Canadian Red Cross

About: Canadian Red Cross is a nonprofit organization based out in Ottawa, Ontario, Canada. It is known for research contribution in the topics: Antibody & Antigen. The organization has 948 authors who have published 780 publications receiving 26733 citations. The organization is also known as: CRC & Canadian Red Cross Society.

Failure of blood-island formation and vasculogenesis in Flk-1-deficient mice.

Abstract: The receptor tyrosine kinase Flk-1 (ref. 1) is believed to play a pivotal role in endothelial development. Expression of the Flk-1 receptor is restricted to endothelial cells and their embryonic precursors, and is complementary to that of its ligand, vascular endothelial growth factor (VEGF), which is an endothelial-specific mitogen. Highest levels of flk-1 expression are observed during embryonic vasculogenesis and angiogenesis, and during pathological processes associated with neovascularization, such as tumour angiogenesis. Because flk-1 expression can be detected in presumptive mesodermal yolk-sac blood-island progenitors as early as 7.0 days postcoitum, Flk-1 may mark the putative common embryonic endothelial and haematopoietic precursor, the haemangioblast, and thus may also be involved in early haematopoiesis. Here we report the generation of mice deficient in Flk-1 by disruption of the gene using homologous recombination in embryonic stem (ES) cells. Embryos homozygous for this mutation die in utero between 8.5 and 9.5 days post-coitum, as a result of an early defect in the development of haematopoietic and endothelial cells. Yolk-sac blood islands were absent at 7.5 days, organized blood vessels could not be observed in the embryo or yolk sac at any stage, and haematopoietic progenitors were severely reduced. These results indicate that Flk-1 is essential for yolk-sac blood-island formation and vasculogenesis in the mouse embryo.

Differential staining of acid glycosaminoglycans (mucopolysaccharides) by Alcian blue in salt solutions

Abstract: The application of the “critical electrolyte concentration” (CEC) concept to the differentiation of acidic glycosaminglycans (mucopolysaccharides) is described. Alcian Blue 8GX stains with increasing selectivity as increasing amounts of magnesium chloride are incorporated into the dye solution. Model experiments with pure polyanions, or artifically carboxylated, phosphorylated and sulphated liver sections, showed that binding of dye to carboxylate or phosphate groups ceased at low electrolyte concentrations (< 0.3M) whereas dye continued to be held by sulphate ester groups at concentrations five to ten times as high. The similarity to the well established cetylpyridinium system for polyanion fractionation is discussed. Sections of tissues chosen to contain predominantly or characteristically carboxylated mucins, and/or sulphate ester polyanions showed a staining pattern entirely similar to the model sections. Goblet cell mucin in rat ileum stained at < 0.4M MgCl2, Cartilage at < 0.6M MgCl2, mast cells at < 0.75M, and corneal stroma at < 1.0M. These results are in agreement with the known contents of sialo-mucin, chondroitin sulphate, heparin and keratansulphate, respectively. The conditions in which this principle can be used in a practical technique are described.