Meningioma and intracranial hemangiopericytoma

Summary Electron microscopic study of 2 intracranial hemangiopericytomas and 7 meningiomas revealed fundamental morphologic differences between the 2 neoplasms. The most significant finding in hemangiopericytoma was the presence of ultrastructure features suggesting leiomyoblastic differentiation. These included characteristic fusiform intracytoplasmic and submembranous dense bodies, abundant cytoplasmic filaments, elongated cells with blunt-ended nuclei and juxtanuclear polarization of organelles. This observation is considered highly significant as an indicator of the pericytic nature of this tumor. In addition, hemangiopericytoma cells sometimes were arranged in spirals around pools of basement membrane-like material, perhaps a manifestation of the biologic capability of the cells to synthetize such material. Meningioma cells displayed as their main feature an ability to produce surface membrane specializations including interdigitations, desmosomes, zonulae adhaerentes and gap junctions. Sometimes the last 3 elements were linearly juxtaposed forming junctional complexes similar to those seen in certain epithelia. It is suggested that the characteristic whorls of meningioma are the result of cell interconnections arising from the specialized junctional attachments. Thus the distinctive morphology of the 2 neoplasms appears to derive from basic biologic properties of their elements.     

Ultrastructural comparisons of neurons of supraoptic and circularis nuclei in normal and dehydrated rats

A quantitative ultrastructural investigation was undertaken to compare the nucleus circularis (NC) and supraoptic nucleus (SON) of the rat both under normal and water-deprived conditions. NC was found to have dramatically more of its cells and membrane surface involved in direct soma-somatic contact than the SON. Water deprivation, even for one day, brought about a significant increase in both percentage of cells and membrane surface in contact in both nuclei, apparently by the retraction of fine glial processes from between the somata. The normal NC was made up of only one ultrastructurally identifiable cell type. The normal NC had no cells showing expanded endoplasmic reticulum, although these were seen following 5 days (but not 1 day) of water deprivation. The normal SON did have 4.4% of its cells showing expanded endoplasmic reticulum. This percentage significantly increased following water deprivation. The vesicle population per area of cytoplasm was very similar between the two normal nuclei. One day of water deprivation brought about a significant increase in < 800 Å vesicles in NC but not the SON. Five days of water deprivation resulted in a significant decrease in the lysosomal population per unit area in both nuclei. Vesicle changes have been discussed in relation to the volume changes in the cells.     

Osteoclast ultrastructure in Paget’s disease

The ultrastructural study of osteoclasts in biopsies from 12 patients with Paget’s disease reveals several cytological anomalies. In particular, nuclear inclusions, consisting essentially of striated filaments about 150 Å in diameter, often organized in bundles and sometimes in paracrystalline arrays, appear to be specific to the disease. Morphologically, the inclusions are remarkably similar to those observed in various cases of viral attack, and the hypothesis of the action of a possible external agent in Paget’s disease cannot be ruled out.     

Functional and fine structural characteristics of the sensory neuron blocking effect of capsaicin

Summary In the eye of rats the long-lasting specific desensitization induced by local or systemic capsaicin treatment is characterized by three phases: 1. complete insensitivity, 2. decreased sensitivity and a tendency to rapid adaptation, 3. normal initial sensitivity with a tendency to rapid adaptation to chemical pain stimuli. A low density of microvesicles and swollen mitochondria were found after local capsaicin treatment in certain nerve endings of the cornea of rats, but no signs of axonal degeneration or alteration in fine structure of non-neural elements were seen. Systemic capsaicin desensitization induced selective mitochondrial swelling in B type of neurons of the trigeminal ganglion which was demonstrable even 60 days after the pretreatment. Actinomycin-D, 8-azaguanine, 6-azauracil, aminopterin, mannomustin or cycloheximide in high doses did not alter the desensitizing effect of systemic capsaicin treatment. However, pretreatment of rats with colchicine or vinblastine prolonged the desensitizing effect of local capsaicin application, probably by inhibiting the axonal flow. It is concluded that capsaicin is a specific sensory neuron blocking agent having a practically irreversible effect in rats and guineapigs.     

The fine structure of the normal,resting terminal ductal-lobular unit of the female breast

Summary The fine structure of the terminal ductal-lobular unit (TDLU) of the normal, resting female breast is described. Tissue used conformed to strict criteria for normal. 4 distinct cell types, were observed, epithelium, myoepithelium, macrophages and lymphocytes. A gradation in structure, especially of myoepithelium, was found between the ductule tip and intralobular duct, apparently reflecting the age and function of each region. Cilia originating from the myoepithelial cells are possibly sensory in function. Epithelial vesicular inclusions may represent minimal secretory activity, transport of material across the cell, or be lysosomal in nature. The capillaries in close contact with the delimiting fibroblasts of the epithelial-stromal junction (ESJ) are described and the zone designated the capillary-fibroblast junction (CFJ). The CFJ is conceived as a regulatory unit similar to the ESJ, and may contribute to dysplasia due to biochemical or functional alterations, or to disruption of the microvascular geometry.     

Some ultrastructural features of the myocardial cells in the hypertrophied human papillary muscle

Summary An ultrastructural study using various electron microscopical techniques has been conducted on biopsy material from the hypertrophied papillary muscle of the human heart. About 75% of the myocardial cells were classified as hypertrophic with diameters ranging from 15 m to 53 m. The increased cell diameter appeared to be the result of an elevated amount of mitochondria and contractile material. The hypertrophied myocytes displayed a general ultrastructural organization in many ways similar to that of the normal sized myocytes. However, the former cells were characterized by focal deposits of excess laminar coat material and abnormal Z-band patterns as well as of multiple intercalated discs. The preferential sites for the production of new sarcomere elements appeared to be in the subsarcolemmal and intercalated disc regions. Adjacent myocardial cells were interconnected by collagen bundles, and, by an elaborate collagen-fibril-microthread-granule lattice. The surface folds were linked to each other by surface cables, which probably constituted a separate category of extracellular material of unknown function. Intramembranous particles were abundant in the sarcolemma proper but scarce in the membranes of the sarcoplasmic vesicles. Such particles were also observed in the lipofuscin granular membrane and in the membranes surrounding the lipid droplets. A framework of transverse cytoskeletal filaments interconnected the Z-bands of adjacent myofibrils and anchored the contractile material to the sarcolemma as well as to the nucleus. A large and lobulated nucleus containing well developed nucleoli together with an abundance of sarcoplasmic free and membrane-attached ribosomes, were interpreted as morphological signs of enhanced synthetic activity in the hypertrophied cell. Degenerative phenomena on the other hand were confined to lysosomal degeneration of worn-out cell constituents that were manifested by the numerous lysosomes and aggregates of lipofuscin granules. Abnormal Z-band patterns as seen in the present material were interpreted as an initial stage in the formation of new contractile elements.     

Uterine stromal morphology of the spayed, virgin rat when prepared with progesterone and oestrogen for implantation

Summary The effect of progesterone and oestrogen on the central uterine stroma has been examined in order to analyze what changes occur when the uterus is hormonally prepared for implantation.Both progesterone and oestrogen, when given separately, cause nucleolar enlargement and growth of the granular endoplasmic reticulum. However, after progesterone treatment the nuclei are large and spherical whereas they are spindle-shaped after oestrogen treatment. When oestrogen is administered to the progesterone-treated rat little change occurs in the stromal morphology.There is little morphological support to the view that oestrogen acts on the stroma to increase endometrial sensitivity. Further, progesterone seems to stimulate the synthesis of RNA and of cellular protein only in the stromal cell while oestrogen has a similar effect in all cell types of the uterus.     

Fine structural changes of myelinated nerve associated with copperhead envenomation

Summary The fine structure of right sciatic nerves of Swiss white mice was studied after being exposed to a venom solution ofAgkistrodon contortrix laticinctus (broad-banded copperhead) and to 0.9% NaCl solutions for periods of 1, 2 or 3 h. There was some Wallerian-like degeneration in all groups of nerves in the experiment. Additional neuropathological changes were noted in the nerves exposed to venom solutions.The connective tissue was affected most severely, while the basal lamina was unaffected. Schwann cells were vacuolated, and in the most extreme case, a type of myelin splitting occurred which was considered as a demyelinative effect. The results were compared to those of Martin and Rosenberg (1968) [15] on studies of the giant squid axon. References to additional fine structural studies of various other neuropathies were given.This investigation was submitted as a partial requirement for the Master of Science Degree, Department of Anatomy, Colorado State University and was supported by U.S. Public Health Service Grant # 5 RO1 GM-15591 and # 5 RO1 FD-00014 and Career Development Award # 5 KO4 GM-41786 from the National Institutes of Health (to A. T. Tu). The work was done in the Electron Microscope Training Laboratory, Colorade State University.     

Ultrastructural studies of metabolically active isolated adult rat heart myocytes.

Myocytes from adult rat heart were isolated by a method recently developed by us in which hearts were pre-perfused with calcium-free phosphate-buffered saline medium containing collagenase and hyaluronidase. This was followed by incubation in the enzyme medium and cellular sedimentation through 3% Ficoll. Myocytes isolated in this manner were metabolically active and morphologically intact. In the present study, scanning and transmission electron microscopy of isolated myocytes showed long cylindrical cells with transverse microridges which corresponded directly with sarcomere lengths. Most cells appeared to be in a fully contracted state. Contractile elements and associated membranes, other intracellular compartments and sarcolemmae were indistinguishable from their in vivo counterparts. Although myocytic basal laminae and other structurally identifiable surface coats were removed by our isolation procedure, sarcolemmae remained remarkably unaffected. Cyclic AMP assays in control and epinephrine- or glucagon-stimulated cells strongly suggested that membranebound receptors were present and the functional integrity of the sarcolemmae was maintained in our preparations.     

Effects of aging on the structural and permeability characteristics of cerebrovasculature in normotensive and hypertensive strains of rats

Summary This study demonstrates that markedly different patterns of age-related changes in blood pressure and body weight occur among normotensive Wistar-Kyoto (WKY) and Sprague-Dawley (SD) rats and spontaneously hypertensive rats (SHR). In addition, a variety of age-related structural alterations occurred in the walls of arterioles, capillaries, and venules of the frontal cortex. These changes include: (1) an increase in the thickness of the vascular wall by deposits of collagen and basal lamina which, in some cases, extended into the surrounding neuropil; (2) the presence of a flocculent material in the adventitia of intracerebral arterioles; (3) vesicular inclusions in perivascular macrophages, pericytes and smooth muscle cells which were labelled with i.v. administered horseradish peroxidase (HRP); (4) fragmentation of smooth muscle cells; and (5) accumulation of lipofuscin-like pigments in perivascular glial processes. The hypertensive rats exhibited these changes, but they were more advanced and more widely distributed throughout the cerebral cortex. The aged hypertensive rats occasionally had large bundles of 10 nm diameter, intermediate filaments in the endothelial cells. Whereas no change in blood-brain barrier permeability to HRP was observed in the aged normotensive rats, all age groups of the hypertensive rats exhibited increased permeability to HRP in the initial segment of penetrating arterioles in laminae I and II of the cerebral cortex.