Chemical induction of spindle disturbances and abnormal chromosome numbers in cultured mammalian cells
Sammanfattning: Early investigations have shown that many chemically different compounds can cause spindle disturbances in eukaryotic cells and that there is an unspecific (physical) mechanism based on the partitioning of the compound into cellular hydrophobic compartments. This suggests that the approach should be quantitative when testing compounds for spindle disturbing activity in vitro; effect/no effect is not the most pertinent question.This study demonstrates how a set of reference compounds can be used in attempts to identify compounds that act by a more specific (chemical) mechanism to disturb the spindle. All experiments were performed with an established cell line (V79 Chinese hamster) which has no mixed function oxidase activity. The results suggest that there is a good qualitative coupling between c-mitosis and aneuploidy with chemical treatment. Among compounds that are particularly active in relation to their lipophilic character are some chlorophenols, caffeine, diamide, diethyl maleate, l-chloro-2, 4-dinitrobenzene and tertiary butylhydroperoxide. This points to Ca2+-sequestration of mitochondria and/or cellular pH-regulation (chlorophenols), Ca2+ release and sequestering by the endoplasmic reticulum (caffeine), enzymatic conjugation to glutathione (diethyl maleate, chlorodinitrobenzene) and hydroperoxide metabolism (t-butylhydroper- oxide) as important target functions for specific activity. The results with some of the agents suggest that there is a critical level of reduced glutathione (60—70% of control) below which the integrity of the spindle is in danger.The concentration response curves for c-mitosis with caffeine, diamide, diethyl maleate and chlorodinitrobenzene were found to have a similar shape. The shape is particular to these four agents among the 22 being tested. From this resemblance and the probable action of caffeine it is hypothesized that the c-mitotic effect of the GSH specific agents can be brought back to an impairement of the regulation of free Ca2+ in the spindle. The involvement of Ca2+ in the c-mitotic effect of t-butylhydrop eroxide is indicated by the coincidence of c-mitosis and a stimulation of the G,->S entry in treated asynchronous cell populations.
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