A bioluminescent assay for the determination of phosphoenolpyruvate carboxykinase activity in nanogram-sized tissue samples

A highly specific and sensitive assay for the determination of phosphoenolpyruvate carboxykinase (PEPCK) in nanogram-sized tissue samples is described. This test system is based on the stoichiometric transformation of phosphoenolpyruvate into ATP. In a subsequent step ATP is quantified by bioluminescent techniques. The applicability of this assay system is shown by measurements in liver samples with normal and high PEPCK activity levels.     

Hydrobiology and organic production in a marl lake of Kashmir Himalayan Valley

L. Naranbagh (alt. 1587 m) is a polymictic, shallow marl lake in the flood-plain valley of Kashmir, India. Macrofloral affinities resemble Potamogeton Type of Forsberg (1965) with alkaline waters, not rich in phosphorus. CaCO₃ precipitation coupled with decline in Ca²⁺ and alkalinity values are characteristic of the lake. Fluctuations in Mg²⁺, Na⁺, K⁺, and Cl^– were relatively conservative. The levels of PO _inf4 ^sup3– -P and NO _inf3 ^sup– -N indicate moderate fertility of the lake water.Persistence of a summer-autumn planktonic algal pulse is related to favourable irradiance, high water temperatures, and increased photosynthetic efficiency values. The most striking seasonality in photosynthetic rates (m^–2 h^–1) between winter minimum (3 mg C_assim) and summer maximum (75.4 mg C_assim) is determined by mainly climatic changes. Energy flow gave annual phytoplankton production of 51.95 × 10² KJ m^–2 for the ecosystem.The nutrient levels and productivity rates suggest mesotrophic status of L. Naranbagh in classic oligoeutrophic classification of lake types.     

卫星影象目视解译方法在湖区植被制图中的应用——以湖南洞庭湖区水域、洲滩植被图为例

植被(包括天然植被、人工植被)作为一种可更新资源始终是遥感应用专家们热心研究的课题。植被分类是植被研究的重要方面之一。利用卫星影象进行植被分类,国内外学者都进行了许多有意义的探索。本文以洞庭湖水域、洲滩植被为对象,试用卫星影象进行植被分类。本文从植被与环境相互依赖关系及在影象上的综合反映出发,提出了影象的景观生态学分析方法;即把影象上色调、形态特征与群落生态学规律结合起来分析,并以此作为植被目视解译的方法。在此基础上,将洞庭湖水域、洲滩划分成五个景观生态模型,17个基本植被类型。     

酵母的不同显色法的研究

在多年采集分离酵母菌的基础上,本文报道其中43属的600多株主要与担子菌有关的酵母及其他酵母的DBB反应,其中某些菌以往尚未测定过,从而广泛比较了担子菌酵母、子囊菌酵母与某些类酵母的区别。此外在方法上,摸索了其他未见报道的重氮盐的显色效果,发现固红B盐对布掷孢酵母(Bulleta Derx)的反应比DBB更灵敏。同时试验了热碱·乙醇处理细胞的快速DBB测试法,用此法测定某些疑难菌株,结果稳定,可大大缩短测试周期,并适用于多毛有气生菌丝的菌类。     

Numerical abundance of myxomycetes (myxogastrids) in soils in the West of England

Abstract A most-probable-number technique was used to quantify the abundance of myxomycetes (myxogastrids) in soil samples taken from 23 'Sites of Special Scientific Interest' and one other site in the West of England. Associated organisms and soil conditions were also recorded. Sixteen of the 24 sites yielded myxomycete plasmodium-forming units (PFUs) in numbers averaging 230 cm⁻³ fresh soil. Where detectable in samples of grassland soil, the numbers ranged from 20–2750 cm⁻³, in woodland soil from 20–800 cm⁻³, and in sand dunes from 80–400 cm⁻³. Repeated sampling revealed changing numbers at single sites. The abundance of PFUs was correlated positively with numbers of soil amoebae, ciliates and nematodes, and with levels of magnesium and soil density, and negatively with organic matter content and levels of NH₄-nitrogen and phosphate. Each PFU probably corresponded to one or several uninucleate cells in the soil rather than to a plasmodium.     

Numerical solution of a nonlinear advance-delay-differential equation from nerve conduction theory

A functional differential equation which is nonlinear and involves forward and backward deviating arguments is solved numerically. The equation models conduction in a myelinated nerve axon in which the myelin completely insulates the membrane, so that the potential change jumps from node to node. The equation is of first order with boundary values given at t=±. The problem is approximated via a difference scheme which solves the problem on a finite interval by utilizing an asymptotic representation at the endpoints, cubic interpolation and iterative techniques to approximate the delays, and a continuation method to start the procedure. The procedure is tested on a class of problems which are solvable analytically to access the scheme's accuracy and stability, then applied to the problem that models propagation in a myelinated axon. The solution's dependence on various model parameters of physical interest is studied. This is the first numerical study of myelinated nerve conduction in which the advance and delay terms are treated explicitly.Supported in part by NSF Grant MCS8301724 and by a Biomedical Research Support Grant 2SO7RR0706618 from NIH     

The hypothalamus of Lacerta sicula R.

Summary An analysis of the preoptic area of the lizard, Lacerta sicula R., with the use of the Golgi method revealed that: 1)in principle, the dendritic pattern of its neurons is relatively simple; 2) the supraoptic nucleus contains large- to medium-sized bipolar or multipolar neurons together with small, usually multipolar nerve cells; 3) the preoptic periventricular gray and the paraventricular nucleus exhibit a varied neuronal typology, including large multipolar or bipolar elements, abundant CSF-contacting neurons, and some tufted elements; and 4) the lateral regions display some conspicuous multipolar neurons.With a financial contribution from Ministero della Pubblica Istruzione     

Comparison of ordinations and classifications of vegetation data

The methodology of comparing the results of multivariate community studies (resemblance matrices, ordinations, hierarchical and nonhierarchical classifications) is reviewed from two viewpoints: basic strategy and measure employed. The basic strategy is determined by 7 choices concerning the type of results, consensus methods or resemblance measures, hypothesis testing or exploratory analysis, lack or presence of reference basis, data set congruence or algorithmic effects, number of factors responsible for differences among results, and the number of properties considered in the comparison. Included is a brief summary of methods applicable to vegetation studies. Examples from a grassland survey demonstrate the utility of comparisons in evaluating the effects of plot size, data type, standardization, taxonomic level and number of species on classifications and ordinations.Abbreviations OUC = Operational Unit of Comparison - PCA = Principal Components Analysis - PCoA = Principal Coordinates Analysis - SSA = Incremental Sum of Squares Agglomeration     

鱼类染色体G—显带的Brd U—BSG方法及白鲢G—带模式图的初步建立

本文报道了一种显示鱼类染色体G-带的BrdU-BsG方法。采用肾细胞短期培养,收获前12小时加入BrdU,使终浓度为10μg/ml。制片经HCl、Ba(OH)_2处理,4×SSC温育。Giemsa染色,显示出白鲢的G-带。其带纹细致清晰,一个细胞的单倍染色体上显示带纹达200条以上,是目前已报道的鱼类多重带中带纹最多的,且反差明显,带纹有特征性,结果较稳定。根据实验结果初步建立了白鲢的G-带模式图。