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  • 2000-2004
  • 1970-1974  (6.229)
  • 1945-1949
  • 1850-1859
  • 1840-1849
Jahr
  • 101
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 137 (1973), S. 97-109 
    ISSN: 1432-0878
    Schlagwort(e): Amoeba proteus ; Adsorptive function of mucoid layer ; Significance for induced endocytosis ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Mucoidschicht von Amoeba proteus enthält saure Mucopolysaccharide und ist funktionell einem Kationenaustauscher vergleichbar. Schwermetallpartikel und Proteine werden in Abhängigkeit vom pH-Wert des Kulturmediums in unterschiedlich starken Mengen an die Mucoidfilamente gebunden. Die dem Plasmalemm unmittelbar aufliegende globuläre Grundschicht besitzt dagegen für die untersuchten Substanzen keine Adsorptionsfunktion und unterscheidet sich demnach sowohl physiologisch als auch chemisch von der filamentartigen Zone. Quantitative Messungen über die pH-abhängige Anlagerung von Ferritin haben ergeben, daß die Mucoidfilamente in der Lage sind, Kationen aus dem Kulturmedium bis zu einer um das 17fache höheren Konzentration anzureichern. Die Ergebnisse der vorliegenden Untersuchung sprechen dafür, daß die Anreicherung derartiger Substanzen an der Zelloberfläche eine notwendige und physiologisch sinnvolle Voraussetzung für die Auslösung einer induzierten Endocytose darstellt.
    Notizen: Summary The mucoid layer of Amoeba proteus contains acid mucopolysaccharides, which are involved in the exchange of cations. Depending on the pH of the external medium, different amounts of heavy metal particles and proteins are bound to the mucoid filaments. The globular ground layer, which is directly apposed to the plasma membrane does not bind any of the substances studied and, therefore, differs from the mucoid filaments in function as well as chemical nature. Measurements of the pH-dependent adsorption of ferritin demonstrate that the mucoid filaments are able to accumulate cations in concentrations 17 times that of the external medium. These results suggest that the accumulation of substances at the cell surface is a prerequisite for the initiation of induced endocytosis.
    Materialart: Digitale Medien
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  • 102
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 137 (1973), S. 177-194 
    ISSN: 1432-0878
    Schlagwort(e): Thyroid gland (Salamander) ; Epithelial cells ; Fine structure ; Vacuolar bodies ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The thyroid gland of adult salamanders, Hynobius nebulosus, in the breeding season was studied by electron microscopy. The follicular cells are different in cell height and fine structures; the taller cells with many cell organelles and granules and the lower cells with a few cell organelles and granules are both present in the same follicle. In the cytoplasm, three types of membrane-bounded granules, namely, cytosomes, colloid droplets, and vacuolar bodies and circular membrane complexes occur. The vacuolar bodies are subdivided into two types; the ordinary type having loosely distributed particles and the specific type containing tubules and/or closely packed filaments, crystalloid structures, except for the particles. The chromophobe colloids within the Bensley-cells correspond to extremely large, ordinary type vacuolar bodies, while the Langendorff-colloid cells possess increased numbers of granular cisternae of endoplasmic reticulum and a ribosome-rich, dense cytoplasmic matrix but not extremely large colloid. The intracytoplasmic circular membrane complexes appear in the Golgi area of cytosome-rich cells. It is suggested that they originate from the Golgi apparatus which was activated to produce many cytosomes. Intranuclear inclusions consisting of microtubules and filaments and tight junctions between two adjacent lateral plasma membranes are occasionally encountered.
    Materialart: Digitale Medien
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  • 103
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 140 (1973), S. 425-432 
    ISSN: 1432-0878
    Schlagwort(e): Muscle innervation ; Myxine glutinosa (L.) ; Dense-core vesicles ; Monoamine fluorescence ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Motor nerve terminals on “white” and “intermediate” muscle fibers of the Atlantic hagfish (Myxine glutinosa, L.) contain translucent synpatic vesicles and about 1–2% dense-core vesicles. Terminals on “red” muscle fibers contain up to 40% dense-core vesicles with diameter 800–1100 Å. Examinations for formaldehyde-induced fluorescence indicate yellow fluorescence (5-HT ?) apparently corresponding with terminal axons on “red” muscle fibers in craniovelar muscles. Possibly “red” muscle fibers of Myxine receive monoaminergic innervation.
    Materialart: Digitale Medien
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  • 104
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 140 (1973), S. 473-479 
    ISSN: 1432-0878
    Schlagwort(e): Testicular feminization ; Rat ; Leydig cells ; Sterility ; Androgens, Steroids ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The interstitial cells of the pseudohermaphrodite rat testis are both hypertrophic and hyperplastic. The cytoplasm is characterized by smooth endoplasmic reticulum which is abundant and variable in form. Mitochondria are numerous and large with tubular cristae and occasional inclusions. Structural features of the Leydig cells indicate potential for increased steroid synthesis. The presence of large numbers of mast cells in the intertubular area is confirmed. Small seminiferous tubules lack advanced germinal elements. Additional connective tissue and myoepithelial layers produce a thickening of the limiting membrane. Some myoepithelial cells are atypical with an electron translucent cytoplasm and nuclei with dense peripheral chromatin. No spermatogenic cells beyond the cap phase of the spermatid are observed. The cytoplasm of Sertoli cells contains large lipid droplets and degenerating germ cells.
    Materialart: Digitale Medien
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  • 105
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 142 (1973), S. 223-239 
    ISSN: 1432-0878
    Schlagwort(e): Subcommissural organ (SCO) ; Basal secretion, Lateral secretion ; Extracellular spaces (ECS) ; Innervation ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Morphological evidence is presented supporting the possibility of basal secretion into hypendymal capillaries of the adult rabbit subcommissural organ (SCO). The synthetic apparatus of the SCO cell is described as well as the heterogeneous granules and vesicles which are concentrated in the basal processes bordering a widened perivascular space. The origin of the electron dense granules, of which two fairly distinct subgroups are found, is discussed. A binding of secretory sacs to the lateral plasma membrane is seen. The possibility of a lateral secretion is supported by the presence of a system of extracellular channels between SCO cells which are filled with a flocculent material resembling that of the secretory sacs. Nerve perikarya which are separated from the SCO by only a few glial fibers are demonstrated. Synapses are described in nerve fascicles bordering on the hypendymal capillaries. The possibility of an innervation of the hypendymal region is discussed as well as possible nervous connections with the pineal gland.
    Materialart: Digitale Medien
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  • 106
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 142 (1973), S. 443-464 
    ISSN: 1432-0878
    Schlagwort(e): Neurosecretion ; Posterior Pituitary gland ; Colchicine ; Axoplasmic flow ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The effect of colchicine on the release of neurosecretory material from the posterior pituitary gland was investigated in the rat in vivo and in vitro. Colchicine was administered subarachnoidally when neurophysin, radiolabelled by injection of (35S) cysteine into the supraoptic nucleus, had accumulated in the neural lobe. Dehydration for 3 days of non-colchicine-treated rats was followed by a 100% reduction of neurophysin-bound radioactivity. When colchicine was given prior to dehydration, the reduction of radioactive neurophysin was less marked. Colchicine treatment alone was likewise followed by a lowering of protein-bound radioactivity in the neural lobe, which may indicate that colchicine, in addition to blocking the rapid axonal transport of neurosecretory material, also impedes the slow transport. The release of radioactive neurophysin in response to depolarizing concentration of potassium in vitro was diminished in the presence of colchicine, the reduction being most pronounced after colchicine treatment in vivo. The biochemical data prove the view that colchicine inhibits the release of neurosecretory material from the neural lobe. The ultrastructural findings support the biochemical data. Thus, colchicine treatment alone or followed by dehydration induced a marked increase in the number of organelles, especially of mitochondria and dense bodies. There was a marked increase in the number of enlarged axons filled with dammed organelles in the infundibulum and neurohypophysis. There was an accumulation of dense core vesicles and microvesicles in the axonal terminals in the neurohypophysis after treatment with either colchicine or colchicine followed by dehydration, which indicates an impediment of the release process. Dehydration alone induced a depletion of the dense core vesicles in the terminals. Out from the combined biochemical and ultrastructural findings possible mechanisms for the action of colchicine are discussed.
    Materialart: Digitale Medien
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  • 107
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 142 (1973), S. 479-513 
    ISSN: 1432-0878
    Schlagwort(e): Median eminence (Frog) ; Tubero-hypophysial system ; Neurosecretory axon types ; Release phenomena ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary By means of electron microscopy, in the median eminence of Rana temporaria, the terminal arborizations of axons of six different types of neurosecretory cells, located in the pars ventralis of the tuber cinereum, were identified. In addition, phenomena connected with the release of neurosecretory material from the axon terminals of these neurosecretory cells into the blood capillaries of the median eminence are described. Preliminary results suggested the existence, in the median eminence, of additional different neurosecretory axon types which could also belong to corresponding neurosecretory cell types probably located in the apical part of the pars ventralis of the tuber cinereum. Moreover, in the external region of the normal median eminence, separate monoaminergic nerve fibres were tentatively identified. Arguments are adduced which plead (1) against the assumption that the ependyma or the pituicytes of the median eminence could produce adenohypophysiotropic hormones; (2) against the inference that the ependymal cells of the median eminence might be involved in the transport of adenohypophysiotropic hormones from the cerebrospinal fluid into the blood capillaries of the median eminence.
    Materialart: Digitale Medien
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  • 108
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 142 (1973), S. 465-477 
    ISSN: 1432-0878
    Schlagwort(e): Rabbit thymus ; Ketosteroids ; Granulated cells ; Histochemistry ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Topochemisch konnten im Kaninchenthymus Ketosteroide nachgewiesen werden, für deren Vorhandensein die chemische Analyse von Thymuslipidextrakten Hinweise ergeben hatte. Die Darstellung der Ketosteroide erfolgte mit der NAHD-Reaktion (Camber, 1949). Diese Befunde dürften als spezifisch gelten, da eine Verfälschung durch freie Gewebsaldehyde, Plasmalogene (Gomori, 1952) und Corticosteroide (Khanolkar et al., 1958) ausgeschlossen wurde. Mit Hilfe der Camber-Methode konnten Granula bestimmter Zellen des Kaninchenthymus selektiv dargestellt werden, die auf Grund morphologischer Kriterien in zwei Gruppen unterteilt wurden. Die Zellen liegen im gesamten Thymusparenchym sowie im Bindegewebe der Septen und der sogenannten „Kapsel“. Prädilektionsorte stellen die Umgebung der Hassallschen Körperchen, die Mark-Rinden-Grenze, der intra- und perivasale Raum sowie die subkapsuläre Zone dar. Beide Zellgruppen sind Sudan III-, PAS- und Eosin-positiv, besitzen eine ausgeprägte gelbgrüne Eigenfluoreszenz und können differentialdiagnostisch gegen Mastzellen abgegrenzt werden. Elektronenmikroskopisch zeigen beide Zellgruppen zahlreiche Übereinstimmungen mit Reifestadien eosinophiler Knochenmarkszellen.
    Notizen: Summary Ketosteroids were demonstrated topochemically in the rabbit thymus following indications given by chemical analysis of thymus lipid extracts. They were revealed by means of the NAHD-reaction (Camber, 1949). The results are thought to be specific, because adulteration by free tissue aldehydes, plasmalogens (Gomori, 1952) and corticosteroids (Khanolkar et al., 1958) can be excluded. The Camber-method selectively reveals the presence of two groups of morphologically differentiable granules in specific rabbit thymus cells which are distributed throughout the entire thymic parenchyme as well as in the connective tissue of the septa and the in so-called “capsule”. They are mainly seen in the vicinity of Hassall's bodies, in the zone between medulla and cortex, the intra- and perivascular space and in the subcapsular space. Both cell groups are Sudan III-, PAS- and eosin-positive, show intensive yellow-green primary fluorescence and can be distinguished from mast cells by differential diagnosis. Electron microscopy reveals that both cell groups show many similarities with the maturation phase of bone marrow eosinophils.
    Materialart: Digitale Medien
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  • 109
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 143 (1973), S. 45-52 
    ISSN: 1432-0878
    Schlagwort(e): Frog (Retina) ; Rod, Outer Segments ; Method of preparation ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Fibrils are demonstrated as an ultrastructural component in ultrathin sections of frog rod outer segments by a modified method of preparation which leads to partial contrast reversal. The relationship between these results and those obtained by conventional treatment leading to positive contrast, is discussed.
    Materialart: Digitale Medien
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  • 110
    ISSN: 1432-0878
    Schlagwort(e): Axonal transport ; Neurosecretion ; Posterior pituitary ; Anesthetics ; Chlorpromazine ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The effects of chlorpromazine (cpz) and tetracaine (tc) on the rapid axonal transport of neurosecretory material (NSM) in the hypothalamo-neurohypophysial system was investigated. Following subarachnoidal injection of these drugs, the incorporation of (35S) cysteine into proteins of the supraoptic nucleus was slightly depressed. The protein-bound radioactivity in the posterior pituitary was markedly lowered in experimental rats which indicates a partial blockage of the rapid axonal transport of NSM along the hypothalamoneurohypophysial tract. Both cpz and tc induced an increase in the number of mitochondria and profiles of granular endoplasmic reticulum. The axons in the infundibulum and neurohypophysis were enlarged by dammed organelles, indicating a blockage of axonal transport. There was an increased number of microvesicles, often arranged in a crystalloid pattern, in the terminals. The number and distribution of neurotubuli and neurofilaments were not changed. A possible stimulatory effect of cpz on the release of NSM from the neural lobe is assumed Possible mechanisms for the action of mitotic inhibitors, transquilizers and local anesthetics are discussed.
    Materialart: Digitale Medien
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  • 111
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 145 (1973), S. 443-445 
    ISSN: 1432-0878
    Schlagwort(e): Haemocyanin ; Pore cells ; Lymnaea stagnalis ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Electron micrographs of pore cells of Lymnaea stagnalis suggest that these cells produce and store haemocyanin.
    Materialart: Digitale Medien
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  • 112
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 145 (1973), S. 417-442 
    ISSN: 1432-0878
    Schlagwort(e): Adrenal chromaffin cells ; Birds ; Cholinergic innervation ; Histochemistry ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary According to their ultrastructure and histochemistry three types of efferent nerve fibers can be distinguished in the bird's adrenal gland. The main part is made up of cholinergic fibers recognizable by a positive reaction for acetylcholinesterase and two specific populations of granules within the synaptic ending. Synaptic vesicles measuring 300 to 500 Å in diameter and dense-cored vesicles with a diameter of about 1 000 Å are discernible. In the periphery of the gland cholinergic axons for the innervation of adrenal cells form large bundles surrounded by a perineural sheath. The bundles cross the capsule and are situated within the adrenal chromaffin cords or at their periphery. Finally small groups of fibers enter a group of chromaffin cells which are surrounded by a basal lamina and which consist of about a dozen or more cells producing adrenaline and noradrenaline. Synaptic endings occur, above all in passeriform species, in the center of a chromaffin cell complex. They are either attached to the innervated cells or their dendrite-like processes, or embedded into the cells, or connected to short spines of the innervated cells. Synaptic and dense-cored vesicles leave the bouton by exocytosis. One synaptic terminal may innervate up to three A- or NA-cells. The existence of different types of synapses for A- and NA-cells cannot be excluded.
    Materialart: Digitale Medien
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  • 113
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 147 (1973), S. 87-105 
    ISSN: 1432-0878
    Schlagwort(e): Motor nerve terminals ; Myxine glutinosa (L.) ; Elongated vesicle profiles ; Dense-core vesicles ; Fixation ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary “White” and “intermediate” parietal muscle fibers of Myxine are innervated focally at one end. Most synaptic vesicles are “empty”. These terminals also contain 1–2% large 800–1.100 Å dense-core vesicles. “Red” fibers of parietal and craniovelar muscle are innervated in a distributed fashion, and the presynaptic profiles contain a higher number of large dense-core vesicles (averaging 9% and 15%, respectively; up to 37%). For all terminals the synaptic gap is 450–600 Å wide, and postsynaptic folds are absent. “Empty” synaptic vesicles exist as round or elongated profiles. The proportion of elongated profiles increases by formation from round ones when increasing the molarity of the buffer in the aldehyde fixative. Furthermore, the proportion of elongated vesicle profiles in terminals on Myxine “white” fibers at different buffer molarities, is identical with that in mammalian motor terminals at similar molarities. On this basis the significance and mode of formation of elongated vesicle profiles is discussed. The conclusion is made that the susceptibility of “flattening” depends on the osmotic pressure of the vesicle contents once the aldehyde has influenced the vesicle membrane. The different vesicle populations in terminals on different types of muscle fibers are significant. Terminals on “red” fibers probably contain serotonin (5-HT) either as sole transmitter or in addition to acetylcholine.
    Materialart: Digitale Medien
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  • 114
    ISSN: 1432-0878
    Schlagwort(e): Ventromedial hypothalamic nuclei ; Nucleolus-like cytoplasmic inclusions ; Albino mouse ; Phase microscopy ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die ventromedialen Hypothalamuskerne von Mäusen nach Goldthioglucose-Injektion und von Kontrollmäusen wurden phasenoptisch und elektronen-mikroskopisch untersucht. Die neuronalen Perikaryen und Fortsätze enthielten nucleolusähnliche, phasenkontrast- und elektronenmikroskopisch sichtbare Einschlußkörper. Diese bestanden aus rundlichen, nicht membranbegrenzten Anhäufungen eines granulär oder filamentär erscheinenden Materials von unterschiedlicher Dichte. Gelegentlich wurden auch längliche Formen beobachtet. Sogar in stark geschädigten Nervenzellen waren die Einschlüsse noch als relativ gut erhaltene Strukturen zu erkennen. Es wird die Hypothese aufgestellt, daβ die nucleolusähnlichen Körper eine Depot- oder Transitform von schnell verfügbarem Material darstellen, welches entweder in den Perikaryen angehäuft oder in den Fortsätzen zum Ort der Verwendung und/oder Freisetzung transportiert wird.
    Notizen: Summary The ventromedial hypothalamic nuclei of goldthioglucose-treated and control mice were examined by phase and electron microscopy. Neuronal perikarya and processes contained nucleolus-resembling inclusion bodies detectable by phase and electron microscopy. The inclusions consisted of round unbounded masses of granular- or filamentous-appearing material of variable density. Elongated forms were occasionally seen. Even in damaged nerve cell bodies and processes the inclusions were recognizable as relatively well-preserved structures. The hypothesis is presented that they represent a storage or transit form of readily available material which is either piled up in the perikaryon or moved along its processes before being finally used and/or released.
    Materialart: Digitale Medien
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  • 115
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 146 (1973), S. 403-416 
    ISSN: 1432-0878
    Schlagwort(e): Avian interrenal gland ; Cholinergic innervation ; P-type nerve fibers ; Adrenergic terminals ; 6-OHDA ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary In all bird species investigated interrenal cells are reached by cholinergic nerve fibers forming synapses without postsynaptic membrane thickenings at their basis, more rarely at the lateral or apical cell surfaces. The density of innervation is considerably low if compared to the adrenal chromaffin organ; it is about 3 mm nerve length per 1 mm3 interrenal tissue in the house sparrow, 5 in the domestic fowl and 8 inCorvus frugilegus. P-type fibers which are only rarely to be seen also penetrate the basal lamina surrounding interrenal cells. Adrenergic fibers are only found outside the basal lamina.
    Materialart: Digitale Medien
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  • 116
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 146 (1973), S. 553-564 
    ISSN: 1432-0878
    Schlagwort(e): Salivary gland Moth ; Protein secretion ; Fluid secretion ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The salivary glands of the moth,Manduca sexta, are described, emphasizing correlations between structure and function in an attempt to explain the production of a dilute saliva. Each of the paired glands consists of five distinct regions: protein secreting, fluid secreting, thin duct, bulbous duct, and common duct. Each region constists of a single, ultrastructurally distinct, cell type. It is proposed that the protein and fluid secreting regions produce an enzyme-containing primary saliva isosmotic with the haemolymph; this saliva is modified in the remaining regions of the gland to yield a dilute saliva.
    Materialart: Digitale Medien
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  • 117
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 139 (1973), S. 271-284 
    ISSN: 1432-0878
    Schlagwort(e): Saccus vasculosus ; Rainbow trout ; Coronet cell ; Sea water adaptation ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The coronet cells of saccus vasculosus of fresh-water living and sea-water adapted rainbow trout were studied with the electron microscope, with special regard to changes in the latter group. Only quantitative differences were observed, namely a raised number of mitochondria in the apical region and the head and also a concentration of the agranular endoplasmic reticulum with a higher amount of electron-dense material and vesicles around the Golgi saccules. Together, these findings suggest a secretory function for the coronet cell. A supposed transport of vesicles from the head region of the coronet cell out into the globules is suggested. Interrelation between primary and secondary vesicles is discussed.
    Materialart: Digitale Medien
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  • 118
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 139 (1973), S. 253-269 
    ISSN: 1432-0878
    Schlagwort(e): Branchial gland ; Cephalopoda ; Fine structure ; Hemocyanin ; Histochemistry ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Licht- und elektronenmikroskopische Untersuchungen an der Branchialdrüse verschiedener Cephalopoden (Sepia officinalis, Octopus vulgaris, Loligo vulgaris, Eledone moschata) zeigen, daß das Drüsengewebe des stark vaskularisierten Organs aus einem sekretorisch aktiven Zelltypus mit ausgeprägtem endoplasmatischen Retikulum besteht. In den Zisternen des endoplasmatischen Retikulums lassen sich granuläre und ringförmige Strukturen (Durchmesser: 45–65 Å und 170 Å) nachweisen, die in Größe und Gestalt mit den Hämocyanin-Einheiten in den Gefäßen und Lakunen übereinstimmen und durch randlichen Zerfall der Zellen in den Blutraum auszuwandern scheinen. Die histochemischen Untersuchungen ergeben eine positive Reaktion für Monoaminoxydase, aber vergleichsweise geringe Phosphatase- und Dehydrogenase-Aktivitäten. Diese Befunde sowie der histochemisch nachgewiesene hohe Kupfergehalt des Drüsengewebes sprechen für eine hämopoetische, d.h. hämocyaninbildende Funktion der Kiemendrüse.
    Notizen: Summary Light and electron microscopic investigations on the branchial gland of different Cephalopoda (Sepia officinalis, Octopus vulgaris, Loligo vulgaris, Eledone moschata) show that the gland tissue, strongly vascularized, consists of an actively secreting cell type with a remarkable endoplasmatic reticulum. In the cisternae of the endoplasmatic reticulum granular and ring-shaped structures can be identified (diameter: 45–65 Å and 170 Å) which correspond in size and shape with the hemocyanin units in the vessels and lacunae and which seem to emigrate into the blood space caused by the peripheral decay of the cells. Histochemical investigations show a positive reaction for monoaminoxidase, but comparatively low phosphatase and dehydrogenase activities. These results, and also the high content of histochemically identified copper in the gland tissue, seem to indicate a hemopoetic, i.e. hemocyanin-forming function for the branchial gland.
    Materialart: Digitale Medien
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  • 119
    ISSN: 1432-0878
    Schlagwort(e): Insect molting ; Hemocytopoietic tissue ; Prothoracic glands ; Irradiation ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary It has been shown in previous studies that the endocrine control of molting is blocked by selective X-irradiation of the hemocytopoietic tissue of young last instar larvae of Locusta migratoria, the treated animals surviving as larvae for months without ever initiating a molt. The aim of the present study is to determine, on both a morphological and a physiological basis, if the block is related to a precocious functional involution of the prothoracic glands, known to elaborate a molting hormone. The prothoracic glands of normal animals clearly show morphological signs of functional involution during the late fifth (last) larval instar and degenerate completely some days after the imaginal molt. In the prothoracic glands of X-ray treated animals (selective irradiation of the hemocytopoietic tissue, the prothoracic glands being shielded), the signs of intense secretory activity persist up to 40 days following the irradiation. No signs of involution could ever be noticed in the prothoracic glands of such larvae. The irradiation of the hemocytopoietic tissue thus not only blocks molting, but also prevents the normal involution of the prothoracic glands. Extirpation of the prothoracic glands in young larvae of Locusta is known to result in the inhibition of the subsequent molt. Implantation of prothoracic glands from normal donors of the same age restores molting in fifth instar larvae previously deprived of their own glands. Using these results in physiological assays for the implanted prothoracic glands, we chose as donors irradiated animals of different ages and young normally developing adults. The prothoracic glands of irradiated animals fully retain their physiological activity after the X-ray treatment and are able to induce molting in larvae deprived of their own glands. It appears that the radiosensitive cells of the hemocytopoietic tissue of Locusta produce a substance which, while having no overt influence on the functioning of the prothoracic glands, is necessary for molting and probably acts in synergy with the prothoracic factor (molting hormone).
    Materialart: Digitale Medien
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  • 120
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 138 (1973), S. 23-30 
    ISSN: 1432-0878
    Schlagwort(e): Germ cell ; Human degeneration ; Intercellular bridges ; Oogenesis ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Intercellular bridges between developing germ cells were observed in human fetal ovaries at 10 to 20 weeks gestation. Bridges were frequently found between cells in early stages of degeneration, with similar regressive changes being present in the conjoined cells. In advanced stages of cellular degeneration, bridges were less frequently found and were generally distorted and partially disrupted. Similarity in appearance of adjacent degenerating cells was common, even in late stages of degeneration. These observations suggest that cellular interconnection may be responsible for synchronous degeneration of germ cells during oogenesis.
    Materialart: Digitale Medien
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  • 121
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 136 (1973), S. 501-510 
    ISSN: 1432-0878
    Schlagwort(e): Pancreas ; Fowl ; Innervation ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The fine structure of the pancreatic nerves of the domestic fowl has been studied. Naked axon beadings were found in membranous contact with endocrine as well as exocrine cells. From an anatomical point of view it seems reasonable to suggest that the endocrine glands might be subjected to some influence of the autonomic nervous system.
    Materialart: Digitale Medien
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  • 122
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 136 (1973), S. 511-520 
    ISSN: 1432-0878
    Schlagwort(e): Muscle spindle ; Sensory ending ; Rat ; Development ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary A fine structural study of sternothyroid muscle spindles of young adult rat demonstrates the rare occurrence of unique nerve endings. These endings are situated in the juxta-equatorial region of nuclear-bag fibers, adjacent to the annulo-spiral sensory endings. They consist of a bundle of terminal axons less than 0.3 μ in diameter and appear to be disposed nearly longitudinally to the axis of the intrafusal fibers. Whereas, the annulo-spiral endings consist of a single axon, coiling around the intrafusal fibers. Transverse sections of these muscle spindles reveal these unique endings scattered around the muscle fibers, fitting into depressions on their surface. The innermost axons directly face the muscle surface and are separated by a narrow gap less than 200 Å in width. No Schwann cell process appears to be associated with these endings. From their unique multi-axonal composition, these endings are termed “bundled endings”. Investigations of developing muscle spindles show the occasional presence of a similar multi-axonal composition of sensory endings in perinatal rats. It is suggested that “bundled endings” are sensory in nature, carrying an immature feature over to adult life.
    Materialart: Digitale Medien
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  • 123
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 136 (1973), S. 521-533 
    ISSN: 1432-0878
    Schlagwort(e): Thymus ; Bursa of Fabricius ; Chick embryo ; Lymphoid precursor cell, Lymphoid cell homing ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Lymphoid precursor cell structure in the earliest stages of lymphoid development of the chick thymus and bursa of Fabricius was investigated light- and electron microscopically. The first lymphoid precursor cells around (8 days' incubation) and within (9 days') the epithelial thymus show the morphological features of motile cells, viz. pseudopodia and cytoplasmic bundles of filaments. Subsequent differentiation into lymphoid cells includes disappearance of pseudopodia and filaments, and appearance of a layer of marginal condensed heterochromatin in the nuclei. The first lymphoid precursor cells in the bursa mesenchyme (11 days' incubation) and bursa epithelial bud (12 days') are also characterized as motile cells; the intra-vascular lymphoid cells (13 days') of the bursa, though resembling the lymphoid cells in other localizations, lack their irregular cytoplasmic contours. The motile lymphoid cells in the early stages of lymphoid development of the chick thymus and bursa are not identical, but are distinguished by their cytoplasmic and nuclear organization: endoplasmic reticulum profiles and marginal heterochromatin, present in lymphoid cells of the bursa, are absent in those of the thymus. These and other data suggest that thymus and bursa lymphoid cells originate in different haemopoietic organs, those of the thymus in the yolk sac and those of the bursa in the spleen.
    Materialart: Digitale Medien
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  • 124
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 136 (1973), S. 545-568 
    ISSN: 1432-0878
    Schlagwort(e): Pericardial gland ; Octopus ; Excretory organ ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The branchial heart appendage of Octopus dofleini martini has been investigated electron microscopically. This organ is dominated by peripherally lobed blood sinuses. It contains free hemocyanin (often aligned in rows), amoebocytes, endothelial cells, and muscle cells which occur mainly in connection with neurons. The neurons are often exposed to the blood. The blood sinuses are enclosed by a basement membrane which contains collagen equivalents and fine fibrillar elements. The sinuses are covered by two different epithelia: 1) the epithelium in the caoity of the appendage consisting of irregularly shaped cells with processes, the so called (∼ 30 μ high) podocytes, and 2) the epithelium (∼ 40 μ in height) on the surface of the organ, which is composed of two parts: a) a “lacuna”-forming portion directly adjacent to the basement membrane, which is topped by b) a continuous tissue portion with occasional “lacuna”-canals. The intercellular spaces of the inner and outer epithelium are connected. The structures of these epithelial cells are discussed in relation to the formation of the pericardial fluid.
    Materialart: Digitale Medien
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  • 125
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 137 (1973), S. 167-175 
    ISSN: 1432-0878
    Schlagwort(e): Leydig cells ; Mouse ; Ring-shaped nucleolus ; Endoplasmic reticulum ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Many mature Leydig cells of adult mice contain annular nucleoli. In the cytoplasm of these cells, there is an abundance of agranular endoplasmic reticulum and its modifications, i.e. membranous whorls and double-walled tubules. By contrast, the cytoplasm of Leydig cells with compact nucleoli shows abundant free ribosomes and granular endoplasmic reticulum. It is assumed that the granular endoplasmic reticulum shifts to the agranular endoplasmic reticulum and its modifications during the differentiation of the Leydig cell. For the maturation of the Leydig cell the annular nucleoli may play an important role.
    Materialart: Digitale Medien
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  • 126
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 137 (1973), S. 159-166 
    ISSN: 1432-0878
    Schlagwort(e): Ovum ; Mouse ; Membranes ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Ultrastructural studies have revealed the presence of unusual membrane complexes within developing mouse oocytes. These structures, most obvious 18 days post fertilization, are found in the nucleus or cytoplasm of cells in meiotic prophase. The complexes, usually found in small groups, are characterized by a slightly bowed appearance, and a thin middle section that is vesiculated at each end. At high magnification the middle section exhibits a pentalaminar structure similar to tight junctional complexes, while the looped membranes of the vesiculated ends are trilaminar in appearance. In addition to being free in the nucleoplasm or cytoplasm, the complexes are also seen in continuity with the inner and outer leaflets of the nuclear envelope, and with typical membranes forming cytoplasmic tubular systems. The possible formation of these complexes from blebs or vesicles derived from the nuclear envelope is presented and the role that these structures may play in developing oocytes is discussed.
    Materialart: Digitale Medien
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  • 127
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 137 (1973), S. 195-208 
    ISSN: 1432-0878
    Schlagwort(e): Thyroid (Salamander) ; Influence of TSH ; Epithelial cells ; Crystalloid structures ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The effect of thyrotropic hormone (TSH) on the salamander thyroid gland was studied by electron microscopy. The following sequence of changes in the follicular cells was observed: (1) 1–1.5 hrs after a single administration of 1 i.u. of TSH, many large colloid droplets appear in the apical cytoplasm; (2) within about 2 hrs hereafter, most of them are replaced by large vacuolar bodies, and cytosomes are remarkably decreased; (3) 2.5–3 hrs after two administrations of 1 i.u. of TSH at an interval of 20 hrs, large vacuolar bodies with or without filaments are frequently observed but cytosomes are hardly encountered; (4) in the group placed at room temperature for 10 days after a single administration of TSH, large vacuolar bodies almost disappear; (5) in the group placed in the ice room for 10 days after the same treatment, large vacuolar bodies with or without filaments frequently appear but cytosomes almost disappear; and (6) in some of large vacuolar bodies with filaments the different stages of crystalloid formation are discernible. From these findings, it is suggested that large colloid droplets are changed into large vacuolar bodies and that crystalloid originates from large vacuolar bodies with filaments, probably as a result of interrupted hydrolysis caused by a deficiency of cytosomes.
    Materialart: Digitale Medien
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  • 128
    ISSN: 1432-0878
    Schlagwort(e): Pituitary gland ; Male ; Triturus cristatus carnifex Laur. ; “Globular basophil cells” ; Antiandrogen treatment ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The adenohypophysis of the newt Triturus cristatus carnifex Laur. shows three types of cells: 1) cells with granules of about 350–550 mμ in diameter, 2) cells with small granules of 200–250 mμ in diameter and globules with a cristal-like arrangement containing cylinders with a diameter of about 960 Å and 3) cells containing small granules only. The AA. discuss the ultrastructural changes of the gland and the modifications of sexual secondary characters (S.S.C.) in animals given Cyproterone acetate (1/2 mg every three days). The animals have been treated for a period of time varying between 3 and 5 months, starting in October-November, when S.S.C. begin to develop again. At the end of the treatment the newths showed a loss of S.S.C., and the ultrastructure of the adenohypophysis resembled that of castrated animals, i.e.: great swelling of R.E.R. and partial degranulation of glycoprotein secreting cells which contain the 200 mμ granules and the globules. The S.E.R. showed also swelling and hyperactivity.
    Materialart: Digitale Medien
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  • 129
    ISSN: 1432-0878
    Schlagwort(e): Optic nerve ; Myelination ; Hypocholesteremic drug ; Exogenous and endogenous cholesterol ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The effect of AY-9944, an inhibitory cholesterol biosynthesis, on the myelination of the optic nerve of rats was studied. Suckling rats were injected intraperitoneally with the drug every other day from birth, and were sacrificed at 10, 20 and 30 days of age together with littermate controls. The analysis is based on counting, at the electron-microscope level, the number of unmyelinated axons and the number of myelin lamellae surrounding each myelinating axon. The results indicate that a decrease in endogenous cholesterol by AY 9944, induced an overall retardation of the myelination process in the optic nerve: a larger proportion of myelinated axons and smaller number of myelin lamellae around the myelinating axons, when compared with the littermate controls, was observed. Exogenous cholesterol from the maternal milk did not compensate for a lack in endogenous cholesterol. Degenerating myelin sheaths were frequently seen in the experimental optic nerves at 20 and 30 days of age. Numerous membranous, intracytoplasmic drug-induced inclusions were found at all ages studied.
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  • 130
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 140 (1973), S. 101-124 
    ISSN: 1432-0878
    Schlagwort(e): Kidney ; Contractile structures ; Embryonic metanephros ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Cytoplasmic filaments have been observed in the cells of normal and pathological kidneys. These filaments are usually grouped into bundles anchored to electron dense bodies underlying the cell membrane. In the embryonic human metanephros the filaments are found within the cells of different portions of the nephron at various stages of development. They appear first in the podocytes, almost simultaneously in the Bowman's capsule and tubular cells, then in the “mesangial cells”, and finally in the cells of the media of the afferent glomerular and interlobular arterioles. The presence of filaments and their attachment bodies in the mammalian nephron suggests that the podocytes and the so-called mesangial cells have a contractile activity, thus representing an intraglomerular apparatus which regulates the intravascular pressure, blood flow and filtration rate in the glomerular capillaries, whilst the contractile activity of the Bowman's capsule and proximal, distal, and collecting tubules, could facilitate the progression of the filtrate. The increase in number of the filaments in some pathological conditions is probably related to the functional changes of the intraluminal pressure in the glomerular capillaries, in the Bowman's space, and in the tubular lumen.
    Materialart: Digitale Medien
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  • 131
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 140 (1973), S. 39-75 
    ISSN: 1432-0878
    Schlagwort(e): Johnston's organ ; Camponotus vagus (Hymenoptera, Formicidae) ; Chordotonal structure, Scolopidia ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Beschreibung / Inhaltsverzeichnis: Résumé L'organe de Johnston de Camponotus vagus est composé par un ensemble d'environ 55 structures chordotonales, chacune étant formée par une ou plusieurs scolopidies. Les terminaisons dendritiques de tous les organes chordotonaux aboutissent sous des cônes cuticulaires insérés dans la membrane d'articulation entre le pédicelle et le troisième article antennaire. Chaque scolopidie est composée de 3 dendrites; les trois segments proximaux sont entourés par une même cellule enveloppe CE1 fortement accolée aux cellules épithéliales adjacentes au moyen d'attaches spécifiques. Au niveau des racines ciliaires et des segments ciliaires les trois dendrites sont enveloppés dans une cellule scolopale qui sécrète des colonnes scolopales autour de chaque dendrite et ayant des points de jonctions avec ceux-ci. Ces colonnes scolopales se réunissent ensuite pour entourer les trois dendrites dans un cylindre scolopal unique. A partir des dilatations ciliaires les dendrites évoluent de façon différente; certains s'interrompent très tôt dans le cylindre scolopal alors que d'autres s'élèvent plus haut jusqu'à l'articulation, leur extrémité distale étant coiffée d'un tube cuticulaire. Par structure chordotonale il n'y a généralement qu'un dendrite — quel que soit le nombre des scolopidies à l'origine de la structure — qui est relié à la membrane articulaire par une «tigelle cuticulaire intermédiaire». Chaque structure chordotonale est formée par une scolopidie, ou le regroupement de plusieurs identiques à celle décrite ci-dessus. Le plus souvent les premières cellules enveloppes CE1 présentent des zones d'affrontement membranaires entre CE1 des scolopidies d'un même organe chrodotonal. A partir du niveau des cellules scolopales, deux cellules enveloppes CE2 et CE3, se relayent successivement, formant un manchon autour des groupements scolopidiaux, déterminant ainsi l'unité sensorielle. On a observé et décrit des différenciations intercellulaires à tous les niveaux du système, entre éléments nerveux d'une part et éléments nerveux et structures associées d'autre part. Des inclusions particulières telles des microtubules associées en chaîne au moyen de bras ont notamment été décrites au niveau de structures de jonctions. Le rôle des divers structures et caractères spécifiques rencontrés lors de la description de l'ensemble de la structure réceptrice est envisagé dans le sens des mécanismes de transduction.
    Notizen: Summary Johnston's organ of Camponotus vagus is composed of 55 chordotonal structures, each of them being formed by one or several scolopidia. The dendritic endings of the chordotonal organs are in contact with cuticular cones which occur at the articular joint between pedicellus and the third antennal segment. Each scolopidium is composed of three dendrites. The three proximal segments are enclosed by one cell, CE1, which is connected with neighbouring epithelial cells by specific attachment zones containing microtubules. At the level of the ciliary roots and of the dendritic ciliary segments, the three dendrites are enclosed by the scolopal cell which secretes the scolopal rod around each dendrite. Some junctions occur between the dendrites and the scolopal cell. The scolopal rods are interconnected constituting the scolopal ring. The distal portion of each dendrite exhibits a different ultrastructure: some of them are short and terminate in the scolopal ring while others continue to the joint, here being covered by a cuticular canal. Generally there is only one dendrite which is connected with the joint by a cuticular stalk. Each chordotonal structure is formed by one or several scolopidia. Very often the first ensheathing cells, CE1, of one organ are connected by some intercellular differentiations. Above the scolopal cells two other ensheathing cells, CE2 and CE3 are to be found. These cells define each sensory unit. Intercellular differentiations are described at all levels of the system, between neural elements on the one hand and between neural elements and associated structures on the other hand. Specific inclusions such as associated “arm-bearing” microtubules are described near some of the junctions. The possible role of these specific structures in the process of impulse conduction in mechanoreceptors is discussed. The results are compared with those obtained from Johnston's organs of other species. Their functional significance is discussed.
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  • 132
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 140 (1973), S. 125-144 
    ISSN: 1432-0878
    Schlagwort(e): Spermatogenesis ; Meiosis ; Drosophila melanogaster ; Synaptinemal complex ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Meiosis in male Drosophila melanogaster was studied with the electron microscope. The number and the distribution of ring channels between individual members of a cluster of primary spermatocytes was determined from serial sections. The tubules with a diameter of 45 nm characteristic for meiotic prophase nuclei gave a chromatin type reaction, when treated with EDTA according to Bernhard's technique, thus suggesting that these tubules contain DNA. A material resembling central regions of synaptinemal complexes was observed in the nucleolus of primary spermatocytes during the downward movement in the testis. It is suggested that they represent unused precursors to central components of synaptinemal complexes, which are absent at pachytene of Drosophila males. Up to six tail fibers (kinetosomes + axonemes) were observed in every primary spermatocyte prior to meiosis.
    Materialart: Digitale Medien
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  • 133
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 140 (1973), S. 203-216 
    ISSN: 1432-0878
    Schlagwort(e): Synapses ; Development ; Chick embryo ; Cell culture ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The formation and development of synaptic contacts between dissociated chick spinal cord neurons has been investigated. By the 6th day in vitro “immature” profiles with few vesicles were observed. By 14–18 days “mature” types with numerous vesicles were found, indistinguishable from those of newly hatched chick spinal cord. After this period degeneration occurred, and was especially marked in the post-synaptic element. Such degeneration could be postponed by the addition of small numbers of somatic muscle cells. The Kanaseki and Kadota (1969) technique was applied to the study of coated vesicles at various stages of synaptic development.
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  • 134
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 140 (1973), S. 187-202 
    ISSN: 1432-0878
    Schlagwort(e): Macrophage ; Differentiation ; Triolein ; Stereology ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The results of an objective two- and three-dimensional analysis of the morphological features of normal and triolein-induced mouse peritoneal macrophages are reported. An “equivalent circle“ technique for resolving the effects of volume and surface area on volume-to-surface parameters is described. The method is a simple comparative one which does not require the actual determination of cell volume. Macrophage stimulation promoted increases in mean cell size, cytoplasmic granularity and volume-to-surface ratio. In addition, a reduction in nuclear volume-to-surface ratio accompanied in vivo stimulation. Nucleocytoplasmic ratio remained constant. The equivalent circle procedure showed that the increase in cellular volume-to-surface ratio was due largely to the increase in cell volume; the decrease in nuclear volume-to-surface ratio was primarily the result of a substantial increase in nuclear membrane surface area. Stereological estimations suggest that interiorized cell membrane (in the form of triolein-containing phagosomes) is replaced by newly reconstructed surface membrane.
    Materialart: Digitale Medien
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  • 135
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 140 (1973), S. 235-259 
    ISSN: 1432-0878
    Schlagwort(e): Ciliated protozoa ; Loxophyllum and Prorodon ; Trichocysts ; Toxicysts ; Expulsion mechanism ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Nesselkapseltrichocysten der Ciliaten Loxophyllum und Prorodon wurden hinsichtlich ihrer Feinstruktur sowie des Ausschleuderungsablaufes untersucht. Loxophyllum besitzt zwei morphologisch unterscheidbare Sorten von Toxicysten, wohingegen Prorodon nur eine Art dieser Organelle aufweist (Krüger, 1936). Wie an Hand gehemmter Stadien gezeigt werden kann, verläuft die Ausschleuderung bis auf geringfügige Variationen bei den drei Sorten in der gleichen Art: Schläuche, die im ruhenden Zustand bereits in den endgültigen Dimensionen in der Toxicystenkapsel eng ineinandergeschachtelt vorliegen, werden handschuhfingerförmig umgestülpt und verlassen hierdurch die Kapsel und damit den Zellkörper. Dieser Prozeß ist mit der Ausscheidung einer teils fädigen, teils amorphen Substanz gekoppelt. Der Umstülpungsvorgang der Innenstruktur der Nesselkapseltrichocysten wird mit den völlig andersartigen, während der Ausschleuderung von Mucocysten und Spindeltrichocysten ablaufenden morphologischen Veränderungen verglichen. Es zeigte sich, daß aufgrund ihrer differierenden Feinstrukturen und Funktionsweisen in den Nesselkapseltrichocysten einerseits und in den Mucocysten sowie Spindeltrichocysten andererseits zwei grundsätzlich voneinander verschiedene Organellentypen gesehen werden müssen.
    Notizen: Summary The toxicysts of the ciliates Loxophyllum meleagris and Prorodon teres were examined with regard to fine structure and expulsion mechanism. Loxophyllum possesses two morphologically distinct types of toxicysts, whereas in Prorodon only one type is present. As can be shown by discharge inhibition experiments, the expulsion mechanisms, except for small variations, are identical in all three types: Tubes, which in their resting state lie closely packed one within the other possess already at this state their final dimensions; they are inverted, thereby leaving the capsule and thus the cell body. This process is correlated with the excretion of a substance partly filamentous, partly amorphous. The inversion of the tubes during the expulsion is compared to the fundamentally different morphological alterations during discharge of mucocysts and spindle trichocysts. The differences and similarities in fine structure and function between toxicysts on the one hand and mucocysts and spindle trichocysts on the other, indicate that two rather than three fundamentally different organelle types must be distinguished.
    Materialart: Digitale Medien
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  • 136
    ISSN: 1432-0878
    Schlagwort(e): Superior colliculus ; Primate, Galago ; Optic terminals ; Eye enucleation ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Several types of terminals were found in the three superficial collicular layers of Galago. At least two axon terminals with round vesicles (R1 and R2) could be distinguished on the basis of vesicle packing and electron density of the cytoplasmic and mitochondrial matrices. R1 axon terminals were characterized by aggregations of vesicles in an electron lucent cytoplasm and mitochondria with a relatively dark matrix, while in R2 axon terminals the vesicles were more evenly distributed in an electron dense cytoplasm and the mitochondrial matrix was pale. R2 endings occurred in clusters in the stratum griseum superficiale; they were absent in the stratum zonale. R1 endings were found in all three superficial collicular layers. Both types of R terminals made asymmetrical contacts with small dendrites, dendritic spines and F profiles. Profiles containing flattened vesicles and establishing symmetrical contacts were numerous, and many could be identified as dendrites by accepting as criteria for dendrites evenly spaced microtubules, clusters of ribosomes and the fact that these F profiles were postsynaptic to other terminals. F terminals were presynaptic to other F profiles, dendrites and somata; they were postsynaptic to R terminals and took part in serial synapses. Dendrodendritic contacts were frequent, somatodendritic contacts rare. After eye enucleation most R2 axon terminals underwent the electron dense degenerative reaction. The degeneration process was a lengthy one; many degenerating boutons were found 30 days after axotomy and some persisted up to 180 days postoperatively. There was strong indication that the superior colliculus received more crossed than uncrossed retinofugal fibers. The crossed and uncrossed retinocollicular axons terminated in two different substrata of the stratum griseum superficiale.
    Materialart: Digitale Medien
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  • 137
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 140 (1973), S. 357-368 
    ISSN: 1432-0878
    Schlagwort(e): Muscle spindle ; Guinea-pig ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Nuclear bag and nuclear chain intrafusal fibres are present in guinea-pig muscle spindles. Unlike muscle spindles in other species two types of nuclear chain fibre seem to be present. The electron microscopical appearance of one type of nuclear chain fibre is similar to that of nuclear bag fibres. It is suggested that under tension the nuclei of small nuclear bag fibres become sufficiently displaced to form nuclear chain-like fibres. The frequent occurrence of fibres which combine some of the properties of both nuclear bag and nuclear chain fibres indicates the possible occurrence of a third type of intrafusal fibre. The sensory innervation of guinea-pig muscle spindles is similar to that of the cat and the rat. Three types of motor nerve ending which could be classified according to the complexity of their subneural apparatus were seen.
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  • 138
    ISSN: 1432-0878
    Schlagwort(e): Intestine, Lampetra fluviatilis ; Serotonin-, dopamine-, noradrenaline-containing neurons ; Identification by histochemistry ; Electron microscopy ; Biochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Monoamine-containing neurons in the gut of Lampetra fluviatilis are characterized by histochemical, electron microscopical and biochemical methods. Strongly yellow fluorescent, probably serotonin-containing intrinsic neurons are found along the entire length of the intestine. Their processes aggregate to form large bundles of mainly non-terminal axons, constituting a subepithelial fibre plexus. This subepithelial, ganglion cell comprising plexus is connected to a wide-meshed subserosal plexus which has ganglion cells of different size and few varicose, single axons. Intermingled with both plexus there occur — in the anterior and middle but not in the preanal portion of the lamprey intestine — scattered green fluorescent intrinsic perikarya, emanating faintly green fluorescent, poorly varicosed axons. The formaldehyde-induced neuronal fluorophores conform to serotonin (yellow fluorescent compound), noradrenaline, and dopamine (green fluorescent substance), as revealed in microspectrofluorimetric recordings. The electron microscopical analysis of the yellow fluorescent intrinsic neurons in the terminal hindgut shows nerve cell pericarya and axons equipped with a typical population of occasional small granular and many large granular vesicles (750–1600 Å). The number and opacity of cores of the small and the osmiophilia of the cores of the large granular vesicles are significantly increased following short-term treatment with 5,6-dihydroxytryptamine. Long-term treatment with 5,6- or 5,7-dihydroxytryptamine provokes severe signs of ultrastructure impairment and eventual degeneration in the supposed serotonin-containing axons, besides indications of piling-up of organelles in the non-terminal axons due to arrest of axonal transport. Chromatography of acid extracts from the lamprey intestine, gills and kidney reveals the presence of serotonin (besides another unidentified indoleamine) and dopamine and noradrenaline in the gut, but only dopamine in the brain. The detection of serotonin, noradrenaline and dopamine in the lamprey gut is confirmed by chemical determinations. The occurrence of intrinsic serotonin-, noradrenaline- and dopamine-containing neurons in the gut of Lampetra fluviatilis deviates from the established pattern of innervation of the vertebrate intestine and is considered to be a remnant of an autonomic innervation principle common in invertebrates.
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  • 139
    ISSN: 1432-0878
    Schlagwort(e): Neurosecretory cells ; Lateral ; Locust ; Histochemistry ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Beschreibung / Inhaltsverzeichnis: Résumé L'étude histologique, histochimique et ultrastructurale des péricaryones neurosécréteurs latéraux de Locusta précise leur nombre et leur localisation. Elle révèle que le neurosécrétat latéral est semblable morphologiquement (forme et diamètre des granules élémentaires) au neurosécrétat A de la pars intercerebralis. Cependant, il en diffère histochimiquement par la présence d'une composante glucidique. Elle confirme l'hypothèse émise pour les péricaryones neurosécréteurs de la pars intercerebralis (Girardie et Girardie, 1967), de l'unicité cellulaire chez Locusta des types A et B selon la nomenclature de Johansson (1958). Elle suggère que les péricaryones latéraux pourraient être des cellules neurosécrétrices très actives.
    Notizen: Summary The number (8 to 12) and position of the lateral neurosecretory cells have been established in Locusta by a histological, histochemical and ultrastructural study. The neurosecretory material of the lateral cells contains glycoprotein and is, in this way, histochemically different from medial A cells neurosecretory material. However, the morphological aspect (shape, diameter) of elementary dense core vesicles in the lateral and medial A neurosecretory cells is similar. This study confirms the idea (Girardie and Girardie, 1967) that, in Locusta, A cells and B cells (Johansson, 1958) are in fact two physiological aspects of one cell type. It also suggests that the lateral cells could be very active neurosecretory cells.
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  • 140
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 141 (1973), S. 223-233 
    ISSN: 1432-0878
    Schlagwort(e): Laryngeal muscles ; Tree Frog, Hyla aborea arborea (L.) ; Fine structure ; Motor endplates ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Um Hinweise auf die Funktion des Kehlkopfes bei der Rufabgabe zu bekommen, führten wir eine vergleichende elektronenmikroskopische Untersuchung an den vier Kehlkopfmuskeln rufaktiver Laubfrösche durch. Zum weiteren Vergleich studierten wir auch einen Extremitätenmuskel. Die Kehlkopfmuskeln sind untereinander gleich gebaut, unterscheiden sich aber in mehrfacher Hinsicht vom Extremitätenmuskel: Ihre Myofibrillen sind nur ein Drittel so dick. Die Kehlkopfmuskeln enthalten sehr viele, auffallend große und dichte Mitochondrien; das sarcoplasmatische Retikulum ist mächtig entwickelt. Sie enthalten außerdem sehr viel Fett, das stets mit den Mitochondrien assoziiert ist. In beiden Muskeltypen kommt Glykogen vor; seine Menge ist in den Kehlkopfmuskeln jedoch größer als im Extremitätenmuskel. Die Zahl der motorischen Endplatten ist in den Kehlkopfmuskeln 25 mal höher als im M. plantaris longus. Die Zahl der Triaden pro Sarcomer und ihre Anordnung ist bei den beiden Muskeltypen gleich. Die Kehlkopfmuskeln winterstarrer Hyla-Männchen unterscheiden sich in ihrem Feinbau und Fettgehalt nicht von den Muskeln rufaktiver Tiere.
    Notizen: Summary In order to obtain information on the function of the larynx during vocalization, a comparative electron microscopic study was made of the four laryngeal muscles of male tree frogs druing their vocalizing phase. A skeletal muscle (m. plantaris longus) was examined for comparison. The fine structure of the laryngeal muscles is uniform, but differs from skeletal muscles in several respects: the diameter of the myofibrils of the laryngeal muscles is only 1/3 that of the skeletal muscle. They contain many strikingly large and dense mitochondria. There is a strongly developed sarcoplasmic reticulum. Laryngeal muscles contain large quantities of fat which is always associated with mitochondria. Laryngeal muscles contain more glycogen than skeletal muscle. The number of motor endplates in laryngeal muscles is 25 times larger than in m. plantaris longus. The number of triads per sarcomere and their location is the same in both types of muscle. The laryngeal muscles of hibernating and active tree frogs do not show any difference with respect to fine structure and amount of fat.
    Materialart: Digitale Medien
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  • 141
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 141 (1973), S. 427-442 
    ISSN: 1432-0878
    Schlagwort(e): Hypoglossal nucleus (Rat) ; Axotomy ; Glia ; Microglia ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wird unter besonderer Berücksichtigung der Glia über den Feinbau des Hypoglossuskerns normaler Albinoratten und nach Axotomie berichtet. Untersucht wurden Tiere vom 12.–90. Lebenstag. Folgende Ergebnisse sind neu: Weder bei jungen noch bei erwachsenen Ratten kommt im Hypoglossuskern Mikroglia vor. Etwa ab. 3. Tag nach Axotomie kann bei erwachsenen Tieren Mikroglia nachgewiesen werden. Sie entsteht aus aktivierten und proliferierten Oligodendrocyten und pericytenähnlichen Bindegewebszellen. Die Mikroglia umhüllt die Nervenzellen. Eine Aktivierung und Hypertrophie von Astrocyten erfolgt etwa ab 8. Tag nach Axotomie. Von diesem Tage an drängen sich Astrocytenfortsätze zwischen Mikroglia und Nervenzelloberfläche. Die Mikroglia beginnt zu degenerieren. Bei Jungtieren bewirkt die Axotomie nur geringgradige Veränderungen. Schon beim Normaltier findet man aktive Oligodendroglia und Astrocyten sowie häufig pericytenähnliche Bindegewebszellen.
    Notizen: Summary The ultrastructure of the Nucleus hypoglossi in normal albino rats and following axotomy is described with special reference to the glia. Animals 12 to 90 days old were investigated. The following results are new: Normally in young and adult rats microglia is absent in the nucleus. Following axotomy from the 3rd day no microglia can be demonstrated in adult rats. It originates from activated and proliferated oligodendrocytes and pericyte-like cells of the vascular connective tissue. These cells surround the neurons. An activation and hypertrophy of astrocytes is visible from the 8th postoperative day on. Astrocyte processes make contacts with the perikarya and separate the microglia from the neurons. Microglia cells then show signs of degeneration. In young animals alterations following axotomy are only sparse. Already normally activated oligodendrocytes and astrocytes as well as pericyte-like connective tissue cells can be seen.
    Materialart: Digitale Medien
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  • 142
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 141 (1973), S. 443-458 
    ISSN: 1432-0878
    Schlagwort(e): Microtubules ; Vinblastine ; Kidney tubules ; Podocytes ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Vinblastine sulfate was administered to adult rats by intravenous injections. Kidney cortex was fixed after 1, 2, or 5 hours of treatment and studied by routine transmission electron microscopy. In control animals, cells of distal convoluted tubules possessed numerous microtubules with an average diameter of 280 Å. In treated animals, the microtubules of these cells were reduced in number, and paracrystalline inclusions characteristic of vinblastine treatment were common. Macrotubules (570 Å average diameter) were also present and often were seen close to, or in apparent continuity with, paracrystals. Since the work of others indicates that vinblastine-induced paracrystals contain microtubular protein (tubulin), observation of continuities between paracrystals and macrotubules is interpreted as evidence that macrotubules are also composed of tubulin and that macrotubules may become incorporated into paracrystals. Unlike the ordinary microtubules of cells of the distal tubules, vinblastine-induced macrotubules exhibited cross-striations in longitudinal view and subunit structure in cross section. Macrotubules and paracrystals were also observed in cells of the proximal convoluted tubule, mesangium, glomerular endothelium, parietal epithelium of Bowman's capsule, and visceral epithelium of Bowman's capsule. Continuities between macrotubules and paracrystals, although relatively common in occurrence in distal tubule cells, were only rarely seen in the other kinds of cells examined.
    Materialart: Digitale Medien
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  • 143
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 141 (1973), S. 561-573 
    ISSN: 1432-0878
    Schlagwort(e): Wound healing ; Lymnaea stagnalis ; Amoebocytes ; Phagocytosis ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The process of wound healing in Lymnaea stagnalis was studied by light and electron microscopy. Snails were wounded by making incisions in the skin. The observations showed that the wounds are closed by muscular contraction and by formation of thrombi of blood amoebocytes. These thrombi form a large amoebocyte plug. During the first 72 hrs after incision thin tubules (diameter 175–225 Å) were observed between the amoebocytes in the plug. Possibly these tubules represent a blood clotting protein. The round amoebocytes constituting the plug can be regarded as normal blood amoebocytes. First, ultrastructurally they closely resemble the amoebocytes of the circulating blood. Second, not only blood amoebocytes but also plug amoebocytes of snails injected with India ink before incision contained ink particles, indicating that the cells are of one type. Apparently due to phagocytosis of cell debris the number of lysosomes in plug amoebocytes increased during the first days after incision. Eighteen to twenty four hrs after incision the first signs of differentiation of round plug amoebocytes into flattened cells were observed. Between these cells collagen was seen from 3–5 days after incision and onwards. It is suggested that these flattened amoebocytes produce collagen fibrils. These cells are structurally different from collagen producing fibroblasts and from muscle cells of the surrounding connective tissue. Transformations of amoebocytes into these two latter cell types were not found. Ninety days after incision the connective tissue in the wound area is still different from that on non-injured sites.
    Materialart: Digitale Medien
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  • 144
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 142 (1973), S. 193-204 
    ISSN: 1432-0878
    Schlagwort(e): Neuromuscular junction ; Development ; Cholinesterases ; Axonal transport, Neurotubules, Colchicine, Vinblastine ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Colchicine (0.1 M) or vinblastine (0.01 M) was locally applied on the sciatic nerves of newborn rats. Both colchicine and vinblastine caused reversible disappearance of axonal neurotubules and appearance of increased amounts of neurofilaments at the site of application. Subsequent morphogenesis of myoneural junctions in the tibialis anterior muscle was studied after histochemical demonstration of acetylcholinesterase (AChE; E.C. 3.1.1.7) and non-specific cholinesterase (Ns. ChE; E.C. 3.1.1.8) activity in the myoneural area. Development of the postsynaptic muscle plasma membrane of the myoneural junction was arrested in the ipsilateral, but not in the contralateral control side, for a period of about three weeks following treatment with the test substances. After this delay the myoneural morphogenesis continued normally and neurotubules were seen in the axoplasm. Since disruption of neurotubules is likely to cause blockage of the intratubular axoplasmic transport system, it seems possible that the neurotrophic influence responsible for the development of the postsynaptic muscle membrane is mediated through a secretory product transported along axons intratubularly to the nerve endings.
    Materialart: Digitale Medien
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  • 145
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 142 (1973), S. 367-386 
    ISSN: 1432-0878
    Schlagwort(e): Testicular interstitial cells ; Rana esculenta ; Seasonal changes ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Saisonabhängige Veränderungen in der Morphologie der Leydigzellen von Rana esculenta wurden über den Zeitraum eines Jahres in Licht- und Elektronenmikroskop untersucht. In den Monaten November bis Februar kommen im Zytoplasma der Leydigzellen kleine Mitochondrien des tubulären Typs, Vesikel des glatten endoplasmatischen Retikulum und freie Ribosomen vor, Fettvakuolen treten nur vereinzelt auf, der Golgikomplex ist gering entwickelt. In der Zeit von März bis Juni nimmt die Zahl der Zellorganellen zu. Es erscheinen in Gruppen angeordnete Lysosomen und außer den kleinen Mitochondrien Riesenmitochondrien, des Golgifeld ist größer, die Fettvakuolen sind vermehrt. Sowohl die kleinen als auch die Riesenmitochondrien enthalten Kristalle, die aus osmiophilen globulären Einschlußkörpern hervorzugehen scheinen. In den Monaten Juni/Juli ist fast der ganze Zelleib einer Leydigzelle von Fettvakuolen ausgefüllt. Die Zahl der Riesenmitochondrien und Lysosomen verringert sich, das Golgifeld ist wieder unauffällig. Eine Beziehung zwischen der Vermehrung und Entfaltung der Zellorganellen und der in der Literatur angegebenen Phase der gesteigerten Steroidproduktion konnte festgestellt werden. Das Auftreten der Riesenmitochondrien und Lysosomen und ihre Bedeutung für die saisonbedingte Entwicklung und Involution der Leydigzellen wird diskutiert.
    Notizen: Summary Seasonal changes in the structure of the testicular interstitial cells in Rana esculenta were investigated. Throughout November–February, small mitochondria of the tubular type, visicles of the smooth endoplasmic reticulum and free ribosomes predominate and the cytoplasm contains few lipid droplets and a poorly developed Golgi apparatus. During the period from March to June the cell organelles increase in number. There are numerous aggregated lysosomes and conspicuous accumulations of lipid droplets. Besides small mitochondria increasing numbers of giant mitochondria occur and the Golgi complex is enlarged. The small and giant mitochondria contain crystals which seem to originate from osmiophilic globular inclusion bodies. During June and July the whole cytoplasm may be filled with lipid droplets. Concomitantly there is a decrease in the number of lysosomes and giant mitochondria and the Golgi apparatus is in a state of involution. Possible correlations between the development of the cell organelles and the period of increased steroid production are pointed out. The appearance of giant mitochondria and lysosomes and their importance for seasonal Leydig cell development and involution are discussed.
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  • 146
    ISSN: 1432-0878
    Schlagwort(e): Prostate ; Tissue culture ; Androgens ; Hormones ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The explants of the rat ventral prostate were cultured on a chemically defined medium and the effects of individual hormones viz. testosterone, hydrocortisone and insulin on the fine structure of the epithelial cells were investigated. The epithelial cells without hormones underwent regressive changes resembling those seen in vivo after castration. Large autophagic vacuoles, residual bodies and dilations of rough endoplasmic reticulum (ER) were noted on day 2 of the culture. Four days later the amount of rough ER was markedly decreased and no secretory vesicles were visible. The treatment of the explants with testosterone resulted in an apparent intensification of the morphological equivalents of secretion. Beside the well developed rough ER and Golgi complex, numerous large secretory vesicles with flocculent content were observed. These observations are compatible with the idea that testosterone promotes the formation and probably also the excretion of the secretion in the epithelial cells. Testosterone also prevented partially the appearance of the signs of cellular degeneration. The most characteristic feature of hydrocortisone-treated epithelial cells was the copious supply of rough ER. Of particular interest was the formation of endoplasmic reticulum whorls which could not be observed in control and testosterone-treated cells. Hydrocortisone was shown to promote the formation of juvenile secretory vesicles on the second day. Insulin delayed the onset of the degeneration of the epithelial cells. Marked degenerative changes were, however, noted on day 6. There was no specific ultrastructural characteristic that could be interpreted to be specific for insulin action in the epithelial cell.
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  • 147
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 143 (1973), S. 495-504 
    ISSN: 1432-0878
    Schlagwort(e): Neuromuscular junction ; Teleosts and amphibia ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The structure of the terminal neuromuscular junctions found close to the insertions of myotomal muscle fibres in teleost fish and amphibia is described, and it is concluded that in both groups, the pattern of innervation is essentially similar. Different degrees of complexity are described, both in the terminal nerve branches, and in the sub-junctional apparatus. It is suggested that the terminal pattern of innervation is an adaptation to the requirements of rapid swimming.
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  • 148
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 146 (1973), S. 309-317 
    ISSN: 1432-0878
    Schlagwort(e): Adrenal cortex ; Prostaglandin E1 ; Autoradiography ; Electron microscopy ; Lipid analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary To determine whether or not prostaglandins enter adrenocortical parenchymal cells,3H-PGE1 was injected intravenously into rats. In histological preparations, grains denoting activity were noted in intracellular lipid droplets and nuclei and in sinusoids. At the fine structural level, activity was observed in lipid droplets, mitochondria, the agranular endoplasmic reticulum, nuclei and the plasma membrane. Biochemical lipid analyses of the adrenals revealed activity in the cholesterol and cholesterol ester fractions. Large amounts of unaltered3H-PGE1 and its degradation products were also present. Compared to the liver, the adrenal was more effective in degrading prostaglandin, when expressed on a weight basis. The possible roles of the organelles in PGE1 degradation and in prostaglandin-related hormone synthesis are discussed.
    Materialart: Digitale Medien
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  • 149
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 146 (1973), S. 385-402 
    ISSN: 1432-0878
    Schlagwort(e): Interrenal cells ; Avian adrenal gland ; Lipid exocytosis ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Cords of interrenal-cells of birds resemble “tubes without lumina”, which are lined by columnar cells arranged in double rows. A subcapsular and an inner zone of the interrenal gland may be distinguished according to the structure of their mitochondria, the existence of smooth and rough surfaced endoplasmic reticulum, and the lipid contents. The cells of the inner zone are clearly polarized. The extrusion of lipid by exocytosis is discussed. It is often difficult to decide, whether ultrastructural details are species - specific or indicate a certain state of function.
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  • 150
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 145 (1973), S. 557-575 
    ISSN: 1432-0878
    Schlagwort(e): Avian adrenal gland ; Adrenergic nerve fibers ; p-Type nerve fibers ; 6-Hydroxydopamine ; Fluorescence microscopy ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Apart from cholinergic nerve fibers, which make up the main part of efferent fibers to the avian adrenal gland (Unsicker, 1973b), adrenergic, purinergic and afferent nerve fibers occur. Adrenergic nerve fibers are much more rare than cholinergic fibers. With the Falck-Hillarp fluorescence method they can be demonstrated in the capsule of the gland, in the pericapsular tissue and near blood vessels. By their green fluorescent varicosities they may be distinguished characteristically from undulating yellow fluorescent ramifications of small nerve cells which are found in the ganglia of the adrenal gland and below the capsule. The varicosities of adrenergic axons exhibit small (450 to 700 Å in diameter) and large (900 to 1300 Å in diameter) granular vesicles with a dense core which is usually situated excentrically. After the application of 6-hydroxydopamine degenerative changes appear in the varicosities. Adrenergic axons are not confined to blood vessels but can be found as well in close proximity of chromaffin cells. Probably adrenergic fibers are the axons of large ganglion cells which are situated mainly within the ganglia of the adrenal gland and in the periphery of the organ and whose dendritic endings show small granular vesicles after treatment with 6-OHDA. A third type of nerve fiber is characterized by varicosities containing dense-cored vesicles with a thin light halo, the mean diameter (1250 Å) of which exceeds that of the morphologically similar granular vesicles in cholinergic synapses. Those fibers resemble neurosecretory and purinergic axons and are therefore called p-type fibers. They cannot be stained with chromalum-hematoxyline-phloxine. Axon dilations showing aggregates of mitochondria, myelin bodies and dense-cored vesicles of different shape and diameter are considered to be afferent nerve endings. Blood vessels in the capsule of the gland are innervated by both cholinergic and adrenergic fibers.
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  • 151
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 146 (1973), S. 83-102 
    ISSN: 1432-0878
    Schlagwort(e): Cartilage (Guinea pig) ; Chondrocytes ; Proteoglycans ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The guinea-pig rib cartilage consists of chondrocytes dispersed in an intercellular substance composed of collagen fibrils, often characteristically cross-striated, and polygonal granules. Electron-dense membrane-bounded matrix vesicles are also observed intercellularly, especially in the central, partly calcified zone of the cartilage. With respect to their location in a cross-section of the rib, the chondrocytes differ in size, shape and intracellular fine structure. Thus, three separate types of cells are recognized. Peripheral chondrocytes have a flattened shape and are largely occupied by the nucleus. In the cytoplasm, the granular endoplasmic reticulum is the most extensive organelle. Intermediate chondrocytes are oval or round in shape. The endoplasmic reticulum and the Golgi complex are both prominent. Mitochondria and membrane-bounded cytoplasmic dense bodies are more numerous than in the peripheral cells. The ground cytoplasm often contains a few lipid droplets. In the central chondrocytes, such droplets sometimes fill the entire cytoplasm. Concomitantly, the nucleus is usually completely heterochromatic and the cells are therefore regarded as being metabolically inert. After preparations including ruthenium red staining en bloc, the general stainability of the chondrocytes is decreased. Intracellularly, positive ruthenium red staining of granular material within the Golgi vacuoles are to be observed. Extracellularly, the matrix granules are stained with this polyvalent, cationic dye. Extraction of the cartilage with 4 M guanidine-HCl removes all matrix granules and about 70% of the proteoglycans, measured as hexosamine, from the tissue. It is concluded that the matrix granules contain proteoglycan complexes.
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  • 152
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 147 (1973), S. 107-125 
    ISSN: 1432-0878
    Schlagwort(e): Melanophores ; Teleost (Pterophyllum scalare) ; Pigment migration ; Microtubules ; Electron microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The ultrastructure of the melanophores of Pterophyllum scalare was studied with respect to changes in cell shape during melanosome migration and the number and distribution of microtubules within the cell extensions. Cells were fixed with pigment fully aggregated or fully dispersed. All measurements were carried out on cross sections of cell processes, i.e. sections cut perpendicular to the long axis of the cell extensions. Cross sections of processes of melanophores with dispersed pigment are more or less ovoid in shape, and microtubules are arranged predominantly just below the cell membrane. These microtubules exhibit a relatively constant centre-to-centre spacing of about 55–65 nm. Processes of melanophores with aggregated pigment seem to be collapsed; their volume is substantially decreased but their circumference equals that of dispersed melanophores. The number of microtubules is reduced, and their regular arrangement is lost. The differences in microtubule number associated with the aggregated or dispersed state occur irrespective of the nature of the agent inducing dispersion or aggregation. In addition, apparent insertion of microtubules into the plasma membrane of the cell processes and associations of microtubules with cytoplasmic densities in the cell centre are described. The results indicate a rapid disassembly and assembly of microtubules associated with pigment movements. The possible role of microtubule associations with cell membrane and densities as sites of microtubule polymerization is briefly discussed.
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  • 153
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 121-125 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 154
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Despite its being weaker base poly(2-vinylpyridine) polymerized DL-β-phenylalanine NCA at a much faster rate than pyridine and α-picoline. Poly(2-vinylpyridine) adsorbs NCA by hydrogen bonding with the cooperation of a few pyridine groups. This results in a high local concentration of NCA. The syndiotactic configuration of pyridine group seemed to be least suitable for the cooperative hydrogen bonding. Adsorbed NCA is activated to form an “activated” NCA which in turn reacts with an NCA adsorbed on the same polymer chain. Since the polymer chain is flexible, this intramolecular reaction takes place frequently, resulting in the acceleration of polymerization. The intramolecular reaction along the polymer chain is dependent on the degree of polymerization of polymer catalyst. A suitable model was proposed for the intramolecular reaction to explain the effect of degree of polymerization.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 155
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 5-Bromouracil-substituted DNA was isolated form B. Subtilis and phage PBSH. The three DNA fractions of Different densities (TT, TB, and BB) were irradiated with u.v. (313nm). The number of single-strand and double-strand breaks was determined. The breakage rates are given. It was found that in hybrid DNA (TB) double-strand breaks occur depending linearly on dose. In BB-DNA the observed double-Strand bresks can be divided into two fractions with a linear and quadratic dose dependence respectively. The results can be explained by assuming intramolecular energy transfer from the BU-containing strand to its complementary strand.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 156
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 229-235 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Differential enthalpic analysis of a series of 3′,5′-cyclic nucleotides indicates that homolytic cleavage of the six-membered phosphate ring occurs either immediately prior to or concurrent with decomposition of the crystal lattice. Homolysis is followed by a rapid polymerization to yield oligonucleotides. The enthalpies of these reactions have, with the exception of guanosine 3′,5′-cyclic phosphate, almost identical values of 25 kcal/mole. The anomalous case is attributed to a more stabilized phosphate ring as a result of hydrogen bonding through the two position of the purine ring. The pair of overlapping exothermic peaks observed in each of the thermograms for cAMP and cIMP is related to the presence of two conformational arrangements within the unit cell of each compound.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 157
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 243-255 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The total energy and the electronic properties of some syn purine nucleosides have been determined as a function of the rotation angle around the C-N glycosidic linkage. Invariably, the crystallographic coordinates provide a state lying at or very near the minimum on the potential energy curve according to the extended Hückel parametrization here employed. The ribose moiety always carries a net positive charge whereas the base is always negatively charged. Changes in dipole moment magnitudes for the overall structure as well as in net atomic charges are noted upon rotation around the glycosidic linkage indicating that potential functions for polynucleotides may be in error if such changes are ignored.
    Zusätzliches Material: 2 Ill.
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  • 158
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 341-352 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Measuring the equivalent noise resistance of Na-DNA solutions in NaCl provides in formation about the free ino atmosphere. In an Arrhenius type diagram, the helix → coil transition is clearly brought Out. A Calculation of the number of free ions in the solution as function of temperature, reveals once more the process of ejection of compensating Na+ ions form the macromolecules during the thermal transconformation.
    Zusätzliches Material: 7 Ill.
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  • 159
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 423-433 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Optical properties in different solvents of gramicidin-bis (salicylaldimine) Cu(II) and (5-I-salicyladimine) Cu(II) chelates are intercepted in terms of their molecular structure. A molecular model for the inversion of Contton effects in two different classes of solvents is proposed. This explanation is supported by the study of optical properties of model compounds.
    Zusätzliches Material: 7 Ill.
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  • 160
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 161
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Syntheses are described for two N-benzyloxycarbonylpeptide tert-butoxycarbonylhydrazides which correspond to positions 24-34 and 35-44, respectively, of the primary structure of baker's yeast iso-1-cytochrome c. The two peptide derivatives were coupled via the azide procedure to form the N-benzyloxycarbonylheneicosapeptide tert-butoxycarbonylhydrazide (sequence 24-44).
    Materialart: Digitale Medien
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  • 162
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 647-654 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The primary amine initiated homopolymerization of γ-benzyl-L-glutamate NCA in dioxane at 25°C, 35°C, 50°C, and 65°C has been investigated. The reactions were virtually independent of temperature indicating an activation energy of less than 1 kcal/mole. The entropy of activation was estimated to be -65 entropy units at 300°K. The reaction proceeded in two stages. The first stage was zero-order with respect to monomer, whereas the second was first-order with respect to monomer. Both stages were first-order with respect to initiator. These results were interpreted by assuming that the rate constant for propagation was not independent of the degree of polymerization up to the point where a conformational transition to α-helix occurred.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 163
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The synthesis is described of the N-benzyloxycarbonyldecapeptide tert-butoxycarbonylhydrazide, which corresponds to the sequence 57-66 of baker's yeast iso-1-cytochrome c. The peptide derivative was synthesized coupling two smaller subunits via the Rudinger modified azide procedure.
    Materialart: Digitale Medien
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  • 164
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 791-798 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of interaction between proflavine and poly I.poly C at 25°C, neutral pH, and moderate ionic strength have been studied by relaxation methods. The qualitative features of this system resemble those previously reported by Crothers and co-workers for proflavine-DNA and proflavine-poly A·poly U interactions-two relaxations are observed coresponding to a fast bimolecular step followed by a slower isomerization. These results can best be accommodated by a two-step mechanism leading from the free dye through an “outside-bound” complex to the intercalated complex. Quantitative comparison of the various rate constants for proflavine binding to different double-helical polynucleotides shows that the rates are slower for both ribohomopolymer pairs than for DNA. The rates for poly I·poly C are approximately three times faster than these for poly A·poly U.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 165
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Infrared and Raman spectra of aqueous poly(rA-rU)·poly(rA-rU), the double-helical complex containing strands of alternating riboadenylate and ribouridylate residues, display significant differences from one another and from corresponding spectra of poly(rA)·poly(rU), the double-helical complex of riboadenylate and ribouridylate homopolymers. Parallel studies on the copolymer and homopolymer complexes by cesium sulfate density gradient centrifugation, ultraviolet absorption spectroscopy, hydrogenion titration, 1-N oxidation of adenine residues by monoperphthalic acid and X-ray diffraction reveal, however, that the geometry of base pairing between adenine and uracil is closely similar in each complex and apparently of the Watson-Crick type. Therefore the differences observed between vibrational spectra of poly (rA-rU)·poly (rA-rU) and poly(rA)·poly(rU) are not due to different base-pairing schemes but may be attributed to differences in vibrational coupling between vertically stacked bases. Vibrational coupling may also account for the differences between infrared and Raman spectra of the same complex. Thus, the present results indicate that infrared and Raman frequencies of RNA in the region 1750-1550 cm-1 should be dependent on the base sequence.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 166
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 857-867 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A simple model is introduced to investigate the stability of a sedimenting entanglement. The sedimenting entanglement is represented by a sedimenting sieve. Solvent can pass through it, but single-chain molecules that flow into it become entangled and their flow decreases or, if permanent entanglements form, ceases entirely. With this model we are able to find the conditions under which the mass of a sedimenting entanglement remains constant, grows or decays to a stable value, grows beyond limit, or decays to the mass of a single chain. The theory is applied to the sedimentation of small concentrations of large chain molecules in solutions of small chain molecules in solutions of small chain molecules for the case in which the entanglements are long-lived. Equations are derived which, (1) give the stable entanglement mass as a function of rotor speed and concentration and, (2) for a given concentration predict the rotor speed at which the entanglement mass grows without limit. Numerical results for small concentrations of T2 DNA sedimenting in solutions of T7 DNA are presented.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 167
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 931-936 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 168
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 169
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 993-1010 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The solution bebavior of poly-L-proline Form II has been studied in water and aqueous salt solutions by both elastic and quasi-elastic light -scattering techniques. The results of this study suggest that polyproline Form II can exist in water at 24 °C as an associated polymer complex and that certain salts which do not appear to affect the helix integrity, e.g., guanidinium-HCl, resutl in dissociation of the aggregate. Other neutral salts, of the variety effective in mediating unfolding of the Form II helix (e.g., 4M NaClO4) also induce aggregate dissociation, but 4M CaCl2 results in enhanced aggregation of polyproline. Kinetic experiments indicate that a time of 20 hours is necessary for the completion of the “large” to “small” transformation (at 22°C) which is induced by the addition of 4M NaClO4. Thus it appears that neutral salts additives in aqueous solutions of polyproline influence both the state of aggregation and the conformation of this polymer.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 170
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1047-1052 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The dielectric relaxation of namtive DNA and DNA-proflavine complexes at different DNA phosphate (P) to dye (D) ratios, were investigated in the frequency range 100 c/sec to 100 Kc/sec. The proflavine molecules were found to have a profound effect on the static dielectric constant and the relaxation time of the polymers. The static dielectric constant was oberserved to decrese with increasing level of added proflavine. At P/D = 1, the variation of dielectric constant with frequency was small. Relaxation time (τ) was greater for the DNA-proflavine complexes compared to that for free DNA, Maximum value of the relaxation time was obtained at P/D = 10. The increase in the relaxation time and decrease in the static dielectric constant were attributed to the increase in length and meutralization of surface charges of the DNA molecules, respectively, as aresult of proflavine binding.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 171
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1011-1019 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Fluorescence depolarization experiments performed on labaled poly-L-proline Forme II suggest the occurrence of aggrgation in water while 6M guanidinium-HCl induces dissociation. The solvent 4M CaCl2 results in a reduction of polymer structural orgganization. These findings corroborate suggestion of polyproline aggregation and solution behavior in aqueous neutral salt solytion (see preceding article).
    Zusätzliches Material: 3 Ill.
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  • 172
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1053-1062 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A detailed study on the deuterium NMR of hydrated collagen in the presence of alkali and alkaline earth salt is reported. The effect of different salts in reducing the deuteron quadrupole splitting are similer at low molar content of salt. At higher salt contents, larger ions are more effective. The ressults are explained by the blocking of water binding sites to collagen by hydrated ions. When the temperature is reduced, only part of the adsorbed water iss frozen, and the amount of “unfreezable water” decreases with the increase in ionic sizes(LiCl 〈 MgCl2 〈 KCL 〈 KCNS). The freezing temperature is also lowered in the presence of salts. A description of the structure of hydrated collagen based upon the observed facts is given.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 173
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Poly-γ-L-glutamic acid has been synthesized by the activated pentachlorophenyl ester polymerization method and the molecule weight of the polymer was found to be 16,000. Comparative conformational studies on the synthetic and on the native polyglutamic acid mbtained from B. anthracis and B. subtilis were carried out using optical rotatory dispersion, circular dichroism, peptide absorption spectrum, and titration data. These results show that poly-γ-glutamic acid does not exhibit any conformational order under the conditions of investigation. At low degrees of ionization, restriction of conformational freedom via random “hypercoiling” of the chain appears likely.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 174
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Ultraviolet absorption, fluorescence excitation and emission, and fluorescence anisotropy demonstrate that the polycyclic aromatic hydrocarbone 3,4-benzpyrene, Pyrene, anthracene, and 9-methylanthracene bind to histone IV after the sow conformational change in the presence of divalent phosphate anion. These hydrocarbons do not bind, within our limits of detection, to histone IV in the diosorderde form at low pH or to the form produced by the fast conformational change when the slow change is prevented. High anisotropy values for the bound hydrocarbon indicate a high degree of aggregation for the histone IV.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 175
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1437-1444 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The aggregation of native acid-soluble collagen (N-ASC) and of pronase-treated acid soluble collagen (P-ASC) was examined in solution under conditions which varied from those of minimum collagen-collagen interaction to those leading to incipient fiber formation. Molecular weights and weight distributions were determined in the analytical ultracentrifuge using the Yphantis high speed sedimentation equilibrium and Aarchiblad approach-to-equilibrim techniques. The aggregation was pH and ionic strength dependent in each case. Under conditions of minimum aggregation (low pH, low ionic strength), N-ASC showed the presence of permant aggregates. At higher pH and ionic strength, a higher fraction of aggregate was formed but these were of the same charcter and molecular weight as the permanent aggregates. The aggregates were of a single molecular size, with a weight of 1.5 × 106 daltons, compared with a monomer collagen weight of 3.1 × 105 daltons. The P-ASC formed aggregates also but to a much lower extent and the maximum aggregate size corresponded to dimers in molecular weight. These data show the major importance of molecular end-regions in collagen aggregation to form native type fibers and, by virtue of the discrete size of the N-ASC aggregates, support the microfibrillar hypothesis for the assembly of collagen fibrills.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 176
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1387-1419 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The sedimentation coefficient and intrinsic viscosity of nicked and closed circular PM2 bacteriophage DNA have been measured as a function of pH in the alkaline region. A gradual increase in the sidimentation coefficient, and a corresponding decrease in the intrinsic viscosity, are observed for the superhelical (closed) circle in the pH region from 10.5 to about 10.9. This has been tentatively interpreted in terms of the known dependence of sedimentation coefficient upon the number of superhelical turns. At slightly higher pH values, the curve passes through the minimum (sedimentation coefficient) and maximum (intrinsic viscosity) expected when the superhelical turns present at neutral pH are unwound by partial alkaline denaturation. Sedimentation studies of the relaxed (nicked) circular species have revealed the existence of DNA forms in the pH region from 11.27 to 11.37 which sediment considerably faster than the closed circle in the same pH region. These have been identified as partially denatured nicked circles, in which varying fractions of the duplex structure have undergone alkaline denaturation, but strand separation has not yet occurred. Varying fractions of a slower species, either undenatured or completely denatured nicked circles, are also observed in some of these experiments. A corresponding result is observed in the intrinsic viscosity vs. pH curve.When nicked circular PM2 DNA is exposed to various alkaline pH's, rapidly neutralized, and sedimented at neutral pH, the expected sharp transition from native to denatured (strand-separated) molecules is seen. However, a very narrow pH range is noted in which native and denatured forms coexist in a single experiment. The above experiments carried out upon the closed form also reveal a narrow pH range in which the bulk of the transition from native closed circles to the collapsed cyclic coil takes place, in acccord with an earlier study on a different DNA. This transition is shown never to be completely effected, however, as there is a fraction (7-8%)of the closed circles which renature to the native form, regardless of the alkaline pH employed. This same phenomenon was not observed in the case of artificially closed λb2b5c DNA circles. Possible explanations for some of the above results are discussed.
    Zusätzliches Material: 8 Ill.
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  • 177
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1505-1513 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Polymerizations of DL-phenylalanine NCA by block copolymers of sarcosine and DL-phenylalanine, designated by (Phe)m(Sar)n and capable of reaction at the phenylalanyl terminal, were investigated in nitrobenzene solution at 25°C. With increasing n for constant m (m = 0, 1, 2, and 5), the polymerization rate greatly increased. Previously the acceleration of the initiation reaction in the polymerization of DL-phenylalanine NCA by polysarcosine (m = 0) was reported. The present results showing the acceleration by the copolymers of sarcosine and DL-phenylalanine indicate the presence of the polymer effect in the propagation reaction as well. However, the polymer effect was most marked with polysarcosine (m = 0), and decreased with increasing m.The same polymerizations by sequential copolymers composed of ten sarcosine units and two DL-phenylalanine units were also investigated. Again with these copolymer catalysts the polymerization rate was larger than that by monomeric amines. But the polymer effect decreased sharply when the phenylalanine units take positions near the terminal amine group of the copolymer catalyst.These two deteriorating effects of the phenylalanine unit have been interpreted in terms of the decrease of the flexibility of polymer chain, caused possibly by an intramolecular hydrogen bond of the phenylalanine unit.
    Zusätzliches Material: 3 Ill.
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  • 178
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2057-2073 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Accurate equilibrium binding data for the oxygenation of hemoglobin are used (a) to show that various models for cooperativity are inconsistent with the best available experimental data, (b) to determine the equilibrium constants for binding of 2,3-diphosphoglycerate to hemoglobin molecules in intermediate stages of oxygenation, and (c) to deduce a mechanism for allosteric effects in hemoglobin which is consistent with the best available experimental data. The total free energy of cooperativity is defined and discussed.
    Zusätzliches Material: 2 Ill.
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  • 179
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2151-2159 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A conductivity dispersion has been measured at very low frequencies (VLF) on several concentrated DNA solutions. By measuring simultaneously their electric birefringence decay, it is shown that the dielectric relaxation (which is related to the conductivity dispersion) is due to the molecular orientation. Different polarization mechanisms are discussed. It is concluded that the DNA polarizability measured in the VLF range can only be explained by the orientation of a permanent ionic dipole. It is suggested that such permanent dipoles could be caused by small differences in the ionic composition between the two molecular “ends;” the difference could either be stable (asymmetrical localization of protein impurities for instance) or transient (fluctuating dipoles explained by the Kirkwood-Schumaker theory).
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 180
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 181
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2199-2209 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In the present work, the synthesis of the three primary oligomers of α-L-glutamic acid is described; the general formula is the following: [I] The choice of protective groups at the both ends of the chain allows for the good solubility in the water and the liberation of free carboxyl groups on the side chain. Thus, models are obtained for the study of thermodynamic properties of solutions and especially of the interactions between polyanions and cations. The prepared products are characterized by different techniques such as mass spectrometry potentiometry, tonometry, and thin-layer chromatography. The results are in agreement and lead to the conclusions that the molecules have the general formula of [I] and are stereoregular.
    Materialart: Digitale Medien
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  • 182
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In continuation of our studies on the effect of the base and the phosphate groups on the glycosyl and the sugar-phosphate backbone conformation, we have carried out semi-empirical potential energy calculations on the common 5′- and 3′5′-ribopyrimidine mono- and diphosphates by considering simultaneous rotations about the glycosyl (χ) and the C(4′)-C(5′) (ψ) bonds. This calculation provides an assessment of the nature and orientation of the base on the sugar-phosphate backbone conformation of nucleotides and polynucleotides. It is found that the attractive inetractions between the 5′-phosphate group and the base mutually stabilize the antiand the gauche-gauche (gg) conformations about χ and ψ, respectively, in 5′-ribopyrimidine nucleotides. The introduction of the 3′-phosphate group as in 3′,5′-ribopyrimidine diphosphates, still leaves the anti-gg as the most favored conformation with the important difference that the probability of occurrence of the anti, gauche-trans (gt) is how substantially increased. This is dependent to a large extent on the sugar conformation and to a lesser extent on the base. Uracil and thymine show a greater probability for the anti-gt than cytosine. The syn conformation is considerably less likely and its occurrence is also dependent on the base type, cytosine showing a lesser tendency than uracil and thymine. For the syn base, the most favourec conformation for ψ is gt, since gg is sterically disallowed and tg is destabilized by electrostatic repulsive interactions between the 3′ and 5′-phosphate groups. Thus, there is a striking correlation between the glycoysl and the backbone C(4′)-C(5′) bond conformations. The rest of the bonds of the backbone are considerable less dependent on the glycosyl conformation. These studies reveal that in poly-ribopyrimidine nucletides the majority of the nucleotide residues are expected to occur in the anti-gg conformation.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 183
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2335-2349 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effect of poly dispersity on the nuclear magnetic resonance spectra of samples of poly-γ-benzyl-L-glutamateein the helix-random coil transition is studied. In the transitionregion the α-CH proton resonance shows two peaks whose behavior does not change appreciably upon fractionation by gel permeation chromatography. Theoretical spectra were computed with both a polydispersity model of the transition and a model for slow nucleationof helix from completely random coil molecules. The results suggest that the double peak behavior in the nmr spectra results from a slow rate of helix nucleation rather than polydispersity.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 184
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2691-2712 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A conformational analysis has been carried out for the cyclic peptide antibiotic alamethicin. Unlikely structures were first eliminated by constructing van der Waals' energy maps for near-neighbor contacts and using these maps to generate forty complete alamethicin structures free of steric overlaps. The energies of the forty conformations were minimized; optimizing all dihedral angles first in sets and then simultaneously, to give a family of five low-energy structures. In the conformation of lowest energy three of the seven α-amino isobutyric acid residues occur in a six-residue α-helix and three at the two chain reversals. Judged by the change in conformational energy as a function of the change in dihedral angle, the flexibility of the chain is determined by both the type of peptide unit and its position in the molecule.The model has features consistent with reported circular dichorism and surface balance measurements and has two polar centers separated by a lipophilic region. It does not contain the large central pore required by some theories for the action of alamethicin on cell membrances. It therefore probably acts by altering membrance structres rather than by shuttling ions through a pore in the membrance.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 185
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The conformation and packing scheme for guanosine-3′, 5′-cytidine monophosphate, GpC, were computed by minimizing the classical potential energy. The lowest energy conformation of the isolated molecule had dihedral angles in the range of helical RNA's and the sugar pucker was C3′ endo. This was used as the starting conformation in a packing search over orientation space, the dihedral angles being flexible in this step also. The packing search was restricted by constraints from our x-ray data, namely, (1) the dimensions of the monoclinic unit cell and its pseudo-C2 symmetry (the real space group is P21), (2) the location of the phosphorous atom, and (3) the orientation of the bases. In addition, a geometric function was devised to impose Watson-Crick base pairing. Thus, a trial structure could be sought without explicit inclusion of intermolecular potentials. An interactive computer graphics system was used for visualizing the calculated structures.The packing searches yielded two lowest energy schemes in which the molecules had the same conformation (similar to double-helical RNA) but different orientations within the unit cell. One of these was refined by standard x-ray methods to a discrepancy index of 14.4% in the C2 pseudocell. This served as the starting structure for the subsequent refinement in the real P21 cell.5
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 186
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2789-2802 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A model for the hydration behavior of human stratum corneum has been developed from measurements on in vitro samples isolated in a manner which minimized tissue treatment and trauma. Water sorption/desorption rate measurements as a function of water activity, temperature, and tissue integrity are reported. These data, together with thermodynamic data (infrared and nmr results reported earlier) are consistent with a model in which rapidly sorbed/desorbed water (ca. 0.5 mg water/mg stratum corneum) is associated with (“bound” by) the tissue, while slowly sorbed/desorbed “free” water (up to 12 mg water/mg stratum corneum) is kinetically restricted and probably intracellular in location. Both equilibrium water binding and desorption kinetic data suggest structural changes of this cellular water barrier upon hydration. Evidence for hysteresis in water sorption isotherms (reported by others) could not be reproduced.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 187
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2831-2852 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Poly(ortho-, meta-, and para-γ-nitrobenzyl-L-glutamates) were studied by circular dichroism (CD) and optical rotatory dispersion (ORD) in two helicogenic solvents, hexafluoroisopropanol (HFIP) and dichloroethane (EDC), and two non-helicogenic solvents, dichloracetic acid (DCA) and trifluoroacetic acid (TFA). The corresponding glutamates were also studied in DCA and TFA. The symmetric nitrobenzylic chromophore is optically active when the polymers are in solution in DCA and TFA. The corresponding glutamates are also optically active under the same conditions. Thus, it was not possible to explain the origin of the optical activity of the side-chain chromophore when the polymer is in solution in a helicogenic solvent. Nevertheless, from a side-chain dichroic band, a helix-coil transition curve was determined and the stability of each poly(γ-nitrobenzyl-L-glutamate) given; this stability depends on the position of the nitro substituent on the aromatic ring.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 188
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 7 (1973), S. 33-41 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 189
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 7 (1973), S. 82-89 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 190
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 7 (1973) 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 191
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 53-64 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Sedimentation constant and intrinsic viscosity were measured on purified tropocollagens extracted from earthworm-cuticle and lathyritic ratskin. A cartesian diver viscometer was used to make viscosity measurements at small shear stress and to avoid the effects of surface forces. By comparing the experimental data with the hydrodynamic theories of wormlike-coil of Ullman a value of 1300 Å has been assigned for the persistence length of these tropocollagens. Other factors which may affect the estimate are discussed.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 192
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 45-51 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The CD spectra of DNA from various sources (T2; T4; Cd; Escherichia coli; calf thymus; Streptomyces chrysomalis) were investigated. A new band Δε210 in the CD spectra of glucosylated DNA of the T even phages was found. The temperature dependence of the CD spectra of DNA was obtained over a wide range of temperatures, including those of the helix-coil transition.The band Δε275 for all DNAs does not appreciably change in the range of the helix-coil transition. The monotonic increase of this band before melting, and its decrease after melting is observed with an increase in temperature.The amplitude of the CD band Δε245 for all the DNAs studied and Δε210 (glucosylated DNA) parallels the change of E260 absorbance.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 193
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 575-587 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: By analyzing the effect of urea and guanidine hydrochloride on the circular dichroism of many polypeptides and proteins, it is concluded that under conditions of high concentration of the perturbant and at low temperatures the resultant state approached is that of a local extended helix structure instead of a completely random coil. Intensification by urea and guanidine hydrochloride of the circular dichroism bands of poly-L-proline II leads to the proof that the mechanism of interaction of urea and guanidine hydrochloride with proteins is through hydrogen bonding to the backbone carbonyl group.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 194
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 541-558 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The interactions between chondroitin-6-sulfate (chondroitin sulfate C) and poly-L-lysine have been studied as models for investigation of possible complex formation between fibrous proteins and mucopolysaccharides. Results obtained using circular dichroism spectroscopy show that poly-L-lysine adopts the α-helical conformation in dilute aqueous salt solution at pH 7 when mixed with chondroitin-6-sulfate, rather than the “charged-coil” observed in the absence of this mucopolysaccharide. This conformation-directing interaction is at a maximum when the ratio of lysine to disaccharide residues is 1 : 1. Changes in the CD spectrum of a 1 : 1 mixture following increase in the salt concentration, or addition of non-polar solvents, indicate that the interaction is ionic in nature. No such effects are observed for non-sulfated mucopolysaccharides mixed with poly-L-lysine, suggesting that, for chondroitin-6-sulfate, it is the sulfate groups rather than the carboxyls which interact with the amine groups of the polypeptide.Elevation of the temperature leads to disruption of the interactions between the polypeptide and polysaccharide species. A sharp melting transition occurs at 47.0 ± 1.0°C, when the poly-L-lysine reverts to the “charged-coil” conformation. The sharp transition suggests that regular ionic bonds are formed between the polypeptide and polysaccharide. These results suggest that a conformation-directing interaction may occur between sulfated mucopolysaccharides and the polar regions of collagen and other fibrous proteins.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 195
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 627-636 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A coupling constant-dihedral angle correlation for the H—Cα—Cβ—H system of amino acid residues in peptides has been derived from a set of model compounds covering the full range of dihedral angles. The expression obtained, J = 11.0 cos2 θ -1.4 cos θ + 1.6 sin2θ, is close to those already used in pmr studies of peptide conformation, and provides a firmer foundation for them. A factor limiting the precision of this and other “Karplus relations” is illustrated.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 196
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 655-674 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The ultraviolet absorption, linear dichroism, circular dichroism, and oriented circular dichroism of collagen are reported and the spectra are resolved into a self-consistent set of bands in accord with exciton theory. The parallel band at 200 nm has 40% of the π → π* intensity; the perpendicular band is placed at 189 nm yielding a splitting of 2700 cm-1. The circular dichroism is resolved into two Gaussians at λ∥ and λτ (rotational strengths +14 × 10-40 and -32 × 10-40 esu2. cm2) plus a large non-Gaussian (“helix”) band with ampplitude -25,000° at 201 nm. These data appear to be in reasonably good accord with recent calculations.Measurements of the absorption, linear dichroism and circular dichroism of polyproline I and II are also reported and are resolved into their component bands. Polyproline I is in good accord with exciton theory, whereas polyproline II remains unsatisfactory.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 197
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The synthesis is described of the N-benzyloxycarbonylundecapeptide tert-butoxycarbonylhydrazide corresponding to the sequence 82-92 of baker's yeast iso-I-cytochrome c.
    Materialart: Digitale Medien
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  • 198
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The synthesis is described of the protected hexadecapeptide corresponding to the C-terminal sequence 93-108 of baker's yeast iso-I-cytochrome c. The cysteine residue in position 107 of the natural sequence has been substituted by a threonine residue. The rationale of this substitution as well as the synthetic route to the preparation of the hexadecapeptide derivative is discussed.
    Materialart: Digitale Medien
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  • 199
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 825-834 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The geometrical properties of collagen molecules place certain restrictions on possible three-dimensional packing models. With certain reasonable assumptions involving the macromolecular structure of collagen, a model for the surface topography of the monomeric unit is developed and two possible models for molecular packing, one hexagonal and the other non-hexagonal, are inferred. The non-hexagonal packing model is identical to the pentagonal unit fibril first postulated by J. W. Smith on different grounds, while the hexagonal model is one of three previously suggested by us on more general assumptions. The two models are compared to available data on collagen packing, and the bulk of the evidence would seem to favor the pentagonal model.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 200
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 869-876 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Zones of T2 DNA were sedimented through uniform solutions of T7 DNA to determine if the smaller DNA molecules would become entangled in the larger. No entanglement could be demonstrated even at high DNA concentrations. It is suggested that molecular entanglement is not responsible for the sudden loss of DNA from solution which occurs in high centrifugal fields. This communication also includes observations on the effects of rotor speed on the sedimentation behavior of DNA in high centrifugal fields, distortion of zone shape at high concentrations, and hydrodynamic interactions between DNA and MS2 bacteriophage particles.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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