Effects of cereal type and feed particle size on morphological characteristics, epithelial cell proliferation, and lectin binding patterns in the large intestine of pigs

The present study was undertaken to investigate the effects of cereal type and feed particle size on the morphological characteristics and epithelial cell proliferation of the large intestinal tissue in pigs. Forty pigs, weighing approximately 30 kg, were fed diets containing either coarsely or finely milled barley or wheat for a period of 4 wk. Tissue samples were taken from the cecum and from the proximal, medial, and distal colon at slaughter. The pigs fed the coarse diets had significantly larger crypts, in terms of height as well as volume, than did pigs fed the fine diets. The cereal type had no effect on the mucosal architecture. The epithelial cell proliferation, in terms of counted native mitoses in the crypts, was significantly higher in pigs fed the coarse barley diet than in pigs fed the coarse wheat diet or the fine diets. The volume of the mucin granules in the crypts constituted from 32 to 52% of the crypt volume and was greatest in the pigs fed the coarse diets. This effect of feed particle size was observed for neutral as well as for acidic mucins and sulfomucins. Lectin binding patterns indicated that more of the terminal sugars on glycoconjugates of the apical membrane on the mucosal surface were the sialic acid alpha-2,3 neuraminic acid, but less were mannose in the pigs fed the coarse barley diet. Distinct regional differences were observed among the intestinal sites. These included a decline in the epithelial cell proliferation and an increase in the volume of mucin in the crypts along the intestinal tract. Furthermore, the sialic acid alpha-2,3 neuraminic acid was more abundant in the medial colon than in the cecum; the contrary was seen for mannose and galactose. This study shows that the feed particle size of barley and wheat diets, more than the cereal type itself, affects the mucosal architecture, epithelial cell proliferation, and production and composition of the mucins in the large intestine of pigs. The study suggests that pigs fed a coarse diet are better protected against intestinal infections than pigs fed a fine diet.     

Multiple fistulas and tracheobronchial stenoses require extensive stenting of the central airways and esophagus in squamous-cell carcinoma

In general, it is presumed that colonic epithelial stem cells are the principal cell type at risk of incurring the series of somatic mutations leading to carcinoma, since all other epithelial cell types are short-lived. Mutant stem cell clonal expansion increases the risk for subsequent mutations and is therefore a potentially important step in carcinogenesis. The stem cells reside in colonic crypts, simple tubular foldings of the epithelium, and thus counting crypts provides an indirect means to determine stem cell numbers. The normal crypt population is known to expand through a process of crypt replication and this is thought to result in a corresponding expansion of the epithelial stem cell population. A simple mathematical model of the population dynamics of normal and mutant crypts (crypts containing mutant stem cells) is developed and used to estimate a lower bound on the relative rate of expansion of the mutant stem cell population. The model predicts that if mutant and normal crypt populations expand at the same rate, and if the mutation rate is small relative to the rate of growth, then the fraction of clusters of mutant crypts composed of only a single mutant crypt should steadily decrease with age towards one-half. Aberrant crypts are easily recognizable lesions in human colon which have frequently been shown to contain cells with K-ras and occasionally APC gene mutations. Application of the model to recent counts of aberrant crypt cluster sizes indicate that the aberrant crypt population, and the contained mutant stem cell population, is expanding substantially faster than normal.     

Expression and turnover of an interstitial matrix component of the pericryptal sheath in neonatal mice

The aim of the present study was to determine the expression and turnover of antigen 1/130, a component of the interstitial matrix associated with collagen fibrils in the pericryptal sheath, in neonatal mice (CD1). Anti-laminin was used as a control. Starting on day 9 after birth, monoclonal antibody 1/130 (Mab-1/130) or anti-laminin were either fed orogastrically or injected intraperitoneally twice daily for 3 days. Bound immunoglobulins were disclosed by indirect immunofluorescence at days 12, 16, 23, 30 and 40. Sections from duodenum, ileum and colon were incubated together on the same glass slide. At day 12, the levels of labelling in orogastrically fed animals with Mab-1/130 exhibited a proximo-distal gradient (duodenum>ileum>colon); labelling with anti-laminin was found in the duodenum only. In injected animals, the levels of labelling with both antibodies showed the same gradient (duodenum>ileum>colon). At day 23, Mab-1/130 was still detected in both groups in the duodenum and ileum, whereas anti-laminin was barely detectable and only in the duodenum. At day 30, in animals fed as above or injected intraperitoneally, Mab-1/130 was present in the duodenum at the bottom of the crypts; anti-laminin was completely absent. During the postnatal period, the turnover of antigen-1/130 appeared to be slow and, as the crypts elongated, the mesenchymal pericryptal sheath did not co-migrate with the epithelial cells.     

Influence of diets containing high and low risk factors for colon cancer on early stages of carcinogenesis in human flora-associated (HFA) rats

Germ-free rats colonised with a human intestinal flora were fed diets containing high risk (HR) or low risk (LR) factors for colorectal cancer, and putative biomarkers were evaluated in the colonic mucosa; (i) proliferation, (ii) 1,2-dimethylhydrazine (DMH)-induced aberrant crypt foci and (iii) DMH-induced DNA damage. The HR diet was high in fat (45% of calories) and low in calcium and fibre, reflecting levels characteristic of typical western diets. The LR diet was low in fat (<5% of calories), and high in calcium and fibre. The nutrient/energy ratio of the two diets were similar. Mucosal crypt cell proliferation, assessed after microdissection, was higher on the LR diet (mean number of mitoses per crypt was 2.65 on the LR diet, and 1.62 on the HR diet; P < 0.05). Aberrant crypt foci (ACF) were assessed in the mucosa 12 weeks after DMH treatment. On the HR diet there were significantly more small ACF with 1 and 2 crypts per focus, but fewer ACF with 3, 5 and 7 or more crypts per focus. There was no significant difference in total ACF or the total number of crypts. The effect of diet on DNA damage in the colon was assessed in vivo by the comet assay. Animals were fed a HR or LR diet for 12 weeks before treatment with DMH or saline. For carcinogen-treated animals, DNA damage was significantly higher in colon cells from animals on the HR diet. On the LR diet both DNA damage and the induction of small ACF were reduced despite an increase in cell proliferation. The increase in large ACF on the LR diet may be attributable to elevated crypt cell proliferation possibly increasing crypt fission rates.     

Effects of epidermal growth factor and dimethylhydrazine on crypt size, cell proliferation, and crypt fission in the rat colon. Cell proliferation and crypt fission are controlled independently

Crypt fission is now established as an important mechanism of intestinal growth and regeneration. It has been proposed that increased crypt size is the stimulus for crypt fission, because crypts preparing for fission are generally larger. Consequently, we investigated the effects of epidermal growth factor (EGF) and dimethylhydrazine, which are both known to stimulate crypt cell proliferation, on crypt fission in the rat intestine. We also examined whether the effects of EGF on both proliferation and crypt fission are modified by the pretreatment with dimethylhydrazine for 16 weeks, dimethylhydrazine was then discontinued for 8 weeks, followed by intravenous infusion of EGF for 1 week. There were four groups: vehicle alone, EGF alone, dimethylhydrazine alone, and dimethylhydrazine followed by EGF infusion. The rats were killed at 25 weeks and rates of intestinal crypt cell production, crypt size, and crypt fission were determined. Intravenously infused EGF significantly increased crypt cell production rate, but the magnitude of the effect decreased from the proximal to the distal colon. EGF caused an increase in crypt area, possibly reflecting an increase in crypt size. Importantly dimethylhydrazine had no significant effect on crypt cell production rate nor on crypt area in the distal colon, but it did cause an increase in crypt area in the mid-colon. The crypt fission index was significantly decreased by EGF and increased by dimethylhydrazine. There was no qualitative interaction between EGF and dimethylhydrazine. These results demonstrate the marked proliferative effect of intravenously infused EGF in the colon of orally fed rats, with significant site effects (P = 0.0007); the effect was greatest in the proximal colon and disappeared in the distal colon. The observation that EGF reduced crypt fission indicates that increased cell proliferation, per se, is not a stimulus for crypt fission. This is further supported by the observation that dimethylhydrazine increases crypt fission in crypts of normal size in the distal colon without significantly increasing cell proliferation. These results suggest that increasing crypt cellularity by proliferation is not sufficient to induce crypt fission, and factors other than increased crypt size by proliferation can control crypt fission. It is also probable that cell proliferation and crypt fission are independently regulated. Crypt fission appears to play a considerable role in the intestinal response to carcinogens.     

Prolonged hypoxia alters endothelial barrier function

The purpose of this study was to determine whether the protective effect of fish oil against colon carcinogenesis is due to decreased proliferation, increased differentiation and/or increased apoptosis. Male Sprague Dawley rats (n = 260) were fed one of two oils (corn or fish) and two fibers (pectin or cellulose), plus or minus the carcinogen azoxymethane (AOM). Rats were killed at wk 18 (n = 80) or 36 (n = 180) for cytokinetic measurements. In vivo cell proliferation was measured by incorporation of bromodeoxyuridine into DNA, differentiation by binding of Dolichos biflorus agglutinin and apoptosis by immunoperoxidase detection of digoxigenin labeled genomic DNA. Fish oil resulted in a lower adenocarcinoma incidence (56.1 vs. 70.3%) compared with corn oil. There was no effect of fat or fiber on number of proliferative cells/crypt column in either the proximal or distal colon. In contrast, fish oil resulted in a greater degree of differentiation compared with corn oil in both colonic sites. In addition, fish oil resulted in a higher number of apoptotic cells/crypt column in both the proximal and distal colon as compared with corn oil. AOM treatment increased the ratio of proliferative cells/crypt column to apoptotic cells/crypt column in both the proximal and distal colon compared with saline controls. Fish oil, however, resulted in a lower ratio in both sites in the colon as compared with corn oil. These results suggest that an increase in apoptosis and differentiation, rather than a decrease in proliferation, accounts for the protective effect of fish oil against experimentally induced colon tumorigenesis.     

Gut-trophic effects of keratinocyte growth factor in rat small intestine and colon during enteral refeeding

BACKGROUND: Keratinocyte growth factor (KGF) induces proliferation of gut epithelium in rat models, but KGF-nutrient interactions have not been studied. An experimental model of fasting-induced gut atrophy followed by different levels of enteral refeeding was used to investigate the influence of nutrient availability on the gut-trophic effects of exogenous KGF. METHODS: After a 3-day fast, rats were enterally refed either ad libitum or at 25% of ad libitum intake for 3 subsequent days. Either intraperitoneal KGF (5 mg/kg/d) or saline was given in each dietary regimen. Wet weight, DNA, and protein content were measured as indices of full-thickness cellularity in duodenum, jejunum, ileum, and colon. Villus height in small bowel segments and crypt depth in all gut tissues were measured as specific indices of mucosal growth. RESULTS: Refeeding at 25% of ad libitum intake significantly decreased full-thickness cellularity and mucosal growth indices in duodenum, jejunum, and ileum. In the colon, only protein content fell significantly and crypt depth was maintained. KGF administration during 25% refeeding did not alter full-thickness indices in any small bowel segment or affect jejunal mucosal growth. In contrast, KGF normalized duodenal villus height (p < .01) and duodenal and ileal crypt depth (p < .05) only in the 25%-refed model. KGF significantly increased ileal villus height in both ad libitum and 25%-refed rats (by 43% and 48%, respectively, p < .05) and markedly increased colonic cellularity and mucosal crypt depth with both levels of refeeding (p < .01). CONCLUSIONS: Rat small bowel growth is more sensitive than colon to the level of enteral refeeding after a 3-day fast. KGF administration does not affect jejunal growth, but specifically prevents atrophy of duodenal and ileal mucosa during hypocaloric, hyponitrogenous refeeding. In ileum and colon, some KGF-mediated growth responses are independent of the level of enteral refeeding. Thus gut-trophic effects of KGF and KGF interactions with the level of nutrient intake are tissue-specific.     

Complex co-localization of chromogranins and neurohormones in the human gastrointestinal tract

Co-localization of chromogranin (Cg) A, B, and C has been studied in different neuroendocrine cell types in histologically normal mucosa from human gastrointestinal tract (corpus, antrum, duodenum, ileum, and colon) using single-, double-, and triple-immunofluorescence stainings. Virtually all enterochromaffin (EC) cells contained CgA, and those in the luminal two thirds of the antral mucosa and villi of small intestine often also contained CgB. A few EC cells in the duodenal crypts contained CgC. Most gastrin cells harbored both CgB and CgA, although rather more CgB than CgA, but some gastrin cells contained all three types, i.e., also CgC. Some CCK cells also contained all three chromogranins. Enteroglucagon cells in the duodenal villi contained CgA and some CgB. CgA (but not B or C) was found in some secretin, GIP, enteroglucagon/peptide YY, and neurotensin cells. A few somatostatin cells contained CgA but neither CgB nor CgC. CgA and C were found mainly in the basal cell region, whereas CgB occurred more diffusely throughout the cytoplasm. This varying distribution suggests that not all secretory granules contain CgA, or that CgB may occur in a nongranular form. The varying composition of the different chromogranins may reflect their complex functional roles in the widespread neuroendocrine system.     

Constitutive activation of the gastrin-releasing peptide receptor expressed by the nonmalignant human colon epithelial cell line NCM460

Gastrin-releasing peptide (GRP) causes multiple effects in humans by activating a specific heptaspanning receptor. Within the gastrointestinal tract, GRP receptors (GRP-R) are not normally expressed by mucosal epithelial cells except for those lining the gastric antrum. In contrast, recent studies have shown that up to 40% of resected colon cancers aberrantly express this receptor. This is important because the GRP-R can cause the proliferation of many, but not all, tissues in which it is expressed. Since GRP and other agonists are not known to exist in the colonic lumen, it has not been clear how or even if GRP-R expression in colon cancer contributes to cell proliferation. To evaluate the functional consequence of GRP-R expression on colonic epithelium, we transfected the recently isolated nonmalignant human colon epithelial cell line NCM460 with the cDNA for this receptor. All NCM460 cell lines expressing varying numbers of GRP-R bound selected agonists and antagonists indistinguishably from receptors expressed by other human tissues. Furthermore GRP-R-expressing transfected cell lines, but not wild-type NCM460 cells, proliferated independently of serum or other growth factors. Further evaluation revealed that GRP-R in these cells tonically stimulated G alpha q/11, resulting in increased phospholipase C activation. Since transfected cells do not secrete GRP, nor is their growth influenced by exposure to receptor-specific antagonists, these data indicate that GRP-R ectopically expressed by NCM460 cells are constitutively active. This report provides the first evidence of mutation-independent heptaspanning receptor constitutive activation resulting in cell proliferation, and identifies a potential mechanism whereby the GRP-R may act as an oncogene in human colon cancer.     

Immune complex-dissociated p24 antigen in congenital or perinatal HIV infection: role in the diagnosis and assessment of risk of infection in infants

Both suppressor oncogene and proliferative activity are believed to indicate colon cancer risk. The retinoblastoma (Rb) gene is a suppressor oncogene affecting cell differentiation. Retinoblastoma gene inactivation is associated with tumour development. However, the relation of the Rb protein to cell proliferation and colon tumour formation is unknown. Retinoblastoma protein quantity was correlated with proliferative activity in flat, unaffected mucosa specimens from 36 cancer patients, 21 non-cancer control subjects and in 29 tumour tissue samples from cancer patients. Nuclear Rb protein was measured by using automated CAS-200 image analysis of monoclonal antibody labelled frozen sections from fresh, surgically removed tissue. All colon cells within 15 whole crypts were imaged. Proliferative activity was also measured by using analysis with Ki-67 monoclonal antibody. Retinoblastoma protein content correlated directly with proliferative activity in flat mucosa of non-cancer control subjects (r = 0.63; P < 0.001; n = 21). A significant correlation was also found in flat mucosa specimens of non-metastatic (Duke's stages A and B) cancer patients (r = 0.52; P < 0.01; n = 22). However, Rb protein did not correlate with proliferation in flat mucosa from metastatic (Duke's stages C and D) cancer patients (r = 0.03; NS; n = 14) or in cancer tissue (r = 0.068; NS; n = 29). Mucosal Rb protein in the colon normally increases as proliferation increases. Dissociation between Rb protein and colon proliferation may occur in flat mucosa in patients with a higher risk of metastatic tumour growth. Future studies comparing Rb protein quantity and proliferative activity may help identify high-risk colon cancer patients.     

Chemoprevention of azoxymethane-induced rat colon carcinogenesis by a xanthine oxidase inhibitor, 1'-acetoxychavicol acetate

In our studies to find natural compounds with chemopreventive efficacy in foods, using azoxymethane (AOM)-induced colonic aberrant crypt foci and colonic mucosal cell proliferation as biomarkers, a xanthine oxidase inhibitor, 1'-acetoxychavicol acetate (ACA), present in the edible plant Languas galanga from Thailand was found to be effective. This study was conducted to test the ability of ACA to inhibit AOM-induced colon tumorigenesis when it was fed to rats during the initiation or post-initiation phase. Male F344 rats were given three weekly s.c. injections of AOM (15 mg/kg body weight) to induce colonic neoplasms. They were fed diet containing 100 or 500 ppm ACA for 4 weeks, starting one week before the first dosing of AOM (the initiation feeding). The other groups were fed the ACA diet for 34 weeks, starting one week after the last AOM injection (the post-initiation feeding). At the termination of the study (week 38), AOM had induced 71% incidence of colonic adenocarcinoma (12/17 rats). The initiation feeding with ACA caused significant reduction in the incidence of colon carcinoma (54% inhibition by 100 ppm ACA feeding and 77% inhibition by 500 ppm ACA feeding, P = 0.03 and P = 0.001, respectively). The post-initiation feeding with ACA also suppressed the incidence of colonic carcinoma (45% inhibition by 100 ppm ACA feeding and 93% inhibition by 500 ppm ACA feeding, P = 0.06 and P = 0.00003, respectively). Such inhibition was dose-dependent and was associated with suppression of proliferation biomarkers, such as ornithine decarboxylase activity in the colonic mucosa, and blood and colonic mucosal polyamine contents. ACA also elevated the activities of phase II enzymes, glutathione S-transferase (GST) and quinone reductase (QR), in the liver and colon. These results indicate that ACA could inhibit the development of AOM-induced colon tumorigenesis through its suppression of cell proliferation in the colonic mucosa and its induction of GST and QR. The results confirm our previous finding that ACA feeding effectively suppressed the development of colonic aberrant crypt foci. These findings suggest possible chemopreventive ability of ACA against colon tumorigenesis.     

Effect of missed hemodialysis treatments on mortality in patients with end-stage renal disease

Dietary fibre is believed to protect against a range of Western diseases, including colorectal cancer. Whole plant cell walls make up most of the dietary fibre in Western diets, but their role in disease protection has rarely been studied. At least in vitro, suberized plant cell walls possess novel properties that suggest they could have exceptional potential for cancer protection. Our aim was to test in a rat model the abilities of suberized cell walls from potato skins and commercial cork to decrease gastrointestinal transit time and to protect against the development of aberrant crypts, an early marker of colon cancer. Groups of six rats were fed a modified AIN-76 diet as the control diet and this diet supplemented with 5% dietary fibre from the following sources: commercial cork, commercial-cork cell walls and potato-skin cell walls. A diet supplemented with wheat bran was used as a positive control. The colon carcinogen IQ (2-amino-3-methylimidazo[4,5-f]quinoline) was administered for 3 weeks and after another 12 weeks the number of aberrant crypts determined. Transit times were determined after feeding the diets for 4 weeks. Compared with rats fed the control diet, rats fed diets supplemented with the suberized cell-wall preparations had decreased transit times and had significantly fewer aberrant crypts, with no aberrant crypt foci containing four or more crypts. The diets supplemented with suberized cell walls were more effective than thediet supplemented with wheat bran. We conclude that suberized and lignified cell walls, but particularly suberized, may play an important role in protection against Western diseases, including colorectal cancer. Failure to distinguish suberized and lignified plant cell walls from other sources of non-starch polysaccharides may provide a major limitation in current assessments of the role of dietary fibre in preventing colorectal cancer in humans.     

Inhibition of development of N,N'-dimethylhydrazine-induced rat colonic aberrant crypt foci by pre, post and simultaneous treatments with 24R,25-dihydroxyvitamin D3

It has recently been reported that new vitamin D3 derivatives can exert inhibitory effects on colon carcinogenesis in rats. In the present study the chemopreventive potential of 24R,25-dihydroxyvitamin D3 (24R,25(OH)2vitamin D3) was assessed in a murine model of colon carcinogenesis. In experiment 1, male 6-week-old F344 rats were administered N,N'-dimethylhydrazine (DMH) 20 mg/kg s.c. once a week 4 times. The rats were fed 24R,25(OH)2vitamin D3 at 10 ppm in the diet prior to (pre), together with (simultaneous) or after (post) DMH treatment. Modifying effects were assessed using aberrant crypt foci (ACF), putative preneoplastic lesions, as the end point markers in this model of colon carcinogenesis. After 8 weeks, pre and more markedly simultaneous administration of 24R,25(OH)2vitamin D3 was found to have reduced the total numbers of ACF and significantly inhibited the development of foci. After 16 weeks, numbers of foci with > or = 4 crypts, which are more likely to progress to tumors, were significantly reduced. The most pronounced inhibition of ACF development was noted in rats fed the 24R,25(OH)2vitamin D3 after DMH administration. The reduction was particularly marked in the proximal colon. Blood levels of calcium were not significantly increased over the control levels in groups administered DMH and the vitamin. Immunohistochemical staining showed numbers of proliferating cell nuclear antigen-positive cells to be lower in the colonic epithelia of rats fed the vitamin D3 metabolite than in the controls. In experiment 2, the effect of 24R,25(OH)2vitamin D3 on the alterations in c-fos, c-myc and c-jun oncogene expression in response to DMH administration was examined by northern blot analysis. The early increase in expression of ornithine decarboxylase (ODC) activity was not altered by 24R,25(OH)2vitamin D3. The results suggest that 24R,25(OH)2vitamin D3 is a cancer chemopreventive agent which may suppresses DMH induction of lesions and their subsequent development via an antiproliferative action.     

Methodological findings and considerations in measuring colorectal epithelial cell proliferation in humans

The methodological issues for measuring colorectal epithelial cell proliferation, an intermediate end point for studies of colon neoplasia, in epidemiological studies are deceptively numerous and complex, with few methodological data available. Accordingly, during our experience with measuring colorectal epithelial cell proliferation from nearly 500 participants attending over 1300 study visits over a 6-year period, we recorded data on a variety of measurement variations. Methods investigated included rectal biopsy technique, general histological and labeling procedures [including the tritiated thymidine, 5-bromodeoxyuridine (BrdUrd), and the proliferating cell nuclear antigen (PCNA) immunohistochemical techniques used to label S-phase cells in colonic crypts in rectal biopsy specimens], biopsy scoring procedures, and summary scoring methods. Findings include that the PCNA technique was the simplest, most economical, and least time-consuming. The BrdUrd labeling failure rate was 15% versus < 1% for PCNA. The percentage of labeled cells (labeling index) was highest using PCNA in biopsies processed without prior incubation, intermediate using PCNA in biopsies processed with prior incubation as for BrdUrd, and lowest using BrdUrd. The percentage of labeled cells that were in the upper 40% of the crypt (phi h) was higher using BrdUrd than PCNA; visit-to-visit correlations were higher using PCNA (r = 0.51 versus 0.35), and visit-to-visit variability was lower and between-person variability was higher using PCNA. Intra- and inter-rater reliabilities for the techniques were comparable (PCNA intra-rater r = 0.93, inter-rater r = 0.92). The PCNA technique, compared to the BrdUrd technique, is more feasible and reliable, provides a more accurate estimate of the labeling index, and cell proliferation measures determined with PCNA have statistical properties that are generally more favorable for detecting differences in clinical trials. Thus, the PCNA technique may be preferable to techniques requiring incubation of biopsies. Other methodological findings lead us to recommend that, for larger studies measuring colorectal epithelial cell proliferation on outpatient rectal biopsies, biopsies should be taken 10 cm above the anus using a flexible, preferably jumbo cup, endoscopic forceps through a rigid sigmoidoscope, and histological sections should be 3 microns thick taken 50 microns apart.     

Differential effects of deoxycholic acid on proliferation of neoplastic and differentiated colonocytes in vitro

The secondary bile acid deoxycholic acid is believed to be a promoter of large bowel cancer, in part by inducing colonic epithelial proliferation. The effects of deoxycholic acid on [3H]thymidine incorporation by the human colon cancer cell line HT29 and two differentiated subclones were measured and compared. The subclone HT29-C1 has features of mature absorptive cells and HT29-N2 cells secrete mucus under cholinergic control. The three cell lines were treated with deoxycholic acid (DCA) at concentrations of 0, 5, 10, 50, 100, 150, and 300 microM for 3, 6, 9, 15, 24, and 48 hr. A significant increase in proliferation was noted in HT29 cells only at 6 hr with 5 and 10 microM deoxycholic acid. Neither the subclone HT29-C1, nor HT29-N2 cells exhibited significant change in [3H]thymidine incorporation with DCA at these concentrations or time points. Higher doses of deoxycholic acid above 50 microM and duration of exposure greater than 24 hr were cytotoxic to all three cell lines. The proliferative effects of DCA in HT29 cells were not paralleled by changes in protein kinase C activity or protein kinase C isoform expression. Quantitative and qualitative differences in PKC isoform expression were not noted in the three cell lines used in this study. The proliferative effects of DCA on HT29 cells appear to be independent of the PKC signal transduction pathway.     

International trends in the incidence of cervical cancer: I. Adenocarcinoma and adenosquamous cell carcinomas

The integrin alpha9beta1 is one of the recently identified integrins whose expression is restricted to specialized tissues. Its exact function is still unknown. In the present study, we have analyzed the expression of the alpha9 subunit in human fetal and adult small intestinal and colonic epithelia as well as in intestinal cell lines by indirect immunofluorescence, immunoprecipitation, Western blot, and Northern blot. In intact tissues, the antigen was restricted to the basolateral domain of epithelial cells in intestinal crypts at the fetal stage and was absent in the adult. The alpha9beta1 integrin was also detected in the intestinal cell lines HIEC-6 and Caco-2/15. The presence of alpha9beta1 in HIEC-6 was found to be consistent with their proliferative crypt-like status. In Caco-2/15 cells, the integrin was present at high levels in proliferating cells but was downregulated when cells cease to grow and undertake their differentiation. EGF treatment, which is known to maintain Caco-2/15 cells in a proliferative state, resulted in higher levels of alpha9 as compared to control cells. Taken together, these observations suggest a relation between integrin alpha9beta1 expression and proliferation in human intestinal cells.     

Cell kinetic evaluation of human colonic aberrant crypts. (Colorectal Cancer Study Group of the University of Modena and the Health Care District 16, Modena, Italy)

Foci of aberrant crypts (ACF) have been observed on the unsectioned, methylene blue-stained mucosal surface of the human colon. Experimental evidence and the histological features of the lesions suggest that they might be early events in colon cancer development. The main objective of the present study was to evaluate cell kinetic properties of ACF in the human colon. Five samples of colon mucosa were collected immediately after operation following the administration of 500 mg of 5'-bromo-2'-deoxyuridine prior to surgery. ACF were then identified on the fixed, unsectioned, methylene blue-stained mucosal surface under a light microscope. Some specimens containing ACF were serially sectioned perpendicular to the luminal surface of the intestine, along with specimens of normal-appearing mucosa. Several sections were prepared for the immunohistochemical identification of 5'-bromo-2'-deoxyuridine-incorporating cells (in the S phase of the cell cycle). The results of this study demonstrated that aberrant crypts have more cells per crypt than normal glands. Total labeling index and labeling index values in each of the five longitudinal compartments in which each crypt was divided showed an increased total proliferative activity in all ACF examined, although limited to the lower crypt compartments in almost all aberrant crypts evaluated. These findings are in keeping with previous cell kinetic studies and observations in experimental animals and provide evidence of the involvement of human aberrant crypts in the stepwise process leading from normal mucosa to colon cancer.     

Guanylin, an endogenous ligand for C-type guanylate cyclase, is produced by goblet cells in the rat intestine

BACKGROUND & AIMS: Guanylin activates an intestinal guanylate cyclase (GCC) and stimulates electrolyte movement across the gut epithelium. Cells expressing guanylin messenger RNA have been localized to the epithelial cell layer of the intestine; however, the identity of the guanylin-producing cells has not been determined. The aim of this study was to identify cells that express guanylin in the rat intestine. METHODS: Antibodies were raised against defined proguanylin epitopes, evaluated by Western blotting, and used for immunoperoxidase histochemistry. RESULTS: Guanylin-like immunoreactivity was localized to a subset of goblet cells. In the small intestine, most, perhaps all, goblet cells in the villi were immunopositive, as were some goblet cells in upper crypts; however, goblet cells deep within crypts were unlabeled. In the colon, goblet cells clustered in the necks and around the openings of crypts were immunopositive, whereas (as in the small intestine) goblet cells in deeper crypt regions were unlabeled. In some animals, immunoreactive columnar epithelial cells were also observed in the colon (although such cells were not apparent in the small intestine). Relative labeling of columnar cells varied from animal to animal. CONCLUSIONS: Guanylin is expressed in mature goblet cells. If secreted in conjunction with mucin, it could play a role in the hydration of mucus.