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  • 1
    Electronic Resource
    Electronic Resource
    Structure and function of prothoracic glands and oenocytes in embryos and last larval instars of Oncopeltus fasciatus Dallas (Insecta, Heteroptera) (1976)
    Springer
    Cell & tissue research 171 (1976), S. 331-350 
    Details
    ISSN: 1432-0878
    Keywords: Ecdysial glands ; Ecdysone ; Embryos, larvae ; Oncopeltus fasciatus (Insecta, Heteroptera) ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Active prothoracic glands and oenocytes of last larval stage are both characteristized by well-developed smooth and rough endoplasmic reticulum (ER). Prothoracic glands also show plasma membrane infoldings, but not oenocytes which contain a large number of pleomorphic vesicles. 2. The fine structure of embryonic oenocytes corresponds after blastokinesis with that of active larval and adult cells. Thus, an activity in the late embryo can be assumed. Embryonic prothoracic glands reveal no signs of activity: smooth and rough ER are absent. The subcellular structure resembles that of organ anlagen, i.e. not yet fully differentiated tissue. Hormone synthesis is not likely. 3. Ecdysone titer was determined throughout embryonic development and in mature adults. Although prothoracic glands break down during adult ecdysis, imagines contain in the Calliphora-bioassay active factors: females 0.9 CU/g and males 0.5 CU/g. As sites of synthesis the oenocytes are suggested. 4. A relatively high ecdysone titer of 7 CU/g is measured in newly deposited eggs. The hormone is presumably of maternal origin. Subsequent to blastokinesis the hormone content increases dramatically up to about 180 CU/g, apparently due to endocrine function of the embryo. Oenocytes are proposed as the source of ecdysone during late embryonic development. 5. The function of ecdysone during early and advanced embryogenesis, especially in view of “embryonic molts”, is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224658
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  • 2
    Electronic Resource
    Electronic Resource
    Elektronenmikroskopische Studien über eine extrazellulär auftretende Substanz in der Muskulatur des Insekts Oncopeltus fasciatus Dallas (1973)
    Springer
    Cell & tissue research 137 (1973), S. 541-551 
    Details
    ISSN: 1432-0878
    Keywords: Muscles ; Insects ; Extracellular substance ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Im Stroma von Aorta und Retrocerebralkomplex sowie von verschiedenen Muskeln (Oberschenkel-, Mitteldarm-, Speicheldrüsen-, Samenleiter- und Eileitermuskeln), jedoch nicht im Stroma der Flugmuskulatur und des Herzschlauches, kommt eine fibrillär strukturierte Substanz (X-Substanz) von außerordentlich hoher Elektronendichte vor. In der Aorta, wo die größten Mengen an X-Substanz gefunden wurden, tritt besonders in den Muskelzellen älterer Tiere im Sarcoplasma und an der Plasmamembran eine körnige Substanz mittlerer Elektronendichte auf, welche auf Grund morphologischer Ähnlichkeit als Z-Material gedeutet wurde. Offenbar entsteht die X-Substanz, die in ihrer typischen Erscheinungsform nur extrazellulär beobachtet wurde, aus diesem Material. Da alte Tiere mehr X-Substanz aufweisen als jüngere, scheint es sich um die Abscheidung eines Altersprodukts zu handeln. Herkunft und Aussehen lassen ein langkettiges Protein vermuten. Muskeln, in denen X-Substanz vorkommt, enthalten auch viele Axone mit Neurosekreten; jedoch lassen sich bislang keine näheren Beziehungen zwischen diesen beiden Faktoren herstellen. Die X-Substanz wird offensichtlich vom Stroma weitertransportiert und wahrscheinlich von Blutzellen aufgenommen.
    Notes: Summary A fibrous substance (X substance) of exceptionally high electron density is found in the stroma of aorta, retrocerebral complex, and several muscles (leg, midgut, salivary glands, vas deferens and oviduct), but not in the stroma of flight muscles and heart. The aorta, where the largest amount of X substance occurs, shows within the muscle cells, especially of older animals, a granular substance of moderate electron density in the sarcoplasm and adjacent to the plasma membrane. On account of its morphological similarity this material is considered as Z material. The X substance, which in its typical appearance was seen only extracellularly, seems to be derived from this granular Z material. Since old animals show more X substance than younger ones, it appears to be an aging product. Its origin and appearance point to a protein with long chain structure. Muscles containing much X substance show many neurosecretory fibers. However, no tangible relationship between these two parameters has been established. The X substance is evidently transported by the stroma and probably taken up by hemocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307229
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrastructure of differentiating hemocytes in the embryo of Oncopeltus fasciatus Dallas (Insecta, Heteroptera) (1978)
    Springer
    Cell & tissue research 187 (1978), S. 479-488 
    Details
    ISSN: 1432-0878
    Keywords: Embryonic hemocytes ; Insecta ; Oncopeltus fasciatus ; Differentiation ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The hemocytes of Oncopeltus differentiate rather early during embryogenesis. They are segregated by the mesoderm soon after its formation (about 50h after egg deposition). Newly segregated hemocytes show the “typical” features of “embryonic” cells: many free ribosomes, a few strands of rough ER, the cisternae of which are considerably distended, electron lucent vacuoles around the periphery, and glycogen deposits. A few hours thereafter the hemocytes undergo striking subcellular changes. First, glycogen, electron lucent vacuoles and rough ER disappear and phagocytotic activity can be observed. Golgi complexes become well expressed and give rise to electron dense vesicles which fuse to larger bodies. Then, rough ER develops again and occupies large areas of the cytoplasm. Its cisternae are often considerably distended by proteinaceous secretions. All hemocytes undergo the same steps of differentiation. Embryonic hemocytes obviously play a decisive role in the elimination of waste products, in particular of tissue debris that results from programmed cellular death. The significance of the conspicuous protein secretions is not fully understood. They may participate in the deposition of the acellular connective tissue, or may have some of the other functions ascribed to insect blood cells. Larvae and imagines of Oncopeltus have four types of hemocytes, which agree rather well with those found in Rhodnius (Lai-Fook, 1970). All embryonic hemocytes, aside from the newly segregated ones, represent plasmatocytes but, unlike plasmatocytes of postembryonic stages, they contain no large inclusion bodies. Newly segregated embryonic hemocytes, in addition to their “typical embryonic” features, have some similarities with larval and adult prohemocytes. Oenocytoids and granulocytophagous cells are absent in the embryo. Some aspects concerning the differentiation and classification of hemocytes are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229612
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  • 4
    Electronic Resource
    Electronic Resource
    Electron microscopic study on the larval and adult corpus allatum of Oncopeltus fasciatus dallas (insecta, heteroptera) (1973)
    Springer
    Cell & tissue research 145 (1973), S. 447-458 
    Details
    ISSN: 1432-0878
    Keywords: Corpus allatum ; Oncopeltus fasciatus ; Larvae ; Imagines ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The ultrastructure of the corpora allata of last larval instars and adults of Oncopeltus was studied. The unpaired gland undergoes submicroscopic alterations and shows signs of degradation in old animals. The organ is partly covered and penetrated by corpus cardiacum tissue. Axons with different types of neurosecretory granules form synaptoid contacts with the corpus allatum cells. 2. “Dark” and “light” gland cells can be differentiated on account of the degree of electron density. The former predominate during the last larval stage and in the young imago, the latter in mature males and females. It is highly probable that the “light” cells are the active (i.e. hormone producing) ones and the “dark” cells the inactive ones. 3. The active cells are characterized by rough endoplasmatic reticulum (often in whorls), small amounts of smooth endoplasmatic reticulum and many multivesicular bodies. Abundant free ribosomes, a not particularly well developed Golgi apparatus, dense bodies, and cytolysomes are present in active and inactive cells. 4. The nuclei contain one to four prominent and variously shaped nucleoli, which show differences between adult males and females with respect to their location in the nucleus. 5. The corpus allatum cells of Oncopeltus are obviously engaged in extensive protein synthesis. Tangible structural indications for the manufacture of juvenile hormone were not observed. Possible sites of hormone release are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00306717
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