Determination of 8-methoxypsoralen in plasma by scanning fluorometry after thin-layer chromatography

A rapid and sensitive method is described for determining 8-methoxypsoralen in plasma. Plasma samples are acidified with 6 mol/liter and heated in a boiling water bath to release the plasma-bound drug nondestructively. It then is extracted into a solvent mixture consisting of benzene/ethyl acetate (9/1 by vol). The solvent phase is separated, evaporated, and an aliquot of the dissolved residue is thin-layer chromatographed, with benzene/ethyl acetete (9/1) as developing solvent. The plate is dried and the spots, made visible under ultraviolet light (320-400 nm), are scanned. The smallest amount detectable is 20 ng; the overall analytical recovery from plasma is 84%. We used the method to determine the drug in the plasma of rabbits after intravenous and oral administration of 10 mg, and in one patient after an oral dose of 30 mg.     

Relapsing polychondritis studied by computed tomography

Computed tomographic findings in a patient with relapsing polychondritis are described. Collapse of the cartilage of the nose and calcification in cartilages of the ears were clearly demonstrated. CT scanning was also helpful in evaluating the tracheobronchial tree for airway compromise, which could prove fatal in this condition.     

Sex differences in voluntary fluid intake by older adults during exercise

PURPOSE: This study compared the voluntary fluid intake behavior of older men and women (54-70 yr) when provided cold, palatable beverages and ample opportunity to drink between repeated bouts of exercise in the heat. METHODS: Thirteen men and 14 women performed four bouts of 15-min cycling at 65% VO2peak followed by 15 min of rest at 30 degrees C and 50% relative humidity. In separate trials, subjects drank either a carbohydrate-electrolyte solution (CES) or water ad libitum during the rest periods and were unaware that their fluid intake was being measured. RESULTS: Fluid intake behavior was repeatable (intraclass correlation coefficient = 0.75), and subjects drank enough of either beverage to match sweating rates and maintain their body mass (BM). Fluid intake per kilogram of BM was greater with CES (18.7 +/- 2.2 vs 15.1 +/- 2.1 mL x kg(-1); P < 0.05), and plasma volume (PV) was better maintained during the CES trials (-1.3 +/- 1.1 vs -4.2 +/- 1.1% during the second half of the session). Women drank significantly more water than the men on a per kilogram basis (17.2 +/- 2.9 vs 12.8 +/- 1.7 mL x kg(-1) BM), and one woman (BM = 45.7 kg) became hyponatremic (S(NA) = 126 mmol x L(-1)) with symptoms during the water trial. CONCLUSION: Older adults drank enough to maintain fluid balance when palatable fluid was readily available; however, CES promoted greater voluntary fluid intake and restored PV losses faster than water. In addition, older women drank more water than men during interval exercise in the heat, which may put smaller women at an increased risk for developing hyponatremia.