Extrapituitary gonadotropin-releasing hormone (GnRH) binding sites in goldfish

In teleosts, as in other vertebrates, the secretion of pituitary gonadotropin (GTH) is mediated by the hypothalamic decapeptide, gonadotropin-releasing hormone (GnRH). Recent findings in teleosts indicate that GnRH receptors are not restricted to the pituitary gonadotropes and are also associated with somatotropes as well as being present in a number of other tissues. In the present study, we provide novel information on GnRH binding in a number of extrapituitary tissues in goldfish. However, we do not intend to provide full characterization of GnRH binding sites in various extrapituitary tissues in goldfish as this would clearly be outside the scope of this paper. In this study we examined GnRH binding in a number of extrapituitary tissues in goldfish and observed specific binding in ovary, testis, brain, liver and kidney. No specific GnRH binding was observed in muscle, skin, gut, gill and heart. In general, the present findings together with the results of other studies carried out in our laboratory demonstrate that mature goldfish ovary and testis contain two classes of GnRH binding sites, high affinity/low capacity and low affinity/high capacity sites with binding characteristics similar to those of the pituitary GnRH receptors. The brain of goldfish was also found to contain two classes of GnRH binding sites, a super-high affinity/low capacity and a low affinity/high capacity sites. Furthermore, study of goldfish liver and kidney demonstrated the presence of a single class of GnRH binding sites with characteristics different from those of pituitary, ovary, testis and brain. Overall, it is evident that goldfish contains a family of GnRH binding sites which can be classified into four groups based on binding affinities: 1) A class of high affinity binding sites present in the pituitary, ovary and testis, 2) a class of super high affinity sites so far only detected in the brain, 3) a class of intermediate-affinity GnRH binding sites in the liver and kidney, and 4) a class of low affinity binding sites present in all the tissues containing specific GnRH binding sites except for liver and kidney.     

In vivo activity of salmon gonadotropin releasing hormone (GnRH), its agonists with structural modifications at positions 6 and 9, mammalian GnRH agonists and native cGnRH-II on the spawning of an Indian catfish

Effects of the native GnRHs and various agonists have been evaluated on the spawning of an Indian catfish, Heteropneustes fossilis. This study tested salmon (s) GnRH agonists and mammalian (m) GnRH agonists where a D-amino acid residue was substituted alone at position 6 or the C-terminal was modified with ethylamide. GnRH agonists with a combination of these structural modifications were also evaluated separately for their effect on the spawning of the catfish. Native sGnRH, [Pro⁹ NEt]-sGnRH agonist and chicken (c) GnRH-II exhibited similar activity and induced spawning within 14–18 h at a dose of 100 g kg^–1 body weight (BW). [D-Lys⁶]-sGnRH agonist and [D-Lys⁶ Pro⁹ NEt]-sGnRH agonist, induced spawning at a dose of 100 g kg^–1 BW and 1 g kg^–1 BW, respectively. The most notable observation in this study was the ineffectiveness of [D-Ala⁶]-mGnRH agonist and [Des Gly¹⁰ D-Ala⁶ Pro⁹ NEt]-mGnRH agonist. The results obtained suggest that substitution at position 6 alone, and in conjunction with an ethylamide-based modification at the C-terminal in the native sGnRH structure, increases the potency of the tested agonists to induce spawning in the catfish. This study also discusses the potential use and incorporation of cGnRH-II for the development of more generic spawning induction therapies.     

Testicular responsiveness to gonadotropic hormonein vitro and Leydig and Sertoli cell ultrastructure during pubertal development of male African catfish (Clarias gariepinus)

The gonadotropin (GTH)-stimulated testicular androgen secretionin vitro and the ultrastructure of Leydig and Sertoli cells was studied during the pubertal development in male African catfish. Testicular weight increased from less than 1 mg in the ninth week of age to nearly 600 mg in the 28th week. Immature testes (stage I: spermatogonia) were highly sensitive to GTH and secreted very high amounts of androgens per mg of tissue. The secretion per mg tissue decreased gradually in stages II (spermatogonia and spermatocytes) and III (spermatogonia, spermatocytes, and spermatids), but precipitously in stage IV (all germ cell stages, including spermatozoa). However, due to the testicular weight gain, the total androgen output per pair of testes increased slightly in stage III and strongly in stage IV. The sensitivity to GTH decreased with the appearance of haploid germ cells in stage III. Leydig cells but not Sertoli cells showed the ultrastructural characteristics of steroid producing cells. Leydig cell morphology did not change in stages I–III, while in stage IV, more smooth endoplasmic reticulum was present. The ultrastructural characteristics of Sertoli cells did not change prominently. Thus, spermatogonial multiplication and spermatocyte formation takes place when the testicular steroidogenic system is highly active and responsive to GTH; whereas the differentiation of haploid germ cells is accompanied by a reduced responsiveness to GTH and by the secretion of several-fold lower androgen amounts per mg of tissue.     

Positive feedback control by the gonads on gonadotropin (GTH) and gonadoliberin (GnRH) levels in experimentally matured female silver eels,Anguilla anguilla

Treatment of sham-operated female silver eels with carp pituitary extract stimulated ovarian development and induced increases in pituitary gonadotropin (GTH) and gonadoliberin (GnRH) contents. Both effects of carp pituitary extract were abolished in ovariectomized eels, indicating the involvement of the gonads. Endogenous sexual steroids, the secretion of which was increased during sexual maturation, should be responsible for the stimulation of GTH and GnRH levels. Ovariectomy itself had no significant effect on pituitary GTH and GnRH contents, reflecting the fact that, at the silver stage, sexual steroid levels are too low to exert any significant effect on pituitary GTH and GnRH. The positive feedback control exerted by the gonads on GTH and GnRH levels during sexual maturation, in the eel as well as in some other teleosts, would produce an amplification of the pubertal stimulation of the hypothalamo-pituitary-gonadal axis.     

Optimal dietary carbohydrate to lipid ratio in African catfish Clarias gariepinus (Burchell 1822)

An 8-week feeding trial was conducted in a recycling water system at 28±1°C to investigate carbohydrate to lipid ratio (CHO:L ratio) in African catfish Clarias gariepinus (12.32±0.04g). Five isonitrogenous (40% crude protein) and isoenergetic (20kJg^–1 gross energy (GE)) fishmeal based diets with varying carbohydrate to lipid (CHO:L g/g) ratios of 0.74, 1.13, 1.66, 2.47 and 3.42 for diets 1–5, were tested, respectively. The diets containing a fixed protein to energy ratio (P:E ratio) of 20-mg proteinkJ^–1 GE were fed to triplicate groups of 20 fish (per 30-L tank). Fish were fed 5% of their body weight per day adjusted fortnightly. Diet 1, containing 14% carbohydrate and 21% lipids with a CHO:L ratio of 0.74 produced the poorest (P<0.05) growth rates, feed and protein efficiency. Increasing carbohydrate content in the diets to 27% concomitant with a reduction in lipid content to 16% with a CHO:L ration of 1.66 of diet 3 significantly improved (P<0.05) growth rates, feed and protein efficiency. A further increase in dietary carbohydrate up to 38% and a decrease in lipids levels to 11% with a CHO:L ratio ranging from 1.66 to 3.42 (diet 3 – 5) did not significantly improve the fish performance. Apparent net protein utilisation (ANPU) of fish fed diet 4 was higher (P<0.05) than for diets 1–3 but did not differ from diet 5. Higher lipid deposition (P<0.05) in whole body and liver were observed with decreasing dietary CHO:L ratios as increasing lipid levels. Whole body protein and liver glycogen content, digestive enzyme activities (protease and lipase) and histological examination of intestine and liver of fish fed varying CHO:L diets did not show any discernible changes among the dietary treatments. However intestinal -amylase activity increased (P<0.05) with increasing dietary carbohydrate levels. This study revealed that African catfish can perform equally well on diets containing carbohydrate ranging from 27 to 38% of the diet, with lipid content ranging from 16 to 11% or at CHO:Lg/g ratio of 1.7–3.4.     

Direct actions of serotonin on gonadotropin-II and growth hormone release from goldfish pituitary cells: interactions with gonadotropin-releasing hormone and dopamine and further evaluation of serotonin receptor specificity

In this study, the direct actions of serotonin (5HT) on gonadotropin (GTH)-II and growth hormone (GH) release in the goldfish were tested at the pituitary cell level. 5HT (10 nM - 10 µM) stimulated GTH-II but inhibited GH release from perifused goldfish pituitary cells in a dose-dependent manner. The minimal effective dose of 5HT tested to suppress basal GH secretion (10 nM) was 10-fold lower than that to stimulate GTH-II release (100 nM). The GTH-II releasing effect of 5HT was abolished by repeated 5HT treatment (10 µM) whereas the corresponding inhibition on GH release was unaffected. These results suggest that 5HT receptors on goldfish gonadotrophs and somatotrophs exhibit intrinsic differences in terms of sensitivity to stimulation and resistance to desensitization. Salmon GTH-releasing hormone (sGnRH, 100 nM) stimulated GTH-II and GH release from goldfish pituitary cells. The GTH-II releasing action of sGnRH was unaffected by simultaneous treatment of 5HT (1 µM). However, the corresponding GH response to sGnRH (100 nM) was inhibited. In the goldfish, dopamine is known to stimulate GH release through activation of pituitary D1 receptors. In the present study, the GH-releasing action of dopamine (1 µM) and the D1 agonist SKF38393 (1 µM) was significantly reduced by 5HT (1 µM). To examine the receptor specificity of 5HT action, the effects of 5HT1 and 5HT2 analogs on GTH-II and GH release were tested in goldfish pituitary cells. The 5HT1 agonist 8OH DPAT (0.1 and 1µM) and 5HT2 agonist methyl 5HT (0.1 1µM) mimicked the GTH-II releasing effect of 5HT. The 5HT1 agonist 8OH DPAT (0.1 and 1µM) also stimulated GH release but the 5HT2 agonist methyl 5HT (0.1 and 1µM) was inhibitory to basal GH secretion. In addition, 5HT (1µM) -stimulated GTH-II release was abolished by the 5HT1 antagonist methiothepin (10µM) and 5HT2 antagonist mianserin (10µM). Similarly, the inhibitory action of 5HT (1µM) on basal GH release was blocked by the 5HT2 antagonist mianserin (10µM). The 5HT1 antagonist methiothepin (10µM) was not effective in this regard. These results, taken together, indicate that 5HT exerts its regulatory actions on GTH-II and GH release in the goldfish directly at the pituitary cell level, probably through interactions with other regulators including sGnRH and dopamine. The GTH-II releasing action of 5HT is mediated through 5HT2 and possibly 5HT1 receptors. The inhibition of 5HT on basal GH release is mediated through 5HT2 receptors only. Apparently, 5HT1 receptors are not involved in this inhibitory action. In this study, a paradoxical stimulatory component of 5HT on GH release by activating 5HT1 receptors is also implicated.     

Quality costs in intensive fish culture: an analysis of African catfish farms in The Netherlands

A quality cost analysis was performed with the cooperation of six full-time African catfish, Clorias gariepinus, farmers in The Netherlands. The relative distribution of the quality costs does not fit a common quality cost model. Possible explanations for this observation are the absence of (1) feedback from customers and (2) well-defined quality criteria. The results show that it is likely that a considerable reduction in quality costs can be achieved with respect to sorting and rewatering. A further reduction is possible if agreement on quality criteria for African catfish can be reached.     

Differential distribution and response to experimental sexual maturation of two forms of brain gonadotropin-releasing hormone (GnRH) in the European eel,Anguilla anguilla

Using specific radioimmunoassays for the two GnRH molecular forms present in the European eel, Anguilla anguilla, (mGnRH and cGnRH II), we compared their distributions in the pituitary and different parts of the brain of female silver eels, as well as the modifications of their levels in experimentally matured female eels (treated with carp pituitary extract). In control eels, mGnRH levels were higher than cGnRH II levels in the pituitary, olfactory lobes and telencephalon, di- and mesencephalon, while the opposite was found in the posterior part of the brain (met- and myelencephalon). Experimental sexual maturation of the gonads significantly increased mGnRH levels in the pituitary and anterior parts of the brain; such a positive effect was not observed on the low cGnRH II levels, which were, in contrast, reduced. These data indicate that the positive feedback of gonadal hormones on GnRH, that we previously demonstrated, would specifically affect the mGnRH form. The differential distribution and control of mGnRH and cGnRH II suggest that these two forms have different physiological roles in the eel. The large increase in mGnRH during sexual maturation suggests the prime implication of this form in the neuroendocrine control of reproduction.     

金鱼生殖细胞多倍化现象分析

通过精巢染色体制片观察金鱼的生殖细胞染色体数,结合流式细胞仪测定成熟精子DNA含量,探讨了金鱼生殖细胞发生过程中染色体特征及产生的精子的倍性。结果表明,金鱼初级精母细胞大部分行正常减数分裂,形成50个二价体,另外还发现17.0%分裂相的二价体数呈现不同程度的加倍现象,观察到了二价体数为100、150、200、250、300,甚至远远超过300的分裂相,与鲫鲤远缘杂交导致生殖细胞染色体数加倍一致,不一样的是金鱼稳定产生DNA含量减半的精子。结果表明,近缘杂交和远缘杂交都可以导致生殖细胞染色体数加倍,但是否能产生染色体数加倍的功能性配子与杂交亲本亲缘关系的远近有关。     

Gonadotropin‐releasing hormone analogue multiple injection potentially accelerated testicular maturation of male yellow catfish (Pelteobagrus fluvidraco,Richardson) in captivity

The potential for accelerating testicular development and final maturation of adult male yellow catfish (Pelteobagrus fluvidraco, Richardson) in captivity was evaluated by using gonadotropin‐releasing hormone analogue (GnRHa) multiple injection, and its possible regulatory mechanism was explored by measurements of luteinizing hormone (LH) and steroid levels. The results showed that GnRHa multiple injection increased gonad‐somatic index (GSI), the sperm count and the milt‐testis index (MTI) and promoted the larvae production by elevated rates of fertilization and hatching, and lowered the rate of deformed larvae. Meanwhile GnRHa treatment decreased the percentages of spermatogonia and spermatocytes, increased the relative sperm density (RSD) and percentages of spermatids and spermatozoa (STZ), suggesting GnRHa treatment could accelerate meiotic division and enhance the formation of spermatids andSTZ. Moreover, pituitary and serum LH, as well as serum T levels were increased after GnRHa multiple injection. Taken together, the present study demonstrated GnRHa multiple injection successfully accelerated the testicular development and maturation of male yellow catfish, which was mediated by the increase in serum LH and T levels that further mediated biological and histological changes of testis. Therefore, GnRHa multiple injection could be a valuable method to induce precocious testicular maturation of adult yellow catfish with gonadal developmental arrest in captivity.     

黄颡鱼促卵泡激素受体基因的克隆及其在雌鱼生殖周期中的表达

为研究黄颡鱼促卵泡激素受体(FSHR)基因的克隆以及该基因在卵巢发育周期中的表达情况,实验首先采用SmartTMRace技术,获得了黄颡鱼促卵泡激素受体基因cDNA全长序列,该基因全长2 340 bp,编码661aa,具有G蛋白偶联受体超家族(G protein-coupled receptor,GPCR)的7个跨膜螺旋区(transmembrane domain)。经分析发现,得到的FSHR基因序列具有9个富含亮氨酸的重复性序列(LRRs);5个潜在的N-端糖基化位点;蛋白激酶C(proteinkinase C,PKC)磷酸化位点(403Y)位于第一个包外环,C-末端(C-terminal domain)G蛋白偶联区域,存在3个蛋白激酶C磷酸化位点(634S,643S,632T)。这些区域可能与FSHR的功能有密切关系。RT-PCR发现,FSHR基因在卵巢和脑中大量表达,在其他组织中均存在少量或微量的表达;在繁殖周期中,卵巢FSHR基因表达从Ⅲ期～Ⅳ期处于较高水平,在Ⅵ期时下降。研究推测,卵巢中FSHR基因参与黄颡鱼卵母细胞成熟及卵黄蛋白的积累过程。     

Bioaccumulation of cadmium and its biochemical effect on selected tissues of the catfish (<Emphasis Type="Italic">Clarias gariepinus</Emphasis>)

The present study examines the pattern of accumulation of cadmium (Cd) and its biochemical effects on selected tissues of a variety of African catfish (Clarias gariepinus), after exposure to various doses of Cd. The results obtained indicate that at the end of 21 days of exposure, the total tissue organ cadmium concentration followed the pattern kidney > gill > liver > muscle for each of the exposure concentrations. The levels of Cd in these organs were higher than those in ambient water. Moreover, while the rate of uptake of Cd increased with time in the kidney, liver and muscle, it decreased in the gill. Superoxide dismutase (SOD) was significantly elevated only in the kidney of catfish treated with 0.2 and 0.4 ppm of Cd for 7 days compared with the control. Conversely, gill SOD was significantly decreased in the same concentrations of Cd-treated catfish relative to the control. Statistically similar levels of SOD were observed in the liver, brain and muscle with all the treatments after the same duration of treatment. In the fish exposed for 21 days, SOD activity was significantly decreased in the kidney with a corresponding increase in lipid peroxidation (LPO), but it manifested only with the 0.2- and 0.4-ppm Cd treatment relative to the control. In the liver, however, Cd exposure significantly increased SOD in the 0.2- and 0.4-ppm treatments of the same duration. In conclusion, the present study indicates that the accumulation of Cd and its effect on SOD and LPO in C. gariepinus is dependent on concentration, tissue and time     

Scale regeneration and calcification in goldfish <Emphasis Type="Italic">Carassius auratus</Emphasis>: quantitative and morphological processes

The time-course changes in calcium and phosphorus contents, dry weight, and area during scale regeneration in the goldfish, Carassius auratus L. were quantified. Histological observations were then conducted to understand the mutual relationship between the quantitative and morphological processes of scale regeneration. The quantitative study revealed that regenerating scales grow most rapidly in area during the first 5 days of regeneration. The gradual decrease in the area growth rate coupled with the continuous linear weight growth over the period of 5–28 days suggests a shift in growth priority from area growth to the apposition, of the basal plate. Calcium and phosphorus deposition proceeded almost linearly during scale regeneration. Calcification of the bony layer preceded that of the basal plate and, after 14 days of regeneration, calcification of the basal plate started and gradually progressed. On day 28, recovery of calcium and phosphorus contents in the regenerating scales were approximatley 72% of ontogenetic scales, which is lower than the rates of area and weight regeneration (104 and 85%, respectively). Late initiation and slow progress of calcification in the basal plate is suggested to be responsible for the slow regeneration in calcium and phosphorus contents.     

SOST基因在淇河鲫肌间骨骨化过程中的表达研究

为探索硬化蛋白(sclerostin,SOST)基因在淇河鲫肌间骨骨化过程中的调控作用,本研究以淇河鲫仔稚鱼为研究对象,利用整体骨骼染色法对肌间骨的形态发生进行观察,并采用q RT-PCR、Western Blot和免疫组织化学技术检测SOST基因在肌间骨不同骨化阶段的m RNA和蛋白表达变化情况。结果显示,淇河鲫发育至24 dpf(day post fertilization),肌膈中出现纤维束;25 dpf髓弓小骨出现,28 dpf脉弓小骨出现,33 dpf髓弓小骨出现分叉,45 dpf肌间小骨发育完全。SOST基因在肌间骨骨化发生各阶段均有表达,23 dpf的表达量最低(P0.05),随着肌间小骨的骨化发育,SOST基因呈递增趋势,45 dpf表达量显著高于其他骨化阶段(P0.05);SOST蛋白在45 dpf时显著高于23和27 dpf(P0.05),与其他发育阶段无显著差异(P0.05)。SOST m RNA和蛋白变化趋势基本相同,都在23dpf处于最低,肌间骨全部出现后表达量达到最高,与淇河鲫肌间骨的形态发生趋势一致。因此,推测SOST与淇河鲫肌间骨骨化具有一定的相关性,可调控肌间骨的分化和形成。     

The existence of gonadotropin-releasing hormone (GnRH) immunoreactivity in the ovary and the effects of GnRHs on the ovarian maturation in the black tiger shrimp Penaeus monodon

Immunocytochemical localization using antibodies against five isoforms of gonadotropin-releasing hormone (GnRH), namely, luteinizing hormone-releasing hormone (LHRH), salmon (s)GnRH, octopus (oct)GnRH, lamprey (l)GnRH-I, and lGnRH-III, showed that only lGnRH-I immunoreactivity (ir-lGnRH-I) was localized in follicular cells of proliferative, vitellogenic, and mature ovaries. The effects of exogenous GnRHs on the ovarian maturation cycle of Penaeus monodon were compared by treating female broodstocks with LHRH, sGnRH, and lGnRH-I. The cycle of ovarian maturation in both eyestalk-ablated and eyestalk-intact shrimp administered with the three isoforms of GnRH was significantly shorter than that of the control animals. Moreover, administrations of all GnRH isoforms showed similar numbers of spawned eggs and the percentage of successful fertilization as in the control animals. These findings suggest that GnRHs may be highly conserved peptides that play an important role in inducing the ovarian maturation in the shrimp.     

不同养殖模式下雌核发育彭泽鲫雌雄鱼性别分化相关基因的表达差异

将同一批经雌核发育产生的F1彭泽鲫(Carassius auratus var.pengze)仔鱼(Pcc)分别置于实验室和池塘进行养殖,结果发现,与池塘养殖雄鱼比例极少相比,实验室养殖中出现了高比例的雄鱼。实验室养殖Pcc F1雄雌比例为(43.6±3.0)%,而池塘养殖Pcc F1雌雄比为(4.7±1.2)%。本研究比较了不同养殖模式下雌雄鱼性腺分化相关基因的表达,结果发现除Pcc-vasa、Pcc-esr1和Pcc-esr2b外,实验室养殖Pcc F1精巢中性腺分化、受体、类固醇合成酶类基因表达极显著(P0.01)或显著(P0.05)高于卵巢中对应基因的表达量。对于池塘养殖的Pcc F1,除Pcc-amh、Pcc-dmrt1b、Pcc-dmrt1c、Pcc-foxl2、Pcc-vasa和Pcc-esr2b外,精巢中性腺分化和受体基因表达极显著(P0.01)或显著(P0.05)高于卵巢中对应基因的表达量;但精巢中绝大部分类固醇合成酶类基因的表达量极显著低于卵巢(P0.01)。实验室和池塘养殖Pcc F1雌雄出现差异表达的基因主要是类固醇合成酶类及调控芳香化酶的转录因子,这些基因的差异表达可能与雌雄激素的合成或调控相关,从而导致不同养殖模式出现不同比例的雄鱼。     

淇河鲫甘露糖受体基因克隆及嗜水气单胞菌感染对其基因表达的影响

为了解淇河鲫甘露糖受体(mannose receptor,MR)的结构特点及其在抗感染免疫反应中的作用,实验通过同源克隆和RACE技术,获得了淇河鲫甘露糖受体(CaMR)全长c DNA,并采用实时荧光定量PCR(qPCR)技术研究了嗜水气单胞菌感染对CaMR组织表达的影响。结果显示,CaMR c DNA全长4473 bp,5′非编码区81 bp,3′非编码区90 bp,编码一个由1433 aa组成的前体蛋白,其中前20 aa为信号肽。CaMR的氨基酸序列和分子结构与其他物种高度相似:胞外一个富含半胱氨酸的结构域(CRD)、一个纤连蛋白II型结构域(FNIID)及8个串连的C型凝集素样结构域(CTLDs),一个跨膜区和一个很短的胞内区。氨基酸同源性和进化分析显示,CaMR与草鱼、团头鲂、斑马鱼等鲤科鱼类的进化关系较近,与草鱼MR的同源性最高(82.4%)。通过qPCR检测到头肾、脾、心脏、肌肉等10种组织中均有表达,其中头肾表达量最高;嗜水气单胞菌感染后,头肾、脾和心脏MR基因的相对表达量均呈先升后降的趋势,而肠道则呈下降趋势,肌肉的表达量变化不显著。本研究为进一步揭示CaMR在免疫反应中的作用机制及其在淇河鲫疾病防治中的应用奠定了基础。     

Metabolic enzyme activities in larvae of the African catfish,Clarias gariepinus: changes in relation to age and nutrition

The influence of ontogeny and nutrition on metabolic enzyme activities in larvae of the African catfish, Clarias gariepinus, was studied. After start of exogenous feeding, the larvae were reared for 10 days under three different nutritional conditions: Artemia nauplii, a dry starter diet, and starvation. The live feed gave the best growth (96 mg within 10 days) whereas the dry diet resulted in low growth (33 mg). This growth difference was reflected in larval RNA and DNA concentrations, but not in the levels of soluble protein. Enzymes representing the following aspects of metabolism have been analysed: NADPH generation (G6PDH, ME), glycolysis (PFK, PK), gluconeogenesis (FDPase), amino acid catabolism (GOT, GPT) and oxidative catabolism (CS). All enzymes were present from the start of exogenous feeding onwards, but their maximum specific activities displayed different developmental patterns. In catfish larvae fed on Artemia, G6PDH and ME activities steadily increased with age and weight of the larvae. CS levels remained, after an immediate enhancement upon onset of exogenous feeding, on a rather stable plateau. The amino acid-degrading enzymes GOT and GPT showed maximum levels at days 3–5 of feeding or at a body weight of 10–20 mg, but decreased thereafter. Activities of PFK, PK and FDPase showed low initial levels, and increased significantly with age and size. Based on the ontogenetic patterns of metabolic enzymes, in C. gariepinus larvae an early and a late developmental phase can be distinguished. During the early phase, the glycolytic and gluconeogenetic capacities are low, whereas they are enforced during the later phase. The oxidative capacity is high both during the early and the late phase. The metabolic changes in catfish development coincide with other major ontogenetic events, e.g., alterations of muscle organization, gill morphology, respiration and stomach structure and function. Rearing catfish larvae on a dry diet instead of Artemia partly altered the developmental pattern described: The ontogenetic elevation of CS, PFK and FDPase was delayed and the early peak in GOT and GPT activities was not realized. Particularly during the early developmental phase, the enzyme behaviour of the larvae fed on dry food was similar to that of starved larvae.Abbreviations CS citrate synthase - FDPase fructose-1,6-diphosphatase - GOT glutamate oxaloacetate transaminase - GPT glutamate pyruvate transaminase - G6PDH glucose-6-phosphate dehydrogenase - ME malic enzyme - PFK phosphofructokinase - PK pyruvate kinase     

Seasonal morphological and biochemical changes of Dahlgren cells implies a potential role of the caudal neurosecretory system (CNSS) in the reproduction cycle of teleostean fish

The purpose of this mini-review is to summarize recent research on the seasonal morphological and biochemical changes of Dahlgren cells in the caudal neurosecretory system (CNSS) of the freshwater teleosts carp Carassius auratus. The quantitative proof for these seasonal changes in the morphology and biochemistry of Dahlgren cells reflects the relationship between the CNSS and the reproduction cycle of fish and implies that the CNSS is probably involved in the reproduction process of fish.     

黄颡鱼促黄体激素受体基因克隆及在雌鱼繁殖周期中的表达

通过简并引物扩增及SmartTM Race技术,首次克隆了黄颡鱼促黄体激素受体(LHR)基因cDNA全长序列.该基因全长2 524 bp,编码701aa,含有属于糖蛋白激素受体(GpHR)家族的典型跨膜螺旋结构区域(TM helix).9个富含亮氨酸的重复性序列(LRRs);4个潜在的N-端糖基化位点:29NFTC,82 NVSR,203 NGSR,548NLTV;24个Ser,6个Thr和5个Tyr磷酸化位点.同时400S为潜在的PKC位点.通过RT-PCR分析组织表达,卵巢繁殖周期中卵巢和脑的表达水平并结合血浆中E2含量的变化,发现LHR在卵巢中大量表达,其次是脑、肾脏、心脏、肝脏和肠存在少量或微量的表达;在卵巢繁殖周期中,卵巢LHR表达从Ⅲ期-V期处于较高水平,V期达到最高峰,随后下降到最低值;而脑的表达高峰出现在Ⅳ期,与血浆中E2变化相一致.推测卵巢和脑中LHR基因参与卵黄的生成,调控卵母细胞的成熟和排卵.