| cell death | <cell biology> Cells die (nonaccidentally) either when they have completed a fixed number of division cycles (around 60, the Hayflick limit) or at some earlier stage when programmed to do so, as in digit separation in vertebrate limb morphogenesis. Whether this is due to an accumulation of errors or a programmed limit is unclear, some transformed cells have undoubtedly escaped the limit. See: apoptosis. (26 Mar 1998) |
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| cell degranulation | The process of losing cytoplasmic granules. This occurs in mast cells, basophils, neutrophils, eosinophils, and platelets when secretory products are released from the granules. (12 Dec 1998) |
| cell determination | The process by which embryonic cells, previously undifferentiated, take on a specific developmental character. Although the mechanism is not fully understood, homeotic proteins coded for by certain gene sequences (the homeobox) appear to trigger the process. Genes for homeotic proteins show remarkable similarity among species. See: morphogenesis, induction, evocator. (05 Mar 2000) |
| cell differentiation | Progressive restriction of the developmental potential and increasing specialization of function which takes place during the development of the embryo and leads to the formation of specialised cells, tissues, and organs. (12 Dec 1998) |
| cell disruption | <technique> The procedures used to get genetically engineered products out of the cells in which they are produced. These procedures may be mechanical, resulting in cell breakage, or depend upon cell lysis, which is caused by adding lysozyme or solvents that affect the cell membrane, or antibiotics or antimetabolites that disrupt or disorganize cell wall growth. (26 Mar 1998) |
| cell division | The separation of one cell into two daughter cells, involving both nuclear division (mitosis) and subsequent cytoplasmic division (cytokinesis). (18 Nov 1997) |
| cell division cycle gene | Genes which control the yeast cell cycle. There are around 50 different genes which do this. (09 Oct 1997) |
| cell division cycle mutant | A yeast cell which has cell division cycle genes that have mutated to become sensitive to temperature, at certain temperatures (usually high ones), various parts of the normal yeast cell cycle become abnormal, and in some strains the yeast cell does not survive at all. (09 Oct 1997) |
| cell division phases | The stages which a cell undergoes when dividing. There are four successive phases: prophase, metaphase, anaphase, and telephase. (12 Dec 1998) |
| cell electrophoresis | <technique> A method for estimating the surface charge of a cell by looking at its rate of movement in an electrical field. Almost all eukaryotic cells have a net negative surface charge. Measurement is complicated by the streaming potential at the wall of the chamber itself and by the fact that the cell is surrounded by a layer of fluid (see double layer). The electrical potential measured (the zeta potential) is actually some distance away from the plasma membrane. One of the more useful modifications is to systematically vary the pH of the suspension fluid to determine the pK of the charged groups responsible (mostly carboxyl groups of sialic acid). (26 Mar 1998) |
| cell extracts | Preparations of cell constituents or subcellular materials, isolates, or substances. (12 Dec 1998) |
| cell fate | <embryology> Of an embryonic parent (progenitor) cell or cell type, the range and distribution of differentiated tissues formed by its daughter cells. For example: cells of the neural crest differentiate to form among other things) cells of the peripheral nervous system. (26 Mar 1998) |
| cell fractionation | <technique> Strictly this should mean the separation of homogeneous sets from a heterogeneous population of cells (by a method such as flow cytometry). The term is more frequently used to mean subcellular fractionation i.e. The separation of different parts of the cell by differential centrifugation, to give nuclear, mitochondrial, microsomal and soluble fractions. (26 Mar 1998) |
| cell-free extract | <cell culture> A liquid that is a mixture of the contents of a particular type of cell, sometimes the organelles are also filtered out of the liquid. (26 Mar 1998) |
| cell-free protein synthesis | <technique> An in vitro method to make proteins, using amino acids, the mRNA corresponding to the protein to be made, and a cell-free extract (the contents of a cell after removal of the cell wall and/or outer cell membranes) for other needed components and enzymes. (26 Mar 1998) |