Ultrastructural aspects of the demolition of human hair in vitro by Chrysosporium tropicum Carmichael.
The pattern of invasion of human hair in vitro by a non-dermatophytic fungus, Chrysosporium tropicum, was studied by transmission and scanning electron microscopy. The components of the hair were attacked in sequence, depending on their level of keratinization, i.e. their content of cystine. In the cuticle, the sequence of digestion was as follows: intercellular material, cytoplasmic membrane, endocuticle, exocuticle, layer A, and a thinner layer below the inner cytoplasmic membrane of the cuticle cells. In the cortex, the order was: cementing material, plasmalemma, intermacrofibrillar material, microfibrils and matrix of the microfibrils. At the same time a different mode of attack was radial penetration of the various layers without regard to degree of keratinization. This occurred by means of perforating hyphae originating in the cuticle from structures similar to appressoria. With both modes of attack, the process showed all the characteristics of enzymatic digestion rather than physical breakdown. Ch. tropicum thus demonstrated important physiological parallels with dermatophytes in its demolition of hair in vitro. This could be of interest in predicting its ability to infect in vivo.
Fusconi
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Dipartimento di Biologia vegetale dell'Università, Torino, Italy.
Filipello-Marchisio
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D002912:Chrysosporium / Q000254:growth & development* / Q000648:ultrastructure; D006197:Hair / Q000382:microbiology* / Q000648:ultrastructure; D006801:Humans; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning