834 resultados para Ciceron, Marco Tulio, 106-43 a.C
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Contiene: Tomus primus],
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The thermal sensitivity and heat shock response of the different races of the mulberry silkworm Bombyx mori have been analysed. The multivoltine race, strains C. Nichi and Pure Mysore showed better survival rates than the bivoltine race, strain NB4D2 exposed to 41 degrees C and above. In general, the fifth instar larvae and the pupae exhibited maximum tolerance compared to the early larval instars, adult moths or the eggs. Exposure up to 39 degrees C for 1 or 2 h was tolerated equally whereas temperatures above 43 degrees C proved to be lethal for all. Treatment of larvae at 41 degrees C for Ih resulted in a variety of physiological alterations including increased heart beat rates, differential haemocyte counts, enlargement of granulocytes and the presence of additional protein species in the tissues and haemolymph. The appearance of a 93 kDa protein in the haemolymph, fat bodies and cuticle, following the heat shocking of larvae in vivo was a characteristic feature in all the three strains examined although the kinetics of their appearance itself was different. In haemolymph, the protein appeared immediately in response to heat shock in C. Nichi reaching the maximal levels in 2-4 h whereas its presence was noticeable only after 2-4 h recovery time in Pure Mysore and bivoltine races. The fat body from both C. Nichi and NB4D2 showed the presence of 93 kDa, 89 kDa and 70 kDa proteins on heat shock. The haemocytes, on the other hand, expressed only a 70 kDa protein consequent to heat shock. The 93 kDa protein in the haemolymph, therefore could have arisen from some other tissue, possibly the fat body. The 93 kDa protein was detected after heat shock in pupae and adult moths as well, although the presence of an additional (56 kDa) protein was also apparent in the adults. The presence of 46 kDa and 28 kDa bands in addition to the 93 kDa band in the cuticular proteins immediately following heat shock was clearly discernible. The 70 kDa band did not show much changes in the cuticular proteins on heat shock. In contrast to the changes in protein profiles seen in tissues and haemolymph following heat shock in vivo, the heat treatment of isolated fat body or haemolymph in vitro resulted in protein degradation.
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El presente estudio tuvo el objetivo de determinar el efecto combinado de los reguladores de crecimiento, tipos de explantes y genotipos estudiados en la inducción de callos y la micropropagación a partir de (YA) (inducción de yemas adventicias y generación de plantas), en los genotipos de quequisque Blanco y Masaya (Xanthosoma sagittifolium (L.) Schott). En el estudio de inducción de callos, se evaluaron medios de cultivo, tipos de explantes (hojas, ápices, peciolos y meristemos), uso de medios fresco y genotipos. En la fase de inducción de yemas adventicias se evaluaron medios de cultivos y genotipos; en la generación de plantas se utilizó un medio de cultivo (AIA 1.5 mgL-1 + 6-BAP 0.5 mgL-1). Para el análisis se representó gráficamente los datos no paramétricos evaluados en los diferentes estudios. Se obtuvo callos a partir de ápices, peciolos y meristemos, excepto en hojas. Los ápices presentaron mayor potencial para la formación de callos. El 2,4-D (1 - 5 mgL-1) fue la auxina que indujo a callos en un mayor número de medios, observándose la formación de callos en un promedio de 38.88 % de los medios que contenían 2,4-D a partir de explantes de ápices y 5.55 % en peciolos. El medio que contenía 6-BAP (2 mgL-1) indujo a callos en un promedio de 62.5 % de los meristemos de ambos genotipos. Al trasladar los explantes de peciolos del medio inicial a un medio fresco conteniendo ambos (2 mgL-1 2,4-D), se indujo a la formación de callos en un promedio de 29.6 %para ambos genotipos. El genotipo Blanco presentó mayor predisposición genética a la generación de callos que el Masaya. Se obtuvo (YA) en ambos genotipos, el genotipo Blanco presentó formación de (YA) en 100% de los medios estudiados y el Masaya en 85.71 %. El 6-BAP produjo mayor porcentaje de (YA) en comparación a la Kinetina, el 6-BAP (3 mgL-1) fue el mejor medio inductor de (YA) para ambos cultivares, en Masaya (85.71 %), y en Blanco (53.3 %) de los explantes sembrados. En la regeneración de plantas se encontró un efecto remanente de las citocininas utilizadas en la fase anterior, el cultivar Masaya presentó mayor formación de plantas.
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A obra De orbis sitv (descrição do mundo), também chamada De chorographia (corografia), foi escrita em três partes, por volta de 43 d.C. Situa a Terra no centro do universo e descreve regiões, costumes e artes da África, Europa e Ásia, sem contudo detalhar suas distâncias e sistemas administrativo. É o único tratado de geografia da Antiguidade escrito em latim clássico. Esta edição traz extensos comentários de Joaquim Vadiano e observações do teólogo João Camerti e de Rodolfo Agrícola.
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重离子束治癌是当今放射治疗中最科学、最先进、最有效的方法,是有代表性的高技术。目前仅有美、日、德实现了该技术,并已取得常规疗法难以实现的疗效。我国近年来开展了“重离子束治癌技术的基础研究”,其中,放射生物学及机理研究是重要内容。本论文从细胞、DNA分子、以及动物个体的三个不同层次上分别研究了重离子束治癌相关的生物学问题。在细胞研究方面。采用HeLa、B 16两种细胞分别研究了X一射线和重离子在水介质中入射的深度与相应细胞的存活率(1一失活率),结果表明:X一射线对细胞的损伤随深度而逐渐衰减(或细胞存活随深度逐渐增加),而重离子对细胞的损伤则为Bragg曲线(或细胞存活为倒Bragg曲线)。研究了25MeV/u ~(40)Ar~(14+)辐照人肝癌细胞SMMC一7721的微核及存活的动态变化,结果表明: 单次照射与分次照射的微核率随时间的变化规律在96h内没有明显区别,受照(单次、分次) 肝癌细胞的存活数随时间表现出衰减趋势,微核率与细胞存活数关系的动态变化为负相关性。研究了6MV X-射线和125.5keV/μm的重离子辐照B 1 6、V79细胞的2Gy存活率(SF2),结果表明:B16和V79细胞的存活率(P<0.01)依赖于不同的辐射性质(X-射线、~(12)C离子),其X-射线与~(12)C离子辐射这两种细胞的存活率之比分别为5.4和1.43,即~(12)C离子辐射增强了X-射线抗性细胞系的敏感性,从而显示了重离子治疗癌症的优势。研究了125.5keV/um的碳离子辐照小鼠黑色素瘤B16、人的宫颈癌HeLa、中国仓鼠肺V79、人的肝癌SMMC-7721四种细胞的相对生物学效率(RBE),得.到了RBE依赖于细胞种类的关系、RBE随细胞存活水平的升高而增加的关系、以及当LET≥125.5keV/μm时,RBE随着LET的增大而变小的关系。在DNA分子研究方面。研究了125.5keV/μm~(12)C~(6+)辐照小鼠黑色素瘤B 16、中国仓鼠肺V79、人的宫颈癌HeLa、人的肝癌SMMC一7721细胞的灵敏度(由D50表示)、DNA双链断裂(DSB)和DNA双链断裂片段分布,结果表明:细胞敏感性与DNA双链断裂之间没有一致的关系,提出了细胞辐射敏感性的一种可能的分子机理,即DNA序列敏感性位点协同DNA双链断裂互补性机理。由此解释了四种细胞系的不同敏感性问题。在动物个体研究方面。研究了57.28MeV/u氧离子50Gy一次性局部照射对B16黑色素瘤小鼠肿瘤生长的抑制作用,并观测了受照小鼠的死亡情况,结果表明:照射B16黑色素瘤后第10天观察,肿瘤生长延迟为6天、肿瘤抑制率为66%,耐受剂量小于50Gy。研究了50MeV/u ~(12)C~(6+)离子辐照对小鼠移植性肿瘤S180的抑制作用、控制率、治愈率和病理组织学变化,结果表明:各剂量组对S180肉瘤的抑制作用均大于90%,高剂量组抑瘤作用明显强于低、中剂量组(P
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On the basis of the thermodynamics of Gibbs, the spinodal for the quasibinary system was derived in the framework of the Sanchez-Lacombe lattice fluid theory. All of the spinodals were calculated based on a model polydisperse polymer mixture, where each polymer contains three different molecular weight subcomponents. According to our calculations, the spinodal depends on both weight-average ((M) over bar (w)) and number-average ((M) over bar (n)) molecular weights, whereas that of the z-average molecular weight is invisible. Moreover, the extreme of the spinodal decreases when the polydispersity index (eta = (M) over bar (w)/(M) over bar (n)) of the polymer increases. The effect of polydispersity on the spinodal decreases when the molecular weight gets larger and can be negligible at a certain large molecular weight. It is well-known that the influence of polydispersity on the phase equilibrium (coexisting curve, cloud point curves) is much more pronounced than on the spinodal. The effect of M, on the spinodal is discussed as it results from the infuluence of composition temperatures, molecular weight, and the latter's distribution on free volume. An approximate expression, which is in the assumptions of v* v(1)* = v(2)* and 1/r --> 0 for both of the polymers, was also derived for simplification. It can be used in high molecular weight, although it failed to make visible the effect of number-average molecular weight on the spinodal.
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从海洋动植物中寻找和筛选具有药用价值的活性先导化合物是海洋药物研发极为重要的理论基础研究。基于中国东南热带和亚热带沿海海域丰富的生物资源,本工作以化学分析和生物活性筛选为导向,以黄海海域习见的绿藻束生刚毛藻、南海三亚附近海域的圆裂短足软珊瑚、海绵Pseudoceratina sp.及广西沿海滩涂的盐生植物海刀豆四种海洋生物为样品,应用现代分析和检测手段对其次生代谢产物及其生物活性进行较系统的研究。 综合利用现代色谱手段和波谱技术,从上述目标生物样品中共分离并结构鉴定化合物74个,其中新化合物10个,新天然产物1个,这一新发现原则性结果,属国内外首次报道。1.对黄海海域束生刚毛藻C. fascicularis的化学成分及其生物活性进行了首次研究,从中得到叶绿素类新化合物Porphyrinolactone 1和新天然产物 20-Chlor-(132-S)-hydroxyphaeophytin a 2,在避光条件下对叶绿素类化合物进行体外NF-κB活性抑制筛选实验, 结果表明化合物1-6对NF-κB都有显著的抑制活性;对叶绿素类化合物首次进行体外蛋白酶体ChT-L的抑制活性实验筛选,化合物2和4对蛋白酶体ChT-L表现出显著的抑制活性,在浓度为50μM时,抑制率分别为70%和73.5%,并对其立体构型和生物活性的构效关系进行探讨;首次从该属得到环阿尔廷三萜类化合物7—12;对所得化合物7—15在浓度为1μg/mL时对肿瘤细胞部分靶蛋白酶的抑制活性测定结果表明,这些化合物对不同的靶蛋白酶表现出较强的抑制活性。2. 从南海圆裂短足软珊瑚中发现孕甾及其糖苷类新化合物22—27。3. 南海海绵Pseudoceratina sp.中发现溴代酪氨酸生物碱类新化合物41—42,组胺酸生物碱类新化合物43,并对其生源关系进行探讨。4. 首次对海刀豆C. maritime的化学成分进行研究,发现紫檀素类化合物61—63,异黄酮4个64—67;对该类化合物61—67首次进行NF-κB和蛋白酶体ChT-L的抑制活性筛选,其中化合物63表现出较强的NF-κB的抑制活性。
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The objective was to identify an appropriate cryoprotectant and protocol for vitrification of red sea bream (Pagrus major) embryos. The toxicity of five single-agent cryoprotectants, dimethyl sulfoxide (DMSO), propylene glycol (PG), ethylene glycol (EG), glycerol (GLY), and methyl alcohol (MeOH), as well as nine cryoprotectant mixtures, were investigated by comparing post-thaw hatching rates. Two vitrifying protocols, a straw method and a solid surface vitrification method (copper floating over liquid nitrogen), were evaluated on the basis of post-thaw embryo morphology. Exposure to single-agent cryoprotectants (10% concentration for 15 min) was not toxic to embryos, whereas for higher concentrations (20 and 30%) and a longer duration of exposure (30 min), DMSO and PG were better tolerated than the other cryoprotectants. Among nine cryoprotectant mixtures, the combination of 20% DMSO + 10% PG + 10% MeOH had the lowest toxicity after exposure for 10 min or 15 min. High percentages of morphologically intact embryos, 50.6 +/- 16.7% (mean +/- S.D.) and 77.8 +/- 15.5%, were achieved by the straw vitrifying method (20.5% DMSO + 15.5% acetamide + 10% PG, thawing at 43 degrees C and washing in 0.5 M sucrose solution for 5 min) and by the solid surface vitrification method (40% GLY, thawing at 22 degrees C and washing in 0.5 M sucrose solution for 5 min). After thawing, morphological changes in the degenerated embryos included shrunken yolks and ruptured chorions. Furthermore, thawed embryos that were morphologically intact did not consistently survive incubation. (C) 2007 Elsevier Inc. All rights reserved.
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The propagation in a rarefied plasma (n(e)less than or similar to 10(15) cm(-3)) of collisionless shock waves and ion-acoustic solitons, excited following the interaction of a long (tau(L)similar to 470 ps) and intense (I similar to 10(15) W cm(-2)) laser pulse with solid targets, has been investigated via proton probing techniques. The shocks' structures and related electric field distributions were reconstructed with high spatial and temporal resolution. The experimental results were interpreted within the framework of the nonlinear wave description based on the Korteweg-de Vries-Burgers equation.
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Variable-temperature magnetic susceptibility measurements in the solid state of the bis complex of tris(1-pyrazolyl)-methane with Fe(II), [Fe(tpm)2](ClO4)2, suggest the existence of singlet-quintet spin crossover with the singlet isomer largely favored at room temperature. In acetonitrile solution, measurement of the absorption spectrum as a function of temperature reveals a spin equilibrium with the quintet population varying from ca. 6% at 233 K to ca. 30% at 295 K. When the complex in solution is irradiated with a laser pulse at wavelengths within the ligand field absorption band of the singlet isomer, ground-state depletion occurs within the pulse duration followed by fast recovery to the original absorbance level with a time constant of 25 +/- 5ns. The recovery time is virtually independent of temperature over the range +23 to -43-degrees-C, but the signal:noise ratio of the transient signals increases with decreasing temperature. The effect was observable at several monitoring wavelengths spanning the LF and MLCT absorption regions of the complex but only when the irradiation wavelength fell within the LF absorption region. Irradiation within the MLCT band produced no effect other than that of laser pulse scatter. The observations are interpreted in terms of photoperturbation of the singlet-quintet spin state equilibrium, which in this case occurs solely through excitation in the ligand field absorption region of the complex and is the first reported instance of this type for a spin-crossover complex in solution.
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Laser-driven proton and ion acceleration is an area of increasing research interest given the recent development of short pulse-high intensity lasers. Several groups have reported experiments to understand whether a laser-driven beam can be applied for radiobiological purposes and in each of these, the method to obtain dose and spectral analysis was slightly different. The difficulty with these studies is that the very large instantaneous dose rate is a challenge for commonly used dosimetry techniques, so that other more sophisticated procedures need to be explored. This paper aims to explain a method for obtaining the energetic spectrum and the dose of a laser-driven proton beam irradiating a cell dish used for radiobiology studies. The procedure includes the use of a magnet to have charge and energy separation of the laser-driven beam, Gafchromic films to have information on dose and partially on energy, and a Monte Carlo code to expand the measured data in order to obtain specific details of the proton spectrum on the cells. Two specific correction factors have to be calculated: one to take into account the variation of the dose response of the films as a function of the proton energy and the other to obtain the dose to the cell layer starting from the dose measured on the films. This method, particularly suited to irradiation delivered in a single laser shot, can be applied in any other radiobiological experiment performed with laser-driven proton beams, with the only condition that the initial proton spectrum has to be at least roughly known. The method was tested in an experiment conducted at Queen's University of Belfast using the TARANIS laser, where the mean energy of the protons crossing the cells was between 0.9 and 5 MeV, the instantaneous dose rate was estimated to be close to 10(9) Gy s(-1) and doses between 0.8 and 5 Gy were delivered to the cells in a single laser shot. The combination of the applied corrections modified the initial estimate of dose by up to 40%.
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