Effect of fuel zinc content on toxicological responses of particulate matter from pellet combustion in vitro.

Significant amounts of transition metals such as zinc, cadmium and copper can become enriched in the fine particle fraction during biomass combustion with Zn being one of the most abundant transition metals in wood combustion. These metals may have an important role in the toxicological properties of particulate matter (PM). Indeed, many epidemiological studies have found associations between mortality and PM Zn content. The role of Zn toxicity on combustion PM was investigated. Pellets enriched with 170, 480 and 2300 mg Zn/kg of fuel were manufactured. Emission samples were generated using a pellet boiler and the four types of PM samples; native, Zn-low, Zn-medium and Zn-high were collected with an impactor from diluted flue gas. The RAW 264.7 macrophage cell line was exposed for 24h to different doses (15, 50,150 and 300 µg ml(-1)) of the emission samples to investigate their ability to cause cytotoxicity, to generate reactive oxygen species (ROS), to altering the cell cycle and to trigger genotoxicity as well as to promote inflammation. Zn enriched pellets combusted in a pellet boiler produced emission PM containing ZnO. Even the Zn-low sample caused extensive cell cycle arrest and there was massive cell death of RAW 264.7 macrophages at the two highest PM doses. Moreover, only the Zn-enriched emission samples induced a dose dependent ROS response in the exposed cells. Inflammatory responses were at a low level but macrophage inflammatory protein 2 reached a statistically significant level after exposure of RAW 264.7 macrophages to ZnO containing emission particles. ZnO content of the samples was associated with significant toxicity in almost all measured endpoints. Thus, ZnO may be a key component producing toxicological responses in the PM emissions from efficient wood combustion. Zn as well as the other transition metals, may contribute a significant amount to the ROS responses evoked by ambient PM.

Effects of a catalytic converter on PCDD/F, chlorophenol and PAH emissions in residential wood combustion.

Catalytic converters can be used to decrease carbon monoxide, organic compounds and soot from small-scale wood-fired appliances. The reduction is based on the oxidation of gaseous and particulate pollutants promoted by catalytic transition metal surfaces. However, many transition metals have also strong catalytic effect on PCDD/F formation. In this study birch logs were burned in a wood-fired stove (18 kW) with and without a catalytic converter with palladium and platinum as catalysts. PCDD/F, chlorophenol and PAH concentrations were analyzed from three phases of combustion (ignition, pyrolysis and burnout) and from the whole combustion cycle. PCDD/F emissions without the catalytic converter were at a level previously measured for wood combustion (0.15-0.74 ng N m(-3)). PAH emissions without the catalytic converter were high (47-85 mg N m(-3)) which is typical for batch combustion of wood logs. Total PAH concentrations were lower (on average 0.8-fold), and chlorophenol and PCDD/F levels were substantially higher (4.3-fold and 8.7-fold, respectively) when the catalytic converter was used. Increase in the chlorophenol and PCDD/F concentrations was most likely due to the catalytic effect of the platinum and palladium. Platinum and palladium may catalyze chlorination of PCDD/Fs via the Deacon reaction or an oxidation process. The influence of emissions from wood combustion to human health and the environment is a sum of effects caused by different compounds formed in the combustion. Therefore, the usage of platinum and palladium based catalytic converters to reduce emissions from residential wood combustion should be critically evaluated before wide-range utilization of the technology.

Extracellular domain of type I receptor for transforming growth factor-beta: molecular modelling using protectin (CD59) as a template.

We have observed that the extracellular domain of T beta RI and protectin (CD59), an inhibitor of the membrane attack complex of complement, share structural features, a distinct spacing of ten cysteines and a C-terminal 'Cys-box'. Based on these common features and the recently determined NMR-structure of protectin, a three-dimensional model for the extracellular domain of T beta RI was constructed. After energy minimization and molecular dynamics simulation, a structure with four extending fingers (pes quattvordigitorum) and two clusters of charged residues was obtained. This model provides a view to the understanding of interactions between T beta RI, T beta RII and TGF beta during ligand recognition and signal transduction.

Novel 13A antigen is an integral protein of the basolateral membrane of rat glomerular podocytes.

BACKGROUND: We described recently the 13A monoclonal antibody recognizing a 120 kilodalton protein located at the bases of podocyte foot processes in rat glomeruli. The antigen was extracellular, either a component of the glomerular basement membrane or an integral membrane protein. As only few markers exist for the basal domain of the podocyte membranes, we wanted to characterize the antigen further. EXPERIMENTAL DESIGN: The distribution of the 13A antigen in rat tissues and cultured cells was studied by immunofluorescence and immunoelectron microscopy. Cultured cells were also used for its biochemical and functional characterization. RESULTS: The antigen was detected in several rat epithelial and smooth muscle tissues. In polarized epithelia, it was restricted to the basolateral membranes, and in stratified epithelia, to the basal cell layer. In contrast to its limited distribution in vivo, the antigen was detected in vitro in several cultured fibroblastoid or epithelial rat cell lines, and in cultured mesangial cells. In nonpolarized cells, it had a diffuse granular distribution at the cell surface, and at the ventral surface, it colocalized with vinculin in areas resembling focal adhesions, as shown by double immunofluorescence staining. In polarized epithelial cells, the 13A antigen was concentrated at the basolateral membranes. By immunoelectron microscopy, it was often present at the tips of cell extensions and at adhesion sites. Pretreatment of cryostat sections or cultured cells with trypsin partially inhibited antibody binding, whereas detergents abolished it totally. The antigen of cultured cells could not be identified by Western blotting or immunoprecipitation techniques. The antibodies did not seem to affect cell growth or adhesion. CONCLUSIONS: The 13A antigen is an integral membrane protein of several rat epithelial tissues and cultured cells, and is particularly abundant in the podocyte foot processes. Although its identity and function remain unknown, the 13A protein is a valuable marker for the basal membrane domain of the podocyte.