Age-related degeneration of the serotoninergic fibers in the zitter rat brain

The serotonin neuron system was studied using immunohistochemical and neurochemical techniques in zitter mutant rats aged 1–14 months, which are characterized by abnormal metabolism of superoxides. The morphology of the serotoninergic neuron system and the serotonin level in the zitter rat were compared to those of age-matched Sprague-Dawley (SD) rats. Up to age 4 month, the density and distribution of serotoninergic fibers in the zitter rat brain were similar to those of control rats. However, several serotoninergic fibers with abnormal morphology, characterized by swollen varicosities, were observed in the cerebral cortex and caudate putamen of 6-month-old zitter rats. The density and distribution of these fibers in other regions of the brain were similar to those of control rats. The abnormal serotoninergic fibers increased in number and extended into other regions of the brain such as the thalamus, hippocampus, and vestibular nucleus. On the other hand, the density of normal serotoninergic fibers decreased throughout the brain of the 14-month-old zitter rat. Abnormal serotoninergic fibers have also been reported in the brain of normal older (24 months) SD rats. Neurochemical analysis revealed lower levels of serotonin, and 5-hydroxyindoleacetic acid, in all cortical areas (prefrontal, parietal, and occipital cortices), the caudate putamen, and the hippocampus of 12-month-old zitter rats. Levels differed significantly in the parietal cortex and hippocampus between the zitter and SD rats. Based on the morphological and neurochemical similarities, the present results suggest that age-related degeneration of serotoninergic fibers occurs in the zitter rat brain. Furthermore, degeneration of serotoninergic fibers appears to be induced by superoxide species. Thus, the zitter rat may provide a good model for studying the neurotoxic effects of superoxide species on the serotoninergic neuron system. Synapse 30:62–70, 1998. © 1998 Wiley-Liss, Inc.     

Auditory brain-stem response in zitter rats with genetic spongiform encephalopathy.

Zitter rats with genetic spongiform encephalopathy and hypomyelination developed an abnormal auditory brain-stem response (ABR) before the appearance of spongy lesions in the central nervous system (CNS). The ABR abnormalities were characterized by a dual peak of wave I, with a longer latency than in normal rats, and decreased or absent waves III and IV. Hypomyelination in both peripheral and central nerves may have been responsible for these abnormalities. The slow negative wave became wide and obscure with aging. These changes accompanied age-dependent progression of spongy changes in the CNS. These findings suggest that at least two mechanisms, one involving hypomyelination and the other causing spongy lesions, are responsible for the brain-stem auditory pathway dysfunction in zitter rats.     

Experimental spongy degeneration of the white matter induced by 6-aminonicotinamide intoxication.

Spongy state and degeneration of the white matter in the 6-aminonicotinamide intoxicated rats were studied neuropathologically and electromicroscopically. Young albino rats, four weeks of age, received 0.1% of 6-aminonicotinamide solution intraperitoneally as a single dose of 10 mg/Kg of body weight. Four hours after the administration, paralysis of the hind limbs occurred in the rats. Neuropathological investigations revealed a characteristic spongy and degenerative change of white matter as well as gray matter of the central nervous system. Corpus callosum, cerebellar cortex, and optic nerves showed edematous and spongy degeneration in the early stage of the experiment. Ultrastructural changes of myelin sheath were initially seen in the vicinity of severely damaged oligodendrocytes. The vacuoles in the myelin, i.e. intramyelinic vacuoles, were formed by splitting between the innermost myelin lamellae and axon. Axons remained usually unchanged in the early stage. The pathogenesis of ultrastructural changes of the white matter in the 6-aminonicotinamide intoxication was discussed.     

Experimental Spongy Degeneration of the White Matter Induced by 6-Aminonicotinamide Intoxication

Spongy state and degeneration of the white matter in the 6-aminonicotinamide intoxicated rats were studied neuropathologically and electromicroscopically. Young albino rats, four weeks of age, received 0.1% of 6-aminonicotinamide solution intraperitoneally as a single dose of 10 mg/Kg of body weight. Four hours after the administration, paralysis of the hind limbs occurred in the rats. Neuropathological investigations revealed a characteristic spongy and degenerative change of white matter as well as gray matter of the central nervous system. Corpus callosum, cerebellar cortex, and optic nerves showed edematous and spongy degeneration in the early stage of the experiment. Ultrastructural changes of myelin sheath were initially seen in the vicinity of severely damaged oligodendrocytes. The vacuoles in the myelin, i.e. intramyelinic vacuoles, were formed by splitting between the innermost myelin lamellae and axon. Axons remained usually unchanged in the early stage. The pathogenesis of ultrastructural changes of the white matter in the 6-aminonicotinamide intoxication was discussed.     

Spongy degeneration in the central nervous system of domestic animals

Summary Severe spongy degeneration of the central nervous system (CNS) was seen in 11 cattle, 19 sheep, 4 pigs and 1 goat, associated with a variety of hepatic diseases, particularly those caused by hepatotoxic pyrrolizidine alkaloids. It was also seen in a milder form in 2 of 8 horses examined, 1 dog of 5 dogs examined, and in 1 rabbit only of a large number of laboratory animals examined.This paper reports results of experiments which confirmed initially that the CNS disease could be caused by pyrrolizidine alkaloid intoxication. This was done by poisoning sheep and calves withSenecio jacobaea, a plant which contains pyrrolozidine alkaloids, and by poisoning lambs with lasiocarpine.As the disease was seen in hepatoses not caused by pyrrolizidine alkaloids, the hypothesis that CNS spongy degeneration in lambs could follow any hepatic disease irrespective of its cause, was tested by poisoning lambs with allyl formate, an hepatotoxin chemically unrelated to pyrrolizidine alkaloids. Three of 4 lambs poisoned by the allyl formate showed spongy degeneration in their brains.As the CNS spongy degeneration was an apparent form of hepatocerebral disease, an experiment was conducted to show that the neural disease in sheep was caused by hyperammonaemia. CNS spongy degeneration developed in the brains of all sheep infused intravenously with ammonium acetate, and advanced spongy changes developed in the sheep infused for more than 3 days. The cerebral changes were probably temporary, since sheep infused for 5 days and retained for 3 weeks showed marked regression of vacuolation.Hyperammonaemia caused by intravenous ammonium acetate infusion is a simple, rapid model of CNS spongy degeneration. The syndrome, CNS spongy degeneration caused by hepatic failure and hyperammonaemia, is probably one of the morphologic expressions of hepatocerebral disease in domestic animals and could be an analogue of similar congenital and hepatocerebral diseases in man.     

Spongy degeneration in the central nervous system of domestic animals

Two experiments were completed in which brains and spinal cords from lambs affected with spongy degeneration of the central nervous system (CNS) were analysed for water, sodium and potassium, as measures of cerebral oedema. In a third experiment, lambs with CNS spongy degeneration were tested for permeability of cerebral blood vessels by intravenous injections of Evans blue. The CNS spongy degeneration was produced by poisoning with the hepatotoxic pyrrolizidine alkaloid lasiocarpine. In the first experiment, 2 male lambs were poisoned by lasiocarpine and a third injected with saline alone. One lamb injected with lasiocarpine showed widespread spongy changes in the CNS and the other 2 showed normal brains. In the second experiment, 5 males lambs were poisoned by lasiocarpine and 5 were injected with saline. Three of the 5 poisoned lambs showed widespread spongy changes, a fourth showed minor vascuolation and the remaining 6 had normal brains...     

Spongy degeneration in the central nervous system of domestic animals

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.     

Pivotal role of attractin in cell survival under oxidative stress in the zitter rat brain with genetic spongiform encephalopathy

Accumulation of reactive oxygen species (ROS), which is generated during energy metabolism, is a cause of physiological aging, neuropathogenesis and numerous diseases, such as Parkinson's and Alzheimer's diseases. Zitter rat is an autosomal recessive mutant, characterized by spongiform degeneration and hypomyelination in the brain, and the phenotype has been suggested to be involved in oxidative stress by the accumulation of ROS. To determine the relation between neurodegeneration of the zitter rat and Attractin (Atrn) gene expression, which was identified as a gene responsible for the zitter, we established fibroblast cells from the zitter rat (Fz) and the Wistar tremor control (WTC) rat (Fw), and transduced Fz cells with the Atrn gene (Fz/Atrn). In the Fz/Atrn cells, accumulation of ROS was repressed, and cell survival against oxidative stress was enhanced to the same level as in Fw cells. Interestingly, phosphorylation of ERK was significantly increased in Fz/Atrn cells by H(2)O(2) stimulus, similarly to Fw cells. Furthermore, activation of ERK was confirmed in the brains of WTC and zitter rats by Western blot analysis and immunohistochemistry. These observations suggested that lack of Atrn gene expression induced neurodegeneration by a decrease in active ERK through an intracellular signaling via oxidative stress.     

Decreased Dopamine and Increased Norepinephrine Levels in the Spontaneously Epileptic Rat, a Double Mutant Rat

Summary: Dopamine (DA) and norepinephrine (NE) brain levels and turnover rate were examined in the spontaneously epileptic rat (SER: zi/zi, tm/tm), a double mutant rat obtained by mating tremor heterozygotes (tml +) with zitter homozygotes associated with epileptic seizures composed of spontaneously occurring tonic convulsion and absence-like seizure. DA and NE levels were also determined in age-matched male zitter, tremor and Kyo:Wistar rats. DA levels in caudate nucleus were significantly lower in adult age (10–12 weeks) SER, which showed epileptic seizures, and zitter rats than in adultKyo:Wistar and tremor rats. DA levels in other areas such as thalamus-hypothalamus, midbrain, and ponsmedulla were not different among SER, zitter, tremor, and Kyo:Wistar rats at age 10–12 weeks. Except in cerebral cortex and hippocampus, there were no differences in brain DA levels between young seizure-free SER (age 5 weeks) and young Kyo:Wistar rats. Furthermore, the turnover rate of DA was significantly lower in caudate nucleus of adult SER than of Kyo:Wistar rat, whereas in pons-medulla there was no difference between the two strains. In contrast, NE levels in the thalamushypothalamus, midbrain, cerebellum and pons-medulla were higher in SER and zitter rats at age 10–12 weeks than in age-matched tremor and Kyo:Wistar rats. Higher NE levels were also observed in midbrain, cerebellum, and pons-medulla of young SER as compared with young Kyo:Wistar rats. Turnover rates of NE were significantly lower in pons-medulla and cerebellum of the adult SER than in those of Kyo:Wistar rat. In genetic studies using backcross mating of zitter and BN rats, decreased DA was also observed in caudate nucleus of backcrossed zitter rats as compared with BN, F₁, and zitter wild-type rats. Increased NE contents were observed in the thalamus-hypothalamus, midbrain, and pons-medulla of zitter rats as compared with other rats, although the increase was also observed in the thalamus-hypothalamus and midbrain of zitter wild-type rats. Results suggest that a decrease in DA in caudate nucleus and an increase in NE in midbrain and pons-medulla are due to the homozygous zi gene, and together with previous findings, suggest that the decrease in DA, although probably not the only cause, facilitates appearance of tonic and absence-like seizures by lowering the threshold triggering such seizures.     

Progressive dopaminergic neurodegeneration of substantia nigra in the zitter mutant rat

Zitter mutant rats exhibit abnormal metabolism of superoxide species and demonstrate progressive degeneration of dopamine (DA) neurons in the substantia nigra (SN). Furthermore, long-term intake of vitamin E, an effective free radical scavenger, prevents the loss of DA neurons caused by free radicals. However, it is unclear how this degeneration progresses. In this study, we ultrastructurally examined cell death in the zitter mutant rat SN. Conventional electron-microscopic examination revealed two different types of neurons in the SN pars compacta. In zitter mutant rats, although the first type (clear neurons) exhibited no obvious ultrastructural changes with aging, the second type (dark neurons) demonstrated age-related damage from 2 months. Immunoelectron-microscopic analysis clarified that the second-type neurons were dopaminergic neurons. In the dopaminergic neuronal somata, many lipofuscin granules and abnormal endoplasmic reticula were observed from 2 months of age, and these dopaminergic neurons showed progressive degeneration with age. Moreover, in zitter mutant rats, abnormally enlarged myelinated axons with dense bodies and splitting myelin with dense material were observed in the SN at 2, 4, and 12 months, and oligodendrocytes with numerous lipofuscin, multivesicular bodies, multilamellar bodies, and dense bodies were frequently observed at 4 and 12 months. These findings clarified that dopaminergic neurons in zitter mutant rats had degenerated with age, and that myelinated axons also exhibited age-related injury. Moreover, ubiquitin-immunohistochemical analysis indicated that the accumulation of products of the endosomal–lysosomal system may be involved in this degeneration.     

Benzodiazepine receptor binding in the spontaneously epileptic rat and its parent strains.

Central type benzodiazepine (BDZ) receptor binding in spontaneously epileptic rats (SER) and their parent strains, tremor rats and zitter rats, and Kyoto/Wistar rats were investigated. Significantly lower BDZ receptor densities (Bmax) and no differences in affinity (KD) were found in the hippocampus of the two epileptic strains, SER and tremor rats, in comparison with Kyoto/Wistar rats and zitter rats. This abnormality is considered to be due to a tremor gene and to be related to absence-like seizures in SER and tremor rats. A significant decrease of KD and an increase of Bmax in the brain stem were found in SER in comparison with Kyoto/Wistar rats. These changes may be due to a zitter gene, since zitter rats show the same tendency, and they may be related to tonic seizures in SER. Bmax was significantly increased in the cerebellum and hippocampus of the zitter rats, while KD was not changed, in comparison with Kyoto/Wistar rats and tremor rats. These changes may reflect the relatively selective loss of tissue lacking BDZ receptors or an upregulation in response to the loss of GABAergic neurons in zitter rats.     

Experimental spongy degeneration in calves

Summary 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 and 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 affected with hepatocerebral diseases and some hereditary disorders.     

Early myelination in zitter rat: morphological, immunocytochemical and morphometric studies.

Early myelination in zitter rat was investigated by light and electron microscopic observations, by immunostaining for myelin basic protein (MBP), proteolipid protein (PLP) and myelin-associated glycoprotein (MAG), and by morphometric analysis from the 1st to the 28th day of age. Although the commencement of myelination in zitter rats was not delayed in comparison with control rats, the density or the number of myelinated fibers in zitter rats was significantly below that in controls, both in the ventral column of the cervical spinal cord and in the optic nerve. In contrast, the density or the number of aberrant myelin sheaths was increased in zitter rats, and this difference became more marked with increasing age. The persistent presence of abnormal membranous structures associated with the oligodendroglial nuclear membrane and the increased number of aberrant myelin sheaths were characteristic to the zitter mutation, although these alterations were also observed transiently in control rats. Quantitative analysis supported the proposition that hypomyelination in zitter rats is primarily pathological and becomes more prominent with advancing age. However, the fundamental structure of the myelin lamellae appeared to be normal and the immunoreactivities for MBP, PLP and MAG were slightly delayed and weakend in comparison with age-matched controls. Thus, in zitter rat there is the functional abnormality of the oligodendrocytes to integrate the processes of membrane biosynthesis and to expel excessive production of membranous structures associated with the membranous organellae such as nuclear membrane, and it is postulated that this functional abnormality is characteristic to only the zitter mutation.     

Correlation between cerebral blood flow and histologic changes in a new rat model of middle cerebral artery occlusion

We describe a new focal ischemia model consisting of unilateral middle cerebral artery occlusion with a silicone rubber cylinder attached to a nylon surgical thread inserted through the internal carotid artery in rats. Recirculation was accomplished by pulling the thread out of the artery. We evaluated the reliability of this model and studied the influence of reperfusion of the brain by measuring regional cerebral blood flow in 30 rats and by using conventional neuropathologic methods after different periods of occlusion in 48 rats. The anterior neocortex and the lateral part of the caudate putamen, which were supplied by the occluded middle cerebral artery, were the regions most frequently damaged. After 1 hour of occlusion in five rats, in the cortex supplied by the occluded artery mean +/- SD blood flow was 0.19 +/- 0.08 ml/g/min (approximately 15% of that in the corresponding region of five sham-operated control rats), and mild scattered ischemic cell change was observed. Three (n = 5) or six (n = 5) hours of occlusion reduced blood flow more severely and caused severe ischemic cell changes in the cortex supplied by the occluded artery in proportion to the duration of ischemia. Characteristically, in five rats subjected to 3 hours of occlusion followed by 3 hours of recirculation, blood flow was restored and spongy edematous change was observed in the cortex supplied by the recirculated artery. This change resulted in hypoperfusion of the neighboring cortical region surrounding the recirculated area. Our model should be useful in various investigations of the influence of reperfusion on focal ischemic brain injury.     

Spontaneous spongy degeneration of the brain stem in SAM-P/8 mice, a newly developed memory-deficient strain

A spontaneous spongy degeneration of the brain stem and spinal cord was discovered in a murine model of accelerated senescence (SAM), cared for under both conventional (SAM-P/8) and specific pathogen-free (SAM-P/8/Ta) conditions. SAM-P/8 and SAM-P/8/Ta showed no clinical neurological abnormalities, yet there was a deterioration in learning and memory abilities. Light microscopic examination revealed a spongy degeneration in the brain stem and spinal cord, in the reticular formation, and proliferation of hypertrophic astrocytes in the spongy area. The spongiform degeneration progressed with advancing age from four to eight months, after which the entire brain was involved. Astrocytosis increased with advancing degeneration. Ultrastructurally, mild dendritic swelling occurred at one month of age. At two months of age, moderate postsynaptic swelling and a widening of intracellular membrane structure were observed, and at age five months there were large vacuoles circumscribed by membranous lamellae, identifiable as myelin. Vacuoles in SAM-P/8 proved to be swollen neuronal processes and oligodendroglial processes. These SAM-P/8 and SAM-P/8/Ta strains of mice are new memory-deficient strains with spontaneous spongy degeneration associated with aging.     

Electron‐microscopic examination of effects of yokukansan,a traditional Japanese medicine,on degeneration of cerebral cells in thiamine‐deficient rats

We previously demonstrated that yokukansan ameliorated not only learning disturbance but also behavioral and psychological symptoms of dementia‐like behaviors (anxiety, aggressiveness) and neurological symptoms (opisthotonus) induced in rats by dietary thiamine deficiency (TD). In the present study, the effects of yokukansan on degeneration of cerebral cells were further examined electron‐microscopically during pre‐symptomatic and symptomatic stages in TD rats. In the pre‐symptomatic TD stage, which appeared as increase in aggressive behaviors on the 21st and 28th days of TD diet‐feeding, severe edematous degeneration of astrocytes was detected by electron microscopy, although the changes were not observed by light microscopy. In the symptomatic TD stage (the 34th day) characterized by development of neurological symptoms, severe sponge‐like degeneration and multiple hemorrhages in the parenchyma were obvious by light microscopy. The electron‐microscopic examination showed degeneration in neurons, oligodendroglias, and myelin sheaths in addition to astrocytes. TD rats, which exhibited multiple hemorrhages light microscopically, showed severe edematous changes and hypertrophy of the foot processes of astrocytes surrounding blood vessels. Administration of yokukansan ameliorated not only the TD‐induced aggressive behavior and neurological symptoms but also degeneration of the cerebral cells. These results suggest that the inhibitory effect of yokukansan on degeneration in various brain cells might be closely related to the amelioration of aggression and neurological symptoms in TD rats.     

Spongy degeneration of the central nervous system in kittens

Summary 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 revealed 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.     

Hepato-cerebral syndrome: genetic and pathological studies in an infant with a dGK mutation

Focal spongy degeneration of the white matter and Purkinje cell loss were the neuropathological hallmarks in an infant with hepato-cerebral syndrome and a 4-bp GATT duplication (nucleotides 763–766) in exon 6 of the dGK gene. Liver disease became manifest in the first months of life and was followed by progressive cirrhosis and death at 31 months. Neurological symptoms appeared later and were mild, in agreement with the limited brain pathology. Molecular analysis of the dGK gene should be performed in infants with cirrhosis even in the absence of CNS involvement.     

Infantile spongy degeneration of the central nervous system associated with glycogen storage and markedly fatty liver

The clinical, biochemical, and pathological features of an unusual expression of infantile spongy degeneration of the central white matter are presented with emphasis on neuropathological observations. The topographical distribution of the spongy change along with the observed defect in myelination were such as to suggest an arrest in development of the white matter in late foetal life. Of additional interest, in the present case, is the observed deposition of glycogen in the brain, heart, and liver along with a markedly fatty liver. Our findings are compared with those in other cases of so-called spongy degeneration, as well as with certain of the aminoacidurias and, as a consequence, we wish to suggest that the basic pathogenetic factor probably lies in a disturbance of the biochemical energy supply system rather than in a disorder of myelin lipid metabolism per se.     

Spongy degeneration of the CNS: an instance of the rare juvenile form

To our knowledge, the juvenile form of spongy degeneration of the CNS (SD-CNS); van Bogaert-Bertrand disease) has been described previously only three times. We report the case of 21 1/4-year-old Japanese woman who was first seen at the age of 11 with growth retardation, ptosis, and ophthalmoplegia. Her progressive neurodegenerative disease included retinitis pigmentosa, blindness, partial deafness, cerebellar dysfunction, hyporeflexia, and muscle wasting. Simultaneous endocrine defects were diabetes mellitus and probable hyperaldosteronism. Heart block developed later. She died of bronchopneumonia. Autopsy showed CNS stigmas typical of spongy degeneration. Additional findings included peripheral nerve demyelination, neurogenic muscle atrophy, pituitary and pancreatic atrophy, right adrenal agenesis, and a left adrenal coritcal lipid-cell adenoma. To our knowledge, our patient was the oldest survivor, the first patient of Japanese ancestry, and had a unique concurrence of certain oculoendocrine defects.