The determination of total nitrogen and total phosphorus concentrations in freshwaters from land use, stock headage and population data: testing of a model for use in conservation and water quality management

1. Nutrient concentrations (particularly N and P) determine the extent to which water bodies are or may become eutrophic. Direct determination of nutrient content on a wide scale is labour intensive but the main sources of N and P are well known. This paper describes and tests an export coefficient model for prediction of total N and total P from: (i) land use, stock headage and human population; (ii) the export rates of N and P from these sources; and (iii) the river discharge. Such a model might be used to forecast the effects of changes in land use in the future and to hindcast past water quality to establish comparative or baseline states for the monitoring of change. 2. The model has been calibrated against observed data for 1988 and validated against sets of observed data for a sequence of earlier years in ten British catchments varying from uplands through rolling, fertile lowlands to the flat topography of East Anglia. 3. The model predicted total N and total P concentrations with high precision (95% of the variance in observed data explained). It has been used in two forms: the first on a specific catchment basis; the second for a larger natural region which contains the catchment with the assumption that all catchments within that region will be similar. Both models gave similar results with little loss of precision in the latter case. This implies that it will be possible to describe the overall pattern of nutrient export in the UK with only a fraction of the effort needed to carry out the calculations for each individual water body. 4. Comparison between land use, stock headage, population numbers and nutrient export for the ten catchments in the pre-war year of 1931, and for 1970 and 1988 show that there has been a substantial loss of rough grazing to fertilized temporary and permanent grasslands, an increase in the hectarage devoted to arable, consistent increases in the stocking of cattle and sheep and a marked movement of humans to these rural catchments. 5. All of these trends have increased the flows of nutrients with more than a doubling of both total N and total P loads during the period. On average in these rural catchments, stock wastes have been the greatest contributors to both N and P exports, with cultivation the next most important source of N and people of P. Ratios of N to P were high in 1931 and remain little changed so that, in these catchments, phosphorus continues to be the nutrient most likely to control algal crops in standing waters supplied by the rivers studied.

Potential role of NF-kappaB in adult neural stem cells: the underrated steersman?

Neural stem cells are precursors of neurons and glial cells. During brain development, these cells proliferate, migrate and differentiate into specific lineages. Recently neural stem cells within the adult central nervous system were identified. Informations are now emerging about regulation of stem cell proliferation, migration and differentiation by numerous soluble factors such as chemokines and cytokines. However, the signal transduction mechanisms downstream of these factors are less clear. Here, we review potential evidences for a novel central role of the transcription factor nuclear factor kappa B (NF-kappaB) in these crucial signal transduction processes. NF-kappaB is an inducible transcription factor detected in neurons, glia and neural stem cells. NF-kappaB was discovered by David Baltimore's laboratory as a transcription factor in lymphocytes. NF-kappaB is involved in many biological processes such as inflammation and innate immunity, development, apoptosis and anti-apoptosis. It has been recently shown that members of the NF-kappaB family are widely expressed by neurons, glia and neural stem cells. In the nervous system, NF-kappaB plays a crucial role in neuronal plasticity, learning, memory consolidation, neuroprotection and neurodegeneration. Recent data suggest an important role of NF-kappaB on proliferation, migration and differentiation of neural stem cells. NF-kappaB is composed of three subunits: two DNA-binding and one inhibitory subunit. Activation of NF-kappaB takes place in the cytoplasm and results in degradation of the inhibitory subunit, thus enabling the nuclear import of the DNA-binding subunits. Within the nucleus, several target genes could be activated. In this review, we suggest a model explaining the multiple action of NF-kappaB on neural stem cells. Furthermore, we discuss the potential role of NF-kappaB within the so-called brain cancer stem cells.

TNF-alpha mediated transport of NF-kappaB to the nucleus is independent of the cytoskeleton-based transport system in non-neuronal cells

In unstimulated cells, proteins of the nuclear factor kappaB (NF-kappaB) transcription factor family are sequestered in the cytoplasm through interactions with IkappaB inhibitor proteins. Tumor necrosis factor alpha (TNF-alpha) activates the degradation of IkappaB-alpha and the nuclear import of cytoplasmic NF-kappaB. Nuclear localization of numerous cellular proteins is mediated by the ability of the cytoskeleton, usually microtubules, to direct their perinuclear accumulation. In a former study we have shown that activated NF-kappaB rapidly moves from distal processes in neurons towards the nucleus. The fast transport rate suggests the involvement of motor proteins in the transport of NF-kappaB. Here we address the question how NF-kappaB arrives at the nuclear membrane before import in non-neuronal cells, i.e., by diffusion alone or with the help of active transport mechanisms. Using confocal microscopy imaging and analysis of nuclear protein extracts, we show that NF-kappaB movement through the cytoplasm to the nucleus is independent of the cytoskeleton, in the three cell lines investigated here. Additionally we demonstrate that NF-kappaB p65 is not associated with the dynein/dynactin molecular motor complex. We propose that cells utilize two distinct mechanisms of NF-kappaB transport: (1) signaling via diffusion over short distances in non-neuronal cells and (2) transport via motor proteins that move along the cytoskeleton in neuronal processes where the distances between sites of NF-kappaB activation and nucleus can be vast.

Microbial community dynamics in the forefield of glaciers

Retreating ice fronts (as a result of a warming climate) expose large expanses of deglaciated forefield, which become colonized by microbes and plants. There has been increasing interest in characterizing the biogeochemical development of these ecosystems using a chronosequence approach. Prior to the establishment of plants, microbes use autochthonously produced and allochthonously delivered nutrients for growth. The microbial community composition is largely made up of heterotrophic microbes (both bacteria and fungi), autotrophic microbes and nitrogen-fixing diazotrophs. Microbial activity is thought to be responsible for the initial build-up of labile nutrient pools, facilitating the growth of higher order plant life in developed soils. However, it is unclear to what extent these ecosystems rely on external sources of nutrients such as ancient carbon pools and periodic nitrogen deposition. Furthermore, the seasonal variation of chronosequence dynamics and the effect of winter are largely unexplored. Modelling this ecosystem will provide a quantitative evaluation of the key processes and could guide the focus of future research. Year-round datasets combined with novel metagenomic techniques will help answer some of the pressing questions in this relatively new but rapidly expanding field, which is of growing interest in the context of future large-scale ice retreat.

Manipulation of lipids in animal-derived foods: can it contribute to public health nutrition?

Foods derived from animals are an important source of nutrients for humans. Concerns have been raised that due to their SFA content, dairy foods may increase the risk of cardiometabolic disease. Prospective studies do not indicate an association between milk consumption and increased disease risk although there are less data for other dairy foods. SFA in dairy products can be partially replaced by cis-MUFA through nutrition of the dairy cow although there are too few human studies to conclude that such modification leads to reduced chronic disease risk. Intakes of LCn-3 FA are sub-optimal in many countries and while foods such as poultry meat can be enriched by inclusion of fish oil in the diet of the birds, fish oil is expensive and has an associated risk that the meat will be oxidatively unstable. Novel sources of LCn-3 FA such as kirll oil, algae, and genetically modified plants may prove to be better candidates for meat enrichment. The value of FA-modified foods cannot be judged by their FA composition alone and there needs to be detailed human intervention studies carried out before judgements concerning improved health value can be made. Practical applications: The amount and FA composition of dietary lipids are known to contribute to the risk of chronic disease in humans which is increasing and becoming very costly to treat. The use of animal nutrition to improve the FA composition of staple foods such as dairy products and poultry meat has considerable potential to reduce chronic risk at population level although judgements must not be based simply on FA composition of the foods.

Cell stress-induced phosphorylation of ATF2 and c-Jun transcription factors in rat ventricular myocytes.

Ventricular myocytes are exposed to various pathologically important cell stresses in vivo. In vitro, extreme stresses (sorbitol-induced hyperosmotic shock in the presence or absence of okadaic acid, and anisomycin) were applied to ventricular myocytes cultured from neonatal rat hearts to induce a robust activation of the 46 and 54 kDa stress-activated protein kinases (SAPKs). These activities were increased in nuclear extracts of cells in the absence of any net import of SAPK protein. Phosphorylation of ATF2 and c-Jun was increased as shown by the appearance of reduced-mobility species on SDS/PAGE, which were sensitive to treatment with protein phosphatase 2A. Hyperosmotic shock and anisomycin had no effect on the abundance of ATF2. In contrast, cell stresses induced a greater than 10-fold increase in total c-Jun immunoreactivity detected on Western blots with antibody to c-Jun (KM-1). Cycloheximide did not inhibit this increase, which we conclude represents phosphorylation of c-Jun. This conclusion was supported by use of a c-Jun(phospho-Ser-73) antibody. Immunostaining of cells also showed increases in nuclear phospho-c-Jun in response to hyperosmotic stress. Severe stress (hyperosmotic shock+okadaic acid for 2 h) induced proteins (migrating at approx. 51 and 57 kDa) that cross-reacted strongly with KM-1 antibodies in both the nucleus and the cytosol. These may represent forms of c-Jun that had undergone further modification. These studies show that stresses induce phosphorylation of transcription factors in ventricular myocytes and we suggest that this response may be pathologically relevant.