变性高效液相色谱技术对创伤弧菌检测的研究

应用PCR结合变性高效液相色谱技术对创伤弧菌进行检测,建立创伤弧菌快速准确的检测新方法。经过DHPLC分析条件优化,在DHPLC非变性温度下分析创伤弧菌特异性PCR扩增产物。同时进行方法特异性、灵敏度、重复性实验。实验结果表明所建立的创伤弧菌PCR-DHPLC检测方法特异性强、灵敏度高、重现性好、结果稳定可靠、检测时间短,检测低限可达到124 CFU/mL,是创伤弧菌快速检测的新技术。     

胸内正压对正常人左室功能影响及其力学原理

目的：探讨胸内正压对正常人左室射血及充盈的影响及其力学原理。方法：超声心动图观测30例正常人初始时与标准乏氏动作张力期10s时左室舒张末容积（LVEDV）、左室收缩末容积（LVESV）、每搏量（SV）、射血分值（EF）、流入道血流速度（E峰、A峰）、E／A值、二尖瓣环舒张早期运动速度（e）及舒张早期充盈压（E/e）的变化。结果：与初始时比较,标准乏氏动作张力期LVEDV、LVESV及SV减低而心率（陬）增快（P均〈0．001）,EF值增加,但无统计学意义（P〉0．05）;E峰与E／A值减低（P均〈O．05）;e没有变化（P〉0．05）．E／e值减低（P〈O．05）。结论：胸内正压对左室游离壁的力学作用促进了左室收缩运动而阻碍了左室舒张运动,会引起EF值增加,E峰及E／A值减低;2,胸内正压降低了肺静脉系统与心脏的跨壁压力,增加了血流阻力也是导致肺静脉系统与左室血液回流减少．E峰减低．E／e值减低的一个原因。     

Anticancer activities of six selected natural compounds of some Cameroonian medicinal plants

Background

Natural products are well recognized as sources of drugs in several human ailments. In the present work, we carried out a preliminary screening of six natural compounds, xanthone V₁ (1); 2-acetylfuro-1,4-naphthoquinone (2); physcion (3); bisvismiaquinone (4); vismiaquinone (5); 1,8-dihydroxy-3-geranyloxy-6-methylanthraquinone (6) against MiaPaCa-2 pancreatic and CCRF-CEM leukemia cells and their multidrug-resistant subline, CEM/ADR5000. Compounds 1 and 2 were then tested in several other cancer cells and their possible mode of action were investigated.

Methodology/Findings

The tested compounds were previously isolated from the Cameroonian medicinal plants Vismia laurentii (1, 3, 4, 5 and 6) and Newbouldia laevis (2). The preliminary cytotoxicity results allowed the selection of xanthone V₁ and 2-acetylfuro-1,4-naphthoquinone, which were then tested on a panel of cancer cell lines. The study was also extended to the analysis of cell cycle distribution, apoptosis induction, caspase 3/7 activation and the anti-angiogenic properties of xanthone V₁ and 2-acetylfuro-1,4-naphthoquinone. IC₅₀ values around or below 4 µg/ml were obtained on 64.29% and 78.57% of the tested cancer cell lines for xanthone V₁ and 2-acetylfuro-1,4-naphthoquinone, respectively. The most sensitive cell lines (IC₅₀<1 µg/ml) were breast MCF-7 (to xanthone V₁), cervix HeLa and Caski (to xanthone V₁ and 2-acetylfuro-1,4-naphthoquinone), leukemia PF-382 and melanoma colo-38 (to 2-acetylfuro-1,4-naphthoquinone). The two compounds showed respectively, 65.8% and 59.6% inhibition of the growth of blood capillaries on the chorioallantoic membrane of quail eggs in the anti-angiogenic assay. Upon treatment with two fold IC₅₀ and after 72 h, the two compounds induced cell cycle arrest in S-phase, and also significant apoptosis in CCRF-CEM leukemia cells. Caspase 3/7 was activated by xanthone V₁.

Conclusions/Significance

The overall results of the present study provided evidence for the cytotoxicity of compounds xanthone V₁ and 2-acetylfuro-1,4-naphthoquinone, and bring supportive data for future investigations that will lead to their use in cancer therapy.     

Spatial and temporal variability of pCO2 and CO2 efflux in seven Amazonian Rivers

Current estimates of CO₂ outgassing from Amazonian rivers and streams have considerable uncertainty since they are based on limited-time surveys of pCO₂ measurements along the Amazon mainstem and mouths of major tributaries, using conservative estimates of gas exchange velocities. In order to refine basin-scale CO₂ efflux estimates from Amazonian rivers, we present a long time (5-year) dataset of direct measurements of CO₂ fluxes, gas transfer velocities and pCO₂ measurements in seven representative rivers of the lowland Amazon basin fluvial network, six non-tidal (Negro, Solimões, Teles Pires, Cristalino, Araguaia and Javaés) and one tidal river (Caxiuanã), with sizes ranging from 4th to 9th order. Surveys were conducted from January 2006 to December 2010, in a total of 389 campaigns covering all stages of their hydrographs. CO₂ fluxes and gas transfer velocities (k) were measured using floating chambers and pCO₂ was measured simultaneously by headspace extraction followed by gas chromatography analysis. Results show high CO₂ flux rate variability among rivers and hydrograph stages, ranging from ?0.8 to 15.3 μmol CO₂ m^?2 s^?1, with unexpected negative fluxes in clear-water rivers during low waters. Non-tidal rivers showed marked seasonal CO₂ flux patterns, with significantly higher exchange during high waters. Seasonality was modulated by pCO₂, which was positive and strongly correlated with discharge. In these rivers k was well correlated with wind speed, which allowed the use of wind data to model k. We estimate a release of 360 ± 60 Tg C year^?1 from Amazonian rivers and streams within a 1.47 million km² quadrant in the central lowland Amazon. Extrapolating these values to the basin upstream of Óbidos, results in an outgassing of 0.8 Pg C to the atmosphere each year. Our results are a step forward in achieving more accurate gas emission values for Amazonian rivers and their role in the annual carbon budget of the Amazon basin.     

Seasonal variation in dissolved carbon concentrations and fluxes in the upper Purus River, southwestern Amazon

One of the less studied components of carbon cycling that could improve our understanding of how and how strongly Amazonian ecosystems act as sinks or sources of carbon is the amount that is carried downstream by rivers. In this paper, we show that a headwater river can carry from 25 to 130 % of the reported sink for Amazonian forests, therefore not being negligible for ecosystem-level carbon budgets. Based on monthly measurements from May 2004 to April 2005 of the upper Purus River, southwestern Amazonia, we found that: water pH, dissolved oxygen, specific electrical conductivity, and dissolved inorganic carbon (DIC) were inversely related to water discharge and precipitation; pCO₂ was directly and strongly related to discharge and precipitation, and to a lesser extent to pH and dissolved oxygen; and dissolved organic carbon (DOC) was not related to any measured variable. Annual flux of dissolved carbon (DIC + DOC) at the sampling site was estimated as 604 ± 55 Gg C a^?1. More than 75 % was in the form of bicarbonate, with the remainder as CO₂ and DOC. This amount is equivalent to 0.15 ± 0.01 Mg C ha^?1 a^?1 in the upstream drainage basin, which is on the same order of magnitude as terrestrial carbon fixation.     

Effects of DOM photochemistry on bacterial metabolism and CO2 evasion during falling water in a humic and a whitewater river in the Brazilian Amazon

In the Amazon river system, the source of the large quantity of CO₂ evading from river surfaces remains unidentified. Photochemical transformation of dissolved organic matter (DOM) into dissolved inorganic carbon (DIC) and low molecular weight organic acids (LMWOAs) is a promising candidate. Few studies in the Amazon river system, and river systems in general, have attempted to quantify the contribution of these specific photoproducts to CO₂ evasion. We conducted photochemical degradation and ¹⁴C addition experiments to measure the rate of production and the impact on bacterial metabolism, respectively, in the black water Rio Negro and in the white water Rio Solimões during low water. We found statistically significant production of both photoproducts in the Rio Negro and none in Rio Solimões. We also found that two photochemically produced LMWOAs??acetic and formic acid??may play a significant role in bacterial metabolism in both rivers. Based on our experimental results, we estimate that photochemically produced CO₂, acetic acid and formic acid alone contribute to only 0.5% of the CO₂ evading from the Rio Negro. Due to our experimental set-up, analytical methods and time of sampling, we caution that our estimate is very conservative. More extensive research is needed before drawing conclusions on the contribution of photochemistry to CO₂ evasion from river surfaces of the Amazon basin.     

Intra and interannual variability in the Madeira River water chemistry and sediment load

Concentrations of cations (Na⁺, Ca²⁺, Mg²⁺, K⁺, NH₄ ⁺), anions (HCO₃ ^?, Cl^?,?NO₃ ^?, SO₄ ^2?, PO₄ ^3?) and suspended sediments in the Madeira River water were?determined near the city of Porto Velho (RO), in order to assess variation in?water chemistry from 2004 to 2007. Calcium and bicarbonate were the dominant?cation and anion, respectively. Significant seasonal differences were found,?with highest concentrations occurring during the dry season, as expected from?the drainage of Andean carbonate-rich substratum. Interannual variations were?also observed, but became significant only when annual average discharge was?25% less than normal. Under this atypical discharge condition, bicarbonate was?replaced by sulfate, and higher suspended sediment concentrations and loads?were also observed. Compared to previously published studies, it appears that?no significant changes in water chemistry have occurred during the last 20?C30?years, although differences in approaches and sampling designs among this and previous studies may not allow detection of modest changes.?The calculated suspended sediment load reported here is close to the values presented elsewhere, reinforcing the relative importance of this river as a?sediment supplier for the Amazon Basin. Seasonality has a significant control?on the chemistry of Madeira River waters, and severe decrease in discharge due?to anthropogenic changes, such as construction of reservoirs or the occurrence?of drier years??a plausible consequence of global climate change??may lead?to modification in the chemical composition as well in the sediment deliver to?the Amazon River.     

Energy Crop and Biotechnology for Biofuel Production

Selection of energy crops is the first priority for large-scale biofuel production in China. As a major topic, it was extensively discussed in the Second International Symposium on Bioen-     

Chronic stress and its effects on adrenal cortex apoptosis in pregnant rats

The model of chronic intermittent stress by immobilization during pregnancy may produce alterations in the mechanisms that maintain adrenal gland homeostasis. In earlier investigations using this model, significant variations in plasma prolactin and corticosterone levels, and adrenal gland weights were observed. We hypothesized that chronic stress causes changes in apoptosis in the adrenal glands of pregnant rats. We identified and quantified apoptotic cells in the adrenal cortex and examined their ultrastructural characteristics using transmission electron microscopy. Adrenal glands of pregnant rats at gestation days 12, 17 and 21 were studied for control and experimental (stressed) rats. Immunolabelling techniques, stereological analysis and image quantification of adrenal gland sections were combined to determine differences in apoptosis in the different cell populations of the adrenal cortex. The apoptotic index of the experimental rats showed a significant reduction at gestation day 17, while at days 12 and 21 there were no differences from controls. Moreover, the apoptotic index of the reticular zones in control and experimental animals showed a significant increase compared to the glomerular and fascicular zones at the three gestation times studied. Chronic stress by immobilization reduced the caspase-dependent apoptotic index at gestation day 17, which may be related to variations in plasma concentrations of estrogens and prolactin.     

Methane emissions from Amazonian Rivers and their contribution to the global methane budget

Methane (CH₄) fluxes from world rivers are still poorly constrained, with measurements restricted mainly to temperate climates. Additional river flux measurements, including spatio‐temporal studies, are important to refine extrapolations. Here we assess the spatio‐temporal variability of CH₄ fluxes from the Amazon and its main tributaries, the Negro, Solimões, Madeira, Tapajós, Xingu, and Pará Rivers, based on direct measurements using floating chambers. Sixteen of 34 sites were measured during low and high water seasons. Significant differences were observed within sites in the same river and among different rivers, types of rivers, and seasons. Ebullition contributed to more than 50% of total emissions for some rivers. Considering only river channels, our data indicate that large rivers in the Amazon Basin release between 0.40 and 0.58 Tg CH₄ yr^?1. Thus, our estimates of CH₄ flux from all tropical rivers and rivers globally were, respectively, 19–51% to 31–84% higher than previous estimates, with large rivers of the Amazon accounting for 22–28% of global river CH₄ emissions.