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D Kritchevsky

Publications and source records attributed to D Kritchevsky.

At least 91 records · Page 5Linked to original sources
PubMed1989

An improved method for oxidation of chromium(III) oxide-containing fecal samples by using sodium peroxide fusion.

A safer method of oxidation of Cr2O3-containing fecal samples from transit-time studies was developed using sodium peroxide to replace perchloric acid as the oxidizing agent. The percentage recovery of Cr2O3 with this method was compared with that of perchloric acid method for samples containing quantities of fecal ash and Cr2O3 typical of those from rodent transit-time studies. Both methods gave relatively constant percentage recoveries for Cr2O3 contents from 0.4 to 10 mg. Over this range, mean (+/- SD) percentage recoveries of Cr2O3 for sodium peroxide fusion and the perchloric acid method were 75.5 +/- 4.3 and 89.9 +/- 2.5, respectively. As long as percentage recovery is constant, the transit time as determined by calculation of the time of 80% excretion of the total recovered Cr2O3 is not affected. Sodium peroxide fusion provides a useful and safer alternative to perchloric acid oxidation in transit-time studies using Cr2O3 as a nonabsorbable marker.

Animals↗
PubMed1989

A comparison of the digestion and absorption of cocoa butter and palm kernel oil and their effects on cholesterol absorption in rats.

Digestion and absorption of cocoa butter and palm kernel oil and their effect on cholesterol absorption were studied in adult male rats. Duodenal and thoracic duct catheters were inserted surgically into the anesthetized rats. After an overnight fast, animals were given a single duodenal dose of an aqueous emulsion containing [1,2-3H]cholesterol and one of the following: corn oil, cocoa butter or palm kernel oil. Digestion and absorption were estimated by recovering the total fatty acids in the thoracic duct lymph over a 24-h collection period (after subtraction of the baseline "endogenous fatty acids" in the lymph). Intestinal absorption of cholesterol into the thoracic duct lymph was reduced significantly (P less than 0.05) in the presence of cocoa butter, compared to absorption when palm kernel oil or corn oil was administered. Compared to the absorption of corn oil (arbitrarily defined as 100%), the absorption of palm kernel oil and cocoa butter was 82 and 63%, respectively. The present study suggests that palm kernel oil absorption was not significantly different from that of corn oil. The lower absorbability of cocoa butter and its inhibitory effect on cholesterol absorption may explain in part why cocoa butter is less hypercholesterolemic and atherogenic than other equally saturated fats.

Analysis of Variance↗
PubMed1989

Determination of degree of energy restriction necessary to reduce DMBA-induced mammary tumorigenesis in rats during the promotion phase.

This study was designed to determine the degree of energy restriction necessary to achieve significant inhibition of mammary tumor promotion in rats treated with 7,12-dimethylbenz[a]anthracene (DMBA). A control group of rats was fed a diet containing 5% corn oil ad libitum. Four other groups were pair-fed to the controls; these rats were subjected to energy restriction of 10, 20, 30, or 40%. Weight gains among the groups were proportional to energy intake. The differences in weight were due primarily to reductions in body fat stores. Tumor incidence was reduced slightly by 20% calorie restriction and significantly by 30 and 40% restriction. There were also reductions in number of tumors per tumor-bearing rat and in mean tumor weight. The groups subjected to 30 and 40% energy restriction had significantly reduced serum levels of insulin in the fasting state. These data suggest that body weight, body fat, and fasting serum insulin correlate with susceptibility to mammary tumor promotion and that insulin may be a growth factor for DMBA-induced tumors.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1988

Diet and colon cancer: assessment of risk by fiber type and food source.

How fiber in the diet is related to the development of colon cancer was assessed in a population-based study conducted on 231 cases and 391 controls in Utah between 1979 and 1983. Crude fiber consistently decreased risk associated with colon cancer in both males [odds ratio (OR) = 0.4] and females (OR = 0.5). Dietary fiber, as analyzed by the method of A. S. Bitner, and neutral detergent fiber were not consistently related to colon cancer risk. Of the noncellulose polysaccharides examined, mannose and galactose were protective against cancers in the ascending colon in males (ORs = 0.5 and 0.3, respectively), whereas galactose and uronic acid were protective against cancers in the ascending colon in females (ORs = 0.5). Highest quartiles of intake of fruits and vegetables were also associated with a decreased risk of colon cancer in males (ORs = 0.3 and 0.6, respectively) and in females (ORs = 0.6 and 0.3, respectively) compared with lowest quartile of intake, whereas high intake of grains was not protective.

Adult↗
PubMed1988

Diet and nutrition research.

The interest in nutrition and cancer, which was high in the 1940s and 1950s, was rekindled in the 1970s and is now more intense than ever. There has been considerable experimental work on dietary fat, but delineation of the precise role(s) of the essential fatty acids is still lacking. There have been few studies on protein or carbohydrate effects and only Visek has adequately addressed the important area of nutrient interactions. More work is needed in the fiber field with regard to the influences of short chain fatty acids, and the standardization of protocols is needed to make the various findings comparable. Currently, fiber data have been accrued using rats of different strains and gender, commercial and semipurified diets, a variety of colon carcinogens, and different routes of administration. The effects of energy restriction (in the literature since 1909) have not been widely studied as to mechanism and influence of energy expenditure (i.e., exercise) and merit more attention.

Diet↗
PubMed1988

Effects of dietary fiber in vervet monkeys fed "Western" diets.

Male Vervet monkeys (7/treatment) were fed a "Western" diet containing 46.2% calories as fat, 39.8% as carbohydrate and 14.0% as protein. The diet was augmented with 10% cellulose or 10% pectin. A third (control) group of seven monkeys was fed a commercial ration augmented with fruit and bread. After 34 weeks, serum cholesterol levels were elevated significantly in the two test groups compared with the controls but there was no difference between the two fiber-fed groups. Serum triglycerides were unaffected. Liver cholesterol levels were the same in all three groups but liver triglyceride levels were lower in the monkeys fed cellulose. Biliary lipids were similar in all three groups as were the calculated lithogenic indices. The average aortic sudanophilia (percent of total area) in the three groups was cellulose, 10.6 +/- 2.5; pectin, 8.1 +/- 2.5; and control, 1.1 +/- 0.4. One animal in each of the groups fed "Western" diet exhibited an atherosclerotic plaque. The results indicate that there is no difference between pectin and cellulose with regard to their effects on either lipidemia or aortic sudanophilia in Vervet monkeys fed a Western-type diet.

Animals↗
PubMed1988

Dietary fiber supplements: effects on serum and liver lipids and on liver phospholipid composition in rats.

Rats (6 per group) were fed semipurified diets containing either particulate fibers (alfalfa, 10%; cellulose, 10%; bran, 10%), a soluble ionic fiber (pectin 5%), soluble, nonionic fibers (guar gum, 5%; Metamucil, 10%), a mixed fiber preparation (Fibyrax, 10%, or an insoluble, ionic bile acid-binding resin (cholestyramine, 2%). The control group was fed the unsupplemented diet. The feeding period, during which diet and water were provided ad libitum, was 28 days. Compared with the control group, serum total cholesterol levels were increased by more than 10% in rats fed alfalfa and decreased by more than 10% in rats fed cellulose, guar gum, Fibyrax and cholestyramine. There were no significant differences in percentage of plasma HDL cholesterol. Serum triglycerides were elevated in the groups fed alfalfa, pectin, guar gum or Fibyrax and reduced in the group fed Metamucil. Plasma phospholipids were elevated in rats fed alfalfa or bran, unaffected in rats fed pectin or Metamucil and reduced in the other groups. Liver total cholesterol was elevated in all groups but those fed wheat bran and cholestyramine. The percentage of liver cholesterol present as ester was elevated in every group except that fed cholestyramine. Liver triglycerides were reduced in rats fed guar gum or Metamucil and elevated in those fed alfalfa. Liver phospholipids were lowered in the group fed cellulose. Liver phospholipids were fractionated by thin layer chromatography to give phosphatidylcholine (PC), phosphatidylethanolamine (PE), sphingomyelin (Sph), lysophosphatidylcholine (LPC) and phosphatidylinositol plus phosphatidylserine (PI + PS).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Low density lipoprotein kinetics in African Green monkeys showing variable cholesterolaemic responses to diets realistic for westernised people.

African Green (vervet) monkeys were fed either an atherogenic Western diet (WD), a prudent diet (PD), or a high carbohydrate diet (HCD) for various lengths of time. Monkeys differed greatly in their response to the WD, and a strong negative correlation was observed between the fractional catabolic rates (FCR) of low density lipoprotein (LDL) and the total plasma cholesterol concentrations (r = -0.83 P = 0.0029). Similarly the individual synthetic rates (SR) of LDL plotted against the total plasma cholesterol concentrations showed a correlation coefficient of r = 0.94 P = 0.01 for WD animals. There was no correlation for PD or HCD animals for either SR or FCR and the total plasma cholesterol concentrations. The aortic lesion scores correlated with the SRs (r = 0.66 P = 0.040) but not with the FCRs. LDL turnover was also studied using 125I-labelled native LDL and methylated 131I-labelled LDL in African Green monkeys showing high or low cholesterolaemic response to an atherogenic Western diet. Measurements after 4 weeks and again after 6 months on the diet showed a decrease in both total and non-receptor mediated clearance of LDL. Receptor-mediated catabolism was significantly lowered in the hyperresponding group (P = 0.0011) and not in the hyporesponding group with a resultant significant difference between the two groups being P = 0.0355 after 6 months. Non-receptor mediated catabolism of LDL was similarly affected in that there was no significant difference between the two groups at 4 weeks but the clearance of methylated LDL was markedly lowered at 6 months, for the hyporesponding group P = 0.0003 and for the hyperresponding group P = 0.0184. Furthermore the hyperresponding group was depressed to a significantly greater extent when compared to the hyporesponding group (P = 0.0241).

Animals↗
PubMed1988

Flordipine, a calcium channel blocker, which does not influence lipidemia or atherosclerosis in cholesterol-fed rabbits.

Data relating to the effects of calcium channel blockers on experimental atherosclerosis in rabbits are inconsistent with most studies finding no effect on either serum lipids or atherosclerosis. We have administered flordipine (5, 15 or 45 mg/kg/day) for 10 weeks to rabbits fed 1% cholesterol and 4% corn oil. At no level of treatment was there an effect on serum or liver lipids or on aortic sudanophilia.

Animals↗
PubMed1988

Dietary fiber and intestinal adaptation: effects on lipid absorption and lymphatic transport in the rat.

Adult male rats fed defined diets containing various fiber supplements or cholestyramine for 4 wk were surgically provided with lymphatic drainage catheters and starved overnight. After duodenal administration of a standard lipid test emulsion, absorption rates and lipoprotein distributions of cholesterol and oleic acid were determined. Prefeeding diets containing cellulose or alfalfa had no significant effect on oleic acid absorption. Diets containing pectin, guar gum, metamucil, mixed fibers (Fibyrax), or cholestyramine caused decreased lymphatic recovery in the initial period; except for the metamucil diet, no decrease was caused in the 24-h recovery, suggesting delayed but not impaired absorption. Fatty acid distribution among lipoproteins and chylomicron size were not altered by diet. All supplements caused a significant reduction in cholesterol absorption during the initial period, and cholesterol absorption remained depressed in animals prefed pectin, guar gum, mixed fibers, metamucil, and cholestyramine.

Animals↗
PubMed1988

Diet and cancer.

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Diet↗
PubMed1988

Dietary fiber.

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Dietary Fiber↗
PubMed1988

Cholesterol vehicle in experimental atherosclerosis. A brief review with special reference to peanut oil.

In general, the level of unsaturation of a fat determines its effect on plasma cholesterol level-the level being lower with more unsaturated fat. However, some exceptions do exist. One such exception is cocoa butter, which is not as cholesterolemic or atherogenic for rabbits as would be expected from its level of saturation. The reason for this anomaly is believed to be the high level of stearic acid present in cocoa butter. Peanut oil is also anaomalous, being unexpectedly atherogenic for monkeys, rabbits, and rats. Randomization of peanut oil reduces its atherogenicity, suggesting that the structure of the triglyceride comprising peanut oil may affect its atherogenic potential. Another possibility is that a lectin present in peanut oil may be responsible for its atherogenic capacity.

Animals↗
PubMed1988

Influence of soy protein or casein on pre-established atherosclerosis in rabbits.

Atherosclerosis was established in rabbits by feeding 1% cholesterol and 4% corn oil for two months. The rabbits were placed into five groups of equal average cholesterol level (2876 mg/dl) one of which was autopsied. The four remaining groups were placed on commercial ration (CR), CR plus 4% corn oil, or semipurified diets containing 14% coconut oil and 25% soy protein or casein. After two months, serum cholesterol levels in CR, CR plus corn oil, soy and casein groups had fallen by 91, 80, 81, and 64%, respectively. Aortic sudanophilia (%) in these four groups had increased by 106, 213, 238, and 25%, respectively. The findings confirm earlier observations that rabbit atherosclerosis does not regress when the atherogenic stimulus is removed.

Animals↗
PubMed1987

Biochemical alterations in 7,12-dimethylbenz[a]anthracene-induced mammary tumors from rats subjected to caloric restriction.

Caloric restriction reduces the incidence and progression of a broad spectrum of neoplastic diseases, yet little is known about the biochemical and molecular mechanisms involved. Profiles of enzyme activities of importance in cellular energy utilization were examined in 7,12-dimethylbenz[a]anthracene-induced (DMBA) mammary adenocarcinomas from rats fed ad libitum or calorically restricted diets. The diets provided equal nutrients except for fewer carbohydrate-derived calories; graded caloric restriction was 10, 20, 30 and 40%. The specific activities of hexokinase, pyruvate kinase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase, malic enzyme and fructose-1,6-bisphosphatase were all elevated to varying degrees in both large palpable and small, non-palpable tumors from calorically restricted hosts compared to activities in tumors from ad libitum-fed rats. Phosphofructokinase activity was increased in palpable tumors from calorically restricted hosts but markedly reduced in non-palpable tumors. These results suggest adaptive or compensatory alterations in tumor enzyme profiles in response to the altered nutritional state of the host.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1987

Inhibition of chemically induced mammary and colon tumor promotion by caloric restriction in rats fed increased dietary fat.

Tumor promotion associated with increased dietary fat may be inhibited by reduction in total caloric intake. This hypothesis was tested in rats given either 7,12-dimethylbenz(a)anthracene to induce mammary tumors or 1,2-dimethylhydrazine to induce colon tumors. One week after dosage with either carcinogen, the rats were fed semipurified diets that provided 4% fat with ad libitum calories or 13.1% fat with a reduction of calories by 40% from ad libitum intake. Rats treated with 7,12-dimethylbenz(a)anthracene and subjected to caloric restriction weighed 40% less than those fed ad libitum; rats treated with 1,2-dimethylhydrazine were heavier at the onset of caloric restriction and lost weight and weighed approximately 40% less than animals fed ad libitum. At 20 weeks after 7,12-dimethylbenz(a)anthracene administration, rats fed ad libitum had 80% tumor incidence while in those fed restricted calories, 20% had tumors (P less than 0.001). All other measures of mammary tumor growth were significantly reduced in rats given restricted calories. Six months after 1,2-dimethylhydrazine administration, colon tumor incidence was 100% in rats fed ad libitum and 53% in those fed the calorie-restricted diet (P less than 0.001). This reduction of colonic carcinogenesis was seen despite a significant increase in mucosal labeling index following [3H]thymidine autoradiography. This paradoxical finding may be due to the increased fat content of the calorie-restricted diet. These data demonstrate that the tumor-promoting effects of dietary fat can be more than offset by a reduction in total caloric intake and that the promoting effect of fat may be due, at least in part, to its greater caloric density.

Animals↗