bluuebunny/crossref_metadata_2025 huggingface dataset:
Percent carboxyhemoglobin in resting humans exposed repeatedly to 1,500 and 7,500 ppm CO
Authors: Tikuisis P. , Buick F. , Kane D. M.
Published: December 2017

Eleven nonsmoking male resting subjects were exposed to two transient CO profiles to examine whether the resultant carboxyhemoglobin (HbCO) differs with CO concentration for a fixed total CO dose and to determine the predictive capability of the theoretical model of Coburn et al. (J. Clin. Invest. 44: 1899–1910, 1965) using measured alveolar ventilation. One profile consisted of five sequential exposures to 1,500 ppm CO for 5 min each and spaced 3 min apart. The other consisted of five sequential exposures to 7,500 ppm CO for 1 min each and spaced 7 min apart. The subjects, therefore, were exposed to the same overall nominal dose of 37,500 ppm.min. During the experiment, the subject's ventilatory functions and respiratory gases were recorded continuously, and the resultant HbCO% was measured in venous blood samples by gas chromatography. Mean increase (+/- SD) in HbCO% per exposure was 2.08 +/- 0.27% for the 1,500 ppm CO exposures and 2.05 +/- 0.29% for the 7,500 ppm CO exposures with no significant difference between the two. When the measured values of the subject's alveolar ventilation were applied to the theoretical model of Coburn et al., the predicted rate of HbCO% formation was found to agree with the experimental results.
Detailed characterization of a tank used for head-out water immersion in humans
Authors: Epstein M. , Norsk P. , Loutzenhiser R. , Sonke P.
Published: December 2017

Water immersion has long been known to produce marked diuresis, natriuresis, and kaliuresis and suppression of the renin-aldosterone system. These effects are mediated primarily by an increase in central blood volume. Immersion has therefore gained increased acceptance in human physiology for the investigation of the effects of central volume expansion on renal function and hormonal responsiveness without altering the composition of the extracellular fluid. An immersion tank used for studies in humans is described. Requisite features to ensure study reproducibility include a constant temperature, capability to alter the depth of immersion by adjusting water height, and the ability to maintain hygienic quality by means of constant circulation of the water through a sand filter. A constant temperature of 34.5 +/- 0.2 degrees C is maintained by thermostatically controlling the heat exchange to a unidirectional closed-circuit water system in the bottom of the immersion tank coursing through a stream source. The level of the water may be adjusted to any desired level by means of a waste line or an inlet of tap water.
Constant-flow perfusion of the hindlimb vascular bed in conscious dogs
Authors: Metting P. J. , Ronau T. F. , Strader J. R. , Britton S. L.
Published: December 2017

Hindlimb vascular bed pressure-flow relationships were evaluated in seven conscious dogs using a newly developed controlled-flow perfusion technique. For controlled-flow perfusion, blood was diverted from a common carotid artery to a roller pump for perfusion of the left hindlimb vascular bed via an artificial vascular graft anastomosed to the left external iliac artery. An occlusion cuff positioned around the external iliac artery proximal to the graft arrested normal hindlimb blood flow during perfusion. Collateral flow was minimized by ligating all other major arteries supplying the left hindlimb. Hindlimb perfusion pressure, measured via the left deep femoral artery, decreased to a plateau value of 19.7 +/- 3.4 mmHg when pump flow was zero. Pressure-flow relationships were evaluated while the dogs were at rest by changing flow in small “square-wave” steps for 3 min each and measuring the steady-state perfusion pressure at each step. The hindlimb was perfused over a wide range of flows (25–450 ml/min) that resulted in perfusion pressures ranging from 40 to 175 mmHg. The hindlimb pressure-flow relationship obtained was indicative of net passive vascular behavior. That is, resistance to flow decreased with increases in flow, such that a curvilinear pressure-flow relationship occurred that was convex to the pressure axis. We conclude that the hindlimb circulation of resting conscious dogs can be perfused using controlled-flow perfusion techniques. These techniques can also be applied to other vascular beds and should be useful for evaluating peripheral vascular responses to drugs and reflexogenic alterations.
Measurement of pleural pressure at low and high frequencies in normal rabbits
Authors: Chartrand D. A. , Ye T. H. , Maarek J. M. , Chang H. K.
Published: December 2017

In eight tracheotomized adult rabbits placed in the supine position, we employed a catheter-tip piezoresistive pressure transducer to measure esophageal pressure (Pes) and assessed the validity of taking the changes in Pes to be the changes in pleural pressure (Ppl). We applied an occlusion test in which the tracheal cannula was occluded during either spontaneous inspiratory efforts or body surface oscillations ranging from 3 to 50 Hz. The relationship between Pes and airway opening pressure (Pao) was recorded. In all instances, the changes in Pes and Pao were virtually identical in both amplitude and phase. We conclude that, as evaluated by the occlusion test, a catheter-tip pressure transducer placed in the esophagus of rabbits can give adequate estimation of local pleural changes up to at least 50 Hz.
Cardiovascular responses to military antishock trouser inflation during standing arm exercise
Authors: Ng A. V. , Hanson P. , Aaron E. A. , Demment R. B. , Conviser J. M. , Nagle F. J.
Published: December 2017

Military antishock trousers (MAST) inflated to 50 mmHg were used with 12 healthy males (mean age 28 +/- 1 yr) to determine the effects of lower-body positive pressure on cardiac output (Q), stroke volume (SV), heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MABP), total peripheral resistance (TPR), and O2 uptake (VO2) during graded arm-cranking exercise. Subjects were studied while standing at rest and at 25, 50, and 75% of maximal arm-cranking VO2. At each level, rest or work was continued for 6 min with MAST inflated and for 6 min with MAST deflated. Order of inflation and deflation was alternated at each experimental rest or exercise level. Measurements were obtained during the last 2 min at each level. Repeated-measures analysis of variance revealed significant increases (P less than 0.001) in Q, SV, and MABP and a consistent decrease in HR with MAST inflation. There was no apparent change in Q/VO2 between inflated and control conditions. There was no effect of MAST inflation on VO2 or TPR. MAST inflation counteracts the gravitational effect of venous return in upright exercise, restoring central blood volume and thereby increasing Q and MABP from control. HR is decreased consequent to increased MABP through arterial baroreflexes. The associated decrease in TPR is not observed, being offset by the mechanical compression of leg vasculature with MAST inflation.
Relationship between distance running mechanics, running economy, and performance
Authors: Williams K. R. , Cavanagh P. R.
Published: December 2017

The relationships between biocmechanical aspects of distance running, running economy (VO2 submax), and performance were investigated. A variety of biomechanical measures for 31 subjects running at 3.6 m/s was obtained, including three-dimensional angular and translational kinematics, ground reaction forces and center of pressure patterns, mechanical power, and anthropometric measures. Physiological measures obtained included maximal and submaximal O2 consumption, muscle fiber composition, and measures of the ability to store and return elastic energy during knee bends. A subset of 16 runners was also evaluated in relation to performance in a 10-km run. Biomechanical variables were identified which showed significant differences or consistent trends between groups separated on the basis of VO2 submax, establishing the importance of biomechanical influences on running economy. It appears that no single variable or small subset of variables can explain differences in economy between individuals but rather that economy is related to a weighted sum of the influences of many variables.
Pulmonary edema with smoke inhalation, undetected by indicator-dilution technique
Authors: Prien T. , Traber L. D. , Herndon D. N. , Stothert J. C. , Lubbesmeyer H. J. , Traber D. L.
Published: December 2017

Despite experimental evidence for an increase in extravascular lung water (EVLW) after inhalation injury, thermal-dye estimations of EVLW, extravascular thermal volume (EVTV), have repeatedly failed to demonstrate its presence in patients. This situation was evaluated in a sheep model. Under halothane anesthesia one lung was insufflated with cotton smoke and the other with air. EVTV values were 8.4 +/- 0.48 ml/kg at base line and were not elevated at 24 h after smoke inhalation (8.3 +/- 0.45 ml/kg; means +/- SE). Gravimetric analysis 24 h after smoke inhalation showed the development of edema in smoke-exposed lungs. The blood-free wet weight-to-dry weight ratio of the smoke-exposed lungs (5.4 +/- 0.32) was significantly higher compared with the contralateral unsmoked lungs (4.3 +/- 0.15; P less than or equal to 0.05). The thermal-dye technique thus underestimates EVLW. Poor perfusion of the smoke-exposed lungs 24 h after injury was demonstrated indirectly by killing a group of sheep with T-61, an agent that causes a dark red coloration of well-perfused lung areas, as well as directly by measurement of blood flow utilizing a radiolabeled microsphere technique. Thus the inability of the thermal-dye technique to detect the lung edema may be the result of poor perfusion of the injured lung.
Lung reperfusion in dogs causes bilateral lung injury
Authors: Bishop M. J. , Chi E. Y. , Cheney F. W.
Published: December 2017

Occlusion of the pulmonary arterial circulation to a lung for prolonged periods has been reported to result in only minimal alterations in lung morphology. We studied the effects of 48 h of pulmonary arterial occlusion followed by 4 h of reperfusion in 18 awake dogs. Because of evidence in other organ systems of O2 radical generation, during reperfusion, nine of the animals were randomly assigned to receive allopurinol, a xanthine oxidase inhibitor, and vitamin E, an antioxidant. Reperfusion resulted in marked edema and inflammatory infiltrates in the reperfused lung but also caused mild edema and inflammation in the contralateral continuously perfused lung. Electron microscopy demonstrated lysis of both capillary endothelial and alveolar epithelial cells bilaterally, with the frequency of cell injury greater on the reperfused side. During reperfusion, body temperatures rose dramatically from 39.4 +/- 0.1 to 40.6 +/- 0.2 degrees C (P less than 0.05) and marked leukopenia developed. There were no differences in any hemodynamic, gas exchange, or morphometric measurements between allopurinol-treated dogs and untreated animals. We conclude that reperfusion causes local and distant injury which does not appear to be mediated by xanthine oxidase-produced O2 radicals.
A graphic analysis of respiratory heat exchange
Authors: Varene P. , Kays C.
Published: December 2017

A new graphic representation of respiratory heat exchange is proposed using the concept of equivalent temperatures directly related to enthalpy values. On such a diagram it is possible to 1) compute the value of the heat exchange (delta H) knowing the inspired temperature (TI) and the partial pressure of water vapor (PIH2O) [or the relative humidity (rhI)] of inspired gas; 2) estimate the variation in delta H following a given variation in TI and PIH2O or, inversely, to choose the variation in TI and PIH2O necessary to obtain a given variation in delta H; 3) dissociate inspiratory and expiratory exchanges and to evaluate the efficiency of the respiratory heat exchange process in different environmental situations; and 4) easily compare the results of different studies published on respiratory heat exchanges in humans or other animal species.
Fetal breathing, sleep state, and cardiovascular responses to graded anemia in sheep
Authors: Koos B. J. , Sameshima H. , Power G. G.
Published: December 2017

Graded anemia was produced for 2 h in 10 unanesthetized fetal sheep by infusing plasma in exchange for fetal blood. This reduced the mean fetal hematocrits during the 1st h of anemia to 19.7 +/- 0.5% [control (C) = 28.2 +/- 1.1%] for mild anemia, 17.4 +/- 0.9% (C = 30.0 +/- 1.1%) for moderate anemia, and 15.1 +/- 1.0% (C = 29.2 +/- 1.3%) for severe anemia. The respective mean arterial O2 contents (CaO2) were 4.46 +/- 0.20, 3.89 +/- 0.24, and 3.22 +/- 0.19 ml/dl. Mean arterial PO2 was reduced significantly (by 2 Torr) only during moderate anemia, and mean arterial pH was decreased only during severe anemia. No significant changes occurred in arterial PCO2. Fetal tachycardia occurred during anemia. Mean arterial pressure was reduced by 2–3 mmHg during mild anemia; however, no significant blood pressure changes were observed for moderate or severe anemia. The incidence of rapid-eye movements and breathing activity was not affected by mild anemia, but the incidence of both was reduced significantly during moderate and severe anemia. It is concluded that 1) a reduction in CaO2 of greater than 2.48 +/- 0.22 ml/dl by hemodilution inhibits rapid-eye movements and breathing activity, and 2) the PO2 signal for inhibition does not come from arterial blood but from lower PO2 in tissue.
Pathological supply dependence of O2 uptake during bacteremia in dogs
Authors: Nelson D. P. , Beyer C. , Samsel R. W. , Wood L. D. , Schumacker P. T.
Published: December 2017

When systemic delivery of O2 [QO2 = cardiac output X arterial O2 content (CaO2)] is reduced, the systemic O2 extraction ratio [(CaO2-concentration of O2 in venous blood/CaO2] increases until a critical limit is reached below which O2 uptake (VO2) becomes limited by delivery. Many patients with adult respiratory distress syndrome exhibit supply dependence of VO2 even at high levels of QO2, which suggests that a peripheral O2 extraction defect may be present. Since many of these patients also suffer from serious bacterial infection, we tested the hypothesis that bacteremia might produce a similar defect in the ability of tissues to maintain VO2 independent of QO2, as QO2 reduced. The critical O2 delivery (QO2crit) and critical extraction ratio (ERcrit) were compared in a control group of dogs and a group receiving a continuous infusion of Pseudomonas aeruginosa (5 x 10(7) organisms/min). Dogs were anesthetized, paralyzed, and ventilated with room air. Systemic QO2 was reduced in stages by hemorrhage as hematocrit was maintained. At each stage, systemic VO2 and QO2 were measured, and the critical point was determined from a plot of VO2 vs. QO2. The mean QO2crit and ERcrit of the bacteremic group (11.4 +/- 2.2 ml.min-1.kg-1 and 0.51 +/- 0.09) were significantly different from control (7.4 +/- 1.2 and 0.71 +/- 0.10) (P less than 0.05). These results suggest that bacterial infection can reduce the ability of peripheral tissues to extract O2 from a limited supply, causing VO2 to become limited by O2 delivery at a stage when a smaller fraction of the delivered O2 has been extracted.(ABSTRACT TRUNCATED AT 250 WORDS)
Respiratory influence of peripheral chemoreceptor stimulation in maturing rabbits
Authors: Schramm C. M. , Grunstein M. M.
Published: December 2017

To evaluate whether the influence of peripheral chemoreceptor (PCR) stimulation is centrally modulated by hypoxia, the respiratory effects of sodium cyanide (NaCN) infusion were compared during room air and 10% O2 inhalation in 18 lightly anesthetized, tracheotomized rabbits of varying postnatal age (1–33 days). During normoxia, noncumulative infusions of NaCN (5–400 micrograms/kg body wt) produced dose-dependent ventilatory (VE) stimulation. Maximal VE stimulation (VEmax) and ventilatory sensitivity to NaCN [i.e., log dose producing 50% of VEmax (log ED50)] did not significantly vary with age, with the average VEmax and log ED50 values amounting to 238% above base line and 1.564 micrograms/kg, respectively. During hypoxia, after initial stimulation (average: 152%), VE progressively decreased and stabilized to 67% above the normoxic base-line level. In contrast to normoxia, subsequent NaCN administration during steady-state hypoxia produced dose-dependent VE depression, occasionally manifested by abrupt apnea. The NaCN effect during hypoxia was significantly related to age (P less than 0.05), as well as to the estimated change in CO2 production during hypoxia (P less than 0.01). Both the respiratory depressant effects of hypoxia alone and in combination with NaCN were abolished after denervation of the peripheral chemoreceptors. These findings demonstrate that while PCR stimulation during normoxia produces ventilatory stimulation, the influence of enhanced PCR input during hypoxia is centrally modulated to produce ventilatory depression.
High-frequency oscillatory ventilation increases canine pulmonary epithelial permeability
Authors: Man G. C. , Ahmed I. H. , Logus J. W. , Man S. F.
Published: December 2017

To investigate the effect of high-frequency oscillatory ventilation (HFOV) on the pulmonary epithelial permeability, we measured the clearance rate of nebulized sodium pertechnetate (99mTcO4-) and diethylenetriaminepentaacetate (99mTc-DTPA) before and after a 4-h period of mechanical ventilation in anesthetized mongrel dogs. The animals also underwent experiments with 4 h of spontaneous breathing (SB) and intermittent positive-pressure ventilation (IPPV) with and without addition of positive end-expiratory pressure (PEEP) for comparison. After IPPV and SB there was no change in the clearance rate of either 99mTcO4- or 99mTc-DTPA. After IPPV + PEEP and HPOV (8 and 16 Hz), there was an increase in the clearance rate of 99mTc-DTPA, but an increase in clearance rate of 99mTcO4- was seen after IPPV + PEEP only. In a separate group of dogs an increase in end-tidal lung volume was demonstrated after 4 h of ventilation with IPPV + PEEP (but not after HFOV), and this may account for the measured increase in 99mTcO4- clearance. We conclude that an increase in 99mTc-DTPA clearance rate after HFOV signifies an increase in pulmonary epithelial permeability, possibly through the mechanism of damage to the intercellular junctions during HFOV.
Gravity-dependent distribution of parietal subpleural interstitial pressure
Authors: Negrini D. , Capelli C. , Morini M. , Miserocchi G.
Published: December 2017

Using liquid-filled catheters, we recorded, in 30 anesthetized, spontaneously breathing supine rabbits, the hydraulic pressure from the parietal subpleural interstitial space (Pspl). Through a small exposed area of parietal pleura a plastic catheter (1 mm ED), with a closed and smooth tip and several holes on the last centimeter, was carefully advanced between the muscular layer and the parietal pleura, tangentially to the pleural surface to reach the submesothelial layer. Simultaneous measurements of pleural liquid pressure (Pliq) were obtained from intrapleurally placed cannulas. End-expiratory Pspl decreased (became more negative) with increasing height (LH) according to the following: Pspl (cmH2O) = -1 - 0.4 LH (cm), the corresponding equation for Pliq being Pliq (cmH2O) = -1.5 – 0.7 LH (cm). Thus at end expiration a transpleural hydraulic pressure difference (Pliq-Pspl) developed at any height, increasing from the bottom to the top of the cavity as Pliq - Pspl (cmH2O) = -0.5 – 0.3 LH (cm). The Pliq-Pspl difference increased during inspiration due to the much smaller tidal change in Pspl than in Pliq. By considering the gravity-dependent distribution of the functional hydrostatic pressure in the systemic capillaries of the pleura (Pc) and the Pspl and Pliq values integrated over the respiratory cycle we estimated that on the average, the Pc-Pspl difference is sevenfold larger than the Pspl-Pliq difference.
Alpha-thrombin-induced pulmonary vasoconstriction
Authors: Horgan M. J. , Fenton J. W. , Malik A. B.
Published: December 2017

We examined the direct effects of thrombin on pulmonary vasomotor tone in isolated guinea pig lungs perfused with Ringer albumin (0.5% g/100 ml). The injection of alpha-thrombin (the native enzyme) resulted in rapid dose-dependent increases in pulmonary arterial pressure (Ppa) and pulmonary capillary pressure (Ppc), which were associated with an increase in the lung effluent thromboxane B2 concentration. The Ppa and Ppc responses decreased with time but then increased again within 40 min after thrombin injection. The increases in Ppc were primarily the result of postcapillary vasoconstriction. Pulmonary edema as evidenced by marked increases (60% from base line) in lung weight occurred within 90 min after thrombin injection. Injection of modified thrombins (i.e., gamma-thrombin lacking the fibrinogen recognition site or i-Pr2P-alpha-thrombin lacking the serine proteolytic site) was not associated with pulmonary hemodynamic or weight changes nor did they block the effects of alpha-thrombin. Indomethacin (a cyclooxygenase inhibitor), dazoxiben (a thromboxane synthase inhibitor), or hirudin (a thrombin antagonist) inhibited the thrombin-induced pulmonary vasoconstriction, as well as the pulmonary edema. We conclude that thrombin-induced pulmonary vasoconstriction is primarily the result of constriction of postcapillary vessels, and the response is mediated by generation of cyclooxygenase-derived metabolites. The edema formation is also dependent on activation of the cyclooxygenase pathway. The proteolytic site of alpha-thrombin is required for the pulmonary vasoconstrictor and edemogenic responses.
Effect of subcellular matrix on glycosaminoglycan synthesis by human lung fibroblasts
Authors: Cui D. J. , Dubaybo B. A. , Durr R. A. , Thet L. A.
Published: December 2017

The influences modulating glycosaminoglycan production by lung cells are not well understood. We examined the effect of three different subcellular matrices, plastic, type I collagen, and reconstituted basement membrane-like material (RBM), on the synthesis of sulfated glycosaminoglycans by cultured IMR-90 human lung fibroblasts. Accumulation of 35SO4-labeled glycosaminoglycans into the cell-matrix layer or medium was measured. Cells on collagen synthesized significantly less total glycosaminoglycans than cells on plastic but had a higher fraction of labeled glycosaminoglycans present in the cell-matrix layer (35 vs. 18%) with the increases being highest for dermatan and chondroitin sulfates. Cells grown on the RBM synthesized significantly more glycosaminoglycans than cells on plastic or collagen and also had 260% more labeled glycosaminoglycans present in the cell-matrix layer than cells on plastic. We conclude that the matrix to which lung fibroblasts are exposed can influence the amount and type of glycosaminoglycans synthesized and the degree of incorporation into the matrix. This may be relevant to fibrotic lungs with increased type I collagen or to severely injured lungs in which intra-alveolar fibroblasts are in contact with denuded basement membranes.
Metabolic responses to exercise in the racehorse: changes in plasma alanine concentration
Authors: Poso A. R. , Soveri T. , Alaviuhkola M. , Lindqvist L. , Alakuijala L. , Maenpaa P. H. , Oksanen H. E.
Published: December 2017

Previous studies in humans have shown that alanine is released from the skeletal muscle in proportion to the work load. We have measured plasma alanine and urea concentrations in well-trained Standardbred and Finnish-bred (cold-blooded) trotters after a graded-intensity exercise and during recovery to study metabolic responses to exercise in this animal model. As controls we measured blood lactate, pyruvate, and glucose concentrations as well as hematocrit values. Metabolic responses to exercise were closely reflected in all these parameters. Plasma alanine increased relatively more than plasma lactate at moderate-intensity exercise near anaerobic threshold. The linear correlation between the intensity of exercise and plasma alanine was similar to that observed earlier in humans. Interestingly, plasma alanine concentrations remained elevated long after the submaximal exercise, whereas the concentration of lactate, pyruvate, and glucose decreased more rapidly. No significant changes were found in plasma urea concentration under these conditions. The most significant differences in the metabolic responses to exercise of the two breeds studied were the higher lactate-to-pyruvate ratios achieved during the high-intensity exercise and the more sensitive increases of plasma alanine even during low-intensity exercise in the Finnish-bred horses. These differences probably reflect different compositions of muscle fiber types in the two breeds. The findings together indicate that plasma alanine is greatly increased in the racehorse during and after a high-intensity exercise and thus is an important vehicle in transporting ammonia and carbon skeletons of products of anaerobic glycolysis out of the muscle tissue.
Influence of pulmonary inflations on discharge of pontile respiratory neurons
Authors: St John W. M.
Published: December 2017

The purpose of this study was to characterize the influence of pulmonary inflations on the discharge patterns of rostral pontile respiratory neurons. Decerebrate and paralyzed cats were ventilated with a servo-respirator which produced patterns of pulmonary inflation, assessed by tracheal pressure, which paralleled alterations in integrated activity of the phrenic nerve. Neurons with respiratory-modulated neuronal activities were recorded in the pneumotaxic region of the nucleus parabrachialis medialis and Kolliker-Fuse nucleus, as well as in the trigeminal motor nucleus. Approximately equal numbers of neurons had phasic and tonic respiratory-modulated discharge patterns. The discharge patterns of most neurons were not qualitatively altered when pulmonary inflation was prevented. However, withholding inflation did cause the recruitment of some respiratory-modulated neuronal activities. Similar findings were obtained in normocapnia and hypercapnia. Results support the concept that the discharge of neurons in the pneumotaxic region may exert phasic, as well as tonic, influences on ventilatory activity.
Myosin subunits and contractile properties of single fibers from hypokinetic rat muscles
Authors: Reiser P. J. , Kasper C. E. , Moss R. L.
Published: December 2017

The effects of prolonged hypokinesia on the contractile properties and myosin isozymes of single fibers from the synergistic fast-twitch plantaris (PL) and slow-twitch soleus (SOL) skeletal muscles of adult rats were studied after 28 days of hindlimb suspension. There was a 31% increase in the mean maximal velocity of unloaded shortening (Vmax) among fibers from SOL with no change in the mean Vmax of fibers from PL after suspension. The myosin heavy and light chain (MHC and MLC) composition of bundles and the MHC composition of single fibers from control and suspended muscles were examined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. There was a marked increase in the relative amount of fast-type MHC's in hypokinetic SOL and a smaller increase in the amount of fast-type MHC's in the PL. Relatively minor changes occurred in the MLC's during hypokinesia. As Vmax increased among individual fibers from control and suspended muscles, the relative amount of fast-type MHC's increased. The results demonstrate that the myosin isozyme composition of skeletal muscle, especially the heavy chains, is altered during hypokinesia, and this finding provides an explanation for changes in Vmax of rat single muscle fibers under the same conditions.
Isometric exercise modifies autonomic baroreflex responses in humans
Authors: Eckberg D. L. , Wallin B. G.
Published: December 2017

The influence of brief, moderate isometric exercise on the earliest vagal and sympathetic responses to changes of afferent carotid baroreceptor activity was studied in 10 healthy young men and women. Vagal-cardiac nerve activity was estimated from changes of electrocardiographic R-R intervals, and postganglionic peroneal nerve muscle sympathetic activity was measured directly from microneurographic recordings. Carotid baroreceptor activity was altered with 5-s periods of 30 Torr pressure or suction applied to a neck chamber during held expiration. Brief handgrip (30% of maximum) significantly reduced base-line R-R intervals, did not modify reductions of R-R intervals during neck pressure, and significantly reduced increases of R-R intervals during neck suction. Handgrip did not significantly increase base-line sympathetic activity from resting levels, but it significantly diminished increases of sympathetic activity during neck pressure and augmented reductions of sympathetic activity during neck suction. Our results suggest that exercise modifies, in small but significant ways, early sympathetic and vagal responses to abrupt changes of arterial baroreceptor input in humans.
Catecholamines abolish vagal but not acetylcholine tone in the intact cat trachea
Authors: Baker D. G. , Don H.
Published: December 2017

To obtain evidence in the airways that catecholamines inhibit cholinergic neurotransmission, we recorded transverse tension in the posterior wall of an upper tracheal segment in anesthetized cats and compared the inhibitory effect of stimulating cervical sympathetic nerves when segment contraction was evoked by endogenous acetylcholine (vagal tone) with the effect when contraction was evoked by exogenous acetylcholine applied directly to the mucosal surface of the tracheal segment (ACh tone). We found that sympathetic stimulation abolished all contraction evoked by vagal tone but reduced ACh tone by only one-half. In a second group of cats we compared the inhibitory effects of sympathetic stimulation and intravenous isoproterenol during vagal and ACh tone and also during tone evoked by exogenous 5-hydroxytryptamine (5-HT tone). Sympathetic stimulation or isoproterenol injection abolished all vagal and 5-HT tone but again reduced ACh tone by only one-half. Our results suggest that catecholamines released from sympathetic nerves or injected into the circulation completely inhibit vagal tone. This inhibition may be partially responsible for inducing relaxation in airway smooth muscle.
Pleural liquid pressure measured with rib capsules in anesthetized ponies
Authors: Olson L. E. , Lai-Fook S. J.
Published: December 2017

Pleural liquid pressure was measured at end expiration in 11 spontaneously breathing anesthetized ponies in the prone and supine positions. A liquid-filled capsule was implanted into a rib to measure pleural liquid pressure with minimal distortion of the pleural space (Wiener-Kronish et al., J. Appl. Physiol. 59: 597-602, 1985). Capsule position relative to lung height was measured from thoracic radiographs taken in each position. In each body position, pleural liquid pressure was most negative in the superior lung regions and least negative in the inferior lung regions. In the supine position, the magnitude of the vertical gradient in pleural liquid pressure was 0.67 cmH2O/cm ht and was not significantly different from 1 cmH2O/cm ht. In the inferior lung regions (less than 50% lung ht), pleural liquid pressure averaged -1.3 cmH2O, indicating a low transpulmonary pressure over the region of the chest where most of the lung mass is located. When animals were in the prone position, the magnitude of the vertical gradient in pleural liquid pressure was 0.14 cmH2O/cm ht and was not statistically different from 0 cmH2O/cm ht. In each body position, mean transpulmonary pressure, measured postmortem, was similar to the estimated magnitude of pleural liquid pressure at 50% lung ht. This suggests that pleural liquid pressure is closely related to pleural surface pressure. These results are consistent with the poor ventilation distribution and reduced lung volumes measured in anesthetized horses in the supine position compared with values measured in horses in the prone position.
Clearance of surfactant phosphatidylcholine from adult rabbit lungs
Authors: Pettenazzo A. , Ikegami M. , Seidner S. , Jobe A.
Published: December 2017

Rabbits were given various doses of rabbit surfactant and treatment doses of approximately 100 mg/kg body wt of calf surfactant and Surfactant TA by tracheal injection. The linear loss of radiolabeled phosphatidylcholine from the total lung (alveolar wash and lung tissue) was 3.1, 1.5, and 1.8%/h for rabbit surfactant, calf surfactant, and Surfactant TA, respectively. After 24 h only 6% rabbit, 19% calf, and 9.7% Surfactant TA phosphatidylcholine were recovered by alveolar wash, and alveolar macrophage fractions contained less than 1% of the injected labeled phosphatidylcholine. The loss of rabbit surfactant phosphatidylcholine 24 h after tracheal injection did not change for doses in the range of 0.5-70 mumol phosphatidylcholine per kilogram, indicating nonsaturable clearance pathways. Very little of the labeled rabbit surfactant phosphatidylcholine lost from the lungs could be recovered in other organs, and 90% of the recovered labeled phosphatidylcholine in the liver was unsaturated, implying de novo synthesis using precursors from degraded phosphatidylcholine. The surfactant did not change endogenous lung phosphatidylcholine synthesis or its secretion to the alveolus. There were no adverse effects of the surfactant treatments noted in healthy rabbits.
Limitations on locomotor performance in squid
Authors: O'Dor R. K.
Published: December 2017

An empirical equation relating O2 consumption (power input) to pressure production during jet-propelled swimming in the squid (Illex illecebrosus) is compared with hydrodynamic estimates of the pressure-flow power output also calculated from pressure data. Resulting estimates of efficiency and stress indicate that the circularly arranged obliquely striated muscles in squid mantle produce maximum tensions about half those of vertebrate cross-striated muscle, that "anaerobic" fibers contribute to aerobic swimming, and that peak pressure production requires an instantaneous power output higher than is thought possible for muscle. Radial muscles probably contribute additional energy via elastic storage in circular collagen fibers. Although higher rates of aerobic power consumption are only found in terrestrial animals at much higher temperatures, the constraint on squid performance is circulation, not ventilation. Anaerobic power consumption is also among the highest ever measured, but the division of labor between "aerobic" and "anaerobic" fibers suggests a system designed to optimize the limited capacity of the circulation.
Nasal delivery of a vasopressin antagonist in dogs
Authors: Liversidge G. G. , Wilson C. G. , Sternson W. L. , Kinter L. B.
Published: December 2017

The dosage form (drop or spray) and site of administration (dorsal or ventral surface of the nostril) profoundly affect the distribution and clearance of a gamma-emitting 99mTc-labeled diethylenetriamine pentaacetic acid (99mTc-DTPA) solution in dogs. The slowest nasal clearance was observed for dorsally administered drops. Administration of drops to the ventral surface or sprays to either dorsal or ventral surface results in rapid clearance and little deposition in the turbinates. The octapeptide vasopressin antagonist, SKF 101926, was administered intravenously (0.3, 1.0, 3.0, and 10 micrograms/kg) and then on separate occasions intranasally (10, 25, and 50 micrograms/kg as a drop to the ventral surface) to four conscious, trained, female, water-loaded, vasopressin-infused dogs. SKF 101926 reversed the antidiuretic response to vasopressin after administration by either the intravenous or intranasal route in a dose-dependent fashion. Peak dilution of urine occurred within 50- to 60-min postdosing by both routes. Estimated doses to reduce vasopressin antidiuresis by 50% were 1.4 micrograms/kg intravenously and 23 micrograms/kg intranasally. After recovery to at least 70% of antidiuretic base line, and then administration of a second dose of SKF 101926 (3 micrograms/kg), subsequent dilution of urine osmolality was inversely related to the magnitude of the previously administered dose. It is concluded that the estimated relative effectiveness of intranasally administered SKF 101926 is 3-21%, compared with intravenous administration. Acute tachyphylaxis to repeated dosing was observed. The mechanism of the apparent tachyphylaxic response was not elucidated. No tachyphylaxis to less frequent (weekly) dosing was observed.
Single breath of CO2 as a clinical test of the peripheral chemoreflex
Authors: McClean P. A. , Phillipson E. A. , Martinez D. , Zamel N.
Published: December 2017

Peripheral chemoreceptor responsiveness is usually examined clinically by hypoxic testing, but the usefulness of this approach is limited by safety considerations, and the interpretation of results may be confounded by the direct central nervous system effects of hypoxia. Therefore we examined the single-breath (SB) CO2 test to determine its reproducibility and applicability as a clinical test of peripheral chemoreceptor function. The technique involved the inhalation of a SB of 13% CO2 in air. The ventilatory response was determined from the increase in ventilation (VE) during the first 20 s after the test breath and from the difference in end-tidal PCO2 between the test breath and preceding control breaths. The peak increase in VE occurred during the second or third breath after the test breath, corresponding to a delay of approximately 10 s. The mean of 10 SB tests administered at 2- to 3-min intervals was taken as the subject's response. Five healthy subjects were tested in this manner on each of 6 consecutive days with the response having an interday coefficient of variation of 25 +/- 6% (SD). The response in 26 healthy females (aged 22-61 yr) was 0.32 +/- 0.11 l.min-1.Torr-1, and in 26 healthy males (aged 24-69 yr) the response was 0.38 +/- 0.14 (P NS). No significant correlation was found between the age of the subjects and their ventilatory response. Thirty-six of the subjects also underwent hyperoxic CO2 rebreathing tests, the response to which is dependent on central chemoreceptor function. No correlation was found between rebreathing and SB tests.(ABSTRACT TRUNCATED AT 250 WORDS)
Genioglossus and breathing responses to airway occlusion: effect of sleep and route of occlusion
Authors: Issa F. G. , Edwards P. , Szeto E. , Lauff D. , Sullivan C.
Published: December 2017

We examined the effect of sleep state on the response of genioglossus muscle (EMGgg) activity to total airway occlusion applied at 1) nasal (N) airway [and thus exposing the upper airway (UAW) to pressure changes] and 2) tracheal (T) airway (thus excluding UAW from pressure changes). A total of 233 tests were performed during wakefulness (W), 98 tests in slow-wave sleep (SWS), and 72 tests in rapid-eye-movement (REM) sleep. Prolongation of inspiratory time (TI) of the first occluded effort occurred in all tests irrespective of behavioral state, with the greatest increase seen in awake N tests. Nasal tests augmented EMGgg activity in the first occluded breath and produced a linear increase in EMGgg during occlusion. The EMGgg activity at any given time during nasal occlusion in SWS was less than that recorded during W tests. There was a marked reduction in EMGgg response to N occlusion during REM sleep. The EMGgg activity during awake T tests was significantly less than that of N tests at any given time during occlusion. There was no relationship between the level of EMGgg activity and asphyxia in T tests performed during SWS and REM sleep. Nasal tests decreased the force generated by the inspiratory pump muscles and the central drive to breathing compared with T tests. These results confirm the important role of the UAW in regulating breathing pattern and indicate that both immediate and progressive load-compensating responses during nasal occlusion are influenced by information arising from the UAW.
Effect of ambient temperature on protein breakdown during prolonged exercise
Authors: Dolny D. G. , Lemon P. W.
Published: December 2017

Male subjects (n = 8) cycled for 90 min in 5, 20, and 30 degrees C environments. Rectal (Tre), chest, and thigh temperatures, O2 consumption (VO2), respiratory exchange ratio (R), and venous concentrations of glucose, free fatty acids (FFA), urea N, lactic acid (LA), norepinephrine (NE), epinephrine (E), and cortisol (C) were measured before, during, and after exercise. Urea N excretion was measured in 72 h of nonexercise, in 72 h of exercise (exercise day + 2 post-exercise days) urine samples, and in exercise sweat. Calculated 72-h protein utilization (means +/- SE) was significantly greater (P less than 0.05) for the 5 (86.9 +/- 27.1 g) and 20 (82.9 +/- 22.7 g) compared with 30 degrees C (34.01 +/- 19.1 g) trial. Regardless of ambient temperature exercise increased the venous concentration of C, E, and NE. These catabolic hormones were greatest in 5, lowest in 20, and intermediate in 30 degrees C. Exercise Tre and VO2 were greatest in the 30 degrees C environment. Venous FFA concentration was significantly higher and R significantly lower in 5 vs. 20 or 30 degrees C, and venous LA concentration was significantly greater in 30 vs. 20 or 5 degrees C. Although these results indicate that exercise protein breakdown is affected by ambient temperatures, the mechanism of action is not due solely to circulating NE, E, and C. Differences in venous FFA and LA across environmental temperatures suggest that alterations in carbohydrate and fat metabolism may have contributed to the observed variable protein utilization.
Elasticity of arterioles and venules in postmortem human lungs
Authors: Yen R. T. , Sobin S. S.
Published: December 2017

The elasticity and branching order of noncapillary microscopic blood vessels less than 100 microns diam were studied in human lungs obtained 7–30 h postmortem, using a silicone elastomer method that selectively filled pulmonary arterioles or venules. The lungs were inflated to 10 cmH2O pressure and a gradient of transmural vascular pressure of 0–17 cm H2O, from lobe base to apex, was established in the silicone-filled vascular system. Histological materials were obtained after airway fixation by formaldehyde solution and analyzed for vessel diameter in the branching order of 1, 2, and 3, with the smallest noncapillary vessel designated as order 1, in accord with the Strahler system. The change in vessel diameter within a branching order at different levels of transmural pressure is a derived measure of vascular elasticity expressed as compliance coefficient alpha, alpha Values are 0.128, 0.164, and 0.210 micron/cmH2O or 0.682, 0.472, and 0.354%/cmH2O, respectively, of orders 1–3 for arterioles and 0.187, 0.215, and 0.250 micron/cmH2O or 0.992, 0.612, and 0.424%/cmH2O, respectively, of orders 1–3 for venules. The percent is normalized with D0, which is the value of diameter (D) when the transmural pressure is zero. These data are compared with those for the cat where alpha = 0.274 for similar juxta-alveolar vessels.
Effect of intravenous catalase on the pulmonary vascular response to endotoxemia in goats
Authors: Maunder R. J. , Winn R. K. , Gleisner J. M. , Hildebrandt J. , Harlan J. M.
Published: December 2017

Neutrophils have been implicated in the pathogenesis of acute lung injury associated with clinical and experimental sepsis. Data from in vitro systems and experimental animals have suggested that neutrophil-derived oxidants, particularly H2O2, may be primarily responsible for endothelial damage, vasoconstriction, and lung edema. With the use of endotoxin infusion as an in vivo model of sepsis we tested the hypothesis that pretreatment with catalase, a peroxide scavenger, would ameliorate the resultant changes in pulmonary vasoconstriction and lung fluid balance. Paired experiments were performed in 16 goats with chronic lung lymph fistulas. One group of animals (n = 7) received endotoxin first alone and then again, several days later, after pretreatment with Ficoll-linked catalase. As a control, identical experiments were performed in a separate group (n = 6) with Ficoll-linked albumin substituted for Ficoll-catalase. A third group (n = 3) was given endotoxin alone and then again during a continuous infusion of catalase. Plasma and lymph levels of catalase were comparable to or exceeded those previously shown to be completely protective in isolated perfused lung preparations and in vitro systems. Endotoxin caused neutropenia, pulmonary arterial hypertension, decreased cardiac output, and increases in lymph flow to approximately three times base line, with a return of all variables toward control values by 6 h. Catalase pretreatment produced no significant differences in any of these variables. These experiments do not support a role for H2O2 as a mediator of acute lung injury due to endotoxemia.
Upper airway pressure-flow relationships in obstructive sleep apnea
Authors: Smith P. L. , Wise R. A. , Gold A. R. , Schwartz A. R. , Permutt S.
Published: December 2017

We examined the pressure-flow relationships in patients with obstructive sleep apnea utilizing the concepts of a Starling resistor. In six patients with obstructive sleep apnea, we applied incremental levels of positive pressure through a nasal mask during non-rapid-eye-movement sleep. A positive critical opening pressure (Pcrit) of 3.3 +/- 3.3 (SD) cmH2O was demonstrated. As nasal pressure was raised above Pcrit, inspiratory airflow increased in proportion to the level of positive pressure applied until apneas were abolished (P less than 0.01). However, at pressures greater than Pcrit, esophageal pressures either did not correlate or correlated inversely with inspiratory airflow provided that esophageal pressure was less than Pcrit. When pressure was applied to a full face mask, inspiratory airflow did not occur and Pcrit could not be obtained at pressures well above Pcrit demonstrated with the nasal mask. These results are consistent with the view that the upper airway functions as a Starling resistor with a collapsible segment in the oropharynx. These findings offer a unifying construct for the association of sleep apnea, periodic hypopnea, and snoring.
Effects of lung congestion and oleic acid injury on the Hering-Breuer reflex
Authors: Lloyd T. C.
Published: December 2017

Breathing and the Hering-Breuer (HB) reflex may be stimulated by congestion and by acute lung injury, but there is disagreement about the effects of both stimuli. This study evaluated these effects using greater stimulus isolation and control of secondary interactions than have previously been employed. Pressurization of lung vessels and left heart and oleic acid injury were individually imposed on anesthetized open-chest dogs perfused with an external pump and gas exchanger. Lungs were inflated in steps before and during those stimuli. The HB reflex was evaluated from graphs of breathing frequency (fr) vs. airway pressure. Congestion itself had no significant sustained effect on fr, but it slightly depressed the HB reflex. Oleic acid tachypnea that was depressed to pretreatment fr by inflation, implying enhancement of the HB response. Capsaicin and oleic acid had similar effects. Vagal cooling to 8 degrees C slightly depressed the effects of oleic acid and capsaicin, had no effect on the sustained fr response to congestion, and reversed the inhibitory effect of inflation. A stimulation of breathing or an enhancement of the HB reflex by congestion was not confirmed, but oleic acid increased fr and the HB reflex.