Monocytes regulate the mechanism of T-cell death by inducing Fas-mediated apoptosis during bacterial infection.

Monocytes and T-cells are critical to the host response to acute bacterial infection but monocytes are primarily viewed as amplifying the inflammatory signal. The mechanisms of cell death regulating T-cell numbers at sites of infection are incompletely characterized. T-cell death in cultures of peripheral blood mononuclear cells (PBMC) showed 'classic' features of apoptosis following exposure to pneumococci. Conversely, purified CD3(+) T-cells cultured with pneumococci demonstrated necrosis with membrane permeabilization. The death of purified CD3(+) T-cells was not inhibited by necrostatin, but required the bacterial toxin pneumolysin. Apoptosis of CD3(+) T-cells in PBMC cultures required 'classical' CD14(+) monocytes, which enhanced T-cell activation. CD3(+) T-cell death was enhanced in HIV-seropositive individuals. Monocyte-mediated CD3(+) T-cell apoptotic death was Fas-dependent both in vitro and in vivo. In the early stages of the T-cell dependent host response to pneumococci reduced Fas ligand mediated T-cell apoptosis was associated with decreased bacterial clearance in the lung and increased bacteremia. In summary monocytes converted pathogen-associated necrosis into Fas-dependent apoptosis and regulated levels of activated T-cells at sites of acute bacterial infection. These changes were associated with enhanced bacterial clearance in the lung and reduced levels of invasive pneumococcal disease

Wetlands as early warning (eco)systems for water resource management

This paper describes a case study which investigated impacts of a change in catchment land use from natural grassland to commercial forestry on the hydrological regime and distribution of vegetation in a small hillslope seepage wetland near Nottingham Road in the KwaZulu-Natal Midlands. Hydrological modelling was used to estimate the reduction, following afforestation, in surface and subsurface stormflow runoff provided to the wetland by its catchment. Stormflow runoff was shown to have decreased substantially following afforestation, and since the wetland had no input association with a stream or river, its reliance upon surface and subsurface runoff derived from its catchment was considered to be high. Zones of wetness within the wetland were delineated based on edaphic characteristics. Wetland vegetation was classified, using TWINSPAN, into 7 communities. After comparing the edaphic-defined and floristic-defined boundaries of the permanent to semi-permanent wetland zone it was discovered that the area of permanent to semi-permanent wetland vegetation had decreased from its pre-disturbance (edaphic-defined) extent. Implications for water resources management are considered, with particular attention paid to determining the Ecological Reserve for wetlands, and the potential role that wetlands could play in providing an early warning of hydrological change in a catchment. Keywords: wetland ecology, delineation, water resources management, Ecological Reserve Water SA Vol. 31(4) 2005: 465-47

Performing the rural through game-angling

Using a performative approach this chapter focuses on how game-anglers, as a distinct cooperative of rural actors, have produced and continue to reproduce rural Britain in ways that are consistent with the scripts, social relations and embodied practices that have underpinned their sport since Victorian times. In doing so it considers how a seemingly innocuous activity that is game-angling brings to bear extremely powerful social and natural forces that work together to produce a negotiated sense and innate sensing of the rural. This rurality, when interrogated, reveals much about the way humans perform nature through assembling particular social constructions along with visceral cues and responses

A comparison of temperature inversion statistics at a coastal and a non-coastal location influenced by the same synoptic regime

The primary aim of this work is to examine to what extent the climatology of atmospheric temperature inversions at one location is site specific, and to what extent it reflects a wider area for which the same synoptic conditions can be assumed. To this end radiosonde data from a coastal and a non-coastal location in eastern England separated by 210 km and influenced by the same synoptic conditions are used. Analysis of these data shows that there is a pronounced difference between the inversion climatologies at the two sites. The vertical distribution of base-heights of inversions has a very distinct maximum at a height of about 200 m at the location proximate to the coast. This maximum is not present at the inland location, and the difference is due to both sea-breezes and advection from the sea due to synoptic-scale wind field. Examining the vertical distributions of base-heights of inversions at the two locations under conditions that either maximize or minimize the effect of sea-breeze it is found that the differences in the two distributions are to a certain extent deterministic (therefore predictable) rather than random, as the dominant mechanisms which are responsible for these differences (diurnal and yearly cycles) have an obvious regularity. Using standard statistical methods it is further shown that, apart from this difference, nearly all other inversion statistics for the two locations are similar when the atmospheric layer from surface to 700 hPa is taken into consideration. However, when only the first inversion in each temperature profile is considered, the inversions activity throughout the year, defined with the aid of an index, in the two locations is not correlated, indicating that for the lowest part of the surface-700 hPa region, local factors overwhelm the synoptic conditions. Thus, these results provide evidence that the inversion climatology at one location can be generalised over a wider area where the same synoptic regime can be assumed. Given that, at least to an extent, any differences in the characteristics of inversions due to local factors can be inferred once the underlying mechanisms are carefully studied, this work has also important implications for micrometeorological studies as for instance the local diffusion and transport of air pollutans