Cloning,expression, and induction by 17-β estradiol (E<Subscript>2</Subscript>) of a vitellogenin gene in the white cloud mountain minnow <Emphasis Type="Italic">Tanichthys albonubes</Emphasis>

Vitellogenins (Vtgs), the precursors for the yolk proteins, are very important for the embryonic development of teleosts, and have also been studied extensively as biomarkers for environmental estrogenic mimics. The cDNA for a Vtg was isolated from the liver of the female white cloud mountain minnow (Tanichthys albonubes) by 3′- and 5′-RACE methods. It is 4,171 bp in full length, and encodes a putative protein of 1,326 amino acids. This putative Vtg, designated as wcmmVtg, contains complete portions of LVI and PV, but lacks the C-terminal half of LVII and thus belongs to type I vitellogenin. In addition to the liver of the female fish, wcmmVtg was also shown to be expressed in the ovary. During ovarian development, the mRNA expression of wcmmVtg in both the liver and ovary was continuously increased from the previtellogenic to late vitellogenic stages, but then decreased significantly at post-spawning stage. In the male fish, expression of wcmmVtg mRNA was induced in the liver by treatment with E₂ (10 and 100 ng/l) for 14 days. These results suggest that the Vtg originated from the ovary of the white cloud mountain minnow may also contribute to the accumulation of yolk proteins during oocyte growth, and that the male white cloud mountain minnow is sensitive to the estrogenic treatment in terms of Vtg mRNA expression, which could also be applied to monitor the environmental estrogenic mimics.     

Cloning,characterization, and expression analysis of a CC chemokine gene from turbot (<Emphasis Type="Italic">Scophthalmus maximus</Emphasis>)

The chemokines are a superfamily of chemotactic cytokines playing an important role in leukocyte chemotaxis. Here, a turbot head kidney cDNA library was constructed in which KC70 was identified as a CC chemokine. Unknown 5′ and 3′ parts of the cDNA were amplified by 5′ and 3′ rapid amplification of cDNA ends (RACE). The complete cDNA of KC70 contains a 59-bp 5′ UTR, a 336-bp ORF, and a 152-bp 3′ UTR. Four exons and three introns were identified in KC70. Phylogenetic analysis showed that KC70 was similar to CCL19. In normal turbot KC70 was expressed in all tissues except brain and skin. Infection of turbot with pathogenic bacteria significantly increased expression of KC70 in the liver. Expression of KC70 in head kidney first increased and then decreased after bacterial challenge. No significant change was observed in the spleen after bacterial challenge. During embryonic development, KC70 was highly expressed after the gastrula stage. These results indicated KC70 plays important and multiple roles in turbot immune response.     

Changes in activities and mRNA expression of lipoprotein lipase and fatty acid synthetase in large yellow croaker,Larimichthys crocea (Richardson), during fasting

Over‐winter fasting and man‐made food deprivation to increase meat quality are common in the process of large yellow croaker (Larimichthys crocea) aquaculture. This study aimed to determine the changes in lipoprotein lipase (LPL) and fatty acid synthetase (FAS) activities and mRNA expressions, and the relationships between these changes and fat content in large yellow croaker liver and muscle tissues during fasting. A total of 2933 bp LPL cDNA, including an open reading frame of 1533 bp encoding 510 amino acids, and a 1233 bp fragment of FAS cDNA coding 411 amino acids were cloned. Expressions of both genes were ubiquitous. During a 35‐day fasting period, the hepatosomatic index and fat content in muscle and liver were significantly decreased (P < 0.05). mRNA levels of LPL increased significantly during the fasting period except the first 3 days, and FAS mRNA levels decreased significantly in both muscle and liver (P < 0.05) although there were some fluctuations. Muscle and liver LPL activities were significantly higher following fasting for 7 days, decreased to the initial value following fasting for 14 days, and elevating significantly afterwards (P < 0.05). FAS activities in muscle and liver maintained a significantly decreasing trend during the short‐term fasting (P < 0.05) and kept obviously rising thereafter (P < 0.05). Activities and mRNA levels of both LPL and FAS were not always consistent, which implied that both pre‐translational and post‐translational regulations existed during fasting. Our results suggest that the reasonable fasting time is 21 days before harvesting when fat content decreased significantly.     

河川沙塘鳢GHR和IGF-2基因克隆及mRNA的时序表达

生长激素/胰岛素样生长因子-轴(growth hormone/insulin-like growth-axis,GH/IGF-轴)是调控鱼类生长的主要内分泌轴线。为探讨生长相关基因GHR、IGF-2对河川沙塘鳢(Odontobutis potamophila)生长发育的调控机制,采用cDNA末端快速扩增(RACE)和实时荧光定量PCR等技术,对河川沙塘鳢的GHR、IGF-2基因进行了克隆和表达模式分析。研究结果显示:河川沙塘鳢GHR基因的cDNA全长序列为2 179 bp,开放阅读框为1 830 bp,共编码609个氨基酸,IGF-2基因的cDNA全长序列为1 586 bp,开放阅读框642 bp,共编码213个氨基酸。采用qRT-PCR方法检测了GHR、IGF-2基因在9个不同组织(脑、肝、心、肌肉、脾、肠、性腺、鳃、肾)和8个胚胎不同发育时期(受精卵期、桑椹胚期、原肠胚期、神经胚期、体节期、口裂期、出膜后1 d、出膜后3 d)的表达情况。结果表明:IGF-2和GHR基因在所检测的9种组织中均有表达,其中以肝脏、肌肉、性腺、脑中的表达量较高,在胚胎发育阶段GHR和IGF-2基因表达呈先上升后下降的趋势,在原肠胚期表达量较高,表明其在胚胎发育过程中发挥重要作用。qRT-PCR进一步比较了雌、雄河川沙塘鳢GHR和IGF-2基因在不同生长发育阶段(90、150、210、270、330 d)脑、肝、肌肉mRNA的表达量,结果表明:各时期雄鱼GHR和IGF-2基因在肝组织中表达量均显著高于雌鱼,肌肉和脑GHR基因mRNA的表达量则无显著差异。而IGF-2基因则仅在雌、雄鱼210 d的脑和150、210 d的肌肉存在显著性差异,推测肝GHR和IGF-2基因mRNA表达的雌雄差异是河川沙塘鳢雌雄生长差异的主要原因之一。     

Effects of experimental hypo- and hyperthyroidism on iodothyronine deiodinases in Nile tilapia, Oreochromis niloticus

In the present study, we examined the effects of experimentally-induced increases or decreases in plasma concentrations of thyroid hormones on iodothyronine deiodinases in tilapia, Oreochromis niloticus. To obtain hyperthyroid tilapia, fish were injected with porcine follicle stimulating hormone (pFSH) 36 hours before sampling or fed on demand for 11 days with tilapia pellets containing 12 ppm T3. Tilapias were made hypothyroid by providing them food containing 0.2% methimazole for 11 days. Plasma T4 and T3 and the in vitro deiodinase activity in liver, kidney, brain and gill were measured at the end of the treatment period. Injection with pFSH caused an increase in plasma T4 but had no influence on plasma T3 levels. A small increase in plasma T3 was observed in T3-fed fish. Plasma levels of both T4 and T3 were decreased by methimazole treatment. We observed no changes in kidney type I deiodinase (D1), whereas liver type II deiodinase (D2) was increased during hypothyroidism and decreased during hyperthyroidism. Hypothyroidism resulted in a significant decrease in brain, gill and liver type III deiodinase (D3). An pFSH-induced increase in T4 stimulated brain and gill D3 but not liver D3, whereas the opposite was true in T3-fed fish. We conclude that the regulation of D1 and D3 in tilapia is probably different compared to mammals.     

Ontogenetic and diel variation in the vertical distribution of larvae of jack mackerel <Emphasis Type="Italic">Trachurus japonicus</Emphasis> in the East China sea

Larvae of jack mackerel Trachurus japonicus were sampled in seven depth layers (0–10 m, 10–20 m, 20–30 m, 30–40 m, 40–50 m, 50–70 m, and 70–100 m), with a closing-type frame net, on 26th–27th February, 2003, at Sta. V (27°50′N, 126°00′E) continental shelf edge in the southern part of East China Sea, to examine their vertical distribution. Most of the larvae (>90%) occurred in the upper 50 m layer during both day and night. In the daytime, larvae of length from 3.0 mm to 4.5 mm were most abundant in the 10–20 m layer, those from 5.0 to 6.0 mm were most abundant in the 20–30 m layer, those from 6.0 to 8.0 mm occurred at greater depth, in the 30–40 m layer, and those more than 9.0 mm were found in the 0–10 m layer and performed ontogenetic vertical migrations. Larvae from 6 mm to 8 mm length performed diurnal vertical migration, for the percentage (16.7%) of larval number in the 0–20 m layer in the daytime increased to 42.1% at night and the percentage (78.1%) in the 20–50 m layer in the daytime decreased to 49.0% at night.