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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 20 (1973), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: An ultrastructural study was made of the spore envelope during development in the microsporidan, Thelohania bracteata. The frozen-etched outer (convex) face of the relatively thin spore coat in the earliest immature stage of development has a granular structure in regular array. The inner (concave) face bears particles as well as depressions arranged in a net-like pattern. The mature spore coat has a substructure of numerous microfibers, ∼8 nm in diameter, arranged in a matrix and forming thin layers which run parallel to the spore surface. The mature spore coat possesses both outer and inner limiting layers. The outer (convex) face of the outer limiting layer is granular. The convex face of inner limiting layer bears many particles as well as many long, narrow depressions. The concave face of the inner limiting layer carries many stud-like projections, ∼40 nm long and 30 nm high, which are complementary to the depressions observed on the convex face. In addition, the concave face has subunits ∼15 nm in diameter, apparently arranged in a hexagonal pattern with a center to center distance of ∼18 nm. The change in size of these projections, depressions, and subunits presumably is related to spore maturation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 19 (1972), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. In the microsporidian, Thelohania bracteata, the polar filament, as it starts to develop in the sporoblast, apparently receives material synthesized by the granular endoplasmic reticulum and Golgi vesicles. In immature spores many dilated sacs are observed in areas where there is less endoplasmic reticulum. These sacs, that persist into the almost mature spore, are probably Golgi-type vesicles and may be related to the formation of the spore coat. The polar filament of the mature spore possesses 8 coils and in cross section or cross-fractured face the electron-dense central portion of the polar filament contains a tubular structure, ringed by 12–14 cylindrical structures. In thin sections, an electron-lucid zone is observed between the core and membrane of the polar filament. The polar filament runs through the highly laminated polaroplast which occupies the anterior portion of the spore. In cross-fractured face the lamellae of the polaroplast are arranged like the petals of a flower. The basal portion of the polar filament is enlarged, appearing arrow-shaped in thin sections and pear-shaped in frozen-etched preparations. Frozen-etched membranes differ in the size and distribution of the surface particles.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. The ultrastructure of a microsporidan pansporoblast was observed with freeze-etching electron microscopy. The cross-fractured face of ovoid mature spores, with the upper part of the spore coat fractured off, revealed the spore membrane; the convex face had many small depressions and the concave face bore fine particles. In cross-section the spore-coat was highly laminated and about 0.5 μ in diameter.In the cytoplasm of the pansporoblast, fluid-filled and finger-print-life profiles of vesicles were observed. The vesicles were approximately 180 nm in diameter and laminated, each lamella being about 15–18 nm thick. In addition to these vesicles, a population of elevations, each with an average diameter of 40 nm, was evenly distributed in the pansporoblast among the spores. No other cytoplasmic organelles were observed within the pansporoblast. The pansporoblast wall was about 15–19 nm thick with particles 15–18 nm in diameter on its outer surface.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 15 (1972), S. 265-273 
    ISSN: 1570-7458
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Wie im Elektronenmikroskop zu sehen ist, führen einen Tag alte Weibchen der autogenen, nordamerikanischen Kriebelmücke, Simulium vittatum Zett., in den Zellen des Fettkörpers reichlich Glykogen. Obwohl der Glykogengehalt während der nächsten zwei Tage der Oogenese rasch abnimmt, behält der Fettkörper unvermindert die Fähigkeit zur Glykogensynthese, wie der rasche Einbau von 14C-Glukose in vivo beweist. Bei Zugabe von Trägerglukose wurde mehr 14C-Glukose als ohne diese eingebaut. Jedoch war der Prozentsatz diastaseresistenter Partikel höher, wenn 14C-Glukose ohne Carrier injiziert wurde, wie autoradiographisch zu erkennen war. Die Häufigkeit dieser diastaseresistenten Partikel und das in den Golgi-Bläschen eingeschlossene elektronendichte Material sowie die zahlreichen Golgi-Komplexe in enger Nachbarschaft der “Glykogen-Region” und das wohlentwickelte endoplasmatische Retikulum lassen vermuten, daß Glykogen in den Fettkörperzellen das Kohlenwasserstoff-Reservoir für die Glykoprotein-Synthese und-Lieferung darstellt. Die ausschließliche Verbreitung von Mitochondrien in der “Glykogen-Region”, welche ebenfalls eng mit dem endoplasmatischen Retikulum verbunden ist, dürfte darauf hinweisen, daß Glykogen außerdem die endogene Energiequelle für den Stoffwechsel in den Fettkörperzellen darstellt.
    Notes: Abstract Glycogen was abundant in fat-body cells of 1-day-old autogenous black-flies (Simulium vittatum Zett.) as seen by electron-microscopy, and decreased during the next 2 days. However, the ability of the fat body to synthesize glycogen remained undiminished. More C14-glucose was incorporated in vivo with added carrier glucose than without. The percentage of “diastase-resistant” particles, as seen by autoradiography, was higher when C14-glucose was injected without the carrier. Along with the abundance of diastase-resistant radioactive particles, the dense material enclosed in the Golgi vesicles, plus the well-developed endoplasmic reticulum and numerous Golgi complexes, suggested that glycogen in the fat-body cell provides carbohydrates for glycoprotein synthesis and export, as well as for an endogenous energy source.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 141 (1973), S. 469-478 
    ISSN: 1432-0878
    Keywords: Microsporida ; Nosema apis ; Developing spore ; Freeze-etching ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The mature spore possesses a thick spore coat and a particle-bearing spore membrane. The highly laminated polaroplast membranes are located at the anterior pole of the spore. Close to its base, the polar filament is surrounded by the polaroplast membrane. The polar filament runs spirally towards the posterior pole of the spore. A large portion of the polar filament is arranged in two layers. A similar arrangement was also observed in immature spores and in the sporoblast stage, although it was not so orderly arranged in the latter. The developing polaroplast membrane was observed in the immature spore, but not in the sporoblast. The sporoblast wall is much thinner than the spore coat, but has the same texture. Endoplasmic reticulum is the most prominent cytoplasmic organelle in the developing stages of Nosema apis. Porous nuclear envelopes are also observed in developing stages. The role of the endoplasmic reticulum in the formation of the polar filament, polaroplast and spore coat, and the function of the spore membrane, are discussed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Metrika 21 (1974), S. 127-132 
    ISSN: 1435-926X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary In this note we have constructed a lower bound for theBayes risk of an arbitrary unbiased estimator for a finite population variance. We also have shown that under certain conditions theHorvitz-Thomson type estimator for the variance is aBayes solution
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 79 (1974), S. 409-412 
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Relocation of particles occurred in the plasma membrane of the symbiotic bacteria in the ovaries of decapitated cockroaches after administration of juvenile hormone. Particles were arranged in a network-like pattern in the plasma membrane of symbiotic bacteria from hormonally treated cockroaches, whereas particles were evenly distributed in the plasma membrane of symbiotic bacteria from untreated cockroaches.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 143 (1974), S. 337-347 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Scanning electron microscopy revealed spores of Nosema apis and Thelohania fibrata to be egg-shaped, but only the mature spore of T. fibrata was shown to possess a horseshoe-like concavity at the posterior pole. Freezeetched preparations indicated that this concavity was due to a thin area of the spore coat. Freeze-etching studies also show spores of N. apis do possess an umbrella-shaped polaroplast, and a polar filament which is arranged in a double layer with over 30 coils. The spore of T. fibrata contains a pear-shaped arrangement of the polaroplast membrane, and a polar filament arranged in a single layer of 22 coils.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Parasitology research 43 (1974), S. 279-284 
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The development of the spore began at the sporoblast stage. The profile of the developing polar filament was defined clearly in the late sporoblast, but its internal structure was still lacking. During this stage, both a vesicular type of endoplasmic reticulum and an endoplasmic reticulum containing cisternae in a parallel arrangement were abundant in the cytoplasm of the sporoblast. Numbers of large, expanded vacuoles were also observed in the cytoplasm. As spore development proceeded, the spore coat increased gradually in thickness. The expanded vacuoles started to take up positions around the anterior portion of the polar filament and to become incorporated into the developing polaroplast, which eventually became a highly-laminated structure in the mature spore. In the mature spore, the fully-developed polar filament possessed a central tube surrounded by 12 cylindrical structures, and the spore coat attained its maximum thickness.
    Type of Medium: Electronic Resource
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