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P C Calder

Publications and source records attributed to P C Calder.

At least 109 records · Page 6Linked to original sources
PubMed1995

Effects of feeding lipids of different fatty acid compositions upon rat lymphocyte proliferation.

Weanling Wistar rats were fed for 8 weeks on a low fat (3% by weight) diet (LF) or on diets containing 15% by weight hydrogenated coconut oil (coconut oil), cocoa butter, cashew kernel oil (cashew oil), canola oil or soya bean oil (soya oil). Each of the high fat diets resulted in inhibition of spleen lymphocyte proliferation in response to concanavalin A (Con A), a T-cell mitogen. Feeding the soya oil diet caused more than 95% inhibition of proliferation, compared with feeding the LF diet. Amongst the high fat diets, feeding the cashew, canola or soya oil diets resulted in inhibition of proliferation compared with feeding the coconut oil diet while feeding the soya oil diet resulted in inhibition of proliferation compared with feeding the cocoa butter or canola oil diets. Proliferation of lymphocytes in response to Con A was also investigated using whole blood culture. Once again, feeding the soya oil diet resulted in a dramatic decrease in proliferation (80%) compared with feeding the LF diet. Feeding the soya oil diet also inhibited proliferation compared with feeding the coconut oil, cocoa butter or cashew oil diets. Feeding the canola oil diet resulted in inhibition of proliferation compared with feeding the LF or cocoa butter diets.

Animals↗
PubMed1995

Comparison of the effects of a range of dietary lipids upon serum and tissue lipid composition in the rat.

Since the type of fat consumed in the diet may play a role in the development of several disorders, it is important to ascertain the effects of different dietary fats upon parameters such as serum lipid levels and adipose deposition. The aim of this study was to determine the effects of feeding rats a range of fats with differing fatty acid compositions. Weanling male rats were fed for 10 weeks on a low fat (LF) diet or on one of five high fat diets, which contained 20% by weight of either hydrogenated coconut oil (HCO), olive oil (OO), safflower oil (SO), evening primrose oil (EPO) or menhaden (fish) oil (MO). Food intake, animal growth, tissue weights at sacrifice, serum and liver lipid concentrations and serum, heart, brain and adipose tissue fatty acid compositions were studied. The food intake of the LF-fed animals was greater than that of animals fed on the high fat diets; there were no differences in food intake between animals fed the high fat diets. The total energy intake was lower for animals fed on the HCO diet than for those fed on the LF, OO, EPO or MO diets; there were no other differences in energy intake between the groups. Animals fed the different diets had almost identical rates of weight gain up to 5 weeks; after this period of rapid growth, the increase in weight was slower in all groups but especially in the LF-fed animals. The LF-fed rats had a lower total weight gain and smaller final weights than rats fed on the high fat diets. Animals fed on the MO diet had a greater weight gain than those fed on the OO or EPO diets and their final weights were greater. The MO diet resulted in greatly increased liver weight compared with each of the other diets. The HCO, OO and EPO diets also increased liver weight compared with the LF diet. The total lipid content of the livers from rats fed the high fat diets was greater than that of those from rats fed the LF diet; the livers from animals fed the MO diet contained more lipid than those from animals fed each of the other diets. MO feeding increased the free cholesterol, cholesterol ester and triacylglycerol contents of the liver.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Incorporation of fatty acids by concanavalin A-stimulated lymphocytes and the effect on fatty acid composition and membrane fluidity.

The fatty acid compositions of the neutral lipid and phospholipid fractions of rat lymph node lymphocytes were characterized. Stimulation of rat lymphocytes with the T-cell mitogen concanavalin A resulted in significant changes in the fatty acid composition of both neutral lipids and phospholipids (a decrease in the proportions of stearic, linoleic and arachidonic acids and an increase in the proportion of oleic acid). Membrane fluidity was measured using nitroxide spin-label e.s.r., and increased during culture with concanavalin A. Culturing the lymphocytes in the absence of mitogen did not affect fatty acid composition or membrane fluidity. The uptake and fate of palmitic, oleic, linoleic and arachidonic acids were studied in detail; there was a time-dependent incorporation of each fatty acid into all lipid classes but each fatty acid had a characteristic fate. Palmitic and arachidonic acids were incorporated principally into phospholipids whereas oleic and linoleic acids were incorporated in similar proportions into phospholipids and triacylglycerols. Oleic acid was incorporated mainly into phosphatidylcholine, palmitic and linoleic acids were incorporated equally into phosphatidylcholine and phosphatidylethanolamine, and arachidonic acid was incorporated mainly into phosphatidylethanolamine. Supplementation of the culture medium with particular fatty acids (myristic, palmitic, stearic, oleic, linoleic, alpha-linolenic, arachidonic, eicosapentaenoic or docosahexaenoic acid) led to enrichment of that fatty acid in both neutral lipids and phospholipids. This generated lymphocytes with phospholipids differing in saturated/unsaturated fatty acid ratio, degree of polyunsaturation, index of unsaturation and n - 6/n - 3 ratio. This method allowed the introduction into lymphocyte phospholipids of fatty acids not normally present (e.g. alpha-linolenic) or usually present in low proportions (eicosapentaenoic and docosahexaenoic). These three n - 3 polyunsaturated fatty acids replaced arachidonic acid in lymphocyte phospholipids. Fatty acid incorporation led to an alteration in lymphocyte membrane fluidity: palmitic and stearic acids decreased fluidity whereas the unsaturated fatty acids increased fluidity. It is proposed that the changes in lymphocyte phospholipid fatty acid composition and membrane fluidity brought about by culture in the presence of polyunsaturated fatty acids are responsible for the inhibition of lymphocyte functions caused by these fatty acids.

Animals↗
PubMed1994

Triacylglycerol metabolism by lymphocytes and the effect of triacylglycerols on lymphocyte proliferation.

This study investigates the ability of lymphocytes to utilize fatty acids originating from triacylglycerols and the effect of triacylglycerols upon mitogen-stimulated lymphocyte proliferation. Lymphocytes isolated from rat lymph nodes, spleen, thymus and lymphatic duct had a lipoprotein lipase activity of approx. 10 units/mg of protein, indicating that the fatty acids of circulating triacylglycerols are accessible to these cells. In culture lymph node lymphocytes hydrolysed triacylglycerols added to the medium as emulsions. Both non-esterified fatty acids and free glycerol appeared in the cell culture medium, but their concentrations indicated that a high proportion of each (65-90% of fatty acids and 60-80% of glycerol) was taken up by the cells. The incorporation and fate of triacylglycerol-fatty acids was studied by culturing the cells in the presence of tri[3H]oleoylglycerol or tri[14C]inoleoylglycerol. Both fatty acids were incorporated into lymphocyte lipids in a time-dependent manner; linoleic acid was incorporated at a significantly greater rate than oleic acid. The majority of oleic acid (greater than 70%) was incorporated into cellular triacylglycerol, while less than 10% was incorporated into phospholipids. In contrast, linoleic acid incorporation into cellular triacylglycerol never exceeded 25%, while up to 45% was incorporated into phospholipids. Triacylglycerols containing polyunsaturated fatty acids inhibited concanavalin A-stimulated lymphocyte proliferation in a concentration- and time-dependent manner; triacylglycerols containing saturated fatty acids or oleic acid were not inhibitory. Such direct effects of certain triacylglycerols on lymphocyte function may explain why some clinical trials of polyunsaturated fatty acid-rich diets have been successful in improving the condition of patients suffering from inflammatory diseases.

Animals↗
PubMed1994

Inhibition of natural killer cell activity by dietary lipids.

Natural killer (NK) cells are a subset of cytotoxic lymphocytes found mainly in blood and the spleen. NK cells play a role in natural immunity to microbes, viruses and tumor cells and are involved in the rejection of grafts. The present study investigated the effects of diets containing oils rich in saturated fatty acids, mono-unsaturated fatty acids, n-6-poly-unsaturated fatty acids (PUFA) or n-3-PUFA on the NK cell activity and on the lymphokine-activated killer (LAK) cell activity of rat spleen lymphocytes. Weanling rats were fed for 10 weeks on a low-fat (LF) diet (approximately 2% fat by weight) or on 1 of 5 high-fat (HF) diets, which contained 20% (by weight) hydrogenated coconut oil (HCO), olive oil (OO), safflower oil (SO), evening primrose oil (EPO) or menhaden (fish) oil (MO). Each of the HF diets suppressed the NK activity of freshly prepared spleen lymphocytes compared with the LF diet; cells from the MO-fed rats exhibited the lowest NK activity. Culture with IFN alpha for 3 h increased the NK activity of spleen lymphocytes from all animals, except those fed the OO diet; the increase in NK activity varied from 20% (LF) to 50% (MO). Although feeding the OO, EPO or MO diets resulted in lower IFN alpha-stimulated NK activity than that obtained by feeding the LF diet, the only consistent significant difference was the lower activity of the cells from the OO-fed rats compared with those from the LF-fed rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Correspondence.

Explore the source record for details and available documents.

Letter↗
PubMed1994

Inhibition of lymphocyte proliferation in vitro by two lipid emulsions with different fatty acid compositions.

The effects of two lipid emulsions upon the proliferation of rat and human lymphocytes in vitro were investigated. The emulsions used were Intralipid, a soya bean oilbased emulsion in widespread clinical use, and Omegavenous, a newly-developed emulsion in which n-3 polyunsaturated fatty acids comprise approximately 40% of the total fatty acids. Both emulsions inhibited lymphocyte proliferation in a concentration- and time-dependent manner. Omegavenous was a much more potent inhibitor than Intralipid.

Journal Article↗
PubMed1994

The effect of dietary lipid manipulation on rat lymphocyte subsets and proliferation.

Polyunsaturated fatty acids (PUFA) have been shown to suppress immune cell functions in vitro. Dietary studies investigating the effects of PUFA-containing oils on lymphocyte functions have yielded contradictory findings: such studies are difficult to compare as there are many variations in protocols. The present study investigated the effects of diets containing oils rich in saturated fatty acids, monounsaturated fatty acids, n-6 PUFA or n-3 PUFA on rat lymphocyte proliferation and on receptor and surface marker expression. Rats were fed for 10 weeks on a low-fat (LF) diet (approximately 2% fat by weight) or on one of five high-fat diets, which contained 20% (by weight) hydrogenated coconut oil (HCO), olive oil (OO), safflower oil (SO), evening primrose oil (EPO) or menhaden (fish) oil (MO). Compared with feeding the LF diet, all of the high-fat diets suppressed the proliferation of lymphocytes from the spleen: although there was no significant effect of diet on the proliferation of lymphocytes from the thymus, there was a trend towards decreased proliferation with high-fat feeding. Feeding the OO, EPO or MO diets significantly suppressed proliferation of mesenteric lymph node lymphocytes compared with feeding the LF, HCO or SO diets. Dietary lipid manipulation had no effect on the proportion of T cells, B cells or monocytes/macrophages in the spleen, thymus or lymph nodes. Dietary lipid manipulation also had no significant effect on the proportions of CD4+ or CD8+ lymphocytes in spleen, thymus or lymph nodes, either in freshly prepared cells or in cells cultured in the presence of mitogen. There were no significant effects of dietary lipid manipulation on the expression of IL-2 receptors or transferrin receptors by concanavalin A (Con A)-stimulated lymphocytes. However, there was a trend towards a decrease in transferrin receptor expression by Con A-stimulated lymphocytes from the thymus and lymph nodes of the MO-fed rats and towards a decrease in the expression of IL-2 receptors by lymphocytes from the spleens and thymi of the MO-fed rats. These observations provide evidence that some dietary oils, particularly OO, EPO and MO, possess immunosuppressive properties and so may be useful in the therapy of diseases involving inappropriate lymphocyte activation.

Animals↗
PubMed1994

The effect of dietary lipid manipulation on hepatic mitochondrial phospholipid fatty acid composition and carnitine palmitoyltransferase I activity.

The maximal activity of the overt from of carnitine palmitoyltransferase I (CPT I; EC 2.3.1.21) and its sensitivity to inhibition by malonyl CoA were measured in mitochondria prepared from the livers of rats which had been fed for 10 weeks on either a low fat diet (LF; 2.4% fat by weight) or on one of four high fat diets which contained 20% by weight of either hydrogenated coconut oil (HCO), olive oil (OO), safflower oil (SO) or menhaden (fish) oil (MO). CPT I activity (i.e. activity per g of liver tissue), was elevated in animals fed the OO, SO or MO diets compared with those fed the LF or HCO diets. Feeding the HCO diet did not result in elevation of CPT I activity compared with feeding the LF diet. CPT I specific activity (i.e. activity per mg mitochondrial protein) was elevated in animals fed SO diet, but not in animals fed any of the other high fat diets. These observations suggest that an elevated fat load is not solely responsible for increasing CPT I activity, but that the fatty acid composition of the diet also plays a role. Hepatic CPT I activity of rats fed the LF diet was most sensitive to inhibition by malonyl CoA ([I50] = 0.53 microM). Each of the high fat diets decreased the sensitivity of CPT I to inhibition by malonyl CoA; CPT I activity in the livers from animals fed the MO diet was the least sensitive to malonyl CoA inhibition ([I50] = 1.8 microM). The fatty acid compositions of the major mitochondrial membrane phospholipids, phosphatidylcholine, phosphatidylethanolamine and cardiolipin were modified according to the fatty acid composition of the diet. Each of these phospholipids had a distinct fatty acid composition and similar effects of dietary lipid manipulation on the fatty acid compositions were observed. Feeding the SO diet resulted in fatty acid compositions which were most similar to those found after feeding the LF diet. Feeding the HCO and OO diets increased the proportions of stearic and oleic acids, respectively, while decreasing the proportion of linoeic acid. Feeding the MO diet resulted in increased proportions of palmitic, palmitoleic, eicosapentaenoic and docosahexaenoic acids and decreased proportions of linoleic and arachidonic acids in each of the phospholipids. It is proposed that the effects of dietary lipid manipulation upon CTP I activity and sensitivity to inhibition by malonyl CoA are due to alterations in the fatty acid composition of the phospholipids in the mitochondrial membrane where CPT I resides.

Animals↗