bluuebunny/crossref_metadata_2025_split huggingface dataset:
Secretory pathways in animal cells: With emphasis on pancreatic acinar cells
Authors: Beaudoin Adrien R. , Grondin Gilles 
Published: February 2005

AbstractStudies over the past three decades have clearly established the existence of at least two distinct pathways for the intracellular transport and release of secretory proteins by animal cells. These have been identified as the regulated and constitutive pathways. Many observations have indicated that in certain cells, such as those of the exocrine pancreas and parotid glands at least, these pathways coexist in the same cells. Although the general scheme of protein transport within these pathways is well established, many fundamental aspects of intracellular transport remain to be unraveled. How are proteins transported through the endoplasmic reticulum? How are the transitional vesicles formed and what are the underlying mechanisms involved in their fusion with the cis‐Golgi cisterna? Even the general mode of transfer through the Golgi stack is debated: Is there a diffusion through the stack by flow through intercisternal tubules and openings or is there a vesicle transfer system where membrane quanta hop from one cisterna to the other? What is the fate of secretory proteins in the trans‐Golgi area and by what mechanisms is a fraction of newly synthesized molecules of a given secretory protein released spontaneously while the majority of such nascent molecules are diverted into a secretory granule compartment? In this review, we have examined these and other aspects of intracellular transport of secretory proteins using pancreatic acinar cells as our reference model and we present some evidence to support the existence of a paragranular pathway of secretion associated with secretory granule maturation.
Localization of glycosylation sites in the golgi apparatus using immunolabeling and cytochemistry
Authors: Roth Jurgen 
Published: February 2005

AbstractThis review summarizes data on the distribution of certain glycosylation steps in the Golgi apparatus as revealed by immunolabeling and lectin techniques. The methodical basis for such investigations was provided by the introduction of the colloidal gold marker system for immunolabeling and the development of new means of tissue processing such as the low‐temperature embedding technique using Lowicryl K4M. The application of these techniques together with highly specific antibodies has provided much of the basis for our current understanding of the Golgi apparatus in functional terms. Thus, in many cell types, three Golgi apparatus compartments can be distinguished, whereas in others no such functional subdivision is evident. Investigations on sialyltransferase distribution have also provided direct evidence that GERL is structurally and functionally part of the Golgi apparatus.
Imaging friction tracks at diamond surfaces using reflection electron microscopy
Authors: Wang Z. L. 
Published: February 2005

AbstractReflection electron microscopy (REM) is applied to image the structure of polished natural diamond (001) surfaces (of 5 × 4 mm size) after friction experiments under a pressure below the critical value. Friction tracks marked by a diamond needle after a single pass movement under a pressure of 13 GPa can be seen in REM images and show non‐uniform contrast. The surface shows relatively dark image contrast at the light contacted area, which is possibly due to the structural modification at the top atomic layer. The high local contacting pressure pushes part of the needle into the surface which causes fracture, resulting in the formation of grooves at the surface. It is possible to have plastic deformation in this process, but no evidence has been found for the presence of cracking. The observations support the adhesion frictional mechanism rather than the micro‐cleavage model.
Fertilization‐Induced changes in the vitelline envelope of echinoderm and amphibian eggs: Self‐assembly of an extracellular matrix
Authors: Larabell Carolyn , Chandler Douglas E. 
Published: February 2005

AbstractThe surface of the unfertilized sea urchin egg is covered by the vitelline layer (VL), a fibrous extracellular matrix that contains receptors for sperm. At fertilization, cortical granule exocytosis releases enzymes and structural proteins that cause the VL to elevate and become remodelled into the mechanically and chemically tough fertilization envelope. This envelope prevents further penetration of sperm and protects the embryo during early development. A thicker, more complex vitelline envelope surrounds the Xenopus laevis egg. This fibrous coat is also restructured at fertilization to produce an impenetrable barrier to sperm. The biochemical steps that occur during self‐assembly of these fertilization envelopes are reviewed, and the ultrastructural changes that occur, as seen in platinum replicas of quick‐frozen, deep‐etched, and rotaryshadowed eggs, are illustrated.
Suitability of different silver enhancement methods applied to 1 nm colloidal gold particles: An immunoelectron microscopic study
Authors: Stierhof York‐Dieter , Humbel Bruno M. , Schwarz Heinz 
Published: February 2005

AbstractIn order to exploit the recently introduced 1 nm gold colloids in routine electron microscopic labeling experiments, an efficient enhancement step for a better visualization of this small marker is a prerequisite. Efficiency and reproducibility of enhancement as well as growth homogeneity of gold particles were evaluated for three different silver intensifying solutions: silver lactate/hydroquinone/gum arabic (Danscher, 1981), Ilford L4/Metol (Bienz et al., 1986), and the commercially available IntenSE M silver enhancement kit (Janssen Pharmaceutica). The best results were obtained by using the silver lactate/hydroquinone/gum arabic mixture. The quality of enhancement of the IntenSE M kit was considerably increased by the addition of the protective colloid gum arabic.
Influence of calcium and amino acids on the osmium impregnation of the endoplasmic reticulum
Authors: Thiery G. , Bergeron M. 
Published: February 2005

AbstractThe aim of this study was to define further the interaction between osmium and organelle content in cells prefixed with glutaraldehyde. We have studied the reaction of osmium with divalent or trivalent cations (calcium, barium, zinc, aluminum, and iron) and various amino acids in the same conditions prevalent in histological techniques, in particular with Thiéry's technique of metal impregnation. Experiments were carried out in vitro in test tubes, on cellulose acetate discs, or with an immunodiffusion apparatus. Some experiments were also carried out with tissue extracts (kidney and intestine). Our studies suggest that calcium is in general essential for the formation of osmium black, but also that lysine is reactive even in the absence of calcium and that a few amino acids–such as tryptophan, ornithine, cysteine, and aspartic acid–are only slightly reactive in the absence of calcium. Other amino acids do not seem to participate in the endoplasmic reticulum osmium impregnation even in the presence of calcium ions. Our studies also suggest that osmium reactivity reflects calcium binding sites and not only calcium content.
Three‐Dimensional imaging of fertilization and early development
Authors: Holy Jon , Simerly Calvin , Paddock Stephen , Schatten Gerald 
Published: February 2005

AbstractThe field of biological microscopy has recently enjoyed major technical advances, exemplified by the development of field‐emission low‐voltage scanning electron microscopes and laser scanning confocal light microscopes. In addition, computer processing of microscopical data is revolutionizing the way morphological information is imaged. In this paper, we illustrate methods by which this new technology can be used to examine events in fertilization and early development in three dimensions. Different types of specimen preparation protocols, using both echinoderm and mammalian gametes and embryos, are evaluated for their ability to preserve accurately the threedimensional organization of these specimens for imaging by both low‐voltage scanning electron microscopy and laser scanning confocal light microscopy.
Confocal microscopy and three‐dimensional reconstruction of electrophysiologically identified neurons in thick brain slices
Authors: Turner J. N. , Swann J. W. , Szarowski D. H. , Smith K. L. , Marko M. , Leith A. 
Published: February 2005

AbstractThree‐dimensional morphology and electrophysiology were correlated from individual neurons in a thick brain slice preparation. The hippocampal formation from immature and adult rats was cut transverse to the longitudinal axis into 500 μ Um‐thick slices which were maintained under physiologic conditions. Individual neurons were impaled and physiologically characterized using microelectrodes. Recordings were made from the soma and in some cases from a dendrite. The impaled neurons were filled through the microelectrode with the fluorescent dye lucifer yellow and imaged by confocal scanning laser microscopy using an analog preprocessor. As many as 180 optical sections were recorded as a function of depth through the slices. Images are presented as a series of optical sections, stereo pairs, or three‐dimensional reconstructions. Both stereo contouring and volume rendering methods were employed, and the reconstructions were viewed from any arbitrary perspective. Dendritic and axonal fields were separated from each other and displayed separately or as different pseudocolors. The three‐dimensional reconstructions provided perspectives that were difficult or impossible to appreciate by viewing the optical sections or conventionally formed stereo pairs.
The use of confocal microscopy and sterecon reconstructions in the analysis of sea urchin embryonic cell division
Authors: Summers Robert G. , Musial Cora E. , Cheng Ping‐Chin , Leith Ardean , Marko Michael 
Published: February 2005

AbstractA laser scanning confocal microscope has been used to investigate the development of the sea urchin embryo. The samples were fixed in Carnoy's solution at various developmental stages, stained for DNA with the Feulgen reaction, and optically sectioned with a BioRad MRC‐500 confocal microscope. Computer‐generated stereographic projection images and a three‐dimensional contour tracing and reconstruction system were employed to investigate the cleavage pattern during the 6th cleavage division. Cell division is found to be asynchronous during the 6th cleavage, with macromere derivatives completing division first, followed by mesomeres, and finally by the outer quartet of micromeres (which begins division only after macromeres and mesomeres have completed their respective divisions). Sixth cleavage produces an embryo comprising 60 cells. Asynchronous division was also observed within individual tiers of blastomeres. Variations in the orientations of cell division axes within individual tiers of cells were also observed. The utility of computer‐graphics reconstruction techniques for both quantitative and qualitative developmental analysis are discussed.
Applications of confocal microscopy to the study of myelin development and neuron structure
Authors: Staugaitis Susan M. , Rowan Todd , Sanes Dan H. , Colman David R. , Smith P. R. 
Published: February 2005

AbstractConfocal laser scanning microscopy has been used to study the localization of myelin basic proteins expressed in nonglial cells, and to probe the three‐dimensional structure of central auditory neurons in the lateral superior olive. The paper focuses on the techniques used to obtain the results. The key roles of confocal microscopy and computer image processing of the images obtained are emphasized as they relate to the discovery of essential structural information about these specimens.
Microfibril‐microvessel connections in the rabbit eye: Correlative confocal and electron microscopy
Authors: Korte Gary E. , Manche Edward E. 
Published: February 2005

AbstractThe connections between elastic tissue and microvessels (arterioles, capillaries, and venules) in the rabbit eye were examined by light and electron microscopy. In particular, confocal scanning laser microscopy of tissue stained with orcein and examined by fluorescence using a rhodamine filter was correlated with electron microscopic observations. The goal was an analysis of the way in which elastic tissue of the uvea (i.e., choroid, ciliary body, and iris) and the optic nerve of the eye connect to the microvessels in these structures. Confocal microscopy revealed these connections advantageously and showed how they link the elastic tissue meshwork in the perivascular tissue spaces with the wall of the blood vessels. Electron microscopy showed that the connections consist of bundles of 10–12 nm diameter microfilaments that insert into vascular basement membranes. These connections may contribute to the vascular response to changes in blood pressure or intraocular pressure in the eye.
Immunoalkaline phosphatase with cerium‐based cytochemistry for double staining at the transmission electron microscopic level
Authors: Rowden Geoffrey , Dean Shirley 
Published: February 2005

AbstractImmunoelectron microscopic localization of surface antigens on lymphocytes is possible using alkaline phosphatase combined with cerium‐based cytochemical methods. Distinctive electron‐dense deposits are easily identified at sites of antibody binding. Mouse splenocytes showing surface immunoglobulin localization and human peripheral blood lymphocytes stained for the MHC‐Class II antigen HLA‐DR illustrate the results. Double staining for murine Ia antigen by the alkaline phosphatase procedure, combined with immunogold labeling of antigens identified on dendritic cells, i.e., NLDC‐145, demonstrates the utility of the cerium cytochemical method.
Circular harmonic averaging of rotary‐shadowed and negatively stained creatine kinase macromolecules
Authors: Winkler H. , Gross H. , Schnyder T. , Kunath W. 
Published: February 2005

AbstractThe structure of mitochondrial creatine kinase is investigated by high‐resolution shadowing at very low temperature and conventional negative staining. The electron microscopic images are analyzed with circular harmonic averaging, a method suited for the processing of single molecules. The rotational alignment and averaging is performed with the circular harmonic components, which allows data compression and several steps of noise reduction to be carried out within the averaging procedure. In addition, the symmetry can be deduced. For the mitochondrial creatine kinase, a fourfold symmetry is found that is compatible with the biochemical and biophysical characterization of the molecule.
Loss of grain boundary segregant during ion milling
Authors: Kenik Edward A. 
Published: February 2005

AbstractIt is shown that material segregated to grain boundaries can be lost during ion milling. This specimen preparation artifact has been studied in the case of bismuth in copper and has also been observed for phosphorus in stainless steel. The loss is associated with specimen heating during ion milling and can be alleviated by good clamping and cooling of the specimen during milling. Specimen heating permits grain boundary diffusion of the segregating element to the specimen surfaces with subsequent loss of segregant from the specimen by evaporation or sputtering during ion milling. Loss of bismuth during in situ heating to 200–300°C is demonstrated. Therefore, care must be taken in specimen preparation for analytical electron microscopy measurement of such segregation. Similar effects may occur during ion milling of other materials, especially those where low thermal conductivity will result in high beam heating. In these cases, care must be taken to avoid loss of segregant during specimen preparation. Additional tests showed that no significant loss of segregant was observed during X‐ray microanalysis, even at nominal room temperature and probe currents five‐fold higher than that normally used for microanalysis.
Negative staining‐carbon film technique: New cellular and molecular applications
Authors: Robin Harris J. 
Published: February 2005

AbstractTwo techniques are presented which extend the original negative staining‐carbon film technique into new areas of cellular and molecular application. These relate (1) to the production of negatively stained specimens of single‐layer plasma membrane split from intact cells during the overall procedure that are negatively stained from the cytoplasmic face and (2) to the production of negatively stained specimens directly from glycerol‐containing protein solutions, membrane or viral suspensions. In both cases in vacuo drying onto mica from glycerol is performed, prior to deposition of a carbon film. (For the cellular technique, freshly cleaved mica is firstly rendered positively charged by immersion in Alcian blue.) This is followed by release of the carbon film plus adsorbed membrane or protein by floating onto water, with subsequent negative staining. Selected preliminary applications using human erythrocyte membrane and the high molecular weight (native) human erythrocyte tripeptidyl peptidase‐II complex are given and considered speculation as to the future application of the techniques is provided.
A fast image simulation technique for high resolution electron microscopy with multicomponent atomic species
Authors: Krakow William 
Published: February 2005

AbstractA new method has been developed for simulating high resolution electron microscope images of weak phase objects via a digital television frame store system and fast Fourier transforms of a graphical representation of structures containing several atomic species. Here masks are constructed which consist of circular disk regions whose areas are proportional to the scattering power of the different atom types. These masks represent the object transmission function. The method extends the previous work on image computations of monatomic species objects using small point‐like model representations of atom positions. Several examples will be given to verify the relative scattering power from masks corresponding to different atomic species such as Y, Ba, Cu, and O, as well as the limitations of this method for representing objects. Image simulations, which are in agreement with experiments, will also be presented for superconducting oxide materials of the form YBa2Cu3O7 using the circular disk method.
Ultrastructural localization of defined sequences of viral RNA and DNA by in situ hybridization of biotinylated DNA probes on sections of herpes simplex virus type 1 infected cells
Authors: Puvion‐Dutilleul Francine , Puvion Edmond 
Published: February 2005

AbstractThe influence of fixation and enzymatic digestions on the ability of a denatured double‐stranded DNA probe to bind specifically to related sequences of RNA and DNA in sections of Lowicryl embedded cells was investigated. Specificity of the hybridization was assessed using a biotinylated cloned subgenomic herpes simplex virus type 1 DNA fragment to localize viral nucleic acids in sections of infected cells. The probe was detected by anti‐biotin antibodies and indirect immunogold labeling. Controls indicated that protease digestion of proteins from the section eliminated non‐specific binding of the probe and labeling of endogenous biotin.Both formaldehyde and glutaraldehyde fixation retained viral RNA in protease digested sections. Its labeling was randomly and sparsely distributed over the fibrillo‐granular network of the infected nucleus and over the ribosome‐rich regions of cytoplasm.Labeling of single‐stranded portions of viral DNA in protease‐RNase digested sections was infrequent. It was located precisely over nucleoids of a few viral nucleocapsids whatever their location in the cell and their stage of maturation.Labeling of double‐stranded viral DNA by denaturation of the DNA in the sections of Lowicryl embedded cells was possible after fixation with formaldehyde but not glutaraldehyde. Among several denaturation protocols, 0.5 N NaOH treatment was best for hybridization of both nonencapsidated and encapsidated viral DNA in protease‐RNase digested sections. Free viral genomes were detected exclusively within the virus‐replicating region of infected nuclei. Labeling of viral nucleoids was independent of their location in the cell. The high percentage of labeled viral nucleoids suggests that the related viral DNA sequence is not aggregated in the nucleoid but is extended and therefore numerous portions of this defined DNA sequence are accessible at the surface of the section for the binding of the probe.
Computer reconstruction of nucleolar architecture by interactive three‐dimensional color display
Authors: Geraud G. , Soyer A. , Hernandez‐Verdun D. 
Published: February 2005

AbstractThe first complete three dimensional ultrastructural reconstruction of pancreatic cell nucleoli, was done using EM and computer 3D‐assisted reconstruction of serial sections with interactive 3D back‐to‐front and color display methods based on voxel representation. The purpose of the study was to depict the architecture of the nucleolar components. We obtained information about the location of the nucleolus within the nuclear volume and about the shape and polarity of the 3 main nucleolar territories.
Cryo‐electron microscopy of vitrified specimens: An approach to the study of bulk specimens
Authors: Erk I. , Delacroix H. , Nicolas G. , Ranck J.‐L. , Lepault J. 
Published: February 2005

AbstractWe are using and developing cryo‐electron microscopy of vitrified specimens. Our main interests concern the structure of muscle and muscular components. Micrographs which generally contain periodic features are analyzed by numerical image processing methods. To detect artifacts induced by the electron microscopy techniques, we correlate our results to those obtained by X‐ray diffraction. In this paper, we describe our approach to the study of bulk specimens. Vitrification of such specimens is assessed by cryo‐X‐ray diffraction. Microscopy is done on cryo‐substituted specimens.
X‐ray microanalysis of cell nuclei
Authors: Quintana Carmen 
Published: February 2005

AbstractThe principal component analysis, a multivariate statistical analysis of data, has been used to process X‐ray microanalytical data from cell nuclei. Sixty‐seven measurements from different areas of chromatin, nucleoli of rat follicular cells, and nucleoli of rat oocyte cells in their antral stage have been studied. The variables are the X‐ray characteristic signals for P, S, Al, Fe, Cu, and Zn. This method demonstrates four distinct groups, the chromatin area, which is associated with a higher concentration of P; the compact mass of oocyte nucleolus which possesses the highest content in S, Al, and Zn, and two groups of nucleolar areas. The fibrillar component is richer in S, Al, and Zn than the granular component. The high degree of correlation between these three elements proves the chemical affinity of metals for the proteins (S being the signature for proteins).Cryoembedding in Lowicryl resin at even lower temperatures (213° K in K11M) after quick cryofixation and cryosubstitution in the absence of chemical fixatives gives good ultrastructural preservation and the possibility of simultaneously performing X‐ray microanalysis and immuno‐cytochemistry.
A computer program for many‐beam image simulation of amplitude‐contrast images
Authors: René Rasmussen D. , Barry Carter C. 
Published: February 2005

AbstractA computer program for the simulation of amplitude‐contrast electron micrographs is described. The program is based on the n‐beam dynamical theory of diffraction contrast as described by Howie and Whelan (see Howie, A., and Whelan, M.J. (1961) Proc. R. Soc. Lond. [Biol]). The displacement fields associated with crystal lattice defects are calculated using linear anisotropic elasticity. The program can be used to simulate images of crystals containing line or planar defects or combinations of these defects. The line defects can be oriented freely within the foil, and are not restricted to being mutually parallel, but must be straight. Different techniques available for solving the diffraction problem, with or without the column approximation, are discussed.