有机碳源对三角褐指藻生长、胞内物质和脂肪酸组分的影响

研究了3种有机碳对三角褐指藻生长、胞内物质和脂肪酸组分的影响。结果表明, 三角褐指藻具有利用有机碳进行兼养生长的能力, 生长速率加快, 倍增时间缩短, 生物量显著提高, 100 mmol/L甘油兼养的生物量最高(713 mg/L), 是自养(460 mg/L)的1.60倍, 乙酸钠和葡萄糖兼养的生物量分别是自养的1.28倍和1.21倍。兼养下蛋白质含量较自养明显下降, 碳水化合物和总脂含量高于自养, 乙酸钠和甘油兼养的总脂含量分别是自养的1.43倍和1.20倍, 葡萄糖兼养的总脂含量与自养无明显差异。3种有机碳兼养的饱和脂肪酸和单不饱和脂肪酸占总脂肪酸的比例增大, 多不饱和脂肪酸比例降低, EPA(eicosapentaenoic acid)比例降低, 乙酸钠兼养的胞内EPA含量(6.23%)和产量(36.59 mg/L)均高于自养, 分别是自养的1.10倍和1.40倍, 甘油和葡萄糖兼养的EPA含量和产量均低于自养。     

光发酵强化三角褐指藻生产岩藻黄素

本研究旨在建立光发酵培养三角褐指藻高效生产岩藻黄素的技术体系。在5 L光发酵罐中,系统研究了兼养条件下初始光强、氮源种类和浓度以及光质对于三角褐指藻生物量浓度和岩藻黄素积累的效果。结果表明,在初始光强为100μmol/(m²·s)红蓝(R:B=6:1)混合光、含氮量为0.02 mol/L的胰蛋白胨和尿素混合氮源(1:1, N mol/N mol)优化条件下,三角褐指藻生物量浓度、岩藻黄素含量和产率分别达到了最大值3.80 g/L、13.44 mg/g和4.70 mg/(L·d),比优化前分别提高了1.41、1.33和2.05倍。本研究开发了强化三角褐指藻光发酵生产岩藻黄素的关键技术,促进了海洋天然产物开发。     

氮源及其浓度对三角褐指藻生长和脂肪酸组成的影响

为了研究氮源的类型和浓度对微藻脂肪酸组成的影响 ,用含有不同浓度NO3 -、NH4 、NH2 CONH2 的培养基 ,对三角褐指藻 (Phaeodactylumtricornutum)进行了培养 ,并测定了其生长和脂肪酸组成。结果表明 ,培养基中不添加氮源时 ,三角褐指藻生长缓慢 ,但多不饱和脂肪酸 (PUFAs)和C18脂肪酸 (C18∶0 ,C18∶2 (n -6) ,C18∶3 (n -6) )占总脂肪酸的比例较高 ;氮浓度较低 (<1 8mmol/L)时 ,三角褐指藻以NH4 为氮源 ,生长较快 ;氮浓度较高 (>3 5mmol/L)时 ,以NH2 CONH2 为氮源 ,生长较快。以NH4 或NH2 CONH2 为氮源时 ,EPA(Eicosapentaenoicacid)和PUFAs占总脂肪酸的比例随着其浓度的增加而上升 ;而以NO3 -为氮源时 ,EPA和PUFAs随着NO3 -浓度增加先上升后下降 ,最适NO3 -浓度为 1 8mmol/L ,此时的EPA占总脂肪酸的比例为 16 7%。EPA占干重 (w/w)的比例 ,不管是哪种氮源 ,均随着氮浓度的增加而升高 ,但是在 0 9— 3 5mmol/L之间 ,3种氮源间EPA含量差异不显著。当氮源浓度为 7 0mmol/L时 ,以NH2 CONH2 为氮源 ,EPA和PUFAs含量最高 ,分别为 2 6 %和 4 4 %。PUFAs占干重的比例随着NO3 -浓度增加而下降 ,随NH2 CONH2 浓度增加而升高 ,而受NH4 浓度变化的影响不显著。     

壬基酚对三角褐指藻的毒性效应及其机理

为了探讨壬基酚(Nonylphenol,NP)对海洋微藻的生态毒性效应,实验选择三角褐指藻(Phaeodactylum triconutum Bohlin)作为受试对象,设置7 个NP 质量浓度梯度(0、0.2、0.4、0.6、0.8、1.0 和2.0 mg·L^-1),测定了不同浓度处理下三角褐指藻的生长情况、光合色素含量、可溶性蛋白含量、丙二醛(MDA)含量及最大光能转化效率(Fv/Fm)以及24 h,48 h,72 h,96 hEC₅₀ 等指标。结果表明,NP 对三角褐指藻的96 h EC50 为0.84 mg·L^-1;当NP 暴露浓度在0.4 mg·L^-1 以上时对三角褐指藻生长表现抑制效应,而且随着NP 质量浓度的增加,生长抑制效应加强,当暴露浓度≥1.0mg·L^-1 时即可造成藻细胞大量死亡,当NP暴露浓度≥2.0mg·L^-1 时,藻细胞基本不能生长。三角褐指藻的细胞密度、可溶性蛋白含量、光合色素含量以及Fv/Fm 等指标随NP 暴露浓度质量浓度的增加而下降的幅度更加显著,暴露处理24 h,MDA 含量随NP 质量浓度的增加而上升,表明较高质量浓度的NP 胁迫,使藻细胞膜脂过氧化程度增强,可能会导致细胞膜结构的破坏和功能的丧失。NP 对三角褐指藻的生长具有明显的毒性效应,并可以造成抗氧化酶系统和光合系统的损伤。     

葡萄糖和乙酸钠对湛江等鞭金藻兼养生长的影响

论文探讨了添加外源性有机碳葡萄糖和乙酸钠对湛江等鞭金藻(Isochrysis zhanjiangensis )生长及胞内总脂百分含量的影响.结果表明:随着葡萄糖和乙酸钠浓度的增加,湛江等鞕金藻的生长和产物积累均表现出先促进后抑制的现象.湛江等鞭金藻兼养利用葡萄糖和乙酸钠促进生长的浓度上限分别为50和30g·L^-1.葡萄糖浓度仅15g·L^-1时,对生物量具有显著促进作用,而乙酸钠浓度2.5～15g·L^-1时,对生物量均具有显著促进作用.葡萄糖对藻细胞内总脂百分含量的促进作用浓度范围是1.0～50g·L^-1,而乙酸钠仅在1.0～15g·L^-1时,表现出显著促进作用.葡萄糖浓度为15g·L^-1时,其生物量、总脂百分含量分别比对照增加了30%、30%.乙酸钠浓度为7.5g·L^-1时,其生物量、总脂百分含量分别比对照增加了30%、30%.添加适量的葡萄糖和乙酸钠能够显著促进湛江等鞭金藻生物量及胞内总脂百分含量,葡萄糖和乙酸钠的最适浓度分别是15g·L^-1和7.5g·L^-1.湛江等鞭金藻利用葡萄糖和乙酸钠进行兼养生长的能力是有限的.     

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。     

Cd2+对三角褐指藻生长及尿苷二磷酸葡萄糖焦磷酸化酶基因表达调控的影响

为了探究Cd2+对三角褐指藻(Phaeodactylum tricornutum)生长及尿苷二磷酸葡萄糖焦磷酸化酶(UDP-glucose pyrophosphorylase, UGPase)基因表达调控的影响, 研究以不同浓度Cd2+处理三角褐指藻, 测定其生长、叶绿素荧光参数、UGP基因转录水平、UGPase活性和金藻昆布多糖含量等指标。结果表明: 低浓度(0.1 μmol/L)Cd2+促进三角褐指藻生长, UGP基因转录水平、UGPase活性和金藻昆布多糖含量分别比对照组提高了100.65%、11.99%和9.77%;而高浓度Cd2+处理组(2和5 μmol/L)各指标均显著降低, UGP基因转录水平较对照组分别下调了50.31%和60.47%, UGPase活性降低56.27%和66.72%, 金藻昆布多糖含量减少42.41%和47.30%。研究首次探究了Cd2+对三角褐指藻UGP基因表达的影响, 表明低浓度Cd2+促进三角褐指藻生长, 上调UGP基因表达, 提高金藻昆布多糖含量, 为Cd2+调控UGP基因的表达提供理论指导。     

三角褐指藻对黑暗胁迫的生理响应

为了研究黑暗条件对三角褐指藻生长及生化组成的影响,并探讨三角褐指藻对黑暗环境的生长适应能力,我们对该藻进行12 d的黑暗处理,着重测定了藻细胞密度、生物量、叶绿素a、可溶性糖和蛋白含量等指标。结果表明,三角褐指藻对黑暗环境表现出一定的适应性忍耐能力,在12 d的长期黑暗胁迫条件下依然可以存活,而藻细胞生化组成对黑暗的响应程度很可能是该藻得以维持细胞低水平生长的主要原因。随着黑暗处理时间的延长,三角褐指藻生长状况受抑制的程度增大,其生长及生化组成与对照组相比发生了极显著的变化。实验结束时,黑暗处理下的藻细胞密度和生物量分别降低到2.93×10⁵ cells·ml^-1和0.011 g·ml^-1,仅为对照的8.0%和37.3%。同样地,黑暗环境也明显地抑制了三角褐指藻体内生化物质的合成与积累,黑暗处理12 d时藻细胞的叶绿素a、可溶性糖和蛋白含量分别比对照降低了约89%、87%和85%。研究结果可为海洋微藻种质的筛选、种质资源库的构建及微藻生物资源的综合开发利用提供参考依据。     

对硫磷对三角褐指藻核酸和蛋白质合成动态的影响

应用同位素标记法研究了对磷磷对三角褐指灌核酸和蛋白质合成动态的影响。结果表明,低浓度的对硫酸（≤１．５ｍｇ／Ｌ）对三角褐指的生长有刺激作用,而高浓度的对硫磷（≥２．０ｍｇ／Ｌ）却严重抑制三角褐指藻的生长,低浓度划硫磷在促进生长的过程中,藻细胞中蛋白质、ＤＮＡ、ＲＮＡ３种大分子物质的合成活跃,其合成速度升高,而在高浓度对硫磷的胁迫下,蛋白质,ＤＮＡ,ＲＮＡ的合成明显地受到了抑制,合成速度降低。     

三角褐指藻在磷营养限制胁迫下的补偿生长效应

以三角褐指藻(Phaeodactylum tricornutum)为研究材料,设置了5个磷营养限制处理:磷营养分量分别设为f/2培养基的1/20(P₁)、1/10(P₂)、1/8(P₃)、1/4(P₄)、1/2(P₅),以f/2为对照(P_ck),在磷限制胁迫下培养10d,然后均以相同密度(2.5×10⁵cells·mL^-1)接种在f/2条件下恢复培养16d,测定了三角褐指藻在磷限制胁迫下和恢复培养阶段的生长状况。结果表明,三角褐指藻在受到磷限制胁迫后,细胞密度、蛋白质和可溶性糖含量都显著低于对照(p<0.05);恢复阶段,P₁、P₂和P₃处理组的细胞密度、平均相对生长率及生物量在恢复培养的中前期显著高于对照(p<0.05),最高平均相对生长率分别为0.73、0.70、0.68d^-1,显著高于对照(0.55d^-1)(p<0.05);P₄处理组的细胞密度和生物量与对照无显著差异;P₅处理组的细胞密度和生物量在恢复培养的中前期显著低于对照(p<0.05);随着培养时间的推移,各处理组与对照之间的差异逐渐缩小,处理组和对照的细胞密度、生物量、蛋白质和可溶性糖含量等均无显著差异。     

Natural sources of normativity

Normativity is widely regarded as being naturalistically problematic. Teleosemantic theories aimed to provide a naturalistic grounding for the normativity of mental representation in biological proper function, but have been subject to a variety of criticisms and would in any case provide only a thin naturalist platform for grounding normativity more generally. Here I present an account that identifies a basic form of valuational normativity in autonomous systems, and show how the account can be extended to encompass key aspects of the normativity of functions and practical reasons.     

Proximate sources of marine biodiversity

When temperature and other kinds of barrier divide formerly continuous populations and confine them to more restricted geographical areas, there is an evolutionary reaction that will, over time, result in the formation of endemic species. In such cases, an allopatric speciation process is considered to have taken place because reproductive isolation was caused by physical means instead of by natural selection. In contrast, when populations exist in a very high-diversity area and remain undivided by physical events, they exhibit a tendency to speciate by means of sympatry (or parapatry). This process, sometimes called competitive or ecological speciation, does involve reproductive isolation by means of natural selection. Populations that exist in geographical provinces bounded by physical barriers add to the overall diversity through the production of endemic species. This increase by species packing is relatively slow due to the very gradual tempo of the allopatric speciation process. Populations existing in centres of origin add to the general diversity through the production of species that are dominant in terms of their ability to spread over large parts of the world. It is proposed that such species are usually formed by sympatric speciation, a process that can be c. 20 times faster than species formation by allopatry. It is not suggested that sympatry is exclusive to centres of origin, nor that allopatry is confined to peripheral provinces. Both processes are widespread, but there do appear to be distinctive geographical concentrations. Considering that numbers of widespread species produced by centres of origin may eventually become subdivided by barriers, and thus give rise to descendants by allopatry, it is difficult to say how much of our present species diversity has come from one source or the other. Both speciation by sympatry from centres of origin and speciation by allopatry in peripheral provinces appear to be important sources of marine biodiversity.     

New sources of pancreatic beta-cells

Two major initiatives are under way to correct the beta-cell deficit of diabetes: one would generate beta-cells ex vivo that are suitable for transplantation, and the second would stimulate regeneration of beta-cells in the pancreas. Studies of ex vivo expansion suggest that beta-cells have a potential for dedifferentiation, expansion, and redifferentiation. Work with mouse and human embryonic stem (ES) cells has not yet produced cells with the phenotype of true beta-cells, but there has been recent progress in directing ES cells to endoderm. Putative islet stem/progenitor cells have been identified in mouse pancreas, and formation of new beta-cells from duct, acinar and liver cells is an active area of investigation. Peptides, including glucagon-like peptide-1/exendin-4 and the combination of epidermal growth factor and gastrin, can stimulate regeneration of beta-cells in vivo. Recent progress in the search for new sources of beta-cells has opened promising new opportunities and spawned clinical trials.     

Alternative sources of natural rubber

Rubber (cis-1,4-polyisoprene) is one of the most important polymers naturally produced by plants because it is a strategic raw material used in more than 40,000 products, including more than 400 medical devices. The sole commercial source, at present, is natural rubber harvested from the Brazilian rubber tree, Hevea brasiliensis. Primarily due to its molecular structure and high molecular weight (>1 million daltons) this rubber has high performance properties that cannot easily be mimicked by artificially produced polymers, such as those derived from, e.g., bacterial poly-hydroxy-alkanoates (PHAs). These high performance properties include resilience, elasticity, abrasion resistance, efficient heat dispersion (minimizing heat build-up under friction), and impact resistance. Medical rubber gloves need to fit well, be break-resistant, allow the wearer to retain fine tactile sensation, and provide an effective barrier against pathogens. The sum of all these characteristics cannot yet be achieved using synthetic gloves. The lack of biodiversity in natural rubber production renders continuity of supply insecure, because of the risk of crop failure, diminishing acreage, and other disadvantages outlined below. A search for alternative sources of natural rubber production has already resulted in a large number of interesting plants and prospects for immediate industrial exploitation of guayule (Parthenium argentatum) as a source of high quality latex. Metabolic engineering will permit the production of new crops designed to accumulate new types of valued isoprenoid metabolites, such as rubber and carotenoids, and new combinations extractable from the same crop. Currently, experiments are underway to genetically improve guayule rubber production strains in both quantitative and qualitative respects. Since the choice for gene activities to be introduced or changed is under debate, we have set up a complementary approach to guayule with yeast species, which may more quickly show the applicability and relevance of genes selected. Although economic considerations may prevent commercial exploitation of new rubber-producing microorganisms, transgenic yeasts and bacteria may yield intermediate or alternative (poly-)isoprenes suitable for specific applications. Received: 9 August 1999 / Received revision: 15 October 1999 / Accepted: 16 October 1999     

Prebiotic sources of biomolecular handedness

Fischer demonstrated (1890–1919) that functional biomolecules are composed specifically of the D-sugars and the L-amino acids, and that in the laboratory synthetic reactions of such molecules propagate with chiral stereoselectivity. Given a primordial enantiomer, biomolecular homochirality followed without the intervention of the chiral natural force conjectured by Pasteur (1860), except prebiotically. Polarized solar radiation and other classical chiral forces were proposed as agencies generating a prebiotic enantiomeric excess, but the forces then known were found to be evenhanded on a time and space average, exemplifying parity conservation (1927). The weak nuclear force, shown to violate parity (1956), was unified with electromagnetism in the electroweak force (1970). Ab initio estimations including the chiral electroweak force indicate that the L-amino acids and the D-sugars are more stable than the corresponding enantiomers. The small energy difference between these enantiomer pairs, with Darwinian reaction kinetics in a flow reactor, account for the choice of biomolecular handedness made when life began.     

Cell sources of liver development

The work is devoted to consequent expression of different cell types' protein markers such as vimentin, desmin, cytokeratins 7, 18, 19, stem cell markers CD34 and Bcl-2 at early stages of human prenatal development. Desmin was revealed in sinusoidal liver cells on 3.5-12 weeks of gestation, in mesenchymal cells of ventral mesentery and hepatoblasts on the 4-7 accordingly. During hepatic period of blood formation such desmin positive sinusoidal cells were found to be located close to blood cells. So called "cholangio-" cytokeratins 7 and 19 showed different expression, the first one was found only in cholangiocytes, while cytokeratin 19 existed in hepatoblasts as well until week 15-16 of prenatal development. Mesenchymal cells of ventral mesentery are positive for cytokeratins 18 and 19 even brighter than hepatoblasts in the 4-7 weeks of gestation. Bcl-2 expression was seen in the same periods in most sinusoidal and mesenchymal cells of ventral mesentery. CD34 positive cells are strongly depicted in liver sinusoids from 4th until 9th weeks of gestation, but probably they are not a source of hepatocytes' development in embryonic ontogenesis. Ventral mesentery mesenchyme was negative for this very marker. These results let us suppose that hepatocytes and cholangiocytes may develop from quite different embryonic sources: cholangyocytes grow exceptionally from duodenum epithelial cells, while there is a strong possibility that hepatoblasts formation occurs with participation of mesenchymal cells.     

Intense fusion neutron sources

The review describes physical principles underlying efficient production of free neutrons, up-to-date possibilities and prospects of creating fission and fusion neutron sources with intensities of 10¹⁵–10²¹ neutrons/s, and schemes of production and application of neutrons in fusion-fission hybrid systems. The physical processes and parameters of high-temperature plasmas are considered at which optimal conditions for producing the largest number of fusion neutrons in systems with magnetic and inertial plasma confinement are achieved. The proposed plasma methods for neutron production are compared with other methods based on fusion reactions in nonplasma media, fission reactions, spallation, and muon catalysis. At present, intense neutron fluxes are mainly used in nanotechnology, biotechnology, material science, and military and fundamental research. In the near future (10–20 years), it will be possible to apply high-power neutron sources in fusion-fission hybrid systems for producing hydrogen, electric power, and technological heat, as well as for manufacturing synthetic nuclear fuel and closing the nuclear fuel cycle. Neutron sources with intensities approaching 10²⁰ neutrons/s may radically change the structure of power industry and considerably influence the fundamental and applied science and innovation technologies. Along with utilizing the energy produced in fusion reactions, the achievement of such high neutron intensities may stimulate wide application of subcritical fast nuclear reactors controlled by neutron sources. Superpower neutron sources will allow one to solve many problems of neutron diagnostics, monitor nano-and biological objects, and carry out radiation testing and modification of volumetric properties of materials at the industrial level. Such sources will considerably (up to 100 times) improve the accuracy of neutron physics experiments and will provide a better understanding of the structure of matter, including that of the neutron itself.