bluuebunny/crossref_metadata_2025 huggingface dataset:
Sustained venoconstriction in man supplemented with CO2 at high altitude
Authors: Cruz J. C. , Grover R. F. , Reeves J. T. , Maher J. T. , Cymerman A. , Denniston J. C.
Published: December 2017

Venoconstriction occurs at high altitude. This study sought to determine whether hypoxia or hypocapnia is the cause of the venoconstriction. Five male subjects were exposed to 4,000–4,400 m (PB 440–465 mmHg) with supplemental 3.77 +/- 0.02% CO2 in a hypobaric chamber for 4 days. Similar alveolar O2 tensions were obtained in four control subjects exposed to 3,500–4,100 m (PB 455–492 mmHg) without CO2. A water-filled plethysmograph was used to determine forearm flow and venous compliance. Systemic blood pressure was measured with the cuff procedure. Catecholamines were measured in 24-h urine collections. Venous compliance fell at high altitude in both groups and was less (P less than 0.01) than control values. Forearm flow and resistance were unaltered at altitude in the group with CO2 supplementation while forearm flow decreased and resistance increased in the hypocapnic group at 72 h of exposure. Urinary catecholamines increased in the group with CO2 and remained unaltered in the hypocapnic group. It is concluded that hypoxia is responsible for decreasing venous compliance, and hypocapnia for increasing resistance and decreasing flow. Group differences observed in urinary catecholamines may be explained by differences in arterial pH.
Skeletal muscle enzymes and fiber composition in male and female track athletes
Authors: Costill D. L. , Daniels J. , Evans W. , Fink W. , Krahenbuhl G. , Saltin B.
Published: December 2017

Muscle samples were obtained from the gastrocnemius of 17 female and 23 male track athletes, 10 untrained women, and 11 untrained men. Portions of the specimen were analyzed for total phosphorylase, lactic dehydrogenase (LDH), and succinate dehydrogenase (SDH) activities. Sections of the muscle were stained for myosin adenosine triphosphatase, NADH2 tetrazolium reductase, and alpha-glycerophosphate dehydrogenase. Maximal oxygen uptake (VO2max) was measured on a treadmill for 23 of the volunteers (6 female athletes, 11 male athletes, 10 untrained women, and 6 untrained men). These measurements confirm earlier reports which suggest that the athlete's preference for strength, speed, and/or endurance events is in part a matter of genetic endowment. Aside from differences in fiber composition and enzymes among middle-distance runners, the only distinction between the sexes was the larger fiber areas of the male athletes. SDH activity was found to correlate 0.79 with VO2max, while muscle LDH appeared to be a function of muscle fiber composition. While sprint- and endurance-trained athletes are characterized by distinct fiber compositions and enzyme activities, participants in strength events (e.g., shot-put) have relatively low muscle enzyme activities and a variety of fiber compositions.
Mechanical properties of the dog renal capsule
Authors: Herbert L. A. , Chen W. C. , Hartmann A. , Garancis J. C.
Published: December 2017

The renal capsule is an important determinant of whole kidney volume/pressure relationships. To gain further insights into its possible role we examined the mechanical properties of the dog renal capsule using standard materials testing procedures. From each of four locations on the kidney surface, the following mechanical properties of the renal capsule were determined: elastic modulus (force/unit of cross-sectional area theoretically required to double the length of the specimen), tensile stiffness (force/unit width theoretically required to double the length of the specimen), ultimate strength (stress at time of fracture of the specimen), and maximum strain (percent strain at time of the fracture of the specimen). We found that the elastic modulus of the renal capsule from all capsular sites was substantially greater than values previously reported for dog aorta. The stiffness of the capsule covering the anterior-posterior surface of the kidney was found to be about 50% greater than the stiffness of the capsule covering the lateral and polar surfaces of the kidney. The ultimate strength of the anterior-posterior capsule was significantly greater than that of the lateral or polar capsule. This finding may explain the clinical observation that the spontaneous rupture of the renal capsule and parenchyma associated with the acute swelling of transplant rejection is confined almost exclusively to the lateral and polar portions of the renal capsule and cortex. The mean maximum strain at each capsular site was about 35%. This degree of circumferential expansion corresponds to about a doubling of kidney volume. Thus, this observation suggests that the renal capsule is at risk to undergo spontaneous rupture when renal volume increases of this magnitude are observed.
Decompression limits for compressed air determined by ultrasonically detected blood bubbles
Authors: Spencer M. P.
Published: December 2017

The direct decompression limits for a group of divers over a range of pressure-time air exposures was determined using ultrasonic detection of venous gas emboli (VGE). In addition to dry chamber exposures, ranging from 233 ft for 7 min to 25 ft for 720 min, we exposed six divers to open ocean dives at 165 ft for 10 min. Findings demonstrated a strong individual propensity to form VGE, correlating with susceptibility to bends. No bends developed without the prior detection of precordial VGE. The present concept of no problems after any period of time at 30 fsw was not confirmed. Isopleths of equal percentage occurrence of VGE were computed between 10 and 60%. Open ocean exposures increased the percentage of VGE and bends, when compared to dry chamber exposures. Limiting tissue half times computed from the 20% VGE isopleth suggested that saturation exposures are controlled by a greater sensitivity of the short-half-time tissues than previously appreciated, rather than by additionally extended half times.
Can impedance characterize the heart?
Authors: Hunter W. , Noordergraaf A.
Published: December 2017

When considering the use of Fourier series in hemodynamics, the question is whether one can relate the frequency components of the flow oscillations to the corresponding ones of pressure using impedance concepts. For the arteries, this method provided the basis for great advances in understanding. However, it is precisely because the arterial tree acts almost linearly while its properties do not change markedly within one beat that frequency analysis achieved such success. For the ventricle, in which the mechanical properties vary widely over the course of one heart cycle, Fourier analysis loses its usefulness. Consequently, we must return to the time domain for formulating a description of the heart as a pump. A time-domain method, the impulse response, is suggested as a possible alternative to impedance.
An inexpensive blood pressure-heart rate computer for laboratory or teaching use
Authors: Martin P.
Published: December 2017

A special-purpose analog computer circuit is described that, given a signal proportional to arterial blood pressure, generates signals equal to systolic, diastolic, pulse, and mean pressure at a calibration of 100 mmHg/V. Heart period and rate are also derived at calibration of 1 s/V and 100 bpm/V, respectively. The outputs are step-function beat-by-beat changes in these six variables suitable either for analog recording, or presentation to a panel meter for digital display.
Effects of hypocapnia and hypocapnic alkalosis on cardiovascular function
Authors: Zwillich C. W. , Pierson D. J. , Creagh E. M. , Weil J. V.
Published: December 2017

Cardiovascular effects of hypocapnia and hypocapnic alkalosis with and without a fluid load were studied in four groups of dogs (group I: fluid load control; group II: fluid load-isolated hypocapnia; group III: fluid load-hypocapnic alkalosis; group IV: no fluid load-hypocapnic alkalosis). Hypocapnic alkalosis was induced by mechanical hyperventilation, and isolated hypocapnia by the simultaneous administration of 0.1 N HCl. Respiratory alkalosis was also studied during administration of a saline fluid load. Cardiac output and stroke volume increased in all groups receiving a fluid load (including isolated hypocapnia and hypocapnic alkalosis groups), but both fell significantly during hypocapnic alkalosis without fluid load. Pulmonary artery wedge pressure rose in groups with hypocapnic alkalosis with fluid load and isolated hypocapnia with fluid load, but did not change significantly with hypocapnic alkalosis without fluid load or in the normocapnic group with fluid load. It is concluded that cardiac output and stroke volume fall in response to hypocapnic alkalosis but both are maintained with a fluid load at the expense of an increased left ventricular preload.
Effects of hypercapnia and flow-resistive loading on tracheal pressure during airway occlusion
Authors: Altose M. D. , Kelsen S. G. , Stanley N. N. , Cherniack N. S. , Fishman A. P.
Published: December 2017

To determine whether the isometric force of concentration of the inspiratory muscles could be used to assess respiratory efferent neural activity, the tracheal pressure generated by the inspiratory muscles during airway occlusion (occluded tracheal pressure) was measured during progressive hypercapnia in anesthetized dogs breathing normally and breathing against added flow-resistive loads. Hypercapnia increased the peak end-inspiratory tracheal pressure and the occluded tracheal pressures generated 100, 200, and 300 ms after the onset of inspiration. The duration of the occluded inspiratory effort generally remained unchanged and the configuration of the pressure tracing was not affected. During normal breathing occluded tracheal pressures increased linearly with tidal volume and with the electrical activity of the diaphragm and the external intercostal muscles both before and after vagotomy. Inspiratory flow-resistive loading reduced the ventilatory response to CO2 but did not affect occluded tracheal pressures at any given PCO2 or the change in pressures with hypercapnia both before and after vagotomy. Similarly, expiratory flow-resistive loading failed to affect occluded tracheal pressures. These results suggest that occluded tracheal pressures measure respiratory efferent neural activity and can be used as indices of CO2 responsivity even during mechanical loading in anesthetized animals.
Respiratory load compensation in infants
Authors: Knill R. , Andrews W. , Bryan A. C. , Bryan M. H.
Published: December 2017

We have studied the respiratory compensation for elastic loads in 15 term and preterm infants. Elastic loads, approximately equal to the infant's effective elastance, were applied to the airway for five breaths while tidal volume and mask pressure were monitored. Motion of the rib cage and abdomen were monitored simultaneously with magnetometers. The studies were done both in active or REM sleep and in quiet or non-REM sleep. During quiet sleep the load immediately reduced the tidal volume by about 50% but a progressive increase in tidal volume occurred over the next four loaded breaths. During active sleep load compensation was disorganized with respect to both tidal volume and frequency, and compensation was significantly less. Active sleep was also characterized by marked rib cage distortion. We suggest that during active sleep there is tonic inhibition of the intercostal muscles, allowing the diaphragm to distort the rib cage. This distortion impairs load compensation by a direct mechanical effect and indirectly by initiating an intercostal-phrenic reflex.
A clinical catheter for continuous blood gas measurement by mass spectrometry
Authors: Brantigan J. W. , Dunn K. L. , Albo D.
Published: December 2017

A new Teflon catheter for continuous in vivo measurement of blood gases by mass spectrometry has an outer diameter of 0.032 in. and can be inserted through percutaneous puncture with an 18-gauge needle. Response time (63% of a total change) is 40 s for oxygen and 65 s for carbon dioxide. When calibrated in analyzed gas at 37 degrees C, the catheter-mass spectrometer system has been shown to analyze tonometered blood with an error of 1.6% for oxygen and 1.9% for carbon dioxide. Temperature dependence is 2.0% per degrees C for oxygen and 1.6% per degrees C for carbon dioxide. The catheter was thrombo-resistant during in vivo use in seven dogs and measurements compared favorably with results of blood sample analyses by standard hospital methods. Compared with previous devices, the new catheter provides size and convenience, advantages that make it more applicable for routine clinical use.
Changes in cold-induced vasodilation during Arctic exercises
Authors: Livingstone S. D.
Published: December 2017

The effect of exposure to cold on cold-induced vasodilation (CIVD) was examined in military personnel who had experienced a 2-wk stay in the Artic. During this time, the daily regimen consisted of long marches over difficult terrain and sleep in unheated tents with diurnal temperatures ranging from -10 to -40 degrees C. In tests conducted before and after the 2-wk period, CIVD was measured in the left middle finger of each subject by its immersion in ice water. After the 2-wk period, the value of mean finger temperature during the test had decreased relative to that observed before the test, the time required before the first vasodilative temperature increase occurred had become greater, and the finger temperature value at which the vasodilative increase was initiated has been lowered. These changes manifest a deleterious effect of cold exposure on the CIVD, contrary to expectations, and suggest that the effect of short-term cold exposure is to produce a general rather than peripheral acclimation in these subjects.
A method to obtain infusion schedules for prescribed blood concentration time courses
Authors: Patlak C. S. , Pettigrew K. D.
Published: December 2017

It is sometimes desirable to obtain a specified blood level which obeys a prescribed mathematical form. Following an approach based on impulse analysis via Laplace Transform techniques, a general method for an input injection schedule which will achieve this goal is derived. Specific infusion schedules are given which attain blood levels that are constant, increase linearly, decay exponentially, and increase exponentially. Further, simpler approximate infusion schedules are also derived whose outputs achieve the desired function after a short time. Two illustrative experimental examples-one for [14C]EDTA-Ca in anesthetized rhesus monkeys and the other for 2-deoxy-D-[1-14C]glucose in the conscious rat-are presented in detail. The assumptions are discussed and an error analysis is performed.
Two-dimensional determination of thermosensitive sites within the goat's hypothalamus
Authors: Jessen C.
Published: December 2017

In two conscious goats with chronically implanted multithermodes the distribution of thermosensitive sites within the anterior hypothalamus was determined. Changes in heat production at Ta=+5 degrees C and changes in respiratory evaporative heat loss at Ta=+33 degrees C in response to discrete temperature stimuli were measured and the magnitude of the responses was correlated with the histologically assessed position of the probes transmitting the stimuli. In both animals the array of probes was centered close to the center of the thermosensitive area. The density of thermosensitive structures increased toward the center of the area covered by the probes. The most sensitive points were situated close to either side of the midline in those frontal planes which contained the nuclei supraoptici and paraventriculares. No difference was found between cold- and warm-sensitive sites.
Effects of external pressure loading on human skin blood flow measured by 133Xe clearance
Authors: Holloway G. A. , Daly C. H. , Kennedy D. , Chimoskey J.
Published: December 2017

Forearm skin blood flow was measured during external pressure loading in normal human subjects using 133Xe washout from intracutaneous injection sites. Pressures ranging between 5 and 150 mmHg were applied through a 3-cm-diameter disc placed over the site of flow determination. The pressure was maintained constant by a servo-controlled loading mechanism. Flow decreased with pressures from 5 to 10 and 30 to 150 mmHg, but remained constant with pressures from 10 to 30 mmHg. Reactive hyperemia occurred following removal of pressures of 90 mmHg or greater, but did not occur following removal of lower pressures. The pressure-flow curve for parasacral skin of paraplegic subjects closely paralleled the pressure-flow curve of normal skin at pressures tested: 5–15 mmHg. These data are interpreted to demonstrate autoregulation of skin blood flow. Autoregulation in parasacral skin of paraplegic subjects suggests a peripheral mechanism. The occurrence of hyperemia at pressures which exceed the ability of skin to autoregulate suggests that both autoregulation and post occlusion hyperemia may have the same mechanism.
Evaluation of a dual-function pH and PCO2 in vivo sensor
Authors: Coon R. L. , Lai N. C. , Kampine J. P.
Published: December 2017

A newly developed, dual-function pH and PCO2 sensor was evaluated in this study. The sensors were placed in the femoral arteries of dogs anesthetized with sodium pentobarbital. Comparisons were made between systemic arterial pH and PCO2 measured using the sensor and those measured from blood samples drawn at 15-min intervals over a 7-h period using a bench instrument. The mean pH of the bench instrument measurements was 7.43. The mean difference of the sensor measurements from the bench instrument measurements for 207 comparisons was 0.0003 pH +/- 0.061 SD. The mean PCO2 of the bench instrument measurements was 40 mmHg. The mean difference of the sensor measurements from those of the bench instrument for 212 comparisons was -1.43 mmHg +/- 5.17 SD. The sensors performed equally well in the presence of metabolic or respiratory acidosis and alkalosis. The dual-function sensors evaluated in this study are useful for trend monitoring of pH and PCO2 over at least a 7-h period without recalibration. With improvement in the consistency of sensor construction, these sensors will be reliable in vivo sensing devices for blood pH and PCO2 and thus valuable research and clinical instruments.
A shower spray facility for accurate control and rapid changes of skin temperature
Authors: Callin G. D.
Published: December 2017

A shower spray facility (SSF) was built to closely clamp the skin temperature of human subjects, while retaining capability for controlled rapid changes. The subject is enclosed from the neck down in a small chamber containing three water spray manifolds which terminate in 64 small shower heads; the manifolds provide independent temperature control of left leg, right leg, and arm/torso. A dual, solenoid-switched plumbing system for each manifold allows rapid, preset temperature changes. Preliminary tests showed that single thermocouples can accurately indicate average skin temperature for each of the three controlled body areas. Initial experiments with spikes, step functions, and periodic wave forms have proven the SSF as a potentially powerful tool for studying mechanisms of human thermoregulation.
Critical thermal maximum in mice
Authors: Wright G. L.
Published: December 2017

The critical thermal maximum (the colonic temperature of heat-induced convulsion and righting reflex loss) and thermoregulatory response of male mice were examined following I, exposure to colonic temperature (Tco) 42 degrees C; II, a single exposure to the critical thermal maximum (Tco 44 degrees C); AND III, acclimation at ambient temperatures of 15 or 30 degrees C for 14 days. The critical thermal maximum (CTM) was greater in 30 degrees C acclimated mice than 15 degrees C acclimated mice but was unchanged in mice surviving exposure to Tco 42 degrees C or the CTM. The heating time to apparent breakdown of thermoregulation coincident with an explosive rise in the Tco during exposure to ambient temperature 40.8 degrees C was increased (100%) during the 48-h period following exposure to Tco 42 degrees. It appeared that mice exposed to severe, short-term heat stress (Tco 42 degrees) undergo a compensatory increase in their thermoregulatory cooling capacity with little or no change in the upper temperature tolerated. The animals did, however, exhibit the capability for adaptive adjustments of the upper thermal limit during extended exposure to the more prolonged and less severe environmental heat stress of acclimation at 30 degrees C.
Rate of bicarbonate-chloride exchange in human red cells at 37 degrees C
Authors: Klocke R. A.
Published: December 2017

The rate of exchange of bicarbonate and chloride ions across the red cell membrane was studied in a continuous flow rapid reaction apparatus at 37 degrees C. A transmembrane gradient both ions was produced by mixture of cells suspended in a solution of one ion with an isosmotic solution of the other ion. Carbonic anhydrase activity was inhibited by acetazolamide to prevent changes in CO2 concentration during the experiments. Chloride and bicarbonate efflux from cells were studied in separate experiments at each experimental pH. Using a least squares technique, values of chloride and bicarbonate permeabilities were fitted to each pair of independent experiments. Chloride permeability averaged 1.1 (+/- 0.2 SD) X 10–4 cm/s and was not affected by change in pH. Recovered bicarbonate permeabilities varied widely, always remaining at least fivefold greater than chloride permeability. While bicarbonate permeability could not be accurately characterized, it appears to be greater than chloride permeability. Analysis of CO2 transfer with the estimated permeabilities indicates that the bicarbonate-chloride exchange by itself probably does not limit CO2 transfer.
Gas embolism due to intravenous FC 80 liquid fluorocarbon
Authors: Sass D. J. , Van Dyke R. A. , Wood E. H. , Johnson S. A. , Didisheim P.
Published: December 2017

Lethal gas embolism always occurs after FC 80 liquid fluorocarbon is injected intravenously (0.1 ml/kg body mass) in dogs breathing room air but not in dogs breathing oxygenated FC 80 liquid fluorocarbon. Gas embolism is not prevented in dogs that have been injected intravenously with FC 80 when they are exposed to 2 ATA (atmospheres absolute) 20% 02–80% N2, 9 ATA 5% O2–95% He, or 1 ATA 100%, O2. In dogs that die of FC 80-induced gas embolism, free gas in the right atrium contains approximately 0.5 g FC 80/liter, and Po2 and Pco2 in the gas are in equilibrium with their corresponding tensions in right atrial blood. These observations are consistent with the hypothesis that PFC 80 in alveolar gas does not equilibrate with PFC 80 (55 mmHg) in blood. The total gas tension in pulmonary capillary blood containing FC 80 and its vapor thus exceeds the total tension of alveolar gases (atmospheric pressure). Bubbles of O2, CO2, N2, FC 80, and water vapor form in the regions of the pulmonary capillary bed where the total tension of gases dissolved in blood exceeds the absolute blood pressure.
Temperature-induced changes in blood acid-base status: pH and PCO2 in a binary buffer
Authors: Reeves R. B.
Published: December 2017

Equations for proton equilibria of a single-phase binary buffer system have been applied to temperature-induced changes in pH and PCO2 of separated dog plasma at constant carbon dioxide content. Predicted behaviour, measured as deltapH/deltaT and deltalog PCO2 /deltaT, and pH and PCO2 as a function of temperature (range 8–45 degrees C), are in reasonable agreement with theory. Theory predicts and data confirm that deltapH/delta T and deltalog PCO2/deltaT functions of temperature; no single “temperature correction factor” is applicable. Comparison of whole blood with binary buffer equations also shows acceptable agreement between theory and experiment. Blood and separated plasma show similar responses in deltapH/deltaT and deltalog PCO2/delta T when compared over identical temperature intervals. For blood or plasma with initial pH (AT 37.5 DEGREES C) values in the range 7.53–7.45 deltapH/delta T (u/ degrees C) values are -0.0139 (37.5–27.5 degrees C) and -0.0192 (19–7 degrees C); comparable deltalog PCO2/deltaT values are 0.0195 (37.5–27.5 degrees C) and 0.0240 (19–7 degrees C). The charge state of protein components in this system remains nearly constant as temperature varies.
Acclimatization in a hot, humid environment: body fluid adjustments
Authors: Senay L. C. , Mitchell D. , Wyndham C. H.
Published: December 2017

Four trained men worked 4 h/day at 40–50% of their maximum aerobic capacity first for 3 days at 25 degrees C db, 18 degrees C wb and then for 10 consecutive days at 45 degrees C db, 32 degrees C wb. Between days 1 and 2 of heat exposure mean total circulating protein (TCP) and plasma volume (PV) increased 11.6% and 9%, respectively. Preexposure TCP and PV increased until day 6 of heat exposure. Of the protein fractions beta-globulins underwent the largest relative increase. During work movement of protein into and out of the vascular compartment was similar in control and acclimatizing subjects but the latter generally maintained a greater amount of protein and fluid within the vascular volume. There was no evidence of salt and water retention. The increase in vascualr volume was ascribed to transfer of interstitial protein and water to the vascular volume. Regression coefficients indicated significant correlations for changes in plasma volume versus heart rate, stroke volume, and cardiac output during acclimatization. It was concluded that the most critical event in heat acclimatization is the expansion of the plasma volume.
Local regulation of collateral ventilation by oxygen and carbon dioxide
Authors: Traystman R. J. , Batra G. K. , Menkes H. A.
Published: December 2017

The effects of changes in CO2 and O2 on the mechanics of collateral ventilation were studied in anesthetized paralyzed dogs. A doublelumen catheter was wedged into a peripheral airway obstructing a segment of lung distal to the catheter. Through one lumen of the catheter, air, 5% CO2 in air, 10% CO2 in air, 5% O2 in N2, or 5% CO2 in N2 was infused at a constant flow (V). Pressure (Ps) was monitored through the other lumen. At functional residual capacity the resistance to collateral flor Rcoll = Ps/V. When V was interrrupted , the time for Ps to fall 63% was defined as the time constant for collateral ventilation, Tcoll. The effective compliance (Cs′) = Tcoll/Rcoll. When air was replaced by 5% CO2, Rcoll fell 46.3% (+/- SE 2.8) and Tcoll fell 41.5% (+/- SE 3.0). When the CO2 concentration was increased from 5% to 10%, Rcoll fell an additional 9.2% (+/- SE 2.2) and Tcoll fell an additional 5.1% (+/- SE 4.4). When air was replaced by 5% O2 in N2, Rcoll rose 36.6% (+/- SE 6.0) and Tcoll rose 13.6% (+/- SE 10.5). No significant changes in Cs′ were noted. We conclude that varying concentrations of CO2 and O2 provide potent mechanisms for the control of collateral ventillation which may be of importance in the regulation of ventillation perfusion relationships at the local level.
Electromechanical stimulator for presenting moving cutaneous stimuli
Authors: Walsh L. F. , Hantman P. , Blank D. L.
Published: December 2017

Recent interest in the neural processing of complex cutaneous stimuli such as moving stimuli has necessitated more versatile stimulating devices. This article describes the construction and application of a relatively inexpensive instrument, utilizing equipment readily available in most neurophysiological laboratories, which provides a variety of moving cutaneous stimuli of selected velocities, excursions, and directions. The electronic portion of the instrument consists of a logically controlled varable rate integrator wired to conform to the electrical and mechanical characteristics of a Grass P5 plug-in. This circuitry operates the remainder of the instrument which consists of a P5 driver amplifier used to drive the pen motor mechanism that provides the moving cutaneous stimulus.
Analytical refinements in animal calorimetry
Authors: McLean J. A. , Watts P. R.
Published: December 2017

An analysis is presented of a system for indirect calorimetric measurement. Emphasis has been placed upon problems associated with the use of large climate-controlled chambers. The dynamics of gas exchange and the influence of ambient conditions on various parameters have been subjected to physical analysis which has led to the following conclusions: 1) Fast-response measurement of heat production can be achieved even if the size and hence washout time of the chamber is large. 2) Accurate continuous measurement of heat production over long periods, without correction for changes in barometric pressure, is possible if suitable instrumentation is chosen. 3) A method for calibration of a paramagnetic oxygen analyzer achieved high accuracy at low cost. 4) The entire system has been checked by simulation of gas exchange in the chamber, by injection of nitrogen at a known rate.
Oxygen uptake measurements during competitive marathon running
Authors: Maron M. B. , Horvath S. M. , Wilkerson J. E. , Gliner J. A.
Published: December 2017

Oxygen uptakes and running speeds of two marathon runners as well as average slopes of the running terrain were measured approximately every 3 miles of a competitive marathon. The runners had energy expenditures requiring from 68 to 100% of their Vo2 max, confirming previous estimates. As the race progressed, both runners exhibited decreases in V92 while running at similar rates and slopes. At 23.4 miles, one runner was found to be utilizing 4.54 l/min, a value equivalent to his Vo2 max.
Phasic reflux of pulmonary blood flow in atelectasis: influence of systemic PO2
Authors: Newell J. C. , Levitzky M. G. , Krasney J. A. , Dutton R. E.
Published: December 2017

In 16 dogs ventilated with 100% O2, control blood flow to the left lung was 35 +/- 2% of aortic flow. When left lung atelectasis was induced, left pulmonary artery flow fell to 19 +/- 2% of aortic flow. A large retrograde component of flow developed in this pulmonary artery, suggesting that blood flows into the pulmonary arteries of both lungs during systole, but flows back out of the collapsed lung and into the uncollapsed lung during diastole. Systemic PaO2 remained above 78 mmHg. Subsequently, when the ventilation of the right lung was changed from oxygen to room air, systemic PaO2 fell to 64 +/- 3 mmHg and atelectatic left lung flow rose from 19 +/- 2% to 28 +/- 2% f aortic flow. This was associated with a reduction in reflux from the atelectatic lung. These results suggest that the attenuation of flow to an atelectatic lung is more pronounced if systemic normoxemia is maintained by adequate oxygenation of the normal lung.
Respiratory mechanics in normal hamsters
Authors: Koo K. W. , Leith D. E. , Sherter C. B. , Snider G. L.
Published: December 2017

Lung volumes and quasi-static deflation volume-pressure relationships were measured in male golden hamsters anesthetized with pentobarbital. Volume was measured with a pressure plethysmograph, and pleural pressure was estimated by the use of a water-filled esophageal catheter. Mean body weight +/- SE was 122.3 +/-3.0 g, mean lung weight was 0.74 +/- 0.2 g or about 0.6% of body weight. Mean lung volume at 25 cmH2O transpulmonary pressure (TLC25) was 7.2 +/- 0.14 ml, 9.78 +/- 0.17 ml/g lung weight or 5.92 +/- 0.06 ml/100 g body weight. Mean functional residual capacity was 2.4 +/- 0.06 ml or 33.3% of TLC25. Mean vital capacity was 5.2 +/- 0.13 ml. Mean quasi-static compliance of lung was 0.63 +/- 0.03 ml/cmH2O. Chord compliance of chest wall between lung volumes of 1 and 4 ml above RV was 3.39 +/- 0.53 ml/cmH2O. At FRC, the chest wall recoiled inward, so that pleural pressure was positive (1.4 +/- 0.13 cmH2O) and the lung was resisting further collapse. The slope of the lung′s deflation volume-pressure curve changed at FRC, ERV was small (0.36 +/- 0.03 ml), and RV was determined by complete airway closure. Thus the mechanisms determining FRC are unusual and include an influence of airway closure.
A mechanical-reflex oscillator hypothesis for parkinsonian hand tremor
Authors: Stiles R. N. , Pozos R. S.
Published: December 2017

Spectral analysis was performed on postural hand tremor records obtained from 22 parkinsonian subjects. Of these 22 subjects, 18 had postural hand tremor that occurred primarily at a single frequency during any one 16-s period. In general, this tremor occurred at different steady-state frequencies (each calculated over 16 s) between about 4 Hz and 8–9 Hz. This frequency decreased approximately 1 Hz for each 10-fold increase in displacement amplitude (root-mean-square, rms, amplitude determined at 16 cm from the wrist), decreasing from 8–9 Hz at about 30 mum to 3.75–4.0 Hz at about 30,000 mum. The major finding was that the frequency of parkinsonian hand tremor was nearly the same as that for hand tremor from normal subjects when these frequenceis were compared at similar rms displacement levels. This comparison, plus a comparison between other aspects of these two kinds of tremor, indicate that the mechanism for parkinsonian hand tremor is similar to that for large-displacement (greater than 100 mum) hand tremor of normal subjects, i.e., a mechanical-reflex oscillator mechanism.
A digital display of neuronal average firing frequencies
Authors: Sabah N. H.
Published: December 2017

A digital instrument is described which displays on a three-digit, seven-segment display the average firing frequency of a neuron. Averaging is done over essentially consecutive timing intervals of 1, 2, 5, 10, 20, or 50 s. Provision is made for overflow indication and for manual resetting. The design is simple, economical in the number of integrated circuits used, and may be adapted for measuring the average frequency of occurrence of events other than neuronal firing.
Servo respirator constructed from a positive-pressure ventilator
Authors: Remmers J. E. , Gautier H.
Published: December 2017

We have constructed an electronically controlled respirator from three commercially available components: a positive-pressure ventilator, a recorder pen motor, and a differential amplifier. Using negative feedback derived from a tracheal pressure signal, the instrument functions as a servo respirator which provides precise control of tracheal pressure. The system's power and response characteristics are well suited for ventilation of anesthetized cats and dogs. The servo respirator can be used as an externallycontrolled respiratory pump which provides flexibility in selection of the parameters of the ventilatory cycle. Alternatively, it can function as a “demand” respirator which generates transthoracic pressure proportional to efferent respiratory discharge.
A new method of measuring skin humidity
Authors: Reinhart H. , Brenneisen G.
Published: December 2017

A device suitable for the long-time measurement of relative skin humidity is described. This is a simple circuit with a resistance bridge for lithium chloride sensors connected to a digitally steered logic circuit, which causes dried air to stream intermittently through a measuring chamber placed on the skin in such a way that the relative humidity over the skin is maintained at a constant level. The number of switching time periods is proportional to the relative humidity (secretion performance) of the skin and can be counted, recorded, or directly fed into a digital calculator. The apparatus, including a two-channel version with skin temperature recording, has proved useful in sleep investigations under extreme climatic conditions.
A development of the oxyhemoglobin dissociation curve analyzer
Authors: Hahn C. E. , Foex P. , Raynor C. M.
Published: December 2017

The development and improvement of an oxyhemoglobin dissociation curve analyzer is described. PO2 electrode performance was improved by electrochemical means and circuits are described for processing the PO2 and pH signalsfrom the analyzer. A circuit for automatically correcting the curve for Bohr shifts from pH 7.40 is described, and the performance of the Bohr shift unit is verified by experiment. The analyzer produces curves under standard conditions of PCO2 40 mmHg, pH 7.40, and 37 degrees C.
Vagal afferents essential for abdominal muscle activity during lung inflation in cats
Authors: Russell J. A. , Bishop B.
Published: December 2017

Maintained inflation of the lung evokes abdominal muscle activity in anesthetized cats only if the vagus nerves are intact, indicating the importance of vagal receptors. The location of these receptors was determined in 14 anesthetized cats by comparing prevagotomy inflation responses of the abdominal muscles and diaphragm to the responses obtained after section of the thoracic vagi at one of three different levels. The abdominal muscle and diaphragm responses to maintained lung inflation persisted following vagotomy below the roots of the lung or denervation of the heart and great vessels. Denervation at the root of the lung, however, abolished the abdominal muscle response and the Hering-Breuer inflation reflex of the diaphragm. It is concluded that pulmonary receptors are essential for the abdominal expiratory activity, but vagal receptors in the abdomen, esophagus, trachea, heart and great vessels are not.
Myocardial interaction between the ventricles
Authors: Santamore W. P. , Lynch P. R. , Meier G. , Heckman J. , Bove A. A.
Published: December 2017

The myocardial interaction between the ventricles was studied using isolated, flow-perfused, paced rabbit hearts beating isovolumically. In general, increasing left ventricular (LV) volume increased right ventricular (RV) diastolic and developed pressures. In particular, with a peak RV volume (RVV), increasing LV volume (LVV) from zero to two-thirds of its peak volume increase RV diastolic pressure by 1.7 mmHg (N=10, P less than 0.001) and RV developed pressure by 1.5 mmHg (N=10,P less than 0.001). For the LV, small RVV caused LV diastolic and developed pressure to increase, while large RVV increased LV diastolic pressure but decreased LV developed pressure. With a LVV held at two-third of peak volume, increasing RVV from zero to its peak volume caused LV diastolic pressure to increase by 2.5 mmHg (N=10,P less than 0.001) and LV developed pressure to decrease by 2.0 mmHg (N=10, P less than 0.001). The position of the interventricular septum correlated with LV diastolic pressure and RV diastolic and developed pressure changes (P less than 0.01). The results demonstrate that the diastolic and developed pressure-volume relationships of either ventricle can be acutely altered by varying the volume of the other ventricle.
Storage telemetric system for detection of radionuclide tracers in humans
Authors: Bojsen J. , Vadstrup S.
Published: December 2017

An external-storage telemetric device for continuous detection and registration of radionuclide tracers in humans is described. The weight of the system is 600 g. A pocket-sized ECG cassette tape recorder with 24-h continuous registration constitutes the storage unit. Two end-window GM detectors (Philips 18515) are used as surface detectors. Both gamma- and beta-emitters are detected by this equipment. The linear range is 100 counts/s. Renal excretion of [125I]iodide during 30 h in a normal person is shown. The disappearance rates are 0.1 h-1 during the day and 0.05 h-1 during the night. The coefficient of variation of the individual slopes has been calculated to less than 5%. A comparison with the analog radiotelemetric equipment is shown. The storage telemetric equipment can be applied outside the hospital, when the patient is ambulatory.
Simple method of hepatic venous blood sampling in the rat
Authors: Yokota M. , Iga T. , Awazu S. , Hanano M.
Published: December 2017

An improved method of hepatic venous blood sampling by catheterization in rats is proposed and applied to the measurement of hepatic blood flow (HBF) by the continuous ICG infusion method in normal rats and in rats treatedchronically with CC1(4). The value of HBF determined by the present method was 0.90 +/- 0.17 (SD) ml/min per g liver under ether anesthesia, which wasconsistent with the reported values determined by other more complicated methods. The applicability of the present method was also shown in CC1(4) chronic intoxicated rats, to give 0.64 +/- 0.11 ml/min per g liver of HBF.
Pressure-flow-volume relationships in pulmonary circulation of normal highlanders
Authors: Lockhart A. , Zelter M. , Mensch-Dechene J. , Antezana G. , Paz-Zamora M. , Vargas E. , Coudert J.
Published: December 2017

Pulmonary vascular pressures and blood flow were measured with and without unilateral pulmonary arterial occlusion (UPAO) at rest and during exercise in 10 normal highlanders at La Paz, Bolivia (altitude, 3,750 m). In 6 other highlanders at rest and during exercise, pulmonary pressures, flow, andblood volume were measured during air breathing (PIO2 congruent to 100 Torr) and 29–30% oxygen (PIO2 congruent to 150 Torr). During air breathing, pulmonary vascular resistance was elevated at rest and did not change with exercise. Pulmonary arterial pressure rose less at rest with UPAO than duringexercise without UPAO, and pulmonary vascular resistance was less in the former. Raising PaO2 to normal sea-level values had no effects on the pulmonary circulation at rest but prevented to a large extent the rise in pulmonaryarterial pressure during exercise. Hence pulmonary vascular resistance during exercise was lower with oxygen than without. Thus, hypoxic vasoconstriction contributed to the pulmonary hypertension during exercise in normal highlanders. Circumstantial evidence suggests that this is related to the profound mixed venous hypoxemia caused by exercise in a hypoxic environment.
Measurement of tissue oxygen with a fluorescent probe
Authors: Longmuir I. S. , Knopp J. A.
Published: December 2017

Evidence is presented that pyrenebutyric acid is nontoxic at the concentrations required for the measurement of fluorescence quenching by physiological concentrations of oxygen. It appears that this molecule can be used tomeasure tissue oxygen since it does not interfere with oxygen consumption. Equally, tissue components do not interfere with the quenching of fluorescence to such an extent as to invalidate the method. The spatial resolution of the technique is limited by some tissue geometrical factors which do not,however, appear to be great enough to prevent its use to measure intercapillary oxygen gradients.
Effects of CO2 on immediate ventilatory response to O2 in preterm infants
Authors: Albersheim S. , Boychuk R. , Seshia M. M. , Cates D. , Rigatto H.
Published: December 2017

We wanted to know wheter the paradoxical response to CO2 under various background concentrations of O2 in preterm infants was mediated at the peripheral chemoreceptors. In five preterm infants we estimated peripheral chemoreceptor activity using the immediate change in ventilation (first 30 s) when 15%, 40%, 60%, or 100% O2 was substituted for 21% O2. Potentiation between O2 and CO2 was assessed by comparing the response with and without 4% CO2. CO2 enhanced the immediate hyperventilation with hypoxia (P less than 0.005) and reduced the immediate hypoventilation with hyperoxia (P less than 0.025 for 40% O2). This effect of CO2 increased from .00% to 15% O2 (P lessthan 0.05). These findings suggest: 1) CO2 interacts with O2 at the peripheral chemoreceptor level, and 2) because this interaction is more pronouncedwith hypoxia, the flatter CO2 response we observed with hypoxia was probably not mediated through the peripheral chemoreceptors and is likely to be central in origin.
Respiratory muscle action inferred from rib cage and abdominal V-P partitioning
Authors: Grimby G. , Goldman M. , Mead J.
Published: December 2017

We measured separate volume-pressure (V-P) relationships or rib cage anddiaphragm-abdomen in seven human subjects during voluntary relaxation of the respiratory muscles, breathing at rest, during exercise, and rebreathingexpired air. Estimates of separate volume displacements of the two parallelchest wall pathways were based on analysis of rib cage and abdominal anteroposterior diameter changes. The pressure developed across each pathway (transthoracic pressure) was partitioned into two serial pressure drops: transdiaphragmatic pressure and transabdominal pressure. We develop the concept that the relationship of volume displacements of structures to pressures developed by the structures during breathing, as compared to the relaxed state,reflects action of respiratory muscles in the structure. We interpret therelationship of rib cage volume displacements to transabdominal pressure(during breathing vs. relaxation) as indicating action of intercostal and accessory muscles only, the separate action of diaphragm on rib cage being measured by transdiaphragmatic pressure. At rest, the diaphragm is the only importantly active respiratory muscle. During increased ventilation activityofother respiratory muscles appears coordinated to assist the optimize diaphragmatic function.
Temperature regulation during severe exercise with some observations on effects of skin wetting
Authors: Davies C. T. , Brotherhood J. R. , Zeidifard E.
Published: December 2017

The thermoregulatory responses to severe exercise of 1-h duration have been studied in 11 healthy subjects, and the effects of skin wetting have been examined in 6 of them. Measurements in the laboratory included metabolic(M) and total (H) heat production, rectal (Tre) and mean skin (Tsk) temperatures, evaporative sweat loss (E), and peripheral tissue conductance (K). In addition Tre and changes in body weight were measured in 18 conpetitors following a 20-km road race run at approximately 90% of their maximal oxygenintake (Vo2 max). The results showed that Tre was curvilinearly related to %Vo2 max. In contrast Tsk was independent of M, H, E, and %Vo2 max, and reached similar and constant values at the end of exercise in all subjects. E was appropriate for a given H, but K was lower in the sedentary subjects than in the athletes. Skin wetting had no effect on Tre but reduced E by 10%.It is suggested that the pattern of Tre rise in excercise reflected the nature of the controlling system and was not due to a failure of the heat-dissipating mechanisms.
Relationship between evaporation rate of sweat and mean sweating rate
Authors: Tam H. S. , Darling R. C. , Downey J. A. , Cheh H. Y.
Published: December 2017

The rate of evaporation of sweat under a step change of ambient temperature (30–45 degrees C) was compared with the mean sweating rate (MSR)computed from five simultaneous resistance hygrometric measurements. Empirical equations derived for the conditions studied enabled a direct conversion fromhygrometric measurements into real evaporative sweat losses and skin wetness for all phases of sweat evaporation. From five chosen skin areas, forehead, forearm, chest, thigh, and calf, it was found that none of these sites gave a local sweating response close to the MSR. In the subjects withaforehead sweating rate within +/- 39% of the MSR, at least four hygrometricsensors were needed to predict the rate of sweat evaporation. For subjects with higher forehead sweating rates, at least five sensors were necessary to calculate the evaporative sweat loss.
Aerobic power as a factor in women's response to work in hot environments
Authors: Drinkwater B. L. , Denton J. E. , Kupprat I. C. , Talag T. S. , Horvath S. M.
Published: December 2017

Twelve young women, athletes (n = 6) and nonathletes (n = 6), walked on a treadmill at loads equivalent to approximately 30% Vo2 max for two 50-minperiods in three environments: 1) 28 degrees C, 45% rh, 2) 35 degrees C, 65% rh, and 3) 48 degrees C, 10% rh. There were no differences between groupsin rectal temperature, heart rate, evaporative heat loss, or mean skin temperature at 28 or 35 degrees C or during the first work period in the 48 degrees C environment. However, a significantly lower cardiac output (Q) andstroke volume (SV) observed for nonathletes by the 46th min of work at 48 degrees C may explain why no nonathletes were able to complete a 2nd h of workwhile four of six athletes successfully finished the period. It appearsthatin conditions of severe heat stress (48 degrees C) athletes were able to maintain a cardiac output sufficient to meet the metabolic requirements and the large increase in peripheral blood flow for a longer period of time thannonathletes.