Exopolyphosphatases in nuclear and mitochondrial fractions during embryogenesis of the hard tick Rhipicephalus (Boophilus) microplus

The present work evaluated polyphosphate (poly P) metabolism in nuclear and mitochondrial fractions during Rhipicephalus microplus embryogenesis. Nuclear poly P decreased and activity of exopolyphosphatase (PPX - polyphosphate-phosphohydrolases; EC 3.6.1.11) increased after embryo cellularization until the end of embryogenesis. The utilization of mitochondrial poly P content occurred between embryo cellularization and segmentation stages. Increasing amounts of total RNA extracted from eggs progressively enhanced nuclear PPX activity, whereas it exerted no effect on mitochondrial PPX activity. The decline in total poly P content after the 7th day of embryogenesis does not reflect the free P(i) increase and the total poly P chain length decrease after embryo cellularization. The Km(app) utilizing poly P(3), poly P(15) and poly P(65) as substrate was almost the same for the nuclear fraction (around 1muM), while the affinity for substrate in mitochondrial fraction was around 10 times higher for poly P(3) (Km(app) = 0.2muM) than for poly P(15) (Km(app) = 2.8muM) and poly P(65) (Km(app) = 3.6muM). PPX activity was stimulated by a factor of two by Mg2+ and Co2+ in the nuclear fraction and only by Mg2+ in the mitochondrial fraction. Heparin (20microg/mL) inhibited nuclear and mitochondrial PPX activity in about 90 and 95% respectively. Together, these data are consistent with the existence of two different PPX isoforms operating in the nuclei and mitochondria of the hard tick R. microplus with distinct metal dependence, inhibitor and activator sensitivities. The data also shed new light on poly P biochemistry during arthropod embryogenesis, opening new routes for future comparative studies on the physiological roles of different poly P pools distributed over cell compartments.     

Precursor-ion mass re-estimation improves peptide identification on hybrid instruments

Mass spectrometry-based proteomics experiments have become an important tool for studying biological systems. Identifying the proteins in complex mixtures by assigning peptide fragmentation spectra to peptide sequences is an important step in the proteomics process. The 1-2 ppm mass-accuracy of hybrid instruments, like the LTQ-FT, has been cited as a key factor in their ability to identify a larger number of peptides with greater confidence than competing instruments. However, in replicate experiments of an 18-protein mixture, we note parent masses deviate 171 ppm, on average, for ion-trap data directed identifications and 8 ppm, on average, for preview Fourier transform (FT) data directed identifications. These deviations are neither caused by poor calibration nor by excessive ion-loading and are most likely due to errors in parent mass estimation. To improve these deviations, we introduce msPrefix, a program to re-estimate a peptide's parent mass from an associated high-accuracy full-scan survey spectrum. In 18-protein mixture experiments, msPrefix parent mass estimates deviate only 1 ppm, on average, from the identified peptides. In a cell lysate experiment searched with a tolerance of 50 ppm, 2295 peptides were confidently identified using native data and 4560 using msPrefixed data. Likewise, in a plasma experiment searched with a tolerance of 50 ppm, 326 peptides were identified using native data and 1216 using msPrefixed data. msPrefix is also able to determine which MS/MS spectra were possibly derived from multiple precursor ions. In complex mixture experiments, we demonstrate that more than 50% of triggered MS/MS may have had multiple precursor ions and note that spectra with multiple candidate ions are less likely to result in an identification using TANDEM. These results demonstrate integration of msPrefix into traditional shotgun proteomics workflows significantly improves identification results.     

ATP synthesis catalyzed by a V-ATPase: an alternative pathway for energy conservation operating in plant vacuoles?

The electrochemical H⁺ gradient generated in tonoplast vesicles isolated from maize seeds was found to be able to drive the reversal of the catalytic cycle of both vacuolar H⁺-pumps (Façanha and de Meis, 1998). Here we describe the reversibility of the vacuolar V-type H⁺-ATPase (V-ATPase) even in the absence of the H⁺ gradient in a water-Me₂SO co-solvent mixture, resulting in net synthesis of [γ-³²P]ATP from [³²P]P_i and ADP. The water-Me₂SO (5 to 20 %) media promoted inhibition of both PP_i hydrolysis and synthesis reactions whereas it slightly affected the ATP hydrolysis and clearly stimulated the ATP synthesis, which was unaffected by uncoupling agents (FCCP, Triton X-100 or NH₄⁺). This effect of Me₂SO on the ATP⇔³²P exchange reaction seems to be related to a decrease of the apparent K_m of the V-ATPase for P_i. The results are in accordance to the concept that the energetics of ATP synthesis catalysis depends on the solvation energies interacting in the enzyme microenvironment. A possible physiological significance of this phenomenon for the metabolism of desiccation-tolerant plant cells is discussed.Key words: bind energy, proton pumps, proton gradient, DMSO, corn seeds, V₁V₀-ATPase, membrane bound H⁺-pyrophosphatase     

Investigation of the antifouling constituents from the brown alga Sargassum muticum (Yendo) Fensholt

One of the most promising alternatives to toxic heavy metal-based paints is offered by the development of antifouling coatings in which the active ingredients are compounds naturally occurring in marine organisms and operating as natural antisettlement agents. Sessile marine macroalgae are remarkably free from settlement by fouling organisms. They produce a wide variety of chemically active metabolites in their surroundings, potentially as an aid to protect themselves against other settling organisms. In this study, a dichloromethane extract from the brown seaweed Sargassum muticum was tested in situ and, after 2 months of immersion, showed less fouling organisms on paints in which the extract was included, compared to paints containing only copper after 2 months of immersion. No barnacles or mussels have been observed on the test rack. Identification by NMR and GC/MS of the effective compound revealed the abundance of palmitic acid, a commonly found fatty acid. Pure palmitic acid showed antibacterial activity at 44 μg mL⁻¹, and also inhibited the growth of the diatom Cylindrotheca closterium at low concentration (EC₅₀ = 45.5 μg mL⁻¹), and the germination of Ulva lactuca spores at 3 μg mL⁻¹. No cytotoxicity was highlighted, which is promising in the aim of the development of an environmentally friendly antifouling paint.     

棉花纤维发育关键酶对氮素的响应及其与纤维比强度形成的关系

大田栽培条件下,于2005～2006年在江苏南京（118°50′E,32°02′N,长江流域下游棉区）以美棉33B（平均比强度32cN／tex）和科棉1号（平均比强度35cN／tex）2个品种为材料,进行氮素水平（O（零氮）,240（适氮）和480kgN／hm^2（高氮））实验,研究棉花纤维发育关键酶（蔗糖合成酶和β-1,3-葡聚糖酶）活性变化特征对氮素的响应及其与纤维比强度形成的关系．结果表明,棉纤维发育关键酶活性及其基因表达强度均受氮素影响,并影响棉纤维素的累积特征及纤维比强度的形成．蔗糖合成酶活性随铃龄增加呈单峰曲线,峰值出现在铃龄31天,其基因表达强度在7～21天维持较高水平;氮素水平间比较,以240kgN／hm^2处理的蔗糖合成酶活性及其基因表达强度最高,酶活性高表达持续时间长．β-1,3-葡聚糖酶活性随铃龄增加呈下降趋势,其基因表达在铃龄7～24天间呈单峰曲线,铃龄18天时达到峰值;氮素水平间比较,以240kgN／hm^2处理的β-1,3-葡聚糖酶活性最高,其基因表达量在纤维发育前期（铃龄9～12天）较低,之后大幅增加且稳定表达．240kgN／hm^2下棉纤维发育关键酶的上述变化促进纤维素累积持续期长且整个纤维发育过程中纤维素累积速率平缓,最终形成纤维比强度较高。     

基于局部茎搜索的RNA二级结构预测算法

RNA的二级结构预测是生物信息学中一个已经有30多年历史的经典问题,基于最小自由能模型(MFE)的优化算法是使用最为广泛的方法．但RNA结构中假结的存在使MFE问题理论上成为一个NP-hard问题,即使采用动态规划等优化算法也会面临时间复杂度高的困难,同时研究还发现,由于受RNA折叠动力学机制以及环境因素的影响,真实的RNA二级结构往往并不处于自由能最小状态．根据RNA折叠的特点,提出了一种启发式搜索算法来预测带假结的RNA二级结构．该算法以RNA的茎为基本单元,采用启发式搜索策略在茎的组合空间中搜索自由能最小并且出现频率最高的RNA二级结构,该算法不仅能显著降低搜索RNA二级结构的时间复杂度,还有助于弥补单纯依赖能量预测RNA二级结构的不足．在多种类型的RNA标准数据集上进行了检验,结果表明,该算法在预测的精度上优于目前国际上几个著名的RNA二级结构预测算法并且具有较高的运行效率．     

Effect and mechanism of acute graft versus host disease on early diffuse murine lung injury following allogeneic stem cell transplantation

To explore the effect and pathogenssis of acute graft-versus-host disease (aGVHD) on early diffuse lung injury in allogeneic hematopoietic stem cell transplantation (allo-HSCT), we established an aGVHD model of C57BL/6→BALB/c mice. Chest computed tomography (CT) scans, histopathology and the levels of cytokines including tumor necrosis factor α (TNFa) and Interferon (IFNg) in lungs were dynamically detected in recipient mice after transplantation. The incidence of aGVHD was respectively 0%, 0% and 100% in simple irradiation group (A), syngeneic transplant group(B) and allogeneic transplant group (C). Chest CT scans of recipient mice were normal in 3 groups on days +3 and +7 after transplantation. CT showed that two of ten mice had bilateral lung diffuse infiltrate on day +12 (on the brink of death) in group A and 6 of 10 mice had bilateral lung diffuse infiltrate on day +14 (3 d after aGVHD occurring) in group C, and were normal on days +12 and +14 in group B after transplantation. Histopathology of lungs in the 3 groups was similar, consisting of minor interstitial pneumonitis on day +3. Group A showed edema, hyperplasia of epithelial cells and widened alveolar interval on day +7, and epithelial cell necrosis, lymphocyte infiltration, hemorrhage, protein leakage, and local consolidation on day +12. The histopathology of group B showed slight edema of epithelial cells on +7 day, which were slighter than that on day +3, and virtually normal on day +14. The histopathology in group C was characterized by the significant expansion and congestion of capillaries, and lymphocyte infiltration on day +7, the acute pneumonitis was present involving tissue edema, lymphocyte and macrophage infiltration, protein leakage and perivascular inflammation on day +14. In group A, the levels of TNFa were lower on day +7 than on day +3. In group B, the levels of TNFa attained a peak on day +3, which decreased on days +7 and +14. In group C, the levels of TNFa were highest on day +7 and there was a significant difference between those on days +7 and +14 (P=0.816). In group A, the levels of IFNg on day +7 were higher than on day +3. In group B, the levels of IFNg increased progressively, but the comparison of IFNg levels in different times had no statistical significance (P=0.521, 0.118, 0.340). In group C, the levels of IFNg attained a peak by day +7 and decreased on day +14. aGVHD is the main cause of early non-infectious lung injury. T lymphocytes and TNFa are possibly implicated in the pathogenesis of acute GVHD-induced lung injury. The decreased levels of IFNg in lung tissues following transplantation might be associated with pulmonary fibrosis in late non-infectious pulmonary complications.     

两种野生灌木幼苗对干旱和盐交叉胁迫的生理响应

长枝木蓼(Ateaphaxis viegata)和刺叶锦鸡儿(Caragana acanthophulla)是乌鲁木齐周边植被组成的重要种,在植被恢复中具有潜在价值。该文通过盆栽控水控盐法研究两种野生灌木幼苗在不同程度的干旱和盐交叉胁迫下的生理反应。结果表明,干旱和盐交叉胁迫下,长枝木蓼可溶性糖增幅较刺叶锦鸡儿大;轻度交叉胁迫时,两种灌木的可溶性糖含量高于仅干旱胁迫或盐胁迫下的。中度和重度交叉胁迫下,长枝木蓼叶片丙二醛含量增幅高于刺叶锦鸡儿。交叉胁迫下,两种灌木叶片叶绿素含量下降,且长枝木蓼叶片的叶绿素含量降幅大于刺叶锦鸡儿。因膜系统的过氧化作用,使MDA含量升高。轻度干旱胁迫提高了两种野生灌木对盐胁迫的耐受能力。两种灌木能很好地适应中度交叉胁迫,重度交叉胁迫对两种灌木的伤害很大,但也能生存。综合比较各参数发现,刺叶锦鸡儿更耐早,而长枝木蓼更耐盐;综合比较各生理参数发现,刺叶锦鸡儿对干旱和盐胁迫的耐受能力较长枝木蓼强。     

Nocturnal windborne migration of ground beetles,particularly Pseudoophonus griseus (Coleoptera: Carabidae), in China

1 A network of light‐traps, an aerial net carried by kytoon (balloon) and two entomological radars were used to investigate whether ground beetles migrate nocturnally through China. The network‐wide, simultaneous sudden increase in light trap catches, and after subsequent decrease, indicated a seasonal long‐distance night migration of ground beetles, with Pseudoophonus griseus (Panzer) predominant, in August. 2 Aerial net trapping indicated that carabids were able to ascend to altitudes of at least 200 m and become windborne. Radar observations indicated that the migratory beetles formed high‐density layer concentrations at approximately 200–300 m. 3 These concentrations were coincident with the top of the temperature inversion and a wind speed maximum, which suggested that the carabids tended to select warm, fast moving air for their long‐distance migration. 4 The ground beetles orientated and displaced towards the downwind direction in southerly winds. Their air speed decreased as the tailwind increased and, thus, migrating beetles appeared to be conserving energy. 5 The mean ± SD displacement speed (ground speed) and air speed were 6.85 ± 1.73 m/s (n= 172) and 4.45 ± 1.54 m/s (n= 172), respectively. The duration of flight, estimated from the variation in area density derived from radar data, was approximately 9–10 h, indicating that the beetles might migrate hundreds of kilometres in a single flight.