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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
PubMed1982

Lectins as markers of human epidermal cell differentiation.

The expression of sugar residues on human epidermal cells was investigated by means of lectin binding, as a way of determining membrane structural changes occurring during the differentiation of the epidermis. Fourteen lectins of different sugar specificity were conjugated with fluorescein isothiocyanate (FITC-lectins) and tested in fluorescence microscopy on frozen sections of normal human epidermis. In parallel, FITC-lectins were tested on psoriatic-involved epidermis to visualize differences in the expression of sugar residues that might occur during abnormal epidermal differentiation. No labelling could be obtained with lectins from Bandeira simplicifolia I, Dolichos biflorus, Limulus poyphemus, Tetragonolobus purpureas, Ulex europeus I, and Triticum vulgaris (group 1 lectins). A "pemphigus-like" intercellular labelling of the whole epidermis, except the stratum corneum, was obtained with lectins from Canavalia ensiformis. Maclura pomifera, Phaseolus vulgaris, and Ricinus communis I (group 2 lectins). A selective intercellular labelling of the stratum spinosum and the stratum granulosum was seen in normal epidermis with lectins from Arachis hypogaea, Glycine max, Helix pomatia, and Sophora japonica (group 3 lectins). In psoriatic epidermis, not only the basal cell layer, but also cells from the adjacent lower stratum spinosum were found to be negative, using FITC-lectins of group 3. These data indicate that the expression of lectin binding sites in normal epidermis differs according to the maturation of the cell from the basal cell to the more mature keratinocyte in the stratum granulosum. They suggest that lectins may be used as markers of epidermal cells in various stages of normal and abnormal differentiation.

Cell Differentiation↗
PubMed1982

[Bone marrow culture, cytochemistry and electron microscopy in agar in patients with preleukemic syndrome and aplastic anemia].

Thirty-seven patients with chronic cytopenia were studied using a CFU-c assay in agar. On the basis of the growth pattern three types of preleukaemic syndrome (PL) and two types of aplastic anaemia were distinguished. Further evaluation of the bone marrow dysfunction was attempted with a combined application of cytochemistry and electron microscopy for the morphologic study of cells proliferating in vitro. Well-defined maturation defects in the growing cells from the bone marrow of patients with PL were demonstrated with cytochemical stainings performed in agar. These results were supported by electron microscopic findings of Auer-body-like inclusions in "statu nascendi" in the vacuoles of preleukaemic cells. On the basis of our results a high risk group of PL for development of overt leukaemia and a group of patients with a grave prognosis in aplastic anaemia were distinguished. The data obtained are relevant for the clinical diagnosis and prognosis of patients with cytopenias.

Adult↗
PubMed1981

[On interactions of drugs on and in the skin/comparative studies on the mutual influences of ethyleneglycol-monosalicylate and benzylnicotinate (author's transl)].

Three radioactively marked substances (on the basis of a carbopol gel, 80% water - isopropanol) were analyzed comparatively in regard to the penetration of ethyleneglycolmonosalicylate and benzylnicotinate to intact and impaired human skin. The objective of the in-vitro study was to gain evidence on possible interaction of the locally applied substances upon skin penetration. Only 5 h after application ethyleneglycolmonosalicylate reaches a steady state of concentration in the corium of approximately 700-800 mumol/l tissue which is maintained (in contrast to nicotinate) even after 16 h exposure time. Benzylnicotinate reaches its maximum concentration (100-200 mumol/l tissue in all living layers of the skin) 100-300 min after application. After simultaneous local application of both substances the penetration of ethyleneglycolmonosalicylate in corium and subcutis is clearly intensified by benzylnicotinate. Substance distribution in skin cross section and kinetics do not change. Penetration of benzylnicotinate however, is delayed by the salicylate (especially at exposure time of 100-300 min). Results of comparative penetration studies with inverted skin (inverse penetration), intact and impaired (stripped) skin allow the following conclusion: penetration limiting of salicylate occurs in the horny layer only due to the optimal liberation. Penetration of nicotinate on the other hand, is already prevented "before" the skin because of insufficient liberation from the vehicle.

Drug Interactions↗
PubMed1980

Minimum phototoxicity dose (MPD). Comparison of conventional light sources and different lasers.

A pilot study was performed on groups of 5-7 volunteers to evaluate the minimum phototoxicity dose (MPD) of several light sources with different UVA qualities to optimise photochemotherapy. Visual observation was more suitable than reflection photometry in determining the threshold and gradation of erythema reactions; thermometry gave poor results. There were no individual differences between the MPD of a PUVA 4000 box and a continuously emitting argon-ion laser with 40 and 400 mW, respectively. The pulsed radiation of a nitrogen laser was the most effective. The limited validity of the Bunsen-Roscoe law for high peak power could thus be tested for a secondary photochemical reaction of the skin. The nitrogen laser (337.1 nm) proved that a repetition rate of 20 Hz was superior to 10 and 40 Hz. The MPD was intraindividually higher at 25 Hz than at 10 and 16.7 Hz for the dye laser tested (325 and 330 nm, respectively).

Dose-Response Relationship, Radiation↗
PubMed1979

Microcalorimetric investigations of the metabolism of isolated human epidermis.

Microcalorimetry was used for the evaluation of metabolic and enzyme activity in human epidermis. The endogenous metabolism with a heat production Q = -2 muW/mg wet weight could be stimulated to Q = -12 muW/mg by adding glucose to the buffer. To test the enzyme activity, hydrogenation of pyruvate to lactate by lactate dehydrogenase (LDH) was chosen as an essential step of anaerobic glycolysis. The LDH activity of epidermis slices amounted to 22 mU/mg epidermis. The microcalorimetric method is discussed as a test procedure for specimens of healthy and diseased skin and for cell cultures.

Calorimetry↗
PubMed1979

The quantitative distribution of percutaneously applied caffeine in the human skin.

The distribution coefficient of caffeine (water/n-Octanol) and the estimation of caffeine in urine after local application indicate to a high permeation rate of caffeine through the skin. This could be confirmed by using different vehicles in vivo and in vitro. 14C labeled caffeine penetrates rapidly the epidermis and corium. The maximum of absorption is reached at 100 min after local application in vivo. In vitro by absence of the transport possibilities of blood and lymph vessels, the concentration at 1,000 min after local application is 450 X higher than in vivo. Therefore, after 1,000 min in vivo the concentration of caffeine in the different skin layers is very low.

Administration, Topical↗