952 resultados para Zeuxis, active 5th century B.C.


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观赏向日葵作为一种新型花卉,具有巨大的市场开发潜力。而花色作为向日葵的重要观赏性状之一,对其的研究却比较少。本文从向日葵花色多样性、花色遗传规律、花色与虫媒传粉的关系及其对向日葵花色遗传的影响做了分析和讨论,利用英国皇家园艺学会比色卡和分光色差仪对向日葵的花色做了归类总结,并且利用高效液相色谱法对向日葵的花青苷成分做了分析研究。 本研究结果表明,彩色向日葵色系可以分为两大类,即黄色系和红色系,其中红色系向日葵的花色变异较小;而黄色系向日葵的花色变异较大,可以再细分为橙黄色和柠檬黄色两个亚类。利用高效液相色谱法测定了39份向日葵舌状花瓣中的花青苷大概有9种(A、B、C、D、E、F、G、H、I),这9种花青苷并不是在所有39份样品中都出现,且红色系向日葵中花青苷的种类较多。花青苷G在红色系和黄色系向日葵中均被检出。对红色向日葵花瓣的花青苷提取液进行多级质谱分析发现,花青苷元类型主要是矢车菊苷元,其糖苷类型主要是和葡萄糖、鼠李糖和/或阿拉伯糖结合;而在纯黄色的向日葵中通过多级质谱分析未检测到这些花青苷,说明矢车菊类花青苷是红色向日葵舌状花红色形成的化学基础。

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An experiment was conducted with Labeo rohita fingerlings in an indoor static fish rearing water system of glass made aquaria. Five experimental diets A, B, C, D and E were formulated containing 33% dietary protein level in five treatments each having two replicates containing 12 fingerlings of mean total initial weight of 13.00±0.2g. Sixty days of feeding trial in this experiment showed that fish fed on diet 'A' containing fish meal and diet 'E' containing mixed plant sources protein had significantly highest and lowest growth respectively. However, no significant difference of growth was found in fish fed on diets C and D containing meat and bone meal, and mix of animal protein source diets respectively. The result showed that the apparent protein digestibility (APD) of diets 'A' and 'E' had significantly best and least values respectively. Food conversion ratio (FCR) and protein efficiency ratio (PER) ranged between 1.37 to 2.17 and 1.38 to 2.18 respectively. On the basis of observed FCR and PER diets 'A' and 'E' produced significantly highest and lowest growth respectively.

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定点突变技术可以对某个已知基因的特定碱基进行定点改变、缺失或者插入,从而改变对应的氨基酸序列和蛋白质结构,因而成为研究蛋白质结构和功能之间的复杂关系的有力工具。对突变基因的表达产物进行研究有助于我们了解蛋白质结构和功能的关系,探讨蛋白质的结构/结构域。 植物体光系统II的大量捕光色素蛋白复合体(LHCIIb)具有多种功能,在自然界不同日光光强下分别执行捕获、传递光能或将过度激发能非光化学耗散的功能。最新的近原子分辨率LHCIIb晶体结构揭示出在LHCIIb穿膜螺旋B/C间的环区具有复杂的超二级结构,其中一个新发现就是在此环区靠近穿膜螺旋C的区域中存在一个反平行股的结构,其功能不明。为了研究此反平行链对于LHCIIb复合体在结构和功能上的意义,我们将了这一区域的3个氨基酸(Val119、His120、Ser123)分别定点突变成Phe、Leu和Gly,并研究了这三个定点突变对LHCIIb结构和功能上的影响。结果如下:1,CD光谱揭示出该反平行链对于调节新黄质及其附近色素群的构象十分重要。虽然这三个突变只造成很少的新黄质丢失(V119F, 0.09; S123G, 0.17; and H120L, 0.26),但是却使色素构象发生了巨大变化。2,将S123突变成G导致复合物对光破坏更加敏感并且更易于聚集,在介质酸化后复合物的荧光淬灭更加显著。这些结果说明这段反平行链对于调节LHCIIb色素构象以及控制LHCIIb聚集体形成和叶绿素荧光产量具有重要作用。 以结构为基础的计算设计方法与定向进化相结合是蛋白质工程的一个发展方向。最近,通过计算设计已成功地向蛋白质引入了新的催化活性、提高了蛋白质的稳定性、设计了酶的催化活性位点、改变了酶的底物特异性等. 目前还没有见到有研究定向地,以理性方式对LHCIIb进行蛋白质设计。我们使用蛋白质的计算机辅助设计工具——RosettaDesign鉴定出一个可以显著提高LHCIIb光、热稳定性的定点突变I124L,并且突变体的的结构和功能与野生型无异。这是首次将计算机辅助设计应用于提高LHCIIb稳定性的研究。

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本文研究了10个大豆品种在吸胀期对冷害的敏感性的差异。结果表明: (1)依据对低温反应的差异,各品种可归为三种类型:a)冷敏感型,低温处理使其各种萌发指标大幅度下降;b)抗冷型,低温处理使其各种萌发指标下降很小;c)中抗型,介于两者之间。 (2)低温导致的冷敏感品种的ATP含量下降幅度大于抗冷型的。 (3)抗冷品种脱氢酶活性高,且低温导致的下降幅度小;而冷敏感品种则相反。 (4)抗冷性越强,SOD活性越高,MDA含量越低,且低温导致的MDA含量的升高也越小。 (5)除个别品种外,低温导致的敏感品种的电导率升高大于抗冷型的。 (6)低温处理下,抗性品种的胚根细胞仍具有较高的ATPase活性,含有大量液泡和内质网;而冷敏感品种不仅ATPase活性低,且只有蛋白体和拟脂体,未见到液泡和内质网。 依据以上结果,提出了大豆吸胀冷害的可能机制:低温下质膜修复与重建、ATP迅速产生及一些酶的活化的受阻可能是大豆吸胀冷害的原初反应,由此导致一系列生理、生化紊乱,以致于萌发缓慢,活力降低。 我们建议萌发生理测定、ATP含量测定及电导实验可用做大豆抗冷性的评价。

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La corriente de Malvinas corre de sur a norte sobre el borde del talud que marca el fin de la plataforma continental patagónica (océano Atlántico sudoccidental), a lo largo de unos 1800 kilómetros. Su presencia da lugar a una zona del mar con muy rica diversidad biológica y ecológica, lo que incluye pesquerías de importancia económica regional. Los datos satelitales permiten avanzar el estudio del mar patagónico en una zona en que las aguas de la plataforma continental cambian de temperatura por efecto de la corriente fría de Malvinas, lo que influye notablemente sobre la vida marina. Este artículo de divulgación científica incluye información sobre frentes oceánicos del Mar Argentino, datos satelitales y detección de ramas y frentes térmicos, la ecología de las especies marinas, finalizando con lecturas sugeridas.

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本文通过细胞遗传学、mtDNARFLP(线粒体DNA、限制性片段长度多态性)和血液蛋白及同工酶3个方面的研究,分析了云南文山黄牛和迪庆黄牛的遗传多样性和遗传分化关系。结果:(1)细胞遗传学云南两个地方黄牛品种的Y染色体形态及其C一带具有显著多态性。文山黄牛和迪庆黄牛分别为一小的近端部和亚申部(或中部)着丝位Y染色体,并分别在Y染色体的臂端部和短臂的臂端部显示弱阳性C一带,说明文山黄牛的父系起源可能是瘤牛(Bosindicus),而迪庆黄牛是普遍牛(Bostaurus)。推测两种Y染色体可能是臂问倒位的结果。(2)mtD-NARFLP两个黄牛品种的111个个体的mtDNA经8种限制性内切酶酶切后,有个酶表现出多态,共检测到17种限制性态型。归结出的3种基因单倍型,分别是A-A-A-A-A-A-A型(瘤斗)、B-B-B-B-B—B-B型(普通型)和A-C-B-B-C-A-A型(耗半Bosgrunniens)。从基因单倍型在群体中的表现可看出,文山黄牛和迪庆黄牛都具有瘤牛和普通牛两种母系起源。但文山黄牛以瘤牛血统为主,迪庆黄牛以普通牛血统为主,而且还可能含有部价耗牛的血统。(3)血液蛋白及同工酶分析了两个黄牛品种的...

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A laboratory-feeding trail was conducted for 45 days with fry of common carp Cyprinus carpio L. (0.45±0.03g) in aquaria in a static indoor fish rearing system. The fry were fed on a pelleted diet containing 33% crude protein having fishmeal as major protein source. The fish fry in five treatments A, B, C, D, and E, each with two replicates were fed on 5% daily ration divided into different feeding frequencies of 2, 3, 4, 5 and 6 times a day respectively in order to observe the growth performance. Each replicate contained 15 fry having total initial weight of 6.87±0.31g. At the end of the feeding trial, significantly different and higher (p<0.05) growth response was observed in treatment C having a feeding frequencies of 4 times a day. Significantly the highest and the lowest percent growth of 334.30 and 218.91% were observed in fish fed on the diet (Treatment C) with 4 times and (Treatment A) 2 times feeding frequencies per day, respectively. Food conversion ratio (FCR) of 1.78 was significantly higher (p

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Let A and B be nonsingular M-matrices. A lower bound on the minimum eigenvalue q(B circle A(-1)) for the Hadamard product of A(-1) and B, and a lower bound on the minimum eigenvalue q(A star B) for the Fan product of A and B are given. In addition, an upper bound on the spectral radius rho(A circle B) of nonnegative matrices A and B is also obtained. These bounds improve several existing results in some cases and the estimating formulas are easier to calculate for they are only depending on the entries of matrices A and B. (C) 2009 Elsevier Inc. All rights reserved.

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Seasonal patterns of 21 fisheries in Karnataka (after isolation from time-series components) are presented. Depending on the pattern of seasonal fluctuation in landings, 19 fisheries have been grouped into five patterns, A, B, C, D and E. Ribbon fishes and 'other clupeids' did not exhibit any significant seasonal pattern. Pattern A with highest landings in the 4th quarter (October to December), followed by the 1, 2 and 3 quarters, is the most common in 10 species/groups (comprising 78% of the total landings). Harmonic analysis has been carried out using the seasonal indices.

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Sixty six samples of frozen fishery products consisting of frozen crab meat, frozen prawns, frozen cuttlefish and frozen mussel collected from nine cold stores situated in and around Cochin city were examined for coagulase positive staphylococci. Forty eight samples (72.72%) revealed the presence of coagulase positive staphylococci, which were then tested for enterotoxigenity, employing cellophane-over-agar method for toxin production and optimum-sensitivity-plate (OSP) method for toxin detection. Seventy seven out of one hundred and two (75.49%) coagulase positive staphylococcal isolates from the above products produced enterotoxins A, B, C, D and E either singly or in combinations. Enterotoxin A and D were detected more often than others. The occurrence of enterotoxigenic staphylococci in frozen fishery product is reported for the first time in this country.

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利用夏季自然发情的云南黄牛为受体,开展了奶牛体内冷冻胚胎移植.留用的114头受体牛中,本地黄牛59头,年龄在3~10岁,均为经产牛,最终移植27头,西杂牛56头(其中2岁以下的青年牛26头),移植29头(青年牛11头),两个品种受体利用率分别为45.8%和51.8%;移植后妊娠率分别为59.3%和55.2%;解冻的63枚胚胎移植给了56头受体牛,A级胚胎单独移植和B、C级胚胎搭配移植最终妊娠结果分别是58.5%(24/41)和53.3%(8/15);发情后第6 d和第7 d移植妊娠率分别为56%和58.1%.结果表明,1~10岁的西杂牛和3~10岁体型较大的本地黄牛均可作为受体移植奶牛胚胎;利用自然发情的云南黄牛做受体移植效果较为理想,是一种经济、方便、适合云南广大农村推广的技术途径;A级胚胎单独移植和B、C级搭配移植可获得较为理想的妊娠结果;处于发情后第6 d和第7 d的云南黄牛都可以作为桑囊期奶牛胚胎的移植受体.

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利用荷斯坦奶牛性控冻精生产性控胚胎的试验.选用澳大利亚进口荷斯坦奶牛为供体,按常规方法进行超数排卵,以国产荷斯坦奶牛性控冻精进行人工授精生产性控胚胎.试验共超排供体牛7头,获胚胎6枚及未受精卵33枚,胚胎中可用的B级和C级胚各1枚,退化胚4枚;移植受体牛2头均未受孕,试验表明性控冻精的质量尤其是有效精子可能是生产性控胚胎的决定因素.