The immunohistologic distribution of fibronectin, laminin, type IV collagen and whole basement membrane was evaluated in liver biopsies from patients with chronic active liver disease. Fibronectin was consistently increased in the areas of piecemeal necrosis, portal tracts and fibrous septa. Laminin was not detected in normal liver parenchyma. In contrast, laminin positive linear basement membrane structures were prevalent in portal tracts, fibrous septa and the peripheral sinusoids of cirrhotic nodules. In areas of piecemeal necrosis, the hepatocytes, single or assembled in "rosettes", were frequently underlined by linear deposits of laminin and type IV collagen. This immunoreactivity was often polarized, being confined to the stromal side of liver cells, while the parenchymal side was negative for both proteins. Electron microscopy revealed a typical basement membrane in corresponding areas. Hepatocytes normally do not produce a basement membrane, but do so following chronic injury. We suggest that the polarized basement membrane accumulation by hepatocytes is a hallmark of hepatocyte regeneration following damage.
The ultrastructural features of 8 human cardiac myxomas were analyzed and correlated with immunohistochemical data, with the aim to clarify the characteristics of the cell lines involved in the tumor genesis. Immunohistochemical studies were performed to detect the presence and the distribution of intracytoplasmic filaments (vimentin, desmin, actin, myosin) as well as myoglobin and factor VIII-related antigen, albumin, and lysozyme. Eighty percent of myxoma cells were simultaneously positive for vimentin, desmin, and actin, whereas 30% of them stained with antifactor VIII and antivimentin antibodies. The submicroscopic analysis revealed two main cell populations: (1) one composed of stellate-shaped cells with scanty organelles and sparse hyaloplasmic filaments scattered throughout the myxoid stroma and forming a loose network with their projections; (2) another one included cells with more cytoplasmic organelles, intermediate filaments, and myofilaments arranged either singly or in both solid and hollow cord-like structures. Our results support the hypothesis that cardiac myxoma may originate from a reserve multipotent mesenchymal cell able to differentiate more or less completely along two major evolutional lines: myoid and endothelial. The tumor tissue thus seems to be involved in vessel formation, suggesting a growth pattern akin to that manifested in other forms of endocardial pathological reactivity in which reserve mesenchymal cells are engaged.
The mucus glycoconjugates produced by conjunctival goblet cells in dry-eye patients were studied by a specific cytochemical reaction in Transmission Electron Microscopy (TEM). Four lectins, proteins of vegetal origin which specifically bind glycosidic residues, (WGA, PNA, SBA and ConA) were used conjugated with colloidal gold as ultrastructural marker. We performed a quantitative analysis by counting the colloidal gold particles present on mucus granules. The results were compared with normal conditions. We found a decrease in sialic acid, N-acetyl-glucosamine, N-acetyl-galactosamine and galactose-N-acetyl-galactosamine and an increase in mannose. The different content of glycoconjugates in goblet cells may reflect in the change of physical and functional properties of mucus. We think these data may be useful in the search for a therapeutic mucomimetic drug.
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