bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulmonary mechanics during exercise in subjects with chronic airflow obstruction
Authors: Stubbing D. G. , Pengelly L. D. , Morse J. L. , Jones N. L.
Published: December 2017

A body plethysmograph was used to measure pulmonary mechanics in six subjects with chronic airflow obstruction during steady states at rest and during exercise at 200 and 400 kpm . min-1. The mean forced expired volume in 1 s was 1.32 liters (39.2% predicted). The flow rates during tidal breathing reached the maximum expiratory flow-volume (MEFV) curve in all but one subject, and on exercise they all reached the MEFV curve. Total lung capacity did not change significantly, but functional residual capacity increased to 104% of the control value (P less than 0.05) and residual volume increased to 113.3% of the control value (P less than 0.02). The MEFV curves did not change and tidal flow rates in excess of th MEFV curve were not seen. Dynamic compliance fell with increasing exercise to 52.8% (P less than 0.01) and static expiratory pulmonary compliance to 90.2% of the control value. Transpulmonary pressures during tidal breathing when expiratory flow reached the MEFV curve increased to progressively higher values as the work load increased. At low work loads there were several subjects with negative transpulmonary pressure when maximum flow rates were present. In patients with chronic airflow obstruction, little change occurs during exercise in pulmonary mechanics; the tidal flow patterns are dominated by the expired flow-volume curve, which is not changed by exercise; maximum flow occurs in some patients when transpulmonary pressure is still negative.
Method for measuring regional heat losses in man
Authors: Gin A. R. , Hayward M. G. , Keatinge W. R.
Published: December 2017

Flexible heat flow devices were constructed from 0.4-mm-thick nylon-reinforced rubber sheet, with multiple copper-constantan thermocouples on each side to measure mean temperature difference across the sheet. A method of calibration is described that corrects for the alteration of local heat loss produced by the device itself. It was shown that such errors would otherwise be large when cutaneous blood flow was high, and tissue insulation low, even with devices as thin as these.
Pressure-volume characteristics of excised human lungs: effects of sex, age, and emphysema
Authors: Berend N. , Skoog C. , Thurlbeck W. M.
Published: December 2017

Static deflationary pressure-volume curves were obtained in 28 emphysema-free (18 male and 10 female) and 39 emphysematous excised human lungs inflated to a maximum transpulmonary pressure (Pl) of 30 cmH2O. In emphysema-free lungs, the lung volumes at Pl 30 cmH2O (V30) were significantly related to body length in males and were significantly larger than predicated total lung capacity in vivo. However, corrected for stature (V30/body length), there was no significant age correlation. In both males and females, highly significant correlations between the PL at 50--90% V30 and age were obtained. There were no significant differences in these regressions between males and females. The emphysematous lungs were divided into three groups with increasing emphysema grades. Progressive decreases in the PL at 50--90% V30 and increases in the V30 were seen in the groups with increasing degrees of emphysema. Significant changes occurred in these measurements even in group 2 with mild emphysema, suggesting that the lesions of emphysema are not directly responsible for these changes.
Reflex effects of left heart and pulmonary vascular distension on airways of dogs
Authors: Lloyd T. C.
Published: December 2017

Two types of experiments were performed in anesthetized dogs on cardiopulmonary bypass to see if pulmonary vascular congestion and left heart distension would induce reflex bronchoconstriction. First we distended the isolated left heart and lung vessels with blood while ventilating the lungs and measuring airflow, tidal volume, and transpulmonary pressures. Congestion reduced dynamic compliance and increased inspiratory resistance. Vagotomy increased compliance and decreased resistance but did not alter the effects of congestion. Then we measured changes in tracheal wall tension while we separately distended the pulmonary vessels and left heart. Left heart distension increased tracheal tension, whereas pulmonary congestion increased tension in some dogs but decreased it in others. All effects were eliminated by vagotomy. We concluded that although left heart distension and pulmonary vascular congestion may reflexly increase airway tone, pulmonary congestion may at some times reflexly reduce tone. None of these reflex changes, however, appear to be important in the modest (approximately 20%) changes in airflow dynamics observed during combined left heart and pulmonary vascular distension.
Longevity of exercising obese hypertensive rats
Authors: Booth F. W. , MacKenzie W. F. , Seider M. J. , Gould E. W.
Published: December 2017

The purpose of this study was to determine whether daily running lengthens the life-span of animals dying prematurely due to cardiovascular disease. We used a strain of rat that is genetically hypertensive and obese and is reported to develop atherosclerosis (Exp. Mol. Pathol. 19: 53--60, 1973). These animals were divided into three groups consisting of runners exercised daily on treadmills from an early age life, food-restricted sedentary rats, and libitum eaters that were sedentary. This latter group had significantly higher average daily food intakes and body weights than either of the other two groups. The average life-span of both sedentary groups was significantly longer than the running group. Runners had a greater frequency of focal myocardial necrosis, but atherosclerosis was absent in all three groups. We speculate that daily running may have accentuated the development of factor s that may have contributed to the early death of runners.
Effect of hydration state of circulatory and thermal regulations
Authors: Nadel E. R. , Fortney S. M. , Wenger C. B.
Published: December 2017

To determine the influence of hydration state upon circulatory controls, we studied four relatively fit subjects during duplicate 30-min cycle ergometer exercise bouts (55% VO2max) in euhydrated, hypohydrated, and hyperhydrated conditions. Ambient temperature was 35 degrees C. Hypohydration was achieved by 4 days of diuretic administration and resulted in a whole-body weight loss of 2.2 kg and a plasma volume decrease of approximately 700 ml. Hyperhydration was achieved by ADH administration plus ingestion of 2 liters water but caused only a minor increase volume. Hypohydration resulted in a significantly reduced cardiac output during exercise; this the result of a reduction in stroke volume of 17 ml.beat-1 without adequate elevation in heart rate. the internal temperature (Tes) threshold for cutaneous vasodilation was elevated by 0.42 degree C in hypohydrated conditions; but once vasodilation occurred, the slope of the arm blood flow:Tes relation was unchanged from control. Maximal arm blood flow was reduced by nearly 50% in hypohydration. These restrictions in cutaneous blood flow served to maintain an already compromised venous return, but due to the limitation of core-to-skin heat transfer, forced Tes to nearly 39 degrees C, significantly higher than in euhydrated conditions.
Metabolic and circulatory responses to wheelchair and arm crank exercise
Authors: Sawka M. N. , Glaser R. M. , Wilde S. W. , von Luhrte T. C.
Published: December 2017

To compare metabolic and circulatory responses for wheelchair ergometer (WERG) and arm crank ergometer (ACE) exercise at equal power-output (PO) levels, wheelchair-dependent (n = 7) and able-bodied (n = 10) subjects exercised at PO levels at 30, 90, 150, and 210 kpm times min-1 for each mode of ergometry. Steady-state values of oxygen uptake (VO2), pulmonary ventilation (VE), ventilatory equivalent of oxygen (VE times VO2-1), cardiac output (Q), stroke volume (SV), arteriovenous oxygen difference (a-VO2), heart rate (HR), systolic blood pressure (SBP), and rate pressure product (RPP) were determined at each PO. With the exception of VE times VO2-1 and a-VO2, each variable tended to increase with PO. Generally, VO2, VE, Q, SV, HR, SBP, and RPP responses were higher for WERG than ACE exercise at each PO level. When Q and RPP were expressed in relation to VO2, both variables were higher for WERG exercise. These data suggest that the wheelchair hand-rim system is inherently more strenuous than arm cranking, and that the latter should be studied further as an alternative method for wheelchair propulsion.
Autonomic mechanisms in the initial heart rate response to standing
Authors: Ewing D. J. , Hume L. , Campbell I. W. , Murray A. , Neilson J. M. , Clarke B. F.
Published: December 2017

Autonomic mechanisms underlying the initial heart rate response to standing were analyzed in nine normal subjects. The normal pattern of response was altered by atropine to a small and gradual R-R interval shortening over 30 beats, with no rebound R-R interval lengthening. With additional propranolol, R-R interval shortening was even less and confined to the first 15-20 beats, whereas propranolol alone did not affect the normal response pattern, showing that this is under vagal control with increased cardiac sympathetic activity occurring only if the vagus is blocked. The response was reproducible in 23 normal subjects. Heart rate variation during quiet standing was almost completely abolished by atropine, but unaffected by propranolol, confirming that it is also under vagal control. In four normal subjects no rebound R-R interval lengthening occurred during either "fast" or "slow" tilt, whereas it was present during both "slow" and "fast" standing. The rebound R-R interval lengthening is determined by the muscular activity involved in standing up, rather than by the speed of the maneuver.
Lung inflation can cause pulmonary edema in zone I of in situ dog lungs
Authors: Albert R. K. , Lakshminarayan S. , Kirk W. , Butler J.
Published: December 2017

We investigated whether increases in lung water can occur due to lung inflation in zone I when alveolar vessels are collapsed. Static left lower lobe alveolar pressure, pulmonary arterial pressure, and pulmonary venous pressure were controlled in living, anesthetized, open-chested dogs. The lobe was inflated with 6% CO2 in air and suspended from a strain gauge, which allowed continual weight recording. The lung was held in zone I conditions. Arterial and venous pressures were equal at either 1 or 5 cmH2O, relative to the base of the 10- to 14-cm-high lobes. Weight changes were measured for 5 min after 5-cmH2O increments of alveolar pressure from 0 or 5 to 30 cmH2O. Lung weight gain due to edema occurred with inflation to alveolar pressures above 10 cmH2O. Greater lung distension resulted in greater rates of weight gain. Weight loss occurred on deflation. The fluid may have leaked from distended extra-alveolar vessels. This mechanism could explain the increased lung water seen with mechanical ventilation and/or positive end-expiratory pressure breathing.
Effects of pulmonary edema on regional pulmonary perfusion in the intact dog lung
Authors: Malik A. B. , van der Zee H. , Neumann P. H. , Gertzberg N. B.
Published: December 2017

Regional pulmonary blood flow was determined in dogs during varying degrees of pulmonary edema induced by infusing 179.2-659.4 ml/kg normal saline over 2-3 h. Pulmonary hemodynamics and regional blood flows were measured during the base-line period and at 30 min postinfusion. The degree of pulmonary edema was determined by the final extravascular lung water-to-bloodless dry lung weight ratio (W/D). In dogs developing gross alveolar edema (W/D of 10.70 +/- 0.88 vs. 3.10 +/- 0.30 in controls), the blood flow was shifted to either upper or dependent lung regions. The shift to the upper regions was associated with an increased (P < 0.05) pulmonary arterial pressure (Ppa), whereas the shift to the dependent lung was not associated with a significant change in Ppa. Breathing 100% O2 did not prevent these shifts, suggesting that they were not due to localized hypoxic pulmonary vasoconstriction. The flow distribution patterns were also not related to regional differences in edema. In contrast to the changes during fulminant edema, blood flow distribution did not change after moderate levels of pulmonary edema (W/D of 6.03 0.69), suggesting that gross alveolar flooding is required for a redistribution of pulmonary blood flow. Flow redistribution to the upper lung during airway flooding may be due to increase in Ppa, whereas the increased flow in the dependent lung during the same degree of edema may be due to "bulging" of alveolar vessels into the air spaces, secondary to a decrease in surface activity.
Uptake of chylomicron triglycerides by contracting skeletal muscle in rats
Authors: Mackie B. G. , Dudley G. A. , Kaciuba-Uscilko H. , Terjung R. L.
Published: December 2017

The influence of muscle stimulation (3 Hz) on the uptake of exogenously administered chylomicron 14C-labeled triglycerides (14C-TG) in the three different muscle fiber types was evaluated in fed and fasted pentobarbital-anesthetized rats. The fractional uptake of 14C-TG in the nonstimulated muscles was lowest in the fast-twitch white, intermediate in the fast-twitch red, and highest in the slow-twitch red muscle fiber section. Fasting doubled the uptake in both high-oxidative red fibers. These 14C-TG uptakes were directly proportional (r = 0.993) to their respective activities of lipoprotein lipase in these fiber types of fed and fasted animals reported by others. Muscle stimulation caused a significant increase in the fractional 14C-TG uptake in all of the fiber types. Although the TG uptake could account for only a small fraction of the total energy needs of the working muscle, it could contribute to the turnover of endogenous TG, especially in the slow-twitch red fibers. Further, the estimated TG uptake rate is sufficient to replace endogenous TG loss with an overnight rest following exercise. These results suggest that plasma TG could play an important role in lipid metabolism, especially in the high-oxidative slow and fast muscle fiber types.
Tonic inspiratory muscle activity as a cause of hyperinflation in histamine-induced asthma
Authors: Muller N. , Bryan A. C. , Zamel N.
Published: December 2017

We studied the change in tonic activity of the inspiratory muscles during acute hyperinflation. Hyperinflation was provoked in two asthmatic and three normal subjects by progressively doubling doses of histamine. Changes in lung volume were determined with magnetometers and with a body plethysmograph. Intercostal muscle activity was recorded with surface electrodes and diaphragmatic activity with esophageal electrodes. Tonic activity was defined as electrical activity in the electromyogram present at end expiration. After histamine the maximal observed increase in plethysmographic thoracic gas volume in the five subjects was 29.8 +/- 6.4% of control (mean +/- SE). Hyperinflation was accompanied by a significant increase in tonic activity of the intercostal muscles (P < 0.01) and the diaphragm (P < 0.01). There was a significant correlation between the increase in thoracic gas volume and the increase in tonic intercostal (r = 0.82, P = 0.003) and diaphragmatic (r = 0.89, P = 0.003) activity. We conclude that histamine-induced hyperinflation is accompanied by persistent inspiratory muscle activity throughout expiration.
Body acceleration distribution and O2 uptake in humans during running and jumping
Authors: Bhattacharya A. , McCutcheon E. P. , Shvartz E. , Greenleaf J. E.
Published: December 2017

Body acceleration distribution and its relation to the mode of generation were determined in eight young males (19-26 yr) who walked and ran on a treadmill operated at four speeds and jumped on a trampoline at four heights. With increasing treadmill speed, peak acceleration at the ankle (Aa = 3.0-12.0 Gz) always exceeded that at the back and forehead (Ab = 0.9-5.0 Gz, and Ah = 0.8-3.9 Gz); these acceleration profiles included higher frequency components than those during jumping. Corresponding ranges of oxygen uptake (VO2) and heart rate (HR) were 0.8-3.0 l/min and 90-180 beats/min, respectively. With increasing jumping height, acceleration levels were more symmetrically distributed (Aa = 3.0-7.0 Gz, Ab = 3.9-6.0 Gz, and Ah = 3.0-5.6 Gz); VO2 and HR ranges were 1.1-2.5 l/min and 102-175 beats/min, respectively. VO2 was linearly related to HR for both types of exercise. The results indicate that, for similar levels of HR and VO2, the magnitude of the biomechanical stimuli is greater with jumping on a trampoline than with running, a finding that might help identify acceleration parameters needed for the design of remedial procedures to avert deconditioning in persons exposed to weightlessness.
Fluid transport across the canine tracheal epithelium
Authors: Welsh M. J. , Widdicombe J. H. , Nadel J. A.
Published: December 2017

We measured the rate of fluid movement across the tracheal epithelium of the dog by an electrical method, modified from that originally described by Wiedner (Rev. Sci. Instrum. 47: 775-6, 1976). The base-line volume flow (Jv) from the submucosa to the mucosa was 44 +/- 23 nl.min-1.cm-2 (mean +/- SE; n = 6). In only three of the tissues was the resting Jv significantly greater than zero. Stimulation with 2 X 10(-3) M aminophylline (a drug that we have shown stimulates Cl secretion under short-circuit conditions) increased Jv in all tissues to a mean of 137 +/- 29 nl.min-1.cm-2 (P < 0.001). We also measured the unidirectional fluxes of Cl with the tissue at its spontaneous electrical potential. During the base-line period, the net flux of Cl was not significantly different from zero. During stimulation with aminophylline, Cl secretion increased to a mean of 1.44 +/- 0.50 microneq.cm-2.h-1. Comparison of the stimulated values of Jv and net Cl secretion suggests that fluid secretion by the trachea is isotonic during stimulation with aminophylline.
Marking the tip location of PO2 microelectrodes or glass micropipettes
Authors: Nair P. , Spande J. I. , Whalen W. J.
Published: December 2017

The necessity of localizing the PO2 recording sites in the carotid body of cats has led us to modify our O2 microelectrode to be able to mark the position of the tip. Gold is sputtered on the electrode, and then iron is plated on the gold. The carotid body of cats was exposed, and PO2 was recorded at different depths in the body after which iron was deposited. At the end of the experiment, the excised body was placed in a 1:1 mixture of 4% potassium ferrocyanide and 4% acetic acid for 1 h or more. After that, the body was fixed in a 1:1 mixture of 40% formaldehyde and 95% ethyl alcohol for 1-2 days. Paraffin sections cut at 10 micrometer revealed the recording sites as bright blue spots. Since the cathode size can be made as small as 1 micrometer, discrete spots (a few microns or larger depending on current and time) can be produced at the PO2 recording sites. Several locations can be marked in a few minutes without damage to the tissue or the electrode. In 21 cats all of the 62 marked spots were found. In 16 peripheral (depth 50-150 micrometers) locations the PO2 averaged 101 Torr and in 46 deep locations 73 Torr. This technique is applicable to glass micropipettes and is a unique tool in correlating the structure and function of various tissues.
Response of alveolar epithelial solute permeability to changes in lung inflation
Authors: Egan E. A.
Published: December 2017

The relation between the solute permeability of th alveolar epithelium, characterized as a pore radius, and lung inflation was studied in anesthetized dogs. Pore radius was calculated from measurements of the rate of efflux of several radiolabeled solutes of known molecular size from alveolar saline. Individual animals were studied at two or more separate inflation volumes. The pore radius during the first volume studied averaged 20 A in high-volume animals (mean inflation 82% of capacity) and 15 A at lower volume (mean inflation, 47% of capacity). The difference was significantly P < 0.05.

Lungs inflated to total capacity showed free solute movement across the lung epithelium. Increasing inflation volume in an animal always produced a larger pore radius. Decreasing the inflation volume did not produce a smaller pore radius; it remained the same or became larger. Volume induced increases in lung epithelial solute permeability do not reverse immediately at lower volumes, suggesting this phenomenon represents lung injury.
Thermal features of the female axilla
Authors: Abrams R. M. , Royston J. P. , Humphrey S. J. , Wolff H. S.
Published: December 2017

Axillary (Tax), vaginal (Tv), and sublingual (Tsl) temperatures were measured in 12 women between 0600 and 0730 h prior to their arising from bed. Isothermal maps made of closed axilla 30 min after thermojunctions had been inserted showed a distribution of several temperatures, the lowest Tv-Tax isotherm occupying approximately 40% of the anteroposterior distance. Tax at this point was 0.1 to 0.5 degrees C less than Tv and -0.03 to 0.26 degrees C less than Tsl. The time course of Tax rise varied considerably among subjects, with the slowest still rising 30 min after insertion, whereas the fastest was almost steady after 3 min. The width of the 0.5 degrees C isotherm along the fold averaged 5.8 cm and occupied about 60% of the axillary width. A significant negative correlation was noted between width of the 0.5 degrees C isotherm and Tv-Tax. Effects on the time course of 1) preexposure to air of the axilla for 5 min and 2) different initial thermometer temperatures (10 and 30 degrees C) were studied in 6 women. Analysis of variance showed a significantly higher value of Tax (10 min)-Tax (3 min), i.e., a slower time course with the cooler thermometer. The effects of exposure of the axilla were much more pronounced.
Lung statics and connective tissues after penicillamine in bleomycin-treated hamsters
Authors: Fedullo A. J. , Karlinsky J. B. , Snider G. L. , Goldstein R. H.
Published: December 2017

Penicillamine was administered intraperitoneally to male golden hamsters for 30 days following a single intratracheal dose of bleomycin. Penicillamine treatment increased soluble collagen and decreased glycosaminoglycans in both normal and fibrotic lungs; total collagen and elastin were not significantly changed in normals but were lower in fibrotic animals. The proportions of the different glycosaminoglycans were not affected by penicillamine treatment. When related to body weight, the total lung capacity, vital capacity, and compliance both at low and high lung volumes were increased in animals that received only penicillamine when compared with animals that did not, but interpretation of these results is difficult because penicillamine-treated animals had low body weights. Lung statics were the same in animals that received penicillamine after bleomycin as in those that received bleomycin only, though penicillamine partially reversed the connective tissue expression of the bleomycin lung injury. We conclude that factors other than connective tissue levels are important in determining the mechanical behavior of fibrotic lungs.
Surfactant metabolism of newborn lamb lungs studied in vivo
Authors: Jobe A. , Ikegami M. , Sarton-Miller I. , Barajas L.
Published: December 2017

Surfactant, microsomal, and lamellar body fractions were isolated from the lungs of 5-day-old lambs 0.21-55 h after the intravenous injection of radiolabeled palmitic acid. The specific activities as cpm/mumol phospholipid phosphate of phosphatidylcholine, saturated phosphatidylcholine, phosphatidylglycerol, and phosphatidylethanolamine were measured. The palmitate-labeled phospholipids disappeared from the lung parenchyma with a half-life of approximately 50 h. The radiolabel disappeared from phosphatidylcholine, saturated phosphatidylcholine, phosphatidylglycerol, and phosphatidylethanolamine of microsomal fractions with initial half-life values of 4.5, 4.6, 1.9, and 23.9 h, respectively. The labeled phospholipids rapidly appeared in the lamellar body fraction and accumulated in the surfactant of the lambs in a linear fashion for 35 h. The curves for the labeling of surfactant with radiolabeled saturated phosphatidylcholine, phosphatidylglycerol, and phosphatidylethanolamine were similar to the curve for phosphatidylcholine.
Practical implementation of the barometric method for measurement of tidal volume
Authors: Epstein R. A. , Epstein M. A. , Haddad G. G. , Mellins R. B.
Published: December 2017

The barometric method is unique in permitting measurement of tidal volume in a totally noninvasive manner. Its application and accuracy have been limited by several complex problems. These include control of inspired gas composition, base-line stability, and asymmetry of processes occurring during inspiration and expiration. A new method is described that addresses these problems and facilitates long-term measurements. New calculations, which avoid previous errors that caused the method to systematically underestimate tidal volume, are illustrated.
Changes in beta-adrenergic responsiveness of rats during chronic cold exposure
Authors: Barney C. C. , Katovich M. J. , Fregly M. J. , Tyler P. E.
Published: December 2017

Administration of isoproterenol (50 micrograms/kg sc) to rats that had been exposed to cold (6 degrees C) for 10, 15, and 25 days was accompanied by a greater increase in tail skin and colonic temperatures than in controls kept at 25 degrees C. Administration of isoproterenol (8 micrograms/kg sc) to cold-treated rats (1, 3, 5, 7, 14, and 28 days) increased heart rates above that of controls. However, resting unstimulated heart rates of cold-treated rats were also increased above that of controls after 1, 3, 5, and 7 days of cold exposure but were not different from controls after 14 and 28 days. Cold exposure also led to time-dependent increases in the weights of heart, adrenals, and interscapular brown fat. Thus, chronic exposure of rats to cold is accompanied by an increase in responsiveness of both heart rate and tail skin and colonic temperatures to beta-adrenergic stimulation. The results also suggest that increases in responsiveness to a beta-adrenergic agonist may not occur at the same time for the different beta-adrenergic-mediated metabolic and cardiovascular responses in cold-treated rats.
Plasma renin activity, vasopressin concentration, and urinary excretory responses to exercise in men
Authors: Wade C. E. , Claybaugh J. R.
Published: December 2017

Plasma vasopressin concentration (PAVP), renal function, and effectors of vasopressin release were evaluated in male volunteers during running at heart rates of 0, 35, 70, and 100% of maximum after 10 h abstinence from water (normal hydration) and at 100% after ingestion of 300 ml water. Plasma renin activity (PRA) and PAVP were linearly correlated and correlated to work intensity over all observations. Changes in PAVP were not correlated with changes in plasma osmolality (POSMOL) and plasma volume (PV) over all observations. Furthermore, despite similar changes in POSMOL, PV, PRA, body weight, mean arterial pressure, and plasma lactate concentration, the increase in PAVP after maximal exercise was greater during normal hydration than the water-supplemented state. Decreased urine flow observed in association with exercise was characterized by increased free water and decreased osmotic and creatinine clearances. Thus increased PAVP associated with exercise appears not to play a role in the concomitant antidiuresis. Vasopressin stimuli are probably variable at different times during exercise and may include factors other than those measured.
Rib cage and abdominal restrictions have different effects on lung mechanics
Authors: Bradley C. A. , Anthonisen N. R.
Published: December 2017

The effects of a variety of restrictive procedures on lung mechanics were studied in eight healthy subjects. Rib cage restriction decreased total lung capacity (TLC) by 43% and significantly increased elastic recoil and maximum expiratory flow (MEF). Subsequent immersion of four subjects with rib cage restriction resulted in no further change in either parameter; shifts of blood volume did not reverse recoil changes during rib cage restriction. Abdominal restriction decreased TLC by 40% and increased MEF and elastic recoil, but recoil was increased significantly less than was the case with rib cage restriction. Further, at a given recoil pressure, MEF was less during rib cage restriction than during either abdominal restriction or no restriction. Measurements of the unevenness of inspired gas distribution by the single-breath nitrogen technique showed increased unevenness during rib cage restriction, which was significantly greater than that during abdominal restriction. We conclude that lung volume restriction induces changes in lung function, but the nature of these changes depends on how the restriction is applied and therefore cannot be ascribed to low lung volume breathing per se.
Basenji-Greyhound dog model of asthma: reactivity to Ascaris suum, citric acid, and methacholine
Authors: Hirshman C. A. , Malley A. , Downes H.
Published: December 2017

Bronchial inhalation challenges to Ascaris suum, citric acid, and methacholine were performed in eight Basenji-Greyhound (BG) crossbreed dogs, five of which were reactive to Ascaris antigen aerosols (AAA). Responses to aerosol challenges were measured as changes in pulmonary resistance (RL) and dynamic compliance (Cdyn) and were compared to responses obtained in five mongrel dogs. Responses to methacholine and citric acid were similar in BG dogs whether Ascaris-sensitive or not, but BG dogs were clearly more reactive than mongrels to both types of nonspecific challenge. Methacholine responses were elicited at 10-30 times lower concentrations in BG dogs than in mongrels; 10% citric acid, which failed to elicit any response in mongrels, increased RL 5- to 10-fold in BG dogs. We conclude that the BG dog demonstrates nonspecific bronchial hyperreactivity, as in human asthma.
Recovery of peripheral chemoreceptor function after denervation in ponies
Authors: Bisgard G. E. , Forster H. V. , Klein J. P.
Published: December 2017

Resting ventilation (PaCO2) and ventilatory responses to acute hypoxia and to intravenous NaCN were assessed over a 4-yr period following cutting of the carotid sinus nerves and stripping the adventitia of the aortic arch. The data indicated essentially complete loss of peripheral chemoreceptor function immediately after surgery and hypoventilation during normoxia (delta PaCO2 = +8.7 Torr). There was a time-dependent, partial recovery of peripheral chemoreceptor function between 2 and 22 mo after surgery. Approximately 10% of the ventilatory response to iv NaCN returned, and 30-40% of the normal response to acute hypoxia was restored. Resting PaCO2 was no longer significantly elevated above normal by 22 mo after surgery. Four years after surgery these animals were unable to sustain normal ventilatory acclimatization to chronic hypoxia just as in an earlier study in the same ponies. Experiments carried out under anesthesia showed that recovered peripheral chemoreceptor sensitivity was not present in the carotid chemoreceptor area. However, sectioning of the aortic nerve caused the animals to again hypoventilate during acute hypoxia, and it nearly eliminated the ventilatory response to NaCN, but normal eucapnic ventilation was retained. We conclude that in the pony aortic chemoreceptors become functional in a time-dependent manner following carotid body denervation.
Cortisol reversal of functional delay of lung maturation in fetuses of diabetic rabbits
Authors: Sosenko I. R. , Hartig-Beecken I. , Frantz I. D.
Published: December 2017

Lung maturation was examined in fetuses of rabbit does made diabetes with alloxan and then given cortisol or saline injections in late gestation. We have previously demonstrated decreased deflation stability and decreased functional surfactant by surface balance without change in lung lavage lecithin-to-sphingomyelin ratio (L/S) or disaturated phosphatidylcholine content (DSPC) in offspring of alloxan rabbits. Pressure-volume curves of fetuses of alloxan rabbits treated with cortisol demonstrated deflation stability intermediate between alloxan and control fetuses. Functional assessment of pulmonary lavage surfactant determined by surface balance was increased to control levels in fetuses of alloxan-cortisol does. There were no changes in DSPC content or L/S in lung lavage among fetuses from control does, those treated with alloxan, or those treated with alloxan than cortisol during late gestation. These findings suggest that maternal cortisol administration in the alloxan diabetic rabbit model produces a specific reversal of the functional delay of lung maturation caused by alloxan diabetes.
Modulation of maximum thermogenesis by feeding in the white rat
Authors: Wang L. C.
Published: December 2017

The present study investigated the availability of substrates as a limiting factor in acute cold exposure. By use of a self-control experimental design, thermogenesis was measured in rats at -10 degrees C under 21% O2-79% He following different feeding regimes. Overnight fasting resulted in the lowest total heat production (9,949 +/- 189 cal/120 min, mean +/- SE, n = 11), maximum rate of thermogenesis (1,320 +/- 23 cal/15 min), and final body temperature (31.0 +/- 0.3 degrees C). The values were significantly lower than those found after overnight rationing (10,630 +/- 231, 1,386 +/- 29, and 32.8 +/- 0.5, respectively) or ad libitum feeding (10,821 +/- 224, 1,395 +/- 27, and 33.5 +/- 0.3). Rats fasted overnight but fed intragastrically a 5-ml substrate mixture (3 kcal/ml) 60 min prior to cold exposure resulted in the highest values for all parameters (11,553 +/- 207, 1,488 +/- 23, and 33.7 +/- 0.4). The increases were not due to the specific dynamic action of food. Since the levels of maximum thermogenesis and cold tolerance can be modulated by feeding, it is evident that substrate availability limits thermogenesis in severe cold independent of respiratory-cardiovascular functions and cellular oxidative capabilities.
Effect of pulmonary artery occlusion and reperfusion on extravascular fluid accumulation
Authors: Barie P. S. , Hakim T. S. , Malik A. B.
Published: December 2017

We determined the effect of pulmonary hypoperfusion on extravascular water accumulation in anesthetized dogs by occluding the left pulmonary artery for 3 h and then reperfusing it for 24 h. The lung was reperfused either at normal left atrial pressure (Pla) or during increased Pla induced by a left atrial balloon. In each case the extravascular water content-to-bloodless dry weight ratio (W/D) of the left lung was compared with that of the right lung. The W/D of the left lung of 3.26 +/- 0.49 ml/g was not significantly different from the value of 2.87 +/- 0.37 for the right lung after the reperfusion at normal Pla. However, the W/D of the left lung of 5.10 +/- 0.38 ml/g was greater (P less than 0.05) than the value of 4.42 +/- 0.34 for the right lung after reperfusion at Pla of 25 Torr. This difference could not be prevented by pretreatment with heparin, suggesting that the increase in lung water content was not due to activation of intravascular coagulation secondary to stasis occurring during the occlusion. Because the left lung was more edematous than the right one, even though both lungs had been subjected to the same increase in Pla, the results suggest that a period of pulmonary hypoperfusion causes an increase in the interstitial protein concentration.
Plasma volume, osmolality, vasopressin, and renin activity during graded exercise in man
Authors: Convertino V. A. , Keil L. C. , Bernauer E. M. , Greenleaf J. E.
Published: December 2017

Plasma volume (PV), renin activity (PRA), and osmotic (Osm), sodium (Na+), and arginine vasopressin (AVP) concentrations were measured in venous blood samples taken before and after three levels of cycle ergometer exercise (100, 175, and 225 W) in 15 young male volunteers. Plasma volume and solute concentrations changed significantly (P less than 0.05, denoted by *) with work intensity. The % delta PV was -3.7%* at 100 W, -8.8%* at 175 W, and -12.4%* at 225 W. Plasma Na+ concentration, Osm, and AVP increase were curvilinear with graded exercise and were significant only when work intensity exceeded 40% VO2max. PRA increase was linear and significant at all work levels. The % delta PV was significantly correlated with delta Osm (r = 0.99*) and delta Na+ (r = 0.89*) but had low correlations with delta AVP (r = 0.22, NS) and delta PRA (r = 0.12, NS). However, delta AVP was significantly correlated with delta Na+ (r = 0.86*) and delta Osm (r = 0.83*), whereas delta PRA had low correlations with delta Na+ (r = 0.33, NS), delta Osm (r = 0.29, NS), and delta AVP (r = 0.43, NS). The data support the hypothesis that a) with exercise, AVP release is a primary factor for fluid and electrolyte regulation as it is highly correlated with the plasma hyperosmolality produced by a net hypotonic plasma efflux; b) an exercise intensity greater than 40% VO2max is required to change plasma osmolality and, thus, stimulate significant AVP release; and c) the stimulation of the renin-angiotensin system is a more general stress response, which responds to increasing sympathetic nervous activity.
Configuration of the chest wall and occlusion pressures in awake humans
Authors: Grassino A. E. , Derenne J. P. , Almirall J. , Milic-Emili J. , Whitelaw W.
Published: December 2017

During CO2 rebreathing in sitting position seven of nine conscious men showed a progressive fall in expiratory reserve volume, most of it due to a decrease in abdominal volume. Diaphragm length at end expiration was thus increased, and some elastic recoil pressure became available to drive inspiration. In four out of six subjects, when CO2 tension was greater than 55 Torr, there was a dip in abdominal pressure at the beginning of inspiration, and the change in transdiaphragmatic pressure during the first 100 ms of an occluded inspiration was smaller than the simultaneous change in mouth pressure (P0.1). In the subjects who showed the smallest diaphragmatic pressure in this 100 ms, electromyogram recordings showed that abdominal activity ceased before the onset of inspiration, and diaphragm activity did not appear until later than 100 ms into inspiration. We conclude that, in four our of our six subjects in the sitting posture, P0.1 can be generated in whole or in part by release of chest wall elastic recoil or in intercostal muscle contraction. In the supine posture, there was no change by end-expiratory chest wall configuration, and onset of diaphragm contraction coincided with beginning of inspiration in the two subjects in whom diaphragm electromyogram was recorded.
Lipolysis and cAMP accumulation in adipocytes in response to physical training
Authors: Shepherd R. E. , Noble E. G. , Klug G. A. , Gollnick P. D.
Published: December 2017

Adenylate cyclase activity is lower in membrane preparations of fat cell homogenates from exercise-trained compared with sedentary rats (J. Appl. Physiol.: Respirat. Environ, Exercise Physiol. 42: 884-888, 1977). In the present investigations lipolysis and cyclic adenosine 3':5'-monophosphate (cAMP) accumulation were measured in isolated parametrial fat cells prepared from sedentary and trained rats. The purpose of these investigations was to determine whether the normal catecholamine-induced increases in cAMP accumulation is affected in isolated adipocytes from endurance-trained rats. The increases in cAMP accumulation in response to isoproterenol (0.01-10 microM) was reduced in fat cells isolated from trained rats. However, glycerol release in response to the same hormonal challenge was greater in these adipocytes. cAMP phosphodiesterase activity measured at 0.125 and 1.025 microM cAMP was greater in the particulate fraction of fat cell homogenates obtained from trained rats as compared with their sedentary counterparts. Hormone-sensitive lipase activity was reduced in crude fat pad homogenate preparations from trained rats if the animals were killed at rest. However, if the animals were run to exhaustion immediately prior to being killed, there were no differences in the hormone-sensitive lipase activity between preparations from trained and nontrained rats. These data indicate that, although cAMP accumulation by isolated fat cells in response to isoproterenol is markedly lower in trained rats, lipolysis and hormone-sensitive lipase activation is not reduced.
Neural response of carotid chemoreceptors following dopamine blockade
Authors: Donnelly D. F. , Smith E. J. , Dutton R. E.
Published: December 2017

The role of endogenous carotid body dopamine in the afferent chemoreceptor circuit was studied by means of haloperidol-induced dopamine antagonism. In 19 cats that were anesthetized with pentobarbital sodium and paralyzed, single carotid body nerve fibers were dissected free and placed on unipolar platinum wire electrodes. In 10 of these cats, the neural response to room air and the last 2 min of 6-min inhalations of 3, 6, and 9% CO2 were recorded, and blood samples were drawn for gas tension measurements. Haloperidol was administered at a dose (250 micrograms/kg) shown to block the inhibitory effect of injected dopamine. Following a 15-min equilibration, the CO2 response was again tested. In four other cats the CO2 response was tested with a hyperoxic background. In the remaining five cats the response to isocapnic hypoxia was recorded during administration of 15, 12, and 8% O2 before and following haloperidol. There was a significant increase in room air discharge activity and in hypoxic sensitivity following haloperidol. However, there was no significant change in hypercapnic sensitivity. These results suggest that there is a modulatory role for endogenous dopamine only in the hypoxic response.
Analysis of error in the determination of respiratory gas exchange at varying FIO2
Authors: Ultman J. S. , Bursztein S.
Published: December 2017

On-line gas exchange monitors have been based on the measurement of both inspired and expired flows (method A) or on the measurement of expired flow only (method B). In both methods, the cancellation of systematic errors is appreciable if calibration errors in the inspiration variables are matched with calibration errors in the corresponding expiration variables. The determination of oxygen consumption (VO2) results in a considerable amplification of random measurement error, which becomes larger as the inspired oxygen fraction (FIO2) is made larger. For example, when in method A all gas compositions and flows are in error by +/- 0.01, the computed value of VO2 will be in error by +/- 0.16 when FIO2 = 0.21 and by +/- 0.40 if FIO2 = 0.50. When air is breathed, method B creates smaller errors than method A, but as FIO2 is increased the error in method B increases sharply and eventually overtakes that of method A. Even at high FIO2 values, the random error in VO2 may be reduced to an acceptable value by estimating it from a sequence of 100 measurement samples requiring a minimum of 5 min to acquire. There is no error amplification in the computation of carbon dioxide production.
Muscle fiber recruitment and blood pressure response to isometric exercise
Authors: Petrofsky J. S. , Phillips C. A. , Sawka M. N. , Hanpeter D. , Lind A. R. , Stafford D.
Published: December 2017

Blood pressure was recorded during fatiguing and nonfatiguing isometric contractions of a slow-twitch muscle (the soleus) and a mixed muscle (the medial gastrocnemius) of the cat. Four tensions were examined in each muscle; 10, 25, 40, and 70% of the muscle's initial strength (tetanic tension of the unfatigued muscle). All experiments were also repeated at two muscle temperatures, 28 and 38 degrees C. For the soleus muscle, there was no change in the blood pressure during isometric contractions. For the medial gastrocnemius muscle, both the systolic and diastolic blood pressure increased markedly when either all or just the fast-twitch motor units were stimulated; however, when only the slow-twitch motor units were stimulated, a lower pressor response was observed. Venous blood samples were drawn before, during, and after fatiguing and nonfatiguing contractions of both muscles to determine the K+ concentration in the venous blood. The mean increase in the K+ concentration during contractions was 0.6 meq/l for the slow-twitch motor units of the soleus and 5.1 meq/l for the motor units in the medial gastrocnemius.
Responses of leukocytes and other hematologic parameters to thermal dehydration
Authors: Ohira Y. , Girandola R. N. , Simpson D. R. , Ikawa S.
Published: December 2017

Effects of thermal dehydration without exercise on leukocyte differentials, serum protein fractions, and other hematologic characteristics were studied in six healthy subjects. Both leukocyte and serum total protein levels increased beyond that predicted by hemoconcentration alone. Eosinophil counts decreased significantly, although other leukocyte counts tended to increase. Serum globulin concentrations tended to increase, but the albumin level did not change. Serum K+ concentration was elevated, but Na+ and Cl- were unaffected. It is suggested that thermal dehydration affects blood leukocyte composition and protein metabolism in many of the same ways as physical exercise.
Critical dependence of respiratory rhythmicity on metabolic CO2 load
Authors: Phillipson E. A. , Duffin J. , Cooper J. D.
Published: December 2017

We examined the dependence of respiratory rhythm generation on the rate of CO2 production (VCO2) in six awake sheep using a venous-to-venous extracorporeal perfusion circuit that included two carbon dioxide membrane lungs (CDML) designed to facilitate the removal of CO2 from blood. As progressively greater proportions of the resting VCO2, of the sheep were removed from the venous blood by the CDML, there were proportional reductions in pulmonary CO2 excretion and in minute volume of ventilation (VE); when CO2 was removed by the CDML at a rate equal to its metabolic production by the sheep, VE fell to zero, with normal values of arterial PCO2, pH, and PO2. The results indicate that effective respiratory rhythm generation is critically dependent on stimuli related to VCO2.
Effects of glycerol feeding before and after exhausting exercise in rats
Authors: Terblanche S. E. , Fell R. D. , Juhlin-Dannfelt A. C. , Craig B. W. , Holloszy J. O.
Published: December 2017

Rats were fed either 1 g of glycerol or 1 g of glucose following exercise to exhaustion. Glucose feeding resulted in a rapid increase in blood glucose, with attainment of peak hyperglycemia within 1 h and of peak muscle glycogen in about 2 h. Feeding 1 g of glycerol resulted in marked elevation of glycerol concentration in blood, liver, and muscle; the highest values, measured 1 h after glycerol feeding, ranged from 29 to 42 mumol/g tissue. Blood glucose and muscle glycogen increased slowly in the glycerol-fed rats and peaked much later than after glucose feeding. In perfused rat hindlimb muscles, negligible amounts of [14C]glycerol were incorporated into glycogen. These findings suggest that muscle is not able to utilize glycerol to a significant extent and that glucose derived from glycerol was the major substrate for muscle glycogen synthesis. Animals fed glycerol before a run to exhaustion were able to exercise significantly longer than control rats (153 +/- 11 min vs. 116 +/- 6 min). The glycerol-fed rats depleted their muscle and liver glycogen stores less rapidly than the controls and were protected against development of hypoglycemia during the exercise.