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R J Neale

Publications and source records attributed to R J Neale.

44 records · Page 3Linked to original sources
PubMed1969

The use of dietary-restricted rat intestine for active transport studies.

1. The effect of dietary restriction (sufficient to produce a loss of about 32% of initial body weight) on intestinal active transport has been studied in the rat by the use of sacs of everted mid-small intestine. Eight D-sugars, four L-sugars and two D-amino acids were employed.2. Dietary restriction enhanced the normally occurring active transport of D-galactose, 3-O-methyl-D-glucose and D-methionine. In addition, sacs of dietary-restricted small intestine were able to concentrate in the serosal fluid D-fucose, D-xylose and D-histidine, which sacs of normal rat intestine could not do. The final (1 hr) serosal/mucosal concentration ratios produced for these actively transported substances were independent of net water movement.3. Sugars which were not concentrated in the serosal fluid of sacs of fully fed or dietary-restricted intestine were D-arabinose, D-fructose, D-glucosamine, D-mannose, L-arabinose, L-fucose, L-sorbose and L-xylose.4. The characteristics of D-fucose and D-xylose active transport suggest that they are transported by the mechanism which actively transports D-glucose. The comparatively low content of D-glucose in dietary-restricted intestine, compared with fully fed intestine, may be part of the explanation for observable active transport of D-fucose and D-xylose by dietary-restricted sacs.5. Thinning of the intestinal wall is believed not to be the cause of the enhanced active transport found during dietary restriction.6. The results show that dietary-restricted rat small intestine may, at times, be more useful than fully fed rat small intestine in the study of intestinal active transport.

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PubMed1968

Active transport of L-glucose by isolated small intestine of the dietary-restricted rat.

1. The effect of semistarvation and complete starvation (sufficient to produce a loss of about 32 and 25% respectively of initial body weight) on the active transport of L-glucose has been studied by the use of sacs of everted mid-small intestine of rats. The animals were allowed free access to water.2. Sacs from animals on a restricted diet transported L-glucose against its concentration gradient, but sacs from fully fed rats did not. Even when sacs from fully fed rats were distended sufficiently to cause them to lose serosal volume, the L-glucose concentration in the final serosal fluid was never greater than that in the final mucosal fluid.3. The L-glucose active transport was independent of net water movement, needed oxygen, was not demonstrable at 27 degrees C, and required Na ions at a concentration of 83 mM or greater. It could be completely inhibited by 10(-6)M phlorrhizin, or 10 mM L-histidine, or 1.39 mM D-glucose. Phlorrhizin at a concentration of 10(-8)M reduced, but did not prevent, L-glucose active transport.4. It seems probable that L-glucose active transport is mediated by the mechanism that actively transports D-glucose.5. Un-incubated mid-small intestine of fully fed rats contained 37.8 mg D-glucose/100 g wet wt. of tissue, whereas semistarved intestine had only 10.8 mg D-glucose/100 g. The lack of demonstrable active transport of L-glucose by normal intestine may possibly have been caused, at least in part, by inhibition of the process by endogenous D-glucose.6. There appeared to be no metabolism of L-glucose by rat intestine, nor conversion to the D-form.7. The hypothesis that sugars require the D-pyranose ring structure for active absorption is no longer tenable.

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