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Biomedical subjects

D M Matthews

Publications and source records attributed to D M Matthews.

At least 55 records · Page 3Linked to original sources
PubMed1983

Trans-mucosal passage of intact peptides in the guinea-pig small intestine in vivo: a re-appraisal.

1. Re-examination of data for the chemical analysis of peptide-bound amino acids in the mesenteric venous blood of anaesthetized guinea-pigs suggests that there are small, but significant, amounts of small peptides in the blood of fasted animals. 2. Furthermore, there is a significant increase in the peptide content of the mesenteric venous blood during intraduodenal infusion of a partial digest of casein. 3. The data are consistent with the view that some 10% of the amino nitrogen entering the mesenteric blood during absorption of a casein digest in vivo may be in the form of small peptides, although it is not possible to define confidence limits for this estimate.

Amino Acids↗
PubMed1980

Driving and insulin-dependent diabetes.

A survey of 250 patients with insulin-dependent diabetes (IDD) holding a full motor vehicle driving licence revealed that 107 (42.8%) had not declared IDD on their application for a driving licence. 70 of these (28% of entire group) claimed that they were unaware of the statutory requirements. There was no difference in the declaration-rate between men and women. 159 patients (66%) declared IDD for their motor insurance. 86 patients (34.4%) had had severe or frequent hypoglycaemia in the preceding six months, during which they had been driving regularly. 34 patients (13.6%) admitted involvement in a driving accident since commencing treatment with insulin, and 13 of these patients were aware that hypoglycaemia had been an important causal factor. The prevalence of diabetic retinopathy and cataracts was considerable, but few patients (2.4%) had severe impairment of vision in both eyes.

Accident Prevention↗
PubMed1980

Kinetics of uptake of lysine and lysyl-lysine by hamster jejunum in vitro.

1. The kinetics of 2-min uptake of L-lysine and L-lysyl-L-lysine have been studied by using rings of everted hamster intestine in vitro, and values for Kt and Vmax. established. 2. On a molar basis, mediated uptake was more rapid for the amino acid than for the peptide. Non-mediated uptake was more rapid for the peptide than for the amino acid. 3. Comparison of relative rates of uptake of lysine from equivalent solutions of lysine and lysyl-lysine showed that at low concentrations, uptake of lysine was less rapid from the peptide than from the amino acid, whereas at high concentrations, uptake of lysine was more rapid from the peptide than from the amino acid. This type of effect of concentration on relative rates of uptake from equivalent solutions of amino acid and peptide has not previously been described.

Animals↗
PubMed1979

Interference by methylcobalamin analogues with synthesis of cobalamin coenzymes in human lymphocytes in vitro.

1. 72 h uptake of cyano[57Co]cobalamin and formation of 57Co-labelled methylcobalamin, adenosylcobalamin and hydroxocobalamin has been estimated with and without the addition of methylcobalamin analogues in phytohaemagglutinin-stimulated lymphocytes from healthy human subjects. 2. Difluorochloromethylcobalamin reduced cell uptake of cyanocobalamin and caused a disproportionate reduction in synthesis of adenosylcobalamin. 3. Methylcobalamin-palladium trichloride reduced cell uptake of cyanobalamin more effectively than did difluorochloromethylcobalamin and reduced the formation of methylcobalamin, adenosylcobalamin and hydroxocobalamin in proportion. 4. The results suggest that in addition to inhibiting uptake of cyanocobalamin, one or both compounds may have interfered directly with the mechanism of synthesis of the cobalamin coenzymes.

Cobamides↗
PubMed1979

Intestinal handling of two tetrapeptides by rodent small intestine in vitro.

Uptake of free Leu and Ala and uptake of these amino acids from the tetrapeptides Leu-Gly-Gly-Gly and Ala-Gly-Gly-Gly has been studied in rings of everted rodent jejunum in vitro. When mediated uptake of free Leu was virtually saturated addition of Leu-Gly-Gly-Gly gave no significant increase in uptake of Leu. Uptake of Leu and of Ala from the tetrapeptides was strongly inhibited by Met, as was uptake of these amino acids from free solution. The results did not suggest that either tetrapeptide was taken up intact by the jejunum.

Alanine↗
PubMed1979

Effects of low cobalamin diet and chronic cyanide toxicity on cobalamin distribution in baboons.

This paper reports the bodily distribution of total cobalamin and individual cobalamins at the termination of an experiment on the effects of a low cobalamin diet and chronic cyanide or thiocyanate administration in baboons. The results show that the distribution of cobalamins in the tissues of the baboon can be altered by a low cobalamin diet and also by chronic intoxication with cyanide, whether or not the animals are on a low cobalamin diet. All animals on the low cobalamin diet showed a reduction in total and individual cobalamins. In blood plasma and erythrocytes, kidney, spleen, testis and brain, the proportion of methylcobalamin tended to be disproportionately reduced in cobalamin-depleted animals. This reduction was lessened or prevented by the administration of cyanide. Neither cyanide not thiocyanate produced a significant increase in the proportion of cyanocobalamin in plasma, though thiocyanate produced a large increase in cyanocobalamin in erythrocytes. In liver, cyanocobalamin was more than doubled by the administration of cyanide to cobalamin-depleted animals.

Animals↗
PubMed1979

Kinetics of mucosal influx of glycylsarcosine, glycine and leucine into hamster jejunum and ileum in vitro.

1. This paper describes an investigation of the kinetics of influx of the dipeptide glycylsarcosine and the amino acids glycine and L-leucine into rings of everted hamster small intestine in vitro, in proximal and distal small intestine (jejunum and ileum). Results were expressed per unit wet weight of intestine. 2. At all concentrations studied (0.1--100 mmol/l), influx of glycylsarcosine was more rapid in the jejunum than in the ileum. In contrast, at all concentrations studied, influx of glycine and leucine was more rapid in the ileum than the jejunum. 3. Estimates of the simple diffusion component in total influx were made. This component became increasingly large as the substrate concentration was raised. After correction for simple diffusion, transport of all three substrates conformed to Michaelis-Menten kinetics in both jejunum and ileum. Values for simple diffusion, apparent Kt and Vmax, are reported. 4. Possibly physiological implications of the results are discussed, and it is pointed out that under experimental conditions similar to our own, simple diffusion is too large a component in total influx to be ignored.

Animals↗
PubMed1979

Superior vena caval stenosis: a complication of transvenous endocardial pacing.

Superior vena caval obstruction is a rare complication of transvenous endocardial pacing and is usually the result of thrombus formation round the pacing electrode (Kosowsky and Barr, 1972). We report a case of superior vena caval obstruction without thrombus formation secondary to localised stenosis at the site of the proximal cut end of a retracted endocardial electrode. This complication of transvenous pacing electrodes has not been described previously.

Constriction, Pathologic↗