The activities of surfactant ions (aD) and counterions (aNa) were directly obtained by the EMF measurement of a concentration cell with an ion-exchange membrane and by pNa measurements respectively for aqueous solutions of sodium dodecyl sulfate (NaDS) below and above the CMC. The mean activity and activity coefficient were also calculated. From these data, together with the surface tension (γ) measured by the Wilhelmy method and the amount of adsorption (Γ) measured by the radiotracer method, the following results were obtained: (1) Mean activity was not constant, but increased with the concentration above the CMC. (2) The Gibbs adsorption isotherm was directly verified from the aD and aNa  vs. concentration relations. (3) The decrease in γ observed above the CMC was in agreement with that calculated from the activity data. (4) The logaD  vs. logaNa plots above the CMC showed a linear relation, indicating the validity of the charged phase separation model as the mechanism of micelle formation. The degree of the counterion attachment of the micelles was found to be 0.73 up to about 80 mmol/l. (5) The intermicellar concentrations of Na+ and DS− ions were calculated; the former increases, while the latter decreases with the concentration. (6) The product of the concentration with an osmotic coefficient was linear with the concentration above the CMC, tangent of the slope being about 0.7.

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Lactosylceramide synthase is an enzyme that catalyzes the transfer of galactose from UDP-Gal to glucosylceramide, and thus participates in the biosynthesis of most glycosphingolipids in mammals. We purified this enzyme over 61,000-fold to near homogeneity with a 29.7% yield from rat brain membrane fractions. The isolation procedure included solubilization with Triton X-100, affinity chromatography on wheat germ agglutinin-agarose and UDP-hexanolamine-agarose, and hydroxylapatite column chromatography, followed by ion exchange chromatography. The final preparation migrated as a broad band with an apparent molecular mass of 61 kDa on SDS-polyacrylamide gel electrophoresis. This apparent molecular mass was reduced to 51 kDa by N-glycanase digestion, suggesting that the enzyme has a glycoprotein nature. The enzyme required Mn 2؉ for its activity, and glucosylceramide was its preferred substrate. The cDNA for the enzyme was cloned from a rat brain cDNA library. The cDNA insert encoded a polypeptide of 382 amino acid residues, with a molecular weight of 44,776. The polypeptide contained eight putative glycosylation sites and a 20-amino acid residue transmembrane domain at its N terminus. Amino acid sequence homology analysis revealed that this enzyme shared 39% homology with mouse ␤-1,4-galactosyltransferase (EC 2.4

In order to clarify the possible role of lipids in the water-holding property of stratum corneum, the forearm skin of 6 healthy male volunteers was treated with acetone/ether (1/1) for 1, 5, 10, and 20 min. A prolonged treatment period of 5-20 min produced a chapped and scaly appearance of the stratum corneum without any inflammatory reactions. Under these conditions, there was a marked decrease in the water-holding capacity of the stratum corneum accompanied by a considerable and selective loss of intercellular lipids such as cholesterol, cholesterol esters, and phospholipids. These impairments persisted until day 4 after treatment. Electron microscopic observation of the altered stratum corneum revealed that naturally occurring intercellular materials were absent, leaving the area with the appearance of a vacant space. These findings suggest an additional and essential role of the specific structural lipids for the water-holding properties of the stratum corneum.

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