Prominent publications by Donald Talbot Downing

KOL Index score: 9406

Mammalian stratum corneum contains multiple intercellular lipid bilayers that constitute the epidermal water barrier. Unlike all other biologic membranes, the epidermal lamellae do not contain phospholipids, as a result of which the ability of the stratum corneum lipid mixture to form bilayers has been questioned. In the present study, a lipid mixture containing only epidermal ceramides (40%), cholesterol (25%), palmitic acid (25%), and cholesteryl sulfate (10%), approximating the ...

Also Ranks for: Stratum Corneum |  cholesterol ceramides |  palmitic acid |  cholesteryl sulfate |  lipid mixtures
KOL Index score: 8760

Wax ester/sterol ester (WE/SE) ratios were measured in samples of vernix caseosa lipid obtained from 21 full-term infants. The mean WE/SE ratio was twice as high in males as in females, suggesting higher average fetal sebum production rates in males, but individual values varied widely and there was considerable overlap between the sexes. Wax esters (a class of lipid produced only by the sebaceous glands) were isolated from 6 of the 21 samples of vernix caseosa lipid and analyzed for ...

Also Ranks for: Vernix Caseosa |  wax esters |  fatty acid composition |  sebaceous gland activity |  sebum production
KOL Index score: 8270

Skin surface lipid samples were collected from the scalps of 40 males, aged 9-15, and the lipid class composition of each was analyzed by quantitative thin layer chromatography. The ratio of wax esters/[cholesterol + cholesterol esters] (WE/[CH + CE]) increased with age. The wax ester, cholesterol ester, triglyceride, and free fatty acid classes were isolated from each sample and the fatty acid compositions were determined by capillary gas chromatography of fatty acid methyl esters ...

Also Ranks for: Fatty Acids |  sebaceous lipids |  wax esters |  gas chromatography |  relative amounts
KOL Index score: 8242

We applied electrospray ionization (ESI) tandem quadrupole mass spectrometry to establish the fragmentation pathways of ceramides under low energy collisional-activated dissociation (CAD) by studying more than thirty compounds in nine subclasses. The product-ion spectra of the [M + Li]+ ions of ceramides contain abundant fragment ions that identify the fatty acyl substituent and the long-chain base (LCB) of the molecules, and thus, the structure of ceramides can be easily determined. ...

Also Ranks for: Mass Spectrometry |  electrospray ionization |  fragment ions |  activated dissociation |  production spectra
KOL Index score: 7558

The fatty acid composition of sebaceous wax esters was examined in 20 children, ages 6-8, using quartz capillary gas chromatography. The results were compared with a previously reported study of wax ester composition in 10 adults, in which the same analytical techniques were used. The children's wax esters showed more variability in the proportions of all fatty acid chain types than was found in adults. The most striking difference between the 2 age groups was in the proportions of ...

Also Ranks for: Wax Esters |  fatty acid |  young children |  sebum secretion |  chain types
KOL Index score: 7550

Fifty-two children, age 5-10, from acne-prone families, were studied for a period of 1 year to examine the interrelationship between sebum, acne, pubertal development, and urinary steroid excretion. In each of the subjects, 30 boys and 22 girls, the composition of forehead skin lipid was determined 4 times yearly by thin-layer chromatography, with measurement of triglycerides, diglycerides, free fatty acids, wax esters, squalene, cholesterol, and cholesterol esters. Twice yearly, ...

Also Ranks for: Children Acne |  wax esters |  lipid composition |  skin surface |  sebum urinary
KOL Index score: 7497

Low- and wide-angle X-ray diffraction were used to determine the structural organization of lipids isolated from the stratum corneum extracellular matrix that forms the major water permeability barrier in mammalian epidermis. Hydrated pig skin ceramides gave a single low-angle reflection of about 62 angstroms and a wide-angle-reflection at 4.15 angstroms. The addition of either cholesterol or fatty acid, the other major lipid components of the skin stratum corneum extracellular matrix, ...

Also Ranks for: Ray Diffraction |  skin lipids |  palmitic acid |  presence ceramide |  lipid mixtures
KOL Index score: 7495

Synthetic detergents produce deleterious effects on human skin as the result of being taken up by the stratum corneum (SC). The present study aimed to determine to what extent a typical detergent enters the SC lipid lamellae, and what effect this might have on the physical properties of the lipids. These effects were studied in large unilamellar liposomes prepared from SC lipids (50% by weight of epidermal ceramides, 28% cholesterol, 17% free fatty acids, and 5% cholesteryl sulfate) by ...

Also Ranks for: Lipid Liposomes |  sodium dodecyl |  stratum corneum |  sulfate sds |  human skin
KOL Index score: 7401

In the present study, we demonstrate that human stratum corneum contains covalently bound lipids accounting for 1.4% of the dry weight of the tissue. The major component (53.3% of the total by weight) is a ceramide (CER-A) consisting of 30 through 34-carbon omega-hydroxyacids amide-linked to sphingosine. The other bound lipids in human stratum corneum include fatty acids (12.7%), omega-hydroxy acids (9.4%), and a second, more polar, omega-hydroxyacid-containing ceramide (CER-B, 24.8%). ...

Also Ranks for: Human Stratum Corneum |  bound lipids |  fatty acids |  lipid envelope |  psoriatic scale
KOL Index score: 7282

The current study was undertaken to determine whether a previously reported murine culture system is an acceptable model for the study of epidermal lipid metabolism. The lipid composition of primary neonatal mouse keratinocyte cultures was determined and compared with that of freshly isolated keratinocytes and whole epidermis. 14C-Labeled arachidonic acid (AA) and linoleic acid (LA) were added to cultures and the incorporation into specific lipids was assessed. The lipid composition of ...

Also Ranks for: Lipid Composition |  arachidonic acid |  cultured chromatography |  epidermal cells |  epidermis fatty
KOL Index score: 7249

Changes in sustainable rates of sebum secretion were followed in twenty patients with severe acne who were receiving oral treatment with 13-cis-retinoic acid in dosages of 0.1, 0.5, or 1.0 mg/kg/day. Sebum secretion was measured by absorption of skin surface lipid into bentonite clay and estimation of the amount of absorbed sebum by measurement of its wax ester component. Pretreatment rates of sebum secretion in the patients were greatly elevated in comparison with previously measured ...

Also Ranks for: Sebum Secretion |  sustainable rates |  dose levels |  retinoic acid |  bentonite clay
KOL Index score: 7199

The permeability barrier of mammalian skin has been analysed in terms of its lipid composition whereas that of the oral mucosa is uncharacterized. As there are differences in permeability between different regions of the oral mucosa, and between the oral mucosa and skin, there may be corresponding differences in the nature of the barrier layer. Lipids were identified by thin-layer chromatography after solvent extraction of separated epithelium; their localization was determined in ...

Also Ranks for: Oral Epithelium |  lipid composition |  porcine epidermis |  permeability differences |  stratum corneum
KOL Index score: 7108

In a recent investigation we showed that murine keratinocyte cultures grown at the air/medium interface in the presence of dermis exhibit morphologic differentiation comparable to that seen in vivo, including the formation of lamellar granules and stratum corneum intercellular lipid lamellae. In the present study, lifted cultures were found to more closely reproduce the lipid composition of the parent epidermal tissue than submerged cultures grown on plastic. In addition, the specific ...

Also Ranks for: Stratum Corneum |  lifted cultures |  linoleic acid |  lipid composition |  lamellar granules
KOL Index score: 7054

Intercellular lipid lamellae in the stratum corneum constitute the barrier to water diffusion and may also play a role in cohesion between corneocytes. The lamellae arise from stacks of lamellar disks that are extruded from the granular cells and then fuse edge-to-edge to form sheets. It has been proposed that each lamellar disk is formed from a flattened vesicle, and therefore consists of two lipid bilayers in close apposition. In the present study, electron microscopic examination of ...

Also Ranks for: Intercellular Lipid Lamellae |  molecular models |  lipid bilayers |  human skin |  water diffusion
KOL Index score: 7016

The intercellular lipid lamellae of stratum corneum constitute the major barrier to percutaneous penetration. Deuterium magnetic resonance and freeze-fracture electron microscopic investigation of hydrated lipid mixtures consisting of ceramides, cholesterol, palmitic acid and cholesteryl sulfate and approximating the stratum corneum intercellular lipid composition, revealed thermally induced polymorphism. The transition temperature of bilayer to hexagonal transition decreased as the ...

Also Ranks for: Stratum Corneum |  ceramides cholesterol |  lipid mixtures |  transition temperature |  palmitic acid

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Donald Talbot Downing:Expert Impact

Concepts for whichDonald Talbot Downinghas direct influence:Fatty acids,  Stratum corneum,  Sebum secretion,  Skin surface,  Pig epidermis,  Cholesteryl sulfate,  Skin surface lipids,  Porcine epidermis.

Donald Talbot Downing:KOL impact

Concepts related to the work of other authors for whichfor which Donald Talbot Downing has influence:Stratum corneum,  Fatty acids,  Human skin,  Acne vulgaris,  Barrier function,  Sebaceous glands,  Atopic dermatitis.



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The Marshall Dermatology Laboratories, Department of Dermatology, The University of Iowa, College of Medicine, Iowa City, Iowa, USA | The Joe Marshall Research Laboratories, Department of Dermatology, 2080 Medical Laboratories, University of Iowa, Io