Aggregation of human lymphoblastoid cells by tumor-promoting phorbol esters and dihydroteleocidin B

Human lymphoblastoid cells transformed by Epstein-Barr virus aggregated rapidly in the presence of tumor-promoting phorbol esters and dihydroteleocidin B. Cell aggregation was almost complete after incubation for 6 hours. In amounts of a few ng, they induced significant aggregation. Their abilities to aggregate cells could be measured quantitatively and correlated well with their effects in promoting skin tumors.     

Unusual patterns of benzo[a]pyrene metabolites and DNA-benzo[a]pyrene adducts produced by human placental microsomes in vitro

Human placental microsomes were incubated with [³H]benzo[a]pyrene (BP) and Salmon sperm DNA and the resulting metabolite-nucleoside complexes resolved by Sephadex LH-20 chromatography. The metabolite pattern was analyzed by high-pressure liquid chromatography (HPLC). The incubates were also co-chromatographed with extracts obtained from incubates with rat liver microsomes and [¹⁴C]BP. Phenols, quinones and 7,8-dihydrodiol were detected in the placental incubates. Both 9,10- and 4,5-dihydrodiols were very low as compared with control rat liver samples. Placental microsomes catalyzed the binding of BP metabolites to DNA in vitro, giving rise to two main complexes which co-chromatographed with rat liver-produced peaks attributable to 7,8-diol-9,10-epoxide and 7,8-oxide and/or quinones when metabolized further. The nucleoside metabolite peaks attributable to 4,5-oxide and 9-phenol-4,5-oxide were lacking when compared with the binding pattern catalyzed by rat liver. Both the total binding and specific metabolite-nucleoside adducts in the placenta correlated with fluorometrically measured aryl hydrocarbon hydroxylase (AHH) activity and with the amount of dihydrodiol formed. The results demonstrate that both the metabolite pattern and the nucleoside-metabolite complexes formed by the placental microsomes in vitro differed greatly from those produced by rat liver microsomes. These studies also suggest that it is not possible to predict specific patterns of DNA binding from AHH measurements or even from BP metabolite patterns, especially when comparing different tissues and species.     

Effect of phospholipid vesicles on the activity of terminal transferase.

The terminal transferase activity is modified in the presence of lipid vesicles. A deep inhibitory effect takes place with phosphatidylserine and phosphatidylinositol, while some stimulation is present with sphingomyelin and almost no effect has been detected with phosphatidylethanolamine vesicles. These effects seem to be related to the charge properties of the lipid membranes.A possible involvement of phospholipids in the mechanism of action of the terminal transferase is suggested.     

Degradation of mutagens from pyrolysates of tryptophan, glutamic acid and globulin by myeloperoxidase.

Mutagenic compounds isolated from pyrolysates of tryptophan, glutamic acid and globulin were broken down by myeloperoxidase and hydrogen peroxide with loss of their mutagenicity toward Salmonella typhimurium TA98. Lactoperoxidase and horseradish peroxidase were as effective as myeloperoxidase in degradation of the mutagens.