bluuebunny/crossref_metadata_2025 huggingface dataset:
HbO2 dissociation in man during prolonged work in chronic hypoxia
Authors: Dempsey J. A. , Thomson J. M. , Forster H. V. , Cerny F. C. , Chosy L. W.
Published: December 2017

In healthy human sojourners to 3,100 m we studied exercise-induced shifts in HbO2 dissociation: their regulation in femoral venous blood and their net effect on estimated capillary PO2 (PC-O2) in working skeletal muscle. Prolonged heavy work effected an increase of 10.3 plus or minus 0.9 mmHg in in vivo P50 (7.30 PH-v, 41 degrees C-v, and 45 Pv-CO2); due entirely to the additive effects of increased venous temperature and [H+]. The rightward curve shift during work at 3,000 m, compared to that at 250 m, produced a similar increase in in vivo P50 but a reduced net effect on PC-O2, because Cv-02 at 3,100 m was reduced similar to 2 ml/100 ml to the lower converging portions of the curve. The lower Cv-O2 (and Pv-O2) at 3,100 M was attributable to a small decrease in total systemic blood flow. The net effect of the rightward curve shift during exercise on mean to end-capillary PO2 was positive in most cases (+1 to +8 mmHg PCO2). However, it was shown that the levels of mean to end-capillary PO2 (28–13 mmHg), which would have been obtained during exercise in the absence of any rightward curve shift, were more than adequate to sustain a steady state of aerobic energy production in working skeletal muscle. These data do not support the concept of a significant contribution to oxygen delivery to working skeletal muscle from in vivo shifts in HbO2 dissociation, during either acclimatization to high altitude or during prolonged muscular work.
Normal values for hypoxic and hypercapnic ventilaroty drives in man
Authors: Hirshman C. A. , McCullough R. E. , Weil J. V.
Published: December 2017

To better determine the range of normal values of hypoxic and hypercapni ventilatroy drives in man, these drives were measured in 40 males and 4 females between 21 and 51 yr of age. The average hypoxic drive, expressed as parameter A, was 186 plus or minus 12.8 (SEM). The average hypercapnic drive, expressed as the slope S, was 2.69 plus or minus 0.19. The range of values for these individuals was large and could not be accounted for by variations in maximal oxygen uptake, age, or sex. However, positive correlations were found between these drives and height and weight, and a positive correlation was found between hypoxic and hypercapnic drive.
A thermal method for the determination of tissue blood flow
Authors: McCaffrey T. V. , McCook R. D.
Published: December 2017

An isothermal flowmeter for the determination of local tissue blood flow is described. Flow is determined by the measurement of the thermal conductivity of the tissue in the vicinity of a heated thermistor maintained at a fixed temperature difference above a reference thermistor. Direct heating of the thermistor is utilized to eliminate the need for specially constructed indirectly heated thermistors. This design results in a device with a voltage output directly proportional to tissue thermal conductivity and to tissue blood flow. The device is shown to be adequate for the qualitative measurement of myocardial blood flow under various situations. Construction is simplified and the size of the circuit reduced by the use of readily available integrated circuits.
Force platforms as ergometers
Authors: Cavagna G. A.
Published: December 2017

Walking and running on the level involves external mechanical work, even when speed averaged over a complete stride remains constant. This work must be performed by the muscles to accelerate and/or raise the center of mass of the body during parts of the stride, replacing energy which is lost as the body slows and/or falls during other parts of the stride. External work can be measured with fair approximation by means of a force plate, which records the horizontal and vertical components of the resultant force applied by the body to the ground over a complete stride. The horizontal force and the vertical force minus the body weight are integrated electronically to determine the instantaneous velocity in each plane. These velocities are squared and multiplied by one-half the mass to yield the instantaneous kinetic energy. The change in potential energy is calculated by integrating vertical velocity as a function of time to yield vertical displacement and multiplying this by body weight. The total mechanical energy as a function of time is obtained by adding the instantaneous kinetic and potential energies. The positive external mechanical work is obtained by adding the increments in total mechanical energy over an integral number of strides.
Postnatal development of pyrogenic sensitivity in guinea pigs
Authors: Blatteis C. M.
Published: December 2017

Despite evidence of thermoregulatory ability from birth, neonates generally are unable to develop fever when challenged with endotoxin. This could be due to their small capacity for heat storage. To test this possibility, the pyrogenicity of S. enteritidis endotoxin (2 mug/kg, iv) was measured at both room (Ta = 25 degrees C) and neutral (Tn = 29–33 degrees C, depending on age) temperatures in 0- to 32-day-old unanesthetized guinea pigs, reared from birth at about 24 degrees C. Control guinea pigs received sterile saline injections in concurrent experiments. Shivering, O2 uptake, and colonic (Tre) and subcutaneous [over the interscapular fat pad (Tbat) and the sacrospinalis muscle (Tsc)] temperatures were recorded continuously for 4 h after injection. Endotoxin generally produced no febrile responses at both ambient temperaturess rises in animals aged 8 or more days; Tbat increased before the other sites in the 8- and 16-day-old animals, and shivering did not occur; by 32 days of age, however, Tbat no longer increased first, and there was shivering. In Tn significant febrile rises were not evident until 32 days of age; control temperatures, however, were elevated during this exposure as compared to at Ta. These results showed therefore that pyrogenic sensitivity is not apparent in guinea pigs during the first postnatal week; thereafter fever responses are evocable, but their detection may be masked by environmentally produced changes in body temperature. The data also indicated that the site of the heat production underlying, in part, endotoxic fevers gradually shifts from brown fat so skeletal muscle during the first month of life.
Shunt dynamics in experimental atrial septal defects
Authors: Alexander J. A. , Rembert J. C. , Sealy W. C. , Greenfield J. C.
Published: December 2017

Inorder to study the hemodynamic variables involving the magnitude, direction, and timing of phasic shunt flow, both the interatrial pressure gradient and blood flow along with other pertinent hemodynamic variables were measured instantaneously across a surgically created atrial septal defect (ASD) in seven awake dogs. Atrial and ventricular pacing and infusion of phenylephrine and isoproterenol were used to alter hemodynamic conditions. The wave form of phasic ASD flow was similar both in configuration and timing to the interatrial pressure gradient. During the cardiac cycle, both left-to-right (L-R) and right-to-left (R-L) shunting occurred: atrial contraction augmented L-R flow; the onset of ventricular contraction was associated with R-L flow; during the latter part of ventricular contraction, flow returned to L-R with the maximum L-R shunting occurring in early diastole. Tachycardia, infusion of phenylephrine and isoproterenol did not alter the phasic flow pattern. Both spontaneous and positive pressure respiration decreased net L-R shunting.
Gas-blood PCO2 gradients during avian gas exchange
Authors: Davies D. G. , Dutton R. E.
Published: December 2017

The avian respiratory system is a crosscurrent gas exchange system. One of the aspects of this type of gas exchange system is that end-expired PCO2 is greater than arterial PCO2, the highest possible value being equal to mixed venous PCO2. We made steady-state measurements of arterial, mixed venous, and end-expired PCO2 in anesthetized, spontaneously breathing chickens during inhalation of room air or 4–8% CO2. We found end-expired PCO2 to be higher than both arterial and mixed venous PCO2, the sign of the differences being such as to oppose passive diffusion. The observation that end-expired PCO2 was higher than arterial PCO2 can be explained on the basis of crosscurrent gas exchange. However, the observation that end-expired PCO2 exceeded mixed venous PCO2 must be accounted for by some other mechanism. The positive end-expired to mixed venous PCO2 gradients can be explained if it is postulated that the charged membrane mechanism suggested by Gurtner et al. (Respiration Physiol. 7: 173–187, 1969) is present in the avian lung.
Appearance of paoproteins of pulmonary surfactant in human amniotic fluid
Authors: King R. J. , Ruch J. , Gikas E. G. , Platzker A. C. , Creasy R. K.
Published: December 2017

We have isolated and partially characterized the protein found in surface-active material from adult human lungs, and have determined the time of appearance of this protein in amniotic fluid. Fluids were drawn at gestational ages from 12 to 44 wk, and were assayed for their concentration of apoprotein by an agglutination immunoassay. Surfactant apoprotein ((defined as that protein which is reproducibly found in purified preparations of surface active material) was usually first detected from 30 to 32 wk gestation, and its concentration increased almost fivefold to a maximum at 37 wk. The change in apoprotein concentration was approximately paralleled by the change in phospholipid concentration. At all gestational ages there was wide variability in both phospholipid and apoprotein concentrations, and the time of appearance of the apoprotein in amniotic fluid differed among fetuses. The results suggest that the presence of surfactant apoprotein in amniotic fluid is coincident with the biochemical and morphological maturation of the fetal lung, and are additional evidence that this apoprotein is cosecreted with the lipids of surface-active material.
Functional evaluation of the rat heart in situ
Authors: Dowell R. T. , Cutilletta A. F. , Sodt P. C.
Published: December 2017

We have developed methods for evaluating muscle function in the intact rat heart in situ using a contractility index (dP/dt)P-1, calculated from left ventricular pressure derivative-left ventricular pressure loop plots. Aortic flow measurements were also taken to further characterize in situ rat heart function. The preparation remained functionally stable and was within physiological blood gas and pH limits for at least 30 min following surgical procedures. The contractility index was not influenced by increased afterload, decreased preload or increased heart rate; however, appropriate changes were observed following isoproterenol and propranolol administration. Appropriate changes in aortic flow measurements were observed also with the above interventions. These studies demonstrate that the in situ rat heart is a stable physiological experimental preparation. It should be useful for evaluating heart function since a contractility index derived from pressure-velocity relationships and measurements necessary for pump function analysis can be obtained simultaneously.
Effect of acute lymphatic obstruction on fluid accumulation in the chest in dogs
Authors: Pang L. M. , Mellins R. B. , Rodriguez-Martinez F.
Published: December 2017

The effect of acute obstruction to lymphatic drainage on fluid accumulation in the lungs, pleura, and pericardium was assessed in the intact dog. Catheters were positioned in the venae cavase, right atrium (RA), left atrium (LA), age on fluid accumulation in the lungs, pleura, and pericardium was assessed in the intact dog. Catheters were positioned in the venae cavae, right atrium (RA), left atrium (LA), and aorta (Ao) of nine anesthetized, spontaneouly breathing dogs, and hydrostic and colloid osmotic pressures were continuously monitored. Lymphatic obstruction was achieved by raising systemic venous pressure to either 10 mmHg or 25 mmHg by a combination of fluid infusion and inflation of balloon catheters in the venae cavae for 2 h. The same constant net intravascular filtration pressure was maintained in both groups by appropriate use of saline or colloid-containing fluids. Pleural and pericardial fluids were measured postmortem and lung water content was determined by weighing before and after drying. Failure to detect greater fluid accumulation at the higher obstructing pressure (25 mmHg) than at the lower obstructing pressure (10 mmHg) suggests that over the range of obstructing pressures used there is no acute change in the magnitude of lymphatic drainage in the chest.
Energy expenditure cutting supercane
Authors: Spurr G. B. , Barac-nieto M. , Maksud M. G.
Published: December 2017

VO2 VE, and heart rates (fH) were measured in 61 Colombian sugarcane cutters while harvesting cane in the AM and PM and in the laboratory during a VO2max test. Productivity and sweat rates were also measured in the field. The subjects had an estimated dietary intake of 2,970 kcal/day, which was lower than calculated daily energy expenditure. During the work measurements the VO2 was 1.5 1/min, VE 48 1/min, and fH 135 beats/min; there were no differences between AM and PM values. The subjects sustained about 35% of VO2max during the 8 h workday, but worked at 57% of VO2max during the tests. Measured energy cost was 7.4 +/- 1.5 kcal/min during the workday. Sweat rates were higher PM than AM (5 KG/8 h day). Grouping of the men according to productivity demonstrated that taller, heavier men were better producers and had lower calculated heart rates at VO2 1.51/min. Efficiency of cane cutting was higher (9%) PM.
Hyperbaric system for oxygen toxicity studies in the toad urinary bladder
Authors: Miller J. H. , Hall D. , Haworth D. , Mendoza S. A.
Published: December 2017

A hyperbaric research system to study the effects on membrane function of oxygen at pressures as high as 20 ATA has been designed. The system includes a pressure chamber capable of holding eight isolated toad bladder short-circuit current apparatuses and unique experimental gassing, diluent addition, and sampling systems which are monitored by a control panel mounted on the side of the pressure chamber. These externally controlled gassing, diluent, and sampling systems permit experimental manipulations at any ambient pressure and are a significant addition to the methodology of hyperbaric research.
Effect of aerosolized isoproterenol on resting myogenic tone in normals
Authors: Stamm A. M. , Clausen J. L. , Tisi G. M.
Published: December 2017

The effects of aerosolized isoproterenol on expiratory (exp) and inspiratory (insp) conductance (Gaw), maximal exp and insp flow (VEmax and VImax), and static elastic recoil pressure (Pst) were measured in 12 normals. Both exp and insp Gaw increased throughout the vital capacity (37% at 50% VC; P less than 0.01). VEmax increased only at 50% VC (9%; P less than 0.01). VImax and Pst did not change. Accordingly, a dichotomy existed between the Gaw and Vmax changes during both exp and insp. We do not attribute this dichotomy to loss of driving pressure or to volume-time-dependent behavior of airway tone. We interpret the increased exp and insp Gaw to indicate isoproterenol deposition within and bronchodilatation of larger central airways (trachea, main stem, lobar, segmental). Since insp Gaw increased and VImax did not, we conclude that the caliber of these central airways is not the exclusive deteminant of VImax, that the caliber of some more distal airways (subsegmental and beyond) did not change, and that these airways are important determinants of VImax. We conclude that non-uniform distribution of isoproterenol could account for the Gaw-Vmax dichotomy during inspiration, and that such non-uniform distribution coupled with resultant increased compliance and compressibility of the downstream segment could account for the Faw-Vmax dichotomy during expiration.
Circulatory effects of prolonged hypoxia before and during antihistamine
Authors: Levasseur J. E. , Kontos H. A. , Richardson D. W. , Patterson J. L.
Published: December 2017

Five chronically instrumented healthy dogs were exposed to a 5-day period of breathing 10% oxygen in a chamber. The response to hypoxia was found to be time dependent. During the first 24 h of hypoxia the circulatory response was characterized by increases in cardiac output, heart rate, pulmonary and systemic arterial blood pressures, and pulmonary vascular resistance. Systemic vascular resistance increased; left atrial pressure decreased. During the early part of hypoxia the animals became hypocapnic; the arterial blood pH rose significantly. During the rest of the hypoxic period cardiac output, heart rate, and arterial blood pH returned to the control values; pulmonary and systemic arterial pressures and pulmonary vascular resistance remained significantly elevated. Systemic vascular resistance rose; left atrial pressure remained below control. This response to hypoxia was not substantially modified when the experiment was repeated during the administration of the antihistamine promethazine, an H1-receptor blocking agent, in a dose which blocked the pulmonary vasoconstrictor response to small doses of exogenous histamine. The circulatory response to acute hypoxia in five anesthetized dogs was not modified by intravenous administration of metiamide, an H2-receptor blocking agent.
Regulation of respiration in sleeping dogs
Authors: Phillipson E. A. , Murphy E. , Kozar L. F.
Published: December 2017

We have examined the respiratory changes that occur during physiological sleep in three dogs with exteriorized cervical vagal loops. Sleep stage was determined by behavioral and EEG criteria. During non-REM (NREM) sleep breathing was slower (mean change, 23%),deeper (mean change, 18%), and less variable (coefficients of variation, 0.05–0.10) than during wakefulness (W); minute volume of ventilation (Ve) decreased (mean change, 14%) and alveolar CO2 pressure (PAco2) increased slightly (mean change, 1.3 mmHg). In addition, the rate of O2 consumption and ventilatory response to hypercapnia were decreased. In contrast, REM sleep was characterized by rapid, shallow, and considerably more irregular (coefficients of variation, 0.18–0.30) breathing; Ve increased markedly and PAco2 decreased (mean change, 5.2 mmHg). Blockade of both cervical vagus nerves produced comparable changes in each stage of sleep (W, NREM, REM): breathing became slower and deeper, but the differences between stages and the marked irregularity in REM sleep persisted. In contrast, the Hering-Breuer inflation reflex (HBIR) was strong in W and NREM sleep, but weak in REM sleep. The results indicate that changes in respiratory control and stability during sleep are not due to fluctuations in vagal influence despite the fact that one vagal reflex (HBIR) was sleep-state dependent.
Occlusion pressures in men rebreathing CO2 under methoxyflurane anesthesia
Authors: Derenne J. P. , Couture J. , Iscoe S. , Whitelaw A. , Milic-Emili J.
Published: December 2017

The effect of general anesthesia on control of breathing was studied by CO2 rebreathing and occlusion pressure measurements in six normal human subjects under methoxyflurane anesthesia. CO2 was found to increase the amplitude of the occlusion pressure wave without changing its shape, so that CO2 responses in terms of the occlusion pressure developed 100 ms after the onset of inspiration (Po/0.1) gave results equivalent to the responses in terms of Po/1.o or any other parameter of the pressure wave. Methoxyflurane depressed the ventilatory response to CO2 but not the occlusion pressure response, implying that the most important action of the anesthetic was to increase the effective elastance of the respiratory system rather than to depress the respiratory centers. The elastance was further increased by CO2, and this mechanical change had the effect of shifting the “apneic threshold” extrapolated from the ventilatory response curve to a lower PAco2. Frequency of breathing, inspiratory and expiratory times were not altered by CO2 in anesthetized subjects.
Microcannulation--a new micropuncture technique application in cat pancreas secretion
Authors: Reber H. A. , Lightwood R.
Published: December 2017

A new micropuncture technique of microcannulation has been developed and applied in cats to study exocrine secretion in the pancreatic ducts. Two micropipets of different diameters are assembled with the smaller pipet (10–20 mum) mounted inside the larger (2–50 mum). Using the combination, a larger pancreatic duct (less than 300 mum) is directly punctured and the inner pipet is advanced into the lumen of a small (20–50 mum) duct, which would otherwise be inaccessible. In anesthetized cats, during maximal stimulation with secretin (GIH 4–6 units/kg per h iv) the average chloride concentration of juice obtained from small ducts (25–50 mum) was 106 +/- 3 meq/1 and from large ducts (50–150 mum) was 75 +/- 5 meq/1. The results were confirmed by conventional micropuncture techniques which were technically more difficult. This method to collect fluid from small ducts is more physiological than direct micropuncture and thus the technique is a useful addition to micropuncture methodology.
Pneumotachograph for flow and volume measurement in normal and dense atmospheres
Authors: Gelfand R. , Lambertsen C. J. , Peterson R. E. , Slater A.
Published: December 2017

Measurement of ventilatory flow during pulmonary function maneuvers and in severe exercise by the pneumotachograph flow transducer in dense atmospheres is handicapped by the inverse relationship between the linear range ofsuch transducers and gas density. This limitation in the usefulness of the pneumotachograph can be overcome by mounting such flow transducers in parallel and taking into account the reduction in peak ventilatory flow transducers in parallel and taking into account the reduction in peak ventilatory flow which occurs with increasing density. The design of such assemblies, their static performance characteristics, and a drift subtractor, constructedto stabilize the output of the pneumotachograph pressure transducer, are described.
New electronics for the Beckman LB-1 carbon dioxide analyzer
Authors: Swanson G. D. , Arena L. , Arancibia A. B. , Bellville J. W.
Published: December 2017

This paper describes an amplifier and linearizer for the Beckman LB-1 carbon dioxide analyzer head. All electronics are solid state and DC regulated in contrast to the original LB-1 amplifier which was of vacuum tube design and AC regulated largely by means of a voltage stabilizer transformer. A new detection principle is adopted which reduces drift due to mechanical imperfections of the chopper motor (e.g., bearing drag), but also offers the advantage that the phasing of the chopper blades is no longer necessary. Furthermore, the amplifier with a digital readout and an end-tidal hold circuit can be built for less than $500 and is plug compatible with the LB-1 head.
Cardiac glycogen repletion after exercise: influence of synthase and glucose 6-phosphate
Authors: Conlee R. K. , Tipton C. M.
Published: December 2017

Previous studies have shown that cardiac glycogen content is replenished to supranormal levels after exercise. To better understand this phenomenon glycogen synthase (GS) %I activity as well as glucose 6-phosphate (G-6-P) and glycogen (G) concentrations were measured in hearts from normal and alloxan diabetic rats killed at various time intervals before or after a treadmill run to exhaustion. In normal animals at exhaustion G was reduced but GS %I and G-6-P were elevated. During 2–8 h of recovery G was elevated, %I depressed, and G-6-P unchanged when compared to their preexercise values. By contrast, diabetic hearts that had elevated G and low %I were characterized by abnormally high G-6-P concentrations. At exhaustion in these hearts %I increased significantly in response to a decrease in G. These findings suggest that glycogen repletion occurs in normal heart as a result of the combined increases in GS %I and G-6-P levels present at the cessation of work. In both normal and diabetic hearts there exists an inverse relationship between G content and GS %I activity.
Effects of cold exposure and dehydration on renal function in black-tailed prairie dogs
Authors: Hamilton J. D. , Pfeiffer E. W.
Published: December 2017

Black-tailed prairie dogs (Cynomys ludovicianus) were deprived of food and water for several weeks during the fall and winter in a cold-room hibernaculum (Ta 5–8 degrees C), and for several days at room temperature during the summer. Body temperatures (Tb) were determined periodically in nine animals by radiotransmitters implanted in the abdomen. Animals deprived of food and water in the summer were killed when maximum urine concentration was achieved. Eight animals in the winter were active when killed after 7–35 days in the hibernaculum with Tb between 18 and 36 degrees C. Five animals that became torpid periodically in the winter were killed after 19–42 days in the hibernaculum when their Tb indicated torpor (Tb less than 13 degrees C). Active animals in the summer and winter possessed pronounced renal corticomedullary urea and sodium concentration gradients. Torpid animals lacked these gradients and had lower urine and plasma osmotic concentrations than active animals. Plasma urea values and terminal osmolal U/P ratios were lowest in torpid prairie dogs.
Extraction and radioimmunoassay of urinary aldosterone in the rat
Authors: Battarbee H. D. , Farrar G. E. , Braley J. K.
Published: December 2017

Results from studies of the rat renin-angiotensin-aldosterone axis have been inconsistent and oftentimes conflicting among various laboratories and have led many investigators to regard the rat as a poor model with which to study this sytem. Many of these discrepancies have been shown to be due to the use of anesthetic agents in experimental protocols. Studies of unanesthesized animals indicate that the rat bears a remarkable resemblance to other mammalian species, but unfortunately the unanesthesized rat lends itself well only to acute studies, usually requiring killing the animal. Herein is described a method which permits the estimation of aldosterone excretory rates in intact, nonstressed, unanesthesized rats. The method is based upon the excretion and radioimmunoassay of urinary “acid-labile” or 3-oxo-conjugate of aldosterone. It is very sensitive, permitting the detection of less than 10 pg of aldosterone conjugate in extracted samples, and when compared to the double-isotope-dilution method, it is relatively inexpensive and much less tedious. Radioimmunoassays of rat urinary aldosterone excretion during 14.75 days of sodium depletion reflected a brisk increase in urinary excretion rate after day 2 and a concomitant reduction in sodium excretion that bears a remarkable resemblance to the excretory patterns described for man.
A modified forced oscillation technique for measurements of respiratory resistance
Authors: Aronsson H. , Solymar L. , Dempsey J. , Bjure J. , Olsson T. , Bake B.
Published: December 2017

We present a modification of forced oscillation technique for automated determination of total respiratory resistance during inspiration. The modifications consist of a computerized signal averaging and an optimization technique in the assessment of the resistance value. Thereby a favorable signal-to-noise ratio is obtained, allowing very low superimposed pressure oscillations. The method is validated by comparison with a conventional esophageal balloon method, by estimating added mechanical resistances in healthy subjects and by measuring the effect of bronchodilation in asthmatic children. The coefficient of variation as obtained from day-to-day measurements was about 7%. Mechanical resistances, estimated as the difference in total resistance with and without external resistance, were within 7% of their values determined for the resistances alone. A significant decrease in resistance was obtained in each of the asthmatic children following bronchodilation.
Influence of body position on dynamic compliance in young subjects
Authors: Sasaki H. , Hida W. , Takishima T.
Published: December 2017

We studied the effect of a postural change from the erect to the supine position on the unevenness of pulmonary ventilation in six normal subjects. Static pressure-volume curves had a similar shape in both positions but the supine curves were shifted such that all transpulmonary pressures were 5–8 cmH2O lower. Dynamic compliance (Cdyn) was measured in seated and supine postures at functional residual capacity (FRC) and also while the seated subjects maintained end-expiratory lung volume at the level of supine FRC. Frequency dependence of Cdyn increased relative to that measured in the seated position at FRC when the subject remained seated but decreased his lung volume, or when he assumed the supine posture. There was no significant difference between Cdyn measured in the supine posture and in the seated at supine FRC. We conclude that the increased frequency dependence seen in the supine posture is largely attributed to the associated decrease of lung volume rather than to position per se.
Mucus clearance: in vivo canine tracheal vs. in vitro bullfrog palate studies
Authors: Giordano A. , Shih C. K. , Holsclaw D. S. , Khan M. A. , Litt M.
Published: December 2017

Tracheal mucociliary clearance was studied by a radioisotope technique in pentothal-anesthetized beagles in the control, atropinized, or dehydrated state. Mucus collected from a tracheal pouch in each dog was used for in vitro bullfrog (Rana cantesbiana) palate clearance studies and compared to the in vivo clearance rates. In all three experimental states, there was a significant correlation between in vivo and in vitro rates, suggesting that tracheal pouch mucus is a good model for investigating the mucociliary flow properties of intact airway mucus. When compared to matched controls, atropine appeared to cause a slowing of the in vivo clearance rate but not of the in vitro rate. Dehydration had no effect on either. The appropriateness of the frog palate method in the study of human respiratory disease (e.g., chronic bronchitis, cystic fibrosis) as well as its potential as an objective method of assessing the effects of various therapeutic modalities in these diseases is discussed.
Infarct size and exercise capacity after myocardial infarction
Authors: Carter C. L. , Amundsen L. R.
Published: December 2017

Estimation of infarct size from serum creatine phosphokinase elevations of 22 acute myocardial infarction (AMI) patients was compared to their functional exercise capacity determined on a bicyle ergometer. Eleven of these patients entered a controlled exercise program for 3–4 mo and were subsequently retested. Aerobic power of the exercise group increased significantly (mean +- SE 1.42 +- 0.5 met) and was also significantly greater than an unpaired control group tested the same number of months after infarct. Patients grouped 2.5–4.5 mo post-AMI demonstrated a correlation between aerobic power and estimated infarct size (r = -0.68, n = 15). This correlation was higher (r = -0.84, n = 11) after 3–4 mo of a controlled exercise program.
Atraumatic measuring of pulmonary capillary blood flow in dogs
Authors: Barrow R. E. , Shult M. D.
Published: December 2017

Pulmonary capillary blood flow (Qc) was measured by a nitrous oxide uptake technique using a capacitance-plethysmograph to measure pulmonary volume changes. One hundred and four paired Qc and total cardiac outputs (Qt) were measured in 13 normal mongrel dogs. The mean Qc was 0.101 +/- 0.020 1-min -1-kg-1 while the mean Qt, measured by dye dilution, was 0.117 +/- 0.025 1-min-1-kg-1. This technique minimizes subject trauma and provides a method for repeated pulmonary capillary blood flow determinations in acute or chronic studies.
Prediction of PO2 from SO2 using the standard oxygen hemoglobin equilibrium curve
Authors: Tien Y. K. , Gabel R. A.
Published: December 2017

We have fitted polynomial equations to three major segments of the standard oxygen hemoglobin equilibrium curve (OHEC) using oxygen saturation (SO2) rather than oxygen tension (PO2) as the independent variable. Hill's transformation contributes substantially to the very small residual errors of PO2, less than 0.21 Torr for all points. This characterization of the OHEC is more precise, and for certain applications more conveniently used than other available equations.
DC proportional heater-cooler temperature controlled for physiological research
Authors: Caldwell W. M.
Published: December 2017

A DC proportional temperature control circuit for driving resistive heaters and Peltier thermoelectric devices in physiological research is described. The instrument, supplying +/- 12.5 V DC at 8 A is designed for temperature control of anesthetized animals, generation of hot or cold thermal stimuli, and control of thermal environments.
[14C]urea and [14C]sucrose as permeability indicators in histamine pulmonary edema
Authors: Brigham K. L. , Harris T. R. , Owen P. J.
Published: December 2017

To see whether, by avoiding red blood cell transport effects, [14C]-sucrose would be a more sensitive lung vascular permeability indicator than [14C]urea, we compared the effects of 4 microgram/kg-min intravenous histamine phosphate infusions on lung vascular permeability-surface area products (PS) for each indicator in the same unanesthetized sheep. Histamine caused hematocrit, PaCO2 and pHa to increase and pulmonary arterial pressure and Pa02 to decrease. [14C]Urea PS (integral extraction calculation) increased from a base line value of 14.7 +/- 1.5 SE ml/s to 17.7 +/- 1.3 (P less than 0.05) with histamine, but [14C]sucrose PS did not change (base line, 6.5 +/- 2.9; histamine, 5.8 +/- 1.2). We conclude that [14C]urea is probably a more useful permeability indicator in the lung circulation than [14C]sucrose, because urea is more sensitive to moderate increases in permeability.
Splanchnic blood flow, O2 consumption, removal of lactate, and output of glucose in highlanders
Authors: Capderou A. , Polianski J. , Mensch-Dechene J. , Drouet L. , Antezana G. , Zelter M. , Lockhart A.
Published: December 2017

An impairment of gluconeogenesis has been proposed to explain the low arterial blood glucose of highlanders. Therefore, we studied splanchnic blood flow, splanchnic uptake of oxygen and lactate, and output of glucose in nine normal and six anemic highlanders at an altitude of 3,750 m. Splanchnic blood flow, arteriovenous difference for oxygen, and oxygen consumption were comparable at rest in both groups and in lowlanders from the literature, whereas splanchnic output of glucose, and uptake of lactate were approximately twice those in lowlanders. After 10 min of mild exercise in 12 subjects (7 normals, 5 anemic), no significant changes in splanchnic hemodynamics and metabolism were found. During 29% oxygen breathing in 8 subjects (5 normals, 3 anemics), arterial lactate, splanchnic uptake of lactate and output of glucose fell to normal sea-level values. We concluded that splanchnic hemodynamics are similar in adapted highlanders and in lowlanders, and that there is no evidence of an impaired gluconeogenesis at the altitude of the present study.
Capillary proliferative activity in myocardium and skeletal muscle of exercised rats
Authors: Ljungqvist A. , Unge G.
Published: December 2017

The capillary proliferative activity in heart and skeletal muscle was studied by autoradiography after in vivo injections of [3H]thymidine in swimming exercised rats. Swimming exercise led to hypertrophy of the myocardium and the muscle fibers of the fore- and hindlimbs. When compared with normal controls a highly significant increase in nuclear incorporation of [3H]thymidine was found in the cells of the myocardial capillary walls. No increased incorporation of [3H]thymidine was found in capillary wall cells of fore- and hindlimb muscles. The findings confirm previous observations of a significant neoformation of myocardial capillary blood vessels in swimming-induced cardiac hypertrophy, whereas any capillary neoformation in the hypertrophying skeletal muscles of this experimental model is insignificant.
Elevated alveolar PCO2 relative to predicted values during normal gas exchange
Authors: Robertson H. T. , Hlastala M. P.
Published: December 2017

A negative aADCO2 has been demonstrated during ventilation with hypercarbic gas mixtures and during rebreathing, but has never been demonstrated during normal gas exchange. This anomalous behavior of CO2 was studied by comparing it to the behavior of five infused inert gases during normal gas exchange in 10 anesthetized mongrel dogs. The distribution of VA/Q heterogeneity and the respiratory dead space in the animals was quantitated using excretion-solubility data from the five infused inert gases. The predicted excretion fraction (PACO2/PVCO2) for CO2 was obtained from the inert gas excretion-solubility curve, using a measured solubility for CO2. The measured excretion fraction for CO2 (PACO2/PVCO2), even after correction for Haldane effect, was significantly greater than the predicted fraction (P less than 0.001). This corresponded to an alveolar PCO2 that exceeded the predicted value by a mean of 5.0 Torr.
Isolated, ventilated, perfused newborn rabbit lung preparation and its assessment
Authors: Olson E. B. , Orbeck H. , Graven S. N. , Zachman R. D.
Published: December 2017

To achieve an isolated, ventilated, perfused newborn rabbit lung preparation, newborn rabbits are anesthetized and ventilated. The pulmonary vasculature is perfused with a Krebs-Ringer bicarbonate solution containing glucose and plasma expanders, and the lungs are isolated in a 37 degrees C chamber at 100% humidity. The success of a perfusion is evaluated on three levels. 1) Visual. 2)mechanical: a, drop in flow of greater than 20% indicates failure; b, an increase of more than 25% of the initial lung weight indicates fluid accumulation and failure. 3) Biochemical: a, the endogenous ATP concentration after perfusion; b, the level of the enzyme choline phosphotransferase (CPT) after perfusion. Isolated, perfused, ventilated newborn rabbit lungs maintained for 4 h with no changes in the monitored physical and mechanical parameters have an endogenous ATP level of 1.06 +/- 0.06 (2 SD) mumol ATP/mg wet weight and a CPT level of 1.34 +/-0.15 (2 SD nmol [14C]CDP-choline per milligram protein in 30 min. These values are stable at a level lower than observed in intact, hypoxic, newborn rabbit's lungs. In constrast, if perfusion is maintained after any of the monitored criteria indicate failure, the endogenous ATP concentration and CPT activity are significantly depressed.
Heat production of fetal sheep brain in utero
Authors: Abrams R. M. , Clapp J. F. , Notelovitz M. , Tyler T. , Cassin S.
Published: December 2017

Thermojunctions were implanted in the brains of 10 near term fetal sheep in utero under halothane anesthesia. Brief total occlusion of fetal brachiocephalic artery was followed immediately by an increase in brain temperature (mean +/- SE) of 0.130 +/- 0.014 degrees C-min-1. Occlusion of main pulmonary artery and ascending aorta, simultaneously, led to a brain temperature increase of 0.144 +/- 0.018 degrees C-min-1. Specific heat of three fetal brains was determined to be 0.898 +/- 0.014 cal-g-1. degrees C-1 or 3.76 +/- 0.059 J-g-1. Rate of fetal brain heat production, computed as the product of the higher rate of temperature change and brain specific heat, was 0.129 +/- 0.014 cal-g-1-min-1 or 9.00 +/- 0.98 mW-g-1.
Collateral flow resistance and time constants in dog and horse lungs
Authors: Robinson N. E. , Sorenson P. R.
Published: December 2017

We studied collateral flow resistance in exsanguinated, excised lower lobes and accessory lobes of dog and horse lungs, respectively. A double lumen catheter obstructed a peripheral airway isolating a segment of the lobe. Oxygen flowed into the segment via a rotameter which measured flow (Vcoll) while the inner catheter recorded segment pressure (Ps). Gas delivered into the segment flowed out via collateral channels. Collateral flow resistance was calculated as (Ps - PL)/Vcoll, where PL = static transpulmonary pressure. Rcoll at PL = 20, 10, and 5 cm H2O averaged 0.24, 1.25, and 2.65 cmH2O.ml-1.s, respectively, in the dog, and 4.53, 6.00, and 12.62 cmH2O.ml-1.s in the horse. At a given PL, Rcoll measured during inflation. At constant PL, Rcoll increased with time at PL = 5 and 10 cmH2O, but was not time dependent at PL = 20 cmH2O. At constant PL, Rcoll increased at Vcoll increased. We conclude Rcoll is greater in horses than in dogs and is a function of PL, Ps - PL, and lung volume history in both species.
Partitioning of inspiratory pressure swings between diaphragm and intercostal/accessory muscles
Authors: Macklem P. T. , Gross D. , Grassino G. A. , Roussos C.
Published: December 2017

We tested the hypothesis that the inspiratory pressure swings across the rib-cage pathway are the sum of transdiaphragmatic pressure (Pdi) and the pressures developed by the intercostal/accessory muscles (Pic). If correct, Pic can only contribute to lowering pleural pressure (Ppl), to the extent that it lowers abdominal pressure (Pab). To test this we measured Pab and Ppl during during Mueller maneuvers in which deltaPab = 0. Because there was no outward displacement of the rib cage, Pic must have contributed to deltaPpl, as did Pdi. Under these conditions the total pressure developed by the inspiratory muscles across the rib-cage pathway was less than Pdi + Pic. Therefore, we rejected the hypothesis. A plot of Pab vs. Ppl during relaxation allows partitioning of the diaphragmatic and intercostal/accessory muscle contributions to inspiratory pressure swings. The analysis indicates that the diaphragm can act both as a fixator, preventing transmission of Ppl to the abdomen and as an agonist. When abdominal muscles remain relaxed it only assumes the latter role to the extent that Pab increases.
Effect of force environment on regional pulmonary displacements and volumes in dogs
Authors: Greenleaf J. F. , Smith H. C. , Chevalier P. A. , Sass D. J. , Bove A. A. , Wood E. H.
Published: December 2017

Regional displacements of lung parenchyma due to respiratory movements at 1 G and 7 Gy were studied in anesthetized dogs in the left decubitus position in a water-filled respirator that provided control of respiratory volumes and rate and minimized inertial shifts in position and shape of the thorax and abdominal contents and related effects on the lungs. Inspiratory movements at 1 G were relatively uniform, although regional volume increased more in the nondependent (right) lung than in the dependent (left) lung. Regional functional residual capacity (FRC) increased in the nondependent lung and decreased in the dependent lung during exposures to 7 Gy. The greatest inspiratory increase in volume occurred near the midlung, where regional FRC changed the least during acceleration. The decrease in dependent and increase in nondependent lung volumes during acceleration are attributed to the increased weight and consequent downward displacement of the higher specific gravity mediastinal contents concomitantly with upward displacement of pulmonary gas, producing an exaggeration of the dependent-to-nondependent gradient in alveolar size.
Longitudinal mixing in pulmonary airways--normal subjects respiring at a constant flow
Authors: Ultman J. S. , Doll B. E. , Spiegel R. , Thomas M. W.
Published: December 2017

We have measured the impulse response of helium and sulfur hexafluoride in the airways of five normal human subjects at a respiratory flow of 400 ml/s. The longitudinal mixing of the inert gases was characterized by the increased volume variance of the expired concentration response. This parameter was measured over the largest possible range of airway penetrations, 30–290 ml. Employing a symmetrical model of the airway geometry, we have computed the values of a mean mixing coefficient from the volume variance data. This mixing coefficient is largest in the large airways and decreases rapidly with increasing penetration; it may be as much as 4,000 times greater than the molecular diffusivity; and it is relatively independent of the inert gas tested, at least up to an airway penetration of 180 ml. These observations are consistent with several preivously proposed mixing mechanisms including axial streaming, turbulent dispersion, and mixing by geometric asymmetry. However, the latter observation appears to rule out the importance of laminar dispersion since mixing by this mechanism is inversely dependent on the molecular diffusivity.
A microampere radiotelemetry transmitter for measurement of temperature from unrestrained subjects
Authors: Jones D. L. , Wang L. C.
Published: December 2017

A miniature radiotelemetry transmitter is described suitable for chronic or acute monitoring of temperatures from animal or human subjects. The transmitters can be easily constructed with little or no electronics background from discrete components readily available from any electronics supplier. Transmitters weighed from 2.5–20 g, had volumes of 0.8–3.5 ml, had normal currents of 50–120 muA with potential transmitter lives of 35 h to greater than 1 yr, and transmission ranges of 10–30 m. Transmitters could be implanted, swallowed, or connected to chronically or acutely attached temperature probes. The design of the telemetry system allows for reception on any commercial FM receiver. Depending on mode of decoding the temperature data transmitter signal can be accurate to measure changes of from 0.15 to 0.015 degrees C. Thus with a minimum of expense and little electronics background a temperature-dependent transmitter system can be constructed for monitoring temperatures from unrestrained subjects.
Urinary catecholamine excretion in temporary residents of high altitude
Authors: Sharma S. C. , Hoon R. S. , Balasubramanian V. , Chadha K. S.
Published: December 2017

Urinary catecholamine excretion was estimated in 50 lowlanders temporarily staying at altitudes above 3,000 m. They were divided in subgroups according to the length of their continuous stay. For comparison, 25 highlanders who were born and brought up at high altitude and 50 lowlanders who had never been to altitudes of more than 1,000 m were also studied. High catecholamine excretion was noted in temporary residents staying at high altitude for up to 30 days as compared to that in lowlanders (P greater than 0.01). The excretion rate gradually returned to basal values thereafter. Catecholamines were essentially similar in lowlanders and highlanders. The significance of these findings is discussed regarding the possible pathogenetic role of the sympathoadrenal system in the development of ill effects in respone to high-altitude exposure.
Nonrebreathing valve for spontaneously breathing or mechanically ventilated animals
Authors: Truog W. E. , Standaert T. A.
Published: December 2017

The design of a small dead space, nonbreathing valve suitable for use in small laboratory animals is presented. The design overcomes previous problems of condensation occurring at valve leaflets, and allows ongoing collection of expired gases should the animal require mechanical ventilation. The valve apparatus performs reliably when in operation for several hours at a time with a variety of small animals.
Motorized minitrack for exercising large animals
Authors: Sanders M. , White F. , Sargeant R. , Peterson T. , Bloor C.
Published: December 2017

A simply constructed device for exercise training large animals, e.g., swine, is described. Basically the device is a small, circular, enclosed track constructed of plywood and metal fence material. A centrally located, vertical shaft powered by a DC motor rotates at a variable speed. Attached to each of four horizontal metal beams extending from the shaft are four suspended partitions which hang freely above the enclosed track surface. As the shaft rotates, the four partitions move in unison, thus forcing animals in each compartment to move at the same pace. The advantages of this device are its cost, low maintenance, and the flexibility to train eight animals by one person. Preliminary results of a study on training pigs are discussed.