A Novel Fluorimetric Method to Investigate Sebaceous Glands in Humans
Propionibacteria are gram-positive anaerobic bacteria which inhabit the deeper parts of sebaceous follicles, normally low in oxygen. They produce porphyrins which are probably partially dispersed into the surrounding medium composed of sebaceous lipids and desquamating cells from the follicular wall . Porphyrins are strongly fluorescent; their excitation maximum is located around 400 nm, emission bands are mainly in the range between 600 and 700 nm . Illumination of the skin with light of the appropriate wavelength allows visualization of fluorescent glands within facial areas and the upper back  (Fig. 1). Assuming that fluorescence intensity and porphyrin content are related, which has been proven in the case of uptake of porphyrins by propionibacteria in culture , and knowing that fluorescence intensity is strongly related to the population density of at P. acnes the skin surface  and that comedones are densely populated with propionibacteria , fluorescence intensity of individual glands could be a marker for comedonal content and for the comedogenic potential of various products (Figs. 2, 3). Previous work has indicated such a link [7, 8]. One of the goals of the present investigations was to establish a relationship between comedogenicity according to the rabbit ear model [9–12] and human porphyrin flouresecence data quantified by image analysis, i. e., the suitability of this noninvasive in vivo method to classify the comedogenic potential of substances in humans while avoiding animal testing.
KeywordsAndrogen Tetracycline Triglyceride Erythromycin Lysozyme
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