不同氮源及氮浓度对真眼点藻纲微藻生长及油脂积累的影响

以真眼点藻纲8株微藻(类波氏真眼点藻(Eustigmatos cf. polyphem)、大真眼点藻(Eustigmatos magnus)、波氏真眼点藻(Eustigmatos polyphem)、魏氏真眼点藻(Eustigmatos vischeri)、斧形魏氏藻(Vischeria helvetica)、点状魏氏藻(Vischeria punctata)、星形魏氏藻(Vischeria stellata)和眼点拟微绿球藻(Nan-nochloropsis oculata))为研究材料, 用3种氮源(硝酸钠、碳酸氢铵或尿素)和4种氮浓度(18、9、6和3 mmol) 在改良的BG-11培养基中对藻细胞进行培养。比较分析这8株微藻在不同培养条件下的藻液pH、生物量、油脂含量、脂肪酸组成的差异, 从而筛选出适合该类微藻生长和油脂积累的最适氮源与最佳氮浓度。结果表明, 这8株微藻均能在3种氮源中生长, 但是随着培养时间延长, 以碳酸氢铵和尿素为氮源时藻液pH逐渐降低, 其变化范围为5.0—6.0, 而以硝酸钠为氮源时藻液pH保持在7.0—8.0, 变化不大。当以尿素为氮源培养时, 能获得较高的生物量, 但是不同藻株在不同尿素浓度时达到最高生物量。最高生物量是波氏真眼点藻(E. polyphem)在9 mmol时达到, 为10.96 g/L。总脂含量分析发现, 在低氮浓度下均能促进8株微藻油脂的积累, 真眼点藻属中的魏氏真眼点藻(E. vischeri)在8株藻中获得最高油脂含量, 达到59.24%。进一步对脂肪酸分析发现, 8株微藻总脂肪酸含量为细胞干重的50%—58%, 主要脂肪酸组成为豆蔻酸(C14鲶0)、棕榈酸(C16鲶0)、棕榈油酸(C16鲶1)、油酸(C18鲶1)和二十碳五烯酸(C20鲶5), 其中拟微绿球藻(N. oculata)细胞中棕榈酸的含量最高占总脂肪酸50%左右; 其他7株微藻细胞中棕榈油酸的含量较高, 其占总脂肪酸含量范围在40%—60%。8株微藻均表现出较高的生物量与油脂积累能力, 以尿素为氮源, 氮浓度为6 mmol时更有利于该类微藻生物量和油脂的积累。总体来说, 真眼点藻纲的微藻是一类极具潜力适合于微藻生物燃料生产的微藻, 而真眼点藻属藻株表现更为明显的优势。     

九种海洋微藻总脂含量及脂肪酸组成分析

从广东沿海分离出9 种海洋微藻(包括6 种绿藻, 2 种金藻, 1 种硅藻), 在低氮并持续通入二氧化碳(1% CO2)条件下测试其总脂含量, 对其中总脂含量超过其干重45%的海洋微藻进行脂肪酸组成分析并优化反应条件。结果表明,9 种海洋微藻的总脂含量存在着明显差异, 介于8.9%-55.77%之间。其中, 海洋小球藻Chlorella sp.、眼点拟微绿球藻Nannochloropsis oculata、绿色巴夫藻Pavlova viridis 和微拟球藻Nannochloropsis sp.的总脂含量超过干重的45%, 而且, 这4 种富油海洋微藻的C16 和C18 脂肪酸含量丰富, C16:0、C16:1(n-7)、C18:1(n-9)含量较高, C14-C18 长链脂肪酸的含量超过总脂肪酸含量的80%。4 种高脂微藻在30 ℃高温培养条件下比生长速率均超过1.0 d−1。研究结果可为高温富油海洋微藻的工业化培养提供参考依据。     

盐度和pH对平凡舟形藻生长和油脂积累的影响

为研究盐度和pH对淡水硅藻生长和油脂含量的影响,对一株分离自野外采集水样中的平凡舟形藻(Navicula trivialis)进行研究,通过设置不同盐度0、0.03、0.06、0.12、0.18和0.24 mol/L和不同pH 4.5、6.0、7.5、8.5、9.5和10.5进行胁迫,测定各处理对平凡舟形藻的生长、叶绿素a含量、叶绿素荧光参数和油脂含量的影响。结果表明:盐浓度为0.12 mol/L、pH 7.5时,平凡舟形藻细胞密度和叶绿素a含量最高;盐浓度为0.24 mol/L、pH 7.5时,总脂含量最高,分别为34.93%和33.5%。结果表明,平凡舟形藻对不同盐度和pH的适应性不同,这在一定程度上影响其生长和油脂含量。     

高、低氮浓度对2株真眼点藻的生长和油脂积累的影响

【目的】研究氮浓度对真眼点藻纲(Eustigmatophyceae)的2株高产油微藻大真眼点藻(Eustigmatos magnus,EM)和波氏真眼点藻(Eustigmatos polyphem,EP)的细胞形态、生长、总脂含量、脂质组成和脂肪酸组成与含量的时序变化规律。【方法】利用高氮(18.0 mmol/L NO3?-N)和低氮(3.6 mmol/L NO3?-N)浓度培养微藻。【结果】形态观察结果表明,大真眼点藻(E. magnus)和波氏真眼点藻(E. polyphem)营养细胞具有1个周生的裂叶状叶绿体,细胞质中有液泡,内含能够振动的颗粒物,以及一个较为明显的红色色素体;生殖方式通过形成2个D形或4个四角形的似亲孢子;随着培养周期的延伸和营养盐的消耗,细胞中油体逐步形成,其数量不断增加,体积不断增大。实验结果表明,初始氮浓度对2种微藻的总脂积累及生长均有显著影响(P<0.05),低氮浓度下2种微藻的生物质浓度分别为9.0 g/L和8.5 g/L,均低于高氮浓度下的生物质浓度。而低氮浓度下2种微藻的总脂、中性脂和总脂肪酸的含量以及总脂、中性脂与总脂肪酸的单位体积产率均明显高于高氮浓度组,其最高值分别为：59.10%、51.90%、46.95%和0.28、0.24、0.22 g/(L·d) (EM);64.20%、56.80%、50.01%和0.32、0.28、0.25 g/(L·d) (EP)。脂肪酸分析结果表明,两种微藻的脂肪酸主要成分均为棕榈酸(C16:0)、棕榈油酸(C16:1)、油酸(C18:1)和二十碳五烯酸(C20:5,EPA),四者的总含量(占总脂肪酸)分别达到85.83%和85.48%,其中棕榈油酸的含量最高。【结论】低氮浓度胁迫有利于大真眼点藻和波氏真眼点藻细胞内油脂的积累,两种微藻均为适合于生产生物柴油的油脂生产藻株。     

光强及氮浓度对丝状绿藻双星藻生长及生化组成的影响

[背景]环境因子和营养因子对微藻的生长和生化组成都有显著的影响,其中光强和氮浓度是最重要的两个条件。[目的]研究不同光强和初始氮浓度对丝状绿藻-双星藻(Zygnema sp.)生长及生化组成的影响。[方法]采用改良的BBM培养基,设置了两组光强[100μmol/(m^2·s)和300μmol/(m^2·s)]和6种初始氮浓度(3、6、9、12、15和18 mmol/L)在柱状光生物反应器中对双星藻进行培养。[结果]在高光强条件下[300μmol/(m^2·s)],12 mmol/L初始氮浓度最有利于双星藻生物质的积累,其最高生物量可以达到6.60 g/L,而初始低氮浓度(3 mmol/L)则促进了油脂和脂肪酸的积累,油脂最高含量占干重的32.13%,且脂肪酸组成主要包括棕榈酸(C16:0)、油酸(C18:1)、亚油酸(C18:2)和亚麻酸(C18:3),其中油酸含量最高达到总脂肪酸含量的55.01%;在低光强条件下[100μmol/(m^2·s)],初始氮浓度为18 mmol/L时,总蛋白质和总碳水化合物的含量达到最高,分别占干重的16.35%和37.70%,而总脂含量仅占干重10.16%。[结论]光强和初始氮浓度对双星藻生长具有较大影响,通过调节光强和初始氮浓度可有效提高双星藻目标代谢产物的积累。     

大庆湖藻的分离、鉴定和高油脂含量筛选

目的:对大庆6个典型湖泊的湖藻进行分离和鉴定,筛选出高油脂含量的大庆湖藻。方法:采用吸管分离法、稀释平板分离法和平板划线法共分离出8株硅藻和5株绿藻,并利用化学方法对所分离的湖藻进行油脂含量测定。结果:所分离13株藻种名称和油脂含量分别为GF-1四尾栅藻9.3%、GF-2鼓藻2.7%、GF-3布朗葡萄藻20.9%、GF-4布纹藻32.6%、HY-1卵囊藻5.5%、HY-2舟形藻37.1%、HY-3二形栅藻6.4%、YL-1舟形藻32.2%、YL-2刀形布纹藻38.3%、YL-3舟形藻34.5%、HQ-1脆杆藻36.6%、QY-1盒形藻33.8%、CY-1脆杆藻29.4%。结论:筛选出YL-2、HY-2和HQ-1三株高油脂含量的大庆湖藻。     

富油微藻的筛选及其产油能力的评价

【目的】筛选具有较快生长速率及较强产油能力的微藻,探究所获得微藻的生理生化性能及不同培养方式对其生物量、产油能力、碳消耗等生长特性的影响与藻种对pH的适应能力。【方法】通过磷酸香草醛测定法及尼罗红染色对微藻进行初筛复筛,通过设置光合自养、异养和混养等3种培养方式,并采用气质联用等方法,研究不同培养方式对所获微藻生长特性、所产油脂脂肪酸组成以及碳代谢等方面的影响。【结果】筛选出两株产油能力较强的藻株H、Z_8,其油脂产量分别可达1.14±0.05 g/L和1.33±0.10 g/L,经形态观察和分子生物学鉴定初步表明藻株H属布朗单针藻(Chlorolobion braunii)、藻株Z_8属链带藻(Desmodesmus intermedius)。构建了不同培养方式下微藻动力学模型,H、Z_8属于生长偶联型。当培养环境的pH处于6.0–9.0,对藻株H、Z_8的总脂量与生物量无明显差异(P0.05)。【结论】筛选获得的藻株H、Z_8中C16与C18脂肪酸占总脂肪酸的比率能达到90%以上。藻种在混养条件下生物量积累优于异养,但异养条件下更加有利于油脂的积累,且H、Z_8均具有较为宽泛的pH适应能力,是具有一定产业化应用潜力的优良产油藻株。     

不同生态条件对绿色巴夫藻生长与脂肪酸组成的影响

研究不同温度、盐度、光照条件对绿色巴夫藻生长和脂肪酸组成的影响。实验结果表明:绿色巴夫藻的适温范围在5—30℃之间,最适为25℃;该藻为低盐度种类,在试验范围内都能生长,其最适盐度为6‰;生长较适宜的光照强度为3000—5000lx。巴夫藻的主要脂肪酸为C14∶0、C16∶0、C16∶1(n-7)、C18∶1(n-9)、C18∶3(n-3)、C18∶4(n-3)、C22∶6(n-3),其中在20℃时C22∶6(n-3)的含量达到最高,且PUFA(n-3)的含量也较高;在低盐度条件下有利于PUFA(n-3)的合成,盐度为6‰时C20∶5(n-3)的含量最高为总脂的6.02%,在盐度为15‰时C22∶6(n-3)的含量达到最高(总脂的17.79%);光照强度对C22∶6(n-3)的影响不大,在3000lx时C20∶5(n-3)的含量较高。结果表明低光照强度下利于PUFA(n-3)的合成,且C22∶6(n-3)的含量较高。     

分离自象山港的15种海洋微藻脂肪酸比较研究

在160μmol.m-2.s-1光强、（20±2）℃条件下对分离自象山港的15种海洋微藻进行培养,在稳定期离心收集,冷冻干燥后用Bligh-Dyer法提取总脂,皂化衍生化后用气相色谱-质谱联用分析系统对其含有的脂肪酸进行定量和定性的分析。结果表明,这15种微藻总脂含量均较高,其中有9种微藻的总脂含量超过干重的10%,中心硅藻纲中共有的含量相对较高的主要脂肪酸为C14∶0、C16∶0、C16∶1（n-7）脂肪酸和EPA,针胞藻纲的赤潮异湾藻则含有高比例的C16∶0、C18∶4（n-3）和EPA,纵裂甲藻纲和甲藻纲中共有的含量相对较高的主要脂肪酸为C16∶0、C18∶4（n-3）、C18∶5（n-3）和DHA,而隶属于定鞭藻门颗石藻纲的颗石藻含量相对较高的主要脂肪酸分别为C16∶0、C18∶4（n-3）和DHA。这些藻是否可以作为生物饵料还需实际养殖投喂效果决定。     

10种海洋微藻总脂、中性脂和极性脂的脂肪酸组成

研究了10种海洋微藻的总脂、中性脂和极性脂的脂肪酸组成特征。海洋微藻的脂肪含量均在15％以上。极性脂一般为海洋微藻的主要脂类,是长链多元不饱和脂肪酸的主要提供者。中性脂含短链脂肪酸较多,为主要的储存脂类。绿藻纲可以将高含量的16:4(n-3)和18:3(n-3)作为化学分类的标记脂肪酸,小球藻和微绿球藻有丰富的20:5(n-3),与绿藻纲显著不同,可能属于大眼藻纲。绿枝藻纲的脂肪酸组成与绿藻纲类似,绿胞藻纲以16:0、18:4(n-3)和20:5(n-3)为主要脂肪酸。脂肪酸组成可用于海洋微藻的分类学研究,并能指导利用海洋微藻生产高度不饱和脂肪酸。     

三角褐指藻基因枪转化体系的建立

三角褐指藻具有较高的脂肪酸含量,是一种很有潜力的生物柴油生产原料。此外,它是多不饱和脂肪酸尤其是二十碳五烯酸（EPA）重要的来源。合适转化体系的缺乏限制了通过基因工程手段对其进行改造。首次采用基因枪方法成功地将外源基因转入三角褐指藻,转化细胞经染色后呈现蓝色,表明外源报告基因β-糖苷酸酶( GUS ) 基因得到了成功的表达。同时还进行了转化参数等因素对转化效率影响的分析,优化了转化条件。结果显示最佳的转化条件为: 每60 μg钨粉包被1 μg质粒DNA,样品室真空度为27英寸汞柱,可裂膜为1500psi,受体与阻挡网距离6 cm。此外,转化载体采用了三角褐指藻内源基因fcp的启动子,实现了外源基因在细胞内的表达。通过5种基因工程中常用抗生素对三角褐指藻生长抑制的研究发现,三角褐指藻对卡那霉素、氨苄青霉素、链霉素和新霉素不敏感,500 mg/L 的卡那霉素、氨苄青霉素和新霉素,以及1000 mg/L 链霉素仍不能抑制其生长;三角褐指藻对氯霉素非常敏感,130 mg/L的氯霉素可以完全抑制其生长,其半抑制浓度为60 mg/L。这为基因工程手段改造三角褐指藻脂肪酸代谢相关途径奠定了基础。     

Seasonal changes in lipid content and composition of the polychaete Nereis (Hediste) diversicolor

The lipid content and composition of Nereis (Hediste) diversicolor O. F. Müller (Annelida, Polychaeta, Nereidae) a mud-dwelling, intertidal errant polychaete in the Tagus estuary (Portugal), were examined on the monthly basis by lipid extraction, TLC and capillary GC. In this estuary, N. diversicolor is by far the dominant species among polychaeta and the main food item in the natural diet of several flatfishes. The biochemical elucidation of its lipid structure and distribution throughout the year, described in this study, provides information not only about the physiological role of lipids in the animal under consideration but also about dietary fatty acid requirements of some flatfishes in the wild and under laboratory conditions.The total lipid content varied between a maximum of 19.3% lyophilized dry weight in February (4.4% fresh weight) and a minimum of 6.6% in August (1.9% fresh weight). The major lipid classes were triacylglycerol, phospholipid, free sterol, free fatty acid, sterol ester/wax ester and alkyldiacylglycerol.The fatty acid composition was rather unsaturated with a 1:2 mean ratio of n-3: n-6. The major fatty acids were C160:0, C18:1n-9, C18:2n-6, and C20:5n-3; there were smaller amounts of C180:0, C18:1n-11, C18:1n-7, C18:3n-3, C20:1, C20:2n-6, C20:4n-6, C22:2, C22:5n-3, and many other fatty acids were detected at trace levels. The unsaturation ranged from 36.9 mg/g dry weight in summer to 107.4 mg/g in winter. An accumulation of fatty acids from plant origin was evident, in particular linoleic acid (C18:2n-6), which was quantitatively one of the major fatty acids throughout the year.     

SV 40-transformed normal and DNA-repair-deficient human fibroblasts can be transfected with high frequency but retain only limited amounts of integrated DNA

The ability of simian virus 40-transformed human fibroblasts to integrate and maintain transfected genomic DNA has been investigated in two normal and six DNA-repair-deficient human cell lines. These cell lines were transfected with DNA containing two selective markers (G418 and hygromycin (Hyg) resistance) separated by random pieces of human DNA of 0-40 kb in length. The transfection frequency for the selected (G418R) marker was between 2 x 10(-4) and 2 x 10(-3) for all cell lines, comparable to many other mammalian systems. About 50% of the G418R colonies were also initially resistant to Hyg. Analysis of the DNA from individual clones expanded for a further month revealed, however, that about one to three copies of the selected marker but only about 0.1 copy per cell of the unselected marker were maintained. Our results were broadly similar for all eight cell lines. Thus the amount of integrated DNA that is stably maintained in these cells is in general very small (less than 50 kb). This may provide an explanation for the difficulties encountered in many laboratories in attempts to correct the defect in DNA-repair-deficient human cells by transfection with genomic DNA. Our results also show that none of several defects in DNA repair has any obvious effect on either the transfection frequency or the amount of stably integrated foreign DNA.     

Assimilation and biosynthesis of lipids in Arctic Calanus species based on feeding experiments with a C labelled diatom

The dominant Arctic Ocean and North Atlantic copepods Calanus hyperboreus, Calanus glacialis, and Calanus finmarchicus were collected in the Greenland Sea and fed ¹³C labelled diatom Thalassiosira weissflogii to follow the transfer and assimilation of carbon, lipid, and individual fatty acids and alcohols. The diatom was grown with ¹³C for 3 to 5 days and fed then to the copepods. During the feeding period of 14 days, total carbon increased in the copepodite stages V of C. hyperboreus and C. finmarchicus, whereas carbon remained almost constant in C. glacialis females. However, total lipid increased in all species and stages. Highest lipid accumulation occurred in C. hyperboreus in which nearly all lipids were exchanged already after 11 days of feeding. In the other species lipid accumulation made up between 22% (C. finmarchicus) and 45% of total lipid (C. glacialis). The proportion of wax esters was high ranging from 76% of total lipid in C. glacialis to 92% in C. finmarchicus. The fatty acid composition of the alga was dominated by 16:1(n-7), 16:0, 20:5(n-3), and 22:6(n-3). The composition of the copepods was similar because of feeding already on diatoms in the field. In addition, the monounsaturated fatty acids and alcohols, 20:1(n-9) and 22:1(n-11), were major components of the copepod lipids. During the feeding period the highest ¹³C labelling was always found in the C₁₆ polyunsaturated fatty acids and in the 16:1(n-7) alcohol. Because these components occurred only in trace amounts in the copepods they totally originated from the diet explaining the high labelling. It is noteworthy that the 16:1(n-7) alcohol originated only from the corresponding dietary and not from the abundant internal fatty acid. The long-chain monounsaturated fatty acids and alcohols, 20:1(n-9) and 22:1(n-11), are not existent in phytoplankton and have to be produced de novo. They were less labelled in the smaller species but highly ¹³C enriched in C. hyperboreus. Although dietary fatty acids were generally retained by the copepods it seems that fatty acids or even lipids were selectively accumulated and turned over due to bodily requirements, and thus, essential polyunsaturated fatty acids were preferentially retained. During feeding mixing, accumulation, and exchange of internal and dietary fatty acids and alcohols occurred as well as utilisation of lipids from both sources for metabolic requirements. The differences in lipid assimilation fit to the different life strategies of the copepods.     

Dietary n-9, n-6, and n-3 fatty acids modify linoleic acid more than arachidonic acid levels in plasma and platelet lipids and minimally affect platelet thromboxane formation in the rabbit

We have studied the effects of semisynthetic diets containing 5% by weight (12% of the energy) of either olive oil (70% oleic acid, OA) or corn oil (58% linoleic acid), or fish oil (Max EPA, containing about 30% eicosapentaenoic, EPA C 20:5 n-3, plus docosahexaenoic, DHA C 22:6 n-3, acids, and less than 2% linoleic acid), fed to male rabbits for a period of five weeks, on plasma and platelet fatty acids and platelet thromboxane formation. Aim of the study was to quantitate the absolute changes of n-6 and n-3 fatty acid levels in plasma and platelet lipid pools after dietary manipulations and to correlate the effects on eicosanoid-precursor fatty acids with those on platelet thromboxane formation. The major differences were found when comparing the group fed fish oil and depleted linoleic acid vs the other groups. The accumulation of n-3 fatty acids in various lipid classes was associated with modifications in the distribution of linoleic acid and arachidonic acid in different lipid pools. In platelets maximal incorporation of n-3 fatty acids occurred in phosphatidyl ethanolamine, which also participated in most of the total arachidonic acid reduction occurring in platelets, and linoleic acid, more than archidonic acid, was replaced by n-3 fatty acids in various phospholipids. The archidonic acid content of phosphatidyl choline was unaffected and that of phosphatidyl inositol only marginally reduced. Thromboxane formation by thrombin stimulated platelets did not differ among the three groups, and this may be related to the minimal changes of arachidonic acid in phosphatidyl choline and phosphatidyl inositol.     

Incorporation into phospholipid classes and metabolism via desaturation and elongation of various 14C-labelled (n-3) and (n-6) polyunsaturated fatty acids in trout astrocytes in primary culture

The incorporation and metabolism of [1-14C]18:3(n-3), [1-14C]20:5(n-3), [1-14C]18:2(n-6), and [1-14C]20:4(n-6) were studied in primary cultures of trout brain astrocytes. There were no significant differences between the amounts of individual fatty acids incorporated into total lipid at 22 degrees C, with greater than 90% of all the fatty acids being incorporated into polar lipid classes. The distributions of 18:2(n-6), 18:3(n-3), and 20:5(n-3) in individual phospholipid classes at 22 degrees C were very similar, with 57-63 and 18-24% being incorporated into phosphatidylcholine and phosphatidylethanolamine, respectively. Approximately equal amounts of 20:4(n-6), approximately 30% of the total, were incorporated into each of phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol. The metabolism of the (n-3) fatty acids to longer-chain and more unsaturated species was significantly greater than that of (n-6) acids, but delta 4-desaturase activity was very low. A culture temperature of 10 degrees C increased the incorporation of all the fatty acids into total lipid and that of C20 fatty acids into polar lipid. At 10 degrees C, the incorporation of C20 fatty acids into phosphatidylethanolamine and phosphatidylinositol was increased, and the incorporation into phosphatidylcholine and phosphatidylserine was decreased. The distribution of C18 fatty acids was unchanged at the lower temperature, as was the desaturation and elongation of all the polyunsaturated fatty acids incorporated.     

胡杨遗传转化体系的建立及抗生素浓度的优化

探讨了不同激素浓度对胡杨叶片分化以及卡那霉素、G418、羧苄青霉素和头孢霉素4种抗生素对胡杨不同培养阶段外植体生长、分化或生根的影响,确定了由农杆菌介导的胡杨遗传转化研究中抗生素种类和转化体的筛选浓度,建立了适于胡杨叶片转化的遗传转化体系。结果表明:胡杨叶片再生的最佳培养基为MS+BA0.5mg/L+NAA0.1～0.2mg/L+白砂糖25g/L+琼脂5g/L;在叶片转化筛选阶段,卡那霉素和G418的适宜浓度分别为10mg/L和7.5mg/L,羧苄青霉素和头孢霉素的适宜浓度为200～600mg/L和200～400mg/L;在抗性芽生根培养时,卡那霉素和G418分别为15～20mg/L和10～15mg/L,羧苄青霉素和头孢霉素为200～800mg/L和200～600mg/L。     

Transfer of n-3 and n-6 polyunsaturated fatty acids from yolk to embryo during development of the king penguin

This study examines the transfer of lipids from the yolk to the embryo of the king penguin, a seabird with a high dietary intake of n-3 fatty acids. The concentrations of total lipid, triacylglycerol (TAG), and phospholipid (PL) in the yolk decreased by ~80% between days 33 and 55 of development, indicating intensive lipid transfer, whereas the concentration of cholesteryl ester (CE) increased threefold, possibly due to recycling. Total lipid concentration in plasma and liver of the embryo increased by twofold from day 40 to hatching due to the accumulation of CE. Yolk lipids contained high amounts of C(20-22) n-3 fatty acids with 22:6(n-3) forming 4 and 10% of the fatty acid mass in TAG and PL, respectively. Both TAG and PL of plasma and liver contained high proportions of 22:6(n-3) ( approximately 15% in plasma and >20% in liver at day 33); liver PL also contained a high proportion of 20:4(n-6) (14%). Thus both 22:6(n-3) and 20:4(n-6), which are, respectively, abundant and deficient in the yolk, undergo biomagnification during transfer to the embryo.     

Regulation of human lymphocyte proliferation by fatty acids

In the present study, the effect of increasing concentrations of palmitic (PA, C16:0), stearic (SA, C18:0), oleic (OA, C18:1, n-9), linoleic (LA, C18:2n-6), docosahexaenoic (DHA, C22:6 n-3) and eicosapentaenoic (EPA, C20:5 n-3) acids on lymphocyte proliferation was investigated. The maximal non-toxic concentrations of these fatty acids for human lymphocytes in vitro were determined. It was also evaluated whether these fatty acids at non-toxic concentrations affect IL-2 induced lymphocyte proliferation and cell cycle progression. OA and LA at 25 microM increased lymphocyte proliferation and at higher concentrations (75 microM and 100 microM) inhibited it. Both fatty acids promoted cell death at 200 microM concentration. PA and SA decreased lymphocyte proliferation at 50 microM and promoted cell death at concentrations of 100 microM and above. EPA and DHA decreased lymphocyte proliferation at 25 and 50 microM being toxic at 50 and 100 microM, respectively. PA, SA, DHA and EPA decreased the stimulatory effect of IL-2 on lymphocyte proliferation, increasing the percentage of cells in G1 phase and decreasing the proportion of cells in S and G2/M phases. OA and LA caused an even greater pronounced effect. The treatment with all fatty acids increased neutral lipid accumulation in the cells but the effect was more pronounced with PA and DHA. In conclusion, PA, SA, DHA and EPA decreased lymphocyte proliferation, whereas OA and LA stimulated it at non-toxic concentrations.     

Incorporation of 14C-labelled polyunsaturated fatty acids by juvenile turbot, Scophthalmus maximus (L.) in vivo

The ability of juvenile turbot, Scophthalmus maximus (L.), to elongate and desaturate various polyunsaturated fatty acids (PUFA) was examined in relation to their lipid composition. Triacylglycerols were the most abundant lipid class present in the fish and phosphatidylcholine was the predominant phospholipid. In all lipid classes examined the levels of (n-3) PUFA exceeded that of (n-6) PUFA. 18C PUFA were minor components in comparison with 20:5(n-3) and 22:6(n-3). 20:4(n-6) was present in highest concentration in phosphatidylinositol in which it accounted for 16.9% of the fatty acids. When the fish were injected with either ¹⁴C-labelled 18:2(n-6), 18:3(n-3), 20:4(n-6), 20:5(n-3) or 22:6(n-3) the highest percentage recovery of radioactivity (69%) in body lipid was observed with 22:6(n-3). With all labelled substrates free fatty acids contained only a small proportion of the total recovered radioactivity whereas triacylglycerols were highly labelled. Phosphatidylcholine/sphingomyelin was the most highly labelled polar lipid fraction. With ¹⁴C-20:4(n-6) as injected substrate, 23.2% of the radioactivity recovered in total lipid was present in phosphatidylinositol in comparison with less than 6% with the other substrates. Only small proportions of radioactivity from ¹⁴C-18:2(n-6) and ¹⁴C-18:3(n-3) were recovered in the 20 and 22C fatty acids of triacylglycerols and total polar lipid. With ¹⁴C-20:5(n-3) as substrate, 27 and 33% of the total radioactivity recovered in the fatty acids of triacylglycerols and polar lipids respectively was present in 22C fatty acids. The corresponding values for ^l4C-20:4(n-6) as substrate were 19 and 18%. The results confirm the limited capacity of turbot to convert 18C PUFA to longer chain PUFA but demonstrate their ability to synthesize 22C PUFA from 20C PUFA. They also suggest a small but specific requirement for 20:4(n-6).