Pathogenesis of Hemorrhage Induced by Rattlesnake Venom: An Electron Microscopic Study

The pathogenesis of hemorrhage induced by rattlesnake (Crotalus atrox) venom was investigated at the electron microscopic level. Swiss-Webster white mice were injected intramuscularly with one-fifth the LD₅₀ dose of whole venom. Muscle samples were obtained by biopsy 2 minutes, 30 minutes and 3 hours after venom injection. Capillaries in the endomysium were in various stages of degeneration. Endothelial cells of damaged capillaries contained dilatated endoplasmic reticulum and perinuclear space, and, in many cases, swollen cytoplasm. Blebbing of endothelial cytoplasm of swollen and nonswollen cells was observed. These changes were followed by rupture of the plasma membrane which resulted in the subsequent extravasation of blood. Platelet aggregations plugged gaps in vessel walls and often completely occluded the lumina of capillaries. The experimental injection of rattlesnake venom induced hemorrhage by rhexis. The same or a similar pathogenesis is probably responsible for hemorrhage which occurs in actual snakebite cases.     

Developing Elastic Tissue: An Electron Microscopic Study

Electron microscopic identification of elastic tissue in normal and disease states has been uncertain due to the lack of a specific electron-dense stain. Recently we introduced a silver porphyrin electron microscopic stain (silver tetraphenylporphine sulfonate) for the identification of adult elastic tissue. This stain has now been employed to study the development of elastic tissue with the aim that new and old elastica can be differentiated at the electron microscopic level. Present observations showed that developing elastica consisted of two distinct morphologic components. Each portion exhibited different staining properties with the silver porphyrin and lead citrate. One component was fibrous and the other amorphous. The fibrous component stained with lead citrate while the amorphous stained with the silver porphyrin. The fibrous component was the first to appear; the amorphous portion appeared later in development and was formed within the fibrous matrix. Mature elastic tissue was devoid of the fibrous component. Based upon the morphologic appearance and staining properties, one can now differentiate between newly formed elastic tissue and the existing one in various disease states.     

Cytolysis Induced by Human Lymphotoxin: Cinemicrographic and Electron Microscopic Observations

By phase-contrast cinemicroscopy, highly purified human lymphotoxin induced two forms of cytolysis—one characterized by slow (1 to 2 hours) swelling (ballooning-type) and the other by sudden (3 to 5 minutes) shrinkage of the cell body and violent agitation of residual debris (popcorn-type). Specifically sensitized lymphocytes likewise caused both forms of lysis, morphologically indistinguishable from lymphotoxin-induced cytolysis. Lymphotoxin also inhibited cell division; mitoses diminished and virtually ceased before the onset of cytolysis. Many of the ultrastructural features preceding early lysis were similar to those associated with failure of osmoregulatory mechanisms—ie, condensation of mitochondria, dilation of rough-surfaced endoplasmic reticulum, separation of polysomes into individual units and expansion of the cell sap. After exposure to lymphotoxin for 12 hours or more, most remaining cells exhibited these same ultrastructural changes but lacked striking mitochondrial lesions.     

CALCITONIN-PRODUCING INSULINOMA: An Immunohistochemical and Electron Microscopic Study

A pancreatic endocrine tumor measuring 1.5×1.0×1.0 cm in a 67-year-old man with recurrent hypoglycemic attacks was examined by immunohistochemistry and electron microscopy. The tumor cells were relatively uniform, and almost all of them were immunoreactive to Insulin. A few calcitoninpositive cells could be identified scattering in tumor cell strands, and the content of calcitonin in the tumor was 85 ng/g wet tissue. Coexistence of insulin and calcitonin in tumor cells was demonstrated by using adjacent semithin sections of the Epon-embedded material. Electron microscopically, the tumor consisted of a single type of cells with secretory granules identical to B-cell granules in the normal counterpart.     

MYOFIBROBLASTS IN FIBROMATOSES An Electron Microscopic Study

Fifteen cases of fibromatoses were analyzed by electron microscopy, the objective being to compare the incidence and frequency of myofibroblasts in each category. Myofibroblasts were identified in all 15 cases and a considerably large number of these cells appeared in palmar fibromatosis, plantar fibromatosis, and nodular fasciitis. In keloid and cicatricial fibromatosis, however, only a small number of these cells were evident. In seven cases of extra-abdominal desmoid fibromatosis, the frequency of myofibroblasts in the component cells ranged from 10% to 64%, with a mean of 30%. The frequency was high in hypercellular lesions and low in hypocellular lesions, assuming that it would be roughly in parallel to the cellularity of the lesion in extra-abdominal desmoid fibromatosis and in other fibromatoses as well. There appeared to be no particular correlation between the number of myofibroblasts and recurrence of the lesion. ACTA PATHOL. JPN. 35 : 533–547, 1985.     

An Electron Microscopic Study of Hepatic Angiomyolipoma

Three cases of hepatic angiomyolipoma, each composed of an intimate mixture of numerous abnormal blood vessels and various-sized fat, spindle and/or epithelioid cells, are presented along with the findings of an electron microscopic study. The spindle cells were confirmed to be smooth muscle by immunohistochemical staining for des-min and by their ultrastructural characteristics. The mature fat cells, smooth muscle cells, immature short spindle cells apparently intermediate or transitional between the former two cell types, and the epithelioid cells were observed adjacent to the endothelial cells. Ultra-structurally, the epithelioid cells were characterized by unusual cytoplasmic organelles such as myofilaments having focal densities and dense attachments, numerous large electron-dense bodies, and a large number of glycogen particles and lipid droplets. Therefore, it is considered that the immature short spindle and epithelioid cells in hepatic angiomyolipoma might be primitive mesenchymal cells having an ability to differentiate toward both smooth muscle and fat cells. Acta Pathol Jpn 39 : 743-749, 1989.     

EXPERIMENTAL RAT CHORIOCARCINOMA An Electron Microscopic Study

Experimental choriocarcinomas of the rat were studied with electron microscopy and compared with the ultrastructure of rat trophoblasts at mid-and late-gestatlonal stage. The choriocarcinoma numbered m-803 contained abundant cytoplasmic organellae and was quite similar to the trophospongial cell at late-gestatlonal stage. The m-801 closely resembled the trophospongial cell at mid-gestational stage. The m-673, which has 3-beta-ol dehydrogenase enzyme system, could not be studied sufficiently inspite of the examination of more than 30 blocks of epon embedded specimen, because of the degeneration and necrosis occurring in the specimens.     

Opacification of Artificial Intraocular Lens: An Electron Microscopic Study

This paper describes the usefulness of electron microscopy in the investigation of the cause of opacification of an intraocular artificial lens (IOL), which affected both the anterior and posterior surfaces of the IOL. The explanted lenses were remarkably similar and were uniformly opaque, with "reticulated" surfaces under dissecting and ordinary light microscopes. TEM showed that the surfaces of the explanted lenses were irregular, and there was a layer of electron-dense granular deposits that extended to a depth of approximately 5 &#119 m into the lens substance. SEM showed a "cerebriform" lens surface with elevated areas alternating with depressed crevices, which corresponded nicely to the TEM appearance. Energy-dispersive x-ray analysis showed that the deposit was composed of calcium, oxygen, and phosphorus, which was later shown to be calcium hydroxyapatite by x-ray diffraction study. Electron microscopy has proven to be an essential tool in the investigation of the cause of this mysterious outbreak of opacification of the surfaces of the artificial lenses. Apart from directly visualizing the lens surfaces in a 2- and 3-dimensional manner, it also provides information on the elemental composition of the deposit. Such findings enable the clinicians and manufacturer to search for the underlying pathogenesis of the abnormal calcium hydroxyapatite crystals deposit.     

Metastatic Melanoma with Balloon Cell Changes: An Electron Microscopic Study

A case of metastatic balloon cell melanoma is presented. The balloon cells are ultrastructurally characterized by the presence of numerous cytoplasmic vacuoles and abnormal melanosomes, which confirm their melanocytic origin. The study supports the concept that the cytoplasmic vacuoles represent grossly dilated melanosomes. The value of electron microscopic examination is emphasized in order to distinguish these lesions from other malignant clear cell tumors.     

Thrombogenesis of the Rabbit Arterial Plaque: An Electron Microscopic Study

Rabbit arteries, de-endothelialized with an intravascular balloon catheter and allowed to heal for 4 weeks, showed intimal changes that were similar to the preatherosclerotic fibromusculoelastic plaques of man. Reinjury of the healed vessels by balloon catheter produced marked quantitative and qualitative alterations of hemostasis, as compared to that in previously uninjured vessels. The most apparent modification of thrombogenesis 10 minutes after injury to the plaque was a large increase in the size of the thrombotic deposits. Features of this exaggerated response were the major participation of fibrin in thrombus formation and greater platelet accumulation. Some platelets and fibrin strands appeared to penetrate into and beneath the neointima. By 3 hours, these deposits had diminished in size, although the hemostatic mass remained larger in the doubly injured vessels.     

CARCINOSARCOMA OF THE ESOPHAGUS: An Immunohistochemical and Electron Microscopic Study

Immunohistochemical and electron microscopic examinations were made of a carcinosarcoma of the esophagus in an 80-year-old man. An immunohistochemical examination showed that sarcomatous spindle cells were vimentinpositive, whereas squamous carcinoma cells were keratin-positive. No coexistence of vimentin and keratin in a single tumor cell was found. Electron microscopically, the sarcomatous spindle cells were characterized by well-developed rough endoplasmic reticulum, abundant intermediate filaments, and the occasional presence of peripheral aggregates of microfilaments. No definite desmosomes were identified among these cells. These results appear to indicate that most of the spindle-shaped tumor cells assume fibroblastic cellular features and synthesize the intermediate filament protein usually expressed in mesenchymal cells, even though such tumor cells could be epithelial in origin.     

Metastatic Melanoma with Balloon Cell Changes: An Electron Microscopic Study

A case of metastatic balloon cell melanoma is presented. The balloon cells are ultrastructurally characterized by the presence of numerous cytoplasmic vacuoles and abnormal melanosomes, which confirm their melanocytic origin. The study supports the concept that the cytoplasmic vacuoles represent grossly dilated melanosomes. The value of electron microscopic examination is emphasized in order to distinguish these lesions from other malignant clear cell tumors.     

An Electron Microscopic Study of Central Nervous System Sarcoidosis

Although the fine structure of extraneural sarcoidosis is well documented, ultrastructural study of central nervous system (CNS) sarcoidosis has been limited. Electron microscopic (EM) examination of 3 biopsy cases of CNS sarcoid revealed a mixed cellular population of lymphocytes, epithelioid cells, and multinucleated giant cells. The epithelioid and multinucleated giant cells shared common ultrastructural features of nuclei and cytoplasm, In addition, they displayed similar specializations of the cell surface, including subplasmalemmal linear densities (SLD) and villous projections. These findings recapitulate those described in extraneural sarcoidosis and other granulomatous disorders. This supports the contention that the macrophages or epithelioid cells present in CNS lesions are derived from the same mononuclear phagocytic system as their systemic counterparts.     

An Electron Microscopic Study of Central Nervous System Sarcoidosis

Although the fine structure of extraneural sarcoidosis is well documented, ultrastructural study of central nervous system (CNS) sarcoidosis has been limited. Electron microscopic (EM) examination of 3 biopsy cases of CNS sarcoid revealed a mixed cellular population of lymphocytes, epithelioid cells, and multinucleated giant cells. The epithelioid and multinucleated giant cells shared common ultrastructural features of nuclei and cytoplasm, In addition, they displayed similar specializations of the cell surface, including subplasmalemmal linear densities (SLD) and villous projections. These findings recapitulate those described in extraneural sarcoidosis and other granulomatous disorders. This supports the contention that the macrophages or epithelioid cells present in CNS lesions are derived from the same mononuclear phagocytic system as their systemic counterparts.