bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous and rapidly repeated cardiac output determinations by dye-dilution method
Authors: Hanson John S. , Tabakin Burton S.
Published: December 2017

Reproducibility of cardiac output determinations by dye dilution at rest and during graded treadmill exercise has been assessed by means of simultaneous, rapidly repeated measurements with two Waters 250-A densitometers at both a single sampling site and from both arms. A total of 232 paired-dilution curves was recorded from 10 normal subjects with both densitometers sampling from the same radial artery, and 158 curves from 9 subjects, one densitometer sampling each radial artery simultaneously. Measurements were made with subjects recumbent and during walking varying from level to a 12° treadmill elevation. With both densitometers sampling the same arterial stream cardiac output variation from the two instruments progressively increased from 7% (0.562 liter/min) at rest to 11% (2.773 liter/min) at peak exercise as represented by a standard deviation of the difference related to mean cardiac output. When two arterial streams were being sampled for each injection, variation between instruments amounted to 9–12% of mean cardiac output. Significantly greater variation was observed in curves obtained within 1 min of each other from the same densitometer.

measurement of cardiac output during exercise; cardiac output technique; variation in dye-dilution technique; bilateral cardiac output measurements; upright treadmill exercise

Submitted on July 12, 1963
Octanoic acid absorption and oxidation in humans
Authors: Schwabe Arthur D. , Bennett Leslie R. , Bowman Lance P.
Published: December 2017

The absorption and oxidation of carboxyl-labeled octanoic acid as determined by monitoring of expired C14O2 was studied in 27 subjects. In 12 normal volunteers there was no significant difference in the recovery of C14O2after oral and intravenous administration of the isotopically labeled octanoic acid. Administration of 100 g glucose by mouth did not seem to inhibit octanoic acid oxidation in ten subjects. Infusion of 1 g unlabeled octanoate also did not significantly affect the oxidation of radioactive octanoate in five subjects. These observations in humans tend to confirm animal studies which have shown that octanoic acid is well absorbed from the gastrointestinal tract and rapidly oxidized. The oxidation of small amounts of this fatty acid appears to proceed at the same rate despite moderate blood levels of glucose or octanoic acid. These characteristics of short chain fatty acid absorption and oxidation can be exploited in the study of fat absorption in human subjects.

intestinal absorption; fatty acid metabolism

Submitted on August 14, 1963
Rapid-responding carbon dioxide and oxygen electrodes
Authors: Fatt Irving
Published: December 2017

Redesign of the Severinghaus pCO2 and the Clark pO2 electrodes yields electrodes which are easier to make and assemble. When used with a new membrane material, paraffin-treated Millipore filter paper, the redesigned Severinghaus pCO2 electrode gives 99% response in 15 sec for a 40 mm Hg change in pCO2 in the region of 15–60 mm Hg pCO2 in either gas or water phase. The redesigned Clark pO2 electrode when used with treated Millipore paper gives 99% of final response in 1.24 sec for a 155 mm Hg change of pO2 in the gas phase in the range 0–160 mm Hg pO2. In aqueous solutions this electrode gives 99% response in 30 sec.

Severinghaus electrode; polarographic oxygen electrode; pCO2 measurement; pO2 measurement

Submitted on March 19, 1963
Effect of intra-alveolar fluid on pulmonary surface tension properties
Authors: Johnson John W. C. , Permutt S. , Sipple John H. , Salem El Sayed
Published: December 2017

In 17 anesthetized dogs, 50–150 ml of isotonic saline or human amniotic fluid were instilled into a degassed lobe and after 2–6 hr of spontaneous or artificial ventilation, the lungs were excised. Static pressure-volume and extract surface tension values were then determined on a fluid- and a nonfluid-instilled lobe from each animal. When compared with nonfluid-instilled lobes the fluid-instilled lobes were found to have proportionately smaller volumes at maximum inflation ( P < .02) and during deflation ( P < .001) as well as regional areas with higher surface tension properties ( P < .001). It is proposed that the pressure-volume studies may furnish a useful means of assessing the anatomical extent of alterations in lung surface tension. There was a significant negative correlation between maximum inflation volumes and maximum surface tensions ( P < .001) as well as between the volumes during deflation and the minimum surface tensions ( P < .001). It is concluded that intra-alveolar fluid may inactivate or displace the surface-active material from the alveolar lining membrane.

amniotic fluid; lung pressure-volume studies; lung surfactant

Submitted on April 11, 1963
Anticipatory, exercise, and recovery heart rates of girls as affected by four running events
Authors: Skubic Vera , Hilgendorf Jane
Published: December 2017

The heart rate response to running various distances was studied using five highly trained girls as subjects. A telemetering instrument was employed so that the testing could be done under actual sport conditions. The findings indicated that 1) the anticipatory heart rate just prior to exercise represented 59% of the total adjustment to exercise, 2) the heart rates during exercise were 2.5 times the resting values, and 3) heart rates observed at the end of the 220-, 440-, 880-yard, and mile events were simila

cardiac function; exercise

Submitted on October 22, 1963
Carbon dioxide and pulmonary ventilation in muscular exercise
Authors: Kao F. F. , Michel C. C. , Mei S. S.
Published: December 2017

The effect of endogenous CO2 from exercising muscles and exogenous CO2 from CO2 inhalation was investigated in six pairs of cross-circulated dogs. The exercising hindlimbs of one dog (neural) were perfused exclusively from a second dog (humoral). The ventilatory response of the neural dog during exercise followed the predicted isometabolic hyperbola toward hyperventilation, whereas the ventilation of the humoral dog followed closely the relationship which existed between V and PaCOCO2 during CO2 inhalation. When the neural dog was given CO2 mixtures during steady state of induced exercise, its ventilation increased in a rectilinear function of the PaCOCO2. The V, PaCOCO2 line intersects the isometabolic curve for the exercise level at a PaCOCO2 close to the resting PaCOCO2. A metabolic acidosis developed in the humoral dog, although the blood flow to the perfused hindlimbs appeared to be adequate during muscular exercise.

cross perfusion; neural control of respiration;

humoral control of respiration; CO2 inhalation; muscle blood flow in exercise; perfusion of leg muscle

Submitted on February 19, 1964
Use of heart rate for evaluating cardiac strain during training in women
Authors: Maxfield Mary E.
Published: December 2017

The usefulness of heart rate information to measure cardiac performance is demonstrated for young women during physical training. Data were studied in terms of rate, total number of beats (cardiac cost), and recovery phenomena. Provided work remained constant, training decreased the heart rate during both work and recovery, with corresponding reduction in the sum of beats (total cardiac cost). If working rates are not obtainable, recovery rates as 1) the sum of beats (recovery cost) or 2) Pavg 1, 2, 3, the average of counts taken during the last 30 sec of the 1st, 2nd, and 3rd min of the recovery period, can substitute for total cost as a measure of cardiac performance. The effect of increasing the work accomplished upon cardiac cost and Pavg 1, 2, 3 is discussed and use of a comparative “standard” for assessing cardiac strain from the value of Pavg 1, 2, 3 is suggested.

physical training; work; heart rate; cardiac cost; recovery pulse evaluation; human female

Submitted on March 17, 1964
Effect of carbon dioxide on heart rate
Authors: Mithoefer John C. , Kazemi Homayoun
Published: December 2017

Pentobarbital, by its sympathomimetic effect, produces tachycardia in the dog which is slowed by hypercapnia. The parasympathomimetic effect of chloralose anesthesia, in the intact dog, results in a slow heart rate which is increased by hypercapnia. This opposite response to CO2 appears related to the opposite autonomic effects of the two agents, since when tachycardia is induced in dogs anesthetized with chloralose, they then respond to hypercapnia by cardiac slowing. In experiments reported here and in data available in the literature, there appears to be a correlation between prehypercapnic heart rate and the chronotropic effect of CO2. Results reported here suggest that cardiac slowing by hypercapnia occurs through a direct effect of CO2 rather than pH and that the mechanism has both central and peripheral mediation; the former transmitted by vagal pathway with a specific site of action at the sinus node.

hypercapnia; effect of anesthetics; mechanism of action; CO2-site of action; interaction between initial rate and rate response

Submitted on May 14, 1964
Energy metabolism and body temperature of the ama
Authors: Kang D. H. , Kim P. K. , Kang B. S. , Song S. H. , Hong S. K.
Published: December 2017

Rectal temperature and oxygen consumption were determined in the ama while diving during the summer and winter. In addition, a dietary survey and a physical-fitness test were conducted. The average rectal temperature fell to 35.3 C after 45 min of work in summer (water temp., 22–26 C) and to 34.8 C after 30 min of work in winter (water temp., 10–13 C). The lowest rectal temperature was 33.2 C in summer and 34.3 C in winter. Vo2 increased to nearly 1 liter/min in summer and to 1.4 liter/min in winter. One can calculate that the total extra energy expenditure for diving work is approximately 1,000 kcal/day in both winter and summer. The actual dietary survey showed that the total caloric intake of the ama is 3,000 kcal/day in both summer and winter, which exceeds the daily requirement for nondiving women of comparable age by 1,000 kcal. The protein intake was not different between summer and winter. Physical fitness, as judged by the score of Harvard step-up test, was significantly better in the ama than in the control in both summer and winter. Moreover, physical fitness was poorer in winter as compared to summer in the control, whereas it was excellent throughout a year in the ama.

cold stress; physical fitness

Submitted on January 15, 1964
Aerobic work capacity and plasma FFA turnover
Authors: Issekutz B. , Miller H. I. , Paul P. , Rodahl K.
Published: December 2017

Mongrel dogs with indwelling arterial and venous catheters ran on a treadmill at a speed of 100 m/min and a grade of 15°. Palmitate-i-C14 was infused at a constant rate; the rate of release and the rate of removal of the plasma FFA were calculated. During exercise the O2 uptake was about the same in all animals, but the rate of increase of the blood lactate varied widely according to the physical condition of the animal. ThereΔ was a negative correlation (P <.001) between the changes in the rate of release of FFA (Δ µEq/ kg min) and the rate of increase of lactate. If this latter exceeded 58 mg/100 ml in 30 min, the FFA turnover decreased below the resting level. Since it is known that lactate infusion in itself decreases the release of FFA, it is concluded that the rise of blood lactate during exercise, which reflects the state of aerobic work capacity, is an important factor affecting the participation of the adipose tissue in the exercise metabolism.

exercise and FFA; physical fitness and FFA; blood lactate and FFA

Submitted on April 27, 1964
Continuous radio telemetry of hypothalamic temperatures from unrestrained animals
Authors: Rawson Robert O. , Stolwijk Jan A. J. , Graichen Hans , Abrams Robert
Published: December 2017

A system of radio telemetry has been designed which continuously records body temperatures of unrestrained animals with a resolution of 0.05 C over transmission distances of 100ˑ1,000 ft, permitting observations on free-running animals for indefinite periods of time. Continuous 24-hr recordings were made of hypothalamic temperatures telemetered from cold-acclimatized and unacclimatized dogs living in cold, neutral, and hot environments. During night hours, dogs usually exhibited a decrease in hypothalamic temperature of 0.5ˑ.0 C below daylight levels. Superimposed on the day-night temperature cycle are marked fluctuations of 0.1ˑ0.5 C at a rate of 0.1 C/min. These variations are associated with the level of motor activity, arousal, and with periods of dozing. Shivering in the cold is exhibited even though hypothalamic temperature may be elevated above a level at which no shivering occurs in a neutral environment.

spontaneous hypothalamic temperature variations; cold-acclimatized dogs; day-night temperature cycle

Submitted on June 3, 1964
An analog computer analysis of Cheyne-Stokes breathing
Authors: Milhorn Howard T. , Guyton A. C.
Published: December 2017

A mathematical model of the human respiratory control system has been developed and utilized, with the aid of an analog computer, to study the influence of the various factors of the system in producing or enhancing Cheyne-Stokes breathing. The model is an extension of Grodins' (1954) two-compartment model (lung and tissue compartments) to which circulation times and ventilatory dead space have been added. The study has shown that only two factors, increased arterial circulation time and increased controller gain (Δ minute ventilation/Δ in respiratory center CO2 concentration), can alone produce sustained oscillation. However, several other factors, such as decreased CO2 production rate and a shift of the controller equation [minute ventilation = a function of respiratory center CO2 concentration] to the right so that more CO2 is exchanged per amount of alveolar ventilation, can enhance the oscillation.

periodic breathing; mathematical model

Submitted on May 7, 1964
Oxygen uptake and change in carbon dioxide tension in human blood stored at 37 C
Authors: Lenfant C. , Aucutt C.
Published: December 2017

The changes in Po2 and Pco2 in human blood samples stored at 37 C were measured. In some samples NaF was added. The mean Po2 decay of samples having a Po2 higher than 150 mm Hg was 2.7 mm Hg/min. This corresponded to an O2 consumption (Vo2) of 8.5 x 10-5 ml/ml per min. When NaF was added Vo2was only 6.3 x 10-5 ml/ml per min. The rate of increase of Pco2 was .11 mm Hg/min in samples without NaF. After NaF had been added no change in Pco2 was observed; the reasons for this finding are discussed. Some of the causes of the changes in Po2 and Pco2 have been studied. The storage temperature affects Po2 by .063 mm Hg/min per °C, and the hematocrit by 3.8 x 10-5 mm Hg/min per % Hct. For Pco2, these effects are .003 mm Hg per min per °C and 9.8 x 10-5 mm Hg/min per % Hct, respectively. The reticulocyte and white cell counts are shown to have an essential role in the rate of change of Po2 and Pco2.

blood metabolism; blood storage; oxygen consumption; CO2 production; Po2, Pco2 measurement; hematocrit

Submitted on July 24, 1964
Resting pulmonary diffusing capacity for CO and O2 at high altitude
Authors: Kreuzer F. , Campagne P. Van Lookeren
Published: December 2017

The possible increase of pulmonary diffusing capacity at high altitude is still controversial. During an expedition on Monte Rosa, Italy, experiments were performed on five male subjects, 27–44 years of age, at rest after a sojourn of 7–10 days at an elevation of 4,560 m, using two independent methods. Pulmonary diffusing capacity for CO (DlCO) was determined with the steady-state method at three levels of oxygenation with inspiratory O2 pressures of 80, 150, and 400 mm Hg both at sea level and at altitude. The evaluation of the O2 pressure diffusion gradients in hypoxia, obtained from the alveolar-arterial O2 pressure gra dients and the arterio-alveolar CO2 pressure gradients in hypoxia, permitted the estimation of the diffusing capacity for O2 (DlO02). There was no significant difference between sea level and high altitude in DlCO at the three levels of oxygenation, in the O2 diffusion gradient and in DlCOCO2 with hypoxia.

alveolar-arterial O2 pressure gradient; arterio-alveolar CO2 pressure gradient; high altitude adaptation; acid-base balance of the blood

Submitted on June 17, 1964
Role of diffusion of oxygen in the respiration of tissues at different temperatures
Authors: Farr Douglas A. , Fuhrman Frederick A.
Published: December 2017

The hypothesis is presented that rates of respiration of sheets and slices of mammalian tissues as measured in vitro are usually lower than the true ones because of inadequate oxygenation in thick preparations and excessive damage to cells in thin ones. Data to support the hypothesis were obtained by a study of Qo2 as a function of temperature. When particles were small enough (avian red blood cells and brain homogenates) that diffusion of oxygen did not limit Qo2, a plot of log Qo2 versus 1/T (T = absolute temperature) yielded a straight line. However, when sheets and slices of tissues were used, such plots yielded lines whose slopes decreased with increase in temperature. For rat diaphragm, oxygenation appeared to be inadequate above 18 C. For rat liver, equations are presented for correcting Qo2 for damage caused by slicing and for inadequate oxygenation at higher temperatures. Data for respiration of tissues in 10% oxygen and at 2 atm oxygen pressure supported the hypothesis.

oxygen tension; tissue slices—limiting thickness; tissue slices—thickness and Qo2

Submitted on May 5, 1964
Pressure-volume response of isolated living main pulmonary artery in dogs
Authors: Frasher Wallace G. , Sobin Sidney S.
Published: December 2017

Isolation of the main pulmonary artery by obturation of the right and left branches under conditions which maintained vasal circulation to the wall was achieved by extracorporeal circulation. Pressure-volume response of the segment was measured directly using a reciprocating essentially sinusoidal volume input at rates of 90, 45, and 180 cycles/min. Using volumes which generated physiologic pressures, a steady-state response starting from rest occurred in 300—500 cycles. At steady state the pressure-volume response was linear and unchanged by these cycling rates. The relaxation pattern during the initial phase was consistent with a single mode of response and closely duplicated the stress-relaxation pattern of a single noncycled input of the same volume. In 34 experiments in 11 animals steady-state volume distensibility (DeltaV x 100/V0 DeltaP) was 2.51% cm H2O. Segment geometry was preserved by luminal casting. An ellipsoidal configuration was apparent in the distended state.

pulmonary-artery distensibility; mechanical behavior of arteries; stress-relaxation; geometry of arteries; tethering; viscoelastic properties of arteries; dynamic elastic response; coefficient of distensibility

Submitted on June 16, 1964
Effect of an anabolic steroid on physical performance of young men
Authors: Fowler William M. , Gardner Gerald W. , Egstrom Glen H.
Published: December 2017

The performance of 47 men was measured during a 16-week study. Eight of the men received placebos; nine received 1-methyl-Delta1-androstenolone acetate, an anabolic steroid; 15 received placebos and exercise; and 15 received the drug and exercise. There were no significant differences in strength, motor performance, or physical working capacity between the control and the androstenolone-supplemented groups. Differences in other factors such as vital capacity, limb circumference, and skin-fold thickness were also nonsignificant. Under the conditions imposed in this study there was no evidence that the anabolic steroid increased strength in young men.

ergogenic drugs; strength measurements and physical working capacity under anabolic steroid therapy

Submitted on December 14, 1964
Solubility of krypton and xenon in blood, protein solutions, and tissue homogenates
Authors: Yeh Shu-Yuan , Peterson Richard E.
Published: December 2017

The solubility of krypton and xenon in human serum albumin solutions, in hemoglobin solutions, in human blood, rabbit muscle, and beef brain homogenates has been measured at 1 atm total pressure and at temperatures of 25, 30, and 37 C. The solubilities of krypton in 1 g human albumin were found to be 0.0624, 0.0412, and 0.0195 ml at 25, 30, and 37 C, respectively. The amount of xenon dissolved in 1 g human albumin was found to be 0.2382, 0.1954, and 0.1493 ml at 25, 30, and 37 C, respectively. The amount of krypton and xenon dissolved in 1 g hemoglobin at 37 C was 0.0247 and 0.3661 ml, respectively. The solubility of cyclopropane in human serum albumin and hemoglobin solutions was calculated from the literature. The solubility coefficient of krypton, xenon, and cyclopropane in these biological solutions was found to be the sum of the solubility coefficients of the respective gas in the individual components of the biological solution. The solubilities of krypton and xenon in biological solutions decrease as temperature is raised.

krypton, xenon, and cyclopropane; measurements of gas solubility; human blood—krypton and xenon solubility; human albumin—krypton, xenon, and cyclopropane solubility; human hemoglobin—krypton, xenon, and cyclopropane solubility; rabbit's muscle homogenate—krypton and xenon solubility; beef's brain homogenate—krypton and xenon solubility

Submitted on September 28, 1964
In vivo and in vitro CO2 blood buffer curves
Authors: Brown E. B. , Clancy Richard L.
Published: December 2017

In vivo CO2 blood buffer curves determined on blood drawn from dogs breathing 100% O2, 15% CO2 in O2, and 25–30% CO2 in O2 have a distinctly lower slope than in vitro curves obtained by equilibrating blood from the same animal with 5, 15, and 30% CO2 in O2. The lower slope of the in vivo curve is due to the greater volume of distribution of bicarbonate in vivo. With hyperventilation of 10–15 min duration the in vivo curve is regularly depressed so that its slope is essentially the same as the in vitro curve. This depression is probably due to an increase in blood lactic acid. The increase in total bicarbonate in the extracellular fluid, resulting from an increase in CO2 tension, is more than can be accounted for by the increase in blood. This suggests that some source of buffer, other than blood, is available to the interstitial fluid.

Note:

(With the Technical Assistance of Patricia Elledge and Rita Herman)

bicarbonate

Submitted on October 28, 1964
Effect of local exercise of forearm muscles on forearm capacitance vessels
Authors: Bevegård B. Sture , Shepherd John T.
Published: December 2017

Normal subjects were studied to determine whether exercise of the muscles of one forearm causes changes in venous tone in that forearm by some local mechanism. Forearm venous pressure-volume relationships and the pressure in “isolated” vein segments were unchanged after exercise of forearm muscles. Following venous occlusion, the forearm volume increases and reaches a plateau later than forearm venous pressure. This delayed volume change increased with increasing venous filling rate regardless of whether this was accomplished by exercise or by other means. Thus, the local mechanism which dilates resistance vessels in active muscles does not seem to change the contractile state of the muscle in the capacity vessels. The viscous properties of the venous wall, however, act to damp the volume oscillations in intervals between muscular contractions when arterial inflow and venous filling rate are high. The ratio between initial rate of rise in forearm venous pressure and volume following venous occlusion could not be used as an index of active changes in tension of the smooth muscle of the capacitance vessels.

strain-gauge plethysmography; isolated vein segments; venous response to varying filling rates; venous response to local exercise; veins and exercise

Submitted on November 16, 1964
Distribution of blood flow and ventilation in saline-filled lung
Authors: West J. B. , Dollery C. T. , Matthews C. M. E. , Zardini P.
Published: December 2017

The airways of degassed greyhound lungs were filled with saline and the lung suspended in a saline bath and perfused with blood. The distribution of blood flow was measured by injecting aggregated I131-labeled albumin into the pulmonary artery and scanning the lung from bottom to top when the particles had been trapped by the small vessels. After equilibrating the alveolar saline with more inhaled iodinated albumin and scanning again, blood flow per unit alveolar volume could be calculated. With vascular pressures which have been shown to cause great topographical inequality of blood flow in the gas-filled lung, blood flow was evenly distributed on the average in the saline-filled preparation, presumably because the hydrostatic pressures difference in the blood vessels were balanced by corresponding pressures in the airways. The topographical distribution of a single breath of iodinated albumin in saline was found to be uniform but there was striking stratified inhomogeneity along the airways. This was due to the slow diffusion rate of albumin in saline and similar effects were seen with inhaled radioactive oxygen and carbon dioxide dissolved in saline. The results show that when the mammalian lung breathes saline, diffusion limitations for oxygen and carbon dioxide within the airways may be an important factor.

aerosols; hydrostatic pressures; increased acceleration; airways diffusion; topographical differences; gas exchange; pressure-flow relations

Submitted on March 18, 1965
A mathematical and physiological model for early distribution of radioiodide in man
Authors: Hays Marguerite T. , Wegner Louis H.
Published: December 2017

A model is proposed for the early distribution of radioiodide in man. This model is formalized as a set of eight simultaneous differential equations, each predicting the rate of change of radioiodide in a compartment. These equations have been fitted by numerical integration on a digital computer to plasma curves from sessions with and without aspiration of gastric contents, curves of the aspirated radioiodide, and thyroidal and renal plasma clearance rates. In this model, plasma radioiodide is distributed reversibly to the erythrocytes, interstitial fluid (space E) and a “slowly diffusible space” (space C). Distribution to the thyroid and kidney is irreversible. Radioiodide distributed to the salivary glands and gastric mucosa must pass through a gastrointestinal cycle before eventual reabsorption from the intestine. Successive compartments of this cycle are the “inaccessible gastric space” (space M), free gastric juice (space S) and the intestine (space D). All of the modes of distribution mentioned are governed by rate constants except for transfer from space S to space D, which occurs as a complete transfer at a fixed interval tau.

gastrointestinal iodide cycle; pooling of radioiodide in gastrointestinal tract; plasma radioiodide curve; multicompartment model; iterative solution of mathematical model

Submitted on September 28, 1964
Oxygen intake and cardiac output during maximal treadmill and bicycle exercise
Authors: Miyamara Miharu , Honda Yoshiyuki
Published: December 2017

Oxygen intake and cardiac output were measured in 17 male students, aged 18–23 years, during maximal treadmill and bicycle ergometer exercise with stepwise incremental loading and constant loading. The average values of oxygen intake and cardiac output during treadmill exercise were higher than during bicycle ergometer exercise, either with incremental loading or constant loading. These differences were statistically significant (P < 0.001–0.01). No statistically significant differences are found in stroke volume, whereas significant differences were seen in maximum heart rate between all four different modes of exercise. Arteriovenous oxygen differences were higher during treadmill exercise than during bicycle ergometer exercise. It is suggested that lower maximum oxygen intake during bicycle ergometer exercise is related to the lower maximum cardiac output and lower arteriovenous oxygen differences as compared with treadmill exercise.

maximum oxygen intake; maximum cardiac output; maximum heart rate; stroke volume during maximal exercise; arteriovenous oxygen difference during maximal exercise; comparison of treadmill and bicycle exercise
A bidirectional respiratory flowmeter using the hot-wire principle
Authors: Yoshiya I. , Nakajima T. , Nagai I. , Jitsukawa S.
Published: December 2017

We have devised a bidirectional respiratory flowmeter using the hot-wire principle. The flow-direction sensor consists of a pair of tungsten wires strung parallel to the platinum hot-wire one on each side of the platinum wire. When the gas stream passes through the transducer, the upstream wire is cooled and the downstream wire is heated by the gas stream producing a temperature difference between the two tungsten wires. The difference in resistance thus produced between them is detected and amplified by a differential amplifier whose output serves as a triggering signal of flow inversion. The switching times of the flow inversion of the present instrument are 3 ms during panting and 10 ms during quiet breathing, when the distances from the platinum wire to the tungsten wires are 1.6 mm. Artifacts produced by the delay in switching are practically negligible. The flowmeter can be adapted for many kinds of respiratory flow measurement, except under the condition when inflammable gases are used.
Correction factors in skin temperature measurement
Authors: Jirak Z. , Jokl M. , Stverak J. , Pechlat R. , Coufalov H.
Published: December 2017

In 14 persons the skin temperature has been measured by means of thermistor thermometer. The influence of the shape of the probe and the pressure exerted on the resulting value of the skin temperature has been proved. In 10 additional men the relation of the temperature difference (deltaT) to the exerted pressure (P) was determined, the regression equations were derived for relation deltaT/P, and the correlation coefficients for recalculation of the temperatures measured by thermistor thermometer with the pressure exerted 20 g to values determined by thermovision. The skin temperature values determined by thermography were used in 24 formulas (3–16 points) for calculation of mean skin temperature. The differences of the means in determining the optimal method (16 points) were evaluated by the t-test and by the percentage expression of aggrement for criteria plus or minus 0.1, plus or minus 0.2, plus or minus 0.5, and plus or minus 0.1 degrees C. For precise laboratory work 10 points of measurement are recommended; for measurement in the field 6 points of measurement are enough. Orientational measurement can be performed very well by means of Ramanathan method (4 points).
Comparison of water immersion and saline infusion as a means of inducing volume expansion in man
Authors: Epstein M. , Pins D. S. , Arrington R. , Denunzio A. G. , Engstrom R.
Published: December 2017

Although previous studies have demonstrated that water immersion to the neck (NI) results in both central hypervolemia and a significant natriuresis, it is unclear whether the magnitude of the “volume stimulus” of NI is comparable to that induced by the extracellular fluid volume expansion (ECVE) induced by acute saline administration. The present study was undertaken therefore to compare the natriuresis induced by these two different stimuli. All subjects were studied on four occasions while in balance on a diet containing 150 meq of sodium and 80 meq of potassium daily: seated control; seated immersion; and saline administration in both the seated and recumbent posture. The increment in UNaV during NI was indistinguishable from that of seated saline. Similarly, the kaliuretic response during NI was similar to that induced by seated saline infusion. In contrast, supine saline infusion resulted in a greater increment in UNaV than either NI or seated saline. The present data indicate that the “volume stimulus” of immersion is identical with that of standard saline-induced ECVE in normal seated subjects. Furthermore, the ability of NI to induce a natriuresis without a concomitant increase in total blood volume and with a decrease in body weight, rather than the increase which attends saline infusion, suggests that NI may be a preferred investigative tool for assessing the effects of ECVE in man.
Orthostatism and heat acclimation
Authors: Shvartz E. , Strydom N. B. , Kotze H.
Published: December 2017

Three groups of subjects (6 subj in each group) underwent the following precedures: group A was given a 20-min head-up tilt at 21 degrees C followed by 4 h of exercise at 33.9 degrees C DB, 32.2 degrees C WB, and a repetition of tilting after exercise in heat; group B underwent the same procedure at 21 degrees C; group C was tilted at 21 degrees C, rested in heat for 4 h and was retilted in heat. The above procedures were repeated for 8 days, and on the last day groups B and C underwent the same treatment as group A. Group A showed the usual decreases in heart rate and rectal temperature and an increase in sweat rate on acclimation. This corresponded to marked improvements in heat-orthostatism. While five subjects in group A fainted during post-exposure tilting on the first exposure, none fainted on the last day. Resting in heat (group C) did not cause any acclimation to work in heat. This corresponded to poor heat-orthostatism after the work-heat procedure when five subjects fainted. Mild training at 21 degrees C (group B) resulted in minor improvements to work in heat as evident by some improvements in heart rate responses after the 1st and 2nd h of exposure. This corresponded to better heat-orthostatism and fewer men fainting than in group C. The results indicated that heat-orthostatism improves on acclimation to the same extent as exercise heart rate and rectal temperature.
Effects of O2 on the ventilatory response to CO2 in preterm infants
Authors: Rigatto H. , De La Torre Verduzco R. , Gates D. B.
Published: December 2017

To measure the effects of O2 on the ventilatory response to CO2 in preterm infants, we studied eight babies (birth wt 1–2 kg; gestational age 32–36 wk) 10 times during the first 11 days of life. After breathing 21% O2 for 3 min, they were given 15%, 21%, 40%, or 100% O2 for 4 min and then 2% CO2 plus the various concentrations of O2 for 4 min each. The mean slopes of the CO2 response curves were 0.013, 0.027, 0.034, and 0.056 1/(min-kg-mmHg PACO2) with 15%, 21%, 40%, and 100% inspired O2, respectively. Thus, the more hypoxic the infant, the flatter was the response to CO2. These findings suggest that in preterm infants 1) the response to inhaled CO2 is the reverse of that seen in adult man where the higher the inspired O2 concentration, the flatter the response, and 2) the respiratory center is depressed during hypoxia.
Depression of ventilation hypoxia in man
Authors: Weiskoff R. B. , Gabel R. A.
Published: December 2017

In five normal male subjects, ventilation, PaO2, and PaCO2 were measured during the rapid progressive isocapnic production of hypoxia (5 min) and during the equally rapid isocapnic reversal of hypoxia. At similar PaO2, PaCO2, and pH, ventilation was less at a time when alveolar PO2 was increasing than when alveolar PO2 was decreasing. We interpret these results as showing that human ventilation is depressed by mild-to-moderate hypoxia (40–60 Torr), that such depression is probably central, and that it is ordinarily masked by peripheral chemoreceptor stimulation. We are not able to distinguish whether the ventilatory depression is caused by decreased central chemoreceptor PCO2 due to an increase in cerebral flow, direct hypoxic depressing of the central respiratory mechanism, or both.
Force-velocity relations and fiber composition in human knee extensor muscles
Authors: Thorstensson A. , Grimby G. , Karlsson J.
Published: December 2017

Standardized measurements of dynamic strength of the kneee extensor muscles were performed in 25 healthy male subjects (17–37 yr) by means of isokinetic contractions, i.e., knee extensions with constant angular velocities. Overall variation between double determinations of maximal torque throughout the 90 degrees arc of motion (0 degrees = fully extended leg) averaged 10% for the different constant velocities chosen. At any given angle of the knee the torque produced was higher for isometric than for dynamic contractions. Dynamic torque decreased gradually with increased speed of shortening. Peak dynamic torque was reached at knee angles in the range: 55–66 degrees, with a displacement toward smaller knee angles with higher angular velocities. Correlations were demonstrated between peak torque produced at the highest speed of muscle shortening and percent as well as relative area of fast twitch fibers in the contracting muscle. In addition muscles with a high percentage of fast twitch fibers had the highest maximal contraction speeds. These observations on intact human skeletal muscle are consistent with earlier findings in animal skeletal muscle preparations.
Total and regional cerebral blood flow during moderate and severe exercise in miniature swine
Authors: Foreman D. L. , Sanders M. , Bloor C. M.
Published: December 2017

To determine the influence of exercise on cerebral blood flow, we ran 14 swine at 3–6 mph and at 0–10% grades on a treadmill for 30 min at moderate and severe levels of exercise. Measuring heart rate, cardiac output, and aortic pressure via implanted probes, we injected 15-mum radiolabeled microspheres via the left atrium before and during exercise. We measured their distribution by gamma spectrometry, determining total cerebral blood flow, regional blood flow, and ratio of flow to gray and white matter. Heart rate, cardiac output, and aortic pressure rose progressively with increasing exercise. Total cerebral flow resembled that reported in humans, i.e., it did not change significantly with exercise. Regional flow distribution also failed to change significantly with exercise. The ratio of gray to white matter flow did not change except to the cerebellum where it rose significantly from resting values at both moderate and severe exercise. Gray matter received more flow than white matter during all three conditions of observation. Cerebral blood flow was remarkably constant during even severe exercise.
Method for measuring hepatic uptake of oxygen or other blood-borne substances in situ
Authors: Lautt W. W.
Published: December 2017

A preparation is described by which hepatic arterial blood flow and portal venous blood flow can be accurately and continuously measured while simultaneously providing a method by which multiple blood samples can be taken from the hepatic artery, portal vein, and hepatic vein without disrupting hepatic hemodynamics or causing hemodilution. By this means hepatic uptake or release of blood-borne substances can be measured in situ and correlated with hemodynamic parameters. In 13 splenectomized cats, oxygen uptake by the denervated liver was 4.5 +/- 0.3 ml . min-1. 100 g-1 of tissue, representing 54% of total oxygen removed by the splanchnic bed. The hepatic hemodynamics determined by this method are similar to those reported by others in vivo and the metabolic state of the liver remained stable for at least 2 h during which an average of 29 blood samples were taken. Advantages of this preparation over other methods of obtaining similar data are discussed.
Polymer membrane sensors for continuous intravascular monitoring of blood pH
Authors: LeBlanc O. H. , Brown J. F. , klebe J. F. , Niedrach L. W. , Slusarczuk G. M. , Stoddard W. H.
Published: December 2017

A new type of pH sensor suitable for chronic intra-vascular implantation by virtue of its small size, flexibility, and ruggedness was constructed and evaluated. The pH-sensitive element was a thin film of an elastromeric polymer made ion permselective to proteons by adding a lipophilic, specific H+-ion carrier. This was coated onto small diameter silver wires to form sensors. In preliminary trials in anesthetized dogs, the sensors permitted continuous, accurate in vivo blood pH measurement with rapid response (less than 0.1 s).
Sweating responses during changes of hypothalamic temperature in the rhesus monkey
Authors: Smiles K. A. , Elizondo R. S. , Barney C. C.
Published: December 2017

A technique is presented for preparing a durable thermode implant in the hypothalamus of the rhesus monkey. In unanesthetized monkeys implanted with thermodes in the anterior hypothalamic area of the brain, a linear relation was found between local sweat rates on the general body surface and clamped hypothalamic temperature. Changes in skin temperature were found to shift the hypothalamic set-point temperature at which sweating began but did not alter the gain of the hypothalamic temperature-sweat rate relationship. This study provides direct support for the concept that central brain temperature and skin temperature interact additively in the control of sweating in higher primates. Due to the very close similarity between these responses and those seen with indirect measurements of brain temperature in men, the rhesus monkey is seen as an excellent experimental analogue for studying human thermoregulation.
Uterine work in parturition
Authors: Kriewall T. J.
Published: December 2017

This paper presents a theoretical analysis relating work expended by the uterus to the synergistic relationship between intrauterine pressure (IUP) and cervical dilatation (CD). By utilizing a geometrical model for the fetal presenting part which is assumed to be in contact with the cervix, the changes in internal volume of the uterus with each contraction can be shown to be functionally related to cervical dilatation. Thus work, expressed in terms of foot-pounds, can be calculated using the integral of pressure times incremental volume. By simulating intrauterine pressure and cervical dilatation with continuous analytical wave forms, the alterations required in uterine work to dilate the cervix are calculated for various wave-form aberrations which are seen in clinical situations. The wave-form aberrations are applied to an elastic cervical model as well as a viscoelastic model. Using the principles of thermodynamics the areas of the fetouterine complex which absorb the work generated by the contractions are defined. It is shown that the efficiency of the contractions to dilate the cervix can be calculated by evaluating the work expended in these various areas of energy absorption. The purpose of this paper is to present the theory upon which clinical findings in obstetrics can be based so that conclusions drawn will be technically sound.
Effect of inspired volume on closing volume
Authors: Holtz B. , Bake B. , Oxhoj H.
Published: December 2017

Closing volume (CV) was ?EASURED WITH THE RESIDENT GAS TECHNIQUE IN 12 HEALTHY SEATED SUBJECTS AGE 22–70 YR, AND IN 8 SUBJECTS WITH THE BOLUS TECHNIQUE. Various volumes were inspired (Vi range: 20–100% vital capacity) fromresidual volume and CV was assessed on the subsequent recording of expired volume versus gas concentration. The results indicate that the resident gastechnique may erroneously underestimate CV at reduced Vi in conformity withcalculations which predict that during expiration, after a certain reduced VI, the nitrogen concentration is identical in the most basallung region and at the mouth. CV obtained with the bolus technique decreased linearly with reduced Vi and the effect appeared to be age dependent according to the equation CV50/CV100=0.0078 X age +1.18, where CV50 and CV100 denote the bolus CV corresponding to Vi=50% and 100% of vital capacity. Therefore, in older subjects, during tidal breathing, airways appear to close at substantially lower lung volume than previously considered.
Superoxide dismutase (SOD) activity in hypoxic mammalian systems
Authors: Liu J. , Simon L. M. , Phillips J. R. , Robin E. D.
Published: December 2017

Superoxide Dismutase (SOD) activity was compared in rabbit peritoneal macrophages (ambient PO2 approximately 15 Torr) and alveolar macrophages (ambient PO2 approximately 100 Torr) and in brain, lung, cardiac muscle, and skeletal muscle of chromically hypoxic mice(ambient PO2 approximately 50 Torr) and normoxic mice (ambient PO2 approximately 150 Torr). Peritoneal macrophages (PM) have significantly less SOD activity than alveolar macrophages (AM) (PM: 2.94 +/- 0.49 (mean +/- SD); AM:6.03 +/- 1.60 units-mg protein -1 (P less than 0.01)). SOD activity of lung and brain homogenates from the hypoxic mice was significantly less than from the normoxic controls. Heart and skeletal muscle SOD activities were not significantly different. These studies show that limitations of O2 supply are associated with reductions in SOD and are consistent with the thesis that SOD plays an important role in protection against oxygen toxicity in mammalian systems.
Fluid and electrolyte shifts during bed rest with isometric and isotonic exercise
Authors: Greenleaf J. E. , Bernauer E. M. , Young H. L. , Morse J. T. , Staley R. W. , Juhos L. T. , Van Beaumont W.
Published: December 2017

Fluid and electrolyte shifts were measured in seven men (19–21 yr) during three 2-wk bed rest (BR) periods, each of which was separated by a 3-wk ambulatory recovery period. During two of the three BR periods they performed isometric exercise and isotonic exercise. No prescribed exercise was given during the other BR period. On day 4 of BR, plasma volume decreased (P less than 0.05) 441 ml (-12.6%) with no exercise, 396 ml (-11.3%) with isometric, and 262 ml (-7.8%) with isotonic exercise; the decreases (NS) of extracellular volume were -4.4%, -2.6%, and -2.7%, respectively. By day 13 of BR, plasma volume stabilized at the lower level with isometric and isotonic exercise and continued to decline with no exercise; but the extracellular volume returned to or above control levels due to an overshoot of the interstitial volume of +320 to +430 ml (2.0–2.7%) that was about equal to the plasma volume loss. During BR there were isocontent losses from the plasma of protein, albumin, globulin, urea N2, uric acid, creatinine, Na, Cl, osmolarity, P, and glucose that were not influenced by either exercise regimen. However, the blood, red blood cell, and plasma volumes, and the Ca and K contents were stabilized during BR by both exercise regimens. The results suggest that during BR, preservation of the extracellular volume takes precedence over maintenance of the plasma volume, and this mechanism is independent of the effects of isometric or isotonic exercise.
Metabolic and cardiovascular responses to norepinephrine in trained and nontrained human subjects
Authors: LeBlanc J. , Boulay M. , Dulac S. , Jobin M. , Labrie A. , Rousseau-Migneron S.
Published: December 2017

Forty young male adults, aged 18–30 yr, with maximal oxygen intake (VO2 max) varying between 35 and 76 ml-kg-1-min-1 were studied. The fasting subjects were perfused for 15 min with saline and thereafter for 30 min with norepinephrine (0.1 mug/kg per min). Blood variables were determined at the end of slaine perfusion, at 15 and 30 min during norepinephrine perfusion and 15 min after the end of NE perfusion. Trained subjects are characterized by lower basal plasma glucose and insulin concentration. NE perfusion produced a larger increase in plasma glucose in the trained subjects. Levels of insulin in the postperfusion period were smaller in the trained group. Serum free fatty acids (FFA) and glycerol increased less in the trained subjects during NE perfusion and this difference persisted in the post-perfusion period. During NE perfusion, blood lactate increased only in the nontrained subjects. Initial heart rate and blood pressure were lower in trained subjects but, during NE perfusion, elevated levels of blood pressure and decreased levels of heart rate were comparable in both groups. Because of similarities in responses to exercise and to NE in trained subjects, the results of the present study suggest a possible role for NE in exercise training.