Roles of water quality and disinfectant application on inactivation of fish pathogenic Streptococcus agalactiae with povidone iodine,quaternary ammonium compounds and glutaraldehyde

Streptococcosis is an important bacterial disease in Nile tilapia causing severe economic losses to tilapia aquaculture worldwide. The effects of water quality (low‐ [LS] and high‐level [HS] soiling, to mimic clean or dirty surface conditions and temperatures) and disinfectant application (diluted concentrations and exposure time) were characterized on the inactivation of Streptococcus agalactiae isolated from diseased tilapia. Five isolates were tested against three commercial disinfectant products with the main ingredients being povidone iodine (Anidine 100?; AD), benzalkonium chloride (Better BKC 80%?; BKC 80), and a mixture of quaternary ammonium compounds and glutaraldehyde (Chloraldehyde?; CR). CR demonstrated highest efficacy to S. agalactiae inactivation, followed by BKC 80 and AD, respectively. Higher‐level soiling, low temperature, diluted concentrations and short exposure time all decreased the disinfectant efficacy. CR and BKC 80 provided more than 5‐log inactivation at 1‐min exposure at 20°C under HS conditions, and also with ten‐fold‐diluted concentrations at 60‐min exposure time at 30°C. However, AD required 10‐min exposure to effectively remove bacteria under LS conditions at 30°C. The results could facilitate aquaculture management planning that leads to operating cost reductions and improvements in biosecurity.     

不同健康程度和抗生素氟苯尼考干预下斑石鲷肠道菌群的结构差异

为了研究不同健康程度和抗生素氟苯尼考干预下斑石鲷肠道菌群结构的差异及其与养殖环境中菌群结构的相关性,采用Illumina Hi Seq PE250高通量测序的方法对健康、亚健康、典型黑身病和口服氟苯尼考条件下的斑石鲷肠道、养殖水体和颗粒饵料中的细菌多样性及群落结构进行了分析比较。结果显示,养殖水体中细菌多样性高于肠道和颗粒饵料。不同健康程度及氟苯尼考干预下斑石鲷肠道中细菌均以变形菌门、厚壁菌门和软壁菌门为主,且对应的操作分类单元(OTU)占样品全部OTU的比例均达到85%以上。黑身病的发生可影响斑石鲷肠道中丰度最高的前20种优势细菌种类的排名次序,其中变形菌门中的弧菌属的相对丰度显著增加,且随着弧菌属丰度的增加,斑石鲷的黑身病症状也逐渐加重。饵料中添加氟苯尼考投喂斑石鲷能使患病鱼肠道弧菌属的丰度从60.33%下降到1.29%,较大程度改变了肠道的菌群结构,并证实氟苯尼考有效防治黑身病。其次,养殖水体和颗粒饵料对斑石鲷肠道菌群也有一定影响,且养殖水体的影响高于颗粒饵料。本研究首次报道了斑石鲷肠道菌群结构,其研究结果为今后斑石鲷的健康养殖、疾病防控及其微生态学研究提供了参考依据和技术支撑。     

温度对马来西亚红罗非鱼越冬期体色的影响

为了解马来西亚红罗非鱼体色分化变异的遗传分子机制,以期解决其越冬期的体色变异问题,本研究比较了越冬期不同温度处理(16、20、25和30°C)对其表观体色、酪氨酸酶活性以及皮肤色素带和黑色素细胞的影响。实验50 d后发现,16°C组大部分鱼体较实验开始时变黑,整个鱼体呈现青灰色,20°C组多数鱼体腹部也变为青灰色。随着温度的升高,红罗非鱼背部皮肤、腹部皮肤和血清中酪氨酸酶的活性逐渐升高,25°C时达到最高值,而随着温度的继续升高,30°C组鱼的酪氨酸酶活性反而降低。血液中tyr m RNA的表达量随着温度的升高而升高,25和30°C组红罗非鱼肌肉中的tyr m RNA表达量也显著高于16和20°C组。切片显微结构发现,随着温度的升高,红罗非鱼背部皮肤的黑色素细胞数量减少。研究表明,马来西亚红罗非鱼越冬期的体色变异可能是其皮肤黑色素细胞数量和体内酪氨酸酶活性改变的结果,深入研究其调控机制有助于了解鱼类体色遗传机理并进行体色性状的改良。     

Detection of Frozen-Thawed Cycles for Frozen Tilapia (Oreochromis) Fillets Using Near Infrared Spectroscopy

Due to the ambient temperature fluctuation during the process of storage, transportation, and sale, frozen fillets may go through frozen-thawed cycles that result in quality changes. In order to detect the frozen-thawed cycles in frozen tilapia fillets, near infrared spectroscopy was applied. The thawing loss, cooking loss, moisture content, total volatile basic nitrogen, and texture profile of fillets in seven frozen-thawed cycles were analyzed to reflect the change of quality. A total of 60 fillets were used to collect the spectra on both dorsal and belly flesh in frozen and thawed state from the first to the seventh cycle. The results showed that there is a better discrimination among the once and the repeated frozen-thawed samples in the frozen state than the thawed state. Frozen samples were still conducive to the differentiation and had higher classification accuracy, ranging from 80% to 93.33%. Dorsal flesh was more beneficial for the differentiation than belly flesh and had the highest accuracy, ranging from 86.67% to 93.33% in the frozen state. These results showed that the nondestructive and fast detection of repeated frozen-thawed cycles in frozen tilapia fillets can be accomplished by near infrared spectroscopy, which has enormous potential for practical application.     

Production of Nile tilapia Oreochromis niloticus grown in BFT using two aeration systems

Aeration systems used in BFT farming need to meet the dissolved oxygen demand from the biota present in the tank, as well as to keep the particulate matter in suspension. In BFT systems, it is common to use blowers, but the choice of an aerator with better efficiency in oxygen transfer and in electric energy consumption is indispensable. The vertical pump model (VPM) aerator is the most used in intensive tilapia production systems in southern Brazil. The objective of this research was to verify if this aerator model can support Nile tilapia farming under BFT system without producing negative impacts on the functionality neither of the biofloc nor in the production indexes. Simultaneous farming on BFT using blowers served as control. Oreochromis niloticus juveniles with an initial density of 7 kg/m³ were used. After 56 days of farming, the VPM aerator obtained significantly better results, both in water quality parameters and in production indexes, when compared to those obtained in the control treatment. The temperature was higher in the treatment of the blowers due to the lower thermal exchange between the atmospheric air and the tank water. Although the VPM caused lower temperatures, it obtained a productivity of 21.2 kg/m³, compared to 20.2 kg/m³ of the blowers. It was concluded that the use of the VPM aerator had no negative influence on both the formation and functionality of the biofloc, obtaining even higher production rates.     

食积胃肠积热动物模型的探索与评价

目的 探索高热量饲料灌胃大鼠制备食积胃肠积热动物模型的方法,并对其进行评价。方法 将幼龄SD大鼠分为正常组与模型组,采用高热量饲料灌胃的方法建立食积胃肠积热模型。采集大鼠宏观表征,检测代谢指标,进行食积胃肠积热的诊断及考证;取大鼠结肠组织,做HE染色,观察大鼠肠组织炎症情况,并以免疫组化法观察大鼠结肠NF-kB p65的表达。结果 与正常组相比,模型组大鼠体态消瘦、体质量增加缓慢、攻击性较强、饮食量降低（P<0.01）、排便时间有延长趋势（P>0.05）、排便量降低（P<0.01）;病理示大鼠结肠黏膜层变薄,杯状细胞数量减少,黏膜下固有层局部充血、水肿、纤维增生,结肠黏膜NF-κB p65呈弥漫性分布,为深棕黄色粗颗粒,有向固有层扩散趋势。模型表征与小儿食积临床诊断要点具有一定符合度,符合食积胃肠积热成模标准。结论 高热量饲料灌胃大鼠制备食积动物模型符合中医学胃肠积热特点。     

无乳链球菌感染尼罗罗非鱼的脑膜炎模型

目的：脑膜炎是罗非鱼无乳链球菌病的特征性临床症状,建立罗非鱼无乳链球菌脑膜炎模型,并制定相应的临床症状及组织病理学评分系统,对研究罗非鱼无乳链球菌病的致病机制具有十分重要的意义。方法：将健康罗非鱼43尾,随机分为4组：对照组(n=10)和试验组(n=33)。3组试验组根据不同感染剂量分为：10₆cfu组(n=11)、10₇cfu组(n=11)、10₈cfu组(n=11)。试验组分别将10₆、10₇、10₈CFU的无乳链球菌菌液腹腔注射罗非鱼复制脑膜炎模型。对感染罗非鱼的临床症状、剖检病变、脑组织(端脑、中脑、小脑、延脑)病理学进行判定,并结合细菌学检测,按照拟定的评分系统评价各组脑膜炎的造模效果,确定最佳造模方案。结果：各试验攻毒组罗非鱼感染后2天均出现不同程度死亡,未见明显神经症状。感染3天后鱼体开始出现异常活动的神经症状及突眼、角膜混浊等病理变化。病理组织学观察可见：蛛网膜下腔和脑软膜上有大量炎性渗出和染成蓝紫色微细颗粒的细菌团块,脑膜充血、水肿、疏松、增厚,有大量的中性白细胞等炎性细胞浸润;脑实质基质疏松水肿,呈海绵状;脑组织炎性细胞浸润,胶质细胞增生等软脑膜炎、脑膜脑炎症状。比较各组得分发现,10₇CFU组的无乳链球菌攻毒罗非鱼造模效果最好：临床症状显著而组内罗非鱼差异性最小,组织病理学观察患病罗非鱼病情和缓适中、利于观察研究。结论：使用10₇CFU无乳链球菌腹腔攻毒罗非鱼可在第3天成功构建脑膜炎模型,造模率为100%。     

尼罗罗非鱼Foxp1a/b的cDNA克隆及表达模式研究

为探讨低等脊椎动物Foxp1与免疫细胞活化及机体雌激素水平的相关性,本研究首次分离克隆了尼罗罗非鱼 (Oreochromis niloticus) Foxp1的开放阅读框序列,并通过real-time PCR对其mRNA表达水平进行检测。结果显示,尼罗罗非鱼具有两种不同基因编码的Foxp1分子,分别命名为OnFoxp1a与OnFoxp1b;OnFoxp1a为1710 bp,由15个外显子编码569个氨基酸,OnFoxp1b为2040 bp,由16个外显子编码679个氨基酸;OnFoxp1a/b均含有Foxp亚家族的特征性结构,即锌指结构、亮氨酸拉链样结构和叉状螺旋结构;与OnFoxp1a相比,OnFoxp1b与高等脊椎动物Foxp1具有更近的亲缘关系。Real-time PCR检测结果显示,OnFoxp1a/b几乎在所有组织中均有表达,OnFoxp1a在精巢中有高水平表达, OnFoxp1b在心脏中有高水平表达,同时OnFoxp1b在免疫相关组织如鳃、脾脏、肾脏、肠等均有中等水平表达;淋巴细胞多克隆刺激剂PHA、PMA、LPS刺激尼罗罗非鱼外周血单个核细胞（PBMC）,结果显示,50 μg/mL PHA和50 ng/mL PMA分别刺激6、12、24 h均显著增强OnFoxp1b的表达 (p＜0.05),20 μg/mL LPS刺激后,OnFoxp1b的表达出现先降低后升高的趋势 (p＜0.05);而OnFoxp1a的表达除50 μg/mL PHA 刺激24 h后有所升高,其余均无显著变化;雌激素处理6月龄雄性尼罗罗非鱼48 h,OnFoxp1a/b在肠、肾脏中的表达显著上调 (p＜0.05),而脾脏中无显著变化 (p>0.05)。综上所述,低等脊椎动物硬骨鱼类两种不同基因编码的Foxp1a/b均为哺乳动物Foxp1的同源分子,但其序列、结构特征、表达模式迥异,提示其功能发生歧化;同时两者的表达与淋巴细胞活化及机体雌激素水平密切相关。     

饲料氧化鱼油引起草鱼肠道黏膜结构屏障损伤

为了研究饲料氧化鱼油对草鱼肠道屏障结构和肠道通透性的影响。(实验目的)以豆油、鱼油、氧化鱼油作为饲料脂肪源,分别设计鱼油组(6F)、豆油组(6S)、2%氧化鱼油(2OF)、4%氧化鱼油(4OF)及6%氧化鱼油(6OF)5组等氮、等能半纯化饲料,在池塘网箱养殖草鱼(平均体重74.8士1.2)72d。采用实时荧光定量PCR(qRT-PCR)的方法,测定了草鱼肠道紧密连接蛋白中闭锁蛋白Occludin,闭合蛋白Claudin3、Claudin15a和胞浆蛋白ZO-1、ZO-2、ZO-3的基因表达活性,并结合肠黏膜细胞间紧密连接结构透射电镜观察结果、肠道通透性标志性指标测定结果综合分析。(实验方法)结果显示：在添加氧化鱼油后,(1)血清二胺氧化酶活性、内毒素和D-乳酸含量都出现显著增加(P<0.05);(2)组成肠黏膜细胞间紧密连接结构的闭合蛋白Claudin-3、Claudin-15a和胞浆蛋白ZO-1、ZO-2、ZO-3基因表达活性显著下调(P<0.05),而闭锁蛋白Occludin基因表达活性出现不同程度的下调,但差异不显著(P>0.05);(3)透射电镜观察结果显示肠黏膜细胞间紧密连接结构出现缝隙;⑷饲料中的AV值、POV值、MDA含量与闭合蛋白Claudin-3、Claudin-15a,胞浆蛋白ZO-1、ZO-2、ZO-3和闭锁蛋白Occludin基因表达活性均显示负相关关系的变化趋势,其中饲料POV值、MDA含量与胞浆蛋白ZO-1基因表达活性呈极显著负相关关系(P<0.05)。(实验结果)结果表明,在饲料中添加氧化鱼油后,氧化鱼油中的过氧化物、丙二醛等油脂氧化产物导致组成肠道黏膜细胞间紧密连接结构的蛋白基因表达活性显著下调、紧密连接物理性结构显著损伤,致使肠黏膜屏障结构的完整性被破坏、肠黏膜通透性显著增加。(实验结论)     

诺氟沙星在奥尼罗非鱼体内的药代动力学及残留研究

在水温(25±2)℃条件下,以20 mg·kg-1鱼体重的剂量给奥尼罗非鱼单次口灌诺氟沙星,高效液相色谱法测定血浆和肌肉组织中的药物浓度,研究诺氟沙星在奥尼罗非鱼体内的代谢及消除规律.结果显示:血药时间数据符合一级吸收二室开放模型,半衰期(T1/2Ka、T1/2α、T1/2β)分别为1.30、1.97、26.36 h,...