bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of the physical structure of biological materials at biosensor interfaces by techniques of increasing magnification from microscopic to molecular scale
Authors: Krull U. J. , Brown R. S. , Vandenberg E. T. , Heckl W. M. 
Published: February 2005

AbstractChemical selectivity of biosensors is derived from biological materials interfaced to the surface of transducing devices. Molecular recognition events lead to macroscopic function suitable for analytical measurements. The structure‐function relationships of biochemical species at interfaces must be established to characterize and optimize biosensor operation. The techniques of ellipsometry, fluorescence microscopy, electron microscopy, and scanning tunneling microscopy are used to investigate the structure of monolayers and multilayers of proteins and lipids at interfaces that are prepared by Langmuir‐Blodgett techniques and by self‐assembly from bulk solution. The relative merits and limitations of the measurement techniques in the determination of aspects of interfacial structure are considered.
Tridimensional ultrastructure of perfusion fixed gastrointestinal epithelial cells by high resolution scanning electron microscopy
Authors: Kendall Cyril W. , Venketeshwer Rao A. , Janezic Susan A. , Temkin Robert J. , Hollenberg Martin J. , Lea Peter J. 
Published: February 2005

AbstractImprovements in the design of modern scanning electron microscopes (SEM) and new methods of specimen preparation incorporating chemical removal of the cytosol and cytoskeleton, now make it possible to view cells and their organelles in three dimensions (3D) at high magnification. In this experiment, high resolution SEM (HRSEM) utilizing new methods of tissue preparation was used to study the intracellular structures of the mouse ileum. In addition, in vivo intestinal perfusion was used to further enhance cellular preservation. Using these modifications it was possible to visualize, in 3D, the fine structure of intestinal epithelial cells and intracellular organelles such as the nucleus, mitochondria, endoplasmic reticulum, and Golgi complex, as well as microvilli and cell membrane. Whole mitochondria appeared as irregularly shaped organelles which contained tubular cristae. Plate‐like cristae were not observed. The brush border was found to be a closely packed array of cylindrical projections. The extensive folding and structural intricacy of lateral cell membranes between absorptive cells could only be appreciated by viewing this tissue with 3D HRSEM. The use of HRSEM to study 3D ultrastructure of cells and their organelles will improve our understanding of the structure‐function relationships in both the healthy and diseased gastrointestinal tract.
Resolution limit of serial sections for 3D reconstruction of tubular cristae in rat liver mitochondria
Authors: Winslow J. L. , Hollenberg M. J. , Lea P. J. 
Published: February 2005

AbstractFollowing stereo, high resolution scanning electron microscopy (HRSEM) of various rat tissue mitochondria prepared by mild glutaraldehyde fixation followed by freeze cleavage and extraction of the cytosol (Lea and Hollenberg, 1989a), a new model for the ultrastructure of mitochondrial cristae has been developed (Lea and Hollenberg, 1989b). The cristae mitochondriales, previously considered in most cells to have a shelf like structure, were found in many cell types including hepatocytes by HRSEM to be tubes which spanned the mitochondrial matrix and were continuous with the inner mitochondrial membrane at both ends. Despite computer aided, serial, reconstruction of serial thin sections examined in the transmission electron microscope (TEM), tubular cristae in mitochondria have not been resolved entirely, even though circular cross sectional profiles of cristae have been observed in the TEM. The current study was undertaken to probe this deficiency and to understand its cause.In this study, the problems of inherent contrast and resolution loss in the digitized image have been reduced by using a computer based, background, extraction process analogous in the computer to the chemical cytosol extraction process used for HRSEM (Lea and Hollenberg, 1988; Hollenberg et al., 1989). Despite the use of this membrane enhancement algorithm, it was still not possible to reconstruct entire tubular cristae, as observed by HRSEM, even when the micrograph negatives were digitized and reprocessed (Lea and Hollenberg, 1989b). A comparison of serial section thickness deduced from the diffraction colour of the respective section (60 nm) to the measured diameter of tubular cristae profiles (30 nm), with membrane thickness of 10 nm, suggested that this size disparity is responsible for the apparent loss of resolution. The sampling theorem from signal analysis indicates that the signals of interest (X, Y vs. Z coordinate values of mitochondrial internal structure) must be sampled at least twice the frequency of their highest frequency. Because the structures are small and embedded in image noise, even thinner serial sections are required in order to obtain enough information for adequate reconstruction. Consequently in practice, the thickness of the serial sections would have to be reduced by four times to less than 8 nm in order to be able to reconstruct tubular mitochondrial cristae 30 nm in diameter and less than 2 nm for membrane shape. Ultra‐thin sections, some 15 nm in thickness, have been reported (Buchanan et al., 1988). However, these sections would be only thin enough to resolve structures greater than 30 nm in diameter. Observation of cristae by HRSEM therefore is essential in order to verify ultrastructure derived by computer based three dimensional reconstruction.
Image analysis of mineralized and non‐mineralized type I collagen fibrils
Authors: Larry Arsenault A. 
Published: February 2005

AbstractTurkey leg tendons at an early stage of mineralization have been thin sectioned and imaged by electron microscopy. At this stage collagen‐associated mineral apatite was found to be present within both the gap and overlap zones. The earliest apatite occurs in a microcrystalline form which gives a rather generalized and characteristic density to both the gap and overlap zones; with subsequent development larger defined apatite crystals arise which span gap/overlap zones. Fourier transformation of such images revealed the major 67 nm axial repeat of the gap/overlap zone plus four other maxima corresponding to repeat spacings of 22, 16, 13, and 11 nm respectively. Computer imaging techniques were used to reconstruct images by using selected spatial frequencies from such transforms. In this manner the subperiodic distributions of mineral were visually enhanced. These subperiodicities are positioned in an asymmetric fashion over the entire D unit repeat aligning with the molecular orientation of the fibril. Analyses of both negatively stained collagen and computer‐generated maps of collagen hydrophobicity were compared to the mineral distribution of collagen. Densitometric comparisons showed a positional correlation between the axial banding patterns of mineralized fibrils and those of negatively stained non‐mineralized fibrils. Comparable spatial frequencies were also present in transforms between hydrophobic maps and mineral distribution of collagen. These results suggest that the lateral clusterings of hydrophobic residues which span the fibril at specific sites in both the gap and overlap zones serve to prohibit early mineral deposition. This observed hydrophobic influence in combination with the gap space appear as contributing factors in the observed axial distribution of mineral within collagen.
Structural organization of the thylakoid membrane: Freeze‐fracture and immunocytochemical analysis
Authors: Olive J. , Vallon O. 
Published: February 2005

AbstractThis article summarizes our ultrastructural studies on the organization of the thylakoid membrane of green algae and higher plants. We have used freeze‐fracture and immunogold labeling to investigate the lateral distribution of the components in the membrane, their interactions, and the folding of their polypeptide chains in the membrane.
Quantitative electron microscopic analysis of DNA‐protein interactions
Authors: Cam Eric Le , Théveny Bernard , Mignotte Bernard , Révet Bernard , Delain Etienne 
Published: February 2005

AbstractElectron microscopy offers a unique potentiality to visualize individual molecules. For the last 30 years it has been used to study the structure and the interactions of various biological macromolecules. The contribution of electron microscopy is important because of its capacity to demonstrate the existence of conformational structures such as kinks, bents, loops, etc., either on naked DNA, or on DNA associated with various proteins or ligands. Increasing interest was given to such observations when it was found that they provide a direct visualization of interacting molecules involved in DNA metabolism and gene regulation. Technical advances in the preparation of the specimens, their observation in the electron microscope, and the image processing by computers have allowed the shifting from qualitative to quantitative analysis, as illustrated by a few examples from our laboratory.
Structural analysis of two‐dimensional arrays of cholera toxin b‐subunit
Authors: Mosser Gervaise , Brisson Alain 
Published: February 2005

AbstractTwo‐dimensional arraysThe term array is used to describe a regular arrangement of motifs without implying the existence of translational symmetry elements between motifs, by distinction with a crystal.
of cholera toxin B‐subunit (CTB) have been obtained by specific interaction with lipid films, as described by Ludwig et al. (1986). The relationship between two types of array, of either rectangular or hexagonal geometry, was analyzed using crystallographic methods of electron image analysis. Our results showed that the type of array obtained was highly dependent on the negative stain used and that both arrays presented related lattice parameters, indicating that they originated from a common unstained structure. Image analysis of hexagonal arrays at 17 Å resolution revealed variable CTB projected structures, ranging from annularly symmetric particles to highly asymmetric particles, very distinct from the pentameric structure resolved from rectangular crystals. The present data suggest that hexagonal arrays result from an imperfect staining of CTB rectangular crystals. The staining distortion is such that the stain layer does not match faithfully the pentameric protein distribution whereas the regular organization of the specimen is maintained.
Advantages of fast‐freeze fixation followed by freeze‐substitution for the preservation of cell integrity
Authors: Nicolas Gisèle 
Published: February 2005

AbstractThe use of fast‐freeze fixation (FFF) followed by freeze‐substitution (FS) has supplied new data in a variety of domains due to the rapidity of this fixation compared to the slow process of the conventional chemical fixation. FFF completely arrests all the cell's biological reactions, and physically immobilizes most molecules within a few milliseconds. This review deals with the main results we obtained concerning the preservation of organelles particularly sensitive to osmotic shock, the maintenance in situ of soluble or depolymerizable cell components, the visualization of brief transient events, and the opening up of new prospects in the field of immunocytochemical labeling.
Preparation of ultra‐thin oxide windows on titanium for tem analysis
Authors: Rådegran G. , Lausmaa J. , Mattsson L. , Rolander U. , Kasemo B. 
Published: February 2005

AbstractUsing submerged jet electropolishing, extremely thin (<10 nm), continuous, thermal oxide “windows” have been prepared on poly crystalline titanium (Ti). The preparation technique is described in detail. It has allowed a systematic investigation of the structure of thermal surface oxide layers on Ti in the thickness range 6–40 nm, corresponding to oxidation temperatures 100–450°C. Auger electron spectroscopy was used for oxide characterization and for depth profiling to determine oxide thickness.The thinnest oxides, < 10 nm, are amorphous, morphologically homogeneous, and with essentially no contrast in the transmission electron microscopy (TEM) pictures. As the oxide thickness is increased up to 40 nm, a texture corresponding to the grain structure of the oxidized metal becomes gradually more visible. At the same time the oxide becomes increasingly more crystalline. The results are compared with previously published corresponding results for thicker anodic oxides on Ti.
Routine cryofixation of plant tissue by propane jet freezing for freeze substitution
Authors: Ding Biao , Turgeon Robert , Parthasarathy M. V. 
Published: February 2005

AbstractCryofixation and freeze substitution methods were developed for ultrastructural studies of cells in complex plant tissues. Leaf tissues and root tips of tobacco (Nicotiana tabacum L. var. Maryland Mammoth) were frozen with a RMC MF7200 propane jet freezer and freeze substituted sequentially with tannic acid and osmium tetroxide/uranyl acetate in acetone. High quality preservation was consistently obtained for epidermal and phloem cells of the leaf, and epidermal, cortical, meristematic, and cap cells of the root tip. Leaf mesophyll cells were also often well frozen. Organelles, including nuclei, endoplasmic reticulum, mitochondria, Golgi bodies, and plastids, showed excellent structural integrity and contrast. Most notable is the superior preservation of the cytoskeleton. Our results demonstrate that the propane jet freezer can be used routinely for high quality cryofixation of higher plant cells in certain complex tissues. This could have important implications for the use of cryofixation approach in a wide range of research in plant biology.
Fine structural characteristics of testicular cord formation in the developing rabbit gonad
Authors: Wartenberg Hubert , Kinsky Inge , Viebahn Christoph , Schmolke Cordula 
Published: February 2005

AbstractThis paper presents morphological (light‐ and electron‐microscopical) evidence for the role of the mesonephros in contributing cells to the differentiating indifferent gonad and, after sexual differentiation, to the testis. A continuous process is revealed during which segregation of cells occurs from the developing and regressing mesonephros. Additionally, the complementary role of the coelomic epithelium in gonadal ridge and testis formation is demonstrated. The differentiation of testicular cords, their remodelling from a primary reticulum, and the composition and further change of the cellular content during the period after sexual differentiation is described using a computer‐aided three‐dimensional reconstruction system. Apart from these morphogenetic events, cytodifferentiation in the somatic cells of the indifferent gonad and of the early differentiated testis is demonstrated using indirect immunof luorescence in combination with monoclonal antibodies to the intermediate filament proteins keratin 8 and 18 and vimentin. The immunohistochemical results show that different forms of cytodifferentiation coexist among the somatic cells present in the indifferent gonad and in the testis early after sexual differentiation.
Capillary pericytes: Perspectives and future trends
Authors: Tilton Ronald G. 
Published: February 2005

AbstractA complete understanding of the microcirculation requires full knowledge of the structure and function of each of the constituent cells, including pericytes. Vascular endothelium and smooth muscle cells have been investigated intensively during the last two decades, but much less is known about the metabolism and function of capillary pericytes. However, the development of new electron microscopy techniques and the application of new cell culture and molecular biology techniques should allow for the rapid elucidation of the cellular biochemistry and the microvascular function and pathology of this ubiquitous capillary cell.
Vasculature of the fish gill: Anatomical correlates of physiological functions
Authors: Olson Kenneth R. 
Published: February 2005

AbstractThe fish gill is a multifunctional organ responsible for respiration, osmoregulation, acid base balance, nitrogen excretion, and metabolism of circulating hormones. Two or more microcirculatory systems subserve these activities and form one of the most complex vascular networks found in any vertebrate. In this article the vascular anatomy of the teleost gill and the role of gill vessels in mediating physiological function are examined. Vascular corrosion replication techniques have been instrumental in resolving the spatial organization of gill microcirculation. Variations in the replication procedures provide information on the interrelationships between the vascular pathways, factors that govern flow distribution, and the physical characteristics of the vessels themselves. Anatomically, gill vessels are as diverse as their physiological functions. Pillar cells, unique to the fish gill, form the lining of the respiratory vasculature and may have substantial metabolic effects on circulating hormones. The non‐respiratory pathways appear to be lined with both typical and unusual endothelial cells, although the fine structure and function(s) of these vessels are largely unknown. To date most of the information on gill vessels has been derived from descriptive morphological studies. Further evaluation of the anatomical and physiological correlations of these tissues is predicated upon the application of histocytochemical, morphometric, and other quantitative methodologies as well as an examination of gills from fish with various evolutionary and environmental backgrounds.
Interrelationships of ultrastructure and function in the microvasculature of normal and ischaemic myocardium
Authors: Gavin John Bevan , Maxwell Linda , Sage Martin David 
Published: February 2005

AbstractThis paper reviews various methods involving electron microscopy that have been used to investigate the ultrastructure of the vasculature of the normal and diseased heart. Whereas scanning electron microscopy is more commonly employed to record surface topography, it can be used to examine freeze‐fracture planes within the myocardium and, using heavy‐metal staining and back‐scattered electron imaging, to examine large 2‐μ‐thick resin‐embedded sections through the heart. The latter technique allows the comparison of structural alterations across the wall of the heart and thus accurate definition of the transmural progression of pathological processes. Transmission electron microscopy can then be used to provide more detailed information from precisely localised regions. Human myocardium can be usefully studied up to 12 hours post‐mortem provided that suitable control material is included. Intravascular tracers including low‐viscosity resin and nuclear track emulsion can be used to determine whether or not particular vessels allow flow at the time of fixation, and thus changes in the pattern of flow through the microvasculature due to ischaemia and reperfusion can be quantified and defined. Particular care is required in the fixation of ischaemic tissues because oxygen dissolved in the fixative can lead to the rapid formation of oxygen‐free radicals on contact with the tissue. This produces artefactual reoxygenation damage characterised by membrane disruption and cell and organelle swelling, which has previously been attributed to ischaemic injury per se. Bubbling glutaraldehyde with nitrogen substantially reduces this artefact.
The anatomy, physiology and comparative aspects of the repugnatorial glands of Orthocricus arboreus (Diplopoda:Spirobolida)
Authors: Woodring J. P. , Blum M. S. 
Published: February 2005

AbstractThe quinoidal secretion, secreted by holocrine action from most gland cells (no cytoplasmic inclusions), of Orthocricus arboreus may ooze out or be sprayed over 30 cm. A thick gland intima and basement membrane protects internal organs. The gland grades into a neck leading to an external orifice. An ejaculatory duct, its lumen closed by cuticular spring action, is formed by invagination of the neck. Part of the duct forms a tongue, which can independently unplug the orifice. Retractor muscles open the ejaculatory duct, secretion flows in from the gland, and the part of the duct nearest the gland closes. Sequential relaxation of the rest of the retractor muscles build up fluid pressure, which results in a spray when the orifice is unplugged. A ligament opposes the pull of the retractor muscles. Opening both duct and orifice results in secretion ooze. No intrinsic gland muscles were found. Intersegmental muscles may produce hemolymph fluid pressure on the gland, thereby contributing to secretion ooze. Illustrations are presented. A table comparing the two basic types of millipede repugnatorial glands (spirobolid and polydesmid), on the levels of structure, histology, secretion, chemistry and function is presented. The polydesmid type (2‐chambered) probably evolved from the spirobolid type (1‐chambered). The secretion of one type would not work in the other type of apparatus. A second table corelates the secretion and ejection mechanism of 23 species of millipeds with their phylogenetic position in the class Diplopoda.
A morphological and histochemical study of the reproductive system of the slug, Philomycus carolinianus (Bosc)
Authors: Kugler Otto E. 
Published: February 2005

AbstractGlycogen, determined by Best's carmine and/or PAS Tripas staining, and alkaline phosphatase, determined by the Gomori technic, occur together throughout the epithelium of the genital tract. Sites of high alkaline‐phosphatase activity are the acinar epithelium, nurse cells, and follicular cells of the ovotestis. Sperm heads are also strongly positive for the enzyme. The nidamental gland cells and the subepithelial mucous cells associated with the loop of the hermaphroditic duct and with the spermatic groove are thionine metachromatic, alcianophilic, PAS‐positive and amylase‐fast. The mucous cells of the genital atrium are PAS‐positive and amylase‐fast but lack both thionine metachromasia and affinity for Alcian blue.
The forebrain of the crossopterygian Latimeria chalumnae Smith
Authors: Nieuwenhuys Rudolf 
Published: February 2005

AbstractIn this paper the telencephalon of Latimeria chalumnae, the only surviving crossopterygian, is described and compared to that of other lower vertebrates. It is concluded that Latimeria cannot be related to a particular group of vertebrates, but stands intermediate between the dipnoans and the actinopterygians in its forebrain structure. With respect to the shape of the subpallium, the structure of the telencephalon medium, and the arrangement of its fiber systems, the latimerian forebrain closely approaches the dipnoan condition. The pallium and membranous structures of the telencephalon of Latimeria, on the contrary, are reminiscent in gross form and histological structure of their actinopterygian homologues.However, not all the structural features of the latimerian forebrain can be related to either the actinopterygian or the dipnoan plan. The subpallium, for instance, is more primitive than that of either group mentioned; in fact, it is more simply organized than that of any other living gnathostome.The forebrain of Latimeria appears to display no special structural affinities to the amphibian forebrain. This is not too surprising, since the Coelacanths, among which Latimeria is classified, represent only a side branch of the Crossopterygii, and are not in the main line of evolution to higher forms. It is known that members of the same class of lower vertebrates may vary considerably in their forebrain structure. Hence, the Rhipidistia, totally extinct Crossopterygii which are believed to have given rise to the terrestrial vertebrates, may have possessed a forebrain quite different from that of Latimeria.