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Biomedical subjects

A Wanner

Publications and source records attributed to A Wanner.

At least 37 records · Page 2Linked to original sources
PubMed1996

Endothelial and epithelial sources of endothelin-1 in sheep bronchi.

Airway smooth muscle tone and growth is regulated by endothelin-1 (ET-1), but the sources of ET-1 in the airway wall have not been clearly defined. We therefore wished to estimate the relative contributions of the epithelium and endothelium to ET-1 production in the bronchi (mean ID 1.7-4.9 mm) of mature normal sheep. Morphometric assessment of bronchial cross-sections revealed a number of epithelial cells three times greater than endothelial cells by direct cell count. In contrast, the overall cell surface density was five to six times greater, and the airway smooth muscle-centered cell surface density was three to four times greater for endothelial cells than for epithelial cells. The expression of preproendothelin-1 mRNA was detected in cultured aortic endothelial cells (as a substitute for bronchial endothelial cells) but not in cultured bronchial epithelial cells, and the former secreted seven times more immunoreactive ET-1 than the latter. These findings show that topographically the endothelium is better positioned for the regulation of ovine bronchial smooth muscle than the epithelium. Furthermore, the findings suggest greater constitutive ET-1 secretion by cultured endothelium than by epithelium.

Animals↗
PubMed1996

Effect of inhaled and intravenous acetylcholine on bronchial blood flow in anesthetized sheep.

The reported effects of cholinergic agonists on bronchial blood flow (Qbr) have been inconsistent. The aim of the present study was to determine whether the inconsistency could be due to the mode of agonist administration (systemic vs. aerosol) or the anatomic site of blood flow in the bronchus (mucosal vs. deep wall). In 10 anesthetized mechanically ventilated adult sheep, we measured Qbr in main bronchi by color-coded microspheres, systemic and pulmonary arterial pressures, cardiac output, and lung resistance (RL) before and after acetylcholine (ACh) administered either as an aerosol (nebulized dose 100 micrograms) or as an intravenous bolus (2 micrograms/kg). Before drug administration, 72% of mean Qbr was distributed to the bronchial mucosa and the remainder was distributed to the deep bronchial wall. For a comparable increase in mean RL (150% for intravenous ACh and 205% for aerosol ACh), mean total Qbr normalized for systemic arterial pressure increased by 291% after intravenous ACh (P < 0.05) and decreased by 9% after aerosol ACh (not significant). Mucosal and deep wall Qbr increased proportionally. Atropine (0.2 microgram/kg) prevented the changes in Qbr and RL after intravenous ACh. Thus intravenous but not aerosol ACh increased blood flow in the mucosa and deep wall of extrapulmonary bronchi. This suggests that the muscarinic receptors mediating vasodilation are more accessible to intravascular than intrabronchial ACh.

Acetylcholine↗
PubMed1996

The interaction of alpha 1-proteinase inhibitor and tissue kallikrein in controlling allergic ovine airway hyperresponsiveness.

We reported previously that the development of airway hyperresponsiveness (AHR) 24 h after antigen challenge in allergic sheep was associated with increased tissue kallikrein activity (TK) and decreased alpha-1-proteinase inhibitor (alpha 1-PI) activity in bronchoalveolar fluid (BAL). The inverse correlation between TK and alpha 1-PI in these experiments suggested that administration of alpha 1-PI might reduce TK activity and block AHR. To test this hypothesis, airway responsiveness, as determined by calculating the cumulative carbachol breath units (BU) that increased specific lung resistance by 400% (PC400), was measured before and 24 h after aerosol challenge with Ascaris suum antigen in seven sheep hypersensitive to this antigen. On the next day, 30 min before the 24 h PC400 measurement, the sheep were treated with either aerosol alpha 1-PI (Prolastin, 10 mg/5 ml) or denatured (DN) prolastin (10 mg/5 ml), which had only 10% of its original activity. BAL was also performed before and 24 h after challenge for the measurement of TK and alpha 1-PI activity. Treatment with DN-Prolastin at 24 h after antigen challenge did not block antigen-induced AHR: PC400 fell from a baseline (mean +/- SE) of 26.0 +/- 3.2 BU to 11.2 +/- 1.5 BU after challenge (p < 0.05). This AHR was associated with increased TK (363%, p < 0.05) and decreased alpha 1-PI activity (65%, p < 0.05). Prolastin treatment at 24 h blocked the AHR: PC400 was 21.0 +/- 2.8 before and 23.2 +/- 3.7 after challenge (p < 0.05 versus DN-Prolastin) and the changes in BAL TK (28% increase) and alpha 1-PI activities (15% increase) were not different from baseline (both p < 0.05 versus DN-Prolastin). There was a significant inverse correlation between alpha 1-PI activity and TK activity in BAL, as well as the changes between baseline and 24 h in alpha 1-PI activity and TK activity in BAL Pretreatment (30 min before antigen challenge) with Prolastin also protected against the antigen-induced AHR. The effect of Prolastin was also seen against aerosol challenge with high-molecular-weight kininogen (HMWK), a substrate of TK. HMWK caused bronchoconstriction which was blocked by Prolastin (p < 0.05), and the bradykinin B2 antagonist, NPC-567 (indicating that kinins were generated), but not DN-Prolastin or the elastase inhibitor, ICI 200, 355. Although the negative association between alpha 1-PI activity and TK activity identified in this study does not prove cause and effect, our findings do raise the possibility that in vivo alpha 1-PI may regulate TK activity and allergen-induced AHR.

Administration, Inhalation↗
PubMed1996

Endothelin-1 depresses tracheal mucus velocity in ovine airways via ET-A receptors.

Endothelin-1 (ET-1) is a potent constrictor of bronchial smooth muscle, but there is limited information on its actions on the airway mucociliary clearance in vivo. The purpose of this study was to determine (1) the effect of aerosolized ET-1 on tracheal mucus velocity (TMV), a marker of mucociliary clearance, in sheep and (2) if the ET-1-induced effects were mediated by ET-A or ET-B receptors. To measure TMV, radiopaque teflon particles were insufflated into six intubated, spontaneously breathing, adult sheep, and the velocity at which these particles traveled up the trachea was measured using a previously reported roentgenographic technique. After baseline TMV measurements, 50 breaths of either ET-1 (10(-7) M) or vehicle (phosphate-buffered saline) were aerosolized into the airways. TMV measurements were then obtained over a 2-h period. After exposure to ET-1, mean TMV decreased significantly as compared with vehicle, the effects being most marked within 30 min after administration (54%, p < 0.05). On subsequent days, animals were pretreated with an aerosolized ET-A receptor antagonist (BQ-123) or an ET-B receptor antagonist (BQ-788) before exposure to ET-1. When ET-1 was given after BQ-123, no significant drop in TMV was noted. In contrast, pretreatment with BQ-788 exhibited no protective effect on the decrease in TMV. The ET-1 effects were not influenced by pretreatment with either the cyclo-oxygenase inhibitor indomethacin or the leukotriene receptor antagonist MK-571, indicating that ET-1-induced depression in TMV does not involve the activation of prostanoids or peptide leukotrienes. Thus, exogenous ET-1 reduces TMV, an in vivo effect that is mediated through stimulation of ET-A receptors.

Aerosols↗
PubMed1996

Effect of hyperventilation on airway mucosal blood flow in normal subjects.

The purpose of this study was to determine the effect of hyperventilation (40 L/min) with room air (25 degrees C; 70% relative humidity) and frigid air (-10 degrees C; 0% relative humidity) on airway mucosal blood flow (Qaw) in normal subjects (n = 7; 26 to 54 yr of age). Qaw was measured with the dimethyl ether uptake technique, which reflects blood flow in the mucosa of large airways corresponding to a 50-ml anatomic dead space segment extending distally from the trachea. Mean (+/- SE) baseline Qaw during quiet (room air) breathing was 6.6 +/- 0.6 ml/min (range, 3.9 to 10.9). Qaw failed to change significantly during and after eucapnic hyperventilation with room air (thermal stress, 224 cal/min). In contrast, eucapnic hyperventilation with frigid air (thermal stress, 720 cal/min) increased Qaw in every subject, with the peak value occurring either during or over a 30-min period after hyperventilation; by 60 min, Qaw had returned toward baseline. The mean maximal Qaw was 310 +/- 49% of baseline (p < 0.05). Neither type of hyperventilation had an effect on airway resistance. We conclude that in normal subjects, Qaw increases during and/or after eucapnic hyperventilation with frigid air, and that this response is related to the magnitude of the thermal stress rather than to the level of ventilation.

Adult↗
PubMed1996

Metaproterenol responsiveness after methacholine- and histamine-induced bronchoconstriction.

We investigated whether the bronchodilator response to a beta-adrenergic agonist is influenced by the mechanism of induced bronchoconstriction. Normal subjects and asymptomatic asthmatics inhaled a dry aerosol (mass median aerodynamic diameter, 1.5 microns) with increasing concentrations of methacholine or histamine to produce a 35% decrease in specific airway conductance (SGaw), followed by a single inhalation of a metaproterenol aerosol. By studying normal subjects and asthmatics, we were able to compare metaproterenol responsiveness after widely divergent doses of the bronchoprovocative agents but the same degree of bronchoconstriction. Airway deposition of methacholine, histamine, and metaproterenol was measured using a quinine fluorescence technique. Mean baseline SGaw, metaproterenol responsiveness, and metaproterenol mass deposited were similar in normal subjects and asthmatics. Likewise, mean SGaw after completion of methacholine and histamine challenge, and the subsequently deposited metaproterenol mass were similar in the two groups. After methacholine challenge (mean +/- SD provocative drug mass causing a 35% decrease in SGaw, PM35: 8.94 +/- 5.96 mumol in normal subject and 0.30 +/- 0.29 mumol in asthmatics), metaproterenol increased mean SGaw by 89 +/- 33% in normal subjects and by 190 +/- 55% in asthmatics (p < 0.05, two-way analysis of variance). After histamine challenge (PM35, 2.92 +/- 2.49 mumol in normal subjects and 0.17 +/- 0.29 mumol in asthmatics), metaproterenol increased mean SGaw by 111 +/- 38% in normal subjects and 113 +/- 69% in asthmatics (p = not significant). Thus, for the same degree of bronchoconstriction, metaproterenol responsiveness was influenced by the dose of methacholine but not the dose of histamine. The differential metaproterenol response could be related to a functional antagonism between muscarinic and beta-adrenergic agonists.

Adrenergic beta-Agonists↗
PubMed1995

Measurement of airway mucosal blood flow with dimethylether: validation with microspheres.

We have recently developed a noninvasive dimethylether (DME) uptake technique to estimate airway mucosal blood flow (Qaw) in humans (12). Because it was not feasible to validate the technique directly, we undertook the present study to compare Qaw as measured by DME (QDME) and by color-coded microspheres (QM) as a standard in seven anesthetized sheep prepared with a carotid and a left atrial catheter. QDME was determined by measuring DME uptake with multiple breath holds after passive inflation with a DME-helium gas mixture, simulating the technique used in humans. After the microspheres were injected into the left atrium, the sheep were killed and the tracheal segment corresponding to the dead space from which DME uptake was determined was removed, and its mucosa was stripped and processed for microsphere counts. Mean QDME was 35.6 ml.min-1.100 g-1 wet tissue (range 9.6-98.0 ml.min-1.100 g-1) and mean QM was 29.1 ml.min-1.100 g-1 (range 7.7-91.5 ml.min-1.100 g-1). There was a strong correlation between QDME and QM (r = 0.89; P = 0.01). Intravenous nitroglycerin and vasopressin caused comparable increases and/or decreases in QDME and QM (r = 0.87; P = 0.02). This suggests that the noninvasive DME uptake method measures Qaw accurately and supports its validity in human studies.

Animals↗
PubMed1995

Hydrogen peroxide-scavenging properties of sheep airway mucus.

Reactive oxygen species released from luminal phagocytes in the airway can potentially injure the airway epithelium. Naturally occurring oxygen radical scavengers must therefore exist to protect the epithelium. This study was designed to determine whether the high-molecular-weight fraction of normal sheep tracheal mucus has hydrogen peroxide (H2O2)-scavenging activity. Lyophilized mucus from 10 sheep was reconstituted in phosphate-buffered saline (PBS) or Krebs-Henseleit buffer. H2O2 was added to these mucus samples to a final concentration of 15 microM, and the level of H2O2 remaining was measured over a 10 min period. From a zero-time level of 17 +/- 1.8 microM (mean +/- SD), the H2O2 concentration fell within 10 min to 8 +/- 1.7 microM in 0.05%; to 3.9 +/- 2.2 microM in 0.1%; to 2.6 +/- 2.4 microM in 0.2%; and to 1.2 +/- 1.5 microM in 0.4% mucus reconstituted in PBS. The results obtained in Krebs-Henseleit buffer were similar. The disappearance of H2O2 was not due to the transformation into hydroxyl radicals. Heat and acid denaturation and cleavage of carbohydrate-free peptides from glycoproteins by pronase E treatment abolished the scavenging potential. Fractionation of 0.4% mucus samples according to molecular weight by gel filtration revealed that only one fraction with proteins of M(r) > 110 kD contained the active scavenger. Polyacrylamide gel electrophoresis and lectin blotting with Ulex europaeus I (UEAI) showed that both the whole mucus and the actively scavenging gel filtration fraction contained a glycoprotein that comigrated with a 205 kD molecular weight marker.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Actual pentamidine dose delivered by Respigard II nebulizer.

The Respigard II nebulizer system is the approved method to deliver pentamidine aerosols in the USA. Although continuous operation of the nebulizer until dryness is a designated regimen, the actual pentamidine dose delivered under the operating condition has not been thoroughly studied. Pentamidine solutions (300 mg in 6 mL water) were nebulized continuously with the Respigard II nebulizer system until dryness (40 min operation). Aerosols were delivered to the lower airways via an oropharyngeal model and sampled on a filter with a standard breathing mode of 20 breaths.min-1 frequency and 750 mL tidal volume. Intermediate samples were also obtained for the initial 20 min delivery. The pentamidine dose delivered to the mouth was 1.6% of the dose placed in the nebulizer. Of the dose delivered to the mouth, 92% was delivered during the initial 20 min period. Aerosol loss in the oropharyngeal model was 15% of the dose delivered to the mouth or 0.24% of the dose initially placed in the nebulizer. Pentamidine dose delivered to the lower airways was a very small fraction of the initial dose in the nebulizer. A partial delivery for the initial 20 min was nearly comparable to complete delivery.

Humans↗
PubMed1994

Effect of lung volume and intrathoracic pressure on airway mucosal blood flow in man.

We have recently described an inert soluble gas uptake technique (using dimethyl-ether, DME) for the non-invasive measurement of airway mucosal blood flow (Qaw) in humans. In the present study, we assessed the effects of lung volume and intrathoracic pressure on Qaw, in healthy non-smokers (age range 19-52 years). Qaw was calculated from the steady-state uptake of DME from a 50 ml segment of the anatomic dead space. The mean (+/- SD) Qaw of three consecutive measurements at a lung volume of FRC + 300 ml was 8.3 +/- 2.3, 8.6 +/- 2.6 and 8.3 +/- 2.7 ml.min-1 (n = 13; coefficient of variation 14 +/- 7%). At zero airway pressure, there was an inverse relationship between apparent Qaw on the one hand and lung volume and anatomic dead space (DS) on the other: mean Qaw was 12.2 +/- 5.3, 8.2 +/- 2.5 and 5.3 +/- 2.2 ml.min-1 at RV + 300 ml (DS = 131 +/- 11 ml), FRC + 300 ml (DS = 153 +/- 12 ml) and TLC (DS = 206 +/- 22 ml) positions, respectively (n = 11; P < 0.05 among all three). At a lung volume of FRC + 300 ml, an increase in intrathoracic pressure to +25 cmH2O (modified Valsalva maneuver) decreased mean Qaw to 3.3 +/- 2.8 ml.min-1 while a decrease in intrathoracic pressure to -35 cmH2O (modified Müller maneuver) increased mean Qaw to 17.1 +/- 7.4 ml.min-1 from a control value of 7.2 +/- 2.2 ml.min-1 (n = 7; P < 0.05 among all three). These results indicate that lung volume has an effect on apparent Qaw, presumably by influencing the depth to which the analyzed anatomical dead space segment extends into the bronchial tree. The results also show that changes in intrathoracic pressure alter Qaw, possibly reflecting concomitant changes in left ventricular output and its distribution to intrathoracic and extrathoracic vascular beds.

Adult↗
PubMed1994

Effect of antigen on the glycoconjugate profile of tracheal secretions and the epithelial glycocalyx in allergic sheep.

To characterize the glycoconjugate composition of tracheal secretions and the apical glycocalyx of the tracheal epithelium under baseline conditions and after antigen challenge, sheep allergic to Ascaris suum were intubated with a double-balloon nasotracheal tube to create a tracheal chamber. After an initial tracheal lavage, the animals were either exposed to intratracheally nebulized phosphate-buffered saline (PBS) (3 ml, n = 6) or A. suum antigen (251,000 protein nitrogen units in 3 ml of PBS, n = 6). Tracheal lavage was repeated 2 hours later, and the animals were killed. An enzyme-linked lectin assay and lectin histochemical analysis were used to characterize carbohydrate residues in lyophilized, resuspended tracheal secretions and the apical glycocalyx of the tracheal epithelium, respectively. Eight lectins were used to detect GalNAc, alpha-Gal, beta-Gal, alpha-Fuc (1-3)Man, alpha-Man/Glu, alpha-Man, and alpha-(2-3)sialyl residues. The amounts of total nondialyzable solids, proteins, and lipids in tracheal secretions were approximately twice as high after exposure to A. suum than after exposure to PBS. All carbohydrate residues were present in tracheal secretions after exposure to PBS and A. suum, but the reactivity was higher after exposure to A. suum for beta-Gal (+125%), alpha-Man/Glu (+150%), alpha-(1-3)Man (+287%), alpha-(2-3)sialyl (+353%), and alpha-Man (+448%) (p < 0.05). Likewise, the apical glycocalyx contained all carbohydrate residues after exposure to PBS and A. suum; afer exposure to A. suum, the reactivity was greater for alpha-GalNAc (+18%), alpha-(2-3)sialyl (+90%), beta-Gal(1-3)GalNAc (+433%), and alpha-(1-3)Man (+482%) (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Tracheal mucosal edema in hydrostatic pulmonary edema.

Airway edema has been described in heart failure, and, in animal experiments, airway narrowing was observed with elevated left atrial pressure (Pla). On the basis of double-indicator-dilution principles using helium and dimethylether, we were able to measure a water compartment of the tracheal mucosa (VH2O) in dogs. Hypervolemia with an attendant increase in Pla caused by infusion of 2 liters of dextran increased VH2O from 368 +/- 71 (SE) to 794 +/- 177 microliters (P < 0.01). Pulmonary arterial wedge and central venous pressures (Pcv) rose concomitantly. Increases in pulmonary arterial wedge and Pcv by a left atrial balloon catheter produced similar increases in VH2O, whereas increases in Pcv alone by a right atrial balloon did not increase VH2O. Increasing VH2O by dextran infusion was associated with an increase in pulmonary resistance from 1.16 +/- 0.19 to 2.15 +/- 0.24 cmH2O.l-1.s (P < 0.01). These observations show that fluid accumulation in the lung during pulmonary congestion also involves extraparenchymal airways and is related to Pla rather than right atrial pressure. This indicates that sufficient collateral drainage exists during right-sided but not left-sided pressure elevations.

Anesthesia↗
PubMed1994

Airway mucosal blood flow in humans. Response to adrenergic agonists.

We measured the uptake of the soluble inert gas dimethyl ether (DME) from a segment of the conducting airways to estimate mucosal blood flow (Qaw) noninvasively. The subjects inhaled, from the functional residual capacity position, a 300-ml gas mixture containing 35% DME, 8% helium, 35% oxygen, and the balance nitrogen; they held their breath for 5 s and then exhaled into a spirometer. During exhalation, the instantaneous concentrations of DME and helium were recorded together with expired gas volume. The maneuver was repeated with breathhold times of 5, 10, 15, and 20 s. We calculated Qaw using the time-dependent decrease in DME concentration in relation to the helium concentration in an expired volume fraction between 80 and 130 ml (representing an anatomic dead-space segment distal to the glottis) and the mean DME concentration. In 10 healthy nonsmokers, mean (+/- SE) Qaw was 8.0 +/- 1.3 ml/min, or 8 +/- 2 microliters/min/cm2 mucosal surface. We obtained a value of 12 +/- 3 microliters/min/cm2 in a validation experiment in sheep. Inhaled methoxamine (nebulized dose 10 mg) caused a 65 +/- 19% decrease (p < 0.05), and albuterol (nebulized dose 2.5 mg) a 92 +/- 17% increase (p < 0.05), in mean Qaw in seven subjects, with the maximum changes occurring immediately or 15 min postinhalation. We conclude that the DME uptake method is an acceptable noninvasive means of estimating airway mucosal blood flow in humans and its modification by vasoactive substances.

Adult↗
PubMed1994

Endothelin-1 promotes mitogenesis in airway smooth muscle cells.

Endothelin exists as three isoforms (ET-1, ET-2, and ET-3) and exhibits vasoconstricting, bronchoconstricting, and growth-promoting properties in vascular smooth muscle. In the airways, ET-1 immunoreactivity and mRNA have been detected and localized to the epithelium, smooth muscle, and endothelium in different species, including humans. It has been suggested that ET-1 may have a role in the airway smooth muscle hyperplasia and hypertrophy seen in patients with bronchial asthma. We studied ovine airway smooth muscle cells (SMC) in vitro and showed saturable binding of [125I]ET-1 with a dissociation constant (Kd) of 0.4 nM and high affinity binding sites (Bmax) for ET-1 (104 fmol/10(6) cells). This binding was functional as ET-1 promoted mitogenesis of these muscle cells as measured by increased cell number in the absence of serum. Twenty-four hours after exposing the cells to graded doses of ET-1 from 1 pM to 1 microM, cell number increased significantly over control in a dose-dependent manner. ET-1 also enhanced the transient expression of c-fos mRNA by 2.5-fold over control, with maximal expression occurring at 30 min. These observations provide evidence that: (1) airway SMC possess high affinity binding sites for ET-1, and (2) ET-1 is mitogenic for airway SMC as determined by increased cell number and amplification of c-fos mRNA expression. ET-1 may have a fundamental role in influencing the growth of smooth muscle in the airways.

Animals↗