牙鲆胚胎玻璃化冷冻及解冻过程中的温度因子与玻璃化率

为避免鱼类胚胎玻璃化冷冻过程中脱玻璃化现象发生,本文对冷冻过程中温度变化及解冻方法进行了研究.在室温13℃下,将含有玻璃化液FVS3的麦管直接投入到-196℃的液氮中,麦管内温度达到-196℃时,所用的时间为15.46±1.38s,降温速率为800℃/min.对玻璃化麦管在35～45℃水浴中解冻时间进行测定.结果显示,解冻所需时间在6.17～7.94s之间,麦管从-196℃升高到13℃的解冻速率为1500～2000℃/min.当水浴温度从37℃逐步升高到72℃时,对水浴表面蒸气温度的变化进行了测定,相应水温下蒸气温度从25.47℃升高到38.6℃.在麦管中加入不同浓度的玻璃化液FVS1、FVS2、FVS3和FVS4进行玻璃化冷冻,然后将麦管分别在37℃水浴中和28.6℃的蒸气中解冻时玻璃化率进行研究.结果显示,在蒸气中解冻时的玻璃化率明显高于水浴中解冻;麦管玻璃化率在水浴中解冻时不稳定,在蒸气中解冻时表现稳定,玻璃化率随着玻璃化液浓度的升高有逐渐升高的趋势.对含有牙鲆胚胎的玻璃化冷冻麦管分别在37℃水浴和28.6℃蒸气中解冻,结果表明,蒸气中解冻时的玻璃化率同样明显高于水浴中解冻.     

快速冷冻对大黄鱼、鲳鱼肌原纤维超微结构的影响

以新鲜大黄鱼、鲳鱼为对照,研究了-18℃普通冷冻、-25℃和-35℃快速冷冻及不同冻藏处理时间对这两种海鱼肌原纤维超微结构的影响。结果表明:无论是普通冷冻还是快速冷冻,随着冻藏时间的延长,两种海鱼的肌原纤维结构均呈现不同程度恶化,快速冷冻的处理效果明显优于普通冷冻。-18℃普通冷冻并冻藏30 d时,大黄鱼肌原纤维断裂扭曲,纤维相互分离,间隙增大,90 d时M带严重损坏;-25℃快速冷冻并于-30℃冻藏90 d时,大黄鱼肌节结构尚完整,但180 d时M带受损严重;-35℃快速冷冻并于-30℃冻藏180 d时,大黄鱼肌原纤维M带仅局部被破坏,明暗带分布尚清晰。两种鱼相比较,在相同冷冻和冻藏处理条件下,鲳鱼的肌原纤维结构损坏较大黄鱼严重,-35℃快速冷冻并于-30℃冻藏90 d时,鲳鱼肌原纤维M带结构已被破坏;150 d时,所有冷冻处理的鲳鱼肌原纤维的肌节条带均已模糊不清。     

反复冷冻-解冻对鲢品质的影响

研究鲢(Hypophthalmichthys molitrix)在冷冻-解冻过程中的品质变化规律。鲢于–18℃条件下冻藏10 d,流水解冻后再贮藏于–18℃条件下,5 d后解冻,共反复冷冻-解冻5次。在解冻1、3、5次后随机取3条鲢测定其解冻损失、蒸煮损失、硬度、咀嚼性、恢复性、硫代巴比妥酸(TBA)值、L*值、b*值、盐溶性蛋白(SSP)含量、Ca2+-ATP酶活性、总巯基含量、表面疏水性和感官值等指标,评价反复冷冻-解冻对鲢品质的影响。结果表明,在第1次冷冻-解冻时,硬度、咀嚼性、恢复性、盐溶性蛋白(SSP)含量和Ca2+-ATP酶活性与鲢初始值相比显著降低(P<0.05),b*值和表面疏水性显著升高(P<0.05);解冻损失、L*值和TBA值在第3次冷冻-解冻时显著上升(P<0.05);总巯基含量在第5次冷冻-解冻时显著下降(P<0.05);而蒸煮损失在冷冻-解冻过程中没有显著变化(P>0.05);感官值在第5次冷冻-解冻时为47,感官品质已不可接受。各指标变化表明,鲢品质会随着反复冷冻-解冻次数增加而下降,在运输、贮藏和销售过程中要防止温度波动,避免反复冻融对鲢品质造成不利影响。     

珍珠龙精子超低温保存的初步研究

为研究适合珍珠龙精子的短期超低温保存方法,比较了不同保存液、保护剂、降温方式、解冻方式对珍珠龙(Scleropages jardini)精液超低温保存后精子活力的影响,初步解释了经超低温短期保存后珍珠龙精子活力明显较鲜精低的原因.结果显示:采用Ringer's液作为保存液,以浓度为16％的二甲亚砜作为保护剂,选取五步法超低温冷冻保存精子[精子缓慢降温至-150℃→液氮面上3 cm(约-170℃),停留4min→液氮面(约-190℃),停留1 min→液氮],40℃水浴解冻,可取得最好的冻后活力,解冻后精子的活力为(36.7±4.1)％.     

利用小型低值鱼生产几种方便食品的加工工艺

一、美味鱼酥 １．原料：新鲜或块冻的梅童鱼为原料。２工艺流程： 预处理（去头、内脏）→洗净→浸泡→沥水→调味腌渍→干燥→二次调味→称量包装→真空封口→高温杀菌→冷却→检查擦干→套外包装袋→装箱 ３．操作要点： （ｌ）冷冻鱼解冻：气温＜２０℃时，隔天出库，平摊于盘中，自然解冻。气温＞２０℃时，当天出库，采用流水解冻。 （２）原料鱼预处理：将鲜鱼或解冻鱼摘除鱼头、内脏，以清水洗净。 （３）浸泡：将以上洗净的鱼沥干称重后投入水槽中，加入３－４倍的清水，浸泡２０ｍｉｎ，浸除血渍、污物。 （４）调味：沥水完毕的…     

玻璃化液对鲢鱼胚胎成活的影响

本文通过５种不同抗冻剂，５５组不同浓度组合，筛选出１１组冷冻时能形成玻璃化最低浓度的抗冻剂和１０组解冻时能形成玻璃化的抗冻剂。并对１１组玻璃化液在低温下的一些物理特性进行了测定。不同组合的玻璃化液其冰点和融点各不相同，最高冰点在－１９．５℃，最低达－３９℃。融点最高－４０℃，最低－９０℃。鳝鱼胚胎在５－ｅ中心跳时间最长达３０分钟，在１０－ｃ、５－ｅ中换１７号解冻液后存活最多，达８９．０％以上。     

介绍六种水产冷冻调理食品加工工艺

调理食品作为一种新兴方便食品,它具有卫生、优质、方便、多样、营养丰富等特点,在国内外市场上很受欢迎。冷冻调理食品业发展较快的有西欧、美国、日本等。日本是亚洲地区冷冻食品销量最大的国家,冷冻调理食品的消费占全部冷冻食品消费的50%以上,且有逐年递增的趋势,发展势态强劲。冷冻调理食品依其调理状态分为三种:1.冷冻前未加热处理过的冷冻调理食品;2.冷冻前已加热处理过的冷冻调理食品;3.不需加热即可食用的冷冻调理食品。一、鱼糜牡蛎饼加工工艺1、原料:采用冷冻鱼糜和新鲜活牡蛎为原料。2、原料处理:冷冻鱼糜采用搅拌解冻法,即将冷…     

猪卵母细胞玻璃化冷冻的研究

用2种不同的配方分别对猪GV期和MⅡ期卵母细胞进行玻璃化冷冻研究,并用孤雌激活的方法检测冷冻-解冻对卵母细胞再发育能力的影响。结果如下:(1)以PBS和TCM1992种配方为冷冻基础液,分别对猪GV期和MⅡ期卵母细胞进行玻璃化冷冻,解冻后对细胞进行体外成熟观察、形态学观察、染色观察,差异不显著;(2)经冷冻-解冻,猪GV期卵母细胞比MⅡ期卵母细胞成活率高、孤雌激活效果好;(3)经冷冻-解冻,猪卵母细胞再发育能力明显低于新鲜细胞,冷冻过程对卵母细胞的发育能力造成了明显的影响。     

大黄鱼酶解脱脂工艺研究

分别用碱性脂肪酶A、碱性脂肪酶B、复合碱性脂肪酶A B对大黄鱼鱼片进行酶水解脱脂的工艺和效果进行比较研究。试验结果表明:复合碱性脂肪酶脱脂效果明显优于单一碱性脂肪酶的脱脂效果,当复合碱性脂肪酶酶液浓度A B=(30 20)U·mL-1,酶解pH值8 9,脱脂时间为50min,脱脂温度为(21±1)℃时,其脱脂率可以达到最高70 28%,残脂率为7 50%。     

Y_(241)型交直流稳压电源逆变器保护电路的小改革

Y_(241)型交直流稳压电源,在群众渔业中已被广泛使用。该电源既可对15W电台中的20GNY3型蓄电池组充电,也可以直接对电台供电,它不仅有过电流、过电压保护作用,还有输入直流电压极性接保护电路的作用。 Y_(241)型电源的交流输入为220V。直流输入为12V。其逆变器部分见图1(其它部分从略)。由图     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

Evaluation of a Fast Method Based on the Presence of Two Restriction Sites in the Mitochondrial ND5 (mt ND5) Gene for the Identification of Scomber Species

The purpose of this work was to evaluate the suitability of a method based on the presence of two restriction sites (for Hae III and Hindf I) in the mitochondrial NADH dehydrogenase subunit 5 (mt ND5) gene to identify Scomber species. The evaluation was performed on 144 reference and market samples by sequencing of the entire 505-bp fragment of the mt ND5 gene and of a 464-bp fragment of the Kocher fragment of the cytochrome b gene (mt Cytb). Sequence analysis of any of the two fragments allows the identification of each of the four Scomber species, but S. japonicus and S. colias had the same restriction sites at the ND5 amplicon and would not have been differentiated by this analysis. Similarly, loss of the Hae III site in some S. scombrus individuals would have misidentified them as not being Scomber. All the market products were correctly labeled except one acquired in Spain labeled as originating in the Atlantic and containing S. japonicus.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).     

The optimal dietary protein level of juvenile silver sillago Sillago sihama at three dietary lipid levels

A 5 × 3 factorial growth trial was conducted to evaluate optimal dietary protein and lipid levels (dietary protein level, DP; dietary lipid level, DL) for juvenile Sillago sihama (S. sihama) (2.0 ± 0.02 g, initial weight). Fish were fed 15 diets containing 5 DPs (350, 400, 450, 500 and 550 g/kg) and 3 DLs (60, 90 and 120 g/kg) for 8 weeks. The interaction between proteins and lipids significantly influenced the feed conversion ratio, condition factor, body composition, antioxidant indices and lipase activity (p < .05). DP 450 g/kg showed the highest average final body weight. DPs 500 and 550 g/kg significantly decreased the protein efficiency ratio (p < .05). DL 120 g/kg showed the highest percentage weight gain. The low feed conversion ratio was found in diets P45L12, P55L9 and P55L12. Diet P45L12 showed high superoxide dismutase activities. DP 450 g/kg showed the lowest average malondialdehyde content. Lipase activity was increased by increasing DP (p < .05) with a fall at DP 550 g/kg. Under the present experimental conditions, the optimal DP for S. sihama was 450 g/kg under the DL 120 g/kg.     

Vitamin D3 and the renal handling of phosphate in American eels

Cholecalciferol (Vitamin D₃) increased plasma inorganic phosphate concentration in American eels,Anguilla rostrata, in a dose-dependent fashion. This response was more marked in phosphate loaded fish. In control as well as phosphate loaded eels the hyperphosphatemic response to D₃ was associated with a sharp reduction in renal phosphate clearance relative to¹⁴C-polyethelene glycol (PEG) clearance. Glomerular filtration and urine flow rates were not affected by D₃. As renal phosphate clearance, even in phosphate loaded eels, never significantly exceeded that of PEG, it is suggested that D₃ reduced the relative clearance rate of phosphate by increasing renal phosphate reabsorption rather than by reducing the tubular secretion of phosphate.