RESUMEN
BACKGROUND: Short-term exposure to outdoor fine particulate matter (particles with a median aerodynamic diameter <2.5 µm (PM2.5)) air pollution has been associated with adverse health effects. Existing literature reviews have been limited in size and scope. METHODS: We conducted a comprehensive, systematic review and meta-analysis of 110 peer-reviewed time series studies indexed in medical databases to May 2011 to assess the evidence for associations between PM2.5 and daily mortality and hospital admissions for a range of diseases and ages. We stratified our analyses by geographical region to determine the consistency of the evidence worldwide and investigated small study bias. RESULTS: Based upon 23 estimates for all-cause mortality, a 10 µg/m(3) increment in PM2.5 was associated with a 1.04% (95% CI 0.52% to 1.56%) increase in the risk of death. Worldwide, there was substantial regional variation (0.25% to 2.08%). Associations for respiratory causes of death were larger than for cardiovascular causes, 1.51% (1.01% to 2.01%) vs 0.84% (0.41% to 1.28%). Positive associations with mortality for most other causes of death and for cardiovascular and respiratory hospital admissions were also observed. We found evidence for small study bias in single-city mortality studies and in multicity studies of cardiovascular disease. CONCLUSIONS: The consistency of the evidence for adverse health effects of short-term exposure to PM2.5 across a range of important health outcomes and diseases supports policy measures to control PM2.5 concentrations. However, reasons for heterogeneity in effect estimates in different regions of the world require further investigation. Small study bias should also be considered in assessing and quantifying health risks from PM2.5.
Asunto(s)
Contaminantes Atmosféricos/toxicidad , Exposición a Riesgos Ambientales/efectos adversos , Hospitalización/estadística & datos numéricos , Mortalidad/tendencias , Material Particulado/toxicidad , Contaminantes Atmosféricos/análisis , Enfermedades Cardiovasculares/mortalidad , Exposición a Riesgos Ambientales/análisis , Humanos , Enfermedades Pulmonares/mortalidad , Tamaño de la Partícula , Material Particulado/análisisRESUMEN
Cross-linking glomerular basement membrane (GBM) has been shown to render it more permeable to protein. Isolated pig GBM was cross-linked with dimethylmalonimidate which reacts selectively with lysine epsilon-NH2 groups or with glutaraldehyde, a less selective cross-linking agent. Studies of the ultrafiltration properties of these materials in vitro using cytochrome c, myoglobin, bovine serum albumin and immunoglobulin showed that cross-linking had markedly increased solvent and protein fluxes as compared with native membranes particularly at higher pressures. Filtration studies with serum demonstrated that the cross-linked membranes were more permeable to serum proteins. Thickness measurements under pressure indicated that cross-linked membrane was less compressed than native membrane as pressure was increased. Pore theory did not provide a suitable model for analysis of the results, but analysis of the results using the fibre-matrix hypothesis indicated that cross-linking had the effect of bundling together the fibres (type IV collagen) in the GBM matrix. The effect of cross-linking on filtration could be explained by a combination of contraction of the membrane, fibre bundling and increased rigidity compared with native membrane. Cross-linking of GBM might lead to long-term damage of the glomerular capillary wall in nephritis, so promoting proteinuria.
Asunto(s)
Membrana Basal/metabolismo , Proteínas Sanguíneas/metabolismo , Glutaral/farmacología , Imidoésteres/farmacología , Glomérulos Renales/metabolismo , Animales , Membrana Basal/efectos de los fármacos , Reactivos de Enlaces Cruzados , Glomerulonefritis/fisiopatología , Matemática , Permeabilidad , Proteinuria/fisiopatología , Porcinos , UltrafiltraciónRESUMEN
The ultrafiltration properties of isolated glomerular basement membrane were studied in vitro by forming membrane fragments into thin films for use as ultrafiltration membranes. The filtration properties of the films were examined using cytochrome c, myoglobin, lysozyme, ovalbumin, lactoglobulin, and serum albumin. The films behaved as compressible filters showing size-dependent rejection of the proteins. The behavior of the films was modelled using the fiber matrix hypothesis which gave good prediction of film behavior. The membrane behaved as a random fiber matrix composed of fibers of 0.8-1.0 nm in radius.