蛋白细胞

蛋白细胞(albuminous cells)是裸子植物韧皮部中唯一与筛胞相连的一种特殊的薄壁组织细胞,其结构和功能相当于被子植物的伴胞。蛋白细胞最早是由 Strasburger(1891)发现并命名的,因此又有人称之为Strasburger 细胞。根据 Stras-     

植物细胞的水孔蛋白

对近年来发现和研究的转运水分跨膜运输的蛋白—水孔蛋白（aquaporins）,从种类、结构、功能调控及生理意义方面作了介绍。     

植物细胞表面蛋白的研究 Ⅲ 烟草细胞表面蛋白的组分

用有机溶剂CM、Tris-HCl缓冲(pH7.5)的生理盐水(TS)和稀碱(AS)溶液分类分离烟草细胞表面蛋白,发现含有10％左右的CM蛋白,30％左右的TS蛋白,60％左右的AS蛋白和一些未经鉴定的碱不溶性物质(AIS)。 CM蛋白的紫外吸收光谱分析,在波长260 nm附近有一吸收峰,波长320 nm处有一个肩,Sephadex LH-20亲脂性柱层析可分离出四个组分,按其光谱特性可分成两大类。TS蛋白主要是一些水解酶,已测出的有过氧化物酶,酯酶、磷酸酶和腺甙三磷酸酶。AS蛋白在Sepharose 4B柱上可分离出两个洗脱峰,SDS-10％聚丙烯酰胺凝胶电泳分离结果表明,主带分子量接近1.5×10~5道尔顿。 显微镜下观察TCSP及其用CM、TS和AS相继提取后的残存物形态,看到悬浮在无离子水中的TCSP表面密布黄色球形颗粒。CM提取后颗粒消失,出现比较平滑的表面。TS提取后残存物表面出现纹理结构和丝状物。AS提取后剩下的是一束束解开的纤维状物质。     

植物细胞G蛋白研究进展

ＧＴＰ结合调节蛋白（ＧＴＰ－ｂｉｎｄｉｎｇｒｅｇｕｌａｔｏｒｙｐｒｏｔｅｉｎｓ）,简称Ｇ蛋白,是活细胞内一类具有重要生理调节功能的蛋白质。此类蛋白由于其生理调节功能有赖于与三磷酸鸟苷（ＧＴＰ）的结合与水解ＧＴＰ的活性而得名。自从７０年代初在动物细胞中首先发现Ｇ蛋白的存在以来,有关Ｇ蛋白的研究发展迅速。现在已不仅知道在几乎所有真核细胞中存在Ｇ蛋白,而且已经证明Ｇ蛋白在细胞信号转导过程中有着非常重要的调节作用［１～６］。Ｇ蛋白的发现和研究,不仅使人们对细胞信号转导以及神经系统的信息传递有了新的进一步…     

杆状病毒细胞凋亡抑制蛋白

杆状病毒是一类数量庞大且相异的DNA病毒.这些病毒通过许多复杂的机制操纵昆虫细胞,其中之一就是调节宿主细胞的凋亡.杆状病毒凋亡抑制蛋白(inhibitor of apoptosis protein,IAP)在调节宿主细胞凋亡的过程中发挥十分重要的作用,许多杆状病毒基因组中都含有IAP基因.本文介绍了杆状病毒IAP基因的生物学特征及最近发现的几种抗宿主细胞凋亡的作用机制.     

热休克蛋白——细胞的内源性保护蛋白

关于应激反应的最初报道是 1 962年Ｒｉ ｔｏｓｓａ等在果蝇唾液腺染色体中发现一种热诱导的“蓬松”现象 ,并具有基因转录活性[1] 。 1 974年Ｔｉｓｓｉｅｒｓ等从热休克果蝇唾液腺细胞中分离出一组特殊蛋白质即热休克蛋白 (ｈｅａｔｓｈｏｃｋｐｒｏｔｅｉｎ ,ＨＳＰ)。目前根据分子量ＨＳＰ可分为 6个家族 ,1 0 0～ 1 1 0ｋＤ大分子ＨＳＰ家族、ＨＳＰ90家族、ＨＳＰ70家族、ＨＳＰ60家族、ＨＳＰ40家族及 1 8～ 3 0ｋＤ的小分子ＨＳＰ家族。其中ＨＳＰ70是最保守和研究最为深入的一种[2 ] 。在正常情况下 ,ＨＳＰ70通过辅助新生肽的折叠…     

HBc蛋白与NIRF蛋白细胞外相互作用鉴定

构建原核表达质粒pGST-HBc,真核表达质粒pFLAG-NIRF,表达并纯化GST-HBc蛋白,表达FLAG-NIRF蛋白,利用GST pull down技术鉴定HBc与NIRF蛋白的相互作用。利用PCR技术分别扩增HBc编码框和NIRF基因全长,并将其分别插入到原核表达载体pGEX-4T-1和真核表达载体p3*FLAG-CMV-10中,构建出pGST-HBc及pFLAG-NIRF。pFLAG-NIRF转染HEK293,培养48 h,收获前10 h加入MG132抑制蛋白酶体,收获细胞,经NP40裂解后离心收集上清pGST-HBc转化BL21(DE3)细菌,优化培养条件使GST-HBc在上清中大量表达,然后用GST4Bgel亲合纯化该蛋白,结合有GST-HBc蛋白与含FLAG-NIRF的细胞上清孵育后,离心收集GST 4Bgel,经洗脱液洗脱后蛋白电泳,western blotting分析。构建了pGST-HBc及pFLAG-NIRF,在上清中成功表达GST-HBc并纯化该蛋白,在细胞中成功表达FLAG-NIRF,GST pull down结果显示两者存在体外相互结合。HBc与NIRF能够在细胞外发生相互结合。     

衣原体蛋白的亚细胞定位

沙眼衣原体(Chlamydia trachomatis,CT)是一种严格细胞内寄生、有独特发育周期的原核细胞型微生物.CT在宿主细胞浆内增殖,形成光镜可见的典型细胞内包涵体,包涵体为CT在宿主细胞内的生长繁殖提供屏障保护,同时也是CT与宿主细胞进行物质交换和信息传递的门户,CT不仅可从宿主细胞摄取营养物质,还可分泌效应蛋白进入宿主细胞质调节宿主细胞功能.CT基因组DNA序列和功能注释完成后,衣原体蛋白的亚细胞定位、结构和功能的研究已成为衣原体研究领域的热点之一[1-3].在CT与宿主细胞相互作用过程中,Inc蛋白、分泌蛋白等衣原体蛋白可能发挥着重要作用,鉴于蛋白质的亚细胞定位情况往往与其功能密切相关,衣原体蛋白在感染细胞中的定位认识成为其功能研究中的重要环节.     

用植物细胞生产重组蛋白

京都大学水学部植物病理学教授古泽(?)男等小组利用一种花叶病毒(BMV),在植物细胞大量生产重组γ干扰素(IFNγ)(全蛋白量的10%)成功。用再现的植物体追试这项结果,可开发在大田生产重组蛋白的分子农业。该氏估算完成这项技术制造重组蛋白每1克约2～3日元。分子农业是比利时 PlantGenetic System 公司提倡的技术,1989年该公司利用油菜籽白蛋白基因,生产低分子的脑内肽获得成功。麒麟啤酒公司与帝京大学共同以烟草花叶病毒为载体用烟草生产脑啡肽。用这种方法只能生产5个氨     

The Cytological Studies on Albuminous Cells in Secondary Phloem of Pinus bungeana

This paper emphatically deals with the ultrastructure of albuminous cells in different stages of development in the secondary phloem of Pinus bungeana. The secondary phloem of Pinus bungeana is composed of sieve cells, axial parenchyma cells, radial plates and rays. Among the constituents, most of upright ray cells and radial plate parenchyma cells are albuminous cells. Although the shape and distribution of this kind of albuminous cells may be different, they possess the following common cytological characteristics. These cells have dense cytoplasm with abundant mitochondria, ribosomes, rough endoplasmic reticula and a large nucleus, the nuclei of some albuminous cells are lobed in shape which increases the outer surface of the nuclei. Usually the albuminous cell contains some starch granules, the quantity of the starch granules in albuminous cells is less than the other parenchyma cells of the secondary phloem. All these cytological characteristics suggest that albuminous cells are active physiologically. The distinguishing characteristics of albuminous cells from other parenchyma ceils are that the albuminous cells are associated with sieve cells through unilateral sieve area and they died together with the sieve cells.     

Studies on Cytochemistry of Albuminous Ceils in Secondary Phloem of Stem in Pinus bungeana Zucc.

Mature albuminous cells which are connected with differentiated and functional sieve cells show rather high activity of acid phosphatase at pH 5.0. No increased activity could be detected in ordinary ray cells, cambium cells and young albuminous cells contiguous with developing sieve cells. Collapsed albuminous cells show little or none of the activity. With ATP as substrate, enzyme localization is the same as with β-glycerolphosphate. When adenosine triphosphatase activity is visualized at pH 7.2 with ATP as substrate, the highest activity still localized in mature albuminous cells. With the development of young albuminous cells, the enzyme activity is being gradually exhibited, but disappearing when the maturecells begin collapsing. On the other hand, in ordinary ray cells the enzyme activity is ahnost not detectable.     

肿瘤干细胞及肝癌肿瘤干细胞

肿瘤干细胞理论认为只有存在于肿瘤中的少量干细胞性质的细胞群体对肿瘤发生和发展起着决定作用,肿瘤是由干细胞突变积累而形成的无限增殖的异常组织,这一理论的提出使人们对肿瘤发生机制的认识上升到了一个新的高度,也引起了研究者的广泛关注;肝癌是我国常见的恶性肿瘤之一,我国肝癌死亡率居世界之首,目前对肝癌的研究是我国恶性肿瘤防治的重点工作,现对当前肿瘤干细胞与肝癌肿瘤干细胞相关方面的最新研究进展作一概述。     

Fusion of Tumour Cells with Host Cells

THE A9 cell is an 8-azaguanine-resistant derivative of the L cell line¹. It lacks the enzyme inosinic acid pyrophosphorylase and is thus unable to grow in media such as HAT² in which endogenous synthesis of nucleic acid is blocked by aminopterin. The A9 line has little ability to grow progressively in vivo. Inocula of 5 × 10⁴ to 2 × 10⁶ cells produced progressive tumours in only 12% of X-irradiated newborn syngeneic C3H mice³. One of these tumours was explanted as a cell suspension into Eagle's minimal essential medium containing 15% foetal calf serum and then subcultivated in this medium with 5% foetal calf serum. At each passage, cells were inoculated into X-irradiated newborn syngeneic C3H or semi-allogeneic C3H×X F₁ mice (X designates a number of different allogeneic parents). Between 80 and 90% of the inoculated animals developed progressive tumours. The cell line was therefore designated A9HT (high take incidence). The karyotype of the A9HT line was found to be similar to that of the A9 line, but with a slightly reduced total chromosome number. The modal chromosome number of A9HT was about 53, compared with about 57 for A9 (see ref. 4). A9 and A9HT both had between 20 and 30 bi-armed chromosomes and a number of marker chromosomes in common. A detailed comparison of the karyotypes of the two lines examined by the quinacrine fluorescence technique has been made⁵. The A9HT line, like its A9 parent, lacks inosinic acid pyrophos-phorylase and is unable to grow in HAT medium.     

Dendritic Cells: Migratory Cells that are Attractive

Dendritic cells (DC) are professional antigen presenting cells, playing an important role in the initiation of T- and T cell dependent immune responses. DC are highly mobile cells and the sequential migration of DC in and out of tissues is accompanied by phenotypical as well as functional changes instrumental to their function as sentinels of the immune system. Herein, we will review recent progress in understanding the origin of DC, their migratory behaviour and their capacity to attract and interact with lymphocytes, with emphasis on the chemokine system.     

体细胞重编程逆转为干细胞的研究进展

目前细胞和发育生物学上的研究成果为生物医学研究提供了广泛的前景.将完全分化的细胞重编程,不经过胚胎逆转为多能干细胞状态,这点燃了再生医学应用的新希望,这一成果从法律、道德、伦理等不同方面被人们所接受.通过体细胞克隆胚胎获得干细胞所面临的破坏胚胎的伦理限制,促使研究者去寻求将分化细胞重编程逆转为干细胞的新方法.主要论述了体细胞重编程的原理、过程及不经过胚胎逆转为多能干细胞的方法.     

Dendritic Cells and Regulatory T Cells in Atherosclerosis

Although macrophages and other immune system cells, especially T cells, have been shown to play disease-promoting roles in atherosclerosis, less is known about the role of antigen presenting cells. Functional, immune stimulating dendritic cells (DCs) have recently been detected in aortic intima, the site of origin of atherosclerosis. We had compared DCs with macrophages in mice with experimental atherosclerosis, to clearly define cell types by developmental and functional criteria. This review summarizes recent advances in studies of DCs in humans and in mouse models of atherosclerosis, as well as providing a simple strategy to measure regulatory T (Treg) cells in the mouse aorta.     

Place Cells,Grid Cells,and Memory

The hippocampal system is critical for storage and retrieval of declarative memories, including memories for locations and events that take place at those locations. Spatial memories place high demands on capacity. Memories must be distinct to be recalled without interference and encoding must be fast. Recent studies have indicated that hippocampal networks allow for fast storage of large quantities of uncorrelated spatial information. The aim of the this article is to review and discuss some of this work, taking as a starting point the discovery of multiple functionally specialized cell types of the hippocampal–entorhinal circuit, such as place, grid, and border cells. We will show that grid cells provide the hippocampus with a metric, as well as a putative mechanism for decorrelation of representations, that the formation of environment-specific place maps depends on mechanisms for long-term plasticity in the hippocampus, and that long-term spatiotemporal memory storage may depend on offline consolidation processes related to sharp-wave ripple activity in the hippocampus. The multitude of representations generated through interactions between a variety of functionally specialized cell types in the entorhinal–hippocampal circuit may be at the heart of the mechanism for declarative memory formation.The scientific study of human memory started with Herman Ebbinghaus, who initiated the quantitative investigation of associative memory processes as they take place (Ebbinghaus 1885). Ebbinghaus described the conditions that influence memory formation and he determined several basic principles of encoding and recall, such as the law of frequency and the effect of time on forgetting. With Ebbinghaus, higher mental functions were brought to the laboratory. In parallel with the human learning tradition that Ebbinghaus started, a new generation of experimental psychologists described the laws of associative learning in animals. With behaviorists like Pavlov, Watson, Hull, Skinner, and Tolman, a rigorous program for identifying the laws of animal learning was initiated. By the middle of the 20th century, a language for associative learning processes had been developed, and many of the fundamental relationships between environment and behavior had been described. What was completely missing, though, was an understanding of the neural activity underlying the formation of the memory. The behaviorists had deliberately shied away from physiological explanations because of the intangible nature of neural activity at that time.Then the climate began to change. Karl Lashley had shown that lesions in the cerebral cortex had predictable effects on behavior in animals (Lashley 1929, 1950), and Donald Hebb introduced concepts and ideas to account for complex brain functions at the neural circuit level, many of which have retained a place in modern neuroscience (Hebb 1949). Both Lashley and Hebb searched for the engram, but they found no specific locus for it. A significant turning point was reached when Scoville and Milner (1957) reported severe loss of memory in an epileptic patient, patient H.M., after bilateral surgical removal of the hippocampal formation and the surrounding medial temporal lobe areas. “After operation this young man could no longer recognize the hospital staff nor find his way to the bathroom, and he seemed to recall nothing of the day-to-day events of his hospital life.” This tragic misfortune inspired decades of research on the function of the hippocampus in memory. H.M.’s memory impairment could be reproduced in memory tasks in animals and studies of H.M., as well as laboratory animals, pointed to a critical role for the hippocampus in declarative memory—memory, which, in humans, can be consciously recalled and declared, such as memories of experiences and facts (Milner et al. 1968; Mishkin 1978; Cohen and Squire 1980; Squire 1992; Corkin 2002). What was missing from these early studies, however, was a way to address the neuronal mechanisms that led information to be stored as memory.The aim of this article is to show how studies of hippocampal neuronal activity during the past few decades have brought us to a point at which a mechanistic basis of memory formation is beginning to surface. An early landmark in this series of investigations was the discovery of place cells, cells that fire selectively at one or few locations in the environment. At first, these cells seemed to be part of the animal’s instantaneous representation of location, independent of memory, but gradually, over the course of several decades, it has become clear that place cells express current as well as past and future locations. In many ways, place cells can be used as readouts of the memories that are stored in the hippocampus. More recent work has also shown that place cells are part of a wider network of spatially modulated neurons, including grid, border, and head direction cells, each with distinct roles in the representation of space and spatial memory. In this article, we shall discuss potential mechanisms by which these cell types, particularly place and grid cells, in conjunction with synaptic plasticity, may form the basis of a mammalian system for fast high-capacity declarative memory.     

种子细胞——组织工程连载之三

种子细胞也是组织工程的核心研究内容,获得足够数量和质量的种子细胞是开展体外组织工程的必要基础。用于组织工程的种子细胞必须具有形成新组织结构的能力,主要来源于自体、同种异体或异种,在具体应用时各有利弊。一些成体干细胞由于不存在伦理争议以及发育分化条件相对简单等优势是重要的种子细胞,包括造血干细胞、骨髓干细胞、神经干细胞、脂肪干细胞、皮肤干细胞。人胚胎干细胞及其组织工程要真正在临床医学中得到应用,还有很长的一段路要走。其他一些细胞也可以作为组织工程种子细胞,包括内皮细胞、上皮细胞、成纤维细胞、骨细胞、成骨细胞、角质细胞、前脂肪细胞、脂肪细胞、肌腱细胞等。这些细胞已分化,分裂能力有限,但仍应用于组织工程。理想的种子细胞具有一定标准。