In vitro induction of abnormal anaphases by contaminating atmospheric dust from the city of Mexicali, Baja California, Mexico

Mexicali dust (MD) is a mixture of particles of potassium aluminum silicates (98 percent) and sodium dioxide (2 percent) that induces pulmonary damage under experimental conditions, and is capable of inducing in vitro chromosomal alterations in exposed lymphocytes. It has been proposed as an atmospheric contaminant with pathogenic potential. among the chromosomal alterations observed, numeric alterations were predominant. The present study was designed to evaluate the capacity of MD to induce anaphasic changes in the Balb c 3T3 cell line. Chrysotile asbestos was used as a positive control. MD was found to induce abnormal anaphases, and the percentage of abnormalities increased as the dose increased (27.41 percent with 20 mg/mL, 29.60 percent with 40 mg/mL and 37.10 percent with 80 mg/mL). Multipolar anaphases constituted the most frequent altertion (69.1 - 78.8 percent), followed by lagging chromosomes (18.2 -29.5 percent) and anaphasic bridges (1.51 - 5.9 percent). The anaphasic alterations induced by MD showed differences in comparison to those observed with asbestos, especially for anaphasic bridges (10.4 percent vs. 1.51 percent, p<0.05). The capacity of MD to induce alterations resported in the process of chromosomal disjunction could explain the numeric aberrations reported previously by the authors of this paper. Therefore, these data support that MD could act as a clastogenic agent

C-anaphases (Common Variant) are unrelated to colchicine and phytohemagglutinin

We wvaluated the effect of different concentrations of colchicine (0.0, 0.1, 0.3, 0.5 µg/ml) and phytohemagglutinin (PHA) (0.10, 0.15, 0.20 µg/ml) on the rate of C-anaphases in lymphocyte cultures from five healthy individuals with the common variant of C-anaphases. For each of the 12 possible combinations, two subjects were randomly tested. The frequency of these variant figures was <3 percent; a single culture (out of six with the colchicine concentration of 0.1 µg/ml) lacked C-anaphases. Multiple variance and Student's t tests revealed, as the only significant difference, a decrease with the colchicine concnetration of 0.3 µg/ml compared with the cultures without colchicie (p<0.05), which exhibited the greatest ratio of C-anaphases. The PHA had no influence on the frequency of C-anaphases. We conclude that the common variant of C-anaphases is unrelated to the colchicine and PHA concentrations tested; moreover, our data confirm the occurrence of such a mitotic variant in colchicine-free cultures

Post-metaphase mitotic events in cells treated with dinitrophenol.

The sequence of post-metaphase mitotic events, such as anaphase movement A and B, chromosome decondensation, nuclear envelope reformation and cytokinesis, has been studied in 2,4-initrophenol (DNP)-treated HeLa cells. The effects of DNP were found to be dose dependent and at concentrations higher than 3 mM, both anaphase A and B movements were totally and nearly instantaneously arrested. It could be shown that cytokinesis did not depend on the completion of anaphase movements. This was also true for nuclear envelope reformation which could take place even around condensed chromosomes arrested in anaphase. The post-metaphase mitotic events do not follow a strict causal sequence, but they can be dissociated from each other in anaphase-arrested cells.