Experience with the antibiotic resistance analysis and DNA fingerprinting in tracking faecal pollution at two lake beaches.

Posting or closing of swimming beaches because of faecal contamination is a widespread problem reported in many locations. In a risk-based approach to this problem, the risk to swimmers' health is assessed by field monitoring of indicator bacteria and the associated risks are managed by source controls and other remedial measures. In risk assessment, great advances have been made in recent years with the introduction of microbial source tracking (MST) techniques. Two such techniques, antibiotic resistance analysis and DNA fingerprinting, were applied in a study of causes of faecal contamination at two lake beaches in Toronto, Ontario. Both methods identified bird faeces as the dominant sources of E. coli. Coping with this type of pollution presents a major environmental challenge.     

Fibroblast growth factor-2 and fibroblast growth factor receptor-1 mRNA expression and peptide localization in placentae from normal and diabetic pregnancies

Soils developed on serpentine rocks cover a large area in Albania which contains large reserves of iron, nickel, chromium and copper and is characterised by a high density of mines and metal smelters. This work was conducted to study the flora associated with serpentine and former industrial and mining sites in Albania. Eight sites were investigated in the south-eastern, central and northern parts of the country. Soils were sampled in the Ap horizon and plants were collected and identified. Plant material was allowed to dry before being ground. Soil and plant samples were analysed for total Ca, Cd, Co, Cr, Cu, Mg, Ni, Pb and Zn. Results showed that each site exhibited a high concentration of one or more metals. The maximum concentrations of metals in soils dry matter (DM) were 14 mg Cd kg-1, 476 mg Co kg-1, 3865 mg Cr kg-1, 1107 mg Cu kg-1, 3579 mg Ni kg-1, 172 mg Pb kg-1 and 2495 mg Zn kg-1. The Mg/Ca ratio in serpentine soils varied from 1 to 7.8. A collection of 58 plant species, members of 44 genera and 17 families, were collected. Alyssum markgrafii in the north and Alyssum murale in the south-eastern serpentines had a concentration of 1.26 and 0.85% Ni in DM, respectively. In the species Herniaria hirsuta, a serpentine plant, concentrations of 808 mg Ni kg-1 and 275 mg Cr kg-1 in DM were recorded. Other taxa (Filago, Inula, Picris, Galamintha, Marrubium, Teucrium, Lotus, Ononis and Xeranthemum) from serpentines had a high, but not exceptional Ni content. Some species collected on serpentines and industrial sites presented rather high concentrations of lead or copper in their above-ground parts, probably related to contamination by soil dust.     

Glucose-6-phosphate dehydrogenase deficiency and malaria

Glucose-6-phosphate dehydrogenase (G6PD) is a cytoplasmic enzyme that is essential for a cell's capacity to withstand oxidant stress. G6PD deficiency is the commonest enzymopathy of humans, affecting over 400 million persons worldwide. The geographical correlation of its distribution with the historical endemicity of malaria suggests that 66PD deficiency has risen in frequency through natural selection by malaria. This is supported by data from in vitro studies that demonstrate impaired growth of P. falciparum parasites in G6PD-deficient erythrocytes. Attempts to confirm that G6PD deficiency is protective in field studies of malaria have yielded conflicting results, but recent results from large case control studies conducted in East and West Africa provide strong evidence that the most common African G6PD deficiency variant, G6PD A-, is associated with a significant reduction in the risk of severe malaria for both G6PD female heterozygotes and male hemizygotes. The effect of female homozygotes on severe malaria remains unclear but can probably be assumed to be similar to that of comparably deficient male hemizygotes.     

Influence of receptor number on the stimulation by salmeterol of gene transcription in CHO-K1 cells transfected with the human beta2-adrenoceptor

We investigated the behavior of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APx), in potato tubers during storage at low temperature. SOD activity increased temporarily within 3 weeks and was higher at 1 degree C than at 20 degrees C. APx activity also increased more at low (1 degree C) than at higher temperatures (5 and 20 degrees C). The contents of ascorbic acid (AsA), which is the substrate of APx, decreased immediately within 3 weeks and then gradually decreased until 15 weeks. The activity of CAT, the other enzyme which can scavenge hydrogen peroxide, decreased once in the first six weeks and thereafter increased to 15 weeks. Thus, the enhancement of the active oxygen-scavenging system that was induced by low temperature in potato tubers could result not only in a decrease of AsA but also in combined increases in APx and CAT activity whose manners were different.     

A neuron membrane mesh representation for visualization of electrophysiological simulations

We present a process to automatically generate three-dimensional mesh representations of the complex, arborized cell membrane surface of cortical neurons (the principal information processing cells of the brain) from nonuniform morphological measurements. Starting from manually sampled morphological points (3D points and diameters) from neurons in a brain slice preparation, we construct a polygonal mesh representation that realistically represents the continuous membrane surface, closely matching the original experimental data. A mapping between the original morphological points and the newly generated mesh enables simulations of electrophysiolgical activity to be visualized on this new membrane representation. We compare the new mesh representation with the state of the art and present a series of use cases and applications of this technique to visualize simulations of single neurons and networks of multiple neurons.     

Ergovaline and peramine production in endophyte-infected tall fescue: Independent regulation and effects of plant and endophyte genotype

Peramine and ergovaline have ecological and economical significance because they possess insect and/or mammalian toxicity properties. The relationship between these endophytically derived alkaloids in tall fescue (Festuca arundinacea Schreb.) is unknown. Seasonal and plant tissue effects on the concentration of peramine and ergovaline was investigated in field and greenhouse experiments. The relationship between the alkaloids and the regulatory effects of endophyte and plant on their content were investigated among progeny of reciprocal crosses between high- and low-ergovaline and peramine plant-endophyte combinations. Variation in peramine concentration ranged from 750 to 1742 µg/kg in greenhouse-grown plants, and there was no seasonal trend in peramine content. There was a correlation (r=0.69) between peramine and ergovaline content among leaf tissues of field-grown plants, but there was no correlation between the alkaloids in the culm (r=0.20) or panicle (r=0.17) tissues. Mean leaf ergovaline concentration of progeny derived from the low-ergovaline parent (163 µg/kg) was less than the midparent value (228 µg/kg), but mean of progeny from the high-ergovaline parent was not different from the mid-parent value. Ranges within each progeny set were approximately double their mean. Mean leaf peramine concentrations of the progeny sets were similar to the mid-parent value (3354 µg/kg) but ranges were from 1716 to 8753 µg/kg. There was no correlation between leaf peramine and ergovaline (r=0.01). These data suggest that endophytically produced alkaloids are independently regulated and are controlled by both plant and endophyte genotype.     

Chromate leaching from inhibited primers: Part I. Characterisation of leaching

Leaching and characterisation studies have been undertaken on two chromate-inhibited epoxy polyamide primers. Leaching was carried out in 5% (w/v) NaCl solutions at different pH values (1, 3, 5 and 7) and the amount of Cr released into solution was monitored over time. Cr release was initially high, but as the immersion time increased the leaching from the primers slowed. Prior to and after immersion, the primers were characterised by a number of techniques including electron microprobe analysis, X-ray microdiffraction, Raman spectroscopy, and positron annihilation lifetime spectroscopy. The unexposed primers were found to contain the inorganic phases SrCrO₄, BaSO₄ and TiO₂ (anatase or rutile). Upon immersion, water uptake by the primers was observed, together with a decrease in the amount of SrCrO₄ in the primers. These studies provide insights into the mechanism of chromate leaching from inhibited primers.     

AIR STRIPPING AND DISSOLUTION RATES OF AROMATIC HYDROCARBON PARTICLES IN A BIOREACTOR

The design of bioremediation reactors for destroying toxic organic compounds requires an understanding of the mass transfer behavior of these chemicals into and out of the vessel. The dissolution rates and air stripping of three aromatic hydrocarbon particles were measured and theoretically modeled in a well mixed bioreactor with varying agitation speed, temperature, slurry concentration and air flow rate. It was confirmed that the dissolution rate of particles is influenced by both solubility and molecular structure. The volumetric mass transfer coeffcient of dissolution increased with higher agitation speeds and higher temperatures. This studyindicates that stripping from the liquid phase to the gas phase was controlled by physical properties: that is high Henry's law constant and relatively low solubility. The mechanistic model successfully predicted the disappearance of particles and the dissolved concentration of aromatic compounds due to simultaneous dissolution and air stripping.