The metabolism of [14C] cymoxanil in the rat

A rat, given a single oral dose of [¹⁴C] cymoxanil, 1-(2-cyano-2-methoxyimino-[2-¹⁴C]-acetyl)-3-ethylurea, eliminated 91% of the radioactivity within 72 h. The urine contained 71%, the faeces 11%, and the expired air about 7% of the radiolabel; no ¹⁴C residue was found in the internal organs. Greater than 70% of the radioactivity in the urine was identified. The major metabolite was characterised as glycine, both free and conjugated, as hippuric acid and phenylaceturic acid [N-(phenylacetyl)-glycine], and probably in the form of polypeptides of low molecular weight. The other metabolites identified included 2-cyano-2-methoxyiminoacetic acid, 2-cyano-2-hydroxyiminoacetic acid and 1-ethylimidazolidine-2, 4, 5-trione. The minor metabolites included succinic acid and 2-oxoglutaric acid which indicated reincorporation of metabolic ¹⁴C. Cymoxanil, as such, was not detected in the urine.     

Clostridium difficile shedding by healthy dogs in Nigeria and Malawi

The objectives of this study were to determine the prevalence and characteristics of Clostridium difficile shedding in owned dogs in Nigeria and Malawi. Clostridium difficile was isolated from 31/120 (26%) dogs in Nigeria and 11/92 (12%) dogs in Malawi (p = 0.012). Overall, 22/42 (52%) isolates were toxigenic; 17/31 (55%) from Nigeria and 5/11 (45%) from Malawi. All toxigenic isolates possessing tcdA and tcdB, and only one also possessed cdtA/B. Sixteen different ribotypes were found, ten (63%) of which were non‐toxigenic. Most isolates corresponded to ribotypes that have been previously identified in humans or livestock. The role of dogs in transmission of C. difficile and the clinical implications of C. difficile shedding in dogs remain unclear. These data indicate that dogs could act as a source of C. difficile for exposure of other species, including humans; however, the true risk is unknown. Further study of the ecology of C. difficile and the role of dogs in disease of humans and other domestic animals is indicated.     

Preliminary pharmacokinetics of tramadol hydrochloride after administration via different routes in male and female B6 mice

Objective

1) To determine the pharmacokinetics of tramadol hydrochloride and its active metabolite, O-desmethyltramadol (M1), after administration through different routes in female and male C57Bl/6 mice; 2) to evaluate the stability of tramadol solutions; and 3) to identify a suitable dose regimen for prospective clinical analgesia in B6 mice.

昆虫内共生菌-昆虫-植物互作关系研究进展

在长期的协同进化过程中,昆虫与其体内的共生菌建立了密切的互利共生关系。昆虫内共生菌不仅能调控宿主昆虫的营养代谢和生殖代谢,还能协助昆虫抵御生物、非生物胁迫,提高昆虫对化学农药的抗性及对寄主植物的适应性等。因此,内共生菌是宿主昆虫生长发育及适应性的重要调控因子。目前,随着组学技术的不断发展,内共生菌在宿主昆虫和寄主植物中的原位功能不断被挖掘,通过对内共生菌-昆虫-植物互作模型的研究,将进一步揭示昆虫内共生菌与昆虫、植物的互作机理,加深对昆虫适应性机制的理解并推进新型害虫防控和靶标技术的研发。本文就昆虫内共生菌的起源、特点、分布和传递,昆虫内共生菌在昆虫-植物-环境互作中的作用,以及昆虫内共生菌研究的方法和新技术等方面进行了综述,并对未来昆虫内共生菌介导的防御效应及昆虫适应性机理等热点问题进行了展望。     

Gradual forest edges can mitigate edge effects on throughfall deposition if their size and shape are well considered

For the protection and promotion of biodiversity in forest edges and interiors, forest edge management practices are put forward like the creation of gradual forest edges (i.e., edges with a gradual increase of vegetation height from open area to forest, e.g., by means of a fringe, a belt, and a mantle). In this study, we tested the mitigating effect of gradual forest edges on the atmospheric deposition of inorganic nitrogen (N) and the potentially acidifying pollutants SO₄²⁻, NO₃⁻, and NH₄⁺ (N + S). We conducted field experiments at three exposed forest edges in Flanders and the Netherlands and compared throughfall deposition at steep edges (i.e., edges with an abrupt transition from open area to forest) and at adjacent gradual edges. Along transects perpendicular to the edges, during three months in both winter and summer, throughfall deposition of Cl⁻, SO₄²⁻, NO₃⁻, and NH₄⁺ was monitored in the forest between 0 and 64 m from the edges and in the gradual edge vegetation. At the smoothest and best fitting gradual edge, the extra N + S throughfall deposition the forest received due to edge effects was lower than at the adjacent steep edge, with on average 80 and 100% in winter and summer, respectively. This was due to a halving of the depth of edge influence and an almost full reduction of the magnitude of edge influence. This decrease in throughfall deposition in the forest was not compensated by the additional throughfall deposition on the gradual edge vegetation itself, resulting in a final decrease in throughfall deposition in the forest edge by 60% in winter and 74% in summer. While this result confirms that gradual edges can mitigate edge effects on atmospheric deposition, the results of the other sites indicate the importance of size and shape of the gradual edge vegetation in mitigating edge effects on deposition: due to insufficient height (‘size’) or inadequate shape of the gradual edge vegetation, only small or insignificant decreases in throughfall deposition were observed. Hence, for mitigating edge effects on N + S and N deposition, our results support the recommendation of creating gradual edges at forests with poorly developed, abrupt edges, but it stresses the importance of a thorough consideration of the shape and size of the gradual edge vegetation in the design and management of gradual forest edges.     

Is European catfish a threat to eels in southern France?

• 1. European eel (Anguilla anguilla) is recognized as a critically endangered species in the northern hemisphere. Threats such as overfishing or pollution are well known as risks for eel populations. However, much less is known about the impact of introduced fish on European eels. In particular, introduced large‐bodied predators could become new predators to eels.
• 2. The potential impact of European catfish (Silurus glanis L) on an eel population in the Camargue, southern France was studied using a combination of stable isotope and gut content analyses.
• 3. Only large‐bodied catfish (>500 mm) can consume numerous fish prey. However, catfish mostly consumed crayfish (Procambarus clarkii), these prey items being found in 79% of the guts of the largest individuals. Eel was absent from the dissected catfish guts. A mixing model based on Bayesian inference revealed that catfish diet included only 5% (0–8.5%) of marine sources (both eel and mullet).
• 4. While local economic interests prompted ecological studies to assess whether catfish exerted a new and strong predatory pressure on eel, this study found that European catfish behaved as an opportunistic omnivore, and as such was not a direct threat as a predator on eel populations in the Camargue. Copyright © 2011 John Wiley & Sons, Ltd.

     

Dietary niche expansion and niche shift in native marble trout (Salmo marmoratus) living in sympatry with introduced rainbow trout (Oncorhynchus mykiss)

The non‐native rainbow trout (Oncorhynchus mykiss) has been introduced worldwide for angling purposes and has established self‐reproducing populations in many parts of the world. Introduced rainbow trout often have negative effects on the native salmonid species, ranging from decrease abundance, growth and survival, to their local extinction. Assessing the effects of introduced rainbow trout on the native species is thus crucial to better set up conservation programmes. In this study, we investigated the effects of non‐native rainbow trout on the diet of native marble trout (Salmo marmoratus) living in the Idrijca River (Slovenia). An impassable waterfall separates the stream in two sectors only a few hundred metres apart: a downstream sector (treatment) in which marble trout live in sympatry (MTs) with rainbow trout (RTs) and an upstream sector (control) in which marble trout live in allopatry (MTa). Specifically, we investigated using stable isotopes the effects of rainbow trout on dietary niche, diet composition, body condition, and lipid content of marble trout. We found dietary niche expansion and niche shift in marble trout living in sympatry with rainbow trout. Compared to MTa, MTs had higher piscivory rate and showed higher body condition and prereproduction lipid content. Our results indicate that the presence of rainbow trout did not have negative effects on marble trout diet and condition and that changes in dietary niche of marble trout are likely to be an adaptive response to the presence of rainbow trout, and further research is needed to better understand.     

应用Le Bissonnais法研究黄土丘陵区土壤团聚体稳定性

 以黄土丘陵区森林草原过渡带燕沟流域植被自然恢复过程中6种植被类型为研究对象,应用LeBissonnais(LB)法测定了不同植被类型下土壤水稳性团聚体,对比分析了LB法3种处理的测定结果与传统湿筛法(Yoder)的差异性。结果表明:在LB法3种湿润处理下,快速湿润处理(FW)对土壤团聚体结构的破坏程度最大,处理后土壤水稳性团聚体以0.05～0.5mm为主;慢速湿润处理(SW)对团聚体的破坏程度最小,处理后土壤水稳性团聚体主要以>2mm团聚体为主;而预湿后扰动处理(WS)对团聚体的破坏程度介于FW和SW之间,处理后土壤团聚体粒径分布比较均匀。说明该区土壤团聚体破坏的主要机制是土壤孔隙中的气泡爆破产生的消散作用。退耕100a期间,植被群落由1年生草本(4a)—多年生灌草(16 a)—半灌木(29 a)—灌木(55 a)—乔木(100a)方向演替过程中,土壤水稳性团聚体由小粒径向大粒径方向转变,土壤结构趋于稳定。LB法3种处理中,FW处理与SW处理所测得>0.5mm团聚体含量和平均重量直径与土壤有机质和物理性黏粒之间存在显著的相关性,而WS处理未达到显著水平(P>0.05)。说明土壤有机质和物理性黏粒主要影响消散和黏粒膨胀引起的崩解作用,而对机械干扰引起的团聚体破坏无明显影响。LB法3种处理中,慢速湿润方法所获得土壤团聚体稳定性特征更接近湿筛法,适宜于黄土丘陵区植被恢复过程中土壤水稳性团聚体的测定。     

农田生物多样性对昆虫的生态调控作用

随着农田作物的单一性种植,植食性昆虫暴发、物种流失等问题日益突出,化学农药大量应用于作物有害生物的防治更加剧了对农田生态系统的破坏和不稳定性.因此,从生物多样性-农田生态系统-植食性昆虫的相互关系入手,探讨生物多样性的保护及其在农业有害生物防控上的应用,回归农田生态系统动态平衡的生态调控举措,成为可持续发展农业领域中研究的焦点之一.本文综述了农田生物多样性对昆虫生态影响的重要性及其生态功能,进一步阐述了农田生物多样性在农业生产中的应用及前景.