Aspects of the adsorption and degradation of isoproturon in a heavy clay soil

Abstract. Degradation of isoproturon in a heavy clay soil followed first-order reaction kinetics with half-lives at 15 °C of 27 and 208 days in the topsoil and subsoil, respectively. Adsorption when shaken with 3 mm sieved samples of the soil fitted the empirical Freundlich relationship with k values of 3.25 in the topsoil and 1.06 in the subsoil. Adsorption in a static system with different sized aggregates of soil did not reach equilibrium, even after 24 hours contact, and the rate of adsorption was slower with larger aggregates. Following an adsorption period of 24 hours, desorption equilibrium was reached more rapidly with larger (6–10 mm) than with smaller (<3 mm) aggregates. Adsorption isotherms measured in a static system with a soil:water ratio typical of field conditions in winter also indicated less adsorption than that measured in shaken, laboratory systems with low soil:water ratios. The rate of change in water extractable residues of the herbicide was more rapid than that of total extract-able residues following application of isoproturon to the heavy clay soil in the field. The implications of the results for isoproturon leaching under field conditions are discussed.     

Effect of host resistance on genetic structure of core and accessory chromosomes in Irish <Emphasis Type="Italic">Zymoseptoria tritici</Emphasis> populations

In agricultural pathosystems resistant cultivars are typically only temporarily effective, as widespread growth of said cultivars drives selection for pathogen genotypes capable of infecting them. A gene-for-gene interaction between Z. tritici and wheat has been demonstrated for one cultivar; however results of studies into the relevance of these interactions in the field remain inconsistent. Because genetic drift does not appear to occur between Z. tritici populations that are not widely geographically separated, according to neutral genetic theory if adaptation to different host cultivars is occurring, reduced genetic variation, and some differentiation between populations sourced from different cultivars should be observed. Selectively neutral microsatellite markers were used to genotype 260 isolates of Z. tritici taken from two naturally infected randomized block trials of four different cultivars, representing a spectrum of resistance to Z. tritici from susceptible to resistant. By calculating genetic parameters such as overall heterozygosity and F _ST from this genotypic data, the presented study aimed to determine if genetic drift or host selection is impacting on the genetic structure of the Irish Z. tritici population. Results indicated that diversity was distributed almost entirely within, rather than among populations, with little or no differentiation, and almost no clone isolates were present in the dataset. However this result was not reflected in the accessory chromosomes, where evidence of minor but significant genetic structure was found. This lack of structure in the core chromosomes and weak structure in the accessory chromosomes confirms that forces of genetic drift and selection are minor compared to sexual reproduction, in concurrence with multiple previous studies on other populations worldwide.     

C型肉毒梭菌肉毒毒素的提取与鉴定

[目的]通过对C型肉毒梭菌肉毒毒素的提取与鉴定,为类毒素和抗毒素的制备及抗原性分析奠定基础.[方法]将分离鉴定得到的C型肉毒梭菌通过扩大培养、产毒培养后将产生的肉毒毒素采用除菌过滤、硫酸铵盐盐析、离心、透析、浓缩的方法从产毒培养基中分离提取出来.再将提取的肉毒毒素通过SDS-PAGE鉴定毒素蛋白的分子量.[结果]分离出来的毒素蛋白重链和轻链分别在98和53 KDa左右,与C型肉毒毒素的理论分子量相符.[结论]提取的肉毒毒素是C型肉毒毒素.     

Apocynin activity in spontaneously hypertensive rats (SHR): preliminary studies in vivo

An elevation in angiotensin II (Ang II) levels is a common occurrence in spontaneously hypertensive rats (SHRs). Infusions of Ang II and a high salt diet increase the activity of NADPH oxidase that stimulates superoxide anion (O⁻²) generation and increases the expression of certain subunits of NADPH oxidase. Apocynin, an NADPH oxidase inhibitor with antihypertensive effects, is able to inhibit the release of superoxide anion by inhibiting NADPH oxidase activity and blocking the migration of p47 phox to the mitochondrial membrane. The aim of our study was to evaluate the antihypertensive effects of apocynin in SHRs and Wistar rats (WKYs) using a micropuncture technique. After microperfusion of both the proximal and distal tubules, we found that SHRs treated with apocynin showed a decrease in the free-flow collection of the proximal tubule (PT), which was not affected in WKYs. Moreover, significant differences were not demonstrated in the distal tubule (DT), probably due a mechanism of compensation that occurs in the loop of Henle. In conclusion, it is possible that the mechanisms of reabsorption in the PT are controlled by the interactions of O⁻² and nitric oxide (NO). These data could suggest a higher activity of NADPH oxidase and increase in reactive oxygen species (ROS) production in the PT during hypertension.

     

Modified live Edwardsiella ictaluri vaccine, AQUAVAC-ESC, lacks multidrug resistance plasmids

Plasmid-mediated antibiotic resistance was first discovered in Edwardsiella ictaluri in the early 1990s, and in 2007 an E. ictaluri isolate harboring an IncA/C plasmid was recovered from a moribund channel catfish Ictalurus punctatus infected with the bacterium. Due to the identification of multidrug resistance plasmids in aquaculture and their potential clinical importance, we sought to determine whether the modified live E. ictaluri vaccine strain in AQUAVAC-ESC harbors such plasmids, so that the use of this vaccine will not directly contribute to the pool of bacteria carrying plasmid-borne resistance. Antimicrobial sensitivity testing of the E. ictaluri parent isolate and vaccine strain demonstrated that both were sensitive to 15 of the 16 antimicrobials tested. Total DNA from each isolate was analyzed by polymerase chain reaction (PCR) using a set of 13 primer pairs specific for conserved regions of the IncA/C plasmid backbone, and no specific products were obtained. PCR-based replicon typing of the parent isolate and vaccine strain demonstrated the absence of the 18 commonly occurring plasmid incompatibility groups. These results demonstrate that the vaccine strain does not carry resistance to commonly used antimicrobials and provide strong support for the absence of IncA/C and other commonly occurring plasmid incompatibility groups. Therefore, its use should not directly contribute to the pool of bacteria carrying plasmid-borne resistance. This work highlights the importance of thoroughly investigating potential vaccine strains for the presence of plasmids or other transmissible elements that may encode resistance to antibiotics.     

The acute toxicity of the death camas (Zigadenus species) alkaloid zygacine in mice, including the effect of methyllycaconitine coadministration on zygacine toxicity

Death camas (Zigadenus spp.) is a common poisonous plant on foothill rangelands in western North America. The steroidal alkaloid zygacine is believed to be the primary toxic component in death camas. Poisonings on rangelands generally occur in the spring when death camas is abundant, whereas other more desirable forage species are limited in availability. In most cases where livestock are poisoned by plants in a range setting, there is more than one potential poisonous plant in that area. One common poisonous plant that is often found growing simultaneously in the same area as death camas is low larkspur (Delphinium nuttallianum). Consequently, the objectives of this study were to conduct acute toxicity studies in mice and to determine if coadministration of low larkspur will exacerbate the toxicity of death camas. We first characterized the acute toxicity of zygacine in mice. The LD(50) of zygacine administered intravenously (i.v.) and orally was 2.0 ± 0.2 and 132 ± 21 mg/kg, respectively. The rate of elimination of zygacine from whole blood was determined to be 0.06 ± 0.01/min, which corresponds to an elimination half-life of 13.0 ± 2.7 min. The i.v. LD(50) of total alkaloid extracts from a Utah and a Nevada collection were 2.8 ± 0.8 and 2.2 ± 0.3 mg/kg, respectively. The i.v. LD(50) of methyllycaconitine (MLA), a major toxic alkaloid in low larkspur, was 4.6 ± 0.5 mg/kg, whereas the i.v. LD(50) of a 1:1 mixture of MLA and zygacine was 2.9 ± 0.7 mg/kg. The clinical signs in mice treated with this mixture were very similar to those of mice treated with zygacine alone, including the time of onset and death. These results suggest that there is an additive effect of coadministering these 2 alkaloids i.v. in mice. The results from this study increase knowledge and understanding regarding the acute toxicity of death camas. As combined intoxications are most likely common, this information will be useful in further developing management recommendations for ranchers and in designing additional experiments to study the toxicity of death camas to livestock.     

Survey of polyphenol constituents in grapes and grape-derived products

A rapid and comprehensive qualitative method has been developed to characterize the different classes of polyphenols, such as anthocyanins, flavonols, phenolic acids, and flavanols/proanthocyanidins, in grape products. The detection was achieved by two runs with the same LC gradient in different MS ionization modes and mobile phase modifiers (positive ionization mode and 0.4% trifluoroacetic acid for anthocyanins and flavonols; negative ionization mode and 0.1% formic acid for phenolic acids and flavanols). From an analysis of the MS and UV data and in comparison with the authenticated standards, a total of 53 compounds were identified, including 33 anthocyanins, 12 flavonols, 4 phenolic acids, and 4 flavanols/proanthocyanidins. With the method developed, a survey was then conducted to qualitatively assess the composition of polyphenols among 29 different grape products including original grape, grape juice, grape wine, and grape-derived dietary supplements, and their chemical profiles were systematically compared. This method provided a comprehensive qualitative insight into the composition of polyphenols in grape-derived products.