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Results for “Embryo, Nonmammalian”

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At least 19 recordsLinked to original sources
PubMed2002

Altering fish embryos with aquaporin-3: an essential step toward successful cryopreservation.

Fish populations are globally threatened by overharvesting and habitat degradation. The ability to bank fish embryos by cryopreservation could be crucial for preserving species diversity, for aquaculture (allowing circannual fish farming), and for managing fish models used in human biomedical research. However, no nonmammalian embryo has ever been successfully cryopreserved. For fish, low membrane permeability prevents cryoprotectants from entering the yolk to prevent cryodamage. Here, we present evidence of a membrane mechanism hindering cryopreservation of fish and propose a novel solution to this obstacle. Zebrafish (Danio rerio) embryos have rectifying membranes that allow water to leave but not to reenter readily. This feature may be an evolutionary trait that allows freshwater embryos to grow in hypoosmotic environments without osmoregulatory organs. However, this trait may also prevent successful fish embryo cryopreservation because both water and cryoprotectants must move into and out of cells. As a solution, we injected zebrafish embryos with mRNA for the aquaporin-3 water channel protein and demonstrated increased membrane permeability to water and to a cryoprotectant. Modeling indicates that sufficient cryoprotectant enters aquaporin-3-expressing zebrafish embryos to allow cryopreservation.

Animals↗
PubMed2005

Overexpression of Nodal promotes differentiation of mouse embryonic stem cells into mesoderm and endoderm at the expense of neuroectoderm formation.

Understanding how to direct the fate of embryonic stem (ES) cells upon differentiation is critical to their eventual use in therapeutic applications. Clues for controlling ES cell differentiation may be found in the early embryo because mouse ES cells form derivatives of all three embryonic germ layers upon injection into blastocysts. One promising candidate for influencing the differentiation of ES cells into the embryonic germ layers is the transforming growth factor-beta (TGF-beta) growth factor, Nodal. Nodal null mouse mutants lack mesoderm, and injection of Nodal mRNA into nonmammalian embryos induces mesodermal and endodermal tissues. We find that overexpression of Nodal in mouse ES cells leads not only to up-regulation of mesodermal and endodermal cell markers but also to downregulation of neuroectodermal markers. These findings demonstrate the importance of Nodal's influence on the differentiation of pluripotent cells to all three of the primary germ layers. Accordingly, altering expression of factors responsible for cell differentiation in the intact embryo provides an approach for directing ES cell fates in vitro toward therapeutically useful cell types.

Animals↗
PubMed2004

Activation of apoptosis and caspase-3 in zebrafish early gastrulae.

Nonmammalian vertebrate embryos do not manifest apoptosis before gastrulation, and it has been suggested that their cells are inhibited from undergoing apoptosis. To study this interesting possibility, the zebrafish (Danio rerio) embryo is an excellent model. However, the appearance of apoptosis varies among species, and many components of cell death are not highly conserved. To undertake the larger investigation, we first need to document by several criteria that cell death in the zebrafish embryo is apoptotic. Exposure of gastrulating germ-ring stage embryos to cycloheximide or staurosporine elicits an arrest in development and cell death within 8 hr. Caspase-3 activity increases, followed by translocation of phosphatidylserine, loss of cell-cell adhesion, cleavage of poly (ADP-ribose) polymerase, terminal deoxynucleotidyl transferase-mediated dNTP-fluorescein nick end labeling (TUNEL)-positive nuclei, internucleosomal DNA fragmentation, chromatin condensation and margination, and blebbing of the nuclear membrane. Thus, by many criteria, cell death in zebrafish is apoptotic; many of the markers of apoptosis found in mammals are conserved in zebrafish; and post-midblastula transition embryos have the capacity to activate a caspase-dependent apoptotic response well before naturally occurring programmed cell death is seen.

Adenosine Diphosphate Ribose↗
PubMed2002

Cell death during development.

There are many ways to measure apoptosis and other forms of programmed cell death in development. Once nonmammalian embryos have passed the midblastula transition, or much earlier in mammalian embryos, apoptosis is similar to that seen in adult organisms, and is used to sculpt the animal, fuse bilateral tissues, and establish the structure of the nervous system and the immune system. Embryos present unique problems in that, in naturally occurring cell deaths, few cells are involved and they are frequently in very restricted regions. Thus, identification of apoptotic or other dying cells is more effectively achieved by microscopy-based techniques than by electrophoretic or cell-sorting techniques. Since embryos have many mitotic cells and are frequently more difficult to fix than adult tissues, it is best to confirm interpretations by the use of two or more independent techniques. Although natural embryonic deaths are frequently programmed and require protein synthesis, activation of a cell death pathway is often post-translational and assays for transcriptional or translational changes-as opposed to changes in aggregation of death-related molecules or proteolytic activation of enzymes-is likely to be uninformative. Also, embryos can frequently exploit partially redundant pathways, such that the phenotype of a knockout or upregulated death-related gene is often rather modest, even though the adult may develop response or regulation problems. For these reasons, the study of cell death in embryos is fascinating but researchers should be cautious in their analyses.

Animals↗