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The sensitivity of P. falciparum to chloroquine, pyronaridine, artesunate and piperaquine (CQ, PD, AT, PQ) was assayed using in vitro microtechnique in south Yunnan in 1990. The resistance rates were 98.7% (75/76), 27.6% (16/58), 13.8% (9/65) and 97.7% (43/44) respectively, and ID50 were 125.0, 19.0, 4.7 and 243.3 nmol/L, respectively. The resistance rate against CQ showed no change as compared to the rates against CQ 5 and 9 years ago; but the ID50 was lower. CQ-resistant P. falciparum showed a marked cross-resistance to PQ, but not to PD and AT. AT-resistant P. falciparum exhibited cross-resistance to the above-mentioned three drugs. PD-resistant P. falciparum showed no cross resistance to AT, but showed cross resistance to CQ and PQ. In comparison with chloroquine-coated plates, the plates coated with pyronaridine, artesunate or piperaquine gave similar results as the former, which were shown by the rise in schizont inhibition rates along with the rise in drug concentration. It indicates that pyronaridine-, artesunate-, and piperaquine-coated plates can be used in the assay of sensitivity of P. falciparum to the three drugs.

Oxygen free radicals, such as the hydroxyl radical generated by interaction of Fe2+ and H2O2 (Fenton reaction), are produced in mammalian cells as a result of aerobic metabolism and under various pathological conditions and are known to elicit mutations and potentially other adverse effects by reacting with DNA bases. Several products thus formed have recently been characterized as hydroxylated derivatives of cytosine, thymine, adenine, and guanine and imidazole-ring-opened derivatives of adenine and guanine in DNA. As shown herein by 32P-postlabeling, incubation of DNA under Fenton reaction conditions led to additional products which, by virtue of resistance to nuclease P1 catalyzed 3'-dephosphorylation and chromatographic behavior, appeared to be bulky adducts rather than small polar, hydroxylated or ring-opened nucleotide derivatives. Two major and five minor DNA derivatives were measured after 32P-postlabeling and TLC mapping of DNA oxidized in vitro under conditions known to lead to formation of reactive oxygen species. Amounts of products formed depended on Fe2+ and H2O2 concentrations and increased in the presence of L-ascorbic acid. One of the two major products was also detected in lung DNA of rats where its amount increased with animal age. Thus, at least one I-compound appeared to have its origin in the interaction of DNA with reactive oxygen species.

Previous work has shown that 7,12-dimethylbenz[a]anthracene (DMBA)-DNA adducts can be converted by 32P-postlabeling to different types of radiolabeled derivatives (nucleoside 3',5'-bisphosphates, nucleoside 5'-monophosphates and dinucleotides), and that the 32P-labeled 3',5'-bisphosphate derivatives can be further characterized by cross-referencing with 3H-labeled nucleoside DMBA adducts, for which structural information is available. This work has now been extended by TLC comparisons of 5'-monophosphate and 3',5'-bisphosphate DMBA adducts. To this end, DMBA-modified DNA was enzymatically hydrolyzed to 3'-monophosphates (Xp + Np) or to dinucleotides (XpN), and these digestion products were 32P-postlabeled by published procedures to yield 3',5'-bisphosphate (*pXp) or 5'-monophosphate (*pX) adducts. Individual *pXp and *pX fractions were isolated from polyethyleneimine (PEI)-cellulose TLC maps and chromatographically compared after enzymatic 3'-dephosphorylations of the 3',5'-bisphosphate (*pXp) derivatives (*pXp----*pX + Pi). Four reactions were standardized and employed for this purpose: (i) 3'-dephosphorylation by extensive digestion with nuclease P1; (ii) 3'-dephosphorylation catalyzed by polynucleotide kinase; (iii) partial dephosphorylation by bacterial alkaline phosphatase; and (iv) partial dephosphorylation by prostatic acid phosphatase. Individual DMBA adducts displayed marked differences with regard to their susceptibility to enzymatic dephosphorylation. The three major and most minor postlabeled 5'-monophosphate DMBA adducts were cross-referenced this way with 3',5'-bisphosphate and nucleoside adducts, so that specific dihydrodiol epoxide-nucleoside 5'-monophosphate adducts can now be identified and measured by 32P-postlabeling.