Oligodendrocytes In Rats Research Articles

Exercise in Adolescence Enhances Callosal White Matter Refinement in the Female Brain in a Rat Model of Fetal Alcohol Spectrum Disorders.

A total of 1 in 20 infants born annually are exposed to alcohol prenatally, which disrupts neurodevelopment and results in several disorders categorized under the umbrella term Fetal Alcohol Spectrum Disorders (FASD). Children and adolescents affected by FASD exhibit delayed maturation of cerebral white matter, which contributes to deficits in executive function, visuospatial processing, sensory integration, and interhemispheric communication. Research using animal models of FASD have uncovered that oligoglia proliferation, differentiation, and survival are vulnerable to alcohol teratogenesis in the male brain due in part to the activation of the neuroimmune system during gestation and infancy. A comprehensive investigation of prenatal alcohol exposure on white matter development in the female brain is limited. This study demonstrated that the number of mature oligodendrocytes and the production of myelin basic protein were reduced first in the female corpus callosum following alcohol exposure in a rat model of FASD. Analysis of myelin-related genes confirmed that myelination occurs earlier in the female corpus callosum compared to their counterparts, irrespective of postnatal treatment. Moreover, dysregulated oligodendrocyte number and myelin basic protein production was observed in the male and female FASD brain in adolescence. Targeted interventions that support white matter development in FASD-affected youth are nonexistent. The capacity for an adolescent exercise intervention to upregulate corpus callosum myelination was evaluated: we discovered that volunteer exercise increases the number of mature oligodendrocytes in alcohol-exposed female rats. This study provides critical evidence that oligoglia differentiation is difficult but not impossible to induce in the female FASD brain in adolescence following a behavioral intervention.

H-ABC tubulinopathy revealed by label-free second harmonic generation microscopy

Hypomyelination with atrophy of the basal ganglia and cerebellum is a recently described tubulinopathy caused by a mutation in the tubulin beta 4a isoform, expressed in oligodendrocytes. The taiep rat is the only spontaneous tubulin beta 4a mutant available for the study of this pathology. We aimed to identify the effects of the tubulin mutation on freshly collected, unstained samples of the central white matter of taiep rats using second harmonic generation microscopy. Cytoskeletal differences between the central white matter of taiep rats and control animals were found. Nonlinear emissions from the processes and somata of oligodendrocytes in tubulin beta 4a mutant rats were consistently detected, in the shape of elongated structures and cell-like bodies, which were never detected in the controls. This signal represents the second harmonic trademark of the disease. The tissue was also fluorescently labeled and analyzed to corroborate the origin of the nonlinear signal. Besides enabling the description of structural and molecular aspects of H-ABC, our data open the door to the diagnostic use of nonlinear optics in the study of neurodegenerative diseases, with the additional advantage of a label-free approach that preserves tissue morphology and vitality.

PSB0788 ameliorates maternal inflammation‐induced periventricular leukomalacia-like injury

ABSTRACT Studies have shown that periventricular leukomalacia (PVL) is a distinctive form of cerebral white matter injury that pertains to myelination disturbances. Maternal inflammation is a main cause of white matter injury. Intrauterine inflammation cellular will be propagated to the developing brain by the entire maternal–placental–fetal axis, and triggers neural immune injury. As a low-affinity receptor, adenosine A2B receptor (A2BAR) requires high concentrations of adenosine to be significantly activated in pathological conditions. We hypothesized that in the maternal inflammation‐induced PVL model, a selective A2BAR antagonist PSB0788 had the potential to prevent the injury. In this work, a total of 18 SD pregnant rats were divided into three groups, and treated with intraperitoneal injection of phosphate buffered saline (PBS), lipopolysaccharide (LPS), or LPS+PSB0788. Placental infection was determined by H&E staining and the inflammatory condition was determined by ELISA. Change of MBP, NG2 and CC-1 in the brain of the rats’ offspring were detected by western blot and immunohistochemistry. Furthermore, LPS-induced maternal inflammation reduced the expression of MBP, which related to the decrease in the numbers of OPCs and mature oligodendrocytes in neonate rats. After treatment with PSB0788, the levels of MBP proteins increased in the rats’ offspring, improved the remyelination. In conclusion, our study shows that the selective A2BAR antagonist PSB0788 plays an important role in promoting the normal development of OPCs in vivo by the maternal inflammation‐induced PVL model. Future studies will focus on the mechanism of PSB0788 in this model.

Effect of the prenatal electromagnetic field exposure on cochlear nucleus neurons and oligodendrocytes in rats.

Electromagnetic radiation from elecromagnetic field (EMF) sources has been an important health concern for a long time. The vast majority of this exposure is due to the widespread use of mobile phones, an important source of the EMF. The EMF generated by mobile phones may have adverse effects on the various biological structures that regulate the body system and function. In this study, it was aimed to evaluate histopathologically the effects of 900-megahertz (MHz) EMF application in the prenatal period on the development of the ventral cochlear nucleus, which is the first place of hearing in the brainstem, at various time points of the postnatal period in rats. In the study, Sprague-Dawley pregnant rats were divided randomly into two groups as the control group and the EMF group. The rats in the EMF group were exposed to a 900-MHz EMF every day until birth, while no EMF was applied to the rats in the control group. Auditory brainstem responses of both groups were recorded on the postnatal 13th day, the day the hearing starts. Newborn rats were sacrificed by anesthesia on days 7, 10, 15, and 30. Contrary to the control group, structural damage in cochlear nuclear neurons and oligodendrocyte cell structures and increased caspase-3 activity were observed in the postnatal period in the EMF groups. However, no significant difference was observed between the groups in terms of structural damage and caspase-3 activity at different stages of the postnatal period when cochlear nucleus development was observed. According to ABS, there was no significant difference between the average latency of waves in both groups. In conclusion, this study shows that 900-MHz electromagnetic waves propagated from mobile phones during the prenatal period have no harmful effects on the development of the ventral cochlear nucleus of rats.

Epidural oscillating field stimulation increases axonal regenerative capacity and myelination after spinal cord trauma.

Oscillating field stimulation (OFS) with regular alterations in the polarity of electric current is a unique, experimental approach to stimulate, support, and potentially guide the outgrowth of both sensory and motor nerve fibers after spinal cord injury (SCI). In previous experiments, we demonstrated the beneficial effects of OFS in a 4-week survival period after SCI. In this study, we observed the major behavioral, morphological, and protein changes in rats after 15 minutes of T9 spinal compression with a 40 g force, followed by long-lasting OFS (50 µA), over a 8-week survival period. Three groups of rats were analyzed: rats after T9 spinal compression (SCI group); SCI rats subjected to implantation of active oscillating field stimulator (OFS + SCI group); and SCI rats subjected to nonfunctional OFS (nOFS + SCI group). Histopathological analysis of spinal tissue indicated a strong impact of epidural OFS on the reduction of tissue and myelin loss after SCI in the segments adjacent to the lesion site. Quantitative fluorescent analysis of the most affected areas of spinal cord tissue revealed a higher number of spared axons and oligodendrocytes of rats in the OFS + SCI group, compared with rats in the SCI and nOFS + SCI groups. The protein levels of neurofilaments (NF-l), growth-associated protein-43 (marker for newly sprouted axons), and myelin basic protein in rats were signifiantly increased in the OFS + SCI group than in the nOFS + SCI and SCI groups. This suggests a supporting role of the OFS in axonal and myelin regeneration after SCI. Moreover, rats in the OFS + SCI group showed great improvements in sensory and motor functions than did rats in the nOFS + SCI and SCI groups. All these findings suggest that long-lasting OFS applied immediately after SCI can provide a good microenviroment for recovery of damaged spinal tissue by triggering regenreative processes in the acute phase of injury.

Pyruvate kinase M2 (PKM2) improve symptoms of post-ischemic stroke depression by activating VEGF to mediate the MAPK/ERK pathway.

PurposeTo evaluate and identify the effects and explore the mechanisms of pyruvate kinase M2 (PKM2) on stroke‐induced post stroke depression (PSD).MethodsRats were separated into six different groups, including sham + saline, Stroke + saline, PSD + saline, PSD + recombinant pyruvate kinase M2 (rPKM2) (112 ng/kg), PSD + rPKM2 (224 ng/kg), and PSD + rPKM2 (224 ng/kg) + bevacizumab. Then, the body weight, sucrose preference rate, immobility time, horizontal movement, and vertical movement were determined to evaluate the effect of PKM2 on improving the depressive behavior of PSD rats. Subsequently, the proliferation of oligodendrocytes in subventricular zone (SVZ) of rats in each group was examined by western blot and immunofluorescent staining. Furthermore, the mRNA and protein expression levels of TNF‐α, IL‐6, and IL‐1β were also detected by qPCR and ELISA to verify the anti‐inflammatory effects of PKM2 on PSD rats. In addition, the protein expression levels of MDA, LDH, and NO were tested to reveal that PKM2 can reduce oxidative stress in PSD rats. The western blot and IHC assays were employed to examine the protein expression levels of VEGF, PKM2, and ERK in PSD rats.ResultsIn this study, the results showed that PKM2 can improve the depressive behavior and proliferation of oligodendrocytes in PSD rats. In addition, PKM2 has anti‐inflammatory and anti‐oxidative stress effects on PSD rats. Meanwhile, PKM2 activated the expression level of VEGF/MAPK/ERK pathway.ConclusionPKM2 improves symptoms of post‐ischemic stroke depression by activating VEGF‐mediated MAPK/ERK pathway.

Expression of Oligodendrocyte and Oligoprogenitor Cell Proteins in Frontal Cortical White and Gray Matter: Impact of Adolescent Development and Ethanol Exposure.

Adolescent development of prefrontal cortex (PFC) parallels maturation of executive functions as well as increasing white matter and myelination. Studies using MRI and other methods find that PFC white matter increases across adolescence into adulthood in both humans and rodents. Adolescent binge drinking is common and has been found to alter adult behaviors and PFC functions. This study examines development of oligoprogenitor (OPC) and oligodendrocytes (OLs) in Wistar rats from adolescence to adulthood within PFC white matter, corpus callosum forceps minor (fmi), PFC gray matter, and the neurogenic subventricular zone (SVZ) using immunohistochemistry for marker proteins. In addition, the effects of adolescent intermittent ethanol exposure [AIE; 5.0 g/kg/day, intragastric, 2 days on/2 days off on postnatal day (P)25–54], which is a weekend binge drinking model, were determined. OPC markers NG2+, PDGFRα+ and Olig2+IHC were differentially impacted by both age and PFC region. In both fmi and SVZ, NG2+IHC cells declined from adolescence to adulthood with AIE increasing adult NG2+IHC cells and their association with microglial marker Iba1. PFC gray matter decline in NG2+IHC in adulthood was not altered by AIE. Both adult maturation and AIE impacted OL expression of PLP+, MBP+, MAG+, MOG+, CNPase+, Olig1+, and Olig2+IHC in all three PFC regions, but in region- and marker-specific patterns. These findings are consistent with PFC region-specific changes in OPC and OL markers from adolescence to adulthood as well as following AIE that could contribute to lasting changes in PFC function.

Viral-based rodent and nonhuman primate models of multiple system atrophy: Fidelity to the human disease

Multiple system atrophy (MSA) is a rare and extremely debilitating progressive neurodegenerative disease characterized by variable combinations of parkinsonism, cerebellar ataxia, dysautonomia, and pyramidal dysfunction. MSA is a unique synucleinopathy, in which alpha synuclein-rich aggregates are present in the cytoplasm of oligodendroglia. The precise origin of the alpha synuclein (aSyn) found in the glial cytoplasmic inclusions (GCIs) as well the mechanisms of neurodegeneration in MSA remain unclear. Despite this fact, cell and animal models of MSA rely on oligodendroglial overexpression of aSyn. In the present study, we utilized a novel oligotrophic AAV, Olig001, to overexpress aSyn specifically in striatal oligodendrocytes of rats and nonhuman primates in an effort to further characterize our novel viral vector-mediated MSA animal models. Using two cohorts of animals with 10-fold differences in Olig001 vector titers, we show a dose-dependent formation of MSA-like pathology in rats. High titer of Olig001-aSyn in these animals were required to produce the formation of pS129+ and proteinase K resistant aSyn-rich GCIs, demyelination, and neurodegeneration. Using this knowledge, we injected high titer Olig001 in the putamen of cynomolgus macaques. After six months, histological analysis showed that oligodendroglial overexpression of aSyn resulted in the formation of hallmark GCIs throughout the putamen, demyelination, a 44% reduction of striatal neurons and a 12% loss of nigral neurons. Furthermore, a robust inflammatory response similar to MSA was produced in Olig001-aSyn NHPs, including microglial activation, astrogliosis, and a robust infiltration of T cells into the CNS. Taken together, oligodendroglial-specific viral vector-mediated overexpression of aSyn in rats and nonhuman primates faithfully reproduces many of the pathological disease hallmarks found in MSA. Future studies utilizing these large animal models of MSA would prove extremely valuable as a pre-clinical platform to test novel therapeutics that are so desperately needed for MSA.

Anti-LINGO-1 antibody treatment improves chronic stress-induced spatial memory impairments and oligodendrocyte loss in the hippocampus

Chronic exposure to stressful conditions may affect spatial learning and memory abilities and the brain structure, and disruptions in oligodendrocyte function may cause cognitive dysfunction. Leucine-rich repeat and immunoglobulin-like domain-containing protein 1 (LINGO-1) is a potent negative regulator of oligodendrocytes and axon myelination. However, the questions we sought to answer in this study are whether hippocampal oligodendrocytes are involved in the pathological process of spatial learning and memory impairments induced by chronic stress (CS) and whether antibodies targeting LINGO-1 improve stress-induced spatial learning and memory impairments by protecting the hippocampal oligodendrocytes in stressed rats. After 4 weeks of CS, rats were randomly divided into either the CS standard group or anti-LINGO-1 group. The anti-LINGO-1 group was treated with an anti-LINGO-1 antibody (8 mg/kg) for 3 weeks; all rats were assessed in the Morris water maze. Immunohistochemical staining and modern stereological methods were used to precisely quantify the total number of 2′,3′-cyclic nucleotide 3′-phosphodiesterase-positive (CNPase+) oligodendrocytes in each subregion of the hippocampus. At the behavioural level, after three weeks of treatment, the anti-LINGO-1 group displayed significantly more platform crossings in the Morris water maze test than the CS standard group. The total swimming distance and swimming speed were not significantly different. In the open field test, the percentage of distance travelled in the central region did not differ between the CS standard group and control group or between the anti-LINGO-1 group and the CS standard group. Unbiased stereological analyses revealed significantly greater total numbers of CNPase+ cells in the CA3 and dentate gyrus (DG) areas of the hippocampus in the anti-LINGO-1 group than in the CS standard group. A significant difference in the total number of CNPase+ cells was not observed in the hippocampal CA1 region between the anti-LINGO-1 and CS standard groups. Based on the results of the present study, the anti-LINGO-1 antibody alleviated spatial memory impairments and protected oligodendrocytes in the hippocampus of chronically stressed rats.

Effect of propofol on myelin basic protein expression and myelination of oligodendrocytes in neonatal SD rats

To investigate the effects of different doses of propofol on myelin basic protein (MBP) synthesis and myelination of oligodendrocytes in neonatal SD rats. A total of 57 neonatal SD rats (7 days old) were randomly divided into control group (n=13), vehicle (fat emulsion) group (n=5), and 25, 50 and 100 mg/kg propofol groups (n=13 in each group). Eight hours after a single intraperitoneal injection of propofol or the vehicle, the rats were examined for expressions of mbp mRNA, caspase-3 mRNA, cleaved caspase-3 and MBP in the brain tissues using qPCR and Western blotting. Immunofluorescence assay was used to detect the apoptosis of the oligodendrocytes at 8 h after the injection and the myelination of the corpus callosum and internal capsule at 24 h. Compared with the control group, the neonatal rats with propofol injections showed significantly down-regulated expressions of mbp mRNA and MBP protein in the brain tissue (P < 0.05). Propofol dose-dependently increased the transcription level of caspase-3 and the protein levels of cleaved caspase-3 at 8 h after the injection (P < 0.05). Propofol injection significantly increased the apoptosis of the oligodendrocytes, and the effect was significantly stronger in 50 and 100 mg/kg groups than in 25 mg/kg group (P < 0.05). At 24 h after propofol injection, myelin formation was significantly decreased in the corpus callosum of the neonatal rats in 100 mg/kg propofol group and in the internal capsule in 50 and 100 mg/kg groups (P < 0.05). In neonatal SD rats, propofol can dose-dependently promote oligodendrocyte apoptosis, decrease MBP expressions in the brain, and suppress myelin formation in the corpus callosum and the internal capsule.

The effects of running exercise on oligodendrocytes in the hippocampus of rats with depression induced by chronic unpredictable stress

Running exercise has been shown to be associated with decreased symptoms of depression. However, the mechanisms underlying these antidepressant effects of running exercise remain relatively unclear. In the current study, we investigated the relationship between depressive symptoms in chronic unpredictable stress (CUS) model rats treated with running exercise and changes in oligodendrocytes in the hippocampus. After 4 weeks of CUS, the model group was randomly divided into a CUS standard group (18 rats) and a CUS running group (15 rats). Then, a 4-week treadmill running trial was performed with the CUS running group. In addition, the behavioral effects of exercise were investigated by means of a sucrose preference test (SPT) and an at the end of the 8th week. Immunohistochemical methods and modern stereological methods were used to precisely quantify the total number of 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase)-positive (CNPase+) oligodendrocytes in each hippocampal subregion. At the behavioral level, after four weeks of running, the CUS running group displayed significantly higher consumption of sucrose water in the SPT than the CUS standard group. Unbiased stereological analyses revealed significantly higher total numbers of CNPase+ cells in the hippocampal CA3 and dentate gyrus regions in the CUS running group than in the CUS standard group, whereas there was no significant difference between the groups in the number of CNPase+ cells in the hippocampal CA1 region. The present results further confirm that exercise can alleviate symptoms and protect hippocampal oligodendrocytes in depressed rats.

Effects of propofol on myelin basic protein expression in oligodendrocytes of SD rats at different developmental stages

To investigate the effect of propofol on myelin basic protein (MBP) expression in oligodendrocytes of SD rats at different developmental stages. This study was conducted in 3?, 7?, 14? and 21?day?old SD rats (40 in each age group). In each group, the rats were randomized equally into control group and experimental group, and in the control group, the rats received an intraperitoneal injection of 25 mg/kg medium?long?chain fat emulsion followed by injections at a half dose every 20 min for 8 h; the rats in the experimental group were given injections of propofolmedium (at the initial dose of 25 mg/kg) in the same manner. The transcriptional levels of MBP and caspase?3 in the brain tissues were detected by qRT?PCR, and the protein expression of MBP was with Western blotting and immunehistochemistry. Compared with those in the control groups, the expression of MBP mRNA was significantly down?regulated while caspase?3 mRNA was up?regulated in 3?, 7? and 14?day?old rats in the experimental groups (P<0.05). The protein expression of MBP in 7? and 14?day?old rats was significantly decreased in the experimental groups compared with the control groups (P<0.05). The expression of caspase?3 mRNA or MBP protein in 21?day?old rats showed no significant difference between the two groups (P>0.05). Propofol can down?regulate the expression of MBP at both the mRNA and protein levels in SD rats, especially in those at 7 and 14 days of age.

The VF rat with abnormal myelinogenesis has a mutation in Dopey1

The vacuole formation (VF) rat is an autosomal recessive myelin mutant characterized by generalized tremor, hypomyelination, and periaxonal vacuole formation of the central nervous system (CNS). Here, we report the most likely causative gene for neurological disease in the VF rat and pursue its roles in the development and maintenance of the CNS myelin. We identified a nonsense mutation in the dopey family member 1 (Dopey1) located on rat chromosome 8. Expression level of Dopey1 mRNA was decreased and DOPEY1 protein was undetectable both in the white and gray matter of the spinal cords in the VF rats. Double immunohistochemistry demonstrated that DOPEY1 was mainly expressed in neurons and oligodendrocytes in the wild-type rats, whereas no positive cells were detected in the VF rats. We also demonstrated a marked reduction in myelin components both at mRNA and protein levels during myelinogenesis in the VF rats. In addition, proteolipid protein and myelin-associated glycoprotein accumulated in oligodendrocyte cell body, suggesting that Dopey1 is likely to be involved in the traffic of myelin components. Our results highlighted the importance of Dopey1 for the development and maintenance of the CNS myelin.

Simvastatin attenuates hypomyelination induced by hypoxia–ischemia in neonatal rats

Objectives: Simvastatin, the most widely used cholesterol-lowering drug, has been reported to protect the adult brain from ischemia. Nevertheless, little is known about its action on developing brain after stroke. Although a few reports have found recently that simvastatin displays anti-inflammation and anti-apoptosis properties and improves the cognitive and morphological consequences in the neonatal rats after hypoxia–ischemia (HI) damage, to our best knowledge, there has been no study of the effect of it on myelin formation after neonatal brain damage. Therefore, we investigated whether simvastatin could promote the myelination of oligodendrocytes in the neonatal rats after HI and explored the possible role of microglial responses in this process.Methods: Postnatal day 7 Sprague–Dawley rats were subjected to HI. White matter integrity and myelination were evaluated by the densitometry of myelin basic protein (MBP) immunostaining. OX-42 immunoreactivity and nissl staining were used for identifying microglial responses and the structure changes of white matter and adjacent gray matter after HI. Simvastatin was administrated prophylactically to rats.Results: HI induced serious hypomyelination especially in external and internal capsules 3 and 7 days after HI, accompanying with microglial activation remarkably. Simvastatin treatment greatly increased the densities of MBP immunostaining, inhibited microglial activation and reduced the numbers of pyknotic cells and neuronal loss.Discussion: The present study shows that simvastatin treatment in neonatal rats attenuates HI-induced developing oligodendrocytes injury and hypomyelination. Its anti-inflammatory properties via suppression of microglial activation are likely to contribute to this action. It provides experimental evidence to support the neuroprotective effects of statins in neonatal ischemic stroke.

Early iron deficiency produces persistent damage to visual tracts in Wistar rats

In this study, morphological changes in the optic nerve were determined by light microscopy in Wistar rats on an iron-deficient diet for 32 days or for 21 days followed by 10 days on an iron-recovery diet. The morphometric findings showed significantly fewer blood vessels and oligodendrocytes in the iron-deficient rats and iron-recovery rats than in the control group, as well as more astrocytes in the iron-recovery rats. Serum iron levels of the iron-deficient rats were significantly lower than those of the controls. On the other hand, iron-recovery rats had normal serum iron levels, but no change in the abnormal morphology of the myelinated axons and morphometric parameters. Our data indicate that iron is necessary for maintenance of the optic nerve cell structure, and morphological damage from iron-deficiency is not easily reverted by iron reposition.

Matrix Metalloproteinase-13 is Activated and is found in the Nucleus of Neural Cells after Cerebral Ischemia

Matrix metalloproteinases (MMPs) have been implicated in the pathophysiology of ischemic stroke. In this study, we investigated the time course of gelatinolytic activation in a rat model of permanent ischemia. We observed an activation of MMPs as early as 30 mins after the ischemic insult, mainly in the nuclei of brain cells. Besides, we explored MMP-13 expression in brain samples of the animal model and stroke deceased patients. We observed an upregulation of active MMP-13 in rat brains (P<0.05) after 90 mins of cerebral ischemia. Human infarct/periinfarct samples also showed higher levels of active MMP-13 (P<0.05) compared with contralateral ones. Interestingly, we found that MMP-13 colocalized with 46-diamidino-2-phenyl indole signal by immunohistochemistry in both humans and rats, suggesting an intranuclear localization for MMP-13. Immunohistochemistry also revealed that MMP-13 was mainly produced by neurons, in both species, but also by oligodendrocytes in rats, and by astrocytes in humans. Finally we subjected a rat primary neuronal culture to oxygen and glucose deprivation (OGD) and we reproduced the nuclear translocation of MMP-13 in vitro. Nuclear extracts from cells confirmed upregulation of active MMP-13 after OGD (P<0.05). These results suggest that MMP-13 activation and its nuclear translocation is an early consequence of an ischemic stimulus.

Cellular responses in the spinal cord during development of hypomyelination in the mv rat

The myelin vacuolation ( mv) rat is an autosomal recessive mutant characterized by hypomyelination and vacuole formation in the myelin throughout the central nervous system (CNS). Previous genetic studies have revealed a null mutation in attractin gene of the mv mutant rat. It has been known that mutation at the attractin locus results in myelin alterations, but their detailed pathogenesis is still unclear. In this study, we examined glial changes in the spinal cord of mv rats at 2, 4, 6, and 8 weeks of age and identified attractin-expressing cells in the rat spinal cord. No abnormality was found in the number and morphology of oligodendrocytes in mv rats at any of the ages examined, although the severity and extent of myelin disorder increased with age. Coincident with the myelin abnormalities, there was progressive astrogliosis from 2 weeks. Marked microglial activation was observed exclusively in the gray matter of mv rats from 6 weeks, coincident with severe myelin disruption. A double-labeling study demonstrated that attractin-expressing cells are mostly oligodendrocytes in the white matter of the spinal cord of wild-type rats, whereas no attractin-positive cells were detected in mv rats. Previous study demonstrated that Luxol fast blue staining pattern and immunoreactivity for myelin basic protein were decreased in mv rats. Therefore, this study indicates that the attractin defect results in oligodendrocyte dysfunction, and is associated with astrogliosis and microglial activation in mv rats. The data suggest that attractin may be directly involved in the function of oligodendrocytes in CNS myelination.

Apoptosis of neurons in rats with experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is a rat model of multiple sclerosis (MS). In MS and EAE, calpain expression is increased in cells of the central nervous system including astrocytes, oligodendrocytes and microglia; as well as infiltrating macrophages and T cells. However, calpain expression in neurons has not previously been reported in the EAE model. Since degeneration of neurons has been demonstrated in progressive cases of MS, and calpain has been implicated in cell death in EAE, it is hypothesized that neurons expressing increased levels of calpain may undergo apoptosis. To test the hypothesis, spinal cords were collected from control and EAE rats from 4 to 12 days after challenge with guinea‐pig myelin and complete Freund's adjuvant. Apoptosis in neurons was determined by combined TUNEL and immunoflourescent staining using a neuron‐specific marker (NeuN). Calpain expression in neurons was determined using double‐immunoflourescent staining with antibodies specific for calpain and NeuN. At 8 and 9 days postchallenge, neither apoptosis nor increased calpain expression were detected in neurons in control or 9 day EAE spinal cord sections. In contrast, at 11 days postinduction neurons in acute EAE were TUNEL‐positive, indicating that cells underwent apoptosis. Further studies are in progress to determine if and when oligodendrocytes in EAE rats are apoptotic. By correlating cell‐specific increases in calpain expression with apoptosis in EAE, a better understanding of the role of calpain in EAE and MS might be achieved. This increased knowledge could suggest a potential benefit of calpain inhibitors in the treatment of EAE and MS.Acknowledgements: Supported in part by grants from NIH‐NINDS.

A rat model for human T lymphocyte virus type I-associated myeloneuropathy: Down-regulation of bcl-2 expression and increase in sensitivity to TNF-α of the spinal oligodendrocytes

We reported that the tumor necrosis factor-α (TNF-α) expression and apoptotic death of oligodendrocytes appeared to be a major pathogenesis of the demyelination of spinal cords of Wistar–King–Aptekman–Hokudai (WKAH) rats with human T lymphocyte virus type I (HTLV-I) infection, HAM rats. In the present study, we examined the sensitivity to TNF-α-induced cell death of in vitro-separated oligodendrocytes from HTLV-I-infected WKAH rats. Although the number of non-viable oligodendrocytes increased by adding recombinant TNF-α, in a dose-dependent manner, in both HTLV-I-infected and uninfected control rats, oligodendrocytes from the infected rats were more susceptible to TNF-α. In situ detection of DNA fragmentation showed apoptotic death of oligodendrocytes. The expression of bcl-2, an anti-apoptotic gene, was strongly down-regulated in oligodendrocytes of the infected rats but not in the control rats. We suggest that the down-regulation of bcl-2 expression in the oligodendrocytes of the HTLV-I-infected rats may increase the susceptibility to TNF-α-induced apoptosis of oligodendrocytes, the result being development of HTLV-I-induced myeloneuropathy in rats.

Optic Nerve Changes in Manganese-deficient Rats

In the present study the changes in the optic nerve due to dietary manganese (Mn) deficiency has examined in Wistar Kyoto rats, since there is a lack of information on the significance of manganese in the optic nerve. After 5 months on a Mn-deficient diet, the optic nerve was examined by light and transmission electron microscopy. The serum manganese level of the deficient rats was significantly lower than that of the controls. The light microscopic findings showed significantly fewer myelinated axons in the Mn-deficient rats and Mn-recovery rats than in the control group, and there were obviously more oligodendrocytes in the recovery rats. Ultrastructural findings were: significantly decreased diameters and lamellae of myelinated axons in the optic nerves of the Mn-deficient rats and abnormal mitochondria in the axons. Rats fed a normal diet for 3 months after 5 months on a Mn deficient diet had a normal serum manganese level, but no change in the abnormal morphology of the myelinated axons. It is concluded that the optic nerve needs manganese for the maintenance of its cell structure.