bluuebunny/crossref_metadata_2025 huggingface dataset:
Cross-bridge regulation by Ca2+-dependent phosphorylation in amphibian smooth muscle
Authors: Wingard C. J. , Nowocin J. M. , Murphy R. A.
Published: December 2017

A covalent regulatory mechanism involving Ca2+-dependent cross-bridge phosphorylation determines both the number of cycling cross bridges and cycling kinetics in mammalian smooth muscle. Our objective was to determine whether a similar regulatory mechanism governed smooth muscle contraction from a poikilothermic amphibian in a test of the hypothesis that myosin regulatory light chain (MRLC) phosphorylation could modulate shortening velocity. We measured MRLC phosphorylation of Rana catesbiana urinary bladder strips at 25°C in tonic contractions in response to K+ depolarization, field stimulation, or carbachol stimulation. The force-length relationship was characterized by a steep ascending limb and a shallow descending limb. There was a rapid rise in unloaded shortening velocity early in a contraction, which then fell and was maintained at low rates while high force was maintained. In support of the hypothesis, we found a positive correlation of the level of myosin phosphorylation and an estimate of tissue shortening velocity. These results suggest that MRLC phosphorylation in amphibian smooth muscle modulates both the number of attached cross bridges (force) and the cross-bridge cycling kinetics (shortening velocity) as in mammalian smooth muscle.
Renal sympathoinhibition mediated by 5-HT1Areceptors in the RVLM during severe hemorrhage in rats
Authors: Dean C. , Bago M.
Published: December 2017

The role of 5-hydroxytryptamine type 1A (5-HT1A) receptors in the rostral ventrolateral medulla (RVLM) in the mediation of the sympathoinhibitory and hypotensive responses to severe hemorrhage was examined in pentobarbital sodium-anesthetized rats. The control response to hemorrhage (1 ml/min to 50 mmHg) consisted of a fall in arterial blood pressure and an initial baroreflex increase in renal sympathetic nerve activity followed after 2 min by a rapid decline in blood pressure accompanied by a decrease in renal sympathetic nerve activity. In response to hemorrhage in animals in which the specific 5-HT1A receptor antagonist WAY-100635 was microinjected into the pressor area of the RVLM, the fall in blood pressure was delayed and attenuated while renal sympathetic nerve activity was increased and maintained above baseline. In barodenervated animals with blockade of RVLM 5-HT1A receptors, there was no change in renal sympathetic nerve activity in response to hemorrhage. These data suggest that renal sympathoinhibition elicited in response to severe hemorrhage is mediated by 5-HT1A receptors in the RVLM.
In utero indomethacin alters O2 delivery to the fetal ductus arteriosus: implications for postnatal patency
Authors: Goldbarg Seth H. , Takahashi Yasushi , Cruz Carolyn , Kajino Hiroki , Roman Christine , Liu Bao Mei , Chen Yao Qi , Mauray Françoise , Clyman Ronald I.
Published: December 2017

Indomethacin produces constriction and hypoxia of the fetal ductus arteriosus. This is associated with death of smooth muscle cells in the ductus wall and an increased incidence of patent ductus arteriosus in the newborn period. We used fetal sheep to determine which factors are responsible for indomethacin-induced hypoxic cell death. Cell death in the ductus wall is directly related to the degree of indomethacin-induced ductus constriction and is present at both moderate and marked degrees of constriction. Both moderate and marked degrees of ductus constriction reduce vasa vasorum flow to the ductus (moderate = 69 ± 25%; marked = 30 ± 16% of preinfusion values) and increase the thickness of the ductus wall. In contrast, ductus luminal blood flow is not affected by moderate degrees of constriction and is reduced only after marked constriction. Although indomethacin increases ductus tone, it has no effect on ductus oxygen consumption. These findings suggest that the hypoxic cell death that occurs during the early stages of indomethacin-induced constriction is primarily due to changes in vasa vasorum blood flow and muscle media thickness.
Estrous influences on micturition thresholds of the female rat before and after bladder inflammation
Authors: Johnson O. L. , Berkley K. J.
Published: December 2017

Recent evidence suggests that lower urinary tract functions may be influenced by reproductive status, particularly under pathophysiological conditions. This study used repeated cystometrograms via a transurethral catheter to investigate the influence of estrous stage on micturition thresholds before and after turpentine-induced bladder inflammation in urethane-anesthetized female rats. Whereas there were no estrous influences on micturition threshold in the uninflamed bladder, micturition thresholds after bladder inflammation were significantly lower in rats in proestrus or estrus than in rats in metestrus or diestrus. Furthermore, the risk that the initial urethral catheterization and preinflammation cystometrogram would produce hematuria was significantly lower in estrus than in the other stages. These estrous influences are not readily explicable by levels of ovarian hormones at the time of testing and may relate instead to dynamic interactions between these hormones and other neuroactive molecules. In addition, the results here have relevance to interpretations of cystometrographic findings in the clinic and basic research.
Effects of tapering neonatal dexamethasone on rat growth, neurodevelopment, and stress response
Authors: Flagel Shelly B. , Vázquez Delia M. , Watson Stanley J. , Neal Charles R.
Published: December 2017

Dexamethasone is commonly used to lessen the morbidity of chronic lung disease in premature infants, but little is known regarding neurological consequences of its prolonged use. To study neurological effects of dexamethasone, we have developed a rat model in which newborn pups are exposed to tapering doses of dexamethasone at a time corresponding neurodevelopmentally to human exposure in the neonatal intensive care unit. On postnatal day (PD) 2, litters were divided into three groups: 1) handled controls, 2) saline-injected animals, and 3) animals injected with tapering doses of intramuscular dexamethasone between PD 3 and 6. Somatic growth and brain weight were decreased in dexamethasone-treated animals. Dexamethasone-treated animals demonstrated delays in gross neurological development on PD 7 and 14 but not PD 20. In late adolescence ( PD 33), dexamethasone-treated animals were less active in light and dark environments, while demonstrating a blunted serum corticosterone response to a novel stress. The dissociation between behavioral and hormonal stress responsiveness suggests that neonatal dexamethasone exposure permanently alters central nervous system function, particularly within the neuroendocrine stress axis. This may lead to increased risk for learning impairment and maladaptive responses to the environment.
Reduced stroke volume related to pleural pressure in obstructive sleep apnea
Authors: Tolle F. A. , Judy W. V. , Yu P. L. , Markand O. N.
Published: December 2017

Left ventricular stroke volume (LVSV) falls during obstructed inspiration in animals and normal human subjects through mechanisms that may be closely related to pleural pressure. In this study we postulated that a similar reduction in LVSV should occur in patients with obstructive sleep apnea (OSA). Daytime polysomnograms were performed in 10 patients with OSA. A noninvasive electrical impedance method was used to determine LVSV. Pleural pressure was measured by esophageal balloon. In comparison with awake values, during OSA we found reductions in LVSV, cardiac output, and heart rate of 18, 27, and 11%, respectively (P less than 0.01). We observed that systolic pleural pressure did not have a significant effect on LVSV (P greater than 0.05). However, at pleural pressures lower than 10 cmH2O below resting expiratory level, there was a linear relationship between falls in LVSV and falls in middiastolic pleural pressure (P less than 0.0001). We concluded that reduced LVSV shown in patients with OSA was significantly related to diastolic pleural pressure level. Our findings suggested reduced preload as the most likely mechanism for decreased cardiac output in OSA.
Ventilation and CSF ions during isocapnic HCl and HNO3 acidosis in conscious rabbits
Authors: Nattie E. E. , Reeder R.
Published: December 2017

In conscious rabbits with preimplanted arterial, central venous, and cisterna magna catheters, we infused HCl or HNO3 over 9 h to reduce plasma [HCO-3] by 9-14 mmol/l. We hypothesized that greater entry into cerebrospinal fluid (CSF) of a strong anion, NO-3 vs. Cl-, would reduce the strong ion difference and the [HCO-3], and we used isocapnic conditions to minimize the effects of PCO2-specific mechanisms of CSF HCO-3 regulation. Although CSF pH decreased slightly in both groups reflecting a small increase in CSF PCO2, we observed no significant change in CSF [HCO-3]. With HCl, there was no significant increase in CSF [Cl-], even though plasma [Cl-] increased 15-16 mmol/l. With HNO3, CSF [NO-3] increased 3.6-7.9 mmol/l, owing to the 18-22 mmol/l increase in plasma [NO-3], and resulted, not in a decrease in [HCO-3], as hypothesized, but in a decrease in [Cl-]. There was no difference in the ventilatory responses of the two groups. These results emphasize the importance of PCO2-dependent mechanisms in determining the CSF [HCO-3] and indicate that the strong anion mechanisms of CSF HCO-3 regulation can utilize changes in both NO-3 and Cl-.
Airway closure in humans does not result in overestimation of plethysmographic lung volume
Authors: Rodenstein D. O. , Francis C. , Stanescu D. C.
Published: December 2017

Exercise Physiol. 52: 638-641, 1982) have shown in dogs that airway closure may induce rib cage deformation and nonhomogeneous alveolar pressure swings, and they have suggested that this could lead to thoracic gas volume (TGV) overestimation by body plethysmography. However, in humans the rib cage is less easy to distort than in dogs. In four healthy volunteers we measured TGV by plethysmography before (B) and during (D) the occlusion of the middle and lower right lobes by a balloon (attached to a double-lumen catheter) positioned in the intermediate right bronchus. Subjects were trained to perform panting maneuvers preferentially with intercostals and accessory muscles or the diaphragm. Five to eleven TGV measurements were made in each subject with each panting pattern B and D occlusion. Balloon inflation resulted in no change in TGV whether low [13.3 +/- 3.4 (SD) cmH2O] or high (46.8 +/- 8.4 cmH2O) transdiaphragmatic pressures (Pdi) were used: TGV 4.0 +/- 0.4 (B) vs. 4.0 +/- 0.4 liters (D) and 4.3 +/- 0.4 (B) vs. 4.3 +/- 0.4 liters (D) for low and high Pdi, respectively. Thus, in trained subjects performing maneuvers aimed to distort the rib cage, no pressure difference was observed between the occluded and the nonoccluded lung during panting against the closed shutter. We conclude that it is unlikely that the mechanism proposed by Brown et al. might explain errors in lung volume measurements by body plethysmography in humans.
Hypohydration and heat acclimation: plasma renin and aldosterone during exercise
Authors: Francesconi R. P. , Sawka M. N. , Pandolf K. B.
Published: December 2017

This study was designed to assess the effects of hydration, acclimation, environment, and exercise on plasma levels of renin and aldosterone. Sixteen subjects exercised (1.34 m X s-1), both pre- and postacclimation, when euhydrated or hypohydrated (-5% of body wt) in a comfortable (20 degrees C, rh = 40%), hot-wet (35 degrees C, rh = 79%), or hot-dry (49 degrees C, rh = 20%) environment. Although light exercise in a thermoneutral environment had no effects on plasma levels of renin activity (PRA) or aldosterone (ALD), exercise in both hot environments resulted in significantly increased levels of both. Increments in both PRA and ALD were greater when hypohydrated, and PRA effects were significantly moderated by heat acclimation in both the euhydration and hypohydration experiments. Although PRA and ALD responses were generally correlated, acclimation did not consistently attenuate ALD increments. We concluded that hydration state, acclimation level, and environmental conditions all affected the responses of PRA and ALD to light exercise.
Changes in brain ECF pH during metabolic acidosis and alkalosis: a microelectrode study
Authors: Javaheri S. , De Hemptinne A. , Vanheel B. , Leusen I.
Published: December 2017

We used pH-sensitive double-barreled microelectrodes to measure brain extracellular fluid (ECF) pH in anesthetized dogs during isocapnic infusion acidosis (HCl) and alkalosis (Na2CO3) of 45-60 min duration. The diameter of the tips of these electrodes varied from less than 1 to 27 micron and were placed 5 mm below the surface of the parietal cortex. In group I (metabolic acidosis, n = 5) mean plasma and brain ECF pH fell significantly by 0.221 and 0.025, respectively, with changes in brain ECF pH being 11.3% of those noted in plasma. In group II (metabolic alkalosis, n = 5) mean plasma and brain ECF pH rose significantly by 0.170 and 0.049, respectively, with changes in brain ECF pH being 28.8% of those noted in plasma. Mean arterial and sagittal venous PCO2 and cisternal cerebrospinal fluid (CSF) acid-base variables did not change significantly during acid or base infusion. We conclude that during transients of isocapnic metabolic acid-base perturbations ionic gradients exist between brain ECF and CSF and that changes in brain ECF pH measured by microelectrodes follow the changes in plasma pH. These pH changes may play an important role in respiratory adaptations of acute metabolic acidosis and alkalosis.
Relationships among pressure, tension, and shape of the diaphragm
Authors: Whitelaw W. A. , Hajdo L. E. , Wallace J. A.
Published: December 2017

The shape of the diaphragm dome was calculated from transdiaphragmatic pressure and tension in the diaphragm. It was assumed that the muscle acts as a free membrane, attached at its edges to the inside of a vertical rib cage circular in cross section, that the attachments are inferior to the point at which the dome makes contract with the rib cage, and that the abdomen is filled with fluid with a hydrostatic gradient in pressure. The shape is different from a section of a sphere, with a radius of curvature substantially greater at the apex of the dome than at the sides. Observed shapes of human hemidiaphragm domes at functional residual capacity are not spherical but closely match the calculated shapes. Best-fitting shapes correspond to transdiaphragmatic pressures of about 3 cmH2O transdiaphragmatic pressure, suggesting that such a pressure and corresponding tension are present in the human diaphragm when it is at rest in an erect subject. In this model; as lung volume increases and the diaphragm shortens, its shape changes in such a way that the ratio between transdiaphragmatic pressure and tension in the diaphragm remains nearly constant, rather than increasing with volume. Such a model can explain the observation that the length-tension relationship of the muscle is much more important than curvature in determining the effectiveness of the diaphragm as a pressure generator.
Barometric plethysmograph: advantages and limitations in recording infant respiration
Authors: Fleming P. J. , Levine M. R. , Goncalves A. L. , Woollard S.
Published: December 2017

The barometric plethysmograph enables recordings to be made of respiration in undisturbed unrestrained infants. Its use has been limited by practical difficulties and errors in calculation of tidal volume (VT). We describe a modification of the method that overcomes the practical difficulties and a series of studies in which the barometric method was directly compared with pneumotachograph measurements of VT in infants. The effects of respiratory pattern and expired air temperature plus the most appropriate formula for calculation of VT under different conditions are described.
Ventilation by high-frequency oscillation of thorax or at trachea in rats
Authors: Harf A. , Bertrand C. , Chang H. K.
Published: December 2017

The efficiency of ventilation by high-frequency oscillation (HFO) applied to the thorax (external HFO) has been compared with that of HFO applied through a tracheal cannula (internal HFO) in a group of normal rats. Anesthetized, paralyzed, tracheotomized rats were placed in a whole-body plethysmograph. External HFO was achieved by varying the pressure surrounding the animal by means of a piston pump connected to the body plethysmograph; internal HFO was obtained in the same animals by connecting the pump to the tracheal cannula. Arterial CO2 and O2 partial pressures were measured in blood sampled from a carotid artery and were compared for external and internal HFO applied at 20 Hz with matched tidal volumes of 0.8, 1.4, 1.9, and 2.4 ml/kg. With increasing tidal volume, the mean arterial CO2 partial pressure decreased progressively from 68 to 30 Torr and was identical in the two modes of HFO; no difference was noted for the CO2 elimination or for the arterial O2 partial pressure. These results indicate that, in terms of gas exchange, external and internal HFO are equally efficient in normal rats.
Effect of mechanical loading on breathing patterns in women
Authors: Axen K. , Haas F. , Gaudino D. , Haas S. S.
Published: December 2017

First-breath ventilatory responses to graded inspiratory elastic and resistive loads were obtained from 80 women unfamiliar with respiratory experimentation. For each load 1) responses from different subjects ranged from a weak tidal volume defense coupled with an increased breathing frequency to a strong tidal volume defense coupled with a decreased frequency; 2) strong tidal volume defenders employed longer inspirations than did weak tidal volume defenders; and 3) individual respiratory frequency responses were mediated by changes in inspiratory and/or expiratory timing. Thus the group response was qualitatively the same as that reported for 80 men. Quantitatively, however, mean inspiratory airflow responses of women exceeded those of men by an amount attributable to women's higher intrinsic respiratory elastance. Tidal volume responses, on the other hand, did not differ significantly, suggesting that men and women produce different neural adjustments to loads. In support of this hypothesis, analysis of respiratory timing responses revealed that 1) men actively prolonged inspiration more than women during resistive loading; and 2) women actively shortened inspiration more than men during elastic loading. These findings indicate that the load-compensating behavior exhibited by men and women is similar but not identical.
Temperature effect on the human dive response in relation to cold water near-drowning
Authors: Hayward J. S. , Hay C. , Matthews B. R. , Overweel C. H. , Radford D. D.
Published: December 2017

To facilitate analysis of mechanisms involved in cold water near-drowning, maximum breath-hold duration (BHD) and diving bradycardia were measured in 160 humans who were submerged in water temperatures from 0 to 35 degrees C at 5 degrees C intervals. For sudden submersion BHD was dependent on water temperature (Tw) according to the equation BHD = 15.01 + 0.92Tw. In cold water (0–15 degrees C), BHD was greatly reduced, being 25–50% of the presubmersion duration. BHD after brief habituation to water temperature and mild, voluntary hyperventilation was more than double that of sudden submersion and was also dependent on water temperature according to the equation BHD = 38.90 + 1.70Tw. Minimum heart rate during both types of submersions (diving bradycardia) was independent of water temperature. The results are pertinent to accidental submersion in cold water and show that decreased breath-holding capacity caused by peripheral cold stimulation reduces the effectiveness of the dive response and facilitates drowning. These findings do not support the postulate that the dive response has an important role in the enhanced resuscitatibility associated with cold water near-drowning, thereby shifting emphasis to hypothermia as the mechanism for this phenomenon.
Estimation of skeletal muscle fiber number by mean fiber dry weight
Authors: Timson B. F. , Dudenhoeffer G. A.
Published: December 2017

The purpose of this study was to determine whether skeletal muscle fiber number could be accurately estimated by the determination of mean fiber dry weight (MFD) and total muscle dry weight. The muscles studied were the soleus, plantaris, gastrocnemius, extensor digitorum longus, tibialis anterior, and biceps brachii of the rat, the anterior latissimus dorsi of the chicken, and the flexor carpi radialis of the cat. Bundles of fibers were carefully separated from the muscle following nitric acid digestion (ND) and placed in groups of similar length. MFD determined from 400 to 800 fibers from each group was used to estimate the number of fibers in the remainder of the group. Estimated fiber number was compared with the fiber number determined in the muscle from the contralateral limb by the ND method. No difference in fiber number was observed between the ND method and the MFD estimation method for any of the muscles used in the study. The results indicate that the MFD estimation method is an accurate and relatively rapid method of fiber number determination in skeletal muscle.
Effects of cell swelling on fluid flow across alveolar epithelium
Authors: Schaeffer J. D. , Kim K. J. , Crandall E. D.
Published: December 2017

The effects of decreased temperature, metabolic inhibition, and hyposmolality on osmotically and hydrostatically driven water flux across bullfrog alveolar epithelium were studied. Lungs were isolated from double-pithed Rana catesbeiana and prepared as sacs. Either an osmotic (0.1 M raffinose) or hydrostatic (6.3–6.6 Torr) pressure gradient was imposed across the tissue. These gradients resulted in the volume flow of water from the alveolar to pleural bath. Control water flux and hydraulic conductivity were estimated from the rate of weight loss of the lung sac. Subsequently water flux and hydraulic conductivity were determined under one of the following conditions: 1) temperature of bathing solutions lowered to 2 degrees C; 2) 1 mM 2,4-dinitrophenol added to both alveolar and pleural baths, or 3) both baths changed to half-isosmotic Ringer solution. The control hydraulic conductivities for osmotic (Lpo) and hydrostatic (Lph) pressure gradients were 3.65(+/- 0.94) X 10(-12) and 2.14(+/- 0.63) X 10(-10) ml/dyn X s, respectively. Under conditions of metabolic inhibition, hyposmolality, and decreased temperature, Lph decreased by 77, 83, and 92%, and Lpo decreased by 56, 34, and 59%, respectively. These results are most consistent with the hypothesis that the decrements in hydraulic conductivity under our experimental conditions are due to epithelial cell swelling and perhaps to changes in the characteristics of the paracellular pathway.
Postnatal maturation of ventilation and breathing pattern in kittens: influence of sleep
Authors: Marlot D. , Bonora M. , Gautier H. , Duron B.
Published: December 2017

Ventilation and breathing pattern were studied in kittens at 1, 2, 3, 4, and 8 wk of life during quiet wakefulness (W), quiet sleep (QS), and active sleep (AS) with the barometric method. Tidal volume (VT), respiratory frequency (f), ventilation (VE), inspiratory time (TI), expiratory time (TE), mean inspiratory flow (VT/TI), and respiratory “duty cycle” (TI/TT) were measured. VT, VE, TI, TE, and VT/TI increased; f decreased and TI/TT remained constant during postnatal development in wakefulness and in both sleep states. No significant difference was observed between AS and QS for all the ventilatory parameters except TI/TT, which was greater in QS than in AS at 2 wk. VE was larger in W than in both AS and QS at all ages. This was mainly due to a greater f, TI/TT remaining constant. VT/TI, which represents an index of the central inspiratory activity, was larger in W than in sleep, VT not being significantly different whatever the stage of consciousness. The results of this study show that in the kitten 1) unlike in the adult cat, ventilation and breathing pattern are similar in QS and in AS; 2) in sleep, the central inspiratory drive appears to be independent of the type of sleep; and 3) in wakefulness, the increase of the central inspiratory activity could be related to important excitatory inputs.
Action of neck accessory muscles on rib cage in dogs
Authors: De Troyer A. , Kelly S.
Published: December 2017

To investigate the action of the neck accessory muscles on the rib cage, we stimulated the sternocleidomastoid and the scalenus muscles separately in supine anesthetized dogs. Hooks screwed into the sternum and ribs were used to measure their axial displacements and the changes in anteroposterior (AP) and transverse (T) diameters of the rib cage. We found that the sternocleidomastoid and scalenus muscles, when they contract alone, cause a large axial displacement of the sternum and the ribs in a cephalad direction and expand the rib cage along both its AP and T diameters. Opening the abdomen increased the cephalad displacement of the ribs and the expansion of the lower rib cage, particularly along its T diameter, but reduced the increase in lung volume. These experiments indicate 1) that the action of the sternocleidomastoid and scalenus muscles on the rib cage is essentially the consequence of a rotation of the ribs' neck axes, resulting from the cephalad displacement of the ribs, and 2) that the fall in abdominal pressure, almost certainly by acting through the zone of apposition of the diaphragm to the rib cage, has a deflationary action on the lower rib cage, more markedly so on its lateral than its anterior wall. The experiments also suggest that the fall in abdominal pressure prevents the diaphragm from moving cephalad and aids the neck accessory muscles in inflating the lungs.
Protein egress and entry rates in pleural fluid and plasma in sheep
Authors: Wiener-Kronish J. P. , Albertine K. H. , Licko V. , Staub N. C.
Published: December 2017

We determined a rate of protein egress from the pleural cavity into thoracic duct lymph in seven anesthetized sheep in whom we had made 10-ml/kg hydrothoraces containing 1% plasma protein labeled with 125I-albumin. The labeled protein left the pleural space at an average rate of 0.02 ml X kg-1 X h-1. In 25 unanesthetized sheep we injected labeled protein intravenously and collected pleural fluid and plasma at intervals up to 48 h. The radioactivity in the sheeps' plasma fell twice as rapidly as the rate observed in humans. The half time for equilibration between plasma and pleural fluid protein specific activity was approximately 6 h. In seven sheep we gave a continuous infusion of tracer protein. In six of these seven sheep we collected superficial cervical lymph. The protein concentration in the lymph was three times that of pleural fluid. The half time for protein specific activity equilibration between plasma and pleural fluid was 5 h and 3–4 h between plasma and superficial cervical lymph. The rate of protein turnover in the pleural space appears to be much slower than previously reported.
Adrenocortical responses to maximal exercise in moderate-altitude natives at 447 Torr
Authors: Maresh C. M. , Noble B. J. , Robertson K. L. , Seip R. L.
Published: December 2017

Serum hydrocortisone and aldosterone (Aldo) responses to maximal exercise were examined in six low-altitude natives (LAN) (373 m or less, aged 19–25 yr) and eight moderate-altitude natives (MAN) (1,830–2,200 m, aged 19–23 yr) at their residence (home) altitudes (740 and 587 Torr, respectively) and later in a hypobaric chamber at a simulated altitude of 4,270 m (447 Torr). After 2 days at their respective residence altitude and in the chamber, each subject exercised to voluntary exhaustion on the bicycle ergometer. Fluid intake was similar in both groups at all testing locations. Preexercise 24-h urinary Aldo was lower in both groups at 447 Torr but only significantly reduced in the LAN group. In general, the changes in maximum exercise cardiorespiratory variables were twice as large in LAN as in MAN subjects going from residence altitude to 447 Torr. Both serum hydrocortisone and Aldo concentrations were increased (P less than 0.01) after exercise in both groups at residence altitude and 447 Torr. Aldo was lower (P less than 0.05) postexercise at 447 Torr than at residence altitude in both groups, but this decrease was more pronounced (P less than 0.01) in the LAN group. Thus it appears that high-altitude Aldo concentrations are more like resident altitude values in MAN than in LAN subjects.
Exercise efficiency during arm ergometry: effects of speed and work rate
Authors: Powers S. K. , Beadle R. E. , Mangum M.
Published: December 2017

The purpose of this investigation was to determine the effects of increasing work rate and speed of movement on efficiency during steady-state arm crank ergometry (ACE). Ten men exercised at speeds of 50, 70, and 90 rpm and four power outputs (15, 30, 45, and 60 W). O2 uptake determinations were made using open-circuit spirometry and energy expenditure was calculated from the respiratory exchange ratio. Gross (work accomplished/energy expended), work (unloaded cranking as base-line correction), and delta (measurable work as base-line correction) efficiencies were computed. A curvilinear relationship was found to exist between work rate and energy expenditure, which dictates that both delta and work efficiency will decrease with increments in work. Work (range 20–29%) and delta (range 14–30%) efficiencies decreased with increases in power output. The result that gross efficiency (range 6–15%) increased with increments in work was due to the decreasing effect of the resting metabolic rate on the total energy expended. Gross, work, and delta efficiencies were lower (P less than 0.05) at 90 rpm when compared with the same work rate at 50 and 70 rpm. Although all of the exercise efficiencies tended to be lower at 70 rpm compared with work at 50 rpm, the difference was significant (P less than 0.05) only at 45 and 60 W. These data suggest that delta and work efficiencies during ACE are decreased with increments in either speed or power output. However, gross efficiency increases as a function of power output but decreases as a function of speed of movement.
Adrenalectomy and surfactant in adult rats
Authors: Liebowitz D. , Massaro G. D. , Massaro D.
Published: December 2017

We examined the effect of adrenalectomy (ADX) on aspects of the surfactant system of adult rats. Five days after bilateral ADX, ADX rats had about 20% less disaturated phosphatidylcholine (DSPC) in lung lavage returns (airway DSPC) than sham-operated rats, but the amount of tissue DSPC was not different between the groups; airway DSPC formed 12.8 +/- 0.5% of total DSPC (airway + tissue) in ADX and 15.9 +/- 0.7% in sham-ADX rats. An ultrastructural morphometric analysis of alveolar type 2 cells did not reveal an effect of ADX on lamellar body volume density or surface-to-volume ratio. ADX rats had heavier lungs (not as a result of edema) than sham-ADX rats. Treatment of ADX rats with hydrocortisone returned the amount of DSPC toward normal and eliminated the increase of lung weight. ADX did not alter the recoil of saline-filled lungs but did slightly increase the recoil of air-filled lungs. We conclude that corticosteroid hormones influence the in vivo functioning of the surfactant system of adult rats, but this effect seems to be slight.
Histamine and leukotrienes mediate pulmonary hypersensitivity to antigen in guinea pigs
Authors: Lamm W. J. , Lai Y. L. , Hildebrandt J.
Published: December 2017

To study roles of histamine and slow-reacting substance of anaphylasis (SRS-A) in mediating airway responses following antigen challenge, mediator antagonists were administered to guinea pigs sensitized with ovalbumin 10 days before the study. Twenty-three animals were divided into the following five treatment groups: 1) saline only (control 1, n = 5); 2) antigen challenged (n = 5); 3) antigen + methapyrilene (antihistamine, n = 5); 4) FPL 55712 only (SRS-A antagonist, control 2; n = 4), and 5) antigen + FPL 55712 (n = 4). Control groups were not sensitized. Experimental values were compared with those of control 1 at equal times after injections. Pulmonary resistance (RL), dynamic compliance (Cdyn), breathing frequency (f), tidal volume, minute ventilation (VE) and systemic arterial pressure were measured for 15–20 min just before (base line) and for up to 30 min after saline or antigen administration. Antigen challenge alone induced maximal respiratory changes at 5 min. RL increased 131 +/- 28% above base line (P less than 0.05), whereas Cdyn decreased slightly (28 +/- 10%, P less than 0.05). Antihistamine almost eliminated all changes in RL but did not affect decreased Cdyn. On the other hand, FPL 55712 eliminated changes in both RL and Cdyn. Both antagonists blocked the transient increase in VE, but neither blocked the rise in f at 5 min. We conclude that antigen-induced bronchoconstriction (RL) may be primarily mediated by histamine, whereas simultaneous alterations in Cdyn may depend mainly on leukotrienes and those in f depend on neither.
Attenuated skin blood flow response to hyperthermia in paraplegic men
Authors: Freund P. R. , Brengelmann G. L. , Rowell L. B. , Halar E.
Published: December 2017

To clarify how skin and internal temperatures interact in control of skin blood flow, five male paraplegic subjects (lesions at the level of thoracic vertebrae 1–11) (29–47 yr old) were heated in water-perfused suits to elevate oral temperature (To) 1–1.5 degrees C. In part I only the insensate skin was heated; sensate skin was kept at 32–34 degrees C. No appreciable elevation of forearm blood flow (FBF) or sweating occurred, even with To at 38 degrees C. In part II the suit was applied to the whole body so that skin temperature was 40 degrees C, except for one arm that remained at 32–34 degrees C for FBF measurement. Sweating was noted above the lesion in all but one subject. FBF increased in all subjects but was far below levels previously reported for hyperthermic normal men; also, thresholds appeared elevated. To the extent that effector connections are intact, attenuated FBF response implies that either 1) some vasoconstrictor bias associated with cardiovascular regulation is active or 2) thermoregulatory effector outflow is diminished. If the latter is true, it follows that the effector outflow reduction relates to diminished afferent input. But the component of the effector outflow contributed by peripheral thermoreception is small; thus these findings may indicate that what is lacking in the afferent input is central thermoreception from below the lesion, possibly from the spinal cord itself.
Effects of stopping exercise training on epinephrine-induced lipolysis in humans
Authors: Martin W. H. , Coyle E. F. , Joyner M. , Santeusanio D. , Ehsani A. A. , Holloszy J. O.
Published: December 2017

It has been reported that in rats endurance exercise training enhances the sensitivity of adipose tissue to the lipolytic action of catecholamines. The purpose of this study was to determine whether endurance training has a similar effect on the lipolytic response to epinephrine in humans. Four days after cessation of training, a constant infusion of epinephrine resulted in a significantly smaller increase in serum free fatty acids (0.57 +/- 0.40 vs. 1.06 +/- 0.30 mM; P less than 0.01) and blood glycerol (0.07 +/- 0.01 vs. 0.12 +/- 0.03 mM; P less than 0.01) and a greater rise in blood lactate (1.24 +/- 0.51 vs. 0.69 +/- 0.44 mM; P less than 0.01) above preinfusion levels than when the subjects were training. No further change in these responses occurred after 2 mo of inactivity. Plasma glucose and glucagon responses to epinephrine remained constant throughout the study. Plasma insulin concentrations before and during epinephrine infusion were higher than in the trained state only after 2 mo of inactivity. These findings suggest that epinephrine-induced lipolysis is enhanced in endurance-exercise-trained individuals but that this adaptation is lost very rapidly after cessation of exercise.
Bioelectric properties and ion flow across excised human bronchi
Authors: Knowles M. , Murray G. , Shallal J. , Askin F. , Ranga V. , Gatzy J. , Boucher R.
Published: December 2017

Bioelectric properties and ion transport of excised human segmental/subsegmental bronchi were measured in specimens from 40 patients. Transepithelial electric potential difference (PD), short-circuit current (Isc), and conductance (G), averaged 5.8 mV (lumen negative), 51 microA X cm-2, and 9 mS X cm-2, respectively. Na+ was absorbed from lumen to interstitium under open- and short-circuit conditions. Cl- flows were symmetrical under short-circuit conditions. Isc was abolished by 10(-4) M ouabain. Amiloride inhibited Isc (the concentration necessary to achieve 50% of the maximal effect = 7 X 10(-7) M) and abolished net Na+ transport. PD and Isc were not reduced to zero by amiloride because a net Cl- secretion was induced that reflected a reduction in Cl- flow in the absorptive direction (Jm----sCl-). Acetylcholine (10(-4) M) induced an electrically silent, matched flow of Na+ (1.7 mueq X cm-1 X h-1) and Cl- (1.9 mueq X cm-12 X h-1) toward the lumen. This response was blocked by atropine. Phenylephrine (10(-5) M) did not affect bioelectric properties or unidirectional ion flows, whereas isoproterenol (10(-5) M) induced a small increase in Isc (10%) without changing net ion flows significantly. We conclude that 1) Na+ absorption is the major active ion transport across excised human bronchi, 2) Na+ absorption is both amiloride and ouabain sensitive, 3) Cl- secretion can be induced by inhibition of the entry of luminal Na+ into the epithelia, and 4) cholinergic more than adrenergic agents modulate basal ion flow, probably by affecting gland output.
Fluid balance in ANTU-injured lungs during crystalloid and colloid infusions
Authors: Rutili G. , Parker J. C. , Taylor A. E.
Published: December 2017

A controversy exists as to the preferred solution for plasma volume replacement and cardiac output maintenance in the presence of lung injury. To evaluate these responses, crystalloid and colloid infusions were compared in dogs treated with 5 mg/kg of alpha-naphthylthiourea (ANTU), which produces a predictable increase in vascular permeability and extravascular water (QW) in the lung. A tracheobronchial lymphatic from the left lung was cannulated and left atrial (Pla) pressure, lymph flow, lymph-to-plasma protein concentration ratios, and thermal dilution cardiac output were monitored. Test infusions were either 15 ml/kg of 6% dextran 70 (DX) or 60 ml/kg of normal saline (NS) infused over 20 min. Solutions were infused 3 h after ANTU as follows: group I (DX); group II (NS), group III (DX, constant Pla); and group IV (NS, constant Pla). In groups III and IV, Pla was maintained constant by bleeding into a reservoir during an exchange transfusion. Postinfusion QW increased to 9.01 and 9.14 g/g blood-free dry wt for groups I and II, respectively, but there was no significant postinfusion increase in QW for groups III and IV compared with the 3-h preinfusion values. However, cardiac output was significantly higher at 5 h in group III compared with group IV. These studies indicate that capillary hydrostatic pressure was the major determinant of QW during the infusions but that DX maintained cardiac output significantly higher because of vascular retention of the colloids.
Newborn puppy cerebral acid-base regulation in experimental asphyxia and recovery
Authors: Nattie E. E. , Edwards W. H. , Marin-Padilla M.
Published: December 2017

We hypothesized that part of the newborn tolerance of asphyxia involves strong ion changes that minimize the cerebral acidosis and hasten its correction in recovery. After exposure of newborn puppies to 15 or 30 min experimental asphyxia (inhalation of gas with fractional concentration of CO2 and of O2 in inspired gas = 0.07–0.08 and 0.02–0.03, respectively), blood lactate increased to 13.2 and 23.4 mmol/l, respectively, brain tissue lactate increased to 14.4 and 19.7 mmol/kg, and cerebrospinal fluid (CSF) lactate increased to 7.6 and 14.4 mmol/l. We presume that the tissue lactate increase reflects increases in brain cell and extracellular fluid lactate concentration. The lactate increase, a change that will decrease the strong ion difference (SID), [HCO3-], and pH, was accompanied by increases in Na+ (plasma, CSF, brain), K+ (plasma, CSF), and osmolality without change in Cl-. After 60-min recovery, plasma and brain lactate decreased significantly, but CSF lactate remained unchanged. [H+] recovery was more complete than that of the strong ions due to hyperventilation-induced hypocapnia. We conclude that during asphyxia-induced lactic acidosis, changes in strong ions occur that lessen the decrease in SID and minimize the acidosis in plasma and CSF. To the extent that the increase in brain tissue sodium reflects increases in intra-and extracellular fluid sodium concentration, the decrease in SID will be less in these compartments as well. In recovery, CSF ionic values change little; plasma and brain tissue lactate decrease with a similar time course, and the [H+] is rapidly returned toward normal by hypocapnia even while the SID is below normal.
Airway responses in offspring of dogs with and without airway hyperreactivity
Authors: Hirshman C. A. , Downes H. , Veith L.
Published: December 2017

We examined airway responsiveness to aerosols of Ascaris suum, citric acid, and methacholine chloride in the offspring of two highly allergic breeds of dogs: Basenji-greyhounds (BG) and Basenjis (B). The BG parents had airway hyperresponsiveness to citric acid and methacholine, whereas the B parents did not. Both BG and B offspring were allergic as measured by many positive skin tests. BG offspring, like their parents, were hyperresponsive to citric acid and methacholine, whereas B offspring were not. We conclude that familial rather than environmental factors are important for the development of nonspecific airway hyperresponsiveness as well as allergy in the BG dog model of asthma. Allergic asthma in these animals represents a combination of two discrete processes: allergy and nonspecific airway hyperresponsiveness.
Positive end-expiratory pressure decreases bronchial blood flow in the dog
Authors: Baile E. M. , Albert R. K. , Kirk W. , Lakshaminarayan S. , Wiggs B. J. , Pare P. D.
Published: December 2017

Positive end-expiratory pressure (PEEP) increases pulmonary vascular resistance, but its effect on the bronchial circulation is unknown. We have compared two techniques for measuring bronchial blood flow in anesthetized, open-chest, ventilated dogs at varying levels of PEEP. Bronchial blood flow ( Qbr ) to the left lower lobe (LLL) and trachea was measured with radiolabeled microspheres. Total Qbr was partitioned into tracheal, bronchial, and parenchymal fractions. We also measured the bronchopulmonary anastomotic flow ( Qbra ) by attaching cannulas from the lobar pulmonary artery and vein to reservoirs, interrupting the LLL pulmonary blood flow and collecting the flow going into the reservoirs. We measured Qbr and Qbra in 10 animals ventilated with varying levels of PEEP (3, 10, and 15 cmH2O) applied randomly. Pulmonary venous pressure was kept at 0 cmH2O. There was no difference observed between Qbr and Qbra at PEEP 3 and 10 cmH2O, but at PEEP 15 cmH2O, Qbr was greater than Qbra , suggesting that at low left atrial pressures bronchial blood flow drains mainly to the left atrium, whereas at elevated alveolar pressures a larger fraction empties into the right side of the heart. PEEP decreased LLL Qbr and Qbra (P less than 0.01). That fraction of Qbr going to the trachea did not change with PEEP. However, the bronchial and parenchymal fractions decreased.
Metabolic availability of glucose ingested 3 h before prolonged exercise in humans
Authors: Jandrain B. , Krzentowski G. , Pirnay F. , Mosora F. , Lacroix M. , Luyckx A. , Lefebvre P.
Published: December 2017

The aim of the present study was to investigate the extent to which an oral load of glucose ingested 3 h before a 4-h exercise bout of moderate intensity represents an energy source readily available during that exercise. Therefore, five healthy male volunteers drank 100 g of naturally labeled [13C]glucose dissolved in 400 ml of water, rested for 3 h, and then exercised on a treadmill for the next 4 h at about 45% of their individual maximum O2 consumption. Total glucose oxidation was derived from nonprotein respiratory quotient and exogenous glucose oxidation evaluated by the 13C methodology as previously described. Total carbohydrate oxidation averaged 285 +/- 17 g during the 7 h of the test, the global amount of carbohydrate oxidized during the exercising period was 253.1 +/- 16.9 g/4 h. Exogenous glucose oxidation averaged 11.3 +/- 0.7 g during the 3-h period of rest and increased markedly after the beginning of exercise, reaching 18.9 +/- 2.2 g/30 min during the first 30 min of exercise; the total amount of exogenous glucose oxidized during the 4 h of exercise was 67.5 +/- 9.4 g. Throughout the whole period of exercise, blood glucose concentrations remained between 3.5 and 4.0 mmol/l. Exercise induced a major fall in plasma insulin levels that reached undetectable values after 3 and 4 h, whereas plasma glucagon levels tended to rise, but their level never significantly exceeded the basal values; plasma free fatty acids and glycerol increased markedly during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)
Adaptive responses of rats trained with reductions in exercise heart rate
Authors: Mullin W. J. , Herrick R. E. , Valdez V. , Baldwin K. M.
Published: December 2017

This study was designed to test the hypothesis that rats trained with marked reductions in exercise heart rate respond with adaptations indicative of increased intrinsic myocardial performance. Therefore, we measured changes in maximum work capacity (VO2max), biochemical-functional indexes of cardiac contractile capacity, and skeletal muscle oxidative capacity in normal-trained (NT) rats and in rats trained while receiving the selective cardiac beta 1-blocking drug atenolol (AT). Training consisted of treadmill running at approximately 80% VO2max (untrained) for 1-h duration, 6 days/wk, for a total of 8 wk. Exercise heart rate of the AT group was markedly reduced and averaged 140 beats/min below the NT group for any given session. Compared with sedentary controls, VO2max was increased by 11%, and red vastus lateralis muscle citrate synthase activity was increased by 28% in both AT and NT groups (P less than 0.05). There were no differences between trained and nontrained groups with regard to Ca2+-regulated myofibril adenosinetriphosphatase. In situ derived left ventricular pressure and the maximum rate of left ventricular pressure development were not augmented relative to sedentary control values when the trained hearts were either stimulated inotropically or maximally afterloaded . These findings suggest that maximum exercise capacity can be enhanced in rodents conditioned with and without limited elevation in exercise heart rate; however, this reduction of exercise heart rate acceleration does not provide a stimulus to enhance the intrinsic functional capacity of the rodent heart.
Comparison of amounts of collagen and elastin in pleura and parenchyma of dog lung
Authors: Oldmixon E. H. , Hoppin F. G.
Published: December 2017

Pressure-volume characteristics of the lung have been thought to be due primarily to the properties of the network of alveolar septa. However, Hajji et al. (J. Appl. Physiol.: Respirat . Environ. Exercise Physiol. 47: 175–181, 1979) attributed a substantial role to the visceral pleura. Seeking a structural explanation for this result, we compared the relative amounts of collagen fibrils and elastin fibers in the visceral pleura and alveolar parenchyma using stereological measurements in five canine lobes. We found about one-fifth as much collagen and one-tenth as much elastin in the pleura as in the alveolar parenchyma. This structural result confirms the functional conclusions of Hajji et al. We argue that such a substantial structure is not needed for protection against overinflation but may have to do with stabilization of lobe shape or handling of frictional forces.