Summary
In the present study the differentiation of rhabdomyoblasts of two carcinosarcomas of the uterus is analysed electronmieroscopically. During the development of rhabdomyoblasts three cell types can be distinguished:
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1.
the undifferentiated mesenchymal cell with abundant ribosomes but few other cell organelles. Usually these cells are already associated to each other in strands of 2–4 cells. Occasionally cytoplasmic areas with numerous nonspecific filaments can be observed.
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2.
the light rhabdomyoblast which is characterized by its conspicuous nonspecific cytoplasmic filaments and its reduction in ribosomes. Specific myofilaments can be visualized only occasionally in this cell type.
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3.
more differentiated rhabdomyoblasts. These cells can be identified clearly by the presence of large numbers of myofibrils and myofibrillar fragments. Highly organized myofibrils as seen in skeletal muscle are seldom found. Transitional forms between these cell types are also observed. The functions of Z-bodies and of the sarcotubular system in the process of myofibrillar differentiation are discussed.
Zusammenfassung
Die Entwicklung von quergestreiften Rhabdomyoblasten in 2 gemischten Schleimhautsarkomen des Uterus konnte licht- und elektronenoptisch analysiert werden. Es lassen sich folgende 2 Differenzierungsphasen unterscheiden:
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1.
Die 1. Phase ist charakterisiert durch die Bildung unspezifischer cytoplasmatischer Filamente. Ausgangspunkt der Differenzierung ist eine primitive mesenchymale Zelle mit reichlichen Ribosomen und wenigen anderen Zellorganellen. Im Cytoplasma dieser Zellen findet man zunächst umschriebene Areale mit zahlreichen unspezifischen Filamenten. Durch erhebliche Proliferation dieser Filamente mit Ausdehnung über den gesamten Cytoplasmaleib sowie durch gleichzeitige zahlenmäßige Abnahme der übrigen Organellen entsteht der sogenannte helle Rhabdomyoblast.
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2.
In der 2. Phase werden die beiden spezifischen Myofilamentsysteme gebildet. Die ersten Myofilamente sind in Form parallel gelagerter Aktin- und Myosinfilamente erkennbar. Auf Querschnitten sind die dünnen Aktinfilamente hexonal um die dicken Myosinfilamente angeordnet. Die Filamentbündel nehmen an Zahl erheblich zu und liegen meist regellos im Cytoplasma. Nur in einzelnen Zellen sind die Filamentbündel in Myofibrillen sarkomerisch hintereinandergeschaltet. Diese hochorganisierten Myofibrillen besitzen eine Querstreifung, wie sie von quergestreiften Skelettmuskelfasern her bekannt ist. Die Rolle der Z-Bänder und des sarkotubulären Systems bei der Ausreifung der Myofibrillen wird diskutiert.
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Böcker, W., Stegner, H.E. Mixed Müllerian tumors of the uterus. Virchows Arch. A Path. Anat. and Histol. 365, 337–349 (1975). https://doi.org/10.1007/BF00471181
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DOI: https://doi.org/10.1007/BF00471181