References of "Waroux, Olivier"
     in
Bookmark and Share    
Full Text
See detailA method allowing long term culture and expansion of chicken primordial germ cells
Tonus, Céline ULg; Waroux, Olivier ULg; Grobet, Luc ULg

Conference (2013, March 12)

We developed an original method allowing long term culture (up to 20 month) of undifferentiated chicken PGCs, with good proliferation rates. We use a co-culture system: PGCs are cultivated in cell culture ... [more ▼]

We developed an original method allowing long term culture (up to 20 month) of undifferentiated chicken PGCs, with good proliferation rates. We use a co-culture system: PGCs are cultivated in cell culture inserts, in the presence of irradiated Buffalo Rat Liver cells. According to our own experience, physical separation of PGCs and feeder cells limits the differentiation of PGCs. Our PGCs lines keep their original phenotype including their gonadal colonization ability. We also developed a novel cryopreservation method based on vitrification, in complement of a slow rate freezing. [less ▲]

Detailed reference viewed: 10 (2 ULg)
Full Text
Peer Reviewed
See detailLong term culture and characterization of chicken primordial germ cells
Tonus, Céline ULg; Waroux, Olivier ULg; Cloquette, Karine et al

Poster (2012, November)

Avian primordial germ cells (PGCs), can keep their germ cells properties and are foreseen as promising tools for developing avian transgenesis and preservation of genetic resources of endangered species ... [more ▼]

Avian primordial germ cells (PGCs), can keep their germ cells properties and are foreseen as promising tools for developing avian transgenesis and preservation of genetic resources of endangered species. We have developed original methods that allow long term (20 month) expansion of primary cultures of undifferentiated PGCs and their efficient cryopreservation. Blood samples were collected from stage 13-18 embryos, pooled, deposited in cell culture inserts and co-cultivated in the presence of irradiated BRL cells. This physically separated co-culture system along with selective culture medium promoted emergence, selection and proliferation of undifferentiated PGCs lines. Overall, 35% of blood samples gave rise to PGCs cell lines originating from three commercial layer breeds and two Belgian endangered breeds. PGCs lines were first characterised for the expression of the stem cells and PGCs characteristic marker SSEA-1 by FACS (expression rate: 90-99%). RT-PCR confirmed expression of germ-line specific markers (CVH, CDH, DAZL), pluripotency markers (cPouV, cSox2, cNanog), telomerase and CXCR4 receptor. In addition, by means of a quantitative PCR amplification of a chromosome W specific sequence, we demonstrated a drift of all our lines towards the male sex (WL), while they were initially isolated from pooled blood samples with statistically equivalent numbers of male and female embryos (35 females: 29 males). PGCs were subsequently efficiently cryopreserved by slow freezing or by a newly developed vitrification method. Labelled PGCs from 10 lines were injected in recipient embryos. Colonization of the genital ridges confirmed that PGCs retain their gonadal migratory ability, both after long-term culture (min 3, max 20 month) and after cryopreservation. [less ▲]

Detailed reference viewed: 92 (14 ULg)
Full Text
Peer Reviewed
See detailM-type channels selectively control bursting in rat dopaminergic neurons
Drion, Guillaume ULg; Bonjean, Maxime; Waroux, Olivier ULg et al

in European Journal of Neuroscience (2010), 31

Detailed reference viewed: 118 (56 ULg)
Full Text
Peer Reviewed
See detailSK Channel blockade promotes burst firing in dorsal raphe serotonergic neurons
Rouchet, Nathalie; Waroux, Olivier ULg; Lamy, Cédric et al

in European Journal of Neuroscience (2008), 28(6), 1108-15

Detailed reference viewed: 3 (2 ULg)
Full Text
Peer Reviewed
See detailSK Channel blockade promotes burst firing in dorsal raphe serotonergic neurons
Rouchet, Nathalie ULg; Waroux, Olivier ULg; Lamy, Cédric ULg et al

in European Journal of Neuroscience (2008), 28(6), 1108-15

Detailed reference viewed: 59 (32 ULg)
Full Text
Peer Reviewed
See detailSK Channel blockade promotes bursting in vivo in dorsal raphe serotonergic neurons
Rouchet, Nathalie; Waroux, Olivier ULg; Alix, Philippe ULg et al

in Acta Physiologica (2008, May 17), 194(supll. 666), -01

Detailed reference viewed: 11 (1 ULg)
Full Text
Peer Reviewed
See detailTCRγδ cells in HPV-associated cervical cancer
Renoux, Virginie ULg; de Leval, Laurence ULg; Waroux, Olivier ULg et al

in Acta Clinica Belgica (2008), 63

Detailed reference viewed: 39 (10 ULg)
See detailDirect induction of burst firing by SK channel blockade in serotonergic neurons in vivo
Rouchet, Nathalie; Waroux, Olivier ULg; Moreau, Jacqueline ULg et al

Scientific conference (2007, November 04)

Small conductance calcium-activated potassium channels (SK channels) are widely expressed throughout the central nervous system and underlie the medium afterhyperpolarization following a single or a train ... [more ▼]

Small conductance calcium-activated potassium channels (SK channels) are widely expressed throughout the central nervous system and underlie the medium afterhyperpolarization following a single or a train of action potentials. It has been shown that they are involved in the regulation of the excitability and the firing pattern of several types of neurons. In vivo, serotonergic (5-HT) neurons of the dorsal raphe nucleus usually show a tonic pattern of discharge, but they can also display repetitive burst firing activity, usually involving doublets of closely spaced (< 20 ms) action potentials. It has been shown that burst firing is correlated with an increase in transmitter release and postsynaptic effects (Gartside et al., Neuroscience, 98, 295-300, 2000). We hypothesized that SK channels modulate the firing pattern of 5-HT neurons. In a preliminary study, extracellular single-cell recordings combined with iontophoresis showed that UCL1684, a water soluble SK blocker (200 µM), significantly increased the % of spikes produced in bursts in 60% of presumed serotonergic neurons in the anesthetized rat. We confirm here this observation by demonstrating that UCL1684 significantly increased the production of doublets in 17 out of 25 serotonergic neurons. In order to explore whether a GABAergic input was involved in this effect, additional experiments were performed in the presence of the specific GABAA antagonist SR 95531. In these conditions, 50 % (5 out of 10) of serotonergic neurons showed an increase in the production of doublets when UCL 1684 was applied (p = 0.31 vs control), suggesting that a GABAergic input is not implicated in the regulation of the firing pattern of 5-HT neurons by the SK blocker. Finally, the effect of SK channel blockade was explored in vitro in slices. Bath application of the SK blocker apamin (300 nM) did not induce bursting in 15 out of 18 neurons (p < 0.001 vs in vivo control conditions), although it did increase the coefficient of variation of the interspike intervals.Taken together, our results suggest that SK blockade induces burst firing in a majority of dorsal raphe serotonergic neurons. This effect does not involve GABAergic interneurons, but requires an input that is only present in vivo. [less ▲]

Detailed reference viewed: 2 (1 ULg)
Full Text
Peer Reviewed
See detailSynthesis and Radioligand Binding Studies of Bis-Isoquinolinium Derivatives as Small Conductance Ca(2+)-Activated K(+) Channel Blockers
Graulich, Amaury ULg; Dilly, Sébastien ULg; Farce, Amaury et al

in Journal of Medicinal Chemistry (2007), 50(21), 5070-5075

Starting from the scaffold of N-methyllaudanosine and N-methylnoscapine, which are known small conductance Ca2+-activated K+ channel blockers, original bis-isoquinolinium derivatives were synthezised and ... [more ▼]

Starting from the scaffold of N-methyllaudanosine and N-methylnoscapine, which are known small conductance Ca2+-activated K+ channel blockers, original bis-isoquinolinium derivatives were synthezised and evaluated using binding studies, electrophysiology, and molecular modeling. These quaternary compounds are powerful blockers, and the most active ones have 10 times more affinity for the channels than dequalinium. The unsubstituted compounds possess a weaker affinity than the analogues having a 6,7-dimethoxy- or a 6,7,8-trimethoxy substitution. The length of the linker has no influence in the alkane derivatives. In relation to the xylene derivatives, the affinities are higher for the ortho and meta isomers. These results are well corroborated by a molecular modeling study. Finally, the most effective compounds have been tested in electrophysiological experiments on midbrain dopaminergic neurons and demonstrate the blocking potential of the apamin-sensitive after-hyperpolarization. [less ▲]

Detailed reference viewed: 75 (23 ULg)
Full Text
Peer Reviewed
See detailSynthesis and radioligand binding studies of methoxylated 1,2,3,4-tetrahydroisoquinolinium derivatives as ligands of the apamin-sensitive Ca2+- activated K+ channels
Graulich, Amaury ULg; Scuvée-Moreau, Jacqueline ULg; Alleva, Livia ULg et al

in Journal of Medicinal Chemistry (2006), 49(24), 7208-7214

Several methoxylated 1,2,3,4-tetrahydroisoquinoliniums derived from N-methyl-laudanosine and N-methyl-noscapine were synthesized and evaluated for their affinity for apamin-sensitive binding sites. The ... [more ▼]

Several methoxylated 1,2,3,4-tetrahydroisoquinoliniums derived from N-methyl-laudanosine and N-methyl-noscapine were synthesized and evaluated for their affinity for apamin-sensitive binding sites. The quaternary ammonium derivatives have a higher affinity with regard to the tertiary amines. 6,7-Dimethoxy analogues possess a higher affinity than the 6,8- and 7,8- dimethoxy isomers. A 3,4-dimethoxybenzyl or a 2-naphthylmethyl moiety in C-1 position are more favorable than a 3,4-dimethoxyphenethyl group. Smaller groups such as propyl or isobutyl are unfavorable. In 6,7-dimethoxy analogues, increasing the size and lipophilicity with a naphthyl group in the C-1 position leads to a slight increase of affinity, while the same group in the 6,7,8- trimethoxy series is less favorable. The 6,7,8- trimethoxy derivative 3f is the first tertiary amine in the series to possess an affinity close to that of N-methyl-laudanosine and N-methyl-noscapine. Moreover, electrophysiological studies show that the most effective compound 4f blocks the apamin-sensitive afterhyperpolarization in rat dopaminergic neurons. [less ▲]

Detailed reference viewed: 28 (13 ULg)
Peer Reviewed
See detailEffect of SK channel blockade on the firing of dorsal raphe neurons in anaesthetized rats
Alleva, Livia ULg; Rouchet, Nathalie; Waroux, Olivier ULg et al

Poster (2006, October 17)

K channels are small conductance calcium-activated potassium channels which trigger an outward current generating an afterhyperpolarization (AHP). This AHP follows a single or a train of action potential ... [more ▼]

K channels are small conductance calcium-activated potassium channels which trigger an outward current generating an afterhyperpolarization (AHP). This AHP follows a single or a train of action potential, and therefore is important in the regulation of the firing frequency and/or pattern of many types of neurons. Serotonergic (5-HT) neurons from the raphe nuclei express SK channels and exhibit a significant AHP which can be efficiently blocked in vitro by apamin and N-methyl laudanosine (NML) (Scuvée-Moreau et al, 2004). In the later study, we found that some but not all neurons (50%) had a significantly increase in their firing rate when positive current was injected after SK channel blockade. In order to determine the physiological relevance of these channels in vivo, single unit extracellular recordings were carried out in anesthetized rats and combined with iontophoresis of the specific non-peptidic SK channel blocker, UCL1684. 5-HT neurons were tested for their inhibitory response to locally applied 5-HT and histological analysis confirmed the localization of the recording site. UCL 1684 was used at a concentration of 200 µM. Out of 11 neurons recorded, 6 showed a significant increase in the production of doublets, with no effect on their mean firing rate as compared to the control condition. The other neurons were completely unaffected. These results suggest that the responsiveness of presumed 5-HT neurons to SK channel block is variable. Although the use of 200 µM UCL allow us to be sure of a sufficient SK blockade at the recording site (Waroux et al, 2005), we can not rule out the possibility that SK channels present at the dendritic level were not completely blocked. In conclusion, SK channels in vivo might play a role in controlling the firing pattern of a subgroup of 5-HT neurons. [less ▲]

Detailed reference viewed: 12 (1 ULg)
Full Text
Peer Reviewed
See detailThe KCNQ channel opener retigabine inhibits the activity of mesencephalic dopaminergic systems of the rat
Hansen, H. H.; Ebbesen, C.; Mathiesen, C. et al

in Journal of Pharmacology and Experimental Therapeutics (The) (2006), 318(3), 1006-1019

Homo- and heteromeric complexes of KCNQ channel subunits are the molecular correlate of the M-current, a neuron-specific voltage-dependent K+ current with a well established role in control of neural ... [more ▼]

Homo- and heteromeric complexes of KCNQ channel subunits are the molecular correlate of the M-current, a neuron-specific voltage-dependent K+ current with a well established role in control of neural excitability. We investigated the effect of KCNQ channel modulators on the activity of dopaminergic neurons in vitro and in vivo in the rat ventral mesencephalon. The firing of dopaminergic neurons recorded in mesencephalic slices was robustly inhibited in a concentration-dependent manner by the KCNQ channel opener N-(2-amino-4-(4-fluorobenzylamino)phenyl) carbamic acid ethyl ester ( retigabine). The effect of retigabine persisted in the presence of tetrodotoxin and simultaneous blockade of GABA A receptors, small-conductance calcium-activated K+ ( SK) channels, and hyperpolarization-activated (I-h) channels, and it was potently reversed by the KCNQ channel blocker 4- pyridinylmethyl-9(10H)-anthracenone (XE991), indicating a direct effect on KCNQ channels. Likewise, in vivo single unit recordings from dopaminergic neurons revealed a prominent reduction in spike activity after systemic administration of retigabine. Furthermore, retigabine inhibited dopamine synthesis and c-Fos expression in the striatum under basal conditions. Retigabine completely blocked the excitatory effect of dopamine D-2 auto-receptor antagonists. Again, the in vitro and in vivo effects of retigabine were completely reversed by preadministration of XE991. Dual immunocytochemistry revealed that KCNQ4 is the major KCNQ channel subunit expressed in all dopaminergic neurons in the mesolimbic and nigrostriatal pathways. Collectively, these observations indicate that retigabine negatively modulates dopaminergic neurotransmission, likely originating from stimulation of mesencephalic KCNQ4 channels. [less ▲]

Detailed reference viewed: 108 (59 ULg)
Full Text
Peer Reviewed
See detailSK channels control the firing pattern of midbrain dopaminergic neurons in vivo
Waroux, Olivier ULg; Massotte, Laurent ULg; Alleva, Livia ULg et al

in European Journal of Neuroscience (2005), 22(12), 3111-3121

A vast body of experimental in vitro work and modelling studies suggests that the firing pattern and/or rate of a majority of midbrain dopaminergic neurons may be controlled in part by Ca2+-activated K ... [more ▼]

A vast body of experimental in vitro work and modelling studies suggests that the firing pattern and/or rate of a majority of midbrain dopaminergic neurons may be controlled in part by Ca2+-activated K+ channels of the SK type. However, due to the lack of suitable tools, in vivo evidence is lacking. We have taken advantage of the development of the water-soluble, medium potency SK blocker N-methyl-laudanosine (CH3-L) to test this hypothesis in anaesthetized rats. In the lateral ventral tegmental area, CH3-L iontophoresis onto dopaminergic neurons significantly increased the coefficient of variation of their interspike intervals and the percentage of spikes generated in bursts as compared to the control condition. The effect of CH3-L persisted in the presence of a specific GABA(A) antagonist, suggesting a direct effect. It was robust and reversible, and was also observed in the substantia nigra. Control experiments demonstrated that the effect of CH3-L could be entirely ascribed to its blockade of SK channels. On the other hand, the firing pattern of noradrenergic neurons was much less affected by CH3-L. We provide here the first demonstration of a major role of SK channels in the control of the switch between tonic and burst firing of dopaminergic neurons in physiological conditions. This study also suggests a new strategy to develop modulators of the dopaminergic (DA) system, which could be of interest in the treatment of Parkinson's disease, and perhaps other diseases in which DA pathways are dysfunctional. [less ▲]

Detailed reference viewed: 74 (25 ULg)