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  • Articles  (634)
  • Humans  (437)
  • Cell & Developmental Biology  (132)
  • Mice  (99)
  • 1990-1994  (634)
  • 1990  (634)
  • Natural Sciences in General  (634)
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  • 1990-1994  (634)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 14 (1990), S. 63-69 
    ISSN: 0741-0581
    Keywords: Filtration barrier ; Renal sections ; Resinless ultrastructure ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Following the removal of polyethylene glycol (PEG) from thin sections, and viewing through the endothelial fenestrae and/or the interpedicel spaces, the rat renal glomerular basement membrane in situ was revealed to consist of meshworks and to be electron-transparent when examined at right angles to the plane of the membrane. By subsequent platinum replication of the embedment-free sections, the lamina densa of the basement membrane appeared as a veil composed of rather closely packed particles. The architecture of the slit diaphragm and the surface morphology of the endothelial cell membrane were also clearly revealed. The present results indicate that the PEG method, with or without replication, can provide valuable information on basement membrane morphology.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 14 (1990), S. 140-151 
    ISSN: 0741-0581
    Keywords: Hepatocyte ; Endocytosis ; Receptor ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 14 (1990), S. 92-105 
    ISSN: 0741-0581
    Keywords: Hepatocyte organelles ; Bile canaliculi ; Postnatal hepatocyte differentiation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: This paper reviews the fine structure and function of hepatocytes during fetal and postnatal development. Bile canaliculi develop to a mature appearance during perinatal and early postnatal periods, while bile secretory function is immature at birth and develops during the postnatal period. The rough endoplasmic reticulum is prominent and remains unchanged in amount during development, and the Golgi complex is large from early stages of fetal life. The smooth endoplasmic reticulum (SER) appears shortly before birth and increases in quantity to the adult level after birth. In mouse hepatocytes, Sv (area per unit cytoplasmic volume) of SER increases in perivenular cells between 1 and 10 days of age, although it remains low in periportal cells. Similarly, Sv of total ER increases in both periportal and perivenular cells between 1 and 5 days of age and then becomes greater in perivenular than periportal cells. This suggests that the postnatal increase in the drug-metabolizing capacity occurs predominantly in perivenular hepatocytes. SER proliferates after phenobarbital (PB) administration in both perivenular and periportal cells in 3-, 5-, and 10-day-old mice, and predominantly in perivenular cells in 20-day-old and adult mice. Thus the conspicuous proliferation of SER in perivenular hepatocytes after PB administration, characteristic of adult liver, becomes manifest during postnatal development. In mouse hepatocytes, Vv (volume per unit cytoplasmic volume) of mitochondrial matrix and peroxisomes and Sv of mitochondrial inner membrane and cristae increase in both periportal and perivenular cells between birth and 10 days of age. Then, Vv of mitochondrial matrix remains unchanged in periportal cells but decreases in perivenular cells. In general, the process of postnatal hepatocyte differentiation appears to include several phases of development; cell organelles develop during the early postnatal period, subsequently the cells undergo both functional and structural heterogeneity, and the late postnatal period after weaning is the time for a marked increase in cell size.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 14 (1990), S. 106-125 
    ISSN: 0741-0581
    Keywords: Aging ; Ultrastructure ; Liver volume ; Lysosomes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Aging is accompanied by a myriad of changes in cell structure, function, and composition. The fact that much of the information concerning age-related alterations in cellular morphology is qualitative precludes meaningful correlations with biochemical changes in order to enhance data interpretation. The mammalian liver has been subjected to both qualitative and quantitative evaluations of hepatocyte structure as a function of aging, i.e., development, maturation, and senescence. Although these data are characterized by considerable variability and, in some instances, blatant contradictions, there exists sufficient agreement in several parameters to permit a consensus in the inbred rat model. Certainly the volume of individual hepatocytes increases with age, and many of the organelle compartments reflect this change. While old rats exhibit a high incidence of polyploidy, there is no definitive evidence to demonstrate a concomitant increase in the binuclear hepatocyte index. Several specific hepatocellular organelles undergo changes in their relative volume or surface area that appear to correlate with functional alterations. The volume density of the lysosomal compartment enlarges significantly during senescence and is accompanied by increased activities of several constituent hydrolases. The hepatic concentration of smooth-surfaced endoplasmic reticulum declines markedly with aging, as does the yield of liver microsomes and the activities of several microsomal enzymes, e.g., mono-oxygenases and glucose-6-phosphatase. However, the responses of the majority of hepatocyte organelles to aging is varied and inconsistent based on the limited data currently available.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 14 (1990), S. 179-207 
    ISSN: 0741-0581
    Keywords: Ultrastructure ; Liver disease ; Hepatitis ; Alcoholic injury ; Storage diseases ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: 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.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 14 (1990), S. 237-246 
    ISSN: 0741-0581
    Keywords: Liver ; Sinusoid ; Phagocytosis ; Endocytosis ; Host defense ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Kupffer cells are macrophages that are attached to the luminal surface or inserted in the endothelial lining of hepatic sinusoids. In this site, Kupffer cells play a key role in host defense by removing foreign, toxic and infective substances from the portal blood and by releasing beneficial mediators. Under some conditions, toxic and vasoactive substances also are released from Kupffer cells which are thought to play a role in a variety of liver diseases. Many of these activities may be modulated by the levels of gut derived endotoxin normally present in the portal blood.The ultrastructural aspects of Kupffer cell structure function in situ are best studied using perfused-fixed livers. In fixed livers, transmission and scanning electron microscopy reveal Kupffer cells during health to be irregular in shape with their exposed surfaces presenting numerous microvilli, filopodia, and lamellopodia. Long filopodia penetrate endothelial fenestrae to secure Kupffer cells to the sinusoid lining. Specific membrane invaginations known as worm-like bodies or vermiform processes are seen in the cytoplasm of Kupffer cells as are numerous endocytotic vesicles and lysosomes which vary in density, shape and size. Sometimes, annulate lamellae connected to the rough endoplasmic reticulum also are found. The principal endocytic mechanisms of Kupffer cells are phagocytosis of particulates and cells, and bristle-coated micropinocytosis for fluid-phase endocytosis of smaller substances. Many of these events are mediated by specific receptors. In some species, Kupffer cells can be distinguished from other sinusoidal lining cells and monocytes by specific cytoplasmic staining or monoclonal antibodies. Kupffer cells have been shown to be of monocytic origin as well as having the capacity for self-replication.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 14 (1990), S. 247-256 
    ISSN: 0741-0581
    Keywords: Sinusoidal cells ; Fat-storing cells ; Ito-cells ; Natural killer cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: 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.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 14 (1990), S. 257-282 
    ISSN: 0741-0581
    Keywords: Sinusoids ; Endothelial cells ; Kupffer cells ; Perisinusoidal cells ; Pit cells ; Space of Disse ; Extracellular matrix ; Disease ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Liver sinusoids are special capillaries that are limited by fenestrated endothelial cells, without a genuine basement membrane, surrounded by perisinusoidal cells storing vitamin A, and harbouring Kupffer cells and pit cells, resident macrophages, and large granular lymphocytes, respectively. Each nonparenchymal cell and parenchymal cell of the liver interacts with all others and with the extracellular matrix. Therefore, the functional ability of each cell is constantly being modified by the metabolic activity of the others.Human liver biopsies (132), needle or surgical, perfusion-fixed with glutaraldehyde and processed for transmission electron microscopy (TEM), and occasionally for scanning electron microscopy (SEM), were examined. The study included liver diseases (such as alcoholic liver diseases, benign and malignant liver tumors, cholestasis of various origins, fulminant hepatitis, acute rejection after orthotopic liver transplantation, Budd-Chiari syndrome), as well as general or extrahepatic diseases (such as diabetes, hemochromatosis, hypervitaminosis A, various hematological disorders), and normal controls.Ultrastructural abnormalities are described and illustrated under two different headings: (1) elementary lesions of sinusoidal cells (endothelial, Kupffer, perisinusoidal and pit cells), nonsinusoidal cells (in the space of Disse and/or in the lumen), the extracellular matrix; and (2) the major pathological entities including perisinusoidal fibrosis, capillarization of sinusoids, sinusoidal dilatation, and peliosis. In the discussion, an overview of the major abnormalities reported in the literature is presented, and some specific questions regarding (1) perisinusoidal fibrosis in liver with normal histology, (2) the overload of perisinusoidal cells with lipids in non-hypervitaminosis A intoxication and (3) the etiological relationship of sinusoidal dilatation, peliosis, perisinusoidal fibrosis, or sinusoidal tumors with drugs and toxic compounds are discussed. In the event that lesions are not specific to any diagnosis, the knowledge of the ultrastructure of sinusoids is extremely useful from the perspective of the liver as an ecosystem.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 15 (1990), S. 81-96 
    ISSN: 0741-0581
    Keywords: Antibody ; GABA ; Glycine ; Acetylcholine ; Auditory system ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Over the last several years our knowledge of neurotransmitter receptors has increased dramatically as receptor types and subtypes have been identified through the development of selective antagonists, neuropharmacological studies, and radioactive ligand binding studies. At the same time major advances were made in the immunocytochemical localization of neurotransmitters and their related enzymes. However, only recently has immunocytochemistry been used to localize neurotransmitter receptors, and these studies have been limited. Four receptors have been localized in the CNS with immunocytochemistry: the nicotinic acetylcholine receptor, the beta-adrenergic receptor, the GABA/benzodiazepine receptor, and the glycine receptor. Of these the glycine receptor has been the most thoroughly characterized. Glycine receptor immunoreactivity is highly concentrated at postsynaptic sites, and the distribution of immunoreactivity appears to correlate closely with glycinergic neurons. However, immunocytochemical studies done on other receptors suggest such a distribution may not always be the case. Some receptors may not be concentrated at postsynaptic sites, and receptor distribution may not always closely fit the distribution of the respective neurotransmitter. Work is rapidly progressing on the purification of other receptors and on the production of selective antibodies which will allow immunocytochemical studies which address these and other questions.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 15 (1990) 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 11
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 15 (1990), S. 104-114 
    ISSN: 0741-0581
    Keywords: Nerve fiber ; Afferent and efferent nerves ; Cochlea ; Fetal inner ear ; Human ear ; SEM ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The cochleas of four human fetuses ranging 22-25 weeks gestation were studied by scanning electron microscopy (SEM) for the purpose of obtaining a better understanding of the nerve fiber arrangement in the human ear. After critical point drying, the specimens were dissected and the floor of the tunnel of Corti and the outer wall of Nuel's space were exposed for observation. Upper cochlear turns, especially the apical turn, seemed to be still immature.Observed nerve fibers were classified into three types:1Spiral fibers: Fibers traveling basalward and following the shape of the cochlea were found in both the tunnel of Corti and Nuel's space and believed to be the afferent nerves responsible for innervating the outer hair cells2Radial fibers: radiating outward from the osseous spiral lamina - one such radial fiber transversing high in the tunnel space (supposedly the efferent nerve servicing the outer hair cells), and another sort of radial fiber (found crossing the tunnel floor), the nature of which was uncertain.3Irregular fibers: Consisting of thin, randomly running fibers within the cochlea. The destination of these fibers was not determined, but possibly they represent transitory nerve branchings of afferent or more probably efferent nerves, which would later regress during maturation.
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 15 (1990), S. 155-164 
    ISSN: 0741-0581
    Keywords: Spiral ganglion ; Freeze-fracture ; Intermediate filaments ; Morphology ; Cytoskeleton ; Membrane ; Labyrinth ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Freeze-fracture analysis of adult spiral ganglion cells of CBA/CBA mice revealed two types of membrane specializations. Most cells (type I) had a smooth surface and were surrounded by Schwann cells. Type II spiral ganglion cells showed numerous membrane specializations with well-delineated indentations similar to those previously found on hair cells adjacent to afferent and efferent nerve endings. Immunomorphological analysis (using well-defined monoclonal antibodies directed against different subclasses of intermediate filament proteins) revealed a unique co-expression of neurofilaments, vimentin and cytokeratins in spiral ganglion cells of 8-to 22-week human fetuses.
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  • 13
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 15 (1990) 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 14
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 15 (1990), S. 245-260 
    ISSN: 0741-0581
    Keywords: Stereocilia ; Postmortem cochlea ; Scanning electron microscopy ; Human ; Guinea pig ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The morphology of hair bundles has been studied by high resolution scanning electron microscopy using a variety of fixatives, including glutaraldehyde, glutaraldehyde-picrate, glutaraldehyde-tannic acid, glutaraldehyde followed by post-fixation in osmium tetroxide, and the osmium thiocarbohydrazide technique. Critical evaluation of several metal coatings, gold, gold-palladium, and platinum has been carried out.Both the surface texture of stereocilia and their cross-links are sensitive to fixation and metal coating. We are of the opinion that glutaraldehyde gives the best general quality of fixation and preservation for all types of cross-links. We have described three major sets of cross-links: first, lateral links connecting stereocilia within the same row; second, lateral links connecting stereocilia of adjacent rows; and third, upward-pointing links, one per stereocilium, connecting the tip of each shorter stereocilium to the lateral surface of the adjacent taller stereocilium. Current physiological and anatomical evidence suggests that the lateral links couple the individual stereocilia within the hair bundle so that they function as a single mechanical unit. The upward-pointing tip links are ideally placed to respond to mechanical deformation of the hair bundle, being stretched when the stereocilia are deflected in the excitatory direction towards the tallest row and relaxed when deflected in the opposite, inhibitory direction.Postmortem morphological changes are detected within 15 minutes of cardiac arrest and become progressively more pronounced in time. These results enabled us to distinguish specific druginduced changes which could not be attributed simply to cell death. Effects of cisplatin and kanamycin upon hair bundles are described. The work reported here is based on studies using the guinea pig cochlea. Some of the postmortem changes described have also been confirmed in human cochleas.It is stressed that many of the postmortem and drug-induced effects can only reliably be studied by high resolution scanning electron microscopy coupled with appropriate prearation procedures.
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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 16 (1990) 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 16 (1990), S. 15-24 
    ISSN: 0741-0581
    Keywords: Intestine ; Mucosal barrier ; Tight junction ; Freeze-fracture ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Rat colonic mucosae fixed in situ in Ussing chambers provided a model of the extrusion of absorptive enterocytes and less commonly of goblet and enteroendocrine cells. The cells were lost at extrusion zones midway between crypt mouths. Even in mucosae in which the number of extruding cells was large, epithelial continuity was maintained as evaluated morphologically and electrophysiologically. Beneath points of remaining contact between desquamating cells and the epithelial sheet, microfilaments of the terminal web formed band-like structures linking adjacent junctional complexes. Freeze-fracture replicas disclosed extensive macular regions of tight junction strands in the plasma membranes of desquamating cells. Tight junctions between newly neighboring cells were often irregular and often occurred beneath the terminal web region. Dithio-threitol enhanced cell loss and increased basal epithelial conductance, but histological continuity was maintained and the mucosae continued to respond typically to bradykinin. These observations suggest that during the loss of senescent enterocytes, tight junctions are maintained; old junctional elements are lost, and tight junctions are formed between remaining adjacent cells. This model offers a means to study the synthesis and turnover of tight junctions and the maintenance of the colonic epithelial barrier.
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  • 17
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 16 (1990), S. 81-82 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 18
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 16 (1990), S. 69-80 
    ISSN: 0741-0581
    Keywords: Secretory granules ; Bipartite ; Golgi apparatus ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Paneth cells in the following species were observed under an electron microscope: human, rhesus monkey, hare, guinea pig, rat, nude rat, mouse, golden hamster, and insect feeder bat. Secretory granules containing homogeneous electron-dense materials were observed in the Paneth cells of humans, monkeys, hares, guinea pigs, and bats; mouse Paneth-cell granules were bipartite (central core and peripheral halo), and the Paneth cells in rats and golden hamsters had secretory granules showing various electron densities. In humans, monkeys, and bats, immature granules near the Golgi apparatus sometimes showed bipartite substructure. The number and size of secretory granules were also diverse among various animal species. Some lysosome-like bodies were commonly observed in peri- or supranuclear regions, though the size and shape of the bodies differed from cell to cell. In apical cytoplasm, small clear vesicles (100-200 nm diameter) were more-or-less observed in all species examined, and it was especially note that rat Paneth cells contained many clear vesicles. Small dense-cored vesicles (150-200 nm diameter) were rare. It is unlikely that the various ultrastructural features of Paneth cells correlate with the phylogenetical classification.
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  • 19
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 15 (1990), S. 397-399 
    ISSN: 0741-0581
    Keywords: YAG scintillator ; TEM ; Image detection ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A new image detection system has been developed to display transmission electron microscope (TEM) images on a CRT without a video camera system. Deflection coils placed in both the upper space of an objective lens and in the lower space of the first intermediate lens scan a small electron probe simultaneously. The electrical signal acquired through an improved scintillator and a photomultiplier is synchronized with the scanning signal and displayed in a similar fashion to a conventional scanning TEM (STEM) instrument. A preliminary system using a 100 kV conventional TEM (CTEM) equipped with a hairpin-type electron gun, produced an image with a spatial resolution of 1 nm.
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  • 20
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    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 15 (1990), S. 383-396 
    ISSN: 0741-0581
    Keywords: Embryo processing ; CNS cytology ; CNS fine structure ; CNS development ; Fixation artifacts ; Embryo dissection ; Telencephalon development ; Lipids in embryos ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: To study cellular shapes, growth patterns, and fine structure during early stages of CNS development in rat embryos, preparative procedures were evaluated and modified to meet two criteria: (1) Coronal semithin sections should reveal undeformed telencephalic hemispheres that were symmetrically expanded on both sides of midline structures and were surrounded by contiguous mesenchyme. (2) In electron micrographs, cells should have intact, undistorted surface membranes, evenly distributed nucleoplasm and well preserved cytoplasmic organelles. To meet these criteria, 378 fetuses with a gestational age of 11-20 days (E11-E20) were used to test and modify procedures for anesthesia, embryo removal and handling, dissection, fixation, dehydration, and embedding of the embryonic CNS. Most specimens were in an early stage of development (E11-E13), which, in case of the neopallial wall, is the preneural period. The tests produced methods that met the above criteria and identified the most common artifacts and their causes. Deformities of the cerebral hemispheres and separations between the brain and its coverings were usually caused by trauma during embryo removal and during handling before fixation. Changes in cellular volumes, especially swelling during fixation and dehydration, were the most important causes of histological artifacts. The procedures and methods that consistently produced the best light and electron microscopic preservation of the E11-E13 rat CNS are described. Fixation was best when the brains were treated with glutaraldehyde and s-collidine buffer, followed by osmium tetroxide in s-collidine buffer. A surprisingly beneficial effect of sodium chloride in the dehydrating alcohol was noted.
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  • 21
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    Journal of Electron Microscopy Technique 15 (1990), S. 416-420 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 22
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    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 16 (1990), S. 1-1 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 23
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    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 16 (1990), S. 25-36 
    ISSN: 0741-0581
    Keywords: Lectins ; Collodial gold ; LR White ; Lowicryl ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The plasmalemmal glycoconjugates of the HT29-18N2 (N2) cell line were characterized on cells grown as (1) undifferentiated multilayers in glucose-containing culture media and (2) monolayers of columnar cells acquiring the goblet cell phenotype in glucose-free media. Lectins were unable to bind sheets of detached N2 cells in the absence of fixation. Following fixation with aldehydes, a dramatic unmasking of lectin binding sites was seen. When fixed monolayers were stained prior to embedding, biotinylated lectins, visualized by the avidin-biotin-complexed peroxidase technique, were more efficient than collodial gold-coupled lectins. Lectin binding sites could also be detected by using collodial gold-coupled lectins to stain monolayers embedded in LR White, Lowicryl K4M, and Lowicryl HM20. The binding of 5 lectins (wheat germ, Dolichos bifluros, peanut, soybean, and Ulex europeus) was found to be independent of the stage of differentiation; “pre-differentiated” columnar cells which had prominent microvilli and no or few mucous secretory granules had identical staining patterns as well-differentiated goblet cells with large numbers of secretory granules. Ricinus communis I was the only lectin whose binding was influenced by the stage of differentiation; it intensely labeled undifferentiated multilayers of N2 cells but only weakly labeled basolateral membranes of differentiated monolayers. Canavalia ensiformas (ConA) caused a moderate and even labeling of both apical and basolateral membranes of fixed monolayers stained prior to embedding, but post-embedding labeling revealed heavy labeling along the lateral margins of all columnar cells and weak to moderate binding along the apical and basal cell surface.
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  • 24
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    Journal of Electron Microscopy Technique 16 (1990), S. 45-55 
    ISSN: 0741-0581
    Keywords: Villi ; Enterocytes ; Microvilli ; Stereology ; Length ; Diameter ; Number ; Surface area ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Different regions of small bowel were examined in five groups of rats in three separate experiments. The effects on mucosal morphology of position along the bowel, induced hypoproliferation (due to fasting), and induced hyperproliferation (due to streptozotocin diabetes) were investigated.Intestines fixed by in situ perfusion with buffered glutaraldehyde were sampled by strictly randomised procedures. Pieces of tissue from segments of roughly equal length were processed for electron microscopy and embedded in resin. Complete transverse sections were cut for light microscopy and estimates of villous surface areas were obtained by stereological methods devised for the purpose. Ultrathin sections from random sectors of the same tissue blocks were sampled systematically to obtain micrographs of the villous surface. These were analysed for quantitative information about microvilli (length, diameter, surface area, and number). Structural quantities from individual segments were pooled to provide values for the entire small bowel.Significant regional differences in villous and microvillous dimensions were found in all groups. The numbers of microvilli per bowel were remarkably constant in all control groups. Other variables were estimated reproducibly in rats of the same sex, strain, and average body weight.Effective absorptive surfaces did not show a linear gradient but tended to peak in middle segments. Neither fasting nor induced diabetes altered the mean length, diameter, or packing density of microvilli. However, surfaces due to villi and microvilli altered commensurately during fasting and induced diabetes. Therefore cell number seems to be the key quantity for determining villous and microvillous surface areas.The findings are discussed in the context of kinetic, biochemical, and physiological changes found in different adaptive states.
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  • 25
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    Journal of Electron Microscopy Technique 16 (1990), S. 83-84 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 26
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    Journal of Electron Microscopy Technique 16 (1990), S. 93-114 
    ISSN: 0741-0581
    Keywords: Ultrastructure ; Biochemistry ; Maturation ; Comparative ; Oocytes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: This review of the anatomical, histological, biochemical, and molecular biological literature on echinoderm oogenesis includes the entire developmental history of oocytes; from their inception to the time they become ova. This is done from a comparative perspective, with reference to members of the five extant echinoderm classes; crinoids, holothurians, asteroids, ophiuroids, and echinoids. I describe the anatomy and fine structure of the echinoderm ovary, with emphasis on both the cellular relationships of the germ line cells to the somatic cells of the inner epithelium, and on the neuromuscular systems. I review the literature on the growth of oogonia into fully formed oocytes, including the process of vitellogenesis, presenting an ultrastructural analysis of the organelles and extracellular structures found in fully formed echinoderm oocytes. Echinoderm oocyte maturation is reviewed and a description of the ultrastructural, biochemical and molecular biological changes thought to occur during this process is presented. Finally, I discuss oocyte ovulation, the severing of cellular connections between the oocyte and its surrounding somatic epithelial cells.
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  • 27
    ISSN: 0741-0581
    Keywords: Stopped-flow ; Rapid-freezing ; Freeze-fracture ; Electron microscopy ; Rapid reactions ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: We have developed an instrument capable of freezing transient intermediates in rapid biochemical reactions for subsequent freeze-fracturing, replication, and viewing by transmission electron microscopy. The machine combines a rapid mixing unit similar to one widely used in chemical kinetics (Johnson, 1986) with a propane jet freezing unit previously used to prepare static samples for freeze-fracturing (Gilkey and Staehelin, 1986). The key element in the system is a unique thin-walled flow cell of copper that allows for injection and aging of the sample, followed by rapid freezing. During freeze-fracturing, a tangential cut is made along the wall of the flow cell to expose the sample for etching and replication. The dead time required for mixing and injection of the reactants into the flow cell is less than 5 ms. Electronic controls allow one to specify, on a millisecond time scale, any time above 5 ms between initiation of the reaction and quenching by rapid freezing.
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  • 28
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    Journal of Electron Microscopy Technique 16 (1990), S. 202-234 
    ISSN: 0741-0581
    Keywords: Xenopus ; Meiosis ; Ultrastructure ; Intracellular signals ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Amphibian oocytes, arrested in prophase I, are stimulated to progress to metaphase II by progesterone. This process is referred to as meiotic maturation and transforms the oocyte, which cannot support the early events of embryogenesis, into the egg, which can. Meiotic maturation entails global reorganization of cell ultrastructure: In the cell cortex, the plasma membrane flattens and the cortical granules undergo redistribution. In the cell periphery, the annulate lamellae disassemble and the mitochondria become dispersed. In the cell interior, the germinal vesicle becomes disassembled and the meiotic spindles form. Marked changes in the cytoskeleton and mRNA distribution also occur throughout the cell. All of these events are temporally correlated with intracellular signalling events: Fluctuations in cAMP levels, changes in pH, phosphorylation and dephosphorylation, and ion flux changes. Evidence suggests that specific intracellular signals are responsible for specific reorganizations of ultrastructure and mRNA distribution.
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  • 29
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    Journal of Electron Microscopy Technique 16 (1990), S. 240-248 
    ISSN: 0741-0581
    Keywords: Energy dispersive x-ray spectrometer ; Thin film ; K-factor ; High voltage transmission electron microscope ; Quantitative standardless analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Qualitative and quantitative x-ray energy dispersive spectroscopy is now used successfully to analyze many features and processes in inorganic samples. When applied to inorganic samples, however, the results are often less satisfactory due to problems of preparation of organic samples, difficulty of measuring x-rays from organic samples, damage of the sample by the electron beam, and other practical problems.In the present study we used a high voltage transmission electron microscope equipped with an energy dispersive x-ray spectrometer to examine accurate quantitative standardless analysis of thin sections of an organic sample, human dentin.Based on our experiments we found the important parameters for quantitative analysis were sample thickness and appropriate choice of model sample. Further, we show that the method of Cliff and Lorimer can be used with biological samples at 200 kV, and we show that quantitative analysis of human dentin can be carried out at 200 kV. Finally, we show that areas of human dentin can be differentiated by their morphological characteristics and x-ray analyses obtained in the transmission electron microscope.
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  • 30
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    Journal of Electron Microscopy Technique 16 (1990), S. 281-297 
    ISSN: 0741-0581
    Keywords: Mammalian spermatozoon ; Surface membrane ; Spermatogenesis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The mammalian spermatozoon is a highly polarized cell whose surface membrane can be divided into five functionally, structurally, and biochemically distinct domains. These domains are formed during spermatogenesis, continue to be modified during passage through the epididymis, and are further refined in the female reproductive tract. The integrity of these domains appears to be necessary for the sperm to perform its function - fusion with the egg and subsequent fertilization. The domains can be identified morphologically by their surface contours and texture, the content, distribution, and organization of intramembranous particles after freeze-fracture, and by the density of surface and cytoplasmic electron-dense coatings in thin sections. By using a variety of labels that stain carbohydrates (lectins), lipids (filipin and polymyxin B), and monoclonal antibodies to specific membrane constituents, the biochemical composition of these contiguous membrane regions has also been partly elucidated. We review here what is known about the structure, composition, and behavior of each membrane domain in the mature sperm and include some information regarding domain formation during spermatogenesis. The sperm is an excellent model system to study the creation and maintenance of cell polarity, granule exocytosis, and fertilization. Hopefully this review will provide impetus for future studies aimed more directly at addressing the relationship of its morphology to its functions.
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  • 31
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    Journal of Electron Microscopy Technique 16 (1990), S. 356-357 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 32
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    Journal of Electron Microscopy Technique 16 (1990), S. 351-355 
    ISSN: 0741-0581
    Keywords: Drying ; Electron microscopy ; Frozen hydrated specimen ; Specimen preparation ; Vitrified specimen ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Evaporation of water cannot be fully avoided when an unsupported thin vitrified film of an aqueous suspension is prepared for cryo-electron microscopy. This results in increasing concentration of solute which could affect the observed material. We have quantitatively studied this effect by measuring the contrast of polystyrene spheres in a metrizamide solution. The drying effect is generally negligible when specimens are prepared on a hydrophilic perforated support but it is frequently important when hydrophobic films are used instead. A flow of humid air, double blotting with minimal exposure of the thin liquid film to the atmosphere, or an automatic plunger optimizing the blotting conditions are simple methods for reducing drying effects. With this third device acting on a hydrophilic supporting film, the increase of solute concentration is limited to less than 20%.
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  • 33
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    Journal of Electron Microscopy Technique 14 (1990), S. 39-45 
    ISSN: 0741-0581
    Keywords: Exocrine pancreas ; Cryofixation ; Cryomicrotomy ; Freeze-drying ; Freeze-substitution ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: 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.
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  • 34
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    Journal of Electron Microscopy Technique 14 (1990), S. 32-38 
    ISSN: 0741-0581
    Keywords: Electron microscopy ; Cell counts ; Nuclear shape ; Section compression ; Lung ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Counts of cells and nuclei from sections provide information central to studying structural changes in cells, tissues, and organs. This study considers some of the practical problems associated with counting cells with the newer random and serial sectioning methods of stereology and tests the hypothesis that similar cell counts can be obtained with both random and serial sectioning methods.Using irregularly shaped nuclei from alveolar cells of the goat lung, we compared cell counts derived from random (electron microscopic) and serial sectioning (light microscopic) methods. The results showed that both sectioning methods gave similar cell counts (107/cm3 of parenchyma) for type 1 epithelial cells (5.0 vs. 5.0; P=1.0), type 2 epithelial cells (8.6 vs. 9.8; P=0.42) and interstitial cells (34.6 vs. 33.4; P=0.64), provided that corrections were introduced for sectionrelated biases and that the nuclei of the random sectioning method were corrected for shape. We found counting biases of 5%-7% for nuclear shape and 16% for section compression. These observations support the hypothesis that similar cell counts can be obtained with random and serial sectioning, even when nuclei have irregular shapes.
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  • 35
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    Journal of Electron Microscopy Technique 14 (1990), S. 46-51 
    ISSN: 0741-0581
    Keywords: Lattice parameter determination ; Crystallographic orientations ; Image analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Oxygen-contaminated, melt-spun, binary Ti-Si alloys have been examined by using transmission electron microscopy. The microstructure of alloys in the range of 4 to 10% Si (by weight) are cellular and consist primarily of α-Ti and the silicide Ti5Si3. Contained only within the Ti5Si3regions are small, approximately spherical particles which are ≤ 10 nm in diameter. Due to their small size, the crystal structure of these particles could not be determined by using conventional diffraction techniques such as Selected Area or Convergent Beam Diffraction. By conducting a number of tilting experiments and observing the moire fringe patterns produced when various matrixTi5Si3 planes were used to image the sample, the crystal structure of the particles and the orientation relationship which exists between them and the matrix were deduced. The unknown particles, termed the Z phase, were found to be hexagonal with slightly different lattice parameters from the matrix Ti5Si3. Their relationship with the matrix was such that they appeared to be totally coherent. This may indicate that Z is an oxide based on the intermetallic Ti5Si3.
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  • 36
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    Journal of Electron Microscopy Technique 14 (1990), S. 70-78 
    ISSN: 0741-0581
    Keywords: Enamel crystals ; High resolution SEM ; Field emission ; Chromium coating ; Gold/palladium decoration ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Until recently high resolution TEM was the only imaging mode capable of probing the atomic lattice structure of crystals composing tooth enamel. Studies designed to determine the polyhedral shape of normal enamel crystals and initiation of carious lesions in enamel crystals were hampered and limited by interpretation of two-dimensional TEM images from thin section and freeze fracture replica specimens lacking depth of field. The newly developed SE-I signal mode for SEM (SE-I/SE-II ratio) can produce images of enamel crystals approaching beam diameter dimensions (0.7-2.0 nm), rivaling the resolution of the TEM technique and generating topographic contrasts for three dimensional imaging at very high magnification (≍1,000,000 X). Ultrathin chromium (Cr) films generate enriched high resolution SE-I contrasts of enamel crystal surfaces and when imaged using an immersion lens field emission SEM operated at high voltage (20-30 KeV) produce unsurpassed topographic contrasts. Since the grain size of Cr is below the resolution of any SEM and is ultrathin (≍1 nm), then SE-I images can provide a more accurate representation of enamel crystal structure than TEM methodologies.Our SE-I SEM observations of normal human enamel crystals reveal fractured spicules which contain angled flat surfaces delineated by a prominent 2 nm wide SE-I edge brightness contrast. Although microscopic observations often show crystals which are hexagonal in cross-section, in both SEM and TEM many other growth habits, including rectangular or irregular crystals (30-40 nm in width) which contain “notches,” are also observed. More detailed morphological studies are therefore required to determine the most likely habit planes and their relevance to the function of the enamel crystals. The granular appearing fine structural contrast imposed onto 〈100〉 lattice planes of sectioned enamel in TEM micrographs is also resolved with topographic contrasts in SE-I micrographs. These granules probably represent one or both of the enamel protein classes.
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  • 37
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    Journal of Electron Microscopy Technique 14 (1990), S. 83-84 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A miniature vise built into a copper stub is described that holds bulk, pre-frozen, hydrated biological specimens during examination under the electron beam of the scanning electron microscope.
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  • 38
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    Journal of Electron Microscopy Technique 14 (1990), S. 86-86 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 39
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    Journal of Electron Microscopy Technique 14 (1990), S. 87-87 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 40
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    Journal of Electron Microscopy Technique 14 (1990), S. 90-91 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 41
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    Journal of Electron Microscopy Technique 14 (1990), S. 89-89 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 42
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    Journal of Electron Microscopy Technique 14 (1990), S. 126-139 
    ISSN: 0741-0581
    Keywords: Carbohydrate ; Metabolism ; Liver ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 43
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    Journal of Electron Microscopy Technique 14 (1990), S. 152-174 
    ISSN: 0741-0581
    Keywords: Liver weight ; Cytochrome P-450 ; Smooth endoplasmic reticulum ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 44
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    Journal of Electron Microscopy Technique 14 (1990), S. 283-284 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 45
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    Journal of Electron Microscopy Technique 14 (1990), S. 289-297 
    ISSN: 0741-0581
    Keywords: Lowicryl K4M and HM20 ; Macrophage ; Ultrastructure preservation ; Immunogold labeling ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: 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.
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  • 46
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    Journal of Electron Microscopy Technique 14 (1990), S. 313-323 
    ISSN: 0741-0581
    Keywords: Fab labelling ; Immunoelectron microscopy ; Immunolabelling ; Fab-gold conjugates ; Antibody-gold conjugates ; Antibody-labelling ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Fab-colloidal gold labelling in conjunction with negative staining and high-resolution electron microscopy was used for targeting single protein units in regular arrays. These were bacteriophage T4 polyheads with Fab-Au2.5, and a specific antibody binding site on the haemagglutinin polypeptide of influenza virus with Fab-Au3, Fab-Au2.5, and Fab-Au1-2. For the latter, IgG-Au3 was also used. Experimental details are summarized to provide generally applicable methods for the preparation of small gold colloids Fab-Au and of labelling.The putative mechanism of protein-gold complex formation and adsorption to preferred sites on Fab and IgG, most probably to sulphur-rich regions, is discussed. The influence of pH during complex formation was found to be of minor importance in the samples investigated. Reported experimental details and our own experiences suggest that the importance of a protein's pI relative to its optimum gold complexing pH critically depends on the nature of the protein in question rather than being of general importance for protein-gold complex stability.
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  • 47
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    Journal of Electron Microscopy Technique 14 (1990), S. 329-334 
    ISSN: 0741-0581
    Keywords: Stimulator ; Polycrystalline ; Grain growth ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: 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.
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  • 48
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    Journal of Electron Microscopy Technique 14 (1990), S. 342-347 
    ISSN: 0741-0581
    Keywords: Quick-freeze deep-etch rotary replication ; Cell monolayers ; Tissue culture ; Specimen preparation ; Freeze-etch artifacts ; Temperature control ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: We have made several technical improvements for quick-freeze, deep-etch replication of monolayers of cells grown on, or attached to, glass coverslips. Cells studied include muscle cells of rat and Xenopus cultured on glass coverslips, and erythrocytes attached to coverslips coated with poly-L-lysine. We describe methods for identifying particular areas of cultures, e.g., clusters of acetylcholine receptors on muscle cells, by light microscopy and then relocating these areas after replication. For good preservation of structure by quick-freezing, it is necessary to ensure that the surface to be frozen is covered by a minimum depth of water (〈 10 μm). Insufficient or excess water left on the sample during freezing causes recognizable artifacts in its replica. We describe two ways to control the water table-one by improving visual control of water removal, the other by blowing excess water off the sample surface with a jet of nitrogen applied during its descent to the freezing block. Finally, we describe a new specimen holder that allows us to etch and replicate six samples at once with good thermal contact between the stage and samples.
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  • 49
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    Journal of Electron Microscopy Technique 14 (1990), S. 348-356 
    ISSN: 0741-0581
    Keywords: Cryofixation ; Cryoprotectant ; Dimethylformamide ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Conditions for cryofixation and freeze-substitution crucial to the ultrastructural preservation of embryonic quail retina were improved. As freeze-substitution makes gentle dehydration and chemical fixation of tissue possible, the suitability of different cryoprotectants were tested in the preceding cryofixation. Additionally, different conditions for chemical prefixation were studied. In cryofixation, all of the “classic” cryoprotectants caused more or less severe tissue destruction. Only dimethylformamide (DMF) and-with certain reservations-dimethylsulfoxide (DMSO) yielded improved structure preservation. Perfusion fixation with a mixture of formaldehyde/glutaraldehyde (FA/GA) was superior to GA alone. In comparison to conventional fixation and dehydration methods, freeze-substitution yielded better ultrastructural preservation of the embryos with fewer artifacts.
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    Journal of Electron Microscopy Technique 15 (1990) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 51
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    Journal of Electron Microscopy Technique 15 (1990), S. 1-1 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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    Journal of Electron Microscopy Technique 15 (1990), S. 20-33 
    ISSN: 0741-0581
    Keywords: Catecholamines ; Ultrastructure ; Synaptic terminals ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The monoamines dopamine, noradrenaline, adrenaline, and serotonin as well as the diamine histamine have a widespread distribution in the central nervous system within synaptic terminals and nonsynaptic varicosities. In certain regions of the central nervous system the monoamines are contained in varicosities that have no synaptic specialization associated with them, suggesting a possible neuromodulatory role for some of the monoamines. The majority of monoamine labelled structures are synaptic terminals which are characterized by the presence of small, clear vesicles (40-60 nm) and large, granular vesicles (70-120 nm) within the terminal. A third population of vesicles - small, granular vesicles - which are visible only after histochemical staining, are probably the equivalent of the small, clear vesicles present after either autoradiographic or immunohistochemical labelling. Most monoamine containing terminals contact dendrites and dendritic spines and, less frequently, neuronal somata and other axons. Both asymmetrical and symmetrical membrane specializations are associated with monoaminergic terminals; however, asymmetrical contacts are the most frequent type found. These ultrastructural results indicate that monoamine containing terminals and varicosities in general share many common morphological features, but still have diverse functions.
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    Journal of Electron Microscopy Technique 15 (1990), S. 49-66 
    ISSN: 0741-0581
    Keywords: Amino acid neurotransmitters ; Spinal cord ; Spinal trigeminal nucleus ; Cochlear nuclei ; Cerebellum ; Hippocampus ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The ultrastructural localization of putative excitatory (glutamate, aspartate) and inhibitory (taurine, glycine) amino acid neurotransmitters is described in several selected rat brain regions. In general, axon terminal profiles immunoreactive for excitatory amino acids formed asymmetric synapses with non-immunoreactive small diameter dendritic profiles or dendritic spines. In the cerebellum, both mossy fiber terminals and parallel fiber terminals were immunoreactive for glutamate and aspartate. In the hippocampus, mossy fiber terminals within the stratum lucidum of the CA3 region were immunoreactive for glutamate. Localization of glutamate and aspartate to cerebellar parallel and mossy fibers, as well as the identification of glutamate in hippocampal mossy fibers, is consistent with the excitatory nature of these fibers as described in previous physiological studies. Glutamate-like immunoreactive terminals were also identified in subnucleus caudalis of the spinal trigeminal nucleus and in the dorsal horn of the spinal cord.Immunoreactive axon terminals for two putative inhibitory neurotransmitters, glycine and taurine, displayed a greater number of morphological variations in synaptic structure. In the cerebellum, taurine-like immunoreactivity was present in both basket cell axon terminals which formed symmetric synapses with Purkinje cell neurons, and in a few mossy fiber terminals which formed asymmetric synapses with dendritic spines. In the area dentata of the hippocampus, taurine-like immunoreactive profiles formed asymmetric synapses with dendritic elements. Glycine-like immunoreactive terminals formed symmetric synapses with cell perikarya in both the ventral horn of the spinal cord and in the cochlear nuclei, and on axon terminals in the spinal trigeminal and cochlear nuclei. In contrast, some glycine-like immunoreactive terminals formed asymmetric synapses with distal dendritic profiles in the spinal cord and spinal trigeminal nucleus. The localization of taurine to cerebellar basket cell axons and glycine to axon terminals that synapse on ventral horn motor neuron perikarya is consistent with the hypothesis that these amino acids are functioning as inhibitory neurotransmitters at these synapses. Taurine localization to cerebellar mossy fibers and to fibers in the molecular layer of the dentate gyrus may be more consistent with a proposed neuromodulator role of taurine.
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    Journal of Electron Microscopy Technique 15 (1990), S. 301-315 
    ISSN: 0741-0581
    Keywords: Inner/Outer spiral sulcus ; Lateral intercellular spaces ; Mitochondria ; Endoplas-mic reticulum ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The intercalated body is a newly discovered organelle in the inner and outer spiral sulcus cells of the mouse organ of Corti. The organelle was found in the cochleas of 14-day and older intact mice and in organs in culture of corresponding ages. The organelle consists of a stack of interconnected cisternae of endoplasmic reticulum and of membrane bound rodlets that are intercalated between, and run parallel to, the cisternae. The cisternal membranes are predominantly smooth, but some may display ribosomes. Most rodlets are from 1 to 2 μm long, about 0.1 μm wide, and contain electron dense material. Mitochondria are commonly associated with or incorporated into the organelle. Some electron micrographs suggest that the rodlets may originate from modified mitochondria. It is our impression that the formation of the organelle begins with the apposition of cisternae and mitochondria. Cisternal-associated mitochondria appear to constrict, elongate, and lose their inner membranes. In both the intact animal and in culture, the cells of the inner and outer spiral sulci display microvilli, apical junctional complexes, lateral intercellular spaces containing interdigitating cell processes, and appear to be involved in fluid formation. Moreover, in culture, the cells of inner and outer spiral sulci as well as some cells proliferating in the outgrowth zone participate in fluid formation, producing large fluid pockets. All these cells commonly contain intercalated bodies. It is possible that in the intact animal, as in culture, intercalated bodies may play a role in fluid regulation in the immediate vicinity of the hair cells.
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    Journal of Electron Microscopy Technique 15 (1990), S. 377-382 
    ISSN: 0741-0581
    Keywords: Vickers indentations ; Magnesium oxide ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Single crystal MgO specimens having low load Vickers indentations were thinned in an ion milling machine employing a single ion gun, and their characteristics were investigated with optical microscopy and high voltage electron microscopy (HVEM). It was found that the state of cleanliness of the specimen chamber of the ion milling machine had a very marked influence on the quality of the thinned specimens. If the specimen chamber was not well cleaned before ion milling a fresh specimen, the latter tended to show amorphisation due to the deposition on the specimen of the debris left in the chamber from the previously ion-milled specimens. Such observations were made from MgO specimens ion milled in several different types of commercial ion milling machine employing a single gun. It is proposed that to obtain good-quality ion milled TEM specimens, it is important to clean the specimen chamber thoroughly prior to milling.
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    Journal of Electron Microscopy Technique 15 (1990), S. 414-415 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Journal of Electron Microscopy Technique 15 (1990), S. 316-317 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Journal of Electron Microscopy Technique 15 (1990), S. 318-319 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Journal of Electron Microscopy Technique 15 (1990), S. 321-321 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 60
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    Journal of Electron Microscopy Technique 15 (1990), S. 322-331 
    ISSN: 0741-0581
    Keywords: Axon transport ; WGA-HRP ; Axonal degeneration ; Autoradiography ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: In order to analyze connections between neurons in the vetebrate central nervous system, methods have been developed to label a given population of axons of known origin so that they can be differentiated from other, non-labeled structures. Three such methods are reviewed here: experimentally induced orthograde (Wallerian) degeneration, axon transport of radioactive proteins demonstrated by autoradiography, and axon transport of macromolecules that can be reacted histochemically to yield a visible reaction product. Each of the methods has particular strengths and weaknesses. Degeneration methods may differentiate between different functional classes of axons which have different fiber diameters. However, degeneration distorts the morphology of axon terminals, making them more difficult to interpret, and degenerating terminals may be removed rapidly by phagocytosis. Autoradiography of radioactive terminals preserves normal fine structure, but the necessary exposure times extend the method by weeks or months, and care must be exercised to distinguish labeled axons from other structures exhibiting background or transneuronal radioactivity. Histochemical methods, such as those used to demonstrate horseradish peroxidase conjugated to wheat germ lectin (WGA-HRP), are sensitive and rapid, but the injection site must be carefully characterized, and the presence of transneuronal label may make interpretation of the results difficult.Experimental methods of axonal labeling have been invaluable in studying neuronal networks. Each of the methods described here may be of particular value, given the nature of the system to be analyzed.
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    Journal of Electron Microscopy Technique 15 (1990), S. 332-351 
    ISSN: 0741-0581
    Keywords: Identified neurones ; Synaptic contacts ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: For more than a century the Golgi method has been providing structural information about the organization of neuronal networks. Recent developments allow the extension of the method to the electron microscopic analysis of the afferent and efferent synaptic connections of identified, Golgi-impregnated neurones. The introduction of degeneration, autoradiographic, enzyme histochemical, and immunocytochemical methods for the characterization of Golgi-impregnated neurones and their pre-and postsynaptic partners makes it possible to establish the origin and also the chemical composition of pre-and postsynaptic elements. Furthermore, for a direct correlation of structure and function the synaptic interconnections between physiologically characterized, intracellularly HRP-filled neurones and Golgi-impregnated cells can be studied. It is thought that most of the neuronal communication takes place at the synaptic junction. In the enterprise of unravelling the circuits underlying the synaptic interactions, the Golgi technique continues to be a powerful tool of analysis.
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    Journal of Electron Microscopy Technique 16 (1990), S. 254-255 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A method is described to strengthen the binding of organic resin to inorganic zeolite, allowing large particles to be microtomed. For FeZSM-5 aggregates the particle size limit increased from 3 μm to greater than 20 μm in diameter by application of this method. This technique can be applied to a variety of oxide powder samples, extending the utility of microtomy as a materials science tool.
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  • 63
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    Journal of Electron Microscopy Technique 16 (1990), S. 298-323 
    ISSN: 0741-0581
    Keywords: In vitro maturation ; In vitro fertilization ; Cytoplasmic phenotype ; Cytoplasmic organization ; Developmental competence ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Cellular aspects of reinitiated meiosis, fertilization, and early preimplantation embryogenesis in the bovine species were examined under in vitro conditions. An analysis of the cytoplasmic distribution of mitochondria, lipid droplets and vesicles in over 5,000 living GV-stage oocytes, with subsequent examination by electron microscopy, indicated that the organization of cytoplasm was pleomorphic and that five distinct cellular phenotypes could be identified. Inspection of oocytes during the resumption of arrested meiosis in vivo and in vitro demonstrated that the subcellular organization of the bovine oocyte cytoplasm remains unchanged during maturation to metaphase II. The influence of culture conditions and media on the frequency of maturation, cytoplasmic organization, fertilizability, and early preimplantation embryogenesis was also determined. The findings indicate that meiotic maturation and fertilization in the bovine species can occur at high frequency under comparatively simple and defined conditions. However, the acquisition of developmental competence for fertilization, and the ability of the egg to develop progressively after fertilization appears to be related to the organization of the cytoplasm at the GV stage. The relationship between cytoplasmic organization and conditions of maturation, fertilization, presence or absence of cumulus cells, and the acquisition of developmental competence is discussed with respect to (1) cell biological aspects of mammalian oocyte maturation, (2) the potential influence of extrinsic factors (e. g., differential intrafollicular biochemistry and morphophysiology) on sub-cellular organization of the GV-stage oocyte, and (3) the finding that morphologically equivalent bovine embryos derived from the in vitro fertilization of in vitro-matured oocytes may be developmentally heterogeneous. The studies also revealed that nuclear and cytoplasmic aberrations which could preclude normal embryogenesis can develop shortly after fertilization. The significance of this finding with respect to cytoplasmic phenotype of the oocyte and conditions of maturation, fertilization, and early embryo culture is discussed.
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    Journal of Electron Microscopy Technique 16 (1990), S. 358-358 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 65
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    Keywords: Cell wall ; LR White ; Spurr ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: We examined the ultrastructure of the cell envelope in Type I, Methylomonas albus (BG8), and Type II, Methylosinus trichosporium (OB3b), methane-oxidizing bacteria by using different fixatives, ruthenium red (RR) combinations and resins. We compared LR White and Spurrembedments with the following fixations: glutaraldehyde/OsO4, two glutaraldehyde-paraformal dehyde, and two different en bloc ruthenium red procedures, one utilizing 0sO4 and the other with glutaraldehyde/OsO4 in sequential fixation. These fixations were also studied by scanning electron microscopy (SEM). Unfixed cells prepared by freeze etch were used for comparison. Transmission electron microscopy of BG8 embedded in LR White resin (with or without ruthenium red) preserved a layer of cup-like structures that were not seen in Spurr resin-embedded cells unless ruthenium red was used. For OB3b, the second RR method preserved beads and filaments where only “spikelike” structures were seen in all other fixations in both resins. By SEM, all fixations preserved a capsular slime layer of BG8 that was removed from some cells by both RR methods. In all SEM fixations, a bead layer was preserved in OB3b that was enhanced by RR. Filaments seen by freeze-etch and thin-section techniques were not seen in SEM. Presence or absence of particular envelope structures in these methanotrophs is dependent on the combination of fixatives and/or resins employed and is species-specific. The chemical preparation methods used resulted in enhanced understanding of the structure and composition of the cell envelope.
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    Journal of Electron Microscopy Technique 14 (1990), S. 285-286 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Journal of Electron Microscopy Technique 14 (1990), S. 287-288 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Journal of Electron Microscopy Technique 14 (1990) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Journal of Electron Microscopy Technique 14 (1990), S. 307-312 
    ISSN: 0741-0581
    Keywords: Zirconia ; Metal - ceramic interface ; Superalloys ; Bonding ; Heat treatment ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: During the microstructural examination of ceramic thermal barrier coatings by transmission electron microscopy (TEM), initial efforts for the preparation of cross-sectional thin foils from interface regions by conventional means were mostly failures. Delamination of the Y2O3-stabilized ZrO2 ceramic coating from the nickel-base alloy substrate sometimes occurred during fine polishing at around 80 μm thickness but mostly occurred during dimpling. Because of this sensitivity, special techniques for mechanical handling were developed so that ion milling could give thin enough regions of the metal-ceramic interface. TEM showed convincingly that the highly fragile nature of the coatings is in fact due to the extensive porosity at the interface developed as a result of heat treatment.
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    Journal of Electron Microscopy Technique 15 (1990), S. 103-103 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Journal of Electron Microscopy Technique 15 (1990), S. 123-143 
    ISSN: 0741-0581
    Keywords: AChE ; ChAT ; Immunoreactivity ; Electron microscopy ; Acetyltransferase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: We have compared the biochemical expression of cholinergic enzymes with the morphological differentiation of efferent nerve fibers and endings in the cochlea of the postnatally developing mouse. Choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) are present in the newborn cochlea at specific activities 63% and 25%, respectively, of their mature levels. The relative increases in ChAT, in AChE, and in its molecular forms over the newborn values start about day 4 and reach maturity by about day 10. The biochemical results correlate well with the massive presence of nerve fibers stained immunocytochemically for ChAT and AChE or enzymatically for AChE in the inner and outer hair cell regions. Ultrastructural studies, however, indicate the presence of only few vesiculated fibers and endings in the inner and outer hair cell regions. The appearance of large, cytologically mature endings occurs only toward the end of the third postnatal week. The discrepancy may be resolved in the electron microscope using the enzymatic staining for AChE. Labeling is seen on many nonvesiculated fibers and endings in the hair cell regions, suggesting that the majority of the efferent fibers in the perinatal organ may be biochemically differentiated but morphologically immature. The results may imply that the efferents to inner and outer hair cells develop earlier than indicated by previous ultrastructural studies. Moreover, the pattern of development suggests that in the cochlea, as in other tissues, the biochemical differentiation of the efferent innervation may precede the morphological maturation.
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    Journal of Electron Microscopy Technique 15 (1990), S. 165-172 
    ISSN: 0741-0581
    Keywords: Perikaryal demyelination ; Nerve death ; Neural presbycusis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Spiral and Scarpa's (vestibular) ganglia of female C57BL/6 mice, ranging in age from 1.5 to 32 months, were examined by light and electron microscopy. The spiral ganglia of C57BL/6 mice undergo sweeping neuronal losses. Based on cytological characteristics that repeat themselves in both young and old mice, we divided perikaryal demyelination and degeneration of spiral ganglia into four arbitary stages: (1) incipient demyelination, myelin sheaths begin to loosen and unravel; (2) contact, the partially demyelinated perikarya abut as the extracellular matrix disappear; (3) clumping, clusters of naked perikarya clump together, cytoplasmic processes surround the exterior of the clump; and (4) resorption, the clumps gradually disintegrate, leaving at completion large, fluid-filled spaces and few cellular remnants. In Scarpa's ganglia, a small number of neurons demyelinate and clump, but none degenerate or undergo resorption.
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    Journal of Electron Microscopy Technique 15 (1990), S. 173-186 
    ISSN: 0741-0581
    Keywords: Freeze-fracture ; Hair cell synapse ; Corti organ ; Inner ear ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The fine structure of both the afferent and efferent hair cell synapses in the sensory epithelium of guinea pig organ of Corti was examined by freeze-fracture electron microscopy. In the afferent synapse, barlike aggregates of intramembrane particles (IMPs) of about 10 nm in diameter were seen on the P-face of the afferent presynaptic membrane directly beneath the presynaptic dense projection which is located in the active zone of the presynaptic membrane. Small and large depressions have been seen on the presynaptic membrane. The former were observed in the proximity of the barlike aggregates, while the latter were observed some distance from the aggregate. In outer hair cells, IMPs of about 10 nm in diameter were seen on the P-face of the afferent postsynaptic membrane at a density of 3,000/μm2.In the efferent synapse, many aggregates composed of from several to tens of large IMPs of 13 nm in diameter were observed on the presynaptic membrane. These aggregates were localized to small membrane depressions, which tended to be deeper as particle number per aggregate increased.Dense populations of IMPs of about 9 nm in diameter were observed on the P-face of the efferent postsynaptic membrane at a density of 4,000/μm2. A fenestrated subsynaptic cistern completely covers the efferent postsynaptic membrane. Moreover, the subsynaptic cistern spans several efferent postsynaptic membranes when efferent synapses are gathered in a group.In the afferent and efferent synapses of hair cells, specializations of the synaptic membranes were represented by marked aggregates characteristic of IMPs. In the efferent synapse, IMP movement inside the synaptic membrane was proposed in relationship to retrival of synaptic vesicle membrane. Structural relationship between the subsynaptic cistern and efferent postsynaptic membrane was revealed.
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    Journal of Electron Microscopy Technique 15 (1990), S. 209-224 
    ISSN: 0741-0581
    Keywords: Ultrastructural immunocytochemistry ; Enkephalins ; Choline acetyltransferase ; GABA ; Glutamate ; Cochlea ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: This paper presents the works and methods of our respective laboratories using electron microscopic immunocytochemistry to identify and localize cochlear neurotransmitters. Antibodies to various prospective neurotransmitters and associated enzymes have been used to study the ultrastructural localization of several candidates for olivocochlear efferent neurotransmitters previously suggested by light microscopic immunocytochemistry. Antibodies against enkephalins label lateral olivocochlear efferent fibers. Antibodies against choline acetyltransferase (ChAT) (an enzyme marker for acetylcholine) label a major population of both lateral and medial efferent fibers and terminals, whereas antibodies to γ-aminobutyric acid (GABA) label what might be a small subpopulation of both the lateral and medial efferent systems. The GABA-like immunostained medial efferent fibers are preferentially located in the upper turns of the guinea pig cochlea, particularly the third turn. Immunoelectron microscopy shows that neither GABA nor ChAT immunolabels all medial efferent terminals, regardless of cochlear turn. All the different types of immunolabeled efferent terminals have been observed to make characteristic synaptic contacts; lateral efferent terminals on afferent dendrites and medial efferent terminals on outer hair cells and occasionally on type II afferent dendrites. Other types of contacts involving GABA-like, and sometimes met-enkephalin-like, immunostained fibers are occasionally seen particularly in the upper turns of the cochlea. Immunoelectron microscopic results suggest that both medial and lateral efferent systems might be further subdivided on the basis of differences in neurotransmitters. Future trends of immunocytochemical research on cochlear neurotransmitters are proposed, particularly colocalization studies, which show a complex pattern of coexistence of neurotransmitters in the lateral efferent system.
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    Journal of Electron Microscopy Technique 15 (1990), S. 280-292 
    ISSN: 0741-0581
    Keywords: Inner ear ; Hair cells ; Cytoskeletal proteins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Immunofluorescence staining and phalloidin labeling have provided localization of actin in the sensory and supporting cells of the inner ear at the light microscopic level. However, with electron microscopy, neither actin nor actin filaments have been found in the outer hair cell body. This paper describes various techniques utilized to preserve and identify cytoplasmic actin at the ultrastructural level. Post-embedding staining of Lowicryl K4M sections, pre-embedding staining of permeabilized cells of the organ of Corti, pre-embedding staining of vibratome sections, and pre-embedding staining of permeabilized dissociated cells documented the presence of actin, but each of these techniques was best suited to localize actin in specific parts of the cell. Cytoplasmic actin was labeled when isolated cells were lightly fixed and membranes were permeabilized with detergent - conditions under which the cell ultrastructure was compromised. Under conditions of optimal fixation, cytoplasmic filaments embedded in the dense granular matrix of the hair cell cytoplasm were observed.
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    Journal of Electron Microscopy Technique 15 (1990), S. 293-300 
    ISSN: 0741-0581
    Keywords: Cochlea ; Cuprolinic blue ; Collagen types II, IX ; Glycosaminoglycans ; Chinchilla ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The ultrastructure of proteoglycans (PGs) in the tectorial membrane (TM) of the mature chinchilla cochlea was investigated using the cationic dye Cuprolinic blue. When used at a high critical electrolyte concentration, Cuprolinic blue has been shown specifically to bind to the glycosaminoglycan residues of sulfated PGs. After Cuprolinic blue treatment, PGs were observed in the TM which were represented as rod-shaped, electron-dense structures. A perifibrillar, primarily orthogonal, array of PGs was associated with the type A protofibrils. These PGs were distributed in 50 nm intervals along the length of the type A protofibrils. A less common orientation was parallel to the axis of the type A protofibrils. PGs did not appear to be associated with the type B protofibrils. Based upon previous results by other investigators, the TM contains types II and IX collagen, and it appears likely that the type A protofibrils are composed of collagen type II. PGs visualized in the TM in this study thus may represent the glycosaminoglycan residue of type IX collagen which is associated with the type II collagen fibrils. Alternatively, the TM PGs may be small dermatan or chondroitin sulfate PGs.
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  • 77
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    Journal of Electron Microscopy Technique 15 (1990) 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 78
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    Journal of Electron Microscopy Technique 15 (1990), S. 369-376 
    ISSN: 0741-0581
    Keywords: Lateral geniculate nucleus ; Electron microscopy ; HRP ; Structure/function correlations ; Identified neurons ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: During the past two decades new techniques have been developed to directly test the dogma that neuronal structure is correlated with neuronal function. In the earliest experiments, Procion yellow was injected into neurons after they had been characterized physiologically; these neurons were then viewed through the light microscope. Recent advances in the method generally employ horseradish peroxidase as the dye which is injected since it diffuses quite readily throughout the injected neuron and produces a stable reaction product for both light and electron microscopic studies. This review explores the utility of examining synaptic circuitry after physiologically recording from axons or neurons and then injecting horseradish peroxidase into them. As a model system, we studied the cat lateral geniculate nucleus and investigated, at the electron microscopic level, the synaptic contribution to this nucleus from retinogeniculate axons, from interneurons, and from the axon collaterals of neurons that project to visual cortex.
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  • 79
    ISSN: 0741-0581
    Keywords: Lectins ; Ultrastructure ; Visual system ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Phaseolus vulgaris leucoagglutinin (PHA-L) is a plant lectin that is anterogradely transported by neurons in the central nervous system. PHA-L is selectively taken up by cells at iontophoretic injection sites and, when immunohistochemically demonstrated, labels individual neurons completely, including their dendrites, axons, and terminal boutons. PHA-L is generally not taken up by fibers passing through the injection site and, because it produces a Golgi-like staining of even very fine axons over long distances, it is sometimes possible to light microscopically reconstruct individual neurons and their entire axon terminal arbors. When prepared for electron microscopy, the PHA-L-labeled terminals are densely and completely stained, allowing their synaptic relationships to be defined. These properties make PHA-L advantageous for studying the patterns of projection and the modes of termination of select groups of neurons in their target nuclei.We used PHA-L to study the extraretinal innervation of the cat's dorsal lateral geniculate nucleus, a thalamic visual center. Although much is known about the retinal contribution to geniculate synaptic circuitry, relatively little is known about other sources of innervation, even though these provide the majority of synaptic terminals in the nucleus (Guillery: Z. Zellforsch., 96:1-38, 39-48, 1969; Wilson et al.: Proc. R. Soc. Lond. [Biol.], 221:441-436, 1984). We used both light and electron microscopy to describe synaptic circuitry from three extraretinal sources of projections to the lateral geniculate nucleus: the visual cortex, the perigeniculate nucleus, and the parabrachial region of the brainstem. Cortical terminals labeled with PHA-L were small and formed asymmetrical synaptic contacts onto small-caliber dendrites of geniculate neurons. Peri-geniculate terminals formed symmetrical synaptic contacts primarily onto small-caliber dendrites, but some synapses were also formed onto the proximal, retinorecipient portions of geniculate dendrites. Parabrachial terminals synaptically contacted the retinorecipient portions of dendritic appendages and shafts, small-caliber dendrites, and the specialized dendritic (F2) terminals of geniculate interneurons. The symmetry of the parabrachial synaptic contacts was variable and was related to the postsynaptic target. Contacts onto dendritic appendages were asymmetrical while those onto dendritic shafts and F2 terminals were symmetrical. Our data suggest that in unlabeled material these brainstem terminals would be difficult to distinguish from cortical or perigeniculate profiles. The positioning of the parabrachial input onto the retinorecipient portions of geniculate dendrites indicates that this projection is well situated to control primary retinal transmission through the nucleus, while the location of most cortical and perigeniculate innervations implicates them in secondary feedback interactions or other aspects of geniculate function.
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  • 80
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    Journal of Electron Microscopy Technique 15 (1990), S. 400-405 
    ISSN: 0741-0581
    Keywords: Extraction replica ; Zr alloys ; Analytical electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A reliable two-stage carbon replica technique has been developed to extract precipitates from zirconium alloys. Using this technique, all precipitating phases can be extracted from Zircaloy-2, Zr-Cr-Fe, and Zr-Nb-Fe alloys. Precipitate identification using EDS X-ray analysis and convergent beam electron diffraction was greatly facilitated in comparison to thin foils. In addition, the sensitivity for the detection of trace elements in particles was increased using extraction replicas. The chemical compositions of the precipitates as determined from both replica and thin foils were in excellent agreement.
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  • 81
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    Journal of Electron Microscopy Technique 15 (1990), S. 406-413 
    ISSN: 0741-0581
    Keywords: HREM ; Helmholtz coil ; Feedback circuit ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Owing to the particular environment of the JEM4000EX HREM at the University of Pennsylvania, it became necessary to control the magnetic environment around the microscope. The unstable magnetic environment included two components, a slowly wandering vertical DC magnetic field and an AC magnetic field. The effects of these fields on the microscope performance were to introduce an uncertainty in the objective lens defocus value over a series of images and to reduce the attainable resolution of the microscope, respectively. A solution is presented in which these fields are stably reduced well within the limits of sensitivity of the JEOL, Ltd. JEM4000EX for high-resolution imaging. This solution is based on a feedback loop using a pseudo-Helmholtz coil to generate a well-defined vertical magnetic field.
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  • 82
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    Journal of Electron Microscopy Technique 16 (1990), S. 37-44 
    ISSN: 0741-0581
    Keywords: Small intestinal morphology ; Immunohistochemistry ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: In the present study, we modified the technique described by Altman et al. (J. Histochem. Cytochem., 32:1217-1223, 1984) for rapid embedding of tissues in Lowicryl K4M. To attain good sections of the small intestine that contained villi, crypts, submucosa, and external muscle layers, we cut 100 μm slices of the full thickness of the wall with a vibratome before embedment and then deoxygenated the resin and tissue before polymerization. The sections we obtained compared favorably with the quality of sections from conventional resins.
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  • 83
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    Journal of Electron Microscopy Technique 16 (1990), S. 2-14 
    ISSN: 0741-0581
    Keywords: Intestine ; Epithelium ; Mucous cells ; Nucleolus ; Cell kinetics ; Ultrastructure ; Protein synthesis ; RNA synthesis ; Stem cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: This article is a summary of our work of several years on the renewal of the intestinal epithelium. A combination of ultrastructural, radioautographic, and light microscopic analyses was carried out using normal tissue and tissue affected by inhibitors of RNA and protein synthesis. Measuring protein synthesis by 3H-leucine radioautography showed that the life span of the columnar (absorptive) cells in the rat small intestine was divisible into two main phases: differentiation (from stem to functional cell) and maturation (from functional to extruding cell), each phase and its subdivisions being well defined morphologically. Differentiation involved a linear rise in the rate of protein synthesis per cell and showed at the same time heterochromatinization and silencing of RNA transcription. Data from various experiments indicated that the cells functioned from stored information (RNA), part of which came from the nucleolus, which underwent marked and characteristic ultrastructural changes. Although transcription from rDNA ceased, the nucleolus released its ribosomal material, which added to the existing protein synthesis, presumably by recruiting excess stored mRNAs. Maturation involved a nearly linear decrease of the rate of protein synthesis per cell to a characteristic low value at which extrusion took place. A gradual exhaustion of the stored RNA was indicated to be the key factor in this decrease. Ultrastructurally, maturation was associated with a gradually increasing vesiculation of rER and Golgi. The results thus imply a regulatory role of cellular protein synthesis level in renewal. This would be an epigenetic response after the genes are silenced. The nucleolus seems to play a central role in this process, and this in turn is reflected in its characteristic ultrastructural changes. The work also included new observations on the epithelium of the rat ascending colon describing a hitherto unrecognized deep crypt mucus-secretory (“DCS”) cell which is a nongoblet mature cell type apparently arising from midcrypt mitoses. In between the DCS cells, occasional slender columnar cells were seen which displayed the ultrastructural features of stem cells. These were probably reserve stem cells. We also observed nongoblet deep crypt mucous cells in the human right colon although fewer in number than in the rat. Nucleolar regulation and the presence of reserve stem cells represent new dimensions in our understanding of renewal. Electron microscopy is an essential tool in this investigation.
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  • 84
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    Journal of Electron Microscopy Technique 16 (1990), S. 56-68 
    ISSN: 0741-0581
    Keywords: Epithelial cells ; Transport ; Intestinal cell ; Flounder ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The polymorphism of the endoplasmic reticulum (ER) in epithelial cells with different transport functions such as the enterocyte suggests that the ER may be involved in some way in molecular transport. To further access this possibility, we examined the ER from the intestine of winter flounder, Pseudopleuronectes americanus, a species which undergoes an annual fast of approximately 6 months' duration, a time during which previous work indicates nutrient carrier number does not change. Fish from June (feeding) and January (8-10 weeks fasted) were sampled. Tissues from the pyloric caeca, foregut, midgut, and hindgut were prepared for electron microscopy using two techniques of staining. Cell height was unaltered in any section, although microvillar length shortened variably. Cellular organization, including position of nuclei, number and distribution of mitochondria, and presence of basolateral membranes, did not change. The ER appeared equally abundant in June and January. However, use of the osmium impregnation technique, which is specific for ER cisternal contents, revealed a change in the impregnation of ER, from a heavily impregnated network in summer to little or no impregnation in winter. These results suggest that a shift in function of the ER had occurred when nutrient transport ceased, and supports a role of the ER in nutrient transport.
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  • 85
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    Journal of Electron Microscopy Technique 16 (1990), S. 89-89 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 86
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    Journal of Electron Microscopy Technique 16 (1990), S. 347-350 
    ISSN: 0741-0581
    Keywords: Tissue culture ; Peripheral nerve ; Immune system cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: This paper describes a method for primary fixation of cultured cells for scanning (SEM) and transmission (TEM) electron microscopy using microwaves alone. This method of fixation takes 8 seconds and is therefore quicker and less expensive than conventional fixation techniques. The preservation of cell morphology is excellent and cultures of mammalian immune system cells and peripheral nervous tissue have been examined using this fixation.
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  • 87
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    Journal of Electron Microscopy Technique 14 (1990) 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 88
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    Journal of Electron Microscopy Technique 14 (1990), S. 13-20 
    ISSN: 0741-0581
    Keywords: ω correction ; Lorentzian angular distribution ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Several basic physical concepts of applying eq. Ik = IσNxt to surface microanalysis by reflection electron energy-loss spectroscopy (REELS) are clarified. Here Ik and I are the integrated intensities of the core ionization edge and the low loss part, σ is the scattering cross section of element x with atomic concentration Nx, and t is the specimen thickness. The reflected inelastic electrons are found to be distributed almost symmetrically around the Bragg sports and can be reasonably described by a Lorentzian function. EELS microanalysis can be performed by using the diffracted sports. The ω correction, arising from the angular contributions of the neighbouring spots into the spectrometer collecting aperture, is required to be considered.
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  • 89
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    Journal of Electron Microscopy Technique 14 (1990), S. 1-5 
    ISSN: 0741-0581
    Keywords: Scanning electron microscopy ; Microanalysis ; Elemental mapping ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: 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.
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  • 90
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    Journal of Electron Microscopy Technique 14 (1990), S. 6-12 
    ISSN: 0741-0581
    Keywords: Direct imaging ; Time-resolved cryo-TEM ; Transient microstructures ; Phospholipid mesophases ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: We describe a new technique, time-resolved cryotransmission electron microscopy (TRC-TEM), that can be used to study changes in microstructure occurring during dynamic processes such as phase transitions and chemical reactions. The sample is prepared on an electron microscope grid maintained at a fixed temperature in a controlled atmosphere. The dynamic process is induced on the grid by a change in pH, salt, or reactant concentration by rapid mixing with appropriate solutions. Alternatively, induction is by rapid change of specimen temperature, or by controlled evaporation of a volatile component. We call such procedures on-the-grid processing. The dynamic process is permitted to run for a defined time and then the thin-film specimen is thermally fixed by plunging into liquid ethane at its freezing point, producing a cryotransmission electron microscopy specimen. By repeating this procedure with varying delays between induction and sample fixation, we can observe transient microstructures. We demonstrate the use of TRC-TEM to study the intermediate structures that form during the transitions between Lα, III, and HII liquid crystalline phases in phospholipid systems. We also identify several other possible applications of the technique.
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  • 91
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    Journal of Electron Microscopy Technique 14 (1990), S. 21-31 
    ISSN: 0741-0581
    Keywords: Freeze-fracture ; Lectin-gold ; Enzyme-gold ; Membrane glycocnjugates ; Phospholipids ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Peldri II, a fluorocarbon compound solid at room temperature, was used as a sublimation dehydrant in place of critical-point drying (CPD) in freeze-fractured cytochemistry. Its applicability to the fracture-label replica method was demonstrated using freeze-fractured rat pancreas labeled with Helix pomatia lectin-gold complex and phospholipase A2-gold complex for the detection of glycoconjugates and phospholipids, respectively. No difference in morphology and labeling pattern was detected in CPD-treated and Peldri II-treated tissue samples. The use of Peldri II was further extended to freeze-fractured rat duodenum labeled with wheat germ agglutininovomucoid-gold complex. Again comparable results were obtained when duodenal samples were prepared according either to the conventional CPD method or to the Peldri II sublimation method. Freeze-fractured replicas of hamster ovaries labeled with Ricinus communis I-gold complex revealed that Peldri II could also be used as a sublimation dehydrant for preparing tissue samples for examination in the scanning electron microscope by the backscattered electron imaging mode.
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  • 92
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    Journal of Electron Microscopy Technique 14 (1990), S. 79-82 
    ISSN: 0741-0581
    Keywords: Ion milling ; Ion beam damage ; Water-soluble substrate ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A method is described for the preparation of cross-sectional samples of thin films for transmission electron microscopy. The technique produces larger amounts of thin region as compared with ion milling and eliminates the problems associated with ion beam damage. The requirement is that the films or multilayers must initially be deposited on a water-soluble substrate such as single-crystal NaCl.
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  • 93
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    Journal of Electron Microscopy Technique 14 (1990), S. 85-86 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: We believe that the paper in question (JEMT 11, 174, 1989) is presented in a way that is misleading.
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  • 94
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    Journal of Electron Microscopy Technique 14 (1990) 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 95
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    Journal of Electron Microscopy Technique 14 (1990), S. 175-176 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 96
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    Journal of Electron Microscopy Technique 14 (1990) 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 97
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    Journal of Electron Microscopy Technique 14 (1990), S. 218-236 
    ISSN: 0741-0581
    Keywords: Endocytosis ; Cell isolation ; Cell culture ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: 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.
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  • 98
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    Journal of Electron Microscopy Technique 14 (1990), S. 177-178 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 99
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    Journal of Electron Microscopy Technique 14 (1990), S. 208-217 
    ISSN: 0741-0581
    Keywords: Hilar biliary plexus ; Periductal sacculi ; Bile ductular plexus ; Peribiliary vascular plexus ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The three-dimensional structure of the biliary tract was studied by scanning electron microscopy (SEM) of biliary casts. The replica of the biliary tract was successfully prepared by retrograde injection of low viscosity resin into the common bile duct. Bile canaliculi are intricate networks in which hexagonal and pentagonal meshworks are interconnected. Each hexagonal or pentagonal meshwork is on a plane, but adjoining meshworks are on different planes. Bile canalicular networks connect with bile ductules at the periphery of the portal tract. The intrahepatic bile duct showed considerable interspecies variation. The human bile duct has plexiform side branches and periductal sacculi, which are most numerous near the liver hilum and fewest in the smaller portal tracts. The hilar plexus and sacculi are present on opposite sides of the bile duct. The plexus formed at the bifurcation of the bile ducts exhibits a plane. Periductal sacculi were also observed in the monkey and pig bile ducts, particularly the latter, while rat bile ducts possess a peculiar portal bile ductular plexus situated between the portal tract and the surrounding liver parenchyma. No such structures were observed in either the dog or rabbit bile ducts. SEM of the biliary casts showed that the biliary tract was not a simple draining tube but had additional structures, such as periductal sacculi and plexiform side branches. These structures, together with the peribiliary vascular plexus, may be implicated in the modification of bile.
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  • 100
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    Journal of Electron Microscopy Technique 14 (1990), S. 335-341 
    ISSN: 0741-0581
    Keywords: Muscle thin filaments ; Actin/Tropomyosin filaments ; Negative stain ; Cryoelectron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A method is described for electron microscopic observation of two-dimensional paracrystals on unsupported lipid monolayers. The method uses a hydrophobic holey C-coated grid placed on a monolayer made positively charged by the inclusion of stearylamine (SA) and has been used to align scallop thin filaments and reconstituted actin/tropomyosin filaments to form paracrystals. The use of unsupported monolayers allows the paracrystals to be viewed in either negative stain or with cryoelectron microscopy. Those paracrystals in frozen hydrated specimens have better order than those with negative stain.It was found that varying the lipid composition between the less fluid distearolyphosphotidylcholine/SA and the more fluid egg yolk phosphotidylcholine/SA alters the size and order of the paracrystals, the more fluid system having smaller, more ordered paracrystalline domains. The advantage of the technique for studying actin/thin filaments is the ability to form large two-dimensional paracrystals under physiological conditions of [Mg2+] and pH.
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