bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of sleep on tensor palatini EMG and upper airway resistance in normal men
Authors: Tangel D. J. , Mezzanotte W. S. , White D. P.
Published: December 2017

We propose that a sleep-induced decrement in the activity of the tensor palatini (TP) muscle could induce airway narrowing in the area posterior to the soft palate and therefore lead to an increase in upper airway resistance in normal subjects. We investigated the TP to determine the influence of sleep on TP muscle activity and the relationship between changing TP activity and upper airway resistance over the entire night and during short sleep-awake transitions. Seven normal male subjects were studied on a single night with wire electrodes placed in both TP muscles. Sleep stage, inspiratory airflow, transpalatal pressure, and TP moving time average electromyogram (EMG) were continuously recorded. In addition, in two of the seven subjects the activity (EMG) of both the TP and the genioglossus muscle simultaneously was recorded throughout the night. Upper airway resistance increased progressively from wakefulness through the various non-rapid-eye-movement sleep stages, as has been previously described. The TP EMG did not commonly demonstrate phasic activity during wakefulness or sleep. However, the tonic EMG decreased progressively and significantly (P less than 0.05) from wakefulness through the non-rapid-eye-movement sleep stages [awake, 4.6 +/- 0.3 (SE) arbitrary units; stage 1, 2.6 +/- 0.3; stage 2, 1.7 +/- 0.5; stage 3/4, 1.5 +/- 0.8]. The mean correlation coefficient between TP EMG and upper airway resistance across all sleep states was (-0.46). This mean correlation improved over discrete sleep-awake transitions (-0.76). No sleep-induced decrement in the genioglossus activity was observed in the two subjects studied.(ABSTRACT TRUNCATED AT 250 WORDS)
Pulmonary and chest wall mechanics in anesthetized paralyzed humans
Authors: D'Angelo E. , Robatto F. M. , Calderini E. , Tavola M. , Bono D. , Torri G. , Milic-Emili J.
Published: December 2017

Pulmonary and chest wall mechanics were studied in 18 anesthetized paralyzed supine humans by use of the technique of rapid airway occlusion during constant-flow inflation. Analysis of the changes in transpulmonary pressure after flow interruption allowed partitioning of the overall resistance of the lung (RL) into two compartments, one (Rint,L) reflecting airway resistance and the other (delta RL) representing the viscoelastic properties of the pulmonary tissues. Similar analysis of the changes in esophageal pressure indicates that chest wall resistance (RW) was due entirely to the viscoelastic properties of the chest wall tissues (delta RW = RW). In line with previous measurements of airway resistance, Rint,L increased with increasing flow and decreased with increasing volume. The opposite was true for both delta RL and delta RW. This behavior was interpreted in terms of a viscoelastic model that allowed computation of the viscoelastic constants of the lung and chest wall. This model also accounts for frequency, volume, and flow dependence of elastance of the lung and chest wall. Static and dynamic elastances, as well as delta R, were higher for the lung than for the chest wall.
Effect of hyperventilation on oxygenation of the brain cortex of newborn piglets
Authors: Wilson D. F. , Pastuszko A. , DiGiacomo J. E. , Pawlowski M. , Schneiderman R. , Delivoria-Papadopoulos M.
Published: December 2017

A new phosphorescence imaging method (Rumsey et al. Science Wash. DC 241: 1649-1651, 1988) has been used to continuously monitor the PO2 in the blood of the cerebral cortex of newborn pigs. A window was prepared in the skull and the brain superfused with artificial cerebrospinal fluid. The phosphorescent probe for PO2, Pd-meso-tetra(4-carboxyphenyl)porphine, was injected directly into the systemic blood. The phosphorescence of the probe was imaged, and the lifetimes were measured using flash illumination and a gated video camera. The PO2 in the blood of the veins and capillary beds of the cortex was calculated from the lifetimes. Systemic blood pressure was continuously monitored while the systemic arterial PCO2, PO2, and blood pH were measured periodically. The PO2 in the blood was quantitated for 60- to 200 microns2 regions within the image (from a total field of approximately 3 mm diam). The PO2 in the microvasculature was not uniform across the viewing field but increased or decreased in each region independently of the other regions. Thus at any point in time the PO2 in a region could be substantially above or below the average value. During hyperventilation, which lowered arterial PCO2 and increased pH of the blood, the average PO2 decreased in proportion to the decrease in arterial PCO2. For example, hyperventilation, which decreased arterial PCO2 from its normal value of 40 Torr to 10 Torr, caused a rapid (within 5 min) decrease in PO2 in the blood of capillaries and veins to approximately one-third of normal.
Mechanism for pressor response to nonexertional heating in the conscious rat
Authors: Kregel K. C. , Overton J. M. , Johnson D. G. , Tipton C. M. , Seals D. R.
Published: December 2017

The purpose of this study was to determine the systemic hemodynamic mechanism(s) underlying the pressor response to nonexertional heat stress in the unrestrained conscious rat. After a 60-min control period [ambient temperature (Ta) 24 degrees C], male Sprague-Dawley rats (260–340 g) were exposed to a Ta of 42 degrees C until a colonic temperature (Tc) of 41 degrees C was attained. As Tc rose from control levels (38.1 +/- 0.1 degrees C) to 41 degrees C, mean arterial blood pressure (carotid artery catheter, n = 33) increased from 124 +/- 2 to 151 +/- 2 mmHg (P less than 0.05). During this period, heart rate increased (395 +/- 5 to 430 +/- 6 beats/min, P less than 0.05) and stroke volume remained unchanged. As a result, ascending aorta blood flow velocity (Doppler flow probe, n = 8), used as an index of cardiac output, did not change from control levels during heating, but there was a progressive Tc-dependent increase in systemic vascular resistance (+30% at end heating, P less than 0.05). This systemic vasoconstrictor response was associated with decreases in blood flow (-31 +/- 9 and -21 +/- 5%) and increases in vascular resistance (94 +/- 16 and 53 +/- 8%; all P less than 0.05) in the superior mesenteric and renal arteries (n = 8 each) and increases in plasma norepinephrine (303 +/- 37 to 1,237 +/- 262 pg/ml) and epinephrine (148 +/- 28 to 708 +/- 145 pg/ml) concentrations (n = 12, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of pyridostigmine bromide on human thermoregulation during cold water immersion
Authors: Prusaczyk W. K. , Sawka M. N.
Published: December 2017

This study examined the effects of an oral 30-mg dose of pyridostigmine bromide (PYR) on thermoregulatory and physiological responses of men undergoing cold stress. Six men were immersed in cold water (20 degrees C) for up to 180 min on two occasions, once each 2 h after ingestion of PYR and 2 h after ingestion of a placebo. With PRY, erythrocyte cholinesterase inhibition was 33 +/- 12% (SD) 110 min postingestion (10 min preimmersion) and 30 +/- 7% at termination of exposure (mean 117 min). Percent cholinesterase inhibition was significantly related to lean body mass (r = -0.91, P less than 0.01). Abdominal discomfort caused termination in three of six PYR experiments but in none of the control experiments (mean exposure time 142 min). During immersion, metabolic rate, ventilatory volume, and respiratory rate increased significantly (P less than 0.05) over preimmersion levels and metabolic rate increased with duration of immersion (P less than 0.01) in both treatment but did not differ between conditions. PYR had no significant effect on rectal temperature, mean body temperature, thermal sensations, heart rate, plasma cortisol, or change in plasma volume. It was concluded that a 30-mg dose of PYR does not increase an individual's susceptibility to hypothermia during cold water immersion; however, in combination with cold stress, PYR may result in marked abdominal cramping and limit cold tolerance.
Influence of active muscle mass on glucose homeostasis during exercise in humans
Authors: Kjaer M. , Kiens B. , Hargreaves M. , Richter E. A.
Published: December 2017

To study the effect of increasing amounts of exercising muscle mass on the relationship between glucose mobilization and peripheral glucose uptake, seven young men (23–28 yr) bicycled for 70 min at a work load of 55–60% VO2max. From minute 30 to 50, arm cranking was added and total work load increased to 82 +/- 4% VO2max. During leg exercise, hepatic glucose production (Ra) increased in parallel with peripheral glucose uptake (Rd) and euglycemia was maintained. During arm + leg exercise, Ra increased more than Rd and accordingly plasma glucose increased from 5.11 +/- 0.22 to 8.00 +/- 0.66 mmol/l (P less than 0.05). Plasma catecholamines increased three- to four-fold more during arm + leg exercise than during leg exercise. Leg glucose uptake increased with time regardless of arm cranking. Net leg lactate release during leg exercise was reverted to a net leg lactate uptake during arm + leg exercise. The rate of glycogen breakdown in exercising leg muscle was not altered by addition of arm cranking. In conclusion, when large amounts of muscle mass are active, plasma catecholamines increase sharply and mobilization of glucose exceeds peripheral glucose uptake. This indicates that mechanisms other than feedback regulation to maintain euglycemia are involved in hormonal and substrate mobilization during intense exercise in humans.
Partitioning of pulmonary responses to inhaled methacholine in puppies
Authors: Sly P. D. , Lanteri C. J.
Published: December 2017

Twelve open-chest mongrel puppies, 8–10 wk old, were studied to localize the site of action of inhaled methacholine within the lungs. Six puppies were challenged with methacholine aerosols and six were challenged with an equal number of nebulizations of normal saline (control group). Pulmonary mechanics were measured during mechanical ventilation and after midexpiratory flow interruptions. Alveolar pressure was measured to allow the partitioning of pulmonary mechanics into airway and tissue components. Good matching between airway opening and alveolar pressures was seen throughout the study. After methacholine challenge, lung resistance increased fivefold. Increases in airway resistance and in the parameters reflecting tissue viscoelastic properties contributed to this increase in lung resistance. Dynamic lung elastance also increased threefold. The response of the methacholine group was statistically different from that of the control group. These data indicate that both the airways and pulmonary parenchyma contribute to the response to inhaled methacholine in 8- to 10-wk-old puppies.
Oxygen cost and oxygen uptake dynamics and recovery with 1 min of exercise in children and adults
Authors: Zanconato S. , Cooper D. M. , Armon Y.
Published: December 2017

To test the hypothesis that O2 uptake (VO2) dynamics are different in adults and children, we examined the response to and recovery from short bursts of exercise in 10 children (7–11 yr) and 13 adults (26–42 yr). Each subject performed 1 min of cycle ergometer exercise at 50% of the anaerobic threshold (AT), 80% AT, and 50% of the difference between the AT and the maximal O2 uptake (VO2max) and 100 and 125% VO2max. Gas exchange was measured breath by breath. The cumulative O2 cost [the integral of VO2 (over baseline) through exercise and 10 min of recovery (ml O2/J)] was independent of work intensity in both children and adults. In above-AT exercise, O2 cost was significantly higher in children [0.25 +/- 0.05 (SD) ml/J] than in adults (0.18 +/- 0.02 ml/J, P less than 0.01). Recovery dynamics of VO2 in above-AT exercise [measured as the time constant (tau VO2) of the best-fit single exponential] were independent of work intensity in children and adults. Recovery tau VO2 was the same in both groups except at 125% VO2max, where tau VO2 was significantly smaller in children (35.5 +/- 5.9 s) than in adults (46.3 +/- 4 s, P less than 0.001). VO2 responses (i.e., time course, kinetics) to short bursts of exercise are, surprisingly, largely independent of work rate (power output) in both adults and children. In children, certain features of the VO2 response to high-intensity exercise are, to a small but significant degree, different from those in adults, indicating an underlying process of physiological maturation.
Contributions of diffusion jet flow and cardiac activity to regional ventilation in CFV
Authors: Venegas J. G. , Yamada Y. , Hales C. A.
Published: December 2017

The magnitude and regional distribution of local gas transport during constant-flow ventilation (CFV) were quantified by imaging the washout of nitrogen 13 (13NN) from anesthetized and paralyzed mongrel dogs with positron emission tomography. Equal jet flows, through two 2-mm-ID bronchial catheters 1 cm distal to the carina, were adjusted to provide eucapnic CFV (total flow = 57.6 ml.s-1.kg-1). Basal, midheart, and apical transverse sections were studied in supine and prone anesthetized dogs. The ventilation per unit volume (sV) of selected areas was computed from local 13NN concentration vs. time curves during washout. To separate the regional contributions of CFV and cardiogenic oscillation to enhanced molecular diffusion, additional supine dogs were also studied during unilateral CFV. In this protocol the CFV jet flow was delivered to a single lung while the contralateral lung was left apneic. For each lung, washout data were obtained under CFV and apnea both living and postmortem animals. The local contributions of diffusion, CFV jet effects, and cardiac activity to gas transport were evaluated and tested for additive and multiplicative synergistic interactions. The regional distribution of gas transport during CFV was found to be highly nonuniform and characterized by higher ventilation to regions located close to the main bronchi and those located in the direction in which the CFV jet pointed. No major differences were observed between supine and prone positions. This regional pattern of ventilation distribution was found to be the result of complementary and nearly multiplicative interaction between the regional effects of the CFV jet, concentrated in the central airways, and the preferential cardiogenic gas transport enhancement in ventral regions close to the heart. The data were also analyzed with a model that divides the regional diffusive gas transport resistance into a central component, affected by the CFV jet, and a peripheral component, affected only by cardiac activity. This analysis showed substantial regional heterogeneities in the effects of the different gas transport mechanisms, which are consistent with the geometry of the bronchial tree and the location of the heart in the dog. The results indicate that regional nonuniformities must be considered when modeling gas transport in CFV.
Errors in predicting maximal oxygen consumption in pregnant women
Authors: Lotgering F. K. , Struijk P. C. , van Doorn M. B. , Wallenburg H. C.
Published: December 2017

This study was designed to determine the accuracy of estimated values of maximal heart rate (HRmax) and oxygen consumption (VO2) during pregnancy. We measured HR and maximal VO2 (VO2max) at rest and during cycle (CE) and treadmill exercise (TE) tests with rapidly increasing exercise intensities during gestation and after delivery. Pregnancy was found to affect the linear relationship of HR and %VO2max so that the intercept increases with advancing gestation and the slope decreases. Estimated maximal HR (HRmax, est), 220 - age (yr) x beats/min, overestimated measured HRmax by 8% (CE) and 5% (TE). For VO2max estimated by Astrand's nomogram (VO2max, est1) and by linear extrapolation of submaximal values of HR and VO2 to HRmax, est (VO2max, est2), individual errors were large (SD 17–28%). Mean VO2max, est1 overestimated measured VO2max by 20% during CE but not during TE (-2%) and elicited the erroneous impression that VO2max decreases during CE in pregnancy. Mean VO2max, est2 values were not significantly different from measured VO2max values. This apparent accuracy resulted from two opposing errors: 1) HRmax, est overestimated HRmax, and 2) above 70% VO2max the slope of the HR-%VO2max relationship was significantly reduced. Therefore neither method to estimate VO2max can replace the measurement of VO2max.
Spinal vasopressin modulates the reflex cardiovascular response to static contraction
Authors: Stebbins C. L. , Ortiz-Acevedo A. , Hill J. M.
Published: December 2017

Recent evidence has demonstrated that arginine vasopressin (AVP) may modulate primary afferent activity of nociceptors in the dorsal horn of the spinal cord. Because nociceptors are group III and IV afferents, spinal AVP also may modulate the activity of group III and IV afferents that cause reflex cardiovascular responses to muscle contraction. Thus, we compared the pressor (mean arterial pressure), myocardial contractile (dP/dt), and heart rate (HR) responses to electrically induced static contraction of the cat hindlimb before and after lumbar intrathecal (IT) injection (L1-L7) of AVP (n = 9), the V1 receptor antagonist d(CH2)5Tyr(Me)AVP (n = 6), the V2 receptor antagonist d(CH2)5[D-Ile2,Ile4,Ala-NH2(9)]AVP (n = 6), and the V2 agonist [Val4,D]AVP (n = 8). After IT injection of AVP (0.1 or 1 nmol) the pressor and contractile responses to static contraction were attenuated by 55 and 44%, respectively. HR was unchanged. Forty-five to 60 min after AVP injection, the contraction-induced pressor and contractile responses were restored to control levels. V1 receptor blockade augmented contraction-induced increases in mean arterial pressure (36%) and dP/dt (49%) but not HR. V2 receptor blockade had no effect on the cardiovascular response to contraction, whereas selective V2 stimulation attenuated the dP/dt (-20%) and HR (-33%) responses but not the pressor response. These results suggest that AVP attenuates the reflex cardiovascular response to contraction by modulating sensory nerve transmission from contracting muscle primarily via a V1 receptor mechanism in the lumbar spinal cord.
Effect of the pericardium on atrial systolic function
Authors: Riddervold F. , Smiseth O. A. , Myhre E. S.
Published: December 2017

The effect of pericardial constraint on atrial systolic function was investigated in nine acutely instrumented anesthetized dogs. Left and right atrial pressures were recorded by high-fidelity catheters; auricular diameters and free wall segment lengths were measured by sonomicrometry. Atrial function curves were constructed by relating atrial systolic dimensional shortening to atrial end-diastolic pressure during progressive volume loading. With the pericardium closed, the function curves were shifted markedly downward and rightward, such that atrial systolic shortening was reduced at any given pressure. There was a concomitant leftward and upward shift of the atrial end-diastolic pressure-dimension relationship. The relationship between atrial systolic shortening and atrial end-diastolic dimension was not shifted. These results suggest that the apparent depression of atrial systolic function with the pericardium closed is due to a restrictive effect of the pericardium on atrial filling. In conclusion, in the acutely dilated heart, the pericardium restricts atrial filling and thus causes a reduction in atrial systolic contribution to ventricular filling.
Effects of simulated microgravity (HDT) on blood fluidity
Authors: Lampe L. , Wienhold K. , Meyer G. , Baisch F. , Maass H. , Hollmann W. , Rost R.
Published: December 2017

Exposures to microgravity and head-down tilt (HDT) produce similar changes in body fluid. This causes an increase in hematocrit that significantly affects hemorheological values. Lack of physical stimulation under bed rest conditions and the relative immobility of the crew during spaceflight also affects the blood fluidity. A group of six healthy male subjects participated as volunteers, and blood samples were collected 10 days before, on day 2 and day 9, and 2 days after the HDT phase. Blood rheology was quantified by plasma viscometry, red cell aggregability, and red cell deformability. A reduced red cell deformability, an indication of the diminished quality of the red blood cells, was measured under HDT conditions that finally led to the so-called “space flight anemia.” Enhanced red cell membrane fragility induced by diminished physical activity and an increase in hemoglobin concentration are responsible for this effect. Plasma viscosity is reduced as a result of diminished plasma proteins. However, despite the reduction in plasma proteins, including fibrinogen, alpha 2-macroglobulin, and immunoglobulin M, red cell aggregation was enhanced, principally because of the increase in hematocrit. Our results of hemorheological alterations under HDT conditions may help to elucidate the formerly documented hematologic changes during spaceflight.
Developmental changes in sequential activation of laryngeal abductor muscle and diaphragm in infants
Authors: Eichenwald E. C. , Howell R. G. , Kosch P. C. , Ungarelli R. A. , Lindsey J. , Stark R.
Published: December 2017

In animals and human adults, upper airway muscle activity usually precedes inspiratory diaphragm activity. We examined the interaction of the posterior cricoarytenoid muscle (PCA), which abducts the larynx, and the diaphragm (DIA) in the control of airflow in newborn infants to assess the effect of maturation on respiratory muscle sequence. We recorded tidal volume, airflow, and DIA and PCA electromyograms (EMG) in 12 full-term, 14 premature, and 10 premature infants with apnea treated with aminophylline. In most breaths, onset of PCA EMG activity preceded onset of DIA EMG activity (lead breaths). In all subjects, we also observed breaths (range 6–61%) in which PCA EMG onset followed DIA EMG onset (lag breaths). DIA neural inspiratory duration and the neuromechanical delay between DIA EMG onset and inspiratory flow were longer in lag than in lead breaths (P < 0.05 and P < 0.01, respectively). The frequency of lag breaths was greater in the premature infants [33 +/- 4% (SE)] than in either the full-term infants (21 +/- 3%, P < 0.03) or the premature infants with apnea treated with aminophylline (16 +/- 2%, P < 0.01). We conclude that the expected sequence of onset of PCA and DIA EMG activity is frequently disrupted in newborn infants. Both maturation and respiratory stimulation with aminophylline improve the coordination of the PCA and DIA.
Turnover of hyaluronan in the rabbit pleural space
Authors: Allen S. J. , Fraser R. E. , Laurent U. B. , Reed R. K. , Laurent T. C.
Published: December 2017

Hyaluronan influences lung fluid balance. The clearance of lung hyaluronan by way of the pulmonary lymphatics and the pleural space is increased when fluid flux into the interstitium is increased. The purpose of this study was to determine the rate at which hyaluronan is removed from the pleural space. We injected hyaluronan, labeled with tritium in the acetyl group, into the pleural space of six rabbits. The appearance of [3H]H2O in serum was measured over time to calculate the turnover rate of hyaluronan. We found that the half-lives ranged between 8 and 15 h and were positively related to the amount of hyaluronan injected. At the end of the experiment, the contralateral pleural space was irrigated to determine the amount of pleural space hyaluronan, which was 0.3 micrograms/kg body wt.
Postnatal development of the denervated lung in normoxia, hypoxia, or hyperoxia
Authors: Dotta A. , Mortola J. P.
Published: December 2017

We asked whether lung innervation was essential for the normal postnatal development of the lung in conditions of normoxia, hypoxia, or hyperoxia. Litters of newborn rats were assigned to a normoxic [inspired oxygen partial pressure (PIO2) = 150 Torr, eight litters], hypoxic (PIO2 = 100 Torr, nine litters), or hyperoxic (PIO2 = 360 Torr, nine litters) group. Each litter consisted of 12 pups. Two days after birth, one-third of the litter had the vagus and sympathetic trunk cut in the neck on the left side [left denervated (L)], one-third was denervated on the right side (R), and one-third was sham-operated (S). From day 3, all pups were exposed to the designed PIO2, until day 8 or days 21–22. Almost all rats, whether S, R, or L, survived in normoxia and hyperoxia, whereas in hypoxia survival at day 22 of R and L was approximately 60–65%. Body growth was the same in S, R, and L and less in hypoxia than in normoxia or hyperoxia. At days 8 and 22, hematocrit and hemoglobin concentration, heart and lung dry and wet weights, and lung DNA content did not differ among S, R, and L, whether the pups were raised in normoxia, hypoxia, or hyperoxia. At days 21–22, aerobic metabolism and breathing pattern, both measured during air breathing, as well as compliance of isolated lungs, were also similar among S, R, and L for each of the conditions in which the pups were raised.(ABSTRACT TRUNCATED AT 250 WORDS)
Discharge patterns of phrenic motoneurons during fictive coughing and vomiting in decerebrate cats
Authors: Milano S. , Grelot L. , Bianchi A. L. , Iscoe S.
Published: December 2017

In decerebrate, paralyzed, and ventilated cats, we recorded the activity of 100 spontaneously active phrenic motor axons during the increased phrenic discharges characteristic of fictive vomiting (FV) and coughing (FC). During control respiratory cycles, approximately one-half the neurons were recruited in the first decile of inspiration; recruitment continued throughout inspiration. During FV, the duration of phrenic discharge was halved; 20 of 26 motoneurons studied were recruited in the first decile of the burst. During FC, recruitment times did not change compared with control, although the duration of the phrenic burst doubled. Discharge frequencies increased and recruitment order of phrenic motoneurons was virtually unaffected during FC and FV. Limited recruitment of previously inactive neurons in the filaments from which we recorded was found during FV and FC. During FV, 1 previously inactive motoneuron was recruited in 16 filaments containing 25 spontaneously active motor axons. During FC, 3 new motoneurons were recruited in addition to the 64 already active in 35 filaments. Recruitment during FV and FC was absent even when recording from filaments known, on the basis of antidromic activation, to contain inactive motor axons. During FV, 10 of 26 motoneurons began their discharges with doublets (interspike interval < 10 ms); doublets occurred in only 4 of 67 motoneurons during FC. Already active phrenic motoneurons contributed to the intense phrenic activity associated with both respiratory (coughing) and nonrespiratory (vomiting) behavior by increases in discharge frequency, earlier recruitment, and doublets; the contribution of previously quiescent motoneurons remains uncertain.
Modification of water and electrolyte metabolism during head-down tilting by hypoglycemia in men
Authors: Hayashi Y. , Murata Y. , Seo H. , Miyamoto N. , Kambe F. , Ohmori S. , Yamamoto C. , Hayamizu S. , Tamura Y. , Matsui N.
Published: December 2017

The effect of hypoglycemic stress on the changes in water and electrolyte metabolism induced by head-down tilting (HDT) was studied. Six healthy men were subjected to postural changes (30 min standing, 2 h HDT, 1 h standing), with or without the intravenous administration of insulin at the beginning of HDT. When insulin was not given, antidiuretic hormone (ADH), cortisol, plasma renin activity (PRA), aldosterone, and catecholamine levels were decreased and atrial natriuretic polypeptide (ANP) levels increased during HDT. These changes were associated with 2.5- and 1.5-fold increases in urine flow and sodium excretion, respectively, when compared with the amounts before HDT. On the other hand, insulin-induced hypoglycemia during HDT produced increases in ADH, cortisol, PRA, aldosterone, and catecholamine levels. At the same time, an exaggerated ANP response by HDT was observed. These hormonal changes were associated with an abolishment of the increases in urine flow and sodium excretion. It is suggested that acute stress modifies the changes in fluid and electrolyte metabolism induced by HDT.
Reactive oxygen in skeletal muscle. II. Extracellular release of free radicals
Authors: Reid M. B. , Shoji T. , Moody M. R. , Entman M. L.
Published: December 2017

We have tested the hypothesis that diaphragm muscle fibers release superoxide anion radicals (O2-.) into the extracellular space. Fiber bundles were isolated from rat diaphragm and incubated in Krebs-Ringer solution containing cytochrome c (10(-5) M), a standard assay for O2-.. Bundles were either passive or active, i.e., directly stimulated to contract rhythmically. After 1 h, absorbance of reduced cytochrome c in the incubation medium was measured at 550 nm. Absorbance was greater in medium exposed to passive muscle than in medium without muscle (P < 0.01), indicating O2-. release by passive muscle. Absorbance was greater in medium exposed to active muscle than in that exposed to passive muscle (P < 0.01), an increase inhibited by superoxide dismutase (10(3) U/ml). Active bundles fatigued; bundles developing the lowest final stresses produced the greatest absorbance increases (P < 0.001), suggesting that the magnitude of fatigue was inversely related to O2-. release. We conclude that O2-. is released by diaphragm myocytes into the interstitium and surrounding medium, a process accelerated by fatiguing muscular contractions.
Selective positive end-expiratory pressure and intracardiac dimensions in dogs
Authors: Veddeng O. J. , Myhre E. S. , Risoe C. , Smiseth O. A.
Published: December 2017

Effects of differential ventilation with general vs. selective right (R) and left (L) positive end-expiratory pressure (PEEP) on left (LV) and right ventricular (RV) end-diastolic dimensions were compared in seven pentobarbital-anesthetized dogs. All three modes of PEEP reduced LV cross-sectional area: general PEEP more than RPEEP and RPEEP more than LPEEP. General PEEP and, to a lesser degree, RPEEP decreased both the LV anteroposterior diameter and LV septum-free wall diameter, whereas LPEEP reduced the LV septum-free wall diameter only. Cardiac output was unaffected by LPEEP, whereas general PEEP (20 cmH2O) reduced cardiac output by 48%, and RPEEP (20 cmH2O) reduced it by 23%. RV septum-free wall diameter was not changed by any mode of PEEP. In conclusion, cardiac output was better maintained with selective PEEP than with general PEEP because LV filling was less impeded with selective PEEP. During LPEEP LV assumed a different configuration than during RPEEP and general PEEP, probably reflecting a different pattern of heart-lung interaction.
Effects of acute hypoxia on renal and endocrine function at rest and during graded exercise in hydrated subjects
Authors: Olsen N. V. , Kanstrup I. L. , Richalet J. P. , Hansen J. M. , Plazen G. , Galen F. X.
Published: December 2017

Renal effects of altitude hypoxia are unclear. Renal and hormonal function was investigated in eight males at rest and during graded exercise at sea level (SL) and 48 h after rapid ascent to 4,350 m (HA). HA did not change resting values of effective renal plasma flow (ERPF), glomerular filtration rate (GFR), sodium clearance (CNa), urine flow, or lithium clearance (CLi), which was used as an index of proximal tubular outflow. At rest, HA increased plasma norepinephrine concentration and decreased plasma concentrations of renin and aldosterone. Exercise decreased ERPF similarly in both environments. Normoxic exercise progressively reduced GFR, but at HA GFR only decreased during heavy exercise. This resulted in a higher filtration fraction during light and moderate hypoxic exercise. However, calculated absolute proximal reabsorption rate (GFR-CLi) at HA was higher during low-intensity exercise, and there were no significant differences between exercise-induced decreases in CLi, CNa, and urine flow at HA compared with SL. Exercise gradually increased plasma norepinephrine, but values were higher at HA during light and moderate exercise. The small changes in the renal response to low-intensity hypoxic exercise may be secondary to increased adrenosympathetic activity. However, antidiuretic and antinatriuretic effects of exercise were maintained in hypoxia and in both environments seemed to be the consequence of decreased proximal tubular outflow. The results demonstrate that renal glomerular and tubular function is well preserved in acute hypoxia despite marked hormonal changes.
Increased normoxic ventilation induced by repetitive hypoxia in conscious dogs
Authors: Cao K. Y. , Zwillich C. W. , Berthon-Jones M. , Sullivan C. E.
Published: December 2017

To determine if a long-lasting increase in normoxic ventilatory drive is induced in conscious animals by repetitive hypoxia, we examined the normoxic [arterial O2 saturation (SaO2) > 93%] ventilatory response following successive episodes of 2-min eucapnic hypoxic challenges (SaO2 = 80%) in awake tracheotomized dogs. End-tidal CO2 was maintained at the resting level during and after repetitive hypoxia. The experimental protocol was performed twice in each of five dogs on separate days. To determine if changes in normoxic ventilation occurred between episodes of repetitive hypoxia, data were compared from six periods (epochs) for all experiments. The mean minute ventilation (VI) during three normoxic periods between episodes of intermittent hypoxia was 135, 154, and 169% of control (P < 0.05). VI during a 30-min recovery period was still higher at 183 and 172% of control (P < 0.05). Normoxic VI between hypoxic and recovery periods was significantly higher than the corresponding values in sham experiments. Our results indicate that a long-lasting increase in normoxic ventilation can be evoked in an awake unanesthetized dog by a short exposure to repetitive hypoxia.
Modulation of respiratory responses to carotid sinus nerve stimulation by brain hypoxia
Authors: Melton J. E. , Yu Q. P. , Neubauer J. A. , Edelman N. H.
Published: December 2017

This study examines the effect of progressive isocapnic CO hypoxemia on respiratory afterdischarge and the phrenic neurogram response to supramaximal carotid sinus nerve (CSN) stimulation. Twelve anesthetized, vagotomized, peripherally chemodenervated, ventilated cats with blood pressure controlled were studied. During isocapnic hypoxemia, the amplitude of the phrenic neurogram was progressively depressed. In contrast, the increase in peak phrenic amplitude produced by CSN stimulation was unchanged, suggesting that the central respiratory response to CSN stimulation is unaffected by progressive hypoxemia. The time constant of respiratory afterdischarge (tau) was calculated from best-fit plots of phrenic amplitude vs. time after cessation of CSN stimulation. Under control conditions the value of tau was 57.7 +/- 3 (SE) s (n = 12). During progressive isocapnic hypoxemia, tau decreased as a linear function of arterial O2 content (CaO2) such that a 40% reduction of CaO2 resulted in a 48% reduction in tau. This reduction of respiratory afterdischarge may contribute to the genesis of periodic breathing during hypoxia.
Methylene blue inhibits hypoxic cerebral vasodilation in awake sheep
Authors: Iwamoto J. , Yoshinaga M. , Yang S. P. , Krasney E. , Krasney J.
Published: December 2017

Cerebral vasodilation in hypoxia may involve endothelium-derived relaxing factor-nitric oxide. Methylene blue (MB), an in vitro inhibitor of soluble guanylate cyclase, was injected intravenously into six adult ewes instrumented chronically with left ventricular, aortic, and sagittal sinus catheters. In normoxia, MB (0.5 mg/kg) did not alter cerebral blood flow (CBF, measured with 15-microns radiolabeled microspheres), cerebral O2 uptake, mean arterial pressure (MAP), heart rate, cerebral lactate release, or cerebral O2 extraction fraction (OEF). After 1 h of normobaric poikilocapnic hypoxia (arterial PO2 40 Torr, arterial O2 saturation 50%), CBF increased from 51 +/- 5.8 to 142 +/- 18.8 ml.min-1 x 100 g-1, cerebral O2 uptake from 3.5 +/- 0.25 to 4.7 +/- 0.41 ml.min-1 x 100 g-1, cerebral lactate release from 2 +/- 10 to 100 +/- 50 mumol.min- x 100 g-1, and heart rate from 107 +/- 5 to 155 +/- 9 beats/min (P < 0.01). MAP and OEF were unchanged from 91 +/- 3 mmHg and 48 +/- 4%, respectively. In hypoxia, 30 min after MB (0.5 mg/kg), CBF declined to 79.3 +/- 11.7 ml.min-1 x 100 g-1 (P < 0.01), brain O2 uptake (4.3 +/- 0.9 ml.min-1 x 100 g-1) and heart rate (133 +/- 9 beats/min) remained elevated, cerebral lactate release became negative (-155 +/- 60 mumol.min-1 x 100 g-1, P < 0.01), OEF increased to 57 +/- 3% (P < 0.01), and MAP (93 +/- 5 mmHg) was unchanged. The sheep became behaviorally depressed, probably because of global cerebral ischemia. These results may be related to interference with a guanylate cyclase-dependent mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)
Alterations of filtration coefficients in pulmonary edema of different pathogenesis
Authors: Koch T. , Duncker H. P. , Rosenkranz S. , Neuhof H. , Van Ackern K.
Published: December 2017

Different pathomechanisms in the development of pulmonary edema are being discussed. We investigated the effect of pathogenetically varying forms of edema on lung vascular barrier function in isolated cell-free perfused rabbit lungs. As an index of permeability, capillary filtration coefficients (Kfc) were determined from the slope of lung weight change over periods of stepwise venous pressure elevation (5, 7.5, and 10 mmHg) before (controls) and 60 min after edema induction. Edema was induced by venous congestion (n = 6), by application of arachidonic acid in the presence of diclofenac sodium (n = 6), and by elastase application (n = 6). Control values ranged from 0.28 to 0.51 ml.min-1 x mmHg-1 x 100 g-1. Kfc was significantly enhanced after edema induction up to 243% of control value in the hydrostatic edema, 357% in the arachidonic acid edema, and 594% in the elastase edema. When the alterations in capillary filtration due to the different types of edema were compared, Kfc was significantly higher in the proteinase edema, indicating an irreversibly damaged barrier function. These data exemplify different pathophysiological characteristics due to the pathogenesis of interstitial edema formation.
Running training attenuates the ACTH responses in rats to swimming and cage-switch stress
Authors: Watanabe T. , Morimoto A. , Sakata Y. , Tan N. , Morimoto K. , Murakami N.
Published: December 2017

The present study was carried out to investigate the effect of running training on adrenocorticotrophic hormone (ACTH) response in rats to swimming or cage-switch stress to determine whether, after physical training, a cross-adaptation develops in the ACTH responses induced by different types of stresses. Rats were trained by two different kinds of exercises and for two different periods of training: 1) swimming for 4 wk (4W-swimming), 2) running for 4 wk (4W-running), and 3) running for 10 wk (10W-running). Remaining rats were used for control for 4 wk (4W-control) and 10 wk (10W-control). The ACTH response induced by swimming stress was reduced after training by swimming (62.4%) or by running (13.8–16.4%). These training periods also attenuated the ACTH response induced by cage-switch stress (62.4% in the swimming group, 23.8–34.6% in the running groups). After swimming stress, the 4W-swimming and 10W-running groups showed smaller increases in blood glucose than the control groups. In addition, the increased levels of blood lactate in all the trained rats were significantly smaller than those in the control groups, suggesting that an adaptation was achieved after physical training. These results suggest that after running training, cross-adaptation is developed in the ACTH response induced by different types of physical (swimming) or psychological (cage-switch) stresses.
Development of pulmonary intravascular macrophage function in newborn lambs
Authors: Longworth K. E. , Westgate A. M. , Grady M. K. , Westcott J. Y. , Staub N. C.
Published: December 2017

We sought to determine whether pulmonary intravascular macrophages are involved in pulmonary vascular sensitivity to intravenously injected particles in sheep. We estimated that newborn lambs have few of these macrophages at birth but develop a 10-fold greater density within 2 wk. Awake, chronically instrumented newborn lambs showed no change in pulmonary vascular driving pressure (pulmonary arterial minus left atrial pressure) after injection of either liposomes [2 +/- 3 (SD) cmH2O; n = 5] or Monastral blue particles (3 +/- 2 cmH2O; n = 6) and showed no net pulmonary production of thromboxane B2, the stable metabolite of the vasoconstrictor thromboxane A2. In contrast, five of those lambs 2 wk later showed both an increase in pulmonary vascular driving pressure after injection of liposomes and Monastral blue (20 +/- 16 and 25 +/- 15 cmH2O, respectively; P < 0.05) and net pulmonary production of thromboxane B2 (171 +/- 103 and 429 +/- 419 pg/ml plasma, respectively; P < 0.05). Older lambs (n = 5) had higher pulmonary uptakes than newborn lambs (n = 6) of radioactive liposomes (47 +/- 13 vs. 12 +/- 10%; P < 0.01) and Monastral blue (53 +/- 6 vs. 21 +/- 10%; P < 0.05). We conclude that pulmonary intravascular macrophages are responsible for the sensitivity of sheep to intravenous foreign particles and are essential for a cascade of processes leading to microvascular injury.
Capsaicin-induced bronchial vasodilation in dogs: central and peripheral neural mechanisms
Authors: Pisarri T. E. , Coleridge J. C. , Coleridge H. M.
Published: December 2017

In 21 anesthetized dogs, we placed a flow probe around the right bronchial artery and examined changes in bronchial blood flow and bronchial vascular conductance when pulmonary C-fibers were stimulated by right atrial injection of capsaicin. When vagus nerves were intact, capsaicin evoked a pulmonary depressor chemoreflex and increased bronchial blood flow by 125% and bronchial vascular conductance by 175%; flow in an adjacent intercostal artery did not increase. Injection of color-coded microspheres revealed that blood flow to mucosa of lower trachea and to a peripheral bronchus doubled, whereas flow to posterior tracheal wall increased little. Cooling (to -1 degree C) or cutting cervical vagi (in 17 dogs) abolished the pulmonary chemoreflex and abolished all bronchial vascular effects in nine dogs but 33% of the vasodilation persisted in eight. In five of six dogs, this persisting vasodilation was potentiated by phosphoramidon (a neutral endopeptidase inhibitor that retards breakdown of neuropeptides released by C-fibers). Atropine reduced the capsaicin-induced bronchial vasodilation by approximately 30%. We conclude that the bronchial vasodilation was largely due to a centrally mediated vagal reflex and that a neuropeptide-dependent axon-reflex component was also present in about one-half the dogs.
Effects of fatigue on the length-tetanic force relationship of the rat diaphragm
Authors: Gauthier A. P. , Faltus R. E. , Macklem P. T. , Bellemare F.
Published: December 2017

It has been established that the in vivo operating length of the diaphragm corresponds to a wide range of the ascending limb of its length-tetanic force relationship. To investigate the length-dependent effects of fatigue on maximum force production, we constructed length-tetanic force relationships of rat costal diaphragm strips in vitro before and after fatigue induced by repetitive supramaximal electrical field stimulations at optimal length. Two levels of fatigue were studied (i.e., force reductions of 40 and 65% at optimal length). Results indicate that fatigue, when evaluated with high-frequency stimulations, causes a proportionately larger decrease in tetanic force at short muscle lengths as seen by a smaller control force-to-fatigue force ratio and an apparent shift in the length at which active force is zero. A possible explanation for the results obtained is failure of propagation of membrane depolarization into the t-tubule system at short muscle lengths, which is aggravated by fatigue evaluated by high-frequency stimulation.
Intended rather than actual movement velocity determines velocity-specific training response
Authors: Behm D. G. , Sale D. G.
Published: December 2017

Eight men and eight women trained 3 days/wk for 16 wk by doing attempted ballistic unilateral ankle dorsiflexions against resistance that either rendered the resultant contractions isometric (one limb) or allowed a relatively high-velocity (5.23 rad/s on an isokinetic dynamometer) movement (other limb). Training sessions consisted of five sets of 10 contractions of each type. Training produced the same high-velocity-specific training response in both limbs (P < 0.001). Peak torque increased most at 5.23 rad/s (38%) in comparison to lower velocities (0, 0.26, 0.52, 1.04, 1.55, 3.02, and 4.19 rad/s). Both limbs also showed similar increases in voluntary isometric rate of torque development (26%) and relaxation (47%) and in evoked tetanus rate of torque development (14%). A similar decrease in evoked twitch time to peak torque (6%) and half-relaxation time (11%) was also observed. Thus, all of these training responses, previously associated specifically with high-velocity resistance training, were produced by a training regimen that prevented an actual rapid movement through a range of movement. The results suggest that the principal stimuli for the high-velocity training response are the repeated attempts to perform ballistic contractions and the high rate of force development of the ensuing contraction. The type of muscle action (isometric or concentric) appears to be of lesser importance.
Blood-tissue transport of exogenous albumin and immunoglobulin G in genetically analbuminemic rats
Authors: Renkin E. M. , Tucker V. L. , Wiig H. , Kaysen G. , Sibley L. , DeCarlo M. , Simanonok K. , Wong M.
Published: December 2017

Tracer uptake studies were carried out in adult female Nagase (NA) strain analbuminemic rats [derived from Sprague-Dawley (SD) stock] and in adult female SD controls to determine the extent to which capillary permeability to plasma proteins is altered in the absence of endogenous albumin. Accessory measurements (arterial pressure, central venous pressure, plasma and interstitial fluid protein concentrations and oncotic pressures, plasma volume, and interstitial fluid volume) confirm the report of Joles et al. [Am. J. Physiol. 257 (Renal Fluid Electrolyte Physiol. 26): F23-F28, 1989] that shows elevated plasma volumes, normal interstitial fluid volumes, nearly normal plasma oncotic pressures (due to elevated globulin concentrations), and lower interstitial fluid oncotic pressures. In skin, skeletal muscles, and heart muscle, clearances of exogenous heterologous (bovine) albumin were 20–40% higher in NA than in SD controls. In intestine, albumin clearances were 20–30% lower. In NA rats blood-to-tissue clearances of heterologous (bovine) immunoglobulin G in skin and heart were higher and in the intestine they were lower than in SD controls; however, clearances in skeletal muscles were not elevated. The differences between NA and SD are small compared with the large increases in macromolecular permeabilities reported by others for organs and single microvessels perfused with albumin-free fluids.(ABSTRACT TRUNCATED AT 250 WORDS)