Response of Net Ecosystem Productivity of Three Boreal Forest Stands to Drought

In 2001–03, continuous eddy covariance measurements of carbon dioxide (CO₂) flux were made above mature boreal aspen, black spruce, and jack pine forests in Saskatchewan, Canada, prior to and during a 3−year drought. During the 1st drought year, ecosystem respiration (R) was reduced at the aspen site due to the drying of surface soil layers. Gross ecosystem photosynthesis (GEP) increased as a result of a warm spring and a slow decrease of deep soil moisture. These conditions resulted in the highest annual net ecosystem productivity (NEP) in the 9 years of flux measurements at this site. During 2002 and 2003, a reduction of 6% and 34% in NEP, respectively, compared to 2000 was observed as the result of reductions in both R and GEP, indicating a conservative response to the drought. Although the drought affected most of western Canada, there was considerable spatial variability in summer rainfall over the 100−km extent of the study area; summer rainfalls in 2001 and 2002 at the two conifer sites minimized the impact of the drought. In 2003, however, precipitation was similarly low at all three sites. Due to low topographic position and consequent poor drainage at the black spruce site and the coarse soil with low water-holding capacity at the jack pine site almost no reduction in R, GEP, and NEP was observed at these two sites. This study shows that the impact of drought on carbon sequestration by boreal forest ecosystems strongly depends on rainfall distribution, soil characteristics, topography, and the presence of vegetation that is well adapted to these conditions.     

Edaphic,Nutritive, and Species Assemblage Differences between Hotspots and Matrix Vegetation: Two African Case Studies

Areas of locally intense and frequent grazing, or ‘hotspots’, are pervasive features in tropical grasslands and savannas. In some ecosystems, hotspot presence is clearly associated with edaphic factors (e.g., high clay content and elevated soil fertility), such as those that develop in abandoned cattle bomas. Studies in a range of other savanna ecosystems, however, have failed to find intrinsic soil differences between hotspots and the surrounding matrix. Also, it remains unclear to what extent hotspots are associated with specific assemblages of nutrient‐rich plant species, as opposed to being a manifestation of intraspecific variation in nutritive quality. We conducted simultaneous studies in Kruger (South Africa) and Serengeti (Tanzania) National Parks to re‐evaluate the role of edaphic correlates of hotspot occurrence and to test whether intraspecific variation in plant quality occurs across hotspot‐matrix boundaries. We sampled soils and plants in paired hotspot and matrix plots at multiple sites within each ecosystem to test our a priori hypothesis that hotspots would be associated with distinct species assemblages and differences in soil fertility. We found clear hotspot‐matrix differences in foliar N, particularly within species, despite finding no differences in any soil or plant–soil variables, including N mineralization potential and mycorrhizal inoculation levels. We found only weak differences in community composition across the boundary, suggesting that intraspecific variation in foliar N rather than species turnover is mainly responsible for the enhanced nutritive value of hotspot vegetation. We propose that grazer–plant interactions may be stronger drivers of hotspot maintenance in these systems than plant–soil interactions.     

Aldehyde dehydrogenase 1B1 (ALDH1B1) is a potential biomarker for human colon cancer

Aldehyde dehydrogenases (ALDHs) belong to a superfamily of NAD(P)⁺-dependent enzymes, which catalyze the oxidation of endogenous and exogenous aldehydes to their corresponding acids. Increased expression and/or activity of ALDHs, particularly ALDH1A1, have been reported to occur in human cancers. It is proposed that the metabolic function of ALDH1A1 confers the “stemness” properties to normal and cancer stem cells. Nevertheless, the identity of ALDH isozymes that contribute to the enhanced ALDH activity in specific types of human cancers remains to be elucidated. ALDH1B1 is a mitochondrial ALDH that metabolizes a wide range of aldehyde substrates including acetaldehyde and products of lipid peroxidation (LPO). In this study, we immunohistochemically examined the expression profile of ALDH1A1 and ALDH1B1 in human adenocarcinomas of colon (N = 40), lung (N = 30), breast (N = 33) and ovary (N = 33) using an NIH tissue array. The immunohistochemical expression of ALDH1A1 or ALDH1B1 in tumor tissues was scored by their intensity (scale = 1–3) and extensiveness (% of total cancer cells). Herein we report a 5.6-fold higher expression score for ALDH1B1 in cancerous tissues than that for ALDH1A1. Remarkably, 39 out of 40 colonic cancer specimens were positive for ALDH1B1 with a staining intensity of 2.8 ± 0.5. Our study demonstrates that ALDH1B1 is more profoundly expressed in the adenocarcinomas examined in this study relative to ALDH1A1 and that ALDH1B1 is dramatically upregulated in human colonic adenocarcinoma, making it a potential biomarker for human colon cancer.     

The genetic association study of TP53 polymorphisms in Saudi obese patients

Obesity is a multifactorial metabolic disorder characterized by low grade chronic inflammation. Rare and novel mutations in genes which are vital in several key pathways have been reported to alter the energy expenditure which regulates body weight. The TP53 or p53 gene plays a prominent role in regulating various metabolic activities such as glycolysis, lipolysis, and glycogen synthesis. Recent genome-wide association studies reported that tumor suppressor gene p53 variants play a critical role in the predisposition of type 2 diabetes and obesity. Till date, no reports are available from the Arabian population; hence the present study was intended to assess the association between p53 variants with risk of obesity development in the Saudi population. We have selected three p53 polymorphisms, rs1642785 (C > G), and rs9894946 (A > G), and rs1042522 (Pro72Arg; C > G) and assessed their association with obesity risk in the Saudi population. Phenotypic and biochemical parameters were also evaluated to check their association with p53 genotypes and obesity. Genotyping was carried out on 136 obese and 122 normal samples. We observed that there is significantly increased prevalence p52 Pro72Arg (rs1042522) polymorphism in obese persons when compared to controls at GG genotype in overall comparison (OR: 2.169, 95% CI: 1.086-4.334, p = 0.02716). Male obese subjects showed three-fold higher risk at GG genotype (OR: 3.275, 95% CI: 1.230-8.716, p = 0.01560) and two-fold risk at G allele (OR: 1.827, 95% CI: 1.128-2.958, p = 0.01388) of p53 variant Pro72Arg respectively. This variant has also shown significant influence on cholesterol, LDL level, and random insulin levels in obese subjects (p ≤ 0.05). In conclusion, p53 Pro72Arg variant is highly prevalent among obese individuals and may act as a genetic modifier for obesity development among Saudis.     

Detection of an East European wolf haplotype puzzles mitochondrial DNA monomorphism of the Italian wolf population

Southern European wolves suffered from reiterated population declines during glacial periods and historically due to human persecution. Differently from other European wolf populations, a single mitochondrial DNA (mtDNA) control region haplotype (W14) has been so far described in the Italian wolves, although no intensive genetic sampling has ever been conducted in historical source populations from central and southern Italy. Using non-invasive genetic techniques, we report the occurrence of an unexpected mtDNA haplotype (W16) in the wolf population of the Abruzzo, Lazio and Molise National Park (PNALM), central Italy. This haplotype, detected in three out of 90 faecal samples from the PNALM, was previously reported in wolves from the North Carpathians, Slovakia and the Balkans only. Microsatellite analysis and molecular sex determination confirmed that the W16 samples belonged to three distinct wolves. Although alternative explanations can be formulated for the origin of this mtDNA haplotype in the otherwise monomorphic Italian wolf population, assignment procedures indicated the likely admixed ancestry of one W16 sample with East European wolves. Anthropogenic introgression with dogs has been detected in the Italian wolf population using nuclear DNA microsatellites, but no population-wide genetic survey had previously reported a mtDNA control region variant in Italian wolves. Our findings strongly suggest that, in addition to wolf × dog hybridization, captive-released wolves or wolf × dog hybrids may successfully interbreed with wolves in the wild, and that human-mediated introgression may occur even in well established protected areas.     

乳腺癌新辅助化疗的研究进展

乳腺癌是一种女性最常见的恶性肿瘤,近年来我国乳腺癌的发病率呈逐年上升趋势。研究证实,新辅助化疗不仅可使不能手术的晚期乳腺癌患者获得手术机会,而且也增加了部分患者的保乳概率,但是约20%的乳腺癌患者不能从新辅助化疗中获益,并影响后续治疗效果。因此,制定合理的、个体化的新辅助化疗方案对于提高乳腺癌患者的生存质量和改善其预后尤为重要。目前,研究已发现的NCT相关的预测因子主要包块肿瘤类型、分子分型、ER、PR、Ki67等,而HER2、TOP2A、P53、PRAP单独作为预测因子的还存在争议。本文主要对乳腺癌新辅助化疗的现状、各种预测因子的作用及其不足之处进行了综述。     

Modulation of types I and III procollagen synthesis at various stages of arterial smooth muscle cell growth in vitro

Collagen synthesis was monitored in cultures of rabbit arterial smooth muscle cells (SMC). Both the rate of collagen synthesis per cell and collagen synthesis as a percent of total protein synthesis were measured at specific intervals from 1 to 14 days after inoculation of smooth muscle cells. The proportions of types I and III collagen present in the conditioned incubation medium and in the cell layer were also examined. After inoculation the cells displayed population expansion typical of SMC in which growth slowed but did not cease after the cells attained confluence. Collagen synthesis rates, expressed as [14C]hydroxyproline per cell, were eight-fold higher in preconfluent cells. In these cultures collagen accounted for more than 20% of the newly synthesized, 14C-labeled protein present as trichloroacetic acid (TCA)-insoluble material in 24 h culture media. In post-confluent cultures, this percentage was reduced to about 7% of the total protein synthesized. Synthesis rates of both collagen and non-collagen protein decreased with increasing time after inoculation. However, the rate of decline of collagen synthesis was three times greater than that seen for non-collagen protein. Early cultures synthesized relatively more type I than type III procollagen. The type I to type III ratio was highest at day 3 and declined after that time to day 14. While the synthesis of both types decreased with increasing age, type I declined at a greater rate resulting in a predominance of type III procollagen secretion by older cultures. We conclude that protein synthesis in general and collagen synthesis in particular are quantitatively and qualitatively dependent upon the growth stage of SMC in vitro.     

PCR-SSCP技术的研究及应用进展

阐述了SSCP技术的建立与发展过程;概述了PCR-SSCP技术的原理、方法、优缺点及突变技术研究进展;总结了PCR-SSCP技术在多个领域中(动物育种、基因突变、基因诊断、基因图谱和连锁分析等)的应用情况;分析了PCR-SSCP技术在分子生物学研究领域中的作用。     

神农架大九湖湿地公园的植被现状与保护对策

大九湖湿地公园共有维管植物103科273属411种,分别占整个神农架自然保护区维管植物科、属、种的51.8%、31.3%和14.9%。在植物地理区系成分上,以温带成分为主。大九湖湿地公园的植被可划分为4个植被型组,7个植被型,20个群系。黑三棱群落(Form.Sparganium stoloniferum)和睡菜群落(Form.Menyanthes trifoliata)为中国首次记载。食虫植物黄花狸藻(Utricularia aurea)和圆叶茅膏菜(Drosera rotundifolia)及苔草群落(Form.Carexargyi)中的浮毛茛(Ranunculus natans)均为神农架地区首次记载,并且圆叶茅膏菜和浮毛茛亦为湖北省首次记载。在全面调查大九湖湿地公园植被现状的基础上,结合大九湖湿地公园存在的主要问题,提出了相应的保护对策。     

甘肃金水湖国家湿地公园景观自然性的时空异质性

景观自然性体现了各景观要素的时空分布格局,对提高生态系统的整体性和稳定性有重要意义.通过解译2003年、2009年和2015年3个时相的遥感影像,利用GIS和层次分析法,研究了甘肃金川金水湖国家湿地公园景观自然性变化规律.结果表明:随着时间的变化,景观结构中景观多样性指数、均匀度指数、斑块丰富度呈增加趋势,景观优势度、景观分离度呈减小趋势;提供栖息地、植物群落维持功能、面积加权平均斑块分维数、植被覆盖度等生态功能指标呈增大趋势;人工干扰指数、人工景观平均面积等生态学干扰指标呈减小趋势,湿地公园的景观自然性指数由2003年的0.4761增加至2015年的0.7485.湿地公园保育和恢复工程的实施改变了土地覆被结构,增强了生态系统的稳定性、生态弹性和服务价值,较大程度上提高了金水湖国家湿地公园的景观自然性.