Cellular and subcellular localization of calcium in gravistimulated corn roots

Summary Antimonate staining procedures and energy dispersive X-ray microanalytical techniques were used to determine the patterns of localization of calcium in nonstimulated and gravistimulated corn roots. In horizontally positioned roots within the region of the developing bend there was a change in the staining from that principally localized within cells of the stele to asymmetric staining within the vacuoles of the cortical cells along the upper root surface. There was little staining in the walls. The pattern observed is quite different from that seen in gravistimulated coleoptiles. Staining of mitochondria, plastids and Golgi stacks was seen in most cell types, but no asymmetry of staining was observed. In the rootcap where graviperception is thought to occur, there was little staining of any cellular organelles.     

Iodine distribution in the thyroid follicles of the hagfish,Eptatretus burgeri and lamprey,Lampetra japonica: Electron-probe X-ray microanalysis

Summary In the thyroid follicles of species of cyclostomes, a hagfish and a lamprey, the distribution of stable iodine was examined by electron-probe X-ray microanalysis. A high concentration of stable iodine, heterogeneously distributed, was observed in the follicular cells of hagfish thyroid follicles. In the lamprey a low concentration of iodine was seen in the follicular lumina. The relative values for stable iodine determined in this way corresponded to values obtained by a chemical analytical method.     

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。     

A stereological method for estimating fish fecundity

This paper describes the application and evaluation of a stereological method for counting fish oocytes. The method has been applied to herring, Clupea harengus L., Dover sole, Solea solea L., and mackerel, Scomber scombrus L., and compared with existing volumetric and/or automated particle counter methods. The stereological method has been shown to given similar results and to have a number of distinct advantages over the other methods.