A light and electron microscopic study of mannosidosis

The present work investigated the light and electron microscopic changes in hypertrophied gingiva in a patient with mannosidosis. The biopsy specimens studied covered a period of 20 months; biopsy specimens were taken before and after a therapeutic trial with oral and local zinc sulfate. The intensity of the disease was progressive, in spite of the zinc, and was characterized by marked hyperplasia of the epithelium and severe inflammation of the stroma. Many of the cells in the inflammatory infiltrate, as well as cells indigenous to the gingiva, showed a striking vacuolation of their cytoplasm. Histiocytes were most numerous and also were most heavily vacuolated, but fibroblasts, endothelial cells, plasma cells, and epithelial cells also manifested the vacuolar change. In the histiocytes, the vacuoles occupied most of the cytoplasm, ranged widely in size, and were contiguous, molded, and intercommunicating. The vacuoles were bound by a single membrane and were filled predominantly by a finely granular material of medium density but also by varying amounts of coarser, darker granules, fragmented membranes, myelin-like figures, lipid droplets, and small vesicles. The vacuoles were interpreted as being consistent with secondary lysosomes that contained excessively stored substrate, similar to what has been observed in the mucopolysaccharidoses, in which the vacuoles have also been demonstrated histochemically and cytochemically to contain acid phosphatase, a known lysosomal marker.     

A light and electron microscopic study of perineuronal glial cells and processes in the rabbit neocortex

The morphology of satellite cells was determined by examining brom formalin fixed tissue stained by the silver carbonate technique, and tissue fixed in gluteraldehyde, post-fixed in osmium and prepared for electron microscopy. Light microscopy indicated that oligodendrocytes and astrocytes were the predominant perineuronal cell types. Cells with intermediate morphological characteristics were also observed. The light microscopic criteria for cellular indentification were the comparative size and shape of the cell bodies, and the number and nature of glial processes. Electron microscopy revealed perineuronal cells with round to oval shaped cell bodies, dense nuclear and cytoplasmic matrices, and a rich compliment of organelles. A second, less numerous, type of satellite cell had a larger, oval, elongate, or somewhat angular cell body, light nuclear and cytoplasmic matrices, and gliofibrils and glycogen. The former correlated well with the light microscopic oligodendrocyte and the latter with the astrocyte. “Dark cells” were not observed in a satellite position with the electron microscope nor were cells observed that conform to Hortega's “spiny microglia” in our silver preparations. Specializations of the plasma membranes of satellite glial cells and neurons were observed, and were interpreted as possible morphological evidence for “transport” between neurons and neuroglia.     

Retinal damage after prolonged exposure to visible light. A light and electron microscopic study

The objective was to study the effects of halothane, a volatile anesthetic, on hepatic metabolism of a second volatile anesthetic, methoxyflurane, and to correlate these biochemical findings with hepatic morphological changes. Microsomal fractions isolated from rats treated with halothane and from control animals were assayed for their capacity to dechlorinate methoxyflurane. Microsomes from halothane-treated rats demonstrated about 2.6 times the capacity to dechlorinate methoxyflurane as microsomes from control animals. Electron microscopy showed that liver cells from halothane-treated animals, when compared with hepatocytes from control rats, had increased amounts of smooth endoplasmic reticulum, an increased number of lipid droplets, and more microbodies per cell. Rough endoplasmic reticulum and glycogen were decreased by halothane treatment. We interpret these results to mean that halothane induces the rough endoplasmic reticulum to synthesize enzymes required for the biotransformation of methoxyflurane. It is suggested that these enzymes are placed in membranes of the rough endoplasmic reticulum. This organelle is converted to smooth endoplasmic reticulum and here the biotransforming enzymes function to dechlorinate methoxyflurane.     

Estrogen-producing adrenocortical carcinoma. A light and electron microscopic study

A case of adrenocortical carcinoma with feminization seen in a man aged 35, is reported. The levels of estron (E1) and estradiol (E2) in the venous blood draining the tumor were high, and it was confirmed by in vitro assay of tumor cells taken from the primary tumor of the left adrenal gland that the tumor produced estrone. The light microscopic examination demonstrated that the primary tumor was composed of mixture of large cells with pleomorphic nuclei and vacuolated cytoplasm and uniform cells with ovoid nuclei and eosinophilic cytoplasm. The electron microscopic examination on the latter cells revealed numerous large and irregularly shaped mitochondria with mostly tubular or lamellar and occasionally vesicular cristae and electron-dense matrix, well-developed smooth-surfaced endoplasmic reticulum in the cytoplasm. However, lipid droplets and lysosomes or lipofuscin granules were scanty. From these findings, it is suggested that cells of the present tumor have characteristics of those in the zona reticularis of the adrenal cortex as well as in the fetal cortex, and the functional property of this tumor is well correlated with its morphological features.     

A light and electron microscopic study of the pecten of the pigeon eye

The pecten in the pigeon is a pleated lamina that consists of blood vessels and interstitial pigment cells. Arterioles with thin, unspecialized endothelium give origin to an exceedingly dense capillary network. The endothelial cells of the capillaries are provided on both the luminal and basal surfaces with thin lamellar processes, constricted at their origins from the cell body. Luminal lamellae are long, erect and have a prevailing longitudinal orientation. Basal lamellae are shorter, more irregularly oriented and more closely compressed. Besides the usual complement of cytoplasmic organelles, a moderate number of coated vesicles and of coated and uncoated inpocketings of the plasmalemma is present in the endothelial cells. A labyrinthine system of interstices surrounds the stalks of the basal lamellae and contains a material that resembles the substance of the basement lamina in density and texture. A similar material is found on the outer surface of the basal lamellae and imperceptibly merges with the ground substance of an unusually thick adventitial layer that is permeated by numerous unit fibrils of collagen. The capillary network is drained by venules, whose wall resembles the capillary wall. The pigment cells contain melanin granules, large mitochondria and many bundles of filaments. They are sandwiched between two basement laminae and separate the blood vessels from the vitreous body. The bridge of the pecten consists of pigment cells with a few interspersed capillaries.     

A light and scanning electron microscopic study of hepatic veno-occlusive disease

Hepatic veno-occlusive disease, which was observed in a patient with hepatic coma, was examined by scanning electron microscopy (SEM), and correlated with its histology. Postmortem examination disclosed microscopic occlusion of the centrilobular and sublobular veins in the liver. These veins were occluded, partially or completely, by intimal and medial thickening of their walls due to proliferation of collagen and reticulin fibers. In addition to venous obliteration, which had not been demonstrated by other techniques, frequent occlusion of the sinusoidal opening into the central veins was observed by SEM. The size and distribution of the openings were irregular in comparison with those in normal controls. There was no evidence of fibrin thrombus formation in the veins. This case exemplified the usefulness of the application of SEM to autopsy material.     

Esthesioneuroblastoma: a light and electron microscopic study

The electron microscopic features of an olfactory esthesioneuroblastoma are described. The tumor cells had well developed neuritic processes containing neurotubules and neurofibrils. In addition, neurosecretory granules, similar to those seen in adrenal neuroblastomas, were present in the main cell body as well as in the neuritic processes. The neurites were also well demonstrated by light microscopic examination when stained by the Palmgren silver method. The importance of demonstration of these processes in establishing a firm diagnosis is stressed. Electron microscopic demonstration of neurites and secretory granules in a nasal tumor is diagnostic of an esthesioneuroblastoma.     

A light and electron microscopic study on the embryonic development of the rat carotid body

The embryonic development of the rat carotid body was studied with electron microscopy. In the 11 mm embryo a cell aggregation consisting of undifferentiated cells and unmyelinated nerve fibers appears on the anterior wall of the third branchial artery. Granule-containing cells appear in the 12 mm embryo and continue to increase in number as the cellular aggregation increases in size and becomes separated from the wall of the third branchial artery. Synapse formation and the appearance of fenestrated capillaries occur almost simultaneously at the 17 mm stage. There are two types of synapses, one with membrane densification and vesicles clustered inside the nerve endings, the other with dense material and vesicles inside the granule-containing cells. At the 20 mm stage the undifferentiated cells send enveloping cytoplasmic processes toward adjacent granule-containing cells and the carotid body anlage displays rudimentary lobules.     

Citrinin nephrotoxicity in rats: A light and electron microscopic study

Citrinin, a myocotoxin produced by Penicillium citrinum, causes hepatic and renal damage. This study describes light and electron microscopic changes in rat kidneys at intervals of 24, 48, 72, and 96 hr following administration of 50 mg/kg citrinin. Twenty-four hours after treatment, the most prominent change was cytoplasmic vacuolization of epithelial cells of proximal convoluted tubules. This vacuolar change involved clusters of proximal convolutions. Such focal changes were distributed throughout the cortex. Other components of the cortex and medulla appeared relatively normal morphologically; distal tubular damage was not observed. At 48 hr following administration of citrinin, multifocal areas of necrotic proximal convoluted tubules were observed. Extensive mineral deposits were present in the necrotic areas. Intact proximal and distal tubules were observed between the necrotic areas, and components of the medulla were not appreciably altered. At 72 hr, various degrees of regeneration of proximal tubular epithelial cells were noted in areas of necrosis in the cortex. Ninety-six hours following citrinin administration, tubular regeneration was still prominent and, in some cases, kidneys appeared completely normal morphologically.     

Non-pyramidal hippocampal projection neurons: A light and electron microscopic study

Summary Following injections of horseradish peroxidase conjugated with wheat germ agglutinin into the medial nucleus accumbens of the rat, a large number of projecting pyramidal neurons in the hippocampus were retrogradely labelled. In addition to this major projection, a few retrogradely labelled cells were tentatively identified at the light microscopic level as non-pyramidal neurons. These presumptive non-pyramidal neurons were found in all hippocampal layers, although they were mainly outside the stratum pyramidale, in the stratum oriens. Ultrastructurally, in serial sections, the non-pyramidal nature of 20 of these neurons was confirmed by their characteristic features such as deeply indented nuclei, occasional intranuclear inclusions, and symmetric and asymmetric synaptic contacts with their somata. Possible-transmitters used by these neurons are discussed.