Intracortical connectivity of layer VI pyramidal neurons in the somatosensory cortex of normal and barrelless mice.

In mice, barrels in layer IV of the somatosensory cortex correspond to the columnar representations of whisker follicles. In barrelless (BRL) mice, barrels are absent, but functionally, a columnar organization persists. Previously we characterized the aberrant geometry of thalamic projection of BRL mice using axonal reconstructions of individual neurons. Here we proceeded with the analysis of the intracortical projections from layer VI pyramidal neurons, to assess their contribution to the columnar organization. From series of tangential sections we reconstructed the axon collaterals of individual layer VI pyramidal neurons in the C2 barrel column that were labelled with biocytin [controls from normal (NOR) strain, 19 cells; BRL strain, nine cells]. Using six morphological parameters in a cluster analysis, we showed that layer VI neurons in NOR mice are distributed into four clusters distinguished by the radial and tangential extent of their intracortical projections. These clusters correlated with the cortical or subcortical projection of the main axon. In BRL mice, neurons were distributed within the same four clusters, but their projections to the granular and supragranular layers were significantly smaller and their tangential projection was less columnar than in NOR mice. However, in both strains the intracortical projections had a preference for the appropriate barrel column (C2), indicating that layer VI pyramidal cells could participate in the functional columnar organization of the barrel cortex. Correlative light and electron microscopy analyses provided morphometric data on the intracortical synaptic boutons and synapses of layer VI pyramidal neurons and revealed that projections to layer IV preferentially target excitatory dendritic spines and shafts.

Prenatal Exposure to DEHP Affects Spermatogenesis and Sperm DNA Methylation in a Strain-Dependent Manner.

Di-(2-ethylhexyl)phtalate (DEHP) is a plasticizer with endocrine disrupting properties found ubiquitously in the environment and altering reproduction in rodents. Here we investigated the impact of prenatal exposure to DEHP on spermatogenesis and DNA sperm methylation in two distinct, selected, and sequenced mice strains. FVB/N and C57BL/6J mice were orally exposed to 300 mg/kg/day of DEHP from gestation day 9 to 19. Prenatal DEHP exposure significantly decreased spermatogenesis in C57BL/6J (fold-change = 0.6, p-value = 8.7*10-4), but not in FVB/N (fold-change = 1, p-value = 0.9). The number of differentially methylated regions (DMRs) by DEHP-exposure across the entire genome showed increased hyper- and decreased hypo-methylation in C57BL/6J compared to FVB/N. At the promoter level, three important subsets of genes were massively affected. Promoters of vomeronasal and olfactory receptors coding genes globally followed the same trend, more pronounced in the C57BL/6J strain, of being hyper-methylated in DEHP related conditions. In contrast, a large set of micro-RNAs were hypo-methylated, with a trend more pronounced in the FVB/N strain. We additionally analyze both the presence of functional genetic variations within genes that were associated with the detected DMRs and that could be involved in spermatogenesis, and DMRs related with the DEHP exposure that affected both strains in an opposite manner. The major finding in this study indicates that prenatal exposure to DEHP can decrease spermatogenesis in a strain-dependent manner and affects sperm DNA methylation in promoters of large sets of genes putatively involved in both sperm chemotaxis and post-transcriptional regulatory mechanisms.

Determination of displacement, stress- and strain-distribution in the human heart: a FE-model on the basis of MR imaging.

The determination of characteristic cardiac parameters, such as displacement, stress and strain distribution are essential for an understanding of the mechanics of the heart. The calculation of these parameters has been limited until recently by the use of idealised mathematical representations of biventricular geometries and by applying simple material laws. On the basis of 20 short axis heart slices and in consideration of linear and nonlinear material behaviour we have developed a FE model with about 100,000 degrees of freedom. Marching Cubes and Phong's incremental shading technique were used to visualise the three dimensional geometry. In a quasistatic FE analysis continuous distribution of regional stress and strain corresponding to the endsystolic state were calculated. Substantial regional variation of the Von Mises stress and the total strain energy were observed at all levels of the heart model. The results of both the linear elastic model and the model with a nonlinear material description (Mooney-Rivlin) were compared. While the stress distribution and peak stress values were found to be comparable, the displacement vectors obtained with the nonlinear model were generally higher in comparison with the linear elastic case indicating the need to include nonlinear effects.

Physical activity attenuates the influence of FTO variants on obesity risk: a meta-analysis of 218,166 adults and 19,268 children.

BACKGROUND: The FTO gene harbors the strongest known susceptibility locus for obesity. While many individual studies have suggested that physical activity (PA) may attenuate the effect of FTO on obesity risk, other studies have not been able to confirm this interaction. To confirm or refute unambiguously whether PA attenuates the association of FTO with obesity risk, we meta-analyzed data from 45 studies of adults (n = 218,166) and nine studies of children and adolescents (n = 19,268). METHODS AND FINDINGS: All studies identified to have data on the FTO rs9939609 variant (or any proxy [r(2)>0.8]) and PA were invited to participate, regardless of ethnicity or age of the participants. PA was standardized by categorizing it into a dichotomous variable (physically inactive versus active) in each study. Overall, 25% of adults and 13% of children were categorized as inactive. Interaction analyses were performed within each study by including the FTO×PA interaction term in an additive model, adjusting for age and sex. Subsequently, random effects meta-analysis was used to pool the interaction terms. In adults, the minor (A-) allele of rs9939609 increased the odds of obesity by 1.23-fold/allele (95% CI 1.20-1.26), but PA attenuated this effect (p(interaction)  = 0.001). More specifically, the minor allele of rs9939609 increased the odds of obesity less in the physically active group (odds ratio  = 1.22/allele, 95% CI 1.19-1.25) than in the inactive group (odds ratio  = 1.30/allele, 95% CI 1.24-1.36). No such interaction was found in children and adolescents. CONCLUSIONS: The association of the FTO risk allele with the odds of obesity is attenuated by 27% in physically active adults, highlighting the importance of PA in particular in those genetically predisposed to obesity.

Evaluation of prenatal ultrasound diagnosis of fetal abdominal wall defects by 19 European registries.

OBJECTIVES: To evaluate the current effectiveness of routine prenatal ultrasound screening in detecting gastroschisis and omphalocele in Europe. DESIGN: Data were collected by 19 congenital malformation registries from 11 European countries. The registries used the same epidemiological methodology and registration system. The study period was 30 months (July 1st 1996-December 31st 1998) and the total number of monitored pregnancies was 690,123. RESULTS: The sensitivity of antenatal ultrasound examination in detecting omphalocele was 75% (103/137). The mean gestational age at the first detection of an anomaly was 18 +/- 6.0 gestational weeks. The overall prenatal detection rate for gastroschisis was 83% (88/106) and the mean gestational age at diagnosis was 20 +/- 7.0 gestational weeks. Detection rates varied between registries from 25 to 100% for omphalocele and from 18 to 100% for gastroschisis. Of the 137 cases of omphalocele less than half of the cases were live births (n = 56; 41%). A high number of cases resulted in fetal deaths (n = 30; 22%) and termination of pregnancy (n = 51; 37%). Of the 106 cases of gastroschisis there were 62 (59%) live births, 13 (12%) ended with intrauterine fetal death and 31 (29%) had the pregnancies terminated. CONCLUSIONS: There is significant regional variation in detection rates in Europe reflecting different policies, equipment and the operators' experience. A high proportion of abdominal wall defects is associated with concurrent malformations, syndromes or chromosomal abnormalities, stressing the need for the introduction of repeated detailed ultrasound examination as a standard procedure. There is still a relatively high rate of elective termination of pregnancies for both defects, even in isolated cases which generally have a good prognosis after surgical repair.

Administering brief motivational interventions to young men: Results from a pilot census transmissible study among 19 year-old francophone Swiss men.

AIMS - To pilot the implementation of brief motivational intervention (BMI) among conscripts, and to test the effectiveness of BMI in young men voluntarily showing up for a single face-to-face alcohol BMI session. Participants were conscripts attending the army recruitment process in Lausanne. This process is mandatory for all Swiss males at age 19 and Lausanne serves all francophone Swiss men. METHODS - Of 3'227 young men that were seen during the army recruitment procedures, 445 voluntarily showed up for a BMI and 367 were included in the study (exclusions were random and unsystematic and related to organizational aspects in the recruitment center). After an initial assessment, subjects were randomized into two groups: an immediate BMI and a 6-month delayed BMI (waiting list design). A 6-month follow-up assessment was conducted in both groups. BMI was a face-to-face 20 minutes counseling session with a psychologist trained in motivational interviewing at baseline and a telephone session for the control group at follow-up. Strategies of BMI included the exploration and evocation of a possible behavior change, importance of future change, readiness to change, and commitment to change. A filmed example of such an intervention is available in French at www.alcoologie.ch. RESULTS - All procedures are now fully implemented and working and the provision of preventive efforts found general approval by the army. 3'227 were eligible for BMI and 445 of them (13.8%) showed up for receiving a BMI. 367 were included in the study, 181 in the BMI group and 186 in the control group. More than 86% of those included were reached at follow-up. With one exception all findings on alcohol use went in the expected direction, i.e. a stronger decrease in alcohol use (or a smaller increase as for usual weekly drinking amount) in the BMI group. The risk for risky single occasion drinking (RSOD) decreased from 57% at-risk users at baseline to 50.6%, i.e. a 6.4% point decrease in the BMI group, while there was only a 0.6% point decrease (from 57.5% to 56.9%) in the control group. Moreover, the study showed that there was a likelihood of crossover effects for other substances like tobacco smoking and cannabis use. Despite these encouraging and consistent positive findings, none reached significance at conventional levels (p < 0.05). DISCUSSION - Data suggest a beneficial impact of BMI on alcohol use outcomes and potential effect on other substance use in 19-year old men attending the army recruitment and showing up voluntarily for BMI. As the main aim was to implement and test feasibility of conducting BMI in this setting none of our findings reached statistical significance. The consistency of findings across measures and substances, however, raises hope that non-significance in the present study does not mean no effect, but mainly insufficient power of this pilot study. [Authors]

Relations of the job demands-control-support model of job strain with personality attributes : a cross-cultural study in Switzerland and South Africa

Among the various work stress models, one of the most popular to date is the job demands-­‐control (JDC) model developed by Karasek (1979), which postulates that work-­‐related strain will be the highest under work conditions characterized by high demands and low autonomy. The absence of social support at work will further increase negative outcomes. However, this model does not apply equally to all individuals and to all cultures. In the following studies, we assessed work characteristics, personality traits, culture-­‐driven individual attributes, and work-­‐related health outcomes, through the administration of questionnaires. The samples consist of Swiss (n = 622) and South African (n = 879) service-­‐oriented employees (from health, finance, education and commerce sectors) and aged from 18 to 65 years old. Results generally confirm the universal contribution of high psychological demands, low decision latitude and low supervisor support at work, as well as high neuroticism predict the worse health outcomes among employees in both countries. Furthermore, low neuroticism plays a moderating role between psychological demands and burnout, while high openness and high conscientiousness each play a moderating role between decision latitude and burnout in South Africa. Results also reveal that culture-­‐driven individual attributes play a role in both countries, but in a unique manner and according to the ethnic group of belonging. Given that organizations are increasingly characterized with multicultural employees as well as increasingly adverse and complex job conditions, our results help in identifying more updated and refined dynamics that are key between the employee and the work environment in today's context. -- L'un des modèles sur le stress au travail des plus répandus est celui développé par Karasek (1979), qui postule qu'une mauvaise santé chez les employés résulte d'une combinaison de demandes psychologiques élevées, d'une latitude décisionnelle faible et de l'absence de soutien social au travail. Néanmoins, ce modèle ne s'applique pas de façon équivalente chez tous les individus et dans toutes les cultures. Dans les études présentées, nous avons mesuré les caractéristiques de travail, les traits de personnalité, les traits culturels et les effets lies à la santé à l'aide de questionnaires. L'échantillon provient de la Suisse (n = 622) et de l'Afrique du Sud (n = 879) et comprend des employés de domaines divers en lien avec le service (notamment des secteurs de la santé, finance, éducation et commerce) tous âgés entre 18 et 65 ans. Les résultats confirment l'universalité des effets directs des demandes au travail, la latitude décisionnelle faible, le soutien social faible provenant du supérieur hiérarchique, ainsi que le névrosisme élevé qui contribuent à un niveau de santé faible au travail, et ce, dans les deux pays. De plus, un niveau faible de névrosisme a un effet de modération entre les demandes au travail et l'épuisement professionnel, alors que l'ouverture élevée et le caractère consciencieux élevé modèrent la relation entre la latitude décisionnelle et l'épuisement professionnel en Afrique du Sud. Nous avons aussi trouvé que les traits culturels jouent un rôle dans les deux pays, mais de façon unique et en fonction du groupe ethnique d'appartenance. Sachant que les organisations sont de plus en plus caractérisées par des employés d'origine ethnique variées, et que les conditions de travail se complexifient, nos résultats contribuent à mieux comprendre les dynamiques entre l'employé et l'environnement de travail contemporain. personnalité, différences individuelles, comparaisons culturelles, culture, stress au travail, épuisement professionnel, santé des employés.

Rapid bacterial genome sequencing: methods and applications in clinical microbiology.

The recent advances in sequencing technologies have given all microbiology laboratories access to whole genome sequencing. Providing that tools for the automated analysis of sequence data and databases for associated meta-data are developed, whole genome sequencing will become a routine tool for large clinical microbiology laboratories. Indeed, the continuing reduction in sequencing costs and the shortening of the 'time to result' makes it an attractive strategy in both research and diagnostics. Here, we review how high-throughput sequencing is revolutionizing clinical microbiology and the promise that it still holds. We discuss major applications, which include: (i) identification of target DNA sequences and antigens to rapidly develop diagnostic tools; (ii) precise strain identification for epidemiological typing and pathogen monitoring during outbreaks; and (iii) investigation of strain properties, such as the presence of antibiotic resistance or virulence factors. In addition, recent developments in comparative metagenomics and single-cell sequencing offer the prospect of a better understanding of complex microbial communities at the global and individual levels, providing a new perspective for understanding host-pathogen interactions. Being a high-resolution tool, high-throughput sequencing will increasingly influence diagnostics, epidemiology, risk management, and patient care.

Dibenzofuran degradation by Sphingomonas wittichii RW1 under environmental stresses

Sphingomonas wittichii is a gram-negative Alpha-proteobacterium, capable of degrading xenobiotic compounds such as dibenzofuran (DBF), dibenzo-p-dioxin, carbazole, 2-hydroxybiphenyl or nitro diphenyl ether herbicides. The metabolism of strain RW1 has been the subject of previous studies and a number of genes involved in DBF degradation have been characterized. It is known that RW1 posseses a unique initial DBF dioxygenase (encoded by the dxnAl gene) that catalyzes the first step in the degradation pathway. None of the organisms known to be able to degrade DBF have a similar dioxygenase, the closest match being the DBF dioxygenase from Rhodococcus sp. with an overall amino acid similarity of 45%. Genes participating in the conversion of the metabolite salicylate via the ortho-cleavage pathway to TCA cycle intermediates were identified as well. Apart from this scarce information, however, there is a lack of global knowledge on the genes that are involved in DBF degradation by strain RW1 and the influence of environmental stresses on DBF-dependent global gene expression. A global analysis is necessary, because it may help to better understand the behaviour of the strain under field conditions and suggest improvements for the current bioaugmentation practice. Chapter 2 describes the results of whole-genome analysis to characterize the genes involved in DBF degradation by RW1. Micro-array analysis allowed us to detect differences in gene transcription when strain RW1 was exposed to DBF. This was complemented by ultra-high throughput sequencing of mutants no longer capable of growing on salicylate and DBF. Some of the genes of the ortho-cleavage pathway were induced 2 to 4 times in the presence of DBF, as well as the initial DBF dioxygenase. However two gene clusters, named 4925 and 5102 were induced up to 19 times in response to DBF induction. The cluster 4925 is putatively participating in a meta-cleavage pathway while the cluster 5102 might be part of a gentisate pathway. The three pathways, ortho-cleavage, meta-cleavage and gentisate pathway seem to be active in parallel when strain RW1 is exposed to DBF, presenting evidence for a redundancy of genes for DBF degradation in the genome of RW1. Chapter 3 focuses on exploiting genetic tools to construct bioreporters representative for DBF degradation in RW1. A set of basic tools for genetic manipulation in Sphingomonas wittichii RW1 was tested and optimized. Both plasmids and mini-transposons were evaluated for their ability to be maintained in RW1 with or without antibiotic selection pressure, and for their ability to lead to fluorescent protein expression in strain RW1 from a constitutive promoter. Putative promoter regions of three of the previously found DBF-induced genes (Swit_4925, Swit_5102 and Swit_4897-dxnAl) were then used to construct eg/^-bioreporters in RW1. Chapter 4 describes the use of the constructed RW1-based bioreporter strains for examining the expression of the DBF degradation pathway genes under microcosm conditions. The bioreporter strains were first exposed to different carbon sources in liquid culture to calibrate the egfp induction. Contrary to our expectations from micro-array analysis only the construct with the promoter from gene cluster 4925 responded to DBF, whereas the other two constructs did not show specific induction with DBF. The response from the bioreporters was subsequently tested for sensitivity to water stress, given that this could have an important impact in soils. Exposure to liquid cultures with decreasing water potential, achieved by NaCl or PEG addition to the growth media, showed that eGFP expression in RW1 from the promoter regions 4925 and 5102 was not directly influenced by water stress, but only through an overall reduction in growth rate. In contrast, expression of eGFP from the dxnAl or an uspA promoter was also directly dependent on the extent of water stress. The RW1 with the 4925 construct was subsequently used in soil microcosms to evaluate DBF bioavailability to the cells in presence or absence of native microbiota or other contaminated material. We found that RW1 could grow on DBF added to soil, but bioreporter expression suggested that competition with native microbiota for DBF intermediates may limit its ability to proliferate to a maximum. Chapter 5 describes the results from the experiments carried out to more specifically detect genes of RW1 that might be implicated in water stress resistance. Hereto we created transposon mutagenesis libraries in RW1, either with a classical mini-Tn5 or with a variant that would express egfp when the transposon would insert in a gene induced under water stress. Classical mutant libraries were screened by replica plating under high and low water stress conditions (achieved by adding NaCl to the agar medium). In addition, we screened for smaller microcolonies formed by mutants in agarose beads that could be analized with flow cytometry. A number of mutants impaired to grow on NaCl-supplemented media were recovered and the transposon insertion sites sequenced. In a second procedure we screened by flow cytometry for mutants with a higher eGFP production after exposure to growth medium with higher NaCl concentrations. Mutants from both libraries rarely overlapped. Discovered gene functions of the transposon insertions pointed to compatible solute synthesis (glutamate and proline), cell membrane synthesis and modification of cell membrane composition. The results obtained in the present study give us a more complete picture of the mechanisms of DBF degradation by S. wittichii RW1, how it reacts to different DBF availability and how the DBF catabolic activity may be affected by the conditions found in contaminated environments. - Sphingomonas wittichii est une alpha-protéobactérie gram-négative, capable de dégrader des composés xénobiotiques tels que le dibenzofurane (DBF), la dibenzo-p-dioxine, le carbazole, le 2-hydroxybiphényle ou les herbicides dérivés du nitro-diphényléther. Le métabolisme de la souche RW1 a fait l'objet d'études antérieures et un certain nombre de gènes impliqués dans la dégradation du DBF ont été caractérisés. Il est connu que RW1 possède une unique dioxygénase DBF initiale (codée par le gène dxnAl) qui catalyse la première étape de la voie de dégradation. Aucun des organismes connus pour être capables de dégrader le DBF n'a de dioxygénase similaire. L'enzyme la plus proche étant la DBF dioxygénase de Rhodococcus sp. avec 45% d'acides aminés conservés. Les gènes qui participent à la transformation du salicylate en métabolites intermédiaires du cycle de Krebs par la voie ort/io-cleavage ont aussi été identifiés. Outre ces informations lacunaires, il y a un manque de connaissances sur l'ensemble des gènes impliqués dans la dégradation du DBF par la souche RW1 ainsi que l'effet des stress environnementaux sur l'expression génétique globale, en présence du DBF. Une analyse globale est nécessaire, car elle peut aider à mieux comprendre le comportement de la souche dans les conditions de terrain et de proposer des améliorations pour l'utilisation de la bio-augmentation comme technique de bio-remédiation. Le chapitre 2 décrit les résultats de l'analyse du génome pour caractériser les gènes impliqués dans la dégradation du DBF par RW1. Une analyse de micro-arrays nous a permis de détecter des différences dans la transcription des gènes lorsque la souche RW1 a été exposée au DBF. L'analyse a été complétée par le criblage à ultra-haut débit de mutants qui n'étaient plus capables de croître avec le salicylate ou le DBF comme seule source de carbone. Certains des gènes de la voie ortho-cleavage, dont la DBF dioxygénase initiale, ont xî été induits 2 à 4 fois, en présence du DBF. Cependant, deux groupes de gènes, nommés 4925 et 5102 ont été induits jusqu'à 19 fois en réponse au DBF. Le cluster 4925 participe probablement dans une voie de meta-cleavage tandis que le cluster 5102 pourrait faire partie d'une voie du gentisate. Les trois voies, ortho-cleavage, meta-cleavage et la voie du gentisate semblent être activées en parallèle lorsque la souche RW1 est exposée au DBF, ce qui représente une redondance de voies pour la dégradation du DBF dans le génome de RW1. Le chapitre 3 se concentre sur l'exploitation des outils génétiques pour la construction de biorapporteurs de la dégradation du DBF par RW1. Un ensemble d'outils de base pour la manipulation génétique dans Sphingomonas wittichii RW1 a été testé et optimisé. Deux plasmides et mini-transposons ont été évalués pour leur capacité à être maintenu dans RW1 avec ou sans pression de sélection par des antibiotiques, et pour leur capacité à exprimer la protéine fluorescente verte (eGFP) dans la souche RW1. Les trois promoteurs des gènes Swit_4925, Swit_5102 et Swit_4897 (dxnAl), induits en réponse au DBF, ont ensuite été utilisés pour construire des biorapporteurs dans RW1. Le chapitre 4 décrit l'utilisation des souches biorapportrices construites pour l'analyse de l'expression des gènes de la voie de dégradation du DBF dans des microcosmes avec différents types de sols. Les souches biorapportrices ont d'abord été exposées à différentes sources de carbone en cultures liquides afin de calibrer l'induction de la eGFP. La construction avec le promoteur du gène 4925 a permis une réponse au DBF. Mais contrairement à nos attentes, basées sur les résultats de l'analyse des micro-arrays, les deux autres constructions n'ont pas montré d'induction spécifique au DBF. La réponse des biorapporteurs a ensuite été testée pour la sensibilité au stress hydrique, étant donné que cela pourrait avoir un impact important dans les microcosmes. La diminution du potentiel hydrique en culture liquide est obtenue par addition de NaCl ou de PEG au milieu de croissance. Nous avons montré que l'expression de la eGFP contrôlée par les promoteurs 4925 et 5102 n'était pas directement influencée par le stress hydrique, mais seulement par une réduction globale des taux de croissance. En revanche, l'expression de la eGFP dépendante des promoteurs dxnAl et uspA était aussi directement dépendante de l'ampleur du stress hydrique. La souche avec la construction 4925 a été utilisée par la suite dans des microcosmes avec différents types de sols pour évaluer la biodisponibilité du DBF en présence ou absence des microbes indigènes et d'autres composés contaminants. Nous avons constaté que RW1 pouvait se développer si le DBF a été ajouté au sol, mais l'expression de la eGFP par le biorapporteur suggère que la compétition avec la microbiota indigène pour les métabolites intermédiaires du DBF peut limiter sa capacité à proliférer de manière optimale. Le chapitre 5 décrit les résultats des expériences réalisées afin de détecter spécifiquement les gènes de RW1 qui pourraient être impliquées dans la résistance au stress hydrique. Ici on a crée des bibliothèques de mutants de RW1 par transposon, soit avec un mini-Tn5 classique ou avec une variante qui exprime la eGFP lorsque le transposon s'insère dans un gène induit par le stress hydrique. Les bibliothèques de mutants ont été criblées par la méthode classique de repiquage sur boîtes, dans des conditions de stress hydrique élevé (obtenu par l'addition de NaCl dans les boîtes). En outre, nous avons criblé des micro¬colonies dans des billes d'agarose qui ont pu être analysées par cytométrie de flux. Un certain nombre de mutants déficients à croître sur des milieux supplémentés avec du NaCl ont été isolés et les sites d'insertion du transposon séquencés. Dans une deuxième procédure nous avons criblé par cytométrie de flux des mutants avec une production de eGFP supérieure, après exposition à un milieu de croissance avec une concentration élevée de NaCl. Les mutants obtenus dans les deux bibliothèques n'étaient pas similaires. Les fonctions des gènes où se trouvent les insertions de transposons sont impliqués dans la synthèse de solutés compatibles (glutamate et de la proline), dans la synthèse de la membrane cellulaire et dans la modification de la composition de la membrane cellulaire. Les résultats obtenus dans la présente étude nous donnent une image plus complète des mécanismes de dégradation du DBF par S. wittichii RW1, comment cette souche réagit à la disponibilité du DBF et comment l'activité catabolique peut être affectée par les conditions rencontrées dans des environnements contaminés.

Positive Torsional Strain Causes the Formation of a Four-Way Junction at Replication Forks.

Research by L. Postow, C. Ullsperger, R.W. Keller, C. Bustamante, A.V. Vologodskii, and N.R. Cozzarelli, J. Biol. Chem. 2001, 276, 2790 Condensation and commentary by Alexander Bucka and Andrzej Stasiak, Universite ´ de Lausanne, Switzerland Purpose of the Study To demonstrate that positive torsional strain generated during DNA replication can lead to reversals of replication forks and, consequently can result in the formation of four-way DNA junctions

Voriconazole-Induced Inhibition of the Fungicidal Activity of Amphotericin B in Candida Strains with Reduced Susceptibility to Voriconazole: an Effect Not Predicted by the MIC Value Alone.

An antagonistic effect of voriconazole on the fungicidal activity of sequential doses of amphotericin B has previously been demonstrated in Candida albicans strains susceptible to voriconazole. Because treatment failure and the need to switch to other antifungals are expected to occur more often in infections that are caused by resistant strains, it was of interest to study whether the antagonistic effect was still seen in Candida strains with reduced susceptibility to voriconazole. With the hypothesis that antagonism will not occur in voriconazole-resistant strains, C. albicans strains with characterized mechanisms of resistance against voriconazole, as well as Candida glabrata and Candida krusei strains with differences in their degrees of susceptibility to voriconazole were exposed to voriconazole or amphotericin B alone, to both drugs simultaneously, or to voriconazole followed by amphotericin B in an in vitro kinetic model. Amphotericin B administered alone or simultaneously with voriconazole resulted in fungicidal activity. When amphotericin B was administered after voriconazole, its activity was reduced (median reduction, 61%; range, 9 to 94%). Levels of voriconazole-dependent inhibition of amphotericin B activity differed significantly among the strains but were not correlated with the MIC values (correlation coefficient, -0.19; P = 0.65). Inhibition was found in C. albicans strains with increases in CDR1 and CDR2 expression but not in the strain with an increase in MDR1 expression. In summary, decreased susceptibility to voriconazole does not abolish voriconazole-dependent inhibition of the fungicidal activity of amphotericin B in voriconazole-resistant Candida strains. The degree of interaction could not be predicted by the MIC value alone.