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E D Wills

Publications and source records attributed to E D Wills.

At least 19 recordsLinked to original sources
PubMed1987

The oxidation of benzo[a]pyrene-7,8-dihydrodiol mediated by lipid peroxidation in the rat intestine and the effect of dietary lipids.

This study has demonstrated that the microsomal fraction of the rat small intestinal mucosa has the capacity to catalyse the oxidation of benzo[a]pyrene(BP)-7,8-diol to BP-diol-epoxides (BPDEs) both by a mechanism involving the mixed-function oxidase system (NADPH-dependent) and as a result of the initiation of peroxidation of the membrane phospholipids by ferrous ions, ascorbate and ADP. The NADPH-dependent reaction was fastest in the proximal part of the intestine and resulted in the formation of approximately equal amounts of BPDE I and BPDE II. The lipid peroxidation-catalysed reaction favoured the production of BPDE I and was maximal in the middle region of the intestine, closely paralleling the rate of lipid peroxidation in the intestinal sections. Feeding rats on a cod liver oil diet, rich in C20:5 and C22:6, significantly increased the incorporation of these fatty acids into the microsomal fractions. This resulted in a greatly increased rate of lipid peroxidation in vitro and a significantly higher rate of lipid peroxidation-catalysed BP-7,8-diol oxidation compared to rats fed fat-free, mono-unsaturated lard or corn oil (58% C18:2) diets. Thus the rate of conversion of BP-7,8-diol to its ultimate carcinogenic forms during lipid peroxidation in the intestinal fractions of rats fed a polyunsaturated fat was quantitatively more important than the NADPH-catalysed reaction as measured in vitro.

Animals↗
PubMed1986

The effect of dietary lipids and antioxidants on the activity of epoxide hydratase in the rat liver and intestine.

The effect of varying the fatty acid composition of the lipid components of the diet on the activity of epoxide hydratase in the rat liver and intestinal mucosa has been studied. Feeding a 10% cod liver oil diet (containing 18% C20:5 and 11% C22:6) resulted in a 3-fold increase in epoxide hydratase activity in the liver and a 1.6-fold increase in the intestine compared to rats fed a fat-free diet. The activity of epoxide hydratase in rats fed a cod liver oil diet was significantly greater than that for the group fed a lard diet (containing mainly saturated and mono-unsaturated fatty acids) containing the same quantity of vitamin E. Thus, the enhancing effect of the cod liver oil diet was due to the polyunsaturated fatty acids in this oil. Dietary corn oil (58% C18:2) also stimulated epoxide hydratase activity in the liver but not in the intestine. Vitamin E levels of up to 500 mg/kg diet were ineffective at inducing epoxide hydratase activity in both the liver and intestine. Significant changes in the fatty acid composition of hepatic and intestinal microsomes took place when rats were fed diets of different fatty acid composition. These changes were such that the proportions of polyunsaturated fatty acids in the microsomal fractions reflected the amounts of these fatty acids in the dietary fat. Hepatic epoxide hydratase activity was found to be positively correlated to the proportion of polyunsaturated fatty acids in the microsomal fractions of the liver.

Animals↗
PubMed1986

The dependence of the rate of BP metabolism in the rat small intestinal mucosa on the composition of the dietary fat.

We studied the effects that dietary fat has on the capacity of preparations of rat small intestinal mucosal cells to metabolize benzo[a]pyrene (BP) in vitro and on the composition of fatty acids in the endoplasmic reticulum of the intestinal mucosa. When rats were fed diets containing different types of fat, there were significant changes in the incorporation of fatty acids into the endoplasmic reticulum of the mucosal cells of the small intestine: the proportions of polyunsaturated fatty acids in the endoplasmic reticulum reflected the amounts of these fatty acids in the dietary fat. The rate of BP oxidation in the intestinal mucosa was dependent on the amount and composition of the dietary fat, but the range and proportions of the metabolites produced were not affected. Dietary C18:2 was particularly important in elevating the rate of BP oxidation, but dietary C20:5 and C22:6 also effectively increased the rate of BP oxidation. The rate of BP oxidation in the small intestine of rats fed different diets was positively correlated with the proportion of polyunsaturated fatty acids in the endoplasmic reticulum of the mucosal cells.

Animals↗
PubMed1986

The oxidation of benzo[a]pyrene mediated by lipid peroxidation in irradiated synthetic diets.

The effect of gamma-irradiation (1000-4000 Gy) on the formation of lipid peroxides and on the oxidation of the environmental carcinogen benzo[a]pyrene (BP) has been studied in mixtures of starch/fat and BP which were used as models for natural foods. When mixtures containing polyunsaturated fats (mackerel oil and cod-liver oil which contain relatively large proportions of C20:5 and C22:6) were exposed to gamma-irradiation, large concentrations of lipid peroxide were formed and a concomitant oxidation of BP to mutagenic and toxic BP quinones took place. The rate of BP oxidation was closely related to the extent of peroxidation of the lipids in the starch mixtures and was dependent on the dose of gamma-irradiation and the presence of air. Mackerel oil also underwent peroxidation during the storage of both irradiated and unirradiated starch/mackerel oil/BP mixtures and this resulted in a significant oxidation of the BP present in these samples. Antioxidants such as vitamin E and BHA inhibited both lipid peroxidation and BP oxidation resulting from gamma-irradiation. These results demonstrate that the species generated during the peroxidation of unsaturated fats in foodstuffs can react with polycyclic aromatic hydrocarbons such as BP and convert them into active mutagenic and toxic products. This has important toxicological implications, particularly as the consumption of polyunsaturated fat in the Western world is increasing and gamma-irradiation may soon be widely used for food sterilization.

Benzo(a)pyrene↗
PubMed1984

The generation of oxidation products of benzo[a]pyrene by lipid peroxidation: a study using gamma-irradiation.

The role which active oxygen and radicals generated by the peroxidation of unsaturated fatty acids could play in the oxidation of benzo[a]pyrene has been studied using gamma-irradiation. Irradiation of benzo[a]pyrene resulted in the formation of benzo[a]pyrene 1,6-, 3,6- and 6,12-quinones and other more polar products which were analysed by h.p.l.c. OH. radicals are believed to be involved in this oxidation. The presence of polyunsaturated fatty acids and polyunsaturated lipids stimulated the formation of benzo[a]pyrene products following gamma-irradiation. Oxidation of benzo[a]pyrene also occurred over a period of days in the presence of autoxidising mackerel oil. The rate of benzo[a]pyrene oxidation was related to the extent of lipid peroxidation as determined by malonaldehyde formation. Malonaldehyde production as a result of peroxidising lipids was inhibited by benzo[a]pyrene which suggested that benzo[a]pyrene reacted directly with lipid peroxy radicals or hydroperoxides generated in the process of lipid peroxidation. These results demonstrate that oxidation products of the peroxidation of lipids and fatty acids are able to react directly with benzo[a]pyrene to form products including benzo[a]pyrene quinones without the presence of enzymes such as the cytochrome P-450 mixed function oxidase system and prostaglandin synthetase. It is possible that benzo[a]pyrene may be activated by these types of reactions in vivo or in vitro when benzo[a]pyrene is in contact with polyunsaturated lipids in foodstuffs or the intestinal lumen and peroxidation of unsaturated fats may play an important role in human carcinogenesis.

Antioxidants↗
PubMed1982

Activation of lysosomal enzymes and tumour regression caused by irradiation and steroid hormones.

The lysosomal enzyme activity and membrane permeability of mouse C3H mammary tumours has been studied using quantitative cytochemical methods following irradiation of the tumours with doses of 1500, 3500 or 6000 rad gamma rays. No change in the lysosomal enzyme activity was observed immediately after irradiation, but increased enzyme activity and increased membrane permeability were observed 24 hr after irradiation with doses of 3500 or 6000 rad. Twenty-four hours after injection of prednisolone there was a marked increase of lysosomal membrane permeability and enzyme activity, and injection of prednisolone soon after irradiation enhanced the effect of irradiation. After a dose of 6000 rad and prednisolone, the lysosomal membrane permeability increased to 191% of the control and the enzyme activity to 326% of the value of the controlled tumours. Measurement of tumour size after irradiation or after a combined treatment with irradiation and prednisolone showed that a close correlation exists between tumours regression and lysosomal enzyme activity. The experiments support the view that lysosomal enzymes play an important role in tumour regression following irradiation.

Acid Phosphatase↗
PubMed1981

The effects of dietary lipid and phenobarbitone on the production and utilization of NADPH in the liver. A combined biochemical and quantitative cytochemical study.

The validity of the concept that cellular NADPH utilization in the cytoplasm can, by quantitative cytochemical procedures, be classified into two pathways (Pathway I, in which NADPH is oxidized via the microsomal electron-transport system, and Pathway II, in which NADPH supplies reducing equivalents for biosynthetic processes) was tested. The amount of NADPH, generated by glucose 6-phosphate dehydrogenase, entering Pathways I and II in the centrilobular and periportal regions was measured by quantitative cytochemistry, and the values obtained were compared with biochemical measurements of mixed-function oxidase and fatty acid synthetase activity after the administration of sodium phenobarbitone or by altering the quantity and nature of the dietary lipid. Phenobarbitone stimulates hepatic mixed-function oxidation measured biochemically and Pathway I, but not Pathway II. Variation in the type and quantity of dietary lipid can also regulate the activity in mixed-function oxidation and alter the amount of NADPH entering Pathways I and II. It is concluded that, in general, the concept of two main pathways of NADPH utilization in the liver is valid, but that the ratios of NADPH utilization in the two pathways gives a better indication of the use of NADPH in vivo than is obtained for absolute values for the two pathways. Moreover, the centrilobular and periportal hepatocytes showed different patterns in their response to changes in dietary lipid and the administration of phenobarbitone. These results indicate the different metabolic roles that these two groups of cells may play in the metabolism of foreign compounds.

Animals↗
PubMed1980

The use of an inexpensive, general purpose microcomputer in quantitative cytochemistry.

A 32K Commodore Pet microcomputer has been interfaced with two Vickers microdensitometers. This system allows for the simultaneous logging of data from two densitometers being operated independently of each other. Software for the statistical analysis of data generated by the densitometers, and for use with the cytochemical bioassay of hormones, is described. The densitometer/Pet system is relatively cheap, reliable, and readily adaptable to other applications.

Computers↗
PubMed1980

Studies of lipid peroxide formation in irradiated synthetic diets and the effects of storage after irradiation.

The effect of irradiation doses of gamma-rays or electrons within the range 100--2000 krad has been studied on lipid peroxide formation in artificial food mixtures containing lard, corn oil or herring oil mixed with starch, casein or other proteins. Lipid peroxide formation after irradiation was very low in lard: starch or corn oil: starch mixtures but very large concentrations of peroxide were formed in irradiated herring oil: starch mixtures. This was mainly a result of the occurrence of the highly unsaturated C20:4, C20:5 and C22:6 fatty acids in the herring oil which readily form lipid peroxide. Lipid peroxide formation immediately after irradiation was much lower after doses of electrons given at a high dose-rate than after similar doses of gamma-rays given at low dose-rates but it increased rapidly in the samples irradiated with electrons during the period immediately following irradiation. Lipid peroxide formation changed rapidly during post-irradiation storage and was dependent on the type of radiation, the dose, the dose-rate, the time after irradiation and the temperatures of the post-irradiation storage. The concentration of peroxide in mixtures irradiated with gamma-rays formed after 2--3 days post-irradiation storage was dose-rate dependent and much greater after irradiation with gamma-rays given at a very low dose-rate than with gamma-rays given at a high dose-rate. Lipid peroxide increased after irradiation much more rapidly at 37 degrees C than at 4 degrees C or 21 degrees C but all irradiated samples a maximum concentration of peroxide was eventually formed, the time delay being temperature dependent. After reaching a maximum, the concentrations of both hydroperoxides and aledhyde breakdown products in all irradiated samples steadily fell to relatively low values. Peroxide yields were greater if the fat was dispersed in an inert medium such as starch than when irradiated in the pure form and were also dependent on the presence of water in the dispersant medium. Proteins such as casein or ovalbumin inhibited lipid peroxide formation in unsaturated fats.

Animal Feed↗
PubMed1980

Effects of antioxidants on lipid peroxide formation in irradiated synthetic diets.

The effect of the antoxidants, vitamin E, propyl gallate (PG), 2-t-butyl-4-methoxy phenol (BHA), 2,6-di-t-butyl-4-methoxy phenol (BHT), nordihydroguaiaretic acid (NDGA) and diphenyl-p-phenylene diamine (DPPD) in concentrations ranging between 0.001 per cent and 0.1 per cent have been tested on lipid peroxide formation in synthetic diet mixtures containing herring oil (10 per cent) mixed with starch (90 per cent) irradiated with gamma-ray doses of 100-2000 krad. On a weight basis NDGA, DPPD, BHA and BHT were most effective and vitamin E and propyl were least effective. An antioxidant concentration of 0.01 per cent normally protected against peroxide formation after a dose of 500 krad but if the dose was increased to 1000 or 2000 krad, much higher doses of antoxidant, up to 0.1 per cent, were required to give protection. Antioxidants prevented peroxide developing during post-irradiation storage even when added after irradiation. Antioxidants were partially or completely destroyed by irradiation with doses of 100 krad or more. The percentage of total antioxidant destroyed depended on the concentration; much greater destruction occurred in dilute solutions than in concentrated solutions. Vitamin E and propyl gallate were most sensitive whereas NDGA was relatively resistant. Antioxidant destruction was much enhanced if irradiation was carried out in presence of herring oil. Free radicals formed in unsaturated fatty acids of the herring oil are believed to be responsible. Lecithin and citric acid, which have been described as antioxidant synergists when added with vitamin E, caused a limited enhancement of its antioxidant action against radiation-induced peroxidation.

Antioxidants↗
PubMed1980

Effect of irradiation on lysosomal enzyme activation in cultured macrophages.

The effect of gamma-rays on lysosomal enzyme activity of normal and immune macrophages of DBA/2 mice cultured in vitro has been studied. Quantitative cytochemical methods have been used for measuring lysosomal enzyme activity. A dose of 500 rad did not significantly affect lysosomal enzyme activity 3 hours after irradiation but caused the activity to increase to 1x4 times the control value 22x5 hours after irradiation. 22x5 hours after a dose of 3000 rad the enzyme activity increased to 2x5 times the control. Lysosomal enzyme activity of the macrophages was also markedly increased by immunization of the mice with D lymphoma cells, before culture in vitro, but irradiation of these cells with a dose of 500 rad caused a further increase in lysosomal enzyme activity. The results indicate that immunization and irradiation both cause stimulation of lysosomal enzyme activity in macrophages but that the mechanisms of activation are unlikely to be identical.

Acid Phosphatase↗
PubMed1979

The distribution of glutathione in the rat liver lobule.

A quantitative cytochemical method was developed for measuring the GSH (reduced glutathione) content of hepatocytes in different regions of the rat liver lobule. Use of this method enabled us to show that GSH is not evenly distributed within the rat liver lobule. The hepatocytes located within 100 micrometer of the central vein contain much less GSH than do those in other regions of the rat liver lobule. We suggest that this partially explains the peculiar susceptibility of these cells to electrophilic attack by toxic metabolites formed via the microsomal cytochrome P-450 system.

Animals↗