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961.
随着生物化工技术的不断发展成熟,通过改造微生物已可以实现二氧化碳、甲烷等温室气体的固定、转化和利用,而电子传递及能量供给对微生物固碳效率起着决定性的作用。本文首先分析了好氧性嗜甲烷菌、化能自养微生物等天然微生物细胞内外的直接、间接电子传递系统。在此基础上,围绕微生物固碳细胞工厂的构建,进一步介绍了基于光能、电能的人工电子供给策略及其对固碳过程中代谢通量、合成路径和供能效率的影响。最后针对微生物固碳的关键共性技术难点,简要展望了可行性的解决方案及相关应用前景。 相似文献
962.
AAV-ITR单链DNA微载体是一种基于腺相关病毒(AAV)倒置末端重复序列(ITR)的基因表达载体(AAV-ITR ss DNA mini vector)。前期研究已证明AAV-ITR单链DNA微载体在HEK 293T细胞中具有较高的转染、表达效率。本文中将相同拷贝数的AAV-ITR单链DNA微载体、3?-ITR末端错配的AAV-ITR单链DNA微载体(AAV-ITRmm ss DNA mutant vector)、AAV-ITR双链DNA和质粒分别用Turbo Fect转入小鼠骨骼肌中,比较检测AAV-ITR单链DNA微载体与其他基因表达载体在小鼠体内1周、1个月及3个月的表达效率。组织切片经荧光显微镜观察及荧光灰度值分析表明,相同分子摩尔数的AAV-ITR单链DNA微载体比AAV-ITR双链DNA和质粒在不同时期表达效率都要高且更稳定。提取注射3个月后的肌肉组织的DNA,用荧光定量PCR分析比较各载体的存留分子数。RT-PCR的结果显示AAV-ITR单链DNA微载体在注射3个月后的存留分子数较其他载体高。综合结果显示AAV-ITR单链DNA微载体在动物体内具有表达效率高和长久稳定的优势,有可能开发为基因治疗的一种高效、稳定的新型载体。 相似文献
963.
Pepper seed quality is sensitive to variations in climatic conditions during seed development, which might be associated with accumulation, distribution and leakage of mineral elements from the seeds. This was examined in hybrid seeds of sweet pepper (Capsicum annuum L. cv.‘Hazera’ 1195) in two experiments during two growing seasons. The mean daily temperature (day/night) and daily total radiation receipt during seed development were 27.9/23.2°C and 8.63 kW m?2 in the summer and 18.3/ 14.9°C and 3.18 kW m?2 in the winter, respectively. Seeds developed in the summer had lower percentage of seedling emergence and leaked a larger portion (45%) of their K content into the water medium than in winter‐developed seeds. Summer seeds accumulated more K and Cl, but less P, Mg, Ca and the weight ratio of linoleic acid to oleic acid was lower than in the winter seeds. The season did not significantly affect N, S and total fatty acids. The most abundant element on the seed coat surface was K in the summer and Ca in the winter seeds. The cotyledon and endosperm of the summer seeds contained relatively higher ratios of K and Ca and lower ratios of P and Mg than the winter seeds. Transportation of mineral nutrients appeared to be involved in the effect of heat and moisture stresses on emergence quality of the pepper seeds. 相似文献
964.
We have performed a very extensive investigation of chromatin folding in different buffers over a wide range of ionic conditions similar to those found in eukaryotic cells. Our results show that in the presence of physiological concentrations of monovalent cations and/or low concentrations of divalent cations, small chicken erythrocyte chromatin fragments and chromatin from HeLa cells observed by transmission electron microscopy (TEM) show a compact folding, forming circular bodies of approximately 35 nm in diameter that were found previously in our laboratory in studies performed under very limited conditions. Since TEM images are obtained with dehydrated samples, we have performed atomic force microscopy (AFM) experiments to analyze chromatin structure in the presence of solutions containing different cation concentrations. The highly compact circular structures (in which individual nucleosomes are not visible as separated units) produced by small chromatin fragments in interphase ionic conditions observed by AFM are equivalent to the structures observed by TEM with chromatin samples prepared under the same ionic conditions. We have also carried out experiments of sedimentation and trypsin digestion of chromatin fragments; the results obtained confirm our AFM observations. Our results suggest that the compaction of bulk interphase chromatin in solution at room temperature is considerably higher than that generally considered in current literature. The dense chromatin folding observed in this study is consistent with the requirement of compact chromatin structures as starting elements for the building of metaphase chromosomes, but poses a difficult physical problem for gene expression during interphase. 相似文献
965.
本文利用扫描电镜观察了我国鳋科的5个属的种类。首次发现在它们的胸部腹面游泳足连接板之下均有一板状结构,其形状与栉齿的着生情况在不同属之间存在着明显的差异,同属不同种之间也不尽相同,这是一个过去未曾被注意过的结构,权且称之为胸板。它是一个独立的结构,不与连接板相连。胸板上的栉齿从形态-功能-适应三位一体分析,它与附着寄主有夭,以免被水流冲走,与无栉齿的相比,应是一个进步性状。 相似文献
966.
Hans-B?rje Jansson A. Jeyaprakash Gerald C. Coles Nahum Marban-Mendoza Bert M. Zuckerman 《Journal of nematology》1986,18(4):570-574
Caenorhabditis elegans and Panagrellus redivivus were investigated for surface carbohydrates using fluorescent-labelled and ferritin-labelled lectins. Rhodamine-labelled Concanavalin A was specifically located in the cephalic region of both species. Rhodamine-labelled wheat germ agglutinin was located over the entire cuticle of P. redivivus but was absent on C. elegans. Rhodamine-labelled peanut agglutinin and Limax flavus agglutinin did not label nematodes of either species. Galactose and sialic acid were not detected on either species, whereas mannose-glucose residues were specifically localized in the head areas of both species. No detectable N-acetylglucosamine occurred on C. elegans, but it was evenly distributed over the cuticle surface of P. redivivus. 相似文献
967.
Siebert, A. E. Jr., Good A. H. and Simmons J. E. 1978. Ultrastructural aspects of early immune damage to Taenia crassiceps metacestodes. International Journal for Parasitology8: 45–53. Changes in the ultrastructure of the tegument and subtegumental cells of intraperitoneally implanted Taenia crassiceps metacestodes were studied by transmission electron microscopy over a 4-week period. Death of metacestodes without involvement of host inflammatory cells is indicated initially by vacuolization of the larval tegument followed by loss of the tegument and subsequent death of the larvae. Changes in the tegument involve loss of the glycocalyx, reduction in the numbers of mitochondria and microtriches present, and loss of secretory capacity. Subtegumental cells show an accumulation of secretory vacuoles and marked disruption of nuclear morphology. Tegument damage is attributed to a complement-mediated lysis of the outer tegument membrane and death of the larvae probably results from loss of tegument function. 相似文献
968.
Toshiyuki Imasawa Kentaro Koike Jerold Chun 《Biochemical and biophysical research communications》2010,392(2):207-211
Sphingosine 1-phosphate (S1P) is a potent sphingolipid mediator that acts through five cognate G protein-coupled receptors (S1P1-S1P5) and regulates many critical biological processes. Recent studies indicated that S1P at nanomolar concentrations significantly reduces cytokine-induced apoptosis of pancreatic β-cells in which genes for S1P1-S1P4 are co-expressed. However, the S1P receptor subtype(s) involved in this effect remains to be clarified. In this study, we investigated the potential role of S1P2 in streptozotocin (STZ)-induced apoptosis of pancreatic β-cells and progression of diabetes. S1P2-deficient (S1P2-/-) mice displayed a greater survive ability, lower blood glucose levels, and smaller numbers of TUNEL-positive apoptotic β-cells to administration of a high dose of STZ than wild-type (WT) mice. S1P2-/- mice showed higher insulin/glucose ratios (an index of relative insulin deficiency) and larger insulin-positive islet areas to administration of a low dose of STZ than WT mice. Moreover, administration of JTE-013, a S1P2-specific antagonist, to WT mice ameliorated STZ-induced blood glucose elevation and reduced the incidence of diabetes. Our findings indicate that blockade of S1P2 signaling attenuates STZ-induced apoptosis of pancreatic β-cells and decreases the incidence of diabetes. 相似文献
969.
970.
苏云金芽胞杆菌幕虫亚种YBT-020具有典型的晶胞粘连表型。在前期的研究中,通过质粒消除实验,推测晶胞粘连现象与YBT-020内生质粒pBMB28有关。为了定位质粒pBMB28上控制晶胞粘连表型的基因,首先对质粒pBMB28进行克隆。利用穿梭载体pEMB0557,成功构建了苏云金芽胞杆菌YBT-020的基因组人工染色体(BAC)文库。前期的研究表明晶体蛋白基因cry28Aa定位在质粒pBMB28上,根据cry28Aa基因序列设计引物,从文库中筛选到含有cry28Aa的重组质粒pBMB231。镜检和SDS-PAGE证明质粒pBMB231转化无晶体突变株BMB171形成的重组子BMB231可以产生Cry28Aa晶体蛋白,但不能恢复晶胞粘连表型。对重组质粒pBMB231的插入片段末端序列测定并设计引物筛选文库,通过染色体步移方式得到4个可以重叠覆盖质粒pBMB28不同区域的克隆子,从而克隆了该质粒。对这4个克隆子末端测序和酶切分析,测算出该质粒的大小约为140 kb。进一步确定应用基因组BAC文库以及重叠片段筛选的方法,可以快速有效的克隆苏云金芽胞杆菌大质粒。 相似文献