Methylation-based molecular margin analysis in hepatocellular carcinoma

The positive surgical margins are associated with postsurgical recurrence in hepatocellular carcinoma patients, and molecular margin analysis is considered more sensitive in detecting preneoplastic lesions than conventional histological margin examination. To evaluate the feasibility of methylation-based molecular margin analysis in HCC and explore its clinical application, we investigated CDKN2A methylation status in the surgical margins of 20 HCC patients using a nested BS-MSP protocol and compared the methylation patterns in resection margins with those in the corresponding tumor and adjacent nonmalignant tissues. The results showed that a considerable frequency (35%, 7 of 20) of CDKN2A methylation was present in histologically negative margins, and methylation pattern analysis might be valuable for studying the cellular origin of recurrent carcinoma. Therefore, methylation-based molecular surgical margin analysis offers a promising tool in prognosis for HCC patients who underwent hepatectomy.     

桂西南喀斯特季雨林木本植物的水力安全

桂西南喀斯特地区生物多样性丰富、特有种多, 同时也是石漠化问题较为严重的区域。由于该喀斯特地区土层浅薄、岩石裸露、表层储水能力差, 植物在干旱季节经常会受到水分胁迫。植物水力学特征不仅是探讨喀斯特地区植物的生理生态适应性的关键, 还能够为石漠化地区的植被恢复提供重要参考。该研究测定了桂西南喀斯特季雨林17种代表性木本植物(包括不同生活型、叶片习性和生境)的木质部脆弱性曲线、最低水势、叶片膨压丧失点和边材密度等水力性状, 结果发现: (1)喀斯特植物木质部导水率丧失50%时的水势值(P₅₀)的种间差异较大(-0.51- -2.51 MPa), 其中常绿种的抗栓塞能力比落叶种强; (2)喀斯特植物的木质部水力安全边界值(最低水势与P₅₀之间的差值)的均值为0.36 MPa, 说明喀斯特森林植物在自然最低水势状况下木质部发生栓塞的程度较高; 但是不同植物种间存在显著差异, 这可能与喀斯特峰丛洼地生境的复杂性以及物种不同的抗旱策略有关; (3)由于喀斯特植物水分适应机制的多样化, 导致木质部水力安全边界与叶片膨压丧失点、边材密度的相关性并不显著。在区域气候干热化的背景下, 结合喀斯特植物的栓塞脆弱性和长期水势监测(尤其极端干旱事件)分析它们的水力安全, 对预测未来喀斯特森林物种分布和群落动态具有重要的指示作用。     

Modeling leaf CO2 assimilation and Photosystem II photochemistry from chlorophyll fluorescence and the photochemical reflectance index

We present a simple model to assess the quantum yield of photochemistry (Φ_P) and CO₂ assimilation rate from two parameters that are detectable by remote sensing: chlorophyll (chl) fluorescence and the photochemical reflectance index (PRI). Φ_P is expressed as a simple function of the chl fluorescence yield (Φ_F) and nonphotochemical quenching (NPQ): Φ_P = 1–bΦ_F(1 + NPQ). Because NPQ is known to be related with PRI, Φ_P can be remotely assessed from solar‐induced fluorescence and the PRI. The CO₂ assimilation rate can be assessed from the estimated Φ_P value with either the maximum carboxylation rate (V_cmax), the intercellular CO₂ concentration (C_i), or parameters of the stomatal conductance model. The model was applied to experimental data obtained for Chenopodium album leaves under various environmental conditions and was able to successfully predict Φ_F values and the CO₂ assimilation rate. The present model will improve the accuracy of assessments of gas exchange rates and primary productivity by remote sensing.     

Soil N and C trace gas fluxes and microbial soil N turnover in a sessile oak (Quercus petraea (Matt.) Liebl.) forest in Hungary

During two intensive field campaigns in summer and autumn 2004 nitrogen (N₂O, NO/NO₂) and carbon (CO₂, CH₄) trace gas exchange between soil and the atmosphere was measured in a sessile oak (Quercus petraea (Matt.) Liebl.) forest in Hungary. The climate can be described as continental temperate. Fluxes were measured with a fully automatic measuring system allowing for high temporal resolution. Mean N₂O emission rates were 1.5 μg N m⁻² h⁻¹ in summer and 3.4 μg N m⁻² h⁻¹ in autumn, respectively. Also mean NO emission rates were higher in autumn (8.4 μg N m⁻² h⁻¹) as compared to summer (6.0 μg N m⁻² h⁻¹). However, as NO₂ deposition rates continuously exceeded NO emission rates (−9.7 μg N m⁻² h⁻¹ in summer and −18.3 μg N m⁻² h⁻¹ in autumn), the forest soil always acted as a net NO _x sink. The mean value of CO₂ fluxes showed only little seasonal differences between summer (81.1 mg C m⁻² h⁻¹) and autumn (74.2 mg C m⁻² h⁻¹) measurements, likewise CH₄uptake (summer: −52.6 μg C m⁻² h⁻¹; autumn: −56.5 μg C m⁻² h⁻¹). In addition, the microbial soil processes net/gross N mineralization, net/gross nitrification and heterotrophic soil respiration as well as inorganic soil nitrogen concentrations and N₂O/CH₄ soil air concentrations in different soil depths were determined. The respiratory quotient (ΔCO_{2 resp} ΔO_{2 resp}⁻¹) for the uppermost mineral soil, which is needed for the calculation of gross nitrification via the Barometric Process Separation (BaPS) technique, was 0.8978 ± 0.008. The mean value of gross nitrification rates showed only little seasonal differences between summer (0.99 μg N kg⁻¹ SDW d⁻¹) and autumn measurements (0.89 μg N kg⁻¹ SDW d⁻¹). Gross rates of N mineralization were highest in the organic layer (20.1–137.9 μg N kg⁻¹ SDW d⁻¹) and significantly lower in the uppermost mineral layer (1.3–2.9 μg N kg⁻¹ SDW d⁻¹). Only for the organic layer seasonality in gross N mineralization rates could be demonstrated, with highest mean values in autumn, most likely caused by fresh litter decomposition. Gross mineralization rates of the organic layer were positively correlated with N₂O emissions and negatively correlated with CH₄ uptake, whereas soil CO₂ emissions were positively correlated with heterotrophic respiration in the uppermost mineral soil layer. The most important abiotic factor influencing C and N trace gas fluxes was soil moisture, while the influence of soil temperature on trace gas exchange rates was high only in autumn.     

基于FORCCHN模型的中国典型森林生态系统碳通量模拟

森林生态系统是陆地碳循环的重要组成部分,其固碳能力显著高于其他陆地生态系统,研究森林生态系统碳通量是认识和理解全球变化对碳循环影响的关键。碳循环模型是研究森林生态系统碳通量有效工具。以长白山温带落叶阔叶林、千烟洲亚热带常绿针叶林、鼎湖山亚热带常绿阔叶林和西双版纳热带雨林等4种中国典型森林生态系统为研究对象,利用涡度相关2003-2012年观测数据,评估FORCCHN模型对生态系统呼吸（ER）,总初级生产力（GPP）,净生态系统生产力（NEP）的模型效果。结果表明：（1） FORCCHN模型能够较好的模拟中国4种典型森林生态系统不同时间尺度的碳通量。落叶阔叶林和常绿针叶林ER和GPP的逐日变化模拟效果较好（ER的相关系数分别为0.94和0.92,GPP的相关系数分别为0.86和0.74）;（2）4种森林生态系统碳通量季节动态模拟值和观测值显著相关（P<0.01）,ER、GPP、NEP的观测值和模拟值的R²分别为0.77-0.93、0.54-0.88和0.15-0.38;模型可以很好地模拟森林生态系统不同季节碳汇（NEP>0）,碳源（NEP<0）的变化规律;（3）4种森林生态系统碳通量模拟值与观测值的年际变化有很好的吻合度,但在数值大小上存在差异,模型高估了常绿阔叶林的ER和GPP,略微低估了其他3种森林生态系统ER和GPP。     

Regeneration of a chimeric retina from single cells in vitro: cell-lineage-dependent formation of radial cell columns by segregated chick and quail cells

Summary We report here that similar to E6-chicken retinal cells, dissociated cells from 5.5-day-old (E5.5) quail retinae reaggregate in rotary culture, multiply about tenfold and reestablish histotypical areas. These cellular aggregates include all nuclear layers either with inversed or correct laminar polarity, depending on the local origin of the cells (called rosetted and laminar in-vitro-retinae (IVR), respectively; Layer and Willbold 1989). In combined cultures, chick and quail cells are evenly mixed only during the first two days of culture. Along with the assembly of single cells into rosettes and then into discrete laminae, sectors of chick and quail cells begin to segregate. They are delineated by borders running radially through all three nuclear layers. Thus, interspecies migration of cells at this advanced stage of differentiation is strongly inhibited. Concomitant with this segregation, coherent radial columns spanning all three layers but containing cells from either species only, can be traced histologically. We conclude that a weak segregation of chick and quail retinal cells takes place already at the single cell level, but that the permanent segregation of entire tissue parts must be due to clonal cellular proliferation within the IVR in conjunction with some developmental-structural mechanism retaining clonal progenies within a columnar order.Abbreviations ECM extracellular matrix - E5.5 days of embryonic age - GCL ganglion cell layer - GC's ganglion cells - i.c. in culture - INL inner nuclear layer - rosetted in-vitro-retina retinal cell organoid aggregated from single cells of the central retina - IPL inner plexiform layer - MRE marginal retinal epithelium - ONL outer nuclear layer - OPL outer plexiform layer - OS ora serrate - PR photoreceptor cell - laminated in-vitro-retina fully laminated retinal cellorganoid resembling an E15-retina aggregated from cells of the eye periphery including RPE - RPE retinal pigment epithelium     

Disputed Areas and the 10-Year Time Frame: A Legal Lacuna?

Where a coastal state intends to delineate, in accordance with Article 76 of the 1982 Law of the Sea Convention, the outer limits of its continental shelf beyond 200 nautical miles, it is to submit scientific and technical data of such proposed limits to the Commission on the Limits of the Continental Shelf within 10 years of the entry into force of the Convention for that state. This obligation has subsequently been subject to a general de facto amendment by which the commencement of the 10-year time frame has been postponed to May 13, 1999, for the states for which the Convention had entered into force prior to the above date. This article discusses whether any provision in the Convention, any subsequent agreement, or any subsequent practice render inoperative the 10-year time frame with regard to those parts of the outer continental shelf that are disputed areas. It is concluded that nothing in the Convention, no subsequent agreements, and no subsequent practice allow for derogation of the 10-year time frame with regard to disputed areas.     

Activatable fluorescent probes in fluorescence-guided surgery: Practical considerations

Fluorescence-guided imaging during surgery is a promising technique that is increasingly used to aid surgeons in identifying sites of tumor and surgical margins. Of the two types of fluorescent probes, always-on and activatable, activatable probes are preferred because they produce higher target-to-background ratios, thus improving sensitivity compared with always-on probes that must contend with considerable background signal. There are two types of activatable probes: 1) enzyme-reactive probes that are normally quenched but can be activated after cleavage by cancer-specific enzymes (activity-based probes) and 2) molecular-binding probes which use cancer targeting moieties such as monoclonal antibodies to target receptors found in abundance on cancers and are activated after internalization and lysosomal processing (binding-based probes). For fluorescence-guided intraoperative surgery, enzyme-reactive probes are superior because they can react quickly, require smaller dosages especially for topical applications, have limited side effects, and have favorable pharmacokinetics. Enzyme-reactive probes are easier to use, fit better into existing work flows in the operating room and have minimal toxicity. Although difficult to prove, it is assumed that the guidance provided to surgeons by these probes results in more effective surgeries with better outcomes for patients. In this review, we compare these two types of activatable fluorescent probes for their ease of use and efficacy.     

Calibration of Terra/MODIS gross primary production over an irrigated cropland on the North China Plain and an alpine meadow on the Tibetan Plateau

This paper evaluated the MODerate resolution Imaging Spectroradiometer (MODIS) gross primary production (GPP) product (MOD17) by using estimated GPP from eddy‐covariance flux measurements over an irrigated winter wheat and maize double‐cropping field on the North China Plain in 2003–2004, and an alpine meadow on the Tibetan Plateau in 2002–2003. The mean annual GPP from MOD17 accounted for 1/2–2/3 of the surface estimated mean annual GPP for the alpine meadow, but only about 1/5–1/3 for the cropland. This underestimation was partly attributed to low estimates of leaf area index by a MODIS product (MOD15) because it is used to calculate absorbed photosynthetically active radiation in the MOD17 algorithm. The main reason is that the parameter maximum light use efficiency (ε_max) in the MOD17 algorithm was underestimated for the two biomes, especially for the cropland. Contrasted to the default, ε_max was optimized using surface measurements. The optimized ε_max for winter wheat, maize and meadow was 1.18, 1.81 and 0.73 g C/MJ, respectively. By using the surface measurements and optimized ε_max , the MOD17 algorithm significantly improved the accuracy of GPP estimates. The optimum MOD17 algorithm explained about 82%, 68%, and 79% of GPP variance for winter wheat, maize, and meadow, respectively. These results suggest that it is necessary to adjust the MOD17 parameters for the estimation of cropland and meadow GPP, particularly over cropland.