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Biomedical subjects

H Schaefer

Publications and source records attributed to H Schaefer.

At least 91 records · Page 5Linked to original sources
PubMed1978

[Penetration of a non-steroidal anti-inflammatory drug into human skin in vitro and in vivo. Tissue concentrations and flow rates of p-butoxyphenylacetohydroxamic acid (author's transl)].

The penetration of p-butoxyphenylacetohydroxamic acid (BPHS; Parfenac) from a crean and an ointment into human skin in vivo and in vitro was investigated. From both preparation forms high tissue concentrations were achieved. Flow rates through the horny layer could be calculated, that from the ointment being considerably higher (3.8 . 10(-8) mol/cm2 . h) than that from the cream (7 . 10(-9) mol/cm2 . h). A control experiment in vivo proved that the in vitro data are relevant. The difference between dermal concentrations in vitro (with abolished capillary function) and that in vitro (with capillary system functioning) reflected the fast absorption of the drug by the vessels.

Administration, Topical↗
PubMed1977

Penetration, permeation, and absorption of triamcinolone acetonide in normal and psoriatic skin.

Penetration studies of radiolabelled Triamcinolone acetonide from ointment or cream preparations revealed that in cases of normal as well as psoriatic skin 70-90% of the applied substance remains on the surface. Normal horny layer stores up to 30% of the steroid. Nevertheless, a rapid penetration into the living layers of the skin is observed, whereby the epidermal concentrations reach levels between 5-10(-6) and 3-10(-5) M (mol per liter of tissue). The excretion in the urine took more than 72 h after removal of the excess of substance from the skin. In psoriatic skin, the epidermal and dermal concentrations were 3-10 times higher than in normal skin. This increase lies in the same range as the one resulting from removal of the horny layer by stripping prior to the application, as reported earlier.

Absorption↗
PubMed1977

Hydrocortisone (cortisol) concentration and penetration gradient.

Hydrocortisone (Cortisol) was incorporated into four different ointments at four concentrations (0.1% 0.3%, 1%, and 3%) and the amounts of the drug penetrating from these preparations into the different layers of excised skin were investigated. The effect of removing the horny layer on the penetration was also determined. Below a level of 1% ointments with intact horny layer and 0.3% with removed layer, a change in the ointment concentration alters the tissue concentration in the ratio 1:1. Above this level doubling of the concentration in the ointments causes an increase of tissue concentrations of only 20-50%. The removal of the horny layer increases the dermal concentrations 100 fold at each ointment concentration. Furthermore, a vasoconstriction test was performed with the different ointments. An increase in the concentrations above the 1% level failed to increase the effect on the vascular system of the skin. The in vitro and in vivo results are discussed with respect to the consequences on affected skin and the therapeutic efficacy of steroid preparations of different concentrations.

Administration, Topical↗
PubMed1976

[Penetrations kinetics and distribution of topically applied estrogens (author's transl)].

The penetration into the single layers of human skin in vitro of 17 alpha-estradiol, 17 beta-estradiol and estriol was investigated. The radiolabeled substances were incorporated into 4 standard ointments and into an alcoholic solution mixture. After application to the skin and after different penetration periods, the horny layer was taken off by adhesive tape stripping. The epidermis and the dermis were separated by slicing them down parallel to the skin surface in a freeze microtome. In each single layer, the amount of substance was determined and calculated relative to the applied quantity and in absolute concentrations (mug per tissue weight and molarity). Besides the expected dependence of the penetration on the type of ointment, there is a distinct dependence on the chemical structure: estriol penetrates considerably slower and in less concentrations into the living layers of the human skin than the estradiols. Furthermore, estriol reaches the dermis only in low concentrations so that this substance may be termed epidermotropic. 17 alpha-estriol which has only weak sexhormone properties in humans penetrates as well as the sexhormone 17 beta-estradiol.

Administration, Topical↗
PubMed1976

Penetration, permeation, and resorption of 8-methoxypsoralen. Comperative in vitro and in vivo studies after topical application of four standard preparations.

The penetration, permeation, and resorption of radioactively labelled 8-Methoxypsoralen was investigated in human skin. Siultaneously, the effects to time and ointment carrier on the penetration kinetics were ascertained. The carriers tested were: vaseline, aqueous wool-wax alcohol ointment, aqueous hydrophilic ointment and polyethylene glycol ointment. The absolute concentrations of 8-Methoxypsoralen were estimated in the horny layer, epidermis and dermis. With the most advantageous carrier, aqueous wool-wax alcohol ointment, 4-6X10(-5) M and 10(-5) M were attained in the epidermis and dermis, respectively. Moreover, it was shown that the substance penetrates rapidly (10 min) into the epidermis and dermis and the high concentrations reached constant over a period of 16 h. Only with a formulation of aqueous wool-wax alcohols is any accumulation at all achieved in the deeper areas of the horny layer. A uniform decrease in drug concentration with increasing depth of the horny layer is found with the other 3 vehicles, whereby slight variations in concentrations pertain from carrier to carrier. 4 h after local application, 8-Methoxypsoralen can be detected in the urine. Regardless of the ointment base employed, 8-Methoxypsoralen is no longer detectable in the urine 40 h after application. In comparison to the oral therapy, the same magnitude of percutaneous resorption into the central compartment is to be derived from the data, if half the body surface is treated locally.

Administration, Topical↗
PubMed1976

Simplification of local therapy of psoriasis with 8-methoxypsoralen. Methods and initial results.

Local 8-methoxypsoralen black-light treatment was carried out on sixty-two patients. For the first time, oil was employed as a preparation base in order to increase the transparency and so the effectiveness of irradiation. Also the need for a descaling pretreatment was avoided. In investigations still being carried out, 27.5% patients showed very good improvement, 48-4% good and 24-2% unsatisfactory results of treatment. In many cases, less than fifteen irradiation sessions were necessary for clinical healing. However, to obtain a uniform pigmentation, additional irradiation proved necessary.

Erythema↗
PubMed1976

Homologous interference of lymphocytic choriomeningitis virus: detection and measurement of interference focus-forming units.

Lymphocytic choriomeninigitis (LCM) virus defective interfering (DI) particles form foci of protected cells in a monolayer under an agarose-containing overlay medium. Foci originate from one cell dually infected with at least 1 interference focus-forming unit and infectious virus. As a result, an interfering factor is produced and released which interacts with neighboring cells, thereby protecting them against cytopathic lysis by challenge virus. The property of individual LCM virus DI particles to induce countable foci has been made the basis of quantitative assay that is comparable in every respect to the plaque assay of infectious virus and is much more sensitive and probably more accurate than other procedures used to measure LCM virus DI particles. LCM virus was passaged, undiluted, 10 times in cell cultures. When yields were analyzed as to concentrations of PFU and interference focus-forming units, both entities were found to fluctuate with the pattern expected from theoretical considerations.

Cell Line↗
PubMed1976

[Penetration, permeation and resorption of heparin. In vivo studies on human skin].

The penetration and permeation of radioactive heparin into human skin was investigated as well as absorption and excretion. Heparin concentrations and vehicles were those that are in common use in practical therapy. It was shown that in spite of its high molecular weight, heparin can penetrate through the intact horny layer barrier. The concentration of heparin found in the skin, e.g. 10 I.U./ml in the epidermis and 0.6 I.U./ml in the corium are biologically relevant and are expected to be able to exert an influence. The penetration rates have shown a clear dependence on the kind of vehicle.

Heparin↗