Les effets cardioprotecteurs de peptides dérivés des sécrétagogues de l’hormone de croissance dans le modèle d’ischémie-reperfusion du myocarde murin

Les peptides sécrétagogues de l’hormone de croissance (GHRP) sont des peptides synthétiques qui stimulent la sécrétion de l’hormone de croissance (HC) après la liaison avec le récepteur de la ghréline (antérieurement appelé le récepteur 1a des sécrétagogues de l’hormone de croissance, GHS-R1a). La ghréline désacylée (UAG) est la forme prédominante de la ghréline en circulation, mais l’UAG ne lie pas le récepteur de la ghréline et ne stimule pas la sécrétion d’hormone de croissance. Des études ont montré que les GHRPs et l’UAG possèdent des effets cardioprotecteurs indépendants de la sécrétion de l’hormone de croissance. L’équipe de Ong a identifié le récepteur CD36, exprimé entre autres par les cardiomyocytes, les macrophages et les adipocytes, comme étant un deuxième site de liaison pour les GHRPs, tandis que le récepteur de l’UAG reste encore inconnu à ce jour. L’objectif général de cette thèse était d’évaluer les effets cardioprotecteurs d’une nouvelle classe d’analogues des GHRPs, les azapeptides, qui présentent une plus grande sélectivité envers le récepteur CD36 par comparaison à celui de la ghréline, et les effets cardioprotecteurs d’un fragment peptidique bioactif de l’UAG, l’UAG6-13, dans la pathologie de la maladie cardiaque ischémique. Le modèle d’ischémie/reperfusion du myocarde (I/RM) a été produit par une ligature chirurgicale de l’artère coronaire antérieure descendante gauche pendant 30 min pour induire une ischémie, suivie d’une reperfusion de 6 ou 48 h chez des souris mâles C57BL/6. Les souris ont été prétraitées dans la première étude avec l’azapeptide CP-3(iv) (289 nmol/kg) ou le véhicule (NaCl 0,9%) de manière quotidienne par voie sous-cutanée (s.c.), et dans la deuxième étude avec l’UAG (100 nmol/kg), l’UAG6-13 (1000 et 3000 nmol/kg) ou le véhicule de manière biquotidienne par voie s.c. avant d’être soumises à une I/RM. Notre première étude a montré que le CP-3(iv) protège contre les dommages liés à l’I/RM par une réduction de la taille de l’infarctus et une préservation de l’hémodynamique cardiaque. Ces effets résultent en partie d’une augmentation du gène de l’adiponectine et des protéines impliquées dans sa transcription au niveau du tissu adipeux, conduisant à une augmentation des taux circulants de l’adiponectine et une réduction des concentrations plasmatiques des acides gras non estérifiés. Au niveau du myocarde, les propriétés anti-oxydatives, anti-apoptotiques et pro-métaboliques de l’adiponectine ont été observées. Aucun de ces effets n’a été observé chez les souris déficientes en CD36 et la récupération de la fonction cardiaque par le CP-3(iv) a été abrogée par un anticorps anti-adiponectine dans le modèle de cœur isolé, démontrant la dépendance du récepteur CD36 et l’importance du rôle de l’adiponectine pour médier les effets cardioprotecteurs du CP-3(iv). Notre deuxième étude a montré que l’UAG et l’UAG6-13 ont réduit le pourcentage de lésions myocardiques et préservé l’hémodynamique cardiaque. Ces effets résultent en grande partie par une diminution des concentrations plasmatiques des cytokines pro-inflammatoires IL-6 et TNF-α. De plus, nos résultats ont montré une diminution de l’apoptose et une activation de la voie AMPK impliquée dans l’oxydation des acides gras au niveau du cœur. Les effets de l’UAG6-13 sont indépendants du récepteur de la ghréline comme démontré par l’ajout concomitant de la D-Lys3-GHRP-6, un antagoniste du récepteur de la ghréline, dans le modèle de cœur isolé. En conclusion, les travaux de cette thèse ont montré que les peptides CP-3(iv) et UAG6-13 possèdent des effets cardioprotecteurs puissants dans la pathologie de l’I/RM et constituent de nouvelles approches thérapeutiques pouvant être appliquées dans les maladies cardiovasculaires ischémiques.Growth hormone-releasing peptides (GHRP) are synthetic peptides that stimulate growth hormone (GH) secretion after binding with the ghrelin receptor (previously known as the growth hormone secretagogue receptor 1a, GHS-R1a). Unacylated ghrelin (UAG) represents the predominant form of ghrelin in circulation, but UAG does not bind to the ghrelin receptor and does not stimulate GH release. Studies have shown that GHRPs and UAG possess cardioprotective effects independent from GH secretion. The group of Ong has identified the CD36 receptor, expressed in cardiomyocytes, macrophages and adipocytes among other cells, as the second binding site for GHRPs, whereas the receptor for UAG is still unknown until this day. The general aim of this thesis was to evaluate the cardioprotective effects of a new class of GHRPs analogues, the azapeptides, which show a higher selectivity towards the CD36 receptor in comparison to that of ghrelin, and the cardioprotective effects of a bioactive peptide fragment of UAG, UAG6-13, in the pathology of ischemic heart disease. The model of myocardial ischemia/reperfusion (MI/R) was generated by a surgical ligation of the left anterior descending coronary artery for 30 min to induce an ischemia, followed by a reperfusion of 6 or 48 h in C57BL/6 male mice. The mice have been pretreated in the first study with azapeptide CP-3(iv) (289 nmol/kg) or the vehicle (0.9% NaCl) daily by subcutaneous (s.c.) injection, and in the second study with UAG (100 nmol/kg), UAG6-13 (1000 nmol/kg and 3000 nmol/kg) or the vehicle twice daily by s.c. injection prior to being subjected to MI/R. Our first study have shown that CP-3(iv) protects against I/RM induced injury by reducing the infarct size and preserving myocardial hemodynamics. These effects result, in part, by an increase in adiponectin production/secretion and proteins involved in its transcription in adipose tissue. This leads to an increase in circulating levels of adiponectin and a decrease in plasma concentration of non-esterified fatty acids. In the myocardium, the anti-oxidative, anti-apoptotic and pro-metabolic properties of adiponectin has been observed. None of these effects was observed in CD36 deficient mice and the function recovery of the heart by CP-3(iv) has been abrogated by an anti-adiponectin antibody in an isolated heart model, showing the dependency for the CD36 receptor and the importance of the role of adiponectin to mediate the cardioprotective effects of CP-3(iv). Our second study showed that UAG and UAG6-13 have reduced the percentage of myocardial lesions and preserved cardiac hemodynamics. These effects result largely by a reduction in plasma concentration of pro-inflammatory cytokines IL-6 and TNF-α. Moreover, our results have shown a reduction in apoptosis and an activation of the AMPK pathway involved in fatty acids oxidation in the heart. The effects of UAG6-13 are independent of the ghrelin receptor as shown by a concomitant addition of D-Lys3-GHRP-6, a ghrelin receptor antagonist, in the model of isolated heart. In conclusion, the work conducted in this thesis have shown that CP-3(iv) and UAG6-13 possess potent cardioprotective effects in the pathology of MI/R and constitute new therapeutic approaches which can be applied in ischemic cardiovascular disease

Rôle du tissu adipeux dans l’effet cardioprotecteur du EP 80317, un ligand sélectif du récepteur CD36

Le récepteur CD36 est impliqué dans le transport des acides gras libres non estérifiés (AGNE) au niveau des tissus cardiaque et périphériques. Les dommages tissulaires et la dysfonction cardiaque observés après une ischémie-reperfusion (I/R) du myocarde sont en partie liés à l’internalisation et au métabolisme oxydatif accrus des AGNE dont la concentration sanguine augmente transitoirement après un infarctus du myocarde, contrairement à ce qui est observé chez des souris déficientes en CD36. Nous avons émis l’hypothèse selon laquelle le EP 80317, un ligand synthétique du récepteur CD36, exercerait un effet cardioprotecteur contre les dommages induits par une ischémie transitoire du myocarde. Nos objectifs étaient 1) de vérifier l’effet cardioprotecteur du EP 80317 et 2) de définir son mécanisme, plus précisément de documenter l’effet du traitement sur le métabolisme lipidique. À cette fin, des souris de type sauvage ont été traitées par le EP 80317 (289 nmol/kg) par voie sous-cutanée pendant 14 jours avant d’être soumises à 30 minutes d’ischémie suivant la ligature de l’artère coronaire gauche descendante et de sa reperfusion pendant une période de 6 ou 48 heures. Le cœur et les tissus périphériques (foie, muscle squelettique et dépôts adipeux) ont été prélevés pour déterminer le profil de certains gènes impliqués dans la régulation du métabolisme lipidique. Nos travaux ont montré que l’effet cardioprotecteur d’un traitement préventif par le EP 80317 est associé à une augmentation transitoire du stockage des triglycérides et d’une réduction des AGNE circulants.The CD36 receptor is involved in the transport of non-esterified fatty acids (NEFA) in cardiac and peripheral tissues. Tissue injury and cardiac dysfunction are in part due to acute internalization and oxidative metabolism of NEFA which concentration rises transiently in the blood following myocardial infarction, in opposition to what is observed in CD36-deficient mice. We hypothesized that EP 80317, a synthetic ligand of the CD36 receptor, provides cardioprotective effect against injuries induced by transient myocardial ischemia. Our objectives were 1) to verify the cardioprotective effect of EP 80317 and 2) to define its mechanism, more precisely to investigate the mechanisms of the treatment on lipid metabolism. For this purpose, wild-type mice were treated with EP 80317 (289 nmol/kg) subcutaneously for 14 days before being submitted to 30 minutes of ischemia following left anterior descending coronary artery ligature and reperfusion for a period of 6 or 48 hours. Heart and peripheral tissues (liver, skeletal muscle and adipose tissue) were harvested to determine the profile of selected genes involved in the regulation of lipid metabolism. Our work has shown that the cardioprotective effect of a pretreatment with EP 80317 is associated with a transient increase of triglycerides storage and reduced circulating NEFA

Paediatric patient safety and the need for aviation black box thinking to learn from and prevent medication errors

Since the publication of To Err Is Human: Building a Safer Health System in 1999, there has been much research conducted into the epidemiology, nature and causes of medication errors in children, from prescribing and supply to administration. It is reassuring to see growing evidence of improving medication safety in children; however, based on media reports, it can be seen that serious and fatal medication errors still occur. This critical opinion article examines the problem of medication errors in children and provides recommendations for research, training of healthcare professionals and a culture shift towards dealing with medication errors. There are three factors that we need to consider to unravel what is missing and why fatal medication errors still occur. (1) Who is involved and affected by the medication error? (2) What factors hinder staff and organisations from learning from mistakes? Does the fear of litigation and criminal charges deter healthcare professionals from voluntarily reporting medication errors? (3) What are the educational needs required to prevent medication errors? It is important to educate future healthcare professionals about medication errors and human factors to prevent these from happening. Further research is required to apply aviation’s ‘black box’ principles in healthcare to record and learn from near misses and errors to prevent future events. There is an urgent need for the black box investigations to be published and made public for the benefit of other organisations that may have similar potential risks for adverse events. International sharing of investigations and learning is also needed

Size dependent tunneling and optical spectroscopy of CdSe quantum rods

Photoluminescence excitation spectroscopy and scanning tunneling spectroscopy are used to study the electronic states in CdSe quantum rods that manifest a transition from a zero dimensional to a one dimensional quantum confined structure. Both optical and tunneling spectra show that the level structure depends primarily on the rod diameter and not on length. With increasing diameter, the band-gap and the excited state level spacings shift to the red. The level structure was assigned using a multi-band effective-mass model, showing a similar dependence on rod dimensions.Comment: Accepted to PRL (nearly final version). 4 pages in revtex, 4 figure

The Deep SWIRE Field. IV. First properties of the sub-mJy galaxy population: redshift distribution, AGN activity and star formation

We present a study of a 20cm selected sample in the Deep SWIRE VLA Field, reaching a limiting flux density of ~13.5 uJy at the image center. In a 0.6x0.6 square degrees field, we are able to assign an optical/IR counterpart to 97% of the radio sources. Up to 11 passbands from the NUV to 4.5um are then used to sample the spectral energy distribution (SED) of these counterparts in order to investigate the nature of the host galaxies. By means of an SED template library and stellar population synthesis models we estimate photometric redshifts, stellar masses, and stellar population properties, dividing the sample in three sub-classes of quiescent, intermediate and star-forming galaxies. We focus on the radio sample in the redshift range 0.3<z<1.3 where we estimate to have a redshift completeness higher than 90%, and study the properties and redshift evolution of these sub-populations. We find that, as expected, the relative contributions of AGN and star-forming galaxies to the uJy population depend on the flux density limit of the sample. At all flux levels a significant population of "green-valley" galaxies is observed. While the actual nature of these sources is not definitely understood, the results of this work may suggest that a significant fraction of faint radio sources might be composite (and possibly transition) objects, thus a simple "AGN vs star-forming" classification might not be appropriate to fully understand what faint radio populations really are.Comment: 18 pages, 16 figures, accepted for publication in Ap

Gene pools and the genetic architecture of domesticated cowpea

Open Access JournalCowpea [Vigna unguiculata (L.) Walp.] is a major tropical legume crop grown in warm to hot areas throughout the world and especially important to the people of sub-Saharan Africa where the crop was domesticated. To date, relatively little is understood about its domestication origins and patterns of genetic variation. In this study, a worldwide collection of cowpea landraces and African ancestral wild cowpea was genotyped with more than 1200 single nucleotide polymorphism markers. Bayesian inference revealed the presence of two major gene pools in cultivated cowpea in Africa. Landraces from gene pool 1 are mostly distributed in western Africa while the majority of gene pool 2 are located in eastern Africa. Each gene pool is most closely related to wild cowpea in the same geographic region, indicating divergent domestication processes leading to the formation of two gene pools. The total genetic variation within landraces from countries outside Africa was slightly greater than within African landraces. Accessions from Asia and Europe were more related to those from western Africa while accessions from the Americas appeared more closely related to those from eastern Africa. This delineation of cowpea germplasm into groups of genetic relatedness will be valuable for guiding introgression efforts in breeding programs and for improving the efficiency of germplasm managemen

Photoacoustic imaging of the human placental vasculature

Minimally invasive fetal interventions require accurate imaging from inside the uterine cavity. Twin‐to‐twin transfusion syndrome (TTTS), a condition considered in this study, occurs from abnormal vascular anastomoses in the placenta that allow blood to flow unevenly between the fetuses. Currently, TTTS is treated fetoscopically by identifying the anastomosing vessels, and then performing laser photocoagulation. However, white light fetoscopy provides limited visibility of placental vasculature, which can lead to missed anastomoses or incomplete photocoagulation. Photoacoustic (PA) imaging is an alternative imaging method that provides contrast for hemoglobin, and in this study, two PA systems were used to visualize chorionic (fetal) superficial and subsurface vasculature in human placentas. The first system comprised an optical parametric oscillator for PA excitation and a 2D Fabry‐Pérot cavity ultrasound sensor; the second, light emitting diode arrays and a 1D clinical linear‐array ultrasound imaging probe. Volumetric photoacoustic images were acquired from ex vivo normal term and TTTS‐treated placentas. It was shown that superficial and subsurface branching blood vessels could be visualized to depths of approximately 7 mm, and that ablated tissue yielded negative image contrast. This study demonstrated the strong potential of PA imaging to guide minimally invasive fetal therapies

Comparison of two multiple-locus variable-number tandem-repeat analysis methods for molecular strain typing of human Brucella melitensis isolates from the Middle East

Brucella species are highly monomorphic, with minimal genetic variation among species, hindering the development of reliable subtyping tools for epidemiologic and phylogenetic analyses. Our objective was to compare two distinct multiple-locus variable-number tandem-repeat analysis (MLVA) subtyping methods on a collection of 101 Brucella melitensis isolates from sporadic human cases of brucellosis in Egypt (n = 83), Qatar (n = 17), and Libya (n = 1). A gel-based MLVA technique, MLVA-15IGM, was compared to an automated capillary electrophoresis-based method, MLVA-15NAU, with each MLVA scheme examining a unique set of variable-number tandem repeats. Both the MLVAIGM and MLVANAU methods were highly discriminatory, resolving 99 and 101 distinct genotypes, respectively, and were able to largely separate genotypes from Egypt and Qatar. The MLVA-15NAU scheme presented higher strain-to-strain diversity in our test population than that observed with the MLVA-15IGM assay. Both schemes were able to genetically correlate some strains originating from the same hospital or region within a country. In addition to comparing the genotyping abilities of these two schemes, we also compared the usability, limitations, and advantages of the two MLVA systems and their applications in the epidemiological genotyping of human B. melitensis strains

The camera of the fifth H.E.S.S. telescope. Part I: System description

In July 2012, as the four ground-based gamma-ray telescopes of the H.E.S.S. (High Energy Stereoscopic System) array reached their tenth year of operation in Khomas Highlands, Namibia, a fifth telescope took its first data as part of the system. This new Cherenkov detector, comprising a 614.5 m^2 reflector with a highly pixelized camera in its focal plane, improves the sensitivity of the current array by a factor two and extends its energy domain down to a few tens of GeV. The present part I of the paper gives a detailed description of the fifth H.E.S.S. telescope's camera, presenting the details of both the hardware and the software, emphasizing the main improvements as compared to previous H.E.S.S. camera technology.Comment: 16 pages, 13 figures, accepted for publication in NIM