Quantitative measurement of blood velocity in zebrafish with optical vector field tomography

Microscopy techniques can readily visualize the finest details of embryo vasculature, but still lack to provide a complete three‐dimensional representation of blood flow parameters. We present an in‐vivo 3D imaging technique, able to reconstruct the blood cell velocity vector over a large volume of zebrafish embryos. This low cost and relatively simple technique is exploited to quantitatively assess blood velocity in the zebrafish tail at different stages of development. (© 2013 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Abrogation of prostaglandin E2/EP4 signaling impairs the development of rag1+ lymphoid precursors in the thymus of zebrafish embryos

PGE(2) is involved in a wide variety of physiological and pathological processes; however, deciphering its role in early mammalian development has been difficult due to the maternal contribution of PGE(2). To overcome this limitation we have investigated the role of PGE(2) during T cell development in zebrafish. In this study, we show that zebrafish ep4a, a PGE(2) receptor isoform of EP4, is expressed at 26 h postfertilization in the dorsal aorta-posterior cardinal vein joint region, which has a high homology with the mammal aorta-gonad-mesonephros area and where definitive hemopoiesis arises. Furthermore, it is expressed in the presumptive thymus rudiment by 48 h postfertilization. Supplementation of PGE(2) results in a strong increase in rag1 levels and cell proliferation in the thymus. In contrast, the inhibition of PGE(2) production, as well as EP4 blockade, abrogates the expression of rag1 in the thymus and that of the lymphoid precursor marker ikaros, not only in the dorsal aorta-posterior cardinal vein joint region but also in the newly identified caudal hemopoietic tissue without affecting early hemopoietic (scl, gata2) and erythropoietic (gata1) markers. These results identify ep4a as the earliest thymus marker and define a novel role for the PGE(2)/EP4 pathway in controlling T cell precursor development in zebrafish.     

Electrical parameters in gallbladders of different species their contribution to the origin of the transmural potential difference

Summary Amphotericin B enhances Na⁺ conductance of the mucosal membrane of gallbladder epithelial cells and in such a way it modifies the brush border electromotive force. On this basis a method to measure cell and shunt resistances by comparing changes of the mucosal membrane potential (V _m ) and of the transmural p.d. (V _ms ) is developed. This method is applied in gallbladders of different vertebrate species (i.e. rabbit, guinea pig, goose, tortoise, toad, trout). The two tested mammals, rabbit and guinea pig, exhibited a lower shunting percentage (89–93%) than the nonmammals (96–97%), but this fact did not bring about a homogeneous positiveV _ms . This means that shunting percent contributes, but it is not the only source of differences inV _ms , in accordance with that reported by Gelarden and Rose (J. Membrane Biol. 19:37, 1974). Moreover, mammals exhibited a lower luminal resistance and a lower ratio between luminal and basolateral resistance than nonmammals. Possible causes of these differences are discussed.     

Differentiation of the vitelline coat in the ascidianCiona intestinalis: an ultrastructural study

Summary We have studied the differentiation of the vitelline coat (VC) of the ascidianCiona intestinalis. In the young previtellogenic oocyte the vitelline coat precursor material (VCPM) makes its first appearance as patches of fibrous material in close apposition to the outer surface of the oocyte. The presence of subcortical vescicles containing a fuzzy electron-dense material and their opening into the oocyte surface parallels the formation of VCPM. Numerous microvillar-like structures emerge from the oocyte surface. When the VCPM completely surrounds the oocyte the microvilli are withdrawn. An overall increase of VCPM parallels the growth of the oocyte. The next step in the differentiation of the vitelline coat consists in the packing of the constituent fibrils in a dense layer at its outer surface, i.e. the one in contact with the follicle cells. At this time the VC is penetrated by microvilli protruding both from the oocyte and follicle cells. The VC reaches its final structure and thickness at the time the test cells are extruded into the perivitelline space.The participation of the follicle cells in VC organization is also discussed.     

A fucosyl glycoprotein component with sperm receptor and sperm-activating activities from the vitelline coat of ciona intestinalis eggs

In this paper we describe a mild procedure which results in the extraction of a glycoprotein fraction from the vitelline coat (VC) of Ciona intestinalis while leaving behind the bulk of the VC components. When acting upon the spermatozoa this fraction inhibits sperm binding to the VC and fertilization and elicits sperm activation including the acrosome reaction. SDS-PAGE shows that it contains the same (fucosyl) glycoprotein components previously recognized in the total extracts of VC. It is suggested that this material contains the sperm receptors or those components of the receptors that are essential for their Chinese function.