Preservation of elastic system fibers and of collagen molecular arrangement and stainability in an Egyptian mummy.

The present findings show that both elastic system fibers and collagen markedly resisted change in tissues more than 2000 years old. The distribution of elastic fibers and elastic-related fibers (namely, oxytalan and elaunin fibers) in mummified tissues coincided with the observations made on the modern human tissues used as controls. The collagenous structures present in tissue sections obtained from the Egyptian mummy studied took on a deeply red colour when stained in the Picrosirius solution indicating that, as well as in the fresh controls, the basic groups in the collagen molecules were available for reacting with the strongly acidic dye Sirius Red. When viewed with polarized light, the collagen in the same tissue sections displayed an increased birefringence, which shows that the collagen molecules in mummified tissues maintain the oriented disposition which is typical of the modern human tissues used as controls. The methods employed have proved to be useful for the delineation of the elastic system fibers and of the collagenous scaffolding, which may be used as valuable landmarks in the study of the histoarchitecture of organs that have undergone considerable distortion.

Morphological and histochemical studies on the collagen in neurinomas, neurofibromas, and fibromas.

The collagen in neurinomas, neurofibromas was studied by optical and electron microscopy. Neurinomas were shown to be composed mainly of thin argyrophilic, weakly birefringent fibers formed by thin collagen fibrils. Fibromas presented only thick, non-argyrophilic, strongly birefringent fibers composed of thick collagen fibrils. Neurofibromas showed populations of the two above-mentioned types of fibers occupying different areas of their parenchyma. These results suggest that the collagen of neurinomas is mainly of type III, while fibromas present collagen type I, and neurofibromas are composed of both types of collagen.

Comparative morphologic and histochemical studies on the collagen of vertebrate arteries.

Arteries of representative species from the main vertebrate classes were studied by a method that quantitates collagen-proteoglycans interaction, by the histochemical Picrosirius polarization method and by electron microscopy. The collagen of the adventitia presents features which are characteristic of collagen type I. The collagen in the tunica media revealed histochemical and ultrastructural aspects which are typical of collagen type III. As these results were consistently observed in all species studied, they suggest the presence of a general structural pattern of collagen distribution in vertebrate arteries.

Morphologic and histochemical evidence for the occurrence of collagenolysis and for the role of neutrophilic polymorphonuclear leukocytes during cervical dilation.

Biopsy specimens of nonpregnant and intrapartum human cervices were studied by electron microscopy, and by the Picrosirius-polarization method which is a specific procedure for the detection of collagen fibers in tissue sections. The results obtained demonstrate a marked reduction of collagen fibers in the intrapartum material as compared to the samples of nonpregnant cervices. Evidence that indicated the presence of a widespread collagenolysis in the intrapartum biopsy specimens was obtained by both optical and electron microscopy, thus suggesting that this might be the main cause of the changes in the cervix that permit it to dilate during parturition. The study of the neutrophilic polymorphonuclear leukocytes in the intrapartum biopsy specimens strongly suggested that these cells participate in this process.

Histochemical and morphological characterization of reticular fibers.

The results presented in this paper show that collagen fibers can be clearly distinguished from reticular fibers using the picrosirius-polarization method. A morphologic and morphometric study of these two types of fibers with electron microscopy shows that reticular fibers are characterized by the smaller diameter of their fibrillar components and the higher content of interfibrillar material, resulting in a loose arrangement of the fibrils. The evidences presented suggest that the amorphous matrix in which fibrils are embedded is responsible for the silver impregnation of reticular fibers. Our results show that the matrix of reticular fibers is characteristically rich in heparitin sulfate, and that the glycosaminoglycans present show a high interaction with the fibrillar component of these fibers.

The collagen of the vertebrate peripheral nervous system.

Nerves and ganglia from a variety of fish, amphibian, reptilian and mammalian species were studied by optical and electron microscopy. Observations using the Picrosirius-polarization method strongly suggest that two different types of collagen fibers are present in the connective tissues of nerves and ganglia. Electron microscopy of nerves and ganglia showed the presence of two different collagen fibril populations, distinguishable on the basis of diameter, located in different compartments of these structures. Thicker fibrils are present in nerve and ganglionic epineurium. Thinner fibrils are present in the endoneurium, surrounding nerve fibers and ganglionic cells, and between the concentric layers of perineurial cells. These results were consistently observed in all species studied and very probably represent a general phenomenon in vertebrates.