No abstract

The International Study of Asthma and Allergies in Childhood (ISAAC) Phase One showed large worldwide variations in the prevalence of symptoms of asthma, rhinoconjunctivitis and eczema, up to 10 to 20 fold between countries. Ecological analyses were undertaken with ISAAC Phase One data to explore factors that may have contributed to these variations, and are summarised and reviewed here.In ISAAC Phase One the prevalence of symptoms in the past 12 months of asthma, rhinoconjunctivitis and eczema were estimated from studies in 463,801 children aged 13 - 14 years in 155 centres in 56 countries, and in 257,800 children aged 6-7 years in 91 centres in 38 countries. Ecological analyses were undertaken between symptom prevalence and the following: Gross National Product per capita (GNP), food intake, immunisation rates, tuberculosis notifications, climatic factors, tobacco consumption, pollen, antibiotic sales, paracetamol sales, and outdoor air pollution.Symptom prevalence of all three conditions was positively associated with GNP, trans fatty acids, paracetamol, and women smoking, and inversely associated with food of plant origin, pollen, immunisations, tuberculosis notifications, air pollution, and men smoking. The magnitude of these associations was small, but consistent in direction between conditions. There were mixed associations of climate and antibiotic sales with symptom prevalence.The potential causality of these associations warrant further investigation. Factors which prevent the development of these conditions, or where there is an absence of a positive correlation at a population level may be as important from the policy viewpoint as a focus on the positive risk factors. Interventions based on small associations may have the potential for a large public health benefit.

Objectives To assess the ability of prenatal ultrasound and magnetic resonance imaging (MRI) to diagnose isolated anomalies of the corpus callosum (ACC) and to further document the long-term prognosis following diagnosis. Methods

The usefulness of the in vitro histamine-release test for the diagnosis of drug allergy appears to be insufficient.

Incubation of eosinophils (EOS) with alveolar macrophage (AM) supernatants isolated from asthmatic subjects followed by stimulation with the calcium ionophore A23187 resulted in enhancement of the capacity of EOS to elaborate leukotriene C4 (LTC4) (mean enhancement 169 +/- 37%, n = 31). Pretreatment of EOS with AM supernatants derived from normal individuals did not enhance LTC4 generation as compared with control medium. Enhancement was maximal when EOS were preincubated with a 1:6 dilution of AM supernatants for 5 min at 37 degrees C and were then stimulated with 5 microM A23187 for 15 min. Separation of AM supernatants by size-exclusion HPLC using a TSK G3000 SW column resulted in a peak of enhancing activity with an estimated molecular mass of approximately 30,000 D. Further purification by anion exchange HPLC using a TSK DEAE 5PW column (pH 7.4) resolved the activity into a minor peak at 0.17 M NaCl and a major peak at 0.2 M NaCl. The activities were distinct from interleukin-1 and tumor necrosis factor. Resolution of the major peak of activity by reverse-phase HPLC using a C18 spherisorb ODS column and a slope gradient of 0 to 100% acetonitrile/0.1% trifluoroacetic acid demonstrated a single peak of activity that eluted at 41% acetonitrile. The enhancing activity was sensitive to trypsin and heat and was neutralized by a specific antibody to granulocyte-macrophage colony-stimulating factor (GM-CSF). Pretreatment of EOS with recombinant GM-CSF primed the cells for enhanced LTC4 generation following subsequent stimulation with A23187. GM-CSF may play a role in the amplification of the eosinophilic inflammation in asthmatic airways.

No abstract

Airways epithelial cells may be involved in the pathogenesis of asthma, but their role remains to be determined. Epithelial cells can release large amounts of 15-hydroxy-eicosatetranoic acid (15-HETE) and smaller amounts of prostaglandin E2 (PGE2) as well as fibronectin, a mediator involved in epithelial repair after injury. Epithelial cells obtained after bronchial brushing of 16 asthmatic (age 38 +/- 5 yr) and 11 normal subjects (age 36 +/- 5 yr) were studied. The percentage of epithelial cells was assessed by immunocytochemistry using an anti-cytokeratin antibody. The viability of the cells was assessed by trypan blue exclusion. The release of 15-HETE PGE2 and fibronectin was studied in resting cells and after A23187 calcium ionophore stimulation. Epithelial cells always comprised more than 86% of cells recovered, and the viability of epithelial cells was significantly (p < 0.001, Mann-Whitney U test) greater in normal subjects (54 +/- 5%) compared with asthmatic subjects (13 +/- 1%). The release of 15-HETE and fibronectin by resting epithelial cells was significantly greater in asthmatics (p < 0.05, Mann-Whitney U test) than in normal subjects. A23187 significantly (p < 0.05, Wilcoxon W test) increased the release of 15-HETE and fibronectin. There was no significant difference in the release of PGE2 by resting cells from either asthmatics or normal subjects, but challenge with A23187 induced a significant (p < 0.03, Wilcoxon W test) increase in PGE2 from cells of asthmatics but not from cells of normal subjects. This study shows that epithelial cells are activated and less viable in asthma and suggests a role for these cells in asthma.

Prostaglandin H synthases or cyclooxygenases 1 (PGHS-1) and 2 (PGHS-2) catalyze the conversion of arachidonic acid to prostaglandin endoperoxides, leading to the formation of prostaglandin and thromboxane mediators of inflammation. The expression of these enzymes in the respiratory epithelium has not been determined, although they may be relevant to the pathophysiology of inflammatory disorders such as asthma and chronic bronchitis (CB). We studied PGHS-1 and PGHS-2 immunoreactivity in bronchial biopsies obtained from 22 patients with chronic stable asthma, seven patients with CB, and 12 normal subjects. Both types of PGHS were mainly expressed in the epithelium (basal and ciliated cells), and PGHS-1 and PGHS-2 were found in 21 of 41 and 34 of 41 biopsies, respectively. We did not find any differences in PGHS expression between the patient populations. There were no correlations between any of the clinical parameters studied or the pathologic patterns and the presence and characteristics of the PGHS immunoreactivities. Thus, both PGHS enzymes are expressed in normal human respiratory epithelium and are not quantitatively upregulated in the main bronchi in stable asthma and CB.