Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Gyrus

  • adult dentate gyrus
  • angular gyrus
  • anterior cingulate gyrus
  • cingulate gyrus
  • dentate gyrus
  • frontal gyrus
  • fusiform gyrus
  • heschl gyrus
  • hippocampal dentate gyrus
  • inferior frontal gyrus
  • leave inferior frontal gyrus
  • lingual gyrus
  • middle frontal gyrus
  • middle temporal gyrus
  • mouse dentate gyrus
  • occipital gyrus
  • parahippocampal gyrus
  • postcentral gyrus
  • precentral gyrus
  • rat dentate gyrus
  • superior frontal gyrus
  • superior temporal gyrus
  • supramarginal gyrus
  • temporal gyrus

  • Terms modified by Gyrus

  • gyrus granule cell

  • Selected Abstracts

    Utility of the Gyrus open forceps in hepatic parenchymal transection

    HPB, Issue 3 2009
    Matthew R. Porembka
    Abstract Objective:, This study aimed to evaluate if the Gyrus open forceps is a safe and efficient tool for hepatic parenchymal transection. Background:, Blood loss during hepatic transection remains a significant risk factor for morbidity and mortality associated with liver surgery. Various electrosurgical devices have been engineered to reduce blood loss. The Gyrus open forceps is a bipolar cautery device which has recently been introduced into hepatic surgery. Methods:, We conducted a single-institution, retrospective review of all liver resections performed from November 2005 through November 2007. Patients undergoing resection of at least two liver segments where the Gyrus was the primary method of transection were included. Patient charts were reviewed; clinicopathological data were collected. Results:, Of the 215 open liver resections performed during the study period, 47 patients met the inclusion criteria. Mean patient age was 61 years; 34% were female. The majority required resection for malignant disease (94%); frequent indications included colorectal metastasis (66%), hepatocellular carcinoma (6%) and cholangiocarcinoma (4%). Right hemihepatectomy (49%), left hemihepatectomy (13%) and right trisectionectomy (13%) were the most frequently performed procedures. A total of 26 patients (55%) underwent a major ancillary procedure concurrently. There were no operative mortalities. Median operative time was 220 min (range 97,398 min). Inflow occlusion was required in nine patients (19%) for a median time of 12 min (range 3,30 min). Median total estimated blood loss was 400 ml (range 10,2000 ml) and 10 patients (21%) required perioperative transfusion. All patients had macroscopically negative margins. Median length of stay was 8 days. Two patients (4%) had clinically significant bile leak. The 30-day postoperative mortality was zero. Conclusions:, Use of the Gyrus open forceps appears to be a safe and efficient manner of hepatic parenchymal transection which allows rapid transection with acceptable blood loss, a low rate of perioperative transfusion, and minimal postoperative bile leak. [source]

    Effect of Chronic Stress and Mifepristone Treatment on Voltage-Dependent Ca2+ Currents in Rat Hippocampal Dentate Gyrus

    N. G. Van Gemert
    Chronic unpredictable stress affects many properties in rat brain. In the dentate gyrus, among other things, increased mRNA expression of the Ca2+ channel ,1C subunit has been found after 21 days of unpredictable stress in combination with acute corticosterone application (100 nM). In the present study, we examined: (i) whether these changes in expression are accompanied by altered Ca2+ currents in rat dentate granule cells recorded on day 22 and (ii) whether treatment with the glucocorticoid receptor antagonist mifepristone during the last 4 days of the stress protocol normalises the putative stress-induced effects. Three weeks of unpredictable stress did not affect Ca2+ current amplitude in dentate granule cells under basal conditions (i.e. after incubation with vehicle solution). However, the sustained Ca2+ current component (which largely depends on the ,1C subunit) was significantly increased in amplitude after chronic stress when slices had been treated with corticosterone 1,4 h before recording. These findings suggest that dentate granule cells are exposed to an increased calcium load after exposure to an acute stressor when they have a history of chronic stress, potentially leading to increased vulnerability of the cells. The present results are in line with the molecular data on Ca2+ channel ,1C subunit expression. A significant three-way interaction between chronic stress, corticosterone application and mifepristone treatment was found, indicating that the combined effect of stress and corticosterone depends on mifepristone cotreatment. Interestingly, current density (defined as total current divided by capacitance) did not differ between the groups. This indicates that the observed changes in Ca2+ current amplitude could be attributable to changes in cell size. [source]

    Corticosteroid Effects on Serotonin Responses in Granule Cells of the Rat Dentate Gyrus

    Y. J. G. Karten
    Abstract Granule cells in the rat dentate gyrus contain mineralocorticoid and glucocorticoid receptors to which the adrenal hormone corticosterone binds with differential affinity. These cells also express various receptor-subtypes for serotonin (5-HT), including the 5-HT1A receptor which mediates a membrane hyperpolarization accompanied by a decrease in membrane resistance. Earlier studies have shown that removal of corticosterone by adrenalectomy, particularly in the dentate gyrus, results in enhanced expression of the 5-HT1A receptor mRNA and increased 5-HT1A receptor binding capacity. This was normalized by activation of mineralocorticoid receptors or concurrent activation of both receptor types. In the present, intracellular recording study in vitro, we examined if the altered levels of 5-HT1A receptor mRNA and protein are associated with changes in the response to 5-HT. We found that the hyperpolarization and resistance decrease induced in granule cells by a submaximal (10 M) dose of 5-HT were unaltered 2,4 days after adrenalectomy, indicating a dissociation between corticosteroid actions on 5-HT1A receptor mRNA/protein levels and functional responses to 5-HT. Subsequent occupation of mineralocorticoid receptors in vitro significantly suppressed the 5-HT induced change in resistance, 1,4 h after steroid application. Compared to this, concurrent activation of glucocorticoid receptors led to large responses to 5-HT. This modulation by steroids was not observed with a higher dose of 5-HT (30 M). The data suggest that with moderate amounts of 5-HT, corticosteroids affect the information flow through the dentate gyrus such that excitatory transmission is promoted with predominant mineralocorticoid receptor activation and attenuated with additional glucocorticoid receptor occupation. [source]

    Effect of Corticosteroid Treatment In Vitro on Adrenalectomy-Induced Impairment of Synaptic Transmission in the Rat Dentate Gyrus

    Removal of the rat adrenals results after 3 days in the appearance of apoptotic cells in the dentate gyrus. Apoptosis is accompanied by an impaired synaptic transmission in the dentate gyrus. Substitution in vivo with a low dose of corticosterone was found to prevent both the appearance of apoptotic cells and the functional impairment. In the present study we determined whether the functional normalisation after corticosterone treatment critically depends on prevention of apoptosis. To address this question, brain slices from rats showing apoptosis after adrenalectomy were treated in vitro with the mineralocorticoid aldosterone (3 nM) or with 30 nM corticosterone, which is assumed to activate both mineralo- and glucocorticoid receptors. Steroids were briefly applied either during recording (acute effects) or several hours before recording (long-term effects). While the slope of the fEPSP recorded in the outer molecular layer of the dentate gyrus in response to perforant path stimulation was not affected up to 1 h after acute administration of the steroids, fEPSP slopes recorded 2.5,3 h after corticosterone or aldosterone treatment were significantly increased, to the level of the sham-operated controls. The results indicate that delayed corticosteroid effects through in vitro activation of mineralocorticoid receptors (MRs) are sufficient to normalise synaptic transmission in the dentate gyrus of ADX rats, even in the presence of apoptotic cells. We tentatively conclude that the impaired synaptic transmission seen after ADX is probably not primarily caused by the appearance of apoptotic cells. [source]

    Differential expression of glycans in the hippocampus of rats trained on an inhibitory learning paradigm

    NEUROPATHOLOGY, Issue 6 2006
    Alejandra Hidalgo
    The glycan chains of glycoconjugates play important roles in cell,cell and cell,matrix interactions. In the CNS, previous studies on learning and memory suggest the importance of oligosaccharides attached to glycoconjugates in the modulation of synaptic connections. We studied the hippocampal glycan distribution of rats subject to an inhibitory avoidance task. The expression of glycans was examined by lectin-histochemistry using Vicia villosa lectin (VVL) for terminal ,/, N-acetylgalactosamine (,/, GalNAc); Galanthus nivalus lectin (GNL) for terminal mannose ,-1,3 (Man ,-1,3); Peanut agglutinin (PNA) for galactose ,-1,3N-acetylgalactosamine (Gal ,-1,3 GalNAc); Erythrina cristagalli lectin (ECL) for galactose ,-1,4 N-acetylglucosamine (Gal ,-1,4 GlcNAc); Sambucus nigra lectin (SNA) for sialic acid ,-2.6 galactose (SA ,-2,6 Gal); Maackia amurensis lectin II (MAL II) for sialic acid ,-2,3 (SA ,-2,3); Wheat germ agglutinin (WGA) for terminal N-acetylglucosamine with/without sialic acid (GlcNAc wo SA); succynilated WGA (sWGA) for terminal N-acetylglucosamine without sialic acid (terminal GlcNAc without SA); Griffonia simplicifolia lectin II (GSL II) for terminal ,/, N-acetylglucosamine (,/, GlcNAc terminal); and Lotus tetragonolobus lectin (LTL) ,,fucose. Two groups of 10 animals were examined: non-trained (Control) and Trained rats. ECL, sWGA and GSL II were negative for both groups in all the hippocampal subfields studied. For both groups, VVL was negative in CA4 and granular cells of the Dentate Gyrus (DG) and LTL was negative in the CA4 subfield. Expression of ,/, GalNAc, , -fucose and GlcNAc in other hippocampal subfields was positive, with no differences between groups. However, expression of Man ,-1,3 was significantly higher in the CA1, CA2, CA3, and CA4 subfields in the Trained group. On the other hand, expression of Gal ,-1,3 GalNAc was significantly low in CA4 and DG in the Trained group. In conclusion, the results here presented indicate that the exposure of rats to an associative behavioral paradigm related to declarative memory, involves some regulatory mechanism/s for the differential patterns of glycan expression. [source]

    Ethanol neurotoxicity and dentate gyrus development

    Takanori Miki
    ABSTRACT Maternal alcohol ingestion during pregnancy adversely affects the developing fetus, often leading to fetal alcohol syndrome (FAS). One of the most severe consequences of FAS is brain damage that is manifested as cognitive, learning, and behavioral deficits. The hippocampus plays a crucial role in such abilities; it is also known as one of the brain regions most vulnerable to ethanol-induced neurotoxicity. Our recent studies using morphometric techniques have further shown that ethanol neurotoxicity appears to affect the development of the dentate gyrus in a region-specific manner; it was found that early postnatal ethanol exposure causes a transitory deficit in the hilus volume of the dentate gyrus. It is strongly speculated that such structural modifications, even transitory ones, appear to result in developmental abnormalities in the brain circuitry and lead to the learning disabilities observed in FAS children. Based on reports on possible factors deciding ethanol neurotoxicity to the brain, we review developmental neurotoxicity to the dentate gyrus of the hippocampal formation. [source]

    Neuroanatomical substrates of social cognition dysfunction in autism

    Kevin Pelphrey
    Abstract In this review article, we summarize recent progress toward understanding the neural structures and circuitry underlying dysfunctional social cognition in autism. We review selected studies from the growing literature that has used the functional neuroimaging techniques of cognitive neuroscience to map out the neuroanatomical substrates of social cognition in autism. We also draw upon functional neuroimaging studies with neurologically normal individuals and individuals with brain lesions to highlight the insights these studies offer that may help elucidate the search for the neural basis of social cognition deficits in autism. We organize this review around key brain structures that have been implicated in the social cognition deficits in autism: (1) the amygdala, (2) the superior temporal sulcus region, and (3) the fusiform gyrus. We review some of what is known about the contribution of each structure to social cognition and then review autism studies that implicate that particular structure. We conclude with a discussion of several potential future directions in the cognitive neuroscience of social deficits in autism. 2004 Wiley-Liss, Inc. MRDD Research Reviews 2004;10:259,271. [source]

    The neuroanatomy and neuroendocrinology of fragile X syndrome

    David Hessl
    Abstract Fragile X syndrome (FXS), caused by a single gene mutation on the X chromosome, offers a unique opportunity for investigation of gene,brain,behavior relationships. Recent advances in molecular genetics, human brain imaging, and behavioral studies have started to unravel the complex pathways leading to the cognitive, psychiatric, and physical features that are unique to this syndrome. In this article, we summarize studies focused on the neuroanatomy and neuroendocrinology of FXS. A review of structural imaging studies of individuals with the full mutation shows that several brain regions are enlarged, including the hippocampus, amygdala, caudate nucleus, and thalamus, even after controlling for overall brain volume. These regions mediate several cognitive and behavioral functions known to be aberrant in FXS such as memory and learning, information and sensory processing, and social and emotional behavior. Two regions, the cerebellar vermis, important for a variety of cognitive tasks and regulation of motor behavior, and the superior temporal gyrus, involved in processing complex auditory stimuli, are reported to be reduced in size relative to controls. Functional imaging, typically limited to females, has emphasized that individuals with FXS do not adequately recruit brain regions that are normally utilized by unaffected individuals to carry out various cognitive tasks, such as arithmetic processing or visual memory tasks. Finally, we review a number of neuroendocrine studies implicating hypothalamic dysfunction in FXS, including abnormal activation of the hypothalamic,pituitary,adrenal (HPA) axis. These studies may help to explain the abnormal stress responses, sleep abnormalities, and physical growth patterns commonly seen in affected individuals. In the future, innovative longitudinal studies to investigate development of neurobiologic and behavioral features over time, and ultimately empirical testing of pharmacological, behavioral, and even molecular genetic interventions using MRI are likely to yield significant positive changes in the lives of persons with FXS, as well as increase our understanding of the development of psychiatric and learning problems in the general population. MRDD Research Reviews 2004;10:17,24. 2004 Wiley-Liss, Inc. [source]

    Effect of canonical Wnt inhibition in the neurogenic cortex, hippocampus, and premigratory dentate gyrus progenitor pool

    Nina Solberg
    Abstract Canonical Wnt signaling is crucial for the correct development of both cortical and hippocampal structures in the dorsal telencephalon. In this study, we examined the role of the canonical Wnt signaling in the dorsal telencephalon of mouse embryos at defined time periods by inhibition of the pathway with ectopic expression of Dkk1. Transgenic mice with the D6-driven Dkk1 gene exhibited reduced canonical Wnt signaling in the cortex and hippocampus. As a result, all hippocampal fields were reduced in size. Neurogenesis in the dentate gyrus was severely reduced both in the premigratory and migratory progenitor pool. The lower number of progenitors in the dentate gyrus was not rescued after migration to the subgranular zone and thus the dentate gyrus lacked the entire internal blade and a part of the external blade from postnatal to adult stages. Developmental Dynamics 237:1799,1811, 2008. 2008 Wiley-Liss, Inc. [source]

    Testosterone and dihydrotestosterone, but not estradiol, enhance survival of new hippocampal neurons in adult male rats

    Mark D. Spritzer
    Abstract Past research suggested that androgens may play a role in the regulation of adult neurogenesis within the dentate gyrus. We tested this hypothesis by manipulating androgen levels in male rats. Castrated or sham castrated male rats were injected with 5-Bromo-2,deoxyuridine (BrdU). BrdU-labeled cells in the dentate gryus were visualized and phenotyped (neural or glial) using immunohistochemistry. Castrated males showed a significant decrease in 30-day cell survival within the dentate gyrus but there was no significant change in cell proliferation relative to control males, indicating that androgens positively affect cell survival, but not cell proliferation. To examine the role of testosterone on hippocampal cell survival, males were injected with testosterone s.c. for 30 days starting the day after BrdU injection. Higher doses (0.5 and 1.0 mg/kg) but not a lower dose (0.25 mg/kg) of testosterone resulted in a significant increase in neurogenesis relative to controls. We next tested the role of testosterone's two major metabolites, dihydrotestosterone (DHT), and estradiol, upon neurogenesis. Thirty days of injections of DHT (0.25 and 0.50 mg/kg) but not estradiol (0.010 and 0.020 mg/kg) resulted in a significant increase in hippocampal neurogenesis. These results suggest that testosterone enhances hippocampal neurogenesis via increased cell survival in the dentate gyrus through an androgen-dependent mechanism. 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007. [source]

    Electrophysiological and morphological characterization of dentate astrocytes in the hippocampus

    Masako Isokawa
    Abstract We studied electrophysiological and morphological properties of astrocytes in the dentate gyrus of the rat hippocampus in slices. Intracellular application of Lucifer yellow revealed two types of morphology: one with a long process extruding from the cell body, and the other with numerous short processes surrounding the cell body. Their electrophysiological properties were either passive, that is, no detectable voltage-dependent conductance, or complex, with Na+/K+ currents similar to those reported in the Ammon's horn astrocytes. We did not find any morphological correlate to the types of electrophysiological profile or dye coupling. Chelation of cytoplasmic calcium ([Ca2+]i) by BAPTA increased the incidence of detecting a low Na+ conductance and transient outward K+ currents. However, an inwardly rectifying K+ current (Kir), a hallmark of differentiated CA1/3 astrocytes, was not a representative K+ -current in the complex dentate astrocytes, suggesting that these astrocytes could retain an immature form of K-currents. Dentate astrocytes may possess a distinct current profile that is different from those in CA1/3 Ammon's horn. 2005 Wiley Periodicals, Inc. J Neurobiol, 2005 [source]

    The effects of social environment on adult neurogenesis in the female prairie vole

    Christie D. Fowler
    Abstract In the mammalian brain, adult neurogenesis has been found to occur primarily in the subventricular zone (SVZ) and dentate gyrus of the hippocampus (DG) and to be influenced by both exogenous and endogenous factors. In the present study, we examined the effects of male exposure or social isolation on neurogenesis in adult female prairie voles (Microtus ochrogaster). Newly proliferated cells labeled by a cell proliferation marker, 5-bromo-2,-deoxyuridine (BrdU), were found in the SVZ and DG, as well as in other brain areas, such as the amygdala, hypothalamus, neocortex, and caudate/putamen. Two days of male exposure significantly increased the number of BrdU-labeled cells in the amygdala and hypothalamus in comparison to social isolation. Three weeks later, group differences in BrdU labeling generally persisted in the amygdala, whereas in the hypothalamus, the male-exposed animals had more BrdU-labeled cells than did the female-exposed animals. In the SVZ, 2 days of social isolation increased the number of BrdU-labeled cells compared to female exposure, but this difference was no longer present 3 weeks later. We have also found that the vast majority of the BrdU-labeled cells contained a neuronal marker, indicating neuronal phenotypes. Finally, group differences in the number of cells undergoing apoptosis were subtle and did not seem to account for the observed differences in BrdU labeling. Together, our data indicate that social environment affects neuron proliferation in a stimulus- and site-specific manner in adult female prairie voles. 2002 Wiley Periodicals, Inc. J Neurobiol 51: 115,128, 2002 [source]

    Social interest and the development of cortical face specialization: What autism teaches us about face processing

    David J. Grelotti
    Abstract Investigations of face processing in persons with an autism spectrum disorder (ASD) inform upon theories of the development of "normal" face processing, and the story that emerges challenges some models of the nature and origin of cortical face specialization. Individuals with an ASD possess deficits in face processing and a lack of a fusiform face area (FFA). Evidence from studies of ASD can be conceptualized best using an expertise framework of face processing rather than models that postulate a face module in the fusiform gyrus. Because persons with an ASD have reduced social interest, they may fail to develop cortical face specialization. Face specialization may develop in normal individuals because they are socially motivated to regard the face, and such motivation promotes expertise for faces. The amygdala is likely the key node in the system that marks objects as emotionally salient and could be crucial to the development of cortical face specialization. 2002 Wiley Periodicals, Inc. Dev Psychobiol 40: 213,225, 2002. DOI 10.1002/dev.10028 [source]

    Perceived quality of maternal care in childhood and structure and function of mothers' brain

    Pilyoung Kim
    Animal studies indicate that early maternal care has long-term effects on brain areas related to social attachment and parenting, whereas neglectful mothering is linked with heightened stress reactivity in the hippocampus across the lifespan. The present study explores the possibility, using magnetic resonance imaging, that perceived quality of maternal care in childhood is associated with brain structure and functional responses to salient infant stimuli among human mothers in the first postpartum month. Mothers who reported higher maternal care in childhood showed larger grey matter volumes in the superior and middle frontal gyri, orbital gyrus, superior temporal gyrus and fusiform gyrus. In response to infant cries, these mothers exhibited higher activations in the middle frontal gyrus, superior temporal gyrus and fusiform gyrus, whereas mothers reporting lower maternal care showed increased hippocampal activations. These findings suggest that maternal care in childhood may be associated with anatomy and functions in brain regions implicated in appropriate responsivity to infant stimuli in human mothers. [source]

    Distinct caspase pathways mediate necrosis and apoptosis in subpopulations of hippocampal neurons after status epilepticus

    EPILEPSIA, Issue 2010
    Maria-Leonor Lopez-Meraz
    Summary Status epilepticus in the immature brain induces neuronal injury in the hippocampal formation, but the mode and mechanism of death are poorly understood. Our laboratory has recently investigated the role of caspase-3, -8, and -9 in neuronal injury, using a lithium,pilocarpine model of status epilepticus in 2-week-old rat pups. Our results showed that dying neurons in the dentate gyrus and CA1-subiculum area do not share the same mechanism of death. In CA1-subiculum, caspase-8 upregulation preceded caspase-3 activation in morphologically necrotic neurons. The pan-caspase inhibitor Q-VD-OPH reduced CA1 damage, showing that caspases contribute to status epilepticus,induced necrosis. In the dentate gyrus, dying neurons were caspase-9 and -3 immunoreactive and morphologically apoptotic. It is not clear why the same seizures cause different types of cell death in neurons that are connected in series along the same hippocampal circuit, but the apoptotic dentate neurons express doublecortin, and do not express calbindin-D28k, suggesting that their immaturity may be a factor in producing an apoptotic mode of death. [source]

    Palilalia, echolalia, and echopraxia,palipraxia as ictal manifestations in a patient with left frontal lobe epilepsy

    EPILEPSIA, Issue 6 2009
    Yang-Je Cho
    Summary Palilalia is a relatively rare pathologic speech behavior and has been reported in various neurologic and psychiatric disorders. We encountered a case of palilalia, echolalia, and echopraxia,palipraxia as ictal phenomena of left frontal lobe epilepsy. A 55-year-old, right-handed man was admitted because of frequent episodes of rapid reiteration of syllables. Video-electroencephalography monitoring revealed stereotypical episodes of palilalia accompanied by rhythmic head nodding and right-arm posturing with ictal discharges over the left frontocentral area. He also displayed echolalia or echopraxia,palipraxia, partially responding to an examiner's stimulus. Magnetic resonance imaging revealed encephalomalacia on the left superior frontal gyrus and ictal single photon emission computed tomography showed hyperperfusion just above the lesion, corresponding to the left supplementary motor area (SMA), and subcortical nuclei. This result suggests that the neuroanatomic substrate involved in the generation of these behaviors as ictal phenomena might exist in the SMA of the left frontal lobe. [source]

    Stress, the hippocampus, and epilepsy

    EPILEPSIA, Issue 4 2009
    Marian Jols
    Summary Stress is among the most frequently self-reported precipitants of seizures in patients with epilepsy. This review considers how important stress mediators like corticotropin-releasing hormone, corticosteroids, and neurosteroids could contribute to this phenomenon. Cellular effects of stress mediators in the rodent hippocampus are highlighted. Overall, corticosterone,with other stress hormones,rapidly enhances CA1/CA3 hippocampal activity shortly after stress. At the same time, corticosterone starts gene-mediated events, which enhance calcium influx several hours later. This later effect serves to normalize activity but also imposes a risk for neuronal injury if and when neurons are concurrently strongly depolarized, for example, during epileptic activity. In the dentate gyrus, stress-induced elevations in corticosteroid level are less effective in changing membrane properties such as calcium influx; here, enhanced inhibitory tone mediated through neurosteroid effects on ,-aminobutyric acid (GABA) receptors might dominate. Under conditions of repetitive stress (e.g., caused from experiencing repetitive and unpredictable seizures) and/or early life stress, hormonal influences on the inhibitory tone, however, are diminished; instead, enhanced calcium influx and increased excitation become more important. In agreement, perinatal stress and elevated steroid levels accelerate epileptogenesis and lower seizure threshold in various animal models for epilepsy. It will be interesting to examine how curtailing the effects of stress in adults, for example, by brief treatment with antiglucocorticoids, may be beneficial to the treatment of epilepsy. [source]

    Retarded kindling progression in mice deficient in the extracellular matrix glycoprotein tenascin-R

    EPILEPSIA, Issue 4 2009
    Katrin Hoffmann
    Summary Purpose:, We investigated the role of the extracellular matrix glycoprotein tenascin-R (TNR) in formation of a hyperexcitable network in the kindling model of epilepsy. The idea that TNR may be important for this process was suggested by previous studies showing that deficiency in TNR leads to abnormalities in synaptic plasticity, perisomatic GABAergic inhibition and more astrocytes in the hippocampus of adult mice. Methods:, Constitutively TNR deficient (TNR,/,) mice and their wild-type littermates received repeated electrical stimulation in the amygdala over several days until they developed fully kindled generalized seizures at which time their brains were studied immunohistochemically. Results:, In TNR,/, mice, kindling progression was retarded compared with wild-type littermate controls. Morphological analysis of the mice used for the kindling studies revealed that, independently of genotype, numbers of parvalbumin-positive interneurons in the dentate gyrus correlated positively with afterdischarge threshold alterations in kindled mice. The kindling-induced increase in the number of S100 expressing astrocytes in the dentate gyrus was enhanced by TNR deficiency and correlated negatively with the kindling rate. Discussion:, Our data support the view that TNR promotes formation of a hyperexcitable network during kindling and suggest that an increase in S100-expressing astrocytes may contribute to retarded epileptogenesis in TNR,/, mice. [source]

    Language lateralization in temporal lobe epilepsy using functional MRI and probabilistic tractography

    EPILEPSIA, Issue 8 2008
    Sebastian Rodrigo
    Summary Purpose: Language functional magnetic resonance imaging (fMRI) is used to noninvasively assess hemispheric language specialization as part of the presurgical work-up in temporal lobe epilepsy (TLE). White matter asymmetries on diffusion tensor imaging (DTI) may be related to language specialization as shown in controls and TLE. To refine our understanding of the effect of epilepsy on the structure,function relationships, we focused on the arcuate fasciculus (ArcF) and the inferior occipitofrontal fasciculus (IOF) and tested the relationship between DTI- and fMRI-based lateralization indices in TLE. Methods: fMRI with three language tasks and DTI were obtained in 20 patients (12 right and 8 left TLE). The ArcF, a major language-related tract, and the IOF were segmented bilaterally using probabilistic tractography to obtain fractional anisotropy (FA) lateralization indices. These were correlated with fMRI-based lateralization indices computed in the inferior frontal gyrus (Pearson's correlation coefficient). Results: fMRI indices were left-lateralized in 16 patients and bilateral or right-lateralized in four. In the ArcF, FA was higher on the left than on the right side, reaching significance in right but not in left TLE. We found a positive correlation between ArcF anisotropy and fMRI-based lateralization indices in right TLE (p < 0.009), but not in left TLE patients. No correlation was observed for the IOF. Conclusions: Right TLE patients with more left-lateralized functional activations also showed a leftward-lateralized arcuate fasciculus. The decoupling between the functional and structural indices of the ArcF underlines the complexity of the language network in left TLE patients. [source]

    Event-related fMRI of Myoclonic Jerks Arising from Dysplastic Cortex

    EPILEPSIA, Issue 9 2006
    John S. Archer
    Summary:,Background: Malformations of cortical development can cause epileptiform activity and myoclonic jerks, yet EEG correlates of jerks can be difficult to obtain. Methods: We studied a woman who had frequent episodes of persistent right-foot jerking since childhood. Ictal and interictal EEG had shown no localizing epileptiform activity. Functional imaging experiments were performed with concurrent video monitoring to document the timing of foot jerks. These studies mapped brain regions controlling voluntary right- and left-foot movements, and spontaneous right-foot jerks. Results: High-resolution structural MR imaging revealed a dysplastic gyrus extending anteriorly off the left central sulcus. Event-related analysis of spontaneous jerks revealed prominent activation of the left precentral gyrus (right-foot motor area), bilateral medial frontal regions (supplementary motor area), and the dysplastic gyrus. Hemodynamic response modeling to foot jerks revealed the hemodynamic response peaked earlier in the dysplastic cortex and SMA regions than in the foot area. Discussion: Event-related fMRI in a patient with spontaneous and induced epileptic foot jerks revealed brain regions active during jerks. The results of this analysis allowed us to tailor subsequent intracerebral recordings. Analysis of the timing of the hemodynamic response showed certain brain regions with an earlier rise in BOLD signal, suggesting a possible initiating role, or different hemodynamic response functions. Hemodynamic response timing should be considered carefully when interpreting event-related studies of epileptiform activity. [source]

    fMRI Lateralization of Expressive Language in Children with Cerebral Lesions

    EPILEPSIA, Issue 6 2006
    Dianne P. Anderson
    Summary:,Purpose: Lateralization of language function is crucial to the planning of surgery in children with frontal or temporal lobe lesions. We examined the utility of functional magnetic resonance imaging (fMRI) as a determinant of lateralization of expressive language in children with cerebral lesions. Methods: fMRI language lateralization was attempted in 35 children (29 with epilepsy) aged 8,18 years with frontal or temporal lobe lesions (28 left hemisphere, five right hemisphere, two bilateral). Axial and coronal fMRI scans through the frontal and temporal lobes were acquired at 1.5 Tesla by using a block-design, covert word-generation paradigm. Activation maps were lateralized by blinded visual inspection and quantitative asymmetry indices (hemispheric and inferior frontal regions of interest, at p < 0.001 uncorrected and p < 0.05 Bonferroni corrected). Results: Thirty children showed significant activation in the inferior frontal gyrus. Lateralization by visual inspection was left in 21, right in six, and bilateral in three, and concordant with hemispheric and inferior frontal quantitative lateralization in 93% of cases. Developmental tumors and dysplasias involving the inferior left frontal lobe had activation overlying or abutting the lesion in five of six cases. fMRI language lateralization was corroborated in six children by frontal cortex stimulation or intracarotid amytal testing and indirectly supported by aphasiology in a further six cases. In two children, fMRI language lateralization was bilateral, and corroborative methods of language lateralization were left. Neither lesion lateralization, patient handedness, nor developmental versus acquired nature of the lesion was associated with language lateralization. Involvement of the left inferior or middle frontal gyri increased the likelihood of atypical language lateralization. Conclusions: fMRI lateralizes language in children with cerebral lesions, although caution is needed in interpretation of individual results. [source]

    Proteomic Identification of the Involvement of the Mitochondrial Rieske Protein in Epilepsy

    EPILEPSIA, Issue 3 2005
    Heike Junker
    Summary:,Purpose: Kindled seizures are widely used to model epileptogenesis, but the molecular mechanisms underlying the attainment of kindling status are largely unknown. Recently we showed that achievement of kindling status in the Sprague,Dawley rat is associated with a critical developmental interval of 25 1 days; the identification of this long, well-defined developmental interval for inducing kindling status makes possible a dissection of the cellular and genetic events underlying this phenomenon and its relation to normal and pathologic brain function. Methods: By using proteomics on cerebral tissue from our new rat kindling model, we undertook a global analysis of protein expression in kindled animals. Some of the identified proteins were further investigated by using immunohistochemistry. Results: We report the identification of a modified variant of the Rieske iron-sulfur protein, a component of the mitochondrial cytochrome bc1 complex, whose isoelectric point is shifted toward more alkaline values in the hippocampus of kindled rats. By immunohistochemistry, the Rieske protein is well expressed in the hippocampus, except in the CA1 subfield, an area of selective vulnerability to seizures in humans and animal models. We also noted an asymmetric, selective expression of the Rieske protein in the subgranular neurons of the dorsal dentate gyrus, a region implicated in neurogenesis. Conclusions: These results indicate that the Rieske protein may play a role in the response of neurons to seizure activity and could give important new insights into the molecular pathogenesis of epilepsy. [source]

    High-frequency Oscillations after Status Epilepticus: Epileptogenesis and Seizure Genesis

    EPILEPSIA, Issue 9 2004
    Anatol Bragin
    Summary:,Purpose: To investigate the temporal relation between high-frequency oscillations (HFOs) in the dentate gyrus and recurrent spontaneous seizures after intrahippocampal kainite-induced status epilepticus. Methods: Recording microelectrodes were implanted bilaterally in different regions of hippocampus and entorhinal cortex. A guide cannula for microinjection of kainic acid (KA) was implanted above the right posterior CA3 area of hippocampus. After recording baseline electrical activity, KA (0.4 ,g/0.2 ,l) was injected. Beginning on the next day, electrographic activity was recorded with video monitoring for seizures every day for 8 h/day for ,30 days. Results: Of the 26 rats studied, 19 revealed the appearance of sharp-wave activity and HFOs in the frequency range of 80 to 500 Hz in the dentate gyrus ipsilateral to the KA injection. In the remaining seven rats, no appreciable activity was noted in this frequency range. In some rats with recurrent seizures, HFOs were in the ripple frequency range (100,200 Hz); in others, HFOs were in the fast ripple frequency range (200,500 Hz), or a mixture of both oscillation frequencies was found. The time of detection of the first HFOs after status epilepticus varied between 1 and 30 days, with a mean of 6.3 2.0 (SEM). Of the 19 rats in which HFO activity appeared, all later developed recurrent spontaneous seizures, whereas none of the rats without HFOs developed seizures. The sooner HFO activity was detected after status epilepticus, the sooner the first spontaneous seizure occurred. A significant inverse relation was found between the time to the first HFO detection and the subsequent rate of spontaneous seizures. Conclusions: A strong correlation was found between a decreased time to detection of HFOs and an increased rate of spontaneous seizures, as well as with a decrease in the duration of the latent period between KA injection and the detection of spontaneous seizures. Two types of HFOs were found after KA injection, one in the frequency range of 100 to 200 Hz, and the other, in the frequency range of 200 to 500 Hz, and both should be considered pathological, suggesting that both are epileptogenic. [source]

    Brain Blood-flow Alterations Induced by Therapeutic Vagus Nerve Stimulation in Partial Epilepsy: II.

    EPILEPSIA, Issue 9 2004
    Low Levels of Stimulation, Prolonged Effects at High
    Summary:,Purpose: To measure vagus nerve stimulation (VNS)-induced cerebral blood flow (CBF) effects after prolonged VNS and to compare these effects with immediate VNS effects on CBF. Methods: Ten consenting partial epilepsy patients had positron emission tomography (PET) with intravenous [15O]H2O. Each had three control scans without VNS and three scans during 30 s of VNS, within 20 h after VNS began (immediate-effect study), and repeated after 3 months of VNS (prolonged study). After intrasubject subtraction of control from stimulation scans, images were anatomically transformed for intersubject averaging and superimposed on magnetic resonance imaging (MRI) for anatomic localization. Changes on t-statistical maps were considered significant at p < 0.05 (corrected for multiple comparisons). Results: During prolonged studies, CBF changes were not observed in any regions that did not have CBF changes during immediate-effect studies. During both types of studies, VNS-induced CBF increases were similarly located in the bilateral thalami, hypothalami, inferior cerebellar hemispheres, and right postcentral gyrus. During immediate-effect studies, VNS decreased bilateral hippocampal, amygdalar, and cingulate CBF and increased bilateral insular CBF; no significant CBF changes were observed in these regions during prolonged studies. Mean seizure frequency decreased by 25% over a 3-month period between immediate and prolonged PET studies, compared with 3 months before VNS began. Conclusions: Seizure control improved during a period over which some immediate VNS-induced CBF changes declined (mainly over cortical regions), whereas other VNS-induced CBF changes persisted (mainly over subcortical regions). Altered synaptic activities at sites of persisting VNS-induced CBF changes may reflect antiseizure actions. [source]

    Correlation of Hippocampal Glucose Oxidation Capacity and Interictal FDG-PET in Temporal Lobe Epilepsy

    EPILEPSIA, Issue 2 2003
    Stefan Vielhaber
    Summary: ,Purpose: Interictal [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) demonstrates temporal hypometabolism in the epileptogenic zone of 60,90% of patients with temporal lobe epilepsy. The pathophysiology of this finding is still unknown. Several studies failed to show a correlation between hippocampal FDG-PET hypometabolism and neuronal cell loss. Because FDG is metabolized by hexokinase bound to the outer mitochondrial membrane, we correlated the glucose-oxidation capacity of hippocampal subfields obtained after surgical resection with the corresponding hippocampal presurgical FDG-PET activity. Methods: In 16 patients with electrophysiologically confirmed temporal lobe epilepsy, we used high-resolution respirometry to determine the basal and maximal glucose-oxidation rates in 400-,m-thick hippocampal subfields obtained after dissection of human hippocampal slices into the CA1 and CA3 pyramidal subfields and the dentate gyrus. Results: We observed a correlation of the FDG-PET activity with the maximal glucose-oxidation rate of the CA3 pyramidal subfields (rp = 0.7, p = 0.003) but not for the regions CA1 and dentate gyrus. In accordance with previous studies, no correlation of the FDG-PET to the neuronal cell density of CA1, CA3, and dentate gyrus was found. Conclusions: The interictal hippocampal FDG-PET hypometabolism in patients with temporal lobe epilepsy is correlated to the glucose-oxidation capacity of the CA3 hippocampal subfield as result of impaired oxidative metabolism. [source]

    MRI Volumetric Analysis in Rasmussen Encephalitis: A Longitudinal Study

    EPILEPSIA, Issue 2 2003
    Masanori Takeoka
    Summary: ,Purpose: Rasmussen encephalitis is a progressive inflammatory process with difficult-to-control focal or lateralized seizure activity, leading to hemispheric dysfunction and atrophy in advanced stages. Anatomic changes of atrophy may be subtle in earlier phases of the disease, and progressive changes on serial scans may be difficult to detect. We report a case of early-stage Rasmussen encephalitis with a relatively stable clinical course in whom we performed magnetic resonance imaging (MRI)-based volumetric analysis over an interval of 1 year, to assess for volumetric changes. Methods: Volumetric analysis was performed on two successive MRI scans obtained at age 5 and 6 years, by using the CARDVIEWS program (J Cogn Neurosci, 1996). The images were segmented into gray- and white-matter structures according to signal intensity of their borders semiautomatically, with manual corrections. The cerebral cortex was further subdivided into smaller parcellation units according to anatomic landmarks identifiable on MRI. Results: Stable left cerebral hemispheric atrophy and progressive atrophy in the left precentral gyrus, left inferior frontal gyrus, and left cerebellar atrophy were detected over the 1-year interval. Conclusions: Volumetric analysis enables early detection and quantification of anatomic changes, identification of focal involvement, and assists in determining the severity of disease and timing for surgical interventions such as hemispherectomy. [source]

    Enhanced Calcium Influx in Hippocampal CA3 Neurons of Spontaneously Epileptic Rats

    EPILEPSIA, Issue 3 2001
    Hiroko Amano
    Summary: ,Purpose: The spontaneously epileptic rat (SER: tm/tm, zi/zi) shows both absence-like seizures and tonic convulsions. Our previous electrophysiologic studies have demonstrated that SER has abnormal excitability of hippocampal CA3 neurons, which shows a long-lasting depolarization shift by a single stimulation of mossy fibers, probably resulting from the Ca2+ channel abnormalities. The present study was performed to determine whether Ca2+ influx is actually enhanced in the CA3 area of SER. Methods: Hippocampal slices were prepared from normal Wistar rats and SER aged 11,16 weeks old, when the epileptic seizures had been observed, and loaded with fura-2AM. Intracellular Ca2+ concentration ([Ca2+]i) was monitored as the ratio of fluorescence intensities excited at wavelengths of 340 and 380 nm (RF340/F380) with photometric devices. Results: High K+ (10,60 mM) applied to the bath for 2 min increased [Ca2+]i in hippocampal CA1, CA3, and dentate gyrus (DG) areas of both the normal rats and SER in a concentration-dependent manner. However, the high K+,induced increase in [Ca2+]i was significantly more pronounced in the CA3 area of the SER than in that of the normal animals, whereas there were no significant differences in high K+,induced increases of [Ca2+]i in CA1 or DG between the SER and controls. The high K+,induced increases in [Ca2+]i of CA1, CA3, and DG were inhibited by nifedipine (1,10 nM), a Ca2+ channel antagonist in both SER and controls. However, the inhibition of the high K+,induced increase in [Ca2+]i by nifedipine (1 nM) was significantly greater in the CA3 area of SER than that of controls. Conclusions: These findings suggest that Ca2+ influx through the L-type Ca2+ channels is much greater in the CA3 area of SER than in that of normal animals and is involved in the epileptic seizures of the SER. [source]

    Abnormal Excitability of Hippocampal CA3 Neurons in Noda Epileptic Rat (NER): Alteration of Seizure with Aging

    EPILEPSIA, Issue 2000
    Ryosuke Hanaya
    Purpose: Noda epileptic rat (NER), a mutant found in thc colony of Crj:Wistar rats, spontaneously shows tonic-clonic convulsions approximately once every 30 hours from 8,16 weeks of age. A long-lasting dcpolarization shift accompanied by repetitivc firings are observed in hippocampal CA3 pyramidal neurons of NER with seizures. Using hippocampal slice preparations of NER, the present electrophysiologi- cal study was performed to elucidate whether this abnormal firing in CA3 neurons developed with age and if abnormality of Ca2+ channel was involved. Methods: Hippocampal slices (40Opm) werc prepared from NER and normal Wistar rats (age; 4,29 weeks). A single rectangular pulse stimulus composed of 0.1-ms duration was delivered to the mossy fibers every 5 seconds though a bipolar electrode placed in the granular cell layer of the dentate gyrus. Intracellular recording was made from the CA3 pyramidal cell using a microelectrode containing 3M KCI intracellular recordings. A Ca2+ spike was elicited by applying a depolarizing pulse (InA, 120ms) in the cell through the recording electrode under a blockadc of Na+ and K+ channels using 1 pM tetrodotoxin and I 0mM tctraethylammonium added to the artificial CSF, respectivcly. Nicardipine (I-IOOnM), a Ca2+ channel blocker, was applicd to the bath. Results: Thirty-seven slices from I9 NER and 6 slices from 4 normal Wishe rats were used. There were no obvious changes in the resting membrane potentials of CA3 neurons between NER and Wistar rats tested. When a single stimulus was delivered to the mossy fibers, a long-lasting depolarization shift accompanied by repetitive firings followed by after-hyperpolarization werc also obtained i n hippocampal CA3 neurons of young NER (4,5 weeks of age) before occurrence of any seizurcs, although the depolarization shift in younger NER was shorter than that in NER aged more than 6 weeks. These abnormal firings werc evokcd in 58% and 30% of all CA3 neurons tested in the younger and mature NER (6,1 5 weeks of age), respectively. Furthermore, abnormal firing was not elicited in NER aged after I6 weeks. Agc-matched Wistar rats showed only single action potentials without any depolarization shift with single mossy fiber stimulation. Bath application of nicardipine (IOnM) inhibited this long-lasting depolarization shift and the accompanying repetitive firing followed by afterhypcrpolarization without affecting the first spike induced by mossy fiber stimulations. Furthermore, nicai-dipine (IOnM) inhibited the Ca2+ spikes elicited by applying a depolarizing pulse in the neurons of NER with seizures, although a higher dose (100nM) did not affect those in Wistar rats. Conclusions: These findings indicate that abnormal excitability of the NER CA3 pyramidal neurons is probably due to abnormality in the Ca2+ channcls. The abnorinal excitability was observed in NER at an age when tonic-clonic convulsions were not detected, suggesting that thc hippocampus may probably scrve as an epileptogenic focus in younger NER and the seizure impulses originating i n this area are transinittcd to the new other seizurc foci in mature NER. [source]

    Cyclosporine Induces Epileptiform Activity in an In Vitro Seizure Model

    EPILEPSIA, Issue 3 2000
    Michael Wong
    Summary: Purpose: Cyclosporine (CSA) toxicity represents a common cause of seizures in transplant patients, but the specific mechanisms by which CSA induces seizures are unknown. Although CSA may promote seizure activity by various metabolic, toxic, vascular, or structural mechanisms, CSA also has been hypothesized to modulate neuronal excitability directly. The objective of this study was to determine if CSA exerts direct epileptogenic actions on neurons in an in vitro seizure model. Methods: Combined hippocampal-entorhinal cortex slices from juvenile rats were exposed directly to artificial cerebro-spinal fluid (ACSF) containing either (a) 1.0 mM magnesium sulfate (control), (b) 1.0 mM sodium sulfate (low-magnesium), or (c) 1.0 mM magnesium sulfate + CSA (1,000,10,000 ng/ml). Spontaneous and evoked extracellular field potentials were recorded simultaneously from the dentate gyrus (DG) and CA3 hippocampal regions. Evoked synaptic responses were elicited by stimulation of the entorhinal cortex/perforant pathway. Results: CSA elicited spontaneous or stimulation-induced epileptiform activity in the DG or CA3 region of ,40% of slices, consisting of brief repetitive "interictal" discharges or prolonged stereotypical "ictal" discharges. Mean latency to epileptiform activity was ,100 min after onset of CSA application. The interictal discharges were inhibited by the non-NMDA antagonist, NBQX. Similar epileptiform activity was observed in low-magnesium ACSF without CSA. In control ACSF alone, epileptiform activity was not seen, except for rare spontaneous potentials in the DG. Conclusions: Direct effects of CSA on neuronal excitability and synaptic transmission may contribute to seizures seen in clinical CSA neurotoxicity. [source]

    Cerebral blood flow in patients with diffuse axonal injury , examination of the easy Z -score imaging system utility

    T. Okamoto
    To evaluate the utility of easy Z -score imaging system (eZIS) in 27 diffuse axonal injury (DAI) cases. Twenty-seven DAI patients were examined with an magnetic resonance imaging (MRI) T2* sequence and with eZIS (seven women, 20 men; age range, 19,35 years; median age: 26.6 years). In this investigation, we excluded patients who exhibited complications such as acute subdural hematoma, acute epidural hematoma, intracerebral hematoma, or brain contusion. We examined the neuropsychological tests and correlated with findings from MRI/eZIS. Furthermore, we evaluated the degree of ventricular enlargement in the bifrontal cerebroventricular index (CVI). Patients were divided into two groups: the enlargement group (bifrontal CVI > 35%, 12 patients) and the non-enlargement group (bifrontal CVI < 35%, 15 patients). All of the patients showed cognitive deficits as observed from the neuropsycological test results. Fifteen out of 27 patients by MRI T1/T2 weighted images and fluid attenuated inversion recovery (FLAIR), 22 out of 27 patients by MRI T2* weighted images and 24 out of 27 patients by eZIS showed abnormal findings. In MRI T2* weighted imaging, the white matter from the frontal lobe, corpus callosum, and brainstem showed abnormal findings. With eZIS, 22 patients (81.5%) showed blood flow degradation in the frontal lobe, and 12 patients (44.4%) in cingulate gyrus. In the enlargement group, Functional Independence Measure, Mini-Mental State Examination, Verbal IQ (VIQ)/Full Scale IQ (FIQ), Trail Making Test-B (TMT-B), and Non-paired of Miyake Paired Test were significantly lower. Amongst 12 patients without ventricular enlargement who had no abnormal findings in MRI T1/T2 weighted images and FLAIR, abnormal findings were detectable in seven patients with MRI T2* weighted imaging and to 10 patients with eZIS. Results of the MRI examination alone cannot fully explain DAI frontal lobe dysfunction. However, addition of the eZIS-assisted analysis derived from the single photon emission computed tomography (SPECT) data enabled us to understand regions where blood flow was decreased, i.e., where neuronal functions conceivably might be reduced. [source]