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Biomedical subjects

W M Abraham

Publications and source records attributed to W M Abraham.

At least 55 records · Page 3Linked to original sources
PubMed1996

The role of alpha 4 integrins in lung pathophysiology.

The alpha 4 integrins are heterodimeric leucocyte cell surface molecules central to their cell and matrix adhesive interactions. The integrin alpha 4 beta 1 interacts with the immunoglobulin superfamily member vascular cell adhesion molecule-1 (VCAM-1), and with an alternatively spliced form of fibronectin. The integrin alpha 4 beta 7 binds not only VCAM-1 and fibronectin, but also the mucosal addressin cell adhesion molecule (MAdCAM). Certain monoclonal antibodies (MoAbs) to the alpha 4 chain of alpha 4 beta 1 and alpha 4 beta 7 can block their in vitro adhesive function. In vivo studies with these MoAbs in lung antigen challenge models in several species demonstrate that alpha 4 integrins play a key role in eosinophil and T-cell recruitment, in the late phase response, and in airways hyperresponsiveness. In particular, MoAb HP1/2 is efficacious in a sheep model of allergic airways challenge, whether given intravenously or as aerosol. To evaluate the mechanism of action of this MoAb, Fab fragments were generated and shown to be equipotent in vitro and as efficacious in vivo as the intact immunoglobulin G (IgG). These data demonstrate that the in vivo efficacy of monoclonal antibody HP1/2 is not due to indirect effects, such as antigen cross-linking, but rather to blockade of alpha 4 integrin adhesive function. Humanized monoclonal antibody or other alpha 4 integrin antagonists may provide novel therapeutics for asthma.

Alternative Splicing↗
PubMed1995

Endothelin-1 contributes to antigen-induced airway hyperresponsiveness.

Endothelin A (ETA)-receptors mediate ET-1 contractions of ovine airway smooth muscle. Therefore, the ETA-receptor antagonist, BQ-123, was used to test the hypothesis that ET-1 contributes to antigen-induced airway responses in sheep allergic to Ascaris suum. We first established the protective effect of BQ-123 by demonstrating that BQ-123 given as an aerosol (0.3 or 1.0 mg/kg in 3 ml buffer) or by continuous intravenous infusion (100 micrograms.kg-1.min-1) significantly blocked the bronchoconstriction to aerosolized ET-1 (0.2-200 micrograms/ml). To determine whether ET-1 contributed to antigen-induced airway responses, BQ-123 was given either as an intravenous infusion (100 micrograms.kg-1.min-1) beginning 30 min before and continuing for 8 h after antigen challenge or as an aerosol (1 mg/kg in 3 ml buffer) 30 min before and 4, 8, and 24 h after antigen challenge. Neither treatment with intravenous infusion nor aerosolized BQ-123 blocked the immediate antigen-induced bronchoconstriction, but both treatments significantly reduced the late response (approximately 50%). The treatments with aerosolized BQ-123 also blocked the antigen-induced airway hyperresponsiveness to inhaled carbachol seen 24 h after challenge. Subsequently, we found that sheep developed airway hyperresponsiveness to inhaled carbachol at 4 and 24 h after ET-1 challenge, an effect that was blocked by aerosolized BQ-123. We conclude that in allergic sheep 1) aerosolized ET-1 causes bronchoconstriction, in part, by stimulation of ETA-receptors, 2) ET-1 is released in the airways after antigen challenge, and 3) this peptide contributes to the severity of the allergic responses, probably by increasing airway smooth muscle responsiveness.

Administration, Inhalation↗
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

Role of tryptase in immediate cutaneous responses in allergic sheep.

In this study, we used a specific tryptase inhibitor, APC-366 [N-(1-hydroxy-2-napthoyl)-L-arginyl-L- prolinamide hydrochloride] to investigate the effect of intradermally administered tryptase and tryptase released by antigen challenge on the immediate cutaneous reaction (ICR) in allergic sheep. The surface areas of cutaneous wheals produced by intradermal injections (0.05 ml) of 1 and 10 ng tryptase alone, tryptase combined with 3 U heparin (tryptase-heparin), or Ascaris suum antigen (10(-5) dilution) with or without pretreatment with APC-366 (1 mg/ml) were measured at 20 and 60 min after challenge. Intradermal injections of 1 and 10 ng tryptase alone (n = 7) produced an ICR of < or = 20% of that obtained after injection of histamine (5% wt/vol). Intradermal injection of tryptase-heparin (n = 7), however, resulted in 50 (1 ng) and 82% (10 ng) of the ICR to histamine (both, P < 0.05 vs. tryptase alone). APC-366 inhibited (P < 0.05) the ICR to 1 and 10 ng tryptase-heparin by > or = 70% at all times (n = 8) but had no effect on the histamine-induced ICR (n = 3). A combination of the histamine H1 antagonist chlorpheniramine (2 mg/kg iv) and the H2 antagonist metiamide (3 mg/kg iv) given 40 min before challenge (n = 8) inhibited the response to 1 and 10 ng tryptase-heparin by 42 and 62% at 20 min and by 96 and 86% at 60 min, respectively (all, P < 0.05). APC-366 also blocked the ICR to A. suum antigen by 68% (P < 0.05) in nine sheep. These results indicate that intradermal injection of tryptase-heparin can induce an ICR. This ICR can be inhibited by APC-366 or a combination of the histamine H1 and H2 antagonists, suggesting that the tryptase response is mediated by histamine. APC-366 also blocks the mast cell-mediated ICR to intradermally injected A. suum antigen. Collectively, these results suggest that tryptase may modulate mast cell histamine release.

Animals↗
PubMed1995

Tryptase inhibitors block allergen-induced airway and inflammatory responses in allergic sheep.

Tryptase, a mast cell serine protease, has been implicated in the pathophysiology of allergic asthma, but formal evidence to support this hypothesis has been limited by the lack of specific inhibitors for use in vivo. Therefore, in this study we examined the effects of two inhibitors of tryptase, APC 366 [N-(1-hydroxy-2-naphthoyl)-L-arginyl-L-prolinamide hydrochloride] and BABIM [bis(5-amidino-2-benzimidazolyl)methane] on antigen-induced early and late responses, airway responsiveness as measured by carbachol provocation, microvascular permeability as measured by bronchoalveolar lavage (BAL) albumin concentrations, and tissue eosinophilia from biopsies in allergic sheep. APC 366 and BABIM were administered by aerosol in all experiments. In vehicle control trials, antigen challenge resulted in peak early and late increases in specific lung resistance (SRL) of (mean +/- SE, n = 6) 259 +/- 30% and 183 +/- 27% over baseline, respectively. Treatment with APC 366 (9 mg/3 ml H2O given 0.5 h before, 4 h after, and 24 h after antigen challenge) slightly reduced the peak early response (194 +/- 41%), but significantly inhibited the late response (38 +/- 6%, p < 0.05 versus control trials). Twenty-four hours after challenge, APC 366 also completely blocked the antigen-induced airway hyperresponsiveness to inhaled carbachol observed in the control trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1995

Morphometric estimation of superoxide generation in allergen-induced airway hyperresponsiveness.

BACKGROUND: We previously reported that the airway hyperresponsiveness (AHR) that follows antigen challenge is mediated, in part, by the generation of reactive oxygen species. The purpose of this study was to provide quantitative morphologic evidence of oxygen radical production in the airways during antigen-induced AHR. EXPERIMENTAL DESIGN: Allergic sheep with a history of early and late bronchial responses to inhaled Ascaris suum antigen were used. The sheep were either challenged with antigen (N = 5) or saline (N = 5) and then euthanized 24 hours later when AHR had been documented to occur. Complete transverse sections of the right cranial lobar bronchus were obtained from the animals and were washed three times in Tris buffer and then incubated for 20 minutes in an oxygenated solution of diaminobenzidine which, in the presence of superoxide and manganese, forms an insoluble amber reaction product. Superoxide dismutase (SOD, 2250 units/ml) and phorbol ester (phorbol myristate acetate, 0.5 microgram/ml) were added to some tissues and used as negative and positive controls, respectively. The bronchial samples were then fixed and embedded in paraffin for light microscopy. The diaminobenzidine reaction product was quantified by determining the volume fraction of reaction product by point counting with a differential interference contrast microscope without counterstain. RESULTS: Diaminobenzidine reaction product increased 5-fold (p < 0.05) in challenged animals, and this response was blocked by SOD. The reaction product was localized in and around the airway epithelium. Antigen challenge also resulted in a 2.4- and 2.0-fold increase in eosinophils and metachromatic cells in the airway wall. There were no differences in the number of neutrophils between groups. Pretreatment of animals (N = 2) with the combination of the 5-lipoxygenase inhibitor (zileuton, 10 mg/kg, po) and the platelet-activating factor antagonist (WEB-2086, 3 mg/kg, i.v.) agents, which have been shown to block AHR and antigen-induced inflammation in the sheep model, also blocked the antigen-induced superoxide formation. CONCLUSIONS: These data suggest that superoxide and increased numbers of mediator-containing inflammatory cells are present in sheep airways 24 hours after antigen challenge. The interaction of this reactive oxygen species with these cells could contribute to the AHR seen at this time.

3,3'-Diaminobenzidine↗
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

Heparin prevents antigen-induced airway hyperresponsiveness: interference with IP3-mediated mast cell degranulation?

We hypothesized that heparin, because of its antiallergic and/or anti-inflammatory properties, modifies airway hyperresponsiveness (AHR). We studied the effects of inhaled heparin on AHR induced by specific antigen or by platelet-activating factor (PAF), a proinflammatory mediator. Specific lung resistance (sRL) was measured in 17 allergic sheep before, immediately after, and serially for up to 2 h after airway challenge with either specific antigen or PAF. Airway responsiveness was expressed as the cumulative provocative dose of carbachol that increased sRL to 4 cmH2O/s [PD4, in breath units (BU; 1 BU = 1 breath of 1% carbachol solution)]. PD4 was determined on a baseline day and on various experimental days 2 h after airway challenge with antigen or PAF, without or after pretreatment with inhaled heparin (1,000 U/kg). Pretreatment with inhaled heparin prevented antigen-induced bronchoconstriction and postantigen AHR. PD4 was 26 +/- 2.6 (SE), 12 +/- 1.7, and 22 +/- 2.8 BU on baseline, antigen control, and postheparin days, respectively. Heparin given immediately after the antigen challenge failed to modify the magnitude and/or duration of antigen-induced bronchoconstrictor response or postantigen AHR. Heparin also failed to prevent PAF-induced changes in sRL and AHR. In vitro heparin inhibited anti-immunoglobin E- and 1,4,5-inositol triphosphate-mediated degranulation of rat peritoneal mast cells without attenuating the effects of the Ca2+ ionophore A-23187. These data suggest that in "acute responders" heparin prevents antigen-induced bronchoconstriction and AHR, possibly by inhibiting 1,4,5-inositol triphosphate-dependent mast cell mediator release and not by its anti-inflammatory action.

Animals↗
PubMed1994

Extracellular metabolites of Pseudomonas aeruginosa produce bronchoconstriction by different mechanisms.

Bacterial supernatants (BS) obtained from broth cultures of Pseudomonas aeruginosa cause bronchoconstriction in sheep, suggesting that BS contain proinflammatory metabolites. In this study we investigated the mechanism(s) responsible for this bronchial effect. BS were obtained from 48 h cultures and sterilized by filtration. Sheep (n = 6) were intubated and swallowed an esophageal balloon for the measurement of specific lung resistance (SRL). Aerosols of BS (3 ml total) immediately increased SRL (541%). Neither aerosolized broth (control) nor inhaled endotoxin in excess of that contained in the BS had an effect. BS challenges were repeated on separate occasions except that the sheep were treated 30 min before challenge with the anticholinergic agent atropine (0.2 mg/kg, intravenously); the anti-allergic agent nedocromil (1 mg/kg, aerosol); the histamine H1 antagonist chlorpheniramine (2 mg/kg); or the bradykinin (BK) B2 receptor antagonists NPC-567 (5 mg/ml, aerosol) or NPC-17761 (1 mg/ml aerosol). The results showed that greater than 90% protection (p < 0.05) was achieved when the animals were pretreated with atropine, nedocromil sodium, or either of the two BK antagonists, but only 27 +/- 21% protection was seen with chlorpheniramine pretreatment. These findings are characteristic of a BK-mediated response. Analysis of bronchoalveolar lavage fluid obtained before and after BS challenge confirmed that i-kinins, but not histamine, increased (p < 0.05) from 61 +/- 7 to 304 +/- 55 pg/ml. Control (broth) challenges produced no such change. To identify the metabolites involved, we tested the effects of aerosolizing two suspected components of BS, 1-hydroxyphenazine (1-HP) and pyocyanine (PYO) in five sheep.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1994

Alpha 4-integrins mediate antigen-induced late bronchial responses and prolonged airway hyperresponsiveness in sheep.

Eosinophils and T lymphocytes are thought to be involved in allergic airway inflammation. Both cells express the alpha 4 beta 1-integrin, very late antigen-4 (VLA-4, CD49d/CD29); alpha 4-integrins can promote cellular adhesion and activation. Therefore, we examined the in vivo effects of a blocking anti-alpha 4 monoclonal antibody, HP 1/2, on antigen-induced early and late bronchial responses, airway hyperresponsiveness, inflammatory cell influx, and peripheral leukocyte counts in allergic sheep. Sheep blood lymphocytes, monocytes, and eosinophils expressed alpha 4 and bound HP 1/2. In control sheep, Ascaris antigen challenge produced early and late increases in specific lung resistance of 380 +/- 42% and 175 +/- 16% over baseline immediately and 7 h after challenge, respectively, as well as airway hyperresponsiveness continuing for 14 d after antigen challenge. Treatment with HP 1/2 (1 mg/kg, i.v.) 30 min before antigen challenge did not affect the early increase in specific lung resistance but inhibited the late-phase increase at 5-8 h by 75% (P < 0.05) and inhibited the post-antigen-induced airway hyperresponsiveness at 1, 2, 7, and 14 d (P < 0.05, for each time). Intravenous HP 1/2 given 2 h after antigen challenge likewise blocked late-phase airway changes and postchallenge airway hyperresponsiveness. Airway administration of HP 1/2 (16-mg dose) was also effective in blocking these antigen-induced changes. Response to HP 1/2 was specific since an isotypic monoclonal antibody, 1E6, was ineffective by intravenous and aerosol administration. Inhibition of leukocyte recruitment did not totally account for the activity of anti-alpha 4 antibody since HP 1/2 neither diminished the eosinopenia or lymphopenia that followed antigen challenge nor consistently altered the composition of leukocytes recovered by bronchoalveolar lavage. Because airway administration of HP 1/2 was also active, HP 1/2 may have inhibited cell activation. Reduction of platelet-activating factor-induced eosinophil peroxidase release from HP 1/2-treated eosinophils supports such a mechanism. These findings indicate a role for alpha 4-integrins in processes that lead to airway late phase responses and persisting airway hyperresponsiveness after antigen challenge.

Aerosols↗
PubMed1993

Effect of nedocromil sodium on specific mediator- and antigen-induced airway responses in allergic sheep.

This study evaluated the airway effects of nedocromil sodium in the sheep model of allergic bronchoconstriction. Nedocromil sodium provided statistically significant protection against both reflex- and mediator-induced bronchoconstriction in allergic sheep as assessed by bronchial responses to inhaled bradykinin and platelet-activating factor, respectively. When administered before antigen challenge, nedocromil sodium blocked both the immediate and late asthmatic response and prevented the subsequent increase in airway hyperresponsiveness. The protective effect of nedocromil sodium against the antigen-induced late response was associated with a significant decrease in the number of airway eosinophils measured by bronchoalveolar lavage. Although nedocromil sodium has no direct bronchodilatory activity, it prevented antigen-induced contractions in sheep tracheal smooth muscle in vitro. These results suggest that nedocromil sodium is active in the sheep model of allergic bronchoconstriction and may be useful in the treatment of reversible obstructive airway disease in human beings.

Animals↗
PubMed1993

The role of 5-lipoxygenase products in preclinical models of asthma.

BACKGROUND: The action of 5-lipoxygenase on arachidonic acid generates potent inflammatory mediators that may contribute to the pathophysiology of asthma. METHODS: Using the potent and selective 5-lipoxygenase inhibitor BI-L-239, we have examined the role of 5-lipoxygenase products in three animal models of asthma. RESULTS: In vitro BI-L-239 inhibited 5-lipoxygenase product generation from human lung mast cells, alveolar macrophages, and peripheral blood leukocytes with a concentration that would provide 50% inhibition values of 28 to 340 nmol/L. A 36-fold selectivity for immunoreactive leukotriene C4 versus immunoreactive prostaglandin D2 inhibition was demonstrated in mast cells. In anesthetized cynomolgus monkeys, inhaled BI-L-239 provided dose-dependent inhibition of the inhaled Ascaris-induced immunoreactive leukotriene C4 release (maximum, 73%; bronchoalveolar lavage [BAL], 20 minutes), late-phase bronchoconstriction (maximum, 41%; +6 to 8 hours), and neutrophil infiltration (maximum, 63%; BAL, +8 hours). In conscious sheep, inhaled BI-L-239 provided dose-dependent inhibition of the inhaled Ascaris-induced late-phase bronchoconstriction (maximum, 66%; +6 to 8 hours) and increase in airway responsiveness (maximum, 82%; carbachol, +24 hours). The acute bronchoconstriction was shortened, and neutrophil infiltration diminished (maximum, 61%; BAL, +8 hours) in this model. Finally in conscious actively sensitized guinea pigs pretreated with pyrilamine and indomethacin, inhaled BI-L-239 attenuated acute bronchoconstriction (maximum, 80%; +5 to 15 minutes), leukocyte infiltration (58%; BAL, +3 days) and increase in airway responsiveness (100%; methacholine, +3 days) induced by three alternate-day ovalbumin inhalations. CONCLUSIONS: In conclusion, results in these three animal models indicate that 5-lipoxygenase products may be major contributors to the bronchoconstriction (especially late phase), leukocyte infiltration, and airway hyperresponsiveness that characterize asthma.

Animals↗
PubMed1993

The effects of a cysteinyl leukotriene antagonist (ONO-1078) on antigen-induced responses in allergic sheep.

The cysteinyl leukotrienes (LTC4/D4/E4) are putative mediators of asthma. In this study we used sheep allergic to Ascaris suum antigen to examine the effects of a novel orally active cysteinyl LT antagonist, ONO-1078, on antigen-induced early and late responses, airway inflammation, post challenge (24 h) airway hyperresponsiveness (AHR) and mucociliary clearance. Airway responses to antigen were determined by measuring specific lung resistance (SRL) before and for 8 h after challenge, bronchoalveolar lavage (BAL) was used to estimate airway inflammation, and airway responsiveness was measured by determining the carbachol dose that increased SRL by 400% (PC400). We also used a radiographic technique to measure the antigen-induced change in tracheal mucus velocity (TMV), a marker of mucociliary clearance. In two trials separated by at least 21 days, sheep were treated once with ONO-1078 (30 mg/kg, p.o.) and once with placebo (0.5% methylcellulose), 2 h before and 4 h after antigen challenge. Treatment with ONO-1078 (n = 7) provided 40% protection (p < 0.10) against the peak early increase in SRL, resulted in a more rapid reversal of the early response, and provided 96% protection against the peak late (6-8 h) increase in SRL. ONO-1078 also inhibited the AHR 24 h after challenge. In the drug trial, PC400 was unchanged as compared to pre-challenge, whereas in the placebo trial, PC400 was decreased 1.4-fold (p < 0.05). Treatment however, did not affect BAL cell numbers or differential.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1993

A specific endothelin-1 antagonist blocks inhaled endothelin-1-induced bronchoconstriction in sheep.

In this study we used conscious sheep to compare the relative potencies of inhaled endothelin- (ET) 1 and ET-3 and to determine whether a newly described selective ET-1 receptor antagonist, [diaminopropionic acid1-Asp15]ET-1 ([Dpr1-Asp15]ET-1), when given as an aerosol blocks ET-1-induced bronchoconstriction. Partial concentration-response curves to ET-1 and ET-3 were obtained by measuring the change in pulmonary airflow resistance (RL) after aerosol challenge. Both ET-1 (n = 6) and ET-3 (n = 4) caused concentration-dependent (10(-10)-10(-7) bronchoconstriction, but ET-3 was 400-fold less potent than ET-1. Pretreatment (30 min) with 25 breaths of 5 x 10(-8) M [Dpr1-Asp15]ET-1 caused a 100-fold rightward shift of the ET-1 concentration-response curve. The activity of the ET-1 antagonist (25 breaths of 5 x 10(-8) M) was compared with that of various control peptides (25 breaths of 10(-8) M). ET-1 (50 breaths of 10(-7) M) caused an increase in RL of 133 +/- 33% (SE) over baseline. [Dpr1-Asp15]ET-1 significantly inhibited this response by 54%. No protection was seen with a monocyclic control peptide or a thrombin receptor peptide. There was, however, a small protective effect (38%, P < 0.05) seen with [Dpr1-Asp15]ET-3, a structurally homologous ET-3 antagonist. [Dpr1-Asp15]ET-1 had no effect on carbachol (n = 3) or leukotriene D4-induced bronchoconstriction. Thus inhaled ET-1 and, to a lesser extent, ET-3 cause concentration-dependent bronchoconstriction in conscious sheep.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerosols↗
PubMed1993

Ovine tracheal muscle contraction in vitro: inhibition by calcium channel blockers gallopamil and verapamil.

We compared the inhibitory effects of calcium channel blockers, gallopamil and verapamil on acetylcholine (Ach)-induced contractions of ovine tracheal muscle in vitro. Adult sheep were sacrificed and tracheal strips were obtained by cutting the single tracheal rings from the mid-trachea. Tracheal strips were suspended in Krebs-Henseleit solution and isometric tension measured upon stimulation with cumulative doses of Ach (10(-7) to 10(-4) M) without and after pretreatment with gallopamil (10(-7) to 10(-6) M) or verapamil (10(-6) to 10(-5) M). In untreated tissues, the mean concentration of Ach required to produce 50% of maximal response (EC50) was 4.3 x 10(-6) M Ach. Both gallopamil and verapamil inhibited the Ach-induced contractions of ovine tracheal smooth muscle, by shifting the dose-response curves to Ach to the right. EC50 Ach for gallopamil (10(-6) M) and verapamil (10(-6) M) was 2.6 x 10(-5) and 5.2 x 10(-6) M, respectively. Dose ratio defined as postantagonist EC50 Ach/control EC50 Ach, was 7.7 for gallopamil and 2.0 for verapamil. Thus, the inhibitory effect of gallopamil was approximately 4-fold more potent than that of verapamil. Gallopamil was 17-fold more potent than verapamil in relaxing precontracted tracheal strips. The dose of calcium antagonists required to produce 25% relaxation (EC25) of tracheal strips precontracted with 10(-4) Ach was 3.7 x 10(-5) M for verapamil and 2.2 x 10(-6) M for gallopamil. These results indicate that gallopamil is effective against Ach-induced contractions of ovine trachealis muscles, and is more potent than verapamil.

Acetylcholine↗
PubMed1993

Oxygen radicals contribute to antigen-induced airway hyperresponsiveness in conscious sheep.

We previously showed that oxygen radicals can induce airway hyperresponsiveness (AHR) in allergic sheep. The purpose of this study was to determine whether antigen challenge results in the generation of free oxygen radicals and if these radicals contribute to antigen-induced AHR. We first determined baseline airway responsiveness in seven Ascaris suum-sensitive sheep by calculating the cumulative provocative concentration of carbachol in breath units (BU; one BU defined as one breath of a 1% wt/vol carbachol solution) that increased specific lung resistance (SRL) 400% over baseline (PC400). On a different day, the sheep underwent inhalation challenge with A. suum antigen, SRL was measured before and immediately after challenge and then hourly for 2 h, at which time SRL had returned to baseline. The postchallenge PC400 was then measured. This procedure was repeated on separate occasions, each at least 14 days apart, except that the sheep were treated with an aerosol of catalase (CAT; 38 mg in 3 ml deionized water), the enzyme that catalyzes the decomposition of hydrogen peroxide (H2O2), at three different times: Trial 1, before antigen and then every 30 min after antigen challenge for 2 h; Trial II, 1 and 2 h after antigen challenge; and Trial III, only at 2 h after antigen challenge. In the control trial, antigen challenge caused a transient (mean +/- SEM) 303 +/- 48% increase in SRL over baseline (p < 0.05), and 2 h later, PC400 was reduced to 11.0 +/- 1.7 BU from a prechallenge value of 24.8 +/- 1.9 BU (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aerosols↗
PubMed1993

Lectin-detectable glycoconjugate profile of the tracheal secretions and epithelial glycocalyx in sheep. Effect of muscarinic stimulation.

Reflex mucus secretion in the airways serves a defense function that includes the binding of bacteria to mucus glycoconjugates thereby preventing bacterial adherence to the epithelium. We therefore compared the lectin-detectable glycoconjugate profile of the epithelial glycocalyx and luminal secretions under baseline conditions and after muscarinic receptor stimulation in the sheep trachea. The sheep were intubated with a double-balloon nasotracheal tube to create a tracheal chamber for collection of secretions. After an initial lavage of the chamber to clear it of secretions, the sheep received an intravenous injection of normal saline, 0.5 mg/kg pilocarpine, or 0.5 mg/kg pilocarpine after pretreatment with 0.2 mg/kg atropine. Tracheal lavage was repeated 2 h later, and the sheep were then killed. An enzyme-linked lectin assay and lectin histochemistry were used to characterize glycoconjugate residues in tracheal secretions and in the apical epithelial glycocalyx, respectively. Eight different lectins were used to detect N-acetyl galactosamine, alpha-galactose, alpha-galactose-N-acetyl galactosamine, beta-galactose, beta-galactose-N-acetyl galactosamine, alpha-fucose, alpha-glucose, alpha-mannose and alpha-(2-3)sialyl residues. After normal saline, reactivity was present for all glycoconjugates in secretions and in the glycocalyx.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗