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Biomedical subjects

N D Nigro

Publications and source records attributed to N D Nigro.

At least 37 records · Page 2Linked to original sources
PubMed1983

Combined preoperative radiation and chemotherapy for squamous cell carcinoma of the anal canal.

Twenty-eight patients with squamous cell carcinoma of the anal canal were treated by preoperative radiation therapy and chemotherapy. The radiation therapy was given for 3000 rad (30 Gy) at 200 rad per day, 5 days a week, to the primary tumor with margin and to the pelvic and inguinal lymph nodes. Chemotherapy was given in the form of 5-fluorouracil infusion 1000 mg/m2 on days 1-4 of the radiation therapy and repeated on days 29-32 of the treatment regimen. Mitomycin C was given in the form of intravenous bolus for 15 mg/m2 on day 1. Surgery was done 4-6 weeks following the last day of radiation treatment. Twelve patients underwent anteroposterior resection, and seven of the 12 had no residual tumor in the surgical specimen, while one patient had microscopic tumor only. An additional 14 patients had complete clinical disappearance of their tumor, and, on excision of the scar, it was found free of microscopic cancer. Two other patients are clinically free of tumor but had no biopsy after therapy. While transient proctitis leukopenia and thrombocytopenia were moderate to severe, no serious complications were observed in these patients. Twenty-two patients are free of tumor and alive one to eight years after treatment. One patient died a cardiac death without tumor four years after surgery. Four patients, all with residual tumor in the specimen, have died of cancer. Their primary lesions were more than 7 cm in maximum diameter at initial examination. One patient died of disseminated disease with no local recurrence after abdominal perineal resection.

Adult↗
PubMed1983

Stimulation of deoxythymidine incorporation in the colon of rats treated intrarectally with bile acids and fats.

The incorporation of tritiated deoxythymidine ([3H]dThd) into colonic DNA of male Sprague-Dawley rats treated intrarectally (i.r.) with bile salts and other substances has been investigated. Instillation of sodium deoxycholate caused an increase in the incorporation of [3H]dThd which was maximal 12 h after treatment. The level of incorporation showed a steep linear dose response from 0.5 mM to 15 mM bile salt. Higher concentrations of deoxycholate up to 300 mM only slightly increased the extent of incorporation when compared to the lower concentration. Several other substances also increased the extent of [3H]dThd incorporation; these include: chenodeoxycholate, lithocholate, sodium dodecyl sulfate, dioctyl sulfosuccinate, corn oil, beef fat, and trioctanoin. Substances which had no effect on [3H]dThd incorporation include cholesterol, dehydrocholate, sodium acetate, dextrose, and mineral oil. Many of the agents which increase colonic [3H]dThd incorporation are also known to enhance colonic tumorigenesis. These findings indicate similarities between the short-term effects, in their respective target tissues, of colon tumor promoters, and classical mouse skin tumor promoters.

Animals↗
PubMed1982

Combined inhibitors of carcinogenesis: effect on azoxymethane-induced intestinal cancer in rats.

Outbred male Sprague-Dawley CD rats were fed a complete semisynthetic diet and were given supplemental low doses (2 ppm) of selenium as H2SeO3 in their drinking water or 50 mg 13-cis-retinoic acid (13-cis-RA) and 2 g beta-sitosterol/kg diet either singly, in combinations of two, or in combinations of all three. Intestinal tumors were induced with eight weekly sc injections of 8 mg azoxymethane (AOM)/kg body weight, and inhibition of tumor formation was determined by tumor counts after 26 weeks. Noncarcinogen controls for each dietary group received eight injections of sterile water. Tumor inhibition was statistically significant in 2 groups of animals: Dietary control animals had a tumor frequency of 5.07 tumors/rat, rats receiving selenium- plus 13-cis-RA supplementation had a tumor frequency of 3.77, and those being given the combination of all three inhibitors had 2.75 tumors/rat. Analysis of fecal steroids from 3 AOM groups (dietary controls, the beta-sitosterol plus 13-cis-RA-supplemented group, and the group receiving all three additives) after 4 months of supplementation showed that the addition of beta-sitosterol to the diet had no effect on acidic or neutral steroids, regardless of the observed difference in tumor frequency. These results suggest that subpharmacologic doses of inhibitors, particularly those that inhibit the process by different mechanisms, while ineffective alone, may provide significant inhibition of tumorigenesis when used in combination.

Animals↗
PubMed1981

Effect of selenium on azoxymethane-induced intestinal cancer in rats fed high fat diet.

The effects of selenium supplementation on azoxymethane-induced intestinal cancer were studied in male Sprague- Dawley rats given 8 weekly injections of azoxymethane (8 mg/kg body wt), and fed a 30% beef fat diet. Selenium-supplemented groups received 8 ppm H2SeO3 in drinking water. Blood selenium levels of supplemented rats increased rapidly the first 9 weeks of the experiment, followed by a plateau significantly higher than that for non-selenium controls. There was a significantly increase in liver and intestinal selenium levels in supplemented groups. The average number of intestinal tumors was 6.5 in the control group, and 3.1 in the selenium-supplemented group. There was a significant reduction in tumor incidence in the proximal half of the colon of selenium-treated rats. There was also increased concentration of tissue selenium in the proximal half of the colon of these rats.

Animals↗
PubMed1981

Animal studies implicating fat and fecal steroids in intestinal cancer.

There is epidemiological and experimental evidenced that the ingestion of excessive amounts of fat enhances intestinal cancer formation. This may be due to the interaction of luminal steroids with the bacterial flora in the colon, forming carcinogens or promoting agents. Increased fecal steroids induced by drugs, diet, or by mechanical means enhance intestinal tumor formation in rats given injections of azoxymethane. The effect appears to be promotional rather than initiative. Dietary fiber inhibits carcinogenesis only when the fat content of the diet is not excessive. Apparently, a quantitative relationship exists between these two dietary elements that further studies may define for prevention of cancer in humans.

Animals↗
PubMed1981

Effect of inhibitors of tumorigenesis on the formation of O6-methylguanine in the colon of 1,2-dimethylhydrazine-treated rats.

The level of O6-methylguanine (O6MeGua) in the colonic DNA of rats treated with 1,2-dimethylhydrazine was determined. The effect of various tumorigenesis inhibitors on the formation of this modified base was also studied. Rats were given a single s.c. injection of 1,2-[14C]dimethylhydrazine. Six hr later, they were killed, and colonic DNA was extracted and analyzed by high-pressure liquid chromatography. The inhibitors tested were disulfiram (DSF), pyrazole, sodium selenite, butylated hydroxyanisole, butylated hydroxytoluene, potassium ascorbate, and 13-cis-retinoic acid. The level of O6MeGua in control rats was 29.9 [(O6MeGua X 10(6)/guanine)]. When rats were fed 0.25% (w/w) DSF, this value was reduced to 10.2, and at 0.5% DSF there was no detectable O6MeGua formed. Injection of pyrazole (40 mg/kg i.p.) 2 hr prior to 1,2-dimethylhydrazine treatment reduced the O6MeGua level to 2.4. All the other tumorigenesis inhibitors had no effect on either O6MeGua levels or the cpm/mg DNA in treated rats. With O6MeGua as a measure of the extent of initiation, these results confirm that DSF and pyrazole inhibit the initiation phase of carcinogenesis. This is to be expected as both have been shown to block the metabolism of azoxymethane, which is a crucial metabolite in the activation of 1,2-dimethylhydrazine. The other substances, all known tumorigenesis inhibitors, may act on the promotional phase of carcinogenesis and are worthy of further study for the role in cancer prevention.

Animals↗
PubMed1979

Effect of dietary fiber on azoxymethane-induced intestinal carcinogenesis in rats.

The effect of alfalfa, bran, and cellulose on intestinal tumor formation and fecal billary steroid levels was studied in male Sprague-Dawley rats given injections of azoxymethane (AOM). Animals received weekly injections of 8 mg AOM/kg and were fed diets containing 10% fiber (wt/wt) and 35% beef fat or 20 or 30% fiber and about 6% beef fat. Control animals in each instance were fed fiber-free diets. The addition of 10% fiber to the high-fat diet did not significantly reduce the intestinal tumor frequency (average No. of tumors/rat). However, addition of 20 or 30% fiber to the 6% fat diet significantly reduced the intestinal tumor frequency. The concentration of fecal biliary steroids (mg/g dry feces) was significantly lowered in the groups with reduced tumor frequencies, whereas the total excretion of fecal biliary steroids (mg/day) did not show a similar correlation. These observations suggest that intestinal tumor frequency can be reduced by increased dietary fiber only when fat intake is not at a high level. The effect of fiber may be due to dilution of promoters and/or carcinogens in the intestinal tract.

Animals↗
PubMed1979

Promotion of azoxymethane-induced intestinal cancer by high-fat diet in rats.

Promotional properties of a high-fat diet in intestinal cancer were studied by feeding a 30% beef fat diet to 8 groups of rats (25 rats/group) for time periods varying from 1 to 21 weeks after 8 weekly s.c. injections of azoxymethane (AOM) (8 mg/ kg). Two other groups were fed the high-fat diet, one for 8 weeks prior to and the other during AOM injections. A 5% fat diet was fed to rats when not on the 30% fat diet and to a control group of 25 animals. High fat diet increased intestinal tumor frequency up to 2-fold when given for at least 4 weeks after but not during or prior to AOM injections; this increase occurred even after a prolonged interval (10 weeks) between the last AOM injection and the high-fat diet. In general, tumor frequency increased according to the length of time animals were fed the high-fat diet after AOM. Therefore, the high-fat diet in this model exhibited most of the properties of promoters developed from murine skin cancer, thus adding support to the concept that excess dietary fat acts at the promotional phase of carcinogenesis.

Animals↗
PubMed1978

Inhibition of azoxymethane-induced intestinal cancer by disulfiram.

Sprague--Dawley rats, both intact and colostomized animals, were given 24 weekly injections of azoxymethane. Rats were fed either Rat Purina Chow or the same diet plus 0.25% disulfiram. In the intact animals, disulfiram reduced tumors from an average of 6.3 to 0.95. The number of rats developing tumors was reduced from 100% to 60%. In colostomized animals, the reduction was from an average of 5.0 to 0.13. Marked inhibition occurred even in the defunctionalized colon. The results suggest that disulfiram blocks the metabolism of azoxymethane to methylazoxymethanol, and also that the inhibitor may act systemically.

Animals↗
PubMed1977

Effect of propylthiouracil on intestinal tumor formation by azoxymethane in rats.

Treatment with propylthiouracil (PTU) resulted in a significant decrease in azoxymethane-induced intestinal tumors, total concentration of fecal bile acids as well as the fecal neutral steroids, cholesterol and coprostanol. Thus, a hypothyroid state induced by PTU treatment may affect intestinal carcinogenesis in this animal model by lowering the concentration of fecal bile acids and neutral steroids.

Adenocarcinoma↗
PubMed1976

Effect of diet high in beef fat on the composition of fecal bile acids during intestinal carcinogenesis in the rat.

Two groups of 20 male Sprague-Dawley rats each were given sc 8 mg azoxymethane/kg body weight and fed a normal diet or one high in beef fat. Control groups were not given azoxymethane. Fat-control animals did not excrete more total bile acids than did the normal-control group but did excrete more deoxycholic acid as the result of increased cholic acid degradation. Azoxymethane itself caused an increase in fecal bile acid concentratation but tended to reduce the level of cholic acid degradation. Fatty acid content in the feces increased in the animals on the fat diet but was not affected by azoxymethane. A fat-diet-dependent increase was apparent in total fecal neutral steroids and a carcinogen-dependent increase in cholesterol degradation. Dietary fat and bile steroids altered by gut microflora were important interrelated factors in the intestinal carcinogenic process of this animal model.

Animals↗
PubMed1975

Effect of dietary beef fat on intestinal tumor formation by azoxymethane in rats.

Two groups of 20 male Sprague-Dawley rats each were given azoxymethane subcutaneously (8 mg/kg body wt) and fed a normal diet or one high in beef fat. Control groups were not given azoxymethane. The rats on the fat diet consumed less food and gained significantly more weight than the animals on the normal diet. Those given high fat and azoxymethane developed more intestinal tumors than did the dietary controls receiving the carcinogen. Furthermore, they had a greater number of larger tumors and more metastases than did the animals fed normally. No intestinal tumors were observed in control groups not receiving azoxymethane. The results show that the diet high in beef fat enhances the carcinogenic effect of azoxymethane in the rat.

Animals↗