bluuebunny/crossref_metadata_2025 huggingface dataset:
Cardiorespiratory responses to exercise distributed between the upper and lower body
Authors: Toner M. M. , Sawka M. N. , Levine L. , Pandolf K. B.
Published: December 2017

The present study examined the influence that distributing exercise between upper (arm crank exercise) and lower (cycle exercise) body muscle groups had on cardiorespiratory responses to constant power output (PO) exercise. Six male volunteers completed five submaximal exercise bouts of 7-min duration at both 76 and 109 W. The arm PO/total PO (% arm) for these bouts was approximately 0, 20, 40, 60, and 100%. At 76 W, O2 uptake (VO2) did not change (P greater than 0.05) from 0 to approximately 20% arm (approximately 1.30 1 x min-1) but increased with increasing percent arm values up to 100% (1.58 1 x min-1). At 109 W, VO2 increased throughout the range of 0 (1.70 1 x min-1) to 100% arm (2.33 1 x min-1). In general, minute ventilation (VE) and respiratory exchange ratio (R) increased with increased percent arm values at 76 and 109 W. The heart rate (HR) responses remained unchanged from 0 to 60% arm at both 76 and 109 W; however, between 60 and 100% arm, a 26-beats x min-1 increase was observed at 76 W (143 beats x min-1 at 100% arm) and a 45-beats x min-1 increase at 109 W (174 beats x min-1 at 100% arm). These data suggested that during upper body exercise, the increased VO2 associated with increased percent arm values was not accompanied by an elevated HR response when at least 40% of the PO was performed by the lower body. This might be attributed to a facilitated venous return and/or a decreased total peripheral resistance when the lower body was involved in the exercise.
Pulmonary denervation in the dog
Authors: Clifford P. S. , Coon R. L. , von Colditz J. H. , Zuperku E. J. , Kampine J. P.
Published: December 2017

To produce a chronically lung-denervated animal model, a single-stage surgical procedure was performed on five beagle dogs. A left thoracotomy allowed hilar stripping of the pulmonary contributions to the left vagus nerve and transection of the right vagal trunk. The criterion for denervation was defined as the absence of the Hering-Breuer reflex (HBR). The five denervated dogs (DD) as well as five control dogs (CD) were evaluated for presence of the HBR under pentobarbital sodium (Nembutal, 30 mg/kg) anesthesia. Between the 3rd and 8th wk postsurgery, the HBR was clearly abolished in the DD but present in the CD. By the 12th-14th wk postsurgery, the HBR was again present in the DD. This relatively uncomplicated surgical procedure effectively produced a lung-denervated animal model. However, reinnervation occurred relatively soon, thus demonstrating the importance of regular frequent evaluation of the HBR when using this and any other surgically produced pulmonary denervation model.
Ventilatory responses to static handgrip exercise
Authors: Muza S. R. , Lee L. Y. , Wiley R. L. , McDonald S. , Zechman F. W.
Published: December 2017

Previous research indicates that fatiguing static exercise causes hyperventilation and a decrease of end-tidal CO2 partial pressure PETCO2. The objectives of this study were 1) to examine the changes in pattern of breathing during static exercise, and 2) to define the isocapnic ventilatory response. Six healthy males were studied once a week at one of three levels of static handgrip exercise: 15, 25, or 30% maximum voluntary contraction (MVC) was sustained for 5 min while holding PETCO2 constant or allowing it to run free. During 25 and 30% MVC, we observed 1) progressive increases in mean tidal volume (VT), inspiratory ventilation (VI), VT/TI, heart rate (HR), and arterial BP, 2) increased breath-to-breath variability of VT, 3) no significant changes in respiratory frequency (f), and 4) progressive decreases in PETCO2. Keeping PETCO2 constant at preexercise levels did not change the pattern or magnitude of the ventilatory response to exercise. The time course and magnitude of the subjects' perceived effort resembled the time course and magnitude of the ventilatory response. The variability of VT during the response to static exercise suggests an element of control instability. The identical ventilatory responses during hypocapnic and isocapnic conditions may result from the slow response of the central chemoreceptors; an overriding influence of muscle afferents; and/or increased central command arising with fatigue.
Activation of alpha-adrenergic response in tracheal smooth muscle: a postreceptor mechanism
Authors: Barnes P. J. , Skoogh B. E. , Brown J. K. , Nadel J. A.
Published: December 2017

We have investigated the activation of alpha-adrenergic contractile responses in dog tracheal smooth muscle. After cholinergic and beta-adrenergic blockade, neither electrical field stimulation nor alpha-adrenergic agonists caused contraction of trachealis strips in vitro, but after exposure to histamine or serotonin a striking contractile response was obtained. Similar activation of the contractile response to norepinephrine was seen in isolated tracheal segments in vivo after exposure to histamine and serotonin. This response was mediated predominantly by alpha 2-adrenoceptors, because the alpha 2-antagonist yohimbine was a potent inhibitor whereas the alpha 1-antagonist prazosin was a weak inhibitor of the response to both electrical stimulation and exogenous agonists. Using [3H]yohimbine to label alpha 2-receptors and [3H]prazosin to label alpha 1-receptors, we confirmed the preponderance of alpha 2-receptors in trachealis membranes but found no increase in either receptor number or affinity after incubating muscle strips with histamine. The magnitude of alpha-adrenergic contraction was significantly related to the magnitude of precontraction by histamine and serotonin both in vitro and in vivo but persisted after washout. Acetylcholine was much less potent in activating the alpha-adrenergic response. We conclude that activation of airway alpha-adrenergic responses involves a postreceptor mechanism not directly related to membrane depolarization, but involving some related process such as activation of calcium channels.
Active inspiratory impedance in halothane-anesthetized humans
Authors: Behrakis P. K. , Higgs B. D. , Baydur A. , Zin W. A. , Milic-Emili J.
Published: December 2017

We have used the method of Siafakas et al. (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 51: 109–121, 1981) to determine active elastance (E'rs) and flow resistance (R'rs) of the respiratory system in eight spontaneously breathing humans anesthetized with halothane. From measurements of flow (V) and volume (V) during unoccluded inspirations and of tracheal pressure (P0tr) during subsequent inspirations with the airways occluded at end expiration, we were able to compute E'rs and R'rs as slopes and intercepts of the following function: -P0tr/V = R'rs + E'rsV/V. These measurements were repeated during inspirations loaded with a series of linear flow resistances (delta R). Neither E'rs nor R'rs was significantly affected by delta R. On the average E'rs and R'rs were, respectively, 34.4 and 16.7% higher than the corresponding passive elastance and flow resistance of the respiratory system, indicating that during active breathing the internal impedance of the respiratory system increases. This provides an internal mechanism by which passive loads are compensated.
Transmembrane potential of isolated rat alveolar type II cells
Authors: Castranova V. , Jones G. S. , Miles P. R.
Published: December 2017

Type II cells were isolated from rat lungs by elastase digestion and purified by centrifugal elutriation. The fluorescent dye, Di-S-C3(5), was used as a probe to monitor transmembrane potential (Em) of cells suspended in N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES)-buffered medium. With this technique, the Em of type II cells was estimated to be -27 +/- 2 mV. This resting Em is very close to the equilibrium potential for chloride (-21 mV), which suggests that chloride is passively distributed in type II cells. The resting Em of type II cells is more dependent on the extracellular concentration of potassium (K+) than on external sodium (Na+); i.e., the membrane depolarizes as external sodium is replaced by potassium, suggesting that in unstimulated type II cells the membrane is more permeable to potassium than to sodium. In addition, the resting potential appears to be due, in part, to the activity of a ouabain-sensitive, Na-K pump, which acts to hyperpolarize type II cells. Addition of a membrane perturbant, phorbol myristate acetate (PMA, 10 micrograms/ml), to a type II cell suspension results in an increase in oxygen consumption and membrane depolarization. Both of these responses are sodium dependent and thus appear to be linked to a PMA-induced increase in sodium permeability.
Ventilatory responses to inspiratory flow-resistive loads in awake and sleeping dogs
Authors: Bowes G. , Kozar L. F. , Andrey S. M. , Phillipson E. A.
Published: December 2017

We studied ventilatory responses to inspiratory flow-resistive loads in six trained dogs, during quiet wakefulness and non-rapid-eye-movement (NREM) sleep. During studies dogs lay quietly in a lateral position and breathed through an endotracheal tube inserted via a chronic tracheostomy. Linear resistances of 6, 10, 19, and 31 cmH2O X l-1 X s were applied during inspiration for only a single breath to assess the immediate ventilatory response. The highest resistance was also applied for five successive breaths to assess the progressive ventilatory response. Ventilatory responses to hyperoxic progressive hypercapnia were also examined, with and without flow-resistive loading. During loading the maintenance of constant states of quiet wakefulness and NREM sleep was confirmed by electroencephalographic monitoring. Ventilation decreased on the first loaded breath and returned to control in a stepwise manner by the fifth loaded breath. No state-related differences were observed in either the immediate or progressive ventilatory responses. During CO2 rebreathing, the slope of the ventilatory response to CO2 was reduced by loading, with the reduction in slope (as percent of control) greater in the NREM state. We therefore conclude that in the dog immediate and progressive ventilatory responses to resistive loads are unaffected by NREM sleep, whereas the decrease in ventilatory response to CO2 resulting from loading tends to be greater in NREM sleep than in quiet wakefulness.
Reabsorption of a saline- or plasma-induced hydrothorax
Authors: Miserocchi G. , Negrini D. , Mariani E. , Passafaro M.
Published: December 2017

In supine rabbits injection of 2 ml of saline into the lower right diaphragmatic region increased pleural liquid pressure at the injection point and, to a minor extent, on the costal and mediastinal side, indicating a redistribution of liquid among the pleural compartments. Over a period of 120 min end-expiratory liquid pressure on the diaphragmatic and costal surfaces approached the control value as a result of local reabsorption. No difference in the time course of liquid pressure was found on injection of either saline or homologous plasma. This was confirmed by measuring the volume of saline or plasma remaining in the cavity 90 min after injection; the net absorption flow amounted to 0.22 ml . kg-1 . h-1. These results suggest that local absorption mechanisms are relatively independent of the Starling pressure gradients acting across the pulmonary-perfused (-10.2 and 6.6 cmH2O with saline and plasma, respectively, the negative sign indicating a reabsorption gradient) and systemically perfused mesothelium (3.3 and 20.1 cmH2O with saline and plasma, respectively).
Maximal shortening of inspiratory muscles: effect of training
Authors: Fanta C. H. , Leith D. E. , Brown R.
Published: December 2017

Normal subjects can increase their vital capacity by appropriate training. We tested whether that change can be achieved by greater maximal shortening of the inspiratory muscles without concomitant increases in peak static inspiratory pressures. Sixteen healthy volunteers participated in the study: eight were randomly assigned to make 20 inhalations to total lung capacity, held for 10 s with the glottis open, each day for 6 wk; the remainder served as nontraining controls. Before and after the 6-wk study period, we made multiple determinations of lung volumes and of curves relating lung volume to maximal static inspiratory (and expiratory) pressure. Control subjects had no significant changes from base line in any variable. In the training group, the mean vital capacity increased 200 +/- 74 ml (P less than 0.05) or 3.9 +/- 1.3% (P less than 0.02), without a significant change in residual volume. After training, the mean maximal inspiratory pressure at the airway opening (PI) at a lung volume equal to the base-line total lung capacity was 27 +/- 8 cmH2O in this group (vs. zero before training; P less than 0.02). Values of PI in the mid-vital capacity range did not change. We conclude that in response to appropriate training stimuli inspiratory muscles can contract to shorter minimal lengths, a capacity potentially important in progressive pulmonary hyperinflation.
Diaphragm in emphysematous hamsters: sarcomere adaptability
Authors: Farkas G. A. , Roussos C.
Published: December 2017

We investigated whether the shift in the diaphragmatic length-tension curve of emphysematous animals was due to changes in either sarcomere number or sarcomere length. In vitro length-tension characteristics of the diaphragm were evaluated in control and emphysematous hamsters. Emphysema was induced by a single endotracheal instillation of elastase. Functional residual capacity, measured by means of a plethysmograph, was about twice that measured in emphysematous animals compared with control animals. Small diaphragmatic bundles were isolated and evaluated for their length-tension characteristics. The length-tension curve of diaphragms from emphysematous animals was displaced toward the left. Maximal tetanic tensions were similar in both groups, whereas optimal bundle length was significantly decreased in the emphysematous animals. Sarcomere number and sarcomere length at optimal length were then calculated for the diaphragmatic bundles. The bundles from emphysematous animals were found to have a significantly reduced number of sarcomeres, as well as a significantly decreased sarcomere length at optimal compared with control values. The total number of sarcomeres were also found to be significantly negatively correlated with the animal's functional residual capacity. From these results, we conclude that the decrease in diaphragmatic length, seen with hyperinflation, is due mainly to a loss of sarcomeres and possibly to a small decrease in sarcomere length measured at optimal bundle length.
Transmural coronary vasodilator reserve and flow distribution during severe exercise in ponies
Authors: Parks C. M. , Manohar M.
Published: December 2017

Transmural distribution of myocardial blood flow and coronary vasodilator reserve (15-microns-diam radionuclide-labeled microspheres) was studied in 11 adult, healthy ponies at rest and during moderate and severe exercise performed on a treadmill (heart rate 56 +/- 4, 154 +/- 3, and 225 +/- 7 beats . min-1, respectively.). Exercise resulted in a marked increase in cardiac output, mean aortic pressure, right ventricular (RV) systolic and end-diastolic pressure, left ventricular (LV) end-diastolic pressure, and the maximum rate of rise of LV pressure LV (dP/dtmax). Accompanying these changes was a pronounced increase in transmural myocardial perfusion. During severe exercise, subendocardial/subepicardial (endo/epi) perfusion ratio for the LV (0.99 +/- 0.02) decreased significantly from control value (1.27 +/- 0.03) but it was not significantly different from 1.00. With adenosine infusion during severe exercise, transmural myocardial blood flow throughout the cardiac ventricles was able to increase significantly further (delta from severe exercise to severe exercise with adenosine, 75% for LV, 68% for septum, and 57% for RV) despite the fact that heart rate, aortic pressure, and RV and LV end-diastolic pressures were unaltered. During severe exercise with adenosine, endo:epi perfusion ratios were 1.11 +/- 0.15 and 1.32 +/- 0.10 for LV and RV, respectively. In the LV, the coronary vasodilator reserve was found to be the least in papillary muscles, where the increment in blood flow during severe exercise with adenosine was only 46% above severe exercise without adenosine. Coronary vasodilator reserve was largest in the middle layers of the LV myocardium (88%). With adenosine infusion during severe exercise, coronary vascular resistance in both LV and RV decreased significantly from that observed during severe exercise alone (27 +/- 2 and 30 +/- 2 mmHg . ml-1 . min . g, respectively) to levels observed during maximal coronary vasodilation induced by adenosine infusion at rest (20 +/- 2 and 18 +/- 2 mmHg . ml-1 . min . g, respectively). These data clearly demonstrate that there remains a marked coronary vasodilator reserve transmurally in the pony myocardium during severe exercise.
Vascular reactivity is increased in rat lungs injured with alpha-naphthylthiourea
Authors: Hill N. S. , Rounds S.
Published: December 2017

We investigated the effects of lung injury due to alpha-naphthylthiourea (ANTU) on pulmonary vascular reactivity. Rats were treated with ANTU (10 mg/kg ip) or the vehicle Tween 80. Four hours later, lungs from ANTU-treated rats had increased wet-to-dry weight ratios, bronchial lavage protein concentrations, and perivascular edema. To test vascular reactivity, lungs were isolated and perfused with blood at constant flow rate, while mean pulmonary arterial pressure was monitored. ANTU-treated lungs vasoconstricted earlier than Tween-treated lungs in response to severe airway hypoxia (fractional inspired O2 0%). ANTU-treated lungs vasoconstricted in response to 10% O2, while Tween-treated lungs failed to respond to 10% O2, indicating that the threshold for hypoxic vasoconstriction was decreased by ANTU. ANTU also decreased the threshold for and increased the magnitude of angiotensin II pressor responses, indicating that the increased vasoreactivity was not specific for hypoxia. Addition of meclofenamate to perfusates increased the rate and magnitude of responses to 0% O2 in Tween-treated lungs, but did not change the responses of ANTU-treated lungs. Light microscopy of ANTU-treated lungs showed no pulmonary arterial obstruction, and electron microscopy revealed mild capillary endothelial cell injury. We conclude that enhanced pulmonary vascular reactivity accompanies the increased-permeability pulmonary edema caused by ANTU. A similar increase in vasoreactivity might contribute to pulmonary hypertension observed in patients with the adult respiratory distress syndrome.
Expiratory flow limitation
Authors: Hyatt R. E.
Published: December 2017

The first major advance in understanding expiratory flow limitation of the lungs came with the description of isovolume pressure-flow curves. These curves documented the existence of a volume-dependent limit to maximal expiratory flow and led directly to the description of the maximal expiratory flow-volume (MEFV) curve. Definitive modeling of flow limitation awaited the description of a localized mechanism that dominated the flow-limiting process. The phenomenon of wave speed limitation of flow was shown to apply to the airways and provided the needed localized mechanism. Using this concept and recent data on airway mechanics and the frictional losses in the flow, a computational model of the MEFV curve has been developed. Further progress will require modeling of inhomogeneous emptying in diseased lungs, perfecting noninvasive techniques of estimating pertinent airway characteristics, and improving techniques for increasing the signal-to-noise ratio in MEFV curves.
Parasympathetic and adrenergic contractile responses in canine trachea and bronchus
Authors: Leff A. R. , Munoz N. M. , Hendrix S. G.
Published: December 2017

We compared the sympathetic and parasympathetic contractile responses of tracheal and third-order bronchial smooth muscle simultaneously in 26 dogs in situ. Stimulus-response curves were generated by bilateral stimulation of the cervical vagus nerves in five dogs to determine the parameters (20 V, 15 Hz, 2-ms duration) causing maximal parasympathetic contraction in trachea and bronchus. In six adrenal-intact (ADi) and five adrenalectomized (ADx) dogs, sympathetically mediated alpha-adrenergic contraction was studied after muscarinic and beta-adrenergic blockade by administering intravenous (iv) 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP). In ADi dogs, the maximal alpha-adrenergic contractile response to iv DMPP was 67.3 +/- 14.8% of the maximal parasympathetic response in trachea and 112 +/- 21% of the maximal parasympathetic response in bronchus (P less than 0.03). In ADx dogs, the maximal alpha-adrenergic-to-parasympathetic stimulation ratios were 17.6 +/- 1.3% in trachea and 41.4 +/- 2.5% in bronchus (P less than 0.001). Comparable relationships were also obtained in pharmacological studies of alpha-adrenergic and cholinergic responses in trachea and bronchus. We conclude that there is substantial heterogeneity in the physiological and pharmacological cholinergic and alpha-adrenergic contractile properties in trachea and bronchus. Relative to cholinergic contraction, both circulating catecholamines and sympathetic innervation cause substantially greater alpha-adrenergic contraction in bronchus than for tracheal smooth muscle.
Regulation of CSF composition--blocking chloride-bicarbonate exchange
Authors: Frankel H. , Kazemi H.
Published: December 2017

The possibility that the increase in cerebrospinal fluid (CSF) [HCO-3] observed during respiratory acidosis could be the result of a decrease in CSF [Cl-] was studied by blocking a putative Cl--HCO-3 exchange transport system. Anesthetized dogs (pentobarbital 30 mg, iv) were given either 4,4′-diisothiocyano-2,2′-disulfonate stilbene (DIDS, 0.02 mumol/kg) or pyridoxal 5-phosphate (P-5-P, 4 mumol/kg) in the lateral cerebral ventricles and maintained either normocapnic (RA) or hypercapnic (5% CO2). CSF and arterial Pco2, pH, [Na+], [K+], [Ca2+], [Cl-], and [lactate] were determined. [HCO-3] was calculated. Samples were drawn before and 4 h after the drug was administered. In control dogs on RA no significant change was observed in any measured parameter after 4 h. Dogs receiving either DIDS or P-5-P and on RA had decreased CSF [Na+] of 2-4 meq/l and CSF [Cl-] of 6 meq/l. CSF [HCO-3] in DIDS dogs decreased approximately 5 meq/l. There was no significant change in CSF [HCO-3] in P dogs. After 4 h of 5% CO2, control dogs had decreased CSF [Cl-] of 3 meq/l and CSF [HCO-3] increased approximately 4 meq/l. Dogs receiving DIDS or P-5-P and breathing 5% CO2 for 4 h had decreased CSF [Cl-] of 6-9 meq/l and [HCO-3] increased of 7-9 meq/l. CSF [Na+] did not change during respiratory acidosis in any group. It was concluded the Cl- transport in CSF can be interfered with by use of blocking agents which inhibit Cl--HCO-3 exchange channels.
Mammalian tracheal dimensions: scaling and physiology
Authors: Leith D. E.
Published: December 2017

Mammalian tracheal dimensions vary with body mass in a way which suggests that expiratory flow limitation, inertance, and resistance are dominant constraints on tracheal design, rather than dead space or minimum work or effort. The fraction of total resistance attributable to the trachea appears to be about the same regardless of body size. Tracheal inertance appears to vary with body mass to the -1/2 power, so that inertial pressures, like elastic and resistive pressures, are invariant with body size and natural frequency, like respiratory frequency, varies with body mass to the -1/4 power. Other dominant constraints on tracheal design may include clearance functions and specialized habitat or behavior.
A constant-velocity cycle ergometer for the study of dynamic muscle function
Authors: McCartney N. , Heigenhauser G. J. , Sargeant A. J. , Jones N. L.
Published: December 2017

A cycle ergometer has been designed to measure the force exerted on the pedal cranks during maximum effort at a variety of constant velocities. Preset crank velocities of 13-166 rpm are established by a controlled 3-hp motor and cannot be overcome by the subject. Torque is measured by strain gauges bonded to the crank shafts; peak torque, peak power, work, and average power are derived for each pedal cycle. Studies in 30 healthy male subjects established reproducibility and normal standards. During exercise for 45 s at a constant velocity of 60 rpm, there was a wide intersubject variation in both maximal torque (118-226 N . m) and the percentage decline in torque (27.2-52.0%). The decline in torque was inversely related to maximal O2 intake (r = 0.84). During short (10-s) periods of exercise at six crank velocities between 60-160 rpm, a linear inverse relationship between maximal peak torque and pedal crank velocity was observed. The peak torque-velocity relationship and the percentage decline in peak torque during 30 s exercise at 60, 100, and 140 rpm were reproducible within a given subject, the coefficient of variation was less than 10%.
Power output and fatigue of human muscle in maximal cycling exercise
Authors: McCartney N. , Heigenhauser G. J. , Jones N. L.
Published: December 2017

We studied maximal torque-velocity relationships and fatigue during short-term maximal exercise on a constant velocity cycle ergometer in 13 healthy male subjects. Maximum torque showed an inverse linear relationship to crank velocity between 60 and 160 rpm, and a direct relationship to thigh muscle volume measured by computerized tomography. Peak torque per liter thigh muscle volume (PT, N X ml-1) was related to crank velocity (CV, rpm) in the following equation: PT = 61.7 - 0.234 CV (r = 0.99). Peak power output was a parabolic function of crank velocity in individual subjects, but maximal power output was achieved at varying crank velocities in different subjects. Fiber type distribution was measured in the two subjects showing the greatest differences and demonstrated that a high proportion of type II fibers may be one factor associated with a high crank velocity for maximal power output. The decline in average power during 30 s of maximal effort was least at 60 rpm (23.7 +/- 4.6% of initial maximal power) and greatest at 140 rpm (58.7 +/- 6.5%). At 60 rpm the decline in power over 30 s was inversely related to maximal oxygen uptake (ml X min-1 X kg-1) (r = 0.69). Total work performed and plasma lactate concentration 3 min after completion of 30-s maximum effort were similar for each crank velocity.
Morphometry of cat pulmonary venous tree
Authors: Yen R. T. , Zhuang F. Y. , Fung Y. C. , Ho H. H. , Tremer H. , Sobin S. S.
Published: December 2017

Morphometric data of the pulmonary veins in the cat right lung are presented. Silicone elastomer casts of the right lungs of five cats were made, measured, counted, and analyzed. The Strahler system is used to describe the branching pattern of the vascular tree. These data are needed for the physicomathematical approach to pulmonary circulation. For all the pulmonary blood vessels lying between the left atrium and the capillary beds, there are a total of 10 orders of vessels in the right upper lobe, 9 orders of vessels in the right middle lobe, and 11 orders of vessels in the right lower lobe. The ratios of the diameters, lengths, and the number of branches in successive orders of vessels are called the diameter, length, and branching ratios, respectively. For the cat pulmonary venous tree, the average branching ratio is 3.521, the average diameter ratio is 1.727, and the average length ratio is 2.402 for vessels of orders 1-3 and 1.532 for vessels of orders 4-10.
A computerized timing algorithm for determination of pulmonary tissue volume
Authors: Petrini M. F. , Dwyer T. M. , Phillips M. S.
Published: December 2017

We developed a computerized method to measure pulmonary tissue volume (Vt) and capillary blood flow (Qc) that requires only a single interface for measurement of a soluble and an insoluble gas. The method uses a timing algorithm that replaces either a marker gas (C18O) or a volume signal. Gas concentrations are stored in digitized form. The data analysis consists of three parts: 1) initial and end-tidal samples found by using minima and maxima; 2) a timing algorithm derived from the end-tidal dead space method (ETDS, J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 44: 782-795, 1978); and 3) calculations of Vt and Qc, also by the ETDS method. Both the timing and Vt and Qc agree well with the hand-calculated values, but the coefficient of variation of Vt is slightly improved (6 vs. 7% manually). We conclude that our computerized method is equivalent to the manual ETDS method, but it is faster and more accurate; in addition, it has the advantage of requiring only one interface without the use of expensive gases.
Alteration of ischemic cardiac function in normal heart by daily exercise
Authors: Knight D. R. , Stone H. L.
Published: December 2017

Myocardial function, tissue blood flow, and heart rate measurements were studied during control and a 2-min occlusion of the left circumflex coronary artery in conscious dogs. These measurements were made in the same dogs before exercise in the untrained state (UT) and after a 4-wk treadmill exercise program in the partially trained condition (PT). Ultrasonic segment length gauges were used to measure myocardial function in the ischemic zone, defined by staining the myocardial tissue. Microspheres (15 microns), labeled with different isotopes, were used to measure the myocardial tissue flow in the normal and ischemic zones. Myocardial function in the ischemic zone of 20 dogs was reduced 71 +/- 6% in the UT condition; however, after PT, the percent reduction in segment length function was only 33 +/- 4% during occlusion. During occlusion, an increase in heart rate of 46 +/- 7% in the UT condition was observed; yet after PT, heart rate increased only 19 +/- 5%. In 5 UT dogs with heart rate held constant (150 beats/min), the decrease from control in tissue blood flow to the ischemic zone in the subendocardium during occlusion was 60 +/- 7%. After PT, the decrease from control in tissue blood flow in the same dogs was 34 +/- 6%. These data indicate that the improved myocardial function during ischemia was a result of the improved coronary collateral blood flow into the ischemic zone after PT.
Different patterns of respiratory reflexes originating in exercising muscle
Authors: Tallarida G. , Baldoni F. , Peruzzi G. , Raimondi G. , Massaro M. , Abate A. , Sangiorgi M.
Published: December 2017

In anesthetized rabbits, rhythmic contractions of the gastrocnemius muscle elicited by stimulating the gastrocnemius nerves (40 trains/min of 0.5-ms rectangular pulses at 2.0-2.5 mult of motor threshold), increased pulmonary ventilation by increasing frequency (f). Expiratory duration (TE) was greatly reduced, while inspiratory time (TI) was much less changed. Mean expiratory flow (VT/TE) was increased consistently more than mean inspiratory flow (VT/TI). Arterial pressure (Pa) and heart rate (HR) were decreased. During tetanic contractions (100 Hz, 2.0-2.5 X T) tidal volume (VT) increased considerably more and f considerably less than during rhythmic exercise, TE was shortened, and TI was only slightly affected. Pa and HR, after a transitory reduction, increased over the resting levels. Similar responses were also obtained in deafferented rabbits with carotid sinus, aortic, and cervical vagus nerves cut. These two patterns of cardiorespiratory changes were initiated by activation of muscle receptors verified by interrupting the afferents from the contracting muscles. It is concluded that, in the anesthetized rabbit, two different muscular reflex mechanisms are involved in controlling the pattern of breathing and ventilation during muscular exercise. One mechanism, predominantly activated during dynamic exercise, decreases TE and increases f, the other mechanism, mainly activated during static exercise, increases the inspiratory drive, thus increasing the depth of breathing.
Biochemical links between cigarette smoking and pulmonary emphysema
Authors: Janoff A.
Published: December 2017

A large body of circumstantial evidence has accumulated in the last 20 yr, suggesting that alveolar effacement in pulmonary emphysema is due to unrestrained proteolytic (elastolytic) activity in lung connective tissue. Even though this hypothesis still requires rigorous proof, newer information is rapidly developing that links the protease-pathogenesis model to the primary environmental risk factor associated with the disease, namely cigarette smoking. A triad of chemical and cellular effects produced by cigarette smoke have been suggested as factors contributing to altered elastin metabolism and eventual development of emphysema in smokers. The present article reviews some of these observations, seeks to place them within the overall framework of the protease model, and attempts to raise questions for future study.
Oxygen toxicity in cultured aortic endothelium: selenium-induced partial protective effect
Authors: Housset B. , Ody C. , Rubin D. B. , Elemer G. , Junod A. F.
Published: December 2017

The time course of biochemical changes related to cell loss and damage during exposure to 95% O2 [DNA and protein content of dishes, lactate dehydrogenase (LDH) release] was studied in postconfluent endothelial cells isolated from pig aorta, cultured in standard medium and in medium supplemented with 2 X 10(-7) M selenomethionine (Se-Met). A fourfold increase in glutathione peroxidase (G-Px) was the only major enzymatic Se-related effect under both normoxic and hyperoxic conditions, the other antioxidant enzymes being little or not at all affected by this treatment. The addition of Se-Met had a clearcut protective action against the cytotoxic effect of O2 as shown by measurements of DNA and protein content of Petri dishes and of LDH release. On the other hand, the most sensitive O2-related effect, namely the decrease in [3H]thymidine incorporation into DNA, was not affected by Se-Met addition. These experiments suggest that some of the O2-related toxic effects (but not the inhibition of DNA synthesis) could be mediated by lipid peroxides, since they were, at least partly, prevented by a Se-Met-induced increase in G-Px activity.
Fluid and electrolyte homeostasis during prolonged exercise at altitude
Authors: Withey W. R. , Milledge J. S. , Williams E. S. , Minty B. D. , Bryson E. I. , Luff N. P. , Older M. W. , Beeley J. M.
Published: December 2017

The combined effect of exercise and altitude on fluid and electrolyte homeostasis was studied over 13 days on six male subjects eating a diet with constant sodium and potassium content. During the first 4 and last 4 days subjects were semisedentary at an altitude of 900 m. In the middle 5 days subjects exercised by hill walking for about 7 h daily at altitudes between 2,678 and 3,629 m. There was a retention of sodium (mean of 202 mM by the end of the exercise-altitude period) and a small retention of water (mean of 0.49 liters). Plasma volume increased by 0.76 liters and packed cell volume fell from a mean of 44.5 to 41.8%. There was no change in plasma sodium concentration. The retention of sodium implies an expansion in the extracellular space of 1.44 liters at the expense of the intracellular space, which decreased by a calculated 1.05 liters. These changes are similar to those resulting from comparable exercise at sea level and opposite to the effect of altitude on resting subjects.
Gas transport during high-frequency ventilation
Authors: Brusasco V. , Knopp T. J. , Rehder K.
Published: December 2017

During high-frequency small-volume ventilation (HFV), the transport rate of gas from the mouth to a lung region is a function of two conductances (conductance is the transfer rate of a gas divided by its partial pressure difference): regional longitudinal gas conductance along the airways (Grlongi) and gas conductance between lung regions (Ginter). Grlongi per unit regional lung (gas) volume [Grlongi/(Vr beta g)] was determined during HFV in 11 anesthetized paralyzed dogs lying supine. The distribution of Grlongi/(Vr beta g) was nearly uniform during HFV when stroke volumes were less than approximately two-thirds of the Fowler dead-space volume. By contrast, the distribution of Grlongi/(Vr beta g) was nonuniform when the stroke volume exceeded approximately two-thirds of the Fowler dead-space volume and the oscillation frequency was 5 Hz. Gas conductance along the airways per unit lung gas volume [average Glongi/(V beta g)], for the entire lung, increased with stroke volume at all frequencies, but for a given product of oscillation frequency and stroke volume, the average Glongi/(V beta g) was greater when stroke volume was large and oscillation frequency was low. The average Glongi/(V beta g) increased with frequency up to a maximal value; the frequency at which the maximum occurred depended on the kinematic viscosity of the inspired gas mixture.
Central origin of biphasic breathing pattern during hypoxia in newborns
Authors: Lawson E. E. , Long W. A.
Published: December 2017

The ventilatory response to moderate hypoxia of both animal and human newborns differs significantly from that of adults. The newborn response is characterized by transient hyperpnea followed by return of ventilation toward or below the control level and even apnea. To determine whether central respiratory control mechanisms are affected by hypoxia in newborns, we used an anesthetized, paralyzed, mechanically ventilated piglet model in which the vagus nerves were cut. Respiratory activity was determined by measuring electrical activity of a cut phrenic nerve. During a 6-min continuous exposure to 15% O2 as the inspired gas, 11 piglets increased their respiratory output to 181 +/- 38% of the control value within 2.5 min. However, by the 6th min the average respiratory output had declined to 104 +/- 25% of the control. During the exposure to hypoxia, the servo-controlled ventilator frequency (an index of CO2 flux to the lungs) was persistently greater than control (28.0 +/- 1.0 vs. 30.5 +/- 1.4 cycles/min; P less than 0.01). These data indicate that the newborn's characteristic breathing response to hypoxia is due to failure of central neural respiratory control mechanisms. Paralysis, constant end-tidal PCO2, and increased ventilator rate during hypoxia exclude changes in pulmonary mechanics or decreased metabolic rate as explanations of the paradoxical decline in respiratory output.
Exercise gas exchange in asthmatics after beta-adrenergic blockade
Authors: Sue D. Y. , Van Meter L. R. , Hansen J. E. , Wasserman K.
Published: December 2017

Pharmacologic beta-adrenergic blockade reduces maximal heart rate (HR) during exercise but variable results have been reported for minute ventilation (VE), CO2 output (VCO2), and O2 uptake (VO2). A total group of 19 subjects with mild asthma was studied. We studied 16 subjects from the group who received placebo or pindolol, a beta-adrenergic antagonist, during 1-min incremental exercise on a cycle ergometer. During incremental exercise, HR, VE, VCO2, and VO2 were less after beta-blockade than after placebo at the same work rate below the anaerobic threshold. Maximal HR, VE, VO2, VCO2, and work rate were significantly less after beta-blockade. In addition, we studied six subjects from the group, including three who had also performed incremental exercise, during the steady state of constant-work cycling exercise. We found no difference in VE, VCO2, or VO2 although HR was less after beta-blockade. We conclude that beta-adrenergic blockade affects gas exchange by delaying the normal cardiovascular response to exercise. Decreased VE during incremental exercise is due to slowed delivery of CO2 load to the lungs rather than alterations in substrate, lung function, or ventilatory control.
Noninvasive method for detecting laryngeal narrowing with low-frequency sound
Authors: Sekizawa K. , Shindoh C. , Hida W. , Suzuki S. , Akaizawa Y. , Shimizu Y. , Sasaki H. , Takishima T.
Published: December 2017

We measured laryngeal narrowing with low-frequency sound in human subjects. A low-frequency sound of 800 Hz was forced into the mouth, and sound-pressure amplitude above (SPAa) and below the vocal cord (SPAb) was detected using two separate microphones at the anterior neck. If the subject voluntarily narrowed the larynx at functional residual capacity, the increased respiratory resistance (Rrs) was only caused by increased laryngeal resistance, and SPAa was increased and SPAb was decreased. The percent changes of SPAa (SPAa%) minus that SPAb (SPAb%) from the initial values (SPAa% - SPAb% = Y) was proportional to the increase of Rrs from the initial control state (X, cmH2O X 1-1 X s); Y = 22.4 X1.20 (coef of correlation, r = 0.96, P less than 0.01). We confirmed similar proportions in dogs by manually narrowing the vocal cord. When laryngeal resistance was directly measured by tracheal puncture with a needle, the proportions between Y and X were not significantly dependent on the increase of Rrs below the vocal cord induced by methacholine inhalation in human subjects and histamine injection in dogs. We concluded that the increase of laryngeal resistance from the initial state could be detected noninvasively by using low-frequency sound.
Ergometric evaluation of pathological gait
Authors: Cavagna G. A. , Tesio L. , Fuchimoto T. , Heglund N. C.
Published: December 2017

At each step of walking, the center of gravity of the body moves up and down and accelerates and decelerates forward with a combined movement that allows an appreciable transfer (R) between gravitational potential energy and kinetic energy, as occurs in a pendulum. The positive work and power to lift the center of gravity, to accelerate it forward, and to maintain its motion in a sagittal plane, the amount of R, the maximal height reached during each step by the center of gravity, and the step length and frequency are all determined by a microcomputer a few minutes after a subject walks on a force platform. This method is applied to the analysis of pathological gait in the attempt to measure quantitatively the alteration of the normal locomotory movement of the center of gravity. The strides of the patient are compared with the strides of normal subjects; in addition, the movement of the center of gravity of the patient during the stance on the affected limb is compared with the movement of the center of gravity during the stance on the unaffected limb, thus giving an index of the asymmetry of locomotion.

biomechanics; locomotion; walking; mechanical work

Submitted on January 21, 1982

Accepted on March 3, 1983
Pulmonary uptake of mannitol as an index of changes in lung epithelial permeability
Authors: Taylor S. M. , Downes H. , Hirshman C. A. , Peters J. E. , Leon D.
Published: December 2017

To develop a simple, inexpensive, and nontoxic test for changes in bronchial permeability we have employed a specific gas chromatographic assay to measure the uptake of mannitol from the lung after administration of an intratracheal aqueous bolus (8 ml of 5% solution). We have tested the ability of our method to detect the known increase in lung epithelial permeability elicited by challenge of previously sensitized animals with aerosols of Ascaris suum antigen. In Ascaris-sensitive Basenji-Greyhound dogs, antigen challenge significantly increased the rate of appearance and peak plasma level of mannitol after administration of the intratracheal bolus. Peak plasma mannitol levels averaged 25 +/- 3 (SE) micrograms/ml in dogs challenged with Ascaris antigen aerosols, and 14 +/- 2 micrograms/ml in the same animals in separate control experiments employing saline aerosols. The method presented could be readily applied to animal and human studies as a simple, inexpensive, and nontoxic indicator of lung epithelial permeability.
A comparison of methods for quantitation of metabolites in skeletal muscle
Authors: Sabina R. L. , Swain J. L. , Hines J. J. , Holmes E. W.
Published: December 2017

Quantitation of gastrocnemius muscle metabolites in mice was evaluated using three commonly employed descriptors: wet weight, total protein, and total creatine. A fourth previously unreported descriptor, NAD+, was also evaluated. In resting muscle the coefficients of variation were similar when the metabolite data were normalized by any of the four descriptors. However, in tetanically stimulated muscle, normalization by wet weight yielded metabolite levels which were 23-25% lower than the results obtained when the data were normalized by total protein, total creatine, or NAD+.
Calculation of substrate oxidation rates in vivo from gaseous exchange
Authors: Frayn K. N.
Published: December 2017

This paper reviews the assumptions involved in calculating rates of carbohydrate and fat oxidation from measurements of O2 consumption, CO2 production, and urinary nitrogen excretion. It is shown that erroneous results are obtained in the presence of metabolic processes such as lipogenesis and gluconeogenesis. The apparent rates calculated under these conditions can, however, be interpreted as net rates of “utilization.” Thus the apparent rate of carbohydrate oxidation is the sum of the rates of utilization for oxidation and for lipogenesis minus the rate at which carbohydrate is formed from amino acids. The apparent rate of fat oxidation is the difference between the rates of oxidation and synthesis from carbohydrate, so that the apparently negative rates encountered in patients infused with glucose do quantitatively represent net rates of synthesis. Other processes such as synthesis of ketone bodies or lactate at rates greater than their utilization can also disturb the calculations, but the magnitude of the effect can be estimated from appropriate measurements. Methods of correcting the observed gaseous exchange in these circumstances are given.
A Hall effect transducer for measuring length changes in mammalian diaphragm
Authors: Peterson C. V. , Otis A. B.
Published: December 2017

When a conductor through which a current is flowing is brought into a magnetic field, the isopotential lines are distorted (E. H. Hall, 1879). When a constant current is made to flow through a Hall generator, the measured voltage perpendicular to the current flow can be made to vary by altering the distance between a permanent magnet and a Hall generator. A length transducer useful for measuring length changes in the diaphragm of a dog is made by connecting a commercially available Hall generator to a Plexiglas plate (5 X 10 X 3 mm, 0.5 g), and suturing the plate to the surface of the muscle. A permanent magnet (20 X 10 X 4 mm, 1.5 g) is attached to the diaphragm at a distance of 2 or 3 cm along the expected direction of length change. Fine wires from the terminals of the Hall generator are connected to an external constant-current source and to solid-state circuitry which provides amplification, linearization, and temperature compensation of the output signal. Model experiments indicate that the length measurements may be accurate within 5% if the distance between the magnet and Hall generator is greater than 5 mm. With this type of transducer measurements of segmental length changes in the diaphragm of an anesthetized dog have been successfully recorded.