RESUMEN
BACKGROUND: Reports on air pollution and asthma exacerbations have been inconsistent, although effects of airborne allergen can be spectacular. With no generalized test for allergen in air, it is not known how far allergen is responsible for nonepidemic exacerbations of the disease. METHODS: Two hundred and ninety-seven patients using bronchodilators aged 18-64 years attending a London practice provided serum samples and were asked to report any acute respiratory events over the coming months. Small particles with a mean aerodynamic diameter <10 microm (PM(10)) were collected using a high volume sampler on the roof of the practice. The ability of airborne particles to bind IgE from the patients was compared for particles sampled on the weekend before their reported exacerbation with particles sampled on the weekend 2 weeks before or after. RESULTS: Exacerbations were associated with a 25% increase in IgE binding to particles collected on the previous weekend compared with the control weekends (95% confidence interval: 10-43%; P = 0.00089). This increase was not higher in patients with positive skin tests or in those sensitized to grass or tree pollens. CONCLUSIONS: Airborne allergen is an important cause of exacerbations even in those with 'intrinsic' asthma. It is important to identify the allergens responsible, as some of these may be controllable. Interpretation of associations of asthma exacerbations with other air pollutants is difficult in the light of these findings.
Asunto(s)
Contaminantes Atmosféricos/efectos adversos , Alérgenos/efectos adversos , Asma/fisiopatología , Hipersensibilidad Inmediata/fisiopatología , Material Particulado/efectos adversos , Trastornos Respiratorios/fisiopatología , Adolescente , Adulto , Contaminantes Atmosféricos/inmunología , Contaminantes Atmosféricos/metabolismo , Contaminación del Aire , Alérgenos/inmunología , Alérgenos/metabolismo , Asma/inmunología , Femenino , Humanos , Hipersensibilidad Inmediata/inmunología , Inmunoglobulina E/sangre , Inmunoglobulina E/metabolismo , Masculino , Persona de Mediana Edad , Material Particulado/inmunología , Material Particulado/metabolismo , Trastornos Respiratorios/inmunología , Pruebas CutáneasRESUMEN
The effects of repeated food deprivation, prior to slaughter, on performance, feeding behaviour and meat quality of pigs was examined. Three experimental treatments were compared. In treatment 1 pigs had ad libitum access to feed up to the point of loading on the day of slaughter. Treatment 2 involved a 12-h fast prior to slaughter and treatment 3 involved a 20-h fast prior to slaughter. Pigs were slaughtered on a weight basis therefore each pen was emptied over a period of weeks. This meant some pigs experienced repeated food deprivation. The feeding pattern of pigs which were deprived of food for 12 h was very similar to that observed before feed restriction. Pigs which were deprived of food for 20 h spent significantly more time at the feeder post fasting. This was particularly marked during the first 2-3 h when access to feed was restored. Feed deprivation for 12 h prior to slaughter did not adversely affect performance, carcass weight, meat quality or welfare in the present study. Fasting for 20 h reduced carcass weight by 1 kg, which was not statistically significant but could result in financial losses related to carcass weight. The negative effects on meat quality, of repeated feed deprivation, resulted from slower growth rates rather than feed deprivation per se.