Effects of seawater and freshwater challenges on the Gh/Igf system in the saline-tolerant blackchin tilapia (Sarotherodon melanotheron)

Prolactin (Prl) and growth hormone (Gh) as well as insulin-like growth factor 1 (Igf1) are involved in the physiological adaptation of fish to varying salinities. The Igfs have been also ascribed other physiological roles during development, growth, reproduction and immune regulation. However, the main emphasis in the investigation of osmoregulatory responses has been the endocrine, liver-derived Igf1 route and local regulation within the liver and osmoregulatory organs. Few studies have focused on the impact of salinity alterations on the Gh/Igf-system within the neuroendocrine and immune systems and particularly in a salinity-tolerant species, such as the blackchin tilapia Sarotherodon melanotheron. This species is tolerant to hypersalinity and saline variations, but it is confronted by severe climate changes in the Saloum inverse estuary. Here we investigated bidirectional effects of increased salinity followed by its decrease on the gene regulation of prl, gh, igf1, igf2, Gh receptor and the tumor-necrosis factor a. A mixed population of sexually mature 14-month old blackchin tilapia adapted to freshwater were first exposed to seawater for one week and then to fresh water for another week. Brain, pituitary, head kidney and spleen were excised at 4 h, 1, 2, 3 and 7 days after both exposures and revealed differential expression patterns. This investigation should give us a better understanding of the role of the Gh/Igf system within the neuroendocrine and immune organs and the impact of bidirectional saline challenges on fish osmoregulation in non-osmoregulatory organs, notably the complex orchestration of growth factors and cytokines

Unanticipated coordination of tris buffer to the Radical SAM cluster of the RimO methylthiotransferase

International audienceRadical SAM enzymes generally contain a [4Fe-4S](2+/1+) (RS cluster) cluster bound to the protein via the three cysteines of a canonical motif CxxxCxxC. The non-cysteinyl iron is used to coordinate SAM via its amino-carboxylate moiety. The coordination-induced proximity between the cluster acting as an electron donor and the adenosyl-sulfonium bond of SAM allows for the homolytic cleavage of the latter leading to the formation of the reactive 5'-deoxyadenosyl radical used for substrate activation. Most of the structures of Radical SAM enzymes have been obtained in the presence of SAM, and therefore, little is known about the situation when SAM is not present. In this report, we show that RimO, a methylthiotransferase belonging to the radical SAM superfamily, binds a Tris molecule in the absence of SAM leading to specific spectroscopic signatures both in Mössbauer and pulsed EPR spectroscopies. These data provide a cautionary note for researchers who work with coordinative unsaturated iron sulfur clusters

Light sources for wavelengths > 2 mu m grown by MBE on InP using a strain relaxed buffer

Light emitting diodes (LEDs) and lasers operating in the 2 to 3 mu m spectral region at room temperature are been demonstrated. The devices were fabricated from InxGa1-xAs/InAsyP1-y double heterostructures grown on n-type InP (100) substrates by molecular beam epitaxy. A strain relaxed buffer layer which incorporates composition reversals was used to reduce the threading dislocation density and to accommodate the large lattice mismatch (up to 2.7%) between the InP substrate and the device active region. Efficient electroluminescence emission at wavelengths between 2 and 3 mu m was obtained from the LEDs at room temperature, while diode lasers exhibited coherent emission in the range 2-2.6 mu m at temperatures up to 130 K. For one of the LEDs a characteristic absorption was readily observed at 2.7 mu m in the diode electroluminescence emission spectrum, corresponding to strong water vapour absorption in the atmosphere. These devices could easily form the key component of an infrared gas sensor for water vapour detection and monitoring at 2.7 mu m in a variety of different applications