Dietary lipid level affects fatty acid composition and hydrolase activities of intestinal brush border membrane in seabass

Triplicate groups of juvenile seabass (initial weight of 241 g) were fed during 13 weeks three isonitrogenous experimental diets containing different lipid levels, 12% (LL group), 21% (ML group) and 30% (HL group). At the end of the experiment, fish weight gain was similar among the 3 dietary groups. Intestinal brush border membranes were purified for each dietary group; one part of the brush border fraction was dedicated to enzyme assays, the remaining fraction being used for lipid extraction followed by fatty acid analysis. The fatty acid composition of the brush border membrane differed among the 3 groups, although the 3 experimental diets had the same fatty acid composition. The increase in dietary lipid level resulted in a lowering in (n-3) polyunsaturated fatty acid (PUFA) paralleled with an increase in monounsaturated fatty acid. A significant reduction in the brush border enzyme activities, namely alkaline phosphatase, aminopeptidase N, -glutamyl transpeptidase and maltase, was also observed with the elevation of the dietary lipid level. The change in activity of intestinal digestive enzymes, which are membrane-bound proteins, could be attributed to the modification of fatty acid composition and fluidity of the brush border membranes (BBM). Such lowering in PUFA and increase in monounsaturated fatty acid in BBM, concomitant with a decline in membrane enzymatic activity, has been described as a malnutrition indicator in mammals. It raises the question of possible disorders of gut functions in fish fed increasing lipid levels.     

精子膜蛋白受精素(Fertilin)研究进展

精子膜蛋白受精素(Fertilin)是参与精卵质膜间相互作用最有特征性的候选分子之一。受精素由α、β两个亚基组成,为精子表面的异二聚体跨膜糖蛋白。fertilin-α(Fα)、Fertilin-β(Fβ)可能在精子发生、精子成熟、精子获能及精卵结合和融合中发挥重要作用。     

1种新型粘土无机膜在水产品加工废水处理中的应用前景

介绍 1种新型粘土无机膜 ,膜平均孔径 2 3～ 2 6nm。与其他无机膜相比 ,该膜制作工艺简单。实验证明 ,该膜对高温具有较强的稳定性 ,对溶剂和化学物质具较强的耐腐蚀作用 ,且蛋白质分离浓缩效率较高 ,非常适用于水产品加工厂的废水处理及蛋白质回收     

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。     

河竹鞭根对长期淹水环境的生理响应

为揭示河竹鞭根对淹水环境的生理响应机制,以在淹水环境中能长期生存的河竹为材料,测定了人工喷灌供水(对照)、淹水6个月的河竹1年生竹鞭上的一级根、二级根的根系活力、抗氧化酶活性和膜脂过氧化、渗透调节物质含量。研究结果表明:河竹根系活力、抗氧化酶活性、MDA含量、相对电导率和可溶性蛋白含量总体上一级根明显高于二级根。长期淹水环境下,河竹一级根、二级根的根系活力、抗氧化酶活性较对照均有显著降低,相对电导率、MDA含量显著升高,水中生长根的根系活力、CAT活性显著高于土中生长根,SOD、POD活性则相反,并能通过维持总体上较高水平的根系活力、抗氧化酶活性、可溶性蛋白含量来适应长期淹水环境的胁迫,尤其是一级根和水中生长根。河竹鞭根通过抗氧化系统的平衡调节作用来适应长期淹水环境,维持生存,其中一级根对淹水环境的响应明显强于二级根,水中生长根在适应淹水环境上起到重要作用。     

覆盖经营对高节竹叶片主要生理特征的影响

以连续2年林地覆盖和不覆盖高节竹（Phyllostachys prominens）林为对象,测定了叶片MDA、可溶性蛋白、可溶性糖含量和抗氧化酶活性、叶绿素值,研究短期林地覆盖经营对高节竹叶片生理特征的影响,结果表明：林地覆盖经营对高节竹2、3年生立竹叶片MDA、可溶性蛋白和可溶性糖含量影响不明显,但对1年生立竹有显著影响;对1~3年生立竹叶片SOD、POD和CAT活性总体上有较明显的影响,并显著提高了叶片叶绿素值。     

浸没式膜生物反应器内膜面传质特性实验

应用粒子图像测速(PIV)技术测试膜面附近的气液两相流动力学特性,在6种不同曝气强度条件下,测试得到膜面附近的液相流场数据,并计算得到膜面传质系数、浓差极化边界层厚度以及膜面切向应力等膜面传质特性参数。结果表明,曝气强度和液相速度对膜面传质特性的影响较大,在一定范围内增加曝气强度可以使得膜面传质特性加强。本文的研究结果为膜生物反应器系统的优化设计提供了研究经验和实验数据。     

不同冻融处理对猪精子顶体膜蛋白表达的影响

为探究不同冷冻解冻方法对猪精子损伤的影响,采用2种常用的冷冻解冻方法处理猪精子,分别对其顶体膜蛋白进行分离,进行SDS-PAGE电泳和总灰度值的检测和分析。结果表明,采用一次稀释法进行猪精液的冷冻保存较二次稀释法解冻后精子活率高,精子顶体膜蛋白组分中除125 ku和90 ku处蛋白表达水平低于二次稀释法外,120 ku、48 ku、36 ku均高于二次稀释法。可见,猪精子在受到更深层次(二次稀释法对精子冷冻解冻损伤大)的冷冻损伤时,伴随着顶体膜蛋白125 ku和90 ku表达水平的升高以及120、48及36 ku表达水平的降低。     

Binding characteristics and regulation of the 17,20β,21-trihydroxy-4-pregnen-3-one (20β-S) receptor on testicular and sperm plasma membranes of spotted seatrout (Cynoscion nebulosus)

The binding characteristics of 17,20,21-trihydroxy-4-pregnen-3-one (20-S) to plasma membranes prepared from the testes and sperm of spotted seatrout (Cynoscion nebulosus) were investigated using a filtration method to retain the bound 20-S. A single class of high affinity (K_d = 17.9 nM), low capacity (B_max = 0.072 nM g^-1 testes) binding sites was identified by saturation and Scatchard analyses on testicular membranes of spermiating spotted seatrout. A corresponding receptor (K_d = 22.17 nM, B_max = 0.00261 nM ml^-1 milt) was also detected in spermatozoan membrane preparations. The rates of 20-S association and dissociation were rapid, both had T_halfs of less than 1 min. Competition studies indicated that the receptor was highly specific for 20-S. 17,20-dihydroxy-4-pregnen-3-one, which had the highest affinity of the other steroids tested, had a relative binding affinity (RBA) of 14.3%. Progesterone, 11-deoxycortisol and testosterone competed with an order of magnitude less affinity (RBA's of 7.4, 1.8 and 1.1%, respectively). Estradiol displayed low affinity for the receptor (RBA = 0.4%) and cortisol did not cause any displacement at 1000-fold excess concentration. Specific 20-S receptor binding was detected in plasma membranes from testes of both spermiating and non-spermiating seatrout and on spermatozoa. Prolonged incubation of testicular fragments from a spermiating fish with gonadotropin (15 IU ml^-1 human chorionic gonadotropin) or forskolin (10 µM) caused a 2–3 fold increase in membrane receptor binding. Previous studies have shown that gonadotropin-induced upregulation of the 20-S plasma membrane receptor in seatrout ovaries is required for the oocytes to become responsive to 20-S and undergo final maturation. The existence of a 20-S membrane receptor on sperm and its upregulation in the testes by gonadotropin raises the possibility that final maturation of spermatozoa in male seatrout may be regulated by a similar mechanism.     

柑桔汁陶瓷膜微滤澄清和污染阻力试验

为了探讨柑桔汁微滤澄清技术及微滤膜污染阻力,建立膜清洗方法,研究以0.2 mm陶瓷膜微滤柑桔汁时膜通量变化及处理效果,结果表明：当温度30℃、压差0.16 MPa及膜面流速4 m/s时,全循环模式下稳定膜通量为22.4 L/(m2·h),浓缩模式下体积浓缩因子为12时,膜通量为10.6 L/(m2·h),澄清汁得率达91.67%;澄清汁浊度仅为0.62 NTU,澄清度高达99.93%,且各主要营养成分变化不大。通过建立膜污染阻力模型,考察操作参数对各分解阻力的影响,进而研究膜污染动力学后发现：压差对不可逆极化层阻力影响最为明显;增大膜面流速显著降低各极化层阻力,但对不可逆污染阻力作用不大;升高温度使得各阻力下降;膜污染可用拟二级速率方程描述。研究污染膜清洗过程,结果表明采用去离子水、1% NaOH和0.5% NaClO混合液、0.2% HNO3溶液依次清洗膜,膜通量可迅速恢复。