Tensioactifs en système biphasique eau/huile : propriétés, transfert et instabilité de Marangoni

Des instabilités hydrodynamiques ont été observées et étudiées pendant le transfert de matière dans deux types de systèmes biphasiques eau/huile. Le premier est un système non réactif impliquant le transfert de deux séries de tensioactifs ioniques (bromure de tétraalkylammonium à longue chaîne (CnTAB, n = 12, 16, 18) et dodécylsulfate de tétraalkylammonium (TAADS)). L'instabilité est, dans ce cas, périodique. Le système bascule alternativement d'un régime de diffusion vers un régime convectif. Le deuxième système est un système réactif, la réaction d'hydrolyse biphasique du chlorure de myristoyle (RCOCl, R = C13H27). Le transfert du chlorure de myristoyle vers la phase aqueuse est induit par la réaction d'hydrolyse qui donne lieu à la formation de composés tensioactifs. Les études réalisées dans la géométrie de la cellule Hele- Shaw ont montré que cette réaction biphasique donne lieu à un régime bien défini de cellules convectives de Marangoni. Notre objectif a consisté dans un premier temps à déterminer de façon quantitative les propriétés physicochimiques de ces systèmes. Nous avons mis au point une méthodologie originale, basée sur la modélisation de données de tension superficielle, permettant de déterminer les propriétés de partage, d'adsorption aux interfaces eau/air et eau/huile et d'agrégation. Nous avons pour les deux séries de composés tensioactifs (CnTAB et TAADS) mis en évidence la formation de microémulsions huile dans l'eau. Nous nous sommes également intéressés aux propriétés cinétiques de transfert et avons observé une dynamique accélérante due à un effet autocatalytique. Pour le système non réactif, cette accélération, observée lors du transfert de la phase organique vers la phase aqueuse, est due à la formation de microémulsions huile dans l'eau. Pour le système réactif, la forme de la cinétique est différente de celle observée pour le simple transfert de tensioactif. La courbe sigmoïde est dans ce cas parfaitement symétrique. Cette observation indique certainement un mécanisme différent du précédent. Il implique également une modification des propriétés de solubilisation de la phase aqueuse mais cette fois non par la formation d'agrégats mais plutôt par la formation de dimères.Hydrodynamics instability have been observed and studied during the mass transfer in two water/oil biphasic systems. The first is a non-reactive system involving the transfer of two series of ionic surfactants (tetraalkylammonium bromide (CnTAB) and tetraalkylammonium dodecylsulfate (TAADS)). In this case, the instability is periodic. The second system is a reactive system, the biphasic hydrolysis of myristoyl chloride (RCOCl). The transfer of myristoyl chloride to the aqueous phase is induced by the hydrolysis reaction leading to the formation of surface-active compounds. Studies in the geometry of the Hele-Shaw cell showed that this biphasic reaction gives rise to a well-defined regime of chemo-Marangoni convection cells. Our objective was initially to determine quantitatively the physicochemical properties of these systems. We have developed a methodology based on the modeling of interfacial tension measurements, to determine the partition and adsorption properties at the water/air and water /oil interface and aggregation. We have showed for the two series of surfactants the formation of oil in water microemulsions. We have also studied the kinetics of transfer and showed a particular dynamic accelerating due to the catalytic effect. For the non-reactive system, this acceleration, observed during the transfer of the organic phase to the aqueous phase, is due to the formation of oil-in-water microemulsions. For the reactive system, the shape of the kinetics is different from that observed for simple transfer of the surfactant. The sigmoid curve in this case is perfectly symmetrical. This observation certainly indicates a mechanism different from above. It also implies a change of solubilization of the aqueous phase but this time not by the formation of aggregates but by the formation of dimers

Importance of voltage-dependent inactivation in N-type calcium channel regulation by G-proteins.: Channel inactivation in G-protein regulation

International audienceDirect regulation of N-type calcium channels by G-proteins is essential to control neuronal excitability and neurotransmitter release. Binding of the G(betagamma) dimer directly onto the channel is characterized by a marked current inhibition ("ON" effect), whereas the pore opening- and time-dependent dissociation of this complex from the channel produce a characteristic set of biophysical modifications ("OFF" effects). Although G-protein dissociation is linked to channel opening, the contribution of channel inactivation to G-protein regulation has been poorly studied. Here, the role of channel inactivation was assessed by examining time-dependent G-protein de-inhibition of Ca(v)2.2 channels in the presence of various inactivation-altering beta subunit constructs. G-protein activation was produced via mu-opioid receptor activation using the DAMGO agonist. Whereas the "ON" effect of G-protein regulation is independent of the type of beta subunit, the "OFF" effects were critically affected by channel inactivation. Channel inactivation acts as a synergistic factor to channel activation for the speed of G-protein dissociation. However, fast inactivating channels also reduce the temporal window of opportunity for G-protein dissociation, resulting in a reduced extent of current recovery, whereas slow inactivating channels undergo a far more complete recovery from inhibition. Taken together, these results provide novel insights on the role of channel inactivation in N-type channel regulation by G-proteins and contribute to the understanding of the physiological consequence of channel inactivation in the modulation of synaptic activity by G-protein coupled receptors

Two PEST-like motifs regulate Ca2+/calpain-mediated cleavage of the CaVbeta3 subunit and provide important determinants for neuronal Ca2+ channel activity.

International audienceAn increase in intracellular Ca2+ due to voltage-gated Ca2+ (CaV) channel opening represents an important trigger for a number of second-messenger-mediated effects ranging from neurotransmitter release to gene activation. Ca2+ entry occurs through the principal pore-forming protein but several ancillary subunits are known to more precisely tune ion influx. Among them, the CaVbeta subunits are perhaps the most important, given that they largely influence the biophysical and pharmacological properties of the channel. Notably, several functional features may be associated with specific structural regions of the CaVbeta subunits emphasizing the relevance of intramolecular domains in the physiology of these proteins. In the current report, we show that CaVbeta3 contains two PEST motifs and undergoes Ca2+ -dependent degradation which can be prevented by the specific calpain inhibitor calpeptin. Using mutant constructs lacking the PEST motifs, we present evidence that they are necessary for the cleavage of CaVbeta3 by calpain. Furthermore, the deletion of the PEST sequences did not affect the binding of CaVbeta3 to the ion-conducting CaV2.2 subunit and, when expressed in human embryonic kidney-293 cells, the PEST motif-deleted CaVbeta3 significantly increased whole-cell current density and retarded channel inactivation. Consistent with this observation, calpeptin treatment of human embryonic kidney-293 cells expressing wild-type CaVbeta3 resulted in an increase in current amplitude. Together, these findings suggest that calpain-mediated CaVbeta3 proteolysis may be an essential process for Ca2+ channel functional regulation

CTGA: the database for genetic disorders in Arab populations

The Arabs comprise a genetically heterogeneous group that resulted from the admixture of different populations throughout history. They share many common characteristics responsible for a considerable proportion of perinatal and neonatal mortalities. To this end, the Centre for Arab Genomic Studies (CAGS) launched a pilot project to construct the ‘Catalogue of Transmission Genetics in Arabs’ (CTGA) database for genetic disorders in Arabs. Information in CTGA is drawn from published research and mined hospital records. The database offers web-based basic and advanced search approaches. In either case, the final search result is a detailed HTML record that includes text-, URL- and graphic-based fields. At present, CTGA hosts entries for 692 phenotypes and 235 related genes described in Arab individuals. Of these, 213 phenotypic descriptions and 22 related genes were observed in the Arab population of the United Arab Emirates (UAE). These results emphasize the role of CTGA as an essential tool to promote scientific research on genetic disorders in the region. The priority of CTGA is to provide timely information on the occurrence of genetic disorders in Arab individuals. It is anticipated that data from Arab countries other than the UAE will be exhaustively searched and incorporated in CTGA ()

Effect of deformation on components of internal stress tensor in grains of FCC-polycristal

Study of contributions of internal stress tensor components in deformed of austenitic steel was carriedout. The tensor components of internal stresses were determined with using bending extinction contours observing on electron microscope images of the steel

Internet-based search of randomised trials relevant to mental health originating in the Arab world

BACKGROUND: The internet is becoming a widely used source of accessing medical research through various on-line databases. This instant access to information is of benefit to busy clinicians and service users around the world. The population of the Arab World is comparable to that of the United States, yet it is widely believed to have a greatly contrasting output of randomised controlled trials related to mental health. This study was designed to investigate the existence of such research in the Arab World and also to investigate the availability of this research on-line. METHODS: Survey of findings from three internet-based potential sources of randomised trials originating from the Arab world and relevant to mental health care. RESULTS: A manual search of an Arabic online current contents service identified 3 studies, MEDLINE, EMBASE, and PsycINFO searches identified only 1 study, and a manual search of a specifically indexed, study-based mental health database, PsiTri, revealed 27 trials. CONCLUSION: There genuinely seem to be few trials from the Arab world and accessing these on-line was problematic. Replication of some studies that guide psychiatric/psychological practice in the Arab world would seem prudent

Breast cancer presentation delays among Arab and national women in the UAE: a qualitative study

© 2016 The Authors. Published by Elsevier. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1016/j.ssmph.2016.02.007Breast cancer (BC) is a disease that has improved prospects for survival if detected and treated early. Delayed help-seeking behavior, with poor survival as a consequence, is an important public health issue in the Middle East. More than 75% of breast cancer patients in the United Arab Emirates (UAE) seek medical advice after experiencing a sign or symptom of the disease and many seek such advice late. Our aim was to explore factors influencing delayed presentation for treatment after self-discovery of symptoms consistent with breast cancer in Arab women in the United Arab Emirates (UAE), and to explore facilitators and barriers of women’s health seeking behavior in the complex religiously dominated society of the UAE. A qualitative descriptive approach using semi-structured interviews was used. We interviewed nineteen BC survivors aged 35–70 who have experienced delayed presentation to treatment after symptomatic recognition of BC. The time interval between initial experience of symptoms consistent with BC, and taking action to seek medical help was between three months to three years. The key themes that emerged from the interviews were varying responses to symptom recognition, fear of societal stigmatization, and concerns regarding abandonment by spouse because of BC. Culture has a strong influence on the decisions of women in the UAE society. The lack of awareness about signs and symptoms of BC and routine screening has an important effect on symptom appraisal and subsequently decision making regarding options for treatment

Health Policy and Systems Research in Twelve Eastern Mediterranean Countries: a stocktaking of production and gaps (2000-2008)

<p>Abstract</p> <p>Background</p> <p>The objectives of this study are to: (1) profile the production of Health Policy and Systems Research (HPSR) published between 2000 and 2008 in 12 countries in the Eastern Mediterranean Region (EMR): Bahrain, Egypt, Jordan, Lebanon, Libya, Morocco, Oman, Palestine, Sudan, Syria, Tunisia, and Yemen; (2) identify gaps; and (3) assess the extent to which existing HPSR produced in the region addresses regional priorities pertaining to Health Financing, Human Resources for Health and the Role of the Non-State Sector. This is the first stocktaking paper of HPSR production and gaps in the EMR.</p> <p>Methods</p> <p>Articles indexed on Medline between years 2000 and 2008 for the 12 study countries were selected. A MeSH term based search was conducted using country names. Articles were assessed using a coding sheet adapted for the region which included themes on: Governance Arrangements, Financial Arrangements, Delivery Arrangements, and Implementation Strategies. Identified articles were matched against regional research priorities to assess the extent to which research production aligns with priorities.</p> <p>Results</p> <p>A total of 1,487 articles (11.94%) fit the criteria in the coding sheet. Results showed an increase in HPSR production which peaked after 2005. Most identified articles focused on Delivery Arrangements (68.1%), and Implementation Strategies (24.4%). Most HPSR addressed priorities in Human Resources for Health (39%<b>)</b>, and some articles focused on Health Financing (12%) and Role of the Non-State Sector (6.1%).</p> <p>Conclusions</p> <p>Despite global calls for producing and translating HPSR into policy, there are still significant gaps in the EMR. More efforts are needed to produce HPSR and align production and translation with the demand for evidence by policymakers. Findings can help inform and direct future plans and activities for the Evidence Informed Policy Network- EMR, World Health Organization- EMR, and the Middle East and North Africa Health Policy Forum, in addition to being useful for countries that host or are planning to host KT platforms in the region.</p