bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of confocal scanning laser microscopy in experimental pathology
Authors: Smith Gary J. , Robert Bagnell C. , Bakewell William E. , Black Kurt A. , Bouldin Thomas W. , Earnhardt Todd S. , Hook Gary E. R. , Pryzwansky Katherine B. 
Published: February 2005

AbstractConfocal scanning laser microscopy (CSLM) represents an exciting new tool for scientific disciplines which focus on mechanistic studies such as experimental pathology. Enhanced resolution in the specimen plane and rejection of out‐of‐focus fluorescence flare allow analysis of specific nucleic acid sequences, enzymes, structural macromolecules, and cellular homeostasis utilizing fluorescent probes. Four different experimental applications are discussed which utilize CSLM to evaluate pathological processes at the subcellular, cellular, and tissue levels. Programmed cell death, or apoptosis, is a natural process of significance both during development and as a response to toxic stimuli. CSLM‐imaging of nuclei of human B lymphoblastoid cells following exposure to a monofunctional alkylating agent suggests that the degradation of chromatin characteristic of apoptosis may occur in asymmetric patterns. Surfactant apoprotein‐A is the major non‐serum protein component of pulmonary surfactant and is essential for the extracellular function of surfactant. CSLM of alveolar type II cells suggests that apoprotein‐A is present in both the cytoplasm, predominantly in lamellar bodies, and in the nucleus. The tumor promoter, phorbol myristate acetate, rapidly stimulated the formation of vacuoles in human neutrophils. CSLM using Lucifer Yellow as a probe suggests that cylindrical vacuoles are formed by fluid‐phase pinocytosis. The blood‐nerve barrier (BNB) in peripheral nerves may be an important target during toxin‐induced neuropathies. Ricin‐induced permeability of the BNB in the rat was rapidly visualized by CSLM as leakage of fluorescein isothiocynate (FITC)‐dextran into the endoneurial compartment.
Large‐area plan‐view sample preparation for gaas‐based systems grown by molecular beam epitaxy
Authors: Howard David J. , Paine David C. , Sacks Robert N. 
Published: February 2005

AbstractWe describe a method for plan‐view transmission electron microscopy (TEM) sample preparation that takes advantage of extreme etch‐rate selectivity in GaAs and AlAs in HF/H2O solutions. GaAs/InxGa1‐xAs/GaAs strained‐layer films (x = 0.05, 0.10, 0.19, 0.22) were chemically lifted off using this technique and were mounted on Cu TEM grids such that TEM transparent areas of up to 1 × 2 mm of constant thickness (196.4 nm) could be viewed. This simple, large‐area plan‐view technique uses only chemical methods and significantly extends the usefulness of TEM for the evaluation of crystal quality in GaAs‐based epitaxial systems. The method requires the growth of a release layer of AlAs (10 nm thick) prior to the layered structure of interest.
Comparisons of the low‐resolution structures of ornithine decarboxylase by electron microscopy and X‐ray crystallography: The utility of methylamine tungstate stain and butvar support film in the study of macromolecules by transmission electron microscopy
Authors: Stoops James K. , Momany Cory , Ernst Stephen R. , Oliver Robert M. , Schroeter John P. , Bretaudiere Jean‐Pierre , Hackert Marvin L. 
Published: February 2005

AbstractThe structure of ornithine decarboxylase (Mr ≈︁ 1.04 × 106) from Lactobacillus 30a was investigated by electron microscopy and x‐ray crystallography. Electron micrographs showed the structure to be well preserved in methylamine tungstate stain. The molecules interacted little with the Butvar support film, yielding three unique projections: a hexagonal ring (front view) and two rod‐shaped projections (edge views). Stereo pairs revealed a novel feature of the Butvar film in that some molecules were suspended in the stain in random orientations. Consequently, the relatedness of the hexagonal ring and the rod‐shaped particles could be demonstrated since some particle shapes interconverted when the stage was tilted ± 45°. The two edge views were related by a 30° rotation about the sixfold axis. Image averaging of the three primary views suggested a dodecamer (point group symmetry 622) composed of two hexameric rings, apparently in an eclipsed configuration. To investigate the structural organization of the complex, the dissociation of the enzyme was studied by electron microscopy. The dissociation process involved the initial breakage of the ring followed by separation of dimers from the ring (one subunit from each of the two hexamers). Thus, the dodecamer forms as a hexamer of dimers rather than a dimer of hexamers. These structural studies were confirmed and extended by x‐ray crystallographic analysis. A 4.0‐Å resolution electron density map revealed two hexameric rings, consisting of six closely associated dimers, tilted approximately 10° with respect to the molecular twofold axis. Electron density projections of the three primary views of the molecule derived from the x‐ray data corresponded closely to those obtained from image averaging of the electron microscopy data, thereby establishing in a novel way the reliability of the electron microscopy studies. Methylamine tungstate stain and Butvar support film therefore offer unique advantages for investigating protein structures by electron microscopy.
A rapid method for the preparation of yeast for immunoelectron microscopy using lowicryl hm‐20
Authors: Anderson Wayne H. , Thompson Ed W. , Zwizinski Craig W. 
Published: February 2005

AbstractWe describe a fixation and embedding procedure for the yeast Saccharomyces cerevisiae using Lowicryl HM‐20 which is rapid, gives excellent fixation, and avoids the low temperature handling normally associated with embedding in this resin. This procedure yields superior structural preservation when compared to the commonly used rapid embedding procedure which employs Lowicryl K4M. We demonstrate that sections prepared using our rapid procedure are suitable for use in immunogold labelling experiments.
Preservation of EDTA‐expanded grid‐mounted chromosomes and nuclei for electron microscopy using a specially designed freeze‐dryer
Authors: Woods Philip S. , Ledbetter Myron C. , Tempel Neal 
Published: February 2005

AbstractWe describe methods for freezing and drying EDTA‐expanded, fixed metaphase chromosomes and nuclei, attached to grids as whole‐mounts, for transmission electron microscopy. These methods use a special apparatus that is simple to construct. While separate freezers and dryers are commercially available, one for freezing blocks of tissue by slamming them against a cold metal surface, and the other for vacuum drying the frozen tissue, our apparatus is designed for gentler, cryogenic liquid plunge freezing and drying, sequentially, in the same apparatus, thus avoiding any compression or damage to the sepcimen. Use of a cryoprotectant is not essential; however, good results are obtained more often when 20% ethanol is used. Freezing is accomplished by rapid propulsion of the grid, with specimens attached, into slushy N2 (‐210°C) within the drying chamber; drying is automatic, by either sublimation under vacuum or by solvent substitution using absolute ethanol followed by acetone, which, in turn, is removed with a critical‐point dryer. The apparatus offers a means of drying chromosomes and nuclei in an expanded state, and avoids the shrinkage of these structures that occurs during stepwise passage through increasing concentrations of ethanol or acetone.
The structure of the developing chick retinal pigment epithelium revealed by high resolution scanning electron microscopy
Authors: Weiser B. A. , Hollenberg M. J. , Mandelcorn M. , Temkin R. J. , Lea P. J. 
Published: February 2005

AbstractThe retinal pigment epithelium (RPE) in the developing eye of chick embryos has been studied during the early stages of development by high resolution scanning electron microscopy (HRSEM). Specimen preparation techniques which involve removal of the cytoplasmic matrix permitted visualization of organelles and other subcellular structures within RPE cells in detail and in three dimensional (3‐D) stereo HRSEM. Using this technique, we were able to examine changes in melanosome structures during development and demonstrate that pigmentation in the RPE was present by day 4 of development. RPE plasma cell membranes showed extensive folding of the apical portion of the membrane closest to the developing neural retina by day 9. Examination of RPE photoreceptor junction revealed photoreceptor inner segments by day 6 and an outer segment by day 9. Mitochondria in the RPE were found to contain tubular cristae only. The ultrastructure in 3‐D of the Golgi apparatus, smooth and rough endoplasmic reticulum, lysosomes and nuclear chromatin of the RPE, and Bruch's layer was revealed by the HRSEM method.
A new computer‐assisted three‐dimensional reconstruction method provides accurate measurement of glomerular mesangial volume
Authors: Cho Carolyn R. , Winslow James , Whiteside Catharine , Lumsden Charles J. 
Published: February 2005

AbstractMany glomerulopathies are characterized by progressive mesangial (interstitial) expansion which can be quantitated by morphometric analysis. The purpose of this study was to analyze mesangial and glomerular volumes using a new computer‐assisted reconstruction (CAR) method. CAR was compared to two standard planar methods, point‐counting and linear integration, for accuracy and time efficiency. In Phase I of the study, a computer‐based model of the mesangial space was created by placing spherical and ellipsoidal objects of known volume into an enclosing volume mimicking the glomerulus. The simulated mesangium occupied approximately 10 percent of the glomerular volume. The model glomerulus was sectioned serially into ten sections of equal thickness and the three morphometric methods applied to determine the mesangial/glomerular volume.The complexity of the mesangial model was varied by increasing the number of mesangial regions from one to ten to 100. The CAR method estimated the model mesangial volume more accurately (1–9 percent error) through each level of complexity compared to point‐counting (3–17 percent error) and linear integration (3–18 percent error). The point‐counting method consistently overestimated (P < 0.05) the fractional mesangial volume for the ten‐ and 100‐region mesangium models.In Phase II of the study, a normal rat glomerulus was sectioned serially (215 sections) and a transmission electron micrograph (TEM) of every fifth section (n = 43) was obtained. Each TEM image (2% of glomerular surface) was digitized for analysis by CAR. Point‐counting and linear integration were also performed on the whole glomerular TEMs (n = 10, randomly chosen). The estimated relative mesangial/glomerular volume was 6.6 ± 0.1 percent by CAR (x̄ ± SD), 9.7 ± 1.5 by linear integration, and 14.9 ± 3.4 by point‐counting. The point‐counting method was most efficient, requiring 40 ± 8 sec/section, followed by CAR at 85 ± 24 sec/section. Linear integration was least efficient (93 ± 23 sec/section).We conclude that CAR is the most accurate morphometric method of the three compared for estimating mesangial and glomerular methods, although it is more time consuming than the point‐counting method and requires more complex instrumentation. CAR is the only method that will analyze the shape and three‐dimensional complexity of glomerular structures using TEMs.
The use of freeze‐substitution and lr gold in the study of rye grass (Lolium perenne) pollen
Authors: Martinez Liza B. , Wick Susan M. 
Published: February 2005

AbstractPollen grains of Lolium perenne (rye grass) were prepared for transmission electron microscopy by rapid freezing in liquid propane, substitution in acetone, methanol or diethyl ether, and embedment in the acrylic resin London Resin gold. These were compared to pollen chemically fixed (CF) in aldehyde/osmium tetroxide and embedded in the epoxy resin Quetol 651. Ultrastructural preservation was superior in freeze‐substituted (FS) pollen, particularly with the use of acetone or methanol. Optimally preserved FS pollen displayed a homogeneous aspect of the cytoplasm and nucleoplasm, and smooth, uninterrupted contour or organelles. A striking difference was also seen in the preservation of inclusions in the intine. Varied forms and sizes of intine inclusions were evident in FS pollen but these were not discernible in the CF image. The FS scheme studied here presents enormous potential for both ultrastructural and immunolabelling studies in rye grass pollen. Problems discussed include artifacts associated with each of the substitution solvents used, and a gradient of freezing damage observed within the pollen grain.
Primitive unit cell volumes obtained from unindexed convergent‐beam electron diffraction patterns
Authors: Le Page Y. , Downham David A. 
Published: February 2005

AbstractProvided that multiple reflection is present, a common occurrence with electron diffraction on microcrystallites, a single unindexed convergent‐beam electron diffraction (CBED) pattern taken with the beam axis parallel to any direct lattice row allows the volume of the primitive cell to be calculated. The film measurements required are the diameters of the successive high‐order Laue zones (HOLZ), the lengths of any two coprime vectors in the zero‐order Laue zone (ZOLZ), and the angle between them. The primitive cell volume is an objective criterion allowing in a simplification in the identification of a phase under study by rapidly eliminating other possible phases. The computer program CELVOL for the calculation of the primitive cell volume from film measurements, or from literature cells, is available from the authors.
High resolution biological scanning electron microscopy: A comparative study of low temperature metal coating techniques
Authors: Hermann René , Müller Martin 
Published: February 2005

AbstractStructural information on the surface of biological specimens can be resolved within molecular dimensions by “in‐lens” field emission scanning electron microscopes when cryo‐methods are used to adequately preserve the native state of the specimen. The visual definition of molecular surface structures depends largely on the metal coating. The thickness of the coating, as well as the temperature at which it is deposited, are among the most important parameters affecting visual definition. These were evaluated on T4 polyheads and T4D phages using chromium double‐axis rotary shadowing (DARS). Micrographs of optimally DARS coated T4 polyheads and T4D phages were compared with chromium planar‐magnetron sputtering (PMS) and unidirectional shadowing with platinum/carbon. Metal deposition was carried out at low temperatures during all three procedures.Optimal visual definition of structural details on the surface of DARS coated T4 polyheads and T4D phages (capsomeres of T4 polyheads and their subunits with diameters of 8 and 3 nm; T4D phage tail fibres with a thickness of 3 nm) is achieved at a thickness of the chromium film greater than the minimum required for metal film coalescence. Chromium DARS coating at room temperature resulted in poor structural definition, whereas DARS at specimen temperatures of −85°C and −150°C, with the chromium thickness optimized for each temperature, yielded good visual detail of polyhead substructures. The visual definition was slightly reduced when DARS coating was carried out at a specimen temperature of −250°C. Adequate structural visibility of T4D phage and T4 polyhead surface structures was achieved with the three coating techniques tested. Smaller filamentous structures, however (e.g., phage tail fibres), were more clearly identified after chromium DARS coating or unidirectional platinum/carbon shadowing than after optimized PMS with chromium. Each method has its own merits.
Ultrastructure of the seminiferous epithelium and intertubular tissue of the human testis
Authors: Kerr J. B. 
Published: February 2005

AbstractThe ultrastructural features of the human testis are reviewed with emphasis upon the process of spermatogenesis and the cytology of the Leydig cells. The seminiferous epithelium is structurally partitioned by the Sertoli cells into basal and adluminal compartments via the specialized tight junctions between the Sertoli cells. Spermatogonia reside in the basal compartment, and, via a series of cell divisions, produce the primary spermatocytes, which at the commencement of their development move into the adluminal compartment, and thus the lengthy process of meiotic maturation is initiated. The fine structure of primary spermatocytes is described together with the complex transformation of the spermatids into spermatozoa during the process of spermiogenesis. Earlier studies of the organization of the human seminiferous epithelium showed that germ cells at different developmental stages formed identifiable collections termed cell associations or stages, but since several stages were seen in a single tubule cross‐section, this gave the impression of an extremely irregular pattern of spermatogenic development. When the topographic arrangement of germ cells was re‐examined with the aid of computer modelling, a highly ordered distribution was revealed, conforming to a helical pattern based on the geometry of spirals. Thus spermatogenesis in the human testis is subjected to a precise regulation in keeping with the ordered arrangement of the germ cells seen in other mammalian species. The intertubular tissue of the human testis is composed of loose connective tissue containing blood vessels, occasional lymph capillaries, macro‐phages, mast cells, and the Leydig cells which occur either as single cells or form small clusters. The Leydig cell cytoplasm contains an abundant supply of smooth endoplasmic reticulum and mitochondria with tubular cristae, both features being characteristic of steroidogenic cells. Human Leydig cells contain large Reinke crystalloids of variable size and number, but their function remains obscure. The frequent occurrence of paracrystalline inclusions within the cytoplasm of the human Leydig cell suggests that these elements are precursors of the Reinke crystalloids.
Preparation by ion milling and TEM investigation of embedded needle‐shaped crystals of H‐Nb2O5
Authors: Krumeich Frank , Mertin Wilhelm 
Published: February 2005

AbstractA method for preparing needle‐shaped and platelike crystals for electron microscopical investigation was elaborated. Crystals of H‐Nb2O5 were embedded in a synthetic resin and disks were cut off perpendicular to the desired direction of observation. The thickness of the sample was reduced by planar grinding and then by using a dimple grinder and furthermore by ion milling with argon ions. With the precision ion milling system small crystal areas were selected and subsequently irradiated. The TEM investigations showed that the desired crystallographic orientation was reached and that the crystal structure has been preserved. The contrast of highly resolved images was reduced by an amorphous surface layer which was not removable.
Real time computer simulation of electron microscope images with tilted illumination: Grain boundary applications
Authors: Krakow W. 
Published: February 2005

AbstractComputer programs have been developed to simulate electron microscope images from digitized graphically represented model structures. Via a television rate image processing system, these programs allow real time, interactive modification of the microscope objective lens parameters, incident beam inclination, and incident beam energy. In addition to explaining the computational methods, the need for using tilted beam illumination is explored to extend microscope resolution. For this study, the subject of grain boundary imaging is analyzed for a copper σ = 5,36.9°,(310) tilt boundary with a [001] common rotation axis. The Cu {200} lattice spacings of ∼1.8Å on both sides of the interface cannot be reliably resolved under axial illumination conditions in a 200 kV microscope. Therefore, either tilted beam modes or higher incident beam energies were explored and the types of image features correlated with atomic position data through the digital frame store system.
Scanning electron microscopy of the capillary loops in the dermal papillae of the hand in primates, including man
Authors: Ikeda Akira , Umeda Naoto , Tsuda Kuniyoshi , Ohta Shigeo 
Published: February 2005

AbstractThe microvasculature of the skin of the hand in primates, including man, was examined by means of scanning electron microscopy of corrosion casts. In this study, the microvascular patterns and structures in different areas of the hand, and the changes in vascular patterns that occur with age, have been described.The typical structure of the capillary loops in the hand can be observed in the ball of the finger of the young adult monkey. The capillary loops were formed out of not just one capillary vessel, but two or three vessels. Each capillary vessel arose and divided into several branches at the papillae, and these became descending limbs. After the loop passed a hairpin turn, the descending limbs were 1.5 times larger than the ascending limbs in the intrapapillary portion, and they became extrapapillary venules. The descending limbs connected with the postcapillary venules in the postpapillary portion and with the horizontal network. The postcapillary venules fused with each other to form the primary and secondary venous arcades. The secondary venous arcades anastomosed with each other and flowed into the subpapillary venules, which run along the dermal furrow in the fingerprint.Changes in vascular patterns with age could be observed. In the infant fingerprint, the vascular systems had not yet differentiated, especially the venous system in the dermis. In the old adult finger, the capillary loops presented complicated features deviating due to aging.
Technique for preparing cross‐section transmission electron microscope specimens from ion‐irradiated ceramics
Authors: Zinkle S. J. , Haltom C. P. , Jenkins L. C. , DuBose C. K. H. 
Published: February 2005

AbstractThe general techniques necessary to produce a high‐quality cross‐sectioned ceramic specimen for transmission electron microscope observation are outlined. A particularly important point is that the width of the glued region between faces of the ceramic specimen must be < 0.2 μm to prevent loss of the near‐surface region during ion milling. A recently developed vise for gluing ceramic cross‐section specimens is described, and some examples of the effect of glue thickness on specimen quality are shown.
Dry fracturing and cutting for techniques for scanning electron microscopy of poly‐vinyl chloride particles: Application to internal structure observations
Authors: Yañez Maria Julia , De Lozano Viviana Sorrivas 
Published: February 2005

AbstractTwo methods for examining the internal structure of poly‐vinyl chloride (PVC) particles are described. Very small PVC particles, polymerized by the emulsion process, were mounted on an aluminium adhesive tape and pressed with a similar tape. Both tapes were then pulled apart so that the specimen was broken in two fractions, which were observed by scanning electron microscopy. On the other hand, bigger PVC particles manufactured by following the suspension polymerization process, were frozen and hand sectioned with a razor blade under liquid nitrogen vapor. The results were highly satisfactory. These methods were easy to implement, the cost of materials for sample preparation was negligible, and they offered the ability to obtain multiple information from a single sample.