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  • Electronic Resource  (64)
  • 2000-2004  (10)
  • 1970-1974  (54)
  • Ultrastructure  (64)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 98 (1974), S. 147-158 
    ISSN: 1432-072X
    Keywords: Allomyces ; Zoospores ; Cell Wall ; Wall Formation ; Lomasome ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 155 (1974), S. 541-554 
    ISSN: 1432-0878
    Keywords: Hypophysectomized rats ; Reorganized stalk ; Ultrastructure ; Salt load
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 201 (2000), S. 51-61 
    ISSN: 1432-0568
    Keywords: Key words Female prostate (Skene gland) ; Ultrastructure ; Secretory (luminal) cells ; Basal (reserve) cells ; Intermediary cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The predominant cells of female prostatic glands lining their lumen were found to be tall cylindrical secretory cells with short stubby microvilli, protuberances of the apical cytoplasm, and with bleb formation. Abundant secretory vacuoles and granules, rough endoplasmic reticulum, developed Golgi complexes and numerous mitochondria are characteristic of their active secretory configuration with apocrine (apical blebs) and merocrine (secretory vacuoles and granules) type of secretion. Basal (reserve) cells were seen to be located between the secretory (luminal) cells and the basement membrane. Their ground cytoplasm is dense with rough endoplasmic reticulum and mitochondria. Their nuclei, unlike those of secretory cells, possess more peripheral condensed chromatin, denser dispersed chromatin and sporadic nucleoli. Besides the two basic types of mature prostatic cells intermediary cells were also seen, located between the basal and secretory cells or in their close vicinity. Their cytoplasm exhibits numerous profiles of rough endoplasmic reticulum and free ribosomes. Secretory vacuoles and granules were mostly practically absent (type 1 intermediary cells) so that they resembled basal (reserve) cells. In some of them, however, as in secretory cells, such secretory elements do gradually appear (type 2 intermediary cells). The finding of intermediary cells in the lining of prostatic glands supports the role of basal (reserve) cells in the renewal of cells in glands of the female prostate. The first ultrastructural analysis of the normal female prostate performed by transmission electron microscopy showed that, as in the postpubertal male, the prostatic glands in the adult female display mature secretory and basal cells. The results of the presented study further corroborate the contemporary concept of the female prostate as a functional genitourinary organ.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 142 (1973), S. 89-102 
    ISSN: 1432-0878
    Keywords: Photoreceptors ; Larva ; Hemichordate ; Ultrastructure ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0878
    Keywords: Hypophysis ; Mouse, rat ; Pars intermedia, rostral zone ; Corticotrophic cells ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1615-6102
    Keywords: Beta vulgaris ; Cyst nematodes ; Histology ; Resistance mechanism ; Syncytium ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using susceptible and resistant sugar beet lines, comparative analyses of root histology and ultrastructure were made during invasion by nematodes and the induction and formation of specific feeding structures (syncytia).The resistant line carried the resistance geneHs1pro−1.Nematodes were able to invade and induce functional syncytia in roots of resistant and susceptible lines. However, syncytia in resistant roots were smaller and less hypertrophied. The vacuolar system of syncytia in susceptible plants contained many small vacuoles. In resistant plants vacuoles were larger but less numerous. Smooth endoplasmic reticulum prevailed in syncytial protoplasts of susceptible plants, whereas almost only rough endoplasmic reticulum occurred in syncytia in resistant plants. The most conspicuous and hitherto undescribed trait of syncytia in resistant roots was the initial appearance of loose, and later compact, aggregations of the endomembrane system which composed most of the endoplasmicreticulum system of syncytia at later stages. Syncytia in resistant plants usually degraded before the nematodes reached their adult stage. The appearance of membrane aggregations and the other resistance-specific features are discussed in relation to their possible effects on syncytium function and role in nematode resistance.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1615-6102
    Keywords: Glutathione ; Root ; Chromosomal aberration ; Ultrastructure ; Picea abies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Young spruce seedlings (Picea abies [L.] Karst.) grown in hydroponic culture were exposed to three different concentrations (50,100, and 500 μM) of reduced glutathione for 24 h. These physiologically relevant concentrations of glutathione had a multiple effect on the investigated tissue. Feeding of glutathione to roots increased the concentrations of thiols (glutathione, cysteine, and γ-glutamyl-cysteine) in roots, decreased the rate of cell divisions, induced mitotic abnormalities, and affected the cell ultrastructure. Electron micrographs showed effects such as advanced vacuolation, dilated rough-endoplasmic-reticulum cisternae, and separations of the plasma membrane from the cell wall.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 10 (1972), S. 38-48 
    ISSN: 1432-0827
    Keywords: Bivalve ; Molluse ; Shell ; Carbonates ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: 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.
    Abstract: 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.
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 7 (1971), S. 191-200 
    ISSN: 1432-0827
    Keywords: Serpulid ; Polychaete ; Hydroxyapatite ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: 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.
    Abstract: 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.
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 186 (2000), S. 347-357 
    ISSN: 1432-1351
    Keywords: Key words Crustacean ; Sensorimotor ; Ultrastructure ; Multilamellar sheath ; Myelinated axons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Speed of nerve impulse conduction is greatly increased by myelin, a multi-layered membranous sheath surrounding axons. Myelinated axons are ubiquitous among the vertebrates, but relatively rare among invertebrates. Electron microscopy of calanoid copepods using rapid cryofixation techniques revealed the widespread presence of myelinated axons. Myelin sheaths of up to 60 layers were found around both sensory and motor axons of the first antenna and interneurons of the ventral nerve cord. Except at nodes, individual lamellae appeared to be continuous and circular, without seams, as opposed to the spiral structure of vertebrate and annelid myelin. The highly organized myelin was characterized by the complete exclusion of cytoplasm from the intracellular spaces of the cell generating it. In regions of compaction, extracytoplasmic space was also eliminated. Focal or fenestration nodes, rather than circumferential ones, were locally common. Myelin lamellae terminated in stepwise fashion at these nodes, appearing to fuse with the axolemma or adjacent myelin lamellae. As with vertebrate myelin, copepod sheaths are designed to minimize both resistive and capacitive current flow through the internodal membrane, greatly speeding nerve impulse conduction. Copepod myelin differs from that of any other group described, while sharing features of every group.
    Type of Medium: Electronic Resource
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