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Biomedical subjects

M J Gibney

Publications and source records attributed to M J Gibney.

At least 127 records · Page 7Linked to original sources
PubMed1983

Acute and chronic immunological response to dietary antigen.

On separate mornings at 14 day intervals groups of six to eight healthy fasting male volunteers drank a 5.5 MJ test meal containing 20% milk, egg or soya protein, or a control protein free preparation. Using a Clq binding test, marked but transient rises in circulating immune complexes were detected 30-120 minutes after the milk and egg meals but not with soya or the control. No such changes were seen when complexes were measured by Raji cell immunoassay. Food antigen specific antibodies were present in the plasma of all subjects but showed no consistent pattern of variation in the postprandial period. In most volunteers a chronic increase in milk (three weeks) or soya (six weeks) consumption produced no changes in circulating immune complexes or antibodies to dietary protein. Although two of 16 milk and six of 52 soya volunteers had substantial rises of one or more classes of plasma food antigen specific antibodies they were matched by a similar number in which a decrease was recorded. These results indicate that the formation of circulating immune complexes may be a physiological response to a large load of dietary antigen but that in most adults a chronic increase of milk or soya consumption does not affect food antibody or immune complex concentrations.

Adult↗
PubMed1982

The effect of polyunsaturated fatty acids on the n-3 and n-6 series on platelet aggregation and platelet and aortic fatty acid composition in rabbits.

Four groups of 6 New Zealand white rabbits were fed for 60 days on a commercial rabbit diet supplemented (60 g/kg) with 1 of 4 sources of fat: corn oil, linseed oil and fish oil, which respectively provided rich sources of linoleic acid (C18:2, n-6), alpha-linolenic acid (C18:3, n-3) and eicosapentaenoic acid (C20:5, n-3), and coconut oil, low in all polyunsaturated fatty acids (PUFA). Platelet-rich plasma was prepared and aggregation induced by ADP (final concentration 0.29-74.3 microM), collagen (2.5-20 micrograms/400 microliters, final concentration) and 2.5 U bovine thrombin, and recorded with a Peyton aggregometer. Platelet aggregation induced by both thrombin and collagen was significantly lower with either n-3 PUFA (fish or linseed oil) than with corn oil (n-6 PUFA) or the low PUFA coconut oil. ADP-induced platelet aggregation was significantly reduced only in animals fed fish-oil. Changes in platelet aggregation were accompanied by increased platelet lipid content of C20:5, n-3 and decreased content of C20:4, n-6, with little change in platelet total C20 fatty acids. Platelet levels of C20:5, n-3 were significantly increased with both the preformed C20:5, n-3 and its precursor C18:3, n-3 in the diet. However, aortic lipid accumulation of C20:5 only occurred with rabbits fed on fish oil. It was concluded that, for collagen and thrombin induced aggregation, C18:3, n-3 and C20:5, n-3 were equally antiaggregatory in rabbits. The implications of this in community nutrition programmes are discussed.

Adipose Tissue↗
PubMed1982

Immune tolerance and atherosclerosis in rabbits. Effect of high-fat and cholesterol-supplemented diets.

Breeding rabbits were fed diets supplemented with 5% milk or soya protein for 1 month before conception and throughout pregnancy and lactation. Four groups of 5 or 6 of their offspring were given high-energy isonitrogenous diets containing either 30% soya or milk protein. Half of the animals from each litter received the same protein as their dams; the remainder were fed the alternative (i.e. dams soya; offspring milk, and vice versa). 0.75% cholesterol was added to the diets between 30 and 120 days after weaning. Animals given the same protein as their dams formed substantially lower amounts of food antigen-specific antibody than rabbits fed a novel protein at weaning but the extent of aortic atherosclerosis was similar in all groups. In a second experiment groups of 5-8 weanling rabbits were fed a cholesterol-free diet containing 30% soya and 17% saturated fat for 1 year. Animals in group 1 were bred from dams given soya but those in groups 2 and 3 were derived from a colony fed a soya-free diet. Rabbits in group 3 were immunised by repeated parenteral injections of soya protein and developed high levels of antisoya antibodies. Group 1 and 2 animals were injected with saline only but antisoya antibodies were substantially higher in animals derived from the soya-free breeding colony. Although serum cholesterol and triglyceride levels were similar in all groups, animals from dams fed soya (group 1) had significantly less aortic atherosclerosis (10% involvement of ascending aorta) than those reared from a colony fed a soya-free diet (group 2; 32%). Parenteral immunization with soya protein (group 3) was not associated with significantly increased atherosclerosis (37%). These findings indicate that perinatal exposure to dietary antigen in rabbits may be important in modulating the systemic immune reaction to food antigens. The magnitude of this systemic response is unlikely to alter the nature or distribution of cholesterol-induced atherosclerosis but may have an important influence on the development of aortic disease produced by prolonged feeding of high-fat, cholesterol-free diets.

Animals↗
PubMed1981

The effect of dietary protein source and saponins on serum lipids and the excretion of bile acids and neutral sterols in rabbits.

1. Four groups of six rabbits were given purified diets in which the dietary variables were protein source (isolated soya-bean protein or cow's-milk protein) with or without saponin supplementation (10 g/kg). 2. Rabbits given soya-based diets showed significantly lower serum concentrations of triglyceride and cholesterol (P less than 0.01). The latter changes were confined to the cholesterol fractions of beta-lipoproteins. 3. These changes in serum cholesterol were associated with a significantly increased excretion of acid and neutral sterols in animals given soya-bean protein. 4. There was no evidence to suggest that the effect of dietary protein source on serum lipids and the excretion of total and individual sterols was influenced by saponin supplementation. 5. These results do not support the hypothesis that the hypocholesterolaemia associated with plant proteins is due to the presence of saponins.

Animals↗
PubMed1981

Immune tolerance produced by pre- and postnatal exposure to dietary antigens.

Circulating food antibody levels were measured by ELISA in groups of weanling rabbits fed 320 g/kg diet soya or milk protein. Soya-fed rabbits of milk-fed mothers (and vice versa) showed at least tenfold increase in antibody levels within 3-4 weeks. In contrast, animals fed the same diet as their dams had received in pregnancy and the postnatal period showed little change in antibody levels. These results indicate that contact with a dietary antigen before birth and during the suckling period is important in the induction of tolerance to food proteins in young animals.

Animals↗
PubMed1980

Antibodies to heated milk protein in coronary heart disease.

Coronary arteriography was used to identify 37 patients with triple coronary vessel disease and 37 patients with no evidence of occlusive coronary atheroma. Two techniques were used to analyse serum levels of antibodies to heated milk protein, passive haemagglutination and enzyme-linked immunosorbent assay. No significant differences in these antibodies were observed between triple and zero vessel disease patients. Even after applying ECG evidence of myocardial infarction as a further criterion for classifying patients, no evidence was obtained to support the hypothesis that serum antibodies to heated milk protein are elevated in coronary heart disease.

Antibody Formation↗
PubMed1980

Milk, serum cholesterol, and the Maasai. A hypothesis.

The Maasai of East Africa have been found to have low serum concentrations of cholesterol and a low incidence of cardiovascular disease in spite of apparently very high milk intakes. On that basis it has been frequently suggested that milk contains a "hypocholesterolaemic factor". The hypocholesterolaemia of the Maasai had also been attributed to a genetic adaptation. We feel that the milk intakes reported for the Maasai are excessively high and that the low incidence of cardiovascular diseases and low levels of serum cholesterol may be adequately explained by their variable and generally low energy intakes.

Adult↗
PubMed1980

Dietary antigens, immune tolerance and atherosclerosis.

To test the hypothesis that a systemic immune response to dietary protein can influence the development of experimental arterial disease rabbits were given diets containing 20% soya protein and 20% fat for 11 months. The substantial levels of circulating antisoya antibody were positively correlated with the macroscopic extent of aortic atheroma. In some arterial changes reminiscent of giant cell arteritis were seen. In subsequent similar experiments the breeding stock had been exposed to a soya containing diet, which was also available to their offspring, the experimental animals, in the perinatal period. The lower antibody titres, and much reduced atheroma in this experiment suggested that the animals had been tolerated to soya protein. In further experiments rabbits, bred on a soya free diet showed much higher levels of antisoya antibody and a giant cell reaction was again identified. It is concluded that the magnitude of the antibody response to dietary protein is an important, and previously unrecognised, factor in the development of experimental atherosclerosis.

Animals↗
PubMed1979

Dietary fibre and blood pressure.

Ninety-four volunteers participated in a three-day weighed dietary survey and had their blood pressures measured once. They were classified according to their fibre intake. Subjects with a high-fibre intake were found to have lower mean blood pressures than those with a low-fibre intake. Forty-two of the volunteers further participated in a group of experiments. Those eating a high-fibre diet decreased their dietary fibre, and those eating a low-fibre diet increased their dietary fibre. The first group (11 subjects) showed increased mean blood pressures after four weeks of eating the experimental diet. The last group (31 subjects) showed decreased mean blood pressures after four weeks of eating the experimental diet. The 11 subjects consuming the low-fibre experimental diet showed a decrease in mean blood pressure when some of the saturated fat in their diet was replaced by polyunsaturated fat. A similar substitution carried out by 14 of the subjects consuming the high-fibre experimental diet also resulted in decreased mean blood pressure, but this was not statistically significant. Twelve more volunteers, with hypertension, were all found to have low-fibre diets. They consumed a high-fibre diet for a six-week experimental period, but their mean blood pressures did not decrease significantly; individual recordings varied substantially during this period.It is suggested that differences in the type and quantity of dietary fibre and fat may be responsible for the lower mean blood pressures of groups of vegetarians compared with similar groups of non-vegetarians.

Adolescent↗