Positive Schiff reactivity of aortic elastin without prior HIO 4 oxidation; influence of maturity and a suggested source of the aldehyde

Histogenesis of unique elastinophilic fibers of elastofibroma: ultrastructural and immunohistochemical studies

Electron microscopy and both light and electron microscopic immunohistochemical tests for elastin were employed to study the morphogenesis of the unique elastinophilic fibers of an elastofibroma removed from the subscapular region of a 62-year-old woman. Ultrastructurally, as shown by tannic acid stain, elastinophilic fibers of the elastofibroma consisted of central cores and outer zones. The latter were composed of various sizes of vaguely demarcated, irregularly shaped amorphous components and compactly and randomly arranged large amounts of microfibrils. The electron microscopic immunohistochemical results showed that the small-sized amorphous components and microfibrils in the outer zones of the elastinophilic fibers were stained evenly and of granular texture, but the vaguely outlined large amorphous components were not stained. These findings were interpreted as indicating that the amorphous components of the outer zones of elastinophilic fibers were less compact and allowed the penetration of antielastin antibody. The unique elastinophilic fibers of elastofibromas appear not to be formed by the degeneration of the fibers but by abnormal elastogenesis, including an abnormal arrangement of microfibrils.

The histochemistry of thiols and disulphides. II. Methodology of differential staining

The reduction of disulphide bonds by various mercaptans and tri-n-butyl-phosphine (TBP) has been examined in paraffin sections of rat tissues. A "re-reduction' procedure demonstrating any residual disulphides shows that nearly equivalent endpoints are reached by all of the reagents at pH 8.5 and room temperature, though at greatly differing rates. TBP is the reductant of choice in that it acts rapidly, cannot cause the thiolation which is more or less pronounced with certain mercaptans and least reverses the prior alkylation of native thiol groups by iodoacetate or N-substituted malemides. Supporting studies establish that, except in highly compact structures, native as well as generated thiol groups can be visualized with satisfactory completeness and specificity by N-(4-aminophenyl)maleimide followed by a diazotization and coupling sequence. These findings provide the basis for the selective staining of disulphides, either alone or differentiated from native thiols in the same section.

Elastin fragment-induced monocyte chemotaxis. The role of desmosines

Elastin fragments generated by the digestion of human and bovine elastin were compared to fragments which had been treated with sodium borohydride for their ability to induce monocyte chemotaxis. No significant decrease in the number of migratory cells was observed between the two groups. Elastin fragments denatured with 8 M urea were devoid of chemotactic activity. These results support the premise that the tertiary structure of elastin fragments and not desmosine content is the most important structural determinant in the induction of elastin fragment-induced monocyte chemotaxis.

Development of elastic fibers of nuchal ligament, aorta, and lung of fetal and postnatal sheep: an ultrastructural and electron microscopic immunohistochemical study

The morphogenesis of elastic fibers of the nuchal ligament, aorta, and lung of sheep was studied by light microscopy, transmission electron microscopy, and immunohistochemical methods for the detection of elastin. The degree of maturation of the amorphous materials of elastic fibers was assessed morphologically in preparations stained by the tannic acid and periodic acid methenamine-silver methods. With both of these methods, the amorphous components of mature fibers stained less intensely than did those of immature fibers. Elastic fibers in early stages of development consisted of many microfibrils and few, small, branching masses of immature amorphous material. Thicker fibers were formed by the coalescence of growing masses of amorphous materials. In late stages of formation of elastic fibers, the mature amorphous materials were associated with few microfibrils; and they were partially surrounded by immature amorphous materials associated with many microfibrils. Antielastin antibody reacted evenly with amorphous materials in very early stages of elastic-fiber development, but reacted only with the other zones of amorphous materials in later stages; it also reacted with the microfibrils in all stages. These findings were interpreted as indicating that the microfibrils were associated with small amounts of elastin on their surfaces. This conclusion is in agreement with ultrastructural observations showing 1) that development of microfibrils precedes that of the amorphous material and 2) that the microfibrils adjacent to the immature amorphous materials are covered with small amounts of tannic acid-positive amorphous materials. These observations suggest that microfibrils serve as sites for elastin deposition, both in early elastogenesis and in subsequent growth of elastic fibers. However, the nature of the interaction between elastin and microfibrils remains unknown.

A comparative light microscopic evaluation of oxytalan fiber staining with a variety of dye substances

Staining of oxytalan fibers in marsupial, eutherian and human periodontal ligaments was surveyed with 65 different dyes. Using the criteria of response to preoxidation, distribution, and morphologic appearance, 27 dye preparations in addition to the Gomori aldehyde-fuchsin, Taenzer-Unna orcein, and Weigert resorcin-fuchsin techniques displayed oxytalan fibers. With two exceptions all dyes were cationic and reacted with varying degrees of excellence with different animals. Most dyes produced their best staining results as concentrated solutions in 3% acetic acid, suggesting involvement of oxidatively engendered polyanions predominantly associated with an acid mucopolysaccharide component of the oxytalan fiber. The significance of carboxyl and sulfur-containing groups should not be overlooked in further studies aiming to elucidate oxytalan fiber chemistry and microstructure. This study supported the view that oxytalan fibers belong to the family of elastic tissues and represent a biologically important system within the periodontal ligament.

A new fluorescent method for the demonstration of macromolecular aldehydes

The fluorochrome, p-hydrazinoacridine (HA), is used to stain selectively natural macromolecular aldehydes as occur in elastic tissue as well as periodic acid (oxidized) or hydrochloric acid (hydrolyzed) engendered polyaldehydes (e.g., respectively of glycogen, mucosubstances and deoxyribonucleic acid). The reaction is independent of SO2 required in Schiff-type reactions. The mechanism of the staining reaction is presumably via the formation of fluorescent hydrazones from aldehyde condensation with HA. Aldehyde blocking agents, i.e., thiosemicarbazide and sodium borohydride, block the staining reactions with HA. In view of the controversy surrounding the mechanism of Schiff-type reactions and the lack of an adequate explanation for the affinity of miscellaneous fluorochromes for elastic tissue, p-hydrazinoacridine appears to be an ideal reagent, combining a simple staining procedure, excellent histological results and a straightforward mechanism for its selectivity.