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Percent root length colonization may not be an appropriate measure of root colonization by arbuscular mycorrhizal fungi (AMF) in all cases. We suggest that AMF will differ in how well percent root length colonization measures the amount of AMF colonization in the root due to differences among AMF in hyphal structure and hyphal aggregation. Although soil hyphal length accounts for hyphal density, we suggest that it does not consider differences in hyphal structure in measurements of external colonization and thus might also misrepresent the true amount of AMF in the soil. To test these suggestions, we measured and compared percent root length colonization and soil hyphal length with root ergosterol and soil ergosterol, respectively, for 21 different species of AMF from three families in a greenhouse experiment. Percent root length colonization predicted intra-radical colonization best for Glomaceae and Acaulosporaceae isolates, while soil hyphal length best represented soil ergosterol for Gigasporaceae isolates. The results show that conventional methods for estimating AMF colonization are not universal for all AMF. Caution is advised when drawing inferences for different groups of AMF.
We investigated the influence of oral administration of amoxycillin, erythromycin and roxithromycin on colonization resistance in healthy volunteers. Antibiotics were administered in a randomized cross-over design. No effect on the colonization resistance of the oropharynx could be demonstrated. Amoxycillin decreased the colonization resistance of the bowel against Enterobacteriaceae and yeasts, whose median concentration in faeces increased 100-fold and 30-fold respectively. Roxithromycin and erythromycin decreased the concentration of Enterobacteriaceae in faeces. Secondary colonization with Enterobacteriaceae was detected as often following roxithromycin as following amoxycillin, but the level of colonization with these bacteria was much higher following amoxycillin. Following roxithromycin and erythromycin the level of secondary colonization did not exceed the original concentration of Enterobacteriaceae, showing that these antibiotics did not decrease the colonization resistance against Enterobacteriaceae. The appearance of secondary colonization in faeces at levels equal to or lower than the concentration of Enterobacteriaceae before administration of antibiotics, should not be regarded as proof of disturbance of colonization resistance.
A striking feature of colon tumors is the significant reduction of goblet cells. Although targeted deletion of Math1 in mice leads to a loss of intestinal secretory cells, including goblet cells, the role of Hath1 in colon tumorigenesis remains unknown. Here we report that Hath1, the human ortholog of Math1, was dramatically down-regulated in colon tumor samples and colon cancer cell lines. Overexpression of Hath1 in HT29, an aggressive colon cancer cell line, resulted in a significant inhibition on cell proliferation, anchorage-independent growth in soft agar and, more importantly, growth of human colon cancer cell xenografts in athymic nude mice. Such inhibition was accompanied by altered expression of a goblet cell differentiation marker, MUC2, and cell cycle regulators cyclin D1 and p27kip1. Hath1 expression also was up-regulated on inhibition of the Wnt pathway, which has been well implicated in colon tumorigenesis. Hence, this study suggests that Hath1 may be a novel factor downstream of the Wnt pathway capable of suppressing anchorage-independent growth of colon cancer cell lines. More importantly, this study is the first to establish a link between down-regulation of Hath1 expression and colon tumorigenesis.
The release of goblet cell mucus (GCM) was examined in immune reaction-system of colonic mucosa of rats (SD rats). We previously reported that in the immune reaction of normal colon of rats, the discharge of colonic GCM was not increased by intrarectal instillation (challenge) of several test-antigens after repeated immunization of single BSA antigen through rectal mucosa, and there was difference in local antigen-antibody reaction on the surface of normal mucosa between small intestine and colon. In the present study we investigated the release of colonic GCM in local antigen-antibody system in rats of damaged colon mucosa, who had repeated immunization of BSA after damage induction by intracolonic infusion of formalin. Consequently, the discharge of colonic GCM increased associated with local antigen-antibody reaction in animals after damage induction by formalin. It is suggested that when the mucosal barrier is disrupted, enhanced release of colonic GCM is occurred by the local immune reaction on the surface of colonic mucosa.
Intestinal permeability to different-sized polyethylene glycols in Crohn's disease of the colon was compared with that in ileal Crohn's disease and in controls without inflammatory bowel affection. The permeability was assessed both after ingestion of the marker (oral load) and after deposition in the colon during colonoscopy (colonic load). After oral load the absorption was least in the patients with colonic Crohn's disease, intermediate in ileal disease, and greatest in the controls. After colonic load, however, the values were highest in colonic Crohn's disease. The study indicated that in Crohn's disease of the colon there is abnormal permeability in apparently uninvolved proximal small intestine as well as in the colon. Since oral load tests preferentially reflect the absorptive properties of the proximal small bowel, regional tests of absorption are important when the aim is to assess the permeability of the distal small intestine or the colon.
AIM: To investigate the effect of the selective cyclooxygenase-2 (COX-2) inhibitor rofecoxib on the incidence of perianastomotic colonic tumors in a model of chemical carcinogenesis in the rat. EXPERIMENTAL DESIGN: Experimental study with 45 male Sprague-Dawley rats randomly assigned to one of three groups: control (n = 15) with colocolic anastomosis and chemical carcinogenesis with 1-2 dimethylhydrazine (1-2 DMH); rofecoxib 0.0027% (n = 15) with colonic anastomosis, chemical carcinogenesis and the addition of dietary rofecoxib at doses of 27 parts per million (ppm), and rofecoxib 0.0058% (n = 15) with colonic anastomosis, chemical carcinogenesis and the addition of dietary rofecoxib at doses of 58 ppm. Carcinogenic induction was performed with 1-2 DMH at a weekly dose of 25 mg/kg of weight for 18 weeks, and colonic tumors induced were analyzed in postoperative week 20. The main parameter evaluated was the percentage of colonic neoplastic tissue, which relates tumor surface area to the colon's surface area. RESULTS: Rofecoxib at doses of 2.5 mg/kg or 0.0058 ppm significantly reduced chemical colon carcinogenesis in rats, both in the perianastomotic area and the rest of the colon (p < 0.01). In the extra-anastomotic area, rofecoxib at doses of 2.5 mg/kg has significantly greater inhibitory effect than rofecoxib in doses of 1.2 mg/kg or 0.0027 ppm (p < 0.005). CONCLUSIONS: Rofecoxib causes a reduction in chemical colon carcinogenesis in rats. This effect is sustained in the perianastomotic area, and the investigation of its role in operated colorectal cancer with risk of locoregional recurrence may therefore be of interest.
Strategies for management of children attending day-care facilities after a case of Haemophilus influenzae type b disease are controversial. The success of chemoprophylaxis in preventing subsequent cases has been variable. Failure of rifampin prophylaxis as currently recommended may result from usage limited to direct contacts of the index patient. This prospective study was designed to ascertain the extent of colonization in household contacts of colonized children attending day-care facilities with an index case of H influenzae disease. Outer membrane protein analysis was used to determine similarity between strains isolated from contacts and index patients. Of children attending six day-care facilities, 15% were colonized with subtypes of H influenzae identical with those of their respective index patients, and 7% of children were colonized with different subtypes. Colonization with identical outer membrane protein subtypes in children from day-care homes was more frequent than in the larger day-care centers (91% v 8%, P less than .00001). Within families of children with identical outer membrane protein subtypes, 25% of household members (17% of parents and 44% of siblings) were colonized despite lack of direct contact with the index patients. This colonization rate was comparable to that of household contacts of index patients (26%). Among household contacts of index patients, especially siblings, colonization with H influenzae tended to be lower if the patient attended day care than if the patient did not attend day care (17% v 73%; P = .05 for siblings). We have found that household contacts of colonized day-care children are a reservoir of H influenzae.(ABSTRACT TRUNCATED AT 250 WORDS)
Peroperative antegrade colonic lavage is often performed before primary anastomosis in emergency colonic surgery. The influence of colonic lavage on bacterial translocation from the obstructed colon was determined. Forty female Wistar rats were studied in four groups: (1) control; (2) non-obstructed with lavage; (3) obstructed; and (4) obstructed with lavage. Ligature obstruction of the rectum was performed in groups 3 and 4. Some 4 days later 35S-radiolabelled Escherichia coli was inoculated into the colon of all animals. Groups 2 and 4 underwent colonic lavage. Lavage in the group 4 animals with left-sided colonic obstruction significantly increased the levels of E. coli in regional nodes, liver, spleen, lung, kidney and blood (as assessed by organ culture and scintillation counting) compared with those in groups 1, 2 and 3 (P < 0.05). These results suggest that peroperative lavage of the obstructed colon significantly increases the level of bacterial translocation.
Although there is considerable evidence that high consumption of red meat may increase the risk of colorectal cancer, data by subsite within the colon are sparse. The objective of our study was to prospectively examine whether the association of red meat consumption with cancer risk varies by subsite within the large bowel. We analyzed data from the Swedish Mammography Cohort of 61,433 women aged 40-75 years and free from diagnosed cancer at baseline in 1987-1990. Diet was assessed at baseline using a self-administered food-frequency questionnaire. Over a mean follow-up of 13.9 years, we identified 234 proximal colon cancers, 155 distal colon cancers and 230 rectal cancers. We observed a significant positive association between red meat consumption and risk of distal colon cancer (p for trend = 0.001) but not of cancers of the proximal colon (p for trend = 0.95) or rectum (p for trend = 0.32). The multivariate rate ratio for women who consumed 94 or more g/day of red meat compared to those who consumed less than 50 g/day was 2.22 (95% confidence interval [CI] 1.34-3.68) for distal colon, 1.03 (95% CI 0.67-1.60) for proximal colon and 1.28 (95% CI 0.83-1.98) for rectum. Although there was no association between consumption of fish and risk of cancer at any subsite, poultry consumption was weakly inversely related to risk of total colorectal cancer (p for trend = 0.04). These findings suggest that high consumption of red meat may substantially increase the risk of distal colon cancer. Future investigations on red meat and colorectal cancer risk should consider cancer subsites separately.
BACKGROUND: Visceral hypersensitivity is one of the mechanisms of irritable bowel syndrome (IBS), but it does not explain the entire symptomatology, i.e., altered bowel habit with abdominal pain relieved by defecation. We tested our hypothesis that an abnormal link between luminal stimulation and mural response may have some role in the pathophysiology of IBS. METHODS: Patients with IBS (n = 10, median 21 years old, 5 male patients, 5 female patients) and healthy control subjects (n = 10, median 21 years old, 5 men, 5 women) were studied. A manometric catheter with three transducers was inserted to the descending colon and a balloon was placed in the distal sigmoid colon. Another catheter with three transducers was inserted to the duodenum. After baseline for 30min, the sigmoid colon was stimulated by balloon distention for 30min followed by recovery for 30min. Balloon distention was repeated 100 times, and each stimulation consisted of a 5-s inflation and a 10-s deflation, with a volume of 50ml maximum. The sensory threshold of balloon inflation was then examined, and plasma adrenocorticotropic hormone (ACTH) was measured with radioimmunoassay. RESULTS: Repetitive colonic distention induced a significant increase in motility indices (mmHg s/s%) of the descending colon in the IBS patients (from 118 +/- 25 to 333 +/- 108, P < 0.05) but not of those in controls (from 90 +/- 16 to 89 +/- 19). A significant group difference (P < 0.05), period effect (P < 0.02), and group x period interactions (P < 0.01) were detected with two-way ANOVA. Duodenal motility indices in controls were significantly reduced by colonic distention (from 169 +/- 25 to 104 +/- 14, P < 0.01), but those in the IBS patients were not (from 156 +/- 17 to 124 +/- 20). The sensory threshold of balloon inflation in the IBS patients (74 +/- 10ml) was significantly lower than that in controls (125 +/- 6ml, P < 0.001). There was no significant difference in plasma ACTH levels between the IBS patients and controls. CONCLUSIONS: Repetitive distention of the distal sigmoid colon below the sensory threshold induced orad exaggerated motility of the colon in IBS patients. The distention inhibited motility of the small intestine in healthy subjects, but this inhibition was blunted in IBS patients. These results suggest that IBS patients may have not only visceral hypersensitivity, but also an abnormal intestinal reflex.
Repetitive treatment with the organotropic colon carcinogen, 1,2-dimethylhydrazine (DMH), produces tumors in susceptible mouse strains that exhibit pathological features associated with the human disease. As in human populations, the genetic background of laboratory animals comprises a significant component to this organ-specific carcinogenesis, and several mouse lines, including AKR/J and DBA/2J are highly resistant to the tumorigenic effects of DMH. During the course of ongoing studies to establish phenotypic differences between susceptible (SWR/J and P/J) and resistant strains, we have examined the colonic mucosa of DMH-treated mice for the presence of aberrant crypt foci (ACF). ACF represent an early morphological lesion in stepwise progression of colon cancer. In Experiment 1, 6-week-old SWR/J and AKR/J mice were injected with DMH (35 and 20 mg/kg, respectively) once a week for 2 weeks. Five weeks later, colons were removed and ACF visualized at low magnification by light microscopy after methylene blue-staining. Only SWR/J mice revealed focal atypia indicative of preneoplastic change. To obtain additional information about their morphology, tissue sections containing ACF were sectioned and stained with H&E. ACF are larger and have a thicker epithelial lining than normal crypts. H&E confirmed the absence of these lesions in untreated SWR/J and DMH-exposed AKR/J mice. In Experiment 2, SWR/J and DBA/2J mice were injected with DMH (35 mg/kg) once a week for 2 weeks. Nine weeks later, colons were analyzed for ACF formation. Comparable to the first experiment, no ACF were observed in the colonic mucosa of the resistant DBA/2J line. In contrast, ACF were readily identified in the middle and distal colons of similarly exposed SWR/J mice. This differential response between resistant and susceptible mouse lines further supports an important role for ACF in the stepwise progression of colon cancer.
The transition from normality to malignancy in colorectal cancer is characterized by alterations in the expression of genes associated with the maintenance of tissue homoeostasis. Butyrate, a product of microbial fermentation of dietary fibre in the colon, is known to regulate a number of genes associated with the processes of proliferation, differentiation and apoptosis of colonic epithelial cells, and, hence, homoeostasis of colonic tissue. We have shown previously that the transport of butyrate into colonocytes is of fundamental importance to butyrate's regulatory ability, and therefore sought to assess the expression profile of butyrate-responsive genes in colon cancer tissue, where the expression of the colonic luminal-membrane butyrate transporter, MCT1 (monocarboxylate transporter 1), is significantly down-regulated. In the present paper, we first employed microarray analysis to assess global changes in butyrate-responsive genes using HT29 human colon carcinoma cells treated with butyrate. There was consistency in the butyrate response of selected genes in two other human colonic cell lines (HCT116 and AA/C1) using quantitative real-time PCR. Furthermore, we report that expression levels of selected butyrate-responsive genes involved in the processes of proliferation, differentiation and apoptosis, are deregulated in colon cancer tissue, correlating with decreased expression of MCT1. These findings support our hypothesis that a reduction in MCT1 expression, and hence butyrate transport, can lead to a reduction in the intracellular butyrate levels required to regulate gene expression. Collectively, our results highlight the important contribution of butyrate transport to the maintenance of tissue homoeostasis and disease prevention.
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.
The higher incidence of colon cancer in African Americans compared with other US racial/ethnic groups is largely unexplained. This report describes associations of total energy and macronutrients with colon cancer risk in African Americans and Whites from a case-control study in North Carolina between 1996 and 2000. Incident cases of histologically confirmed colon cancer, aged 40-80 years (n = 613), and matched controls (n = 996) were interviewed in person to elicit information on potential colon cancer risk factors. A validated food frequency questionnaire adapted to include regional foods was used to assess diet over the year prior to diagnosis or interview date. Cases generally reported higher mean daily intakes of total energy and macronutrients and lower dietary fiber consumption than did controls. Total energy intake was positively associated with colon cancer risk in both racial groups and, although there were some differences by race, high intakes of individual energy sources were also generally associated with two- to threefold increases in risk in models not controlled for total energy. However, these associations largely disappeared when total energy was taken into account. A high level of dietary fiber was associated with a statistically significant 50-60% risk reduction in African Americans and a nonsignificant 30% decreased risk in Whites. Alcohol intake was not statistically significantly associated with colon cancer in either racial group. Total energy intake was consistently associated with colon cancer risk, but associations with individual macronutrients varied somewhat by race and by adjustment for energy intake. These findings may provide an explanation for some of the racial differences in colon cancer incidence.
JC virus (JCV), along with other members of the polyomavirus family, encodes a class of highly conserved proteins, T antigens, that are capable of inducing aneuploidy in cultured cells. We have previously isolated T-antigen DNA variants of JCV from both colon cancer tissues and the corresponding nonneoplastic gastrointestinal tissues, raising new questions about the role of JCV in the development of chromosomal instability of the colon. Based on the sequence of the transcriptional control region (TCR), JCV can be classified as archetype or tandem repeat variants. Among the latter, Mad-1, the prototype virus first isolated from a patient with progressive multifocal leukoencephalopathy, is characterized by lacking the 23- and 66-bp sequences that are present in the archetype and by duplication of a 98-bp sequence. In this study, we evaluated differences in the TCR of JCV isolated from colon cancer tissues and nonneoplastic epithelium. To characterize JCV variants, we first treated eight pairs of DNA samples from colon cancers and noncancerous tissue with topoisomerase I and then amplified and cloned the JCV TCR. We obtained 285 recombinant clones from the JCV TCR, 157 from nonneoplastic samples, and 128 from colon cancer tissues. Of these clones, 262 spanned the length of the JCV Mad-1 TCR: 99.3% from nonneoplastic samples and 82.8% from colon cancer tissues. In sequencing 54 clones in both directions, we did not find archetype JCV either in the nonneoplastic tissue or in the cancer samples. From all colon cancer tissues, 18 clones had a deletion of one 98-bp tandem repeat. This deleted strain was not detected in any of the nonneoplastic tissues (14 versus 0% [chi(2) = 23.6; P < 0.001]). Our study demonstrates that the only JCV strain present in the human colon is Mad-1, and the variant with a single 98-bp sequence is found exclusively in the cancer tissues. This strain may be involved in the development of chromosomal instability.