bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of spinal accessory nerve activity response to changes in chemical drive
Authors: Nishino T. , Yonezawa T. , Honda Y.
Published: December 2017

In anesthetized, vagotomized, and artificially ventilated cats, the electrical activities of the spinal accessory nerve (SAN) and the phrenic nerve (PN) were simultaneously recorded and comparison between the responses of the SAN and the PN to changes in chemical drive was made. Hypercapnia and hypoxia increased SAN activity as well as PN activity, but the SAN had a greater increase in activity than the PN at high levels of arterial Pco2 and at low levels of arterial Po2. Also, doxapram injection increased SAN activity more than PN activity. Following hypocapnic apnea, the reinitiation of PN activity always preceded that of the SAN, indicating that threshold arterial Pco2 for the SAN was higher than for the PN. Thus the responses of SAN activity to changes in chemical drive are qualitatively similar but quantitatively different from those of the PN.
Active and passive respiratory mechanics and control of breathing in kittens
Authors: Zin W. A. , Marlot D. , Bonora M. , Siafakas N. M. , Gautier H. , Milic-Emili J.
Published: December 2017

The effects of heating and cooling on the electrically evoked mechanical and contractile properties of the triceps surae in relation to the maximal dynamic performance of the leg muscles during cycling and vertical jumping have been examined in five healthy male subjects. A mean rise of 3.1 degrees C in muscle temperature (Tm) was associated with a decrease in time to peak tension (TPT) and half-relaxation time (1/2RT) but was without effect on twitch (Pto) and tetanic tension at 20 Hz (Po20) and 40 Hz (Po40) and maximal voluntary contraction (MVC). Reducing Tm by 8.4 degrees C had the opposite effect on TPT and 1/2RT and produced a fall in Pto, Po40, and MVC. The peak power output during cycling (W1) and jumping (W) was linearly related to Tm as well as negatively associated with TPT. The best single guide to W and W1 was given by a ratio of MVC to TPT: W (W) = 626.5 + 79.04 (MVC/TPT)(N/ms; r = +0.82) and W1 (W) = 1,342 + 84.9 (MVC/TPT)(N/ms; r = +0.87). The results underline the importance of the contractile and force generating capacity of human muscle in determining maximal power output and performance during exercise of a few seconds duration.
Impaired memory registration and speed of reasoning caused by low body temperature
Authors: Coleshaw S. R. , Van Someren R. N. , Wolff A. H. , Davis H. M. , Keatinge W. R.
Published: December 2017

Volunteers′ body core temperatures were lowered by immersion in water at 15 degrees C. Aspects of cognitive function were subsequently tested after rewarming had been started in water at 41 degrees C when their skin was warm and they felt comfortable but their body core temperature remained low. Memory registration was found to be impaired progressively when core temperature fell from about 36.7 degrees C; at core temperatures of 34-35 degrees C the impairment caused loss of approximately 70% of data that could normally be retained. However, recall of previously learned data was not impaired at these core temperatures. On a two-digit calculation test, speed of performance was impaired by about 50% at a core temperature of 34-35 degrees C, but provided enough time was available, accuracy of performance was not reduced.
Effect of previous volume history on airway closure
Authors: Greville H. W. , Slykerman L. J. , Easton P. A. , Anthonisen N. R.
Published: December 2017

We studied the effect of volume history on airway closure in six healthy males ranging from 32 to 67 yr of age. The method used was to compare the regional distribution of 133Xe boluses distributed according to N2O uptake during open-glottis breath-hold maneuvers with the regional distribution of boluses of intravenously injected 133Xe. Measurements were made at two lung volumes, one close to residual volume (RV) and the other just below closing volume. The required volume was reached either by expiring from total lung capacity or by inspiring from RV. Although there was considerable airway closure in the basal regions of the lungs at both lung volumes studied, the degree of airway closure was not dependent on the previous volume history. We conclude that the airways concerned with closure have a volume-pressure hysteresis similar to that of the lung parenchyma. Furthermore in normal humans the volume-pressure hysteresis of the lung is not secondary to airway closure.
Expiratory threshold load under extracorporeal circulation: effects of vagal afferents
Authors: Jammes Y. , Bye P. T. , Pardy R. L. , Katsardis C. , Esau S. , Roussos C.
Published: December 2017

Nine anesthetized dogs breathed against an expiratory threshold load (ETL) applied by switching the expiratory circuit into a column of H2O to a depth of 20-30 cm. Arterial blood gas tensions were maintained in the normal range by placing the dogs under arteriovenous bypass to avoid any uncontrolled chemostimulation. There was an increase in integrated electromyogram activity of the diaphragm with the ETL. This was rarely observed after cold block of the vagus nerves which also reduced the evoked expiratory activity. The ventilatory response to hypercapnia was greatly depressed under loaded breathing whether vagal afferents were intact or blocked by cold. Both inspiratory drive and ventilatory timing were affected, suggesting that the central integration of chemosensitive afferents was altered. Proof of supraspinal projections of proprioceptive inputs from abdominal muscles was provided by the demonstration of changes in ventilatory timing during selective activation of muscle spindles in abdominal muscles by high-frequency mechanical vibration applied to the linea alba. Thus these observations suggest that during ETL breathing, a possible interaction exists between chemoreflex drive and proprioceptive afferents.
High-frequency ventilation lengthens expiration in the anesthetized dog
Authors: Banzett R. , Lehr J. , Geffroy B.
Published: December 2017

We tested the response of nine barbiturate-anesthetized dogs to high-frequency ventilation (HFV) (40-55 ml tidal volumes at 15 Hz) while measuring and controlling lung volume and blood gases. When lung volume and PCO2 were held constant, six of the nine responded to HFV by lengthening expiration. In each of these six dogs the maximal response was apnea. The response was immediate. In submaximal responses only expiration was changed; inspiratory time and peak diaphragmatic electrical activity were unaffected. There was a variable effect on abdominal muscle activity. If mean expiratory lung volume was allowed to increase at the onset of HFV, the Hering-Breuer inflation reflex added to the response. The strength of the response depended on level of anesthesia and arterial PO2. Vagotomy abolished the response in all cases. We conclude that oscillation of the respiratory system reflexly prolongs expiration via mechanoreceptors, perhaps those in the lungs.
Mechanical properties of the upper airway
Authors: Cauberghs M. , Van de Woestijne K. P.
Published: December 2017

The series and shunt components of the impedance of the upper airway (Zuaw) were evaluated from measurements obtained during a Valsalva maneuver by means of a modified forced oscillation technique. When the cheeks are supported, the upper airway can be represented by a single distributed transmission line. The homogeneity of this line was confirmed by measuring separately Zuaw and the impedance of the mouth. Correction of the impedance of the respiratory system, determined by means of the forced oscillations technique, for the shunt properties of Zuaw results in some modifications of the frequency dependence of resistance (Rrs) in healthy adults and in marked changes of the absolute values of Rrs in children and in patients with obstructive lung disease.
Airway anesthesia effects on hypercapnic breathing pattern in humans
Authors: Sullivan T. Y. , Yu P. L.
Published: December 2017

Minute ventilation (VE) and breathing pattern during an abrupt increase in fractional CO2 were compared in 10 normal subjects before and after airway anesthesia. Subjects breathed 7% CO2-93% O2 for 5 min before and after inhaling aerosolized lidocaine. As a result of airway anesthesia, VE and tidal volume (VT) were greater during hypercapnia, but there was no effect on inspiratory time (TI). Therefore, airway anesthesia produced an increase in mean inspiratory flow (VT/TI) during hypercapnia. The increase in VT/TI was compatible with an increase in neuromuscular output. There was no effect of airway anesthesia on the inspiratory timing ratio or the shape and position of the curve relating VT and TI. We also compared airway resistance (Raw), thoracic gas volume, forced vital capacity, forced expired volume at 1s, and maximum midexpiratory flow rate before and after airway anesthesia. A small (0.18 cmH2O X l-1 X s) decrease in Raw occurred after airway anesthesia that did not correlate with the effect of airway anesthesia on VT/TI. We conclude that airway receptors accessible to airway anesthesia play a role in hypercapnic VE.
Esophageal pressure in infants at elevated lung volumes and positive airway pressure
Authors: Beardsmore C. S. , Stocks J. , Silverman M.
Published: December 2017

The measurement of esophageal pressure changes (delta Pes) under conditions of elevated lung volume or continuous positive airway pressure (CPAP) was investigated in a group of 17 infants by use of an esophageal balloon. Eleven of the infants were studied in a whole-body plethysmograph, and lung volume was increased by a volume injection technique. Reproducible measurements of lung volume in the plethysmograph showed that changes in mask pressure (delta Pm) were accurate during airway occlusion in 10 of the 11 infants. A progressive elevation of the ratio delta Pes/delta Pm during respiratory efforts against occlusion at lung volumes above the tidal range was observed in 8 of the 11 infants. In only one of these infants could the error have been in delta Pm measurement. Of seven infants (including one common to both studies) studied under CPAP, six also showed this effect, which occurred predominantly in very young or preterm infants. Changes in esophageal pressure in infancy, measured at high lung volumes or pressures, may not be representative of mean pleural pressure changes.
Influence of ischemia and hypoxia on breathing in ducks
Authors: Lillo R. S. , Jones D. R.
Published: December 2017

We examined the influence of whole and lower body hypoxia and lower body ischemia on breathing in White Pekin ducks, Anas platyrhynchos, excluding pathways involving the carotid bodies. Carotid body denervated birds breathing 10 or 5% O2 developed a tachypnea after a latency of 30-100 s. The tachypnea was more pronounced with the more severe hypoxia, resulting in almost a doubling of minute ventilation (VE). Occlusion of the abdominal aorta in unanesthetized ducks produced immediate development of hypertension. Ventilation was unaffected for the 1st min; a tachypnea then developed rapidly and persisted for the duration of the occlusion resulting in a 25% increase in VE. After thoracic spinal section, all ventilatory responses to occlusion were eliminated. Experimental perfusion of the brain and single intact carotid body in unanesthetized ducks with hyperoxic blood during low O2 breathing (6-9% O2) resulted in tachypnea, also after a considerable latency. These results suggest that severe hypoxia can affect breathing in birds via pathways other than those involving the carotid bodies.
Breathing patterns during submaximal and maximal exercise in elite oarsmen
Authors: Clark J. M. , Hagerman F. C. , Gelfand R.
Published: December 2017

Continuous breath-by-breath measurements of ventilatory parameters were performed during submaximal and maximal treadmill exercise in 21 highly conditioned oarsmen. Average maximum values of O2 uptake, minute ventilation (VI), tidal volume (VT), and respiratory frequency (f) were 6.60 l/min (73.5 ml X kg-1 X min-1), 200 l/min, 3.29 l, and 62 breaths/min, respectively. During the transition from moderate to heavy submaximal exercise, VT and f increased progressively. At near-maximal to maximal work loads, VT plateaued and then decreased slightly, while f continued to increase. Increase in f at the start of exercise was achieved predominantly by an abrupt decrease in expiratory duration (TE) with an equally abrupt, but much smaller, decrease in inspiratory duration (TI). During the transition from submaximal to maximal exercise, both TE and TI decreased progressively. Although f appeared to be entrained by stepping rate in a few subjects, the dominant trend during submaximal to maximal exercise was characterized by a relatively small increase in stepping rate with a much larger increment in f. Our data are consistent with the conclusion that exercise breathing patterns are determined by many interacting factors that vary at different work loads, in different individuals, and are probably also influenced by physical conditioning and previous experience.
Effect of a hydrostatic pleural pressure gradient on mechanical behavior of lung lobes
Authors: Murphy B. G. , Plante F. , Engel L. A.
Published: December 2017

Using 133Xe, the vertical distribution of regional volume (Vr) was measured in three regions of excised canine lobes both in air and when completely submerged in saline at 40, 60, 70, and 80% lobar vital capacity (VC). The estimated pleural pressure gradient, derived from values of Vr, distance between regions, and the lobar pressure-volume (PV) curve, underestimated the true gradient by 45%. Conversely, the gradient of Vr was substantially less than predicted. From the mean depth of each region below the waterline, pleural, and hence transpulmonary, pressure (PL) was computed. The values of Vr-PL for each region at 40, 60, and 80% lung volume (VL) were related to the lobar PV curve. Slopes of lines joining initial VL-PL points on the lobar PV curve to corresponding Vr-PL points in submerged lobes represent an effective regional compliance of a lobe undergoing deformation. With one exception this was less than the corresponding homogeneous compliance, indicating a stiffening of the lobe during deformation. Slopes of lines joining Vr-PL points of each region at the three lobar volumes represent effective regional compliance of a deformed lobe undergoing volume change. This was not significantly different from the homogeneous compliance. However, effective compliance can only be an approximate indicator of the forces required for a given volume change due to the inadequacy of PL to represent the unequal stress components induced by lobe deformation.
Effects of cyclooxygenase and lipoxygenase inhibition on lung fluid balance after thrombin
Authors: Bizios R. , Minnear F. L. , van der Zee H. , Malik A. B.
Published: December 2017

We examined the roles of the cyclooxygenase and lipoxygenase pathways in the alterations in lung fluid and protein exchange after pulmonary microembolism. Infusion of alpha-thrombin (T) (55 +/- 13 U/kg) immediately increased mean pulmonary arterial pressure (Ppa) and mean pulmonary vascular resistance (PVR), but both Ppa and PVR waned with time after T. Cyclooxygenase inhibition with either indomethacin or ketoprofen produced sustained increases in Ppa and PVR. The initial increases in Ppa in the cyclooxygenase-inhibited groups (CI) were matched to the control group by administering greater amounts of T. In the control group, T rapidly increased pulmonary lymph flow (Qlym) by two- to threefold, and this was associated with a steady increase in lymph-to-plasma protein concentration ratio (L/P). In contrast, in cyclooxygenase-inhibited (CI) groups, Qlym increased gradually to greater levels than in the control group, and L/P did not change. The effect on lung vascular permeability was determined by inflating a left atrial balloon catheter to raise pulmonary capillary pressure (Pc). An increase in Pc after T in the control group further increased Qlym and did not change L/P, whereas the increase in Pc after T in CI groups further increased Qlym and decreased L/P, indicating that cyclooxygenase inhibition prevented the increase in permeability. We determined whether lipoxygenase activation contributed to the increase in Qlym in CI groups by examining the effects of BW755C, an inhibitor of both cyclooxygenase and lipoxygenase pathways. BW755C resulted in the same increase in Qlym after T as in the control group, but the increase in Qlym was associated with a decrease in L/P. Therefore, inhibition of both pathways prevented the permeability increase and the greater increase in Qlym. The results indicate that cyclooxygenase and lipoxygenase pathways contribute to the increases in pulmonary transvascular fluid and protein fluxes after thrombin.
Metabolism of rats running up and down an incline
Authors: Armstrong R. B. , Laughlin M. H. , Rome L. , Taylor C. R.
Published: December 2017

The purpose of these experiments was to determine oxygen consumption (VO2) in rats as a function of treadmill speed (10, 20, 30, 40, and 50 m . min-1) as they ran on the level and up and down a 16 degree (17.8%) incline. The slopes of the regression lines relating VO2 (ml O2 . kg-1 . min-1) to running speed (m . min-1) were linear for all three inclines. The regression slope for uphill runners (y = 1.25x + 47.7) was greater than the regression slopes for level (y = 0.88x + 41.2) (P less than 0.025) or downhill (y = 0.68x + 39.7) (P less than 0.005) runners, and the regression slope for level runners was greater than that for downhill runners (P less than 0.10). All VO2 measurements were submaximal. In conclusion, incline has a significant effect on the metabolism of rats running on a motor-driven treadmill.
Effects of chronic hypoxia on pulmonary vascular responses to biogenic amines
Authors: Porcelli R. J. , Bergman M. J.
Published: December 2017

The effects of chronic hypoxia on pulmonary vascular resistance changes (% delta Rpv) to histamine, 5-hydroxytryptamine (5-HT), norepinephrine (NE), and KCl were studied in isolated perfused lungs from control rats and rats exposed to 7, 14, and 28 days of hypoxia. Histamine, which produced linear increases in % delta Rpv with increasing doses in the control, was reversed to vasodilation by chronic hypoxia of 7 and 14 days and at 28 days, vasodilation to this amine still predominated (7 out of 10). Control responses to 5-HT were unaltered by 7 days of hypoxia but enhanced at 14 and 28 days. Control responses to NE showed either vasoconstriction or vasodilation; at 7 days of hypoxia, NE had no significant vasoactivity; however, at 14 days, vasoconstriction and vasodilation were both observed, with vasodilation being more effective. Lastly, the pressor responses to KCl were not affected by chronic hypoxia of any duration. These results suggest that chronic hypoxia: 1) does not alter pulmonary vascular contractility (KCl); 2) reduces H1 and alpha-receptor activity while enhancing H2- and beta-receptor activity; and 3) enhances the pressor responses to 5-HT by increasing either the efficacy of this amine or the number of 5-HT vasoconstrictor receptors.
Comparison of the tussive effects of histamine and methacholine in humans
Authors: Chausow A. M. , Banner A. S.
Published: December 2017

The tussive and bronchoconstrictive effects of histamine inhalation in 7 normals, 7 asthmatics, and 24 patients with chronic cough (PCC) were measured by counting coughs during a standard histamine inhalation challenge. All PCC had a tussive response. Fifteen PCC exhibited significant linear correlations between cough count and either the change in forced expiratory volume at 1.0 (delta FEV1) or conductance-volume ratio (sGaw) (delta sGaw). Normals and asthmatics had little or no cough. Metaproterenol pretreatment in seven PCC reduced both the FEV1 and cough response to histamine without changing the relationship between cough and delta FEV1. The tussive and bronchoconstrictive effects of methacholine inhalation were also measured in 7 asthmatics and 16 PCC. One asthmatic coughed. Fifteen PCC coughed. There were significant linear correlations between cough count and delta FEV1 or delta sGaw in 10 PCC. At comparable delta FEV1 and delta sGaw, histamine produced more cough than methacholine. These data indicate that during inhalation of histamine or methacholine by PCC cough is related to, and may be caused by, bronchoconstriction. Histamine also causes cough by an additional mechanism not related to bronchoconstriction.
A simple model of VA/Q distribution for analysis of inert gas elimination data
Authors: Mertens P.
Published: December 2017

A general procedure for fitting compartments models of alveolar ventilation-perfusion ratio (VA/Q) distribution to inert gas elimination data is described. The method can be applied to any model consisting of a number of compartments ventilated and perfused in parallel, each compartment of the model having a fixed predetermined VA/Q ratio. The number of compartments and their VA/Q ratios required for adequately fitting real data have been examined. A 13-compartment model consisting of a shunt, a dead space, and 11 compartments equally spaced on a logarithmic scale from VA/Q of 0.01 to 100 was found to be suitable. The fitting procedure and the 13-compartment model form the basis of a method of analysis of inert gas elimination data. Essentially the method consists of calculating a sample of 30 distributions compatible with the data analyzed taking into account experimental errors in the inert gas measurements. From this sample, the averages and standard deviations of the flows to 13 zones on the VA/Q scale are estimated. The averages are estimates of the true flows to these zones, and the standard deviations give an indication of the range of flows compatible with the data. The method has some advantages over both the enforced-smoothing approach and the Monte Carlo linear programming scheme of Evans and Wagner (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 42: 889-898, 1977).
Noninvasive ventilatory monitoring with bellows pneumographs in supine subjects
Authors: Morel D. R. , Forster A. , Suter P. M.
Published: December 2017

We compared simultaneous measurements of ventilatory movements obtained by a bellows pneumograph (BP) and a respiratory inductive plethysmograph (RIP) vs. integrated volume from a pneumotachograph in seven healthy volunteers during different respiratory patterns. The purpose of this study was to assess if a computer-aided calibration procedure could improve the accuracy of BP, a simple semiquantitative method for noninvasive ventilatory monitoring in supine subjects. Both devices were repeatedly calibrated against a pneumotachograph in the same posture with a computer-aided least-squares method. One calibration maneuver was sufficient to achieve a minimal relative difference in volume measurements between the RIP as well as the BP and the pneumotachograph of less than 1.2 +/- 4.5 (SD) %. The accuracy remained in this range during the subsequent calibrations with time (1 h) and after body movements. However, this difference increased significantly with both devices when the subjects were studied in the lateral decubitus position. The present study indicates that despite theoretical advantages of the RIP, the BP, when properly calibrated, has similar performances in supine subjects for monitoring ventilation; it is simpler and less expensive than the RIP and is devoid of electrical drift and artifacts.
Subtraction of electrocardiographic signal from respiratory electromyogram
Authors: Bloch R.
Published: December 2017

Presented is a method to selectively suppress interfering electrocardiographic artifacts from the surface-recorded respiratory muscle electromyographic (EMG) signal. This method has application in the frequency analysis of respiratory muscle EMG.
A computerized system for densitometric analysis of the microcirculation
Authors: Duling B. R. , Damon D. N. , Donaldson S. R. , Pittman R. N.
Published: December 2017

An analytical system for measuring size, motion, and light absorption of objects in the field of a microscope is described. The design criteria have been chosen to produce a system that permits acquisition of densitometric information at a number of points within the field and permits computation of important variables from the densitometric data. Relatively simple fiber-optics systems for sampling light intensity at selected locations in the microscope field are described. Computer programs are outlined that permit computation of microvessel diameter, red cell velocity, and hemoglobin oxygen saturation. The sampling systems and programs are quite general in nature and should be applicable to other types of related measurements and computing devices.
Bohr effect data for blood gas calculations
Authors: Hlastala M. P. , Woodson R. D.
Published: December 2017

The rate of relaxation of the diaphragm after stimulated (4 subjects) and voluntary (8 subjects) contractions was compared in normal young men. Stimulated contractions were induced by supramaximal unilateral phrenic nerve stimulation and voluntary contractions by short, sharp sniffs of varying tensions against an occluded airway. The rate of relaxation of the diaphragm was calculated from the rate of decline of transdiaphragmatic pressure (Pdi). In both conditions the maximum relaxation rate (MRR) was proportional to the peak transdiaphragmatic pressure (Pdi), whereas the time constant (tau) of the later exponential decline in Pdi was independent of Pdi. The mean +/- SE rate constant of relaxation (MRR/Pdi) was 0.0078 +/- 0.0002 ms-1 and the mean tau was 57 +/- 3.8 ms for stimulated contractions. The rate of relaxation after sniffs was not different, and it was not affected by either the lung volume at which occluded sniffs were performed (in the range of residual volume to functional residual capacity + 1 liter) or by the relative contribution gastric pressure made to Pdi. After diaphragmatic fatigue was induced by inspiring against a high alinear resistance there was a decrease in relaxation rate. In the 1st min postfatigue MRR/Pdi decreased (0.0063 +/- 0.0003 ms-1; P less than 0.005) and tau increased (83 +/- 5 ms; P less than 0.005). Both values returned to prefatigue levels within 5 min of the end of the studies. We conclude that the sniff may prove to be clinically useful in the detection of diaphragmatic fatigue.
A technique for the isolation of submucosal gland cells from cat trachea
Authors: Culp D. J. , Penney D. P. , Marin M. G.
Published: December 2017

We have developed a procedure to isolate submucosal gland cells from cat trachea. The excised trachea was stripped of surface epithelium by stroking the luminal surface with a nylon brush. The remaining submucosa was scraped free from underlying cartilage and minced into small fragments. To disperse glandular cells from these fragments, we subjected the minced tissue to both enzymatic (collagenase and elastase) and mechanical treatment. In 23 preparations of cells we yielded an average (+/- SE) of 8.4 +/- 0.9 (X 10(6] cells. In eight cell preparations 95 +/- 1% of the cells stained with periodic acid-Schiff stain, suggesting that the cells are of glandular origin. We used the following criteria to assess cell viability. The dye trypan blue was excluded by 92 +/- 1% of the cells (n = 23). Under the electron microscope, cellular membranes and organelles appeared normal. The isolated cells consumed oxygen at an average rate of 1.34 +/- 0.05 microliters O2 X h -1 X (10(6) cell) -1, (n = 65). Oxygen consumption was constant for at least 4 h after cell isolation, was inhibited 21% by 10(-4) M ouabain, and was subsequently stimulated to 135% above basal levels by 4 X 10(-5) M dinitrophenol.
Renin-aldosterone and angiotensin-converting enzyme during prolonged altitude exposure
Authors: Milledge J. S. , Catley D. M. , Ward M. P. , Williams E. S. , Clarke C. R.
Published: December 2017

The effect of 7 wk altitude exposure on plasma renin activity (PRA), plasma aldosterone concentration (PAC), and angiotensin-converting enzyme (ACE) activity was studied in 10 male subjects at 4,500 m. There was an initial increase in PRA and a reduction in PAC and ACE. The reduction in ACE was significantly greater in the four subjects who had frequently been exposed to extreme altitudes than in the other six subjects. These changes had returned to control values between 12 and 20 days. Exercise caused a marked elevation of PRA and PAC, but the PAC response to PRA was blunted compared with that at sea level. The ratio PAC/PRA at rest was reduced initially but returned to control values with a similar time course to that of ACE activity. The results are compatible with the hypothesis that ACE activity governs the adrenal response to PRA.
Changes in rate of relaxation of sniffs with diaphragmatic fatigue in humans
Authors: Esau S. A. , Bye P. T. , Pardy R. L.
Published: December 2017

The rate of relaxation of the diaphragm after stimulated (4 subjects) and voluntary (8 subjects) contractions was compared in normal young men. Stimulated contractions were induced by supramaximal unilateral phrenic nerve stimulation and voluntary contractions by short, sharp sniffs of varying tensions against an occluded airway. The rate of relaxation of the diaphragm was calculated from the rate of decline of transdiaphragmatic pressure (Pdi). In both conditions the maximum relaxation rate (MRR) was proportional to the peak transdiaphragmatic pressure (Pdi), whereas the time constant (tau) of the later exponential decline in Pdi was independent of Pdi. The mean +/- SE rate constant of relaxation (MRR/Pdi) was 0.0078 +/- 0.0002 ms-1 and the mean tau was 57 +/- 3.8 ms for stimulated contractions. The rate of relaxation after sniffs was not different, and it was not affected by either the lung volume at which occluded sniffs were performed (in the range of residual volume to functional residual capacity + 1 liter) or by the relative contribution gastric pressure made to Pdi. After diaphragmatic fatigue was induced by inspiring against a high alinear resistance there was a decrease in relaxation rate. In the 1st min postfatigue MRR/Pdi decreased (0.0063 +/- 0.0003 ms-1; P less than 0.005) and tau increased (83 +/- 5 ms; P less than 0.005). Both values returned to prefatigue levels within 5 min of the end of the studies. We conclude that the sniff may prove to be clinically useful in the detection of diaphragmatic fatigue.
Effects of ozone on peripheral lung reactivity
Authors: Gertner A. , Bromberger-Barnea B. , Traystman R. , Menkes H.
Published: December 2017

In previous studies, we demonstrated that local exposures to the lung periphery to 0.1 ppm ozone (O3) produce increases in resistance to flow through the collateral system (Rcs) which are prevented by vagotomy, and the local exposures to 1.0 ppm O3 produces increases in Rcs which are only partially mediated by the parasympathetic system. In the present studies, we evaluated the effects of short exposures to O3 on reactions to H2O and histamine in anesthetized male dogs when no residual effects of the O3 exposures could be detected. For this purpose a fiber-optic bronchoscope was wedged in a segmental airway of anesthetized dogs and was used to deliver O3, aerosols of H2O, histamine (1.5 X 10(-4) mg), and atropine (0.1 mg). Measurements of Rcs were used to monitor responses to these agents. Responses to three successive challenges with H2O and with histamine were not different from each other. A 30-min exposure to 0.1 ppm O3 between the first and second challenge did not alter responses to histamine or H2O. However, a 10-min exposure to 1.0 ppm O3 resulted in a significant increase in responses to both H2O and histamine. No correlation was noted between the magnitude of response to O3 and the increase in response to histamine or H2O following O3 exposure. Parasympathetic blockade (atropine or bilateral cervical vagotomy) abolished the increase in response to H2O but not the increase in response to histamine following exposure to 1.0 ppm O3.(ABSTRACT TRUNCATED AT 250 WORDS)
Characterization of respiratory-modulated activities of hypoglossal motoneurons
Authors: Hwang J. C. , Bartlett D. , St John W. M.
Published: December 2017

In decerebrate, vagotomized, paralyzed, and ventilated cats, activities of the phrenic nerve and single hypoglossal nerve fibers were monitored. The great majority of hypoglossal neuronal activities were inspiratory (I), discharging during a period approximating that of phrenic. Many were not active at normocapnia but were recruited in hypercapnia or hypoxia. Once recruited, discharge frequencies, which rose quickly to near maximal levels in early to midinspiration, significantly increased with further augmentations of drive. Also, the onset of activities became progressively earlier, compared with phrenic discharge, in hypercapnia or hypoxia. Smaller numbers of hypoglossal fiber activities, having inspiratory-expiratory (I-E), expiratory (E), expiratory-inspiratory (E-I), or tonic discharge patterns, were also recorded. Activities of E, I-E, and those I fibers that became I-E in high drive may underlie the early burst of expiratory activity of the hypoglossal nerve. It is concluded that the firing and recruitment patterns of hypoglossal neurons differ from those of phrenic motoneurons. However, responses to chemoreceptor stimuli are similar among the two neuronal groups.
Interaction of sleep state and chemical stimuli in sustaining rhythmic ventilation
Authors: Skatrud J. B. , Dempsey J. A.
Published: December 2017

The effect of sleep state on ventilatory rhythmicity following graded hypocapnia was determined in two normal subjects and one patient with a chronic tracheostomy. Passive positive-pressure hyperventilation (PHV) was performed for 3 min awake and during nonrapid-eye-movement (NREM) sleep with hyperoxia [fractional inspired O2 concentration (FIO2) = 0.50], normoxia and hypoxia (FIO2 = 0.12). During wakefulness, no immediate posthyperventilation apnea was noted following abrupt cessation of PHV in 27 of 28 trials [mean hyperventilation end-tidal CO2 partial pressure (PETCO2) 29 +/- 2 Torr, range 22-35]. During spontaneous breathing in hyperoxia, PETCO2 rose from 40.4 +/- 0.7 Torr awake to 43.2 +/- 1.4 Torr during NREM sleep. PHV during NREM sleep caused apnea when PETCO2 was reduced to 3-6 Torr below NREM sleep levels and 1-2 Torr below the waking level. In hypoxia, PETCO2 increased from 37.1 +/- 0.1 awake to 39.8 +/- 0.1 Torr during NREM sleep. PHV caused apnea when PETCO2 was reduced to levels 1-2 Torr below NREM sleep levels and 1-2 Torr above awake levels. Apnea duration (5-45 s) was significantly correlated to the magnitude of hypocapnia (range 27-41 Torr). PHV caused no apnea when isocapnia was maintained via increased inspired CO2. Prolonged hypoxia caused periodic breathing, and the abrupt transition from short-term hypoxic-induced hyperventilation to acute hyperoxia caused apnea during NREM sleep when PETCO2 was lowered to or below the subject's apneic threshold as predetermined (passively) by PHV. We concluded that effective ventilatory rhythmogenesis in the absence of stimuli associated with wakefulness is critically dependent on chemoreceptor stimulation secondary to PCO2-[H+].
Influence of fasting on glycogen depletion in rats during exercise
Authors: Dohm G. L. , Tapscott E. B. , Barakat H. A. , Kasperek G. J.
Published: December 2017

We recently observed that a 24-h fasted group of rats could run longer than an ad libitum fed control group before becoming exhausted. Because of the demonstrated importance of glycogen levels and free fatty acid availability during endurance exercise, we have investigated several parameters of carbohydrate and lipid metabolism in exercised and nonexercised rats that were either fed ad libitum or fasted for 24 h. A 24-h fast depleted liver glycogen, lowered plasma glucose concentration, decreased muscle glycogen levels, and increased free fatty acid and beta-hydroxybutyrate concentrations in plasma. During exercise the fasted group had lower plasma glucose concentration, higher plasma concentration of free fatty acids and beta-hydroxybutyrate, and a lower muscle glycogen depletion rate than did the ad libitum fed group. Since fasted rats were able to continue running even when plasma glucose had dropped to levels lower than those of fed-exhausted rats, it seems unlikely that blood glucose level, per se, is a factor in causing exhaustion. These results suggest that fasting increases fatty acid utilization during exercise and the resulting “glycogen sparing” effect may result in increased endurance.
Exercise responses in pregnant sheep: oxygen consumption, uterine blood flow, and blood volume
Authors: Lotgering F. K. , Gilbert R. D. , Longo L. D.
Published: December 2017

In an attempt to explore the acute maternal responses to exercise we measured oxygen consumption, uterine blood flow, and blood volume in 13 chronically catheterized pregnant sheep at rest and while exercising on a treadmill. With maximal exercise O2 consumption increased 5.6 times, from a resting value of 5.8 +/- 0.3 (SE) to 32.1 +/- 2.8 ml X min -1 X kg -1, cardiac output increased 2.7 times, from 149 +/- 8 to 404 +/- 32 ml X min -1 X kg -1, and arteriovenous oxygen content difference increased 2.1 times, from 3.9 +/- 0.2 to 8.0 +/- 0.4 ml X dl -1. Total uterine blood flow decreased from a mean resting value of 292 +/- 6 to 222 +/- 19 ml X min -1 X kg fetus -1 near exhaustion during prolonged (40 min) exercise at 70% maximal oxygen consumption. Maternal blood volume decreased 14% (P less than 0.01) from 67.5 +/- 3.7 to 57.8 +/- 3.6 ml X kg -1 during this exercise period, with a 20% decrease in plasma volume without a change in red cell volume. We conclude that uterine blood flow decreases during maternal exercise. However, hemoconcentration helps to maintain a relatively constant oxygen delivery to the uterus.
Mechanism of reduced maximum expiratory flow in methacholine-induced bronchoconstriction in dogs
Authors: Mink S. N.
Published: December 2017

Airway sites of flow limitation [“choke points” (CP)] were identified during forced deflation in open-chest dogs before (C) and after (B) bronchoconstriction was produced by nebulizing a solution of methacholine chloride into their airways. CP were identified in two respective groups. In group I (n = 8) a retrograde catheter was used to locate CP and in the other a Pitot static tube (group II, n = 5), CP were identified at multiple lung volumes (VL) over the lower one-half of total lung capacity. Both groups showed similar findings at each condition. At B, corresponding values of maximum expiratory flow (Vmax) at each VL decreased to about 10% of those at C. Movement of CP relative to their original location varied at each VL and, especially at the lower VL, showed little peripheral movement. In group I, equal pressure points were also measured and were found to move peripherally at all the measured VL. In group II, cross-sectional area (A*) and airway compliance (K) at CP were estimated. During bronchoconstriction, A* decreased at the respective VL, and airways became less compliant. The reduction in Vmax could be explained in terms of changes in A* and K as described by wave-speed theory, and Vmax decreased because A* decreased. The decrease in A* was related in part to an increase in viscous pressure losses that reduced total pressure at CP and also in part to a change in the pressure-area behavior of bronchi at CP. Their relative effects on reducing A* and Vmax were examined.
Total and hindlimb oxygen deficit and "repayment" in hypoxic anesthetized dogs
Authors: Adams R. P. , Cain S. M.
Published: December 2017

Whole-body (WB) and hindlimb [(HL), paw excluded] O2 uptake (VO2) were measured in 26 anesthetized paralyzed dogs while they were ventilated with 9% O2-91% N2 for 15- and 30-min periods and with room air during recovery periods. Ten of the dogs were pretreated with 1 mg/kg propranolol (beta-Blockade). O2 deficit during hypoxia and the excess O2 used during recovery were obtained by assuming that VO2 would have followed the time course described by a line connecting prehypoxic and postrecovery VO2. Amounts of O2 deficit and excess were corrected for changes in O2 stores. O2 excess was seldom as great as O2 deficit in either WB or HL and the two quantities were not obviously related. The rate of HL O2 deficit accumulation decreased with time in hypoxia, whereas WB O2 deficit remained constant. All of HL VO2 was attributed to skeletal muscle so that WB O2 deficit and excess could be partitioned into muscle and nonmuscle portions. The rate of nonmuscle O2 deficit accumulation increased with time, but the nonmuscle portion of O2 excess decreased after the longer hypoxic period. beta-Blockade accentuated but did not change these qualitative relationships. We concluded that neither WB nor HL O2 deficits were fully matched by O2 excess and that regional patterns of O2 deficit accumulation and “repayment” did not necessarily parallel those for WB.
Oxidant- and lipid-induced pulmonary vasoconstriction mediated by arachidonic acid metabolites
Authors: Gurtner G. H. , Knoblauch A. , Smith P. L. , Sies H. , Adkinson N. F.
Published: December 2017

In experiments using isolated rabbit lungs perfused with Krebs-Henseleit buffer in a nonrecirculating manner, we found that administration of an organic peroxide, tert-butyl hydroperoxide (t-bu-OOH), or Intralipid, an esterified mixture of unsaturated fatty acids, caused a marked vasopressor response which was associated with increased levels of thromboxane in the effluent perfusate. The vasopressor response to t-bu-OOH was greater in the lungs of vitamin E-deficient animals, and this could be correlated with an attenuated ability to increase prostacyclin production in these lungs. Conversely, administration of Intralipid to normal lungs caused marked increases in prostacyclin and a smaller pressor response. The magnitude of the pressor response was strongly correlated with the ratio of thromboxane B2 to the prostacyclin metabolite. No release of these mediators was associated with pulmonary vasoconstriction caused by administration of angiotensin II. The pressor response could be completely blocked by administration of indomethacin. We propose that this activation of the cyclooxygenase pathway of arachidonic acid metabolism may be important in the pathophysiology of oxidant lung damage.
Effects of transient pulmonary hypertension on pulmonary vascular permeability
Authors: Minnear F. L. , Barie P. S. , Malik A. B.
Published: December 2017

The effects of a transient increase in pulmonary microvascular pressure (Pmv) on pulmonary fluid and protein exchange were studied in anesthetized sheep in which pulmonary lymph was collected. Pmv was increased to 30-40 mmHg for 15-30 min in 18 sheep by either an intra-aortic injection of norepinephrine (NE) or a rapid inflation of a left atrial balloon. NE injection produced sustained two- to threefold increases in pulmonary lymph flow and protein flux, whereas rapid balloon inflation transiently elevated lymph flow even though Pmv increased to similar levels with both methods. The sustained increases with NE were not due to an increase in vascular permeability but probably the result of a persistent increase in vascular surface area. In three additional animals, Pmv was increased to over 50 mmHg for 15-30 min. In these animals, lymph flow increased only by 49%, but airway edema fluid was present. The ratio of extravascular lung water to bloodless dry lung weight was 5.77 +/- 0.13 as compared with 4.30 +/- 0.11 in sheep subjected to Pmv less than 50 mmHg and to 4.08 +/- 0.19 for controls. These findings indicate that high pressure-induced pulmonary edema depends on a threshold Pmv around 50 mmHg. A combination of high capillary pressure and impaired lymphatic flow may be the bases for the development of neurogenic and catecholamine-induced pulmonary edema.
Hypergravic fields and parallel controllers for thermoregulation
Authors: Monson C. B. , Horowitz J. M. , Horwitz B. A.
Published: December 2017

To test the proposal that mammals have parallel neurocontrollers for temperature regulation, Long-Evans hooded male rats were exposed to cold while in a 3-G field. When exposed to cold, these rats consumed 35% less oxygen/min at 3 G than they did when exposed to cold at 1 G. However, rats acclimated for 6 wk to 5 degrees C consumed oxygen at the same rate during cold exposure at 3 G as at 1 G. Because cold-acclimated rats generate heat primarily by nonshivering thermogenesis while rats acclimated to room temperature rely to a greater extent on shivering, the 35% decrease in oxygen consumption of cold-exposed room-temperature rats in 3-G fields may reflect an inactivation of shivering. These oxygen consumption measurements, together with measurements of core and tail temperatures of rats in 3-G fields, are consistent with the proposal that neurocontrollers for thermoregulation are arranged in parallel and can be uncoupled by hypergravic fields.
Lung mechanics following aspiration of 0.1 N hydrochloric acid
Authors: Winn R. , Stothert J. , Nadir B. , Hildebrandt J.
Published: December 2017

Pressure-volume curves were obtained from excised left lungs of goats at 4, 24, and 48 h after tracheal instillation of 2.5 ml/kg of 0.1 N HCl. Air total lung capacity (TLC) at transpulmonary pressure (PL) = 35 cmH2O was 38.8 ml/kg body weight before acid, and was reduced sharply to 21.1 at 4 h, then increased to 25.6 at 24 h and 32.1 at 48 h. Excess extravascular lung water (EVLW) could account for only part of the volume reductions. Specific compliance ratio of transpulmonary pressure to total lung capacity (CL/TLC) between PL of 5 and 0 cmH2O was reduced from 0.074/cmH2O to 0.050, 0.048, and 0.053/cmH2O, respectively. Saline TLC (PL = 10 cmH2O) changed from 44.8 to 32.4, 34.3, and 45.4 ml/kg, respectively, but CL/TLC did not, suggesting airway obstruction. After injury, trapped volume at PL = 0 increased from 24.9 to 29.2, 43.3, and 37.3% TLC with air, and from 20.3 to 38.5, 33.1, and 28.5%, respectively, with saline. Air volume at a PL = 10 cmH2O on deflation fell from 82.0 to 72.1% TLC at 4 h, but was near control at 24 and 48 h. The reduction in ventilated volume was not reflected in proportionately increased shunt; therefore, some compensatory vasoconstriction must have occurred. We suggest that in affected regions increased surface forces, increased EVLW, and airway obstruction caused reductions of lung volume.
Arousal and breathing responses to airway occlusion in healthy sleeping adults
Authors: Issa F. G. , Sullivan C. E.
Published: December 2017

The arousal and breathing responses to total airway occlusion during sleep were measured in 12 normal subjects (7 males and 5 females) aged 25-36 yr. Subjects slept while breathing through a specially designed nosemask, which was glued to the nose with medical-grade silicon rubber. The lips were sealed together with a thin layer of Silastic. The nosemask was attached to a wide-bore (20 mm ID) rigid tube to allow a constant-bias flow of room air from a blower. Total airway occlusion was achieved by simultaneously inflating two rubber balloons fixed in the inspiratory and expiratory pipes. A total of 39 tests were done in stage III/IV nonrapid-eye movement (NREM) sleep in 11 subjects and 10 tests in rapid-eye-movement (REM) sleep in 5 subjects. The duration of total occlusion tolerated before arousal from NREM sleep varied widely (range 0.9-67.0 s) with a mean duration of 20.4 +/- 2.3 (SE) s. The breathing response to occlusion in NREM sleep was characterised by a breath-by-breath progressive increase in suction pressure achieved by an increase in the rate of inspiratory pressure generation during inspiration. In contrast, during REM sleep, arousal invariably occurred after a short duration of airway occlusion (mean duration 6.2 +/- 1.2 s, maximum duration 11.8 s), and the occlusion induced a rapid shallow breathing pattern. Our results indicate that total nasal occlusion during sleep causes arousal with the response during REM sleep being more predictable and with a generally shorter latency than that in NREM sleep.