bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulmonary blood flow distribution measured by radionuclide-computed tomography
Authors: Maeda H. , Itoh H. , Ishii Y. , Todo G. , Mukai T. , Fujita M. , Kambara H. , Kawai C. , Torizuka K.
Published: December 2017

Distributions of pulmonary blood flow per unit lung volume were measured with subjects in the prone, supine, and sitting positions by means of radionuclide-computed tomography of intravenously administered 99mTc-labeled macroaggregates of human serum albumin. The blood flow was greater in the direction of gravity in all 31 subjects except one with severe mitral valve stenosis. With the subject in a sitting position, four different types of distribution were distinguished. One type had a three-zonal blood flow distribution as previously reported by West and co-workers (J. Appl. Physiol. 19: 713–724, 1964). Pulmonary arterial pressure and venous pressure estimated from this model showed reasonable agreement with pulmonary arterial pressure and capillary wedge pressure measured by Swan-Ganz catheter in 17 supine patients and in 2 sitting patients. The method makes possible noninvasive assessment of pulmonary vascular pressures.
Effects of p-chlorophenylalanine on ventilatory control in goats
Authors: Mitchell G. S. , Smith C. A. , Vidruk E. H. , Jameson L. C. , Dempsey J. A.
Published: December 2017

The effects of tryptophan hydroxylase inhibition with p-chlorophenylalanine (PCPA; 100 mg/kg iv) on ventilatory control were studied in awake goats. Ventilation, CO2 production, and blood gases were measured 16–24 h after PCPA at rest and during mild exercise in normoxia and at rest in hypoxia and hypercapnia. PCPA increased ventilation 36% at rest, predominantly through an effect on respiratory frequency, and decreased arterial PCO2 (PaCO2) 6.5 Torr. Ventilatory gain in exercise (delta VI/deltaVCO2) was increased 20% by PCPA thereby maintaining PaCO2 at its new resting value. Hypoxia (fractional inspired O2 concentration = 0.12) had little effect on ventilation or PaCO2 at rest, either on control or on PCPA test days. Ventilatory sensitivity to CO2 at rest (delta VI/delta PaCO2) was unaffected by PCPA. Bilateral carotid body denervation (CBX) was performed in the animals, and experiments were repeated 3 mo after the first administration of PCPA. CBX alone decreased ventilation 29% and increased PaCO2 9.4 Torr. Administration of PCPA increased ventilation 35%, decreased PaCO2 by 10.2 Torr at rest, and increased ventilatory gain in exercise 26%. Thus carotid bodies are not necessary for the ventilatory response to PCPA. Furthermore, the primary neural pathways associated with exercise or hypercapnia are not specifically affected by inhibition of serotonin metabolism via PCPA.
Human respiration at rest in rapid compression and at high pressures and gas densities
Authors: Gelfand R. , Lambertsen C. J. , Strauss R. , Clark J. M. , Puglia C. D.
Published: December 2017

Ventilation (V), end-tidal PCO2 (PACO2), and CO2 elimination rate were measured in men at rest breathing CO2-free gas over the pressure range 1–50 ATA and the gas density range 0.4–25 g/l, during slow and rapid compressions, at stable elevated ambient pressures and during slow decompressions in several phases of Predictive Studies III-1971 and Predictive Studies IV-1975. Inspired O2 was at or near natural O2 levels during compressions and at stable high pressures; it was 0.5 ATA during decompressions. Rapid compressions to high pressures did not impair respiratory homeostasis. Progressive increase in pulmonary gas flow resistance due to elevation of ambient pressure and inspired gas density to the He-O2 equivalent of 5,000 feet of seawater was not observed to progressively decrease resting V, or to progressively increase resting PACO2. Rather, a complex pattern of change in PACO2 was seen. As both ambient pressure and pulmonary gas flow resistance were progressively raised, PACO2 at first increased, went through a maximum, and then declined towards values near the 1 ATA level. It is suggested that this pattern of PACO2 change results from interaction on ventilation of 1) increase in pulmonary resistance due to elevation of gas density with 2) increase in respiratory drive postulated as due to generalized CNS excitation associated with exposure to high hydrostatic pressure. There may be a similar interaction between increased gas flow resistance and increase in respiratory drive related to nitrogen partial pressure and the narcosis resulting therefrom.
Changes in electromyogram power spectra of facial and jaw-elevator muscles during fatigue
Authors: van Boxtel A. , Goudswaard P. , van der Molen G. M. , van den Bosch W. E.
Published: December 2017

Endurance and changes in electromyogram (EMG) power spectra were investigated during a fatiguing static contraction at 50% of the maximum EMG amplitude in two jaw-elevator muscles (masseter and temporalis) and five facial muscles (frontalis, corrugator supercilii, zygomaticus major, orbicularis oris, and buccinator). Relatively high endurance was found in orbicularis oris, frontalis, and corrugator supercilii muscles; intermediate endurance was found in zygomaticus major, buccinator, and temporalis muscles; and low endurance was found in the masseter muscle. The last muscle showed a relatively fast linear decrease of the median frequency of the power spectrum. The other muscles showed a much slower, exponential decrease. The median frequency appeared to reflect reliably the changes in the shape of the power spectra during fatigue. Large differences between the shape of power spectra of different muscles in the unfatigued state were found. These, however, were unrelated to endurance and degree of spectral shift during fatigue.
Effect of hyperoxia on metabolic and catecholamine responses to prolonged exercise
Authors: Howley E. T. , Cox R. H. , Welch H. G. , Adams R. P.
Published: December 2017

The use of inspired gas mixtures with an oxygen fraction in excess of 0.3 has been associated with a decrease in the gas exchange ratio (R) during prolonged work in humans. It had been hypothesized that the lower R was due to a lower plasma catecholamine concentration caused by the hyperoxia (Med. Sci. Sports 10: 167–170, 1978). We tested this hypothesis by measuring changes in plasma epinephrine and norepinephrine when the subjects were switched from breathing air to 60% O2 (and vice versa) during 40 min of cycle ergometer exercise at 67% maximal oxygen uptake (VO2max). The subject breathed one gas mixture for the first 30 min and was switched to the other in the last 10 min. The order was reversed in the second test. The switch in gas mixtures from air to 60% O2 resulted in a significant reduction in R, heart rate, minute ventilation, blood lactate concentration, and plasma epinephrine concentration (P less than 0.05). The plasma norepinephrine concentration (0.1 greater than P greater than 0.05) and the plasma free fatty acid concentration were not significantly changed. Although the direction of the epinephrine change was consistent with the change in R, the epinephrine change was quantitatively small (20 pg/ml) and of questionable physiological significance. This suggests a direct effect of PO2 on cellular metabolism as one cause of the change in R when the subjects were switched from air to 60% O2.
Sinoaortic contribution to ventilatory control in exercising dogs
Authors: Szlyk P. C. , Pendergast D. R. , Krasney J. A.
Published: December 2017

The role of the sinoaortic reflexes in the regulation of ventilation during exercise was evaluated in seven awake dogs prepared with chronic tracheostomies and arterial catheters. Each dog ran on a treadmill at several work loads before and after sinoaortic denervation and served as its own control. Minute ventilation in the sinoaortic denervated state was significantly reduced from intact values by 10–40% at the mild and moderate levels of exercise [O2 uptake (VO2) = 30–50 ml . kg-1 . min-1] mainly as a result of a lowering respiratory frequency. At higher work loads (VO2 = 70–80 ml . kg-1 . min-1) minute ventilation was similar in the intact and denervated states, but the pattern of ventilation was altered with a higher frequency and a lower tidal volume in the denervated state. The rise in ventilation toward a stable plateau was slower at all work loads in the denervated than in the intact state. After sinoaortic denervation, arterial PCO2(PaCO2) levels were significantly elevated above intact PaCO2 levels during both the preexercise period and the steady state at all exercise levels. These results suggest that the sinoaortic reflexes contribute to both the control of ventilation and the pattern of breathing during mild and heavy levels of exercise in the conscious dog.
Dynamic response of local pulmonary blood flow to alveolar gas tensions: analysis
Authors: Grant B. J. , Schneider A. M.
Published: December 2017

It has been reported that left lower lobe pulmonary blood flow (Q) and alveolar CO2 decrease then oscillate in a progressively damped manner when the lobar inspirate is changed from pure O2 to N2. This damped oscillatory response of lobar Q is abolished by maintaining lobar CO2 constant. We set out to develop the simplest mathematical model that can simulate these experimental results by using techniques derived from control theory. Different models were tested. The simplest model that predicts the experimental data incorporates an exponential decrease of lobar Q to local alveolar hypoxia (time constant 3 min) and a damped oscillatory response of lobar Q to local alveolar hypocapnia. The response to hypocapnia has two components: a vasodilator effect possibly related to intracellular [H+] and a vasoconstrictor effect possibly related to changes of molar CO2. Both these components (time constants of 4.8 min) interact with each other by cross-coupled elements (time constants of 4.8 min). This model can be used to forecast results so that its validity can be tested by experiment.
CO2 diffusing capacity in isolated dog lung lobes and the role of carbonic anhydrase
Authors: Enns T. , Hill E. P.
Published: December 2017

CO2 diffusing capacities (DmCO2) were measured at 22 degrees C on 12 isolated perfused dog lung lobes before and after inhibition of lung tissue carbonic anhydrase (CA) by acetazolamide (Diamox). The hypothesis is that CA in the alveolar-capillary tissue enhances overall transport of CO2 by converting CO2 to HCO-3 within aqueous portions of the tissue. HCO-3 diffuses simultaneously with molecular CO2, increasing the overall CO2 flux, and then converts back to molecular CO2 at the end of the aqueous pathway. To ensure at least partial diffusion limitation, lobes were perfused with phosphate buffer at high pH (7.7) and high flow rates. Plant CA (which is not inhibited significantly by Diamox) was added to the perfusate to provide rapid uptake of CO2 via conversion to HCO-3. After Diamox, DCO2 decreased 39.6%, indicating that CA does increase CO2 transport through lung tissue. Surprisingly, DCO2 exceeds CO diffusing capacity by only 9.3 +/- 2.1 times (without Diamox inhibition) rather than by the factor of 24 predicted by Graham's law on the basis of solubilities and molecular weights of the gases.
Blood volume and protein responses to skin heating and cooling in resting subjects
Authors: Harrison M. H. , Edwards R. J. , Cochrane L. A. , Graveney M. J.
Published: December 2017

The effects of alterations in skin temperature on intravascular volume and protein content have been investigated in resting subjects. With a normal core temperature (Tac) both skin cooling and skin heating caused hemoconcentration, and heating was associated with an increased rate of protein loss from the intravascular space. Raising of the skin temperature after cooling, with Tac depressed, and cooling of the skin after heating, with Tac raised, were associated with an immediate reversal of the hemoconcentration, and gain of protein by the intravascular space. It is concluded that intravascular volume responses to thermal stress are dependent on the skin and core temperatures obtaining immediately prior to imposition of the stress and that, in particular, a low skin temperature predisposes toward hemodilution on subsequent exposure to heat; sweating per se does not necessarily result in hemoconcentration. The association of hemodilution with augmentation of intravascular protein, and the rapidity with which extravascular protein can apparently gain entry to the intravascular space, is taken as indicating a possible direct return of protein through capillary walls.
Reflex control of breathing following inhalation of cigarette smoke in conscious dogs
Authors: Lee L. Y. , Morton R. F. , Hord A. H. , Frazier D. T.
Published: December 2017

The acute ventilatory response to spontaneously inhaled cigarette smoke (750 ml, 10% concentration) was studied in 92 experiments on 6 awake resting dogs. Upon the first or second breath of smoke inhalation, either an apnea or an augmented breath was elicited consistently in each dog, and a hyperpnea occurred subsequently. Minute ventilation (VE) increased from a base line of 3.2 to a peak of 23.9 l/min at 8.3 s (mean values) after the smoke was completely inhaled and returned toward base line in 1–3 min. Cold blocking of both vagi (exteriorized in skin loops) eliminated the initial change in breathing pattern but did not significantly reduce the delayed hyperpnea. Denervation of carotid body chemoreceptors alone abolished 71.5% of the increase in VE induced by cigarette smoke. These results suggest that the apnea or augmented breath immediately following the smoke inhalation is mediated through vagal afferents, whereas the delayed hyperpnea results primarily from the stimulation of carotid body chemoreceptors, presumably by the absorbed nicotine.
Effects of stopping training on size and response to insulin of fat cells in female rats
Authors: Craig B. W. , Thompson K. , Holloszy J. O.
Published: December 2017

The parametrial adipocytes of exercise-trained female rats were smaller and had greater rates of 2-deoxyglucose uptake and glucose oxidation over a wide range of insulin concentrations than the fat cells of sedentary animals of the same age. The fat cells of the sedentary animals had a 180% greater volume than those of the trained rats, despite only a 9% difference in body weight. Following cessation of training adipocyte size increased rapidly; approximately two-thirds of the initial difference in fat cell volume between the trained and sedentary rats had disappeared after 9 days without exercise. Concomitant with the increase in fat cell size, the response of 2-deoxyglucose uptake and glucose oxidation to insulin diminished. There was a close correlation between fat cell size and the magnitude of the response to insulin of both glucose oxidation and 2-deoxyglucose uptake. It appears from these results that the effect of exercise training on the response of adipocytes to insulin is rapidly lost when exercise is stopped.
Coupling of ventilation to pulmonary gas exchange during nonsteady-state work in men
Authors: Wasserman D. H. , Whipp B. J.
Published: December 2017

During steady-state exercise, ventilation increases in proportion to CO2 output (VCO2), regulating arterial PCO2. To characterize the dynamics of ventilatory coupling to VCO2 and O2 uptake (VO2) in the nonsteady-state phase, seven normal subjects performed constant-load cycle ergometry to a series of subanaerobic threshold work rates. Each bout consisted of eight 6-min periods of alternating loaded and unloaded cycling. Ventilation and gas exchange variables were computed breath by breath, with the time-averaged response dynamics being established off-line. Ventilation increased as a linear function of VCO2 in all cases, the relationship being identical in the steady- and the nonsteady-state phases. Ventilation, however, bore a curvilinear relation to VO2, the kinetics of the latter being more rapid. Owing to the kinetic disparity between expired minute ventilation (VE) and VO2, there was an overshoot in the direction of change in VE/VO2 and end-tidal PO2 during the work-rate transition. In contrast, there was no overshoot in the direction of change in VE/VCO2 and end-tidal PCO2 throughout the nonsteady-state period. These data suggest that the exercise hyperpnea is coupled to metabolism in men via a signal proportional to VCO2 in both the nonsteady and steady states of moderate exercise.
Gas mixing within the acinus of the lung
Authors: Engel L. A.
Published: December 2017

The subject is reviewed with an emphasis on recent developments in model analyses. Application of computer technology has facilitated the study of simultaneous convection and diffusion within a complex geometry approximating the airways and air spaces of the lung. During an inspiration of fresh gas the diffusion front separating inspired from “alveolar” gas is stationed within a portion of the acinus where the magnitudes of gas transport by convection and diffusion are similar. This constitutes the peripheral boundary of the Fowler dead space. Asymmetry of intra-acinar branching results in an inequality of gas concentrations within alveolar gas, despite homogeneous volume expansion. This is due to an interaction between diffusion and convection at branch points subtending units of unequal lengths. During a respiratory cycle a “diffusive Pendelluft” between these units results in a “first in-first out” pattern and a sloping alveolar plateau on the expired tracing, despite synchronous and homogeneous volume changes. Experimental results suggest that incomplete alveolar gas mixing constitutes a measurable limitation to gas exchange in the normal lung.
Influence of pulmonary vasoconstriction on lung water and perfusion heterogeneity
Authors: Dawson C. A. , Bronikowski T. A. , Linehan J. H. , Hakim T. S.
Published: December 2017

To determine the influence of pulmonary vasoconstriction on lung tissue perfusion, we examined the effects of hypoxia, sympathetic nerve stimulation, and histamine on vascular resistance, blood, and extravascular volumes, weight, and the distribution of vascular transit times in dog left lower lung lobes perfused in situ. Hypoxia, sympathetic stimulation, and histamine increased pulmonary vascular resistance by 1.96, 1.42, and 2.02 times and increased the relative dispersion of the transit time distributions by 1.49, 1.30, and 1.71 times the control values, respectively. Hypoxia and sympathetic stimulation tended to decrease the blood volume accessible to indocyanine green dye and the lobe weight. On the other hand, histamine infusion, which also decreased the volume accessible to the dye, increased the lobe weight. Despite this increase in weight, histamine infusion resulted in a decrease in the extra-vascular volume accessible to 3HOH. These results indicate that these vasoconstrictor stimuli increased the heterogeneity of transit times through the lung lobe and decreased the flowing blood volume. In addition, histamine decreased the size of the perfused microvascular bed, indicating that pulmonary vasoconstriction can influence the local pattern of microvascular perfusion.
Increased oxygen consumption associated with breathing activity in fetal lambs
Authors: Rurak D. W. , Gruber N. C.
Published: December 2017

To examine the relationship between fetal O2 consumption and fetal breathing movements, we measured O2 consumption, umbilical blood flow, and cardiovascular and blood gas data before, during, and after fetal breathing movements in conscious chronically catheterized fetal lambs. During fetal breathing movements, O2 consumption increased by 30% from a control value of 7.7 +/- 0.7 (SE) ml X min-1 X kg-1. Umbilical blood flow was 210 +/- 21 ml X min-1 X kg-1 before fetal breathing movements; in 9 of 16 samples it increased by 52 +/- 12 ml X min-1 X kg-1, while in the other 7 it decreased by 23 +/- 9 ml X min-1 X kg-1. Umbilical arterial and venous O2 partial pressures and pH fell during fetal breathing movements, and the fall was greater when umbilical blood flow was decreased. Partial CO2 pressure rose in both vessels, and again the increase was greatest when umbilical blood flow fell during fetal breathing movements. Also associated with a fall in umbilical blood flow was the transition from low-amplitude irregular to large-amplitude regular fetal breathing movements. It is concluded that fetal breathing movements increase fetal O2 demands and are associated with a transient deterioration in fetal blood gas status, which is most severe during large-amplitude breathing movements.
Dopamine and carotid body function in the newborn lamb
Authors: Mayock D. E. , Standaert T. A. , Guthrie R. D. , Woodrum D. E.
Published: December 2017

The effect of dopamine on the acute ventilatory response to hypoxia was investigated in four newborn lambs studied on the 1st day of postnatal life and eight lambs studied between 7 and 12 days of age. Studies were accomplished during nonrapid-eye-movement sleep in unanesthetized tracheotomized animals. Changes in minute ventilation (VE/kg), tidal volume, and frequency induced by intravenous bolus injection of dopamine (10 micrograms/kg) or saline control were assessed while animals were breathing room air or N2, before and after carotid body denervation (CBD). Dopamine depressed resting ventilation at both postnatal ages. This effect was greater in the older animals. Dopamine blunted the hypoxia-induced increase in VE/kg at both ages. The magnitude of this depression did not vary with postnatal age. Dopamine induced cessation of respiratory effort at end expiration (apnea) during room air and N2 breathing significantly more often in the older animals. The effect of dopamine was mediated at the carotid body. CBD decreased ventilation by an increase in breath-to-breath interval in older animals, suggesting carotid sinus nerve afferent activity is more important during eucapnic respiration in older animals than in the immediate newborn period.
Time course of the bronchoconstriction induced by inhaled histamine and methacholine
Authors: Cartier A. , Malo J. L. , Begin P. , Sestier M. , Martin R. R.
Published: December 2017

Eleven asthmatic subjects inhaled doubling concentrations of histamine until a near sixfold increase in total pulmonary flow resistance had been reached. This last concentration (C6) of histamine and methacholine was administered on two subsequent separate visits. Specific lung conductance (sGL) dropped to 18.6 +/- 7.9 (SD) and 19.1 +/- 10.3% of initial value after histamine and methacholine, respectively (NS). Whereas the peak action occurred in a similar interval (1–4 min), the mean duration of the subsequent plateau, defined as values of sGL within 20% of the maximum fall was 16.8 +/- 9.8 min for histamine and 74.6 +/- 53.7 min for methacholine (P less than 0.01). The recovery phase from the end of the plateau to base line lasted 25.5 +/- 14.4 min for histamine and 56.7 +/- 38.3 min for methacholine (P less than 0.01). The duration of plateau and recovery phases were not linked with base-line sGL, maximum fall in sGL, or C6. We conclude that for the same induced bronchoconstriction methacholine has a more prolonged action than histamine.
Extra-alveolar vessel contribution to hydrostatic pulmonary edema in in situ dog lungs
Authors: Albert R. K. , Lakshminarayan S. , Charan N. B. , Kirk W. , Butler J.
Published: December 2017

We determined the relative contribution of larger extra-alveolar arteries and veins to hydrostatic edema in in situ dog lungs. Left lower lobe alveolar and vascular pressures were controlled in 24 open-chest, anesthetized, heparinized dogs. Zero pressure was at the lobe base. Normal blood gases were maintained by ventilating the right lung. The left lower lobe was inflated with 5% CO2 and air to an alveolar pressure of 10 or 25 cmH2O and suspended from a strain gauge, which allowed continual weight recording. Vascular pressures were raised to alveolar pressure plus lung height (zone III) before and after pulmonary arterial or venous embolization with 37- to 74-microns polystyrene beads, which isolated the larger extra-alveolar arteries or veins from alveolar vessels. The weight change occurring during the last 3 min of the 5-min hydrostatic stress was taken to represent transvascular fluid flux. At an alveolar pressure of 25 cmH2O (estimated transmural pressure 40 cmH2O), leakage from the larger extra-alveolar arteries and veins accounted for 41 and 32%, respectively, of the total transvascular fluid flux occurring after embolization. At an alveolar pressure of 10 cmH2O (estimated transmural pressure 22 cmH2O), no extra-alveolar vessel leakage occurred. However, when vascular pressures were raised to provide a transmural pressure similar to that present at the higher alveolar pressure, the same contribution from larger extra-alveolar vessels was observed.
Anaerobic threshold, blood lactate, and muscle metabolites in progressive exercise
Authors: Green H. J. , Hughson R. L. , Orr G. W. , Ranney D. A.
Published: December 2017

The purpose of this study was to investigate the interrelationship between the ventilatory anaerobic threshold (VAT), the blood lactate anaerobic threshold (LAT), and the alteration in muscle metabolism. Ten subjects (5 men and 5 women) performed progressive exercise to exhaustion on two occasions for determination of the VAT and the LAT. For both AT criteria, the initial breakpoints (P less than 0.05) in the relationship between ventilation (VE) and O2 uptake (VO2VAT) and lactate (La) and power output (POLAT) were determined by multisegmental linear regression. During three subsequent tests the subjects performed progressive exercise to various percentages of the VO2VAT. Biopsies were obtained from the musculus vastus lateralis for determination of selected glycolytic intermediates at the cessation of exercise. It was found that the VO2VAT, expressed in terms of power output (POVAT), occurred at a higher value (P less than 0.05) than the POLAT (1,004 vs. 621 kg X min-1). Blood La values at these power outputs were 2.09 and 1.25 mM, respectively. Determination of the muscle La concentration at 79, 94, and 110% of VO2VAT indicated significant increases (P less than 0.05) from rest values of 1.59 to 4.49, 6.37, and 11.3 mmol X kg wet wt-1, respectively. It is concluded that the gas exchange AT as determined by the relationship between VE and VO2VAT and the AT as determined by blood La accumulation (LAT) are not coincidental. In addition the elevation in muscle anaerobic glycolysis precedes both the VAT and the blood LAT in this progressive exercise test.
Topographical distribution of regional lung volume in anesthetized dogs
Authors: Hubmayr R. D. , Walters B. J. , Chevalier P. A. , Rodarte J. R. , Olson L. E.
Published: December 2017

The distribution of regional lung volume during static deflation from total lung capacity to functional residual capacity was determined from the positions of intraparenchymal metallic markers ascertained by a biplane video roentgenographic technique in supine and prone anesthetized dogs. Regional lung volumes were linearly related to overall lung volume so that regional volume could be characterized by a ventilation index (VI), which is the ventilation per alveolus relative to the ventilation of the overall lung. For the supine position, there were vertical and cephalocaudal gradients in VI in both the upper and lower lobes. Mean VI was greater in the lower lobe than in the upper lobe, but VI was less than would be predicted from extrapolation of the upper lobe relationship. For the prone position, there was no consistent gradient in VI in any direction. The magnitude of the gradients in VI and the effects of body position suggest that, in the recumbent dog, the thoracic cavity shape is a more important determinant of regional lung volume than is the effect of gravity on the lung itself.
Estimation of human susceptibility to the high-pressure nervous syndrome
Authors: Rostain J. C. , Lemaire C. , Gardette-Chauffour M. C. , Doucet J. , Naquet R.
Published: December 2017

Twenty-four professional divers were put through a series of electroencephalographic (EEG) and psychometric tests at the surface and at 180 m after a fast compression (15 min) in an attempt to determine their susceptibility to high-pressure nervous syndrome (HPNS). The subjects were classified according to the EEG changes between the surface and 180 m: group 0, less than 10% increase in theta-band activity in the anterior region of the scalp; group 1, between 10 and 100% increase in theta-activity; group 2, theta-activity increase above 100%. Eight subjects were selected to make a dive to 450 m to verify the quality of our classification (3 from group 0, 3 from group 1, 2 from group 2). The results showed that, for the psychometric tests, the large individual variability between the surface and 180 m does not allow us to prejudge the behavior of each subject at 450 m, but the classification established from absolute values is stable from the surface to 450 m. For the EEG activities, intensity of the modifications at 450 m can be predicted at group level by a 180-m dive, performed with fast compression and similar breathing mixtures.
Role of mediators in allergic and nonallergic asthma in dogs with hyperreactive airways
Authors: Hirshman C. A. , Peters J. , Butler J. , Hanifin J. M. , Downes H.
Published: December 2017

Basenji-Greyhound crossbreed dogs, with nonspecific airway hyperreactivity, release histamine into the plasma after aerosol challenge with Ascaris antigen and a slow reacting substance (SRS) after aerosol challenge with citric acid or Ascaris antigen. The appearance of SRS in the plasma after citric acid aerosol challenge, without an increase in histamine, closely parallels the changes in pulmonary mechanics. The pulmonary response to citric acid, in contrast to Ascaris antigen, is totally prevented in vivo by FPL 55712, an SRS antagonist. SRS exhibits both pharmacologic properties and chemical characteristics similar to leukotrienes. These studies suggest that SRS may be an important mediator in nonallergic airway constriction in vivo.
Effect of triiodothyronine on body temperature at rest and during exercise in dogs
Authors: Stager J. M.
Published: December 2017

To determine the effect of the thyroid hormones on body temperature at rest and during exercise, five mongrel dogs were trained to run on a treadmill and then treated with exogenous triiodothyronine (T3) (1 mg/kg) to elevate circulating T3 levels or propylthiouracil (PTU) (200 mg/day for 14 days) to lower endogenous T3 levels. When compared with levels in euthyroid controls at rest and during exercise, rectal temperature (Tre) was increased (P less than or equal to 0.01 and P less than or equal to 0.02, rest and exercise, respectively) in T3-treated dogs and decreased (P less than 0.05 and P less than 0.01) in the PTU-treated dogs. Although the rise in Tre from rest to exercise in the PTU trial was slightly less than that of the control runs (1.23 vs 1.44 degrees C, respectively; P = 0.05), it was similar to the rise in Tre observed in the T3 experiments (1.37 degrees C). Because T3 treatment resulted in an elevation in exercise oxygen consumption (VO2), untreated dogs were run at elevated work loads such that their VO2 matched that recorded when pretreated with T3. Exercise Tre in these experiments was lower (P less than 0.02) than after T3 treatment, even though the exercise metabolic rates were equivalent. It was concluded that 1) although T3 alters body temperature, the magnitude of the rise in Tre during exercise is not dependent on T3 concentration and 2) the effects of T3 on body temperature at rest and during exercise are mediated through mechanisms other than alterations in metabolic rate.
Ventilation distribution and density dependence of expiratory flow in asthmatic children
Authors: Cooper D. M. , Mellins R. B. , Mansell A. L.
Published: December 2017

Of 114 asthmatic children, 21% had abnormally steep phase III slopes from a modified single-breath oxygen (SBO2) procedure. We hypothesized that the steep slopes reflect inequality of time constants caused by obstruction of peripheral airways and tested this by using a bronchodilator to reduce overall time constants in subgroups of 10 children with steep slopes (SS) and 20 children with normal slopes (NS). Maximum expiratory flow increased by equivalent degrees (0.65–0.70 l/s) in both groups, but slope decreased significantly only in the SS group. Moreover, the single-breath mixing efficiency of inspired oxygen with resident nitrogen was normal in the NS group but significantly low in the SS group. Density dependence of maximum expiratory flow (DD) was abnormally small in the SS group [15 +/- 6% (SD) increase compared with 57 +/- 13% increase in a separate group of normal children] and was independent of the anatomical dead space. In contrast, DD was normal and varied inversely with anatomical dead space (r = 0.62, P less than 0.01) in the NS group. These results indicate that 1) steep SBO2 slopes found in asthmatic children between acute episodes reflect unequal time constants caused by obstruction of peripheral airways and 2) part of the variation in DD among asthmatic children is caused by variation in convective accelerative pressure losses in major airways.
A pinhole method for measuring chest wall compliance
Authors: Grant J. L. , Moulton D. P.
Published: December 2017

We describe a method of measuring chest wall compliance (Cw) that readily detects whether respiratory muscles are relaxed. The method simulates a normal slow sigh, with the subject exhaling through a needle valve. Cw is calculated from the slope of the volume-esophageal pressure line. With relaxed subjects, repeated measurements yield similar slopes. When subjects cannot relax, the volume-pressure line is irregular and variable. In 26 subjects who could relax, Cw averaged 0.208 +/- 0.05 (SD) l/cmH2O.
Body size, energy metabolism, and the lungs
Authors: Heusner A. A.
Published: December 2017

The theoretical basis for applying the power function y = aMb to the study of structure-function relationships is discussed. Dimensional analysis and the distinction between intensive and extensive properties of animals show that the mass coefficient a represents the effect of intensive or qualitative factors on the considered function or structure. The theoretical mass exponent is a criterion for the constancy of a and the qualitative sameness of the compared structure or function. Examples from respiratory and metabolic physiology are given.
Histamine decreases selectivity of sheep lung blood-lymph barrier
Authors: McNamee J. E.
Published: December 2017

Histamine increases lymph flow and protein flux from the sheep lung. This increase in water and protein movement has been attributed to an increase in lung microvascular permeability-surface area product caused by histamine. Whether it was permeability that was changed or whether it was surface area cannot be discerned from past work. Histamine might increase either of these determinants of transport in the sheep lung. Previous measurements of several plasma protein fractions in plasma and lymph showed no change in the sieving behavior of the microcirculation with intravenous histamine, suggesting that only surface area was changed. In the present study, even larger test molecules were used to probe the limits of transport through the lung's blood-lymph barrier. Fluorescein isothiocyanate-labeled dextrans (FITC-dextran) that can normally permeate lung lymph do so more readily after intravenous histamine infusion (3 micrograms X kg-1 X min-1). Formerly impermeable FITC-dextran fractions also appear after histamine administration. No definitive size limit to the transport of dextran was found in histamine-stimulated sheep lungs. Intra-arterial histamine does not increase lung lymph, protein, or FITC-dextran flow. These results suggest that histamine changes the permeability or sieving characteristics of the lung microvascular barrier making it less size selective to large molecules. Surface area for transport may also increase.
Effect of air embolism on the measurement of extravascular lung thermal volume
Authors: Allison R. C. , Parker J. C. , Duncan C. E. , Taylor A. E.
Published: December 2017

To determine the accuracy of thermal-dye indicator-dilution measurements of lung water during perfusion abnormalities, we embolized air into the lungs of 10 dogs anesthetized with pentobarbital and mechanically ventilated. A control period was followed by a period of air injection (10 ml) and subsequent air infusion (E1), a second period of air injection and infusion (E2), and a recovery period. Thermal and dye-dilution curves were obtained during each period, and cardiac output (CO), total thermal volume, intravascular volume, and extravascular thermal volume (ETV) were calculated. Pulmonary arterial pressure (Ppa) increased from 16 +/- 2 cmH2O during control to 29 +/- 3 cmH2O during E1 and to 40 +/- 3 cmH2O during E2 and decreased to 21 +/- 2 cmH2O during recovery. CO did not change, and pulmonary vascular resistance changed in a pattern similar to Ppa. ETV fell from 113 +/- 8 ml during control to 59 +/- 11 ml during E1 and to 29 +/- 9 ml during E2 and rose to 136 +/- 23 ml during recovery. There was no increase in extravascular lung water or mass determined gravimetrically at the end of the experiments. We conclude that the thermal-dye technique will underestimate lung water in nonedematous lungs if emboli prevent complete diffusion of the thermal indicator.
Pressure-flow relationships in a collaterally ventilating dog lung segment
Authors: Olson L. E. , Rodarte J. R. , Robinson N. E.
Published: December 2017

We evaluated the pressure (P)-flow (V) relationship in collaterally ventilating dog lung segments by passing He, N2, and SF6 through a bronchoscope (5 mm OD) wedged in a peripheral airway. Measurements were made at functional residual capacity (FRC) and two higher lung volumes, keeping segment-to-airway opening pressure constant (3 cmH2O) in five anesthetized, paralyzed, vagotomized, supine dogs. Average flows ranged from 5.0 to 8.0 ml/s for He, 4.5 to 7.5 ml/s for N2, and 3.4 to 4.7 ml/s for SF6. When these data were fitted as P = K1/3/3 mu V + K2 rho V2, density-dependent pressure losses were unimportant when He and N2 were used, suggesting laminar flow with these gases. A dimensionless plot of the total pressure drop relative to a reference dynamic pressure as a function of Reynolds number at the bronchoscope tip suggested that flow through the segment behaved as if it were laminar at Reynolds numbers less than 100. Furthermore, when the airway diameter used to compute the normalized pressure and Reynolds number was scaled as the cubic root of lung volume, curves for all three gases were superimposed, suggesting that the dimensions of intrasegmental/collateral airways scale as lung volume 1/3.
Psychophysics of inspiratory muscle force
Authors: Stubbing D. G. , Ramsdale E. H. , Killian K. J. , Campbell E. J.
Published: December 2017

The perceived magnitude of static inspiratory muscle pressure was studied in normal subjects using psychophysical techniques. The sensory magnitude of a range of inspiratory pressures increased as the magnitude of the pressure increased. When the duration of the inspiratory pressure was controlled, the sensory magnitude also increased as duration increased. The relationship can be described by a single psychophysical function, psi = k x P1.234 x t0.62, where psi is perceived magnitude, P is inspiratory pressure, t is duration, and k is a constant. Use of different muscle groups and changes in lung volume altered the perceived magnitude of static inspiratory pressures. When static inspiratory pressures were generated by the abdomen-diaphragm, the perceived magnitude was significantly greater (P less than 0.01) than when they were generated by the rib cage. When lung volume was increased, the perceived magnitude of pressure was reduced. The results show that the perceived magnitude of static inspiratory pressures is affected by the pressure itself, pressure duration, the muscles used, and the lung volume at which the pressure is generated.
Effect of background loads on the perception of added loads to breathing
Authors: Burdon J. G. , Killian K. J. , Stubbing D. G. , Campbell E. J.
Published: December 2017

Using open-magnitude scaling, we compared the perceived magnitude of externally added resistive and elastic loads to breathing in normal subjects with that perceived when the background load (i.e., the minimum load of the circuit) was increased by the addition of either resistive or elastic loads of increasing magnitude. The study was carried out over four experimental sessions. After a control experiment (no added background load), the background load was increased by the addition of either a resistive or an elastic load for a duration of 3 min. The perceived magnitude of a further series of loads, proportionately increased, was then ascertained. This sequence was then repeated after a further increase in background. The results showed that the perceived magnitude of the load was closely related [mean r = 0.96 +/- 0.01 (SE)] to the magnitude of the physical stimulus expressed as the peak inspiratory pressure by a power function relationship in keeping with Stevens' law. After the increases in background resistance or elastance, there were no significant differences in either exponents or intercepts compared with basal conditions. There was no significant difference in the perceived magnitude of the loads after adaptation. At the smallest load, the perceived magnitude was less than expected from the control experiment. However, this reduction did not reach statistical significance. In the special senses, moderate-to-large stimuli show little change after adaptation, whereas small stimuli are reduced. Although not conclusive, we suggest that the relationship is similar with loaded breathing.
Respiratory movements of the vocal cords
Authors: Brancatisano T. , Collett P. W. , Engel L. A.
Published: December 2017

We examined the movements of the vocal cords during tidal breathing, panting, and large changes in lung volume in 12 normal subjects. The glottis was observed with a fiber-optic bronchoscope, and the glottic image was recorded together with flow, volume, and a time marker onto videotape. Phasic respiratory swings in glottic width (dg) and glottic area (Ag) were reproducible in all subjects but differed substantially between subjects. In the group as a whole dg and Ag increased during inspiration to 10.1 +/- 5.6 mm and 126 +/- 8 mm2 (mean +/- SE), respectively, whereas during expiration the lowest values were 5.7 +/- 0.5 mm and 70 +/- 7 mm2, respectively. These extreme dimensions corresponded closely to the midtidal volume points in the respiratory cycle. Glottic width during vital capacity (VC) expirations was nearly 30% greater at a flow of 1.2 l/s than at 0.5 l/s, but the relationship between dg and lung volume differed between subjects. When swings in dg were minimized by panting, there was no difference in dg between functional residual capacity (FRC) and a volume corresponding to midinspiratory capacity. However, tidal breathing at this lung volume was associated with a 20% decrease in dg compared with breathing at FRC. Our observations indicate a tight coupling between the pattern of glottic movement and the respiratory volume cycle. The results suggest that during voluntary respiratory maneuvers both intrinsic laryngeal and respiratory muscles are recruited, participating as effector organs in ventilatory and respiratory control.
Secretion of Weibel-Palade bodies observed in extra-alveolar vessels of rabbit lung
Authors: McNiff J. M. , Gil J.
Published: December 2017

We fixed rabbit lungs by perfusion of osmium into the pulmonary artery and examined in light and transmission electron microscopy a large number of extra-alveolar vessels with a diameter of 0.1–0.25 mm, with emphasis on Weibel-Palade bodies (endothelial specific granules). Weibel-Palade bodies are organelles specific to endothelial cells. Their function is unknown, but they are useful markers for identification of endothelial cells in culture. We were able to observe release of the content of these bodies into the vascular lumen; this indicates that they are secretory.
Fiber number and size in overloaded chicken anterior latissimus dorsi muscle
Authors: Gollnick P. D. , Parsons D. , Riedy M. , Moore R. L.
Published: December 2017

The relative contribution of increases in fiber area and number was evaluated in the chicken anterior latissimus dorsi (ALD) muscle in which enlargement was induced by hanging a weight on one wing. ALD muscles from wings to which weights had been attached for periods ranging from 6 to 65 days weighed an average of 105% (range 22–225%) more than control muscles. Total muscle fiber number, determined by direct counts after nitric acid digestion and fiber dissection, and the frequency of branched fibers were unchanged by muscular enlargement. Fiber cross-sectional area was greater (P less than 0.01) in the enlarged muscles. A close relationship existed (r = 0.78) between actual muscle weight and weight calculated as the product of fiber volume, total fiber number, and muscle density for the control and enlarged muscles. Histochemical staining revealed a conversion of type IIa to type I fibers in the stretched muscles. These results support the concept that skeletal muscle enlargement in response to chronic overload is produced by hypertrophy of preexisting fibers and not be a formation of new fibers.
Cardiovascular responses to exercise as functions of absolute and relative work load
Authors: Lewis S. F. , Taylor W. F. , Graham R. M. , Pettinger W. A. , Schutte J. E. , Blomqvist C. G.
Published: December 2017

The roles of absolute and relative oxygen uptake (VO2 and percent of muscle group specific VO2 max) as determinants of the cardiovascular and ventilatory responses to exercise over a wide range of active muscle mass have not previously been defined. Six healthy men performed four types of dynamic exercise--one-arm curl, one-arm cranking, and one- and two-leg cycling at four different relative work loads--25, 50, 75, and 100% of VO2 max for the corresponding muscle group. VO2 during maximal one-arm curl, one-arm cranking, and one-leg cycling averaged 20, 50, and 75%, respectively, of that for maximal two-leg cycling. Cardiac output was linearly related to VO2 with a similar slope and intercept for each type of exercise. Heart rate at a given %VO2 max was higher with larger active muscle mass. In relation to %VO2 max, systemic resistance was lower and plasma catecholamine levels were higher with larger active muscle mass. The cardiovascular responses to exercise are determined to a large extent by the active muscle mass and the absolute oxygen uptake, with the principal feature appearing to be the tight linkage between systemic oxygen transport and utilization.
Synchronized cycles in ventilation and vocal activity during spontaneous conversational speech
Authors: Warner R. M. , Waggener T. B. , Kronauer R. E.
Published: December 2017

Ventilation was monitored in 10 human subjects during spontaneous conversational speech to determine whether oscillatory patterns in vocal activity were correlated with oscillatory patterns in ventilation. The 10 subjects were studied as five pairs (or dyads), and spontaneous conversation occurred within each dyad. Patterns with cycle times ranging from 16 to 512 s were studied. Of the 10 subjects in this study, 1 subject showed a very striking pattern of mutual entrainment between low-frequency oscillations in ventilation and in vocal activity, 5 subjects showed somewhat weaker coordination between oscillations in ventilation and vocal activity, and the remaining 4 subjects showed little or no coupling between ventilation and vocal activity. Mutual entrainment between rhythms in ventilation and vocal activity can occur, but this study suggests that there may be great differences among individuals in the degree to which ventilation covaries with vocal activity in spontaneous conversational speech. We hypothesize that degree of entrainment is affected both by the strength of any spontaneous ventilatory patterns and by the extent to which any individual's spontaneous ventilatory pattern matches that of his conversational partner.