Status spongiosus of nervous tissue. Electron microscopic studies

Adult neuronal regeneration in the telencephalon of the killifish Aphaniops hormuzensis

The potential of central nervous system regeneration was evaluated for the first time in the injured brain of the old world killifish Aphaniops hormuzensis. The histomorphological organization in the regeneration procedure was evaluated using the hematoxylin and eosin (H&E) staining and the bromodeoxyuridine (BrdU) immunohistochemistry technique. The histological tissue sections were sampled daily for 10 days. Based on the H&E staining, a large gliosis reaction was detected along with vacuolization and telencephalon deformation on 1-day post-lesion (dpl). The vacuolated zone declined fast and the telencephalon hemisphere recovered on 3 dpl. The symptoms of injured telencephalon nervous tissue were resolved within 7 dpl in both genders. In the BrdU test of the control group, BrdU-labeled cells were observed in the ventricular zone (VZ), pallium (Pa), and lateral pallium (LPa). On 1 dpl, the BrdU⁺ cells accumulated in the VZ, Pa, and LPa (located near the injury area). From 3 dpl onwards, the BrdU⁺ cells were reduced in the telencephalic VZ, Pa, and LPa. Based on the BrdU⁺ results, the adult brain in A. hormuzensis possesses a remarkable capacity for neuronal regeneration. By taking into account the high neural regeneration potency of A. hormuzensis and its relatively short lifespan, it could be concluded that besides the currently known models, the members of aphaniid fishes could probably be valuable animals to study the regeneration phenomenon in the vertebrates.

Disruption of Bmal1 Impairs Blood-Brain Barrier Integrity via Pericyte Dysfunction

Circadian rhythm disturbances are well established in neurological diseases. However, how these disruptions cause homeostatic imbalances remains poorly understood. Brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1) is a major circadian clock transcriptional activator, and Bmal1 deficiency in male Bmal1nestin-/- mice induced marked astroglial activation without affecting the number of astrocytes in the brain and spinal cord. Bmal1 deletion caused blood-brain barrier (BBB) hyperpermeability with an age-dependent loss of pericyte coverage of blood vessels in the brain. Using Nestin-green fluorescent protein (GFP) transgenic mice, we determined that pericytes are Nestin-GFP+ in the adult brain. Bmal1 deletion caused Nestin-GFP+ pericyte dysfunction, including the downregulation of platelet-derived growth factor receptor β (PDGFRβ), a protein necessary for maintaining BBB integrity. Knockdown of Bmal1 downregulated PDGFRβ transcription in the brain pericyte cell line. Thus, the circadian clock component Bmal1 maintains BBB integrity via regulating pericytes.SIGNIFICANCE STATEMENT Circadian rhythm disturbances may play a role in neurodegenerative disorders, such as Alzheimer's disease. Our results revealed that one of the circadian clock components maintains the integrity of the blood-brain barrier (BBB) by regulating vascular-embedded pericytes. These cells were recently identified as a vital component for the control of BBB permeability and cerebral blood flow. Our present study demonstrates the involvement of circadian clock component Bmal1 in BBB homeostasis and highlights the role of Bmal1 dysfunction in multiple neurological diseases.

Regeneration of the adult zebrafish brain from neurogenic radial glia-type progenitors

Severe traumatic injury to the adult mammalian CNS leads to life-long loss of function. By contrast, several non-mammalian vertebrate species, including adult zebrafish, have a remarkable ability to regenerate injured organs, including the CNS. However, the cellular and molecular mechanisms that enable or prevent CNS regeneration are largely unknown. To study brain regeneration mechanisms in adult zebrafish, we developed a traumatic lesion assay, analyzed cellular reactions to injury and show that adult zebrafish can efficiently regenerate brain lesions and lack permanent glial scarring. Using Cre-loxP-based genetic lineage-tracing, we demonstrate that her4.1-positive ventricular radial glia progenitor cells react to injury, proliferate and generate neuroblasts that migrate to the lesion site. The newly generated neurons survive for more than 3 months, are decorated with synaptic contacts and express mature neuronal markers. Thus, regeneration after traumatic lesion of the adult zebrafish brain occurs efficiently from radial glia-type stem/progenitor cells.

Genetically induced adult oligodendrocyte cell death is associated with poor myelin clearance, reduced remyelination, and axonal damage

Loss of oligodendrocytes is a feature of many demyelinating diseases including multiple sclerosis. Here, we have established and characterized a novel model of genetically induced adult oligodendrocyte death. Specific primary loss of adult oligodendrocytes leads to a well defined and highly reproducible course of disease development that can be followed longitudinally by magnetic resonance imaging. Histological and ultrastructural analyses revealed progressive myelin vacuolation, in parallel to disease development that includes motor deficits, tremor, and ataxia. Myelin damage and clearance were associated with induction of oligodendrocyte precursor cell proliferation, albeit with some regional differences. Remyelination was present in the mildly affected corpus callosum. Consequences of acutely induced cell death of adult oligodendrocytes included secondary axonal damage. Microglia were activated in affected areas but without significant influx of B-cells, T-helper cells, or T-cytotoxic cells. Analysis of the model on a RAG-1 (recombination activating gene-1)-deficient background, lacking functional lymphocytes, did not change the observed disease and pathology compared with immune-competent mice. We conclude that this model provides the opportunity to study the consequences of adult oligodendrocyte death in the absence of primary axonal injury and reactive cells of the adaptive immune system. Our results indicate that if the blood-brain barrier is not disrupted, myelin debris is not removed efficiently, remyelination is impaired, and axonal integrity is compromised, likely as the result of myelin detachment. This model will allow the evaluation of strategies aimed at improving remyelination to foster axon protection.

Myelin vacuolation, optic neuropathy and retinal degeneration after closantel overdosage in sheep and in a goat

Toxicity of closantel, a halogenated salicylanilide anthelmintic, is described in 11 sheep and a goat, humanely killed 4-70 days after accidental overdosage. Status spongiosis of the cerebrum and cerebellum was present, its severity decreasing with time after treatment. Ultrastructurally, vacuoles in the cerebral white matter were seen to be intramyelinic due to splitting of myelin lamellae at the intraperiod lines, indicating myelin oedema. In the optic nerves, Wallerian degeneration and eventual fibrosis and atrophy of the nerves followed myelin vacuolation. Lesions in the optic nerves were particularly advanced in the intracanalicular portion, indicating a compressive neuropathy within the optic canal. Acute retinal lesions consisted of papilloedema, necrosis of the outer retinal layers (especially the photoreceptor layer), and retinal separation in tapetal and non-tapetal areas. In more chronic cases, the outer nuclear layer was diffusely attenuated and generally reduced to a single row of cells.

Clinical and pathological effects of short-term cyanide repeated dosing to goats

The purpose of this work is to determine and describe the effects of subacute cyanide toxicity to goats. Eight female goats were divided into two groups. The first group of five animals was treated with 8.0 mg KCN kg(-1) body weight day(-1) for seven consecutive days. The second group of three animals was treated with water as controls. Complete physical examination, including observation for behavior changes, was conducted before and after dosing. One treated animal was euthanized immediately after dosing. Later, two of the remaining treated animals and a control goat were euthanized after a 30-day recovery period. Euthanized animals were necropsied and tissues were collected and prepared for histologic studies. Clinical signs in treated goats were transient and included depression and lethargy, mild hyperpnea and hyperthermia, arrhythmias, abundant salivation, vocalizations, expiratory dyspnea, jerky movements and head pressing. Two goats developed convulsions after day 3 of treatment. One animal developed more permanent behavioral changes as she became less dominant and aggressive. Histologic changes included mild hepatocellular vacuolation and degeneration, mild vacuolation and swelling of the proximal convoluted tubules of the kidneys and spongiosis of the white matter (status spongiosis) of the cerebral white tracts, internal capsule, cerebellar peduncles, spinal cord and peripheral nerves. In summary, sub-lethal cyanide intoxication in goats resulted in behavioral changes, and during the treatment period animals showed delayed signs of toxicity. Significant histologic lesions in goats were observed and need to be characterized further.

Neuropathological findings after continuous intrathecal administration of S(+)-ketamine for the management of neuropathic cancer pain

Questions have been raised about the potential neurotoxicity of the neuraxial use of ketamine although ketamine and its active enantiomer S(+)-ketamine have been used intrathecally and epidurally (caudally) for the management of perioperative pain and in a variety of chronic pain syndromes. Clinical experience following neuraxial administration of S(+)-ketamine has been documented without reference to local central nervous system toxicity following this approach. In addition, there are no preclinical safety data regarding stability, compatibility, and neurotoxicity on intrathecal use of single S(+)-ketamine or combinations of S(+)-ketamine, morphine, bupivacaine, and clonidine. In the present case, the continuous intrathecal administration of S(+)-ketamine, in combination with morphine, bupivacaine, and clonidine resulted in adequate pain relief in a patient suffering from intractable neuropathic cancer pain. However, postmortem observation of the spinal cord and nerve roots revealed severe histological abnormalities including central chromatolysis, nerve cell shrinkage, neuronophagia, microglial upregulation, and gliosis. Based on our results, neuraxial administration of S (+)-ketamine cannot be recommended for clinical practise before a systematic study of toxicology of neuraxial S(+)-ketamine in animals or humans has been performed.

Prenatal toxicity of cyanide in goats—a model for teratological studies in ruminants

Although exposure to cyanogenic plants or cyanide during pregnancy has adverse effects, no teratological study with cyanide has been conducted in goats or any other ruminant. The objective of the present study was to evaluate the effects of the maternal exposure to potassium cyanide (KCN) during pregnancy on both dams and offspring and furthermore, to develop a model for prenatal toxicological studies in ruminants. Twenty-six pregnant goats were allocated into four groups and given 0, 1.0, 2.0, or 3.0mg KCN/kg body weight per day orally (administered via twice-daily gavage) from Day 24 of pregnancy to term. However, one control dam and another from the 3.0mg KCN/kg per day group were sacrificed on Day 120. At birth, the kids were examined carefully for gross abnormalities. Three months after birth, the male kids and one dam from each group were sacrificed for histopathological study. Although clinical signs of poisoning were observed in dams, cyanide treatment did not alter the length of gestation or the number of live kids. Two prognata kids were born in the 3.0mg KCN/kg group, and one dam from the same group aborted two fetuses. There were histological lesions only in the KCN-treated dam (and its fetuses) sacrificed on Day 120; these consisted of an increased number of resorption vacuoles of thyroid follicular colloid, and status spongiosis of nervous white matter. This study proposes a new animal model for teratogenic trials that could be important to evaluate the effects of chemicals throughout pregnancy in goats and potentially other ruminants.

Scrapie-specific neuronal lesions are independent of neuronal PrP expression

In the transmissible spongiform encephalopathies (TSE), accumulation of the abnormal disease-specific prion protein is associated with neurodegeneration. Previous data suggested that abnormal prion protein (PrP) could induce neuronal pathology only when neurons expressed the normal form of PrP, but conflicting evidence also has been reported. Understanding whether neuronal PrP expression is required for TSE neuropathological damage in vivo is essential for determining the mechanism of TSE pathogenesis. Therefore, these experiments were designed to study scrapie pathogenesis in vivo in the absence of neuronal PrP expression. Hamster scrapie (strain 263K) was used to infect transgenic mice expressing hamster PrP in the brain only in astrocytes. These mice previously were shown to develop clinical scrapie, but it was unclear whether the brain pathology was caused by damage to astrocytes, neurons, or other cell types. In this electron microscopic study, neurons demonstrated TSE-specific pathology despite lacking PrP expression. Abnormal PrP was identified around astrocytes, primarily in the extracellular spaces of the neuropil, but astrocytes showed only reactive changes and no damage. Therefore, in this model the pathogenesis of the disease appeared to involve neuronal damage associated with extracellular astrocytic accumulation of abnormal PrP acting upon nearby PrP-negative neurons or triggering the release of non-PrP neurotoxic factors from astrocytes.

Scrapie and chronic wasting disease

Scrapie and CWD share many features. There are marked similarities in the clinical presentations, the lesions, and the pathogenesis of these diseases, and some similarities in the epidemiology. Extrapolation from the scrapie model of TSE disease to CWD--which occurs in three different species, and should not be considered to be uniform in their response--may be erroneous, however. Such differences may influence diagnostics (e.g., the amount and distribution of PrPC in these different species), pathogenesis (e.g., the influence of genetics on susceptibility and resistance), and epidemiology (e.g., the mode and dynamics of transmission and influences of domestication). IHC is used widely for diagnostics and in the study of the pathogenesis of scrapie and CWD. This technique holds promise for antemortem diagnosis of infection in the peripheral lymphoid tissues such as lymphoid follicles of the nictitating membrane and the tonsil.

Neurotoxicity induced by a single oral dose of aniline in rats

The neurotoxicity of aniline and its age-dependent responses were investigated in male rats. Groups of 6 rats, 4-week-old, were treated once with aniline (500, 750 or 1,000 mg/kg) or olive oil by gavage. Additional groups of 6 rats, 7- or 10-week-old, were treated once with 800 mg/kg of aniline or olive oil. Paralytic gait or hindlimb paralysis was observed between post-treatment days 8 and 15 in two out of six rats receiving 1,000 mg/kg of aniline at 4 weeks of age. On post-treatment day 15, spongy change in the white matter of the spinal cord was observed in all rats receiving 750 or 1,000 mg/kg of aniline at 4 weeks of age. The lateral and ventral columns of the thoracic spinal cord were the most severely affected. Spongy change in the facial nerve and spinal trigeminal tracts of pons and medulla oblongata, and mild degeneration of the peripheral nerves was found in 3 out of 6 rats receiving 1,000 mg/kg of aniline. At the ultrastructural level, the spongy change was due to distention of the myelin sheath and splitting of the intraperiod line. Axons were well preserved in the affected nerve fibers. No abnormalities were seen in the neuronal cell bodies. Although transient cyanosis was observed in all rats receiving 800 mg/kg of aniline at 7- or 10-week-old, as well as in rats receiving 750 or 1,000 mg/kg of aniline at 4-week-old, no treatment-related neurobehavioral or morphologic abnormalities were found in the former. These findings demonstrate the neurotoxicity of orally administered aniline for rats, depending upon the age of the animal at the time of administration.

Prion protein (PrP) is not involved in the pathogenesis of spongiform encephalopathy in transgenic mice expressing interleukin-6 in the brain

Transgenic mice expressing interleukin-6 (IL6) in the brain exhibit gliosis, spongiosis and neuronal loss. Based on previous findings, we hypothesized that IL6 could upregulate the prion protein (PrP) gene in the central nervous system (CNS) of these mice. Western and Northern blot analysis showed that PrP protein and mRNA levels were comparable to control levels. Furthermore, ultrastructural characterization revealed that spongiosis was actually located in astrocytes. These results indicate that IL6 does not upregulate the cerebral PrP expression in this animal model and that profound astrocytic alterations precipitate the neuronal degeneration observed.

Kangaroo rats exhibit spongiform degeneration of the central auditory system similar to that found in gerbils

Kangaroo rats develop spongiform degeneration of the central auditory system similar to that seen in the gerbil. Light microscopic and transmission electron microscopic study of the cochlear nucleus and auditory nerve root (ANR) of Dipodomys deserti and D. merriami show that spongiform lesions develop in dendrites and oligodendrocytes of the cochlear nucleus and in oligodendrocytes of the ANR that are morphologically indistinguishable from those extensively described in the Mongolian gerbil, Meriones unguiculatus. As in Mongolian gerbils, the spongiform degeneration in Dipodomys were much more numerous in animals continually exposed to modest levels of low-frequency noise (< 75 dB SPL). The kangaroo rats with extensive spongiform degeneration also show slightly, but significantly, elevated auditory brainstem evoked response (ABR) thresholds to low-frequency stimuli, a result also found in Mongolian gerbils. These results suggest that the elevated ABR thresholds may be the result of spongiform degeneration. Because low-frequency noise-induced spongiform degeneration has now been shown in the cochlear nucleus of animals from separate families of Rodentia (Heteromyidae and Muridae), the possibility should be investigated that similar noise-induced degenerative changes occur in the central auditory system of other mammals with good low-frequency hearing.

Status spongiosis, optic neuropathy, and retinal degeneration in Helichrysum argyrosphaerum poisoning in sheep and a goat

Lesions of natural Helichrysum argyrosphaerum poisoning were studied in eight sheep and one goat. Light microscopic examination revealed widespread, bilaterally symmetrical status spongiosis of the white matter of the brain consistently present in the subependymal area adjacent to the lateral ventricles, cerebellar peduncles, and brain stem in all animals. In three animals, the ultrastructural finding of intramyelinic vacuolation due to splitting of the myelin lamellae at the intraperiod lines indicated myelin edema. There was also mild distension of perivascular and extracellular spaces in the severely affected areas. Significant changes were absent in neurons, glial cells, axons, or blood vessel walls. Myelin edema associated with degeneration and loss of axons and myelin and astrocytic gliosis was present in the intraorbital and intracranial portions of the optic nerves. In the intracanalicular portions of the nerves in three animals that were studied, more chronic lesions consisting of fibrosis and atrophy of the nerve suggested that the optic neuropathy follows compression of the nerve in the optic canal as a result of myelin edema. The toxic principle of the plant also caused a degenerative retinopathy in five animals. The essential histopathologic change was degeneration and loss of the photoreceptor outer segments predominantly in the nontapetal retina. These retinal lesions were associated with hyperplasia and hypertrophy and with migration of the pigmented epithelium, focal retinal separation, and depletion and loss of the nuclear layers.

Neuropathology and pathogenesis of mitochondrial diseases

The majority of patients with mitochondrial disease have significant neuropathology, with the most common features being spongiform degeneration, neuronal loss and gliosis. Although there is considerable overlap between different mitochondrial diseases, the nature and distribution of the lesions is sufficiently distinctive in some cases to suggest a specific diagnosis. On the other hand, a number of different defects in cerebral energy metabolism are associated with common patterns of neuropathology (e.g. Leigh syndrome), suggesting that there is a limited range of responses to this type of metabolic disturbance. There are many descriptions of neuropathological changes in patients with mitochondrial disease, but there has been remarkably little investigation of the underlying pathogenic mechanisms. Comparisons with other conditions of cerebral energy deprivation such as ischaemia/hypoxia and hypoglycaemia suggest a possible role for excitotoxicity initiated by excitatory amino acid neurotransmitters. An additional contributing factor may be peroxynitrite, which is formed from nitric oxide and the oxygen free radicals which accumulate with defects of the mitochondrial electron transport chain. Mitochondrial diseases are often characterized by episodes of neurological dysfunction precipitated by intercurrent illness. Depending on the severity of the metabolic abnormality, each of these episodes carries a risk of further neuronal death and the result is usually progressive accumulation of irreversible damage. The balance between reversible functional impairment and neuronal death during episodes of metabolic imbalance is determined by the effectiveness of various protective mechanisms which may act to limit the damage. These include protective metabolic shielding of neurons by astrocytes and suppression of electrical activity (and hence energy demands) by activation of ATP-gated ion channels. In addition, recent evidence suggests that lactic acid, the biochemical abnormality common to these conditions, may not be toxic at moderately high concentrations but may in fact be protective by reducing the sensitivity of neurons to excitotoxic mechanisms.

Spongiform central nervous system myelinopathy in African dwarf goats

A novel spongiform myelinopathy of the central nervous system (CNS) of eleven African dwarf goats was examined by light and electron microscopy. Histological lesions consisted of extensive vacuolation predominantly of the white matter of the diencephalon, midbrain and cerebellar peduncles, as well as of spinal white matter. Ultrastructurally, vacuoles were shown to be intramyelinic, resulting from the splitting of the outer myelin lamellae at the intraperiod line. A few oligodendrocytes showed vacuolar degeneration of cell bodies and processes. Inflammatory reactions were absent. The observed lesions point to an unknown primary damage of oligodendroglia and central myelin. A hereditary background of the disorder is suspected as all investigated dwarf goats were half-brothers or -sisters and partly descended from the mating of adult females with their own sire.

Neuropathology and the scrapie-kuru connection

When their kinship was surmised 35 years ago, scrapie and kuru were linked mainly by their neuropathologic similarity. Most notable were neuronal degeneration and intense astrocytosis with little, if any, inflammation. Especially eye-catching in kuru were the vacuolated neurons--the histologic hall-mark of scrapie that drew me to the human disease from the start. Because spongiform change in gray matter neuropil is variable and usually lacks prominence in both scrapie and kuru, it was not part of the resemblance I saw in them. Amyloid plaques, so characteristic of kuru, also did not figure in the similarity, for they had not yet been reported in scrapie. Despite the uncertainty at the time about the pathologic essence of scrapie, the two diseases still looked alike. Their eventual connection--however tenuously held together initially by the few likenesses--has survived as a tribute to morphologic observation. It provided the essential link that helped ensure the kinship a lasting place in comparative neuropathology.

Exposure to low frequency noise during rearing induces spongiform lesions in gerbil cochlear nucleus: high frequency exposure does not

Spongiform lesions of the gerbil cochlear nucleus are reduced in number and extent by rearing in acoustic isolation compared with rearing while exposed to normal colony low-frequency background noise. This study tested whether rearing under exposure to noise bands of moderate intensity would increase the number and extent of cochlear nucleus spongiform lesions. Gerbils were reared from weaning to young adulthood in acoustic isolation chambers while continually exposed to moderately intense bands of either high frequency or low frequency noise. Exposure to low frequency noise resulted in lesion number and area densities that were more than twice those seen in gerbils exposed to high frequency noise. Lesion extent in the low frequency group was similar to that in colony-reared gerbils; lesion extent in the high frequency group was similar to gerbils reared in acoustic isolation. Comparisons within the posterior ventral cochlear nucleus revealed that the differences in lesion extent were most pronounced in the middle and dorsal-medial portions, the regions that are most responsive to middle and high frequencies. These finding suggest that the regional restriction of spongiform lesions within the cochlear nucleus does not have a tonotopic basis.

Bovine spongiform encephalopathy: a neuropathological perspective

The occurrence of bovine spongiform encephalopathy (BSE), recognition that it is a new scrapie-like disease epidemic in domestic cattle in the United Kingdom and concern of a remote zoonotic potential has, in four years, produced a plethora of documented information. While much of this information has been communicated outwith the scientific literature, this review attempts to summarise, from a neuropathological viewpoint, the main findings to emerge. The initial studies established the nosological homology of BSE with the subacute spongiform encephalopathies or "prion" diseases of animals and man. Epidemiological data are consistent with an extended common source epidemic originating from an abrupt change, commencing in 1981-82, in the exposure of domestic cattle to a scrapie-like agent in meat and bone meal incorporated into commercial animal feedstuffs. It is currently proposed that the method of production of meat and bone meal has contributed vital factors to the change in exposure. Invariability of the distribution pattern of vacuolar pathology in the natural disease and on primary transmission to cattle suggests a uniformity of the pathogenesis of BSE. Studies in mice suggest uniformity also of the biological properties of different BSE isolates but indicate that the properties differ from those of sheep scrapie isolates. Human health risks, although perceived to be negligible, have been addressed by various strategies including statutory measures and long term monitoring.

Spongy degeneration of white matter in the central nervous system of silver foxes (Vulpes vulpes)

A disorder of central nervous white matter in Norwegian-bred silver foxes is described from the case histories of 21 clinically affected foxes. The main presenting sign of this disorder was caudal limb ataxia, which appeared between 2 1/2 and 4 months of age and progressed over the next 4-8 weeks. Only four affected foxes were allowed to live beyond this period, but they showed moderate to marked improvement. Light microscopic examination of specimens from 16 affected foxes necropsied between 3 1/2 and 6 1/2 months of age revealed lesions that were restricted to the white matter of brain and spinal cord. The lesions were characterized by a symmetrical spongy change with vacuoles of varying sizes and included significant myelin deficiency. There was a relative preservation of axons and nerve cells and no significant inflammation or vascular reaction. An astrocytic hypertrophy was usually associated with the spongy change. Ultrastructural examination of central nervous tissue from two, perfusion-fixed, 6-month-old foxes showed intramyelin vacuoles resulting from splitting of the myelin lamellae at the intraperiod line and was interpreted as indicating myelin edema. Expanded extracellular spaces and watery astrocytic processes also contributed to the vacuolar appearance. Astrocytic processes in affected areas were hypertrophic and contained abundant filaments. Although the 16 silver foxes had severe clinical signs, their lesions had features in common with the juvenile form of Canavan's disease in children and a spongy degeneration reported in Labrador Retrievers; however, the clinical course in the foxes was not uniformly progressive.

White matter ultrastructural pathology of experimental Creutzfeldt-Jakob disease in mice

Creutzfeldt-Jakob disease (CJD), previously regarded as a neurodegenerative disorder strictly of the gray matter, occasionally occurs as a panencephalopathic form which is characterized by severe white matter damage. An ultrastructural study of the white matter pathology in mice experimentally infected with the Fujisaki strain of CJD virus revealed: (1) vacuoles within myelin sheaths, formed by splitting either at the major dense or intraperiod lines, or within axons; (2) macrophages filled with numerous myelin figures, lipid droplets and paracrystalline inclusions; (3) astrocytes actively digesting myelin debris; (4) unusual wrapping of several axons by a common myelin sheath; (5) vesicular degeneration of myelin sheaths; (6) close contact between numerous coated pits and outer myelin lamellae; and (7) proliferation of inner mesaxons. Our data indicate that the damage to myelinated axons in the panencephalopathic type of CJD is accomplished primarily by active degradation of myelin by macrophages and astrocytes and by formation of intra-axonal and intra-myelin vacuoles. The myelin vacuolation is most consistent with that produced by leukolysins released from activated macrophages and astrocytes.

A study of cerebellar and cerebral cortical degeneration in miniature poodle pups with emphasis on the ultrastructure of Purkinje cell changes

In a litter of three Miniature Poodles, a normal female pup contrasted with two males which displayed severe equilibrium and postural disturbances soon after birth. In the male pups diffuse cerebral cortical degeneration accompanied cerebellar cortical atrophy, which was characterized by extensive loss and degeneration of Purkinje neurons. As in some prior histological descriptions of canine cerebellar atrophies, degenerating Purkinje cells appeared either pale, swollen and vacuolated or shrunken and hyperchromatic. Swollen vacuolated cell bodies and condensed necrotic neurons were scattered through the cerebral cortex. Ultrastructural studies revealed that the vacuolar degeneration in Purkinje and cerebral neurons was referable to marked dilation of endoplasmic reticulum and loss of ribosomes. In shrunken Purkinje neurons, increased cytoplasmic eosinophilia was associated with a decline in Nissl bodies and accumulations of mitochondria and especially lamellar bodies. The latter, stacked derivatives of endoplasmic reticulum, were not encountered in shrunken cerebral perikarya. Lamellar bodies reached giant proportions in the dendritic stems of degenerating Purkinje neurons. In Purkinje axons, however, these bodies often were overshadowed by aggregates of axoplasmic tubules. The cytological changes in these Poodle pups were notably different from those reported in earlier ultrastructural studies of canine inherited cerebellar degenerations.

Dialysis encephalopathy: neuropathologic aspects

The clinical, epidemiologic, electroencephalographic, and toxicologic features of dialysis encephalopathy (DE) have been clarified, but the neuropathologic and clinicopathologic aspects of the disease have remained obscure. In three cases of DE associated with a dialysate of high aluminum content, spongy change restricted to the upper layers of the cerebral cortex was found. The spongy change was distributed through the cerebral cortex bilaterally and diffusely, but the left hemisphere was involved more severely and extensively than the right hemisphere, and the opercular portions of the frontal and temporal lobes were affected more than the remainder of those lobes. This topographic distribution correlated with the clinical defects in higher cortical functions, including aphasia. The spongy change consisted of vacuoles in the neuropil and inside nerve cell bodies. The vacuoles in the neuropil were located in dendrites, astrocytic processes, and, possibly, other structures. Thus, DE is a disease of neurons and astrocytes of the cerebral cortex. Although spongy change of the upper layers of the cerebral cortex is a nonspecific abnormality, when it occurs in the distribution described and in the absence of other diffuse cerebral diseases, it is characteristic of DE.

Role of VSV G antigen in the development of experimental spongiform encephalopathy in mice

The ts G31 VSV mutant induced spongiform encephalopathy without any inflammatory response when injected i.c. into the mouse. In electron microscopy, no virions could be detected in spongiform lesions. In contrast, with the wild VSV strain inflammatory lesions were seen, which contained viral particles in great abundance. As previously shown in vitro, when using the ts G 31 mutant at the nonpermissive temperature, the G antigen can spread from membrane to membrane to distant sites, fusing a great number of cells even in the absence of virus multiplication. Therefore, we postulate that a comparable mechanism is responsible for extensive brain lesions originating probably from a relatively small number of G antigen-producing cells. Indeed, the spongious regions seen mainly in the grey matter contained vacuoles, whose walls were clearly stained by peroxidase-labelled immune serum to G antigen, without detectable virions or inflammatory lesions. The vacuoles probably represent altered and swollen dendritic cell membranes. The relationship between spongiosis development and antigen diffusion in the absence of significant virus replication is discussed.

Ultrastructural findings in maple syrup urine disease in Poll Hereford calves

Ultrastructural findings in the nervous systems of two Poll Hereford calves affected with maple syrup urine disease or branched chain ketoacid decarboxylase deficiency are described. The calves were affected within 2 days of birth with a severe generalised central nervous system (CNS) disorder characterised by dullness and weakness, progressing to recumbency and opisthotonus. The urine had an odour of burnt sugar. Analysis of plasma and cerebrospinal fluid demonstrated significantly elevated levels of the branched chain amino acids leucine, isoleucine and valine. Status spongiosus affecting mainly the white matter was recorded at microscopic examination of the CNS, with ultrastructural examination confirming the presence of intramyelinic vacuole formation, suggesting myelin oedema.

Cerebellar plaques in familial Alzheimer's disease (Gerstmann-Sträussler-Scheinker variant?)

A large kindred, with two brothers coming to autopsy, of a syndrome consisting of ataxia, dementia, and some Parkinsonian features is reported; inheritance appears to be autosomal dominant. Neuropathologically, there were plaques and neurofibrillary tangles in the cerebral cortex as well as some in the basal ganglia, particularly reminiscent of the plaques seen in Kuru; there was only minimal spinal cord disease (pyramidal tract field). The problems of classifying this condition--Alzheimer's disease with cerebellar involvement or other entities, such as the Gerstmann-Sträussler-Scheinker condition (1936), especially now that transmission to animals in the latter has been reported--are discussed. Some relevant theoretical considerations derived from animal work, particularly in scrapie, are also reviewed.

Creutzfeld-Jakob disease: clinical, EEG and neuropathological findings in a cluster of eleven patients

10 of 11 Creutzfeld-Jakob disease patients were seen between February 1975 and November 1979. Whilst the clinical and EEG findings were uniform, the neuropathological changes were not: astrogliosis was always diffuse and widespread but the other typical changes (neuronal loss and spongiosis) varied greatly both in degree and location.

'Dystrophic' Purkinje cell dendrites in an infant

A 6 1/2 month old male infant presented a week after his birth with secretory diarrhea of unknown etiology. He was sustained by central hyperalimentation for the rest of his life, and treated for presumed sepsis with a wide variety of antibiotics. The brain showed vacuolation in the diencephalic nuclei and white matter of the brain stem. There were also many clusters of enlarged Purkinje cell dendrites in the molecular layer. In Golgi preparations the primary and secondary dendrites showed segmental swellings and absent tertiary branchlets. The swellings were due to remarkable accumulations of mitochondria. The pathogenesis of the dendritic changes is discussed, and 'dying back' phenomenon is proposed to explain the changes.

Spongiform polioencephalomyelopathy caused by a murine retrovirus. II. Ultrastructural localization of virus replication and spongiform changes in the central nervous system

The development of murine retrovirus induced spongiform polioencephalomyelopathy was studied sequentially by electron microscopy. During the initial 30 days, viral infection of the central nervous system, as evidenced by viral budding from membranes, was limited to the endothelial cells and pericytes. Viral particles were observed in the lumen of blood vessels, extracellular spaces and astrocytic endfeet surrounding blood vessels, but no morphological evidence of productive infection was found in astrocytes or neurons during early development of vacuolation. The earliest lesions in the neuropil consisted of swelling of astroglia followed by vacuolation, initially in axons and dendrites and later in neuronal and astrocytic soma, where vacuoles appeared to arise from dilated cisternae of the Golgi apparatus. Vacuoles contained only amorphous debris and fragments of membranes. Virions budding aberrantly into vacuoles were seen only in mice surviving beyond 35 days. Numerous reactive astrocytes were observed, but inflammatory cells were absent. The ultrastructural changes were remarkably similar to those described in scrapie, Kuru, and Creutzfeldt-Jakob disease.

Hexachlorophene and the central nervous system. Toxic effects in mice and baboons

A study on hexachlorophene encephalopathy in mice and baboons is reported. By light microscopy, a severe spongiform lesion of the central nervous system (CNS) was localized in the white matter, without myelin breakdown or cellular reaction. By electron microscopy, the myelin alteration was characterized by wide intralamellar spaces or "splitting" developed in the intraperiod line of compact sheaths. The acute changes described were induced by administration of the drug by the digestive or cutaneous routes at various dosage levels in an aqueous solution or in talcum powder. The toxic effects depended on the age of the animals, the survival times and the concentrations of hexachlorophene, i.e., 6%, 3%, and 0.5%. The findings are compared with previous reports on the neurotoxicity of hexachlorophene and other chemicals in human and experimental animals. Hexachlorophene cannot be recommended for use in young infants because of its neurotoxicity in very low doses as demonstrated in the present report.

Encephalitis after inhalation of measles virus: a pathogenetic study in hamsters

A neuroadapted strain of measles virus (HNT) was administered by inhalation to newborn hamsters. Primary replication of virus in the lung was followed by the transient appearance of virus in spleen within 7 to 9 days of inoculation. A terminal encephalitis occurred between 6 and 60 days in 31% of infected hamsters, and virus was recovered by explant culture of these brains. Virus could not be cultured directly from brain or tissue homogenates. At least 7% of hamsters that had survived the infection for two months had antibody to measles virus. The histopathological change in morbid animals was limited to the central nervous system (CNS) and consisted of small foci of necrosis, perivascular mononuclear cell infiltrates, intracytoplasmic and intranuclear inclusions, and vacuolated pyknotic neurons. Immunofluorescent studies disclosed measles antigen in the lungs and brain. This hamster model of measles encephalitis following a "natural" route of inoculation appears to represent a faithful reproduction of certain CNS complications of natural measles infection in humans, i.e., measles encephalitis and subacute sclerosing panencephalitis.

Myelin oedema, optic neuropathy and retinopathy in experimental Stypandra imbricata toxicosis

Rats experimentally poisoned with the toxic plant Stypandra imbricata developed acute oedema of central and peripheral myelin and extensive axonal degeneration in the optic nerves. The oedema developed with vacuolation and splitting of myelin lamellae at the intraperiod line. Following recovery from acute intoxication, myelin oedema resolved after 6 to 12 weeks, but severe retinal degeneration and optic nerve atrophy remained. Morphological abnormalities in glial cells and axons were only found in the optic nerves. It was concluded that there is probably also a direct toxic effect on the axons of the optic nerve and the photoreceptor cells of the retina. The chemical nature of the toxin remains to be defined but the marked similarity of its toxic effects to those of hexachlorophene are noted.

Hereditary neuraxial edema in Polled Hereford calves

Two newborn Polled Hereford calves with hereditary neuraxial edema were available for clinical and pathological examination. The affected animals showed extensor spasms and were unable to rise. Pathologic lesions were microscopic and consisted of widespread vacuolation of the neuraxis, chiefly in white matter and less markedly in grey matter. The lesions were most severe in the brain stem and cerebellar white matter. Examination of the breeding record indicated sire-daughters matings and thus a probably autosomal recessive mode of inheritance.

Studies on hexachlorophene-induced myelin lesions in the trigeminal root transitional region in developing and adult mice

Hexachlorophene (HCP)-induced intramyelinic vacuolation was studied in the transitional region of the trigeminal root of suckling and adult mice. HCP produced an extensive vacuolation in the central compartment of the region in both suckling and adult mice, while in the peripheral compartment myelin lesions were only seen in mice less than 16 days of age. Gas chromatographic measurements showed that in suckling mice the blood concentration of HCP decreased with age, apparently reflecting a faster elimination of HCP from the blood. By substantially increasing the HCP dose, higher blood concentrations were obtained in adult than less the 16-day-old mice; in spite of this, PNS myelin changes occurred only in the latter. Thus, by observing the HCP effect on the transitional region, where CNS and PNS directly meet, it is concluded that CNS of both suckling and adult mice is more severely effected by HCP than PNS, and that the reaction of the PNS myelin is age-dependent during the period of myelinogenesis; it is particularly vulnerable to a cytotoxic edema inducing substance.

The role of the subependymal plate in glial tumorigenesis

We have studied the sequential morphological events of glial tumorigenesis in neonatal dogs, using high titer subgroup C Bratislava-77 Avian Sarcoma Virus, given as 0.01 ml by intraventricular inoculation. The cells of the subependymal plate are those which seem to form the gliomas; cytoplasmic alterations are evident within 24 h after inoculation and microfoci of gliomas, contiguous with the subependymal plate of the lateral ventricles, are visible within 7 days. Independent tumors are present by the 10th post-inoculation day. These studies support the hypothesis of Globus and Kuhlenbeck, which implicates the cells of the subependymal palte in glial tumorigenesis.

Experimental spongy degeneration in calves

Experimental reproduction and ultrastructural findings of spongy degeneration of the central nervous system of hyperammonemic calves are described. Hyperammonemia was produced by intravenous infusion of ammonium acetate. Histologic findings were stereotyped in all calves and characterized by widespread vacuolation of white and grey matter of the brain spinal cord. Electron microscopy revealed widespread intramyelinic vacuoles, some expansion of extracellular spaces and swollen mitochondria. There were minimal changes in neurons, axons and glia, and little evidence of myelin breakdown. Hyperammonemia may be one of the pathogeneses involved in the CNS spongy degeneration in man and domestic animals effected with hepatocerebral diseases and some hereditary disorders.

Slow virus infections

Slow viruses produce diseases whose incubation periods range from several months to many years. Because of this long latency period, the lack of inflammation produced by these diseases and the lack of recoverable virus particles, it is only recently that the association has been made between the viruses and the diseases they cause. The detailed study of kuru, a neurologic affliction of a remote tribe of cannibals in New Guinea, was responsible for the synthesis of new and previously gathered information into a unified framework to explain not only kuru but other diseases as well. Since then, animal models, transmission experiments and histologic and biochemical studies have unveiled new links connecting viruses to previously obscure neurologic, neurophthalmic and ophthalmic entities.

Spongy degeneration of the central nervous system in kittens

The paper describes the clinical and morphological features of a congenital neurological disease affecting two in-bred litter-mate kittens. The principal neurological features were ataxia and dysmetria. In one of the kittens light microscopy revealed widespread vacuolation of white and grey matter of the brain and spinal cord. Electron microscopy revealved intra-myelinic vacuolation and some expansion of the extracellular space. Neuronal, axonal and glial changes were not seen, nor was there evidence of myelin breakdown. The entity is compared with congenital brain oedema of calves and spongy degeneration of the CNS in man.

Spongy degeneration in the central nervous system of domestic animals. Part I: Morphology

Spongy degeneration or status spongiosus of the central nervous system (CNS) was described in a number of domestic animal species, notably sheep, cattle, pigs and in one goat. The condition was characterized by diffuse or focal vacuolation, or polymicrocavitation of the CNS, particularly the white matter. The vacuolation showed a well defined pattern of distribution following a number of myelinated tracts in CNS white matter, in isolated fibres crossing grey matter in the brain stem, and along grey and white matter borders in the cerebrum and spinal cord. The vacuoles were not altered by a variety of methods of rapid brain fixation, processing and staining. The appearance of the vacuolation repeatedly favouring the same areas in the CNS in a large number of animals studied, its common origin either by hepatocerebral disease or hyperammonaemia, strongly suggests that CNS spongy degeneration of domestic animals is a distinct disease entity.