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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 98 (1974), S. 147-158 
    ISSN: 1432-072X
    Schlagwort(e): Allomyces ; Zoospores ; Cell Wall ; Wall Formation ; Lomasome ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Ultrastructural observations on encysting haploid zoospores of Allomyces arbuscula are presented with special reference to cell wall deposition. Multivesicular bodies are observed in the cytoplasm of zoospores 15 min after inoculation, lomasomes after 30 min and fine membrane profiles between the plasmalemma and the cyst wall are observed after 4 h indicating a possible system for secretion of cell wall components.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 155 (1974), S. 541-554 
    ISSN: 1432-0878
    Schlagwort(e): Hypophysectomized rats ; Reorganized stalk ; Ultrastructure ; Salt load
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The reorganized stalk of hypophysectomized rats, either “intact” or subjected to a 6-day salt load, has been studied by light and electron microscopy. PAF-positive neurosecretory material is seen mainly in the periphery of the reorganized stalk, usually in 2–5 μ nerve swellings of animals operated two months before. Nerve swellings make contact with a dense capillary network. Three types of nerve fibres and their swellings are distinguished according to the size of elementary granules. Peptidergic A1 and A2 types contain granules with a maximum diameter of 170 and 130 nm respectively; monoaminergic B type fibres have granules of 100 nm in diameter. A1 type axonal swellings are the most numerous and can be tentatively divided into four subtypes according to their ultrastructure and relationships with capillaries and pituicytes. Swellings of types b and c, making direct contact with capillaries or pituicyte perikarya, usually contain few granules and numerous synaptic vesicles arranged frequently in clusters in the “active” zones. It is assumed that they are especially active in the release of peptide neurohormones. It is also hypothesized that in the hypophysectomized rats peptide neurohormones are released not only directly into the pericapillary space but also into the intercellular cleft, especially at sites of neuron-pituicyte junctions. Nerve swellings of type a, separated from the pericapillary space by thin pituicyte processes, usually contain numerous neurosecretory granules. It is suggested that vascular “end-feet” of pituicytes may somehow reduce neurohormone release. The depletion of PAF-positive material as well as the decreased granule content even after a salt load of only 1 per cent shows that the reorganized stalk is functional as a neurohaemal organ, but has a diminished hormone reserve. This, together with a primitive cytomyeloangioarchitecture speaks for morphological and functional imperfection of the reorganized stalk.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 142 (1973), S. 89-102 
    ISSN: 1432-0878
    Schlagwort(e): Photoreceptors ; Larva ; Hemichordate ; Ultrastructure ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The eyespots of tornariae of enteropneusts (Ptychodera flava from Hawaiian waters and an unknown species from southern California) were studied by electron microscopy. An ocellus is composed of two types of cells: sensory and supportive. The former is characterized by a bulbous cilium (with 9+2 axoneme) at its distal end, one or sometimes two arrays of microvilli from its sides below the cilium, and a basal axon. The latter features large, clear vesicles which presumably contained the reddish-orange pigment seen in the ocellus of a living larva. Five-day old tornariae of P. flava are positively phototactic. Both cilium and microvilli may function as photoreceptors. The tornarian ocellus studied is compared with eyespots of other invertebrates, and the evolutionary significance of its putative photoreceptors is discussed.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1432-0878
    Schlagwort(e): Hypophysis ; Mouse, rat ; Pars intermedia, rostral zone ; Corticotrophic cells ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary In the mouse, the rostral zone of the pars intermedia is almost exclusively composed of typical corticotrophic cells. They are located around and even within the neural stalk, at the level of transition between stalk and neural lobe. In the rat, the corticotrophic cells of the rostral zone are found in scattered islets among the MSH producing cells, and also in the neural lobe. In both the rat and mouse, these cells are in direct contact with various types of nerve terminals. Synaptoid contacts with aminergic and neurosecretory nerve fibers are observed. Furthermore they are also closely related to the hypophysial portal vessels. Following adrenalectomy, the cells located in the neurohypophysis always react more intensely than tose in the rostral zone. The functional significance of these corticotrophic cells which are subject to both humoral and neural regulation remains as yet hypothetical. Their participation in neurogenic stress response seems probable.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 10 (1972), S. 38-48 
    ISSN: 1432-0827
    Schlagwort(e): Bivalve ; Molluse ; Shell ; Carbonates ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé La technique du bombardement à l'aide d'ion d'argon est utilisée pour réduire l'épaisseur de la coquille de carbonate de calcium des bivalvesMytilus etMercenaria pour examen au microscope électronique par transmission et en diffraction électronique; une comparaison est réalisée à l'aide de répliques simples, servant de témoins. Les résultats obtenus confirment les études antérieures de répliques et de microscopie par balayage. De plus, une structure “aérée” est mise en évidence dans la coquille des aragonites, et surtout dans le nacre deMytilus. Cette structure est interprêtée comme un artefact induit par la chaleur, formé par l'inclusion d'eau et de matériel organique, interprétation qui concorde avec les études chimiques et de microscopie électronique.
    Kurzfassung: Zusammenfassung Die Beschießung mit Argonionen wurde angewendet, um die Dicke von Calciumcarbonat-Schalen der zweischaligen MuschelnMytilus undMercenaria zu reduzieren. Diese Technik erlaubte die Ausführung von Transmissions-Elektronenmikroskopie und Elektronendiffraktion, wobei gleiche Proben nach einer bereits bestehenden Methode vorbereitet und als Kontrollen herangezogen wurden. Es wurden zusätzliche Resultate zu den Muschelstruktur-studien erhalten, welche früher publizierte Arbeiten unterstützen, die mit der Abklatschmethode und der Raster-Elektronenmikroskopie ausgeführt worden waren. Zusätzlich wurde eine „schaumartige” Struktur der Muschelaragoniten, besonders im Perlmutter vonMytilus, beobachtet. Da es sich um ein durch Hitze verursachtes Artefakt handelt, wird diese Struktur als Einschlüsse von Wasser und organischem Material interpretiert, was den Befunden von verschiedenen veröffentlichten chemischen und elektronenmikroskopischen Arbeiten entspricht.
    Notizen: Abstract Use is made of the argon ion-bombardment technique to reduce the thickness of calcium carbonate shells of the bivalvesMytilus andMercenaria for transmission electron microscopy and electron diffraction, with comparison of single-stage replicas of similar specimens serving as controls. As an additional approach to shell structure studies, it gives results which support earlier published work with both replicas and scanning microscopy. In addition, a “frothy” structure is detected in the shell aragonites, especially inMytilus nacre. As a heat-induced artifact, it is interpreted as representing trapped water and organic material inclusions, an interpretation consistent with several published chemical and electron microscope studies.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 7 (1971), S. 191-200 
    ISSN: 1432-0827
    Schlagwort(e): Serpulid ; Polychaete ; Hydroxyapatite ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Beschreibung / Inhaltsverzeichnis: Résumé Un petit groupe de cellules épithéliales de la surface antérieure du col du serpulidePomatoceros caeruleus contient des vacuoles, remplies de matériel cristallin. Les cristaux présenttent des aspects rhomboédriques ou rectangulaires. La diffraction électronique montre qu'ils sont constitués par de l'hydroxyleapatite et du phosphate de calcium et de magnésium. Les apex des cellules sont bordés de microvillosités. Certaines cellules ont des cils apicaux. Un appareil de Golgi est visible dans le cytoplasme apical. De nombreuses mitochondries sont dissé minées dans le cytoplasme. Le role éventuel de ces cellules, a contenu minéral, dans la mise en réserve de calcium et/ou de phosphore est envisagé.
    Kurzfassung: Zusammenfassung Ein kleiner Zellverband im Epithel der vorderen Oberfläche am Hals des SerpulidsPomatoceros caeruleus enthält membrangebundene Vakuolen, welche mit kristallinem Material gefüllt sind. Die Kristalle haben rhomboide oder rechteckige Formen; mittels Elektronendiffraktion konnte nachgewiesen werden, daß sie aus Hydroxyapatit und Calciummagnesiumphosphat bestehen. Die oberen Enden der Zellen sind von Microvilli eingefaßt. Einige der Zellen haben zudem apikale Zilien. Die Zellen enthalten Golgi-Apparate im apikalen Cytoplasma. Eine große Anzahl von Mitochondrien sind über das, ganze Cytoplasma verteilt. Die mögliche Funktion dieser mineralhaltigen Zellen als Aufbewahrungsorte für Calcium und/oder Phosphor wird besprochen.
    Notizen: Abstract A small patch of cells in the epithelium of the anterior surface of the collar of the serpulidPomatoceros caeruleus contains membrane-bound vacuoles filled with crystalline material. The crystals have rhomboidal or rectangular profiles and have been shown by electron diffraction analysis to be composed of hydroxyapatite and calcium magnesium phosphate. The apices of the cells are bordered by microvilli. Some cells also have apical cilia. The cells contain Golgi complexes in the apical cytoplasm. Large numbers of mitochondria are distributed thoughout the cytoplasm. The possible function of these mineral-containing cells as sites for storage of calcium and/or phosphorus is discussed.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 143 (1974), S. 239-254 
    ISSN: 1432-0568
    Schlagwort(e): Oocyte ; Follicle cells ; Intercellular bridges ; Lizard ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1. Intercellular bridges connect the oocyte with its surrounding follicle cells. 2. Fibrillar bundles and microtubules are oriented along the length of the bridge. Mitochrondria, endoplasmic reticulum, multivesicular vesicles and other cytoplasmic components are also present in this region. 3. This communication may be very important for the flow of nutrients necessary for the growth of the oocyte.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 147 (1974), S. 45-62 
    ISSN: 1432-0568
    Schlagwort(e): Baboon ; Cleavage stages ; Embryos ; Preimplantation ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Résumé La structure et l'ultrastructure des embryons de babouin sont étudiées dans la période précédant l'implantation. Six stades du développement embryonnaire sont observés 2, 3, 4, 5, 7 et 8 jours après la date présumée de fécondation. Dans les 3 premiers cas, on compte respectivement 2, 8 et 24 blastoméres. A 5 jours, il y a 30 à 40 cellules et un nombre dépassant 60, ultérieurement. Des cellules trophoblastiques primitives se différencient à 7 jours et une cavité de segmentation en forme de croissant apparaît au 8 ème jour. La zone pellucide est toujours présente à 8 jours, la période de préimplantation semblant plus longue chez le babouin que chez l'homme. Des particules de type C sont décrites dans la zone pellucide et les espaces périvitellin et interblastomériques. La transformation des mitochondries, des changements dans la répartition des ribosomes, des corps multivésiculaires, pseudocristallins et figures myéliniques, des nucléoles et amas granuleux intra-nucléaires s'observent chez le babouin comme chez certains autres Mammifères; par contre, les faisceaux fibrillaires cytoplasmiques sont absents. L'étude des changements de l'ultrastructure provoqués par des hormones et drogues permettrait de mieux évaluer la nocivité de ces substances pendant les premiers stades du développement embryonnaire des Primates.
    Notizen: Summary The baboon preimplantation stages were examined using light and electron microscopy. Six cases were studied at 2, 3, 4, 5, 7 and 8 days estimated fertilization age. The first 3 specimens were composed of 2, 8 and 24 blastomeres respectively. At 5 days, 30 to 40 cells were counted and more than 60 cells in later stages. Primitive “trophoblast cells” differentiate at 7 days and a crescentic blastocoele appears at 8 days. Shedding of the zona pellucida is not observed in the 7 and 8 day specimens. The preimplantation period is longer in the baboon than in man. C-type viruses are observed in the zona pellucida, in the perivitelline and interblastomeric spaces. Microvilli and caveolae cover the periphery of the baboon conceptus. As in many other mammals, transformation of the mitochondria, changes in the ribosomes distribution, multivesicular bodies, myelin figures, nucleoli and intranuclear clusters of granules are described in the baboon. Cytoplasmic fibrous strands are not present as in the mouse. Experiments on the influence of hormones and drugs on ultrastructural changes would help to evaluate the importance of biohazards during the early development of primates.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 147 (1974), S. 1-18 
    ISSN: 1432-0568
    Schlagwort(e): Mouse kidney ; Thin limbs ; Ultrastructure ; Renal concentrating mechanism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The thin limbs of the loops of Henle in the mouse kidney have been investigated by conventional electron microscopy. Resulting from light microscopic investigations, a distinction in the epithelia of short and long loops can be demonstrated. Ultrastructurally, the thin limbs (descending) of short loops are composed of a uniformly thin and simple epithelium. In contrast, long loops (thin descending and ascending) are composed of three different epithelial types which are representative of a distinctly more complex epithelial system. Two epithelial types were observed in the thin descending limbs of long loops and the third type was observed in the ascending thin limbs. Based upon these findings it is suggested that the thin descending limbs of short and long loops of Henle in the mouse kidney cannot perform the same functions in the renal concentrating mechanism.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Acta neuropathologica 30 (1974), S. 277-285 
    ISSN: 1432-0533
    Schlagwort(e): Chick Embryo ; Brain ; Blood Vessels ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The fine structure of the blood vessels was studied in the developing brain of chick embryo. The blood vessels were present in the embryos first examined (4 days after incubation) and their number increased in subsequent stages. The endothelial cells were generally large and showed junctional complexes, many microvilli and a large number of cytoplasmic organelles. Many tubular bodies and coated vesicles were also present. The tubular bodies were sometimes noted near the Golgi apparatus, suggesting their origin from this organelle. The mitochondria in the endothelial cells were generally larger than those in the surrounding neuropil. An ill-defined basement membrane-like substance was noted outside some endothelial cells on the 11th day and well formed basement membrane was present in the vessels of 18 day old embryos. A complete subpial astrocytic basement membrane was present from the early stage studied (4 days).
    Materialart: Digitale Medien
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