bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulmonary capillary recruitment during airway hypoxia in the dog
Authors: Wagner W. W. , Latham L. P.
Published: December 2017

To study the effect of hypoxia on the pulmonary capillaries, windows were inserted in the chest wall of 9 pentobarbital-anesthetized dogs. A microscope with an image-superimposing device was used to make drawings of the perfused capillaries. Summed lengths of individual perfused capillaries in the drawing were determined with a map-measuring tool. Total capillary length was constant between PaO2 of 160 and 70 Torr. As PaO2 fell below 70 Torr, recruitment of previously unperfused capillaries occurred in every case; at PaO2 of 40 Torr, the total length of perfused capillaries was about 4 times greater than during normoxia. There was no correlation between the recruitment of capillaries and alterations in left atrial pressure, only a weak correlation with cardiac output changes, but a very strong correlation with increased pulmonary artery pressure. This implies that recruitment was probably caused by vasoconstriction within the lung.
Augmentation of sickling process due to turbulent blood flow
Authors: Stein P. D. , Sabbah H. N. , Mandal A. K.
Published: December 2017

The purpose of this study was to determine if the fluid mechanical stresses associated with turbulent blood flow can contribute to the sickling process. Blood from seven patients with sickle cell disease was subjected to intermediate and high levels of turbulent flow in vitro. Turbulence was quantitated by hot film anemometry. Control samples showed 20 +/- 3% sickled cells. Cells subjected to intermediate levels of turbulent flow showed 26 +/- 4% sickling (P less than 0.01); and blood subjected to high intensities of turbulence showed 31 +/- 4% sickling (P less than 0.01). A quantitative count by electronmicroscopy, performed in one patient, showed polymerization of the hemoglobin indicative of sickling in more cells subjected to turbulence than in the control sample. A turbulence-reducing agent, polyethylene oxide, diminished the augmentation of the sickling process as it reduced turbulence at comparable Reynolds numbers. These results support the hypothesis that a deleterious effect upon hemoglobin SS erythrocytes may occur due to the mechanical stresses of turbulent flow. The agitation associated with turbulent flow presumably modifies the stabilizing factors of the intracellular colloidal solution of hemoglobin, thereby contributing to sol-gel transformation. Such hydrodynamic stresses may supplement the previously described factors which contribute to sickle cell crises.
Local regulation of pulmonary blood flow and ventilation-perfusion ratios in the coatimundi
Authors: Grant B. J. , Davies E. E. , Jones H. A. , Hughes J. M.
Published: December 2017

Small catheters (ca. 3 mm diam at tip) were wedged in subsegmental bronchi in anesthetized coatimundi (Nasua nasua) during spontaneous breathing. Mixed expired gases of a group of lobules were sampled continuously without contamination from neighboring units, and local tidal volume, frequency, carbon dioxide production, and oxygen consumption were measured, as well as mixed venous PO2 and PCO2. Local ventilation-perfusion ratio, alveolar PO2, PCO2, and blood flow were calculated. There was a 22% reduction (range 15–38) in local perfusion (as percent of flow at PAO2 100 mmHg) per 10 mmHg fall in local alveolar oxygen tension over the PAO2 range 150–36 mmHg. Local hypercapnia had little effect on local flow. Local tidal volume (ca. 1% of total tidal volume) was unaffected by changes in alveolar gas tensions. The contribution of vasoconstriction or vasodilatation, as a negative feedback system, to the stability of local PAO2 was greatest close to the physiologic range (65–85 mmHg) falloderate efficiency.
Probe for production and measurement of acute mitral regurgitant flow in dog
Authors: Kleber A. G. , Simon R. , Rutishauser W.
Published: December 2017

A probe for production and measurement of acute mitral regurgitation in dogs is described. It consists of a tube that is introduced into the mitral valve through the left atrial appendage. Regurgitant flow through the tube is measured by an electromagnetic device. Variation of flow and zero flow are achieved by narrowing or occluding the tube with a rubber cuff. In animals weighing 30–50 kg, the probe does not produce significant mitral stenosis and the mitral leaflets fit closely around the probe during ventricular systole. The instantaneous relationship between mitral regurgitant flow (MRF) and the gradient between left ventricular and left atrial pressure shows a marked delay of MRF at the beginning and end of regurgitation. This delay can be attributed to some extent to electrical phase lag and to the small movement of the probe relative to the mitral valve during the cardiac cycle. Measurement of regurgitant stroke volume is affected by this movement only to a small extent.
Lactate metabolism in resting and exercising dogs
Authors: Issekutz B. , Shaw W. A. , Issekutz A. C.
Published: December 2017

The effect of treadmill run on the turnover rates of glucose ([2-3H]glucose) and lactate ([U-14C]lactate), on the rates of oxidation (ROX) of lactate, and its conversion to glucose (L LEADS TO G) were measured with the primed constant-infusion technique. Comparable lactate turnover rates were obtained at rest by infusing epinephrine, or Na-L(+)-lactate with or without norepinephrine. With increasing lactate levels (L) the rate of disappearance (RdL), ROX, and L leads to G increase in a linear manner. At the same lactate level, RdL, ROX, and L leads to G are significantly higher in the running dog. Exercise increased the metabolic clearance rate of lactate threefold. At rest ROX and L leads to G represented about 50% and 18–19% of RdL, respectively. The corresponding values in the running dogs were 55% and 25%, respectively. At rest about 9% of the hepatic glucose output arose from lactate while during exercise this varied from 7 to 26% depending on RdL. It is concluded that a) the working muscle produces and utilizes lactate at the same time, and b) “in vivo” the major factor which controls both ROX and gluconeogenesis is the substrate supply.
Central circulation during exercise after venesection and reinfusion of red blood cells
Authors: Ekblom B. , Wilson G. , Astrand P. O.
Published: December 2017

To study central circulation at different levels of hemoglobin (Hb) concentration, five subjects performed submaximal and maximal exercise in three different situations: 1) control, 2) after venesection of 800 ml of whole blood, and 3) after reinfusion of the red blood cells about 30–35 days after venesection. Maximal oxygen uptake (VO2 max) decreased from 4.27 l-min-1) at control to 4.03 l-min-1 after venesection (P less than 0.05) and increased to 4.61 l-min-1 after reinfusion (P less than 0.05). Maximal values on cardiac output (Q), heart rate (HR), and stroke volume (SV) were the same in the three situations. Thus, there was no compensatory increase in Qmax due to the lowered arterial oxygen content (Cao2) after venesection. An increase of the Cao2 (Hb concentration) and a lowering of the Cvo2 contributed equally to the increased VO2 max after reinfusion. At a given submaximal VO2, HR and blood lactates were increased at lowered Hb concentration and decreased at increased Hb concentration over control levels. Correlation coefficient for the change in Q in relation to the acute change in Hb concentration at a given submaximal VO2 was -0.49 (P less than 0.05).
Dual contribution theory of regulation of CSF HCO3 in respiratory acidosis
Authors: Hasan F. M. , Kazemi H.
Published: December 2017

Regulation of CSF HCO3-in respiratory acidosis was studied in light of the “dual contribution theory,” which proposed that there were two sources for the CSF HCO3-increase: 1) HCO3-by diffusion from plasma and 2) HCO3-generated in the CNS and catalyzed by the local carbonic anhydrase (J. Appl. Physiol. 38: 504–512, 1975). In anesthetized dogs with an increase in Paco2 of 30 mmHg for 4 h the plasma HCO3 increased 2 meq/1 and CSF 6 meq/1. In combined respiratory and metabolic acidosis, plasma HCO3-did not increase but CSF HCO3-increased 6 meq/1. In combined acidosis and intraventricular injections of acetazolamide no increase in plasma or CSF HCO3-occurred. In combined respiratory acidosis and metabolic alkalosis and intraventricular acetazolamide, plasma HCO3-increased 15 meq/1 but CSF HCO3-increased 6 meq/1. Brain and CSF ammonia increased linearly and selectively with the increase in the relative contribution of CNS HCO3-increase. Therefore regulation of CSF HCO3-in respiratory acidosis depends on both components of the dual contribution theory, where each component can provide the total CSF HCO3-increase under appropriate experimental conditions. The control mechanism may be sensitive to changes in [H+] on the brain side of the blood-brain barrier.
Autonomic thermoregulation in squirrel monkey when behavioral regulation is limited
Authors: Adair E. R.
Published: December 2017

Squirrel monkeys (Saimiri sciureus) in a cold environment (10, 0, or -5 degrees C) learned to partially control their chamber air temperature by pulling a chain for 10-s reinforcements of 30 degrees C air. A maximal response rate of 5/min produced an average air temperature (24–27 degrees C), well below their preferred 35 degrees C. Metabolic heat production was elebtaed 0.3–1.0 W/kg. Preoptic cooling (via stereotaxically implanted thermodes) stimulated increased metabolic heat production, with a resultant rise in core temperature. Preoptic warming stimulated reduced heat production and some peripheral vasodilation, resulting in a fall in core tenperature. The metabolic response of all animals was directly related to the skin-to-air temperature difference (Tsk - TA). Usually, mean skin temperature remained essentially unchanges as a result of a steady behavioral response rate. An increase in metabolic heat production was observed in one monkey during preoptic warming. The study demonstrated that even when behavioral thermoregulation is inefficient, it is generally sustained with maximal vigor over long periods. This behavior is then supplemented by appropriate autonomic adjustments when necessary to achieve full regulation of the body temperature.
Solubility of 92 in blood with different hemoglobin concentrations at low temperatures
Authors: Christoforides C. , Hedley-Whyte J.
Published: December 2017

The Brunsen solubility coefficients for O2 in blood obtained from healthy nonsmoking subjects have been determined at 0, 6, and 12 degrees C for bloods of hemoglobin concentrations 5.6, 10.2, 15.7, and 22.5 g/100 ml. Direct gasometric measurements show that blood has a relative solubility (alphabeta/alphah2o) different for each hemoglobin concentration but constant for any given hemoglobin concentration at the temperatures studied (0.6, and 12 degrees C). For hemoglobin concentrations 5.6, 10.2, 15.7, and 22.5 g/100 ml alphabetao degrees C/alphabeta 12 degrees C rations were 1.36, 1.35, 1.35, and 1.35, respectively. The alpha H20(0 degrees C)/alpha H20(12 degrees C) ratio is 1.34. Consequently, it was possible to construct a table for the Brunsen solubility coefficients for O2 in blood from O to 15 degrees C of different hemoglobulin concentrations. Values from 10 to 15 degrees C published in the Biologal Hanbook, Respiration and Circulation, based on extrapolations from previous direct measurements of temperatures from 18 to 37 degrees C differ only 1% from our present results.
A model of graded ischemia in the isolated perfused rat heart
Authors: Kligfield P. , Horner H. , Brachfeld N.
Published: December 2017

Insertion of a flow pump into the Langendorff retrograde perfusion apparatus has permitted the production of stable, graded ischemia in hearts whose hemodynamic and metabolic response may be evaluated. Ventricular pressures were monitored with a modified balloon and catheter-tip manometer system, and oxygen consumption , lactate and glucose metabolism, and tissue high-energy phosphate stores measured. A 15-min stabilization period in 56 paced hearts was followed by 15 min of either full, 40, 30, 20, or 10% coronary flow, after which the ventricular tissue was freeze-clamped for tissue assay. Tissue creatine phosphate fell progressively from 23.7 in full flow hearts to 9.9 mumol/g dry wt after 90% reduction in flow. This was accompanied by a graded reduction in ATP from 20.3 to 14.0 mumol/g dry wt and a rise in AMP from 1.1 to 2.6 mumol/g dry wt. Tissue lactate rose progressively from 22.3 to 60.1 mumol/g dry wt. Hemodynamic function correlated with coronary flow. This preparation offers an opportunity to study pharmacological and metabolic interventions in ischemic heart disease.
Ventilatory responses to the metabolic acidosis of treadmill and cycle ergometry
Authors: Koyal S. N. , Whipp B. J. , Huntsman D. , Bray G. A. , Wasserman K.
Published: December 2017

Ventilation and acid-base responses were studied at comparable levels of O2 uptake during cycle ergometer and treadmill exercise, to determine the extent to which the type of exercise affects these responses. Twenty male subjects performed 50-, 100-, and 150-W cycle ergometer exercise and three work rates of similar O2 uptake on a treadmill. At comparable oxygen uptakes, arterial lactate and VE were higher and arterial pH and bicarbonate were lower for cycle ergometer than treadmill exercise. These differences could be accounted for by the greater degree of metabolic acidosis during cycle ergometer work. The increment in VE over that predicted (from an extrapolation of the linear relationship of the VE-VO2 relationship for low work rates) was linearly related to the decrease in arterial bicarbonate; VE was increased by approximately 4 1/min for each meq/1 of bicarbonate decrease for both treadmill and cycle ergometry.
Estimation of cardiac output by an N2O rebreathing method in adults and children
Authors: Zeidifard E. , Godfrey S. , Davies E. E.
Published: December 2017

A nitrous oxide rebreathing method was used to measure recirculation time and cardiac output (as pulmonary blood flow) in adults and children during exercise. The method was compared with the indirect (CO2) Fick rebreathing method in almost simultaneous measurements of cardiac output. Recirculation time varied from about 15 s at rest to 8.5 s at high levels of exercise,and was slightly longer in children than adults. Cardiac output estimated by both methods was within the normal range for children and adults, being lower for a given oxygen consumption in children. For the adults the mean intrasubject variability of the N2O rebreathing method, measured as the coefficient of variation of cardiac output, was in the range of 6–8% at all levels of work. This was lower than reported for other N2O rebreathing methods,and similar to values based on the indirect (CO2) Fick, direct (O2) Fick, and dye-dilution methods of estimating cardiac output. The method is therefore proposed as a noninvasive technique suitable for rapid, accurate, and reproducible measurements of cardiac output.
Influence of posture on flow dependence of distribution of inhaled 133Xe boli
Authors: Sybrecht G. , Landau L. , Murphy B. G. , Engel L. A. , Martin R. R. , Macklem P. T.
Published: December 2017

The second 100 ml of gas inspired at constant flow rates (V) from 0.1 to2.5 l/s was tagged with 133Xe to determine the apicobasal bolus distribution ratio (VAlvA/VAlvB) for seven normal subjects in both the upright and supine postures. Gas was preferentially distributed to the base at low V. As Vincreased, redistribution to the apex occurred but was greater in the supine posture. As apicobasal time constant differences should be minimal in thesupine posture, the greater flow dependence of bolus distribution suggests that the pressure swing was greater over apical zones than basal zones. Model studies indicate that the pressure differences (deltaPd) necessary topredict the measured VAlvA/VAlvB at all flow rates are less than 1.0 cmH2O.Such sensitivity of gas distribution to deltaPd at both low and high flow rates makes it appear relatively insensitive to regional compliance and resistance.
Nonadrenergic inhibitory nervous system in human airways
Authors: Richardson J. , Beland J.
Published: December 2017

Human airways, from the middle of the trachea to the distal bronchi, were studied in vitro for the presence of inhibitory nerves. The tissue was obtained from operations and from recent autopsies. Electrical field stimulation of the tissues demonstrated cholinergic, excitatory nerves and their effect was blocked by atropine. Field stimulation of the tissues, in the presence of atropine, relaxed the smooth muscle even when the muscle was contracted by histamine. The field stimulation-induced relaxation was neither blocked nor modified by adrenergic blocking agents. Maximum relaxation of the bronchial muscle was obtained with a pulse duration of 1–2 ms, 70 V,and frequencies of 20 Hz and greater. The tracheal smooth muscle showed 85%of maximal relaxation with a frequency of 10 Hz. Tetrodotoxin, blocked the field stimulation-induced relaxation for pulse durations of 2 ms; this indicated that nerves were being stimulated. The airway system shows some of the characteristics of the nonadrenergic inhibitory system in the gastrointestinal tract and of the system reported in the guinea pig trachealis muscle.No evidence of adrenergic inhibitory fibers was found in the bronchial muscle with either pharmacological or histochemical techniques. These findings suggest that the nonadrenergic inhibitory system is the principal inhibitory system for the smooth muscle of human airways. We suggest that a defect in the airway system, such as that shown in the gastrointestinal tract, may be an explanation for the hyperreactive airways of asthma and chronic bronchitis.
Design for a micropowered multichannel PAM/FM biotelemetry system for brain research
Authors: Wertz R. , Maeda G. , Willey T. J.
Published: December 2017

A design for a 12-channel pulse amplitude-modulated/FM biotelemetry system is described. The biotelemeter mounts on an animal's head close to the electrode probes to record and transmit brain electrical data. The size of the unit is 4.5 x 6.5 x 2 cm and it weighs about 60 g. It is designedto acquire EEG and other physiological data where the requirement is to obtain bioelectrical activity without cable encumbrance or confining behavioral restrictions. The telemeter consumes about 800 muW of power and operates for approximately 3 continous days before it is necessary to exchange the utilization of complementary metal oxide semiconductor (CMOS) integrated circuits. Transmission range is typically about 10 m.
Pulmonary capillary permeability to HRP in dogs: a physiological and morphological study
Authors: Michel R. P. , Inoue S. , Hogg J. C.
Published: December 2017

Pulmonary capillary permeability was studied in 10 normal anesthetized dogs using horseradish peroxidase (HRP) as tracer. Physiological studies involved measurement of left ventricular, pulmonary arterial, and wedge pressures, and of right lymphatic duct (RLD) and thoracic duct lymph flows. Plasma and interstitial oncotic pressures were calculated from protein measurements. After 1 h of lymph collection, HRP was injected intravenously at three total dose levels, low (20–30 mg/kg), medium (55 mg/kg), and high (110–120 mg/kg) as a bolus followed by smaller doses over 1.5–3 h. HRP was measured colorimetrically in plasma and lymph and appeared in the first RLD lymph sample collected at all dose levels. Electron microscopic studies to examine the passage of HRP from plasma to RLD, while less sensitive in that HRP was seen only at the high dose, showed that it crossed pulmonary capillaries under normal physiological conditions. Freeze-cleaving studies suggest this may have occurred through pathways in the interendothelial space caused by discontinuities in the junctional strands of tight junctions.
Dependency of hypoxic pulmonary vasoconstriction on temperature
Authors: Benumof J. L. , Wahrenbrock E. A.
Published: December 2017

We studied the effect of temperature change on hypoxic pulmonary vasoconstriction. Selective hypoxia on the left lower lobe of the lung in open-chested dogs at 37 degrees C caused the electromagnetically measured blood flow to the lobe to decrease 51 +/- 5 (SE)% and its vascular resistance to increase 155 +/- 25%. Testing hypoxic response. The hypoxic response at 31.1 +/- 0.4 degrees C was only a 26 +/- 6% decrease in lobar blood flow compared to the hypoxic response at 40.0 +/- 0.5 degrees C which was a 60 +/- 5% decrease in lobar blood flow. Hypothermia itself was associated with a significant increase in pulmonary vascular resistance. We conclude that hypothermia inhibits and hyperthermia enhances hypoxic pulmonary vasoconstriction. The mechanism of inhibition may involve prehypoxic vasoconstriction.
Role of bulk fluid flow in protein permeability of the dog lung alveolar membrane
Authors: Gee M. H. , Staub N. C.
Published: December 2017

In five anesthetized, closed-thorax dogs, we measured net tracer albumin (RISA) uptake rate from an isosmotic buffer-filled lung lobe for 6 h; 3 h at each of two different alveolar RISA concentrations. We calculated the permeability coefficient assuming a two-compartment (alveolar fluid and plasma) diffusional model. In every dog the permeability coefficient decreased after the alveolar RISA concentration was increased. After freezing the lungs terminally, we found the fluid-filled lobes had extensive free interstitial fluid perivascular cuffs, indicating a third compartment filled by bulk flow. In separate experiments, we filled isolated lung lobes with buffer containing RISA and microsampled free interstitial fluid. The free interstitial fluid RISA concentration averaged 90% of airway concentration. The interstitium appears to fill by bulk flow through low-resistance channels. Tracer protein uptake from a fluid-filled lung lobe involves three fluid compartments. We postulate fluid and protein enter the interstitium by bulk flow along a hydrostatic pressure gradient, and protein then diffuses into plasma from the interstitium.
Temperature and per se hydrostatic pressure reversal of pentobarbital anesthesia in fish
Authors: Belaud A. , Barthelemy L. , Peyraud C.
Published: December 2017

Investigations have been made into the effects of temperature (between 10 and 19 degrees C) on the one hand, and hydrostatic pressure per se (101 ATA) on the other, on recovery time from anesthesia (pentobarbital) in a fish (Salmo gairdneri R). At each of the two pressures studied (1 and 101 ATA) the rise in temperature shortens the recovery period, after a treatment by a constant dose of pentobarbital. Under hyperbaric pressure conditions (101 ATA) the duration of anesthesia is lower than the control value obtained at barometric pressure, whatever the temperature. The analysis of the results shows a similarity between the effects of temperature and pressure on the recovery from pentobarbital anesthesia on the one hand and on chemical kinetics on the other. The results support the hypothesis of the direct action of hydrostatic pressure per se at molecular level.
Effect of chronic exposure to cold on some responses to catecholamines
Authors: Fregly M. J. , Field F. P. , Nelson E. L. , Tyler P. E. , Dasler R.
Published: December 2017

An objective of these studies was to test the responsiveness of cold-adapted (8 wk, 5 degrees C) rats to a specific beta-adrenergic agonist. Twenty-four hours after removal from cold, increases in tail skin temperature (Tsk) and colonic temperature (Tco) were measured for 2 h in air at 25 degrees C following subcutaneous (sc) administration of 28, 70 or 136 mug d,l-isoproterenol sulfate dihydrate/kg body wt to restrained male rats. Cold-adapted rats responded to each dose of isoproterenol with greater increases in Tsk than controls. Tco of both groups increased at the two highest doses, but cold-adapted rats showed a greater rise. Thus, cold-adapted rats showed greater metabolic (Tco) and vascular (Tsk) responsiveness to the beta-adrenergic agonist, isoproterenol, than nonadapted controls. No effect of the alpha-adrenergic agonist, phenylephrine (50 or 100 mug/kg body weight, sc), was observed on Tco or Tsk. A second objective was to study the tension developed by aortic smooth muscle rings of cold-adapted and control rats both during stimulation of alpha-adrenergic receptors by norepinephrine and membrane depolarization by KCl. Adaptation to cold air appeared to suppress alpha-adrenergic responsiveness in aortic segments but did not alter responsiveness to KCl. This suggests an unchanged contractile mechanism in aortic rings of cold-adapted rats and a reduced responsiveness either at the level of the alpha-receptor or at a site immediately beyond.
Neonatal chest wall afferents and regulation of respiration
Authors: Hagan R. , Bryan A. C. , Bryan M. H. , Gulston G.
Published: December 2017

We have studied two groups of eight preterm infants, relating chest wall afferent information to respiratory timing. Rib cage and abdominal motion were monitored by magnetometers and flow and tidal volume via a face mask. In the first group, studies were done in REM sleep when spontaneously occurring distortion of the rib cage occurred and a significant linear relationship between the rate of distortion of the chest wall and shortening of the inspiratory time (Ti) was found in all infants. Reduction in this distortion by the use of continuous positive airway pressure (CPAP) or continuous negative pressure at the body surface (CNeg) was associated with a significant (P less than 0.01) lengthening of Ti. Absence of changes in Ti when pressure was applied in quiet sleep suggested that lung volume or chemical changes were not involved. In the second group of infants we artificially generated the afferent inflow by using vibratory stimuli applied in one intercostal interspace and produced a significant (P less than 0.05) shortening in Ti. We suggest that the distortion of the rib cage in REM sleep generates afferent information from intercostal muscle spindles that is related to the rate of distortion and this, via a supraspinal reflex, inhibits phrenic motoneuron discharge. It may then be of importance in the etiology of apneic episodes in these infants. Applied pressure may be of benefit because it reduces an inhibitory afferent inflow.
Thermoregulatory heat production in man: prediction equation based on skin and core temperatures
Authors: Hayward J. S. , Eckerson J. D. , Collis M. L.
Published: December 2017

The relationship of metabolic rate to skin and core temperatures was measured in eight subjects cooled in 10 degrees C water. Reference core temperatures, based on the tympanic and rectal sites, were 41.0 and 41.4 degrees C, respectively. Reference mean skin temperatures were 41.8 and 42.2 degrees C when determined in relation to tympanic and rectal temperatures, respectively. These results enabled construction of equations for predicting the steady-state metabolic rate (MR, W-kg-1) of nonexercising man according to thermal inputs from the skin (Tsk) and core (Tty or Tre) MR = 0.0356(Tsk - 41.8)(Tty - 41.0) or, MR = 0.0314(Tsk - 42.2)(Tre - 41.4). Each equation was limited by the low level of basal metabolic rate (1.1 W-kg-1) and by the high level of peak metabolic rate (6.4 W-kg-1). Evaluation of these equations showed satisfactory agreement with previous observations and concepts on the regulation of heat production in man.
Regional intrapulmonary gas distribution in awake and anesthetized-paralyzed man
Authors: Rehder K. , Sessler A. D. , Rodarte J. R.
Published: December 2017

Intrapulmonary distribution of ventilation/unit lung volume was studied in 28 volunteers in the sitting, supine, or right lateral decubitus position, either awake or anesthetized-paralyzed and mechanically ventilated. We found significant differences between the awake state and anesthesia-paralysis with mechanical ventilation in 1) intrapulmonary gas distribution, and 2) the vertical gradient of regional functional residual capacities for the subjects in the lateral decubitus position, but not for those in the sitting and supine positions. The effect of increasing the tidal volume on distribution of ventilation was significantly different 1) between the three body positions for a given state, and 2) between the two states for a given body position. The data suggest thoracoabdominal mechanics are different in the three body positions and that anesthesia-paralysis and mechanical ventilation may cause a different pattern of expansion of the respiratory system than spontaneous breathing in the awake state.
Comparison of arm versus leg work in induction of acute episodes of asthma
Authors: Strauss R. H. , Haynes R. L. , Ingram R. H. , McFadden E. R.
Published: December 2017

The severity of exercise-induced asthma varies with the type of exercise performed. To determine whether such variation could be attributed to the use of different muscle groups, we exercised arms separately from legs using a bicycle ergometer. First, arms were exercised to exhaustion, then legs were exercised at the same load for the same duration. Arm work resulted in greater ventilation, heart rate, hydrogen ion concentration, and airway obstruction than did leg work. Later, legs were exercised to exhaustion using a load more than twice that of the arm work. Both the exhausting leg work and exhausting arm work resulted in significant bronchospasm and acidosis, whereas the nonexhausting leg work did not. These data suggest that, in arm and/or leg exercise, the relationship of work load to muscle mass is a determinant of airway obstruction.
Temperature control system for water-perfused suits
Authors: Brengelmann G. L. , McKeag M. , Rowell L. B.
Published: December 2017

A system used to control skin temperature in human subjects wearing water-perfused garments is described, It supplies 8 l/min at 10 psi with water temperature controlled within +/-0.1 degree C. Temperature control is facilitated by a low circulating thermal mass and a fast responding heater based on a commercially available quartz heat lamp. The system is open so that hot or cold water can be added from the building mains to produce rates of change or water temperature exceeding 5 degrees C/min. These capabilities allow semiautomatic control of skin temperature within +/-1 degree C of desired wave forms. Potential hazards and associated safety devices are described.
Turnover of fibrinogen, plasminogen, and prothrombin during exercise in man
Authors: Collen D. , Semeraro N. , Tricot J. P. , Vermylen J.
Published: December 2017

The turnover of biologically intact high-purity 125I- and 131I-labeled fibrinogen, plasminogen, and/or prothrombin was studied in 16 untrained healthy subjects before and during strenuous physical exercise on a bicycle ergometer (repeated 4 times/day for 2 days). The exertion resulted in the well-known changes in the coagulation and fibrinolytic tests but did not induce changes in the concentration of fibrinogen, plasminogen, or prothrombin in the plasma. A significantly increased catabolism of fibrinogen and plasminogen but not of prothrombin was observed. The extent of Aalpha-chain degradation of fibrinogen in the plasma was quantitated before and 2 h after exercise, and a significant increase in degraded Aalpha chains was found in the postexercise samples. Immunochemical estimation of plasmin-antiplasmin complex in four subjects revealed a small increase after exercise in three of them. All these data support the concept that plasminogen activation and plasmin-induced fibrinogen degradation occur to some extent in man following strenuous physical exercise.
Dynamic and steady-state respiratory responses to bicycle exercise
Authors: Pearce D. H. , Milhorn H. T.
Published: December 2017

The transient respiratory responses of 10 normal male volunteers to step changes in work load from 0 to 300, 600, and 800 kpm/min were determined by breath-by-breath analysis for tidal volume, minute ventilation, respiratory frequency, end-tidal oxygen and carbon dioxide tensins, oxygen uptake, carbon dioxide elimination, respiratory exchange ratio, and heart rate. Ten experiments were averaged on a 5-s interval basis. Quantitative measures of the dynamics (delay times, half-times, times to peaks, times to plateaus, and plateau amplitudes) are presented. These parameters generally vary with work load and reflect the speed of response of various components of the system. Rapid ventilatory responses were seen at the initiation and termination of exercise; however, they required up to 32.5 s for full development. Repeated runs on three subjects at 600 kpm/min indicate that the experiments are grossly repeatable. The data, at the initiation of exercise, are consistent with the concept of cardiodynamic hyperpnea while the results are not as clear-cut at the termination of exercise.
Specific airway conductance in relation to postconceptional age during infancy
Authors: Stocks J. , Godfrey S.
Published: December 2017

Thoracic gas volume (TGV) and airway conductance (Gaw) were measured in 69 healthy infants during the 1st yr of life, using an adaptation of the whole body plethysmographic technique in which a heated rebreathing system was used to eliminate temperature differences in respired gas. There was highly significant correlations between TGV and body wt (r=0.99), and between Gaw and TGV (r=0.97) in all the infants. However, the relationship between Gaw and TGV (i.e., specific conductance (SGaw)) was dependent on postconceptional age (PCA) in preterm infants, falling from 0.50 s-1-cmH2O-1 at 31 wk to 0.32 s-1-cmH2O-1 at 40 wk PCA. Gestational age and postnatal age per se did not affect this relationship, showing it to be a maturational event unaffected by the time of birth. After 40 wk, the decrease in SGaw was far more gradual throughout the 1st yr of life. Black and Chinese infants were found to have significantly higher values for SGaw than their White counterparts, which may be due to anatomical differences in nasal structure.
Significance of sympathetic innervation of pulmonary vessels in response to acute hypoxia
Authors: Szidon J. P. , Flint J. F.
Published: December 2017

The role of the autonomic nervous system on the pulmonary vascular response to hypoxia was studied in anesthetized open-chest dogs. Acute hypoxia elicited reversible decreases in the slope of the instantaneous diameter-pressure relationship of the main pulmonary artery. These decrements in vascular compliance during hypoxia were prevented by either bilateral thoracic sympathectomy or by section of the cervical vagus and glossopharyngeal nerves and were reproduced by bolus injections of lobeline (0.1 mg) at the root of the aorta. Using separation of the airways with a tracheal divider, the effects of systemic and of alveolar hypoxia on vascular resistance of the left caudal lobe were compared. Systemic hypoxia in the absence of alveolar hypoxia had no effect on pulmonary vascular resistance. Alveolar hypoxia elicited reversible increases in vascular resistance that were not prevented by sympathectomy. It is concluded that at least two vascular sites of action and two mechanisms are involved in the pulmonary vascular response to hypoxia.
Diaphragmatic fatigue in man
Authors: Roussos C. S. , Macklem P. T.
Published: December 2017

The time required (tlim) to produce fatigue of the diaphragm was determined in three normal seated subjects, breathing through a variety of high alinear, inspiratory resistances. During each breath in all experimental runs the subject generated a transdiaphragmatic pressure (Pdi) which was a predetermined fraction of his maximum inspiratory Pdi (Pdimax) at functional residual capacity. The breathing test was performed until the subject was unable to generate this Pdi. The relationship between Pdi/Pdimax and tlim was curvilinear so that when Pdi/Pdimax was small tlim increased markedly for little changes in Pdi/Pdimax. The value of Pdi/Pdimax that could be generated indefinitely (Pdicrit) was around 0.4. Hypoxia appeared to have no influence on Pdicrit, but probably led to a reduction in tlim at Pdi greater than Pdicrit for equal rates of energy consumption. Insofar as the behavior of the diaphragm reflects that of other respiratory muscles it appears that quite high inspiratory loads can be tolerated indefinitely. However, when the energy consumption of the respiratory muscles exceeds a critical level, fatigue should develop. This may be a mechanism of respiratory failure in a variety in a variety of lung diseases.
Respiratory parameter estimation using forced oscillatory impedance data
Authors: Tsai M. J. , Pimmel R. L. , Stiff E. J. , Bromberg P. A. , Hamlin R. L.
Published: December 2017

The frequency dependency of the magnitude and phase angle of total respiratory impedance was measured in apneic dogs at functional residual capacity during forced oscillation by a special electronics unit. Regression analysis of these data yielded estimates of total respiratory resistance (RFO), inertance (IFO), and compliance (CFO). After correcting for the effects of the endotracheal tube, mean control values (+/-SE) of RFO, IFO, and CFO for the clinically normal dogs were 1.30+/-0.10 cmH2O–1–1-s, 0.0114+/-0.0022 cmH2O–1–1-s2, and 0.0306+/-0.0009 1-cm H2O–1, respectively. Estimates obtained with added resistance, a less dense gas, and abdominal weighting were consistent with predicted effects. In four dogs with mild respiratory symptoms, mean RFO was significantly elevated with no change in IFO or CFO. Independent measurements of resistance and compliance during tidal ventilation correlated well with RFO (r=0.87) and CFO (r=0.80), but RFO and CFO were, on the average, 71% of the tidal breathing values. Thus, the method provides precise estimates of RFO, IFO, and CFO, and allows detection of small changes in these parameters.
Thoracic reflexes stabilizing loaded ventilation in normal and cord-injured man
Authors: Axen K. , Bergofsky E. H.
Published: December 2017

The ability to regulate tidal volume was quantified in 24 cervical cord-injured patients by comparing the “effective” elastance (E′rs) observed during single-breath elastic loads to the passive respiratory elastance (Ers) measured separately with relaxed muscles. Thirteen patients, the majority of whom had an abnormal subjective perception of loading, usually failed to demonstrate any tidal volume compensation under load conditions (i.e. E′rs less than or equal to Ers). This impaired tidal volume defense, which could not be attributed either to diaphragmatic paralysis or rib cage instability, was accompanied by a markedly shortened inspiratory duration and, hence, a prematurely terminated phrenic motoneuron output. Conversely, those patients who developed a larger then previously reported “effective” elastance (i.e., E′rs greater than or equal to 2Ers) described loading as an inspiratory obstruction, as did all our normal subjects, and usually prolonged loaded inspiratory duration, probably by a consciously mediated mechanism. These findings are consistent with the hypothesis that, in spontaneously breathing intact man, thoracic sensory receptors normally maintain phrenic motoneuron output under load conditions and thereby promote tidal volume stability.
Renin, aldosterone, electrolyte, and cortisol responses to hypoxic decompression
Authors: Sutton J. R. , Viol G. W. , Gray G. W. , McFadden M. , Keane P. M.
Published: December 2017

Responses of plasma renin activity, plasma aldosterone, plasma cortisol, and plasma electrolyte concentration and urinary electrolyte and aldosterone excretion were studied in four men during hypoxic decompression to a stimulated altitude of 4,760 m in a pressure chamber. Three of the four subjects developed significant acute mountain sickness. Plasma sodium and potassium concentrations were unchanged. No significant change in plasma renin activity was observed, but values tended to fall. Plasma aldosterone concentration was depressed while plasma cortisol was elevated and diurnal variation lost. Urinary sodium excretion was unchanged, but urinary potassium and aldosterone excretion were decreased. The decrease in plasma and urinary aldosterone and urinary potassium in the absence of change in plasma renin activity or plasma potassium is of uncertain origin. It is unlikely to be due to a decrease in adrenocorticotropin secretion since plasma cortisol rose during the same time. None of the changes could be causally implicated in the development of acute mountain sickness although the increase in plasma cortisol was greatest in the most ill.
Muscular efficiency during steady-rate exercise. II. Effects of walking speed and work rate
Authors: Donovan C. M. , Brooks G. A.
Published: December 2017

A comparison of walking against vertical (gradient) and horizontal (trailing weight) forces was made during steady-rate exercise at 0.250, 500, and 750 kg-m/min with speeds of 3,0, 4.5, and 6.0 km/h. In all cases exponential relationships between energy expenditure (calculated from the steady-rate respiration) and increasing work rate and speed were observed which indicated that muscular efficiency during walking is inversely related to speed and work rate. “Work” (level, unloaded walking as the baseline correction), “delta” (measured work rate as the baseline correction), and “instantaneous” (derived from the equation describing the caloric cost of work) efficiencies were computed. All definitions yielded decreasing efficiencies with increasing work rates. At work rates above 250 kg-m/min the curves describing the relationship between energy expenditure and work rate were parallel for vertical and horizontal forces, indicating equivalent efficiencies in this range. Only the delta and instantaneous definitions accurately described these relationships for vertical and horizontal work. Determinations of combined work loads (gradient plus trailing weight) were made and the energy costs of both types of work found to be additive.
Postcapillary changes in blood pH in vivo during carbonic anhydrase inhibition
Authors: Crandall E. D. , Bidani A. , Forster R. E.
Published: December 2017

A rapidly responding stopped-flow glass pH electrode apparatus was used to investigate pH changes in blood in vivo after it exits from an exchange capillary. Arterial blood was drawn from anesthetized animals through the apparatus. Temperature and pH of the blood in the electrode chamber were continuously recorded, both during withdrawal and after flow was stopped. Blood pH did not change after stopping flow in control experiments. When benzolamide (2 mg/kg) was given to inhibit carbonic anhydrase activity available to plasma (e.g., due to lysis) while having less effect on intracellular activity, pH increased 0.02–0.04 (t1/2 approximately 8 s) after stopping flow. Administration of acetazolamide (50 mg/kg) resulted in pH decreasing 0.07–0.10 (t1/2 approximately 15 s) after stopping flow. Ventilation for 1 min with N2 resulted in an increased rise in pH for the benzolamide-treated animals but a decreased fall in pH for the acetazolamide-treated animals. These shifts in arterial blood pH after gas exchange are largely due to disequilibrium of [H+] between red cells and plasma at the end of the pulmonary capillary.
Fatty acid profile and cholesterol in skeletal muscle of trained and untrained men
Authors: Thomas T. R. , Londeree B. R. , Gerhardt K. O. , Gehrke C. W.
Published: December 2017

To compare the fatty acid distribution and cholesterol composition in trained and untrained isolated skeletal muscle membranes, a needle biopsy was performed on the vastus lateralis of the 10 distance runners and 10 sedentary men. The muscle sample was homogenized and centrifuged at 100,000 X g; the resulting pellet was analyzed by gas-liquid chromatography for individual fatty acids and cholesterol. The percentage of palmitic acid was significantly lower in the trained muscle tissue. Samples from the distance runners also tended to have a more frequent appearance of linolenic and eicosatrienoic acids, longer fatty acid hydrocarbon chains, and lower cholesterol concentration. It was concluded that trained muscles have an increased membrane fluidity which could beneficially affect the activity of membrane-bound enzymes and active transport. Longer chain length in the membrane lipids may be a means of producing an inner membrane cohesiveness in muscles of trained individuals.
Effects of acute prolonged hypoxia on cardiovascular dynamics in dogs
Authors: Borgia J. F. , Horvath S. M.
Published: December 2017

Intact anesthetized dogs were exposed for 75 min to either 5.75, 9.0, or 12.0% oxygen in nitrogen. Although pulmonary artery pressures were significantly elevated in all hypoxic exposures, systemic hypertension occurred only at the onset of severe hypoxia(5.75% O2). Coronary blood flow increased from an average of 130 during normoxia to a peak of 400 ml/100 g per min during inhalation of 5.75% O2, and coronary sinus oxygen tensions of 8 Torr and oxygen contents of 1.1 ml/100 ml were sustained for 75 min without biochemical, functional, or electrophysiological evidence of myocardial ischemia. Cardiac index (CI) increased significantly only during severe hypoxia (5.75% O2) with the greatest elevation after 30 min. Subsequently, CI decreased concomitantly with a 27% elevation in arterial hemoglobin concentration and oxygen-carrying capacity. It is concluded that the hypoxic threshold for significant elevations of cardiac output is between 6.0 and 9.0% O2.
Environmental synchronizers of squirrel monkey circadian rhythms
Authors: Sulzman F. M. , Fuller C. A. , Moore-Ede M. C.
Published: December 2017

Various temporal signals in the environment were tested to determine if they could synchronize the circadian timing system of the squirrel monkey (Saimiri sciureus). The influence of cycles of light and dark, eating and fasting, water availability and deprivation, warm and cool temperature, sound and quiet, and social interaction and isolation was examined on the drinking and activity rhythms of unrestrained monkeys. In the absence of other time cues, 24-h cycles of each of these potential synchronizers were applied for up to 3 wk, and the periods of the monkey's circadian rhythms were examined. Only light-dark cycles and cycles of food availability were shown to be entraining agents, since they were effective in determining the period and phase of rhythmic variables. In the presence of each of the other environmental cycles, the monkey's circadian rhythms exhibited free-running periods which were significantly different from 24 h with all possible phase relationships between the rhythms and the environmental cycles being examined.
Placental diffusing capacity for carbon monoxide and oxygen in unanesthetized sheep
Authors: Longo L. D. , Ching K. S.
Published: December 2017

We measured placental diffusing capacity for carbon monoxide (DpCO) in 10 unanesthetized sheep with catheters chronically implanted in maternal and fetal vessels. Serially measured DpCO during the last third of gestation averaged 0.55 +/- 0.02 (SEM) ml.(min.Torr.kg fetal wt)-1, essentially the same value as that previously reported in anesthetized, acutely operated animals. While placental CO diffusing capacity increased as a function of gestational age when expressed as ml.(min.Torr)(-1), it remained constant when calculated per kg fetal wt. In eight experiments, DpCO showed no change following the administration of several drugs which combine with cytochrome P450. We interpret this as evidence against the carrier hypothesis for placental CO exchange. We calculated the placental diffusing capacity for oxygen to be 0.68 ml.(min.Torr.kg)-1 and the mean maternal-to-fetal capillary Po2 difference to be 10 Torr. Caculations predict that maternal and fetal oxygen partial pressures equilibrate in end-capillary blood during the course of a single transit in placental exchange vessels; thus placental oxygen exchange is not limited by diffusion.