Electron microscopy in the study of myofibroblastic lesions

Electron microscopy in the diagnosis and academic study of myofibroblastic lesions is discussed. Myofibroblasts from granulation tissue and tumor stroma are regarded as the nearest equivalent to a "normal" myofibroblast population with which to define myofibroblastic differentiation in tumoral and pseudotumoral lesions. Histological features include a plump-spindle-cell morphology, with an ill-defined cytoplasm paler and less fibrillar than in smooth-muscle cells, and matrix collagen. Myofibroblasts stain for alpha-smooth-muscle actin, fibronectin, and vimentin. Desmin is found in some lesional myofibroblasts. The main ultrastructural features are prominent rough endoplasmic reticulum, modestly developed myofilaments with focal densities ("stress fibers"), and fibronexus junctions. The latter are foci on the cell surface where intracellular myofilaments and extracellular fibronectin filaments converge. Myofibroblastic lesions vary in the extent to which they mirror this overall phenotype. Hypertrophic scar, Dupuytren's disease, nodular fasciitis, the fibromatoses, and inflammatory myofibroblastic tumors have the most developed myofibroblastic features. Keloid, postoperative spindle-cell nodule, and fibroma of tendon sheath are less well differentiated. Myofibroblastoma is among many lesions described as myofibroblastic which, however, appear to show a kind of smooth-muscle differentiation. Some spindle-cell malignancies express myofibroblastic features.     

Experimental canine adenovirus glomerulonephritis: persistence of glomerular lesions after oral challenge.

Ten dogs were given canine adenovirus by the non-lethal oral route. Eight dogs were biopsied at 10 days after administration of virus in order to establish the presence of immune-complex glomerulonephritis. At this time, granular deposits of IgG, IgM, C3 and viral antigen were observed in a mesangial location and electrondense deposits were found. The dogs were then killed up to 40 days after receiving virus and, in all cases, deposits of immunoglobulins and complement together with the mesangial proliferative lesions were found to have persisted.     

Electron microscopy of granulomatous lesions of the liver in primary biliary cirrhosis

Three granulomas in the portal tract and 9 bile ducts with typical features of chronic non-suppurative destructive cholangitis (CNSDC) associated with dispersed epithelioid cells were examined by electron microscopy in 10 patients with primary biliary cirrhosis (PBC). Vesicular epithelioid cells, which contained numerous single-membrane bound vesicles, predominated in the granulomas. On the other hand, immature epithelioid cells and activated macrophages were more often observed near epithelial cells of the bile ducts with CNSDC than in the granulomas. These macrophages seemed to be activated by epithelial cells of the bile ducts and develop into epithelioid cells. Honeycomb-like membranous labyrinths containing electron dense substances were frequently observed in epithelioid cells and were likely a special form of phagosome. The substances in the labyrinths seemed to be derived from organellae of necrotic cells and extracellular interstitial tissues. Subplasmalemmal linear densities (SPLD) were observed at the cytoplasmic boundary and at intracytoplasmic membranous labyrinth. The roles of SPLD were discussed.     

Electron microscopy of Akabane virus.

Electron microscopy of negatively stained purified virus and of thin sections of infected cells and tissues showed Akabane virus being similar in morphology and morphogenesis to members of the family Bunyaviridae.     

Electron microscopy of Campylobacter jejuni.

Stools from 56 patients with gastroenteritis were cultured for Campylobacter jejuni. The five strains isolated were examined by electron microscopy. The campylobacter cells were pleomorphic and most displayed appearances similar to those of V. fetus. Morphological changes were observed in cultures subjected to prolonged incubation.     

Early glomerular lesions in amyloidosis

Virchows Archiv - Our investigations on early glomerular changes in renal amyloidosis showed the following:     

Experimental paracoccidioidomycosis in dogs.

The aim of this study was to evaluate the susceptibility of dogs to develop paracoccidioidomycosis by experimental infection. Puppies were inoculated with Paracoccidioides brasiliensis by an intravenous route and two out of four died 1 week postinoculation, showing, at histopathological analysis, granulomas in the lungs, spleen and liver. P. brasiliensis was isolated from these organs. The animals that survived the infection showed a strong reaction when skin was tested with gp43, a specific antigen of P. brasiliensis. These animals were killed at 1 and 5 months after infection, and no lesions, macroscopic or microscopic, were observed in the lungs, spleen or liver; furthermore no P. brasiliensis culture was obtained from these organs. These results suggest that dogs can develop paracoccidioidomycosis and reinforces the importance of this animal as a sensitive indicator of P. brasiliensis in the environment.     

Electron microscopy of undecalcified human bone.

An alternative approach for the electron microscopical examination of undecalcified human bone was investigated. The method required bone to be chilled to -70 degrees C, sectioned at 10 microns in a special bone cryostat, and these sections to be fixed and embedded for ultrathin sectioning. Good preservation of bone cells was seen. The advantages of this method are that it allows numerous particular regions of the 10 microns thick sections to be selected under normal light microscopy, and these regions to be then selected for electron microscopy. The 10 microns sections allow for excellent penetration of the fixative and thus better preservation of the tissue is more likely.     

Electron microscopy: a method for the diagnosis of inherited metabolic storage diseases. Electron microscopy in diagnosis

In the diagnosis of inherited metabolic diseases, electron microscopy has become an important method complementary to clinical, histological and biochemical assays. The characteristic ultrastructure of stored material as well as the site of accumulation in the cell are shown in a number of metabolic disorders. The most prominent advantages of electron microscopical techniques as compared to alternative techniques are discussed. One of the advantages is the fact that ultrastructural investigation requires only tissue samples of very small size, and another that its results may be obtained within two days. Moreover, transmission electron microscopy permits new and promising analytical methods such as quantitative estimation of organellar changes (morphometry) and energy dispersive X-ray elemental analysis (EDX).     

Electron microscopic observations on the participation of blood leukocytes in the production of some renal glomerular lesions

Summary A study was carried out on the electron microscopic aspects of percutaneous renal biopsy samples from a case of periarteritis nodosa.Apart from deposits of fibrinoid and protein material, the presence of a large number of leukocytes, with the predominance of mononuclear leukocytes, was found in some of the glomeruli with hypercellularity revealed by light microscopy. The mononuclear leukocytes as well as the polynuclears present exhibited margination, with incomplete diapedesis processes and their fixation under the capillary endothelium, as well as sequestration within the thickness of the capillary wall owing to the formation of a new lamina densa layer. Subsequently, the capillary wall became thickened and deformed, producing the hypercellularity features observed in light microscopy.These alterations are explained as being caused by hypersensitivity processes in the course of periarteritis nodosa.     

Electron microscopy of endothelial cells in culture: I. Transmission electron microscopy

Summary Endothelial cells in culture can be identified by structural and functional characteristics. To examine the ultrastructure of the undisturbed endothelial cell monolayer, methods are described for in situ fixation and embedment in the tissue culture flask. Subsequent sectioning and staining for electron microscopy are carried out without detachment of the cell layer from the flask.     

Electron microscopy of disorders of skeletal muscle.

Some of the common pathologic changes in the muscle fiber as viewed with the electron microscope are considered. These include myofilament and Z band abnormalities, alterations of the sarcotubular system, mitochondrial aberrations and glycogen accumulations. Correlations with light microscopic findings are mentioned when pertinent. The diagnostic significance of the various ultrastructural changes is discussed.     

Electron microscopy procedure influences detection of rotaviruses.

Technical parameters of electron microscope staining procedures (type of stain, pH of stain, and time of staining) influence particle integrity for three groups of rotaviruses. Simian rotavirus SA11 (group A), Chinese adult diarrhea rotavirus and porcine rotavirus-like agent (group B), and porcine pararotavirus (group C) were tested. All rotavirus strains were quite stable in uranyl acetate and phosphotungstic acid at pH 4.5 and relatively stable in ammonium molybdate. However, staining with phosphotungstic acid at higher pH values with increased staining time yielded a reduction in the number of particles and particles that were broken or degraded to single-shelled particles or core particles. The different staining procedures were also tested in immunoelectron microscopy experiments. Antibody molecules bound to rotavirus particles were observed clearly only with phosphotungstic acid staining and not with uranyl acetate. We therefore recommend that uranyl acetate and phosphotungstic acid at pH 4.5 be used for negative staining of rotaviruses; phosphotungstic acid at pH 4.5 is optimal for immunoelectron microscopy. These technical points may be critical for rotavirus detection and are important for studies pertaining to the epidemiology and clinical importance of the non-group A rotaviruses.