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Biomedical subjects

W Gehring

Publications and source records attributed to W Gehring.

At least 19 recordsLinked to original sources
PubMed2004

Nicotinic acid/niacinamide and the skin.

Nicotinic acid (also generally known as niacin) and niacinamide (also known as nicotinamide) are similarly effective as a vitamin because they can be converted into each other within the organism. The blanket term vitamin B(3) is used for both. Niacinamide is a component of important coenzymes involved in hydrogen transfer. Here, the two codehydrogenases, nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) are of central importance. Topical application of niacinamide has a stabilizing effect on epidermal barrier function, seen as a reduction in transepidermal water loss and an improvement in the moisture content of the horny layer. Niacinamide leads to an increase in protein synthesis (e.g. keratin), has a stimulating effect on ceramide synthesis, speeds up the differentiation of keratinocytes, and raises intracellular NADP levels. In ageing skin, topical application of niacinamide improves the surface structure, smoothes out wrinkles and inhibits photocarcinogenesis. It is possible to demonstrate anti-inflammatory effects in acne, rosacea and nitrogen mustard-induced irritation. Because of its verifiable beneficial effects, niacinamide would be a suitable component in cosmetic products for use in disorders of epidermal barrier function, for ageing skin, for improving pigmentary disorders and for use on skin prone to acne.

Journal Article↗
PubMed2003

[Effects of emulsions on the stratum corneum barrier and hydration].

The appearance of the skin depends greatly on the hydration of the stratum corneum which is regulated by water binding substances of the corneocytes and also by the quality of the stratum corneum lipids. Furthermore these lipids are responsible for the barrier function. In patients with atopic dermatitis, the water binding capacity and the barrier function of the stratum corneum are reduced even in clinically healthy skin areas. Emollients can damage the stratum corneum and lead to desiccation and a disturbance of the barrier. This effect is a result of an increased permeability of the barrier lipids and direct damage to the keratinocytes and corneocytes. The degree of damage of the barrier caused by emollients in dermatological vehicles has not been sufficiently investigated. As suggested by hypothetical considerations, such an effect is not expected and cannot be demonstrated in water-in-oil-emulsions. Oil-in-water-emulsions without glycerol as well as lipophilic and hydrophilic microemulsions do damage the barrier function. Both types of microemulsions additionally lead to a dehydration of the stratum corneum. The damaging effect of oil-in-water-emulsions can be reduced by the addition of glycerol and urea.

Body Water↗
PubMed2003

O/W emulsions compromise the stratum corneum barrier and improve drug penetration.

BACKGROUND: W/O emulsions improve the stratum corneum barrier, while microemulsions tend to compromise it. We, therefore, were interested to explore the effects of O/W emulsions on the stratum corneum barrier. METHODS: Aqueous Cream BP 2001, Clioquinol Cream BP 1999 without clioquinol, Nonionic Hydrophilic Cream DAB 2001 without glycerol, Hydrophilic Skin Emulsion Base NRF S. 25., point of time 2001, without glycerol, and Base Cream DAC were tested versus untreated controls in 29 healthy volunteers for 7 days. Outcome measures included transepidermal water loss (TEWL), skin redness (chromametry a*-value) and erythrocyte circulation in the subpapillary vessels (laser Doppler). Barrier compromise was subsequently explored by performing the hydrocortisone blanching test using Hydrocortisone Cream 0.5% NRF 11.36. (outcome measure: a*-value) in 15 subjects and the sodium lauryl sulfate (SLS) irritation test (outcome measures: TEWL, a*-value, laser Doppler) in 14 subjects. RESULTS: Pretreatment with the test emulsions produced increases in TEWL (statistically significant for all test emulsions), a*-value (statistically significant for Aqueous Cream BP 2001 and Base Cream DAC), and laser Doppler value (statistically significant for all emulsions except Base Cream DAC). Hydrocortisone penetration was statistically significantly increased with all test emulsions versus untreated contols. SLS irritation was mostly statistically significantly increased versus untreated controls when analyzing the study endpoint-baseline difference. CONCLUSIONS: O/W emulsions may compromise the stratum corneum barrier and improve drug penetration.

Adult↗
PubMed2001

[Clinical effect of salicylic acid and high dose urea applied according to the standardized New German Formulary].

OBJECTIVE: To determine whether salicylic acid and high dose urea in five different NRF (New German Formulary) formulations have an effect on stratum corneum. METHODS: 20 healthy volunteers had their stratum corneum blacked with silver nitrate and a photographic developer, and a chromameter (a*-value) was used to determine the amount of discoloration produced by the study products and the drug free vehicles after 24 hours semiocclusive application and 24 hours later. The change in fingerpad ridge width produced by the study formulations and drugfree vehicles was determined at the same time, using the Hikoscope Dermatoscope after 30 and 35 minutes' use under an occlusive dressing. The results obtained with the two methods were correlated. RESULTS: All study formulations were effective. There were differences in the time course of the effects on the stratum corneum. The fingerpad ridge width method is not a measure of keratolytic activity because there were no significant correlations between the results obtained with the two methods. Also, 40% urea was keratolytic in the silver nitrate test, but had no effect of fingerpad ridge width. CONCLUSIONS: All NRF study formulations were effective in the stratum corneum. The fingerpad ridge width method is not a measure of keratolytic activity but rather of an other unknown effect of salicylic acid.

Administration, Topical↗
PubMed2000

Phosphorylation status of the SCR homeodomain determines its functional activity: essential role for protein phosphatase 2A,B'.

Sex combs reduced (SCR) is a Drosophila Hox protein that determines the identity of the labial and prothoracic segments. In search of factors that might associate with SCR to control its activity and/or specificity, we performed a yeast two-hybrid screen. A Drosophila homologue of the regulatory subunit (B'/PR61) of serine-threonine protein phosphatase 2A (dPP2A,B') specifically interacted with the SCR homeodomain. The N-terminal arm within the SCR homeodomain was shown to be a target of phosphorylation/dephosphorylation by cAMP-dependent protein kinase A and protein phosphatase 2A, respectively. In vivo analyses revealed that mutant forms of SCR mimicking constitutively dephosphorylated or phosphorylated states of the homeodomain were active or inactive, respectively. Inactivity of the phosphorylated mimic form was attributed to impaired DNA binding. Specific ablation of dPP2A,B' gene activity by double-stranded RNA-mediated genetic interference resulted in embryos without salivary glands, an SCR null phenotype. Our data demonstrate an essential role for Drosophila PP2A,B' in positively modulating SCR function.

Amino Acid Sequence↗
PubMed2000

Effect of topically applied dexpanthenol on epidermal barrier function and stratum corneum hydration. Results of a human in vivo study.

In a randomized, double-blind, placebo-controlled study the effect of topical dexpanthenol (CAS 81-13-0) formulated in two different lipophilic vehicles on epidermal barrier function in vivo was carried out. Seven days' treatment with dexpanthenol improved stratum corneum hydration and reduced transepidermal water loss. Active treatment was statistically different from the vehicle control on both measures. Our results suggest that topical dexpanthenol formulated in either lipophilic vehicle stabilizes the skin barrier function.

Administration, Topical↗
PubMed1999

Effect of topically applied evening primrose oil on epidermal barrier function in atopic dermatitis as a function of vehicle.

The aim of this study was to establish the effect on barrier function in atopic dermatitis of topical evening primrose oil in an amphiphilic and a stable water-in-oil emulsion. The studies were vehicle-controlled in two populations of 20 atopic subjects. Barrier function was assessed in terms of transepidermal water loss and stratum corneum hydration after a 4-week treatment period and a 1-week treatment-free period. A barrier function test with sodium lauryl sulphate (SLS) and nicotinic acid ester was also carried out. Evening primrose oil proved to have a stabilising effect on the stratum corneum barrier, but this was apparent only with the water-in-oil emulsion, not the amphiphilic emulsion. The choice of vehicle is therefore an extremely important factor in the efficacy of topically applied evening primrose oil.

Administration, Topical↗
PubMed1999

Antibacterial efficacy of benzoyl peroxide in phospholipid liposomes. A vehicle-controlled, comparative study in patients with papulopustular acne.

BACKGROUND: Literature reports indicate that phospholipid liposomes facilitate the accumulation of active agents in the infundibulum. OBJECTIVE: The study hypothesis of an improved antibacterial efficacy of benzoyl peroxide (BPO) in phospholipid liposomes was tested in comparison with a commercial and a pharmacopoeial BPO preparation. METHODS: The infundibular bacterial samples were obtained with the Permabond technique from 20 acne patients who had been treated with the test substances (vehicle-controlled) for 2 weeks twice per day in a single-blinded, comparative study on the upper back. RESULTS: A significant antibacterial effect in the infundibula (Propionibacteria and Micrococcaceae, both: p < 0.001) for a BPO phospholipid liposome formulation could be demonstrated. In comparison to the other significantly efficacious BPO formulations which were also tested (commercial product and pharmacopoeial formulation), the BPO phospholipid liposome formulation showed a significantly greater antibacterial efficacy for Propionibacteria and Micrococcaceae (both: p < 0.01). CONCLUSION: A BPO formulation in phospholipid liposomes may represent an improvement of the conventional external BPO treatment of acne.

Acne Vulgaris↗
PubMed1999

Tolerance profile of retinol, retinaldehyde and retinoic acid under maximized and long-term clinical conditions.

BACKGROUND: Topical retinoic acid (RA) causes irritation of the skin. To prevent this side effect, natural precursors of RA have been proposed. The aim of the present study was to compare the local tolerance profiles of retinol (ROL), retinaldehyde (RAL) and RA. METHODS: ROL, RAL and RA were studied using repeated insult patch tests for 14 days (n = 6). Similarly, RAL and RA were assessed in long-term clinical use for 44 weeks (n = 355). Clinical scoring on irritation, measurement of transepidermal water loss (barrier function) and laser Doppler blood flow perfusion units (irritation) were performed. RESULTS: Under maximized conditions, an equally low irritation potential for ROL and RAL and a more pronounced irritant effect with RA could be demonstrated clinically (p < 0.05 in the intergroup analysis). Furthermore, RAL and RA induced more scaling than ROL (p < 0.05), and ROL and RA tended to induce more burning/pruritus than RAL (nonsignificant). The TEWL values were low with ROL and high with RAL and RA (nonsignificant, intergroup analysis). The laser Doppler measurements confirmed pro-irritating effects of RA and the nonirritating effects of ROL and RAL (p = 0. 001, intergroup analysis). The long-term clinical study showed that the study population developed a high frequency of erythema (44% of the population), scaling (35%) and burning/pruritus (29%) with RA in the first 4 weeks of treatment, whereas these 3 parameters were significantly less frequent with RAL (p < 0.0001 in the intergroup analysis). CONCLUSION: The natural retinoids ROL and RAL do have a good tolerance profile, in contrast with the irritating potential of RA.

Administration, Cutaneous↗
PubMed1998

[Modification of stratum corneum quality by glycerin-containing external ointments].

The effects of glycerol are discussed in detail. Glycerol can lead to a transition of crystalline lipid structures within the horny layer lipids into liquid crystalline states. Especially if applied in oil/water-emulsions it improves, the hydration of the horny layers better than urea. In addition, if facilitates the dissolution of desmosomes within the superior layers of the horny layer enhancing desquamation. Furthermore, by using glycerol, the mechanical properties of the skin can be influenced; long term used leads to increased elasticity. The roughness of the horny layer is reduced, which can be explained by the abrasive and/or the hydrating effect. Glycerol used in o/w-emulsions also protects against the influence of tensides or noxious lipophilic agents. Presumably a flux from the base of the epidermis towards its surface triggers the regeneration of the barrier. Finally, glycerol can lead--similarly to urea--to an improvement in active agent penetration, as has been proven for hexylnicotinate.

Animals↗
PubMed1998

Predictive washing test for evaluation of individual eczema risk.

It was the aim of our studies to estimate predictively the individual eczema risk for persons due to repetitive contact with washing-active substances, by a barrier function test on clinically healthy skin over 2 weeks. Within the scope of the study 3 groups with different atopy scores were compared. As washing solutions, 0.1 m SLS and a slightly acid soap-free washing emulsion were used in comparison to tap water. Prior to the 1st washing procedure, on days 3, 5, 8, 10, and 12, the transepidermal water loss, the horny layer moisture, and the skin blood flow were measured as parameters of barrier function, as well as the inflammatory reaction. The results prove that the atopy score has only limited validity as a predictive method for the acceptance of washing-active substances. The repetitive washing test, however, seems to be more adequate for evaluating the individual barrier function as well as the eczema risk. Irritation by a washing procedure may be greatly influenced by choice of the washing solution.

Adult↗
PubMed1998

Opposing effects of glycerol on the protective function of the horny layer against irritants and on the penetration of hexyl nicotinate.

BACKGROUND: It is known that glycerol in an oil-in-water emulsion has a protective effect against irritating substances. OBJECTIVE: To answer the question: is the protection effect of glycerol based on a regenerative process? METHODS: Upon irritation by either tape stripping or acetone treatment, we applied glycerol to the skin surface under an occlusive dressing to create transepidermal water movement. As a control we used water under the occlusive dressing on the contralateral forearm. After 5 h we compared the barrier function using biological tests. RESULTS: A significant improvement of the protective barrier function was observed in the glycerol-treated areas, as shown by the alkali resistance and by the irritant effect of dimethyl sulfoxide (DMSO) as well as sodium lauryl sulfate. Surprisingly, at the same time penetration of hexyl nicotinate improved on the glycerol-treated areas. A direct physicochemical protection effect on the surface of the skin was ruled out in additional studies using NaOH and DMSO. CONCLUSIONS: Under the given conditions glycerol leads to a more rapid reconstitution of the protective skin barrier and initiates a regenerative skin protection. In contrast to that, it is acting as a penetration enhancer.

Adult↗
PubMed1998

Influence of vitamin E acetate on stratum corneum hydration.

The influence of vitamin E (tocopherol, CAS 10191-41-0) on stratum corneum hydration was tested in O/W and W/O emulsions. Additionally, the O/W emulsion was used in an in vivo/in vitro method to gravimetrically obtain evidence concerning the water-binding capacity of the stratum corneum. In the W/O emulsion, 2.5%, 5%, and 7.5% vitamin E were compared. With both types of emulsions, vitamin E increased the stratum corneum hydration statistically significantly (p = 0.0002). In addition, we could provide evidence of an enhanced water-binding capacity after treatment with vitamin E (p = 0.05). For the hydrating effect of vitamin E. its concentration is of importance. The optimum concentration turned out to be 5%.

Adolescent↗
PubMed1997

Squid Pax-6 and eye development.

Pax-6 in vertebrates and its homolog eyeless in Drosophila are known to be essential for eye development. Here we investigate the role of Pax-6 in eye development in another major systematic group, molluscs. We demonstrate that alternatively spliced RNAs derived from a single Pax-6 gene in the squid (Loligo opalescens) are expressed in the embryonic eye, olfactory organ, brain, and arms. Despite significant sequence differences between squid Pax-6 and Drosophila eyeless in the region outside the paired- and homeodomains, squid Pax-6 is able to induce the formation of ectopic eyes in Drosophila. Our results support the idea that Pax-6 related genes are necessary for eye and olfactory system formation throughout the animal kingdom.

Amino Acid Sequence↗
PubMed1995

Damage to the skin by repetitive washing.

Damage to the skin following the repeated use of 2 different wash solutions was investigated. Stratum corneum capacitative resistance, stratum corneum lipids, transepidermal water loss, skin surface pH, laser Doppler flow and skin reddening were determined. All skin function parameters already showed a marked change after a single wash (e.g., the median of TEWL values increased by more than 0.5 g/m2 h). Repetitive washing for 1 week led to a further deterioration of TEWL and corneometry values (e.g., TEWL increased for about 2.9 g/m2 h after repetitive washing with sodium lauryl sulfate). The rate of skin function regeneration after repetitive washing was unaltered compared to regeneration after a single wash. The surfactants used showed quantitatively differing effects on corneometry, TEWL and laser Doppler flow (e.g., after repetitive washing with Geliderm, the median of TEWL values increased only up to 1.55 g/m2 h). However, damage arising from repetitive washing could not be completely prevented by the selection of a mild surfactant. Skin function regeneration showed no difference with the 2 surfactants used.

Adult↗