Effects of dietary carbohydrate/lipid ratios on growth performance,body composition and glucose metabolism of fingerling blunt snout bream Megalobrama amblycephala

This study aimed to investigate the optimum dietary carbohydrate/lipid (CHO/L) ratio for fingerling blunt snout bream Megalobrama amblycephala (average initial weight: 6.61 ± 0.03 g). Six isonitrogenous and isoenergetic diets were formulated to contain various CHO/L ratios ranging from 1.62 to 24.20. Each diet was tested in four replicates for 10 weeks. Specific growth rate (SGR), feed conversion ratio and nitrogen and energy retention all improved significantly (P < 0.05) as dietary CHO/L ratios decreased from 24.20 to 5.64 but showed little difference (P > 0.05) as dietary CHO/L ratios ranged from 2.45 to 5.64. Hepatosomatic index increased significantly (P < 0.05) as dietary CHO/L ratios increased, whereas intraperitoneal fat ratio showed an opposite trend (P < 0.05). Opposite to moisture content, lipid content of whole body and carcass all increased significantly (P < 0.05) as dietary CHO/L ratios decreased. Liver lipid content showed little difference (P > 0.05) among all the treatments, while liver glycogen content increased significantly (P < 0.05) with increasing CHO/L ratios. High dietary carbohydrate enhanced the activities of liver hexokinase, pyruvate kinase and glucose‐6‐phosphate dehydrogenase but did not induce hyperglycaemia. Based on the second‐order polynomial regression analysis of SGR, the optimal dietary carbohydrate and lipid contents for fingerling blunt snout bream were 291.7 and 81.4 g kg⁻¹, respectively, with a corresponding dietary CHO/L ratio of 3.58.     

Linear models to predict the digestible lipid content of fish diets

Values for the digestible contents of nutrients in diets and feed ingredients are of utmost importance in nutritional strategies for fish. Prediction from dietary composition would eliminate lengthy, tedious and demanding digestibility experiments with fish. Apparent digestible lipid (DL) content [range 7.6–353.4 g kg⁻¹ dry matter (DM)] in compound diets can be predicted with high accuracy ( n  = 610; studies =127; fish species = 34; R ² = 0.9515; RMSE = 16.9504) from dietary crude lipid (CL) content (range 12.0–388.7 g kg⁻¹ DM) by the linear regression equation DL =−2.7303 + 0.9123 CL. Validation of this equation against 65 values from 15 independent studies presented R ² and mean prediction error (MPE) values of 0.9947 and 0.0671, respectively. The corresponding equation for 37 individual feed ingredients evaluated in 24 studies with 18 fish species ( n  = 180) was found to be DL = −1.5824 + 0.8654 CL ( R ² = 0.9717; RMSE = 8.3765). However, validation of the latter is currently hampered by a lack of independent values.     

Effect of a seaweed mixture on serum lipid level and platelet aggregation in rats

ABSTRACT:   To assess the effect of a seaweed mixture on lipid levels in serum as well as platelet aggregation in rats, Eisenia bicyclis ('Arame'), Hizikia fusiformis ('Hijiki') and Undaria pinnatifida sporophylls ('Mekabu'), all brown seaweeds, and Porphyra yezoensis ('Susabinori'), a red seaweed, were powdered and mixed in a ratio of 45:30:20:5 (w/w). When rats were fed a cholesterol-rich diet containing this mixture of seaweeds (9–10% w/w) for 28 days, serum total cholesterol, LDL-cholesterol, free cholesterol, and triglyceride levels declined significantly to 49.7%, 48.1%, 49.0% and 74.8%, respectively, of those of the control. Serum HDL-cholesterol, however, was unchanged. Though activated partial thromboplatin time, prothrombin time, antithrombin III activity, and fibrinogen levels in plasma were unchanged, the maximal ADP- and collagen-induced platelet aggregation decreased significantly to 89.0% and 85.5% control levels, respectively. These results indicate that this mixture of E. bicyclis , H. fusiformis , U. pinnatifida sporophylls, and P. yezoensis , is useful for the prevention of hyperlipidemia and thrombosis in rats.     

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     

铅胁迫对大叶黄杨铅积累量及叶片生理特性的影响

采用盆栽方法研究了大叶黄杨(Euonymusjaponicus)在单一铅胁迫下对各器官铅积累及叶片生理指标的影响.结果表明:随着土壤铅浓度的增高,大叶黄杨的生物量、叶片叶绿素含量和叶绿素a/b值逐渐下降;植物各器官铅积累量逐渐增加.铅在大叶黄杨体内分布的规律是:根>茎>叶;超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性在低浓度范围内呈现上升的趋势,表现出一定的适应能力;在高浓度处理水平时,3种酶活性呈现下降趋势,并都低于对照;叶片膜透性则表现出随胁迫强度的增加而上升.从生理指标反映出:在铅浓度300 mg/kg范围胁迫时,大叶黄杨具有较强的适应能力.     

Effect of hypo- and hyper-saline conditions on osmolarity and fatty acid composition of juvenile shrimp Litopenaeus vannamei (Boone, 1931) fed low- and high-HUFA diets

Litopenaeus vannamei (Boone) grown in ponds are exposed to salinities of less than 5 g L^?1 during inland shrimp culture or to more than 40 g L^?1 from evaporation and reduced water exchange in dry, hot climates. However, dietary requirements for shrimp grown in low or high salinities are not well defined, particularly for fatty acids. Feeding shrimp postlarvae with highly unsaturated fatty acids (HUFA) enhances tolerance to acute exposure to low salinity, as a result of better nutritional status, or/and specific effects of HUFA on membrane function and osmoregulation mechanisms. This study analysed the effect of HUFA supplementation (3% vs. 34%) on L. vannamei juveniles reared for 21 days at low (5 g L^?1), medium (30 g L^?1) and high salinities (50 g L^?1). Juveniles grown at 5 g L^?1 had lower survival compared with controls (30 g L^?1) or shrimp grown at 50 g L^?1, but no significant effect on survival was observed as a result of HUFA enrichment. In contrast, growth was significantly lower for shrimp grown at 50 g L^?1, but this effect was compensated by the HUFA‐enriched diet. Osmotic pressure in haemolymph was affected by salinity, but not by HUFA enrichment. Shrimp fed HUFA‐enriched diets had significantly higher levels of eicosapentaenoic acid and docosahexaenoic acid in hepatopancreas and gills. These results demonstrate that growth at high salinities is enhanced with diets containing high HUFA levels, but that HUFA‐enriched diets have no effect on shrimp reared at low salinities.     

刺参血系统的超微结构观察与功能探讨

在光学显微镜、扫描电镜和透射电镜下观察刺参血系统的组织细胞结构，探讨血系统的生理功能，结果显示：(1)刺参的血系统由复杂的管网构成，排列紧密的血管上皮细胞和上皮下连续成层的基膜，构成血系统中连续而封闭的管状结构，管腔中充满血液，血系统的管网承担了血管输送血液的功能，并通过与呼吸树的连接完成血液的气体交换。(2)血管上皮细胞游离面的细胞膜、微绒毛和吞饮小泡呈酸性磷酸酶阳性反应，表明细胞具有吸收功能。血管上皮细胞内的小泡在管壁内外的物质运输中起作用。由单层细胞和基膜构成的血管壁是血液与体腔液进行物质交换的场所。(3)血管上皮细胞富含内质网、脂滴、线粒体及分泌自噬体，具有类固醇激素分泌细胞的超微结构特点，可能与刺参体内的固醇合成有关。     

Effects of dietary vitamin E level on growth and tissue lipid peroxidation of soft-shelled turtle, Pelodiscus sinensis (Wiegmann)

A feeding trial was conducted to determine the effect of dietary vitamin E supplementation on growth, liver lipid peroxidation and liver and muscle vitamin E level of soft‐shelled turtle, Pelodiscus sinensis. Eight experimental diets analysed to contain 0–457 IU vitamin E kg^?1 were fed to juvenile soft‐shelled turtle of 4.8 g initial body weight for 12 weeks. Weight gain (WG) of the turtles fed the diet containing no vitamin E was significantly lower than those fed diets containing 83–457 IU vitamin E kg^?1 (P<0.05). Feed conversion ratio and protein efficiency ratio showed similar trends to that of WG. No significant difference (P>0.05) was found in whole‐body composition among turtles fed the different diets. Dietary vitamin E requirement using WG as the response and estimated using the broken‐line regression model is approximately 88 IU kg^?1. Liver and muscle vitamin E content increased when dietary vitamin E level increased. Ascorbate‐induced lipid peroxidation in liver tissue of turtles fed diets containing 0 and 17 IU vitamin E kg^?1 was significantly (P<0.05) greater than those fed diets containing high vitamin E (≥35 IU kg^?1).     

Effect of dietary carbohydrate-to-lipid ratios on growth, lipid deposition and metabolic hepatic enzymes in juvenile Senegalese sole (Solea senegalensis, Kaup)

A study was undertaken to determine the effect of various dietary carbohydrate‐to‐lipid ratios on growth performance, whole‐body composition and tissue lipid content in Senegalese sole (Solea senegalensis) juveniles. Data on the dietary regulation of key hepatic enzymes of the lipogenic and glycolytic pathways (glucose‐6‐phosphate dehydrogenase, G6PD; malic enzyme, ME; fatty acid synthetase, FAS; pyruvate kinase, PK and glucokinase, GK) were also generated. Four isonitrogenous (crude protein: 52% dry matter (DM)) diets were formulated to contain one of two lipid levels (11% and 21% DM). Within each dietary lipid level, the nature of the carbohydrate fraction (raw or extruded peas) was varied. Triplicate groups of 54 sole (initial body weight: 23.6±1.2 g) were grown in recirculated seawater over 67 days. Fish were fed using automated feeders. At the end of the study, whole‐body, liver, viscera and muscle samples were withdrawn for analyses. During the experimental period, the mean fish weight about doubled in all treatments. No significant differences were found in growth performance (ranging from 1.1% to 1.4% body weight day^?1) among dietary treatments. High‐fat diets increased whole‐body fat content. Similarly, daily fat gain ranged from 0.54 to 0.78 g kg^?1 day^?1 and highest values were found in fish fed high‐lipid diets. Dietary treatments also affected tissue lipid content (liver, viscera and muscle), with highest values in fish fed high‐fat diets. The nature of dietary carbohydrates had little influence on performance criteria, but affected tissue lipid deposition. The activities of G6PD, ME and FAS were depressed by elevated levels of dietary lipid, confirming the inhibitory effect of dietary fats on lipid biosynthesis. At both dietary lipid levels, ME and FAS activities were little affected by dietary carbohydrate. Activities of PK and GK were not affected by the starch level of the diets. In Senegalese sole juveniles, the lipogenic pathway is more susceptible to modulation by dietary means (particularly through lipid intake) than the glycolytic pathway.     

遮荫下2种热带树苗叶片光合特性和抗氧化酶系统对自然降温的响应

选取 2种遮荫条件下 (8%、2 5 %全光照 )西双版纳地区热带雨林上层树种滇南红厚壳和中层树种玉蕊的幼苗 ,测定了雨季末自然降温过程中 2种植物叶片光合特性、抗氧化酶 (SOD、CAT、APX)活性、丙二醛 (MDA)含量的变化。研究结果表明 :低温使 2种植物单位面积叶绿素含量和净光合速率明显下降 ,生长在中等光强下的幼苗比低光强下的幼苗下降的比率大 ,滇南红厚壳比玉蕊下降的比率大。在降温初期 ,即从 10月到 12月初 ,2种光强下 2种植物SOD和APX活性上升 ,CAT活性出现波动 ,黎明光化学效率和MDA含量基本没有变化 ,光合机构没有受到氧化破坏。 12月末 ,中等光强下滇南红厚壳黎明光化学效率降低 ,SOD和APX活性有所下降 ,MDA含量显著上升 ;而低光强下的滇南红厚壳和 2种光强下玉蕊SOD和APX活性仍在上升 ,MDA含量变化较小。这表明 ,2种光强下 2种热带树苗是以不同的方式响应自然降温 ,低温对中等光强下的植物比低光强下的影响大 ,上层树种滇南红厚壳受到的影响比中层树种玉蕊大。同时 ,根据降温过程中抗氧化酶活性和MDA含量的变化 ,大致可将西双版纳热带雨林幼苗对低温的响应分为 2个阶段 ,即第 1阶段为低温适应阶段 ,抗氧化酶活性上升 ,光合机构没有受到明显的氧化破坏 ;第 2阶段 ,中等光强下滇南红厚壳抗氧化酶