bluuebunny/crossref_metadata_2025 huggingface dataset:
Action potential correlates of pressure-induced changes in cardiac conduction
Authors: Doubt T. J. , Hogan P. M.
Published: December 2017

Microelectrode studies were undertaken to determine the cellular bases for hydrostatic pressure effects on impulse propagation and refractoriness in cardiac muscle. Canine Purkinje fibers, at 37 degrees C, were exposed to increases in hydrostatic pressure to 150 ATA. At 150 ATA membrane excitability was depressed and the maximum upstroke velocity (Vmax) of the action potential was reduced by 10%. Furthermore, the curve relating Vmax to takeoff potential (membrane responsiveness relation) shifted downward and to the right with the half inactivation voltage shifting in the hyperpolarizing direction by about 4 mV. Decreases in excitability and responsiveness occurred concomitantly with pressure-induced decreases in impulse conduction. Action potential duration (APD) increased significantly at 150 ATA. APD measured at -20 mV, -60 mV, and at maximum repolarization averaged 20.7, 15.5, and 13.5% longer than their respective 1-ATA values. The combined effects of increased APD and depressed responsiveness account for increased tissue refractoriness. The implications of the findings with regard to the arrhythmogenic nature of high hydrostatic pressure are discussed.
Measurement of pulmonary edema in intact dogs by transthoracic gamma-ray attenuation
Authors: Simon D. S. , Murray J. F. , Staub N. C.
Published: December 2017

We evaluated the attenuation of the 122 keV gamma ray of cobalt-57 across the thorax of anesthetized dogs as a method for following the time course of lung water changes in acute pulmonary edema induced by either increased microvascular permeability or increased microvascular hydrostatic pressure. The gamma rays traversed the thorax centered on the seventh rib laterally where the lung mass in the beam path was greatest. Calibration measurements in isolated lung lobes demonstrated the high sensitivity and inherent accuracy of the method over a wide range of lung water contents. In control dogs reproducibility averaged +/-3%. Increased permeability edema led to large rapid increases in the transthoracic gamma ray attenuation (TGA), while increased pressure caused an immediate, modest increase in TGA (vascular congestion) followed by a slow further increase over 2 h. There was a fairly good correlation between the increase in extravascular lung water and the change in TGA. The method is simple, safe, and noninvasive and appears to be useful for following the time course of lung water accumulation in generalized lung edema in anesthetized animals.
Middle ear gas exchange in isobaric counterdiffusion
Authors: Dueker C. W. , Lambertsen C. J. , Rosowski J. J. , Saunders J. C.
Published: December 2017

Nitrous oxide entry into the middle ear gas space was studied in cats in relation to anesthesia and the vestibular dysfunction caused by isobaric inert gas counter-diffusion in diving. A catheter implanted in the auditory bulla was used for direct gas sampling and pressure measurements. Experiments were designed to evaluate the participation of the eustachian tube, mucosal blood vessels, and tympanic membrane in middle ear gas exchange. The eustachian tube did not contribute to N2O entry and the mucosal blood supply only contributed about one-third of the total N2O accumulation. Diffusion across the tympanic membrane accounted for most of the N2O entering the middle ear from ambient and respiratory environments containing N2O.
Hysteresis of contracted airway smooth muscle
Authors: Sasaki H. , Hoppin F. G.
Published: December 2017

How does smooth muscle tone affect the properties of airways during breathing maneuvers? We have studied the dynamic relationships of airway pressure and cross-sectional area in excised dog lobes and isolated tracheal segments during simulated breathing maneuvers. When contracted by carbachol, airways developed complex hysteretic behavior, becoming less compliant in small tidal breaths and rapid deflations, and grossly hysteretic in large tidal maneuvers. For a given sequence of maneuvers the patterns of hysteresis varied with timing. Analogous behavior was seen during length-cycling of dog trachealis muscle strips. The mechanisms suggested by the hysteretic patterns of muscle length-tensional plots are 1) slipping of contractile filaments at threshold forces during lengthening and 2) active shortening of contractile filaments that is slow relative to many respiratory events. The observed behavior indicates that measurements of pulmonary function that depend on airway caliber or stiffness should become increasingly affected by the sequence, amplitude, and timing of breathing maneuvers as smooth muscle tone increases. The stiffness for small amplitude cycling may be favorable for local control of ventilation by parenchymal smooth muscle.
Lack of intracellular bubble formation in microorganisms at very high gas supersaturations
Authors: Hemmingsen E. A. , Hemmingsen B. B.
Published: December 2017

Eucaryotic unicellular (a yeast, a cellular slime mold, and various protozoans) and two multicellular (aschelminths) microorganisms were saturated with gas at high pressures and rapidly decompressed. No effect was observed with pressures of argon up to 125 atm, nitrogen up to 175 atm, and helium up to 350 atm, showing that the induced gas supersaturations did not cause intracellular bubbles to form. With 25--50 atm higher gas pressures, the decompression usually produced killing and cell rupture, although differences in tolerances existed among the various organisms. Substantial fractions of the populations survived gas supersaturations well above the threshold values for massive spontaneous nucleation of bubbles in the water. When killing occurred, external rather than internal bubbles appeared to be the cause. Even with the 300 atm argon or nitrogen pressures, yeast cells were unaffected, apparently because of the external protection provided by their cell wall. It is concluded that the gas supersaturations required for intracellular formation of bubbles generally are at least equal to and probably higher than the bubble nucleation thresholds for water or aqueous solutions.
Effects of hypophysectomy and dexamethasone on rat adrenal response to microwaves
Authors: Lotz W. G. , Michaelson S. M.
Published: December 2017

Circulating corticosterone levels were measured to compare the adrenocortical response to acute microwave exposure of normal, hypophysectomized, or sham-hypophysectomized rats. Plasma corticosterone levels in acutely hypophysectomized rats exposed to 60 mW/cm2 for 60 min were below control levels, indicating that the microwave-induced corticosterone response observed in normal, intact rats is dependent on ACTH secretion by the pituitary. In other groups of rats pretreated with dexamethasone before being exposed to microwaves for 60 min, the corticosterone response to a 50-mW/cm2 exposure was completely suppressed by doses equal to or greater than 3.2 micrograms dexamethasone/100 g body weight. However, the corticosterone response to a 70-mW/cm2 exposure was only partially suppressed by prior administration of 3.2 or 5.6 micrograms dexamethasone/100 g BW. The evidence obtained in these experiments, in conjunction with the results of other experiments previously reported, is consistent with the hypothesis that the stimulation of the adrenal axis in the microwave-exposed rat is a systemic, integrative process due to a general hyperthermia.
Effects of graded reduction of brain blood flow on chemical control of breathing
Authors: Chapman R. W. , Santiago T. V. , Edelman N. H.
Published: December 2017

We measured ventilatory responses to CO2 (delta VI/delta PCO2) and transient hypoxia (delta VI/delta SaO2) during reductions of brain blood flow (BBF) to 70% and 50% of control in unanesthetized goats. Increase in inspiratory volume per change in CO2 tension (delta VI/delta PCO2) was measured during rebreathing with sampling of both arterial and cerebral venous blood; increase in inspiratory volume per fall in arterial oxygen saturation (delta VI/delta SaO2) was assessed by the transient N2 inhalation method. Delta VI/delta SaO2 did not significantly change at 70% BBF, but was depressed at 50% BBF. Delta VI/delta PCO2 increased (0.94 +/- 0.18 to 1.29 +/- 0.24 l . min-1 . Torr-1) at 70% BBF if arterial CO2 tension were used to represent the CO2 stimulus but was unchanged if venous CO2 tension were used. At 50% BBF, delta VI/delta PCO2 was depressed (0.38 +/- 0.13 l . min-1 . Torr-1) for both representations of the CO2 stimulus. Brain ischemia increased blood pressure and heart rate but blunted the increase in BBF caused by hypercapnia. We conclude that 1) moderate brain ischemia (70% BBF) does not affect chemosensitivity to hypoxia and CO2, 2) delta VI/delta PCO2 may not be accurately determined from PaCO2 during brain ischemia because cerebrovascular reactivity to CO2 is depressed, and 3) severe brain ischemia (50% BBF) blunts delta VI/delta SaO2 and delta VI/delta PCO2, probably as a consequence of hypoxic depression of the respiratory neurons.
Ventilatory responses to CO2 and lung inflation in tonic versus phasic REM sleep
Authors: Sullivan C. E. , Murphy E. , Kozar L. F. , Phillipson E. A.
Published: December 2017

Ventilatory responses to CO2 and to lung inflation were compared in four dogs during tonic and phasic segments of rapid-eye-movement (REM) sleep. Phasic REM sleep (P-REM) was identified by the presence of bursts of rapid eye movements, visible muscle twitchings, and frequent phasic discharges in the nuchal electromyogram. These features were absent during tonic REM sleep (T-REM). During P-REM the response of minute volume of ventilation (VI) to progressive hypercapnia (0.58 +/- 0.19 (l/min)/Torr, mean +/- SE) was significantly less than in slow-wave sleep (SWS) (1.40 +/- 0.14; P less than 0.05). In contrast, during T-REM the response (1.48 +/- 0.19) was similar to that in SWS. Similarly, during P-REM the duration of apnea (5.9 +/- 1.5 s) elicited by sustained inflation of the lungs with 1.0 liter of air, was significantly shorter than in SWS (25.8 +/- 0.8); in contrast, during T-REM the duration of apnea (17.8 +/- 3.6) was similar to that in SWS. The results indicate that previously described decreases in VI responses to CO2 and apneic responses to lung inflation during P-REM, compared to SWS, are related to the phasic phenomena of REM sleep, rather than to the REM sleep state per se.
Measurement of lung volumes from supine portable chest radiographs
Authors: Ries A. L. , Clausen J. L. , Friedman P. J.
Published: December 2017

Lung volumes in supine nonambulatory patients are physiological parameters often difficult to measure with current techniques (plethysmograph, gas dilution). Existing radiographic methods for measuring lung volumes require standard upright chest radiographs. Accordingly, in 31 normal supine adults, we determined helium-dilution functional residual and total lung capacities and measured planimetric lung field areas (LFA) from corresponding portable anteroposterior and lateral radiographs. Low radiation dose methods, which delivered less than 10% of that from standard portable X-ray technique, were utilized. Correlation between lung volume and radiographic LFA was highly significant (r = 0.96, SEE = 10.6%). Multiple-step regressions using height and chest diameter correction factors reduced variance, but weight and radiographic magnification factors did not. In 17 additional subjects studied for validation, the regression equations accurately predicted radiographic lung volume. Thus, this technique can provide accurate and rapid measurement of lung volume in studies involving supine patients.
A head-out exercise body plethysmograph
Authors: Niinimaa V. , Cole P. , Mintz S. , Shephard R. J.
Published: December 2017

A head-out exercise body plethysmograph has been developed to facilitate investigations of the extrathoracic airways. An airtight seal around the neck is provided by a pliable sheet of dental dam braced by a tubular bean bag. A set of bicycle pedals is connected by a chain drive, axle, and wall-mounted sealed ball bearing to an external ergometer. The box is air-conditioned to allow exercise up to work loads of 200 W with a temperature increase of less than 1 degree C above ambient laboratory readings. Nose, mouth, and extrathoracic airways are easily accessible for airflow and pressure measurements. O2, CO2, and humidity levels of respired air are not disturbed, verbal communication with the subject is possible, and the subject is unlikely to feel claustrophobic. The plethysmograph has a flat frequency response to 4.2 Hz; it thus functions accurately in both resting and exercise measurements of respiratory minute ventilation. The plethysmograph can also be used for determinations of nasal and oral airflow and pressure, and the study of breathing patterns.
Cerebral blood flow during normocapnic hyperoxia in the unanesthetized pony
Authors: Busija D. W. , Orr J. A. , Rankin J. H. , Liang H. K. , Wagerle L. C.
Published: December 2017

The effect of hyperoxia on cerebral blood flow (CBF) was examined in 12 unanesthetized ponies. CBF was determined using radioactive microspheres, 15 micrometer in diam, durijng inspriation of the following gases: 1) room air (control); 2) 40% I2 in N2; and 3) approximately 100% O2 with 2.2-4.5% CO2 added to maintain isocapnia. CBF did not change from control values during either level of hyperoxia. However, cerebrospinal fluid (CSF) carbon dioxide tension (PCO2) increased during 40% O2 (delta 1.0 Torr) and approximately 100% O2 (delta 2.9 Torr). This rise in CSF PCO2, not due to a change in CBF, may have resulted from a decrease in the CO2 carrying capacity of cerebral venous blood during hyperoxia (Haldane effect). Although respiration did not change during 40% O2, expired minute volume increased 25% during approximately 100% O2 due to an increase in tidal volume. This rise in respiration was not associated with changes in any of the conventional stimuli to breathing (arterial pH, O2 tension, or PCO2 or CSF pH). One possible explanation was that cerebral extracellular fluid pH, in the vicinity of the central chemoreceptors, or cerebral intracellular fluid pH changed in a direction unlike CSF pH. An alternate explanation was that the CO2 in the inspired gas activated CO2-sensitive receptors in the lungs.
Voluntary hypohydration in 10- to 12-year-old boys
Authors: Bar-Or O. , Dotan R. , Inbar O. , Rotshtein A. , Zonder H.
Published: December 2017

This study was performed to determine whether a) children voluntarily dehydrate while exercising in hot climate; b) such dehydration affects their well-being and thermoregulation. Eleven 10p to 12-yr old, partially acclimatized boys underwent two work-in-the-heat protocols (cycle rides, 45% aerobic capacity at 39 degrees C, 45% rh). During one session they drank only voluntarily when thirsty (VD). In the other, drinking was forced (FD) to replenish fluid losses. VD induced a progressively increasing fluid loss (0.3% of body wt.h-1) due to insufficient drinking (72% of intake in FD). URinary output was lower (55.7 vs. 81.6 ml.h-1) and its osmolality higher (880 vs. 523 meq.1-1) than during FD. Sweat rate, rectal (Tre) and mean skin (T-sk) temperatures, heart rate, rate of perceived exertion, sweat gland counts, blood hemoglobin, hematocrit (Hct), serum electrolytes, and total proteins did not differ between sessions. However, the rise of Tre, Hct, and proteins positively correlated with hypohydration level. It is concluded that exercising children progressively dehydrate when not forced to drink. At equal levels of % weight loss they have greater Tre rise than do lean adults.
Left ventricular performance characteristics in trained and sedentary dogs
Authors: Ritzer T. F. , Bove A. A. , Carey R. A.
Published: December 2017

Training effects on left ventricular (LV) performance were studied in 14 dogs. Nine had chronically implanted LV pressure transducers, five dogs had sham operations. Ventriculographic evaluation of LV function was performed initially in all animals. The sham-operated dogs were killed. The remaining nine dogs were divided into an exercise group (n - 5) and a sedentary group (n = 4). The exercise group ran on a treadmill for 10 wk with a progressively more rigorous routine. The trained dogs had a decreased heart rate response to graded exercise after 10 wk. At similar heart rates, LV end-diastolic volume (pre: 30.3 +/- 3.0, post: 41.8 +/- 2.4 ml) increased significantly after training (P less than 0.05), but ejection fraction was unchanged (pre: 0.68 +/- 0.03, post: 0.67 +/- 0.06). Stroke work (pre: 1848 +/- 199 X 103, post: 4968 +/- 168 X 103 dyn-cm, P less than 0.05) also increased after training. In the presence of a tachycardia, peak dP/dt and peak contractile element shortening velocity showed increases after training. No significant changes in LV volumes, pump performance, or contractility indices were found in the sedentary group. Chronic endurance training alters the size, and appears to improve pump performance of the LV.
Echocardiographic left ventricular masses in distance runners and weight lifters
Authors: Longhurst J. C. , Kelly A. R. , Gonyea W. J. , Mitchell J. H.
Published: December 2017

Sixty individuals including 17 competitive weight lifters (CWL), 12 competitive long-distance runners (LDR), 7 amateus (noncompetitive) weight lifters (AWL), 14 heavy controls (HC), and 10 light controls (LC) were studied at supine rest with echocardiographic determination of the left venticular mass (LVM) by the Penn convention. Lean body mass (LBM) was estimated by the Wilmore-Behnke method. The absolute LVM (mean +/- SE) was increased in the two competitive athlete groups compared to controls (LDR: 195 +/- 12; CWL: 190 +/- 10 vs. LC: 122 +/- 10; HC: 151 +/- 9 g). The AWL had a mass (174 +/- 20 g) intermediate between the LDR-CWL and the HC-LC groups. A significant (P = 0.033) correlation of LVM was found with LBM although the correlation coefficient was low (r = 0.276). Normalizing LVM by LBM revealed a significantly higher mass for LDR compared to all other groups but equalized CWL and HC (LDR: 3.2 +/- 0.2; CWL: 2.5 +/- 0.1; AWL: 2.5 +/- 0.2; HC: 2.3 +/- 0.2; LC: 2.0 +/- 0.2 g). These data suggest that training for competitive long-distance running (dynamic training) elevates LVM compared to nonathletic controls and CWL. On the other hand, training for weight lifting (static training) increases absolute LVM but only to the extent that LBM is increased.
Noradrenergic inhibitory innervation of canine airways
Authors: Russell J. A.
Published: December 2017

The inhibitory innervation of canine airways was examined in isolated trachealis strips and helical strips of airways having outside diameters of 5 and 1.5 mm. Exogenous norepinephrine (10-8 M to 10-3 M) did not alter resting tone but relaxed airways contracted by 10-5 M histamine. Relaxations produced by norepinephrine were antagonized by 10-6 M propranolol, demonstrating the presence of beta-adrenergic receptors. Trans-ural electric stimulation also inhibited contractions produced by histamine. These electrically induced relaxations were blocked by tetrodotoxin and were reduced in magnitude by propranolol, indicating the involvement of a sympathetic neural mechanism. The inhibitory response to electric stimulation was attenuated in airways from catecholamine-depleted dogs and abolished in four of nine catecholamine-depleted airways pretreated with propranolol. Exogenous tyramine (10-5 M) also relaxed histamine-induced contractions, and this effect was blocked by propranolol or catecholamine depletion. The study showed that beta-adrenergic receptors from the trachea to 1.5-mm airways are innervated and that this sympathetic system constitutes the primary inhibitory innervation of airway smooth muscle in the dog.
Forces involved in lobar atelectasis in intact dogs
Authors: Ford G. T. , Bradley C. A. , Anthonisen N. R.
Published: December 2017

When an excised lung lobe undergoes atelectasis, its shape differs from that observed when lobar atelectasis occurs in an intact animal: the chest wall deforms the collapsing lobe. In eight anesthetized dogs in the left lateral position we measured lung volume and transpulmonary pressure during the development of atelectasis. We then induced atelectasis of the left lower lobe with the rest of the lung maintained at FRC and measured lobar volume and "translobar" (lobar minus esophageal) pressure. Lung and lobar volumes were measured by prebreathing the animal with 88% O2-12% N2, occluding the airway and observing the increase in lung or lobar N2 concentration. When the left lower lobe alone collapsed, translobar pressures were more negative than transpulmonary pressure at the same relative volume when the whole lung collapsed. This pressure difference, which represents the deforming force applied to the lobe minus the pressure costs of deformation, averaged 3 cmH2O at 50% FRC. Infusion of 25 ml of normal saline into the pleural space sharply reduced the difference pulmonary pressure during lung collapse: this difference was abolished at 80% FRC and halved at 50% FRC. The large effect of the small volume of fluid suggested that deforming forces were largely generated in relatively local areas, such as regions of the chest wall with sharp angulation.
Effects of exercising rats during pregnancy
Authors: Wilson N. C. , Gisolfi C. V.
Published: December 2017

To determine the effects of exercise during pregnancy on the cardiovascular system of their progeny, female Sprague-Dawley rats were assigned to one of four groups: 1) trained-nontrained (T-NT) animals who ran for 7 wk at 35 m/min before but not during pregnancy; 2) T-T animals who ran at 35 m/min before and at 32 m/min during pregnancy; 3) control (C) animals who did not exercise; and 4) NT-T animals who only ran (16 m/min) during pregnancy. Significant increases in skeletal muscle cytochrome found between exercised (NT-T, T-T) and nonexercised (C, T-NT) mothers; C animals had significantly lower maximal oxygen consumption (VO2max) values than T-T animals at the end of pregnancy. Offspring mortality was greater (P less than 0.05) in the T-T compared with the C group during the 28 days following birth. Maternal exercise had no significant influence on VO2max in the offspring or on myocardial blood flow when these animals were ventilated with either hypoxic (10% O2) or normoxic (21% O2) gases. Right ventricular fiber areas were smaller (P less than 0.05) in T-T and NT-T animals compared with the T-NT group; no significant changes were observed in the left ventricle. Capillary density and fiber-to-capillary ratios were not different in either the right or left ventricle. These results indicate that mild or heavy exercise does not influence VO2max, coronary blood flow in response to stress, or myocardial structure in the male offspring of rats trained during pregnancy.
Postural effects on lung volumes and asynchronous ventilation in anesthetized horses
Authors: Sorenson P. R. , Robinson N. E.
Published: December 2017

Quasi-static pressure-volume curves and single-breath nitrogen washouts were performed simultaneously on eight anesthetized horses (average body wt = 485 kg) in left lateral, right lateral, prone, and supine postures (sequence randomized). The shift from prone to lateral or supine posture decreased expiratory reserve volume (ERV), vital capacity (VC), residual volume (RV), functional residual capacity (FRC), and total lung capacity (TLC); RV and FRC expressed as %TLC were unchanged, suggesting that in the lateral and supine postures a significant portion of the lung volume was not recruited by VC maneuvers. Phase III slope increased from 0.13 %N2/l in prone horses to 0.34 %N2/l in the lateral and supine positions. The onset of phase IV was not significantly different from FRC in the prone or laterally recombent animal, but exceeded FRC in the supine horse. The sequence of body positions had no effect on any of our results indicating that all changes in lung volumes and regional asynchronous ventilation c;n be reversed by placing the horse in the prone posture. The reduction in lung volume and increased asynchronous ventilation in the lateral and supine horse suggests that impaired gas exchange in anesthetized horses is predominantly related to posture, and not general anesthesia.
Ventilatory control during exercise with increased external dead space
Authors: Ward S. A. , Whipp B. J.
Published: December 2017

Effects of increased external dead space (VD) on ventilatory control in steady-state exercise were determined in three healthy adults. The subjects performed cycle ergometer exercise on six occasions, each with a different VD (range: 0.1--1.0 liter); work rate was incremented every 5 min by 15--20 W. Minute ventilation (VE), CO2 output (VCO2), and mean alveolar PCO2 (PACO2) were measured in the steady state. Without VD, the VE-VCO2 relationship was linear, having a small positive VE intercept, and PACO2 was constant, independent of VCO2. Increased VD was associated with an upward shift of the VE-VCO2 relationship, and an elevated PACO2, again independent of VCO2. At each work rate, the increases in VE accompanying increased VD were no greater than could be expected from a conventional CO2 inhalation study. It is concluded that increasing external dead space does not impair the ability of the human respiratory system to regulate PACO2 during exercise except for resetting the regulated PCO2 level.
Viscosity and density dependence during maximal flow in man
Authors: Staats B. A. , Wilson T. A. , Lai-Fook S. J. , Rodarte J. R. , Hyatt R. E.
Published: December 2017

Maximal expiratory flow curves were obtained from ten healthy subjects white breathing air and three other gas mixtures with different densities and viscosities. From these data, the magnitudes of the dependence of maximal flow on gas density and viscosity were obtained. The scaling laws of fluid mechanics, together with a model for the flow-limiting mechanism, were used to obtain a prediction of the relationship between the density dependence and the viscosity dependence of maximal flow. Although the data for individual subjects were too variable to allow a precise comparison with this prediction, the relationship between the mean density dependence and the mean viscosity dependence of all usbjects agreed with the theoretic prediction. This agreement supports the assumption, which is frequently made, that flow resistance rather than tissue visoelasticity is the dominant contributor to peripheral resistance. Information on the relationships between the pressure drop to the flow-limiting segment and flow, gas density and viscosity, and lung volume were also obtained.
Contraction of dog trachealis muscle in vivo: role of alpha-adrenergic receptors
Authors: Beinfield W. H. , Seifter J.
Published: December 2017

Contraction, relaxation, and longitudinal tension were recorded by isometric strain gauge arches attached to cervical tracheal muscle (CTM) in 60 spontaneously breathing dogs anesthetized with pentobarbital. Intravenous norepinephrine (NE) (3 X 10(-9), 6 X 10(-9), 1.2 X 10(-8), and 2.4 x 10(-8) mol/kg) increased spontaneous mechanical activities (SMA) and caused dose related contraction of CTM in all dogs even though there was no pretreatment with beta-blockers. These activities were first potentiated by propranolol and then prevented by phentolamine. NE briefly decreased SMA and induced CTM relaxation prior to the onset of contraction in one-third of dogs. Propranolol prevented this initial relaxation. CTM responses induced by NE were 1) not significantly altered by atropine, tripelennamine, bilateral vagotomy, curarization, and complete tracheal transection below transducer sites; 2) unrelated to passive constriction of cervical trachea associated with airway elongation; and 3) independent of reflexes initiated by elevations of systemic arterial pressure. The moles per kilogram doses of acetylcholine were found to exceed those of NE when their intravenous administration caused equal CTM contractions in the same dog. These findings are consistent with the existence of alpha-adrenergic receptors in CTM.
Small-animal ergometer
Authors: Russell J. C. , Campagna P. D. , Wenger H. A.
Published: December 2017

A continuous vertical ladder ergometer for small animals has been developed. This device, operating at a (variable) downward velocity, obliges the subject animal to climb continuously, thus imposing a steady quantifiable work rate or power output. The power output of the animal is given simply by P = W X V X 9.80 X 10(-3) sin theta, where P is the power output in watts, W the animals' weight in grams, V the ladder velocity in meters per second, and theta the angle between horizontal and the ladder surface. Wistar rats have been readily taught to climb on the ergometer and demonstrate high levels of physical effort with no injuries. Rats of 350 g body wt are able to climb at 0.25 m/s for period of 15 min. The maximal power output of rats varies between 0.5 and 1.1 W. The ergometer design is compatible with conditioning and exercise programs for small animals as well as with quantitative measurements of power output and physiological parameters such as heart rate and gas exchange.
Chronic lung lymph fistula in the goat
Authors: Winn R. , Nadir B. , Gleisner J. , Hildebrandt J.
Published: December 2017

Goats have been prepared with chronic lung lymph fistulas in a manner similar to that described in sheep. Only one thoracotomy is needed to resect the posterior portion of the caudal mediastinal lymph node and to cannulate the main efferent duct. Comparison of data from the goat and from the sheep was accomplished by infusion histamine and by increasing left atrial and systemic venous pressures. Histamine infusion resulted in an increase in lymph flow (QL) from a base-line level of 7.3 36 ml/h and an increase in lymph-to-plasma protein ratio (L/P) FROM 0.70 to 0.82 (n = 2). In goats subjected to an increase in microvascular pressure averaging 18.2 cmH2O, QL increased from a base line of 6.7 to 23.0 ml/h, while the L/P decreased by 0.21 (n = 5). Elevation of systemic venous pressure by 8-9 cmH2O did not change QL (n = 4). Thus, the cannulation in the goat is similar to the sheep in response to induced permeability edema and hydrostatic edema, and similar with respect to lymph purity tests.
Respiratory mechanics and timing during sleep in occlusive sleep apnea
Authors: Martin R. J. , Pennock B. E. , Orr W. C. , Sanders M. H. , Rogers R. M.
Published: December 2017

Six human obese subjects with the sleep apnea hypersomnolence syndrome associated with upper airway occlusion (UAO) were studied during sleep to characterize respiration. Measurements included the timing components of ventilation, pulmonary resistance, flow, and esophageal and gastric pressures before and during UAOs. During the period between UAOs, the resistance progressively increased (9.4-18.1 cmH2O/l(-1) . s, P less than 0.05) as the ventilation decreased (1.82-0.77 l/s, P less than 0.05), but without changes in esophageal pressure swings. During this period, inspiratory time-to-total cycle time decreased (0.42-0.25 s, P less than 0.05) due to expiratory phase prolongation. The apnea began after expiration and terminated on inspiration with the maximal swings in esophageal and gastric pressure near the termination. During the UAO, the respiratory cycle time decreased slightly, but the expiratory pause time was significantly shortened immediately before ventilation. We suggest that the UAO is but one aspect of this syndrome and that a decrease in central nervous system activity diminishes the respiratory drive before the onset of the UAO.
Comparison of microvascular filtration characteristics in isolated and intact lungs
Authors: Morriss A. W. , Drake R. E. , Gabel J. C.
Published: December 2017

To determine whether the microvascular membrane of isolated perfused dog lungs is damaged by the isolation procedure, we compared the filtration coefficient (Kf,c) and minimum capillary pressure (Pcc) required to cause continuous edema formation in 10 intact and 8 isolated dog lower left lobes. We used the same gravimetric technique to measure Kf,c and Pcc in both preparations. The Kf,c averaged 0.09 +/- 0.03 (SD) ml . min-1 . Torr-1 . 100 g-1 in the intact and 0.30 +/- 0.16 in the isolated lobes; Pcc averaged 20.1 +/- 4.7 and 1.7 +/- 3.6 Torr in the intact and isolated lobes, respectively. Both Pcc and Kf,c were significantly different in the two preparations (P less than 0.01). These data indicate that the increased tendency of isolated lungs to become edematous at lower pressures may be caused by damage to the microvascular membranes.
Effect of edema on pulmonary blood flow in the isolated perfused dog lung lobe
Authors: Bhattacharya J. , Nakahara K. , Staub N. C.
Published: December 2017

We determined the relationship between the amount of edema and changes in blood flow in the isolated, perfused, and ventilated lower lobe of dog lung. We held vascular pressure constant and measured lobe weight and flow continuously. Vascular pressures were set to produce minimal weight gain in four lobes (controls) and large weight gain in six lobes (edema). In all lobes, the outflow pressure exceeded alveolar pressure at end expiration (zone III conditions). The control lobes gained an average of 20% in weight over 4 h, but blood flow remained constant. They showed interstitial edema histologically and extravascular lung water was increased 38%. The edema lobes gained weight rapidly, ultimately tripling their weight. In these lobes, blood flow remained constant until lobe weight had doubled; then flow decreased progressively to low levels. These lobes showed extensive alveolar edema histologically and extravascular lung water was increased 238%. Pulmonary blood flow is not affected by interstitial edema, but is markedly reduced when alveolar flooding occurs.
Analysis of pulmonary vascular interdependence in excised dog lobes
Authors: Smith J. C. , Mitzner W.
Published: December 2017

The pressure-volume behavior of intraparenchymal extra-alveolar arteries and veins was measured at various lung inflation states by inflating and deflating the vasculatures with air. The vascular volumes at specific vascular pressures (Pv) and transpulmonary pressures (Ptp) were partitioned into components of axial length and cross-sectional area. An analysis of the interrelationships between the perivascular pressure (Px), the vascular pressure vs. cross-sectional area behavior, and the Ptp is presented. For in vivo values of Pv, at functional residual capacity, the vascular-parenchymal mechanical interaction was small and values of arterial and venous Px approximately Ppl. With increasing Ptp to 30 cmH2O, values of both the arterial and venous Px relative to Ppl (Px - Ppl) decreased to approximately -5 cmH2O, indicating that the magnitude of the vascular-parenchymal interaction with increasing Ptp is similar for both arteries and veins in the in vivo state. At any fixed Ptp, values of arterial and venous Px - Ppl decreased nearly linearly with decreasing vascular cross-sectional area. These results were generally consistent with a linear continuum elasticity solution relating stress and deformation in the perivascular parenchyma.
Effect of prenatal isoxsuprine on pulmonary oxygen toxicity in the newborn rat
Authors: Frank L. , Summerville J. , Massaro D.
Published: December 2017

Isoxsuprine, a beta-sympathomimetic agent used clinically to delay premature parturition and to possibly accelerate fetal lung maturation, was administered to pregnant rats at 48 and 24 h prior to delivery. Newborn rats were placed in 96-98% O2 (or room air) to determine if the prenatal isoxsuprine treatment compromised their tolerance to prolonged hyperoxic exposure. (Exogenous catecholamines are known to exacerbate O2 toxicity in adult animals). Survival of the isoxsuprine-treated pups in O2 (52%) was no different than for control neonates exposed to hyperoxia for 7 days (57%) (P = 0.22). Body weight, lung weight, lung protein, and DNA content of the newborns were also not altered by the prenatal isoxsuprine treatment. Lung antioxidant enzyme activities for superoxide dismutase, catalase, and glutathione peroxidase were the same at birth in the isoxsuprine-treated and control rat pups, and the enzyme activities increased in response to hyperoxic exposure in each group to an equivalent degree. Thus, in utero treatment with isoxsuprine had no apparent adverse effect on newborn rats exposed to a prolonged O2 challenge.
Muscle respiratory capacity and fiber type as determinants of the lactate threshold
Authors: Ivy J. L. , Withers R. T. , Van Handel P. J. , Elger D. H. , Costill D. L.
Published: December 2017

This study examined the relationship between the respiratory capacity of an individual's skeletal muscle and the work rate at which blood lactate accumulation begins (lactate threshold). Comparisons were also made among fiber type, VO2max, and the lactate threshold. Muscle biopsies were taken from the vastus lateralis muscle for determination of respiratory capacity and fiber type (myosin ATPase). The lactate threshold was assessed in terms of both the absolute work rate (VO2) and relative work rate (%VO2max). The capacity of muscle homogenates to oxidize pyruvate was significantly (P less than 0.01) related to the absolute (r = 0.94) and relative (r = 0.83) lactate thresholds. Significant positive correlations (P less than 0.01) were also found between the percent of slow-twitch fibers and absolute (r = 0.74) and relative (r = 0.70) lactate thresholds. The results suggest that the muscle's respiratory capacity is of primary importance in determining the work rate at which blood lactate accumulation begins. They also suggest that the proportion of slow-twitch fibers may play an important role in determining the relative lactate threshold.
Effect of work intensity and duration on recovery O2
Authors: Hagberg J. M. , Mullin J. P. , Nagle F. J.
Published: December 2017

This study was undertaken to determine the effects of exercise intensity and duration on the time course and magnitude of recovery O2. Eighteen men exercised at 50, 65, and 80% of maximal O2 consumption (VO2max) for 5 and 20 min. Each exercise bout was preceded and followed by cycling at 150 kpm.min-1, which established the base-line VO2 used in this study. The magnitude of the rapid component of recovery O2 was proportional to exercise intensity and was not altered by exercise duration. The slow component of recovery O2 was not significantly altered by exercise intensity or duration at 50 and 65% of VO2max. However, after 20 min of exercise at 80% of VO2max, the slow component of recovery 02 was 5 times (p less than 0.01) larger than after the 5-min exercise at 80% of VO2max. End-exercise blood lactate level was also higher after the 20-min bout at 80% of VO2max; however, at most, 30% of the difference between the magnitude of the slow components of recovery O2 after the 5- and 20-min rides at 80% of VO2max could be accounted for by lactate metabolism. The Q10 effect of temperature on metabolism could account for 60-70% of the slow components of recovery O2 at all work rates and durations. It could also account for the remaining 70% of the increase in the slow component after the 20-min exercise at 80% of VO2max.
Using a comb filter to describe time-varying biological rhythmicities
Authors: Brusil P. J. , Waggener T. B. , Kronauer R. E.
Published: December 2017

A modular high-pressure chamber is described. This chamber will allow stable microelectrode recordings to be made for a variety of intracellular preparations at pressure of 200-300 atmospheres absolute. Its features include internal temperature control, easy visibility, continuous perfusion, electrical penetrations, and manipulation of several internal controls while the system is at pressure. The small size and high versatility of the Wilson chamber make it a convenient and inexpensive research unit for experiments in the moderately high-pressure ranges that affect biological preparations.
A versatile high-pressure chamber for electrophysiological measurements
Authors: Parmentier J. L. , Shrivastav B. B. , Bennett P. B.
Published: December 2017

A modular high-pressure chamber is described. This chamber will allow stable microelectrode recordings to be made for a variety of intracellular preparations at pressure of 200-300 atmospheres absolute. Its features include internal temperature control, easy visibility, continuous perfusion, electrical penetrations, and manipulation of several internal controls while the system is at pressure. The small size and high versatility of the Wilson chamber make it a convenient and inexpensive research unit for experiments in the moderately high-pressure ranges that affect biological preparations.
Arachidonate raises vascular resistance but not permeability in lungs of awake sheep
Authors: Ogletree M. L. , Brigham K. L.
Published: December 2017

Prostaglandins have been implicated as mediators of pulmonary hypertension in a variety of reactions, but the agents responsible for pathological increases in lung vascular permeability have not been determined. To test the hypothesis that products of arachidonic acid metabolism produce pulmonary vasoconstriction and alter lung vascular permeability, we infused purified sodium arachidonate (25-100 micrograms . kg-1 . min-1) into chronically instrumented unanesthetized sheep prepared for collection of lung lymph. Arachidonate produced dose-related increases in pulmonary artery pressure and lung lymph flow with corresponding decreases in the lymph-to-plasma protein concentration ratio. Lung lymph responses were like those caused by mechanically elevating left atrial pressure. Infusion of indomethacin or sodium eicosatetraynoate inhibited hemodynamic and lung lymph responses to arachidonate. We conclude a) that arachidonate must be converted to prostaglandin cyclic endoperoxides to produce pulmonary hypertension and increased flow of protein-poor lung lymph and b) that under normal conditions, no detectable increase in lung vascular permeability results from either arachidonate itself or the combined products of arachidonate metabolism via cyclooxygenase and/or lipoxygenase.
Effects of hypoxia on respiratory control in neonates at high altitude
Authors: Cotton E. K. , Grunstein M. M.
Published: December 2017

The respiratory responses to acute hypoxia were investigated in 21 newborn infants in Leadville, CO. Time-related changes in pulmonary ventilation (VE) described four distinct phases to the hypoxic response characterized by an abrupt initial decrease (phase I), a transient subsequent increase (phase II) and decrease (phase III), and a further transient decrease upon termination of the hypoxic challenge (phase IV). Based on the degree of respiratory stimulation during phase II, the subjects were divided into two groups, "responders" and "nonresponders." In both groups in VE were attributed to variation in tidal volume (VT), inspiratory duration (TI), and breath duration being little affected. The latter indicated an absence of vagal volume-related modulation of respiratory pattern. In all subjects, a fixed linear function described the relationship between the mean inspiratory flows at 0.3 s after inspiratory onset (i.e., V0.3/0.3) ant at end inspiration (i.e., VT/TI). Thus, changes in respiratory output with hypoxia are attributed to variations in both the "gain" and "shape" of the inspiratory drive.
Effect of initial muscle glycogen levels on protein catabolism during exercise
Authors: Lemon P. W. , Mullin J. P.
Published: December 2017

Serum urea increases with exercise duration suggest prolonged exercise may be analogous to starvation where protein catabolism is known to occur. The purpose of this investigation was to alter muscle glycogen levels and to study the effect on protein catabolism. Six subjects (27-30 yr) pedaled a cycle ergometer for 1 h at 61% VO2max (mean VO2 = 2.33 +/- 0.7 1 . min-1) 1) after CHO loading (CHOL) and 2) after CHO depletion (CHOD). The following urea N measures were made: pre-exercise serum and urine, exercise serum and sweat (15-min serial samples), and serum and urine during 240 recovery min. Results demonstrated that 1) exercise serum urea N increased in CHOD attaining significance (P less than 0.01) at 60 min; 2) serum urea N increases continued into recovery at all measurement points of CHOD (P less than 0.01) and at 240 min of CHOL (P less than 0.05); 3) sweat urea N increased 154.2-fold (CHOD) and 65.6-fold (CHOL) (P less than 0.05). Calculations indicate that CHOD sweat urea N excretion was equivalent to a protein breakdown of 13.7 g . h-1 or 10.4% of the total caloric cost. It was concluded that protein is utilized during exercise to a greater extent than is generally assumed and that under certain conditions protein carbon may contribute significantly to exercise caloric cost.
Effect of ventilation and diffusion nonuniformity on DLCO (exhaled) in a lung model
Authors: Cotton D. J. , Graham B. L.
Published: December 2017

Recent studies have shown that diffusing capacities measured at multiple intervals during a single exhalation [DLCO(exhaled)] remained constant with lung volume in normal subjects, but decreased with decreasing lung volume in patients who may have had diffusion nonuniformity. We have examined the theoretical basis of these results by determining what factors affected DLCO(exhaled) in a computerized lung model in which diffusion in each compartment remained constant with lung volume. DLCO(exhaled) decreased with decreasing lung volume when a small lung region lacked diffusion. However, the change in DLCO(exhaled) with lung volume was also affected by nonuniform ventilation and these effects could not be eliminated by correcting the carbon monoxide decay and the simultaneous decay of helium. DLCO(exhaled) values were also influenced by the exhaled flow rate in the presence of nonuniform ventilation and/or nonuniform diffusion. However, prolonging the period of breath holding prior to exhalation reduced DLCO(exhaled) values at all lung volumes when non-uniform diffusion was simulated, but did not affect DLCO(exhaled) when only nonuniform ventilation was simulated.
Metabolic recovery from exhaustive activity by a large lizard
Authors: Gleeson T. T.
Published: December 2017

Gas exchange (VO2 and VCO2) and blood lactate concentration were measured in the lizard Amblyrhynchus cristatus at 25 and 35 degrees C during resting, running, and recovery after exhaustion (less than or equal to 180 min) to analyze the temperature dependency of metabolic recovery in this lizard. Amblyrhynchus exhausted twice as fast (4.2 vs. 8.8 min) at 25 degrees C than when running at the same speed at 35 degrees C. At both temperatures, VO2 and VCO2 increased rapidly during activity and declined toward resting levels during recovery in a manner similar to other vertebrates. Respiratory quotients (R, where R = VCO2/VO2) exceeded 2.0 after exhaustion at both temperatures. Extensive lactate production occurred during activity; blood lactate concentrations ranged from 1.0 to 1.7 mg lactate/ml blood after activity. Net lactate removal exhibited a temperature dependence. Blood lactate concentrations remained elevated hours after VO2 returned to normal. Endurance was reduced in lizards that had recovered aerobically but still possessed high lactate concentrations. The temporal separation of the excess oxygen consumption and lactate removal suggests that the concept of the lactacid oxygen debt is not applicable to this animal. The temperature dependence of total metabolic recovery suggests a benefit for Amblyrhynchus that select warm basking temperatures following strenuous activity.