病毒感染中的“双刃剑”——热激蛋白70

热激蛋白70(heat shock protein,Hsp70)是目前最为受人们关注的一类蛋白质因子,从低等细菌到高等人类中普遍存在,它结构保守、功能多样。Hsp70像是生物有机体的"防弹衣",使生物体在饥饿、酷热、氧化、感染等条件下避开不利因素的攻击;同时,它也是病菌、病毒等攻击寄主时的"作案工具",所以我们可以称之为细胞的"双刃剑"。本文主要对Hsp70的结构以及病毒感染过程中的"双刃"作用情况进行了综述。     

Incompatibility behavior of a symbiotic plasmid pMH7653Rb in <Emphasis Type="Italic">Mesorhizobium huakuii</Emphasis> 7653R

Mesorhizobium huakuii strain 7653R harbored two indigenous plasmids named pMH7653Ra and pMH7653Rb. The larger plasmid pMH7653Rb (symbiotic plasmid) was transferred to M. huakuii HN308SR harboring three plasmids: pMHHN308a, pMHHN308b and pMHHN308c, and HN3015SR harboring three plasmids: pMHHN3015a, pMHHN3015b and pMHHN3015c by tri-parent mating. Two stable indigenous plasmids, pMHHN308b and pMHHN308c of HN308SR, were co-eliminated due to the introduction of pMH7653Rb, and the transconjugant was named HN308SRN14. The results implied that pMH7653Rb and pMHHN308b, pMHHN308c were incompatible and might have been ascribed to the same incompatible group. The plasmid profiles of transconjugant HN3015SRN14 showed that the second largest plasmid pMHHN3015b of HN3015SR was cured due to the introduction of pMH7653Rb. The results also implied that pMH7653Rb and pMHHN3015b were incompatible. Results from plant nodulation tests showed that pMH7653Rb could only maintain the nodulation ability in transconjugant HN308SRN14 and its nodule number was more than that of wild strain HN308SR, but could not replace the nitrogen fixation effect of pMHHN308b and pMHHN308c. The plasmid cured mutant HN308SRN14D harboring only pMHHN308a formed null nodules that demonstrated pMHHN308a was relevant to nodulation ability. HN3015SRN14 harboring pMH7653Rb, pMHHN3015a and pMHHN3015c formed null nodules while HN3015SRN14D containing pMHHN3015a and pMHHN3015c lost the nodulation ability. The plasmid replication repC-like gene sequences were detected by a polymerase chain reaction from 7653R, HN308, HN3015, HN308SRN14 and HN3015SRN14. The repC gene sequence similarities of the strains tested attained 99%.     

The formation of Ca<Superscript>2+</Superscript> gradients at the cleavage furrows during cytokinesis of Zebrafish embryos

In dividing embryos, a localized elevation in intracellular Ca²⁺ ([Ca²⁺]_i) at the cleavage furrow has been shown to be essential for cytokinesis. However, the underlying mechanisms for generating and maintaining these [Ca²⁺]_i gradients throughout cytokinesis are not fully understood. In the present study, we analyzed the role of inositol 1,4,5-trisphosphate receptors (IP₃Rs) and endoplasmic reticulum (ER) distribution in determining the intracellular Ca²⁺ gradients in early zebrafish blastomeres. Application of the injected Ca²⁺ indicator, Indo-1, showed that during the first cell division a standing Ca²⁺ gradient was formed ∼35 min after fertilization, with the [Ca²⁺]_i spatially decaying from 500–600 nmol/L at the cleavage furrow to 100–200 nmol/L around the nucleus. While the IP3R immunohistochemical fluorescence was relatively concentrated in the peri-furrow region, ER labeling was relatively enriched in both peri-furrow and peri-nuclear regions. Numeric simulation suggested that a divergence in the spatial distribution of IP3R and the locations of Ca²⁺ uptake within the ER was essential for the formation of a standing Ca²⁺ gradient, and the Ca²⁺ gradient could only be well-established under an optimal stoichiometry of Ca²⁺ uptake and release. Indeed, while inhibition of IP3R Ca²⁺ release blocked the generation of the Ca²⁺ gradient at a lower [Ca²⁺]_i level, both Ca²⁺ release stimulation by inositol 1,4,5-trisphosphate (IP3) injection and ER Ca²⁺ pump inhibition by cyclopiazonic acid also eliminated the Ca²⁺ gradients at higher [Ca²⁺]_i levels. Our results suggest a dynamic relationship between ER-mediated Ca²⁺ release and uptake that underlies the maintenance of the perifurrow Ca²⁺ gradient and is essential for cytokinesis of zebrafish embryos.     

褪黑素对胃癌小鼠Survivin表达的影响

目的探讨褪黑素对胃癌小鼠Survivin表达的影响。方法选用6-8周龄SPF级615近交系小鼠,接种胃癌MFC细胞,建立荷瘤小鼠模型并给予不同剂量的褪黑素处理,用Real-time PCR法和Western blot法检测肿瘤组织中Survivin mRNA和蛋白的表达。结果 Real-time PCR和Western-blot检测显示褪黑素各干预组小鼠胃癌组织中Survivin基因的表达水平下降且随褪黑素剂量增大而降低。结论褪黑素具有下调survivin的作用。褪黑素降低survivin的表达,可能是褪黑素抑制肿瘤的作用机制之一。     

NaHSO3对桃树的生理效应及产量品质的影响

于桃树果实膨大期喷施１００ｐｐｍ ＮａＨＳＯ２可获得增产、优质、早熟的效果。此与ｎａＨＳＯ２能增加叶绿素含量、提高光合速率、比叶重、促进希尔反应,抑制硝酸还原酶、过氧氢酶活性,增加单果重等多重生理效应相关。     

Operon prediction in Pyrococcus furiosus

Identification of operons in the hyperthermophilic archaeon Pyrococcus furiosus represents an important step to understanding the regulatory mechanisms that enable the organism to adapt and thrive in extreme environments. We have predicted operons in P.furiosus by combining the results from three existing algorithms using a neural network (NN). These algorithms use intergenic distances, phylogenetic profiles, functional categories and gene-order conservation in their operon prediction. Our method takes as inputs the confidence scores of the three programs, and outputs a prediction of whether adjacent genes on the same strand belong to the same operon. In addition, we have applied Gene Ontology (GO) and KEGG pathway information to improve the accuracy of our algorithm. The parameters of this NN predictor are trained on a subset of all experimentally verified operon gene pairs of Bacillus subtilis. It subsequently achieved 86.5% prediction accuracy when applied to a subset of gene pairs for Escherichia coli, which is substantially better than any of the three prediction programs. Using this new algorithm, we predicted 470 operons in the P.furiosus genome. Of these, 349 were validated using DNA microarray data.     

树突状细胞在肾小管间质纤维化中作用及缬沙坦的干预调节

探讨树突状细胞(DC)在肾纤维化大鼠肾小管间质中分布,以及缬沙坦对DC浸润聚集的干预作用。建立肾大部切除大鼠模型,随机分为正常组(n=18),假手术组(n=18),模型组(n=18),缬沙坦治疗组(n=18)。分别于建模1、4、12周取肾组织,采用HE和Masson染色评定各组肾小管间质纤维化(TIF)程度;采用免疫双染及荧光图像分析法,观察DC-SIGN DC在各组大鼠肾组织中分布变化;采用免疫组化方法,观察P-选择素以及TGF-β1、α-平滑肌肌动蛋白(α-SMA)、III型胶元(ColIII)、纤维连接蛋白(FN)在上述肾组织中表达;以及RT-PCR检测P-选择素、TGF-β1、α-SMA、ColIII、FN的mRNA水平。结果显示,(1)模型组DC-SIGN DC主要分布于肾小管、肾间质和肾血管,以肾间质最为明显;其分布数量于12周较1和4周呈明显增多,且与慢性肾功能减退呈正相关。(2)12周时手术组大鼠肾小管间质区P-选择素、TGF-β1、α-SMA、ColIII、FN mRNA转录水平和蛋白质表达均明显增加,并与TIF程度以及DC-SIGN DC分布数量呈正相关。(3)经缬沙坦治疗后,DC-SIGN DC分布减少,以及P-选择素、TGF-β1、α-SMA、ColIII、FN mRNA转录水平和蛋白质表达下降,TIF程度减轻及肾功能改善。研究结果表明,DC启动参与了肾小管间质纤维化形成,并与肾功能损害程度密切相关。缬沙坦对此具有明显的抑制和肾脏保护作用。     

Below-canopy CO2 flux and its environmental response characteristics in a coniferous and broad-leaved mixed forest in Dinghushan, China

Accurate estimation of below-canopy CO₂ flux (Fcb) in typical forest ecosystems is of great importance to validate terrestrial carbon balance models. Continuous eddy covariance measurements of Fcb were conducted in a coniferous and broad-leaved mixed forest located in Dinghushan Nature Reserve of South China. Using year-round data, Fcb dynamics and its environmental response were analyzed, and the results mainly showed that: (1) Fcb decreased during daytime which indicated that the understory of the forest continued photosynthesis throughout the year; however, understory and soil acted as CO₂ source as a whole. (2) Using soil temperature (Ts) as a dependent variable, all of Van’t Hoff equation, Arrhenius equation and Lloyd-Taylor equation can explain a considerable variation of Fcb. Among those three equations Lloyd-Taylor equation is the best to reflect the relationship between soil respiration and temperature for its ability in revealing the variation of Q₁₀ with temperature. (3) Fcb derived from Lloyd-Taylor equation is utterly determined by Ts, while Fcb derived from the multiplicative model is driven by Ts and soil moisture (Ms). The multiplicative model can reflect the synthetic effect of Ts and Ms; therefore it explains more Fcb variations than Lloyd-Taylor equation does. (4)Fcb derived from the multiplicative model was higher than that from Lloyd-Taylor equation when Ms was relatively high; on the contrary, Fcb derived from the multiplicative model was lower than that from Lloyd-Taylor equation when Ms was low, indicating that Ms might be a main factor affecting Fcb when the ecosystem is stressed by low-moisture. (5) Annual Fcb of the forest in 2003 was estimated as (787.4±296.8) gCm^-2a^-1, which was 17% lower than soil respiration measured by statistic chamber method. CO₂ flux measured by eddy covariance is often underestimated, and further study therefore calls for emphasis on methods quantifying Fcb components of respiration of soil, as well as respiration and photosynthesis of understory vegetations.