Extraction of osmium zinc iodide staining material in keratinosomes

A cytochemical study of dense granules in the rat junctional epithelium

To clarify the details of intracytoplasmic granules in the junctional epithelium (JE) of the rat gingiva, phosphotungstic acid (PTA) staining, acid phosphatase cytochemistry and zinc iodide-osmium (ZIO) staining were carried out. Condensing granules containing homogeneous electron-dense materials, measuring about 260 nm in diameter, have been observed at the peripheral cytoplasm of the JE. These granules reveal PTA-positive, ZIO-positive and acid phosphatase-positive staining. These results indicate that the granules contain glycoprotein, phospholipid, lipoprotein and lysosomal enzymes. From their composition and morphology, it is suggested that these granules in the JE may contribute secretory function and secrete glycoproteins or glycolipids. Although it is unclear whether the dense granules correspond to membrane-coating granules by our staining methods, it is surmised that, if the dense granules can engage in establishment of the barrier function, then this role is impeded by the large intercellular space in the JE.

Histochemical aspects concerning the synthesis and the fate of cholesterol into the epidermis

By means of a suitable histochemical method free cholesterol and its esters could be detected into the epidermis layers. The results show that in the stratum spinosum keratinocytes free cholesterol appears as an amorphous or granular structure apparently protein unbound; into the stratum granulosum keratinocytes the cholesterol becomes protein-bound and its most part undergoes esterified. The extracellular compartment nearly the stratum granulosum contains a little amount of cholesterol esters loosely bound to proteins. The results suggest that free cholesterol after being synthesized into the cytoplasm of the stratum spinosum and granulosum keratinocytes, it is partially esterified and becomes protein-bound, appearing as fine granules within the cytoplasm of the granulous cells. From this site it takes to fates:1. Its most part remains into the granulous cell cytoplasm and at the same time the granulous cell develop to the horny cell it is placed on the thick cell membrane inner surface contributing to its thickness; 2. Another part after reaching the extracellular compartment it is spread over the thick membrane out surface. Inside the thick cell membrane, into the horny layer, free cholesterol is continuously esterified since the keratinizing cell migrate to the periphery; however even at the most peripheral layers the free cholesterol predominates. Either free cholesterol or its esters, contained into the keratinizing cell thick membrane, were excreted throughout the horny layer exfoliation. The keratinizing cell cytoplasm does not contain neither free cholesterol nor its esters.

Zinc iodide-osmium staining of membrane-coating granules in keratinized and non-keratinized mammalian oral epithelium

Specimens of keratinized and non-keratinized oral epithelium were examined in the electron microscope after being stained with zinc iodide-osmium. In both types of tissue, reaction was seen in unmyelinated nerves, in the specific granules of epithelial Langerhans cells and within lysosome-like organelles and small vesicles associated with Golgi systems. In keratinized epithelia, the reaction was also present in the membrane-coating granules and between the deepest cells of the keratinized layer. In contrast, the membrane-coating granules of non-keratinized epithelia lacked Zn iodide-osmium staining despite the presence of reaction in adjacent Golgi systems. It is suggested that Zn iodide-osmium stains glycolipid or glycoprotein material in the cell. This material is elaborated in the Golgi systems from which lysosomes and the membrane-coating granules of keratinized tissues are probably derived.

Staining of oral epithelium with the zinc iodide-osmium reaction

Some of the parameters affecting the staining of keratinized oral epithelium with the zinc iodide-osmium reaction were examined using light and electron microscopy and electron probe microanalysis. Factors examined were block size, incubation temperature and the effect of aldehyde prefixation. Large blocks (4 mm cube) were subdivided after incubation and the staining of the centre and edge compared. Generally the reaction was more variable at the edge than in the centre. Small block (1 mm cube) showed a more intense reaction when incubated at 24 degrees C than at 4 degrees C. In all these preparations, final reaction product was seen over Golgi systems, lysosome-like bodies, membrane-coating granules and, in the more intensely stained regions, over endoplasmic reticulum and nuclear membranes as well. In prefixed material, mitochondria were frequently stained in addition to the other organelles. Energy dispersive analysis showed the reaction product to be similar in all preparations and to contain high levels of zinc and osmium but not iodine.

The staphylococcal scalded skin syndrome. An experimental histochemical and electron microscopic study

Histochemical and electron microscopic studies were carried out on the newborn mouse model of the staphylococcal scalded skin syndrome to investigate the mechanism of action of the staphylococcal epidermolytic toxin that causes it. Histochemical studies showed that an intra-epidermal split develops below the subcorneal zone which is rich in catabolic enzymes (the so-called esterase-acid phosphatase-rich band). However, histochemical alterations in the enzyme pattern could not be demonstrated. The earliest change revealed by electron microscopy was a widening of the intercellular space, with the formation of microvilli at the level between the stratum spinosum and stratum granulosum where the split later occurs. A clearing of the peripheral cytoplasm along the cell membranes was also revealed. In pre-split areas, adhesion between cell membranes of adjacent cells seems to be lost; desmosomes continue to hold the cells together but the split develops when these are broken by mechanical pressure. Later, damaged cell membranes may be seen. Extracellular keratinosomes remain unchanged. Although these findings do not agree with the already divergent results of other studies, they help support the findings of all groups that cases of the Lyell syndrome produced by staphylococci do not occur through necrolysis; it is therefore inappropriate to continue applying the term 'toxic epidermal necrolysis' to such cases.

Trends in electron microscopy of skin

Some trends in electron microscopy of skin have emerged and should be pursued in the future. The fine structure and some basic cellular reaction patterns of epidermal cells are discussed to illustrate the interplay of morphologic, cytochemical, and tracer studies. Intracytoplasmic membranes and secretory granules, lysosomes and endocytic mechanisms, cytomembranes and cell surface specialization are discussed to show how these can be used to arrive at a more meaningful interpretation of structure. Despite all advances, however, a great deal more needs to be done before the details of skin structure are completely elucidated.

Studies of the mechanism of epidermal injury by a Staphylococcal epidermolytic toxin

Experimental animal models of the two forms of toxic epidermal necrolysis have been reviewed: a murine model of staphylococcal-induced epidermolysis and a hamster model of graft-versus-host disease. In the former, a protein exotoxin, epidermolysin, has been purified and characterized. The exotoxin has a molecular weight of approximately 30,000 and causes a split beneath the granular layer. It is effective at 3 times 10(-12) moles. Epidermolysin does not require an intact complement system for its action since B10D2 mice deficient in C5 or mice injected with the decomplementing agent in cobra venom factor were susceptible to its epidermolytic effects. Neither are immunocompetent thymocytes required for the action of the toxin since hairless, athymic adult (nu/nu) mice are susceptible. A few reports of epidermolysis due to an exotoxin of group I Staphylococcus aureus have appeared. This toxin is antigenically different from the exotoxin of group II organisms. A model of drug-induced toxic epidermal necrolysis has been described in hamsters, but the toxic principle released from sensitized lymphoid cells has not yet been characterized.