Biomedical subjects
Publications and source records attributed to E Uhoda.
Sun emits a vast array of electromagnetic radiations. After a long but fast journey, the spectrum of visible and ultraviolet light, and infrared radiations reaches the furthermost boundaries of the Earth. Only a fraction of them reaches the biosphere. Photogeoclimatology primarily depends on this energy and is modulated by the latitude, soil relief, seasons and nycthemeral cycle.
The optical properties of skin and of chromophores orientate and absorbe light. The resulting skin colour can be assessed by visual inspection or by objective methods. Spectrophotometry, tristimulus colorimetry and computerized image analysis are well codified methods. Epidermal melanisation is detected with great sensitivity under ultraviolet light illumination.
All the ocular structures, from cornea to retinal layer, can be damaged by exposure to the light radiations. Acute keratitis combined with conjunctivitis will result from an intensive photic exposure. On the other hand, pterygion more likely represents the consequence of chronic exposure to the ultraviolet rays. Exposure to the ultraviolet rays has been involved in the appearance of the typical yellow pigments of the nuclear cataract. Indeed, the physiopathological mechanisms are now progressively better understood. The progression of retinal degenerations might be influenced by uncontrolled exposure to ultraviolet rays, particularly during childhood. It is therefore useful to protect the eyes against ultraviolet sunrays. Filtering glasses seem to be one of the most effective ways to reach that objective.
Few studies have been performed to assess the risk of skin damage by cyclodextrins (CD) and they have yielded contradictory results. The present study was conducted using the corneoxenometry bioassay on human stratum corneum to compare the skin compatibility of CD currently used in pharmaceutical preparations (betaCD, gammaCD, Rameb, Dimeb, Trimeb, HP-betaCD and HP-gammaCD) and that of new amphiphilic CD derivatives, namely, the phospholipidyl-CD (DMPE-Dimeb and DMPE-Trimeb). All the tested CD were well tolerated by the stratum corneum at a concentration of 5%. However, inter-individual reactivity was larger for DMPE-Dimeb, suggesting a more aggressive trend for this compound. Cutaneous Index of Mildness values obtained confirm that Dimeb is able to extract some skin components and shows that DMPE-Dimeb performs similarly.
Skin is subjected to many environmental threats, some of which altering the structure and function of the stratum corneum. Among them, surfactants are recognized factors that may influence irritant contact dermatitis. The present study was conducted to compare the variations in skin capacitance and corneosurfametry (CSM) reactivity before and after skin exposure to repeated subclinical injuries by 2 hand dishwashing liquids. A forearm immersion test was performed on 30 healthy volunteers. 2 daily soak sessions were performed for 5 days. At inclusion and the day following the last soak session, skin capacitance was measured and cyanoacrylate skin-surface strippings were harvested. The latter specimens were used for the ex vivo microwave CSM. Both types of assessments clearly differentiated the 2 hand dishwashing liquids. The forearm immersion test allowed the discriminant sensitivity of CSM to increase. Intact skin capacitance did not predict CSM data. By contrast, a significant correlation was found between the post-test conductance and the corresponding CSM data. In conclusion, a forearm immersion test under realistic conditions can discriminate the irritation potential between surfactant-based products by measuring skin conductance and performing CSM. In vivo skin preconditioning by surfactants increases CSM sensitivity to the same surfactants.
Dietary deficiencies are multiple and some of them may induce specific changes in the skin biology and structure. Vitamin A deficiency is well identified as a cause of xerosis and follicular keratosis. Skin of the forehead and balding scalp was examined in 3 homeless alcoholic men who suffered from altered liver functions and denutrition including carotene and vitamin A deficiencies. The ultraviolet light-enhanced visualization (ULEV) method was used with a computer-assisted video camera equipped with an internal ultraviolet-emitting unit. Twenty healthy age- and phototype-matched men served as controls. Subclinical alterations of the stratum corneum and tiny follicular horny spikes at the skin surface were disclosed by ULEV. They were consistent with discrete flakiness on the forearms. By contrast, skin of the face and scalp showed follicular horny impactions corresponding to kerosis without any evidence for interfollicular xerosis. The skin condition was markedly improved after a 10-week dietary normalization. It is concluded that the ULEV method reveals some of the mildest and subclinical skin changes secondary to carotene and vitamin A deficiency. It could tentatively be used as a cheap and non-invasive aid in clinical screening programs among populations at risk.
Rough skin or xerosis, known by the laity as dry skin, results from a defect in the stratum corneum desquamation which normally remains imperceptible. This condition is negatively influenced by winter climatic conditions. Atopic dermatitis and trophic changes related to post-menopause, ageing, diabetes mellitus, as well as other endrocrine and metabolic disturbances are also involved in this process. Xerosis can be improved at various degrees by emollients, humectants, hydrating agents and squamolytic agents.