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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 149 (1976), S. 289-295 
    ISSN: 1432-0568
    Keywords: Scanning and transmission electron microscopy ; Baboon ; Cleavage stages ; Microvilli ; Cell junctions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Scanning and transmission electron microscopy were used to study baboon preimplantation embryos 3 to 5 days E.F.A. (estimated fertilization age), ranging from about 16 to more than 60 cells. The peripheral blastomeres were covered with microvilli scattered on the convex outer surface and along the borders of the intercellular furrows. In younger morulae, some longer microvilli may bridge over the furrow separating contiguous blastomeres. A few blastomeres showed poorly developed microvilli. Blastomeres of smaller diameter than the others may arise from more recent cleavage. Cell junctions as well as small intercellular spaces were noted at the apposition of the blastomere plasma membranes whereas surface intercellular ridges were not observed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 161 (1975), S. 329-341 
    ISSN: 1432-0878
    Keywords: Spermatozoa ; Boar, bull, ram ; Surface ultrastructure ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Résumé La morphologie comparée des spermatozoïdes éjaculés de Verrat, Taureau et Bélier a été étudiée au microscope à balayage. Le sperme lavé est fixé dans le glutaraldéhyde ou le mélange acide picrique-formaldéhyde-glutaraldéhyde. Les échantillons sont le plus souvent désséchés par la méthode du point critique (Fréon) sur un filtre et aussi dans l'air sur une lamelle de verre. La tête des spermatozoïdes de ces trois espèces présente la même forme en pagaie aplatie formée de trois régions principales: les deux segments, antérieur, entouré d'un épaississement marginal, et équatorial de l'acrosome et la région postacrosomique. La plupart des differentiations de la lame postacrosomique décrites en microscopie électronique à transmission sont visibles à travers la membrane plasmique, particulièrement après dessication à l'air. La morphologie superficielle du cou et des différentes parties du flagelle est aussi observable. Des différences spécifiques sont mises en évidence: chez le verrat seulement, par exemple, la surface de l'acrosome apparaît granuleuse, et aucune bordure antérieure dentelée de la lame postacrosomique n'est visible. La microscopie à balayage permet d'observer les grands traits et de fins détails de la morphologie superficielle d'un échantillon de sperme et aussi d'étudier les effects de traitements sur des spermatozoïdes (congélation, extraction de l'acrosome).
    Notes: Summary The comparative ultrastructure of ejaculated boar, bull and ram spermatozoa is studied by scanning electron microscopy. After washing, the spermatozoa are fixed in glutaraldehyde or in picric acid-formaldehyde-glutaraldehyde mixture. Samples are prepared either by critical point drying (Freon) on Millipore filters or by air drying on glass cover slips. In all the species studied, three regions may be distinguished in the paddle-shaped head of the sperm: an anterior segment (surrounded by the marginal thickening) and an equatorial segment constituting together the acrosome, and the postacrosomal region. Most of the feature of the postacrosomal lamina described in transmission electron microscopy are visible through the plasma membrane, particularly after air drying. The surface morphology of the neck and of the different segments of the flagellum is also evident. Some species differences are encountered, e.g. rough surface of acrosome and absence of serrations in postacrosomal lamina of boar spermatozoa only. The techniques employed result in good general morphology and fine resolution of surface detail of the sperm samples; they also permit analysis of spermatozoa treated by freezing or submitted to acrosomal extraction.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 13 (1978), S. 241-252 
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Résumé Les alliages de nickel-phosphore et de nickel-bore préparés pour oxydo-réduction en phase liquide sont dans leur état initial amorphes ou imparfaitement cristallisés. Au cours d'un traitement thermique approprié, une diffusion atomique précède la cristallisation du nickel, des phosphures ou des borures de nickel. Les différentes étapes de l'évolution structurale des alliages sont suivies par ATD et par diffraction X. L'évolution de la résistivité électrique de ces mêmes alliages, au cours de montées linéaires en température, confirme les résultats obtenus par ATD et diffraction X.
    Abstract: Zusammenfassung Die für Oxydoreduktionszwecke in flüssiger Phase hergestellten Nickel-Phosphor und Nickel-Bor Legierungen sind in ihrem Ausgangszustand amorf oder teilkristallin. Im Laufe einer geeigneten thermischen Behandlung geht der Kristallisation des Nickels, der Nickelphosphide und Nickelboride eine atomare Diffusion voraus. Die verschiedenen Stufen der strukturellen Entwicklung der Legierungen werden mittels DTA und Röntgendiffraktion verfolgt. Die Verfolgung des elektrischen Widerstands der Legierungen bei linearen Temperaturanstiegen bestätigte die mittels DTA und Röntgendiffraktionen erhaltenen Ergebnisse.
    Notes: Abstract The nickel-phosphorus and nickel-boron alloys prepared for oxidation-reduction in the liquid phase are amorphous or perfectly crystallized in their initial form. An atomic diffusion precedes the crystallization of nickel, nickel phosphides or nickel borides in the course of appropriate thermal treatment. The different stages of the structural development of the alloys were followed by DTA and X-ray diffraction. The changes in the electrical conductivities of the same alloys as a function of linearly increasing temperature confirmed the results obtained with the aid of DTA and X-ray diffraction.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 151 (1978), S. 39-53 
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The ultrastructure of spermatozoa from the cauda epididymidis and vas deferens of Octodon degus  -  a Chilean hystricomorph rodent - is presented. The head of spermatozoa measured 7.7 μm long by 5.9 μm wide and the tail was 41 μm long. The head was flattened dorso-ventrally and ovate in outline. The acrosome was the most distinctive feature of O. degus spermatozoa. In a frontal view of the head, the rim of the acrosome surrounding the nucleus had the shape of an inverted U. The acrosomal region covering the plane of the flattened head exhibited dome-shaped protrusions. Transverse or sagittal sections of acrosomal protrusions showed that the plasma membrane and outer acrosomal membrane were evaginated, while the inner acrosomal membrane followed the contour of the nucleus. The protrusions were not distributed at random and they were absent in the equatorial segment and in the rim of the acrosome.In frontal views, near the boundary between the acrosome and post-acrosomal region, fine rods about 170 nm long ran obliquely on the caudal part of the equatorial segment. Behind the same boundary, the post-acrosomal region showed a serrated border.Phosphotungstic acid treatment at pH 0.3 produced staining at the surface of the sperm as well as within a superficial layer of the marginal thickening of the acrosome and on the acrosomal protuberances.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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