bluuebunny/crossref_metadata_2025 huggingface dataset:
Arytenoideus muscle activity in normal adult humans during wakefulness and sleep
Authors: Kuna S. T. , Insalaco G. , Villeponteaux R. D.
Published: December 2017

The respiratory-related activity of the arytenoideus (AR) muscle, a vocal cord adductor, was investigated in 10 healthy adults during wakefulness and sleep. AR activity was measured with intramuscular hooked-wire electrodes implanted by means of a fiber-optic nasopharyngoscope. Correct placement of the electrodes was confirmed by discharge patterns during voluntary maneuvers. The AR usually exhibited respiratory-related activity during quiet breathing in all awake subjects. Tonic activity was frequently present throughout the respiratory cycle. The pattern of phasic discharge during wakefulness exhibited considerable intrasubject variability both in timing and level of activity. Phasic activity usually began in midinspiration and terminated in mid- to late expiration. Periods of biphasic discharge were observed in four subjects. Phasic discharge primarily confined to expiration was also commonly observed. During quiet breathing in wakefulness, the level of phasic AR activity appeared to be directly related to the time of expiration. The AR was electrically silent in the six subjects who achieved stable periods of non-rapid-eye-movement sleep. Rapid-eye-movement sleep was observed in three subjects and was associated with sporadic paroxysmal bursts of AR activity. The results during wakefulness indicate that vocal cord adduction in expiration is an active phenomenon and suggest that the larynx may have an active role in braking exhalation.
Vagal afferent activity increases dynamical dimension of respiration in rats
Authors: Sammon M. P. , Bruce E. N.
Published: December 2017

Geometric and numerical techniques from nonlinear dynamics are employed to characterize the respiratory patterns of adult rats. In phase space constructions from volume measurements, the respiratory behavior of the vagotomized rat is seen to be unimodal and periodic, whereas that of the vagi-intact animal is bimodal and sensitive to initial conditions and displays stretching and folding of trajectories. By use of the correlation integral, the dimension and entropy were estimated for the respiratory patterns of five urethan-anesthetized rats (before and after vagotomy) and two awake animals (resting, vagi intact only). The results indicate that the central respiratory pattern of the anesthetized vagotomized rat behaves primarily as a single degree-of-freedom oscillator, which can be moved into a regime of low-order chaos in the presence of feedback from pulmonary stretch receptors, contributing significantly to the variability observed in the respiratory pattern of the vagi-intact animal. A model designed to emulate the Hering-Breuer inflation reflex demonstrates that the inspiration-inhibiting action of the reflex interacting with the oscillator at a critical phase transition is sufficient to drive the central pattern generator output into low-order chaos.
Respiratory compliance during sedation, anesthesia, and paralysis in infants and young children
Authors: Fletcher M. E. , Stack C. , Ewart M. , Davies C. J. , Ridley S. , Hatch D. J. , Stocks J.
Published: December 2017

Although total respiratory compliance (Crs) has been shown to fall in adults on induction of halothane anesthesia, no successful paired studies have been reported in children. The multiple occlusion technique was used to measure Crs in 17 infants and young children during sedated sleep (CrsS) and shortly after, following induction of halothane anesthesia (CrsA). Crs fell in all but one infant after induction of anesthesia, with a mean fall of 34.7% (range 0-58%). This was accompanied by a reduction in tidal volume and increase in frequency in every case. In 7 of the 17 children, who were to be paralyzed for surgical purposes, Crs was also measured in this anesthetized-paralyzed state. When tidal volume administered during manual ventilation was similar to that observed during measurement of CrsA, Crs during this low-volume ventilation was similar to CrsA. When tidal volume was increased and Crs remeasured, there was a significant increase in every case, with the high-volume Crs within 10% of CrsS in all but one child, in whom there was a 31.4% increase with respect to CrsS. Changes in tidal volume accounted for approximately 50% of the variability in each state. These results demonstrate a highly significant fall in Crs in infants and young children after induction of halothane anesthesia. In addition it appears that this reduction in Crs can be reversed by paralyzing the child and manually ventilating with tidal volumes approximating those seen during sedation.
Differential respiratory effects of HCO3- and CO2 applied on ventral medullary surface of rats
Authors: Tojima H. , Kuriyama T. , Fukuda Y.
Published: December 2017

To estimate whether H+ is the unique stimulus of the medullary chemosensor, ventilatory effects of HCO3- and/or CO2 applied on the ventral medullary surface using an improved superfusion technique and of CO2 inhalation were compared in halothane-anesthetized spontaneously breathing rats. Superfusion with low [HCO3-]-acid mock cerebrospinal fluid (CSF) (normal Pco2) induced a significant increase in ventilation, with an accompanying reduction in endtidal Pco2 (PETco2). High [HCO3-]-alkaline CSF depressed ventilation. Changes in Pco2 of superfusing CSF, on the other hand, had no significant effect despite the similar changes in pH. Simultaneous decrease in [HCO3-] and Pco2 of mock CSF with normal pH also maintained stimulated respiration. CO2 inhalation during superfusion with various [HCO3-] solutions caused further increase in ventilation as PETco2 increased. The results suggest that the surface area of the rat ventral medulla contains HCO3- (or H+)-sensitive respiratory neural substrates which are, however, little affected by CO2 in the subarachnoid fluid. A CO2 (or CO2-induced H+)-sensitive chemosensor responsible for the increase in ventilation during CO2 inhalation may exist elsewhere functionally apart from the HCO3- (or H+)-sensitive sensor in the examined surface area.
Adrenal activation and the prolactin response to exercise in eumenorrheic and amenorrheic runners
Authors: De Souza M. J. , Maguire M. S. , Maresh C. M. , Kraemer W. J. , Rubin K. R. , Loucks A. B.
Published: December 2017

Adrenocorticotropic hormone (ACTH), cortisol, and prolactin responses following maximal and submaximal (40 min at 80% maximal O2 consumption) running were studied in eumenorrheic (ER; n = 8, 29.0 +/- 1.5 yr) and amenorrheic (AR; n = 8, 24.5 +/- 2.0 yr) runners. ER were studied in the early follicular and midluteal phases of the menstrual cycle. Physical, training, and gynecological characteristics were similar, and cardiorespiratory and metabolic responses to the exercises were indistinguishable in the groups. ACTH, cortisol, and prolactin data from the follicular luteal phases in ER were combined for comparison to AR, because no differences were noted between the menstrual phases at rest. Similar preexercise ACTH levels and responses following exercise occurred in both groups, but preexercise cortisol levels were elevated (ER = 293.1 +/- 46.3, AR = 479.6 +/- 42.4 nmol/l) and cortisol responses blunted in AR. Adrenal sensitivity was blunted in AR compared with ER after submaximal (ER = 121.9 +/- 17.4, AR = 51.7 +/- 13.6) and maximal exercise (ER = 27.9 +/- 9.2, AR = 12.1 +/- 3.8). Preexercise prolactin levels were reduced (ER = 16.4 +/- 2.7, AR = 10 +/- 2.3 micrograms/l), and prolactin responses to maximal exercises were blunted in AR, despite high lactate levels (11.4 +/- 0.4 mmol/l). We conclude that 1) control for menstrual phase in ER is important in studies of prolactin responses following exercise but not in studies of ACTH and cortisol responses following exercise, 2) cortisol responses following submaximal and maximal exercise in AR are blunted at the adrenal level, 3) prolactin responses following submaximal and maximal exercise are also blunted in AR, and 4) prolactin responses following exercise may be mediated by adrenal activation.
Presynaptic regulation of cardiac sympathetic function in hypoxic guinea pigs
Authors: Whiteis C. A. , Lund D. D. , Schmid P. G.
Published: December 2017

In the normal heart, presynaptic cholinergic muscarinic and alpha 2-adrenergic mechanisms modify the fractional rate constant for norepinephrine (NE) synthesis (kNE), an index of sympathetic neural function. To evaluate presynaptic regulation of kNE, conscious guinea pigs subjected to normoxia and then hypoxia (n = 7-8 in each group) were pretreated with 1) vehicle; 2) a cholinergic muscarinic antagonist, methyl atropine; 3) an alpha 2-antagonist, yohimbine; or 4) a combination of the two. An increase of kNE was determined from incorporation of radiolabeled tyrosine into NE in a control period (arterial PO2 130 +/- 1.7 Torr, PCO2 36 +/- 0.5 Torr) and during a hypoxic state (PO2 49.6 +/- 1.0 Torr, PCO2 36 +/- 0.5 Torr). Hypoxia activated kNE in the atrioventricular node and right ventricular moderator band in vehicle-treated animals (P less than 0.05). Sympathetic activation was more general, however, because alpha 2-presynaptic influence acted to limit kNE in all tissues tested (P less than 0.05) except muscle, spleen, and posterior left ventricle. Cholinergic muscarinic presynaptic restraint on kNE was detected during hypoxia only in the left atrial appendage and lung (P less than 0.05). These data indicate that hypoxia increases kNE in the heart, but restraint by cholinergic muscarinic and alpha 2-adrenergic presynaptic mechanisms limits increases in neurotransmitter synthesis and noradrenergic activation regionally.
Ventilatory compensation for lactacidosis in ponies: role of carotid chemoreceptors and lung afferents
Authors: Erickson B. K. , Forster H. V. , Pan L. G. , Lowry T. F. , Brown D. R. , Forster M. A. , Forster A. L.
Published: December 2017

We investigated changes in arterial PCO2 (PaCO2) and pulmonary ventilation (VE) in normal, carotid chemoreceptor-denervated, and hilar nerve-denervated ponies during intravenous lactic acid infusion at rest and treadmill exercise at 1.8 mph-5% grade (mild) and 1.8 mph-15% grade (moderate). Lactic acid, (0.5 M) infusion of 0.10, 0.13, and 0.20 ml.min-1.kg-1 at rest and mild and moderate exercise increased arterial [H+] linearly throughout the 10 min of acid infusion. At 10 min of infusion, arterial [H+] had increased approximately 20 nmol/l (0.2 pH units) for each condition and group. Under most conditions, the temporal pattern of PaCO2 during acid infusion was biphasic. At rest and during mild exercise in all groups, and in carotid chemoreceptor-denervated ponies during moderate exercise, PaCO2 increased approximately 2 Torr (P less than 0.05) during the first 2 min of acid infusion. However, in normal ponies during moderate exercise, PaCO2 was not changed from control in the first 2 min of infusion. Between 2 and 10 min of infusion at rest and mild and moderate exercise in all groups, there was a 5-Torr significant decrease in PaCO2, which did not differ (P greater than 0.10) between groups. VE increased between 15-30 s and 2 min of infusion, but VE changed minimally between 2 and 10 min of infusion at rest and exercise in all groups of ponies. We conclude that lactacidosis does increase VE at rest and submaximal exercise in the pony.(ABSTRACT TRUNCATED AT 250 WORDS)
Cardiovascular adaptations in Andean natives after 6 wk of exposure to sea level
Authors: McKenzie D. C. , Goodman L. S. , Nath C. , Davidson B. , Matheson G. O. , Parkhouse W. S. , Hochachka P. W. , Allen P. S. , Stanley C. , Ammann W.
Published: December 2017

Six male Quechua Indians (34.0 +/- 1.1 yr, 159.5 +/- 2.1 cm, 60.5 +/- 1.6 kg), life-long residents of La Raya, Peru (4,350-m altitude with an average barometric pressure of 460 Torr), were studied using noninvasive methods to determine the structural and functional changes in the cardiovascular system in response to a 6-wk deacclimation period at sea level. Cardiac output, stroke volume, and left ventricular ejection fractions were determined using radionuclide angiographic techniques at rest and during exercise on a cycle ergometer at 40, 60, and 90% of a previously determined maximal O2 consumption. Subjects at rest were subjected to two-dimensional and M-mode echocardiograms and a standard 12-lead electrocardiogram. Hemoglobin and hematocrit were measured on arrival at sea level by use of a Coulter Stacker S+ analyzer. After a 6-wk deacclimation period, all variables were remeasured using the identical methodology. Hemoglobin values decreased significantly over the deacclimation period (15.7 +/- 1.1 to 13.5 +/- 1.2 g/dl; P less than 0.01). The results indicate that the removal of these high-altitude-adapted natives from 4,300 m to sea level for 6 wk results in only minor changes to the cardiac structure and function as measured by these noninvasive techniques.
Pattern of simulated snoring is different through mouth and nose
Authors: Liistro G. , Stanescu D. , Veriter C.
Published: December 2017

Cineradiography of the pharynx during simulated snoring was done in 6 healthy volunteers, and supraglottic pressure and flow rate were recorded in 12 others. We observed, immediately before snoring, a decrease in the sagittal diameter of the oropharynx followed, during snoring, by high-frequency oscillations of soft palate and pharyngeal walls. The pattern of soft palate oscillations was different while snoring through the nose or mouth. During inspiratory snoring through the nose, the soft palate remained in close contact with the back of the tongue and only the uvula presented high-frequency oscillations. Snoring through the mouth resulted in ample high-frequency oscillations of the whole soft palate. Frequency of airflow and supraglottic pressure oscillations was less (P less than 0.05) during mouth (28.2 +/- 7.5 Hz) than during nasal snoring (77.8 +/- 36.7 Hz). This difference may be related to the smaller oscillating mass (i.e., uvula) during nasal snoring. At variance with our previous data, which showed that snoring during sleep, in both heavy (nonapneic) snorers and obstructive sleep apnea patients, was systematically preceded by flow limitation, this was not true during simulated snoring.
Effect of chest wall vibration on breathlessness in normal subjects
Authors: Manning H. L. , Basner R. , Ringler J. , Rand C. , Fencl V. , Weinberger S. E. , Weiss J. W. , Schwartzstein R. M.
Published: December 2017

This study evaluated the effect of chest wall vibration (115 Hz) on breathlessness. Breathlessness was induced in normal subjects by a combination of hypercapnia and an inspiratory resistive load; both minute ventilation and end-tidal CO2 were kept constant. Cross-modality matching was used to rate breathlessness. Ratings during intercostal vibration were expressed as a percentage of ratings during the control condition (either deltoid vibration or no vibration). To evaluate their potential contribution to any changes in breathlessness, we assessed several aspects of ventilation, including chest wall configuration, functional residual capacity (FRC), and the ventilatory response to steady-state hypercapnia. Intercostal vibration reduced breathlessness ratings by 6.5 +/- 5.7% compared with deltoid vibration (P less than 0.05) and by 7.0 +/- 8.3% compared with no vibration (P less than 0.05). The reduction in breathlessness was accompanied by either no change or negligible change in minute ventilation, tidal volume, frequency, duty cycle, compartmental ventilation, FRC, and the steady-state hypercapnic response. We conclude that chest wall vibration reduces breathlessness and speculate that it may do so through stimulation of receptors in the chest wall.
Pulmonary blood flow and ventilation-perfusion heterogeneity
Authors: Domino K. B. , Eisenstein B. L. , Cheney F. W. , Hlastala M. P.
Published: December 2017

We studied the independent influence of changes in perfusion on pulmonary gas exchange in the left lower lobe (LLL) of anesthetized dogs. Blood flow to the LLL (QLLL) was raised 50% (increased QLLL) or reduced 50% (decreased QLLL) from baseline by partial occlusion of the right or left pulmonary artery, respectively. Minute ventilation and alveolar PCO2 of the LLL remained constant throughout the study. We determined ventilation-perfusion distributions of the LLL using the multiple inert gas elimination technique. Increased QLLL impaired LLL pulmonary gas exchange. All dispersion indexes and all arterial-alveolar difference areas increased (P less than 0.01). Decreased QLLL increased the log standard deviation of the perfusion distribution (P less than 0.05) and reduced the log standard deviation of the ventilation distribution (P less than 0.01) but did not affect the dispersion indexes or alveolar-arterial difference areas. We conclude that ventilation-perfusion heterogeneity is increased by independent changes in perfusion from normal baseline blood flow, even when ventilation and alveolar gas composition remain constant.
Role of the sympathetic nervous system in cold-induced hypertension in rats
Authors: Papanek P. E. , Wood C. E. , Fregly M. J.
Published: December 2017

Hypertension develops in rats exposed chronically to cold [6 +/- 2 degrees C (SE)] and includes both an elevation of mean arterial pressure and cardiac hypertrophy. Previous studies suggest that cold-exposed animals, at least initially, have a large sustained increase in the activity of their sympathetic nervous system, suggesting a failure of the baroreceptor system to provide sufficient negative feedback to the central nervous system. The present study was designed to investigate whether alterations in the activity of the sympathetic nervous system, including the baroreceptor reflex, occur during exposure to cold and whether they contribute to cold-induced hypertension. Twenty male rats were prepared with indwelling catheters in the femoral artery and vein. Ten of the rats were exposed to cold (6 +/- 2 degrees C) chronically, while the remaining 10 were kept at 26 +/- 2 degrees C. Withdrawal of arterial blood samples (less than 5 ml/kg), measurement of direct arterial pressures, and measurement of baroreflex function were carried out at 0800 h at intervals throughout the experiment. Norepinephrine and epinephrine concentrations in plasma were also determined at intervals throughout the experiment. Systolic, diastolic, and mean blood pressures of cold-exposed rats were increased to levels significantly above those of controls. The sensitivity of the baroreflex (delta heart period/delta mean arterial pressure) was decreased in the cold-treated group. The concentration of norepinephrine in plasma increased after 24 h of exposure to cold and remained elevated throughout the experiment, whereas the concentration of epinephrine in plasma increased initially but returned to control levels after 19 days of exposure to cold.(ABSTRACT TRUNCATED AT 250 WORDS)
Decreased reliance on lactate during exercise after acclimatization to 4,300 m
Authors: Brooks G. A. , Butterfield G. E. , Wolfe R. R. , Groves B. M. , Mazzeo R. S. , Sutton J. R. , Wolfel E. E. , Reeves J. T.
Published: December 2017

We hypothesized that the increased exercise arterial lactate concentration on arrival at high altitude and the subsequent decrease with acclimatization were caused by changes in blood lactate flux. Seven healthy men [age 23 +/- 2 (SE) yr, wt 72.2 +/- 1.6 kg] on a controlled diet were studied in the postabsorptive condition at sea level, on acute exposure to 4,300 m, and after 3 wk of acclimatization to 4,300 m. Subjects received a primed-continuous infusion of [6,6–2D]glucose (Brooks et al. J. Appl. Physiol. 70:919–927, 1991) and [3–13C]lactate and rested for a minimum of 90 min followed immediately by 45 min of exercise at 101 +/- 3 W, which elicited 51.1 +/- 1% of the sea level peak O2 consumption (VO2peak; 65 +/- 2% of both acute altitude and acclimatization). During rest at sea level, lactate appearance rate (Ra) was 0.52 +/- 0.03 mg.kg-1.min-1; this increased sixfold during exercise to 3.24 +/- 0.19 mg.kg-1.min-1. On acute exposure, resting lactate Ra rose from sea level values to 2.2 +/- 0.2 mg.kg-1.min-1. During exercise on acute exposure, lactate Ra rose to 18.6 +/- 2.9 mg.kg-1.min-1. Resting lactate Ra after acclimatization (1.77 +/- 0.25 mg.kg-1.min-1) was intermediate between sea level and acute exposure values. During exercise after acclimatization, lactate Ra (9.2 +/- 0.7 mg.kg-1.min-1) rose from resting values but was intermediate between sea level and acute exposure values. The increased exercise arterial lactate concentration response on arrival at high altitude and subsequent decrease with acclimatization are due to changes in blood lactate appearance.(ABSTRACT TRUNCATED AT 250 WORDS)
Simple validation for the hepatic venous cannula implanted chronically in conscious rats
Authors: Huang M. T.
Published: December 2017

A method for the detection of vena caval contamination in blood taken from hepatic venous cannulas in conscious rats was described. The procedures included 1) bolus injection of tritiated water (50 microCi) through a cannula into the abdominal inferior vena cava and 2) continuous blood sampling (less than 0.2 ml) from the hepatic venous cannula for 2 min into a 180-cm piece of Tygon tubing, starting concurrently with tracer injection. The washout of tritium was determined from samples in 15-cm sections of Tygon tubing. Because circulation from the inferior vena cava to the hepatic vein is interceded by the systemic circulation, the washout of tritium from a valid hepatic venous cannula should resemble the pattern determined elsewhere in the systemic circulation. In the current study, the reference systemic washout was determined in the superior vena cava of a group of rats similarly injected with tritiated water in the inferior vena cava. The maximum of tritium washout derived from a valid hepatic venous cannula should fall in the range encompassed by one standard deviation of the mean of the maximum of the reference (1,400 to 1,930 cpm/sample). The maximum of the washout pattern derived from the invalid cannula, which lay adjacent to the site of injection, was expected to exceed this range. On the basis of these criteria, hepatic blood flow (HBF) was determined by sulfbromophthalein (BSP) extraction in groups of rats with valid and invalid cannulas. HBF in rats with valid hepatic venous cannulas was 2.58 +/- 0.15 in the conscious state and 2.76 +/- 0.26 ml.min-1.g wet wt-1 in the ketamine-anesthetized state.(ABSTRACT TRUNCATED AT 250 WORDS)
Plasma protein osmotic pressure equations and nomogram for sheep
Authors: Yamada S. , Grady M. K. , Licko V. , Staub N. C.
Published: December 2017

The equations developed by Landis and Pappenheimer (Handbook of Physiology. Circulation, 1963, p. 961–1034) for calculating the protein osmotic pressure of human plasma proteins have been frequently used for other animal species without regard to the fractional albumin concentration or correction for protein-protein interaction. Using an electronic osmometer, we remeasured the protein osmotic pressure of purified sheep albumin and sheep plasma partially depleted of albumin. We measured protein osmotic pressures of serial dilutions over the concentration range 0–180 g/l for albumin and 0–100 g/l for the albumin-depleted proteins at room temperature (26 degrees C). Using a nonlinear least squares parameter-fitting computer program, we obtained the equation of best fit for purified albumin, and then we used that equation together with the measured albumin fraction to obtain the best-fit equation for the nonalbumin proteins. The equation for albumin is IIcmH2O,39 degrees C = 0.382C + 0.0028C2 + 0.000013C3, where C is albumin concentration in g/l. The equation for the nonalbumin fraction is IIcmH2O,39 degrees C = 0.119C + 0.0016C2. Up to 200- and 100-g/l protein concentration, respectively, these equations give the least standard error of the estimate for each of the virial coefficients. The computed number-average molecular weight for the nonalbumin proteins is 222,000. Using the new equations, we constructed a nomogram, based on the one of Nitta and co-workers (Tohoku J. Exp. Med. 135: 43–49, 1981). We tested the nomogram using 144 random samples of sheep plasma and lymph from 31 sheep. We obtained a correlation coefficient of 0.99 between the measured and nomogram estimates of protein osmotic pressure.
Ultrastructural appearances of pulmonary capillaries at high transmural pressures
Authors: Tsukimoto K. , Mathieu-Costello O. , Prediletto R. , Elliott A. R. , West J. B.
Published: December 2017

Electronmicroscopic appearances of pulmonary capillaries were studied in rabbit lungs perfused in situ when the capillary transmural pressure (Ptm) was systematically raised from 12.5 to 72.5 +/- 2.5 cmH2O. The animals were anesthetized and exsanguinated, and after the chest was opened, the pulmonary artery and left atrium were cannulated and attached to reservoirs. The lungs were perfused with autologous blood for 1 min, and this was followed by saline-dextran and then buffered glutaraldehyde to fix the lungs for electron microscopy. Normal appearances were seen at 12.5 cmH2O Ptm. At 52.5 and 72.5 cmH2O Ptm, striking discontinuities of the capillary endothelium and alveolar epithelium were seen. A few disruptions were seen at 32.5 cmH2O Ptm (mostly in one animal), but the number of breaks per millimeter cell lining increased markedly up to 72.5 cmH20 Ptm, where the mean frequency was 27.8 +/- 8.6 and 13.6 +/- 1.4 (SE) breaks/mm for endothelium and epithelium, respectively. In some instances, all layers of the blood-gas barrier were disrupted and erythrocytes could be seen moving into the alveolar spaces. In about half the endothelial and epithelial breaks, the basement membranes remained intact. The average break lengths for both endothelium and epithelium did not change significantly with pressure. The width of the blood-gas barrier increased at 52.5 and 72.5 cmH2O Ptm as a result of widening of the interstitium caused by edema. The cause of the disruptions is believed to be stress failure of the capillary wall. The results show that high capillary hydrostatic pressures cause major changes in the ultrastructure of the walls of the capillaries, leading to a high-permeability form of edema.
Dynamic response of the peripheral chemoreflex loop to changes in end-tidal O2
Authors: Berkenbosch A. , DeGoede J. , Ward D. S. , Olievier C. N. , VanHartevelt J.
Published: December 2017

We studied the peripheral ventilatory response dynamics to changes in end-tidal O2 tension (PETO2) in 13 cats anesthetized with alpha-chloralose-urethan. The arterial O2 tension in the medulla oblongata was kept constant using the technique of artificial perfusion of the brain stem. At constant end-tidal CO2 tension, 72 ventilatory on-responses due to stepwise changes in PETO2 from hyperoxia (45–55 kPa) to hypoxia (4.7–9.0 kPa) and 62 ventilatory off-responses due to changes from hypoxia to hyperoxia were assessed. We fitted two exponential functions with the same time delay to the breath-by-breath ventilation and found a fast and a slow component in 85% of the ventilatory on-responses and in 76% of the off-responses. The time constant of the fast component of the ventilatory on-response was 1.6 +/- 1.5 (SD) s, and that of the off-response was 2.4 +/- 1.3 s; the gain of the on-response was smaller than that of the off-response (P = 0.020). For the slow component, the time constant of the on-response (72.6 +/- 36.4 s) was larger (P = 0.028) than that of the off-response (43.7 +/- 28.3 s), whereas the gain of the on-response exceeded that of the off-response (P = 0.031). We conclude that the ventilatory response of the peripheral chemoreflex loop to stepwise changes in PETO2 contains a fast and a slow component.
Effect of dietary restriction and/or exercise on 23-h metabolic rate and body composition in female rats
Authors: Ballor D. L.
Published: December 2017

This study examined the effects of three levels of dietary intake [ad libitum fed (AL), moderately severe (MSR), and severe restriction (SR)] and two levels of exercise [cage confinement (CC) and exercise training (E)] on 23-h resting metabolic rate (RMR) and body composition in 47 female Sprague-Dawley rats. At the end of the 9-wk study, the MSR and SR groups weighed approximately 81 and 61%, respectively, of the AL-CC group. RMR was depressed for the MSR and SR groups compared with the AL-CC group. This was true whether expressed on an absolute (ml/min) or relative (ml.min-1.kg-0.75) basis. On a relative basis, which accounts for changes caused by weight loss alone, the RMR decreased by approximately 12 and 19%, respectively, for the MSR and SR groups compared with the AL-CC group. Although E resulted in significant differences in fat mass, percent fat, percent water, and heart mass between the AL groups, there were no significant differences between E and CC groups at either the MSR or SR level of dietary intake for any of the variables measured (i.e., body composition, muscle mass, RMR). Thus E does not appear to affect the composition of lost weight or RMR during diet-induced weight loss for female rats of normal weight.
Contribution of excising legs to the slow component of oxygen uptake kinetics in humans
Authors: Poole D. C. , Schaffartzik W. , Knight D. R. , Derion T. , Kennedy B. , Guy H. J. , Prediletto R. , Wagner P. D.
Published: December 2017

Rates of performing work that engender a sustained lactic acidosis evidence a slow component of pulmonary O2 uptake (VO2) kinetics. This slow component delays or obviates the attainment of a stable VO2 and elevates VO2 above that predicted from considerations of work rate. The mechanistic basis for this slow component is obscure. Competing hypotheses depend on its origin within either the exercising limbs or the rest of the body. To resolve this question, six healthy males performed light nonfatiguing [approximately 50% maximal O2 uptake (VO2max)] and severe fatiguing cycle ergometry, and simultaneous measurements were made of pulmonary VO2 and leg blood flow by thermodilution. Blood was sampled 1) from the femoral vein for O2 and CO2 pressures and O2 content, lactate, pH, epinephrine, norepinephrine, and potassium concentrations, and temperature and 2) from the radial artery for O2 and CO2 pressures, O2 content, lactate concentration, and pH. Two-leg VO2 was thus calculated as the product of 2 X blood flow and arteriovenous O2 difference. Blood pressure was measured in the radial artery and femoral vein. During light exercise, both pulmonary and leg VO2 remained stable from minute 3 to the end of exercise (26 min). In contrast, during severe exercise [295 +/- 10 (SE) W], pulmonary VO2 increased 19.8 +/- 2.4% (P less than 0.05) from minute 3 to fatigue (occurring on average at 20.8 min). Over the same period, leg VO2 increased by 24.2 +/- 5.2% (P less than 0.05). Increases of leg and pulmonary VO2 were highly correlated (r = 0.911), and augmented leg VO2 could account for 86% of the rise in pulmonary VO2.(ABSTRACT TRUNCATED AT 250 WORDS)
Lung ischemia-reperfusion injury in awake sheep: protection with verapamil
Authors: Wickersham N. E. , Johnson J. J. , Meyrick B. O. , Gilroy R. J. , Loyd J. E.
Published: December 2017

We caused unilateral lung ischemia-reperfusion injury in awake sheep by simultaneously occluding the left pulmonary artery and left main stem bronchus for 12 h. The occluded left lung was inflated with nitrogen. Reperfusion resulted in an elevation of lung lymph flow from 1.3 to 5.0 ml/15 min and an increase in lymph-to-plsma protein concentration ratios. Reperfusion, but not ischemia alone, caused an increase in wet-to-dry weight ratios in both the reperfused left lung and the contralateral right lung. Granulocytes increased in both lungs during the ischemic period and after reperfusion, and hypoxemia developed after reperfusion. The calcium channel antagonist, verapamil, given just before reperfusion, caused a marked attenuation in the reperfusion-induced changes in the lung lymph variables and wet-to-dry weight ratio. However, verapamil did not affect the hypoxemia or granulocyte sequestration seen after reperfusion. We conclude that reperfusion of ischemic sheep lung results in increased microvascular permeability that can be partially prevented by verapamil.
Leg exercise conditioning increases peak forearm blood flow
Authors: Silber D. , McLaughlin D. , Sinoway L.
Published: December 2017

To examine whether forearm vascular adaptations could occur after upright-leg exercise training, the reactive hyperemic blood flow after 10 min of forearm circulatory arrest (RHBF10) was studied. RHBF10 was examined in seven subjects before, at 2 wk, and after the completion of 4 wk of bicycle ergometer training. Maximal O2 consumption (VO2max) for leg ergometer work increased 13% (P less than 0.05) over 4 wk. Over that period of time RHBF10 in the forearm increased 50% (P less than 0.05), with a reciprocal drop in minimum vascular resistance. Resting heart rate decreased 15% (P less than 0.05) during the same period. Changes in RHBF10 and VO2max were noted after 2 wk of training. Mean arterial pressure did not change. We conclude that vascular adaptations can occur in the forearm muscle beds, even though the training regimen is designed to condition the lower extremities.
Alveolar and lung liquid clearance in the absence of pulmonary blood flow in sheep
Authors: Jayr C. , Matthay M. A.
Published: December 2017

The effect of removing pulmonary blood flow on the clearance of excess liquid and protein from the air spaces and interstitium of the normal lung was studied in anesthetized ventilated sheep. To eliminate pulmonary blood flow to one lung, the left pulmonary artery was occluded. Autologous serum (3 ml/kg) with 125I-labeled albumin was then instilled into the left lower lobe. Hemodynamics and lung lymph were measured, and the lungs were removed after 4 h. Alveolar protein concentration over 4 h was used as the index of alveolar liquid clearance. Total lung liquid clearance was measured by the gravimetric method. The percent increase in alveolar protein concentration over baseline was similar between sheep without pulmonary blood flow (33.8 +/- 17.4) and with pulmonary blood flow (31.1 +/- 14.6); thus, alveolar liquid clearance was not changed by the absence of pulmonary blood flow. Also, in the absence of pulmonary blood flow, lung liquid clearance (as percent of instilled) over 4 h was 27.1 +/- 3.8 (n = 7), which was not significantly different from control experiments with pulmonary blood flow (26.4 +/- 7.1, n = 7). In the sheep without pulmonary blood flow, bronchopulmonary anastomotic flow was 41.5 +/- 21.3 ml/min. To further reduce blood flow to the lung, both the left pulmonary artery and the bronchoesophageal artery were occluded, which reduced bronchopulmonary anastomotic flow to the left lung to 12.0 +/- 9.3 ml/min. This further reduction in blood flow did not, however, change alveolar or lung liquid clearance. Even with this low blood flow to the left lung, the removal of 125I-albumin from the lung was not altered.(ABSTRACT TRUNCATED AT 250 WORDS)
Perfusate cytochrome c reduction in isolated rabbit lungs
Authors: Bongard R. D. , Roerig D. L. , Johnston M. R. , Dawson C. A.
Published: December 2017

The reduction of ferricytochrome c within the perfusate in isolated lung perfusion systems has been demonstrated previously. We carried out the present study 1) to determine what reducing agents might be responsible for this reduction and 2) to determine whether the cytochrome c (cyto c) reduction within the recirculating perfusion system can be accounted for by relatively stable reducing agents released into the perfusate or whether some of the reduction is dependent on short-lived agents and/or proximity to the source of the agents within the lungs. Experiments were carried out with the use of isolated rabbit lungs perfused for 1 h in a recirculating system. In one group of experiments, ferricytochrome c was included in the recirculating perfusion system. In another group, the cyto c was added to produce the same concentration in samples after they were removed from a cyto c-free recirculating system. The recirculating cyto c was reduced at a rate of approximately 1.76 mumol/h, and approximately 22% was inhibitable by superoxide dismutase. Most of the rest could be inhibited by ascorbate oxidase within the recirculating perfusate. When the ferricytochrome c was added to the samples removed from the cyto c-free perfusion system, virtually the entire cyto c reducing capacity was inhibitable by ascorbate oxidase. Although reduced glutathione did accumulate in the recirculating perfusate, the quantity was not sufficient to have an important role in the cyto c reduction. We conclude that most of the cyto c reducing capacity within the lung perfusate could be accounted for by ascorbate released from the lungs.(ABSTRACT TRUNCATED AT 250 WORDS)
Mechanism of vasoconstriction in the rat's tail when warmed locally
Authors: Sakurada S. , Shido O. , Nagasaka T.
Published: December 2017

The vascular response of the tail to local warming was investigated in urethan-anesthetized rats whose colonic temperature was maintained at 39.5 degrees C with an intravenous thermode at an ambient temperature of 23 degrees C. The tail, covered with thin latex tubing, was immersed in temperature-controlled water initially kept at 35 degrees C. The tail was warmed by raising the water bath temperature from 35 to 44 degrees C at a constant rate. Tail blood flow (BF), mean arterial blood pressure (BP), and tail skin temperature (Tsk) were measured before and during the local warming. Tail vascular conductance (VC) was computed as 100 x tail BF/BP. When Tsk exceeded 37 degrees C, tail BF and VC significantly decreased from the levels at Tsk of 35 degrees C, and significant reductions in tail BF and VC occurred until Tsk reached 42 degrees C. Surgical deafferentation of the tail, chemical sympathectomy with 6-hydroxydopamine (100 mg/kg), and alpha-blockade with phentolamine (7 or 40.1–45.5 mg/kg) or phenoxybenzamine (5 mg/kg) failed to stop the decrease in tail BF and VC during the local warming. These results suggest that a reflex via the central nervous system and the alpha-adrenergic sympathetic nervous system is not indispensable for heat-induced vasoconstriction (HIVC). It is therefore assumed that, at least in the rat's tail, HIVC predominantly originates from a local vascular response to high temperature.
Effect of aminophylline on transpulmonary passage of venous air emboli in pigs
Authors: Vik A. , Jenssen B. M. , Brubakk A. O.
Published: December 2017

Aminophylline has been shown to dramatically reduce the filtering capacity of the lung in dogs during venous air embolism. Similarities have been pointed out between the cardiovascular and respiratory systems of the pig and of humans. We therefore wanted to find out whether aminophylline also modifies the transpulmonary spillover of microbubbles to the arterial circulation of the pig. Twenty-eight pigs were anesthetized with pentobarbital sodium and mechanically ventilated. Aminophylline was injected intravenously into 10 of the pigs before the introduction of air bubbles into the right ventricle, while the other 18 pigs served as controls. A transesophageal echocardiographic probe was used to detect eventual air bubbles in the left atrium or in the aorta. Pigs received either air infusion, at rates varying from 0.05 to 0.20 ml.kg-1.min-1, or calibrated microbubbles, 5–300 microns diam. We found that aminophylline-treated pigs did not show any change in spillover incidence compared with controls. Furthermore, in both groups the spillover during continuous air infusion seemed to be a preterminal event, because the pigs had very low arterial pressure when arterial bubbles were observed. Finally, there was an increase in mean pulmonary arterial pressure from 18 +/- 3.4 to 26 +/- 2.2 (SD) mmHg (n = 4, P less than 0.01) in aminophylline-treated pigs after a bolus injection of microbubbles (less than or equal to 50 microns, total volume less than 0.5 ml). Our results suggest that aminophylline does not modify the transpulmonary passage of microbubbles in this porcine model. In addition, it would seem that the pulmonary circulation of the pig is sensitive to very small volumes of air, when injected as microbubbles.
Low-intensity training produces muscle adaptations in rats with femoral artery stenosis
Authors: Yang H. T. , Ogilvie R. W. , Terjung R. L.
Published: December 2017

The effectiveness of a mild-intensity exercise program to induce adaptations within skeletal muscle of animals with peripheral arterial insufficiency was evaluated using an isolated perfused hindlimb preparation at a muscle blood flow similar to the peak found in vivo. Adult rats were subjected to bilateral femoral artery stenosis sufficient to limit peak blood flow during exercise but not alter resting blood flow. Stenosed-trained (Sten-Trained) rats walked on a treadmill at an easily achieved speed (20 m/min with a 15% grade) 5 days wk. Exercise tolerance improved from 10 min initially to 2 h/day. Non-stenosed-sedentary (Non-Sten-Sed) and stenosed-sedentary (Sten-Sed) animals were limited to cage activity. Oxygen delivery to the contracting muscles was similar among groups (7.0 +/- 0.4, 7.3 +/- 0.6, and 6.6 +/- 0.6 mumol.min-1.g-1 in Non-Sten-Sed, Sten-Sed, and Sten-Trained, respectively; n = 13 each). Force development was better maintained by Sten-Trained muscle (P less than 0.001) during a sequence of tetanic contraction conditions. Peak oxygen consumption was greater (P less than 0.05) in the Sten-Trained (5.23 +/- 0.34 mumol.min-1.g-1) than in Non-Sten-Sed (4.08 +/- 0.35) and Sten-Sed (4.34 +/- 0.37) rats. The increased peak oxygen extraction (P less than 0.05) by the muscle of the Sten-Trained rats (82.5 +/- 7.1% of oxygen inflow vs. 58.7 +/- 4.7 and 57.4 +/- 5.0%, respectively) was probably related to the increased muscle capillarity and mitochondrial enzyme activity.(ABSTRACT TRUNCATED AT 250 WORDS)
pH-induced effects on median frequency and conduction velocity of the myoelectric signal
Authors: Brody L. R. , Pollock M. T. , Roy S. H. , De Luca C. J. , Celli B.
Published: December 2017

H+ accumulation at the sarcolemma is believed to play a key role in determining the electrophysiological correlates of fatigue. This paper describes an in vitro method to externally manipulate muscle pH while measuring the resultant effect on surface-detected median frequency (MDF) and conduction velocity (CV) parameters. Hamster muscle diaphragm strips (n = 8) were isolated with the phrenic nerve intact and placed in an oxygenated Krebs bath (26 degrees C). The muscle was clamped to a noncompliant load cell to measure isometric contractile tension. Tetanic contraction was developed via 40-Hz supermaximal stimulation of the phrenic nerve. Differential signals were recorded from three electromyogram (EMG) detection surfaces for computation of CV (via the phase shift in the EMG signals) and MDF. Repeated trials were conducted at bath pHs of 7.4, 7.0, and 6.6. Bath pH was altered by aerating predetermined concentrations of O2 and CO2 into the bath. Decreases in bath pH resulted in decreases in both initial MDF and initial CV. The differences in initial MDF and initial CV were significant (P less than 0.001) for each of the bath pH conditions. In general, the change in bath pH resulted in an equal percent change in initial MDF and initial CV. This suggests that the change in bath pH caused a decrease in CV without significantly altering the fundamental shape of the M wave. In contrast, the EMG was altered differently during stimulated contractions. During stimulation, the rate of decay of CV was 65% of the rate of decay of MDF.(ABSTRACT TRUNCATED AT 250 WORDS)
Human serum catalase decreases endothelial cell injury from hydrogen peroxide
Authors: Leff J. A. , Oppegard M. A. , Terada L. S. , McCarty E. C. , Repine J. E.
Published: December 2017

Serum from normal human subjects contained variable amounts of catalase activity, which was inhibitable by heat, azide, trichloroacetic acid (TCA), or aminotriazole treatment. Serum also decreased hydrogen peroxide (H2O2) concentrations in vitro and H2O2-mediated injury to cultured endothelial cells. By comparison, heat-, azide-, TCA-, or aminotriazole-treated serum neither decreased H2O2 concentrations in vitro nor reduced H2O2-mediated damage to endothelial cells. We conclude that serum catalase activity can alter H2O2-dependent reactions. We speculate that variations in serum catalase activity may alter individual susceptibility to oxidant-mediated vascular disease or be a factor when added to test systems in vitro.
Sodium salicylate centrally augments ventilation through cholinergic mechanisms
Authors: Fleming H. , Burton M. , Johnson D. C. , Kazemi H.
Published: December 2017

Several different stimuli, including hydrogen ions, may exert their effect on central ventilatory control through cholinergic mechanisms. Salicylates are known to be central respiratory stimulants. Therefore this study explored whether the ventilatory effect of sodium salicylate (SAL) is through cholinergic mechanisms. Ventriculocisternal perfusion was used in spontaneously breathing anesthetized (pentobarbital sodium, 30 mg/kg) mongrel dogs to study the effects of SAL (50 mM), atropine (ATR, 4.8 mM), and SAL-ATR on ventilation. After 15 min of perfusion with mock cerebrospinal fluid, each test agent was perfused for 15 min at a rate of 1 ml/min. Cardiovascular and ventilatory parameters were monitored. Values at 15 min of test agent perfusion were compared with values at 15 min of mock cerebrospinal fluid perfusion, with each animal used as its own control. Body temperature was kept between 37.5 and 39.0 degrees C. Perfusion with SAL increased minute ventilation (VE) by 54% (P less than 0.005) and respiratory frequency by 50% (P less than 0.005). Tidal volume was not changed, but mean inspiratory flow rate increased (P less than 0.05). Perfusion with ATR decreased VE by 22% (P less than 0.1), and perfusion with SAL-ATR decreased VE by 20% (P = 0.01). No significant cardiovascular changes were noted in any group. We conclude that SAL increases VE centrally, primarily by increasing respiratory frequency. Because ATR blocked this effect, cholinergic mechanisms are probably involved in the salicylates' central stimulation of ventilation.
Rate of rise of intrapulmonary CO2 drives breathing frequency in garter snakes
Authors: Furilla R. A.
Published: December 2017

Garter snakes increase ventilation in response to elevated venous PCO2 without a concomitant rise in arterial PCO2 (Furilla et al. Respir. Physiol. 83: 47–60, 1991). Elevating venous PCO2 will increase the PCO2 gradient between pulmonary arterial blood and intrapulmonary gas during inspiration, leading to a greater rate of rise of intrapulmonary CO2 after inspiration. Because the lung contains CO2-sensitive receptors, I assessed the effect of the rate of rise of intrapulmonary CO2 on ventilation in unidirectionally ventilated snakes. CO2 concentration was altered using a digital gas mixer connected to a personal computer. Breathing frequency was highly correlated with the rate of rise intrapulmonary CO2 but only slightly affected by peak intrapulmonary CO2. On the other hand, tidal volume was more closely related to peak intrapulmonary CO2 than to the rate of rise of CO2. Bilateral pulmonary or cervical vagotomy nearly eliminated the ventilatory response associated with altered CO2 rise times but had little influence on the tidal volume response to the rate of rise of CO2. The mechanism whereby breathing frequency is controlled by the rate of rise of intrapulmonary CO2 is likely to originate with intrapulmonary chemoreceptors and may be important in the control of breathing during exercise.