Glial Cell Counts Research Articles

Exploring the therapeutic potential: Apelin-13's neuroprotective effects foster sustained functional motor recovery in a rat model of Huntington's disease.

Huntington's disease (HD) is a hereditary condition considered by the progressive degeneration of nerve cells in the brain, resultant in motor dysfunction and cognitive impairment. Despite current treatment modalities including pharmaceuticals and various therapies, a definitive cure remains elusive. Therefore, this study investigates the therapeutic potential effect of Apelin-13 in HD management. Thirty male Wistar rats were allocated into three groups: a control group, a group with HD, and a group with both HD and administered Apelin-13. Apelin-13 was administered continuously over a 28-day period at a dosage of around 30 mg/kg to mitigate inflammation in rats subjected to 3-NP injection within an experimental HD model. Behavioral tests, such as rotarod, electromyography (EMG), elevated plus maze, and open field assessments, demonstrated that Apelin-13 improved motor function and coordination in rats injected with 3-NP. Apelin-13 treatment significantly increased neuronal density and decreased glial cell counts compared to the control group. Immunohistochemistry analysis revealed reduced gliosis and expression of inflammatory factors in the treatment group. Moreover, Apelin-13 administration led to elevated levels of glutathione and reduced reactive oxygen species (ROS) level in the treated group. Apelin-13 demonstrates neuroprotective effects, leading to improved movement and reduced inflammatory and fibrotic factors in the HD model.

Effects of ozone treatment to the levels of neurodegeneration biomarkers after rotenone induced rat model of Parkinson’s disease

The study investigated the effects of ozone treatment on the neurodegeneration of stereotaxic rotenone-induced parkinson's disease (PD) model. The model was confirmed using the apomorphine rotation test. α-synuclein, amyloid-β, Tau, phosphorylated Tau, as well as tyrosine hydroxylase(+), nNOS(+), and glial cell counts were used to evaluate neurodegeneration in the substantia nigra pars compacta and ventral tegmental area. The experiment involved 48 Sprague-Dawley rats divided into four groups: dimethyl sulfoxide (DMSO), DMSO with ozone (O), DMSO/rotenone (R), and D/R/O. Ozone treatment significantly improved tissue α-synuclein level and TH+, nNOS+, and glial cell counts compared to the rotenone-only group. The study suggests that ozone treatment may have beneficial effects on PD biomarkers in the rotenone model. Further studies on ozone dosage, duration, and administration methods in humans could provide more evidence for its potential use in Parkinson's disease treatment.

Study of neuroprotective activity of new acetylcholinesterase inhibitors TVA and TVS in experimental model of Alzheimer’s disease

Introduction: Alzheimer’s disease (AD) is a severe neurodegenerative disease characterized by loss of synaptic connection between neurons of the cortex and subcortical regions. The cholinergic deficit is a consistent and early finding in AD, hence acetylcholinesterase inhibitors (AChEIs) are used for symptomatic improvement of AD. Most of these therapeutic agents are hepatotoxic, leading to liver failure and other complications. Therefore, the study of new AChEIs with less toxic impact and better effectivity is a topical challenge. In view of this, we synthesized novel chemical compounds: TVA and TVS that possess AChEI activity and studied their neuroprotective effect in an experimental AD model.
 Materials and methods: Studies were performed on white rats. Acute toxicity studies were performed by Karber’s method. AD was induced via bilateral intracerebroventricular administration of Aβ 25–35. Histopathological examinations were performed in the hippocampus and the entorhinal cortex. Liver tissue was additionally examined to monitor the hepatotoxicity of these compounds.
 Results: Studies of the hippocampus showed that compared to control and TVA-treated groups, under the influence of TVS there were few morphological alterations. Experimental groups showed an increase in the glial cell count, compared to the intact animals. In comparison to the AD group, the increase in microglia was not that prominent under the action of the novel compounds. Under the influence of TVA and TVS, the entorhinal cortex was more susceptible to neuronal injury, although TVS protected pyramidal neurons. Also, the group treated with TVA had signs of acute liver damage, while under the influence of TVS there were no signs of liver changes.
 Discussion: Histopathological examination showed that the neurodegenerative processes in the hippocampus, as well as in the entorhinal cortex, were significantly reduced under the influence of TVS, compared with the control group. At the same time, TVA had no significant effect on the protection of neuronal cells. Also, TVS was less toxic, and there was no sign of hepatotoxicity during the experiments.
 Conclusion: These studies demonstrated that TVS possesses neuroprotective activity and reduces neuronal damage induced by Aβ.
 Graphical abstract:

Artificial gravity partially protects space-induced neurological deficits in Drosophila melanogaster.

Spaceflight poses risks to the central nervous system (CNS), and understanding neurological responses is important for future missions. We report CNS changes in Drosophila aboard the International Space Station in response to spaceflight microgravity (SFμg) and artificially simulated Earth gravity (SF1g) via inflight centrifugation as a countermeasure. While inflight behavioral analyses of SFμg exhibit increased activity, postflight analysis displays significant climbing defects, highlighting the sensitivity of behavior to altered gravity. Multi-omics analysis shows alterations in metabolic, oxidative stress and synaptic transmission pathways in both SFμg and SF1g; however, neurological changes immediately postflight, including neuronal loss, glial cell count alterations, oxidative damage, and apoptosis, are seen only in SFμg. Additionally, progressive neuronal loss and a glial phenotype in SF1g and SFμg brains, with pronounced phenotypes in SFμg, are seen upon acclimation to Earth conditions. Overall, our results indicate that artificial gravity partially protects the CNS from the adverse effects of spaceflight.

Brain Volume Loss, Astrocyte Reduction, and Inflammation in Anorexia Nervosa.

Anorexia nervosa is the third most common chronic disease in adolescence and is characterized by low body weight, body image distortion, weight phobia, and severe somatic consequences. Among the latter, marked brain volume reduction has been linked to astrocyte cell count reduction of about 50% in gray and white matter, while neuronal and other glial cell counts remain normal. Exact underlying mechanisms remain elusive; however, first results point to important roles of the catabolic state and the very low gonadal steroid hormones in these patients. They also appear to involve inflammatory states of "hungry astrocytes" and interactions with the gut microbiota. Functional impairments could affect the role of astrocytes in supporting neurons metabolically, neurotransmitter reuptake, and synapse formation, among others. These could be implicated in reduced learning, mood alterations, and sleep disturbances often seen in patients with AN and help explain their rigidity and difficulties in relearning processes in psychotherapy during starvation.

Neuroprotective effect of ACTH on collagenase-induced peri-intraventricular hemorrhage in newborn male rats

Peri-intraventricular hemorrhage (PIVH) is a common and serious prematurity-related complication in neonates. Adrenocorticotropic hormone (ACTH) has neuroprotective actions and is a candidate to ameliorate brain damage following PIVH. Here, we tested the efficacy of ACTH1-24 on a collagenase-induced lesion of the germinal matrix (GM) in newborn male rats. Animals received microinjection of the vehicle (PBS, 2 µl) or collagenase type VII (0.3 IU) into the GM/periventricular tissue on postnatal day (PN) 2. Twelve hours later pups received microinjection of either the agonist ACTH1-24 (0.048 mg/kg), or the antagonist SHU9119 (antagonist of MCR3/MCR4 receptors, 0.01 mg/kg), or their combination. Morphological outcomes included striatal injury extension, neuronal and glial cells counting, and immunohistochemical expression of brain lesion biomarkers ipsilateral and contralateral to the hemorrhagic site. Data were evaluated on PN 8. Collagenase induced PIVH and severe ipsilateral striatal lesion. ACTH1-24 dampened the deleterious effects of collagenase-induced hemorrhage in significantly reducing the extension of the damaged area, the striatal neuronal and glial losses, and the immunoreactive expression of the GFAP, S100β, and NG2-glia biomarkers in the affected periventricular area. SHU9119 blocked the glial density rescuing effect of ACTH1-24. ACTH1-24 could be further evaluated to determine its suitability for preclinical models of PVH in premature infants.

NF-κB Signaling in Astrocytes Modulates Brain Inflammation and Neuronal Injury Following Sequential Exposure to Manganese and MPTP During Development and Aging.

Chronic exposure to manganese (Mn) is associated with neuroinflammation and extrapyramidal motor deficits resembling features of Parkinson's disease. Activation of astrocytes and microglia is implicated in neuronal injury from Mn but it is not known whether early life exposure to Mn may predispose glia to more severe inflammatory responses during aging. We therefore examined astrocyte nuclear factor kappa B (NF-κB) signaling in mediating innate immune inflammatory responses during multiple neurotoxic exposures spanning juvenile development into adulthood. MnCl2 was given in drinking water for 30-day postweaning to both wildtype mice and astrocyte-specific knockout (KO) mice lacking I kappa B kinase 2, the central upstream activator of NF-κB. Following juvenile exposure to Mn, mice were subsequently administered 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) at 4 months of age. Animals were evaluated for behavioral alterations and brain tissue was analyzed for catecholamine neurotransmitters. Stereological analysis of neuronal and glial cell counts from multiple brain regions indicated that juvenile exposure to Mn amplified glial activation and neuronal loss from MPTP exposure in the caudate-putamen and globus pallidus, as well as increased the severity of neurobehavioral deficits in open field activity assays. These alterations were prevented in astrocyte-specific I kappa B kinase 2 KO mice. Juvenile exposure to Mn increased the number of neurotoxic A1 astrocytes expressing C3 as well as the number of activated microglia in adult mice following MPTP challenge, both of which were inhibited in KO mice. These results demonstrate that exposure to Mn during juvenile development heightens the innate immune inflammatory response in glia during a subsequent neurotoxic challenge through NF-κB signaling in astrocytes.

FR 50% in pregnancy results in different neuron and glial cell count (astrocytes, olygodendrocytes, and microglia) in the cerebrum and cerebellum of newborn Rattus norvegicus

Objectives: To analyze the difference neuronal and glial (astrocytes, oligodendrocyte, microglia) cell count in cerebrum and cerebellum of Rattus norvegicus newborns with 50% food restriction and control group.Materials and Methods: This was an analytical experimental study with single blind randomized post test only control group design using animals subjects Rattus norvegicus. This study was conducted at Animal laboratory, Veterinary Faculty, Universitas Airlangga. Animal subjects were divided into FR50% group and control. Neuron and glial (astrocytes, oligodendrocytes, microglia) counts were analyzed using comparison test, with CI 95%.Results: There was a significant difference in cerebrum and cerebellum neuron cell count between intervention and control group (9.88+3.59 vs 16.88+2.553; p=0.000 and 7.5+1.789 vs 11.44+4.56; p=0.02). There was no difference in cerebrum and cerebellum glial cell count. There was a significant difference in cerebellum astrocyte between intervention and control group (80.94+24.255 vs 59.69+18.77; p=0.02) but no difference in cerebrum. There was a significant difference in cerebrum and cerebellum oligodendrocyte between intervention and control group (14.06+12.195 vs 25.13+8.609; p<0.000 and 13.63+6.712 vs 24.00+8.862; p=0.001), and there were significant difference in cerebrum and cerebellum microglia cell between intervention and control group (5.25+3.435 vs 4.94+3.838; p=0.620 and 8.81+4.119 vs 5.25+1.483; p=0.004).Conclusion: Food Restriction 50% (FR50%) in Rattus norvegicus decreased cerebrum and cerebellum neuron cell and oligodendrocyte count and increased cerebrum and cerebellum microglial count.

Susceptibility MRI captures nigral pathology in patients with parkinsonian syndromes.

Parkinsonisms are neurodegenerative disorders characterized pathologically by α-synuclein-positive (e.g., PD, diffuse Lewy body disease, and MSA) and/or tau-positive (e.g., PSP, cortical basal degeneration) pathology. Using R2* and quantitative susceptibility mapping, susceptibility changes have been reported in the midbrain of living parkinsonian patients, although the exact underlying pathology of these alterations is unknown. The current study investigated the pathological correlates of these susceptibility MRI measures. In vivo MRIs (T1- and T2-weighted, and T2*) and pathology were obtained from 14 subjects enrolled in an NINDS PD Biomarker Program (PDBP). We assessed R2* and quantitative susceptibility mapping values in the SN, semiquantitative α-synuclein, tau, and iron values, as well as neuronal and glial counts. Data were analyzed using age-adjusted Spearman correlations. R2* was associated significantly with nigral α-synuclein (r = 0.746; P = 0.003). Quantitative susceptibility mapping correlated significantly with Perls' (r = 0.758; P = 0.003), but not with other pathological measurements. Neither measurement correlated with tau or glial cell counts (r ≤ 0.11; P ≥ 0.129). Susceptibility MRI measurements capture nigral pathologies associated with parkinsonian syndromes. Whereas quantitative susceptibility mapping is more sensitive to iron, R2* may reflect pathological aspects of the disorders beyond iron such as α-synuclein. They may be invaluable tools in diagnosing differential parkinsonian syndromes, and tracking in living patients the dynamic changes associated with the pathological progression of these disorders. © 2018 International Parkinson and Movement Disorder Society.

Assemblages A and B of Giardia duodenalis reduce enteric glial cells in the small intestine in mice.

Infection of Giardia duodenalis is one of the most common human parasitic disease worldwide. This infection may be related to important changes in the enteric nervous system. The objective of this study was to evaluate the myenteric and submucosal plexuses, the intestinal muscle layer, and gastrointestinal transit in mice infected with assemblages A and B of G. duodenalis. Swiss albino mice (Mus musculus) were infected with assemblages A and B of G. duodenalis for 15days. Gastrointestinal transit time was evaluated before euthanasia. Duodenum and jejunum were removed for histological and immunohistochemical analyses. It was observed a reduction in the enteric glial cell count and a decrease in the ratio of enteric glial cells to neurons. The number of neurons did not change, but morphological changes were observed in the duodenum and jejunum in both plexuses, including an increase in the nuclear area and a reduction of cell bodies in the myenteric plexus and a decrease in the nuclear area in the submucosal plexus. A reduction of the thickness of the muscle layer was observed in the duodenum, with no significant differences in the gastrointestinal transit times. Assemblages A and B of G. duodenalis decrease the number of enteric glial cells in the myenteric and submucosal plexuses, decrease the thickness of the muscle layer, and change the morphology of neurons. Graphical abstract ᅟ.

Neuro-Glio-Vascular Complexes of the Brain After Acute Ischemia

The purpose of the study is to compare the structural and functional state of neuro-glio-vascular microstructural complexes of the somatosensory cortex (SSC), CA1 of the hippocampus and amygdala of the brain of white rats under normal conditions and after acute ischemia caused by a 20-minute occlusion of common carotid arteries. Materials and methods. In this experiment, neurons, astrocytes, endotheliocytes, pericytes, basal membrane of the microvessels were studied in the normal (n=5) and the reperfusion period (1, 3, 7, 14, 21 and 30 days, n=30) using electron and fluorescence microscopy (DAPI staining). The morphometric analysis was carried out using the ImageJ 1.46 software. Results. During the recovery period after ischemia was noted reactive (edema-swelling, tinctorial properties of cells) and compensatory-restoration (hyperplasia, hypertrophy, proliferation, increased transcytosis) changes in neuro-glia-vascular complexes. After ischemia, the number of neurons decreased (by 8.7%—55,3%), and the glial cell count 2—3 fold increased. Increasing neuroglial index (NGI) was accompanied by: 1) the emergence of microvessels with numerous branched processes of pericytes, 2) the complication of the spatial organization of basal membranes, and 3) the structural features of activation of transcytosis processes (large number of caveolae, smooth and clathrin vesicles, large vesicles) in pericytes and endothelial cells. Conclusion. These findings indicate the compensatory-restoration changes in the components of neuro-gliovascular complexes SSC, CA1 of the hippocampus and amygdala of white rat’s brain after a 20-minute occlusion of the common carotid arteries. The most complete implementation of mechanisms for the protection and repair of damaged neurons occurs in the SSC and amygdala exhibiting high NGI values.

Increased Neuron Number and Head Size in Autism

N THIS ISSUE OF JAMA, THE REPORT BY COURCHESNE AND colleagues 1 documents an increase in neuron number intheprefrontalcortex(PFC)inmalechildrenandadolescents with autism. Those findings build on Leo Kanner’s original observations 2 in 1943 and 2 decades of recent research investigating macrocephaly in autism. Macrocephaly occurs in 20% of individuals with autism on average and is usually due to megalencephaly—abnormal enlargement of the brain during childhood. 3 The enlargementisrarelypresentatbirth;itdevelopsduringearlychildhood when head growth accelerates during the first 18 months of life. 4 Mean total brain, lobar, white matter, and gray matter volumes, including volume of the cortex, are significantlyincreasedby2to3yearsofageinchildrenwith autism when compared with typically developing and also nonautistic developmentally delayed individuals. 5-7 The excessive head growth and brain growth occur prior to most clinical manifestations of the disorder, raising the possibility that the mechanisms that cause excessive growth also play a role in the primary developmental neuropathology of autism. The purpose of the study by Courchesne et al 1 was to investigate the neural underpinnings of brain overgrowth in autismat the cellular level. In this postmortemtissue study, the investigators focused on cortical gray matter, specifically the PFC, which is one of the brain regions highly implicatedinthedisorder,andsoughttoansweracriticalquestioninautismresearch: is brain overgrowthassociated with increased size and number of neurons, glial cells, or both? The investigators found 79% more neurons in the dorsolateral PFC (DL-PFC) and 29% more neurons in the mesial PFC (M-PFC) in 7 brains from boys with autism compared with 6 brains of typically developing children (controls). There were no apparent group differences in neuron size or in glial cell counts. Prefrontal neuron number and brain weight were significantly correlated in the control group but not in the autism group. The authors speculated that the latter finding may indicate that the brains of some individuals with autism are undersized relative to their prefrontal cortical neuron count. Equally possible is an increaseofprefrontalcorticalneuronnumberanddensityrelativetotypicalbrainweight.Thebrainsofautismcases3and 4 in the study by Courchesne et al 1 are specific examples of such an alternative explanation, having increased numbers of neurons in the PFC (2.21 and 2.18 billion; eTable 5 in the article 1 ) and weights within the range of control brain weights. Postmortem brain tissue studies in autism research, and in general, are difficult to conduct due to limited availability of brain samples, non-representativeness of the samples, variable causes of death, potentially long postmortem intervals, and differences in brain extraction, sectioning and tissueprocessingprotocolsandcellcountingmethods. 8 Most if not all case-control tissue sample sizes are small, and representative population-based postmortem reference data, similar to those currently available from large normative samples of in vivo pediatric brain imaging, 9 do not exist.

A comparison of neurotoxicity in cerebellum produced by dermal application of chlorpyrifos in young and adult mice

Chlorpyrifos (CPF), an organophosphate pesticide inhibits acetylcholinesterase (AChE) and causes neuromuscular incoordination among children and elderly. The objectives of the present study were to compare the neurotoxic effects of dermal application of CPF on the cerebellum in the parameters of glial fibrillary acidic protein (GFAP) expression in young and adult mice and to correlate with the changes in acetylcholinesterase levels. Male Balb/c mice, 150days old (adult) and 18days old (young) were dermally applied with ½ LD(50) of CPF over the tails for 14days. Serum AChE concentration was estimated and GFAP immunostaining was performed on sagittal paraffin sections through the vermis of cerebellum. Although reduced in both age-groups exposed to CPF, percentage of reduction in serum AChE was more in adult compared to the young. Under GFAP immunostaining, brown colour fibres and glial cells were observed in cerebellar cortex and medulla in both the experimental groups. The mean GFAP-positive glial cell count in cerebellar medulla per mm(2) of section was significantly (p<0.05) increased in adult mice exposed to CPF when compared with age-matched control. In conclusion, this study confirmed that dermal exposure of CPF was able to exert neurotoxic effect in both young and adult mice. However, the quantitative results revealed that adult mice showed more GFAP expression in cerebellum when compared with the young, when exposed to CPF.

KI-67 Expression in the Cerebellum of Dogs with Distemper

SUMMARY As the canine distemper virus (CDV) induces demyelination in the central nervous system, partially due to losses of glial cells, the aim of the present study was to determine the Ki67 immunoreactivity in demyelinated regions from cerebellum of dogs with acute and chronic CDV infection. Cerebella from naturally infected dogs (n = 12) were routinely processed for histopathology and the observed lesions were conventionally classified as acute (n = 6) or chronic (n = 6) cases. Immunohistochemical analyses were performed in parallel for detecting the CDV antigen using a mouse anti-CDV monoclonal antibody and for evaluating the proliferation index using a rabbit anti-Ki67 polyclonal antibody. Histological and immunohistochemical findings were compared to healthy cerebellum controls (n = 6). Contrary to controls, cerebella from infected dogs exhibited demyelinated areas, often moderate to severe, in which the viral presence was confirmed. Regarding the demyelination percentage, no significant difference was found between acute and chronic cases. The glial Ki67 proliferation indexes were roughly similar in the 2 groups of infected dogs and were markedly higher than in controls whereas the mean Ki67 immunopositive glial cell counts were dramatically increased in chronically infected dogs compared to the controls or to the acutely affected dogs. These results show that the glial cell proliferation progresses with the same intensity in both acute and chronic cases, although the total number of Ki67 positive cells is higher in chronically infected dogs, suggesting that compensatory mechanisms for counteracting demyelination.

Cell pathology in mood disorders.

In new, exciting, neuroanatomic studies on postmortem tissues from patients with mood disorders, quantitative cytomorphologic differences can be shown at the microscopic level. These investigations provide direct evidence that mood disorders are characterized by marked reductions in glial cell number and density in addition to subtle alterations in the density and size of cortical neurons in frontolimbic brain regions. Importantly, this corresponds with clinical neuroimaging studies and preclinical animal studies that suggest cell atrophy, cell loss, or impairments in neuroplasticity and cellular resilience may underlie the neurobiology of major depressive disorder and bipolar manic-depressive disorder. Because this represents a departure from modern efforts to understand mood disorders, published reports are scarce and based on rather small sample sizes. This article reviews the current findings from postmortem studies on glial and neuronal cell counts in primary mood disorders and discusses a possible link between cellular changes and the action of psychotherapeutic drugs.

Hippocampal pathology in refractory temporal lobe epilepsy: T2-weighted signal change reflects dentate gliosis.

The MR and pathologic features of hippocampal sclerosis (HS) are well described and include volume decrease and T2-weighted signal increase for MRI, and neuron cell loss and gliosis for pathology. To confirm the established correlation between hippocampal volumes and neuron cell counts, and to study the still controversial association between signal change and gliosis. The authors studied 44 patients (22 men and 22 women; mean age at surgery, 37 years) with refractory temporal lobe epilepsy. Quantitative assessment of hippocampal volumes and T2 relaxometry, and neuron and glial cell count in the region CA1 and molecular layer of the dentate gyrus was performed. The proportion of glial fibrillary acidic protein (GFAP)-positive glial cells (reactive astrocytes) was indicated. In a stepwise regression, the ipsilateral hippocampal volume was predicted best by the neuron cell count in the dentate gyrus (p = 0.005, r = 0.4). Hippocampal T2 time, however, was predicted best by the glial cell count in the dentate gyrus (p = 0.01, r = 0.4). None of the other cell counts contributed to either model. In the dentate, 31% of the glial cells were reactive astrocytes, whereas in CA1, 5% were reactive. The results confirmed the correlation between hippocampal volumes and neuron cell counts. T2-weighted signal increase in the hippocampus was mainly influenced by gliosis in the dentate gyrus, where a high proportion of glial cells show abnormal activity. This activity may reflect changes important in the development of hippocampal epileptogenicity.

Tumor Necrosis Factor α Is Toxic to Embryonic Mesencephalic Dopamine Neurons

Levels of the proinflammatory cytokine tumor necrosis factor α (TNFα) are increased in postmortem brain and cerebral spinal fluid from patients with Parkinson's disease (PD). This observation provides a basis for associating TNFα with neurodegeneration, but a specific toxicity in dopamine (DA) neurons has not been firmly established. Therefore, we investigated TNFα-induced toxicity in DA neurons by utilizing primary cultures of embryonic rat mesencephalon. Exposure to TNFα resulted in a dose-dependent decrease in DA neurons as evidenced by decreased numbers of tyrosine hydroxylase-immunoreactive (THir) cells. TNFα toxicity was selective for DA neurons in that neither glial cell counts nor the total number of neurons was decreased and no general cytotoxicity was evidenced by lactate dehydrogenase assay. Many of the cells which remained immunoreactive for TH had shrunken and rounded cell bodies with broken, blunted, or absent processes. However, TNFα-treated cultures also contained some THir cells which appeared to be undamaged and possibly resistant to TNFα-induced toxicity. Additionally, immunocytochemistry revealed basal expression of TNFα receptor 1 (p55, R1) and TNFα receptor 2 (p75, R2) on all cells within the mesencephalic cultures to some degree, even though only DA neurons were affected by TNFα treatment. These data strongly suggest that TNFα mediates cell death in a sensitive population of DA neurons and support the potential involvement of proinflammatory cytokines in the degeneration of DA neurons in PD.

Morphological and morphometric studies of the dysmyelinating mutant, the Long Evans shaker rat.

The Long Evans shaker (les) rat is a recently identified CNS myelin mutant with an autosomal recessive mode of inheritance. Although scattered myelin sheaths are present in some areas of the CNS, most notably the ventral spinal cord in the young neonatal rat, this myelin is gradually lost, and 8-12 weeks little myelin is present throughout the CNS. Despite this severe myelin deficiency, some mutants may live beyond one year of age. Rare, thin myelin sheaths that are present early in development lack myelin basic protein (MBP) and on ultrastructural examination are poorly compacted and lack a major dense line. Many oligodendrocytes develop an accumulation of vesicles and membranous bodies, but no abnormal cell death is observed. In the optic nerve, cell kinetic studies show an increase in proliferation at early time points in les, while total glial cell counts are also increased in les from 2 months of age. In situ hybridization studies demonstrate that the numbers of mature oligodendrocytes are similar to controls early in life and increase with time compared to controls. There is both a progressive astrocyte hypertrophy and microgliosis. While les has a mutation in the myelin basic protein (mbp) gene, it is dissimilar in both genotype and phenotype to the previously described mbp mouse mutants, shiverer (shi) and shiverer(mld). Unlike shi and its allele, where myelin increases with time and oligodendrocytes become ultrastructurally normal, les oligodendrocytes are permanently disabled, continue to demonstrate cytoplasmic abnormalities, and fail to produce myelin beyond the first weeks of life.

Hippocampal MRI volumetrics and temporal lobe substrates in medial temporal lobe epilepsy

Forty-nine consecutive patients undergoing anteromedial temporal lobe resection for medically intractable temporal lobe seizures, and averaging 2 yr (range 6 mo to 4 yr) postoperative follow-up, were selected for a retrospective study. This study correlated magnetic resonance imaging (MRI) derived hippocampal volumetrics, preoperative demographics, postoperative seizure control, and tissue analysis, including hippocampal CA (cornu ammonis) field neuronal, and glial cell counts, and immunohistochemistry (IHC) evidence for dentate sprouting and reorganization. These measures were compared in hippocampi with or without an adjacent presumptive epileptogenic temporal lobe mass. Mesial temporal sclerosis (MTS) was defined as >50% neuronal cell loss averaged across all CA fields with NPY (neuropeptide-y) and somatostatin reorganization. These patients may or may not include granule cell sprouting as determined by dynorphin staining. Patients were divided into two groups based on CA field neuronal cell counts, one averaging >50% cell loss and one averaging <50% cell loss. For the MTS group ( N = 38), 89% had significant volumetric atrophy of the ipsilateral hippocampus, 74% had dentate reorganization, and complete seizure control was seen in 76% of these patients. In one subgroup of the <50% cell loss group, patients with medial temporal lobe epilepsy caused by a mass in the medial temporal lobe (mass group) ( N = 6), 33% demonstrated significant volumetric atrophy of the hippocampus ipsilateral to the mass, 0% had dentate sprouting, and seizures were completely controlled in 67%. For the second subgroup of the <50% cell loss group, patients without mass lesions ( N = 5) who were classified as the paradoxical medial temporal lobe epilepsy group (paradoxical group), 20% had ipsilateral hippocampal atrophy, 0% had dentate reorganization, and complete seizure control was seen in 60% of these patients. In conclusion, for the MTS group, hippocampal atrophy proven by MRI volumetrics was highly predictive of significant neuronal cell loss and an excellent indicator of success. However, in patients who had a foreign mass, hippocampal atrophy was not necessarily indicative of significant neuronal cell loss and MRI volumetrics was not a factor in the determination of a successful outcome. Furthermore, patients without mass lesions who have normal volumetrics but demonstrate hippocampal disease through invasive electrode monitoring, are likely to have paradoxical medial temporal lobe epilepsy, seizures beginning at a later age, and a lower, but not insignificant, success rate than the classical mesial temporal sclerosis group.

GUINEA-PIG SPINAL-CORD AS A MODEL FOR THE STUDY OF LATE RADIATION-INJURY AND REPAIR

The risk of normal tissue damage imposes severe limitations on the radiotherapy of malignant tumours. The aim of this study was to examine the morphology of late radiation injury with special reference to microvasculature in the irradiated guinea pig spinal cord. Gamma radiation from a cobalt-60 source was used to irradiate the lumbar region of guinea pigs. A total dose of up to 94.5 Gy was given using 4.5 Gy fractions. Twenty such guinea pigs which survived more than 2 years post-irradiation were deeply anaesthetized and Mercox resin was perfused through the thoracic aorta. Ten minutes following perfusion, irradiated segments of the spinal cords were removed and either fixed in formalin for histology and morphometry or corroded in KOH for microvascular cast preparation. The latter were observed under the scanning electron microscope. All irradiated specimens showed multifocal white matter vacuolation. None of these spaces communicated with blood vessels. No such vacuolation was observed in grey matter. Glial cell counts in the irradiated white matter were reduced. Microvascular morphometry revealed 3.30% of the area was occupied by vasculature in the non-irradiated white matter. The corresponding value for irradiated white matter was 2.38% (p=0.003). No difference in the vascular area was noted in the non-irradiated grey matter (9.75%) and irradiated grey matter (10.36%; p=0.36) Microvascular casts did not reveal telangiectasia. However, irradiated specimens showed focal avascular regions. This was consistent with the light microscopic observation of focal degeneration and necrosis of irradiated white matter. These results suggest that late radiation injury in guinea pigs results primarily from damage to glial elements and the microvasculature is secondarily affected.