大黄鱼 DIGIRR通过抑制MyD88-NF-κB的激活参与免疫调控

为研究大黄鱼双免疫球蛋白白细胞介素1受体相关分子 (double immunoglobulin interleukin-1 receptor-related molecule, DIGIRR) 在免疫反应中的作用,本实验克隆了大黄鱼DIGIRR (LcDIGIRR) 的编码区序列;采用荧光定量PCR (qPCR) 对大黄鱼各组织及免疫刺激后的脾脏、头肾等组织及大黄鱼肾细胞系 (LCK) 中的LcDIGIRR表达情况进行了检测;构建了重组表达质粒pTurboGFP-DIGIRR及pcDNA3.1-DIGIRR,分别以绿色荧光蛋白 (GFP) 为报告基因及双荧光素酶报告系统,研究了LcDIGIRR的亚细胞定位及过表达后对NF-κB启动子活性的调控。结果显示,LcDIGIRR的开放读码框 (ORF) 包含1575 bp核苷酸,编码 524 个氨基酸,理论分子量为59.4kDa、等电点 (pI) 为5.76,N端包含2个免疫球蛋白 (Ig) 结构域,1个跨膜区及1个Toll/白细胞介素-1受体 (TIR) 结构域,属于保守的硬骨鱼类DIGIRR家族;qPCR分析表明LcDIGIRR在大黄鱼多组织均有表达,其中在肠道中表达量最高;采用变形假单胞菌 (Pseudomonas plecoglossicida) 及脂多糖 (LPS)、鞭毛蛋白、多聚肌-胞苷酸 [poly (I:C)]等分别进行体内与体外刺激,均可诱导其表达量显著增加 (P < 0.05);亚细胞定位结果显示LcDIGIRR主要存在于细胞的膜质区;过表达LcDIGIRR能够显著抑制NF-κB及MyD88介导的NF-κB的转录激活 (P < 0.05)。以上结果表明LcDIGIRR可能通过抑制NF-κB的转录激活,在大黄鱼的免疫反应中发挥负调控作用。     

斑节对虾relish基因的克隆及免疫刺激对其mRNA表达水平的影响

relish是Rel/NF-κB家族的重要成员之一。本研究在构建的斑节对虾(Penaeus monodon)肝胰腺转录组文库中克隆得到PmRelish基因,其全长5 112 bp,包括3 561 bp的ORF,推测编码1个含1 186个氨基酸的蛋白。PmRelish的蛋白具有Rel/NF-κB蛋白家族的典型结构特征,包括N端的RHD结构域,核定位信号,C端的6个锚蛋白重复序列以及死亡结构域,表明该蛋白是NF-κB1亚型。该基因在所检测组织中呈组成型表达,并在血细胞表达量最高。使用定量PCR检测PmRelish基因在不同免疫刺激条件下在肝胰腺中的mRNA表达情况,结果显示,肝胰腺PmRelish基因是诱导型表达,并被创伤弧菌、金黄色葡萄球菌和白斑综合征病毒(WSSV)调控表达,其中被创伤弧菌上调表达最显著。进一步证明了病毒核酸类似物Poly(I:C)、R484可激活PmRelish的表达。上述研究结果说明Relish是斑节对虾的重要免疫因子,可能通过直接或间接作用参与对细菌和病毒的免疫反应。     

日本鳗鲡TBK1基因的克隆与免疫功能分析

为了阐明鱼类TANK结合激酶1 (TBK1)在免疫应答密切相关的NF-κB、I型IFN及MAPK信号通路中的调控作用，本实验通过cDNA末端快速扩增技术(SMART RACE)从日本鳗鲡中克隆了TBK1基因cDNA全长序列，命名为AjTBK1，利用实时荧光定量PCR (qRT-PCR)检测了在体和离体状态下不同病原体相关分子模式(PAMPs)及嗜水气单胞菌对日本鳗鲡AjTBK1基因表达水平变化的影响，通过构建绿色荧光蛋白pEGFP-TBK1和pCMV-TBK1真核表达质粒对Aj TBK1亚细胞定位以及Aj TBK1过表达对NF-κB、AP-1、IFN-β启动子荧光素酶活性的激活作用进行研究。蛋白质序列分析显示，日本鳗鲡AjTBK1编码731个氨基酸，其三维丝带空间结构与人类TBK1相似，具有保守的激酶结构域(KD)、泛素样结构域(ULD)、二聚化支架结构域(SDD)以及C端结构域(CTD)，在系统发育树中与其他鱼类TBK1家族聚为一支。qRT-PCR检测发现AjTBK1在多种组织中广泛表达，且在肝脏和肠中高表达。经LPS、poly I:C、嗜水气单胞菌免疫注射后，AjTBK1基因表达水...     

大黄鱼UBXN1基因鉴定及其过表达后的转录组分析

为探究UBXN1在大黄鱼抗盾纤毛虫感染中的作用及其可能涉及的免疫信号通路,本实验采用RT-PCR鉴定了大黄鱼UBXN1基因,并利用在线软件对其序列特征进行生物信息学分析; 采用实时荧光定量 PCR(qPCR)探究UBXN1在多个组织的表达情况,及盾纤毛虫感染下的表达变化;免疫荧光分析UBXN1的亚细胞定位;转录组筛选UBXN1过表达后的差异表达基因。结果显示：UBXN1基因cDNA全长为915 bp,编码304 个氨基酸。蛋白序列同源比对和结构预测表明UBXN1是一个进化保守的蛋白,包含UBA和UBX结构域。qPCR分析表明UBXN1呈组成型分布表达,脑中表达量最高,其次是肝脏、心脏和肾脏,在肌肉中表达量最低;盾纤毛虫感染大黄鱼,UBXN1在脾脏、脑、肝脏和肾脏表达量早期显著升高,后期逐步恢复至正常水平。亚细胞定位分析表明,UBXN1在大黄鱼肾脏细胞质和细胞核均有表达。在293T细胞过表达UBXN1,转录组分析筛选到12个上调基因,4个下调基因,其中RPL41/RPL39/XIST/RNA45SN4表达量显著增加,而ATP8/ND4L表达量显著减少。这些研究结果表明UBXN1在大黄鱼抗寄生虫免疫应答中发挥重要作用, 并为进一步深入研究UBXN1的免疫调控信号通路奠定基础, 这是目前在鱼类首次报道UBXN1。     

中华鳖IRF4基因克隆及免疫功能研究

干扰素调节因子IRF4基因仅表达于免疫相关细胞,在先天性免疫和特异性免疫中发挥重要作用。本研究根据中华鳖高通量测序预测的IRF4基因序列(GenBank登录号:XM_014581444),设计特异性引物扩增片段验证其编码区;通过荧光定量检测IRF4基因在健康中华鳖中组织表达情况以及脂多糖、聚肌胞苷酸诱导后在外周血淋巴细胞中的表达情况;构建真核表达载体p3xflag-IRF4,检测过表达IRF4基因后细胞对中华鳖虹彩病毒的敏感性,以及对干扰素启动子、NF-κB启动子的活性。试验结果显示,IRF4基因编码区和GenBank中序列完全相同,其推测的氨基酸序列含有1个DNA结合结构域和1个IRF相关结构域;荧光定量结果分析显示,IRF4基因表达于所检测的组织和器官,其中在血液、肝、脾中表达较高,脂多糖和聚肌胞苷酸均能诱导外周血淋巴细胞中IRF4基因的表达;过表达IRF4基因后降低细胞对中华鳖虹彩病毒的敏感性,过表达IRF4基因能显著诱导干扰素启动子活性,抑制NF-κB启动子活性。上述结果为更深入研究中华鳖IRF4参与机体免疫应答提供基础。     

牙鲆NOD2基因的表达分析及在抗迟缓爱德华氏菌感染过程中的功能

本研究利用实验室已建牙鲆(Paralichthys olivaceus)转录组数据库预测得到牙鲆NOD2基因(PoNOD2),并利用PCR技术进行序列验证。同时,设计迟缓爱德华氏菌注射感染牙鲆成鱼和体外免疫刺激牙鲆鳃细胞系实验,探究PoNOD2基因在抗菌免疫反应中的作用。PoNOD2基因的开放阅读框长度为2964 bp,编码988个氨基酸。PoNOD2蛋白有3种保守结构域,包括C-末端LRR,中心NACHT和N-末端CARD结构域。实时荧光定量PCR结果显示,在所检测牙鲆组织中,迟缓爱德华氏菌的侵染能显著上调PoNOD2的表达。体外免疫刺激牙鲆鳃细胞系实验显示,在PGN、PolyⅠ:C和迟缓爱德华氏菌刺激下,PoNOD2表达上调。亚细胞定位显示,PoNOD2蛋白定位于牙鲆鳃细胞的细胞质中。在迟缓爱德华氏菌侵染牙鲆鳃细胞过程中,PoNOD2基因的过表达能够抑制细菌生长,并引起IL-1β、IL-6和IL-8等炎性细胞因子的表达上调。结果表明,PoNOD2在抑制迟缓爱德华氏菌生长以及调节牙鲆对病原菌的免疫应答中发挥重要作用。     

水飞蓟素对建鲤肝细胞DNA损伤的保护作用及相关细胞因子的影响

为了评价水飞蓟素对建鲤肝组织损伤的保护作用,探索其可能的保肝机制,本研究用含水飞蓟素(0.1、0.5和1.0 g/kg)的饲料饲喂建鲤60 d,再腹腔注射30%四氯化碳(CCl4)植物油混合液,损伤72 h后采集肝组织,分别研究肝指数、肝细胞DNA损伤、肝组织病理切片、核转录因子NF-κB/C-Rel及细胞因子i NOS和IL-1β的mRNA表达量的变化。结果显示,0.5和1.0 g/kg的水飞蓟素能显著抑制CCl4导致的建鲤肝指数增大,同时能有效减少肝细胞DNA断片的产生,对肝细胞彗星的慧尾长、尾部DNA百分含量、尾矩及Olive尾矩等损伤指标均有显著改善作用;水飞蓟素能明显减轻CCl4作用导致的肝组织广泛性空泡变性、细胞轮廓不清、核固缩和核溶解等组织学病变;0.5和1.0 g/kg的水飞蓟素能显著抑制CCl4诱导的NF-κB/C-Rel和i NOS表达量的增加,而低、中、高浓度的药物均能显著下调IL-1β的表达量;随着水飞蓟素浓度的增大,对肝指数、肝细胞DNA损伤、病理切片及细胞因子的mRNA表达的影响均表现出剂量效应。结果表明,水飞蓟素能有效改善肝细胞DNA的损伤程度,其保肝作用可能与抑制NF-κB活化及下调其下游细胞因子i NOS和IL-1β的表达有关。     

金银花提取物改善脂多糖致大鼠急性肺损伤作用机制研究

目的探讨金银花提取物(Louicera japonica Thunb.Extract,LTE)对脂多糖(LPS)诱导的大鼠急性肺损伤的保护作用及其机制。方法 LTE高、低剂量组大鼠分别按生药量70 g/kg、35 g/kg灌胃给予LTE,1次/d,连续灌胃7 d。实验于末次给药后1h开始,模型组和药物干预各组尾静脉注射LPS(5 mg/kg)复制大鼠急性肺损伤(ALI)模型。LPS作用第6 h末麻醉大鼠后进行肺泡灌洗和取肺组织。结果 LTE能减少急性肺损伤大鼠支气管肺泡灌洗液(BALF)中炎性细胞数目(中性粒细胞和巨噬细胞),降低肺组织中肿瘤坏死因子(TNF-α)与白介素-1β(IL-1β)含量,降低NF-κB p65蛋白表达,抑制NF-κB信号通道。结论 LTE对肺组织炎性因子的产生具有抑制作用,减轻了LPS致大鼠ALI的损伤程度,这种抑制作用可能与其抑制NF-κB信号通路有关。     

血红蛋白介导草鱼肾细胞凋亡的机制

本研究以草鱼CIK细胞为研究对象,系统研究血红蛋白对CIK细胞的损伤机制。首先,本研究观察了血红蛋白和血红素刺激CIK细胞后细胞的生长情况,观察结果显示,血红蛋白和血红素明显抑制CIK细胞的正常生长。其次,检测了血红蛋白和血红素刺激对CIK细胞内铁代谢相关基因的表达情况,结果表明,血红蛋白和血红素的刺激不同程度的上调了铁代谢相关基因的表达。然后,本研究也检测了血红蛋白和血红素刺激CIK细胞后,细胞炎症和抗氧化酶相关基因的表达情况,研究表明,血红蛋白和血红素可以通过NF-κB途径激活下游炎症因子的表达,如促炎因子TNF-α,IL-1β和IL-6,抑炎因子IL-10以及趋化因子IL-4和IL-8等,也同时激活了超氧化物歧化酶（Superoxide dismutase,SOD）、过氧化氢酶（Catalase,CAT）和谷胱甘肽过氧化物酶（Glutathione peroxidase,GSH-PX）三种抗氧化酶基因的表达水平。为进一步检测血红蛋白对CIK细胞的毒性作用,本研究也检测了血红蛋白刺激CIK细胞后,细胞内铁离子和ROS的变化情况,结果显示血红蛋白的刺激显著增加了细胞内铁离子和ROS的含量。最后,我们也检测了血红蛋白和血红素刺激CIK细胞后,胞凋亡相关基因的表达情况,结果显示,血红蛋白和血红素都在不同程度上显著激活了CIK细胞凋亡相关基因的表达水平。总之,本研究结果表明,高氧化活性的血红蛋白可以激活细胞内铁代谢和炎症因子相关基因的表达,同时增加细胞内铁离子和ROS水平导致CIK细胞凋亡基因的高表达。     

草鱼肝细胞外泌体的分离鉴定及其对肝细胞miR-122/33和免疫相关基因表达的影响

外泌体是具有磷脂双分子膜结构的纳米级囊泡,能够参与机体多种生理过程。实验探讨了草鱼肝细胞外泌体的分离鉴定方法,并初步研究外泌体对草鱼肝细胞中miRNAs及免疫相关基因表达的影响。实验以草鱼肝细胞L8824为材料,通过超速离心获得外泌体,利用电子显微镜观察外泌体形态,采用纳米颗粒示踪分析(nanoparticle tracking analysis,NTA)技术检测外泌体粒径和数量,同时利用Western blot分析其标志蛋白CD63的表达,最后用正常肝细胞和油酸诱导的脂肪肝细胞源外泌体孵育草鱼肝细胞,通过Real-time qPCR技术检测两种不同来源的外泌体对草鱼肝细胞中miR-122/33及免疫相关基因(TNF-α,NF-κB,IL-1β,IL-6和IL-10)转录水平的影响。结果显示,草鱼肝细胞外泌体为30~150 nm的不均匀囊泡,呈圆形或椭圆形,有完整的膜结构;外泌体标志蛋白CD63呈阳性表达;NTA技术检测显示外泌体囊泡占所有囊泡的50%以上;脂肪肝细胞源外泌体显著提高了肝细胞中miR-122及炎症因子TNF-α、IL-1β和IL-6的mRNA转录水平。研究表明,通过超速离心法可成功分离草鱼肝细胞外泌体,且脂肪肝细胞源外泌体在草鱼肝细胞免疫调节中可能发挥重要作用。     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

Evaluation of a Fast Method Based on the Presence of Two Restriction Sites in the Mitochondrial ND5 (mt ND5) Gene for the Identification of Scomber Species

The purpose of this work was to evaluate the suitability of a method based on the presence of two restriction sites (for Hae III and Hindf I) in the mitochondrial NADH dehydrogenase subunit 5 (mt ND5) gene to identify Scomber species. The evaluation was performed on 144 reference and market samples by sequencing of the entire 505-bp fragment of the mt ND5 gene and of a 464-bp fragment of the Kocher fragment of the cytochrome b gene (mt Cytb). Sequence analysis of any of the two fragments allows the identification of each of the four Scomber species, but S. japonicus and S. colias had the same restriction sites at the ND5 amplicon and would not have been differentiated by this analysis. Similarly, loss of the Hae III site in some S. scombrus individuals would have misidentified them as not being Scomber. All the market products were correctly labeled except one acquired in Spain labeled as originating in the Atlantic and containing S. japonicus.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).     

The optimal dietary protein level of juvenile silver sillago Sillago sihama at three dietary lipid levels

A 5 × 3 factorial growth trial was conducted to evaluate optimal dietary protein and lipid levels (dietary protein level, DP; dietary lipid level, DL) for juvenile Sillago sihama (S. sihama) (2.0 ± 0.02 g, initial weight). Fish were fed 15 diets containing 5 DPs (350, 400, 450, 500 and 550 g/kg) and 3 DLs (60, 90 and 120 g/kg) for 8 weeks. The interaction between proteins and lipids significantly influenced the feed conversion ratio, condition factor, body composition, antioxidant indices and lipase activity (p < .05). DP 450 g/kg showed the highest average final body weight. DPs 500 and 550 g/kg significantly decreased the protein efficiency ratio (p < .05). DL 120 g/kg showed the highest percentage weight gain. The low feed conversion ratio was found in diets P45L12, P55L9 and P55L12. Diet P45L12 showed high superoxide dismutase activities. DP 450 g/kg showed the lowest average malondialdehyde content. Lipase activity was increased by increasing DP (p < .05) with a fall at DP 550 g/kg. Under the present experimental conditions, the optimal DP for S. sihama was 450 g/kg under the DL 120 g/kg.     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17 (E₂), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E₂ and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E₂ and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.