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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 115 (1993), S. 11590-11593 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Structural changes in neurons in the cervical anterior horn of ageing mice have been studied. The main age-related neurocytological change observed during this study is progressive accumulation of lipofuscin. The pigment was present in some nerve cells as early as six weeks after birth. Various types of membrane-bound granules encountered in the anterior horn cells were characterized on the basis of their shape, size and fine structure into primary lysosome-like (L1) granules (dense bodies), autophagic vacuole-like (L2) granules and mature (L3) pigment granules of complex substructure and irregular configuration.L1,L3 andL3 types of granules appear to represent respectively early, intermediate and mature stages in a developmental continuum of lipofuscin pigment granules. Transitional stages suggest that matureL3 pigment granules evolve by gradual alteration of lysosome-likeL1 andL2 granules. A probable sequence of morphologic events accompanying the transformation of lysosome-like granules into mature lipofuscin pigment granules is suggested.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The entry zone of trigeminal sensory root fibers displays a “glial dome” covered by a basal lamina. This zone constitutes the “fibrous cone” of gross descriptions of the root and demarcates a sharp transition from peripheral to central nervous system. The dome consists of closely interwoven astrocyte processes, and appears to be identical to the subpial astrocyte meshwork elsewhere in the central nervous system. In the peripheral portion of the root, axons are surrounded by Schwann cells; those associated with myelin sheaths display distinctive laminar inclusions and pinocytotic vesicles lacking in Schwann cells which surround unmyelinated axons. In the peripheral region, separate and distinct endoneurial and perineurial layers of collagen could not always be identified. In the central part of the root, Schwann cells, fibroblasts, and collagen are absent and from the point of transition, the axons are principally surrounded by astrocytes. Oligodendrocytes are relatively rare in the transitional zone. The axonal transition from central to peripheral, occurs at nodes of Ranvier where the basal lamina of the dome is continuous with the basal lamina of the Schwann cell of the last peripheral internode. Some “islands” of glial tissue are interspersed in the root and ganglion but it was not established if these are completely discontinuous with the central “glial dome.” No ganglion cells have been found in such “islands,” nor in the glial dome.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 16 (1995), S. 984-1010 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio molecular orbital calculations have been carried out on over 50 model organic molecules and ions to provide the data necessary in the determination of torsional parameters for a force field involving polypeptides. The rotational energy profiles were obtained at the HF/6-31G*//HF/6-31G* level. The results were supported, in many cases, by full geometry optimizations and with consideration of correlation corrections at the MP2 level. With the exception of the dihedral angle being studied, all of the molecules were fully optimized with C1 symmetry. © 1995 by John Wiley & Sons, Inc.
    Additional Material: 26 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cytological changes accompanying the maturation of erythrocytes in the “Pacific hagfish” (Eptatretus stoutii) were studied. Great numbers of immature and mitotically dividing red blood cells in the peripheral circulation of the hagfish appear to indicate that extensive differentiation and proliferation occurs in the blood stream of this animal. The immature erythrocytes contained mitochondria, Golgi membranes, centrioles, microtubules and a high density of ribosomes in the cytoplasm. Intermediate stages revealed lysosomes in the cytoplasm. With progressive differentiation the hagfish erythrocytes accumulate hemoglobin and lose most of their cytoplasmic organelles. The various cytoplasmic organelles are apparently lost through a degradation process brought about by lysosomal autolysis. The undigested products of degradation such as mitochondrial and other intercellular membranes are apparently extruded by way of the plasma membrane. The plasma membrane of young as well as mature erythrocytes display evidence of intense pinocytotic activity. The nucleolus undergoes a reduction in size with progressive maturation. The cytoplasm of mature erythrocytes consists predominantly of hemoglobin. An equatorial microtubular marginal band is identifiable in differentiating erythrocytes.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 118 (1966), S. 437-459 
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The ultrastructural features of oligodendrocytes have been studied in a zone of cerebral cortex in which all neurons are destroyed and numerous processes damaged by heavy ionizing particles. This type of lesion fails to reveal signs of vascular inflammation and classical “gitter cells” in light microscopy or any signs of debris fragments in electron microscopy. Oligodendrocyte satellites of neurons or their processes display an acute swelling associated with signs of neuronal damage. This is followed by a marked increase in a morphologically rich variety of dense osmiophilic organelles of granular, lamellar, crystalline or amorphous sub-structure. Acid phosphatase activity has been demonstrated in some of these organelles, thus implying a participation in “lysosomal” intracellular breakdown. Invasion by microgliacytes and phagocytosis was not observed. Present evidence supports the efficacy of intracellular mechanisms in the breakdown of degenerating material and suggests a re-evaluation of the evidence for identification of microglia on the basis of granular inclusions.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 160 (1981), S. 247-255 
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Light microscopic histochemistry for alkaline phosphatase was employed in a study of the development of vascular sprouting, with respect to time and distribution, in the rat cerebral cortex. Sprouts were counted in the full thickness of the cerebral cortex at each day from birth to 21 days of age. Several distinct bursts of sprouting activity were observed at specific times and levels of cortex. From birth to 4 days of age, sprouting was intense in the superficial third of the cortex. At 7 to 8 days, a burst of sprouting was found which was greatest in the middle third. Additional bursts of sprouting appeared at 10 and 14 days.Developing vessels with characteristics of arteries, capillaries, or sprouts were alkaline-phosphatase positive, while veins were not. It is concluded that alkaline phosphatase is a useful marker for identification of both mature and immature vasculature, as it reveals patent and nonpatent vessels, and the sprouts which are precursors of the mature vascular bed. New vessels developing in the cortex arise mainly from blind sprouts of capillaries, evidently in response to the metabolic demands imposed by the maturational process.At birth, the majority of intracortical vessels are capillaries. By 10 days of age, most perforating vessels from the surface have taken on arterial or venous characteristics. The findings are discussed in connection with morphological and biochemical differentiation and the pattern of vascularization in the mature cerebral cortex.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 160 (1981), S. 257-265 
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Alkaline phosphatase cytochemistry was employed to study the distribution of this enzyme in blood vessels during vascular differentiation and maturation during the postnatal development of the rat cerebral cortex. Enzyme reaction product was present in early vascular sprouts, and also throughout the subsequent maturation and differentiation of capillaries and arterial vessels. Cerebral capillaries appeared to be patent soon after the fusion of a sprout tip with another vessel; no evidence for delayed or synchronous opening was obtained. The distribution of alkaline phosphatase reaction product in vessel walls changed during vascular maturation. In vascular sprouts, reaction product was found mainly in the narrow lumen. As vessels became patent, reaction product appeared also on abluminal surfaces, at first chiefly in the narrow spaces between overlapping vascular cells. As vessels matured, reaction product became more generally distributed around the abluminal surface. In relatively mature capillaries and arterial vessels, it was restricted largely to endothelial cell surfaces and the spaces between smooth muscle cells. The significance of this distribution is unknown. Some possible explanations, including the possibility of artifact, are discussed. No alkaline phosphatase reaction product was found in differentiated veins.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 118 (1966), S. 411-435 
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Electron microscopic examination of rat cerebral gray and white matter following formaldehyde or glutaraldehyde vascular perfusion reveals distinctive morphological features for identification of oligodendrocytes. These elements are situated as satellites of neurons (perikarya, dendrites and axons), and display a wide range of nuclear and cytoplasmic densities which tend to parallel each other. Cytoplasmic density appears to be an uncertain criterion for neuroglial identification, but oligodendrocytes are recognizable by the following distinctive features: large quantities of free ribosomes or ribosomal rosettes, numerous nuclear pores and light patches of otherwise dense chromatin adjacent to the pores, extensive cytoplasmic microtubules, absence of broad processes seen in other cerebral elements but presence of numerous fine processes which can occasionally be traced to form the outer mesaxon of myelin sheaths, absence of glycogen and fine gliofibrils uniquely present in astrocytes, and the usual presence of thin rims of perinuclear cytoplasm frequently associated with large dilatations of the nuclear cleft. Arguments are adduced for rejecting the identification of “dark” glial elements as microglia. The relation of oligodendrocytes to myelin and the functional significance of the wide spectrum in cytoplasmic density are considered in relation to the synthetic demands of adjacent neurons.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 125 (1969), S. 247-269 
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Numerous optic nerve fibers persist for a period of up to 20 months following enucleation in reptiles, although it is unlikely that a significant number of efferent fibers are present. After varying survival periods, almost all nerve fibers display distinct morphological changes probably associated with degeneration, but most features previously associated with early stages of degeneration can be seen in long-survival material except for the early and rapid loss of all non-myelinated fibers and a honeycomb tubular degeneration associated with the inner and outer myelin layers. Distinct sequential stages of axon and myelin degeneration could not be ascertained despite the slow rate of degeneration in poikilotherms. The varieties of abnormal axon morphology are documented and considered in terms of current light microscopic staining methods.
    Type of Medium: Electronic Resource
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