ETHYL ALCOHOL REDUCTION OF SALMONELLA TYPHIMURIUM IN POULTRY FEED

This study was designed to evaluate the effect of ethyl alcohol as a potential treatment for reduction of Salmonella populations in poultry feed. Growth rate of S. typhimurium in tryptic soy broth was significantly reduced by addition of greater than 0.3% volume/volume of ethyl alcohol and growth was completely inhibited by addition of 5% ethyl alcohol. Ethyl alcohol concentrations of 20% volume/weight and greater significantly reduced initial S.typhimurium populations in poultry feed (for 20% treated, 2.31 ± 0.31 vs 3.39 ± 0.29 for untreated; P < 0.05). When feed treatment was administered either before or after inoculation of S. typhimurium with 60% ethyl alcohol or 0.04% buffered propionic acid, populations in feeds treated after inoculation were decreased to a nondetection level (< 1.0 log₁₀ CFU/g) by ethyl alcohol treatment but not by other treatments. Ethyl alcohol treatment may have the potential for reducing Salmonella spp. contamination in poultry feed.     

二甲基亚砜毒性研究

二甲基亚砜（Dimethyl sulfoxide DMSO）是一种含硫有机化合物,被誉为＂万能溶剂＂,广泛用作溶剂和反应试剂。在医药工业中,DMSO可直接用作某些药物的原料及载体。DMSO本身有消炎止痛,利尿,镇静等作用,亦誉为＂万灵药＂,常作为止痛药物的活性组分添加于药物之中。DMSO也是一种渗透性保护剂,能够降低细胞冰点,减少冰晶的形成,减轻自由基对细胞损害,改变生物膜对电解质、药物、毒物和代谢产物的通透性。DMSO作为组蛋白去乙酰化酶抑制剂（Histone Deacetylases-inhibitor HDACi）的一种,同样具有恢复组蛋白的乙酰化与去乙酰化平衡,抑制细胞程序性死亡,修复DNA双螺旋结构,抗放射性损伤,抗炎症反应及抗癌作用。鉴于其应用广泛,本文就其物理特性及毒性研究做一综述。     

Palatability and feeding preferences of Uresiphita maorialis (Lepidoptera: Crambidae) for three Sophora species

In a three-hour bioassay, we tested the palatability and feeding preferences of Uresiphita maorialis (kōwhai moth) for Sophora tetraptera, Sophora microphylla and Sophora prostrata. Palatability tests showed no differences among the Sophora species. Feeding preferences, on the other hand, showed that S. tetraptera and S. microphylla leaves are preferred over S. prostrata leaves. Our results support our field observations in Wellington city parks and gardens showing that S. tetraptera and S. microphylla plants frequently have higher densities of larvae than S. prostrata.     

岱海流域土地利用动态模拟及生态系统服务价值测算

北方内陆湖泊面积萎缩严重,岱海作为典型的内陆湖之一,其面积变化尤为显著.为研究岱海湖面积变化及岱海流域生态系统服务价值(Esv)的动态趋势,本研究运用CA-Markov模型,基于1989-2018年6期的土地利用数据,预测2026年的土地利用状况,并采用当量因子法,对岱海流域ESV进行评估.结果 表明:岱海湖若不进行生...     

CYCLOHEXIMIDE AS A MEDIA AMENDMENT FOR ENUMERATING BACTERIAL POPULATIONS IN ANIMAL FEEDS

The present study was designed to evaluate cycloheximide as a potential media amendment for differential bacterial and fungal enumeration of animal feeds. The objectives of this study were to determine the effect of cycloheximide on bacterial growth rates and to evaluate its efficacy for the reduction of indigenous spreading fungi when enumerating bacterial populations in three types of feeds and after short or long-term storage. Escherichia coli, Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes and Pseudomonas fluorescens were grown in tryptic soy broth containing cycloheximide to determine its effect on bacterial specific growth rates. Growth rates of B. cereus and S. aureus were significantly decreased by the addition of 600 and 1000 mg/L cycloheximide respectively, but other pure cultures were not significantly influenced by cycloheximide addition. Intrinsic bacterial populations from feed were not significantly affected by cycloheximide additions at concentrations from 10 to 300 mg/L, but the indigenous spreading molds from feeds were significantly decreased by these cycloheximide concentrations and were decreased below detection levels by 300 mg/L of cycloheximide. The addition of 300 mg/L of cycloheximide effectively eliminates fungal growth for accurate enumeration of bacterial populations in feeds.     

INDIGENOUS POULTRY FEED MICROFLORA RESPONSE TO ETHYL ALCOHOL AND BUFFERED PROPIONIC ACID ADDITION

The present study was designed to compare ethyl alcohol with buffered propionic acid feed treatment on the survival of indigenous poultry feed bacteria and fungi. The aerobic bacterial poultry feed populations were not substantially reduced by either ethyl alcohol or buffered propionic acid treatments. Likewise, indigenous poultry feed fungal populations also were not markedly reduced by buffered propionic acid treatment of the feed but fungal poultry feed populations exposed to ethyl alcohol treatments were significantly lower (P<0.05) than fungal populations recovered from either control and buffered propionic acid treated feeds. Ethyl alcohol treatment may have potential for reducing fungal contamination in poultry feed.     

微塑料对湖泊生态系统初级生产者的影响

塑料的广泛应用导致大量微塑料进入环境,尤其是水环境,从而产生环境风险。浮游植物等自养生物是湖泊系统的主要初级生产者,是湖泊食物链的关键组成部分,为食物链的上游提供能量和物质基础。同时,浮游植物也是对微塑料响应最敏感的类群。了解湖泊浮游植物等初级生产者对微塑料的响应是探究微塑料对湖泊生态系统功能影响的重要基础。总结了全球湖泊生态系统微塑料的丰度、类型、尺寸、来源等分布特征,系统分析了微塑料暴露对浮游植物等初级生产者细胞结构、基因表达和生长,以及对浮游植物叶绿素a含量、光合活性的影响,并总结了其中的影响机制。总体而言,微塑料会降低初级生产者的叶绿素a含量,剂量越高、尺寸越小,这种抑制作用越强烈;同时,微塑料也会作用于初级生产者,造成细胞膜损伤、DNA损伤,调控其相关功能基因表达,抑制其生长和光合活性等。然而,湖泊生态系统微塑料的实际检出浓度远低于室内暴露实验中的添加剂量,微塑料结构和组分也更为复杂,野外观测结果与室内培养实验之间还不能建立直接的对应关系。因此,未来的相关研究应集中在如何有效联系野外观测结果与室内培养实验结果,进一步聚焦建立可靠的、可应用推广的微塑料浓度与初级生产者之间的剂量-效应关系模型,探究微塑料对湖泊初级生产者的作用机制,为刻画微塑料对湖泊生态系统初级生产者及其功能的作用机制提供科学支撑。     

喀斯特断陷盆地区不同恢复阶段群落物种组成与多样性特征

研究自然植被恢复过程中的物种组成、群落结构及生物多样性的变化,能够为人工促进植被恢复的树种选择与群落结构的优化配置提供重要依据。本研究以空间代替时间对喀斯特断陷盆地典型区云南省建水县不同天然植被(草丛、灌丛、乔木林)进行群落学调查,对不同恢复阶段的植物群落按乔木、灌木、草本进行分层,分析各恢复阶段植物群落的物种组成、水平和垂直结构、生物多样性。结果表明:在总面积为3200 m²的12个样地中,共记录43科72属94种维管束植物,优势种以壳斗科(Fagaceae)、鼠李科(Rhamnaceae)、紫金牛科(Myrsinaceae)、蔷薇科(Rosaceae)、木犀科(Oleaceae)等科的植物为主;在草丛→灌丛→乔木林的恢复过程中,群落物种组成中的科数、属数、种数逐渐增加,低矮和小径级植物个体数所占比例逐渐减少,但整体仍以低矮的小径级植物为主。草本植物的丰富度和Shannon指数在植被恢复的初期即草丛阶段最大,而均匀度指数则以灌丛阶段最大;木本植物的丰富度和Shannon指数随着植被的恢复逐渐增大,但均匀度指数随着植被的恢复逐渐下降;随着植被的恢复,草本层和乔木层...     

质粒超螺旋比例对其细胞转染效率及表达的影响

检测质粒开环、闭环比例不同时对其细胞转染效率及表达的影响。构建携带人肝细胞生长因子基因的质粒(pcDNA3-HGF)及携带LacZ报告基因的质粒(pcDNA3-LacZ),用核酸纯化试剂盒提取开环、闭环比例不同的质粒,然后用LipofectAMINE介导它们分别转染NIH3T3细胞,采用X-Gal染色和ELISA法分别观察转染效率和表达活性。结果表明,用超螺旋比例分别为85.45%和48.44%的质粒pcDNA3-LacZ转染生长旺盛的NIH3T3细胞,48h检测转染效率分别为23.4%±3.8%和9.3%±2.5%,前者约是后者的2.5倍。用超螺旋比例分别为93.28%和40.53%的质粒pcDNA3-HGF转染1×106NIH3T3细胞,ELISA法检测48h细胞培养上清中HGF的表达量分别为46.5±6.3ng和25.6±4.2ng,前者是后者的1.8倍。初步认为质粒开环、闭环比例不同对其细胞转染效率及表达有一定影响,超螺旋比例高时其转染效率及表达量较高。