bluuebunny/crossref_metadata_2025_split huggingface dataset:
Renal cell culture
Authors: Kreisberg Jeffrey I. , Wilson Patricia D. 
Published: February 2005

AbstractMethods for the establishment and growth of renal cell types in culture are reviewed, with emphasis on current trends. General techniques available for the isolation and culture of glomerular cells have progressed from explant to enzyme dissociation and cloning techniques. The growth characteristics and properties of cultured glomerular endothelial, epithelial, mesangial, and bone‐marrow‐derived cells are discussed. Studies are described in which cultures of contractile mesangial cells have led to an elucidation of their role both in normally functioning glomeruli and in disease states. Renal tubule culture techniques also have progressed from mixed tissue explants and cell isolates to fractionation of enriched tubule populations and growth of specific, individually microdissected proximal convoluted, proximal straight, thick ascending limb of Henle's loop, and collecting tubules. The differentiated tubule epithelial‐specific properties of such primary cultures are discussed in relation to those of permanently growing cell lines such as MDCK and LLC‐PK1. Renal tubule cultures will be invaluable for the study of the role of hormones and extracellular matrix in epithelial growth and polarity of normal structure and function. In addition, in vitro models of cultured renal tubules have been established to study the effects of age, nephrotoxins, and anoxic injury.
Introduction to the computer image processing of electron micrographs of two‐dimensionally ordered biological structures
Authors: Stewart Murray 
Published: February 2005

AbstractMethods are described for the analysis of electron micrographs of regular biological objects. Fourier‐based processing of one‐dimensionally ordered arrays is described by way of introduction, before analysing two‐dimensional crystals in projection with the aim of enhancing signal:noise ratio and thus of feint features that were initially obscured. This form of analysis is then extended to decomposing the moiré patterns formed when sheets overlap, thereby enabling the separation of interfering image patterns. Analogous forms of an analysis can also be applied to objects with rotational symmetry. Methods for treating the effect of the microscope imaging system and compensating for lattice disorder in crystalline specimens are also discussed.
Computer image processing of electron micrographs of biological structures with helical symmetry
Authors: Stewart Murray 
Published: February 2005

AbstractMethods are described for the analysis of electron micrographs of biological objects with helical symmetry and for the production of three‐dimensional models of these structures using computer image reconstruction methods. Fourier‐based processing of one‐ and two‐dimensionally ordered planar arrays is described by way of introduction, before analysing the special properties of helices and their transforms. Conceiving helical objects as a sum of helical waves (analogous to the sum of planar waves used to describe a planar crystal) is shown to facilitate analysis and enable three‐dimensional models to be produced, often from a single view of the object. The corresponding Fourier transform of such a sum of helical waves consists of a sum of Bessel function terms along layer lines. Special problems deriving from the overlapping along layer lines of terms of different Bessel order are discussed, and methods to separate these terms, based on analysing a number of different azimuthal views of the object by least squares, are described. Corrections to alleviate many technical and specimen‐related problems are discussed in conjunction with a consideration of the computer methods used to actually process an image. A range of examples of helical objects, including viruses, microtubules, flagella, actin, and myosin filaments, are discussed to illustrate the range of problems that can be addressed by computer reconstruction methods.
Three‐Dimensional reconstruction of single particles from random and nonrandom tilt series
Authors: Radermacher Michael 
Published: February 2005

AbstractTo overcome the radiation damage‐induced limitations to the resolution of three‐dimensional reconstructions from electron microscopic tilt series, novel reconstruction schemes have been developed that require only a single exposure of the specimen. The tilt series collected with these methods have random projection directions. First, three‐dimensional reconstruction techniques are described that are applicable to data obtained from tilt series with regular tilt geometry, followed by the extensions of these techniques to permit analysis of projection series with randomly spaced tilts. The main emphasis is placed on the weighted back‐projection methods, which have recently been extended so as to be applicable to random tilt series. Besides a description of the algorithms, the complete procedure for a threedimensional reconstruction from a single‐exposure, random conical tilt series is explained, including the determination of the azimuthal angles, the alignment scheme for conical tilt series, the dependence of the achievable resolution on the number of projections for regular conical and single‐axis geometries, and the method to calculate the actual resolution of two‐dimensional image averages and of three‐dimensional reconstructions using the phase residual and Fourier ring correlation criteria. Examples are given of biological specimens to which these three‐dimensional reconstruction methods have been applied.
High‐resolution rlectron microscopic investigation of supported platinum particles reduced at high temperatures
Authors: Wang L. , Qiao G. W. , Ye H. Q. , Kuo K. H. , Chen Y. X. 
Published: February 2005

AbstractHigh‐resolution electron microscopy has been used to characterize the platinum particles supported on TiO2 or ZnO. After reduction at elevated temperatures, the metallic particles display a regular, faceted shape, and several superstructures, Pt3 Ti(C), Pt3 Ti(H), PtTi, and PtZn, have been found. These results, which may involve strong metal‐support interaction, have been confirmed by optical diffraction and image simulation.
Preparation of cultured mammalian cells for transmission and scanning electron microscopy using aclar film
Authors: Kingsley R. E. , Cole N. L. 
Published: February 2005

AbstractCommon methods for the preparation of cultured cells for concurrent light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are not completely satisfactory. This article describes how we grow mammalian cells on plastic disks made from Aclar film. Aclar is a transparent fluorinated‐chlorinated thermoplastic that contains no volatile components and is, for all practical purposes, chemically inert. Cells adhere to it readily and remain attached after fixation, dehydration, and critical‐point drying or embedding. The film also accepts heavy metal coating by ionic bombardment and is extremely stable in the vacuum of the SEM. LM observations are unhindered by Aclar, since the film is as transparent as glass. Fluorescence microscopy is possible with this film, since it exhibits no detectable autofluorescence. During SEM observation, the film has great dimensional stability, and the cells and heavy metal coating remain attached to the Aclar even under high‐resolution operating conditions. TEM processing of specimens grown on Aclar is simplified by the fact that Aclar does not stick to the epoxy resins used in EM. Furthermore, Aclar is easily sectioned and does not damage knives used in ultramicrotomy. The use of Aclar film considerably simplifies the preparation of cultured cells for all types of microscopy. This method is particularly useful in correlating surface features between SEM and TEM observations.
Synaptic organization of the globus pallidus
Authors: Difiglia Marian , Rafols Jose A. 
Published: February 2005

AbstractThe synaptic organization of the globus pallidus is reviewed with respect to present knowledge about neurons, fibers, axon terminals, and their intrinsic synaptic relationships. Information derived from studies employing Nissl stains, Golgi impregnations, lesion degeneration techniques, immunohistochemistry, and anterograde axonal labeling in various species are presented along with ultrastructural data. Studies indicate that the globus pallidus contains a principal efferent neuron with smooth or spiny dendrites and simple or complex terminal dendritic arborizations. This cell type receives convergent inputs from intrinsic and extrinsic sources and uses γ‐aminobutyric acid as a transmitter. A smaller and separate population of pallidal projection neurons contains acetylcholine. Two other less frequent neuronal types, of small and medium size, have also been recognized. Three to six types of axonal boutons forming synaptic contacts with pallidal neurons have been recognized in various studies. Among these, three types (types I, II, and III) are the most prevalent. Studies indicate that the most frequent category (type I) originates from neostriatal neurons via radial fiber projections and contains immunoreactive GABA and enkephalins. The synaptic architecture of the globus pallidus is dominated by a mosaic‐like arrangement of long dendrites that are ensheathed by longitudinally oriented axons making synapses en passant. Triadic synapses involving dendrites that are pre‐ and postsynaptic are encountered infrequently. Because both striatopallidal and pallidothalamic connections are inhibitory, pallidal target neurons in the thalamus may be “disinhibited” when the neostriatum is activated.
Synaptic organization of the striatum
Authors: Gerfen Charles R. 
Published: February 2005

AbstractThe striatum, the main component of the basal ganglia, is composed of mainly one type of neuron, the so‐called medium spiny neuron. This neuron cell type, which constitutes over 90% of striatal neurons, is the major output neuron of the striatum. Combined ultrastructural neuroanatomical methods have elucidated the organization of afferent connectivity to these neurons. The major physiologic function of striatal efferent activity appears to be inhibition of tonically active GABAergic neurons in the globus pallidus and substantia nigra pars reticulata. Thus, the excitatory input from the cerebral cortex, whose afferents make asymmetric synapses with the spines of medium spiny neurons, appears to drive the efferent activity of the striatum. Other extrinsic and intrinsic afferent synapses are situated in a position to regulate the effect of the corticostriatal excitatory input to the medium spiny neurons. For example, dopaminergic afferents from the midbrain make mainly symmetric synapses with the spine necks and dendritic shafts of the medium spiny neurons. Medium spiny neurons themselves have local axon collaterals, in addition to their efferent axon that exits the striatum, which serve to link together local clusters of medium spiny neurons. These local axon collaterals, which contain either GABA, substance P, or enkephalin, also make mainly symmetric synapses with the necks of spines or dendritic shafts of medium spiny neurons. Other afferents with similar synaptic connections to these neurons arise from cholinergic or somatostatinergic striatal intrisinic neurons. Additionally, the patterns of extrinsic and intrinsic afferents to medium spiny neurons and their extrinsic projections are related to the organization of medium spiny neurons into two mosaically organized macroscopic compartments, the striatal patches and matrix.
Determination of experimental and theoretical kASi factors for a 200‐kV analytical electron microscope
Authors: Sheridan Patrick J. 
Published: February 2005

AbstractThe relative sensitivity of an analytical electron microscope and energy‐dispersive x‐ray detector to x‐rays of various elements is investigated through an extensive kASi factor study. Elemental standards, primarily National Bureau of Standards multielement research glasses, were dry‐ground into submicrometer‐sized particles and analyzed at 200 kV accelerating potential. The effect of self‐absorption of x‐rays by the particle has been corrected for, allowing the experimental kASi factors from this study to approximate those that could be obtained from “infinitely thin” specimens.Whenever possible, elemental k‐factors were determined by the analysis of many (up to a maximum of nine) different standard materials. Experimental kASi factors were calculated for a wide range of Kα, Lα, and Mα x‐ray lines. For comparison, theoretical kASi factors, employing a variety of ionization cross sections, were computed. Good agreement is obtained between several of the theoretical k‐factor models and the experimental results. Mass volatilization of Na and K from the small glass particles during analysis is discussed, as are observations that the grinding and/or dispersing of standard materials in a liquid (such as ethanol) may promote leaching of certain elements from the particle matrix.
Use of Peldri II (a fluorocarbon solid at room temperature) as an alternative to critical point drying for biological tissues
Authors: Kennedy John R. , Williams Richard W. , Gray John P. 
Published: February 2005

AbstractA new chemical, Peldri II, is evaluated as a compound for drying soft biological tissues for scanning electron microscopy. Peldri II, a fluorocarbon, is a solid at room temperature and is a liquid above 25°C. Cells or tissues are embedded in Peldri II by immersing them in the liquid form and allowing it to solidify. Once solidified, Peldri II will sublime with or without vacuum to dry tissues, probably without introducing surface tension. Several types of cells and tissues have been examined to compare preservation with Peldri II and critical point drying techniques. No differences were detected between the two techniques when normal surface structures were examined. Peldri II appears to be a significant improvement over hexamethyldisilazane as a drying agent for scanning electron microscopy. It is also very convenient for drying large numbers of samples.
Improved preservation of bacterila capsule for electron microscopy
Authors: Jacques Mario , Graham Lori 
Published: February 2005

AbstractConventional fixation for thin‐section electron microscopy is insufficient to preserve bacterial capsular material, a highly hydrated structure which collapses during dehydration and embedding. Boyles et al. (1984, 1985) have recently introduced a modified aldehyde fixation process in which the addition of a primary amine was found to improve the preservation of actin filaments, the basement membrane material and cell surface glycocalyx of mouse tissues. To the best of our knowledge, the application of diamines to the analysis of bacterial ultrastructure has not been reported in the literature. In the present study, excellent preservation of bacterial capsular material was seen when a diamine (lysine) was used together with glutaraldehyde in conventional embedding procedures.
Magnetic field emission gun with zirconiated emitter
Authors: Troyon M. 
Published: February 2005

AbstractA magnetic‐field‐superimposed field emission gun with low aberrations and equipped with a zirconiated tungsten emitter has been developed for applications where very stable high probe currents are required. It has been tested on a conventional electron microscope at 10 kV and on an electron beam testing system at 1 kV. Probe current i = 250 nA in a probe size d = 0.4 μm is obtained at 10 kV; at 1 kV the resolution is 0.1 μm with i = 5 nA, and 0.4 μm with i = 30 nA. For these probe currents, the spatial broadening effect due to electron–electron interactions in the beam is the preponderant factor limiting the probe size.
Ultrastructural localization of DNA on ultrathin sections of resin‐embedded tissues by the lactoferrin‐gold complex
Authors: Benhamou Nicole 
Published: February 2005

AbstractLactoferrin, a DNA‐binding protein, was complexed to colloidal gold and applied on ultrathin sections of resin‐embedded plant tissues and bacterial cultures. Optimal results were obtained when lactoferrin was tagged to colloidal gold particles at pH 9.2. Postfixation with osmium tetroxide and embedding with Epon did not prevent the accessibility of the protein towards its corresponding binding sites. In plant nuclei, labeling was observed over the dense chromatin and to a lesser extent over the dispersed chromatin. Nucleolar labeling was preferentially located over the dense fibrillar component. Gold particles were also found to be associated with chloroplasts and mitochondria. In prokaryotic cells, a dispersed labeling was noted over the cytoplasm and, in some cases, the aggregation of few gold particles suggested the presence of packed DNA fibrils. Various control experiments confirmed the specificity of the labeling pattern obtained. Lactoferrin‐gold complex appears to be a valuable probe for the intracellular demonstration of DNA molecules in double‐fixed and Epon‐embedded tissues.
Observation of GaAs—AlxGa1 — x as heterostructures and quantum‐well‐wire structures using backscattered electron image
Authors: Hirayama Yoshiro , Okamoto Hiroshi 
Published: February 2005

AbstractAs a microscale tool for observing GaAs‐Alx Ga1–xAs heterostructures, backscattered electron (BE) images in the scanning electron microscope (SEM) were compared with conventional secondary electron (SE) images. BE images were found to be more sensitive to compositional differences between GaAs and AlxGa1–xAs and less sensitive to surface roughness. BE images have a spatial resolution of 10 nm or better. This method enables the nondestructive observation of ultrafine lateral periodic structures, such as quantum‐well‐wire (QWW) structures, fabricated by compositional disordering technology using focused Ga ion‐beam (Ga‐FIB) implantation into GaAs‐AlxGa1–xAs material.
Use of membrane filters and osmium tetroxide etching in the preparation of sperm for scanning electron microscopy
Authors: Van Der Horst Gerhard , Kitchin Robert M. , Curry Patrick T. , Atherton Robert W. 
Published: February 2005

AbstractA new method was developed which is suitable for the preparation of mammalian sperm for scanning electron microscopy under either laboratory or field conditions. Samples of ejaculates from humans, two ferret species, and epididymal sperm from the African elephant were diluted in Millonig phosphate buffer and then fixed in glutaraldehyde solution. A small sample of the fixed sperm suspension was diluted in the same buffer, withdrawn with a syringe, and injected very slowly onto either a cellulose acetate or a polycarbonate membrane filter. This step was essential to concentrate the dilute sperm samples. During the various dilution steps most of the granular prostatic secretions were lost. However, a protein‐like sheath, which remained attached to most sperm, obscured the surface features and had to be removed for SEM studies. It was removed by prolonged fixation/etching in 1% osmium tetroxide. Membrane filters containing sperm on their surfaces then were dehydrated, dried by the critical point drying method, and sputter coated with gold. Polycarbonate filters were superior to cellulose acetate filters in producing a flat and homogeneous background.
Application of ion‐beam etching techniques to the fine structure of biological specimens as examined with a field emission SEM at low voltage
Authors: Yonehara Katsuhisa , Baba Norio , Kanaya Koichi 
Published: February 2005

AbstractThe term “etching,” in electron microscopy, refers to the removal of specimen surface layers and includes chemical, electrolytic, and ion‐beam methods. The ion‐beam etching process is used to remove layers of a target material by bombarding it with ionized gas molecules. Recently, the method has been applied to the field of biological specimens; however, the practical procedures for such organic materials have not been developed. In the present study, we used an apparatus in which a beam of argon ions is collimated and focused by electrostatic lenses onto an appropriate target. We demonstrated the optimum conditions to observe biological specimens that were treated with osmium tetroxide and tannic acid. The specimens were examined uncoated at low accelerating voltage using a field emission scanning electron microscope.According to our experiments, when a biological specimen was observed under high‐resolution conditions at over 50,000x magnification, the optimum condition of ion‐beam etching consisted of an accelerating voltage of E = 1 keV and an ion‐beam dose of It = 360 ∼ 400 μA. min, depending on parts of the specimens. In order to decrease overetching, we had to choose factors such as E = 1 ∼ 2 keV and It = 500 μA. min.
Three‐dimensional morphometrical study of dendritic spines of the granule cell in the rat dentate gyrus with HVEM stereo images
Authors: Hama Kiyoshi , Arii Tatsuo , Kosaka Toshio 
Published: February 2005

AbstractNumber, length, and diameters of dendritic spines of the granule cell in the dorsal leaf of the rat dentate gyrus were measured by using high‐voltage electron microscope stereo images of 5‐m̈m‐thick Golgi preparations with the aid of a three‐dimensional image analyzer system.Spine densities of 2.02 ± 0.28, 2.28 ± 0.33, and 3.36± 0.35 per 1 μm at distal, middle, and proximal portions of the dendrite were obtained. These values were about 1.6‐fold of the previous light microscopical report.Mean three‐dimensional spine length were 1.244 ± 0.506 μm, 1.262 ± 0.563 μm, and 1.254 ± 0.584 μm at distal, middle, and proximal portions, respectively, which were about 1.4 times longer than those measured in two dimensions.By using measured morphometrical parameters of spines such as lengths, diameters, and population densities, total spine surface areas of 2.401 μm2, 2.806 μm2, and 4.180 μm2 per 1 μm of the dendrite at distal, middle, and proximal portions, respectively, were obtained. The total surface area of dendrite was about doubled by the addition of the spines at each dendritic portion.The advantageous features and the problems of the present method are discussed.
Lysosomal movements during heterophagy and autophagy: With special reference to nematolysosome and wrapping lysosome
Authors: Sakai Masahiro , Araki Nobukazu , Ogawa Kazuo 
Published: February 2005

AbstractRecent studies on lysosomal movements during heterophagy and autophagy performed in our laboratory for the past several years were reviewed; methods for the investigation of lysosomes and the cytoskeleton in these studies mainly involved electron microscopic cytochemistry.Lysosomal movements during heterophagy were observed in cultured rat alveolar macrophages taking up horseradish peroxidase (HRP) and rat peroxidase‐antiperoxidase (PAP) by fluid‐phase pinocytosis and adsorptive pinocytosis, respectively. A characteristic lysosomal change which was induced by the pinocytosis was the appearance of long, threadlike lysosomes (nematolysosomes) in the cytoplasm. The effects of actin filament destabilizer and antimicrotubular drug on lysosomal changes revealed that the appearance of nematolysosomes was dependent on the presence of both actin filaments and microtubules. The close morphological relationship between lysosomes and cytoskeletal elements, such as actin filaments and microtubules in the alveolar macrophages, supports the participation of the cytoskeletal system in the regulatory mechanism of lysosomal movements.In the study of the lysosomal wrapping mechanism (LWM), which is one type of lysosomal movement that occurs during autophagy, it was found that the occurrence of LWM was dependent on energy—namely, the supply of ATP—and on the presence of actin filaments. However, deconstruction of microtubules induced or favored the occurrence of LWM. It is conceivable that the LWM is also related to the cytoskeletal system.We conclude that intracellular dynamics of lysosomes during heterophagy and autophagy are largely a consequence of complicated modulation by the cytoskeletal system.