Fusion of cells

Myoblasts may differentiate and fuse without undergoing DNA synthesis (Nadel-Ginard, 1978), but fusion does not occur in calcium-free medium. Thus, if chick embryo myoblasts are set up in calcium-free (< 20/xM Ca2+) DMEM containing 5% heat inactivated FBS and 2% chick embryo extract (Appendix 1) the fusion which normally starts at around 24 h fails to occur. Addition of 1.4 mM CaCl 2 after 50 h will now produce synchronised fusion of cells (Wakelam and Pette, 1982). 

Fig. 2. (A) C8166 T-lymphoblastoid cells growing in culture. These grow characteristically in large clumps. Single cells can be seen at the edge of the clumps. (B) The same cells acutely infected with HIVIIIB. Large multinucleated cells are produced when sufficient viral proteins are expressed on the surface of the cells allowing fusion of cell membranes.

Fusion from without occurs when syncytia form quickly with high-titer virus. Fusion from within occurs when low-titer HIV requires several rounds or replication to occur, in a culture, before sufficient virus particles are present to cause the fusion of cell membranes. 

An RNA aptamer has been selected to activate the carboxylic acid of amino acids that mimics the formation of a mixed phosphate anhydride synthesis of aminoacyl tRNA synthetases. The optimal aptamer requires only Ca + for the reaction, and operates at low pH with Xm 50 mM and /ccat 1.1 min for the activation of leucine. This lends support to the concept of translation in an RNA-based world. An RNA-cleaving DNAzyme has been used to target a chemokine receptor required by HIV-1 for entry into susceptible cells. The DNAzyme was found to be very efficient, and specifically interfered with the fusion of cells that harboured the T-lymphocytotropic HIV-1 envelope. 

Boland, T, et ah, Gell and organ printing 2. Fusion of cell aggregates in three-dimensional gels. Anat Rec 2003, 272A, 497-502. 

The fusion of cells and of cell nuclei (A) occurs in sexual fertilization. Hybrid cells containing several nuclei, including examples of union from different species, have been prepared by fusion of the separate cells using killed virus to effect the fusion. In some cases, fusion of nuclei was observed also (Harris and Watkins 1965). 

ABSTRACT A brief history of the behavior of materials in nonuniform electrical fields is presented, followed by a theory of dielectrophoretic force and the derivation of the general force equation. Attention is paid to the several classes of polarization which lead to the experimental considerations of induced cellular dielectrophoresis. A distinction between batch and continuous methods is discussed, with a focus on a new microtechnique. While dielectrophoresis can induce aggregation of materials, i.e., cells, other orientational applications exist. Cell division, cellular spin resonance, and pulse-fusion of cells form topics appropriate to the realm of high-frequency electrical oscillations and are discussed in the context of living material. 

H. Rivera, H. A. Pohl, S. Cherski, and M. Swicord, Electrical Fusion of Cells and Nuclei in Vitro A Preliminary Note, J. Biol Phys. 11, 63-65 (1983). 

High-Throughput Pairing and Fusion of Cells with Passive Hydrodynamic Traps... 

Besides this "s3mthetic route, the combination of natural and polymerizable membrane components is principally possible via the fusion of cell membranes with polymerizable vesicles. Fusion of cells is possible using dielectrophoresis and dielectric breakdown. Since it was possible to prepare giant" vesicles (visible under the light microscope) these techniques were also successfully applied to vesicle-vesicle fusion. Investigations on cell-vesicle fusion are currently under way. 

Viruses can induce fusion of cells. Detergents can modify this action and a report on the effects of detergents on virus- or chemically-induced fusion of erythrocytes has been published. The extent of activation or inhibition by surfactants of Sandai virus-induced fusion was determined primarily by the... 

The latter often give excellent yields of hybridomas probably because the freezing mixture contains dimethyl sulfoxide which is known to assist fusion of cell membranes. 

Modem biotechnology has been defined as the application of a) In vitro nucleic acid techniques, including recombinant deoxyribonucleic acid (DNA) and direct injection of nucleic acid into cells or organelles, or b) Fusion of cells beyond the taxonomic family, that overcome natural physiological reproductive or recombination barriers and that are not techniques used in traditional breeding and selection, in the Cartagena Protocol on Biosafety (SCBD, 2000) and by the Codex Alimentarius Commission (Codex, 2003a). 

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