Carbohydrate embryonal cells

Figure 10-7 Cell adhesion and control of stem cell fate through MOE (A) metabolic incorporation of AcsManNTGc (10) results in the replacement of the natural cell surface sialic acid NeuSAc with the thiol-containing counterpart NeuSTGc (B) glycocalyx-displayed thiols are ideally situated to attach to exogenous surfaces with complementary chemical properties such as gold (C) Novel carbohydrate-mediated thiol-gold cell adhesion leads to the differentiation of human embryonic cells to neurons as described in detail in ref. 32.

Historically, the development of animal cell culture systems has been dependent upon the development of new types of tissue culture media. Mouse L cells and HeLa cells were developed using a balanced salt solution supplemented with blood plasma, an embryonic tissue extract, and/or serum. In 1955 Eagle developed a nutritionally defined medium, containing all of the essential amino acids, vitamins, cofactors, carbohydrates, salts, and small amounts of dialyzed serum (Table 1). He demonstrated that this minimal essential medium (MEM) supported the long-term growth of mouse L and HeLa ceils. Eagle s MEM was so well defined that the omission of a single essential nutrient eventually resulted in the death of these animal cells in culture. 

The seeds of dicotyledonous plants have two cotyledons, or seed leaves, which are part of the embryo. The cotyledons usually are the main storage tissue, although in some plants (such as castor bean) the endosperm also has a storage function. During development in the field, seeds gradually accumulate storage oils, proteins and carbohydrates (Table 3.1). In the seed, the cotyledon structure is relatively simple. The remainder of the embryo, the embryonic axis, consists mostly of undifferentiated cells, but provascular tissue can be detected that develops into vascular tissue in the seedling. 

Recent studies have demonstrated that cell-surface expression of specific complex carbohydrates is associated with various stages of embryonic development and cell differentiation (4-7). Abnormalities in the expression of complex... 

Targeted delivery has also been used to investigate the structure of carbohydrates needed to obtain discrimination of cellular uptake between liver and tumor cells [184], A study was performed by doubly modifying BSA with both a fluorophore (via Lys isothiocyanate derivatization) and different fucose derivatives (via Tyr diazotization). Similar studies have used EDC-mediated coupling to also attach therapeutic agents for delivery to human embryonal carcinoma cells [185]. 

Song Y, Withers DA, Hakomori S. Globoside-dependent adhesion of human embryonal carcinoma cells, based on carbohydrate-carbohydrate interaction, initiates signal transduction and induces enhanced activity of transcription factors API and CREB. J. Biol. Chem. 1998 273 2517-2525. 

The physical and chemical properties of dry beans are primary factors in determining subsequent final product quality. Dry bean seed structure is comprised of a seed coat and an embryonic cotyledon. Structurally, seed coat, cell walls, middle lamella and other cellular membranes greatly influence performance. Further, chemical components (carbohydrates, proteins, phytate, polyphenols and lignin) directly influence quality. 

In summary, gene knockout mouse technology has allowed us to determine the function of cell surface carbohydrates in mouse embryos in recent years. Some glycosyltransferases-deficient mutant mouse showed severe phenotypes, including embryonic lethality. However, we have not yet identified the mechanisms underlying these phenotypes. Identification of critical carbohydrate structure (s), specific proteins carrying specific carbohydrate structure(s), and the counter-receptors for those carbohydrates should be identified in future studies. 

A membrane-associated glycoprotein has been solubilized by proteolytic digestion of membranes of rat mammary carcinoma cells. The material was not further characterized other than by its affinity for Lens culinaris lectin. A class of glycoproteins recognized as cell-surface markers by lectins and antibody appears to be expressed on the surface of embryonal carcinoma cells. Because of their unusual structural characteristics and abundance, the carbohydrate chains may play a role in the early stages of embryogenesis. 

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