Hereditary diffuse leukoencephalopathy with axonal spheroids: More than just a rare disease.

Hereditary diffuse leukoencephalopathy with spheroids (HDLS) is a progressive white matter disease with a wide range of clinical symptoms including dementia, behavioral changes, seizures, pyramidal signs, ataxia, and parkinsonism.(1-3) Affected individuals develop symptoms in their early 40s with an average survival time of 10 years. HDLS is inherited as an autosomal dominant trait. Recently, mutations in the colony-stimulating factor 1 receptor gene (CSF-1R) were identified as the genetic cause of HDLS.(4) White matter lesions, easily demonstrated on MRI studies, involve predominantly the frontal lobes and corpus callosum with subsequent cortical atrophy. MRI abnormalities are present prior to symptom onset.(5,6) Histopathology shows widespread myelin and axon destruction with axonal dilations termed spheroids, as well as pigmented macrophages.

Evaluation pré-post d'une intervention de prévention du VIH auprès des hommes qui ont des rapports sexuels avec des hommes, Suisse 2012

Contexte: L'intervention "Break The Chains" 2012 de l'OFSP a l'intention des gays visait à informer sur la primo-infection et a inciter a un test de dépistage VIH. Design: L'évaluation a recouru a un design Pre-Post avec 2 dispositifs: A) enquête par questionnaire Internet avec une vague avant la campagne et une après (transversal repete); B) 1) relevé centré sur le canton de Zurich du nombre de test effectues par des gays durant le premier semestre 2012 utilisant des données récoltées par Sentinella, par les centres de test utilisant l'application BerDa et auprès des praticiens de HIV-Prakt; et 2) recueil d'information par le questionnaire internet post-intervention des intentions d'effectuer un test VIH. Résultats: 366 HSH ont répondu au questionnaire de la phase pré-, et 964 à la phase post-intervention. 69.8% ont entendu parler de la campagne. Parmi les répondants ayant identifie le message, 48.6% se sont sentis concernes. Avant la campagne, 34.2% des répondants identifiaient les 4 symptômes de la primo-infection, 46.4% se sentaient bien informes et 79.2% connaissaient le délai minimum pour qu'un test informe sur une absence d'infection; après la campagne, ces proportions étaient 39.6%, 62.0% et 85.2%. 17.1% des répondants ont déclaré avoir fait/avoir l'intention de faire, un test VIH suite à la campagne. Le nombre de tests effectues par les répondants Internet montre effectivement un pic dans le 2e trimestre 2012; les données BerDa montrent une stabilité du nombre total de tests. Les données épidémiologiques montrent une augmentation de la proportion et du nombre d'infections récentes détectées durant ce 2e trimestre, mais une diminution des infections anciennes. Conclusions: L'intervention BTC a amélioré légèrement les connaissances relatives à la phase de primo-infection du VIH et a la nécessité d'effectuer un test VIH. Elle semble avoir incite le public cible à effectuer un test VIH qui n'aurait pas été réalisé autrement et a peut-être ainsi contribuer a la détection d'infections récentes.

Plants and tortoises: mutations in the Arabidopsis jasmonate pathway increase feeding in a vertebrate herbivore.

Photosynthetic tissues, the major food source of many invertebrates and vertebrates, are well defended. Many defence traits in leaves are controlled via the jasmonate signalling pathway in which jasmonate acts as a hormone by binding to a receptor to activate responses that lead to increased resistance to invertebrate folivores. We predicted that mutations in jasmonate synthesis might also increase the vulnerability of leaves to vertebrate folivores and tested this hypothesis using the Eastern Hermann's tortoise (Eurotestudo boettgeri) and an Arabidopsis thaliana (Brassicaceae) allene oxide synthase (aos) mutant unable to synthesize jasmonate. Tortoises preferred the aos mutant over the wild type (WT). Based on these results, we then investigated the effect of mutating jasmonate perception using a segregating population of the recessive A. thaliana jasmonate receptor mutant coronatine insensitive1-1 (coi1-1). Genotyping of these plants after tortoise feeding revealed that the homozygous coi1-1 receptor mutant was consumed more readily than the heterozygous mutant or the WT. Therefore, the plant's ability to synthesize or perceive jasmonate reduces feeding by a vertebrate herbivore. We also tested whether or not tortoise feeding behaviour was influenced by glucosinolates, the principal defence chemicals in Arabidopsis leaves with known roles in defence against many generalist insects. However, in contrast to what has been observed with such insects, leaves in which the levels of these compounds were reduced genetically were consumed at a similar rate to those of the WT.

Spectrally selective B1-insensitive T2 magnetization preparation sequence.

A T(2) magnetization-preparation (T(2) Prep) sequence is proposed that is insensitive to B(1) field variations and simultaneously provides fat suppression without any further increase in specific absorption rate (SAR). Increased B(1) inhomogeneity at higher magnetic field strength (B(0) > or = 3T) necessitates a preparation sequence that is less sensitive to B(1) variations. For the proposed technique, T(2) weighting in the image is achieved using a segmented B(1)-insensitive rotation (BIR-4) adiabatic pulse by inserting two equally long delays, one after the initial reverse adiabatic half passage (AHP), and the other before the final AHP segment of a BIR-4 pulse. This sequence yields T(2) weighting with both B(1) and B(0) insensitivity. To simultaneously suppress fat signal (at the cost of B(0) insensitivity), the second delay is prolonged so that fat accumulates additional phase due to its chemical shift. Numerical simulations as well as phantom and in vivo image acquisitions were performed to show the efficacy of the proposed technique.

Direct Effect of Birth Weight on Childhood Blood Pressure: a Causal Mediation Analysis

Background: Numerous studies have shown a negative association between birth weight (BW) and blood pressure (BP) later in life. To estimate the direct effect of BW on BP, it is conventional to condition on current weight (CW). However, such conditioning can induce collider stratification bias in the estimate of the direct effect. Objective: To bound the potential bias due to U, an unmeasured common cause of CW and BP, on the estimate of the (controlled) direct effect of BW on BP. Methods: Data from a school based study in Switzerland were used (N = 4,005; 2,010 B/1,995 G; mean age: 12.3 yr [range: 10.1-14.9]). Measured common causes of BW-BP (SES, smoking, body weight, and hypertension status of the mother) and CW-BP (breastfeeding and child's physical activity and diet) were identified with DAGs. Linear regression models were fitted to estimate the association between BW and BP. Sensitivity analyses were conducted to assess the potential effect of U on the association between BW and BP. U was assumed 1) to be a binary variable that affected BP by the same magnitude in low BWand in normal BW children and 2) to have a different prevalence in low BW children and in normal BW children for a given CW. Results: A small negative association was observed between BW and BP [beta: -0.3 mmHg/kg (95% CI: -0.9 to 0.3)]. The association was strengthened upon conditioning for CW [beta: -1.5 mmHg/kg (95% CI: -2.1 to -0.9)]. Upon further conditioning on common causes of BW-BP and CW-BP, the association did not change substantially [beta: -1.4 mmHg/kg (95% CI: -2.0 to -0.8)]. The negative association could be explained by U only if U was strongly associated with BP and if there was a large difference in the prevalence of U between low BWand normal BW children. Conclusion: The observed negative association between BW and BP upon adjustment for CW was not easily explained by an unmeasured common cause of CWand BP.

Association between melanism, physiology and behaviour: a role for the melanocortin system.

The melanocortin system is implicated in the expression of many phenotypic traits. Activation of the melanocortin MC(1) receptor by melanocortin hormones induces the production of brown/black eumelanic pigments, while activation of the four other melanocortin receptors affects other physiological and behavioural functions including stress response, energy homeostasis, anti-inflammatory and sexual activity, aggressiveness and resistance to oxidative stress. We recently proposed the hypothesis that some melanocortin-physiological and -behavioural traits are correlated within individuals. This hypothesis predicts that the degree of eumelanin production may, in some cases, be associated with the regulation of glucocorticoids, immunity, resistance to oxidative stress, energy homeostasis, sexual activity, and aggressiveness. A review of the zoological literature and detailed experimental studies in a free-living population of barn owls (Tyto alba) showed that indeed melanic coloration is often correlated with the predicted physiological and behavioural traits. Support for predictions of the hypothesis that covariations between coloration and other phenotypic traits stem from pleiotropic effects of the melanocortin system raises a number of theoretical and empirical issues from evolutionary and pharmacological point of views.

Toll-Interacting Protein Deficiency Leads to Increased Susceptibility to Acute and Chronic Colitis.

BACKGROUND: Sensing of bacterial products via Toll-like receptors is critical to maintain gut immune homeostasis. The Toll-Interacting Protein (Tollip) inhibits downstream signaling through the IL-1 receptor, TLR-2 and TLR-4. Here,we aimed to address the role of Tollip in acute and chronic inflammatory responses in the gut. MATERIAL AND METHODS: WT or Tollip-deficient mice were exposed to dextran sulfate sodium (DSS) 1.5% in the drinking water during 7 days. To generate bone-marrow chimeras, WT or Tollip deficient mice were 900-rads irradiated, transplanted with WT or Tollip deficient bone-marrow cells and challenged with DSS 2-3 months after transplantation. IL-10 deficient mice were bred with Tollip deficient mice and colitis was compared at various time points. RESULTS: Upon DSS exposure, Tollip-deficient mice had increased body weight loss and increased pro-inflammatory cytokine expression compared to WT controls. Challenge of bone-marrow chimeras showed that colitis susceptibility was also increased when Tollip deficiency was restricted to non-hematopoietic cells. DSS-exposure lead to a disorganized distribution of zona-occludens-1, a tight junction marker and increased number of apoptotic, cleaved caspase 3 positive, epithelial cells in Tollip-deficient compared to WT mice. Chronic colitis was also affected by Tollip deficiency as Tollip/IL-10 deficient mice had more severe histological stigmata of colitis and higher IL-17 expression than IL-10 deficient controls. CONCLUSION: Tollip in non-hematopoietic cells is critical for adequate response to a chemical-induced stress in the gut and to hamper chronic bacteria-driven colitis. Modulation of epithelial cell integrity via Tollip likely contributes to the observed defects.

Blood pressure, cardiac, and renal responses to salt and deoxycorticosterone acetate in mice: role of Renin genes.

Several studies have demonstrated that mice are polymorphic for the number of renin genes, with some inbred strains harboring one gene (Ren-1(c)) and other strains containing two genes (Ren-1(d) and Ren-2). In this study, the effects of 1% salt and deoxycorticosterone acetate (DOCA)/salt were investigated in one- and two-renin gene mice, for elucidation of the role of renin in the modulation of BP, cardiac, and renal responses to salt and DOCA. The results demonstrated that, under baseline conditions, mice with two renin genes exhibited 10-fold higher plasma renin activity, 100-fold higher plasma renin concentrations, elevated BP (which was angiotensin II-dependent), and an increased cardiac weight index, compared with one-renin gene mice (all P < 0.01). The presence of two renin genes markedly increased the BP, cardiac, and renal responses to salt. The number of renin genes also modulated the responses to DOCA/salt. In one-renin gene mice, DOCA/salt induced significant renal and cardiac hypertrophy (P < 0.01) even in the absence of any increase in BP. Treatment with losartan, an angiotensin II AT(1) receptor antagonist, decreased BP in two-renin gene mice but not in one-renin gene mice. However, losartan prevented the development of cardiac hypertrophy in both groups of mice. In conclusion, these data demonstrate that renin genes are important determinants of BP and of the responses to salt and DOCA in mice. The results confirm that the Ren-2 gene, which controls renin production mainly in the submaxillary gland, is physiologically active in mice and is not subject to the usual negative feedback control. Finally, these data provide further evidence that mineralocorticoids promote cardiac hypertrophy even in the absence of BP changes. This hypertrophic process is mediated in part by the activation of angiotensin II AT(1) receptors.

Roles of transient guidepost neurons in corpus callosum formation and guidance

RESUMENeurones transitoires jouant un rôle de cibles intermédiaires dans le guidage des axones du corps calleuxLe guidage axonal est une étape clé permettant aux neurones d'établir des connexions synaptiques et de s'intégrer dans un réseau neural fonctionnel de manière spécifique. Des cellules-cibles intermédiaires appelées « guidepost » aident les axones à parcourir de longues distances dans le cerveau en leur fournissant des informations directionnelles tout au long de leur trajet. Il a été démontré que des sous-populations de cellules gliales au niveau de la ligne médiane guident les axones du corps calleux (CC) d'un hémisphère vers l'autre. Bien qu'il fût observé que le CC en développement contenait aussi des neurones, leur rôle était resté jusqu'alors inconnu.La publication de nos résultats a montré que pendant le développement embryonnaire, le CC contient des glies mais aussi un nombre considérable de neurones glutamatergiques et GABAergiques, nécessaires à la formation du corps calleux (Niquille et al., PLoS Biology, 2009). Dans ce travail, j'ai utilisé des techniques de morphologie et d'imagerie confocale 3D pour définir le cadre neuro-anatomique de notre modèle. De plus, à l'aide de transplantations sur tranches in vitro, de co-explants, d'expression de siRNA dans des cultures de neurones primaires et d'analyse in vivo sur des souris knock-out, nous avons démontré que les neurones du CC guident les axones callosaux en partie grâce à l'action attractive du facteur de guidage Sema3C sur son récepteur Npn- 1.Récemment, nous avons étudié l'origine, les aspects dynamiques de ces processus, ainsi que les mécanismes moléculaires impliqués dans la mise en place de ce faisceau axonal (Niquille et al., soumis). Tout d'abord, nous avons précisé l'origine et l'identité des neurones guidepost GABAergiques du CC par une étude approfondie de traçage génétique in vivo. J'ai identifié, dans le CC, deux populations distinctes de neurones GABAergiques venant des éminences ganglionnaires médiane (MGE) et caudale (CGE). J'ai ensuite étudié plus en détail les interactions dynamiques entre neurones et axones du corps calleux par microscopie confocale en temps réel. Puis nous avons défini le rôle de chaque sous-population neuronale dans le guidage des axones callosaux et de manière intéressante les neurones GABAergic dérivés de la MGE comme ceux de la CGE se sont révélés avoir une action attractive pour les axones callosaux dans des expériences de transplantation. Enfin, nous avons clarifié la base moléculaire de ces mécanismes de guidage par FACS sorting associé à un large criblage génétique de molécules d'intérêt par une technique très sensible de RT-PCR et ensuite ces résultats ont été validés par hybridation in situ.Nous avons également étudié si les neurones guidepost du CC étaient impliqués dans son agénésie (absence de CC), présente dans nombreux syndromes congénitaux chez 1 humain. Le gène homéotique Aristaless (Arx) contrôle la migration des neurones GABAergiques et sa mutation conduit à de nombreuses pathologies humaines, notamment la lissencéphalie liée à IX avec organes génitaux anormaux (XLAG) et agénésie du CC. Fait intéressant, nous avons constaté qu'ARX est exprimé dans toutes les populations GABAergiques guidepost du CC et que les embryons mutant pour Arx présentent une perte drastique de ces neurones accompagnée de défauts de navigation des axones (Niquille et al., en préparation). En outre, nous avons découvert que les souris déficientes pour le facteur de transcription ciliogenic RFX3 souffrent d'une agénésie du CC associé avec des défauts de mise en place de la ligne médiane et une désorganisation secondaire des neurones glutamatergiques guidepost (Benadiba et al., submitted). Ceci suggère fortement l'implication potentielle des deux types de neurones guidepost dans l'agénésie du CC chez l'humain.Ainsi, mon travail de thèse révèle de nouvelles fonctions pour ces neurones transitoires dans le guidage axonal et apporte de nouvelles perspectives sur les rôles respectifs des cellules neuronales et gliales dans ce processus.ABSTRACTRole of transient guidepost neurons in corpus callosum development and guidanceAxonal guidance is a key step that allows neurons to build specific synaptic connections and to specifically integrate in a functional neural network. Intermediate targets or guidepost cells act as critical elements that help to guide axons through long distance in the brain and provide information all along their travel. Subpopulations of midline glial cells have been shown to guide corpus callosum (CC) axons to the contralateral cerebral hemisphere. While neuronal cells are also present in the developing corpus callosum, their role still remains elusive.Our published results unravelled that, during embryonic development, the CC is populated in addition to astroglia by numerous glutamatergic and GABAergic guidepost neurons that are essential for the correct midline crossing of callosal axons (Niquille et al., PLoS Biology, 2009). In this work, I have combined morphological and 3D confocal imaging techniques to define the neuro- anatomical frame of our system. Moreover, with the use of in vitro transplantations in slices, co- explant experiments, siRNA manipulations on primary neuronal culture and in vivo analysis of knock-out mice we have been able to demonstrate that CC neurons direct callosal axon outgrowth, in part through the attractive action of Sema3C on its Npn-1 receptor.Recently, we have studied the origin, the dynamic aspects of these processes as well as the molecular mechanisms involved in the establishment of this axonal tract (Niquille et al., submitted). First, we have clarified the origin and the identity of the CC GABAergic guidepost neurons using extensive in vivo cell fate-mapping experiments. We identified two distinct GABAergic neuronal subpopulations, originating from the medial (MGE) and caudal (CGE) ganglionic eminences. I then studied in more details the dynamic interactions between CC neurons and callosal axons by confocal time-lapse video microscopy and I have also further characterized the role of each guidepost neuronal subpopulation in callosal guidance. Interestingly, MGE- and CGE-derived GABAergic neurons are both attractive for callosal axons in transplantation experiments. Finally, we have dissected the molecular basis of these guidance mechanisms by using FACS sorting combined with an extensive genetic screen for molecules of interest by a sensitive RT-PCR technique, as well as, in situ hybridization.I have also investigated whether CC guidepost neurons are involved in agenesis of the CC which occurs in numerous human congenital syndromes. Aristaless-related homeobox gene (Arx) regulates GABAergic neuron migration and its mutation leads to numerous human pathologies including X-linked lissencephaly with abnormal genitalia (XLAG) and severe CC agenesis. Interestingly, I found that ARX is expressed in all the guidepost GABAergic neuronal populations of the CC and that Arx-/- embryos exhibit a drastic loss of CC GABAergic interneurons accompanied by callosal axon navigation defects (Niquille et al, in preparation). In addition, we discovered that mice deficient for the ciliogenic transcription factor RFX3 suffer from CC agenesis associated with early midline patterning defects and a secondary disorganisation of guidepost glutamatergic neurons (Benadiba et al., submitted). This strongly points out the potential implication of both types of guidepost neurons in human CC agenesis.Taken together, my thesis work reveals novel functions for transient neurons in axonal guidance and brings new perspectives on the respective roles of neuronal and glial cells in these processes.

Abatacept improves health-related quality of life, pain, sleep quality, and daily participation in subjects with juvenile idiopathic arthritis.

OBJECTIVE: To assess health-related quality of life (HRQOL) in abatacept-treated children/adolescents with juvenile idiopathic arthritis (JIA). METHODS: In this phase III, double-blind, placebo-controlled trial, subjects with active polyarticular course JIA and an inadequate response/intolerance to ≥1 disease-modifying antirheumatic drug (including biologics) received abatacept 10 mg/kg plus methotrexate (MTX) during the 4-month open-label period (period A). Subjects achieving the American College of Rheumatology Pediatric 30 criteria for improvement (defined "responders") were randomized to abatacept or placebo (plus MTX) in the 6-month double-blind withdrawal period (period B). HRQOL assessments included 15 Child Health Questionnaire (CHQ) health concepts plus the physical (PhS) and psychosocial summary scores (PsS), pain (100-mm visual analog scale), the Children's Sleep Habits Questionnaire, and a daily activity participation questionnaire. RESULTS: A total of 190 subjects from period A and 122 from period B were eligible for analysis. In period A, there were substantial improvements across all of the CHQ domains (greatest improvement was in pain/discomfort) and the PhS (8.3 units) and PsS (4.3 units) with abatacept. At the end of period B, abatacept-treated subjects had greater improvements versus placebo in all domains (except behavior) and both summary scores. Similar improvement patterns were seen with pain and sleep. For participation in daily activities, an additional 2.6 school days/month and 2.3 parents' usual activity days/month were gained in period A responders with abatacept, and further gains were made in period B (1.9 versus 0.9 [P = 0.033] and 0.2 versus -1.3 [P = 0.109] school days/month and parents' usual activity days/month, respectively, in abatacept- versus placebo-treated subjects). CONCLUSION: Improvements in HRQOL were observed with abatacept, providing real-life tangible benefits to children with JIA and their parents/caregivers.

The metabolic syndrome in hypertension: European society of hypertension position statement.

The metabolic syndrome considerably increases the risk of cardiovascular and renal events in hypertension. It has been associated with a wide range of classical and new cardiovascular risk factors as well as with early signs of subclinical cardiovascular and renal damage. Obesity and insulin resistance, beside a constellation of independent factors, which include molecules of hepatic, vascular, and immunologic origin with proinflammatory properties, have been implicated in the pathogenesis. The close relationships among the different components of the syndrome and their associated disturbances make it difficult to understand what the underlying causes and consequences are. At each of these key points, insulin resistance and obesity/proinflammatory molecules, interaction of demographics, lifestyle, genetic factors, and environmental fetal programming results in the final phenotype. High prevalence of end-organ damage and poor prognosis has been demonstrated in a large number of cross-sectional and a few number of prospective studies. The objective of treatment is both to reduce the high risk of a cardiovascular or a renal event and to prevent the much greater chance that metabolic syndrome patients have to develop type 2 diabetes or hypertension. Treatment consists in the opposition to the underlying mechanisms of the metabolic syndrome, adopting lifestyle interventions that effectively reduce visceral obesity with or without the use of drugs that oppose the development of insulin resistance or body weight gain. Treatment of the individual components of the syndrome is also necessary. Concerning blood pressure control, it should be based on lifestyle changes, diet, and physical exercise, which allows for weight reduction and improves muscular blood flow. When antihypertensive drugs are necessary, angiotensin-converting enzyme inhibitors, angiotensin II-AT1 receptor blockers, or even calcium channel blockers are preferable over diuretics and classical beta-blockers in monotherapy, if no compelling indications are present for its use. If a combination of drugs is required, low-dose diuretics can be used. A combination of thiazide diuretics and beta-blockers should be avoided.

Emerging therapies for gout.

Over the past decade much has been learned about the mechanisms of crystal-induced inflammation and renal excretion of uric acid, which has led to more specific targeting of gout therapies and a more potent approach to future management of gout. This article outlines agents being developed for more aggressive lowering of urate and more specific anti-inflammatory activity. The emerging urate-lowering therapies include lesinurad, arhalofenate, ulodesine, and levotofisopam. Novel gout-specific anti-inflammatories include the interleukin-1β inhibitors anakinra, canakinumab, and rilonacept, the melanocortins, and caspase inhibitors. The historic shortcomings of current gout treatment may, in part, be overcome by these novel approaches.

Tissue-specific opposing functions of the inflammasome adaptor ASC in the regulation of epithelial skin carcinogenesis.

A chronic inflammatory microenvironment favors tumor progression through molecular mechanisms that are still incompletely defined. In inflammation-induced skin cancers, IL-1 receptor- or caspase-1-deficient mice, or mice specifically deficient for the inflammasome adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD) in myeloid cells, had reduced tumor incidence, pointing to a role for IL-1 signaling and inflammasome activation in tumor development. However, mice fully deficient for ASC were not protected, and mice specifically deficient for ASC in keratinocytes developed more tumors than controls, suggesting that, in contrast to its proinflammatory role in myeloid cells, ASC acts as a tumor-suppressor in keratinocytes. Accordingly, ASC protein expression was lost in human cutaneous squamous cell carcinoma, but not in psoriatic skin lesions. Stimulation of primary mouse keratinocytes or the human keratinocyte cell line HaCaT with UVB induced an ASC-dependent phosphorylation of p53 and expression of p53 target genes. In HaCaT cells, ASC interacted with p53 at the endogenous level upon UVB irradiation. Thus, ASC in different tissues may influence tumor growth in opposite directions: it has a proinflammatory role in infiltrating cells that favors tumor development, but it also limits keratinocyte proliferation in response to noxious stimuli, possibly through p53 activation, which helps suppressing tumors.

The effects of losartan on renal function in the newborn rabbit.

The low GFR of newborns is maintained by various factors including the renin-angiotensin system. We previously established the importance of angiotensin II in the newborn kidney, using the angiotensin-converting enzyme inhibitor perindoprilat. The present study was designed to complement these observations by evaluating the role of angiotensin-type 1 (AT(1)) receptors, using losartan, a specific AT(1)-receptor blocker. Increasing doses of losartan were infused into anesthetized, ventilated, newborn rabbits. Renal function and hemodynamic variables were assessed using inulin and para-aminohippuric acid clearances as markers of GFR and renal plasma flow, respectively. Losartan 0.1 mg/kg slightly decreased mean blood pressure (-11%) and increased diuresis (+22%). These changes can be explained by inhibition of the AT(1)-mediated vasoconstrictive and antidiuretic effects of angiotensin, and activation of vasodilating and diuretic AT(2) receptors widely expressed in the neonatal period. GFR and renal blood flow were not modified. Losartan 0.3 mg/kg decreased mean blood pressure significantly (-15%), probably by inhibiting systemic AT(1) receptors. GFR significantly decreased (-25%), whereas renal blood flow remained stable. The decrease in filtration fraction (-21%) indicates predominant efferent vasodilation. At 3 mg/kg, the systemic hypotensive effect of losartan was marked (mean blood pressure, -28%), with decreased GFR and renal blood flow (-57% and -51%, respectively), a stable filtration fraction, and an increase in renal vascular resistance by 124%. The renal response to this dose can be considered as reflex vasoconstriction of afferent and efferent arterioles, rather than specific receptor antagonism. We conclude that under physiologic conditions, the renin-angiotensin is critically involved in the maintenance of GFR in the immature kidney.

The DNA damage response to adeno-associated virus : centrosome overduplication and induction of cell death independently of the spindle checkpoint

Summary: Adeno-associated virus type 2 (AAV2) is a small virus containing single-stranded DNA of approximately 4.7kb in size. Both ends of the viral genome are flanked with inverted terminal repeat sequences (ITRs), which serve as primers for viral replication. Previous work in our laboratory has shown that AAV2 DNA with ultraviolet radiation-generated crosslinks (UV-AAV2) provokes a DNA damage response in the host cell by mimicking a stalled replication fork. Infection of cells with UV-AAV2 leads to a p53-and Chk1-mediated cell cycle arrest at the G2/M border of the cell cycle. However, tumour cells lacking the tumour suppressor protein p53 cannot sustain this arrest and enter a prolonged impaired mitosis, the outcome of which is cell death. The aim of my thesis was to investigate how UV-inactivated AAV2 kilts p53-deficient cancer cells. I found that the UV-AAV2-induced DNA damage signalling induces centriole overduplication in infected cells. The virus is able to uncouple the centriole duplication cycle from the cell cycle, leading to amplified centrosome numbers. Chk1 colocalises with centrosomes in the infected cells and the centrosome overduplication is dependent on the presence of Chk1, as well as on the activities of ATR and Cdk kinases and on the G2 arrest. The UV-AAV2-induced DNA damage signalling inhibits the degradation of cyclin B 1 and securin by the anaphase promoting complex, suggesting that the spindle checkpoint is activated in these mitotic cells. Interference with the spindle checkpoint components Mad2 and BubR1 revealed that the UV-AAV2-provoked mitotic catastrophe occurs independently of spindle checkpoint function, This work shows that, in the p53 deficient cells, UV-AAV2 triggers mitotic catastrophe associated with a dramatic Chk1-dependent overduplication of centrioles and the consequent formation of multiple spindle poles in mitosis. Résumé Le virus associé à l'adénovirus type 2 (AAV2) est un petit virus contenant un simple brin d'ADN d'environ 4.7kb. Des expériences antérieures dans notre laboratoire ont montré que les liens intramoléculaires sur l'ADN de AAV2 provoqués paz l'irradiation aux ultraviolets (UV) ressemblent à une fourche de réplication bloquée, ce qui provoque une réponse aux dommages à l'ADN dans la cellule hôte. L'infection des cellules avec UV-AAV2 résulte en un arrêt du cycle cellulaire à la transition G2/M entraîné par les protéines ATR et Chk1. Cependant, les cellules tumorales auxquelles il manque le suppresseur de tumeur p53 ne peuvent pas tenir cet arrêt et entrent dans une mitose anormale et prolongée qui se terminera par la mort cellulaire. Le but de ma thèse était d'étudier comment l'AAV2 inactivé par l'irradiation UV tue les cellules cancéreuses n'ayant pas p53. Je montre ici que le signal de dommages à l'ADN induit par UV-AAV2 génère une surduplication des centrioles dans les cellules infectées. Le virus est capable de dissocier le cycle de duplication du centriole du cycle cellulaire ce qui crée un nombre amplifié de centrosomes. Chk1 est co-localisé avec le centrosome dans les cellules infectées et la swduplication du centrosome est dépendante de la présence de Chk1, de l'activité des kinases ATR et Cdk et de l'arrêt en G2 de la cellule. Le signal d'ADN endommagé induit par UV-AAV2 réprime la dégradation des protéines cycline B1 et securine par le complexe promoteur de l'anaphase (APC), ce qui suggère que le point de contrôle du fuseau mitotique est activé dans ces cellules en mitose. L'étude d'interférence avec des éléments du point de contrôle du fuseau mitotique, Mad2 et BubR1, a révélé que la catastrophe mitotique provoquée paz UV-AAV2 survient indépendamment du point de contrôle du fuseau mitotique. Ce travail montre que dans les cellules déficientes en p53, UV-AAV2 induit une catastrophe mitotique associée à une surduplication des centrioles dépendant de Chk1 et ayant pour conséquence dramatique la formation de multiples fuseaux mitotiques dans la cellule en mitose.