bluuebunny/crossref_metadata_2025 huggingface dataset:
EELS log‐ratio technique for specimen‐thickness measurement in the TEM
Authors: Malis T. , Cheng S. C. , Egerton R. F.
Published: February 2005

We discuss measurement of the local thickness t of a transmission microscope specimen from the log‐ratio formula t = λ In (It/I0) where It and I0 are the total and zero‐loss areas under the electron‐energy loss spectrum. We have measured the total inelastic mean free path λ in 11 materials of varying atomic number Z and have parameterized the results in the form λ = 106F (E0/Em)/ln (2βE0/Em) where F = (1 + E0/1,022)/(1 + E0/511)2, the incident energy E0 is in keV, the spectrum collection semiangle β is in mrad, and Em = 7.6Z0.36. This formulation should allow absolute thickness to be determined to an accuracy of ±20% in most inorganic specimens.
Technique for preparing cross‐section transmission electron microscopy specimens from ceramic oxide braze joints
Authors: Santella Michael L. , Fisher Alex T. , Haltom C. Paul
Published: February 2005

A method for preparing cross‐section transmission electron microscopy specimens from alumina and partially stabilized zirconia braze joints is described. The technique relies on masking a mechanically dimpled 3mm disc in order to avoid preferential thinning of the metallic braze filler alloy during ion milling. The results presented show that specimens made by this technique are suitable for characterizing the fine microstructural details of interfacial reactions at oxide surfaces that occur during brazing.
Analytical electron microscopy study of high Tc superconductor YBa2Cu3O7
Authors: Sabatini R. L. , Heald S. M. , Suenaga Masaki , Moodenbaugh A. R. , Jones R. H.
Published: February 2005

The high Tc superconducting material YBa2Cu3O7 shows a complex relationship between microstructure and oxygen content, which are controlled by length of heat treatment, atmosphere, and quench rate. An AEM investigation studying changes in the oxygen near edge features was undertaken. Electron energy loss spectroscopy (EELS) measurements have the important advantage that they can be made on single crystal grains, allowing orentation‐dependent studies. Both ion‐milled and crushed samples with varying O2 content were analyzed. The structure of YBaCu3O7 was determined by neutron diffraction to be orthorhombic with distinct Cu‐O chains along the b‐axis as well as Cu‐O planes in the a—b plane. Therefore, by looking for a crystallographic dependence of the oxygen K‐edge one might be able to distinguish inequivalent oxygen atoms by their core level binding energy and correlate site occupancy with varying O2 content. The EELS results on the oxygen K‐edge are strongly dependent on oxygen content, most noticeably when the c‐axis is parallel to the electron beam.
Electron microscopy study of twin behavior in GdBa2Cu3Ox and YBa2Cu3Ox
Authors: Mitchell T. E. , Roy T. , Schwarz R. B. , Smith J. F. , Wohlleben D.
Published: February 2005

Twins are ubiquitous in the perovskite superconductors. They form during cooling from high temperatures through the tetragonal‐to‐orthorhombic phase transformation. Their behavior has been studied by transmission electron microscopy using a liquid‐nitrogen‐cooled specimen holder. It is observed that extra twins sometimes form in coarse‐twinned regions to give a “refined” twin structure; this is thought to be induced by thermal stresses from the electron beam. Prolonged electron irradiation (with little beam heating) results in transformation to tetragonal with a loss of the twin structure; this is probably due to disordering of the oxygen sublattice by knock‐on displacement. The same transformations can be induced by deliberate electron beam heating. In both cases the twinned orthorhombic structure can be restored by re‐ordering of the oxygen ions, in the first case by removing the beam and in the second case by allowing the specimen to cool.
Digitization of electron micrographs: A comparison of three different types of scanners
Authors: Olofsson Anders , Kavéus Urban , Hebert Hans
Published: February 2005

Some aspects of digitization of electron micrographs have been investigated. The performances of a flat‐bed, a rotating drum, and a diode array scanner have been evaluated. Estimates have been achieved for resolution, mechanical and optical stability, and optical density response. It is concluded that for routine transmission electron microscopy of, for example, negatively stained biologic specimens, a diode array scanner produces data good enough to obtain resolutions at a level normally expected. High speed is the major advantage with this type of equipment. However, for high‐resolution work it is necessary to use a conventional scanner with a relatively slow scan speed.
Ultrathin cryosections in the plane of cell monolayers: Evaluation of their potential for antibody localization studies of the cytoskeleton
Authors: Langanger Gabriele , De Mey Jan
Published: February 2005

In spite of the fact that the preembedding method is satisfactory for the ultrastructural localization of cytoskeletal proteins, there is a need for a localization method that retains the cells' ground substance, delicate filament arrangements, and membrane‐filament interactions and provides a good delineation of ultrastructural detail. Ultracryomicrotomy, a resinless sectioning method, can combine good morphology with optimal antibody labeling. Until now, however, it has not been possible to section cell monolayers parallel to their plane of growth. This is a prerequisite for the localization of proteins along segments of filaments, contained within the section thickness. We describe such a method and give a first appreciation of its potential for antibody localization studies of cytoskeletal proteins. The method consists of seeding cells on a parallel 0.75‐mm‐thick gelatin substrate that can later be cut and used as a mounting block. An adapted negative staining has yielded a very useful delineation of the well‐preserved structures within the cells, even in combination with immunogold labeling. The latter has been in its indirect version less satisfactory in dense microfilament bundles because of penetration problems, and more satisfactory on microtubules. Clearly, the penetration properties of gold probes will have to be improved before this method will become widely applicable. The availability of a sectioning method like this will provide the basis for further progress. There will be many cases which will justify the use of this relatively more difficult approach.
Quantitative X‐ray microanalysis of biological specimens
Authors: Roomans Godfried M.
Published: February 2005

Qualitative X‐ray microanalysis of biological specimens requires an approach that is somewhat different from that used in the materials sciences. The first step is deconvolution and background subtraction on the obtained spectrum. The further treatment depends on the type of specimen: thin, thick, or semithick. For thin sections, the continuum method of quantitation is most often used, but it should be combined with an accurate correction for extraneous background. However, alternative methods to determine local mass should also be considered. In the analysis of biological bulk specimens, the ZAF‐correction method appears to be less useful, primarily because of the uneven surface of biological specimens. The peak‐to‐local background model may be a more adequate method for thick specimens that are not mounted on a thick substrate. Quantitative X‐ray microanalysis of biological specimens generally requires the use of standards that preferably should resemble the specimen in chemical and physical properties. Special problems in biological microanalysis include low count rates, specimen instability and mass loss, extraneous contributions to the spectrum, and preparative artifacts affecting quantitation. A relatively recent development in X‐ray microanalysis of biological specimens is the quantitative determination of local water content.
Quantitative X‐ray analysis of biological fluids: The microdroplet technique
Authors: Roinel Nicole
Published: February 2005

X‐ray microanalysis can be used to quantitatively determine the elemental composition of microvolumes of biological fluids. This article describes the various steps in preparation of microdroplets for analysis: The manufacturing of micropipettes, the preparation of the specimen support, the deposition of droplets on the support, shock‐freezing, and lyophilization. Examples of common artifacts (incomplete rehydration prior to freezing or partial rehydration after lyophilization) are demonstrated. Analysis can be carried out either by wavelength‐dispersive analysis, which is the most sensitive method, or by energy‐dispersive analysis, which is more commonly available. The mininum detectable concentration is 0.05 mmol · liter−1 for 0.1‐nl samples analyzed by wavelength‐dispersive spectrometry and 0.5–1 mmol · liter−1 for samples analyzed by energy‐dispersive spectrometry. A major problem, especially in wavelength‐dispersive analysis, where high beam currents are used, is radiation damage to the specimen; in particular chloride (but also other elements) can be lost. Quantitative analysis requires the use of standard solutions with elemental concentration in the same range as those present in the specimen.
Morphological alterations of the glomerular (visceral) epithelium in response to pathological and experimental situations
Authors: Andrews Peter
Published: February 2005

The glomerular (visceral) layer of Bowman's capsule is comprised of a unique population of cells which have been termed “podocytes.:” Arising from these cells are large major processes and numerous smaller foot processes which completely surround underlying glomerular capillary loops. Podocyte foot processes interdigitate with each other and are separated by spaces (filtration slits) which are designed to facilitate flow of a large amount of filtrate across the glomerular wall. Podocytes exhibit dramatic morphological changes in response to the nephrotic syndrome and some forms of acute renal failure and may play an important role in the pathophysiology of these conditions. In vitro and in vivo studies have shown that a reduction in the sialic acid component of a thick anionic surface coat plays a major role in the morphological changes that these cells exhibit in the nephrotic syndrome. Also, it has been shown that filamentous actin concentrated mainly within podocyte foot processes are the contractile elements responsible for altering the shapes of these processes. There is evidence to suggest that by altering the shapes of their foot processes, podocytes in the normal kidney are able to alter the number of fully patent filtration slits and thereby actively regulate the rate of solute efflux across the glomerular wall. In vitro and in vivo studies have indicated that cytoplasmic microtubules are probably not involved in alterations of the podocyte foot processes but do appear important in maintaining the morphological integrity of podocyte cell bodies and their major processes. In the present paper, the morphological changes which glomerular podocytes exhibit in response to the nephrotic syndrome, various forms of acute renal failure, and during in vitro incubation are discussed along with studies of the possible roles of cytoplasmic microtubules, microtubules, and the glomerular anionic surface coat in these changes.
Identification of molecules in the kidney utilizing immunocytochemistry
Authors: Kashgarian Michael
Published: February 2005

Immunocytochemistry of the kidney is a unique method to integrate physiology, biochemistry, and molecular biology with morphology. Both mono‐ and polyclonal antibody reagents are useful and each has advantages and disadvantages. Specificity with low background is of the greatest importance. Tissue preparation techniques depend on the antigen being studied as well as the methodology to be used. Pre‐ and postembedding techniques combined with visualization with peroxidase reaction products or with particulate markers such as ferritin and gold must be chosen for each individual circumstance to be studied. Important applications in the kidney have included studies of glomerular antigens, specific transport proteins, and segment‐specific antigens of unknown specificity. Future utilization of this technique with new molecular probes will greatly enhance our knowledge of the biology of the kidney.
Hypoxic injury to medullary thick ascending limbs in perfused rat kidneys: Reversible and irreversible phases
Authors: Brezis M. , Kopolovic J. , Rosen S.
Published: February 2005

The tubular epithelial cells located in the renal medulla are normally working in a hypoxic milieu. In isolated rat kidneys perfused with a cell‐free medium, the medullary thick ascending limbs of Henle's loop are selectively and reproducibly injured by the imbalance between oxygen demand and supply in this area. Hypoxic lesions rapidly progress from reversible to irreversible forms of cell damage. Reversible injury consists of chromatin margination and mitochondrial swelling, which can disappear upon restoration of an adequate balance of oxygenation. Irreversible injury consists of nuclear pyknosis and cytoplasmic fragmentation, lesions which persist after re‐oxygenation or even progress to cell death. Reversible and irreversible phases of hypoxic injury in this distal tubule segment are comparable to, but different from, those previously defined for the proximal tubule.
Image registration in electron microscopy: Application of a robust method
Authors: Bonnet Noël , Liehn Jean‐Claude
Published: February 2005

The geometric registration of two electron microscopic images generally is performed by maximizing the cross‐correlation coefficient between them. We show that a new similarity measure (the number of sign changes) is useful for performing simultaneously geometric and gray‐level registration. This method is robust, which means that it provides a good estimation of the parameters even in the presence of outliers that cannot be described by the registration model.
The use of specimen tilt in transmission electron microscopy of the central nervous system
Authors: Milroy Antonia M. , Ralston Diane D.
Published: February 2005

Thin sections of nervous tissue were viewed at different tilt angles using a transmission electron microscope equipped with a eucentric goniometer stage. In a comparison study of various degrees of tilt, one can observe additional morphological features within synaptic profiles, define subsynaptic structures such as Taxi‐bodies, and clearly see the crystalline formation of cytochemical tracers. This study demonstrates the value of tilting thin‐sections in the analysis of synapses and other biological material at the ultrastructural level.
Morphology of synapses in the autonomic nervous system
Authors: Smolen Arnold J.
Published: February 2005

The ultrastructure of synapses in the autonomic nervous system is reviewed. The synaptic organization of the parasympathetic ganglia is relatively simple. Preganglionic axons form synapses either on the soma or on short perikaryal processes of the ganglionic neurons. The presynaptic terminals have a cholinergic morphology and contain mainly small clear vesicles with a few large dense cored vesicles. A few neuropeptides have been localized to the large dense cored vesicles of these terminals. The postganglionic parasympathetic axons ramify within their target tissues where they form close associations, but not true synaptic contacts. Sites of release of transmitter are recognized morphologically as varicosities along the length of the axon that contain clusters of small clear vesicles with a few large dense cored vesicles. The organization of the sympathetic nervous system is somewhat more complex. In addition to acetylcholine, enkephalin also exists in these terminals, probably in the large dense cored vesicles. There are at least three types of ganglion cell neurons in the paravertebral portion of the sympathetic nervous system: those that contain norepinephrine alone, those that contain norepinephrine along with neuropeptide Y, and those that contain acetylcholine and vasoactive intestinal polypeptide. The first type provides innervation to the parenchyma of the target tissues, while the second mainly innervates blood vessels. The third type innervates the sweat glands. In the prevertebral ganglia, a fourth type of neuron exists that contains norepinephrine and somatostatin. This neuron probably innervates the gut. Preganglionic terminals of the cholinergic type form synaptic connections mainly with the dendrites of the sympathetic ganglion neurons. In addition to the types of synapses described for the paravertebral ganglia, neurons in the prevertebral ganglia receive synaptic connections from dorsal root ganglia and from the enteric nervous system. The sympathetic ganglia also contain interneurons that receive preganglionic synapses and form efferent synapses with some of the principal ganglion cells. The interneurons have been shown to contain a variety of transmitters, including norepinephrine, epinephrine, dopamine, serotonin, and a number of neuropeptides. The postganglionic sympathetic axons have a similar morphology to the parasympathetic axons. They form networks in their targets, and the axons display varicosities with concentrations of both small and large vesicles. After appropriate fixation, these vesicles are seen to possess dense cores. The morphology of the enteric nervous system has the greatest complexity. There are sensory neurons, interneurons and motor neurons of various types. In addition, it receives extrinsic connections from both the sympathetic and parasympathetic nervous system. The synaptic ultrastructure is correspondingly complex, with a large number of different, morphologically disticnt types of synaptic terminals. The function and transmitter content of these terminals is beginning to be elucidated.
Insulin and C‐peptide (proinsulin) packaging: A quantitative immunocytochemical approach
Authors: Hammel Ilan , Kalina Moshe
Published: February 2005

C‐peptide and insulin antigenic sites in rat pancreatic β cells were both labeled by the protein A and immunogold techniques. Gold bead density in the secretory granules was correlated with granule size distribution. Our results demonstrate that the distribution patterns of antigenic sites for C‐peptide (which also represents proinsulin sites) and insulin are similar when granule size distribution is correlated to the density of antigenic sites. It was found that the ratio of C‐peptide to insulin in granules is independent of granule size. Examination of frequency histograms by a Kolmogorov‐Smirnov analysis excluded the possibility that the antigenic sites of C‐peptide and insulin are distributed in the same manner. Mean gold bead density for insulin antigen (97 ± 24) was slightly higher than C‐peptide density (64 ± 18). The efficiency of labeling was found to be very low; less than 0.1% of the theoretically estimated antigenic sites were labeled.
Improved chondrocyte morphology and glycogen retention in the secondary center of ossification following osmium‐potassium ferrocyanide fixation
Authors: Shepard Nora , Mitchell Nelson
Published: February 2005

The use of osmium‐potassium ferrocyanide as the secondary fixative greatly improved chondrocyte preservation and stabilized the cartilage matrix proteoglycan. The proteoglycan was similar in appearance to that seen following fixation in the presence of cationic dyes. Extensive glycogen preservation was noted in these cells, occupying the area prior to and during the formation of the secondary center of ossification. The volume and organization of the glycogen within the cell cytoplasm were greater than that following buffered osmium fixation, and the cellular vacuoles within were greatly reduced.

The cells forming the secondary center prior to the onset of mineralization were of greatest interest, because other studies compared them with the primary growth plate and described them as showing signs of hypertrophy as early as 5 days postnatally, as is found in the primary growth plate. Our observations indicate that glycogen is present in these cells, and cellular enlargement was not present. The cells do not resemble the hypertrophic chondrocytes of the primary growth plate, as far as cytoplasmic content is concerned, and we suggest that they may contribute to the development of the secondary center in a different fashion.
Silver enhancement of gold probes (5–40 nm): Single and double labeling of antigenic sites on cell surfaces imaged with backscattered electrons
Authors: Namork Ellen , Heier Hans Erik
Published: February 2005

Silver enhancement of immunogold‐labeled cells was carried out to increase the applicability of colloidal gold probes for visualization in the backscatter electron imaging (BEI) mode of a scanning electron microscope. Optimum conditions were established for single particle discrimination and differential counting of labeling density at low magnifications. Red blood cells double‐labeled with 15 + 40 nm and 5 + 20 nm gold probes were silver‐enhanced for 6 min and 20 min, respectively, at which times both pairs of labels increased to about 25 + 50 nm. The gold probes still appeared spherical after enhancement and were easily discriminated. Cells were also single‐labeled with the above probes and enhanced accordingly. The present method enables visualization of individual particles of any probe size, labeling one, or simultaneously two, antigenic sites on cell surfaces. The silver enhancement procedure thereby allows cells to be labeled with small probes with increased labeling efficiency.
Achievement of atomic resolution electron microscopy
Authors: Smith David J.
Published: February 2005

Atomic‐level details are easily resolved in the latest generation of intermediate voltage electron microscopes, but structural information on the same scale can only be extracted under certain specific conditions. Some understanding of imaging theory, as well as an awareness of correct operating conditions, is required for reliable image interpretation. Several representative examples are chosen to illustrate the possibilities for atomic‐resolution imaging of materials, and perspectives and outlook for the technique are briefly discussed.
Fortran source listing for simulating three‐dimensional convergent beam patterns with absorption by the Bloch wave method
Authors: Zuo J. M. , Gjonnes K. , Spence J. C. H.
Published: February 2005

The FORTRAN source code is given for a computer program that calculates the two‐dimensional intensity distribution in convergent‐beam transmission electron microdiffraction (CBED) patterns from perfect crystals. The program uses the eigenvalue or Bloch‐ware method. It allows three‐dimensional dynamical diffraction, and so includes all higher‐order Laue zone effects without approximation. No symmetry reduction is included. The program accepts noncentrosymmetric or centrosymmetric crystal structures and allows absorption corrections to be included. It uses the “EISPACK” subroutines for the diagonalisation of a general complex matrix. Up to 100 CBED disks may be included. The code is also available via “Bitnet”.
Ultrastructural features of the AIDS virus (HIV) and its morphogenesis
Authors: Nakai Masuyo , Goto Toshiyuki , Imura Shunro
Published: February 2005

HIV particles were usually seen on the surface of established lymphoid cells derived from AIDS patients or on CEM cells infected with HIV, and sometimes in cytoplasmic vacuoles. The virus particles were formed by a budding process from the plasma membrane of an infected cell. The budding particles were of a doughnut form. Various profiles of virus particles were seen extracellularly: type 1 had a bar‐shaped, electron‐dense core, type 2 had a central and type 3 an eccentric electron‐dense round core, type 4 was doughnut‐shaped, and type 5 had a layered core. However, projection patterns of the AIDS virus model suggested that type 1, 2 and 3 particles are similar. Therefore, the AIDS virus may be one of three main types: with or without a dense core, and with a layered core. It is thought that a particle with a layered core and a doughnut‐type particle may be immature viruses.
Fine architecture of the splenic terminal vascular bed as revealed by arterial and venous pressure‐loading perfusion fixation
Authors: Suzuki Teruo , Hataba Yoshiaki , Sasaki Hiroyuki
Published: February 2005

The three‐dimensional fine architecture of the red pulp of human and animal spleens, which as fixed by a modified version of the arterial and venous pressure‐loading perfusion fixation (AVPL perfusion fixation) method, is demonstrated by scanning and transmission electron microscopy. In the human spleen, changes in splenomegalias associated with hereditary spherocytosis and chronic portal hypertension are also introduced in addition to the normal architecture of the red pulp of spleens removed from patients with stomach cancer. The AVPL perfusion fixation of these spleens clearly visualized complicated three‐dimensional fine architecture of the red pulp and provided much important information on in situ morphology and dynamic change of the terminal vascular bed, including venous pressure‐dependent size change of the stomata and three‐dimensional shapes of the capillary terminal, with positive proof of their opening into the cordal reticular tissue. In studies of the spleen associated with portal hypertension, the AVPL perfusion fixation is considered a necessary technique for analysis of the structural deviation closely relating to a very high venous pressure.
Analytical scanning electron microscopy for solid surface
Authors: Ichinokawa T.
Published: February 2005

A scanning electron microscope of ultra‐high‐vacuum (UHV‐SEM) with a field emission gun (FEG) is operated at the primary electron energies of from 100 eV to 3 keV. The instrument can form the images that contain information on surface chemical composition, chemical bonding state (electronic structure), and surface crystal structure in a microscopic resolution of several hundred angstroms (Å) using the techniques of scanning Auger electron microscope, scanning electron energy loss microscope, and scanning low‐energy electron diffraction (LEED) microscope. A scanning tunneling microscope (STM) also has been combined with the SEM in order to obtain the atomic resolution for the solid surface.

The instrumentation and examples of their applications are presented both for scanning LEED microscopy and STM.
High‐resolution electron microscopy study on crystal structures of high‐Tc superconductors
Authors: Hiraga Kenji , Oku Takeo , Shindo Daisuke , Hirabayashi Makoto
Published: February 2005

Recent studies of high‐resolution electron microscopy on the high‐Tc superconductors of Y‐Ba‐Cu‐O and Bi‐Ca‐Sr‐Cu‐O are presented. The observed images of crystals thinner than 3 nm, taken under conditions that approached the Scherzer defocus condition, directly show the arrangements of cations and oxygen‐vacant positions. The results reveal structural characteristics of the atomic scale; this offers important insights into the origin of the high‐Tc superconductivity. The usefulness of high‐resolution electron microscopy for studying complicated crystal structures is demonstrated for the high‐Tc oxides.
Ultrastructural demonstration of exocytosis in the intact rat adrenal medulla
Authors: Carmichael Stephen W. , Brooks Jack C. , Malhotra Ravi K. , Wakade Taruna D. , Wakade Arun R.
Published: February 2005

Evidence is presented for morphological proof of exocytosis in the rat adrenal medulla in situ. Techniques were modified to allow perfusion of the intact adrenal gland with secretagogues (or electrical stimulation) followed by tannic acid. Unstimulated specimens demonstrated exocytotic (omega‐shaped) profiles filled with flocculent material. This flocculation was also seen in the intercellular space. Stimulation of the adrenal medulla also resulted in the appearance of exocytotic profiles and an accumulation of the flocculent mass. This was often most evident in the subendothelial space. This is the first demonstration of exocytosis in the rat adrenal medulla by electron microscopy. The techniques used in this study will be useful for studying the pathway of secretory products of the adrenal chromaffin cell before they enter the vascular system.
Vagal paraganglia of the rat
Authors: Kummer Wolfgang , Neuhuber Winfried L.
Published: February 2005

Paraganglia are associated with every branch of the rat vagus nerve except the pharyngeal branch. Some of the paraganglia closely resemble the glomus caroticum, whereas others appear like small, intensely fluorescent (SIF) cells of autonomic ganglia. The paraganglionic cells of SIF cell‐like bodies (SLB) store catecholamines (the most abundant is probably noradrenaline) and in some cases neurotensin. The innervation pattern of SLB is variable and their physiological role remains unclear.

Paraganglionic cells of glomus‐like bodies (GLB) predominantly store dopamine and probably also to a lesser extent noradrenaline. These putative chemoreceptor organs receive sensory innervation from nodose ganglion neurons as revealed by degeneration experiments and by anterograde neuronal tracing. Substance P‐ and calcitonin gene‐related peptide‐immunoreactive fibres seen in the region of vascular entry into the GLB may account for some of these sensory fibres, but the peptide/classical transmitter stored in sensory terminals synapsing on paraganglionic cells is unknown. Ultrastructural immunocytochemistry revealed vasoactive intestinal polypeptide (VIP)‐immunoreactive fibres lying in the interstitial space between paraganglionic cells and large capillaries. These fibres may originate from VIP‐immunoreactive neurons, being frequently attached to GLB. The major difference between GLB and the glomus caroticum concerns their blood supply and related innervation: Arteries and arterioles do not penetrate into GLB and, accordingly, noradrenaline‐ and neuropeptide Y‐containing nerve fibres are lacking within GLB. This peculiar arrangement of paraganglionic parenchyma and arterial blood supply may be one of the reasons for the different physiological properties of vagal and carotid arterial chemoreceptors.
Immunocytochemical localization of neuropeptides in the adrenal medulla
Authors: Pelto‐Huikko Markku
Published: February 2005

The distribution of neuropeptides exhibits pronounced interspecies heterogeneity. Neuropeptides may function as hormones secreted from chromaffin cells or as neurotransmitters/neuromodulators released from nerve terminals. However, other possible functions such as trophic or intracellular effects should also be considered. Thus, to understand the role of neuropeptides, it is important to explore their localization in different species. The distribution of enkephalins, neurotensin, neuropeptide Y, calcitonin gene‐related peptide, and galanin in the adrenal medulla of rat, cat, hamster, and mouse is presented in detail.
Glucocorticoid‐induced pnmt‐immunoreactive sympathetic cells in the superior cervical ganglion of the rat
Authors: Päivärinta Heikki , Pickel V. M. , Eränkö L. , Joh T. H.
Published: February 2005

Light and electron microscopic immunocytochemical techniques were used to study the effect of glucocorticoids on the development of phenylethanolamine‐N‐methyltransferase (PNMT)‐immunoreactive cells in the superior cervical ganglion (SCG) of early postnatal rats. Rats were injected daily with hydrocortisone acetate on postnatal days 2—6. The first PNMT‐immunoreactive cells were detected 6 hours after the first glucocorticoid injection and their number increased after subsequent injections. No PNMT‐immunoreactive cells were detected in uninjected controls. PNMT‐immunoreactive fibres were seen in the ganglion 6 hours after the first glucocorticoid injection. The PNMT‐immunoreactive cells consistently showed processes 2 days after beginning the glucocorticoid treatment, and long processes and fibre networks were seen in ganglia of 7‐day‐old rats. However, no PNMT‐immunoreactive fibres were seen in the iris, which is innervated by the SCG.

Ultrastructurally, most of the PNMT‐immunoreactive cells had the look of small granule‐containing (SGC) cells, including heterochromatin clumps along the nuclear envelope and in the center of the nucleoplasm as well as dense core vesicles. SGC cells, nonimmunoreactive to PNMT antiserum, also were seen. However, some PNMT‐immunoreactive cells showed ultrastructural characteristics of nerve cells. In contrast to the SGC cells, these cells were characterized by a voluminous cytoplasm, dispersed nuclear heterochromatin, and a lack of granular vesicles. These results demonstrate that glucocorticoids induce PNMT immunoreactivity both in SGC cells and also in cells with characteristics of principal neurons.
Practical phase identification by convergent beam electron diffraction
Authors: Mansfield John
Published: February 2005

The purpose of this article is to present a practical guide to the identification of phases in the analytical electron microscope with the aid of convergent beam electron diffraction. There is included a step‐by‐step approach to phase analysis, from the possible choices of the form of the specimen through how to explore reciprocal space in order to perform a full phase identification, either by symmetry analysis or by simple comparison of a pattern observed in the microscope with a previously recorded pattern (fingerprinting). There is a strong emphasis on practical hints and useful shortcuts.
Determination of unit cell
Authors: Ayer Raghavan
Published: February 2005

The ability to obtain diffraction patterns with a large angular view has significantly enhanced the ease and potential of electron diffraction studies in the determination of unit cells and identification of submicron phases. Convergent beam electron diffraction (CBED) provides a two‐dimensional projection of the three‐dimensional reciprocal lattice and can be utilized to reconstruct the unit cell dimensions. In particular, the spacing of the reciprocal lattice layers parallel to the electron beam and the location and distribution of the reflections in the first and higher order Laue zones with respect to the zero layer provide information which cannot be obtained from the zero layer pattern alone. This additional information permits the identification of crystal structures of phases under investigation with previously established ones or the determination of new structure, if previously unknown. The article describes the principles of the analysis and illustrates the application of the methods with examples from commercial material systems.
Convergent beam diffraction studies of interfaces, defects, and multilayers
Authors: Cherns D. , Preston A. R.
Published: February 2005

This paper explains how the convergent beam electron diffraction (CBED) and large angle convergent beam (LACBED) techniques can be used to study crystal defects, bicrystals, and multilayers. It is shown how the LACBED technique in particular can be used to derive the magnitude and sign of the Burgers vectors of dislocations and displacements at stacking faults. For bicrystals and multilayers examined in plan‐view, LACBED gives the rocking curve for a chosen reflection. This enables layer strains to be measured to ∼ 0.1% and composition profiles derived for both periodic and aperiodic structures. It is shown that a simple kinematic approach can be used to interpret the essential results in most cases.
Freeze‐fracture cytochemistry: Review of methods
Authors: Severs Nicholas J.
Published: February 2005

“Freeze‐fracture cytochemistry” encompasses a diversity of recently developed techniques in which freeze‐fracture and cytochemistry are combined. Cytochemical labeling may, in principle, be integrated into one of three basic points in the standard freeze‐fracture procedure; (1) before the specimen is frozen, (2) after it has been fractured, or (3) after it has been platinum shadowed and/or carbon coated. Visualization of the labeled cellular structures can be achieved by a variety of different methodologies. For example, the markers (usually colloidal gold particles) may be viewed embedded within a replica, or attached to it via fragments of membrane (or other cellular components). Sectioning is a central strategy in a number of techniques, either in combination with or in place of replication. The different combinations of methods that have been devised are not, for the most part, alternative ways of arriving at the same result; each provides quite distinct information about specific classes of membrane component or other structure in the cell. The purpose of this review is to present, within a single article, a systematic survey of the full range of techniques currently available in freeze‐fracture cytochemistry. Emphasis is placed on explaining the principles underlying the methods and on illustrating their applications. With the success recently achieved, freeze‐fracture cytochemistry has moved from the phase of experimental development to a position in which it may be expected increasingly to make significant contributions across a wide spectrum of problems in cell and membrane biology.
Freeze‐fracture of lipids and model membrane systems
Authors: Hope Michael J. , Wong Kim F. , Cullis Pieter R.
Published: February 2005

Model membrane systems are used extensively in all aspects of membrane research, and freeze‐fracture is the preeminent procedure for directly visualizing local structure in these lipid dispersions. Here we describe in detail the formation of liposomes and how freeze‐fracture is routinely employed as a complementary technique to biophysical and biochemical procedures in the characterization of multilamellar vesicles (most commonly known as liposomes) and unilamellar vesicles. Many preparative procedures exist for the formation of multi‐ and unilamellar vesicles. Examples of each system are given and their properties as well as freeze‐fracture morphology are discussed. The detection of lipid‐phase transitions is considered, in particular, with emphasis on the application of freeze‐fracture to the study of lipid polymorphism. We briefly discuss the fracturing of apolar lipids which do not adopt bilayer structures but which can be stabilized into microemulsions by a phospholipid monolayer. Finally, a critical assessment is made of filipin as a morphological marker for cholesterol domains in the plane of the bilayer.
Preparing and analyzing fractured archaeological fibers
Authors: Angel Allen , Jakes Kathryn A.
Published: February 2005

A technique was developed to prepare archaeological fiber cross sections for electron microscopic examination and x‐ray analysis. Use of this new method allows chemical and morphological information to be obtained from the interior of a single fiber or yarn. Fibers are fractured while frozen and then freeze dried. Following mounting and carbon coating, fibers are examined by scanning and backscatter electron microscopy and then analyzed by using energydispersive spectrometry. Elemental distribution is mapped by using image‐processing software. In this report, the described technique is employed in the examination of ancient fibers from three different long‐term storage environments (moist buried, dry buried, museum stored). Data obtained by examining the interior of fibers such as these provide insight into the conditions of a fiber's growth, the treatments applied during the fiber's processing and use, and the conditions in which the fiber was stored.
Morphology of rat exocrine pancreas prepared by anhydrous cryo‐procedures
Authors: Roos Norbert , Kinde Ulla , Morgan John A.
Published: February 2005

This paper describes and compares the morphology of a relatively complex tissue, the exocrine pancreas, prepared by state‐of‐the‐art anhydrous cryoprocedures. Cryopreparative procedures are being used increasingly for a wide range of applications, for example, electron‐probe x‐ray microanalysis and immunocytochemical localization of antigenic molecules, because they preserve the composition of the specimen better than procedures involving aqueous media. Some doubts have remained concerning the morphology of cryosections and the precise identification of subcellular structures.

We show that thin and sufficiently large cryosections of fresh biological tissues can be produced using commercially available hardware. The freeze‐dried cryosections display high intrinsic contrast, are stable under the beam, and allow identification of intracellular fine structure.
Fine structure of hepatocytes during the etiology of several common pathologies
Authors: Schaff Zsuzsa , Lapis Karoly
Published: February 2005

Hepatocytes respond to injury by a few basic pathological reactions that are reflected in cell death, different types of degeneration, regeneration, or tumorous transformation. At the ultrastructural level, alterations of cell organelles can be observed in different combinations as a result of the injury, depending on the etiological agent(s) or pathological conditions developed. Nuclear bodies, dilation and fragmentation of rough endoplasmic reticulum (rer), swelling of mitochondria, and an increased number of lysosomes occur during acute viral hepatitis. The core and surface components of the hepatitis B virus can be localized in the liver cells in chronic hepatitis and in carriers. Close contact of hepatocytic and lymphocytic cell membranes were observed in chronic active hepatitis. Hepatocytes surrounded by an increased amount of collagen fibers are characteristic of cirrhosis. Loosely arranged, fine fibrils or condensed forms of Mallory bodies are pathognomic for alcoholic injury. A wide spectrum of alterations are noted after drug treatment: the proliferation of smooth endoplasmic reticulum (ser) as an adaptive phenomenon, focal or complete necrosis of the cell, inflammation, and the like. The fine structural analysis of hepatocytic inclusions in storage diseases has a differential diagnostic value. The storage of copper and other elements can be measured by x‐ray microanalysis. The study of the hepatocytic differentiation in liver tumors is highly important in establishing the diagnosis and in proving the hepatocytic origin of the tumor.
Sinusoidal endothelial cells of the liver: Fine structure and function in relation to age
Authors: Margreet De Leeuw A. , Brouwer Adriaan , Knook Dick L.
Published: February 2005

Liver endothelial cells form a continuous lining of the liver capillaries, or sinusoids, separating parenchymal cells and fat‐storing cells from sinusoidal blood. Liver sinusoidal endothelial cells differ in fine structure from endothelial cells lining larger blood vessels and from other capillary endothelia in that they lack a distinct basement membrane and also contain open pores, or fenestrae, in the thin cytoplasmic projections which constitute the sinusoidal wall. This distinctive morphology supports the protective role played by liver endothelium, the cells forming a general barrier against pathogenic agents and serving as a selective sieve for substances passing from the blood to parenchymal and fat‐storing cells, and vice versa. Sinusoidal endothelial cells, furthermore, significantly participate in the metabolic and clearance functions of the liver. They have been shown to be involved in the endocytosis and metabolism of a wide range of macromolecules, including glycoproteins, lipoproteins, extracellular matrix components, and inert colloids, establishing endothelial cells as a vital link in the complex network of cellular interactions and cooperation in the liver. Fine structural studies in combination with the development of cell isolation and culture techniques from both experimental animal and human liver have greatly contributed to the elucidation of these endothelial cell functions. Morphological and biochemical investigations have both revealed little changes with age except for an accumulation of iron ferritin and a decrease in the activities of glucose‐6‐phosphatase, Mg‐ATPase, and in glucagon‐stimulated adenylcyclase. Future studies are likely to disclose more fully the role of sinusoidal endothelial cells in the regulation of liver hemodynamics, in liver metabolism and blood clearance, in the maintenance of hepatic structure, in the pathogenesis of various liver diseases, and in the aging process in the liver.
Ultrastructure and function of hepatic fat‐storing and pit cells
Authors: Geerts Albert , Bouwens Luc , Wisse Eddie
Published: February 2005

The present paper reviews the literature on the ultrastructure and function of sinusoidal fat‐storing cells and pit cells in the mammalian liver.

Ultrastructurally, fat‐storing cells are characterized by the presence of cytoplasmic fat droplets, well developed rough endoplasmic reticulum; a Golgi complex; multivesicular bodies; one or two centrioles; and few, rather small, lysosomes. These lysosomes are sometimes associated with fat droplets. Fat‐storing cells may bear a cilium and project characteristic cytoplasmic processes into the space of Disse. These processes contain microtubules and filaments. Fat‐storing cells are the main storage site of retinol esters in the mammalian body. Moreover, these cells have the potential of synthesizing several connective tissue components including the collagens type I, III, and IV; fibronectin; laminin; heparan sulfate; chondroitin sulfate; and dermatan sulfate.

Pit cells are polarized cells, with most organelles localized at one site of the nucleus near the cytocentre. They are characterized electron microscopically by the presence of dense cytoplasmic granules with a specific ultrastructure, by rod‐cored vesicles, and by multivesicular bodies. It has recently been shown that pit cells have natural killer activity to certain tumor cells and have many features in common with large granular lymphocytes. They therefore may act in the liver as a first line of defense against neoplasia, metastasis, and viral infections.
Improved sectioning and ultrastructure of bacteria and animal cells embedded in lowicryl
Authors: Bénichou J. C. , Fréhel C. , Ryter A.
Published: February 2005

Lowicryl K4M‐embedded Gram‐positive and Gram‐negative bacteria have a tendency to separate between the cell surface and the resin. This often leads to distortion of bacteria and more especially of mycobacteria. We describe attempts made to overcome this technical problem. Different assays were made on Bacillus subtilis, Escherichia coli, and Mycobacterium avium: (1) Modification of the bacterial surface by coating of bacteria with proteinic compounds; (2) treatment of bacteria with metallic salts known to modify cell wall polysaccharides; and (3) comparison between Lowicryl K4M and HM20.

Conditions have been found in which the separation of all bacterial species from the resin is abolished. The most important factor appeared to be the treatment of bacteria before dehydration, with 0.5% uranyl acetate for 30 min. The second most important factor, especially for M. avium and to a lower extent for Gram‐negative bacteria, was the use of Lowicryl HM20. Pre‐embedding in gelatin instead of agar improved sectioning of M. avium, but had no effects on the other bacterial species. These conditions applied to macrophages infected with Shigella dysenteriae or M. avium also gave excellent results.

In addition to sectioning improvement of bacteria, uranyl acetate improved the ultrastructure of bacteria and macrophages. All organelles were more clearly delineated and, hence, more easily identified. Finally, it was shown that UA treatment did not affect immunogold labeling of a variety of antigens.
Microstructure and growth of ZnTe films
Authors: Chaudhuri Subhadra , Mondal Abdulla , Pal Arun Kumar
Published: February 2005

The microstructure and growth of ZnTe films deposited onto glass and freshly cleaved NaCl substrates are carefully studied by a TEM. Effect of different stimulator on the grain growth is also described.