bluuebunny/crossref_metadata_2025 huggingface dataset:
Interactions between local and reflex influences on human forearm skin blood flow
Authors: Johnson J. M. , Brengelmann G. L. , Rowell L. B.
Published: December 2017

A three-part experiment was designed to examine interactions between local and reflex influences on forearm skin blood flow (SkBF). In part I locally increasing arm skin temperature (Tsk) to 42.5 degrees C was not associated with increases in underlying forearm muscle blood flow, esophageal temperature (Tes), or forearm blood flow in the contralateral cool arm. In part II whole-body Tsk was held at 38 or 40 degrees C and the surface temperature of one arm held at 38 or 42 degrees C for prolonged periods. SkBF in the heated arm rose rapidly with the elevation in body Tsk and arm Tsk continued to rise as Tes rose. SkBF in the arm kept at 32 degrees C paralleled rising Tes. In six studies, SkBF in the cool arm ultimately converged with SkBF in the heated arm. In eight other studies, heated arm SkBF maintained an offset above cool arm SkBF throughout the period of whole-body heating. In part III, local arm Tsk of 42.5 degrees C did not abolish skin vasoconstrictor response to lower body negative pressure. We conclude that local and reflex influences to skin interact so as to modify the degree but not the pattern of skin vasomotor response.
Ventilation in conscious dogs during acute and chronic hypercapnia
Authors: Jennings D. B. , Chen C. C.
Published: December 2017

Minute ventilation was measured in conscious dogs, at rest and during exercise (1 mph), over 60 min immediately following the acute inhalation of 5% carbon dioxide in air and at 2, 4, 7, and 14 days while breathing the same gas mixture in a chamber. The dogs were also studied in the immediate period of air recovery from chronic hypercapnia and 1 day later. Control studies were carried out with the dogs breathing air in the chamber under comparable conditions. A triphasic ventilation change was ovserved in dogs at rest over the 14 days of hypercapnia. After an initial marked increase in ventilation during acute hypercapnia, ventilation returned to control levels by2 days and then appeared to be elevated above control studies from 4 to 14 days at a time when blood acid-base balance became compensated. When the same dogs were studied during exercise, ventilation was also not different from air control at 2 days of hypercapnia; however during exercise, unlike the resting studies, there was only a tendency for a secondary increase in ventilation at 7 and 14 days of hypercapnia. During the immediate recovery from chronic hypercapnia when the dogs breathed air there was no evidence of hypoventilation either at rest or exercise despite arterial alkalosis. At 24 h of recovery it appeared that dogs while at rest had a slightly reduced ventilatory response to 5% carbon dioxide relative to control studies. The findings provide suggestive evidence that other factors, in addition to acid-base balance, might contribute to the regulation of ventilation during chronic hypercapnia and the recovery from chronic hypercapnia.
Genetic influence on normal variability of maximum expiratory flow-volume curves
Authors: Man S. F. , Zamel N.
Published: December 2017

To determine the importance of genetic influence on the variability of maximum expiratory flow-volume (MEFV) curves in normal individuals, MEFV curves breathing air and a mixture of 80% helium and 20% oxygen (He-O2), lung volumes, specific airway conductance, and closing capacity (CC) were obtained in 10 pairs of identical and 6 pairs of nonidentical twins, all nonsmokers and asymptomatic. For a given pair of identical twins, MEFV curves on air were more similar than those of a pair of nonidentical twins (P less than0.02). The intrapair differences of identical twins were smaller than nonidentical twins of maximum expiratory flow (Vmax) at 60% of total lung capacity (TLC) on air (P less than 0.001) and on He-O2 (P less than 0.01). However, intrapair differences of Vmax at 40% TLC and CC were not significantly different in the two groups. Since Vmax at 60% TLC on air and He-O2 are dependent on the geometry of large airways these findings are suggestive that the geometry of large airways may be related to genetic factors. The relationship of the geometry of the peripheral airways and genetic factors has notbeen defined.
Cardiorespiratory deconditioning with static and dynamic leg exercise during bed rest
Authors: Stremel R. W. , Convertino V. A. , Bernauer E. M. , Greenleaf J. E.
Published: December 2017

Bed rest deconditioning was assessed in seven healthy men (19–22 yr) following three 14-day periods of controlled activity during recumbencyby measuring submaximal and maximal oxygen uptake (VO2), ventilation (VE), heart rate, and plasma volume. Exercise regimens were performed in the supine position and included a) two 30-min periods daily of intermittent staticexercise at 21% of maximal leg extension force, and b) two 30-min periods of dynamic bicycle ergometer exercise daily at 68% of VO2max. No prescribed exercise was performed during the third bed rest period. Compared with their respective pre-bed rest control values, VO2max decreased (P less than 0.05) under all exercise conditions; -12.3% with no exercise, -9.2% with dynamic exercise, but only -4.8% with static exercise. Maximal heart rate was increased by 3.3% to 4.9% (P less than 0.05) under the three exercise conditions, while plasma volume decreased (P less than 0.05) -15.1% with no exercise and -10.1% with static, but only -7.8% (NS) with dynamic exercise. Sinceneither the static nor dynamic exercise training regimes minimized the changes in all the variables studied, some combination of these two types of exercise may be necessary for maximum protection from the effects of the bed deconditioning.
Venous ultrasound catheter-tip technique for evaluation of arterial hemodynamics
Authors: Nealeigh R. C. , Miller C. W. , McLeod F. D.
Published: December 2017

A variety of devices has been used for measuring flow properties of deep-lying arteries, but many have limitations. This paper describes a relatively nontraumatic intravenous approach which uses a catheter in connection with a pulsed ultrasonic Doppler velocity meter (PUDVM) and an ultrasound echo track. The venous ultrasound catheter (VUC) has permitted measurements oflocal instantaneols blood velocity, flow, and wall motion in the abdominal aorta and iliac arteries of beagle dogs; evaluation studies have been conducted to compare the VUC recordings with an independent method for measuringblood flow and wall motion. Coupling of this catheter-tip device with the PUDVM and echo track provides chronic measurements of hemodynamic parametersin these deep vessels which were virtually impossible to obtain previously.This technique may prove useful in monitoring vessel pathology longitudinally as well as in basic experimental situations requiring flow and arterial wall mechanical properties.
Mechanics of the rib cage and diaphragm during sleep
Authors: Tusiewicz K. , Moldofsky H. , Bryan A. C. , Bryan M. H.
Published: December 2017

The pattern of motion of the rib cage and abdomen/diaphragm was studied in three normal subjects during sleep. Sleep state was monitored by electroencephalograph and electrocculograph. Intercostal electromyographs (EMG's) were recorded from the second interspace parasternally. Abdominothoracic motion was monitored with magnetometers and these signals calibrated by isovolume lines either immediately before going to sleep, or if there was movement, on awakening. Respiration was recorded using a jerkin plethysmograph. In the awake subject in the supine position, the rib cage contributed 44% to the tidal volume and had essentially the same contribution in quiet sleep. However, in active or rapid eye movement sleep the rib cage contribution fell to 19% of the tidal volume. This was accompanied by a marked reduction in the intercostal EMG. With the subject in the upright position the rib cage appears to be passively driven by the diaphragm. However, the present data suggest that active contraction of the intercostal muscles is required for normal rib cage expansion in the supine position.
Muscle fiber activity as a function of speed and gait
Authors: Armstrong R. B. , Marum P. , Saubert C. W. , Seeherman H. J. , Taylor C. R.
Published: December 2017

These experiments were designed to test the hypothesis that locomotory gait transitions occur when some critical cross-sectional area of active muscle is reached as animals increase speed within a gait. We used glycogen depletion as evidence of muscle fiber activity and selected an experimental animal in which all muscle fibers in the locomotory muscles rely extensively on glycogen as a substrate--the lion. We found a high correlation between biochemically and histochemically determined rates of glycogen depletion (r = 0.906). Rates of glycogen depletion in the biceps femoris and triceps brachii muscles increased logarithmically with speed with no discontinuities at the gait transitions. However, we found large discontinuities both in the total cross-sectional area of muscle that showed depletion and in the rates at which the different types of fibers depleted glycogen at the trot-gallop transition. Our results indicate that 1) gait transition did not occur at a maximum tension level either for a particular type of fiber or the whole muscle, and 2) different configurations of motor units within an individual muscle may be recruited as an animal changes gait.
Prediction of heat tolerance from heart rate and rectal temperature in a temperate environment
Authors: Shvartz E. , Shibolet S. , Meroz A. , Magazanik A. , Shapiro Y.
Published: December 2017

To determine if heat tolerance could be predicted from responses to exercise in temperature conditions, 51 young men performed 15 min of bench stepping at an average work load of 80 W at 23 degrees C. On the following day they attempted to perform 3 h of bench stepping at 40 W in heat (39.3 degrees C dry bulb, 30.3 degrees C wet bulb). Of these subjects, 4 were heat intolerant, judged by previous heat stroke episodes during field marches, 12 were heat acclimated, and 35 were unacclimated. The heat-intolerant subjects showed the highest heart rates (HR) and rectal temperatures (Tre) at 23 degrees C and in heat, and the acclimated subjects showed the lowest corresponding values. HR and Tre in each environment were combined into a single score, from 10, indicating the poorest responses, to 100, indicating the best responses. These scores at 23 degrees C when correlated with the corresponding scores in heat resulted in a linear correlation coefficient of r = 0.94 with a standard error of estimate of 8.6%. Scores of the heat-intolerant subjects were below 35, and those of the acclimated subjects were between 70 and 100. Thus heat tolerance can accurately be predicted for HR and Tre responses to exercise at room temperature.
Kinetics of gas exchange and ventilation in transitions from rest or prior exercise
Authors: Diamond L. B. , Casaburi R. , Wasserman K. , Whipp B. J.
Published: December 2017

Seven normal subjects each performed three transitions to a subanaerobic threshold work rate on a cycle ergometer: 1) from rest, 2) from a low work rate (both at 60 rpm), and 3) from a low work rate at 40 rpm to the high work rate at 80 rpm. Oxygen uptake (VO2), carbon dioxide output (VCO2), and ventilation (VE) were computed breath-by-breath and response kinetics extracted. The mean half-times of VO2, VCO2, and VE were 32, 44, and 49 s, respectively, and were not appreciably affected by the prior exercise or by variation of pedal rate. The kinetics of VE was highly correlated with VCO2 (r = 0.94), with VCO2 leading VE, providing further description of the relation of the exercise hyperpnea to CO2 flow to the lungs.
Cardiopulmonary function in dogs during lung lavage and unilateral hypoxia
Authors: Silbaugh S. A. , Muggenburg B. A. , Mauderly J. L. , Crain C. R.
Published: December 2017

Changes in cardiopulmonary function in Beagle dogs were studied during two methods of lung lavage and during unilateral hypoxia. In one method of lavage, dogs were hyperventilated and saline was instilled relatively rapidly through a single-lumen tracheal tube. In another lavage method, a double-lumen tube separated right and left bronchi and saline was instilled more slowly into the dog's right lung. Unilateral hypoxia was produced by directing right lung airflow to a rebreathing bag. Few blood gas or venous admixture changes occurred during single-lumen lavage, but blood oxygen decreased and venous admixture increased during both double-lumen lavage and unilateral hypoxia. Heart rate, cardiac output, and systemic arterial pressure decreased during single-lumen lavage, but not during double-lumen lavage or unilateral hypoxia. Apparently, most alveoli were gas filled during single-lumen lavage and unilateral hypoxia was not imposed. Similar changes during double-lumen lavage and unilateral hypoxia suggested that unilateral hypoxia was a major change-producing factor during double-lumen lavage.
Catecholamines in coronary sinus during exercise in man before and after training
Authors: Cousineau D. , Ferguson R. J. , de Champlain J. , Gauthier P. , Cote P. , Bourassa M.
Published: December 2017

Coronary patients exercised on an ergometric bicycle before and after physical training. Plasma catecholamines were sampled simultaneously at the arterial and coronary sinus levels and assayed with a radioenzymatic method. The increase in the level of coronary sinus catecholamines exceeded the increase in the arterial level, indicating a liberation of catecholamines by the myocardium and an activation of the peripheral sympathetic fibers during exercise. With high work loads, these values no longer differed, suggesting that the additional increase in circulating catecholamines originate from extra-myocardial stores, presumably the adrenal medulla. Arterial catecholamine levels were significantly correlated with work loads, heart rate, changes in systolic blood pressure, and rate-pressure product. After physical training, arterial catecholamine increases for various work loads were lower; these lower elevations were associated with diminished responses in heart rate and systolic blood pressure, resulting in a lower rate-pressure product. Physical training results in diminished sympathetic responses for a given level of exercise, which could be associated with the clinical improvement of these patients.
Influence of arterial hypoxia on cardiac and coronary dynamics in the conscious sinoaortic-denervated dog
Authors: Krasney J. A. , Koehler R. C.
Published: December 2017

Arterial hypoxia was produced in 10 conscious, chronically instrumented, tracheostomized dogs by allowing them to breathe 7.5% O2 in N2 for 10 min. Hypoxia (Pao2 = 28 +/- 0.7 (SE) Torr) caused significant increases in coronary blood flow (+196%), left ventricular dP/dt max (+60%), aortic blood flow (+48%), heart rate (+50%), and left ventricular systolic (+12%) and aortic (+10%) pressures. Left ventricular end-diastolic pressure and stroke volume were unchanged, while systemic (-30%) and coronary diastolic (-66%) vascular resistances declined significantly. When equivalent levels of arterial hypoxia were produced in four of these dogs after chronic sinoaortic denervation, the coronary, cardiac, and systemic hemodynamic responses were not significantly different, with the exception that the small arterial pressure response was abolished. Thus the peripheral chemoreflexes are not essential for the normal coronary vasodilator and cardiac adjustments to occur during hypoxia in the conscious dog. The data support the hypothesis that a large part of the cardiac adjustments to hypoxia is initiated outside the sinoaortic reflexogenic zones, probably within the central nervous system.
Role of autonomic nervous system controlling surface tension in fetal rabbit lungs
Authors: Corbet A. J. , Flax P. , Rudolph A. J.
Published: December 2017

After the maternal abdomen was opened under methoxyflurane anesthesia, fetal rabbits of 27.5 days gestation were given injections through the intact uterine wall of saline, pilocarpine, isoxsuprine, muscarine, phenylephrine, atropine, phenoxybenzamine, or propranolo, alone or in appropriate combinations. Fetal rabbits were delivered by hysterotomy and killed without breathing 2.5 h later. Static pressure-volume curves with air showed improved retention on deflation in fetal rabbits that had injections of pilocarpine, or isoxsuprine, but not of muscarine or phenylephrine. The effect of pilocarpine on the pressure-volume curve was blocked by atropine, phenoxybenzamine, and propranolol, and the effect of isoxsuprine was blocked by propranolol but not phenoxybenzamine. The data suggest that pilocarpine produces secretion of surfactant into lung air spaces by exciting the sympathetic nervous system, a known function of pilocarpine, rather than the parasympathetic nervous system. This may result in stimulation of the same beta-adrenergic receptors affected by isoxsuprine which is also thought to stimulate surfactant secretion.
Diminished hormonal responses to exercise in trained rats
Authors: Galbo H. , Richter E. A. , Holst J. J. , Christensen N. J.
Published: December 2017

Male rats (120 g) either were subjected to a 12-wk physical training program (T rats) or were sedentary controls (C rats). Subsequently the rats were killed at rest or after a 45- or 90-min forced swim. At rest, T rats had higher liver and muscle glycogen concentrations but lower plasma insulin. During exercise, blood glucose increased 60% in T rats but decreased 20% in C rats. Plasma glucagon and insulin concentrations did not change in T rats but plasma glucagon increased and insulin decreased markedly in C rats. Plasma epinephrine (90 min: range, 0.78–2.96 ng-ml-1, (T) vs. 4.42–15.67 (C)) and norepinephrine (90 min: 0.70–2.22 (T) vs. 2.50–6.10 (C)) were lower in T than in C rats. Hepatic glycogen decreased substantially and, as with muscle glycogen, the decrease was parallel in T and C rats. The plasma concentrations of free fatty acids were higher but lactate and alanine lower in T than in C rats. In trained rats the hormonal response to exercise is blunted partly due to higher glucose concentrations. In these rats adipose tissue sensitivity to catecholamines is increased, and changes in glucagon and insulin concentrations are not necessary for increased lipolysis and hepatic glycogen depletion during exercise.
Transient O2 uptake response at the onset of exercise
Authors: Hagberg J. M. , Nagle F. J. , Carlson J. L.
Published: December 2017

One purpose of this study was to determine whether the half time of the oxygen consumption (VO2) response at the onset of exercise varies with work intensity. Fifteen subjects performed 5 min of bicycle ergometer exercise across a range of relative work loads with VO2 determined continuously via computer analysis. The results revealed that the half time of the VO2 response increased as work intensity increased. Our second purpose was to determine whether VO2 response kinetics are dependent on the maximum oxygen uptake (VO2max) of the subject. When VO2 response kinetics were compared at equal absolute work loads for a highly trained (n = 8, mean VO2max = 70.2 ml/kg.min) and an untrained (n = 7, mean VO2max = 49.7 ml/kg.min) group, the highly trained group had a more rapid VO2 response (P less than 0.05). The same tendency was evident at equal relative work loads but the differences were not significant. The more rapid adaptation of the highly trained subjects at absolute work loads may be caused by the enzymatic and circulatory adaptations which result from endurance training. The more rapid adjustment of VO2 at the onset of exercise may explain the slower phosphagen and glycogen depletion found in highly trained subjects following short-term work at equal absolute loads.
Mechanism of the attenuated cardiac response to beta-adrenergic stimulation in chronic hypoxia
Authors: Maher J. T. , Deniiston J. C. , Wolfe D. L. , Cymerman A.
Published: December 2017

A blunting of the chronotropic and inotropic responses of the heart to beta-adrenergic stimulation occurs following chronic exposure to hypobaric hypoxia. To pursue the mechanism(s) involved, observations were made in six intact, conscious goats at sea level and in another six goats maintained in a decompression chamber at 445 Torr (approximately 4,300m) for 10 days (Pao2 = 43 Torr). No significant group differences in cardiac frequency and various indices of myocardial performance (peak dP/dt, time-to-peak dP/dt, Vmax) were demonstrable either before or after cholinergic blockade with intravenous atropine methyl bromide, 1 mg/kg. Following hemodynamic studies, thoracotomies were performed and full-thickness biopsies were obtained from the free wall of each of the cardiac chambers. Neither monoamine oxidase activity nor norepinephrine level of any region of the heart was altered by chronic hypoxia. However, a twofold increase (P less than 0.001) in catechol O-methyltransferase activity above sea-level values was found in both the atria and ventricles of the hypoxic animals. Thus, the attenuation in cardiac responsiveness to beta-adrenoceptor stimulation in chronic hypoxia appears unrelated to the level of vagal activity, but may be attributable to enhanced enzymatic inactivation of catecholamines.
Inhibition of rat bronchiolar oxygen consumption by plasma proteins
Authors: Navari R. M. , Patterson J. L.
Published: December 2017

The oxygen consumption of rat bronchioles suspended in a physiological salt solution containing plasma proteins was measured with the Cartesian diver microrespirometer. The oxygen consumption of the bronchiolar tissue 100–300 and 300–400 micrometer in diam was significantly (P greater than 0.01) reduced as the protein concentration of the suspending solution was increased from the low to the high extreme of the normal plasma physiological range and as the diffusion distance through the suspending medium was increased from 25 to 50 micrometer. The reduction in the bronchiolar oxygen consumption was significantly (P greater than 0.01) reversed by using 95% oxygen-5% nitrogen instead of air as the diffusing gas in the Cartesian diver. Measurements of the oxygen diffusivity in the protein solutions using a diaphragm diffusion cell showed a large decrease in the diffusivity as the plasma protein concentration was increased over the same concentration range used in the oxygen consumption studies. These results suggest that the reduction in oxygen consumption was secondary to a decrease in oxygen diffusion and may provide at least a partial explanation for the diffusion abnormalities which exist in noncardiogenic pulmonary edema in which there is an increase in microvascular membrane permeability to proteins.
Alcohol and respiratory and body temperature changes during tepid water immersion
Authors: Martin S. , Cooper K. E.
Published: December 2017

Resting subjects were immersed for 30 min in water at 22 and 30 degrees C after drinking alcohol. Total ventilation, end-tidal PCO2, rectal temperature, aural temperature, mean skin temperature, heart rate, and oxygen consumption were recorded during the experiments. Blood samples taken before the immersion period were analyzed by gas-liquid chromatography. The mean blood alcohol levels were 82.50 +/- 9.93 mg.(100 ml)-1 and 100.6 +/- 12.64 mg (100 ml)-1 for the immersions at 22 and 30 degrees C, respectively. There was no significant change in body temperature measured aurally or rectally, mean surface skin temperature, or heart rate at either water temperature tested. Total expired ventilation was significantly attenuated for the last 15 min of the immersion at 22 degrees C, after alcohol consumption as compared to the ventilation change in water at 22 degrees C without ethanol. This response was not consistently significantly altered during immersion in water at 30 degrees C. It is evident that during a 30-min immersion in tepid water with a high blood alcohol level, body heat loss is not affected but some changes in ventilation do occur.
Effects of intravenous histamine on lung mechanics in man after beta-blockade
Authors: Ploy-Song-Sand Y. , Corbin R. P. , Engel L. A.
Published: December 2017

In six nonatopic normal subjects, neither intravenous histamine infusion (0.3 mg.kg-1.min-1) nor intravenous propanolol (10 mg) alone produced significant change in pulmonary mechanics. Histamine infusion after propranolol resulted in an increase in pulmonary resistance (RL) from 2.1 +/- 0.41 (mean +/- 1 SE) to 3.3 +/- 0.76 cmH2O./-1.S-1 (P greater than 0.05); maximal flow at 50% total lung capacity (Vmax 50) decreased from 3.6 +/- 0.35 to 2.7 +/- 0.44 l/s (P greater than 0.01). Similar changes in Vmax 50 were observed during partial forced expiratory maneuvers from end-tidal inspiration (PEFV). On 80:20 helium-oxygen mixture Vmax 50 during maximal expiration (MEFV) decreased from 4.9 +/- 0.61 to 3.4 +/- 0.61 l/s (P greater than 0.005) and during PEFV diminished from 4.6 +/- 0.61 to 2.8 +/- 0.46 l/s (P greater than 0.005). Density dependence (deltaVmax 50) decreased significantly (P greater than 0.05) during PEFV but not during MEFV. There were no significant changes in tidal pulmonary compliance, in closing volume and closing capacity (resident gas technique), and in inflation and deflation pressure-volume curves. We conclude that iv histamine in low doses constricts peripheral conducting airways in man but this effect is masked by histamine-induced release of catecholamines from the adrenal glands.
Analysis of postcapillary pH changes in blood in vivo after gas exchange
Authors: Bidani A. , Crandall E. D. , Forster R. E.
Published: December 2017

A quantitative description of the reaction and transport processes that take place in blood during and after gas exchange in capillaries is developed and used to interpret recently reported experimental results. Included in the computation are 1) CO2-H2CO3 hydration-dehydration reactions in plasma and erythrocytes, 2) CO2 reactions with hemoglobin, 3) O2 binding to hemoglobin, 4) buffering of H+ intra- and extracellularly, 5) HCO3- Cl- exchange across the red cell membrane, 6) diffusion of gases between alveolar gas and blood, and 7) transcellular movement of water. Ion and water fluxes are described assuming passive diffusion down their electrochemical potential gradients. Recent data on the magnitude of the Bohr and Haldane shifts and on carbamate formation in the presence of 2,3-diphosphoglycerate are used. The analysis is used to examine the direction, magnitude, and time course of plasma pH changes in blood leaving the pulmonary capillaries and is shown to preduct results that agree very closely with recently reported experimental measurements in vivo. The time computed for plasma pH equilibration after gas exchange when carbonic anhydrase activity is absent from plasma is so great that blood may never be in complete electrochemical equilibrium as it travels around the circulation in normal man.
Pulmonary tissue volume in dogs during pulmonary edema
Authors: Peterson B. T. , Petrini M. F. , Hyde R. W. , Schreiner B. F.
Published: December 2017

Pulmonary tissue volume (Vt) and pulmonary capillary blood flow (Qc) were measured in anesthetized dogs by analyzing end-expiratory concentrations of dimethyl ether (DME), acetylene (C2H2), and sulfur hexafluoride during a 30-s rebreathing maneuver. Vt was compared to the postmortem lung weight of control dogs and dogs with hemodynamic and nonhemodynamic (alloxan) pulmonary edema. Qc was compared to the cardiac output measured by dye dilution. A 100-ml increase in alveolar volume (VA) in the range of 1–2 liters resulted in a 9 +/- 3 ml increase in Vt. Vt measured at a VA of 1.9 liters measures 114 +/- 18% of the postmortem lung weight in 20 control dogs and in 6 dogs with moderate edema (lung weight < 250% of predicted). Vt measured only 53 +/- 14% of the lung weight in 11 dogs with more severe edema. DME and C2H2 gave the smae mean values of Vt, but the reproducibility of a series of 3–7 measurements was greater with DME (coefficient of variation was 5% with DME and 8% C2H2). Qc measured 96 +/ 15% of the cardiac output during the rebreathing maneuver, but the maneuver caused a 4–40% fall in the cardiac output. These data show that Vt determined by rebreathing DME is between 86% and 135% of the lung weight in dogs with pulmonary edema until the lung weight is greater than 250% of the predicted value.
Critical size of newborn homeotherms
Authors: Balmer R. T. , Strobusch A. D.
Published: December 2017

Page 571: R. T. Balmer and A. D. Strobusch. “Critical size of newborn homeotherms.” Page 574: Eq. 31 has the wrong final exponent. It should read

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This error results in Eqs. 37, 39, 40, 41, and 42 also being wrong. Equation 37 now has the form

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where

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and

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Equations 39, 40, and 41 are the algebraic manipulations required in using the new Eq. 37 (given above) in Eq. 38 of the paper. Equation 42 is the final result, which in its correct form is now

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where, for T0 – T∞ = 5°C, rocc = 0.80 cm. Thus, even though the error in Eq. 31 was rather significant, it had remarkably little effect on the final result, Eq. 42. Page 577: the line labeled cylinder in Fig. 5 should be raised slightly (it should pass through the point critical radius = 0.8 cm, T0 – T∞ = 5°C) bringing it closer to the line labeled sphere.

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Mechanics of the human diaphragm during voluntary contraction: dynamics
Authors: Goldman M. D. , Grassino A. , Mead J. , Sears T. A.
Published: December 2017

We determined the static, isometric relationship between diaphragmatic EMG (Edi) and transdiaphragmatic pressure (Pdi) in man at specified abdominothoracic configurations, assessed with magnetometers. During inspiratory airflow, measurements of Edi and Pdi were taken as the respiratory system passed through the same configuration as obtained during the static isometric contractions, allowing a comparison of static and dynamic contractions of the diaphragm at a given length and curvature. When voluntary inspiratory maneuvers are performed with no associated outward displacement of the abdominal wall, or with slight inward displacement, the Pdi developed dynamically is the same as that developed statically at a given Edi. When outward movement of the abdominal wall occurs during inspiratory airflow, the Pdi developed dynamically depends on the rate of abdominal displacement, not on overall inspiratory airflow rate. We conclude that the velocity of shortening of the diaphragm increases directly as the rate of abdominal displacement. We construct a pressure-flow analogue of the force-velocity relationship for the diaphragm and discuss the functional implications of these observations in relation to spontaneous breathing.
Cardiac hypertrophy in response to dynamic conditioning in female athletes
Authors: Zeldis S. M. , Morganroth J. , Rubler S.
Published: December 2017

Ten female field hockey players were studied to determine if prolonged dynamic conditioning results in an increased left ventricular internal dimension at end diastole (LVIDD) and if this increase correlates with maximal oxygen consumption (VO2max). At peak season, echocardiograms were obtained and VO2max determined during maximal treadmill exercise. VO2max, LVIDD index (LVIDD/body surface area (BSA)), and ventricular septal and posterior wall thickness were compared to agematched nonathletic women. Mean LVIDD index was significantly greater in athletes than in controls: 29.3 +/- 0.9 mm/m2 vs. 26.3 +/- 0.6, P less than 0.005. Echocardiographic wall measurements did not differ significantly in the two groups. Mean VO2max for the athletes was significantly greater than controls: 51.7 +/- 4.0 ml O2.kg-1.min-1 vs. 41.2 +/- 2.1, P less than 0.001. VO2max correlated significantly with LVIDD index; r = 0.92, P less than 0.001. Female athletes show an increased LVIDD in response to dynamic conditioning similar to that seen in male athletes. The proficiency of athletic performance as measured by VO2max may be related to the heart's ability to increase LVIDD since there is a high correlation between VO2max and LVIDD index.
Catalysis of CO2 reactions by lung carbonic anhydrase
Authors: Klocke R. A.
Published: December 2017

Steady-state carbon dioxide excretion was studied in isolated bloodless lung preparations perfused with bicarbonate solutions. Addition of acetazolamide produced a prompt, significant decrease in the volume of excreted CO2 under all conditions studied. Excreted CO2 was derived from two sources: CO2 dissolved in the perfusate and CO2 produced by dehydration of bicarbonate in the pulmonary capillary. The relative quantity of these two sources was determined by measurement of the simultaneous excretion of acetylene. Determination of the rate of CO2 production permitted the calculation of capillary blood volume, mean capillary transit time, and the degree of catalysis of CO2 reactions by carbonic anhydrase present in the lung. Contamination of perfusate with blood carbonic anhydrase was ruled out by measuring hemoglobin concentration and carbonic anhydrase activity in pulmonary venous drainage. Comparison of steady-state CO2 production during control conditions and carbonic anhydrase inhibition indicated that bicarbonate in plasma has access to sufficient lung carbonic anhydrase to catalyze the CO2 hydration-dehydration reaction by a factor of five.
Cellular adaptations of the ventilatory muscles to a chronic increased respiratory load
Authors: Keens T. G. , Chen V. , Patel P. , O'Brien P. , Levison H. , Ianuzzo C. D.
Published: December 2017

It is not known whether cellular adaptations of the ventilatory muscles are induced by increased respiratory loads. A chronic respiratory load was produced in rats by tracheal banding. Five weeks after the imposition of this increased load, biochemical and histochemical analyses were performed on the diaphragm and intercostal muscles. The oxidative capacity, as indicated by succinate dehydrogenase (SDH) activity, increased 38% in the diaphragm. The capacity for beta-oxidation fatty acids, as indicated by 3-hydroxy-acyl-CoA dehydrogenase (HADH) activity, increased 29%. The glycolytic capacity, as indicated by phosphofructokinase (PFK) activity, did not change. Similar enzymatic adaptations were observed in the intercostal muscles. The proportion of slow-twitch muscle fibers, as indicated by the myofibrillar adenosine triphosphatase (ATPase) stain, increased in the diaphragm, but not in the intercostal muscles. Thus, these ventilatory muscles responded with an increase in their oxidative capacity, and the diaphragm reponded with an increase in the proportion of muscle fibers having the myofibriller ATPase staining characteristic of slow-twich fibers. We conclude that cellular adaptations are induced in the ventilatory muscles by chronic increased respiratory loads.
Effects of exercise on sleep
Authors: Walker J. M. , Floyd T. C. , Fein G. , Cavness C. , Lualhati R. , Feinburg I.
Published: December 2017

We tested the hypothesis that EEG sleep stages 3 and 4 (slow-wave sleep, SWS) would be increased as a function of either acute of chronic exercise. Ten distance runners were matched with 10 nonrunners, and their sleep was recorded under both habitual (runners running and nonrunners not running, 3 night) and abruptly changed (runners not running and nonrunners running, 1 night) conditions. Analyses of both visually scored SWS and computer measures of delta activity during non-rapid eye-movement (NREM) sleep failed to support the SWS-exercise hypothesis. The runners showed a significantly higher proportion and a greater absolute amount of NREM sleep than the nonrunners. The runners showed less rapid eye-movement activity during sleep than the nonrunners under both experimental conditions, indicating a strong and unexpected effect of physical fitness on this measure. Modest afternoon exercise in nonrunners was associated with a strong trend toward elevated heart rate during sleep. Mood tests and personality profiles revealed few differences, either between groups or within groups, as a function of exercise.
Respiratory responses to intravenous and intrapulmonary CO2 in awake dogs
Authors: Greco E. C. , Fordyce W. E. , Gonzalez F. , Reischl P. , Grodins F. S.
Published: December 2017

Ventilatory responses to CO2 inhalation and CO2 infusion were compared in the awake dog. The CO2 was introduced directly into the systemic venous blood via a membrane gas exchanger in a femoral arteriovenous shunt circuit, and the extracorporeal blood flow, QX, was maintained constant at one of two rates: low, 0.5 l/min; or high, 2.0 l/min. A total of 13 experiments was performed in four dogs comprising 50 control and 25 inhalation and infusion observations at each of the two flow rates. Comparison of CO2-response curve slopes, S = delta V E/delta PaCO2, between CO2 inhalation and infusion showed no significant difference either within or between flow rates. The mean value of S for all conditions was 1.88 l/min per Torr with a 95% confidence interval of 1.66 -2.14. An independent additive ventilatory drive amounting to 28% of low-flow control VE was found at the highflow rate. We conclude that at constant blood flow the responses to both CO2 inhalation and infusion are hypercapnic and not significantly different.
Carbon dioxide--a major determinant of collateral ventilation
Authors: Traystman R. J. , Terry P. B. , Menkes H. A.
Published: December 2017

The effects of local or systemic CO2 and changes in pulmonary vascular pressure and flow on the mechanics of collateral ventilation were studied in anesthetized, paralyzed dogs. The resistance to collateral ventilation (Rcoll) decreased by 36.1% when the air being infused into the obstructed segment was replaced with 10% CO2 while the animal was ventilated with air. When the air used to ventilate the animals was replaced with 10% CO2 while air was infused into the segment, Rcoll decreased by 38.6%. When blood flow into the pulmonary artery was stopped (stop flow), pulmonary artery and left atrial pressure decreased. Rcoll increased following stop flow to 125% of control; however, the fall in pulmonary vascular pressures preceded the change in Rcoll. The increase in Rcoll with stop flow was markedly reduced when 10% CO2 was infused into the segment. We conclude that collateral channels respond both to the local infusion of CO2 and to the CO2 concentration in the surrounding lung and/or blood, and that the state of distention of pulmonary vessels surrounding collateral ventilatory channels is not a primary determinant of Rcoll. In addition we conclude that bronchiolar channels rather than interalveolar pores are the pathways for collateral ventilation.
Red cell oxygen affinity in fetal sheep: role of 2,3-DPG and adult hemoglobin
Authors: Bard H. , Fouron J. C. , Robillard J. E. , Cornet A. , Soukini M. A.
Published: December 2017

Studies were carried out during fetal life in sheep to determine the relationship of 2,3-diphosphoglycerate (DPG), the intracellular red cell and extracellular pH, and the switchover to adult hemoglobin synthesis in regulating the position of the fetal red cell oxygen-affinity curve in utero. Adult hemoglobin first appeared near 120 days of gestation. The mean oxygen tension at which hemoglobin is half saturated (P50) prior to 120 days of gestation remained constant at 13.9 +/- 0.3 (SD) Torr and then increased gradually as gestation continued, reaching 19 Torr at term. During the interval of fetal life studied, the level of DPG was 4.43 +/- 1.63 (SD) micromol/g Hb and the deltapH between plasma and red blood cells was 0.227 +/- 0.038 (SD); neither was affected by gestational age. The decrease in the red cell oxygen affinity after 120 days of gestation ocrrelated with the amount of adult hemoglobin present in the fetus (r = 0.78; P less than 0.001). This decrease can be attributed only to the amount of the adult-type hemoglobin present, and not to DPG, or to changes in the deltapH between plasma and red blood cells, because both remained stable during the last trimester.
Metabolic and cardiovascular adjustment to arm training
Authors: Magel J. R. , McArdle W. D. , Toner M. , Delio D. J.
Published: December 2017

Maximal and submaximal metabolic and cardiovascular measures and work capacity were studied in control (n = 7) and experimental (n = 9) subjects (S's) during arm work prior to and following 10 wk of interval arm training. These measures were oxygen uptake (VO2), minute ventilation (VE), heart rate (HR), respiratory exchange ratio (R), cardiac output (Q), stroke volume (SV), and arteriovenous oxygen difference ((a--v)O2 diff). In addition, maximal oxygen uptake (VO2max) was measured in both groups during treadmill running. Experimental S's showed significant increases (P less than 0.01) in peak VO2 (438 ml.min-1), max VE (17.7 l.min-1), max (a--v)O2 diff (20.8 ml.l-1), and work time (9.2 min) during arm ergometry, while maximum values of Q, SV, HR, and R remained unchanged. In addition, submaximal heart rates were significantly lower during arm ergometry after training. VO2max during treadmill running remained essentially unchanged. No changes in metabolic and physiological measures were noted for the controls after the 10-wk training period. The results support the concept of training specificity for VO2max, and indicate that the improvement in peak VO2 in arm ergometry reflects enhanced oxygen utilization due to an expanded (a--v)O2 diff.
Relation between oxygen uptake and developed tension in dog skeletal muscle
Authors: Wilson B. A. , Stainsby W. N.
Published: December 2017

Isometric developed tension of in situ gastro-cnemius-plantaris and semitendinosus muscles of the dog was increased 30% with twitch contraction frequency over the range of 0.5--2.0 tw/sc. Developed tension was decreased 75% after 30--40 min of 11--14 tw/s contractions, fatigue. Recovery from fatigue was slow. Intravenously injected K+ after fatigue increased developed tension 50%. Infusions of epinephrine, norepinephrine, and ouabain did not change developed tension. When the oxygen uptake of gastrocnemius-plantaris muscle was measured during twitch contractions at 0.5, 1.0, and 2.0 tw/s before and after fatigue and after injection of K+, the oxygen uptake was found to be directly related to the developed tension.
Pulmonary capillary and permeability during hemorrhagic shock
Authors: Todd T. R. , Baile E. , Hogg J. C.
Published: December 2017

In previous experiments from this laboratory horseradish peroxidase was used to study the structural and functional characteristics of the normal canine pulmonary capillary membrane. The present study used the same technique to try to determine if any change occurred in the pulmonary capillary as a result of hemorrhagic shock. We found that hemorrhagic shock caused a fall (5 expt) or no change (2 expt) in estimated pulmonary transcapillary pressure based on Starling's equation. However, lymphatic flow from the lungs increased. Estimated of filtration coefficients showed a highly significant increase (P less than 0.01) during the hypotensive period. Pulmonary lymphatic protein concentrations were not altered, indicating that water and protein continued to traverse the membrane in the same proportions as under normotensive conditions. These data are consistent with recent observations of minimal changes in the intercellular junctions of the capillary endothelium following hemorrhagic shock made independently on lung tissue from these experiments.
Alpha-adrenergic receptors in human and canine tracheal and bronchial smooth muscle
Authors: Kneussl M. P. , Richardson J. B.
Published: December 2017

We studied the reactions of human tracheal and bronchial smooth muscle and canine trachealis muscle to adrenergic agonists. Human tissue was obtained from recent autopsies of patients with normal lungs and patients with respiratory disorders, and canine tissue was obtained from animals used in other experiments. The muscle was mounted in tissue baths fitted with platinum wire electrodes and the mechanical activity was recorded. Norepinephrine added to the normal human or canine tissue in concentrations up to 10(-5) M caused no reaction. In the normal human and in the dog, pretreatment with histamine or KCl changed this response and when norepinephrine was added the tissue contracted. This contraction was blocked by phentolamine or N,N'-bis-(O-methoxybenzylaminohexyl)-cystamine tetrahydrochloride (BHC). In diseased tissue, the addition of norepinephrine resulted in a contraction that was blocked by phentolamine or BHC and no pretreatment with histamine or KCl was required. These findings demonstrate alpha-receptors in human and canine airway smooth muscle, and there is a difference between normal and diseased human tissue in the reaction of these tissues to alpha-adrenergic agonists.
Glycogen depletion in exercising rats infused with glucose, lactate, or pyruvate
Authors: Bagby G. J. , Green H. J. , Katsuta S. , Gollnick P. D.
Published: December 2017

The influence of an intravenous infusion of glucose, lactate, or pyruvate on the work capacity and rates of glycogen depletion in the liver and hindlimb skeletal muscles of rats has been studied. Running time to exhaustion at a speed of 21 m/min on a treadmill at a +10 degrees incline was prolonged by glucose infusion but shortened by lactate or pyruvate infusions. Blood glucose concentrations were only lowered in the terminal stages of the exercise, whereas at this point lactate was elevated. Declines in liver and muscle glycogen concentrations were retarded by glucose infusion but accelerated by either lactate or pyruvate infusions. In all cases a marked depletion of both muscle and liver glycogen existed at the point of exhaustion. It is concluded from the lack of any major elevation of glucose, lactate, or pyruvate in the blood of the rats during running that these materials were taken up and oxidized, presumably by the working muscles. These observations suggest that skeletal muscle can take up large amounts of glucose and when it is supplied from an external source this can exert a glycogen sparing effect on the liver and working skeletal muscles.
Cardiovascular effects of whole-body heating in spontaneously hypertensive rats
Authors: Wright G. , Knecht E. , Toraason M.
Published: December 2017

The cardiovascular response to severe whole-body heating was examined in anesthetized spontaneously hypertensive (SH) (mean BP = 140 Torr) and normotensive (N) rats (mean BP = 96 Torr). Elevation of colonic temperature to 44 degrees C resulted in an initial increase in arterial pressure (mean BP: SH = 199 Torr, N = 124 Torr) with a subsequent severe hypotension. There was little evidence to suggest that this collapse in systemic pressure was related to a direct heat impairment of cardiac function. It was more likely the result of a progressive venodilation which produced venous pooling and decreased venous return. The arterial blood pressure response to exogenous catecholamine challenge decreased at elevated temperatures. This suggests that there was a deterioration of the vasoconstrictor response and indicated a possible effect of heat at the receptor or effector level. There were significant differences between the responses of normotensive and hypertensive rats to whole-body heating suggesting an enhanced cardiovascular sensitivity in hypertensive rats that may partially explain earlier reports of inferior thermoregulation and heat intolerance in these animals.