bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the configuration of maximum expiratory flow-volume curves
Authors: Mead J.
Published: December 2017

The ratios of the instantaneous tangent slopes to corresponding chord slopes are sensitive to curvatures of flow-volume curves; and these dimensionless slope ratios, SR, plotted against fractional volumes remaining to be expired, VCf, are sensitive to the shape of flow-volume curves but insenitive to flow or volume magnitudes. SR-VCf curves predicted for lungs which empty homogeneously differ substantially from those predicted for lungs which empty nonhomogeneously, the latter showing systematic increases in SR with VCf which may extend beyond the homogeneous range. SR-VCf curves for some 80 healthy subjects show systematic changes with age (range 6–64 yr), but all are consistent with advanced obstructive lung disease (chronic bronchitis, emphysema, asthma) are consistent with nonhomogeneous emptying, but it does not seem likely that SR-VCf curves will prove useful for detecting early stages of disease.
Free autografting of entire limb muscles in the cat: histochemistry and biochemistry
Authors: Maxwell L. C. , Faulkner J. A. , Mufti S. A. , Turowski A. M.
Published: December 2017

Fifty extensor digitorium longus muscles of 25 cats were autografted, 33 with and 17 without prior denervation. After 50 days, no significant differences were observed between predenervated and nonpredenervated autografts. Autografted muscles weighed 48% of the weight of control muscles. Few original muscle fibers survived and within 2 wk autografts contained regenerating muscle fibers. The mean cross-sectional area of muscle fibers in the autografts reached 125% of the value for control nontransplanted muscles. The mean percentage of fibers classified high oxidative in autografted muscles was 67% of values for control muscles. SDH activity of autografted muscle homogenates reached 55% of control values. Up to 60 days after surgery autografts had only fast-twitch fibers. At 170 days autografts remained 95% fast twitch in composition. Revascularization began within 4 days, but the capillary to fiber ratio of long term autografts reached only 60% of control values. Although fiber hypertrophy suggests that cats use autografted muscles, lower than control succinate dehydrogenase activity may result from altered recruitment.
Developmental pattern of muscle fiber types in human ventilatory muscles
Authors: Keens T. G. , Bryan A. C. , Levison H. , Ianuzzo C. D.
Published: December 2017

Premature infants tolerate respiratory loads poorly. This may reflect incomplete development of the ventilatory muscles (VM) causing poor resistance to fatigue. To study the developmental pattern of human VM, 31 postmortem specimens of diaphragm and intercostal muscles were obtained. Individual muscle fibers were classified as type I (slow-twitch, high-oxidative) or type II (fast-twich, low-oxidative) using histochemical staining methods for myofibrillar adenosine triphosphatase (M-ATPase) (pH 10.30) and nicotinamide adenine dinucleotide (NADH) tetrazolium reductase. In the diaphragm, premature infants (less than 37 wk gestation) had only 9.7 +/- 1.3% type I fibers, full-term newborns 25.0 +/- 1.1%, and older subjects (greater than 2 yr of age) 54.9 +/- 1.3%. There was no further increase after 8 mo postpartum. In the intercostal muscles, premature infants had only 19.0 +/- 4.8% type I fibers, full-term newborns 45.7 +/- 1.3%, and older subjects 65.2 +/- 2.6%. There was no further increase after 2 mo postpartum. These findings suggest the ventilatory muscles of newborn infants are more susceptible to fatigue than those of older subjects. This may contribute significantly to respiratory problems in the neonate.
Carbohydrate, lipid and amino acid metabolism following physical exercise in man
Authors: Holm G. , Bjorntorp P. , Jagenburg R.
Published: December 2017

To elucidate early metabolic adaptations of physical training obese and nonobese subjects were studied before and at different intervals after 1 h of bicycle exercise at 70% of maximal working capacity. Four h after exercise intravenous glucose tolerance (IVGT) and plasma level of alanine were decreased. Compared to the diurnal variation plasma concentration of cortisol was increased. Twenty-four hours after exercise plasma concentrations of cortisol and trihlycerides were decreased. Furthermore, plasma insulin during IVGT test was decreased and blood glycerol increased in the obese subjects. There were no changes in basal insulin, IVGT, or plasma levels of amino acids which were elevated in the obese subjects (valine, isoleucine, leucine, tyrosine, phenylalanine). Forty-eight hours after exercise plasma insulin during IVGT test and plasma triglycerides remained decreased in the obese subjects. Low cortisol levels 24 h after exercise might result in increased insulin effect leading to low plasma insulin levels seen in physically trained subjects. Elevated glycerol levels in the obese subjects might be the first sign of diminishing fat stores secondary to increased lipolysis.
Tracer priming the bicarbonate pool
Authors: Allsop J. R. , Wolfe R. R. , Burke J. F.
Published: December 2017

We have described a technique whereby the time necessary to reach an equilibrium enrichment of expired CO2 during a primed-constant infusion of [U-13C]glucose was shortened from 7 to 8 h to 1 hour or less. We applied the theory of the primed-constant infusion technique to the bicarbonate pool, with the “constant infusion” of labeled carbon dioxide originating from oxidation of the infused [13C]glucose rather than from a labeled infusion of bicarbonate.
Impedance cardiography for estimating cardiac output during submaximal and maximal work
Authors: Kobayashi Y. , Andoh Y. , Fujinami T. , Nakayama K. , Takada K. , Takeuchi T. , Okamoto M.
Published: December 2017

Impedance cardiography was used to estimate cardiac output in 10 men during rest and within 5 s after exercise on a bicycle ergometer, including work up to and including maximal aerobic capacity. An indwelling venous catheter permitted simultaneous sampling of venous blood for observing changes in hematocrit associated with each exercise level. Cardiac output, calculated from a standard equation which assumes a constant value of 150 omega.cm for the electrical resistivity of blood, was compared with corresponding calculations in which blood resistivity was individually determined as a function of hematocrit. It is concluded that many of the discrepancies in the literature related to values for cardiac output obtained during exercise by the impedance method may be inherent in calculations that do not consider the changing electrical resistivity of the blood with a changing hematocrit.
VA/Q inhomogeneity and AaDO2 in man during exercise: effect of SF6 breathing
Authors: Gledhill N. , Froese A. B. , Buick F. J. , Bryan A. C.
Published: December 2017

Pulmonary gas exchange was studied in five normal subjects both at rest and during moderate steady-state exercise on a bicycle ergometer while breathing a) room air and b) a mixture of 20.9% O2-balance sulfur hexafluoride (SF6). The alveolar-arterial oxygen pressure differences (AaDO2) widened significantly from rest to exercise. Breathing the O2-SF6 mixture reduced the AaDo2 significantly from 10.9 to 4.2 Torr at rest and from 15.5 to 10.1 Torr during exercise (P less than or equal to 0.01). There were no concurrent changes in metabolism, cardiac output, or heart rate during the SF6 breathing. Possible changes in the anatomic shunt fraction, alveolar-end-capillary equilibration, or the distribution of blood flow cannot account for these observations. We conclude that the AaDO2 increase during exercise reflects an inhomogeneity of ventilation-perfusion ratios (VA/Q) most probably arising within regions of the lung (intraregional inhomogeneity) rather than between regions (interregional inhomogeneity).
Mechanisms of pulsus paradoxus in upper airway obstruction
Authors: Parsons G. H. , Green J. F.
Published: December 2017

Pulsus paradoxus, a greater than 10 Torr systolic pressure fluctuation during the respiratory cycle, is seen in upper airway obstruction. To test the hypotheses 1) that blood is pooled in the pulmonary circulation with reduced return to the left heart during inspiration and 2) that inspiration increases left ventricular afterload, the following was done. Esophageal pressure (Pes), pericardial pressure (Pp), left atrial transmural pressure (Platm), and left ventricular transmural pressure at end-isovolumic systole (Plvtm) were recorded during partially obstructed inspirations in spontaneously breathing dogs anesthetized with pentobarbital (25 mg/kg). Changes in Pes and Pp were nearly identical (r = 0.9883) confirming that changes in Pes adequately reflect changes in Pp. During inspiration Platm and Plvtm increased 0.5 and 0.4 Torr, respectively, per Torr decrease in Pes suggesting that increased blood return to left atrium and increased left ventricular afterload occur. Similar changes were observed during near constant thoracic volume (total airway block) and cardiac reflex blockade (atropine 0.05 mg/kg and propranolol 0.5 mg/kg). Thus mechanical factors including left ventricular afterload appear of major importance in producing pulsus paradoxus in upper airway obstruction.
Influences of physical conditioning and deconditioning on coronary vasculature of dogs
Authors: Wyatt H. L. , Mitchell J.
Published: December 2017

To investigate the effects of physical conditioning and deconditioning on the coronary vasculature, eight dogs were exercised by treadmill running. Five dogs were deconditioned by confinement in cages following the conditioning period. A technique was developed and validated for measuring circumflex coronary artery diameter from magnified projections of standardized coronary angiograms. Myocardial capillary density, perimeter, and basement membrane thickness were determined from electron microscopy of serial ventricular septal biopsy samples. Physical conditioning caused a small but statistically significant increase in cross-sectional area of the circumflex artery. Although physical conditioning caused no statistically significant changes in the myocardial capillaries, trends were apparent for increases in density and perimeter of myocardial capillaries and a decrease in basement membrane thickness. Physical deconditioning caused statistically significant reductions in cross-sectional area of the circumflex artery and in myocardial capillary density but little change in perimeter or basement membrane thickness of myocardial capillaries. The results suggest that physical conditioning may be associated with an improvement in coronary vascular capacity which may regress rapidly with deconditioning.
An electrode for PN2O and PO2 analysis in blood and gas
Authors: Albery W. J. , Brooks W. N. , Gibson S. P. , Hahn C. E.
Published: December 2017

The development of a new polarographic sensor for measuring simultaneously both N2O and O2, in either gas or blood, is described. The cathode is made of silver, and it is shown that silver deposition on normal platinum or gold cathode electrodes can result in an enhancement of a PO2 signal, when measured in the presence of nitrous oxide. Silver can be deposited on the cathode by means of Ag+ ions diffusing through the electrolyte from an Ag/AgCl reference electrode. The use of an Ag cathode enables both O2 and N2O signals to be measured.
Pulmonary circulation of the harbor seal
Authors: Sinnett E. E. , Kooyman G. L. , Wahrenbrock E. A.
Published: December 2017

Cardiac output (Q) and pulmonary arterial pressure (Ppa) were measured under various conditions in four harbor seals (Phoca vitulina) weighing 35--52 kg. In seals anesthetized with halothane, Q averaged 3.47 l/min; in awake resting seals, Q averaged 11.5 l/min; and during surface dives (i.e., at atmospheric pressure) Q averaged 1.99 l/min. Stroke volume was one-third and two-thirds of the awake resting value during anesthesia and diving, respectively. Systolic Ppa was usually 40--50 Torr in anesthetized and awake resting seals, but was about 10 Torr lower during both surface and compression (i.e., elevated ambient pressure) dives. Diastolic Ppa was constant and high during anesthesia and quite variable in awake resting seals. During both surface and compression dives the diastolic Ppa often fell to the same level as right atrial pressure. We conclude that Q and Ppa are high in awake resting seals and that pulmonary blood flow may cease between beats during diving.
Sodium intake and the effects of isoproterenol and exercise on plasma renin in man
Authors: Leenen F. H. , Boer P. , Geyskes G. G.
Published: December 2017

Changes in heart rate, blood pressure, and plasma renin activity (PRA) were assessed during infusion of increasing doses of isoproterenol and during increasing work loads of dynamic exercise in five normal young men. Studies were performed at three levels of dietary sodium restriction: normal, moderately, and more severely restricted. Isoproterenol induced the expected dose-related increases in heart rate, systolic blood pressure, and PRA and decreases in diastolic blood pressure. Changes in dietary sodium intake affected these changes only to a minor degree. Dynamic exercise also induced the expected work-load-related increases in heart rate, systolic blood pressure, and PRA and decreases in diastolic blood pressure. Also these changes were not significantly affected by changes in dietary sodium intake. Apparently dietary sodium restriction does not sensitize the renin-releasing mechanisms to sympathetic stimulation.
Ventilatory muscle training and the oxygen cost of sustained hyperpnea
Authors: Bradley M. E. , Leith D. E.
Published: December 2017

We measured the oxygen cost of breathing during sustained voluntary normocarbic hyperpnea in 12 subjects (4 endurance trainers, 4 strength trainers, and 4 controls) before and after a 5-wk training program limited to the ventilatory muscles (Leith, D. E., and M. E. Bradley. J. Appl. Physiol. 41: 508–516, 1976). “Steady-state” measurements of oxygen consumption were made at pulmonary ventilations ranging from 103 to 250 l/min. There were marked differences in the relationship between the metabolic cost of breathing and pulmonary ventilations between subjects. Spontaneously chosen respiratory frequencies ranged from 80 to 120 breaths/min and varied widely, even in a given subject, suggesting that the optima for frequency are broad or that optimization was imperfect. The subject group who performed endurance training increased by 19% the level of hyperpnea that they could sustain for 7––15 min, and increased their oxygen consumptions during this hyperpnea by an average of 67%. Following a 15-wk period of detraining, endurance trainers had lost 50% of their gains in the ventilations that they could sustain and in the accompanying oxygen consumptions. We conclude that ventilatory muscle endurance training can appreciably increase the aerobic endurance of the respiratory muscles.
Airway reactivity to nitrates in normal and mild asthmatic subjects
Authors: Utell M. J. , Swinburne A. J. , Hyde R. W. , Speers D. M. , Gibb F. R. , Morrow P. E.
Published: December 2017

Epidemiologic studies have reported increased symptoms in young asthmatics when atmospheric pollutants containing nitrates and sulfates are elevated. To determine if inorganic nitrate pollutants cause increased airway reactivity in humans, 10 normal volunteers and 11 mild asthmatics inhaled a sodium nitrate (NaNO3) aerosol with an aerodynamic diameter of 0.46 micron at a concentration of 7,000 microgram/m3, a level 100--1,000 times greater than reported urban levels for nitrates. A sodium chloride (NaCl) aerosol of similar characteristics served as a control. By double-blind randomization, each subject breathed NaCl or NaNO3 for a 16-min period and again 2--4 h later. Deposition studies showed 32--78% retention of the inhaled aerosol. Functional residual capacity, airway resistance, forced vital capacity, 1-s forced expiratory volume, and maximum and partial expiratory flow rates at 60 and 40% of total lung capacity did not significantly change during or after exposure. All subjects remained asymptomatic. To establish if aerosol exposure increased reactivity to a known bronchoconstrictor, subjects inhaled 0.025--1.0% carbachol following the 16-min exposure. Although prior inhalation of NaNO3 or NaCl aerosols did not significantly alter the effect of carbachol on pulmonary function, two asthmatics demonstrated mild potentiation of the carbachol bronchoconstrictor response after nitrate exposure. These results suggest that in normal subjects and mild asthmatics short-term NaNO3 exposure does not alter pulmonary function.
Redistribution of pulmonary blood flow in the dog with PEEP ventilation
Authors: Hedenstierna G. , White F. C. , Mazzone R. , Wagner P. D.
Published: December 2017

The effects of positive end-expiratory pressure (PEEP) at 20 cmH2O on the distribution of pulmonary blood flow was studied in intact dogs and isolated lung preparations. Measurements were made of a) the continuous distribution of ventilation-perfusion ratios (VA/Q), b) the vertical distribution of pulmonary blood flow, and c) the dimensions of the microvasculature. Without PEEP the distributions of ventilation and perfusion were unimodal and centered on a VA/Q close to one. Dependent regions received 5–10 times more of cardiac output than uppermost regions. With PEEP the distribution showed a bimodal character, one mode of normal VA/Q and the other comprising one-third of ventilation, lying between VA/Q of 10 and 100. Cardiac output was reduced two- to threefold and blood flow in the uppermost regions was grossly reduced but not eliminated. Bimodal distributions were also found in isolated lungs with PEEP, and histological examination of rapidly frozen lung tissue showed that alveolar capillaries were closed in the uppermost, poorly perfused regions, whereas alveolar corner vessels remained open. We suggest that the blood flow through these corner vessels is responsible for the additional, high VA/Q mode during PEEP.
Stroke volume and systolic time interval adjustments during bicycle exercise
Authors: Vanfraechem J. H.
Published: December 2017

By use of the impedance noninvasive method, cardiac output (Q), stroke volume (SV), heart rate (HR), Heather index (HI), and systolic time interval (STI) values were studied in 17 subjects working at 25, 50, and 75% of their maximal oxygen uptake (Vo2 max) on a Monark bicycle. A significant increase in SV at each work load and a concomitant decrease in positive expiratory pressure (PEP), left ventricular ejection time (LVET), and PEP/LVET were observed. The linear regression equation at 75% Vo2 max between LVET and HR and SV confirms the close relationship between these parameters. The significa-t increase of the contractility index (HI) showing the stress response of the myocardium is clearly assessed. At 75% work load, its correlation with SV is low; but the high level of the correlation (r = 0.90) between HI and HR in the stress response. Consequently the changes in STI and HI provide valuable information on SV adjustment during calibrated effort responses. Consequently, the changes in STI and HI, the relationship between STI and SV, and the study of SV, HR, and Q provide valuable information about the adjustment of these parameters during calibrated efforts.
Contribution of rib cage and abdomen-diaphragm to tidal volume during CO2 rebreathing
Authors: Pengelly L. D. , Tarshis A. M. , Rebuck A. S.
Published: December 2017

In man, there is wide interindividual range in the tidal volume response to CO2. To determine which (rib cage or abdomen-diaphragm) compartment had a greater influence on this range, ventilatory response to CO2 was measured, using Read's method, in eight men and two women seated in a constant-pressure body plethysmograph. Rib cage and abdominal tidal volume was simultaneously measured using magnetometers. Correcting for body size, the tidal volume response of the abdominal compartment was similar in all subjects, whereas that of the rib cage was larger in subjects with high tidal volume response to CO2; a significant correlation was found (P less than 0.01). Rib cage volume displacement lagged behind abdominal in all subjects; phase lag was greatest in the subject with the lowest ventilatory response to CO2. These results suggest that, at high levels of ventilation, a larger volume displacement of the rib cage may reflect a more effective coupling of the diaphragm pressure generator to it or alternatively a reduction in its impedance relative to the abdominal compartment.
Thermal increment provided by inhalation rewarming from hypothermia
Authors: Morrison J. B. , Conn M. L. , Hayward J. S.
Published: December 2017

To quantify the core temperature gain derived from inhalation rewarming, 10 subjects were immersed in seawater (mean temperature 12 degrees C) until a 2 degree C drop in rectal temperature occurred, and were then rewarmed by breathing hot saturated air at 45 degrees C for 30 min. Each subject was rewarmed once breathing air and once rebreathing a controlled fraction of expired air adjusted to produce a hyperventilation of 50 l/min. After 30 min of rewarming mean rectal temperature had increased 0.39 degrees C in subjects breathing air compared with 0.77 degrees C in those hyperventilating (P less than 0.01). Corresponding gains in tympanic temperatures were 1.1 and 1.5 degrees C, respectively. Calculations indicate that the additional heat input with hyperventilation yielded a core (rectal) temperature gain of 5.1 X 10(-4) degrees C/l. It is concluded that each additional 10 l/min of ventilation of hot saturated air will increase the rate of core rewarming from hypothermia by approximately 0.3 degrees C/h.
Effect of hyperoxia on oxygen consumption in exercising ponies
Authors: Stanek K. A. , Nagle F. J. , Bisgard G. E. , Byrnes W. C.
Published: December 2017

Published reports of oxygen consumption (VO2) during exercise in hyperoxia are equivocal. By and large, when measured at the lung using respiratory gas equations, VO2 is elevated in hyperoxia and, when measured at the blood-tissue level using the cardiovascular Fick (CVF) equation, it is unchanged. We sought to provide some insight into this problem by making through the use of both equations simultaneous determinations of VO2 during hyperoxia in exercising ponies. In normoxia, during treadmill exercise (115 m/min, 10% grade) of seven ponies, there was no difference in exercise VO2, whether it was measured by the Haldane transformation (HT) or CVF equations (P greater than 0.05). In hyperoxia, the exercise VO2 was significantly increased from the normoxia condition (P less than 0.05) when measured by the HT equation but not when measured by the CVF equation (P greater than 0.05). By use of the CVF equation as the method of choice for VO2 determinations in hyperoxia, the present data show no change in exercise VO2 in the hyperoxic condition.
Regional differences in abdominal muscle activity during various maneuvers in humans
Authors: Strohl K. P. , Mead J. , Banzett R. B. , Loring S. H. , Kosch P. C.
Published: December 2017

To determine if regional differences exist in the activity of abdominal muscles during respiratory and nonrespiratory maneuvers, we studied four healthy subjects by comparing electromyographic (EMG) activity from surface electrodes placed lateral to rectus muscle, one pair on the upper abdomen and the other on the lower abdomen. In one subject EMG recordings were made from wires placed in various layers of the abdominal wall. Relative positions and changes in size of anatomic structures during maneuvers were determined from real-time ultrasonography of the abdominal wall. Expulsive or valsalva maneuvers evoked the same relative EMG activity in the upper and lower abdomen. In the resting supine posture no EMG activity was detectable; however, in the standing posture greater tonic EMG activity appeared in the lower abdomen. During rebreathing, phasic EMG activity during expiration was greater in the upper than in the lower abdomen in all subjects. Observations from ultrasonographic and electromyographic evaluations suggest that the control of abdominal muscles and their influence on respiratory mechanics are potentially more complex than has been suggested by previous reports.
An asymmetrical model of the airways of the dog lung
Authors: Horsfield K. , Kemp W. , Phillips S.
Published: December 2017

A resin cast of the bronchial tree of a dog was studied down to branches of 0.5-mm diameter. The branches were ordered, and the number of branches, mean diameter, and mean length of branches in each order were determined. The model was developed from these data with the property that delta, the difference in order between the two daughter branches at a bifurcation, is identical for all parent branches of a given order. This property facilitates the use of the model for the calculation of physiological variables such as input impedance (Fredberg and Hoenig, ASME J. Biomech. Eng. 100: 57–66, 1978), and the comparison of such results with those obtained from symmetrical models (Sidell and Fredberg, ASME J. Biomech. Eng. 100: 131–138, 1978).
Mechanical cardiopulmonary interdependence
Authors: Lloyd T. C.
Published: December 2017

We studied cardiopulmonary interdependence in ten pentobarbital sodium-anesthetized dogs by 1) measuring the increase of left atrial pressure (Pla) required to hold cardiac output (Q) constant on application of a positive end-expiratory pressure (PEEP), 2) determining the reduction of Pla required to mimic the Q fall observed when PEEP was applied while Pla was held constant, and 3) comparing left ventricular pressure-volume curves measured in freshly dead dogs during ventilation with and without PEEP. The atrial pressure changes can be divided into terms for pleural pressure change, lung deformation, and an undefined residual component and can be used to obtain a compliance opposing ventricular filling. Another compliance was derived from the pressure-volume curves. The latter compliance (6.8 ml/cm H2O) significantly exceeded the former (3.9 ml/cm H2O). The difference may have been caused by ventricular interdependence. The respiratory system compliance opposing ventricular filling was approximately one-twentieth of that predicted from lung and chest wall compliances. Deformation of lungs and chest wall appears to be a significant component of the elastic load imposed on ventricular diastolic filling.
Role of the carotid chemoreceptors in regulation of inspiratory onset
Authors: Bowes G. , Andrey S. M. , Kozar L. F. , Phillipson E. A.
Published: December 2017

We studied the effect of intermittent tidal breaths of CO2-enriched air (3–9% CO2) on the duration of expiratory time (TE) in five trained dogs, before and after (3 dogs) bilateral surgical denervation of the carotid bodies (CBD). During studies the dogs lay quietly, either awake or in nonrapid-eye-movement sleep, and breathed through a cuffed endotracheal tube inserted via a chronic tracheostomy. Studies were conducted during bilateral blockade of the cervical vagus nerves (VB), achieved by circulating cold alcohol through radiators placed around exteriorized vagal skin loops. Prior to CBD, single breaths of CO2 significantly shortened TE and thus advanced the onset of the subsequent inspiration. Further, the decrease in TE induced by the CO2 stimulus was in direct proportion to the inspired CO2 concentration. Thus 3% CO2 shortened TE by 1.82 +/- 0.93 (SD) s, and 9% CO2 by 3.44 +/- 1.53 s. Changes in TE occurred in the absence of associated changes in either tidal volume or inspiratory time. After CBD, test breaths of CO2 failed to shorten TE during VB. We conclude that the carotid bodies have the ability to mediate changes in the timing of inspiratory onset in response to a transient CO2 stimulus.
Exercise hyperventilation in patients with McArdle's disease
Authors: Hagberg J. M. , Coyle E. F. , Carroll J. E. , Miller J. M. , Martin W. H. , Brooke M. H.
Published: December 2017

This study was undertaken to determine if patients who lack muscle phosphorylase (i.e., McArdle's disease), and therefore the ability to produce lactic acid during exercise, demonstrate a normal hyperventilatory response during progressive incremental exercise. As expected these patients did not increase their blood lactate above resting levels, whereas the blood lactate levels of normal subjects increased 8- to 10-fold during maximal exercise. The venous pH of the normal subjects decreased markedly during exercise that resulted in hyperventilation. The patients demonstrated a distinct increase in ventilation with respect to O2 consumption similar to that seen in normal individuals during submaximal exercise. However their hyperventilation resulted in an increase in pH because there was no underlying metabolic acidosis. End-tidal partial pressures of O2 and CO2 also reflected a distinct hyperventilation in both groups at approximately 70–85% maximal O2 consumption. These data show that hyperventilation occurs during intense exercise, even when there is no increase in plasma [H+]. Since arterial CO2 levels were decreasing and O2 levels were increasing during the hyperventilation, it is possible that nonhumoral stimuli originating in the active muscles or in the brain elicit the hyperventilation observed during intense exercise.
Resistance of mucus-lined tubes to steady and oscillatory airflow
Authors: King M. , Chang H. K. , Weber M. E.
Published: December 2017

We examined the effects of quantity and physical properties of mucus on resistance to steady and oscillatory flows in a circular tube. Gels with similar rheological properties to canine tracheal mucus were prepared from hog gastric mucin or locust bean gum cross-linked with Na2B4O7. A horizontal straight tube (D 1.85 cm) was lined with these mucus simulants to depths ranging from 0.3 to 1.0 mm. The pressure difference over a 50-cm portion of the tube and the volumetric flow rate were determined simultaneously. Low-amplitude oscillatory flow were generated with a modified Harvard pump. For steady flow, the resistance at low Reynolds number (Re) increased with increasing gel depth only to the extent expected for simple constriction of the tube cross-sectional area. The same was true for oscillatory (0.25--6 Hz) flow resistance at low flow amplitude (corresponding to Re less than 4,000). No effect of gel cross-link density at low Re was observed. At high steady-flow rates, and for high-amplitude oscillatory flow, resistance increased beyond that predicted for simple constriction. Plots of friction factor (f) vs. Re showed a critical point (Recrit) of the order of 1.5 x 10(4), at which f increased sharply. Recrit, which corresponded to the onset of wave formation in the lining layer, was insensitive to changes in gel depth. However, gel cross-link density did affect the onset of wave formation: in oscillatory flow Recrit was shifted to higher Re, and the rise in f in steady flow was blunted with high degrees of cross-linking. The existence of Recrit and its association with wave formation are consistent with predictions based on two-phase flow theory.
Computerized determination of pneumotachometer characteristics using a calibrated syringe
Authors: Yeh M. P. , Gardner R. M. , Adams T. D. , Yanowitz F. G.
Published: December 2017

A computerized method has been developed to determine the conductance characteristics of pneumotachometers. Conductance values of the flowmeter, which correspond to all pressure values, can be determined by a weighted averaging technique, when multiple strokes of a precision 3-liter calibrated syringe are used. The conductance values then allow the measured differential pressures to be converted, point by point, into flows. The accuracy of measured volumes is within +/- 0.5% for a 100-stroke calibration process, and calibration with 50 strokes provides +/- 1% accuracy. The method improves the accuracy of the on-line measurements of ventilation. O2 consumption, and CO2 production during exercise.
Regional distribution of ventilation at residual volume in induced bronchospasm
Authors: Delaunois L. , Boileau R. , Diodatti J. , Gauthier J. , Martin R. R.
Published: December 2017

The regional distribution of a bolus of gas inhaled at residual volume (RV) is attributed to regional airway closure and is responsible for the phase IV of the single-breath washout during the following deflation. As bronchospasm increases the range of airway opening pressures through the lung, the regional distribution of the bolus could change with effects on the shape of the single-breath washout. We investigated the regional distribution of boluses inhaled at RV and their single-breath washouts during methacholine-induced bronchospasm in prone dogs. With increasing total lung resistance (RL) we first observed in five out of eight animals a preferential “redistribution” of the bolus to the upper caudal regions of the lung, which could be partially attributed to the increased lung volume at RV. When maximal RL was attained, the bolus was evenly distributed through all regions of the lung in these animals with disappearance of phase IV and increased slope of phase III, and a final decrease of tracer concentration at low lung volumes was observed. We conclude from these data that increased bronchomotor tone in dogs results in a less homogeneous intraregional distribution of the bolus with increased slope of phase III and in a more even interregional distribution leading to disappearance of phase IV. In severe bronchospasm the downward slope at low lung volume suggests intraregional closed lung units emptying through collateral pathways into still open neighboring units.
Sweating sensitivity and capacity of women in relation to age
Authors: Drinkwater B. L. , Bedi J. F. , Loucks A. B. , Roche S. , Horvath S. M.
Published: December 2017

Ten postmenopausal and ten younger women rested for 2 h in a 40 degrees C, 22.2-Torr vapor pressure environment. Sweating response was monitored by resistance hygrometry for onset, a platform balance for whole-body sweat rate, and five individual capsules for regional sweat rate. Other variables measured included forearm blood flow, heart rate (HR), mean skin (Tsk) and rectal (Tre) temperatures, sweat electrolytes (Na+ and K+), oxygen uptake, and plasma volume changes. Preliminary tests included maximal aerobic power (VO2max) and percent body fat. Heat stress did not elicit any significant differences in sweating response between age groups. Indices of heat strain, Tre and HR, were also similar for both groups. The only significant difference between younger and older women was a higher Na+ concentration in the forearm sweat of postmenopausal women. No thermoregulatory responses were related to age, but both sweat rate (r = 0.48) and peak Tsk (r = -0.43) were related to VO2max. For healthy, active, older women aging did not diminish the functional capacity of the sweating mechanism to cope with heat stress while resting in this specific thermal environment.
Antidiuretic hormone responses to eucapnic and hypocapnic hypoxia in humans
Authors: Claybaugh J. R. , Wade C. E. , Sato A. K. , Cucinell S. A. , Lane J. C. , Maher J. T.
Published: December 2017

Urinary excretion rate of antidiuretic hormone (UADHV) was studied in male volunteers in response to hypobaric hypoxia. The first series consisted of three groups. The chamber was decompressed to 465, 495, and 438 Torr during high-altitude (HA) exposure for groups I (n = 5), II (n = 5), and III (n = 4), respectively. In group I, the chamber air contained 3.77% CO2 to prevent alkalosis. The level of hypoxemia was similar in groups I and II. Mean 24-h UADHV was unchanged in group I, but increased 96% (P less than 0.05) and 180% (P less than 0.05) in groups II and III, respectively, on day 1 at HA and was normal during subsequent days at HA regardless of symptoms of acute mountain sickness. Shorter sampling intervals employed in a second series of experiments conducted at 495 Torr revealed a twofold increase in UADHV (P less than 0.05) 8–12 h after ascent in eight asymptomatic subjects; UADHV returned to base line within 9 h and remained low. The symptomatic subjects both had increased UADHV (3- and 8-fold from base line) between 2 and 4 h after ascent. Increased UADHV in asymptomatic subjects may be a result of the concomitant decrease in plasma volume, both of which appeared to be eliminated by CO2 supplementation.
Frequency spectra of flow and volume events for forced vital capacity
Authors: Lemen R. J. , Gerdes C. B. , Wegmann M. J. , Perrin K. J.
Published: December 2017

We determined the frequency content of forced expiratory flow-time (FT) and volume-time (VT) curves by a fast Fourier transform to determine the dynamic responses required of devices to reproduce these curves. We analyzed 304 FT and VT curves from 15 normal (N) subjects (ages 8– yr), 15 cystic fibrosis (CF) patients (ages 7–36 yr), and 9 smokers (S, ages 20–63 yr). The highest frequency (HF) with significant amplitude content, defined as the highest frequency with 5% or more amplitude of the fundamental, for FT curves in N (mean +/- SD, 5.06 +/- 0.7 Hz) was significantly (P less than 0.05) lower than in CF (6.43 +/- 0.9 Hz) and S (6.49 +/- 1.8 Hz). These differences were due predominantly to flow transients at high lung volumes in CF and S. No significant differences in HF of VT curves were noted among N (3.0 +/- 1.4 Hz), CF (2.9 +/- 1.4 Hz), and S (1.7 +/- 1.5 Hz). All subjects had HF for FT of 12 Hz or less and for VT of 6 Hz or less. For spirometric recordings our results suggest that the amplitude response of flow- and volume-measuring devices should be flat (+/- 5%) up to 12 Hz for flow signals and up to 6 Hz for volume signals.
CO2 elimination by high-frequency oscillations in dogs--effects of histamine infusion
Authors: Rossing T. H. , Slutsky A. S. , Ingram R. H. , Kamm R. D. , Shapiro A. H. , Drazen J. M.
Published: December 2017

Effective gas exchange can be achieved in normal dogs by ventilation at frequencies of 4–20 Hz using stroke volumes (SV) smaller than the anatomic dead space. CO2 elimination is largely a function of tracheal SV-frequency product (Vosc) in anesthetized, paralyzed dogs with normal lungs. To determine the effect of constriction of small airways on gas exchange during such high-frequency ventilation (HFV), we ventilated five anesthetized, paralyzed, and vagotomized dogs via a tracheal cannula before and during intravenous histamine infusion. Vosc was varied by varying the frequency while keeping SV constant. For low Vosc, CO2 elimination (VCO2) increased directly with Vosc during control and histamine experiments. At high Vosc, VCO2 continued to increase directly with Vosc during the control study, but during histamine infusion VCO2 was lower than control values. Eucapnia could be maintained in each dog during HFV, even during airway constriction. During histamine infusion the frequency-dependent mechanical properties of the lung influence the delivery of the HFV SV to the respiratory zone, and this may explain the lower VCO2 observed.
Effects of lung volume on airway resistance during induced constriction in papain-treated rabbits
Authors: Nagase T. , Matsui H. , Sudo E. , Matsuse T. , Ludwig M. S. , Fukuchi Y.
Published: December 2017

It has been reported that both the elasticity of the cartilage and airway-parenchymal interdependence can modify shortening of the airway smooth muscle and airway narrowing during induced constriction. We hypothesized that induced softening of the cartilage could alter airway compliance and/or the forces of mechanical interdependence, resulting in an increased degree of airway narrowing in response to a contractile stimulus. To test this hypothesis, we compared the effects of changing lung volume on airway resistance (Raw) under baseline conditions and during methacholine (MCh)-induced constriction in papain-treated (n = 6) and control rabbits (n = 6). With use of the alveolar capsule technique, Raw was directly measured under baseline conditions at different levels of end-expiratory transpulmonary pressure (Ptp = 4-12 cmH2O). Then aerosolized MCh was delivered (0.2-25 mg/ml) and measurements were performed at different levels of Ptp (4 and 12 cmH2O). From measured tracheal flow and tracheal and alveolar pressure in open-chest animals during mechanical ventilation (tidal volume = 6 ml/kg, breathing frequency = 1 Hz), we calculated Raw by subtracting tissue resistance from lung resistance. Papain treatment significantly increased Raw both under baseline conditions and after induced constriction. We found that increasing Ptp decreased Raw before and after MCh in both groups; however, the effects of changing Ptp on Raw were less in papain-treated animals. These observations suggest that both cartilage elasticity and mechanical interdependence are important determinants of airway smooth muscle shortening. The observation that volume dependence of Raw was less in papain-treated animals is consistent with the hypothesis that papain effects significant changes in the parenchymal attachments.
Effect of altitude and socioeconomic status on VO2max and anaerobic power in prepubertal Bolivian girls
Authors: Blonc S. , Fellmann N. , Bedu M. , Falgairette G. , De Jonge R. , Obert P. , Beaune B. , Spielvogel H. , Tellez W. , Quintela A. , San Miguel J. L. , Coudert J.
Published: December 2017

The aim of this work was to evaluate the effects of high altitude and low socioeconomic status (SES) on aerobic and anaerobic power in 11-yr-old Bolivian girls. At both high (3,600 m) and low (420 m) altitudes, low-SES groups of girls were compared to similarly aged, high-SES girls. At low altitude, low-SES girls were also compared with younger high-SES girls with the same anthropometric characteristics. Anthropometric data were similar between high-SES and low-SES girls at both altitudes, but low-SES girls showed a 9-mo growth delay. Maximal O2 uptake was significantly lower for low-SES girls at both altitudes. Values did not differ when expressed relative to body weight at high altitude for high-SES vs. low-SES girls (37.6 +/- 1.2 vs. 39.3 +/- 1.0 ml.min-1.kg body wt-1), but a difference persisted at low altitude between high- and low-SES girls (37.5 +/- 1.0 vs. 34.7 +/- 0.7 ml.min-1.kg body wt-1). Anaerobic power (Pmax, force-velocity test; Pwing, Wingate test) was reduced for low-SES girls at both altitudes, whatever the mode of expression. For a given SES, the relative anaerobic performances were lower at low altitude. At low altitude, low-SES girls developed lower anaerobic power than did younger high-SES girls with similar anthropometric characteristics. In conclusion, at both altitudes, the reduction of anaerobic performances observed in girls of low SES could not be totally explained by anthropometric factors. Structural and/or functional muscle alterations are suggested. Moreover, at low altitude, tropical and other factors may have contributed to differences in performance between low- and high-SES girls.
Nitrovasodilator repletion increases TNF-alpha-induced pulmonary edema
Authors: Johnson A. , Ferro T. J.
Published: December 2017

We tested the hypothesis that nitrovasodilator repletion enhances tumor necrosis factor-alpha (TNF-alpha) -induced pulmonary edema. Lungs were isolated from control guinea pigs or 4 h after the intraperitoneal injection of TNF-alpha (1.60 x 10(5) U/kg). In the control and TNF-alpha-injected lungs, the thromboxane mimetic U-46619 (155 pmol/min) caused increases in pulmonary capillary pressure (Ppc) and lung weight (delta W). In control lungs, the nitrovasodilator agonist S-nitroso-N-acetyl-penicillamine (SNAP, 1 microM) attenuated the U-46619-induced increases in Ppc. In lungs injected with TNF-alpha, SNAP had no effect on Ppc and increased delta W. The peroxynitrite (ONOO-) scavenger urate (35 mM) prevented the TNF-alpha +SNAP-induced increases in Ppc and delta W. In addition, chemically synthesized ONOO- (4.0 mM) enhanced U-46619-induced increases in delta W. The data indicate that nitric oxide repletion enhances TNF-alpha-induced pulmonary edema, possibly via ONOO-.
Responses of rabbit superior colliculus neurons to repeated visual stimuli
Authors: Oyster C. W. , Takahashi E. S.
Published: December 2017

It has been shown that cells in the superficial layers of the superior colliculus exhibit response decrements when a visual stimulus is repeated. These response decrements have some of the properties associated with habituation, in particular, 1) spontaneous recovery and 2) habituation rate dependent on stimulus frequency. These observations have been made in two classes of neurons; direction-selective cells and so-called modified concentric cells. All of these neurons had small receptive fields and well-defined response properties. Some neurons in both the direction-selective and modified concentric groups do not show habituation. On the basis of area-threshold curves and other observations, it is suggested that those neurons which habituate possess strong inhibitory inputs which are weak or lacking in thenonhabituating neurons. This generalization leads to a hypothesis that inhibition in the superior colliculus has a long decay time and that a response to a given stimulus is affected by inhibition activated by preceding stimuli.
Vestibular nystagmus and teleost oculomotor neurons: functions of electrotonic coupling and dendritic impulse initiation
Authors: Korn H. , Bennett M. V.
Published: December 2017

1. Nystagmus in the horizontal plane is evoked in fish by mechanical stimulation of the ampulla of the horizontal semicircular canal or by electrical stimulation of the nerve from this canal. The movements are conjugate and the slow phase is away from the side of stimulation. 2. Medial rectus motoneurons were recorded from intracellularly, during nystagmus. During the slow phase (induced by ipsilateral stimulation), impulses arise abruptly from the base line and appear to arise at a distance from the cell body. During the fast phase (evoked by contralateral stimulation), impulses appear to arise from large PSPs that must be generated at or near the cell body. 3. In the curarized fish, stimulation of the nerve from the contralateral horizontal canal evokes spikes that arise from large EPSPs and that are blocked relatively easily by hyperpolarizing currents. Stimulation of the nerve from the ipsilateral horizontal canal evokes spikes that arise abruptly from the base line and that are much more difficult to block by hyperpolarizing currents. Little if any underlying PSP is observed when these impulses are delayed or blocked. Thus impulses evoked by stimulation of contralateral and ipsilateral side are initiated near to and far from the cell soma, respectively. 4. If impulses evoked by contralateral stimulation fail to excite the cell body due to injury, antidromic spikes are not occluded. Thus contralateral stimulation initiates impulses in the dendrites. 5. Cell bodies of neighboring motoneurons are coupled electrotonically, and graded antidromic stimulation evokes graded depolarizing potentials which result from electrotonic spread of spike activity from adjacent neurons. These depolarizing potentials are adequate to excite the cells in the presence of a background EPSP evoked by contralateral canal stimulation. In this manner coupling tends to synchronize cells during the fast phase of the nystagmus. 6. Antidromic responses of neighboring cells fail to interact with dendritic inputs to a particular cell, although indirect evidence indicates antidromic spikes invade the impulse-initiating regions in the dendrites. Thus coupling between dendrites is negligible and dendritic inputs can mediate the smoothly graded movements of the slow nystagmic phase. Coupling between somata is too weak to cause significant interaction between dendritically evoked impulses (unless the cell bodies are depolarized by EPSPs). 7. Rhythmic firing can be recorded in a single presynaptic fiber corresponding to either the slow or the fast phase of nystagmus, but not to both. Oculomotor neurons appear to be "relay cells" that, during the fast phase of the nystagmus receive a synchronized synaptic input which is initiated in a higher level command nucleus.