bluuebunny/crossref_metadata_2025 huggingface dataset:
Sweating response in man during transient rises of air temperature
Authors: Libert J. P. , Candas V. , Vogt J. J.
Published: December 2017

Nude men were exposed to neutral environments (Ta = 28 degrees C, Pw = 20 mbar) changing to warm environments (Ta = 50 degrees C, Pw = 20 mbar). The transient period from neutral to warm environment lasted 4 min (dTA/DT = 5.50 degrees C/min) or 20 min (DTa/dt = 1.10 degrees C/min) or 40 min (dTa/dt = 0.55 degrees C/min) or 60 min (dTa/dt = 0.37 degrees C/min). Continuous measurements were made of rectal and mean skin temperatures and of body weigth loss. Sweating started before appreciable variation in rectal temperature. Onset of sweating could be explained by a peripheral proportional and rate control. Unsteady-state sweating can be predicted by summated stimulation of skin and rectal temperatures. This stimulation could be increased for some subjects by a multiplicative effect due to differences in local skin temperatures. This multiplicative effect occurred during the first transient period.
Sympathetic influence on alveolar surface activity in hyperventilated dog
Authors: Kobayashi T. , Kishizuchi S. , Murakami S.
Published: December 2017

Hyperventilating IPPB, defined as intermittent positive-pressure breathing with a frequency of 32 beats/min and inspiratory pressure of 30 cmH2O, was administered for 14 h to open-chested anesthetized dogs in which nerves to one bronchus were operatively blocked. In the nerve-intact lungs, the lung stability index calculated from the pressure-volume relationship decreased with the duration of the hyperventilating IPPB (correlation coefficient r = -0.66, P less than 0.001), and atelectasis and hemorrhage appeared. In the nerve-blocked lungs, the index did not decrease during the 14 h of hyperventilating IPPB, and the appearance was almost normal. After pharmacologic sympathetic block with phenoxybenzamine, the lung stability index of both the operatively nerve-blocked lung and the nerve-intact lung was not decreased by hyperventilating IPPB. From these findings, we conclude that sympathetic block can protect pulmonary surface activity from the adverse effects of hyperventilating IPPB.
Influence of limb length on a stepping exercise
Authors: Shahnawaz H.
Published: December 2017

The effect of limb length on responses to the step-test exercise was studied in 10 subjects of various heights; oxygen consumption values served as an indicator. Mean oxygen consumption was found to be significantly related to limb length in the step-test exercise. This was demonstrated when subjects with different limb lengths were tested as a standard work load (i.e., 10 m/min x body wt) but at seven different bench heights and correspondingly adjusted stepping rates. The minimum values for oxygen consumption were obtained when the bench height was near 50% (45–55%) of subject's limb length.
2-Deoxy-D-glucose uptake by lung slices from fed and fasted rats
Authors: Chaisson C. F. , Massaro D.
Published: December 2017

We studied the uptake and phosphorylation of 2-deoxy-D-[1–14C]glucose (2-[14C]DG) by lung slices from fed and fasted rats to obtain information on the effect of starvation on surgar transport by the lung. We found that 2-[14C]DG is taken up and phosphorylated by the lung, but that, as in other tissues it is not metabolized beyond the phosphorylation step. The accumulation of 2-[14C]DG as free 2-DG does not require energy, fails to show saturation in the range studied (5–100 mM), and is not inhibited by exogenous glucose. The phosphorylation of 2-DG by the lung is energy dependent, saturable, and competitively inhibited by exogenous glucose. Fasting does not interfere with the intracellular accumulation of unphosphorylated 2-DG but causes about a 40% decrease in the accumulation of phosphorylated 2-DG. We conclude that membrane transport does not limit uptake of 2-DG; fasting decreases the phosphorylation of 2-DG.
Influence of abdominal gas on the Boyle's law determination of thoracic gas volume
Authors: Brown R. , Hoppin F. G. , Ingram R. H. , Saunders N. A. , McFadden E. R.
Published: December 2017

In a body plethysmograph we have demonstrated differences in total lung capacity (TLC) derived from panting maneuvers performed at different levels in the vital capacity. In almost all cases, the discrepancies were due to the magnitude of the abdominal gas volume (AGV) and the relative magnitude of abdominal and thoracic pressure swings during the panting mandeuver. When panting was performed at functional residual capacity (FRC), the effect of AGV compression on the determination of thoracid gas volume (TGV) was small. Of 11 individuals studied 2 were known to have mild asthma. Compression and decompression of AGV appeared to be an insufficient explanation for discrepancies in derived TLC's in these two, suggesting that other as yet unidentified factors may influence the plethysmographic determination of TGV.
Simultaneous helium and nitrogen single-breath washout: lung model simulation
Authors: Kaneko K.
Published: December 2017

By use of a model, simultaneous bolus and resident N2-washout curves are simulated to examine the effects of inhomogeneous lung elasticity and unequal critical airway closing pressure. Pathological conditions are divided into A, B, and C, where dominant lesions involve the upper, entire vertical, and lower regions, respectively. In elastic inhomogeneity, the He plateau (phase III) is upward, flat, or downward in conditions A, B, and C, respectively, depending on the vertical location of the lesion. Conversely, the N2 plateau is upward in three conditions, reflecting overall interregional and intraregional inhomogeneity. The terminal He rise (phase IV) has a clear relationship to the airway closure than the terminal N2 rise. The present study supports the previous prediction that the simultaneous bolus and N2-washout study provides additional information. This analysis will improve the means for assessing mechanical disorders in diseased lungs.
Blood gas changes during panting in a small East African antelope, the dik-dik
Authors: Maskrey M. , Hoppe P. P. , Bamford O. S.
Published: December 2017

Five adult male dik-dik (Madoqua kirkii) were exposed in a climatic chamber to an air temperature of 45 degrees C. Measurements were made of rectal temperature (Tre) and respiratory frequency (f) and arterial blood samples taken before and during heat exposure were analyzed for pH, PCO2 and PO2. During exposure, Tre and f increased in all animals. In the first 80 min dik-dik displayed thermal tachypnea and minor changes in blood gases. Continued exposure lead to hyperpnea accompanied by a fall in PaCO2 and a rise in pH. PaCO2 at first fell and then increased toward or above control levels. The dik-dik did not display second phase breathing. This observation confirms that second phase breathing is not essential to the development of respiratory alkalosis. The main conclusion of the study is that the dik-dik, unlike another heat-adapted antelope, the wildebeest (Taylor, Robertshaw, and Hoffmann. Am. J. Physiol. 217:907–910, 1969), is unable to resist alkalosis during heat stress.
Computer-aided measurement of breath volume and time components using magnetometers
Authors: Stagg D. , Goldman M. , Davis J. N.
Published: December 2017

A computer-assisted method is developed for analyzing volume and time components of individual breaths using a previously developed magnetometer method for recording anteroposterior (AP) diameters of rib cage and abdomen. Calibration constants for the magnetometer system are computed during simultaneous measurements of airflow at the mouth for several breaths during spontaneous breathing. Tidal volume and inspiratory and expiratory times can then be computed from the magnetometer signals alone, without imposing respiratory devices at the subject's airway. No respiratory isovolume maneuvers are necessary. Results from normal subjects and from one patient with bilateral diaphragmatic paralysis show that the magnetometer analysis is closely comparable to standard measurements made from airflow recordings. The magnetometer technique thus provides an accurate means of measuring volume and time components of breathing in man, avoiding the behavioral or reflex effects induced by mouthpiece, nose clip, or face mask. Because no special respiratory maneuvers are required for calibration, the technique will be well suited to the study of breathing in those who are ill.
Isobaric inert gas supersaturation: observations, theory, and predictions
Authors: Collins J. M.
Published: December 2017

An isobaric inert gas supersaturation model incorporating both diffusion and perfusion properties of biological tissue is presented in a form which allows ready comparison with experimental observations. This model requires only measurement of inert gas flux and blood gas solubility in order to evaluate –counterdiffusion potential”. Inert gas flux across the skin of Yorkshire piglets anesthetized with pentobarbital was measured for He, Ne, CH4, C2H4, N2O, and SF6. Model predictions based upon these data compare favorably with published reports of isobaric inert gas supersaturation, as well as several previously unpublished observations. The possibility of supersaturation resulting from the use of hydrogen as a breathing gas in a helium environment is also discussed, and extensive animal testing is recommended before potentially dangerous human exposure occurs.
Ventilatory response to medroxyprogesterone acetate in normal subjects: time course and mechanism
Authors: Skatrud J. B. , Dempsey J. A. , Kaiser D. G.
Published: December 2017

The time course of ventilatory adaptation to medroxyprogesterone acetate (MPA) and potential mediators of this response in plasma and lumbar CSF were determined in five healthy adult males. A significant decrease in arterial PCO2 (PACO2) at rest and exercise was noted within 48 h of drug administration with the maximum effect reached within 7 days and amounting to a 5-Torr decrement in PACO2. Blood and lumbar cerebrospinal fluid pH because significantly alkaline to control as soon as the ventilatory resporse was noted and remained alkaline during the treatment period. The ventilatory and dP/dt max response to exogenous CO2 was unchanged but their response to moderate exercise was increased after MPA. MPA-rlated materials were detected in both the plasma and CSF as soon as the ventilatory response was noted. The increase in CSF MPA-related materials approximated the unbound fraction determined in plasma. We conclude that [H+] in plasma and CSF is a function rather than a cause of ventilator acclimatization to MPA. MPA-related materials are capable of crossing the blood-brain barrier and could potentially exert their ventilatory stimulant effect by some central mechanism.
Vagal and aerosol histamine interactions on airway responses in dogs
Authors: Loring S. H. , Drazen J. M. , Snapper J. R. , Ingram R. H.
Published: December 2017

Histamine aerosol was administered to 10 anesthetized paralyzed artificially ventilated dogs whose vagi were first intact, then cut, and then peripherally stimulated. Pulmonary resistance (RL) was measured and dose-response curves determined in the three conditions. The dogs were divided into two groups based on the initial response to histamine with the vagi intact. The low-dose (LD) group had a greater than or equal to 50% increase in RL when exposed to a histamine concentration of 1.0 mg/ml. The high-dose (HD) group had a greater than or equal to 50% increase in RL when exposed to an aerosol containing 3.0 mg/ml histamine or more. In both groups there was a dose-related increase in RL with histamine with the vagi intact, cut, or stimulated. In three of the LD dogs there was a greater than additive interaction between vagal stimulation and inhaled histamine, whereas in the HD dogs the interaction was at most additive. With the vagi cut, both groups had a significantly lesser histamine response. The results show that differences in histamine responsiveness between dogs is in part related to varying degrees of nonreflex histamine-vagal interaction.
Effects of lung volume and electrode position on the esophageal diaphragmatic EMG
Authors: Kim M. J. , Druz W. S. , Danon J. , Machnach W. , Sharp J. T.
Published: December 2017

In anesthetized dogs studied both supine and prone, the electromyogram (EMG) of the diaphragm recorded directly from three portions of the diaphragm (crural, anterior, and costal) was compared with simultaneous recordings of the diaphragmatic EMG recorded from 10 sites in the esophagus and stomach. Effects upon the EMG of lung volume change and esophageal electrode position change were determined during bilateral supramaximal tetanic phrenic stimulation with airway occluded. Lung volume change had little effect upon the directly recorded EMG. The effect of lung volume change upon the EMG recorded from the esophagus was somewhat greater and marked change was noted as the esophageal recording site was varied. In supine dogs two sites of maximal signal were observed, one 1 cm above the cardia and the other 4--6 cm below the cardia. In prone dogs a single site for maximal signal was observed 3 cm above the cardia. An electrode site as close to the cardia as possible appears to be optimal from the point of view of variation in signal due to lung volume change and due to body position change. Gastric balloon stabilization is recommended. Proximity of the electrode and posterior gastric wall to the diaphragmatic crura may explain the maximal EMG signal recorded below the cardia.
Pulmonary vasomotion and the distribution of vascular resistance in a dog lung lobe
Authors: Grimm D. J. , Dawson C. A. , Hakim T. S. , Linehan J. H.
Published: December 2017

We examined the influence of stellate ganglion stimulation, hypoxia, and the infusion of norepinephrine, PGF2alpha, serotonin, and histamine on the longitudinal distribution of vascular resistance and intravascular pressures in an isolated left lower lobe of the dog lung using the low-viscosity bolus technique. Sympathetic stimulation, norepinephrine, serotonin, PGF2alpha, and hypoxia increased total pulmonary vascular resistance by increasing the resistance, primarily on the arterial or upstream side of the volume midpoint, whereas histamine increased the resistance near the venous end of the lobar vascular bed. Hypoxia increased the volume upstream from the site of maximum resistance, suggesting that the larger lobar arteries were distended by the elevated lobar artery pressure. Sympathetic stimulation, norepinephrine, PGF2alpha, and serotonin, on the other hand, had little effect on the volume upstream from the maximum resistance, suggesting that these vasomotor stimuli prevented distension of the larger arteries.
Sensitization of tolerant mice to cold with a serum factor induced by endotoxin
Authors: Couch R. E. , Moore R. N. , Berry L. J.
Published: December 2017

Endotoxin-tolerant mice are sensitized to cold (5 degrees C) stress by an injection of 0.4 ml serum collected from zymosan-pretreated mice 2 h after an intravenous (iv) injection of 25 microgram endotoxin. Deaths begin after 6 h and most animals die by 10 h, The factor in serum believed to be responsible for this effect is called glucocorticoid antagonizing factor (GAF). Tolerant mice given 10 microgram endotoxin live for 10 h and two-thirds survive for 24 h. Serum from endotoxin-poisoned conventional mice reduces survival time significantly but not as dramatically as that from zymosan-primed mice. The latter serum, but not endotoxin, causes a rapid drop in the core temperature of tolerant mice housed at 5 degrees C and inhibits the endogenous induction of phosphoenolpyruvate carboxykinase (PEPCK) (EC 4.1.1.32) in tolerant mice exposed for 4--5 h to the cold. An injection of 25 microgram endotoxin does not have this effect on the enzyme. Serum that produces these responses also sensitizes mice to endotoxin lethality and blocks the protection normally afforded against endotoxin by adrenocorticoids.
Unilateral pulmonary edema in rabbits after reexpansion of collapsed lung
Authors: Pavlin J. , Cheney F. W.
Published: December 2017

The effects of the mode of reinflation and of the duration of prior collapse on the development of unilateral pulmonary edema following reexpansion of collapsed lung were studied in a rabbit model simulating the human syndrome of “reexpansion pulmonary edema.” The right lungs of rabbits were maintained in an atelectatic state for 0.5 h to 8 days, by injection of air into the pleural space. Reexpansion was achieved in 2 h by application of positive pressure to the airway while a chest tube was connected to underwater seal, or by application of negative pressure (-20 to -100 Torr) to a screened window in the partietal pleura. The lung surface pressures we actually applied by the two methods are not known. Animals were then killed and pulmonary edema was determined by wet-to-dry weight ratios. The incidence of unilateral pulmonary edema increased as the duration of prior collapse was increased (85% after 7--8 days; 17% after 3 days; and 0% after 0,5 h) when reinflated with -100 Torr applied to the pleural window. Although the incidence was less, it also occurred following the use of pleural window pressure less negative than -100 Torr, and after reinflation by positive airway pressure.
Adaptations in skeletal muscle following strength training
Authors: Costill D. L. , Coyle E. F. , Fink W. F. , Lesmes G. R. , Witzmann F. A.
Published: December 2017

Five men were studied before and after 7 wk of isokinetic strength training to determine its effects on muscle enzyme activities and fiber composition. One of the subject's legs was trained using 10 repeated 6-s maximal work bouts, while the other leg performed repeated 30-s maximal knee extension exercise. The total work accomplished by each leg was constant. Training 4 times/wk achieved similar gains in peak torque for both legs at the training velocity (3.14 rad/s) and at slower speeds. Fatigability of the knee extensor muscles, as measured by a 60-s exercise test, was similar in both legs after training. Biopsy specimens showed significant changes in the % of the muscle area composed of type I and IIa fibers as a result of both strength training programs. In terms of muscle enzymes, only the 30 s exercise program resulted in elevated glycolytic, ATP-CP and mitochondrial activities. Despite these changes, none of the parameters measured were found to be related to the gains in either muscle strength or fatigability during maximal isokinetic contractions.
Effect of intrapulmonary hematocrit maldistribution on O2, CO2, and inert gas exchange
Authors: Young I. H. , Wagner P. D.
Published: December 2017

The potential effect of intrapulmonary variations in hematocrit on gas exchange has been studied in theoretical models of the lung containing maldistribution of both hematocrit (Hct) and ventilation-perfusion (VA/Q) ratio. Hematocrit inequality enhanced gas exchange when units of low VA/Q were given a low Hct, arterial PO2 rising by as much as 14 Torr and PCO2 falling by up to 2 Torr depending on the particular distributions of Hct and VA/Q, whereas gas exchange was depressed when units of low VA/Q had a high Hct. After measuring inert gas solubilities in both dog and human blood of different Hct, the effect of Hct inequality on inert gas exchange was similarly assessed. Solubility was found to increase with HCT for less soluble gases. Because of this, conditions for enhancement of inert and O2 exchange by HCt inequality coincided, and it was found that in general the effects on O2 and inert gas transfer were quantitatively internally consistent. Even when Hct inequality was extreme, the resulting perturbation of inert gas concentrations was sufficiently small that the main features of the recovered VA/Q distributions were unaltered.
Pulmonary effects of acute and chronic antigen exposure of immunized guinea pigs
Authors: Pare P. D. , Michoud M. C. , Boucher R. C. , Hogg J. C.
Published: December 2017

Subdivisions of lung volume and pressure-volume (PV) curves of the lung and chest wall were measured in guinea pigs immunized to ovalbumin before and after acute (group 1) and chronic (group 2) antigen exposure. The histopathology produced in chronically exposed animals was also assessed. Animals were anesthetized with pentobarbital sodium and studied in a pressure-sensitive body plethysmograph, using a fluid-filled esophageal catheter to measure transpulmonary pressure (PL). Functional residual capacity (FRC) was determined by the Boyle's law technique; total lung capacity (TLC) was defined as the lung volume at a PL of 30 cmH20, and residual volume (RV) was defined as the lung volume at a transrespiratory pressure of -50 cmH2O. Acute antigen challenge of group 1 animals resulted in a decrease in TLC (22%), and increases in FRC (20%) and RV (110%), suggesting combined bronchoconstriction and alveolar duct constriction. Chronic antigen exposure of group 2 animals resulted in minimal changes in subdivisions of lung volume and PV curves, and produced a histological lesion resembling allergic alveolitis rather than asthma.
Effect of exercise on nasal mucous velocity and nasal airflow resistance in normal subjects
Authors: Saketkhoo K. , Kaplan I. , Sackner M. A.
Published: December 2017

Nasal mucous velocity and nasal airflow resistance were measured in nine healthy subjects before, during 5 min, and 1 h after submaximal exercise of 20 min with a cycle ergometer set in such a way that heart rate ranged from 125 to 135 beats/min. Nasal mucous velocity rose from a base line of 7.6–12.7 mm/min during exercise and returned to the base-line value 5 and 60 min after exercise. The mean expiratory nasal airflow resistance at a flow of 0.4 l/s decreased from a base line of 1.6–0.6 cmH2O . (l/s)-1 during exercise and returned to the baseline value 5 and 60 min after exercise.
Pulmonary microvascular response to hemorrhagic shock, resuscitation, and recovery
Authors: Demling R. H. , Niehaus G. , Will J. A.
Published: December 2017

We studied the effect of hemorrhagic shock, resuscitation, and recovery on the pulmonary microcirculation. We used lung lymph flow (QL) and lymph-to-plasma protein ratio as sensitive indices of transvascular fluid filtration rate and protein permeability. We measured pulmonary vascular pressures, cardiac output, blood gases, lymph flow, and lymph and plasma proteins before and during a 2-h period of shock, a 3-h period of resuscitation, and a 72-h period of recovery, in nine unanesthetized sheep with chronic lung lymph fistula. We found a 30% decrease in QL during early shock as animals were bled into bags containing an acetate citrate dextrose solution until aortic pressure was 50 Torr. QL gradually increased to or exceeded base line in five of nine animals during late shock as pulmonary vascula resistance increased by 250%. During the 3-h resuscitation period, mean QL increased by 110%, with the lymph-to-plasma protein ratio being significantly decreased, indicating no protein permeability change. In five of nine studies, lymph became visible bloody. The increased QL and lymph RBCs were felt to be secondary to an elevation in microvascular pressure. During the recovery period, pressures and QL returned to base line.
Control of respiratory evaporative heat loss in exercising goats
Authors: Mercer J. B. , Jessen C.
Published: December 2017

Investigations were carried out to determine whether a nonthermal input is involved in the control of respiratory evaporative heat loss (REHL) in exercising goats. Two goats were implanted with hypothalamic perfusion thermodes and three goats were implanted with intravascular heat exchangers to clamp hypothalamic temperature and total body core temperature, respectively. At 30 degrees C air temperature REHL was measured while the animals were resting or walking on a treadmill (3 km.h-1, 5 degrees gradient). When the hypothalamic temperature was clamped between 33.0 and 43.0 degrees C the slopes of the responses relating increased REHL to hypothalamic temperature were similar during rest and exercise. However, the threshold hypothalamic temperatures for the increased REHL responses were lower during exercise than at rest, presumably due to higher extrahypothalamic temperatures. When the body core temperature was clamped between 37.0 and 40.4 degrees C the slopes of the responses relating increased REHL to total body core temperature during exercise showed only minor differences compared to those at rest, none of them conclusively indicating nonthermal influences.
Anaerobic threshold alterations caused by endurance training in middle-aged men
Authors: Davis J. A. , Frank M. H. , Whipp B. J. , Wasserman K.
Published: December 2017

Nine previously sedentary middle-aged males underwent cycle endurance training 45 min/day for 9 wk with an average attendance of 4.1 days/wk. Seven males served as controls. Before and after the training period, the subjects performed three cycle ergometer tests. Work rate was incremented by 15 W/min, to the limit of the subjects' tolerance, in the first two tests; the third test consisted of contant-load cycling at an O2 uptake (VO2) just below the pretraining anaerobic threshold (AT). After training, the AT increased significantly by 44%, expressed as absolute VO2, and by 15%, expressed relative to VO2 max. Significant increases were also noted in VO2max (25%), maximal minute ventilation (19%), and maximal work rate (28%). The test-retest correlation coefficients for the AT (%VO2max) were 0.91, pre- and posttraining. Training did not alter steady-state VO2 during the submaximal exercise test whereas significant decreases occurred in CO2 output, VE, respiratory quotient, and VE/VO2. No changes occurred in the control subjects during this period. These results demonstrate that the AT is profoundly influenced by endurance training in previously sedentary middle-aged males.
Influence of progesterone on arterial blood and CSF acid-base balance in women
Authors: Machida H.
Published: December 2017

To study the mechanism of the action of progesterone on pulmonary ventilation during pregnancy, arterial and cerebrospinal fluid (CSF) acid-base parameters were measured in 59 pregnant and 36 nonpregnant women at the periods of follicular phase, luteal phase, early pregnancy, late pregnancy, and puerperium. Marked respiratory alkalosis in both arterial blood and CSF was observed in pregnancy and puerperium. The degree of hypocapnia observed in the luteal phase and during pregnancy was closely related to the progesterone level in arterial blood. In conclusion, it is unlikely that the observed hyperventilation results from stimulation at the central chemosensitive areas or peripheral chemoreceptors.
Rate of uptake of carbon monoxide at different inspired concentrations in humans
Authors: Jones H. A. , Clark J. C. , Davies E. E. , Forster R. E. , Hughes J. M.
Published: December 2017

The rate of uptake of carbon monoxide (CO) in the lungs of normal subjects were measured at inspired concentrations of less than 1, 300, and 3,000 ppm (less than 0.0001–0.3%) using radioactive CO (11CO). In nine subjects the rate of uptake was monitored at the mouth during rebreathing. At inspired CO concentrations of approximately 1, 300, and 3,000 ppm and a mean alveolar O2 fraction of 0.15, the mean lung diffusing capacity was 25.8, 26.4, and 25.3 ml . min-1. Torr-1, respectively. In seven subjects the measurements were repeated after a period of O2 breathing, giving a mean alveolar O2 fraction of 0.78. The calculated membrane diffusing capacity was 31.9, 33.7, and 32.0 ml . min-1. Torr-1 at less than 1, 300, and 3,000 ppm inspired CO. We conclude that there is no difference in the rate of uptake of CO over the range of concentrations studied in these experiments. No evidence for the presence of a facilitated transport system for CO in the normal human lung was found.
Lobe weight gain and vascular, alveolar, and peribronchial interstitial fluid pressures
Authors: Hida W. , Inoue H. , Hildebrandt J.
Published: December 2017

Interstitial fluid movements in acute pulmonary edema were studied by recording interstitial fluid pressure [Px (f)] relative to pleural pressure (atmospheric), together with lobe weight gain or loss (delta W). Px (f) was measured by wicks inserted between lobar bronchus and artery while alveolar pressure (PA) was fixed at either 5 or 20 cmH2O. When vascular pressure (Pvas) was raised abruptly from -5 to +25 cmH2O by air inflation for 60 min, Px (f) became abruptly less negative, then remained stable. However, during vascular inflation with plasma, delta W began a steady increase, but plotted against delta W, Px(f) became less negative in several phases. After an immediate rise due to interdependence effects following vascular distension, Px (f) remained almost unchanged for 4–7 min as delta W increased 15–80% of initial lobe weight (Wi), representing a transport lag between leakage and measuring sites and suggesting that interstitial edema was not homogeneous. Next, Px (f) increased progressively as weight increased a further 70–200% of Wi and finally slowed its rise near zero pressure. When Pvas was lowered, Px (f) became abruptly more negative, again by interdependence; however, as delta W then decreased 20–50% of Wi over 30 min, Px (f) did not change consistently. It was possible to relate the rate of weight gain occurring between 2 and 5 min after Pvas was raised to two pressure gradients, Pvas - Px (f) and Pvas - PA, and to relate the time lag to filtration rate and Pvas - Px (f).
Mechanical factors and the regulation of perfusion through atelectatic lung in pigs
Authors: Enjeti S. , Terry P. B. , Menkes H. A. , Traystman R. J.
Published: December 2017

The role of mechanical interdependence in the perfusion of atelectatic lung was studied in two ways: a) regional hemodynamics were compared before (control) and after the development of lobar and sublobar atelectasis, and b) the effect of thoracotomy on regional hemodynamics was assessed. With lobar atelectasis mean lobar blood flow and vascular conductance decreased to 60% of control. Sublobar atelectasis caused mean sublobar blood flow and vascular conductance to decrease to 6% of control. Opening the chest after production of lobar atelectasis caused blood flow to fall to 50% of control. When sublobar atelectasis was produced in the open chest, sublobar blood flow decreased to 25% of control measurements made prior to thoracotomy. We conclude that with a closed chest, sublobar vascular distortion mediated by mechanical interdependence may be an important mechanism responsible for the differences in hemodynamic responses to atelectasis between lobes and sublobar regions.
Active impedance of respiratory system in anesthetized cats
Authors: Zin W. A. , Pengelly L. D. , Milic-Emili J.
Published: December 2017

We have assessed the validity of the method of Siafakas et al. (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 51: 10913;121, 1981) for determining active elastance (E'rs) and flow resistance (R'rs) of the respiratory system. In six cats anesthetized with pentobarbital sodium we have measured flow, volume, and tracheal occlusion pressure during spontaneous breathing. This allowed us to compute E'rs and R'rs. From these data and the occlusion pressure wave we predicted the time course of volume during inspirations with added linear flow resistances (delta R). These were compared to the actual loaded inspirograms. The agreement was generally good, except for small predictable discrepancies with the highest delta R values, which could be attributed to decompression of thoracic gas. These results indicate that the approach of Siakafas et al. to determine E'rs and R'rs is valid. In addition, we have quantified the “terminal inhibition” of inspiratory activity, which occurs toward the end of unoccluded breaths (both loaded and unloaded).
Cardiac output as a controller of ventilation through changes in right ventricular load
Authors: Jones P. W. , Huszczuk A. , Wasserman K.
Published: December 2017

Ventilatory responses to changes in right ventricular (RV) load were studied in spontaneous breathing anesthetized dogs. Moving average RV pressure leads to (PRV) was used as an index of the RV strain. RV load was changed in two ways: 1) cardiac output (Q) was increased by infusion of isoproterenol (0.7–1.2 micrograms/min) and reduced by infusion of vasopressin (0.3–0.5 U/min); and 2) RV pressure was increased independently on Q by partial balloon obstruction of the RV outflow. When Q was changed by drug infusion there was a linear correlation between leads to PRV and Q (avg r = 0.04). Well-correlated linear relationships were found between expired minute ventilation (VE) and leads to PRV (avg r greater than 0.03), the slopes and intercepts of which were not significantly different whether leads to PRV was changed by altering Q, partial obstruction of RV outflow, or combining both procedures. Bilateral vagotomy did not alter the VE/leads to PRV slope resulting from RV balloon inflations. It is suggested that the RV strain may act as a controller of ventilation and provide a link between Q and VE.
Ionic content and regulation of cellular volume in rat alveolar type II cells
Authors: Jones G. S. , Miles P. R. , Lantz R. C. , Hinton D. E. , Castranova V.
Published: December 2017

Alveolar type II epithelial cells were isolated by elastase digestion of rat lungs and purified by centrifugal elutriation. This method yields an enriched fraction of 1 x 10(7) cells/rat containing 85% pure type II pneumocytes. Purified type II cells exhibit a high rate of oxygen consumption, 215 nmol O2 . 10(6) cells-1 . h-1, which is unaffected by the addition of succinate. Type II cells contain 2 microliters H2O/10(7) cells and are approximately 325–330 micrometers 3 in volume. These pneumocytes contain 107 nmol K/l cell H2O and 70 mmol Cl/l cell H2O. In addition, type II cells have a high Na content, i.e., 156 mmol/l cell H2O. However, most of this Na is bound with only 33% being exchangeable. Therefore, the cytoplasmic concentration of free Na is 51 mmol/l cell H2O. Na uptake is very rapid and type II cells i.e., specific activity equilibrium is reached in 15 min with a half time of 5 min. In addition to this large passive transport of Na, type II cells exhibit a highly active Na-K pump involved in the regulation of cellular volume. Volume regulation is inhibited by a decrease in temperature (2 degrees C) and by the addition of ouabain (10(-4) M), Hg (10(-5) M), or Cu (10(-3) M).
Protection from O2 toxicity by preexposure to hypoxia: lung antioxidant enzyme role
Authors: Frank L.
Published: December 2017

Adult rats preexposed to 10% O2 for 3 days had marked tolerance to hyperoxia-induced lung damage and lethality. The survival of preexposed vs. nonpreexposed rats at 72 h of hyperoxic exposure was 62/62 vs. 7/47 (15%), P less than 0.0001; and after 7 days in 9613;98% O2, the comparative survival was 31/33 (94%) vs. 1/20 (5%), P less than 0.0005. Hypoxic exposure produced significant elevations in rat lung superoxide dismutase, catalase, glutathione peroxidase, and glucose-6-phosphate dehydrogenase activities. In contrast, in adult mice and hamsters, no increased lung antioxidant enzyme levels were produced by preexposure to hypoxia and no significant tolerance to high O2 was realized. (Lethal time50 values for hypoxia-preexposed and nonpreexposed mice, 5.2 and 4.4 days, respectively; and for hamsters, 6.4 and 6.1 days, respectively.) Thus the protective effect of hypoxic preexposure is correlated with adaptive changes in lung antioxidant enzyme activity. Evidence in the literature suggests that superoxide anion (O-2) and H2O2 production may increase under hypoxic conditions. Increased cellular concentrations of their normal substrates could stimulate antioxidant enzyme rises during the preexposure period in hypoxia.
Thermoregulatory responses of patients with extensive healed burns
Authors: Shapiro Y. , Epstein Y. , Ben-Simchon C. , Tsur H.
Published: December 2017

Two groups (A, n = 4; B, n = 6) of young male subjects with deep second- and third-degree healed burns (burned area: 48.6 +/- 3.6 and 23.7 +/- 3.1% of the total skin surface area in groups A and B, respectively) and a group of healthy subjects (C, n = 10) underwent a 3-h exposure to 40 degrees C, 50% rh, stepping on a bench 32 cm high, at a rate of 12 steps/min (Vo2 = 1.05 +/- 0.06 l X min-1). Rectal temperature (Tre), mean skin temperature (Tsk), and heart rate (HR) of group A were significantly higher than those of groups B and C; i.e., at the end of the 1st h Tre was 38.7, 37.9, and 37.7 degrees C; Tsk was 37.3, 36.4, and 37.0 degrees C; HR was 151, 105, and 110 beats X min-1 in groups A, B and C respectively. Maximal evaporative cooling capacity (Emax) was 4.9 +/- 0.1, 7.2 +/- 0.5, and 10.2 +/- 0.4 W X kg-1 in groups A, B and C, respectively, while the required evaporation capacity for thermoequilibrium (Ereq) was similar in all groups (6.7 +/- 0.1, 6.8 +/- 0.1, and 6.6 +/- 0.1 W X kg-1). Total sweat rate (msw) was 594 +/- 13, 602 +/- 29, and 485 +/- 34 g X h-1 in groups A, B and C, respectively, msw normalized to healthy skin area (msw/AH) was 671 +/- 75, 449 +/- 29, and 280 +/- 16 g X h-1 X m-2 in groups A, B and C, respectively. Sweating sensitivity normalized to healthy skin area (msw/AH X delta Tre) was similar in all three groups. It is suggested that the similarity between groups B and C can be explained by the compensatory sweating from the healthy skin of group B, which was sufficient because Emax greater than Ereq. In group A, Emax less than Ereq; therefore thermoequilibrium could not be maintained despite high compensatory sweat rate from the healthy skin. The similarity in msw/AH X delta Tre supports the assumption that elevation in Tre is the main drive of sweat regulation and that sweat rate is a function of delta Tre and healthy skin surface area.
Dynamic behavior of lung parenchyma in shear
Authors: Coughlin M. F. , Suki B. , Stamenovic D.
Published: December 2017

Dynamic shear properties of excised rabbit lungs were studied by measuring creep deformation after application of a step indentation force to the pleural surfaces by a rigid cylindrical punch. The punch diameter was 9.5 mm, and punch forces were 2,4, and 6 g. Measurements were made at lung volumes of 40, 60, and 90% of the total lung capacity before and after lavage with 3-dimethyl siloxane, which provided a constant surface tension of 16 dyn/cm at the alveolar surfaces. A power-law model was fitted to creep data and then transformed into the frequency (f) domain by using Laplace transforms. The optimum model parameters were used to calculate shear elastance (E mu), shear resistance (R mu), and shear hysteresivity (2 pi fR mu/E mu) between 0.01 and 2.0 Hz. It was found that E mu slightly increased and R mu decreased nearly hyperbolically with increasing f, both decreased with increasing indentation force, and both increased with increasing mean lung volume. Shear hysteresivity decreased sharply from 0.01 to 0.25 Hz and then assumed a nearly steady value that was an order of magnitude lower than the value reported previously for uniformly oscillated lungs. Changes in E mu and R mu after lavage were correlated with changes in transpulmonary pressure and not with changes in surface film properties. These results suggest that in the breathing range of frequencies 1) the energy loss of lung parenchyma is a much smaller fraction of the stored elastic energy in shear than in uniformly oscillated lungs and 2) transpulmonary pressure, not dynamic properties of surface film, is the primary determinant of lung dynamic properties in shear.
Flow limitation in normal infants: a new method for forced expiratory maneuvers from raised lung volumes
Authors: Feher A. , Castile R. , Kisling J. , Angelicchio C. , Filbrun D. , Flucke R. , Tepper R.
Published: December 2017

Forced expiratory maneuvers generated by rapid thoracic compression have been used to assess airway function in infants. It remains unclear whether flow limitation can be achieved in healthy infants because low pressure transmission across the chest wall and inspiratory effort may limit the maximum transpulmonary pressure developed during the maneuver. We have found that several rapid inflations to a lung volume set at an airway pressure of 30 cmH2O (V80) briefly inhibit respiratory effort and allow forced expiration to proceed from V80 to residual volume. We used a water-filled esophageal catheter to measure isovolume pressure-flow curves in seven healthy infants (3-88 mo). Forced vital capacity (FVC) was defined as the volume between V80 and residual volume. Pressure transmission between the compression jacket and the esophagus decreased with decreasing lung volume and averaged 60 and 37% at 50 and 75% of expired FVC, respectively. Subjects demonstrated plateaus in their isovolume pressure-flow curves at 50% of expired FVC and lower lung volumes. We conclude that this new methodology enables forced expiratory maneuvers to achieve flow limitation in healthy infants over at least the lower portion of their lung volume.
Acute mild hypothermia in awake unrestrained rats induces a mixed acid-base disorder
Authors: Alfaro V. , Palacios L.
Published: December 2017

The interactions between components that contribute to acid-base homeostasis were studied in the first steps of acute hypothermia [body temperature (Tb) 37-31 degrees C] in awake unrestrained rats as an experimental model of accidental hypothermia in mammals. The concurrent changes in blood gases, plasma ions, and plasma protein concentrations in arterial blood were analyzed. Acute decreases in Tb decreased PCO2 and increased pH. The ratio of Na+ concentration to Cl- concentration increased at 35-33 degrees C Tb, leading to an increase in the plasma strong ion difference ([SID]). These increases were transient, and levels returned to baseline at lower Tb (31 degrees C). Lack of change in hematocrit, hemoglobin, plasma osmolality, or plasma protein concentration indicated stability in plasma volume. Therefore, [SID] changes were related to ionic shifts with respect to the extravascular space and not to ionic depletion. A feasible role in this ionic exchange for contracting skeletal muscle during shivering thermogenesis is given. Significant decrease in HCO3- concentration at lower Tb (31 degrees C) was related to an apparent increase in relative ventilation (lung ventilation per unit of CO2 removed). It is concluded that, during the first stages of body cooling, the blood acid-base status of conscious hypothermic rats is affected by PCO2 changes, apparently because of uncoupled changes between ventilation and metabolism, but it is also affected by a transitory metabolic disorder due to ion imbalance.
Reticulospinal neurons with and without monosynaptic inputs from cerebellar nuclei
Authors: Eccles J. C. , Nicoll R. A. , Schwarz W. F. , Taborikova H. , Willey T. J.
Published: December 2017

An account is given of the responses of 557 medial reticular neurons with axons projecting down the spinal cord. All 30 experiments were on decerebrated unanesthetized cats paralyzed by Flaxedil. Recording from single neurons was by extracellular glass microelectrodes. Identification was first by location (confirmed by subsequent histology) in the medial reticular nucleus of medulla or pons, and second by antidromic activation from cord stimulation at C2 and L2 segmental levels. Axonal conduction velocities were calculated from the latency differential between L2 and C2 antidromic responses, and were usually in the range of 90-140 m/s; but about 25% were slower, ranging down to 30 m/s. Stimulation by electrodes in the ipsilateral and contralateral fastigial nuclei differentiated reticulospinal neurons into two classes according to whether they did or did not receive monosynaptic inputs, the respective populations of fully investigated neurons being 270 and 174. The fastigioreticular neurons were distinguished by a higher background frequency with mean values of 28 as against 15/s. There were also significant diffences in both the excitatory and inhibitory responses to afferent volleys from forelimb and hindlimb nerves. Comparison of the respective latency histograms showed that the responses of neurons with a fastigial input had an excess of latencies in the ranges that can be correlated with the latency histograms observed for fastigial responses. Thus, there is evidence for the effectiveness of the fastigial input and so for the pathway with monosynaptic linkage: Purkinje cells of cerebellar vermis yields fastigial neurons yields medial reticular neurons projecting down the spinal cord. Adequate stimulation of cutaneous receptors by pad taps and air-jet stimulation of hairy skin in a disppointingly small action when compared with fastigical responses. Explanations of this deficiency are suggested. Another discrpancy from the fastigial responses is that the medial reticular neurons have much wider receptive fields with little discrimination between ipsilateral and contralateral and between forelimb and hindlimb. Stimulation of the ipsilateral tegmental tract was tested on 183 reticulospinal neurons, 112 being with fastigial inputs. In about half there was a powerful monosynaptic excitation, which would identify such neurons as being on the pathway from mesencephalic and diencephalic centers to the spinal cord. There is a general discussion of transmission across successive synaptic relays, where specificity is sacrificed to integration.
Capacities of humans and monkeys to discriminate vibratory stimuli of different frequency and amplitude: a correlation between neural events and psychological measurements
Authors: LaMotte R. H. , Mountcastle V. B.
Published: December 2017

The capacities of monkeys and humans to discriminate between mechanical sinusoids differing in amplitude or frequency were measured in a two-alternative, forced-choice task. The difference limen for amplitude discrimination for both species remained constant near 10% of the standard amplitude over the range of 17-30 dB, relative to detection threshold. Equal subjective intensity curves in the 20-40 Hz range were determined at 20 and 29 dB, relative to detection threshold. These curves followed the threshold curve and were identical for the two species. The difference limen for frequency discrimination averaged 1.8 Hz for humans and 2.7 Hz for monkeys; the range of values for the two species overlapped nearly completely. The small sizes of these difference limens indicate, we believe, the capacity of highly trained individuals of either species to ascertain small differences in the temporal order of somesthetic stimuli and of the neural events evoked by them. In one series of experiments we demonstrated that subjects of both species possess two threshold for two different aspects of flutter-vibration which are displaced from each other along the intensive continuum. For either species, the minimum level of stimulus amplitude required for threshold frequency discrimination is about 8 dB above that sufficient for detection. This difference in amplitude is called the atonal interval and matches that observed between absolute and tuning thresholds for quickly adapting, mechanoreceptor afferents (the Meissner afferents) which innervate the glabrous skin of the monkey hand. These and previous findings have permitted a number of direct correlations between behavioral and neural events as regards the sense of flutter. The neural codes for the intensity and frequency of flutter appear to be different. The capacity to detect the presence of a mechanical sinusoid and the capacity to judge its subjective intensity are likely to depend on criterion levels of activity in the total population of Meissner afferents, the former on the appearance of any activity (absolute threshold) in a small population of the most sensitive of these fibers and the latter on the overall size of the active population of neuronal elements at each level of amplitude. The total activity in the relevant neural population elicited by sinusoids of increasing amplitude defines a prothetic continuum along which subjects can judge the magnitude of sensation..