Effect on Cell Division

Colchicine can arrest plant and animal cell division in vitro and in vivo. Mitosis is arrested in metaphase because of failure of spindle formation. Cells with the highest rates of division are affected earliest. High concentrations may completely prevent cells from entering mitosis, and they often die. The action also is characteristic of the vinca alkaloids (vincristine and vinblastine), podophyllotoxin, and griseofulvin. 

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Human Effects on cell division + Bulsma and DeFrance 1976... 

Variation in the magnesium (Mg) content of the medium may exert a marked effect on cell division of some bacteria. In a Mg-deficient medium, Gram-positive rods grow in the form of long filaments. Such filaments revert to normal forms when transferred to the same medium supplemented with suitable concentrations of Mg. Filament formation is enhanced by the addition of zinc and cobalt. Inhibition of cell division occurs also in media supplemented with an excess of Mg. 

The dicarboximides inhibit spore germination and cause increased branching, swelling and lysis of germ tubes and hyphal tips. Effects on cell division have been reported but no major inhibition of nucleic acid metabolism, respiration, protein or lipid synthesis has been observed. 

Colchicine is an important naturally occurring tropolone derivative. It is isolated from the autumn crocus and is used in medicine for the treatment of gout. It also has an effect on cell division and is used in plant genetic studies to cause doubling of chromosomes. The structure has been confirmed by total synthesis. 

Tamoxifen decreases the rate of proliferation of breast cancer cells in vitro by inhibiting the estrogen-dependent production of specific proteins and growth factors that exert autocrine effects on cell division. Antiandrogenic compounds antagonize the effects of testosterone and are of value in the treatment of hirsutism and other masculinizing syndromes. 

North Carolina State University, Crop Sciences Department Raleigh, NC Research on the mechanism of aluminum toxicity in plants. This study will determine the extent of aluminum accumulation inside cells at the root apex using microanalytical techniques and will define associated effects on cell division, cell expansion, and cellular accumulation of calcium and magnesium. U.S. Department of Agriculture... 

The induced inhibition of longitudinal growth by tetcyclacis results both from inhibited cell elongation and from reduced cell division. The relative proportions to which cell elongation and cell division contribute to the shortening effect varied in trials with maize, sunflowers, and soybeans, i.e., the influence effected via cell division increased with an increase in concentration of the PBR. The inhibitory effect on cell division detected in intact plants has been confirmed in cell suspension cultures of the same plant species (11). 

Jones, R.W. and M.N. Huffman. Fish embryos as bioassay material in testing chemicals for effects on cell division and differentiation. Trans. Am. Microsc. Soc. 76 177-183, 1957. 

Effects on Cell Division and Cell Death Rates. The cell division and cell death rates in the TSCE and MSCE model cannot be estimated independently when using incidence data alone however, the approximate net cell proliferation rate, -(p + q) = (a - f3- Pt i) is an identifiable parameter (Heidenreich et al. 1997). The effects of nongenotoxic agents on cancer risk can be evaluated by estimating the effect of such agents on the cell proliferation (or promotion) rate in the TSCE or MSCE model. 

Isoindoles are not known to occur as natural products again, there is a marked contrast with the indoles. However, the cytochalasins, a group of mold metabolites having a marked effect on cell division, contain a highly substituted isoindoline nucleus (3). Cytochalasins A and B (4 and 5) have been obtained from Helminthosporium dematioideum,1 cytochalasins C and D (6 and 7) from Metarrhizium anisopliae,8 and the cytochalasins 8 and 9 from the fungus Phomopsis paspalli found on an Indian millet.9... 

Auxin has been implicated in a bewildering array of growth responses. At the level of the cell, these responses involve rapid changes in cell expansion, effects on cell division and meristem activity, as well as differentiation of specific cell types [1]. In an effort to understand molecular aspects of auxin signaling, many researchers have focused on rapid biochemical responses associated with auxin-induced cell elongation. These include activation of a plasma membrane H -ATPase [2], changes in the behavior of ion channels... 

This analysis will determine if the herbicidal effect on cell division is at interphase (Gj, S, G2) or mitosis. 

Types of Cell Division Effects. Classification of herbicidal effects on cell division is not uniform. This has lead to confusion about the action of herbicides on cell division. Terms such as "mitotic poisons", "meristem active", and "mitotic inhibitors" have been used to describe the same effect of a herbicide on cell division. A more useful classification of herbicidal effects would be to divide herbicides into 2 classes those inhibiting cell division and those disrupting cell division (Figure 1). Inhibition of cell division will result in treated meristems that only contain interphase cells. If cell division is disrupted, one or more mitotic stages normally present in the meristem tissue will not be found. These two effects on cell division result from different mechanisms. 

The effects on cell division mentioned in the first paragraph of this note are absent in cells which have been transferred to an inorganic medium (Plesner et al., 1964) between the penultimate sixth and the ultimate seventh heat shock. Agents were added just after EH7. As demonstrated by B. A. Lowy and V. Leick (1969) there is no synthesis of DNA between synchronous divisions 1 and 2 in such cells. 

Since there is believed to be a threshold dose below which such nonmutagenic toxins exert no effect on cell division, according to Ames and Gold (1990), At the low doses of most human exposures (where cell-killing and mitogenesis do not occur), the hazards [of nonmutagenic toxins] may be much lower than is commonly assumed and often will be zero (p. 971). 

Cell division in higher plants requires both cytokinin and auxin. While the cytokinins exhibit the most dramatic effects on cell division they are ineffective in the absence of auxin. The effects of cytokinin and auxin on cell division vary with concentration and with the state of differentiation of the cells. Nondividing differentiated cells are induced to divide when exposed to cytokinin and auxin, while division in rapidly dividing meristematic cells is more likely to be retarded in their presence. This indicates that the control sites for cell cycling may be altered during differentiation, perhaps by a shift in sensitivity to auxins and cytokinins. 

Jacobs, R.S., S. White, and L. Wilson Selective Compounds Derived from Marine Organisms Effects on Cell Division in Fertilized Sea Urchin Eggs. Fed. Proc. 40, 26 (1981). 

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