Assessing the numerical accuracy of the impedance method

The impedance method has been used extensively to calculate induced electric fields and currents in tissue as a result of applied electromagnetic fields. However, there has previously been no known method for an a priori assessment of the numerical accuracy of the results found by this method. Here, we present a method which permits an a priori assessment of the numerical accuracy of the impedance method applied to physiologically meaningful problems in bioengineering. The assessment method relies on estimating the condition number associated with the impedance matrix for problems with varying shapes, sizes, conductivities, anisotropies, and implementation strategies. Equations have been provided which predict the number of significant figures lost due to poor matrix conditioning as a function of these variables. The results show that, for problems of moderate size and uncomplicated geometry, applied fields should be measured or calculated accurately to at least five or six significant figures. As resolutions are increased and material properties are more widely divergent even more significant figures are needed. The equations provided here should ensure that solutions found from the impedance method are calculated accurately.     

A mesoscopic technique for the study of the development of the peripheral system in rat foetuses

In order to study the morphogenesis of the nervous system in the rat an acetylcholinesterase in toto method for staining nervous tissue in rat foetuses was developed. Procedure: Rat foetuses of 14-22 days are fixed "en bloc" for 24 hours in a cold sucrose-formol solution. Fixed specimens are rinsed for 2 days in cold 0.22 M sucrose in a sodiumcacodylate buffer (pH 7.2). The specimens are cut (mid-)sagittally with the aid of a razor-blade, and incubated in a medium of acetylthiocholine iodide in acetate buffer (pH 5.0). Then, dehydration in glycerine/water mixtures of increasing glycerine content follows. The specimens may be stored in pure glycerine or embedded in epoxy-resin blocks and can be studied under a binocular dissecting microscope. In using this in toto staining method both the continuity of the central and peripheral parts of the nervous system as well as details up to the level of individual perikarya and motor endplates are preserved. With this mesoscopic method the three-dimensional architecture of the peripheral nervous system and its topological relations to other structures can be studies in one specimen. The exact procedure and the results as well as a method for embedding specimens in epoxy-resin blocks for teaching purposes are described. The advantages of this mesoscopic staining method for foetuses are discussed.     

A rapid volumetric method for the analysis of the food of fishes

A volumetric method in which the stomach contents are squashed to a uniform depth and the volume is derived from the area of the squash has been evaluated. The apparatus is simple in constiuction and the method applicable to a wide range of fish sizes. The overall error of the method may be as low as 3.5 % for well macerated material, though for hard bodied food animals the coefficient of variation may be up to 8 %. These volumetric determinations are not directly proportional to gravimetric measurements but logarithmic conversion curves are readily derived.     

On the application of the unlabelled peroxidase-antiperoxidase method to the investigations of the nervous tissue

The unlabelled peroxidase-antiperoxidase (PAP) method was applied to the nervous tissue, to investigate whether there are cells which show the localisation of immunoglobulins of IgG, IgA and IgM type. The experiments performed have shown no positive reaction with the PAP method in normal brain tissue. In tumor tissue some cells, rich in cytoplasm of gemistocyte-like appearance or reactive astrocytes stained positively with the PAP method. The reliablility and specificity of the reaction is discussed.     

FMEA法在医疗风险管理中的应用现状与展望

面对日趋严峻的医疗风险问题,如何识别和应对风险已经成为整个医疗行业共同面对的议题。文章以失效模式与效应分析法在医疗风险管理中的应用为研究对象,探讨失效模式与效应分析法的具体实施方法和目前在国内外医疗行业的应用现状,并对失效模式与效应分析法在未来医疗风险管理中的应用予以展望。     

Estimation of the randomness of the overlapping of cellular structures

Methods for estimation of randomness of mutual overlaps of cells, their parts, and intracellular structures are developed. Two methods are proposed: a "method of areas" based on the estimation of the area of overlaps of randomly located figures, and a "method of contours" based on the evaluation of the number of intersections of linear structures located randomly. Examples are given as applied to cells and cellular nuclei, in particular during contact inhibition of cellular movement.     

Assessing the ecological integrity of a grassland ecosystem: the applicability and rapidity of the SAGraSS method

The Grassland Biome is currently one of the most threatened biomes in South Africa and is in dire need of a biomonitoring protocol. The components of ecological integrity in these ecosystems are, however, too diverse and time-consuming to measure scrupulously. It is therefore necessary to develop a set of grassland indicators that are efficient and rapid in their assessment of grassland ecosystem integrity. The South African Grassland Scoring System (SAGraSS), based on the grassland insect community, is such a suggested indicator. The present study is the first to investigate the applicability and rapidity of this proposed method. Although SAGraSS scores correlated significantly with Ecological Index values (the most commonly used index by which veld condition is evaluated in central South Africa), the method proved to be tedious and the identification of insects taxing. We offer a number of changes to make the SAGraSS method a more rapid method of assessment.     

Inferring the trajectory of genetic variance in the course of artificial selection

A method is proposed to infer genetic parameters within a cohort, using data from all individuals in an experiment. An application is the study of changes in additive genetic variance over generations, employing data from all generations. Inferences about the genetic variance in a given generation are based on its marginal posterior distribution, estimated via Markov chain Monte Carlo methods. As defined, the additive genetic variance within the group is directly related to the amount of selection response to be expected if parents are chosen within the group. Results from a simulated selection experiment are used to illustrate properties of the method. Four sets of data are analysed: directional selection with and without environmental trend, and random selection, with and without environmental trend. In all cases, posterior credibility intervals of size 95% assign relatively high density to values of the additive genetic variance and heritability in the neighbourhood of the true values. Properties and generalizations of the method are discussed.     

Erythroid cells of the bone marrow of the mouse

The bone marrow of three intact male mice of C57Bl/6 line, fixed by perfusion of isotonic fixative of Karnovsky, has been studied by means of the scanning electron microscopy method. The surface of erythroid cells, that are immediately connected with macrophages of the erythroblasts islets, is analysed. According to the surface form, the erythroid cells are devided into 5 types. Every maturation stage of the erythroid cells is characterized by a certain type of surface. For identification of basophilic and polychromatophilic proerythrocytes the combined method of light and electron scanning microscopy of the cells in suspension is used. The bone marrow cells, obtained from the two male mice of C57Bl/6 line are fixed with the same fixative on special glasses with grids traced on them, stained after Romanovsky-Giemsa method and in moist preparations are examined in the light microscope. After further treatment the surface of the same cells in studied in the scanning electron microscope.     

FISH检测宫颈脱落细胞与宫颈组织中hTERC基因制片方法的研究

目的:探讨FISH实验中用直接涂片法、盐水制片法、TCT制片法、低渗滴片法制片法和宫颈切片组织取材方法对于FISH成功率的影响.方法:收集2008年3月至2009年3月青岛大学医学院附属医院妇科162例宫颈脱落细胞标本及2008年5月至2009年3月手术切除或活检的宫颈组织63例,用荧光原位杂交(FISH)方法检测hTERC基因.结果:直接涂片法、盐水制片法、生理盐水法、TCT制片法和石蜡包埋组织切片法hTERC基因杂交成功率分别为58.3%,65%,55%,87.1%,85.7%,TCT制片高于其它四组;低渗滴片法背景干净度、细胞形态、裸核数量满意度最高;TCT制片法细胞数量满意率最高;石蜡包埋组织切片法荧光信号满意率最高.结论:在检测hTERC基因的宫颈癌筛查中,TCT制片法明显优于其他方法,而在指导宫颈病变及宫颈癌的治疗中,石蜡包埋组织切片法的染色体破坏最小,实际意义更大.     

An assay method for the prediction of tumor promoting potential of chemicals by the use of Bhas 42 cells

It has become an important task to develop a simple in vitro method for the detection of non-genotoxic carcinogens, among which tumor promoters are included. Bhas 42 cells are v-Ha-ras-transfected BALB/c 3T3 cells and are regarded as initiated cells in the 2-stage transformation paradigm. We designed a method for detecting tumor promoters by the use of Bhas 42 cells at advanced passage generation. In this method, the cells are cultured in six-well plates for 17 days during which test chemicals are added in the medium for 11 days from days 3 to 14. The end-point of the assay is the induction of transformed foci. When the tumor promoter TPA was used, a significant number of transformed foci were induced concentration-dependently, whereas only a few foci were observed in control cultures. When various chemicals were examined by the method, a reasonable correlation was observed with the reported tumor-promoting ability in animal experiments. We propose that the Bhas 42 cell transformation method is practical and useful for the detection of tumor promoters.     

Use of the micronucleus test in the screening and monitoring of mutagens

Data from literature on the use of micronuclear test to determine mutagenicity in agents of physical, chemical and biological nature are presented. The objects on which this method is used most frequently are enumerated. Great attention is paid to the analysis of micronuclei in blood erythrocytes and bone marrow of animals. It is shown that the animal sex, age and the way of mutagen injection are of great importance in micronuclear testing of mutagens. Methodical papers concerning the peculiarities of fixation colour, analysis and mathematical testing are given. Mutagen factors tested by the method of micronuclear analysis are enumerated. A high resolution and small labour input of the micronuclear test are shown.     

Evaluation of the time course of neurotransmitter release from the measured PSC and MPSC

A method for obtaining delay histograms for the time course of neurotransmitter release is presented. The delay histogram is derived from the measured psc (or the sum of several psc's) and the mpsc (obtained experimentally or otherwise) by means of a simple, quick, mathematical procedure. The procedure may be automated for the greater part. No approximation of the mpsc shape is performed, and the method is applicable to all quantal contents. For low and medium quantal contents, the delay histograms obtained by the method are compared to those obtained by direct analysis. A reasonable agreement is achieved. An experiment of high quantal content, for which direct analysis is impossible, is then analysed using the new method. Difficulties which may arise when applying the procedure and methods to overcome them are discussed at length. Other methods are set forth in the Discussion.     

A potentiometric rapid method of determining the level of phenylacetic acid during the production of beta-lactam antibiotics

A potentiometric rapid method for control of phenylacetic acid (PAA) concentration in production of ++beta-lactam antibiotics is described. The method is based on ion selective electrodes with a film membrane. The results of the theoretical and experimental studies on estimation of the electrode selectivity specific of PAA in the presence of various interfering ions are presented. It was shown possible to use the electrodes for PAA control in the media containing nitrates, bicarbonates and chlorides. Recommendations how to use the ion selective electrodes at various stages in production of ++beta-lactam antibiotics are given. Prospects for improving the method and designing an instrument for rapid assay of phenyl acetate ion activity are discussed.     

Unbiasedness of the Estimator of the Function of Expected Value in the Mixed Linear Model

The traditional method for estimating the linear function of fixed parameters in mixed linear model is a two-stage procedure. In the first stage of this procedure the variance components estimators are calculated and next in the second stage these estimators are taken as true values of variance components to estimating the linear function of fixed parameters according to generalized least squares method. In this paper the general mixed linear model is considered in which a matrix related to fixed parameters and or/a dispersion matrix of observation vector may be deficient in rank. It is shown that the estimators of a set of functions of fixed parameters obtained in second stage are unbiased if only the observation vector is symmetrically distributed about its expected value and the estimators of variance components from first stage are translation-invariant and are even functions of the observation vector.     

An Examination of the Refractometric Method for Determining the Water Potential of Plant Tissues

Some sources of error in refractometric determinations of waterpotential are examined and methods of correcting for them oravoiding them are discussed, as well as their relevance to Shardakov’s(Schlieren) method. The sources of the exudation from cut tissues,which causes a rise in the refractive index of water and affectsthat of solutions, are investigated. The exudation consistsmainly of sap released from cut and damaged cells. The amountof sap exuded is independent of the concentration of the externalsolution. A method of estimating the extent of the error thusincurred in water potential determinations is described. Errorarising also from the admixture of cell-wall water to the referencesolutions, lowering their effective concentration, and othersources of error are briefly described. A method of eliminating the curvature in graphs of change ofrefractive index plotted against molarity is suggested. Themethod permits the data from all concentrations to be used indetermining the null point for water exchange, instead of thosenear to the null point only.     

Methods for the estimation of the number and quality of animal cells immobilized in carbohydrate gels.

Rapid and reliable methods for the determination of survival, proliferation, and metabolic activity of immobilized cells in gels are described. The first method is based on an MTT assay that measures qualitatively and quantitatively the metabolic activity of the cells. The second method determines cell number by measuring the amount of DNA available for Feulgen staining. In the third method, two fluorescent dyes are used to differentially stain viable and dead cells. The fourth method involves the use of glutaraldehyde to protect the cells when melting the gel to facilitate hemocytometric count. The presented techniques should help to test the efficiency of the immobilization procedures and to monitor the growth and survival of immobilized cells.     

Tracking the gaze of birds

Accurate measurements of what birds are looking at are valuable to most studies of vision and visually guided behaviour in avian species. Compared to human visual research, studies of gaze behaviour in birds are limited. A new laser-based method that can be used to quantify several aspects of a given sequence of gaze shifts and fixations is presented. Using near infrared light to estimate gaze direction is a relatively simple and cheap method to study visually guided behaviour. It has the potential to contribute significantly to the ornithological research by allowing the quantification of several behavioural traits of birds. Other methods are discussed and compared to the use of infrared light, and possible fields of application are suggested.     

Influence of the position on the bicycle on the frontal area in road cyclists

The aims of the present study were to determine whether the estimations of the frontal area of the combined cyclist-bicycle (APCB) obtained with the Heil's non-logarithmic prediction equations (NPE) in the stem position (SP), brake hoods position (BHP) and drops position (DP) are comparable to the measured APCB with the computerized planimetry (CP) method, and to analyse with the CP method and the NPE the influence of the body position on the APCB. Nineteen participants competing in the Spanish Road Cycling First division took part in the study. The NPE overestimated the APCB in the BHP and in the DP compared with the measured APCB with the CP method (6.9% and 5.1%, respectively; p<0.05). Significant differences among the three positions were obtained with the CP method. The overestimation of the APCB with the NPE in the BHP and in the DP and the less sensitivity of the NPE to show significant differences between the SP and DP suggest that the NPE are not appropriate to accurately predict the APCB.     

Preliminary Report on the Development of a Diffusion-in-Gel Method for the Diagnosis of Ram Epididymitis

A simple gel-diffusion technique is described for the diagnosis of ram epididymitis caused by Brucella ovis. The results are shown to be very similar to those obtained by the complement-fixation test, which is currently the standard method of diagnosis. The method is suitable for use in the field and is expected to facilitate the control of ram epididymitis in areas where laboratory facilities are not available.