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Biomedical subjects

S Makki

Publications and source records attributed to S Makki.

29 records · Page 2Linked to original sources
PubMed1990

Chronopharmacokinetics of 5-methoxypsoralen.

Diurnal variations in drug pharmacokinetics are a well known phenomenon. Chronopharmacology studies now appear to be attracting increasing interest with a view to establishing an optimum therapeutic prescription. In order to determine possible chronobiological variations of 5-methoxypsoralen (5-MOP) pharmacokinetic, 5-MOP blood concentrations were quantified in 8 healthy subjects after drug ingestion at different times during the day. Stolk's High Performance Liquid Chromatography technique was used to assess the 5-MOP serum concentrations. Each subject underwent three pharmacokinetic studies after oral ingestion of 5-MOP (1.2 mg/kg), in conjunction with a standardized low-lipid meal. The first pharmacokinetic study was started in the morning, the second in the afternoon and the third in the evening. Drug intake was at intervals of 2 days, to avoid drug accumulation. The results showed that the evening intake of the drug induced a higher 5-MOP maximum concentration and a higher 'area under curve' than morning or afternoon ingestion. This study suggests an optimized PUVA therapy, when performed in the evening.

5-Methoxypsoralen↗
PubMed1982

Skin care in childhood.

Childhood (3 to 9 years) is a calm period of constant growth throughout which social contacts are discovered and intelligence and discretion take place. Consequently, most diseases are infectious. Microrelief was found twice shallower and skin (epidermis + dermis) twice thinner than in adults. Intervals between furrows were reduced parallel to total body surface, thus ruling out the possible existence of special shelters favouring bacterial growth. Sweating is lower, as are skin surface lipid levels, in contrast to the post-natal period, inducing dryness of skin. Although total skin stiffness in vivo was found to be identical to young adult skin, skin chapping is much more frequent. Since detergents as well as extended hot baths may reduce the stratum corneum water binding capacity, they should be used with discretion. Hence, skin care in this period of age should be based upon different criteria than in adults.

Child↗
PubMed1979

A quantitative method for the assessment of the microtopography of human skin.

The skin relief influences the exterior aspect of the skin which is very sensitive to aging. It could also be related to the mechanical properties and structure of both dermis and stratum corneum. Consequently, quantitative measurement of the skin surface roughness would seem most useful, as it would permit a quantification of skin aging, an in vivo analysis of mechanical forces acting on the skin structure, and the detection of abnormalities otherwise not visible. The method described comprises three steps: (1) making a silicone rubber negative replica, (2) making an Araldite positive cast, (3) roughness measurement of the cast with a device commonly used in engineering, which provides quantitative parameters: Ra, Rp, Rt, Rmax and others. The reliability of each of these steps was checked, and also the absolute need to locate precisely the site of sampling and to know the angle of the scanning direction with the main axis of the limb or the body. The method seems useful for studying aging, either normal or affected by UV rays and other physiopathological events influencing the skin surface.

Aging↗
PubMedDate not supplied

Ex vivo cutaneous absorption assessmentof a stabilized ascorbic acid formulation using a microdialysis system.

BACKGROUND: Reactive oxygen species generated by ultraviolet light result in photocarcinogenic and photoaging changes in the skin. Antioxidants protect the skin from these insults. OBJECTIVE: The aim of this study was to determine the ex vivo ascorbic acid penetration and its degradation in the skin after its topical application from an 8% new formulation. METHOD: Ascorbic acid was applied to human skin fragments. Ascorbic acid and its metabolites were collected by microdialysis and assessed by gas chromatography mass spectrometry. RESULTS: After topical application of the new formulation, the ascorbic acid level achieved was 8.5% higher than [corrected] times the normal tissue value. This high ascorbic acid dermal concentration remained constant if a topical application was made every 8 h. No degradation of ascorbic acid was detected. CONCLUSION: Ascorbic acid penetrates rapidly after its topical application. The persistent reservoir of ascorbic acid provides an important and attractive photoprotection strategy.

Administration, Topical↗