Landscape dynamics and fire activity since 6740 cal yr BP in the Cantabrian region (La Molina peat bog, Puente Viesgo, Spain)

A lack of paleobotanic studies with adequate resolution and multiproxy approaches has limited proper discussion of vegetation dynamics in Cantabria and of the role of fires in the configuration of the plant landscape during the Holocene in the northwest part of the Iberian peninsula. The pollen diagram of La Molina peat bog in Puente Viesgo (43 ‹15 Œ38 N.3 ‹58 Œ37 W; ETRS89), located at 484 m.a.s.l., and the study of its sedimentary charcoals allowed the acquisition of a continuous and thorough fire sequence for the last 6 700 cal yr BP and an understanding of its relationship to the forest. The results show the importance of human influence on the incidence and characteristics of fire activity during the different phases studied: the Neolithic, Bronze Age, Iron Age, Roman period, and Middle Ages. A synergy seems to exist between dry climate periods (especially during Bond events 3 and 4) and a greater presence of biomass. As the Holocene advances, vegetation coverage clearly tends to decrease. This study provides key elements for understanding the role of fire activity in the forest dynamics of deciduous and evergreen Quercus, Corylus, Pinus, Fagus, and Alnus and demonstrates the strongly artificialized character of the present landscape

Phenotypical and functional analysis of macrophages infected with PRRS virus

The PRRS virus shows a specific tropism for cells of the porcine monocyte/macrophage lineage. These cells play important roles both in innate and acquired immunity, performing a great variety of functions that include phagocytosis, scavenging at sites of tissue injury, killing of microbes and tumor cells, processing and presentation of antigens to lymphocytes and cytokine production. The aim of this study was to investigate the effect of the virus on different functional capacities of these cells. We have analysed the effect of the virus on the expression of different pro-inflammatory cytokines synthesised by the macrophage and the effect of the virus on the respiratory burst. We have also analysed the effect of TNF-$\alpha$ on virus replication and the modulation of different macrophage and monocyte cell surface molecules by the virus. Porcine alveolar macrophages (PAM) obtained from 3-week old healthy piglets were activated with 10 ng/mL of phorbol 12-myristate-1, 3-acetate (PMA) in the presence or absence of a European isolate (5710) of the PRRS virus (MOI = 1). Two and six hours later, the RNA from 10$^7$ cells/sample were extracted and a RT-PCR was carried out with specific primers for TNF-$\alpha$, IL-1 and MIP-1$\beta$. In other experiments, PAM were treated under different conditions with porcine recombinant TNF-$\alpha$ (100 ng/ml) and infected with 10-fold dilutions of the PRRS virus, starting at a MOI of 1. Seven days later the cytopathic effect was recorded. Oxidative burst. After being infected or not with the PRRS virus (MOI = 1) for 16 h the PAM were activated with PMA and the hydrogen peroxide concentration was measured by flow cytometry, using the di-chlorofluorescein method. The African swine fever and Classical swine fever viruses were included as controls. The modulation of the expression of different leukocyte surface antigens (CD11a and CD11b, CD45, SLA-I, SLA-II, SWC3, 3F7/11, 3B11/11 and 2A10/11) by the PRRS virus was studied by two-colour staining, using monoclonal antibodies (mAbs) to these molecules labeled in red and, as a marker of viral infection, a mAb to the viral nucleoprotein labeled in green. These analyses were performed on infected and on non-infected PAM. The PRRS virus strongly reduced the TNF-$\alpha$ mRNA expression, dependent of PMA activation (46% inhibition) in PAM. There was only a slight difference between cells activated for 2 or 6 hours. The production of IL-1 mRNA under the same conditions, was inhibited only after 6 hours of incubation (50% inhibition). Its production after 2 hours was not affected. Regarding MIP-1$\beta$ expression, the presence of the virus inhibited its expression by 37% after 2 hours of incubation; this inhibition increased up to 83% after 6 hours. Pre-treatment of PAM for 24 hours with 100 ng/mL of recombinant porcine TNF-$\alpha$ resulted in a reduction of 0.8 log in the virus output. When TNF-$\alpha$ was maintained in culture, a 2 log reduction was obtained. PAM stimulated with PMA showed an increase in their production of hydrogen peroxide, that was reduced when cells were infected by the virus for 16 hours. However, when these cells were infected by the African swine fever or Classical swine fever in similar conditions, this inhibitory effect was not seen. Infection of PAM did not show an effect on the expression of adhesion molecules such as CD11a and CD11b, nor CD45, SLA-class II molecules or SWC3. However, a clear down modulation of SLA-class I molecules was observed when infected and non-infected cells were compared. Molecules recognised by mAbs 3F7/11 and 3B11/11 were also down modulated. Finally, only cells expressing the 2A10 molecule more intensely were infected. Our results show an important disability of infected macrophages to generate an inflammatory response. The PRRS virus interferes with the production of proinflammatory cytokines. In addition, we have found that the virus is sensitive to TNF-$\alpha$. In this respect, it would be interesting to investigate the synergistic effect of this cytokine with other antiviral cytokines, such as IFN, which also seems to be affected by the virus. The reduction of hydrogen peroxide production in PAM stimulated with PMA after being in the presence of the virus, also reflects an alteration of the oxidative burst metabolism as a consequence of virus activity. The virus also causes a slight reduction in the expression of SLA-class I antigens that may be important in the recognition of infected cells by cytotoxic T lymphocytes. Other surface receptors (3B11/11 and 3F7/11) also appear down regulated after infection. However, at the present we do not know their function nor the significance of this reduction in macrophage activity. All these effects may provide the virus with some evasion strategies from the immune response, facilitating its spreading. On the contrary, the disfunction of macrophages caused by the virus may increase host susceptibility to secondary infections

Effect of milling conditions and binder phase content on liquid phase sintering of heat treatable WCNi-Co-Cr-Al-Ti cemented carbides

The binder phase of WC based cemented carbides has been alloyed by adding two different aluminium compounds, AlN and TiAl3, to mixtures comprised of WC, Ni, Co and Cr3C2 powders. A more efficient alloying effect is obtained by TiAl3 additions likely due to its higher dissolution rate during liquid phase sintering. Shrinkage and melting phenomena are strongly affected by the energy of the milling process and the amount of metallic additions. The use of higher milling rotation speed induces higher oxidation of the powder mixtures and the subsequent formation of a higher volume fraction of alumina particles after sintering. Densification and WC grain growth are hindered by increasing the Al addition. Thus, full densification of alloys with higher Al additions require the use of HIP after standard vacuum sintering cycles. As-HIPed WC-Ni-Co-Cr-Al-Ti samples present a binder phase with precipitation of gamma prime similar to that found in as-cast Ni superalloys. The size, volume fraction and morphology of these precipitates has been modified by applying a standard solution treatment (1150 °C-2 h) followed by fast air cooling and subsequent aging at 600 °C and different dwelling times. Age hardening effects have been confirmed in the composition consisting of WC-12 wt% Co-12 wt% Ni-1.7 wt% Cr3C2-5 wt% TiAl3 after 100 h at this temperature