References of "Goessens, Guy"
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See detailStructure, function and assembly of the nucleolus.
Scheer, U.; Thiry, Marc ULg; Goessens, Guy ULg

in Trends in Cell Biology (1993), 3(7), 236-41

Most events of ribosome biogenesis--such as transcription of the ribosomal RNA (rRNA) genes, processing of their primary transcripts into mature rRNAs and assembly with ribosomal and nonribosomal proteins ... [more ▼]

Most events of ribosome biogenesis--such as transcription of the ribosomal RNA (rRNA) genes, processing of their primary transcripts into mature rRNAs and assembly with ribosomal and nonribosomal proteins to form the preribosomes--are confined to a special nuclear compartment, the nucleolus. Immunogold labelling and in situ hybridization at the ultrastructural level are providing novel insights into structure-function relationships of the nucleolus, and in vitro systems are beginning to shed light on the molecular mechanisms involved in the reforming of nucleoli after mitosis. [less ▲]

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See detailUltrastructural distribution of DNA within the nucleolus of various animal cell lines or tissues revealed by terminal deoxynucleotidyl transferase.
Thiry, Marc ULg; Ploton, D.; Menager, M. et al

in Cell & Tissue Research (1993), 271(1), 33-45

We have used the highly sensitive in situ terminal deoxynucleotidyl transferase method, applied to ultrathin sections, to investigate the location of DNA within nucleoli of various animal cells. In all ... [more ▼]

We have used the highly sensitive in situ terminal deoxynucleotidyl transferase method, applied to ultrathin sections, to investigate the location of DNA within nucleoli of various animal cells. In all the nucleoli studied, intense labelling is revealed over the peri- and intranucleolar condensed chromatin. Gold particles are also consistently found over the fibrillar centres, especially at their periphery, namely in the border area between the fibrillar centres and the dense fibrillar component, whereas the dense fibrillar component itself seems to be free of label in nucleoli in which these two compartments can be distinguished. We conclude that, in transcriptionally active nucleoli of this type, DNA is a characteristic constituent of the fibrillar centres, distinguishing them functionally from the dense fibrillar component. Some nucleoli exhibit neither fibrillar centres nor a dense fibrillar component, but have a single, albeit heterogeneous accumulation of fibrillar material; gold particles are consistently seen over some parts of this fibrillar compartment. This suggests that certain parts of the fibrillar material are functionally similar to the fibrillar centres of those nucleoli that possess them. [less ▲]

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See detailUltrastructural detection of RNA within the nucleolus by molecular immunocytochemistry
Thiry, Marc ULg; Goessens, Guy ULg

in Histochemical Journal (The) (1992), 24

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See detailUltrastructural modifications of the nucleolus in the course of oogenesis in an oviparous Teleost (Barbus barbus L.).
Thiry, Marc ULg; Lepoint, Alain; Poncin, Pascal ULg et al

in Histochemical Journal (The) (1992), 24

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See detailBiochemical, bioenergetic and ultrastructural survey of the adaptations induced in a skeletal muscle by a chronic electrical stimulation and its cessation
Focant, B.; Sluse, Francis ULg; Huriaux, F. et al

in Carraro, U.; Salmons, S. (Eds.) Basic and applied myology : Perspectives for the 90's (1992)

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See detailLocation of DNA within the nucleolus of rat oocytes during the early stages of follicular growth.
Thiry, Marc ULg; Goessens, Guy ULg

in International Journal of Developmental Biology (1992), 36(1), 139-42

We have investigated the DNA distribution within the rat oocyte nucleolus during the early stages of follicular growth by means of the in situ terminal deoxynucleotidyl transferase method. In the ... [more ▼]

We have investigated the DNA distribution within the rat oocyte nucleolus during the early stages of follicular growth by means of the in situ terminal deoxynucleotidyl transferase method. In the fibrillogranular nucleolus, label is visualized on small clumps of peri- and intranucleolar chromatin. Such labeled clumps are frequently observed inside the interstices surrounding the fibrillar centers. Label is also consistently found in the fibrillar centers whereas the dense fibrillar component and the granular component are devoid of gold particles. These results contradict earlier data but conform with other recent immunocytochemical observations, obtained in nucleoli of a variety of somatic cell types, concerning the correlation between structure and function in the nucleolus. [less ▲]

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See detailWhere, within the nucleolus, are the rRNA genes located?
Thiry, Marc ULg; Goessens, Guy ULg

in Experimental Cell Research (1992), 200(1), 1-4

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See detailCytochemical distinction of various nucleolar components in insect cells.
Thiry, Marc ULg; Schoonbroodt, Stéphanie ULg; Goessens, Guy ULg

in Biology of the Cell (1991), 72(1-2), 133-40

The fine structure of the insect Sf9 cell nucleolus has been investigated by means of different cytochemical and immunocytochemical techniques at the electron microscope level. Apart from a few ... [more ▼]

The fine structure of the insect Sf9 cell nucleolus has been investigated by means of different cytochemical and immunocytochemical techniques at the electron microscope level. Apart from a few perinucleolar condensed chromatin clumps, the insect cell nucleolus comprises two compartments. The first of these consists of a roundish compact zone formed of fibrillar material. The other is composed of fibrillar and granular structures organized into a network separated by interstitial spaces. But, unlike mammalian cell nucleoli, any fibrillar center has been observed in the Sf9 cell nucleolus, even after actinomycin D treatment. We also show that the compact fibrillar zone of Sf9 cell nucleoli contains silver-stainable material and DNA. In actinomycin D-treated cells, a preferential contact of this compact fibrillar zone with condensed chromatin has been visualized. Finally, silver-stainable material has been found to persist throughout the whole mitosis. These results suggest that the compact fibrillar zone at the insect Sf9 cell nucleolus should, at least partly, correspond to the fibrillar center of mammalian cell nucleoli. [less ▲]

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See detailLocalization of nucleolar chromatin by immunocytochemistry and in situ hybridization at the electron microscopic level.
Thiry, Marc ULg; Scheer, U.; Goessens, Guy ULg

in Electron Microscopy Reviews (1991), 4(1), 85-110

Nucleoli are the morphological expression of the activity of a defined set of chromosomal segments bearing rRNA genes. The topological distribution and composition of the intranucleolar chromatin as well ... [more ▼]

Nucleoli are the morphological expression of the activity of a defined set of chromosomal segments bearing rRNA genes. The topological distribution and composition of the intranucleolar chromatin as well as the definition of nucleolar structures in which enzymes of the rDNA transcription machinery reside have been investigated in mammalian cells by various immunogold labelling approaches at the ultrastructural level. The precise intranucleolar location of rRNA genes has been further specified by electron microscopic in situ hybridization with a non-autoradiographic procedure. Our results indicate that the fibrillar centers are the sole nucleolar structures where rDNA, core histones, RNA polymerase I and DNA topoisomerase I are located together. Taking into account the potential value and limitations of immunoelectron microscopic techniques, we propose that transcription of the rRNA genes takes place within the confines of the fibrillar centers, probably close to the boundary regions to the surrounding dense fibrillar component. [less ▲]

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See detailDistinguishing the sites of pre-rRNA synthesis and accumulation in Ehrlich tumor cell nucleoli.
Thiry, Marc ULg; Goessens, Guy ULg

in Journal of Cell Science (1991), 99 ( Pt 4)

The precise location of transcribing rRNA genes within Ehrlich tumor cell nucleoli has been investigated using two approaches: high-resolution autoradiography of cells pulse-labelled with tritiated ... [more ▼]

The precise location of transcribing rRNA genes within Ehrlich tumor cell nucleoli has been investigated using two approaches: high-resolution autoradiography of cells pulse-labelled with tritiated uridine, varying the exposure time, and in situ-in vitro transcription coupled with an immunogold labelling procedure. When autoradiographic preparations are exposed for a short time, silver grains are found associated almost exclusively with interphasic cell nucleoli. Labelling of extranucleolar areas requires longer exposure. Within the nucleolus, the first sites to be revealed are in the dense fibrillar component. Prolonging exposure increases labelling over the dense fibrillar component, with label becoming more and more apparent over the fibrillar centers. Under these conditions, however, labelling does not extend into the granular component, and no background is observed. Initiation of transcription on ultrathin cell sections occurs preferentially at the borders of condensed chromatin blocks and in their close vicinity. The condensed chromatin areas themselves remain unlabelled. Inside most nucleoli, gold-particle clusters are mainly detected in the fibrillar centers, especially at their periphery, whereas the dense fibrillar component and the granular component remain devoid of label. These results, together with previous observations made on the same cell type, clearly indicate that the fibrillar centers are the sites of rRNA gene transcription in Ehrlich tumor cell nucleoli, while the dense fibrillar component is the site of pre-rRNA accumulation. [less ▲]

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See detailUltrastructural cytochemistry of the mammalian cell nucleolus.
Derenzini, Massimo; Thiry, Marc ULg; Goessens, Guy ULg

in Journal of Histochemistry and Cytochemistry : Official Journal of the Histochemistry Society (1990), 38(9), 1237-56

In the present review on the organization of the mammalian cell nucleolus, we report and discuss data obtained during the past 10 years by means of cytochemical and immunocytochemical ultrastructural ... [more ▼]

In the present review on the organization of the mammalian cell nucleolus, we report and discuss data obtained during the past 10 years by means of cytochemical and immunocytochemical ultrastructural techniques. Particular emphasis is placed on the following topics: location of the nucleolus organizer regions in interphasic nucleolar components, structure of nucleolar chromatin in situ, and the structure-function relationship of the nucleolar components. The cytochemical and immunocytochemical results are compared and the concordant data are stressed for each topic. [less ▲]

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See detailUltrastructural and cytochemical studies on extranucleolar bodies in rat oocytes at the preovulatory follicle stage.
Antoine, Nadine ULg; Thiry, Marc ULg; Goessens, Guy ULg

in Biology of the Cell (1989), 65(1), 61-6

At the antral follicle stage, the nucleolus is entirely composed of a homogeneous proteinic compact mass. This nucleolar compaction during oogenesis seems to be a general feature in mammalian oocytes ... [more ▼]

At the antral follicle stage, the nucleolus is entirely composed of a homogeneous proteinic compact mass. This nucleolar compaction during oogenesis seems to be a general feature in mammalian oocytes. However, when oocyte maturation is induced by gonadotropin hormone (LH), oocytes enter into preovulatory stage. All the nucleoli are vacuolated and extranucleolar bodies appear in the germinal vesicle near the nucleolar mass. Based on the results obtained by ultrastructural cytochemical stainings, we postulate that these extranucleolar bodies originate from the nucleolar mass itself. The presence of the extranucleolar bodies could reflect the extrusion of nucleolar material, essentially ribonucleoproteins, into the ooplasm. This material could persist after fertilization in the pronuclei until the resumption of transcription at the early stage of embryogenesis. [less ▲]

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See detailElectron microscopy proves Jo-1 antigen to be predominantly cytoplasmic but also nuclear.
Thiry, Marc ULg; Humbel, R.; Dicato, M. et al

in Biomedicine & Pharmacotherapy (1988), 42(7), 469-71

The Jo-1 antigen is a specific marker for autoimmune myositis with an excellent correlation with associated interstitial lung disease. Using an electron microscopy immunogold technique, we were able to ... [more ▼]

The Jo-1 antigen is a specific marker for autoimmune myositis with an excellent correlation with associated interstitial lung disease. Using an electron microscopy immunogold technique, we were able to show that the antigen was predominantly cytoplasmic. [less ▲]

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See detailLocalization of DNA within Ehrlich tumour cell nucleoli by immunoelectron microscopy.
Thiry, Marc ULg; Scheer, U.; Goessens, Guy ULg

in Biology of the Cell (1988), 63(1), 27-34

The distribution of DNA in Ehrlich tumour cell nucleoli was investigated by means of an immunocytochemical approach involving a monoclonal antibody directed against double- and single-stranded DNA ... [more ▼]

The distribution of DNA in Ehrlich tumour cell nucleoli was investigated by means of an immunocytochemical approach involving a monoclonal antibody directed against double- and single-stranded DNA. Immunolabelling was performed either before or after the embedding process. The postembedding labelling method allows better ultrastructural preservation than the preembedding labelling method. In particular, the various nucleolar components are well preserved and identifiable. In the nucleolus, labelling is particularly concentrated over the perinucleolar chromatin and over its intranucleolar invaginations, which penetrate the nucleolar body and often terminate at the fibrillar centres. In addition, aggregates of gold particles are found in the fibrillar centres, preferentially towards the peripheral regions. By contrast, the dense fibrillar component is completely devoid of labelling. The results seem to indicate that DNA containing the rDNA genes is located in the fibrillar centres, with a preference for the peripheral regions. This finding suggests that transcription of the rDNA genes should occur within the confines of the fibrillar centre, probably close to the boundary region of the surrounding dense fibrillar component. The results are discussed in the light of present knowledge of the functional organization of the nucleolus. [less ▲]

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See detailComparative study of the condensation of chicken erythrocyte and calf thymus chromatins by di- and multivalent cations.
Marquet, R.; Colson, Pierre ULg; Matton, Anne-Marie ULg et al

in Journal of Biomolecular Structure & Dynamics (1988), 5(4), 839-57

The condensation of chicken erythrocyte (CE) and calf thymus (CT) chromatins upon addition of di- and multivalent cations has been studied using turbidity, precipitation and electric dichroism ... [more ▼]

The condensation of chicken erythrocyte (CE) and calf thymus (CT) chromatins upon addition of di- and multivalent cations has been studied using turbidity, precipitation and electric dichroism measurements. For all the cations investigated (Mg2+, Tb3+, Co(NH3)6(3+), spermidine Spd2+ and spermine Sp4+) condensation of CE chromatin occurred before the onset of aggregation, while aggregation of CT chromatin started before condensation with all cations except Mg2+ and Tb3+. Precipitation of CE chromatin required lower di- and multivalent cations concentrations than CT chromatin. The electric dichroism data for both chromatins, at low ionic strength in the absence of di- or multivalent cations, indicated that the nucleoprotein molecules were not totally decondensed but that a "precondensed" state was already present. A positive electric dichroism was observed for the most condensed chromatin fibers, in agreement with the "cross-linker" models. Tb3+ led to less compact condensed particles as judged from the electric dichroism observations, but electron microscopy revealed that "30 nm fibers" were formed. Very little aggregation was produced by Tb3+. On the contrary, spermine produced very large networks of condensed molecules, but large spheroidal particles were also observed. The condensation of CE chromatin happened without changes of solution conductivity upon cation salt addition, regardless of the condensing cation, indicating a cooperative uptake of the ions during this process. [less ▲]

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See detailImmunoelectron microscopic study of nucleolar DNA during mitosis in Ehrlich tumor cells.
Thiry, Marc ULg; Scheer, U.; Goessens, Guy ULg

in European Journal of Cell Biology (1988), 47(2), 346-57

In order to investigate the DNA localization within Ehrlich tumor cell nucleoli during mitosis, two recent immunocytochemical methods using either an anti-DNA or an anti-bromodeoxyuridine (BrdU ... [more ▼]

In order to investigate the DNA localization within Ehrlich tumor cell nucleoli during mitosis, two recent immunocytochemical methods using either an anti-DNA or an anti-bromodeoxyuridine (BrdU) monoclonal antibody have been applied. In both cases, the immunogold labeling has been performed on ultrathin sections of cells embedded either in Lowicryl K4M or in Epon, respectively. Identical results are observed with both immunocytochemical approaches. In the interphase nucleolus, besides the labeling of the perinucleolar chromatin shell and of its intranucleolar invaginations which penetrate into the nucleolar body and often terminate at the fibrillar centers, a few gold particles are also preferentially found towards the peripheral region of the fibrillar centers. In contrast, the dense fibrillar component and the granular component are never labeled. During mitosis, the fibrillar centers persist at the chromosomal nucleolus organizing regions (NOR's) and can be selectively stained by the silver method. However, these metaphase fibrillar centers are no longer decorated by the DNA- or BrdU antibodies. These results indicate that until the end of prophase, rRNA genes are present inside the fibrillar center material, disappear during metaphase and reappear in reconstituting nucleoli during telophase. Thus, fibrillar centers appear to represent structures sui generis, which are populated by rRNA genes only when the nucleolus is functionally active. In segregated nucleoli after actinomycin D treatment, the DNA labeling is exclusively restricted to the perinucleolar chromatin blocks. These findings also suggest that the DNA content of the fibrillar center material varies according to the rRNA transcription level of the cells. The results are discussed in the light of the present knowledge of the functional organization of the nucleolus. [less ▲]

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