Influence of traffic on the PM10 and PM2.5 urban aerosol fractions in Madrid (Spain)

A preliminary assessment carried out in Madrid demonstrates the difficulty of compliance with the new European PM(10) tolerances. Daily and annual limiting values would be exceeded at almost all the network stations under the terms of the directive's second stage. An experimental study, based on the chemical characterisation of the PM(10) and PM(2.5) fractions sampled at a representative urban site, provides the major mass contents of these two fractions. These are mainly related to two different particle sources: combustion processes including traffic emissions and mineral-origin particles. Nonmineral carbon is the major component of particulate matter in this region, mostly in the PM(2.5) fraction, increasing its contribution in wintertime. The second largest component identified in the PM(10) mass, is associated with crustal origin particles and is more relevant in summer, whereas the second largest contributor to PM(2.5) is secondary particles. In general, PM(10) and PM(2.5) concentrations show good agreement with traffic-related pollutants, such as nitrogen oxides and CO, being time-correlated in winter pollution episodes. PM(1) and PM(2.5) have been simultaneous and continuously measured indicating road transport as the main source of these finer fractions. Mineral contribution has been mainly identified in the coarser particles associated with dust resuspension and some long-range transport events of Saharan dust, although they are also present in the finer PM(2.5) fraction.

Expression of isoforms of the neural cell adhesion molecule (NCAM) and polysialic acid during the development of the Bufo arenarum olfactory system

The neural cell adhesion molecule (NCAM), a member of the immunoglobulin superfamily that promotes Ca(2+)-independent cell-cell adhesion, is expressed as various isoforms generated by alternative splicing. In this study, the expression of the 180 kDa isoform (180-NCAM), total NCAM (180, 140 and 120 kDa isoforms) and the polysialic acid moiety of NCAM (PSA) were analyzed during the development of the olfactory system of the toad Bufo arenarum using specific antibodies and immunofluorescence light microscopy. NCAM and PSA were not found in the ectodermal thickening corresponding to the olfactory placode at early larval stage (stage 17), but by stage 19, total NCAM, 180-NCAM and PSA were all expressed in the invaginating olfactory placode at the sites of cell-cell contact and in the differentiating olfactory epithelium. Later, NCAM isoforms and PSA were found also in the primary fibers of the olfactory nerve and in the olfactory bulb. However, the expression of 180-NCAM decreased near the end of larval development and was absent in post-metamorphic and adult animals. In contrast, total NCAM (representing 140 and/or 120 kDa isoforms) and PSA continued to be expressed in olfactory tissues of post-metamorphic and adult animals, consistent with the persistent neural plasticity of this tissue. Because 180-NCAM has been associated with non-proliferating neurons, its down-regulation in post-metamorphic and adult olfactory system may be associated with the regenerative capability and continuous cell turnover documented for this region in adult animals.