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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 177-190 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The conformational properties of optically active macromolecules are considered. A statistical zigzag model is used for the calculation of averaged physical properties. The macromolecule is considered to consist of segments of two different types with a statistical distribution of lengths. The expressions for the mean square of the end-to-end vector h2 and the dipole moment μ2 and also of the mean optical anisotropy ΔA and the anisotropy of the optical rotation tensor ΔG were obtained in the cases of freely jointed and freely rotating segments. The equations obtained were applied to the problem of the helix-coil transition. In the case of poly-α-olefins the values of h2, μ2, and ΔA, are larger than corresponding values for typical optically inactive macromolecules. The anisotropies ΔA and ΔG of two poly-α-olefins of similar structures were calculated. The polarizability theory of optical activity was used for the calculations of ΔG. The values obtained for ΔA are similar, but the values of ΔG differ markedly. The possibility of obtaining valuable information about the structure of optically active macromolecules in solution by a study of anisotropy of the optical rotation tensor is considered.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 8 (1970), S. 2265-2274 
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several new types of polybenzimidazoquinazolines with a different recurring unit have been prepared by solution polycondensation in polyphosphoric acid followed by heating at elevated temperature under reduced pressure. The polymers thus obtained were light yellow to brown powdery materials hardly soluble in common organic solvents and soluble in concentrated sulfuric acid. The inherent viscosity of the polymers ranged from 0.1 to 0.58 and showed good thermal stability.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 8 (1970), S. 3503-3510 
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of isomerization of butenes by boron trifluoride with acetic acid or methanol as cocatalysts have been re-examined. The results, over a wide concentration range, and at temperatures from -20 to +20°C, are consistent with previous data, but it is shown that the previously suggested mechanism cannot apply. By using deuterated acetic acid as cocatalyst it has been found that isomerization exactly parallels protonation, which is consistent with a mechanism involving a classical carbonium ion.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 15 (1970), S. 34-44 
    ISSN: 1432-0533
    Keywords: Ultrastructure ; Degeneration ; Necrosis of Muscle ; Dystrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die ultrastrukturellen und histochemischen Merkmale von drei Muskelfaserveränderungen — Faserverzweigung, große Fasern und nekrotische Fasern — wurden an 129 dystrophischen Bar Harbor-Mäusen untersucht. Die Pathogenese dieser Veränderungen, die als Schädigungsfolgen aufgefaßt werden, wird diskutiert. Obwohl diese Veränderungen nicht als spezifisch angesehen werden, sind sie doch charackteristisch für die Histopathologie der Muskeldystrophie, so daß das Verständnis des Mechanismus, der diese abnormen Muskelfasern hervorbringt, zur Kenntnis des dystrophischen Prozesses beitragen dürfte.
    Notes: Summary Ultrastructural and histochemical features of three muscle fiber changes — branched fibers, large fibers and necrotic fibers — have been studied in Bar Harbor strain 129 dystrophic mice. The pathogenesis of these changes, which are considered to be responses to injury, have been discussed. Although these changes are not regarded as specific, they are characteristic of the histopathology of muscular dystrophy, so that an understanding of the mechanisms which produce these abnormal muscle fibers should contribute to the knowledge of the dystrophic process.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1106
    Keywords: Brain slices ; Ultrastructure ; Synaptic potential ; Metabolism ; Olfactory cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The fine structure and electrical activity were studied in thin brain sections prepared from the olfactory cortex of the guinea pig and incubated in vitro in standard and modified conditions. In the standard medium, the potential response was maintained with no marked changes for 4–5 hours and thereafter gradually decreased. The ultrastructure of the tissue was well preserved for the initial 2 hours of incubation. After incubation for 5 hours, many empty spaces were noted. Some dendritic stumps lost fine internal structure, but most of the synapses were apparently normal. Cyanide suppressed the potential response, and caused swelling of the nerve terminals and a decrease in the number of synaptic vesicles. The recovery of the response in the standard medium was not accompanied by a full restoration in the fine structure. If slices were incubated in the absence of glucose and oxygen, with cyanide in glucose-free medium, or at a low temperature, the potential response was irreversibly depressed. In these slices, numerous wide spaces of low electron density were noted which were concluded to have been derived, at least partly, from the swollen dendrites.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 111 (1970), S. 293-315 
    ISSN: 1432-0878
    Keywords: Herring bodies ; Ultrastructure ; Degeneration ; Regeneration ; Neurosecretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The Herring bodies in the posterior lobe of the bovine hypophysis are very large (2–600 μ) and can be classified into three types. The type I Herring body contains an accumulation of neurosecretory granules. These Herring bodies are very scarce and should not be confused with the numerous, but small, axonal swellings which also contain neurosecretory granules. The type II Herring body is characterized by the presence of a varying number of normal, moderately electron dense and “empty” vesicles, autophagic vacuoles, multilamellate bodies and occasional mitochondria. These Herring bodies are frequently observed. The type III Herring body is typified by the presence of dense vesicles connected to tubular formations which contain material of variable electron density, of filaments, and of long slender and very numerous mitochondria. The presence of multilamellate bodies and autophagic vacuoles suggests that the type II Herring body is in a degenerating phase. This concept is further substantiated by the similarity between this type of Herring body and transected neurosecretory axons in which degeneration is occurring. A similar comparison suggests that the type III Herring body is undergoing a regenerative process. Our current concept of the structure and function of Herring bodies is revised in the discussion.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0878
    Keywords: Corpora cardiaca ; Insects ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Résumé L'étude infrastructurale des corpora cardiaca de Locusta révèle l'existence de 3 types de fibres neurosécrétrices (portion neurohémale) et d'un seul type de cellules glandulaires (portion endocrine intrinsèque). Elle permet également d'envisager les modalités du rejet des sécrétions exogènes et endogènes.
    Notes: Summary An ultrastructural study of the corpora cardiaca of Locusta migratoria migratorioides shows three neurosecretory fiber types in the neurohaemal part of these organs; only one cellular type constitutes the intrinsic glandular part of the corpora cardiaca. This study also shows sites of release of stored extrinsic neurosecretory material and of products elaborated by intrinsic glandular cells of the corpora cardiaca.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0878
    Keywords: Neurosecretory Pathways ; Insects ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Résumé L'étude infrastructurale des nerfs cardiaques afférents et des nerfs allato-cardiaques qui entrent dans la constitution du système neurosécréteur rétrocérébral de Locusta migratoria migratorioides (R. et F.) révèle l'existence des trois types de fibres neurosécrétrices définis dans les corpora cardiaca. Une quatrième catégorie de fibres caractérisées par la présence de vésicules claires existe dans les nerfs allato-cardiaques et dans les corpora allata. L'origine des fibres et l'évolution des grains de neurosécrétion au cours de leur transit sont envisagées.
    Notes: Summary An ultrastructural study of the nervi corporis cardiaci and nervi corporis allati, which are part of the retrocerebral neurosecretory system of Locusta migratoria migratorioides, reveals the existence of three neurosecretory fiber types. A fourth neurosecretory fibertype with electron lucent vesicles is also present in the nervi corporis allati and in the corpora allata. The fibers are characterized by differences in the size and electron opacity of the neurosecretory granules. The origin of the various neurosecretory fiber types and the evolution of the neurosecretory granules are discussed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 109 (1970), S. 356-379 
    ISSN: 1432-0878
    Keywords: Gingivo-Dental junction ; Human ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Résumé L'étude ultrastructurale de la jonction gingivo-dentaire humaine a permis de montrer que les membranes cytoplasmiques des cellules épithéliales superficielles, revêtues de nombreux hémi-desmosomes, sont en rapport avec les cristaux d'apatite de l'émail par l'intermédiaire d'un espace intercellulaire, de 400 à 1200 Å d'épaisseur, rempli d'un matériel finement granulaire, soit directement soit par interposition d'une cuticule discontinue, d'épaisseur variable, qui est appliquée à la surface de l'émail uniquement sur des dents, ayant effectué leur éruption. Cette cuticule, dont l'origine salivaire peut être exclue, subit une apposition de la surface de l'émail vers la périphérie. L'attache épithéliale n'est pas kératinisée, mais des faisceaux de tonofibrilles sont visibles dans les cellules. Une certaine tendance à la kératinisation a été parfois notée au niveau du sillon gingivo-dentaire. De nombreux polynucléaires éosinophiles et neutrophiles et des lymphocytes migrent à travers la jonction et le sillon gingivo-dentaires cliniquement normaux. Un élargissement des espaces intercellulaires, des ruptures de la membrane basale et des desmosomes, une accumulation parfois importante de glycogène, des noyaux polylobés et des oedèmes intracellulaires y ont également été notés. Enfin une rupture en ≪atimbre poste≫ entre les cellules épithéliales de la jonction, ainsi qu'une rupture entre l'émail et les cellules épithéliales superficielles contribuent à l'approfondissement du sillon gingivo-dentaire.
    Notes: Summary The ultrastructural investigation of the human gingivo-dental junction shows that the plasmalemmata of the superficial epithelial cells, coated by numerous hemi-desmosomes, are related to the enamel apatite crystals through a finely granular intercellular space, 400 to 1200 Å in thickness, either directly or through a discontinuous dense cuticle, of irregular thickness, which is attached to the enamel surface of erupted teeth. This cuticle, of none salivary origin, is deposited from the enamel surface to the outside. The epithelial junction is not keratinized, but numerous tonofibrils bundles occur in the cells. A certain tendency toward keratinization was sometimes observed in the crevicular epithelium. Numerous eosinophilic and neutrophilic polymorphonuclear leukocytes, and lymphocytes migrate through the clinically normal crevicular and junctionnal epithelium. Intercellular space dilatations, basement membrane and desmosomes ruptures, important intracellular accumulations of glycogen, multilobulated nuclei and intracellular edemas are also sometimes observed. A serrated rupture between epithelial cells of the junction as well as a rupture between enamel and the most superficial epithelial cells contributes to the deepening of the gingival sulcus.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-0878
    Keywords: Isopod hindgut ; Histology ; Histochemistry ; Ultrastructure ; Osmo-regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The tubular hindgut of the intertidal herbivorous isopod, Dynamene bidentata, consists of a long dorso-ventrally flattened anterior region, surrounded by a network of muscles, and a short muscular sphincter which grades into a pair of anal flaps. The monolayer of epithelial cells forming the wall of the hindgut appears to take no part in the production of digestive enzymes, food absorption, or glycogen and lipid storage. One function of the hindgut is to propel undigested food material, enclosed within a peritrophic membrane, to the sphincter and anal flaps where faecal pellets are formed and ejected. At the fine structural level lateral plasma membranes, often partially obliterated by microtubules, are visible. The basal plasma membrane of a typical epithelial cell is deeply infolded, associated with mitochondria, and pinocytotic. The apical plasma membrane is irregularly folded, engaged in pinocytosis, and often encloses subcuticular spaces containing an acid mucopolysaccharide substance. An intima, composed of a thin double-layered epicuticle, and a thick acid mucopolysaccharide-positive endocuticle, overlies the cells. The endocuticle may selectively bind substances to the apical plasma membrane before they are engulfed by pinocytosis. The cells resemble those of osmoregulatory organs and may help counterbalance changes in the haemolymph concentration resulting from the intertidal existence of this isopod.
    Type of Medium: Electronic Resource
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