泥螺肝胰腺细胞的超微结构和功能     

应雪萍 《海洋科学》2007,31(10):41-46

利用透射电镜技术研究了泥螺(Bullactaexarata)肝胰腺细胞的超微结构。结果表明,泥螺的肝胰腺主要由4类细胞构成:泡状细胞(B细胞)、吸收细胞(R细胞)、纤维细胞(F细胞)和胚细胞(E细胞)。B细胞大,长柱状,胞质中有许多消化泡;R细胞的脂滴数量多,体积大,具少量的线粒体;F细胞含有极丰富的粗面内质网、线粒体等结构,但脂滴的数量远远少于R细胞。E细胞为多边形,核大而圆,粗面内质网少,线粒体小而狭长。根据这4种细胞的超微结构特点,指出了泥螺肝胰腺的功能,并探讨了肝胰腺细胞的分化序列。  相似文献   

长江口中肋骨条藻赤潮发生全过程调查报告

──浮游植物群落结构及细胞形态研究   总被引：6，自引：0，他引：6  

沈竑  洪君超 《海洋与湖沼》1994,25(6):591-595

于1990年6月在长江口赤潮多发区定点观测到一次中肋骨条藻赤潮发生的全过程，对中肋骨条藻赤潮发生过程中浮游植物群落结构的变动及细胞形态的变化进行研究。结果表明，（1）中肋骨条藻赤潮发生前，水体中甲藻数量多于硅藻；赤潮发生后，中肋骨条藻增殖，逐渐成为主要优势种，硅藻在数量上超过了甲藻；浮游植物种类丰度指数的大小能较好地反映赤潮发生的各个阶段。（2）赤潮发生过程中，中肋骨条藻细胞增殖率次序为：发展阶段＞维持阶段＞起始阶段。（3）在赤潮发生的维持阶段后期和消亡阶段，有5％-7．8％的中肋骨条藻形成休眠孢子，一个中肋骨条藻细胞仅形成一个休眠孢子，且同一个中肋骨条藻群体链上的所有细胞形成休眠孢子是同步的。  相似文献   

An in vitro procedure for evaluation of early stage oxidative stress in an established fish cell line applied to investigation of PHAH and pesticide toxicity   总被引：1，自引：0，他引：1  

Ruiz-Leal M  George S 《Marine environmental research》2004,58(2-5):631-635

Oxidative stress by increased production of reactive oxygen species such as superoxide has been implicated in the toxicity of PCB's and non-target toxicity of many pesticides. We report the development of a microplate-based method for determination of early stage oxidative stress using an established cell line (EPC) from a skin tumour of carp Cyprinus carpio L. and 2',7'-dichlorodihydrofluorescein diacetate (H(2)-DCFDA) as a fluorescent probe for detection of reactive oxygen species (ROS) formation. Sublethal concentrations of the herbicide Paraquat, an established redox cycling agent and a crude PCB mixture, Arochlor 1254 elicited a linear increase in ROS formation over 2 h exposure which was some 45- and 10-fold higher, respectively, than attributable to basal respiration, confirming the suitability and response of the test system. Whilst in vivo studies in mammals have implicated early stage oxidative stress in the toxicity of pesticides, we did not observe an increase in ROS production after exposure of EPC cells to sublethal concentrations of Carbaryl, 2,4-DDT, Lindane or Malathion implying that this is not the causative mechanism of acute toxicity in this fish cell line. The apparent involvement of oxidative stress in their mammalian toxicity may therefore be an indirect effect or dependent upon compound metabolism.  相似文献   

Distribution of selenium and arsenic in differentiated multicellular eukaryotic fossils and their significance     

《地学前缘(英文版)》2020,11(3):821-833

We present variation patterns of trace elements within different sequences of the Ediacaran Doushantuo Formation(DST,635-551 million years ago),and inside the cells of the earliest differentiated multicellular eukaryotic fossils of the Weng'an biota in the Weng'an County of Guizhou Province.The results showed that selenium is the most enriched and significantly varied trace element among the 22 trace elements throughout the DST,followed by arsenic.The highest selenium and arsenic content sequences are consistent with the first appeared sequence of the earliest differentiated multicellular eukaryotic fossils Megasphaera at the middle to upper parts of the DST.Nanoman secondary ion mass spectrometry analyses show that selenium and arsenic have an inhomogeneous and punctate distribution in the nucleus and cytoplasm.The nucleus has anomalously enriched levels of selenium and arsenic among the organelles.The selenium and arsenic concentrations exhibit a positive correlation with the diversity of fossilized Megasphaera.These new findings give us a clue that the anomalous enrichment of selenium and arsenic might contributes to the cell differentiation in Ediacaran Doushantuo period.  相似文献   

Pedogenically degenerated illite and chlorite lattices aid to palaeoclimatic reconstruction for chronologically constrained(8-130 ka) loess-palaeosols of Dilpur Formation,Kashmir,India     

《地学前缘(英文版)》2020,11(4):1353-1367

Chronologically well-constrained loess-palaeosols(recorded glacial and inter-glacial climate) revealed pedogenesis induced ionic substitutions,caused end-member compositional deviations in illite and chlorite,linked to widespread climatic changes occurred during Late Pleistocene.Further,micro-level climatic resolution is yet to be resolved.Thus,layer-wise X-ray diffraction analyses of clay separates,followed by Rietveld refinement revealed varied cell parameters and interatomic distances.Obtained values for detrital and pedogenic illite and chlorite when plotted against stratigraphic succession show notable changes in the crystallographic axes.The illite lattices associated with inadequately pedogenized palaeosols have been altered into illite/smectite mixed layers,but,the chlorite lattices represent expansion of a-,b-and contraction of c-axes with much greater amount of distortions,suggestive of warm-humid and acidic environment.The detrital 48,44 and 83,74 bonded illite and chlorite with2 sub-types each,when pedogenized retained 48,44 and 34;and 83 and 74 bonds(in their neo-formed 3 and 2 sub-types),respectively.The Al-O bond shows expansion,but,unchanged Si-O and decreased Si-K and K-O bonds show loss of Al and retention of Si and K ions in the illite lattices.The illite with 32 atoms and 48 bonds represent contraction of K-O,Si-K,Al-O and Si-O bonds caused bond reinforcement;however,loss of Al~(3+)reflects all-out illite alteration.Owing to Al-O and K-O bond expansion,major K~+ and Al~(3+) ionic loss occurred during the LGM,however,further ionic loss depends upon the magnitude of the loess-palaeosol weathering that they have suffered.The clilate sensitive Fe,Mg and Al ionic losses for Fe-O,Mg-O and Al_(11)-O_9 bond length expansions were recognized in the chlorite lattices.Such ionic losses are common,but,complete distortion is attributed to Al,Si,Fe and Mg ionic losses,followed by weakening of Al-O,Si-O,Fe-O and Mg-O bonds.Though,Si-O_4 and Fe_1-O_4 bonds,and Si and Fe_(1 st) ions remain intact.Thus,three major glacial episodes of ～5 ka each occurred under alkaline environment,but,intervened by two successive cycles of 55 ka each,encompassing three alternate warm and cold climatic sub-cycles of 12-15 ka.But,the coldness increases with each warm-cold sub-cycle that attained the glacial maxima.Further,these events correlate well with the deep-sea records of the North Atlantic(MIS-1 to MIS-5 e) and CLP loess-palaeosols(～127 ka).  相似文献   

基于手机定位方法的研究与精度分析     

张帅  范荣双  梁勇  王晓 《全球定位系统》2011,36(2):45-48

对手机定位方法进行研究,通过实验采集数据,对手机定位的精度和导航的准确度进行检验。仅从GPS这种方式进行实验检测可知,手机GPS方式定位的精度在50m以内,无论是在市区还是郊区变化不大。手机以目前的精度足以满足大家出行需要。  相似文献   

Evaluation of cell lysis procedures and use of a micro fluidic system for an automated DNA-based cell identification in interplanetary missions     

J.A. Hall  E. Felnagle  M. Fries  S. Spearing  L. Monaco  A Steele   《Planetary and Space Science》2006,54(15):1600-1611

A Modular Assay System for Solar System Exploration (MASSE) is being developed to include sample handling, pre-treatment, separation and analysis of biological target compounds by both DNA and protein microarrays. To better design sensitive and accurate initial upstream sample handling of the MASSE instrument, experiments investigating the sensitivity and potential extraction bias of commercially available DNA extraction kits between classes of environmentally relevant prokaryotes such as gram-negative bacteria (Escherichia coli), gram-positive bacteria (Bacillus megatarium), and Archaea (Haloarcula marismortui) were performed. For extractions of both planktonic cultures and spiked Mars simulated regolith, FTA^® paper demonstrated the highest sensitivity, with detection as low as 1×10¹ cells and 3.3×10² cells, respectively. In addition to the highest sensitivity, custom modified application of FTA^® paper extraction protocol is the simplest in terms of incorporation into MASSE and displayed little bias in sensitivity with respect to prokaryotic cell type. The implementation of FTA paper for environmental microbiology investigations appears to be a viable and effective option potentially negating the need for other pre-concentration steps such as filtration and negating concerns regarding extraction efficiency of cells. In addition to investigations on useful technology for upstream sample handling in MASSE, we have also evaluated the potential for μTAS to be employed in the MASSE instrument by employing proprietary lab-on-a-chip development technology to investigate the potential for microfluidic cell lysis of different prokaryotic cells employing both chemical and biological lysis agents. Real-time bright-field microscopy and quantitative PMT detection indicated that that gram positive, gram negative and archaeal cells were effectively lyzed in a few seconds using the microfluidic chip protocol developed. This included employing a lysis buffer with components including lysozyme, Protease, Proteinase K, Tween-20 and TritonX-100. The effectiveness of antibiotics and other chemical lysis agents were also screened and demonstrated partial effectiveness on all three cell types. This work demonstrates a step wise approach to evaluating the efficacy and sensitivity of commercial macro-scale technology and state-of-the-art developmental microfluidic technology under consideration for incorporation into the remotely operated MASSE instrument currently under development at the Carnegie Institution of Washington.  相似文献   

Metabolic patterning of biosilicification     

Derek R. Amores  Lesley A. Warren   《Chemical Geology》2009,268(1-2):81-88

Here we show a discernibly unique biosilicification pattern for live, metabolically active Synechococcus cyanobacterial cell surfaces compared to dead Synechococcus cells under identical experimental conditions. The live cell treatments showed signs of cell division and the growth of fimbriae indicating metabolic activity during the 5-day silicification experiment. Live treatment cells were also recultivable after the experiments confirming their continued viability. The metabolically active live cyanobacteria treatment bound twice the amount of colloidal SiO₂ and held it more tightly compared to the dead cell treatment. Further, biosilicification of the live, actively metabolizing bacteria was unipolar, leaving the core surface largely unencrusted. In contrast, biosilicification of the dead cells was heterogeneous, occurring across the entire cell surface with no observable localized pattern. The directed biosilicification localization of live cell surfaces is likely a bacterial strategy to protect the cell functionality against the potentially inhibitory effects of mineral encrustation. Localization of silica biominerals to the polar end of the cell is also consistent with reported bacteria regulated cell polarity, which, under the experimental pH of 3, would enable localized differential attraction between the charged colloidal silica (+) particles and the bacterial cell polar surface (−). Our results show a novel metabolically-linked distinct colloidal SiO₂ biomineralization fingerprint, suggesting a putative biomineralization signature.  相似文献   

利用热液金刚石压腔开展扎布耶石（碳酸锂）结晶实验的研究     

丁欣  李建康  李胜虎  王娴 《地质学报》2016,90(5):873-878

花岗伟晶岩一般赋存了大量富晶体包裹体,扎布耶石(碳酸锂)是锂辉石中富晶体包裹体内的主要矿物之一,因此,扎布耶石的形成机制和温压条件对富晶体包裹体的捕获条件有重要的指示意义。本文通过热液金刚石压腔(HDAC)开展Li_2CO_3-H_2O体系的结晶实验,9组实验结果表明,扎布耶石的成核温度是550(±30)℃,大约在温度降低15℃后,晶体停止快速生长,而后缓慢生长直至在400(±50)℃完全停止生长。扎布耶石的生长主要集中在550~400℃,而与压力影响不大,处于锂辉石的稳定温度范围内,这佐证了富晶体包裹体中的扎布耶石可以是捕获流体直接结晶形成的晶体。扎布耶石开始结晶后经历了快速生长,导致包裹体内部压力降低,这可能是富晶体包裹体内存在方石英的原因之一。  相似文献   

论海洋无脊椎动物染色体操作过程中中心体对细胞分裂和倍性的影响   总被引：5，自引：1，他引：5  

李孝绪 《海洋与湖沼》1995,26(4):439-444

根据对中心体研究的最新进展，着重论述了杂色体组操作过程中中心体对细胞分裂和倍性的影响。在海洋无脊椎动物多倍体育种中，其染色体组的加倍多是通过抑制细胞分裂实现的，然而正是在此操作的同时也改变了细胞中中心体的数目。在双中心粒中心体细胞中，由于中心体数目的变化将直接影响到下一次细胞分裂中期纺锤体的极性（单极、双极或多极），进而影响到姊妹染色体的分离及细胞的分裂和倍性。深入仔细地开展有关这方面的研究，不仅可以揭示细胞分裂的许多奥密，而且可以为海洋无脊椎动物染色体组工程的研究提供细胞学基础，达到事半功倍的效果。  相似文献