Competence of cells

Part of an organism is said to be determined to form a specific structure provided it still forms that structure when placed in a new environment. Three concepts are implicit in this definition. First, determination results from stable changes in phenotype that persist in the absence of the factors that initiated the change. This allows structures to "remember" past events and leads to the progressive nature of development. Second, determination alters the competence of cells, i.e., their capacity to respond to specific signals. Finally, determination is relative. It depends on the conditions of the experiment as well as the properties of the developing structure. Thus developmental states stable in one environment are not necessarily stable in some other environment. 

E. The Combined Effect of Dimethylsulfoxide and DEAE-Dextran on the Competence of Cells for Infection by Viral RNA... 

Comparable results were obtained when macromolecular synthesis in HeLa cells was inhibited by infection with the DNA-containing frog virus 3 (Koch, unpublished) the competence of cells for viral RNA was reversibly affected by infection with frog virus 3 whereas the competence for RF-RNA was not restored within 120 minutes of incubation at 37° C. Cellular competence for infection by viral RNA and RF-RNA is enhanced by various polycations, by DMSO and by VP4 in differing degrees. Thus, cellular competence for RF-RNA is maximal when the cells are sensitized by DEAE-dextran alone (Koch and Bishop, 1968), and cannot be further stimulated by poly-L-omithine or DMSO (Koch, unpublished). However, cellular competence for infection by viral RNA is 5 to 10 times higher when cells are exposed to DEAE-dextran and DMSO or DEAE-dextran and poly-L-ornithine than to DEAE-dextran alone (Koch, 1971b, and unpublished). 

The separation of cells from the culture media or fermentation broth is the first step in a bioproduct recovery sequence. Whereas centrifugation is common for recombinant bacterial cells (see Centrifugal separation), the final removal of CHO cells utilizes sterile-filtration techniques. Safety concerns with respect to contamination of the product with CHO cells were addressed by confirming the absence of cells in the product, and their relative noninfectivity with respect to immune competent rodents injected with a large number of CHO cells. 

The covalent bond is the strongest force that holds molecules together (Table 2-1). Noncovalent forces, while of lesser magnitude, make significant contributions to the structure, stability, and functional competence of macromolecules in living cells. These forces, which can be either attractive or repulsive, involve interactions both within the biomolecule and between it and the water that forms the principal component of the surrounding environment. 

Pharmaceutical Removal of suspended matter is a frequent application for MF. Processes may be either clarification, in which the main product is a clarified liquid, or solids recovery. Separating cells or their fragments from broth is the most common application. Clarification of the broth in preparation for product recovery is the usual objective, but the primary goal may be recovery of cells. Cross-flow microfiltration competes w l with centrifugation, conventional filtration by rotary vacuum filter or filter press and decantation. MF delivers a cleaner permeate, an uncontaminated, concentrated cell product... 

Effective management of microbiology collections requires that the cultures meet current and future international standard requirements of biotechnology industries. The knowledge and competence of the scientists performing cell culture work obviously impact the quality of the cultures. 

Gautier Can you do the experiment to check whether this difference in responsiveness between G1 and G2 is dependent on transcription Another explanation would be that the passage into S phase changes the transcriptional competence of the cell. 

GM-CSF and IL-3 have been shown to compete for receptors in some types of cells (e.g. eosinophils and KG-1 cells), indicating some structural homology between GM-CSF and IL-3 receptors, perhaps because they share certain subunits or adapter proteins. GM-CSF occupancy results in phosphorylation of certain proteins, and because the receptor possesses no inherent kinase activity, receptor occupancy must be linked to kinase activity via the generation of second messenger molecules. Pretreatment of cells with pertussis toxin abolishes the effects of GM-CSF, indicating the involvement of G-proteins in signal transduction. Priming of neutrophil functions with GM-CSF involves the activation of phospholipases A2 and D. 

Immunologically competent cells, whether they are T or B lymphocytes, have membrane receptors that are specific for an antigen. It is basically the binding of the antigen to the specific receptor on the appropriate lymphocyte which initiates the whole process, stimulating the cell to proliferate and producing a clone of identical cells, a process known as clonal selection . The nature of the secondary response is due in the main to this large number of cells now available. 

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