鲟鱼GtH放射免疫测定方法的建立及催产前后史氏鲟血清GtH含量的变化

用蛋白质快速液相层析(FPLC)分离俄罗斯鲟鱼脑垂体促性腺激素（GtH）,共获得GtH纯化蛋白4.6mg。用SDS-PAGE变性胶电泳图谱初步分析纯化蛋白,用反相高效液相色谱（rpHPLC）分离出两个亚基,质谱测定α亚基分子量：15603KD,两个β亚基分子量分别为14338KD和14694KD。制备了鲟鱼GtH的兔抗血清多克隆抗体,采用氯胺T法用125I标记抗原,用羊抗兔γ球蛋白做二抗,建立鲟鱼GtH的放射免疫测定方法。测定了催产前后不同时间史氏鲟血清中GtH含量的变化,统计分析表明成功排卵的雌鱼比未排卵和阴性对照组在催产后12小时和16小时GTH分泌量升高显著,最高达到234ng/ml;催产效应时间与催产后血清中GtH的含量紧密相关。     

促黄体素释放激素和多巴胺拮抗物对鲇促性腺激素释放的作用

以珠江流域鲇为研究对象，分别在性腺发育早期、性腺发育晚期、性腺发育成熟与产卵前期、性腺退化期注射促黄体素释放激素类似物和多巴胺D2受体拮抗物，处理后6h、12h、24h测定血液中的促性腺激素水平变化。结果表明，在性腺发育的各个时期，促黄体素释放激素类似物和多巴胺D2受体拮抗物联合注射能显著剂激鲇促性腺激素分泌；鲇脑垂体促性腺激素的分泌受下丘脑释放的促性腺素释放激素和多巴胺的双重调节，多巴胺只能抑制促性腺素释放激素诱导的促性腺激素分泌。在建立鲇人工繁殖技术时，可采用促黄体素释放激素类似物和多巴胺D2受体拮抗物联合注射方法。     

In vivo activity of native GnRHs and their analogues on ovulation in the African catfish, Clarias gariepinus (Burchell)

Four distinct forms of native gonadotropin‐releasing hormone (GnRH) and two newly designed analogues were tested for their in vivo activity to induce ovulation in African catfish. The effects of these peptides on ovulatory parameters were compared with those of carp pituitary and [d ‐Ala⁶, Pro⁹‐NEt]‐mammalian GnRH analogue (mGnRHa), two tested ovulation‐inducing agents in African catfish. Assessment of ovulation was carried out by determining the ovulation ratio and the relative quantity of egg produced. From the results of the experiments, the order of potency of the native GnRH peptides is summarized as chicken GnRH‐II (cGnRH‐II) >salmon GnRH (sGnRH) >mammalian GnRH >chicken GnRH‐I (cGnRH‐I). Chicken GnRH‐II was as potent as mGnRHa while cGnRH‐I was totally ineffective. The new d ‐Orn⁶‐cGnRH‐II and d ‐Orn⁶‐sGnRH with a substitution at position 6 with d ‐isomer residue were as potent as the most extensively used mGnRHa, indicating that the position 6 modification might be more crucial than the substitution at the C‐terminal. On the basis of our results, the potential use and incorporation of cGnRH‐II and sGnRH for the development of more generic spawning induction therapies are suggested.     

Effects of common carp (Cyprinus carpio Linnaeus, 1758) and the African catfish (Clarias gariepinus Burchell, 1822) on growth and reproductive performance of native tilapia Oreochromis shiranus (Boulenger, 1896)

A study was conducted to assess the effects of common carp and the African catfish on growth and reproduction of the native tilapia Oreochromis shiranus in Malawi. The study was done from 1 May to 1 October 2018 at the National Aquaculture Centre (NAC), Zomba. Four triplicated treatments were used: O. shiranus + carp (T1), O. shiranus + catfish (T2), O. shiranus + carp + catfish polyculture (T3) and O. shiranus monoculture (T4). Fish were stocked at uniform density of 0.8 fish/m². Data collection was done once every month. Results showed that O. shiranus mean weight gain (%), specific growth rate (% body weight/day), average daily gain (g fish^?1 day^?1) and condition factor (g/cm³) were highest in T3 and lowest in T1 and T4 treatments. T3 had better water quality regime and higher tilapia biomass than T1 and T4 treatments. Tilapia fry production (no. fry pond^?1 day^?1) was highest in T4 but did not significantly differ (p > .05) between T2 and T3 treatments. It is concluded that the farming of common carp in aquatic ecosystems containing the African catfish may not adversely affect growth and reproduction of O. shiranus and that the polyculture of the African catfish, common carp and tilapia can be adopted to mitigate the potential adverse effects of carp on the environment and improve tilapia growth.     

Effect of Japanese catfish Silurus asotus lipid intake on the lipid components of plasma and liver in adult mice

SUMMARY: The effect of Japanese catfish Silurus asotus lipid intake on the lipid metabolism of male adult mice was determined by measuring the total cholesterol, triacylglycerol, phospholipid, and fatty acid content of plasma and liver. Mice were fed diets containing 5% lard, 5% Thai catfish oil, 5% Japanese catfish lipids, or 5% sardine lipids for 4 weeks. The arachidonic acid (20 : 4n-6) content was highest in the livers of mice fed the Japanese catfish lipid diet and docosahexaenoic acid (22 : 6n-3) content was higher in livers of the Japanese catfish lipid and sardine lipid diet groups than those of the lard and Thai catfish diet groups. However, no significant differences were observed in the 22 : 6n-3 levels in either plasma or liver between the Japanese catfish lipid and sardine lipid diet groups. Although the Japanese catfish lipid diet contains, by far, the highest cholesterol content (143 mg/100 g), there was no significant difference in the plasma cholesterol levels between the lard, Thai catfish oil and Japanese catfish lipid diet groups. However, the liver cholesterol levels of mice fed the Japanese catfish lipid diet were lower than those of mice fed the Thai catfish oil diet, and were similar to those of animals fed a sardine lipid diet. These results suggest that Japanese catfish lipids are suitable components of the diet for ingestion of 20 : 4n-6 and 22 : 6n-3, and for decreasing the cholesterol content of liver.     

Effects of dietary inclusion of various concentrations of Scutellaria baicalensis Georgi extract on growth,body composition,serum chemistry and challenge test of far eastern catfish (Silurus asotus)

Effects of various concentrations of Scutellaria baicalensis (SB) extract in diets on growth, body composition, serum chemistry and disease challenge test of far eastern catfish (Silurus asotus) were determined and compared with a commercially available immune enhancer. Eight experimental diets were prepared in triplicate: control (Con) diet without supplementation of SB and SB‐0.25, SB‐0.5, SB‐1, SB‐2, SB‐3 and SB‐5 diets containing SB at concentrations of 0.25, 0.5, 1, 2, 3 and 5%, respectively. In addition, 0.1% of a commercial immune enhancer product (CP) was also tested. No significant difference in weight gain of fish was found. Feed consumption, feed efficiency ratio and protein retention of fish were not affected by the experimental diets. At the end of the 8‐week feeding trial, 10 externally normal fish from each tank were infected by Vibrio anguillarum or Strepotococcus iniae. Cumulative mortality of fish fed the Con diet was higher than that of fish fed the all other diets in 10 and 25 days after V. anguillarum or S. iniae infection. Results of this study indicated that dietary inclusion of SB extract was effective in improving survival of eastern catfish after V. anguillarum and S. iniae infection, but the various concentrations of SB did not affect fish performance.     

Effects of dietary fermented by‐product of mushroom,Pleurotus ostreatus,as an additive on growth,serological characteristics and nonspecific immune responses in juvenile Amur catfish,Silurus asotus

The present experiment was conducted to evaluate the efficacy of dietary fermented by‐product of mushroom, Pleurotus ostreatus, (FBPM) as an additive in juvenile Amur catfish, Silurus asotus. Five diets were formulated to contain 0%, 0.1%, 0.2%, 0.4% and 0.8% (FBPM₀, FBPM_0.1, FBPM_0.2, FBPM_0.4 and FBPM_0.8 respectively) of FBPM. Fifteen fish averaging 5.7 ± 0.1 g (Mean ± SD) were fed one of the five diets in triplicate groups at 3–4% of wet body weight/day for 8 weeks. Average weight gain (WG) and specific growth rate (SGR) of fish fed FBPM_0.1 and FBPM_0.2 diets were significantly higher than those of fish fed FBPM₀. Hematocrit contents of fish fed FBPM_0.2 were significantly higher than that of fish fed FBPM₀. Lysozyme activity of fish fed FBPM_0.1 was significantly higher than those of fish fed FBPM₀, FBPM_0.2, FBPM_0.4 and FBPM_0.8, while chemiluminescent (CL) responses of fish fed FBPM_0.2 was significantly higher than those of fish fed FBPM₀, FBPM_0.1, FBPM_0.4 and FBPM_0.8. Broken line regression analysis of WG showed that optimum dietary FBPM levels based on WG could be 0.11%. Therefore, these results suggested that the optimum dietary inclusion level of mushroom, Pleurotus ostreatus by‐product fermented using lactobacillus and yeast could be greater than 0.11% but less than 0.2% based on WG and immunological responses in Amur catfish, Silurus asotus without any adverse effects on serological characteristics and body composition.     

Studies on the mode of action of neuropeptide Y (NPY) on maturational gonadotropin (GtH) secretion from perifused rainbow trout pituitary glands

The action of neuropeptide Y (NPY) and gonadotropin releasing hormone (s-GnRH) have been compared on the release of gonadotropin (GtH) by perifused rainbow trout pituitary glands sampled from freshly ovulated female rainbow trout. We have already demonstrated that NPY stimulated the secretion of GtH in vitro. The pituitary responses to s-GnRH and NPY were similar either after repeated 10 min infusions or a one hour prolonged application. In both cases, after the first application, the pituitary did not responded to subsequent secretagogues stimulations, and appeared to be desensitized. The stimulatory action of s-GnRH was partly inhibited (60%) by LH-RH antagonist (DpGlu¹, DPhe², DTrp^3–6) LH-RH, which completely inhibited the response to NPY in perifused pituitary glands sampled from freshly ovulated females, but did not modify the response of pituitaries taken from vitellogenic animals in which NPY induced a transient inhibition of the GtH secretion. These results may indicate that the mode of action of NPY would differ between vitellogenic and matured animals. NPY also stimulated the GtH secretion from perifused pituitary dispersed cells prepared from pituitaries taken from freshly ovulated rainbow trout, indicating that NPY may act directly on the pituitary gonadotropic cells to stimulate GtH secretion.     

Effects of immersion of larvae in oestradiol-17β on feminization, structural changes of gonad and growth performance in the Far Eastern catfish Silurus asotus (Linnaeus)

Immersion of 1‐day‐old Silurus asotus (Linnaeus) larvae in 50, 100 or 200 μg L^?1 oestradiol‐17β for 15 days altered gonad differentiation and gonadal morphology. The survival of the group immersed at the highest dose (200 μg L^?1) was reduced significantly (86%), whereas survival of the groups immersed at the lower doses was as high as that of untreated controls (94%). The sex ratio of the untreated group was close to 1:1 (female–male); however, the incidence of females was significantly higher in groups immersed in doses of 50, 100 and 200 μg L^?1, i.e. 86%, 92% and 99.4%, respectively. Ovarian morphology of feminized individuals was different to that of the controls; the ovary was morphologically rather similar to testis although it contained fully matured oocytes. Morphological changes in genital organs were also noted in fish exposed to oestradiol‐17β the shape and size of genital papilla were intermediate between those of normal male and female. During a 4‐month growth trial after the exposure, the feminized fish showed significantly improved growth performance over normal genetic males (P < 0.05), although the growth was not equal to that of normal genetic females (P < 0.05).     

Intestinal morphology and histology of the striped catfish Pseudoplatystoma fasciatum (Linnaeus, 1766) fed dry diets

This study unveils histological features of the intestinal tract of juvenile striped catfish Pseudoplatystoma fasciatum (Linnaeus, 1776) in three size classes (weight, standard length): I – 36.84 ± 10.19 g, 14.52 ± 1.54 cm; II – 59.03 ± 11.47 g, 17.17 ± 1.06 cm; III – 89.72 ± 18.70 g, 20.79 ± 1.55 cm, respectively. Histological organization of the juvenile speckled catfish intestine bears features common to the carnivorous fish, but the organ presents some convolutions that indicate a certain degree of dietary flexibility, a surprising trend, common only to omnivorous Siluriforms. The architecture of the mucosa of the speckled catfish intestine indicates that the species concentrates digestion and absorption of nutrients in the medium intestine, a common feature among carnivorous Teleosts.     

Induced spawning of hatchery-raised Brazilian catfish, cachara Pseudoplatystoma fasciatum (Linnaeus, 1766)

In the months of January 2001 and 2002, female cachara Pseudoplatystoma fasciatum were selected during their first and second gonadal maturation (2 years and 7 months old and 3 years and 7 months old, respectively) with an of oocyte diameter of 937.5 μm (82.5% with central nuclei and 17.5% with peripheral nuclei). Nine females in first maturation received two doses of carp pituitary extract (CPE), 0.5 mg/kg and 5.0 mg/kg; seven received two doses of human chorionic gonadotropin (hCG), 5 and 10 IU/g; five received doses of 0.5 CPE mg/kg and 5 hCG IU/g (CPE+hCG); and four received 0.9% saline (saline). Nine females from CPE and seven from hCG presented oocytes with the same diameter at the moment of oocyte release (100% with germinal vesicle breakdown and fertilization rate of 53.44±18.3 and 54.81±11.8%; larvae number of 165,330±94.1 and 158,570±20.6, respectively). The five females from CPE+hCG did not respond to the hormonal treatment. The four females from the saline group did not ovulate. In January 2002, 6 of 15 selected females that were going through the second reproductive cycle received CPE (five received hCG and four received saline), showing oocyte diameters similar to the ones in the first maturation. At stripping, CPE females had an oocyte diameter of 1062.5 μm (the hCG females had oocyte diameters ranging from 937.5 to 1125.0 μm; fertilization rates of 56.08±30.9 and 81.90±17.3%; 364,547±244 and 633,129±190, larvae, respectively). The fertilization rates and larvae number were higher in the second gonad maturation, both for CPE and hCG.     

Dietary levamisole modulates the immune response and disease resistance of Asian catfish Clarias batrachus (Linnaeus)

In order to determine the immunomodulatory effect of dietary levamisole in Asian catfish (Clarias batrachus), fish were fed four different diets for 10 days: a formulated diet as control and the same diet supplemented with 50, 150 or 450 mg levamisole kg^?1 feed. The serum bacterial agglutination titre against Aeromonas hydrophila as a measure of specific immunity, serum haemagglutination titre, natural haemolytic complement activity (ACH₅₀), myeloperoxidase and lysozyme activities, total protein level and oxidative radical production by neutrophils as a measure of non‐specific immunity as well as disease resistance against A. hydrophila challenge to separate vaccinated and non‐vaccinated groups were evaluated at 0, 1, 2 and 3 weeks after last administration of levamisole. Levamisole supplement at the lowest level (50 mg kg^?1) significantly enhanced oxidative radical production and serum myeloperoxidase (MPO) content immediately after 10 days of feeding, which reached peak values after 3 and 2 weeks of feeding respectively. Haemolytic complement and haemagglutination titre were significantly enhanced after 3 and 1 weeks respectively. Haemolytic complement activity and MPO activities were significantly raised to 150 mg kg^?1 after 3 and 2 weeks, respectively. At the highest level of levamisole feeding (450 mg kg^?1) significant decreases in superoxide production and complement activity were measured immediately after levamisole feeding, which returned to the normal level after 1 week post‐ feeding. Fish were challenged with a virulent strain of A. hydrophila at 0, 1, 2 and 3 weeks after levamisole feeding, and the cumulative per cent survival was recorded over 10 days. Feeding levamisole at 50, 150 or 450 mg kg^?1 increased per cent survival in vaccinated fish immediately after levamisole feeding, and survival was significantly higher at 450 mg kg^?1. There was no difference in mortality patterns in non‐vaccinated fish. The results support the use of levamisole at 50 mg kg^?1 feed for 10 days as an immunostimulant in Asian catfish farming.     

LHRH-A、DA对施氏鲟脑垂体碎片释放GtH的影响

为了探讨在古老的软骨硬鳞鱼中促性腺激素(GtH)的双重内分泌调节作用,本实验设计用离体灌流的方法研究促黄体素释放激素类似物(LHRH-A)和多巴胺(DA)对施氏鲟脑垂体碎片分泌GtH的影响。引入10、100和1 000 nmol/L 3个浓度的LHRH-A对施氏鲟脑垂体碎片3次脉冲式刺激实验;每次间隔1 h,持续5 min,研究不同剂量LHRH-A对鲟鱼脑垂体释放GtH的作用;用200 nmol/L DA对施氏鲟脑垂体碎片持续2 h灌流后引入5 min的1 000nmol/L LHRH-A刺激实验,研究DA如何抑制鲟鱼脑垂体释放GtH。每5 min收集一管灌流液,用放射免疫测定法(RIA)检测灌流液中GtH的含量。结果显示,低剂量LHRH-A随着刺激引入脑垂体释放GtH出现波浪式的增加,中、高剂量出现释放延后现象。LHRH-A在10nmol/L到1 000 nmol/L范围内对刺激脑垂体释放GtH没有剂量依存关系。DA对施氏鲟脑垂体碎片GtH的分泌没有显著影响,但是可以抑制LHRH-A引起的GtH分泌,即DA不能抑制施氏鲟GtH的基础分泌,而只能抑制LHRH-A诱导的GtH分泌。研究结果证明,在高等硬骨鱼类中存在的双重神经内分泌调节在古老的鲟鱼中也存在。     

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.     

Steroidogenesis by ovaries and testes of the European catfish,the wels (Silurus glanis), in vitro

Testosterone, 3,17-dihydroxy-5-pregnen-20-one, 17,20-dihydroxy-4-pregnen-3-one (17,20P) and 5-pregnane-3,17,20-triol were identified as the major metabolites of [³H] 17-hydroxyprogesterone in ovarian incubations of the European catfish Silurus glanis. 17,20P and the reduced triol were present only in ovaries from fish primed with carp hypophysial homogenate (chh) while testosterone yields were significantly higher in controls than in treated fish. 11-Ketotestosterone, 11-hydroxytestosterone and 17,20-dihydroxy-4-pregnen-3-one (17,20P) were identified as the major metabolites of [³H]17-hydroxyprogesterone in in vitro incubations of testes of a spermiating catfish. There was no significant production of conjugates or other water soluble metabolites by either sex. The stimulation of plasma 17,20P, 17,20P and 11-hydroxytestosterone by chh in primed but not control males suggests that the role of these steroids in spermiation should be further examined.     

日粮中鱼蛋白水解物对黄颡鱼生长、体成分和血清生理指标的影响

为了探讨鱼蛋白水解物对黄颡鱼生产性能的影响,以日本鳀粉为对照,以实用型黄颡鱼饲料配方模式为基础开展实验:1以30.5%鱼粉为对照(FM),在相同配方模式下,以6%鱼蛋白水解物(MPH6)替代20%的鱼粉;2以30.5%鱼粉为对照(FM),在无鱼粉日粮中分别添加3%(FPH3)、6%(FPH6)、12%(FPH12)鱼蛋白水解物;共设计5组等氮等能实验日粮,在池塘网箱中养殖黄颡鱼[初始体质量(30.08±0.35)g]60 d。结果显示:与FM相比,FPH12在SGR、FCR、PRR和FRR方面均无显著差异,而MPH6、FPH3、FPH6组SGR降低了15.45%~24.39%,FCR升高了32.14%~42.86%,MPH6、FPH6差异显著,在PRR和FRR方面,MPH6、FPH3、FPH6组PRR降低了21.11%~27.78%,MPH6组FRR降低了41.51%;全鱼水分、粗蛋白、粗脂肪和灰分各组间差异不显著,FPH3、FPH6、FPH12肌肉多种游离氨基酸水平显著高于FM,其中Thr、Val、His与其在日粮中的水平显著相关;FPH6组HSI显著低于FM,鱼蛋白水解物对CP、VSI、肠体比的影响不显著;血清AST、ALT、HDL、LDL、TP、CHOL、TG无显著差异,FPH3组ALB显著低于FM。研究表明:黄颡鱼日粮中,12%鱼蛋白水解物(干物质)与30.5%鱼粉在生长速度、饲料效率、血清生理指标等方面具有一定的等效性;过高的植物蛋白日粮影响了黄颡鱼的生产性能;饲喂鱼蛋白水解物日粮使黄颡鱼肌肉游离氨基酸的含量升高,特别是呈味氨基酸的含量增加。