Differentiated cells

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Phosphorylation is the reversible process of introducing a phosphate group onto a protein. Phosphorylation occurs on the hydroxyamino acids serine and threonine or on tyrosine residues targeted by Ser/Thr kinases and tyrosine kinases respectively. Dephosphorylation is catalyzed by phosphatases. Phosphorylation is a key mechanism for rapid posttranslational modulation of protein function. It is widely exploited in cellular processes to control various aspects of cell signaling, cell proliferation, cell differentiation, cell survival, cell metabolism, cell motility, and gene transcription. 

Tubulins arose very early during the course of evolution of unicellular eukaryotes and provide the machinery for the equipartitioning of chromosomes in mitosis, cell locomotion, and the maintenance of cell shape. The primordial genes that coded for tubulins likely were few in number. As metazoan evolution progressed, natural selection processes conserved multiple and mutant tubulin genes in response to the requirements for differentiated cell types (Sullivan, 1988). 

Included among other differentiating cell lines which have been established in culture, is the human promyelocytic cell line HL-60, which differentiates into more mature myeloid cells upon treatment with retinoic acid and prostaglandin E] (PGEi). Friend erythroleukemia cells differentiate into hemoglobin-producing cells when treated with either dimethyl sulfoxide, or hexamethylene bis-acetamide. 

The importance of the basal medium in culturing normal cells was demonstrated by Dr. Richard Ham (Ham and McKeehan, 1979). Dr. Ham s laboratory developed a number of different types of culture media, in which the concentrations of the individual nutritional components have been optimized to support the growth of specific types of normal, differentiated cells. The most widely used is nutrient mixture FI2, which contains nonessential, as well as essential, amino acids, a number of lipids, and trace elements (Table 5). 

The author thanks Drs. Jane Bottenstein and Bernard Schimmer for photographs of differentiated cells, and The Educational Technology Department of The State University of New York at Buffalo for illustrations. This work was supported in part by The National Institutes of Health Grant 9 ROl DK4028607. 

Under stable conditions of extremely low productivity imposed by mineral nutrient stress (position 7 in Fig. lb) there is little seasonal change in biomass. Leaves and roots often have a functional life of several years and there is usually an uncoupling of resource capture from growth (Grime, 1977 Chapin, 1980). Because of the slow turnover of plant parts, differentiating cells occupy a small proportion of the biomass and morphogenetic... 

Ray P. Krishnamoorthy N. Ray A Emerging functions of c-kit and its ligand stem cell factor in dendritic cells regulators of T cell differentiation. Cell Cycle 2008 7 2826-2832. 

The differentiation of cells occurs concomitantly to modifications of wall components. The nature of the pectins of the walls changes under the action of enzymes, among which esterases, secreted between the apical meristematic cells and the more basal differentiated cells. The apposition of new layers of pectins with different compositions at the inner surface of the walls is another mechanism by which the cells adapt their immediate environment. Using the 2F4 antibody, we have observed, in plant suspensions as well as in tissues, a third mechanism involved in wall modification. Numerous invaginations of the... 

Progenitor cell An immature or precursor cell that can divide and give rise to a differentiated cell. 

Key Words Chemokines lymphocyte development T-cell differentiation cell trafficking memory thymus bone marrow. 

The proteins encoded by most proto-oncogenes are normally expressed in a variety of differentiated cell types, where they generally function as... 

Edgar The larva is a fully functional animal made up of terminally differentiated cells, but its purpose is to be an incubator for these imaginal discs that make the fly. It has to bulk up on mass and it transfers this biomass to the discs as they grow. I think it is a really simple way for an organism that is already differentiated to grow. It is a sort of stripped-down cell cycle that can respond to nutrition. There is no need for those cells to proliferate. 

Most mammalian cell types develop from precursor cells that divide a limited number of times before they stop and terminally differentiate. In no case do we understand why the cells stop dividing when they do. The stopping mechanisms are important because they determine how many differentiated cells are produced and when differentiation begins. We have been studying the stopping mechanism in oligodendrocyte precursor cells (OPCs) isolated from the developing optic nerve of rats and mice. 

The superficial cells are irregular arrays of polygonal cells with a diameter of 40-60 pm and a thickness of 2-6 pm each. These cells, the most differentiated cells of the epithelium, possess microvilli in their apical surfaces, which are covered with a glycocalyx. It is, however, controversial whether mucus exists on their surface [58,59], As cell division occurs in the basal cells of the cornea, the daughter cells move toward the surface while becoming more differentiated. As the daughter cells migrate toward the outermost layer, the superficial cells are... 

Gu, W., Schneider, J.W., Condorelli, G., Kaushal, S., Mahdavi, V. and Nadal-Ginard, B. (1993) Interaction of myogenic factors and the retinoblastoma protein mediates muscle cell commitment and differentiation. Cell 72, 309-324. 

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