Microbial Metabolite Signaling Is Required for Systemic Iron Homeostasis

1. Download : Download high-res image (173KB)
2. Download : Download full-size image

     

叶角、光呼吸和热耗散协同作用减轻大豆幼叶光抑制

研究了大豆叶片逐步展开过程中的色素组成、气体交换、荧光动力学以及叶片角度等特性。随着叶片展开程度的增加 ,叶绿素含量和叶绿素 a/ b比值增加 ;光合速率 (Pn)也增加 ,揭示叶片展开过程中光合机构是逐步完善的。自然状态下 ,不同展开程度的叶片均未发生明显的光抑制 ;但将叶片平展并暴露在 12 0 0μmol/ (m2 · s)光下时幼叶发生严重的光抑制 ,伴随叶面积的增加光抑制程度减轻。强光下 ,尽管幼叶光呼吸 (Pr)的测定值较低 ,但幼叶光呼吸与总光合之比 (Pr/ Pm)较高。将叶片平展置于强光下时 ,幼叶的实际光化学效率 (ΦPSII)明显下调 ,非光化学猝灭 (NPQ)大幅增加 ;幼叶叶黄素库较大 ,光下积累较多的脱环氧化组分 ,揭示幼叶依赖叶黄素循环的热耗散增强。自然条件下测量叶片角度 ,观察到在叶片展开过程中叶柄夹角逐渐增加 ;日动态过程中幼叶的悬挂角随光强增加而明显减小 ,完全展开叶的悬挂角变化幅度很小。叶片角度的变化使实际照射到幼叶叶表的光强减少。推测较强的光呼吸、依赖叶黄素循环的热耗散以及较大的叶角变化可能是自然状态下幼叶未发生严重光抑制的原因     

趋化因子基因对HIV-1外膜蛋白基因疫苗诱导的免疫应答的影响

研究趋化因子基因对HIV-1外膜蛋白基因疫苗诱导免疫应答的影响,以探求防治HIV的新策略。将 pVAX1GP120联合RANTES、MIP-1α基因或者pVAX1GP120单独免疫Balb／c小鼠,采用ELISA检测免疫小鼠 的特异性抗体和IFN-γ水平,用MTT比色法检测免疫小鼠脾淋巴细胞的增殖,用乳酸脱氢酶(LDH)试验检测小 鼠特异性细胞毒性T淋巴细胞(CTL)的应答。与pVAX1GP120免疫组比较,pVAX1GP120联合RANTES、MIP- 1α基因免疫组小鼠血清的抗HIV-1gp120抗体滴度升高,有显著性差异(p<0．01);与pVAX1GP120免疫组比较, pVAX1GP120联合RANTES、MIP-1α基因免疫组小鼠血清的IFN-γ升高,有显著性差异(p<0．01); pVAX1GP120联合RANTES、MIP-1α基因免疫组小鼠的脾淋巴细胞增殖实验刺激指数(SI)以及特异性CTL活性 均高于pVAX1GP120免疫组,有显著性差异(p<0．01)。RANTES、MIP-1α基因联合HIV-1外膜蛋白基因疫苗免 疫小鼠,可能增强HIV特异性Th1细胞和CTL反应,RANTES、MIP-1α基因对体液免疫有加强作用。因此, RANTES、MIP-1α基因对于HIV-1外膜蛋白基因疫苗具有较好应用前景的免疫佐剂。     

Reaction of haem containing proteins and enzymes with hydroperoxides: The radical view

The reaction between hydroperoxides and the haem group of proteins and enzymes is important for the function of many enzymes but has also been implicated in a number of pathological conditions where oxygen binding proteins interact with hydrogen peroxide or other peroxides. The haem group in the oxidized Fe³⁺ (ferric) state reacts with hydroperoxides with a formation of the Fe⁴⁺=O (oxoferryl) haem state and a free radical primarily located on the π-system of the haem. The radical is then transferred to an amino acid residue of the protein and undergoes further transfer and transformation processes. The free radicals formed in this reaction are reviewed for a number of proteins and enzymes. Their previously published EPR spectra are analysed in a comparative way. The radicals directly detected in most systems are tyrosyl radicals and the peroxyl radicals formed on tryptophan and possibly cysteine. The locations of the radicals in the proteins have been reported as follows: Tyr133 in soybean leghaemoglobin; αTyr42, αTrp14, βTrp15, βCys93, (αTyr24−αHis20), all in the α- and β-subunits of human haemoglobin; Tyr103, Tyr151 and Trp14 in sperm whale myoglobin; Tyr103, Tyr146 and Trp14 in horse myoglobin; Trp14, Tyr103 and Cys110 in human Mb. The sequence of events leading to radical formation, transformation and transfer, both intra- and intermolecularly, is considered. The free radicals induced by peroxides in the enzymes are reviewed. Those include: lignin peroxidase, cytochrome c peroxidase, cytochrome c oxidase, turnip isoperoxidase 7, bovine catalase, two isoforms of prostaglandin H synthase, Mycobacterium tuberculosis and Synechocystis PCC6803 catalase-peroxidases.     

The histological analysis,colorimetric evaluation,and chemical quantification of melanin content in ‘suntanned’ fish

Human melanocytes respond to UV irradiation by increasing the synthesis of melanin. While much is now understood of the pathways governing this process and the nature of the melanin synthesized, little is known of melanins produced by lower vertebrates and their capacity to respond to UV. Here we report that a fish, red seabream, can undergo ‘suntanning’. Histological, colorimetric and chemical assays were performed for suntanned red seabream fish bred in net cages to analyse the melanins and compared with shaded or wild red seabream fish. For color evaluation, the L* values of suntanned fish were dramatically lower than those in the other two groups. Pyrrole‐2,3,5‐tricarboxylic acid (PTCA), an indicator of eumelanin, was detected in suntanned fish at five times higher levels than in shaded or wild fish while 4‐amino‐3‐hydroxyphenyl‐alanine (4‐AHP), a marker for pheomelanin, could not be detected in any of the samples. Histological analysis showed that melanocytes in the suntanned skin enlarged and increased in number to form a monolayer at the surface of the skin. Analysis of L* values and PTCA levels showed quite a high correlation coefficient (r = ?0.843). When comparing shaded and wild red seabream fish, the scores were closer but some significant differences were still found in some body areas. These results indicate that eumelanin accumulates in suntanned fish during the increase in skin color, which is induced by sunlight, presumably by ultraviolet radiation.     

从核rDNA序列探讨隙蛛亚科Coelotinae的分类地位

隙蛛亚科Coelotinae主要分布于东亚地区,其中我国的已有种类占到全世界种数的一半以上,因此对于我国隙蛛类蜘蛛的研究已经成为世界暗蛛科研究的重点之一。隙蛛亚科属于无筛器类群,于1893年,由Cambridge以隙蛛属为模式属而建立,归属于无筛器的漏斗蛛科。之后,虽然经历了数次修订     

Phylogeny of Molting Protostomes (Ecdysozoa) as Inferred from 18S and 28S rRNA Gene Sequences

Phylogenetic relationships within the group of molting protostomes were reconstructed by comparing the sets of 18S and 28S rRNA gene sequences considered either separately or in combination. The reliability of reconstructions was estimated from the bootstrap indices for major phylogenetic tree nodes and from the degree of congruence of phylogenetic trees obtained by different methods. By either criterion, the phylogenetic trees reconstructed on the basis of both 18 and 28S rRNA gene sequences were better than those based on the 18S or 28S sequences alone. The results of reconstruction are consistent with the phylogenetic hypothesis classifying protostomes into two major clades: molting Ecdysozoa (Priapulida + Kinorhyncha, Nematoda + Nematomorpha, Onychophora + Tardigrada, Myriapoda + Chelicerata, and Crustacea + Hexapoda) and nonmolting Lophotrochozoa (Plathelminthes, Nemertini, Annelida, Mollusca, Echiura, and Sipuncula). Nematomorphs (Nematomorpha) do not belong to the clade Cephalorhyncha (Priapulida + Kinorhyncha). It is concluded that combined data on the 18S and 28S rRNA gene sequences provide a more reliable basis for phylogenetic inferences.__________Translated from Molekulyarnaya Biologiya, Vol. 39, No. 4, 2005, pp. 590–601.Original Russian Text Copyright © 2005 by Petrov, Vladychenskaya.     

假单胞菌M18调控因子GacA与RsmA的相关性及对抗生物质合成代谢调控机制的分析

假单胞菌M18是一株可同时合成并分泌吩嗪-1-羧酸(Phenazine-1-carboxylic acid,PCA)和藤黄绿脓菌素(Pyoluteorin,Plt)两种抗生物质的生防菌株。为了进一步研究假单胞菌M18抗生物质合成代谢的调控方式与机制,在分别构建gacAr、smA等单基因突变株基础上,又构建了gacArsmA双基因突变株M18GR以及gacA′-l′acZ和rsmA′-′lacZ等翻译融合表达载体(pMEGA和pMERA)。通过在PPM和KMB两种培养基中发酵培养和两种抗生物质PCA和Plt的HPLC定量测定显示,双突变株M18GR的PCA和Plt的合成量不论在PPM还是在KMB培养基中都介于单突变株M18G和M18R之间。由实验结果分析推测,两种调控因子对抗生物质合成的调控作用不是发生在转录水平,很可能发生在转录后水平。由β-半乳糖苷酶的定量分析表明,在假单胞菌M18中,两种调控因子不存在自诱导机制;虽然GacA未调控RsmA的合成,但RsmA可能部分正向调控GacA的表达。     

香溪河官庄坪库湾叶绿素a 及初级生产力的分布特征

2005年2月—4月对三峡库区香溪河进行了定点初级生产力及相关影响因子的研究,分析了官庄坪库湾叶绿素a含量和初级生产力的时空分布特征。结果表明,叶绿素a含量、初级生产力在各水层的变化具有相同的周期性,均存在5个峰值,平均每个周期为7—10d左右,但两者不同步。官庄坪测站的真光层深度为10m左右,介于湖泊与海洋之间,光补偿点为4—5m。初级生产力最大值出现在水下0.5m处,并沿物理深度逐渐降低;叶绿素a含量最大值则出现在水下2m处。水温的垂直变化在后期差异明显,各水层日平均水温增量(ΔT/d)与平均毛初级生产、净初级生产存在极显著的相关性。     

转录因子Foxo3a高表达对小鼠T淋巴瘤EL-4细胞周期和凋亡的影响

为了研究转录因子Foxo3a高表达对小鼠T淋巴瘤EL-4细胞周期和凋亡的影响,采用电穿孔法将真核表达载体pEGFP-N1/Foxo3a转染小鼠T淋巴瘤细胞系EL-4细胞,并通过聚合酶链式反应和免疫印迹法分别检测Foxo3a mRNA及蛋白表达。转录因子Foxo3a高表达后,采用细胞计数法绘制其细胞生长曲线;采用荧光显微镜法及流式细胞仪定性和定量观察典型EL-4细胞凋亡形态特征、细胞凋亡百分率及细胞周期变化情况。结果表明,转录因子Foxo3a真核表达质粒pEGFP-N1/Foxo3a经酶切鉴定及测序检测序列正确。转染pEGFP-N1/Foxo3a的小鼠EL-4细胞表达Foxo3a mRNA和蛋白水平显著升高。Foxo3a高表达明显抑制EL-4细胞的增殖能力,并使EL-4细胞发生明显G2期阻滞(P<0.001)。Foxo3a基因高表达后,荧光显微镜可以观察到典型凋亡的细胞形态。同时,EL-4细胞凋亡百分率显著升高(P<0.01)。结果提示,Foxo3a高表达可以有效抑制小鼠T淋巴瘤细胞体外细胞增殖,使细胞周期G2时相阻滞,并具有诱导细胞凋亡的作用。