A quantitative electron microscopic study of atypical structures in normal human cerebral cortex.

Biopsy samples of the cerebral cortex from four normal human brains were examined in the electron microscope for the presence of abnormalities related to neurones and neuroglia. Atypical forms of axons, axon terminals and dendrites, many of them similar to those described in a variety of pathological and experimental material, were found to occur in small but appreciable numbers. Neuroglia exhibiting atypical inclusions occurred but were much less common. Physiologically altered neuronal perikarya were not encountered apart from one neuronal death. An area of 3.6 x 10(5) mu2 was scanned from each brain and atypical structures were categorised and counted. The possible implications of the presence of these structures in normal brain in discussed and the need for neuropathologists and neuroanatomists to be aware of the existence of atypical forms of neuronal processes in normal human and animal brains is emphasised.     

Application of alcian blue in the electron microscopic study of mouse and human cerebral cortex nerve cells.

Alcian blue is a cationic dye which has been used in the histochemical field for the demonstration of polyanions especially carboxylated and sulphated. The results obtained in neurons when this dye was applied to human and mouse cerebral cortex and studied with the electron microscope are the object of the present report. The CNS of normal adult mice was fixed by vascular perfusion with 2% glutaraldehyde-0.1 M sodium cacodylate-0.1 M sucrose at pH = 6.8 followed by the same fixative with the addition of 0.5% alcian blue. After perfusion, brain cortex was taken out, sectioned into small blocks and immersed in a fresh similar mixture and subsequently in OSO4. Blocks were dehydrated and embedded in araldite. Ultrathin sections were doubly stained with uranyl and lead salts. Human brain cortex taken from patients with cerebral edema was fixed by immersion with 6.5% glutaraldehyde-0.1 M sodium phosphate, pH = 7.4 followed by embedding in warm agar and sectioning in slices of 30 mum thickness which were impregnated by immersion in a mixture of 1% alcian blue-acetate buffer-3% glutaraldehyde at pH = 3.5 for 9 to 15 h at 4 degrees C and subsequently immersed in 1% buffered OSO4-0.1 M sucrose, pH = 7.4 for 2 h at 4 degrees S. Sections were dehydrated and embedded in araldite. Ultrathin sections were doubly stained by uranyl and lead salts. We have denominated the complete procedure in both instances GABOUL technique. The submicroscopic study of both tissues, at nerve cells, revealed the presence of an electron dense homogeneous substance thoroughly dispersed at the hyaloplasmic matrix of perikarya, processes and even synaptic endings. This substance was more evident around free and attached ribosomes, GOLGI apparatus, complex vesicles, dense bodies, microtubules, subsurface cisternae and synaptic vesicles. Canaliculi of endoplasmic reticulum and even the perinuclear cistern also showed a moderate content. It is suggested that this electron dense substance, being alcianophilic, has a polyanionic character and thus may partially correspond to acid polysaccharides since these compounds have already been previously confirmed in such neurons by biochemical and light microscope histochemical techniques.     

Nerve cell death types in the edematous human cerebral cortex

Cortical biopsies of 18 patients with clinical diagnosis of congenital hydrocephalus, brain trauma, and vascular anomaly were examined with the transmission electron microscope to study the distinct and overlapped morphological cell types of nerve cell death in the human edematous cerebral cortex. The nerve cells showed lobulated and shrunken nucleus, irregular enlargement and fragmentation of perinuclear cistern, with areas of apparently intact nuclear pore complexes alternating with regions of nuclear pore complex disassembly. The nucleolus appears unaltered in moderate edema and with distorted nucleolar subcompartments in severe edema. Most nonpyramidal nerve cells, astrocytes and oligodendrocytes underwent an oncotic-apoptotic-necrotic continuum featured by swollen nucleoplasm, cytoplasm, and cell organelles, chromatin condensation and marginalization, and formation of apoptotic bodies. In a lesser proportion other nonpyramidal nerve cells, astrocytes and oligodendrocytes only showed apoptosis or oncosis. Autophagic cell death characterized by presence of autophagic vacuoles of lysosomal origin was rarely seen. The above findings suggest that different mechanisms of nerve cell death occur in the human edematous cerebral cortex related with brain trauma, congenital hydrocephalus, vascular anomaly, and their anoxic-ischemic conditions. An oncotic-apoptotic continuum process leading to necrosis predominates in human cerebral cortex nerve cell populations. The nerve cell death is discussed in relation with the severity of brain edema, anoxic-ischemic conditions of brain parenchyma, oxidative stress, glutamate excitotoxicity, calcium overload, and caspase dependent and independent mechanisms.     

A scanning and transmission electron microscopic study of human nodular goitre

This paper is a concurrent scanning and transmission electron microscopic study of 13 cases of nodular goitre.     

Nerve cell nuclear and nucleolar abnormalities in the human oedematous cerebral cortex. An electron microscopic study using cortical biopsies

Cerebral cortical biopsies of 17 patients with clinical diagnosis of congenital hydrocephalus, complicated brain trauma, cerebellar syndrome and vascular anomaly were examined with the transmission electron microscope to study the nuclear and nucleolar abnormalities induced by moderate and severe brain oedema, and the associated anoxic-ischemic conditions of brain tissue. In infant patients with congenital hydrocephalus and Arnold-Chiari malformation two different structural patterns of immature chromatin organization were found: the clear type characterized by a clear granular and fibrillar structure of euchromatin, scarce heterochromatin masses and few perichromatin granules, and a dense granular and fibrillar euchromatin with abundant and scattered heterochromatin masses, and increased number of perichromatin granules. The lobulated nuclei exhibited an irregularly dilated and fragmented perinuclear cistern, and areas of apparently intact nuclear pore complexes alternating with regions of nuclear pore complex disassembly. In moderate traumatic brain injuries some nucleoli exhibit apparent intact nucleolar substructures, and in severe brain oedema some nucleoli appeared shrunken and irregularly outlined with one or two fibrillar centers, and others were disintegrated. The nuclear and nucleolar morphological alterations are discussed in relation with oxidative stress, peroxidative damage, hemoglobin-induced cytotoxicity, calcium overload, glutamate excitotoxicity, and caspase activation.     

Morphological changes in the cerebral cortex after a stroke

29 brains of right-handed persons who died within the period of 4 hours to 6 years after the stroke were studies. The patients had various disorders of speech and movements, partial or complete speech recovery was observed in 10 cases. Aphasias resulted from the lesions of associative fibers connecting the speech zones of the brain cortex, direct destruction of speech regions, in cases of hematoma pressure on cortex speech areas. Changes in neurons, nerve fibres and neuroglia in the cortex of speech areas were determined by the time passed after the stroke. They were also dependent on the site and size of the focus and, to a certain extent, correlated with a clinical picture. The changes also depended on localization and the size of lesion. Sometimes the changes correlated with clinical data. Clinical and morphological comparisons indicate that a correlation exists between speech recovery degree and the intensity of repairing processes in neurons and nerve fibres in cortical speech areas.     

A transmission electron microscopic study of macromelanosomes in sporadic dysplastic naevi.

Melanosomes in sporadic dysplastic nevi were examined by transmission electron microscope. In particular the structure of macromelansomes was observed. Macromelanosomes were present in both nevus cells and keratinocytes. They were round and consisted of a core structure and a cortex structure. The core was composed of electron-dense amorphous material and electron-lucent microvesicles. The cortex contained grains of different sizes and electron densities. Occasionally small melanosomes were observed in the cortex. Electron-lucent microvesicles were also present in small spherical and ellipsoid melanosomes. Melanosome complexes observed in nevus cells contained degrading melanosomes with electronlucent microvesicles, dispersed microvesicles and grains. Melanosome complexes with structures resembling those found in macromelanosomes were also present. The result of the investigation suggests that melanosome complexes found in nevus cells might become macromelanosomes through autophagy.     

An electron microscopic study of plasmatic arterionecrosis in the human cerebral arteries

Summary An electron microscopic study of the intracerebral arteries from 9 hypertensive cases was performed in order to elucidate the morphogenesis of the plasmatic arterionecrosis which was considered to be the direct cause of hypertensive intracerebral hemorrhage. In the preceding stage of the arterial lesions, marked necrosis of medial smooth muscle cells and increase of basement membrane-like substance in the intima and media were observed. The lumina of these arteries were slightly dilated. The dilatation and hemodynamic factors were supposed to cause endothelial injury resulting in blood plasma insudation into the intima through the opened spaces between endothelial cells. The insudated blood plasma dispersed and dissolved the basement membrane-like substance, collagen and elastic fibers in the arterial wall, leading to the development of the plasmatic arterionecrosis.This study was supported by a Grant-in-Aid for Scientific Research of the Japanese Ministry of Education (No. 857052).     

The reactive oligodendrocyte. An electron microscopic study of cerebral cortex following alpha particle irradiation

The ultrastructural features of oligodendrocytes have been studied in a zone of cerebral cortex in which all neurons are destroyed and numerous processes damaged by heavy ionizing particles. This type of lesion fails to reveal signs of vascular inflammation and classical “gitter cells” in light microscopy or any signs of debris fragments in electron microscopy. Oligodendrocyte satellites of neurons or their processes display an acute swelling associated with signs of neuronal damage. This is followed by a marked increase in a morphologically rich variety of dense osmiophilic organelles of granular, lamellar, crystalline or amorphous sub-structure. Acid phosphatase activity has been demonstrated in some of these organelles, thus implying a participation in “lysosomal” intracellular breakdown. Invasion by microgliacytes and phagocytosis was not observed. Present evidence supports the efficacy of intracellular mechanisms in the breakdown of degenerating material and suggests a re-evaluation of the evidence for identification of microglia on the basis of granular inclusions.     

An electron microscopic study of dendritic degeneration in the cerebral cortex resulting from laminar lesions

Summary The morphological characteristics of dendrites in layers of the cerebral cortex above laminar lesions induced by ionizing particle irradiation have been studied in the striate field of rat at various survival times. Within two weeks following irradiation an increasing number of dendrites display unusual alterations inferred to be signs of degeneration.Degenerating dendrites can be characterized by a dense cytoplasmic matrix, disruption of mitochondria, presence of dense bodies, irregular outline and a marked alteration of the plasmalemma in its dimensions and staining properties. Some degenerating dendrites possess a large accumulation of dense subsynaptic material and are contacted by synapses with enlarged and altered synaptic clefts. A few dendrites contain extensive membranous whorls. Engulfment by reactive astrocyte processes is a common feature and often includes the presynaptic axonal knob, but only the degenerating dendrite has been observed within glial cytoplasm. The inference that the majority of degenerating dendrites in this material are apical dendrites of pyramidal cells suggests that either shaft synapses are common for these cells, protuberances may retract during degeneration, or spines are lost due to loss of afferent terminals.Supported by research grants from the United States Public Health Service, NB-4578 and NB-6594.     

An electron microscopic study of the mediodorsal cerebral cortex in the lizard Agama agama

Summary An electron microscopic analysis was made of the small-celled part of the mediodorsal cortex of the lizard Agama agama. This cortex consists of four layers: Superficial plexiform layer, cellular layer, deep plexiform layer and fiber layer. In the superficial plexiform layer one type of solitary neuron with smooth dendrites is present.Three types of axon terminals can be observed: terminals with a moderately electron dense matrix packed with spherical vesicles (S1 type), axon terminals with an electron lucent matrix containing fewer spherical synaptic vesicles than the S1 type (S2 type) and axon terminals with an electron lucent matrix and scattered pleomorphic synaptic vesicles (F type). F type axon terminals are larger than S terminals. At the pial surface endfeet of tanycytic processes form a limiting glial layer, contacting one another by means of gap junctions. In the cellular layer perikarya of pyramidal neurons are densely packed. The karyoplasm of these neurons shows either evenly dispersed or discretely clumped chromatin. Spiny dendrites arise from the perikarya and extend into both the superficial and deep plexiform layers. The structure of the deep plexiform layer is roughly similar to that of the superficial plexiform layer. The fiber layer contains the majority of the afferent and efferent axons of the mediodorsal cortex. The axons are myelinated and unmyelinated. Between the fibers, scattered solitary neurons are present, often accompanied by glial cells.The lateral ventricle beneath the fiber layer is lined by a single row of ependymal tanycytes. Tanycytic processes traverse the cortical layers and may form endfeet at the pial surface. Protoplasmic excresenses from some ependymal cells protrude into the ventricle.     

Secretory mechanisms of human ceruminous glands: A transmission and scanning electron microscopic study

Two secretory mechanisms (eccrine and apocrine) were observed by transmission and scanning electron microscopy in the same secretory cells of the human ceruminous glands. The eccrine secretion occurs as a typical exocytosis by fusion of the limiting membrane of the secretory granule with the apical plasmalemma. The apocrine secretion is more complex and takes place by sequential steps: bulging of the cellular apex into the lumen, constriction of the projection, and detachment of it from the cell. This mechanism generally causes the removal of the entire projection all at once by decapitation at its base; some variations of this process have been found, however, and are described in the present work. A double membrane, apparently separating the apical protrusion from the rest of the cell, is noticeable in our photographs. Nevertheless, even if this membrane is very similar to a demarcation layer, we consider it as an intercellular double membrane separating two obliquely sectioned cells.     

Chronic intracellular leucocytoclastic bacterial vitritis. A transmission electron microscopic study of the monocytes

Vitritis, the presence of leucocytes in the acellular ocular vitreous, often accompanies ocular vasculitis (V). Non-cultivatable intracellular mollicutes (M), i.e. cell wall deficient bacteria, readily identified by transmission electron microscopy (TEM), are well known plant vascular pathogens. Recently similar intracellular polymorphonuclear leucocytes (PMNL) and lymphocytes (L) parasitising/destroying and mouse ocular and lethal systemic V producing M-like bacteria were reported to be a common cause of human ocular V. In this TEM restudy of 8 human and 3 mouse VM induced chronic ocular V materials severe nuclear and cytoplasmic alterations associated with generalized cytoskeletal nuclear-anchoring 0.005-0.010 micron particles, 0.01-0.05 micron diameter branching filaments and tubules, and trilaminar membrane bound complex internal structure containing 0.1-1.9 micron spherules, all indistinguishable from VM, were observed within 1-3% of the monocytes in all 11 specimens. The results indicate that VM also parasitise and destroy both human and mouse monocytes. VM induced alterations in monocytes, PMNL, and L are compared, and the monocyte nuclear damage/Rifampin beneficial effect relationship in VM induced ocular V is discussed.