bluuebunny/crossref_metadata_2025 huggingface dataset:
Fibrinogenolysis and fibrinolysis with strenuous exercise
Authors: Ferguson E. W. , Barr C. F. , Bernier L. L.
Published: December 2017

Twenty healthy young men were exercised on a treadmill according to the protocol of Balke and Ware. Mean duration of exercise was 24.9 +/- 5.7 min and mean maximum heart rate was 195 +/- 9. Fibrinolytic activity was markedly accelerated with euglobulin lysis times decreasing to 36% of control values and fibrinogen-fibrin degradation products increasing 109% after exercise. Assays for fibrin monomer were negative in all samples. In vivo fibrinogen A alpha-chin degradation was assessed by sodium dodecyl sulfate polyacrylamide gel electrophoresis of reduced samples of fibrin monomer isolated by clotting plasma samples in the presence of 0.1 M epsilon-aminocaproic acid and 1% disodium ethylenediaminetetraacetate. The A alpha-chain, the fibrinogen chain most susceptible to plasmin degeneration, showed no evidence of increased degeneration after exercise. Gel scans showed no decrease in the ratio of total alpha-chain to beta- and gamma-chains after exercise. The ratio of intact alpha 1 chain (alpha 1, 67,000 mol wt) to total alpha-chain was 0.66 +/- 0.13 before exercise, 0.64 +/- 0.14 immediately after exercise, and 0.65 +/- 0.13 1 h after exercise. The rate and extent of crosslinking of the alpha-chain of fibrin formed by clotting plasma samples was unaltered by exericse. These data suggest that physiologically significant fibrinogenolysis does not occur with strenuous exercise, even when fibrinolytic activity is markedly accelerated.
Adrenocortical function in rats chronically exposed to high altitude
Authors: Ou L. C. , Tenney S. M.
Published: December 2017

In rats exposed to a simulated altitude of 5,486 m for 3 mo, pituitary and adrenal glands hypertrophied and plasma levels of corticosterone increased more than threefold over sea-level controls. The in vitro rates of corticosterone production by the quartered adrenal gland were significantly enhanced, but the responsiveness of the adrenal gland to ACTH remained normal.
Influence of air velocity and heat acclimation on human skin wettedness and sweating efficiency
Authors: Candas V. , Libert J. P. , Vogt J. J.
Published: December 2017

Before and after heat acclimation, four male resting subjects were exposed to humid heat that caused levels of skin wettedness ranging from 50 to 100%. The physical experimental conditions were chosen so that the same skin wettedness was attained with modification of only the ambient water vapor pressure, at two wind speeds (0.6 and 0.9 m . s-1). The esophageal temperature (Tes), mean skin temperature (Tsk), sweating rate (msw), and dripping sweat rate (mdr) were recorded; the amounts of local drippage in the same thermal conditions before and after acclimation were also determined. The relationship between the evaporative efficiency of sweating (eta sw) and the skin wettedness (w) is reported, as is the influence of the subject's acclimation to humid heat on adjustments of skin wettedness. The effects of the air velocity on the coefficient of evaporation and on sweating efficiency are discussed. Beneficial increases in evaporation were achievable by increasing skin wettedness only when there was a consistent drippage, which differed from one body area to another and from one subject to another. The relation of drift in body temperature to skin wettedness changed with the acclimation of the subjects.
Breathing frequency responses to pulmonary CO2 in an isolated lobe of the canine lung
Authors: Nilsestuen J. O. , Coon R. L. , Igler F. O. , Zuperku E. J. , Kampine J. P.
Published: December 2017

Recent studies have indicated that the breathing frequency responses to inspired CO2 in part result from changes in pulmonary stretch receptor activity. Pulmonary CO2 may alter frequency by direct inhibition of stretch receptor discharge, or secondarily, by changes in airway mechanics. The vascularly isolated left lower lobe (LLL) of the canine lung was used to determine the effect of hypocapnic airway constriction on the pulmonary CO2 reflex. The upper and middle lobes of the left lung were removed and the right vagus nerve sectioned. Blood was recirculated through the LLL. Diaphragm electromyogram was used as an index of respiratory center activity and to trigger ventilation of the left lower lobe. Lobar hypocapnia increased peak airway pressure and reduced respiratory rate. However, infusion of isoproterenol or the use of a mechanical overflow system to block the airway pressure response prevented the frequency changes associated with CO2. Although both the direct and mechanical effects of CO2 on stretch receptors may contribute to the reflex, in the LLL preparation the mechanical effects predominate.
Disappearance of norepinephrine from the circulation following strenuous exercise
Authors: Hagberg J. M. , Hickson R. C. , McLane J. A. , Ehsani A. A. , Winder W. W.
Published: December 2017

Five subjects who had been training vigorously for 2 mo worked 5 min on the cycle ergometer at 1,480 +/- 100 kpm/min and at 1,920 kpm/min on separate days. Plasma norepinephrine (NE), blood lactate, and heart rate were determined during the postexercise periods. The same subjects were also tested at 1,480 +/- 100 kpm/min after a 2-mo detraining period, when subjects did not train. At 1,920 +/- 80 kpm/min, plasma NE was 4 ng/ml at the end of exercise. The NE concentration increased slightly in the first min postexercise, then decreased with a half-time of 2.8 min between 1 and 11 min postexercise. Detraining for 2 mo did not markedly affect the rate of disappearance of NE in the postexercise period in these five subjects. Between 11 and 30 min postexercise (1,480 +/- 100 kpm/min), heart rate was 25 beats/min higher after detraining, while NE was not significantly different. These data provide evidence that more rapid recovery of heart rate in trained individuals during this period is not likely due to a more rapid recovery from the sympathetic response to exercise.
Control of forearm venous volume during exercise and body heating
Authors: Wenger C. B. , Roberts M. F.
Published: December 2017

Subjects ate ice to cool sufficiently to constrict the superficial forearm veins. After ice-eating, esophageal temperature (Tes) recovered from local cooling in 10-15 min, and thereafter reflected body core temperature. Eight skin temperatures (Tsk) were measured, and a weighted mean (Tsk) computed. The left wrist was suspended 5-6 in. above shoulder level, and left forearm skin temperature was maintained at 35 degrees C with a controlled-temperature air stream. Forearm venous volume (FVV) w-s the volume difference between the forearm drained by gravity and the forearm congested by a pneumatic cuff inflated to 32 Torr. Subjects were warmed either by storage of resting metabolic heat or by cycle exercise at 40-45% of maximal O2 consumption. Exercise experiments were conducted in ambient temperatures of 15, 25, and 35 degrees C, and resting experiments in 25 and 35 degrees C. FVV rose linearly with Tes, but during exercise FVV was lower than at the same Tes and Tsk during rest, and the difference was greater at high Tsk and FVV. Our data fit the equation FVV-FVV0 = (a1 Tes + a2 Tsk - b).[1 - phi (W).(Tsk - T-sk0)], where phi (W) is a function of exercise, and phi (W) = 0 at rest.
Reappraisal of extravascular lung thermal volume as a measure of pulmonary edema
Authors: Noble W. H. , Kay J. C. , Maret K. H. , Caskanette G.
Published: December 2017

Previous papers have evaluated extravascular thermal volume of the lung (ETVL) as a measure of lung water by using median transit time (tmed) rather than the correct mean transit time (tmean). Calculation of ETVL using tmean (ETVLmean) and tmed (ETVLmed) gave an excellent relationship, ETVLmean = 1.48 ETVLmed - 0.74 (r = 0.99). This allowed us to calculate a new ratio of ETVLmean to PETW = 1.55 +/- 0.17, WHERE PETW is the postmortem value of pulmonary extravascular tissue weight. Thermistors were placed in dogs to determine the contribution of chest wall, pleural and pericardial fluid, left heart, bronchi, and lung gas to the ETVL measurement. We found ETVLmean greater than PETW because of thermal distributioninto left heart (18 +/- 2% of ETVL), bronchi (estimate 7% of ETVL), pulmonary arteries and veins (estimate 7% of ETVL), and perhaps a small portion of chest wall. We could not detect any portion of lung gas or pleural or pericardial effusions as a part of the ETVL measurement. When the distribution into left heart, bronchi, pulmonary arteries, and veins is removed ETVLmean/PETW = 1.07.
Intercostal muscle reflexes and sleep breathing patterns in the human infant
Authors: Thach B. T. , Abroms I. F. , Frantz I. D. , Sotrel A. , Bruce E. N. , Goldman M. D.
Published: December 2017

Breathing variability and apnea characteristic of rapid eye movement (REM) sleep was investigated in a newborn infant with complete interruption of intercostal to phrenic neural pathways due to intrapartem transection of the cervical spinal cord. Breath-to-breath variability in inspiratory duration (TI), breath duration (Ttot), tidal volume (VT), and ventilation (VI) was significantly greater in REM than in quiet sleep and was similar to the variability in these parameters seen in normal infants. In addition, brief periods of diaphragmeatic apnea were observed during REM sleep. The phenomenon of shortened TI during airway occlusion previously attributed to intercostal-to-phrenic reflexes was examined in the quadriplegic infant and in seven healthy term infants. The frequency of this response was increased when airway occlusion was delayed until after onset of inspiration. Shortening of TI by occlusion occurred no less frequently in the quadriplegic than in the control infants. The constant paradoxical inward movement of the rib cage during inspiration observed in the quadriplegic infant suggests that supraspinal innervation of intercostal muscle limits such paradoxical movements in the normal infant. The quadriplegic infant's end-expiratory volume was consistently above his passive functional residual capacity, as inferred from respiratory volume and pressure measurements.
Effect of altered gas diffusivity on alveolar gas exchange-a theoretical study
Authors: Nixon W. , Pack A.
Published: December 2017

Experimental studies have established that alveolar gas exchange is inversely relation to the molecular diffusivity of gas in the lung airways. The mechanism underlying this relationship is, however, unclear. To investigate this phenomenon, the conditions relevant to the experimental studies are simulated using a computational model of pulmonary gas transport. Results from these simulations suggest that the inverse relationship found experimentally can largely be explained on the basis of the intra-acinar stratification of blood flow and gas concentrations. Gas having a relatively low molecular diffusivity is not transported as far into the acinus as gas having a higher diffusivity. When these relative intra-acinar gas distributions interact with the blood flow distribution, which has been shown experimentally to be weighted towards the proximal alveoli, more gas exchange occurs in the low molecular diffusivity mixture. Consideration of the various other mechanisms that have been proposed to explain the experimental findings.he inverse dependence suggests that they are of little significance. In particular, our studies remove the need to invoke Taylor diffusion to explain the experimental findings.
Mechanism of ozone-induced tachypneic response to hypoxia and hypercapnia in conscious dogs
Authors: Lee L. Y. , Djokic T. D. , Dumont C. , Graf P. D. , Nadel J. A.
Published: December 2017

In seven studies on three dogs exercising on a treadmill (1.6 km/h), we studied the effect of ozone on ventilatory responses to hypercapnia and to hypoxia. After ozone exposure (0.67 +/- 0.02 ppm by vol; 2 h), the responses of minute volume of ventilation (VE) to progressive hypercapnia and hypoxia were not changed, but the breathing pattern in response to these stimuli changed. We analyzed the breathing pattern by plotting the relationship between VE and tidal volume (VT). During progressive hypercapnia, the slope of VE-VT relationship increased from a control value of 36.1 +/- 1.6 (mean +/- SE) to 93.5 +/- 8.9 min-1 after ozone (n = 7, P less than 0.005); during hypoxia, the slope increased from a control value of 46.1 +/- 8.6 to 142.7 +/- 18.3 min-1 after ozone (n = 6, P less than 0.005). The ozone-induced tachypneic responses to hypercapnia and hypoxia were not affected by inhalation of atropine sulfate or isoproterenol aerosols, but were completely abolished by bilateral vagal blockade. These findings indicate an effect of ozone on the vagal receptors located in the airways and lungs that causes reflex tachypnea during hypercapnia and hypoxia.
A hypodermic needle PO2 electrode
Authors: Whalen W. J. , Spande J. I.
Published: December 2017

Several glass-covered gold wires (5-10 micrometer diam) connected to an insulated lead wire are embedded with epoxy inside a stainless steel needle (e.g., 25 gauge). The epoxy, glass, and gold wire are carefully ground off down to the bevel of the needle, and the gold wires recessed electrolytically using NaCN. Oxygen tension (PO2) is measured polarographically, usually using a separate Ag-Agcl reference electrode. However, the stainless steel needle, connected to the shield of the coaxial lead, can also be used as the reference. The PO2 electrode shows little or no stir sensitivity and has a response time(to 100%) of 1-2 s.
Bone CO2-titration curves in acute hypercapnia obtained with a modified titration technique
Authors: Pasquale S. M. , Messier A. A. , Shea M. L. , Schaefer K. E.
Published: December 2017

Bone CO2-titration curves were obtained in mature rats weighing 500-600 g. Animals were exposed for one hour to 1, 3, 5, 10, or 15% CO2 in air. Measurements of bone CO2, were made using a modified titrimetric analysis on fresh and oven-dried samples of paired rat femurs. A manometric method was used for comparison. Arterial blood samples were obtained for measurements of partial pressure of CO2 in arterial blood (PaCO2). Within the range of environmental CO2 concentrations studied, a linear relationship was observed between the PaCO2 and the increment in fresh bone CO2 content. This relationship is defined by the equation: delta fresh bone CO2 (mmol/kg) = 61.8 +/- 0.68 PaCO2. The CO2 increment was confined to a heat-labile, presumably soluble pool comprising 10.5% of the total bone CO2 content. No change in the water content of the bone was observed as a result of acute CO2 exposure. The results of this study demonstrate the rapid in vivo CO2 uptake of bone in response to exposure to increased CO2 levels.
Smoothing of MEFV curves by digital filtering of flow as a function of volume
Authors: Bruce E. N. , Jackson A. C.
Published: December 2017

Noise in flow records limits the degree to which one can characterize local features of maximum expiratory flow-volume (MEFV) curves, i.e., the volume dependence of flow over small volume intervals such as 5-10% of the vital capacity. Such noise includes instrument noise, cardiogenic pulsations, and rapid flow oscillations due to audible turbulence. Noise removal by analog filtering of the flow vs. time signal often is unacceptable because the initial rapid onset of flow can be severely distorted. A digital technique for directly filtering the flow vs. volume record that does not distort the initial rapid flow transient has been developed. Flow values are determined at 256 volume points equally spaced over the vital capacity. This sequence of flow values is passed through a linear phase, finite impulse response, Hamming window filter. The output sequence of filtered flow values, plotted against the corresponding volumes, quantitatively retains the local shape features of the MEFV curve without the noise.
Frequency dependence of dynamic compliance analyzed from one cycle of breathing
Authors: Sasaki T. , Suzuki S. , Sugiyama M. , Takishima T.
Published: December 2017

An analytical method for testing frequency dependence of dynamic compliance (Cdyn) from a Fourier-series analysis of flow and transpulmonary pressure in a single cycle of breathing was described and compared to the conventional method in an electrical model, in excised dog lobes and in human subjects. In the electrical model, the frequency dependence of Cdyn in the Fourier method corresponded exactly with the theoretical frequency dependence of Cdyn. A frequency dependence of Cdyn was evaluated by a ratio of Cdyn at 1 Hz to Cdyn at zero frequency, C1Hz/CoHz, from the regression line between Cdyn and the frequency in excised dog lobes and human subjects. In healthy nonsmokers, C1Hz/CoHz was significantly smaller in the Fourier method than in the conventional method. The discrepancy of frequency dependence of Cdyn between the two methods was thought to be possibly due to the effects of the nonsinusoidal breathing pattern on the conventional method, and due to the effects of a volume-dependent compliance on the Fourier method.
Medullary respiratory neuron activity: relationship to tonic and phasic REM sleep
Authors: Orem J.
Published: December 2017

This study analyzes the relationship of brain stem respiratory neuron activity to the tonic and phasic events of rapid-eye-movement (REM) sleep. Dorsal and ventral medullary respiratory neurons were recorded in sleeping cats. Discharges of inspiratory and expiratory cells increased in number and frequency with increases in pontogeniculooccipital (PGO) spiking (phasic REM activity). Across neurons the correlations between PGO wave frequency and respiratory neuron activity were positively related to the discharge levels of the neurons: the more active the cell, the greater the relationship to PGO activity. Tonic REM influences on respiratory neurons were calculated by extrapolating from the regression line relating PGO frequency and neuron activity to the hypothetical state of no PGO activity. These calculated levels, when compared to non-REM sleep levels, showed that tonic REM mechanisms reduced the activity of some neurons and activated others. Ventral medullary respiratory activity generally was decreased during tonic rem, whereas dorsal respiratory group cells were variously activated and inactivated. These results demonstrate an association of brain stem respiratory activity to nonrespiratory REM sleep variables.
Vasomotor thresholds in the squirrel monkey: effects of central and peripheral temperature
Authors: Lynch W. C. , Adair E. R. , Adams B. W.
Published: December 2017

Six squirrel monkeys (Saimiri sciureus) participated in two ex,eriments examining how central (preoptic/anterior hypothalamic, Tpo) and peripheral (ambient, Ta, or mean skin, Tsk) temperatures influence peripheral vasomotion. In the first experiment, four monkeys with unilateral preoptic thermodes were exposed to a wide range of central (23 degrees C less than Tpo less than 44 degrees C) and peripheral (10 degrees C less than Ta less than 38 degrees C) temperatures. Results indicated that the skin of both tail and foot vasodilates at discrete but unique Ta thresholds (Tpo congruent to 39 degrees C) and that raising Tpo lowers these thresholds. In the second experiment, results from two monkeys implanted with bilateral thermodes surrounding the preoptic area replicated those of experiment 1. Subsequent tests with these two monkeys on the quantitative interaction between central and peripheral temperatures indicated that the dilation threshold is approximately a linear function of Tpo and Tsk. These effects are related to the interaction between central and peripheral inputs to the thermoregulatory system.
Hemoglobin affinity for oxygen during short-term exhaustive exercise
Authors: Klein J. P. , Forster H. V. , Stewart R. D. , Wu A.
Published: December 2017

We assessed hemoglobin affinity for oxygen (standard P50: pH 7.40, PCO2 40 Torr, temperature 37 degrees C) in 3 series of studies of 16 male subjects who performed exhaustive treadmill exercise of 10 min duration. Standard P50 was significantly elevated (0.7--2.5 Torr) during the last minute of and for 30 min following exercise. Exercise while carboxyhemoglobin (HbCO) was acutely elevated to 5% did not affect std P50 any differently than exercise alone. 2,3-Diphosphoglycerate (2,3-DPG) was significantly elevated after exercise, but not during or 30 min postexercise, and it correlated significantly with P50 in 2 studies (r, 0.43--0.68). ATP (mumol/100 ml) was significantly elevated only 3 min postexercise. Serum [Na+], [K+], [Cl-], osmolarity, and hemoglobin (Hb) concentration were significantly elevated during exercise with [Na+] osmolarity, and [Hb] remaining significantly elevated postexercise. There was no significant correlation between std P50 and any of these variables. Multiple correlation regression analysis between P50 and 2,3-DPG, ATP, and [Na+] yields a coefficient of 0.86. We conclude this type of exercise is unique in causing a small change in std P50 that appears to be mediated by several factors.
Determinants of transvascular fluid shifts in zone I lungs
Authors: Nicolaysen G. , Hauge A.
Published: December 2017

We studied the fluid shifts in isolated, plasma-perfused rabbit lungs kept completely within zone I. The rate of fluid filtration or reabsorption was determined gravimetrically. A rise in alveolar pressure at constant pleural and vascular pressures reduced th rate of filtration or increased the rate of reabsorption in seven of eight lungs. In seven of seven lungs a reduction in pleural pressure at constant alveolar and vascular pressures increased the rate of filtration or decreased the rate of reabsorption. Thus, a given rise in lung volume had opposite effects depending on whether this rise was caused by an increased alveolar or reduced pleural pressure. Therefore, the exchange vessels studied cannot be true extra-alveolar vessels, which always expand (reflecting a rise in transmural pressure) with a rise in lung volume. When alveolar and pleural pressures were equally increased at constant vascular pressure, the rate of filtration was reduced in four of four lungs. The results can be explained through the existence of exchange vessels situated neither in the alveolar septae proper nor among the true extra-alveolar vessels. The vessels in the alveolar junctions are the most likely candidates.
A new method for analyzing multiple-breath nitrogen washout curves
Authors: Light R. W. , George R. B. , Meneely G. R. , Chouest L. J. , Rosekrans R. H.
Published: December 2017

Multiple-breath nitrogen washout (MBNW) curves from 39 normal and 45 patients with varying degrees of airway obstruction were analyzed with the following equation: log log [(F0N2 - F infinity N2)/(FN2 - F infinity N2)] = B log (V/FRC) +A, where F0N2 is the initial, F infinity N2 is the equilibrium, and FN2 is the end-tidal fractional nitrogen concentration after a volume (V) of air in liters have been exchanged, and FRC is the measured functional residual capacity of the individual. All 84 curves were well described with the equation when all points corresponding to FN2 below 0.40 were used. The coefficient of determination (r2) exceeded 0.990 in 56/84 (67%) of the transformed curves and the lowest coefficient of determination was 0.946. This suggests that the MBNW can be described by two numbers, B called the index of uniformity, and A the index of efficiency. The ability of these two indices and the lung clearance index (LCI) to identify individuals as abnormal and to separate groups with varying degrees of airway obstruction was compared. B identified more individuals (33/45) as abnormal than did A(15/45) or LCI (19/45). B was also superior to A or LCI in separating groups with varying degrees of airway obstruction. This analysis allows the complex MBNW curve to be described by two numbers that vary depending on the degree of airway obstruction.
Dynamics of ventilation, heart rate, and gas exchange: sinusoidal and impulse work loads in man
Authors: Bakker H. K. , Struikenkamp R. S. , De Vries G. A.
Published: December 2017

Dynamic characteristics of ventilation, heart rate, and gas exchange in response to sinusoidally varying work loads were analyzed in four male subjects, exercising in the upright position on a bicycle ergometer. Mean work-load and sinusoidal amplitude were about 1.5 and 0.9 W/kg, fat-free mass), respectively. Seven different frequencies were used, the periods ranging from 12 to 0.75 min. To further investigate the linearity of the variables under study, 10-s impulse loads were also applied to three of the four subjects. Harmonic analysis of the sine-wave data and comparison of the sine-wave fundamental responses with the impulse frequency responses showed that only O2 uptake behaves in a linear fashion. Ventilation and CO2 production showed quasi- to nonlinear behaviors, whereas the responses of heart rate and alveolar partial pressures were clearly dependent on the type of forcing used. By means of mathematical parameter identification techniques, it was found that the individual frequency responses of O2 uptake could be almost completely described by a four-parameter transfer function with parameter values showing second-order underdamped to critically damped dynamics.
Angiotensin I conversion and vascular reactivity in pathophysiological states in dogs
Authors: Leuenberger P. J. , Stalcup S. A. , Greenbaum L. M. , Mellins R. B. , Turino G. M.
Published: December 2017

To determine if angiotension converting enzyme activity is altered by acute pathophysiological insults, we assessed angiotensin I conversion using a blood pressure response technique in anesthetized dogs studied during acute 100% O2 breathing and acute acid-base derangements. Also, we determined systemic vascular reactivity to angiotensin II by measuring the magnitude and duration of the arterial blood pressure response to intra-arterial injections of angiotensin II under these same conditions. Angiotensin I conversion found in normoxia [91 +/- 7 (SD)%] was unchanged by acute acidosis, alkalosis, and hyperoxia. During acute hyperoxia the mean half time of the hypertensive response increased from 68 +/- 25 (SD) s at a PaO2 of 112 +/- 18 (SD) Torr to 100 +/- 34 (SD) s at a PaO2 of 491 +/- 47 (SD) Torr (P less than 0.01). No other pathophysiological condition studied had any effect on reactivity of systemic vasculature to angiotensin II. We conclude that, except during acute hypoxia as previously shown, converting enzyme activity is resistant to other pathophysiological insults and that vascular responsiveness to angiotensin II is enhanced by hyperoxia.
Relationship of CSF pH, O2, and CO2 responses in metabolic acidosis and alkalosis in humans
Authors: Irsigler G. B. , Stafford M. J. , Severinghaus J. W.
Published: December 2017

The effect of induced metabolic acidosis (48 h of NH4Cl ingestion, BE - 10.6 +/- 1.1) and alkalosis (43 h of NaHCO3- ingestion BE 8.8 +/- 1.6) on arterial and lumber CSF pH, Pco2, and HCO3- and ventilatory responses to CO2 and to hypoxia was assessed in five healthy men. In acidosis lumbar CSF pH rose 0.033 +/- 0.02 (P less than 0.05). In alkalosis CSF pH was unchanged. Ventilatory response lines to CO2 at high O2 were displaced to the left in acidosis (9.0 +/- 1.4 Torr) and to the right in alkalosis (4.5 +/- 1.5 Torr) with no change in slope. The ventilatory response to hypoxia (delta V40) was increased in acidosis (P less than 0.05) and it was decreased in four subjects in alkalosis (P, not significant). We conclude that the altered ventilatory drives of steady-state metabolic imbalance are mediated by peripheral chemoreceptors, and in acidosis the medullary respiratory chemoreceptor drive is decreased.
Shrinkage of lung after chemical fixation for analysis of pulmonary structure-function relations
Authors: Mazzone R. W. , Kornblau S. , Durand C. M.
Published: December 2017

Glutaraldehyde is widely used to chemically fix lungs for analysis of pulmonary structure-function relations. Accurate interpretation of observations on fixed tissue requires a clear definition of any artifacts, such as tissue shrinkage, resulting from fixation with glutaraldehyde. Two experimental procedures were used in this study to examine possible shrinkage artifacts resulting from fixation of lung by glutaraldehyde. In the first, isolated perfused dog lungs were rapidly frozen at different transpulmonary pressures. Samples were then freeze substituted at -50 degrees C using 70% ethylene glycol with and without fixatives present. In the second series of experiments, the left lungs of mongrel dogs were fixed by vascular perfusion with glutaraldehyde at different transpulmonary pressures. In both series of experiments any changes in linear dimensions resulting from the fixation procedure were measured. Also, the presence of aldehyde was demonstrated by a positive reaction with Schiff reagent. The results demonstrate that lung tissue fixed either by vascular perfusion or freeze substitution tends to shrink to about the same extent. This shrinkage is reasonably constant at about 9% for transpulmonary pressures of 5 and 15 cmH2O and increases to about 15% when the transpulmonary pressure reaches 25 cmH20.
Cardiac contractile proteins and sarcoplasmic reticulum in hearts of rats trained by running
Authors: Penpargkul S. , Malhotra A. , Schaible T. , Scheuer J.
Published: December 2017

Rats were trained with two running protocols previously demonstrated to result in enhanced cardiac performance. Control groups included free-eating sedentary animals and food-restricted animals in which the body weights were the same as the runners. Calcium binding by isolated sarcoplasmic reticulum (SR) was slightly but significantly increased in SR from runners at low but not high calcium concentrations at 15 s and 1 min. Calcium uptake in the presence of 1 mM oxalate was increased in SR from runners. Actomyosin ATPase activity was increased by 10% (P less than 0.001) with one running protocol but not with the other. Myosin Ca2+ ATPase activity and actin-activated ATPase activity were also slightly increased in hearts of runners. In food-restricted cardiac actomyosin ATPase was significantly decreased. Actomyosin ATPase activity was found to be normal in hearts of sedentary animals subjected to water immersion without exercise. Therefore, physical training of rats by running, which produces a cardiac mechanical advantage similar to training by swimming, is not accompanied by cardiac biochemical changes of the same magnitude as in the hearts of swimmers.
Effect of platelet depletion on lung vascular permeability after microemboli in sheep
Authors: Binder A. S. , Kageler W. , Perel A. , Flick M. R. , Staub N. C.
Published: December 2017

To test whether platelets are necessary for the increased vascular permeability associated with microemboli, we used 16 anesthetized sheep in which we measured lung lymph flow, pulmonary arterial and left atrial pressures, thermodilution cardiac output, and lymph/plasma protein concentration. Injecting glass bead microemboli (200 micrometers diam) until pulmonary vascular resistance increased to three times base-line values caused lung lymph flow to increase at nearly constant lymph-to-plasma protein concentration ratio that is characteristic of increased microvascular permeability. Antiplatelet serum alone caused transient increases in pulmonary vascular resitance and lung lymph flow, but produced no change in steady-state lung fluid balance. After depleting platelets by greater than 97%, tripling pulmonary vascular resistance with emboli resulted in increases in lung lymph and protein flow comparable to that seen in untreated sheep. We injected twice the amount of beads in thrombocytopenic sheep compared to untreated sheep. We conclude that, although platelets do augment the pulmonary hypertension after emboli, they are not essential for the microemboli vascular injury.
A model for hypokinesia: effects on muscle atrophy in the rat
Authors: Musacchia X. J. , Deavers D. R. , Meininger G. A. , Davis T. P.
Published: December 2017

Hypokinesia in the hindlimbs of rats were induced by suspension; a newly developed harness system was used. The animal was able to use its forelimbs to maneuver, within a 140 degrees arc, to obtain food and water and to permit limited grooming of the forequarters. The hindlimbs were nonload bearing for 7 days; following a 7-day period of hypodynamia, selected animals were placed in metabolic cages for 7 days to study recovery from hypokinesia. During the 7-day period of hypokinesia there was evidence of muscle atrophy. Gastrocnemius weight decreased, renal papillary urea content increased, and daily urinary losses of urea, NH3, and 3-methylhistidine increased. During the 7-day recovery period muscle mass and excretion rate of urea, NH3 and 3-methylhistidine returned to control levels. Calcium balance was positive throughout the 7-day period of hypokinesia. Hypertrophy of the adrenals suggested the occurrence of some level of stress despite the apparent behavioral adjustment to the suspension harness. It was concluded that significant muscle atrophy and parallel changes in nitrogen metabolism occur in suspended rats and these changes are readily reversible.
Lung deformations at minimal volume
Authors: Kallok M. J. , Lai-Fook S. J.
Published: December 2017

Minimal volume (MV, gas plus tissue volume at zero transpulmonary pressure) was determined in excised dog lobes after inflation with air and with saline. MV was significantly greater in saline-filled lobes than air-filled lobes. Air inflation was performed with the lobe supported in two different ways, which were chosen to produce different deformations: 1) supported on the cephalic surface and 2) hung by strings attached to the cephalic surface. MV measured in hung lobes was significantly greater than MV measured in supported lobes. The problem of excised lobes deformed by gravity was analyzed in the two configurations using linear elasticity. The saline volume was assumed to be the stress-free state for the lobe, and the volume change was computed from the stress-free state due to the gravitational deformation. The analysis suggests that the difference between saline and air MV is due primarily to the gravitational deformation of air-filled lungs.
Exercise efficiency: validity of base-line subtractions
Authors: Stainbsy W. N. , Gladden L. B. , Barclay J. K. , Wilson B. A.
Published: December 2017

In evaluating the efficiency of humans performing exercise, base-line subtractions have been used in an attempt to determine the efficiency of the muscles in performing the external work. Despite the fact that base lines have been criticized previously, they have been widely used without adequate analysis of the implications involved. Calculations of efficiencies using data available in the literature for isolated muscle preparations revealed that base-line subtractions result in unreasonably high efficiencies. This suggests strongly that the base lines are invalid. To be valid, a base line must continue unchanged under all the conditions in which it is applied. Previously published data indicate clearly that exercise base lines change with increasing work rate and are therefore invalid. The use of base lines is further complicated by elastic energy storage in some types of exercise. Although exercise efficiencies using base line subtractions may be useful, they do not indicate muscle efficiency. Perhaps future studies of exercise metabolism should be directed less at refining base lines and more toward describing and quantifying the determinants of energy expenditure.
A self-retaining nasal flowmeter for preterm infants
Authors: Brouillette R. T. , Thach B. T.
Published: December 2017

A nasal flowmeter suitable for preterm infants is described. It is made from a commercially available nasal cannula and 400-mesh stainless steel screen. Low dead space (0.35 ml) and low resistance (1.3 cmH2O . 100 ml-1 . s) are advantages. Light weight and compact design have eliminated the need for extensive restraint of the subject. Also, the investigator need not hold the flowmeter in place. These features make accurate measurement of respiratory airflow and tidal volume possible during polygraphic monitoring studies lasting several hours.
Effects of respiratory apparatus on breathing pattern
Authors: Askanazi J. , Silverberg P. A. , Foster R. J. , Hyman A. I. , Milic-Emili J. , Kinney J. M.
Published: December 2017

The effects of ventilatory apparatus on breathing pattern and gas exchange were studied in normal supine subjects. Using a canopy system, measurements of O2 consumption, CO2 production, tidal volume (VT), frequency (f), minute ventilation, mean inspiratory flow, and inspiratory, and expiratory time (TI and TE) were made and compared to data obtained with the use of a mask (m) and mouthpiece plus noseclip (mp + nc). Use of the m or mp + nc caused a 32.5 and 15.5% increase in VT, respectively, whereas f, TI, and TE remained unchanged. As TI did not change the increase in VT was caused entirely by increased inspiratory flow.
Effects of atropine on respiratory heat loss in asthma
Authors: Breslin F. J. , McFadden E. R. , Ingram R. H. , Deal E. C.
Published: December 2017

We have previously observed that although atropine does not alter the magnitude of the response to exercise while breathing cold air, it does cause the predominant site of obstruction to move into the lung periphery. To determine if this effect was due to changes in the conditioning of inspired air, we measured respiratory heat loss (RHL) and retrotracheal (Trt) and retrocardiac esophageal temperature in eight asthmatics while they performed eucapnic hyperventilation with cold air before and after the inhalation of atropine. Multiple aspects of pulmonary mechanics were also recorded. Significant and equivalent airway obstruction developed with and without atropine (control delta FEV1 = 1.0 +/- 0.2 (SE) liter; postatropine = 0.9 +/- 0.3 liter). Despite this, RHL was 17.1% greater and Trt fell 16% more after atropine. These data demonstrate that atropine can influence heat transfer within the lung and alter the sites of conditioning.
Effect of induced erythrocythemia on aerobic work capacity
Authors: Buick F. J. , Gledhill N. , Froese A. B. , Spriet L. , Meyers E. C.
Published: December 2017

The aerobic work capacity of 11 highly trained runners was studied employing a double-blind design 1) before phlebotomy (C1), 2) following restoration of normocythemia (C2), 3) after a sham reinfusion of 50 ml of saline (sham), 4) following autologous reinfusion of approximately 900 ml of freeze-preserved blood (reinfusion), and 5) upon reestablishment of control hematologic levels after erythrocythemia (C3). There were no hematologic differences among C1, C2, sham, and C3, but following reinfusion, hemoglobin was significantly elevated (15.7-16.7 g . 100 ml-1). Maximum O2 consumption (VO2max) and running time to exhaustion were significantly increased 24 h postreinfusion (5.11-5.37 l . min-1 and 7.20-9.65 min, respectively) and 7 days postreinfusion. When sham preceded reinfusion, VO2 max and time to exhaustion were the same as control. However, 16 wk postreinfusion, despite the return to normal hematologic values, VO2max remained significantly above control levels at sham and C3. These findings indicate that there is a distinct increase in VO2max following induced erythrocythemia and suggest that oxygen transport limits maximal aerobic capacity.
Functional delay in lung maturation in fetuses of diabetic rabbits
Authors: Sosenko I. R. , Lawson E. E. , Demottaz V. , Frantz I. D.
Published: December 2017

Lung maturation was studied in fetuses of rabbits made diabetic with alloxan. Lung maturation was examined functionally with pressure-volume curves and by determining surfactant content of lung lavage on a surface balance, and biochemically by measuring disaturated phosphatidylcholine content (DSPC) and lecithin: sphingomyelin ratio (L/S) of lung lavage and DSPC content of lung tissue. Pressure-volume curves of 27.5-day fetuses of diabetic does demonstrated less deflation stability. Functional assessment of pulmonary lavage surfactant measured on a surface balance was less in diabetic fetuses at both 27.5 and 29.5 days of gestation. There were no differences in DSPC content or L/S of lung wash or DSPC in whole-lung tissue between diabetic and control fetuses. The discordance between surfactant function and concentrations of major surfactant phospholipids suggests that surfactant in fetuses of diabetic animals is qualitatively different from that in the normal fetus. These findings may explain why analysis of amniotic fluid phospholipid content sometimes fails to predict risk of respiratory distressed syndrome correctly in human diabetic pregnancies.
Positive end-expiratory pressure shifts left ventricular diastolic pressure-area curves
Authors: Haynes J. B. , Carson S. D. , Whitney W. P. , Zerbe G. O. , Hyers T. M. , Steele P.
Published: December 2017

Positive end-expiratory pressure (PEEP) ventilation is frequently associated with reduction in cardiac output despite unchanged transmural left ventricular (LV) end-diastolic pressure. These findings have been interpreted to indicate decreased contractility, but could also be explained by altered LV diastolic pressure-volume characteristics. To study this possibility, radiopaque markers were inserted into a plane of the LV in nine dogs. Transmural pressure (LV-pericardial) was synchronized with LV area during ventilation with zero end-expiratory pressure and with 15 cmH2O PEEP. Mean polynomial curves derived from the diastolic pressure-area data demonstrated that PEEP shifted the curves upward so that a given diastolic area was associated with a higher transmural LV pressure (P less than 0.0001). PEEP decreased end-diastolic area and stroke area, both of which were normalized with dextran volume expansion. Restoration of stroke area by normalizing end-diastolic area with volume expansion suggests the initial changes with PEEP were due to a decrease in preload rather than in contractility.
Importance of airway closure in limiting maximal expiration in normal man
Authors: Davis C. , Campbell E. J. , Openshaw P. , Pride N. B. , Woodroof G.
Published: December 2017

To elucidate the importance of airway closure in limiting maximum expiration, two complementary plethysmographic techniques have been used to estimate the volume of and pressure within the trapped thoracic gas. Three young (19-23 yr) and three older (43-66 yr) subjects were studied. The first study defined the curve of possible pressure-volume relationships for the trapped gas; the second study attempted to estimate the volume of trapped gas. In the first study the subject in a Mead plethysmograph expired through a pneumotachograph and back into the box. A reduction in box volume greater than that caused by drying and cooling of expired gas implies gas compression due mainly to airway closure. In the second study a known volume of air was withdrawn from the mouth at full expiration and changes in box volume and mouth pressure were recorded. The apparent volume in pressure communication with the mouth (Vpc) was calculated using Boyle's law. In the young subjects we did not detect thoracic gas compression although there was evidence of trapped gas (RV-Vpc greater than 0). In the older subjects there was a larger volume of trapped gas that was compressed to pressures of more than 22 cmH2O. Airway closure appears to limit maximal expiration in older subjects.
Excursion of vibrating microelectrodes in tissue
Authors: Kanabus E. W. , Feldstein C. , Crawford D. W.
Published: December 2017

A vibrating microelectrode holder consisting of a support rod attached to the cone of a miniature loudspeaker facilitates electrode penetration into arterial wall tissue, eliminates surface dimpling, and relieves polarographic artifacts believed to be due to tissue compression. The longitudinal vibratory excursion of free microelectrode tips, measured with strobe illumination microscopy, varies from less than 0.9 to 137 micron depending on energizing voltage and frequency. Tissue penetration is achieved most effectively at the resonance frequency, about 200 Hz for the present system. Total tip excursion is not diminished when the electrode is penetrated into excised rabbit femoral artery, but tip motion relative to surrounding tissue is considerably attenuated because the arterial wall holds the electrode shaft rather firmly and follows its movements. This relative motion in tissue is only 2.7 +/- 0.8 micron at 200 Hz and 0.05 V and can be reduced further at higher frequencies without sacrificing the penetration advantages of the system. Thus under proper vibratory conditions microelectrodes can be easily inserted into the arterial wall with minimal tissue disturbance.
Airway area by acoustic reflections measured at the mouth
Authors: Fredberg J. J. , Wohl M. E. , Glass G. M. , Dorkin H. L.
Published: December 2017

We tested the hypothesis that features of upper airway and tracheal geometry can be inferred from acoustic reflection data recorded at the mouth. In six subjects we computed inferences of airway cross-sectional area vs. distance and compared them with measurements obtained from orthogonal radiographic projections of the trachea. The acoustic data show local area maxima at the uvula and hypopharynx and local minima at the oropharynx and the glottis. With subjects breathing air the inferred tracheal areas markedly exceeded the radiographic measurements. With subjects breathing 80% He-20% O2 there was good intrasubject agreement between acoustic and radiographic data in spite of large intersubject variability. The average coefficient of variation of tracheal area determinations for five trials in all subjects was 0.16. These studies suggest that features of airway geometry between the mouth and carina can be determined accurately and noninvasively in individual subjects from high-frequency reflection data measured at the mouth.
Sensitivity of bronchoprovocation and tracheal mucous velocity in detecting airway responses to O3
Authors: Abraham W. M. , Januszkiewicz A. J. , Mingle M. , Welker M. , Wanner A. , Sackner M. A.
Published: December 2017

This study was undertaken to determine whether measurements of tracheal mucous velocity or airway reactivity to inhaled carbachol more sensitively detect airway effects of inhaled ozone (O3) in conscious sheep. Dose-response curves of mean pulmonary flow resistance (RL) to carbachol were obtained by measuring RL after five breaths of carbachol aerosol with stepwise increases in drug concentration. The animals then breathed 0.5 ppm O3 through an endotracheal tube for 2 h. The dose-response curves were repeated immediately after the 0.5 ppm O3 exposure and 24 h later. In the eight sheep studied, there were no significant alterations in base-line RL immediately after or 24 h after 0.5 ppm O3. Airway hyperreactivity was not apparent immediately after the sheep breathed 0.5 ppm O3, but it was evident 24 h later. In contrast, six sheep that breathed 0.5 ppm O3 in the same manner for 2 h did not show a significant depression in tracheal mucous velocity the same day or 24 h later. Exposure to 1 ppm O3 for 2 h resulted in airway hyperreactivity immediately after the exposure and elevated base-line RL 24 h later; 2 ppm O3 produced an increase in base-line RL immediately after exposure. We conclude that, in conscious sheep, airway hyperreactivity appears to be a more sensitive indicator of airway effects produced by short-term exposure to 0.5 ppm O3 than depression of tracheal mucous velocity.