Histochemical demonstration of disulfide-groups in the lamina propria of human seminiferous tubules

Mid-dermal elastolysis: an ultrastructural and biochemical study

Mid-dermal elastolysis (MDE) is a particular elastic tissue disorder in which selective loss of elastic fibres occurs in the mid-dermis. It is clinically characterized by the appearance of fine wrinkling of the epidermis and perifollicular protrusion which gives the skin an aged appearance. It is sometimes associated with an inflammatory event such as urticaria while other cases are regarded as idiopathic. The pathogenesis of MDE is still obscure. Some authors have underlined the role of macrophage activation and others have imputed UV radiation. We report here a typical case of MDE arising after several attacks of solar urticaria. Electron microscopic and biochemical studies were carried out. Ultrastructural examination showed active elastophagocytosis by macrophages and mast cells, often degranulated, near phagocytosing cells. Biochemical studies demonstrated that fibroblasts derived from lesional skin of the MDE patient produced high levels of elastase and cathepsin G compared with fibroblasts from a healthy sex- and age-matched control. Phagocytosis of morphologically normal elastic tissue is a noticeable characteristic feature of MDE. In our case mast-cell activation and the abnormal synthesis and/or release of fibroblast elastolytic enzymes seemed to play a role in the pathogenesis of the MDE.

Elaunin fibres in the basement membrane of sweat gland secretory coil are rich in disulfide-groups

Disulfide-groups of elaunin fibres of sweat gland basement membrane are demonstrated a) by thiosulfation/aldehyde-fuchsin staining or thiosulfation/Alcian Blue + 0.8 M MgCl2 staining, and b) by identifying SH-groups after reduction with sodiumthioglycollate. Elaunin fibres share this staining behaviour with "elastic fibre microfibrils" and with oxytalan fibres.

Histochemical staining of lymphatic anchoring filaments

Lymphatic anchoring filaments are stained by means of histochemical methods that demonstrate disulfide-groups. Thiosulfation of sections either followed by aldehyde-fuchsin staining or by Alcian Blue +0.8 M MgCl2 staining has been used. Lymphatic anchoring filaments display striking fine structural similarities to "elastic fiber microfibrils" and both kinds of fibers are characterized by disulfide content.

The distribution of disulfide-groups in Descemet's membrane, lens capsule, and zonular fibers

Zonular fibers contain large quantities of disulfide-groups which histochemically can be demonstrated after thiosulfation or reduction with sodium thioglycollate. Zonular fibers share these staining behaviours with oxytalan fibers and elastic fiber microfibrils. Smaller amounts of disulfide-groups can be demonstrated when visualized by means of the thioglycollate/ferric-ferricyanide method. Diffusion of acidic staining solutions seems to be limited in Descemet's membrane and in the lens capsule: only surfaces of these membranes become reactive after thiosulfation. It is assumed that the distribution of disulfide-groups in Descemet's membrane and in the lens capsule shows the distribution of type IV collagen.