bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxidation of cerebral cytochrome aa3 by oxygen plus carbon dioxide at hyperbaric pressures
Authors: Hempel F. G. , Jobsis F. F. , LaManna J. L. , Rosenthal M. R. , Saltzman H. A.
Published: December 2017

The reduction-oxidation level of cytochrome aa3 in the intact cerebral cortex of cerveau isole or pentobarbital-anesthetized cats was monitored by means of dual-beam reflectance spectrophotometry. Respiratory gases containing varying fractions of carbon dioxide and oxygen were administered at increased pressures, allowing titration of the cytochrome redox state from maximum reduction during nitrogen ventilation to the completely oxidized state. We show that the fully oxidized state could be reached with about 5% CO2–95% O2 inspired at 4 ATA. Maximum oxidation was achieved only through the relaxation of oxygen-induced vasoconstriction of the cerebral vessels, as our data indicated that large blood volume responses accompanied the increases in inspired carbon dioxide. With out technique, we have established that under resting air-breathing conditions cytochrome aa3 is about 85% reduced in the cat cerebral cortex, and that the absorption peak for cytochrome aa3 in situ is located near 602 nm. A free energy change of an additional 8 kcal is calculated to occur with donation of an electron pair from 85% reduced cytochrome aa3 to oxygen as compared to a 1% reduction level.
Improved method for cannulation of the right lymph duct in dogs
Authors: Vreim C. E. , Ohkuda K.
Published: December 2017

We have developed a relatively simple technique for cannulating the right lymph duct in the dog. We have successfully cannulated 19 of 20 dogs and have obtained stable lymph flows for up to 6 h. We make a skin incision over the origin of the pectoralis superficialis muscle and extend it laterally and cephalically until it is parallel and lateral to the external jugular vein. Using the cephalic vein as a landmark, we identify the cervical lymphatic which lies deep to the external jugular vein. We trace the cervical lymphatic posteriorly to the lymphatic ampulla, which is located at the external jugular and axillary venous junction. The ampulla receives the cervical, axillary, and right lymph ducts. We place a ligature around the ampulla and tie it off, forming a lymphatic pouch and obstruction lymph flow into the vein. We then cannulate the cervical lymphatic and advance the catheter into the ampulla and tie it in place. All lymphatic branches draining into the ampulla, except the right lymph duct, are ligated, enabling us to collect lymph form only the right duct. The high success rate is due, we believe, to the fact that we approach the right duct high in the neck and cannulate via the cervical lymphatic. We avoid direct dissection over the right lymph duct, and usually we do not have to cannulate the right duct directly.
Measurement of digital blood pressure after local cooling
Authors: Nielsen S. L. , Lassen N. A.
Published: December 2017

A double-inlet plastic cuff was designed for local cooling and systolic blood pressure measurement on the middle phalanx of the fingers. With a tourniquet on the proximal phalanx of one finger, cooling for 5 min made the digital artery temperature equal the skin temperature. The difference between the systolic pressure in a control finger and in the cooled finger give the reopening pressure in the digital arteries. At 30, 25, 20, 15, and 10 degrees C, respectively the percent decrease of the finger pressure was 0.2 (0.2), 1.5 (2.5), 8.5 (3.7), 11.4 (3.4), and 15.3 (3.1) in normal young women. In patients with primary or secondary Raynaud's phenomenon, the arterial tone showed an abrupt increase that most often led to complete closure of the digital arteries. The pathological response was expressed as an increased threshold temperature or a well-defined closing temperature that showed only small variations during standardized conditions.
Measurement of oxygen consumption: assessing the accuracy of a method
Authors: Lister G. , Hoffman J. I. , Rudolph A. M.
Published: December 2017

We have previously described a flow through system for measuring oxygen consumption in infants and children. Because of the need to assess the accuracy of the system periodically, we have developed a simple procedure for doing so. This procedure also provides a means for troubleshooting if the system is not functioning properly and may be applied to other types of flow-through systems for similar purposes.
Response of prepubertal girls and college women to work in the heat
Authors: Drinkwater B. L. , Kupprat I. C. , Denton J. E. , Crist J. L. , Horvath S. M.
Published: December 2017

Five prepubertal females and five college women, matched for aerobic power, walked on a treadmill at approximately 30% VO2 max for two 50-min periods in three environments: 1) 28 degrees C, 45% rh, 2) 35 degrees C, 65% rh, and 3) 48 degrees C, 10% rh. In the mild heat (28 degrees C) both groups were able to work 100 min with no discomfort. At 35 and 48 degrees C tolerance time for the prepubertal subjects averaged 84.4 and 37.0 min, respectively; for adults, 100 and 75.0 min. At all temperatures the girls had higher heart rates and a lower stroke index, and finished the walks with a higher rectal temperature. There were no differences between groups in cardiac index, mean skin temperature, forearm blood flow, or percent loss in body weight. The proportion of the thermal load dissipated by the two groups was similar but the route for heat transfer was related to the BSA/wt ratio and environmental conditions. Marked circulatory instability was a primary factor in the lower tolerance of the prepubertal girls to work in the heat probably due to a shift in blood volume from the central to the peripheral circulation.
Pulmonary mechanics in normal rats
Authors: Diamond L. , O'Donnell M.
Published: December 2017

A versatile, whole-body pressure, or volume plethysmographic system for the study of pulmonary mechanics in anesthetized, tracheotomized rats has been described. Lung volumes and lung compliance values were in good agreement with those previously reported. Pulmonary resistance and chest wall compliance values were lower than those previously reported. Total dynamic compliance remained independent of respiratory frequency between 40 and 320 breaths/min. Flow-limiting behavior was demonstrated from a series of imposed forced expiratory maneuvers of graded effort. With a deflation pressure of 30 cmH2O, the effort-independent range of maximum flow extended to 40–50% of vital capacity. Maximal flow-static recoil pressure relationships were essentially linear over the effort independent portion of the flow-volume curve. Substitution of a low-density gas mixture (80% He-20% O2) for air resulted in increased forced expiratory flow rates but the magnitude of the response was considerably less than that which has been reported in man.
Adrenocortical function in response to myocardial necrosis in exercise-trained rats
Authors: Severson J. A. , Fell R. D. , Griffith D. R.
Published: December 2017

Plasma corticosterone concentrations and in vitro adrenal secretion of corticosterone was determined in exercise-trained rats. Virgin, male rats, 100 days of age, were trained for an 11-wk period by treadmill running. Following the training program, rats were subjected to two subcutaneous injections of l-isoproterenol 24 h apart and killed 24 h after the second injection. All exercise-trained rats survived isoproterenol treatment, while 44% of the control rats died. Plasma corticosterone concentrations were elevated only in exercise-trained rats treated with isoproterenol. Control rats treated with isoproterenol had plasma corticosterone concentrations similar to that in control and exercise-treated rats given placebo injections. Exercise training reduced adrenocortical responsiveness to ACTH in vitro, but isoproterenol treatment increased in vitro responsiveness to ACTH in exercise-trained and control rats. Total unstimulated corticosterone secretion rates in vitro were similar. The reason for better rat survival in exercise-trained rats is unknown; however, improved energy metabolism, depressed aldosterone secretion, or both are suggested as reasons for the better survival of exercise-trained rats.
Canine ventilation after acid-base infusions, exercise, and carotid body denervation
Authors: Bainton C. R.
Published: December 2017

We studied the effect of exercise and carotid body denervation on the ventilatory response which occurs following acute acid-base infusions. Studies were done in 6 dogs prepared with chronic tracheostomies and carotid loops. Ventilation (VE) and arterial pH were measured at rest and during exercise before and after infusions of lactic acid (70 meq), HCl (26 meq), NaHCO3 (45 and 90 meq), or normal saline alone (250 ml). The VE response to [H+] is expressed as 1.min-1/[H+] in nmol.kgH2O-1. Before carotid body denervation (CBD), the response was 0.1 l.min-1[H+] at rest, 1.2 1.min-1/[H+] during exercise. After CBD there was no ventilatory response to [H+] at rest or during exercise. We conclude that 1) Exercise potentiates the [H+] stimulus to breathing. 2) For small changes in arterial [H+], this exercise potentiation is a function of the carotid body. 3) Therefore, that exercise potentiates the carotid body response directly and/or the central projection of this input in the central nervous system. 4) Finally, since carotid body denervation eliminates only 7% (0.8 1.min-1) of ventilation at pH 7.35 in these dogs, that the effective threshold for this ventilatory response approximates a pH slightly greater than 7.35.
Ventilatory and gas exchange responses to cycling with sinusoidally varying pedal rate
Authors: Casaburi R. , Whipp B. J. , Wasserman K. , Koyal S. N.
Published: December 2017

To investigate factors controlling ventilation under conditions where the applied work load remains constant, but where hypothesized proprioceptive influences would be expected to vary, five subjects exercised at a constant work rate of 50 W on a cycle ergometer at pedaling rates which varied sinusoidally between 40 and 80 rpm. Each subject exercised continuously for 30 min at each of five sinusoidal periods. Minute ventilation (VE), carbon dioxide output (VCO2), oxygen uptake (VO2), and heart rate were computed breath-by-breath and amplitude and phase relations were extracted. We observed small fluctuations in VCO2 and VO2 engendered by varying metabolic requirements of moving the legs at varying rates. VE fluctuations were closely in phase with VCO2 and the amplitudes of the fluctuations were highly significantly correlated (r = 0.83, P less than 0.001); consequently end-tidal carbon dioxide tension fluctuations were small. Variation of pedaling rate, therefore, did not produce a ventilatory response independent of the effect of VCO2. The ventilatory responses to these forcings are inconsistent with an appreciable role for neurally mediated influences from the exercising limbs and provide further evidence that the exercise hyperpnea is linked to CO2 flow to the central circulation.
Aerobic power as related to body growth and training in Japanese boys: a longitudinal study
Authors: Kobayashi K. , Kitamura K. , Miura M. , Sodeyama H. , Murase Y. , Miyashita M. , Matsui H.
Published: December 2017

Maximal aerobic power was measured for 5–6 successive years in 50 Japanese schoolboys starting from the age of 9 or 13 yr. and for 2–3 yr in 6 superior junior runners from the age of 14 yr. A large increase in aerobic power was observed during the adolescent growth spurt for 7 schoolboys who trained between the ages of 9 and 14 yr. Aerobic power for 43 average schoolboys increased from 45.0 to 52.2 ml/kg.min between the ages of 13 and 17 yr. The aerobic power of 6 superior junior runners increased from 63.4 to 73.4 ml/kg.min between the ages of 14 and 17 yr. A remarkable increase in aerobic power was not observed in trained boys before the age of peak height growth velocity (PHV). Beginning approximately 1 yr prior to the age of PHV and thereafter, training effectively increased aerobic power above the normal increase attributable to age and growth. The highly developed aerobic power found in superior junior runners may have been derived from strenuous training and partially by genetically superior endowment.
Effects of respiration on cardiac performance
Authors: Robotham J. L. , Lixfeld W. , Holland L. , MacGregor D. , Bryan A. C. , Rabson J.
Published: December 2017

The conventional explanation for the fall in left ventricular stroke volume (LVSV) with inspiration is that blood pools in the lungs, thereby decreasing pulmonary venous return. In anesthetized dogs, we have found an increase in left ventricular filling pressure (LVFP) with both constant and increasing lung volume during an inspiratory effort. Transmural aortic diastolic pressure rises as LVSV falls and LVFP rises consistent with the hypothesis that a fall in pleural pressure afterloads the left ventricle. Additionally the increase found in right ventricular filling pressure with inspiration may adversely affect LV performance by decreasing LV compliance and/or contractility. Our findings are incompatible with pooling of blood in the lungs being the primary determinant of the fall in LVSV with inspiration.
Relationship of central and peripheral airway resistance to lung volume in dogs
Authors: Hoppin F. G. , Green M. , Morgan M. S.
Published: December 2017

We could not reconcile reported relationships between lung resistance measurements and lung volume with bronchographic and anatomic studies showing that airway diameters change monotonically with lung volume and that small airways change diameter proportionately at least as much as large ones. Accordingly we measured central and peripheral airways resistances with a new technique. The relevant pressures were measured with a tracheal cannula, a wedged retrograde catheter, and two parenchymal needles in seven open-chested dogs while pleural pressure was oscillated at 1 Hz. In contrast to previous studies, the volume dependency of peripheral resistance was at least as great as that of central resistance with vagi intact, the volume dependencies of central and peripheral resistances were not abolished by vagotomy, and neither resistance increased systematically at high volumes. Volume dependency of central resistance resembled predictions for isotropic expansion of airways with vagi cut but increased with bronchomotor tone. These results fit generally with bronchographic data. Previous studies may have been affected by volume dependency due to “tissue resistance” and catheter phase lags.
Effect of ambient temperature on development of prostaglandin E1 hyperthermia in the rhesus monkey
Authors: Barney C. C. , Elizondo R. S.
Published: December 2017

Prostaglandin E1 (PGE1) hyperthermia (fever) was studied at ambient temperatures (Ta) of 18, 27, and 35 degrees C in four male unanesthetized rhesus monkeys (Macaca mulatta) implanted with four guide tubes and one reentrant tube within the preoptic anterior hypothalamus (PO/AH). Rectal, hypothalamic, and mean weighted skin temperatures, O2 consumption, CO2 production, and respiratory and total evaporative water losses were measured continuously before and during PGE1 fever at each Ta. The febrile reponse to PO/AH PGE1 injection was dose responsive and was less at a Ta of 35 degrees C than at the other Ta's. At a Ta of 18 degrees C, fever was brought about primarily by an increase in metabolic rate. At a Ta of 27 degrees C, fever was produced by an increase in metabolic rate and by skin vasoconstriction. At a Ta of 35 degrees C, fever was the result of an increase in metabolic rate and a decrease in sweating evaporative heat loss. At each Ta some generalized skin vasconstriction also occurred. During the plateau phase of the fever, the measured heat losses and gains returned to near control levels. The data indicate that the rhesus monkey shows specific thermoregulatory responses to PO/AH PGE1 injection and would be a good model for the study of thermoregulation during fever in higher primates.
Aerosol transport in the human lung from analysis of single breaths
Authors: Taulbee D. B. , Yu C. P. , Heyder J.
Published: December 2017

Experimental and theoretical results are presented for the single-breath inhalation of an aerosol with 0.5- and 1-micrometer particles of bis(2-ethylhexyl) sebacate droplets. Experimental results show that the recovery from the tidal volume decreases with increasing tidal volume and increases with increasing flow rate. The reserve volume recovery does not vary much with either flow rate or tidal volume. Experimental values for reserve volume recoveries for 1-micrometer particles were slightly larger than those for 0.5-micrometer particles, indicating intrinsic particle motion plays some role in the mixing process for larger particles. Calculated results from a convection-diffusion equation for the aerosol concentration are compared with the experimental results, with the aim of testing the hypotheses of the theoretical model. Detailed comparisons between theory and experiment for the exhalation profiles demonstrate that most of the mixing between the tidal and reserve volumes occurs in the alveolar region of the lung, as postulated in the model. Mechanical mixing in the upper airways plays a relatively minor role in the overall mixing process. Theoretical results for the recoveries show the same trends with tidal volume and flow rate as does experiment, and the agreement is good. Calculated values for the mixing of the tidal aerosol range from about 0.06 at a tidal volume of 400 cm3 to 0.23 at 2,000 cm3, and no variations with flow rate was found.
Current-to-voltage convertor for measurement of oxygen
Authors: Prazma J. , Smith D. , Jochem W. J.
Published: December 2017

A highly sensitive, miniature, inexpensive circuit for the measurement of PO2 in vivo has been described. The circuit is constructed from a current-to-voltage convertor, clamping circuit, differential amplifier, and reverse voltage and overvoltage protector. The design of the circuit allows us to apply voltage bias to the measuring electrode while grounding the preparation. The clamping circuit holds the selected bias voltage constant while the differential amplifier subtracts this bias potential from the PO2 signal yielding an output voltage that is proportional to the current sensed by the oxygen electrode. The circuit is protected from reverse voltage and overvoltage.
Regulation of intracellular pH in lungs and other tissues during hypercapnia
Authors: Wood S. C. , Schaefer K. E.
Published: December 2017

Using a 14C-labeled DMO, 36Cl and 3H method, we have determined the in vivo buffering capacity of lung, kidney, heart, skeletal muscle, and extracellular fluid (ECF) of guinea pigs during hypercapnia (FICO2 = 0.15). After 1 days' exposureto 15% CO2, both the relative CO2 buffer values (delta HCO3/deltapH) and the “%pH regulation” were lung greater than kidney greater than heart greater than ECF greater than skeletal muscle. For lung tissue the intracellular pH was significantly decreased only during acute (8 h) hypercapnia and had completely returned to control values after 7 days with arterial PCO2 congruent to 122 Torr. Kidney and cardiac muscle also showed ca. 100% regulation of pH at 7 days, whereas skeletal muscle and ECF showed only 80 and 70% pH regulation, respectively. The results are discussed with respect to the important (and pH-dependent) metabolic functions of the lung and kidney.
Static mechanical properties of bronchi in normal excised human lungs
Authors: Prakash U. B. , Hyatt R. E.
Published: December 2017

Bronchographic studies were performed on 22 normal human lungs at transpulmonary pressures between 20 and 0 cmH2O. Pressure-diameter behavior of 322 bronchi was evaluated. In younger (less than 40 yr) subjects, the airways of males showed greater recoil than those of females. No difference between sexes was seen in older (greater than 40 yr) subjects. Bronchi less than 2.1 mm diam had a significant decrease in recoil with increasing age in males but not in females. Small bronchi had greater recoil than large bronchi in both sexes in the younger group but not in the older group. The younger group had evidence of anisotropic behavior of the bronchi not seen in the older group. The percentage decrease in lung volume for a given decrease in transpulmonary pressure was less in the older than in the younger subjects in both sexes. Measurements of the cube root of lung volume, bronchial length, and the position of markers attached to the pleura indicated that the lungs deflated in an overall, isotropic manner down to a pressure of 3 cmH2O.
Comparison of metabolic and ventilatory responses of men to various lifting tasks and bicycle ergometry
Authors: Petrofsky J. S. , Lind A. R.
Published: December 2017

Four male volunteers served as subjects to examine the metabolic and ventilatory cost of both positive and negative lifting tasks as compared to bicycle ergometry. In different experiments, four boxes weighing 0.91, 6.82, 22.73, and 36.36 kg were lifted up to or down from a height of 60 cm at rates as high as 70 lifts/min for periods of 4 min. The data were then compared to those obtained from bicycling at a rate of 50 rpm at work loads up to 1,500 kmp/min. Work at any given box weight had a substantially higher oxygen and ventilatory cost than similar levels of work on the bicycle ergometer. The reason for these differences appeared to lie in the energy cost of moving parts of the body. When the weight of the boxes was low, there was little difference between the oxygen cost of positive and negative work, but as the weight of the boxes increased, the expected physiological differences in positive and negative work was established.
Energy expenditure during simulated rowing
Authors: Hagerman F. C. , Connors M. C. , Gault J. A. , Hagerman G. R. , Polinski W. J.
Published: December 2017

Metabolic function was measured by open-circuit spirometry for 310 competitive oarsmen during and following a 6-min maximal rowing ergometer exercise. Aerobic and anaerobic energy contributions to exercise were estimated by calculating exercise O2 cost and O2 debt.O2 debt was measured for 30 min of recovery using oxygen consumption (Vo2) during light rowing as the base line. Venous blood lactates were analyzed at rest and at 5 and 30 min of recovery. Maximal ventilation volumes ranged from 175 to 22l 1/min while Vo2 max values averaged 5,950 ml/min and 67.6 ml/kg min. Maximal venous blood lactates ranged from 126 to 240 mg/100 ml. Average O2 debt equaled 13.4 liters. The total energy cost for simulated rowing was calculated at 221.5 kcal assuming 5 kcal/l O2 with aerobic metabolism contributing 70% to the total energy released and anaerobiosis providing the remaining 30%. Vo2 values for each minute of exercise reflect a severe steady state since oarsmen work at 96–98% of maximal aerobic capacity. O2 debt and lactate measurements attest to the severity of exercise and dominance of anaerobic metabolism during early stages of work.
Effects of physical training and lean body mass of plasma amino acids in man
Authors: Holm G. , Sullivan L. , Jagenburg R. , Bjorntorp P.
Published: December 2017

Postabsorptive plasma amino acid and insulin concentrations were determined in subjects with hyperplastic obesity and in nonobese controls before and after a 6-wk period of physical training. After the training period the plasma concentrations of insulin and leucine decreased and the concentration of alanine increased in the obese subjects. No changes were noticed in the controls. The obese subjects had elevated plasma levels of valine, isoleucine, leucine, tyrosine, and phenylalanine before as well as after physical training. The concentrations of these amino acids were correlated to the plasma insulin level and to lean body mass before but only to lean body mass after physical training. It is suggested that the lean body mass, whick is higher in hyperplastic obesity, contributes to the elevated concentrations of amino acids, and it is unlikely that the insulin decreases in the obese subjects after physical training is mediated through an effect of amino acids on insulin secretion.
Respiratory mechanics in the anesthetized rat
Authors: Lai Y. L. , Hildebrandt J.
Published: December 2017

Functional residual capacity (FRC) and pressure-volume (PV) curves of the lung, chest wall, and total respiratory system were studied in 15 anesthetized rats, weighing 307 +/- 10 (SE) g. Pleural pressure was estimated from the esophageal pressure measured with a water-filled catheter. The FRC determined by body plethysmograph was slightly and significantly larger than FRC determined from saline displacement of excised lungs. The difference may be accounted for by O2 uptake by lung tissue, escape of CO2 through the pleura, and abdominal gas. Paralysis in the prone position did not affect FRC, and abdominal gas content contributed only slightly to the FRC measured by body plethysmograph. Values of various pulmonary parameters (mean +/- SE) were as follows: residual volume, 1.26 +/- 0.13 ml; FRC, 2.51 +/- 0.20 ml; total lung capacity, 12.23 +/- 0.55 ml; compliance of the lung, 0.90 +/- 0.06 ml/cmH2O; chest wall compliance, 1.50 +/- 0.11 ml/cmH2O; and respiratory system compliance, 0.57 +/- 0.03 ml/cmH2O. The lung PV curve did not show a consistent change after the chest was opened.
Electron microscopy of lung rapidly frozen under controlled physiological conditions
Authors: Mazzone R. W. , Durand C. M. , West J. B.
Published: December 2017

Light microscopy of lung rapidly frozen under controlled physiological conditions has been very successful in correlating pulmonary structure and function. However, to study some aspects of pulmonary capillary morphology, the higher resolution of electron microscopy (EM) is necessary. To date, most EM of lung has involed the instillation of a fixative through the airways or vascular system, techniques that probably alter the normal pressure relationships of the capillaries and therefore their morphology. We describe here a technique for rapidly freezing lung to a depth of 1--2 mm below the pleural surface and preparing sections for EM. Lungs from open-chest rats were frozen at various transpulmonary pressures with cold (--80 degrees C) 70% ethylene glycol. Small pieces were then fixed with a solution containing glutaraldehyde and paraformaldehyde for 24 h at --50 degrees C. Staining was with osmium tetroxide and uranyl acetate. Lung frozen at high volumes showed marked stretching of the alveolar septa with severe deformation of the capillaries. Lung frozen at low inflation pressures revealed open capillaries containing numerous red blood cells; in addition, infolding of the alveolar wall was frequently seen. We conclude that this technique gives a level of preservation of rapidly frozen lung suitable for electron microscopy.
Estimating central and peripheral respiratory resistance
Authors: Pimmel R. L. , Tsai M. J. , Winter D. C. , Bromberg P. A.
Published: December 2017

An analytic approach for fractionating total respiratory resistance into central (Rc) and peripheral (Rp) components is presented. In the analysis, linear regression equations relating the logarithm of the measured total resistance to the logarithm of frequency are derived for data spanning the frequency range 1–16 Hz. The computed slope and intercept are used to obtain estimates of the fraction of the resistance in the periphery (Fp) and of Rp and Rc. Data from anesthetized, closed-chested dogs in a control state and with an external resistor (1.37 cmH2O.1–1.s) were used to test the approach. Mean values +/- SE's for control data were: Fp = 0.400 +/- 0.039, Rp = 1.37 +/- 0.16 cm H2O.1–1.s, and Rc = 1.98 +/- 0.10 cmH2O.1–1.s. Mean values of Rp obtained with and without added resistance were not significantly different (P less than 0.1). The increase in the mean values of Rc represented 85% of the value of the added resistance but was significantly different from the known value of the external resistance (P less than 0.05). These data suggest that it may be possible to fractionate total respiratory resistance into central and peripheral components using the frequency dependence of forced oscillatory resistance.
Effects of angiotensin antagonism at rest and during exercise in sodium-deplete man
Authors: Fagard R. , Amery A. , Reybrouck T. , Lijnen P. , Billiet L. , Bogaert M. , Moerman E. , De Schaepdryver A.
Published: December 2017

Mean intra-arterial pressure (P-), heart rate (HR), cardiac index (CI), total peripheral resistance index (TPRI), and plasma renin activity (PRA), norepinephrine (PNE), and epinephrine (PE) were estimated in five normal male subjects placed on a low-sodium diet for the previous 7 days. Subjects were studied during rest in recumbency and during intravenous infusion of either glucose or saralasin in a) recumbent position, b) sitting position on the bicycle ergometer, and c) during submaximal graded exercise. At rest recumbent saralasin induced pressure changes that were closely related to logPRA. During exercise the increase in P- was significantly lower during saralasin as compared to glucose from 110 W on, related to a greater reduction in TPRI. The increase of PRA during exercise was about three times greater with saralasin as compared to glucose, but the rises in PNE and PE were similar in both series of tests. Angiotensin II may thus have a role in the maintenance of P- in the supine sodium-deplete normal subjects, and stimulation of the renin angiotensin system during physical exercise contributes to a minor extent to the increase in P- in these conditions.
Dynamics of respiratory VT response to isocapnic pHa forcing in chemodenervated cats
Authors: Borison H. L. , Gonsalves S. F. , Montgomery S. P. , McCarthy L. E.
Published: December 2017

Arterial blood pH (pHa) was continuously monitored in decerebrate or pentobarbital-anesthetized cats with a rapidly responding hydrogen ion sensor inserted into the aorta. Alveolar carbon dioxide partial pressure and pHa were controlled independently during infusions of 1 N NaHCO3 or 0.5 N HCl into the inferior vena cava. Shifts in pHa up to 0.3 unit were effected isocapnically within 2.5–20 s over a working pHa range of 6.9–7.7. Before carotid sinus neurotomy, average onset latency of the tidal volume (VT) response to acid and alkaline pHa shifts was less than 5 S and the average VT response half time was less than 8.5 s regardless of whether the vagus nerves had been interrupted. After carotid sinus neurotomy, the deltaVT onset latency was approximately doubled, whereas the response half time was prolonged about eightfold on the average. Subsequent vagotomy tended further to increase the responding time lag. Nevertheless, the minimum response latency after peripheral chemodenervation was less than the deltapHa forcing rise time. It is concluded that the central chemoreceptors promptly sense pH change in the arterial blood and that neural processes adjust the time course of the respiratory response through the VT controller.
Fibrinogen clearance from alveoli
Authors: Meyer E. C. , Ottaviano R. , Higgins J. J.
Published: December 2017

In experiments lasting 311 +/- 8 (SE) min, we studied the clearance of 125I-fibrinogen ([125I])RIF) from distal lung units of anesthetized, ventilated dogs. We instilled varying concentrations of isosmolar, citrated [125I]RIF ranging from 0.75 to 4 mg/ml into alveoli of individual dogs, and we monitored clearance by the use of external detectors and blood and lymph sampling. Approximately 9% [125I]RIF passed into proximal airways according to detector signal analysis. Excluding airway flow, whole lung clearance of [125I]RIF occurred by degradation to small molecules that rapidly became evenly distributed in body extracellular water. The degradation appeared to take place within the distal airway and not within the lung interstitium because 131I-fibrinogen, injected intravenously, was degraded less in passing from plasma to right duct lymph. The intra-alveolar kinetics of [125I]RIF had 1.5 reaction order with a specific rate of 1.27 X 10(-5) ml(3/2)-mg(-1/2)-min(-1). The data indicate that fibrinogen clearance from alveoli occurs by both transbronchial bulk flow and intraalveolar degradation.
Effects of exercise training on coronary reactive hyperemia and blood flow in the dog
Authors: Laughlin M. H. , Diana J. N. , Tipton C. M.
Published: December 2017

The reactive hyperemic responses to 10-s coronary occlusions were studied in seven sedentary-control (C) and eight exercise-trained (T) anesthetized dogs, with electromagnetic flowmeters placed on the left anterior descending coronary artery. Radiolabeled microspheres (9 +/- 0.8 micron) were used to measure resting coronary flow per gram and to study the effects of isoproterenol infusion (ISO) (1 mg/kg-min) on total and regional coronary flow. Base-line coronary flow per 100 g was significantly greater in the T dogs (122 +/- 7) than in C dogs (100 +/- 4). During ISO, T and C coronary resistances did not differ significantly, whereas the effects of ISO on total and regional coronary flow were quite different in T dogs as compared to C dogs. C and T hyperemic flow debt repayments did not differ significantly; however, the peak reactive hyperemic flow in T dogs (344 +/- 12%) was significantly greater than the control (306 +/- 10%). Since resting coronary flow per gram was greater in T dogs, the greater peak reactive hyperemic flow implies that T dogs have an increased coronary reserve. Although the mechanisms involved are unclear, the results of this study indicate that chronic exercise training may have beneficial effects on coronary physiology.
A respiratory jacket for ventilatory measurements in children
Authors: Kattan M. , Miyasaka K. , Volgyesi G. , Froese A. B.
Published: December 2017

The properties of an air-filled polyurethane-coated nylon jacket for measuring volume parameters were determined on a model and in 13 subjects. There was a linear relationship between jacket pressure on a logarithmic scale and the lung volume change over an operating pressure range of 0.7–6 cmH2O. The magnitude of pressure change was frequency dependent. The magnitude of a calibration signal was reduced by superimposed tidal breathing. For the jacket tested, the calibration signal during tidal breathing was 87% of the calibration during apnea. With these properties established, a calibration technique was devised and tested on 13 infants. Corrected tidal volumes (VT) obtained with the jacket correlated well with those obtained with a pneumotachograph (r = 0.986). At the operating pressures used the jacket caused no significant change in functional residual capacity (FRC), VT, or frequency. The jacket is a reliable technique for measurement of VT and immediate changes in FRC in awake children.
Influence of age and physical activity on central hemodynamics and lung function in active adults
Authors: Kanstrup I. L. , Ekblom B.
Published: December 2017

Five female and seven male physically active adults were studied twice within a 13-yr interval. The individual state of physical activity was mainly unchanged. Maximal oxygen uptake (VO2 max) was reduced in all subjects except one female, in whom it remained unchanged. During maximal exercise, cardiac output (Q) in males was unchanged. In females, Q was significantly increased due to increased stroke volume (SV). In both sexes, the reduced VO2 max was explained by a smaller arteriovenous O2 difference (mixed venous O2 content (C-VO2) significantly increased). For a given submaximal VO2, Q was increased in both sexes and heart rate was unchanged. Thus, SV was increased and arteriovenous O2 difference was reduced due to increased C-VO2. Another four males were studied several times in various states of physical fitness during an 11-yr period. The reduced VO2 max from peak value was due to a reduced Qmax (SV smaller), whereas the arteriovenous O2 difference and C-VO2 were unchanged. Our results indicate that the observed changes in circulatory response to submaximal and maximal exercise in physically active adults may to a large extent be due to an effect of “detraining.”
Cardiovascular responses to muscle ischemia in man--dependency on muscle mass
Authors: Freund P. R. , Hobbs S. F. , Rowell L. B.
Published: December 2017

We sought to determine whether the pressor response to exercise-induced muscle ischemia is related to the mass of tissue rendered ischemic. Six men repeatedly exercised for 5 min at a fixed load between 75 and 150 W (bicycle ergometer). Thirty seconds before the end of exercise, circulation to one calf, two calves, one leg, and two legs was arrested with pneumatic cuffs in successive tests with 15-min recovery periods interspersed. Each occlusion was maintained until the 3rd min of exercise recovery. During postexercise occlusion we observed 1) mean arterial pressure (MAP) was elevated in proportion to the mass of ischemic muscle, 2) forearm blood flow (FBF) was elevated during the overlap of occlusion with exercise but did not show a uniform response during the following 3 min of occlusion--either vasoconstriction or vasodilation occurred, 3) heart rate (HR) was elevated only when two legs were occluded, and 4) occlusion did not affect ventilation or endtidal CO2. We conclude that the ischemic pressor response is muscle mass-dependent. Our findings suggest that the baroreflex alters peripheral vascular resistance so as to aid in the maintenance of elevated MAP.
Distribution of bronchodilatation in normal subjects: beta agonist versus atropine
Authors: Hensley M. J. , O'Cain C. F. , McFadden E. R. , Ingram R. H.
Published: December 2017

Bronchodilatation was produced in normal subjects by the inhalation of a parasympatholytic agent (atropine) and the response was compared to that occurring after the inhalation of a beta-adrenergic agent (isoetharine). Doses were chosen that resulted in equivalent increases in specific airway conductance (78 +/- 9% for atropine; 88 +/- 21% for isoetharine). Anatomic dead space and volume at the onset of the terminal nitrogen rise (closing volume) were measured before and after each agent. Although there was no difference in the degree of overall bronchodilatation after the two drugs, anatomical dead space increased significantly more after atropine than isoetharine (+17% vs. +6%, P less than 0.01), and closing volume increased significantly after isoetharine (P less than 0.005) but did not change with atropine. We interpret these differences to indicate a greater effect of cholinergic antagonists on the more central airways and a greater effect of beta-adrenergic stimulants on peripheral airways.
Mixing technique for study of oxygen-hemoglobin equilibrium: a critical evaluation
Authors: Scheid P. , Meyer M.
Published: December 2017

In the mixing technique for study of oxygen-hemoglobin equilibrium, the O2 saturation (SO2) of a blood mixture is calculated from the volume ratio at which an oxygenated sample is mixed with a deoxygenated sample, and the PO2 in the mixture is measured polarographically. Any predetermined level of SO2 may be obtained by proper choice of the volume ratio. It is shown that the volume and oxygen saturation of the mixed samples are by far the most critical parameters in calculating SO2, and a method is suggested by which the volume ratio is accurately measured by weighing the blood samples before mixing. Other parameters that influence determination of SO2, e.g., the O2 capacity of the blood, are much less important. The method has been applied to establish the O2 dissociation curve in human blood, and good reproducibility and agreement with standard curves were obtained. Measurements in rabbit blood yielded similarly satisfactory results. The technique is particularly applicable to problems that require exact adjustment of SO2 to a predetermined value, such as determination of the half-saturation pressure or of the Bohr effect at various levels of O2 saturation.
Estimation of response slopes in respiratory control using directional statistics
Authors: Daubenspeck J. A. , Ogden R. D.
Published: December 2017

The ventilatory sensitivity to alveolar PCO2 and slope of the straight line relating VE to VT are two examples of response slopes of interest in respiratory control. Statistical techniques have not been available to analyze repeated direct estimations of these slopes by paired consideration of initial and final responses to a stimulus. Rather, existing statistical techniques sacrifice much information by describing the response slope as that of the line which, in some sense, best fits the unpaired responses. We have adapted techniques established for the statistical analysis of directional data to analyze direct measurements of these physiological response slopes and have found that the application of these directional techniques can result in better estimation of the ventilatory sensitivity to CO2, for example, than is provided using unpaired analysis techniques.
"Paradoxical" reduction in postexercise ejection time and increased transthoracic impedance
Authors: Nakamura Y. , Kotilainen P. , Haffty B. , Jolda R. , Bishop R. , Spodick D.
Published: December 2017

Despite decreasing heart rate, left ventricular ejection time (LVET) transiently falls immediately following bicycle exercise. In seven normal, untrained subjects LVET decreases at 15 s postexercise corresponded (r = 0.78) with an increase in transthoracic electrical impedance (Z) consistent with decreased venous return to the thorax. Because the determinants of LVET are stroke volume (SV) and ejection rate, the deltaZ implies that decreased SV contributed to the “paradoxical” fall in LVET.
Is inert gas washout from the tissues limited by diffusion?
Authors: Ohta Y. , Song S. H. , Groom A. C. , Farhi L. E.
Published: December 2017

To determine the extent to which diffusion may limit the exchange of gases stored in the tissues, nine dogs were allowed to breathe an O2-N2-Ar mixture until saturation was achieved; the inspired gas was then changed to one containing neither N2 nor Ar, and the level of these two species in the arterial and in the mixed venous blood was monitored during the washout. A theoretical analysis shows that in a situation where peripheral gas transport is limited entirely by perfusion, the washout curves should be identical, provided concentrations are expressed as a fraction of the initial value. When the process is restricted by diffusion through the tissues, Ar is expected to lag because of its higher molecular weight. In all animals, the rate of elimination of the two tracers was the same, indicating that the time course of storage or release of inert gas from body stores is governed (mainly or entirely) by perfusion.
Comparative thermoregulatory responses of resting men and women
Authors: Cunningham D. J. , Stolwijk J. A. , Wenger C. B.
Published: December 2017

Three men and three women were exposed to transients of air temperature (range, 16--48 degrees C). Whole-body sweating rate, local tissue heat flows, and O2 consumption in the cold were linearly related to a weighted sum of tympanic and mean skin temperatures, called “central drive,” During changes in air temperature, changes in subjects' scaled estimates of thermal sensation and discomfort led changes in the physiological responses and central drive. Women's thermoregulatory responses were similar to the men's, but were shifted toward higher (warmer) values of central drive. This shift was about 0.3 degrees C for responses to heat and about 0.6 degrees C for responses to cold. With respect to the women, the mean thus showed delayed responses to the cold, and approached steady state in the cold more slowly.
Effect of decompression per se on nitrogen elimination
Authors: Hills B. A.
Published: December 2017

The elimination of nitrogen from each of 10 unanesthetized guinea pigs has been monitored after switching to a nitrogen-free breathing mix (normoxic He:O2), either without decompression or on decompression to 2.21 or 1 ATA, following an exposure of 2 h at 4 ATA on normoxic N2;O2. Normoxic conditions were maintained throughout to avoid vasomotor effects of oxygen that could have complicated interpretations derived from previous studies. Results confirmed that inert gas washout rates decrease with decompression per se. This can be explained simply on the basis of the decrease in driving force for nitrogen elimination caused by depositing gas into bubbles where they form in tissue in a somewhat random manner. A very rough estimate shows that about 83% of all body tissue retained its gas in supersaturated solution on decompression to 2.21 ATA but only 79% did so at 1 ATA.
Effects of exercise, vitamin E, and ozone on pulmonary function and lipid peroxidation
Authors: Dillard C. J. , Litov R. E. , Savin W. M. , Dumelin E. E. , Tappel A. L.
Published: December 2017

Expired pentane, an index of lipid peroxidation, and pulmonary function were measured as a function of exercise for 1 h with and without exposure to 0.3 ppm ozone. In experiment 1, 10 subjects who exercised on a bicycle ergometer at 50% of maximal oxygen consumption while being exposed to 0.3 ppm ozone had increased lung residual volume and decreased vital capacity, maximal midexpiratory flow rate, and forced expiratory volume in 1 s. In experiment 2, breath collected into a spirometer filled with hydrocarbon-scrubbed air showed increased pentane from the stress of exercise but no effect of ozone. During rest and exercise in experiment 3, two of six subjects had higher pentane levels than the other subjects. Following daily supplementation with 1,200 IU dl-alpha-tocopherol for 2 wk, the mean production of pentane during rest and exercise was significantly lowered, and there was no difference in pentane production among the subjects. It was concluded that lipid peroxidation occurs during exercise and that it is attenuated by vitamin E.
Effect of hypercapnia on hypoxic ventilatory drive in carotid body-resected man
Authors: Swanson George D. , Whipp Brian J. , Kaufman Robert D. , Aqleh Kamel A. , Winter Benjamin , Bellville J. Weldon
Published: December 2017

Steplike end-tidal hypoxic drives (Petcoco2, = 53 Torr) lasting for 5 min were generated in a group of normal subjects and a group of carotid body-resected subjects when end-tidal CO2, was maintained constant under eucapnic (Petcoco2 = 39 Torr) and hypercapnic (Petcoco2 = 49 Torr) conditions. The hypoxic ventilatory response of the normal subjects was prompt and significant in eucapnia and was enhanced in the hypercapnic state, evidencing CO2-O2 interaction. In contrast, the carotid body-resected subjects did not respond to eucapnic hypoxia but did demonstrate a small but significant ventilatory response to hypoxia against the hypercapnic background. This suggests that the aortic bodies in man may contribute a small component of the hypoxic ventilatory drive under hypercapnic conditions, although the possibility of neuromalike ending regeneration cannot be excluded.
Interaction between sodium and chloride transport in canine tracheal mucosa
Authors: Al-Bazzaz F. J. , Al-Awqati Q.
Published: December 2017

Canine tracheal mucosae were dissected and mounted as flat sheets in Ussing chambers. Unidirectional isotope fluxes of 22Na and 36Cl were performed across paired mucosae from the same animal. The average spontaneous potential difference was 42 + 1.2 mV (mean +/- SE) lumen negative. The short-circuit current (SCC) 3.09 +/- 0.36 mueq/cm2.h was accounted for by a net Cl secretion of 2.46 +/- 0.26 mueq/cm2.h toward the mucosa and net Na absorption of 0.46 +/- 0.13 mueq/cm2.h toward submucosa. Removal of Cl depressed SCC but had no effect on unidirectional or net Na transport (n = 7). By contrast, removal of Na (n = 6) or the addition of ouabain (n = 7) abolished net Cl secretion and greatly reduced SCC. Theophylline (n = 6) added to the submucosal bath no significant effect on Na transport but stimulated SCC and Cl secretion, suggesting hormonal regulation of Cl transport. The results suggest that the active transport of Na and Cl in this epithelium occur by electrically conductive pathways, i.e., the transport is “electrogenic.” Further it appears that Na transport is independent of the presence of Cl but that Cl transport depends on some parameter of active Na transport.