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D H Smyth

Publications and source records attributed to D H Smyth.

At least 19 recordsLinked to original sources
PubMed1974

The effect of fasting on hexose transfer in rat intestine.

1. A technique has been developed whereby accurately defined segments of rat intestine can be isolated in vivo, and this technique was used to study the influence of fasting on hexose transport.2. In the distal ileum the transport of glucose and galactose was stimulated by fasting. The effect was specific as neither amino acid transport nor the permeability of the luminal membrane of the absorbing epithelium was altered by fasting. The increased hexose transport was accompanied by a reduced accumulation of hexose in the gut wall. In the proximal jejunum hexose transport was not stimulated by fasting.3. The results of in vitro experiments show the relative importance of hexose metabolism in providing energy for transport in different regions of the small intestine in both fed and fasted animals. In conditions where hexose metabolism was reduced, e.g. by fluoride, the proximal jejunum behaved more like the distal ileum and a stimulation of hexose transport in response to fasting was demonstrable in vivo.4. Motility studies showed that phenol red introduced into the stomach reached the ileum sooner, achieved a higher concentration and remained there for a longer period of time in the fasted animal.5. The changes in carbohydrate metabolism, hexose transport capacity and gastrointestinal motility are discussed in relation to adaptations of the rat to fasting.

Animals↗
PubMed1972

Metabolism and transfer of choline in hamster small intestine.

1. The transfer and metabolism of choline was studied with sacs of everted intestine of hamster.2. Approximately half the choline transferred from the mucosal fluid may be metabolized. High voltage electrophoresis, paper chromatography and ion exchange chromatography have been used to identify this meta bolite as betaine.3. The concentration of choline and betaine together accumulating in the gut wall and serosal fluid are greater than that of choline present initially in the mucosal fluid indicating some kind of specific mechanism for choline transport.4. A detailed analysis of choline transfer suggests that the movement of choline cannot be accounted for by simple diffusion. The concentration of choline accumulating in the gut wall and serosal fluid, the inhibitory effects of hemicholinium-3 and alpha-methylglucoside on choline transfer, and the insensitivity of betaine transfer to hemicholinium-3 suggest a specific active transport process for choline independent of active betaine transport.

Animals↗
PubMed1971

Transfer of alanine isomers by rat small intestine.

1. A study was made of the transfer of L-alanine, D-alanine and beta-alanine by sacs of everted small intestine of the rat.2. D-Alanine and beta-alanine are transported against a concentration gradient and in this respect resemble L-alanine.3. Transfer of all three isomers was stimulated in presence of glucose, but stimulation was much greater with D-alanine and beta-alanine.4. Transfer of all three isomers was inhibited by galactose.5. The effect of hexoses on amino acid transfer was relatively independent of the effect on fluid transfer.6. L-Methionine inhibited transfer of the three isomers in descending order, L-alanine, D-alanine and beta-alanine, while the magnitude of sarcosine inhibition was in the reverse order.7. At the concentration used (1 mM), L-alanine was transferred mostly by the methionine carrier, and beta-alanine mostly by the sarcosine carrier. D-Alanine occupied an intermediate position.

Alanine↗
PubMed1971

Intestinal transfer of choline in rat and hamster.

1. The transfer of choline was studied with sacs of everted intestine of rat and hamster.2. The choline transfer can be divided into two components, a diffusion process and a saturable process. The latter plays a relatively greater part at low concentrations of choline, which include the physiological concentration in the plasma. The saturable process is better seen in the hamster than in the rat.3. Intestinal transfer of choline is influenced by substances altering the availability of energy in the cell, and by some substances chemically or pharmacologically related to choline. These findings are consistent with some kind of specific mechanism for choline transfer.4. Part of the choline taken up by the cell appears as a metabolite not yet identified. The formation of the metabolite is a saturable process and is abolished by anaerobic conditions and by homogenization.5. The results are also discussed in relation to parameters of transfer.

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