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Biomedical subjects

J D Grant

Publications and source records attributed to J D Grant.

15 recordsLinked to original sources

Assessment of lactose absorption by measurement of urinary galactose.

Individuals with sufficient intestinal lactase hydrolyze ingested lactose to galactose and glucose and these monosaccharides are absorbed. Lactose is not digested completely when intestinal lactase activity is low and the disaccharide is malabsorbed. Breath hydrogen excretion after lactose ingestion is used commonly to diagnose lactose malabsorption. However, no direct tests are currently used to assess lactose absorption. We tested a new method of assessing lactose absorption in 26 healthy individuals. Each subject ingested 50 g of lactose. Participants were evaluated for lactose malabsorption using a standard 3-h breath hydrogen test. In addition, the urinary excretions of galactose, lactose, and creatinine were quantitated for 3-5 h after lactose ingestion. On the basis of breath hydrogen analysis after lactose ingestion, 12 individuals were lactose malabsorbers (defined as a rise in the breath hydrogen concentration of greater than 20 parts per million above the baseline value). The 14 subjects who did not malabsorb lactose by breath hydrogen testing (defined as a rise in the breath hydrogen concentration of less than or equal to 20 parts per million above the baseline value), had significantly more galactose in their urine 1, 2, and 3 h after lactose ingestion than lactose malabsorbers. The ratio of excreted lactose to excreted galactose was significantly decreased in lactose absorbers compared with lactose malabsorbers (p less than 0.001). Determination of the ratio of urinary galactose to urinary creatinine separated lactose absorbers from lactose malabsorbers completely (p less than 0.001). We conclude from this study that the determination of urinary galactose, urinary lactose/galactose ratio, and urinary galactose/creatinine ratio may be used to assess lactose digestion and absorption in healthy adults.

Adolescent

Plasma concentrations of delta-9-tetrahydrocannabinol and impaired motor function.

Fifty-nine volunteer subjects were allowed to smoke marijuana cigarettes until a satisfactory level of 'high' was obtained. They then had blood samples taken 5, 30, 90 and 150 min following smoking after which they were tested with the roadside sobriety test. Attempts to correlate passing or failing on three coordination tests with plasma concentrations of delta-9-tetrahydrocannabinol (THC) showed that if concentrations measured at 5 min were ignored, failures were almost inevitably associated with plasma concentrations of THC above 25-30 ng/ml. Overall, 94% of subjects failed to pass the test 90 min after smoking and 60% after 150 min, despite the fact that by then plasma concentrations were rather low. It would seem that establishing a clear relation between THC plasma concentrations and clinical impairment will be much more difficult than it has been for alcohol.

Adult

Significant developments in radioimmune methods applied to delta 9-THC and its 9-substituted metabolites.

Novel RIA's have been developed for marijuana detection. Modified simple techniques measure the "acute" metabolites in minute saliva, breath, and dried blood samples. Solid purified antibody matches the sensitivity and yields sensitivity values identical to liquid assays. The importance of the polar 9-substituted metabolites (9SM) of THC in acute users is shown by time course data that indicate their levels remain high in the critical post-intoxication period when delta 9-THC clears from the blood. Therefore a single-tube assay using solid-phase reagents was constructed to quantitate simultaneously delta 9-THC and 9SM. When delta 9-THC values are low or questionable in subject samples, 9SM would appear useful to confirm or refute acute marijuana use.

Animals

delta 9-Tetrahydrocannabinol by GLC-MS validated radioimmunoassays of hemolyzed blood or serum.

A direct radioimmunoassay (RIA) of delta 9-tetrahydrocannabinol (delta 9-THC) in unextracted hemolyzed blood or serum is described. The dose-response curve in the range of 5-50 ng/mL (serum or blood) was linear on log-logit transformation and iterative weighted regression. Validation studies included testing for precision, accuracy and antibody specificity as well as confirmation of RIA results (marijuana smoker samples) by gas liquid chromatography-mass spectroscopy (GLC-MS). This routine method will greatly augment cannabinoid investigative programs.

Animals