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Early Embryonic Stages (early + embryonic_stage)
Selected AbstractsRepulsive guidance molecule/neogenin: a novel ligand-receptor system playing multiple roles in neural developmentDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 6 2004Eiji Matsunaga The repulsive guidance molecule (RGM) is a membrane-bound protein originally isolated as an axon guidance molecule in the visual system. Recently, the transmembrane protein, neogenin, has been identified as the RGM receptor. In vitro analysis with retinal explants showed that RGM repels temporal retinal axons and collapses their growth cones through neogenin-mediated signaling. However, RGM and neogenin are also broadly expressed at the early embryonic stage, suggesting that they do not only control the guidance of visual axons. Gene expression perturbation experiments in chick embryos showed that neogenin induces cell death, and its ligand, RGM, blocks the pro-apoptotic activity of neogenin. Thus, RGM/neogenin is a novel dependence ligand/receptor couple as well as an axon guidance molecular complex. [source] Expression of the hyaluronan receptor LYVE-1 is not restricted to the lymphatic vasculature; LYVE-1 is also expressed on embryonic blood vesselsDEVELOPMENTAL DYNAMICS, Issue 7 2008Emma J. Gordon Abstract Expression of the hyaluronan receptor LYVE-1 is one of few available criteria used to discriminate lymphatic vessels from blood vessels. Until now, endothelial LYVE-1 expression was reported to be restricted to lymphatic vessels and to lymph node, liver, and spleen sinuses. Here, we provide the first evidence that LYVE-1 is expressed on blood vessels of the yolk sac during mouse embryogenesis. LYVE-1 is ubiquitously expressed in the yolk sac capillary plexus at E9.5, then becomes progressively down-regulated on arterial endothelium during vascular remodelling. LYVE-1 is also expressed on intra-embryonic arterial and venous endothelium at early embryonic stages and on endothelial cells of the lung and endocardium throughout embryogenesis. These findings have important implications for the use of LYVE-1 as a specific marker of the lymphatic vasculature during embryogenesis and neo-lymphangiogenesis. Our data are also the first demonstration, to our knowledge, that the mouse yolk sac is devoid of lymphatic vessels. Developmental Dynamics 237:1901,1909, 2008. © 2008 Wiley-Liss, Inc. [source] Distribution of neurotrophin-3 during the ontogeny and regeneration of the lizard (Gallotia galloti) visual systemDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2008E. Santos Abstract We have previously described the spontaneous regeneration of retinal ganglion cell axons after optic nerve (ON) transection in the adult Gallotia galloti. As neurotrophin-3 (NT-3) is involved in neuronal differentiation, survival and synaptic plasticity, we performed a comparative immunohistochemical study of NT-3 during the ontogeny and regeneration (after 0.5, 1, 3, 6, 9, and 12 months postlesion) of the lizard visual system to reveal its distribution and changes during these events. For characterization of NT-3+ cells, we performed double labelings using the neuronal markers HuC-D, Pax6 and parvalbumin (Parv), the microglial marker tomato lectin or Lycopersicon esculentum agglutinin (LEA), and the astroglial markers vimentin (Vim) and glial fibrillary acidic protein (GFAP). Subpopulations of retinal and tectal neurons were NT-3+ from early embryonic stages to adulthood. Nerve fibers within the retinal nerve fiber layer, both plexiform layers and the retinorecipient layers in the optic tectum (OT) were also stained. In addition, NT-3+/GFAP+ and NT-3+/Vim+ astrocytes were detected in the ON, chiasm and optic tract in postnatal and adult lizards. At 1 month postlesion, abundant NT-3+/GFAP+ astrocytes and NT-3,/LEA+ microglia/macrophages were stained in the lesioned ON, whereas NT-3 became downregulated in the experimental retina and OT. Interestingly, at 9 and 12 months postlesion, the staining in the experimental retina resembled that in control animals, whereas bundles of putative regrown fibers showed a disorganized staining pattern in the OT. Altogether, we demonstrate that NT-3 is widely distributed in the lizard visual system and its changes after ON transection might be permissive for the successful axonal regrowth. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2008 [source] Early neural activity and dendritic growth in turtle retinal ganglion cellsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2006Vandana Mehta Abstract Early neural activity, both prenatal spontaneous bursts and early visual experience, is believed to be important for dendritic proliferation and for the maturation of neural circuitry in the developing retina. In this study, we have investigated the possible role of early neural activity in shaping developing turtle retinal ganglion cell (RGC) dendritic arbors. RGCs were back-labelled from the optic nerve with horseradish peroxidase (HRP). Changes in dendritic growth patterns were examined across development and following chronic blockade or modification of spontaneous activity and/or visual experience. Dendrites reach peak proliferation at embryonic stage 25 (S25, one week before hatching), followed by pruning in large field RGCs around the time of hatching. When spontaneous activity is chronically blocked in vivo from early embryonic stages (S22) with curare, a cholinergic nicotinic antagonist, RGC dendritic growth is inhibited. On the other hand, enhancement of spontaneous activity by dark-rearing (Sernagor & Grzywacz (1996)Curr. Biol., 6, 1503,1508) promotes dendritic proliferation in large-field RGCs, an effect that is counteracted by exposure to curare from hatching. We also recorded spontaneous activity from individual RGCs labelled with lucifer yellow (LY). We found a tendency of RGCs with large dendritic fields to be spontaneously more active than small-field cells. From all these observations, we conclude that immature spontaneous activity promotes dendritic growth in developing RGCs. [source] Expression of the aspartate/glutamate mitochondrial carriers aralar1 and citrin during development and in adult rat tissuesFEBS JOURNAL, Issue 13 2002Araceli Del Arco Aralar1 and citrin are members of the subfamily of calcium-binding mitochondrial carriers and correspond to two isoforms of the mitochondrial aspartate/glutamate carrier (AGC). These proteins are activated by Ca2+ acting on the external side of the inner mitochondrial membrane. Although it is known that aralar1 is expressed mainly in skeletal muscle, heart and brain, whereas citrin is present in liver, kidney and heart, the precise tissue distribution of the two proteins in embryonic and adult tissues is largely unknown. We investigated the pattern of expression of aralar1 and citrin in murine embryonic and adult tissues at the mRNA and protein levels. In situ hybridization analysis indicates that both isoforms are expressed strongly in the branchial arches, dermomyotome, limb and tail buds at early embryonic stages. However, citrin was more abundant in the ectodermal components of these structures whereas aralarl had a predominantly mesenchymal localization. The strong expression of citrin in the liver was acquired postnatally, whereas the characteristic expression of aralar1 in skeletal muscle was detected at E18 and that in the heart began early in development (E11) and was preferentially localized to auricular myocardium in late embryonic stages. Aralar1 was also expressed in bone marrow, T-lymphocytes and macrophages, including Kupffer cells in the liver, indicating that this is the major AGC isoform present in the hematopoietic system. Both aralar1 and citrin were expressed in fetal gut and adult stomach, ovary, testis, and pancreas, but only aralar1 is enriched in lung and insulin-secreting ,,cells. These results show that aralar1 is expressed in many more tissues than originally believed and is absent from hepatocytes, where citrin is the only AGC isoform present. This explains why citrin deficiency in humans (type II citrullinemia) only affects the liver and suggests that aralar1 may compensate for the lack of citrin in other tissues. [source] The effect of different kinds of electrolyte and non-electrolyte solutions on the survival rate and morphology of zebrafish Danio rerio embryosJOURNAL OF FISH BIOLOGY, Issue 7 2009F. Lahnsteiner The effect of electrolyte and non-electrolyte solutions on the survival and on the morphology of zebrafish Danio rerio embryos was investigated. Embryos in different ontogenetic stages were incubated in electrolyte (NaCl, KCl, MgCl2 and CaCl2) and non-electrolyte solutions [sucrose and polyvinylalcohol (PVA)] of different concentrations for 5 , 15 min. The embryos were hatched to the long-pec stage and the effective concentrations which caused a 50% decrease in embryo development (EC50) were determined. The morphometric changes, which were caused by the test solutions, were measured. Ion channel blockers were used to see if active ion transport played a role for embryo survival. Finally, dechorionated embryos were exposed to the test solutions to get indications about the importance of chorion and perivitelline space. For 12 hours post fertilization (hpf) embryos and a 15 min exposure period, EC50 was highest for MgCl2 (1·60 mol l,1), followed by sucrose (0·73 mol l,1), NaCl (0·49 mol l,1), KCl (0·44 mol l,1), CaCl2 (0·43 mol l,1) and PVA [0·0005 mol l,1 (2·2%)]. EC50 were lower for early embryonic stages than for advanced stages for all solutions with exception of MgCl2 and sucrose. At the EC50, MgCl2 and CaCl2 solutions did not induce morphometric changes. NaCl and sucrose solutions induced reversible morphometric changes, which were compensated within 10 min. Only the EC50 of KCl and PVA solutions induced permanent morphometric changes, which could not be compensated. Incubation of embryos in electrolyte and non-electrolyte solutions together with ouabain (blocker of Na+, K+ ATPase), HgCl3 (dose-dependent inhibition of aquaporine channels), verapamil (inhibition of calcium and magnesium uptake) and amiloride (inhibition of sodium uptake) significantly decreased the per cent of embryos developing to the long-pec stage in comparison to the same solutions without blockers. Ouabain and HgCl3 also induced morphometric changes. For dechorionated embryos the survival rates in water and in the different test solutions were similar to untreated embryos. [source] Identification of porcine Lhx3 and SF1 as candidate genes for QTL affecting growth and reproduction traits in swineANIMAL GENETICS, Issue 6 2001T. P. L. Smith The distal portion of the long arm of porcine chromosome 1 has been shown to harbour several quantitative trait loci affecting growth and reproductive traits in swine. In order to identify potential candidate genes that might underlie these effects, a comparative mapping analysis was undertaken to define the extent of orthologous segments of human chromosome 9. A microsatellite associated with heat shock protein (HSP) A5 was used to define the proximal boundary of the quantitative trait loci (QTL) region, which suggests the human orthologue of the gene(s) responsible for the observed effects lies between HSPA5 and the q arm telomere of human chromosome 9. Examination of this region revealed two candidate genes with known roles in production of hormones essential to growth and reproductive function. The steroidogenic factor 1 and Lhx3 LIM homeodomain transcription factor genes were mapped to 123 and 155 cM, respectively, of the Sus scrofa chromosome 1 (SSC1) linkage group, placing both genes within the confidence interval for the observed QTL. To further evaluate Lhx3, we examined the expression profile during porcine embryonic development. Low levels were detected at early embryonic stages, when development of the nervous system is proceeding. A transient increase in expression level is observed during the time of pituitary organogenesis and again at the time of differentiation of anterior pituitary cells, with relatively high levels of expression persisting in the adult pituitary gland. This ontology is consistent with Lhx3 being a candidate gene for the QTL. [source] Haeckel's ABC of evolution and developmentBIOLOGICAL REVIEWS, Issue 4 2002MICHAEL K. RICHARDSON ABSTRACT One of the central, unresolved controversies in biology concerns the distribution of primitive versus advanced characters at different stages of vertebrate development. This controversy has major implications for evolutionary developmental biology and phylogenetics. Ernst Haeckel addressed the issue with his Biogenetic Law, and his embryo drawings functioned as supporting data. We re-examine Haeckel's work and its significance for modern efforts to develop a rigorous comparative framework for developmental studies. Haeckel's comparative embryology was evolutionary but non-quantitative. It was based on developmental sequences, and treated heterochrony as a sequence change. It is not always clear whether he believed in recapitulation of single characters or entire stages. The Biogenetic Law is supported by several recent studies - if applied to single characters only. Haeckel's important but overlooked alphabetical analogy of evolution and development is an advance on von Baer. Haeckel recognized the evolutionary diversity in early embryonic stages, in line with modern thinking. He did not necessarily advocate the strict form of recapitulation and terminal addition commonly attributed to him. Haeckel's much-criticized embryo drawings are important as phylogenetic hypotheses, teaching aids, and evidence for evolution. While some criticisms of the drawings are legitimate, others are more tendentious. In opposition to Haeckel and his embryo drawings, Wilhelm His made major advances towards developing a quantitative comparative embryology based on morphometrics. Unfortunately His's work in this area is largely forgotten. Despite his obvious flaws, Haeckel can be seen as the father of a sequence-based phylogenetic embryology. [source] | ||||||||||