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See detailKarsts des craies et calcarénites de la Montagne Saint-Pierre (Basse Meuse liégeoise)
Willems, Luc ULg; Rodet, Joël; Ek, Camille ULg et al

in Bulletin des Chercheurs de la Wallonie (2007), XLVI

The “Montagne Saint-Pierre” (Sint Pietersberg) is a separate part of the Hesbaye plateau, isolated between the lower valleys of the Geer and the Meuse rivers. It is exploited by a big open-air quarry and ... [more ▼]

The “Montagne Saint-Pierre” (Sint Pietersberg) is a separate part of the Hesbaye plateau, isolated between the lower valleys of the Geer and the Meuse rivers. It is exploited by a big open-air quarry and by numerous underground quarries developing galleries on hundreds of kilometers long. Excavated in Cretaceous chalk and calcarenite, these artificial networks allow an exceptional 3-D observation of karsts inside a very porous and permeable rock, less favourable to a concentrated solution. The most numerous of them are “organ pipes” or “earth pipes”. They are vertical tubular solution pipes that may exceed 60 m in depth. Sponge networks and subhorizontal caves occur, without any visible connection with fracturation. Finally, downwards to at least 20 m below the alluvial plain of the Meuse river, pluridecametric nodes of weathered chalk are found. By their size and rounded morphology, the nodes resemble to the natural caves occurring in the calcarenite and intersected by the underground quarries. All the studied karsts allow us to propose a scenario for the genesis of a polyphase karst system. Independently of surface conditions, caves are generated deeply in the phreatic zone (endokarsts). During the downcutting of theMeuse valley, and related to the fluvial terraces, solution pipes (input karsts) are generated. Due to the valley incision and to the lowering of the aquifer,theses solution pipes progress downward and cut the endokarsts. A concentrated water circulation takes place. In the dewatered upper part of the system, caves cut by solution pipes are rapidly filled by superficial deposits. The high porosity of the calcarenite makes it comparable to a sponge. The rock absorbs quickly the out-flows coming from the surface and causes a rapid deposit of the fine particles transported inside horizontal passages. The sealing of these conduits allows their conservation inside a very crumbly rock. [less ▲]

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See detailKarsts en roches cristallines silicatées non carbonatées. Cas dans des gneiss : la grotte de Mfoula, Sud Cameroun
Willems, Luc ULg; Pouclet, André; Vicat, Jean-Paul

in Actes des Journées Européennes de l'AFK 2003 (2003)

Since the Seventies, a séries of phenomena developed in non carbonated silicated rocks question the traditional vision of karst. The term of karst is used in the meaning of "any feature of the classical ... [more ▼]

Since the Seventies, a séries of phenomena developed in non carbonated silicated rocks question the traditional vision of karst. The term of karst is used in the meaning of "any feature of the classical karst morphology (caves, sink-holes, lapiaz...) where dissolution plays the main genetic action and this in any kind of rocks". The cave of Guéssédoundou illustrâtes a karst in métagabbros. It opens at the top of a small hill, in a dépression twenty meters long and three to four meters deep. The walls of this dépression are subvertical and the bottom is partially occupied by angular pluridecimetric blocks. The cave is opened on several meters in the southern side of the dépression and is prolonged in the form of too narrow conduits to be explore. The bedrock is a metagabbro with fine grains, slightly weathered, crossed by decimetric quartzose veins. Gabbroïc texture is preserved, as well as part of magmatic plagioclases. The remainder is transformed into a mixture of white feldspar and clinozoisite. Pyroxene are pseudomorphosed in actinote and chlorite. The site dépression was created along a N 10° shear zone where rocks suffered important fracturation and fluid transfers, as shown by its silification and ferruginisation.. Moreover, a East-West schistosity, former to shearing, structures the gabbro. The présence of angular blocks of variable size and the absence of human activity trace on the site show that the dépression was formed naturally by collapse of the roof of a more vast cavity whose current cave would be the visible residual prolongation. The absence of flow traces and mechanical abrasion means that this cavity is due only to chemical érosion . At the cave entry and on the subvertical walls of the dépression were formed by alveoli a few centimètres to a few décimètres in diameter. Thèse alveoli of wall are known in other lithologies, in particular in limestones. The absence of salts within the rock draws aside a formation by sait weathering. The smooth aspect and non fractured walls of the cells cannot resuit from a corrosion to a fracturing node. The closed aspect of the dépression and the absence of flow trace eliminate the assumptions from formation by water swirls or eolisation. The genesis of the cave must be earlier to the installation of a weathering cover since the rock is little deteriorated and the alveoli are not developed on a quite particular level which would correspond to a précise pedogenic horizon. Only a generalized dissolution of the métagabbros, in relation to a slow solution circulation, being carried out with the favour of the fracturing plans of the shearing zone makes it possible to explain the formation of the alveoli. The inversion of relief results from a weaker érosion of the rocks made more résistant to this place by the quartz seam mainstay and by the ferruginisation along the shearing zone. In the other hand, the crushed rocks, become porous, drained the infiltrations of meteoric water, facilitating the dissolution processes. The study of the site of Guéssédoundou shows that karstic phenomena can also exist in silico-aluminous formations of crystalline rocks [less ▲]

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See detailKarsts en roches cristallines silicatées non carbonatées.. Cas dans les métagabbros : grotte de Guessédoundou, Niger occidental
Willems, Luc ULg; Pouclet, André; Vicat, Jean-Paul

in Rodet, Joël (Ed.) Actes des Journées Européennes de l'AFK 2003 (2003)

Since the Seventies, a séries of phenomena developed in non carbonated silicated rocks question the traditional vision of karst. The term of karst is used in the meaning of "any feature of the classical ... [more ▼]

Since the Seventies, a séries of phenomena developed in non carbonated silicated rocks question the traditional vision of karst. The term of karst is used in the meaning of "any feature of the classical karst morphology (caves, sink-holes, lapiaz...) where dissolution plays the main genetic action and this in any kind of rocks". The cave of Guéssédoundou illustrâtes a karst in métagabbros. It opens at the top of a small hill, in a dépression twenty meters long and three to four meters deep. The walls of this dépression are subvertical and the bottom is partially occupied by angular pluridecimetric blocks. The cave is opened on several meters in the southern side of the dépression and is prolonged in the form of too narrow conduits to be explore. The bedrock is a metagabbro with fine grains, slightly weathered, crossed by decimetric quartzose veins. Gabbroïc texture is preserved, as well as part of magmatic plagioclases. The remainder is transformed into a mixture of white feldspar and clinozoisite. Pyroxene are pseudomorphosed in actinote and chlorite. The site dépression was created along a N 10° shear zone where rocks suffered important fracturation and fluid transfers, as shown by its silification and ferruginisation.. Moreover, a East-West schistosity, former to shearing, structures the gabbro. The présence of angular blocks of variable size and the absence of human activity trace on the site show that the dépression was formed naturally by collapse of the roof of a more vast cavity whose current cave would be the visible residual prolongation. The absence of flow traces and mechanical abrasion means that this cavity is due only to chemical érosion . At the cave entry and on the subvertical walls of the dépression were formed by alveoli a few centimètres to a few décimètres in diameter. Thèse alveoli of wall are known in other lithologies, in particular in limestones. The absence of salts within the rock draws aside a formation by sait weathering. The smooth aspect and non fractured walls of the cells cannot resuit from a corrosion to a fracturing node. The closed aspect of the dépression and the absence of flow trace eliminate the assumptions from formation by water swirls or eolisation. The genesis of the cave must be earlier to the installation of a weathering cover since the rock is little deteriorated and the alveoli are not developed on a quite particular level which would correspond to a précise pedogenic horizon. Only a generalized dissolution of the métagabbros, in relation to a slow solution circulation, being carried out with the favour of the fracturing plans of the shearing zone makes it possible to explain the formation of the alveoli. The inversion of relief results from a weaker érosion of the rocks made more résistant to this place by the quartz seam mainstay and by the ferruginisation along the shearing zone. In the other hand, the crushed rocks, become porous, drained the infiltrations of meteoric water, facilitating the dissolution processes. The study of the site of Guéssédoundou shows that karstic phenomena can also exist in silico-aluminous formations of crystalline rocks. [less ▲]

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See detailKarsts en roches non carbonatées - l'exemple des quartzites et des itabérites de Minas Gerais, Brésil
Willems, Luc ULg; Rodet, Joël; Auler, Augusto et al

in Rodet, Joël (Ed.) Actes des Journées Européennes de l'AFK 2003 (2003)

The state of Minas Gérais, Brazil, contains numerous karsts booth inside carbonated and non carbonated rocks. Différent caves are found in quartzite and Itaberite formations (Banded Iron formation). The ... [more ▼]

The state of Minas Gérais, Brazil, contains numerous karsts booth inside carbonated and non carbonated rocks. Différent caves are found in quartzite and Itaberite formations (Banded Iron formation). The term karst is used in the meaning of "any features of the classical karst morphology (caves, sink-holes, lapies...) where dissolution plays the main genetically action and this in any kind of rocks". In some areas, lapiaz and kamenitza affect wide landscapes (area of Diamantina, Natural Parc of Rio Preto). Several caves are found and some of these are several kilomeetres long (grutta do Bromelias, Natural Parc of Ibitipoca). Inside caves, we found numerous forms like dissolution alveoli, spelothems, .... Many times, the cave sides and solutional forms are covered by crust which solidify a very crumbly quartzite. Différent morphologies show an primary solutional stage of the rocks before a physical erosional stage which destroy the earliest forms (piping, river érosion, collapsing). [less ▲]

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See detailKarsts in sandstones and quartzites of Minas Gerais, Brazil
Willems, Luc ULg; Rodet, Joël; Pouclet, André et al

in Cadernos do Laboratorio Xeolóxico de Laxe (2008), 33

The state of Minas Gerais (Brazil) is characterized by significant karst regions, which develop <br /><br />in both sandstone and quartzite terrains and display complex suites of underground and ... [more ▼]

The state of Minas Gerais (Brazil) is characterized by significant karst regions, which develop <br /><br />in both sandstone and quartzite terrains and display complex suites of underground and surfaceforms. In the Espinhaço Ridge, Central Minas Gerais, several caves of up to a few hundred metres long, occur in the surroundings of the town of Diamantina. Some of these caves, such as Salitre actually consist of swallow-holes. Other horizontal caves are characterized by corrosion forms generated in the phreatic zone. In some places, such as in the Rio Preto area, these phreatic forms are overprinted by ceiling tubes, suggesting a polyphase karst evolution, prior to the draining in the cave. Remains of paths, with circular cross section up to one metre in diameter, can be found through residual tower-like surface landforms widely present in the landscapes. Their dissection is due to a generalised karstification in the area, resulting in closed canyons, megakarrens and kamenitzas. In Southern Minas Gerais, close to the Mantiqueira Ridge, the caves of the Ibitipoca state park can reach more than 2 km in length. These caves are associated with a very large hanging geological syncline. Several of these caves contain active streams, which flow for hundreds of metres before disappearing in sand-choked passages. Keyhole cross sections characterize steeply descending passages in these caves, indicatinga chan ge from slow phreatic flow towards a faster vadose flow responsible for the vertical incision of the passage. Such change is probably related to base level lowering and/or to turn in the direction of the water flow. Several generations of wall-pockets, from a few centimetres to over a metre long, occur into the caves. These features are good indicators of the initial phase of speleogenesis, generating the initial conduits by their coalescence. This mechanism is also responsible for cut-off meanders. In the area, the main river flows along the syncline axis and cuts through a rock barrier, generating a tunnel-like passage. This cave drains, through resurgences in its walls, part of the water that flows in other caves located in the flank of the syncline. [less ▲]

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See detailKarsts in sandstones and quatrzites of Minas Gerais, Brazil
Willems, Luc ULg; Rodet, J.; Pouclet, A. et al

Poster (2007)

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See detailKarsts in silicated and non carbonated rocks
Willems, Luc ULg

Conference (2011)

Karsts in silicated and non carbonated rocks refer to morphologies similar to those found in limestones (caves, lapies, polje…) as being equally generated by predominantly dissolution processes. Their ... [more ▼]

Karsts in silicated and non carbonated rocks refer to morphologies similar to those found in limestones (caves, lapies, polje…) as being equally generated by predominantly dissolution processes. Their discovery in allegedly not very soluble rocks raises the question of existing water resources in lithologies which are rarely considered from this point of view. A rough inventory of this kind of karsts shows that they essentially develop in sandstones and quartzites. Other silicated lithologies such as granites or gneisses seem to contain only a few examples. Karsts in silicated and non carbonated rocks are found at all latitudes, though mainly in the warm and temperate climate zones of the world. Nevertheless, these conclusions may result from the lack of systematic prospecting in numerous regions of the world. Typically, most studied cavities are located in Paleozoic to Proterozoic rocks. Underground networks can stretch for several kilometers. Two types of cavities can be identified. The first one is characterized by cave entrances located in a cliff or in a raised hillside. These subhorizontal cavities end blind within the rock massif. No trace of fracturing authorizing mechanical erosion by flows, which would explain their genesis, was ever recorded. The second type of cavities is characterized by the presence of an underground stream which disappears in a siphon or in some impenetrable passages. In some cases, an important granular disintegration of the surrounding rock produces quantities of sand which seal large pre-existent voids. The latter were formed in different physico-chemical conditions than those present in the open air environment. An initial deep karstification is possible despite the surface environment. Secondary morphologies on the cave walls (alveoli, pillars of dissolution, passages with “key hole” section, ceiling bells …) enable us to partially reconstitute the genesis of these caves. It would start in a phreatic environment with the development of spots of dissolution along deep water circulations. Initially, independent cavities grow and interconnect to form embryonal karst networks. The incision of valleys and the weathering processes progressing from the surface can intersect these. Physical erosion then becomes more prominent than chemical erosion. The pre-existent forms, depending on their organization, can either be dismantled or contribute to the evolution of a complex karst network. A comprehensive study of karsts in silicated and non carbonated rocks is an opportunity to a better understanding of generally inaccessible deep karstification, including in the carbonated rocks. Moreover, the presence of these karsts and sometimes of underground rivers in regions hit by chronic droughts represents a potential of water resources disregarded today. [less ▲]

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See detailKarsts siliceux au Niger occidental".
Willems, Luc ULg

in Proceedings of The 12th International Congress of Speleology, Vol. I, Symp. 8: Karst Geomorphology (1997)

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See detailLes karsts siliceux d'Afrique
Vicat, Jean-Paul; Willems, Luc ULg

in Géosciences au Cameroun @ collection Géocam (1998), 1

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See detailKaryotype of dormice Eliomys quercinus from Tirol (Austria)
Ramalhinho, M. D.; Libois, Roland ULg

in Acta Theriologica (2005), 50(1), 133-136

A karyotype of 2n = 52 chromosomes was found in two Eliomys quercinus (Linnaeus, 1766) specimens from two different localities of Tirol (Austria). The karyotype is similar to the one described in the ... [more ▼]

A karyotype of 2n = 52 chromosomes was found in two Eliomys quercinus (Linnaeus, 1766) specimens from two different localities of Tirol (Austria). The karyotype is similar to the one described in the Italian Alps, suggesting that these mountains were not a barrier to the northern expansion of this chromosomal race. [less ▲]

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See detailThe karyotype of the Formentera island garden dormouse, Eliomys quercinus ophiusae
Ramalhinho, Graça; Libois, Roland ULg

in Belgian Journal of Zoology (2001), 131(1), 83-85

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See detailKashin-Beck Disease: evaluation of mineral intake in young Tibetan children from endemic areas
Dermience, Michael ULg

Master's dissertation (2010)

Kashin-Beck disease is an endemic and chronic osteochondropathy. This disease principally occurs in the Tibet Autonomous Region and in several provinces of the People’s Republic of China. Although many ... [more ▼]

Kashin-Beck disease is an endemic and chronic osteochondropathy. This disease principally occurs in the Tibet Autonomous Region and in several provinces of the People’s Republic of China. Although many studies have already been conducted and many others are still underway, its ethiology remains unknown. A multifactorial hypothesis has been proposed: selenium deficiency, high concentration of organic matters in drinking water (fulvic acids) and mycotoxin poisoning by fungi infecting cereals. This original study aimed to measure the mineral contents of the food most often consumed in severe endemic regions and then to evaluate the daily intake of minerals in young Tibetan children from endemic areas. The mineral elements were selected in relation to their implications in bone metabolism. A sampling campaign split up into two time periods (winter and spring) was carried out. Ten families from two distinct regions were selected based on three criteria: they live in endemic areas; they include a 3 to 5 year-old child; this child has a KBD brother or sister. At the same time, a nutritional survey was made by the means of a prospective questionnaire in order to list the 24h food intake of the 3 to 5 year-old child. This survey highlighted the extremely monotonous cereal-based Tibetan diet. An analytical method for the minerals was developed as follows: mineralization of samples performed by microwave-assisted wet process; mineralized solutions measured by several atomic absorption or emission spectrometric methods and molecular absorption spectrometric methods. The analytical method was validated by mean of certified reference materials. Mean food contents were calculated and compared to food composition reference tables. High iron contents and selenium deficiencies were highlighted in several foods. Daily intakes were estimated combining mineral measurements and nutritional survey results. These were compared to dietary reference intakes from reference tables. This estimation reveals some crucial points: we confirm a marked deficiency in calcium; Ca/P ratios are always low; iron and copper intakes are excessive; zinc is the most probably deficient; while selenium could be deficient; manganese intakes often exceed toxicity thresholds. Nevertheless, this study encounters some limits. The bioavailability of minerals is a critical point that deserves further investigations. Moreover, a larger study over a longer term covering both endemic and non-endemic regions is required for definite conclusions to be reached. [less ▲]

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See detailKashin-Beck Disease: evaluation of mineral intake in young Tibetan children from endemic areas
DERMIENCE, Michael ULg; Maesen, Philippe ULg; Mathieu, Françoise et al

Poster (2010, October 26)

Kashin-Beck disease is an endemic and chronic osteochondropathy. This disease principally occurs in the Tibet Autonomous Region and in several provinces of the People’s Republic of China. Although many ... [more ▼]

Kashin-Beck disease is an endemic and chronic osteochondropathy. This disease principally occurs in the Tibet Autonomous Region and in several provinces of the People’s Republic of China. Although many studies have already been conducted and many others are still underway, its ethiology remains unknown. A multifactorial hypothesis has been proposed: selenium deficiency, high concentration of organic matters in drinking water (fulvic acids) and mycotoxin poisoning by fungi infecting cereals. This original study aimed to measure the mineral contents of the food most often consumed in severe endemic regions and then to evaluate the daily intake of minerals in young Tibetan children from endemic areas. The mineral elements were selected in relation to their implications in bone metabolism. A sampling campaign split up into two time periods (winter and spring) was carried out. Ten families from two distinct regions were selected based on three criteria: they live in endemic areas; they include a 3 to 5 year-old child; this child has a KBD brother or sister. At the same time, a nutritional survey was made by the means of a prospective questionnaire in order to list the 24h food intake of the 3 to 5 year-old child. This survey highlighted the extremely monotonous cereal-based Tibetan diet. An analytical method for the minerals was developed as follows: mineralization of samples performed by microwave-assisted wet process; mineralized solutions measured by several atomic absorption or emission spectrometric methods and molecular absorption spectrometric methods. The analytical method was validated by mean of certified reference materials. Mean food contents were calculated and compared to food composition reference tables. High iron contents and selenium deficiencies were highlighted in several foods. Daily intakes were estimated combining mineral measurements and nutritional survey results. These were compared to dietary reference intakes from reference tables. This estimation reveals some crucial points: we confirm a marked deficiency in calcium; Ca/P ratios are always low; iron and copper intakes are excessive; zinc is the most probably deficient; while selenium could be deficient; manganese intakes often exceed toxicity thresholds. Nevertheless, this study encounters some limits. The bioavailability of minerals is a critical point that deserves further investigations. Moreover, a larger study over a longer term covering both endemic and non-endemic regions is required for definite conclusions to be reached. [less ▲]

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See detailKatanga Business - Pale Peko Bantu: Notes sur deux moments de cinéma postcolonial belge
Hamers, Jérémy ULg

in French Forum (2011), 35(n°2-3, Spring Fall 2010), 95-113

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See detailKatharsis
Pontzen, Alexandra ULg; Göritz, Anja

in Kiesow; Korte (Eds.) EGB. Emotionales Gesetzbuch. Dekalog der Gefühle (2005)

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See detailKATP channel openers: tissue selectivity of original 3-alkylaminopyrido- and 3-alkylaminobenzothiadiazine 1,1 -dioxides
Lebrun, P.; Becker, B.; Morel, N. et al

in Biochemical Pharmacology (2008), 75

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See detailKBD is an agro-environmental disease: The south central Tibet input
Haubruge, Eric ULg; Chasseur, Camille; Lognay, Georges ULg et al

Conference (2008, August)

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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 ▲]

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See detailKCNQ2 and KCNQ3 potassium channel genes in benign familial neonatal convulsions: expansion of the functional and mutation spectrum.
Singh, Nanda A; Westenskow, Peter; Charlier, Carole ULg et al

in Brain : A Journal of Neurology (2003), 126(Pt 12), 2726-37

Benign familial neonatal convulsions (BFNC) is a rare autosomal dominant generalized epilepsy of the newborn infant. Seizures occur repeatedly in the first days of life and remit by approximately 4 months ... [more ▼]

Benign familial neonatal convulsions (BFNC) is a rare autosomal dominant generalized epilepsy of the newborn infant. Seizures occur repeatedly in the first days of life and remit by approximately 4 months of age. Previously our laboratory cloned two novel potassium channel genes, KCNQ2 and KCNQ3, and showed that they are mutated in patients with BFNC. In this report, we characterize the breakpoints of a previously reported interstitial deletion in the KCNQ2 gene and show that only KCNQ2 is deleted. We identify 11 novel mutations in KCNQ2 and one novel mutation in the KCNQ3 potassium channel genes. In one family, the phenotype extends beyond neonatal seizures and includes rolandic seizures, and a subset of families has onset of seizures in infancy. In the Xenopus oocyte expression system, we characterize five KCNQ2 and one KCNQ3 disease-causing mutations. These mutations cause a variable loss of function, and selective effects on the biophysical properties of KCNQ2/KCNQ3 heteromultimeric channels. We report here the first dominant negative mutation in KCNQ2 that has a phenotype of neonatal seizures without permanent clinical CNS impairment. [less ▲]

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