Biomedical subjects

S W Colton

Publications and source records attributed to S W Colton.

10 recordsLinked to original sources

PubMed1987

Skin lipids: an update.

The stratum corneum lipids, responsible for the epidermal water barrier, consist principally of ceramides, cholesterol, cholesteryl sulfate, and free fatty acids. These lipids are arranged in multiple intercellular lamellae that provide an efficient water barrier because of the crystalline array of the straight and predominantly saturated lipid chains. Interlamellar linkages provided by lipids based on 30-carbon omega-hydroxyacids may be responsible for holding together the intercellular lamellae as well as for assembly of the lamellar granules of the granular cells. The normally ordered exfoliation of corneocytes as they arrive at the surface seems to require hydrolysis of the cholesteryl sulfate to free cholesterol. The sebaceous glands secrete continuously, producing sebum that consists predominantly of triglycerides, wax esters, and squalene. High rates of sebum production per sebocyte result in low levels of linoleate in the sebaceous esters, subjecting the follicular epithelium to essential fatty acid deficiency and the characteristic hyperkeratosis that results in comedo formation. Suppression of sebum production by drugs elevates sebum linoleate concentration and relieves follicular hyperkeratosis. Thus, sebum continues to be a prime suspect in the crime of acne. Low levels of sebaceous gland activity are not correlated with the occurrence of dry skin.

Acne Vulgaris↗

PubMed1986

Skin surface lipids of the mink.

Skin surface lipids from mink (Mustela vison) were collected in acetone and analyzed by thin-layer chromatography and gas chromatography. The principal components were wax monoesters (92%), cholesteryl esters (5%), free fatty acids (1%), fatty alcohols (1%) and cholesterol (1%). The fatty acids and alcohols contained in these lipids were composed principally of homologous series of straight chained omega 7-unsaturated structures (C16-C24), accompanied by lesser proportions of homologous series of saturated (C14-C22) and omega 9-unsaturated (C18-C22) structures.

Animals↗

PubMed1985

Comparison of acetate and glucose incorporation into rat and horse skin lipids.

The relative efficiency of acetate and glucose as substrates for the biosynthesis of lipids in the skin of the rat and horse was examined using in vivo pulse labelling of skin with [1-14C]acetate and [U-14C]glucose by intradermal injections. The resulting radiolabelled lipids were recovered in the rat by punch biopsy as well as by daily, long-term skin surface lipid collections and in the horse by punch biopsy of the injection sites. The lipids were examined by liquid scintillation and by a combination of thin-layer chromatography and autoradiography. In both species the recovery of radiolabel in the non-polar lipids was much higher after a pulse of [1-14C]acetate than after a pulse of [U-14C]glucose. In the rat, the skin surface lipids labelled through acetate contained sufficient radiolabel to allow observation of the time course of excretion of 14C in the major non-polar lipid classes. The results suggest that the biosynthesis of these lipid classes in the sebaceous glands of the rat are not entirely synchronous. In the skin lipid extracts of the horse, all of the major lipid classes, including phospholipids and glycolipids, were labelled through acetate. In contrast, none of the non-polar lipids and very little of the polar lipids were labelled through glucose.

Acetates↗

PubMed1985

The time-course of lipid biosynthesis in horse skin.

To observe the time-course of formation of sebaceous lipids in the horse, skin was pulse-labelled in vivo by intradermal injection of [1-14C]acetate and the injection sites were harvested at intervals for up to 12 days by skin punch biopsy. The distribution of radioactivity among the major neutral lipid classes and the phospholipids from these biopsies showed that, soon after pulse-labelling, the phospholipids were highly labelled followed by a long-term decrease in radioactivity. Over the same period, the low initial labelling of the dominant component, the equolides (giant ring omega-lactones, C32-C36), was followed by a long-term increase in radioactivity. This suggests a post-pulse transferance of radioactivity from the phospholipids to the equolides, presumably in the fatty acids. Of the phospholipid fatty acids from horse dermis, including sebaceous glands, 33% were found to contain iso-branched structures unique to horse sebaceous lipids. Of the iso-branched fatty acids, 40% were delta 9-18:1 and delta 9- and delta 11-20:1 acids, which are structurally appropriate to be precursors for the monounsaturated equolides. These findings strengthen the hypothesis that the sebaceous phospholipids of horse skin serve as long-term lipid intermediates in the biosynthesis of the equolides during sebaceous cell development.

Acetates↗

PubMed1985

Measurement of the time between biosynthesis and surface excretion of sebaceous lipids in the horse.

The time between the biosynthesis and excretion of sebum to the skin surface of the horse was examined by in vivo intradermal injection of [1-14C]acetate followed by periodic surface lipid collections. The radiolabelling of the major neutral lipid classes, equolides (giant ring omega-lactones, C32-C36) and cholesteryl esters, was evaluated by thin-layer chromatography and autoradiography. The distribution of radioactivity within the monounsaturated equolides was examined by oxidative fragmentation and evaluation of the products. A peak of radioactivity in the equolides and cholesteryl esters occurred 15-21 days and 10-16 days, respectively, after injection. The time-courses of specific radioactivity of the two types of equolide oxidation fragments were also found to be dissimilar. The results are interpreted as indicating that in the biosynthesis of a large proportion of the equolides, de novo fatty acid synthesis was not followed immediately by fatty acid chain elongation. The phospholipids of the sebaceous cells are proposed as the long-term intermediate in which fatty acids reside between these two biosynthetic processes.

Animals↗

PubMed1984

Structures of the dienoic lactones of horse sebum.

The C34, C36, and C38 dienoic omega-lactones were isolated from sebum of the horse (Equus caballus) and the double bond positions were determined by stepwise chemical dissection and analysis of the fragments. The structures found could be formed by delta 9-desaturation at the C18-stage of fatty acid biosynthesis followed by a second delta 9-desaturation when the chains reached C24, C26, C28, C30, or C32 and then addition of one to seven 2-carbon units. These findings provide insight into the dimensions and organization of the endoplasmic reticulum in cells of the sebaceous glands.

Animals↗

PubMed1983

Comparison of the hydroxyacids from the epidermis and from the sebaceous glands of the horse.

The acylglucosylceramides were isolated from the polar lipids of horse epidermis and examined to determine whether the component omega-hydroxyacids are straight chained as in the corresponding lipids from pig epidermis or branched as in horse sebum. The hydroxyacids from horse epidermis were found to be almost entirely straight chained compounds. The results indicate that sebaceous glands, although derived from epidermal cells, have evolved independent pathways of lipid metabolism.

Animals↗

PubMed1983

Variation in skin surface lipid composition among the Equidae.

Skin surface lipids from Equus caballus, E. przewalskii, E. asinus, E. grevyi, E. hemionus onager and a mule (E. asinus/E. caballus) were analyzed in detail. In all species the surface lipid mixtures consisted of giant-ring lactones, cholesterol, cholesteryl esters and minor amounts of wax diesters. In E. caballus, the lactone hydroxyacids were entirely branched chained, while in E. asinus and E. grevyi they were almost exclusively straight chained. In E. przewalskii, the onager and the mule there were both straight and branched chain hydroxyacid lactones. These results are in harmony with published interpretations of the evolutionary relationships among Equus species.

Animals↗

PubMed1983

Skin lipids.

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Aging↗

PubMed1980

Skin surface lipids of the horse.

Skin surface lipids from the sides of male and female horses (Equus caballus) were collected in acetone and analyzed by thin layer chromatography and gas liquid chromatography. The sole components in both sexes were cholesterol, cholesteryl esters and the lactones of 32-, 32- and 36-carbon omega-hydroxy acids, each including a methyl group in the n-1 position. Most of the lactones were monounsaturated (either n-8 or n-10), but small amounts of saturated and dienoic species were present. A pooled sample of the skin surface lipids contained 14% cholesterol, 38% cholesteryl esters and 48% lactones.

Animals↗