Studies on the effect of Vinblastine on normal and tumour cell show that semi-conservative DNA synthesis correlates with the enzymatic activity of thymidine kinase. DNA repair investigations performed with Yoshida-Ascites cells indicate an inhibitory effect on the ligase system after Vinblastine treatment and gamma irradiation.

In preliminary investigations the influence of orally administered dimethyl mercury on the motor coordination of rats was tested. An ED50 = 65.9±1.7 mg Hg/kg for standard equilibration test of the motor coordination has been found.

In the first part of our studies DNA sedimentation behaviour during a mitotic cycle of the unicellular green algaChlorella pyrenoidosa was investigated. In the S-phase a decrease in sedimentation rate of akaline-denatured DNA could be observed. Alkaline sucrose density gradient analysis was used to examine the repair of radiation-induced single strand breaks in DNA in various stages of the cell cycle. Three characteristic phases of the growth period were chosen: autospore phase, early beginning of DNA replication and maximum DNA synthesis. Our results indicate that DNA damage is different within the cell cycle, but the repair of radiation-induced DNA strand scissions is only to a small degree dependent on the cell stage.

Ingestigations on the thymidine kinase activities within a cell-cycle of synchronously growing Chlorella cells showed a marked increase of the enzyme-activity towards the end of the DNA-reduplication. Immediately after γ-irradiation with doses of 15 krad and 35 krad, no significant changes in activity could be found; three hours after irradiation a remarkable decrease of the enzyme-activity was observed.

DNA-repair after gamma irradiation was investigated in a stage of synchronousChlorella cells in which no active DNA synthesis occurs. A modified method of alkaline sucrose gradient centrifugation was used.

Es wurde eine Anlage zur Züchtung synchroner Chlorellakuhuten konstruiert, die auf Grund einer automatischen Verdünnungsvorrichtung eine einfache Möglichkeit für eine Dauersynchronisation bietet. Bei voller Ausnützung der Anlage kann bis zu 100 g Algenmaterial (Feuchtgewicht) je Zyklus geerntet werden