bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine structural cytology of the adenohypophysis in rat and man
Authors: Horvath Eva , Kovacs Kalman
Published: February 2005

The present review deals with the use of electron microscopy in the identification of pituitary cell types as well as the assessment of their functional state, in rat and man. Application of immunoelectron microscopy, especially immunogold techniques, utilizing multiple labeling in establishing differentiation and hormone content of cell types, is emphasized. Recent evidence of plurihormonality in various pituitary cell types indicates that the once axiomatic one cell‐one hormone theory is untenable and that the present perception of pituitary cell types and their function requires modification. Detection of hormonal and nonhormonal substances in pituitary cell types, not associated with their known endocrine function, suggests that hypophysial cells may have yet unknown roles, possibly in the realm of paracrine and autocrine regulation.
Junctional complexes and cell polarity in the urinary tubule
Authors: Brown Dennis , Orci Lelio
Published: February 2005

In this review, we demonstrate how differentiated membrane domains can be detected in epithelial cells using conventional light and electron microscopy, freeze‐fracture electron microscopy and the immunoand cytochemical detection of membrane components. Using specific examples from the kidney, we show how the polarized insertion of these components into either apical or basolateral plasma membrane regions on either side of the tight junction barrier is related to specific functions of principal and intercalated cells in the collecting duct. In addition, distinct basal and lateral membrane domains have been revealed in some cells that are maintained in the absence of a tight junctional barrier in the plane of the membrane. This suggests that other factors, possibly related to cytoskeletal elements, may be involved in the functional segregation of these membrane areas. We propose that epithelial cell plasma membranes should be subdivided into apical, lateral and basal regions, and that the term “basolateral” may be an oversimplification.
Relationship between structure and function in renal proximal tubule
Authors: Welling Larry W. , Welling Dan J.
Published: February 2005

Epithelia which support large transepithelial fluid movements are generally found to have histologic specializations which increase the surface areas of the cell membranes across which flows occur. A relationship between structure and function seems obvious in those cases. On the other hand, the area increasing specializations may also result in complicated shapes for the cells and their adjacent intercellular channels. In this paper we review the means for examining cell shape by quantitative stereologic techniques and the results obtained for the epithelium of the proximal renal tubule. We conclude that cell shape not only is a critical ingredient in any structure‐function correlation for that tissue but also a “fingerprint” and a powerful tool with which one can predict and study epithelial absorptive flows and their driving forces.
Morphology of the minipig kidney
Authors: Dobyan Dennis C. , Bulger Ruth Ellen
Published: February 2005

The minipig has a multilobar kidney with a wide cortex and short papilla. The vascular bundles are of a simple type. Although short and long looped nephrons are both present, the short looped kind predominates. The minipig has many morphological similarities to dog and human kidneys. One particularly unique feature of the minipig papillary collecting duct cells, however, is the presence of electron‐dense granules in the basal cytoplasm which appear to be secreted into the lateral intercellular spaces, perhaps forming a water‐tight seal in a manner analogous to membrane‐coating granules found in the epidermis of skin.
Ultrastructural investigation of renal biopsies: A discussion of artifacts and special methodology
Authors: Olsen T. Steen , Racusen Lorraine C. , Solez Kim
Published: February 2005

The aim of this presentation is to draw attention to the problems inherent in evaluating the ultrastructure of percutaneous renal biopsies and to discuss some of the special techniques which are useful in this area. It is important to realize that the ultrastructure as it appears in this kind of material does not necessarily reflect conditions in vivo. Comparison with suitable reference material may, however, permit reliable conclusions in terms of pathological diagnosis and pathogenesis. It is advocated that purely qualitative methods, which until now have predominated in ultrastructure work with renal biopsies, be replaced by morphometry and semiquantitative methods when it is possible and practical to do so in any research situation.
Correlation averaging of a badly distorted lattice: The surface protein of Pyrodictium occultum
Authors: Hegerl Reiner , Baumeister Wolfgang
Published: February 2005

The surface protein of the archaebacterium Pyrodictium occultum forms two‐dimensional periodic arrays of extremely poor order. Two variants of correlation averaging have been applied in order to retrieve the unit cell structure from electron micrographs of negatively stained samples: straightforward correlation averaging correcting for lateral displacements only and a more elaborate approach, including a partial compensation for rotational disorder. Surprisingly, both routes yield virtually identical structures. Inclusion of molecular motifs from highly disordered domains, which are rejected in the “straightforward” approach, appears not to improve resolution, possibly because the high local strain tends to distort the individual molecules.
Volume determination of TEM specimens containing particles or precipitates
Authors: Hare Thomas M. , Russ John C. , Lane Jay E.
Published: February 2005

The volume of thin foil specimens, which contain precipitate or other particles, viewed in the TEM is needed to determine particle density and spacing. It can be determined from the locations of the particles, measured using stereo pairs. A calculation that determines the volume between planes (not necessarily parallel or horizontal) that enclose the points is described. These planes will systematically underestimate the actual surface spacing and hence the volume, but a simple correction factor based on the number of points used in the fit can be used to estimate the actual volume. The method is tested, and its accuracy is evaluated using simulated data and applied to precipitate particles in creep‐tested silicon carbide.
Controlled vascular corrosion casting of the rabbit eye
Authors: Fahrenbach W. H. , Bacon D. R. , Morrison J. C. , Van Buskirk E. M.
Published: February 2005

We have refined the technique of vascular corrosion casting with methacrylate to permit the reproduction of physiological states of vascular tone and to produce sturdy castings of ocular microvasculature. The method entails careful maintenance of homeostasis up to the moment of plastic perfusion, avoidance of vascular rinsing or fixation with the attendant anoxia, reduction of the viscosity of the casting resin without impairing the properties of the resultant polymer, addition of a cross‐linking agent to increase the strength of the plastic, and injection at physiological temperature and pressure. This casting regimen reproduces the normal anatomical conditions of blood vessels and can be used to demonstrate altered conditions of vascular tone. In all instances, the second, untouched eye serves as a control for unilateral manipulations. Special problems of replicating the ocular vasculature are related to the intraocular pressure, which opposes the vascular perfusion pressure and constitutes an impediment to perfusion.
An accurate temperature monitoring device for balzers rotary cold tables
Authors: Barry Vanwinkle W. , Graham William F.
Published: February 2005

In the Balzers rotary cold table, the recording thermocouple is located 45 mm below the specimen stage. As a result, there is inconsistency between the temperature indicated by the thermocouple gauge and the actual temperature of the specimen carrier. This inconsistency is most notable and can lead to problems when the cold table temperature is changed, such as during the procedure when fracturing at one temperature is followed by etching at a higher temperature.

In this article, we describe modifications to the Balzers rotary cold table that permit the constant measurement of actual specimen temperature in the stationary, off, and rotating positions. The changes involve the use of a miniature temperature‐sensing diode (TFD‐Omega), mounted on the cradle that accepts standard counterflow, rapid‐loading specimen stages.
Laboratory use of the personal computer: A program in MS‐DOS BASIC, for generating specimen labels and data sheets for electron microscopy
Authors: Ulrich Roger G.
Published: February 2005

Conventionally, all specimen vial and block labels are handwritten or typed, a labor‐intensive process open to human error, particularly in a lab that processes large numbers of samples. The computer program described in this report was developed to reduce or elimiate this problem. The program is menu‐driven, asking specific information from the user, and runs on an IBM PC (or compatible). It is designed to accurately produce specimen collection vial labels, resin block labels, and data sheets for inclusion in a research notebook. A task that in the past may have required much time at the typewriter can now be accomplished without error in a few minutes. Although designed to fit the needs of a pathology laboratory, the program (written in BASIC) can be easily modified to fit other applications.
Structural and functional correlates of synaptic transmission in the vertebrate neuromuscular junction
Authors: Rash John E. , Walrond John P. , Morita Michio , McCracken Thomas O.
Published: February 2005

Because vertebrate neuromuscular junctions are readily accessible for experimental manipulation, they have provided a superb model in which to examine and test functional correlates of chemical synaptic transmission. In the neuromuscular synapse, acetylcholine receptors have been localized to the crests of the junctional folds and visualized by a variety of ultrastructural techniques. By using ultrarapid freezing techniques with a temporal resolution of less than 1 msec, quantal transmitter release has been correlated with synaptic vesicle exocytosis at discrete sites called “active zones.” Mechanisms for synaptic vesicle membrane retrieval and recycling have been identified by using immunological approaches and correlated with endocytosis via coated pits and coated vesicles. In this review, available ultrastructural, physiological, immunological, and biochemical data have been used to construct an ultrastructural model of neuromuscular synaptic transmission that correlates structure and function at the molecular level.
A surface durable and strongly bonded phosphor viewing screen for T.E.M.
Authors: Beauregard Paul
Published: February 2005

A simple procedure is described for the preparation of a totally inorganic, durable, strongly bonded, and non‐shrinking phosphor viewing screen. The procedure requires no special apparatus or skills in order to prepare a fairly uniform high resolution screen in only about 0.5 hours plus drying time. The screens are suitable for use on an automatic exposure system where mechanical shock can destroy a screen.
Synaptic organization of primary axons in trigeminal nucleus oralis
Authors: Falls William M.
Published: February 2005

This report examines the morphology and synaptic connections of small‐diameter primary trigeminal axons that terminate in the border zone (BZ) and ventrolateral (VL) subdivisions of rat trigeminal nucleus oralis (Vo). Primary axons were made visible for light and electron microscopic analysis by utilizing the method of anterograde transport of horseradish peroxidase. BZ receives the terminal arborizations of two different populations of small‐diameter primary axons. One of these arises from unmyelinated parent fibers and terminates in the dorsal one‐half of BZ, while the other has small myelinated parent branches that arborize throughout the subdivision. Terminating within VL are the arbors of a second population of small myelinated primary axons. The endings of all three populations of primary axons lie in synaptic glomeruli. Endings in both subdivisions derived from small myelinated parent fibers lie centrally in glomeruli. Those in VL form axodendritic synapses on numerous dendritic shafts and spines, while endings in BZ glomeruli make at least one axodendritic synapse on one or two dendritic shafts. Endings of unmyelinated primary axons in BZ lie at the periphery of glomeruli where each forms a single axodendritic synapse on a central dendrite. It is at these asymmetrical axodendritic synapses that these three populations of primary axons are thought to transfer their inputs directly to the dendritic arbors of second‐order BZ and VL neurons. Common to all three glomeruli is one or more small axonal endings filled with flattened synaptic vesicles that establish axoaxonic synapses on the primary ending as well as axodendritic synapses on the dendritic element(s) receiving primary input. In view of their symmetrical to intermediate synaptic contacts, these endings are thought to belong to axons derived from at least one source that can inhibit or diminish the firing rate of second‐order BZ and VL neurons in response to primary input.
Cellular mechanisms controlling the strength of synapses
Authors: Wilson Charles J.
Published: February 2005

The mechanisms suspected as contributors to the regulation of synaptic strength act at a variety of sites along the causal chain that links activity in a presynaptic neuron to activity in a postsynaptic one. At several places in this chain, morphological factors are expected to have a powerful influence, and at several others, key insights into the mechanisms controlling synaptic action have been achieved using morphological techniques. A variety of presynaptic mechanisms controlling the release of neurotransmitter have been most directly shown to regulate the potency of synaptic connections. Traditional interpretations of the effect of postsynaptic geometry on synaptic strength need to be reevaluated in light of new views of the functional properties of dendritic membrane, and the new neurophysiological data must be incorporated into a more comprehensive view of the behavior of spatially distributed excitable membrane with specific patterns of distributed synaptic inputs.
Digital image processing of crystalline specimens examined by electron microscopy
Authors: Kanaya Koichi
Published: February 2005

Crystalline specimens imaged in the electron microscope are analysed using digital processing. Some principles of structural analysis using the method of Fourier decomposition are discussed. Complementary techniques, such as enhancement by gradient and Laplacian operators, have been found useful in analysing electron micrographs.

The application of these techniques to some problems in Materials Science and Biology are reviewed. By selecting and phase‐correcting spots in the computed diffraction pattern, it was possible to localize atoms, molecules, and their defective arrangement in evaporated gold, sputter‐deposited tungsten films, and single crystals of cadmium selenide.

Digital processing based on the theory of helical diffraction was used to explore the three‐dimensional arrangement of molecules in cellular components of alveolar soft part sarcoma, Hirano bodies, and neurofibrillar tangles in the human brain.
Differential morphometric values induced in Golgi apparatus of higher plant cells by aldehyde and permanganate fixation
Authors: Gonzalez‐Reyes José A. , Gracia‐Navarro Francisco , Garcia‐Herdugo Gregorio , Hidalgo Antonio , Navas Plácido
Published: February 2005

In order to determine the best conditions to carry out quantitative ultrastructural studies in plant specimens, five different fixation techniques, including some of the most reported electron microscopy fixatives (glutaraldehyde‐paraformaldehyde, osmium tetroxide, potassium permanganate), were assayed in onion root meristems to check their ability to induce morphometric changes in Golgi apparatus ultrastructure. Although the parameters evaluated showed in all cases the same tendency, values obtained after permanganate fixation were always higher than those found after aldehyde techniques (especially aldehyde‐osmium). Aldehyde followed by osmium fixation appears as the most indicated fixation method when accurate quantitative ultrastructural studies are to be developed.
A new freeze‐drying device for platinum replica studies of cell surface and cytoskeleton: An example using immunogold‐labeled human erythrocytes
Authors: Lupu Florea , Constantinescu Elena
Published: February 2005

We designed and built a freeze‐drying device that ensures the protection of the specimens against contaminants during mounting on the cold stage of the freeze‐fracture machine, transferring into the vacuum chamber and deep etching. The device consists of a copper cap that covers the specimen and a thermal connection that ensures thermal transfer between the microtome arm and the copper cap. This device was used to study the ultrastructural features of the erythrocyte membrane skeleton and the immunocytchemical localization of spectrin in an “in situ” approach, by freeze drying and platinum rotary shadowing. Human erythrocytes adhered to polylysine‐coated coverslips and were broken by a stream of buffer that mimics the intracellular ionic environment (“inside buffer”). The samples were prefixed in periodate‐lysine‐paraformaaldehyde fixative, labeled with antispectrin 5‐nm gold particles, fixed in glutaraldehyde, mordanted in tannic acid, postfixed in OsO4, repeatedly washed in water, rinsed quickly in 30% ethanol, freeze‐dried, and rotary‐shadowed. Electron microscopic examination of the replicas revealed the skeletal network on the inner surface of the erythrocyte membrane. Immunocytochemical labeling proved that spectrin represents a fibrillar component of the network. Our data confirm the speculative model of the molecular organization of the erythrocyte skeleton, based on studies on in vitro association of proteic constituents. Both the technique and the device developed by us may lead to a deeper understanding of the spatial organization of the cytoskeletal network of more complex cell types.
Calibration methods for quantitative image processing in electron microscopy
Authors: Lamvik Michael K. , Davilla Scott
Published: February 2005

An image can be represented digitally as a matrix of numbers. When those numbers are linearly related to a property of the object, such as mass per unit area, a simple integration of an image area leads to a total of that property, such as the mass of a particle that is represented in a selected area.

Following techniques pioneered by Bahr and Zeitler, we illustrate the use of photographic densitometry of films exposed in an electron microscope to measure electron scattering. The transmission of an electron micrograph will be linear with respect to mass thickness for a particular value of background brightfield density, hence allowing determination of the mass of microscopic particles. We show here a digital computer method for conveniently establishing the linear condition by quantitative image processing using micrographs of polystyrene spheres. The method also serves to produce calibration curves for cases where the transfer from transmission to mass thickness is not linear. We also illustrate how an inexpensive computer is used to display and integrate regions of micrographs to determine particle mass.
Preparation of collagen gel matrices for light and electron microscopy
Authors: Turner J. W. , Sandra A.
Published: February 2005

Cells grown on type I hydrated collagen gels require special techniques for sample preparation and processing in order to optimize the removal of all reagents from the collagen matrix and prevent artifactual shrinkage. This method includes cutting out a small block of the collagen gel, postfixation, and transfer to a scintillation vial for further processing. These additional steps ensure that all sides of the block will come in contact with solutions and reduces the possibility of reagent trapping within the collagen matrix. Additionally, in our study the collagen gel and endothelial cells that form a monolayer on the surface are oriented to allow the microtomist greater assurance of cutting true cross sections, thus saving time and increasing reproducibility. The dehydration sequence is also modified, with an increase in the times and additional steps, especially in the higher concentrations of dehydrant.
Which image parameter(s) for the automation of the electron microscope?
Authors: Bonnet N. , Zinzindohoue P.
Published: February 2005

Experiments on automating the transmission electron microscope rely on the search for minimum variance. This image parameter gives satisfactory results for automatic focusing, astigmatism correction, and beam alignment. We investigate here the different image descriptors that might also be used; we conclude that texture parameters, which are directional, would be better candidates correcting astigmatism and beam tilt.
Examples of high‐resolution electron microscopy (HREM) investigation of complex oxides related to perovskite
Authors: Hervieu Maryvonne
Published: February 2005

The properties of oxides may be drastically influenced by their microstructures. Thus the knowledge of nonstoichiometric mechanisms is an essential tool for the conception of new inorganic compounds by solid‐state chemist. Through three chosen examples of complex oxides with perovskite‐related structure, these points are illustrated. The new families of phosphate tungsten bronzes, the antiferromagnetic AMn1 − x FexO3 – y, and the copper oxides LCuO3 – x (La = Ba, Y, La) were studied by high‐resolution electron microscopy (HREM) in order to analyze the mechanisms of nonstoichiometry, the defects of which can modify their physical properties (magnetism or electronic conductivity) and the factors that govern their stabilization.
Electronic core level microanalyses and microscopies in multipurpose apparatus
Authors: Cazaux Jacques , Gramari Daniel , Jbara Omar , Mouze Dominique , Nassiopoulos Androula , Thomas Xavier
Published: February 2005

Using an instrument equipped with two electron guns, an electron analyzer, and a Si(Li) diode detector, we developed microanalytical techniques based on inner‐shell electron excitations by incident electrons and X‐rays, that is, electron energy‐loss spectroscopy (EELS) in the reflection mode; electron probe microanalysis (EPMA) and X‐ray appearance potential spectroscopy (XAPS); electron‐induced Auger electron spectroscopy (e‐AES); X‐ray photoelectron spectroscopy (XPS), X‐ray absorption spectroscopy (XAS); X‐ray induced AES (XAES), X‐ray fluorescence analysis (XRF), and scanning X‐ray radiography (SXR). The corresponding characteristic images (including X‐ray microradiography and X‐ray photoelectron microscopy) were obtained in the scanning mode. The principle of the apparatus is described. Each spectroscopy and microscopy is illustrated by an example. Their performance and limits are discussed.
Transmission electron microscopy studies in relation to production of solar cells from polycrystalline silicon sheets (R.A.D. process)
Authors: Gervais Annick
Published: February 2005

Ribbon against drop (R.A.D.) ribbons exhibit a polycrystalline texture similar to that of most melt‐grown ribbons; we review here the defects of as‐grown materials as well as after the solar cells' production.
An application of high‐resolution transmission electron microscopy to the study of the fine structure of dislocations in potassium feldspars
Authors: Zheng Yuanlin , Gandais Madeleine
Published: February 2005

An application of high‐resolution transmission electron microscopy (HRTEM) to the study of two types of dislocations in potassium feldspars (K‐feldspars) is shown here. HRTEM images were submitted to a filtering in order to improve their interpretation. One type of dislocation—(010)[001]/2—appears to be dissociated, with (010)[001]/2 planar defect, whereas the other one—(010)[110]/2—is perfect. This result helps provide an understanding of dislocation activation in this material.
Optimal preparatory procedures of cryofixation for immunocytochemistry
Authors: Ichikawa Misao , Sasaki Katsunori , Ichikawa Atsushi
Published: February 2005

To examine the optimal preparatory procedures of cryofixation for immunocytochemistry, the labeling density over the antigenic sites in cells processed by various protocols of freeze‐substitution and embedding was quantitatively evaluated. Fresh tissue blocks of gerbil parotid gland were quickly frozen by a metal contact method using liquid helium and freezesubstituted with one of the following media: 4% OsO4 in acetone or 0.4% OsO4 in acetone or 0.3% glutaraldehyde in acetone. They were then embedded in either an Epon‐Araldite mixture or Araldite 6005, which were polymerized at 60°C and 50°C, respectively. Some frozen samples substituted with aldehyde‐containing acetone were embedded in Lowicryl K4M (polymerized at —30°C). Immunocytochemical localization of amylase was examined by indirect immunostaining by using antigerbil parotid amylase antibody and protein A/gold complex. Thin sections of epoxyresin‐embedded materials were treated with oxidizing agents before immunostaining. The central dense core of heterogeneous secretory granules in the acinar cells was heavily labeled with immunogold, regardless of substitution media and embedding resins employed. The labeling density on thin sections of all the cryofixed materials examined was about 1.5 times or more as high as in those processed by conventional chemical fixation. The highest value of the labeling density was obtained from material which was substituted with 0.3% glutaraldehyde in acetone and embedded in Araldite 6005. Substitution with osmium‐containing acetone appeared not to seriously affect immunoreactivity of the antigenic sites and was advantageous because of the distinctive images of membranes. Advantages and disadvantages of the individual protocols employed are discussed.
High‐resolution electron microscopy of ceramic interfaces
Authors: Ishida Yoichi , Hagege Serge , Ichinose Hideki , Takahashi Yutaka
Published: February 2005

Three observations described here were chosen not only to represent our recent interface studies in ceramics, but also to demonstrate how different the present status of interface research is with respect to the level of high‐resolution electron microscopy. Certain common features may be found among the problems of ceramic interface studies. Importance of basal plane grain boundary, for example, is one of the characteristics of this type of heterogeneous compound. The crystalline heterogeneity has been ignored largely in the grain boundary structure study since it has been developed primarily for cubic metals. The new area of basic grain boundary interface structure study is opened now that description of this type of interface has become engineeringly important.
Adrenal chromaffin cells as transplants in animal models of parkinson's disease
Authors: Hansen John T. , Bing Guoying , Notter Mary F. D. , Kordower Jeffrey H. , Fiandaca Massimo S. , Gash Don M.
Published: February 2005

The field of neural transplantation has moved rapidly forward in the last decade. Initially, fetal cells were used as implants to investigate their potential to ameliorate deficits in animal models of Parkinson's disease. However, because of the moral and legal problems associated with the use of fetal tissues in humans, alternative sources of donor tissue were sought which possessed the structural and functional characteristics needed to improve motor function in Parkinsonian patients. To date, one of the most promising tissues being investigated is the adrenal medulla, whose chromaffin cells possess an inherent plasticity of form and function. Transplanted chromaffin cells currently are being studied by a variety of approaches, including electron microscopy, in mouse, rat, and primate models of Parkinson's disease. An overview of the role of the chromaffin cell in this exciting and clinically important arena is briefly reviewed, with an emphasis on the fine structure of implanted chromaffin cells.
Mitotic cell division in the extraadrenal chromaffin system of various species
Authors: Mascorro Joe A. , Yates Robert D.
Published: February 2005

Mitotic activity often has been reported in embryonic and fetal sympathetic neuroblasts, principal sympathoblasts, and primitive sympathetic cells in various species at different stages of development. Postnatal adrenal medullary cells also are known to undergo mitosis, but such dividing capabilities rarely have been observed in the true postnatal extraadrenal chromaffin system. Although few in number, this work nevertheless has clearly identified such cells in varying stages of the mitotic cycle in the young dog, Syrian hamster, mouse, rabbit, and rat. The dividing cells were noted in paraaortic chromaffin organs, paraganglia, and within the inferior mesenteric ganglion as well. They displayed the morphological character usually associated with their adrenal medullary catecholaminergic counterparts, including numerous dense‐cored vesicles known to be the harbingers of catecholamines and various peptides. Nerve endings were not noticed upon the mitotic cells. The phenomenon of dividing extraadrenal chromaffin cells augments existing data and perhaps suggests that these cells are more endocrine than neural in type and subservient to the adrenal medulla in its classic endocrine function.
The cytoplasmic matrix of the adrenal chromaffin cells of rats under normal and stressed conditions
Authors: Kondo Hisatake
Published: February 2005

In embedment‐free electron microscopy with polyethylene glycol embedding and subsequent deembedding, the conventional cytoplasm of the chromaffin cells was revealed to consist of a three‐dimensional lattice of microtrabeculae and gives the impression that the chromaffin granules are held in place by the lattice. After the restraint stress, a substantial number of chromaffin cells were almost free of granules, and the microtrabecular lattice was much more compact than that in cytoplasmic regions occupied with remaining granules or increased mitochondria. In immunocytochemistry, actin immunofluorescence was confined to the subplasmalemmal regions, while tubulin and tropomyosin immunofluorescence appeared throughout the entire cytoplasm of normal chromaffin cells. After the stress, the immunofluorescence for actin and tubulin increased in intensity, while that for tropomyosin decreased. Immunogold labelings for actin and tubulin were found mainly on the thinner subplasmalemmal microtrabeculae and the thicker perikaryal ones, respectively, while some were deposited in the form of small aggregates on portions of microtrabeculae. No specific association between the gold labelings for actin or tubulin and the chromaffin granules was found, even in the subplasmalemmal regions. A hypothetical interpretation was proposed in which a more compact lattice of the microtrabeculae in spatial association with a looser lattice represents a gelated state of the cytoplasm. The significance of the gel—sol transition of the cytoplasmic matrix in relation to the secretory mechanism was discussed.
Development and plasticity of adrenal chromaffin cells: Cues based on in vitro studies
Authors: Hofmann Hans‐Dieter , Seidl Klaus , Unsicker Klaus
Published: February 2005

Neural 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

Sympathetic 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

The 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

The 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

Convergent‐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: A personal history
Authors: Steere Russell L.
Published: February 2005

The sequence of events leading to the development of freeze‐fracture replication is described. Subsequent developments discussed include complementary replicas, replica interpretation with stereo micrograph and reversal negatives, replica reinforcement, and control of resistance evaporation.
Freeze‐fracture of manufactured foods
Authors: Humphreys Susie H.
Published: February 2005

Manufacture 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

We 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

Oxygen‐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

We 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

Following 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

A 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

This 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.