ABSTRACTS 373 Evaluation of facial care products Michael S. Christensen, Ph.D., Vick Divisions Research Development, One Far Mill Crossing, Shelton, CT 06484. The facial skin of many individuals is excessively oily or excessively dry. Skin care products thus need to be compatible with either oily or dry skin. This holds true whether the formulations are for cosmetic purposes only or for delivery of thera- peutic (acne) or prophylactic (sunscreen) agents to the skin. Formulating such compatible products requires accurate, objective assessment of oiliness in-vivo. Oiliness is assessed by measuring skin surface friction this characteristic varies on dif- ferent parts of the face and it may be altered by product application. Dryness is assessed by measur- ing the tautness of the stratum corneum which may result, for example, from ordinary washing with soap and water, or from application of products which have a drying effect on the skin. In this assessment, we use a gas-bearing electrodynamom- eter suitably adapted for measurements on the face. These objective measurements correlate well with clinical appraisals of oiliness and dryness, and the comparison has shown that differences that can be perceived by product users are easily measured by our instrumentation. SOCIETY OF COSMETIC CHEMISTS FRONTIERS OF SCIENCE LECTURE H. Gobind Khorana, Ph.D., Massachusetts Insti- tute of Technology, Cambridge, MA 02139. This lecture contains four parts. 1) Origins of Nucleic Acids. Since the discovery of nucleic acids in 1869, work progressed for about 80 years on the develop- ment of their chemical structures: the chemistry of pyrimidines and purines, nucleosides and nucleo- tides. This culminated in the elucidation of the polynucleotidic structures in 1953 and this, in turn, led to the Watson-Crick model. A second indepen- dent development relates to the biological func- tions of the nucleic acids and in particular their role as genetic material and the participation of a variety of nucleotide intermediates in intermediary meta- bolism. 2) The Synthesis of Nucleic Acids. Work on the chemical synthesis of nucleic acids began in the 50's and 60's and the main steps in the development are reviewed. 3) The Genetic Code. A combination of biochemical methods and chemical synthesis led to the elucidation of this central biological problem. A brief review of the solution to this problem is given. 4) Total Synthesis of Genes and IVork on Recombinant DNA. In more recent years, methods have been developed for the total synthesis of genes as well as for the sequence determination of nucleic acids. The two together have led to exciting new developments in the work on recombinant DNA. The last part of the lecture is devoted to principles of some of the current work involving techniques of recombinant DNA. SYMPOSIUM ON LIPIDS Stratum corneum lipids Peter M. Elias, M.D., Veterans Administration Medical Center, 4150 Clement Street, San Francis- co, CA 94121. Evidence from freeze-fracture replicas of several mammalian stratified squamous epithelia provides the first solid clue that the stratum corneum is a two-compartment system of lipid-depleted cells embedded in multi-lamellar lipid domains. Rela- tively complete lipid biochemical data are now available from human, pig, and neonatal mouse stratum corneum all suggest that the stratum corneum is devoid of phospholipids, but enriched in several neutral lipids and sphingolipids. During progression from the inner to the outer stratum corneum, additional changes in composition prob- ably occur cholesterol sulfate is desulfated to cholesterol, and glycolipids are deglycosylated to ceramides. Specific enzymes that catabolize both of these processes have been found in the outer epidermis. Evidence is growing that these biochem- ical transitions are important for the formation of a water-resistant barrier and for stratum corneum cohesion desquamation. The two-compartment model also has other important implications for pathways of percutaneous transport, reservoir effects, vehicle delivery systems, and the water- holding capacity of the stratum corneum that are discussed. The structure and physiological role of lipids in the epidermal barrier to percutaneous water loss Donald T. Downing, Ph.D., Philip W. Wertz, Ph.D., University of Iowa College of Medicine, Iowa City, IA 52242. It has long been recognized that the epidermal barrier to water lbss possessed by terrestrial verte- brates is dependent upon the lipids of the stratum corneum. Studies have shown that the lipids exist principally in the spaces between horny cells and consist predominantly of highly polar, non-phos- phorus-containing structures. The stratum corneum lipids consist of cholesterol, free fatty acids, ceram- ides and gangliosides. In the living cells of the epidermis there is in addition a series of glucosyl- ceramides. The authors have now determined the structures and detailed composition of each of the series of ceramides and glucosylceramides from pig epidermis. As a result, the structure and location of

374 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS the least polar glucosylceramide has suggested a specific role in assembly of the lameliar granules in the epidermal granular cells. Epidermal tissues of birds and reptiles have also been found to contain lameliar granules and ceramides, gluco- sylceramides, and gangliosides. However, in these animals, unlike mammals, much of the polar lipid remains within the cells when they keratinize and the glucosylceramides are not lost from the keratinized tissues. Nevertheless, it is the polar lipids which appear to constitute the barrier to water loss in all of the terrestrial vertebrates the nonpolar lipids, such as those produced by the sebaceous glands in mammals, the preen glands in birds, and the epidermis in reptiles, do not contribute significantly to the water barrier. Sebum: composition and secretion rate Derek R. Highley, Ph.D., Mary Kay Cosmetics, Inc., 1330 Regal Row, Dallas, TX 75247. Methodology for the accurate and reproducible determination of sebum composition and secretion rate is of considerable interest. This is because of the role of sebum in the etiology of ache and the number of cosmetic products that are designed to overcome its negative effects on the appearance of skin and hair. Implicit in the validity of methods used to measure sebum secretion rate is the assumption that the rate of secretion is independent of the amount of sebum or surface lipid present on the skin surface. The gravimetric and photometric techniques are most frequently employed to mea- sure this phenomenon. Both have advantages and drawbacks. Thin layer chromatography is used for qualitative and quantitative analysis of sebum and surface lipid composition. Infrared spectroscopy is also used as a qualitative measure. The techniques related to the measurement of sebum secretion rate and to the analysis of sebum and surface lipid are discussed in detail. Advantages, shortcomings and precautions required are emphasized. Some factors affecting the perception of hair oiliness James L. Solan, Gillette Research Institute, 1413 Research Blvd., Rockville, MD 20850. The appearance of human hair changes with time after washing until a point is reached where it is perceived to be oily. This is a consumer-perceived attribute and represents the interaction of a number of objective physical hair properties, rather than a unique measurable property. Some of the important factors include the amount, type, and excretion rate of lipid material, lipid properties, sweat compo- nents, endogenous and exogenous particulate deposits and hair geometry, density and spacing. A discussion of all of these factors being beyond the scope of this paper, attention is focused on certain of these hair properties, and experimental tech- niques for hair condition assessment as well as for collection and evaluation of hair soil are described. Statistical techniques employed to determine the interaction of the many factors involved in the oily condition and the identification of the dominant parameters are described. In addition, the results of initial attempts to develop a mathematical relation- ship between the relevant physical properties are presented.