摘要:

AbstractThe effect of dietary cholesterol on the development of colonic preneoplastic aberrant crypts, as well as its influence on the proliferative status of the intestinal epithelium, was investigated in mice exposed to the chemical carcinogen azoxymethane. Two strains of mice, CS7BL/6J and BALB/cJ, were fed a semisynthetic diet containing 0% (control), 1.25%, or 5.00% cholesterol for eight weeks. During the first four weeks of the experiment, mice were given weekly injections of azoxymethane. Cholesterol supplementation significantly increased the formation of aberrant crypts (p<0.0001), enhanced the rate of cell proliferation (p<0.0001), altered the cell proliferative pattern, and increased crypt height (p<0.05) and the total number of cells per crypt (p<0.01) in the colonic epithelium of both mouse strains. C57BL/6J mice developed a greater number of aberrant crypts (p<0.0001). However, a diet‐strain interaction was not observed. The results of this study indicate that dietary cholesterol enhances colon carcinogenesis in the murine colon and therefore may be an important factor in the etiology of large bowel cancer in humans.

ISSN:0163-5581    

DOI:10.1080/01635589209514178

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

AbstractThe effects of combined dietary vitamin E supplementation and a relatively low increase in selenium levels on 7,12‐dimethylbenz[a]anthracene (DMBA) induction of lipid peroxidation in the short term and development of mammary tumors in the long term were investigated in female Sprague‐Dawley rats. Control animals were fed the basal diet (20 mg/kg vitamin E and 0.6 mg/kg selenium) throughout the experiment. Three other groups received a high vitamin E diet (235 mg/kg vitamin E and 0.6 mg/kg selenium) at different times, the first two from three weeks after DMBA treatment and the other throughout the experiment. When the vitamin E diet with selenium supplementation was applied until three weeks after DMBA or until the termination of the experiment, tumor yields (tumors per rat) were significantly inhibited compared with the control group. On the other hand, delaying the supplementation of vitamin E until three weeks postcarcinogen produced no prophylactic effect. The elevation of lipid peroxidation levels observed immediately after DMBA administration was also significantly inhibited in both mammary fat pads and livers of animals in the high vitamin E group. It was therefore concluded that the inhibitory effect of vitamin E in combination with selenium on tumorigenesis might be causally related to reduction of carcinogen treatment associated with lipid peroxidation, the latter presumably playing an important role in DMBA‐induced mammary carcinogenesis.

ISSN:0163-5581    

DOI:10.1080/01635589209514179

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

AbstractThis study was conducted to determine whether oral and/or topical selenium (Se) supplementation can reduce the incidence of acute and/or chronic damage to the skin (i.e., sunburn and pigmentation and/or skin cancer, respectively) induced by ultraviolet (UV) irradiation in mice. Groups of 38 BALB:c female mice or 16 Skh:2 hairless pigmented mice were treated with 1) lotion vehicle, 2) 0.02% L‐selenomethionine (SeMet) lotion, or 3) vehicle and 1.5 ppm SeMet in the drinking water. Within each group, 30 BALB:c mice or 12 Skh:2 mice were given UV irradiation (Westinghouse FS 40 bulbs) three times per week in doses of 0.575 and 0.24 J/cm2, respectively. The animals’weights and food intakes and the Se concentrations of skin and liver were measured. Skin biopsies were taken from the backs and abdomens of all animals to evaluate the relative amounts of Se and the damage by UV irradiation. Skin pigmentation was scored, and the total number of clinically detectable skin tumors per animal was counted weekly. Results showed that the skin Se concentrations in areas of application of the lotion containing SeMet were greater than those of animals given comparable oral doses, while the Se concentrations of untreated skin and liver were similar to those of animals receiving oral Se. Mice treated with Se showed no signs of toxicity and had significantly less skin damage by UV irradiation, as indicated by reduced inflammation and pigmentation and by later onset and lesser incidence of skin cancer.

ISSN:0163-5581    

DOI:10.1080/01635589209514180

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

AbstractWe studied to what extent dietary fiber may affect uptake, retention, and excretion of a food carcinogen (2‐amino‐3,8‐dimethylimidazo[4,5‐f]quinoxaline, MeIQx) occurring in fried meat. Four diets—one fiber‐free control and three containing either insoluble dietary fiber isolated from sorghum (100 g/kg) and wheat bran (100 g/kg) or the highly soluble pectin (50 g/kg)—were investigated. The fiber diets were given in amounts of 10 g/day to rats. Thus, each rat received 1 or 0.5 g fiber and 100μg 2‐14C‐labeled MeIQx uniformly mixed in its daily diet. A 4‐day adaptation period with unlabeled MeIQx was followed by a 5‐day experimental period with14C‐labeled MeIQx, during which urine and feces were collected separately for analysis of radioactivity and mutagenicity. Furthermore the composition and the ferment‐ability of the dietary fiber were determined. The present study shows that a diet containing fiber, especially fiber isolated from sorghum and wheat bran, affects the excretion pattern of the food carcinogen MeIQx in a manner suggesting a lower uptake and a decreased transit time through the gastrointestinal tract in a more diluted form than a nonflber diet. Furthermore, less radioactivity was retained in the kidneys with sorghum and wheat bran than with the other two diets. On the other hand, none of these types of dietary fiber affected the retention of the hepatocarcinogen MeIQx in the liver 24 hours after the last oral intake. DNA adducts were formed to a higher extent in the kidney than in the liver. The highest levels were found in animals given the wheat bran diet.

ISSN:0163-5581    

DOI:10.1080/01635589209514181

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

AbstractThe cancer protective effects of flaxseed suggested by our previous short‐term study were tested in a long‐term tumorigenesis experiment. Feeding rats 5% flaxseed flour supplemented in a high‐fat diet at the promotional stage of tumorigenesis, i.e., after 7,12‐dimethyl‐benz[a]anthracene administration, significantly reduced by 66.7% the size of the tumors that occurred. Although flaxseed feeding at the initiation stage also tended to reduce the number of tumors per tumor‐bearing animal, significant differences were seen only between the group fed flaxseed throughout the experiment and the promotional group. Therefore the effect of flaxseed on mammary tumorigenesis is not consistent. Although it was speculated that the effect may be related to the lignans enterolactone and enterodiol produced in such large quantities on the ingestion of flaxseed, further studies are required to clarify the role of lignans and other flaxseed constituents in mammary tumorigenesis.

ISSN:0163-5581    

DOI:10.1080/01635589209514182

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

AbstractStrain CD‐1 female mice exposed prenatally to diethylstilbestrol (DES) or vehicle were placed on semipurified diets containing 2.6%, 10%, 20%, or 29% fat by weight at four weeks of age. These mice were used as a breeding colony for a few weeks and then maintained to terminal illness on the semipurified diets. Females exposed prenatally to DES developed mammary tumors, pituitary tumors, and glandular tumors of the reproductive tract. There was no significant difference in tumor frequency between low‐and high‐fat dietary groups. Fewer tumors appeared in the vehicle‐exposed mice, as expected, and their frequency did not differ between the dietary groups. Pregnancy reduced tumor frequency in DES‐exposed mice, but the incidence of pregnancy was not significantly different between low‐and high‐fat dietary groups. In the adult the failure of a high‐fat diet to increase the frequency of reproductive system tumors induced prenatally is in marked contrast to the effectiveness of high‐fat diets in promoting mammary tumors induced by carcinogens given to rats postna‐tally. This difference is critical in the interpretation of epidemiological studies. The relationship of dietary fat to reproductive system cancer in human populations was reviewed in comparison with these two animal models. The epidemiological literature was found to be more consistent with the animal model, showing high sensitivity to dietary fat prenatally but no significant sensitivity at the adult stage of life.

ISSN:0163-5581    

DOI:10.1080/01635589209514183

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

AbstractThe effect of ethanol on the initiation of diethylnitrosamine‐(DEN) induced liver carcinogenesis was investigated in rats. In the first experiment, eight‐week‐old male Wistar rats were maintained on four liquid diets: a basal diet (Group 1), a low‐carbohydrate (low‐CHO) diet (Group 2), a basal diet + ethanol (Group 3), or a low‐CHO diet + ethanol (Group 4). After three weeks on these diets, 50 mg/kg of DEN was injected intraperitoneally. The plasma glutamic‐oxaloacetic transaminase activity in Group 4 was higher 24 hours after DEN administration than in Groups 1 and 3. The plasma glutamic‐pyruvic transaminase activity in Groups 3 and 4 was higher than in Groups 1 and 2. The number ofγ‐glutamyltranspeptidase‐positive foci per unit liver area 41 weeks after DEN administration was higher in Group 4 than in Group 1. The area ofγ‐glutamyltranspeptidase‐positive foci was greater in Groups 2 and 4 than in Group 1.In the second experiment, Groups 1 and 4 were given DEN orally (25 or 75 mg/kg). Plasma glutamic‐oxaloacetic transaminase and glutamic‐pyruvic transaminase activities 24 hours after DEN administration were significantly higher in Group 4 than in Group 1, but only when the dose of DEN was 75 mg/kg. In contrast, the number and area of placental glutathione S‐transferase‐positive foci per unit liver area were greater in Group 4 than in Group 1 only after 25 mg/kg of DEN. Thus the severity of hepatotoxicity and the incidence of precancerous liver lesions were not necessarily correlated. These findings together indicate that a combination of ethanol and a low‐CHO diet enhances DEN‐induced liver carcinogenesis in rats by increasing the bioactivation of DEN in the liver.

ISSN:0163-5581    

DOI:10.1080/01635589209514184

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

AbstractAmerican Indian women in the Southwest have high rates of cervical cancer and cervical dysplasia in contrast to low rates of cancers for other sites. Despite their high rates of cervical disease, no published information has specifically examined risk factors for cervical cancer or cervical dysplasia among American Indian women. We carried out a pilot case‐control study of cervical dysplasia in southwestern American Indian women to examine the relationship of dietary intake of vitamin C, folacin, vitamin E, carotenoids, and retinol with cervical cytological abnormalities. Twenty‐four‐hour dietary recalls were collected from women with cervical dysplasia (n = 42) and women with normal cervical cytologies (n = 58). Macro‐and micronutrient intake was estimated from these recalls utilizing food and nutrient data from the USDA Survey Nutrient Database. Although mean differences between cases and controls were not statistically significant for any of the micronutrients examined, women with low intake of vitamin C, folacin, and vitamin E were at increased risk of having cervical dysplasia when the data were analyzed as stratified for level of intake (low vs. high intake odds ratios were 3.0 for vitamin C, 3.3 for folacin, and 1.7 for vitamin E). The relationship between dietary micronutrients and cervical dysplasia among American Indian women warrants further investigation using more refined measures of dietary micronutrient intake, together with consideration of other risk factors for cervical disease.

ISSN:0163-5581    

DOI:10.1080/01635589209514185

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

AbstractThere is evidence that highly unsaturated omega‐3 fatty acids present in fish oils can provide a cancer‐protective effect; however, when added to laboratory rodent formulations, these fatty acids are subject to rapid and/or extensive oxidation and other chemical changes by exposure to air, light, or heat during processing of pellets or when stored for various lengths of time. An animal diet with 16% refined fish oil and 4% corn oil was commercially prepared with antioxidants (butylated hydroxytoluene and butylated hydroxyquinone in addition toα‐tocopherol) present, and precautions were taken to prevent oxidation at all stages of production and handling. Fatty acid composition of dried powdered diet as well as freshly processed dried pellets was analyzed from four lots at the beginning and end of a 45‐day feeding period. Additionally, fatty acid analyses were carried out on pellets dried by both vacuum and air techniques, and pellets were left exposed to air at room temperature for 96 hours. No statistical difference in overall fatty acid composition was observed among lots due to pelletization or drying procedures. Moreover, 4 days of exposure of pellets to air at ambient temperatures and 45 days of freezer storage had no significant effect on their fatty acid composition. It would appear that rodent diets containing omega‐3 fatty acids can be reliably prepared commercially and safely substituted for diets prepared manually and in bulk on a weekly basis.

ISSN:0163-5581    

DOI:10.1080/01635589209514186

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

AbstractWe measured total serum copper and ceruloplasmin levels in pre‐and postmenopausal Stage I and II breast cancer (BC) patients and omnivorous and vegetarian controls. The omnivorous groups included 14 premenopausal women [33±6 (SD) yrs] and 11 postmenopausal women (57±5 yrs), and the vegetarian groups were comprised of 12 premenopausal subjects (34±7 yrs) and 11 postmenopausal subjects (59±5 yrs). There were 13 premenopausal BC patients (39±7 yrs) and 10 postmenopausal BC patients (66±6 yrs). Fasting serum samples were taken on three consecutive days, typically four times in the year. Serum ceruloplasmin levels (g/l) were measured by nephelometry utilizing monoclonal antiserum, and total serum copper levels (μmol/1) were determined by proton‐induced X‐ray emission analysis. Premenopausal patients had higher serum copper levels than their controls (mean 18.7 vs. 16.6, p<0.03). For ceruloplasmin, the postmenopausal BC patients had significantly lower levels than pooled postmenopausal controls (0.309 vs. 0.370, p<0.001). The copper‐to‐ceruloplasmin ratio was significantly higher in the pooled cancer groups than in the pooled control groups (3.69 vs. 3.21, p<0.001), with similar patterns in both pre‐and postmenopausal classes. This high serum copper‐to‐ceruloplasmin ratio in BC patients may reflect disordered copper metabolism in this disease, which could also have implications for the origin of, or the response to, the cancer process.

ISSN:0163-5581    

DOI:10.1080/01635589209514187

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor