Improved Screening Test for Idiopathic Infantile Hypercalcemia Confirms Residual Levels of Serum 24,25-(OH) D in Affected Patients.

CYP24A1 mutations are now accepted as a cause of idiopathic infantile hypercalcemia (IIH). A rapid liquid-chromatography tandem mass spectrometry (LC-MS/MS)-based blood test enabling measurement of the 25-OH-D :24,25-(OH) D ratio (R) can identify IIH patients on the basis of reduced C24-hydroxylation of 25-OH-D by CYP24A1 in vivo. Although values of this ratio are significantly elevated in IIH, somewhat surprisingly, serum 24,25-(OH) D remains detectable.

A hydrodynamic approach to the measurement of the permeability of small molecules across artificial membranes.

An in situ analytical approach to the measurement of supported liquid membrane permeability is reported. The method consists of a spectrophotometric method to measure transport through a membrane-supported lipid solution, using a rotating-diffusion cell configuration to overcome limits arising from transport through the aqueous solution boundary layer in stationary systems. Rotation frequencies are almost two orders of magnitude higher than those employed previously for rotating-diffusion studies of membrane transport.