ABSTRACT
Atrioventricular septal defect occurs with a high prevalence in both human Down syndrome (trisomy 21) and the animal model for this disorder, murine trisomy 16 (Ts-16). The embryologic basis of this defect is the failure of the endocardial cushions to fuse. Quantitatively, Ts-16 hearts, when compared to normal mouse embryos, were not significantly different in either the estimates of whole heart volume or endocardial cushion volume. However, both the raw number of cardiac mesenchyme cells and the cellular density were reduced significantly. Qualitatively, endocardial cushion shape was elongated. Immunohistochemistry revealed an apparent delay in the temporally regulated expression of cytotactin and fibronectin during cushion development. Also, anti-heparan sulfate staining was noted on newly formed cardiac mesenchymal cells. These results suggest that the failure of endocardial cushion fusion in the Ts-16 mouse may be related to an elongated shape of the cushions and an inhibition or delay in the induction, transformation, or seeding of cardiac mesenchymal cells.
Subject(s)
Disease Models, Animal , Down Syndrome/complications , Endocardial Cushion Defects/embryology , Gene Expression Regulation, Developmental , Animals , Down Syndrome/embryology , Endocardial Cushion Defects/metabolism , Endocardial Cushion Defects/pathology , Fibronectins/metabolism , Gestational Age , Heparitin Sulfate/metabolism , Immunohistochemistry , Mesoderm/pathology , Mice , Mice, Mutant Strains , Tenascin/metabolismABSTRACT
ES/130 is a novel 130-kDa protein that has been linked previously to the transformation of endocardial endothelium into cushion mesenchyme. In the present study we report the localization of protein and mRNA for ES/130 in stages 7-plus through 20 chick embryos and present functional data related to a potential mechanism for ES/130. The temporal and spatial regulation of ES/130 expression suggests that this epithelial-to-mesenchymal transformation is a result of homogenetic induction. Functional studies indicate that myocardially derived ES/130 elicits expression of this protein by target AV endothelial cells, which is linked to a signal transduction cascade. The localization of ES/130 to other sites of inductive interactions (e.g., limb bud ectoderm, gut, and notochord) implies that this protein may have a more widespread importance to embryogenesis beyond its involvement in cardiac cushion tissue formation.
Subject(s)
Avian Proteins , Extracellular Matrix Proteins/metabolism , Heart/embryology , Mesoderm/physiology , Animals , Base Sequence , Cells, Cultured , Chick Embryo , Down-Regulation , Embryonic Induction , Endothelium/cytology , Endothelium/embryology , Extracellular Matrix Proteins/genetics , Gene Expression Regulation, Developmental , Immunohistochemistry , In Situ Hybridization , Molecular Sequence Data , Morphogenesis , RNA, Messenger/metabolism , Signal Transduction , Time FactorsABSTRACT
The ability of viable and glutaraldehyde-fixed, stationary-phase yeast cells of Candida albicans to bind concanavalin A and monospecific antiserum for antigenic factor 1 was examined. Both fluorescence flow cytometric analysis and transmission electron microscopy indicated that glutaraldehyde-fixed cells bound less of the two reagents than did unfixed viable cells.
Subject(s)
Aldehydes , Antigens, Fungal/metabolism , Candida albicans/metabolism , Glutaral , Receptors, Concanavalin A/drug effects , Antigens, Fungal/immunology , Candida albicans/ultrastructure , Cell Wall/metabolism , Cell Wall/ultrastructure , Fixatives , Flow Cytometry , Fluorescent Antibody Technique , Mannans/immunology , Mannans/metabolism , Receptors, Concanavalin A/ultrastructureABSTRACT
Fresh pullet eggs (White Leghorn strain) were incubated from 19-2ldium-gold and observed in a Cambridge S4 scanning electron microscope. Shrunken cells with intracellular yolk granules embossed on the surface are produced by the strongly hypertonic Karnovsky's fixer (Final: 2010 mOsm). Embryos fixed with modified Karnovsky's fixer (Final: 373 mOsm) possess surfaces with irregular microappendages. Swollen cells with few microappendages are observed when embryos are fixed in a hypotonic environment (Final: 250 mOsm or less). Ideal fixatives preserve a relatively flat surface, with cells bordered by smoothsurface microappendages. For adequate SEM fixation, fixative vehicle should be approximately isotonic for tissue, with aldehyde (2% or less) added to vehicle.
Subject(s)
Chick Embryo/cytology , Fixatives , Microscopy, Electron, Scanning , Animals , Glutaral , Osmolar ConcentrationABSTRACT
Fresh pullet eggs (White Leghorn Strain) were incubated from 6-19 hours. Blastoderms were fixed in situ with aldehyde fixative, post-osmicated in 2% OsO4, dehydrated in acetone, critical-point-dried, mounted ventral side up, coated with palladium-gold wire and observed in a Cambridge Stereoscan S4 scanning electron microscope. Large extracellular yolk granules had a smooth surface and appeared to break up into smaller particles. Similar particles have been observed intracellularly in transmission electron microscopy. Numerous microappendages, mostly ruffles, suggest phagocytosis as a method of absorption of yolk granules into the cells. Absorption of yolk by the cells of the blastoderm involves an initial break up of yolk granules followed by phagocytosis.
