Groundwater Macrocrustaceans as Natural Indicators of the Ariège Alluvial Aquifer

The macrocrustacean fauna from an alluvial aquifer in the French Pyrénées was investigated using 15 wells scattered over the floodplain. Wells were sampled at three contrasting periods for faunal, phy‐sical and chemical variables to investigate relationships between amphipod, isopod distributions and environmental factors. The assemblages, dominated by stygobite amphipod species, showed an overall persistence between the sampling dates. Groundwater quality exhibited between‐site variations related to agriculturally‐induced pollution. Low correlations existed between water quality and fauna distribution patterns. At the scale of the aquifer, groundwater contamination did not influence the macrocrustacean distribution. The spatial distribution of amphipods and isopods was clearly related to hydrogeology and hydrodynamics: strong relationships were found between the assemblages composition and the hydrological context of the stations (wells from the alluvial plain and from the alluvial terrace). With respect to spatial and temporal scales and providing adequate sampling methods, macrocrustaceans then constitute natural indicators of groundwater hydrodynamics in the Ariège aquifer.     

The effects of calcium and lanthanide ions on the activity of bovine heart nicotinamide adenine dinucleotide-specific isocitrate dehydrogenase

(i) The activity of purified NAD-specific isocitrate dehydrogenase from bovine heart was stimulated by free Ca²⁺ in the presence of ADP and subsaturating levels of magnesium isocitrate, but not in absence of ADP. However, Ca²⁺ was not absolutely required for ADP activation. This was particularly apparent when free Mg²⁺ was kept low (0.0024–0.020 mm) and the substrate magnesium dl-isocitrate ranged from 0.07–0.25 mm. When kinetic constants were determined at pH 7.4 under these conditions and in the absence of ethylene glycol bis(β-aminoethyl ether) N,N′-tetraacetate, Ca²⁺ had little or no effect on K_m (app) for ADP; the stimulation of rate by Ca²⁺ was mainly due to increased V (app). With subsaturating ADP, there was an interdependence in the interaction of the enzyme with substrate and Ca²⁺. Thus, with ADP constant (0.30 mm) the values of K_m (app) for magnesium dl-isocitrate declined from 0.35 mm at zero Ca²⁺ to 0.19 mm with saturating Ca²⁺ without affecting V; K_m (app) for free Ca²⁺ declined with increasing magnesium isocitrate to a limiting K_m of 0.3 μm. (ii) Ethylene glycol bis(β-aminoethyl ether)-N,N′-tetraacetate, frequently used as a calcium buffer, inhibited enzyme activity with and without ADP. (iii) The enzyme was not inhibited by the calmodulin inhibitors trifluoperazine and chlorpromazine. Inhibition by lanthanide ions of the isocitrate dehydrogenase was competitive with magnesium isocitrate and not with respect to Ca²⁺. The values of K_is (1.8 to 3.1 μm) for La³⁺, Yb³⁺, Gd³⁺, Eu³⁺, Tb³⁺, and Er³⁺ were about two orders of magnitude smaller than K_m for magnesium dl-isocitrate.     

Nucleotide sequence and genomic structure analyses of the p70 subunit of the human Ku autoantigen: evidence for a family of genes encoding Ku (p70)-related polypeptides

cDNA encoding the p70 polypeptide subunit of the human Ku autoantigen was isolated. In vitro expression analysis of the cDNA demonstrates that it encodes the entire open reading frame. Nucleotide sequence analysis and comparison to other previously described sequences indicate the existence of several single-nucleotide and amino acid polymorphisms. Southern blot analyses demonstrate the presence of multiple copies of homologous DNA sequences in the human genome. These data support the hypothesis that multiple genes encode a family of Ku(p70)-related polypeptides.     

Determination of isoprostaglandin F2α type III in human urine by gas chromatography–electronic impact mass spectrometry. Comparison with enzyme immunoassay

F₂-Isoprostanes are stable lipid peroxidation products of arachidonic acid, the quantification of which provides an index of oxidative stress in vivo. We describe a method for analysing isoprostaglandin F_2α type III (15-F_2t-IsoP) in biological fluids. The method involves solid-phase extraction on octadecyl endcapped and aminopropyl cartridges. After conversion to trimethylsilyl ester trimethylsilyl ether derivatives, isoprostaglandin F_2α type III is analysed by mass spectrometry, operated in electronic impact selected ion monitoring mode. We have compared enzyme immunoassay (EIA; Cayman, Ann Arbor, MI, USA) to this method with 30 human urine aliquots following the same extraction procedure in order to determine the agreement between both methods. Isoprostaglandin F_2α type III concentrations determined with gas chromatography–mass spectrometry (GC–MS) did not agree with those determined with EIA. Our results suggest that GC–MS and EIA do not measure the same compounds. As a consequence, comparison of clinical results using GC–MS and EIA should be avoided.     

Live imaging of prions reveals nascent PrPSc in cell-surface,raft-associated amyloid strings and webs

Mammalian prions refold host glycosylphosphatidylinositol-anchored PrP^C into β-sheet–rich PrP^Sc. PrP^Sc is rapidly truncated into a C-terminal PrP27-30 core that is stable for days in endolysosomes. The nature of cell-associated prions, their attachment to membranes and rafts, and their subcellular locations are poorly understood; live prion visualization has not previously been achieved. A key obstacle has been the inaccessibility of PrP27-30 epitopes. We overcame this hurdle by focusing on nascent full-length PrP^Sc rather than on its truncated PrP27-30 product. We show that N-terminal PrP^Sc epitopes are exposed in their physiological context and visualize, for the first time, PrP^Sc in living cells. PrP^Sc resides for hours in unexpected cell-surface, slow moving strings and webs, sheltered from endocytosis. Prion strings observed by light and scanning electron microscopy were thin, micrometer-long structures. They were firmly cell associated, resisted phosphatidylinositol-specific phospholipase C, aligned with raft markers, fluoresced with thioflavin, and were rapidly abolished by anti-prion glycans. Prion strings and webs are the first demonstration of membrane-anchored PrP^Sc amyloids.     

The conservation imperative and setting plant taxonomic research priorities in South Africa

For more than a decade it has been internationally recognised that efforts should be made to remedy the concern that taxonomy is an endangered discipline in the grips of rapid decline. In acknowledgement of the perceived continuing marginalisation of taxonomy, the Darwin Declaration recognised the need to enhance the taxonomic capacity of members who are party to the CBD, and beyond. South Africa is one of the most biodiversity rich countries globally, and the unique and rich flora of the country brings with it a significant conservation imperative. Although the country, and southern African subregion for that matter, has a strong history of taxonomic endeavour, stretching back for over a century, it also suffers from a lack of human and other resources to adequately address its taxonomic needs. This inevitably calls for a process of priority-setting to ensure the wise use of available funding. As one example, it is shown that 1,009 indigenous South African plant taxa are regarded as Data Deficient for taxonomic reasons, following the completion of a recent comprehensive Red Listing exercise. Although not the only criterion to be considered when prioritising taxonomic research, efforts focused on these groups represent a significant opportunity for taxonomists to align their work with national priorities.     

Are landscape-based wetland condition indices reflected by invertebrate and diatom communities?

Assessments of wetland condition are generally based on measures of variables related to plants or large animals (birds, fish), and catchment or landscape features. This approach ignores the considerable biodiversity and functional values of small aquatic organisms. The aim of this study was to assess the correspondence between landscape-based indices of wetland condition and the community composition of both aquatic invertebrates and diatoms across a broad range of wetlands in the West Coast region of New Zealand. Aquatic invertebrates and diatoms were sampled from 29 lowland wetlands subject to varying degrees of catchment modification. Wetland condition was assessed independently using two methods: a field-based method to give the Wetland Condition Index, and a GIS-based method that gave an Index of Ecological Integrity. Strong relationships existed between community composition and pH, so we partitioned the community data into groups according to wetland pH. We found only weak relationships between wetland condition scores and invertebrate and diatom communities within each pH group. In most cases, data describing the nutrient status of the water had the strongest influence on invertebrate and diatom communities. Lack of strong associations between measured wetland condition indices and either diatom or invertebrate community composition suggests that neither index was dominated by variables directly influencing the aquatic component of wetland biota. The challenges now are to identify the critical variables, and to develop complementary wetland scoring systems that better reflect the status of small aquatic organisms.