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关键词： 肝脏组织工程   胚胎干细胞   肝细胞  

摘要： 肝脏组织工程是新近兴起的一门学科 ,其目的是经过培养形成有独立代谢功能的肝脏器官。其中 ,种子细胞来源是关键 ,胚胎干细胞由于不存在来源短缺及异种排斥问题 ,是理想的选择 ,现在许多学者进行了由胚胎干细胞向肝细胞的转化研究 ,并与人工材料 ,基因调控等技术结合 ,取得了显著的进展 ,这些研究解决了许多理论和实践上的问题 。

关键词： 组织培养   棉花   胚胎发生   直接诱导   植株再生  

摘要： 选用陆地棉(GossypiumhirsutumL.)品种中棉所12,首次直接诱导获得棉花体细胞胚胎发生,并获得了再生植株。结果表明,激素是影响棉花体细胞胚胎直接发生的重要因素,单独使用ZT可直接诱导获得棉花胚性愈伤组织和胚状体,2,4-D的添加虽有利于愈伤组织的形成,但却没能直接诱导获得胚性愈伤组织,IAA的添加削弱了ZT的诱导效果。下胚轴、子叶和胚根直接诱导获得胚胎发生的能力不同,其中以子叶的分化能力最强,胚根次之,下胚轴较差。实验中,棉花体细胞胚胎直接发生的最高频率为11.42%,占诱导获得总愈伤组织的44.44%。

关键词： polyembryonic rice   egg apparatus   embryo sac   apogamety   reproduction  

摘要： The structural and histochemical changes of the egg apparatus in the polyembryonic rice ( Oryza sativa L.), ApⅢ with the highest frequence of additional embryos among the polyembryonic rice investigated, before and after fertilization were studied and compared with those of normal and other polyembryonic rices in a similar developmental period. A total of 2 932 ovules were observed and each of them contained only a single embryo sac with a set of egg apparatus. Among 1 655 embryo sacs, there were 1 643 embryo sacs (99.27%) with one normal egg apparatus in each embryo sac, and only 12 embryo sacs (0.73%) from the remainder with 4_celled egg apparatus, i.e. two eggs and two synergids. Neither the numerous poly_egg apparatus and egg_like cells, nor the double set of embryo sacs each containing one egg apparatus and other abnormal egg apparatus in single ovary, which were reported by earlier investigators to have high frequency of embryo production in SB_1 and ApⅣ, were observed. The egg cell was located at the subterminal site of the micropylar end of embryo sac. The cytoplasm of egg cell was rich in protein materials and polysaccharide grains, which did not disappear until the division of zygote. The prominent nucleus was closely surrounded by protein and polysaccharide grains, which did not disappear until the division of zygote. No cytological difference was found between egg cells from the normal and abnormal egg apparatus. The two synergids were fully developed and situated at the upper most part of the micropylar end of the mature embryo sac. In most embryo sacs, the synergids were flask_shaped with longer necks, and a widened cap_shaped top, in close contact with the micropyle. The synergids had a well developed filiform apparatus. The characteristic appearance of the filiform apparatus as well as the cap_neck region of synergids before and after pollen tube penetration were easily distinguishable from the egg cell. The structure, the stainability with Coomas

关键词： 组织学   多媒体教学   组织胚胎学   教学  

摘要： 在组织学与胚胎学的教学中,对于刚刚转入专业学习的医学新生来说,入门引导与医学科学相应学习法的指点是非常重要的.作为一名青年教师,要以饱满的热情投入到教学中去,积极主动地探索有效的教学手段和教学方法,并尽快掌握.

关键词： 组织块法   体外培养   人胚胎   神经干细胞  

摘要： 目的　探索体外分离、培养人胚胎脑组织神经干细胞的实用方法。方法　从人胚胎脑额叶皮层分离组织块 ,采用DMEM/F12 +N2无血清培养基 ,进行体外培养、传代。采用免疫细胞化学法鉴定神经干细胞和分化后的其他细胞表型。结果　从人胚胎脑额叶皮层分离的细胞具有增殖和多向分化潜能 ,可进行传代培养 ,获得的细胞中大部分为Nestin表达阳性的细胞。诱导分化后可以出现NSE、GFAP表达阳性的细胞。结论　用上述方法分离培养的细胞具有神经干细胞的特性 ,并表达Nestin蛋白 ,认为是神经干细胞。

关键词： adaxial-abaxial axis   class IKNOX genes   CUC   embryogenesis   shoot apical meristem  

摘要： The shoot apical meristem (SAM) is essential for organ formation in higher plants. How the SAM is formed during plant development is poorly understood, however. In this review, we focus on several recent studies that provide new insights into the mechanism of SAM formation during embryogenesis. Recently, positive and negative regulators of the class I KNOX genes, which are thought to be necessary for SAM formation, have been identified;the Arabidopsis CUP-SHAPED COTYLEDON (CUC) genes are required for the expression of a class I KNOX gene, SHOOT MERISSTEMLES (STM) during embryogenesis, and the Arabidopsis ASYMMETRIC LEAVES1 (AS1), AS2, and several other genes negatively regulate KNOX gene expression in cotyledon primordia. Also, several genes that are involved in the formation of the adaxial-abaxial axis of cotyledons seem to regulate embryonic SAM formation.

关键词： forage grass   monocot   Paspalum notatum Flugge   somatic embryos   tissue culture  

摘要： Bahiagrass (Paspalum notatum Flugge) is a warm season forage grass widely cultivated in southeastern U.S. and South America. The cultivar Tifton 9 has several desirable characteristics such as high forage yield, more vigor at the seedling stage, etc.;but its forage quality is very low. As an initial step for future genetic manipulations to improve its forage characteristics, we have optimized in vitro culture conditions for plant regeneration. In this report, we describe an efficient method for embryogenic callus induction and plant regeneration from bahiagrass (cv. Tifton 9) seed explants, which are readily available and easy to manipulate, compared to other explant sources reported in the literature. Murashige and Skoog (MS) medium containing 30 muM dicamba and 5 muM 6-benzyladenine (BA) was optimal for callus induction and growth. Out of 9734 seeds cultured, 65.7% germinated and 21.4% produced embryogenic callus on this medium. Shoot formation was best when embryogenic calluses induced in this medium were transferred to MS medium supplemented with 5 muM BA and 1 muM gibberellic acid with 1640 plantlets formed per gram fresh weight of callus tissue. When transferred to hormone-free SH medium, shoot systems produced well-developed root systems. The resulting plantlets grew normally produced viable seeds when transferred to soil in the greenhouse. Histochemical staining for GUS activity arising from transient expression of the introduced uidA (beta-glucuronidase) gene indicated that bahiagrass embryogenic callus produced by this method is suitable for gene transfer via biolistic bombardment;and it can serve as a good target tissue for future genetic manipulations to improve the forage quality of bahiagrass (cv. Tifton 9).

关键词： hypoxia   GABA(A)   receptor   neurosteroid   barbiturate   CNS  

摘要： Using a previously developed model of acute normobaric hypoxic hypoxia on chick embryos, here we studied at embryonic day 12 the in vitro effect of two positive allosteric modulators of GABA binding, the barbiturate sodium pentobarbital and the neurosteroid allopregnanolone. In both cases an increase in E-max values in membranes obtained from hypoxic embryos was observed. Studies of GABA-gated chloride influx showed that there were no differences in maximal chloride uptake between hypoxic and control membranes. We have already demonstrated that maximal density of GABA binding sites was decreased after hypoxia, suggesting that each of the remaining GABA, receptors display a greater chloride flux than controls. To further characterize GABA(A) receptor alterations, GABA-gated chloride influx modulated by the above barbiturate and neurosteroid was determined, finding that E-max values were increased 60% and 42%, respectively. The increase in Cl- influx per receptor subsequent to hypoxic trauma, and the enhancement in the modulatory properties studied, may mediate neuronal damage by potential changes in subunit interaction at the GABA(A) receptor level. (C) 2002 Elsevier Science B.V. All rights reserved.

关键词： Cells  

摘要： During angiogenesis, endothelial cells undergo proliferation, reorganization, and stabilization to establish a mature vascular network. This process is critical for establishing a functional circulatory system during development and contributes to the pathological process of tumor growth. Here we report that embryos deficient for the ERK5 MAPK die between embryonic days 10.5 and 11.5 with angiogenic failure and cardiovascular defects. We show that ERK5 deficiency leads to an increased expression of the vascular endothelial growth factor (VEGF), dysregulation of which has been shown to impede angiogenic remodeling and vascular stabilization. Our data also reveal that ERK5 negatively regulates transcription from the vegf locus during hypoxic responses. Importantly, ERK5 is required at an earlier developmental stage than p38a, and p38a does not compensate for ERK5 deficiency. These results demonstrate that ERK5 plays a specific role in the regulation of early angiogenesis.

关键词： 肺泡上皮   模拟练习   人体解剖学与组织胚胎学   中央电大   中央广播电视大学   透明层  

摘要： 1名词解释(1)三联体 (2)关节囊(3)肝胰壶腹 (4)黄斑(5)反射弧 (6)锥体系