Quantifying potato pathogen DNA in soil

An improved method for the direct extraction of DNA from soil involving processing of a relatively large sample (60 g) was developed. The accurate and reliable detection and quantification of the soil-borne potato pathogens Colletotrichum coccodes (black dot), Rhizoctonia solani (black scurf) and Spongospora subterranea (powdery scab) following inoculation of soils was demonstrated. With this method, low levels of target DNA (30–40 pg DNA/g soil) could be detected in field soils. DNA recovery was proportionate across a wide range of inoculum (R² > 0.86) and there was no effect of soil type on the recovery of C. coccodes. The method was used to assess levels of naturally occurring pathogen DNA in 122 soil samples obtained from commercial potato fields.     

New Rangeland Residents in Wyoming? A Survey of Exurban Landowners

Rapid conversion of rural land to exurban development and the ensuing impacts on natural resources have been well-documented, but information about exurban landowners is lacking. To address this knowledge gap, we surveyed exurban landowners in six Wyoming counties and documented demographic characteristics, motivations, knowledge, and attitudes about natural resources and land management. The overall response rate was 55.6%. Generally, respondents were of retirement age, had lived in Wyoming for about 13 yr, and were raised in areas with a population < 10 000. Wyoming respondents lived in exurbia for the lifestyle and aesthetic values and did not expect economic gains from their property. Most respondents had knowledge about, and interest in, invasive species, water quality, landscaping, and gardening. More than half of respondents (54%) had never looked for information regarding land management. Information from this study can be used to strengthen the development and delivery of educational programs. Programs that focus on water quality or weed control likely will appeal to more exurban landowners than those that focus solely on grazing management. Our findings provide an accurate characterization of this audience and their motivations and attitudes regarding land management, and suggest that using a multipronged approach for outreach efforts, which includes both cost- and time-efficient ways to conduct important land management practices, might increase participation in educational programs.     

Prevalence of Bartonella species antibodies and Bartonella species DNA in the blood of cats with and without fever

The purpose of this study was to determine whether there are associations between Bartonella species antibody (enzyme-linked immunosorbent assay (ELISA) and Western blot (WB)) and polymerase chain reaction assay results in cats with and without fever. Afebrile control cats (39/93; 42.0%) were more likely to have Bartonella species antibodies than cats with fever (29/93; 31.2%). The difference in prevalence of Bartonella species deoxyribonucleic acid (DNA) in blood of cats with fever (14/81; 17.3%) as compared to afebrile control cats (6/81; 7.4%) approached statistical significance (P=0.0571). Bartonella species ELISA or WB results frequently did not correlate to the presence or absence of Bartonella species DNA in blood. The results of this study indicate that in cats, Bartonella species antibody tests cannot predict whether fever is due to Bartonella species infection and should not be used to determine the Bartonella species infection status.     

Dietary Protein Requirement of Juvenile Cachara Catfish,Pseudoplatystoma reticulatum

Cachara, Pseudoplatystoma reticulatum, is a high commercial value carnivorous catfish in Brazil, but whose dietary protein requirement is still unknown. Aiming to determine this requirement, groups of 15 juveniles (16.08 ± 1.13 g) were fed isoenergetic diets (4600 kcal/kg gross energy) with increasing levels of crude protein (30, 35, 40, 45, 50, and 55%). After 60 d, regression analysis revealed a quadratic effect (P < 0.05) of increasing dietary crude protein concentration on growth variables. The highest weight gain and specific growth rate as well as the best feed conversion were shown by fish fed the 50% crude‐protein diet. Similarly, protease activities were significantly higher (P < 0.05) in fish fed 50% crude protein. However, the highest protein retention was observed in fish fed the 45% crude‐protein diet. Protein and dry matter digestibilities did not differ (P > 0.05) for diets containing 40, 45, or 50% crude protein. Therefore, based on weight gain and at a dietary energy concentration of 4600 kcal/kg, the estimated protein requirement for juvenile cachara between 16 and 85 g is 49.25% crude protein. This is equivalent to 44.79% digestible protein and a gross energy to digestible protein ratio of 10.27 kcal/g.     

Plankton dynamics: observed and modelled responses to physical conditions in Prince William Sound,Alaska

Plankton populations in Prince William Sound, Alaska, exhibited pronounced seasonal, annual and longer‐period variability in composition and standing stock in response to physically influenced differences in nutrient availability, and possibly currents that modify local biomass by exchanges with water from the bordering Gulf of Alaska. During springs in which early, strong physical stratification developed, intense, short‐lived phytoplankton blooms occurred. These blooms had relatively short residence times in the water column. In contrast, during springs in which slower, weaker stratification developed, phytoplankton blooms were prolonged and took longer to peak. These slower blooms prolonged the period of phytoplankton production, prolonged interaction with the springtime grazing community and led to the incorporation of more organic matter into pelagic food webs. A coupled biological‐physical simulation of plankton production was used to examine the implications of seasonally varying air and mixed‐layer temperatures, surface winds and incident light on the timing, duration, annual production and standing stock of plankton. Our modelling results reproduced the observed characteristics of the springtime production cycle, and the magnitude of zooplankton stocks for the period 1992–97 but not for 1981–91. These results suggest that for most of the 1990s, bottom‐up influences on nutrient supplies controlled levels of primary consumers, whereas for the 11 years before that, other unknown factors dominated this process. We present the results of a comprehensive, multiyear study of relationships between plankton and physical limitations, and a retrospective analysis of earlier conditions to explore the possible causes for these differences.     

Cortisol stimulates intestinal fluid uptake in Atlantic salmon (Salmo salar) in the post-smolt stage

The fluid uptake rate of the posterior intestine of salmonids increases during the parr-smolt transformation. Intestinal fluid uptake in post-smolt Atlantic salmon was investigated after treatment with cortisol and growth hormone (GH), alone or together. Two replicate experiments were conducted in August 1991 and August 1992. Cortisol was emulsified in vegetable shortening and vegetable oil (1:1) and implanted into the peritoneal cavity. GH was administered as intraperitoneal injections in a saline vehicle on days 0 and 2. On days 5 and 6, plasma cortisol levels, gill Na⁺,K⁺-ATPase activity, andin vitro measurements of fluid transport rate (J_v) across the posterior intestine were measured. Implants of cortisol elevated the plasma cortisol levels within a physiological range, and resulted in elevated gill Na⁺,K⁺-ATPase activity, as expected. The fluid uptake rate across the posterior intestine was roughly doubled by cortisol treatment. GH treatment did not affect intestinal fluid transport, gill Na⁺,K⁺-ATPase activity, or plasma cortisol concentrations. The seawater-adapting increase in the rate of fluid uptake by the posterior intestine of smolting salmon is probably stimulated by elevated plasma cortisol concentrations.     

Differential leaf‐litter processing by native (Gammarus pulex) and invasive (Dikerogammarus villosus) freshwater crustaceans under environmental extremes

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What is your diagnosis? Blood smear from an injured red‐tailed hawk

Abstract: An injured juvenile red‐tailed hawk (Buteo jamaicensis) was evaluated at the Veterinary Medical Teaching Hospital at the University of California, Davis. The hawk was quiet, alert, and emaciated, and had a closed comminuted, mid‐diaphyseal ulnar fracture. CBC results included heterophilia with a left shift, monocytosis, and increased plasma fibrinogen concentration. The blood smear included rare heterophils containing small, dark blue inclusions approximately 1–2 μm in diameter that ranged from round to coccobacillary in shape and formed variably shaped aggregates; the morphology of the inclusions was suspicious for Chlamydophila or Ehrlichia spp. pathogens. The hawk died, and histopathologic examination of tissues obtained at necropsy found severe multifocal histiocytic and heterophilic splenitis in addition to chronic hepatitis, myocarditis and epicarditis, meningoencephalitis, and airsacculitis. Using immunohistochemistry the presence of Chlamydia/Chlamydophila spp. antigen within multiple tissues was confirmed. Chlamydophila psittaci DNA was demonstrated in whole blood and fresh splenic tissue via real‐time PCR. Direct fluorescent antibody staining of air‐dried blood smears was positive in rare leukocytes for Chlamydia/Chlamydophila spp. antigen, and immunocytochemical staining of blood smears for Chlamydia/Chlamydophila spp. antigen was focally positive in rare heterophils. These findings may represent the first reported diagnosis of natural avian C. psittaci infection by visualization of organisms in peripheral blood heterophils. Immunocytochemical evaluation of blood smears was valuable in confirming the diagnosis and may be a useful antemortem test to discriminate between bacteria and other inclusions within heterophils.