Validation of a whole-body cortisol extraction procedure for channel catfish (<Emphasis Type="Italic">Ictalurus punctatus</Emphasis>) fry

We validated a whole-body cortisol extraction technique for channel catfish, Ictalurus punctatus, fry. Three volume enhancement methods were tested: CAL method (zero calibrator A diluent added to lipid extract), PBS method (phosphate buffered saline added to lipid extract), and VO method (food grade vegetable oil added to lipid extract). The volume enhancement extracts were evaluated using a commercial radioimmunoassay kit. Sensitivity, accuracy, precision, reproducibility, and parallelism could not be determined for the PBS method as cortisol levels were not detected in any of the extracted samples. Intra-assay coefficient of variation (CV) for the CAL and VO methods were 7.3 and 8.3%, respectively, while inter-assay CV were 9.6 and 10.6%, respectively. Based on the sensitivity, accuracy, precision, reproducibility, and parallelism results, we conclude that the CAL method is the most appropriate method for volume enhancement of catfish fry lipid extract. Using the CAL method to detect cortisol in catfish fry, fish were stressed daily for 2 weeks. Fry weights were similar throughout the study while whole-body cortisol levels were higher (P < 0.01) in stressed fish after 1 day of stress. These data show the CAL method can effectively measure whole-body cortisol in catfish fry.     

Soybean root suberin and partial resistance to root rot caused by Phytophthora sojae

Phytophthora sojae is the causal agent of root and stem rot of soybean (Glycine max). Various cultivars with partial resistance to the pathogen have been developed to mitigate this damage. Herein, two contrasting genotypes, the cultivar Conrad (with strong partial resistance) and the line OX760-6 (with weak partial resistance), were compared regarding their amounts of preformed and induced suberin components, and to early events during the P. sojae infection process. To colonize the root, hyphae grew through the suberized middle lamellae between epidermal cells. This took 2 to 3 h longer in Conrad than in OX760-6, giving Conrad plants more time to establish their chemical defenses. Subsequent growth of hyphae through the endodermis was also delayed in Conrad. This cultivar had more preformed aliphatic suberin than the line OX760-6 and was induced to form more aliphatic suberin several days prior to that of OX760-6. However, the induced suberin was formed subsequent to the initial infection process. Eventually, the amount of induced suberin (measured 8 days postinoculation) was the same in both genotypes. Preformed root epidermal suberin provides a target for selection and development of new soybean cultivars with higher levels of expression of partial resistance to P. sojae.     

Incidence,Growth, and Inactivation of Listeria monocytogenes in Cooked and Peeled Cold-Water Shrimp

ABSTRACT

Cooked and peeled cold-water shrimp (Pandalus jordani) naturally contaminated with Listeria monocytogenes were obtained from a processor for a series of studies to determine the level of contamination and growth characteristics of this bacterium in the naturally contaminated product. L. monocytogenes was isolated from every 25-g sample of individually quick frozen (IQF) shrimp that was tested. The level of contamination in each composite sample ranged from 5 to 16 colony forming units (CFU) per 25 g. When individual shrimp taken from the 25-g sample portions were tested separately, samples positive for L. monocytogenes ranged from 1 of 12 to 5 of 15 shrimp tested. The project also evaluated the effectiveness of three methods to inactivate the bacterium: ozone, chlorine dioxide, and steam as possible product reconditioning strategies. Ozone and chlorine dioxide were both found to be ineffective reconditioning treatments for shrimp naturally contaminated with L. monocytogenes. Experiments with steam conducted at the laboratory and later at the shrimp processing plant verified that shrimp contaminated with L. monocytogenes could be safely reconditioned by steam pasteurization. Steam was used successfully to pasteurize several thousand pounds of contaminated shrimp in the processing plant. When the naturally contaminated product was packaged in either oxygen-permeable or impermeable films and stored at 5°C and 10°C, the product was deemed spoiled by sensory evaluation after 9 days of storage, at which time the L. monocytogenes population were 3 × 10⁴ CFU per g. By comparison, when an isolate (strain 4311) from naturally contaminated shrimp was inoculated onto the pasteurized shrimp at a concentration of 12 cells /25g, the L. monocytogenes population reached 3.0 × 10⁸ per g after 9 days of storage. The pasteurization process used in this study would not be effective in inactivation of Clostridium botulinum. Ready-to-eat-shrimp must therefore be stored below 3°C or frozen.     

ORIGINAL ARTICLE: Lutein exposure,in ovo or in the diet,reduces parameters of inflammation in the liver and spleen laying‐type chicks (Gallus gallus domesticus)

These trials examined whether the demonstrated effects of embryonic and dietary carotenoid exposure on the inflammatory immune response in fast growing chickens also occur in slow growing chickens. The systemic and local inflammatory responses of chicks were examined in two experiments with two in ovo lutein levels (C+, carotenoid replete; or C?, carotenoid‐deplete), two dietary lutein levels (0 or 40 mg lutein/kg diet), and two inflammatory challenges [no exposure or lipopolysaccharide (LPS)‐vaccinated]. At 24 h after LPS vaccination, spleen weight was not affected by diet or in ovo lutein, but liver weight increased from C+ eggs (p < 0.01), and in LPS‐vaccinated chicks fed 0 mg lutein (p < 0.05), but not in chicks fed 40 mg lutein. Plasma carotenoids and liver carotenoids were reduced post‐LPS (p < 0.05). Splenic IL‐6 mRNA abundance was the greatest post‐LPS in C? chicks fed 40 mg lutein vs. C+ chicks fed 40 mg lutein (p < 0.05). Hepatic IL‐6, iNOS and TGFβ and splenic iNOS and TGFβ were not affected by in ovo or dietary lutein. The systemic and local inflammatory results are similar to those observed in fast growing chickens, and support that lutein‐depleted birds have greater inflammatory responses.     

Insight into the mechanism of the influenza A proton channel from a structure in a lipid bilayer

The M2 protein from the influenza A virus, an acid-activated proton-selective channel, has been the subject of numerous conductance, structural, and computational studies. However, little is known at the atomic level about the heart of the functional mechanism for this tetrameric protein, a His(37)-Trp(41) cluster. We report the structure of the M2 conductance domain (residues 22 to 62) in a lipid bilayer, which displays the defining features of the native protein that have not been attainable from structures solubilized by detergents. We propose that the tetrameric His(37)-Trp(41) cluster guides protons through the channel by forming and breaking hydrogen bonds between adjacent pairs of histidines and through specific interactions of the histidines with the tryptophan gate. This mechanism explains the main observations on M2 proton conductance.     

Mulching effects on vegetation recovery following high severity wildfire in north-central Washington State,USA

Straw mulch application after high severity wildfire has gained favor in recent years due to its efficacy in reducing soil erosion hazards. However, possible collateral effects of mulching on post-fire vegetation recovery have received relatively little study. We assessed mulching effects on plant cover and species richness, tree seedling establishment, and exotic species densities in the second year following the 2006 Tripod Wildfire in north-central Washington State, USA, by observing vegetation responses to spatial variability in mulch cover and depth. Mulch cover averaged about 35%, with a median depth of 0.5 cm. Vegetation recovery was generally slow, with median plant cover of only 10%. Tree seedling densities were low and spatially variable. Vegetative cover, species richness, and seedling densities all declined with increasing elevation. Mulch cover was positively associated with plant cover, plant species richness, and conifer seedling densities when second year mulch cover did not exceed 40%. Only when mulch cover exceeded 70% did mulching begin to negatively affect vegetation recovery relative to areas with no mulch. Vegetation responses to mulch depth were minimal at depths under 3 cm, but quite strong when mulch depth exceeded 5 cm. Exotic plant frequency and density were positively associated with mulch cover, but exotic plant cover was low on average (<1%). In this study, mulch added significant cover to sites with slow natural recovery of vegetation, thereby likely reducing erosion hazard. Mulching also appears to have facilitated native plant recovery and conifer seedling establishment except at very high application levels, easing management concerns about longer-term impacts of mulching treatments on post-fire vegetation recovery.     

Dry coniferous forest restoration and understory plant diversity: The importance of community heterogeneity and the scale of observation

Maintaining understory plant species diversity is an important management goal as forest restoration and fuel reduction treatments are applied extensively to dry coniferous forests of western North America. However, understory diversity is a function of both local species richness (number of species in a sample unit) and community heterogeneity (beta diversity) at multiple spatial scales, while studies of restoration treatment effects often only examine local species richness at one or two spatial scales. We studied experimental thinning and prescribed fire treatment effects on understory plant species richness and community heterogeneity at three spatial scales using additive diversity partitioning. We also evaluated treatment effects on understory plant species colonization and extirpation at two spatial scales. There was no evidence that active restoration treatments reduced species richness or increased local extirpation of species. Restoration treatments significantly increased herbaceous species richness at the treatment-unit level primarily by increasing community heterogeneity among sampling points within the units. The combination of thinning and burning produced the greatest increase in community heterogeneity, and increased colonization by species that were not sampled prior to treatment. These results suggest that restoration treatments designed primarily to reduce fire hazard and promote sustainable conditions in these fire-adapted ecosystems can also increase community heterogeneity and facilitate colonization by new understory species without significant local extirpation of extant species.