A Positive Regulatory Loop between foxi3a and foxi3b Is Essential for Specification and Differentiation of Zebrafish Epidermal Ionocytes

BACKGROUND: Epidermal ionocytes play essential roles in the transepithelial transportation of ions, water, and acid-base balance in fish embryos before their branchial counterparts are fully functional. However, the mechanism controlling epidermal ionocyte specification and differentiation remains unknown. METHODOLOGY/PRINCIPAL FINDINGS: In zebrafish, we demonstrated that Delta-Notch-mediated lateral inhibition plays a vital role in singling out epidermal ionocyte progenitors from epidermal stem cells. The entire epidermal ionocyte domain of genetic mutants and morphants, which failed to transmit the DeltaC-Notch1a/Notch3 signal from sending cells (epidermal ionocytes) to receiving cells (epidermal stem cells), differentiates into epidermal ionocytes. The low Notch activity in epidermal ionocyte progenitors is permissive for activating winged helix/forkhead box transcription factors of foxi3a and foxi3b. Through gain- and loss-of-function assays, we show that the foxi3a-foxi3b regulatory loop functions as a master regulator to mediate a dual role of specifying epidermal ionocyte progenitors as well as of subsequently promoting differentiation of Na(+),K(+)-ATPase-rich cells and H(+)-ATPase-rich cells in a concentration-dependent manner. CONCLUSIONS/SIGNIFICANCE: This study provides a framework to show the molecular mechanism controlling epidermal ionocyte specification and differentiation in a low vertebrate for the first time. We propose that the positive regulatory loop between foxi3a and foxi3b not only drives early ionocyte differentiation but also prevents the complete blockage of ionocyte differentiation when the master regulator of foxi3 function is unilaterally compromised

The Impact of Mercenaries and Private Military and Security Companies on Civil War Severity between 1946 and 2002

Research has long abandoned the view that only states wage war. On the contrary, civil war research has produced an impressive body of literature on violent non-state actors. Still, a particular group of actors—mercenaries—has been widely neglected so far, although they have participated in numerous conflicts in the second half of the twentieth century. Whether their presence aggravated or improved the situation is a matter of dispute. Some believe that the additional military capabilities provided by mercenaries help to end civil wars quickly without increased bloodshed, while others deem mercenaries greedy and bloodthirsty combatants who contribute to making civil wars more brutal, while a third opinion differentiates between different types of mercenaries. This article tests the impact of mercenaries on civil war severity. The evidence indicates that the presence of both mercenaries and private military and security contractors increases its severity

Roles and Required Technical Resources

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Implications for the United Kingdom’s

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Prepared for the United Kingdom‘s Ministry of Defence

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Tartu Ülikooli Õppe- ja Katsemetskonna Kastre Peravalla metsandike plaanid (kvartalid nr 200-293)

PlaanidTartu Ülikooli Õppe- ja Katsemetskonna Kastre Peravalla metsandike takseerkirjeldused aastatest 1922, 1923. Kvartalite nr 200-293 käsikirjalised originaalplaanid on mõõtkavas 1:2500. Koloreeritud plaanid sisaldavad kvartalite numbreid, leppemärkide seletusi, ilmakaari, graafilist mõõtkava, autorite nimesid. Autorite nimedes võib esineda eksimusi. Loetamatud nimed puuduvad autorite loendis

Tartu Ülikooli Õppe- ja Katsemetskonna Kastre Peravalla metsandike plaanid (kvartalid nr 101-199)

PlaanidTartu Ülikooli Õppe- ja Katsemetskonna Kastre Peravalla metsandike takseerkirjeldused aastatest 1922, 1923, 1924. Kvartalite nr 101-199 käsikirjalised originaalplaanid on mõõtkavas 1:2500. Koloreeritud plaanid sisaldavad kvartalite numbreid, leppemärkide seletusi, ilmakaari, graafilist mõõtkava, autorite nimesid. Autorite nimedes võib esineda eksimusi. Loetamatud nimed puuduvad autorite loendis