bluuebunny/crossref_metadata_2025 huggingface dataset:
Diaphragm electrical activity during negative lower torso pressure in quadriplegic men
Authors: Banzett R. B. , Inbar G. F. , Brown R. , Goldman M. , Rossier A. , Mead J.
Published: December 2017

We recorded the diaphragm electromyogram (EMG) of quadriplegic men before and during exposure of the lower torso to continuous negative pressure, which caused shortening of the inspiratory muscles by expanding the respiratory system by one tidal volume. The moving-time-averaged diaphragm EMG was larger during expansion of the respiratory system. When we repeated the experiment with subjects who breathed through a mouthpiece, we found qualitatively similar EMG changes and little or no change in tidal volume or end-tidal CO2 partial pressure. When the pressure was applied or removed rapidly, changes in EMG occurred within one or two breaths. Because end-tidal CO2 partial pressure did not increase, and because the response was rapid, we suggest that the response results from proprioceptive, rather than chemoreceptive, reflexes. As most of these men had complete spinal lesions at C6 or C7 the afferent pathways are likely to be vagal or phrenic.
Responses of aortic chemoreceptors before and after pneumothorax in the cat
Authors: Pokorski M. , Mokashi A. , Mulligan E. , Nishino T. , Lahiri S.
Published: December 2017

That the response of aortic chemoreceptors to hypercapnia is considerably smaller than that of carotid chemoreceptors is well accepted, but the mechanism for the difference is not known. It has been suggested that surgical exposure of the carotid body may contribute to the difference. Accordingly, the response of aortic body chemoreceptors to CO2 would be expected to resemble quantitatively that of carotid chemoreceptors after exposure of the aortic bodies by pneumothorax. The effect of opening the chest on aortic and carotid chemoreceptor responses to several levels of arterial CO2 and O2 tension and arterial blood pressure were studied in anesthetized cats. The activity of aortic chemoreceptors increased in spite of a decreased stimulus level in the thoracic cavity after pneumothorax. The activity remained higher than the control at all levels of arterial CO2 and O2 tension and arterial blood pressure. However, the slopes of CO2 response curves, which were initially small, did not change after pneumothorax. Thus a change in the normal environment of the aortic bodies by experimental manipulation did not cause the aortic chemoreceptor responses to resemble those of carotid chemoreceptors.
Influence of alterations in Starling forces on visceral pleural fluid movement
Authors: Kinasewitz G. T. , Fishman A. P.
Published: December 2017

The influence of alterations in hydrostatic and oncotic pressure gradients on fluid movement across the visceral pleura was examined in 16 spontaneously breathing anesthetized dogs. The left lung was enclosed in a water-impermeable polyethylene membrane, creating a visceral pleural space; visceral fluid movement was determined as the formation or reabsorption of fluid in this space. Aortic, pulmonary arterial, right and left atrial, and pleural pressures were monitored; oncotic pressure was calculated from the protein concentration of plasma and pleural fluid. Left atrial pressure was varied from 0 to 30 mmHg and pulmonary arterial pressure from 15 to 36 mmHg by inflating atrial balloon catheters; the plasma-to-pleural fluid oncotic gradient was varied from 6.8 to 19.3 mmHg by infusing saline. The movement of fluid across the visceral pleura was significantly (P less than 0.001) related to the effective (transmural hydrostatic pressure minus oncotic gradient) pulmonary arterial (r = 0.87) and left atrial pressures (r = 0.92). The filtration coefficient of the visceral pleura estimated by our technique was 1.1 x 10(-6) ml.s-1.cmH2O-1.cm-2. These results not only confirm the concept that fluid flux across the visceral pleura is determined by the action of Starling forces across this membrane but also provide an estimate of the filtration coefficient for the visceral pleura.
Effects of 5-hydroxytryptamine on neuroeffector junction in human pulmonary artery
Authors: Freeman W. K. , Rorie D. K. , Tyce G. M.
Published: December 2017

The effects of 5-hydroxytryptamine on release of norepinephrine and on contraction of smooth muscle in human pulmonary artery were studied. Helical strips were prepared from intra-parenchymal arteries removed 3–18 h after death. The strips were labeled with L-[7–3H]norepinephrine and mounted for superfusion and isometric tension recording. Electrical stimulation (10 V, 2 ms, 2 Hz) of the strips increased the release of total radioactivity; this release was blocked by tetrodotoxin. 5-Hydroxytryptamine (10(-5) M) exerted a cocaine-sensitive, indirect sympathomimetic effect on the overflow of norepinephrine from resting strips. This action was not blocked by methysergide. No effect of 5-hydroxytryptamine on release of norepinephrine from electrically stimulated tissue could be demonstrated. 5-Hydroxytryptamine (10(-5) M) also caused contractions of pulmonary smooth muscle, not blocked by phentolamine (10(-5) M) but mediated in part through methysergide-sensitive 5-hydroxytryptamine receptors.
Regional differences in bioelectric properties and ion flow in excised canine airways
Authors: Boucher R. C. , Stutts M. J. , Gatzy J. T.
Published: December 2017

Absorption of airway liquid, as it moves from the large surface area of distal airways to more central airway surfaces, is considered to be essential for regulation of the depth of airway liquid. The short-circuited excised canine trachea, however, secretes Cl- and absorbs a lesser amount of Na+. We compared bioelectric properties and unidirectional ion flows across epithelia excised from trachea and mainstem and 4th- to 6th-generation bronchi. Compared with trachea, 4th- to 6th-generation bronchi exhibited a lower potential difference (8.9 compared with 35 mV) and higher direct-current conductance (6.9 compared with 2.1 mS . cm-2). Corresponding values for main-stem bronchus were intermediate. Under short-circuit conditions, the trachea secreted Cl- (1.75 mueq . cm-2 . h-1) and absorbed Na+ (1.15 mueq . cm-2 . h-1). K+ fluxes were symmetric. Main-stem bronchus exhibited a similar pattern of ion flow. Subsegmental bronchi absorbed 2.0 mueq Na+ . cm-2 . h-1 and secreted 0.04 mueq K+ . cm-2 . h-1, but net Cl- transport was absent. Under open circuit, Na+ absorption persisted in all regions, but net Cl- secretion disappeared in the trachea and main-stem bronchi. Na+ absorption was uniformly abolished by addition of ouabain (3 x 10(-5) M) to the submucosal bath. We conclude that NaCl absorption dominates resting ion translocation in canine bronchi and that liquid absorption probably occurs at these sites in vivo.
Measurement of metabolic rate in hyperoxia
Authors: Welch H. G. , Pedersen P. K.
Published: December 2017

The conventional Douglas bag calculation for estimating O2 uptake (VO2) during exercise in normoxia and hyperoxia, VO2 = VE . (FIO2 . FEN2/FIN2 - FEO2), was tested against two other valid calculations: the Fick equation, VO2 = VI . FIO2 - VE . FEO2, and the equation VO2 = VI - VE - VCO2 (VE and VI are expired and inspired ventilation, respectively; FEO2 and FIO2 are expired and inspired O2 contents, respectively; FEN2 and FIN2 are expired and inspired N2 contents, respectively; and VCO2 is CO2 production.). These calculations are based on different assumptions, in part, and are affected to a varying degree of errors in volume or gas fraction measurements. With the conventional Douglas bag technique, we found evidence of an overestimate of VO2 during hyperoxia. After the introduction of a mixing chamber for sampling expired air, the means of the three methods were not significantly different. The variability among the methods was least with the conventional calculation but increased with higher O2 fractions. The average VO2 for submaximal exercise in hyperoxia was not significantly different from that of normoxia. VO2 max was significantly higher in hyperoxia. The increased variability of the Douglas bag method in hyperoxia may lead to overestimates of VO2 max unless special precautions are taken.
Pulmonary vasoconstrictor responses to graded decreases in precapillary blood PO2 in intact-chest cat
Authors: Hyman A. L. , Higashida R. T. , Spannhake E. W. , Kadowitz P. J.
Published: December 2017

The effects of graded changes in pulmonary lobar arterial blood PO2 and ventilatory hypoxia were investigated in the intact-chest cat under conditions of controlled lobar blood flow. A reduction in precapillary PO2 from systemic arterial levels to below 60 Torr increased lobar arterial pressure. Ventilation with 10% O2 increased lobar arterial pressure, and responses to ventilatory hypoxia and precapillary hypoxemia were independent but additive. The magnitude of the pressor response to precapillary hypoxemia was similar in experiments in which the lung was autoperfused with right atrial blood or cross-perfused with aortic blood from a donor cat breathing 10% O2. During retrograde perfusion of the ventilated lung, a reduction in pulmonary venous PO2 to 40 Torr did not affect inflow pressure. The present data suggest that sensor sites upstream to the alveolar-capillary region in segments of lobar artery unexposed to alveolar gas sense a reduction in precapillary blood PO2 and elicit a pulmonary vasoconstrictor response. The sensor site in the precapillary segment is independent of sensors in the alveolar-capillary-exposed segment region, and the effects of stimulation of both sensors on the pulmonary vascular bed are additive. In addition, the present data indicate that sensors in the pulmonary veins do not sense a reduction in PO2 in venous blood and elicit a vasoconstrictor response. These data suggest that the mixed venous blood PO2 may exert an important regulatory role in controlling pulmonary arterial pressure and pulmonary vascular resistance in the cat under normal and pathological conditions.
Pneumotachograph calibration for inspiratory and expiratory flows during HeO2 breathing
Authors: Muller N. L. , Zamel N.
Published: December 2017

Maximum expiratory flows during breathing of a 80% helium-20% oxygen mixture (HeO2) are commonly used to determine the site of airflow limitation. To do this test the flowmeter is usually calibrated with the inspired gases, and the airflows are measured during expiration. We tested the adequacy of such calibration maneuvers by using two identical flowmeters in series through a bag-in-box system. Different gases were flowed though the test pneumotachograph into a bag contained in a closed box connected to the second pneumotachograph. Distension of the bag caused air to flow from the box through this second pneumotachograph. Our results indicate that when breathing HeO2, the flowmeter correction for different gas viscosity, compared with air, should be 20% for inspired HeO2 and 12% for expired gases. Inspired gases therefore cannot be used to calibrate the flowmeters when assessing expiratory flows.
Carbohydrate ingestion before exercise: comparison of glucose, fructose, and sweet placebo
Authors: Koivisto V. A. , Karonen S. L. , Nikkila E. A.
Published: December 2017

To examine the effect of various carbohydrates on the metabolic and hormonal response to exercise, 75 g glucose, fructose, or placebo were given to nine well-trained males (VO2 max 60 +/- 1 ml . kg-1 . min-1) 45 min before cycle ergometer exercise performed at 75% VO2 max for 30 min. After glucose ingestion, the rise in plasma glucose was 3-fold (P less than 0.005) in plasma insulin 2.5-fold (P less than 0.01) greater than after fructose. During exercise, after glucose administration plasma glucose fell from 5.3 +/- 0.3 to 2.5 +/- 0.2 mmol/l (P less than 0.001) and after fructose from 4.5 +/- 0.1 to 3.9 +/- 0.3 mmol/l (P less than 0.05). The fall in plasma glucose was closely related to the preexercise levels of plasma insulin (r = 0.82, P less than 0.001) and glucose (r = 0.81, P less than 0.001). Both glucose and fructose ingestion decreased the FFA levels by 40–50% (P less than 0.005) and during exercise they remained 30–40% lower after carbohydrate than placebo administration (P less than 0.02). This study suggests that glucose ingestion prior to exercise results in hypoglycemia during vigorous exercise, this rapid fall in plasma glucose is mediated, at least in part, by hyperinsulinemia, and fructose ingestion is associated with a modest rise in plasma insulin and does not result in hypoglycemia during exercise.
Respiratory and stepping frequencies in conscious exercising cats
Authors: Iscoe S.
Published: December 2017

The incidence of entrainment between respiratory and stepping frequencies has been investigated in exercising cats. Stainless steel wire electrodes were surgically implanted in the right hemidiaphragm, quadriceps, and hamstring muscles of six cats. Electromyograms were recorded while the cats were at rest or walking on a treadmill at speeds between 0.31 and 1.67 m/s (6 km/h). Autocorrelation of diaphragmatic activity showed cats to have two respiratory patterns: regular (maintained periodicity in the autocorrelogram) or irregular (flat autocorrelogram). Autocorrelation of quadriceps or hamstring activity revealed stepping frequency. Cross correlation of diaphragmatic vs. quadriceps or hamstring activities revealed the presence of entrainment between respiration and stepping. In four cats, entrainment was either very weak or absent, but the other two cats clearly showed entrainment of the two activities, even in the absence of a regular respiratory rhythm. In conclusion, at speeds up to 1.67 m/s, respiratory frequency is not tightly locked to stepping frequency in cats; however, the occurrence of entrainment in some instances clearly indicates the existence of neural circuitry linking these two pattern generators.
Exercise recovery above and below anaerobic threshold following maximal work
Authors: Stamford B. A. , Weltman A. , Moffatt R. , Sady S.
Published: December 2017

The purpose of this study was to determine the effects of resting and exercise recovery above [70% of maximum O2 uptake (VO2 max)] and below [40% of VO2 max] anaerobic threshold (AT) on blood lactate disappearance following maximal exercise. Blood lactate concentrations at rest (0.9 mM) and during exercise at 40% (1.3 mM) and 70% (3.5 mM) of VO2 max without preceding maximal exercise were determined on separate occasions and represented base lines for each condition. The rate of blood lactate disappearance from peak values was ascertained from single-component exponential curves fit for each individual subject for each condition using both the determined and resting base lines. When determined base lines were utilized, there were no significant differences in curve parameters between the 40 and 70% of VO2 max recoveries, and both were significantly different from the resting recovery. When a resting base line (0.9 mM) was utilized for all conditions, 40% of VO2 max demonstrated a significantly faster half time than either 70% of VO2 max or resting recovery. No differences were found between 70% of VO2 max and resting recovery. It was concluded that interpretation of the effectiveness of exercise recovery above and below AT with respect to blood lactate disappearance is influenced by the base-line blood lactate concentration utilized in the calculation of exponential half times.
Interaction of PVO2 with PAO2 on hypoxic pulmonary vasoconstriction
Authors: Benumof J. L. , Pirlo A. F. , Johanson I. , Trousdale F. R.
Published: December 2017

We tested the hypothesis that decreases in alveolar O2 pressure (PAO2) of a large lung compartment would, through decreases in arterial O2 pressure (PaO2) and mixed venous O2 pressure (PVO2), result in decreases in PAO2 of the remaining small lung compartment; thus large-compartment hypoxic pulmonary vasoconstriction (HPV) would be accompanied by concomitant small-compartment HPV. In eight pentobarbital-anesthetized dogs, whose left lower lobe (LLL) inspired oxygen concentration (FIO2) was constantly 0.21, selective stepwise reductions in the rest of the lung (RL) FIO2 from 1.0 to 0.15 caused the electromagnetically measured LLL blood flow (QLLL/Qt), pulmonary vascular resistance of RL (PVRRL), and PVRLLL to increase while RL PAO2, PaO2, PVO2, and LLL PAO2 progressively decreased. Stepwise reductions in RL FIO2 from 0.15 to 0.06 caused QLLL/Qt and PVRRL to decrease, PVRLLL To further increase, while RL PAO2, PaO2, PVO2, and LLL PAO2 progressively decreased further. Based on previously established PAO2 levels of maximum HPV gain and LLL dose-response curves, the RL FIO2-induced changes in QLLL/QT can be explained by different rates of change in RL and LLL PAO2 and PVR. Thus, our findings indicate that if decreases in RL FIO2 cause, in turn, large decreases in PaO2, PVO2 and "normoxic" lung PAO2, then PVO2 is an important determinant of the magnitude of the HPV response.
Edema affects intra-alveolar fluid pressures and interdependence in dog lungs
Authors: Parker J. C. , Allison R. C. , Taylor A. E.
Published: December 2017

The pressures in occluded, fluid-filled segments of lung were measured in closed-chest supine dogs ventilated with positive pressure at a constant tidal volume. Segment fluid pressures decreased in response to lung inflation and were used with esophageal and airway pressures to calculate an index of bronchiolar-parenchymal interdependence. Animals were subjected to three sequential 5% body wt infusions of Tyrode's solution followed by a 20- to 30 min-recovery period after each infusion. The interdependence index decreased significantly following each infusion, with infusions as small as 1% body wt producing a detectable decrease. The mean pressures in the Tyrode's solution-filled segments generally increased in response to the infusions, but the time course of the response was variable. The base-line pressure in Tyrode's solution-filled segments was -4.8 +/- 2.4 cmH2O. This increased to -1.1 +/- 2.7 cmH2O after a total of 15% body wt had been infused. At the same time, extravascular lung water increased by approximately 17%. Thus negative collapse pressures in the occluded segments were opposed by mechanical stresses transmitted through alveolar wall attachments. This counterbalancing stress was consistently reduced by both increased tissue hydration and increased pulmonary vascular pressure.
Postinspiratory mixing in the lung and cardiogenic oscillations
Authors: Arieli R. , Olszowka A. J. , Van Liew H. D.
Published: December 2017

Subjects inspired a 300-ml bolus of indicator gas cocktail (5% each of SF6, Ar, Ne, and He) form residual volume (RV), then inspired air to functional residual capacity (FRC). There was no evidence that a 10-s breath hold changed the relative concentrations or amounts of indicator gases in phases III and IV of expiration or allowed additional gas to mix into the RV, but the breath hold caused cardiogenic oscillations (CO) in expired gas to decrease in height. The units responsible for cardiogenic troughs and peaks are different from the units responsible for phases III and IV, respectively, in that the oscillation troughs had a lower He/SF6 ratio than the peaks whereas phase III had a higher He/SF6 than phase IV. We explain the CO as due to variation in mechanical properties, leading to variation in response to the pressure wave caused by the heart, in units that are relatively near to each other. We conclude that there is little or no postinspiratory mixing between distant lung units, but the dampening of CO suggests that units that are close to each other can mix if time is allowed.
Metabolism and thermoregulation during stages of sleep in humans exposed to heat and cold
Authors: Haskell E. H. , Palca J. W. , Walker J. M. , Berger R. J. , Heller H. C.
Published: December 2017

Electrophysiological stages of sleep, oxygen consumption (VO2), and skin (Tsk) and rectal (Tre) temperatures were recorded from six virtually naked male subjects exposed to ambient temperatures (Ta) of 21, 24, 29, 34, and 37 degrees C. VO2 increased during sleep as a whole as Ta departed from thermoneutrality (29 degrees C) and was significantly greater during rapid-eye-movement (REM) sleep than during adjacent nonrapid-eye-movement (NREM) periods at low and high Ta but not at 29 degrees C. Tsk showed small but significant increases during REM sleep at 29, 34, and 37 degrees C, but Tre did not change during REM sleep at any Ta. Shivering was present during wakefulness at 21 and 24 degrees C but occurred only occasionally during stages 1 and 2 sleep at 21 degrees C. The increases in VO2 and the absence of marked changes in vasomotor tone during REM sleep in the cold were unexpected and possibly indicate that REM sleep is not as thermally disruptive in humans as in other mammals.
Temperature dependence of dipalmitoyl phosphatidylcholine monolayer stability
Authors: Goerke J. , Gonzales J.
Published: December 2017

Dipalmitoyl phosphatidylcholine is the principal component of lung surfactant, and knowledge of its behavior as a film spread at the air-water interface is essential for understanding how lung surfactant itself works. We therefore studied the collapse rates of very low surface tension air-water monolayers of dipalmitoyl, dimyristoyl, and palmitoyl-myristoyl phosphatidylcholines at different temperatures. In each case we found that the monolayers abruptly became unstable at temperature 3–4 degree C above their bulk lipid-water phase transition temperatures (Tc). This accords with a comparable increase in Tc occurring in bulk systems subjected to high pressure. These findings are also consistent with the behavior of isolated rat lungs, which have been found to require higher transmural pressures to maintain a given volume on deflation when kept at temperature above the Tc of dipalmitoyl phosphatidylcholine.
Impaired surfactant phospholipid metabolism in hyperoxic mouse lungs
Authors: Gross N. J. , Smith D. M.
Published: December 2017

We studied the effect of 98% O2 on the amounts of and in vivo and in vitro synthesis rates of lung phospholipids in the mouse. The alveolar fluid obtained by multiple endobronchial lavages showed a decline in the amounts of all phospholipids between 48 and 72 h. The proportion of phosphatidylcholine that was disaturated did not change up to 96 h. Smaller decreases in phosphatidylcholine of the lung tissue were found at the same times. Between 48 and 72 h the turnover of total and disaturated phosphatidylcholine was greatly decreased, and transit time for both from lung to alveolar fluid was prolonged. At 60 h in vitro incorporation by lung slices of both glycerol and palmitate into disaturated phospholipids was reduced by approximately half, the distribution of label into various phospholipid classes being unchanged. We interpret these data as supporting the hypothesis that hyperoxia impairs the synthesis of surfactant phospholipids in the lung and their transport to the alveolar surface, and that this results in a decrease in the phospholipid content of the alveolar lining layer. These effects could account for altered pulmonary mechanical properties and contribute to the morbidity and mortality of O2 toxicity.
Central venous bubbles and mixed venous nitrogen in goats following decompression
Authors: D'Aoust B. G. , Swanson H. T. , White R. , Dunford R. , Mahoney J.
Published: December 2017

Decompression of awake goats from saturation at 1, 2, and 3 ATA of air has been carried out using ultrasonic Doppler bubble detection, central venous blood inert gas measurement, and cardiac output measurement. The results of these experiments indicate that the decrease in nitrogen elimination rate as an apparent result of decompression cannot be due to excessive cardiac output or mass transport of a large amount of inert gas to the lungs as bubbles. Rather, the rapid drop in mixed venous nitrogen content is consistent with a generalized decrease in tissue-to-blood nitrogen elimination. This in turn appears to be due to a cardiovascular response to the decompression insult as was previously reported for dogs (D'Aoust et al., J. Appl. Physiol. 41: 348--355, 1976) at 1, 2, and 3 ATA; addition of ultrasonic Doppler monitoring and cardiac output in the present studies allowed measurement of the degree of latency in the appearance of bubbles at a central venous location. This time period includes that required for bubble formation, growth, and vascular transport of the bubbles to the Doppler detector. All results of these studies are consistent with the interpretation that due to a decompression insult, which probably includes bubble formation, some degree of hemostasis, and other hematologic sequelae, the transport of tissue inert gas to the capillary venous blood is retarded, thus providing the rapid apparent decrease in mixed venous blood inert gas content. These results demonstrate what is most likely a general response to a severe but not crucial decompression by the cardiovascular system.
Total lung lymph flow and fluid compartmentation in edematous dog lungs
Authors: Parker J. C. , Crain M. , Grimbert F. , Rutili G. , Taylor A. E.
Published: December 2017

The effect of fluid volume loading on lung tissue fluid compartments and pulmonary lymph flow was studied in 7 dogs. A bolus of 125I-labeled albumin was administered 1 h after a 10--15% body weight Tyrode infusion. Then concentrations of labeled and endogenous albumin in pulmonary lymph and plasma were monitored for 4--6 h. The time course of plasma and lymph [125I]albumin specific activities was analyzed using kinetic and both the linear and nonlinear solute flux equations. Plasma specific activity exhibited a two-component decay with mean rate constants of 2.65 and 0.071 h-1. Albumin equilibrated between plasma and lymph at a rate of 0.327 h-1, or with a half time of 2.12 h. For albumin, the mean permeability-surface area product was 0.043 ml/min, and total distribution volume was 22.6 ml. This indicated that the cannulated lymphatics drained 25% of total lung weight, and that lung lymph flow was 0.063 ml . min-1 . 100 g-1 in normally hydrated lungs, and 0.225 ml . min-1 . 100 g-1 in edematous lungs. During edema the extravascular 99mTc-DTPA (diethylenetriamine pentaacetic acid) space increased by 79% and the total extravascular lung water by 40%. The extravascular albumin space was only one-third that predicted for the extent of edema. This indicates a significant volume of edema fluid sequestered in tissue compartments, such as perivascular cuffs and alveolar spaces, which did not equilibrate rapidly with capillary filtrate draining into the pulmonary lymphatics.
Corrections for the response time and delay of mass spectrometers
Authors: Arieli R. , Van Liew H. D.
Published: December 2017

Computations based on mass spectrometer (MS) outputs will be incorrect unless the delay for drawing the sample into the instrument and response time of the instrument are accounted for. When we changed concentration abruptly in two different mass spectrometers, the responses were sigmoid shaped not exponential, and time constants derived from the main part of the response curves were 43–60 ms; single-exponent corrections using these values caused the corrected waveform to overshoot. For a better correction, we used a two-exponent correction, C2 = Co + (Y1 + Y2) (d2C0/dt) + Y1Y2 (d2C0/dt2), where C0 is MS output as a function of time t, C2 is corrected concentration, and Y1 and Y2 are time constants. Assumption of a third exponent was of little value. For a successful correction Y1 must be smaller than a measured one-exponent time constant. We used two-thirds of the measured value for Y1 and then calculated Y2 from the once-corrected response. The second-order correction approximates a square output in response to a square input. To deal with delay time in a way that would give good resolution of dynamic changes and also be compatible with our response-time correction, we corrected for the difference between time of the input event and time that the output reaches 20% of full response. We validated our methods by integrations of amounts of gases drawn into and out of a syringe and in human breaths.
Glycogen and nonspecific adaptation to cold
Authors: LeBlanc J. , Labrie A.
Published: December 2017

Exposure to moderate cold for a few weeks causes adaptation through the development of nonshivering thermogenesis primarily in the brown adipose tissue. Exposure to severe cold by repeated short exposures also causes adaptation but by mechanisms that seem to be different. These latter results were confirmed in mice. It was also found that this type of adaptation is nonspecific because it can be produced by other stresses such as swimming or fasting. Simultaneous determinations of glycogen in the liver and soleus and tibialis muscles indicated a possible role for this substrate in cold resistance. Repeated cold exposure (8 times at -15 degrees C for 10 min), swimming for 3 h, or fasting for 48 h--all reduced the glycogen stores when measured immediately after the stress. However, the levels of glycogen were significantly increased above the initial values (P less than 0.01) when the determinations were made 24 h later. Cold tolerance measured by resistance to hypothermia at -5 degrees C was improved only when the test was done 24 h after the stress had taken place. Thus, cold resistance, as described in this study, is nonspecific and our results suggest that glycogen stores could serve as a rate-limiting substrate.
Ascorbate uptake by isolated rat lung cells
Authors: Wright J. R. , Castranova V. , Colby H. D. , Miles P. R.
Published: December 2017

Experiments were done to determine the intracellular concentration of ascorbate in isolated rat lung cells and the concentration in plasma and to study ascorbate influx in these cells. The intracellular ascorbate concentration was 2.25 mM and the plasma level was about 0.14 mM; i.e., the lung cell ascorbate concentration was about 16 times greater than the plasma level. When the cells were incubated in medium containing physiological levels of ascorbate (0.1 mM), influx increased linearly up to 60 min of incubation and was 0.54 +/- 0.04 nmol.10(7) cells-1.h-1. Influx was dependent on the extracellular ascorbate concentration. At concentrations ranging from 0.025 to 1 mM, uptake appeared to exhibit saturation kinetics with an apparent Km of 0.16 mM. At physiological levels of extracellular ascorbate (0.1 mM) at least 90% of the uptake appeared to be carrier mediated, and this influx was inhibited by various metabolic inhibitors. In addition, ascorbate influx was inhibited by ouabain and removal of extracellular sodium. These results suggest that lung cells contain a transport mechanism for ascorbate that is energy-dependent and that may be coupled to Na+ influx.
Pattern of diaphragmatic activity during forced expiratory vital capacity
Authors: Melissinos C. G. , Bruce E. N. , Goldman M. D. , Elliott E. , Mead J.
Published: December 2017

We measured transdiaphragmatic pressure (Pdi) during forced expiratory vital capacity (FVC) maneuvers in 13 normal subjects and electromyographic activity of the diaphragm (edi) in 8 of these subjects. In all subjects, Pdi increased at the initiation of the FVC. In most, this increase lasted 30--50 ms and reached levels well above the Pdi observed at total lung capacity (TLC). After the initial transient increase, approximately half of the subjects demonstrated a substantial fall in Pdi to values near the relaxation level in the mid-vital capacity (VC) volume range, while half showed a second large increase in Pdi in this volume range. Seven of eight subjects tested showed a rapid decrease in Edi at the onset of the FVC, reaching a minimum in 30--50 ms. After this initial transient decrease, Edi increased in six subjects in the mid-VC volume range, in association with secondary rises in Pdi. In two subjects, Edi remained low throughout the remainder of the FVC, and Pdi in the mid VC range was generally lower. These results are consistent with the conclusion that the diaphragm is neither electromyographically silent nor mechanically unimportant during the FVC. Changes in abdominothoracic configuration, superimposed upon “antagonistic” activity of the diaphragm, result in substantial reductions in pleural (esophageal) pressure that may influence regional lung emptying during the FVC.
Effects of naloxone on carotid body chemoreception and ventilation in the cat
Authors: Pokorski M. , Lahiri S.
Published: December 2017

The effects of intravenous injection of naloxone (0.4 mg.kg-1), an opiate antagonist, on the responses of carotid body chemoreceptor discharge and ventilation to steady-state levels of hypoxia and hypercapnia were investigated in 12 anesthesized cats. After naloxone, carotid chemoreceptor response to hypoxia (PaO2 60--30 Torr) was enhanced, a finding that suggested that the endogenous enkephalin-like peptide present in the carotid body inhibits carotid chemoreceptors. This reasoning is supported by the observation that close intra-arterial injection of met-enkephalin inhibits carotid chemoreceptors and that the effect is blocked by naloxone. After naloxone, ventilation was stimulated even in the absence of a significant stimulation of carotid chemoreceptors during hyperoxia, indicating that ventilation is normally suppressed by endogenous opiates in the central nervous system, an effect disinhibited by naloxone. Also, the ventilatory effect of the peripheral chemoreceptor input was augmented after naloxone.
Effect of blood volume on sweating rate and body fluids in exercising humans
Authors: Fortney S. M. , Nadel E. R. , Wenger C. B. , Bove J. R.
Published: December 2017

Five relatively fit men performed cycle ergometer exercise (65–70% VO2max) for up to 30 min at 30 degrees C, 40% rh. The data from control (normo-volemic), hypovolemic [8.7% reduction in blood volume (BV) induced by diuretics], and hypervolemic [7.9% expansion of BV induced by infusion if isotonic serum albumin] tests revealed significant effects of BV on body fluid and sweating responses. During control exercise, BV decreased an average (+/- SE) 370 +/- 64 ml at 20 min. A significantly smaller loss occurred after 20 min of hypovolemic exercise (270 +/- 29 ml). The decrease in BV during 30 min of hypervolemic exercise (541 +/- 43 ml) was significantly greater than during control (421 +/- 50 ml). Blood volume reduction also significantly altered the control of sweating rate independent of changes in plasma osmolality. The slope of the sweating rate-to-esophageal temperature relationship (SR/Tes) was significantly reduced from the mean value of 1.07 +/- 0.16 and 1.09 +/- 0.18 mg X min-1 X cm-2 X degrees C-1 during control tests, measured from the chest and arm, respectively, to 0.64 +/- 0.11 and 0.63 +/- 0.11 mg X min-1 X cm-2 X degrees C-1 during hypovolemia. The SR/Tes slope was unchanged in hypovolemia over active tissues (calf). Hypervolemia had no effect on the control of sweating at any site. Both the body fluid and sweating responses during hypovolemia act to conserve circulating blood volume during exercise.
Alterations in responses to drugs of atria from white rats acclimated to hypobaric hypoxia
Authors: Hughes M. J. , Kopetzky M. T. , Messiha F. , Light K. , Barnes C. D.
Published: December 2017

To test the hypothesis that acclimation to simulated high altitude (SHA) may occur in the tissues as well as in the systemic regulatory apparatus of an organism, atria isolated from young rats acclimated to SHA of 6,000 m and from control rats were observed under normoxic conditions. SHA atria have slower spontaneous heart rates than atria isolated from controls (209 +/- 4 vs. 228 +/- 3, P less than 0.001). SHA atria are more sensitive to pentobarbital sodium (P less than 0.001) and ethanol (P less than 0.06): spontaneous mechanical activity stops at a lower drug concentration in SHA than in control atria. SHA atria are less sensitive to norepinephrine in the concentration range of 7.9 X 10(-9) to 3.1 X 10(-6) M and respond to increased bath concentrations (3.8, 5.8 and 7.8 mM) of calcium with a significantly (P less than 0.04) smaller chronotropic response and a greater inotropic response than atria from control animals. These data support the above-mentioned hypothesis.
Differences in airway reactivity in normal and allergic sheep after exposure to sulfur dioxide
Authors: Abraham W. M. , Oliver W. , Welker M. J. , King M. M. , Wanner A. , Sackner M. A.
Published: December 2017

The effect of breathing 5 ppm sulfur dioxide (SO2) on airway reactivity was studied in both normal and allergic conscious sheep. Allergic sheep were defined as animals in which inhalation of Ascaris suum extract resulted in bronchospasm as evidenced by an increase in mean pulmonary flow resistance (RL), hyperinflation, and a fall in dynamic compliance. Airway reactivity was assessed by measuring the increase of RL after 18 breaths of 0.25% carbachol (c), from an initial RL value obtained after 18 breaths of buffered saline (s) [RL(c-s)]. RL and RL(c-s) were determined prior to, immediately after, and 24 h after exposure to 5 ppm SO4 for 4 h. In both groups RL remained unchanged after SO2 exposure. Prior to exposure, RL(c-s) was not significantly different in seven normal (0.3 +/- 0.1) and seven allergic sheep [0.4 +/- 0.2 (SD) cmH2O X l–1 X s], and there was no significant change in RL (c-s) immediately after SO2 exposure in either group. Twenty-four h later, RL(c-s) RL(c-s) increased to 0.7 +/- 0.8 (P less than 0.2) in normal and to 1.8 +/- 0.9 cmH2O X l-1 X s (P less than 0.01) in allergic sheep. Because the increase in RL(c-s) after 24 h was greater (P less than 0.01) in allergic than in normal sheep, we conclude that SO2 exposure increased airway reactivity more in the former than in the latter.
Breath-by-breath measurement of true alveolar gas exchange
Authors: Beaver W. L. , Lamarra N. , Wasserman K.
Published: December 2017

A method has been developed for on-line breath-by-breath calculation of alveolar gas exchange by correcting the gas exchange measured at the mouth for changes in lung gas stores. The corrections are applied to the total lung gas exchange, which is found by directly subtracting expired from inspired volume of each gas. Corrections are made for both breath-to-breath changes in lung volumes and changes in alveolar gas concentrations. The lung volume correction term has the effect of reducing the large error sensitivity of O2 exchange that has, in the past, resulted from direct determination by total lung gas exchange. Error each gas. Corrections are made for both breath-to-breath changes in lung volumes and changes in alveolar gas concentrations. The lung volume correction term has the effect of reducing the large error sensitivity of O2 exchange that has, in the past, resulted from direct determination by total lung gas exchange. Error each gas. Corrections are made for both breath-to-breath changes in lung volumes and changes in alveolar gas concentrations. The lung volume correction term has the effect of reducing the large error sensitivity of O2 exchange that has, in the past, resulted from direct determination by total lung gas exchange. Error sensitivity analysis shows that the effect of inaccuracies due to errors in measuring gas flow or gas concentrations are similar in magnitude to those in the open-circuit method that has traditionally been used. The algorithm for alveolar gas exchange has been implemented in a computer program for on-line respiratory analysis alongside the open-circuit calculation of gas exchange at the mouth that has been used in out laboratory. By use of several experimental studies, it is shown that there are very apparent breath-to-breath differences between the gas exchange measured by the two methods. During metabolic and respiratory transients, these differences often have significant influence on interpretation of the underlying physiology.
Effect of calcium on sulfated mucous glycoprotein secretion in dog trachea
Authors: Marin M. G. , Estep J. A. , Zorn J. P.
Published: December 2017

In this experiment utilizing dog trachea we determined the effect of calcium concentration in the bathing media on the kinetics of secretion of sulfate incorporated into mucous glycoprotein. The results showed that in eight tracheas the secretion rate of 269 +/- 65 pmol SO4 . cm-2 . hr-1 (mean +/- SE) of tissues bathed in solution lacking calcium throughout the experiment was significantly less than the rate of 526 +/- 87 pmol SO4 . cm-2 . hr-1 of tissues bathed in solution containing 1.9 mM Ca2+. When tissues bathed in 1.9 mM CA2+ were incubated with 35SO4 to a constant secretion rate and then placed in 0 mM Ca2+ solution, the secretion of incorporated sulfate was unchanged relative to tissues bathed 1.9 mM Ca2+ throughout the experiment. Pool size of 727 +/- 150 pmol SO4/cm2 in tissues incubated in 0 mM Ca2+ throughout the experiment was significantly less than the pool size of 1,069 +/- 190 pmol SO4/cm2 in 1.9 mM Ca2+ solutions. This study showed that either the uptake of sulfate and/or biosynthetic pool size of sulfate incorporated into mucous glycoproteins was decreased in solution lacking calcium. However, release of sulfate incorporated into mucous glycoprotein in the lumen was independent of calcium in the external bathing media.
Effects of temperature on the duration of arousal episodes during hibernation
Authors: French A. R.
Published: December 2017

The length of time that the ground squirrels Spermophilus beldingi and S. lateralis remained at high body temperatures following periodic arousals from hibernation increased as environmental temperature increased over the range of 5–20 degree C. This trend was evident in comparisons among different animals that hibernated at different temperatures and in individuals that hibernated at different temperatures in successive years. At any one temperature, the duration of these euthermic intervals in S. beldingi was correlated with body size. Large adult males remained at high body temperatures longer than adult females, which in turn remained euthermic longer than small juveniles. In addition, these squirrels spent less time at high body temperatures following bouts of torpor that were interrupted prematurely by environmental disturbances. These results are consistent with an amplify the theory that arousals are initiated by, and necessary for the elimination of, some chemical imbalance, which develops while hibernators metabolize at low body temperatures.
Influence of the right ventricle on canine left ventricular function with PEEP
Authors: Scharf S. M. , Brown R.
Published: December 2017

In anesthetized dogs we evaluated the influence of increased right ventricular (RV) pressures on left ventricular (LV) function by comparing the hemodynamic effects of increases in RV afterload (pulmonary arterial pressure) produced by positive end-expiratory pressure (PEEP) with those due to pulmonary arterial occlusion (PAO). Left atrial (Pla) and right atrial (Pra) pressures increased with PEEP and PAO [for Pla: 3.1 +/- 0.7 Torr (PEEP), 2.4 +/- 0.9 Torr (PAO); for Pra: 2.9 +/- 0.4 Torr (PEEP), 3.1 +/- 1.2 Torr (PAO)]. RV septal-free wall dimension (RVD) increased, and LV septal-posterolateral dimension (L2) decreased with both conditions [increases in RVD: 1.9 +/- 0.3 mm (PEEP), 2.2 +/- 0.5 mm (PAO); decrease in L2: 1.1 +/- 0.4 mm (PEEP), 0.9 +/- 0.3 mm (PAO)]. Extracorporeal bypass of the great veins did not alter these findings. LV function curves showed less stroke work at any Pla during PEEP, this being unaffected by vagotomy. When the RV was bypassed, there were no PEEP or PAO related changes in Pla or LV function. Thus diminished LV function with PEEP is probably due to the influence on the LV of a stressed RV in this situation.
Increased excretion of urea and N tau -methylhistidine by rats and humans after a bout of exercise
Authors: Dohm G. L. , Williams R. T. , Kasperek G. J. , van Rij A. M.
Published: December 2017

This study was undertaken to investigate whether an exercise bout increases muscle protein degradation and amino acid catabolism. The excretion of urea and N tau -methylhistidine before and after an exercise bout was determined for both rats and human subjects. The rats ran on a treadmill until they could no longer run. Two groups of human subjects completed strenuous exercise bouts: one group (runners) ran 10–12 miles while the other group (weight lifters) performed a standard power lift routine that lasted approximately 1 h. In rats, urea excretion was elevated for the first 12 h after the exercise bout whereas N tau -methylhistidine excretion was elevated for 48 h following exercise. The increased N tau -methylhistidine excretion after exercise supports previous reports of increased protein degradation in the perfused hindquarter and increased levels of essential amino acids in muscle, liver, and plasma of exercised rats. In human subjects, both running and weight lifting resulted in increased excretion of urea and N tau -methylhistidine. The results of the present study support the hypothesis that muscle protein breakdown and amino acid catabolism are increased by exercise.
Uneven driving pressures and redistribution of intrapulmonary blood flow
Authors: Murray J. F. , Hoeffel J. M. , Jibelian G.
Published: December 2017

Pulmonary arterial pressure (Ppa) and airway pressure (Paw) change equally when Paw varies widely in normal lungs under zone 2 conditions. To evaluate the mechanism underlying the decrease in Ppa at a given Paw in edematous lungs, we measured the quantity of right-to-left shunting of blood (Qs/QT) with sulfur hexafluoride (SF6) using in situ perfused dog lungs from five control animals, five animals with bronchial occlusion, and eight animals with oleic acid-induced pulmonary edema. Under base-line conditions when positive end-expiratory pressure (PEEP) was increased from 5 to 15 cmH2O, Ppa increased because Paw was fully transmitted to Ppa. After bronchial occlusion at 5 cmH2O PEEP, observed QS/QT was less than predicted (P less than 0.01) on the basis of regional conductances, but at 15 cmH2O observed and predicted QS/QT did not differ (P greater than 0.5). In five of eight dogs with oleic acid-induced pulmonary edema. QS/QT increased when PEEP was increased. We conclude that pressure barriers that create nonuniform driving pressures cause a decrease in Ppa and a redistribution of blood flow.
Glucose, glucagon, and insulin during adrenergic blockade in exercising sheep
Authors: Brockman R. P. , Halvorson R.
Published: December 2017

The interrelationships of glucagon and insulin with the sympathetic system on glucose turnover during exercise were examined in sheep. Six sheep were run for 45 min on a treadmill with and without alpha- and/or beta-adrenergic blockade. The exercise-induced increase in glucose appearance, as assessed by infusion of [2–3H]glucose, was reduced during the first 25 min of exercise by phentolamine administration. The metabolic clearance rate of glucose also was greater during exercise with phentolamine treatment than without. Phentolamine was associated with a rise in insulin concentrations and appeared to delay the exercise-induced rise in glucagon. Propranolol administration had no effect on glucose turnover and plasma glucagon and insulin. Nor did it have any effect on the changes in glucose, insulin, or glucagon induced by phentolamine administration. These observations are consistent with the alpha-adrenergic mediation of the sympathetic influences on insulin and glucagon secretion, which may account in part for the glucose adaptations to exercise in sheep. However, direct affects of circulating catecholamines on and increased stimulation of sympathetic innervation to the liver cannot be ruled out.