Hyperplastic Lymphoid Tissue in HIV/AIDS: An Electron Microscopic Study

The purpose of this study was to characterize the ultrastructure of lymphoid tissue from HIV/AIDS patients and to evaluate it as a reservoir and source of HIV. HIV has been demonstrated in lymph nodes and tonsils and adenoids, by immunohistochemistry (IHC), in situ hybridization (ISH), and transmission electron microscopy (TEM), to be associated with germinal center (GC) follicular dendritic cells (FDC). The presence of HIV in the larger gastrointestinal tract-associated lymphoid tissue (GALT) has been much less studied. Whether FDC themselves are productively infected by HIV in any of the lymphoid sites is controversial. Lymph nodes, tonsils, and gastrointestinal biopsies were fixed in neutral buffered glutaraldehyde and prepared for TEM. Mature HIV particles were abundant in GC of hyperplastic lymph nodes, tonsils, and the GALT. They were enmeshed within an electron-dense matrix associated with an all-encompassing branching FDC network of processes. HIV particles were seen budding from both FDC and lymphocytes. The greatest numbers of particles were seen in hyperplastic lymphoid tissue from untreated individuals and in lymph nodes co-infected with opportunistic organisms, such as Mycobacterium aviumcomplex. In addition to HIV, unidentifiable “particles” of varying sizes, possibly including other viruses, were regularly seen in association with FDC. Ultrastructural study graphically demonstrated the abundance of HIV particles associated with the complex FDC network of hyperplastic lymph nodes, tonsils, and GALT. HIV was shown to productively infect FDC, as well as lymphocytes.     

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.     

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.     

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.     

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.     

Myonecrosis Induced by Rattlesnake Venom: An Electron Microscopic Study

The myonecrotic effect of rattlesnake (Crotalus viridis viridis) venom on mouse skeletal muscle was studied. The biceps femoris muscle was examined with the electron microscope after one-fourth the LD₅₀ of the crude venom was injected into the gracilis and semimembranosus muscles. Focal areas of myonecrosis were abundant. Injured fibers contained dilated sarcoplasmic reticulum, disoriented, coagulated myofilamentous components and condensed, rounded and enlarged mitochondria. The external lamina and sarcolemma remained intact in many fibers. Hemorrhage was apparent in the endomysial connective tissue, and hemolysis was discernible. In areas where the erythrocytes were tightly packed between the muscle fibers, there was disruption of the external lamina and sarcolemma. Degeneration of the fibers in these areas was pronounced. These findings correlate well with the breakdown of muscle fibers by various methods described in the literature. Myonecrosis induced by snake venom may serve as a useful model for studying muscle necrosis because of its rapid onset and relative ease of induction.     

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.     

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.     

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.     

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.     

Radiation-Induced Cardiomyopathy: II. An Electron Microscopic Study of Myocardial Microvasculature

Sequential ultrastructural lesions of rabbit myocardial microvasculature after a single dose (1008 or 1300 rads) of local x-irradiation are described. Vascular permeability status was assessed through use of ferritin and colloidal carbon. Endothelial cell swelling and increased vascular permeability were the most conspicuous lesions during the first week following irradiation. Increased vascular permeability, as indicated by the observed ferritin and carbon distribution, appears to be a result of altered pinocytotic transport and widening of endothelial junctional gaps. These lesions, on day 14 and later, were followed by basement membrane thickening, endothelial cell extrusions and bleb formation, platelet sequestration, abnormal endothelial cell phagocytosis and appearance of myelin-like figures within the endothelial cells.