迟缓爱德华菌菌蜕疫苗对罗非鱼注射和口服免疫的效果分析

通过腹腔注射、口服两种免疫途径探讨迟缓爱德华菌菌蜕疫苗对罗非鱼Oreochromis niloticus的免疫保护效果。将制备的迟缓爱德华菌菌蜕疫苗（ETG）和福尔马林灭活疫苗（FKC）采用腹腔注射、口服两种免疫途径免疫罗非鱼,分别于免疫后14d、21d和28d采集罗非鱼血清、头肾、脾脏,测定血清中抗体IgM水平,血清中酸性磷酸酶（ACP酶）、超氧化物歧化酶（SOD酶）活性及罗非鱼头肾和脾脏中白介素（IL-1）、肿瘤坏死因子（TNF）、干扰素（IFN）、Caspase3等细胞因子的相对表达量,并通过攻毒试验得到菌蜕疫苗、福尔马林灭活疫苗两种疫苗的相对免疫保护率。免疫组罗非鱼的血清抗体水平均极显著高于（P<0.01）对照组,ETG注射组抗体效价极显著高于（P<0.01）FKC口服组。免疫28d,免疫组SOD、ACP酶活力显著高于（P<0.05）对照组（Group E、F）;在头肾中,免疫组（Group A、B）TNF、IL-1和IFN的相对表达量显著高于（P<0.05）对照组（Group E、F）。在免疫保护试验中,所有免疫组的免疫保护率均显著高于（P<0.05）对照组,注射、口服菌蜕疫苗的相对保护率分别为79%、77%,注射、口服灭活疫苗组的的相对保护率分别为62%、60%,但两种疫苗免疫保护率无显著差异。试验研制的菌蜕疫苗得到更高的免疫保护率,菌蜕疫苗在预防罗非鱼爱德华菌病中有良好的研究价值和应用前景。     

尼罗罗非鱼traf6基因表达谱及信号转导

肿瘤坏死因子受体相关因子6(TRAF6)是一种重要的接头蛋白,在Toll样受体/白细胞介素-1受体(TLR/IL-1R)超家族所触发的信号通路中起重要作用,与先天性免疫密切相关。文章研究了尼罗罗非鱼(Oreochromis niloticus)traf6的表达模式和初步的功能。在健康鱼中,traf6转录本广泛表达于所有受检组织中,在血液中表达水平最高,在肝脏中最低。在不同的胚胎发育阶段也检测到traf6的表达。在无乳链球菌体内感染后,大多数受检组织中traf6 mRNA的表达量上调。此外,LPS、Poly I:C和S.agalactiae可显著诱导尼罗罗非鱼巨噬细胞traf6的表达。此外,在HEK293T细胞中过表达表明,TRAF6分布于细胞质中,可显著提高NF-κB的活性。免疫共沉淀(Co-IP)实验表明,TRAF6可与IRAK1(白细胞介素-1受体相关激酶1)相互作用,IRAK1在TLR/IL-1R信号通路中也起重要作用。在体内,TLR2、TLR21和TLR13b的过表达可上调traf6 mRNA的表达水平,表明TRAF6参与了TLR2、TLR21和TLR13b介导的信号转导,提示TRAF6在病原体入侵的免疫应答中起重要作用。     

温度和盐度对吉富品系尼罗罗非鱼幼鱼鳃Na+-K+-ATPase活力的联合效应

试验采用中心组合设计(central composite face-centered design,CCF)和响应曲面法(response surface methodology,RSM)研究了温度(12—34℃)和盐度(0—26)两因素对体长为(4.36±0.105)cm,体重为(2.45±0.153)g的吉富品系尼罗罗非鱼(GIFT Nile tilapia,Oreochromis niloticus;简称吉富罗非鱼)幼鱼鳃Na+-K+-ATPase活力的联合效应。结果表明:(1)温度和盐度的一次效应和二次效应对Na+-K+-ATPase活力影响极显著(P<0.01),温度和盐度的互作效应不显著(P>0.05);(2)经响应曲面法分析,随着温度和盐度的增大,Na+-K+-ATPase活力呈先减小后增大的趋势;(3)建立了Na+-K+-ATPase活力与温度、盐度间关系的模型方程(R2=0.9829,Pred.R2=0.8550,P<0.01),并可用于预测吉富罗非鱼幼鱼鳃Na+-K+-ATPase的活力;(4)优化结果显示,温度为24.15℃,盐度为11.75时,Na+-K+-ATPase活力最小为0.62μmol无机磷.mg-1蛋白.h-1,满意度函数值高达0.961。Na+-K+-ATPase活力可以作为检测罗非鱼生长性能的指标,其活力较低时,一般反映了鱼体生存环境适宜,生长代谢旺盛,消耗于渗透调节的能量较少。     

Ultrastructural analysis of the developing follicle during early vitellogenesis in tilapia,Oreochromis niloticus,with special reference to the steroid-producing cells

The development and distribution of steroid producing cells (SPCs) in the ovary of tilapia have been studied by light and electron microscopy. At 40–50 d after hatching, these cells are seen only in the vicinity of blood vessels; there are no SPCs in the interstitial region, nor in the thecal layer enclosing young oocytes at the peri-nucleolus stage. By 70–80 d after hatching, the number of SPCs in the area near blood vessels has increased, and the capillaries have spread among the developing peri-nucleolar stage oocytes, and into the ovarian tunica. Clusters of SPCs have also migrated into the interstitial region and into the tunica along with these capillaries. In the ovary 100 d after hatching, some SPCs can be found in the thecal layer enclosing vitellogenic oocytes. Moreover, masses of SPCs can now be observed infiltrating the thecal layer of the oocyte. Serum testosterone (T) and estradiol-17 (E2) levels at 40–70 d after hatching, are low (T, 0.75–1.10 ng/ml, E2, 0.36–1.08 ng/ml), but at 100 d, plasma E2, but not T, is elevated (T, 1.95 ng/ml, E2, 4.65 ng/ml). These results suggest that SPCs appearing in the vicinity of blood vessels move into the interstitial region between oocytes, and finally enclose the oocytes at an early vitellogenic stage. It is interesting to note that the enclosure of oocytes by SPCs coincides with significant increases in E2 production.     

Mitotic chromosomal abnormalities and DNA polymorphism in the Nile tilapia (Oreochromis niloticus,Linnaeus, 1758) as a biomarker for water pollution by heavy metals

Mitotic chromosomal aberrations and DNA polymorphism (RAPD marker) were carried out on the Nile tilapia Oreochromis niloticus collected from five sites in Minia governorate, Egypt to test their applicability as biomonitors for heavy metal contaminants of water. The diploid chromosome number of O. niloticus population was 2 n = 44. Different types of chromosomal aberrations were recorded (e.g., deletion, ring, centromeric attenuation, end-to-end association, dicentric chromosome, stickiness chromosomes, endomitosis, fragments and chromatid gap). The chromosomal aberrations varied between O. niloticus population collected from five sites, and the most common type was ring (R) chromosomes. Samples obtained from Bahr Yousef and Irrigation drain exhibited the highest aberration frequency. The frequency of chromosomal aberration was positively correlated with the concentration of heavy metals where their concentration in the surface water of Irrigation drain and Bahr Yousef exceeded the limits defined by WHO as well as the concentration of Pb in muscles. The RAPD marker was also used to identify genetic variation among Nile tilapia samples collected from five different water sources. It created polymorphic and unique bands that can be used as genetic markers to track DNA variations. The dendrogram also revealed that exposure to heavy metal pollution causes gradual accumulation of variance, whereas areas subjected to environmental stress showed higher genetic variation and clustered together.     

Cellular and epithelial adjustments to altered salinity in the gill and opercular epithelium of a cichlid fish (Oreochromis mossambicus)

Morphological features of the gill and opercular epithelia of tilapia (Oreochromis mossambicus) have been compared in fish acclimated to either fresh water (FW) or hypersaline water (60 S) by scanning electron and fluorescence microscopy. In hyperosmoregulating, i.e., FW-acclimated, tilapia only those mitochondria-rich (MR) cells present on the filament epithelium of the gill were exposed to the external medium. After acclimation of fish to hypersaline water these cells become more numerous, hypertrophy extensively, and form apical crypts not only in the gill filament but also in the opercular epithelium. Regardless of salinity, MR cells were never found to be exposed to the external medium on the secondary lamellae. In addition, two types of pavement cells were identified having distinct morphologies, which were unaffected by salinity. The gill filaments and the inner operculum were generally found to be covered by pavement cells with microridges, whereas the secondary lamellae were covered exclusively by smooth pavement cells.     

Sex determination in the genus Oreochromis

Summary Sex ratios from 62 single-pair matings of normal broodstock O. aureus were highly heterogeneous with an overall deficit of males (41.4%). Peaks in the sex ratio frequency distribution occurred at 11, 35 and 13 (malefemale). Hybridisation of O. aureus with O. mossambicus, O. spilums and O. niloticus produced highly variable sex ratios, suggesting a complexity of hybrid sex determination. Few valid inferences could be made regarding intraspecific sex determination from these hybrid data. Sex ratios from progeny testing of sex-reversed males (13) and most sex-reversed females (10) provide evidence for female heterogamety in O. aureus. Several aberrant ratios observed suggest Mendelian inheritance of an autosomal recessive gene (F,f), epistatic to the major sex-determining gene (W,Z). Sex ratios of triploids and gynogens support the hypothesis of recombination between the centromere and the major sex-determining locus. Progeny testing of a female mitogyne demonstrated the viability of a novel WW superfemale, which gave only female offspring. Not all data could be explained by a two-factor model of sex determination. Further exceptional sex ratios may be accounted for by rare autosomal or environmental sex-modifying factors. It is concluded that O. aureus has a multifactorial mechanism of sex determination with the underlying primary mechanism of female heterogamety.     

Massive fish kills within the Nyanza Gulf of Lake Victoria,Kenya

The morphometry and hydrology of the Nyanza Gulf of Lake Victoria can be greatly affected by violent storms. This can result in a condition in which nutrient-rich bottom mud is mixed with the sediment-laden runoff water from neighbouring marshes and rivers. This situation can lead to massive fish kills. It is such an event in 1984 which will be described that caused the sudden death of over 400 000 fish weighing over 2400 tonnes.The unusually low precipitation in the catchment area during that year resulted in a drop in the lake level from 12.4 to 11.8 m. This low water level, combined with a severe storm created the conditions which caused this large fish kill. The species affected were Lates niloticus and Oreochromis niloticus. Mortality was attributed to several factors which included high levels of suspended material in the water column (detritus and algae) which clogged the gills of the fish, low dissolved oxygen, low pH, and high concentrations of algae.     

Endolymphatic calcium supply for fish otolith growth takes place via the proximal portion of the otocyst

The presence of calcium within the utricle of larval cichlid fish Oreochromis mossambicus was analysed by means of energy-filtering transmission electron microscopy. Electron-spectroscopic imaging and electron energy loss spectra revealed discrete calcium precipitations that were more numerous in the proximal endolymph than in the distal endolymph, clearly indicating a decreasing proximo-distal gradient. This decreasing proximo-distal gradient was also present within the proximal endolymph between the sensory epithelium and the otolith. Further calcium particles covered the peripheral proteinaceous layer of the otolith. They were especially pronounced at the proximal surface of the otolith indicating that otolithic calcium incorporation takes place here. Other calcium precipitates accumulated at the macular junctions clearly supporting an earlier assumption according to which the endolymph is supplied with calcium via a paracellular pathway. The present results clearly show that the apical region of the macular epithelium is involved in the release of calcium and that the calcium supply of the otoliths takes place via the proximal endolymph.This work was financially supported by the German Aerospace Center (DLR) e.V. (FKZ: 50 WB 9997)