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 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The aim of the experiment was to study the effect of three specialized food rations on activity of superoxide dismutase (SOD) in tissues of rats with transplanted Walker's carcinosarcoma 256 exposed to carminomycin. It was shown that the three specialized rations were able to significantly modify the SOD activity in the tissues of the rats with Walker's carcinosarcoma 256 at the background of treatment with carminomycin. Thus, the ration enriched with copper and zinc salts and folic acid activated SOD in the animals of all the groups. Still, the effect was higher in the tumor-bearing animals and the rats treated with carminomycin i.e. under conditions of oxidative stress. The use of the ration enriched with sulfur-containing amino acids, sodium selenide and vitamin E led to decreasing of the efficiency of the fermentative dismutation of O2 in the healthy rats and marked activating of SOD in the tumor-bearing animals. The ration containing lyophilized vegetables and vitamin E provided a significant increase in the SOD activity in the healthy rats. However, its potential was not sufficient for overcoming the SOD inhibiting effect of the tumor growth.
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PMID:[Alimentary methods of maintaining the superoxide dismutase activity in the tissues of rats during growth of a transplanted tumor and administration of carminomycin]. 195 87

Although the pathogenesis of asbestos-induced pulmonary damage is still not completely understood, an important role has been attributed to active oxygen species. In the present paper we present results of a study investigating the effect of crocidolite asbestos inhalation on different lung antioxidant enzymes in rats. During the development of pulmonary fibrosis induced by crocidolite asbestos, lung superoxide dismutase, catalase and selenium-dependent glutathione peroxidase activities increased, indicating an adaptive response to increased pulmonary oxidant stress. However, this adaptive response obviously is not sufficient to protect the lung from asbestos-induced pulmonary damage. Considering the role of active oxygen species in both the fibrotic process and tumor promotion, it is hypothesized that antioxidants may also protect the lung from chronic asbestos-induced pulmonary damage such as bronchogenic carcinoma.
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PMID:Increases in endogenous antioxidant enzymes during asbestos inhalation in rats. 196 19

The presence of androgen receptor (AR) in prostate cancer has been linked to the androgen-dependent nature of the tumor and has also been shown to have prognostic significance; it also appears to be a positive prognostic indicator in breast cancer. However, due to the relatively low AR concentrations in most tumors and the inherently low specific activity of tritium, the assay of AR based on available 3H-ligands is not sensitive enough to measure accurately the amount of receptor in small specimens. A 125I-ligand like those available for the estrogen and progesterone receptors would be helpful, but development of such a ligand for AR has not been very successful. Although several androgen analogues containing iodine, bromine, or selenium have been synthesized specifically as potential probes for AR, none have shown any significant affinity or specificity for the receptor. We therefore undertook the synthesis of new potential AR ligands which could be radioiodinated, and determined their affinities for AR (from rat uterus and MCF-7 human breast cancer cells) by using a competition assay. We have examined both 5 alpha-dihydrotestosterone (5 alpha-DHT) and 19-nortestosterone analogues and have identified two such compounds which showed high AR affinity: (17 alpha,20E)-17 beta-hydroxy-21-iodo-5 alpha-pregn-20-en-3-one (17 alpha-[E)-iodovinyl)-5 alpha-DHT, 9) and 17 beta-hydroxy-7 alpha-methyl-(17 alpha,20E)-21-iodo-19-norpregna-4,20-dien-3- one (7 alpha-methyl-17 alpha-[E)-iodovinyl)-19-nortestosterone, 11). In fact, the affinity of the latter for human AR was found to be superior to that of 5 alpha-DHT itself. These iodovinyl analogues could be easily prepared in the radioiodinated form, and should prove to be extremely useful in assaying low levels of AR in small specimens.
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PMID:A potential radioiodinated ligand for androgen receptor: 7 alpha-methyl-17 alpha-(2'-(E)-iodovinyl)-19-nortestosterone. 200 46

Cancer transformation of normal cells has been shown to be a multistep procedure, where a primary change is initiated by endogenous or exogenous alteration in nuclear DNA. Further activation of oncogenes or deletion of tumor suppressor genes is then required to transform the normal cell to a proliferating cancer cell. This process requires many years in humans. Epidemiological evidence and case-control studies have pointed to substances with a potential as cancer chemopreventative. Basic science has elucidated possible mechanisms on initiation and promotion of carcinogenesis behind the chemopreventive action of retinoids, other vitamins and selenium. These substances are presently being investigated in intervention studies to prevent cancer in high risk groups and the general population.
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PMID:[Chemoprevention of cancer. Epidemiology and basic research point to new directions]. 202 41

Tumor cell resistance to anthracyclines has been associated with increased activity against free radicals. Here, we have investigated the direct effect of doxorubicin (DOX) in the modulation of glutathione level and antioxidant activities in DOX-sensitive and-resistant cells (288 fold). The glutathione level in untreated cells was 88% greater in resistant than in sensitive cells. The activities of the superoxide dismutase, glutathione -S-transferase and glutathione reductase were respectively 24, 15 and 38% higher in resistant cells than in their sensitive counterparts. In contrast, catalase and total glutathione peroxidase were reduced in resistant cells by 18 and 21% respectively. Moreover, the activity of selenium-dependent glutathione peroxidase was lowered by 47% in the resistant as compared to the sensitive cells. Exposure of sensitive or resistant cells to low doses of DOX did not affect these levels in either cell variant. It is concluded therefore that resistance to anthracyclines may not always be associated with an elevated level of intracellular antioxidant activity enzymes.
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PMID:Modulation of the antioxidant activities in dox-sensitive and -resistant Friend leukemia cells. Effect of doxorubicin. 206 48

The anticarcinogenic activity of selenium in animal models is well established. The active forms of selenium involved have not been identified to date, but conversion of selenium via hydrogen selenide (H2Se) to methylated forms such as dimethylselenide and trimethylselenonium ion is an important metabolic fate. By controlling the entry of selenium into various points within this pathway through selection of appropriate starting compounds, it is possible to pinpoint more closely the form(s) of selenium responsible for its anticarcinogenic activity. Selenobetaine in the chloride form [(CH3)2Se+CH2COOH] and its methyl ester are extensively metabolized in the rat to mono-, di-, and trimethylated selenides, largely bypassing the inorganic H2Se intermediary pool. The chemopreventive efficacy of these selenobetaines was determined at 1 and 2 ppm selenium supplemented in the diet throughout the duration of the experiment using the dimethylbenz(a)anthracene induced mammary tumor model in rats. There was a dose-dependent inhibitory response to both compounds, and they appeared to be slightly more active than selenite. These doses were without any adverse effects on the animals. Coadministration of selenobetaine with arsenite (5 ppm arsenic) enhanced the tumor-suppressive effect of selenobetaine, although arsenic by itself was totally inactive. Arsenite is known to inhibit certain steps in selenium methylation. The substantial prophylactic efficacy of methylated selenides and the enhancement by arsenite suggest that partially methylated forms of selenium may be directly involved in the anticarcinogenic action of selenium.
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PMID:Activity of methylated forms of selenium in cancer prevention. 210 64

Selenium (Se) is an essential nutritional factor with a chemopreventive potential. This study examined the ability of C57BL/6J mice, maintained for 8 weeks on Se-deficient (0.02 ppm Se), normal (0.20 ppm Se), or Se-supplemented (2.00 ppm Se) Torula yeast-based diets, to generate cytotoxic lymphocytes (CTL) and to destroy tumor cells. CTL were generated in vivo by intraperitoneal immunization with P815 cells and in vitro by allogeneic stimulation of cells from animals maintained on a normal diet in media supplemented with 1 x 10(-9) to 1 x 10(-6) M Se (as selenite). Lymphocytes from animals maintained on the Se-supplemented diet had a greater ability to destroy tumor cells than lymphocytes from animals maintained on the normal diet, whereas Se deficiency reduced the cytotoxicity. The effects on cytotoxicity were accompanied by parallel changes in the levels of lymphotoxin produced. The greatest enhancement of tumor cytodestruction occurred with supplementation of 1 x 10(-7) M Se, whereas with 1 x 10(-6) M there was inhibition of the cytotoxic responses. The stimulatory effect of Se occurred during the phase of CTL generation rather than during the lytic phase of cytotoxicity. These results indicated that Se supplementation enhances CTL generation and the ability of a host to destroy malignant cells, whereas Se deficiency has the opposite effect.
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PMID:Selenium and immune cell functions. II. Effect on lymphocyte-mediated cytotoxicity. 210 6

The study was conducted to determine the effect of four forms of selenium on inhibition of DMBA-induced mammary tumors. BALB/c virgin female mice were fed the AIN-76 diet containing 0.2 or 2.0 ppm Se as selenite, selenate, selenomethionine, or selenocystine prior to and for 6 months post DMBA-treatment. At necropsy, mammary glands were histologically treated for confirmation of adenocarcinomas and the livers were removed for analysis of glutathione-peroxidase (GSHPx) activity and selenium concentrations. Dietary levels or forms of selenium had no effect on body weights. Inorganic selenium fed at 2.0 ppm Se (selenite and selenate) decreased mammary tumor incidence, but organic selenium (selenomethionine and selenocystine) had no effect on mammary tumor incidence. Hepatic GSHPx activity was highest with the 2.0 ppm selenium as selenocystine diet, but hepatic selenium levels were highest with the 2.0 ppm selenium as selenite. This study showed that the dietary form of selenium affects inhibition of mammary tumorigenesis. Furthermore, the study suggested that the pathways for selenium incorporation into GSHPx and for tumor inhibition are different.
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PMID:The effect of four chemical forms of selenium on mammary tumor incidence in BALB/c female mice treated with 7-12-dimethylbenz[a]anthracene. 210 2

The effects of selenium (Na2SeO3) on aflatoxin B1 (AFB1)-induced hepatic neoplasia were studied in the rat. Putative preneoplastic foci and nodules composed of basophilic, eosinophilic, and clear cells developed early. Basophilic foci were seen first; in the later stages basophilic and eosinophilic nodules predominated. At each stage the AFB1 + Se groups showed fewer and smaller foci and nodules than the AFB1 - Se group. The number of foci in the AFB1 + 3 ppm Se group and their mean area were smaller than those in the 6 ppm Se + AFB1 group. At the end of the experiment hepatocellular carcinoma (HCC) was found in 11/18 rats (61%) of the AFB1 - Se group. HCC was not found in either of the groups given AFB1 + Se. We conclude that Se had an inhibitory effect on the initiation and promotion stages of AFB1-induced preneoplastic foci and nodules. Se also prevented progression of these nodules to HCC even after cessation of AFB1 administration. The inhibitory effect of Se at 3 ppm was greater than at 6 ppm. The 6 ppm Se group also showed evidence of toxicity.
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PMID:Effect of selenium on aflatoxin hepatocarcinogenesis in the rat. 210 86

In addition to differences in needs for dietary quality and quantity, humans, as individuals and as subsets of the population, are exposed to variations in climate, stress, environmental contaminants and other confounding factors which likely impinge on susceptibility to cancer. Despite the complexity of lifestyles and dietary habits, it is impressive to review available data on the relation of nutrients to cancer. There is sufficient parallelism between controlled animal studies and human behavior that we are compelled to believe that a variety of essential nutrients can modify carcinogenesis in humans and in lower animals. The micronutrients which appear to meet criteria for classifying them as protective agents in animal models include vitamin A and some of the synthetic retinoids; beta carotene; folic acid; vitamin C; choline/methionine; zinc, and selenium. Some of the others have suggestive effects but in the view of this author, the data are often equivocal, inadequate, or conflicting. These observations clearly support the proposal that animal studies have made enormous contributions in the past 15-20 years to our understanding of carcinogenesis and that this will continue into the future. From the data now available we can state with confidence that animal studies have shown that nutrients can modify the carcinogenesis process at specific sites and through a variety of mechanisms. These include effects on the formation of carcinogens from precursors; effects on metabolism of the carcinogen; effects on one or more stages of initiation, promotion, and progression; host defense mechanisms; cellular differentiation and on growth and metastasis of the tumor. The tools of the molecular biology, just now emerging in the field of nutrition, should have an immense impact on determining more accurately where nutrients exert their effects, how this is accomplished, and to suggest appropriate prevention and intervention techniques. Using molecular biology, combined with traditional and newer methods of toxicology and pathology, we should be able within a few years to better understand carcinogenesis and with such knowledge in hand to make sound recommendations about dietary habits to the public.
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PMID:Roles of micronutrients in cancer prevention: recent evidence from the laboratory. 219 21


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