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 effects of induced prenatal hypothyroidism on lamb mandibular third primary molars

Intrauterine thyroidectomies were performed on nine lambs on or about the ninety-sixth postconception day. Seven other control and shamoperated lambs, and the cretin lambs were sacrificed immediately after birth. The mandibles were removed and sectioned at the midline. The right side molars were removed by dissection and caliper measured. The distal cusps of the third primary molars were sectioned, dehydrated, and embedded in Bioplastic. A slow speed diamond saw was used to section the plastic blocks and the embedded teeth. Subsequent grinding and polishing produced high quality 75 micrometer sections of the lamb molar cusps. No significant differences in tooth size or enamel thickness existed. Microscopic examinations show that parts of the cretin enamel were poorly calcified, an observation that was correlated to the intrauterine thyroidectomies. The data suggest that hypothyroidism alters ameloblastic activity during the secretory phase of enamel formation.

Collagen in the cellular and fibrotic stages of scleroderma

The collagen in localized and systemic scleroderma skin was studied by light microscopy with silver impregnation (50 patients), electron microscopy (14 patients), and immunofluorescence microscopy using specific antibodies against Type I and Type III collagens (12 patients). In the cellular stage, the dermis and adipose tissue revealed perivascular or diffuse cellular infiltrates (mostly lymphocytes, plasma cells, and macrophages), accompanied by deposition of Type III collagen. The lower dermis also showed an increase in Type III collagen. In the fibrotic stage, the papillary layer showed a reduction and/or clumping of Type III collagen as compared to normal skin. The lower dermis and the adipose tissue revealed compact collagen consisting exclusively of Type I collagen or a mixture of Type I and Type III collagen. The pattern of Type III collagen distribution was similar to that of reticulin, thus suggesting that at least some reticulin fibrils may represent Type III collagen.

Nodular lymphoma: an ultrastructural study of its relationship to germinal centers and a correlation of light and electron microscopic findings

This study describes the ultrastructural findings in 16 cases of nodular lymphoma, and compares these with normal germinal centers in order to determine the possible germinal center origin of the lymphomas. Long branching desmosome-associated dendritic reticulum cells, characteristic of germinal centers, were found in all 16 cases of nodular lymphoma. Desmosomes were observed only between dendritic cells and not between lymphoid cells, and they were seen in only 1 of 7 cases of diffuse lymphoma. Cells comprising the nodular lymphomas share cytologic features, such as nuclear blebs and marked nuclear indentations, with germinal center cells. It appears that nodular lymphomas have a close anatomical relationship to germinal centers, although their actual origin from these sites is not established by this study. They are composed of lymphoid cells; we have no evidence to confirm the view that nodular lymphomas are derived from dendritic cells. Light and electron microscopic findings have been compared in order to establish the nature of large "histiocyte-like" cells in the nodular lymphomas. Many of these cells appear to represent transformed lymphocytes rather than histiocytes. They are more numerous in so-called mixed "histiocytic" lymphocytic lymphomas than in poorly differentiated lymphocytic lymphomas, which otherwise are ultrastructurally similar. This study casts doubt upon the existence of a mixed lymphocytic and histiocytic lymphoma within the spectrum of the nodular lymphomas, and indicates that a cytologic continuum exists between cells interpreted as poorly differentiated lymphocytes and those heretofore identified as histiocytes.

Reis-Bücklers' dystrophy. A clinico-pathological study

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