ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    facet.materialart.
    Unknown
    The eggshell ofDrosophlla melanogaster (1991)
    Springer
    Details
    Publication Date: 1991-01-01
    Print ISSN: 0949-944X
    Electronic ISSN: 1432-041X
    Topics: Biology
    Published by Springer
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 2
    Electronic Resource
    Electronic Resource
    The eggshell ofDrosophlla melanogaster (1991)
    Springer
    Development genes and evolution 200 (1991), S. 95-103 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila melanogaster ; Eggshell ; Micropylar canal ; Microtubules ; Paracrystalline structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The micropylar apparatus (MA) inDrosophila melanogaster (Diptera: Drosophilidae) is a 25 μm long protrusion on the anterior pole of the eggshell, and it contains the 0.8 μm wide micropylar canal through which the spermatozoon penetrates the eggshell. The canal terminates in the paracrystalline structure thus forming the “pocket”. The MA is secreted during oogenesis by the micropylar follicle cells (border cells and peripheral cells). Morphogenesis of the micropylar canal starts before stage 11A, when two of the border cells form two thin extensions containing microfilaments and penetrate the paracrystalline structure. Microtubules found at the base of the extensions participate in the formation of two projections. Adjacent follicle cells secrete the chorionic part of the MA, whilst the two projections elongate and twist during stages 12 and 13. Microtubules run parallel to the long axis of the projections and probably are related to cellular elongation during the formation of the projections. The paracrystalline structure is composed of lamellae having a periodicity of about 50 nm, which is maintained possibly due to the lateral fibrils connecting the lamellae. These lamellae consist of small fragments secreted during stages 10–11 by the border cells. The paracrystalline structure and the spongy vitelline membrane are condensed after egg maturation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00637189
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Ultrastructural features and formation of the micropylar apparatus in the cherry fly Rhagoletis cerasi (1991)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 208 (1991), S. 205-214 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The micropylar apparatus (MA) in Rhagoletis cerasi (Diptera, Tephritidae) is located at the anterior pole of the egg and consists of two parts: an outer chorion and an inner vitelline membrane. Sperm entry takes place through the micropylar canal, 2.0-2.5 μm in diameter, which penetrates the micropylar endochorion and terminates in the thick vitelline membrane, thus forming the “pocket.” The pore of the micropylar canal, i.e., the micropyle, is covered by the exochorionic tuft.The formation of the MA is accomplished by 40 micropylar cells during oogenesis. These cells secrete the successive eggshell layers: the vitelline membrane, the wax layer, the innermost chorionic layer, the micropylar endochorion, and the exochorion. Two among 40 micropylar cells differentiate and form two tightly connected projections. The latter contain a bundle of parallel microtubules and participate in the formation of the micropylar canal and the pocket. At the tip of the projections there are two thin extensions full of microfilaments. In late developmental stages the two projections and the extensions degenerate and leave the canal and the pocket behind. We also discuss the structural features of the MA in relation to its physiology among Diptera.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052080206
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Structure and morphogenesis of the eggshell and micropylar apparatus in the olive fly, Dacus oleae (Diptera: Tephritidae) (1991)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 209 (1991), S. 39-52 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The egg of the olive fly, Dacus oleae (Diptera, Tephritidae), is laid inside olives and the larva eventually destroys the fruit. The oocyte is surrounded by several distinct layers which are produced during choriogenesis. The chorion covering the main body of the egg outside of the vitelline membrane includes a “wax” layer, an innermost chorionic layer, an endochorion consisting of inner and outer layers separated by pillars and cavities similar to their counterparts in Drosophila melanogaster, as well as inner and outer exochorionic layers. The anterior pole is shaped like an inverted cup, which is chiefly hollow around its base and has very large openings communicating with the environment. Holes through the surface of the endochorion result from deposition of endochorionic substance around follicular cell microvilli. An opening at the apex of the cup provides an entrance for sperm entering the micropylar canal, which traverses the endochorion and continues into a “pocket” in a thickened vitelline protrusion. The micropylar canal is formed by deposition of endochorion and vitelline membrane around an elongated pair of follicular cell extensions. These extensions later degenerate and leave an empty canal about 5 μm in diameter and the narrower pocket about 1 μm in diameter. Respiration is thought to be facilitated by openings at the base of the anterior pole as well as by openings through the “plastron” around the main body of the shell.
    Additional Material: 36 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052090105
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...