Treadmill exercise increases cell proliferation in hippocampal dentate gyrus in alcohol-intoxicated rats

AIM

Effect of treadmill exercise on hippocampal cell proliferation under normal conditions has been well documented; however, this effect under alcohol intoxication conditions is not clarified, yet. In the present study, the effect of treadmill exercise on cell proliferation in the dentate gyrus in alcohol-intoxicated rats was investigated.

METHODS

EXPERIMENTAL DESIGN

comparative investigation on number of 5-bromo-2'-deoxyuridine (BrdU)-positive cells in the dentate gyrus 8 days after commencement.

SETTING

animal laboratory.

PARTICIPANTS

male Sprague-Dawley rats of 5 weeks in age weighing 150+/-10 g.

INTERVENTION

animals were divided into 4 groups: the control-rest group, the control-exercise group, the alcohol-treated-rest group, and the alcohol-treated-exercise group. Animals of the alcohol-treated groups were injected intraperitoneally with alcohol (2 g/kg) once a day for 3 days. All animals were injected BrdU (50 mg/kg) intraperitoneally, and rats of exercise groups were made to run on treadmill for 30 min each day for 5 days following alcohol administration.

MEASURES

mean number of BrdU-positive cells in dentate gyrus was observed via immunohistochemistry.

RESULTS

Treadmill exercise significantly increased the number of BrdU-positive cells in the dentate gyrus. Also, treatment with alcohol for 3 days inhibited cell proliferation and treadmill exercise alleviated alcohol-induced inhibition of new cell formation.

CONCLUSION

These results suggest the possibility that treadmill exercise may help in improvement following alcohol-induced brain damage.

Human anti-beta-amyloid antibodies block beta-amyloid fibril formation and prevent beta-amyloid-induced neurotoxicity

The accumulation of beta-amyloid (A beta) in neuritic plaques is thought to be causative for the progression of Alzheimer's disease (AD). Recently, both active immunization and passive administration of A beta antibodies dramatically attenuated amyloid plaque deposition, neuritic dystrophy, astrogliosis and behaviour deficits in transgenic animals. In addition, we and others have found that titres of naturally occurring anti-A beta antibodies in the CSF of AD patients are significantly lower than those in age-matched controls. Treatment with intravenous immunoglobulins (a preparation that contained anti-A beta antibodies) significantly lowered CSF levels of A beta in non-demented patients. In this study, anti-A beta antibodies were isolated from immunoglobulin preparations and these anti-A beta antibodies strongly block fibril formation or disrupt formation of fibrilar structures. Furthermore, these antibodies almost completely prevented neurotoxicity of A beta. In contrast, immunoglobulins depleted of anti-A beta antibodies had little effect on A beta fibril formation or protection of neuronal cells. This study supports the findings that human anti-A beta antibodies may interfere with the pathogenesis of AD by more than one mechanism, and administration of polyclonal human anti-A beta antibodies isolated from plasma is a potential therapeutic agent to prevent or slow down disease progression.

Dexamethasone aggravates hippocampal apoptosis and learning deficiency in pneumococcal meningitis in infant rats

In an infant rat model of pneumococcal meningitis the effect of dexamethasone on neuronal injury in the hippocampus and on learning disability after recovery from the disease was examined. Treatment with dexamethasone or vehicle was started 18 h after infection, concomitant with antibiotics. Neuronal apoptosis in the hippocampal dentate gyrus 34 h after infection was significantly aggravated by dexamethasone treatment compared with vehicle controls (p = 0.02). Three weeks after acute pneumococcal meningitis, learning capacity of animals was assessed in the Morris water maze. The results showed a significantly impaired learning performance of infected animals treated with dexamethasone compared with vehicle controls (p = 0.01). Dexamethasone had no effect on hippocampal injury or learning in uninfected controls. Thus, dexamethasone as adjuvant therapy increased hippocampal cell injury and reduced learning capacity in this model of pneumococcal meningitis in infant rats.

Depressed new neurons--adult hippocampal neurogenesis and a cellular plasticity hypothesis of major depression

In a novel theory, a failure of adult hippocampal neurogenesis has been proposed to provide the biological and cellular basis of major depression. The as yet unresolved function of the new hippocampal neurons will have to be in the center of any attempt to prove this hypothesis. Only knowledge of normal functional relevance of new neurons will allow an assessment of their potential role in disturbed hippocampal function in depression; however, major depression is not primarily a hippocampal disorder. We therefore propose that consideration of the neurogenesis hypothesis of depression be the most prominent aspect of a more general cellular plasticity hypothesis.

Contralateral medial temporal lobe damage in right but not left temporal lobe epilepsy: a (1)H magnetic resonance spectroscopy study

BACKGROUND

Proton magnetic resonance spectroscopy (MRS) of the hippocampus is useful in lateralising the epileptic focus in temporal lobe epilepsy for subsequent surgical resection. Previous studies have reported abnormal contralateral MRS values in up to 50% of the patients.

OBJECTIVE

To identify the contributing factors to contralateral damage, as determined by MRS, and its extension in patients with temporal lobe epilepsy.

METHODS

Single voxel MRS was carried out in the hippocampus and lateral temporal neocortex of both hemispheres in 13 patients with left temporal lobe epilepsy (LTLE) and 16 patients with right temporal lobe epilepsy (RTLE). All patients had mesial temporal lobe epilepsy with hippocampal sclerosis. Controls were 21 healthy volunteers of comparable age.

RESULTS

Consistent with previous studies, the NAA/(Cho+Cr) ratio was abnormally low in the hippocampus ipsilateral to the focus (p < 0.0001), and there were lower values in both patient groups in the ipsilateral temporal neocortex (p < 0.0001). Patients with RTLE had left hippocampal MRS anomalies (p = 0.0018), whereas the right hippocampus seemed to be undamaged in LTLE patients.

CONCLUSIONS

Unilateral mesial temporal lobe epilepsy is associated with widespread metabolic abnormalities which involve contralateral mesial and neocortical temporal lobe structures. These abnormalities appear to be more pronounced in patients with RTLE.

Expression of death-associated protein kinase and recruitment to the tumor necrosis factor signaling pathway following brief seizures

Death-associated protein (DAP) kinase is calcium-regulated and known to function downstream of death receptors, prompting us to examine its role in the mechanism of seizure-induced neuronal death. Brief seizures were focally evoked in rats, eliciting neuronal death within the CA3 subfield of the hippocampus, and to a lesser extent, cortex. Western blotting confirmed expression of DAP kinase within hippocampus and cortex at the predicted weight of approximately 160 kDa. Immunohistochemistry revealed seizures triggered a significant increase in numbers of DAP kinase-expressing cells within CA3 and cortex, without affecting cell counts within seizure-resistant CA2 or the dentate gyrus. Numbers of DAP kinase-expressing cells were increased in relation to specific patterns of injury-causing seizure activity, electrographically defined. Seizures caused an early increase in DAP kinase binding to actin, and association with calmodulin. Co-immunoprecipitation studies also revealed seizures triggered binding of DAP kinase to the tumor necrosis factor receptor 1 and the Fas-associated death domain protein, commensurate with caspase-8 proteolysis. In contrast, within surviving fields of the hippocampus, DAP kinase interacted with the molecular chaperone 14-3-3. These data suggest DAP kinase is involved in the molecular pathways activated during seizure-induced neuronal death.

Abnormalities in hippocampi remote from the seizure focus: a T2 relaxometry study

The aim of this study was to determine whether partial epilepsy is associated with abnormalities in hippocampi that are not the primary seizure focus. As hippocampal T2 relaxometry is useful for identifying abnormalities that are not obvious on visual assessment of MRI, this was the method employed. Of 457 consecutive children and young adults from whom T2 relaxometry data were obtained, 96 had well characterized partial epilepsy and were enrolled, along with 27 control subjects. The patients were divided on the basis of clinical, video-EEG and visual MRI assessment into three groups: (i) those with temporal lobe epilepsy (TLE) and mesial temporal sclerosis (MTS) (MTS-TLE); (ii) lesional TLE (l-TLE); or (iii) extratemporal epilepsy (ETE). There was a significant and similar prolongation of T2 relaxation time identified in hippocampi remote from the seizure focus in all patient groups when compared with control subjects. In the non-sclerotic hippocampus of patients with MTS, T2 relaxation time was prolonged by a mean of 3.3 ms [95% confidence interval (CI), 0.8-5.9 ms; P = 0.01], patients with l-TLE had prolongation of T2 relaxation time by a mean of 4.3 ms (95% CI, 1.8-7.1 ms; P = 0.001) and those with ETE had prolongation of T2 relaxation time by a mean of 3.7 ms (95% CI, 1.6-6.6 ms; P = 0.006) compared with control subjects after adjustment for age. Unsurprisingly, in patients with MTS-TLE, T2 relaxation time in the sclerotic hippocampus was prolonged by a mean of 19 ms (95% CI = 14.6-22.4 ms; P < 0.001). The similarity in the extent of prolongation of T2 relaxation time in hippocampi that are not the primary epileptogenic focus, the wide variety of structural associations and the varied sites of epileptogenic foci, considered together, suggest that the abnormalities are likely to be caused by ongoing seizure activity rather than by underlying aetiology or site of epileptogenic focus.

Decreased estrogen receptor-alpha expression in hippocampal neurons in relation to hyperphosphorylated tau in Alzheimer patients

Emerging evidence has demonstrated the neuroprotection of estrogen in Alzheimer's disease (AD). The hippocampus, an important target of estrogen action, is severely affected in the Alzheimer process. The aim of present study was to detect the distribution of estrogen receptor-alpha (ER-alpha) and the relationship between ER-alpha-containing neurons and the pretangles stained by Alz-50 in the hippocampus of AD patients. The results showed that more than half of hippocampal neurons expressed ER-alpha. The number of cytoplasmic ER-alpha-positive neurons was significantly decreased in the CA1 and CA2 subfields of AD hippocampus, but the ratio of these ER-alpha-expressing neurons to the nucleolated neuronal profiles stained by thionin was not different between the two groups. Interestingly, the number of nuclear ER-alpha-staining neurons was also markedly decreased in the CA1 and CA2 subfields of AD hippocampus, and the percentage of these nuclear staining neurons was also significantly decreased in the same subfields. Furthermore, some double-labeled neurons containing ER-alpha and Alz-50 were found in AD patients. However, in these double-labeled neurons, ER-alpha was only located in the cytoplasm. Thus, we hypothesize that the nuclear ER-alpha may play more important roles of neuroprotection during the process of AD.

Statistical shape analysis of neuroanatomical structures based on medial models

Knowledge about the biological variability of anatomical objects is essential for statistical shape analysis and discrimination between healthy and pathological structures. This paper describes a novel approach that incorporates the variability of an object population into the generation of a characteristic 3D shape model. The proposed shape representation is a coarse-scale sampled medial description derived from a fine-scale spherical harmonics (SPHARM) boundary description. This medial description is composed of a net of medial samples (m-rep) with fixed graph properties. The medial model is computed automatically from a predefined shape space using pruned 3D Voronoi skeletons. A new method determines the stable medial branching topology from the shape space. An intrinsic coordinate system and an implicit correspondence between shapes is defined on the medial manifold. Several studies of biological structures clearly demonstrate that the novel representation has the promise to describe shape changes in a natural and intuitive way. A new medial shape similarity study of group differences between monozygotic and dizygotic twins in lateral ventricle shape demonstrates the meaningful and powerful representation of local and global form.

Neuronal activity-dependent increase of net matrix metalloproteinase activity is associated with MMP-9 neurotoxicity after kainate

Matrix metalloproteinases (MMPs) and the tissue inhibitors of MMPs (TIMPs) are emerging as important modulators of brain physiopathology. Dramatic changes in the expression of MMPs and TIMPs occur during excitotoxic/neuroinflammatory processes. However, only the measurement of net protease activity is relevant physiologically, and the functional consequences of MMP/TIMP ratio modifications in the brain remain elusive. In order to assess MMP activity and effects in brain tissue, we combined in vivo and organotypic culture models of kainate (KA)-induced excitotoxicity to provoke selective neuronal death and neuroinflammation in the hippocampus. Using in situ zymography, we show that KA-induced excitotoxic seizures in rats increase net MMP activity in hippocampal neurons 8 h after seizures, before their death, and that this increase is neuronal activity-dependent. Three days after KA, proteolytic activity increases in blood vessels and reactive glial cells of vulnerable areas, in relation with neuroinflammation. At 7 and 15 days, proteolysis remains high in blood vessels whereas it is reduced in glia. In organotypic hippocampal cultures, which lack blood cell-mediated inflammation and extrinsic connections, a broad-spectrum inhibitor of MMPs (MMPI), but also a selective MMP-9 inhibitor, protect hippocampal neurons against KA-induced excitotoxicity. Moreover, recombinant MMP-9, but not MMP-2, induces selective pyramidal cell death in these cultures and KA-induced neuronal activity exacerbates the neuronal death promoting effects of MMP-9. These data strongly implicate MMPs, and MMP-9 in particular, in both excitotoxic neuronal damage and subsequent neuroinflammatory processes, and suggest that selective MMPIs could be therapeutically relevant in related neurological disorders.

Preliminary evidence that estrogen protects against age-related hippocampal atrophy

Few studies have examined gender differences in hippocampal volumes, and the potential effect of estrogen on these measures has not been well studied. We used MRI to measure hippocampal volumes in elderly Mexican American men and women subjects in order to determine if there were gender differences and if estrogen replacement therapy (ERT) had an effect on hippocampal volume in postmenopausal women. MRI measures of hippocampal volumes (normalized to intracranial volume) were compared in 59 women and 38 men. Further comparisons were made between men subjects, women subjects taking ERT, and women subjects not taking ERT. There were no significant effects of gender on normalized hippocampal volumes. However, women subjects taking ERT had larger right hippocampal volumes than women subjects not taking ERT and larger anterior hippocampal volumes than men subjects and women subjects not taking ERT. These findings suggest a neuroprotective effect of estrogen.

Seven cDNAs enriched following hippocampal lesion: possible roles in neuronal responses to injury

Synaptic plasticity is important for formation of long-term memories and in re-establishment of function following injury. Seven cDNAs enriched following lesion in the hippocampus of the rat have been isolated using a PCR-based cDNA suppression subtraction hybridization. Sequence analysis resulted in the identification of two genes with known roles in synaptic development and neuronal activities: astrotactin and calcineurin. These two neuron-specific genes have established roles in development or synaptogenesis. Sequence analysis of the other five additional genes shows that two are likely to be involved in G-protein signaling pathways, one is a WD repeat protein, and the remaining two are entirely novel. All seven candidates are expressed in the hippocampus and, in some cases, cortical layers of adult brains. RT-PCR data show that expression increases following synaptogenic lesion. Immunocytochemical analysis in primary hippocampal neurons showed that Calcineurin immunoreactivity was redistributed in neurons during 2 weeks in culture. This redistribution suggests that Calcineurin's role changes during neurite outgrowth immediately prior to synapse formation in vitro. In addition, inhibiting Calcineurin activity with cyclosporin A enhanced neurite outgrowth, suggesting that Calcineurin has a regulatory role in axon sprouting. The discovery of previously unknown genes involved in the response to neurodegeneration will contribute to our understanding of neural development, responses to CNS trauma, and neurodegenerative diseases.

Stroke in the developing brain and intractable epilepsy: effect of timing on hippocampal sclerosis

A detailed study was made of the pathology of specimens removed by hemispherectomy for the treatment of intractable epilepsy in children with unilateral middle cerebral artery stroke. Neuropathological criteria were used to differentiate strokes that occurred in early intrauterine development (before 28 weeks gestational age) from those occurring in the last trimester, at birth, or after birth: 19 children had early strokes and 21 late. There was no difference in seizure history or occurrence of febrile convulsions in these two groups. Hippocampal tissue was available in 20 patients; pathology in the hippocampus, remote from the infarcted area, showed a marked difference between early-onset and late-onset groups. Hippocampal sclerosis was uncommon in children with early-onset strokes but developed in most of the children whose strokes were of later origin. However, hippocampal sclerosis was more closely related to a clinical history of a late initial precipitating insult irrespective of infarct timing. These findings demonstrate the changing vulnerability of the developing brain and show that hippocampal pathology is more closely related to the timing of an insult than seizure history or the occurrence of febrile convulsions.

Activation of p38 kinase in the gerbil hippocampus showing ischemic tolerance

Ischemic tolerance is a phenomenon in which brief episodes of ischemia protect against the lethal effects of subsequent periods of prolonged ischemia. The authors investigated the activation of p38 mitogen-activated protein kinase (p38) in the gerbil hippocampus by Western blotting and immunohistochemistry to clarify the role of p38 kinase in ischemic tolerance. After the 2-minute global ischemia, immunoreactivity indicating active p38 was enhanced at 6 hours of reperfusion and continuously demonstrated 72 hours after ischemia in CA1 and CA3 neurons. Pretreatment with SB203580, an inhibitor of active p38 (0-30 micromol/l), 30 minutes before the 2-minute ischemia reduced the ischemic tolerance effect in a dose-dependent manner. Immunoblot analysis indicated that alteration of the phosphorylation pattern of p38 kinase in the hippocampus after subsequent lethal ischemia was induced by the preconditioning. These findings suggest that lasting activation of p38 may contribute to ischemic tolerance in CA1 neurons of the hippocampus and that components of the p38 cascade can be target molecules to modify neuronal survival after ischemia.

Significance of fornix atrophy in temporal lobe epilepsy surgery outcome

BACKGROUND

Previous magnetic resonance imaging (MRI) studies have shown concurrent fornix atrophy in a large proportion of patients with hippocampal atrophy. The contribution of the fornix as an independent preoperative determinant of surgical outcome is unknown.

OBJECTIVE

To evaluate the contribution of the fornix as a determinant of surgical outcome in patients with preoperatively determined temporal lobe epilepsy.

METHODS

We selected 78 patients who had undergone anterior temporal lobectomy for intractable temporal lobe epilepsy at the University of Alabama at Birmingham Epilepsy Center during a 24-month period. All patients underwent standard presurgical investigations and intracranial investigations when needed. Magnetic resonance imaging volumetric studies were performed prior to surgery using previously published techniques. Patients were assessed regularly for postoperative seizure control. Outcome after at least 3 years was evaluated using Engel's classification for epilepsy. The chi2 test was used to compare categorical data.

RESULTS

Seventy-eight patients were included in this study. Eight patients were excluded because of inadequate follow-up. Thirty-five patients (44.9%) had unilateral isolated hippocampal atrophy exclusively on MRI volumetry, 29 (37.2%) had unilateral hippocampal atrophy with ipsilateral fornix atrophy, and 6 (7.7%) had isolated fornix atrophy without hippocampal atrophy. Twenty-eight patients (80%) in the unilateral hippocampal atrophy group were seizure free (ie, Engel class 1: patients who are completely seizure free with no aura and who do not receive antiepileptic drugs) compared with 21 patients (73%) in the fornix and hippocampal atrophy group (P =.57). All 6 patients with isolated fornix atrophy achieved an Engel's class 1 outcome.

CONCLUSIONS

These findings suggest that identification of fornix atrophy with or without associated hippocampal atrophy is not an important preoperative determinant of surgical outcome. However, in the presence of a normal hippocampus, fornix atrophy may be valuable in predicting seizure-free outcome.

Morphology of the inner structure of the hippocampal formation in Alzheimer disease

BACKGROUND AND PURPOSE

To our knowledge, inner structural alterations of the hippocampus have never been demonstrated because of the lack of contrast between the hippocampus proper and the superficial medullary lamina. We sought to demonstrate the anatomic details of the inner hippocampus and to elucidate its alterations in Alzheimer disease (AD) in vivo.

METHODS

We obtained multishot diffusion- and T2-weighted MR images in 14 healthy control subjects and 26 patients with mild or moderate AD (diagnosis based on Mini-Mental Status Examination scores). We measured the width of the subiculum, CA1 and CA3-4, and the height of CA3-4 on coronal images.

RESULTS

The subiculum and hippocampus proper were demonstrated as whirlpool-shaped hyperintense areas, and the superficial medullary lamina was visible as a hypointense structure along the inner margin of the hippocampus proper. Regarding the width of the subiculum and CA1, intergroup analysis revealed significant differences between the control and mild or moderate AD groups. In the width of CA3-4, we found no significant difference between the control and mild AD groups; however, differences between the control and moderate AD groups and between the mild and moderate AD groups were significant. In the height of CA3-4, we observed no significant differences between groups.

CONCLUSION

We clearly visualized the inner structure of the hippocampal formation by using multishot diffusion-weighted imaging. The subiculum and CA1 are the most vulnerable regions in AD, and atrophy of these structures was evident in both mild and moderate AD.

Analysis of parahippocampal gyrus in 115 patients with hippocampal sclerosis

PURPOSE: Analysis of the parahippocampal gyrus (PHG) involvement in 115 patients with hippocampal sclerosis (HS) by MR imaging. The simultaneous occurrence of ipsilateral fornix (F) and mamillary body (MB) volume loss was checked also. These findings were correlated with the side of hippocampal involvement, the sex, patient´s age, and the symptoms onset. METHOD: The MR images of 115 patients with HS were studied retrospectively. All the examinations were performed on 1.5 T units (SIGNA, GE, Milwaukee, WI) and included high resolution coronal T2-weighted images (3 mm thickness, 0.6 mm gap). RESULTS: The patient's age ranged between 3.5 and 80 years (mean 34.1); 62 (53.9%) were female and 53 (46.1%) were male. There were HS on the left side in 53 (46.0%), on the right side in 51 (44.3%), and bilateral in 11 (9.7%). In 43 (37.3%) cases there were ipsilateral PHG volume loss and signal hyper intensity on T2-weighted imaging. In 29 (25.2%) cases there were ipsilateral fornix volume loss and in 10 (34.5%) of this there were also ipsilateral MB changes. In abnormal PHG, 23 (53.4%) were on the left side, 17 (39.5%) were on the right side, and 3 (7.1%) were bilateral. There were fornix changes in 15 (34.8%) cases and MB volume loss in 5 (11.6%) cases. Pertinent clinical data were obtained in only 18 (41.8%) of the PHG lesion cases and 11 (61.1%) of these patients had epileptic attacks for more than 20 years before the examination. CONCLUSION: PHG involvement must be investigated in patients with HS and we suggest that the term mesial temporal sclerosis should be used only if there are also changes at this anatomical site.

Dissociating atrophy and hypometabolism impact on episodic memory in mild cognitive impairment

The present study aims to unravel, in the same study, both morphological and functional specific substrates of encoding versus retrieval deficits in patients with amnestic mild cognitive impairment (MCI). For this purpose, 21 highly screened MCI patients with isolated memory impairment, who attended a memory clinic and fulfilled operational criteria for MCI, underwent (i) two episodic memory subtests designed to assess preferentially either incidental encoding or retrieval capacity; (ii) a high-resolution T1-weighted volume MRI scan; and (iii) a resting state [18F]fluoro-2-deoxy-D-glucose PET study. Using statistical parametric mapping, positive correlations between memory scores on one hand, and grey matter density and normalized partial volume effect-corrected brain glucose utilization (ncCMRglc) on the other hand, were computed. Deficits in both encoding and retrieval were correlated with declines in hippocampal region grey matter density. The encoding subtest also correlated with hippocampal ncCMRglc, whereas the retrieval subtest correlated with the posterior cingulate area ncCMRglc only. The present findings highlight a distinction in the neural substrates of encoding and retrieval deficits in MCI. Furthermore, they unravel a partial dissociation between metabolic and structural correlates, suggesting distinct interpretations. Hippocampal atrophy was related to both encoding and retrieval deficits, possibly reflecting a direct effect on hippocampal functioning, as well as an indirect effect, through remote functional disruption, on posterior cingulate region synaptic function, respectively.

Protective effect of erythropoietin in neonatal hypoxic ischemia in mice

The effect of systemic erythropoietin pretreatment on hypoxic ischemic injury was examined in neonatal mice. Injury was significantly less in cortex, hippocampus, striatum and thalamus of erythropoietin-treated animals (5 U/g vs vehicle) 24 h after hypoxic ischemia and in all of these regions except hippocampus at 7 days. Activated caspase-3- and activated NFkappaB-immunoreactive neurons were observed in the injured areas; these areas were smaller in the erythropoietin group. To our knowledge, this is the first report demonstrating persistent neuroprotective effects of erythropoietin in neonatal mice.

Hippocampal injury and neurobehavioral deficits are improved by PD 81,723 following hyperglycemic cerebral ischemia

We investigated the effects of PD 81,723, an allosteric enhancer for the adenosine A(1) receptor subtype, on hippocampal injury and Morris water maze (MWM) performance following hyperglycemic cerebral ischemia and reperfusion (4-VO, 10 min) in the rat. PD 81,723 (3 or 10 mg/kg) or the equivalent volume of saline was administered intraperitoneally 30 min prior to ischemia. Moderate hyperglycemia was achieved by administration of D-glucose (3g/kg, i.p.) 15 min prior to induction of ischemia. Morris water maze trials were performed on the 6th, 7th, and 8th days after the ischemic insult. The rat brains were sectioned (8 microm), stained with cresyl violet/acid fuchsin, and evaluated for hippocampal ischemic injury by an experimenter blinded to the treatment conditions. At the higher dose, PD 81,723 (10 mg/kg) had no effect on hippocampal injury or MWM performance following hyperglycemic ischemia compared to corresponding saline-treated animals. In contrast, a lower dose of PD 81,723 (3 mg/kg) resulted in significant (P < 0.05, n = 8) reduction of hippocampal injury following hyperglycemic ischemia. Furthermore, corresponding Morris water maze performance (latency, learning index, and cumulative distance swum) was significantly improved by PD 81,723 (P < 0.05, n = 8). The results of the present study suggest that, in the presence of PD 81,723, an A(1) allosteric enhancer, endogenously produced adenosine is sufficient to exert significant neuroprotection during hyperglycemic ischemia. Moreover, the present study provides further evidence for a neuromodulatory role of adenosine during hyperglycemic ischemia.

The brain in diabetes: molecular changes in neurons and their implications for end-organ damage

Although secondary end-organ damage in diabetes has generally been thought to result from long-term passive shunting of excess glucose through alternative metabolic pathways, recent studies have elucidated a second mechanism of pathogenesis that involves active changes in gene expression in neurons of the CNS. These changes in gene expression result in molecular and functional changes that can become maladaptive over time. In this review, we examine two neuronal populations in the brain that have been studied in human beings and animal models of diabetes. First, we discuss overactivation of magnocellular neurosecretory cells within the hypothalamus and how it relates to the development of diabetic nephropathy. And second, we describe how changes in hippocampal synaptic plasticity can lead to cognitive and behavioural deficits in chronic diabetes. Changes in neuronal gene expression in diabetes represent a new pathway for diabetic pathogenesis. This pathway may hold clues for the development of therapies that, via the targeting of neurons, can slow or prevent the development of diabetic end-organ damage.

Overexpression of the human major vault protein in gangliogliomas

PURPOSE

Recent evidence has been obtained that the major vault protein (MVP) may play a role in multidrug resistance (MDR). We investigated the expression and cellular localization of MVP in gangliogliomas (GGs), which are increasingly recognized causes of chronic pharmacoresistant epilepsy.

METHODS

Surgical tumor specimens (n = 30), as well as peritumoral and control brain tissues, were examined for the cellular distribution pattern of MVP with immunocytochemistry. Western blot analysis showed a consistent increase in MVP expression in GGs compared with that in control cortex.

RESULTS

In normal brain, MVP expression was below detection in glial and neuronal cells, and only low immunoreactivity (IR) levels were detected in blood vessels. MVP expression was observed in the neuronal component of 30 of 30 GGs and in a population of tumor glial cells. In the majority of the tumors, strong MVP IR was found in lesional vessels. Perilesional regions did not show increased staining in vessels or in neuronal and glial cells compared with normal cortex. However, expression of MVP was detected in the hippocampus in cases with dual pathology.

CONCLUSIONS

The increased expression of MVP in GGs is another example of an MDR-related protein that is upregulated in patients with refractory epilepsy. Further research is necessary to investigate whether it could play role in the mechanisms underlying drug resistance in chronic human epilepsy.

Apparent diffusion coefficient measurements in the hippocampi in patients with temporal lobe seizures

BACKGROUND AND PURPOSE

Loss of neurons results in a relative increase in extracellular space that may lead to altered apparent diffusion coefficient (ADC) values in the hippocampi of patients with seizures. Our purpose was to determine if ADC values along the long axis of hippocampi are useful in evaluating patients with partial complex seizures.

METHODS

Hippocampi of 23 patients with partial complex seizures and 25 healthy volunteers were evaluated with MR imaging and ADC maps. MR images were evaluated for loss of volume and/or high signal intensity on T2-weighted images and compared with ADC maps. ADCs were compared between patients and controls, as were ADCs along the length of each hippocampus. Mean and SDs were obtained for each measurement, and level of significance was determined (P <.05). The relationship between clinical lateralization and MR imaging and ADCs was studied.

RESULTS

No significant variations were found in the ADCs in controls (side to side and along hippocampi). In patients, abnormalities were seen with MR imaging alone in 16, with ADC in 14, and with both in 21. Of 23 hippocampi with an abnormal MR appearance, 14 had abnormal ADCs. Nine hippocampi with a normal MR appearance had abnormal ADCs. Normal MR appearance and ADCs were seen in 13 hippocampi. Most abnormal ADCs were seen in the anterior aspect of the hippocampi. All differences were statistically significant. Of 19 patients who underwent clinical testing, unequivocal lateralization was established in 10. Concordance between clinical tests and MR imaging, ADC, and MR imaging plus ADC was found in five, five, and seven patients, respectively.

CONCLUSION

Visual assessment was better than ADCs alone for detection of abnormal hippocampi. MR imaging plus ADCs was better than either technique alone. ADCs may be abnormal when MR images are unremarkable. Concordance with clinical lateralization was better when MR imaging and ADC were jointly evaluated than when either technique was evaluated separately.