bluuebunny/crossref_metadata_2025 huggingface dataset:
Airway compliance and flow limitation during forced expiration in dogs
Authors: Pedersen O. F. , Thiessen B. , Lyager S.
Published: December 2017

Bronchial pressure measured by means of a Pitot static probe, esophageal pressure, and airflow were monitored during forced lung deflations in six anesthetized dogs. Dynamic transmural pressure-cross-sectional area area curves (Ptm-A curves) were constructed for three intrathoracic tracheal positions and one right lower lobal bronchial position. From the Ptm-A curves the maximal possible flow (Vmax) through the airways at each of the four positions was calculated and compared with the overall maximal flow obtained during the same deflation. The peak of the maximal expiratory flow-volume curve (MEFV curve) equaled the calculated Vmax at more than one position in the trachea but did not reach the Vmax calculated for the more peripheral position. During the transition between the peak and the plateau of the MEFV curve, the Ptm-A curve often changed shape, indicating an abrupt change in the “tube law,” probably due to changes in axial tension of the airway. During the flow-volume curve plateau, measured flow was near an estimated Vmax at a single point in the trachea. At lower lung volumes where the MEFV curve descends from the plateau, measured flow equaled Vmax calculated for the right lower lobe position. This indicates that after an initial period with no localized choking a “choke point” develops and eventually moves toward the periphery. We conclude that measurement of dynamic Ptm-A curves allows a precise prediction of maximal expiratory flows from the properties of the airways.
Effect of physical training on coronary collateral circulation of the rat
Authors: Koerner J. E. , Terjung R. L.
Published: December 2017

The influence of physical training on coronary collateral circulation following acute ligation of the left coronary artery was determined in pentobarbital-anesthetized rats. Coronary blood flows were determined with 15-microns microspheres during a wide range of perfusion pressures and during adenosine infusion. The demarcation between normal and ischemic tissue was achieved using nitroblue tetrazolium strain and thioflavin S fluorescence. Contractile performance was not altered by training, with the exception of a lower left ventricular end-diastolic pressure when afterload was elevated. Blood flow to and the size of the central ischemic zone were not influenced by training. However, in border zones, where collateral dependent flow is expected to be most pronounced, blood flow as a percent of normal was increased (16%, P less than 0.02) in trained animals. This increased was abolished by coronary vasodilation with adenosine. These results indicate that training caused a limited increase in collateral blood flow to the border zone. Further, tissue reactivity to adenosine following short periods of ischemia is normal in trained rats but decreased in border (11%) and ischemic (21%, P less than 0.05) zones in sedentary rats. Whether his small increase in blood flow to the border tissue, along with a retained capacity for dilatation, could lead to an improved salvage of tissue remains to be evaluated.
Propranolol uptake by dog lung: effect of pulmonary artery occlusion and shock lung
Authors: Pang J. A. , Blackburn J. P. , Butland R. J. , Corrin B. , Williams T. R. , Geddes D. M.
Published: December 2017

First-pass lung uptake of propranolol in catheterized ambulant dogs was measured by comparison the difference between the ratios of [14C]propranolol to indocyanine green (ICG) before and after a single passage through the pulmonary circulation. Uptake was 56 +/- 5, 53 +/- 8, and 61 +/- 10% (mean +/- SD) when 0.02, 0.2, and 2.0 mg of propranolol were injected, respectively. There was a negative though unimportant correlation between percent uptake and cardiac output. Analysis of paired propranolol and ICG outflow curves confirmed the lack of saturation with increasing dose and suggested the involvement of simple diffusion. In four dogs uptake fell from 4.76 +/- 6.8 to 40.4 +/- 8.2% (0.05 greater than P greater than 0.025) during partial occlusion of the pulmonary circulation by a Swan-Ganz catheter balloon and rose again to 51.2 +/- 6.4% after relief of the occlusion. Propranolol uptake, measured serially in five dogs with indwelling catheters, was initially 55% but fell linearly to 30% over 2 wk (r = -0.59, P less than 0.001), and necropsy showed pathological features of shock lung. A similar study performed on three dogs within 4 days of catheterization showed no change in uptake of the drug. Propranolol uptake appears to reflect both quantitative and qualitative changes in the pulmonary endothelium. This method may therefore be valuable in studying the pulmonary endothelium in health and disease.
Selective effect of microembolization on pulmonary removal of biogenic amines
Authors: Flink J. R. , Pitt B. R. , Hammond G. L. , Gillis C. N.
Published: December 2017

Pulmonary amine extraction (E) was measured by triple-indicator dilution techniques from bolus injections of trace amounts of 5-hydroxy[14C]tryptamine ([14C]HT)m [3H]norepinephrine ([3H]NE), indocyanine green dye before and after glass-bead embolization in 23 anesthetized dogs. Control E(5-[14C]-HT) was 89.7 +/- 1.7%; 10 min after embolization (which approximately doubled pulmonary artery pressure and pulmonary vascular resistance), E(5-[14C]HT) was significantly reduced to 65.9 +/- 3.0% (kappa +/- SE; n = 10) (P less than 0.01). Control E([3H]NE) (40.1 +/- 4.5%) was unaffected by embolization. Imipramine (8 mg/kg) depressed control E(5-[14C]HT) to 38.7 +/- 1.5% and control E([3H]NE)d to 35.0 +/- 3.9% (P less than 0.05; n = 4). In these animals, pulmonary hemodynamic changes secondary to embolization were comparable to those in non-drug-treated dogs, but E(5-[14C]HT) and E([3H]NE) were not further depressed. Progressive pulmonary lobar artery ligation (n = 5) did not affect amine extraction until perfusion was limited to one lobe. The selectivity of the effect of embolization on E(5-[14C]HT), the lack of an effect on imipramine-insensitive E(5-[14C]HT) extraction, and the much smaller changes after progressive lobar ligation indicate that, although derecruitment of vascular surface area secondary to mechanical obstruction may contribute to postembolization depression of E(5-[14C]HT), additional mechanisms such as local saturation of 5-HT uptake or selective damage to endothelial cell transport of 5-HT may underlie these observations.
A respiratory mask for resting and exercising dogs
Authors: Stavert D. M. , Reischl P. , O'Loughlin B. J.
Published: December 2017

A respiratory face mask has been developed for use with unsedated beagles trained to run on a treadmill. The latex rubber mask, shaped to fit the animal's muzzle, incorporates two modified, commercially available, pulmonary valves for separating inspiratory and expiratory flows. The mask has a dead space of 30 cm3 and a flow resistance below 1 cmH2O . 1(-1) . s. The flexible mask is used to measure breath-by-breath respiratory variables over extended periods of time during rest and exercise.
Restricted dextran transport in the sheep lung lymph preparation
Authors: McNamee J. E.
Published: December 2017

The ease with which plasma proteins and other large solutes enter sheep lung lymph had led previous investigators to conclude that such large molecules probably move through a pathway that has transport properties similar to pores 100 nm or larger in radius. To test this hypothesis, the transport of some very large solutes into lung lymph was measured. Dextran fractions having Stokes-Einstein radii of 10--150 nm were prepared and labeled with fluorescein isothiocyanate (FITC). Five sheep were given 2--2.5 g FITC-dextran 24--36 h prior to cannulation of the efferent duct of the caudal mediastinal lymph node. Analysis of paired plasma and lymph samples for fluorescence as a function of molecular size gave the following results. FITC-dextran 10 nm in radius appeared in sheep lung lymph at 0.30 +/- 0.06 of its plasma concentration. Larger FITC-dextran molecules appeared at still lower concentrations until, above 35 nm, fluorescence could no longer be detected in lymph. The restriction to transport of FITC-dextran was found to be inconsistent with values predicted by a pore pathway 100 nm or larger. These data are compatible with a pore pathway 22--35 nm in radius.
Determinants and consequences of ventilatory responses to competitive endurance running
Authors: Hanson P. , Claremont A. , Dempsey J. , Reddan W.
Published: December 2017

Pulmonary ventilation and pattern, arterial blood gases, and [H+] were studied in 15 highly trained runners [maximum O2 consumption (VO2 max) 53--82 ml . kg-1 . min-1] during road racing (24 km, n = 5) and 60--70 min of treadmill running (70--75% VO2 max, n = 13). The predominant response throughout prolonged treadmill running and especially road running was a tachypneic, respiratory alkalosis (-5 to -12 Torr PaCO2) that was evident early in the exercise. Time-dependent increases in breathing frequency (10--40%, 6--60 min work), expired ventilation, and dead space ventilation were common in prolonged work; these were especially evident in two subjects even as VO2 fell during road racing under hot humid conditions. The tachypneic hyperventilation was 1) most often accompanied by alkaline [H+]a, 2) associated with time-dependent elevation in rectal temperature (1--1.5 degrees C) and circulating norepinephrine (5--20 x rest), 3) quickly alleviated via hyperoxia after 60--70 min of exercise, and 4) was shown to result from increased running velocity in separate experiments that compared walking vs. running at similar CO2 excretion and [HCO-3]a. In highly trained runners competing under favorable environmental conditions and optional pace selection, we view the net effects of the hyperventilatory response to be truly advantageous, whereby the benefits to pulmonary gas exchange and [H+] regulation outweigh the expense of some inefficiency in ventilatory work and pattern and a departure from steady-state homeostasis.
Gas mixing in a model of the pulmonary acinus with asymmetrical alveolar ducts
Authors: Bowes C. , Cumming G. , Horsfield K. , Loughhead J. , Preston S.
Published: December 2017

An asymmetrical model of the human pulmonary acinus is described, in which elements of volume are represented by nodes joined by conductors permitting convective flow and molecular diffusion. The method of analysis permits simultaneous convection, diffusion, and dimensional change in any direction and requires only simple boundary conditions. Inspiration of O2 into a resident gas of 79% N2 followed by expiration was simulated at two flows. On expiration the slope of the alveolar plateau was 1.7%, and the alveolar N2 mixing efficiency was 97.0%. A symmetrical but otherwise similar model gave a slope of zero and a mixing efficiency of 99.9%. The patterns of gas concentration within the asymmetrical acinus during the respiratory cycle confirm and extend previous observations on the interactions between simultaneous convection and diffusion in asymmetrical structures (16, 21, 22). Even though these in combination within alveolar duct asymmetry can account for the slope of the alveolar plateau, they are insufficient to account for the failure of complete gas mixing found in normal subjects.
Micropuncture measurement of lung microvascular pressure during 5-HT infusion
Authors: Bhattacharya J. , Nanjo S. , Staub N. C.
Published: December 2017

We punctured subpleural microvessels in 19 isolated blood-perfused dog lung lobes to determine the effect of 5-hydroxytryptamine (5-HT) on the pulmonary microvascular pressure profile. Maintaining lobe airway pressure at 6 cmH2O and lobe venous pressure at 10 cmH2O we infused saline alone (10 microliter/min) in 10 control lobes and 5-HT in saline solution (100--150 micrograms/min) in 9 lobes. We measured pressures in subpleural microvessels using micropipettes connected to a servo-null system. The 5-HT infusion doubled lobar vascular resistance. In all microvessels upstream from the 150-micrometer venules, pressure was higher than in the control lobes. In contrast to the control lobes, pressure dropped markedly from the lobar artery to the 50-micrometer arterioles and from the venous capillaries to the 50-micrometer venules. We conclude that 5-HT not only constricted arterioles, but also raised lung microvascular pressure by constricting postcapillary venules.
Nonhomogeneous alveolar pressure swings: effect of different respiratory muscles
Authors: Brown R. , Scharf S. M. , Ingram R.
Published: December 2017

We tested the hypothesis in dogs that during isovolumic inspiratory efforts the degree of nonhomogeneity of alveolar pressure changes is influenced by regional differences in respiratory muscle activity. Pressure distal to an occluded right lower lobe bronchus (PRLL) was compared with pressure in the occluded airway opening (PaO) during spontaneous inspiratory efforts (S), during right (RP), left (LP), and bilateral (BP) phrenic nerve stimulation, and during spontaneous inspiratory efforts after cutting both phrenic nerves (SCP), Upper and lower rib cage and abdominal dimensional changes were monitored by magnetometers. PRLL was greater than Pao during S and the difference was greater during BP and greater during RP, whereas with LP and SCP Pao exceeded PRLL. Compared with S, during RP, LP, and BP there was greater upper rib cage inward motion relative to abdominal outward motion. SCP resulted in opposite upper rib cage-abdomen relative motions. Thus activities of various muscle groups produced different regional pressures and deformations of rib cage and abdomen. These results may relate to potential errors in plethysmographic determination of thoracic gas volume in the presence of airway closure.
Contractile force of canine tracheal smooth muscle during continuous stretch
Authors: Gunst S. J. , Russell J. A.
Published: December 2017

Canine tracheal smooth muscle strips were mounted horizontally in a tissue bath between a force transducer and a motor-driven movable steel rod, which was used to change muscle length. Muscle length and force were continuously measured during stretch and simultaneously plotted on an X-Y recorder. Active force during stretch was investigated as follows: an initial length was set with the muscle relaxed, where it was contracted isometrically with acetylcholine. After active force reached a steady state, muscle length was decreased until the total tension was equal to zero. The muscle was then stretched slowly to obtain a continuous length-force curve. Results show that force during stretch increases as the length at which the initial isometric contraction is elicited, is decreased. A possible interpretation is that during tonic muscle contraction, the contractile element is able to shorten very slowly relative to the rate at which the muscle was retracted. Thus, the contractile element length established during isometric contraction would affect the muscle force obtained during subsequent stretch of the muscle.
Maternal hyperventilation helps preserve arterial oxygenation during high-altitude pregnancy
Authors: Moore L. G. , Jahnigen D. , Rounds S. S. , Reeves J. T. , Grover R. F.
Published: December 2017

We examined arterial oxygenation during pregnancy and 3 mo postpartum in 35 nonsmoking residents of Leadville, CO (elevation 3,100 m) to determine how well and by what mechanisms maternal arterial oxygenation was maintained during pregnancy at high altitude. Hyperventilation raised arterial O2 saturation above that in the nonpregnant state. Respiratory alkalosis persisted throughout pregnancy, shifting the O2-hemoglobin dissociation curve to the left, further facilitating O2 loading in the lung. However, a decrease in blood hemoglobin concentration and a slight increase in the alveolar-arterial O2 gradient in the late pregnancy caused the arterial O2 content to fall below that in the nonpregnant state. Compared to published sea level values, the Leadville women had higher ventilation and hemoglobin values, yielding arterial O2 contents as high as in pregnant women at sea level. Thus, ventilation and hemoglobin concentration were important variables contributing to O2 ttransport during pregnancy at high altitude.
Extravascular, extracellular water in rabbit lung using Na and sucrose indicators
Authors: Pavlin D. J. , Haschke R. H. , Nessly M. L. , Cheney F. W.
Published: December 2017

We compared the volume of the pulmonary extravascular, extracellular water space using sodium and sucrose indicators in 8 normal and 11 edematous rabbit lungs by steady-state techniques. The volume of the extravascular, extracellular space (EVECW), expressed in milliliters per gram dry lung, was determined from the volume of distribution of 24Na, [3H]sucrose, or total sodium in 1) supernatant solutions obtained by centrifugation of homogenized lung or 2) intact lung fragments. There was no significant difference in EVECW measured in normal lungs [24Na 1.88 +/- (SD) 0.31; [3H]sucrose 1.84 +/- (SD) 0.27] or edematous lungs [24Na 4.78 +/- (SD) 1.44; [3H]sucrose 4.41 +/- (SD) 1.33] when comparing supernate solutions of homogenized lungs. Similarly, there was no significant difference between the volumes of distribution (EVECW) of these two isotopes when measured in intact fragments of normal lung [24Na 2.08 +/- (SD) 0.28; [3H]sucrose 1.68 +/- (SD) 0.37]. The volume of EVECW measured in supernates was less than in fragments with both isotopes. Washing the centrifuged tissue pellet and adding the wash activity to the initial supernate activity yielded results that were equal to the fragment technique. The failure to detect significant differences between 24Na and [3H]sucrose spaces in the lung suggests that the contribution on intracellular sodium to the measurement of lung water is small and relatively insignificant, at least within the confines of this experiment.
The muscarinic receptors of airway smooth muscle: their characterization in vitro
Authors: Murlas C. , Nadel J. A. , Roberts J. M.
Published: December 2017

We have used radioligand binding and in vitro muscle contraction techniques to characterize the muscarinic cholinergic receptors of canine tracheal smooth muscle. The tritiated muscarinic antagonist, quinuclidinyl benzilate ([3H]QNB), bound no particulate preparations of tracheal smooth muscle with high affinity, saturability, pharmacologic specificity, and stereoselectivity. The equilibrium dissociation constant for the binding reaction was 33 +/- 3 pM (mean +/- SE). The concentration of binding sites was 410 +/- 34 pmol/g protein. The ability of muscarinic agents to inhibit [3H]QNB binding paralleled their relative effects on tracheal smooth muscle contraction in vitro. We found the anesthetic agents, lidocaine and tetracaine, and the nicotonic cholinergic antagonist d-tubocurarine, were competitive inhibitors of [3H]QNB binding to the tracheal smooth muscle preparations. Histamine, aminophylline, and adrenergic agonists did not act as competitive inhibitors. The guanine nucleotide, guanyl-5′-imidodiphosphate, reduced the ability of the muscarinic agonist, acetylcholine, to compete with high affinity for [3H]QNB binding site(s) in tracheal smooth muscle but had minimal effects on the binding of the muscarinic antagonist, atropine. THe radioligand binding and in vitro contraction techniques described are being used to study the possible alteration of muscarinic receptors of airway smooth muscle in disease or from treatment.
Respiratory mechanics of a small carnivore: the ferret
Authors: Vinegar A. , Sinnett E. E. , Kosch P. C.
Published: December 2017

The ferret, Mustela putorius furo, is a small relatively inexpensive carnivore with minimal housing requirements. Measurements were made from anesthetized tracheotomized supine males. Values obtained during tidal breathing for six animals (576 +/- 12 g) were as follows: tidal volume, 6.06 +/- 0.30 ml; respiratory frequency, 26.7 +/- 3.9 breaths min-1; dynamic lung compliance, 2.48 +/- 0.21 ml cmH2O-1; pulmonary resistance, 22.56 +/- 1.61 cmH2O . l–1 . s. Pressure-volume curves from nine ferrets revealed almost infinitely compliant chest walls so that lung and total respiratory system curves were essentially the same. Total lung capacity (TLC, 89 +/- 5 ml) and functional residual capacity (17.8 +/- 2.0 ml) were determined by gas freeing the lungs in vivo. The TLC of these ferrets is about the same as in 2.5-kg rabbits. Maximum expiratory flow-volume curves showed peak flows of 10.1 vital capacities (VC) . s-1 at 75% VC and flows of 8.4 and 5.4 VC . s-1 at 50 and 25% VC.
Effect of nitroglycerin on DL of normal subjects at rest and during exercise
Authors: Nemery B. , Piret L. , Brasseur L. , Frans A.
Published: December 2017

By use of the single-breath diffusing capacity for carbon monoxide (DL) as an index of the pulmonary capillary filling, the effects of 3 mg sublingual nitroglycerin (NTG) were studied in eight healthy subjects at rest and during exercise. At rest, NTG induced a significant and persistent decrease of DL when subjects were sitting or supine (60 min of observation) and also when they were in the lateral decubitus or supine with legs up position (30 min of observation). Subjects in the supine positions showed more pronounced percentage decreases in DL than when sitting. In the sitting position 1 mg NTG also induces a decrease of DL. During a moderate upright cycloergometer exercise, NTG also induces a significant decrease of DL; the decrease is smaller and of shorter duration (less than 15 min) than at rest, but it reappears as soon as the exercise is stopped. The decrease of DL may be attributed to an outward shift of blood from the thorax to the periphery or to a redistribution of lung perfusion consequent to changes in pulmonary vascular pressures.
Depressed pulmonary removal of [3H]prostaglandin E1 after prolonged cardiopulmonary bypass
Authors: Pitt B. R. , Hammond G. L. , Gillis C. N.
Published: December 2017

Pulmonary removal of [3H]prostaglandin E1 ([3H]PGE1) was measured by double indicator-dilution techniques after bolus injections of indocyanine green and trace amounts of [3H]PGE1 before and after 1–3 h of total cardiopulmonary bypass (CPB) or 3 h of left-heart bypass (LHB) in 18 anesthetized dogs. Before bypass, pulmonary removal was 85.7 +/- 1.2% (means +/- SE, n = 18) and was unchanged on restoration of normal circulation after 1–2 h of CPB (80.6 +/- 1.8%, n = 7) or 3 h of LHB (87.4 +/- 1.6%, n = 4). However, on restoration of normal pulmonary arterial blood flow after 3 h of CPB, removal was significantly decreased to 74.5 +/- 2.2% (P less than 0.01, n = 7). Postbypass depression of [3H]PGE1 removal may explain our previous observations that intrabypass elevations in endogenous immunoreactive prostaglandin E in dogs were not entirely reversible on cessation of 3–4 h of CPB. Possible factors underlying depression of post-CPB pulmonary removal of [3H]PGE1 include: 1) local saturation of [3H]PGE1 removal secondary to intrapulmonary or intravascular release of prostaglandin E, 2) inhibition of prostaglandin dehydrogenase activity, or 3) damage to endothelial cell transport of [3H]PGE1 from the pulmonary microcirculation.
Central and regional circulatory adaptations to one-leg training
Authors: Klausen K. , Secher N. H. , Clausen J. P. , Hartling O. , Trap-Jensen J.
Published: December 2017

Six young healthy male subjects performed submaximal and maximal exercise on bicycle ergometers with one leg and two legs before and after 8 wk of one-leg training with each of both legs. The following variables were measured during one- and two-leg exercise: oxygen uptake, heart rate, mean arterial blood pressure, cardiac output, leg blood flow, and iliac arteriovenous differences for oxygen and lactate. After training the maximal oxygen uptake during one- and two-leg exercise was increased by 19 and 11%, respectively. The corresponding cardiac outputs increased by 16 and 11%, respectively. During submaximal one-leg exercise, heart rate decreased by 11%, whereas a decrease of only 2% was seen during submaximal two-leg exercise. Mean blood pressure decreased by about 10 Torr in both types of exercise and during both submaximal and maximal exercise. Maximal leg blood flow increased only by 1.2 l/min during one-leg exercise. Leg blood flow and leg oxygen uptake were smaller during two-leg exercise than during one-leg exercise and more so after training. These findings indicate that one-leg exercise, compared with two-leg exercise, involves circulatory adaptations that respond differently to one-leg training. The findings further imply that oxygen supply to one large muscle group of exercising muscles may be limited by vasoconstriction when another large group of muscles is exercising simultaneously.
Effects of inhaled sympathomimetics on obstructive response to respiratory heat loss
Authors: Rossing T. H. , Weiss J. W. , Breslin F. J. , Ingram R. H. , McFadden E. R.
Published: December 2017

To investigate the influence of inhaled sympathomimetics on the obstructive response to airway cooling, we had six asymptomatic atopic asthmatics perform eucapnic hyperventilation with frigid air at various levels of ventilation after pretreatment with aerosols of metaproterenol or placebo in a random blind fashion. In control experiments, eucapnic hyperventilation produced a progressive decrease in 1-s forced expiratory volume in a stimulus-response fashion as the level of ventilation rose in successive challenges. Metaproterenol did not produce an all-or-none blockade, but rather a parallel shift in the stimulus-response curve so that its protective effects could be overcome by increasing the stimulus. There was no effect on respiratory heat loss. These results explain, in a quantitative fashion, why a treatment schedule that permits a person with asthma to perform a given exercise task without difficulty becomes ineffective as the thermal burden or severity of the task increases.
Characteristics of adjustment of lung diffusing capacity to work
Authors: Fisher J. T. , Cerny F. J.
Published: December 2017

The response of lung diffusing capacity for CO (DLCO) to the onset of exercise or a change in work load was studied in four healthy males. Single-breath DLCO was measured during the transients 1) from rest to 40% of maximum O2 uptake (VO2 max); 2) from rest to 80% VO2 max; and 3) from steady-state exercise at 40 to 80% VO2 max. Protocols 1 and 2 consisted of 8.5 min of exercise while 3 consisted of 10.5 min of exercise at 40% VO2 max followed by 8.5 min at 80% VO2 max. DLCO was measured at 10, 20, 30, 60, 90, 240, and 510 s after onset of change in load. Half times of the responses (1, 39: 2, 43; 3, 56 s) were not statistically different. The percentage of the total response completed at each time interval indicated that 3 was significantly (P less than 0.05) slower than 1 and 2 at 10 and 20 s. The rapid response of DLCO at the onset of exercise may reflect a neural component in pulmonary vascular control during exercise.
Central and peripheral inputs in sweating regulation during thermal transients
Authors: Libert J. P. , Candas V. , Vogt J. J. , Mairiaux P.
Published: December 2017

Eight nude resting men were exposed to consecutive heating-cooling cycles of air and wall temperatures varying from 28 to 45 degrees C in a sawtooth pattern using one of the following slopes: +/- 3.40, +/- 2.27, +/- 1.70, +/- 1.42, or +/- 1.13 degrees C . min-1. Ambient vapor pressure and air velocity were kept constant at 20.0 mbar and 0.9 m . s-1, respectively. Continuous measurements were made of rectal, esophageal, and mean skin temperatures. Local upper limb sweating response was measured from an arm chamber under a local thermal clamp. The results point out the insufficiency of an explantation based on a simple additive function of core and skin temperatures for describing the sweating regulation. During transient thermal loads, a multiplicative interaction of mean skin and core temperatures must also be taken into account for describing the central drive for local sweating response. The interindividual differences observed in the sweating regulation mechanism seem to be linked to a nonlinearity in the response of the thermoregulatory system.
Effects of acute cold exposure on muscle amino acid and protein in rats
Authors: Smith O. L. , Huszar G. , Davidson S. B. , Davis E.
Published: December 2017

To test the effects of acute cold on muscle amino acid and protein 1) rats were exposed to 4 degrees C for 24 h, functionally hepatectomized (eviscerated) and accumulation in the blood used to indicate changes in amino acid release from the tissues; 2) other rats were left intact, and urinary excretion of 3-methylhistidine (proportional to muscle protein breakdown) determined during cold exposure. In the eviscerated group, cold enhanced loss of total amino acids from the tissues (as alpha-amino nitrogen), but the loss (213 +/- 14.8% of basal in 2 h) was not due to excess alanine (180 +/- 8.5%). By comparison, in fasted rats total amino acid was 182 +/- 12.3, alanine 309 +/- 17.2%. Also, the cold-induced loss resembled the effects of streptozotocin diabetes and depended on a depression by cold of serum insulin (to 35.7 +/- 2.3 muU/ml). Therefore it was prevented when insulin was restored by infusion (40 mU . 100 g-1 . h-1) or by adrenodemedullation before cold exposure. Epinephrine (10 micrograms/100 g sc) depressed insulin in the latter and permitted amino acid release to recur. In intact rats, 3-methylhistidine excretion was unaffected by cold. The results suggest that although cold fails to stimulate alanine synthesis or protein breakdown, it inhibits insulin release sympathetically, thereby diminishing the amount of amino acid incorporated into muscle protein.
Hypoxemia reflexly increases secretion from tracheal submucosal glands in dogs
Authors: Davis B. , Chinn R. , Gold J. , Popovac D. , Widdicombe J. G. , Nadel J. A.
Published: December 2017

We anesthetized dogs, ventilated their lungs via the lower trachea, and exposed the epithelial surface of the upper trachea and coated it with powdered tantalum. Secretions from submucosal gland ducts formed elevations (hillocks) in the tantalum layer; we counted the number of hillocks that appeared in a 1.2-cm2 field. In 12 dogs, during normoxemia, 12 +/- 2 hillocks/cm2 formed in 90 s; during severe hypoxemia [fractional inspired O2 concentration (FIO2) = 0.05], 40 +/- 4 hillocks/cm2 formed in 90 s. Injections of sodium cyanide (25–75 micrograms) into the arterial supply to the carotid body also stimulated tracheal submucosal gland secretion. Secretory response to hypoxemia was suppressed by 1) section of both carotid sinus body nerves in six dogs and 2) section of both superior laryngeal nerves and vagus nerves in six other dogs. During mild hypoxemia (FIO2 = 0.10 or 0.15) tracheal submucosal gland secretion still increased. We conclude that hypoxemia increases secretion from submucosal glands in canine trachea by a carotid body chemoreflex.
Effects of streptozotocin diabetes, insulin treatment, and training on the diaphragm
Authors: Ianuzzo C. D. , Noble E. G. , Hamilton N. , Dabrowski B.
Published: December 2017

The adaptive capability of the diaphragm, the only skeletal muscle considered a vital organ, has received little investigative attention compared with the limb muscles. Since it is chronically active, we asked whether it will adapt to exercise training and if so to what extent. Metabolic adaptations of the diaphragm to exercise training were studied under three conditions: normal, streptozotocin-diabetic, and diabetic receiving insulin treatment. The activities of hexokinase (HK), phosphorylase, and phosphofructokinase (PFK) in the diaphragm of sedentary diabetic Sprague-Dawley albino rats were 22–36% lower than in normal animals. Insulin treatment returned PFK and HK to normal and above normal, respectively. Tricarboxylic acid cycle marker enzymes were not affected by the diabetic condition or insulin treatment. beta-Oxidation enzyme 3-hydroxyacyl-CoA dehydrogenase (HADH) was 60% higher than normal in the diabetic diaphragm and returned to normal with insulin treatment. Training resulted in increases in the glycolytic and aerobic capacities of all groups. The aerobic changes were similar to those of limb muscles. HADH activity was increased in the normal and diabetic insulin-treated trained groups, but because of its already high activity in the diabetic diaphragm, it did not require an adaptation.
An automated, indirect assessment of cardiac output during rest and exercise
Authors: Wilmore J. H. , Farrell P. A. , Norton A. C. , Cote R. W. , Coyle E. F. , Ewy G. A. , Temkin L. P. , Billing J. E.
Published: December 2017

The present study describes a modification of the equilibration CO2-rebreathing technique for determining cardiac output (Q), utilizing the Beckman Metabolic Measurement Cart (MMC) to provide partial automation of the procedures described by Jones et al. (Clinical Exercise Testing. Philadelphia, PA: Saunders, 1975). Q was determined in six normal healthy males to establish the reliability of the technique at rest, and during exercise at power outputs of 49 and 98 W, or 300 and 600 kpm/min. An additional 11 patients, who were symptomatic for coronary artery disease and scheduled for right and left heart catheterization, were used in validating these procedures against Q determined by the thermodilution method. The automated CO2-rebreathing procedure was found to be reliable at rest and during exercise, and demonstrated a direct linear relationship with VO2 (r = 0.90). Also, this procedure correlated (r = 0.87) with the thermodilution method during supine rest, and both methods were quite consistent between trials within the same subject. It was concluded that the CO2-rebreathing procedure used in this study, as interfaced with the Beckman MMC, provides reasonable estimates of Q, both in patients during supine rest, and in normal healthy subjects at rest and during low to moderate levels of exercise.
Bohr effect and slope of the oxygen dissociation curve after physical training
Authors: Braumann K. M. , Boning D. , Trost F.
Published: December 2017

Three O2 dissociation curves from venous blood [taken at rest (A), after in vitro acidification with lactic acid (B), and after exhaustive exercise (C)] were determined in eight athletes twice in a year in detrained and fully trained state. The steepness of the standard O2 dissociation curve becomes greater during the training period (increase in Hill's n from 2.68 +/- 0.10 to 2.96 +/- 0.15). There was a concomitant small rise in the intraerythrocytic organic phosphate concentrations. Bohr coefficients (BC) were calculated for blood O2 saturations ranging from 10 to 80% by comparing the dissociation curves A and B (“in vitro” BC) and curves A and C (“in vivo” BC). In detrained and trained state the in vivo BC show their maximal values at low saturation levels, in contrast the in vitro BC exhibit maximal values at middle saturations. During the training period there was an increase in the in vivo BC as well as in the in vitro BC at low saturations. These alterations may lead to augmented O2 extraction from a given volume of blood by up to 15% during heavy work in trained state. The reason for these observations could be an altered erythrocyte population.
Superficial shell insulation in resting and exercising men in cold water
Authors: Veicsteinas A. , Ferretti G. , Rennie D. W.
Published: December 2017

From measurements of subcutaneous fat temperature (Tsf) at known depths below the surface, skin surface temperature (Tsk), and direct skin heat flux (H), the superficial shell isulation (Iss) of the thigh (fat + skin) was calculated as Iss (degrees C.m2.w-1) = (Tsf - Tsk)/H in nine male subjects immersed head out in a well-stirred water bath. Also, at critical water temperature (CWT = 28–33 degrees C), eight of the subjects rested for 3 h, enabling overall maximal tissue insulation (It,max) to be calculated as It,max (degrees C.m2.W-1) = (Tre - Tw)/(0.92 M +/- delta S), where Tre is rectal temperature, Tw is water temperature, M is metabolic rate, and s is loss or gain of body heat. Five subjects performed up to 2 h of mild leg cycling, preceded and followed by 60 min of rest, and both thigh Iss and overall It were measured during exercise. Iss increased from minimal values in Tw greater than 33 degrees C to maximal values (Iss,max) at CWT or below. Iss,max was linearly related to tissue thickness (d) in millimeters of fat plus skin, Iss,max (degrees C.m2.W-1) = 0.0048d-0.0052; r = 0.95, n = 37, and was not influenced by leg exercise up to a metabolic rate of 150 W.m-2 in CWT despite large increases in Tsf and H and large decreases in overall It. The slope of Iss,max vs. depth, 0.0048 degrees C.m2.W-1.mm-1, is almost identical to thermal resistivity of fat in vitro, suggesting that the superficial shell is unperfused in CWT at rest or during mild exercise. When maximal superficial shell insulation (It,ss,max) for the whole body was calculated with allowance for differing fat thicknesses and surface areas of body regions, it could account for only 10–15% of overall It,max at rest and 35–40% of overall It in mild exercise. We suggest that the poorly perfused muscle shell plays a more important role as a defense against cooling at CWT than does the superficial shell (fat + skin), particularly at rest.
Lung fluid balance after pulmonary embolization: effects of thrombin vs. fibrin aggregates
Authors: Johnson A. , Tahamont M. V. , Kaplan J. E. , Malik A. B.
Published: December 2017

We examined the relationship between the activation of fibrinolysis and the increase in lung vascular permeability after pulmonary microembolization (PM). Sheep were prepared with lung lymph fistulas to assess pulmonary transvascular fluid and protein dynamics. Studies were made in three groups: group I (n = 8) in which PM was induced by an iv infusion of thrombin (60 +/- 13 NIH U/kg); group II (n = 7) in which PM was induced by an iv infusion of 50-micrometers-diameter fibrin microaggregates (0.32 +/- 0.009 g/kg); and group III in which the left atrial pressure was increased by 10–15 Torr by inflation of a balloon catheter. Thrombin caused an increase in pulmonary lymph flow (Qlym) without a change in the lymph-to-plasma protein concentration ratio (L/P ratio) indicating an increase in the lung vascular permeability to proteins. Fibrin microaggregates also increased Qlym, but the increase was associated with a decrease in the L/P ratio. The results in the latter group were similar to those obtained after left atrial hypertension in normal sheep. The increase in permeability after PM induced with thrombin was associated with large increases in the plasma concentration of fibrin degradation products, as compared with PM induced by fibrin microaggregates. The process of intravascular coagulation with the resultant generation of fibrinolysis and fibrin degradation products may be required for the increase in lung vascular permeability to proteins after pulmonary microembolization.
Heart rate adaptation to exercise training in cardiac-denervated dogs
Authors: Ordway G. A. , Charles J. B. , Randall D. C. , Billman G. E. , Wekstein D. R.
Published: December 2017

To determine the effect of cardiac denervation on the development of a training-induced decrease in heart rate at rest and during submaximal exercise, six cardiac-denervated (CD) and six sham-operated (SO) dogs were exercise trained by means of a 6-wk treadmill running program. Gastrocnemius citrate synthase activity increased significantly to the same degree in CD and SO dogs indicating that both groups were equally trained. Resting heart rates (RHR) for SO dogs decreased significantly from 64 +/- 4.8 to 51 +/- 3.2 beats/min (mean +/- SE) from pre- to posttraining. CD dogs showed no changes in RHR (95 +/- 3.5 to 96 +/- 5.3 beats/min). Heart rate responses of SO dogs to a standardized, submaximal exercise test decreased significantly from pre- to posttraining. However, CD dogs displayed no decrease in heart rate responses to the standardized, submaximal exercise test. Additionally, at pre- and posttraining, as heart rates rose in response to exercise test intensity, they increased to a significantly greater degree in SO dogs compared with CD dogs. The results indicate that in dogs, cardiac denervation prevents the decreases in resting heart rate and heart rate during submaximal exercise normally associated with endurance exercise training.
Effect of elevated PICO2 on metabolic rate in humans and ponies
Authors: Kaminski R. P. , Forster H. V. , Klein J. P. , Pan L. G. , Bisgard G. E. , Hamilton L. H.
Published: December 2017

The primary purpose of this study was to determine the effect of acute (20–30 min) elevations of inspired CO2 partial pressure (PICO2) on whole-body O2 consumption (VO2). In human subjects, VO2 increased approximately 15 ml.min-1.m-2 with each 7-Torr increment in PICO2 from 0.4 to 28 Torr (P less than 0.05), but VO2 did not change significantly when PICO2 was increased from 28 to 35 and 42 Torr (P greater than 0.05). In ponies, VO2 did not change when PICO2 was increased from 0.7 to 7 Torr (P greater than 0.05), but it increased about 6 ml.min-1.m-2 with each 7-Torr increment in PICO2 from 7 to 28 Torr, and it increased 18 ml.min-1.m-2 when PICO2 was increased from 28 to 42 Torr (P less than 0.05). At low PICO2 the delta VO2/ delta VE was 25 and 7 ml/l for humans and ponies, respectively, where VE is pulmonary ventilation. These values exceeded the expected O2 cost of breathing; hence, some factor, such as shivering or nonshivering thermogenesis, contributed to the elevated VO2. At high PICO2, VE increased without a proportional increase in VO2; thus the delta VO2/ delta VE decreased to about 2.5 ml/l in ponies and to near 0.0 in humans. Accordingly, at high PICO2 some VO2-suppressing factor partially counteracted those factors stimulating VO2. The maximum decrease from control pHa was 0.061 and 0.038 in humans and ponies, respectively. It is questionable whether this mild acidosis was sufficient to suppress VO2. In both species, pulmonary excretion of metabolic CO2 and the respiratory exchange ratio were below control during CO2 inhalation (P less than 0.01), which suggested an increased tissue storage of CO2.
A method for using microspheres to measure muscle blood flow in exercising rats
Authors: Laughlin M. H. , Armstrong R. B. , White J. , Rouk K.
Published: December 2017

A catheter-implantation procedure allowing use of the radiolabeled microsphere (MS) technique for measuring skeletal muscle blood flow (BF) in rats during high-speed treadmill running was desired. Attempts to use existing procedures were unsuccessful. We found that Silastic catheters (0.02 in. ID X 0.037 in. OD) placed in the ascending aorta (for MS infusions) and the renal artery (for reference sample withdrawal) minimized these exercise performance problems. It was then necessary to establish that aortic MS infusions result in good MS-blood mixing. We tested the method with the following: 1) the radioactivities found in reference withdrawal samples taken from two locations in the aorta were compared after left ventricular (LV) infusion and after aortic infusion; 2) BFs to bilaterally paired tissues were compared in anesthetized and conscious rats with LV and aortic infusions; 3) the distribution of MSs in the muscles was studied histologically; and 4) BFs in bilaterally paired tissues were compared in rats with aortic MS infusions during treadmill running. The results indicate that 1) the percent difference between the radioactivities found in the proximal and distal reference withdraw samples was the same for LV and aortic MS infusions; 2) BF to bilaterally paired tissue samples was the same with both LV or aortic MS infusions; 3) the MSs were distributed uniformly within muscles, and MS aggregation was not a significant problem; and 4) BFs to bilaterally paired tissue samples were the same in exercising rats. We conclude that this technique can be used to measure muscle BF in rats running on a treadmill.
Effect of habitual exercise on left ventricular response to exercise
Authors: Anholm J. D. , Foster C. , Carpenter J. , Pollock M. L. , Hellman C. K. , Schmidt D. H.
Published: December 2017

To evaluate the effects of chronic physical exercise on left ventricular ejection fraction (LVEF) and ejection rate (LVER), radionuclide angiography was performed at rest and during upright-bicycle exercise in 45 healthy men. The subjects varied widely in exercise habits and working capacity. They were divided into three subgroups on the basis of habitual physical activity. Aerobic training was done more than 7, 2–4, and less than 1 h/wk by subgroups of athletes, trained, and untrained men, respectively. The results indicate marked differences in work capacity (298, 233, and 181 W in the athletes, trained, and untrained groups, respectively). Resting LVEF (72, 69, and 68%) and LVER (4.1, 3.4, and 3.6 s-1) were not significantly different among the groups. With maximal exercise, however, small but statistically significant differences in LVEF (75, 69, and 68%; P less than 0.05 athletes vs. trained and athletes vs. untrained) and in LVER (7.5, 6.3, and 5.2 s-1; P less than 0.05 among all groups) were observed. Work capacity was, however, poorly correlated with exercise LVEF (r = 0.18) and LVER (r = 0.47). The results of this study indicate that the enhanced working capacity observed secondary to increases in habitual physical activity can be attributed to differences in LVEF and LVER only in the most general terms. Accordingly the results agree with previous suggestions based primarily on echocardiographic data that the primary cardiac adaptation to exercise is dimensional rather than functional in character.
An intercostal retractometer for estimation of intrapleural pressure changes in infants
Authors: Heldt G. P. , Clements J. A. , McIlroy M. B. , Tooley W. H.
Published: December 2017

An intercostal retractometer was developed for estimation of intrapleural pressure changes in infants. It consists of a flat reference plate which floats over the interspace and is attached to the skin by a flexible plastic film. The pressure inside the device is measured with a strain gauge. The volume inside the device is adjusted, so that the intercostal space is brought to a condition of flatness and pressure changes in the device correlate linearly with intrapleural pressure changes. The retractometer is calibrated against overall intrapleural pressure changes by matching its output to changes in airway pressure during occlusion of the airway. The calibration factor is qualitatively proportional to the thickness of the subcutaneous tissue. Retractometer and intrapleural pressures were simultaneously measured in two infant rhesus monkeys with small pneumothoraces. Esophageal and retractometer pressures were compared in seven preterm infants with an average weight of 1345 g. The device estimated the monkeys' intrapleural pressure changes to within 1.2 cmH2O and the human preterm infants' esophageal pressure changes to within 1.3 cmH2O (95% confidence limits of a linear regression).
Distribution of vascular resistance and compliance in a dog lung lobe
Authors: Linehan J. H. , Dawson C. A. , Rickaby D. A.
Published: December 2017

We have modeled the left lower dog lung lobe as three serial compartments, each containing resistance (R) and compliance (C). The intracompartmental arrangement of R and C was chosen to permit their evaluation from pressure data obtained following occlusion of the venous outflow. We found that two mathematically distinct models permitted evaluation of the distribution of R and C. The models were complementary in that when used together the R and C of the three compartments could be determined. The central compartment had 46% of the lobar vascular resistance and 75% of the lobar vascular compliance under control conditions. We found that serotonin and histamine, which increased the resistance proximal and distal to the central compartment, respectively, did not increase the central resistance. Therefore, we conclude that the central compartment includes the capillary bed. The equilibrium pressure (Pd), obtained when arterial inflow and venous outflow were simultaneously occluded, was in close agreement with the average preocclusion pressure of the central compartment, indicating that Pd is close to the pulmonary microvascular pressure.