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To explore the immunological roles of dietary fiber, male 4-wk-old Sprague-Dawley rats were fed for 2 wk cellulose (water-insoluble), konjak mannan (water-soluble), pectin (water-soluble) or chitosan (acid-soluble) at 5 g/100 g diet. Serum IgE concentrations in rats fed konjak mannan, pectin and chitosan were significantly lower than in those fed cellulose (mean [+ or -] SEM: 5.0 [+ or -] 1.1, 3.6 [+ or -] 1.3, 3.0 [+ or -] 1.2 and 9.6 [+ or -] 1.9 [[micro]gram]/L, respectively). Rats fed pectin had significantly higher serum IgA and IgG concentrations (358 [+ or -] 38 and 424 [+ or -] 36 mg/L for IgA and IgG, respectively) than those fed cellulose (240 [+ or -] 31 and 337 [+ or -] 25 mg/L) or chitosan (176 [+ or -] 22 and 379 [+ or -] 23 mg/L), while the IgM concentration did not differ among the groups. Concentrations of IgA, IgG and IgM in mesenteric lymph node (MLN) lymphocytes generally were greater, while IgE concentration was lower, in rats fed pectin and chitosan than in those fed cellulose. The proportion of [CD4.sup.+] T-cells in MLN lymphocytes was also dietary fiber-dependent, and the [CD4.sup.+]/[CD8.sup.+] ratio was significantly higher in the pectin fed group than in all other groups. Under certain experimental conditions, MLN lymphocytes from rats fed pectin had markedly greater interferon-[Gamma] concentration than cells from other groups, while the effect on tumor necrosis factor-[Alpha] concentration was less marked. Thus, dietary fiber may have an immunoregulatory effect on the intestinal immune system of rats. KEY WORDS: * dietary fiber * immunoglobulin * mesenteric lymph node * lymphocytes * cytokine * rats

A range of human and animal studies have shown that rice bran oil (RBO) is an edible oil of preference for improving serum cholesterol levels and lipoprotein profiles with similarity to the more commonly used vegetable oils such as corn oil and safflower oil. Of particular interest is the observation that blending RBO with safflower oil at a definite proportion (7:3, wt/wt) magnifies the hypocholesterolemic efficacy, compared with the effect of each oil alone. Although the mechanism underlying this effect is not apparent at present, the blending may have a practical significance. The blending effect was reproduced in rats fed a cholesterol-enriched diet, and there was also a decrease in liver cholesterol. The occurrence of peculiar components such as [Gamma]-oryzanol and tocotrienols could be responsible for the hypocholesterolemic effect of RBO. KEY WORDS: * rice bran oil * cholesterol * [Gamma]-oryzanol * humans * rats

Effects of dietary protein on oxidized cholesterol-induced alterations in linoleic acid and cholesterol metabolism were studied in 4-wk-old male Sprague-Dawley rats, using casein and soybean protein as dietary protein sources. The rats were fed one of the two proteins in cholesterol-free, 0.3% cholesterol or 0.3% oxidized cholesterol mixture diets using a pair-feeding protocol for 3 wk. In the soybean pro-tein-fed group, rats fed oxidized cholesterol did not have lower activity of liver microsomal [Delta]6 desaturase, the rate-limiting enzyme in the metabolism of linoleic acid to arachidonic acid, compared with rats fed cholesterol-free diet, whereas in the casein-fed group the desaturase activity was significantly greater in rats fed oxidized cholesterol than in those fed cholesterol-free diet. This was in contrast to a significant reduction in liver microsornal [Delta]6 desaturase activity by cholesterol, irrespective of protein source. In general, these changes were reflected in the desaturation indices of liver phospholipids. Furthermore, soybean protein significantly increased the fecal excretion of neutral and acidic steroids and tended to reduce (P = 0.082) the accumulation of oxidized cholesterols in the liver. Thus, soybean protein partly modified some of the undesirable effects of oxidized cholesterol through its hypocholesterolemic effect and possibly through the modulation of hepatic [Delta]6 desaturase activity. J. Nutr. 126: 1635-1643, 1996. INDEXING KEY WORDS: * oxidized cholesterol * soybean protein * casein * [Delta]6 desaturase * rats

Rats were fed purified diets containing 10% fat with constant (n-6):(n-3) polyunsaturated fatty acids [(n-6):(n-3); 2.3-2.6] and polyunsaturated:saturated fatty acids (1) ratios. This was obtained with [Alpha]-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid added at 1 g/100 g diet. Eicosapentaenoic acid and docosahexaenoic acid were added as the ethyl esters. The concentration of plasma cholesterol in rats fed docosahexaenoic acid was significantly lower than in those fed [Alpha]-linolenic acid. The concentration of plasma triglyceride was significantly lower in rats fed eicosapentaenoic acid than in those fed docosahexaenoic acid. Docosahexaenoic acid significantly reduced hepatic cholesterol compared with [Alpha]-linolenic acid and eicosapentaenoic acid. Both eicosapentaenoic acid and docosahexaenoic acid decreased hepatic triglyceride compared with [Alpha]-linolenic acid, but this effect was more pronounced in the docosahexaenoic acid group. There was no significant difference in fecal excretion of neutral and acidic steroids and apparent fat absorption. In rats fed docosahexaenoic acid, the proportion of arachidonic acid in liver microsomal phosphatidylcholine was lower than in those fed eicosapentaenoic acid. The same tendency was observed in plasma, platelet and aortic phosphatidylcholine and liver microsomal phosphatidyl-ethanolamine and phosphatidylinositol. Dietary docosahexaenoic acid, but not eicosapentaenoic acid, significantly decreased aortic production of prostacyclin compared to [Alpha]-linolenic acid, whereas platelet aggregation by collagen was not affected by the difference in dietary (n-3) polyunsaturated fatty acids. INDEXING KEY WORDS: docosahexaenoic acid; lipid metabolism; [Alpha]-linolenic acid; eicosapentaenoic acid; rats

PAF binding to receptors and PAF-induced platelet aggregation are inhibited by phomactin D, and phomactin B, B1, B2 and C antagonized PAF action at higher concentrations. All the phomactins are isolated from Phoma sp., a marine fungus. The binding activity is influenced by the conformation of the bicyclic ring system and its hydroxy group substitution pattern.

To examine the effect of different saturated fatty acids on the dietary cholesterol-induced elevation of serum cholesterol concentration and suppression of LDL catabolism, for 4 wk hamsters were fed purified diets containing 8% purified fats in which saturated fatty acids, lauric, myristic, palmitic and stearic acids were the sole variable. The dietary fat was composed of 50% saturated fatty acid, 30% oleic acid and 20% linoleic acid (polyunsaturated:saturated = 0.4). In hamsters fed the cholesterol-containing diet, fat containing stearic acid, compared with the fats containing other saturated fatty acids resulted in greater fractional catabolic rate of (125I)-labeled homologous LDL, greater fecal excretion of neutral steroids and lower liver cholesterol concentration, although the elevation of serum cholesterol concentration due to consuming a cholesterol-containing diet was not ameliorated. Stearic acid fat resulted in greater excretion of fecal fatty acids and lower apparent absorption of the dietary fats in hamsters fed diets with and without cholesterol. In hamsters fed the cholesterol-free diets, type of dietary fat did not affect the fractional catabolic rate of LDL, although stearic acid fat resulted in greater fecal neutral steroid excretion and lower serum and liver cholesterol concentrations. These observations suggested that purified fat containing stearic acid results in lower plasma cholesterol concentration in hamsters via stimulation of neutral steroid excretion, but addition of cholesterol to the diets obscures this effect.