Roger Mongeau

Calorie restriction and cellular proliferation in various tissues of the female Swiss Webster mouse

Two experiments have been conducted to determine the effects of calorie restriction on cellular proliferation in female mouse tissues. In the first experiment, 25% calorie restriction led to a decrease in cellular proliferation, measured by the [3H]thymidine labeling index, in each of the 7 tissues examined. The duct lining cells of the mammary gland were the most affected. This conclusion was confirmed in the second experiment in which levels of 0, 10, 20, 30 and 40% calorie restriction were employed. The difference in response of the duct cells of the mammary gland and the crypt cells of the colo-rectum is discussed in light of the opinion that the formation of cancer of these tissues in humans may be markedly affected by diet.

Chemical and nutritional studies of flaxseed (variety Linott) in rats

Abstract The nutritional effects of flaxseed ( Linum usitatissimum , variety Linott) were studied in the rat. In addition, thermal and storage stabilities of flaxseed were evaluated. Weanling rats were fed diets containing ground flaxseed at levels of 0, 10, 20, or 40% for 90 days. No differences were found in the food intake nor in body and organ weights. Serum triglyceride, total cholesterol, and the low-density lipoprotein (LDL) cholesterol concentrations were significantly lower in the rats fed the 20% and 40% flaxseed diets compared to the 0% flaxseed group. The high-density lipoprotein (HDL) cholesterol concentration and the LDL:HDL-cholesterol ratio were generally lower in the flaxseed-fed rats when compared to the 0% flaxseed group, but a significant lowering occurred only in the 40% flaxseed group. The incorporation of flaxseed in the diet caused significant elevations in the levels of the α-linolenic acid in adipose tissue and in organs. Higher amounts of eicosapentaenoic, docosapentaenoic, and docosahexaenoic acids were observed in the heart and liver of flaxseed-fed rats when compared to the 0% flaxseed group. A significant lowering of tissue vitamin E levels and an elevation of urinary thiobarbituric reacting substances occurred only in the 40% flaxseed group, which suggested that low to moderate intakes of flaxseed did not impart an oxidative stress on rat tissues. Dietary fiber in flaxseed appeared to be largely fermentable and was associated with a large increase in fecal moisture. The phytate in flaxseed had no effect on zinc status. The oil in both the intact and the ground flaxseeds was found to be thermally and oxidatively stable.

Relationship between dietary fiber levels and protein digestibility in selected foods as determined in rats

Samples of 15 food products and feces obtained by feeding them to rats were analysed for dietary fiber fractions. The food products were added as the sole source of protein in 8% protein diets, making up 8.8–51.6% of the diets. Diets were supplemented with 0.54–5.00% purified cellulose to make them more comparable in total fiber. Fiber analyses of food products revealed that the protein sources provided 0.06–7.27% total dietary fiber. The true protein digestibility in rats was negatively correlated with the total food fiber level (r=−0.69,P<0.01) or with the food cellulose level (r=−0.82,P<0.01) but it was positively correlated (r=+0.81,P<0.01) with the purified cellulose level. No relationship was found between protein digestibility and fiber fermentability. Results indicate that several food fiber fractions and possibly associated substances influenced protein digestibility. Purified cellulose did not have the same physiological behavior as food cellulose from the viewpoint of protein digestibility and fiber fermentability.

Effect of dietary cereal brans on the metabolism of calcium, phosphorous and magnesium in a long term rat study

Abstract The effect of cereal brans on the mineral metabolism of rats was studied in a seven month long experiment. Seven groups (10 each) of male and female Sprague-Dawley weanling rats were fed ad lib for 7 weeks, diets containing cellulose, oat bran, hard red spring wheat bran, soft white wheat bran, corn bran and rodent lab chow at 4% or 14% total dietary fibre. In the seventh week (Phase 1) a mineral balance study was conducted on five randomly selected rats from each group. During week 8 these animals were killed and liver, heart, muscle and femur collected from each animal. The remaining animals were continued on the same diets for 21 more weeks. A second amineral balance study was carried out during week 24 (Phase 2) and the animals were killed during week 29 after colonic function tests during weeks 25–28. The diet, urine, feces and tissues were analysed for calcium, phosphorus, magnesium, phytate (in diet and feces only) and trace elements. Results on macro-mineral elements indicated that the fractional absorption of calcium, phosphorus and magnesium by male and female rats was not significantly different (P≤0.01). Absorption was affected by the level of the total mineral in the diet and not by the kind of fibre source. Variation in the digestibility of phytate was probably caused by the phytase activity in the bran rather than its phytate content. Digestibility during week 24 was less than during week 7 in most cases. The diets did not appreciably affect mineral levels in soft tissues and bone except the females in all purified diet groups showed severe nephrocalcinosis in both phases. Kidneys of males fed some diets showed mild calcification in phase 2. The absence of nephrocalcinosis in females fed the rat chow was associated with low levels of urinary phosphorus and also to the fluoride and high magnesium content of the chow.

Effects of dietary fiber on vitamin E status in rats: dose-response to wheat bran

The possible deleterious effects of wheat fiber on vitamin E status were investigated in rats fed semipurified diets supplemented with graded doses (4, 8, 12, 16 or 20%) of Hard Red Spring Wheat Bran, providing 2–10% fiber. After 42 days of experimental feeding, the levels of α-and λ-tocopherol were determined in plasma, liver, pancreas and white adipose tissue (WAT). Total lipids in plasma and total fat excreted in feces were measured. Levels of λ-tocopherol were 5–50 times lower than those of α-tocopherol. Increasing wheat fiber from 2 to 10% in the diet did not significantly decrease levels of vitamers in the four tissues examined. There was a trend towards lower plasma lipid levels with increased percentage fiber in diet. Total fat excretion in feces increased linearly (r2=0.61, P<0.01) between 4 and 10% fiber in diet. When compared to a fiber-free diet, some fiber diets induced lower levels (P<0.05) of α-tocopherol in plasma (4%) and liver (2–6, 10%), but normal diets are not devoid of fiber. It is concluded that addition of wheat fiber to a low or moderate fiber diet has no detrimental effect on vitamin E status in the rat, in spite of increased (+68%, P<0.01) fecal fat excretion

Dietary and Caloric Restriction: Its Effect on Cellular Proliferation in Selected Mouse Tissues

There is much experimental but very limited clinical evidence that dietary restriction has a beneficial effect in reducing the incidence of naturally occurring and induced cancer formation. Restriction has also been suggested to be advantageous in other respects (Weindruch et al. 1986), including increasing longevity and improving the effectiveness of certain aspects of the immune system. The effect of dietary and caloric restriction on experimental carcinogenesis has been recognized for many years, the sentinel observations being due to Tannenbaum (1940a, 1942; Tannenbaum and Silverstone 1957). Many others have confirmed Tannenbaum’s initial observations (Andreou and Morgan 1981; White 1961; Ross and Bras 1973; Klurfeld et al. 1987). Information on the possible advantageous effect of dietary restriction in humans has proved much more elusive. Although Tannenbaum (1940b) obtained some evidence for a correlation between excessive body weight and cancer from human insurance records, further information has not been adequate to demonstrate this conclusively. In fact, there is a major controversy whether mammary and colonic tumorigenesis in humans is dependent on the high lipid content of the North American diet or on excess calories [National Academy of Sciences (USA) 1980, 1982].

Calories, Fat, Fibers, and Cellular Proliferation in Swiss Webster Mice

Increased cellular proliferation has been associated with the enhanced expression of several key stages in carcinogenesis. A standard protocol was used to investigate the effect of specific dietary regimens on cellular proliferation. Young adult Swiss Webster mice were fed for 30 days with modified AIN-76A semi-purified diets designed to illustrate the effects of the levels of dietary or calorie restriction, different fibers and bulking agents, and different fats on cellular proliferation. Female mice were used for the restriction and fat studies, males for the fiber and bulking agent studies. Vaginal smears were taken from females from treatment day 15, and the mice killed 2 days following the first estrus following 30 days feeding; males were killed on the 30th day. One hour before death, mice were injected ip with 0.25 micro Ci/g 3[H]-thymidine. Slides were prepared for radioautography and histopathology. Both dietary and calorie restriction led to reduced 3[H]-thymidine labeling indices in each of the seven tissues studied, the mammary gland being the most severely affected. Different fibers and bulking agents, in specific cases, reduced labeling in the duodenum but not to a consistent statistically significant extent in the colon or colo-rectal region. In the duodenum, oat bran and oat gum were the most effective while wood cellulose (alphacel) had no effect. Investigations on the effects of different fats is continuing. High levels of lard, menhaden oil, or cod liver oil as the fat component of the AIN-76A diet, led to much higher levels of labeled cells in the mammary gland or colo-rectal region than did fat components rich in vegetable oils. The labeling indices appeared to be inversely correlated with the level of linoleic acid in the diet, a presumption that has been confirmed by investigating a series of diets containing different levels of this acid. Anti-oxidants were not used in any of these fat-modified diets. The overall results obtained in these studies clearly indicate the utility of cellular proliferation studies in investigating the effects of dietary modifications.