bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal effects of injecting norepinephrine into hypothalamus of the rat during rest and exercise
Authors: Gisolfi C. V. , Christman J. V.
Published: December 2017

Norepinephrine (NE) was injected bilaterally through implanted guide cannulas into the anterior hypothalamus (AH) of conscious male Sprague-Dawley rats (300-360 g) at rest and just before treadmill exercise (21.5 m/min for 30 min).

Colonic (Tc), tail-skin (Ts), and ambient (Ta) temperatures were monitored each minute by use of a telethermometer. At rest (Ta = 23 degrees C), intrahypothalamic injections of 0.5-40.0 micrograms of NE, in a total of 1.0 microliter delivered within 30 s, produced a dose-dependent hypothermia with a 3-5 degrees C rise in Ts. NE (10 micrograms) injected 2 min before exercise (Ta = 23 degrees C) caused an immediate rise in Ts and a mean decline in Tc of 0.9 +/- 0.1 degree C (SE) below resting levels during exercise. This decline in Tc was statistically the same as that observed after the injections of 10 micrograms of NE at rest. Under control exercise conditions, Tc rose approximately 1 degree C and was associated with an initial decline (0.5 degrees C) followed by a rise (4.0 degrees C) in Ts. When the alpha-adrenergic receptor blocker phentolamine was injected 5-15 min before exercise, it caused a significant (P < 0.01) elevation in Tc during the ensuing exercise compared with controls. These results indicate that 1) over a dose range 0.5-40.0 micrograms, NE microinjected into the AH of the rt produces only hypothermia; 2) alpha-adrenergic receptors in the AH participate in the mediation of heat dissipation when the thermoregulatory system is challenged by the endogenous heat stress of exercise; and 3) exercise per se provides a nonthermal input to the temperature regulatory system that enhances heat dissipation.
Effect of timing, flow, lung volume, and threshold pressures on resistive load detection
Authors: Killian K. J. , Mahutte C. K. , Howell J. B. , Campbell E. J.
Published: December 2017

The acuity of resistive load detection (RLD) has been tested by comparing threshold detection (delta R50) under control conditions with that obtained when loads were applied at different times in inspiration, with different inspiratory flows, at different lung volumes, and with different background loads. For loads applied suddenly during established inspiratory flow, the mean delta R50 was 0.94 +/- 0.04 (+/- SEE) cmH2O . 1(-1) . s compared with 0.42 +/- 0.13 cmH2O . 1(-1) . s (P < 0.01) for loads applied before inspiration, suggesting that information generated early in the breath is important and the RLD is not subserved by a simple peripheral proprioceptive mechanism. Rapid voluntary inspiration through nonlinear resistances did not improve RLD (mean delta R50 0.86 cmH2O . 1(-1) . s compared with a control of 0.56 cmH2O . 1(-1) . s; P < 0.05) despite the much greater pressures and resistances at high flow rates, further suggesting that detection of a resistive load occurs early in inspiration. Alteration of the background load by breathing at increased lung volume (1 liter above FRC) or by breathing against a standing pressure of 1 or 3 cmH2O (i.e., pressure independent of volume or flow) did not significantly reduce RLD. This suggests that the change in pressure due to the added load, expressed as a fraction of the total driving pressure, cannot subserve RLD. Our results suggest that external resistive load detection is subserved by the relation between pressure and flow over the early part of inspiration.
A theoretical model of protein, fluid, and small molecule transport in the lung
Authors: Harris T. R. , Roselli R. J.
Published: December 2017

The purposes of this research were to derive a mathematical model of blood-intestinal transport for the lung and to study the ability of this model to describe the results of previous lymph-collection and multiple-indicator experiments on the lungs of unanesthetized sheep. We used a three-pore model of the microvascular barrier to describe lymph flow, lymph-to-plasma ratios (L/P) of eight endogenous proteins, and the microvascular permeability-surface area (PST) of the lungs to [14C]urea in sheep experiments under base-line conditions and after acute elevation of the left atrial pressure. The results indicate that endothelial pathways consisting of a small pore (28 A), intermediate pore (180 A), and a large pore (1,000 A) can describe experimental L/P values and PST. The description of lymph flow required either than interstitial fluid pressure increase with left atrial pressure or that postcapillary venous resistance decrease relative to precapillary values. We concluded that multiple-pore theory is a useful approach to the description of lung blood-interstitial transport.
Cardiac responses to exercise training in male and female rats
Authors: Schaible T. F. , Penpargkul S. , Scheuer J.
Published: December 2017

The purpose of the present study was to determine if contractile function adapts to physical training in the same way in hearts of male and female rats. Male and female rats were trained with a running program sufficient to cause equal increases in cytochrome oxidase activity in gastrocnemius muscles in both groups. Hearts were then studied in an isolated perfused working rat heart apparatus with varying preloads and fixed afterloads. Five groups were studied: 1) free-eating sedentary males (MS-FE); 2) running males (MR); 3) sedentary females (FS); 4) running females (FR); and 5) food-restricted sedentary; males (MS-FR). Heart weights were similar in MS-FE and MR and in FS, FR, and MS-Fr. Stroke work, stroke volume, coronary flow, and myocardial oxygen consumption were significantly higher in MR than in MS-FE but were almost identical in FR and FS. MS-FR showed stroke work, stroke volume, and ejection fractions that were similar to MR but higher than MS-FE and both female groups. Thus when hearts of equal weights were compared, a training effect was only seen in males. These results suggest that despite similar skeletal muscle adaptations, hearts of male rats adapt to physical training by running with improved intrinsic performance, whereas hearts of female rats do not.
Cat carotid body: oxygen consumption and other parameters
Authors: Whalen W. J. , Nair P. , Sidebotham T. , Spande J. , Lacerna M.
Published: December 2017

Cats were anesthetized with pentobarbital, pump ventilated with air, and given heparin, and the carotid body (CB) was vascularly isolated except for the supplying artery. The CB could be normally blood perfused, or alternatively, perfused with Locke's solution; flow of either could be stopped suddenly. Sinus nerve discharge was measured. Tissue oxygen tension (TPO2) in the CB was measured with an O2 microelectrode. Oxygen consumption rates (VO2) calculated from the disappearance curve of O2 during stopped flow were PO2 dependent. When TPO2 was high (100-130 Torr), VO2 (ml.100 g-1.min-1) averaged 1.9 +/- 0.18 (SE) during blood perfusion and either 1.9 +/- 0.1 during perfusion with Locke's solution equilibrated with 25% O2-5% CO2-70% N2 or 1.4 +/- 0.08 when the Locke's solution was equilibrated with air. This significant effect of CO2 could have been due to the delayed onset of sinus nerve discharge when CO2 was not added to the perfusion solution. The number of red blood cells in histological sections from CB frozen during stopped flow of blood was significantly below normal. We concluded that the similarity of the disappearance curves during stopped flow of blood and Locke's solutions was primarily due to the extrusion of red blood cells. In five experiments the broken-off tip of the O2 microelectrode was found in the core of the CB.
Sensitivity of forced expiration indices to induced changes in peripheral airway resistance
Authors: Racineux J. L. , Peslin R. , Hannhart B.
Published: December 2017

To assess the actual sensitivity of forced expiration indices to changes in the resistance of peripheral airways, maximal expiratory flow-volume curves were obtained in 30 normal subjects breathing air and breathing an O2-Ne-SF6 gas mixture having the same density as air but a 45% larger viscosity. The measurements were made using a bag-in-box system to circumvent calibration problems, and the data were processed digitally. Besides the usual forced expiration indices, slope ratios, as described by Mead (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 44: 156-165, 1978), and transit time indices were also computed. Breathing the viscous mixture, the largest changes were seen with the slope ratio measured at 60% forced vital capacity, followed by other slope ratios, the standard deviation of transit times, and maximal flows at low lung volumes. However, when the data were compared using the t test for paired measurements, the most significant changes were found with the forced expiratory volumes at 1 and 2 s, due to their low within-subject variability. These indices may therefore by considered as the most suitable for detecting changes in individuals.
Effects of added inspiratory loads on load detection thresholds
Authors: Burki N. K.
Published: December 2017

To examine the effects of continuously added background inspiratory loads on the difference thresholds for resistive (delta R50) and elastic load detection (delta E50), 12 healthy subjects were studied. The results showed that, whereas the addition of a constant background elastic load significantly altered delta R50, the addition of a constant background resistive load did not significantly affect delta E 50. These results can be explained on the basis that the addition of a constant elastic load alters the total sensory information a midbreath, where resistive load detection occurs, but the addition of a constant resistive load does not affect elastic load detection, which occurs at the end of the breath where flow-dependent information is minimal.
Role of platelet serotonin in the canine pulmonary response to endotoxin
Authors: Murphy T. L. , Allison R. C. , Weisman I. M. , McCaffree D. R. , Gray B. A.
Published: December 2017

There is evidence suggesting a role for platelet serotonin (5-HT) in the immediate pulmonary response to endotoxin in the dog (J. Appl. Physiol. 23: 47, 1967). To further define this role, autologous canine platelets were labeled with 5-[14C]HT in vitro and then reinfused. Subsequently Escherichia coli endotoxin (0.55:B-5, Difco), 2.5 mg/kg, was injected. Within 5 min dynamic compliance (CL) fell by more than 50%, and nonelastic resistance (RL) increased by more than 200%. Despite a 95% decrease in platelet count, less than 10% of the platelet 5-HT was released as determined by changes in the radioactivity of platelet-poor plasma (PPP) prepared from both aortic and pulmonary artery blood. As a positive control, injected of bovine collagen produced a similar decrease in platelet count that was associated with a significant increase in the radioactivity of aortic and pulmonary artery PPP. FInally, rapid injection of a dose of 5-HT equivalent to 25% of the 5-HT in circulating platelets did not cause a change in CL or RL equivalent to that produced by endotoxin. From these data we conclude that endotoxin injection does not cause immediate massive platelet activation and that platelet 5-HT does not play a major role in the immediate pulmonary response to endotoxin.
Use of an acoustic helium analyzer for measuring lung volumes
Authors: Krumpe P. E. , MacDannald H. J. , Finley T. N. , Schear H. E. , Hall J. , Cribbs D.
Published: December 2017

We have evaluated the use of an acoustic gas analyzer (AGA) for the measurement of total lung capacity (TLC) by single-breath helium dilution. The AGA has a rapid response time (0-90% response = 160 ms for 10% He), is linear for helium concentration of 0.1-10%, is stable over a wide range of ambient temperatures, and is small and portable. We plotted the output of the AGA vs. expired lung volume after a vital capacity breath of 10% He. However, since the AGA is sensitive to changes in speed of sound relative to air, the AGA output signal also reports an artifact due to alveolar gases. We corrected for this artifact by replotting a single-breath expiration after a vital capacity breath of room air. Mean alveolar helium concentration (HeA) was then measured by planimetry, using this alveolar gas curve as the base line. TLC was calculated using the HeA from the corrected AGA output and compared with TLC calculated from HeA simultaneously measured using a mass spectrometer (MS). In 12 normal subjects and 9 patients with chronic obstructive pulmonary disease (COPD) TLC-AGA and TLC-MS were compared by linear regression analysis; correlation coefficient (r) was 0.973 for normals and 0.968 for COPD patients (P less than 0.001). This single-breath; estimation of TLC using the corrected signal of the AGA vs. Expired volume seems ideally suited for the measurement of subdivisions of lung volume in field studies.
Control of exercise-induced muscular glycogenolysis by adrenal medullary hormones in rats
Authors: Richter E. A. , Galbo H. , Christensen N. J.
Published: December 2017

We have previously shown that adrenodemedullation combined with chemical sympathectomy decreases the exercise-induced muscular glycogen breakdown in rats. Now we have elucidated to what extent the effect of combined adrenodemedullation and sympathectomy can be ascribed to the lack of either the adrenal medulla or of the peripheral sympathetic nerve endings. Rats were either adrenodemedullated or underwent sham operation and subsequent unilateral hindleg sympathectomy. Three weeks after adrenodemedullation and 1 wk after sympathectomy, the rats either rested or swam with a tail weight for 75 min or continued swimming to exhaustion. The exercise-induced muscular glycogenolysis was markedly impeded by adrenodemedullation but not by sympathectomy. During the first 75 min of exercise, hepatic glycogenolysis was decreased in adrenodemedullated rats compared with sham-operated rats, and blood glucose only increased in the latter. At exhaustion, plasma insulin and glucagon were higher and lower, respectively, in adrenodemedullated rats than in sham-operated rats, whereas blood glucose did not differ significantly between these groups. During prolonged swimming in rats, adrenomedullary hormones enhance muscular glycogenolysis, glucagon secretion, and the early hepatic glycogenolysis but inhibit insulin secretion.
A test to determine parameters of aerobic function during exercise
Authors: Whipp B. J. , Davis J. A. , Torres F. , Wasserman K.
Published: December 2017

A short-duration cycle ergometer exercise test has been developed that allows four parameters of aerobic function to be discerned. These are the maximum O2 uptake, anaerobic threshold, work efficiency, and the time constant for O2 uptake kinetics. The test form is a ramp of 4-8 min duration to the limit of tolerance. The parameters determined from the ramp faithfully reproduced those obtained from several standard procedures. We conclude that a profile of aerobic function in man can be obtained from a single short-duration ramp test.
Chest wall shape during forced expiratory maneuvers
Authors: Melissinos C. G. , Goldman M. , Bruce E. , Elliott E. , Mead J.
Published: December 2017

Abdominothoracic shape during the forced vital capacity was studied in 10 normal subjects using magnetometers to monitor anteroposterior diameters at the level of the manubrium, xiphoid, and epigastrium, lateral rib cage diameter at the xiphoid level, and vertical motion of the rib cage. Thoracic cross-sectional area change at the xiphoid level was found to lag lung volume change, due to an early paradoxical increase (or lack of change), of lower anteroposterior rib cage diameter. To the extent that the resulting rib cage deformation can influence the pleural pressure gradient, the observed shape changes provide a potential mechanism for early preferential emptying of the upper lobes and later more homogeneous emptying in forced, compared to slow, vital capacity maneuvers. Comparisons of shape changes during Valsalva and abdominal expiratory ("expulsive") maneuvers suggest that lower rib cage deformation may not simply be due to the action of rib cage muscles affecting predominantly the lateral rib cage but rather the results of diaphragmatic activity and the influence of abdominal shape on the lower rib cage.
Exercise and the cAMP system in rat adipose tissue II. Nucleotide catabolism
Authors: Palmer W. K. , Kalina C. A. , Studney T. A. , Oscai L. B.
Published: December 2017

In this study the effect of exercise training on the adenosine 3',5'-cyclic monophosphate (cAMP) system of rat adipose tissue has been investigated. The basal amount of cAMP for the exercising rats was 0.179 +/- 0.021 nmol/10(6) cells, the same value as for the controls. Phosphodiesterase activities (low and high Km) remained unaffected as a result of the program of treadmill running. Kinetic constants for the low- and high-Km phosphodiesterases revealed that the affinity of the enzymes for substrate (cAMP) was unaltered by physical training. Finally, ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid, possibly through its effect on calmodulin, stimulated or inhibited (depending on concentration) phosphodiesterase activity in the same direction and to a similar extent in extracts of adipose tissue from runners and controls. Taken together, these data clearly demonstrate the exercise training has no effect on the cAMP system of adipose tissue in male rats.
Effect of a constant arterial CO2 tension on respiratory pattern in hear-stressed sheep
Authors: Maskrey M. , Hales J. R. , Fawcett A. A.
Published: December 2017

Sheep were exposed in a climate chamber to a hot humid environment under two conditions: breathing atmospheric air and breathing air enriched with CO2. Measurements were made of rectal temperature (Tre), respiratory frequency (fR), mean arterial pressure (BP), heart rate (fH), and arterial O2 tension (PO2), CO2 tension (PCO2), and pH; depth of breathing was also estimated. Tre increased at a similar rate under both conditions. When breathing air, sheep exhibited rapid shallow panting followed by slower deeper (second phase) breathing during which they became severely hypocapnic and alkalotic. When the sheep breathed CO2-enriched air at a rate allowing normocapnia to be maintained, fR was lower and the depth of breathing greater, but the sequence of changes in respiratory activity was similar to that with air breathing. BP, fH, and PO2 each increased to a similar extent under both conditions. It is concluded that the normal biphasic panting response to severe heat stress in sheep is largely independent of arterial PCO2.
Distribution of vesicles in cells of air-blood barrier in the rabbit
Authors: Gil J. , Silage D. A. , McNiff J. M.
Published: December 2017

Vesicular transport has been proposed as a pressure-independent shuttle mechanism for transport of macromolecules across thin cells. The vesicular populations of cells found in the gas-exchanging parenchyma were quantitated by morphometric means. We found that the numerical densities (number of vesicles/unit of volume) were comparable in endothelial (131/micrometer 3) and epithelial (145/microm3) type I cells but much smaller for interstitial cells. The vesicular loads or numbers of vesicles/unit of surface area were computed separately for each cell front (luminal and abluminal) and found to be similar for all surfaces, ranging from 150 to 196/micrometer 2 except for the interstitial front of epithelial cells where the load was higher (230/micrometer 2). Although this represents a very high transport potential, little can be said about vesicular effective performance because of insufficient knowledge of vesicular biology and biophysics. A frequent observation in the capillary network is attenuations of endothelial cells, which are thinner than the vesicular diameter and devoid of vesicles.
Single motor unit activity in the diaphragm of cat during pressure breathing
Authors: Bishop B. , Settle S. , Hirsch J.
Published: December 2017

In this study we analyzed the breath-by-breath activity of single motor units in the diaphragm slip of allobarbital-anesthetized cats during quiet breathing and during continuous positive- and negative-pressure breathing. Our objective was to determine whether single motor units, on the basis of their activities, can be separated into discrete subpopulations or whether they fall on a continuum analogous to that of motor units of hindlimb muscles. The firing profiles of each unit were characterized for each pressure level by the onset and peak firing frequencies, onset latency, duration of firing, number of impulses per breath, and minimal frequency, when appropriate. Units with shorter onset latencies had higher peak frequencies, longer firing durations, and increased firing frequencies than did units with longer onset latencies. These comparative relationships persisted even though the activity of every motor unit was altered during pressure breathing. During positive-pressure breathing onset latencies were lengthened, and durations of firing were shortened with little change in onset or peak frequencies. Late units might be silenced. During negative-pressure breathing onset latencies were shortened, and durations of firing were lengthened, sufficiently in some cases to fill the expiratory pause. In addition, previously inactive units were recruited late in inspiration for short, relatively high frequency bursts during inspiration. The results support the concept that the phrenic motoneuron pool is comprised of three discrete subpopulations.
Effects of hypoxia on density of beta-adrenergic receptors
Authors: Voelkel N. F. , Hegstrand L. , Reeves J. T. , McMurty I. F. , Molinoff P. B.
Published: December 2017

Exposure to chronic hypoxia results in a lower resting heart rate and a blunted cardiovascular responsiveness to beta-adrenergic receptor stimulation. Possible effects of acclimatization to high altitude on the binding of [125I]iodohydroxybenzylpindolol to beta-adrenergic receptors on membranes of right and left ventricles of rat heart were determined. Chronic high-altitude exposure led to a decrease in the density of beta-adrenergic receptors in nonhypertrophied left ventricles as well as in hypertrophied right ventricles. The affinity of the receptor for the radioligand was not changed by the exposure to high altitude, suggesting that the properties of the receptor were not affected. Basal and isoproterenol-stimulated adenylate cyclase activities were decreased in membranes prepared from hearts and pulmonary arteries of rats acclimatized to high altitude. The loss of cardiac beta-adrenergic receptors in rats adapted to high altitude was prevented by the chronic coadministration of a low dose of DL-propranolol. The results suggest that changes in beta-adrenergic receptor density may partially explain the hemodynamic adaptation that occurs with chronic hypoxia. These decreases may be due to a loss of functional beta-adrenergic receptors caused by chronically elevated concentrations of circulating neurally released catecholamines.
Age and altitude tolerance in rats: temperature, plasma enzymes, and corticosterone
Authors: Altland P. D. , Rattner B. A.
Published: December 2017

Tolerance to a 4-h altitude exposure (6,096-8,230 m) was determined in immature, young, and old male rats. The critical survival thresholds were 8,230 m for immature rats and 7,620 m for young and old rats. Hypothermia in immature rats was directly related to hypoxic severity. Body weight loss, elevated plasma corticosterone concentration, and a mean body temperature of 32.5 degrees C were characteristics of immature rats that survived at the critical threshold. Body temperature, weight change, and plasma corticosterone concentration were similar at all altitudes in young adult and old rats. Plasma enzyme activities were relatively unchanged in immature rats, but aspartate aminotransferase (EC 2.6.1.1) and lactate dehydrogenase (EC 1.1.1.27) activities in old rats, in addition to fructose-diphosphate aldolase (EC 4.1.2.13) activity in young adults, were initially elevated (P less than 0.05) at the critical survival threshold (7,620 m). Body temperature and plasma corticosterone (but not plasma enzyme activities) are important criteria for determining altitude tolerance of immature rats. However, plasma asparatate aminotransferase and lactate dehydrogenase activities are more suitable criteria for assessing tolerance in young adult and old rats.
Inhibitory innervation to the guinea pig trachealis muscle
Authors: Yip P. , Palombini B. , Coburn R. F.
Published: December 2017

The inhibitory innervation of the cervical trachea was studied in situ in anesthetized male guinea pigs. We measured effects of electrical stimulation of vagal motor and sympathetic trunk nerve fibers, during atropine, on trachealis muscle tension. Effects of direct transmural stimulation of trachealis muscle were also determined. We confirmed the dual nature of the inhibitory innervation to this muscle. Vagal motor inhibitory nerves are shown to be preganglionic. Neural transmission at the level of the ganglia is characterized by filtering of high frequency action potentials. The neurotransmitter at the myoneural junction is unidentified but is not norepinephrine. Maximal relaxation accounts for about 20-40% of maximal relaxations seen with transmural stimulation of trachealis muscle in the presence of atropine. Sympathetic trunk nerve fibers are also preganglionic. Neurotransmission at the level of the ganglia is apparently 1:1 at high-action potential frequencies. Norepinephrine released presynaptically has access to smooth muscle beta- but not alpha-receptors. Maximal adrenergic relaxations account for 60-80% of total transmural stimulation relaxations. Transmural stimulation relaxations appear to be accounted for by release of neurotransmitter from sympathetic adrenergic plus vagal nonadrenergic postganglionic nerve fibers.
Prostaglandin E1 uptake by isolated cat lungs perfused with physiological salt solution
Authors: Linehan J. H. , Dawson C. A. , Wagner-Weber V. M.
Published: December 2017

The instantaneous extraction of prostaglandin E1 (PGE1) was measured after a bolus injection of PGE1 and [14C]dextran in to the pulmonary artery of isolated cat lungs perfused with a physiological salt solution [Krebs-Ringer-bicarbonate buffer (KRB)]. The extraction ratio vs. time curves exhibited characteristic shapes. For low injected doses of PGE1, the extraction ratios were constant early in time, whereas for high doses, they were concave upward. To evaluate the data, we used a model assuming homogeneous perfusion and a saturable uptake mechanism (Michaelis-Menten kinetics) for the PGE1. The model was used in a linear regression analysis to estimate Vmax and Km. The kinetic parameters were compared with our previous results for blood-perfused lungs, and it was found that the values of Km were significantly smaller than in blood-perfused lungs but that the values of Vmax were not significantly different. These results were consistent with the observation that PGE1 uptake was greater in KRB- than in blood-perfused lungs when the dose of PGE1 was low but that the difference disappeared at high doses. The absence of plasma protein binding in KRB-perfused lungs may be responsible for the lower Km.
Respiratory neuromuscular output during breath holding
Authors: Whitelaw W. A. , McBride B. , Amar J. , Corbet K.
Published: December 2017

The involuntary respiratory muscle contractions that occur during breath holding were found in almost all of 52 subjects and were regular in a majority. In detailed studies, subjects rebreathed a mixture of 8% CO2 in O2 and then held their breath on an occluded mouthpiece, with glottis open, at functional residual capacity. Contractions monitored as waves of negative pressure were reproducible and increased in amplitude and frequency through the breath hold, but the breakpoint did not always correspond to the same pressure or frequency. Frequency and the time derivative of pressure (dP/dt) of contractions were much higher during breath holding than frequency of breathing and dP/dt of occluded breaths at the same gas tensions during rebreathing. Contractions were reduced in amplitude after the subject took three breaths without altering gas tensions. The results are consistent with the hypothesis that contractions contribute to dyspnea in breath breath holding, but there is not a simple correlation between their magnitude and the degree of dyspnea.
Blood oxygen content in microliter samples using an easy-to-build galvanic oxygen cell
Authors: Grubb B. R. , Mills C. D.
Published: December 2017

We have designed a simple, inexpensive, easy-to-build and operate apparatus for measuring blood oxygen content. The galvanic oxygen cell (fuel cell) requires as little as 1 microliter of blood and has a measuring time of 1-3 min. It is well suited for measuring oxygen content in fluids low in oxygen inasmuch as the sensitivity of the instrument is variable. Either air or water (at a known temperature and oxygen tension) can be used for calibration. No significant differences in blood oxygen content measured with our cell or the Van Slyke manometric method were found.
Temperature regulation in the dog in helium-oxygen environments
Authors: Stein P. M. , Ederstrom H. E.
Published: December 2017

Helium-oxygen mixtures have been reported to alter thermoregulation in humans and animals because of convective heat transfer differences between a helium-oxygen and a nitrogen-oxygen environment. Thermoregulation in unrestrained dogs was tested in a chamber at temperatures of 23, 33, and 43 degrees C, in air or 80% helium-20% oxygen (HeO). Respirations in air in these temperatures were 15, 134, and 322 breaths/min, respectively. Heart rates increased with chamber temperature, averaging 69 at 23, 82 at 33, and 103 beats/min at 43 degrees C. In HeO, responses to increasing temperatures differed from air. Respiration was 13 at 23, 49 at 33, and 336 breaths/min at 43 degrees C. Heart rates were 79 at 23, 70 at 33, and 97 at 43 degrees C. Rectal temperatures rose in both atmospheres at 43 degrees C. Shivering occurred in dogs in HeO at 23 degrees C but not in air. Results indicated that the dogs' thermoregulatory responses were markedly different in the two gas mixtures due to convective heat transfer differences, which were especially noticeable when responses in HeO at 33 degrees C were compared to those in air.
Pathophysiology of gas exchange and pulmonary perfusion in pneumococcal lobar pneumonia in dogs
Authors: Light R. B. , Mink S. N. , Wood L. D.
Published: December 2017

We placed an inoculum of Streptococcus pneumoniae type III into a left lower lobe bronchus of six dogs (group P), and in six other dogs (Group C) a sterile control inoculum was used. Measurements of shunt (Qs/Qt) and venous admixture (Qva/Qt) were made immediately before (day 1) and 48 h after (day 3) inoculation. All dogs in group P had extensive lobar pneumonia confirmed radiologically and at autopsy, whereas Group C had only small sterile lesions at the site of inoculation. In group P, mean Qs/Qt and Qva/Qt increased significantly to 0.15 and 0.21, respectively. Mean lobar Qs/Qt, calculated using blood samples from lobar veins at thoracotomy on day 3, was markedly increased in the pneumonia lobe (0.69) compared with the contralateral lower lobe (0.08), and alveolar ventilation of that lobe approached zero. Perfusion of the infected lobe determined by radioactive microspheres showed a variable and statistically nonsignificant decrease between control and infected states that was not affected by oxygen breathing. In group C there was no change between days 1 and 3 in gas exchange or in distribution of pulmonary perfusion. We conclude that hypoxemia in pneumonia was due to both increased shunt and venous admixture in the infected regions, and that local hypoxic vasoconstriction was in most instances ineffective in directing blood flow away from the consolidated lobe.
Detection of diaphragmatic fatigue in man by phrenic stimulation
Authors: Aubier M. , Farkas G. , De Troyer A. , Mozes R. , Roussos C.
Published: December 2017

Transdiaphragmatic pressure (Pdi) was measured at functional residual capacity (FRC) in four normal seated subjects during supramaximal, supraclavicular transcutaneous stimulation of one phrenic nerve (10, 20, 50, and 100 Hz--0.1 ms duration) before and after diaphragmatic fatigue, produced by breathing through a high alinear inspiratory resistance. Constancy of chest wall configuration was achieved by placing a cast around the abdomen and the lower one-fourth of the rib cage. Pdi increased with frequency of stimulation, so that at 10, 20, and 50 Hz, the Pdi generated was 32 +/- 4 (SE), 70 +/- 3, and 98 +/- 2% of Pdi at 100 Hz, respectively. After diaphragmatic fatigue, Pdi was less than control at all frequencies of stimulation. Recovery for high stimulation frequencies was complete at 10 min, but at low stimulation frequencies recovery was slow: after 30 min of recovery, Pdi at 20 Hz was 31 +/- 7% of the control value. It is concluded that diaphragmatic fatigue can be detected in man by transcutaneous stimulation of the phrenic nerve and that diaphragmatic strength after fatigue recovers faster at high than at low frequencies of stimulation. Furthermore, it is suggested that this long-lasting element of fatigue might occur in patients with chronic obstructive lung disease, predisposing them to respiratory failure.
Relative responses of aortic body and carotid body chemoreceptors to carboxyhemoglobinemia
Authors: Lahiri S. , Mulligan E. , Nishino T. , Mokashi A. , Davies R. O.
Published: December 2017

The effects of carbon monoxide inhalation and of consequent carboxyhemoglobinemia (HbCO) on the discharge rates of aortic body and carotid body chemoreceptor afferents were investigated in 18 anesthetized cats. In 10 experiments both aortic and carotid chemoreceptor activities were monitored simultaneously. Carbon monoxide inhalation during normoxia always stimulated aortic chemoreceptors before carotid chemoreceptors, and the steady-state response of aortic chemoreceptors to HbCO was greater than that of most carotid chemoreceptors. Only 2 of the 18 carotid chemoreceptor fibers tested showed a distinct increase in activity in response to moderate increases in HbCO%. Thus, oxyhemoglobin contributed substantially to maintain tissue PO2 of all aortic chemoreceptors and of a few carotid chemoreceptors. Hyperoxia diminished the response of both aortic and carotid chemoreceptors to HbCO, indicating a lowered tissue PO2 as the stimulus source. We hypothesize that the aortic bodies have a much lower perfusion relative to their O2 utilization compared to the carotid bodies. As a consequence, the aortic chemoreceptors are able to act as a sensitive monitor of O2 delivery and to generate a circulatory chemoreflex for O2 homeostasis. carotid chemoreceptors monitor O2 tension and initiate strong reflex effects on the level of ventilation.
Effects of colchicine or cytochalasin B on pulmonary macrophage endocytosis in vivo
Authors: Valberg P. A. , Brain J. D. , Kane D.
Published: December 2017

Pulmonary macrophages defend lung surfaces by ingesting deposited particles. We investigated to what extent this uptake of particles can be modulated in vivo by two drugs, colchicine and cytochalasin B (CytB). 198Au colloidal gold, in isotonic saline carrier fluid, was intratracheally instilled into male Syrian golden hamsters. The uptake of these particles by pulmonary macrophages was measured when the carrier fluid contained only colloidal gold and when this test particle was combined with graded doses of either drug. We found that macrophage uptake of the particles 1 h after instillation was depressed 37% when colchicine was added to the instillate (150 micrograms/100 g BW). Depression of particle uptake was also seen with CytB at 15 micrograms/100 g BW. Experiments with tritiated colchicine and CytB showed that both drugs were rapidly cleared from the lungs early in the 1 h phagocytic period. The effect of intravenous colchicine and CytB on the clearance of intravenously injected gold colloid by the liver and spleen reticuloendothelial system was negligible. The results of these experiments, in conjunction with in vitro effects of colchicine and CytB, provide insight into the components of cell function active in particle uptake in situ.
Sequential analysis of the bronchoalveolar milieu in conscious sheep
Authors: Begin R. , Rola-Pleszczynski M. , Sirois P. , Masse S. , Nadeau D. , Bureau M. A.
Published: December 2017

A conscious sheep model was developed to study sequentially the alveolar milieu by respiratory physiological measurements, transbronchial lung biopsy, and bronchoalveolar lavage. The former included all lung volumes, respiratory mechanics, and gas exchange measurements. For all these measurements, intraindividual variations were similar to those reported in humans or anesthetized primates. They were not significantly altered by the repetition of each procedure of the study. Transbronchial lung biopsy specimens were adequate in 80% of cases and yielded 100 alveoli and more in 75% of specimens (mean alveolar count = 690; bronchioles = 4.1; vessels = 3.2). Bronchoalveolar lavage (BAL) yielded a 60% effluent and a mean of over 9 X 10(6) cells in each of the three sets of measurements. BAL was found to induce a mild transient hypoxemia that was completely resolved within 2 h. Cellular and biochemical analyses of BAL effluent in the three series done at 2-wk intervals did not change significantly. It is concluded that the procedures repeated on the conscious sheep model at 2-wk intervals do not influence the respiratory physiological measurements, lung histopathology, or the BAL analyses.
Development of patterns of respiratory activity in unanesthetized fetal sheep in utero
Authors: Bowes G. , Adamson T. M. , Ritchie B. C. , Dowling M. , Wilkinson M. H. , Maloney J. E.
Published: December 2017

Respiratory activity (diaphragmatic electromyogram) was recorded in six unanesthetized in utero fetal lambs, between 0.7 of gestation and term. Respiratory patterns generated by the fetus showed developmental changes that included 1) an emergence of a periodic modulation of respiratory rate producing alternating active and quite phases (mean cycle length of 37 min between 130 and 140 days' gestation; 2) an increase in percentage apnea (expiratory time greater than 10 s) from 20% at 110 days to 60% at 140 days; and 3) a linear decrease in the 2-h average respiratory rate, while mean rate during active phases showed no consistent gestational decline. Electrocortical and electroocular activity was monitored in three of six fetuses; however, discrete sleep state patterns could not be consistently identified. The results demonstrate a gestational change in the respiratory patterns of the developing fetus and suggest an orderly maturation of the mechanisms controlling respiratory neuronal output.
Renal function, aldosterone, and vasopressin excretion following repeated long-distance running
Authors: Wade C. E. , Dressendorfer R. H. , O'Brien J. C. , Claybaugh J. R.
Published: December 2017

Renal and endocrine responses were studied in 10 male runners during a 20-day 500-km race. Overnight urine and prerun blood samples were taken prior to running on days 1, 2, 5, 8, 14, 17, and 20. Day 13 followed 70 h of rest. Urine flow rate, osmotic clearance, tubular free water reabsorption, urinary vasopressin excretion rate, and body weight were not significantly changed. Creatinine clearance was constant except for an elevation on day 5. Plasma osmolality was elevated on days 2, 14, and 17. Plasma sodium was increased (P less than 0.05) on days 2 and 13 but reduced on day 20. The percentage of filtered sodium excreted was significantly reduced on all nights following running and elevated on recovery day 13. Urinary aldosterone excretion rate was significantly elevated 162, 117, and 97% on days 5, 8, and 20 and returned to control levels on day 13 after 70 h of rest. These data suggest that in response to repeated long-distance running normal fluid balance is regained within 12 h. However, it is necessary to conserve sodium for at least 24 h after exercise as evidenced by the decrease in the percent filtered sodium excreted and continued elevation of aldosterone excretion.
Effect of acclimatization to heat on the regulation of sweating during moderate and severe exercise
Authors: Davies C. T.
Published: December 2017

Sweat regulation in two male subjects, one an athlete in training, was examined over a range of exercise intensities and environmental temperatures. The results after artificial heat acclimatization in the nonathlete showed that sweating rate over 1 h of maximal exercise increased to the same level as the athlete, but his evaporative sweat loss remained significantly (15%) lower. Rectal temperature (Tre) was reduced for a given oxygen intake (VO2) and relative work load (%VO2 max), but the difference in Tre/%VO2 max between the subjects was not significant. At different mean skin temperatures (Tsk), relative sweat rate (%msw, max), for a given Tre was unaffected and the relationship of %mSW, max with Tre was the same in both subjects. Lowering the relative work load (and thus Tre) displaced the Tre/%msw, max relationship to the right, and regression lines for different %VO2 max were parallel. The multiple regression equation %msw, max = -1,531 +/- 36.67 Tre (degrees C) + 6.08 Tsk (degrees C) (r = +0.92), related the parameters and was independent of the subject's fitness and state of acclimatization providing %msw, max was expressed in terms of the appropriate msw, max at the time of measurement.
Cardiovascular and respiratory reflexes from muscles during dynamic and static exercise
Authors: Tallarida G. , Baldoni F. , Peruzzi G. , Raimondi G. , Massaro M. , Sangiorgi M.
Published: December 2017

In anesthetized and deafferented rabbits, rhythmic and static contractions of the hindlimb muscles were elicited by stimulating the femoral nerve at 3 and 100 Hz with the intensity of 2.0-2.5 times threshold for the motor fibers. Rhythmic contractions caused a decrease in systemic blood pressure, heart rate, and vascular resistance of the resting hindlimb with hyperpnea. Tetanic contractions caused a rise in arterial pressure, in vascular resistance of the nonexercising hindlimb, and in pulmonary ventilation with small increases in heart rate. These responses were not obtained after sectioning the somatic nerves of the exercised limb or when the cut central end of the femoral nerve or the intact nerve in curarized animals was stimulated with the same intensity of 2.0-2.5 times the motor threshold. Both depressor and pressor responses were, therefore, reflexes initiated in the contracting limbs. Removal of the skin from the exercising limb did not change the typical patterns of response. The most likely source of the observed reflexes is that from receptors activated by metabolites released in the exercising muscles.
Direct and reflex bronchoconstriction induced by histamine aerosol inhalation in dogs
Authors: Yanta M. A. , Loring S. H. , Ingram R. H. , Drazen J. M.
Published: December 2017

Histamine aerosols were administered to nine anesthetized, paralyzed, mechanically ventilated mongrel dogs with the cervical vagi first intact, then sectioned, and then peripherally stimulated at two intensities. Pulmonary resistance (RL) was measured, and dose-response curves were constructed in the four conditions. All dogs had dose-related increases in RL with increasing histamine aerosol concentrations. After the vagi were cut, the degree to which constant levels of vagal stimulation altered the dose-response relationships was assessed by examining the slopes and positions of the RL vs. histamine curves. Four of the nine animals studied showed evidence of increasing vagal efferent activity as the concentration of histamine in the aerosol increased, but three did not. Two of the dogs had equivocal responses in that increasing activity was suggested but not clearly demonstrated. These results indicate that, in addition to direct effects of histamine, the extent of and basis for vagal interaction with this stimulus varies among dogs. The results suggest that the basis of vagal interaction is related to either constant efferent activity (tone) or increasing efferent activity (reflexes).
Effects of intrapleural pressure changes on canine left ventricular function
Authors: Wead W. B. , Norton J. F.
Published: December 2017

Left ventricular diameter, pressure, and dP/dt, as well as aortic and intrapleural pressures, were recorded simultaneously from 10 acute anethetized mongrel dogs. Normal inspiration produced a significant decrease in end-diastolic diameter (46.9 +/- 1.2 to 43.1 +/- 1.0 mm) and end-systolic diameter (35.5 +/- 1.4 to 34.2 +/- 1.7 mm), reducing stroke diameter 2.5 mm. Airway occlusion (greater than or equal to 60%) produced a reduction in the decrease of end-diastolic diameter seen with normal inspiration and, to a lesser degree, in end-systolic diameter. Because only acute airway occlusion greater than or equal to 80% produced a significant increase in left ventricular afterload, the authors conclude that normal spontaneous inspiration results in a decrease in left ventricular preload due to pooling of blood in the pulmonary vasculature. The data suggest that this decrease in left ventricular preload is the predominant mechanism responsible for the inspiratory decrease in left ventricular stroke volume.
Role of albumin in prevention of edema in perfused rabbit lungs
Authors: Chang R. S. , Wright K. , Effros R. M.
Published: December 2017

Edema formation was studied using in situ rabbit lungs perfused with normal 5.0 g/dl) and low (0.1 g/dl) albumin solutions. Measurements were made of the ratio of wet weight to dry weight of the lungs corrected for the residual vascular volume, [(W/D)ev] and the ratio of extravascular 22Na+ to extravascular water volume. Edema formation in the 5 g/dl lungs was insignificant during a 60-min perfusion interval. A moderate amount of edema was found in 0.1 g/dl lungs: (W/D)ev = 5.30 +/- 0.12 (SE) compared with 4.66 +/- 0.11 in the 5 g/dl lungs. Much greater rates of edema formation were found in the 0.1 g/dl lungs when left atrial pressures were increased from 0 to 10 Torr; (W/D)ev reached 7.89 +/- 0.50 in 60 min compared with 5.66 +/- 0.23 in the 5 g/dl lungs. No additional edema formation occurred when albumin concentrations were decreased from 0.1 g/dl to below 0.01 g/dl. Albumin concentration gradients across the capillary wall appear to increase with elevations in capillary pressure.
Regulation of bronchomotor tone by lung inflation in asthmatic and nonasthmatic subjects
Authors: Fish J. E. , Ankin M. G. , Kelly J. F. , Peterman V. I.
Published: December 2017

We examined the effects of lung inflation on induced airway obstruction in 14 atopic asthmatic and 14 atopic nonasthmatic subjects. Subjects were challenged with aerosols of methacholine (MCh) and pollen antigen (Ag), and the effects of inflation were assessed with partial ad full flow-volume curves and by comparing airway conductance measurements before and after deep inspiration to total lung capacity (TLC). Whereas bronchoconstriction was transiently abolished or reduced with inspiration in nonasthmatics, these effects were absent or diminished in asthmatic subjects. Dissimilarities could not be explained by differences in base-line lung function or degree of obstruction produced. Deep inspiration had a greater effect in reducing airway obstruction produced with MCh than with Ag in nonasthmatics. In addition, atropine pretreatment had no effect on inspiration responses in asthmatics given Ag, suggesting that vagal reflexes were not the cause of an impaired ability to reduce bronchomotor tone by lung inflation. Our findings reveal the existence of an intrinsic means of regulating bronchomotor toe by active changes in lung volume and that such a mechanism is impaired in asthma. We suggest that airway hyperactivity in asthma is perhaps less a reflection of enhanced end-organ responsiveness than a reflection of this impaired capacity.