Development of a multiplex loop-mediated isothermal amplification assay to detect shiga toxin-producing Escherichia coli in cattle

A multiplex loop-mediated isothermal amplification (mLAMP) assay was developed for simultaneous detection of the stx1 and stx2 genes and applied for detection of shiga toxin-producing Escherichia coli (STEC) in cattle farm samples. Two target genes were distinguished based on T_m values of 85.03 ± 0.54℃ for stx1 and 87.47 ± 0.35℃ for stx2. The mLAMP assay was specific (100% inclusivity and exclusivity), sensitive (with a detection limit as low as 10 fg/µL), and quantifiable (R² = 0.9313). The efficacy and sensitivity were measured to evaluate applicability of the mLAMP assay to cattle farm samples. A total of 12 (12/253; 4.7%) and 17 (17/253; 6.7%) STEC O157, and 11 (11/236; 4.7%) non-O157 STEC strains were isolated from cattle farm samples by conventional selective culture, immunomagnetic separation, and PCR-based culture methods, respectively. The coinciding multiplex PCR and mLAMP results for the types of shiga toxin revealed the value of the mLAMP assay in terms of accuracy and rapidity for characterizing shiga toxin genes. Furthermore, the high detection rate of specific genes from enrichment broth samples indicates the potential utility of this assay as a screening method for detecting STEC in cattle farm samples.     

温度和食物对褶皱臂尾轮虫种群增长及繁殖的影响

本试验设3个温度（20、25和30℃）和3个食物浓度（1×106、10×106和20×106 cells/mL）,研究不同温度和不同食物浓度对褶皱臂尾轮虫种群增长及繁殖的影响。试验期为10 d。结果表明,最大种群密度均随温度和食物浓度的升高而先增加后减少。温度为25℃食物浓度为10×106 cells/mL时,最大种群密度为74.39±1.81 ind/mL,与其他组比差异显著（P〈0.05）。随温度升高,轮虫的最大种群密度高峰值出现的时间也呈现逐渐前移的趋势,最大种群增长率则随温度和食物浓度的增加而升高。温度30℃食物20×106 cells/mL时,最大种群增长率为0.70±0.013,与其他组比差异显著（P〈0.05）。食物浓度对轮虫的怀卵率有显著影响,在同一温度下最大怀卵率随食物浓度的升高而增大,食物为20×106 cells/mL的最大怀卵率为56.43±1.07%,与其他浓度组比差异显著（P〈0.05）。在本试验条件下,温度和食物对褶皱臂尾轮虫的种群增长及繁殖均有显著影响。温度25℃食物浓度10×106 cells/mL为培养条件的最优组合。     

The effect of stocking density of Chinese mitten crab Eriocheir sinensis on rice and crab seed yields in rice-crab culture systems

Normally Chinese mitten crab Eriocheir sinensis were cultured for 2 years, 1 year is cultured from crab larvae to seeds or button sized crab in ponds, tanks or rice fields, the another year is cultured from seeds to market size in ponds, reservoirs or other waters. The present study was conducted to determine the effect of stocking density (0, 3.75, 15, 30 and 60 inds. per m², respectively) of Chinese mitten crab larvae on rice and crab seed yields in rice-crab culture systems using land-based enclosures (4 m × 7 m, with three replicates for each stocking density) at the Panjin Guanghe Fisheries Co. Ltd, in the Liaohe Delta, China. Zoobenthos biomass, production of crab and rice paddy, and economical profit among the treatments were determined. The experiment showed that zoobenthos biomass in rice-crab culture systems was relatively variant and not significantly correlated to these stocking density. The biomass of aquatic plant declined significantly with increasing stocking density. Specific growth rates (SGR) and survival rates of the crab were significantly higher at the lower stocking density (P < 0.05); in addition, the ratio of precocious crab and total crab significantly increased with the stocking density increasing (P < 0.05); There were not significant effect of presence of crab on yields of rice straw and rice paddy (P > 0.05). Net crab yield and net profit were the highest at the 15 treatment (P < 0.05), however, the net profits among 3.75, 15 and 30 treatments did not show significant difference (P > 0.05) economically. Based on the observations above, a stocking density of 3.75 to 30 inds. per m² was considered reasonable in rice-crab culture system.     

Dietary microbial phytase supplementation and the utilization of phosphorus, trace minerals and protein by rainbow trout [Oncorhynchus mykiss (Walbaum)] fed soybean meal-based diets

Effects of thermal and enzymatic treatments of soybean meal on apparent absorption of total phosphorus, phytate phosphorus, nitrogen (protein), ash, calcium, magnesium, copper, iron, manganese, strontium and zinc were examined using rainbow trout, Oncorhynchus mykiss (Walbaum), as the test species. Absorption of the test nutrients was estimated using yttrium as an inert non-absorbable indicator. Thermal treatments (microwaving, dry roasting, steam heating, cooking) had no measurable effect on the apparent absorption of phosphorus and other minerals. Phytase supplementation increased the apparent absorption of phosphorus, nitrogen (protein), ash, calcium, magnesium, copper, iron, strontium and zinc in low-ash diets containing soybean meal, but had little effect in high-ash diets containing both soybean and fish meal. In low-ash diets, the apparent absorption of phosphorus increased in accord with the level of phytase added to the diet, from 27% (no phytase added) up to 90% (phytase added, 4000 units kg⁻¹ diet) or 93% (predigested with phytase, 200 units kg⁻¹ soybean meal). In high-ash diets, dietary acidification with citric acid decreased the effect of phytase, whereas in low-ash diets, acidification markedly increased the effect of the enzyme. Excretion of phosphorus in the faeces of fish fed a low-ash diet containing phytase-treated soybean meal was 0.32 g per kg diet consumed, a 95%−98% reduction compared with phosphorus excretion by fish consuming commercial trout feeds.     

绥芬河污染对大麻哈鱼、滩头雅罗鱼及水生生物影响的调查监测

绥芬河为中俄共有河，是黑龙江省的产鱼区之一，本介绍了该河流水质常规分析，工厂污水分析、鱼体残毒分析、浮游动物、浮游植物、底栖生物、着生藻类定性、定量及鱼类急性致毒性试验结果，同时进行了水质评价。结果表明：该河流经环境治理，水质状况得以改善，属于寡污带河流，基本达到渔业水质标准，是我国少有的清洁河流，对该河流洄流的四种大麻哈鱼、两种滩头鱼和生存的其它水生生物不构成危害性影响。     

Purification and characterization of a cysteine-like protease from the body wall of the sea cucumber <Emphasis Type="Italic">Stichopus japonicus</Emphasis>

The sea cucumber (Stichopus japonicus) is able to undergo autolysis in response to a variety of environmental and mechanical cues. Within the framework of a long-term study of this phenomenon we have purified a protease from the body wall of the sea cucumber by means of ion-exchange chromatography with DE-52 cellulose and gel filtration chromatography with Sephadex G-100. The final enzyme preparation was nearly homogeneous on polyacrylamide gel electrophoresis, and its molecular weight was estimated to be approximately 35.5 kDa. The purified enzyme exhibited a maximum activity for the hydrolysis of casein at pH 7.0 and 50°C and a remarkable stability at pH 4.0–7.0 and 40–60°C. Based on the inhibition and activation profiles obtained with numerous specific protease inhibitors and an activator, the protease purified from the body wall of the sea cucumber was defined to be a cysteine-like protease.     

抹香鲸的食物及其捕食习性

抹香鲸与头足类的捕食与被捕食关系，是海洋食物网中的重要组成部分。1978年在山东省胶南县海滩搁浅了一头抹香鲸，经对从其胃中取到的43个头足类角质颚分析鉴定，共发现帆乌贼等7个属。通过将其与世界其他海域抹香鲸胃中头足类组成的比较，论述了抹香鲸的捕食习性，抹香鲸与头足类在营养级金字塔中的位置，拟出了抹香鲸——头足类营养联系的模式。     

海南龙血树查尔酮合酶基因(DcCHS)的克隆及表达分析

利用RT-PCR和RACE技术对海南龙血树查尔酮合酶基因进行克隆,得到1条1 456 bp的cDNA序列,命名为DcCHS。DcCHS含有1 173 bp的阅读框架、99 bp的5′非编码区和184 bp的3′非编码区,编码390个氨基酸。DcCHS与其他植物的CHS氨基酸序列同源性高达84%以上,具有高度保守的CHS_like结构域、活性位点以及信号序列。推测DcCHS的分子量为42.7 ku,等电点pI为6.14,稳定性极差,具有15个磷酸化位点,无跨膜结构,无信号肽,亚细胞定位在细胞质的可能性较大,并预测了蛋白质的二级、三级结构。组织特异性分析结果表明,DcCHS在花中的表达远远高于根、茎、叶和果实。