bluuebunny/crossref_metadata_2025 huggingface dataset:
Longitudinal distribution of vascular compliance in the canine lung
Authors: Brower R. G. , Wise R. A. , Hassapoyannes C. , Hausknecht M. , Permutt S.
Published: December 2017

With an isolated perfused canine lung, the compliance of pulmonary circulation was measured and partitioned into components corresponding to alveolar and extra-alveolar compartments. When the lungs were in zone 3, changes in outflow pressure (delta Po) affected all portions of the vasculature causing a change in lung blood volume (delta V). Thus the ratio delta V/delta Po in zone 3 represented the compliance of the entire pulmonary circulation (Cp) plus that of the left atrium (Cla). When the lungs were in zone 2, changes in Po affected only the extra-alveolar vessels that were downstream from the site of critical closure in the alveolar vessels. Thus the ratio delta V/delta Po with forward flow in zone 2 represented the compliance of the venous extra-alveolar vessels (Cv) plus Cla. With reverse flow in zone 2, delta V/delta Po represented the compliance of the arterial extra-alveolar vessels (Ca). The compliance of the alveolar compartment (Calv) was calculated from the difference between Cp and the sum of Ca + Cv. When Po was 6–11 mmHg, Cp was 0.393 +/- 0.0380 (SE) ml X mmHg-1 X kg-1 with forward perfusion and 0.263 +/- 0.0206 (SE) ml X mmHg-1 X kg-1 with reverse perfusion. Calv was 79 and 68% of Cp with forward and reverse perfusion, respectively. When Po was raised to 16–21 mmHg, Cp decreased to 0.225 +/- 0.0235 (SE) ml X mmHg-1 X kg-1 and 0.183 +/- 0.0133 (SE) ml X mmHg-1 X kg-1 with forward and reverse perfusion, respectively. Calv also decreased but remained the largest contributor to Cp. We conclude that the major site of pulmonary vascular compliance in the canine lung is the alveolar compartment, with minor contributions from the arterial and venous extra-alveolar segments.
Effect of lung volume on pulmonary mechanics in guinea pigs
Authors: Watson J. W. , Jackson A. C. , Drazen J. M.
Published: December 2017

The lung volume (VL) dependence of several dynamic pulmonary mechanical properties of the guinea pig lung were determined over the range of the vital capacity (10–100% VC) with the vagi intact and sectioned. We found dynamic compliance to be strongly VL dependent, decreasing as much as 85% between functional residual capacity (FRC) and total lung capacity (TLC). Below FRC, dynamic compliance either remained unchanged or decreased, depending upon the technique used in its measurement. Pulmonary resistance (RL) decreased monotonically with increasing VL, whereas pulmonary conductance was linearly related to VL. Conductance was much less sensitive to VL than compliance, increasing only 28% between FRC and TLC. The sensitivity of pulmonary conductance to VL was substantially increased by subtracting the resistance of the tracheal cannula from RL. Specific pulmonary conductance was not independent of VL but decreased approximately 45% over the range of the VC. Pulmonary inertance was found to be unaffected by VL. Extrapolation from these data indicate that small differences in FRC, which might be expected within and between studies relying on pulmonary mechanical measurements, would most strongly affect compliance estimates and only moderately alter resistance estimates. It also indicates that the use of specific pulmonary conductance does not remove VL as an independent variable.
Neutrophil kinetics in O2-exposed rabbits
Authors: Steinberg Harry , Das Dipak K. , Cerreta Joseph M. , Cantor Jerome D.
Published: December 2017

Page 775: Harry Steinberg, Dipak K. Das, Joseph M. Cerreta, and Jerome D. Cantor. “Neutrophil kinetics in O2-exposed rabbits.” Page 775: the correct affiliation for J. M. Cerreta should read: St. John's University, Jamaica, New York.
Esophageal and tympanic temperature responses to core blood temperature changes during hyperthermia
Authors: Shiraki K. , Konda N. , Sagawa S.
Published: December 2017

Esophageal, rectal, tympanic, and central blood temperature, i.e., pulmonary artery and aortic arch, were recorded in three patients during iatrogenic whole-body hyperthermia for the treatment of advanced malignant metastatic cancer. Aortic temperature closely followed changes in pulmonary arterial temperature, with an average delay time of 27 s. Esophageal temperature reflected quantitatively and more quickly (avg lag time, 80 s) the temperature changes in the pulmonary artery than tympanic membrane temperature. Tympanic temperature was consistently lower than the blood temperature of the heart during steady state. Therefore it is suggested that esophageal temperature is a preferable index of central blood temperature. Additionally, measurement of esophageal temperature can be made more easily and safely than tympanic membrane temperature.
Respiratory volume perception through the nose and mouth determined noninvasively
Authors: Fox J. , Kreisman H. , Colacone A. , Wolkove N.
Published: December 2017

The relative importance of the nose vs. the mouth in the perception of respiratory volumes has never been assessed, nor have previous respiratory perception studies been performed noninvasively. Using respiratory inductive plethysmography, we monitored 12 normal subjects noninvasively when breathing either exclusively through the nose or mouth. The sensation of inspired volume mouth breathing was compared with that of nose breathing over a wide range of the inspiratory capacity. The psychophysical techniques of tidal volume duplication, tidal volume doubling, and magnitude estimation were utilized. A just noticeable difference was calculated from the constant error of the tidal volume duplication trials. The exponents for magnitude estimation were 1.06 and 1.07 for nose and mouth breathing, respectively. The other psychophysical techniques also revealed no differences in nose and mouth volume perception. These results suggest that tidal volume changes are perceived equally well through the nose and mouth. Furthermore, the location of the receptors, important in volume perception, is probably at a distal point common to the nose and mouth.
A new photometric method for oxygen consumption measurements in cell suspensions
Authors: Mueller-Klieser W. , Zander R. , Vaupel P.
Published: December 2017

A new technique is described for measuring O2 consumption rates and O2 concentrations in suspensions of respiring cells. Aliquots of a cell suspension kept in a special thermostated precision syringe are injected into the measuring system in defined time intervals. The O2 content of these samples is determined photometrically, as reported previously. The O2 consumption per cellular wet weight and/or per single cell can be calculated from the cell volume fraction, the physical density, the cell concentration in the suspension, and the time-dependent decline of the O2 concentration in the precision syringe. The minimum detectable amount of O2 is 0.1 microliter O2, which corresponds to 0.001 (vol/vol) of O2 if a 100-microliters sample of suspended cells is analyzed. Reproducibility of the O2 consumption measurement is 9% of the measured value. The advantages offered by this method are the straightforward calibration in absolute terms, the short time required for one analysis (2–6 min), a high sensitivity, the simultaneous determination of overall O2 concentration and O2 consumption rates in cell suspensions, and the great variability in the application.
Skeletal muscle lactate dehydrogenase isozyme alterations in men and women marathon runners
Authors: Apple F. S. , Rogers M. A.
Published: December 2017

Total lactate dehydrogenase (LD) and LD isozyme activities in gastrocnemius muscle from trained men and women runners were measured in response to the chronic stress of training for a marathon race (42.2 km). Following 9 wk of training, total LD activity in skeletal muscle from men and women runners significantly (P less than 0.02) decreased 2.26 and 2.25 U/mg protein, respectively. However, men's total LD activities were significantly (P less than 0.001) less than the women's both before and after training. Significant (P less than 0.05) increases in LD1 activities in skeletal muscle in men and women runners were also observed after training. No significant correlations were detected between percent fiber type composition in men or women vs. the changes in total LD activity, changes in LD1 activity, maximal O2 consumption or training distance averaged per week after the training period. The biochemical adaptations in skeletal muscle that occurred in the LD isozyme composition in both men and women runners make the runners skeletal muscle appear similar to heart muscle in LD1 and LD2 activities.
Growth rate of perivascular cuffs in liquid-inflated dog lung lobes
Authors: Conhaim R. L.
Published: December 2017

In the early stages of pulmonary edema, excess liquid leaving the pulmonary exchange vessels accumulates in the peribronchovascular interstitium where it forms large peribronchovascular cuffs. The peribronchovascular interstitium therefore acts as a reservoir to protect the air spaces from alveolar flooding. The rate of liquid accumulation and the liquid storage capacity of the cuffs determine how quickly alveolar flooding is likely to follow once edema formation has begun. To measure the rate and capacity of interstitial filling we inflated 11 isolated degassed dog lung lobes with liquid to an inflation pressure of 14 cmH2O (total lung capacity) for 1–300 min, then froze the lobes in liquid N2. We made photographs of 20 randomly selected 12 X 8-mm cross sections from each lobe and measured cuff volume from the photographs by point-counting. We found that cuff volume increased from 2.2% of air-space volume after 1 min of inflation to 9.3% after 300 min. To measure the driving pressure responsible for cuff formation we used micropipettes to measure subpleural interstitial liquid pressure at the hilum of three additional lobes. With liquid inflation pressure set to 14 cmH2O interstitial pressure rose exponentially to 11.5 cmH2O. Interstitial compliance calculated from our volume and pressure measurements equaled 0.09 ml X cmH2O–1 X g wet wt-1, a value similar to that measured in air-inflated lungs. Goldberg [Am. J. Physiol. 239 (Heart Circ. Physiol. 8): H189-H198, 1980] has likened interstitial filling to the charging of a capacitor, a process that follows a monoexponential time course.(ABSTRACT TRUNCATED AT 250 WORDS)
Synthesis of surfactant-associated protein, 35,000 daltons, in fetal lung
Authors: Weaver T. E. , Ross G. , Daugherty C. , Whitsett J. A.
Published: December 2017

The major human pulmonary surfactant-associated protein of 35,000 daltons (Da) (SAP-35), consists of a group of related proteins of 27,000-36,000 Da, with isoelectric points ranging from pH 4.6 to 5.2. SAP-35 precursors were identified by immunoprecipitation of protein products of in vitro translation of normal adult human poly(A)+ mRNA with human SAP-35 antiserum. The translation products nearly comigrated with the most basic components of alveolar SAP-35 (mol mass = 24,500-27,000 Da). Processing of the primary translation products by canine pancreatic microsomal membranes increased their apparent molecular weight to 29,000-30,000-Da forms, which were sensitive to endoglycosidase F, suggesting the addition of asparagine-linked oligosaccharides to the molecules. A smaller protein of 24,500 Da was generated during treatment with canine microsomal membranes likely representing cleavage of a signal peptide. SAP-35 was not detected in explants of [35S]methionine-labeled fetal lung (20–24 wk gestation) after 1 day of culture or immunoprecipitates of in vitro translated poly(A)+ mRNA isolated from fetal human lung. However, after 3–5 days of organ culture, synthesis of SAP-35 was readily detected by immunoprecipitation of [35S] methionine-labeled tissue. Fully sialylated (neuraminidase-sensitive forms) comigrated with fully glycosylated SAP-35 isolated from human surfactant. High mannose (endoglycosidase H-sensitive precursors) were also synthesized by the organ cultures and were distinct from the secreted form in surfactant. Synthesis of surfactant-associated SAP-35 and its precursors was induced in association with morphological maturation of the type II epithelial cell during organ culture of human fetal lung.
Respiratory mechanics in men following a deep air dive
Authors: Catron P. W. , Bertoncini J. , Layton R. P. , Bradley M. E. , Flynn E. T.
Published: December 2017

The mechanical properties of the lungs were measured in 10 men before and after a simulated air dive to 285 ft of seawater (87 m). The objective was to determine whether a dive likely to produce pulmonary bubble emboli would alter lung mechanics. Lung function was measured predive and at 1, 2, 3, 6, 7, and 23 h postdive. Measurements of lung function were also made at identical times on a control day when no dive was made. Each set of measurements included precordial Doppler signals, pulmonary resistance, quasistatic lung compliance, forced vital capacity (FVC), forced expired volume after 1.0 s (FEV 1.0), the ratio of FEV 1.0 to FVC (FEV 1.0/FVC%), and maximal airflow after 50 and 75% of the vital capacity had been expired (Vmax50 and Vmax75, respectively). Base-line measurements of pulmonary resistance and quasistatic compliance were normal in all subjects. FVC and FEV 1.0 were greater than predicted for most subjects and were increased proportionately so that the FEV 1.0/FVC% was normal. Following the dive, bubble signals were heard in four subjects, and two subjects had mild symptoms of decompression sickness. No subject demonstrated any alteration in lung function that could be attributed to the dive. We concluded that stressful decompressions capable of producing “silent” pulmonary bubble emboli do not alter lung mechanics.
Pulmonary arterial distension does not cause pulmonary vasoconstriction
Authors: Lloyd T. C.
Published: December 2017

Distension of the main pulmonary artery or its major branches with an intraluminal balloon has been reported to cause pulmonary vasoconstriction by an unknown mechanism. This study was an attempt to confirm the pressor response and explore its cause. Several balloon distension methods were tried and discarded because they caused unintentional obstruction. Ultimately, I inflated a balloon placed retrogradely and confined to the left main pulmonary artery of six anesthetized open-chest dogs after ligating left lobar arterial branches. Blood flow and systemic gas composition were controlled by interposing an external pump oxygenator between the left ventricle and aorta. Pressures in the aorta, main pulmonary artery, and left atrium were recorded. Alveolar hypoxia was used as an independent test of pulmonary vasoreactivity. Although hypoxic pressor responses occurred, challenges with arterial distension did not change lung perfusion pressure. Silicone rubber casts were made of the arteries of six dogs used in pilot experiments. These revealed the limited lengths in which distenders can be placed without unintentional encroachment on flow. I could not support the conclusion that arterial distension causes vasoconstriction and am suspicious that the perfusion pressure increases reported by others may have been caused by undetected obstruction of a major arterial branch.
Baroreflex responsiveness is maintained during isometric exercise in humans
Authors: Ebert T. J.
Published: December 2017

The simultaneous rise in heart rate and arterial pressure during isometric handgrip exercise suggests that arterial baroreflex control may be altered. We applied incremental intensities of neck suction and pressure to nine healthy young men to alter carotid sinus transmural pressure. Carotid stimuli were delivered during 1) supine control, 2) “anticipation” of beginning exercise, and 3) handgrip (20% of maximum voluntary contraction). Anticipation was a quiet period, immediately preceding the beginning of handgrip, when no muscular work was being performed. Compared with control, the R-R interval prolongation and mean arterial pressure decline provoked by carotid stimuli were decreased during the anticipation period. These data suggest that influences from higher central neural locations may alter baroreflex function. Furthermore, we derived stimulus-response curves relating carotid sinus transmural pressure to changes in R-R interval and mean arterial pressure. These curves were shifted during handgrip; however, calculated regression slopes were not changed from control. The data indicate that isometric handgrip exercise has a specific influence on human carotid baroreflex control of arterial pressure and heart period: baroreflex function curves are shifted rightward during handgrip, whereas baroreflex sensitivity is unchanged. Furthermore, central neural influences may be partially involved in these alterations.
Influence of the ventral surface of the medulla on tracheal responses to CO2
Authors: Deal E. C. , Haxhiu M. A. , Norcia M. P. , Mitra J. , Cherniack N. S.
Published: December 2017

These studies investigated the role of the intermediate area of the ventral surface of the medulla (VMS) in the tracheal constriction produced by hypercapnia. Experiments were performed in chloralose-anesthetized, paralyzed, and artificially ventilated cats. Airway responses were assessed from pressure changes in a bypassed segment of the rostral cervical trachea. Hyperoxic hypercapnia increased tracheal pressure and phrenic nerve activity. Intravenous atropine pretreatment or vagotomy abolished the changes in tracheal pressure without affecting phrenic nerve discharge. Rapid cooling of the intermediate area reversed the tracheal constriction produced by hypercapnia. Graded cooling produced a progressive reduction in the changes in maximal tracheal pressure and phrenic nerve discharge responses caused by hypercapnia. Cooling the intermediate area to 20 degrees C significantly elevated the CO2 thresholds of both responses. These findings demonstrate that structures near the intermediate area of the VMS play a role in the neural cholinergic responses of the tracheal segment to CO2. It is possible that neurons or fibers in intermediate area influence the motor nuclei innervating the trachea. Alternatively, airway tone may be linked to respiratory motor activity so that medullary interventions that influence respiratory motor activity also alter bronchomotor tone.
Estimates of ventilation from body surface measurements in unrestrained subjects
Authors: McCool F. D. , Kelly K. B. , Loring S. H. , Greaves I. A. , Mead J.
Published: December 2017

To make estimates of ventilation from measurements of body surface movements in unrestrained subjects, we measured changes in linear dimensions and cross-sectional areas of the rib cage (RC) and abdomen (AB) of six healthy unrestrained subjects during a variety of maneuvers. RC and AB anteroposterior diameters and abdominal length in the cephalocaudal axis (axial displacement) were measured with magnetometers, and RC and AB cross-sectional areas were measured with a respiratory inductance plethysmograph. Flow was measured at the mouth with a pneumotachograph and integrated electrically to give volume. Volume and body surface measurements were analyzed by multiple linear regression. Addition of the axial measurements to either the anteroposterior dimensions or cross-sectional areas of RC and AB improved estimates of tidal volume in all subjects (P less than 0.01). With measurements of axial displacement and cross-sectional area of the RC and AB, tidal volume could be reliably estimated to within 20% of actual ventilation. We conclude that measurement of axial displacements improves estimates of ventilation in unrestrained subjects.
Effect of hypoproteinemia on lung fluid balance in awake newborn lambs
Authors: Hazinski T. A. , Bland R. D. , Hansen T. N. , Sedin E. G. , Goldberg R. B.
Published: December 2017

To study the influence of plasma protein concentration on fluid balance in the newborn lung, we measured pulmonary arterial and left atrial pressures, lung lymph flow, and concentrations of protein in lymph and plasma of eight lambs, 2–3 wk old, before and after we reduced their plasma protein concentration from 5.8 +/- 0.3 to 3.6 +/- 0.6 g/dl. Each lamb underwent two studies, interrupted by a 3-day period in which we drained protein-rich systemic lymph through a thoracic duct fistula and replaced fluid losses with feedings of a protein-free solution of electrolytes and glucose. Each study consisted of a 2-h control period followed by 4 h of increased lung microvascular pressure produced by inflation of a balloon in the left atrium. Body weight and vascular pressures did not differ significantly during the two studies, but lung lymph flow increased from 2.6 +/- 0.1 ml/h during normoproteinemia to 4.1 +/- 0.1 ml/h during hypoproteinemia. During development of hypoproteinemia, the average difference in protein osmotic pressure between plasma and lymph decreased by 1.6 +/- 2 Torr at normal left atrial pressure and by 4.9 +/- 2.2 Torr at elevated left atrial pressure. When applied to the Starling equation governing microvascular fluid balance, these changes in liquid driving pressure were sufficient to account for the observed increases in lung fluid filtration; reduction of plasma protein concentration did not cause a statistically significant change in calculated filtration coefficient. Protein loss did not influence net protein clearance from the lungs nor did it accentuate the increase in lymph flow associated with left atrial pressure elevation.(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of perceived musical rhythm on respiratory pattern
Authors: Haas F. , Distenfeld S. , Axen K.
Published: December 2017

The effects of rhythmic input on breath period (TT) under constant metabolic drive were assessed in 10 musically trained and 10 untrained subjects. They tapped to a metronome and then to four musical segments, each for 5 min. Ten of these subjects (5 from each group) also listened to the selections without tapping. TT, beat period (TB), and phase coupling (PC) were assessed during the last 20 breaths of each presentation. TT coefficient of variation decreased significantly (P less than 0.001) in all subjects (base line = 23%; listening = 15%; listening and tapping = 10%). Significant correlation between rhythm and TT, indicating relative entrainment, was found in half of the subjects (r greater than 0.45; P less than 0.01). Significant integer TT/TB ratio and PC, both indicating tight entrainment between rhythm and breathing, were observed in 12 subjects (though not consistently in each one). These data advance the following hypothesis: musical rhythm can be a zeitgeber (i.e., pacemaker), with its ability to entrain respiration dependent on the strength of its signal relative to spurious signals from the higher neural centers that introduce noise into the central pattern generator. Tapping reinforces the zeitgeber, increasing its signal-to-noise ratio and thereby promoting entrainment.
CSF acid-base regulation and ventilation in iso- and hypocapnic Hacetate acidosis
Authors: Nattie E. E. , Moore P.
Published: December 2017

Intravenous infusion in conscious rabbits of Hacetate decreases both arterial CO2 partial pressure PaCO2 and cerebrospinal fluid (CSF) HCO3- more than observed with HCl or HNO3 infusion. These acids did not affect CSF HCO3- in isocapnic conditions, and this study asks whether Hacetate infusion will do so. Arterial, central venous, and cisterna magna catheters were implanted in pentobarbital-anesthetized rabbits and all subsequent measurements were performed in the conscious state. Hacetate was infused intravenously over 6 h to decrease plasma HCO3- the same amount in a group allowed to decrease its PaCO2 in response to the acid (hypocapnic) and one in which PaCO2 was maintained at control levels (isocapnic). CSF HCO3- decreased significantly in isocapnia, although the change was less than in hypocapnia. Stoichiometrically by 6 h the measured CSF HCO3- change was balanced by an increase in acetate in hypocapnia and the sum of an increase in acetate and a decrease in chloride in isocapnia. Mechanistically, net acetate entry into CSF appears to involve an exchange for chloride as proposed for NO3-/Cl- and a process that lowers CSF HCO3-. This process could be competitive replacement of HCO3- by acetate in the CSF production mechanism or nonionic diffusive entry of Hacetate into CSF with subsequent titration of HCO3-. The decreases in CSF HCO3- result from the acetate mechanism and the hypocapnic effect on Cl- and HCO3-. The greater ventilatory response results from the greater CSF acidification or a specific effect of acetate per se.
Glucose feeding and exercise in trained rats: mechanisms for glycogen sparing
Authors: Kuipers H. , Costill D. L. , Porter D. A. , Fink W. J. , Morse W. M.
Published: December 2017

This investigation studied the effect of an oral glucose feeding on glycogen sparing during exercise in non-glycogen-depleted and glycogen-depleted endurance-trained rats. The non-glycogen-depleted rats received via a stomach tube 2 ml of a 20% glucose solution labeled with [U-14C]glucose just prior to exercise (1 h at 25 m/min). Another group of rats ran for 40 min at higher intensity to deplete glycogen stores, after which they received the same glucose feeding and continued running for 1 h at 25 m/min. The initial 40-min run depleted glycogen in heart, skeletal muscle, and liver. In the non-glycogen-depleted rats the glucose feeding spared glycogen in the liver, primarily from the oxidation of blood-borne glucose in muscle. In the glycogen-depleted rats, muscle glycogen was repleted after the feeding, but sources other than the administered glucose also contributed to glycogen synthesis. The results suggest that glycogen depletion rather than the glucose feeding per se stimulates glycogen resynthesis in muscle during exercise in endurance-trained rats.
Endurance exercise training reduces lactate production
Authors: Favier R. J. , Constable S. H. , Chen M. , Holloszy J. O.
Published: December 2017

In situ muscle stimulation in trained and untrained rats was used to reevaluate whether adaptations induced by endurance exercise training result in decreased lactate production by contracting muscles. The gastrocnemius-plantaris-soleus muscle group was stimulated to perform isotonic contractions. After 3 min of stimulation with 100-ms trains at 50 Hz at 60/min, the increases in lactate concentration in the plantaris, soleus, and fast-twitch red muscle (deep portion of lateral head of gastrocnemius) were only approximately 50% as great in trained as in sedentary rats. In the predominantly fast-twitch white superficial portion of the medial head of the gastrocnemius the increase in lactate concentration was 28% less in the trained than in the sedentary group. The decreases in muscle glycogen concentration seen after 3 min of stimulation at 60 trains/min were smaller in the trained than in the untrained group. The reduction in lactate accumulation that occurred in the different muscles in response to training was roughly proportional to the degree of glycogen sparing. These results show that endurance training induces adaptations that result in a slower production of lactate by muscle during contractile activity.
Distribution of cyclooxygenase products with cyclooxygenase inhibition in isolated dog lung
Authors: Littner M. R. , Kazmi G. M. , Lott F. D.
Published: December 2017

Arachidonic acid metabolism can lead to synthesis of cyclooxygenase products in the lung as indicated by measurement of such products in the perfusate of isolated lungs perfused with a salt solution. However, a reduction in levels of cyclooxygenase products in the perfusate may not accurately reflect the inhibition of levels of such products as measured in lung parenchyma. We infused sodium arachidonate into the pulmonary circulation of isolated dog lungs perfused with a salt solution and measured parenchymal, as well as perfusate, levels of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), prostaglandin F2 alpha (PGF2 alpha), prostaglandin E2 (PGE2), and thromboxane B2 (TxB2). These studies were repeated with indomethacin (a cyclooxygenase enzyme inhibitor) in the perfusate. We found that indomethacin leads to a marked reduction in perfusate levels of PGF2 alpha, PGE2, 6-keto-PGF1 alpha, and TxB2, as well as a marked reduction in parenchymal levels of 6-keto-PGF1 alpha and TxB2 when parenchymal levels of PGF2 alpha and PGE2 are not reduced. We conclude that, with some cyclooxygenase products, a reduction in levels of these products in the perfusate of isolated lungs may not indicate inhibition of levels of these products in the lung parenchyma and that a reduction in one parenchymal product may not predict the reduction of other parenchymal products. It can be speculated that some of the physiological actions of indomethacin in isolated lungs may result from incomplete or selective inhibition of synthesis of pulmonary cyclooxygenase products.
Vertical gradient of pulmonary capillary transit times
Authors: Wagner W. W. , Latham L. P. , Hanson W. L. , Hofmeister S. E. , Capen R. L.
Published: December 2017

The key determinants of alveolar capillary perfusion are transit times and the extent of recruitment. Capillaries are known to be heavily recruited in the dependent lung, but there are no direct data that bear on how capillary transit times might be affected by gravity. We directly determined mean capillary transit times on the surface of the upper, middle, and lower lung by measuring the passage of fluorescent dye through the capillaries using in vivo television microscopy. In anesthetized dogs, mean capillary transit times averaged 12.3 s in the upper lung, 3.1 s in the midlung, and 1.6 s in the lower lung. This near order of magnitude variation in speed of blood transit establishes that there is a vertical gradient of capillary transit times in the lung. As expected, dependent capillary networks were nearly fully recruited, whereas relatively few capillaries were perfused in the upper lung. The lengthy transit times and sparsely perfused capillary beds in the upper lung combine to provide a substantial part of pulmonary gas exchange reserve.
Enhanced lipolysis is not evident in adipocytes from exercise-trained SHR
Authors: Shepherd R. E. , Bah M. D. , Nelson K. M.
Published: December 2017

Adipocytes from spontaneously hypertensive rats (SHR) are not as responsive to isoproterenol or dibutyryl adenosine 3′,5′-cyclic monophosphate (cAMP) stimulation compared with Sprague-Dawley or Wistar-Kyoto rats. Lipolytic activity in adipocytes from trained normotensive rats was enhanced in response to 1 microM isoproterenol and 0.5 mM dibutyryl cAMP but not in adipocytes from trained SHR. Decreases in isoproterenol-stimulated (1 microM) cAMP accumulation were evident in adipocytes from trained normotensive rats but not in adipocytes from trained SHR. Basal and agonist-induced lipolysis in fat cells isolated from both normotensive rats and SHR immediately following a 60-min run was increased in both sedentary and trained rats. Adenylate cyclase activity in fat cell membranes was blunted in sedentary and trained SHR both in the absence and presence of 100 microM 5′-guanylyl imidophosphate. No apparent differences existed in antagonist affinity of binding sites for the antagonist dihydroalprenolol in normal rats or SHR. Evidence for a change in affinity of agonist isoproterenol might be indicated based on the enhanced potency of isoproterenol to stimulate lipolysis in trained normal rats. beta-Adrenergic receptor density and antagonist affinity were not different in normotensive rats and SHR in response to training. However, displacement of [3H]dihydroalprenolol in adipocytes from SHR required greater concentrations of isoproterenol compared with adipocytes from normotensive rats, further suggestive of increased agonist affinity of binding sites in normal rats. These data suggest a postreceptor lesion of the lipolytic pathway in adipocytes from spontaneously hypertensive rats, possibly at the guanine nucleotide regulatory protein level.(ABSTRACT TRUNCATED AT 250 WORDS)
Induction of periodic breathing during sleep causes upper airway obstruction in humans
Authors: Onal E. , Burrows D. L. , Hart R. H. , Lopata M.
Published: December 2017

To test the hypothesis that occlusive apneas result from sleep-induced periodic breathing in association with some degree of upper airway compromise, periodic breathing was induced during non-rapid-eye-movement (NREM) sleep by administering hypoxic gas mixtures with and without applied external inspiratory resistance (9 cmH2O X l-1 X s) in five normal male volunteers. In addition to standard polysomnography for sleep staging and respiratory pattern monitoring, esophageal pressure, tidal volume (VT), and airflow were measured via an esophageal catheter and pneumotachograph, respectively, with the latter attached to a tight-fitting face mask, allowing calculation of total pulmonary system resistance (Rp). During stage I/II NREM sleep minimal period breathing was evident in two of the subjects; however, in four subjects during hypoxia and/or relief from hypoxia, with and without added resistance, pronounced periodic breathing developed with waxing and waning of VT, sometimes with apneic phases. Resistive loading without hypoxia did not cause periodicity. At the nadir of periodic changes in VT, Rp was usually at its highest and there was a significant linear relationship between Rp and 1/VT, indicating the development of obstructive hypopneas. In one subject without added resistance and in the same subject and in another during resistive loading, upper airway obstruction at the nadir of the periodic fluctuations in VT was observed. We conclude that periodic breathing resulting in periodic diminution of upper airway muscle activity is associated with increased upper airway resistance that predisposes upper airways to collapse.
Closed-circuit metabolic system with multiple applications
Authors: Molnar J. A. , Cunningham J. J. , Miyatani S. , Vizulis A. , Wright J. D. , Burke J. F.
Published: December 2017

A closed-circuit metabolic system has been designed and tested for multiple applications. Air pressure within a closed chamber is regulated electronically while allowing for respiratory gas exchange. Compared with a previously reported standard indirect calorimetry system, the new device had by virtue of longer duration of measurement improved precision (coefficient of variation 3% vs. 14%) during studies of O2 consumption both at room temperature and at 5 degrees C. In addition, a more physiological atmospheric environment is maintained. This system has also been utilized for simultaneously labeling groups of up to 20 weanling rats with 18O2 over a 2-day period and for exposure of rats to a hyperoxic (84% O2), normobaric environment for 4-day periods. Potential applications include maintenance of pressure (hypobaric through hyperbaric) and O2 (hypoxic through hyperoxic) controlled environments, exposure to toxic gases, study of diurnal variations in metabolic rate, measurement of metabolic expenditure with activity, and adaptation to other species including humans.
Effect of systemic venous pressure elevation on lymph flow and lung edema formation
Authors: Laine G. A. , Allen S. J. , Katz J. , Gabel J. C. , Drake R. E.
Published: December 2017

Pulmonary lymph drains into the thoracic duct and then into the systemic venous circulation. Since systemic venous pressure (SVP) must be overcome before pulmonary lymph can flow, variations in SVP may affect lymph flow rate and therefore the rate of fluid accumulation within the lung. The importance of this issue is evident when one considers the variety of clinical interventions that increase SVP and promote pulmonary edema formation, such as volume infusion, positive-pressure ventilation, and various vasoactive drug therapies. We recorded pulmonary arterial pressure (PAP), left atrial pressure (LAP), and SVP in chronic unanesthetized sheep. Occlusion balloons were placed in the left atrium and superior vena cava to control their respective pressures. The superior vena caval occluder was placed above the azygos vein so that bronchial venous pressure would not be elevated when the balloon was inflated. Three-hour experiments were carried out at various LAP levels with and without SVP being elevated to 20 mmHg. The amount of fluid present in the lung was determined by the wet-to-dry weight ratio method. At control LAP levels, no significant difference in lung fluid accumulation could be shown between animals with control and elevated SVP levels. When LAP was elevated above control a significantly greater amount of pulmonary fluid accumulated in animals with elevated SVP levels compared with those with control SVP levels. We conclude that significant excess pulmonary edema formation will occur when SVP is elevated at pulmonary microvascular pressures not normally associated with rapid fluid accumulation.
Active and passive respiratory mechanics in anesthetized dogs
Authors: Zin W. A. , Boddener A. , Silva P. R. , Pinto T. M. , Milic-Emili J.
Published: December 2017

In six spontaneously breathing anesthetized dogs (pentobarbital sodium, 30 mg/kg) airflow, volume, and tracheal and esophageal pressures were measured. The active and passive mechanical properties of the total respiratory system, lung, and chest wall were calculated. The average passive values of respiratory system, lung, and chest wall elastances amounted to, respectively, 50.1, 32.3, and 17.7 cmH2O X l-1. Resistive pressure-vs.-flow relationships for the relaxed respiratory system, lung, and chest wall were also determined; a linear relationship was found for the former (the total passive intrinsic resistance averaged 4.1 cmH2O X l-1 X s), whereas power functions best described the others: the pulmonary pressure-flow relationship exhibited an upward concavity, which for the chest wall presented an upward convexity. The average active elastance and resistance of the respiratory system were, respectively, 64.0 cmH2O X l-1 and 5.4 cmH2O X l-1 X s. The greater active impedance reflects pressure losses due to force-length and force-velocity properties of the inspiratory muscles and those due to distortion of the respiratory system from its relaxed configuration.
Effect of water immersion on cardiopulmonary physiology at high gravity (+Gz)
Authors: Arieli R. , Boutellier U. , Farhi L. E.
Published: December 2017

We compared the cardiopulmonary physiology of eight subjects exposed to 1, 2, and 3 Gz during immersion (35 degrees C) to the heart level with control dry rides. Immersion should almost cancel the effects of gravity on systemic circulation and should leave the lung alone to gravitational influence. During steady-state breathing we measured ventilation, O2 consumption (VO2), CO2 production, end-tidal PCO2 (PACO2), and heart frequency (fH). Using CO2 rebreathing techniques, we measured cardiac output, functional residual capacity, equivalent lung tissue volume, and mixed venous O2 content, and we calculated arterial PCO2 (PaCO2). As Gz increased, ventilation, fH, and VO2 rose markedly, and PACO2 and PaCO2 decreased greatly in dry ride, but during immersion these variables changed very little in the same direction. Functional residual capacity was lower during immersion and decreased in both the dry and immersed states as Gz increased, probably reflecting closure effects. Cardiac output decreased as Gz increased in dry rides and was elevated and unaffected by Gz during immersion. We conclude that most of the changes we observed during acceleration are due to the effect on the systemic circulation, rather than to the effect on the lung itself.
Atropine unmasks bed-rest effect: a spectral analysis of cardiac interbeat intervals
Authors: Goldberger A. L. , Goldwater D. , Bhargava V.
Published: December 2017

Bed-rest deconditioning is suspected to reduce cardiac reserve, possibly by impairing autonomic function. Heart rate response in normal subjects reveals considerable variability, reflected by a relatively broadband interbeat interval power spectrum. A reduction in this autonomically modulated variability would be predicted to cause a narrowing of the spectrum. We retrospectively analyzed data from 10 aerobically conditioned men (age range 35–49 yr) who had undergone orthostatic tolerance testing with lower body negative pressure pre-bed rest and after 7–10 days of bed rest, while on placebo and after intravenous atropine. Spectra were derived by Fourier analysis of 128 interbeat interval data sets. Spectral power was estimated by computing the root-mean-square (rms) values (mean +/- SD) for the band encompassing the 2nd to 64th harmonics from subjects with a sufficient number of beats: placebo rms is 93 +/- 33 ms for pre-bed rest and 84 +/- 38 ms for bed rest (NS, n = 6); atropine rms is 63 +/- 24 ms for pre-bed rest and 40 +/- 23 ms for bed rest (P less than 0.01; n = 7). These data suggest that atropine “unmasks” a deconditioning effect of bed rest in athletic men, evidenced by a reduction in interbeat interval spectral power not apparent with placebo. Spectral analysis offers a useful means of quantitating the effects of bed-rest deconditioning and autonomic perturbations on cardiac dynamics.
Effect of posture on vital capacity
Authors: Appel M. , Childs A. , Healey E. , Markowitz S. , Wong S. , Mead J.
Published: December 2017

The influence of some extreme body postures on vital capacity (VC) was examined in young adult humans. Two postures required full support of body weight by the arms: arms up, hanging from a bar, and arms down with hands gripping parallel bars. Three involved muscles that flex and extend the trunk: a partial sit-up position while supine and nearly maximal spinal extension and flexion while standing. Changes at the inspiratory and expiratory volume extremes were recognized by having the subjects do two VC efforts: the first standing and the second in the posture in question while continuing to breathe on the spirometer. Control observations in which the second of a VC pair was performed in an unstressed posture allowed correction for the influence of rebreathing. The changes in corrected VC were small, the greatest being an average reduction of approximately 8% in the partial sit-up position. During full support of body weight by the arms, the VC was slightly increased due to a significant increase in the inspiratory extreme and no change in the expiratory extreme. Spinal extension produced small increases in lung volume at both extremes with no significant change in VC, whereas spinal flexion did not influence the upper extreme but did increase lung volume at the lower extreme. The changes are discussed in terms of trunk muscle action.
Respiratory muscle interaction during NREM sleep in patients with occlusive apnea
Authors: Onal E. , Lopata M.
Published: December 2017

To study respiratory muscle interaction in patients with occlusive apnea, diaphragmatic electromyogram (EMGdi) and gastric, pleural, and transdiaphragmatic pressures (Pga, Ppl, and Pdi, respectively) were studied in seven patients during non-rapid-eye-movement (NREM) sleep. Diaphragmatic force output, as assessed by Pdi, followed the periodic changes in EMGdi but during the occlusive phase the increase in Pdi was more than the increase in EMGdi. This increase in Pdi was essentially due to an increase in Ppl, since Pga and EMGdi had a linear relationship (r = 0.98, P less than 0.001) that did not change during the occlusive and ventilatory phases. Abdominal muscle recruitment evident in Pga and abdominal motion tracings during the occlusive phase when paradoxical rib cage motion was observed suggested that this increase in diaphragmatic efficiency was likely due to a change in diaphragmatic length-tension characteristics. These results demonstrate that, in patients with occlusive apneas, the diaphragm is the predominant respiratory muscle during NREM sleep and that its function is supported by abdominal muscle recruitment.
Nonocclusive chronic vascular catheterization of conscious unrestrained baboons
Authors: Phippard A. F. , Garner M. G. , Thompson J. F. , Maclean J. M. , Fletcher P. J. , Horvath J. S. , Duggin G. G. , Tiller D. J.
Published: December 2017

A surgical technique is described for chronic arterial and venous catheterization of unrestrained adult baboons. Vascular access was achieved through a small (5 cm) abdominal incision and an extraperitoneal approach to the iliac vessels, which minimizes postoperative morbidity, discomfort, and restriction of movement. The method permits secure but nonocclusive catheterization, confirmed by angiography. Catheters were removed without further surgery, leaving the baboons intact for reuse. Catheters placed in the distal common or proximal external iliac vessels were all patent when removed at 46–61 days. The results demonstrate arterial pressure, pulse rates, drug administration, blood sampling, and plasma volume measurement as examples of the technique's application in conscious unrestrained baboons.
Prolonged exposure of mice to He-O2 at high pressure: effects on seizure and anesthesia liability
Authors: Brauer R. W. , Dutcher J. A. , Hinson W. , Vorus W. S.
Published: December 2017

Multiday exposures of CD-1 mice to He-O2 atmospheres at pressures from 30 to 100 atm result in marked increases of threshold pressures for type I high-pressure neurological syndrome seizures. The effect develops with a half time (t1/2) of 12 h and is reversible (t1/2 = 7 h). The maximum enhancement of Pc is attained at a conditioning pressure of 80 ATA. Pressure conditioning also results in suppression of the compression rate effect on Pc. Furthermore, reserpine blocks the increase in Pc during prolonged pressure exposure. The entire effect thus appears to be an extension in time of the monoaminergic compression rate effect on Pc. Pressure conditioning does not modify anesthesia tolerance, unlike N2 habituation which affects anesthesia threshold pressure as well as Pc. The results are compared with the effects of habituation to inert-gas narcotics and the implications of the data for an understanding of inert-gas high-pressure antagonism in intact animals are discussed.
Effect of methylene blue on cardiac output response to exercise in dogs
Authors: Imai N. , Paley J. I. , Barold H. S. , Liang C. S.
Published: December 2017

To determine whether the increase in cardiac output during mild to moderate exercise is related to an increase in the tissue redox potential, we compared the responses of cardiac output, total body oxygen consumption, and arterial blood lactate-to-pyruvate ratio (a measure of NADH/NAD) to treadmill exercise between dogs treated with normal saline and those treated with a hydrogen acceptor, new methylene blue. Normal saline was infused into the left atrium in the first group of dogs at a rate of 0.38 ml/min throughout the treadmill exercise (2.5 mph and 5.0 mph on a 6% incline, each for 20 min). In the second group, methylene blue was administered as a loading dose (4 mg/kg) before exercise, followed by a continuous infusion (0.15 mg X kg-1 X min-1) throughout exercise. A similar infusion of methylene blue was given to a third group of dogs without exercise; it reduced the arterial lactate-to-pyruvate ratio from 6.70 +/- 0.35 to 4.12 +/- 0.27 but had no or little effects on cardiac output, heart rate, arterial pressure, and left ventricular dP/dt and (dP/dt)/P. Treadmill exercise doubled cardiac output and increased total body O2 consumption three- to fourfold in the first two groups but increased arterial blood lactate-to-pyruvate ratio only in group 1 (6.0 +/- 0.54 to 9.97 +/- 0.91). The relationship between cardiac output and total body O2 consumption was unaffected by the simultaneous administration of methylene blue during exercise. Groups 1 and 2 also did not differ in their heart rate, left ventricular dP/dt and (dP/dt)/P, and plasma catecholamine responses to exercise.(ABSTRACT TRUNCATED AT 250 WORDS)