Lipid peroxidation caused by chinoform-ferric chelate in cultured neural retinal cells

Summary Incorporation of chinoform-ferric chelate was demonstrable in cultured neural retinal cells of chick embryos after 1 h of incubation, and the lipid peroxide level in the cells was increased strikingly 1 h thereafter. On the other hand, free ferric ions were scarcely incorporated into the cells, and a significant increase in the lipid peroxide level in the cells was not observed. These data indicate that chinoform is carrier of iron for its passage through cell membranes and that the incorporated iron induces lipid peroxidation which in turn leads to neural cell degeneration.This work was supported in part by a grant from the Ministry of Health and Welfare of Japan     

Activation of the carcinogen N-hydroxy-2-acetylaminofluorene by rat mammary peroxidase

A peroxidase preparation from rat mammary gland parenchymal cells, a target tissue of arylamine carcinogens, was shown to activate the carcinogen N-hydroxy-2-acetylaminofluorene via a nitroxyl free radical intermediate to the more active carcinogens nitrosofluorene and N-acetoxy-2-acetylaminofluorene. Hydrogen peroxide, cumene hydroperoxide, and linoleic acid hydroperoxide were effective as substrates. The antioxidants ascorbate, propyl gallate and reduced glutathione prevented the free radical activation route.     

Activation of the carcinogen N-hydroxy-2-acetylaminofluorene by rat mammary peroxidase

Summary A peroxidase preparation from rat mammary gland parenchymal cells, a target tissue of arylamine carcinogens, was shown to activate the carcinogen N-hydroxy-2-acetylaminofluorene via a nitroxyl free radical intermediate to the more active carcinogens nitrosofluorene and N-acetoxy-2-acetylaminofluorene. Hydrogen peroxide, cumene hydroperoxide, and linoleic acid hydroperoxide were effective as substrates. The antioxidants ascorbate, propyl gallate and reduced glutathione prevented the free radical activation route.     

Degeneration of retinal neuroblasts by chinoform-ferric chelate

Summary The possible mechanism of neuropathic effect of chinoform was investigated using cultured retinal neuroblasts from chick embryos. Retinal neuroblasts completely degenerated by chinoform-ferric chelate within a day. This change, however, was not observed with free chinoform or ferric ion.a-Tocopherol had a potent protective effect on the toxicity of the chelate. From these results, it was concluded that the lipid peroxidation due to ferric ion chelated with chinoform incorporated into the membrane of nerve tissues is the most important step in induction of the neuropathy.This work was supported in part by a grant from the Ministry of Health and Welfare of Japan.Correspondence should be addressed to K. Yagi, Institute of Biochemistry, Faculty of Medicine, University of Nagoya, Nagoya 466, Japan.     

The metabolism of the soil fumigant 1,2-dibromo-3-chloropropane in the rat

Summary The soil fumigant 1,2-dibromo-3-chloropropane (I) undergoes hydrolysis in the rat to a series of epoxide metabolites. Alkylation of glutathione by these epoxides produces 2 urinary metabolites identified as the mercapturic acids VI (R=COCH₃) and VII (R=COCH₃). Hydrolysis of the epoxides produces the male antifertility agentsa-chlorohydrin (IX, X=Cl) anda-bromohydrin (IX, X=Br) which are oxidatively metabolized to oxalic acid (XII), thus causing renal damage. These metabolic pathways can explain the toxic nature of the fumigant as a carcinogen, a male chemosterilant and as an agent causing kidney damage.This work was supported in part by the National Health and Medical Research Council of Australia.     

Lipid transport in the migrating Monarch butterfly,Danaus p. plexippus

Summary The transport of lipid in the haemolymph of the Monarch butterfly during its fall migration was examined. Diglyceride was the major lipid class of 2 electrophoretically distinct lipoprotein fractions in both males and females. Triglycerides, hydrocarbons, free fatty acids, phosphatidyl cholines and phosphatidyl ethanolamines were minor components of these lipoproteins. Differences in lipid transport attributable to sex were not detected.This study is a contribution of the Missouri Agricultural Experiment Station, Journal series No. 8520.     

The problem of detecting a free glutamate decrease in the dorsal sensory neuron following dorsal root crush

Summary Dorsal root crush results in a highly significant decrease in the free glutamate/total free amino acid concentration ratio over an extended time period. Perhaps this is a good measurement to use in glutamate crush studies.This work was supported by Research Grant No. USPH-5-RO1-NS-10508 from the National Institutes of Health.     

Lipid peroxidation caused by chinoform-ferric chelate in cultured neural retinal cells

Incorporation of chinoform-ferric chelate was demonstrable in cultured neural retinal cells of chick embryos after 1 h of incubation, and the lipid peroxide level in the cells was increased strikingly 1 h thereafter. On the other hand, free ferric ions were scarcely incorporated into the cells, and a significant increase in the lipid peroxide level in the cells was not observed. These data indicate that chinoform is carrier of iron for its passage through cell membranes and that the incorporated iron induces lipid peroxidation which in turn leads to neural cell degeneration.     

Early skin responses of hibernating and nonhibernating ground squirrels to topical applications of DMBA

Summary Skin patches on hibernating and nonhibernating ground squirrels were treated with multiple topical applications of the carcinogen 7,12-dimethylbenza(a)anthracene. Nonhibernators showed blistering, peeling, drying, hair loss, increased vascularization and hyperpigmentation in proportion to DMBA concentration. The latter was apparently due to a) an increased number of dermal and epidermal melanocytes and b) the appearance of melanocytes with large coarse cytoplasmic granules. Notably, hibernators remained free of gross skin changes and were histologically similar to untreated controls. Acknowledgments. This study was supported by Biomedical Research Support Grant No. 5-SO7-RR05413-20. I wish to thank Mrs Mary Gregory for her help with the silver-methenamine borate technique, Mr Albert Geiser for the photomicrographs and Dr George B. Kemper for his contributions in general.     

Tumorigenic effect of topical mechlorethamine,BCNU and CCNU in mice

Summary Mice were painted with mechlorethamine (HN2), carmustine (BCNU) and lomustine (CCNU) for up to 33 weeks. HN2 was a potent carcinogen, producing squamous cell carcinomas in 9 of 33 mice in 1 series. BCNU was a weak carcinogen. CCNU produced no tumors in 1 series.Supported in part by PHS grant CA-14825 from the National Cancer Institute.     

Influence of corpora allata and brain extract on the lipid release from the fat body of termite queen Odontotermes assmuthi

Summary Short term in vitro experiments on the influence of the extracts of corpora allata and brain from the termite queenOdontotermes assmuthi on the lipid release from the fat body into the haemolymph indicated that the extract of corpora allata does not influence the lipid mobilization, whereas the brain extract increases the free fatty acid level in the haemolymph. It is believed that the brain extract stimulates triglyceride hydrolysis in the fat body.     

Hyperinsulinemia,hyperproinsulinemia and insulin resistance in the metabolic syndrome

For better comprehension of the metabolic syndrome, it is necessary to differentiate the effect of insulin on glucose metabolism on the one hand, and on other metabolic activities on the other hand. Whereas glucose utilization is affected by insulin resistance, the effect of insulin on lipid metabolism, ion and aminoacid transport does not seem to be diminished. Lipid metabolism, however, seems to play a crucial role in the induction of the vicious cycle. Increased energy and fat ingestion may be due to an increased number of galanin secreting cells in the hypothalamus. The excessive fat intake results in an increased rate of release of insulin and increased influx of triglycerides into the blood. From these triglycerides an excess of free fatty acids is released by the action of lipoprotein lipase. The increased plasma free fatty acid level then results in insulin resistance affecting glucose metabolism. Also, these free fatty acids may impair the secretion of insulin. Induction of insulin resistance results in higher glucose levels, which may cause hyperinsulinemia. Hyperinsulinemia maintains the elevation of triglycerides. When diabetes becomes overt and elevated glucose levels prevail, the hyperinsulinism acts on the metabolic pathways which are still sensitive to insulin, namely lipid metabolism, aminoacid transport and ion transport.     

Phospholipase D: a lipid centric review

Phospholipase D (PLD) hydrolyzes the phosphodiester bond of the glycerolipid phosphatidylcholine, resulting in the production of phosphatidic acid and free choline. Phosphatidic acid is widely considered to be the intracellular lipid mediator of many of the biological functions attributed to PLD. However, phosphatidic acid is a tightly regulated lipid in cells and can be converted to other potentially bioactive lipids, including diacylglycerol and lysophosphatidic acid. PLD activities have been described in multiple organisms, including plants, mammals, bacteria and yeast. In mammalian systems, PLD activity regulates the actin cytoskeleton, vesicle trafficking for secretion and endocytosis, and receptor signaling. PLD is in turn regulated by phosphatidylinositol-4,5-bisphosphate, protein kinase C and ADP Ribosylation Factor and Rho family GTPases. This review focuses on the lipid precursors and products of mammalian PLD metabolism, especially phosphatidic acid and the roles this lipid performs in the mediation of the functions of PLD.     

Unordered structured of proinsulin C-peptide in aqueous solution and in the presence of lipid vesicles

Proinsulin C-peptide ameliorates renal and autonomic nerve function and increases skeletal muscle blood flow, oxygen uptake and glucose transport in patients with insulin-dependent diabetes mellitus. These effects have in part been ascribed to the stimulatory influence of C-peptide on Na+,K+-ATPase and endothelial nitric oxide synthase. To evaluate the capacity of C-peptide to insert into lipid bilayers and form ion channels, C-peptide secondary structure and membrane interactions were studied with circular dichroism spectroscopy and size exclusion chromatography. C-peptide is shown to lack a stable secondary structure, both when part of proinsulin and when free in aqueous solution, although the N-terminal third of the peptide exhibits an alpha-helical conformation in trifluoroethanol. Moreover, C-peptide remains disordered in the aqueous solvent in the presence of lipid vesicles, regardless of vesicle composition. In conclusion, C-peptide is unlikely to elicit physiological effects through stable conformation-dependent interactions with lipid membranes.     

Endogenous synthesis of lipid yolk in mosquito oocytes

Summary Morphological and physiological evidence indicate that lipid yolk in the mosquito is synthesized only within the oocyte within dense fields of free ribosomes. It does not come from the fat body or any other exogenous source.We are grateful to Dr A. L. Steinhauer for his support. Scientific article No. A2373, contribution No. 5388 of the Maryland Agricultural Experiment Station.     

Age-related lipid peroxidation in the digestive gland of mussels: The role of the antioxidant defence systems

Summary The main cellular defence systems against free radical-mediated oxidative stress are significantly reduced in the dige⁺ive gland of aged (>10 years old) compared to younger (2–4 years old) mussels (Mytilus edulis L.). Moreover, the concentration of lipid peroxidation products (malondialdehyde) is increased in the same age group with respect to younger animals. The obtained data indicate that an impairment of the antioxidant defence systems would render the older animals more susceptible to peroxidative stress, thus supporting the general significance of the free radical theory of aging.     

Effect of 5-thio-D-glucose on testicular lipids of mice

Summary Spermatogenesis is reported to be completely inhibited by 5-thio-D-glucose in mice. In an investigation of this inhibition, testicular lipid constituents, namely, total lipids, phospholipids, triacylglycerol, free and total cholesterol, 3-hydroxy-3-methylglutaryl-coenzyme A reductase and NADPH generators like glucose-6-phosphate dehydrogenase, intubation for 21 days. Significant increase in cholesteryl ester, glucose-6-phosphate dehydrogenase activity and malic enzyme and a decrease in free cholesterol and phospholipids were observed.Acknowledgments. We are thankful to the Director, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry 6, India for permission to do the work and Mr T. Natarajan, Department of Biochemistry of ministerial assistance.     

Differential scanning calorimetry of chromaffin granule membranes

Summary Differential scanning calorimetry thermograms of native chromaffin granule membranes exhibit several peaks in the 15–35°C region. Extraction of cholesterol increases the size of the melting peaks. Addition of Ca²⁺ ions does not seem to influence the lipid transitions.This research was supported in part by a grant from the United States-Israel Binational Science Foundation (BSF), Jerusalem, Israel. A.S. acknowledges partial support for this research from a National Science Foundation Grant PCM 04079, and from National Institutes of Health grants CA 08748 ans CA 18759.     

Differential effect of silybin on the Fe2+-ADP and t-butyl hydroperoxide-induced microsomal lipid peroxidation

We have observed a differential effect of silybin dihemisuccinate on rat liver microsomal oxygen consumption and on lipid peroxidation induced by NADPH-Fe2+-ADP and t-butyl hydroperoxide. These results are ascribed to the antioxidant properties of the flavonoid. The differences observed in the effect of the catalysts may be a consequence of the different capacity of silybin to act as a scavenger of free radicals formed by NADPH-Fe2+-ADP or t-butyl hydroperoxide.