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Query: UMLS:C0699790 (colon cancer)
 28,837 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role which the human colon fulfils in digestion and metabolism remains largely undocumented. Its capacity to conserve water and electrolytes is well known although how this is controlled is uncertain. In the animal kingdom, calcium and magnesium absorption from the colon are improtant as are absorption and synthesis of vitamins. The abundant microflora of the human colon gives it unique properties. Dietary residue is metabolised forming short-chain fatty acids, hydrogen, carbon dioxide and methane; whilst 20% of urea synthesised in man is broken down in the colon to ammonia, which is reabsorbed, and carbonic acid. The microflora also degrades a wide variety of organic compounds including food additives, drugs, bile salts, and cholesterol which may be relevant to the development of colon cancer. Regional differences in colonic function also exist making interpretation of data from this relatively inaccessible organ more difficult.
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PMID:The colon: Absorptive, seccretory and metabolic functions. 120 9

Fermentation in the large bowel has been postulated to play a protective role against colon cancer. Hydrogen and methane are end products of this fermentation process and are absorbed into the bloodstream and excreted via expired air in the breath. Breath levels of hydrogen and, to a lesser extent, methane correlate strongly with colonic fermentation and may serve as useful biomarkers for this process. In a preliminary study to assess the usefulness of these two markers in epidemiologic studies, we followed the hourly excretion of the two gases in expired alveolar air for 48 hr in 20 healthy subjects, using a Quintron gas chromatograph equipped with a solid-state detector specific for reducing gases. All subjects excreted hydrogen, but 71% did not excrete methane. Possible atmospheric contamination of the samples was corrected for on the basis of breath carbon dioxide levels. A clear circadian pattern of excretion was observed for breath hydrogen, with a decrease during the early morning followed by a progressive increase during the rest of the day. Methane excretion was constant throughout the day. This study shows that four samples collected at convenient times (0600, 1300, 1800, and 2200 hr) are optimal to characterize individuals by their breath excretions of hydrogen and methane during a 24-hr period.
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PMID:Use of breath hydrogen and methane as markers of colonic fermentation in epidemiologic studies: circadian patterns of excretion. 148 49

Seven human colon cell lines were studied by infrared spectroscopy including study of several spectral parameters under high pressure (pressure tuning spectroscopy). The results were compared to those obtained from the study of normal and malignant colon tissues (B. Rigas et al., Proc. Natl. Acad. Sci. USA, 87: 8140-8144, 1990; P. T. T. Wong and B. Rigas., Appl. Spectrosc., 44: 1715, 1990). The seven adenocarcinoma cell lines displayed almost all of the important spectroscopic features of colon cancer tissues: (a) increased hydrogen-bonding of the phosphodiester groups of nucleic acids; (b) decreased hydrogen-bonding of the C--OH groups of carbohydrates and proteins; (c) a prominent band at 972 cm-1; and (d) a shift of the band normally appearing at 1082 cm-1 to 1086 cm-1. These cell lines differed spectroscopically from the colon cancer tissues in that: (a) they displayed a band at 991 cm-1, which is weak in colon tissues; and (b) the packing and degree of disorder of membrane lipids were close to those observed in normal colonic tissues. These findings (i) establish IR spectroscopy, used in combination with pressure tuning, as a useful method to address problems of tumor biology in cell culture systems, (ii) indicate that these cell lines offer a useful experimental model to explore the origin of the spectroscopic changes that we observed in colon cancer tissues, and (iii) support the idea that the malignant colonocyte is the likely source of all or most spectroscopic abnormalities of human colon cancer.
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PMID:Human colon adenocarcinoma cell lines display infrared spectroscopic features of malignant colon tissues. 172 89

Mice were treated with griseofulvin (GF) containing diet or control diet for 12 months. The livers from mice fed griseofulvin showed large tumors that were excised and used for analysis. The infrared spectra from control liver tissue and tumor tissue from GF livers were measured and compared as a function of pressure up to 27 kbar. Many changes in the infrared spectral features of the tumor tissue were observed. Results showed that neoplasm formation involved structural modifications of nucleic acids, lipids, carbohydrates, and proteins in the liver cells, which were detected from the abnormal vibrations of the functional groups in these biomolecules. The amount of glycogen was dramatically decreased in the tumor tissue compared to the control tissue. Important changes in the strength of hydrogen-bondings in the phosphodiester backbone of the nucleic acids and in the C-O groups of tissue proteins and carbohydrates were observed. Stronger interchain interactions and thus close interchain packing among the lipids in the GF liver were evident. These results showed very close similarities with those obtained with other types of tumors such as human colon cancer, suggesting that a common pattern of molecular changes has been identified in neoplastic transformation.
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PMID:Distinctive infrared spectral features in liver tumor tissues of mice: evidence of structural modifications at the molecular level. 174 16

Epidemiological data suggest that increased risk of colon cancer is correlated with a higher fecal pH. Although some experimental studies have shown a protective effect against experimentally induced colon cancer by acidifying colonic contents, others have shown that a more acidified colonic content is associated with increased cell proliferation and enhanced tumorigenesis. It is now clear that simply acidifying colonic contents will not consistently result in decreased tumorigenesis. Perhaps the key is how colonic contents are acidified--a decrease in base production or an increase in acid production. Or, more important than luminal pH itself, may be a factor affected by changes in hydrogen ion concentration. This paper reviews the determinants of colonic luminal pH and their dietary sources and discusses important physiological consequences of modifying the pH of colonic contents.
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PMID:Determinants and consequences of colonic luminal pH: implications for colon cancer. 179 10

Pancreatic cancer mucins have several carbohydrate antigens that are potentially useful in the detection of pancreatic cancers, but little is known about the core polypeptides of pancreatic cancer mucins. In this study, purified mucin from SW1990 pancreatic cancer xenografts was deglycosylated by treatment with hydrogen fluoride to give pancreatic cancer apomucin. Consistent with near-complete removal of carbohydrate, the apomucin had 10- to 70-fold decreased binding of lectins and, unlike the native mucin, served as an acceptor for polypeptidyl N-acetylgalactosaminyl transferase. Antibodies prepared against the apomucin did not bind to native mucin, and antibodies that bound to native mucin did not bind to apomucin. On the basis of cross-reaction with deglycosylated colon cancer mucin and intestinal mucin repeat peptide, apomucins from SW1990 pancreatic cancer xenografts contain the intestinal mucin repeat peptide. On the basis of binding of breast cancer-reactive monoclonal antibodies 139H2, DF3, and HMFG-2, apomucins from SW1990 pancreatic cancer xenografts also have the mammary mucin repeat peptide. Using complementary DNA probes specific for intestinal mucin and breast mucin sequences, both types of apomucin mRNA were detected in nude mouse xenografts of SW1990 cells. In immunohistochemical staining, antibody against deglycosylated SW1990 mucin stained normal breast and pancreas but not normal colon. Some pancreatic and mammary cancers and most colonic cancers, however, were stained by antibodies against both intestinal apomucin and mammary apomucin. We conclude that pancreatic cancers can produce mucins with the intestinal repeat peptide as well as those with mammary repeat peptide sequences.
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PMID:Relationship of pancreatic cancer apomucin to mammary and intestinal apomucins. 198 13

Hepatic glucose production (HGP) and glucose carbon recycling are traditionally estimated by the combined use of hydrogen and carbon-labeled glucose tracers. A single-isotope method such as that of Reichard et al. for the determination of HGP and glucose carbon recycling requires the determination of activities in different glucose carbons by chemical degradation. Since the 13C content in the glucose carbon skeleton can be determined from mass fragmentography, the use of 13C-labeled glucose and mass fragmentography can provide a single-isotope method for the quantification of the recycled carbons. Correction for the recycling makes it possible to determine the true HGP. In this study, (1-13C1)glucose and mass fragmentography were used for the determination of HGP and glucose carbon recycling in six colon cancer patients. Molar enrichment of the molecular ion (m/z 328 cluster of glucose aldonitrile pentaacetate) was used to determine 'uncorrected' HGP, which was 1.93 +/- 0.11 mg kg-1 min-1 (mean +/- s.e.m.). The difference in molar enrichment of the molecular ion C1-C6 (m/z 328) and the ion corresponding to C1-C4 fragment (m/z 242) was used to determine the contribution of recycled label carbon. After this correction, the 'corrected' HGP was 2.04 +/- 0.12 mg kg-1 min-1, which is not significantly different from the 'true' HGP rate of 2.05 +/- 0.15 mg kg-1 min-1 determined by using (6-3H)glucose. HGP determined from the enrichment of the molecular ion C1-C6 underestimates true HGP, as expected. The corrected HGPs correlate well with those from 6-3H method (r = 0.86, y = 1.06x - 0.12; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Correction of glucose carbon recycling for the determination of 'true' hepatic glucose production rates by (1-13C1)glucose. 205 92

The prevention of cancer by agents in our diet has led to the concept that oxygen radicals are a necessary component of a variety of human cancers including breast, colon and prostatic cancer. These cancers are putatively promoted by estradiol, bile acids and androgens. Epidemiological studies have shown that these cancers are suppressed in vegetarian populations. Vegetable components that may be responsible for this cancer prevention are Vitamin A, retinoids and protease inhibitors (PIs). These agents have been shown to suppress the formation of hydrogen peroxide in promoter-induced neutrophils. They also have been shown to block two-stage carcinogenesis and breast cancer when fed to animals. PIs also suppress experimentally-induced colon cancer and spontaneous liver cancer. Moreover, a new series of cancer-preventive agents, Sarcophytols (isolated by Fujiki and co-workers), are capable of suppressing two-stage carcinogenesis, breast and colon cancers in rodents when given in low concentrations. Sarcophytols were also active suppressors of H2O2 formation of 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-induced neutrophils. These observations point to an essential role of oxygen radicals in carcinogenesis. Suppression of the oxygen radical response of neutrophils in relation to cancer preventive agents is a facile assay of these important substances. The mechanism of action of oxygen radicals in promoting carcinogenesis is a multiple one, including: (1) activation of oncogenes, (2) modification of DNA bases, and (3) formation of single-strand breaks leading to poly(ADP)ribose polymerase activation.
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PMID:Prevention of cancer by agents that suppress oxygen radical formation. 206 Aug 47

This hypothesis paper reviews diverse evidence suggesting that intracolonic production of oxygen radicals may play a role in carcinogenesis. The hypothesis began to evolve when the author made the chance discovery that 1/10,000 dilutions of feces generated detectable quantities of highly reactive hydroxyl radicals (HO.). The rate of HO. formation, detected using DMSO as a molecular probe, was quite remarkable, corresponding to that which would be produced by over 10,000 rads of gamma irradiation per day, absorbed in the periphery of the fecal mass adjacent to the mucosa. The relatively high concentrations of iron in feces, together with the ability of bile pigments to act as iron chelators that support Fenton chemistry, may very well permit efficient HO. generation from superoxide and hydrogen peroxide produced by bacterial metabolism. Such free radical generation in feces could provide a missing link in our understanding of the etiology of colon cancer: the oxidation of procarcinogens either by fecal HO., or by secondary peroxyl radicals (ROO.) to form active carcinogens or mitogenic tumor promotors. Intracolonic free radical formation may explain the high incidence of cancer in the colon and rectum, compared to other regions of the GI tract, as well as the observed correlations of a higher incidence of colon cancer with red meat in the diet, which increases stool iron, and with excessive fat in the diet, which may increase the fecal content of procarcinogens and bile pigments.
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PMID:Free radicals and the etiology of colon cancer. 218 44

Breath methane and hydrogen, plasma acetate, serum selenium, vitamin A and beta-carotene were measured in 47 patients from whom colonic polyps had been removed by endoscopic polypectomy between 3 months and 2 years previously. Patients were compared with 39 control subjects in whom no abnormality was detected during colonoscopy. The proportion of methane exhalers was significantly (p less than 0.0005) higher in patients after polypectomy (66.0%) than in controls (28.2%). Mean plasma acetate was lower (p less than 0.025) in post-polypectomy patients (70.5 microM) than in control subjects (97.1 microM) while breath hydrogen was similar in both groups. The serum concentrations of the antioxidants selenium and beta-carotene showed no differences between the groups whereas vitamin A was higher (p less than 0.01) in serum samples of patients after polypectomy than of controls. These findings indicate that the colonic environment in post-polypectomy patients exhibits certain characteristics which may be related to the formation of benign tumors and possibly colon cancer.
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PMID:Metabolic and nutritional parameters in patients after colonic polypectomy. 322 Jan 81


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