A mechanism of carbapenem resistance due to a new insertion element (ISPa133) in Pseudomonas aeruginosa

This study explored the evolutionary mechanism by which the clinical isolate PA110514 yields the imipenemresistant derivative PA116136. Both isolates were examined by PFGE and SDS-PAGE, which led to the identification of a new insertion sequence, ISPa133. This element was shown to have distinct chromosomal locations in each of the original isolates that appeared to explain the differences in imipenem susceptibilty. In strain PA110514, ISPa133 is located 56 nucleotides upstream of the translational start codon, which has no effect on expression of the porin OprD. However, in strain PA116136 ISPa133 it is located in front of nucleotide 696 and, by interrupting the coding region, causes a loss of OprD expression, thus conferring imipenem resistance. In vitro experiments mimicking the natural conditions of selective pressure yielded imipenem-resistant strains in which ISPa133 similarly interrupted oprD. A mechanism is proposed whereby ISPa133 acts as a mobile switch, with its position in oprD depending on the degree of selective pressure exerted by imipenem

A mechanism of carbapenem resistance due to a new insertion element (ISPa133) in Pseudomonas aeruginosa

This study explored the evolutionary mechanism by which the clinical isolate PA110514 yields the imipenemresistant derivative PA116136. Both isolates were examined by PFGE and SDS-PAGE, which led to the identification of a new insertion sequence, ISPa133. This element was shown to have distinct chromosomal locations in each of the original isolates that appeared to explain the differences in imipenem susceptibilty. In strain PA110514, ISPa133 is located 56 nucleotides upstream of the translational start codon, which has no effect on expression of the porin OprD. However, in strain PA116136 ISPa133 it is located in front of nucleotide 696 and, by interrupting the coding region, causes a loss of OprD expression, thus conferring imipenem resistance. In vitro experiments mimicking the natural conditions of selective pressure yielded imipenem-resistant strains in which ISPa133 similarly interrupted oprD. A mechanism is proposed whereby ISPa133 acts as a mobile switch, with its position in oprD depending on the degree of selective pressure exerted by imipenem

A mechanism of carbapenem resistance due to a new insertion element (ISPa133) in Pseudomonas aeruginosa

This study explored the evolutionary mechanism by which the clinical isolate PA110514 yields the imipenemresistant derivative PA116136. Both isolates were examined by PFGE and SDS-PAGE, which led to the identification of a new insertion sequence, ISPa133. This element was shown to have distinct chromosomal locations in each of the original isolates that appeared to explain the differences in imipenem susceptibilty. In strain PA110514, ISPa133 is located 56 nucleotides upstream of the translational start codon, which has no effect on expression of the porin OprD. However, in strain PA116136 ISPa133 it is located in front of nucleotide 696 and, by interrupting the coding region, causes a loss of OprD expression, thus conferring imipenem resistance. In vitro experiments mimicking the natural conditions of selective pressure yielded imipenem-resistant strains in which ISPa133 similarly interrupted oprD. A mechanism is proposed whereby ISPa133 acts as a mobile switch, with its position in oprD depending on the degree of selective pressure exerted by imipenem

A mechanism of carbapenem resistance due to a new insertion element (ISPa133) in Pseudomonas aeruginosa

This study explored the evolutionary mechanism by which the clinical isolate PA110514 yields the imipenemresistant derivative PA116136. Both isolates were examined by PFGE and SDS-PAGE, which led to the identification of a new insertion sequence, ISPa133. This element was shown to have distinct chromosomal locations in each of the original isolates that appeared to explain the differences in imipenem susceptibilty. In strain PA110514, ISPa133 is located 56 nucleotides upstream of the translational start codon, which has no effect on expression of the porin OprD. However, in strain PA116136 ISPa133 it is located in front of nucleotide 696 and, by interrupting the coding region, causes a loss of OprD expression, thus conferring imipenem resistance. In vitro experiments mimicking the natural conditions of selective pressure yielded imipenem-resistant strains in which ISPa133 similarly interrupted oprD. A mechanism is proposed whereby ISPa133 acts as a mobile switch, with its position in oprD depending on the degree of selective pressure exerted by imipenem

A mechanism of carbapenem resistance due to a new insertion element (ISPa133) in Pseudomonas aeruginosa

This study explored the evolutionary mechanism by which the clinical isolate PA110514 yields the imipenemresistant derivative PA116136. Both isolates were examined by PFGE and SDS-PAGE, which led to the identification of a new insertion sequence, ISPa133. This element was shown to have distinct chromosomal locations in each of the original isolates that appeared to explain the differences in imipenem susceptibilty. In strain PA110514, ISPa133 is located 56 nucleotides upstream of the translational start codon, which has no effect on expression of the porin OprD. However, in strain PA116136 ISPa133 it is located in front of nucleotide 696 and, by interrupting the coding region, causes a loss of OprD expression, thus conferring imipenem resistance. In vitro experiments mimicking the natural conditions of selective pressure yielded imipenem-resistant strains in which ISPa133 similarly interrupted oprD. A mechanism is proposed whereby ISPa133 acts as a mobile switch, with its position in oprD depending on the degree of selective pressure exerted by imipenem

Monitoring of crystallization processes by using infrared spectroscopy and multivariate methods

Väitöstutkimuksessa on tarkasteltuinfrapunaspektroskopian ja monimuuttujaisten aineistonkäsittelymenetelmien soveltamista kiteytysprosessin monitoroinnissa ja kidemäisen tuotteen analysoinnissa. Parhaillaan kiteytysprosessitutkimuksessa maailmanlaajuisesti tutkitaan intensiivisesti erilaisten mittausmenetelmien soveltamista kiteytysprosessin ilmiöidenjatkuvaan mittaamiseen niin nestefaasista kuin syntyvistä kiteistäkin. Lisäksi tuotteen karakterisointi on välttämätöntä tuotteen laadun varmistamiseksi. Erityisesti lääkeaineiden valmistuksessa kiinnostusta tämäntyyppiseen tutkimukseen edistää Yhdysvaltain elintarvike- ja lääkeaineviraston (FDA) prosessianalyyttisiintekniikoihin (PAT) liittyvä ohjeistus, jossa määritellään laajasti vaatimukset lääkeaineiden valmistuksessa ja tuotteen karakterisoinnissa tarvittaville mittauksille turvallisten valmistusprosessien takaamiseksi. Jäähdytyskiteytyson erityisesti lääketeollisuudessa paljon käytetty erotusmenetelmä kiinteän raakatuotteen puhdistuksessa. Menetelmässä puhdistettava kiinteä raaka-aine liuotetaan sopivaan liuottimeen suhteellisen korkeassa lämpötilassa. Puhdistettavan aineen liukoisuus käytettävään liuottimeen laskee lämpötilan laskiessa, joten systeemiä jäähdytettäessä liuenneen aineen konsentraatio prosessissa ylittää liukoisuuskonsentraation. Tällaiseen ylikylläiseen systeemiin pyrkii muodostumaan uusia kiteitä tai olemassa olevat kiteet kasvavat. Ylikylläisyys on yksi tärkeimmistä kidetuotteen laatuun vaikuttavista tekijöistä. Jäähdytyskiteytyksessä syntyvän tuotteen ominaisuuksiin voidaan vaikuttaa mm. liuottimen valinnalla, jäähdytyprofiililla ja sekoituksella. Lisäksi kiteytysprosessin käynnistymisvaihe eli ensimmäisten kiteiden muodostumishetki vaikuttaa tuotteen ominaisuuksiin. Kidemäisen tuotteen laatu määritellään kiteiden keskimääräisen koon, koko- ja muotojakaumansekä puhtauden perusteella. Lääketeollisuudessa on usein vaatimuksena, että tuote edustaa tiettyä polymorfimuotoa, mikä tarkoittaa molekyylien kykyä järjestäytyä kidehilassa usealla eri tavalla. Edellä mainitut ominaisuudet vaikuttavat tuotteen jatkokäsiteltävyyteen, kuten mm. suodattuvuuteen, jauhautuvuuteen ja tabletoitavuuteen. Lisäksi polymorfiamuodolla on vaikutusta moniin tuotteen käytettävyysominaisuuksiin, kuten esim. lääkeaineen liukenemisnopeuteen elimistössä. Väitöstyössä on tutkittu sulfatiatsolin jäähdytyskiteytystä käyttäen useita eri liuotinseoksia ja jäähdytysprofiileja sekä tarkasteltu näiden tekijöiden vaikutustatuotteen laatuominaisuuksiin. Infrapunaspektroskopia on laajalti kemian alan tutkimuksissa sovellettava menetelmä. Siinä mitataan tutkittavan näytteenmolekyylien värähtelyjen aiheuttamia spektrimuutoksia IR alueella. Tutkimuksessa prosessinaikaiset mittaukset toteutettiin in-situ reaktoriin sijoitettavalla uppoanturilla käyttäen vaimennettuun kokonaisheijastukseen (ATR) perustuvaa Fourier muunnettua infrapuna (FTIR) spektroskopiaa. Jauhemaiset näytteet mitattiin off-line diffuusioheijastukseen (DRIFT) perustuvalla FTIR spektroskopialla. Monimuuttujamenetelmillä (kemometria) voidaan useita satoja, jopa tuhansia muuttujia käsittävä spektridata jalostaa kvalitatiiviseksi (laadulliseksi) tai kvantitatiiviseksi (määrälliseksi) prosessia kuvaavaksi informaatioksi. Väitöstyössä tarkasteltiin laajasti erilaisten monimuuttujamenetelmien soveltamista mahdollisimman monipuolisen prosessia kuvaavan informaation saamiseksi mitatusta spektriaineistosta. Väitöstyön tuloksena on ehdotettu kalibrointirutiini liuenneen aineen konsentraation ja edelleen ylikylläisyystason mittaamiseksi kiteytysprosessin aikana. Kalibrointirutiinin kehittämiseen kuuluivat aineiston hyvyyden tarkastelumenetelmät, aineiston esikäsittelymenetelmät, varsinainen kalibrointimallinnus sekä mallin validointi. Näin saadaan reaaliaikaista informaatiota kiteytysprosessin ajavasta voimasta, mikä edelleen parantaa kyseisen prosessin tuntemusta ja hallittavuutta. Ylikylläisyystason vaikutuksia syntyvän kidetuotteen laatuun seurattiin usein kiteytyskokein. Työssä on esitetty myös monimuuttujaiseen tilastolliseen prosessinseurantaan perustuva menetelmä, jolla voidaan ennustaa spontaania primääristä ytimenmuodostumishetkeä mitatusta spektriaineistosta sekä mahdollisesti päätellä ydintymisessä syntyvä polymorfimuoto. Ehdotettua menetelmää hyödyntäen voidaan paitsi ennakoida kideytimien muodostumista myös havaita mahdolliset häiriötilanteet kiteytysprosessin alkuhetkillä. Syntyvää polymorfimuotoa ennustamalla voidaan havaita ei-toivotun polymorfin ydintyminen,ja mahdollisesti muuttaa kiteytyksen ohjausta halutun polymorfimuodon saavuttamiseksi. Monimuuttujamenetelmiä sovellettiin myös kiteytyspanosten välisen vaihtelun määrittämiseen mitatusta spektriaineistosta. Tämäntyyppisestä analyysistä saatua informaatiota voidaan hyödyntää kiteytysprosessien suunnittelussa ja optimoinnissa. Väitöstyössä testattiin IR spektroskopian ja erilaisten monimuuttujamenetelmien soveltuvuutta kidetuotteen polymorfikoostumuksen nopeaan määritykseen. Jauhemaisten näytteiden luokittelu eri polymorfeja sisältäviin näytteisiin voitiin tehdä käyttäen tarkoitukseen soveltuvia monimuuttujaisia luokittelumenetelmiä. Tämä tarjoaa nopean menetelmän jauhemaisen näytteen polymorfikoostumuksen karkeaan arviointiin, eli siihen mitä yksittäistä polymorfia kyseinen näyte pääasiassa sisältää. Varsinainen kvantitatiivinen analyysi, eli sen selvittäminen paljonko esim. painoprosentteina näyte sisältää eri polymorfeja, vaatii kaikki polymorfit kattavan fysikaalisen kalibrointisarjan, mikä voi olla puhtaiden polymorfien huonon saatavuuden takia hankalaa.

Control and Simulation of Batch Crystallization

Concerning process control of batch cooling crystallization the present work focused on the cooling profile and seeding technique. Secondly, the influence of additives on batch-wise precipitation process was investigated. Moreover, a Computational Fluid Dynamics (CFD) model for simulation of controlled batch cooling crystallization was developed. A novel cooling model to control supersaturation level during batch-wise cooling crystallization was introduced. The crystallization kinetics together with operating conditions, i.e. seed loading, cooling rate and batch time, were taken into account in the model. Especially, the supersaturation- and suspension density- dependent secondary nucleation was included in the model. The interaction between the operating conditions and their influence on the control target, i.e. the constant level of supersaturation, were studied with the aid of a numerical solution for the cooling model. Further, the batch cooling crystallization was simulated with the ideal mixing model and CFD model. The moment transformation of the population balance, together with the mass and heat balances, were solved numerically in the simulation. In order to clarify a relationship betweenthe operating conditions and product sizes, a system chart was developed for anideal mixing condition. The utilization of the system chart to determine the appropriate operating condition to meet a required product size was introduced. With CFD simulation, batch crystallization, operated following a specified coolingmode, was studied in the crystallizers having different geometries and scales. The introduced cooling model and simulation results were verified experimentallyfor potassium dihydrogen phosphate (KDP) and the novelties of the proposed control policies were demonstrated using potassium sulfate by comparing with the published results in the literature. The study on the batch-wise precipitation showed that immiscible additives could promote the agglomeration of a derivative of benzoic acid, which facilitated the filterability of the crystal product.

Towards desired crystalline product properties: In-situ monitoring of batch crystallization

The objective of industrial crystallization is to obtain a crystalline product which has the desired crystal size distribution, mean crystal size, crystal shape, purity, polymorphic and pseudopolymorphic form. Effective control of the product quality requires an understanding of the thermodynamics of the crystallizing system and the effects of operation parameters on the crystalline product properties. Therefore, obtaining reliable in-line information about crystal properties and supersaturation, which is the driving force of crystallization, would be very advantageous. Advanced techniques, such asRaman spectroscopy, attenuated total reflection Fourier transform infrared (ATR FTIR) spectroscopy, and in-line imaging techniques, offer great potential for obtaining reliable information during crystallization, and thus giving a better understanding of the fundamental mechanisms (nucleation and crystal growth) involved. In the present work, the relative stability of anhydrate and dihydrate carbamazepine in mixed solvents containing water and ethanol were investigated. The kinetics of the solvent mediated phase transformation of the anhydrate to hydrate in the mixed solvents was studied using an in-line Raman immersion probe. The effects of the operation parameters in terms of solvent composition, temperature and the use of certain additives on the phase transformation kineticswere explored. Comparison of the off-line measured solute concentration and the solid-phase composition measured by in-line Raman spectroscopy allowedthe identification of the fundamental processes during the phase transformation. The effects of thermodynamic and kinetic factors on the anhydrate/hydrate phase of carbamazepine crystals during cooling crystallization were also investigated. The effect of certain additives on the batch cooling crystallization of potassium dihydrogen phosphate (KDP) wasinvestigated. The crystal growth rate of a certain crystal face was determined from images taken with an in-line video microscope. An in-line image processing method was developed to characterize the size and shape of thecrystals. An ATR FTIR and a laser reflection particle size analyzer were used to study the effects of cooling modes and seeding parameters onthe final crystal size distribution of an organic compound C15. Based on the obtained results, an operation condition was proposed which gives improved product property in terms of increased mean crystal size and narrowersize distribution.

A mechanism of carbapenem resistance due to a new insertion element (ISPa133) in Pseudomonas aeruginosa

This study explored the evolutionary mechanism by which the clinical isolate PA110514 yields the imipenemresistant derivative PA116136. Both isolates were examined by PFGE and SDS-PAGE, which led to the identification of a new insertion sequence, ISPa133. This element was shown to have distinct chromosomal locations in each of the original isolates that appeared to explain the differences in imipenem susceptibilty. In strain PA110514, ISPa133 is located 56 nucleotides upstream of the translational start codon, which has no effect on expression of the porin OprD. However, in strain PA116136 ISPa133 it is located in front of nucleotide 696 and, by interrupting the coding region, causes a loss of OprD expression, thus conferring imipenem resistance. In vitro experiments mimicking the natural conditions of selective pressure yielded imipenem-resistant strains in which ISPa133 similarly interrupted oprD. A mechanism is proposed whereby ISPa133 acts as a mobile switch, with its position in oprD depending on the degree of selective pressure exerted by imipenem

A mechanism of carbapenem resistance due to a new insertion element (ISPa133) in Pseudomonas aeruginosa

This study explored the evolutionary mechanism by which the clinical isolate PA110514 yields the imipenemresistant derivative PA116136. Both isolates were examined by PFGE and SDS-PAGE, which led to the identification of a new insertion sequence, ISPa133. This element was shown to have distinct chromosomal locations in each of the original isolates that appeared to explain the differences in imipenem susceptibilty. In strain PA110514, ISPa133 is located 56 nucleotides upstream of the translational start codon, which has no effect on expression of the porin OprD. However, in strain PA116136 ISPa133 it is located in front of nucleotide 696 and, by interrupting the coding region, causes a loss of OprD expression, thus conferring imipenem resistance. In vitro experiments mimicking the natural conditions of selective pressure yielded imipenem-resistant strains in which ISPa133 similarly interrupted oprD. A mechanism is proposed whereby ISPa133 acts as a mobile switch, with its position in oprD depending on the degree of selective pressure exerted by imipenem

A mechanism of carbapenem resistance due to a new insertion element (ISPa133) in Pseudomonas aeruginosa

This study explored the evolutionary mechanism by which the clinical isolate PA110514 yields the imipenemresistant derivative PA116136. Both isolates were examined by PFGE and SDS-PAGE, which led to the identification of a new insertion sequence, ISPa133. This element was shown to have distinct chromosomal locations in each of the original isolates that appeared to explain the differences in imipenem susceptibilty. In strain PA110514, ISPa133 is located 56 nucleotides upstream of the translational start codon, which has no effect on expression of the porin OprD. However, in strain PA116136 ISPa133 it is located in front of nucleotide 696 and, by interrupting the coding region, causes a loss of OprD expression, thus conferring imipenem resistance. In vitro experiments mimicking the natural conditions of selective pressure yielded imipenem-resistant strains in which ISPa133 similarly interrupted oprD. A mechanism is proposed whereby ISPa133 acts as a mobile switch, with its position in oprD depending on the degree of selective pressure exerted by imipenem

Correlations of glycogen synthase and phosphorylase activities with glycogen concentration in human muscle biopsies. Evidence for a double-feedback mechanism regulating glycogen synthesis and breakdown.

The purpose of this study was to verify in man the relationships of muscle glycogen synthase and phosphorylase activities with glycogen concentration that were reported in animal studies. The upper level of glycogen concentration in muscle is known to be tightly controlled, and glycogen concentration was reported to have an inhibitory effect on synthase activity and a stimulatory effect on phosphorylase activity. Glycogen synthase and phosphorylase activity and glycogen concentration were measured in muscle biopsies in a group of nine normal subjects after stimulating an increase of their muscle glycogen concentration through either an intravenous glucose-insulin infusion to stimulate glycogen synthesis, or an Intralipid (Vitrum, Stockholm, Sweden) infusion in the basal state to inhibit glycogen mobilization by favoring lipid oxidation at the expense of glucose oxidation. Phosphorylase activity increased from 71.3 +/- 21.0 to 152.8 +/- 20.0 nmol/min/mg protein (P < .005) after the glucose-insulin infusion. Phosphorylase activity was positively correlated with glycogen concentration (P = .005 and P = .0001) after the glucose-insulin and Intralipid infusions, respectively. Insulin-stimulated glycogen synthase activity was significantly negatively correlated with glycogen concentration at the end of the Intralipid infusion (P < .005). In conclusion, by demonstrating a negative correlation of glycogen concentration with glycogen synthase and a positive correlation with phosphorylase, this study might confirm in man the double-feedback mechanism by which changes in glycogen concentration regulate glycogen synthase and phosphorylase activities. It suggests that this mechanism might play an important role in the regulation of glucose storage.

The death receptor antagonist FAIM promotes neurite outgrowth by a mechanism that depends on ERK and NF-κB signaling

Fas apoptosis inhibitory molecule (FAIM) is a protein identified as an antagonist of Fas-induced cell death. We show that FAIM overexpression fails to rescue neurons from trophic factor deprivation, but exerts a marked neurite growth–promoting action in different neuronal systems. Whereas FAIM overexpression greatly enhanced neurite outgrowth from PC12 cells and sympathetic neurons grown with nerve growth factor (NGF), reduction of endogenous FAIM levels by RNAi decreased neurite outgrowth in these cells. FAIM overexpression promoted NF-κB activation, and blocking this activation by using a super-repressor IκBα or by carrying out experiments using cortical neurons from mice that lack the p65 NF-κB subunit prevented FAIM-induced neurite outgrowth. The effect of FAIM on neurite outgrowth was also blocked by inhibition of the Ras–ERK pathway. Finally, we show that FAIM interacts with both Trk and p75 neurotrophin receptor NGF receptors in a ligand-dependent manner. These results reveal a new function of FAIM in promoting neurite outgrowth by a mechanism involving activation of the Ras–ERK pathway and NF-κB.

The monocarboxylate transporter MCT4 : mechanism of regulation in astrocytes and its putative role in cerebral ischemia

Despite its small fraction of the total body weight (2%), the brain contributes for 20% and 25% respectively of the total oxygen and glucose consumption of the whole body. Indeed, glucose has been considered the energy substrate par excellence for the brain. However, evidence accumulated over the last half century revealed an important role for the monocarboxylate lactate in fulfilling the energy needs of neurons. This is particularly true during physiological neuronal activation and in pathological conditions. Lactate transport into and out of the cell is mediated by a family of proton-linked transporters called monocarboxylate transporters (MCTs). In the central nervous system, only three of them have been well characterized: MCT2 is the predominant neuronal isoform, while the other non¬neuronal cell types of the brain express the ubiquitous isoform MCT1. Quite recently, the MCT4 isoform has been described in astrocytes. Due to its high transport capacity compared to the other two isoforms, MCT4 is particularly adapted for glycolytic cells. Because of its recent discovery in the brain, nothing was known about its regulation in the central nervous system. Here we show that MCT4 is regulated by oxygen levels in primary cultures of astrocytes in a time- and concentration-dependent manner via the hypoxia inducible factor-la (HIF-la). Moreover, we showed that MCT4 expression is essential for astrocyte survival under low oxygen conditions. In parallel, we investigated the possible implication of the pyruvate kinase isoform Pkm2, a strong enhancer of glycolysis, in its regulation. Then we showed that MCT4 expression, as well as the expression of the other two MCT isoforms, is altered in a murine model of stroke. Surprisingly, neurons started to express MCT4, as well as MCT1, under such conditions. Altogether, these data suggest that MCT4, due to its high transport capacity for lactate, may be the isoform that enables cells to operate a major metabolic adaptation in response to pathological situations that alter metabolic homeostasis of the brain. -- Le cerveau représente 2% du poids corporel total, mais il contribue pour 20% de la consommation totale d'oxygène et 25% de celle de glucose au repos. Le glucose est considéré comme le substrat énergétique par excellence pour le cerveau. Néanmoins, depuis un demi- siècle maintenant, de plus en plus de travaux ont démontré que le lactate joue un rôle majeur dans le métabolisme cérébral et est capable du subvenir aux besoins énergétiques des neurones. Le lactate est tout particulièrement nécessaire pendant l'activation neuronale ainsi qu'en situation pathologique. Le transport du lactate à travers la barrière hématoencéphalique ainsi qu'à travers les membranes cellulaires est assuré par la famille des transporteurs aux monocarboxylates (MCTs). Dans le système nerveux central, uniquement trois d'entre eux ont été décrits: MCT2 est considéré comme le transporteur neuronal, alors que les autres types cellulaires qui constituent le cerveau expriment l'isoforme ubiquitaire MCT1. Récemment, l'isoforme MCT4 a été rapportée sur les astrocytes. Dû à sa grande capacité de transport pour le lactate, MCT4 est tout particulièrement adapté pour soutenir le métabolisme des cellules hautement glycolytiques, comme les astrocytes. En raison de sa toute récente découverte, les aspects comprenant sa régulation et son rôle dans le cerveau sont pour l'instant méconnus. Les résultats exposés dans ce travail démontrent dans un premier temps que l'expression de MCT4 est régulée par les niveaux d'oxygène dans les cultures d'astrocytes corticaux par le biais du facteur de transcription HIF-la. De plus, nous avons démontré que l'expression de MCT4 est essentielle à la survie des astrocytes quand le niveau d'oxygénation baisse. En parallèle, des résultats préliminaires suggèrent que l'isoforme 2 de la pyruvate kinase, un puissant régulateur de la glycolyse, pourrait jouer un rôle dans la régulation de MCT4. Dans la deuxième partie du travail nous avons démontré que l'expression de MCT4, ainsi que celle de MCT1 et MCT2, est altérée dans un modèle murin d'ischémie cérébrale. De façon surprenante, les neurones expriment MCT4 dans cette condition, alors que ce n'est pas le cas en condition physiologique. En tenant compte de ces résultats, nous suggérons que MCT4, dû à sa particulièrement grande capacité de transport pour le lactate, représente le MCT qui permet aux cellules du système nerveux central, notamment les astrocytes et les neurones, de s'adapter à de très fortes perturbations de l'homéostasie métabolique du cerveau qui surviennent en condition pathologique.