Domestic exposure to fungal allergenic particles determined by halogen immunoassay using subject's serum versus particles carrying three non-fungal allergens determined by allergen-specific HIA.

UNLABELLED: Studies that estimate indoor aeroallergen exposure typically measure a pre-selected limited range of allergens. In this study, inhalable aeroallergen particles were quantified using the halogen immunoassay (HIA) to determine the contribution of fungal and non-fungal aeroallergens to total allergen exposure. Bioaerosols from 39 homes of fungal-allergic subjects were sampled using inhalable fraction samplers and immunostained by HIA using resident subject's immunoglobulin E (IgE) to detect allergen-laden particles. Fungal aerosols as well as particles carrying mite, cat, and cockroach allergens were identified and enumerated by HIA. Reservoir dust-mite (Der p 1), cat (Fel d 1), and cockroach (Bla g 1) allergen concentrations were quantified by ELISA. Fungal particles that bound subject's IgE in the HIA were 1.7 (bedroom)- and 1.4 (living room)-fold more concentrated than Der p 1, Fel d 1, and Bla g 1 allergen particles combined. Predominant fungal conidia that bound IgE were derived from common environmental genera including Cladosporium and other fungi that produce amerospores. Airborne mite, cat, and cockroach allergen particle counts were not associated with reservoir concentrations determined by ELISA. This study demonstrates that inhalable fungal aerosols are the predominant aeroallergen sources in Sydney homes and should be considered in future exposure assessments. PRACTICAL IMPLICATIONS: Indoor allergen exposure assessment studies have primarily focused on a limited range of allergen sources in samples derived from reservoir dust samples. Using an innovative immunodiagnostic approach, this study demonstrates that fungal bioaerosols are the dominant source of aeroallergen exposure in the domestic environment, providing unique insight into domestic aeroallergen exposure.

Airway smooth muscle thickness in asthma is related to severity but not duration of asthma.

Asthma is characterised by an increased airway smooth muscle (ASM) area (ASM(area)) within the airway wall. The present study examined the relationship of factors including severity and duration of asthma to ASM(area). The perimeter of the basement membrane (PBM) and ASM(area) were measured on transverse sections of large and small airways from post mortem cases of fatal (n = 107) and nonfatal asthma (n = 37) and from control subjects (n = 69). The thickness of ASM (ASM(area)/PBM) was compared between asthma groups using multivariate linear regression. When all airways were considered together, ASM(area)/PBM (in millimetres) was increased in nonfatal (median 0.04; interquartile range 0.013-0.051; p = 0.034) and fatal cases of asthma (0.048; 0.025-0.078; p<0.001) compared with controls (0.036; 0.024-0.042). Compared with cases of nonfatal asthma, ASM(area)/PBM was greater in cases of fatal asthma in large (p<0.001) and medium (p<0.001), but not small, airways. ASM(area)/PBM was not related to duration of asthma, age of onset of asthma, sex or smoking. No effect due to study centre, other than that due to sampling strategy, was found. The thickness of the ASM layer is increased in asthma and is related to the severity of asthma but not its duration.

Cystic fibrosis: benefits and clinical outcome.

Diagnosis of cystic fibrosis (CF), the most common life-limiting recessive genetic condition in the caucasian population, via NBS is now occurring in many regions of the world. There is evidence that newborn screening (NBS) for CF may prevent malnutrition in infants with pancreatic-insufficient CF and may have an impact upon later growth and development. Progression of lung disease in CF is the major determinant of quality of life and of survival. There is no clear evidence of an advantage for those diagnosed by NBS programmes in terms of the progression of lung disease as measured by lung function. Some studies show better preservation of lung function, while others fail to show such an outcome. This is also true for respiratory infections and acquisition of the most significant respiratory pathogen in CF-Pseudomonas aeruginosa. There is, however, evidence that an advantage may be accrued by early diagnosis made possible by NBS in terms of lung disease as measured by pulmonary imaging. Those diagnosed via NBS have an apparent advantage in terms of a reduction in the number and duration of hospitalizations, particularly in infancy, as well as the need for antibiotic usage. There is also evidence from a number of sources for a lifetime survival advantage for those with CF diagnosed via NBS programmes, with the most significant advantage being for survival during infancy.

Contraction to big endothelin-1, big endothelin-2 and big endothelin-3, and endothelin-converting enzyme inhibition in human isolated bronchi.

All three endothelin precursor peptides, i.e. big endothelin-1 (big ET-1), big endothelin-2 (big ET-2) and big endothelin-3 (big ET-3), produced contractile responses in human isolated bronchi, demonstrating the presence of functional endothelin-converting enzyme (ECE) in this tissue. The maximal contractile responses were equal to 108.4+/-8.0% (0.1 microM big ET-1; n=4), 85.2+/-11.8% (0.1 microM big ET-2; n=7) and 43.0+/-7.2% (0.1 microM big ET-3; n=5) of the reference response to acetylcholine (1 mM). The response to big ET-1 (0.1 microM), but not endothelin-1 (ET-1, 0.1 microM), was diminished after overnight storage of the tissue at 4 degrees C, demonstrating instability of the enzyme. The responses to all three big-endothelins were significantly inhibited, by the ECE inhibitors CGS 26393 and CGS 26303, in a concentration-related manner. The responses to the mature peptides ET-1, endothelin-2 (ET-2), and endothelin-3 (ET-3) were unaffected by CGS 26393 and CGS 26303. Phosphoramidon (10 microM) also produced an inhibition of the response to big ET-1 that was equivalent to that produced by CGS 26393 (10 microM). Combination of CGS 26393 (10 microM) and phosphoramidon (10 microM) did not produce an additive inhibition. These results demonstrate the presence of functional ECE for all three big endothelins in human bronchus and inhibition of the enzyme by newly developed orally active ECE inhibitors, as well as phosphoramidon. British Journal of Pharmacology (2000) 129, 170 - 176

The mechanism of action of endothelin in human lung.

1 The peptides endothelin-1 (ET-1) and endothelin-2 (ET-2) elicited potent and sustained contractions of human isolated bronchus and pulmonary artery. 2 ET-1 is one of the most potent contractile agonists investigated in these tissues with an EC50 value of 18.3 nM (95% confidence interval: 12.9, 25.9 nM: n = 26) in bronchus and 3.2 nM (95% confidence interval: 0.4, 23.9 nM; n = 5) in the arterial preparation. 3 ET-1 is 2.5 times more potent than ET-2 in both the airway and vascular tissues, and both forms of the peptide have geometric mean EC50 values 5 times greater than in the isolated bronchial tissue than in the pulmonary artery. 4 Neither pretreatment with the voltage-dependent calcium (VDC) channel antagonist verapamil (10 microM) nor with indomethacin (25 microM) significantly altered the response curve to ET-1 in human isolated bronchus. Removal of calcium from the Krebs-Henseleit solution did not affect ET-1-induced responses. 5 Specific binding on the smooth muscle of human airway and pulmonary arterial tissue to both ET-1 and ET-2 was detected in autoradiographic studies. There appeared to be no difference between the peptides in the location nor the density of binding sites. 6 We conclude that contraction of human bronchial tissue by ET-1 is not dependent upon influence of extracellular calcium nor release of prostaglandins or thromboxane A2. It is likely that the action of ET-1 in this tissue is due to binding of this peptide to specific receptors located on the smooth muscle.

Phosphoramidon potentiates the contractile response to endothelin-3, but not endothelin-1 in isolated airway tissue.

1. Phosphoramidon (10 microM) markedly increased the contractile response to endothelin-3 in human and rabbit bronchus in vitro. In human tissue the contractile response to 0.3 microM endothelin-3 was significantly increased from 54 +/- 12% to 137 +/- 34% (of the response to 1 nM acetylcholine) in the presence of phosphoramidon. Similarly, in rabbit isolated bronchus, the endothelin-3-induced response was increased from 34 +/- 5% to 61 +/- 7%. 2. In addition, the potency (as measured by EC30 values) of this peptide in human and rabbit airways was significantly augmented in the presence of the enzyme inhibitor. The geometric mean EC30 value was decreased from 53 nM (95% CI:15, 190) to 8 nM (95% CI:3, 23) in human bronchus and from 150 nM (95% CI:89, 250) to 23 nM (95% CI:11, 50) in rabbit tissue. 3. Neither the potency nor the response (at 0.3 microM) to endothelin-3 in canine bronchial rings was altered after incubation of the tissue in phosphoramidon. 4. A previous study carried out in human airways has implied that the difference in potency between endothelin-1 and endothelin-3 may be attributed to a heterogeneous endothelin receptor population. The results of our study, while also demonstrating this difference in potency, have shown that this marked difference, as well as that obvious in rabbit airway tissue can be abolished in the presence of phosphoramidon. 5. Phosphoramidon produced no change in the cumulative concentration-response curve for endothelin-1 in airway tissue from the three species studied. 6. These results suggest that a phosphoramidon-sensitive enzyme (probably neutral endopeptidase) found in lung, may be responsible for local degradation of endothelin-3, but not endothelin-l in human and rabbit isolated bronchus.

Does the disease state influence the responsiveness of human airways studied in vitro?

Human airway tissue has been used in vitro to study mechanisms of airway disease. However, there has never been a comprehensive study that has looked at the influence of disease on the subsequent in vitro responsiveness of human airways. In this study, we obtained airway tissue from patients who were undergoing resection of the lung for carcinoma. We then compared the airway responsiveness in these tissues and in tissues from patients who had undergone lung transplantation for alpha-1-antitrypsin deficiency, emphysema, or cystic fibrosis with the responsiveness in tissues obtained from donor lungs, i.e., nondiseased. When the relationships between concentration and response were compared, we found that for histamine, electrical field stimulation, levcromakalim, and isoproterenol similar responses could be expected in tissues obtained from all the sources studied. This was not true for acetylcholine in that there were significantly lower responses in tissues from patients with alpha-1-antitrypsin deficiency (P = 0.02; n = 9) or from patients having a lung resected for carcinoma (P = 0.01; n = 6) compared with that of the nondiseased group (n = 6). Similarly, for carbachol, the responses were significantly lower in the alpha-1-antitrypsin deficiency group (P = 0.001; n = 10) and in specimens resected for carcinoma (P = 0.001; n = 6) than in the nondiseased group (n = 9). We conclude that, apart from acetylcholine and carbachol, contractile and relaxant agonists give similar responses when used in human airway tissues from various sources. Our results highlight the importance of stating the source of tissue when human airways are to be studied.

The impact of meconium ileus on the clinical course of children with cystic fibrosis.

The present study was designed to compare the clinical course of children diagnosed with cystic fibrosis (CF) in infancy due to the presence of meconium ileus (MI) with children diagnosed by way of a newborn screening programme (non-MI). A matched case-control study design was used. Matching was performed on the basis of sex and date of birth. All children born in New South Wales, Australia after 1980 and who had attended the CF clinic at The Children's Hospital at Westmead since diagnosis were included as possible cases or controls. Parameters pertaining to the clinical course were compared in 39 matched pairs. MI children had a significantly worse pulmonary status. The forced expiratory volume in one second was 16.3 +/- 5.2% higher (p<0.001, n=21 pairs) and the forced vital capacity value 10.5 +/- 4.7%, higher (p<0.05, n=21 pairs) in non-MI children. The difference between the pairs (18.6 +/- 4.4 MI and 20.5 +/- 3.4 non-MI) in the Shwachman chest radiograph score was statistically significant (p<0.05, n=39 pairs). There were no significant differences in any other assessed parameters, such as height, weight, the presence of liver function abnormalities, the frequency of hospitalization or airway microbial colonization. Meconium ileus may be an early indication of a more severe phenotype of cystic fibrosis. This was suggested by the significantly lower pulmonary function found in children with a history of meconium ileus compared to age- and sex-matched children who did not have meconium ileus.

Endothelin receptors and activity differ in human, dog, and rabbit lung.

In this study, we have examined dog and rabbit airways as potential models for human airways in regard to the activity of endothelin. The receptors involved in the response to endothelin-1 (ET-1) in airway tissue from human, rabbit, and dog lung were investigated, as was the mechanism responsible for the contraction to ET-1 in tissue from the three species. By using specific endothelin receptor agonists and antagonists, we have demonstrated that ETB receptors predominate in rabbit and human airways and ETA receptors in dog airways. The contraction to ET-1 is not dependent on cyclooxygenase products of arachidonic acid, as indomethacin had no effect on the response to ET-1. Extracellular calcium influx via voltage-dependent channels is necessary for contraction to ET-1 in rabbit and dog airways. These results are in contrast to our previously reported results in human airways, in which neither removal of extracellular calcium nor verapamil affected the ET-1 response. The sustained phase of the contraction to ET-1 in all three species may be mediated in part by activation of protein kinase C (PKC), as the inhibitor staurosporine significantly altered the time course of the response to endothelin. We therefore conclude that in rabbit airways ET-1 activates ETB receptors, triggers the influx of extracellular calcium through voltage-dependent channels, and induces a contractile response that is, in part, dependent upon stimulation of PKC. The same mechanism is triggered in dog bronchus; however, the receptors involved in this species are of the ETA type. Finally, in human airways, the contractile response to ET-1, while independent of extracellular calcium influx, is dependent upon PKC activation after binding of the peptide to ETB receptors.

Endothelin-3 increases transmission in the rabbit pulmonary parasympathetic nervous system.

The effect of endothelin-3 (ET-3) on the response to parasympathetic nerve stimulation of rabbit isolated bronchus was examined. The site of action of ET-3 in the pulmonary parasympathetic nervous system was also investigated. ET-3 induced a concentration-dependent increase in the response to electrical field stimulation. The response was atropine sensitive and therefore cholinergically mediated. At a concentration of 10 nM, ET-3 increased the response to field stimulation to 205 +/- 42% of the initial response. The effect was concentration-related, as 100 nM further increased this response to 315 +/- 69%. The responsiveness of the tissue to exogenous acetylcholine was not affected by ET-3. Therefore ET-3 has a neuromodulatory role on cholinergic parasympathetic transmission in rabbit airways exerted at a prejunctional site.

Functional and autoradiographic studies of endothelin-1 and endothelin-2 in human bronchi, pulmonary arteries, and airway parasympathetic ganglia.

We compared the contractile potency and efficacy of two of the forms of endothelin (endothelin-1 and endothelin-2) on human bronchi and pulmonary arteries in vitro and examined the effects of sarafotoxin on the bronchial preparations. In addition, we used autoradiographic methods to investigate the location of binding sites for both forms of endothelin within human lung. Endothelin-1 (ET-1) was 2.5 times more potent than endothelin-2 (ET-2) in both the airway and vascular tissues, and both forms of the peptide were 5 times more potent in the isolated pulmonary artery than in the bronchial tissue. There were no differences in the magnitude of the contractions generated by ET-1 and ET-2 in either tissue type. Sarafotoxin also produced a contractile response in the bronchi that was equipotent to ET-1 but of a greater magnitude. Specific binding on the smooth muscle of bronchus, pulmonary artery, and alveolar walls to both ET-1 and ET-2 was detected in autoradiographic studies. In addition, binding sites for both forms of the peptide were localized to parasympathetic ganglia within the airways, where the presence of muscarinic receptors was also confirmed with [3H]QNB. There appeared to be no difference between the endothelins in the location or the density of binding sites. These results indicate that endothelin may have a neuromodulatory role in the airways as well as a direct contractile action on the bronchial and arterial smooth muscle.

The maintenance of functional activity in human isolated bronchus after cryopreservation.

Cryopreservation has been successfully used in the in vitro study of pharmacological responses of animal tissues and, to a limited extent, of human tissue. In this study, we examined the effect of cryopreservation on reactivity of human bronchus which was stored for a period of up to 3 weeks. Thirty-two bronchial rings were obtained from each of four transplantation donors (four male, aged 32 +/- 15 years SD). Eight rings from each patient were studied on day 0 (the day of retrieval) and an additional eight on days 7, 14 and 21, after cryopreservation in 1.8 M dimethyl sulfoxide in 1 ml foetal bovine serum at -190 degrees C. On day 0, all tissues from all patients contracted in response to either histamine or carbachol or relaxed in response to isoprenaline or levcromakalim. There was no significant difference in the mean Tmax or pD2 values for any agonist on days 7, 14 and 21 when responses were compared with those obtained on day 0. The major change induced by cryopreservation was observed in the response to antigen. Tissues from three of the four donors contracted to the administration of Dermatophagoides pteronyssinus on day 0. However, when tissues from these same donors were studied on days 7, 14 and 21, they did not contract to this antigen. The results of this study indicate that human bronchial tissue may be successfully cryopreserved to maintain contractile and relaxant responses to various agonists. However, the response to antigen in tissues, which on day 0 of study were determined to be sensitized, was not present after cryopreservation.

Levcromakalim- and isoprenaline-induced relaxation of human isolated airways--role of the epithelium and of K+ channel activation.

In this study we have investigated the mechanism of action of levcromakalim and isoprenaline in human isolated airways with respect to the K+ channels they activate and the possibility that these smooth muscle relaxants activate K+ channels on the airway epithelium. Mechanical removal of the epithelial layer (mean percentage of epithelium present 20 +/- 3%, n = 20 tissues) did not affect the relaxation responses to levcromakalim or isoprenaline, either in terms of maximal relaxation or sensitivity. Whilst having no effect on isoprenaline-induced relaxation, studied from basal tone, the ATP-sensitive K+ channel blocker BRL 31660 (10, 30 and 50 microM) reduced relaxation responses induced (from basal tone) by levcromakalim from 74 +/- 6% (of the maximal response to isoprenaline) to 48 +/- 12% (n = 7), 9 +/- 9% (n = 4) and 0 (n = 4), respectively. Charybdotoxin, a blocker of high conductance Ca(2+)-activated K+ channels, at concentrations of 30 and 100 nM, had no effect on either levcromakalim- or or isoprenaline-induced relaxation responses and yet charybdotoxin was active at KCa channels in outside-out patches of hippocampal granule cells. Moreover, tetraethylammonium (10 mM) inhibited neither isoprenaline- nor levcromakalim-induced relaxation. This study has demonstrated that the relaxation responses elicited in human bronchus to isoprenaline and levcromakalim are likely to be the result of direct effects on the smooth muscle with no contribution from epithelial receptors or K+ channels. The actions of levcromakalim appear to be mediated only via activation of KATP channels. Further, we have made the important observation that, under the experimental conditions of our study, isoprenaline does not activate the KCa channel to produce relaxation in human bronchus.

Parasympathetic neurotransmission in rabbit isolated bronchus is modulated at prejunctional sites via endothelinB receptor stimulation.

OBJECTIVE: The aim of this study was to investigate the mechanism involved in endothelin-induced potentiation of the response to parasympathetic nerve stimulation. METHODOLOGY: We used autoradiographic and functional studies in rabbit isolated bronchi. RESULTS: Autoradiography revealed dense binding sites for radiolabelled endothelin-3 over bronchial parasympathetic ganglia. The contractile response of the bronchus to electrical field stimulation was significantly potentiated by endothelin-3, endothelin-1, sarafotoxin S6c and BQ-3020 to 326+/-53%, 293+/-63%, 514+/-119% and 655+/-178%, respectively, of control values. The endothelin-3-induced potentiation of neurally evoked responses was not affected by the presence of propranolol, phentolamine or hexamethonium. The potentiation was also unaltered by pretreatment with the endothelinA receptor antagonist BQ-123 (3 micromol/L), but was significantly reduced in the presence of the combined endothelinA/endothelinB receptor antagonist PD 145065, indicating that the potentiation was mediated via endothelinB receptors. Confirmation of endothelinB receptor involvement in the neuropotentiation was obtained by demonstration of a significant amelioration of the potentiation in the presence of the endothelinB receptor selective antagonist BQ-788, and after endothelinB receptor desensitization by the endothelin, receptor selective agonist sarafotoxin S6b. CONCLUSIONS: These results suggest that the endothelin-induced potentiation of parasympathetic neural responses in the rabbit bronchus is mediated via endothelinB receptor activation.

Neutrophil-induced human bronchial hyperresponsiveness in vitro--pharmacological modulation.

Although it has been postulated that inflammatory cells cause the bronchial hyperresponsiveness which is diagnostic of asthma, until recently there has been little direct evidence of such a link. We have recently shown that calcium ionophore-activated human neutrophils and eosinophils can induce a state of human airway hyperresponsiveness in vitro. In this study we have shown that the anti-inflammatory agent nedocromil sodium, 10(-7) M, inhibited the hyperresponsiveness induced by products released from ionophore activated neutrophils but did not inhibit the release of leukotriene B4 from the same cells. Neutrophil-induced bronchial hyperresponsiveness was also inhibited by pre-treatment of the bronchial tissues with a thromboxane A2 and prostaglandin receptor antagonist, GR32191, 10(-7) M. These findings indicate that cyclooxygenase products are involved in bronchial hyperresponsiveness induced by inflammatory cell products in vitro and that their release can be inhibited by nedocromil sodium.

Effect of respiratory syncytial virus on subsequent allergic sensitization to ovalbumin in guinea-pigs.

Children with acute respiratory syncytial virus (RSV) bronchiolitis often develop recurrent wheezing, asthma and allergic sensitization, but the role of RSV in the pathogenesis of these sequelae is unclear. This study examined whether RSV infection potentiates subsequent allergic sensitization, airway hyperresponsiveness (AHR) and airway inflammation induced by repeated exposures to aerosolized ovalbumin (OA) in guinea-pigs. Guinea-pigs received either RSV or sham inoculum, followed by exposures to OA- or saline-containing aerosols to form the following groups: 1) noninfected, nonsensitized controls (sham/saline group); 2) RSV-infected, nonsensitized animals (RSV/ saline group); 3) noninfected, OA-sensitized animals (sham/OA group); 4) RSV infection and first OA exposure on the same day (RSV/OA group), and 5) RSV infection six days prior to first OA exposure (RSV6/OA group). Three days after the final aerosol exposure, circulating OA-specific immunoglobulin (Ig)G1 antibody titres and AHR to inhalation acetylcholine challenge were measured and morphometry performed to evaluate allergic inflammation of the airways. OA-exposed animals developed OA-specific IgG1 antibodies, AHR and airway eosinophilia (sham/OA, RSV/OA and RSV6/OA groups. RSV infection alone induced significant AHR and airway eosinophilia (RSV/saline group). RSV infection, and concomitant exposure to OA (RSV/OA group) enhanced OA-specific IgG1 antibodies, but not airway eosinophilia or AHR. Such increases were not observed in the RSV6/OA group. In conclusion, respiratory syncytial virus potentiates the production of ovalbumin-specific immunoglobulin G1 antibodies in guinea-pigs, but circulating titres of these antibodies do not reflect the extent of airway hyperresponsiveness or airway inflammation. In addition, respiratory syncytial virus infection alone can produce slight increases in airway hyperresponsiveness that are associated with increased numbers of eosinophils in the airways.

Airway structure and function in Eisenmenger's syndrome.

The responsiveness of airways from patients with Eisenmenger's syndrome (n = 5) was compared with that in airways from organ donors (n = 10). Enhanced contractile responses to cholinergic stimulation were found in airways from patients with Eisenmenger's syndrome. The maximal responses to acetylcholine, carbachol, and parasympathetic nerve stimulation in airway tissue from these patients were 221%, 139%, and 152%, respectively, of the maximal responses obtained in donor tissue. Further, relaxation responses to isoproterenol and levocromakalim were absent (n = 2) or markedly impaired (n = 3) in airways from patients with Eisenmenger's syndrome. This attenuated relaxation response was nonspecific in that it was also absent after vasoactive intestinal peptide, sodium nitroprusside, papaverine, and electrical field application. These observations can most likely be explained by a decrease in intrinsic smooth muscle tone, as precontraction of airways revealed relaxation responses that were equivalent to those obtained in donor tissues. Morphometric analysis of tissues used for the functional studies revealed no differences in the airway dimensions (internal perimeter) or airway wall components (e.g., smooth muscle, cartilage) or total area to explain these observations. Although the mechanism for this observed decrease in intrinsic airway smooth muscle tone is not certain, it may be due to alteration in the substructure of the airway wall or, alternatively, may result from the continued release of depressant factors in the vicinity of the smooth muscle which permanently alters smooth muscle responsiveness.

Sensitization decreases relaxation in human isolated airways.

Passively sensitized human isolated airways provide an opportunity to study some aspects of bronchial hyperresponsiveness in vitro. Since it has been suggested that excessive airway narrowing could be due to impaired relaxation, we examined the effect of a variety of agents producing relaxation via different mechanisms, i.e., verapamil and lemakalim (a calcium channel antagonist and a potassium channel opener, respectively) and isoproterenol, forskolin, and dibutyryl cAMP (modulators of the beta-adrenoceptor signal transduction pathway). Human bronchial rings, obtained at thoracotomy, were passively sensitized by incubation in serum from atopic asthmatic patients, and control rings were incubated in serum from nonatopic subjects. We also studied bronchial rings from five spontaneously sensitized human lung specimens. Responses to the relaxant compounds were measured isometrically. Passive sensitization significantly decreased the efficacy of verapamil in maximally contracted tissues from 60 +/- 10 to 45 +/- 7% of the maximal carbachol response (n = 6, p < 0.05) and that of lemakalim from 51 +/- 16 to 38 +/- 14% (n = 7, p < 0.05) in tissues at baseline tone. Similarly, spontaneously sensitized tissues relaxed less to lemakalim (64 +/- 6% of the maximal response to isoproterenol, n = 5, p < 0.05) than did nonsensitized tissues (80 +/- 4%). Sensitization did not alter responses to isoproterenol, forskolin, and dibutyryl cAMP. We conclude that sensitization of human isolated airways reduces relaxation responses that depend upon activation of ion channels but not those that depend upon activation of beta-adrenoceptors and transduction processes directly coupled to these receptors.

A multicentre randomized placebo-controlled double-blind study on the efficacy of Ketotifen in infants with chronic cough or wheeze.

The efficacy of Ketotifen was examined in the treatment of 113 infants between 6 and 36 months of age presenting with a history of cough and/or wheeze in a multicentre randomized placebo-controlled double-blind study. A 4 week no-medication baseline phase preceded the 16 week treatment phase in which infants took 2.5 mL twice daily of either placebo or Ketotifen (0.5 mg) syrup; this was followed by a 4 week wash-out phase. Diary card evaluation was performed by the parent or guardian for the duration of the study and recorded wheeze and cough twice daily as well as medication used. The percentage of symptom-free days decreased significantly in both groups (P < 0.005) with placebo-treated infants experiencing significantly more symptom-free days compared with the Ketotifen group (P < 0.01), although this difference was never more than 10% in any 4 week treatment period. Symptom severity scores and use of beta-agonist medication were also less in the placebo-treated infants but did not reach statistical significance. This study was unable to show a therapeutic advantage of Ketotifen over placebo in this group of infants with chronic cough and/or wheeze and the apparent statistical advantage of placebo is not a clinically relevant finding.