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  • 1
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    An electron microscope study of spermiogenesis in Spirorbis (Laeospira) m�rchi Levinsen (Polychaeta) (1967)
    Springer
    Details
    Publication Date: 1967-01-01
    Print ISSN: 0302-766X
    Electronic ISSN: 1432-0878
    Topics: Biology , Medicine
    Published by Springer
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  • 2
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    A cytological and quantitative study of neoblasts in the naidOphidonais serpentina (Oligochaeta) (1974)
    Springer
    Details
    Publication Date: 1974-01-01
    Print ISSN: 0949-944X
    Electronic ISSN: 1432-041X
    Topics: Biology
    Published by Springer
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  • 3
    Electronic Resource
    Electronic Resource
    A cytological and quantitative study of neoblasts in the naidOphidonais serpentina (Oligochaeta) (1974)
    Springer
    Development genes and evolution 174 (1974), S. 234-249 
    Details
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The fine structure of the neoblasts in the naidOphidonais serpentina has been examined. The neoblasts of control worms have a relatively large nucleus, containing a large nucleolus, a sparse amount of rough endoplasmic reticulum, and an abundance of free ribosomes and mitochondria. Although Golgi membranes have been demonstrated, there is no evidence that the neoblasts are secretory in nature. Neoblasts form loose cell-to-cell contacts with one another and with peritoneal cells. In worms 12 hours after posterior transection, the neoblasts found at the end of the severed ventral nerve cord have rounded up and are no longer spindle-shaped. Counts of neoblasts immediately after posterior transection indicate that they are equally distributed in the last five segments. A statistical analysis of their distribution during posterior regeneration reveals a significant increase in neoblasts in the last three segments and a migration of neoblasts toward the wound. The role of neoblasts in oligochaete posterior regeneration is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00573227
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  • 4
    Electronic Resource
    Electronic Resource
    Abdominal segment formation in Spirorbis moerchi (Polychaeta) (1981)
    Springer
    Zoomorphology 97 (1981), S. 225-245 
    Details
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development of abdominal segments in Spirorbis moerchi (Polychaeta: Annelida) was studied by light and electron microscopy. Abdominal segments develop in strict succession from anterior to posterior. Segmentation is initiated in the mesoderm and is followed by segmentation of the ectoderm. The mesoderm of the abdominal segments arises entirely from pygidial residual mesoderm; inward migration of cells from the pygidial ectoderm to give rise to mesoderm does not occur. The primordial germ cells remain distinct from the residual mesoderm of the pygidial growth region. After several abdominal segments have developed, the primordial germ cells “migrate” posteriorly from the achaetous region, invade the abdominal segments, and give rise to the retroperitoneal gonads. Abdominal segment formation is discussed in terms of heteronomy, primordial germ cell origin, gonad formation, and development of the circulatory system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310278
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  • 5
    Electronic Resource
    Electronic Resource
    An electron microscope study of spermiogenesis in Spirorbis (Laeospira) mörchi Levinsen (Polychaeta) (1967)
    Springer
    Cell & tissue research 83 (1967), S. 231-248 
    Details
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. In the hermaphroditic polychaete Spirorbis (Laeospira) mörchi, early spermatids develop in clusters within the coelom of the male segments. The cells within a single cluster are all in the same stage of development and are connected by an extensive cytoplasmic bridge system. 2. The acrosome forms in a single lamella of the Golgi apparatus which bears a close association to the plasma membrane. The final position of the acrosome is at a point considerably removed from the site of formation. 3. The nuclear changes culminating in condensation and elongation of the head are described. A rearrangement of cytoplasmic microtubules occurs simultaneously with nuclear elongation. 4. Redundant nuclear envelope, resulting from nuclear volume reduction, is pinched off in the form of four vesicles. The latter structures are lost with the residual cytoplasm. 5. Pour spherical mitochondria elongate to become incorporated into the middle-piece. A rearrangement of microtubules also occurs simultaneously with mitochondrial elongation. Cytoplasmic microtubules are absent from the fully formed sperm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00362404
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  • 6
    Electronic Resource
    Electronic Resource
    The relationship of early oocytes to putative neoblasts in the serpulid Spirorbis borealisWork supported by a grant (GB 18429) form N.S.F. (1972)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 137 (1972), S. 215-227 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The fine structure of the ovary in the serpulid Spirorbis borealis has been described. The ovarian wall consists of from one to several layers of peritoneal cells. Peritoneal cell processes extend deep into the ovary and may be seen between developing oocytes. Although young oocytes may also be in close apposition to one another, intercellular bridges have not been observed. When primary oocytes at the surface of the ovary reach a diameter of about 20 μ, they start to erupt into the coelom. Ovulation results from a simple separation of overlying peritoneal cells which lack specialized cell-to-cell contacts. Once a free surface of an ovulating oocyte is exposed to the coelom, microvilli and primary coat develop. Previtellogenic coelomic oocytes are often observed in close proximity to putative neoblasts (perivasal cells), which suggests a possible functional relationship. The confusion that extists between germ cells, peritoneal cells, and so-called neoblasts in polychaetes is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051370207
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  • 7
    Electronic Resource
    Electronic Resource
    Cytological observations on the so-called neoblasts in the serpulid SpirorbisThis work was supported by a Faculty Research grant from the Graduate Council of the University of Massachusetts. (1969)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 128 (1969), S. 241-259 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The purported “neoblasts” of the serpulid Spirorbis have been studied in Spirorbis (Paradexiospira) vitreus and Spirorbis (Laeospira) borealis at both the light and electron microscopic levels. These perivasal cells occur in greatest abundance around the ventral blood vessel of the achaetous region. In light microscope preparations, the perivasal cells are intensely basophilic, containing basally situated nuclei, and relatively large nucleoli. The fine structure of the perivasal cells reveals that they contain an abundance of rough endoplasmic reticulum, well-developed Golgi complex, heterogeneous dense bodies, and cytolysomes. The respiratory pigment chlorocruorin, which has a diameter of about 230 Å and is believed to be composed of two superimposed hexagonal components, has been localized within: cisternae of the rough endoplasmic reticulum, elements of the Golgi complex, and membrane-bounded vesicles at the base of the perivasal cells. Evidence is advanced which strongly suggests that molecules of chlorocruorin are transported from the perivasal cells into the lumen of the vessel by reverse pinocytosis. It is concluded that whatever other functional role(s) the perivasal cells of Spirorbis may have, a major function is the synthesis and secretion of chlorocruorin. Whether the perivasal cells can be considered to be pluripotent is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051280207
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  • 8
    Electronic Resource
    Electronic Resource
    A fine structural analysis of the epidermis and cuticle of the oligochaete aeolosoma Bengalense stephensonWork supported by grant GB 18429 from N.S.F. (1971)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 135 (1971), S. 185-211 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The fine structure of the epidermis and cuticle has been described for the oligochaete Aeolosoma bengalense. The epidermis is a pseudostratified epithelium and consists of the following cell types: ciliated and nonciliated supportive cells, pigment cells and associated satellite cells, mucous cells, basal cells, and ciliated non-supportive columnar cells. Overlying and restricted to the supportive cells is a delicate cuticle composed of: (a) a discontinuous layer of membrane-bounded surface particles; (b) a thin filamentous layer of moderate electron density just under the surface particles; (c) a thicker inner filamentous layer of low electron density. Digestion with pronase effectively removes the cuticle. This, together with the fact that it stains with alcian blue and ruthenium red, indicates that the cuticle contains an acid mucopolysaccharide. Regeneration of the cuticle, following pronase treatment, is marked by the elaboration of numerous microvilli by the supportive cells. Most of the microvilli are transitory and evidence supports a microvillar origin for the cuticular surface particles. The presence of cuticular surface particles may be a characteristic shared in common by all oligochaetes and, perhaps, some polychaetes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051350205
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