bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of transcendental meditation on breathing and respiratory control
Authors: Wolkove N. , Kreisman H. , Darragh D. , Cohen C. , Frank H.
Published: December 2017

We studied the effect of transcendental meditation (TM) on breathing using 16 experienced meditators and 16 control subjects. In controls, there was no significant difference in minute ventilation (VE), respiratory pattern, or hypercapnic response, whether breathing with eyes open-awake (CA), or with eyes closed-relaxing (CR). In meditators, VE decreased significantly during quiet breathing from 14.0 +/- 0.7 1/min with eyes open-awake (MA) to 12.4 +/- 0.6 1/min during meditation (MM) (P less than 0.02). The change in VE during meditation was due to a decrease in tidal volume (VT) resulting from a shortened inspiratory time (TI). Meditation was associated with a decreased response to progressive hypercapnia from 3.7 +/- 0.4 to 2.5 +/- 0.21 X min-1 X Torr-1 during MA and MM trials, respectively (P less than 0.01). During meditation VT was smaller at a given alveolar PCO2 than during MA studies because of a decrease in mean inspiratory flow rate (VT/TI). These observations suggest that an alteration in wakefulness, more subtle than sleep or the unconscious state, can significantly affect the chemical and neural regulation of breathing.
Function of canine diaphragm with hypovolemic shock and beta-adrenergic blockade
Authors: Scharf S. M. , Bark H.
Published: December 2017

In anesthetized mongrel dogs we investigated the effects of hypovolemia and beta-adrenergic stimulation on the decrease in force generation by the diaphragm [transdiaphragmatic pressure (Pdi)] during electrical stimulation of the phrenic nerves for 1 h. In seven normovolemic dogs with arterial pressure (Pa) of approximately 125 Torr, Pdi fell approximately 48% from an initial value of 35 +/- 4.8 Torr. In dogs made moderately hypovolemic, Pdi was actually higher than with normovolemia (P less than 0.01). In dogs made severely hypovolemic, Pa approximately 50 Torr, Pdi at the start of pacing was less than with normovolemia (25 +/- 1.5 Torr) and remained so during phrenic nerve stimulation. When beta-adrenergic blockade with propranolol was added to moderate hypovolemia, the values of Pdi became similar to those of severe hypovolemia. Analysis of the relative contributions of gastric pressure and pleural pressure revealed that the factor responsible for maintaining Pdi with moderate hypovolemia was pleural pressure. Changes in thoracic gas volume and chest wall configuration did not explain the changes we saw in diaphragm function. Analysis of the relationship between rib cage motion and pleural pressure confirmed our finding of the greater pleural pressure generation with sympathetic stimulation that accompanies hypovolemia. These studies demonstrated that 1) severe hypovolemia impaired diaphragm function, 2) diaphragm function was maintained with moderate hypovolemia by beta-adrenergic stimulation, and 3) with hypovolemia-associated sympathetic stimulation there was an increase in force generation by the intercostal muscles.
Micromethod for dynamic determination of O2 dissociation curves using a PO2 electrode
Authors: Barnhart M. C.
Published: December 2017

A nonspectrophotometric method is described for measurement of the O2 dissociation curve and O2 capacity of a 50-microliter sample of fluid. PO2 is recorded by a microprocessor as the sample is oxygenated and then deoxygenated by exposure to isocapnic gas mixtures across a gas-permeable membrane. The time course of deoxygenation and the O2 conductance of the membrane are used in calculating the O2 capacity of the sample and the dissociation curve. The method is sensitive and is best suited to samples of low O2 capacity and affinity. Measurements on buffer-diluted human blood agree with standard values.
Exercise performance with added dead space in chronic airflow obstruction
Authors: Brown S. E. , King R. R. , Temerlin S. M. , Stansbury D. W. , Mahutte C. K. , Light R. W.
Published: December 2017

Individuals with chronic airflow obstruction (CAO) are thought to have limited exercise tolerance primarily because of impaired ventilatory mechanics. We studied the effects of added external dead space (DS) on exercise capacity [maximum O2 consumption (VO2max)], maximum exercise ventilation (VEmax), and blood gases (arterial PO2, PCO2, pH) in 22 patients with CAO [forced expired volume at 1 s (FEV1) = 0.96 +/- 0.41 liter]. Maximum exercise testing (Emax) was performed by incremental cycle ergometry. Patients exercised at base line (BL) and with DS (0.25 liter if FEV1 less than 0.8, and 0.50 liter if FEV1 greater than 0.8 liter), in random-order single-blind fashion. DS resulted in a 12.2% increase in VEmax (P less than 0.001); tidal volume increased (P less than 0.025) while respiratory frequency was unchanged. The VO2max and maximum CO2 production decreased (P less than 0.001) with DS. Arterial PCO2 at rest and at exhaustion increased with DS (P less than 0.001). The pH and arterial PO2 showed small declines at rest and at Emax. Thus, at the lower maximum work load achieved with DS, the patients ventilated more and tolerated a higher arterial PCO2 and a lower arterial PO2 and pH before stopping from dyspnea as compared with the BL exercise run. In contrast, the VO2max of nine normal control subjects was unaffected by the addition of DS. Although VEmax can be increased in CAO patients with DS, this increase is not sufficient to prevent further CO2 retention or a decrease in exercise capacity. We conclude that exercise performance is limited primarily by impaired ventilatory mechanics in CAO.
Effects and mechanism of action of terbutaline on diaphragmatic contractility and fatigue
Authors: Aubier M. , Viires N. , Murciano D. , Medrano G. , Lecocguic Y. , Pariente R.
Published: December 2017

We studied the effects of intravenously administered terbutaline on diaphragmatic force and fatigue during electrical stimulation of the diaphragm in 17 anesthetized dogs. The diaphragm was stimulated indirectly through the phrenic nerves with electrodes placed around the fifth roots and directly with electrodes surgically implanted in the abdominal side of each hemidiaphragm. Transdiaphragmatic pressure (Pdi) during direct or indirect supramaximal 2-s stimulation applied over a frequency range of 10–100 Hz was measured with balloon catheters during tracheal occlusion at functional residual capacity. In seven dogs the administration of terbutaline (0.5 mg) had no effect on Pdi at any stimulation frequency applied directly or indirectly. The effect of terbutaline (0.5 mg) on diaphragmatic fatigue was then tested in 10 other dogs. Diaphragmatic fatigue was produced by continuous 20-Hz electrical supramaxial stimulation of the phrenic nerves during 30 min. At the end of the fatigue procedure Pdi decreased by 50 +/- 5 and 30 +/- 8% of control values at 10 and 100 Hz, respectively, for either direct or indirect stimulation. The decrease in Pdi for low frequencies of stimulation (10 and 20 Hz) lasted 100 +/- 18 min, whereas it lasted only 40 +/- 10 min for the high frequencies (50 and 100 Hz). When terbutaline (0.5 mg) was administered after the fatiguing procedure, Pdi increased within 15 min by 20 +/- 4% at 10 Hz and by 12 +/- 3% at 100 Hz for either direct or indirect stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)
Airway response to inhaled methacholine in healthy nonsmoking twins
Authors: Zamel N. , Leroux M. , Vanderdoelen J. L.
Published: December 2017

The variability of maximum expiratory flows is genetically determined, and the airway response to chronic cigarette smoking is also influenced by genetic factors. In nonsmoking nonatopic healthy individuals there is a wide variability of acute airway responses to bronchoactive drugs. The present study was designed to investigate whether this variability might also be genetically determined. We tested this hypothesis by measuring the threshold of airway response to inhaled methacholine using a partial flow-volume curve as the index of response in 10 monozygotic (MZ) and 10 dizygotic (DZ) healthy nonsmoking pairs of twins. Methacholine aerosol was given in doubling doses from number 1 (0.031 mg/ml) to number 11 (32 mg/ml). The mean threshold (+/-SD) for the MZ twins was dose 4.5 +/- 2.4 and for the DZ twins was 7.2 +/- 2.0 (P = 0.0004). No explanation could be found for the difference in mean threshold between MZ and DZ twins. The mean intrapair difference in threshold (+/-SD) for the MZ twins was 2.7 +/- 1.6 doubling doses and for the DZ twins was 2.4 +/- 1.8 (P = 0.7). Slope of dose response to methacholine and intrapair differences were not different between MZ and DZ twins. The present study supports the view that environmental factors are more important than genetic factors in determining the variability of acute airway responsiveness to bronchoactive drugs in healthy nonsmoking individuals.
Respiratory effects of progressive asphyxia in rabbit pups and adult rabbits
Authors: Trippenbach T. , Affleck R. , Kelly G.
Published: December 2017

Effects of prolonged airway occlusion were investigated in anesthetized and vagotomized 9-to 15-day-old pups and adult rabbits. The changes and temporal relationships between “integrated” phrenic activity, external intercostal electromyogram (INT), and esophageal pressure (Pes) were examined. Each occlusion resulted in hyperpnea, apnea, and gasping. Blood pressure recorded during the occlusion showed a marked decrease. During hyperpnea, the rate of changes and maximal amplitudes in Pes and INT were similar in both age groups. The increase in integrated phrenic activity (PHR) was significantly greater in young rabbits. In both age groups, changes in INT during gasping followed a similar time course and exceeded those in PHR. Maximal values of the three parameters were concurrent in adults, whereas the increase in INT peaked later than PHR and Pes in rabbit pups. In adult rabbits, PHR, INT, and Pes, during the last gasp, decreased to the values of the first hyperpnea breath. In rabbit pups, Pes of the last gasp decreased significantly below this value while INT was still elevated. This Pes decrease could result from inspiratory muscle dysfunction in the pups. Thus in rabbit pups, 1) greater changes in PHR were necessary to produce a given change in Pes than in adult rabbits; 2) activity of the external intercostal muscles was not efficient in developing pressure under conditions of asphyxia; and 3) the independent activation of diaphragmatic and intercostal motoneurons is not of vagal origin. Additionally, the results led us to conclude that Pes can serve as a close approximation of respiratory drive in adult rabbits. This parameter, however, cannot be used as an index of central inspiratory activity during gasping in rabbit pups.
Comparative features of Starling-lymphatic interaction at the pleural level in mammals
Authors: Miserocchi G. , Negrini D. , Mortola J. P.
Published: December 2017

Pleural liquid pressure was measured with saline-filled cannulas in rats, rabbits, cats, pups (4–5 days and 2 mo), small and large dogs, and pigs. On both the costal and mediastinal sides pleural liquid pressure at a level corresponding to the tricuspid valve decreased with increasing body mass; because this behavior was more marked on the mediastinal than on the costal side, a horizontal costomediastinal pleural liquid pressure gradient developed. No differences in liquid pressure were found in animals of different age but of similar size. The protein concentration and the volume-to-body weight ratio of the collected pleural liquid were also found to decrease with increasing body mass. For plasma colloid osmotic pressure, no size-related differences in the Starling balance seem to occur on costal side, whereas such balance shifts toward filtration at mediastinal level with increasing body mass. The lower liquid pressure found with increasing body mass is discussed in terms of lower conductance of the mesothelia and possibly greater lymphatic action. In terms of the Starling-lymphatic interaction we suggest that lymphatics can generate a pressure only slightly lower than that reflecting the equilibrium of the Starling balance of forces.
Skin gas tensions and resistances measured by mass spectrometry in adults
Authors: Targett R. C. , Kocher O. , Muramatsu K. , McIlroy M. B.
Published: December 2017

We used a dual-sampling chamber 2.5 cm in diameter, controlled by an Apple II microcomputer, to measure gas tensions in the skin of adults by mass spectrometry. The tensions of O2, CO2, N2, and water vapor and the resistances to the flows of gases through the skin were calculated from the voltages for the different gases passing through two separate membranes of different permeability. We compared the skin O2 and CO2 tensions with arterial values in 13 patients with lung disease during a standardized exercise test. The skin values followed changes in the arterial values. The regression line relating skin to arterial O2 tension had a slope of 1.05 and that for CO2 a slope of 1.51. We conclude that mass spectrometry is capable of providing measurements of gas tension from the heated skin that are similar to those found using electrochemical methods in adults.
Ten years of "civilization": fitness of Canadian Inuit
Authors: Rode A. , Shephard R. J.
Published: December 2017

Data on the cardiorespiratory fitness of the Canadian Inuit has been obtained before and after 10 yr exposure to “white civilization.” The population tested comprises 201 males (aged 9–76 yr) and 143 females (aged 10–69 yr), about 70% of the eligible population of Igloolik (69 degrees 40′N). During direct maximum tests to exhaustion, a higher maximum heart rate was attained in 1980–81 (194.4 beats X min-1) than in 1970–71 (184.5 beats X min-1); this probably reflects a closer approach to a centrally limited maximum as the Inuit have become familiar with white investigators. The Astrand nomogram currently underestimates the directly measured maximum O2 intake (VO2max) by some 3% in subjects making a good maximum effort. Comparing the 1980–81 data with results for 1970–71, there has been a 15% decrease of predicted VO2max, accompanied by a 2- to 4-kg increase of body mass, accumulation of subcutaneous fat, and a decrease of leg extension strength, these changes affecting all subjects except boys aged 9–15 yr. It is suggested that the loss of personal fitness is related to adoption of a more sedentary lifestyle, particularly the use of tracked vehicles in place of walking through deep snow.
Relationship of hypoxic ventilatory response to exercise performance on Mount Everest
Authors: Schoene R. B. , Lahiri S. , Hackett P. H. , Peters R. M. , Milledge J. S. , Pizzo C. J. , Sarnquist F. H. , Boyer S. J. , Graber D. J. , Maret K. H. , et al.
Published: December 2017

At very high altitude, exercise performance in the human sojourner may depend on a sufficient hypoxic ventilatory response (HVR). To study the relationship of HVR to exercise performance at high altitude, we studied HVR at sea level and 5,400 m and exercise ventilation at sea level, 5,400 m, and 6,300 m in nine members of the American Medical Research Expedition to Everest. The relationship of HVR between individuals was maintained when HVR was repeated after acclimatization to 5,400 m (P less than 0.05). There was a significant correlation in all subjects between HVR and ventilatory equivalent during exercise at sea level (r = 0.704, P less than 0.05). Subjects were then grouped into high (H) and low (L) HVR responders (ventilation increase to end-tidal PO2 of 40 Torr = 21.2 +/- 5.4 and 5.6 +/- 0.9 1 X min-1, respectively. At low and moderate levels of exercise, ventilation at sea level and after acclimatization to 6,300 m was higher in the high HVR group. At 6,300 m blood O2 saturation (Sao2%) decreased from rest to maximum exercise: H = 8.3 +/- 1.8%, L = 20.0 +/- 2.5% (P less than 0.01). HVR correlated inversely in all subjects with the decrease in Sao2 from rest to maximum exercise (P less than 0.05). Climbers with the highest HVR values reached and slept at higher altitudes. We conclude that the relative value of HVR in our group of climbers was not significantly altered after acclimatization; HVR predicts exercise ventilation at sea level and high altitude; the drop in Sao2% that occurs with exercise is inversely related to HVR; and sojourners with high HVR may perform better at extreme altitude.
Contribution of lung stretch depressor reflex to nonlinear fall in cardiac output during PEEP
Authors: Schreuder J. J. , Jansen J. R. , Versprille A.
Published: December 2017

The hypothesis that lung stretch reflexes elicit negative cardiovascular effects during positive end-expiratory pressure (PEEP) application in a ramp procedure up to 15 cmH2O was tested in piglets under steady-state anesthesia and muscle relaxation. The effects of lung stretch on hemodynamics were studied by comparing the differences in responses during PEEP application with two different tidal volumes. In both ventilatory conditions cardiac output and aortic pressure decreased nonlinearly in three phases with the rise of PEEP: a gradual decrease in phase I, a sharp decrease in phase II, and again a more gradual decrease in phase III. Heart rate decreased significantly in phase II. In the series with the larger tidal volume, implying more lung stretch during insufflation, phase II was between a PEEP of 2.6 and 9 cmH2O. In the series with the smaller tidal volume, phase II occurred between 5.7 and 10.5 cmH2O. To assess the contribution of lung stretch reflexes to the decrease in cardiac output we also related cardiac output to the changes in central venous pressure. Again a nonlinear response was observed, indicating that an additional effect besides the rise in mean central venous pressure was involved in the decrease in cardiac output. During ventilation with the smaller tidal volume, phase II of the decrease in cardiac output was also shifted to higher values of mean central venous pressure, which only could be ascribed to the differences in lung stretch at insufflation. It appeared that under circumstances of artificial ventilation the onset of the reflex is determined by a characteristic threshold of lung stretch.(ABSTRACT TRUNCATED AT 250 WORDS)
Ventilatory response to chronic metabolic acidosis and alkalosis in the dog
Authors: Madias N. E. , Bossert W. H. , Adrogue H. J.
Published: December 2017

Systematic data are not available with regard to the anticipated appropriate responses of arterial PCO2 to primary alterations in plasma bicarbonate concentration. In the present study, we attempted to rigorously characterize the ventilatory response to chronic metabolic acid-base disturbances of graded severity in the dog. Animals with metabolic acidosis produced by prolonged HCl feeding and metabolic alkalosis of three different modes of generation, i.e., diuretics (ethacrynic acid or chlorothiazide), gastric drainage, and administration of deoxycorticosterone acetate (alone or in conjunction with oral sodium bicarbonate), were examined. The results indicate the existence of a significant and highly predictable ventilatory response to chronic metabolic acid-base disturbances. Moreover, the magnitude of the ventilatory response appears to be uniform throughout a wide spectrum of chronic metabolic acid-base disorders extending from severe metabolic acidosis to severe metabolic alkalosis; on average, arterial PCO2 is expected to change by 0.74 Torr for a 1-meq/l chronic change in plasma bicarbonate concentration of metabolic origin. Furthermore, the data suggest that the ventilatory response to chronic metabolic alkalosis is independent of the particular mode of generation.
Effect of breathing pattern on esophageal pressure gradients in humans
Authors: Irvin C. G. , Sampson M. , Engel L. , Grassino A. E.
Published: December 2017

This study examines the hypothesis that respiratory muscle action alters regional pleural pressures. Seven normal volunteers were studied in the seated posture with three esophageal balloons positioned in the upper, middle, and lower esophagus. The intraesophageal pressure swings were recorded during natural breathing, enhanced rib cage, and enhanced diaphragmatic breathing. The pressures were also recorded at three frequencies ranging from 12 to 60 breaths/min. Data were processed with an ensemble average technique that largely removes cardiogenic artifact. During quiet natural breathing, the pressure swings in the lower esophagus were, on the average, 30% larger than the pressure swings in the upper esophagus but became nearly equal as the frequency increased to 60 breaths/min. Rib cage breathing nearly abolished the intraesophageal dynamic pressure differences, whereas abdominal breathing preserved the observed pressure difference even at 60 breaths/min. We concluded that muscle action can affect intrathoracic pressures in a regional way depending on the groups of muscles that are active. These results are discussed in terms of the topographical distribution of ventilation.
Effects of histamine, serotonin, and norepinephrine on circulation of dog lungs
Authors: Rippe B. , Allison R. C. , Parker J. C. , Taylor A. E.
Published: December 2017

The action of histamine (H), serotonin (5-HT), and norepinephrine (NE) on the lung vasculature was evaluated in isolated blood-perfused dog lung lobes using isogravimetric techniques. Pre- and postcapillary resistances, isogravimetric capillary pressure (Pc,i), capillary filtration pressure (Pc,f), capillary filtration coefficient (Kf,c), and vascular pressure-volume relationships were measured. For constant-flow conditions, all drugs induced marked increases in both pre- and postcapillary resistances and increased Pc,f. The rise in Pc,f was most pronounced for H and least marked for NE and 5-HT. For constant-pressure perfusion, Pc,f increased slightly for H but not for NE and 5-HT, while total vascular resistance increased 4–5 times for all drugs. Vascular distensibility and volumes decreased markedly for NE and 5-HT but only slightly for H. None of the drugs appeared to alter capillary permeability because Kf,c and Pc,i measured during the infusions were not different from control.
Indomethacin-induced fetal breathing: mechanism and site of action
Authors: Jansen A. H. , De Boeck C. , Ioffe S. , Chernick V.
Published: December 2017

The mechanism and site of action of indomethacin-induced fetal breathing (FB) was investigated in 26 chronically prepared fetal lambs. Indomethacin, which preferentially blocks prostaglandin production, was infused into the fetal circulation in two stages, 60 mg in 10 min and 60 mg over 7 h. Indomethacin stimulated sleep-state independent FB that was greatly reduced or abolished by infusions of prostaglandin E2 (PGE2). Infusions of nordihydroguaiaretic acid, which preferentially blocks the synthesis of leukotrienes, had no consistent effect on either fetal sleep or breathing activity when administered alone or after indomethacin. This suggests that the characteristic FB induced by indomethacin is due to inhibition of prostaglandin synthesis (PGE2) and not due to an overproduction of leukotrienes. The indomethacin effect on FB was observed in all fetuses tested including those deprived of peripheral chemoreceptor function, vagotomy, decortication, or spinal cord section at the T1 level. Complete constriction of the ductus arteriosus for many hours had no effect on FB. We conclude that inhibition of PGE2 synthesis stimulates FB by a central mechanism other than the cortex.
Selective activation of quadriceps muscle fibers according to bicycling rate
Authors: Citterio G. , Agostoni E.
Published: December 2017

Moving average electromyography (MA) of quadriceps muscle bellies has been recorded during bicycling at different rates (30–70 cycles/min) or forces (1–3 kg). For power increments (50–100%) achieved by increasing force at constant rate, MA during pedal downstroke always increased. For similar power increments achieved by increasing the rate at constant force, MA did not increase (37% of cases), increased less (37%), or increased similarly (26%). Investigations by others on the rat suggest that the lack of increase of MA despite power increment was not compensated by other muscle activity; hence it indicates a shift from slow to fast fibers, which provide greater power per unit stimulus. Smaller increase of MA with increasing rate rather than force at isopower could depend on this shift or on muscle properties, if operating on ascending limb of power-velocity curve. This, however, does not seem the case for slow fibers, which should develop peak power at about 25 cycles/min. Hence, fibers of quadriceps muscle of humans seem selectively activated according to movement speed, as previously found in inspiratory muscles of rabbits.
Arterial blood acid-base regulation during exercise in rats
Authors: Fregosi R. F. , Dempsey J. A.
Published: December 2017

For the first time in the rat, we described the effects of exercise on arterial acid-base status and examined the role of chemical stimuli as determinants of the hyperventilatory response in this species. O2 consumption (VO2), CO2 production (VCO2), arterial blood gases, arterial lactate concentration ([LA-]a), and rectal temperature (Tre) were measured in non-trained male rats at rest and during 10 min of treadmill exercise at various intensities. During mild exercise (2.5-fold increase in VCO2), PaCO2 fell 5.5 +/- 0.6 Torr, and despite a small but significant increase in [LA-]a, respiratory alkalosis prevailed [change in arterial pH (delta pHa) = 0.034 +/- 0.006]. Arterial PO2 (PaO2) increased 4.1 +/- 1.5 Torr and Tre increased 0.6 +/- 0.1 degrees C. A progressive hyperventilation occurred from mild to heavy exercise. This response was not attributable to arterial hypoxemia or acidosis and it was not affected by preventing the exercise-induced increase in body temperature. During maximal exercise, VO2 increased 3.4-fold (72 +/- 1.50 ml X kg-1 X min-1) and VCO2 increased 4.5-fold (74 +/- 1.90 ml X kg-1 X min-1), resulting in a 9-fold increase in [LA-]a and a severe metabolic acidosis (pHa 7.31 +/- 0.02). A marked hyperventilation [arterial PCO2 (PaCO2) 28.5 +/- 1.4 Torr] resulted in partial compensation of pHa, but almost all of this hyperventilation occurred before the onset of metabolic acidosis, [i.e., at less than 65% maximum VO2 (VO2max)], and the increased [H+]a with further elevations in VO2 produced no further hypocapnia.(ABSTRACT TRUNCATED AT 250 WORDS)
Hemoglobin concentration and aerobic work capacity in women following induced erythrocythemia
Authors: Robertson R. J. , Gilcher R. , Metz K. F. , Caspersen C. J. , Allison T. G. , Abbott R. A. , Skrinar G. S. , Krause J. R. , Nixon P. A.
Published: December 2017

The effect of induced erythrocythemia on hemoglobin concentration ([Hb]) and aerobic work capacity was determined for nine women. Cycle tests were performed at prereinfusion (T1), 2 days after a placebo infusion (T2), 2 days postreinfusion of 334 ml of red blood cells (T3), 8 days postreinfusion (T4), and 14 days postreinfusion (T5). T1 and T2 responses did not differ, negating a placebo effect. [Hb] increased from 12.7 g X dl at T1 to 14.7 g X dl at T3 and then remained constant at T4 and T5. Hematocrit increased from 38.1% at T1 to 44.9% at T3 and then remained constant at T4 and T5. Submaximal O2 uptake (VO2) and stroke volume (SV) did not change from T1 through T5. Submaximal cardiac output (Q) and heart rate (HR) decreased from T1 to T3 and then remained constant at T4 and T5. Arteriovenous O2 difference increased from T1 to T3 and then remained constant at T4 and T5. Maximal VO2 was greater at T3 (2.65 l X min-1), T4 (2.66 l X min-1), and T5 (2.60 l X min-1) than at T1 (2.41 l X min-1). Physical work capacity was greater at T3 (10,740 kg X m), T4 (10,980 kg X m), and T5 (10,380 kg X m) than at T1 (8,747 kg X m). Maximal values for Q, HR, and SV were unchanged from T1 through T5. At maximum, arteriovenous O2 difference and Hb flow rate increased from T1 to T3 and then remained constant at T4 and T5. The greater postreinfusion [Hb] improved O2 transport capacity and appeared to regulate circulatory responses.
Conservation of blood plasma fluids in hamadryas baboons after thermal dehydration
Authors: Zurovsky Y. , Shkolnik A. , Ovadia M.
Published: December 2017

After 2 days of water deprivation in a warm climate, Papio hamadryas baboons lost 10% of their body mass, 12.5% of their total body water (3H2O) space, but only 4% of their plasma volume [Evans blue (EB) space]. Hematocrit and hemoglobin concentration as well as blood viscosity and blood pressure were not affected by thermal dehydration. Plasma colloid osmotic pressure (COP) in the dehydrated animals was, however, 8 Torr higher than in fully hydrated baboons. Total mass and concentration of plasma albumin, and protein concentration increased after dehydration. Both half times (T 1/2) of EB and T 1/2 of 131I-serum albumin were twice as high as in the dehydrated animal than in the fully hydrated ones. Incorporation rate of L-[3H]leucine in the plasma proteins was similarly higher in the dehydrated animals. The capacity of the P. hamadryas baboon to maintain its plasma volume at the expense of losses from other body fluid compartments is related to an increase in the blood COP that is brought about by a more efficient retention of albumin and an increase in its rate of synthesis.
Voluntary dehydration and alliesthesia for water
Authors: Hubbard R. W. , Sandick B. L. , Matthew W. T. , Francesconi R. P. , Sampson J. B. , Durkot M. J. , Maller O. , Engell D. B.
Published: December 2017

The purpose of this experiment was to explore the complex relationship between fluid consumption and consumption factors (thirst, voluntary dehydration, water alliesthesia, palatability, work-rest cycle) during a simulated 14.5-km desert walk (treadmill, 1.34 m X s-1, 5% grade, 40 degrees C dry bulb/26 degrees C wet bulb, and wind speed of approximately 1.2 m X s-1). Twenty-nine subjects were tested (30 min X h-1, 6 h) on each of two nonconsecutive days. The subjects were randomly assigned to one of three groups: tap water (n = 8), iodine-treated tap water (n = 11), or iodine-treated flavored tap water (n = 10). The temperature of the water was 40 degrees C during one trial and 15 degrees C on the other. Mean sweat losses (6 h) varied between 1.4 kg (warm iodine-treated; 232 +/- 44 g X h-1) and 3.0 kg (cool iodine-treated flavored; 509 +/- 50 g X h-1). Warm drinks were consumed at a lower rate than cool drinks (negative and positive alliesthesia). This decreased consumption resulted in the highest percent body weight losses (2.8 and 3.2%). Cooling and flavoring effects on consumption were additive and increased the rate of intake by 120%. The apparent paradox between reduced consumption concomitant with severe dehydration and hyperthermia is attributed to negative alliesthesia for warm water rather than an apparent inadequacy of the thirst mechanism. The reluctance to drink warm iodine-treated water resulted in significant hyperthermia, dehydration, hypovolemia, and, in two cases, heat illness.
Temporal delay of venous blood correlates with onset of exercise hyperpnea
Authors: VanBenthuysen K. M. , Swanson G. D. , Weil J. V.
Published: December 2017

We tested the hypothesis that humoral factors contribute to the onset of exercise hyperpnea in an electrically induced model of isocapnic exercise in alpha-chloralose-anesthetized dogs. A cannula placed in the inferior vena cava (IVC) permitted hindlimb venous blood to flow either directly to the lungs or through a variable-length extracorporeal circuit. Mean transit times (MTT) of blood from exercising hindlimbs were measured from the arrival at the pulmonary artery of green dye injected into the saphenous vein. Onset of hyperpnea was determined by the half time of the ventilatory response (T 1/2), the time required to reach 50% of the steady-state ventilation. In seven dogs, T 1/2 was directly related to MTT (P less than 0.001), suggesting that blood-borne substances released at the onset of exercise contribute to the hyperpneic response. The T 1/2-MTT relation persisted following L2 cord transection (n = 4), suggesting that intraspinal afferents are not required for this response. Chemoreceptor denervation (n = 4) slowed the onset of exercise hyperpnea but did not alter the T 1/2-MTT relation. In this model of electrically induced “exercise” in which neurogenic influences have been minimized, humoral factors alone may stimulate ventilation sufficiently to produce arterial isocapnia.
Contractile activity increases glucose uptake by muscle in severely diabetic rats
Authors: Wallberg-Henriksson H. , Holloszy J. O.
Published: December 2017

Muscle contractile activity is associated with an acceleration of glucose transport into muscle. It has been reported that the acceleration of glucose uptake by contractile activity in perfused rat muscles requires the presence of insulin in the perfusate. This claim was investigated using the perfused rat hindlimb preparation in the present study. Rats were made diabetic by injection of 125 mg/kg of streptozotocin and either studied 72 h later or maintained on insulin for 2 wk and then studied 3 days after cessation of insulin therapy. Only rats with plasma insulin levels too low to measure were used. The hindlimbs were washed out with 630 ml of medium over 75 min using a single flow-through washout before muscle stimulation. Despite the absence of insulin in the perfusion medium, stimulation of muscle contraction resulted in large increases in glucose uptake in both the diabetic and control rats. These findings do not support the claim that the stimulatory effect of muscle contraction on glucose uptake by perfused rat muscles requires the presence of insulin.
Potent stimulation of glycoprotein secretion in canine trachea by substance P
Authors: Coles S. J. , Neill K. H. , Reid L. M.
Published: December 2017

The effects have been investigated of the regulatory peptides, substance P (SP) and bombesin, on the secretion of [14C]glucosamine-labeled trichloroacetic acid-phosphotungstic acid precipitable glycoproteins by canine tracheal explants. SP (10(10) to 10(-7) M) induced a dose-dependent increase in secretion of high-molecular-weight (greater than 2 X 10(6) radiolabeled glycoproteins predominantly from the submucosal glands. On a molar basis, SP [median effective concentration (EC50) = 8.2 X 10(-10) M] was about 1,000-fold more potent than methacholine (EC50 = 6.3 X 10(-7) M). Bombesin (10(-10) to 10(-4) M) had no effect on glycoprotein secretion. The time course of SP effect was characterized by an initial stimulation of glycoprotein secretion followed by a period of inhibition, suggesting that it rapidly exhausts a pool of glycoprotein, possibly that present within the duct lumen of the submucosal gland. Consistent with this are the findings that SP-induced secretion of glycoprotein was augmented by preincubation with methacholine while methacholine-induced secretion was diminished by preincubation with SP. Our findings show that SP is a potent stimulant of airway glycoprotein secretion in vitro and suggest that it acts by increasing the rate of clearance of mucus from the ducts of the submucosal gland, possibly by induced constriction of the secretory tubules and collecting duct. A role is discussed for SP in mucus hypersecretion induced by local axonal reflexes in the airway mucosa.
Regional interdependence in calf lungs
Authors: Robinson N. E. , Ingersoll R. , Slocombe R. F. , Olson L. E.
Published: December 2017

We measured K, an index of interdependence in sublobar segments of both intact and excised calf lungs. In excised and intact lungs, segment volume was held constant while the lung was inflated. K in excised lungs was of small magnitude but was greater in caudal than in cranial and middle lobes. When isolated segments in a variety of regions and with a variety of shapes were studied, K was positively correlated with the interface area between the segment and the remainder of the lung, was negatively correlated with the pleural surface area of the segment, but was not correlated with segment volume. In a given region of lung, however, small segments had a greater interdependence than large segments. In intact lungs of anesthetized calves, K was an order of magnitude greater than in excised lungs, confirming that the chest wall is the major determinant of interdependence. There were no lobar differences in K in intact lungs.
Mechanisms of substance P-induced contraction of rabbit airway smooth muscle
Authors: Tanaka D. T. , Grunstein M. M.
Published: December 2017

The contractile effects of substance P (SP) were studied in isolated rabbit tracheal smooth muscle (TSM) segments in vitro. Noncumulative administration of SP produced dose-dependent increases in TSM tension. The mean (+/- SE) peak isometric tension (Tmax) with SP was 35.7 (+/- 6.2%) of the corresponding Tmax response to methacholine. The dose of agonist producing 50% of Tmax (ED50) was significantly lower for SP, averaging 1.8 (+/- 0.4) X 10(-7) M, vs. 1.7 (+/- 0.32) X 10(-6) M for methacholine. Blockade of both parasympathetic ganglia with hexamethonium (10(-4) M) and neural transmission with tetrodotoxin (1 microgram/ml) had no effect on the TSM response to SP. On the other hand, TSM contraction to an ED50 dose of SP was 1) augmented by a mean (+/- SE) of 470 (+/- 110%) following pretreatment with the cholinesterase inhibitor, neostigmine (10(-6) M);2) inhibited by a mean (+/- SE) of 35 (+/- 15%) with the cholinergic antagonist, atropine (10(-4) M); and 3) also inhibited by a mean (+/- SE) of 45 (+/- 11%) following inhibition of acetylcholine synthesis with hemicholinium-3 (10(-4) M). Antagonists to 5-hydroxytryptamine, alpha 1-adrenergic, and histamine receptor binding had no effect on TSM contraction with SP. In contrast, the SP antagonist, D-Pro2,D-Trp7,9-SP, markedly inhibited TSM contraction to SP. Our findings indicate that rabbit TSM is sensitive to SP and its contraction is in part mediated by a peripheral cholinergic action, likely involving the accelerated release of acetylcholine at the airway neuromuscular junction.
Weight loss and changes in body composition at high altitude
Authors: Boyer S. J. , Blume F. D.
Published: December 2017

Little is known about weight loss and changes in body composition at extreme altitude. As part of the American Medical Research Expedition to Everest in 1981 we measured body weight, body fat, limb circumferences, dietary intake, 72-h stool fats, and 5-h urine xylose excretion at various altitudes on Caucasian and Sherpa expedition members. In Caucasians, loss of body fat accounted for 70.5% of the mean 1.9-kg weight loss during the approach march at moderate altitude but for only 27.2% of the mean 4.0-kg weight loss during residence above 5,400 m. There was a significant proportionate decrease in arm and leg circumferences during residence above 5,400 m (1.5 and 2.9 cm, respectively). On the other hand, Sherpas, who arrived in Base Camp with half as much body fat as members (9.1% vs. 18.4%), maintained weight and limb circumferences during residence above 5,400 m. Fat absorption decreased 48.5% in three subjects, and xylose excretion decreased 24.3% in six of seven subjects at 6,300 m relative to sea level. It appears that muscle catabolism and malabsorption contribute significantly to weight loss at high altitude. High percent body fat does not protect against loss of muscle tissue. Sherpas do not appear susceptible to some of the changes affecting Caucasians.
Pulmonary surfactant: an interdisciplinary approach
Authors: Notter R. H. , Finkelstein J. N.
Published: December 2017

Pulmonary surfactant research is considered from the perspective of interdisciplinary correlations based on information acquired from biophysics and physical chemistry, biochemistry, cell biology, physiology, and medicine. Current views of the important molecular constituents of the pulmonary surfactant system are described and related to the biophysical surface properties necessary to generate appropriate effects on respiratory physiology. The fundamental importance of multidisciplinary characterizations of lung surfactant, together with correlations between these descriptions, is stressed throughout. The primary advantage of such an approach is that it provides broad but coordinated principles and data with which to test hypotheses of lung surfactant function and roles in respiratory physiology and pathophysiology. This perspective is used to examine available information about the functional composition of lung surfactant, its surface tension-lowering properties at physiological temperature and humidity, and considerations relevant to the formulation of effective exogenous surface-active mixtures in the treatment of surfactant-deficient states. Also discussed is the biophysical state in vivo of pulmonary surfactant at the alveolar level, including current knowledge of the alveolar hypophase as well as the concept of functional surfactant acting in predominantly dry alveoli in the normal lung.
Regional differences in expansion in excised dog lung lobes
Authors: Olson L. E. , Rodarte J. R.
Published: December 2017

The position of small metallic markers embedded within the lung parenchyma and glued to the pleural surface of four excised right caudal dog lobes were determined during stepwise deflation from an airway opening pressure of 25 cmH2O in air-filled suspended lobes and 8 cmH2O in saline-filled lobes submerged in saline. Changes in the volumes of tetrahedrons formed by four noncoplanar markers were taken as regional lung volume changes at the centroids of the tetrahedron. In both air- and saline-filled lobes at all volumes below total lobe capacity (TLC) there was considerable variability in regional volume. The variability occurred at the first step below TLC and increased with deflation. Regions behaved consistently; regions that were proportionally larger or smaller than the overall lobe at any step tended to be larger or smaller, respectively, at all steps. There was a significant correlation between the regional behavior of the air- and saline-filled lobes. The variability of regional volume did not follow any clear topographical orientation. These results indicate there is considerable variability of lung compliance within small regions. This heterogeneity of regional parenchymal properties may be the anatomical basis of the nonuniformity of regional ventilation known to occur in intact animals and excised lobes within small regions at the same vertical height.
Interstitial fluid volumes and albumin spaces in pulmonary oxygen toxicity
Authors: Matalon S. , Egan E. A.
Published: December 2017

In rabbits exposed to 100% O2 at 1 ATA from 48 to 72 h, we measured the accumulation of intravenously injected 125I-bovine albumin, [57Co]cyanocobalamin, and 51Cr-erythrocytes in the intestine, skeletal muscle, heart, and lungs. From these data, we calculated the extravascular albumin and cyanocobalamin spaces (EVAS, EVECS) and the partition of water among vascular, interstitial, and cellular compartments in these organs. All variables remained at their base-line levels at 48 h in O2. At 64-66 h, the lung EVECS remained unchanged, but its EVAS increased by 210%. This change occurred after the previously documented increase of the alveolar epithelial permeability to solute and of the pulmonary conductance to water but before the appearance of pulmonary edema and arterial hypoxemia. The only change in the systemic circulation was a 17% increase of the heart EVAS. The increased heart and lung EVAS values, in the absence of any fluid volume shifts, are consistent with damage to the tissue polysaccharides of these organs by the toxic O2 species.
Nonuniform brain blood flow response to hypoxia in unanesthetized cats
Authors: Neubauer J. A. , Edelman N. H.
Published: December 2017

In seven unanesthetized cats, radiolabeled microspheres were used to determine regional brain blood flow (rBBF) to the medulla-pons (M-P), midbrain-thalamus (M-T), cerebellum (Cb), and cortex (Cx) during three conditions: 1) control [arterial O2 tension (PaO2) = 81 Torr, arterial CO2 tension (PaCO2) = 26 Torr]; 2) hypocapnic hypoxia (PaO2 = 39 Torr, PaCO2 = 22 Torr); and 3) isocapnic hypoxia (PaO2 = 47 Torr, PaCO2 = 26 Torr). Hypoxia increased blood flow significantly more in the caudal brain stem (M-P) than in the Cx (P less than 0.05) during both hypocapnic hypoxia (M-P/Cx: +33/ +17 ml X min-1 X 100 g-1) and isocapnic hypoxia (M-P/Cx: +13/ -2 ml X min-1 X 100 g-1). Since sympathetic innervation is greater anatomically to rostral than to caudal vessels, we examined the rBBF response to hypocapnic hypoxia in seven additional cats after unilateral superior cervical gangliectomy. All seven cats had a reduction in the cortical-to-caudal brain stem trend on the denervated side of the brain (M-P/Cx: +27/+28 ml X min-1 X 100 g-1) compared with the intact side of the brain (M-P/Cx: +34/+24 ml X min-1 X 100 g-1) owing to both increases in Cx and decreases in M-P flows. We conclude that in unanesthetized cats hypoxia causes a greater increase in the caudal brain stem compared with cortical blood flow, and this differential response is related to modulation by the sympathetic nervous system.(ABSTRACT TRUNCATED AT 250 WORDS)
Estimation of isogravimetric capillary pressure by a filtration method in skeletal muscle and lung
Authors: Korthuis R. J. , Townsley M. I. , Rippe B. , Taylor A. E.
Published: December 2017

Pre- to postcapillary resistance ratios (Ra/Rv) and isogravimetric capillary pressures (Pc,i) were estimated using a modified filtration method and compared with estimates obtained by application of traditional isogravimetric techniques in isolated rat hindquarters and canine lungs. Pc,i's and Ra/Rv's were estimated using both methods in rat hindquarters perfused with whole blood or an artificial plasma and in blood-perfused canine lung. In each of the three experimental conditions studied, the modified filtration method yielded the same Pc,i and Ra/Rv as the isogravimetric technique. Maximal vasodilation of the rat hindquarter with papaverine reduced Ra/Rv approximately fourfold to a level which was not different from that obtained in hindquarters perfused with artificial plasma, although Pc,i was unchanged. These results indicate that the more easily applied modified filtration method provides an excellent measurement of Ra/Rv and Pc,i in whole organ studies.
Frequency dependence of plethysmographic measurement of thoracic gas volume
Authors: Brown R. , Slutsky A. S.
Published: December 2017

With airways obstruction, panting frequency affects plethysmographically determined thoracic gas volume (Vtg) because the extrathoracic airway acts as a shunt capacitor. Stanescu et al. (19) suggested that in the calculation of Vtg, use of esophageal (delta Pes) rather than mouth pressure (delta Pm) swings might eliminate the problem. We measured total lung capacity (TLC) plethysmographically in 10 subjects with chronic airways obstruction (CAO) and in four normal subjects. TLC (using delta Pm) was derived from Vtg obtained from slow-(approximately 1 Hz) and fast- (approximately 4 Hz) panting frequencies. In the normal subjects and four subjects with CAO, TLC was also obtained using delta Pes. In these subjects abdominal gas compression and decompression did not contribute significantly to the frequency dependence of TLC. In CAO, TLC was frequency dependent in direct proportion to the severity of obstruction. Although the frequency dependence was greater using delta Pm to calculate Vtg, it also occurred using delta Pes. Thus it could not be explained entirely by the shunt capacitor effect of the extrathoracic airways. The residual and significant overestimations of TLC (reflected by frequency dependency of TLC derived from Vtg calculated from delta Pes) may be explained by interregional nonhomogeneities during the panting maneuver.