土壤动物对川西高山/亚高山森林凋落物分解的贡献

采用凋落物分解袋法,研究了土壤动物对川西高山/亚高山森林代表性植物康定柳、方枝柏、红桦和岷江冷杉凋落物在分解第一年(2011年11月-2012年10月)不同关键时期质量损失的贡献.结果表明: 在凋落物第一年的分解过程中, 不同物种凋落物的分解速率大小依次为康定柳＞红桦＞岷江冷杉＞方枝柏,且均为生长季节大于冻融季节.土壤动物对凋落物分解的贡献率(P_fau)为方枝柏(26.7%)＞岷江冷杉(18.8%)＞红桦(15.7%)＞康定柳(13.2%),其中康定柳和方枝柏的P_fau在生长季节大于冻融季节,而红桦和岷江冷杉的P_fau为冻融季节大于生长季节.冻融季节土壤动物的作用与凋落物初始C、P和N/P显著相关,而生长季节则与N、C/N、木质素、木质素/纤维素显著相关.     

藏东南急尖长苞冷杉林林隙土壤线虫群落特征

为了解西藏东南部急尖长苞冷杉林林隙土壤线虫群落特征,对林隙、非林隙土壤0~30 cm范围内不同深度土层的线虫群落进行调查,并用线虫个体密度、生物多样性指数和营养类群指数等特征值分析了土壤线虫群落的结构及多样性特点.结果表明： 采用浅盘法分离得到土壤线虫26801 条,隶属于2纲5目40科64属;线虫个体密度平均为3552 条·100 g-1干土,表聚性极强.垫咽属、丝垫刃属为林隙土壤线虫优势属;食细菌性线虫为主要营养类群.土壤有机质的分解兼有真菌分解和细菌分解两种途径.线虫的生物多样性及丰富度与林隙面积有关.土壤线虫群落特征表明,林隙具有异于郁闭林分和林间空地的特性,在环境指示方面具有应用潜力.     

植物光合作用模型参数的温度依存性研究进展

综述了植物光合作用与温度响应模型研究的进展,围绕光合作用生化模型的4个主要参数：胞间CO₂浓度、RuBP最大碳同化速率(V_{c max})的活化能、RuBP最大再生速率(J_max)的活化能和J_max/V_{c max},讨论了影响光合作用 温度响应曲线的内在机理.随着生长温度的升高,所有物种的V_{c max}活化能均呈增加趋势,而其他参数的变化因物种不同而存在明显差异,说明V_{c max}的活化能可能是决定光合作用温度依存性的首要参数.最后分析了研究中存在的问题并提出研究展望,认为应整合叶片与群落水平的光合作用模型,从叶面积、太阳辐射、冠层结构、冠层小气候和光合能力等方面研究植物群落对全球变化的响应机理.这对于人们理解和准确估算植物生长、群落碳收支和生态系统初级生产力具有重要意义.     

RACE法克隆甜菜NR基因及生物信息学分析

硝酸还原酶是氮素代谢的关键酶和限速酶,研究硝酸还原酶的功能对提高甜菜的产量具有重要作用。运用RACE法克隆出甜菜的硝酸还原酶基因,并利用生物信息学对甜菜NR进行主要结构分析和功能预测,并使其在拟南芥中表达,观察根对向重性应答过程中的弯曲情况。结果表〖JP2〗明,利用RACE法克隆得到甜菜NR cDNA全长为2 760 bp;甜菜NR为易溶、亲水性强的蛋白;二级结构预测结果显示,甜菜NR为混合型蛋白;甜菜NR含有钼辅因子、细胞色素b5、FAD及NADH结合域,具有跨膜区域,但不含有信号肽;利用拟南芥突变体观察到野生型比突变体的弯曲较快,暗示甜菜的NR基因可能通过调节NO积〖JP〗累参与植物向重性应答。     

紫藤瘤不同溶剂提取部位抗农作物病原真菌活性研究

采用十字交叉法测定紫藤瘤不同溶剂提取物对农作物病原真菌的抑制作用。结果表明:紫藤瘤水提取物在5 mg?mL 1浓度下几乎无抗真菌活性。石油醚、乙酸乙酯和正丁醇提取物在5 mg?mL 1浓度下对辣椒枯萎、小麦赤霉病菌的抑菌率在50%左右,对油菜菌核菌的抑菌效果显著,抑制率高达100%。     

RNA的m6A修饰与心血管疾病

N~6-甲基腺嘌呤(N6-methyladenosine,m~6A)是存在于多种RNA中的化学修饰方式,最常见于mRNA。RNA的m~6A含量和效应受到甲基转移酶(Writers)、去甲基酶(Erasers)和甲基化阅读蛋白(Readers)的动态调控。与DNA甲基化修饰和组蛋白修饰相似,它们都参与了多种生物学过程,并与多种疾病的发生发展相关。本文先简要综述m~6A修饰的动态过程及生物学功能,然后重点介绍m~6A修饰与心血管疾病关系的研究进展。     

南水北调工程（中段）对汉江中下游流域水环境的影响

The Hanjiang River is the most important tributary ofthe Changjiang River,which has alength of1570km.Theconfluence of the river withthe Yangtze Riveris at Wuhancity.Fromthe Danjiangkoutothe Nianpanshanextendsthemiddle reach of the Hanjiang River,whichis240kmlongand represents a forkriver section,havingtributaries suchas the Bei River,the Nan River,the Tangbai River,andothers.The lower reach extents from Nianpanshan to theestuary,stretching over409km.,This stretchis a curvedriver sectio…     

Reduction of sample heterogeneity through use of population substructure: an example from a population of African American families with sarcoidosis

Sarcoidosis is a granulomatous inflammatory disorder of complex etiology with significant linkage to chromosome 5, and marginal linkage was observed to five other chromosomes in African Americans (AAs) in our previously published genome scan. Because genetic factors underlying complex disease are often population specific, genetic analysis of samples with diverse ancestry (i.e., ethnic confounding) can lead to loss of power. Ethnic confounding is often addressed by stratifying on self-reported race, a controversial and less-than-perfect construct. Here, we propose linkage analysis stratified by genetically determined ancestry as an alternative approach for reducing ethnic confounding. Using data from the 380 microsatellite markers genotyped in the aforementioned genome scan, we clustered AA families into subpopulations on the basis of ancestry similarity. Evidence of two genetically distinct groups was found: subpopulation one (S1) comprised 219 of the 229 families, subpopulation two (S2) consisted of six families (the remaining four families were a mixture). Stratified linkage results suggest that only the S1 families contributed to previously identified linkage signals at 1p22, 3p21-14, 11p15, and 17q21 and that only the S2 families contributed to those found at 5p15-13 and 20q13. Signals on 2p25, 5q11, 5q35, and 9q34 remained significant in both subpopulations, and evidence of a new susceptibility locus at 2q37 was found in S2. These results demonstrate the usefulness of stratifying on genetically determined ancestry, to create genetically homogeneous subsets--more reliable and less controversial than race-stratified subsets--in which to identify genetic factors. Our findings support the presence of sarcoidosis-susceptibility genes in regions identified elsewhere but indicate that these genes are likely to be ancestry specific.     

Optimization of shunt placement for the Norwood surgery using multi-domain modeling

An idealized systemic-to-pulmonary shunt anatomy is parameterized and coupled to a closed loop, lumped parameter network (LPN) in a multidomain model of the Norwood surgical anatomy. The LPN approach is essential for obtaining information on global changes in cardiac output and oxygen delivery resulting from changes in local geometry and physiology. The LPN is fully coupled to a custom 3D finite element solver using a semi-implicit approach to model the heart and downstream circulation. This closed loop multidomain model is then integrated with a fully automated derivative-free optimization algorithm to obtain optimal shunt geometries with variable parameters of shunt diameter, anastomosis location, and angles. Three objective functions: (1) systemic; (2) coronary; and (3) combined systemic and coronary oxygen deliveries are maximized. Results show that a smaller shunt diameter with a distal shunt-brachiocephalic anastomosis is optimal for systemic oxygen delivery, whereas a more proximal anastomosis is optimal for coronary oxygen delivery and a shunt between these two anatomies is optimal for both systemic and coronary oxygen deliveries. Results are used to quantify the origin of blood flow going through the shunt and its relationship with shunt geometry. Results show that coronary artery flow is directly related to shunt position.     

Ethnic disparity in hemoglobin A1c levels among normoglycemic offspring of parents with type 2 diabetes mellitus

ObjectiveTo investigate the racial/ethnic disparities in hemoglobin A_1c levels among nondiabetic persons with similar parental history of type 2 diabetes mellitus.MethodsWe studied a community-based sample of adult offspring of parents with type 2 diabetes mellitus. Measurements included anthropometry, hematology assessments, serial fasting plasma glucose, oral glucose tolerance testing, plasma insulin, hemoglobin A_1c, insulin sensitivity, and b-cell function, using a homeostasis model assessment.ResultsThe study included 302 participants (135 white, 167 black). Compared with white participants, black participants had lower fasting plasma glucose levels (91.9 ± 0.51 mg/dL vs 93.6 ± 0.50 mg/dL, P = .015), lower area under the curve of plasma glucose during oral glucose tolerance testing (P = <.001), higher body mass index (31.1 ± 0.61 kg/m² vs 28.5 ± 0.57 kg/m², P = <.001), and similar insulin sensitivity and b-cell function. Hemoglobin A_1c was higher in black participants than in white participants (5.68 ± 0.033% vs 5.45 ± 0.028%, P <.001). The absolute black-white difference in hemoglobin A_1c level of approximately 0.22% persisted after adjusting for age, hemoglobin, hematocrit, body mass index, waist circumference, fasting plasma glucose, glucose area under the curve, and other covariates.ConclusionsAmong healthy offspring of parents with type 2 diabetes mellitus in this study, African American participants had higher hemoglobin A_1c levels than white participants after adjusting for age, adiposity, blood glucose, and known variables. Thus, plasma glucose level is more valid than hemoglobin A_1c for diagnosing prediabetes or diabetes in black persons. (Endocr Pract. 2012; 18:356-362)