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  • 1
    Electronic Resource
    Electronic Resource
    Fine structure of Sertoli cells in three marine snails with a discussion on the functional morphology of Sertoli cells in general (1986)
    Springer
    Cell & tissue research 245 (1986), S. 305-313 
    Details
    ISSN: 1432-0878
    Keywords: Sertoli cells ; Nurse cells ; Spermatogenesis ; Mollusca ; Prosobranchia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of Sertoli cells in three marine prosobranch molluscs has been studied with light- and electron microscopy. Sertoli cells of prosobranchs are modified columnar epithelial cells that maintain continuous contact with the basal lamina and extend from it to the lumen of a testicular tubule. Spermatogenesis takes place between adjacent Sertoli cells, but a continuous layer of cytoplasm separates the spermatogonia from the basal lamina, thus restricting the basal compartment to spermatogonium mother cells. Substances traversing the basal lamina from the interstitial space must pass either through or between the Sertoli cells. However, between the cells, a permeability barrier composed of septate and desmosome-like junctions blocks the passage of substances, such as the tracer lanthanum nitrate. The basally-located nucleus is irregularly shaped with fine granular euchromatin and some peripheral heterochromatin; satellite karyosomes border the nucleolus. There is an extensive intracellular digestive system that is used effectively to phagocytize waste sperm and residual cytoplasm. Cytoplasmic processes of Sertoli cells penetrate throughout the germinal epithelium. In some prosobranchs that exhibit sperm polymorphism these processes must coordinate to bring together a clone of eupyrene sperm and a carrier sperm at a particular time in development. The only cytoskeletal elements available within the processes to generate such movements are microtubules. We propose that the term ‘nurse cell’, which has been used in the past to describe at least three different cell types, including Sertoli cells and apyrene sperm, be restricted to abortive oogonia that contribute to development of an oocyte.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213936
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  • 2
    Electronic Resource
    Electronic Resource
    The fine structure of the polymorphic spermatozoa of Fusitriton oregonensis (Mollusca: Gastropoda), with notes on the cytochemistry of the internal secretions (1982)
    Springer
    Cell & tissue research 227 (1982), S. 235-255 
    Details
    ISSN: 1432-0878
    Keywords: Sperm polymorphism ; Ultrastructure ; Mollusca ; Prosobranchia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The prosobranch Fusitriton oregonensis exhibits an unusual form of sperm polymorphism. The viable, eupyrene sperm are attached in groups of about fifty to worm-shaped, apyrene, carrier sperm. There is a second apyrene sperm, which is lancet-shaped and has a different internal organization than the carrier, but does not transport eupyrene sperm. The eupyrene sperm are filiform (185 μm long), with a conical acrosome, elongate nucleus and midpiece. They contain large stores of glycogen in the principal piece, together with an unusually high proportion of protein. The latter is due to a complex interconnecting system of fibres that supports the tail internally. A distinct annulus is located, characteristically, at the junction between midpiece and principal piece. The carrier sperm has a core of about 112 axonemes that arise from basal bodies in the anterior end and extend through its entire length of 36 μm. The basal bodies have unstriated rootlets that are embedded in a granular cap. Large membrane-bound “yolk bodies” are arranged along the length of the carrier sperm, on either side of the median axonemal core. Dense bodies, which may be indigestible residues formed from the degeneration of the nucleus, are excreted by exocytosis. Individual carrier sperm are capable of “corkscrew” propulsion, resembling that of spirochaetes. The lancet sperm is three times as long as the carrier. The sixteen or so axonemes, which are arranged peripherally like a cage enclosing the cytoplasm, originate from a dense centriolar plate in the anterior end. The cytoplasm is filled with secretions including small yolk granules, dense bodies (also excreted), clear vesicles, and a membranated granular secretion that resembles mucus. The possible functions of the lancet and carrier sperm are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210883
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    Paper (German National Licenses)
    Fulltext
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