Studies on the role of specific dietary fibres in protection against colorectal cancer

Although dietary fibre is generally thought to protect against the development of colorectal cancer, some of the results of animal and epidemiological studies are equivocal. We believe that this may be because the term dietary fibre covers a range of complex materials and some may protect but others may not. Dietary fibre is mainly composed of plant cell walls which vary in composition and properties according cell type and plant species. In addition to polysaccharides, the walls of some plant cell types contain the hydrophobic polymers lignin or suberin. Two groups of mechanisms have been proposed for the way dietary fibres may protect against colorectal cancer: those in which the dietary fibre may act directly and those in which the dietary fibre may have an indirect effect as a consequence of it being degraded by colonic bacterial enzymes and the products fermented. Direct mechanisms include the adsorption of carcinogens onto undegraded dietary fibres which pass out of the intestinal tract in the faeces. we have shown that different types of plant cell walls adsorbed a range of carcinogens, including heterocyclic aromatic amines, to different extents. Cell walls that contained lignin or suberin adsorbed hydrophobic carcinogens particularly well. Furthermore, the presence of lignin, and probably suberin, in the walls makes them resistant to degradation in the colon. Wheat bran, which is a good source of dietary fibre, contains some cell types with lignified walls. We used Fischer-344 rats to test the ability of wheat bran to protect against the formation of aberrant crypts (which are considered to be precursors to colon cancer) caused by the heterocyclic aromatic amine, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). Our results indicate that wheat bran protects and probably does so by a direct mechanism.     

Influence of diets containing high and low risk factors for colon cancer on early stages of carcinogenesis in human flora-associated (HFA) rats

Germ-free rats colonised with a human intestinal flora were fed diets containing high risk (HR) or low risk (LR) factors for colorectal cancer, and putative biomarkers were evaluated in the colonic mucosa; (i) proliferation, (ii) 1,2-dimethylhydrazine (DMH)-induced aberrant crypt foci and (iii) DMH-induced DNA damage. The HR diet was high in fat (45% of calories) and low in calcium and fibre, reflecting levels characteristic of typical western diets. The LR diet was low in fat (<5% of calories), and high in calcium and fibre. The nutrient/energy ratio of the two diets were similar. Mucosal crypt cell proliferation, assessed after microdissection, was higher on the LR diet (mean number of mitoses per crypt was 2.65 on the LR diet, and 1.62 on the HR diet; P < 0.05). Aberrant crypt foci (ACF) were assessed in the mucosa 12 weeks after DMH treatment. On the HR diet there were significantly more small ACF with 1 and 2 crypts per focus, but fewer ACF with 3, 5 and 7 or more crypts per focus. There was no significant difference in total ACF or the total number of crypts. The effect of diet on DNA damage in the colon was assessed in vivo by the comet assay. Animals were fed a HR or LR diet for 12 weeks before treatment with DMH or saline. For carcinogen-treated animals, DNA damage was significantly higher in colon cells from animals on the HR diet. On the LR diet both DNA damage and the induction of small ACF were reduced despite an increase in cell proliferation. The increase in large ACF on the LR diet may be attributable to elevated crypt cell proliferation possibly increasing crypt fission rates.     

The effects of whole wheat, wheat bran and zinc in the diet on the absorption and accumulation of cadmium in rats

The purpose of the present study was to determine if the inclusion of whole-grain wheat or wheat bran in the diet or the addition of Zn to the diet affects the absorption and accumulation of Cd. Five groups of six rats each were fed deionized water and one of five diets composed of one part basic diet and one part wheat crispbread for 6 weeks. The accumulation of Cd in the liver and kidneys was measured using atomic absorption spectrometry and estimated by measuring the absorption and retention of 109Cd from a single meal after 3 weeks on the diets. The fractional accumulation of Cd in the liver and kidneys was lower in rats fed on whole-wheat and bran diets than in those fed on wheat-endosperm diets. As adding Zn or Cd to endosperm diets to approximate the bran and whole-wheat diet levels had no effect on the fractional Cd absorption, the reduced absorption from the whole-wheat and bran diets is probably not due to their higher Zn and Cd concentrations but may be due to their higher fibre or phytate concentrations. The amount of Cd accumulated in the liver and kidneys of the rats fed on whole-wheat and bran diets was higher than that in rats fed on the endosperm diet. Thus, the reduction in the fractional Cd accumulation from the whole-wheat and bran diets is not sufficient to compensate for their higher Cd concentrations.     

The role of apoptosis in the modulation of colon carcinogenesis by dietary fat and by the organoselenium compound 1,4-phenylenebis(methylene)selenocyanate

Studies in laboratory animals have demonstrated that dietary supplements of organoselenium, 1,4-phenylenebis(methylene)selenocyanate (p-XSC) inhibit colon carcinogenesis. Diverse chemopreventive agents and clinically used anticancer drugs have been shown to induce apoptosis in colonic tumors. Inducing apoptosis is a key mechanism for the effectiveness of some chemopreventive agents; however, failure of apoptosis is now believed to contribute to the development of human cancer. In this study, we determined the number of apoptotic bodies in the colon tumors of rats fed a low-fat (LF) or a high-fat (HF) diet with or without p-XSC treatment. At 5 weeks of age, male F344 rats were divided into four groups, which were then maintained on one of the following diets: LF, 5% corn oil; HF, 23.5% corn oil; and LF and HF supplemented with 20 ppm p-XSC. In addition, the LF or HF diet with p-XSC supplements was administered either during the initiation stage or postinitiation. At 7 weeks of age, all rats except those intended for vehicle (normal saline) treatment were given 15 mg/kg of body weight of azoxymethane once weekly for 2 weeks. The animals were sacrificed 38 weeks after carcinogen treatment, and their colonic tumors were examined for appearance of apoptosis. The LF diet significantly increased the percentage of apoptosis as compared to the HF diet; the percentage of apoptosis in LF and HF diets were 12.4 and 2.9. The colon tumors that were present in the groups fed p-XSC together with a LF or a HF diet after carcinogen administration (postinitiation period) had a higher number of apoptotic bodies than those that were present in the animals fed p-XSC before carcinogen treatment (initiation period). The extent of apoptosis was weak when p-XSC was given with a HF diet (4.4%) during the initiation phase, but it was high significant when p-XSC was administered with LF diet (25.2%). Taken together, our data suggest that administration of LF diet supplemented with p-XSC increases apoptosis as compared to a HF diet alone.     

Low dietary protein impairs blood coagulation in BHE/cdb rats

The influence of dietary protein on blood coagulation tests was evaluated in BHE/cdb rats. Three experiments were conducted in order to compare effects of diets with low (8 g/100 g diet) or high (38 g/100 g diet) protein, to establish values for coagulation tests at intermediate (12-30 g/100 g diet) concentrations of dietary protein, and to compare feeding identical quantities of diets with 8 g protein/100 g diet vs. 18 g protein/100 g diet. After 4 wk of feeding the semipurified diets, bleeding time exceeded 15 min in the groups fed low protein diets, compared to a range of 3-6 min for the groups fed high protein diets. Several in vitro tests of coagulation were abnormal in the rats fed low protein diets. For example, prothrombin time averaged 27 +/- 8 s in rats fed 8 g protein/100 g diet plus beef tallow, but 17 +/- 1 s in rats fed 38 g protein/100 g diet plus tallow. The coagulation deficit in rats fed low protein was not affected by fat source (tallow vs. menhaden oil), but fibrinogen was elevated in rats fed diets with menhaden oil. Conversely, no differences in coagulation tests were observed among rats fed 12-30 g protein/100 g diet. Bleeding times ranged from 7 to 9 min, and prothrombin time was 17-18 s. Significant differences in plasma fibrinogen concentration and prothrombin time were observed in rats fed 8 vs. 18 g protein/100 g diet at a fixed rate of 6 g/100 g body weight. Platelet and blood cell numbers were unaffected by dietary protein. The evidence for multiple deficits in the coagulation system suggests that hepatic function in BHE/cdb rats may become impaired when the rats are fed low protein diets of the composition used here.     

Dietary components modify the ability of garlic to suppress 7,12-dimethylbenz(a)anthracene-induced mammary DNA adducts

Various dietary components were evaluated as factors influencing garlic's ability to depress rat mammary cell DNA adducts resulting from 7,12-dimethylbenz(a)anthracene (DMBA) treatment. Diets with or without garlic powder (20 g/kg) were provided for 2 wk before DMBA treatment (25 mg/kg body weight). Rats fed diets containing 36 g casein/100 g diet had 31% fewer (P < 0.05) mammary cell DNA adducts than those fed 12 g/100 g. Garlic supplementation significantly (P < 0.05) reduced DNA adducts in rats fed either 12 or 36 g casein/100 g by 35 and 32% respectively. In the absence of dietary garlic, DNA adducts were 23% lower (P < 0.05) in rats provided a diet containing supplemental L-methionine at 0.9 g/100 g than at 0.3 g/100 g. However, adduct inhibition by garlic supplementation was greater in rats fed the lower (P < 0.05) amount of methionine (54 vs. 26% inhibition). Adduct levels in rats fed diets with 20 g corn oil/100 g were twice those occurring in rats fed 5 g/100 g (P < 0.05), regardless of adjustment for energy density. Garlic supplementation prevented the increase in DNA adducts caused by increasing dietary corn oil. Combining dietary supplements of garlic, selenite (0.5 mg/kg diet) and retinyl acetate (328 mg/kg diet) inhibited the occurrence of DNA adducts to a greater degree than when each was supplied individually. These studies demonstrate that while dietary garlic can reduce DNA adduct formation in mammary tissue caused by DMBA, this protection is influenced by several dietary components.     

Update on pediatric heart transplantation. Long-term complications

We have previously observed changes in colon cell proliferation in growing rats fed different levels of dietary fat as beef tallow or corn oil. Here we measured cellular proliferation at 18 and 30 weeks in the colon of rats fed beef tallow or corn oil and treated with the chemical carcinogen azoxymethane. Additionally, we assessed colon cell membrane lipid composition after 18 weeks on the defined diets and tumor incidence at 30 weeks. Dietary fat type and quantity significantly affected colon cell proliferation. Membrane phospholipids and free fatty acids were significantly affected by fat type. Tumor incidence was not affected by diet type. We conclude that dietary fat induces changes in cell membrane lipid composition and proliferation in the colon and these changes may be related to the development of tumors.     

Effects of dietary fiber and salt mixtures on the cholesterol metabolism of rats

The isotopic dilution method, which permits the in vivo measurements of the rates of the processes involved in cholesterol turnover, has been applied to rats fed a commercial stock diet or a basal semipurified diet in which either the nature and proportions of the source of dietary fiber or the salt mixture were changed. The cholesterolemia was about 100 mg/100 g in rats fed agar-agar, cellulose, bran or the stock diet. Pectin addition (5%) lowered significantly the plasma concentration of cholesterol (70 mg/100 g). Changes in the source of dietary fiber or salt mixture have moderate effects on the absorption coefficient of dietary cholesterol (range 58.2%-82%). In comparison to agar-agar, cellulose at 2.3% in the diet significantly lowered this coefficient, but larger amounts of cellulose (6.8% or 12.3%), or pectin (5%) were without effect, while bran addition (10%) tended to slightly decrease cholesterol absorption. Hence, high levels of cellulose in the diet increased the absorption coefficient in comparison to a low cellulose diet. A decrease of this coefficient was also observed when the calcium content of the diet was increased. Cholesterol biosynthesis and fecal excretion were inversely correlated to the absorption coefficient of dietary cholesterol in rats fed all of the semipurified diets indicating, as previously shown, that the intestine was the major source of biosynthesized cholesterol diverted into the plasma. However, feeding a commercial stock diet greatly increased the cholesterogenesis and the fecal elimination of bile acids, suggesting a high hepatic cholesterogenesis.     

A comparison of in vivo and in vitro strain with posterior fixed partial dentures

Formulated diets associated with a high risk (HR) or low risk (LR) for colon cancer were used to assess the effect of diet on putative metabolic biomarkers in human flora-associated rats: The HR diet was high in fat and sucrose and low in calcium and fiber; the LR diet was low in fat and high in starch, calcium, and fiber. The nutrient-to-energy ratio and energy intake were the same for both diets. Body and liver weights were significantly higher in animals fed the HR diet, possibly due to greater energy availability from fat. Cecal weights were significantly higher in animals fed the LR diet, presumably due to a bulking effect of the fiber and increased bacterial biomass. The HR diet significantly altered cecal bacterial enzyme activity: beta-glucuronidase activity increased 2.5-fold, and beta-glucosidase activity was halved. Ammonia production and the bacterial metabolism of 2-amino-3-methyl-7H-imidazo[4,5-f] quinoline (IQ) to 7-hydroxy-IQ (7OHIQ) were significantly higher in animals fed the HR diet. The HR diet, which contained factors common to diets consumed throughout the Western world, increased beta-glucuronidase activity, elevated cecal ammonia concentrations, and enhanced the genotoxic risk from 7OHIQ formation, three putative metabolic biomarkers of colorectal cancer. The significance of the reduction in beta-glucosidase is unclear.     

Effects of different types of dietary fiber preparations isolated from bamboo shoots, edible burdock, apple and corn on fecal steroid profiles of rats

This study was conducted to evaluate the effects of different types of dietary fibers (DF) under the conditions with or without cholesterol (Chol) loading on the amount and composition of steroids in rat feces. Rats were fed Chol-unsupplied diets containing 10% lard and 5% DF preparation isolated from four kinds of food, bamboo shoots, edible burdock, apple and corn, for three weeks. The respective diets were supplemented with 0.5% Chol and then given to the rats for a further two weeks. The excretion of total bile acid (BA) and several major BAs increased significantly in the apple group with or without Chol loading when compared with that in the cellulose (CP) or other DF groups. The tendency in the apple group was more noticeable when the diet was supplemented with Chol. This is presumably a major reason for the tendency of decrease in serum and liver Chol concentrations in the apple group. The ratio of secondary BAs to total BA in the feces was significantly low in the apple group. Although the lithocholic acid (LCA)/deoxycholic acid (DCA) ratio, a risk index for colorectal cancer, was significantly lower in the bamboo, burdock and apple groups than in the CP or corn groups when given the diet without Chol, the differences disappeared with the addition of Chol. The proportion of coprostanol, a secondary metabolite of Chol, was smaller in the former three groups than in the CP or corn groups. These results suggest that the intake of some DF by host animals works beneficially for the microbial conversion of BA and Chol in the large intestine but that the addition of Chol acts to cancel such beneficial effects.     

Influence of environmental temperature on in vivo energy expenditure in vitro ouabain-sensitive respiration in duodenal mucosa and liver in rats fed different levels of dietary fiber or protein

Seventy two Wistar rats were used in two repeat studies to investigate the effect of environmental temperature (18 degrees C or 28 degrees C) and increasing levels of dietary fibre (low, 68 g/kg DM; medium 110 g/kg DM; high, 157 g/kg DM) or protein (low, 91 g/kg DM; medium, 171 g/kg DM; high, 262 g/kg DM) on digestive tract, visceral organ size, energy metabolism, and respiration attributable to Na+,K(+)-ATPase activity in duodenal mucosa and liver. Total and ouabain-sensitive (a measure of Na+,K(+)-ATPase activity) O2 consumption in vitro of tissues were measured polarographically using a Clark-style YSI biological O2 monitor. Whole body heat production (in vivo) was measured using open-circuit respiration chambers. The weight of the visceral organs was higher in rats housed at 18 degrees C than at 28 degrees C. The empty weight of the small intestine, caecum, and colon increased as the level of dietary fibre increased (P 0.05). Heat production as a proportion of metabolizable energy was higher (P < 0.05) at 18 degrees C than at 28 degrees C in the first experiment but this difference was significant in the second experiment. Rats fed the low protein diet had significantly higher (P > 0.05) heat production than those fed medium or high protein diets. Compared to 28 degrees C, environmental temperature of 18 degrees C caused an increased total and ouabain-sensitive O2 consumption in duodenal mucosa. There was no significant effect of environmental temperature on total and ouabain-sensitive O2 consumption in the liver. However, ouabain-sensitive O2 consumption in liver was significantly higher (P 0.05) when rats were fed a low protein diet compared to the medium or high protein diet. Total and ouabain-sensitive O2 consumption increased in duodenal mucosa of rats fed low level of dietary fibre compared to the medium or high dietary fibre diets. The in vitro results corresponded with the whole animal energy expenditure and O2 consumption in vivo.     

Effects of cereal type and feed particle size on morphological characteristics, epithelial cell proliferation, and lectin binding patterns in the large intestine of pigs

The present study was undertaken to investigate the effects of cereal type and feed particle size on the morphological characteristics and epithelial cell proliferation of the large intestinal tissue in pigs. Forty pigs, weighing approximately 30 kg, were fed diets containing either coarsely or finely milled barley or wheat for a period of 4 wk. Tissue samples were taken from the cecum and from the proximal, medial, and distal colon at slaughter. The pigs fed the coarse diets had significantly larger crypts, in terms of height as well as volume, than did pigs fed the fine diets. The cereal type had no effect on the mucosal architecture. The epithelial cell proliferation, in terms of counted native mitoses in the crypts, was significantly higher in pigs fed the coarse barley diet than in pigs fed the coarse wheat diet or the fine diets. The volume of the mucin granules in the crypts constituted from 32 to 52% of the crypt volume and was greatest in the pigs fed the coarse diets. This effect of feed particle size was observed for neutral as well as for acidic mucins and sulfomucins. Lectin binding patterns indicated that more of the terminal sugars on glycoconjugates of the apical membrane on the mucosal surface were the sialic acid alpha-2,3 neuraminic acid, but less were mannose in the pigs fed the coarse barley diet. Distinct regional differences were observed among the intestinal sites. These included a decline in the epithelial cell proliferation and an increase in the volume of mucin in the crypts along the intestinal tract. Furthermore, the sialic acid alpha-2,3 neuraminic acid was more abundant in the medial colon than in the cecum; the contrary was seen for mannose and galactose. This study shows that the feed particle size of barley and wheat diets, more than the cereal type itself, affects the mucosal architecture, epithelial cell proliferation, and production and composition of the mucins in the large intestine of pigs. The study suggests that pigs fed a coarse diet are better protected against intestinal infections than pigs fed a fine diet.     

Transcriptional activation of the human c-myc gene by simian virus 40 large T antigen without binding to p53 and RB proteins in the transient expression system

Male adult Wistar rats were randomly divided into four groups in a 2 x 2 factorial design and were fed diets containing cooked-stored polished rice (CSPR), with and without 0.7 g/100 g of Nebacitin [bacitracinneomycin sulfate (2:1, wt/wt)] and with and without 1 g cholesterol/100 g diet. The CSPR diet contained 1.87 g resistant starch/100 g. After 4 wk, arterial blood and liver were collected. Feces were collected during the last 7 d. Rats fed the diet with Nebacitin and cholesterol had higher serum total cholesterol than the rats fed diets without cholesterol. Serum triglyceride concentration was greater in rats fed Nebacitin, regardless of dietary cholesterol concentration. Rats fed the diet with Nebacitin and cholesterol had higher serum LDL cholesterol concentration and liver total cholesterol concentration than rats fed the other three diets. Rats fed the CSPR diet with Nebacitin both with and without cholesterol had a higher fecal resistant starch concentration and excretion and lower serum short-chain fatty acid concentration than rats fed the diets without Nabacitin. Hepatic cholesterol concentration was greater in rats fed Nebacitin only when the diet also contained cholesterol. Therefore, dietary Nebacitin alters lipid metabolism in rats, and some effects are most pronounced in those also fed cholesterol.     

Dietary flavonoids reduce lipid peroxidation in rats fed polyunsaturated or monounsaturated fat diets

We investigated the influence of dietary flavonoids on alpha-tocopherol status and LDL peroxidation in rats fed diets enriched in either polyunsaturated fatty acids (PUFA) or monounsaturated fatty acids (MUFA). Diets equalized for alpha-tocopherol concentrations were or were not supplemented with 8 g/kg diet of flavonoids (quercetin + catechin, 2:1). After 4 wk of feeding, plasma lipid concentrations were lower in rats fed PUFA than in those fed MUFA with a significant correlation between plasma alpha-tocopherol and cholesterol concentrations, r = 0.94, P < 0. 0001). Dietary lipids influenced the fatty acid composition of VLDL + LDL more than that of HDL or microsomes. The resistance of VLDL + LDL to copper-induced oxidation was higher in rats fed MUFA than in those fed PUFA as assessed by the lower production of conjugated dienes and thiobarbituric acid reactive substances (TBARS) and by the >100% longer lag time for dienes production. (P < 0.0001). Dietary flavonoids significantly reduced by 22% the amounts of dienes produced during 12 h of oxidation in rats fed diets rich in PUFA and lengthened lag time 43% in those fed MUFA. Microsomes of rats fed MUFA produced approximately 50% less TBARS than those of rats fed PUFA (P < 0.0001) and they contained more alpha-tocopherol in rats fed MUFA than in those fed PUFA with higher values (P < 0. 0001) in both groups supplemented with flavonoids (P < 0.0001). Our findings suggest that the intake of dietary flavonoids is beneficial not only when diets are rich in PUFA but also when they are rich in MUFA. It seems likely that these substances contribute to the antioxidant defense and reduce the consumption of alpha-tocopherol in both lipoproteins and membranes.     

Chemoprevention of colon cancer by organoselenium compounds and impact of high- or low-fat diets

BACKGROUND: Observational and experimental studies have suggested that dietary supplementation with selenium can inhibit the development of colon cancer. However, many forms of selenium are toxic. Consequently, the development of efficacious compounds with low toxicity has been pursued. PURPOSE: Two synthetic organoselenium compounds, p-methoxy-benzyl selenocyanate (p-methoxy-BSC) and 1,4-phenylenebis(methylene)selenocyanate (p-XSC), were tested for their ability to inhibit colon carcinogenesis in rats that were treated with the carcinogen azoxymethane and fed low- or high-fat diets. METHODS: Groups of 5-week-old male F344 rats (42 animals/ group) were fed either a high-fat diet or a low-fat diet with or without added p-methoxy-BSC (10 or 20 parts per million [ppm]) or p-XSC (20 ppm). Two weeks later, 30 animals in each group received a subcutaneous injection of azoxymethane (15 mg/kg body weight); 1 week later, they received a second injection. The remaining 12 rats in each group received two injections of saline. Three days after the second injection of carcinogen or saline, animals being fed diets with p-methoxy-BSC or p-XSC were switched to corresponding organoselenium-free low- or high-fat diets for the remainder of the study to determine the effects of the selenium compounds on the initiation phase of colon carcinogenesis. At that time, groups of animals that had been maintained on organoselenium-free low- or high-fat diets were switched to diets containing p-methoxy-BSC or p-XSC until the end of the study to determine the effects of these compounds on the postinitiation phase of colon carcinogenesis. All animals were killed during the 38th week after azoxymethane or saline treatment, and histopathologic analysis of the colon tumors was performed. Colon tumor incidence and multiplicity were analyzed statistically. RESULTS: No obvious toxic effects were observed following dietary administration of 10 or 20 ppmp-methoxy-BSC or 20 ppm p-XSC. Administration of 20 ppm p-methoxy-BSC in a high-fat diet during the initiation and postinitiation phases of colon carcinogenesis significantly (statistically) reduced colon tumor incidence; 10 ppmp-methoxy-BSC in a high-fat diet significantly reduced colon tumor incidence but only when it was given during the postinitiation phase. Colon tumor incidence was also significantly reduced when 20 ppm p-XSC was given in a high-fat diet during the initiation phase of colon carcinogenesis. When 20 ppm p-XSC was administered in either a high-fat diet or a low-fat diet during the postinitiation phase, both colon tumor incidence and multiplicity were significantly reduced; the greatest reductions were in animals fed a low-fat diet. CONCLUSIONS: In this model system, p-methoxy-BSC and p-XSC are effective agents for the chemoprevention of colon cancer. The effects of p-XSC were enhanced in animals fed a low-fat diet.     

Dietary biotin requirement for maximum growth of juvenile grass shrimp, Penaeus monodon

A feeding trial was conducted to estimate the minimal dietary biotin requirement for juvenile grass shrimp, Penaeus monodon. Purified diets with eight levels (0, 0.2, 0.5, 1.0, 3.0, 6.0, 10.0 and 20.0 mg/kg) of supplemental biotin were fed to P. monodon (mean weight 0. 26 +/- 0.01 g) for 8 wk. Each diet was fed to three replicate groups of shrimp. Shrimp fed diets supplemented with biotin (0.2-20.0 mg/kg) had significantly (P < 0.05) higher weight gain, feed efficiency and protein efficiency ratio than those fed the unsupplemented control diet. Weight gain was high in shrimp fed 3. 0-10.0 mg biotin/kg diet and lowest in shrimp fed 相似文献   

Supplemental arginine and ornithine do not affect splenocyte proliferation in surgically treated rats

The present study was designed to determine whether arginine or ornithine supplementation enhanced immune responsiveness in surgically stressed rats. Young rats (130 to 150 g; n = 72) were fed one of three nonpurified diets: control, arginine-supplemented (30 g/kg of diet), or supplemented with ornithine on an equimolar basis to supplemental arginine. Control and ornithine-supplemented diets were made isonitrogenous to the arginine-supplemented diet with alanine. Food intake and body weight were monitored throughout the experimental period. Eight days after initiation of dietary treatments, 36 rats were given dorsal skin wounds. Rats were killed 7 days later. Blood was collected, spleen and thymus were weighed, and splenocytes were isolated to measure proliferation in response to mitogens and interleukin-2 production. Food intake, body weight gain, and thymus weight were lower in rats subjected to surgery than in controls rats (p < .01). Neither supplemental dietary arginine nor ornithine affected food intake, body weight gain, thymus weight, splenocyte proliferation, or splenocyte interleukin-2 production in any treatment group (p < .1). These data suggest that low-level dietary supplementation of arginine and ornithine did not ameliorate detrimental effects of minor surgery in rats.     

Effects of variations in the proportions of saturated, monounsaturated and polyunsaturated fatty acids in the rat diet on spleen lymphocyte functions

To obtain further information about the immunomodulatory effects of specific dietary fatty acids, weanling male rats were fed for 6 weeks on high-fat (178 g/kg) diets which differed according to the principal fatty acids present. The nine diets used differed in their contents of palmitic, oleic, linoleic and alpha-linolenic acids; as a result the total polyunsaturated fatty acid (PUFA) content and the PUFA:saturated fatty acid ratio varied (from 17.8 to 58.5 g/100 g fatty acids and from 0.28 to 5.56 respectively). The n-6 PUFA:n-3 PUFA ratio was kept constant in all diets at approximately 7.0. The fatty acid composition of the serum and of spleen lymphocytes were significantly influenced by that of the diet fed. The ex vivo proliferation of spleen lymphocytes decreased as the level of oleic acid in the diet increased. Spleen natural killer cell activity decreased as the oleic acid content of the diet increased and increased as the palmitic acid content of the diet increased. The extent of the effects of these fatty acids on lymphocyte functions was modified by the nature of the background fatty acid composition of the diet.     

The cholesterol-lowering properties of a psyllium-based breakfast cereal in hamsters

Hamsters were fed high fiber diets containing cellulose, wheat bran or psyllium. The psyllium was incorporated into high fiber, ready-to-eat (RTE) flakes that were used to formulate the test diet. All the diets contained 0.125% cholesterol. The study was terminated after three weeks. Food intake, weight gain and feed efficiency were not significantly different in the three groups. Serum total and HDL cholesterol levels were reduced significantly by the psyllium diet. Serum triglycerides were 26% lower in the hamsters fed psyllium but because of the large variation the difference did not reach statistical significance. Liver total cholesterol and cholesteryl ester levels were significantly lower in the hamsters fed psyllium. Liver triglycerides were highest in the psyllium-fed hamsters and liver phospholipid levels were similar in the three groups. Liver cholesterol and triglyceride levels were higher in hamsters fed cellulose than in those fed wheat bran. Psyllium formulated into an RTE cereal was effective in reducing serum and liver cholesterol levels in hamsters.     

Responses and physiological modifications of intestinal sucrase in rats fed diets containing various carbohydrates

Weaning rats were submitted during 3 months to complet and balanced diets where only glucidic constituent varied. They were sacrified when fed or after 16 h fasting. 1. The value of intestinal sucrose K(M) is higher in rats fed on glucose dietary than in rats fed on sucrose, fructose or glucose + fructose dietary. These modifications are independant of the states of digestion. 2. The V(MAX) is diversely influenced by the states of digestion: hydric diet increases the V(MAX) in animals fed on sucrose diet when intestinal repletion has the same effect in animals receiving glucose diet. Fructose diet decreases it irreversibility in both cases. 3. Growth of animals is sagging respectively in order from sucrose and glucose diets to glucose + fructose and fructose diets, then weight of organes is unaffected. It was noted that perirenal and epididymal fats are more abundant in rats nourished with glucose diet than with fructose diet. 4. The glucoregulation is correctly effectued in either starved or fed animals and shows an available adaptation of organism in energetic utilisation of various studied sugars. Plasmatic, hepatis and intestinal free fatty acids levels are constant and equal in all series of expements in spite of important variations of reverse fat.