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Biomedical subjects

K K Carroll

Publications and source records attributed to K K Carroll.

At least 109 records · Page 6Linked to original sources
PubMed1980

Lipids and carcinogenesis.

Experiments with animals and epidemiological data on human populations have provided evidence that high fat diets increase the incidence of certain types of cancer, such as breast cancer and colon cancer. High fat diets enhance mammary tumorigenesis in rats only when the fat contains a certain minimal level of essential fatty acids. Dietary fat appears to act as a promoter rather than affecting initiation of mammary tumors. It may do this by producing a more favorable environment for development and growth of tumor cells, either by changing the hormonal environment, by altering the properties of cell membranes thorugh changes in their lipid composition, or by other mechanisms, such as alterations in immune responses to tumor cells. The effect of dietary fat on colon cancer may be related to increased production and excretion of bile acids, some of which have been shown to be promoters of intestinal cancer in animals. It may be possible to utilize this knowledge of the effects of dietary fat on carcionogenesis to develop new methods for prevention and treatment of breast and colon cancer.

Carcinogens↗
PubMed1980

Effects of dietary protein on turnover, oxidation, and absorption of cholesterol, and on steroid excretion in rabbits.

Rabbits fed a low fat, cholesterol-free, semipurified diet containing casein became hypercholesterolemic (congruent to 300 mg/dl) after 5 weeks on diet. Rabbits on a similar diet containing soy protein isolate had low plasma cholesterols comparable to those on commercial feed (40--60 mg/dl). Cholesterol turnover, which conformed to a two-pool model, were determined by analysis of the decay of plasma cholesterol specific activity after a single intravenous injections of [26-14C]cholesterol. Rabbits on the soy protein diet or commercial feed showed a much faster rate of cholesterol turnover and a reduced size of pool A compared to rabbits on the casein diet. They also oxidized [26-14C]cholesterol to respiratory 14CO2 at much faster rates. Analysis of fecal steroid by gas--liquid chromatography indicated that bile acid and neutral steroid excretion was increased on the soy protein and commercial diets, relative to the casein diet. Cholesterol was absorbed to a greater extent on the casein diet. Addition of 15% (w/w) butter to the semipurified diets had little effect on the above parameters of cholesterol metabolism. Comparison of cholesterol turnover measured by kinetic analysis, combined sterol balance, or analysis of fecal steroids by gas--liquid chromatography, showed that all three methods gave similar results. Measurement of bile acid production by oxidation of [26-14C]cholesterol to respiratory 14CO2 also gave results comparable to those obtained by analysis of fecal bile acids.

Animals↗
PubMed1979

Plasma lipoprotein changes in suckling and weanling rabbits fed semipurified diets.

The distribution and composition of the plasma lipoproteins were studied in suckling rabbits and in rabbits either weaned to or fed as young adults cholesterol-free, semipurified diets containing protein of animal (casein) or plant (soy protein isolate) origin. The raised cholesterol levels of the suckling period resulted in an increase of very low density and intermediate density lipoproteins in a making similar to that seen in adult rabbits fed a high fat diet supplemented with cholesterol. Young rabbits fed the cholesterol-free, semipurified, diet containing casein also became hypercholesterolemic but, in this case, the increased cholesterol was found primarily in lipoproteins of intermediate density. Cholesterol levels remained low in those rabbits fed the soy protein isolate diet, and the lipoprotein distribution was somewhat similar to that of chow-fed animals. It appears that the raised cholesterol levels during the suckling period result in different lipoprotein patterns to those produced in young adult animals by a cholesterol-free, semipurified diet.

Aging↗
PubMed1979

Dietary polyunsaturated fat versus saturated fat in relation to mammary carcinogenesis.

High levels of dietary fat have been shown to promote the development of mammary tumors induced in rats by 7,12-dimethylbenz(alpha)anthracene, and polyunsaturated fats were found to be more effective than saturated fats. In further studies it was found that diets containing 3% sunflowerseed oil (polyunsaturated fat) and 17% beef tallow or coconut oil (saturated fats) enhance tumorigenesis as much as a diet containing 20% sunflowerseed oil. Rats on these diets developed at least twice as many tumors as those fed diets containing either 3% sunflowerseed oil or 20% of the saturated fats alone. These results are in accord with human epidemiological data which show that breast cancer mortality in different countries is positively correlated with total fat intake but not with intake of polyunsaturated fat. Total fat intake varies greatly in different countries, but most human diets probably contain levels of polyunsaturated fat at least equivalent to 3% sunflowerseed oil.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1979

Effects of dietary carbohydrate on cholesterol metabolism in rats and rabbits.

Semipurified diets produce a marked hypercholesterolemia in rabbits and tend to elevate the level of plasma cholesterol in rats. They also decrease rates of oxidation of [26-14C]cholesterol to respiratory 14CO2 and excretion of label in fecal lipid, compared with commercial feed. In both species, the hypercholesterolemia was prevented and the rate of oxidation of [26-14C]cholesterol increased by using unmodified potato starch as the carbohydrate component of the semipurified diets. Potato starch was poorly digested by rats but appeared to be well utilized by rabbits. A semipurifed diet containing cooked potato starch gave results in rats comparable to those obtained with diets containing other types of carbohydrate. Cooked potato starch produced diarrhea in rabbits, thus complicating interpretation of the results. When the diarrhea was treated with antibiotics, the results were similar to those obtained with other carbohydrates. Rats fed commercial diet which had been heated in an oven or autoclaved had higher plasma levels than those fed untreated commercial diet but no significant differences in rates of oxidation or excretion of cholesterol were observed.

Animals↗
PubMed1979

Influence of diet on plasma cholesterol concentrations in suckling and weanling rabbits.

Rabbits were weaned to different semipurified diets to determine which characteristics of the diet were required to maintain the hypercholesterolemia of the suckling period. Gradual weaning to a diet similar in fat, cholesterol, protein and carbohydrate content to rabbit milk maintained and enhanced the hypercholesterolemia. Reduction of the cholesterol content, and to some extent the fat content of this diet, decreased the plasma cholesterol level, but the type of dietary protein did not alter the results. After weaning, however, animals fed milk protein (casein) in the absence of dietary cholesterol became hypercholesterolemic, whereas those fed plant protein (soy protein isolate) remained normocholesterolemic.

Animal Population Groups↗
PubMed1979

Relationship between amount and type of dietary fat in promotion of mammary carcinogenesis induced by 7,12-dimethylbenz[a]anthracene.

Female Sprague-Dawley rats were fed semipurified diets containing various fats, either alone or in combination, to provide different amounts of dietary fat and linoleic acid. One week before commencing the diets, each rat received an intra-gastric dose of the carcinogen 7,12-dimethylbenz[a]anthracene. Rats fed diets containing mixtures of 3% sunflower seed oil and 17% of either tallow or coconut oil developed twice as many tumors as those fed 3% sunflower seed oil or 20% of either saturated fat alone. Tumor yields in the rats fed these mixed-fat diets were comparable to those in rats fed a 20% lard diet, which provided about the same amount of linoleic acid. No further increase in tumor yield was observed in rats fed a 20% sunflower seed oil diet that contained more than five times as much linoleic acid. These results show that a certain amount of polyunsaturated fat, as well as a high level of dietary fat, is required to promote mammary carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1978

Occurrence of dolichol in human tissues.

The concentration of dolichol has been determined in various human tissues obtained at autopsy. The highest levels ( 3000 microgram/g wet weight) were found in testes. Liver and several other endocrine tissues contained about 1000 microgram/g. Lower levels were present in other tissues examines. Only a small proportion of the total dolichol in human tissues was esterified to fatty acids.

Diterpenes↗
PubMed1978

The role of dietary protein in hypercholesterolemia and atherosclerosis.

Rabbits become hypercholesterolemic and develop atherosclerotic lesions when fed a cholesterol-free, semipurified diet. This provides a useful experimental model in which a moderate hypercholesterolemia can be maintained for long periods of time. The elevation of plasma cholesterol and development of atherosclerosis are dependent on the kind of protein in the diet and can be prevented by replacing casein with isolated soy protein. Feeding trials with enzymatic digests or mixtures of amino acids indicate that this difference is at least partly due to the differing amino acid composition of the two proteins. Rabbits on the soy protein diet showed higher rates of oxidation and turnover of cholesterol than those on the casein diet. Dietary protein has generally been considered to be of little significance in the etiology of atherosclerosis in humans, but evidence is accumulating which indicates that it can have a significant influence on human plasma cholesterol levels.

Animals↗
PubMed1978

Dietary fiber and cholesterol metabolism in rabbits and rats.

Rabbits fed semipurified diets have elevated plasma cholesterol levels, and they oxidize [26-14C]cholesterol to expired 14CO2 more slowly than rabbits on a natural ingredient diet. Addition of several different types of fibrous material to a semipurified diet failed to prevent the hypercholesterolemic response. Rats on semipurified diets also oxidized [26-14C]cholesterol more slowly and tended to have somewhat higher plasma cholesterol levels than rats on commercial feed. Cholesterol oxidation was not stimulated by addition of fibrous materials to the semipurified diet, but rats fed a semipurified diet containing raw potato starch oxidized cholesterol at a rate comparable to that of rats on commercial diet. Raw potato starch was poorly digested by the rats. Cooked potato starch was well digested and failed to stimulate the rate of oxidation of cholesterol. A semipurified diet containing raw potato starch did not produce a hypercholesterolemic response in rabbits, even though the raw starch was well digested.

Animal Feed↗
PubMed1978

Hypocholesterolemic effect of substituting soybean protein for animal protein in the diet of healthy young women.

The effect of dietary protein on the level of plasma cholesterol in young, healthy, normolipidemic women was investigated in two separate studies by feeding either a conventional diet containing mixed protein, or a plant protein diet in which the animal protein of the first diet was replaced by soy protein meat analogues and soy milk. The diets were similar with respect to carbohydrate, fat and sterol composition. The first study, lasting 73 days and involving six subjects, gave an indication that plasma cholesterol levels were lower on the plant protein diet. The second study, which incorporated a number of improvements based on experience, lasted 78 days and used a cross-over design involving two groups of five subjects each. In this study, the mean plasma cholesterol level was found to be significantly lower on the plant protein diet.

Adult↗
PubMed1977

Plasma cholesterol levels in suckling and weaned kittens, puppies, and guinea pigs.

Plasma cholesterol levels in kittens and puppies were low at birth, rose during the suckling period, and then decreased at about the time of weaning. The increase during the suckling period was much greater in puppies than in kittens. No significant differences in plasma cholesterol levels were observed in puppies fed two different types of diet, horse meat or dog chow, after weaning. Guinea pigs had lower plasma cholesterols than either kittens or puppies. The level was highest on the first day after birth, decreased during the next 3 wk, and then remained fairly constant after the animals were weaned.

Aging↗