Azelastine reduces allergen-induced nasal response: a clinical and rhinomanometric assessment

The effect of azelastine 2 mg b.d. p.o. for 10 days on grass pollen-induced nasal responses in 16 patients with grass pollen allergic rhinitis has been assessed. The study was a double blind, randomized, placebo controlled, crossover trial, with a 10-14 day wash-out period. Patients were challenged with grass pollen before and after placebo and azelastine. The response was assessed by measurement of nasal resistance using active posterior rhinomanometry, by weighing nasal secretions, and by counting sneezes. The sensation of nasal obstruction was assessed with a visual analogue scale. After measurement of baseline total nasal resistance, doubling doses of allergen were sprayed into both nostrils at 15 min intervals until the nasal resistance was doubled. Cumulative doses of allergen that doubled prechallenge nasal resistance, numbers of sneezes and the amounts of nasal secretions were similar before azelastine as well as before and after placebo (cumulative dose, mean, (microgram): 2.3, 4.2 and 2.1 respectively, N.S.). After azelastine, the cumulative dose of allergen was increased (7.3 micrograms), and nasal secretions and the number of sneezes were decreased. The visual analogue scores were similar before and after azelastine as well as before and after the placebo. It is concluded that azelastine reduced the allergen-induced nasal responses.

Bronchial provocation tests in small animals: a quantified and automated procedure

Bronchial provocation tests using aerosols in laboratory animals are difficult to standardize and quantify, because the amount of drug actually reaching the airways is unknown. To improve the quantification of aerosolized inhaled stimuli, we designed an apparatus that allows, in anesthetized intubated ventilated animals, control of temperature and hygrometry of inspired air, computerized measurement of pulmonary resistance, and fully automated delivery of a known amount of aerosolized drug directly into the trachea. Calibration of the aerosol delivery involved direct measurement of liquid delivered at the tip of the tracheal cannula. Despite all our efforts at standardization and full automation of all steps, reproducibility of aerosol delivery was poor, with stroke-by-stroke differences of 26 or 42%, according to whether an air-jet or an ultrasonic nebulizer was used. Histamine dose-response curves performed in 15 guinea pigs with this device confirmed marked differences among animals and also disclosed large intraindividual changes in bronchial responsiveness.

Improvement in exercise performance by inhalation of methoxamine in patients with impaired left ventricular function

BACKGROUND

Bronchial hyperresponsiveness to cholinergic stimuli such as the inhalation of methacholine is common in patients with impaired left ventricular function. Such hyperresponsiveness is best explained by cholinergic vasodilation of blood vessels in the small airways, with extravasation of plasma due to high left ventricular filling pressure. Because this vasodilation may be prevented by the inhalation of the vasoconstrictor agent methoxamine, we studied the effect of methoxamine on exercise performance in patients with chronic left ventricular dysfunction.

METHODS

We studied 19 patients with a mean left ventricular ejection fraction of 22 +/- 4 percent and moderate exertional dyspnea. In the first part of the study, we performed treadmill exercise tests in 10 patients (group 1) at a constant maximal workload to assess the effects of 10 mg of inhaled methoxamine on the duration of exercise (a measure of endurance). In the second part of the study, we used a graded exercise protocol in nine additional patients (group 2) to assess the effects of inhaled methoxamine on maximal exercise capacity and oxygen consumption. Both studies were carried out after the patients inhaled methoxamine or placebo given according to a randomized, double-blind, crossover design.

RESULTS

In group 1, the mean (+/- SD) duration of exercise increased from 293 +/- 136 seconds after the inhalation of placebo to 612 +/- 257 seconds after the inhalation of methoxamine (P = 0.001). In group 2, exercise time (a measure of maximal exercise capacity) increased from 526 +/- 236 seconds after placebo administration to 578 +/- 255 seconds after methoxamine (P = 0.006), and peak oxygen consumption increased from 18.5 +/- 6.0 to 20.0 +/- 6.0 ml per minute per kilogram of body weight (P = 0.03).

CONCLUSIONS

The inhalation of methoxamine enhanced exercise performance in patients with chronic left ventricular dysfunction. However, the improvement in the duration of exercise at a constant workload (endurance) was much more than the improvement in maximal exercise capacity assessed with a progressive workload. These data suggest that exercise-induced vasodilation of airway vessels may contribute to exertional dyspnea in such patients. Whether or not inhaled methoxamine can provide long-term benefit in patients with heart failure will require further study.

Relationship between spontaneous dyspnoea and lability of airway obstruction in asthma

1. As marked lability of bronchial obstruction is a risk factor for asthma severity, it may influence dyspnoea, the most common subjective complaint in asthma. We therefore studied the relationship between spontaneous dyspnoea and the degree of bronchial lability, as assessed by the daily variability in peak expiratory flow rate and the bronchial responsiveness to either carbachol or salbutamol, in 33 stable symptomatic asthmatic patients. 2. Three times daily, for 10 consecutive days, the patients rated the intensity of their dyspnoea on a visual analogue scale and immediately afterwards recorded their peak expiratory flow rate. Within the next 5 days, we determined the bronchial response by measuring the forced expiratory volume in 1 s and the specific resistance of airways to either carbachol or salbutamol according to baseline airway obstruction. 3. We characterized dyspnoea for each patient by using two parameters: (1) the relationship with underlying airway obstruction, as assessed by the correlation coefficient r between dyspnoea scores and corresponding values of peak expiratory flow rate (r DSc-PEFR), and (2) the intensity, as assessed by the mean visual analogue scale dyspnoea score adjusted for comparable airway obstruction. Bronchial lability was characterized by (1) variability in mean daily peak expiratory flow rate and (2) bronchial responsiveness to either carbachol (as assessed by the threshold dose and the slope of the dose-response curve) or salbutamol (as assessed by the threshold dose and maximal response). We assessed the relationship between dyspnoea and bronchial lability by correlating each of their respective characteristics. 4. We found large inter-subject differences in both characteristics of dyspnoea.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro bronchial hyperresponsiveness after lung transplantation in the rat

In this study, we examined the effect of unilateral lung transplantation on in vitro responses of bronchial smooth muscle to electrical field stimulation (EFS) and exogenous acetylcholine (ACh). In syngeneic Lewis rats, we compared the contractile responses of the left hilar transplanted bronchus with that of the nontransplanted right bronchus and the left and right bronchi from control and sham-operated animals. Atropine-sensitive bronchial contraction to EFS was greater on left transplanted than on right nontransplanted bronchi at all frequencies and voltages used. In control and sham-operated animals, contractile responses to EFS were identical on left and right sides and similar to the responses of the right nontransplanted bronchus of the lung transplant recipient. Concentration-response curves to exogenous ACh were similar on transplanted and all control bronchi. Intramural cholinergic nerve cell bodies reactive for acetylcholinesterase were present in the transplanted bronchus. We conclude that EFS-induced cholinergic contraction of rat bronchial smooth muscle is enhanced after lung transplantation. Enhancement is not a result of medication, inflammation, or rejection, absent from our syngeneic transplant, or of upregulation of muscarinic post-junctional receptors because the response to exogenous ACh was normal. Hence, an increased release of ACh from cholinergic nerve terminals may occur, due either to hyperexcitability of postganglionic parasympathetic nerves or to loss of inhibitory mechanism resulting from interruption of neural connections with the central nervous system.

Protein design on computers. Five new proteins: Shpilka, Grendel, Fingerclasp, Leather, and Aida

What is the current state of the art in protein design? This question was approached in a recent two-week protein design workshop sponsored by EMBO and held at the EMBL in Heidelberg. The goals were to test available design tools and to explore new design strategies. Five novel proteins were designed: Shpilka, a sandwich of two four-stranded beta-sheets, a scaffold on which to explore variations in loop topology; Grendel, a four-helical membrane anchor, ready for fusion to water-soluble functional domains; Finger-clasp, a dimer of interdigitating beta-beta-alpha units, the simplest variant of the "handshake" structural class; Aida, an antibody binding surface intended to be specific for flavodoxin; Leather--a minimal NAD binding domain, extracted from a larger protein. Each design is available as a set of three-dimensional coordinates, the corresponding amino acid sequence and a set of analytical results. The designs are placed in the public domain for scrutiny, improvement, and possible experimental verification.

Best mode of expression of acute reversibility of airway obstruction in patients with asthma: application to a new beta-2 agonist, RU 42 173

Lung function tests must distinguish a true drug-induced bronchial response from changes not related to the drug itself, mainly due to intra-individual variability. We compared the variability and ability to detect true drug-induced bronchodilation of 3 modes of expression of the increase in forced expiratory volume in 1 second (delta FEV1) following administration of a 0.25 mg single oral dose of RU 42 173, a new beta 2-agonist. The study was performed in 12 patients with reversible obstructive asthma in a double-blind, crossover, placebo-controlled, randomized manner. The variability of each index was assessed by calculating the coefficient of variation (SD/mean). True drug-induced bronchodilation was assessed by calculating the F value of each index corresponding to the ratio of between-treatment to within-group differences. Three modes of expression of delta FEV1 were compared: delta FEV1 (L) = the absolute increase in FEV1, delta FEV1 (% baseline) and delta FEV1 (% predicted) where delta FEV1 (L) is divided by baseline FEV1 or predicted FEV1, respectively. A statistically significant increase in FEV1 was found up to respectively 3, 2 and 4 hours after dosing when using delta FEV1 (L), delta FEV1 (% baseline) and delta FEV1 (% predicted). The highest F value was obtained for delta FEV1 (% predicted). The coefficient of variation was lower with delta FEV1 (% predicted) than delta FEV1 (L) and delta FEV1 (% baseline). In conclusion, RU 42 173 showed a bronchodilating effect which appears to be clinically relevant. delta FEV1 (% predicted) was to be the least variable and most powerful index and should be preferred to delta FEV1 (L) and even more to delta FEV1 (% baseline) to assess the acute airway response to a bronchodilator drug.

Decreased bronchial response to methacholine in IDDM patients with autonomic neuropathy

This study was designed to evaluate the involvement of airways innervation during diabetic autonomic neuropathy. Bronchial response to methacholine was assessed by inhalation of serially doubling doses in 22 insulin-dependent diabetes mellitus (IDDM) patients and 11 nondiabetic control subjects selected for their nonsmoking habits. Cardiovascular autonomic control was studied by four standardized tests, i.e., blood pressure and heart-rate variations during orthostatism, heart-rate variation during Valsalva maneuver, and deep breathing. Magnitude and time-course of response to methacholine were similar in nondiabetic subjects and IDDM patients without any abnormal result on cardiovascular tests. Conversely, bronchial response to methacholine was markedly reduced in IDDM patients with one or more abnormal results by cardiovascular assessment of autonomic control. In the IDDM patients, bronchial response to methacholine was significantly correlated to indexes of cardiovascular autonomic control. These results suggest that, during diabetic neuropathy, innervation of the airways likewise involves cardiac autonomic control and leads to impairment of defense reflexes of the airways.

The alpha 1-adrenergic agonist methoxamine and the "loop" diuretic frusemide reduce nasal potential difference

Pretreatment by inhalation with the alpha 1-adrenergic agonist methoxamine and the "loop" diuretic frusemide reduces the bronchial response to certain airway challenges in asthma. To test whether these drugs may act by altering airway epithelial ion and water transport, their effect on nasal potential difference (PD) when applied topically in eight normal volunteers was measured. For comparison, the effect of the Na(+)-channel blocking drug amiloride and the beta 2-adrenergic agonist salbutamol was also tested. Both methoxamine and frusemide significantly reduced PD: at the highest concentration given (10(-3) mol.l-1), there was a mean drop in PD from baseline of 39.5% following methoxamine treatment (p less than 0.05) and a mean drop of 30.2% following frusemide (p less than 0.05). Neither drug was as effective as amiloride, which caused a mean drop in PD of 27.5% from baseline at 10(-6) mol.l-1 and a drop of 71.6% at 10(-3) mol.l-1 (p less than 0.01 for each concentration). Salbutamol had no significant effect on PD (p greater than 0.05). We conclude that methoxamine and frusemide may derive their protective effect on some bronchial challenge, at least in part, from their effect on airway epithelial ion flux.

The alpha 1-adrenergic agonist methoxamine and the "loop" diuretic frusemide reduce nasal potential difference

Pretreatment by inhalation with the alpha 1-adrenergic agonist methoxamine and the "loop" diuretic frusemide reduces the bronchial response to certain airway challenges in asthma. To test whether these drugs may act by altering airway epithelial ion and water transport, their effect on nasal potential difference (PD) when applied topically in eight normal volunteers was measured. For comparison, the effect of the Na(+)-channel blocking drug amiloride and the beta 2-adrenergic agonist salbutamol was also tested. Both methoxamine and frusemide significantly reduced PD: at the highest concentration given (10(-3) mol.l-1), there was a mean drop in PD from baseline of 39.5% following methoxamine treatment (p less than 0.05) and a mean drop of 30.2% following frusemide (p less than 0.05). Neither drug was as effective as amiloride, which caused a mean drop in PD of 27.5% from baseline at 10(-6) mol.l-1 and a drop of 71.6% at 10(-3) mol.l-1 (p less than 0.01 for each concentration). Salbutamol had no significant effect on PD (p greater than 0.05). We conclude that methoxamine and frusemide may derive their protective effect on some bronchial challenge, at least in part, from their effect on airway epithelial ion flux.

A single-compartment model cannot describe passive expiration in intubated, paralysed humans

The time-course of thoracic volume changes (respiratory inductive plethysmograph) during relaxed expiration was studied in 11 intubated, paralysed, mechanically ventilated subjects. The semilog volume-time curves show that expiration is governed by two apparently separate mechanisms: one causes emptying of most of the expired volume (approximately 80%) with a time constant of 0.50 +/- 0.22 s for a baseline tidal volume of 0.44 +/- 0.12 l (mean +/- SD) and 0.37 +/- 0.14 s when the tidal volume is reduced (VTP); the other contributes a relatively small amount to the expired volume over a significantly longer time, the time constant amounting to 3.27 +/- 1.54 s for baseline VT and 2.95 +/- 1.65 s for VTp. The first mechanism probably reflects the standard elastic and flow resistive properties of the respiratory system, while the second, slower compartment, is probably an expression of the viscoelastic properties of the pulmonary and chest wall tissues.

A single-compartment model cannot describe passive expiration in intubated, paralysed humans

The time-course of thoracic volume changes (respiratory inductive plethysmograph) during relaxed expiration was studied in 11 intubated, paralysed, mechanically ventilated subjects. The semilog volume-time curves show that expiration is governed by two apparently separate mechanisms: one causes emptying of most of the expired volume (approximately 80%) with a time constant of 0.50 +/- 0.22 s for a baseline tidal volume of 0.44 +/- 0.12 l (mean +/- SD) and 0.37 +/- 0.14 s when the tidal volume is reduced (VTP); the other contributes a relatively small amount to the expired volume over a significantly longer time, the time constant amounting to 3.27 +/- 1.54 s for baseline VT and 2.95 +/- 1.65 s for VTp. The first mechanism probably reflects the standard elastic and flow resistive properties of the respiratory system, while the second, slower compartment, is probably an expression of the viscoelastic properties of the pulmonary and chest wall tissues.

Effects of SK&F 104353, a leukotriene receptor antagonist, on the bronchial responses to histamine in subjects with asthma: a comparative study with terfenadine

We compared the effects of pretreatment of 800 micrograms of inhaled Smith Kline & French (SK&F) 104353, a leukotriene receptor antagonist, and 120 mg of oral terfenadine on the bronchial responses to inhaled histamine in 12 subjects with asthma. The study took place on 3 different days and was conducted according to a double-blind, crossover, double-dummy, randomized, and placebo-controlled design. There was no difference in baseline and prechallenge FEV1 after placebo, SK&F 104353, and terfenadine administration. The median ratio of the provocative dose causing a 20% fall in FEV1 from baseline (PD20) with terfenadine over PD20 with placebo was 12.36 (range, 3.2 to 30.3; p less than 0.01) and that of PD20 with SK&F 104353 over PD20 with placebo was 1.51 (range, 0.8 to 5.9; not significant). Analysis of individual results demonstrated a shift toward the right of the dose-response curves to histamine with SK&F 104353 compared to that with placebo in three subjects, whereas the active compound did not exhibit any protective effect against histamine in the remaining nine subjects. We conclude that there is a leukotriene component to the bronchial responses to histamine in some, but not all, subjects. This component remains, however, small and does not appear to be clinically important in the population of subjects with asthma that was studied.

Inflation of antishock trousers increases bronchial response to methacholine in healthy subjects

We studied changes in lung volumes and in bronchial response to methacholine chloride (MC) challenge when antishock trousers (AST) were inflated at venous occlusion pressure in healthy subjects in the standing posture, a maneuver known to shift blood toward lung vessels. On inflation of bladders isolated to lower limbs, lung volumes did not change but bronchial response to MC increased, as evidenced by a greater fall in the forced expiratory volume in 1 s (FEV1) at the highest dose of MC used compared with control without AST inflation (delta FEV1 = 0.94 +/- 0.40 vs. 0.66 +/- 0.46 liter, P less than 0.001). Full inflation of AST, i.e., lower limb and abdominal bladder inflated, significantly reduced vital capacity (P less than 0.001), functional residual capacity (P less than 0.01), and FEV1 (P less than 0.01) and enhanced the bronchial response to MC challenge compared with partial AST inflation (delta FEV1 = 1.28 +/- 0.47 liter, P less than 0.05). Because there was no significant reduction of lung volumes on partial AST inflation, the enhanced bronchial response to MC cannot be explained solely by changes in base-line lung volumes. An alternative explanation might be a congestion and/or edema of the airway wall on AST inflation. Therefore, to investigate further the mechanism of the increased bronchial response to MC, we pretreated the subjects with the inhaled alpha 1-adrenergic agonist methoxamine, which has both direct bronchoconstrictor and bronchial vasoconstrictor effects.(ABSTRACT TRUNCATED AT 250 WORDS)

[Mechanisms of exertion dyspnea in cardiac insufficiency]

Effort dyspnea in cardiac failure corresponds to a subjective perception of difficulty in breathing which is itself secondary to a disproportion between the central bulbar respiratory regulation and the level of pulmonary ventilation attained. In cardiac failure, this situation is the result of dysfunction of both the respiratory apparatus and the skeletal striated muscle during exercise. During exercise a rise in left ventricular end diastolic pressure causes: a reduction in pulmonary compliance. The bronchial and alveolar capillaries drain into the pulmonary veins. The congestion of these capillaries and the resulting oedema makes the lung "stiffer"; an increase in the resistances of the small airways due to direct compression by congested bronchial vessels. The physiological dead space increases: the respiratory muscles ventilate pulmonary zones which are not perfused to no benefit. The reduction of pulmonary compliance, the increased resistances of the airways and of the physiological dead space all contribute to increase the work of the respiratory muscles. In addition to these mechanical phenomena, there is greater stimulation of the respiratory centre in the brain stem by the metabolic abnormalities of the skeletal striated muscles. During effort, they rapidly function under anaerobic conditions and the resulting hyperproduction of lactate and carbon dioxide stimulates the respiratory centres.

[Vasomotility of the bronchial circulation in cardiac failure]

The bronchial circulation is a physiological left-to-left shunt; the venous return of the bronchial arteries vascularising the intra-pulmonary bronchi drains directly into the left heart chambers. In cardiac failure, increased left ventricular filling pressures affects the bronchial circulation and causes stasis and congestion. Congestion of the arterial and venous bronchial microcirculation leads to thickening of the bronchial mucosa and submucosa, resulting in a tendency to obstruct small and medium-sized airways. The bronchial circulation can be explored indirectly in cardiac failure by the spirometric response to adrenergic agonists and antagonists administered by inhalation: bronchial vasomotor phenomena explain the symptomatology of cardiac asthma and also seem to play a role in the genesis of the dyspnoea of effort in patients with cardiac failure.

[Non-prostanoid endothelium-derived factors. Physiologic roles and possible implications in cardiovascular pathology]

Non prostanoid endothelium-derived relaxing and contracting factors (EDRF and EDCF, respectively) are released by endothelial cells and act on the underlying vascular smooth muscle. It is now established that EDRF is nitric oxide (NO), whereas EDCF has been recently identified as a 21 residue peptide, called endothelin. However, circumstantial evidence suggests that there may be more than one EDRF and/or EDCF. EDRF (NO) induces relaxation of the underlying vascular smooth muscle by enhancing intracellular level of cyclic guanosine monophosphate. The mechanisms of action of endothelin are still to be defined. It seems however that influx of extracellular calcium may partly account for its action. Although important findings have been made recently, most of the hypotheseses, at our current stage of knowledge, about the respective roles of EDRF and EDCF in disease have still to be proved. However, it is preferable from now to think in terms of balance (or imbalance) between these two factors which, probably, have both a fundamental role and very likely interact with each other in maintaining and regulating vascular tone in man.

Mechanical effects of PEEP in patients with adult respiratory distress syndrome

In 10 patients with adult respiratory distress syndrome, we studied the effects on respiratory system mechanics of two levels of positive end-expiratory pressure (PEEP), best PEEP (BP) and half of this value (HBP), using a respiratory inductive plethysmograph (RIP) combined with a super syringe. We found the following. 1) Inflation compliance of pressure-volume (PV) curves did not change significantly. 2) End-expiratory volume increased with HBP and further with BP (278 +/- 186 and 464 +/- 313 ml, respectively, P less than 0.01). This increase was positively correlated with inflation compliance for HBP and BP (r = 0.794, P less than 0.01 and r = 0.876, P less than 0.01, respectively). 3) No dynamic hyper-inflation was detected on mechanical ventilation at zero end-expiratory pressure (ZEEP), and the time constant of the respiratory system was in the normal range (0.79 +/- 0.21 s). 4) Hysteresis of PVrip curves, which were corrected for gas exchange, decreased significantly with PEEP (P less than 0.05). We conclude that PEEP does not change inflation PV curve but induces an increase in intrathoracic volume whose magnitude is related to compliance and PEEP level. The reduction of hysteresis with PEEP suggests less gas trapping and thus a functional improvement.