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G Geuens

Publications and source records attributed to G Geuens.

At least 19 recordsLinked to original sources
PubMed2002

Pseudodystrophy. A conversion disorder mimicking reflex sympathetic dystrophy.

The authors suggest some criteria by which pseudodystrophy and reflex sympathetic dystrophy, although sharing some similar clinical features, can be distinguished as two different conditions, each requiring its own approach and management. The most important distinction is found on bone scintigraphy. In reflex sympathetic dystrophy the bone scan shows a typical increased tracer uptake (at least during stages I and II); in pseudodystrophy there is a normal or decreased tracer uptake in the affected region. Moreover the vascularization is increased in reflex sympathetic dystrophy stage I, whereas in pseudodystrophy hypovascularization is found from the beginning. The clinical features, as well as the results of technical investigations, psychological evaluation and treatment of 4 patients with pseudodystrophy are presented. The importance of distinguishing this condition from reflex sympathetic dystrophy is stressed.

Adolescent↗
PubMed1989

Microtubule dynamics investigated by microinjection of Paramecium axonemal tubulin: lack of nucleation but proximal assembly of microtubules at the kinetochore during prometaphase.

Microtubule (MT) dynamics in PtK2 cells have been investigated using in vivo injection of unmodified Paramecium ciliary tubulin and time-lapse fixation. The sites of incorporation of the axonemal tubulin were localized using a specific antibody which does not react with vertebrate cytoplasmic tubulin (Adoutte, A., M. Claisse, R. Maunoury, and J. Beisson. 1985. J. Mol. Evol. 22:220-229), followed by immunogold labeling, Nanovid microscopy, and ultrastructural observation of the same cells. We confirm data from microinjection of labeled tubulins in other cell types (Soltys, B. J., and G. G. Borisy. 1985. J. Cell Biol. 100:1682-1689; Mitchison, T., L. Evans, E. Schulze, and M. Kirschner. 1986. Cell. 45:515-527; Schulze, E., and M. Kirschner. 1986. J. Cell Biol. 102:1020-1031). In agreement with the dynamic instability model (Mitchison, T., and M. Kirschner. 1984. Nature (Lond.). 312:237-242), during interphase, fast (2.6 microns/min) distal growth of MTs occurs, together with new centrosomal nucleation. Most of the cytoplasmic MT complex is replaced within 15-30 min. During mitosis, astral MTs display the same pattern of renewal, but the turnover of the MT system is much faster (approximately 6 min). We have concentrated on the construction of the kinetochore fibers during prometaphase and observe that (a) incorporation of tubulin in the vicinity of the kinetochores is not seen during prophase and early prometaphase as long as the kinetochores are not yet connected to a pole by MTs; (b) proximal time-dependent incorporation occurs only into preexisting kinetochore MTs emanating from centrosomes. Consequently, in undisturbed prometaphase cells, the kinetochores probably do not act as independent nucleation sites. This confirms a model in which, at prometaphase, fast probing centrosomal MTs are grabbed by the kinetochores, where tubulin incorporation then takes place.

Animals↗
PubMed1986

The use of submicroscopic gold particles combined with video contrast enhancement as a simple molecular probe for the living cell.

We describe a new approach to probe the molecular biology of the living cell that uses small colloidal gold particles coupled to specific ligands. They are visualized in cells by bright-field, video enhanced contrast microscopy. We describe the basic aspects of the technique and provide examples of applications to intracellular motility, cell membrane dynamics, receptor translocation, internalization, and intracellular routing. We also provide examples of the use of this approach in immunospecific labelling of cells and tissue sections.

Animals↗
PubMed1986

Ultrastructural colocalization of tyrosinated and detyrosinated alpha-tubulin in interphase and mitotic cells.

Immunofluorescence with specific peptide antibodies has previously established that tyrosinated (Tyr) and detyrosinated (Glu) tubulin, the two species generated by posttranslational modification of the COOH-terminus of alpha-tubulin, are present in distinct, but overlapping, subsets of microtubules in cultured cells (Gundersen, G. G., M. H. Kalnoski, and J. C. Bulinski, 1984, Cell, 38:779-789). Similar results were observed by light microscopic immunogold staining in the two cell types used in this study, CV1 and PtK2 cells: most microtubules were stained with the Tyr antibody, whereas only a few were stained with the Glu antibody. We have examined immunogold-stained preparations by electron microscopy to extend these results. In general, electron microscopic localization confirmed results obtained at the light microscopic level: the majority of the microtubules in CV1 and PtK2 cells were nearly continuously labeled with the Tyr antibody, whereas only a few were heavily labeled with the Glu antibody. However, in contrast to the light microscopic staining, we found that all microtubules of interphase and mitotic CV1 and PtK2 cells contained detectable Tyr and Glu immunoreactivity at the electron microscopic level. No specific localization of either species was observed in microtubules near particular organelles (e.g., mitochondria or intermediate filaments). Quantification of the relative levels of Glu and Tyr immunoreactivity in individual interphase and metaphase microtubules showed that all classes of spindle microtubules (i.e., kinetochore, polar, and astral) contained nearly the same level of Glu immunoreactivity; this level of Glu immunoreactivity was lower than that found in all interphase microtubules. Most interphase microtubules had low levels of Glu immunoreactivity, whereas a few had relatively high levels; the latter corresponded to morphologically sinuous microtubules. Quantification of the relative levels of Tyr and Glu immunoreactivity in segments along individual microtubules suggested that the level of Tyr (or Glu) tubulin in a given microtubule was uniform along its length. Understanding how microtubules with different levels of Tyr and Glu tubulin arise will be important for understanding the role of tyrosination/detyrosination in microtubule function. Additionally, the coexistence of microtubules with different levels of the two species may have important implications for microtubule dynamics in vivo.

Animals↗
PubMed1985

Probing microtubule-dependent intracellular motility with nanometre particle video ultramicroscopy (nanovid ultramicroscopy).

Colloidal gold particles of 20 to 40 nm diameter stabilized with polyethylene glycol (PEG) were microinjected in PTK2 cells. Aggregates and individual particles, which are smaller than the theoretical limit of resolution of the optical microscope and invisible to the eye are discernible from organelles by reflection of polarized light. They are optimally visualized using transmitted light and electronic subtraction of diffuse background light. The gold particles show saltatory motion. The direction, speed, median distance travelled and frequency of saltations are indiscernible from measurements made on cell organelles in the same preparations. Because microtubule treadmilling has been implicated as a potential motor for organelle motility, gold particles coupled to monoclonal antibodies, recognizing the alpha-subunit of tubulin (Kilmartin et al., 1982), were injected. These particles, often forming linear arrays, assumed entirely fixed positions in the cell. The results suggest that there is a transport system associated with microtubules which can carry synthetic particles through the cell without the need for them being covered with specific proteins. Microtubule treadmilling does not seem to be involved. The possibility of following 20-40 nm particles and probably even smaller ones, that can be coupled to most proteins, within living cells provides a tool of wide applicability to study the fate and behaviour of such proteins. It is suggested that this new method be called nanoparticle video ultramicroscopy or nanovid ultramicroscopy.

Animals↗
PubMed1983

The interaction between microtubules and intermediate filaments in cultured cells treated with taxol and nocodazole.

Using double-label immunofluorescence and electron microscopy we studied the interaction between microtubules (MT) and intermediate filaments (IF) in MO cells treated with various combinations of taxol and nocodazole. With taxol, the organized MT of cultured cells are replaced by free MT and MT bundles. This rearrangement of MT is followed by a rearrangement of the IF. As in untreated cells a close association between these two filamentous systems is observed. In cells pretreated with nocodazole followed by addition of taxol, to induce the bundles of free MT, the preexisting IF coils disappear and IF associate with the MT. From these experiments we conclude that an interaction between MT and IF exists independent of the normal organisation of the MT system. The redistribution of IF always follows the redistribution of MT. The data show that MT determine the spatial distribution of IF which most probably involves some kind of physicochemical link.

Alkaloids↗
PubMed1983

Microtubules and microfilaments in ageing hamster embryo fibroblasts in vitro.

Microtubules and microfilaments were investigated in hamster lung fibroblasts, during their in vitro life-span. These cells show a senescence process characterized by a drastic phenotypic change, resulting in two phenotypes: the type 1 cells, characteristic of young cultures and the type 2 cells appearing progressively with culture passages. Microtubules and microfilaments were observed at the TEM and also visualized by the unlabelled peroxidase-anti-peroxidase method. Moreover, the susceptibility of microtubules to nocodazole was tested in type 1 and 2 cells. We could not provide evidence for a different susceptibility to the drug. However the depolymerization wave occurred centripetally in type 1 cells whilst centrifugally in type 2 cells. These observations are discussed in relationship with the early arrest of division growth of the type 2 differentiated cells.

Animals↗
PubMed1981

Nucleated assembly of mitotic microtubules in living PTK2 cells after release from nocodazole treatment.

The reassembly of microtubules is described in mitotic cells after release from nocodazole-induced block. The formation of microtubules was followed by light microscopic immunocytochemical staining using the PAP method, combined with toluidine blue staining of the chromatin. The light microscopic observations on whole cells were compared with ultrastructural observations on thin sections. This step is essential to ascertain complete destruction of microtubules during the nocodazole treatment and to correlate immunocytochemical staining with the presence of microtubules. Removal of nocodazole (10 or 1 micrograms/ml) after a sufficiently long incubation to induce a complete disappearance of microtubules resulted in the appearance of tubulin staining specifically associated with the centromeres and with one or two isolated points in the cytoplasm. Electron microscopy confirmed that the staining was due to the massive accumulation of small microtubules at the kinetochores and centrosomes. Kinetochore nucleation was seen only in association with condensed metaphase-stage chromosomes and not with the less-condensed prophase chromosomes. In a second type of experiment cells were allowed to enter mitosis in the presence of an incompletely active concentration of nocodazole (0.1 microgram/ml). The construction of the mitotic spindle was arrested; however, short microtubules were assembled at the kinetochores and centrosomes. These experiments demonstrate that in living mitotic PTK2 cells the kinetochores, as well as the centrosomes, exert a nucleating action on tubulin assembly. The further elongation of microtubules after removal of nocodazole was seen to occur preferentially along axes between the centrosomes and the kinetochores. This resulted in the construction of normal metaphases that evolved through anaphase and telophase. We have attempted to formulate a hypothesis that may explain the oriented assembly that seems to be essential in the construction of the spindle.

Animals↗
PubMed1981

Taxol induces the assembly of free microtubules in living cells and blocks the organizing capacity of the centrosomes and kinetochores.

Taxol, a potent promoter of microtubule polymerization in vitro, induces massive assembly of free microtubules in cultured cells as visualized by immunocytochemistry and electron microscopy. The centrosomes and kinetochores largely lost their capacity to organize microtubule assembly, as became evident by the disappearance of the cytoplasmic microtubule complex and the mitotic spindle. The taxol-induced microtubules were partially resistant to nocodazole, an inhibitor of tubulin polymerization. Moreover, taxol induced microtubule assembly in cells pretreated with nocodazole. Increasing the ratio of nocodazole to taxol restored the ability of the centrosomes and kinetochores to specifically induce microtubule assembly in their immediate vicinity. The data suggest that taxol lowers the critical tubulin concentration in vivo as well as in vitro and that the organizing capacity of the microtubule-organizing centers depends on the cytoplasmic polymerization threshold.

Alkaloids↗
PubMed1981

Immunoelectron microscopic localization of the 210,000-mol wt microtubule-associated protein in cultured cells of primates.

Results from ultrastructural immunocytochemistry on glutaraldehyde-fixed cells confirmed and extended findings previously obtained with immunofluorescence. A microtubule-associated protein (MAP) of 210,000 molecular weight was shown to be specifically associated with all cytoplasmic and mitotic microtubules along their entire length in primate cells. Specific labeling with the anti-MAP antibody could not be detected on any other subcellular structures, notably the centrosomes, kinetochores, microfilaments, and intermediate filaments. Treatment with the microtubule-disrupting drug, nocodazole, induced diffusion of the MAP throughout the cytoplasm. During repolymerization of microtubules following disassembly by nocodazole, the association of the MAP with the microtubules was intermediate and complete. When cells were treated with vinblastine, the tubulin paracrystals formed were heavily stained by the antibody. Neither sodium azide nor taxol affected the association of the MAP with microtubules.

Alkaloids↗