Fibrillary accumulations in oligodendrogial processes of rats subjected to protocaval anastomosis

Corpora-amylacea and the family of polyglucosan diseases

The history, characters, composition and topography of corpora amylacea (CA) in man and the analogous polyglucosan bodies (PGB) in other species are documented, noting particularly the wide variation in the numbers found with age and in neurological disease. Their origins from both neurons and glia and their probable migrations and ultimate fate are discussed. Their presence is also noted in other organs, particularly in the heart. The occurrence in isolated cases of occasional 'massive' usually focal accumulations of similar polyglucosan bodies in association with certain chronic neurological diseases is noted and the specific conditions Adult Polyglucosan body disease and type IV glycogenosis where they are found throughout the nervous system in great excess is discussed. The distinctive differences of CA from the PGB of Lafora body disease and Bielschowsky body disease are emphasised. When considering their functional roles, a parallel is briefly drawn on the one hand between normal CA and the bodies in the polyglucosan disorders and on the other with the lysosomal system and its associated storage diseases. It is suggested that these two systems are complementary ways by which large, metabolically active cells such as neurons, astrocytes, cardiac myocytes and probably many other cell types, dispose of the products of stressful metabolic events throughout life and the continuing underlying process of aging and degradation of long lived cellular proteins. Each debris disposal system must be regulated in its own way and must inevitably, a priori, be heir to metabolic defects that give rise in each to its own set of metabolic disorders.

Diurnal rhythm returns to normal after elimination of portacaval shunting

Previous studies showed that portacaval shunting causes metabolic and behavioral changes in rats. Most metabolic changes reversed within 1-2 wk after restoration of normal circulation. However, the rate of cerebral glucose metabolism (CMRGlc) remained depressed in some areas. The question arose whether complete recovery was possible. Therefore, a long-term behavioral study was undertaken to determine the time course of recovery. Diurnal activity was monitored for 48 h each week over a period of 14 wk: 2 wk before shunting, 6 wk after shunting, and 6 wk after restoration of normal hepatic circulation. Nighttime activity was depressed within 1 wk of shunting and did not change. Normal circulation to the liver was reestablished after 6 wk. The diurnal cycle was normal 3 wk later. Thus, although recovery of the diurnal rhythm is possible, the relatively long period necessary suggests the correction of a significant structural or chemical abnormality. A study of CMRGlc was made using the behavioral study as an index of the time necessary for recovery. CMRGlc returned to normal throughout the brain 6 wk after cessation of shunting except in the hippocampus and amygdala (7-8% decrease).

Elucidation of three-dimensional ultrastructure of Hirano bodies by the quick-freeze, deep-etch and replica method

To clarify the yet controversial fine structure of Hirano bodies, we made three-dimensional observations of the tissues from the right hippocampus obtained at autopsy of elderly patients by the quick-freeze, deep-etch and replica method. The basic structure of Hirano bodies was a unit lamella, a closely attached pair of sheets composed of parallel-running smooth filaments, 10 to 12 nm in diameter with 12-nm interspaces. In the unit lamella, filaments from each of the overlapping sheets crossed obliquely at acute or obtuse angles to form lattice-like meshworks. The unit lamellae were arranged in a folded, waved or concentric manner, and connected or supported by cross-linking filaments of the same width. The distance between these unit lamellae was about 50 nm. Occasionally the sheets were separated or fused making layers of one to three sheets. At the periphery of the bodies parallel filaments were dispersed into individual filaments of similar size or directly attached to the cytoplasmic membrane.

Alterations of oligodendrocytes and demyelination in the spinal cord of patients with mitochondrial encephalomyopathy

The spinal cords of 2 autopsied patients with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) were examined. Histologically, the spinal cords showed a spongy state due to the presence of distended myelinated fibers with enlarged periaxonal spaces. Ultrastructurally, the affected fibers showed extensive microvacuolation of the inner myelin sheath with occasional vesicular changes. The presence of macrophages near the degenerated myelin was a frequent finding. The stripping of myelin lamellae by macrophage was observed, with frequent appearance of denuded axons. Furthermore, prominent morphological changes were observed in oligodendrocytes. These findings indicate that demyelination, probably secondary to the degeneration of oligodendrocytes, occurs in the spinal cord of MELAS.

Hirano bodies and other cytoskeletal abnormalities develop in fetal rat CNS grafts isolated for long periods in peripheral nerve

Dissociated cells from the telencephalic region of 12-day-old rat embryos were cultured in vitro for 3-5 days and transplanted into segments of the sciatic nerve of adult inbred rats. Transplanted progenitor cells survived, differentiated, and expressed various morphological and molecular features characteristic of neurons and glia. Six to twelve months after grafting, many neurons underwent changes compatible with an alteration of their cytoskeleton. These included: (1) a strong perikaryal immunoreactivity to the monoclonal antibody RT97, directed against the 200-kDa phosphorylated neurofilament subunit and (2) the formation of Hirano bodies within dendrites. Similar cytoskeletal abnormalities are seen as part of the spectrum of changes that occur in some human neurodegenerative diseases and in aging. The approach we have used may provide new possibilities for the study of the pathogenesis of these lesions under controlled laboratory conditions.

Morphometric and densitometric investigations of protoplasmic astrocytes and neurons in human hepatic encephalopathy

Morphometric and densitometric evaluations were made of nuclei of astrocytes and nerve cells of 49 cases with chronic liver diseases and of 9 control cases. The data measured from Nissl-stained specimens of putamen were compared with clinical degrees of encephalopathy and with blood ammonia levels. The parameters measured included nuclear area and optical density of nuclei. The nuclear area of astrocytes (AAREA), on average, was found to grow significantly along with aggravation of encephalopathy, that growth being from 39 micron 2 in the control group to about 60 micron 2 in cases of severe encephalopathy. Furthermore the proportion of astrocyte nuclei with an area above 70 micron 2 (ALRG) and the proportion of the optical light area of the total nuclear area (AHOLE) rises. Mean compactness (ACEXT) and mean extinction of astrocyte nuclei (AMEXT) dropped along with growing severity of encephalopathy. Mean blood ammonia levels rose from 42 mumol/l in cases with no microscopically detectable signs of encephalopathy to about six times higher values in cases with severe encephalopathy. Optical density of astrocyte nuclei was negatively correlated and mean nuclear area positively correlated to blood ammonia levels. No characteristic morphometric and densitometric changes of nerve cell nuclei were recordable from the putamen.

Cytoskeletal protein abnormalities in neurodegenerative diseases

The nervous system is a rich source of filamentous proteins that assume critical roles in determining and maintaining neuronal form and function. Neurons contain three major classes of these cytoskeletal organelles: microtubules, intermediate filaments, and microfilaments. They also contain a variety of proteins that organize them and serve to connect them with each other. Such major neurodegenerative diseases as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, as well as a variety of toxic neuropathies, are characterized pathologically by intraneuronal filamentous inclusions. Recent studies using biochemical and immunocytochemical techniques have established that these abnormalities represent disorganized states of the neuronal cytoskeleton and have determined some of the specific molecular constituents of these inclusions. This knowledge has led to new ways of thinking about their origins.

The structure analysis of Hirano bodies by digital processing on electron micrographs

To clarify the structure of Hirano bodies, electron micrographs of Hirano bodies taken at various tilting angles have been studied by digital image analysis. On the electron micrographs, the beaded filaments of Hirano bodies were turned into a pattern of lattice-like arrays by changing the tilting angles. Based on computer-processed diffraction patterns and filtered images, it is proposed that the filaments of Hirano bodies are helical strands with a pitch of 185 A. A model for the helical strand drawn by microcomputer at various angles of rotation is in accordance with the filtered images of the tilted filaments. Computer simulation also reveals that the helical strands appear to be lattice-like when they are arranged in parallel.

Hirano body in an inflammatory cell of leptomeningeal vessel infected by fungus Paecilomyces

An intracytoplasmic microfilamentous lattice, ultrastructurally identical to Hirano body, was found in an inflammatory cell within a leptomeningeal vessel wall infected by fungus Paecilomyces javanicus. The structure was well preserved and not associated with phagosomes. This is the first report of Hirano body found in an inflammatory cell at the site of fungal infection. The present finding suggests that the formation of Hirano body is non-specific and not restricted to the cell of the neuro-muscular system.

Hirano-bodies in the distal symmetric polyneuropathy of the spontaneously diabetic BB-Wistar rat

Lattice-like cytoplasmic inclusions have been demonstrated in a variety of pathologic conditions of the CNS and PNS in both man and animals. We describe 2 types of such inclusions occurring in association with the distal central-peripheral symmetric polyneuropathy of the spontaneously diabetic BB-Wistar rat. In the literature, both these lattice-like inclusions have been referred to as Hirano-bodies, but have not been separated on the basis of different measurements, locations or possible origins.

The brain in experimental portal-systemic encephalopathy. I. Morphological changes in three animal models

Morphological features of three models of portal-systemic encephalopathy in the rat were studied and compared with plasma ammonia levels and clinical observations. Carbon tetrachloride-induced cirrhosis with terminal coma produced a wide variety of structural changes in the brain whose severity was related to plasma ammonia levels at the time of death. These changes included diffuse gliosis, Alzheimer cells and focal neuronal necrosis but did not include spongiform changes in cerebral or cerebellar cortex. Porta-caval anastomosis (PCA) did not appear to produce any significant neurological symptoms. Rats with PCA of durations 1-30 weeks were studied and over this time the structural changes included astrocytic nuclear swelling, swelling of perivascular astrocytic foot-processes and spongiform change in the molecular layer of the cerebellum. No evidence of Alzheimer cells or gliosis was seen and plasma ammonia levels at no stage exceed twice the normal levels. Porta-caval anastomosis followed by gavage feeding with ammoniated cationic exchange resin produced severe neurological symptoms and marked hyperammonaemia. In these animals not only astrocytes but oligodendrocytes and neurons showed nuclear and cytoplasmic swelling and numerous Alzheimer type II cells were seen, together with a diffuse gliosis, but no evidence of spongiform change in the cerebral or cerebellar cortex was seen. It is concluded that ammonium ions are important in the genesis of morphological changes in the brain in rat models of portal-systemic encephalopathy, but the relevance of these changes to neurological dysfunction is uncertain.

Studies on acetylcholinesterase and gamma-glutamyltranspeptidase in mouse brain in ammonia toxicity

Short- and long-term ammonia toxicity was induced in mice by intraperitoneal injection, respectively, of single and six doses of 0.6 mM ammonium acetate per 100 g of body weight. The animals were sacrificed half an hour after either the single injection or after the last injection of six doses. Under these experimental conditions the ammonia levels were found to be elevated twofold in cerebral cortex, brain stem, and basal ganglia after the administration of a single dose of ammonium acetate. A fourfold increase in the content of ammonia was observed in cerebral cortex, brain stem, and basal ganglia after six injections. An elevation in the activity of pseudocholinesterase (enzyme localized in brain capillaries and glial cells) in all the above four regions resulted as a short-term effect of ammonia toxicity. True acetylcholinesterase was found to be elevated in all the four regions in short-term and in long-term ammonia toxicity. Gamma-glutamyltranspeptidase (GGTP), another enzyme localized in cerebral capillaries and glial cells, was found to be depressed in all the regions of the brain in both short- and long-term ammonia toxicity. The implications of these results are discussed in relation to glial cell function.

Hirano bodies in myelinated fibers of hepatic encephalopathy

Inclusions, essentially identical to Hirano bodies, were observed in the substantia nigra, dentate nuclei, and frontal lobes in three autopsy cases of hepatic encephalopathy. Similar inclusions were not observed in these areas in nine controls. The inclusions were mainly seen in the inner loops of the myelinated fibers, between the myelin lamellae, and among degenerated myelin sheaths. The same inclusions were rarely observed in postsynaptic terminals.

Hirano bodies in the axon of peripheral nerves in a case with progressive external ophthalmoplegia with multisystemic involvements

Inclusions, ultrastructurally identical with Hirano bodies which were previously believed to be limited to the central nervous system (CNS), were found both within peripheral myelinated nerve axons and within terminal axons of neuromuscular junctions in the ocular muscles of an autopsied woman who had suffered from progressive external ophthalmoplegia with multisystemic involvements. Electron micrographs showed the inclusions to consist of beaded filaments or lattice-like structures with filamentous elements continuing onto neurofilaments in the axon. The corelation of these new pathological findings in peripheral nerve axons and ophthalmoplegia is discussed.

Chronic metabolic effects of ammonia in mouse brain

Chronic ammonia toxicity in experimental mice was induced by exposing them for 2 and 5 days to 5 % (v/v) ammonia solution. The enzymes concerned with glutamate metabolism (aspartate-, alanine- and tyrosine aminotransferases, glutamate dehydrogenase and glutamine synthetase) and (Na+ + K+)-ATPase were estimated in the three regions of brain (cerebellum, cerebral cortex and brain stem) and in liver. Glutamate, aspartate, alanine, glutamine and GABA, RNA and protein were also estimated in the three regions of brain and liver. A significant rise in the activity of (Na+ + K+)-ATPase in all the three regions of brain along with a fall in the activity of alanine aminotransferase was noticed. Changes in the activities of other enzymes were also observed. A significant increase in alanine and a decrease in glutamic acid was observed while no change was observed in the content of other amino acids belonging to the glutamate family. As a result of this, changes in the ratios of glutamate/glutamine and glutamate + aspartate/GABA was observed. The results indicated that the brain was in a state of more depression and less of excitation. Under these conditions the liver tissue was showing a profound rise in the activity of the enzymes of glutamate metabolism. The results are further discussed.

Morphometric studies of rat glial cell ultrastructure after urease-induced hyperammonaemia

The ultrastructure of astrocytes and oligodendrocytes was investigated in hyperammonaemic rats injected daily with urease for 4 days. Glial cells were randomly photographed and magnified x28 000. Cell and nuclear sizes were estimated by planimetry and mitochondrial size and density were measured by image analysis. After 4 days of hyperammonaemia the astrocyte cytoplasmic area was increased by 46%. Mitochondrial area was increased by 20%, but after correction for cytoplasmic oedema the number and size of mitochondria were not significantly increased. The nuclear and cytoplasmic areas of oligodendrocytes were unchanged. The mitochondria of oligodendrocytes were small in the hyperammonaemic group and so was their percentage area to cytoplasmic area, but their numbers were unchanged. It was concluded that hyperammonaemia induces astrocyte oedema and increases the astrocyte mitochondrial content. These findings support the assumption that the astrocytes are the active cells in the brain metabolism of ammonia. The decrease in oligodendrocyte mitochondrial content could be considered a point against an active function of oligodendrocyte mitochondria in ammonia metabolism in hyperammonaemia.

Crystalloid inclusions reminiscent of Hirano bodies in autolyzed peripheral nerve of normal wistar rats

In a study of experimental autolysis of peripheral nerves of normal Wistar rats, crystalloid inclusions similar to Hirano bodies were observed. They occurred in the nuclei and cytoplasms of Schwann cells and in myelinated axons. They first developed after a 12-h autolysis and increased in number and size with time. Their fine structure, localization, and morphogenesis are discussed in relation to the autolysis of the cellular organelles.

Systemic lupus erythematosus clinically resembling multiple sclerosis and with unusual pathological and ultrastructural features

A case of systemic lupus erythematosus is described which clinically resembled multiple sclerosis and in which the lesions were restricted to the central nervous system. The necropsy findings of vascular thickening and necrosis in the spinal cord and in a posterior nerve root explain the main clinical abnormalities. Clinical signs of the terminal peritonitis secondary to cholecystitis were absent or minimised probably because of the steroid therapy and spinal cord necrosis. Primary demyelination was not demonstrated though electronmicroscopy revealed lattice fibrillar inclusions within a few myelin sheaths. An unusual ultrastructural feature was the finding of "rod-shaped tubular bodies" in large numbers in the endothelial cells of cerebral blood vessels. The incidence and morphology of these organelles are compared with those of the intracisternal tubuloreticular structures (TRS) commonly found in systemic lupus erythematosus.

Light and electron microscopic observations on the relationship between Hirano bodies, neuron and glial perikarya in the human hippocampus

Hippocampi from two intellectually normal and four demented subjects were examined in autopsy material. Large Hirano bodies seen by light and electron microscopy were thought to be glial in origin and not to be produced by the perikarya of neurons as has been suggested in the literature. Myelination of two Hirano bodies found in the stratum lacunosum-granulosum where neuron perikarya are rare suggests that these bodies are produced by oligodendroglia. Hirano bodies were found to be associated with neurons showing granulovaculoar degeneration. With electron microscope they were frequently seen to be divided by clefts filled with amorphous material which possibly consisted of free ribosomes.

Effects of ammonia on monoamine oxidase and enzymes of GABA metabolism in mouse brain

Acute and chronic ammonia toxicity was produced in the mice by intraperitoneal injection of ammonium chloride (200 mg/kg) and by exposure of mice to ammonia vapours (5% v/v) continuously for 2 days and 5 days respectively. The ammonia content was elevated in the cerebellum, cerebral cortex and brain stem and in liver. In acute ammonia intoxication there was a decrease in the monoamine oxidase (MAO) activity in all the three regions of brain. In chronic ammonia toxicity (2 days of exposure) a significant increase in the activity of MAO was observed in the cerebral cortex while in cerebellum and brain stem there was a significant decrease. In cerebral cortex and cerebellum there was a rise in the activity of MAO as a result of exposure to ammonia vapours for 5 days. A significant decrease was observed in the activity of glutamate decarboxylase (GAD) in all the three regions of the brain both in acute and chronic ammonia toxicity (2 days). There was a decrease in the activity of this enzyme only in the cerebral cortex in the animals exposed to ammonia for 5 days. The activity of GABA-aminotransferase (GABA-T) showed a significant rise in cerebellum and a fall in the brain stem in acute ammonia toxicity. In chronic ammonia toxicity GABA-T showed a rise in all the three regions of brain. Chronic ammonia toxicity produced a significant decrease in the content of glutamate in all the three regions without a significant change in the content of aspartate. GABA and glutamine. The content of alanine increased in all the three regions of brain under these experimental conditions. The ratio of glutamate + aspartate/GABA and glutamate/glutamine showed a decrease in all the three regions as a result of ammonia toxicity.

Rod-shaped filamentous inclusions and other ultrastructural features in a cerebellar astrocytoma

A biopsy specimen of a cerebellar astrocytoma from a 14-year-old girl was studied by light and electron microscopy. Histologically the tumor showed a mixture of loose and compact areas with numerous Rosenthal fibers. By electron microscopy most tumor cells contained, besides the usual organelles, large amounts of 70 to 100 A thick filaments. Classical Rosenthal fibers were also identified. In addition many cell bodies and processes were sprinkled with fragments of Rosenthal fiber material. Ordered filamentous arrays (so-called Hirano bodies) were seen in a number of tumor astrocytes. They are considered to be a nonspecific arrangement of filament units largely devoid of cytopathologic significance. Other ultrastructural features of some tumor cells were inchoate forms of the granulated bodies of conventional histology, paired cisternal elements of rough endoplasmic reticulum, and honeycomb-like profiles of transversely cut cylindrical units of smooth endoplasmic reticulum. Microtubular bodies were numerous in the endothelial cells of the tumor vessels.

The effect of portocaval anastomosis on the permeability to horseradish peroxidase of cerebral vessels of the rat

The blood-brain barrier to horseradish peroxidase (HRP) was tested in rats with hepatic encephalopathy induced by portocaval anastomosis. An increased number of vesicles containing HRP was seen in endothelial cells. Basement membranes of some vessels and the adjacent neuropil were filled with HRP. Astrocytes showed swollen end-feet. The cytoplasm of astrocytes adjacent to HRP containing basement membranes was evenly filled with HRP. This phenomenon could be caused either by cellular hyperactivity or by leaking membranes due to cell damage.

High molecular weight microtubule-associated proteins bind to actin lattices (Hirano bodies)

Hirano bodies are filamentous, paracrystalline inclusions that are found in dendrites and cell bodies of neurons in Alzheimer's and other neurodegenerative diseases. Actin appears to be a major component of these structures. We present evidence that tropomyosin and high molecular weight microtubule-associated proteins (MAPs) are also components of Hirano bodies. Although an association between actin and MAPs has been noted in vitro, interactions in vivo have not heretofore been demonstrated. Since microtubules are not present in Hirano bodies, and anti-tubulin and anti-neurofilament antibodies do not bind to Hirano bodies, the association between MAPs and these inclusions is likely a result of interactions between MAPs and actin, and not MAPs and microtubules or neurofilaments.