Premature chromosome condensation in hamster cells treated with cytochalasin B

Premature chromosome condensation and chromosome despiralization in Syrian hamster cells transformed in vitro

In vitro neoplastic transformation of Syrian hamster cells by chemical carcinogens or Simian adeno-7 virus results in cell lines that have rare cells possessing some chromosomes identical to those referred to as premature chromosome condensation or despiralization. These phenomena occurred without the addition of viruses known to promote cell fusion.

Control of nuclear division in sv40 and adenovirus type 12 transformed mouse 3t3 cells

Untransformed, non-tumorigenic mouse cells respond to cytochalasin B (CB) with limited nuclear division. BALB/c mouse embryo fibroblasts (MEF) and both BALB/c 3T3 and Swiss 3T3 cells become binucleated in the presence of CB and cells with three or more nuclei are very rare or undetectable. MEF are diploid (40 chromosomes) and 3T3 cells are subtetraploid (74-76 chromosomes). Transformation of MEF by SV40 produces a dramatic change in response to CB. These cells, which contain SV40 T-antigen, become highly multinucleated in the presence of CB. More than 20% of the cells have at least seven nuclei. Also premature chromosome condensation (PCC), an abnormality rare in CB-treated normal cells but one which is common to highly multinucleated cells, is frequent and occurs in at least 10% of mitoses. SV40-transformed MEF have 40 or 80 chromosomes, e.g. are diploid or tetraploid. Transformation of 3T3 by SV40 or adenovirus type 12 does not result in a marked change in the response to CB. Although some trinucleate and tetranucleate cells are formed, cells with more nuclei are undetectable or rare. PCC is also rare. These cells show chromosome numbers somewhat lower than their untransformed parents and in one line the chromosome number appears to decrease with passage of the cells. This failure to undergo a marked change in responsiveness to CB following transformation is not a characteristic of all transformed 3T3 cells. SVT2, a line of 3T3 which was transformed by SV40 prior to its establishment as a continuous line, responds to CB with a high degree of multinucleation. These cells are diploid. These results suggests that 3T3 cells are constitutive for controlled nuclear division and that this feature may be related to chromosome constitution.

Premature chromosme condensation in the bone marrow of Chinese hamster after application of bleomycin in vivo

The Chinese hamster bone marrow was used as a test system in vivo to analyse the chromosome-danaging effect of bleomycin. Both chromosome and chromatid aberrations were found. Mitoses with aberrations (Ma) show a linear dose-effect relationship after a recovery time of 24 h, the same hold true for cells with micronuclei (Cm) and for mitoses with premature chromosome condensation (PCC). The dose-effect relationships for Ma, Cm and PCC run parallel to each other with Ma at the highest and PCC at the lowest level (Ma greater than Cm greater than PCC). The time-effect relationships for Ma, Cm and PCC show that after 12 h recovery time there are no PCCs but the highest frequencies of Ma and Cm indicating that most cells are in their first post-treatment mitoses or Gi-phases at this fixation time. In addition to the frequency determinations autoradiographic analysis were performed to clarigy the nature of the PCCs. The results are interpreted as follows: bleomycin induces chromosomal aberrations that in turn give rise to micronuclei by means of lagging chromatin, main and micronuclei eventually become asynchronous in their cell cycles and mitosing main nuclei induce PCC in the micronuclei.