engleski

The influence of mercuric chloride on neoblast division in regenerating planarian Polycelis felina (Daly.)

The effects of mercuric chloride on neoblast mitotic activity in regenerating planarian Polycelis felina (Daly.) were investigated. Mitotic abnormalities and chromosomal aberrations were evaluated after 6-hour treatment and 24-hour post-treatment recovery period. The blastema were fixed, and examined cytologically through routine lactoorceine squash preparations. Mitotic indices were also determined. Mercuric chloride induced a dose-dependent decrease in neoblast mitotic activity, accompanied with disturbances in distribution of cells over mitotic phases. Different cytological abnormalities with varying frequency were observed. Marked mitotic depression was concentration-dependent. Early post-treatment toxic effects of inorganic mercury in regenerating planarians were associated with mitotic spindle disturbances. Immediately after treatment mitotic abnormalities were prevalent over chromosomal and C-mitosis was the most prominent one. After 24-hour recovery period in survived animals a prevalence of chromosomal over mitotic aberrations was observed. Moreover, after recovery period the proportions of cells with chromosome stickiness in all treated animals were significantly increased compared to their post-treatment values. Observed impairments in dividing planarian neoblasts could be related to mitotic spindle arrest contributing to retardations and delays, and high mortality rate, especially in animals treated with higher concentration tested. The results obtained indicated usefulness of short-term invertebrate assays as an alternative to in vitro pre-screening of toxic chemicals.

planarian; neoblast division; mercuric chloride; mitotic and chromosomal aberrations

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