Acute isodense epidural hematoma on computed tomography.

Computed tomography (CT) has proven to be invaluable in the diagnosis of craniocerebral injuries. Acute epidural hematomas have been described as having a characteristic appearance on CT of a lenticular shaped area of blood density most commonly situated over the cerebral convexity. This case demonstrates an acute epidural hematoma that is essentially isodense with brain tissue.

Studies on the interaction of cholesterol with diester- and dietherlecithin.

The lamellar repeat distances of aqueous dispersions of rac-1,2-dioctadec-9'-cis-enyl-glycero-3-phosphorylcholine (dietherlecithin) and 1,2-dioctade-9'-cis-enoyl-sn-glycero-3-phosphorylcholine (diesterlecithin) have been measured by X-ray diffraction as a function of water concentration. The point of maximum hydration was found to be 43% (w/w) for dietherlecithin and diesterlecithin respectively; the corresponding lamellar repeat distances being 62.3 å and 60.5 ã. Incorporation of cholesterol above maximum hydration results in the initial increase in the lamellar repeat distance with a maximum around cholesterol concentrations of 25 and 33 mol% for dietherlecithin and die diesterlecithin respectively. The apparent partial specific volumes fo the two lecithins and for lecithin--cholesterol mixtures in sonicated aqueous dispersions were measured. Values of 1.024 cm3-g-1 and 0.987 cm3-g(-1) were obtained for diether- and diesterlecithin, respectively, at 20 degrees C. Diesterlecithin-cholesterol mixtures showed a very small change in partial specific volume while mixtures of dietherlecithin-cholesterol showed a very marked decrease with increasing proportions of cholesterol. From these data a series of structure parameters are derived for the two lecithins and possible implications for the nature of the lecithin-cholesterol interaction are discussed.