稻米籽粒应力松弛特性的研究

稻米籽粒的松弛特性在其生产、质量控制中起着重要作用。本文通过试验获得了稻米籽粒应力松弛特性的力学指标如Maxwell单元个数、松弛模量、松弛时间等,并研究了稻米籽粒应力松弛特性与稻米品质性状的关系,通过多元逐步回归建立了回归方程,可以为稻米加工装置的设计以及稻米的质量评价提供理论依据,为预测机械损伤、提高产品质量、探索新的控制方法和判断依据提供最佳参数。     

盐胁迫对雨生红球藻虾青素累积、虾青素合成相关酶基因表达和抗氧化指标的影响

为探讨盐胁迫对雨生红球藻(Haematococcus pluvialis)虾青素合成的影响与机理,以及雨生红球藻各抗氧化机制之间的关系,本研究采用生化和分子生物学方法研究了不同浓度(0.04 mol/L、0.08 mol/L、0.12 mol/L和0.16 mol/L)和不同时间(3 d、6 d和9 d)的盐(Na Cl)胁迫对雨生红球藻生长、虾青素积累、番茄红素β-环化酶(Lcy)、β-胡萝卜素羟化酶(Crt R-B)和β-胡萝卜素酮化酶(Bkt)基因表达、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和谷胱甘肽过氧化物酶(GSH-Px)的活性以及丙二醛(MDA)含量的影响。结果表明,各胁迫时间的雨生红球藻的密度均随着盐胁迫浓度的增加而不断下降,在盐胁迫的第9天,雨生红球藻的死亡率和孢子比例均随着盐胁迫浓度的增加而不断升高;雨生红球藻虾青素含量、Lcy、Crt R-B和Bkt基因表达量均随着盐胁迫浓度和时间的增加而不断提高;雨生红球藻SOD、CAT和GSH-Px活性以及MDA含量在不同浓度和不同时间的盐胁迫下与对照组(0.00 mol/L Na Cl)相比均升高,且在不同时间的0.12 mol/L Na Cl胁迫下与对照组相比均显著升高(P0.05);雨生红球藻虾青素含量、Lcy、Crt R-B和Bkt基因表达量在盐胁迫的早期(第3天)和中期(第6天)阶段较低,在盐胁迫的后期(第9天)阶段较高,而SOD、CAT和GSH-Px活性以及MDA含量在盐胁迫的早期和中期阶段较高,在盐胁迫的后期阶段较低。实验结果说明了适当浓度和时间的盐胁迫能促进雨生红球藻累积虾青素,雨生红球藻在盐胁迫下主要是通过提高虾青素合成相关酶基因的转录水平来促进虾青素的合成,其虾青素和抗氧化酶的抗氧化活性可能互为补充,共同保护雨生红球藻免受盐胁迫的氧化损伤。     

盐度胁迫及昼夜变化对鲻鱼幼鱼消化酶活力的影响

研究了S0（盐度为0）、S10、S20、S33（对照）和S40 5个盐度梯度14d内盐度胁迫及其昼夜变化对鲻鱼（Mugil cephalus）幼鱼蛋白酶和淀粉酶比活力的影响。结果显示：1）盐度胁迫对鲻鱼幼鱼的消化酶活力有显著影响（P〈0．05）。不同盐度的蛋白酶和淀粉酶活力的变化规律都是在第0天～第7天升高,第7天～第14天降低,最终时（第14天）S0～S33蛋白酶活力呈上升趋势,S33～S40下降;S0～S20淀粉酶活力差异不显著（P〉0．05）,S20～S33呈上升,S33～S40下降,且差异显著（P〈0．05）;2）对鲻鱼幼鱼消化酶活性昼夜变化的测定表明,蛋白酶和淀粉酶活性的最高值分别在12：00和15：00,最低值均出现在6：00。因此,夜间设置定时投喂,可促进鱼类快速健康生长。     

斑节对虾GLUT1基因cDNA的克隆与表达分析

该研究利用RACE技术克隆获得了斑节对虾(Penaeus monodon) GLUT1 (glucose transporter type 1)的cDNA全长序列;采用实时荧光定量的方法研究了PmGLUT1在斑节对虾幼体发育过程中、各个组织中及低盐胁迫下的差异表达情况。该基因cDNA开放阅读框(ORF)全长1 476 bp,可编码491个氨基酸。检测PmGLUT1基因从受精卵至仔虾期发育过程的表达情况,结果显示,PmGLUT1在幼体发育各期的表达量有所波动,但总体呈现上升趋势。组织表达分析发现,PmGLUT1在鳃组织中的表达量最高,肝胰腺次之,在卵巢中的表达量最低。急性低盐胁迫后,PmGLUT1在肝胰腺中的表达水平显著高于对照组(P<0.05),但在鳃中的表达水平显著低于对照组(P<0.05)。研究结果表明,Pm GLUT1可能在斑节对虾幼体发育及机体应对低盐胁迫过程中具有重要作用,这为进一步研究葡萄糖转运蛋白基因在斑节对虾幼体发育调控和耐低盐胁迫应答中的分子机制提供了理论依据。     

Adapting bioenergetic factorial modelling to understand the implications of heat stress on barramundi (Lates calcarifer) growth,feed utilisation and optimal protein and energy requirements – potential strategies for dealing with climate change?

The implications of temperature on bioenergetics for barramundi (Lates calcarifer) were defined in an improved factorial model that encompassed revised parameters accounting for effects over the temperature range of 16–39 °C and size range of 10–3000 g. A revised growth function describing weight gain by barramundi as a function of fish weight and temperature was derived from farm and laboratory data and included a term for a shift in optimal temperature with fish size: Gain (g fish^?1 day^?1) = (K + xT + yT ² + zT³) * (weight)^ax+b. Maintenance energy and protein demand functions were also derived on a similar form, and all three functions combined to form the basis of a factorial model for energy and protein demand. Using this model, optimal iterative feed specifications were defined for a range of fish sizes at temperatures of 25, 30 and 35 °C. A feed demand model was also developed based on the demand for digestible energy (DE) at each of these temperatures. The model shows that at high temperatures (35 °C), there is an increase in digestible protein (DP) to DE demand, and that with increasing size, there is a decrease in the DP to DE demand.     

Oxidative stress in juvenile chinook salmon, Oncorhynchus tshawytscha (Walbaum)

Juvenile chinook salmon, Oncorhynchus tshawytscha (Walbaum), were held in 8–11°C freshwater, starved for 3 days and subjected to a low‐water stressor to determine the relationship between the general stress response and oxidative stress. Lipid peroxidation (LPO) levels (lipid hydroperoxides) were measured in kidney, liver and brain samples taken at the beginning of the experiment (0‐h unstressed controls) and at 6, 24 and 48 h after application of a continuous low‐water stressor. Tissue samples were also taken at 48 h from fish that had not been exposed to the stressor (48‐h unstressed controls). Exposure to the low‐water stressor affected LPO in kidney and brain tissues. In kidney, LPO decreased 6 h after imposition of the stressor; similar but less pronounced decreases also occurred in the liver and brain. At 48 h, LPO increased (in comparison with 6‐h stressed tissues) in the kidney and brain. In comparison with 48‐h unstressed controls, LPO levels were higher in the kidney and brain of stressed fish. Although preliminary, results suggest that stress can cause oxidative tissue damage in juvenile chinook salmon. Measures of oxidative stress have shown similar responses to stress in mammals; however, further research is needed to determine the extent of the stress–oxidative stress relationship and the underlying physiological mechanisms in fish.     

Effects of dietary lipids on body composition and liver function in juvenile red drum, Sciaenops ocellatus

This study was conducted to evaluate the effects of different concentrations of dietary lipids on body composition and liver function in juvenile red drum, Sciaenops ocellatus. Diets were formulated to contain 40% crude protein from solvent-extracted menhaden fish meal and 0, 7, 14 or 21% lipid from menhaden fish oil. The basal diet, without supplemental fish oil, contained lipid at 0.4% of dry weight. The diets were fed to groups of 25 juvenile red drum initially averaging 7.3 ± 0.18 g fish^–1 in a recirculating culture system for 8 weeks and weight gain was recorded. After an additional 8 weeks, 16 fish from each treatment were sacrificed and the following measurements were recorded: hepatosomatic index (HSI), intraperitoneal fat (IPF) ratio, and liver -tocopherol, malondialdehyde (MDA) formation, and cytochrome P-4501A activity (measured as 7-ethoxyresorufin O-deethylase (EROD) activity). The activity of alanine and aspartate aminotransferases and concentrations of -tocopherol also were measured in plasma.Weight gain was significantly (p<0.05) affected by dietary lipid concentration, with values ranging from 361% of initial weight for fish fed the basal diet to 527% of initial weight for fish fed the diet containing 7% lipid. The HSI and IPF ratio values also were significantly affected by lipid with the lowest values recorded for fish fed the basal diet and the highest values observed in fish fed the diet containing 21% lipid. Increasing dietary lipid significantly increased oxidative stress as reflected in reduced -tocopherol in liver and plasma and increased MDA formation in the liver, although no overt pathological signs were observed. These findings suggest that lipid concentrations between 7 and 14%, when the diet contains 60 IU vitamin E kg^–1, are likely to limit oxidative stress and result in normal physiological responses of red drum.     

Changes in selected stress and immune‐related genes in Atlantic cod,Gadus morhua,following overcrowding

Using Atlantic cod, Gadus morhua, as a model for the stress response in gadoid fish, the changes in the expression of some stress and immune genes as well as the profiles of plasma cortisol were examined. Adult fish were kept at a density of ca. 100 kg m^?3 by lowering the water level in the rearing tank for 1 h and this short‐term crowding stress was repeated thrice over a 12‐h interval period. Blood samples were collected before exposure and at 2, 24 and 72 h post crowding. Plasma cortisol level significantly increased at 2 h post crowding but returned to pre‐crowding levels 24 h after exposure. The relative expression of the stress response genes, glucose transporter‐3 and a putative heat shock protein 70 significantly increased at 2 and 24 h post crowding respectively. Significant up‐regulation of the pro‐inflammatory cytokines, interleukin (IL)‐1β and IL‐8, as well as anti‐bacterial genes, g‐type lysozyme and bactericidal permeability‐increasing protein/lipopolysaccharide‐binding protein (BPI/LBP) was also observed at 2 h and the levels were maintained until 72 h post exposure, except for BPI/LBP which had maximum up‐regulation at 24 h. The present observations have implications with respect to fish welfare and assessment of the health status of the farmed fish.     

浒苔中MnSOD和CAT基因克隆和表达分析

实验以大型绿藻浒苔为材料,克隆了其抗氧化系统关键酶锰超氧化物歧化酶(manganese superoxide dismutase,Mn SOD)和过氧化氢酶(catalase,CAT)基因的部分片段,利用荧光定量PCR技术研究了Mn SOD和CAT对温度和水杨酸作用的响应规律。结果获得浒苔318 bp的Mn SOD基因,该Mn SOD推测的氨基酸序列与裂片石莼Mn SOD相似性最高为89%;获得了229 bp的CAT基因,该浒苔CAT编码氨基酸序列与裂片石莼和雨生红球藻CAT序列相似性分别为99%和93%。在利用M n SOD和CAT氨基酸序列构建的系统树中,浒苔均先与裂片石莼聚类,再与其他绿藻聚在一起。不同温度对浒苔Mn SOD和CAT基因表达影响表明,35℃高温培养对浒苔Mn SOD和CAT基因表达影响最显著,其表达量分别为25℃培养的2.18倍和2.05倍;5℃低温培养次之;而15℃与25℃培养对M n SOD和CAT基因表达影响差异不显著(P0.05)。在高温35℃下,添加0.1 mmol/L水杨酸后Mn SOD和CAT基因表达量分别为各自对照的2.08倍和5.30倍,而0.01 mmol/L水杨酸添加后基因表达与对照差异不显著(P0.05)。研究表明,Mn SOD和CAT基因表达的增强不仅是浒苔对高温胁迫的响应,而且也是水杨酸缓解高温对浒苔不利影响的方式之一。     

Effect of maturity and storage temperature on the development of peteca in lemons (Citrus limon (L.) Burm. F.) cv. Eureka

To evaluate the effect of maturity and storage temperature on the development of the physiological disorder peteca, lemons cv. Eureka were harvested from a grove with northern exposure located in Mallarauco (33°45′ Latitude South) Metropolitan Region of Chile, at 2 levels of maturity (silver or yellow). After storage for 60 d at 3 or 7 °C, under 90% R.H., fruits were evaluated visually for incidence of epidermal and subepidermal peteca. At that time, the concentration of galacturonic acid and degree of methylation were measured in the albedo, and calcium, hydrogen peroxides and total oxalate concentrations, peroxidase and polyphenoloxidase (PPO) activities were determined in the juice and albedo. Yellow lemons at 3 °C developed more epidermal peteca than fruit stored at 7 °C, and that silver fruit stored at 3 and 7 °C, with these last lemons presenting a higher pectin quality than fruit stored at 3 °C. Maturity and temperature interacted significantly on the concentrations of peroxide and calcium in the albedo, which in average were much higher than in the juice, while for PPO and peroxidases, this interaction was highly significant both in juice and albedo, with higher activity in the albedo. These biochemical evaluations suggest that peteca is a result of some kind of stress on the fruit. It is concluded that yellow lemons are more prone to develop peteca than silver fruit. They will develop greater incidence of the disorder when stored at temperatures as low as 3 °C for 60 d, and that this condition affects the degree of methylation in the albedo, which would end up altering the quality of pectins.