Ultrastructure and behavior of the nucleoli and fibrillar centers during cell differentiation of liver erythroblasts of 12-day-old mouse embryos

The transformation of nucleolus and its structural components in the main groups of erythroid cells (from pronormoblasts to reticulocytes and dividing ones) has been studied. It is shown that during inactivation of the nucleolus, the granular component is reduced, and the degree of chromatin condensation increases. Enlargement and "naking" of fibrillar centres are also observed. At the stage of basophilic and polychromatophilic erythroblasts, the nucleolus has a mushroom-like shape with well developed fibrillar centres, which lie at the border of the nucleolus. Nucleolar RNP components consist predominantly of a fibrillar component and forms "caps" of these mushroom-like structures. Therefore, at this stage "free" fibrillar centres are found on ultrathin sections, if the section plane runs only through the fibrillar centre, or through ring-shaped nucleoli, i.e. the fibrillar centre surrounded by sheet of nucleolar RNP fibrilles, when the mushroom-like nucleolus is cut tangentially. Using serial section technique, small round nucleoli with an extremely weakly developed RNP material or free fibrillar centres, resembling those in telophase nuclei, are shown on the terminal stage of nucleolus transformation. It is noted that the main groups of erythroid cells differ from each other not only in the chromatin condensation degree, but also in the development of nucleolus material and in the size of fibrillar centres. However, such differences exist in either cell group. Consequently, we can distinguish between cell populations being on different stages of maturation. On this basis, we described on intermediate population of cells, which possess signs of pronormoblasts and basophilic erythroblasts. In all the cases, strands of electron opaque material bound with the condensed chromatin are present in fibrillar centres.(ABSTRACT TRUNCATED AT 250 WORDS)     

核苷酸转换因子的特性及其在植物中的研究现状

热激蛋白HSP70是一类细胞必需的具有ATPase活性的分子伴侣。ADP的脱离是HSP70分子伴侣体系能够完成其功能循环的限速步骤,该反应步骤由核苷酸交换因子（NEFs）加速,因此,NEFs是HSP70分子伴侣体系中的一类关键辅助因子。本文总结了有关NEFs的研究成果以及植物NEFs的最新研究进展。     

Coexistence of nitrifiers, denitrifiers and Anammox bacteria in a sequencing batch biofilm reactor as revealed by PCR-DGGE

Aims:  The bacterial diversity in a sequencing batch biofilm reactor (SBBR) treating landfill leachate was studied to explain the mechanism of nitrogen removal.
Methods and Results:  The total microbial DNA was extracted from samples collected from landfill leachate and biofilm of the reactor with the removal efficiencies of NH₄⁺-N higher than 97% and that of chemical oxygen demand (determined by K₂Cr₂O₇, COD_Cr) higher than 86%. Denaturing gradient gel electrophoresis (DGGE) fingerprints based on total community 16S rRNA genes were analyzed with statistical methods, and excised DNA bands were sequenced. The results of phylogenetic analyses revealed high diversity within the SBBR biofilm community, and DGGE banding patterns showed that the community structure in the biofilm remained stable during the running period.
Conclusions:  A coexistence of nitrifiers, including ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, denitrifiers, including aerobic or anaerobic denitrifying bacteria and Anammox bacteria were detected, which might be the real matter of high removal efficiencies of NH₄⁺-N and COD_Cr in the reactor.
Significance and Impact of the Study:  The findings in this study indicated that PCR-DGGE analysis could be used for microbial community detection as prior method, and the SBBR technique could provide preferable growing environment for bacteria with N removal function.     

B型酪氨酸激酶受体的轴浆转运

脑源性神经营养因子(brain-derived neurotrophic factor,BDNF)在发育及成熟的中枢神经系统(central nervoussystem,CNS)中起到举足轻重的调节作用,而其中绝大部分作用由其B型酪氨酸激酶受体(tyrosine kinase receptortype B,TrkB)介导,因此TrkB在神经元中的轴浆转运过程显得尤为重要。本文从动力蛋白、潜在调节分子、细胞骨架蛋白等方面对TrkB轴浆转运分子机制的研究进展进行综述,并就其进一步研究提出一系列的问题与展望。     

青海东部人工生态公益林近自然经营的林分结构调整

依据研究区5种典型人工林近自然状况,以人工生态公益林的近自然经营管理为目标,提出林分结构调整策略与方法。主要从林分结构、物种组成、年龄及枯死木几个方面考虑选取了垂直结构、水平结构、草本盖度及其多样性、天然更新、物种多样性、组成系数、直径分布、枯木比例、健康木比例10个指标,应用基于单位圆的π值法则,采取定性与定量相结合的方法,对5种林分的近自然状态做出评价并依据评价结果提出相应改造措施。青海云杉-白桦混交林（ω_PB=0.4786）属于远近自然林分,此类林分在密度合理的情况下无需过多人为抚育;青杨-白桦混交林（ω_BP=0.2664）属于近人工林,此类林分以伐除病虫害严重的青杨、调整密度和补植青海云杉为主;青海云杉-青杨混交林（ω_PP=0.2283）属于近人工林,此类林分以伐除病虫害严重的青杨、调整密度和补植白桦为主;青海云杉-落叶松混交林（ω_PL=0.1872）属于人工林,此类林分以调整密度和补植白桦为主;青海云杉纯林（ω_P=0.0190）属于人工林,此类林分以调整密度和营造杉桦混交林为主。通过近自然度评价与分析,为当地近自然经营提供了直观可靠的依据。在进行林分结构调整时,首先通过伐除干扰木来调整林分密度,其次要营造针阔混交林分,其中以青海云杉和白桦混交林为主要目标林分。     

不同光质对辣椒叶色黄化突变体光合生理特性的影响研究

以辣椒叶色黄化突变体yl1及其野生型6421为试材,用白光、蓝光、红光、绿光、紫光、黄光和远红光不同光质进行处理,考察其表型、生理及光合特性的变化特征,探究光质对黄叶辣椒植株生长发育的影响。结果显示：(1)蓝光与红光对辣椒幼苗的生长有促进作用,黄光和远红光则会显著抑制幼苗生长,6421生长受不同光质的抑制影响比yl1更大。(2)两个辣椒材料光合色素含量在不同光质下均不同程度降低;6421叶绿素总含量和类胡萝卜素含量在不同光质下均高于yl1,yl1和6421叶片的光合色素含量分别在紫光和黄光下最低。(3)蓝光和绿光能显著提高yl1的净光合速率(P_n),而不同光质处理均显著降低了6421的P_n。(4)紫光处理使yl1的PSⅡ潜在活性(F_v/F_o)和最大光化学效率(F_v/F_m)值均显著降低且显著低于6421,但升高了光化学猝灭系数(qP)和非光化学猝灭系数(NPQ)。(5)蓝光、红光和绿光均能提高辣椒的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(...     

根癌农杆菌介导的定点敲除技术在红色红曲菌中的应用

红曲菌(Monascus spp.)是一种重要的丝状真菌, 广泛应用于食品和医药领域中。目前, 由于对红曲菌遗传背景了解的很少, 因而对其重要功能基因的研究报道很少。本研究采用根癌农杆菌介导的转化技术对红色红曲菌(Monascus ruber)中推断的G-蛋白信号调节子mrfA基因的RGS功能域进行定点缺失研究, 探讨基于同源重组为基础的基因定点缺失技术在红曲菌基因功能鉴定中的可行性。构建的敲除载体pC805S左右同源臂长度分别为958 bp和824 bp, 将其转入受体菌M. ruber 中, 得到的138株转化子中, 有26株转化子发生了同源重组, 重组率达到18.8%。实验结果表明该技术作为红曲菌基因功能鉴定的方法是可行的。     

昆虫飞行能力研究进展

昆虫的迁飞导致害虫区域性大规模爆发,给农业带来极大的灾难。研究昆虫的飞行能力将为明确迁飞性昆虫的迁飞规律提供理论参考。本文综述分析了昆虫飞行能力的研究方法及应用范围,详细阐述了影响昆虫飞行能力的主要因素如自身个体间差异、环境、食物胁迫、振翅频率、生殖等及飞行对昆虫的影响,并就昆虫飞行能力研究中存在的问题及未来的研究方向进行了展望。     

Fatty acid ethyl esters in the liverwort Conocephalum conicum

A series of fatty acid ethyl esters ranging from C₁₄ to C₂₄ was isolated from a hexane extract of the liverwort Conocephalum conicum, these esters accounted for 77% of the extract. The ethyl esters consisting of even-numbered fatty acids were predominant and ethyl palmitate was the major constituent.     

Cyclic adenosine monophosphate content and its regulatory characteristics in Chinese hamster cells with genetically determined changes in the cell surface

The intra- and extracellular concentrations of cyclic adenosine monophosphate (cAMP) in cell line CHO-K1, sensitive (clone 773) and resistant to cytotoxic action of ethidium bromide (EBr), colchicine (Cr) and actinomycin D (ADr), as well as the amount of cAMP in response to isoproterenol, 10% serum and ethidium bromide (EB) in these cells were studied. The increased level of cAMP in EBr- and, Cr-cells, and the decreased one--in ADr cells was found as compared with sensitive cells. The amount of cAMP extruded in the surrounding medium was lower for EBr- and Cr-cells and higher for ADr-cells, in comparison with sensitive cells. All the variants of resistant cells were characterized by a less intensive but a longer reaction for isoproterenol, as compared with sensitive cells. In all the investigated variants 10% serum induced a remarkable increase in the intracellular cAMP by the 2nd hour after their insignificant decrease. 1 mcg/ml concentration of EBr increased intracellular cAMP only in 773-cells. The rules changing the cAMP level to isoproterenol and EB2; are determined by differences in reaction of adenylate cyclase, as it has been demonstrated for the 773- and EBr-cells.