Ctr1 transports silver into mammalian cells

Silver is a non-essential, toxic metal. The use of silver as an antimicrobial agent in many applications and its presence as a contaminant in foods and air can lead to accumulation in tissues. Despite its widespread use, the systems involved in the uptake of silver into mammalian cells are presently unknown. Previous studies have shown that copper uptake at the plasma membrane by copper transporter 1 (Ctr1) is inhibited by an excess of silver, suggesting that Ctr1 may function in importing silver into cells. In this study we examined directly the role of Ctr1 in the accumulation of silver in mammalian cells using over-expression experiments and mouse embryonic fibroblast cells lacking Ctr1. COS-7 cells transfected to express a human Ctr1-green fluorescent protein (hCtr1-GFP) fusion protein hyper-accumulated silver when incubated in medium supplemented with low micromolar concentrations (2.5–10 μmol/L) of AgNO₃. An hCtr1-GFPM150L,M154L variant deficient for copper transport failed to stimulate accumulation of silver. Mouse embryonic fibroblast cells lacking Ctr1 showed approximately a 50% reduction in silver content when incubated in silver-supplemented medium compared to a wild-type isogenic cell line. Collectively, these data demonstrate that Ctr1 transports both copper and silver and suggest that Ctr1 is an important transport protein in the accumulation of silver in mammalian cells.     

Effects of light on cyanide‐resistant respiration and alternative oxidase function in Arabidopsis seedlings

Mitochondrial alternative oxidase (AOX), the unique respiratory terminal oxidase in plants, catalyzes the energy wasteful cyanide (CN)‐resistant respiration and plays a role in optimizing photosynthesis. Although it has been demonstrated that leaf AOX is upregulated after illumination, the in vivo mechanism of AOX upregulation by light and its physiological significance are still unknown. In this report, red light and blue light‐induced AOX (especially AOX1a) expressions were characterized. Phytochromes, phototropins and cryptochromes, all these photoreceptors mediate the light‐response of AOX1a gene. When aox1a mutant seedlings were grown under a high‐light (HL) condition, photobleaching was more evident in the mutant than the wild‐type plants. More reactive oxygen species (ROS) accumulation and inefficient dissipation of chloroplast reducing‐equivalents in aox1a mutant may account for its worse adaptation to HL stress. When etiolated seedlings were exposed to illumination for 4 h, chlorophyll accumulation was largely delayed in aox1a plants. We first suggest that more reduction of the photosynthetic electron transport chain and more accumulation of reducing‐equivalents in the mutant during de‐etiolation might be the main reasons.     

Genetic uniformity characterizes the invasive spread of water hyacinth (Eichhornia crassipes), a clonal aquatic plant

Aquatic plant invasions are often associated with long‐distance dispersal of vegetative propagules and prolific clonal reproduction. These reproductive features combined with genetic bottlenecks have the potential to severely limit genetic diversity in invasive populations. To investigate this question we conducted a global scale population genetic survey using amplified fragment length polymorphism markers of the world’s most successful aquatic plant invader –Eichhornia crassipes (water hyacinth). We sampled 1140 ramets from 54 populations from the native (South America) and introduced range (Asia, Africa, Europe, North America, Central America and the Caribbean). Although we detected 49 clones, introduced populations exhibited very low genetic diversity and little differentiation compared with those from the native range, and ～80% of introduced populations were composed of a single clone. A widespread clone (‘W’) detected in two Peruvian populations accounted for 70.9% of the individuals sampled and dominated in 74.5% of the introduced populations. However, samples from Bangladesh and Indonesia were composed of different genotypes, implicating multiple introductions to the introduced range. Nine of 47 introduced populations contained clonal diversity suggesting that sexual recruitment occurs in some invasive sites where environmental conditions favour seedling establishment. The global patterns of genetic diversity in E. crassipes likely result from severe genetic bottlenecks during colonization and prolific clonal propagation. The prevalence of the ‘W’ genotype throughout the invasive range may be explained by stochastic sampling, or possibly because of pre‐adaptation of the ‘W’ genotype to tolerate low temperatures.     

Forest refugia revisited: nSSRs and cpDNA sequences support historical isolation in a wide‐spread African tree with high colonization capacity,Milicia excelsa (Moraceae)

The impact of the Pleistocene climate oscillations on the structure of biodiversity in tropical regions remains poorly understood. In this study, the forest refuge theory is examined at the molecular level in Milicia excelsa, a dioecious tree with a continuous range throughout tropical Africa. Eight nuclear microsatellites (nSSRs) and two sequences and one microsatellite from chloroplast DNA (cpDNA) showed a deep divide between samples from Benin and those from Lower Guinea. This suggests that these populations were isolated in separate geographical regions, probably for several glacial cycles of the Pleistocene, and that the nuclear gene pools were not homogenized despite M. excelsa’s wind‐pollination syndrome. The divide could also be related to seed dispersal patterns, which should be largely determined by the migration behaviour of M. excelsa’s main seed disperser, the frugivorous bat Eidolon helvum. Within Lower Guinea, a north–south divide, observed with both marker types despite weak genetic structure (nSSRs: F_ST = 0.035, cpDNA: G_ST = 0.506), suggested the existence of separate Pleistocene refugia in Cameroon and the Gabon/Congo region. We inferred a pollen‐to‐seed dispersal distance ratio of c. 1.8, consistent with wide‐ranging gene dispersal by both wind and bats. Simulations in an Approximate Bayesian Computation framework suggested low nSSR and cpDNA mutation rates, but imprecise estimates of other demographic parameters, probably due to a substantial gene flow between the Lower Guinean gene pools. The decline of genetic diversity detected in some Gabonese populations could be a consequence of the relatively recent establishment of a closed canopy forest, which could negatively affect M. excelsa’s reproductive system.     

Selective angiotensin II AT2 receptor agonists with reduced CYP 450 inhibition

Structural alterations to the benzylic position of the first drug-like selective angiotensin II AT₂ receptor agonist (1) have been performed, with the emphasis to reduce the CYP 450 inhibitory property of the initial structure. The imidazole moiety, responsible for the CYP 450 inhibitory effect in 1, was replaced with various heterocycles. In addition, the modes of attachment of the heterocycles, that is, carbon versus nitrogen attachment, and introduction of carbonyl functionalities to the benzylic position have been evaluated. In all the three series, AT₂ receptor ligands with affinity in the lower nanomolar range were identified. None of the analogues, regardless of the substituents, exhibited any affinity for the AT₁ receptor. Compounds with substantially reduced inhibition of the CYP 450 enzymes were obtained. Among them the compound 60 was found to induce neurite elongation in NG 108-15 cells and served as potent AT₂ selective agonist.     

Biological Control of Sheep Parasites using Duddingtonia flagrans: Trials on Commercial Farms in Sweden

   

Trials were conducted on 3 commercial sheep farms in Sweden to assess the effect of administering spores of the nematode trapping fungus, Duddingtonia flagrans, together with supplementary feed to lactating ewes for the first 6 weeks from turn-out on pastures in spring. Also control groups of ewes, receiving only feed supplement, were established on all 3 farms. Groups were monitored by intensive parasitological investigation. The ewes and their lambs were moved in late June to saved pastures for summer grazing, the lambs receiving an anthelmintic treatment at this time. After approximately 6 weeks on summer pasture the lambs were weaned, treated a second time with anthelmintic, and returned to their original lambing pastures for finishing. Decisions as to when lambs were to be marketed were entirely at the discretion of the farmer co-operators. No difference in lamb performance was found between the two treatments on all three farms. This was attributed to the high levels of nutrition initially of the ewes limiting their post-partum rise in nematode faecal egg counts in spring, which in turn resulted in low levels of nematode infection on pastures throughout the autumn period. Additionally, pastures were of good quality for the lambs during the finishing period, so they grew at optimal rates as far as the farmers were concerned.     

A systematic map of genetic variation in Plasmodium falciparum

Discovering novel genes involved in immune evasion and drug resistance in the human malaria parasite, Plasmodium falciparum, is of critical importance to global health. Such knowledge may assist in the development of new effective vaccines and in the appropriate use of antimalarial drugs. By performing a full-genome scan of allelic variability in 14 field and laboratory strains of P. falciparum, we comprehensively identified approximately 500 genes evolving at higher than neutral rates. The majority of the most variable genes have paralogs within the P. falciparum genome and may be subject to a different evolutionary clock than those without. The group of 211 variable genes without paralogs contains most known immunogens and a few drug targets, consistent with the idea that the human immune system and drug use is driving parasite evolution. We also reveal gene-amplification events including one surrounding pfmdr1, the P. falciparum multidrug-resistance gene, and a previously uncharacterized amplification centered around the P. falciparum GTP cyclohydrolase gene, the first enzyme in the folate biosynthesis pathway. Although GTP cyclohydrolase is not the known target of any current drugs, downstream members of the pathway are targeted by several widely used antimalarials. We speculate that an amplification of the GTP cyclohydrolase enzyme in the folate biosynthesis pathway may increase flux through this pathway and facilitate parasite resistance to antifolate drugs.     

Role of nurse plants in Araucaria Forest expansion over grassland in south Brazil

Abstract Araucaria Forest expansion over grassland takes place under wet climate conditions and low disturbance and it is hypothesized that isolated trees established on grassland facilitate the establishment of forest woody species beneath their canopies. Forest with Araucaria angustifolia is a particular type of Brazilian Atlantic Forest and the main forest type on the highland plateau in south Brazil, often forming mosaics with natural Campos grassland. The objectives of this paper were to evaluate the role of isolated shrubs and trees as colonization sites for seedlings of Araucaria Forest woody species on grassland, to determine which species function as preferential nurse plants in the process and the importance of vertebrate diaspore dispersal on the structure of seedling communities beneath nurse plants. The study was conducted in São Francisco de Paula, Rio Grande do Sul State, where we sampled isolated shrubs and trees in natural grassland near Araucaria Forest edges. Seedlings were counted and identified, and seedling diaspore dispersal syndromes, size and colour were registered. We detected 11 woody species with a potential role in nucleating grassland colonization by forest species. Beneath the canopies of nurse plants more forest species seedlings were found compared with open field grassland and the seedlings had diaspores mostly dispersed by vertebrates. Also, more seedlings were found under the canopy of A. angustifolia than beneath other nurse plant species. We conclude that A. angustifolia trees established on grassland act as nurse plants, by attracting disperser birds that promote colonization of the site by other forest species seedlings, and that under low level of grassland disturbance, conservation of frugivorous vertebrate assemblages may increase forest expansion over natural grassland and also facilitate the regeneration of degraded forest areas.