bluuebunny/crossref_metadata_2025 huggingface dataset:
Composition of cerebral fluids in goats adapted to high altitude
Authors: Fencl V. , Gabel R. A. , Wolfe D.
Published: December 2017

Page 510: In the supplementary tabulated data deposited as NAPS Document 03492, there are some misprints and computational inconsistencies in the data on HCO‑3and Cl– fluxes, and a systematic error in the reported transependymal fluxes of lactate at sea level (SL) and at high altitude (HA). These data have been revised, and a corrected version of the supplementary tables has been deposited.

Page 511: Data presented in Table 4, giving parameters (±SE) of regressions of transependymal fluxes (y) of HCO‑3and Cl– on the differences in concentrations of these ions between the inflow perfusate and in the goat's CSF (x), should read: Cl– flux at SL: y = (0.39 ± 0.03)x – (0.09 ± 0.22), r = 0.94; at HA: y = (0.40 ± 0.05)x – (0.05 ± 0.26), r = 0.90; both y-intercepts not significantly different from zero; HCO–3 flux at SL: y = (0.37 ± 0.03)x + (0.25± 0.16), r = 0.92, y-intercept not significantly different from zero; at HA: y = (0.44 ± 0.04)x + (2.53 ± 0.26), r = 0.91, y-intercept significantly greater than zero (P<0.001, F test; value of x at y = 0 is –5.8 mmol/kg H2O, with the upper 95% tolerance limit of –4.0 mmol/kg H2O). All the significance tests give the same results as presented in Table 4. Thus the conclusions drawn from the data are unchanged.

The mean value (±SE) of the lactate fluxes at SL was –158 ±0.06 μmol/min, and at HL –3.28 ± 0.17 μmol/min (not –0.09 ± 0.04 and –1.47 ± 0.17 μmol/min, respectively, as indicated on page 511). The negative transependymal flux (washout of lactate) at HA was significantly greater than at SL (P<0.005, t test for independent means). It was twice as great at HA than at SL, rather than 16 times higher, as indicated in the Abstract and on page 512.

Page 512, column 2, paragraph 1: To interpret the data, it is suggested that"in goats adapted to HA, there exists a steady-state concentration gradient of [HCO‑3]…, with a lower [HCO‑3]in cerebral ISF than in CSF," which "may be, at least in part, owing to a concentration gradient of lactate going in the opposite direction." This interpretation remains unchanged by the correction in lactate fluxes: The mean (±SE) increase in negative transependymal flux (washout) of lactate associated with adaptation to HA was 1.72 ± 0.28 μmol/min, which accounted for 68% of the mean positive transependymal flux of HCO‑3(2.53 ± 0.26 μmol/min, see above) in goats adapted to HA, when the ventriculocisternal system was perfused with fluid having bicarbonate concentration equal to that normally found in the goats'cisternal CSF. Thus, the conclusion that the"the fluid surrounding the central chemoreceptors appears to be more acidic in goats acclimatized to HA than at SL despite the alkalosis in cisternal CSF" continues to be substantiated by the corrected data.
Populations of rat skeletal muscle mitochondria after exercise and immobilization
Authors: Krieger D. A. , Tate C. A. , McMillin-Wood J. , Booth F. W.
Published: December 2017

We slightly modified an existing procedure (Palmer et al., J. Biol. Chem. 252: 8731-8739, 1977) to isolate two distinct populations of mitochondria from rat skeletal muscle; initial brief Polytron homogenization released the subsarcolemmal mitochondria, and brief exposure of the resultant intact myofibrils to the proteolytic enzyme, Nagarse, extracted the intermyofibrillar mitochondria. The intermyofibrillar mitochondria differed from the subsarcolemmal mitochondr. ia by higher state III respiration measurements and enzymatic activities. These two populations of mitochondria were then isolated from the gastrocnemius muscle that had been induced to perform different amounts of contractile activity. The endurance training program of daily running significantly increased state III respiration and respiratory control index in the subsarcolemmal mitochondria, but the program did not increase these measurements in the intermyofibrillar mitochondria. In addition, 2 days of hindlimb immobilization resulted in a significant decrease in state II respiration and the respiratory control index of the subsarcolemmal mitochondria; however, immobilization did not affect the intermyofibrillar mitochondria. These measurements suggest that the subsarcolemmal mitochondria adapt in response to chronic changes in the level of contractile activity.
Fluid shifts and endocrine responses during chair rest and water immersion in man
Authors: Greenleaf J. E. , Shvartz E. , Kravik S. , Keil I. C.
Published: December 2017

To determine the effect of external water pressure per se on intercompartmental fluid volume shifts, plasma and urine electrolytes, osmotic and endocrine responses were compared in four men (21-22 yr) during 8 h of water immersion (TH2O = 34.4 degrees C) and during 8 h of chair rest (Ta = 22.5 degrees C), followed by16 h of bed rest in both regimens. Water intake was 1,800 ml during 8-h exposures. Urine volume during immersion was 2,954 ml/8 h and 1,538 ml/8 h (P less than 0.01) during chair rest; the respective decreases in extracellular volume (ECV) were 2,230 ml/8 h and 1,892 ml/8 h. Losses from the intersititial volume (1.81 vs. 1.67 liters) and plasma volume (0.43 vs. 0.23 liters) during immersion and chair rest, respectively, were approximately proportional to theri normal ratios. With a negative H2O balance (corrected for blood withdrawal) during immersion of 1,234 ml and a positive balance (190 ml) during chair rest, there appeared to be a shift of ECV to the intracellular compartment in both regimens. There was suppression of both plasma arginine vasopressin (AVP) and renin activity (PRA) during chair rest and immersion. It appears that the increased central blood volume, as opposed to increased plasma osmolality, is the primary stimulus for AVP suppression.In hyperhydrated subjects, about half (6.7%) of the immersion plasma volume loss of 12.6% could be attributed to orthostatic responses associated with the upright body position during chair rest and the remaining half to the external water pressure.
Faster adjustment to and recovery from submaximal exercise in the trained state
Authors: Hagberg J. M. , Hickson R. C. , Ehsani A. A. , Holloszy J. O.
Published: December 2017

This study was undertaken to evaluate the effects of endurance exercise training on O2 deficit and O2 debt, and on the time courses of the adjustment to, and recovery from, submaximal exercise of oxygen uptake (VO2) carbon dioxide production (VCO2), minute ventilation (VE), and heart rate (HR). Eight subjects participated in a 9-wk-long exercise program that increased their VO2max by 24%. It was found that O2 deficit and O2 debt were lower at the same absolute work rate and not significantly different at the same relative work rate after training. The increases in VO2, VCO2, VE, and HR at the onset of constant load submaximal work, and the decreases in VO2, VCO2, VE, and HR in recovery were more rapid at both the same absolute and the same relative work rates after training. These results show that the adaptations to endurance exercise training enable an individual to adjust to the energy requirement of constant load submaximal work more rapidly, resulting in a smaller O2 deficit. The rate of recovery is also more rapid after training, resulting in a smaller O2 debt.
Aldosterone and ADH response to heat and dehydration in cattle
Authors: El-Nouty F. D. , Elbanna I. M. , Davis T. P. , Johnson H. D.
Published: December 2017

The effect of heat (35 degrees C) and dehydration under heat (30 h) on plasma levels of antidiuretic hormone (ADH) and aldosterone was studied on four nonpregnant dry Holstein cows. Heat exposure caused a rapid significant rise in plasma ADH without significant changes in hematocrit (Hct), small but significant increase in urine output and a significant reduction in total plasma protein. Dehydration under heat caused a sharp increase in ADH levels associated with a significant decrease in urine output and a significant increase in plasma protein, blood Hct, and serum osmolality. A significant reduction in plasma aldosterone level was observed after 24 h of heat exposure. This was associated with a slight rise in urinary sodium excretion and a significant reduction in serum sodium. Both serum and urinary potassium concentrations were significantly lower under heat. Dehydration resulted in a slow rise in aldosterone but did not reach thermoneutral level. This is probably due to the inhibitory effect of higher serum sodium observed during dehydration on plasma aldosterone secretion. The rise in ADH and decrease in aldosterone during heat exposure may explain why cattle are one of the few species that do not concentrate urine during heat exposure.
Hemodynamics in awake rabbits during hyperbaric helium-oxygen exposure
Authors: Boerboom L. E. , Boelkins J. N.
Published: December 2017

Although man is being exposed to hyperbaric environments more frequently, the effects of these environments and the inert gases used are not clearly defined. We therefore designed an experiment to examine both the effects of helium and elevated pressure on the cardiovascular system in conscious rabbits exposed to normoxic levels of a helium-oxygen (He-O2) gas mixture at 1 and 11 atmospheres absolute (ATA) for 2 h. Variables studied included heart rate, blood pressure, cardiac output, systemic vascular resistance, organ blood flow, and resistance to flow. The only change observed was a decrease in heart rate from a control of 284 +/- 7 (mean +/- SE) to 246 +/- 12 beats/min after 2 h of breathing He-O2 at 1 ATA. We therefore conclude that the cardiovascular system is not adversely affected by helium or elevated pressure as used in this experiment.
Influence of starvation on enzyme-induced emphysema
Authors: Sahebjami H. , Vassallo C. L.
Published: December 2017

Adult rats were exposed to an aerosol of 10% papain for 8 h twice in a 2-wk interval. The control rats were exposed to isotonic saline in the same manner. Three weeks after the final exposure rats were divided into four groups: emphysema-fed, emphysema-starved, control-fed, and control-starved. Starved animals received one-third of their measured daily food consumption and water ad libitum for 6 wk. Final body weight, dry and wet weights of lungs and postfixation lung volume (VL) were significantly lower in starved rats. Dry-to-wet weight ratios were not significantly different among the groups, but VL/body weight was significantly higher in starved animals. Elastic recoil pressure of lung tissue determined in saline-filled lungs decreased and chord compliance over mid- and high-volume ranges increased significantly in starved animals both in control and emphysema groups. Mean linear intercept of air spaces was greater and internal surface area was smaller in starved rats in each group. Therefore, it appears that starvation aggravates the preexisting emphysematous processes in rat lungs.
Lightweight remotely actuated switching valve for rebreathing exercise studies
Authors: Ellis D. G. , Lampman R. M.
Published: December 2017

A new type of switching valve used in rebreathing studies for estimating cardiac output is described. This valve employs a unique deformable elastic element, actuated by low-pressure compressed air, to effect switching. The capability for remote operation (via a compressed air line) and the light weight of the valve (110 g) make the valve especially well suited to exercise stress testing studies. Two valves of this type have been satisfactorily used in graded exercise stress tests in a clinical setting for over 2 yr.
Effect of dichloroacetate on plasma lactic acid in exercising dogs
Authors: Merrill G. F. , Zambraski E. J. , Grassl S. M.
Published: December 2017

Dichloroacetate sodium (DCA) has been shown to reduce circulating levels of lactic acid (LA) under a variety of experimental and clinical conditions. We have examined the effect of DCA on the lactacidemia of exercise in treadmill-exercised dogs. One group of animals (n = 8) was tested at light, moderate, and heavy exercise work loads. Plasma LA, 19 +/- 2mg/dl at rest, increased to 26 +/- 4, 38 +/- 5, and 52 +/- 6 mg/dl during the three workloads, respectively. In the same animals, when identical treadmill tests were conducted after DCA (100 mg/kg, iv), the rise in LA was significantly attenuated. Lactic acid values were 11 +/- 2 mg/dl at rest after DCA and 15 +/- 2, 20 +/- 4, and 23 +/- 3 mg/dl for the light, moderate, and heavy workloads, respectively. Another group of dogs (n = 6) performed prolonged moderate exercise. Under untreated conditions, LA increased from 24 +/- 1 mg/dl at rest, to 41 +/- 6 mg/dl at 10 min, and 50 +/- 5 mg/dl at 50 min. During repeat tests, DCA was given at 12 min when LA was 30 +/- 6 mg/dl. At 50 min, LA was 18 +/- 3 mg/dl or 60% lower than that observed during the untreated run. Because DCA has been shown to increase pyruvate dehydrogenase enzyme activity, these data suggest that this enzyme may be an important factor in LA metabolism during exercise.
Chronic propranolol treatment blunts right ventricular hypertrophy in rats at high altitude
Authors: Voelkel N. F. , McMurtry I. F. , Reeves J. T.
Published: December 2017

Chronic beta-receptor blockade has been reported to inhibit right ventricular hypertrophy in rats at high altitude. If so, we wanted to determine whether beta-receptor blockade or some other drug action were involved and whether the heart, the lung vessels, or blood alterations were affected. In rats, chronic treatment with DL-propranolol (2 mg/kg ip once daily) reduced right ventricular hypertrophy and polycythemia of chronic high altitude. D-Propranolol and metoprolol did not reduce hypoxia-induced right ventricular hypertrophy or polycythemia. In isolated lungs from low-altitude rats treated chronically with DL-propranolol or with D-propranolol the pressor response to acute hypoxia was blunted. Chronic DL-propranolol blunted the acute hypoxic pressor response and angiotensin II induced vasoconstriction in lungs from high-altitude rats. Two effects of DL-propranolol treatment were seen: 1) blockade of beta 2-adrenergic receptors, which reduced the right ventricular hypertrophy of high altitude through reduction of hematocrit; and 2) a non-beta-effect, which reduced vascular responsiveness to acute hypoxia in the isolated lung preparation.
Variable open-loop gain in the control of thermogenesis in cold-exposed rabbits
Authors: Stitt J. T.
Published: December 2017

We have previously demonstrated a multiplicative interaction between mean skin temperature (Tsk) and hypothalamic temperature (Thy) in the control of thermogenesis in cold exposed rabbits. Such a model predicts that open-loop gain will not be constant, but will vary according to the direction and degree of Thy displacements and to the prevailing level of Tsk when Thy is altered. Open-loop gain was calculated from steady-state displacements in body temperature induced by sustained step displacements in Thy. Hypothalamic temperature of rabbits was clamped at various levels ranging from 2 degrees C above to 3 degrees C below normal Thy and the resulting changes in rectal temperature attained at steady state were recorded. Experiments were conducted at ambient temperatures (Ta) of 2 degrees and 15 degrees C. Open-loop gain in response to hypothalamic heating was always greater than that obtained in response to equivalent levels of hypothalamic cooling. Furthermore, at lower levels of Tsk (Ta = 2 degrees C) open-loop gain was greater for all levels of Thy displacement when compared to that measured at higher levels of Tsk (Ta = 15 degrees C).
Upper airway patency in the human infant: influence of airway pressure and posture
Authors: Wilson S. L. , Thach B. T. , Brouillette R. T. , Abu-Osba Y. K.
Published: December 2017

We have determined the influence of transmural pressure and neck posture on upper airway patency in infants after death. In natural resting postures, the airway was closed at transmural pressures not exceeding those normally seen during peak inspiratory airflow in the living infant, implying that a neuromuscular mechanism is necessary to maintain airway patency during life. Neck flexion raised closing pressure, making the airway more susceptible to collapse, whereas neck extension lowered closing pressure, making the airway more resistant to collapse. When the angle of flexion was kept constant, closing pressure was not significantly altered by turning the head or positioning the infant prone. Pressures above the corresponding closing pressure were required to reopen the closed airway, suggesting that the walls of the closed airway tended to adhere and implying that surface forces can impose an added load to airway-maintaining musculature during obstructive apnea in the living infant.
Bradykinin stimulates afferent vagal C-fibers in intrapulmonary airways of dogs
Authors: Kaufman M. P. , Coleridge H. M. , Coleridge J. C. , Baker D. G.
Published: December 2017

Bradykinin is released in the lungs in asthma and pulmonary anaphylaxis. It has negligible direct bronchoconstrictor effects in humans or dogs, but inhaled as aerosol it causes cough and reflex bronchoconstriction in asthmatics and some normal subjects. The afferent nerves responsible for these reflex effects have not been identified. We recorded vagal impulses in anesthetized dogs to determine whether lung afferents were stimulated by bradykinin. C-fiber endings in the intrapulmonary airways accessible from the systemic circulation were stimulated by bradykinin injected into the left atrium (0.5-1.0 micrograms/kg) or bronchial artery (1.5 micrograms), activity increasing 15-fold on average. C-fiber endings accessible from the pulmonary circulation were relatively insensitive to bradykinin. Bradykinin caused a small increase in firing of some rapidly adapting (irritant) receptors, but the effect appeared to be secondary to vascular changes. Bradykinin had variable effects on slowly adapting stretch receptors, but did not stimulate them directly. Thus vagally mediated sensory or reflex effects initiated by bradykinin in the lung are probably due to stimulation of “bronchial” C-fibers.
Human respiratory control at high ambient pressures and inspired gas densities
Authors: Gelfand R. , Lambertsen C. J. , Peterson R. E.
Published: December 2017

Four men, exposed to the pressure equivalent of 1,200 ft of seawater (37 ATA) for 6 days in a CO2-free, normoxic helium-oxygen environment (Predictive Studies III-1971, Aviation Space Environ. Med. 4: 843-855, 1977), had no evident respiratory distress at work, at rest, or asleep. Ventilatory responses of two men to CO2 were measured in 20-min acute exposures to mixtures of oxygen (173 Torr) with nitrogen, crude neon, and helium over a gas density range of 0.4-22 g/l and a pressure range of 1-37 ATA during stepwise compression of 37 ATA. Analysis of delta V/delta PACO2 as functions of pressure, of density, and of density-to-viscosity ratios shows that increased gas density, but not nitrogen narcosis, is associated with gross diminution of the ventilatory response to CO2. A small ventilatory response to CO2 is predicted for liquid breathing when viscosity is included as a parameter in the analysis. Other findings associated with increased gas densities and progressive elevation of inspired CO2 concentration are disruption of the normal patterns of tidal volume and frequency of breathing and reduction in the range of linear respiratory response to CO2.
Alteration of histamine response by H2-receptor antagonism in the guinea pig
Authors: Drazen J. M. , Venugopalan C. S. , Schneider M. W.
Published: December 2017

Effects of H2-receptor antagonism on the response to histamine was studied in the guinea pig in vivo and in vitro. The H2-receptor antagonist, metiamide (100 micro M), resulted in an enhanced histamine response in eight of eight parenchymal strips and in four of eight tracheal spirals. On the average the parenchymal strips were 20-fold more sensitive to histamine (P less than 0.001), whereas the tracheal spirals demonstrated an insignificant, 20%, increase in sensitivity after metiamide treatment. These results are consistent with the hypothesis that there are inhibitory H2-receptors in guinea pig airways and they predominate in the periphery. When we determined the effects of H2-antagonism on the histamine response in vivo we found that the histamine response was enhanced only in animals that had been treated with the beta-receptor antagonist propranolol. In these animals there was a mean 2.2-fold increase in histamine sensitivity. These results suggest that although there are inhibitory H2-receptors in the guinea pig lung, their role in modulating the in vivo response is much less than beta-adrenergic mechanisms.
Role of thermal and exercise factors in the mechanism of hypervolemia
Authors: Convertino V. A. , Greenleaf J. E. , Bernauer E. M.
Published: December 2017

Our purpose was to determine whether the chronic increase in plasma volume (PV), resulting from heat exposure (HE) and exercise training (ET), was due only to elevated rectal temperature (Tre) or whether there were additional nonthermal factors related to the exercise. Eight men were divided into two groups. The HE group sat for 2 h/day (Tdb = 42 degrees C, 93% rh) for 8 consecutive days; Tre was raised by 1.72 +/- 0.04 degrees C to 38.5 degrees C each day. The ET group rode a bicycle ergometer for 2 h/day for 8 days (Tdb = 25 degrees C, 60% rh) at a load (60-65 Vo2max) that gave the same area under their Tre curve. PV increased by 177 ml (4.9%, P less than 0.05) in the HE group and by 427 ml (12.0%, P less than 0.05) in the ET group. This exercise-induced hypervolemia was associated with thermal factor(s) that contributed 40% and nonthermal factors that accounted for the remaining 60%. Some nonthermal, exercise-induced factors were twofold greater increases in plasma osmotic and vasopressin levels during exercise, and a fivefold increase in resting plasma protein (albumin) content.
Canopy ventilation monitor for quantitative measurement of ventilation during sleep
Authors: Sorkin B. , Rapoport D. M. , Falk D. B. , Goldring R. M.
Published: December 2017

A portable, easily assembled system that allows quantitative monitoring of ventilation in the sleeping human subject is described. It is a modification of the system used by Kinney et al. (Metab. Clin. Exp. 13: 205-211, 1964) and Spencer et al. (J. Appl. Physiol. 33: 523-528, 1972). The system directly measures gas flow without reliance on indirect CO2 or temperature sensors or on chest wall motion. It is comfortable and reflects the tidal volume with an accuracy of 92%. It also allows measurement of oxygen consumption and CO2 production. The gas breathed by the subject can be varied in composition. Two illustrative examples of the use of the system are given: 1) a case of obstructive apnea; and 2) a case in which a drop in arterial oxygen saturation is explained by quantified hypoventilation undetected by a nasal CO2 probe.
Influence of physical exercise on sex-hormone metabolism
Authors: Keizer H. A. , Poortman J. , Bunnik G. S.
Published: December 2017

We have studied the effects of short-term exercise on the degradation rate of estradiol (E2) measured as the metabolic clearance rate (MCRE2). Six young women (mean age 20.7 yr) volunteered for this study in which we investigated the influence of a submaximal bicycle ergometer load on the MCRE2. All measurements were done in the morning of the 7th to 10th day of the menstrual cycle. [3H]estradiol 17 beta ([3H]E2) was administered intravenously at a constant rate by an infusion pump. During the exercise period on the bicycle ergometer (70% VO2max, 10 min) and the recovery period (25% VO2max, 30 min), several blood samples were taken in which the [3H]E2 concentration was estimated. The results showed a strong decrease in the MCRE2 (range 18-67%) at the end of the work load for all the volunteers. At the end of the recovery period, the MCR was still lower than the basal value (range 30-50%). The possible mechanisms and relevance of these exercise-induced MCR changes of estradiol are discussed.
Phasic changes in bone CO2 fractions, calcium, and phosphorus during chronic hypercapnia
Authors: Schaefer K. E. , Pasquale S. , Messier A. A. , Shea M.
Published: December 2017

The bone CO2 buffering system and bone calcium and phosphorus were studied in guinea pigs exposed to 1% CO2 for periods up to 8 wk and killed at weekly intervals together with control animals of the same age. Measurements were made of arterial CO2 tension, pH, standard bicarbonate, and bone Ca and P. Heat-stabile bone CO2 (carbonate) was determined as dry bone CO2 and heat-labile bone CO2 (bicarbonate) as delta wet-dry bone CO2. During the first 3-4 wk of exposure to 1% CO2, a systemic acidosis was found as indicated in a lowered pH, increased arterial CO2 tension, and decreased standard bicarbonate. The acidosis subsided during the last 4 wk of exposure. Phasic changes in bone bicarbonate were observed as shown in immediate rise lasting for 2 wk followed by a 2-wk decline and second rise after 6 and 8 wk. Bone carbonate exhibited the opposite change during the first 4 wk and thereafter remained stable at an elevated level. Bone Ca and P fell in association with increasing bone bicarbonate and rose with increasing bone carbonate.
Intracellular metabolism of the apoproteins of pulmonary surfactant in rat lung
Authors: King R. J. , Martin H.
Published: December 2017

We studied the metabolic turnover of the major apoproteins of pulmonary surfactant from rat lung and compared it with similar studies on the metabolism of dipalmitoyl phosphatidylcholine (DPPC). At varying times after the injection of tritiated leucine or tritiated palmitate we isolated the alveolar cells and alveolar fluid and measured the incorporation of the radioactive leucine into the 35,000-dalton (apoprotein A) and 10,000-dalton (apoprotein B) apoproteins of surfactant and of the radioactive palmitate into DPPC. Maximum labeling of apoprotein A in type II cells occurred within 1 h after injection of the precursor and declined in the next 19 h. The labeling of intracellular DPPC followed the same time course. The labeling of apoprotein B in type II cells was low, and the change of its labeling with time was not consistent with its being secreted by these cells. Both proteins were labeled in alveolar fluid and in alveolar macrophages. The results indicate that apoprotein A is synthesized by type II cells and is probably secreted as part of the surfactant complex. Apoprotein B is not secreted by type II cells with the same time course as apoprotein A or the lipids of surfactant, but our results do not define its origin or physiological purpose.
Na+ and Ca2+ ingestion: plasma volume-electrolyte distribution at rest and exercise
Authors: Greenleaf J. E. , Brock P. J.
Published: December 2017

Plasma volume (PV), protein, and electrolyte shifts were measured in two groups of five men in the supine position during rest, exercise (40-47% VO2max), and recovery in cool (Ta = 26.5 degrees C) and hot (Ta = 39.4 degrees C) environments. They drank 16-17 ml/kg hypertonic (1.5%) NaCl, isotonic (0.9%) NaCl, or hypertonic (1.5%) calcium gluconate solutions during the preexercise rest period. Hyper-Na consumption retarded the rise in PV (hypervolemia) at rest in the cool but not in the heat. Ingestion of iso-Na and hyper-Na resulted in twofold greater hypervolemia at rest in the heat. During exercise and recovery, PV was highest with hyper-Na in the heat. Hyper-Ca prevented the normal hypervolemic response at rest in both environments. The normal hypervolemic responses during exercise were not influenced by any drink composition. The results suggest hypertonic drinks may be better for maintaining PV levels during exercise in heat; but calcium must be used with care.
Reflection spectrophotometric measurement of O2 uptake in pulmonary arterioles of cats
Authors: Conhaim R. L. , Staub N. C.
Published: December 2017

We have attempted to determine both experimentally and theoretically whether a significant quantity of oxygen enters the pulmonary blood before it reaches the alveolar wall capillaries. We built a microspectrophotometer that allowed us to record oxyhemoglobin saturation values with light reflected from transected frozen pulmonary arteries as small as 100 microns in diameter. We prepared anesthetized cats to provide optimal conditions for precapillary oxygenation, quickly froze their lungs with chilled liquid propane, and removed these lungs. We examined lung cross sections with the microspectrophotometer and recorded data indicating the presence of precapillary oxygenation. These data did not tell us how much this process normally contributes to total lung oxygenation because propane did not freeze the lungs fast enough to capture conditions exactly as they are in life. We therefore made several calculations to estimate the extent of precapillary oxygenation using available data on pulmonary arterial geometry and diffusing capacity. We concluded that pulmonary arterial blood may be as much as 15% oxygenated by this process at rest and as much as 100% during oxygen breathing.
Splenic erythropoiesis in polycythemic response of the rat to high-altitude exposure
Authors: Ou L. C. , Kim D. , Layton W. M. , Smith R. P.
Published: December 2017

Intact rats exposed for 30 days to various levels of simulated altitude from 12,000 (3,658 m) to 20,000 ft (6,096 m) showed a sharp increase in circulating red blood cells in reticulocytes, and in spleen-to-body weight ratios above 15,000 ft (4.572 m). Nucleated erythrocytes in splenic section increased significantly at 18,000 ft (5,486 m), but not at 12,000 ft. Acute splenectomy 1 day before killing sharply reduced the reticulocyte counts at 18,000 and 20,000 ft, but the red cell counts were not reduced at any altitude by the operation. Indeed, at 18,000 ft the splenectomy significantly increased the degree of polycythemia. With altitude exposure the spleen but not the liver or the bone marrow showed an increased 59Fe uptake that was related to the degree of hypoxia. These results suggest that the rat spleen of the present strain carries the full load of the erythropoietic effort in response to a hypoxic stimulus, and that it may exert an inhibitory influence on any extraerythropoietic effort by the bone marrow. In intact rats returned from 18,000 ft to sea level, the reticulocytosis is reversed much more slowly than it is in splenectomized rats, suggesting the presence of a persistent stimulus initiated by hypoxia or a committed pool of reticulocyte precursors.
Respiratory pattern changes during costovertebral joint movement
Authors: Shannon R.
Published: December 2017

Experiments were conducted to determine if costovertebral joint manipulation (CVJM) could influence the respiratory pattern. Phrenic efferent activity (PA) was monitored in dogs that were anesthetized with Dial-urethane, vagotomized, paralyzed, and artificially ventilated. Ribs 6-10 (bilaterally) were cut and separated from ribs 5-11. Branches of thoracic nerves 5-11 were cut, leaving only the joint nerve supply intact. Manual joint movement in an inspiratory or expiratory direction had an inhibitory effect on PA. Sustained displacement of the ribs could inhibit PA for a duration equal to numerous respiratory cycles. CVJM in synchrony with PA resulted in an increased respiratory rate. The inspiratory inhibitory effect of joint receptor stimulation was elicited with manual chest compression in vagotomized spontaneously breathing dogs, but not with artificial lung inflation or deflation. It is concluded that the effect of CVJM on the respiratory pattern is due to stimulation of joint mechanoreceptors, and that they exert their influence in part via the medullary-pontine rhythm generator.
beta-Adrenergic stimulation of respiratory ciliary activity
Authors: Verdugo P. , Johnson N. T. , Tam P. Y.
Published: December 2017

We investigated the effect of isoproterenol on ciliary activity using a mucus-free preparation of cultured ciliated cells of the rabbit trachea. The frequency of ciliary beating was monitored by dynamic laser-scattering spectroscopy. The results demonstrated that isoproterenol directly stimulates the activity of ciliated cells of the respiratory epithelium and that this effect is beta-adrenergic specific inasmuch as the observed stimulation can be blocked by propranolol.
Characterization of Na-K-ATPase in dog tracheal epithelium: enzymatic and ion transport measurements
Authors: Westenfelder C. , Earnest W. R. , Al-Bazzaz F.
Published: December 2017

The dog tracheal epithelium actively secretes Cl and absorbs Na. The possible dependency of this electrolyte transport on a Mg-dependent, Na-K-activated adenosine triphosphatase (Na-K-ATPase, EC 3.6.1.3) was examined. The characteristics of this enzyme system were investigated using homogenates of tracheal epithelium. The electrical properties and ion fluxes of this epithelium were determined in tissues mounted in Ussing chambers. Addition of Na and K produced an approximate 50% activation of basal Mg-ATPase activity. The apparent Km values for ATP, Na, K, and Mg were 0.4, 12.7, 1.9, and 1.6 mM, respectively. The total specific ATPase activity was 8.1 ± 0.4 and that of the Mg-ATPase 4.3 ± 0.1 mumol Pi. mg protein -1.h-1. Addition of ouabain (1 muM) or omission of K from the submucosal bathing solution reduced potential difference (PD) and short-circuit current (SCC) significantly. Relatively low concentrations (0.1 mM or less) of ethacrynic acid, furosemide, or 2,4-dinitrophenol (2,4-DNP) depressed SCC and PD significantly, i.e., at concentrations that were without effect on the Na-K-ATPase activity. Ethacrynic acid inhibited Cl secretion, whereas 2,4-DNP lowered both Na and Cl transport. These data demonstrate that 1) the tracheal mucosa of dogs contains a Na-K-ATPase at relatively high specific activity, 2) this enzyme is likely contained in the basal aspect of this membrane, 3) it appears to be essential for maintenance of Cl secretion, and 4) Cl secretion can be reduced (by ethacrynic acid, furosemide, and 2,4-DNP) without Na-K-ATPase inhibition.
Effects of oleic acid-induced pulmonary edema on lung mechanics
Authors: Grossman R. F. , Jones J. G. , Murray J. F.
Published: December 2017

In 25 rabbits anesthetized with pentobarbital sodium and paralyzed with succinylcholine chloride, we investigated the contributions of four factors that might cause the decreased static lung compliance found in oleic acid-induced pulmonary edema: 1) foam, 2) accumulation of fluid in the interstitial spaces, 3) loss of ventilatable units secondary to alveolar flooding, and 4) increased surface tension. Pulmonary edema, reflected by a 115% increase in mean post-mortem extravascular bloodless lung water content, decreased compliance 47% and tripled alveolar-arterial PO2 difference. Removing foam by degassing did not affect compliance measurements. Filling the lungs with saline caused similar changes in control and edematous animals. Because the 38% decrease in functional residual capacity was largely attributable to water accumulation, we concluded that loss of ventilatable units accounted for virtually all the decreased static lung compliance. The role of increased surface tension could not be determined directly but was considered relatively less important.
Single-breath diffusing capacity and lung volumes in small laboratory mammals
Authors: Takezawa J. , Miller F. J. , O'Neil J. J.
Published: December 2017

We measured the single-breath diffusing capacity for carbon monoxide (DLCO), total lung capacity (TLC), functional residual capacity (FRC), and residual volume (RV) in anesthetized male hamsters, rats, guinea pigs, and rabbits whose weights varied from 40 to 3,500 g. TLC (defined as an airway pressure of 25 cmH2O) was calculated by neon dilution. The DLCO was estimated by a modification of the single-breath method. There was a high correlation between body weight and our measurement of both the diffusing capacity and the lung volumes. No significant difference in DLCO was observed in rats when measured in different body positions, at airway pressures of 10 or 20 cmH2O, from FRC or RV, in male or female rats, or following hyperventilation.
Physiological responses to maximal effort wheelchair and arm crank ergometry
Authors: Glaser R. M. , Sawka M. N. , Brune M. F. , Wilde S. W.
Published: December 2017

The purpose of this investigation was to compare physical work capacity (PWC), peak oxygen uptake (peak VO2), maximal pulmonary ventilation (VEmax), maximal heart rate (HRmax), and maximal blood lactate concentration (LAmax) for wheelchair ergometer (WERG) and arm crank ergometer (ACE) exercise. For this, wheelchair-dependent (n = 6) and able-bodied (n = 10) subjects completed a progressive intensity, discontinuous test for each mode of exercise. Each test was terminated by physical exhaustion and/or an inability to maintain a flywheel velocity of 180 m.min-1. Relatively high correlation coefficients were found between values obtained during the two modes of ergometry for PWC, peak VO2, VEmax, and HRmax. WERG exercise was found to elicit a significantly (P less than 0.05) lower PWC (by 36%), HRmax (by 7%), and LAmax (by 26%) than ACE exercise. Peak VO2 and VEmax, however, were similar for both exercise modes. These data suggest that either exercise mode may be used for fitness testing and training of people who cannot use their legs and that arm cranking may be a superior method to propel wheelchairs.
End-tidal CO2 response to low levels of inspired CO2 in awake beagle dogs
Authors: Reischl P. , Stavert D. M. , Lewis S. M. , Murdock L. C. , O'Loughlin B. J.
Published: December 2017

The steady-state end-tidal CO2 tension (PCO2) was examined during control and 1% CO2 inhalation periods in awake beagle dogs with an intact airway breathing through a low dead-space respiratory mask. A total of eight experiments were performed in four dogs, comprising 31 control observations and 23 CO2 inhalation observations. The 1% inhaled CO2 produced a significant increase in the steady-state end-tidal PCO2 comparable to the expected 1 Torr predicted from conventional CO2 control of ventilation. We conclude that 1% inhaled CO2 results in a hypercapnia. Any protocol that is to resolve the question of whether mechanisms are acting during low levels of inhaled CO2 such that ventilation increases without any change in arterial PCO2 must have sufficient resolving power to discriminate changes in gas tension in magnitude predicted from conventional (i.e., arterial PCO2) control of ventilation.
Alteration by hyperoxia of ventilatory dynamics during sinusoidal work
Authors: Casaburi R. , Stremel R. W. , Whipp B. J. , Beaver W. L. , Wasserman K.
Published: December 2017

The effects of hyperoxia on ventilatory and gas exchange dynamics were studied utilizing sinusoidal work rate forcings. Five subjects exercised on 14 occasions on a cycle ergometer for 30 min with a sinusoidally varying work load. Tests were performed at seven frequencies of work load during air or 100% O2 inspiration. From the breath-by-breath responses to these tests, dynamic characteristics were analyzed by extracting the mean level, amplitude of oscillation, and phase lag for each six variables with digital computer techniques. Calculation of the time constant (tau) of the ventilatory responses demonstrated that ventilatory kinetics were slower during hyperoxia than during normoxia (P less than 0.025; avg 1.56 and 1.13 min, respectively). Further, for identical work rate fluctuations, end-tidal CO2 tension fluctuations were increased by hyperpoxia. Ventilation during hyperoxia is slower to respond to variations in the level of metabolically produced CO2, presumably because hyperoxia attenuates carotid body output; the arterial CO2 tension is consequently less tightly regulated.
Mixed venous CO2 tension during exercise
Authors: Auchincloss J. H. , Gilbert R. , Kuppinger M. , Peppi D.
Published: December 2017

A series of experiments was undertaken in a total of 95 adult subjects, of whom 25 had coronary artery disease, to evaluate the extrapolation (Defares) CO2 rebreathing method vs. the equilibrium (Collier) method for estimating mixed venous CO2 tension. Collier values were corrected for the downstream effect, whereas Defares values were uncorrected. Although the methods gave similar mean values in separate series with normal subjects walking on a treadmill set at 123 W for 3 min, Collier values had a coefficient of variation (CV) of 2.5% in duplicate determinations and Defares values had a CV of 4.5%. In paired comparisons Defares values averaged either higher or lower than Collier values depending on variations in technique and the analysis of Defares tracings. Collier values were essentially unaffected by the duration of the rebreathing period (10 vs. 15 s). The Collier technique appears to be superior for the exercise evaluation of cardiac output in healthy and diseased subjects when the goal is obtain values at 82 or 123 W in single test sessions.
Equilibrium of CO2 reactions in the pulmonary capillary
Authors: Klocke R. A.
Published: December 2017

Steady-state CO2 excretion was measured in isolated blood-free rabbit lungs perfused with bicarbonate solutions. CO2 in the expired ventilation was either present initially in the perfusate as dissolved CO2 or produced from bicarbonate during pulmonary capillary transit. The two components were separated by measurement of simultaneous acetylene excretion. Bovine carbonic anhydrase and acetazolamide were sequentially added to the perfusate to determine the effects of maximal enzyme catalysis and inhibition of native lung carbonic anhydrase on CO2 production. Control CO2 production was significantly greater than that observed during inhibition of native lung carbonic anhydrase, confirming previous observations that bicarbonate has access to the tissue enzyme. Addition of excess carbonic anhydrase increased CO2 production by a statistically, but not physiologically, significant amount. These data demonstrate that CO2 reactions outside the erythrocyte attain 97% completion during pulmonary capillary transit. Under control and catalyzed conditions, alveolar and venous CO2 tens ions and pH were essentially identical to equilibrium values determined by in vitro tonometry.
Prediction of maximal expiratory flow in excised human lungs
Authors: Hyatt R. E. , Wilson T. A. , Bar-Yishay E.
Published: December 2017

The predictions of the wave-speed theory of flow limitations were tested against measured values of maximal expiratory flow (Vmax) in nine normal excised human lungs. We obtained static pressure-volume curves and deflation pressure-area (PA) curves of the first three to four airway generations. The pressure drop from the alveolus to the flow-limitation site was assumed to consist of a peripheral frictional loss (estimated from a catheter upstream from the flow-limitation site) and a convective acceleration pressure drop. Predicted Vmax was determined graphically by finding the lowest flow for which the Bernoulli PA curve was tangent to one of the bronchial PA curves. At the point of tangency, local flow speed equals local wave speed. At low lung volumes a point of tangency with the PA curves of the first few generations did not exist, and the flow-limitation site was assumed to be the minimal bronchial area at zero transpulmonary pressure. There was good agreement between measured and predicted Vmax. Measured Vmax was not different from Vmax predicted from normal living man. The wave-speed theory predicted flow over much of the vital capacity, but other mechanisms may limit flow at low lung volumes.
Influence of exercise type, hydration, and heat on plasma volume shifts in men
Authors: Gaebelein C. J. , Senay L. C.
Published: December 2017

Four male Caucasians were studied during cycle ergometer exercise and stair stepping in a hot wet environment (32 degrees C db, 30 degrees C wb) after exertion was equated by matching heart rates during training. With each exercise, one session was conducted after 24 h of water deprivation, the other 50 min after ingestion of an amount of water equal to 1% body weight. Venous blood samples were obtained 24 h before each exercise and before and at 10-min intervals during each exercise. No changes in osmolality were found during stair stepping. A progressive osmoconcentration, however, occurred during cycling after dehydration and an initial osmoconcentration with little subsequent change accompanied ergometer exercise after hydration. This latter effect was due to a consistent osmodilution in all subjects, but occurring at different times during the session in each. All attained an osmolality of 290 mosmol/kg before dilution. Because this value is above the threshold of arginine vasopressin release, this hormone may have been responsible for the osmodilution. Therefore, the preexercise osmolality and the rate at which the threshold for vasopressin release is attained may determine whether osmodilution, osmoconcentration, or both occur during exercise.
Hemodynamic effects of positive-pressure inflation
Authors: Scharf S. M. , Brown R. , Saunders N. , Green L. H.
Published: December 2017

In 14 anesthetized mongrel dogs, we studied the factors that influenced aortic systolic pressure (PaO) and peak aortic systolic flow (Qao) during positive-pressure inflations at three respiratory rates: 8, 14, and 24 breaths/min. At all three respiratory rates, pulmonary arterial flow fell by 15% of the preinspiratory value by end inhalation. Qao also fell at all three respiratory rates, reaching a nadir close to end exhalation (EE). Qao fell less (7% of the base line) at the fast respiratory rate than at the medium and slow respiratory rates (15% of the base line). Pao rose more during the early part of inflation at the medium and fast rates (5 ± 0.9 Torr) than at the slow rate (3 ± 0.7 Torr); then Pao fell to a nadir near EE at the slow (-5.6 ± 1.6 Torr) and at the medium (-2.3 ± 1 Torr) respiratory rates. At the fast rate it fell to a value not different from control (0.1 ± 0.5 Torr). The ratio of peak arterial pressure to peak arterial flow increased throughout inflation reaching a peak at EE. A model was developed that predicted the major qualitative features of the changes in Qao seen in these studies. Changes in Pao resulted from the interaction between decreases in Qao and transmitted increases in pleural pressure, and are modified by changes in systemic impedance.
Hydrostatic weighing at residual volume and functional residual capacity
Authors: Thomas T. R. , Etheridge G. L.
Published: December 2017

Hydrostatic weighing (HW) was performed at both residual volume (RV) and functional residual capacity (FRC) to determine if underwater weighing at different lung volumes affected the measurement of body density. Subjects were 43 males, 18-25 yr. Subjects were submerged in the prone position, and the lung volume was measured by helium dilution at the time of the underwater weighing. Underwater weight was first assessed at FRC followed by assessment at RV. Changes in lung volume were accurately reflected in the underwater weight. Body density (D) was not different with the use of the FRC (mean D = 1.0778) or RV (mean D = 1.0781) data. Percent fat values for the FRC and RV data were 9.3 ± 5.4 and 9.2 ± 5.1%, respectively, and were not statistically different. The results indicate that the difference between percent fat determinations by HW in the prone position at FRC and RV is negligible. Because measurement of underwater weight at FRC is more comfortable for the subject, this may be the method of choice when the lung volume can be measured during the underwater weighing.