bluuebunny/crossref_metadata_2025 huggingface dataset:
Cardiovascular and sweating responses to water ingestion during dehydration
Authors: Senay Leo C. , Christensen Margaret L.
Published: December 2017

The experiments reported are concerned with cardiovascular and sudomotor events preceding, accompanying, and following ingestion of water by five dehydrating subjects 8.75 hr after entrance into a heat chamber (43.3 C DB, 29 C WB). Certain skin areas such as the cheek showed increases in evaporative heat loss before subjects came in contact with water. This reflex could be initiated by saline ingestion but the degree of skin and oral temperature changes appeared to depend on tonicity of fluid ingested. The gustatory reflex was not thought to be the initiating agent for sudomotor responses. Increases in cutaneous blood flow appeared to begin almost as promptly as sweating responses but took considerably longer to develop. Ingestion of saline, though initiating a sweating response, did not alter heart rate, blood pressure, or cutaneous blood flow. It is suggested that fluid ingestion, regardless of tonicity, triggers reflex sweating over the body surface. Intensity and duration of this sudomotor response, as well as initiation of cardiovascular changes, apparently depend on tonicity of ingested fluid.

cutaneous blood flow; skin temperature; regional sweating

Submitted on November 27, 1964
Pulmonary diffusing capacity and capillary blood flow during forward acceleration
Authors: Power Gordon G. , Hyde Richard W. , Sever Raymond J. , Hoppin Frederic G. , Nairn Jean R.
Published: December 2017

We studied possible causes of the decreased arterial oxygen saturation seen when a subject is accelerated in a centrifuge by measuring simultaneously the pulmonary diffusing capacity, DlCO, and the effective pulmonary capillary blood flow, Qc, using breath-holding techniques with carbon monoxide and acetylene. After 1 min of forward ("eyeballs in") acceleration at eight times normal gravity, 8 G, average Dl decreased 35% from an initial control of 33.7 to 21.5 ml/(min x mm Hg) in four subjects. Although this decrease was statistically significant, the values observed were not low enough to indicate that impaired diffusion was a prime cause of arterial unsaturation. Average Qc decreased 35% during acceleration from an initial control value of 12.9 to 8.2 liters/min, also a significant change. These values may have indicated that total pulmonary blood flow was reduced, but a more likely explanation is that a large portion of pulmonary flow perfused nonventilated regions. Dl and Qc returned toward initial control levels within 8 min after acceleration in most instances.

lung volume during acceleration

Submitted on March 1, 1965
Deep diving and short decompression by breathing mixed gases
Authors: Keller H. , Bühlmann A. A.
Published: December 2017

A series of test dives carried out by 14 subjects in depths between 130 and 1,000 ft. for periods varying between 5 min and 2 hr revealed that changes of the inert gas in the breathing mixture permit a considerable shortening of the decompression time. The physical and physiological basis of the method is discussed.

physiological properties of He, N2, and Ar related to molecular weight and solubility; differences in diffusion rate and saturation speed of He, N2, and Ar

Submitted on January 18, 1965
Effect of muscular exercise in a hot environment on canine fibrinolytic activity
Authors: Bedrak E.
Published: December 2017

The effect of muscular exercise, heat stress, and muscular exercise plus heat stress on the euglobulin fibrinolytic enzyme system was determined in 11 Alsatian dogs prior to and after acclimatization in a hot environment. All the physiological stresses employed, particularly muscular exercise in a hot environment, enhanced the fibrinolytic activity and lowered plasma fibrinogen levels in all animals, especially in the nonacclimatized. The increased fibrinolytic activity, as measured by fibrin plate methods, was primarily related to plasminogen activator and to a lesser degree to active plasmin. In acclimatized animals at rest, the activity of plasminogen activator is lower, that of plasmin is relatively unchanged, while the level of plasma fibrinogen tends to be higher than in nonacclimatized animals at rest.

euglobulin fibrinolytic activity and heat acclimatization in dogs; heat stress; plasminogen activator; plasmin fibrinogen and heat acclimatization; nonacclimatized and heat-acclimatized dogs

Submitted on November 23, 1964
Pyridoxine and GABA as antagonists to drug-induced convulsions in monkeys
Authors: Kopeloff Lenore M. , Chusid Joseph G.
Published: December 2017

The antagonistic properties of pyridoxine and gamma aminobutyric acid (GABA) toward convulsant drugs were evaluated by determining their in vivo protective effects when administered parenterally prior to challenge. In a group of 28 monkeys composed of 19 chronic epileptics and 9 controls, pyridoxine and GABA provided variable grades of protection against the convulsant actions of methoxypyridoxine, semicarbazide, and to a lesser degree, pentamethylenetetrazol (Metrazol) and 3,3-methylethylglutarimide (Megimide). Neither pyridoxine nor GABA protected epileptic, brain-operated nonepileptic, or normal monkeys from the convulsant actions of parenteral picrotoxin. No evidence therefore was found in these experiments to support the suggestion that GABA (or pyridoxine) and picrotoxin are antagonistic to each other.

experimental epilepsy in Macaca mulatta; gamma aminobutyric acid and vitamin B6 as anticonvulsants

Submitted on February 15, 1965
Distribution of inspired gas during ventilation without respiratory movements
Authors: Lichtneckert Stefan J. A. , Lundgren Claes E. G.
Published: December 2017

Normal subjects were ventilated by means of a barospirator, which allows cyclical ventilation without respiratory movements. It was thus possible to eliminate the influence that distension may have and allow flow resistance in the airways and the volume of the air spaces ventilated through them to become the main factors defining the distribution of inspired gas. Distribution of inspired gas was measured by nitrogen-elimination technique and by calculation of the index of alveolar ventilation. It could be demonstrated that the distribution of inspired gas in ventilation without respiratory movements is uneven, which is asscribed to different relations between the above-mentioned resistance volume factors in different parts of the lungs.

airway resistance; index of alveolar ventilation; barospirator ventilation; mechanics of breathing; lung function; nitrogen-elimination curves; artificial respiration

Submitted on December 31, 1964
Gas chromatography and pulmonary diffusing capacity measurements
Authors: Danzer L. A. , Kearns K. L. , Cohn J. E.
Published: December 2017

A gas chromatographic system is described which accurately measures low levels of neon and carbon monoxide in high concentrations of oxygen. The system contains a special parallel column package used in conjunction with a venting valve. Accurate reproducible analyses for Ne, CO, CO2, O2 and N2 are obtained from a single 10-ml gas sample.

respiratory gas analysis; carbon monoxide in oxygen, determination; neon in oxygen, determination

Submitted on December 2, 1964
Effect of temperature on solubility of O2 in human plasma
Authors: Christoforides C. , Laasberg L. H. , Hedley-Whyte John
Published: December 2017

(See PDF)

Page 58: in table 2, agr Blood values ascribed to Handbook of Raspiration should read 28 C 0.0285; 18 C No value.
Tremor analyzer for small laboratory animals
Authors: Silverman R. W. , Jenden D. J.
Published: December 2017

The design considerations and construction for a complete tremor analyzer have been reviewed. A design description of a working analyzer is presented which uses a loudspeaker as an electro-mechanical transducer. The electrical signal is amplified, filtered, rectified, and integrated to provide a continuous minute-to-minute indication of tremor amplitude.

tremor tranducer; oxotremorine

Submitted on September 8, 1969
Circulatory impairment during exposure to ambient pressures of 4 mm Hg and 55 mm Hg
Authors: Pratt Alfred J. , Stone Hubert L. , Stegall Hugh F. , Kaufman William C.
Published: December 2017

The extent that the circulation is impaired under near-vacuum conditions was investigated in five anesthetized dogs and one anesthetized chimpanzee decompressed from 380 mm Hg to 4 mm Hg in l–2 s and maintained at 4 mm Hg for 60 s. Blood flow velocity, measured within the thoracic aorta with a catheter-tip Doppler flowmeter, severely decreased in dogs within 30 s and approximated cessation in the chimpanzee after 10 s. Aortic and vena caval pressures tended to equalize in dogs; equilibrium and subsequent pressure gradient inversion resulted in the chimpanzee. Mechanical events associated with gas expansion and especially water vaporization were believed largely responsible for these effects. Anoxic bradycardia, similar in both species, ensued also. Anoxic anoxia, uncomplicated by water vaporization after decompression from 431 mm Hg to 55 mm Hg, failed to seriously impair cardiovascular function in dogs, but apparently was accompanied in the chimpanzee by mechanical events from gas expansion sufficient to block the circulation. Differences in responses in these two species probably involved the physical characteristics of the torso.

altitude; anoxia; ebullism; gas expansion; near-vacuum exposure; rapid decompression
Computation of transit time distributions using sampled data Laplace transforms
Authors: Neufeld G. R.
Published: December 2017

Page 148: G. R. Neufeld. “Computation of transit time distributions using sampled data Laplace transforms.” Page 149: in column 2, lines 15 and 16 should read:

(See PDF)
Normal arterial blood pH, oxygen, and carbon dioxide tensions in unanesthetized dogs
Authors: Feigl Eric O. , D'Alecy Louis G.
Published: December 2017

Femoral artery blood samples from 30 unanesthetized unrestrained nonpanting dogs were analyzed. Average normal pH was 7.42 (sd 0.03), mean Po2 89.5 mm Hg (sd 4.4), and Pco2 36.8 mm Hg (sd 2.4). pH was determined with a glass electrode. Pco2 was measured using a Severinghaus electrode. Po2 was determined with a Clark-type polarographic polypropylene-covered electrode. Measurements were made at 39 C (normal dog rectal temperature).

blood gas; Clark electrode; Severinghaus electrode
A stable, sensitive, low-compliance capacitance force transducer
Authors: Hamrell B. B. , Panaanan R. , Trono J. , Alpert N. R.
Published: December 2017

The measurement of active and passive force levels in heart muscle requires short-and long-term base-line stability. The capacitance force transducer described here represents an optimization of the relationship between sensitivity, compliance, and frequency response in a design that minimizes long-term base-line drift related to thermal gradients within the apparatus. Thermal stability of the instrument is obtained with the use of quartz and Invar in the construction of the variable capacitor, the maintenance of internal transducer temperature at a constant level well above ambient, and the use of thermally insulating air gaps. Sensitivity ranges from 1.0 to 2.0 V/g wt in the several instruments tested, the output is linear, compliance is negligible with static loads up to 6 g wt, hysteresis is not significant with transient loading with 20 g wt, and long-term drift is greater than or equal to 0.050 g wt. These instruments are designed for use with myocardial preparations but can be adapted for skeletal muscle experiments.
Glucose metabolism in thyroidectomized and normal dogs during rest and acute cold exposure
Authors: Paul P. , Donohue M. , Holmes W. L.
Published: December 2017

Uniformly labeled (14C)glucose was infused iv at a constant rate into unanesthetized surgically thyroidectomized (THY) and normal dogs during the basal state at 22 degrees C and during cold exposure at 4–5 degrees C. 02 uptake, CO2 output, and plasma glucose levels were determined; from these rates of glucose turnover and oxidation were calculated. Comparison of THY with normal dogs shows that at a mean plasma glucose level of 103 mg/100 ml, a significantly lower glucose turnover rate was observed in THY dogs on the basis of a kg body weight, body surface area (m-2), but not per cal BMR. The same percentage of glucose turnover was immediately oxidized in THY and normal dogs, accounting for 16 and 15% of the total caloric expenditure, respectively. Acute cold exposure increased energy expenditure in both THY and normal dogs without a change in glucose level or turnover rate. However, the percentage of glucose turnover which was immediately oxidized as well as the amount of glucose oxidized increased significantly and proportionally to the increase in energy expenditure so that the percent of calories derived from plasma glucose oxidation remained the same as that observed during the control period.
Pulmonary venous waterfall and perivenous pressure in the living dog
Authors: Smith H. C. , Butler J.
Published: December 2017

Evidence has been obtained that a waterfall effect occurs in the pulmonary veins of the living dog. Anesthetized open-chest dogs were used. Small catheters were passed from the left atrium retrogradely up the pulmonary veins and venous tributaries until they finally pierced the venous walls. They were then pulled out through the surface of the lung until their bellshaped inner ends wedged in small side branches of the vein. They were used to measure upstream venous pressures via the occluded tributary without occlusion of the vein. The pulmonary lymphatics and bronchial circulation were untouched. Alveolar pressure (transpulmonary pressure, Ptp) was held constant during the periods of measurement. We found that intrapulmonary (upstream) venous pressures did not rise with elevation of left atrial (downstream) pressures at any Ptp until a pressure of at least 7 cmH2O above the base of the lung was exceeded. This left atrial pressure (below which a venous waterfall or flow-limiting segment effect was present) increased with Ptp when Ptp exceeded about 15 cmH2O. The waterfall occurs in the larger veins at the lung surface. Its presence and location suggest that intrapulmonary veins in the living animal are held open by the surrounding lung tissue and that neither the flow through them nor their contained volume is influenced by left atrial pressure when this is low.
A new method for the measurement of percent oxyhemoglobin
Authors: Pittman R. N. , Duling B. R.
Published: December 2017

A new method is presented for the spectrophotometric determination of percent oxyhemoglobin (percent saturation) in whole blood. The method is based on a theory of light absorption and scattering by particulate suspensions and requires the measurement of optical densities (D) of blood at three closely spaced wavelengths. The contribution of scattering to the optical density at each wavelength is determined from optical density values at two isosbestic wavelengths (546 and 520 nm) and the optical density at the third wavelength (555 nm) is related to the extent of oxygenation of the hemoglobin. The wavelength independence of the scattering contribution (B) induced by red cells was established from 510 and 575 nm. The optical density of red blood cell suspensions was measured with a spectrophotometer and a linear relationship was found between percent saturation and the corrected optical density ratio, (D555 B)/(D546 B). For a given saturation, this ratio was independent of optical path length (0.1–2 mm) and hematocrit (3–50%).
Assessment of Scholander micromethod for gas concentrations versus weighing method
Authors: Gaudebout C. , Blayo M. C.
Published: December 2017

Three gaseous mixtures in N2, of varying concentrations of CO2 (3.60, 5.79, and 9.36%) and O2 (22.18, 15.12, and 6.82%), respectively, were prepared by precise weighings, which may serve as absolute measures. These mixtures were analyzed with two apparatuses by the Scholander micromethod. Taking into account the influence of several factors (apparatuses, order of analyses, etc, it appears that differences between apparatuses were not significant in five of six cases and the effect of order was significant in O2 (P less than 0.01) but not in CO2 for the set of measurements. When compared with weighings, measurements differed only in one apparatus (P less than 0.02) in two of six cases and by no more than 0.02%. The relation between weighings and measurements was highly significant (P less than 10(-9) and no lack of fit to linearity occurs. Side effects of the factors considered and interactions between them are discussed. In conclusion, the micromethod of Scholander gives accurate results, in very good agreement with the reference values provided that certain technical precautions are observed.
A new method for calibrating indicator dilution curves
Authors: Boyle J. , Diamond P.
Published: December 2017

A technique is proposed and experiments carried out to validate an in vivo method of calibrating ascorbate dilution curves. Cardiac output measured by the proposed method (COi) was compared to cardiac output measured by electromagnetic flowmeter (COe). COe averaged 1,281 mg/min and COi averaged 1,284 ml/min (P greater than 0.90). Correlation between the two methods was 0.92. It is concluded that the proposed method measures CO with reasonable accuracy and provides a number of advantages over the usual method of measuring blood flow by means of indicators.
Preferential use of casing (girth) measures for estimating body volume and density
Authors: Weltman A. , Katch V.
Published: December 2017

Theoretical justification for the preferential use of casing (circumference) measurements for estimating total body volume (TBV) and body density (Db) was studied in 24 female subjects (mean age 20 yr, mean wt 58 kg). Multiple linear regression equations resulted in R = On-0.99 with a standard error no larger than 1.69 liters for predicting TBV and R = Oa-Oh with a standard error no larger than 0.0084 g/ml for predicting Db. Validations of these regression equations using two additional samples of subjects resulted in validity coefficients of r = 0 –0.99. All the correlation coefficients were statistically significant (P less than 0.01).
Continuous in vivo measurement of arterial PO2 in humans
Authors: Jank K. , de Hemptinne J. , Swietochowski A. , Demeester M.
Published: December 2017

A system suitable for prolonged continuous in vivo measurement of human arterial PO2 is described. The system uses a polarographic electrode developed by Kimmich and Kreuzer, inserted in a specially made shunt between the radial artery and an antecubital vein. Nhe electrode surface is maintained in a fixed position parallel to the flow of blood; blood velocity dependency is small owing to the high flow rate achieved (more than 40 cm/s); clotting is prevented by the material used and the continuous instillation of heparin through the arterial end of the shunt. The system has been tested in vitro; it is stable (variation less than 0.5% in 24 h), linear and precise (plus or minus 0.2%) in a broad range of PO2 values (from about 10 mmHg to more than 700 mmHg); its response time is 0.4 s per 95% of deflection. It has been applied to 35 patients for periods ranging between 6 and 24 h; most of the patients were ventilated by an Engstrom respirator.
Limitations to maximum oxygen uptake in arms, leg, and combined arm-leg ergometry
Authors: Reybrouck T. , Heigenhauser G. F. , Faulkner J. A.
Published: December 2017

Our purpose was to study the effect of arm, leg, and combined arm-leg ergometry on the oxygen uptake (Vo2), cardiac output (Q), ventilation, and anaerobic threshold (AT) of three healthy men. At submaximum work intensities, Vo2 was not significantly different in the three tasks, but differences were observed for heart rate, ventilation, and Q. The AT was reached at progressively higher work rates in arm, leg and combined arm-leg ergometry, respectively. The Vo2 max in arm ergometry averaged 68 percent of the Vo2max in leg ergometry and 60 percent of Vo2 max in combined arm-leg ergometry. Two subjects with Vo2max's less than 45 ml/kg-min had a mean Vo2max in combined arm-leg ergometry 19 per cent higher than in leg ergometry. A third subject, with a Vo2max greater than 50 ml/kg-min, showed no change. Differences in Vo2max were primarily due to the differences in Q. Skeletal muscle blood flow appears to be a critical factor in the limitation of Vo2max in arm or leg ergometry.
A self-contained calibration unit for use with intracellular recording systems
Authors: Pruett J. K. , Francis W. W.
Published: December 2017

A relatively inexpensive solid state device designed for calibration of amplifiers and recorders used in microelectrode studies is described. The device is imposed between the ground electrode and the amplifier and provides three calibration signals; 100 mV DC for calibrating amplitude a variable-frequency square wave, 100 mV in amplitude use for capacitance neutralization, and a 100-mV, essentially square-wave signal with variable rate of rise and fall used for calibrating electronic differentiating circuits. The instrument is self-contained and battery powered. It was designed to remain in the circuit while recording. Calibration can be accomplished with the microelectrode in the circuit or with a dummy load.
A method for the placement of His bundle electrodes and production of atrioventricular block in dogs
Authors: Baum T. , Peters J. R. , Butz F. , Much D. R.
Published: December 2017

A multibarrell electrode designed for the location of the His bundle (HB) in open-chest dogs is described. The barrels may be used for the introduction of electrodes into the region of the HB for recording or pacing or for the injection of formaldehyde into the area to produce atrioventricular block.
Measurement of renal interstitial fluid pressure with polyethylene matrix capsules
Authors: Ott C. E. , Cuche J. L. , Knox F. G.
Published: December 2017

The renal interstitial fluid pressure was measured in dogs from small chronically implanted solid capsules made of porous polyethylene matrix material (pore size approximately 60 mum). Tissue does not grow into the polyethylene and the matrix creates a permanent fluid-filled space in communication with the interstitium. The fluid pressure in the capsule matrix was measured from a tube leading from the capsule with an active servo-null pressure-measuring device. Renal interstitial fluid pressure measured from 28 hydropenic dogs averaged 6.1 plus or minus 0.51 mmHg (SE). Increasing oncotic pressure inside the capsule to 90 mmHg resulted in a small but significant increase in hydrostatic pressure inside the capsule of 3.3 plus or minus 0.46 mmHg. However, the hydrostatic pressure returned to control levels within 30 min. In vitro studies indicated that the pressure measured from the capsule was highly sensitive to change in surrounding hydrostatic pressure, but insensitive to change in surrounding oncotic pressure. Histological studies showed a small layer of connective tissue surrounding the capsule less than 100 mum thick in many areas. There was no evidence of inflammation or tissue rejection. It is concluded that the small chronically implanted polyethylene capsule is a reliable method for the measurement of renal interstitial fluid pressure.
Simulation of regional lung emptying during slow and forced expirations
Authors: Pardaens J. , van de Woestijne K. P. , Clement J.
Published: December 2017

Regional lung emptying was simulated by means of a bialveolar lung model. The influence of bronchial asymmetry and the vertical pleural pressure gradient was evaluated. The model suggests that 1) in vivo the influence of the pleural pressure gradient prevails over that of the bronchial asymmetry; 2) in the presence of this gradient, the shape of phases III and IV of the single-breath washout curves obtained following inspiration of a tracer gas bolus at residual volume is determined by the recoil pressure-volume curve of the lung, by the vertical displacements of the alveoli, and,, at higher flow rates, by the elastic characteristics of the airways; 3) if the pleural pressure gradient is independent of lung volume and of flow rate, the factors mentioned in 2 suffice to produce single-breath washout curves (phases III and IV) and regional vs. overall lung volume relationships corresponding to those observed in vivo; 4) the configuration of the maximal expiratory flow-volume curve is relatively insensitive to pulmonary and bronchial asymmetry, at least in healthy individuals.
A high accuracy linear rate meter
Authors: Wyss C. R.
Published: December 2017

By implementing analog computer techniques using digital circuits, an instantaneous rate meter was built with approximately 100 times the accuracy of commercially available rate meters. The circuit is accurate to within +/- 0.2 events/min over a range of rates of 0.2–900 epm. Modifications can be made to provide a digital display of rate. The circuit design techniques used in developing the rate meter may be used to generate a wide variety of functions of time with very high accuracy.
Substrate utilization by the inactive leg during one-leg or arm exercise
Authors: Ahlborg G. , Hagenfeldt L. , Wahren J.
Published: December 2017

Substrate utilization by the nonexercising leg was studied in healthy subjects during one-leg exercise at an average work load of 105 W for 40 min (n equals 8) or during arm exercise at 65 W for 20 min (n equals 5). During one-leg exercise both the blood flow and the A-FV difference of oxygen for the non exercising leg rose, resulting in an approximately five fold increment in oxygen uptake. EMG activity of the leg was increased above basal. Despite unchanged or falling arterial levels of insulin, the A-FV difference for glucose across the nonexercising leg rose during exercise and the estimated glucose uptake increased approximately fourfold. Release of lactate in the basal state reverted to a significant net uptake of lactate by the nonexercising leg. During arm exercise there was a 20–70% rise in leg blood flow and the leg oxygen uptake rose 25–45% in spite of minimal EMG activity from the thigh muscles. There was a large uptake of lactate by the legs during arm exercise. We conclude that several important metabolic alterations take place in the nonexercising leg tissues during physical exertion: 1) blood flow and oxygen uptake rise, partly as a consequence of motor activation; 2) substrate utilization shifts from a predominant FFA uptake in the basal state to a greater utilization of carbohydrate; 3) nonexercising muscle, and possibly adipose tissue, play an important role in the removal of lactate during exercise.
Effects of hypoxic and CO hypoxia on isolated hearts
Authors: Scharf S. M. , Permutt S. , Bromberger-Barnea B.
Published: December 2017

Isolated perfused dog hearts were made hypoxic by respiring the support dog with low oxygen (hypoxic hypoxia) or with carbon monoxide (CO hypoxia). Each heart was exposed to both types of hypoxia, separately. Effects on coronary flow (Qt), coronary vascular resistance, cardiac oxygen consumption (Vo2), and contractility (%deltadP/dt) were studied. Two series of experiments were done. Series I: At constant perfusion pressure. As oxygen content (Cao2) was lowered from 20 to 5 vol%, Qt doubled with hypoxic hypoxia and almost tripled with CO hypoxia (P less than 0.01). Vo2 and contractility increased with both types of hypoxia. Beta-adrenergic blockade eliminated the increase in VO2 and contractility but not the difference in Qt increase between hypoxic and CO hypoxia. Series II: At constant Qt (with beta-blockade), vascular resistance decreased more with CO than hypoxic hypoxia. Finally, alpha-blockade eliminated the difference in vascular resistance and thus with complete (alpha and beta) blockade, the two types of hypoxia have the same effect and are indistinguishable.
Nonrebreathing valve system for small animal respiratory measurements
Authors: Barrow R. E.
Published: December 2017

Flow resistence, frequency response, and backflow characteristics of a nonrebreathing valve system applicable to measuring small animal respiratory volumes are described. Unidirectional valves, molded from liquid resin, were fitted into a modified Y tube for direct use on an endotracheal tube or face mask. Valve size and dead space volume can be scaled to fit several small animal species. In this system, valve resistance was 2.0 and 5.6 mm of water for steady flow rates of 0.5 and 3.0 1/min, respectively.
Body fluid responses of heat-tolerant and intolerant men to work in a hot wet environment
Authors: Senay L. C. , Kok R.
Published: December 2017

Acclimatization to heat before proceeding underground is a requirement for each South African mine laborer. Certain individuals among this large population cannot be acclimatized to heat (33.3 degrees C db, 31.7 degrees C wb) and are classified as heat intolerant. In this study certain body fluid responses to heat and work were compared between a group of 19 heat-tolerant (HT) and of 15 heat-intolerant (HI) subjects. To the factors known to affect heat tolerance such as age, weight, and oxygen consumption must now be added differences in body fluid responses. The HI group of subjects failed to hemodilute to the same degree as the HT group though working at the same relative work loads (30% and 50% VO2 max). As the 4-h work period (33.3 degrees C db, 31.7 degrees C wb) continued, the HI group did not maintain hemodilution in spite of the lower absolute work loads, sweat rates, and water deficits suffered by this group. From analysis of blood constituent changes it was suggested that the reason for the differences noted in body fluid dynamics concerned plasma protein equilibrium across capillary walls as well as the protein population of interstitial spaces.
Factors affecting a single-breath N2 washout phase IV
Authors: Kaneko K.
Published: December 2017

A lung model was constructed to examine the effects of the following factors on the phase IV of a single-breath N2 washout: the lung's elasticity change with age, closing pressure (CP), regional volume (Volr) distribution, pleural pressure, and gradient (Grad). The analysis revealed 1) when the CP was assumed to be + 1.0 cmH2O, predicted changes in closing capacity (CC) due to alterations in elasticity agreed with previous experimental results for individuals above 40 yr; for younger age groups, the predicted values were apparently larger, suggesting the CP may be near zero; 2) difference in Volr distribution alone caused alterations in CC and the slope of phase IV; 3) for 1 cmH2O elevation of CP, closing capacity /total lung capacity (CC/TLC) was predicted to increase about 8%; 4) for 0.1 cmHiO/cm Grad increase, CC/TLC was predicted to rise approximately 7%. In conclusion, multiple factors affect phase IV.
Blood pressure responses as an indicator of the anesthetic level in ground squirrels
Authors: Gur M. , Purple R. L.
Published: December 2017

In many experiments in visual physiology which employ halothane anesthesia, it is difficult to judge accurately an animal's anesthetic state, particularly so because of the necessity for paralysis and artificial respiration. For the ground squirrel (Citellus tridecemlineatus and C. mexicanus), we find that measures of arterial pressure response to a noxious stimulus combined with mean arterial pressure allow for an accurate division of halothane anesthetic state into five stages. All five stages are identified and are the same regardless of whether the animal is unparalyzed or is paralyzed and artificially respired. Use of these measures in long-term experiments allows for recognition of and adjustment for small perturbations of anesthetic state that may occur even though inhaled halothane concentration remains constant.
Maturational effects on respiratory responses to carbon dioxide in premature infants
Authors: Frantz I. D. , Adler S. M. , Thach B. T. , Taeusch H. W.
Published: December 2017

The respiratory responses of 18 premature infants to breathing steady-state levels of carbon dioxide were quantified by conventional minute ventilation measurements and by measuring the pressure generated after end-expiratory airway occlusions. Since no flow or volume changes occur following airway occlusion, the CO2 response obtained by this measurement is independent of vagal stretch receptor influence and mechanical changes in the lungs. When studied at 3–4 days of postnatal age, a group of 29–32-wk gestation infants had a mean slope of ventilatory response to CO2 of 10.8 +/- 5.6 ml-min-1-kg-1-mmHg-1 as compared to 53.5 +/- 10.8 ml-min-1-kg-1-mmHg-1 (P less than 0.005) for a group of 33–36 wk. When these infants were restudied at 7–10days of age, the slopes were 21.6+/- 6.6 and 58.4 +/- 10.6 ml-min-1-kg-1-mmHg-1 (P less than 0.01), respectively. The mask pressure response paralleled minute ventilation. We conclude that the increase in ventilatory responseto carbon dioxide seen with maturation is not due only to changing mechanical features of the lungs, but to increased sensitivity of respiratory centers to carbon dioxide.
Gas-blood CO2 equilibration in parabronchial lungs of birds
Authors: Meyer M. , Worth H. , Scheid P.
Published: December 2017

We have conducted two experimental series in the chicken in order to study CO2 exchange in the parabronchial lungs of birds.In the first series, the animals were artifically ventilated and end-expired PCO2, PE'CO2,was measured and compared with mixed venous PCO2, PVCO2. On the average, PECO2 exceeded PVCO2 by 2.8 Torr. In the second series, rebreathing was used to investigate the mechanism of this positive (PE'-PV)CO2 difference.Lung gas PCO2 was found to equilibrate with PVCO2 if both CO2 and O2 exchange in the lung was abolished during rebreathing. Only if O2 uptake continued, we observed a positive gas-to-mixed venous blood PCO2 difference. The results suggest that positive gas-blood PCO2 differences both during rebreathing and steady-state ventilation are brought about by the Haldane effect.Model calculations show that in the homogeneous avian lung, unlike in the alveolar lung, the Haldane effect can produce positive (PE'-PV)CO2 differences during steady-state breathing due to the peculiarities of the crosscurrent arrangement and parabronchial ventilation and blood perfusion.
Small inexpensive anesthetic apparatus for rats
Authors: Cooke W. J.
Published: December 2017

An anesthetic apparatus is described that is capable of delivering easily controlled, constant ether-air mixtures to rats and other small laboratory animals. The apparatus is readily calibrated and is stable for extended periods of time under laboratory conditions. In addition, the apparatus can be constructed of commonly available components.
Blood-perfused working isolated rat heart
Authors: Duvelleroy M. A. , Duruble M. , Martin J. L. , Teisseire B. , Droulez J. , Cain M.
Published: December 2017

We describe a method for perfusion of a working isolated rat heart with washed erythrocytes suspended in a Krebs-Henseleit bicarbonate buffer containing bovine albumin (fraction V). With washed pig red cells, as hematocritwas varied between 0 and 40%, coronary flow (CF), aortic flow (AF), external work (W), and myocardial oxygen consumption (MVO2) were measured. Hemodynamic data at a hematocrit of 30% (CF = 5.4 +/- 0.7 ml/min per g, AF = 75 +/- 8 ml/min per g) were identical with those reported for the intact animal.Coronary sinus PO2 was highest with a red cell-free perfusate suggesting that coronary flow is partially shunted. Human red cells obtained from bankedblood, were tried also with success. With careful filtration, the preparation is stable for 2 h and well suited for study of the dynamics of myocardial oxygen delivery.
Human coagulation abnormalities during acute exposure to hypobaric hypoxia
Authors: Maher J. T. , Levine P. H. , Cymerman A.
Published: December 2017

Multiple coagulation studies were carried out in eight healthy young menat sea level (SL) and after 1, 24, and 48 h at a simulated altitude of 4,400 m. Platelet aggregation, as induced by ADP, epinephrine, and collagen, was not significantly altered by high-altitude (HA) exposure. Mean 2,3-diphosphoglycerate, a physiological inhibitor of platelet aggregation, rose (P less than 0.001) after 24 h at HA and remained elevated while no changes in circulating catecholamines were observed. Platelet count, factor 3 availability, and membrane lipid peroxide formation were likewise unaltered at HA, as were prothrombin and thrombin times and protamine paracoagulation test. However, mean partial thromboplastin time was significantly shortened (P less than 0.01) after 1 and 24 h at HA, recovering to SL control by 48 h. Fibrinogen and factor VIII levels also fell (P less than 0.01 and P less than 0.02) after 1 h at HA but returned to the preexposure values by 24 h. Fibrin degradation products were transiently detectable in three subjects at HA. Thus, although normal platelet function did not appear to be modified by short-term exposure to simulated high altitude, evidence for a coagulopathy was obtained.
Effects of acceleration on thermoregulatory responses of unanesthetized rats
Authors: Fuller C. A. , Horowitz J. M. , Horwitz B. A.
Published: December 2017

Upon exposure of rats to 2 G environments (achieved by centrifugation), there occurred a rapid decrease in colonic temperature (Tco) followed, after about 50 min, by a slow recovery toward precentrifugation levels. The initial drop in Tco was accompanied by decreases in hypothalamic and spinal cord temperatures and increases in tail temperature (Tta). In contrast to this anomalous response (i.e., increased heat loss (manifested by increased Tta) despite decreasing temperature at spinal and hypothalamic thermoreceptor areas) the return toward normal Tco appeared to involve appropriate thermoregulatory responses. The initial fall in Tco was decreased in magnitude by inverting the rat during acceleration, thereby suggesting that mechanical forces acting on the brain may underlie this temperature decrease. Exposure to cold during centrifugation allowed further examination of the thermoregulatory system. Unlike the initial acceleration-induced changes, the cold-evoked fall in Tco was not accompanied by increasing Tta and was modified by the environmental conditioning of the rats. These results are consistent with the view that exposure to 2 G adversely affects the thermoregulatory ability of rats challenged by cold.
Spinal cord thermosensitivity and sorting of neural signals in cold-exposed rats
Authors: Fuller C. A. , Horowitz J. M. , Horwitz B. A.
Published: December 2017

In the present study, data relevant to the presence or absence of sorting of neural signals were obtained by evaluating the thermal responses to spinal warming in the chronically prepared rat. Specifically, shivering activity and the rate of oxygen consumption (VO2) were measured in unanesthetized rats during cold exposure (10–16 degrees C). Warming the spinal cord at the level of T2 resulted in a significant decrease in shivering (P less than 0.001), without a significant change in VO2. The shivering response was reversed upon cessation of heating. These results are interpreted as indicating a direct influence of spinal cord temperature on shivering but not nonshivering thermogenesis in the rat. Similarly, in previous work with the rat, we have obtained data supporting hypothalamic receptor control of nonshivering but not shivering heat production. These findings are thus consistent with the suggestion that in the rat there occurs a sorting of neural signals. That is, impulses from the three thermoreceptor locations are not integrated in an identical manner for the control of shivering and nonshivering thermogenesis.
Hypoxia-induced metabolic and core temperature changes in the squirrel monkey
Authors: Horstman D. H. , Banderet L. E.
Published: December 2017

To identify components of reduced core temperature (Tre) with exposure to hypoxia, oxygen uptake (VO2) and skin temperatures were measured in chair-restrained squirrel monkeys during conditions of 21% O2, 11% O2, and 11% O2 + 5% CO2. Exposure to 11% O2 resulted in a 20% decrease in VO2 and a 1.8 degrees C reduction of Tre with skin temperatures closely paralleling Tre. The addition of 5% CO2 to 11% O2 effectively blocked the decrease of both VO2 and Tre. The responses of one monkey (LD) exhibiting decreased Tre (greater than 2.0 degrees C) and 20% decrease in VO2 were compared to those of another (SD) exhibiting decreased Tre (less than 0.5 degrees C) and little change of VO2 under the same experimental conditions. Increased mean arterial blood pressure (BPa) and heart rate (HR) occurred for monkey SD, while for monkey LD BPa decreased and HR increased slightly. Arterial pressure of oxygen (PaO2) and calculated arterial saturation of oxygen (SaO2) were higher, while PaCO2 was lower for monkey SD than for monkey LD. When 5% CO2 was added to 11% O2 both animals exhibited decreased PaO2, little change of Tre, VO2, PaCO2, arterial pH, and calculated SaO2, and increased BPa and HR. These data suggest that decreased Tre resulted from reduced heat production and reduced oxygen transport was primarily responsible for reduction of heat production.
Changes in lung mechanics induced by acute isocapnic hypoxia
Authors: Saunders N. A. , Betts M. F. , Pengelly L. D. , Rebuck A. S.
Published: December 2017

We measured lung mechanics in seven healthy males during acute isocapnic hypoxia (PAO2 = 40–50 Torr; PACO2 = 38–42 Torr). Hypoxia was accompanied by increases in total lung capacity (mean increase +/- SD; 0.40 +/- 0.24 liters; P less than 0.005) functional residual capacity (0.34 +/- 0.25 liters; P less than 0.01) and residual volume (0.56 +/- 0.44 liters; P less than 0.02) in all subjects. Specific conductance of the lung decreased during hypoxia (P less than 0.02). The static deflation pressure-volume curve of the lung was shifted upward during hypoxia in all subjects. Resting end-expiratory recoil pressure of the lung was slightly, but not significantly lower during hypoxtic expiratory lung compliance was greater during hypoxia (0.39 +/- 0.04 l/cmH2O) than control measurements (0.31 +/- 0.05 l/cmH2O; P less than 0.005). No change was noted in dynamic lung compliance. All changes in lung mechanics were reversed within three minutes of reoxygenation. We conclude that acute isocapnic hypoxia increases total lung capacity in man and suggest that this may be due to the effect of hypoxia on the airways and pulmonary circulation.
Mechanical response of pulmonary artery under aerobic and hypoxic conditions
Authors: Souhrada J. F. , Dickey D. W.
Published: December 2017

The present study demonstrates the reactivity of isolated main pulmonary artery (MPA) from guinea pigs and rats to two vasoactive drugs, norepinephrine (NE) and histamine (H), in substrate-rich and substrate-free medium, under both aerobic (PO2 = 95 +/- 0.5 Torr) and hypoxic conditions (PO2 = 30 +/- 1 Torr). The sensitivity of MPA from guinea pigs to NE and H during aerobic conditions is not significantly affected by the absence of substrate in the experimental medium. Furthermore, it is demonstrated that in the substrate-rich experimental medium (5.5 mM glucose), the reactivity of MPA from guinea pigs to NE and H is not significantly affected by acute hypoxia as compared with the response of MPA during aerobic conditions. These experiments contrast with data obtained when substrate is absent from the experimental medium. The dose-response curves of MPA from guinea pigs to NE and H under this condition were significantly blunted during hypoxia. Following the completion of the dose-response curves during aerobic conditions, with both NE and H, spontaneous mechanical activities were seen in the guinea pig MPA. On the other hand, it was demonstrated that during aerobic and hypoxic conditions MPA's isolated from rats exhibit no physiological response to histamine even when administered in the dose required to produce the maximal response in MPA isolated from guinea pigs. The sensitivity of MPA from rats to NE during aerobic conditions is not significantly affected by the absence of substrate in the experimental medium. However, when the preparation was exposed to hypoxia, the presence of substrate failed to maintain the reactivity of MPA to norepinephrine. In addition, MPA isolated from rats demonstrated a smaller contractile response to NE than those from guinea pigs. Furthermore, no spontaneous mechanical activities were observed after norepinephrine or histamine administration. The present study, in addition to pointing out species differences, shows the important role of exogenous substrate in maintaining the reactivity of pulmonary vascular smooth muscle during hypoxia.
Measurement of mucociliary clearance from the trachea of conscious and anesthetized rats
Authors: Patrick G. , Stirling C.
Published: December 2017

A technique is described whereby particles are injected as a suspension into the trachea of conscious rats. Tracheostomy and cannulation are performed under halothane, but the particles are injected 10 min after recovery. Clearance of BaSO4 particles labeled with 133Ba was determined with a collimated slit gamma-counter, either aligned with the region of particle deposition or used to scan along the animal. Compared with clearance up the trachea in conscous rats, the effect of halothane, thiopental and pentobarbital was to inhibit clearance. With halothane, clearance was resumed at the control rate 0–3 min after anesthesia lasting 7–9 min.
Frequency dependence of ventilation distribution in normal and obstructed lungs
Authors: Jones R. L. , Overton T. R. , Sproule B. J.
Published: December 2017

Differences in regional pulmonary time constant may cause ventilation distribution to vary with breathing frequency and frequency-dependent changes in regional ventilation per unit volume might be expected. We measured the regional distribution of inhaled xenon-133 (133Xe) at 10 and 60 breaths/min in normal subjects and in patients with a clinical diagnosis of chornic bronchitis or asthma. Breathing frequency had no siqnificant effect on ventilation distribution in normals but in patients with chronic bronchitis ventilation decreased in the lower lung regions at 60 breaths/min compared with 10 breaths/min. In six asthmatic patients the lung regions demonstrating the greatest frequency-dependent reductions in ventilation, which were assumed to have the greatest time constants, also showed decreased ventilation-perfusion ratios (V/Q) measured by standard 133Xe techniques. Bronchodilator increased ventilation more than perfusion in these regions and thus V/Q ratio increased toward the normal range. These results imply that measurement of the frequency dependence of regional ventilation provides information about the relative distribution of airway obstruction, and that airway function in the most obstructed lung regions in asthmatics is improved following bronchodilator therapy.
Hemodynamics of the lesser mouse deer, Tragulus javanicus
Authors: Weathers W. W. , Snyder G. K.
Published: December 2017

Mouse deer possess the smallest known erythrocytes. In contrast to the usual biconcave shape, mouse deer corpuscles are spherical which results in an appreciable increase in vitro blood viscosity. In the absence of compensation, increased viscosity should produce hemodynamic consequences. However, we find that cardiac output, arterial pressure, and total peripheral resistance are all within normal limits, while packed cell volume is considerably lower than normal. We suggest that reduced packed cell volume represents a compensation for the spherical shape of the corpuscles, serving to maintain blood viscosity and dependent hemodynamic parameters within normal limits. These results contrast markedly with the pattern observed in man where conditions which result in a high in vitro blood viscosity also have significant hemodynamic consequences. Mean values for three mouse deer were: body mass, 1.18 kg; packed cell volume, 29.8%; heart rate, 182 beats/min; cardiac output, 145 ml-(kg-min)-1., mean arterial pressure, 99 Torr; total peripheral resistance, 4.90 X 10(5) dyn-s-cm-5.