Wirkung von Ozon auf M�useascitestumorzellen und auf H�hnerfibroblasten in der Gewebekultur

Thymidine kinase enzyme variants in Physarum polycephalum; change of pattern during the synchronous mitotic cycle

“…Frozen samples were quickly thawed, disrupted with a Potter-Elvehjem homogeniser and centrifuged for 1 h at 150 000 X g. Thymidine kinase activity and protein were determined in the supernatant. The enzyme assay mixture (total volume 70 ~1) contained 86 mM Tris-HCl pH 7.5, 8.7 mM ATP-Na, 8.7 mM MgClz , 2.6 mM EDTA-Na, 3.6 mM mercaptoethanol, 2.5 mg/ml bovine serum albumin, 18% w/v glycerol, 3.6 PM [ l4 C] thymidine (60 mCi/mmol, 0.215 pCi/ml), and plasmodial extract (0.5-1.0 mg protein/ml); aliquots (20 pl) were pipetted onto pieces of anion exchange paper (Whatman DE 81; 1.6 X i.0 cm) after 0, 15, and 30 min incubation at 26'C and processed as described [ 1,2]. The amount of [ l4 C] thymidine phosphorylated and retained on the paper was measured by liquid scintillation counting.…”

“…Thymidine kinase activity (EC 2.7.1.75) exhibits periodic changes in macroplasmodia of Physantm polycephalum correlated with the synchronous nuclear division cycle [ 1,2]. Studies with inhibitors of RNA and protein synthesis suggest that production of this enzyme is mainly restricted to a small segment (1 h) of the 10 h nuclear cycle starting shortly prior to the onset of the synchronous mitosis [3].…”