Digesta viscosity, nutrient digestibility and organ weights in African catfish (Clarias gariepinus) fed diets supplemented with different levels of a soluble non-starch polysaccharide

The objective of the present study was to investigate if dietary soluble non‐starch polysaccharides (NSP) increase digesta viscosity, reduce nutrient digestibility and increase organ weights in African catfish. The fish (mean weight 80 g) were fed diets supplemented with the soluble NSP guar gum at three levels, 0 g kg^?1 (GG0), 40 g kg^?1 (GG4) and 80 g kg^?1 (GG8). Guar gum inclusion significantly increased digesta viscosity in the proximal (GG0: 1.7 centipoise or cP; GG4: 84.9 cP; GG8: 98.3 cP) and distal (GG0: 1.9 cP; GG4: 109.8 cP; GG8: 66.4 cP) intestine. Apparent digestibility coefficients (ADC) were significantly lower for the GG8 diet than the GG0 diet (dry matter: 52% versus 69%; protein: 77% versus 90%; ash: 41% versus 54%; energy: 60% versus 77%). The ADC of dry matter and energy were significantly lower for the GG4 diet than the GG0 diet. The relative growth rate of metabolic weight (14.5–15.4 g kg^?0.8 day^?1) and feed conversion ratio (0.8) did not differ between diets. Fish fed the GG8 diet had a significantly higher somatic stomach index than GG0 fish (0.71% versus 0.65% body weight). The intestinal somatic index tended to increase with increasing guar gum supplementation (GG0: 1.08%; GG4: 1.23%; GG8: 1.59%). In conclusion, high digesta viscosities in the guar gum fed fish may explain the observed reduced nutrient digestibilities and increases in digestive organ weights.     

斑点叉尾趋化因子SCYA126基因及其可变剪接

通过探针杂交筛选斑点叉尾(Ictalurus punctatus)BAC基因组文库,利用引物步移的方法对阳性克隆BAC047 K12进行序列测定,得到2 815 bp的SCYA126基因组序列。序列分析表明,SCYA126基因由2个外显子和1个内含子组成;外显子拼接的序列与SCYA126cDNA序列完全一致,编码92个氨基酸,在N端含有2个相邻的半胱氨酸(CC)和2个不相邻的半胱氨酸,为典型的CC趋化因子亚家族成员;其上游调控序列包含TATA框启动子序列和一些与免疫相关的转录因子结合位点。另外,根据与GenBank接收号为BM029630的EST序列的比较分析,发现SCYA126基因组中的内含子没有被剪接,导致翻译后可能产生N端部分缺失的SCYA126蛋白。在胰脏和肝脏中确认了高表达的包含内含子的mRNA的存在,而且其表达量要明显高于正常剪接的SCYA126mRNA。[中国水产科学,2007,14(1):1-7]     

Pubertal development of male African catfish,Clarias gariepinus. In vitro steroidogenesis by testis and interrenal tissue and plasma levels of sexual steroids

In fish, sex steroids initiate and/or accelerate the maturation of the brain-pituitary-gonad axis. In order to obtain information on the steroid milieu during the pubertal development of male African catfish, we have monitored the conversion of [³H]-pregnenolone and [³H]-androstenedione by testis and [³H]-pregnenolone by interrenal tissue fragmentsin vitro. Pubertal development occurs between two and six months of age. Testicular development proceeds through four main stages that are characterised histologically by the presence of spermatogonia (stage I), spermatogonia and spermatocytes (stage II), spermatogonia, spermatocytes and spermatids (stage III), and all germ cells including spermatozoa (stage IV). 11β-Hydroxyandrostenedione and cortisol were the main products of testes and interrenal tissue, respectively, in all stages of the pubertal development; a change in the steroidogenic pattern was not observed during this period. The interrenal tissue displayed no significant conversion of [³H]-pregnenolone to 11-oxygenated androgens. Blood plasma was analyzed for the presence of five androgens; testosterone, 11β-hydroxytestosterone, 11β-hydroxyandrostenedione, androstenetrione, and 11-ketotestosterone. 11-Ketotestosterone was the quantitatively dominating androgen in the circulation at all stages of development, which was more pronounced in stages III and IV. The obvious differences between thein vitro andin vivo results, namely 11β-hydroxyandrostenedione being the main testicular productvs. 11-ketotestosterone dominating in the blood, may indicate that 11β-hydroxyandrostenedione is converted to 11-ketotestosterone at extratesticular sites.     

Effect of cryoprotectants, extenders and freezing rates on the fertilization rate of frozen striped catfish, Pangasius hypophthalmus (Sauvage), sperm

The effects of four cryoprotectants (methanol, MeOH; dimethyl sulphoxide, DMSO; dimethyl acetamide, DMA; and ethylene glycol, EG), three extenders (calcium‐free Hanks' balanced salt solution, C‐F HBSS, Hanks' balanced salt solution, HBSS and sodium chloride, NaCl) and two different freezing procedures (one‐ and two‐step) on the cryopreservation of striped catfish (Pangasius hypophthalmus (Sauvage)) sperm were investigated. Sperm were frozen using a controlled‐rate freezer in 250 μL straws and stored for 2 weeks in a liquid nitrogen (LN₂) container. They were then airthawed at room temperature, and fertilization, motility and viability were assessed. The highest fertilization rate of 41% (81% of control) was achieved with the combination of 12% DMSO and 0.9% NaCl using a one‐step freezing procedure (10°C min^?1). Also, DMA resulted in a higher fertilization rate (30% or 51% of the control) than MeOH (18% or 38% of the control) or EG (8% or 12% of the control). In addition, the three extenders used did not affect fertilization rates after cryopreservation with each cryoprotectant. There were no significant differences among the three cryoprotectant concentrations and between the one‐ and two‐step freezing procedures. However, fertilization rates of cryopreserved sperm were significantly lower than the controls (P<0.05). The results of this study indicate that high fertilization rates of striped catfish eggs can be achieved using cryopreserved sperm when frozen at 10°C min^?1 in DMSO or DMA with either 0.9% NaCl or C‐F HBSS.     

Intra- and interspecific phenotypic characteristics of fish-pathogenic Edwardsiella ictaluri and E. tarda

Intra‐ and interspecific characteristics of fish‐pathogenic Edwardsiella ictaluri, and E. tarda were determined by numerical analysis of gel electrophoresed protein profiles, fatty acid methyl esters (FAMEs) and immunoblotting. The 18 E. ictaluri isolates revealed a high degree of homogeneity (70% similarity or higher) in their protein profiles and 95% similarity in their FAME, while the nine E. tarda isolates revealed 30% similarity in their protein profiles and 95% similarity in their FAME. Immunoblots probed for antigenic epitopes with goat antiserum produced against E. ictaluri and E. tarda, respectively, revealed that E. ictaluri were more homogeneous compared with the E. tarda isolates. Overall, there was a considerable degree of relatedness between the two species. Our findings suggest that phenotypically E. ictaluri represents a clonal bacterial population structure compared with the less monomorphic E. tarda.     

Inherent variation in growth efficiency of African catfish Clarias gariepinus (Burchell, 1822) juveniles

Understanding the major causes of growth variation is crucial for the success of fish farming since its reduction contributes to maximize production efficiency, reduce food waste and improve water quality. The growth variation observed in aquaculture has been associated with the establishment of social hierarchies. However, some studies suggest that this variation may not be mainly a consequence of social hierarchies but mainly a result of inherent (genetic) differences. This study investigates the magnitude of individual responses, independently of group effects (fish housed individually), in growth efficiency and feeding behaviour of African catfish Clarias gariepinus (Burchell 1822). Despite the low variation in initial body weight (6.5%) and cumulative feed consumption (7.5%) over the experimental period, catfish exhibited high variation in final body weight (18.1%), specific growth rate (17.2%) and feed conversion ratio (27.9%), suggesting that individual variation in growth efficiency is important in determining growth rate. This individual variation may be related with individual differences in protein/fat deposition since faster growing fish deposited more protein and less fat than slower growing fish. Pronounced individual differences in feeding behaviour (reaction towards feed and time spent eating) were also observed and correlated with individual differences in growth efficiency. Fast eaters were the fast growers. We suggest that the growth variation observed in African catfish may be inherent and that the use of grading to increase uniformity should be further investigated.     

Effects of exogenous neurohormone, gonadotropin (GtH) and dopaminergic drugs on the serum GtH content and ovulatory responsiveness of wild catfish, Silurus asotus (Linnaeus, 1758)

Wild female catfish Silurus asotus (Linnaeus, 1758) were injected with domperidone (DOM) alone, [d ‐Ala⁶, Pro⁹ Net]‐luteinizing hormone‐releasing hormone (LHRH‐A) alone once or twice, LHRH‐A plus DOM once or twice simultaneously at 6‐h intervals, LHRH‐A plus carp pituitary extract (CPE) twice simultaneously at 6‐h intervals and LHRH‐A plus human chorionic gonadotropin (HCG) twice simultaneously 6 h apart respectively. The results indicated that injection of LHRH‐A at a dosage of 0.01–0.02 μg g^?1 body weight (BWt) alone induced a low but significant increase in serum gonadotropin (GtH) (P<0.05) and resulted in a very low ovulation rate, while DOM at a dosage of 5 μg g^?1 BWt alone did not induce an increase in the serum GtH levels and ovulation; in contrast, LHRH‐A at a dosage of 0.01 μg g^?1 BWt plus DOM at a dosage of 5 μg g^?1 BWt (termed the Linpe technique) increased the serum GtH (P<0.05) significantly and induced an ovulatory rate of 100%, while LHRH‐A plus CPE or HCG resulted in an increase in the serum GtH (P<0.05) and high ovulatory rate, although the latency period was longer when fish were given LHRH‐A plus HCG or CPE.     

Transwell contact co-culture promotes growth and differentiation of single-dissociated iPSCs

AIM：To investigate the promoting role of Transwell contact co-culture system in the growth and differentiation of single-dissociated induced pluripotent stem cells (iPSCs). METHODS：Bovine corneal endothelial cells (CECs) at passage 1~2 (P1~2) were seeded on the underside of Transwell inserts placed into culture plates and were cultured in 37 ℃ and 5% CO2 for 8 h. Accutase digestion and 40 μm filter process disaggregated colony-aggregated iPSCs into single-dissociated iPSCs, and the cells were seeded on the inside of Transwell inserts with CECs in medium of mTeSR1 for 3 d and then in low-glucose DMEM supplemented with 10% FBS for 2 weeks. The characteristics and differentiation markers were evaluated by real-time fluorescence quantitative polymerase chain reaction (qPCR), immunofluorescence staining, live & dead cell staining and alkaline phosphatase (ALP) staining. The group of iPSCs cultured in conventional medium was used as control group 1. The group of single-dissociated iPSCs co-cultured with CECs was set as experimental group, while single-dissociated iPSCs without co-culture were as control group 2. RESULTS：The bovine CECs showed typical hexagonal cobblestone shape. iPSCs showed colony-like growth, while became single-dissociated cells after Transwell contact co-culture with bovine CECs for 3 d. The single-dissociated iPSCs positively expressed the undifferentiated markers, Nanog and Oct4. The mRNA expression levels of Nanog, Oct4 and Sox2 between experimental group and control group 1 were both positive and had no statistical significance difference (P>0.05). The dead cells in experimental group decreased significantly, and there was statistically significant difference compared to control group 2 (P<0.01). After 14 d of induced differentiation co-culture, the single-dissociated iPSCs showed rather uniform polygonal morphology, increased dimension and no obvious colony existence. Negative ALP staining, positive immunofluorescence staining for ZO-1, AQP1 and CD31, and negative for CD34 and CD133 were also observed. The results of qPCR showed that the mRNA expression of Oct4, Nanog and Sox2 significantly decreased, and had statistically significant difference compared with control group 1 (P<0.01). CONCLUSION：When co-cultured with bovine CECs, iPSCs morphologically changed to endothelial-like cells and expressed some markers of CECs. Transwell contact co-culture system not only enhances the growth of single-dissociated iPSCs, but also promotes their differentiation.     

酵母免疫多糖对受免斑点叉尾免疫应答的增强作用

在饲料中添加定量的酵母免疫多糖,投喂注射接种了福尔马林灭活的嗜水气单胞菌(Aeromonas hydrophila)菌苗的斑点叉尾(Ictalurus punctatus),28 d后通过测定供试鱼的增重量、血清中凝集抗体效价、溶菌酶活性、谷丙转氨酶活性(SGPT)、血清总蛋白含量、白细胞吞噬活性以及活菌攻毒后的免疫保护率(RPS),探讨了酵母免疫多糖对受免斑点叉尾免疫应答的增强作用。结果表明,用添加200.0 mg/(kg.d)酵母免疫多糖的饲料投喂受免斑点叉尾,不仅可以使受免斑点叉尾对灭活嗜水气单胞菌的免疫应答水平提高,增强抵抗嗜水气单胞菌人工感染的能力,而且还具有一定的促进生长和改善肝功能的作用。