bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature-induced changes in blood acid-base status: Donnan rCl and red cell volume
Authors: Reeves R. B.
Published: December 2017

The Donnan ratio for chloride ion (rCl) was determined for human red cells in plasma utilizing 36Cl. The effect of altered PCO2 and pH on rCl was followed in two ways. CO2 partial pressure was varied (1–1.5% CO2 in O2; pH range 7.1–7.9) at 37.5 degrees C (isothermal); PCO2 and pH were also changed by altering temperature (range 5–45 degrees C) at constant CO2 content (temperature induced). At pH 7.4 and 37.5 degrees C, rCl was 0.631 +/- 0.0269 (SE, N = 5); isothermal drcl/dpH = -0.306 +/- 0.0234. When measured under conditions of variable temperature at constant CO2 content (pH range 7.3–7.9), drcl/dpH = .018 +/- 0.0232, significantly different from isothermal response (P less than 0.001). Hematocrit (H) changes with pH for conditions of initial H(7.4) of 0.45, under these conditions were also determined: isothermal dH/dpH = -0.031 +/- 0.0019; temperature induced, -0.004 +/- 0.0009. Temperature change alone at constant carbon dioxide content produces no significant change in distribution of chloride ions or water between erythrocyte and plasma compartments.
Acclimatization in a hot, humid environment: energy exchange, body temperature, and sweating
Authors: Mitchell D. , Senay L. C. , Wyndham C. H. , van Rensburg A. J. , Rogers G. G. , Strydom N. B.
Published: December 2017

Four trained young men, worked for 4 h/day at 43–50% of their maximum aerobic capacity for 3 days at 25 degrees C db, 18 degrees C wb and then for 10 consecutive days at 45 degrees C db, 32 degrees C wb. Their thermal status was assessed using direct calorimetry. As a group, the men showed classical acclimization responses, but there were marked individual differences. The calorimetric analysis revealed that reductions in strain were associated with minor changes in heat balance confined to the first and last hours of exposure. Events occurring within the first 4 days appeared to have little effect on body temperatures. Significant decreases in body temperature took place only when sweat and evaporation rate increased. A 10% increase in evaporation rate was accompanied by a 30% increase in sweat rate and a 200% increase in unevaporated sweat; thus, there is a wasteful overproduction of sweat. By the 10th day skin temperature was confined to the level necessary to evaporate sufficient sweat to achieve thermal balance with a fully wet body surface. The efficiency of heat transport within the body did not change with acclimatization.
Acclimization in a hot, humid environment: cardiovascular adjustments
Authors: Wyndham C. H. , Rogers G. G. , Senay L. C. , Mitchell D.
Published: December 2017

Four trained young men worked for 4 h/day at 40–50% of their maximum aerobic capacity first for 3 days at 25 degrees C db, 18 degrees C wb, and then for 10 consecutive days at 45 degrees C db, 32 degrees C wb. This portion of the study was mainly concerned with central circulatory changes during acclimatization. The central circulatory adaptation to work in heat could be divided into four distinct phases: phase I (day 1) was characterized by a progressive fall in stroke volume (SV) during heat exposure but cardiac output (CO) was maintained above control values by high heart rates. Phase II (days 2 and 3) was marked by increases in SV ande decreases in heart rate but with little change in CO from phase I. During phase III (days 4–8 of acclimatization), CO increased due to increases in SV. Phase IV (days 6–8) was associated with decreases in rectal and skin temperature towards control levels. SV and HR both decline in this phase so that CO was not elevated greatly above control levels. The results indicated that central circulatory and temperature regulating events are not casually associated in acclimatization.
Technique for serial right and left ventricular endocardial biopsy in dogs
Authors: Blaufuss A. , Garner D. , Adomian G. E. , Criley J. M. , Laks M. M.
Published: December 2017

A method is described for obtaining left and right ventricular endocardial biopsies repeatedly over a period of 3–6 mo in the dog. The left ventricular endocardial biopsy technique consists of the placement of a catheter via the venous route across the atrial septum and into the left ventricle. The biopsy catheter is in turn placed within this transseptal catheter. Tissues obtained by this method were satisfactory for both light and electron microscopic examination. At postmortem examination, only minimal and insignificant damage existed at the biopsy site. Consequently, we recommend this technique for the study of progressive pathologic changes in the endocardium that occur during the course of an experiment which can be identified and quantified in comparison to the control state.
Fluid-filled blood pressure measurement systems
Authors: Li J. K. , van Brummelen A. G. , Noordergraaf A.
Published: December 2017

The performance of catheter-manometer systems for the measurement of pulsatile pressure has been evaluated by both experimental techniques and theoretical considerations. The former approach has shown, on occasion, multiple maxima in the amplitude response. The latter has been approached in a variety of ways, ranging from extreme lumping to application of transmission line theory while employing different configurations in the system's representation. Multiple maxima have also been seen, The present paper identifies the sources of the differences found and compares the relative merits of various theoretical approaches. It introduces the compliance of the system as a figure of merit and provides a simple first-order approximation formula for evaluation of the quality of a system. Damping and impedance matching to improve the system′s frequency response were studied. It was found that they were not needed in a very stiff or a very compliant system, nor should one worry about the representation of such a system.
Direct Fick application for measurement of cardiac output in rat
Authors: Walsh G. M. , Tsuchiya M. , Frohlich E. D.
Published: December 2017

The direct Fick procedure for cardiac output determination in rat was validated by simultaneous comparison with electromagnetic flowmeter techniques. Significant coefficients of correlation were obtained between absolute cardiac output values (r = 0.789, P less than 0.001), increases (r = 0.768, P less than 0.001) and decreases (r = 0.672, P less than 0.01) in cardiac output detected by the two methods. As demonstrated in other species, cardiac output values of the Fick procedure in the rat were between 40 and 58% greater than respective electromagnetic flow probe values; however, percent changes in cardiac output obtained by the two methods were similar. The larger values of cardiac output obtained by the direct Fick method may be related, to a great extent, to the distribution of blood flow to the coronary and bronchial circulations. Fick cardiac output measurements were reproducible within rats, and the degree of variation in values among rats was similar to that obtained with the flowmeter procedure. The result indicate that the Fick meth od provides a valid estimation of cardiac output in the rat, with the ability to detect moderate changes (22–36%) in cardiac output.
Changes in distribution of cardiac output by surface-induced deep hypothermia in dogs
Authors: Kawashima Y. , Okada K. , Kosugi I. , In-Nami H. , Yamaguchi Y.
Published: December 2017

The effects of surface-induced deep hypothermia on organ blood flow and on the distribution of cardiac output were investigated in the anesthetized dog. Organ flows were determined by the radioactive microsphere technique. Phenoxybenzamine (POB) was administered prior to hypothermia to minimize vasoconstriction and hence facilitate cooling. Measurements were made before POB, on stabilization after POB, and during hypothermia. Cardiac output was reduced by POB as was blood flow to the pancreas, small intestine, and skeletal muscle. Hypothermia, following POB, produced a further fall in Q and during this maneuver blood flow fell in all organs and vascular beds studied. The relative distribution of Q during hypothermia was essentially the same as in the control except the brain, kidneys, and pancreas received a smaller fraction of the total output. The relatively normal distribution of a reduced cardiac output during hypothermia was in marked contrast to distribution of comparable low cardiac output induced by hemorrhage. In the latter condition, the fraction of the cardiac output perfusing the brain, kidneys, adrenals, and hepatic artery was increased.
Renal and intrarenal blood flow distribution in swine during severe exercise
Authors: Sanders M. , Rasmussen S. , Cooper D. , Bloor C.
Published: December 2017

It is known that a compensatory reduction and diversion of renal flow occurs in severe exercise in humans but not in dogs. We investigated this in miniature swine by measuring changes in total renal blood flow (TRF) and intra-renal blood flow (IRBF) distribution with tracer microspheres (15 +/- 5 mum) at rest and during steady-state exercise at 4.8–7.2 kph and 0% grade, and during severe exercise at 4.8–7.2 kph and 10% grade. We measured heart rate and cardiac output (Q) via implanted probes. TRF was determined as a percent of Q and as ml/100 g per min. IRBF was determined for the outer cortex, inner cortex, outer medulla, and inner medulla. Our results show that renal blood flow is significantly (P less than 0.05) reduced in pigs with exercise. Steady-state exercise reduced flow to about 66% of control and severe exercise reduced renal flow to 30% of control. IRBF was unchanged throughout. These results show that the exercising pig augments blood flow to skeletal muscle by reducing blood flow to kidneys, a response known to occur in man.
Delineation of flow-limiting segment and predicted airway resistance by movable catheter
Authors: Smaldone G. C. , Bergofsky E. H.
Published: December 2017

Using intrabronchial lateral pressure catheters, we determined the precise location and movement of the flow-limiting segment (FLS) in excised dog and human lungs; under maximal flow conditions, profiles of resistance and transmural pressure from the “mouth” to segmental bronchi were also obtained. In the same lungs, using the interrupter technique, IVFP curves were constructed; with these curves and lung compliance, the relationship between Vmax and Pel was studied using the analysis of Pride et al. The FLS consisted of well-demarcated short lengths (2–3 cm) of the trachea at large lung volumes which moved to lobar or semental bronchi at small volumes (10–20% TLC). These relationships, coupled with observations of the movement of the equal pressure point (EPP), support the idea that in the excised lung the location of the FLS is determined by both the location of the EPP and the compliance of the downstream airway wall; thus FLS MAY NOT FOLLOW UPSTREAM MOVEMENTS OF EPP until EPP reaches a more compliant segment of the bronchial tree (lobar and proximal segmental bronchi). Upstream resistance (Rs) and transmural pressure of collapse (Ptm′) calculated indirectly from the slope and intercept of the Vmax vs. Pel relationship accurately predicted values of resistance and transmural pressure measured directly in the same lungs at a point just upstream to FLS.
Pulmonary elasticity in children and adolescents
Authors: Zapletal A. , Paul T. , Samanek M.
Published: December 2017

Static (Cst(L)), dynamic (Cdyn(L)), and “specific lung compliance (CL/TLC, CL/FRC) and the elastic recoil pressure of the lungs (Pst/(L)) were measured in 131 healthy children and the adolescents (age 6 to 17 years) from simultaneous recordings of esophageal pressure and lung volume. Esophageal elastance and vertical esophageal pressure gradients were also studied. Pst(L), measured at different lung volumes (fractional) from the expiratory quasi-static pressure-volume (PV) curves of the lungs, increased significantly with increasing body height, age, and body surface. Cst(L), determined from the midportion of PV curves, and Cdyn(L) measured during normal breathing at frequencies around 20/min also increased significantly with somatic growth. “Specific” Cst(L) decreased with increasing body height, age, and body surface. “Specific” Cdyn(L), esophageal elastance, and the vertical esophageal pressure gradient were independent of body height, age, and body surface, Cdyn(L) was less than Cst(L) mainly in smaller and younger children, and was not considered a valid index of pulmonary elasticity. Values of Pst(L), “specific” Cst(L), and the change of slope of the midportion of PV curves in children and adolescents suggested developmental changes of pulmonary elasticity in man over the age range studied.
Digital stimulator control system for introducing premature stimuli
Authors: Branch C. E. , Barnes C. C. , Waldo A. L. , Beckett S. D.
Published: December 2017

A control system to convert a general-purpose stimulator into one which will generate premature stimuli at variable but controlled intervals is described. The control system was developed to sense spontaneous cardiac depolarizations and inject premature stimuli at preset elapsed times after every 10th or every spontaneous depolarization. The delay may be set by an analog circuit or by digital thumb-wheel switches. The output of the stimulator also may be coupled to the input, permitting the use of the system as a standard asynchronous stimulator with digital control of the pulse interval. A block diagram is presented to permit duplication of the system using standard digital and analog integrated circuits.
Implantable electrode for recording nerve signals in awake animals
Authors: Ninomiya I. , Yonezawa Y. , Wilson M. F.
Published: December 2017

An implantable electrode assembly consisting of collagen and metallic electrodes was constructed to measure simultaneously neural signals from the intact nerve and bioelectrical noises in awake animals. Mechanical artifacts, due to bodily movement, were negligibly small. The impedance of the collagen electrodes, measured in awake cats 6-7 days after implantation surgery, ranged from 39.8-11.5 komega at a frequency range of 20-5 kHz. Aortic nerve activity and renal nerve activity, measured in awake conditions using the collagen electrode, showed grouped activity synchronous with the cardiac cycle. Results indicate that most of the remal nerve activity was from postganglionic sympathetic fibers and was inhibited by the baroceptor reflex inthe same cardiac cycle.
Plasma renin, angiotensin II, and plasma and urinary aldosterone in running exercise
Authors: Kosunen K. J. , Pakarinen A. J.
Published: December 2017

Plasma renin activity (PRA), renin concentration (PRC), angiotensin II and urinary aldosterone of four male athletes were investigated before and after a running exercise of 3 X 300 m. After the exercise, there were markedincreases in all these parameters. The maximal increases (of the means and the ranges), found in the samples taken 30 min after the exercise, were: 108% (27–230%, P less than 0.05) in PRA, 490% (240–800%, P less than 0.01) inPRC, 830% (400–1,970%, P less than 0.025) in plasma angiotensin II and 1,600% (160–3,920%, P less than 0.02) in plasma aldosterone. The increase in the urinary excretion of aldosterone was 120% (42–180%, P less than 0.025). This study demonstrates that intense physical exercise may cause marked changes in all the three main components of the renin-angiotensin-aldosterone system. The significance of these changes for the physiological function of the human organism in physical stress needs further investigation.
Automic innervation of dog coronary arteries
Authors: Denn M. J. , Stone H. L.
Published: December 2017

The autonomic innervation of canine coronary arteries has been examined using the Falck and Owman technique for demonstrating catecholamines and a modification of the Koelle technique for the demonstration of cholinesterase.The experimental protocol included an examination of the neural innervation of the major coronary arteries: LCC, LAD, and RCA. A consistent, relatively dense adrenergic innervation was noted. A gradient in the degree of cholinergic innervation was: LAD less than RCA less than LCC. Light microscopic examination of the hearts of dogs subjected to either cervical vagotomy or total extrinsic cardiac denervation was performed. Additional surgical procedures included removal of the left stellate ganglion and a preferentialstripping of the LCC. These studies demonstrated the intrinsic nature of parasympathetic coronary innervation. Following all surgical procedure no variations in density of cholinergic innervation were noted, indicating that these fibers are probably postganglionic parasympathetic fibers arising fromintrinsic ganglia within the ventricles. These ganglia may be located at thebase of the great vessels and send their fibers to the coronary vessels viathe septal artery.
Baroreflex sensitivity and carotid sinus dimensions in dogs with coarctation
Authors: Bonchek L. I. , Doctor A. , Rees P. M.
Published: December 2017

Baroreflex sensitivity (BRS) has not been assessed in coarctation, though it is diminished in renal and essential hypertension. Previous experimental studies of coarctation have dealt primarily with renal mechanisms of hypertension, and have relied on constricting the aorta in adult animals. We banded the thoracic aorta in newborn puppies, and performed studies 2 yr later. Blood pressure (BP) elevations, abundant chest wall collaterals, the absence of heart failure, and subsequent necropsy confirmed the full syndromeof natural coarctation in all dogs. Transient BP elevations were induced inconscious, unrestrained dogs with intravenous phenylephrine injections. Reflex bradycardia was quantitated by plotting each pulse interval in microseconds against BP of the preceding beat, and expressing BRS as the linear regression coefficient (slope) in ms/mmHg. Mean BRS in 10 dogs with coarctation did not differ significantly (P greater than 0.1) from 8 normal controls.Carotid sinus diameter (CSD) was also assessed. Carotid arteries were fixedin vivo by prolonged exposure to glutaraldehyde to prevent contraction, then were excised and measured in a calibrated microscope. Mean CSD in 10 dogswith coarctation was significantly greater (P less than 0.01) than in 10control dogs. The unexpectedly normal BRS in experimental coarctation may be due to changes in CSD induced by hypertension; such changes may only developin growing animals. Experimental studies of coarctation should use a preparation that mimics the natural lesion.
Physiological aging of champion runners
Authors: Robinson S. , Dill D. B. , Robinson R. D. , Tzankoff S. P. , Wagner J. A.
Published: December 2017

The physiological adjustments to aerobic work (5.6 km/h, up a 9% grade) and to exhausting treadmill work of former champion middle-distance runnerswere determined in 1971, at ages 47–68 yr, 25–43 yr after their competitive careers in track. In the resting state the former athletes as a group are very much like nonathletes of the same ages. Efficiency in the aerobic walk was the same in both groups and did not change with age in either, but the former athletes on the average performed the walk with lessstrain as indicated by lower blood lactates, “ventilatory equivalents,” and heart rates than nonathletes at corresponding ages. Mean VO2max of the runners declined from 71.4 ml/min-kg-1 in youth to 41.8 at a meanage of 56.6 yr, as compared with mean values of 50.6 and 36.5 ml/min-kg-1innonathletes at corresponding ages. VO2max had declined below the averageof nonathletic men in only two of the former runners. Mean maximal heart rate declined with age from 186 to 180 in the runners, and from 199 to 186 innonathletes at corresponding ages. Ventilatory responses of men in both groupswere closely related to the increases of blood lactate in both aerobic and maximal work.
Reduced surface tension in lungs of fetal rabbits injected with pilocarpine
Authors: Corbet A. J. , Flax P. , Rudolph A. J.
Published: December 2017

After opening the maternal abdomen under methoxyflurane anesthesia, fetal rabbits 25.5–28.5 days gestation were given an intraperitoneal injection of pilocarpine (150 mg/kg) or saline through the intact uterine wall. They were delivered by hysterotomy and sacrificed without breathing 2.5 hlater. Newborn rabbits 29.5 days gestation received an injection of pilocarpine or saline at birth and breathed 30–120 min. Other newborn rabbits 29.5 days gestation were alternately sacrificed at birth or after breathing 30 min. Static pressure-volume curves with air showed decreased recoiland improved air retention on deflation in fetal rabbits 25.5–27.5 days injected with pilocarpine. There was no change in the static pressure-volume curve of lungs filled with saline. The data suggest that pilocarpine reduced surface tension by producing secretion of surfactant into air spaces. No change in lung recoil occurred with pilocarpine at 28.5 days, or withpilocarpine or breathing at 29.5 days. This may mean that air spaces at 28.5–29.5 days contained optimal surfactant, so further secretion of surfactant stimulated by pilocarpine or breathing failed to reduce surface tension.
Energetics of isometric exercise in man
Authors: Cerretelli P. , Veicsteinas A. , Fumagalli M. , Dell'orto L.
Published: December 2017

In isometric contractions of the plantar flexors (5–40% of maximal tension, Tmax), VO2 is linearly related to the force exerted, averaging 2 ml/min-kg of tension. At tension levels above 5% Tmax the lactic acid contribution to the overall energy demand is constant at about 20%. Therefore, up to at least 40% Tmax,-muscle blood flow is not totally occluded, though it is impaired even at low force levels. Below 5% Tmax no lactic acid (LA) accumulates in blood. The energy required for the development of the tension is linearly related to the force exerted up to 33% Tmax, thereafter increasing disproportionately. In the transition from rest to static contractions of the plantar and forearm flexors (30 and 40% Tmax, respectively) VO2 increases initially to 200% of the controls, leveling off later at 150%. During recovery, VO2 increases up to 200% of the initial resting level, due to the payment of a large O2 debt, decreasing then with a t 1/2 of about 30 s. The glycolytic component is relatively more important in isometric contractions of the forearm than of the plantar flexors. No LA accumulates in static contractions of the plantar flexors of 5–10 s duration interrupted by equal pauses.
Respiratory, circulatory, and ECG changes during acute exposure to high altitude
Authors: Laciga P. , Koller E. A.
Published: December 2017

Quantitative electrocardiographic and accessory circulatory and respiratory mass spectrographic and accessory circulatory and respiratory mass spectrographic studies were carried out on 30 young, healthy subjects at rest during moderately acute, standardized stepwise exposure to simulated altitude up to 7,000 m (PAO2 26.9 mmHg). The ECG (Einthoven and Wilson leads) and the respiratory gases were recorded synchronously during ascent and descent. The extensive data assembled, summarized in six tables and illustrated inseven graphs, represent the basis for future investigations on the single factors which underlie hypoxia-induced ECG changes during exposure to high altitude.
Effect of ascorbic acid on rate of heat acclimatization
Authors: Strydom N. B. , Kotze H. F. , van der Walt W. H. , Rogers G. G.
Published: December 2017

There is some indication in the literature that ascorbic acid (vitamin C) may reduce the physiological responses to heat stress. Consequently, the effect of ascorbic acid ingestion on heat-strain indicators has been studied on a group of 60 mining recruits undergoing climatic room acclimatization. Of the 60 men, 19 received a daily dose of 250 mg ascorbic acid; 21 a daily dose of 500 mg ascorbic acid; and 20 received a placebo daily. Measurements of rectal temperature, heart rate, and hourly sweat rate were made on all subjects during the 4 h of heat exposure per day for 10 days. The wet bulb temperature was 32.2 degrees C, the dry bulb 33.9 degrees C, the air movement 0.4 m/s, and the work rate 35 W. The results indicate that the rate and degree of acclimatization, as assessed by 4th-h rectal temperature, is enhanced by ascorbic acid supplementation and that no differences in response could be shown between daily dosages of 250 and 500 mg of vitamin C.
Effects of water immersion on renal hemodynamics in normal man
Authors: Epstein M. , Levinson R. , Loutzenhiser R.
Published: December 2017

Although previous studies have demonstrated that water immersion to the neck (NI) results in a significant natriuresis and diuresis, the mechanisms are incompletely delineated. Since recent studies have demonstrated that NI induces a marked increase in cardiac index, it is possible that, as a consequence, renal hemodynamics may be augmented markedly during NI thereby mediating the encountered renal changes. The present study was undertaken to delineate the effects of NI on renal plasma flow and glomerular filtration rate as assessed by the clearance of PAH (CPAH) and inulin (CIn), respectively. Nine normal male subjects were studied on two occasions, control and NI. The conditions of seated posture and time of day were identical. Immersion did not alter CIn or CPAH at a time when sodium excretion was increasing markedly. The constancy of CPAH during NI suggests that renal blood flow is unaltered and that the natriuresis of NI is mediated independently of alterations in overall renal perfusion. The sluggish decline of a naturiuresis during recovery is consistent with the presence of a humoral factor contributing to the encountered natriuresis.
Effect of mechanical factors on the relation between rate and depth of breathing in cats
Authors: Miserocchi G. , Milic-Emili J.
Published: December 2017

In anesthetized tracheotomized cats we compared the time sequence of ventilatory events with neurological events (electrical activity of the diaphragm) during the breathing cycle. We found that under control conditions a phase shift existed between the neurological and the spirometric duration ofinspiration, amounting to about 150 ms. This phase shift was increased by increasing the time constant of the respiratory system (resistive loading) and decreased by decreasing it (elastic loading). These phase shifts resulted in a difference in the appreciation of the volume responsible for the termination of inspiration (Hering-Breuer inhibition) because the volume corresponding to the end of the neurological event was somewhat smaller than the final tidal volume reached.
Plasma renin activity, angiotensin II, and aldosterone during intense heat stress
Authors: Kosunen K. J. , Pakarinen A. J. , Kuoppasalmi K. , Adlercreutz H.
Published: December 2017

Plasma renin activity (PRA), angiotensin II, and aldosterone levels, arterial blood pressure, and heart rate of six male students were investigated during and after heat stress in a sauna bath. Increased PRA, angiotensin II, and aldosterone levels were found both during and after sauna. The greatest mean increases in PRA (94.9 +/- 10.4% SE, P less than 0.005) and angiotensin II (196 +/- 54.7% SE, P less than 0.02) were observed at the end of the heat stress (at 20 min), and that in plasma aldosterone (505 +/- 209% SE, P less than 0.02) 30 min after the sauna. The heart rate roughly doubled during the heat stress and there was a transient increase followed by a decrease in systolic blood pressure and a decrease in diastolic blood pressure. This study demonstrates that intense heat stress can cause remarkable changes in the three main components of the renin-angiotensin-aldosterone system.
Evaluation of the isolated paced rat heart
Authors: Taylor P. B. , Cerny F. J.
Published: December 2017

Ventricular performance and coronary flow in Langendorff perfused rat hearts were measured over a wide range of perfusion pressures and heart rates. A change in aortic pressure from 60 to 120 mmHg induced a linear increasein coronary flow, ventricular systolic pressure, and contractility. Ventricular pacing from 300 to 600 beats/min under a constant afterload had no effect on coronary flow. Systolic pressure remained stable up to 400–450 beats/min and then decreased 14% at 600 beats/min compared to the nonpaced controls. When contraction rate exceeded 450 beats/min diastolic pressure progressively increased as the heart rate was elevated. Contractility decreased rapidly between 450 and 600 beats/min under all perfusion pressures. These data indicate that this heart model is physiologically stable with heart rates less than 450 beats/min and may be useful in studying tachycardia-induced work overload.
Exercise stress and enzyme-induced emphysema
Authors: Sahebjami H. , Vassallo C. L.
Published: December 2017

Rats were exposed to an aerosol of 10% papain for 8 h found in pilot studies to produce marked emphysema. One week after exposure some animals were forced to exercise in a motor-driven activity wheel 2 h daily for 4 wk, while others remained at rest. Another group of rats which served as the control were exposed to saline under the same conditions and divided into exercise and rest groups. Elastic recoil pressure (Pst) of lung was measured from static deflation pressure-volume curves with air and saline. Pst measured in air-filled lungs was not significantly different between the emphysema-rest and emphysema-exercise groups. When inflated with saline the Pst was significantly reduced in the emphysema-exercise compared to the emphysema-rest group at high and mid (100, 80, 60%) lung volumes. Pst in air- and saline-filled lungs was not significantly different between the control-rest and control-exercise groups. We therefore conclude that mechanical stress resulting from physical exercise decreased Pst of lung tissue in emphysematous rats.
Comparison of spontaneous and positive-pressure breathing in supine normal subjects
Authors: Bynum L. J. , Wilson J. E. , Pierce A. K.
Published: December 2017

Distribution of ventilation (V) and perfusion (Q) was studied with 133Xe in eight supine, normal subjects comparing spontaneous breathing (SB) and intermittent positive-pressure breathing (IPPB). Tidal volume, inspiratory flow, and breathing frequency measured during SB were closely matched during automatically triggered IPPB. V and Q in the lung bases (adjacent to the diaphragm) were decreased relative to other regions during SB and further diminished by IPPB at similar volumes. During IPPB, basilar V and Q improvedwhen tidal volume was increased; however; spontaneous hyperinflation resulted in significantly higher basilar V and Q than large tidal volumes delivered by IPPB. Thus, changes in lung volumes and gas exchange in the supine posture are attributable to impaired V and Q in the bases but not in dependent (posterior) regions. IPPB further reduces basilar V and Q, possibly due to loss of interdependence resulting from diminished respiratory muscle contraction. These findings may explain atelectasis during prolonged IPPB in supine patients. Although large tidal volumes improve basilar V during IPPB, spontaneous deep breaths are more effective and may prevent atelectasis better than IPPB at similar tidal volumes.
Modulation of carotid baroreflex responsiveness in man: effects of posture and propranolol
Authors: Eckberg D. L. , Abboud F. M. , Mark A. L.
Published: December 2017

Carotid baroreceptors were stimulated with graded neck suction in supine and standing volunteers, before and after autonomic blockade, to determine the influence of posture on baroreflex responsiveness. Propranolol significantly augmented baroreflex pulse interval prolongation in the supine position. Upright posture did not modify baroreflex pulse interval responses prior to propranolol, but significantly augmented responses after propranolol. The results suggest that standing enhances baroreflex sensitivity, but that under normal circumstances, this effect is masked by beta-adrenergic stimulation. Augmentation of baroreflex pulse interval prolongation in the supine and standing positions by propranolol may contribute to the effectiveness of this drug in angina pectoris and labile hypertension.
Determinants of regional distribution of a bolus inhaled from residual volume
Authors: Hales C. A. , Gibbons R. , Burnham C. , Kazemi H.
Published: December 2017

The volume of lung at residual volume (RV) which fails to receive an inhaled tracer bolus (EXV) was quantitated in 13 normals by comparison of a scintigram of the distribution of a tracer bolus inhaled from RV (BORV) with a scintigram at RV of lung equilibrated with the tracer (EQRV). EXV was found in the dependent lung in the erect position in all subjects but also occurred to a lesser degree at the apex in 11 of 13 subjects. Basal EXV ranged from 1 to 7% of TLC, and unlike apical EXV increased with age (r= 0.91, P less than 0.01). EXV in the decubitus position shifted largely to the dependent lung with none remaining in the original erect apical and basal locations, demonstrating that gravity determined EXV location. Nitrous oxide, which is highly diffusible, failed in four subjects to carry the tracer to basal EXV even though perfusion was documented to persist to this area, implying basal EXV airways were closed, not narrowed. In one of the four subjects apical EXV was readily definable. Nitrous oxide carried tracer into this region, implying patent apical EXV airways.
Freezing temperature of finger skin
Authors: Wilson O. , Goldman R. F. , Molnar G. W.
Published: December 2017

In 45 subjects, 154 frostnips of the finger were induced by cooling in air at -15 degrees C with various wind speeds. The mean supercooled skin temperature at which frostnip appeared was -9.4 degrees C. The mean skin temperature rise due to heat of fusion at ice crystallization was 5.3 degrees C.The skin temperature rose to what was termed the apparent freezing point. The relation of this point to the supercooled skin temperature was analyzed for the three wind speeds used. An apparent freezing point for a condition of no supercooling was calculated, estimating the highest temperature at which skin freezes at a given wind speed. The validity of the obtained differences in apparent freezing point was tested by an analysis of covariance. Although not statistically significant, the data suggest that the apparent freezing point with no supercooling decreases with increasing wind velocity.The highest calculated apparent freezing point at -15 degrees C and 6.8 m/swas 1.2 degrees C lower than the true freezing point for skin previously determined in brine, which is a statistically significant difference.
Ventilatory stimulation by sodium salicylate: rols of thoracic receptors
Authors: Levine S.
Published: December 2017

To explore the possibility that salicylates can stimulate VE via an extracranial mechanism, heads of dogs were perfused entirely by a support dog with blood of unchanging gas composition; spinal cord remained intact. The carotid bodies lay within the region of the perfused head; the aortic bodieswere denervated. Intra-arterial infusion of sodium salicylate (150–225 mg/kg) into the body of these head-perfused animals elicited large increases inVE (188+/-11%), although significant amounts of salicylate did not reach the head or carotid body. In any case, when the same dose of salicylate was selectively administered to the head, increases in VE were limited to23+-8%. To determine the contribution of thoracic receptors to the increasein VEelicited by salicylates, a subsequent group of head-perfused animals underwent complete spinal transection at the first lumbar level. Nnetheless,intra-arterial infusion of sodium salicylate (150–225 mg/kg) into the body of these head-perfused animals still elicited large increases in VE (111+/-13%). It is concluded that thoracic receptors (other than the aorticbodies) mediate a significant portion of the increase in VE elicited by intra-arterial infusion of sodium salicylate.
Influence of glucose ingestion on fuel-hormone response during prolonged exercise
Authors: Ahlborg G. , Felig P.
Published: December 2017

Healthy subjects were studied at rest and during 4 h of exercise at approximately 30% of maximal oxygen uptake. At 90 min of exercise 200 g glucose were ingested. A control group was studied during prolonged exercise without glucose administration. Glucose ingestion was followed by a 35% rise in arterial glucose, a 60–70% fall in arterial FFA and glycerol and a two- to threefold rise in arterial insulin. Plasma glucagon, which rose fourfold in controls, failed to rise in the glucose-fed subjects. Glucose uptake by the exercising legs was twofold greater than in controls, accounting for 60% of leg oxygen consumption. Splanchnic glucose output rose rapidly after glucose ingestion to values twice those observed in controls. However, splanchnic uptake of gluconeogenic precursors (lactate, pyruvate and glycerol) fell by 70–100%. Total splanchnic glucose escape after glucose ingestion was 84 +/- 5 g representing 42% of the ingested load. It is concluded that glucose ingestion during prolonged exercise results in a) augmented uptake and oxidation of glucose by the exercising legs, b) diminished lipolysis, c) augmented splanchnic glucose escape in association with decreased hepatic gluconeogenesis, d) retention of half of the ingested glucose within the splanchnic bed, and e) reversal of exercise-induced stimulation of glucagon secretion.
Variation of respiratory sinus arrhythmia with age
Authors: Hellman J. B. , Stacy R. W.
Published: December 2017

Respiratory sinus arrhythmia was measured on 24 male subjects whose agesranged from 21 to 65 yr, using a technique in which respiration was coupledto heart rate, so that there were 6 heartbeats per inspiration and 6 heartbeats per expiration. This voluntary cardiorespiratory coupling reduced the variance of heart rates measured at various points in the respiratory cycle. Fourier analysis was used to obtain the fundamental of heart rate and respiratory volume. A high correlation coefficient (-0.83) was found betweenpercent of variation of heart rate from the average heart rate (PB) and theage of the subject. Linear regression analysis performed on these data produced the equation: PB = 23.2–0.35 (age). Since sinus arrhythmia at thelow respiratory frequencies used probably reflects the viability of the cardiorespiratory control systems, we believe this provides a simple noninvasive method for the study of the overall competence of the system responsiblefor respiratory sinus arrhythmia.
Pulmonary function changes in ozone-interaction of concentration and ventilation
Authors: Silverman F. , Folinsbee L. J. , Barnard J. , Shephard R. J.
Published: December 2017

A total of 28 healthy young subjects have been exposed for 2 h to ozone (0.37–0.75 ppm) under conditions of either rest or intermittent light exercise (sufficient to increase the respiratory minute volume by a factor of 2.5). All pulmonary function tests (vital capacity, forced expiratory volume, maximum expiratory flow-volume curve, slope of phase III of alveolar nitrogen plateau) showed a significant deterioration relative to parallelcontrol experiments. Responses were related to the dose of ozone as calculated from the product of concentration, exposure time, and respiratory minute volume during exposure, changes at 1 h averaging approximately one-half those seen at 2 h.
Acute response to venous distention in the extremity of the dog
Authors: Conrad M. C.
Published: December 2017

Aortic and vena caval pressures, right and left iliac flows. and pedal small artery and small vein pressures were recorded in mongrel dogs prior to and for 90 min following ligation of the right iliac, femoral, medical saphenous, and lateral saphenous veins. Total, arterial, small vessel and venous resistances were calculated. Measurements were repeated following alpha-receptor blockade (phenoxybenzamine) and perfusion of the extremities with a calcium chelator (EGTA). Results indicated that venous ligation resulted in constriction of small vessels in both the occluded and contralateral extremities and constriction of veins in the occluded extremity only. Relativeresponses of right and left vascular bed to alpha-blockade and EGTA perfusion suggested that small vessels were constricted bilaterally by enhanced sympathetic stimulation and that veins and small vessels were constricted on the occluded side in response to a local myogenic stimulus.
Sodium o-iodobenzoate and hemoglobin-oxygen affinity: in vivo effects
Authors: Litwin S. B. , Skogen W. F. , McCreadie S. R. , Laver M. B.
Published: December 2017

Sodium o-iodobenzoate (OISB) was given intravenously to 15 dogs to test the in vivo effect of this drug on the oxyhemoglobin dissociation curve. Administration of a single dose of 500 mg/kg was followed by an average increase in P50 (PO2 at 50% oxyhemoglobin saturation) of 3.6 mmHg from 26.8 +/- 0.5 to 30.4 +/- 1.8 mmHg (corrected to pH 7.4). This elevation was sustained for 7 days. During intravenous infusions of 200 mg/kg every other day for3 wk, there was a sustained increase in P50 of 2.6 mmHg from 27.8 +/- 1.1 to 30.4 +/- 0.9 mmHg. All dogs survived the experiment and no ill effects ofthe drug were noted. An increase in serum lactate and pyruvate occurred in all animals following acute or chronic exposure to the drug. There was nosignificant change in whole blood pH, 2,3-diphosphoglycerate concentrations, intracellular pH, or serum total phosphate. Multiple infusions of sodiumcyanate (50 mg/kg per day) reduced P50 by an average of 12.2 +/- 0.3 mmHg. Asubsequent single infusion of OISB (500 mg/kg) failed to increase P50. Our preliminary data indicate that pharmacological manipulation of hemoglobin O2 affinity is possible with organic compounds unrelated to erythrocyte metabolism.
Effect of pretest temperature on aerosol penetration and clearance in donkeys
Authors: Bohning D. E. , Albert R. E. , Lippmann M. , Cohen V. R.
Published: December 2017

Pretest temperature and humidity were correlated with tracheobronchial particle penetration and clearance data from donkeys housed in unheated outdoor facilities and tested after spending 1–2 h in a temperature- andhumidity-controlled laboratory. The animals inhaled an inert insoluble radioisotope-labeled monodisperse aerosol for several minutes. Its retention was monitored continuously for 3 h by external gamma detection. Aerosol deposition pattern and bronchial clearance were linearly correlated with pretestoutdoor temperature which ranged from -10 to 30 degrees C. The fraction depositing in the unciliated regions of the lung decreased 0.6% per degrees C drop in outdoor temperature. Overall bronchial transport decreased at least1.5%per degrees C decrease. Multiple linear regression analysis and correction for the positive correlation between temperature and humidity left no significant residual humidity dependence. Acclimatization of the animals in the laboratory for 6 h before testing significantly reduced these effects.
Spontaneous activity and heat avoidance of mice
Authors: Murakami H. , Kinoshita K.
Published: December 2017

Experiments were conducted with eight female mice on the avoidance of heat stress over the ambient temperature range from 25 to 34 degrees C. Significant avoidance behavior of the animals was observed at Ta = 30 degrees C, becoming more noticeable as the ambient temperature was raised. When exposed to heat, the animals showed peaks of avoidance during the second half of the dark period. This result seemed closely related to the spontaneous activity pattern of mice which reached a maximum between 1800 and 2000 at each experimental temperature. In this experiment, mice were more apt to choose a comfortable place during their inactive period than during their active period. This hypothesis on the relation between mice's heat avoidance and spontaneous activity was supported by the results of an additional experiment conducted in a cold environment of Ta = 18 degrees C.
Hypothalamic thermoregulatory pathways in the rat
Authors: Gilbert T. M. , Blatteis C. M.
Published: December 2017

The cutaneous blood flow (mbl), rate of oxygen consumption (Vo2), rectal (Tre) and cutaneous (Tsk) temperatures, and shivering activity were measured in unanthetized male rats during a 2-h exposure to 26, 33, or 5 degrees C 2 wk after selective bilateral hypothalamic microknife cuts. Animals with preoptic-anterior hypothalamic (PO/AH) junction cuts 1.5 or 3.0 mm lateral to the midline, as well as parasagittal cuts which separated connections between the PO/AH and medial forebrain bundle exhibited a higher mbl at 26 degrees C than did sham-operated rats. At 5 degrees C the extended (3.0 mm) PO/AH cuts as well as the parasagittal cuts prevented cutaneous vasoconstriction but had no effect on shivering activity; hence Tre was not maintained. None of the cuts demonstrably impaired thermoregulation in the 33 degrees C environment. These results suggest that different sites in the hypothalamus may separately control cold-induced skin vasoconstriction and shivering activity, as well as heat-induced skin vasodilation. It would seem therefore that the integrity of the PO/AH is indispensable in rats for cold-induced cutaneous vasoconstriction but not for cold thermogenesis, and also not for heat-induced cutaneous vasodilation.
Altered control of skin blood flow during exercise at high internal temperatures
Authors: Brengelmann G. L. , Johnson J. M. , Hermansen L. , Rowell L. B.
Published: December 2017

We have investigated further the behavior of skin blood flow (SkBF) as internal temperature (measured as esophageal temperature (Tes)) rises in a heated exercising man. A previous study showed that when skin temperature (Tsk) is driven up in exercising men, the increase in SkBF is less than that found for the same Tes and Tsk in a resting man. In this study, we extended our observations into the range of higher Tes to see if SkBF (measured plethysmographically as changes in forearm blood flow) could be driven to higher levels despite competition with skeletal muscle for cardiac output. After Tsk was elevated to 38 degrees C by means of water-perfused suits, subjects exercised at 525–900 kp.m/min (86–147 W) for 17–30 min while Tsk was held at 38 degrees C. We found that SkBF increase per unit increase in Tes is attenuated at higher Tes. In seven men, the average slope obtained from linear regression of FBF on Tes below 38 degrees C was 7.6 flow units/degrees C. Above 38 degrees C, the average was 2.12 flow units/degrees C. In some subjects, the FBF response appeared virtually saturated at a plateau despite a steady rate of increase in Tes with time. Clearly, SkBF does not increase in direct proportion to Tes without bound. Other stimuli (presumably related to blood pressure regulation) interact either to reduce the rate of SkBF increase or to prevent any further increase after Tes exceeds 38 degrees C.
Volume of isoflow: effect of distribution of ventilation
Authors: Fairshter R. D. , Wilson A. F.
Published: December 2017

Volume of isoflow was determined in smokers and nonsmokers following one (VisoV1) and three (VisoV3) inhalations 80% helium 20% oxygen. In addition, distribution of ventilation was measured by single breath nitrogen washout and end-tidal helium concentration was determined following 1–3 breaths of a helium-oxygen mixture. In all subjects (smokers and non smokers), VisoV1 was significantly higher than VisoV3. Furthermore, VisoV1 was abnormal in 55.6% of smokers, whereas VisoV3 was abnormal in only 38.9%. Differences between VisoV1 and VisoV3 (VisoV1 - VisoV3 = deltaVisoV) were significantly larger in smokers. Non-uniform distribution of ventilation was associated with larger values of delta VisoV and lower end-tidal helium concentrations. VisoV1 is a more effective method than VisoV3 in distinguishing smokers with small airways obstruction from nonsmokers. This enhanced sensitivity can be explained by the observation that the effects of maldistribution of ventilation upon helium concentration in the late expirate are minimized after three breaths of a helium-oxygen mixture.