bluuebunny/crossref_metadata_2025 huggingface dataset:
Alveolar dead space, alveolar shunt, and transpulmonary pressure
Authors: Workman J. M. , Penman R. W. B. , Bromberger-Barnea B. , Permutt S. , Riley R. L.
Published: December 2017

The effect of transpulmonary pressure (Ptp) on gas exchange in the dog lung was studied in 10 open-chested dogs. Rates of pulmonary perfusion and ventilation were held constant (right heart bypass and pump respirator) while Ptp was varied. Alveolar dead space ventilation and alveolar shunt perfusion were calculated from CO2 and O2 gradients. The results are finally expressed in terms of a three-compartment lung model. It is shown that a misinterpretation is possible if alveolar dead space or alveolar shunt compartments are expressed as fractions, respectively, of all ventilated or all perfused alveoli, therefore each has been expressed as a fraction of the whole lung. It is concluded that the alveolar shunt compartment decreased as Ptp was increased, over the lower range of Ptp studied. No significant change was detected in the alveolar dead space compartment, as Ptp was varied.

alveolar-arterial O2 gradient; anatomical dead space; arterial-alveolar CO2 gradient; distribution of pulmonary perfusion; distribution of pulmonary ventilation; right heart bypass preparation; ventilation/perfusion relationships

Submitted on February 16, 1965
A small, lightweight precordial counter for determination of cardiac output
Authors: Gorten Ralph J.
Published: December 2017

A compact, lightweight scintillation detector which can be firmly attached to the anterior chest was fabricated in order to better adapt the isotope-precordial counting technic for measurements of cardiac output during exercise. In this manner useful indicator-dilution curves can be obtained without arterial puncture at light-to-heavy levels of bicycle ergometer or treadmill exercise. The use of a thin crystal and the omission of lead shielding and collimation of the detector is possible with a soft-energy gamma-emitting indicator of blood flow such as iodinated (I125) albumin.

cardiac output during exercise; lightweight precordial scintillation detector; iodione 125; isotope-precordial counting technic

Submitted on May 28, 1965
Diffusivity of oxygen in blood serum
Authors: Yoshida F. , Ohshima N.
Published: December 2017

Page 915: Yoshida, F., and N. Ohshima, “Diffusivity of oxygen in blood serum.” The sentence near the end of the first paragraph of the introduction (p. 915) should read; “The values of diffusivity of oxygen in serum at 25 C ranged from 1.63 to 2.21 x 1O–5 cm2/sec depending on the thickness of the layer.”
Normal values for semen collected from Spanish goats by two methods
Authors: Austin J. W. , Leidy R. B. , Krise G. M. , Hupp E. W.
Published: December 2017

page 369: J. W. Austin, R. B, Leidy, G. M. Krise, and E. W. Hupp. “Normal values for semen collected from Spanish goats by two methods.” Page 369, footnote 1 should read, “This investigation was supported in part by Grant RH00330, National Center for Radiological Health, Public Health Service.”
Microscopy and viscometry of blood flowing under uniform shear rate(rheoscopy)
Authors: Schmid-Schoenbein Holger , Wells Roe , Schildkraut Robert
Published: December 2017

Transparent cone and plate in a Wells-Brookfield LVT viscometer allow direct microscopic observation ( x 60–400 magnification) of blood flowing under specific rates of shear (0.6–1,380 set–1) while simultaneously measuring shear stress. The viscometer is placed on the stage of an inverted microscope; observation in bright-field and dark-field illumination is made through a thin optical quartz inserted in the plate. The range of shear rates is extended by the use of different cone angles and can be adapted to any desired level by driving the viscometer motor with a sine-wave generator with variable output. The use of the instrument confirmed recent theories about the role of reversible red cell aggregation upon the rheology of blood at low shear rates. The influence of quantified flow forces on reversible red cell aggregation and irreversible platelet aggregation can be examined directly.

blood rheology; microscopy of blood flow; platelet aggregation; red cell aggregation

Submitted on August 5, 1968
Nature of induction of tryptophan pyrrolase in cold exposure
Authors: Sitaramam V. , Ramasarma T.
Published: December 2017

The activity of hepatic tryptophan pyrrolase in rats exposed to cold increased rapidly and reached a maximum of three-fold at 8 h. On continued exposure up to 48 h stress, the activity partly decreased but remained at a level higher than the initial. Withdrawal from the cold stress reversed the change. Adrenalectomy or treatment with inhibitors of protein synthesis abolished the increase in the enzyme activity during cold stress indicating a possible involvement of corticosteroids and de novo protein synthesis. Treatment with drugs known to block autonomic nervous system failed to inhibit the cold-mediated increase in enzyme activity. The results suggest that the increase in enzyme activity obtained on cold exposure is mediated by corticosteroids and not by either indoleaklylamines or autonomic nervous system. The changes in the enzyme obtained under cold stress with respect to the overshoot phenomenon, relationship to the degree of stress and reversibility on withdrawal from the stress indicate the “adaptate” nature of the response.
Brain temperature during reversible upper respiratory bypass
Authors: Kluger M. J. , D'Alecy L. G.
Published: December 2017

Seven male New Zealand white rabbits were trained to run in an exercise wheel. At least 5 days prior to experimentation, each rabbit had a reversible tracheal bypass canula and a hypothalamic thermocouple guide tube chronically implanted. The reversible tracheal bypass enabled the rabbit to breathe normally (through its upper respiratory pathways) or to be placed on bypass (breathe through its neck). Prior to and following exercise, hypothalamic temperature in rabbits breathing normally was lower than rectal temperature. This difference was greatest following a mild heat stress induced by exercise. When the rabbits breathed through the bypass, there were no differences between hypothalamic and rectal temperature. These data suggest that even in a species such as the rabbit, which lacks a carotid rate, hypothalamic temperature is influenced by upper respiratory cooking of venous blood and that the ensuing transfer of heat from the warmer internal carotid artery to the cooler venous sinuses can effectively cool the brain.
Intrauterine pressure wave-form characteristics of spontaneous first stage labor
Authors: Seitchik J. , Chatkoff M. L.
Published: December 2017

Intrauterine pressure wave-form parameters were measured in 827 contractions obtained from 26 patients in spontaneous labor. The coefficients of correlation between the maximal and minimal rates of pressure change and the maximal pressure amplitude were 0.78 and 0.63, respectively, and greater than or equal to 0.70 in 22/26 patients. Contractions partitioned into decile statistical groups of the pressure amplitude and both maximal and minimal rates. A linear relationship between these parameters has therefore been established. Contractions of greater amplitude tend to be longer, but the relationship between duration and amplitude is nonlinear with a limiting maximum contraction time. The duration of the midportion of the pressure wave appears invariate with respect to wave amplitude and only start-up and termination times increase with increasing amplitude. Mean values and standard deviations of the maximal amplitude (40.4 +/- 16.9mmHg). the maximal (2.4 +/- 0.9 mmHg/s) and minimal (-2.1+/- 0.9 mmHg/s)rates of pressure change, and the total duration of contractions (68.6 +/- 17.8s) were determined.
Gastroesophageal dynamics during immersion in water to the neck
Authors: Johnson L. F. , Lin Y. C. , Hong S. K.
Published: December 2017

This investigation was undertaken to study the effect of hydrostatic pressure on gastroesophageal dynamics during immersion in thermoneutral water to the neck. In 5 healthy male subjects (normal end-expiratory), gastric pressure (PG), esophageal pressure (PE), location and pressure of distal esophageal sphincter (des), location of respiratory inversion point (RIP), and gastroesophageal pH gradient were measured standing in air (A), standing in water to the neck (B), and standing in air with abdominal compression (C). The pressure was measured with a Honeywell esophageal catheter (model 31) with built-in pressure transducer. A Beckman stomach pH electrode (no. 39042) was positioned adjacent to the pressure transducer. PG increased from 4.6 +/- 0.6 (SE) mmHg in A to nearly 20 mmHg in B and C, while PE increased from -6.0 +/- 0.8 mmHg in A to -0.8 +/- 1.0 and -3.4 +/- 0.9 mmHg in B and C, respectively. However, PDES was always 11-15 mmHg higher than PG. The superior limit of DES was displaced cephalad by indicating a stretching of DES and a shortening of the esophagus. Qualitatively similar findings were obtained in C. In all experiments, the esophageal pH remained above 6, and no alteration in the amplitude of primary peristaltic waves was seen. It is concluded that a head-out immersion with increased gastroesophageal pressure gradient predisposes to gastric reflux in the absence of a competent DES mechanism.
Effect of circulating FFA on lactate production by skeletal muscle during stimulation
Authors: Dunn R. B. , Critz J. B.
Published: December 2017

The present experiments were undertaken to study the effects of FFA on lactate production by skeletal muscle during stimulation. In the first group, dogs were anesthetized with sodium pentobarbital and given no anticoagulant. The second group was also anesthetized with sodium pentobarbital but in addition given heparin and a fat-albumin infusion to elevate FFA. Stimulating the nerves to a group of skeletal muscles in the hindlimb (1.5/s) increased muscle blood flow 2.4-fold in both groups. In the first group stimulation did not alter the arteriovenous difference of lactate across the muscles. The difference was close to zero before and during stimulation. However in the second group, in which FFA were elevated, stimulation produced a large increase in muscle lactate production. In both groups there were no differences in the L/P ratio of muscle venous blood during stimulation. These results indicate that an increase in lactate production following muscle stimulation is not necessarily related to a state of tissue hypoxia.
Influence of lung parenchyma on collapsibility of dog bronchi
Authors: Takishima T. , Sasaki H. , Sasaki T.
Published: December 2017

In five excised dog lobes in the distended state, we inserted several small beads into the bronchi roughly at their third branches and glued them airtight to the bronchial wall with adhesive substance, except for one which was open and through which the entire lobe could be expanded via collateral channels. This permitted us to measure the volume-pressure behavior of bronchi at different fixed lung tensions. From differences in pressure-volume curves of both the bronchi in situ and the bronchi intact within the lung showed a remarkably greater resistance to collapsing that dissected bronchi, and this characteristic tended to be much more intense when lung tension was increased. Determinants of maximum expiratory flow were discussed with these findings.
Interrelationship of FFA and glycerol turnovers in resting and exercising dogs
Authors: Shaw W. A. , Issekutz T. B. , Issekutz B.
Published: December 2017

Dogs with indwelling arterial and venous catheters ran on a treadmill on a 10% or on a 15% slope at 100 m/min. Glycerol turnover ([2–3H]-glycerol) and FFA turnover ([1–14C]palmitate) were measured simultaneously. Both turnovers were greatly increased by exercise. Similar increases were produced in resting dogs by norepinephrine infusions (0.5 mug/kg-min). At rest, as well as during exercise, there was a straight-line correlation between the ratio of disappearance of each substrate and their respective plasma concentrations. Over a wide range there was a straight-line correlation between the rate of production of FFA (RaFFA) and that of glycerol (RaGLY) at rest as well as during exercise. At any given RaFFA, RaGLY was higher in the running than in the resting dog. At rest the ratio of RaFFA/RaGLY was found to give the theoretical value of 3.0 only when RaFFA was 10–15 mumol/kg-min, below this the ratio was lower and above this it was higher. During exercise the ratio was lower than at rest and at heavier load lower than at lighter work. The results suggest that in vivo a combination of partial and complete lipolysis as well as reesterification occurs. The glucose equivalent of the glycerol turnover (if 100% converted) represents (under the given experimental conditions) 14–18% of the hepatic glucose output on the 15% slope and 20–25% of it on the 10% slope.
Adaptation of brain monoamine synthesis to hypoxia in the rat
Authors: Davis J. N.
Published: December 2017

Oxygen is a substrate in the synthesis of the neurotransmitters, norepinephrine, dopamine, and serotonin. Changes in environmental oxygen appear to cause corresponding alterations in brain monoamine synthesis in vivo. The effect of chronic hypoxia was studied by exposing rats to 10% oxygen for up to 36 h. Brain monoamine synthesis, estimated in vivo, decreased initially and then returned to control levels, despite continued exposure to 10% oxygen. During this apparent adaptation to hypoxia, there were no changes in the concentration of brain serotonin, norepinephrine, dopamine, or tryptophan, while brain tryosine increased after 24 h of exposure. Tyrosine hydroxylase activity in vitro was not altered by the exposure to 10% oxygen. Evidence of hypoxic adaptation in these rats, a rightward shift of their hemoglobin dissociation curves, was found after 24 h of exposure. The adaptation of brain monoamine synthesis to hypoxia appeared to correlate with adaptive changes in brain tissue oxygen rather than any change in the intraneuronal regulation of amine synthesis.
Quantitation of pharyngeal motor function in normal human subjects
Authors: Dodds W. J. , Hogan W. J. , Lydon S. B. , Stewart E. T. , Stef J. J. , Arndorfer R. C.
Published: December 2017

A need exists for accurate pressure recording of pharyngeal motor events. Results of this study indicate that accurate quantitation of pharyngeal motor activity is not possible using a water-filled catheter system, even when high infusion rates are used. An intraluminal strain gauge system, however, achieves high-fidelity recording. Quantitation of pharyngeal peristalsis using the intraluminal strain gauge system reveals peristaltic pressure amplitudes higher than those hitherto recorded. In normal subjects, peristaltic amplitude averages about 200 mmHg in the hypopharynx, complexes in one subject being as high as 600 mmHg. A zone of relatively low pressure exists in the oropharynx. Mean pharyngeal wave duration decreases progressively in an aboral direction, from 1.0 to 0.3 s, and peristaltic wave speeds range between 9 and 25 cm/s. Accurate quantitation of pharyngeal peristaltic variables provides the necessary basis for characterization and assessment of pharyngeal motor disorders.
Properties of lung parenchyma in distortion
Authors: Hoppin F. G. , Lee G. C. , Dawson S. V.
Published: December 2017

This study offers a basis for evaluating and developing models of stress-strain behavior of the lung in distortion. Tensile forces were applied along three axes to cubes of dog lung parenchyma. With axially symmetrical force-loading, expansion was reasonably symmetrical and pressure-volume relationships were reasonably conventional in range, hysteresis, and time-dependent behavior. When the force load was changed on one axis only, that axis appeared more compliant than it did during symmetrical loading and the other axes changed length in the opposite sign. Similar distortion was apparent at the alveolar level. Data for five specimens over a range of applied loads are filed with the National Auxiliary Publications Service; graphical examples are presented herein. Relationship among the compliances for symmetrical and asymmetrical loadings were consistent with elastic theory. We derived the elastic coefficients, bulk and Young's moduli, and Poisson's ratio from the data. Poison's ratio was about 0.30 in air-filled specimens, but was lower (0.16–0.24) and increases with stress in saline-filled specimens.
Luft's syndrome: O2 cost of exercise and chemical control of breathing
Authors: Edelman N. H. , Santiago T. V. , Conn H. L.
Published: December 2017

The oxygen cost of exercise and chemical control of breathing were studied in a subject with Luft's syndrome, a disorder in which skeletal muscle mitochondria have a high “resting” O2 consumption which is imcreased only slightly by stimulation with excess phosphate acceptor, but a normal P/O ratio. The O2 consumption was more than three times normal (1.05 1/min) at rest but could be doubled when stimulated by maximal exercise. The O2 cost of exercise was similar to that of normal subjects. At rest, arterial blood PCO2 and ventilatory response to CO2 were normal, while ventilatory response to hypoxia was four times the predicted value. The data 1) confirm, in vivo, the normal respiratory efficiency of skeletal muscles in this disorder; 2) suggest that in vitro estimates of the extent to which mitochondrial respiration can be stimulated may not correlate with in vivo determinations; and 3) suggests that hypermetabolism per se can cause the ventilatory adjustments which are associated with exercise in normal subjects.
Effect of ventilation on pulmonary blood volume of the fetal lamb
Authors: Walker A. M. , Alcorn D. G. , Cannata J. C. , Maloney J. E. , Ritchie B. C.
Published: December 2017

Blood volume changes in the fetal lung following the onset of ventilation were studied by isotopic measurement of red blood cell and plasma volume in rapidly frozen lungs of ten near term fetal lambs. Total pulmonary blood volumes of fetal lambs ventilated with 3% O2 and 7% CO2 in nitrogen (so that blood gas levels were little changed from fetal values), or with air, were compared with measurements in unventilated lambs. Regional correlations of blood volume and blood flow (measured with isotope-labeled microemboli) within the lungs were also examined. Total pulmonary blood volume averaged 5.6 ml/kg body weight in unventilated fetal lambs and was approximately 43% greated in fetal lambs after 5–20 min of air ventilation, but not significantly different in lambs ventilated with 3% O2 and 7% CO2 in nitrogen. Thus it is ventilation with air, rather than the introduction of gas into the alveoli, which enlarges the fetal pulmonary vascular bed. Regional pulmonary blood volume and blood flow were correlated, though poorly, in air-ventilated lungs, but not in lungs ventilated with 3% O2 and 7% CO2 in nitrogen; this suggests that a common factor may operate to increase both blood flow and blood volume in the fetal lung following the introduction of air.
Comparison of proximal tubule fluid-to-plasma ultrafiltrate chloride ratio in rats and dogs
Authors: Marchand G. R. , Ott C. E. , Cuche J. L. , Knox F. G.
Published: December 2017

Previous studies in rats have demonstrated that the concentration of chloride in proximal tubule fluid is greater than that in plasma. The gradient reaches a free-flow steady-state level in the early proximal tubule and is maintained throughout the accessible proximal tubule. On the other hand, studies in dogs are in conflict regarding either the existence of a gradient or the development of a free-flow steady-state level. Since a species difference of tubule fluid to plasma chloride (TF/PC1) may exist, the present study was done to systematically compare the tubule fluid to ultrafiltrate chloride ratio (TF/UFC1) in hydropenic rats and dogs during normal acid-base balance. Chloride was analyzed by microelectrometric titration. In the rat the TFC1 and UFC1 concentrations were 139 +/- 1.4 and 120 +/- 1.2 meq/1, respectively. In the dog the TFC1 and UFC1 concentrations were 138 +/- 1.3 and 121 +/- 1.5 meq/1, respectively. Thus, there was no significant difference in the TF/UFC1 ratio between the rat (1.17 +/- 0.02) and the dog (1.14 +/- 0.01). Furthermore, regression analysis indicates that there is no correlation between TF/UFC1 and TF/PIn in either the rat or dog, which suggests that the gradient originates early in the proximal tubule and is maintained throughout the accessible proximal tubule in both species.
Systolic time intervals during +Gz acceleration
Authors: Graboys T. B. , Michaelson E. D.
Published: December 2017

Systolic time intervals (STI) were recorded in 8 healthy male volunteersbefore, during, and after 30-s exposures to +3 Gz, +5 Gz, and +7 Gz acceleration. Heart rate (HR) increased at all +Gz levels, as did the HR correctedQSIc interval, left ventricular ejection time (LVETc), preejection period (PEPc) and PEP/LVET. These changes in STI were also proportional to the +Gz level. At the higher +Gz levels, PEPc and PEP/LVET continued to increase early in the recovery period, but HR and all STI returned to control after 60s of recovery. Although physiological variables other than myocardial contractility, such as preload and afterload may influence STI during +Gz the effects of +Gz on stroke volume (SV) and cardiac output (CO) were estimated using previously described relationships between STI and invasively determined indices of cardiovascular function. In general CO increased as SV decreased. During recovery, HR and CO fell and CO remained slightly below controllevels, primarily because estimated SV remained low. This study demonstrates the feasibility of using STI to estimate noninvasively the transient changes in cardiovascular function during +Gz acceleration.
Physiologic limits to work in the heat and evaporative coefficient for women
Authors: Kamon E. , Avellini B.
Published: December 2017

Ten heat-acclimated females exercised seminude on a treadmill at 30% Vo2 max (M=152 W-m-2) under eight air temperatures (Ta) ranging from 30 degrees C to 52 degrees C. Each experiment involved 1 h of fixed and a 2nd h of progressively increasing water vapor pressure (Pw) with either air movement of 1 m-s-1 or still air. The equilibrium values of rectal temperature (Tre), mean skin temperature (Tsk),and heart rate (HR) reached in the 1st h were forced upwards in the 2nd h by the rising Pw. The critical Pw was defined by the Tre inflection point for each Ta. The loci of the critical Pw were used to delineate the thermal limits on the psychrometric chart and were used to derive the effective evaporative coefficient (Ke') applicable to the ambient capacity for evaporative cooling (Emax). The derived Ke' was 17.6 +/- 4.2 W-m-2 (mean +/- SD) for v0.6m-s-1. Isotherms constructed on the basis of the obtained Ke, Tsk, and sweating capacity were higher than the physiologically based Pw limits.
Method for chronic recording of electroencephalographic activity in conscious dogs
Authors: Ferrario C. M. , Averill D. B. , Nadzam G. R. , Porritt D. S. , McCubbin J. W.
Published: December 2017

The difficulties involved in recording high-quality electroencephalograms chronically from conscious dogs have been resolved by devising an implantable pure silver electrode assembly that can be screwed permanently into the skull. The assembly eliminates electromyographic artifacts and provides high-fidelity tracings. Construction is simple and commercially available, inexpensive parts are used. Highly satisfactory records can be obtained overperiods of months.
Localization of airway constriction using gases of varying density and viscosity
Authors: Drazen J. M. , Loring S. H. , Ingram R. H.
Published: December 2017

The relationship between the major site of airway constriction and change in total pulmonary resistance while breathing gases of varying density and viscosity was studied in five anesthetized dogs pretreated with atropine. Using an airway catheter, central and peripheral components of pulmonary resistance were measured by forced oscillation. Total pulmonary resistance was measured at 0.5 1/s with lungs air-filled, at 0.25 1/s with the lungs filled with 80% helium-20% oxygen (RL-He), and at 1.0 1/s with 80% sulfur hexafluoride-20% oxygen (RL-SF6). Intravenous histamine infusion resulted in a predominantly peripheral resistance increase as determined by the airway catheter and a much larger percentage increase in RL-He than in RL-SF6. Tracheal banding produced a purely central resistance increase and a greater change in RL-SF6 than in FL-He. These results support theoretical predictions that the predominant site of airways constriction can be determined without on airway catheter by comparing relative changes in total pulmonary resistance using different flow regimes.
Effects of lower body negative pressure (LBNP) on the distribution of body fluids
Authors: Foux A. , Seliktar R. , Valero A.
Published: December 2017

Reduction of pressure on the lower part of the human body is believed to be capable of altering the normal fluid distribution. This could serve as a therapeutic method for emergency relief of the effects of hypertension, or it could be used as counterbalance for zero gravity and assist in preparing astronauts for reentry into the gravitational field. The present work describes a technique of assessment of the fluid shift caused by such pressure reduction. Thirty experiments were performed on four healthy subjects. The shift of fluid was assessed by measuring changes in body weight distribution of the tested subjects. The shift of fluid was assessed by measuring changes in body weight distribution of the tested subjects. The experimental results show that two processes may have taken place within the human body: shift of blood within the vascular system and diffusion of fluids from the circulatory system to the tissues. The total fluid shift ranges between 1 and 2 kg. It was proportional to the pressure gradient and exponential with time. The systolic blood pressure was reduced with the pressure reduction while the pulse rate increased.
Mechanical work of breathing derived from rib cage and abdominal V-P partitioning
Authors: Goldman M. D. , Grimby G. , Mead J.
Published: December 2017

Estimates of the mechanical work of breathing derived from measurements of separate rib cage and abdominal volume displacements, each plotted against transthoracic pressure, include the elastic cost of chest wall distortion which may occur during breathing. Inspiratory work is partitioned between the diaphragm and the rib cage musculature by adding measurements of transabdominal pressure. The mechanical work of breathing derived from separate rib cage and abdominal volume-pressure (V-P) tracings (the sum of work done by the diaphragm, rib cage, and abdominal musculature) is compared with ventilatory work estimated from the Campbell diagram (which does not include any distortional work). During resting breathing the two estimates are closely comparable, consistent with little or no distortion of the chest wall during quiet breathing. As ventilation increases, the estimate developed from rib cage and abdominal tracings reveals systematically greater mechanical work than is estimated from the Campbell diagram, consistent with distortion of the chest wall from the relaxed thoracoabdominal configuration at higher levels of ventilation. At ventilations achieved during exercise, the Campbell diagram may underestimate the work of breathing by up to 25%.
New respiratory gas valve support for graded exercise studies
Authors: Ellis D. G. , Lampman R. M.
Published: December 2017

We describe a new support structure for respiratory gas valves for use in exercise studies. Use of this structure largely avoids problems of large inertial reactions and feelings of confinement on the part of the subject which have characterized previous systems. The support mechanism consists ofa spring-reacted, pivoted boom carried on the end of a counterbalanced swinging beam. This device was designed for use on an adjustable slope motor-driven treadmill, but may be adapted to a variety of other experimental arrangements.
Muscle glycogen repletion after high-intensity intermittent exercise
Authors: MacDougall J. D. , Ward G. R. , Sutton J. R.
Published: December 2017

Six subjects exercised to exhaustion on a cycle ergometer at intensities corresponding to approximately 140% of their maximal aerobic power. Subjects attempted to pedal for 1-min intervals with 3-min rest periods between, and continued until 30 s of exercise could no longer be maintained. Venous blood was sampled for lactate and glucose analysis. Muscle biopsies were extracted from the quadriceps before and immediately after exercise and at 2-, 5-, 12-, and 24-h intervals thereafter for total glycogen analysis. Three subjects consumed a mixed controlled diet (approx. 3,100 kcal) during the 24 h after exercise, and three consumed the same diet plus an additional 2,500/kcal carbohydrate. Following exercise, glycogen concentration had dropped to a mean value of approximately 28% of its preexercise value. After 2 h, it had recovered to 39%, at 5 h to 53%, at 12 h to 67%, and at 24 h to 102% of its preexercise value, with no difference in resynthesis rate between the two groups. It was concluded that, following glycogen depletion through intense intermittent exercise, complete recovery to preexercise values may be accomplished within 24 h; and that within this time period, the rate of resynthesis cannot be accelerated by a higher than normal carbohydrate intake.
Lung mast cell density and distribution in chronically hypoxic animals
Authors: Tucker A. , McMurtry I. F. , Alexander A. F. , Reeves J. T. , Grover R. F.
Published: December 2017

Changes in the density and distribution of pulmonary mast cells were determined in six mammalian species exposed to hypobaric hypoxia (PB = 435 Torr) for 19–48 days. Control animals were studied at 1,600 m (PB = 635 Torr). Total lung mast cell hyperplasia was observed only in calves exposed to high altitude. Pigs, rats, and sheep exhibited small, but insignificant, increases in mast cell density. Perivascular mast cell proliferation adjacent to vessels of 30–500 mum in diameter was seen in both calves and pigs. Bronchial, alveolar septal, and systemic tissue (tongue) mast cell hyperplasia was not observed in any of the species. Three indices of pulmonary hypertension (right ventricular hypertrophy, medial thickness of pulmonary arteries, and pulmonary arterial pressure) correlated with perivascular mast cell density. The findings indicate that perivascular mast cell proliferation may relate more to the morphological pulmonary vascular changes and to pulmonary hypertension than to hypoxia, leading to the speculation that mast cells increase in number in response to the hypertension, rather than to mediate and maintain the hypertension.
cAMP in temperature- and ADH-regulating centers after thermal stress
Authors: Kornbluth I. , Siegel R. A. , Conforti N. , Chowers I.
Published: December 2017

cAMP concentrations in temperature-regulating sites of the brain and plasma osmolality were measured after exposure of male rats to 36 degrees C and 37–42% rh. for 10, 20, or 30 min. Plasma osmolality was affected by none of the heat exposures. In both the preoptic area and the posterior medial hypothalamus, cAMP concentrations were increased compared to controls, after 10, 20 and 30 min of heat exposure. In the supraoptic-paraventricular nuclei, neither 10 nor 20 min of exposure resulted in augmented cAMP concentrations; but after 30 min of heat exposure, cAMP levels in these nuclei were significantly greater than in controls. Neurohypophysial cAMP concentrations were increased after both 10 and 30 min of exposure. Cerebral cortical cAMP concentrations were not affected by thermal stress. It is concluded that cAMP is involved in the neural mechanisms which are brought into play to regulate body temperature during acute heat exposure. The significance of this involvement and its relation to the overall temperature-regulating mechanisms of the body are discussed.
Turbulent airflow meter for long-term monitoring in patient-ventilator circuits
Authors: Elliott S. E. , Shore J. H. , Barnes C. W. , Lindauer J. , Osborn J. J.
Published: December 2017

A new type of flowmeter is described which operates on the principle that pressure drop (deltaP) produced by turbulent volume flow (V) through a simple resistance chamber obeys a relation of V = K (deltaP)0.50. Data are given showing that the device follows a true power law with a single exponent for airflows ranging from 3.5 to 270 l/min. Standard instrumentation and a linearization circuit are used with the new flowmeter to provide linear steady-state and alternating airflow measurements up to peak rates of 150 l/min and frequency to 15 Hz. Data are presented comparing integrated airflow readings from the new turbulent flowmeter and a laminar-type flowmeter. The turbulent airflow meter appears to offer increased reliability for long-term patient monitoring use in patient-ventilator circuits.
Forces applied to cranks of a bicycle ergometer during one- and two-leg cycling
Authors: Sargeant A. J. , Davies C. T.
Published: December 2017

An examination was made of the comparability of one- and two-leg exercise performed pedaling a stationary bicycle ergometer. The pattern of force exerted on both cranks was examined by means of a specially adapted ergometer which is described. The mean of the peak force in each cycle (MPF) was linearly related to work load (W) in both forms of exercise, and if account was taken of the doubled work output in two-leg cycling there was no significant difference between the MPF/W relationships; these are given by the equations one-leg: MPF (kg) = 11.23 + 0.065 (W in kpm/min) two-leg MPF (kg) = 10.76 + 0.032 (W in kpm/min). Calculation from the force records of the work performed on the cranks (WCR net) showed good agreement (r = 0.98, P less than 0.001) with the work load set on the ergometer. Analysis of the proportion of work done in leg extension and flexion phases of cycling revealed no differences between one- and two-leg exercise or between the right and left legs. The majority (approximately 80%) of Wer net being performed in leg extension is described by: Wer net (extension)) = 10.6 +/- 0.8 (W cr net total). In one-leg exercise (W greater than 900 kpm/min) the variation in rotation speed during a normal cycle ranged from +20 to --30% of the mean speed compared with +/- 10% in two-leg exercise.
Modification of renin and aldosterone response to heat by acclimatization in man
Authors: Finberg J. P. , Berlyne G. M.
Published: December 2017

Plasma renin activity (PRA) and aldosterone concentration (PA) increased in eight men following a brief (30--40 min) heat exposure (50 degrees C dry bulb, 25 degrees C wet bulb) with light work. Sweat loss was less than 1% body weight. Plasma cortisol concentration was unchanged or decreased. In four subjects, a standard heat test was repeated in winter and summer (natural acclimatization). The increase in PRA and PA following heat exposure was less in summer than in winter. Four other subjects were artificially acclimated by daily work periods of 90 min at 50 degrees C for 7 days (artificial acclimation). Heat-induced elevation in PRA was considerably reduced by artificial acclimation, although postheat PA was reduced in only two of the four subjects. The small degree of sweat loss under the conditions of these experiments shows that circulating renin and aldosterone levels are increased in the heat even when a significant sodium deficit is not incurred.
Role of the parasympathetic system in antigen-induced bronchospasm
Authors: Rosenthal R. R. , Norman P. S. , Summer W. R. , Permutt S.
Published: December 2017

Human subjects, sensitive to ragweed, inhaled aerosols of increasing concentrations of ragweed pollen extract in the presence and absence of pretreatment with inhaled atropine. The cumulative dose of antigen required for a 35% decrease in airways conductance was termed PD35. Atropine, 1.2 or 5 mg, increased airways conductance before antigenic challenge but did not alter signigicantly the PD35 for ragweed extract, although these doses of atropine inhibited airways responses to inhaled methacholine chloride and citric acid. We conclude that the cholinergic nervous system plays a modulating role in bronchomotor tone and responses to irritants, but that parasympathetic reflexes are not invariably a major component of human bronchial responses to inhaled allergen.
Rheological properties of microliter quantities of normal mucus
Authors: King M. , Macklem P. T.
Published: December 2017

Microliter quantities of normal canine tracheobronchial mucus were obtained by direct sampling from the tracheas of anesthetized dogs. The rheological properties of the mucus samples were determined using a newly developed magnetic rheometer. The data show a very rapid decrease in dynamic viscosity with increasing frequency, and a much less rapid increase in elasticity. Mean values of elasticity and viscosity at 1 rad-s-1 for seven dogs were ca. 300 dyn-cm-2 and ca. 75 P, respectively. The steady-state viscosity values were ca. 3 X 10(4) P, i.e., two orders of magnitude higher than the highest dynamic values measured. The significance of the rheological behavior in terms of the clearance of secretions from the lung is discussed.
Morphometry of the distal air spaces in lungs of aging dogs
Authors: Hyde D. M. , Robinson N. E. , Gillespie J. R. , Tyler W. S.
Published: December 2017

Changes in pulmonary morphometric measurements with age were examined by manual and automated methods in 14 normal beagle dogs aged 289–3,694 days. The study was instituted as a statistical adjunct to previous morphological studies on these dogs that showed anthracosis and associated dilatations in the distal airways in aged dogs. With increasing age, the volumetric density of alveolar ducts increased concomitantly with decreases in the volumetric densities of alveoli and alveolar parenchymal tissue. The numerical and surface densities of alveoli also decreased with age. A comparison of an automated method with accepted manual methods showed no significant differences in stereological measurements of the distal air spaces with the exception of an overestimation of surface density by the automated method. The automated method was found to be a satisfactory method for evaluating the relative differences in alveolar surface densities and the volumetric densities of respiratory air space and parenchymal tissue.
Quantification of diaphragmatic EMG response to CO2 rebreathing in humans
Authors: Lopata M. , Evanich M. J. , Lourenco R. V.
Published: December 2017

To determine a reliable quantitative method of measuring diaphragmatic EMG (EMGdi), electrical activity of the diaphragm was obtained via an esophageal electrode during CO2 rebreathing in 6 normal males and processed three different ways: 1) integration (area), 2) as a moving time average, and 3) as a moving time variance. Integrated activity was quantified in terms of total activity and inspiratory activity. In addition, average total activity and average inspiratory activity were calculated. Moving average and moving variance were analyzed in terms of rate of rise (slope) and peak activities. All integration parameters, except average inspiratory activity, were poorly correlated to changes in PCO2, minute ventilation, and inspiratory muscle force, during rebreathing. Moving average and variance responses to rebreathing were linear with high correlation coefficients, with the slope measures showing the overall best correlations. There was no significant difference between average and variance EMGdi parameters in their responses to rebreathing. Time-related quantification of EMGdi, including average inspiratory activity, and particularly moving average and moving variance, appear to be reliable methods for quantitating neural drive to the respiratory muscles during CO2 rebreathing.
An anesthetized dog heatstroke model
Authors: Bynum G. , Patton J. , Bowers W. , Leav I. , Wolfe D. , Hamlet M. , Marsili M.
Published: December 2017

This study was undertaken to develop an anesthetized dog heatstroke model. Forty-six animals were anesthetized with pentobarbital sodium (25 mg/kg) intravenously, and maintained at an ambient temperature of (42–46 degrees C) with a water-heated blanket over 2.5–3.0 h until rectal temperatures rose to 43.0–44.5 degrees C. Animals then cooled passively until death occurred or until 18 h elapsed, and were prepared for autopsy. Liver, kidney, and brain temperature, mean weighted skin temperature, mean weighted surface heat loss, and metabolic rates were obtained. There were no significant differences between liver, kidney, brain, and rectal temperatures during the heating and cooling periods. Cardiac output rose to 127% of initial value, and dropped rapidly to zero at 43.4 degrees C rectal temperature. The rapid decline was accompanied by a doubling of heart rate and a rapid drop in blood pressure and respiratory rate. Cheyne-Stokes respiration and apnea preceded bradycardia followed by asystole or ventricular fibrillation. Certain serum constituents demonstrated modest elevations suggestive of widespread tissue damage. Autopsy did not reveal a clear pattern of heat injury, with the exception of consistent congestion of the major organs and karyorrhexis of lymphocytes. These data are in agreement with similar data from human heatstroke victims and other heatstroke modeling in dogs, and support the concept that the anesthetized dog can in many respects provide an adequate model for human heatstroke.
Effect of training on the response of plasma glucagon to exercise
Authors: Gyntelberg F. , Rennie M. J. , Hickson R. C. , Holloszy J. O.
Published: December 2017

This study was undertaken to determine whether the increase in plasma glucagon concentration that occurs in response to prolonged exercise is modified by endurance exercise training. Eight subjects participated in an exercise program, consisting of running and bicycling, 4 days/wk for 10 wk. The training program resulted in an average increase in VO2 max of 18%. The average increase in plasma glucagon during a 60-min long bicycle exercise test that required 60% of the subjects' VO2 max was 107+/-28 pg/ml, from 116+/-14 pg/ml at rest to 223+/-37 pg/ml after 60 min of exercise, prior to training. After training the same absolute work rate resulted in an increase in plasma glucagon of only 20+/-6 pg/ml, from 125+/-20 to 145+/-16 pg/ml (P less than 0.02). A similar blunting of the glucagon response to exercise was seen during work of the same relative intensity after training. Plasma insulin concentration decreased from 18.1+/-2.5 to 7.6+/-1.6 muunits/ml during the 60 min of exercise before training. A similar decrease in insulin concentration was seen at the same relative work rate after training. However, the decrease in plasma insulin at the same absolute work rate, from 18.5+/-3.0 to 12.5+/-1.8 muunits/ml, was significantly smaller after training (P less than 0.05).
Estimation of composition of weight loss in man: a comparison of methods
Authors: Yang M. U. , Wang J. , Pierson R. M. , Van Itallie T. B.
Published: December 2017

Five different procedures were used to estimate composition of weight loss by six obese individuals maintained on low-calorie regimens: 1) energy-nitrogen (E-N) balance; 2) total body water-nitrogen balance (TBW-N); 3) total body water (TBW); 4) total body potassium (TBK); and 5) an anthropometric method. Quantity of weight lost by obese subjects during comparison periods lasting 25–40 days ranged from 7.9 to 17.1 kg. Expressed as percent of aggregate weight loss, collective fat loss was 47.6 by E-N balance; 46.3 by TBW-N balance; 51.7 by TBK; 50.9 by anthrometry; and 33 by TBW. The E-N balance method yielded a tight cluster of individual means, whereas the other procedures gave a wide scatter of means. For short-term studies, the E-N balance procedure, although tedious and difficult, should yield results less variable than those generated by any of the other methods examined.
Plasma volume and intravascular protein masses in trained boys and fit young men
Authors: Koch G. , Rocker L.
Published: December 2017

Plasma volumes and intravascular protein masses were measured in eight well-trained boys (VO2 max = 59.6 +/- 6.5 ml/kg body wt) aged 13–15 yr and compared with two groups of adult athletes aged 17–20 yr (VO2 max = 61.8 +/- 3.4 ml/kg body wt) and 24–30 yr (VO2 max = 63.3 +/- 4.1 ml/kg body wt), respectively. The trained boys had larger plasma volumes and increased intravascular masses of albumin and hepatogenic globulins as compared with values available for children with normal physical activity. There was no significant difference between the boys and the adults concerning maximal oxygen uptake, plasma volume, albumin, immunoglobins, and haptoglobin, when allowance was made for differences in body dimensions; probably due to the young age, however, the boys had considerably higher relative alpha2-macroglobulin and transferrin masses. Endurance training apparently elicits the same response of the plasma protein system regardless of age, at least after pubertal age has been attained. The overall effect of these changes implies an increase of the water binding capacity of the plasma
Effects of lung inflation on longitudinal distribution of pulmonary vascular resistance
Authors: Dawson C. A. , Grimm D. J. , Linehan J. H.
Published: December 2017

A low-viscosity bolus technique was employed to determine the influence of lung inflation on the distribution of pulmonary vascular resistance in isolated cat lungs. When the lungs were collapsed, the longitudinal distribution of resistance was concentrated near the proximal (arterial) part of the vascular bed. As the lungs were inflated, the resistance became more evenly distributed with the maximum located close to the midpoint of the total blood volume. The fraction of total pressure drop across the lung which occurred proximal to the midpoint of the total lung blood volume decreased from 0.69 in the collapsed lung to 0.43 at a transpulmonary pressure of 16 cmH2O.
New apparatus for exercising a monkey seated in a primate chair
Authors: Gisolfi C. V. , Mora F. , Nattermann R. , Myers R. D.
Published: December 2017

A new apparatus and method for exercising a monkey seated in a primate chair are described. The apparatus consists of a set of hand and foot bars mounted at either end of a rocker arm that pivots in a vertical plane. This arm is connected by a steel cable to a wooden box that houses lead weights. By simultaneously pushing the foot bar and pulling the hand bar, the monkey lifts a weight and triggers a microswitch which releases a banana-flavored food pellet into a well close to the animal's mouth. The amount of work performed is varied by changing the a) amount of weight to be lifted, b) distance the weight must be lifted, or c) number of times that the animal lifts the weight for a single reward. During 30 min of exercise, the heart rate of a given monkey rose 120 beats/min, respiratory rate 24/min, and colonic temperature 1.2 degrees C above base-line values. Total work performed in 30 min varied from 250 to 360 kpm. Major advantages of this apparatus over a treadmill or bicycle ergometer are that the animal 1) is restrained sufficiently to permit the delicate experimental manipulations and physiological measurements, 2) can be exercised strenuously in a quantitative fashion, and 3) is readily trained to perform the task in a short time.