Morphodynamics of the axolotl epidermis (Siredon mixicanum Shaw) under the influence of exogenously applied thyroxin. 3. Epidermis of the metamorphosed axolotl
Fährmann, W.
Zeitschrift für Mikroskopisch-Anatomische Forschung 84(1): 1-25
1971
ISSN/ISBN: 0044-3107 PMID: 5139157 Document Number: 5510
The epidermis of the metamorphosed axolotl consists of a keratinising stratified squamous epithelium (height 40 to 50 µm). In addition to the common epidermal cells, which form the main component of the epithelium, sparsely distributed X-cells may be observed. Leydig cells are totally absent. Tonofibrils are very prominent in the cellular region. They are absent the stratum basale, but are present in increasing numbers towards the apikal areas of the stratum intermedium. While with light microscopic investigation (iron hematoxylin) structural details in the upper stratum intermedium are lost, electron microscopic investigation reveals numerous condensed tonofibrils. Even with electron microscopic analysis, the structure of the stratum corneum remains unclear. This obscuring of details affects all cellular elements in this region and leads to the formation of an inhomogeneous matrix. The stratum corneum is very thin (2 to 6 µm) and consists of one or two cellular layers. Large granules may be found in all the cell layers of the metamorphosed epidermis. The material is PAS-positive, diastase-resistant and can undergo reversible acetylation. The granules are less frequent in the stratum basale. The greatest number is to be found in the stratum intermedium. They can be demonstrated even with chrome-alum hematoxylin or aledhydefuchsin stains after preceding oxydation. In the upper stratum intermedium the granules are leas densely distributed and scattered granules may be found in the stratum corneum. With electron microscopic investigation the granules, with a diameter of 0.2 to 0.5 µm show no striking morphological differences throughout the non-keratinised cells. In the stratum corneum they show indistinct contours and differently manifest signs of dissolution. Other granular elements (small granules) with a diameter of only 0.1 to 0.15 µm are preferentially found in the penultimate layer of the stratum intermedium. With light microscopy one finds numerous granules bunched together, and they can only be demonstrated with the PAS-reaction. No peculiarities are seen in the only moderately developed Golgi-complexes and endoplasmic reticulum. The latter can be found in both the stratum intermedium and the stratum basale, in the form of single vesicles and short irregular tunnels. The desmosomes are numerous and modifications may be observed in the stratum corneum and between the stratum corneum and intermedium. Since the stratum intermedium is terminated apically by the zonulae occludentes, two separate intercellular systems can be distinguished.
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