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Biomedical subjects

R A Goodlad

Publications and source records attributed to R A Goodlad.

102 records · Page 6Linked to original sources
PubMed1987

Simultaneous measurement of intestinal crypt cell production rate and water absorption.

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.

Animals↗
PubMed1987

Proliferative effects of 'fibre' on the intestinal epithelium: relationship to gastrin, enteroglucagon and PYY.

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.

Animals↗
PubMed1987

Proliferative effects of urogastrone-EGF on the intestinal epithelium.

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.

Animals↗
PubMed1985

Urogastrone-epidermal growth factor is trophic to the intestinal epithelium of parenterally fed rats.

The weight of the stomach, small intestine and colon and the mucosal crypt cell production rate of these tissues were significantly decreased after 10 days on an isocaloric TPN diet when compared to orally fed controls. Continuous infusion of recombinant beta urogastrone, at a dose below that needed to inhibit gastric acid secretion, largely prevented this decrease in crypt cell production rate and gastrointestinal tissue weights.

Animals↗
PubMed1985

Is raised plasma peptide YY after intestinal resection in the rat responsible for the trophic response?

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.

Animals↗
PubMed1984

The effects of starvation and refeeding on intestinal cell proliferation in the mouse.

The effects of starvation and refeeding on intestinal cell proliferation were studied in four sites of the mouse intestine. Control mice were studied at different times of day in order to compensate for any circadian variations in proliferation. A circadian rhythm in crypt cell production rate was observed in all the sites of the small intestine and colon, and this rhythm appeared to be entrained to the food intake. The fractional crypt cell production rate decreased in all sites of the intestine after 24 h starvation, and remained low until 9 h after refeeding, when there was a marked increase in the crypt cell production rate of all the small intestinal sites, especially the proximal sites. There was little change in colonic crypt cell production rate until 12 h after refeeding, when there was a large increase in cell production. The crypt cell production rate of all sites then returned to control values for the remainder of the investigation. Crypt cell number decreased after refeeding and villus cell number increased, however a similar effect was observed in the control animals, nevertheless the changes in villus cell population of the refed mice occurred before any increase in crypt cell production, suggesting that cell migration from crypt to villi is not immediately dependent on cell proliferation.

Animals↗
PubMed1984

Relative contribution of Peyer's patches to intestinal DNA content and tritiated thymidine content of the mouse small intestine.

The quantification of mucosal DNA as a measure of epithelial cellularity has been criticized because it would include the non-epithelial cell populations present in the mucosa. The weight, DNA content and tritiated thymidine uptake of Peyer's patches and the remaining mucosa were measured and compared. Although the Peyer's patches only contribute 2.5% to the weight of the small intestine, they contained 12% of the DNA and 7% of the tritiated thymidine which would be found in a mucosal scrape.

Animals↗
PubMed1983

Cell proliferation, plasma enteroglucagon and plasma gastrin levels in starved and refed rats.

The effects of starvation and refeeding on intestinal cell proliferation at several sites of the rat gastrointestinal tract were studied and used as a model of altered cell proliferation in order to investigate the relationship between the rate of cell production and plasma gastrin and enteroglucagon. There was a marked fall in crypt cell production rate after four days starvation, with the proximal sites of the gut being most affected. The response to refeeding varied with site, suggesting that there was more than one mechanism for the control of intestinal cell proliferation. Plasma gastrin and enteroglucagon both fell to one fifth of their control level after starvation. Plasma gastrin increased slowly after refeeding, whilst plasma enteroglucagon increased rapidly to values significantly above control. Plasma gastrin was only correlated with crypt cell production in the duodenum, while plasma enteroglucagon was correlated with crypt cell production rate at several sites, indicating that enteroglucagon may be involved in the control of intestinal cell production.

Animals↗
PubMed1981

Some effects of diet on the mitotic index and the cell cycle of the ruminal epithelium of sheep.

The mitotic index of the ruminal epithelium increased rapidly when the diet of sheep was changed from one based on roughage to a concentrate-based diet. After several days the mitotic index declined to a new level which was slightly higher than that observed initially. Autoradiography of sections of rumen epithelium was used to construct percent labelled mitoses curves, from which the duration of the phases of the cell cycle was determined. The duration of the cell cycle was about 24 hr but decreased to 17 hr when cell proliferation was stimulated by changing the diet of the sheep from roughage to concentrate. The decrease in cell cycle time was mainly the result of the decreased duration of the phase of DNA synthesis (S phase). Data obtained from measurement of the cell cycle, together with the labelling index, were used to calculate the turnover times of the basal cell layer, and to estimate 'turnover' times for the entire epithelium. The mean turnover time for the epithelium was 16.5 days when sheep were fed a roughage-based diet, 10.9 days when fed a concentrate basal diet and 4.3 days when the sheep were in transition between the roughage and the concentrate diets.

Animals↗
PubMed1980

Digestion of epithelial tissue of the rumen wall by adherent bacteria in infused and conventionally fed sheep.

Comparisons were made, by light and electron microscopy, of the rumen epithelium of sheep fed conventionally and fed by infusion of volatile fatty acids and buffer into the rumen and casein into the abomasum. Similar bacterial colonization of the epithelium was observed in each case. The mitotic index of epithelial cells in infused sheep was high, as it was in barley-fed animals, while the mitotic index of cells from animals receiving roughage was low. The bacterial flora appeared to be actively digesting the epithelial cells. The fate of sloughed epithelial cells in the rumen fluid of sheep fed by infusion was also studied. The sloughed cells were rapidly digested, probably by their attached flora of facultatively anaerobic, highly proteolytic bacteria, leaving abundant highly keratinized remnants in rumen fluid. The importance of epithelial cell turnover and of proteolysis by partially facultative bacteria in the rumen is discussed.

Animal Feed↗