Interlaboratory evaluation of a real-time multiplex polymerase chain reaction method for identification of salmon and trout species in commercial products

This interlaboratory study evaluated a real-time multiplex polymerase chain reaction (PCR) method for identification of salmon and trout species in a range of commercial products in North America. Eighty salmon and trout products were tested with this method by three independent laboratories. Samples were collected in the United States and Canada, and only the collecting institution was aware of the species declaration. Following analysis with real-time PCR, all three laboratories were able to identify species in 79 of the 80 products, with 100% agreement on species assignment. A low level of fraud was detected, with only four products (5%) found to be substituted or mixtures of two species. The results for two of the fraudulent products were confirmed with alternate methods, but the other two products were heavily processed and could not be verified with methods other than real-time PCR. Overall, the results of this study show the usefulness and versatility of this real-time PCR method for the identification of commercial salmon and trout species.     

MONOPOTASSIUM PHOSPHATE AS AN IN-SEASON FERTIGATION OPTION FOR POTATO

Monopotassium phosphate (MKP) is a potential option for fertigating phosphorus (P) in potato (Solanum tuberosum L.) when petioles are low in P and high in nitrogen (N); which is a situation where using ammonium polyphosphate (APP) could potentially result in excessive N application. Fertilizer trials were conducted in 2004–2006 with 0 or 56 kg P₂O₅ ha^?1 fertigated as either APP or MKP as a supplement to the pre-plant P (112 or 224 kg P₂O₅ ha^?1) broadcast applied to all plots. Supplemental P fertigation increased petiole P concentration, US No. 1 yield, and total yield over the control not receiving any in-season P fertilizer regardless of source. In addition, MKP increased tuber specific gravity. These results support previous studies showing that fertigated P can be used to increase potato yields when petiole P concentrations are low and that MKP is a viable substitute for APP fertilizer when fertigation is necessary.     

Rapid impact of Impatiens glandulifera control on above‐ and belowground invertebrate communities

The annual plant Impatiens glandulifera (Himalayan balsam) is the most widespread invasive non‐native weed in the British Isles. Manual control is widely used, but is costly and laborious. Recently, biological control using the rust fungus Puccinia komarovii var. glanduliferae has been trialled. We designed an experiment to assess the impact of these control methods on invertebrate communities in relation to unmanaged and uninvaded habitats, and to determine whether mycorrhizal inoculation aided post‐control recovery of these communities. Sixty invaded and twenty uninvaded field soil blocks were transplanted to the experiment site, where a mycorrhizal inoculum was added to half of all blocks. Biological and mechanical control treatments were applied to twenty invaded blocks independently; the twenty remaining invaded blocks were left intact. Above‐ and belowground invertebrate samples were collected from the blocks at the end of the growing season. Overall, aboveground invertebrate abundance increased with the removal of I. glandulifera, and several groups showed signs of recovery within one growing season. The effect of mechanical control was more variable in belowground invertebrates. Biological control did not affect aboveground invertebrate abundance but resulted in large increases in populations of belowground Collembola. Our experiment demonstrates that mechanical removal of I. glandulifera can cause rapid increases in invertebrate abundance and that its biological control with P. komarovii var. glanduliferae also has the potential to benefit native invertebrate communities.     

Neoamphimedine circumvents metnase-enhanced DNA topoisomerase IIα activity through ATP-competitive inhibition

Type IIα DNA topoisomerase (TopoIIα) is among the most important clinical drug targets for the treatment of cancer. Recently, the DNA repair protein Metnase was shown to enhance TopoIIα activity and increase resistance to TopoIIα poisons. Using in vitro DNA decatenation assays we show that neoamphimedine potently inhibits TopoIIα-dependent DNA decatenation in the presence of Metnase. Cell proliferation assays demonstrate that neoamphimedine can inhibit Metnase-enhanced cell growth with an IC(50) of 0.5 μM. Additionally, we find that the apparent K(m) of TopoIIα for ATP increases linearly with higher concentrations of neoamphimedine, indicating ATP-competitive inhibition, which is substantiated by molecular modeling. These findings support the continued development of neoamphimedine as an anticancer agent, particularly in solid tumors that over-express Metnase.     

Competitive interactions between juvenile trembling aspen and lodgepole pine: A comparison of two interior British Columbia ecosystems

To facilitate ecosystem-specific management of juvenile mixtures of lodgepole pine (Pinus contorta Dougl. Ex Loud. Var. latifolia Engelm.) and trembling aspen (Populus tremuloides Michx.) in south-central British Columbia, we compared the characteristics of pine–aspen competition between a moist sub-boreal spruce and a dry interior Douglas-fir ecosystem. A total of 252 lodgepole pine and their neighbourhoods were examined across four untreated stands, each of which was sampled three times between ages 12 and 24 years. Pine diameter and height decreased with increasing density of trembling aspen at least as tall as the target pine (tall aspen) in both ecosystems. Regression analysis was used to examine the ability of tall aspen density and four competition indices (CIs) to predict pine size. Tall aspen density, which is easily assessed in the field, accounted for 63% and 69% of the variation in pine diameter and height in 20–24 year-old stands, respectively. The most successful competition index, based on the basal diameter ratio (BDR) of trembling aspen to pine accounted for, respectively, 78% and 73% of the variation. In the same stands, R² values were 1–5% lower when tall aspen density and BDR at age 15–19 years were used to predict size of 20–24-year-old pine.     

Generalist feeding strategies in Arctic freshwater fish: A mechanism for dealing with extreme environments

Generalist feeding strategies are favoured in stressful or variable environments where flexibility in ecological traits is beneficial. Species that feed across multiple habitat types and trophic levels may impart stability on food webs through the use of readily available, alternative energy pools. In lakes, generalist fish species may take advantage of spatially and temporally variable prey by consuming both benthic and pelagic prey to meet their energy demands. Using stomach content and stable isotope analyses, we examined the feeding habits of fish species in Alaska's Arctic Coastal Plain (ACP) lakes to determine the prevalence of generalist feeding strategies as a mechanism for persistence in extreme environments (e.g. low productivity, extreme cold and short growing season). Generalist and flexible feeding strategies were evident in five common fish species. Fish fed on benthic and pelagic (or nektonic) prey and across trophic levels. Three species were clearly omnivorous, feeding on fish and their shared invertebrate prey. Dietary differences based on stomach content analysis often exceeded 70%, and overlap in dietary niches based on shared isotopic space varied from zero to 40%. Metrics of community‐wide trophic structure varied with the number and identity of species involved and on the dietary overlap and niche size of individual fishes. Accumulation of energy from shared carbon sources by Arctic fishes creates redundancy in food webs, increasing likely resistance to perturbations or stochastic events. Therefore, the generalist and omnivorous feeding strategies employed by ACP fish may maintain energy flow and food web stability in extreme environments.     

Isolation and characterization of primary canine lens epithelial cells

OBJECTIVE: The purpose of this study was to characterize the proliferation and differentiation of primary canine lens epithelial cells (LEC) under standard culture conditions. PROCEDURE: Canine LEC were isolated by mechanical dissection of the canine globe and enzymatic digestion of the lens capsule from fresh lenses. Isolated capsules and cell suspensions were seeded in laminin-coated culture flasks. Canine LEC proliferated and formed monolayers, which could be passaged and maintained for approximately 2 weeks. Cells were characterized morphologically and cell lysates examined for expression of protein markers of epithelial origin and differentiation. RESULTS: Canine LEC exhibit morphologic characteristics of epithelial cells when cultured on laminin/lysine coated flasks. Expression of epithelial cell marker, cytokeratin 5, was highest at passage 1 and diminished with increasing passage number. Expression of gamma-crystallin, a protein found only in differentiated lens fiber cells, increased at passage 6. A laminin/lysine-coated surface supported optimal proliferation of canine LEC. Both an initial seeding density of 1 x 10(5) cells/cm(2) and culture in Dulbecco's modified essential media (DMEM) supplemented with 10% FBS supported a doubling time of less than 48 h in canine LEC. CONCLUSION: This study demonstrates that primary canine LEC retain the characteristics of lens epithelial cells prior to passage 6 under the described culture conditions and represent a suitable in vitro model for investigating lens physiology and cataractogenesis.