform deposition throughout the lung, but with little aerosol collection in large airways, c) rapid-shallow ventilation results in enhanced large-airway deposition and marked heterogeneity in deposition distribution, and d) slow-shallow breathing enhances small-airway deposition. The deposition distributions characteristic of different breathing patterns were apparent on the visual displays from the gamma camera and autoradiographs. These techniques showed particle retention changing across lobar divisions, as a function of distance from the hilum, and across the lungs in both the caudal-to-cranial and dorsal-to-ventral directions.
Effect of exercise on postprandial gastric secretion and emptying in humans
Authors: Feldman M. , Nixon J. V.
Published: December 2017

The effect of strenuous physical exercise on postprandial gastric acid secretion and gastric emptying was evaluated in untrained healthy volunteers. Subjects exercised for 45 min on a stationary bicycle at 50 or 70% of their maximal work load, beginning 45 min after a steak meal. Compared with a control study during which subjects sat on the bicycle without exercising, exercise had no significant effect on the gastric acid secretory response to the meal (control, 31.9 +/- 8.3 mmol/120 min; exercise, 32.2 +/- 7.8 mmol/120 min) or on the amount of nonabsorbable meal marker that emptied from the stomach in 120 min (control, 88 +/- 3%; exercise, 87 +/- 4%). Increases in serum triglyceride levels after the meal were also unaffected by exercise, suggesting that absorption of dietary lipid was unimpaired by exercise. These studies indicate that strenuous exercise shortly after a meal has little effect on postprandial gastric secretory or motor function in humans.
Plasma prostaglandins, renin, and catecholamines at rest and during exercise in hypertensive humans
Authors: Lijnen P. , Fagard R. , Staessen J. , Amery A.
Published: December 2017

Plasma prostaglandins (PGE and PGF alpha), catecholamine concentration, and plasma renin activity (PRA) were measured during an uninterrupted graded exercise test on the bicycle ergometer in 11 hypertensive patients. Blood was withdrawn from the brachial and pulmonary arteries after 30 min of recumbent rest, after 15 min of rest sitting, and at the final work load of the exercise test, which averaged 143 +/- 16.5 W. Exercise did not provoke a significant change in these plasma PGE or PGF alpha concentrations, whereas a rise (P less than 0.001) in arterial PRA and (nor)epinephrine concentration was observed. It is thus unlikely that PGE or PGF alpha is an important determinant of PRA release during exercise, although circulating levels of PGE and PGF alpha do not necessarily reflect release rate or activity in the kidney.
Homogeneous nucleation of gas bubbles in vivo
Authors: Weathersby P. K. , Homer L. D. , Flynn E. T.
Published: December 2017

Several current theories of decompression sickness (DCS) presume the preexistence of gas bubble nuclei in tissue, because the de novo nucleation of gas bubbles in the body is thought to be theoretically impossible. Reexamination of nucleation theory reveals the overwhelming importance of two parameters: gas supersaturation and tissue surface tension (gamma). For the high gamma of pure water nucleation theoretically requires more than 1,000 ATA supersaturation. Lower values of gamma allow nucleation to occur with vastly smaller supersaturations. Application of homogeneous nucleation theory can provide reasonable fits to both rat and human pressure-reduction data with values of gamma within the range reported for biological fluids (below 5 dyn/cm). The initial bubble sizes predicted are 0.1 micron or less. The presence of heterogeneous sites, for example crevices and lipid surfaces, makes nucleation even more likely.
Lung fluid balance in lambs before and after birth
Authors: Bland R. D. , Hansen T. N. , Haberkern C. M. , Bressack M. A. , Hazinski T. A. , Raj J. U. , Goldberg R. B.
Published: December 2017

To study lung fluid balance before and after birth, we measured lung lymph flow and concentrations of protein in lymph and plasma of 22 unanesthetized fetal lambs and compared results with previous studies done on 26 newborn lambs, 1–2 wk old. Lymph flow, relative to lung mass, was less in fetuses than in newborns; lymph protein clearance was not significantly different. Less lymph flow before birth probably reflects less available surface area for fluid exchange in microcirculation of fetal lungs, compared with newborn lungs, with no difference in endothelial permeability to protein. Extravascular lung water, measured gravimetrically for 24 fetuses (10 without labor, nine in labor, five 6 h after vaginal birth), decreased by 45% (15 +/- 2 g/kg body wt) before birth and by an additional 38% (6 +/- 1 g/kg) after birth. In five lambs killed after birth, we measured lung lymph flow before and during labor and for 6 h after breathing began. Lymph flow was unaffected by labor but increased transiently after birth, accounting for 11% of the liquid removed from lungs postnatally. Liquid clearance studies performed in eight anesthetized 3-wk-old lambs confirmed the observation that lung lymphatics drain only a small fraction of liquid in potential air spaces. Most of that liquid probably leaves the lungs directly through pulmonary circulation.
Effects of posture on flow-volume curve configuration in normal humans
Authors: Castile R. , Mead J. , Jackson A. , Wohl M. E. , Stokes D.
Published: December 2017

Tien et al. (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 46: 565–570, 1979) found reproducible details in the configuration of averaged maximal expiratory flow-volume curves and suggested that these details may correspond to sudden relocations of airway choke points. The occurrence of choke points depends on factors affecting local airway pressure-diameter behavior. We postulated that changes in posture as they affect the distribution of lung recoil on airways might change the locations of choke points and thereby alter flow-volume configuration. Twenty normal adults performed five flow-volume curves in each of four postures (standing, supine, right, and left lateral recumbent). Volume was measured with a Krogh spirometer and airflow with a Fleisch No. 4 pneumotachometer. Curves were digitally filtered and plotted relative to upright total lung capacity. Five curves in each posture were averaged at increments of 0.1 l/s of flow and average volumes at given flows were compared using the Student's t test. Significant differences (P less than 0.01) in mean volumes at given flows occurred in all subjects from standing to supine and/or right to left lateral postures. Large changes in configuration were apparent in one of the two postural pairs in eight subjects. We conclude that changes in posture result in significant changes in flow-volume configuration in most normal adults. These findings are consistent with the wave-speed theory of flow limitation and suggest that small changes in local airway stresses can significantly alter the location and motion of airway choke points during forced expiration.
Reduction in fertility of male mice after exposure to high environmental pressure
Authors: Baden J. M. , Dore C. J. , Green C. J. , Monk S. , Halsey M. J. , Wardley-Smith B.
Published: December 2017

Male mice were exposed to 50 ATA heliox pressure to study whether their functional fertility was affected. In series I, control mice were exposed to 1 ATA air; in series II controls were exposed to 5 ATA heliox, which enabled the PO2 and environmental temperature to be maintained at equivalent levels to the pressure group. After exposure during one spermatogenic cycle, the mice were mated with untreated females. There was a dramatic reduction in fertility in the pressure groups, with males in both series I and II showing a 65% reduction in fertility. Overall results were as follows: 19.5% pregnant females mated with the pressure groups compared with 55% pregnant in the control groups. Litter sizes in the pressure groups were reduced by 44%, but there was no evidence of any pressure-related teratological effect. This reduction in fertility appears to be due to high pressure per se and not to the high environmental temperature and PO2 associated with heliox atmospheres.
O2 transport during exercise following blood reinfusion
Authors: Thomson J. M. , Stone J. A. , Ginsburg A. D. , Hamilton P.
Published: December 2017

Reasons for an increase in maximal O2 consumption (VO2max) following blood reinfusion remain unclear; thus the present investigation was undertaken to examine the arterial and femoral venous blood gases during submaximal and maximal exercise. Four untrained males (22–25 yr) performed modified Balke work capacity tests under control conditions (Hct = 42.4 +/- 0.8%; Hb = 14.7 +/- 0.5 g X 100 ml-1) and following autologous blood reinfusion (Hct = 46.2 +/- 1.3%; Hb = 16.4 +/- 0.9 g X 100 ml-1). VO2 was determined by open-circuit spirometry and cardiac output by the N2O method; radial arterial and deep femoral venous blood were sampled at each work load throughout the incremental work tests. Following blood reinfusion, subjects' VO2max increased (P less than 0.05) from 4.0 (in control) to 4.5 1 X min-1. Throughout submaximal exercise arterial PO2 remained relatively constant (between 80.1 +/- 4.4 and 89.1 +/- 5.0 Torr) and cardiac output unchanged, comparing the two experimental conditions. Femoral venous PO2 values were almost identical throughout the work capacity tests, declining at exhaustion to 15.7 +/- 1.5 Torr in control and to 13.8 +/- 3.3 Torr postreinfusion. It appeared that the subjects' increase in VO2max postreinfusion was due to an increased O2 supplied to the tissue [i.e., cardiac output (Q) X arterial O2 content (CaO2)] by the central circulation. This resulted from a small (10%) increase in Q and a constant elevation in CaO2 of 1.7http://hwmaint.jap.physiology.org/cgi/content/abstract/53/4/992 2.2 ml X 100 ml-1, since virtually no changes were observed in the femoral venous blood postreinfusion and the acid-base status and temperature, important determinant of O2 dissociation, were (almost) identical, comparing the two experimental conditions.
Restoration of thermoregulatory response to body cooling by cooling hands and feet
Authors: Van Someren R. N. , Coleshaw S. R. , Mincer P. J. , Keatinge W. R.
Published: December 2017

Deep body temperature fell progressively by 0.5–1.4 degrees C during 3-h immersions in 29 degrees C water. Both in unacclimatized volunteers and, to a lesser degree, in divers in cold-water training, cooling the hands and feet for 1 h in 12 degrees C water during such immersion caused sensation of cold, shivering, and rise in metabolic rate; it caused body temperature to rise in unacclimatized subjects and halted its fall in divers. Tissue conductances generally fell a little in divers but rose in unacclimatized subjects, probably because of muscle blood flow associated with the greater shivering in the latter. Soaking the skin for 4 h produced no major changes in cutaneous thermal sensation assessed in the forearm, though with seawater it sometimes reduced cold sensation and with distilled water sometimes reduced warm sensation, a little. It is concluded that uniform skin temperature of 29 degrees C often induces insufficient heat-gain reflexes to maintain body temperature and that cooling of the extremities can restore adequate thermoregulatory response.
Acute fasting and fiber number in rat soleus muscle
Authors: Parsons D. , Riedy M. , Moore R. L. , Gollnick P. D.
Published: December 2017

The influence of fasting on fiber number in the soleus muscle (SM) of weanling male and female rats was investigated. For female rats, comparisons were made among groups of animals fed normally, rats fasted and then fed until prefast body weight was regained, and animals that grew to maturity. For male rats, comparisons were made only between control and fasted groups. Prior to the experimental treatments the SM was surgically removed from one leg. There was a 40% loss in body weight after fasting. Although major weight losses occurred in most muscles and organs, there was no change in the SM. Over the same period SM weight increased 31% in normal animals. Total fiber number (direct counts after nitric acid digestion) was unaltered by the treatments. Although wide variation existed between animals, total fiber number between legs for the same animal was closely correlated (r = 0.98). SM weight for male rats calculated from fiber length, cross-sectional area, and total fiber number could account for from 91 to 99% of the total muscle weight. There was no change in fiber number from weaning to maturity. It is concluded that fiber number is unchanged by fasting or during normal maturation.
Neuroepithelial cells in fish gill primary lamellae
Authors: Dunel-Erb S. , Bailly Y. , Laurent P.
Published: December 2017

Formaldehyde-induced fluorescence reveals numerous serotonin-containing cells within the primary epithelium of the fish gill. These cells are isolated or clustered and are supported by the epithelial basal lamina. They never reach the external medium and are found on the internal side of the primary lamellae, facing the respiratory water flow. With the electron microscope, these cells are found to contain dense-cored vesicles (DCV) of 80–100 nm. Nerve profiles are consistently found close to DCV cells. After having crossed the basal lamina, nerve fibers form endings on DCV-containing cells. These endings display both small clear vesicles and DCV and are in direct contact with DCV cells. Specific membrane alterations are suggestive of efferent synapses. These cells are considered neuroepithelial cells, similar to those found within the wall of lung airways in mammals and submammalian vertebrates. Structure and localization are suggestive of a tissue O2 sensor.
Comparative brain oxygenation and mitochondrial redox activity in turtles and rats
Authors: Sick T. J. , Lutz P. L. , LaManna J. C. , Rosenthal M.
Published: December 2017

Comparisons were made between brain oxygenation and cytochrome c oxidase (cytochrome aa3) redox status in turtles (Pseudymys scripta) and rats. Although average brain O2 tension (PtO2) during normoxia was similar in turtle telencephalon and rat parietal cortex, a greater frequency of high and low values of PtO2 occurred in rats, which may indicate a steeper O2 gradient between capillaries and cells. When the fractional inspired O2 concentration (FIO2) was increased, PtO2 was elevated and cytochrome aa3 became more oxidized, whereas decreased FIo2 produced opposite changes in both species. In turtle brain, however, the relationship between PtO2 and cytochrome aa3 redox state was nearly linear over a wide range of PtO2 values. In rats, this relationship was steeper at PtO2 below normoxia and approached a plateau at Pto2 values above normoxia. Turtle brain cytochrome aa3 appeared more reduced in normoxia, which may be due either to lower affinity for O2 or to enhanced substrate supply. These results indicate that differences in resistance to hypoxia/anoxia observed between rats and turtles are probably not due to differences in O2 availability. Rather, it is likely that differences in redox activities of cytochrome aa3 and/or in substrate use play a role in the relative insensitivity of turtle brain to O2 deprivation.
Intrapulmonary CO2 receptor discharge at different levels of venous PCO2
Authors: Tallman R. D. , Grodins F. S.
Published: December 2017

It has been suggested that avian intrapulmonary CO2-sensitive receptors (IPC) may be capable of affecting ventilation in response to changes in lung CO2 load. The purpose of this study was to record IPC discharge activity in spontaneously breathing ducks when venous PCO2 was elevated or lowered from resting levels. This was accomplished using an extracorporeal venovenous blood bypass circuit, which included a 0.8-m2 silicone membrane blood oxygenator. Adult male Pekin ducks were anesthetized and tracheostomized. Single-unit activity was recorded from 42 IPC. During venous CO2 loading, there was no difference in the average IPC discharge from control despite an increase in the rate of CO2 excretion (VCO2) to twice the resting level. Venous CO2 unloading decreased VCO2 by one-half but did not significantly affect inspiratory IPC discharge and resulted in only a small increase in expiratory discharge. In contrast, inhalation of 3% CO2 greatly reduced inspiratory discharge. Reflex adjustments in tracheal flow appear to be responsible for maintaining IPC discharge at control levels when venous PCO2 changes.
Gas exchange during high-frequency ventilation of the chicken
Authors: Banzett R. B. , Lehr J. L.
Published: December 2017

Recent studies have shown that high-frequency ventilation (HFV) at 1–30 Hz is capable of maintaining adequate gas exchange in humans and dogs even when tidal volumes are substantially less than dead space. We evaluated the effectiveness of HFV in roosters by comparing CO2 elimination during various frequencies and tidal volumes of HFV with CO2 elimination during conventional mechanical ventilation. Sinusoidal oscillations were applied at the tracheal cannula. A bias flow provided fresh gas at the top of the tracheal cannula. Three conclusions emerge from the data. 1) HFV enhances gas transport in the chicken as it does in mammals. 2) At low oscillatory flows (amplitude X frequency) CO2 elimination depends on both frequency and tidal volume, whereas at higher flows CO2 elimination depends more strongly on tidal volume. The flow at which this transition occurs is relatively lower than in humans and much lower than in dogs. 3) HFV at volumes below dead space is usually not capable of maintaining adequate gas exchange in the chicken in contrast to results in dogs and humans.
Respiratory properties of blood from embryos of highland vs. lowland geese
Authors: Snyder G. K. , Black C. P. , Birchard G. F. , Lucich R.
Published: December 2017

Respiratory properties of whole blood during development were studied in embryos of the bar-headed and Canada geese. In both species, affinity of the blood for O2 [expressed as O2 half-saturation pressure (P50)] increased with development, to a low and stable value. The low and stable P50 at pH 7.4 for the bar-headed goose, 20.1 +/- 0.3 Torr, is significantly lower than that for the Canada goose, 26.9 +/- 0.8 Torr. The data suggest a higher Bohr effect for the bar-headed goose. Hill's coefficients, buffering capacity, red cell 2,3-diphosphoglycerate, and blood hemoglobin concentrations are similar in both species. We suggest that the affinity of the whole blood for O2 is an important genetically based adaptation to ensure a high O2 content in the blood in the face of reductions in ambient PO2 associated with nesting at high altitudes. The higher Bohr effect may ensure high tissue PO2 in the presence of the high-affinity hemoglobin.
Functional properties of embryonic chicken hemoglobins
Authors: Baumann R. , Padeken S. , Haller E. A.
Published: December 2017

We have investigated the O2-binding properties of the four embryonic hemoglobins (Hb P, Hb P′, Hb M, and Hb E) under various conditions and compared the results with measurements on early embryonic chicken blood between 3 and 6 days of incubation. The O2-binding curve of embryonic blood is polyphasic. Hill's coefficient changes continuously from less than or equal to 1 at low O2 saturation to a value of approximately equal to 8 in the upper saturation range. The high cooperativity is coupled with a very low O2 affinity in the middle range of the O2-binding curve. Between 3 and 6 days of development the O2 affinity and cooperativity as well as the Bohr effect of embryonic blood change drastically, without corresponding alterations of the hemoglobin pattern or ATP concentration. The functional properties of the embryonic blood cannot be simulated with the isolated embryonic hemoglobins at physiological concentrations of ATP, hemoglobin, and protons. On the other hand, freshly prepared hemolysate shows the same functional pattern as the embryonic blood. The results suggest that embryonic red blood cells may contain other low-molecular-weight substances that reduce the O2 affinity and increase the cooperativity of the major embryonic hemoglobins, Hb P and Hb P′, presumably by promoting tetramer-tetramer aggregation.
O2 tension in the spinal cord of the avian embryo
Authors: Stokes B. T.
Published: December 2017

A small recessed-tip O2 microelectrode was used to construct frequency distributions of PO2 in the chicken embryonic spinal cord during the last week of development (15–20 days). PO2 was remarkably low and stable at a given spinal locus. Electrode movement led to little change in the absolute level of tissue PO2 for a given day in the development. Spontaneous fluctuations occurred, predominantly in the motor columns, whose frequencies were dependent on the stage of incubation. PO2 decreased progressively; the most significant decline occurred between 16 and 17 days in ovo [19.2 +/- 1.7 (SD) to 11.5 +/- 2.7 Torr, respectively]. This decline in tissue PO2 at 16 days precedes dramatic alterations in spinal cord electrical activity and the resulting embryonic behavior.
Effects of inhaled CO2 on airway stretch receptors in the newborn dog
Authors: Fisher J. T. , Sant'Ambrogio G.
Published: December 2017

The response of 96 slowly adapting airway stretch receptors (SARs) to inhaled CO2 was studied in 26 puppies, which were anesthetized, paralyzed, and passively ventilated with the chest open. Both inhibitory and excitatory influences were obtained during CO2 inhalation depending on the presence or absence of a partially intact parasympathetic innervation and the receptor location. In puppies in the vagotomized condition, tracheal SARs of the youngest puppies (1–10 days) were inhibited (68% of control discharge), whereas bronchial SARs were unaffected by CO2. In the older age groups (12–17 and 26–30 days) there was a gradual acquisition of the adult response with a progressive increase in the inhibitory action of CO2 on bronchial SARs, whereas tracheal SARs became less affected. An excitatory action of CO2 could be found if the contralateral vagus nerve was intact. This response, which was abolished by vagotomy or atropine, was limited to tracheal SARs (occurring in 8 out of 23 receptors with the remainder inhibited) and was not accompanied by changes in transpulmonary pressure. Considering that only one-half of the functional efferent innervation of the trachea was present (i.e., left vagus only) and that the response has never been reported in the adult, the stimulation of SAR activity via smooth muscle contraction may represent a mechanism that could severely limit the neonate's ability to respond to periods of apnea or asphyxia.
Surfactant homeostasis in the rat lung during swimming exercise
Authors: Nicholas T. E. , Power J. H. , Barr H. A.
Published: December 2017

Swimming rats for up to 2 h in water at 34 +/- 1 degree C increased the rate of breathing by 60% and tidal volume by 200–300%. In each case we infused 20 muCi X kg-1 [methyl-3H]choline chloride, via a caudal vein, 3 h prior to the end of swimming. Maximum specific activity of tissue phospholipid (PL) and alveolar PL (PLalv) occurred in 1 and 12 h, respectively. Total PLalv, specific activity of PLalv and the percentage of total PL released (%A/T) increased within 10 min of start of swimming and were sustained for at least 2 h of swimming [PLalv in mg X g dry lung-1: 5 s swim, 7.3 +/- 0.96 (mean +/- SD; n = 15 rats); 1-h swim, 10.1 +/- 1.1 (n = 23 rats)]. After a 1-h swim, PLalv returned to control within 4 h. Pretreatment with propranolol hydrochloride (10 mg X kg-1) (P), atropine methyl nitrate (3 mg X kg-1) (A), indomethacin (15 mg X kg-1), and cyproheptadine (1 mg X kg-1) did not alter the increase in PLalv with swimming, however, both P and A reduced the increase in specific activity of PLalv and %A/T. We suggest that the exercise releases surfactant from two pools: a readily released pool that responds to direct distortion of the alveolar type II cell and a pool that is under sympathetic nervous control.
Effect of converting enzyme inhibition on pulmonary edema after microembolization
Authors: Kivlen C. M. , Johnson A. , Pittman T. , Guile A. J. , Malik A. B.
Published: December 2017

We examined the effect of converting enzyme inhibition with captopril (SQ 14,225) on pulmonary hemodynamics and on accumulation of extravascular lung water after microembolization in dogs. Pulmonary microembolization, induced with glass beads (200 microns diam), increased the mean pulmonary arterial pressure to approximately 40 Torr in both control and captopril-treated animals. The increase in pulmonary vascular resistance (PVR) in control animals was sustained during the 75 min of study and was associated with an increase in the extravascular lung water content-to-bloodless dry lung weight ratio (W/D) from a normal value of 2.84 +/- 0.22 to 4.53 +/- 0.24 ml/g (P less than 0.01) after embolization. In the captopril-treated group, the PVR increased gradually, such that the value at 75 min postembolization was greater than in controls (P less than 0.05). The W/D in the captopril-treated group of 4.62 +/- 0.19 ml/g was greater than the value of 2.83 +/- 0.10 ml/g in nonembolized captopril-treated animals, but the degrees of edema in the control and captopril-treated animals were not different. A similar degree of embolization induced during infusion of 5 micrograms X kg-1 X h-1 of bradykinin also did not enhance the pulmonary edema, and there was also a greater increase in PVR than in control animals after embolization. These findings suggest that bradykinin does not contribute to the degree of pulmonary edema after microembolization.
Cerebral interstitial fluid acid-base status follows arterial acid-base perturbations
Authors: Davies D. G. , Nolan W. F.
Published: December 2017

Cerebral interstitial fluid (ISF) pH of ventral medulla or thalamus, cisternal cerebrospinal fluid (CSF) pH, and arterial blood pH, PCO2, and [HCO-3] were measured in chloralose-urethan-anesthetized, gallamine-paralyzed New Zealand White rabbits during 30-min episodes of either HCl or NaHCO3 intravenous infusions. ISF pH was measured continuously with glass microelectrodes (1- to 2-microns tip diameter). Cisternal CSF pH was measured continuously with an indwelling pH probe (1-mm tip diameter). Both ventral medullary and thalamic ISF [H+] changed significantly, whereas arterial PCO2 remained constant. CSF [H+] did not change. We conclude from these data that 1) changes in blood acid-base conditions are rapidly reflected in cerebral ISF and 2) transient differences in [H+] and [HCO-3] can exist between cerebral ISF and CSF.
Dose-response effects of atropine on thermal stimulus-response relationships in asthma
Authors: Griffin M. P. , Fung K. F. , Ingram R. H. , McFadden E. R.
Published: December 2017

To determine how cholinergic blockade modifies the stimulus-response relationships to thermal provocations, we had seven asthmatics perform increasing levels of eucapnic hyperventilation of subfreezing air (-10.6 +/- 1.9 degrees C) after pretreatment with aerosols of saline and atropine in doses of 0.25, 0.5, 1.0, 3.0, and 6.0 mg. Testing was performed on 5 separate days with both placebo and a single dose of drug. In control experiments, increasing ventilation produced a progressive decrease in the 1-s forced expiratory volume in a stimulus-response fashion. There were no significant differences between any placebo study. Atropine pretreatment did not abolish the obstructive response to airway cooling at any dose but, rather, shifted the stimulus-response curve to the right, so that the effects of muscarinic blockade could be overcome by increasing the stimulus. There were no significant differences between the results observed with 0.25 or 6 mg of atropine. These data demonstrate that cholinergic mechanisms play, at best, a very minor role in exercise-induced bronchospasm and offer a unifying explanation for the disparate findings in the literature regarding antimuscarinic agents in this condition.