啮齿动物鉴别虫蛀种子的能力及其对坚果植物更新的潜在影响

作为种子捕食者和种子扩散者, 啮齿动物对产坚果植物的自然更新有很大作用。然而, 对啮齿动物鉴别虫蛀种子的能力颇有争议。2001 年秋季在中国四川都江堰市实验林场, 以3 种比例(I₁∶S = 1∶1 , I₁∶S = 4∶1 和I₁∶I₂∶S = 1∶1∶1)供给啮齿动物4 种壳斗科种子: 栓皮栎( Quercus variabilis) 、枹树( Q. serrata) 、青冈( Cyclobalanopsis glauca) 和栲树( Castanopsis fargesii) 的3 种坚果型(即饱满种子(S) , 不含象虫的虫蛀种子(I₁) 和含象虫的虫蛀种子( I₂ ) 验证了啮齿动物能够准确地鉴别虫蛀种子这一假说。结果表明, 在3 种比例下4 种坚果的虫蛀种子的消失速率均慢于饱满种子。即使虫蛀种子的比例增加, 啮齿动物显著地搬走了更多的饱满种子(67%～92%) 。当虫蛀种子的比例增加时, 虫蛀种子就地消耗和拒绝的比例降低, 搬走比例增加。啮齿动物并不拒绝虫蛀种子, 这可能与它们的可利用性(如象虫可以作为蛋白质的补充) 和数量以及它们的觅食行为有关。结果证实啮齿动物能准确地鉴别虫蛀种子, 从而有区别地搬走并贮藏更多的饱满种子, 消耗一部分可以利用的虫蛀种子(包括其内的象虫) 。这样, 啮齿动物通过对饱满种子和虫蛀种子的鉴别和选择会影响不同种子的命运, 从而对这些坚果植物的自然更新产生影响。     

Prelude to oral microbes and chronic diseases: past,present and future

Associations between oral and systemic health are ancient. Oral opportunistic bacteria, particularly, Porphyromonas gingivalis and Fusobacterium nucleatum, have recently been deviated from their traditional roles as periodontal pathogens and arguably ascended to central players based on their participations in complex co-dependent mechanisms of diverse systemic chronic diseases risk and pathogenesis, including cancers, rheumatoid-arthritis, and diabetes.     

植物群落中物种小尺度空间结构研究

植物群落中, 物种小尺度空间结构影响着种群或群落的动态及有关的生态学过程。植物主要是和它同种或异种的邻近个体相互作用,植物个体周围的局部环境和大空间尺度下群落的平均水平是完全不同的。群落中的许多过程都影响小尺度空间结构的形成和动态,同样,局部空间结构反过来影响着植物的生长、更新和凋亡等重要过程。鉴于目前对小尺度空间结构进行的大量研究以及其重要性,有必要对其研究进展进行适当的总结,以期明确将来进一步的研究方向。该文以此为出发点,首先介绍了植物群落中物种小尺度空间结构产生的6个原因:1)生境的空间异质性;2)植物繁殖体的传播;3)植物之间的相互作用;4)生物环境(动物和微生物)的作用;5)外界干扰的作用;6)多因子综合作用。然后阐述了小尺度空间结构意义及对生物多样性、植物种群遗传学和恢复生态学研究的影响。最后对目前物种小尺度空间结构研究存在的几点问题及将来的研究方向作以下归纳:1)大尺度植被动态的研究应该整合小尺度空间结构的信息;2)不论从生物学还是生态学上来讲, 植被小尺度空间结构的研究应该把植物作为中心,确定适当的尺度和采取合理的空间统计方法;3)充分重视小尺度空间结构在退化生态系统恢复中的应用意义;4)注重从小尺度的局部格局研究入手对群落总体特征进行整合;5)植物群落动态研究中,物种小尺度空间结构与平均场假说相结合的必要性。     

Domain architecture of the atypical Arf-family GTPase Arl13b involved in cilia formation

Arl13b is an atypical Arf/Arl-family GTPase consisting of an extending large C-terminal region (C domain) and Arf-homologous GTP-binding motifs in the N terminus (N domain). Although Arl13b appears to be involved in cilia formation, its precise function and roles of the domains remain unknown. Here, we show the unique domain architecture of Arl13b by analyzing the relationship between its biochemical properties and cilia formation. Arl13b binds guanine nucleotides and specifically localizes to cilia. The ciliary localization of Arl13b requires both N and C domains but is independent of its guanine nucleotide-binding ability. Arl13b is capable of self-associating via N domain, and overexpression of N domain inhibits not only cilia formation but also the maintenance of pre-generated cilia. These findings suggest that N and C domains of Arl13b cooperatively regulate its ciliary localization and that N domain-dependent self-association of Arl13b may be important for its function in cilia biogenesis.     

Über die Mikrovillibildung im fetalen Rattendünndarm

Zusammenfassung Die Frage, auf welche Weise die Enterocyten des fetalen Rattendünndarms das für die Mikrovillibildung benötigte Membranmaterial liefern, wurde elektronenmikroskopisch untersucht. Es wird angenommen, daß hufeisenförmige Strukturen, die aus mit elektronendichtem Material bedeckten Elementarmembranen bestehen und möglicherweise Längsschnitten durch kappenförmige Gebilde entsprechen, in das apicale Plasmalemm eingebaut werden und für die Bildung der Mikrovillispitzen verantwortlich sind. Diese Annahme gründet sich in erster Linie auf die Feststellung eines nahezu identischen Durchmessers von Hufeisen und Mikrovilli, auf die Lokalisation der Hufeisen im Terminalgespinst und ihr zahlenmäßiges Verhalten während der Mikrovillibildung. Die Hufeisen entstehen im Golgi-Apparat.

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The formation of microvilli in the fetal rat small intestine

Summary The origin of membranes required for the formation of microvilli has been investigated electronmicroscopically in enterocytes of fetal rat small intestine. It is assumed that horseshoe-like structures consisting of unit membranes covered with electron-dense material, which probably represent longitudinal sections through cap-like structures, are incorporated into the apical cell membrane and give rise to the tips of microvilli. This assumption is based chiefly on the almost identical diameters of horseshoes and microvilli, the localization of horseshoes in the terminal web, and the time of appearance and disappearance of horseshoes with regard to development of microvilli. There are indications that the horseshoes originate in the Golgi apparatus.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Biochemical characterization of small heat shock protein HspB8 (Hsp22)–Bag3 interaction

Interaction of human Bag3 with small heat shock proteins HspB6, HspB8 and its K141E mutant was analyzed by different biochemical methods. The data of size-exclusion chromatography indicate that the wild type HspB8 forms tight complexes with Bag3. K141E mutant of HspB8 and especially HspB6 weaker interact with Bag3. The data of chemical crosslinking and analytical ultracentrifugation indicate that in vitro the stoichiometry of complexes formed by HspB8 and Bag3 is variable and is dependent on concentration of protein partners. Interaction of Bag3 and HspB8 is accompanied by increase of thermal stability measured by intrinsic tryptophan fluorescence and increased resistance to limited chymotrypsinolysis. The data of size-exclusion chromatography, analytical ultracentrifugation and limited proteolysis indicate that Bag3 belongs to the group of intrinsically disordered proteins. It is supposed that having unordered structure Bag3 might weakly interact with different small heat shock proteins which recognize unfolded proteins and this interaction is especially strong with intrinsically disordered HspB8. The complexes formed by Bag3 and HspB8 might have variable stoichiometry and can participate in different processes including clearing of the cell from improperly folded proteins.     

咳嗽变异性哮喘（CVA）与小气道功能相关性分析

目的：探讨咳嗽变异性哮喘（CVA）患者小气道功能检查对其诊断,治疗的意义。方法：对254例以慢性咳嗽为主的患者行肺功能检查并行支气管激发试验,回顾性分析小气道病变及气道高反应性检查结果与咳嗽变异性哮喘（CVA）的相关性。结果：有小气道功能障碍者接受吸入乙酰甲胆碱激发试验,气道反应性明显增高。有小气道功能障碍确诊咳嗽变异性哮喘（CVA）组起始阻力、反应阈值及阻力上升度与非哮喘组相比差异有统计学意义（P〈0.01）。结论：检查小气道功能障碍有助于哮喘的诊断,治疗及预后随访。     

极小种群野生植物坡垒的生境特征及其对幼苗多度的影响

极小种群野生植物坡垒(Hopea hainanensis)曾经是热带低地雨林的优势种, 但由于商业采伐和刀耕火种等严重人类干扰及自然更新困难, 致使其种群数量急剧下降到最小可存活的界限, 急需开展种群的拯救恢复工作。而对于坡垒生境适宜性及更新限制的了解, 是进行种群保护及恢复的基础。本文在对野生坡垒种群及其生境因子调查测定的基础上, 分析了生物与非生物生境特征及其对坡垒种群更新幼苗多度的影响。结果表明: 坡垒种群从幼苗至幼树阶段存在着严重的增补限制。坡度小、土壤含水量和有效磷含量高、母株胸径和冠幅较大、伴生种胸高断面积中等的环境是坡垒幼苗较为适宜的生境, 且坡垒幼苗多度与坡度及土壤pH值显著负相关, 与土壤含水量及土壤全磷含量显著正相关。这些研究结果为极小种群野生植物坡垒的就地保护与种群复壮提供了科学依据。     

Assessing the Conformational Changes of pb5, the Receptor-binding Protein of Phage T5, upon Binding to Its Escherichia coli Receptor FhuA

Within tailed bacteriophages, interaction of the receptor-binding protein (RBP) with the target cell triggers viral DNA ejection into the host cytoplasm. In the case of phage T5, the RBP pb5 and the receptor FhuA, an outer membrane protein of Escherichia coli, have been identified. Here, we use small angle neutron scattering and electron microscopy to investigate the FhuA-pb5 complex. Specific deuteration of one of the partners allows the complete masking in small angle neutron scattering of the surfactant and unlabeled proteins when the complex is solubilized in the fluorinated surfactant F₆-DigluM. Thus, individual structures within a membrane protein complex can be described. The solution structure of FhuA agrees with its crystal structure; that of pb5 shows an elongated shape. Neither displays significant conformational changes upon interaction. The mechanism of signal transduction within phage T5 thus appears different from that of phages binding cell wall saccharides, for which structural information is available.