978 resultados para accessory nuclei


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The mouse tumor cell 5180 and human liver carcinoma cell SMC 7721 cells were first treated with R-PE and its subunits (alpha, beta, gamma subunits), then irradiated with Argon laser (496 nm, 28.8 J/cm(2)). Survival rate was measured by MTT method. In order to compare the phototoxicity in normal cells, the mouse marrow cells were treated with photofrin II and beta-subunit, irradiated with 45 J/cm(2) of light; survival rate was also measured by MTT method. The result showed that R-PE subunits had better PDT effect on s180 cells than R-PE and lower phototoxicity in marrow cells than photofrin II Flow cytometric analysis showed that PDT results in a growth inhibition and a G(0)-G(1) cell cycle arrest in SMC 7721 cells. The tumor cells inhibited by PDT in vivo were morphologically observed by TEM, the tumor cell death was daze to the occlusion of tumor blood vessels and inducement of cell programmed death in nuclei. Therefore, with the advantage in special fluorescence activity, loth molecular weight, good light absorbent character and weak phototoxicity, R-PE subunit is art attractive option for improving the selectivity of PDT.

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Morphology and culture studies on germlings of Sargassum thunbergii (Mertens et Roth) Kuntze were carried out under controlled laboratory conditions. Growth characteristics of these germlings grown under different temperatures (from 10 to 25A degrees C), irradiances (from 9 to 88 mu mol photons m(-2) s(-1)), and under blue and white light conditions are described. The development of embryonic germlings follows the classic "8 nuclei 1 egg" type described for Sargassaceae. Fertilized eggs spent 5-6 h developing into multicellular germlings with abundant rhizoids after fertilization. Under conditions of 20A degrees C, 44 mu mol photons m(-2) s(-1) and photoperiod of 12 h, young germlings with one or two leaflets reached 2-3 mm in length after 8 weeks. Temperature variations (10, 15, 20, 25A degrees C) under 88 mu mol photons m(-2) s(-1) significantly influenced the growth rate within the first week, although this effect became less obvious after 8 weeks, especially at 15 and 20A degrees C. Variation in germling growth was highly significant under different irradiances (9, 18, 44, 88 mu mol photons m(-2) s(-1)) at 25A degrees C. Low temperature (10A degrees C) reduced germling growth. Growth of germlings cultured under blue light was lower than in white light. Optimal growth of these germlings occurred at 25A degrees C and 44 mu mol photons m(-2) s(-1).

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Thermal analysis and thermolysis kinetics of three kinds of seaweeds and fir wood (M. glyptostriboides Huet Cheng), a kind of typical land plant, had been conducted. The results showed that thermal stability follows the order of Grateloupia filicina < Ulva lactuca < Dictyopteris divaricata < fir wood. A notable difference on heat flow between seaweeds and fir wood during thermolysis was that the former were mainly connected with exothermic processes at relatively lower temperature regimes. while the latter was connected with an apparent endotherm at a relatively higher temperature regime followed by a maximum exothermic peak. This suggested that the heat coupling might be realized if co-thermolysis of seaweeds and fir wood were carried out. The main devolatilization phase of each seaweed could be described by Avrami-Erofeev equation, which indicated that thermolysis of seaweeds follows the mechanism of random nucleation and nuclei growth, whereas that of fir wood by Z-L-T equation and its thermolysis mechanism was three-dimensional diffusion. The activation energies calculated for both seaweeds and fir wood increase as conversion increases. However, those for the former have wider distribution. (c) 2006 Elsevier Ltd. All rights reserved.

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Since 1988 growers of bay scallop Argopecten irradians in China have been experiencing mortality in their cultured stocks. Although poorly documented, mortality apparently began near Qingdao and has since spread to other areas of Shandong and Liaoning provinces. Samples of cultured scallops were collected from several growing areas in these provinces and analyzed by histological methods for pathogens. An unidentified haplosporidian parasite was observed in a high proportion of scallops from two of the stocks examined. Most infections were of low intensity, but one heavy infection was also observed. Only plasmodia stages were observed; they occurred intercellularly in connective tissues throughout the scallops. Plasmodia were spherical to oval, varied from 4.0 to 17.0 mu m in diameter and contained from 2 to 18 nuclei. Absence of spores prevented generic assignment of the parasite. The source and pathogenicity of the haplosporidian could not be assessed without additional research. No other microbial parasites (i.e. rickettsia-like, chlamydia-like or kidney coccidia) were observed in any of the scallops examined.

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This paper reports the mega-, micro-sporogenesis and female-, male-gametogenesis of Swertia cincta for the first time, with the aim of discussing the systematic position of section Platynema and section Ophelia of Swertia. Anthers are tetrasporangiate. The development of anther walls conforms to the dicotyledonous type. The tapetum cells have dual origin and are similar to the glandular type. There are two middle layers. The endothecium and epidermis persist. Cytokinesis in the microsporrocyte meiosis is simultaneous type and the microscpore teads are tetrahedral. Pollen grains are 3-celled. The ovary is bicarpellum and unilocular. The placentation is of suparietal placentation with 12 series of ovules. The ovules. The ovule is unitegmic, tenuinucellar and ana-campylotropous, The embryo sac orignates from the single-archesporial cell. The one chalazal megaspore in lienar tetrad become the functional megasore. The development of embryo sac is of the polygonum type. Before fertilization, two polar nuclei fuse into one secondary nucleus. Three antipodal cells persisted and divided into 5-8 cells. A comparison between two sections indicates that section Plathnema is better treated as distinct section and is more advanced than section Ophelia according to the evolutionary trends of embryological characters.

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The systematic and taxonomic position of Biebersteinia Stephan has long been in dispute. The present paper describes for the first time the karyomorphology of two species in Biebersteinia Stephan. Both species commonly showed the interphase nuclei of the simple chromocenter type and the mitotic prophase chromosomes of the interstitial type. The karyotype formulae of both B. heterostemon and B. odora were 2n=10=2m(2sec)+8sm(2sec), belonging to the 3A type of Stebbins' classification. The karyotype of this genus is recorded for the first time. The basic chromosome numbers of four of the five known species of Biebersteinia have been recorded as x=5. The combination of resting nuclei of the simple chromocenter type, mitotic prophase chromosomes of the interstitial type, two pairs of chromosomes with four obvious secondary constrictions at the mitotic prophase and metaphase stages, and the peculiar 3A karyotype in Biebersteinia can be regarded as the karymorphological marker of this genus. The karyomorphological data presented here do not support the traditional grouping of this genus in Geraniaceae. The unique karyomorphology of Biebersteinia justifies its familiar or ordinal status, which is congruent with embryological, anatomical, chemical and molecular data. The systematic position of Biebersteinia needs further study.

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The embryological characters of Crawfurdia delavayi Frabnch. are described and the systematic relationships of Crawfurdia discussed. Anthers are tetrasporangiate. The development of anther walls conforms to the Dicotyledonous type. The tapetum is of single origin. The development of the tapetum with uninucleate cells is of the glandular type. The tapetal cells on the connective side show radial elongation or periclinal division and intrude into the anther locule. The epidermis of anther walls persists and its cells become pillar and fibrous, and the endothecium degenerates. The ovary is bicarpellary and unilocular. The placentation is typically parietal with 8 rows of anatropous ovules. The development of embryo sac is of the polygonum type. Before fertilization, two polar nuclei fuse into a secondary nucleus. Three antipodal cells persist. Flowers are protandrous. Fertilization is porogamous. The development of the endosperm is of the nuclear type. The embryogeny corresponds to the solanad type physalis II variation. The embryological data indicate that it is better to separate Crawfurdia from Gentiana as an independent genus.

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矿物PVT状态方程是研究矿物在一定温压条件下的晶胞体积与温度、压力之间的关系,依据这个基本关系,可以了解矿物在高温高压下的密度、弹性、热膨胀等性质。矿物PVT状态方程的研究可以了解矿物在地球深部存在的结构状态,为进一步的理论计算提供基础的数据,其结果也可以与天然和人工地震的地震波反演的结果对比,对地球深部的地质作用过程、物质结构状态和组成进行限制。然而,目前矿物PVT状态方程的研究主要集中在氧化物矿物和上地幔主要矿物(橄榄石和辉石)及其高压相(瓦兹利石、林伍德石、方镁铁矿、Majorite、Mg-Perovskite、Ca-Perovskite)的研究上,对石榴石、尖晶石等地幔常见副矿物和硫化物矿物的PVT状态方程的研究很少。 作者在参与搭建并完善金刚石压腔外加温系统的基础上,利用北京同步辐射X射线衍射实验技术结合金刚石压腔外加温技术对天然铁铝榴石、锰铝榴石、铬尖晶石进行了PVT状态方程的研究,同时对闪锌矿、辰砂、方铅矿、辉钼矿、辉锑矿等硫化物矿物进行了相变及状态方程的研究。结合前人研究成果,讨论了类质同象置换对镁铝-铁铝系列石榴石、锰铝-铁铝系列石榴石、尖晶石和硫化物矿物相变及状态方程的影响。获得了以下研究结果: 1)镁铝-铁铝系列石榴石和锰铝-铁铝系列石榴石的体弹模量都随着铁铝榴石组分的增加而增大。其主要原因是在二价阳离子位置上Fe2+取代了Mg2+、Mn2+。在镁铝-铁铝榴石系列中Mg2+的共价键半径(1.36Å)要大于Fe2+的共价键半径(1.17Å),而Mg2+-O键长(2.270Å)与铁铝榴石中的Fe2+-O(2.299Å)键长基本相当。在锰铝-铁铝榴石系列中, 尽管Mn2+的共价键半径(1.17Å)与铁铝榴石中的Fe2+共价键半径(1.17Å)相等,但是Mn2+-O键长(2.326Å)大于Fe2+-O键长(2.299Å)。较小的键长和共价键半径将会增强离子间的结合力,从而具有较强的抗压缩能力,因此随铁铝榴石组分的增加,镁铝-铁铝榴石系列和锰铝-铁铝榴石系列具有较大的体弹模量。 2)首次获得了铬尖晶石((Mg0.6766Fe0.2808Na0.0073Ti0.0014)0.9661(Cr1.4874Al0.5367)2.0241O4)的体弹模量的温度导数。结合前人关于其他组分尖晶石的实验结果发现,尖晶石中在四面体位置上发生Fe2+-Mg2+置换对体弹模量的影响要大于在八面体位置上发生Cr3+-Al3+置换对体弹模量的影响。而造成铬尖晶石的体弹模量值比其他组分尖晶石的体弹模量值大的主要原因也是四面体位置上的Fe2+-Mg2+的类质置换。 3)依据获得的尖晶石和石榴石的状态方程计算了不同地幔岩模型(橄榄岩和榴辉岩模型)的密度值在上地幔温压条件下的变化情况。结果表明,在尖晶石二辉橄榄岩模型中尖晶石含量的改变(2%-10%)会引起较大的密度变化(2.2%);在石榴石二辉橄榄岩(石榴石含量14%-20%)和榴辉岩(石榴石含量37%-45%)模型中石榴石含量的变化几乎未引起其密度值的变化,但石榴石是这两种地幔岩模型中的重要组成矿物。 4)首次获得了辰砂的Cinnabar相、方铅矿的B33相、辉钼矿、辉锑矿体弹模量的温度导数和热膨胀系数。讨论了闪锌矿、辰砂、方铅矿的相变情况。 5)总结了锌的、汞的、铅的硫族化合物发生结构相变的规律。认为造成锌的、汞的、铅的硫族化合物的相变压力随阴离子原子序数的增加(S→Se→Te)而逐渐减小的原因是:元素周期表中相对较大原子序数的原子具有更多的核内电子,引起价电子及导带电子的有效位能相对变弱,引起电离能降低,因此在相对较低的压力下就容易发生结构相变。 6)分析了ZnS中Fe2+替代Zn2+、Sb2S3-Bi2S3、MoS2-WS2以及同族相同结构不同组分的简单硫化物矿物的阴、阳离子对体弹模量值的影响。认为简单硫化物矿物的体弹模量值取决于阴、阳离子的离子半径、电负性以及键长。

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The variation of surface compositions on amorphous Ni80.4W1.5P18.1 alloy by O-2 oxidation and H-2 reduction treatments have been studied by XPS, UPS and ISS. It shows that addition of tungsten in the amorphous Ni-P alloy leads to dramatic changes of the relating component distributions in the surface layers before and after these treatments. Oxidation of a Ni80.4W1.5P18.1 amorphous alloy in 1 bar of oxygen at 513 K caused a significant segregation of nickel in different oxide states at the surface. The subsequent reduction of the oxidized surface with I bar hydrogen at 553 K resulted in only a small portion of Ni and P being reduced into elemental states, while most of them was found to combine to form a kind of nickel phosphate compound. On the other hand, under the same conditions, the oxidation and reduction of a Ni80P20 alloy gave rise to metallic Ni and elemental P as the predominate species on the alloy surface. The addition of W in the amorphous alloy might act as nuclei for a favorable formation of the phosphate structure which was proposed to be an active species for hydrogen-relating catalytic reactions. (C) 1999 Elsevier Science B.V. All rights reserved.

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To explore the neural mechanisms underlying conditioned immunomodulation, this study employed the classical taste aversion (CTA) behavioral paradigm to establish the conditioned humoral and cellular immunosuppression (CIS) in Wistar rats, by paring saccharin (CS) with intraperitoneal (i.p.) injection of an immunosuppressive drug cyclophophamide (UCS). C-fos immunohistochemistry method was used to observe the changes of the neuronal activities in the rat brain during the acquisition, expression and extinction of the conditioned immunosuppression (CIS). The followings are the main results: 1. Five days after one trial of CS-UCS paring, reexposure to CS alone significantly decreased the level of the anti-ovalbumin (OVA) IgG in the peripheral serum. Two trials of CS-UCS paring and three reexposures to CS not only resulted in further suppression of the primary immune response, but also reduced the numbers of peripheral lymphocytes and white blood cells. This finding indicates that CS can induce suppression of the immune function, and the magnitude of the effects is dependent on the intensity of training. 2. On day 5 following two trials of CS-UCS pairing, CS suppressed the spleen lymphocytes responsiveness to mitogens ConA, PHA and PWM, and decreased the numbers of peripheral lymphocytes and white blood cells. On day 15, only PHA induced lymphocyte proliferation was suppressed by CS. On day 30, presentation of CS did not have any effect on these immune parameters. These results suggest that the conditioned suppression of the cellular immune function can retain 5-15 days, and extinct after 30 days. 3. CTA was easily induced by one or two CS-UCS parings, and remained robust even after 30 days. These data demonstrate that CIS can be dissociated from CTA, and they may be mediated by different neural mechanisms. 4. Immunohistochemistry assays revealed a broad pattern of c-fos expression throughout the rat brain following the CS-UCS pairing and reexposure to CS, suggesting that many brain regions are involved in CIS. Some brain areas including the solitary tract nucleus (Sol), lateral parabrachial nucleus (LPB) and insular cortex (IC), showed high level c-fos expressions in response to both CS and UCS, suggesting that they may be involved in the transmission and integration of the CS and UCS signals in the brain. There were dense c-FOS positive neurons in the paraverntricular nucleus (PVN) and supraoptic nucleus (SO) of hypothalamus, subfornical organ (SFO) and area postrema (AP) etc. after two trials of CS-UCS paring and after the reexposure to CS 5 days later, but not in the first training and after the extinction of CIS (30 days later). The results reflect that these nuclei may have an important role in CIS expression, and may also response to the immunosuppression of UCS. The conditioned training and reexposure to CS 5 days later induced high level c-fos expression in the cingulate cortex (Cg), central amygdaloid nucleus (Ce), intermediate part of lateral septal nucleus (LSI) and ventrolateral parabrachial nucleus (VLPB) etc. But c-fos induction was not apparent when presenting CS 30 days later. These brain regions are mainly involved in CIS, and may be critical structures in the acquisition and expression of CIS. Some brain regions, including the frontal cortex (Fr), ventral orbital cortex (VO), IC, perirhinal cortex (PRh), LPB and the medial part of solitary nucleus (SolM), showed robust c-FOS expression following the conditioning training and reexposure to CS both on day 5 and day 30, suggesting that they are critically involved in CTA.

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Growth of MCM-22 zeolite films on glass substrates was studied with the focus on the understanding of the unusual vertical crystal orientation. The films formed were characterized by scanning electron microscopy and X-ray diffraction. Separate thin disk-like MCM-22 crystals were found vertically oriented at the early crystallization stage. With crystallization the crystals grew into thick disks and finally into continuous films. The vertically oriented MCM-22 thin crystals could be developed from the orientation of columnar MCM-22 nuclei, which have larger parameters in their c-directions than those in a and b directions. The preferred orientation of MCM-22 nuclei and the fast growth rate in the layer direction are responsible for the vertical growth of MCM-22 zeolite films. (C) 2001 Elsevier Science B.V. All rights reserved.

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EI Mikhailova, SP Sosnikhina, GA Kirillova, OA Tikholiz, VG Smirnov, RN Jones and G Jenkins (2001). Nuclear dispositions of subtelomeric and pericentromeric chromosomal domains during meiosis in asynaptic mutants of rye (Secale cereale L.). Journal of Cell Science, 114 (10), 1875-1882. Sponsorship: Russian Foundation for Basic Research (grants 00-04-48522/ 99-04-48182) RAE2008

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Conjugative plasmids play a vital role in bacterial adaptation through horizontal gene transfer. Explaining how plasmids persist in host populations however is difficult, given the high costs often associated with plasmid carriage. Compensatory evolution to ameliorate this cost can rescue plasmids from extinction. In a recently published study we showed that compensatory evolution repeatedly targeted the same bacterial regulatory system, GacA/GacS, in populations of plasmid-carrying bacteria evolving across a range of selective environments. Mutations in these genes arose rapidly and completely eliminated the cost of plasmid carriage. Here we extend our analysis using an individual based model to explore the dynamics of compensatory evolution in this system. We show that mutations which ameliorate the cost of plasmid carriage can prevent both the loss of plasmids from the population and the fixation of accessory traits on the bacterial chromosome. We discuss how dependent the outcome of compensatory evolution is on the strength and availability of such mutations and the rate at which beneficial accessory traits integrate on the host chromosome.

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A neuroanatomical parcellation system is described which encompasses the entire cerebral cortex and the cerebellum. The cortical system modified version of the scheme described by Caviness et al. (1996) and is designed particularly for studies of speech processing. The cerebellum is parcellated into 6 cortical regions of interest (ROIs) and an ROI representing the deep cerebellar nuclei in each hemisphere. The boundaries of each ROI are based on individual anatomical markers that are clearly visible from standard structural MRI acquistions. The system permits averaginh of functional imaging data sets from multiple sujects while accounting for individual anatomical variability. Used in conjuction with region-of-interest analysis techniques such as that described by Nieto-Castanon et al. (2003), the parcellation system provides a more powerful means of analyzing functional data.