Peroxidation of the dried thin film of lipid by high-energy alpha particles from a cyclotron

High-energy alpha particles produced a dose-dependent linear increase in different lipid peroxidation products (e.g., malondialdehyde (MDA), conjugated dienes, and hydroperoxides) in the dried thin film state. An inverse dose-rate effect was observed when the dose rate was varied by changing either the alpha-particle fluence rate or the alpha-particle energy. The antioxidants alpha-tocopherol and butylated hydroxytoluene (BHT) suppressed the alpha-particle-induced lipid peroxidation in the dried thin film state, and in this respect alpha-tocopherol was found superior to BHT. It was found that alpha-tocopherol was equally efficient in inhibiting lipid peroxidations by alpha particles and ultraviolet light.     

Synthesis of leucine enkephalin derivatives: structure-function studies

Nucleoli isolated from livers of rats injected intraperitoneally with one dose of thioacetamide had a five-fold increase in the rate of RNA synthesis $\text{in vitro}$ when compared with livers of rats treated with saline or CCl₄. The stimulation was maximal 24 hours after treatment and decreased to control values 73 hours after treatment. The enhanced level of nucleolar activity was maintained at that level when thioacetamide was injected daily. Along with the increase in the endogenous activity there was a 7-fold increase in the “free” RNA polymerase I activity determined by blocking the bound enzyme with actinomycin D (7). The nucleoli of the thioacetamide-treated rats offer a useful model of modulation of ribosomal gene function.     

Effects of antifilarial drugs on the activities of the oxidative enzymes of mitochondria and microsomes of rat liver and kidneys

Centperazine or diethylcarbamazine, administered at various dose levels to rats inhibited the activity of succinate dehydrogenase significantly in 4 hrs in liver. Centperazine also inhibited the activity of cytochrome-c oxidase but stimulated the activity of benzo (a) pyrene hydroxylase in liver. In kidneys, activities of succinate dehydrogenase, cytochrome-c oxidase and aniline hydroxylase were significantly inhibited by centperazine only, however, the activity of benzo (a) pyrene hydroxylase was inhibited by both the drugs. These drugs had no effect on the activity of aminopyrene N-demethylase and cytochrome P-450 contents of liver and kidneys.     

Evidence for the involvement of singlet oxygen in the photodestruction by chloroaluminum phthalocyanine tetrasulfonate

In recent years, choloroaluminum phthalocyanine tetrasulfonate (A1PCTS) has been shown to be a promising photosensitizer for the photodynamic therapy (PDT) of cancer. Although its mechanism of photodynamic action is not well defined, A1PCTS is going to be under clinical trials of PDT. In this study, in vitro addition of A1PCTS to a suspension of rat epidermal microsomes followed by irradiation with red light (approximately 675 nm) resulted in significant destruction of cytochrome P-450 and associated monooxygenase activities. The photodestructive effect was dependent on both the dose of A1PCTS and the duration of light exposure. Studies using various quenchers of reactive oxygen species showed that only scavengers of singlet oxygen such as histidine, 2,5-dimethylfuran, beta-carotene and sodium azide afforded substantial protection against photodestruction. Our data indicate the direct involvement of singlet oxygen in the A1PCTS-mediated photodestructive process.     

Electrophoretic and biochemical studies of human aldehyde dehydrogenase isozymes in various tissues

Four major ALDH isozymes have been identified in human tissues using starch gel electrophoresis and isoelectric focusing. The isozyme bands have been termed as ALDH I, II, III and IV according to their decreasing electrophoretic migration and increasing isoelectric point. The isozymes have been partially purified via preparative isoelectric focusing. Kinetic characteristics of ALDH I and II were found to be quite similar to ALDH enzyme 2 and enzyme 1 described earlier by Greenfield and Pietruszko (Biochem Biophys Acta, $\text{483}$ 35–45 1977). ALDH III and IV showed a very high Km for propionaldehyde (1.0–1.5 mM at pH 9.5) and were not inhibited by disulfiram at pH 9.5. A variant phenotype of ALDH which lacked in isozyme I was detected in various tissues from Japanese individuals. Comparative kinetic properties of normal and variant enzyme are given.     

A note on suxamethonium sensitivity and serum cholinesterase variants

Summary Sera from 21 cases of prolonged apnoea which showed normal phenotype (UU) on the basis of dibucaine and fluoride inhibition were re-examined by replacing the substrate benzoylcholine with succinylcholine (suxamethonium). 9 samples had normal enzyme activity but low dibucaine number (DN=<20) indicating the atypical variant; 6 sera showed no detectable enzyme activity. The remaining 6 samples had enzyme activity and DN comparable with healthy controls. The occurence of new variants of serum cholinesterase sensitive only to succinylcholine is suggested.Dedicated to Prof. Dr. med. J. Kühnau on his 75th birthday.