1,721,210 research outputs found
Dietary carbohydrates modify azoxymethane-induced intestinal carcinogenesis in rats
Get PDFThe effect of different dietary carbohydrates (sucrose, cornstarch and high amylose cornstarch) on intestinal carcinogenesis was studied in male Sprague-Dawley rats treated subcutaneously with azoxymethane (AOM) at a weekly dose of 8 mg/kg body wt for 8 wk. The diets, high in fat and low in calcium and fiber, were fed during and after AOM treatment. The number of colonic adenomas per rat in the groups fed either starch was lower (P < 0.05) than the number in the sucrose-fed rats [1.06 +/- 0.38, 0.30 +/- 0.10 and 0.41 +/- 0.22 (mean +/- SEM), in the sucrose-, cornstarch- and high amylose cornstarch-fed groups, respectively]. The incidence of total intestinal tumors (adenomas + adenocarcinomas) was not affected by dietary treatment. However, the incidence of tumors in the small intestine of the rats fed the two cornstarch diets tended to be slightly lower than for rats fed the sucrose diet (P = 0.075). Adenoma dysplasia and adenocarcinoma differentiation were similar among the rats fed the three diets. However, the adenocarcinomas in the rats fed the cornstarch diet were significantly smaller than those in the rats fed sucrose [0.99 +/- 0.14 cm2 (n = 13), 0.56 +/- 0.14 cm2 (n = 13) and 0.55 +/- 0.17 cm2 (n = 9) in rats fed the sucrose, cornstarch and high amylose starch diets, respectively]. Moreover, in the rats fed the cornstarch diet, the adenocarcinomas showed lower invasive potential than those in rats fed the sucrose diet. The results suggest an overall inhibition of AOM-induced carcinogenesis in rats fed the cornstarch diets
Frequent mutation of Apc gene in rat colon tumors and mucin-depleted foci (MDF), preneoplastic lesions in experimental colon carcinogenesis
No full textMucin-depleted foci (MDF) are microscopic dysplastic lesions induced in the colon of rodents by specific colon carcinogens. Most MDF show Wnt pathway activation whereas only a subset shows mutations in the Ctnnb1 gene, coding for β-catenin. Since Apc is a member of the Wnt pathway and the most frequent mutated gene in human colon cancer, we tested whether MDF harbor Apc mutations. F344 rats were treated twice with 150 mg/kg of 1,2-dimethylhydrazine (DMH). Fifteen or 28 weeks later MDF, Aberrant Crypt Foci (ACF) and tumors were collected. We screened a segment of the Apc gene, comprising the region homologous to the Mutation Cluster Region (MCR) of human APC, which frequently shows mutations in experimental colon tumors. Mutations were identified by PCR amplification and sequencing in 6/24 MDF (25%), 7/23 tumors (30%), 0/24 ACF (0%). Most of the mutations (92%) in MDF and tumors were localized in a region upstream from the MCR. All mutations were single base substitutions and mainly formed by G:C → A:T and C:G→ T:A transitions. The pattern of nucleotide changes was similar in MDF and tumors and, interestingly, the same mutation in codon 1047 was found in 2 MDF and in 3 tumors. Four out of the six mutations found in MDF were nonsense mutations and two were missense. All mutations in tumors determined a protein truncation. These results show that Apc mutations are present in MDF with a frequency similar to that of tumors, strengthening the evidence that they are precancerous lesions in colon carcinogenesis
High dietary fat increases polyamine content of murine mammary glands
No full textFemale C57BL/6J mice, nine weeks old, were fed diets differing in the amount and type of fat (5% and 23.5% w/w olive oil and corn oil), for a period of two weeks. The levels of total and individual polyamines putrescine, spermidine and spermine) were measured in the mammary glands after two weeks of experimental diet. For this analysis we used a liquid-liquid chromatography apparatus equipped with a fluorescence detector. The levels of putrescine and spermine were higher in the 23.5% fat diets compared to the 5% fat diets. This increase was induced by olive and corn oil, while the content of spermidine increased only in high olive oil diets. Mice in estrus had higher polyamine levels in mammary tissue than mice in diestrus on the same diet. The results were analyzed with a regression analysis model considering the interaction of variables like estrus, diestrus, type of polyamine and type of dietary fat. The increase in mammary polyamine levels induced by high dietary fats is an indicator of increased proliferation since cell polyamines increase during the early phase of cell growth both in normal and in cancer mammary tissues. Although the role of dietary fat in mammary carcinogenesis has not been well established yet, our data demonstrate that a variation of cell proliferation induced by fat may modify the response to chemical carcinogens
Characterisation of aberrant crypt foci in carcinogen-treated rats: association with intestinal carcinogenesis
Get PDFCarcinogen-treated rats develop foci of aberrant crypts in the colon (ACFs) that have been interpreted as preneoplastic lesions. To characterise ACFs further, we studied in the unsectioned colon of rats the number, multiplicity, some morphological characteristics and the type of mucin production in ACFs. In ACFs observed 115 days after the administration of 50 mg kg-1 1,2-dimethylhydrazine (DMH), crypt multiplicity [number of aberrant crypts (AC) per focus] was positively correlated (P 14 crypts) and a borderline significant association (P = 0.057) between the presence of tumours and sialomucin-producing ACFs. We found no association between the number of ACFs, ACF multiplicity and the presence of tumours
Long-term dietary extra-virgin olive oil rich in polyphenols reverses age-related dysfunctions in motor coordination and contextual memory in mice: role of oxidative stress
No full textThe aim of this study was to evaluate the effects of olive oil phenols on brain aging in mice and to verify whether
the antioxidant and antiinflammatory activities of these polyphenols were involved. C57Bl/6J mice were fed
from middle age to senescence with extra-virgin olive oil (10% wt/wt dry diet) rich in phenols (total polyphenol
dose/day, 6mg/kg). Behavioral tests were employed to assess cognitive, motor, and emotional behavior after 6
or 12 months of treatment. Parameters of oxidative status and inflammation were measured in different brain
areas at the same times and evaluated for correlation with behavioral changes. The treatment with olive oil
phenols improved contextual memory in the step-down test to levels similar to young animals and prevented
the age-related impairment in motor coordination in the rotarod test. This motor effect was correlated with
reduced lipid peroxidation in the cerebellum ( p < 0.05), whereas the memory effect did not correlate with
oxidation or inflammation parameters. In conclusion, this work points out that natural polyphenols contained in
extra-virgin olive oil can improve some age-related dysfunctions by differentially affecting different brain areas.
Such a modulation can be obtained with an olive oil intake that is normal in the Mediterranean area, provided
that the oil has a sufficiently high content of polyphenols
Modification of azoxymethane intestinal carcinogenesis in rats by feeding sucrose boluses, pasta, and glucose
No full textWe studied whether repeated boluses of sucrose or diets containing carbohydrates with a variable glycemic index (GI) affect intestinal carcinogenesis in rats. Male F344 rats were treated twice (1 wk apart) with 15 mg/kg sc azoxymethane (AOM) and then divided into four experimental dietary groups with different carbohydrate composition and administration schedules: the sucrose group was fed 44% (wt/wt) sucrose (GI = 65), the bolus group was fed sucrose as carbohydrate and 43 boluses of sucrose (10-15 g/kg) at various time intervals, the pasta group was fed pasta [77% (wt/wt) cooked pasta, GI = 55], and the glucose group was fed 44% (wt/wt) glucose (GI = 97). All nutrients, including carbohydrates, were provided in similar amount to the different groups. The experiment was terminated between Day 230 and Day 245 after AOM administration. At this time the pasta group had significantly higher cecal short-chain fatty acids than the other groups. Intestinal adenomas and cancers occurred with the same frequency in the bolus, sucrose, and glucose groups. On the contrary, we observed a significant decrease (p = 0.03) in the cumulative incidence of intestinal adenomas, but not adenocarcinomas, in the pasta group compared with the sucrose group (intestinal adenoma incidence in the pasta group was 31% compared with 63% in the sucrose group, 46% in the bolus group, and 37% in the glucose group). In conclusion, these results do not support the hypothesis that sucrose boluses or carbohydrates with a high GI stimulate colon carcinogenesis, but they indicate that foods such as pasta may exert a protective effect
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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