Excitotoxicity can be mediated through an interaction within the optic nerve; activation of cell body NMDA receptors is not required

Axonal trauma leads to a series of pathologic events that can culminate in neuronal death. Although the precise mechanisms of retinal ganglion cell death after optic nerve crush in the rat model have not been elucidated, glutamate antagonists can protect retinal ganglion cells after optic nerve axotomy. We therefore explored whether a glutamate congener was toxic if applied directly within the optic nerve, or if toxicity depended upon an interaction at the cell body level. NMDA reduced retinal ganglion cell survival when applied directly into the rat optic nerve. Glutamate can be toxic if administered within the optic nerve; a direct effect at the cell body is not necessary. Future work will help to additionally unravel the steps by which axotomy induces excitotoxic damage to ganglion cells, and perhaps indicate protective interventions.     

Introduced northern pike predation on salmonids in southcentral Alaska

Northern pike (Esox lucius) are opportunistic predators that can switch to alternative prey species after preferred prey have declined. This trophic adaptability allows invasive pike to have negative effects on aquatic food webs. In Southcentral Alaska, invasive pike are a substantial concern because they have spread to important spawning and rearing habitat for salmonids and are hypothesised to be responsible for recent salmonid declines. We described the relative importance of salmonids and other prey species to pike diets in the Deshka River and Alexander Creek in Southcentral Alaska. Salmonids were once abundant in both rivers, but they are now rare in Alexander Creek. In the Deshka River, we found that juvenile Chinook salmon (Oncorhynchus tshawytscha) and coho salmon (O. kisutch) dominated pike diets and that small pike consumed more of these salmonids than large pike. In Alexander Creek, pike diets reflected the distribution of spawning salmonids, which decrease with distance upstream. Although salmonids dominated pike diets in the lowest reach of the stream, Arctic lamprey (Lampetra camtschatica) and slimy sculpin (Cottus cognatus) dominated pike diets in the middle and upper reaches. In both rivers, pike density did not influence diet and pike consumed smaller prey items than predicted by their gape‐width. Our data suggest that (1) juvenile salmonids are a dominant prey item for pike, (2) small pike are the primary consumers of juvenile salmonids and (3) pike consume other native fish species when juvenile salmonids are less abundant. Implications of this trophic adaptability are that invasive pike can continue to increase while driving multiple species to low abundance.     

Pseudallescheria boydii species complex fungal rhinitis and sinusitis in a dog

A 9 yr old male castrated Australian shepherd mixed-breed dog with a 3 mo history of intermittent unilateral epistaxis was diagnosed with Pseudallescheria boydii species complex fungal rhinitis and sinusitis. This fungal organism is a rare cause of disease in dogs and an emerging human pathogen. The dog was successfully treated with topical clotrimazole.     

Determination of critical soil water content and matric potential for wind erosion

Purpose  

Soil strength and thus stability concerning wind erosion are controlled by the soil water content. The concept of soil critical water content (Θ_crit.) for deflation was extended to include matric potential (Ψ_crit.) as well. The focus of this paper is to quantify the Θ_crit. and Ψ_crit. as the upper boundary for wind erosion or as the lower boundary for soil strength, to model the Ψ_crit. at the immediate soil surface (0–0.2 cm) and to evaluate the effect of soil moisture upon erosion as a function of time and sampling height.     

Foliar application of systemic insecticides disrupts feeding behavior of the whitefly Bemisia tabaci MEAM1 and the transmission of tomato chlorosis virus in potato plants

Journal of Pest Science - The whiteflies of the Bemisia tabaci (Genn.) complex (Hemiptera: Aleyrodidae) are serious agricultural pests that cause severe losses to vegetable, ornamental and fiber...     

Estimating Electrical Conductivity of Compost Extracts At Different Extraction Ratios

Electrical conductivity (EC) was measured on extracts from four different types of compost using two different dilution techniques. When EC was measured on extracts obtained using a saturated paste method, EC varied by 20-25% of the mean measurement. When EC was measured on extracts obtained using a quantitative dilution procedure over a range of dilution ratios, EC varied by less than 10% of the mean. For dilution ratios less than 8 (ml water/g dry compost), the increase in EC was less than expected, suggesting that at the lower dilution ratios salts were incompletely extracted or did not completely diffuse from the particle interior to the extractable solution. A method of comparing compost EC measurements obtained using different dilution ratios, including the saturated paste dilution, is presented. This method predicted the EC of the saturated paste extract in three of the four compost samples tested. These methods could be integrated into a computer data spreadsheet for a typical composting operation. Thus, this work has implications for better sampling techniques and simpler analyses for estimating the EC of compost samples.     

Infusion of glucagon-like peptide 2 with an arginine deficient diet increases endogenous arginine synthesis from proline in parenterally-fed neonatal piglets

Parenteral feeding can be used to induce intestinal atrophy in piglets, and this atrophy is believed to be associated with the inability of parenterally-fed piglets to maintain arginine status via synthesis. Glucagon-like peptide 2 (GLP-2) has been shown to maintain intestinal structure and blood flow during intravenous feeding. GLP-2 infusion was hypothesized to increase the rate of endogenous arginine synthesis from proline in parenterally-fed piglets receiving an arginine deficient diet. Male piglets (n = 10, 1.5–2.0 kg), fitted with jugular vein catheters for diet and isotope infusion, and femoral vein catheters for blood sampling (d 0), were allocated to a continuous infusion of either GLP-2 (10 nmol/kg/d) or saline into the jugular vein. Piglets received 2 d of a complete diet, followed by 5 d of an arginine deficient (0.60 g/kg/d) diet. A primed, constant infusion of [guanido-¹⁴C]arginine measured arginine flux (d 6), and of [U-¹⁴C]proline (d 7) measured proline conversion to arginine. There were no differences between groups in plasma ammonia, urea and arginine concentrations and arginine flux. Piglets receiving GLP-2 had a greater jejunal mucosal mass (P = 0.003) and a two-fold greater rate of arginine synthesis from proline (P = 0.03). This study indicates that the intestinal metabolism of circulating precursors may be important for arginine synthesis in parenterally-fed neonates.