Répercussions hémodynamiques rénales de la surcharge salée aiguë isotonique chez le chien

Intrarenal hemodynamic changes during acute isotonic saline loading in the dog. 85Kr autoradiograms, perfusions of silastic and injections of thioflavine S labelled red blood cells (R.B.C.) have been used to study the intrarenal hemodynamic changes induced in the dog by an acute isotonic expansion of the extracellular fluid volume. The silastic injected specimens showed a generalized vasodilatation, without however, any change of the diameter of the glomerular tufts. As the ratio of the number of labelled R.B.C. of the superficial glomeruli to the number of the R.B.C. of the juxtamedullary glomeruli has decreased, we can conclude that the relative juxtamedullary glomerular capillary volume has increased. The autoradiographs showed that the velocity of the blood flow increased in the superficial cortex and the vasa recta and decreases in the juxtamedullary cortical region. This slowing seems to be due to the marked dilatation of the capillary bed of the latter region. It is then concluded that the natriuresis could be linked mainly to changes of peritubular factors induced by the vasodilatation which is itself more marked in the juxtamedullary cortex.Répercussions hémodynamiques rénales de la surcharge salée aiguë isotonique chez le chien. Les changements hémodynamiques intrarénaux ont été étudiés chez des chiens soumis à une surcharge salée isotonique aiguë, à l'aide d'autoradiographies au Kr85, de perfusion de silastic et d'injections de globules rouges marqués à la Thioflavine S. La surcharge a entraîné une vasodilatation rénale généralisée (moules au silastic). Le décompte des globules rouges marqués par glomérule montra une diminution du leur nombre dans les glomérules superficiels par rapport aux glomérules juxtamédullaires. Ceci traduit une augmentation relative du volume capillaire glomérulaire juxtamédullaire. Par ailleurs, la vitesse du flux sanguin (autoradiographies) a augments dans le cortex superficiel, les vasa recta et diminué dans la région juxtamédullaire. Une dilatation excessive du lit capillaire de cette dernière semble expliquer le ralentissement de son flux sanguin. Le diamètre des floculi glomérulaires n'a pas changé sous l'effet de la surcharge. La natriurèse peut ainsi être reliée principalement à la baisse de réabsorption tubulaire secondaire aux changements des facteurs péritubulaires induits par la vasodilatation, elle-même maximale au niveau du cortex interne

Isoproterenol and 8-bromo-cyclic adenosine monophosphate stimulate the expression of the angiotensinogen gene in opossum kidney cells

Isoproterenol and 8-bromo-cyclic adenosine monophosphate stimulate the expression of the angiotensinogen gene in opossum kidney cells. To investigate whether the expression of the renal angiotensinogen (ANG) gene is regulated by β-adrenoceptors and the cAMP-dependent protein kinase A pathway, we introduced stably the fusion gene containing the 5′-flanking regulatory sequence of the ANG gene with a human growth hormone (hGH) gene as a reporter, pOGH (ANG N-1498/+18), into opossum kidney (OK) cells. We successfully obtained several stable transformants with a high expression of the pOGH (ANG N-1498/+18) fusion gene. One stable transformant (OK 27) that is able to maintain the expression of pOGH (ANG N-1498/+18) in culture for more than a year was used in the present study. The level of expression of the pOGH (ANG N-1498/+18) in OK 27 was evaluated by the amount of immunoreactive-hGH (IR-hGH) secreted into the culture medium. The addition of isoproterenol (10-11 M to 10-9 M) stimulated the expression of pOGH (ANG N-1498/+18) and increased the accumulation of intracellular cAMP. Higher concentrations of isoproterenol (that is, greater than 10-9 M) had low or minimal effect. In contrast, the addition of 8-bromo-cAMP (8-Br-cAMP) and forskolin stimulated the expression of pOGH (ANG N-1498/+18) in a dose-dependent manner. The stimulatory effect of isoproterenol was blocked by the presence of propranolol, atenolol and ICI 118,551. The addition of ICI 118,551, however, was less effective than atenolol. Furthermore, the stimulatory effect of isoproterenol and 8-Br-cAMP on the expression of the pOGH (ANG N-1498/+18) was inhibited by the presence of Rp-cAMP (an inhibitor of cAMP-dependent protein kinase AI and II). These studies demonstrated that the expression of the pOGH (ANG N-1498/+18) in OK cells is stimulated by β-adrenoceptors and the cAMP-dependent protein kinase A pathway. Our data indicate that OK 27 cells provide a useful model to study the regulation of expression of the ANG gene in vitro

The safety net role of inland fishing in the subsistence strategy of multi-active forest dwellers in southern Cameroon

The Mvae and the Ntumu, two African rainforest ethnic groups belonging to same Fang linguistic sub-group, live together as good neighbors in the Ntem watershed of southern Cameroon. Like most forest dwellers in the Congo Basin, these two societies have implemented a multi-active type of subsistence economy: hunting, trapping, gathering and fishing are practiced in addition to a predominant slash-and-burn agriculture. The aim of this paper is to emphasize that these ethnic groups, which do not have fishery as their most salient production domain, have nevertheless acquired a remarkable expertise in wild fishery, notably through a diversity of techniques and socio-ecological conditions of practice. The sizable variety of fishing methods takes advantage of the great vascularity of the hydrographic network and involves in a complementary way all the members of the community — young and old, of both genders, in solo, in pairs or in larger groups of participants. This large range of possibilities ensures a continuous provision of fish over the year and establishes inland capture fishery as a real safety net that can provide — in all circumstances and in sufficient quantities — resources that are culturally valued, that are an appreciable extra-source of income, and whose nutritional role is acknowledged. Despite of being the pervasive basis of the subsistence economy of forest peoples in Central Africa, the contribution of inland capture fishery to the livelihoods of Congo basin forest dwellers remains unobtrusive and is overlooked by development agencies

Biomimetic versus enzymatic high-potential electrocatalytic reduction of hydrogen peroxide on a functionalized carbon nanotube electrode

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Direct Electrochemistry of Bilirubin Oxidase from Magnaporthe orizae on Covalently-Functionalized MWCNT for the Design of High-Performance Oxygen-Reducing Biocathodes

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Functionalizable Glyconanoparticles for a Versatile Redox Platform

International audienceA series of new glyconanoparticles (GNPs) was obtained by self-assembly by direct nanoprecipitation of a mixture of two carbohydrate amphiphilic copolymers consisting of polystyrene-block-β-cyclodextrin and polystyrene-block-maltoheptaose with different mass ratios, respectively 0–100, 10–90, 50–50 and 0–100%. Characterizations for all these GNPs were achieved using dynamic light scattering, scanning and transmission electron microscopy techniques, highlighting their spherical morphology and their nanometric size (diameter range 20–40 nm). In addition, by using the inclusion properties of cyclodextrin, these glyconanoparticles were successfully post-functionalized using a water-soluble redox compound, such as anthraquinone sulfonate (AQS) and characterized by cyclic voltammetry. The resulting glyconanoparticles exhibit the classical electroactivity of free AQS in solution. The amount of AQS immobilized by host–guest interactions is proportional to the percentage of polystyrene-block-β-cyclodextrin entering into the composition of GNPs. The modulation of the surface density of the β-cyclodextrin at the shell of the GNPs may constitute an attractive way for the elaboration of different electroactive GNPs and even GNPs modified by biotinylated protein