An Ecological Risk Assessment of Ammonia in the Aquatic Environment

Ammonia is released in the environment by many industries and other human activities. The major quantifiable sources of ammonia released to aquatic ecosystems across Canada are municipal wastewater treatment plants, at an estimated total quantity of 62,000 tonnes per year. Given the sources of ammonia releases in the environment and the properties of the substance, terrestrial plants and aquatic organisms are potential risk targets. A tiered assessment approach has been used to determine the ecological risk in the aquatic environment from ammonia released in municipal wastewater effluents. The results obtained for two case studies with the probabilistic risk analysis used in the highest tier support the conclusion that the conditions encountered in these two locations can lead to ammonia concentrations capable of producing an adverse ecological impact.     

Molecular evolution of voltage-sensitive ion channel genes: on the origins of electrical excitability

We have analyzed nucleic acid and amino acid sequence alignments of a variety of voltage-sensitive ion channels, using several methods for phylogenetic tree reconstruction. Ancient duplications within this family gave rise to three distantly related groups, one consisting of the Na+ and Ca++ channels, another the K+ channels, and a third including the cyclic nucleotide-binding channels. A series of gene duplications produced at least seven mammalian homologues of the Drosophila Shaker K+ channel; clones of only three of these genes are available from all three mammalian species examined (mouse, rat, and human), pointing to specific genes that have yet to be recovered in one or another of these species. The Shaw-related K+ channels and the Na+ channel family have also undergone considerable expansion in mammals, relative to flies. These expansions presumably reflect the needs of the high degree of physiological and neuronal complexity of mammals. Analysis of the separate domains of the four-domain channels (Ca++ and Na+) supports their having evolved by two sequential gene duplications and implies the historical existence of a functional two-domain channel.      

Highly Efficient Flexible Hybrid Nanocrystal‐Cu(In,Ga)Se2 (CIGS) Solar Cells

A novel scheme for hybridizing inkjet‐printed thin film Cu(In,Ga)Se₂ (CIGS) solar cells with self‐assembled clusters of nanocrystal quantum dots (NQDs), which provides a 10.9% relative enhancement of the photon conversion efficiency (PCE), is demonstrated. A non‐uniform layer of NQD aggregates is deposited between the transparent conductive oxide and a CdS/CIGS p‐n junction using low cost pulsed‐spray deposition. Hybridization significantly improves the external quantum efficiency of the hybrid devices in the absorption range of the NQDs and in the red to near‐IR parts of the spectrum. The low wavelength response enhancement is found to be induced by luminescent down‐shifting (LDS) from the NQD layer, while the increase at longer wavelengths is attributed to internal scattering from NQD aggregates. LDS is demonstrated using time‐resolved spectroscopy, and the morphology of the NQD layer is investigated in fluorescence microscopy and cross‐sectional transmission electron microscopy. The influence of the NQD dose on the PCE of the hybrid devices is investigated and an optimum value is obtained. The low costs and limited material consumptions associated with pulsed‐spray deposition make these flexible hybrid devices promising candidates to help push thin‐film photovoltaic technology towards grid parity.     

B lymphocytes not required for progression from insulitis to diabetes in non-obese diabetic mice

Previous studies have implicated B lymphocytes in the pathogenesis of diabetes in the non-obese diabetic (NOD) mouse. While it is clear that B lymphocytes are necessary, it has not been clear at which stage of disease they play a role; early, late or both. To clarify when B lymphocytes are needed, T lymphocytes were transferred from 5-week-old NOD female mice to age-matched NOD/severe combined immunodeficiency (SCID) recipient mice. NOD/SCID mice, which lack functionally mature T and B lymphocytes, do not normally develop insulitis or insulin-dependent diabetes melitus (IDDM). The NOD/SCID mice that received purified T lymphocytes from 5-week-old NOD mice subsequently developed insulitis and diabetes even though they did not have detectable B lymphocytes. This suggests that while B lymphocytes may be essential for an initial priming event they are not requisite for disease progression in the NOD mouse.     

Secretin modulation of behavioral and physiological functions in the rat

The effect of secretin on behavioral and physiological functions in the rat was investigated. Secretin injected intracerebroventricularly (ICV) significantly increased defecation and decreased novel-object approaches in rats. The peptide showed no significant effects on stereotypic behavior (gnawing, grooming and rearing), open-field locomotor activity however was significantly decreased, an effect that was probably due to a decreased propensity for the rats to initiate locomotor responses. In addition, secretin showed significant effects on respiration rate in anesthetized rats. When the peptide was injected in the lateral ventricle a decrease in respiration rate occurred, but when the brain was perfused from the lateral ventricle to the cisterna magna increases in respiration rate occurred. These data, combined with the facts that secretin and secretin receptors have been identified in the brain indicate that secretin may play a neurotransmitter or neuroregulator role in the central nervous system.     

Genetic variation in foraging traits among inbred lines of a predatory mite

Response of predators to herbivore-induced plant volatiles can affect the length of time a predator spends in a prey patch and the probability of a predator finding a new prey patch. Variation in response to herbivore-induced plant volatiles may lead to different foraging decisions among individuals, thereby affecting both within-patch dynamics and between-patch dispersal. We found significant phenotypic and additive genetic variation in two behavioral assays of response to herbivore-induced plant volatiles among inbred isofemale lines of the predatory mite, Phytoseiulus persimilis. In wind-tunnel tests to measure patch residence time, adult female predators from certain lines left prey patches sooner than others when a distant source of herbivore-induced plant volatiles was presented; whereas such variation disappeared when no distant volatiles were presented. In a measure of patch location, certain lines were more likely than others to locate a prey-infested leaf disc; again there was no difference when uninfested leaf discs were used. Patch location was negatively correlated with patch residence. That is, lines that were more likely to leave a prey patch in the presence of distant volatiles were also more likely to find an odor source (ie, prey patch) from a distance of 20 cm. These two foraging-related behaviors are heritable. A continuous distribution of both behaviors indicated that several to many loci may be responsible for these behavioral traits. Our line-crossing experiments suggested that maternal influence could be excluded. Substantial phenotypic variation in two other foraging-related traits, consumption and oviposition, were also detected among inbred lines. Consumption and oviposition were positively correlated; however, the relationship (slope) varied among inbred lines, suggesting that predatory mites vary in food conversion efficiency. A relationship was detected between patch residence and consumption. Patch location, as one important foraging trait, appeared to be negatively related to consumption, suggesting a trade-off between searching for patches and reproduction.     

Discovery of novel inhibitors of Trypanosoma cruzi trans-sialidase from in silico screening

trans-Sialidase from Trypanosoma cruzi (TcTS) has emerged as a potential drug target for treatment of Chagas disease. Here, we report the results of virtual screening for the discovery of novel TcTS inhibitors, which targeted both the sialic acid and sialic acid acceptor sites of this enzyme. A library prepared from the Evotec database of commercially available compounds was screened using the molecular docking program GOLD, following the application of drug-likeness filters. Twenty-three compounds selected from the top-scoring ligands were purchased and assayed using a fluorimetric assay. Novel inhibitor scaffolds, with IC₅₀ values in the submillimolar range were discovered. The 3-benzothiazol-2-yl-4-phenyl-but-3-enoic acid scaffold was studied in more detail, and TcTS inhibition was confirmed by an alternative sialic acid transfer assay. Attempts to obtain crystal structures of these compounds with TcTS proved unsuccessful but provided evidence of ligand binding at the active site.     

Transverse sarcomere splitting. A possible means of longitudinal growth in crab muscles

Transversely split sarcomeres are seen in mouthpart muscles of the blue crab in the electron microscope. Sarcomeres split only at the H zone. Two new sarcomeres are formed by a Z disk which appears in the H zone of the splitting sarcomere. Splitting may involve breaking of the thick filaments in the H zone, elongation of these filaments, and formation of both new actin filaments and Z-disk materials, Sarcomere splitting would allow longitudinal growth of muscle cells without lengthening of sarcomeres and concomitant changes in contractile properties.     

Vacuum ultraviolet circular dichroism of fibronectin. Dominant tyrosine effects

The spectroscopic authenticity of a very intense negative band at about 183 nm reported previously from conventional circular dichroism (c.d.) studies of bovine plasma fibronectin has now been confirmed by vacuum ultraviolet c.d. measurements on two prototype spectrometers, one using a conventional light source and the other using synchrotron radiation. Closely similar spectra were obtained from both instruments, and from both solid films and solutions. The spectra show no obvious parentage in the known c.d. of the peptide backbone, but have marked similarities to the c.d. of N-acetyltyrosineamide, both in the strong band at 183 nm and in a characteristic positive band at 230 nm, It is concluded that the c.d. of fibronectin is dominated by contributions from tyrosine side-chains and that, as suggested previously, these may provide a sensitive probe for molecular organization and interactions.