Transcriptomic analysis of crustacean neuropeptide signaling during the moult cycle in the green shore crab, Carcinus maenas

Abstract Background Ecdysis is an innate behaviour programme by which all arthropods moult their exoskeletons. The complex suite of interacting neuropeptides that orchestrate ecdysis is well studied in insects, but details of the crustacean ecdysis cassette are fragmented and our understanding of this process is comparatively crude, preventing a meaningful evolutionary comparison. To begin to address this issue we identified transcripts coding for neuropeptides and their putative receptors in the central nervous system (CNS) and Y-organs (YO) within the crab, Carcinus maenas, and mapped their expression profiles across accurately defined stages of the moult cycle using RNA-sequencing. We also studied gene expression within the epidermally-derived YO, the only defined role for which is the synthesis of ecdysteroid moulting hormones, to elucidate peptides and G protein-coupled receptors (GPCRs) that might have a function in ecdysis. Results Transcriptome mining of the CNS transcriptome yielded neuropeptide transcripts representing 47 neuropeptide families and 66 putative GPCRs. Neuropeptide transcripts that were differentially expressed across the moult cycle included carcikinin, crustacean hyperglycemic hormone-2, and crustacean cardioactive peptide, whilst a single putative neuropeptide receptor, proctolin R1, was differentially expressed. Carcikinin mRNA in particular exhibited dramatic increases in expression pre-moult, suggesting a role in ecdysis regulation. Crustacean hyperglycemic hormone-2 mRNA expression was elevated post- and pre-moult whilst that for crustacean cardioactive peptide, which regulates insect ecdysis and plays a role in stereotyped motor activity during crustacean ecdysis, was elevated in pre-moult. In the YO, several putative neuropeptide receptor transcripts were differentially expressed across the moult cycle, as was the mRNA for the neuropeptide, neuroparsin-1. Whilst differential gene expression of putative neuropeptide receptors was expected, the discovery and differential expression of neuropeptide transcripts was surprising. Analysis of GPCR transcript expression between YO and epidermis revealed 11 to be upregulated in the YO and thus are now candidates for peptide control of ecdysis. Conclusions The data presented represent a comprehensive survey of the deduced C. maenas neuropeptidome and putative GPCRs. Importantly, we have described the differential expression profiles of these transcripts across accurately staged moult cycles in tissues key to the ecdysis programme. This study provides important avenues for the future exploration of functionality of receptor-ligand pairs in crustaceans

Comparison of uranium- and thorium-based plutonium-recycling in a pressurized water reactor

The accumulation of civil Plutonium from nuclear energy production continuously attains attention as a world wide safety concern. A reliable elimination of the civil Plutonium as well as that from dismantling of nuclear war heads rnay be achieved only by its fission ; intermediate storage or deep underground disposal whatever technical line is followed - allows only a temporary limited "elimination" of that weapons grade material. Plutonium can be fissioned either in today's nuclear reactors or with future reactors or accelerator driven systems being constructed especially for this tack. The application of Thorium based nuclear fuels, containing Plutonium as a fissile material, allows a very efficient consumption of Plutonium as the breeding chain of Thorium produces no Plutonium. $^{233}$U is breed instead, which in some ways is classified less dangerous than Plutonium. This paper reports the results of a comparison of Thorium based fuels in pressurised water reactors with Uranium based mixed oxide fuels up to burn-ups of100 GWd/t$_{HM}$. First, consumption ratios for Plutonium and Transuranium elements are compared. lt turned out that the application of Thorium based fuel doubles the consumption ratio of Plutonium in comparison to Uranium mixed oxide fuel. This also becomes evident evaluating the mass balances with respect to the generated nuclear energy. Also in this rase the Thorium based fuel demonstrates its superior performance; it generates rnore than 90 % of the energy due to Plutonium fissioning, thus performing approximately 40 % better than Uranium based mixed oxide fuel. But the large amounts of Transuranium elements remaining in both types of fuel are disadvantageous; thus these fuels may not be seen as a solution of the Plutonium problem for the purposes of avoiding large Plutonium amounts to be disposed off. Besides the valuation of consumption ratios the Feed back due to the change of fuel raust be evaluated with respect to the safety behaviour of the reactor. Basing on the reactivity feedback coefficients of the fuel temperature, the moderator temperature, the boron concentration and the voided core, it can be shown, that Thorium based mixed oxide fuel performs better than Uranium based mixed oxide fuel. But both types of fuel run into trouble, if very high burn-ups are desired. Due to high initial Plutonium concentrations the void coefficient tends to become positive. A final judgement of this result needs a more detailed core layout analysis. With respect to final disposal both the reprocessing residuals from the UO$_{2}$-fuel and the spent mixed oxide fuels do not perform significantly different. On the one hand rnore than 40 % of the initial Plutonium remains in the spent mixed oxide fuel, on the other hand no Minor Actinides are separated from UO$_{2}$ fuel, which contribute to 10 % to the mass of Transuranium elements. That's why the toxicity potential may not change significantly with respect to spent UO$_{2}$ fuel. As the long [...

Protonenfenster und Flüssigmetalltarget für eine beschleuniigergetriebeneTransmutationsanlage

Today's concepts of the fuel cycle intend timt high level nuclear waste produced by nuclear reactors shall be disposed in dem geological forrnations. This idea has been criticized because of the extremly long terms needed to mach an unobjectionable level by radioactive decay. A chemical seperation of isotopes wich very long half-lifes from the waste-stream and a subsequently nuclear transmutation into short living isotopes gives us the possibilty to shorten the time needed for a safe enclosure down to 1000 years. For this period technical barriers are able to guarantee a save enclosure of the waste. From the point of view of savety, non-critical accelerator driven transmutation is a very interesting solution. Protons are accelerated up to high energies and impinge onto a target where they produce a high neutron flux as a result of spallation reactions. These neutrons are necessary for the transmutation of the bong living isotopes. The investigations of this doctoral thesis describe the construction of a proton beam window, which seperates the accelerator vacuum fror the target, and the evaluation of a liquid metall target. Aspects concerning heat transfer, theory of strength of materials, neutron physics and safety have been considered