Infusion of lipid into the ileum delays the transit of a meal through the stomach and small intestine and could therefore influence the rate and degree of nutrient absorption. Experiments were carried out on human volunteers to investigate the effect of infusion of lipid into either the duodenum or ileum on blood glucose, insulin and gastric emptying after ingestion of a mashed potato meal. Infusions of lipid into either the duodenum or the ileum significantly reduced or abolished the immediate postprandial rises in blood glucose and insulin and significantly delayed gastric emptying. Blood glucose and insulin rose shortly after the lipid infusion terminated. Addition of corn oil to a meal of mashed potato also reduced blood glucose and insulin and delayed gastric emptying. Intestinal lipid can thus modify the glycaemic and insulinaemic responses to a meal, and this modulation probably explains the reduced metabolic responses to a meal containing fat compared with a fat free meal. This principle could be of value in the dietary control of diabetes mellitus.
Plasma and erythrocyte lithium levels have been determined repeatedly in twelve patients taking lithium carbonate for affective disorders. In any individual the plot of the plasma lithium level against erythrocyte/plasma ratio is linear, but the ratio can either increase or decrease with increasing plasma lithium concentration. Erythrocyte/plasma ratio is an unsound basis for comparing individual responses to lithium.
The reduction in the conversion of ornithine to proline by fibroblasts from a patient with hyperornithinaemia with hyperammonaemia and homocitrullinuria cannot be explained by a reduced uptake of exogenous ornithine, an altered total intracellular ornithine content, or reduced conversion of gamma-glutamate semialdehyde to proline. However, neither could the postulated defect in mitochondrial ornithine uptake be demonstrated using the digitonin method. Increasing the ornithine concentration in the medium increased the incorporation of 14C label from ornithine into protein in both the patient's and control cells. In the patient's cells the apparent Km for ornithine was ten times that of the controls, although the Vmax values were comparable. This result parallels the clinical response to ornithine supplementation.
Five patients suffering from periodic affective disorders with short mood-cycles were treated with rubidium chloride, producing peak erythrocyte concentrations between 9 and 13 mmol/l. Loading with rubidium was associated with decreased total body potassium, but red-cell potassium was unchanged. Regular mood-cycling was disturbed, together with the associated body-weight changes. There was a slight extracellular "metabolic" acidosis. Electrolyte concentrations fluctuate abnormally in these patients, and two muscle biopsy specimens had very low potassium contents.
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