200
4TH ANNUAL MEETING, HEIDELBERG
voh,e the centromeric regions predominantly, are between two telocentrics or telocentric and metacentric, but seldom between two metacentrics. This indicates a re>triction on the association between two lnetacentrics in the interphase. (c) In the MSWBS tumour cells, the centromeric heterochrolnatin was involved more often in interchanges (about (~5°o) than in intercalary blocks. Intrachanges involving the marker telocentric were common. There was no restriction between two, biarined chromosomes to form exchanges. The overall frequency of intrachanges was very low in this cell line. The significance of these findings will be discussed.
9 KARIM, J., U. BUCKEL AND G. ROHRBORN, Institut ftir Antropologie und Huiuangenetik der Universit~it Heidelberg, 60 Heidelberg I, Neuenheinlerfeld 328 (West Germany).
Frequency of chromosome aberrations in bone m a r r o w cells of Chinese hamsters after t r e a t m e n t with cyclophosphamide or caffeine alone or together Our investigations checked whether caffeine acts synergistically with alkylating agents such as cyclophosphamide. Three experimental series were performed: one with caffeine alone (dose 2oo mg/kg), another with cyclophosphamide ahme (dose 4 ° mg/kg), and a third with caffeine plus cyclophosphamide (dose 2oo mg,'kg+4o mg/kg respectively) at the same time. Chromosolne preparations of bone narrow cells were made 6 and 24 h after the second treatment (application interval 24 h). Caffeine alone was not mutagenic. However it increased the high mutagenicity of cyclophosphamide, not additivelv but rather synergistically. This work was sponsored by the Deutsche Forschungsgemeinschaft.
10 RIZZONI, l~I., F. SPIRITO, P. PERTICONE, R. DE SAI.VIA, R. RICORDY, ('. TANZARELLA AND F. PALITTI, Centro di Studio di Genetica Evoluzionistica del C.N.R. and Istituto di Genetica, Universit/~ di Roma, Rome (Italy).
M i t o t i c anomalies as the source of mutation of the genome: polyploidization cyclesmsegregation in m a m m a l i a n cell population Substances that act on tile spindle and, more generally, on tile process of nfitosis, determine the formation of cells having a different number of chromosomes from that of the mother cell, either by the non-division of the latter (polyploidization) or by the anomalous distribution of the chromosomes to the daughter cells (multipolar mitoses, nondisjunction), or by both mechanisms. These substances can therefore be considered as nmtagens, the sources of mutation of the genome. In proliferating cell populations, this type of mutation may result in the formation of cell clones, with new genetic and chromosome assortments, capable of competing advantageously with the initial cell population and proliferating more rapidly. This situation involves considerable risks of somatic genetic damage for the indivi-
4TH ANNUAL MEETING, HEIDELBERG
voh,e the centromeric regions predominantly, are between two telocentrics or telocentric and metacentric, but seldom between two metacentrics. This indicates a re>triction on the association between two lnetacentrics in the interphase. (c) In the MSWBS tumour cells, the centromeric heterochrolnatin was involved more often in interchanges (about (~5°o) than in intercalary blocks. Intrachanges involving the marker telocentric were common. There was no restriction between two, biarined chromosomes to form exchanges. The overall frequency of intrachanges was very low in this cell line. The significance of these findings will be discussed.
9 KARIM, J., U. BUCKEL AND G. ROHRBORN, Institut ftir Antropologie und Huiuangenetik der Universit~it Heidelberg, 60 Heidelberg I, Neuenheinlerfeld 328 (West Germany).
Frequency of chromosome aberrations in bone m a r r o w cells of Chinese hamsters after t r e a t m e n t with cyclophosphamide or caffeine alone or together Our investigations checked whether caffeine acts synergistically with alkylating agents such as cyclophosphamide. Three experimental series were performed: one with caffeine alone (dose 2oo mg/kg), another with cyclophosphamide ahme (dose 4 ° mg/kg), and a third with caffeine plus cyclophosphamide (dose 2oo mg,'kg+4o mg/kg respectively) at the same time. Chromosolne preparations of bone narrow cells were made 6 and 24 h after the second treatment (application interval 24 h). Caffeine alone was not mutagenic. However it increased the high mutagenicity of cyclophosphamide, not additivelv but rather synergistically. This work was sponsored by the Deutsche Forschungsgemeinschaft.
10 RIZZONI, l~I., F. SPIRITO, P. PERTICONE, R. DE SAI.VIA, R. RICORDY, ('. TANZARELLA AND F. PALITTI, Centro di Studio di Genetica Evoluzionistica del C.N.R. and Istituto di Genetica, Universit/~ di Roma, Rome (Italy).
M i t o t i c anomalies as the source of mutation of the genome: polyploidization cyclesmsegregation in m a m m a l i a n cell population Substances that act on tile spindle and, more generally, on tile process of nfitosis, determine the formation of cells having a different number of chromosomes from that of the mother cell, either by the non-division of the latter (polyploidization) or by the anomalous distribution of the chromosomes to the daughter cells (multipolar mitoses, nondisjunction), or by both mechanisms. These substances can therefore be considered as nmtagens, the sources of mutation of the genome. In proliferating cell populations, this type of mutation may result in the formation of cell clones, with new genetic and chromosome assortments, capable of competing advantageously with the initial cell population and proliferating more rapidly. This situation involves considerable risks of somatic genetic damage for the indivi-
