Mitotic frequency

It is often difficult to avoid introducing some degree of synchronous growth in a culture simply as a results of routine operations. Thus Stubblefield et al. (1967) found that subculture of Don-C cells every 24 h exerted a selection pressure favouring cells with a 12 h generation time and highest mitotic frequencies at about 7 and 19 h. 

Gene Action, Mitotic Frequency, and Morphogenesis in Higher Plants... 

RELATIONSHIP BETWEEN MITOTIC FREQUENCY AND ORIENTATION OF MITOSES... 

Eleven male volunteers aged 20-30 years ingested lead acetate for 49 days. PbB levels were kept at approximately 40 pg/dL. The frequency of chromosome aberrations was assayed after lymphocyte culture for 72 hours and found to be no different from that of 10 controls. The lymphocytes from lead-exposed subjects did show a higher mitotic activity (Bulsma and DeFrance 1976). 

The in vivo micronucleus test is used for the detection of damage to chromosomes as well as the mitotic apparatus in bone marrow or peripheral blood cells of rodents. The assay system has been well standardized.14-17 The basic features of the test system are (1) the effect of the test chemical is observed in anucleated polychromatic erythrocytes (PCEs) (2) PCEs have a relatively short lifespan, so that any micronuclei they contain must have been generated as a result of recently induced chromosome damage (3) micronuclei are readily identifiable and their distribution is well defined and (4) the frequency of induced micronuclei in PCEs is dependent on sampling times. 

Mitotic abnormalities Back mutation frequency Chromosomal aberrations... 

A small increase in somatic mutation frequency was reported in the eye-colour spot test with Drosophila melanogaster exposed to di(2-ethylhexyl) phthalate in the feed but no effect was observed in two independent wing-spot tests. In a single study, mitotic recombination was not induced by di(2-ethylhexyl) phthalate neither was sex-linked recessive lethal mutation induced in two studies in D. melanogaster treated with di(2-ethylhexyl) phthalate in the feed or by injection. When administered to D. melanogaster, di(2-ethylhexyl) phthalate and A-nitrosodiethylamine induced DNA double-strand breakage and DNA repair, although neither compound was active when administered alone. 

Chromosomal aberrations were not induced by di(2-ethylhexyl) phthalate in any of eight studies in various types of cultured cells in the absence of metabolic activation. Only three of these studies for chromosomal aberrations included an exogenous metabolic activation system. Of these, one, using Syrian hamster embryo cells, found an increase in aberration frequency. Weak effects were detected for the induction of aneuploidy and mitotic division aberrations in Chinese hamster lung cells. 

The electrodes were powered by an audio amplifier whose input frequency was set by an audio oscillator. The impedance of the chamber, 6 Q, was perfectly matched to the output impedance of the amplifier. To test the proper functioning of the apparatus before putting in mammalian cells, we used the common bacterium Escherichia coli. These, and prokaryotic cells generally, do not show mitotic figures in division. After the bacterial population reached a steady state, the electric field was turned on. The density... 

---