Complementary Roles of the Hippocampus and the Dorsomedial Striatum during Spatial and Sequence-Based Navigation Behavior

We investigated the neural bases of navigation based on spatial or sequential egocentric representation during the completion of the starmaze, a complex goal-directed navigation task. In this maze, mice had to swim along a path composed of three choice points to find a hidden platform. As reported previously, this task can be solved by using two hippocampal-dependent strategies encoded in parallel i) the allocentric strategy requiring encoding of the contextual information, and ii) the sequential egocentric strategy requiring temporal encoding of a sequence of successive body movements associated to specific choice points. Mice were trained during one day and tested the following day in a single probe trial to reveal which of the two strategies was spontaneously preferred by each animal. Imaging of the activity-dependent gene c-fos revealed that both strategies are supported by an overlapping network involving the dorsal hippocampus, the dorsomedial striatum (DMS) and the medial prefrontal cortex. A significant higher activation of the ventral CA1 subregion was observed when mice used the sequential egocentric strategy. To investigate the potential different roles of the dorsal hippocampus and the DMS in both types of navigation, we performed region-specific excitotoxic lesions of each of these two structures. Dorsal hippocampus lesioned mice were unable to optimally learn the sequence but improved their performances by developing a serial strategy instead. DMS lesioned mice were severely impaired, failing to learn the task. Our data support the view that the hippocampus organizes information into a spatio-temporal representation, which can then be used by the DMS to perform goal-directed navigation.     

虎耳草科落新妇族的研究

本文探讨了落新妇族Trib．Astilbeae的系统发育和地理分布。依据进化论、被子植物性状演化总趋势和外类群比较,确认了该族及其外类群Penthorum的重要性状(染色体基数,花粉纹饰,胎座式,心皮、雄蕊、花瓣和萼片数目,萼片脉型,叶型)的极性。采用徐克学(1989)最大同步法做了分支分析,推导出了该族的系统树图。系统树图表明：Rodgersia和Astilboides是一单系类群,而Astilbe为其姊妹群; Rodgersia较Astilbe进化,Astilboides则居二者之间;Penthorum是落新妇族的姊妹群,且与之有共同祖先。迄今为止,已知落新妇族共有24种和13变种(原变种除外)。分布于Takhtajan(1986)的东亚区、大西洋-北美区、伊朗-土兰区和马来西亚区。在东亚区,日本、朝鲜和中国(吉林-辽宁东部)有3属、17种和变种,占该族种与变种总数的45．9％,其中,含有不同演化水平的类群和该族原始种有Astilbe platyphylla,A.simplicifolia和Rodgersia podophylla,此地区是该族的起源中心、现代分布中心和分化中心。 横断山地区有2属、11种和变种,占29．7％,是另一现代分布中心。本族较进化的种Astilbe biternata、A. indica、A.khasiana和Rodgersia nepalensis等,均出现于远离起源中心地区。据此推断,本族植物的散布路线可能是从日本、朝鲜和中国(吉林-辽宁东部)向北通过东西伯利亚和白令陆桥,继而向东南进入北美东南部;向南经中国南部至菲律宾和爪哇,向西南越秦岭-大巴山山地、横断山,入喜马拉雅。落新妇属 Astilbe和鬼灯檠属Rodgersia均分布于亚洲大陆和日本岛屿,而日本于晚第三纪以来,即与亚洲大陆分离,故落新妇属和鬼灯檠属的形成,当在日本与亚洲大陆分离之前。据此推知,落新妇族的起源时间可能在早第三纪,或可追溯至晚白垩纪。     

Are fire,soil fertility and toxicity,water availability,plant functional diversity,and litter decomposition related in a Neotropical savanna?

Understanding how biodiversity and ecosystem functioning respond to changes in the environment is fundamental to the maintenance of ecosystem function. In realistic scenarios, the biodiversity-ecosystem functioning path may account for only a small share of all factors determining ecosystem function. Here, we investigated the strength to which variations in environmental characteristics in a Neotropical savanna affected functional diversity and decomposition. We sought an integrative approach, testing a number of pairwise hypotheses about how the environment, biodiversity, and functioning were linked. We used structural equation modelling to connect fire frequency, soil fertility, exchangeable Al, water availability, functional diversity of woody plants, tree density, tree height, and litter decomposition rates in a causal chain. We found significant effects of soil nutrients, water availability, and Al on functional diversity and litter decomposition. Fire did not have a significant direct effect on functional diversity or litter decomposition. However, fire was connected to both variables through soil fertility. Functional diversity did not influence rates of litter decomposition. The mediated effects that emerged from pairwise interactions are encouraging not only for predicting the functional consequences of changes in environmental variables and biodiversity, but also to caution against predictions based on only environmental or only biodiversity change.     

实验恒河猴糖尿病动物模型建立及视网膜并发症的研究

[目的]糖尿病是由于多种因素和遗传因素导致体内胰岛素相对或绝对分泌不足,而引起的代谢性内分泌疾病,它以血糖、尿糖升高为特点,起病隐蔽,通过并发症使人致残致死,是继心血管、癌症之后的第三大致死性疾病,很可能成为21世纪人类的“第一杀手”(1,2)。本文采用人工诱导的方法,建立恒河猴糖尿病动物模型,研究糖尿病疾病的发展和及其并发症的发生、发展规律和防治措施,同时对于治疗糖尿病新药的安全性评价和药物疗效的观察具有广阔的运用前景。[方法]选用成熟的、健康的、雄性恒河猴9只,随机分成三个组,其中高剂量组(60mg/kg)1只,中剂量组(45m…     

Receptor-mediated transcytosis of botulinum neurotoxin A through intestinal cell monolayers

Botulism is mainly acquired by the oral route, and botulinum neurotoxin (BoNT) escapes the gastrointestinal tract by crossing the digestive epithelial barrier prior to gaining access to the nerve endings. Here, we show that biologically active BoNT/A crosses intestinal cell monolayers via a receptor-mediated transcytosis, including a transport inhibition at 4°C and a passage at 37°C in a saturable manner within 30–60 min. BoNT/A passage rate was about 10-fold more efficient through the intestinal crypt cell line m-IC_cl2, than through the carcinoma Caco-2 or T84 cells, and was not increased when BoNT/A was associated with the non-toxic proteins (botulinum complex). Like for neuronal cells, BoNT/A binding to intestinal cells was mediated by the half C-terminal domain as tested by fluorescence-activated cytometry and by transcytosis competition assay. A 'double receptor model' has been proposed in which BoNT/A interacts with gangliosides of GD_1b and GT_1b series as well as SV2 protein. Gangliosides of GD_1b and GT_1b series and recombinant intravesicular SV2-C domain partially impaired BoNT/A transcytosis, suggesting a putative role of gangliosides and SV2 or a related protein in BoNT/A transcytosis through Caco-2 and m-IC_cl2 cells.     

Different expression levels of the TAP peptide transporter lead to recognition of different antigenic peptides by tumor-specific CTL

Decreased antigenicity of cancer cells is a major problem in tumor immunology. This is often acquired by an expression defect in the TAP. However, it has been reported that certain murine Ags appear on the target cell surface upon impairment of TAP expression. In this study, we identified a human CTL epitope belonging to this Ag category. This epitope is derived from preprocalcitonin (ppCT) signal peptide and is generated within the endoplasmic reticulum by signal peptidase and signal peptide peptidase. Lung cancer cells bearing this antigenic peptide displayed low levels of TAP, but restoration of their expression by IFN-γ treatment or TAP1 and TAP2 gene transfer abrogated ppCT Ag presentation. In contrast, TAP upregulation in the same tumor cells increased their recognition by proteasome/TAP-dependent peptide-specific CTLs. Thus, to our knowledge, ppCT(16-25) is the first human tumor epitope whose surface expression requires loss or downregulation of TAP. Lung tumors frequently display low levels of TAP molecules and might thus be ignored by the immune system. Our results suggest that emerging signal peptidase-generated peptides represent alternative T cell targets, which permit CTLs to destroy TAP-impaired tumors and thus overcome tumor escape from CD8(+) T cell immunity.     

植物转基因位置依赖性沉默与位置效应

植物基因组能够识别外源基因的出现及所整合的特异位置并产生相应反应,通过分析嘧啶甲基化的信号及模式,比较不同表达水平转基因的整合位点及基因组环境差异,植物转基因位置依赖性沉默和位置效应的机理得到进一步揭示;讨论了位置效应的研究方法和克服策略。