Histopathological nerve and skeletal muscle changes in rats subjected to persistent insulin-induced hypoglycemia

New insulin analogues with a longer duration of action and a flatter pharmacodynamic profile are developed to improve convenience and safety for diabetic patients. During the nonclinical development of such analogues, safety studies must be conducted in nondiabetic rats, which consequently are rendered chronically hypoglycemic. A rat comparator model using human insulin would be valuable, as it would enable differentiation between effects related to either persistent insulin-induced hypoglycemia (IIH) or a new analogue per se. Such a model could alleviate the need for an in-study-comparator and thereby reduce the number of animals used during development. Thus, the aims of the present study were i) to develop a preclinical animal model of persistent hypoglycemia in rats using human insulin infusion for four weeks and ii) to investigate histopathological changes in sciatic nerves and quadriceps femoris muscle tissue, as little is known about the response to persistent hypoglycemia in these tissues. Histopathologic changes in insulin-infused animals included axonal degeneration and myofibre degeneration. To our knowledge, this is the first study to show that persistent IIH provokes peripheral nerve and skeletal myofiber degeneration within the same animals. This suggests that the model can serve as a nonclinical comparator model during development of long-acting insulin analogues.     

基于地形因子的土壤有机碳最优估算模型

基于数字地面模型(Digital Terrain Model,DTM),同时考虑因子组合和分辨率构建土壤有机碳(SOC)最优估算模型。在7 100 km2范围内,选取了71个分辨率和22个地形因子中不多于5个因子的所有可能组合,构造了2 514 820个模型。采样点随机分为两组,6 362个训练样点构造数据挖掘模型,其他2 208个为验证样点。根据模型相关系数r值大小从中选取了不同个数因子组合以及相应分辨率的最优模型,并根据这些模型生成对应的土壤有机碳图。结果表明:单个地形因子模型和栅格大小之间的关系表现出多样化,并不是分辨率越高模型结果越好。单因子模型r值的大小并不能决定其在因子组合模型中的重要性。不同的因子及其组合有其特定的最适分辨率,最佳分辨率范围约为60~150 m。综合数据的存储空间和计算量、模型复杂度、预测精度以及空间表达能力,该地区最优模型由相对坡位、高程、归一化高程及多尺度山谷平坦指数等4个变量组成,对应分辨率为121.6 m。同时与多种克里格空间插值方法生成的土壤有机碳空间分布图进行了对比分析,发现无论几个变量的组合,其空间预测能力均较克里格空间插值方法更能表达SOC的空间变化,预测精度也较高。     

Glacial survival of boreal trees in northern Scandinavia

It is commonly believed that trees were absent in Scandinavia during the last glaciation and first recolonized the Scandinavian Peninsula with the retreat of its ice sheet some 9000 years ago. Here, we show the presence of a rare mitochondrial DNA haplotype of spruce that appears unique to Scandinavia and with its highest frequency to the west-an area believed to sustain ice-free refugia during most of the last ice age. We further show the survival of DNA from this haplotype in lake sediments and pollen of Tr?ndelag in central Norway dating back ~10,300 years and chloroplast DNA of pine and spruce in lake sediments adjacent to the ice-free And?ya refugium in northwestern Norway as early as ~22,000 and 17,700 years ago, respectively. Our findings imply that conifer trees survived in ice-free refugia of Scandinavia during the last glaciation, challenging current views on survival and spread of trees as a response to climate changes.     

Identification of genes for resistance to Puccinia striiformis f. sp. hordei in 18 barley genotypes

Barley genotypes Hor 1428, Hor 2926, Hor 3209, BBA 2890, Abyssinian 14, Grannelose Zweizeilige, and Stauffers Obersulzer are resistant to all races of Puccinia striiformis f. sp. hordei so far detected in the U.S.A. Heils Franken, Cambrinus, Astrix, Emir, Hiproly, Varunda, Trumpf,Mazurka, Bigo, BBA 2890, and I 5 are resistant to some races and susceptible to others. Previous studies showed that Hor 1428, Hor 2926, Hor 3209, Abyssinian 14, Stauffers Obersulzer, I 5, Heils Franken, Emir, Astrix, Hiproly, Varunda, and Trumpf each have two genes, and BBA 2890, Grannelose Zweizeilige, Cambrinus, Mazurka, Bigo, and BBA 809 each have a single genefor resistance. To determine the genes in specific genotypes and their relationships, all possible crosses were made among the 18 genotypes. Seedlings of parents and F₂ progeny were tested under controlledconditions for resistance to selected races that were avirulent on both parents. Based on segregation within the individual crosses to selected races, at least 26 of 30 genes detected in the 18 genotypes were different. Allelic and linkage relationships of some of the genes were determined. The genetic information should be useful for understanding the host-pathogen interactions and for control of stripe rust using resistance.     

利用PCR在已克隆基因末端添加终止密码的方法与应用*

PCR产物直接克隆技术的发明,极大地方便了基因克隆工作[1].但是在实验过程中载体与目的基因连接处经常会出现碱基突变.     

Spectroscopic (IR,NMR) characterization of water-soluble organic substances extracted from straw,straw incubated with Pleurotus ostreatus,and straw compost

Water extracts from fresh wheat and barley straw, straw incubated with Pleurotus ostreatus, and straw compost were studied by IR, ¹H NMR, and ¹³C NMR spectroscopy. During incubation lignin was degraded, water extractability increased, and water extracts were rich in polysaccharides. After composting solubility decreased and the water extracts were rich in aromatic, methoxyl, and carboxyl C, but poor in O-alkyl C indicating that during composting mainly polysaccharides had been mineralized. GPC revealed that water extracts from straw compost contained polysaccharides, peptides, C- and O-substituted aromatics, and alkyl compounds.     

Evaluation of World Reference Base for Soil Resources and FAO Soil Map of the World using nationwide grid soil data from Denmark

Abstract. Soil classification is a tool for stratifying and generalizing information on soil resources but most systems are tailored to handle only slightly disturbed soil. We tested the applicability of the legend of the FAO-Unesco Soil Map of the World and the new World Reference Base for Soil Resources by classifying at the highest order 831 profiles from a nationwide 7 km grid survey in Denmark, where soils are developed in Quaternary glacial and marine sediments and intensively farmed. Comparison of the variability of pH and % clay +% silt of the master horizons (A, E, B, and C) within and between the major well-drained soil groupings shows that liming, fertilizing and ploughing have produced significantly deeper A-horizons with higher pH, lower % humus and C:N ratios on the two-thirds of the country that is cultivated. ‘Anthropogenic’ mollic and umbric horizons are a common result but the liming causes a random final classification of these surface horizons and, hence, random allocation of the soils in both systems. It separates cultivated soils and their undisturbed equivalents, and results in considerable within-group variation in soil texture. Grouping of cultivated and undisturbed soils, on the other hand, results in wide within-horizon pH ranges for most groups, again compromising the advantage of making useful general statements on the basis of classification. We propose that anthropogenic mollic and umbric horizons should be allowed in any soil group and that ‘anthric properties’ should be used to distinguish between profoundly changed cultivated soils and largely undisturbed soils, hereby constructing a two-tier system within each highest-order soil group. We classified the soils according to this proposal. The results show generally narrower ranges for both pH and % clay +% silt. We evaluated the within-group homogeneity by multivariate analysis of variance of pH, % clay +% silt, % clay, % humus, C:N ratio, exchangeable cations, and CEC. The results (Wilks's Lamda) show a higher degree of group compactness compared to the original FAO and World Reference Base systems.     

沙漠油田地面集输管网腐蚀机理研究

通过对新疆彩南油田集输管网腐蚀现状及腐蚀机理的分析得出，管网腐蚀可归纳为两类：一类是常态性腐蚀；另一类是异态性腐蚀，即由于地形起塞的壁剪切力和与之相伴随的固体颗粒磨蚀，加快了管网腐蚀穿孔速率，导致管道剧烈腐蚀。第一类腐蚀始终存在于整个集输管网当中，而第二类腐蚀常常发生于管道的上坡段。