Ultrastructural demonstration of endogenous peroxidatic activity in mammalian arterial wall

Cytochemical expression of epidermal peroxidase and cytochrome oxidase activities in pathological skin conditions of man

The cytochemical expression of epidermal peroxidase and cytochrome oxidase activity was recently well documented in normal human skin. We report here its expression in basal and squamous cell carcinomas, actinic keratoses, psoriasis, allergic contact dermatitis, seborrheic keratoses, and autosomal dominant ichthyosis vulgaris. The two enzyme activities were evaluated using the diaminobenzidine method. If present, the two enzymes were always localized in the same organelles as in normal epidermis: endogenous peroxidase in the nuclear envelope and endoplasmic reticulum, and cytochrome oxidase in mitochondria. In basal and squamous carcinomas, actinic keratoses and psoriasis, the keratinocytes lost their peroxidase activity, but maintained their cytochrome oxidase activity. In seborrheic keratoses, allergic contact dermatitis and ichthyosis vulgaris, the cytochrome oxidase activity was greatly reduced or abolished in keratinocytes, Langerhans' cells, and melanocytes, whereas the peroxidase activity was present as in normal epidermis. These results indicate that the two peroxidatic enzymes studied are not interrelated and alternatively suppressed by different cellular dysfunctions.

Peroxidase-positive endothelial cells in rat liver

Rat liver fixed by perfusion with low glutaraldehyde concentrations was incubated in diaminobenzidine-containing medium to stain for peroxidase. Endogenous peroxidatic activity was found not only in Kupffer cells but also in the endothelial cells lining the sinusoids and central veins. The reaction product was localized in the nuclear envelope and endoplasmic reticulum. The peroxidatic activity in endothelial cells showed a concentration-dependent sensitivity to glutaraldehyde: in liver samples fixed with 0.25% glutaraldehyde, approx. 23% of the sinusoidal endothelial cells and 65% of central vein endothelium were peroxidase-positive; with 0.5% glutaraldehyde, only approx. 8% of the sinusoidal endothelial cells contained detectable amounts of the reaction product; with 1.5% glutaraldehyde all endothelial cells were consistently peroxidase-negative. No peroxidatic activity could be found in liver endothelial cells following isolation by centrifugal elutriation. Endothelial cell peroxidase may possibly be involved in defense responses of liver and/or, as a part of prostaglandin synthase system, in prostanoid production.

Endogenous peroxidase activity in mononuclear phagocytes

The diaminobenzidine (DAB) technique has been used to visualize the subcellular localization of peroxidatic enzymes in mononuclear phagocytes. The latter cells are part of the mononuclear phagocyte system (MPS), which includes the monocytes in the bone marrow and blood, their precursors in the bone marrow, and the resident macrophages in the tissues. The DAB cytochemistry has revealed distinct subcellular distribution patterns of peroxidase in the mononuclear phagocytes. Thus the technique facilitates the identification of the various phagocyte types: Promonocytes contain peroxidase reaction in the nuclear envelope, endoplasmic reticulum, Golgi apparatus, and cytoplasmic granules. Monocytes exhibit the reaction product only in cytoplasmic granules. Most resident macrophages show the activity only in the nuclear envelope and endoplasmic reticulum. Furthermore, new phagocyte types have been detected based on the peroxidase cytochemistry. Intermediate cells between monocytes and resident macrophages contain reaction product in the nuclear envelope, endoplasmic reticulum and cytoplasmic granules. The resident macrophages can be divided into two subtypes. Most of them exhibit the pattern noted above. Some, however, are totally devoid of peroxidase reaction. Most studies on peroxidase cytochemistry of monocytes and macrophages agree that the peroxidase patterns reflect differentiation or maturation stages of one cell line. Some authors, however, still interpret the patterns as invariable characteristics of separate cell lines. As to the function of the peroxidase in phagocytes, the cytochemical findings imply that two different peroxidatic enzymes exist in the latter cells: one peroxidase is synthesized in the endoplasmic reticulum of promonocytes and transported to granules via the Golgi apparatus. The synthesis ceases when the promonocyte matures to the monocyte. Upon phagocytosis the peroxidase is discharged into the phagosomes. Biochemical and functional studies have indicated that this peroxidase (myeloperoxidase) is part of a microbicidal system operating in host defence mechanisms. The other enzyme with peroxidatic activity is confined to the nuclear envelope and endoplasmic reticulum of resident macrophages in-situ and of monocytes at early stages in culture. As suggested by the subcellular distribution, the inhibition by peroxidase blockers, and the localization during phagocytosis studies, the latter peroxidase is functionally different from the myeloperoxidase.(ABSTRACT TRUNCATED AT 400 WORDS)

Ultrastructural demonstration of endogeneous peroxidase activity in mammalian epidermis

With the diaminobenzidine method, endogenous peroxidase activity was demonstrated in the nuclear envelope and in the endoplasmic reticulum of non-keratinized keratinocytes and Langerhans cells of the epidermis of the newborn mouse, adult guinea pig and man. In the guinea pig all non-keratinized layers of keratinocytes showed this enzyme activity, whereas in the two other species examined peroxidase activity was limited to the suprabasal layers. The most pronounced activity was found in the Langerhans cells. The melanocytes were negative. With the same method, cytochrome c/cytochrome oxidase activity could be localized in the mitochondria of all epidermal cells of mouse and man, but not in the guinea pig.