Biomedical subjects
Publications and source records attributed to G Goessens.
Adenosine induces a massive nucleolar disorganization both in chick embryo fibroblasts and Ehrlich ascitic tumour cells in which the fibrillar centre is the only persistent structure. We discuss these observations in term of RNA synthesis inhibition as fibrillar centres are the Nucleolus-Organizing Regions (NOR's).
Nucleolar ultrastructure has been studied in absorptive cells of the intestinal villi and in undifferentiated cells of the crypts of Lieberkühn. In the top of the villi, the nucleoli are composed of fibrillar centres associated with dense chromatin. These observations seem to be related to RNA synthesis inhibition.
A technique based on the use of silver solutions, which selectively stains the nucleolus-organising regions (NORs) in chromosomes, was applied to interphase Ehrlich tumour cells. The results indicate that nucleolar fibrillar centres correspond to the NORs.
By means of diaminobenzidine staining method, the relations between fibrillar centres and nucleolus-associated chromatin are analyzed in Ehrlich tumour cell nucleoli. There is a continuity between fibrillar centres and condensed intra-nucleolar chromatin. The meaning of these connections is discussed.
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Nucleoli were studied in chick fibroblasts cultured in vitro, under normal or under experimental conditions, and in several mammalian cell types in vivo. All these cells frequently contain nucleoli with fibrillar centres. The nucleolar fibrillar centres are composed of fibrous material of low electron density and are always intimately associated with the dense fibrillar component. Their morphology is very similar to that analysed cytochemically in Ehrlich tumour cells. It therefore appears that they could be related to the nucleolar organizers as suggested in Ehrlich tumour cells.
Modifications of cell shape induced in cultured newborn rat astroblasts by serum deprivation or dibutyryladenosine 3'-5' monophosphate (dBcAMP) are described. Serum suppression modifies the adhesitivity of the cells to the substrate, but this modification is not consistent with a true differentiation. The main ultrastructural feature of dBcAMP-treated astroblasts is the presence of an extensive system of 90 A microfilaments, while control cells are relatively devoid of these structures.
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Chick embryo fibroblasts cultivated in vitro and Ehrlich ascites tumor cells (in vivo or in vitro) have been treated with amphotericin B. Cell multiplication is strongly inhibited. Large clear zones appear in the fibroblast nucleoi (phase-contrast and electron-microscope observations). Many treated fibroblasts and tumour cells have a high DNA content (pre-mitotic or polyploid level; measurements by cytophotometry). However, the RNA content (cytophotometry) and the total protein content (cytophotometry and micro-interferometry) are relatively low in the tumour cells. As shown by autoradiography, DNA synthesis is active but RNA synthesis and, in some cases, protein synthesis are inhibited. Due to this unbalanced growth, the cells cannot divide.
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