bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development and plasticity of adrenal chromaffin cells: Cues based on in vitro studies
Authors: Hofmann Hans‐Dieter , Seidl Klaus , Unsicker Klaus 
Published: February 2005

AbstractNeural crest derived precursors of the sympathoadrenal cell lineage give rise to two major cell types that differ in a number of morphological, ultrastructural, and biochemical characteristics: principal sympathetic neurons and chromaffin cells of the adrenal medulla. The present article reviews experimental studies performed on cultured adrenal medullary cells and designed to unravel the nature of epigenetic signals governing the developmental choice between the endocrine chromaffin and the neuronal sympathetic phenotype. Emphasis is placed on the role of glucocorticoids in initiation, development, and maintenance of the endocrine chromaffin phenotype and apparently antagonistic influences exerted by nerve growth factor (NGF) in vitro, resulting in the acquisition of neuronal properties by differentiated chromaffin cells. Experimental data from in vitro studies are compatible with the following conclusions. Glucocorticoids represent the decisive signal for the initial induction of endocrine differentiation. Moreover, high steroid hormone concentrations, as present in the adrenal medulla, are a prerequisite for the maturation of chromaffin cells. Even in a differentiated state, the endocrine phenotype is unstable in the absence of glucocorticoids, and the cells seem to reenter the neuronal developmental pathway. Under these conditions, cellular survival and differentiation into sympathetic neurons become NGF‐dependent, as in normal sympathetic development. Thus, the effects of NGF survival, neurite outgrowth, and transmitter synthesis of cultured chromaffin cells probably do not reflect the induction of a specific phenotype, but they may be interpreted as a general neurotrophic support observable with other responsive cell types.
Small, intensely fluorescent cells and the paraneuron concept
Authors: Matthews Margaret R. 
Published: February 2005

AbstractSympathetic ganglia contain large principal nerve cells and, in addition, many smaller cells that resemble the endocrine cells of the adrenal medulla in morphology and chromaffinity. The advent of the formaldehyde‐induced fluorescence technique proved to be an invaluable tool for studying this unique cell type, and it was this method that accounted for their descriptive name of small, intensely fluorescent cells, now universally abbreviated to SIF cells. Electron microscopy also proved of great importance in detailing the structure of SIF cells and their relationship with neighbouring neurones. Fine structural observations revealed that the cells contained numerous dense‐cored granules, and this led to their electron microscopic name of small, granule‐containing cells. SIF cells are most abundant, and very well studied, in the rat superior cervical ganglion, where they both receive and give synapses. Early researchers suggested that SIF cells were interneurones appropriately situated between pre‐ and postganglionic elements and thus capable of influencing ganglion signals. SIF cells also are known to exist in the form of richly vascularized, compact clusters of varying size. Clustered chromaffin cells do not necessarily give rise to processes that would contact the principal neurones. The existence of singly occurring as well as clustered SIF cells has given rise to a proposed designation of type I and type II cells, with I representing the interneuronal‐like form and II possibly performing as an endocrine‐like component. Despite a wealth of knowledge concerning SIF cells, their exact role(s) in the overall functioning of the autonomic nervous system is still not completely understood.
Techniques of convergent beam electron diffraction
Authors: Vincent R. 
Published: February 2005

AbstractThe techniques required to record standard convergent beam electron diffraction patterns in an analytical electron microscope are discussed in detail, with emphasis on the design of electron optics in commercial instruments. Practical comments are included on specimen preparation, the influence of crystal defects, tilting to major zone axes, and alignment of the instrument. The influence of parameters under experimental control such as probe size, accelerating voltage, temperature, specimen tickness, and convergence angle is discussed in detail. Some comments are included on the alignment and limitations of large angle patterns formed by a defocused probe.
Applications of convergent beam electron diffraction in materials science
Authors: Eaglesham D. J. 
Published: February 2005

AbstractThe methods by which Convergent Beam Electron Diffraction (CBED) is used to solve practical problems in materials science are reviewed. Particular emphasis is placed on those applications where a consensus has developed on the potential difficulties, but these problems have never been explicitly treated in the literature. Point‐group determination using CBED is a standard technique, but there are several different experimental methods which are outlined here; the different approaches and the information obtained are compared. These point‐symmetry determinations are shown to rely heavily on elimating the large number of potential artefacts: the possible sources of symmetry‐breaking are summarised, and their salient features are identified. This should give a prescription for demonstrating whether symmetry‐breaking arises through crystal structure, defects, strain, or specimen morphology. In space‐group determinations the practical approach is now fairly standard, but the article draws attention to some anomalies. Strain and lattice parameter determinations are also standard, but a consensus is beginnning to emerge that the interpretive difficulties involved in allowing for thin film relaxation are extremely severe: a few of these difficulties are outlined. Finally, the article also addresses some of the techniques which have been used to extract structural or compositional information from CBED: the experimental approach depends on the specific problem, and the article aims to provide some examples to illustrate what is possible.
Progress toward structure determination
Authors: Gjønnes J. , Olsen A. , Matsuhata H. 
Published: February 2005

AbstractConvergent‐beam electron diffraction provides more precise measurements of diffracted intensity than the traditional method of selected‐area diffraction. The intensity is recorded at well‐defined beam directions for each reflection in the pattern within disks defined by the incident cone of rays. Measurements relating to structure factors or parameters can be arranged in different ways: intensities at the zone axis position; Kossel line profiles or integrated intensities across Kossel lines; conditions for vanishing contrast at a Kossel line (e.g., critical voltage); separation between Kossel line segments at intersections. Examples of application to refinement of structure parameters (zone axis intensities) and structure factor determination (Kossel line methods) are given.The relation of these magnitudes to theory is discussed, especially for the Kossel line methods. These are described in terms of effective Fourier potentials or gaps at the Bloch‐wave dispersion surface. Use of the methods for refinement of structure parameters and structure factors is reviewed with special attention to recent developments. This is seen along two lines: (1) extended scope for the more accurate methods in order to cover larger unit cells and (2) better precision in measurements of intensities.
Freeze‐fracture of manufactured foods
Authors: Humphreys Susie H. 
Published: February 2005

AbstractManufacture of food products with desired texture and stability increasingly benefits from an understanding of the food microstructure. Freeze‐fracture is advantageous in gaining this understanding because it avoids alterations of hydration, retains fat, and maximally preserves air cells. This paper reviews insightful applications of freeze‐fracture to various food crystals, colloids, gels, emulsions, and foams.
Time‐resolved cryotransmission electron microscopy
Authors: Talmon Yeshayahu , Burns Janet L. , Chestnut Matthew H. , Siegel David P. 
Published: February 2005

AbstractWe describe a new technique, time‐resolved cryotransmission electron microscopy (TRC‐TEM), that can be used to study changes in microstructure occurring during dynamic processes such as phase transitions and chemical reactions. The sample is prepared on an electron microscope grid maintained at a fixed temperature in a controlled atmosphere. The dynamic process is induced on the grid by a change in pH, salt, or reactant concentration by rapid mixing with appropriate solutions. Alternatively, induction is by rapid change of specimen temperature, or by controlled evaporation of a volatile component. We call such procedures on‐the‐grid processing. The dynamic process is permitted to run for a defined time and then the thin‐film specimen is thermally fixed by plunging into liquid ethane at its freezing point, producing a cryotransmission electron microscopy specimen. By repeating this procedure with varying delays between induction and sample fixation, we can observe transient microstructures. We demonstrate the use of TRC‐TEM to study the intermediate structures that form during the transitions between Lα, III, and HII liquid crystalline phases in phospholipid systems. We also identify several other possible applications of the technique.
Moiré fringe analysis of small precipitates in melt‐spun titanium‐silicon alloys
Authors: Chumbley L. S. , Fraser H. L. 
Published: February 2005

AbstractOxygen‐contaminated, melt‐spun, binary Ti‐Si alloys have been examined by using transmission electron microscopy. The microstructure of alloys in the range of 4 to 10% Si (by weight) are cellular and consist primarily of α‐Ti and the silicide Ti5Si3. Contained only within the Ti5Si3regions are small, approximately spherical particles which are ⩽ 10 nm in diameter. Due to their small size, the crystal structure of these particles could not be determined by using conventional diffraction techniques such as Selected Area or Convergent Beam Diffraction. By conducting a number of tilting experiments and observing the moire fringe patterns produced when various matrixTi5Si3 planes were used to image the sample, the crystal structure of the particles and the orientation relationship which exists between them and the matrix were deduced. The unknown particles, termed the Z phase, were found to be hexagonal with slightly different lattice parameters from the matrix Ti5Si3. Their relationship with the matrix was such that they appeared to be totally coherent. This may indicate that Z is an oxide based on the intermetallic Ti5Si3.
Effect of fixation‐resin combinations and ruthenium red on elucidating outer envelope structure and surface morphology of two methanotrophic bacteria
Authors: Fassel Theresa A. , Schaller Marilyn J. , Lidstrom Mary E. , Remsen Charles C. 
Published: February 2005

AbstractWe examined the ultrastructure of the cell envelope in Type I, Methylomonas albus (BG8), and Type II, Methylosinus trichosporium (OB3b), methane‐oxidizing bacteria by using different fixatives, ruthenium red (RR) combinations and resins. We compared LR White and Spurrembedments with the following fixations: glutaraldehyde/OsO4, two glutaraldehyde‐paraformal dehyde, and two different en bloc ruthenium red procedures, one utilizing 0sO4 and the other with glutaraldehyde/OsO4 in sequential fixation. These fixations were also studied by scanning electron microscopy (SEM). Unfixed cells prepared by freeze etch were used for comparison. Transmission electron microscopy of BG8 embedded in LR White resin (with or without ruthenium red) preserved a layer of cup‐like structures that were not seen in Spurr resin‐embedded cells unless ruthenium red was used. For OB3b, the second RR method preserved beads and filaments where only “spikelike” structures were seen in all other fixations in both resins. By SEM, all fixations preserved a capsular slime layer of BG8 that was removed from some cells by both RR methods. In all SEM fixations, a bead layer was preserved in OB3b that was enhanced by RR. Filaments seen by freeze‐etch and thin‐section techniques were not seen in SEM. Presence or absence of particular envelope structures in these methanotrophs is dependent on the combination of fixatives and/or resins employed and is species‐specific. The chemical preparation methods used resulted in enhanced understanding of the structure and composition of the cell envelope.
Rat kidney glomerular basement membrane visualized in situ by embedment‐free sectioning and subsequent platinum‐carbon replication
Authors: Kondo Hisatake 
Published: February 2005

AbstractFollowing the removal of polyethylene glycol (PEG) from thin sections, and viewing through the endothelial fenestrae and/or the interpedicel spaces, the rat renal glomerular basement membrane in situ was revealed to consist of meshworks and to be electron‐transparent when examined at right angles to the plane of the membrane. By subsequent platinum replication of the embedment‐free sections, the lamina densa of the basement membrane appeared as a veil composed of rather closely packed particles. The architecture of the slit diaphragm and the surface morphology of the endothelial cell membrane were also clearly revealed. The present results indicate that the PEG method, with or without replication, can provide valuable information on basement membrane morphology.
A novel technique for the preparation of thin films for cross‐sectional transmission electron microscopy
Authors: Heuer J. P. , Howitt D. G. 
Published: February 2005

AbstractA method is described for the preparation of cross‐sectional samples of thin films for transmission electron microscopy. The technique produces larger amounts of thin region as compared with ion milling and eliminates the problems associated with ion beam damage. The requirement is that the films or multilayers must initially be deposited on a water‐soluble substrate such as single‐crystal NaCl.
Fine structure and function of hepatocytes during development
Authors: Kanamura Shinsuke , Kanai Kazuo , Watanabe Jun 
Published: February 2005

AbstractThis paper reviews the fine structure and function of hepatocytes during fetal and postnatal development. Bile canaliculi develop to a mature appearance during perinatal and early postnatal periods, while bile secretory function is immature at birth and develops during the postnatal period. The rough endoplasmic reticulum is prominent and remains unchanged in amount during development, and the Golgi complex is large from early stages of fetal life. The smooth endoplasmic reticulum (SER) appears shortly before birth and increases in quantity to the adult level after birth. In mouse hepatocytes, Sv (area per unit cytoplasmic volume) of SER increases in perivenular cells between 1 and 10 days of age, although it remains low in periportal cells. Similarly, Sv of total ER increases in both periportal and perivenular cells between 1 and 5 days of age and then becomes greater in perivenular than periportal cells. This suggests that the postnatal increase in the drug‐metabolizing capacity occurs predominantly in perivenular hepatocytes. SER proliferates after phenobarbital (PB) administration in both perivenular and periportal cells in 3‐, 5‐, and 10‐day‐old mice, and predominantly in perivenular cells in 20‐day‐old and adult mice. Thus the conspicuous proliferation of SER in perivenular hepatocytes after PB administration, characteristic of adult liver, becomes manifest during postnatal development. In mouse hepatocytes, Vv (volume per unit cytoplasmic volume) of mitochondrial matrix and peroxisomes and Sv of mitochondrial inner membrane and cristae increase in both periportal and perivenular cells between birth and 10 days of age. Then, Vv of mitochondrial matrix remains unchanged in periportal cells but decreases in perivenular cells. In general, the process of postnatal hepatocyte differentiation appears to include several phases of development; cell organelles develop during the early postnatal period, subsequently the cells undergo both functional and structural heterogeneity, and the late postnatal period after weaning is the time for a marked increase in cell size.
Three‐dimensional fine structure of the biliary tract: Scanning electron microscopy of biliary casts
Authors: Yamamoto Kazuhide , Itoshima Tatsuya , Tsuji Takao , Murakami Takuro 
Published: February 2005

AbstractThe three‐dimensional structure of the biliary tract was studied by scanning electron microscopy (SEM) of biliary casts. The replica of the biliary tract was successfully prepared by retrograde injection of low viscosity resin into the common bile duct. Bile canaliculi are intricate networks in which hexagonal and pentagonal meshworks are interconnected. Each hexagonal or pentagonal meshwork is on a plane, but adjoining meshworks are on different planes. Bile canalicular networks connect with bile ductules at the periphery of the portal tract. The intrahepatic bile duct showed considerable interspecies variation. The human bile duct has plexiform side branches and periductal sacculi, which are most numerous near the liver hilum and fewest in the smaller portal tracts. The hilar plexus and sacculi are present on opposite sides of the bile duct. The plexus formed at the bifurcation of the bile ducts exhibits a plane. Periductal sacculi were also observed in the monkey and pig bile ducts, particularly the latter, while rat bile ducts possess a peculiar portal bile ductular plexus situated between the portal tract and the surrounding liver parenchyma. No such structures were observed in either the dog or rabbit bile ducts. SEM of the biliary casts showed that the biliary tract was not a simple draining tube but had additional structures, such as periductal sacculi and plexiform side branches. These structures, together with the peribiliary vascular plexus, may be implicated in the modification of bile.
Scanning electron microscopic study of immunogold‐labeled human leukocytes
Authors: Helinski Ernest H. , Bootsma George H. , McGroarty Roy J. , Ovak Geraldine M. , De Harven Etienne , Pauly John L. 
Published: February 2005

AbstractFor many years critical point drying (CPD) has been the method of choice for preparing cells for scanning electron microscopy (SEM). Described herein is a simple, efficient, inexpensive, reproducible, and safe procedure using Peldri II, a proprietary fluorocarbon compound that is solid at room temperature and a liquid above 25°C, as a sublimation dehydrant for processing specimens for SEM. The utility of Peldri II was demonstrated in studies using leukocytes from the blood of healthy donors and patients with leukemia as well as from long‐term lymphoblastoid cell lines. The application of the proposed Peldri II procedure was further documented in SEM studies in which the expression and distribution of the interleukin‐2 receptor (IL‐2R) on leukocyte surface membranes was imaged using colloidal gold‐labeled antibodies (i.e., immunogold). When compared with current SEM preparation procedures using CPD, Peldri II is a useful alternative that is thought to offer several important advantages.
Preparation of cross‐sectional specimens of ceramic thermal barrier coatings for transmission electron microscopy
Authors: Unal O. , Heuer A. H. , Mitchell T. E. 
Published: February 2005

AbstractDuring the microstructural examination of ceramic thermal barrier coatings by transmission electron microscopy (TEM), initial efforts for the preparation of cross‐sectional thin foils from interface regions by conventional means were mostly failures. Delamination of the Y2O3‐stabilized ZrO2 ceramic coating from the nickel‐base alloy substrate sometimes occurred during fine polishing at around 80 μm thickness but mostly occurred during dimpling. Because of this sensitivity, special techniques for mechanical handling were developed so that ion milling could give thin enough regions of the metal‐ceramic interface. TEM showed convincingly that the highly fragile nature of the coatings is in fact due to the extensive porosity at the interface developed as a result of heat treatment.
Small colloidal gold conjugated to fab fragments or to immunoglobulin g as high‐resolution labels for electron microscopy: A technical overview
Authors: Baschong W. , Wrigley N. G. 
Published: February 2005

AbstractFab‐colloidal gold labelling in conjunction with negative staining and high‐resolution electron microscopy was used for targeting single protein units in regular arrays. These were bacteriophage T4 polyheads with Fab‐Au2.5, and a specific antibody binding site on the haemagglutinin polypeptide of influenza virus with Fab‐Au3, Fab‐Au2.5, and Fab‐Au1‐2. For the latter, IgG‐Au3 was also used. Experimental details are summarized to provide generally applicable methods for the preparation of small gold colloids Fab‐Au and of labelling.The putative mechanism of protein‐gold complex formation and adsorption to preferred sites on Fab and IgG, most probably to sulphur‐rich regions, is discussed. The influence of pH during complex formation was found to be of minor importance in the samples investigated. Reported experimental details and our own experiences suggest that the importance of a protein's pI relative to its optimum gold complexing pH critically depends on the nature of the protein in question rather than being of general importance for protein‐gold complex stability.
Preparation of bone for high‐voltage electron microscopic radioautography
Authors: Pylypas Susan P. , Schurath Rodica M. , Johnson Roger B. 
Published: February 2005

AbstractThis paper presents a reliable technique for the preparation of radioautographic specimens for study by high‐voltage electron microscopy. Tissues are fixed by ventricular perfusion of aldehydes, sectioned, collected on slides, and coated with nuclear track emulsion using a coating machine. Sections are developed after 17 weeks' exposure in either undiluted Microdol‐X or diluted D‐19 developer, fixed in 25% sodium thiosulfate, and stained through the emulsion with uranyl acetate in absolute methanol and aqueous lead citrate. The technique produces sections of even thickness and staining density with negligible numbers of background grains and non‐specific labeling. In this report, the efficacy of this technique for the study of the periosteal surface of demineralized alveolar bone specimens is demonstrated.
Improved cryoprotection and freeze‐substitution of embryonic quail retina: A tem study on ultrastructural preservation
Authors: Meissner Dieter H. , Schwarz Heinz 
Published: February 2005

AbstractConditions for cryofixation and freeze‐substitution crucial to the ultrastructural preservation of embryonic quail retina were improved. As freeze‐substitution makes gentle dehydration and chemical fixation of tissue possible, the suitability of different cryoprotectants were tested in the preceding cryofixation. Additionally, different conditions for chemical prefixation were studied. In cryofixation, all of the “classic” cryoprotectants caused more or less severe tissue destruction. Only dimethylformamide (DMF) and–with certain reservations–dimethylsulfoxide (DMSO) yielded improved structure preservation. Perfusion fixation with a mixture of formaldehyde/glutaraldehyde (FA/GA) was superior to GA alone. In comparison to conventional fixation and dehydration methods, freeze‐substitution yielded better ultrastructural preservation of the embryos with fewer artifacts.