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  • Articles  (154)
  • Electron microscopy  (115)
  • permeability  (39)
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  • Articles  (154)
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  • Wiley-Blackwell  (114)
  • Springer  (40)
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  • 1
    Electronic Resource
    Electronic Resource
    The effect of the illumination time when treating port-wine stains (1995)
    Springer
    Lasers in medical science 10 (1995), S. 93-104 
    Details
    ISSN: 1435-604X
    Keywords: Copper vapour laser ; Electron microscopy ; Illumination time ; Numerical modelling ; Optimal treatment ; Port-wine stain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract This paper reports the electron microscopy results obtained from two patients who were treated with 5 W of yellow (578 nm) light from a copper vapour laser with an illumination time of 3.6 ms and a 0.3 mm spot diameter. The endpoint of treatment was transient blanching. Following treatment, erythema was observed. There was minimal damage to the epidermis and non-vascular tissue such as the nerve fibres. There was severe damage to the endothelial cells of the ectatic vessels. Twenty-four hours after treatment, platelet activation and collagen were present, indicating that these vessels were no longer viable. Theoretical calculations are used to determine the flow of heat within and away from a 50μm diameter vessel. From this, heating of the entire vessel is shown to occur with illumination times of 4 ms, with minimal heating of the non-vascular tissue. Shorter illuminations do not heat the entire vessel, while the use of longer illumination times will cause excessive damage to the surrounding non-vascular tissue. Illumination times close to 4 ms must be regarded as optimal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02150846
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  • 2
    Electronic Resource
    Electronic Resource
    Histomorphological aspects of vascular anastomosis established by laser (1991)
    Springer
    Lasers in medical science 6 (1991), S. 363-366 
    Details
    ISSN: 1435-604X
    Keywords: Laser vascular welding ; Tissue fusion ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The central problem in microsurgery is the reconstruction of small vessels. The long operating time, foreign body granuloma formation around the suture material as well as aneurysmal alterations of the vessel wall after conventional suture technique make the search for alternatives indispensable. Some of these disadvantages can be avoided as demonstrated by our animal experiments and histological examinations in laser-assisted anastomosing. The aim of this study is to show these aspects in connection with laser application and compare them with conventional suture techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02030894
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  • 3
    Electronic Resource
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    A Simple Model for the Variation of Permeability due to Partial Saturation in Dual Scale Porous Media (1997)
    Springer
    Transport in porous media 27 (1997), S. 243-264 
    Details
    ISSN: 1573-1634
    Keywords: permeability ; Darcy's law ; unsaturated flow ; dual scale ; resin transfer molding ; liquid injection molding.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The main focus of this work is to model macroscopically the effects of partial saturation upon the permeability of dual scale fibrous media made of fiber bundles when a Newtonian viscous fluid impregnates it. A new phenomenological model is proposed to explain the discrepancies between experimental pressure results and analytical predictions based on Darcy's law. This model incorporates the essential features of relative permeability but without the necessity of measuring saturation of the liquid for its prediction. The model is very relevant for the small scale industrial systems where a liquid is forced to flow through a fibrous porous medium. It requires four parameters. Two of them are the two permeability values based on the two length scales. One length scale is of the order of magnitude of the individual fiber radius and corresponds to the permeability of the completely staurated medium, the other is of the order of magnitude of the distance between the fiber bundles and corresponds to the permeability of the partially saturated medium. The other two parameters are the lengths of the two partially saturated regions of the flow domain. The two lengths of the partially saturated region and the permeability of the fully saturated flow domain can be directly measured from the experiments. The excellent agreement between the model and the experimental results of inlet pressure profile with respect to time suggests that this model may be used to describe the variation of the permeability behind a moving front in such porous media for correct pressure prediction. It may also be used to characterize the fibrous medium by determining the two different permeabilities and the relative importance of the unsaturated portion of the flow domain for a given architecture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006544107324
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  • 4
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    The thermogravitational effect in porous media: A modelling approach (1992)
    Springer
    Transport in porous media 9 (1992), S. 223-240 
    Details
    ISSN: 1573-1634
    Keywords: Thermodiffusion ; Soret effect ; thermogravitational effect ; irreversible thermodynamics ; porous medium ; permeability ; transport model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The thermogravitational effect may induce large concentration contrasts, particularly in porous media. This phenomenon arises from a coupling of the Soret effect and convection currents in a temperature field. The present study of this phenomenon is motivated by the safety assessment of nuclear waste repositories, which are sources of thermal energy. Here, we present a modelling approach of laboratory experiments carried out at the University of Toulouse. The results of this model, though more adequate than the analytical solution to account for the influence of permeability, remain far from the experimental ones. In conclusion, it appears that the research must now focus on both a comprehensive phenomenology of the transport processes and experiments with new dimensional constraints.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00611968
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  • 5
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    Mean field calculation of effective permeability based on fractal pore space (1992)
    Springer
    Transport in porous media 8 (1992), S. 93-97 
    Details
    ISSN: 1573-1634
    Keywords: Porous rock ; permeability ; porosity ; fractal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Effective permeability for porous rocks is calculated using mean field theory. We make two simplifying assumptions about the internal conductances in a network representation of the porous rock: (i) Pore space is characterized by a uniform fractal scaling; (ii) the internal conductances depend only on the characteristic pore sizes. Within these approximations, it is possible to derive a simple probability density for the internal conductances which is used for calculating effective permeability. Good agreement between calculations and experimental data of permeability vs. porosity is achieved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616894
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  • 6
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    Implication of fractal geometry for fluid flow properties of sedimentary rocks (1992)
    Springer
    Transport in porous media 8 (1992), S. 133-147 
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    ISSN: 1573-1634
    Keywords: Fractal ; multifractal ; sedimentary rocks ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract It is demonstrated that a certain amount of order can be extracted from an apparently random distribution of pores in sedimentary rocks by exploiting the scaling characteristics of the geometry of the porespace with the help of fractal statistics. A simple fractal model of a sedimentary rock is built, and is tested against both the Archie law for conductivity and the Carman-Kozeny equation for permeability. We demonstrate how multifractal scaling of pore-volume can be used as a tool for rock characterization by computing its experimentalf(α) spectrum, which can be modelled by a simple two-scale Cantor set.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617114
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  • 7
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    Biocompatibility of MPC: in vivo evaluation for clinical application (2000)
    Springer
    Journal of artificial organs 3 (2000), S. 39-46 
    Details
    ISSN: 1619-0904
    Keywords: Poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate) (MPC) ; In vivo biocompatibility ; Artificial endocrine pancreas ; Electron microscopy ; Glucose sensor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Biocompatibility is important to assure a mild body reaction to an implanted device and its long-term stability and functionality. In diabetes research, subcutaneously implanted glucose monitoring systems need biocompatible surfaces for long-term application. The biocompatibility of poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate) (MPC), a material similar to the phospholipid layer of a cell membrane, was compared in vivo with the biocompatibility of polyurethane (PU), polyvinyl alcohol (PVA), and cuprophane (CUP). Needle-type glucose sensors and hollow-fiber probes used for microdialysis were coated with these four different biomaterials and implanted subcutaneously in 18 rats and 7 healthy volunteers. At set intervals, the implants and, in the case of the rats, also the surrounding tissue were removed and characterized by light and electron microscopy. MPC-coated sensors and hollow-fiber probes showed smooth and thin deposits in flat layers, whereas the surface deposits on PU- and PVA-coated sensors and those on CUP hollow-fiber probes appeared as rough, irregular, and dense attachments of aggregated cells and protein. This study confirmed results from earlier in vitro tests by showing the biocompatibility and reliability of MPC. Even though the amount of protein and cells attached to the MPC surface was not as low as expected from in vitro experiments, the biocompatibility and long-term stability of the implanted devices were superior to those of PU, PVA, and CUP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02479925
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  • 8
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    Effective-medium treatment of flow through anisotropic fracture system — Improved permeability estimates using a new lattice mapping (1992)
    Springer
    Transport in porous media 9 (1992), S. 287-295 
    Details
    ISSN: 1573-1634
    Keywords: Anisotropic fracture system ; effective medium theory ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The permeability tensor of a fractured reservoir, which will typically be anisotropic because of the presence of stress, is an important parameter to be taken into account when formulating a production strategy for the reservoir. Extensive computational effort is involved in calculating the permeabilities of model fracture systems by solving the fluid flow equations through finite realisations of the systems, and this renders a search for alternative techniques worthwhile. An attractive approach is to perform a rough mapping of the fracture system onto a lattice so that effective medium theory can be applied. For isotropic systems that are well-connected, this technique works well, but it gives increasingly poor results as the degree of anisotropy increases. In this contribution, a refinement of the lattice mapping is presented that incorporates an important aspect of the randomness present in the original system. This greatly increases the applicability of the technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00611972
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  • 9
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    Wavelet upscaling based on piecewise bilinear approximation of the permeability field (1996)
    Springer
    Transport in porous media 23 (1996), S. 125-134 
    Details
    ISSN: 1573-1634
    Keywords: permeability ; upscaling ; flow prediction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A method for upscaling of permeability in heterogeneous porous media is presented. The upscaled field takes the form K = e Y , where Y, in two dimensions, is a piecewise bilinear function. The method is tested on a number of random permeability fields, with different integral scale/correlation length and variance. The numerical results show that this method conserves much more of the heterogeneous fingering than classical block-based upscaling methods, e.g., geometric mean.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00178122
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  • 10
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    Permeability evolution induced by the precipitation of an advected solute: Effect of the microscopic and the macroscopic scales competition on the clogging mechanism (1996)
    Springer
    Transport in porous media 24 (1996), S. 341-375 
    Details
    ISSN: 1573-1634
    Keywords: precipitation ; porous medium ; clogging ; feedback mechanism ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A model is proposed for coupling the one-dimensional transport of solute with surface precipitation kinetics which induces the clogging of an initially homogeneous porous medium. The aim is to focus the non-linear feedback effect between the transport and the chemical reaction through the permeability of the medium. A Lagrangian formulation, used to solve the coupled differential equations, gives semi-analytical expressions of the hydrodynamic quantities. A detailed analysis reveals that the competition between the microscopic and macroscopic scales controls the clogging mechanism, which differs depends on whether short or long times are considered. In order to illustrate this analysis, more quantitative results were obtained in the case of a second and zeroth order kinetic. It was necessary to circumvent the semi-analytic character of the solutions problem by successive approximation. A comparison with results obtained by simulations displays a good agreement during the most part of the clogging time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00154097
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  • 11
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    Two-phase flow in heterogeneous porous media: The method of large-scale averaging (1988)
    Springer
    Transport in porous media 3 (1988), S. 357-413 
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    ISSN: 1573-1634
    Keywords: Two-phase flow ; heterogeneous porous media ; large-scale averaging ; permeability ; capillary pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The analysis of two-phase flow in porous media begins with the Stokes equations and an appropriate set of boundary conditions. Local volume averaging can then be used to produce the well known extension of Darcy's law for two-phase flow. In addition, a method of closure exists that can be used to predict the individual permeability tensors for each phase. For a heterogeneous porous medium, the local volume average closure problem becomes exceedingly complex and an alternate theoretical resolution of the problem is necessary. This is provided by the method of large-scale averaging which is used to average the Darcy-scale equations over a region that is large compared to the length scale of the heterogeneities. In this paper we present the derivation of the large-scale averaged continuity and momentum equations, and we develop a method of closure that can be used to predict the large-scale permeability tensors and the large-scale capillary pressure. The closure problem is limited by the principle of local mechanical equilibrium. This means that the local fluid distribution is determined by capillary pressure-saturation relations and is not constrained by the solution of an evolutionary transport equation. Special attention is given to the fact that both fluids can be trapped in regions where the saturation is equal to the irreducible saturation, in addition to being trapped in regions where the saturation is greater than the irreducible saturation. Theoretical results are given for stratified porous media and a two-dimensional model for a heterogeneous porous medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233177
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  • 12
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    Effects of NAPL Contaminants on the Permeability of a Soil‐Bentonite Slurry Wall Material (2000)
    Springer
    Transport in porous media 38 (2000), S. 43-56 
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    ISSN: 1573-1634
    Keywords: NAPL ; hydraulic conductivity ; permeability ; slurry walls ; soil ; bentonite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Soil‐bentonite slurry walls are designed to inhibit the subsurface movement of contaminants from hazardous waste sites. Although it is generally accepted that high concentrations of organic compounds will adversely affect soil‐bentonite slurry walls and clay liners, previous research investigating the effects of NAPLs on the conductivity of clay wall materials has been inconclusive. In this study the effects of various organics (benzene, aniline, trichloroethylene, ethylene dichloride, methylene chloride) on the effective conductivity of a typical soil‐bentonite slurry wall material were studied under two effective stress conditions, 200 and 52 kPa. The hydraulic conductivity for the soil‐bentonite material permeated with water averaged 1.52×10-8 cm s-1. Compared to water, there was little change in conductivity when the sample was permeated with a solution containing a NAPL compound at its solubility limit, except for aniline. However, there was a one to two order of magnitude decrease in conductivity when the sample was permeated with a pure NAPL for all NAPLs tested. When the soil‐bentonite material was permeated with a water/NAPL/water/NAPL sequence, the conductivity decreased one to two orders of magnitude when a NAPL was introduced following water; however, when water was reintroduced after the NAPL, the conductivity increased to the initial hydraulic conductivity. The conductivity again decreased one to two orders of magnitude when the NAPL was reintroduced. This trend occurred for all NAPLs tested, and the fluid properties of the NAPL compounds alone did not account for the decrease in conductivity compared to water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006655015509
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  • 13
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    Data interpretation problems to be expected in the study of coupled fluid flow in porous media (1989)
    Springer
    Transport in porous media 4 (1989), S. 185-198 
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    ISSN: 1573-1634
    Keywords: Transport coefficients ; coupling ; fluid flow ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract On the basis of recent work, it would appear that the transport coefficients descriptive of certain idealized cases of coupled flow of immiscible fluids in porous media, can be determined in principle by calculations employing well-defined experimental data. Other considerations show, however, that even small errors inherent in laboratory observations sometimes will have an enormously large effect on the accuracy of the calculated values. On the other hand, it often will be the case that values for the transport coefficients are not needed individually, as long as those particular functions which appear lumped together in the equations of motion, can be calculated from the same data but with less error. In any case, it will be clear that error problems will be, to some extent, mitigated when very accurate instrumentation is available to control and measure the fluxes and driving forces that give rise to the transport processes under study. Thus, the aim of this paper is to present an error analysis that will facilitate laboratory design in preparation for experimental work, and will also facilitate the interpretation of the data that eventually are to be obtained. Another aim is to underscore the risks taken by those who fail to take coupling effects into account just because the potential importance of them is not appreciated or not clearly revealed by existing data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00134996
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  • 14
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    The effect of anisotropic permeability on free convective boundary layer flow in porous media (1995)
    Springer
    Transport in porous media 19 (1995), S. 79-92 
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    ISSN: 1573-1634
    Keywords: Porous medium ; convection ; boundary layer ; anisotropy ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The effect of an anisotropic permeability on thermal boundary layer flow in porous media is studied. The convective flow is induced by a vertical, uniformly heated surface embedded in a fluid-saturated medium. A leading-order boundary layer theory is presented. It is shown that the thickness of the resulting boundary layer flow is different from that obtained in an isotropic porous medium. In general, an anisotropic permeability induces a fluid drift in the spanwise direction, the strength of which depends on the precise nature of the anisotropy. Conditions are found which determine whether or not the boundary layer flow is three-dimensional.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00716050
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  • 15
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    Permeability of a random array of fractures of widely varying apertures (1987)
    Springer
    Transport in porous media 2 (1987), S. 31-43 
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    ISSN: 1573-1634
    Keywords: Homogenization ; permeability ; percolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract We modelize a fractured rock by a random array of plane cracks of finite extent having a very broad distribution of apertures (or of hydraulic conductances). If the rock is permeable, the flow will essentially take place along a ‘subnetwork’ made of the less resistant cracks. Using an analogy with the treatment of variable range transport in semiconductors, we evaluate the homogenization length and the permeability of this disordered network. This evaluation makes use of the notion of the critical bonds which are the weakest cracks among the good ones necessary for percolation; the remaining weaker bonds make a negligible contribution to the permeability. The method is applicable to other examples of transport in very heterogeneous macroscopic random materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208535
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  • 16
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    Factorization of Transport Coefficients in Macroporous Media (2000)
    Springer
    Transport in porous media 41 (2000), S. 305-323 
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    ISSN: 1573-1634
    Keywords: irreversible thermodynamics ; permeability ; transport coefficients ; linearization ; averaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract We prove the fundamental theorem about factorization of the phenomenological coefficients for transport in macroporous media. By factorization we mean the representation of the transport coefficients as products of geometric parameters of the porous medium and the parameters characteristic of the multicomponent fluid saturating the porous space. The two permeabilities of the porous medium, the convective and the diffusional ones, are separated. A similarity between the diffusional permeability and the porosity–tortuosity factor of the Kozeny–Carman theory is demonstrated. We do not make any specific assumption about stochastic or deterministic structure of the porous medium. The fluxes in fluid on the pore level are described by general relations of the non-equilibrium thermodynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006695206975
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  • 17
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    The Effect of Asphalt Precipitation on Flow Behavior and Production of a Fractured Carbonate Oil Reservoir During Gas Injection (2000)
    Springer
    Transport in porous media 41 (2000), S. 325-347 
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    ISSN: 1573-1634
    Keywords: fractured reservoir ; permeability ; injectivity index ; asphalt precipitation ; computer simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The first field data, collected over an 11 year period, are presented which indicate the possible effect of asphalt precipitation on the permeability and injectivity index of a fractured carbonate oil reservoir. The asphalt aggregates were formed during enhanced oil recovery by injection of a rich gas into the reservoir. The data indicate that, while at the initial stages of the operations the permeability and injectivity index decrease, at later times they appear to oscillate with the process time, with apparent oscillations' periods that depend on the heterogeneity of the reservoir. Two classes of plausible mechanisms that give rise to such oscillatory behavior are discussed. One relies on the changes in the structure of the reservoir's fractures, while the other one is based on asphalt precipitation in the reservoir. Computer simulations of flow and precipitation of asphalt aggregates in a pore network model of the reservoir are carried out. The results appear to support our proposition that asphalt formation and precipitation in the reservoir are the main mechanism for the observed behavior of the injectivity index. We also develop a stochastic continuum model that accurately predicts the time-dependence of the reservoir's permeability and injectivity index during the gas injection process.
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    URL: http://dx.doi.org/10.1023/A:1006759524127
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  • 18
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    Effective properties for flow calculations (1995)
    Springer
    Transport in porous media 20 (1995), S. 169-196 
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    ISSN: 1573-1634
    Keywords: effective flow properties ; reservoir geology ; permeability ; transmissibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract In this paper we discuss the background to the problems of finding effective flow properties when moving from a detailed representation of reservoir geology to a coarse gridded model required for reservoir performance simulation. In so doing we synthesize the pictures of permeability and transmissibility and show how they may be used to capture the effects of the boundary conditions on the upscaling. These same concepts are applied to the renormalization method of calculating permeability, to show its promise as an accurate, yet fast method.
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    URL: http://dx.doi.org/10.1007/BF00616929
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  • 19
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    Numerical and analytical study to estimate the effect of two length scales upon the permeability of a fibrous porous medium (1995)
    Springer
    Transport in porous media 21 (1995), S. 1-17 
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    ISSN: 1573-1634
    Keywords: Resin transfer molding ; permeability ; fibrous porous medium ; porous cylinders ; creeping flow ; length scales
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A fibrous porous medium with two length scales is modeled as a bed of porous cylinders aligned perpendicular to the flow of viscous fluid. The flow behavior is described using Stokes and Darcy flow equations in the regions around (higher length scale) and within the cylinders (lower length scale) respectively. The typical ratio of higher and lower length-scale regions enable us to invoke lubrication approximation and simplify the equations to develop a closed form solution for the overall permeability of this dual-scale porous medium. A parametric analysis is performed to explore the dependence of permeability on factors such as the volumetric ratio of higher and lower length-scale regions, permeability and size of inclusions in the smaller length-scale region. The analytical model is compared with the numerical results and the trend is compared with the experiments.
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    URL: http://dx.doi.org/10.1007/BF00615332
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  • 20
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    A stochastic model for the permeability characteristics of saturated cemented porous media undergoing freezing (1996)
    Springer
    Transport in porous media 22 (1996), S. 345-357 
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    ISSN: 1573-1634
    Keywords: permeability ; stochastic model ; freezing ; porous cemented materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract As the temperature of a saturated porous medium drops, the water in the pores starts to freeze. Since the temperature at which the phase change takes place is dependent on the pore size, the permeability of the medium changes continuously. Simultaneously, due to the expansion of water on freezing, it is forced to migrate through the pore body thus inducing stresses in material matrix. The stresses developed and the consequent frost damage are therefore dependent on the change in the permeability characteristics of the medium on freezing. This paper deals with the numerical prediction of permeability characteristics of porous cemented media saturated with water undergoing progressive freezing. A bond percolation model is used to generate the pore structure according to an assumed poresize distribution. Permeability of the medium at various temperatures is computed by solving the network problem. The computed results are compared with other analytical and experimental results. The proposed model predicts a threshold temperature below which permeability drops to zero. This phenomenon is crucial in developing a deeper understanding of the mechanism of frost damage to cemented porous materials such as bricks, stone, concrete, etc.
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    URL: http://dx.doi.org/10.1007/BF00161631
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  • 21
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    A Simple Model of a Two-Layered High-Temperature Liquid-Dominated Geothermal Reservoir as a Part of a Large-Scale Hydrothermal Convection System (1998)
    Springer
    Transport in porous media 33 (1998), S. 3-27 
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    ISSN: 1573-1634
    Keywords: geothermal reservoir ; high temperature ; Kakkonda ; natural convection ; numerical modeling ; permeability ; super-critical fluid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The Kakkonda geothermal reservoir, Japan, is a typical high-temperature liquid-dominated geothermal reservoir, except for its distinctive two-layered temperature structure. It has a shallow permeable reservoir of 230–260°, and a deep less permeable reservoir of 350–360°. Geology and hydrology indicate that the shallow reservoir is one to two orders of magnitude more permeable than the deep reservoir, but that the two reservoirs communicate. It has been widely assumed in engineering and scientific circles that the connection between the two reservoirs is a zero or low permeability barrier to fluid flow. We show that this hypothesis is untenable, based on both physical evidence and numerical simulation. We numerically model the evolution of the geothermal system as it heats after emplacement of an intrusion. The two-layered temperature structure is found to be a consequence of the permeability difference, i.e. the two-layered permeability structure.
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    URL: http://dx.doi.org/10.1023/A:1006533307354
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  • 22
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    Macroscale Properties of Porous Media from a Network Model of Biofilm Processes (1998)
    Springer
    Transport in porous media 31 (1998), S. 39-66 
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    ISSN: 1573-1634
    Keywords: network model ; biofilm ; biobarrier ; permeability ; Monod kinetics ; adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract We demonstrate how a network model can predict porosity and permeability changes in a porous medium as a result of biofilm buildup in the pore spaces. A biofilm consists of bacteria and extracellular polymeric substances (EPS) bonded together and attached to a surface. In this case, the surface consists of the walls of the porous medium, which we model as a random network of pipes. Our model contains five species. Four of these are bacteria and EPS in both fluid and adsorbed phases. The fifth species is nutrient, which we assume to reside in the fluid phase only. Bacteria and EPS transfer between the adsorbed and fluid phases through adsorption and erosion or sloughing. The adsorbed species influence the effective radii of the pipes in the network, which affect the porosity and permeability. We develop a technique for integrating the coupled system of ordinary and partial differential equations that govern transport of these species in the network. We examine ensemble averages of simulations using different arrays of pipe radii having identical statistics. These averages show how different rate parameters in the biofilm transport processes affect the concentration and permeability profiles.
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    URL: http://dx.doi.org/10.1023/A:1006506104835
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    Fractal porous media I: Longitudinal stokes flow in random carpets (1987)
    Springer
    Transport in porous media 2 (1987), S. 553-569 
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    ISSN: 1573-1634
    Keywords: Porous media ; permeability ; random ; fractal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Two-dimensional porous media whose random cross-sections are derived from site percolation are constructed. The longitudinal flow of a Newtonian fluid in the Stokes approximation is then computed and the longitudinal permeability is obtained. Two methods are used and yield the same result when porosity is low. The Carman equation is shown to apply within ±7% when porosity is within the range from 0 to 0.75. Finally, random structures derived from stick percolation are investigated; results are qualitatively the same, but the Carman equation yields a poorer approximation.
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    URL: http://dx.doi.org/10.1007/BF00192155
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    Fractal porous media II: Geometry of porous geological structures (1987)
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    Transport in porous media 2 (1987), S. 571-596 
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    ISSN: 1573-1634
    Keywords: Porous media ; fractal ; permeability ; transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Some geological structures are analysed and found to be fractal. An interesting feature is the very large range of scales involved; the spreading dimension is also measured for some of them. The consequences of these measurements on the analysis of transport processes in porous media are presented - the existence of fractal structures multiplies the variety of actual porous media.
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    Numerical solution and sensitivity analysis of filter cake permeability and resistance to model parameters (1993)
    Springer
    Transport in porous media 10 (1993), S. 235-255 
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    ISSN: 1573-1634
    Keywords: Filter cakes ; permeability ; matrix compressibility modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The migration and capture of solid particles in porous media occur in fields as diverse as water and wastewater treatment, well drilling, and in various liquid-solid separation processes. Filter cakes are formed when a liquid containing solid particles is forced through a pervious surface which allows the liquid transport while retaining solid particles. Following a literature survey, a governing equation for the cake thickness is obtained by considering the instantaneous mass balance. Later, numerical solutions for the cake thickness, cake permeability, cake resistance, solid particle velocity (cake compression rate) and concentration of suspended particles are obtained and a sensitivity analysis is conducted. The sensitivity analysis shows that the cake permeability and cake resistance are more sensitive to the rate constant of cake erosion than they are to the rate constant of particle capture. However, the concentration of suspended solid particles, and the solid velocity are mostly sensitive to the slurry parameter and the rate constant of particle trapping. Moreover, cake permeability, compressibility, concentration of suspended particles, and the solid velocity are very sensitive to the concentration at the filter septum. Finally, as expected, with a thicker slurry, more particles are captured inside the cake, thus forming a thicker and more resistant cake. Also, as more particles are being filtered at the filter septum, a thinner cake is formed and a smaller effluent concentration is achieved.
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    URL: http://dx.doi.org/10.1007/BF00616811
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    Fractal porous media IV: Three-dimensional stokes flow through random media and regular fractals (1990)
    Springer
    Transport in porous media 5 (1990), S. 325-340 
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    ISSN: 1573-1634
    Keywords: Porous media ; three-dimensional ; permeability ; random ; fractal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The three-dimensional Stokes flow of a Newtonian fluid through random and/or fractal media is numerically determined. The permeability of these media is derived. Results relative to these structures are presented and discussed. The validity of the Carman equation and of a simple scaling argument is questioned.
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    URL: http://dx.doi.org/10.1007/BF01141990
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    Hydraulic radius and transport in reconstructed model three-dimensional porous media (1994)
    Springer
    Transport in porous media 17 (1994), S. 221-238 
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    ISSN: 1573-1634
    Keywords: building technology ; conductivity ; critical diameter ; hydraulic radius ; permeability ; porous media ; reconstruction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Methods for reconstructing three-dimensional porous media from two-dimensional cross sections are evaluated in terms of the transport properties of the reconstructed systems. Two-dimensional slices are selected at random from model three-dimensional microstructures, based on penetrable spheres, and processed to create a reconstructed representation of the original system. Permeability, conductivity, and a critial pore diameter are computed for the original and reconstructed microstructures to assess the validity of the reconstruction technique. A surface curvature algorithm is utilized to further modify the reconstructed systems by matching the hydraulic radius of the reconstructed three-dimensional system to that of the two-dimensional slice. While having only minor effects on conductivity, this modification significantly improves the agreement between permeabilities and critical diameters of the original and reconstructed systems for porosities in the range of 25–40%. For lower porosities, critical pore diameter is unaffected by the curvature modification so that little improvement between original and reconstructed permeabilities is obtained by matching hydraulic radii.
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    An equation of motion for an incompressible Newtonian fluid in a packed bed (1995)
    Springer
    Transport in porous media 18 (1995), S. 185-198 
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    ISSN: 1573-1634
    Keywords: Finite element ; permeability ; Navier-Stokes ; packed bed ; spherical particles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The application of a volume average Navier-Stokes equation for the prediction of pressure drop in packed beds consisting of uniform spherical particles is presented. The development of the bed permeability from an assumed porous microstructure model is given. The final model is quasi-empirical in nature, and is able to correlate a wide variety of literature data over a large Reynolds number range. In beds with wall effects present the model correlates experimental data with an error of less than 10%. Numerical solutions of the volume averaged equation are obtained using a penalty finite element method.
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    URL: http://dx.doi.org/10.1007/BF01064677
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    Network model evaluation of permeability and spatial correlation in a real random sphere packing (1993)
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    Transport in porous media 11 (1993), S. 53-70 
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    ISSN: 1573-1634
    Keywords: Correlation ; permeability ; network model ; sphere pack ; percolation ; tessellation
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract In principle, network models can replicate exactly the microstructure of porous media. In practice, however, network models have been constructed using various assumptions concerning pore structure. This paper presents a network model of a real, disordered porous medium that invokes no assumptions regarding pore structure. The calculated permeability of the model agrees well with measured permeabilities, providing a new and more rigorous confirmation of the validity of the network approach. Several assumptions commonly used in constructing network models are found to be invalid for a random packing of equal spheres. In addition, the model permits quantification of the effect of pore-scale correlation (departure from randomness) upon permeability. The effect is comparable to reported discrepancies between measured permeabilities and predictions of other network models. The implications of this finding are twofold. First, a key assumption of several theories of transport in porous media, namely that pore dimensions are randomly distributed upon a network, may be invalid for real porous systems. Second, efforts both to model and to measure pore-scale correlations could yield more accurate predictions of permeability.
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    Nuclear magnetic resonance imaging of miscible fingering in porous media (1993)
    Springer
    Transport in porous media 12 (1993), S. 107-123 
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    ISSN: 1573-1634
    Keywords: Nuclear magnetic resonance imaging (MRI) ; miscible displacement ; buoyancy ; three-dimensional ; diffusion ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Nuclear Magnetic Resonance Imaging (MRI) can noninvasively map the spatial distribution of Nuclear Magnetic Resonance (NMR)-sensitive nuclei. This can be utilized to investigate the transport of fluids (and solute molecules) in three-dimensional model systems. In this study, MRI was applied to the buoyancy-driven transport of aqueous solutions, across an unstable interface in a three-dimensional box model in the limit of a small Péclet number (Pe〈0.4). It is demonstrated that MRI is capable of distinguishing between convective transport (‘fingering’) and molecular diffusion and is able to quantify these processes. The results indicate that for homogeneous porous media, the total fluid volume displaced through the interface and the amplitude of the fastest growing finger are linearly correlated with time. These linear relations yielded mean and maximal displacement velocities which are related by a constant dimensionless value (2.4±0.1). The mean displacement velocity (U) allows us to calculate the media permeability which was consistent between experiments (1.4±0.1×10−7cm2).U is linearly correlated with the initial density gradient, as predicted by theory. An extrapolation of the density gradient to zero velocity enables an approximate determination of the critical density gradient for the onset of instability in our system (0.9±0.3×10−3 g/cm3), a value consistent with the value predicted by a calculation based upon the modified Rayleigh number. These results suggest that MRI can be used to study complex fluid patterns in three-dimensional box models, offering a greater flexibility for the simulation of natural conditions than conventional experimental modelling methods.
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    Fractal porous media (1993)
    Springer
    Transport in porous media 13 (1993), S. 41-78 
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    ISSN: 1573-1634
    Keywords: Fractal ; permeability ; conductivity ; transports
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The transport properties of continuous deterministic fractals are reviewed. The method of construction, the fractal dimension, and the major features of transport are summarized. Then the major single-phase transports are addressed; attention is focused on the numerical results and on the analytical arguments which may be used to derive these results in a simple way, whenever it is possible.
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    An experimental investigation of dispersion in layered porous media (1994)
    Springer
    Transport in porous media 15 (1994), S. 15-30 
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    ISSN: 1573-1634
    Keywords: Experiment ; dispersion ; layered heterogeneity ; permeability ; averaging ; permutation
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Experiments were run in three linear, homogeneous, nonuniform porous media constructed in lucite columns using spherical glass beads. The columns were also joined end to end to create an in series layered heterogeneous porous media. Each column, all combinations of columns and several permutations were studied with a factorial experimental design to determine the effects of porosity, permeability, velocity, length, and column order upon dispersion. Attempts to predict the heterogeneous results from the homogeneous results were made, and a statistical regression based on the factorial design was calculated. Results showed that no simple averaging procedure accurately predicted the heterogeneous results. The statistical regression showed permeability, velocity, viscosity, length and column order to be significant.
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    Flow characteristics of anisotropic structures constructed with porous layers (1994)
    Springer
    Transport in porous media 15 (1994), S. 151-173 
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    ISSN: 1573-1634
    Keywords: Anisotropic ; porous media ; flow characteristic ; permeability ; Forchheimer extension ; regression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Artificial structures, serving as the solid matrix of anisotropic porous media and satisfying the requirement needed for flow visualization, were constructed with the perforated Polypropylene plates in order to improve the understanding of transport phenomena occurring in anisotropic porous media. This paper reports the regressed correlations of the experimental pressure gradient and filtration velocity data of three anisotropic and one isotropic porous media measured along two mutually orthogonal directions, which correspond to the principal axes of the permeability tensor, for the filtration velocities ranging from 0.2 to 12 mm/s with water as the fluid. To reflect the observed data, the regression equation with two types of deviations was formulated, in which the pressure gradient is represented by the sum of the linear and nonlinear terms of the filtration velocity. The physical model developed for the linear term assumes the solid matrix as repeated circular orifices when the filtration velocity approaches zero. The exponent of the filtration velocity in the nonlinear term was determined to be that of the Forchheimer extension. Also, four models for the coefficient of the nonlinear term were examined and the results were compared. The distribution of the residuals (the differences between the observed and the correlated values) validated the suggested regression procedure and the resulting correlations.
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    The relative importance of convective and conductive effects in two-phase geothermal fields (1994)
    Springer
    Transport in porous media 16 (1994), S. 289-298 
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    ISSN: 1573-1634
    Keywords: Two-phase ; conduction ; theory ; permeability ; effective conductivities ; geothermal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Conductive and convective transport are related in two phase porous media, provided capillary effects are negligible. This paper shows that the role of conduction will be unimportant, relative to convective effects, for sufficiently high temperatures and sufficiently high permeabilities. An approximately linear relationship holds between temperature and the logarithm of permeability, above which conduction is unimportant relative to convection.
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    Network Model of Flow, Transport and Biofilm Effects in Porous Media (1998)
    Springer
    Transport in porous media 30 (1998), S. 1-23 
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    ISSN: 1573-1634
    Keywords: biofilm ; network model ; permeability ; transport ; numerical diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract In this paper, we develop a network model to determine porosity and permeability changes in a porous medium as a result of changes in the amount of biomass. The biomass is in the form of biofilms. Biofilms form when certain types of bacteria reproduce, bond to surfaces, and produce extracellular polymer (EPS) filaments that link together the bacteria. The pore spaces are modeled as a system of interconnected pipes in two and three dimensions. The radii of the pipes are given by a lognormal probability distribution. Volumetric flow rates through each of the pipes, and through the medium, are determined by solving a linear system of equations, with a symmetric and positive definite matrix. Transport through the medium is modeled by upwind, explicit finite difference approximations in the individual pipes. Methods for handling the boundary conditions between pipes and for visualizing the results of numerical simulations are developed. Increases in biomass, as a result of transport and reaction, decrease the pipe radii, which decreases the permeability of the medium. Relationships between biomass accumulation and permeability and porosity reduction are presented.
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    Effects of serial and parallel pore nonuniformities: Results from two models of the porous structure (1996)
    Springer
    Transport in porous media 25 (1996), S. 335-350 
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    ISSN: 1573-1634
    Keywords: Cauchy-Schwarz-Bunjakovskij inequality ; computational fluid dynamics ; effective diffusivity ; permeability ; pore-size distribution ; specific surface area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The effects of parallel-type and serial-type pore nonuniformities on the effective diffusivity and the permeability of a porous material were evaluated, constant porosity and constant specific surface area being assumed. Two structural models were considered. In the first model, the porous structure was described as a bundle of cylindrical capillaries penetrating the whole thickness of the material and in the other it was described instead as a collection of randomly distributed obstacles hindering transport. Both models predicted that parallel-type pore nonuniformities produce an increase in permeability compared with uniform structures having the same porosity and specific surface area. Both models also predicted that the increase in permeability due to parallel-type pore nonuniformities would be larger than the increase in effective diffusivity. Regarding serial-type pore nonuniformities, both models predicted a decrease in permeability and that this decrease would be greater than the decrease in effective diffusivity. The predicted changes in effective diffusivity due to nonuniformities of the sample differed for the two structural models.
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    Preferential Flow-Paths Detection for Heterogeneous Reservoirs Using a New Renormalization Technique (1997)
    Springer
    Transport in porous media 26 (1997), S. 1-23 
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    ISSN: 1573-1634
    Keywords: upscaling ; renormalization ; permeability ; local flux ; heterogeneity.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract We have devised a renormalization scheme which allows very fast determination of preferential flow-paths and of up-scaled permeabilities of 2D heterogeneous porous media. In the case of 2D log-normal and isotropically distributed permeability-fields, the resulting equivalent permeabilities are very close to the geometric mean, which is in good agreement with a rigorous result of Matheron. It is also found to work well for geostatistically anisotropic media when comparing the resulting equivalent permeabilities with a direct solution of the finite-difference equations. The method works exactly as King's does, although the renormalization scheme was modified to obtain tensorial equivalent permeabilities using periodic boundary conditions for the pressure gradient. To obtain an estimation of the local fluxes, the basic idea is that if at each renormalization iteration all the intermediate renormalized permeabilities are stored in memory, we are able to compute -- ad reversum -- an approximation of the small-scale flux map under a given macroscopic pressure gradient. The method is very rapid as it involves a number of calculations that vary linearly with the number of elementary grid blocks. In this sense, the renormalization algorithm can be viewed as a rapid approximate pressure solver. The ‘exact’ reference flow-rate map (for the finite-difference algorithm) was computed using a classical linear system inversion. It can be shown that the preferential flow paths are well detected by the approximate method, although errors may occur in the local flow direction.
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    Fractal porous media III: Transversal Stokes flow through random and Sierpinski carpets (1988)
    Springer
    Transport in porous media 3 (1988), S. 185-198 
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    ISSN: 1573-1634
    Keywords: Porous media ; permeability ; random ; fractal
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The transversal Stokes flow of a Newtonian fluid through random and Sierpinski carpets is numerically calculated and the transversal permeability derived. In random carpets derived from site percolation, the average macroscopic permeability varies as (ε- ɛ c)3/2, close to the critical porosityɛ c. This exponent is found to be slightly different from the conductivity exponent. Results for Sierpinski carpets are presented up to the fourth generation. The Carman equation is not verified in these two model porous media.
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    Infiltration of Liquid Metals in Porous Compacts: Modeling of Permeabilities During Reactive Melt Infiltration (1999)
    Springer
    Transport in porous media 36 (1999), S. 43-68 
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    ISSN: 1573-1634
    Keywords: reactive melt infiltration ; ceramic ; composites ; porous compacts ; permeability ; modeling.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Reactive infiltration is a fast and cost-effective technique for manufacturing ceramic-matrix composites (CMCs). CMCs are used in elevated temperature applications like rocket engine casings, jet nozzles, gas turbine blades and nuclear cladding. There is an urgent need for minimizing experimental costs as well as optimizing process parameters during manufacture, so that we have minimized manufacturing costs and reduced infiltration times. Towards this end, the objective of this research was to develop an integrated micro-macro model of reactive flow of molten silicon in a porous preform consisting of carbon-coated silicon carbide fibers and then optimize process parameters computationally. The overall objective of the research was to arrive at a modified equation of Darcy's law for flow through a porous medium with the help of numerical/computational modeling. This paper deals with the flow of silicon through porous carbon at the macro level. The macro flow of silicon was integrated with an available micro model by determining the transient porosity from the micro model and using it in Darcy's law written for the macro flow of silicon. From the results of this study, we recommend suitable process parameters such as initial temperature of the solid reactant and the specific kind of reactants to be used for achieving complete infiltration. These conclusions are drawn after observation of the rate of decrease of permeability with more reaction.
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    Validation of the Slow Compressional Wave in Porous Media: Comparison of Experiments and Numerical Simulations (1999)
    Springer
    Transport in porous media 36 (1999), S. 149-160 
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    ISSN: 1573-1634
    Keywords: poroelasticity ; Biot's theory ; slow wave ; permeability ; acoustics.
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract We perform numerical simulation of ultrasonic experiments on poroelastic samples, in which Biot's slow compressional wave had been observed. The simulation is performed using OASES modeling code, which allows to compute elastic wave fields in layered poroelastic media. Modeled were the experiments of Plona (1980), Rasolofosaon (1988), and our own measurements. In all the three situations, a good agreement between experiment and simulations has been observed. This further confirms the fact that Biot's theory of poroelasticity, on which the simulations were based, adequately describes the behavior of the porous materials under investigations at ultrasonic frequencies.
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    A personal computer based implementation of the maximum-likelihood method of analysis of electron microscope autoradiographs (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 20 (1992), S. 73-86 
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    ISSN: 1059-910X
    Keywords: Electron microscopy ; Autoradiography ; Maximum-likelihood estimation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The maximum-likelihood (ML) method for the quantitative analysis of electron-microscopic autoradiographs has been shown to be substantially superior to the conventional crossfire (CF) method. It can generate reliable and accurate tracer concentration estimates with far fewer micrographs and produce valid estimates even at counts low enough to preclude the use of the crossfire method while eliminating the need for special ad hoc treatment of narrow membranous structures as well as the secondary verification of the tracer concentration estimates.Despite these significant advantages, the large computational requirements of the ML method has to date hampered its widespread use. In this paper, we present a new line-integration method that allows us to reduce the computational requirements of the ML method to a point where it becomes feasible to implement it on a small computer system of the type typically available to a laboratory user of EM autoradiography. We present the complete line-integration method for the particular case of EM autoradiography with tritium, and show how it can be adapted to other isotopes.We have constructed a software package that implements the complete maximum-likelihood method on the IBM PC class of machines using our line-integration method. Features of this software package which are of particular importance to the research community are device independence, which makes it usable with a large variety of currently available laboratory equipment, and easy portability of the software and data between different computer systems.
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    Preservation and visualization of molecular structure in detergent-extracted whole mounts of cultured cells (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 22 (1992), S. 130-150 
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    ISSN: 1059-910X
    Keywords: Electron microscopy ; Scanning electron microscopy ; High resolution ; Cytoskeleton ; Biological specimen preparation ; Cultured cells ; Electrophoresis ; Bifunctional crosslinking reagents ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Today's electron microscopes have a resolution sufficient to resolve supramolecular structures. However, the methods used to prepare biological samples for electron microscopy often limit our ability to achieve the resolution that is theoretically possible. We use whole mounts of detergent-extracted cells grown on Formvar-coated gold grids as a model system to evaluate various steps in the preparation of biological samples for high resolution scanning electron microscopy (SEM)Factors that are important in determining the structure and composition of detergent-extracted cells include the nature of the detergent and the composition of the extraction vehicle. Chelation of calcium is extremely important to stabilize and preserve the cytoskeletal filaments. We have also demonstrated both morphologically and by gel electrophoresis that treatment of cells with bifunctional protein crosslinkers before or during extraction with detergent can significantly enhance the preservation of both proteins and supramolecular structures.The methods used to dry samples are a major determinant of the quality of structural preservation. For cytoskeletons freeze-drying (FD) is superior to critical point-drying (CPD), one reason being that CPD samples have to be dehydrated, thereby causing more shrinkage as compared to FD samples. The high pressures to which samples are exposed during CPD may also cause increased shrinkage, and water contamination during CPD causes severe structural damage. We have obtained the best structural preservation of detergent-extracted and fixed cells by manually plunging them into liquid propane and drying over night in a freeze-drayer.The factor that most limits achievement of high resolution in SEM is the metal coat, which has to be very thin, uniform, and free of grain in order not to hide structures or to create artifactual ones. We have found that sputter-coating with 1-3 nm of tungsten (W) or niobium )Nb( gives extremely fine-grained films as well as satisfactory emission of secondary electrons. These samples can also be examined at high resolution by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The best preservation and visualization of supramolecular structures have been obtained using cryosputtering, in which the samples are freeze-dried and then sputter-coated within the freeze-dryer while still frozen. © 1992 Wiley-Liss, Inc.
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    Quantitative morphology for biologists and computer scientists: I. Computer-aided tutorial for biological stereology (version 1.0) (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 21 (1992), S. 338-346 
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    ISSN: 1059-910X
    Keywords: Tutorial ; Electron microscopy ; Light microscopy ; Software ; Quantitative morphology ; Stereology ; Morphometry ; Simulations ; Terminology ; Data types ; Sampling ; Hierarchies ; Interpretation of data ; Bio-Matrix Project ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: This paper describes a computer-aided tutorial for biological stereology. Stereology, a type of quantitative morphology, includes a collection of statistical methods that quantify the structural compartments that can be viewed in sections with light and electron microscopy. These methods provide volume, surface, length, shape, and number data, and help define the quantitative relationships among the structural compartments of biological hierarchies. Hierarchies, which connect structural data ranging in size from molecules to organs, serve as a central core to which the data of biological databases can be linked. The tutorial focuses on two objectives. It provides the user primarily interested in using quantitative morphology databases with background information, and offers a set of state-of-the-art tools to researchers wishing to use these methods in the laboratory. The main topics of the tutorial include: introduction to quantitative morphology, symbols/terms, data types, sampling, hierarchies, data interpretation, and utilities. The tutorial runs under the MS-DOS operating system and requires at least an IBM PC AT (or compatible), a color monitor (EGA, VGA), 540 KB of RAM, and 3 MB of hard disk space. © 1992 Wiley-Liss, Inc.
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    Computer assisted data collection for stereology: Rationale and description of point counting stereology (PCS) software (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 21 (1992), S. 347-354 
    Details
    ISSN: 1059-910X
    Keywords: Quantitative morphology ; Morphometry ; Light microscopy ; Electron microscopy ; PCS System III ; MS-DOS ; UNIX ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The paper describes microcomputer software for point counting stereology. Stereology includes a collection of statistical methods that quantify the images of light and transmission electron microscopy. The methods use test grids placed over images to collect raw data, which includes counts of points, intersections, transections, and profiles. In turn, the counts are included in stereological equations that give estimates of compartmental volumes, surfaces, lengths, or numbers. These parameters describe the composition of a structure in three-dimensional space. The PCS (point counting stereology) System Software III serves as a data collection, storage, and management tool. Users set up point counting protocols without programming, enter data by pressing predefined function (MS-DOS) or alphabetic keys (UNIX), store data in files, select files for analysis, and calculate results as stereological densities. The latest version of the PCS software includes a new user interface and is designed as a research “front end” that can feed data either into the calculation tools of a stereology tutorial (Bolender, 1992, this issue) or into the analysis routines of quantitative morphology databases (Bolender and Bluhm, 1992). © 1992 Wiley-Liss, Inc.
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    Ultrastructural evidence for the axonal localization of caudodorsal cell hormone mRNA in the central nervous system of the mollusc Lymnaea stagnalis (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 25 (1993), S. 12-18 
    Details
    ISSN: 1059-910X
    Keywords: In situ hybridization ; Digoxigenin ; Electron microscopy ; Cryosections ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The technique of in situ hybridization has been used to evaluate the expression of an ovulation hormone mRNA (caudodorsal cell hormone; CDCH) in the central nervous system (CNS) of the mollusc Lymnaea stagnalis. Hybridization with radioactive as well as with nonradioactive labeled oligonucleotide and plasmid probes revealed a specific labeling on cell bodies of caudodorsal cells (CDCs), which are known to produce CDCH, on the light microscopical level. In addition, specific labeling was observed outside the cell bodies, as far as the cerebral commissure, where CDCH is released in the haemolymph. To investigate whether these signals represent an axonal localization of the CDCH mRNA, we performed in situ hybridization at the electron microscopical (EM) level. The results showed an intraaxonal localization of CDCH mRNA with digoxigenin labeled oligonucleotide and plasmid probes. Gold labeling was observed in secretion granules, and double labeling experiments showed that these granules also contain CDCH. This specific intragranular localization suggest that CDCH mRNA is transported through the axon and released by exocytosis in the haemolymph. © 1993 Wiley-Liss, Inc.
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    Protocol of electron microscope in situ nucleic acid hybridization for the exclusive detection of double-stranded DNA sequences in cells containing large amounts of homologous single-stranded DNA and RNA sequences: Application to adenovirus type 5 infected Hela cells (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 25 (1993), S. 2-11 
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    ISSN: 1059-910X
    Keywords: Double-stranded viral DNA ; Electron microscopy ; HeLa cell ; In situ hybridization ; Lytic infection ; S1 nuclease ; Replication ; Viral Ad5 genomes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: In order to gain a further insight into the relationships of the complex process of replication of adenovirus genomes to the substructures which occur in the nuclei of adenovirus type 5 (Ad5) infected HeLa cells, we have visualized directly, at the electron microscopic level, viral double-stranded DNA (dsDNA) in late infected nuclei by the use of a post-embedding in situ hybridization technique with a biotinylated specific DNA probe. The procedure is based on the removal of single-stranded (ss) nucleic acids by S1 nuclease. The highest levels of signal density for viral dsDNA were detected over the fibrils of the large, centrally located viral genome storage site and over the viral nucleoids of both clustered and isolated viruses. Lower but significant signals were observed over the fibrillo-granular network of the peripheral replicative zones, where both transcription and replication of viral DNA occur. On the other hand, the labeling of the enclosed viral ssDNA accumulation sites, also involved in viral replication but not transcription, was negligible, which suggests that, in the latter, the newly synthesized viral dsDNA immediately extends into the adjacent peripheral replicative zone to be transcribed and/or replicated.
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    Quantitative aspects of synapses on Golgi-impregnated neurons (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 23 (1992), S. 334-352 
    Details
    ISSN: 1059-910X
    Keywords: Identified neurons ; Quantification ; Rotating/tilting ; Synaptic contacts ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: With the classical Golgi techniques, numerous types of neurons can be distinguished in the cerebral cortex, each with a specific dendritic geometry and pattern of axonal ramifications. In the present review we describe two techniques which allow quantification of synapses on identified neurons: (1) Golgi-rapid impregnation-gold toning-electron microscopy, and (2) Golgi-Kopsch impregnation-gold toning-electron microscopy in combination with staining of the tissue with ethanolic phosphotungstic acid (E-PTA). Both techniques were applied on neurons in the visual cortex of young and adult rabbits. By means of rotating and tilting specimens in the electron microscope, the nondistinctive ultrastructure of obliquely sectioned synapses can be circumvented, leading to precise estimates of asymmetrical vs. symmetrical synapses without complete reconstruction of the neuron. © 1992 Wiley-Liss, Inc.
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    Environmental scanning electron microscope (ESEM) evaluation of crystal and plaque formation associated with biocorrosion (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 25 (1993), S. 429-433 
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    ISSN: 1059-910X
    Keywords: Biocorrosion ; Sulfate-reducing bacteria ; Biofilm ; Desulfovibrio ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The biofilm attributed to Desulfovibrio vulgaris growing in the presence of ferrous metals was examined with an environmental scanning electron microscope. This novel microscope produced images of iron sulfide colloids and other iron containing structures that had not been reported previously. A plaque composed of iron sulfide enveloped the surface of the corroding metal while crystals containing magnesium, iron, sulfur, and phosphorus were present in the culture where corrosion was in progress. A structure resembling the tubercule found in aerobic corrosion was observed on stainless steel undergoing biocorrosion and the elements present in this structure included sulfur, iron, chloride, calcium, potassium, and chromium. © 1993 Wiley-Liss, Inc.
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    Rapid primary microwave-glutaraldehyde fixation preserves the plasma membrane and intracellular structures of the protozoan Tritrichomonas foetus (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 25 (1993), S. 286-290 
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    ISSN: 1059-910X
    Keywords: Microwave fixation ; Freeze-fracture ; Electron microscopy ; Protozoan ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Tritrichomonas foetus, a pathogenic protozoan, was used as a model to analyse microwave-stimulated fixation as a procedure of preparation of biological samples for electron microscopy of thin sections and freeze-fracture replicas. Good preservation of the protozoan structure was achieved by microwave-stimulated fixation and Epon polymerization. The membrane structure, as visualized in freeze-fracture replicas, was well preserved. © 1993 Wiley-Liss, Inc.
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    Peripheral sensilla of some lower invertebrates: The platyhelminthes and nematoda (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 22 (1992), S. 285-297 
    Details
    ISSN: 1059-910X
    Keywords: Electron microscopy ; Evolution ; Flatworms ; Nematodes ; Nervous system ; Review ; Sense organs ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The flatworms (Platyhelminthes) and the round worms (Nematoda) are phylexhibiting strikingly different levels of cellular organization. In both, sensilla are composed of the endings of sensory dendrites intercalated into their epidermis.In flatworms, sensilla that penetrate the syncytial epidermis bear sensory processes derived from cilia. In free-living species, the sensory processes more closely resemble motile cilia, while in parasites, greater deviations occur from the classical cilium pattern. Estimates of the function of the various sensilla have been largely arbitrary, and remain based on ultrastructural features.Sensilla in round worms lie below or within a heavy secreted cuticle. Two glia-like cell types occur. The socket cell mediates contact with cuticle and is responsible for cuticular modifications essential for operation of the sensillum. The sheath cell forms a receptor cavity around the sensory processes and regulates its environment. Sensory processes vary greatly from the classical cilium pattern. Absence of a basal body, but preservation of a ciliary necklace, suggests that the latter has a primary importance in sensory transduction. Estimates of function are based largely on ultrastructural features and analogies to arthropod sensilla. Genetic studies with the free-living nematode Caenorhabditis are beginning to demonstrate details of function and development.Speculations on the roles of basal bodies, rootlets, and vesicles and on the significance of recessed sensilla are given. © 1992 Wiley-Liss, Inc.
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    Phylogeny of the vomeronasal system and of receptor cell types in the olfactory and vomeronasal epithelia of vertebrates (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 23 (1992), S. 1-21 
    Details
    ISSN: 1059-910X
    Keywords: Cilia ; Microvilli ; Ultrastructure ; Electron microscopy ; Evolution ; Cladistics ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: In this paper, the evolutionary origin of the vomeronasal system as a discrete sensory system separate from olfaction is examined. The presence of a discrete vomeronasal system appears to be a derived character in tetrapods, and its presence in larval amphibians indicates that the system did not arise as a terrestrial adaptation. The vomeronasal system has been lost independently in several taxa, including crocodilians, some bats, cetaceans, and some primates. The presence of microvillar receptor cells in the vomeronasal epithelium appears to be the ancestral condition for tetrapods, and alternative hypotheses concerning the ancestral condition for receptor cell types in the vertebrate olfactory epithelium are discussed. Finally, the possibility that the vomeronasal system is present in some fishes in a form that has not been recognized is discussed in relation to the phylogenetic distribution of receptor cell types in vertebrates. © 1992 Wiley-Liss, Inc.
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    Fine structure of olfactory epithelia of gastropod molluscs (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 22 (1992), S. 307-324 
    Details
    ISSN: 1059-910X
    Keywords: Sensory ; Chemosensory ; Ultrastructure ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Among gastropod molluscs the chemical senses are most important for location of distant objects. They are used in food finding, locating mates, avoiding predators, trail following, and homing. Chemoreceptors are commonly associated with the oral area, the tentacles, and the osphradium, which lies in the mantle cavity.Most chemosensory neurons are primary sensory neurons, although secondary sensory cells have been reported in the osphradium of some prosobranch gastropods. Most chemosensory organs contain sensory cells with ciliated sensory endings that are in contact with the external environment. Some sensory endings have only microvilli or have no surface elaborations. Cilia on sensory endings are commonly of the conventional type, but some species have modified cilia; some lack rootlets, some have an abnormal microtubular content, and some have paddle-shaped endings. The perikarya of sensory neurons may be within the sensory epithelium, below it, or in ganglia near the sensory surface. In some groups of gastropods there are peripheral ganglia in the olfactory pathway; in others chemosensory axons appear to pass directly to the CNS.Olfactory epithelia of terrestrial pulmonates have modified brush borders with long branching plasmatic processes and a spongy layer of cytoplasmic tubules which extend from the epithelial cells. Sensory endings of the olfactory receptors are entirely within this spongy layer. Aquatic pulmonates may have a similar spongy layer in their olfactory epithelia, but the cilia of sensory endings, as well as motile cilia of epithelial cells, extend well beyond the spongy layer. © 1992 Wiley-Liss, Inc.
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    The aesthetasc concept: Structural variations of putative olfactory receptor cell complexes in crustacea (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 22 (1992), S. 325-335 
    Details
    ISSN: 1059-910X
    Keywords: Sensilla ; Electron microscopy ; Sexual dimorphism ; Homology ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The structure of the aesthetascs has been investigated in the prawn Macrobrachium rosenbergii (larvae and juveniles), the opossum shrimp Neomysis integer, the euphausid Meganyctiphanes, and in the water-fleas Daphnia magna and D. longispina. The aesthetascs, that are thought to represent olfactory receptors, exhibit a considerable structural variation, ranging from the well known aesthetascs of higher crustaceans (lobster, crab, crayfish) to the corresponding sensilla found in the water-fleas and the males of opossum shrimps. The two following morphological characteristics of the aesthetascs are thought to indicate an olfactory function: the shape of the cuticular hair that is long and essentially hose-shaped, and the thin, loosely arranged cuticle of at least the outer part of the cuticular hair. The presence of other structural elements such as sensory cells, cilia, and enveloping cells are vital for the olfactory function, but the development is variable, which makes their use in the morphological definition of aesthetascs problematic. © 1992 Wiley-Liss, Inc.
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    Fine structure of olfactory sensilla in myriapods and arachnids (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 22 (1992), S. 372-391 
    Details
    ISSN: 1059-910X
    Keywords: Olfactory chemoreceptors ; Electron microscopy ; Wall structures ; Sheath cells ; Dendrites ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Structural features of various types of olfactory sensilla are reviewed. (1). Sensilla basiconica which differ in form and size are found on the antennae of centipedes and millipedes. Their walls show longitudinal slits or grooves that either open into the sensillum lumen or do not penetrate the cuticle. In other such sensilla the outer surface is pierced by pores and the inner surface grooved and pocketed. These sensilla are innervated by one to six sensory cells. Their unbranched outer dendritic segments extend to the tip of the sensillum. The sensory cells are surrounded by two or three sheath cells which terminate at the sensillum base or form a continuous tube around the entire length of the outer dendritic segments. (2) Temporal organs of centipides are located between the insertion of the antenna and the ocelli. These sensilla consist of a shallow cuticular ring with a central sensory plate made up by a layer of unperforated cuticle or a capsule with a mushroom-shaped structure inside formed by fibrous-looking cuticle. A dozen sensory cells with unbranched outer dendritic segments innervate each sensillum. They extend toward the sensory cuticle and pass just below it. Numerous sheath cell processes run parallel to the outer dendritic segments up to the sensory cuticle. (3) Thread-like flagella of Pauropoda are found on the antennae. They possess a flexible unperforated cuticular wall. These sensilla contain nine sensory cells surrounded by several sheath cells which form a continuous cytoplasmic tube around the outer dendritic segments. (4) Single-walled sensilla with numerous plugged pores penetrating the cuticular wall occur on the tarsus of the first leg in ticks. Each sensillum is innervated by 4-15 sensory cells. Three sheath cells terminate in the base of the sensillum. (5) Double-walled sensilla with spoke canals are found on the first tarsus of ticks. Their shaft is longitudinally grooved. Pore canals lead inward from the bottom of the grooves and open into vase-shaped chambers. From its base these canals extend into the lumen of the sensillum which contains unbranched outer dendritic segments of 1-2 sensory cells. (6) Single-walled sensilla with pore openings occur on the distal tarsal segments of the first leg of whip spiders. These sensilla are innervated by 40-45 sensory cells. Their unbranched outer dendritic segments fill the shaft lumen and extend partly into the wall pores. Microvillus-shaped sheath cell processes line the inner surface of the cuticular wall. (7) Tarsal organs are located dorsally on the tarsus of all legs and pedipalps of spiders. These sensory organs consist of a cuticular capsule with a dome-shaped projection inside. It is situated on the proximal sidewall of the capsule and possesses 7 pore canals that enclose the dendritic tips of 2-3 sensory cells, giving a total of 20 sensory cells. Each group of dendrites terminating in an individual pore canal is encased by 2 sheath cells. © 1992 Wiley-Liss, Inc.
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    Characterization of the suprachiasmatic nucleus in organotypic slice explant cultures (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 25 (1993), S. 46-60 
    Details
    ISSN: 1059-910X
    Keywords: Vasopressin ; Vasoactive intestinal polypeptide ; Gastrin releasing peptide ; GABA ; In vitro ; In situ hybridization histochemistry ; Electron microscopy ; Circadian pacemaker ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Suprachiasmatic nuclei (SCN) from hypothalami of postnatal rats were maintained for 18-39 days in vitro as organotypic slice explants. Neuronal subtypes containing vasopressin (VP), vasoactive intestinal polypeptide (VIP), gastrin releasing hormone (GRP), and GABA were immunocytochemically identifiable in these cultures. In situ hybridization histochemistry was compatible with these SCN slice explant cultures, and mRNA encoding for VP was detected bilaterally within these nuclei. After 18 days in vitro, both VP mRNA and VP immunoreactivity increased from levels present on postnatal days 4 (the earliest age from which the explanted tissue was derived) to levels typical of adult SCNs. In contrast, the GRP expression remained low, characteristic of early postnatal animals and far lower than adult levels. This suggests that the developmental cues or programs necessary for enhanced VP expression are maintained in these cultures, while those affecting GRP expression are absent or inhibited. VIP-containing neurons were numerous in the cultures. Culture slices appeared healthy, and similar numbers and distributions of identifiable neurons within the SCN were observed, whether or not the slices were grown in the presence of serum. EM analysis revealed that the SCN in vitro is composed of tightly packed neurons, processes, and abundant synapses containing both clear and dense core vesicles, closely resembling the SCN in vivo. Vasopressinergic neuronal somata contained extensive Golgi systems and labeled secretory granules, the latter organelle being present also within processes and synaptic terminals. GABA-immunopositive processes and synaptic profiles were abundant, with labeling occurring particularly over secretory vesicles and mitochondria. This slice culture system effectively maintained much of the intrinsic organization and cellular components of the SCN for long periods in vitro and should be an excellent model system for studying the intrinsic molecular mechanisms and extrinsic cues which regulate neuronal phenotype in this circadian pacemaker. Published 1993 Wiley-Liss, Inc.
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    Simulation of dislocations imaged moiré fringe contrast (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 24 (1993), S. 185-192 
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    ISSN: 1059-910X
    Keywords: Electron microscopy ; Epitaxy ; Dislocations ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Transemission electron microscope (TEM) images of dislocations as produced via moiré fringe contrast are simulated using many-beam diffraction theory. The effect of edge dislocations on both parallel and rotational moiré fringe patterns is considered. For the parallel moiré fringe pattern, images of dislocations both perpendicular to the film plane and those inclined to the film plane are produced. The effect of an inclined dislocation is shown to cause a distortion of the dislocation image. Finally, a comparison between predicted and experimentally observed images is made, with the results indicating that threating dislocations in the FeAl/GaAs system have line directions nearly perpendicular to the (001)FeAl/GaAs film plane. © 1993 Wiley-Liss, Inc.
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    Age-Related changes in cartilage proteoglycans: Quantitative electron microscopic studies (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 28 (1994), S. 398-408 
    Details
    ISSN: 1059-910X
    Keywords: Aging ; Proteoglycans ; Electron microscopy ; Intervertebral disc ; Hyaline cartilage ; Nucleus pulposus ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Biochemical and biophysical studies have shown that the composition and sedimentation velocity of cartilage proteoglycans change with age, but these investigations cannot demonstrate the alterations in molecular structure responsible for these changes. Development of quantitative electron microscopic methods has made it possible to define the age-related structural changes in aggregating proteoglycans and to correlate the alterations in their structure with changes in tissue composition and morphology. Electron microscopic measurement of human and animal hyaline cartilage proteoglycans has shown that with increasing age the length of the chondroitin sulfate-rich region of aggregating proteoglycan monomers (aggrecan molecules) decreases, the variability in aggrecan length increases, the density of aggrecan keratan sulfate chains increases, the number of monomers per aggregate decreases, and the proportion of monomers that aggregate declines. Proteoglycans from the nucleus pulposus of the intervertebral disc show similar but more dramatic age-related alterations. At birth, nucleus pulposus aggrecan molecules are smaller and more variable in length than those found in articular cartilage. Within the first year of human life, the populations of aggregates and large aggrecan molecules analogous to those found in articular cartilage decline until few if any of these molecules remain in the central disc tissues of skeletally mature individuals. The mechanisms of the age-related changes in cartilage proteoglycans have not been fully explained, but measurement of proteoglycans synthesized by chondrocytes of different ages suggests that alterations in synthesis produce at least some of the age-related changes in aggrecan molecules. Degradation of aggrecan chondroitin sulfate-rich regions in the matrix probably also contributes to the structural changes seen by electron microscopy. Age-related changes in proteoglycan aggregation may be due to alterations in link protein function or inhibition of aggregation of newly synthesized aggrecan molecules by accumulation of degraded aggrecan molecules. © 1994 Wiley-Liss, Inc.
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    Calculation of overall tilt angles for a double tilt holder in a TEM (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 28 (1994), S. 448-451 
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    ISSN: 1059-910X
    Keywords: Angular relationship ; Tilting ; Electron microscopy ; Goniometer ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A simple formula has been derived for the tilt angle of a specimen in terms of the two tilt angles of a side entry, double tilt holder in a transmission electron microscope. An expression for calculating the direction of the apparent tilt axis in relation to the observed diffraction pattern has also been derived. The accuracy and reproducibility of specimen tilting has been assessed experimentally. © 1994 Wiley-Liss, Inc.
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    Adenosine 5′-triphosphate promotes mineralization in differentiating chick limb-bud mesenchymal cell cultures (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 28 (1994), S. 492-504 
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    ISSN: 1059-910X
    Keywords: Calcification ; Hydroxyapatite ; Matrix synthesis ; FT-IR microscopy ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: When chick limb-bud mesenchymal cells are plated in micromass culture, they differentiate to form a mineralizable cartilage matrix. Previous studies have demonstrated that, when the total inorganic phosphate concentration of the medium is adjusted to 3-4 mM by adding inorganic phosphate to the basal medium, the mineralized matrix formed resembles that of chick calcified cartilage in ovo. When the high-energy phosphates adenosine 5′-triphosphate (ATP) or creatine phosphate are used as supplements in place of inorganic phosphate, the mineralized matrix as analyzed by electron microscopy and Fourier transform infrared microscopy is also similar to that in ovo. This is in marked contrast to the mineralized matrix formed in the presence of 2.5-5 mM β-glycerophosphate, where mineral deposition is random and mineral crystal sizes in general are larger. This is also in contrast to the known ability of ATP to inhibit mineral deposition in solution in the absence of cells.In the differentiating mesenchymal cell culture system, ATP does not alter the rate of cell proliferation (DNA content), the rate of matrix synthesis (3H-leucine uptake), the mean crystallite length, or the rate of mineral deposition (45Ca uptake) when contrasted with cultures supplemented with inorganic phosphate. However, ATP does increase the mineral to matrix ratio, especially around the edge of the culture, where a type I collagen matrix is present. It is suggested that ATP promotes mineral deposition by providing a high-energy phosphate source, which may be used to phosphorylate extracellular matrix proteins and to regulate calcium flux through cell membranes. © 1994 Wiley-Liss, Inc.
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    Improved ultrastructural preservation of rat ciliary body after high pressure freezing and freeze substitution: A perspective view based upon comparison with tissue processed according to a conventional protocol or by osmium tetroxide/microwave fixation (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. 11-22 
    Details
    ISSN: 1059-910X
    Keywords: Cryofixation ; Electron microscopy ; Extracellular material ; Microtubules ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Conventional fixation of the delicate, highly folded rat ciliary body and its iridial extension, as well as of vitreal structures, is associated with the induction of a number of artifacts, thus limiting the reliability of morphological interpretations. Improved ultrastructural preservation may be achieved by microwave heating in combination with osmium tetroxide fixation. This protocol, although simple and cheap, yields results, particularly with respect to the extracellular matrix compartment between inner and outer ciliary epithelial cells, which are not greatly inferior to those obtained by implementing the sophisticated high pressure freezing and freeze substitution technique. The latter affords good to very good ultrastructural preservation of epithelium and stromal components, such as blood vessels, neural elements, smooth muscle cells, fibrocytes, and free cells, up to a depth of 50-100 μm from the tissue surface. Its superiority over osmium tetroxide/microwave fixation is revealed in the cytoplasmic, intraorganellar, and vitreal matrix compartments, which incur no obvious losses. © 1994 Wiley-Liss, Inc.
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    Fine structure of Tritrichomonas foetus as seen using cryotechniques (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. 37-46 
    Details
    ISSN: 1059-910X
    Keywords: Tritrichomonas foetus ; Freeze-fracture ; Electron microscopy ; Fast-freezing fixation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Tritrichomonas foetus was studied using different physical and chemical fixation methods such as fast-freezing (by high pressure, “slam-freezing,” and jet-propane), freeze-substitution, conventional freeze-fracture and deep-etching, cryoultramicrotomy, and routine preparation for transmission electron microscopy. The use of fast-freezing fixation (FFF) proved to be superior in terms of structural preservation due to the rapidity of this fixation compared to that obtained using conventional chemical fixation. The low temperature techniques used here were useful to confirm data already obtained by conventional freeze-fracture using chemical fixation and cryoprotection, such as the presence of flagellar rosettes and costa structure. Cryoultramicrotomy and slam-freezing also demonstrated the presence of hair-like structures projecting out from the protozoan surface. New aspects of organelles of T. foetus were demonstrated. Published 1994 by Wiley-Liss, Inc.
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    Liquid crystalline order of biopolymers in cuticles and bones (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 420-428 
    Details
    ISSN: 1059-910X
    Keywords: Self-assemblies ; Chitin ; Collagen ; Polarizing microscopy ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Microscopic studies at different scales have shown that in biological tissues the three-dimensional arrangement of chitin-protein or of collagen fibrillar networks can follow the same spatial distributions as those described in certain liquid crystals. The present work reviews the structural analogies established between the dense fibrillar organic matrix found in two materials: crab cuticles and compact bones. In both systems mobile fringes are described in polarizing microscopy, periodic cleavage aspects in scanning electron microscopy (SEM), and arced patterns in transmission electron microscopy (TEM). In parallel to these structural data, results obtained in vitro are recalled which corroborate the relationship established between ordered arrays of biopolymers and liquid crystalline assembly principles, highly concentrated solutions of purified collagen molecules spontaneously form ordered assemblies characterized in polarizing microscopy as cholesteric phases. This particular state of matter joins both fluidity and order and could correspond to a transient state of collagen or chitin secretion, before the stiffening of these skeletal structures, bone or cuticle, by molecular cross-links and crystalline deposition. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/jemt.1070270508
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    Ultrastructural diagnosis of human pituitary adenomas (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 20 (1992), S. 107-135 
    Details
    ISSN: 1059-910X
    Keywords: Electron microscopy ; Endocrine neoplasm ; Pituitary adenomas ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Electron microscopy, which has been instrumental in the characterization of normal pituitary cell types, has also played a crucial role in the mirphologic classification pituitary adenomas arising in the presently known 5 cell types, and in the recognition of 3 adenoma types with yet undisclosed cell derivation. This review deals with the application of electron microscopy for study of pituitary adenomas in order to provide specific pathological diagnosis and aid the clinician in selecting appropriate postoperative treatment. In addition to the ultrastructural appearance and diagnostic features of 15 adenoma types, the morphology of hyperplastic proliferations and that of known normal counterparts of various adenoma types are also discussed. Specific morphologic diagnosis of pituitary lesions is important not only for adequate postoperative management of patient, but is also a prerequisite for study of the natural history and biological behaviour of various adenoma types.
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    URL: http://dx.doi.org/10.1002/jemt.1070200202
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    The ultrstructure of neuronal-pinealocytic interconnections in the monkey pineal (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 21 (1992), S. 124-135 
    Details
    ISSN: 1059-910X
    Keywords: Pinealocyte ; Pineal-neuron ; Synapses ; Ribbon synapse ; Innervation ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Recent ultrastructural studies of neuronal-pinealocytic interconnections in the monkey pineal are reviewed. The pinealocytes in the adult monkey show almost all of the cytological specializations known in subprimate mammals. Adjacent pinealocytes are functionally coupled through ribbon synapses on cell bodies and gap junctions on cell bodies and cell processes. The pinealocytes receive direct synaptic contacts of nerve fibers with cholinergic terminal morphology. Nerve cells restricted to the central portion of the pineal receive synaptic contacts with more than three different morphologically defined types of nerve terminals. In addition to nerve terminals containing small clear vesicles or vesicles of pleomorphic morphology, a pinealocyte's terminal process containing the synaptic ribbon forms a true synaptic contact on the nerve cell body. The diversity of synapses on these nerve cells strongly suggests multiple origins of these neurons rather than a single peripheral parasympathetic origin. The possible involvement of pineal neurons in an intrinsic circuit that regulates the function of pinealocytes and integrates the neural input from the central as well as the peripheral nervous systems is discussed.
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    Fine structure of the vomeronasal and septal olfactory epithelia and of glandular structures (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 23 (1992), S. 86-97 
    Details
    ISSN: 1059-910X
    Keywords: Accessory olfactory ; Nasal glands ; Odorant binding protein ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The vomeronasal and septal olfactory organs are two neurosensory structures in the mammalian nasal septum which are poorly understood relative to the main olfactory system. The vomeronasal organ is a paired, blind-ending tubular structure that opens rostrally into the nasal cavity in some species and into the incisive ducts in others. When present in mammals, the septal olfactory organ is an island of olfactory mucosa positioned such that it is in the primary air pathway in the caudal portion of the nasal cavity. Mammalian nasal glands, with a diverse histochemical and ultrastructural morphology, secrete a variety of substances onto the mucosal surface. One of these substances, odorant binding protein, localized in bovine nasal glands and lateral nasal glands of rodents may be important in the capture and conveyance of odorant molecules to olfactory receptors. The objectives of this paper are to present original data while reviewing the literature on the ultrastructure of vomeronasal and septal olfactory neuroepithelia, and of vomeronasal, bovine nasal, and lateral nasal glands. Nasal tissues from pigs, calves, and hamsters were prepared for electron microscopy. Neurosensory epithelia of the porcine vomeronasal organ and the hamster septal olfactory organ are similar to that described for the vomeronasal and septal olfactory organs of other mammals. Bovine nasal and rodent lateral nasal glands consist of subregions which differ morphologically; the most abundant acinar cell type in the bovine nasal gland contains lightly electron dense secretory granules while that of the rodent lateral nasal gland contains both small electron dense and large, electron lucent granules. The porcine vomeronasal gland contains numerous small, dense granules of a diverse morphology. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/jemt.1070230108
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    Morphological study of the effects of intranasal zinc sulfate irrigation on the mouse olfactory epithelium and olfactory bulb (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 24 (1993), S. 195-213 
    Details
    ISSN: 1059-910X
    Keywords: Deafferentation ; Regeneration ; Sensory afferents ; Electron microscopy ; Olfactory receptor cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The effects of intranasal zinc sulfate (ZnSO4) irrigation on the morphology of the olfactory epithelium and olfactory bulb were studied in mice with short survival times (as early as 1 day) and with long survival times (up to 593 days) after the irrigation procedure. As in several previous studies, the olfactory epithelium was completely destroyed within a few days after the ZnSO4 treatment. Within 2-4 days, the septum and turbinates were covered by a new, cuboidal epithelium, the cells of which differed significantly from any cells normally seen in the olfactory epithelium. Slowly, over several months, small areas of the olfactory epithelium regenerated in many of the animals.The ultrastructural changes occurring in the olfactory bulb from 1 to 25 days (the reactive stage) were characterized by degenerating olfactory axons and axon terminals, hypertrophy of astroglial cell processes, and proliferation of or extravasation by phagocytic cells. By 25 days after intranasal ZnSO4 irrigation, the number of reactive glial processes and phagocytic cells returned to normal. In some mice with survival times of 150 days or longer, there was reinnervation of small areas of the olfactory bulb by regenerated olfactory axons. These new olfactory axons innervated only superficial glomeruli or the outer portions of deeper glomeruli, but they formed synaptic contacts with mitral/tufted cells and periglomerular cells that did not differ from control animals. These findings were supported by tract-tracing experiments with 3H-amino acids and by behavioral analysis.In summary, the ultrastructural changes observed in the olfactory bulb in this study were not significantly different from those observed after surgical lesions of the olfactory epithelium or nerve. The olfactory bulb, however, never fully recovered; glomeruli remained shrunken (though with normal dendro-dendritic synaptic connections), and there was minimal olfactory axon reinnervation. © 1993 Wiley-Liss, Inc.
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    Dynamics of golgi impregnation in neurons (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 23 (1992), S. 264-274 
    Details
    ISSN: 1059-910X
    Keywords: CNS ; Light microscopy ; Electron microscopy ; Cerebral cortex ; Nerve cell ; Impregnation method ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: This paper describes the early stages of impregnation by the Golgi rapid method in sections and blocks of brain tissue. Aldehyde-fixed and potassium dichromate-treated sections of cerebral cortex were placed on glass slides and coverslipped. The dichromate solution was then replaced by a silver nitrate solution, and events taking place in the section were monitored and time-lapse recorded until the impregnation was interrupted and the sections subsequently prepared for electron microscopy. The tissue blocks, fixed and chromated in the same way, were placed into a silver nitrate solution for 30 min to 24 h and the progress of impregnation compared with the results obtained in the sections on the glass slides.Two basic modes of impregnation were observed, apparently in direct relation to the process of crystallization of silver chromate: crystals of silver chromate growing directly from the surface of the tissue into the nerve cell via its transected plasma membranes, and microcrystalline precipitate of silver chromate spreading into the nerve cell from nucleation centres dispersed in the tissue. The precipitate grows inside the cell as in a preformed channel until the cell has been filled. If the nucleation begins extracellularly, the precipitate extends into the narrow intercellular gaps. Electron microscopy showed that the crystalline precipitate consisted of multilamellar formations containing dense coalesced granules that did not cross plasma or endocellular membrane boundaries. © 1992 Wiley-Liss, Inc.
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    Morphological effects of diabetes on the granular ducts and acini of the rat submandibular gland (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 61-70 
    Details
    ISSN: 1059-910X
    Keywords: Salivary gland ; Diabetes ; Insulin ; Electron microscopy ; Streptozotocin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Effects of experimental diabetes on rat submandibular glands have been documented, but earlier reports suggested that diabetes caused an extensive cellular degeneration and a replacement of the parenchymal cells by fibrous connective tissue. Such observations, however, are difficult to reconcile with the relatively normal physiological responsiveness of the gland (Anderson and Suleiman, 1989). This study, therefore, reexamined the histological, histochemical and ultrastructural effects of streptozotocin-induced diabetes on rat submandibular glands. The tissues were examined at 3 weeks, and 3 and 6 months after the induction of diabetes, and compared with glands from age-matched controls by both light and electron microscopy. Light microscopically, the proportional volumes of the acini and granular ducts remained constant in control rats at about 48% and 38% respectively. In diabetic animals the volume density of the acini increased progressively to 62%, whereas that of the granular ducts decreased to 20%. The diameter and number of granular ducts were reduced in diabetic animals, but acinar cell profile area was only affected 6 months after the induction of diabetes. Ultrastructurally, there was an accumulation of lipid in the acinar cells and, with increasing duration of diabetes, the number of autophagic structures in both the acini and the granular ducts increased. Although there was evidence of some cellular degeneration it was never excessive. Morphometry showed that the volume density of secretory granules within the acinar cells was unaffected, but there was a significant reduction in the volume density of secretory granules within the granular ducts. Thus, in the rat submandibular gland the greatest effect of streptozotocin-induced diabetes was to cause hypotrophic changes in the cells of the granular ducts. The relative contributions of a direct effect of insulin insufficiency and the hypogonadal effects of diabetes, however, are not known. © 1994 Wiley-Liss, Inc.
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    Immunogold labelling of leukemic hairy cells with the B-ly7 monoclonal antibody: An SEM and TEM study (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 28 (1994), S. 356-367 
    Details
    ISSN: 1059-910X
    Keywords: Hairy cell leukemia ; Immunogold labelling ; B-ly7 antibody ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Two cases of hairy cell leukemia have been studied by immuno-TEM and immuno-SEM after immunogold labelling of the cell surface antigen recognized by the B-ly7 monoclonal antibody.Most hairy cells appeared significantly labeled, although the density of the expression of the antigen, as demonstrated by immunogold labelling, seems variable from cell to cell. Moreover, some cells with the morphology of hairy cells and which could not be identified as monocytes were not labeled. Labelling for the antigen identified by the B-ly7 mAb does not seem to correlate with the presence of ribosome lamellae complexes which were present only in one of the two cases studied. Rare lymphocytes of unidentified lineage were labeled. Monocytes were significantly absent from the samples of peripheral blood of the two patients studied. In one normal control sample, monocytes were observed unlabelled.The results are discussed in reference to the pathogenesis of hairy cell leukemia, its surprisingly low mitotic rate, and its distinct response to chemotherapy. © 1994 Wiley-Liss, Inc.
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    Comparison of nuclear hydration in boar spermatozoa before and after freeze-thawing: Contrast analysis of cells embedded in bromide-labeled medium (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 21 (1992), S. 249-254 
    Details
    ISSN: 1059-910X
    Keywords: Electron microscopy ; Water ; Image analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Epon labeled with bromide was used to embed ejaculated and freeze-thawed spermatozoa, with the hypothesis that it replaces most of cell water. Image analysis of relative contrasts between sperm nuclei and the surrounding medium revealed that when used in low concentrations, bromide is mostly absorbed to the nuclear structures. For higher concentrations, the chromatin is saturated, and the increase in contrast can be used to calculate relative differences in the hydration of nuclei. Boar sperm nuclei are more hydrated after freeze-thawing than before. © 1992 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/jemt.1070210308
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    Synaptic organization and development of the antennal lobe in insects (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 24 (1993), S. 260-280 
    Details
    ISSN: 1059-910X
    Keywords: Neuroanatomy ; Invertebrate brain ; Neurons ; Glial cells ; Olfactory system ; Immunocytochemistry ; Electron microscopy ; Neural development ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Many insects possess a highly developed sense of smell. This paper summarizes the cellular and synaptic organization of the antennal (olfactory) lobe of the insect brain and then reviews morphological and fine-structural aspects of the development of the lobe. Visualization of synapses between classes of neurons identified by physiological, morphological, or transmitter-cytochemical properties has provided insights into arrangements of contacts and their possible roles in information processing. Studies of development have revealed the requirement for afferent axons from the antenna for the formation of olfactory glomeruli, where virtually all of the synapses in the lobe occur, and have suggested the possibility that glial cells play a role in the instructive influence of the axons on their target neurons in the lobe. The findings reviewed in this paper are primarily from one representative hemimetabolous insect, the American cockroach, and one representative holometabolous insect, a hawkmoth, and comparisons are made with vertebrate systems when appropriate. © 1993 Wiley-Liss, Inc.
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    Computer-assisted morphometry: Point, intersection, and profile counting and three-dimensional reconstruction (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 21 (1992), S. 262-270 
    Details
    ISSN: 1059-910X
    Keywords: Stereology ; Software ; Coordinate geometry ; Volume density, Surface density ; Numerical density ; Serial sections ; Light microscopy ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The use of computers in morphometry can involve (1) automated image analysis, semiautomated image analysis and point, intersection, intercept and profile counts of two-dimensional images on tissue sections with mathematical extrapolation to the third dimension, (2) direct measurement of volumes, surfaces, lengths, and curvature using x,y,z coordinates of serial sectioned images, or (3) stereologic techniques and serial sections which is a combination of 1 and 2 above. Automated and semiautomated image analysis are generally restricted to specimens that are characterized by differential contrast such as interalveolar septa in the lung or histochemically stained mucous granules in pulmonary epithelium. Point, intersection, and profile counts using hand-held, notebook PCs, portable PCs, or standard PCs and MS-DOS - based application programs are extremely efficient, precise, affordable, and convenient methods of quantitating average values of a population. When morphometric measurements of individual structures are required, computer-assisted three-dimensional reconstruction using x,y,z coordinates of the surface outline from serial sections is a tedious yet precise method. We describe a computer program that efficiently estimates mean caliper diameter, volume, and surface area with less than five percent error with five sections per structure. We also describe a program that does digital image subtraction on serial sections, superimposes digitally generated test systems on biological images, and accumulates point, intersection, and profile counts using a Macintosh II series computer. © 1992 Wiley-Liss, Inc.
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    Ultrastructural and functional connectivity of intracellularly stained neurones in the vertebrate retina: Correlative analyses (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 24 (1993), S. 43-66 
    Details
    ISSN: 1059-910X
    Keywords: Retina ; Intracellular staining ; Horseradish peroxidase ; Electron microscopy ; Cone ; Horizontal cell ; Bipolar cell ; Amacrine cell ; Ganglion cell ; Neurotransmitter ; Synaptic plasticity ; Spinules ; Rhodamine ; Double labelling ; Postembedding immunohistochemistry ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A variety of intracellular recording and staining techniques has been used to establish structure-function and, in some cases, structure-function-neurochemical correlations in fish, turtle, and cat retinae. Cone photoreceptor-horizontal cell connectivity has been studied extensively in the cyprinid fish retina by intracellular staining with horseradish peroxidase (HRP) and subsequent electron microscopy. The available data suggest that horizontal cell dendrites around the ridge of the synaptic ribbon are postsynaptic, whilst finger-like extensions (“spinules”) of lateral dendrites function as inhibitory feedback terminals. An interesting feature of this inter-action is its plasticity: the feedback pathway is suppressed in the dark and becomes potentiated by light adaptation of the retina.Intracellular recordings and stainings of ganglion cells in both turtle and cat retinae have been possible. Prelabelling of ganglion cells by retrograde transport of rhodamine from the tectum allows ganglion cells to be stained under visual control, and their synaptic inputs determined by electron microscopy. Such studies have been extended to double labelling by using autoradiography or postembedding immunohistochemistry to identify the neurotransmitter content of the labelled cell and/or the neurotransmitter(s) converging upon it. It is envisaged that further applications of intracellular staining followed by double- or even triple-labelling will continue to enhance greatly our understanding of the functional architecture of the vertebrate retina. © 1993 Wiley-Liss, Inc.
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    Quantitative analysis of the porous structure of a petroleum reservoir (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 25 (1993), S. 173-174 
    Details
    ISSN: 1059-910X
    Keywords: Porosity ; Mathematical Morphology ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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    URL: http://dx.doi.org/10.1002/jemt.1070250210
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    Biosynthetic routing of pulmonary surfactant proteins in alveolar type II cells (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 26 (1993), S. 366-373 
    Details
    ISSN: 1059-910X
    Keywords: Immunogold labeling ; Electron microscopy ; Lung ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Surfactant proteins A, B, and C (SP-A, SP-B, and SP-C) are synthesized in alveolar type II cells. SP-B and SP-C are both synthesized as large precursor molecules that are proteolytically processed to their mature sizes. In a previous immunoelectron microscopic study, we showed that precursor SP-B is processed to its mature size in multivesicular bodies. In the present study, using a specific antibody aginst precursor SP-C, we demonstrate that precursor SP-C is present in the same intracellular compartments of the biosynthetic pathway, i.e., endoplasmic reticulum, Golgi complex, and multivesicular bodies, as precursor SP-B. Since mature SP-C is known to be present in multilamellar bodies, this suggests a biosynthetic routing and site of processing of this protein similar to those of SP-B. Double-labeling experiments using antibodies against SP-A, precursor SP-B, precursor SP-C, and an antibody against HA I, an adaptor protein involved in the budding of transport vesicles from the Golgi complex, showed that the different surfactant proteins traverse and exit the Golgi complex via the same route. The surfactant proteins do not exit the Golgi complex via HA I-positive coated buds or vesicles. These data are in accordance with the concept that SP-A, SP-B, and SP-C are transported together through the same biosynthetic pathway via multivesicular bodies to multilamellar bodies. © 1993 Wiley-Liss, Inc.
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    Pathology of the salivary glands: The contribution of electron microscopy (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 46-60 
    Details
    ISSN: 1059-910X
    Keywords: Salivary gland ; Tumor ; Differentiation ; Classification ; Experimental studies ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Electron microscopy has a limited role in the diagnosis of primary salivary gland tumors, although it can be helpful in metastatic lesions of possible salivary gland origin. The diversity of subtypes in salivary gland tumors, as well as the range of histomorphology within any one subtype, is unparalleled in any other human tumor. This and their relative infrequency causes diagnostic problems for pathologists. Ultrastructural techniques have been of major importance in determining the inter-relationship of these tumors for classification purposes, revealing the subtle variations in common cellular differentiation pathways, determining the organization of tumor cells, and displaying the importance of extracellular matrix materials in establishing diagnostic criteria for each of the many subtypes. Electron microscopy has also been valuable in non-neoplastic salivary gland disease and has an increasing role in experimental studies involving tissue from human and animal salivary parenchyma. © 1994 Wiley-Liss, Inc.
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    Cytochrome c oxidase: Structural studies by electron microscopy of two-dimensional crystals (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 319-332 
    Details
    ISSN: 1059-910X
    Keywords: Cytochrome oxidase ; Electron microscopy ; Image processing ; Electron transport ; Mitochondria ; Membrane protein ; Membrane structure ; Protein structure ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Cytochrome c oxidase is a complex integral membrane protein consisting of 13 different polypeptide chains and four metal centers having a total molecular weight of approximately 200,000 daltons. It can be isolated in two 2-dimensional crystalline forms differing in aggregation state of the enzyme. One crystal form consists of cytochrome oxidase dimers (approximately 400,000 daltons) embedded unidirectionally in the lipid bilayer of a collapsed vesicle while the other form consists of crystalline sheets of cytochrome oxidase monomers. Both crystal forms have been studied by electron microscopy during the past two decades, and this paper summarizes the results of early structural studies as well as more recent results applying techniques of cryelectron microscopy and digital image processing. The structure of frozen-hydrated cytochrome oxidase dimers at 20 Å resolution is discussed as well as the packing of monomers within dimers and the site of cytochrome c binding. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/jemt.1070270407
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    Image analysis of the extracellular matrix (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 28 (1994), S. 409-421 
    Details
    ISSN: 1059-910X
    Keywords: Extracellular matrix ; Image analysis ; 3D reconstruction ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The epiphyseal growth plate and articular cartilage matrices were preserved by slam freezing and freeze substitution to optimally retain the native organization for both cellular and matrix components. These specimens were stained and examined using conventional electron microscopic methods. The highly integrated, proteoglycan-rich matrices were examined by computer image analysis using such parameters as distribution, connectivity, orientation, and a variety of morphometric analyses. Also, different aspects of electron tomography and 3D rendering of matrix vesicles and their associated mineral deposits from epiphyseal growth plates and turkey leg tendons are presented. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/jemt.1070280507
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    Light microscopic distribution of some cholinergic markers in the rat and rabbit locus coeruleus and the nucleus angularis grisea periventricularis of the domestic pig (Sus scrofa): A correlative electron microscopic investigation of cholinergic receptor proteins in the rabbit (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. 186-199 
    Details
    ISSN: 1059-910X
    Keywords: Acetylcholinesterase ; Choline acetyltransferase ; Muscarinic ; nicotinic receptor ; Immunohistochemistry ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Cholinergic modulation of locus coeruleus (LC) neurons evokes a variety of neuronal and behavioural effects. In an attempt to understand the LC cholinergic circuit, several markers has been investigated and compared. (Immuno)-histochemical and autoradiographic methods have been used on rat, rabbit, and pig tissue. To identify the boundaries of the LC in each of these species, sections through the entire brainstem have been stained for tyrosine hydroxylase. The results that the pig does not possess a LC proper that conforms to the accepted features of this cell group. However, in this location fusiform cells reminiscent of LC interneurons are still present. This group of fusiform neurons has been named the nucleus angularis grisea periventricularis (NAGP).LC cells of the rat and rabbit show strong acetylcholinesterase (AChE) activity. In the pig the NAGP is markedly free from AChE staining. Muscarinic binding sites are densely distributed over the rabbit LC and adjacent region. The rat and rabbit LC neurons synthesise both muscarinic (mAChR) and nicotinic receptor protein (nAChR). In the pig NAGP region mAChR and nAChR positive cell bodies are almost absent, while some nAChR immunoreactive dendrites are present. The light microscopic data in the rabbit have been confirmed by electron microscopic analysis.It is concluded that the general concept of a noradrenergic LC that is present throughout mammals is questionable. At present, choline acetyltransferase immunoreactive terminals that closely correspond to the other cholinergic components in the rat or rabbit LC have not been observed. However, in these species the cholinergic sensitivity of LC cells is mediated via both muscarinic and nicotinic receptors on somata and dendrites. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/jemt.1070290303
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    Subcellular distribution of peptides associated with gastric mucosal healing and neoplasia (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 31 (1995), S. 234-247 
    Details
    ISSN: 1059-910X
    Keywords: Immunolocalisation ; Electron microscopy ; Ultrastructure ; hSP ; pS2 ; TFG α ; EGFR ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The trefoil peptides pS2 and human spasmolytic peptide are putative growth factors, particularly associated with mucus-producing cells of the gastrointestinal tract including those of the stomach. The receptor for transforming growth factor alpha (TGF α) takes its name from one of its alternative ligands, epidermal growth factor and is called the epidermal growth factor receptor. Although there is immunoreactive epidermal growth factor in the stomach, it is TGF α and the epidermal growth factor receptor that are abundant. Immunolabelling at electron microscope level allows for subcellular localisation of antigens; pS2 and human spasmolytic peptide co-localise to cytomembranes, including the Golgi apparatus, and thecae of surface/pit mucous cells. TGF α is abundant on the membranes of tubulovesicles of parietal cells and is also present in chief cells: in mucous producing cells it can be detected but not in association with mucous. The distribution of the epidermal growth factor receptor mimics that of TGF α but with preferential clustering on the basolateral membranes of gastric cells. The trefoil peptides are associated with healing and probably act, together with mucus, to protect the gastric mucosa and maintain a viable environment. TGF α, transduced via the epidermal growth factor receptor, inhibits gastric acid secretion, thus aids the trefoils in the maintenance of a gastric microenvironment conducive to healing after damage. TGF α, however, is also a potent mitogen; while this property plays a vital part in repairing mucosal defects, if this peptide or indeed its receptor are overexpressed, the result can be neoplasia. © 1995 Wiley-Liss, Inc.
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    Ultrastructure of human parathyroid cells in health and disease (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 32 (1995), S. 164-179 
    Details
    ISSN: 1059-910X
    Keywords: Parathyroid gland ; Hyperparathyroidism ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Parathyroid glands (n = 271) removed from 130 patients were examined by light and electron microscopy. A standardized method of tissue processing was employed and morphometry was performed. The aim of the paper is to provide a description of the human parathyroid chief cell ultrastructure in health and disease, with quantitative evaluation of structures involved in secretion of parathyroid hormone in a large case series, and to discuss their role in current diagnostic histopathology. The patients were euparathyroid (n = 10), or affected by primary (n = 97), secondary (n = 8), or tertiary (n = 15) hyperparathyroidism. In normal glands, solid parenchyma was composed of chief cells, large clear cells, transitional-oxyphil cells, and oxyphil cells. Chief cell hyperplasia, pseudo-adenomatous hyperplasia, adenoma, water-clear cell hyperplasia, and carcinoma were the most usual forms of parathyroid disease responsible for primary hyperparathyroidism. In chief cell hyperplasia, all the parathyroid glands were enlarged and the chief cells were in an active state of hormone secretion, with a large Golgi complex, abundant rough endoplasmic reticulum (RER), small lipid droplets, and tortuous plasma membrane. In pseudo-adenomatous hyperplasia, one gland was enlarged and the others displayed a normal size; however, electron microscopic examination and morphometric analysis showed that all the glands had active cells. Adenomas displayed a pattern similar to those of pseudo-adenomatous hyperplasia, with one gland enlarged and the others of normal size. However, ultrastructural examination and morphometry showed that the normal-size glands were hypo-active. Water-clear cell hyperplasia showed cells filled with cytoplasmic vacuoles. In these cells, structures with intermediate features between secretory granules and vacuoles were visible. Nucleo-cytoplasmic atypias were frequently visible in parathyroid carcinoma cells. In secondary and tertiary hyperplasia, active chief cells were regularly mixed with oxyphil or transitional-oxyphil cells. The tertiary hyperplasia was characterized by RER-associated structures that were not found in the normal or other pathologic conditions. These results demonstrate that electron microscopy and morphometry represent useful tools in parathyroid histopathology. © 1995 Wiley-Liss, Inc.
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    Electron microscopic image analysis of cardiac gap junction membrane crystals (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 31 (1995), S. 452-466 
    Details
    ISSN: 1059-910X
    Keywords: Connexins ; Intercellular communication ; Crystallization ; Electron microscopy ; Image analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Cardiac gap junctions play an important functional role in the myocardium by electrically coupling adjacent cells, thereby providing a low resistance pathway for cell-to-cell propagation of the action potential. Two-dimensional crystallization of biochemically isolated rat ventricular gap junctions has been accomplished by an in situ method in which membrane suspensions are sequentially dialyzed against low concentrations of deoxycholate and dodecyl-β-D-maltoside. Lipids are partially extracted without solubilizing the protein, and the increased protein concentration facilitates two-dimensional crystallization in the native membrane environment. The two-dimensional crystals have a nominal resolution of 16 Å and display plane group symmetry p6 with a = b = 85 Å and γ = 120°. Projection density maps show that the connexons in cardiac gap junctions are formed by a hexameric cluste rof α1 connexin subunits. Protease cleavage of α1 connexin from 43 to 30 kDa releases ∼13kDa from the carboxy-tail, and the projection density maps are not significantly altered. Uranyl acetate stain penetrates the ion channel, whereas phospho-tungstic acid is preferentially deposited over the lipid regions. This differential staining can be used to selectively probe the central channel of the connexon and the interface between the connexon and the lipid. The hexameric design of α1 connexons appears to be a recurring quaternary motif for the multigene family of gap junction proteins. © 1995 Wiley-Liss, Inc.
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    Ultrastructural characterization of neurons recorded intracellularly in vivo and injected with lucifer yellow: Advantages of immunogold-silver vs. immunoperoxidase labeling (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 30 (1995), S. 427-436 
    Details
    ISSN: 1059-910X
    Keywords: In vivo intracellular recording ; Electron microscopy ; Preembedding immunohistochemistry ; Frontal cortex ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Immunoperoxidase labeling of lucifer yellow provides a sensitive method for morphological characterization of neurons recorded intracellularly in vitro or in vivo. However, the reaction product is often so dense that it obscures ultrastructural details necessary for the analysis of synaptic contacts onto individually filled neurons. In the present study, we describe a silver intensification procedure using 1 nm gold labeling of lucifer yellow as an optimal means for immunocytochemically identifying single physiologically characterized neurons at the ultrastructural level. Single neurons in the frontal cortex of anesthetized rats were impaled in vivo and filled with lucifer yellow. The brians were then perfused with an acrolein fixative. Single vibratome sections through the recording site were reacted with a rabbit antibody directed against lucifer yellow followed by goat anti-rabbit 1 nm gold-labeled IgG and silver intensified. For comparison, additional sections were processed for immunoperoxidase detection of lucifer yellow. Labeled sections were processed for light microscopy or embedded in plastic for electron microscopy. The immunogold-silver label as well as peroxidase reaction product of lucifer yellow was readily detected in cell bodies, proximal and distal dendrites, and spines. However, in contrast to immunoperoxidase, the immunogold-silver reaction did not obscure subcellular orgnelles. Most importantly, the synaptic junctions formed by afferents to the filled neuron were more easily identifiable following the immunogold-silver procedure. This clear visualization of postsynaptic densities is essential for examining synaptic circuitry between afferents and physiologically characterized neurons. © 1995 Wiley-Liss, Inc.
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    Immunocytochemistry, autoradiography, in situ hybridization, selective stains: Complementary tools for ultrastructural study of structure-function relationships in the nucleus. Applications to adenovirus-infected cells (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 31 (1995), S. 22-43 
    Details
    ISSN: 1059-910X
    Keywords: Adenovirus ; Autoradiography ; Biotinylated probe ; Cytochemistry ; Electron microscopy ; Immunocytochemistry ; In situ hybridization ; Replication ; Transcription ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A significant amount of new information on structure-function relationships in nuclei of adenovirus-infected cells has accumulated during the last decade as a result of the combined use of several new cytochemical techniques. Localization of viral DNA on ultrathin sections of infected cells has been investigated at the ultrastructural level by using specific DNA staining and immunocytochemistry with monoclonal anti-DNA antibodies. Both techniques, however, concomitantly visualize cellular and viral DNA. The specific stain for DNA reveals the configuration of the DNA molecules in the different nuclear substructures, whateer their synthetic activities. The immunodetection of DNA reveals that specific antibodies strongly bind to DNA of condensed host chromatin and to both encapsidated and nonencapsidated inactive viral genomes. However, the observation of an abnormally low level of labeling over the substructures in which synthetic activities of viral genomes are known to be intense demonstrates a serious limitation of this technique for the detection of active DNA. Postembedding in situ hybridization is the most useful method for identifying with certainty the structures containing defined nucleic acid sequences. By using a biotinylated viral DNA probe, in situ hybridization provides specific identification of structures containing either viral DNA or viral RNA molecules. In addition, with appropriate pretreatment of the sections, it is possible to reveal either all the viral DNA-that is, both double- and single-stranded DNA molecules (dsDNA, ssDNA)-or more specific species such as only ssDNA or only dsDNA molecules. The replicative and transcriptional activities of viral genomes are determined by high-resolution autoradiography. Autoradiography after a short pulse incorporation of appropriate radioactive precursors by infected cells reveals the sites of cellular and viral DNA replication or trancription. A short pulse followed by chase periods of different durations reveals the progressive migration of the cellular and viral synthesized products. The in situ distribution of the viral 72 kDa DNA-binding protein, a highly phosphorylated protein which protects the viral ssDNA, is revealed either by immunocytochemistry with specific antibodies or by the bismuth staining method which stains all highly phosphorylated proteins, including both cellular and viral proteins. The combined results of all these cytochemical procedures reveal the composition and functions of some of the structures induced by adenovirus infection. They demonstrate that viral genomes engaged in replication lead to the formation of replicative foci in which two compartments rapidly develop, one of which results from the aggregation of single strands of viral DNA and their accompanying 72 kDa protein. Conversely, ssDNA and 72 kDa protein are rare in the other compartment which is the main site of replication and transcription of viral genomes. The procedural aspects and the contributions of electron microscope cytochemistry to an understanding of the biology of Ad5 viruses can serve as a basic framework for the study of other biological systems. © 1995 Wiley-Liss, Inc.
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    Microwave fixation: Understanding the variables to achieve rapid reproducible results (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 32 (1995), S. 246-254 
    Details
    ISSN: 1059-910X
    Keywords: Electron microscopy ; Microwave fixation ; Microwave irradiation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The use of microwave irradiation for rapid chemical fixation of tissues in electron microscopy is a subject of current interest. The effect of water load size and location, sample placement in the oven cavity (hot or cold spots), and time on tissue preservation were examined. The use of a microwave container (4 dram vial) encased in 60 ml of ice in a 100 ml polyethylene beaker and a 0% power setting between two 100% power settings (time interval) provided reliable control of temperature during microwave irradiation. High brightness neon lights provided a quick and easy method to identify and map hot and cold spots within the oven cavity. Using microwave irradiation for rapid glutaraldehyde and osmium tetroxide fixation of tissues (Pacific yew needle and mouse kidney and liver) for electron microscopy yielded preservation equal or better than routine immersion fixation when a time interval, a cold spot (as the sample location), and an ice-encased vial were used during microwave fixation. These adaptations provided reliable control of fixation conditions in an 800 watt laboratory microwave oven. © 1995 Wiley-Liss, Inc.
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    New anionic polyelectrolyte hydrogel for corneal surgery (1997)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 37 (1997), S. 548-553 
    Details
    ISSN: 0021-9304
    Keywords: hydrogel ; biocompatibility ; permeability ; complement activation ; AN-69 dialysis membrane ; synthetic biopolymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A new high-water-content (78%) anionic polyelectrolyte hydrogel was obtained by phase inversion (demixion) of a polymer solution containing 9.0% poly(acrylonitrile sodium methallylsulphonate), 85.0% dimethylformamide, and 6.0% saline solution (0.9% NaCl). The hydrogel is permeable to water, saline, urea, creatinine, glucose, human albumin, and saline-dissolved oxygen. Investigation of the interactions between human serum and surfaces prepared with the new yielded hydrogel, compared to serum interaction with silica-free silicone (RTV), regenerated cellulose (Cuprophan), MMA/PVP copolymer (Lidofilcon), PMMA (Perspex), PTFE (Gore-Tex), and poly(acrylonitrile sodium methallylsulphonate) hemodialysis membrane (AN-69), showed the hydrogel and hemodialysis membrane (both prepared with AN-69 copolymer) to be the only materials devoid of complement (C′)-activating ability. © 1997 John Wiley & Sons, Inc. J. Biomed Mater Res, 37, 548-553, 1997.
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    Engineering the tissue which encapsulates subcutaneous implants. II. Plasma-tissue exchange properties (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 586-597 
    Details
    ISSN: 0021-9304
    Keywords: subcutaneous implants ; porosity ; vasculature ; permeability ; PVA ; PTFE ; encapsulation ; foreign body response ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This study assesses the plasma-tissue exchange characteristics of the capsular tissue that forms around implants and how they are affected by implant porosity. The number of vessels and their permeability to rhodamine were measured by intravascular injection of the fluorophore tracer into Sprague-Dawley rats that hosted for 3-4 months polyvinyl alcohol (PVA) and polytetrafluoroethylene (PTFE) subcutaneous implants. Rats were implanted with four pore sizes of PVA - a nonporous PVA (PVA-skin), and 5, 60, and 700 micron mean pore sizes (PVA-5, PVA-60, and PVA-700, respectively) - and two pore sizes of PTFE: 0.50 (PTFE-0.5) and 5.0 (PTFE-5) mean micron pore sizes. Photodensitometric image analysis was used to quantify the local tracer extravasation and, hence the permeability coefficients of isolated vessels around the implants. The number of functional vessels within 100 μm of the implants highlighted by the lissamine-rhodamine tracer were counted with fluorescence microscopy and with H&E stained sections using brightfield microscopy. The permeability of vessels did not vary substantially with implant pore size but generally were lower than those measured for surrounding subcutis. Pore size, however, had a dramatic effect on the vascular density of tissue-encapsulating implants: the number of microvessels (under 10 μm in radius) within the tissue surrounding the porous implants was higher than the number around nonporous implants. Pore sizes on the order of cellular dimensions incited optimal neovascularization; the vascular density around PVA-60 implants was six times higher (p 〈 .001) and three times higher (p 〈 .001) than those around PVA-0 implants in the fluorescent images and in brightfield, respectively. Moreover, brightfield microscopy showed the number of vessels around PVA-60 implants was almost double those in normal subcutis. The results suggest that optimal vascular density around long-term implants, such as sensors, biofluid cell constructs, and immunoisolated cell systems, may be engineered with pore size. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 586-597, 1998.
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    Position stabilization of EELS spectra (1985)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 2 (1985), S. 167-169 
    Details
    ISSN: 0741-0581
    Keywords: Electron microscopy ; EELS ; feedback system ; peak stabilization ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The position of the zero-loss peak in electron energy-loss spectra was sensed with a double photo diode. A signal, proportional to the disturbances from a central position, was amplified and fed back into a deflection coil in order to compensate for the origin of the disturbances. Thus, slow variations of the position of characteristic edges in the EEL spectrum could be reduced by a factor 100, and 60 Hz oscillations could be reduced by a factor 5.
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    A deposition technique for the imaging and analysis of protein interactions with metal and semiconductor surfaces (1985)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 2 (1985), S. 285-292 
    Details
    ISSN: 0741-0581
    Keywords: Electron microscopy ; Edge-projection TEM ; Field-emission ; Rho protein ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A new technique for placing biological molecules on metal, insulator, and semiconductor surfaces is described. The procedure requires only 10 μl of solution containing molecules at a concentration of 0.1 - 10 μg/ml. The use of a buffer that does not affect metal substrates, the possibility of fixing the molecules in solution prior to deposition, and the ability to minimize surface tension forces during air drying are other features of the new protocol. Simultaneous deposition on TEM grids and highly curved substrates permits biomolecular adsorption on technologically interesting materials to be visualized in the transmission electron microscope.
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    Computer simulation and analysis of high-resolution electron microscope images and diffraction patterns with partial coherence, hollow cone illumination, and virtual apertures (1984)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 1 (1984), S. 107-130 
    Details
    ISSN: 0741-0581
    Keywords: Phase contrast ; Computer simulation ; Partial coherence ; Electron microscopy ; Convergent beam ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A general method for computing high-resolution conventional transmission electron microscope images and diffraction patterns, when there are different types of partially coherent illumination conditions, is described. Examples of convergent beam, hollow cone, and virtual aperture illumination conditions are given in the context of interpreting image features. A comparison of real and computed diffraction patterns shows that, in practice, many innovative imaging modes are possible, which can be verified prior to real microscope experiments.
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    Immunolocalization of Alpha-Actinin in Adult Chicken Skeletal Muscles (1987)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 6 (1987), S. 357-366 
    Details
    ISSN: 0741-0581
    Keywords: Electron microscopy ; Immunolabeling ; Skeletal muscle ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Immunoelectron microscopy techniques were used to localize alpha-actinin within the Z lattice of adult skeletal muscles. Analysis of electron micrographs by direct visualization demonstrated that anti-alpha-actinin Fab fragments bound throughout the Z lattice. A low-resolution scanning densitometry technique was developed to quantitate the visual increase in the density of the Z lattice. These techniques did not allow determination of the particular component of the Z lattice, amorphous matrix, axial filaments, or cross-connecting filaments with which the antibody was associated. Therefore, additional techniques, including direct measurement of filament diameters and optical diffraction, were utilized in determining which components of the Z lattice bound anti-alpha-actinin Fab fragments. These analyses suggest that the antibody binding is distributed evenly throughout the lattice, along the filaments, and between them and is confined to the region of double overlap of the ends of the thin filaments.
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    Fungal infections in the acquired immunodeficiency syndrome (1988)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 8 (1988), S. 115-131 
    Details
    ISSN: 0741-0581
    Keywords: Electron microscopy ; Fungal diagnosis ; Fungal therapy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Defects in cell-mediated immunity caused by infection with the human immunodeficiency virus (HIV) render AIDS patients particularly susceptible to fungal pathogens. Signs and symptoms of serious infection may be nonspecific, and early diagnosis and institution of antifungal therapy is essential to decrease morbidity and mortality in this patient population. In a symptomatic individual, invasive procedures are often required to establish a microbiologic diagnosis, and histopathologic examination of tissue by light and electron microscopy is often the first indication of a serious fungal infection in an AIDS patient.
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    Evaluation of high-resolution electron microscopy as a method for studying Y-Ba-Cu-O superconductors (1988)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 8 (1988), S. 273-284 
    Details
    ISSN: 0741-0581
    Keywords: Superconductors ; Electron microscopy ; Perovskites ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: High-resolution transmission electron microscopes operating at 300 and 400 kV were used to investigate the crystallography and microstructure of the perovskitelike YBa2Cu3O7-x. In this paper, we evaluate the performance attainable with these microscopes both empirically and by computer modelling. Based upon the assumption that oxygen may be a key to superconductivity properties, we have also investigated the visibility of the oxygen sites as well as the heavier yttrium and barium ion positions and the lighter Cu atom positions. We propose a scheme for observing different twin orientations in these structures and hence the oxygen atom positions seen in projection for the [100] and [010].Our observations of both thick and thin regions of Y-Ba-Cu-O materials are reported as well as the problems of adjusting microscope parameters and specimen alignment to obtain interpretable images. We also give a preliminary report on the effects of heat treatment as seen in high-resolution micrographs to assess disorder of the heavy atoms and oxygen vacancies.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060080306
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  • 94
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    Structure of the M Band (1987)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 6 (1987), S. 131-141 
    Details
    ISSN: 0741-0581
    Keywords: Skeletal muscle ; Myofibrils ; Fish ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: We have studied the structure of the M band in fish skeletal muscle using thin sectioning and deep-etching rotary shadowing. A reconstruction of the M band from these images shows it to be formed by obliquely arranged struts, which join the thick filaments to each other. Thickening of the thick filaments' profiles and nodal points where the struts cross each other are responsible for the fine sublines visible in longitudinal sections of the M band region.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060060204
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  • 95
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    Ultrastructural morphometric image analysis applied to estimation of condensed chromatin in normal and neoplastic lymphocytes (1985)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 2 (1985), S. 597-609 
    Details
    ISSN: 0741-0581
    Keywords: Electron microscopy ; Morphometry ; Lymphocytes ; Lymphoma ; Nucleus ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Currently, quantitative studies of malignant lymphoma are being performed in an attempt to improve the classification of non-Hodgkin's lymphoma (NHL) for diagnostic, prognostic, and therapeutic purposes. Morphometric image analysis is one method that can be employed in cases of NHL to obtain objective data of nuclear parameters; condensed chromatin being a compartment of the nucleus best measured at the ultrastructural level. This report assesses similarities or differences in the amount, distribution, and arrangement of condensed chromatin in nuclear profiles of normal and neoplastic lymphocytes in human surgical biopsy specimens. Morphometric data derived from electron micrographs of lymphocytes in germinal centers of lymph nodes with reactive hyperplasia (three cases) and small cell types of NHL two examples of malignant lymphoma, well differentiated lymphocytic type (ML, WDL) and three cases of malignant lymphoma, poorly differentiated lymphocytic type (ML, PDL) are compared. Results indicate that the distribution of condensed chromatin, i.e., the size of aggregates, and their spatial placement within the nucleus varies more than the amount (both mean area per profile or mean volume) of this nuclear parameter, and that this applies to normal as well as neoplastic lymphocytes. When a series of condensed chromatin parameters were statistically compared, no major differences could be detected between lymphocytes in normal tissues and those in ML, WDL and ML, PDL, but considerable differences were found in each of the nuclear morphotypes in the individual cases within the groups. This degree of variation in nuclear characteristics within normal tissues and the two lymphoma categories has not been previously recognized. Clearly, the technique of morphometric analysis, as applied to electron micrographs, can provide new and useful data that must be appreciated if classification schemes currently used in NHL are to improve and reflect biologic considerations.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060020611
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  • 96
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    Mycobacterium Avium-intracellulare complex infections in the acquired immunodeficiency syndrome (1988)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 8 (1988), S. 105-113 
    Details
    ISSN: 0741-0581
    Keywords: Electron microscopy ; Histopathology ; Mycobacterium diagnosis ; Mycobacterium therapy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: This reviw examines an important bacterial infection in acquired immunodeficiency syndrome (AIDS). Despite occasional infections with bacteria such as Streptococcus pneumoniae, Haemophilus influenzae, Salmonella, and Nocardia in patients with AIDS, the primary problems of AIDS and invading bacterial infections center around mycobacteropsos. A unique feature of AIDS has been the common identification of disseminated infections with Mycobacterium avium-intracellulare. The following discussion examines our present understading of this group of organisms and how they interact with the compromised host.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060080107
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  • 97
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    Freezing and drying of biological tissues with a toggle-link helium freezer and an improved freeze-drying apparatus: Application to neuropeptide immunocytochemistry (1986)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 4 (1986), S. 315-328 
    Details
    ISSN: 0741-0581
    Keywords: Electron microscopy ; Immunocytochemistry ; Enkephalin ; Brain ; Liver ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A freezing apparatus has been developed for bringing blocks of tissue into contact with a block of sapphire chilled to 17°K. A toggle linkage minimizes rebound by slowing the rate of approach of the tissue to the cold surface to a velocity of zero. A glove box limits condensation on the surface of the sapphire, and a miniature moist chamber protects the specimen from drying and premature freezing. About 50 blocks of tissue can be frozen in an hour and a half by using 5 liters of liquid helium. The tissue is then frozendried at controlled temperature, fixed with OsO4 vapor, and infiltrated with epoxy resin in a simple bench-top freeze-drier without breaking vacuum. About two-thirds of the blocks are useful for electron microscopy. Brain tissue frozen and dried by using these methods retains enough immunoreactivity for enkephalin in plastic sections to permit its detection with immunohistochemistry by using both the light microscope (with immunofluorescence) and the electron microscope (with colloidal gold).
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060040402
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  • 98
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    Image registration in electron microscopy: Application of a robust method (1988)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 10 (1988), S. 27-33 
    Details
    ISSN: 0741-0581
    Keywords: Electron microscopy ; Image processing ; Image registration ; Robustness ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The geometric registration of two electron microscopic images generally is performed by maximizing the cross-correlation coefficient between them. We show that a new similarity measure (the number of sign changes) is useful for performing simultaneously geometric and gray-level registration. This method is robust, which means that it provides a good estimation of the parameters even in the presence of outliers that cannot be described by the registration model.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060100105
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  • 99
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    Procedural guide to specimen handling for the ultrastructural pathology service laboratory (1987)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 6 (1987), S. 255-301 
    Details
    ISSN: 0741-0581
    Keywords: Fixation ; Processing ; Electron microscopy ; Human biopsies ; Diagnosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Transmission electron microscopy serves a useful and often diagnostic purpose in the analysis of human disease. The emerging discipline of ultrastructural pathology serves a much wider field than that of kidney pathology and, of necessity, requires two essential elements. These are (1) the interpretive knowledge which covers all cells in all tissues which compose all organs, their normal substructural composition, and the ultrastructural expression of all of the basic mechanisms of the pathobiology of human disease, and (2) technically excellent preparations of these varied specimens.In this review, we emphasize the technical aspects necessary for the preparation of these specimens. These include the handling of varied specimens from the time of interruption of blood flow to the sample until fixation, fixation methodology, and routine processing methods for electron microscopy. Specialized techniques that are readily accomplished in an ultrastructural pathology service laboratory are also described. These include methods for the demonstration of glycogen, peroxidase(s), the glycocalyx. We also describe the preparation of permanent, alkaline Giemsa-stained 1-μm plastic sections for light microscopic diagnosis, the use of an agar-pelleting technique to change cell suspensions into readily handled blocks, and the use of Spurr's (J. Ultrastruct. Res. 26:31, 1969) low viscosity embedding for all skin and heavily collagenized specimens.The diagnostic report for individual samples can routinely be available within 24 hours of specimen arrival in the ultrastructural pathology laboratory with the methods we review here. Examples of these varied samples of human tissues and cells and methods for preparing them are illustrated. We have found such methods useful for diagnostic purposes, e.g., to identify the site of origin of a brain metastasis as the alveolar cell (type II pneumocyte) of the lung, based on the presence of typical lamellar (surfactant) bodies in the metastatic tumor cells (Dvorak and Monahan-Earley: Norelco Reporter 32:29-36, 1985c), as well as to describe for the first time a new tumor, such as the gut autonomic nerve (GAN) tumor (Walker and Dvorak: Arch. Pathol. Lab. Med. 110:309-316, 1986) or a cell injury process, axonal necrosis, to be characteristic of Crohn's disease (Dvorak et al.: Hum. Pathol. 11:620-634, 1980d; Dvorak and Silen: Ann. Surg. 201:53-63, 1985).
    Additional Material: 49 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060060302
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  • 100
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    Quasicrystals and noncrystallographic symmetry (1987)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 7 (1987), S. 277-282 
    Details
    ISSN: 0741-0581
    Keywords: Electron microscopy ; Electron diffraction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: New findings on quasicrystals with icosahedral, octagonal, decagonal, and dodecagonal symmetries obtained recently in the Beijing Laboratory of Electron Microscopy, Chinese Academy of Sciences, are presented. Special emphasis is put on the relation between quasicrystalline and crystalline structures. The important role played by electron diffraction and high-resolution electron microscopy in revealing these quasiperiodic structures is pointed out.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060070406
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