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Background: The histogenesis of human colorectal hyperplastic polyps and colorectal adenomas is poorly understood even now., Method: Human colorectal adenomas, hyperplastic polyps, and normal colorectal mucosae (patients with familial adenomatous polyposis and hereditary non-polyposis colorectal carcinoma were excluded) were obtained during colonoscopy and microdissected into individual crypts. Morphology, cell proliferation characteristics, and fission indices of crypts isolated from these lesions were then studied., Results: Crypts isolated from colorectal adenomas and colorectal hyperplastic polyps were significantly larger (p<0.001) than crypts from normal colorectal mucosae. Crypt fission was an uncommon event in normal colonic mucosae but common in crypts isolated from adenomas and hyperplastic polyps (p<0.001). Analysis of the distribution of mitoses suggested an upward expansion of the proliferation compartment in adenomas to the surface of the crypt with no reversal of proliferating cell distribution, as has previously been described., Conclusions: Sporadic human colorectal adenomas and hyperplastic polyps grow by the process of crypt fission. Expansion of the proliferative compartment was demonstrated in crypts from adenomas, consistent with deregulation of cell cycle control.

Background and Aims: Epidermal growth factor (EGF) is a potent mitogen for the gastrointestinal tract and also influences the number of new crypts formed by crypt fission. The time course of these events and possible linkage between these two complementary mechanisms is however poorly understood. We therefore examined the temporal relationship of proliferation and fission in rats treated with EGF., Methods: Osmotic minipumps were implanted subcutaneously into male Wistar rats to infuse EGF continuously (60 microg/rat/day) for periods of 1-14 days. Proliferation and crypt branching were quantified following vincristine induced metaphase arrest and morphometric assessment of microdissected tissue., Results: In the small intestine, EGF significantly increased epithelial cell proliferation and crypt and villus area after 24 hours of EGF, although maximal effects were only reached following six days of infusion. EGF also resulted in an approximate 30% reduction in crypt fission in the small bowel. In the colon, EGF caused a twofold increase in epithelial cell proliferation one day after infusion, from 15.3 (2.3) to 29.6 (3.5) metaphases per crypt (p<0.01). Maximal effects were seen in rats receiving EGF for seven days. For all time points, colonic crypt size increased in response to EGF. The amount of branching increased following one day of infusion with EGF (from 15.3 (1.9) to 32.4 (5.5)%; p<0.001) but was significantly lower (approximately 25% of control values) following longer periods of infusion. Crypt fission did not correlate with crypt area., Conclusion: EGF has profound effects on cell proliferation and also altered crypt fission, with its actions on crypt fission most pronounced in the colon where it first increased and then decreased fission. EGF can thus be a potent stimulus for crypt fission during short term infusion and may reduce the number of branched crypts present in a resting or quiescent stage. Growth factors can alter cell mass by two separate but linked mechanisms, namely altered cell production and crypt fission.

Background: Several papers have indicated that glutamine is a preferred fuel for the enterocyte and that it can increase intestinal epithelial cell proliferation., Aims: To investigate the effects of glutamine on intestinal epithelial cell proliferation in the parenterally fed rat., Methods: Five groups of six rats were fed parenterally; a group of orally fed rats was also studied. Crypt cell proliferation was studied after six days using native mitoses in microdissected crypts and bromodeoxyuridine labelling., Results: No effect of treatment was seen on intestinal weight; however, the weights of the small intestine, caecum, and colon were all significantly heavier in the orally fed group than in the total parenteral nutrition groups (p<0.001). There was no effect of any of the glutamine treatments on mitotic activity in the small intestine. In the colon there was a small increase in native mitoses with glutamine (p=0.03). There was also an indication of increased proliferative activity in the first fifth of the small intestine and colon with glutamine. Little effect of glutamine on bromodeoxyuridine labelling in either site was observed, but there was a small but significant reduction in growth fraction of the colon of the glutamine treated group. The labelling distribution curve from sections and the mitotic distribution curve obtained from crypt squashes showed a good correlation., Conclusion: Glutamine has a small, but significant effect on mitotic activity but only in the colon. Modest effects on the distribution of labelled cells were also seen.

Background: Non-steroidal anti-inflammatory drugs (NSAIDs) are effective for arthritis but cause gastrointestinal injury. Bovine colostrum is a rich source of growth factors and is marketed as a health food supplement., Aims: To examine whether spray dried, defatted colostrum or milk preparations could reduce gastrointestinal injury caused by indomethacin., Methods: Effects of test solutions, administered orally, were examined using an indomethacin restraint rat model of gastric damage and an indomethacin mouse model of small intestinal injury. Effects on migration of the human colonic carcinoma cell line HT-29 and rat small intestinal cell line RIE-1 were assessed using a wounded monolayer assay system (used as an in vitro model of wound repair) and effects on proliferation determined using [3H]thymidine incorporation., Results: Pretreatment with 0.5 or 1 ml colostral preparation reduced gastric injury by 30% and 60% respectively in rats. A milk preparation was much less efficacious. Recombinant transforming growth factor beta added at a dose similar to that found in the colostrum preparation (12.5 ng/rat), reduced injury by about 60%. Addition of colostrum to drinking water (10% vol/vol) prevented villus shortening in the mouse model of small intestinal injury. Addition of milk preparation was ineffective. Colostrum increased proliferation and cell migration of RIE-1 and HT-29 cells. These effects were mainly due to constituents of the colostrum with molecular weights greater than 30 kDa., Conclusions: Bovine colostrum could provide a novel, inexpensive approach for the prevention and treatment of the injurious effects of NSAIDs on the gut and may also be of value for the treatment of other ulcerative conditions of the bowel.

Background: Fermentable dietary fibre has many effects on the gastrointestinal tract. One is to alter epithelial crypt cell proliferation, especially in the colon. A discrepancy between epithelial cell production rates and intestinal weights has been noted previously: crypt cell production rates only increase if bacterial fermentation occurs, but intestinal wet weight can increase in the same animals without bacterial fermentation of fibre., Aims: To quantify intestinal cell populations in order to resolve the above paradox., Methods: Conventional and germ-free rats were fed fibre-free or fibre supplemented diets and their intestines were quantified by morphometry., Results: There was evidence of fibre associated muscle hypertrophy in the colon, but the main effect of fibre was an increase in the number of crypts per circumference and also the number of branched crypts in the proximal colon in both groups. There was also a large increase in the number of branched crypts in the mid colon of the germ-free rats (both fibre-free and fibre supplemented). Fibre had a direct (bacteria independent) effect on goblet cells in the small intestine and a direct effect on the goblet cells in the colon, which was attenuated by the presence of bacteria. There was a notable decline in the number of enteroendocrine cells in the small intestine of the germ-free animals., Conclusions: Fibre has several direct and indirect effects on the gut. In the proximal colon it can directly increase the number of crypts present. This provides a means for increasing intestinal mass in addition to intestinal crypt cell production.

While the proliferative effects of gastrin in the gastric fundus are well established, there is a considerable degree of confusion regarding the role of gastrin on the growth of the small intestine and colon. The hypothesis that gastrin is trophic throughout the gut was tested by giving three doses of pentagastrin and one of gastrin 17 to rats maintained by total parenteral nutrition (TPN). The rats were fed intravenously for one week, with the various peptides added to the TPN diet. The number of vincristine arrested metaphases per gland or crypt was then scored to determine the proliferative state. Both gastrin 17 and pentagastrin were found to be trophic in the gastric fundus, but not to the gastric antrum. A proliferative response was also seen in the duodenum, but with little evidence of a dose response element. No effect on small bowel weight was seen, and no proliferative effect was noted in the mid small bowel, thus the duodenal effect could be attributed to a local action of increased acid output on the duodenum, not a general role throughout the small intestine. No proliferative effects of pentagastrin or gastrin were seen in the colon. It is therefore concluded that the trophic role of gastrin is restricted to the gastric fundus and the proximal duodenum.

Diet is of fundamental importance in the healthy functioning of alimentary epithelium, or during the disease process. Specifically, the incidence of 'non-hereditary' gastrointestinal disease varies widely throughout the world, partly because of different cultural and dietary habits. The aim of this review is to outline the mechanisms that modulate normal mucosal development and growth in the small and large intestine. In addition a brief mention will be made of morphological changes in certain pathological conditions.

Results from a recent, new assay suggest that omeprazole, a potent inhibitor of gastric acid secretion, is genotoxic. The principle of this assay is that the non-proliferating zone of surface gastric epithelial cells can be selectively removed by controlled digestion so that any incorporation of tritiated thymidine into these cells represents unscheduled DNA synthesis. Parietal cells (which are located below the uppermost proliferating cells) and proliferating cells in semiconservative, regular DNA synthesis could always be shown in the digested fraction, and as regular DNA synthesis takes up a thousand fold more thymidine than unscheduled DNA synthesis, any signal from unscheduled synthesis would therefore be swamped. The digestion process was also uneven, as histological analysis showed denuded patches of mucosa, and gland like structures were seen in the digest. Quantification of the number of silver grains over the nuclei showed no increase in low level labelling after omeprazole administration, indicating that there was no unscheduled DNA synthesis. The labelling index of undigested gastric tissue from omeprazole treated rats was not significantly different from that of the control group, despite an increase in the plasma gastrin value.

The wet weight of the stomach, small intestine, caecum, and colon were significantly reduced (p less than 0.001) in intravenously fed rats compared with orally fed controls. Human epidermal growth factor (urogastrone) reversed this atrophy. Detailed analysis of the small intestine showed a similar effect on intestinal crypt cell population, mitoses per crypt, and protein content. Brush border gamma glutamyltransferase and alpha glucosidase activities were reduced by up to 50% throughout the small intestine of the animals fed intravenously. The specific activities (mU/mg protein) were unchanged, as a concomitant decrease in the tissue weight and protein content also occurred. Intestinal brush border enzyme activities in the rats treated with urogastrone-epidermal growth factor were restored to those seen in the orally fed rats except for alpha glucosidase activity in the proximal gut. In addition, the specific activity of gamma glutamyltransferase was highly significantly increased (p less than 0.01) in all regions of the small intestine. Thus, although urogastrone administration prevents the decrease in brush border enzyme activity seen after the removal of luminal nutrition, the response seems to differ depending on the intestinal location, with the specific activities of some enzymes being higher than those seen in orally fed rats. Urogastrone-epidermal growth factor can thus significantly increase the functional ability of the intestine in addition to its trophic effects.

The relationship between the adaptive response and plasma PYY concentrations after small bowel resection has been investigated. Seventy five per cent proximal small bowel resection resulted in a rise in plasma PYY at six days from 28 +/- 3.1 to 85 +/- 12.3 pmol/l (p less than 0.001) and this difference was maintained to 48 days. Plasma PYY correlates both with crypt cell production rate (CCPR) in the ileum and with plasma enteroglucagon levels. In a second study, PYY or saline was infused over a 12 day period. There were no significant changes in intestinal wet weight or CCPR in any part of the bowel studied. This indicates that it is unlikely that PYY exerts a major trophic effect on the gastrointestinal tract.

Refeeding starved rats with a fibre free 'elemental' diet increased crypt cell production rate (CCPR) in the proximal small intestine but not in the distal regions of the gut. Little effect on CCPR was seen when inert bulk (kaolin) was added to the 'elemental' diet. Addition of a poorly fermentable dietary 'fibre' (purified wood cellulose) had little effect on intestinal epithelial cell proliferation except in the distal colon where it significantly increased CCPR. A more readily fermentable 'fibre' (purified wheat bran) caused a large proliferative response in the proximal, mid and distal colon and in the distal small intestine. A gel forming 'fibre' also stimulated proliferation in the distal colon. There was no significant correlation between CCPR and plasma gastrin concentrations, but plasma enteroglucagon concentrations were significantly correlated with CCPR in almost all the sites studied. Plasma PYY concentrations also showed some correlation with CCPR, especially in the colon. Thus, whilst inert bulk cannot stimulate colonic epithelial cell proliferation, fermentable 'fibre' is capable of stimulating proliferation in the colon, and especially in the distal colon: it can also stimulate proliferation in the distal small intestine and it is likely that plasma enteroglucagon may have a role to play in this process.

Intestinal cell proliferation and cell production is best quantified by measuring the rate of accumulation of vincristine arrested metaphases in microdissected intestinal crypts to determine the crypt cell production rate (CCPR). Studies of intestinal adaptation could be much more informative if a valid measure of intestinal function could also be included. One such method is the water absorption capacity. The CCPR of the jejunum and intestinal water absorption were measured in 19 groups of hypo and hyperproliferative rats which were in a 'steady state' of cell production and turnover. The minimum values were obtained after hypophysectomy and the maximum values were observed in lactation. Crypt cell production rate and absorption were significantly correlated (p less than 0.001) to each other. There was a significant (p less than 0.001) correlation between both CCPR and absorption and dry weight of the intestinal segment studies and food intake. Body weight was a poor predictor of either CCPR or absorption. The combined study of CCPR and water absorption is thus a practical and convenient approach to the study of intestinal cell proliferation and intestinal adaptation.

The effects of B-urogastrone/human epidermal growth factor on intestinal epithelial cell proliferation were studied in rats in which intestinal cell proliferation was reduced to a steady state basal level (by maintaining the rats on total parenteral nutrition). Increasing doses of urogastrone progressively raised the two hour collection of metaphases and intestinal weights. The crypt cell production rate was measured in animals maintained parenterally with or without urogastrone, and in rats fed a standard laboratory ration. Continuous infusion of 15 micrograms per rat per day of recombinant beta urogastrone (a dose which has a minimal effect on gastric acid secretion) significantly increased cell proliferation and intestinal tissue weights throughout the gastrointestinal tract. Intravenous infusion of urogastrone was also effective in restoring cell proliferation when it was infused after the intestine had become hypoproliferative. Urogastrone administered through an intragastric cannula thrice daily had no significant effect on either intestinal weight, crypt cell production rate, or metaphase collection.

The effects of the methyl ester analogue of prostaglandin E1, misoprostol, on gastric epithelial cell proliferation were investigated in six dogs given 300 micrograms/kg/day of misoprostol orally for 11 weeks and in six control dogs given placebo for 11 weeks. Misoprostol treatment resulted in a 36% increase in stomach weight (p less than 0.01) and a 30% increase in the length (measured as the cell column count from the base/neck junction to the surface) of the fundic gastric glands (p less than 0.01). This mucosal hyperplasia was predominantly caused by enlargement of the foveolar region of the gland, with little change occurring in the neck or in the isthmus. The hyperplasia was the result of an increased number of mitotic (p less than 0.01) and DNA synthesising cells (p less than 0.05) in each gastric gland, which resulted in a significant increase in the gland cell production rate, from 22.5 to 42.6 cells per gland per day (p less than 0.05).

Refeeding starved rats with an elemental diet resulted in a marked increase in crypt cell production rate (CCPR) in the proximal small intestine but not in the distal regions of the gut. Little effect on CCPR was noted when inert bulk (kaolin) was added to the elemental diet. Addition of a poorly fermentable dietary fibre (purified wood cellulose) had little effect on intestinal epithelial cell proliferation except in the distal colon where it significantly increased CCPR. A more readily fermentable fibre (purified wheat bran) caused a large proliferative response in the proximal, mid, and distal colon and in the distal small intestine. A gel forming fibre only significantly stimulated proliferation in the distal colon; the rats in this group, however, did not eat all the food given. There was no significant correlation between CCPR and plasma gastrin concentrations, but plasma enteroglucagon concentrations were significantly correlated with CCPR in almost all the sites studied. Plasma PYY concentrations also showed some correlation with CCPR, especially in the colon. Thus while inert bulk cannot stimulate colonic epithelial cell proliferation fermentable fibre is capable of stimulating proliferation in the colon, and especially in the distal colon: it can also stimulate proliferation in the distal small intestine and it is likely that plasma enteroglucagon may have a role to play in this process.

The aim of the present experiment was to investigate the role of hind gut fermentation in the proliferative response of the intestinal epithelium to dietary fibre. We have previously shown that refeeding starved rats with an elemental diet supplemented with fermentable dietary fibre (but not inert bulk) is capable of stimulating intestinal epithelial cell proliferation throughout the gastrointestinal tract. Three groups of 10 germ free (GF) rats and three groups of 10 conventional (CV) rats, were used. All groups were starved for three days and then refed for two days with either an elemental diet (Flexical); Flexical plus 30% kaolin; or Flexical plus 30% of a fibre mixture. Cell production was determined by the accumulation of vincristine arrested metaphases in microdissected crypts. There was no significant difference between refeeding the rats with an elemental diet alone or with kaolin supplementation, however, the addition of fibre in CV rats was associated with a significant increase in intestinal crypt cell production rate in both the small intestine (p less than 0.01) and the colon (p less than 0.001). This marked proliferative effects of fibre was abolished in the GF rats. It can be concluded that it is the products of hind gut fermentation, not fibre per se that stimulate intestinal epithelial cell proliferation in the colon and small intestine.

The effects of beta-urogastrone/human epidermal growth factor (URO-EGF) on intestinal epithelial cell proliferation were studied in rats in which intestinal cell proliferation had been reduced to a steady state basal level, by maintaining the rats on total parenteral nutrition. The accumulation of arrested metaphases over a two hour time period was determined in a dose response study. Increasing doses of URO-EGF progressively raised the two hour collection of metaphases and intestinal weights. Intravenous infusion of URO-EGF was also effective in restoring cell proliferation when it was infused after the intestine had become hypoproliferative. beta-urogastrone/human epidermal growth factor administered through an intragastric cannulae thrice daily had no significant effect on intestinal weight or crypt cell production rate or metaphase collection. It is proposed that one of the in vivo actions of urogastrone-epidermal growth factor is the maintenance of gastrointestinal growth and that this occurs through a systemic rather than a luminal mechanism.