bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulmonary ventilation, blood gases, and blood pH after training of the arms or the legs
Authors: Rasmussen B. , Klausen K. , Clausen J. P. , Trap-Jensen J.
Published: December 2017

In two groups of young healthy subjects who performed arm training (N = 5) and leg training (N = 5), respectively, the respiratory adaptation to submaximal exercise with trained and nontrained muscle groups was compared by measurement of the ventilatory equivalent (Ve/Vo2, pH, and blood gases (Pco2, Po2, and So2) in arterial blood and in venous blood from exercising extremities. After training Ve/Vo2 was significantly reduced during exercise with trained muscles, but unchanged during exercise with nontrained muscles. The reduction in Ve/Vo2 was closely related to a less pronounced increase in heart rate and in arterial lactate content, but showed no quantitative correlation to changes in arterial adaptations in trained muscles are mainly responsible for the reduction in Ve/Vo2. After training during exercise with trained as well as nontrained muscles a shift to the right of the blood oxygen dissociation curve occurred as extremities was lower while corresponding Po2 was higher.
Excretion of retained fluoride in man
Authors: Spencer H. , Kramer L. , Osis D. , Wiatrowski E.
Published: December 2017

In fluoride studies performed in man the excess fluoride excretions in urine and stool over and above the base-line excretions were determined following the discontinuation of fluoride supplements. The fluoride supplements contained either 9.1 mg fluoride as sodium fluoride, given daily for 32 days, or 7.6 mg fluoride as fish protein concentrate (FPC), given daily for 26 days. Following discontinuation of these fluoride supplements the excess fluoride excretions were low and of short duration, in most cases for 6–12 days. Since the fluoride supplements were given for a known period of time, the fluoride retention could be calculated from the fluoride balances, and the excess fluoride excretion corresponded to 9.1% of the retained fluoride given as NaF and to 14.1% of the retained fluoride given as FPC. The excess fluoride was predominantly excreted via the kidney, i.e., 87% of the total excess fluoride excretion was passed in urine and only 13% in stool.
A simple relation between performance in running and maximal aerobic power
Authors: Margaria R. , Aghemo P. , Pinera Limas F.
Published: December 2017

As the cost of running amounts to about 1 cal per m covered and per kg of body weight, when the aerobic power (VO2, ml/min kg) is known and the energy from glycolysis assumed to be about equal to the energy from oxidations in 1 min, the time employed to cover a given distance can be predicted: a nomogram is given to facilitate the calculation. Conversely from the time employed to cover a given distance the aerobic power in VO2, ml/kg times min can be calculated.
Apparatus for intracellular electrophysiological measurements at 200 ATA
Authors: Henderson J. V. , Morin R. A. , Lanphier E. H.
Published: December 2017

An apparatus has been constructed and tested at pressures to 200 ATA which meets the basic requirements for intracellular microelectrode work. Standard microelectrodes, unaffected by pressure in this range, were used with lobster axon and frog sartorius fibers and action potentials have been recorded at pressure up to 151 ATA. The chamber itself has a simple roll-in door and a modular design that recommends it as a highly convenient multipurpose vessel for work at moderately high pressures.
Nonshivering thermogenesis and cold resistance in rats under severe cold conditions
Authors: Heroux O. , Page E. , Leblanc J. , Leduc J. , Gilbert R. , Villemaire A. , Rivest P.
Published: December 2017

Following either chronic exposure to 6 degrees C, or outdoor winter exposure, or chronic treatment with tyramine rats were exposed to -40 degrees C and their oxygen consumption and colonic temperature monitored. Fall in body temperature with time of exposure followed a sigmoid curve which had an inflection point around 32.9 degrees C. Both the time required for body temperature to reach this point and hypothermic resistance defined as the total O2 consumed up to the inflection time were useful indices of resistance to severe cold; Three days before the cold tests, capacity for norepinephrine-induced nonshivering thermogenesis was measured in all animals by examination of their metabolic response to tyraminemthe magnitude of response to tyramine correlated well with hypothermic resistance only for those rats chroncally treated with tyramine. It is concluded that it is impossible to predict with any reasonable degree of confidence the cold resistance of a rat from its tyramine response. In cold-acclimated rats, factors in addition to norepinephrine sensitivity are significantly involved in cold resistance and deserve further studies.
Effects of mechanical loading and hypercapnia on inspiratory muscle EMG
Authors: Altose M. D. , Stanley N. N. , Cherniack N. S. , Fishman A. P.
Published: December 2017

The electromyograms of the diaphragm and an external intercostal muscle were analyzed to see if the effects of hypercapnia on inspiratory muscle electrical activity could be distinguished from those of mechanical loading and to determine whether changes in inspiratory muscle electrical activity were a sueful measure of CO2 response during mechanical loading. Anesthetized dogs were studied: 1) during progressive hypercapnia without mechanical loading, 2) during flow-resistive and elastic loading at constant PCO2, and 3) during progressive hypercapnia and mechanical loading. Both mechanical loading and hypercapnia increased total inspiratory diaphragmatic and intercostal muscle electrical activity. However, inspiratory duration was increased by mechanical loads but reduced by hypercapnia. Because of these changes in inspiratory duration, the average rate of diaphragmatic electrical activity remained unaffected by mechanical loading before and after vagotomy but was increased by hypercapnia. In contrast, both hypercapnia and mechanical loading increased the average rate of intercostal muscle electrical activity. There was a greater increase in both total and average rate of intercostal muscle electrical activity during hypercapnia in the presence of mechanical loading than during unloaded breathing. However, the change in total and average rate of diaphragmatic electrical activity with PCO2 was unaffected by added mechanical loads. These results suggest that diaphragmatic but not intercostal muscle electrical activity can be used as an index of CO2 response even during mechanical loading.
Specificity of autonomic influences on cardiac responses during myocardial ischemia
Authors: Kaspar R. L. , Barnes G. E. , Peterson D. F. , Bishop V. S.
Published: December 2017

A possible role of the autonomic nervous system in the left ventricular response to acute regional myocardial ischemia was sought in conscious dogs instrumented for measurement of left ventricular pressure, internal diameter, and aortic flow. Ischemia produced by occluding the left circumflex coronary artery caused tachycardia and reduced contractility. Changes during control occlusions were compared with those during occlusion.s after beta-adrenergic blockade, parasympathetic blockade, and combined sympathetic and parasymphatetic blockade. Beta-blockade did reduce the tachycardia and slightly reduced left ventricular diameter changes in response to coronary occlusion. Results obtained in animals following surgical cardiac sympathectomy indicated reduced tachycardia and no effects on other parameters. The principal effect of parasympathetic blockade was to augment the increase in end diastolic diameter during occlusion Right atrial pacing indicated this change was due to higher initial heart rates. Combined parasympathetic and sympathetic blockade did not alter inotropic responses to coronary occlusion. Results indicated that inotropic support due to changes in activity in autonomic nerves is not increased during acute occlusion of the left circumflex coronary artery.
Resistance of intrathoracic airways of healthy subjects during periodic flow
Authors: Finucane K. E. , Dawson S. V. , Phelan P. D. , Mead J.
Published: December 2017

The resistance and reactance of lower airways were measured as functions of the frequency and amplitude of periodic flow in three healthy subjects by relating flow, produced with a piston pump, to the difference between lateral tracheal and alveolar pressure, estimated plethysmorgraphically. Resistance consistently increased with frequency; reactance was small never exceeding resistance. This result cannot be explained by distortion of velocity profiles by inertia because, in long pipes, resistance increases only when inertial forces are large and reactance exceeds resistance. Theoretical analyses of airway resistance suggested that the results reflected inhomogeneity. In lung models which considered airway wall distensibility and inertial reactance of airways, resistance increased with frequency and inertial reactance was small. These results imply that in health, as in lung disease, resistance is determined by the distribution of resistance and reactance within the lung and is not simply the total resistance of the individual airways. As flow amplitude increased at constant frequency, flow-pressure relationships became distorted and resistance increased, due probably to motion of airway walls and further distortion of velocity profiles
Estimation of alveolar pressure during forced oscillation of the respiratory system
Authors: Finucane K. E. , Mead J.
Published: December 2017

A method for obtaining a continuous estimate of alveolar pressure (PAlv) during periodic flow is described; it was developed to improve the precision of measurements of airway and respiratory tissue impedance using the improved resolution of relatively high-frequency (approximately 5 Hz) singlas. The respiratory system was modulated with a piston pump, and lung volume and the volume change due to compression and expansion of alveolar gas were measured plethysmorgraphically; these signals and an analog divider were used to obtain a continuous solution of Boyle's law during flow. The plethysmorgraph was of the “flow” type; with it volume changes at frequencies up to 10 Hz and with rates of change up to 6 l/s were measured without amplitude or phase distortion. The method permits control of frequency and flow amplitude during PAlv measurement and calibration of PAlv in the absence of an active chest wall. However, it is technically complex.
Recording the cardiac interbeat interval distribution
Authors: Mansourian P. , Masironi R. , Nicoud J. D. , Steffen P.
Published: December 2017

A compact device is described, which picks up the R wave of the ECG, calculates the duration of successive interbeat intervals, classifies them in eight classes and stores the receptive counts in an integrated-circuit register. The distribution of intervals counted over the experimental period is retrieved through a separate numerical readout device.
Plasma volumes and constituents of heat-exposed men before and after acclimatization
Authors: Senay L. C.
Published: December 2017

Five men underwent a 2-wk exercise regimen and were then exposed to 45 degrees C db, 28 degrees C wb, wind speed 1 m/s for 12 h while at rest. Body weight was maintained with 0.1% saline. One week later the exposure was repeated without rehydration. After heat acclimatization, the 12-h experiments were repeated. Frequent body weights, rectal temperatures, and venous blood samples were obtained. Results indicated that hemodilution upon acute heat exposure is partially due to protein influx into the vascular volume and the hemodilution allowed considerable loss of body water before plasma volume returned to preexposure values. Water within the vascular volume appeared to be in equilibrium with that in other body compartments before but not after acclimatization. Acclimatization altered the rate of protein transfer (and water movement) such that hemodilution was accomplished more rapidly than before acclimatization. Early hemodilution was quite labile and depended upon subject hydration during the first hour of heat exposure.
Abnormal tubular permeability in hypothermic perfused kidneys
Authors: Small A. , Bell R. T. , Filo R. S.
Published: December 2017

Isolated canine kidneys perfused with cryoprecipitated plasma at 15 degrees C exhibit unexpectedly low inulin clearance (CIn) and creatinine clearance (CCr) rates. CIn and CCr, as well as p-aminohoppurate (PAH) clearance, varied linearly with urine flow rate, whether the variations in urine flow were spontaneous or induced, either by elevating perfusion pressure or by adding mannitol to the perfusate. Retrograde intraureteral injection (RII) of an isotonic fluid containing dextran, inulin, and PAH, followed by a period of ureteral occlusion and subsequent serial recollection of the injected fluid, revealed that inulin and PAH, relative to dextran, were lost from distal tubular fluid. Similar experiments in anesthetized dogs indicated no loss of inulin or PAH from tubules of in situ kidneys. Renal venous perfusate, collected from isolated kidneys during the low pressure phase of the RII, contained the following percentages of the quantities injected intraluminally: dextran, 9.22%; inulin, 11.0%; and PAH, 22.0%. These data indicate that a low measured glomerular filtration rate in hypothermic perfused kidneys is partly due to diffusion of inulin or creatinine out of the tubular lumen.
Effects of CO-2 and extracellular H+ iontophoresis on single cell activity in the cat brainstem
Authors: Marino P. L. , Lamb T. W.
Published: December 2017

The activity of single cells in deep regions of the medulla oblongata was observed both during CO2 inhalation and during the extracellular iontophoresis of hydrogen ions in peripheral chemoreceptor-denervated cats. All 53 neurons that fired in synchrony with some part of the ventilatory cycle showed increased firing during CO2 inhalation; yet none responded in a graded fashion to the extracellular application of hydrogen ions. Seventy-one of the 74 nonperiodic cells studied showed no response to CO2 inhalation. Of the 3 nonperiodic cells that did respond to CO2, 2 also responded in a graded fashion to the extracellular iontophoresis of hydrogen ions. It is concluded that the cell bodies of medullary neurons with respiratory periodicity are relatively insensitive to hydrogen ions. Further the paucity of hydrogen ion-sensitive cells found in deep areas of the medulla does not support the notion that medullary hydrogen ion chemoreception is largely achieved by structures located deep in the lower brainstem.
Circulation in rats with Guerin carcinoma
Authors: Takacs L. , Debreczeni L. A. , Farsang C.
Published: December 2017

After implantation of Guerin carcinoma in rats, cardiac output (by Evans-blue dilution), distribution of the organ fractions of cardiac output (by Sapirsteins's isotope indicator fractionation technique), nutritive blood flow and circulatory resistance of the organs (including the tumor) were studied. The following parameters were altered proportionately to the weight of the tumor (0.39–84.0 g): a) weight of gut and carcass diminished; b) cardiac index increased, blood pressure and total peripheral resistance decreased; c) tumor fraction of cardiac output was augmented; d) blood flow of the organs increased and their circulatory resistance decreased. Hematocrit decreased from 47.2 to 31.0% 20 days after tumor implantation. In rats with tumor the changes of blood flow may be conditioned by both anemia and the decrease in organ weight.
Total work rate of breathing optimization in CO-2 inhalation and exercise
Authors: Yamashiro S. M. , Daubenspeck J. A. , Lauritsen T. N. , Grodins F. S.
Published: December 2017

The hypothesis that respiratory frequency and the relative durations of inspiration and expiration are regulated according to a total cycle work rate minimization criterion was explored. Effects of negative work performed by the respiratory muscles and dead space variation as a function of tidal volume were included in a formulation which yielded a theoretically predictable optimal frequency and relative duration of inspiration and expiration at all levels of ventilation. Predicted cycle characteristics based on measured mechanical parameters were compared with data taken during CO-2 inhalation (3 and 5%) and moderate exercise (MRR = 3 and 6) in three normal human subjects. No major difference in breathing pattern was observed between CO-2 inhalation and exercise. Results suggest that conditions for minimization of total cycle work rate are achieved asympototically as the level of ventilation rises above the resting level. At rest and at low levels of hyperpnea complete work rate optimization is not achieved.
A respiratory venous chemoreceptor in the young puppy
Authors: Kollmeyer K. R. , Kleinman L. I.
Published: December 2017

An extracorporeal venovenous shunt system utilizing a membrane oxygenator to alter venous blood gases was used to study the regulation of ventilation in 28 newborn and 4 adult dogs. There was no effect of the extracorporeal circuit per se (without the oxygenator in the system) on essential cardiovascular or respiratory function. When the puppies were placed on the extracorporeal circuit with the oxygenator in the system to effect changes in mixed venous blood gas composition there was a significant increase in venous P02 (Pv02), a decrease in venous Pco2 (Pvco2), a rise in venous pH (PHv), and a marked fall in minute ventilation (VE). There were no significant changes in cardiovascular function or arterial blood gases to account for the depression of ventilation. Acute changes in Pvo2 produced appropriate directional changes of VE under conditions where other arterial and venous blood gases were held constant. At a low Pvco2/Paco2 ratio, ventilation was depressed compared to those conditions with a high ratio. At any Pvc02/Paco2 ratio, ventilation could be depressed by raising the Pvo2. In adult animals ventilation could not be altered by changing venous blood gases. These experiments support the existence of a respiratory chemoreceptor sensitive to both PO2 and PCO2 in the prepulmonary or venous circulation of the newborn animal.
Positive airway pressure and vertical transpulmonary pressure gradient in man
Authors: Rehder K. , Abboud N. , Rodarte J. R. , Hyatt R. E.
Published: December 2017

Static transpulmonary pressure (Pao-Pes) and the vertical gradient of transpulmonary pressure were determined in five sitting conscious normal subjects at mean airway pressures of 0 (ambient), 11, and 21 cmH2O. All subjects exhibited a nonuniform transpulmonary pressure gradient down the esophagus. The vertical pressure gradient was consistently larger in the lower (8–20cm below esophageal artifact) than in the middle region (0–8cm) of the esophagus. The gradient was not significantly altered by continuous positive airway pressure (11 and 21 cmH2O) or by changes in lung volume (60, 70, and 80% of total lung capacity (TLC)). Continuous positive airway pressure also did not result in a consistent change of the overall static pressure-volume curve of the lung. There was a small but statistically significant increase in TLC with each increase in airway pressure.
Thermoregulation during marathon running in cool, moderate, and hot environments
Authors: Adams W. C. , Fox R. H. , Fry A. J. , MacDonald I. C.
Published: December 2017

A well-trained subject, age 38, ran continously for periods ranging from 60 to 165 min on a motor-driven treadmill at 255.7 m/min while confronted with an airflow equivalent to running speed in cool, moderate, and hot environments. After a period of intensive heat acclimatization, treadmill runs were repeated in the moderate and hot conditions. Measurements were also obtained outdoors in a competitive marathon race. Sweat rate (SR) and mean skin temperature (Ts) were linearly related to Tdb. Acclimatization did not alter VO2max or metabolic rate during the treadmill runs, but heart rat (HR),rectal temperature (Tre), and Ts were lower, SR was higher, and maximal run duration longer in the hot environment, postacclimatization. Maximum runs in the hot environment were terminated by a spiralling increase in Tre to hyperthermic levels, due largely to a marked reduction in cutaneous blood flow, probably reflecting cardiovascular overload from the combined muscular and thermoregulatory blood flow demands, coupled with the effects of progressive dehydration. Utilizing partitional calorimetry and the subject's metabolic heat production, two examples of limiting environmental conditions for his marathon running speed were given.
Influence of breathing pattern on oxygen exchange during hypoxia and exercise
Authors: Hanson P. G. , Lin K. H. , McIlroy M. B.
Published: December 2017

During hypoxia, arterial oxygen saturation (SaO2) measured by ear oximeter shows cyclic fluctuations which are related to the pattern and rate of breathing. Continuous recordings of SaO2 may be corrected for distortion, due to circulatory transport, to yield approximate values for pulmonary end-capillary saturation (Sc2O2). This permits calculation of the corresponding end-capillary PO2 (Pc2O2). We have used this technique to study the effect of spontaneous and imposed breathing patterns on mean Pc2O2, amplitude of Pc2O2 (delta Pc2O2) and minute ventilation (VE). The studies were conducted during mild hypoxia, at rest and exercise. The amplitude of delta Pc2O2 is inversely related to breathing frequency. When frequency is constant, patterns with with prolonged expiration or end-expiratory pauses produce large delta Pc2O2 and greater VE. This effect is reversed with prolonged inspiration or end-inspiratory pauses. Spontaneous breathing patterns produced smaller delta Pc2O2, with lower VE than imposed patterns. These findings are compatible with animal studies which suggest the magnitude of PaO2 fluctuations produced by the breathing pattern may act as a feedback stimulus to ventilation. The breathing patterns, which are spontaneously chosen, produce the minimum delta Pc2O2 and VE.
Incomplete compensation of CSF [H+] in man during acclimatization to high altitude (48300 M)
Authors: Forster H. V. , Dempsey J. A. , Chosy L. W.
Published: December 2017

This study has assessed the regulation of arterial blood and cerebrospinal fluid acid-base status in seven healthy men, at 250 m altitude and after 5 and 10–11 days sojourn at 4,300 m altitude (PaO2 = 39 mmHg day 1 to 48 mmHg day 11). We assumed that observed changes in lumbar spinal fluid acid-base status paralleled those in cisternal CSF, under these relatively steady-state conditions. Ventilatory acclimatization during the sojourn (-14 mmHg PaCO2 at day 11) was accompanied by: 1) reductions in [HCO3-] (-5 to -7 meq/1) which were similar in arterial blood and CSF; 2) substantial, yet incomplete, compensation (70–75%) of both CSF and blood pH; and 3) a level of CSF pH which was maintained significantly alkaline (+0.05 +/- 0.01) to normoxic control values. These data at 4,300 m confirmed and extended our previous findings for more moderate conditions of chronic hypoxia. It was postulated that the magnitude and time course of pH compensation in the CSF during chronic hypoxia and/or hypocapnia are determined by corresponding changes in plasma [HCO2-].
Strength of pulmonary vascular response to regional alveolar hypoxia
Authors: Hales C. A. , Ahluwalia B. , Kazemi H.
Published: December 2017

Regional alveolar hypoxia in the lung induces regional pulmonary vasoconstriction which diverts blood flow from the hypoxic area. However, the predominant determinant of the distribution of perfusion in the normal erect lung is gravity so that more perfusion occurs at the base than at the apex. To determine the strength of the regional alveolar hypoxic response in diverting flow with or against the gravity gradient a divided tracheal cannula was placed in anesthetized dogs and unilateral alveolar hypoxia created by venilating one lung with nitrogen while ventilating the other lung with oxygen to preserve normal systemic oxygentation. Scintigrams of the distribution of perfusion obtained with intravenous 13-N and the MGH positron camera revealed a 34 and 32 per cent decrease in perfusion to the hypoxic lung in the supine and erect positions and a 26 per cent decrease in the decubitus position with the hypoxic lung dependent (P equal to 0.94 from supine shift), indicating nearly equal vasoconstriction with shift of perfusion away from the hypoxic lung in all positions. Analysis of regional shifts in perfusion revealed an equal vasoconstrictor response from apex to base in the supine position but a greater response in the lower lung zones in the erect position where perfusion was also greatest.
Saturation dependency of the Bohr effect: interactions among H-+, CO2, and DPG
Authors: Hlastala M. P. , Woodson R. D.
Published: December 2017

The Bohr effect was measured in normal whole blood and in blood with low DPG concentration as a function of oxygen saturation. pH was changed by varying CO2 concentration (CO2 Bohr effect) or by addition of isotonic NaOH or HC1 at constant PCO2 (fixed acid Bohr effect). At nornal DPG concentration CO2 Bohr effect was -0.52 at 50% blood oxygen saturation, increasing in magnitude at lower saturation and decreasing in magnitude at higher saturation. In DPG depleted blood with base excess (BE) similar to 0 meq/1, there was similar dependence of CO2 Bohr effect on oxygen saturation. At BE similar to -10 meq/1, influence of saturation was comparable, but the magnitude of the Bohr effect was markedly increased at all saturations. Fixed acid Bohr effect at normal DPG concentration was -0.45 at saturations of 50–90% but decreased at lower saturations. In DPG-depleted blood fixed acid Bohr effect averaged about -0.33 with minimal variation with saturation. Influence of DPG on oxygen affinity was greater at intermediate saturations and less at saturations below 20% and above 80%. Effect of CO2, independent of pH, was many fold greater at lower oxygen saturations than at higher saturations. These results support the suggestion that the alpha chain of hemoglobin is the site of the initial oxygenation reaction. Physiologically they indicate that the relative contribution of CO2 and fixed acid, as well as the level of oxygen saturation and DPG concentration, may be important in determining PO2 of capillary blood and resulting oxygen delivery.
Muscular efficiency during steady-rate exercise: effects of speed and work rate
Authors: Gaesser G. A. , Brooks G. A.
Published: December 2017

In a comparison of traditional and theoretical exercise efficiency calculations male subjects were studied during steady-rate cycle ergometer exercises of “0,” 200, 400, 600, and 800 kgm/min while pedaling at 40, 60, 80, and 100 rpm. Gross (no base-line correction), net (resting metabolism as base-line correction), work (unloading cycling as base-line correction), and delta (measurable work rate as base-line correction) efficiencies were computed. The result that gross (range 7.5–20.4%) and net (9.8–24.1%) efficiencies increased with increments in work rate was considered to be an artifact of calculation. A LINEAR OR SLIGHTLY EXPONENTIAL RELATIONSHIP BETWEEN CALORIC OUTPUT AND WORK RATE DICTATES EITHER CONSTANT OR DECREASING EFFICIENCY WITH INCREMENTS IN WORK. The delta efficiency (24.4–34.0%) definition produced this result. Due to the difficulty in obtaining 0 work equivalents, the work efficiency definition proved difficult to apply. All definitions yielded the result of decreasing efficiency with increments in speed. Since the theoretical-thermodynamic computation (assuming mitochondrial P/O = 3.0 and delta G = -11.0 kcal/mol for ATP) holds only for CHO, the traditional mode of computation (based upon VO2 and R) was judged to be superior since R less than 1.0. Assuming a constant phosphorylative-coupling efficiency of 60%, the mechanical contraction-coupling efficiency appears to vary between 41 and 57%.
Glycogen replenishment following exercise: effects of denervation and tenotomy
Authors: Ratliff R. A. , Lamb D. R.
Published: December 2017

To examine the role of the nervous system in the rapid replenishment of muscle glycogen that occurs after exhaustive exercise, glycogen stores and glycogen synthetase activity of normal gastrocnemius muscles of untrained and trained guinea pigs were compared to glycogen and synthetase activity of trained gastrocnemius muscles that were denervated or tenotomized immediately after exhaustive exercise and then allowed to recover for 48 h. The trained tenotomized muscles, but not the denervated muscles, had significantly (P smaller than 0.05) less glycogen than the trained normal muscles. These results suggest that neither nerve impulse conduction nor tropic substances contained in neural tissue proximal to the site of denervation mediate glycogen replenishment after exercise. The active, glucose 6-phosphate independent (I) form of glycogen synthetase activity was reduced by both denervation and tenotomy at 48 h after exercise with no significant (P greater than 0.05) differences detected for the total of I and D (glucose 6-phosphate dependent) synthetase activity. Synthetase I relative to total synthetase activity was similar in trained and untrained normal muscles, both of which had significantly (P smaller than 0.05) greater relative I activities than denervated or tenotomized muscles. These synthetase data show that elevated glycogen stores following recovery from exercise may be observed in the absence of increased levels of glycogen synthetase activity.
Site of central chemosensitivity in fetal sheep
Authors: Jansen A. H. , Chernick V.
Published: December 2017

The heart rate, blood pressure, and respiratory response to topically applied cyanide on the ventrolateral medullary surface and upper spinal cord was studied on exteriorized sinaortic-denervated fetal lambs under pentobarbital anesthesia. On all sites tested cyanide produced a rapid increase in heart rate and blood pressure (P smaller than 0.05) which was most pronounced from the area adjacent to the nerve roots IX to XI (mean 32%). Respiratory efforts consisting of 1–8 gasps were induced in half the applications to the medulla but never when the pledgets were applied to the spinal cord. The mean delay to response was 43 s (range 13–102 s). After cautery of the chemosensitive areas, topical application of cyanide failed to stimulate gasping, whereas intravenous cyanide or cord clamping still produced a vigorous respiratory response. It is concluded that sympathetic stimulation of the heart and blood vessels can originate centrally in response to local histotoxic hypoxia of the ventral medulla and upper spinal cord. Furthermore, it is proposed that in the apneic fetus histotoxic hypoxia of the medulla initiates respiration possibly by stimulating a special gasping mechanism which is separate from the respiratory center responsible for rhythmic breathing after birth. The responsible neurons must be located at least 2 mm beneath the ventral medullary surface.
Effect of sojourn at 4,300 m altitude on electroencephalogram and visual evoked response
Authors: Forster H. V. , Soto R. J. , Dempsey J. A. , Hosko M. J.
Published: December 2017

The purpose of the present study was to determine the effect of sojourn at high altitude on cerebral electrical activity. Electroencephalographic (EEG) and visual evoked responses (VER) were recorded from seven healthy males under the following conditions: 1) during the first 2–3 h at 4,300 m altitude when Pao2 was maintained at 90 mmHg (control condition), 2) during the first 2–3 h of hypoxia (Pao2 = 40 mmHg), and 3) at 24- to 48-h intervals during the first 9–12 days of hypoxia. Electrode placement was according to the 10–20 International Electrode System. The VER was recorded from an electrode at the inion referred to the left ear. We found no significant changes from control cerebral electrical activity during the first 2–3 h of hypoxia. One subject's VER amplitude was greater than control on the 2nd and 3rd days of hypoxia and a similar change from control was consistently evident in a second subject beginning the 5th day of hypoxia. These changes suggest cortical depression. After the 5th day changes occurred in the remaining subjects which would be consistent with cortical excitation. In three subjects, EEG frequency was increased, amplitude decreased, and/or spiking became evident. In four subjects VER amplitude was reduced. Our findings provide support for the hypothesis that certain behavioral and physiological changes induced by sojourn at altitude could be caused by alterations in central nervous system function.
Estimation of cardiac output by analysis of respiratory gas exchange
Authors: Homer L. D. , Denysyk B.
Published: December 2017

Cardiac output is estimated by least squares fitting of a model of pulmonary gas exchange to measurements of respiratory gas composition obtained with a mass spectrometer during a rebreathing maneuver. This new technique estimates cardiac output on spontaneously breathing subjects at rest and requires neither central venous nor arterial blood samples. Principal features of the technique are the use of multiple gases simultaneously in the analysis, the use of a mathematical model for breath-to-breath evaluation of gas exchange, and simultaneous estimation of gas exchange and alveolar gas tensions with the same instrumentation. The technique is compared with thermal dilution estimates in dogs before and during hemorrhagic shock. Two-thirds of these estimates were within 20% of one another. The standard deviation of replication was 15%. Shortcomings, possibilities for improvement, and possible applications are discussed.
A new method for fabrication of latex cuffs
Authors: Peluso Francesco P. , Melbin Jules , Noordergraaf Abraham , Pyle R Lee
Published: December 2017

A new and simple method is presented that is suitable for the fabrication of inflatable cuffs for any gross vascular size. The method lends itself to mass production which is particularly useful for the fabrication of small cuffs. The procedure generally consists of spraying latex on a rotating cylinder in two separable layers. An activating tube is inserted between the layers and the edges sealed. Outward expansion is prevented by means of a suitable backing material.
Aldosterone dynamics during graded exercise at sea level and high altitude
Authors: Maher J. T. , Jones L. G. , Hartley L. H. , Williams G. H. , Rose L. I.
Published: December 2017

Hormonal responses to graded exercise of eight low altitude residents were examined at sea level (SL) and after 1 (acute) and 11 (chronic) days at 4,300 m (HA). Caloric, water, and electrolyte intakes were controlled, as were temperature and humidity. Blood was sampled at rest and during light and moderate upright bicycle exercise (20 min at 40% and 75% of maximal O2 uptake, respectively). Mean VO2 max at HA was 27% lower than at SL. Resting plasma levels of aldosterone (Aldo), renin, and angiotensin II (A II) were significantly lower (P smaller than 0.05) on day 1 at HA compared to SL, but returned to SL values by day 11. Plasma cortisol values at rest were similar at SL and HA and were not significantly altered by light or moderate exercise. Renin, A II, and Aldo rose progressively with increasing workload in each environment. With acute HA, renin and Aldo were lower than at either SL or chronic HA. The chronic HA levels tended to approximate SL findings, implying adaptation. The data suggest that aldosterone is predominantly under the control of the renin-angiotensin system during graded exercise at sea level and that the response of this system is altered on acute high-altitude exposure.
Influence of expiratory flow on closing capacity at low expiratory flow rates
Authors: Rodarte J. R. , Hyatt R. E. , Cortese D. A.
Published: December 2017

Single-breath oxygen (SBO2) tests at expiratory flow rates of 0.2, 0.5, and 1.01/s were performed by 10 normal subjects in a body plethysmograph. Closing capacity (CC)--the absolute lung volume at which phase IV began--increased significantly with increases in flow. Five subjects were restudied with a 200-ml bolus of 100% N2 inspired from residual volume after N2 washout by breathing 100% O2 and similar results were obtained. An additional five subjects performed SBO2 tests in the standing, supine, and prone positions; closing volume (CV)--the lung volume above residual volume at which phase IV began--also increased with increases of expiratory flow. The observed increase in CC with increasing flow did not appear to result from dependent lung regions reaching some critical “closing volume” at a higher overall lung volume. In normal subjects, the phase IV increase in NI concentration may be caused by the asynchronous onset of flow limitation occurring initially in dependent regions.
Role of vagal stimuli in exercise ventilation in dogs with experimental pneumonitis
Authors: Phillipson E. A. , Murphy E. , Kozar L. F. , Schultze R. K.
Published: December 2017

We have investigated the possibility that afferent vagal stimuli may be responsible for the excessive ventilatory drive during exercise characteristic of many diffuse pulmonary parenchymal diseases. Studies were performed on four conscious dogs with cervical vagal loops, in whom experimental pneumonitis was induced by the intravenous administration of complete Freund's adjuvant. Control measurements were made over a 3-mo interval prior to induction of disease which then ran a course of 6 wk. The disease was characterized histologically by a diffuse interstitial pneumonitis during the first week, and by a proliferative granulomatosis during the subsequent 4–5 wk. Physiologic disturbances at rest included decreased total lung and functional residual capacities; increased lung elastic recoil; and decreased carbon monoxide diffusing capacity. During mild-to-moderate steady-state exercise, the minute volume of ventilation (VE) and respiratory frequency (f) were increased significantly compared to control values; tidal volume (VT) was decreased significantly; and exercise tolerance (ET) was impaired. Complete cervical vagal blockade abolished the abnormally high VE, decreased f, and increased VT in all dogs, and improved ET in at least two dogs. The results indicate that afferent vagal stimuli were responsible for the excessive ventilation during exercise and contributed to the abnormal pattern of breathing.
Experimental cardiac necrosis in hypobaric and anemic hypoxia
Authors: McGrath J. J. , Ostadal B. , Prochazka J. , Wachtlova M. , Rychterova V.
Published: December 2017

Resistance to isoproterenol-induced cardiac necrosis (IPRO) was compared in rats exposed to two types of hypoxia (i.e., hypobaric and anemic). IPRO was induced by two consecutive, subcutaneous injections of isoproterenol (80 mg/kg) at 24-h intervals. The animals were killed on the third day and the severity of the lesion was evaluated on a 0 (no damage) to 4 (severely damaged) scale. White male rats (HA) were exposed in a barometric chamber to a simulated altitude of 7,000 m (307 mmHg) for 4 h/day for 24 days. Two groups of control rats were kept at sea level; one group (SLA) was the same age and one group (SLW) was the same weight as the altitude-exposed rats. The HA rats were significantly more resistant to IPRO with a mean necrogenic rating of 1.8 compared to 3.3 for the SLA and SLW rats. Infant rats (AA) were made anemic by feeding full-cream milk and glucose for 100 days after weaning. Two groups of control animals were fed a standard laboratory diet; one group (AC) was the same age and one group (AW) was the same weight as the AA rats. There was no significant difference in the necrogenic ratings of the AA (3.3), AC (3.5), or WC (3.7) hearts. Thus, hypobaric hypoxia affords some protection against IPRO which is not afforded by anemic hypoxia. Similarities and differences in the two hypoxias are discussed.
Ventilatory interaction between hypoxia and [H+] at chemoreceptors of man
Authors: Gabel R. A. , Weiskopf R. B.
Published: December 2017

By measuring ventilation during isocapnic progressive hypoxia, peripheral chemoreceptor sensitivity to acute hypoxia (deltaV40) was measured in five normal young men under four sets of conditions: 1) at sea level at the subject's resting PCO2, 2) at sea level with PCO2 5 Torr above resting PCO2, 3) after 24 h at a simulated altitude of 4,267 m (PB = 447 Torr) at the subject's resting PCO2 measured during acute hyperoxia, and 4) after 24 h at high altitude, with PCO2 elevated to the subject's sea-level resting PCO2. With this experimental design, we were able to systematically vary the PCO2 and [H+] at the peripheral and central chemoreceptors of man. When mean pHa was decreased from 7.424 to 7.377 without significant change in PACO2, the mean deltaV40 increased from 18.0 to 55.9 1/min. Conversely, when mean PACO2 was altered between 33.8 and 41.6 Torr with pHa held relatively constant, the mean deltaV40 did not change. This suggests that it is the H+ and not CO2 which interacts with hypoxia in stimulating the ventilation of man. An additional finding was that the intrinsic sensitivity of the peripheral chemoreceptors to acute hypoxia did not change during 24 h of acclimatization to high altitude.
A modified measurement of respiratory resistance by forced oscillation during normal breathing
Authors: Stanescu D. C. , Fesler R. , Veriter C. , Fans A. , Brasseur L.
Published: December 2017

We have modified the measurements of the resistance of the respiratory system, Rrs, by the forced oscillation technique and we have developed equipment to automatically compute Rrs. Flow rate and mouth pressure are treated by selective averaging filters that remove the interference of the subject's respiratory flow on the imposed oscillations. The filtered mean Rrs represents a weighted ensemble average computer over both inspiration and expiration. This method avoids aberrant Rrs values, decreases the variability, and yields an unbiased mean Rrs. Rrs may be measured during slow or rapid spontaneous breathing, in normals and in obstructive patients, over a range of 3–9 Hz. A good reproducibility of Rrs at several days' interval was demonstrated. Frequency dependence of Rrs was found in patients with obstructive lung disease but not in healthy nonsmokers.
Computerized method for analyzing maximum and partial expiratory flow-volume curves
Authors: Soto R. J. , Forster H. V. , Rasmussen B.
Published: December 2017

Computerized instrumentation and software have been developed to obtain maximum expiratory flow-volume (MEFV) and partial expiratory flow-volume (PEFV) curves. The computerized system calculates and prints out the flow at 25% and 40% of control vital capacity (VC), the expiratory volume, peak expiratory flow rate and expiratory volume at one second (FEV1) divided by VC, the latter expressed as a percent. The flow-volume curves can be displayed on an oscilloscope or plotter and stored on magnetic tape. A pilot study was completed to demonstrate the reliability and validity of the data obtained.
Multichannel subcarrier ECG, respiration, and temperature biotelemetry system
Authors: Smith E. N. , Salb T. J.
Published: December 2017

A three-channel biotelemetry system measuring ECG, respiration, and body temperature is described. The transmitter employs a 6-kHz subcarrier oscillator and is small enough for surgical implantation in animals the size of rats or larger. The frequency modulated 6-kHz tone from the reciver can be demodulated directly or recorded on an inexpensive cassette tape recorder for future analysis. The transmitter cost is approximately $35.00 and measures 3 times 1 cm. A battery life of several weeks and transmitter range of 10–100 m is typical. Transmission is on the FM broadcast band (88-108 MHz) and reception from an inexpensive FM portable receiver is possible.
Body surface area in the infant rat
Authors: Conklin P. M.
Published: December 2017

Body surface area (SA), one index used to minimize size differences in metabolic studies, was estimated by a coating method in rats aged 1, 7, 14, and 21 days (d) (n = 100–107). Body weights (BW) at each age varied about twofold. Regression equations were calculated for SA (cm2) vs. BW (g) (SA = 8.73 + 2.29 BW, 17.79 + 1.71 BW, -4.92 + 2.16 BW, and 53.68 + .82 BW at 1, 7, 14, and 21 days, respectively) and log SA vs. log BW (SA = 6.71 BW0-667, 9.12 BW0-577, 1.73 BW1–042, and 18.97 BW0–412). All the latter differed significantly from SA = 10 BE2/3, frequently used with adult mammals. Correlation coefficients were approximately 0.6–0.9 and did not differ with mode of expressing results. Regressions, whether linear or logarithmic, differed significantly among ages, apparently reflecting appreciable conformational changes in the rapidly growing and maturing preweanling rat.
Hypothermia and rewarming induced by surface and He-O2 inhalate temperature control
Authors: Beran A. V. , Proctor K. G. , Sperling D. R.
Published: December 2017

Hypothermia and rewarming were induced by a combination of temperature-controlled surface and inhalate methods in rabbits. To facilitate respiratory heat exchange, inhalate-respiratory tract temperature and humidity gradients and thermal conductivity were increased. In addition, the upper respiratory tract was bypassed by an endotracheal tube. To aid in maintaining satisfactory circulatory dynamics, hypercapnia and hypoxia were induced. The combined surface and inhalate method produced a markedly more effective rate of cooling than surface temperature-controlled method alone. Animals survived core temperatures as low as 20.9 degrees C with no complications. The noninvasive simplicity of this method suggests its potential applicability in many clinical situations.
Effect of carotid body resection on ventilatory and acid-base control during exercise
Authors: Wasserman K. , Whipp B. J. , Koyal S. N. , Cleary M. G.
Published: December 2017

To investigate the role of the carotid bodies in exercise hyperpnea and acid-base control, normal and carotid body-resected subjects (CBR) were studied during constant-load and incremental exercise. There was no significant difference in the first-breath ventilatory responses to exercise between the groups; some subjects in each reproducibly exhibited abrupt responses. The subsequent change in Ve toward steady state was slower in the CBR group. The steady-state ventilatory responses were the same in both groups at work rates below the anaerobic threshold (AT). However, above the AT, the hyperpnea was less marked in the CBR group. Ve and acid-base measurements revealed that the CBR group failed to hyperventilate in response to the metabolic acidosis of either constant-load or incremental exercise. We conclude that the carotid bodies 1) are not responsible for the initial exercise hyperpnea, 2) do affect the time course of Ve to its steady state, and 3) are responsible for the respiratory compensation for the metabolic acidosis of exercise.
Maximal oxygen uptake during treadmill walking and running at various speeds
Authors: Stamford B. A.
Published: December 2017

Three groups of male subjects, average fitness (AF, N = 12), high fitness (HF, N = 7) and highly fit competitive race walkers (CRW, N = 3) performed maximal treadmill tests walking at 3.5 and 4.5 mph and running at 4.5, 5.5, 7.0, and 8.5 mph. In addition, the HF group performed a running test at 10.0 mph and the CRW group performed a walking test at 5.5 mph. All maximal oxygen uptake (VO2 max) tests with the exception of the 3.5 mph walking test (modified Balke test) were discontinuous in nature. VO2 max obtained from walking tests was similar regardless of speed within each group. Walking VO2 max was significantly lower than running VO2 max which was found to be similar over a speed range of 4.5 to 8.5 mph in the AF group. Running at 4.5 mph (HF group) and 4.5 and 5.5 mph (CRW group) resulted in lower VO2 max levels than running at speeds greater than or equal to 7.0 mph. Associated physiological variables (heart rate, ventilation, and respiratory exchange ratio) did not demonstrate a discernable pattern with reference to mode of locomotion (walking versus running) or speed. It was concluded that VO2 max elicited during walking is independent of speed and less than VO2 max obtained during running. Running VO2 max was interrelated with speed of running and state of training.