Effects of sex ratio, stocking density and age of hybrid tilapia on seed production in concrete tanks in Saudi Arabia

The influence of sex ratio, stocking density and age of hybrid tilapia (Oreochromis niloticus X O. aureus) brood fish on seed production in concrete tanks were evaluated in 1992 and 1993. A sex ratio of 1:2 and 1:3 (male: female) and a density of 2 fish m-2 gave the best result with respect to number of seed female-1 day-1 and number of seed kg-1-1 female day-1. Maximum seed production female-1 day-1 was recorded for 3-year-old females and the minimum for 1-year-olds, but in terms of seed kg-1 female day-1 and seed m-2 day-1, 1-year-olds produced the maximum number of seed followed by 2-, 3- and 4-year-old females. Seasonal pattern in seed production was apparently influenced by season and temperature. From the first harvest on 21 April 1993 the production increased gradually, reaching a peak during the third harvest and a second peak during the sixth harvest. Thereafter seed production gradually decreased, reaching a minimum during the tenth harvest on 27 October 1993. No seed were found during the last harvest of 18 November 1993. Maximum production coincided with the highest water temperature of around 28°C.     

Effects of dietary carbohydrate level on growth and body composition of juvenile tilapia, Oreochromis niloticus×O. aureus

A growth trial was conducted to feed juvenile tilapia (initial weight, 9.1±0.1 g), Oreochromis niloticus×O. aureus, isonitrogenous diets for 8 weeks. Six diets were formulated containing 29% crude protein from casein and gelatin, 10% crude fat from soybean oil and refined soybean lecithin and varying levels of corn starch ranging from 6% to 46% at increments of 8%, with corresponding energy to protein (E/P) ratios of 35.6, 37.9, 40.2, 42.5, 44.8 and 47.1 kJ g^?1. Weight gain (WG), specific growth rate, feed efficiency ratio and protein efficiency ratio were significantly higher in fish fed diets with starch ≥22% (or E/P ratio ≥40.2 kJ g^?1) than in fish fed diets with 6% or 14% starch (or E/P ratio of 35.6 or 37.9 kJ g^?1). No further improvement was measured when dietary starch content increased beyond 22%. Body protein retention showed the same general pattern as WG, and was highest in fish fed the 22% starch diet. Body composition was significantly affected by dietary starch level. Fish fed diets with starch ≥30% had significantly higher lipid content than fish fed diets with 6% or 14% starch. Ash content was negatively correlated with starch inclusion level, but moisture and protein contents did not show discernible trends among treatments. Results indicate that hybrid tilapia can utilize 46% dietary starch without growth retardation, while 22% starch in feed for juvenile tilapia containing 29% protein and 10% lipid, or an E/P ratio of 37.9 kJ g^?1 is optimal.     

分泌抗金黄色葡萄球菌细菌素乳酸菌的分离鉴定

为分离和筛选产抗金黄色葡萄球菌乳酸菌素的优势乳酸菌,利用乳酸菌分离培养基MRS从收集的各种腌制菜汁中分离培养乳酸菌,通过细菌培养特性、革兰氏染色特点、生理生化特性初步鉴定,同时根据Genbank中乳酸菌的16SrDNA序列设计特异性引物,采用PCR方法进一步鉴定,并以金黄色葡萄球菌为指示菌对乳酸菌的发酵上清液进行抑菌特性研究。结果表明,从腌渍菜汁中分离获得90株产酸菌,通过形态学、生理生化特性和PCR鉴定,结果73株产酸菌为乳酸杆菌;分泌产物抑菌试验表明,有10株菌具有抑制金黄色葡萄球菌活性,经酸排除和过氧化氢排除试验,仍然有5株乳酸菌的分泌产物具有抑制金黄色葡萄球菌活性。可见,从腌渍菜汁分离到的乳酸菌具有抑制金黄色葡萄球菌活性的特性,主要是通过分泌乳酸菌素来发挥作用。     

金黄色葡萄球菌快速检测方法的研究进展

金黄色葡萄球菌是引起人类细菌性食物中毒及奶牛乳房炎的重要细菌之一,在自然界中广泛分布。本文将重点介绍金黄色葡萄球菌的几种快速检测方法。     

尼罗非鲫和奥利亚非鲫线粒体DNA遗传差异的研究

以酶切MitochondrialDNA（mtDNA）技术检测了尼罗非鲫和奥利亚非鲫的mtDNA。测得两种鱼线粒体基因组的大小都约为16．83kb。在使用的6种酶中，只有PvuⅡ在所检测的15尾尼罗非鲫mtDNA上产生了多态片段，3尾鱼的mtDNA产生了4个片段，12尾鱼的mtDNA产生3个片段。而6种酶在所有15尾奥利亚非鲫中均未检到多态片段。比较两种鱼的mtDNA酶切片段，仅PvuⅡ的酶切结果有所不同，尼罗非鲫mtDNA上有3个或4个PvuⅡ位点，但奥利亚非鲫mtDNA上有5个位点，因此，PvuⅡ的酶切位点可作为鉴别它们的分子遗传标记。     

Observations on the reproductive performance of three mouth-brooding tilapia species in low-salinity underground water

The reproductive performance and seed production of three mouth‐brooding tilapia species, Oreochromis spilurus (Günther), Oreochromis aureus (Steindachner) and Taiwanese red tilapia hybrid, were compared in low‐salinity underground water (3–5 g L^?1) to select species with the highest reproductive rate. Two‐year‐old males and females having average body weights of 454 and 259 g, respectively, were stocked in 2‐m³ fibreglass breeding tanks (two tanks per species) at 1:3 male to female sex ratio and at average density of three fish m^?2. Seeds (unhatched eggs; yolk‐sac fry and the swim‐up fry) were collected weekly for 112 days. The results showed O. spilurus to have significantly higher (P<0.05) mean spawning parameters expressed as total seed tank^?1 (84 154), seed kg female^?1 day^?1 (284), seed m^?2 day^?1 (190.3) and seed female^?1 day^?1 (76.3), than O. aureus and red tilapia. Monthly seed production in O. spilurus and red tilapia gradually increased from May, peaked in July and declined in August, while in O. aureus, it continued to decrease from May to August. In this study, the observed production levels of seed in O. spilurus were among the highest levels reported for tilapia; therefore, O. spilurus could be selected as a potential candidate for mass seed production in commercial tilapia hatcheries.     

乳制品中金黄色葡萄球菌PCR快速检测方法的建立

为快速检测乳制品中的金黄色葡萄球菌,本研究将纳米氢氧化钛和纳米氢氧化锆固定在滤纸片上以去除PCR反应抑制因子,并以Nuc为靶基因,建立一种无需样品前增菌的PCR快速检测方法,同时确定该方法的特异性、灵敏度和实用性,并评估该方法所用试剂在冷冻保存条件下的稳定性与实用性。结果表明,该PCR快速检测方法在检测97株目标菌及83株非目标菌后未出现假阳性或假阴性结果;该方法无需增菌处理,可在4 h内完成检测,检测限为10¹ CFU·25 g^-1或10¹ CFU·25 mL^-1;该方法与传统检测方法在实际乳制品样品中金黄色葡萄球菌的检出率及活菌检测率均一致(符合率100%);此外,该检测方法所用试剂在-20℃冷冻条件下可稳定保存至少12个月。综上所述,本研究建立的PCR快速检测方法特异性强、灵敏度高,且实用性良好,能有效去除样品基质中的PCR反应抑制因子,为乳制品中金黄色葡萄球菌的快速检测提供了参考依据。     

定点突变阻止金黄色葡萄球菌α-溶血素溶血活性

金黄色葡萄球菌分泌的α-溶血素是导致肺炎的重要致病因子。为进一步研究金黄色葡萄球菌α-溶血素(α-hla)的分子致病机理以及对其进行免疫预防,对α-hla第35位氨基酸进行了定点突变。用聚合酶链式反应(PCR)技术,从S.aureus wood46株基因组中扩增出α-hla基因,再利用重叠延伸PCR技术,将第35位带正电荷的组氨酸(密码子为CAC)突变为非极性的亮氨酸(密码子为CTC)。hlaH35L基因测序结果显示第35位的组氨酸突变为亮氨酸,构建的重组表达质粒pET-28a-c(+)/hla和pET-28a-c(+)/hlaH35L在E.coli BL21(DE3)中得到表达,重组蛋白α-Hla及hlaH35L大小均为33.4 kDa,α-Hla引起兔红细胞溶血,hlaH35L未引起兔红细胞溶血。成功表达并获得了失去溶血毒性的重组蛋白hlaH35L。     

高温逆境对黄金葛叶片中渗透调节物质积累的影响

以3~5个叶片的黄金葛扦插苗为试材,采用单因素随机区组设计,设4个温度处理,3次重复,测定不同温度、不同时间处理下黄金葛叶片内渗透调节物质含量的变化。结果表明,在同一时间高温胁迫下,随温度的不断升高,黄金葛叶片的可溶性蛋白含量整体呈下降趋势,可溶性糖含量呈上升趋势;同一温度处理下,在35℃,不同时间处理可溶性蛋白含量和可溶性糖含量变化不大,在45℃处理40 h,可溶性蛋白含量比胁迫初期降低了35.02%,而可溶性糖含量比胁迫初期增加了97.06%。     

成纤维上皮细胞炎症反应模型的建立

利用培养金黄色葡萄球菌培养基过滤液建立成纤维上皮细胞炎症反应模型，用于观察和研究炎症反应过程中细胞形态的变化。将培养金黄色葡萄球菌培养基除菌过滤冻干，用细胞培养基稀释，按照一定蛋白含量加到上皮细胞的培养基中，制作细胞炎症反应模型。结果显示，成纤维上皮细胞发生炎症反应，高浓度细菌滤过液的细胞形态发生变化，细胞边缘模糊不清，细胞出现空泡，随着培养时间的延长低浓度的大量大型细胞开始增加；在添加金黄色葡萄球菌培养基滤过液培养24h后利用^3H—TdR方法测定细胞增殖率，细胞增殖差异是显著的。结果表明，建立细胞炎症反应模型是可行的，并为以后炎症反应机理研究和抗炎性反应药物研究奠定了基础。