A review of antimicrobial peptides: defensins and related cationic peptides

Cationic antimicrobial peptides are present throughout the plant and animal kingdoms and bear striking structural and functional similarities across species lines. They provide primitive, nonspecific means of combating a variety of bacteria, fungi, enveloped viruses, and protozoa. Some are also cytotoxic against host cells, including neoplastic cells. Cationic antimicrobial peptides may play various roles in inflammation and tissue repair. Antimicrobial peptides are found in epithelial tissues regularly exposed to microbial attack as well as in cells whose primary function is defense against potential pathogens. They constitute an important part of the nonoxidative antimicrobial arsenal of leukocytes. They are preformed and/or readily synthesized when the cells are stimulated by exposure to pathogens. They exert their effects directly by inserting into membranes of target cells and forming ion channels which increase membrane permeability; however, antimicrobial peptides can also act as opsonins to facilitate phagocytosis. Resistance to defensins is a virulence factor for organisms such as Salmonella sp. The study of cationic antimicrobial peptides is increasing our understanding of innate immunity, inflammation, and the pathogenesis of genetic diseases such as specific granule disease in humans. Therapeutic applications of antimicrobial peptides are currently under investigation.     

Investigation of the distance to slaughterhouses and weather parameters in the occurrence of porcine reproductive and respiratory syndrome outbreaks in U.S. swine breeding herds

Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically important diseases affecting the swine industry. The main objective of this study was to assess whether sow farm distance to slaughterhouses and meteorological variables were associated with PRRS outbreaks. This case-control study paired 104 sow farms with or without a reported PRRS outbreak (N = 208) during the same period. Data on the distance to the closest slaughterhouse, swine density, presence of an air filtration system, or a neighboring farm, and weather conditions were collected, and a multivariable conditional logistic regression model was created to investigate the association between variables of interest and the occurrence of a PRRS outbreak.Swine density, presence of an air filtration system, presence of a neighboring farm, and PRRS herd-level status before the outbreak were associated with the occurrence of PRRS outbreaks. Farms in areas with higher swine density and nearby swine farms had increased odds of reporting an outbreak compared to farms in low swine density areas and farms having no neighbors. Under the conditions of this study, none of the meteorological variables or the distance to the closest slaughterhouse were associated with occurrence of PRRS outbreaks.     

Induced expression of selected plant defence related genes in pot azalea, <Emphasis Type="Italic">Rhododendron simsii</Emphasis> hybrid

A set of putative marker genes to study plant defense responses against Polyphagotarsonemus latus, a key pest in the production of Rhododendron simsii hybrids, was selected and validated. Genes belonged to the biosynthetic pathway of phytohormones jasmonic acid (JA) (RsLOX, RsAOS, RsAOC, RsOPR3 and RsJMT) and salicylic acid (SA) (RsPAL and RsICS). Furthermore, RsPPO, a putative marker gene for oxidative stress response was successfully cloned from R. simsii. A CTAB-based extraction protocol was optimized to assure excellent RNA quality for subsequent RT-qPCR analysis. The RT-qPCR protocol was extensively tested and RsRG7 and RsRG14 were selected as reference genes from a geNorm pilot study. Validation of the marker genes was done after application with elicitors [methyl jasmonate (MeJA), coronatine, β-aminobutyric acid and acibenzolar-Smethyl] or wounding. Both 100 μM MeJA and 0.1 μM coronatine had a significant effect on the expression of all marker genes. Foliar application of MeJA on the shoots resulted in a significantly earlier response when compared to root application and subsequent sampling of the shoots. Expression patterns after MeJA treatment were generally the same in six R. simsii genotypes: ‘Nordlicht’, ‘Elien’, ‘Aiko Pink’, ‘Michelle Marie’, ‘Mevrouw Gerard Kint’ and ‘Sachsenstern’. Wounding resulted in the same expression patterns as MeJA treatment except for RsJMT. None of the genotypes showed a significant induction of the latter gene 6 h upon wounding. Findings of these experiments indicated that the tolerant genotype ‘Elien’ has low basal expression levels of RsPPO. This might be the first step towards the breeding of mite-tolerant genotypes.     

Dust levels and control methods in poultry houses

This article summarizes information from the papers and posters presented at the international symposium on "Dust Control in Animal Production Facilities", held in Aarhus (Denmark) on 30 May-2 June 1999. Dust concentrations in poultry houses vary from 0.02 to 81.33 mg/m3 for inhalable dust and from 0.01 to 6.5 mg/m3 for respirable dust. Houses with caged laying hens showed the lowest dust concentrations, i.e., less than 2 mg/m3, while the dust concentrations in the other housing systems, e.g., perchery and aviary systems, were often four to five times higher. Other factors affecting the dust concentrations are animal category, animal activity, bedding materials and season. The most important sources of dust seem to be the animals and their excrements. Further studies on the effects of housing systems on dust sources and their compounds are desired for development of a healthier working environment in poultry production facilities. Adjustment of the relative humidity (RH) of the air in a broiler house to 75% will have an effect on inhalable dust, but not on respirable dust. A slight immediate effect on the respirable dust was observed after fogging with pure water or water with rapeseed oil. In an aviary system, a 50 to 65% reduction of the inhalable dust concentration was found after spraying water with 10% of oil and pure water, respectively. To obtain a higher dust reducing efficiency, improvement of techniques for application of droplets onto dust sources will be desired.     

Historical Trace Metal Accumulation in the Sediments of an Urbanized Region of the Lake Champlain Watershed, Burlington, Vermont

This study documents the history ofpollution inputs in the Burlington region of LakeChamplain, Vermont using measurements of anthropogenicmetals (Cu, Zn, Cr, Pb, Cd, and Ag) in four age-datedsediment cores. Sediments record a history ofcontamination in a region and can be used to assessthe changing threat to biota over time and to evaluatethe effectiveness of discharge regulations onanthropogenic inputs.Grain size, magnetic susceptibility, radiometricdating and pollen stratigraphy were combined withtrace metal data to provide an assessment of thehistory of contamination over the last 350 yr inthe Burlington region of Lake Champlain. Magneticsusceptibility was initially used to identify land-usehistory for each site because it is a proxy indicatorof soil erosion. Historical trends in metal inputs inthe Burlington region from the seventeenth through thetwentieth centuries are reflected in downcorevariations in metal concentrations and accumulationrates. Metal concentrations increase above backgroundvalues in the early to mid nineteenth century. Themetal input rate to the sediments increases around1920 and maximum concentrations and accumulation ratesare observed in the late 1960s. Decreases inconcentration and accumulation rate between 1970 andthe present are observed for most metals. Theobserved trends are primarily a function of variationsin anthropogenic inputs and not variations in sedimentgrain size. Grain size data were used to removetexture variations from the metal profiles and resultsshow trends in the anthropogenic metal signals remain. Radiometric dating and pollen stratigraphy providewell-constrained dates for the sediments therebyallowing the metal profiles to be interpreted in termsof land-use history.     

Whitened kernel surface: A fast and reliable method for assessing Fusarium severity on cereal grains by digital picture analysis

Fusarium head blight (FHB) is a cereal disease of major importance responsible for yield losses and mycotoxin contaminations in grains. Here, we introduce a new measurement approach to quantify FHB severity on grains based on the evaluation of the whitened kernel surface (WKS) using digital image analysis. The applicability of WKS was assessed on two bread wheat and one triticale grain sample sets (265 samples). Pearson correlation coefficients between Fusarium‐damaged kernels (FDK) and WKS range from r = 0.77 to r = 0.81 and from r = 0.61 to r = 0.86 for the correlation between deoxynivalenol (DON) content and WKS. This new scoring method facilitates fast and reliable assessment of the resistance to kernel infection and shows significant correlation with mycotoxin content. WKS can be automated and does not suffer from the “human factor” inherent to visual scorings. As a low‐cost and fast approach, this method appears particularly attractive for breeding and genetic analysis of FHB resistance where typically large numbers of experimental lines need to be evaluated, and for which WKS is suggested as an alternative to visual FDK scorings.     

De invloed van enkele milieufactoren op de vatbaarheid van erwten voor Botrytis cinerea

In a temperature and nutrient experiment with Rondo peas marked differences were observed in the degree of infection of the plants byBotrytis cinerea. After harvesting the ripe plants these differences were clearly expressed in the percentage of seeds with a chalky appearence, due to invasion by the mycelium ofB. cinerea. Comparatively high percentages of chalky peas were found when the plants were grown at a temperature of 20°C during the day and 15°C during the night. Omitting calcium or magnesium from the nutrient solution did not significantly influence the percentage of chalky peas, but omitting potassium from two weeks before flowering until the end of ripening increased the percentage of chalky peas significantly. This suggests that potassium deficiency before and during flowering makes the plant more susceptible toB. cinerea infection.Samenvatting In een temperatuur- en voedingsproef met Rondo erwten werden opvallende verschillen waargenomen in aantasting van de planten doorBotrytis cinerea. Na het oogsten van de rijpe planten kwamen deze verschillen duidelijk tot uiting in het percentage kalkerwten; dit zijn zaden die door het mycelium vanB. cinerea zijn doorwoekerd. Er werden relatief hoge percentages kalkerwten gevonden bij een temperatuur van 20°C overdag en 15°C's nachts. Het weglaten van calcium of magnesium uit de voedingsoplossing had geen betrouwbare invloed op het percentage kalkerwten, maar het weglaten van kalium vanaf 14 dagen voor de bloei tot het einde van de afrijping verhoogde het percentage kalkerwten zeer belangrijk. Dit wijst er op dat kaliumgebrek vóór en tijdens de bloei de planten vatbaarder maakt voorB. cinerea.