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Sample records for alters dentate granule

  1. Radiation-induced alterations in synaptic neurotransmission of dentate granule cells depend on the dose and species of charged particles.

    PubMed

    Marty, V N; Vlkolinsky, R; Minassian, N; Cohen, T; Nelson, G A; Spigelman, I

    2014-12-01

    The evaluation of potential health risks associated with neuronal exposure to space radiation is critical for future long duration space travel. The purpose of this study was to evaluate and compare the effects of low-dose proton and high-energy charged particle (HZE) radiation on electrophysiological parameters of the granule cells in the dentate gyrus (DG) of the hippocampus and its associated functional consequences. We examined excitatory and inhibitory neurotransmission in DG granule cells (DGCs) in dorsal hippocampal slices from male C57BL/6 mice at 3 months after whole body irradiation with accelerated proton, silicon or iron particles. Multielectrode arrays were used to investigate evoked field synaptic potentials, an extracellular measurement of synaptic excitability in the perforant path to DG synaptic pathway. Whole-cell patch clamp recordings were used to measure miniature excitatory postsynaptic currents (mEPSCs) and miniature inhibitory postsynaptic currents (mIPSCs) in DGCs. Exposure to proton radiation increased synaptic excitability and produced dose-dependent decreases in amplitude and charge transfer of mIPSCs, without affecting the expression of γ-aminobutyric acid type A receptor α2, β3 and γ2 subunits determined by Western blotting. Exposure to silicon radiation had no significant effects on synaptic excitability, mEPSCs or mIPSCs of DGCs. Exposure to iron radiation had no effect on synaptic excitability and mIPSCs, but significantly increased mEPSC frequency at 1 Gy, without changes in mEPSC kinetics, suggesting a presynaptic mechanism. Overall, the data suggest that proton and HZE exposure results in radiation dose- and species-dependent long-lasting alterations in synaptic neurotransmission, which could cause radiation-induced impairment of hippocampal-dependent cognitive functions. PMID:25402556

  2. Prenatal alcohol exposure alters synaptic activity of adult hippocampal dentate granule cells under conditions of enriched environment.

    PubMed

    Kajimoto, Kenta; Valenzuela, C Fernando; Allan, Andrea M; Ge, Shaoyu; Gu, Yan; Cunningham, Lee Anna

    2016-08-01

    Prenatal alcohol exposure (PAE) results in fetal alcohol spectrum disorder (FASD), which is characterized by a wide range of cognitive and behavioral deficits that may be linked to impaired hippocampal function and adult neurogenesis. Preclinical studies in mouse models of FASD indicate that PAE markedly attenuates enrichment-mediated increases in the number of adult-generated hippocampal dentate granule cells (aDGCs), but whether synaptic activity is also affected has not been studied. Here, we utilized retroviral birth-dating coupled with whole cell patch electrophysiological recordings to assess the effects of PAE on enrichment-mediated changes in excitatory and inhibitory synaptic activity as a function of DGC age. We found that exposure to an enriched environment (EE) had no effect on baseline synaptic activity of 4- or 8-week-old aDGCs from control mice, but significantly enhanced the excitatory/inhibitory ratio of synaptic activity in 8-week-old aDGCs from PAE mice. In contrast, exposure to EE significantly enhanced the excitatory/inhibitory ratio of synaptic activity in older pre-existing DGCs situated in the outer dentate granule cell layer (i.e., those generated during embryonic development; dDGCs) in control mice, an effect that was blunted in PAE mice. These findings indicate distinct electrophysiological responses of hippocampal DGCs to behavioral challenge based on cellular ontogenetic age, and suggest that PAE disrupts EE-mediated changes in overall hippocampal network activity. These findings may have implications for future therapeutic targeting of hippocampal dentate circuitry in clinical FASD. © 2016 Wiley Periodicals, Inc. PMID:27009742

  3. Clonal Analysis of Newborn Hippocampal Dentate Granule Cell Proliferation and Development in Temporal Lobe Epilepsy123

    PubMed Central

    LaSarge, Candi L.; McAuliffe, John J.

    2015-01-01

    Abstract Hippocampal dentate granule cells are among the few neuronal cell types generated throughout adult life in mammals. In the normal brain, new granule cells are generated from progenitors in the subgranular zone and integrate in a typical fashion. During the development of epilepsy, granule cell integration is profoundly altered. The new cells migrate to ectopic locations and develop misoriented “basal” dendrites. Although it has been established that these abnormal cells are newly generated, it is not known whether they arise ubiquitously throughout the progenitor cell pool or are derived from a smaller number of “bad actor” progenitors. To explore this question, we conducted a clonal analysis study in mice expressing the Brainbow fluorescent protein reporter construct in dentate granule cell progenitors. Mice were examined 2 months after pilocarpine-induced status epilepticus, a treatment that leads to the development of epilepsy. Brain sections were rendered translucent so that entire hippocampi could be reconstructed and all fluorescently labeled cells identified. Our findings reveal that a small number of progenitors produce the majority of ectopic cells following status epilepticus, indicating that either the affected progenitors or their local microenvironments have become pathological. By contrast, granule cells with “basal” dendrites were equally distributed among clonal groups. This indicates that these progenitors can produce normal cells and suggests that global factors sporadically disrupt the dendritic development of some new cells. Together, these findings strongly predict that distinct mechanisms regulate different aspects of granule cell pathology in epilepsy. PMID:26756038

  4. In vivo imaging of dendritic pruning in dentate granule cells.

    PubMed

    Gonçalves, J Tiago; Bloyd, Cooper W; Shtrahman, Matthew; Johnston, Stephen T; Schafer, Simon T; Parylak, Sarah L; Tran, Thanh; Chang, Tina; Gage, Fred H

    2016-06-01

    We longitudinally imaged the developing dendrites of adult-born mouse dentate granule cells (DGCs) in vivo and found that they underwent over-branching and pruning. Exposure to an enriched environment and constraint of dendritic growth by disrupting Wnt signaling led to increased branch addition and accelerated growth, which were, however, counteracted by earlier and more extensive pruning. Our results indicate that pruning is regulated in a homeostatic fashion to oppose excessive branching and promote a similar dendrite structure in DGCs. PMID:27135217

  5. PTEN deletion from adult-generated dentate granule cells disrupts granule cell mossy fiber axon structure

    PubMed Central

    LaSarge, Candi L.; Santos, Victor R; Danzer, Steve C.

    2015-01-01

    Dysregulation of the mTOR-signaling pathway is implicated in the development of temporal lobe epilepsy. In mice, deletion of PTEN from hippocampal dentate granule cells leads to mTOR hyperactivation and promotes the rapid onset of spontaneous seizures. The mechanism by which these abnormal cells initiate epileptogenesis, however, is unclear. PTEN-knockout granule cells develop abnormally, exhibiting morphological features indicative of increased excitatory input. If these cells are directly responsible for seizure genesis, it follows that they should also possess increased output. To test this prediction, dentate granule cell axon morphology was quantified in control and PTEN-knockout mice. Unexpectedly, PTEN deletion increased giant mossy fiber bouton spacing along the axon length, suggesting reduced innervation of CA3. Increased width of the mossy fiber axon pathway in stratum lucidum, however, which likely reflects an unusual increase in mossy fiber axon collateralization in this region, offset the reduction in boutons per axon length. These morphological changes predicts a net increase in granule cell >> CA3 innervation. Increased diameter of axons from PTEN-knockout cells would further enhance granule cell >> CA3 communication. Altogether, these findings suggest that amplified information flow through the hippocampal circuit contributes to seizure occurrence in the PTEN-knockout mouse model of temporal lobe epilepsy. PMID:25600212

  6. Young Dentate Granule Cells Mediate Pattern Separation whereas Old Granule Cells Contribute to Pattern Completion

    PubMed Central

    Nakashiba, Toshiaki; Cushman, Jesse D.; Pelkey, Kenneth A.; Renaudineau, Sophie; Buhl, Derek L.; McHugh, Thomas J.; Barrera, Vanessa Rodriguez; Chittajallu, Ramesh; Iwamoto, Keisuke S.; McBain, Chris J.; Fanselow, Michael S.; Tonegawa, Susumu

    2012-01-01

    Summary Adult-born granule cells (GCs), a minor population of cells in the hippocampal dentate gyrus, are highly active during the first few weeks following functional integration into the neuronal network (young GCs), distinguishing them from less active older adult-born GCs and the major population of dentate GCs generated developmentally (together, old GCs). We created a transgenic mouse in which output of old GCs was specifically inhibited while leaving a substantial portion of young GCs intact. These mice exhibited enhanced or normal pattern separation between similar contexts that was reduced following removal of young GCs by X-ray irradiation. Furthermore, mutant mice exhibited deficits in rapid pattern completion. Therefore, pattern separation of similar contexts requires adult-born young GCs while old GCs are unnecessary, whereas older GCs contribute to the rapid recall by pattern completion. Our data suggest that as adult-born GCs age, their function switches from pattern separation to rapid pattern completion. PMID:22365813

  7. Mature granule cells of the dentate gyrus-Passive bystanders or principal performers in hippocampal function?

    PubMed

    Lopez-Rojas, Jeffrey; Kreutz, Michael R

    2016-05-01

    The dentate gyrus is the main entrance of highly processed information to the hippocampus which derives from associative cortices and it is one of the few privileged areas in the brain where adult neurogenesis occurs. This creates the unique situation that neurons of diverse maturation stages are part of one neuronal network at any given point in life. While recently adult-born cells have a low induction threshold for long-term potentiation several studies suggest that following maturation granule cells are poorly excitable and they exhibit reduced Hebbian synaptic plasticity to an extent that it was even suggested that they functionally retire. Here, we review the functional properties of mature granule cells and discuss how plasticity of intrinsic excitability and alterations in excitation-inhibition balance might impact on their role in hippocampal information processing. PMID:26949226

  8. Plasticity of intrinsic excitability in mature granule cells of the dentate gyrus

    PubMed Central

    Lopez-Rojas, Jeffrey; Heine, Martin; Kreutz, Michael R.

    2016-01-01

    The dentate gyrus is the main entry gate for cortical input to the hippocampus and one of the few brain areas where adult neurogenesis occurs. Several studies have shown that it is relatively difficult to induce synaptic plasticity in mature but not in newborn dentate granule cells. In the present work we have systematically addressed how classical protocols to induce synaptic plasticity affect action potential firing and intrinsic excitability in mature granule cells. We found that stimulation paradigms considered to be relevant for learning processes consistently modified the probability to generate action potentials in response to a given synaptic input in mature cells, in some paradigms even without any modification of synaptic strength. Collectively the results suggest that plasticity of intrinsic dendritic excitability has a lower induction-threshold than synaptic plasticity in mature granule cells and that this form of plasticity might be an important mechanism by which mature granule cells contribute to hippocampal function. PMID:26857841

  9. Rapid erasure of hippocampal memory following inhibition of dentate gyrus granule cells

    PubMed Central

    Madroñal, Noelia; Delgado-García, José M.; Fernández-Guizán, Azahara; Chatterjee, Jayanta; Köhn, Maja; Mattucci, Camilla; Jain, Apar; Tsetsenis, Theodoros; Illarionova, Anna; Grinevich, Valery; Gross, Cornelius T.; Gruart, Agnès

    2016-01-01

    The hippocampus is critical for the acquisition and retrieval of episodic and contextual memories. Lesions of the dentate gyrus, a principal input of the hippocampus, block memory acquisition, but it remains unclear whether this region also plays a role in memory retrieval. Here we combine cell-type specific neural inhibition with electrophysiological measurements of learning-associated plasticity in behaving mice to demonstrate that dentate gyrus granule cells are not required for memory retrieval, but instead have an unexpected role in memory maintenance. Furthermore, we demonstrate the translational potential of our findings by showing that pharmacological activation of an endogenous inhibitory receptor expressed selectively in dentate gyrus granule cells can induce a rapid loss of hippocampal memory. These findings open a new avenue for the targeted erasure of episodic and contextual memories. PMID:26988806

  10. Rapid erasure of hippocampal memory following inhibition of dentate gyrus granule cells.

    PubMed

    Madroñal, Noelia; Delgado-García, José M; Fernández-Guizán, Azahara; Chatterjee, Jayanta; Köhn, Maja; Mattucci, Camilla; Jain, Apar; Tsetsenis, Theodoros; Illarionova, Anna; Grinevich, Valery; Gross, Cornelius T; Gruart, Agnès

    2016-01-01

    The hippocampus is critical for the acquisition and retrieval of episodic and contextual memories. Lesions of the dentate gyrus, a principal input of the hippocampus, block memory acquisition, but it remains unclear whether this region also plays a role in memory retrieval. Here we combine cell-type specific neural inhibition with electrophysiological measurements of learning-associated plasticity in behaving mice to demonstrate that dentate gyrus granule cells are not required for memory retrieval, but instead have an unexpected role in memory maintenance. Furthermore, we demonstrate the translational potential of our findings by showing that pharmacological activation of an endogenous inhibitory receptor expressed selectively in dentate gyrus granule cells can induce a rapid loss of hippocampal memory. These findings open a new avenue for the targeted erasure of episodic and contextual memories. PMID:26988806

  11. Synaptosomal-associated protein 25 mutation induces immaturity of the dentate granule cells of adult mice

    PubMed Central

    2013-01-01

    Background Synaptosomal-associated protein, 25 kDa (SNAP-25) regulates the exocytosis of neurotransmitters. Growing evidence suggests that SNAP-25 is involved in neuropsychiatric disorders, such as schizophrenia, attention-deficit/hyperactivity disorder, and epilepsy. Recently, increases in anxiety-related behaviors and epilepsy have been observed in SNAP-25 knock-in (KI) mice, which have a single amino acid substitution of Ala for Ser187. However, the molecular and cellular mechanisms underlying the abnormalities in this mutant remain unknown. Results In this study, we found that a significant number of dentate gyrus (DG) granule cells was histologically and electrophysiologically similar to immature DG neurons in the dentate gyrus of the adult mutants, a phenomenon termed the “immature DG” (iDG). SNAP-25 KI mice and other mice possessing the iDG phenotype, i.e., alpha-calcium/calmodulin-dependent protein kinase II heterozygous mice, Schnurri-2 knockout mice, and mice treated with the antidepressant fluoxetine, showed similar molecular expression patterns, with over 100 genes similarly altered. A working memory deficit was also identified in mutant mice during a spontaneous forced alternation task using a modified T-maze, a behavioral task known to be dependent on hippocampal function. Chronic treatments with the antiepileptic drug valproate abolished the iDG phenotype and the working memory deficit in mutants. Conclusions These findings suggest that the substitution of Ala for Ser187 in SNAP-25 induces the iDG phenotype, which can also be caused by epilepsy, and led to a severe working memory deficit. In addition, the iDG phenotype in adulthood is likely an endophenotype for at least a part of some common psychiatric disorders. PMID:23497716

  12. Adult-born hippocampal dentate granule cells undergoing maturation modulate learning and memory in the brain

    PubMed Central

    Deng, Wei; Saxe, Michael D.; Gallina, Iryna S.; Gage, Fred H.

    2009-01-01

    Adult-born dentate granule cells (DGCs) contribute to learning and memory, yet it remains unknown when adult-born DGCs become involved in the cognitive processes. During neurogenesis, immature dentate granule cells (DGCs) display distinctive physiological characteristics while undergoing morphological maturation before final integration into the neural circuits. The survival and activity of the adult-born DGCs can be influenced by the experience of the animal during a critical period when newborn DGCs are still immature. To assess the temporal importance of adult neurogenesis, we developed a transgenic mouse model that allowed us to transiently reduce the numbers of adult-born DGCs in a temporally regulatable manner. We found that mice with a reduced population of adult-born DGCs at the immature stage were deficient in forming robust, long-term spatial memory and displayed impaired performance in extinction tasks. These results suggest that immature DGCs that undergo maturation make important contributions to learning and memory. PMID:19864566

  13. Seizure-Induced Motility of Differentiated Dentate Granule Cells Is Prevented by the Central Reelin Fragment.

    PubMed

    Orcinha, Catarina; Münzner, Gert; Gerlach, Johannes; Kilias, Antje; Follo, Marie; Egert, Ulrich; Haas, Carola A

    2016-01-01

    Granule cell dispersion (GCD) represents a pathological widening of the granule cell layer in the dentate gyrus and it is frequently observed in patients with mesial temporal lobe epilepsy (MTLE). Recent studies in human MTLE specimens and in animal epilepsy models have shown that a decreased expression and functional inactivation of the extracellular matrix protein Reelin correlates with GCD formation, but causal evidence is still lacking. Here, we used unilateral kainate (KA) injection into the mouse hippocampus, an established MTLE animal model, to precisely map the loss of reelin mRNA-synthesizing neurons in relation to GCD along the septotemporal axis of the epileptic hippocampus. We show that reelin mRNA-producing neurons are mainly lost in the hilus and that this loss precisely correlates with the occurrence of GCD. To monitor GCD formation in real time, we used organotypic hippocampal slice cultures (OHSCs) prepared from mice which express enhanced green fluorescent protein (eGFP) primarily in differentiated dentate granule cells. Using life cell microscopy we observed that increasing doses of KA resulted in an enhanced motility of eGFP-positive granule cells. Moreover, KA treatment of OHSC resulted in a rapid loss of Reelin-producing interneurons mainly in the hilus, as observed in vivo. A detailed analysis of the migration behavior of individual eGFP-positive granule cells revealed that the majority of these neurons actively migrate toward the hilar region, where Reelin-producing neurons are lost. Treatment with KA and subsequent addition of the recombinant R3-6 Reelin fragment significantly prevented the movement of eGFP-positive granule cells. Together, these findings suggest that GCD formation is indeed triggered by a loss of Reelin in hilar interneurons. PMID:27516734

  14. Seizure-Induced Motility of Differentiated Dentate Granule Cells Is Prevented by the Central Reelin Fragment

    PubMed Central

    Orcinha, Catarina; Münzner, Gert; Gerlach, Johannes; Kilias, Antje; Follo, Marie; Egert, Ulrich; Haas, Carola A.

    2016-01-01

    Granule cell dispersion (GCD) represents a pathological widening of the granule cell layer in the dentate gyrus and it is frequently observed in patients with mesial temporal lobe epilepsy (MTLE). Recent studies in human MTLE specimens and in animal epilepsy models have shown that a decreased expression and functional inactivation of the extracellular matrix protein Reelin correlates with GCD formation, but causal evidence is still lacking. Here, we used unilateral kainate (KA) injection into the mouse hippocampus, an established MTLE animal model, to precisely map the loss of reelin mRNA-synthesizing neurons in relation to GCD along the septotemporal axis of the epileptic hippocampus. We show that reelin mRNA-producing neurons are mainly lost in the hilus and that this loss precisely correlates with the occurrence of GCD. To monitor GCD formation in real time, we used organotypic hippocampal slice cultures (OHSCs) prepared from mice which express enhanced green fluorescent protein (eGFP) primarily in differentiated dentate granule cells. Using life cell microscopy we observed that increasing doses of KA resulted in an enhanced motility of eGFP-positive granule cells. Moreover, KA treatment of OHSC resulted in a rapid loss of Reelin-producing interneurons mainly in the hilus, as observed in vivo. A detailed analysis of the migration behavior of individual eGFP-positive granule cells revealed that the majority of these neurons actively migrate toward the hilar region, where Reelin-producing neurons are lost. Treatment with KA and subsequent addition of the recombinant R3–6 Reelin fragment significantly prevented the movement of eGFP-positive granule cells. Together, these findings suggest that GCD formation is indeed triggered by a loss of Reelin in hilar interneurons. PMID:27516734

  15. Corruption of the dentate gyrus by "dominant" granule cells: Implications for dentate gyrus function in health and disease.

    PubMed

    Scharfman, Helen E; Myers, Catherine E

    2016-03-01

    The dentate gyrus (DG) and area CA3 of the hippocampus are highly organized lamellar structures which have been implicated in specific cognitive functions such as pattern separation and pattern completion. Here we describe how the anatomical organization and physiology of the DG and CA3 are consistent with structures that perform pattern separation and completion. We then raise a new idea related to the complex circuitry of the DG and CA3 where CA3 pyramidal cell 'backprojections' play a potentially important role in the sparse firing of granule cells (GCs), considered important in pattern separation. We also propose that GC axons, the mossy fibers, already known for their highly specialized structure, have a dynamic function that imparts variance--'mossy fiber variance'--which is important to pattern separation and completion. Computational modeling is used to show that when a subset of GCs become 'dominant,' one consequence is loss of variance in the activity of mossy fiber axons and a reduction in pattern separation and completion in the model. Empirical data are then provided using an example of 'dominant' GCs--subsets of GCs that develop abnormally and have increased excitability. Notably, these abnormal GCs have been identified in animal models of disease where DG-dependent behaviors are impaired. Together these data provide insight into pattern separation and completion, and suggest that behavioral impairment could arise from dominance of a subset of GCs in the DG-CA3 network. PMID:26391451

  16. Endogenous zinc depresses GABAergic transmission via T-type Ca2+ channels and broadens the time window for integration of glutamatergic inputs in dentate granule cells

    PubMed Central

    Grauert, Antonia; Engel, Dominique; Ruiz, Arnaud J

    2014-01-01

    Abstract Zinc actions on synaptic transmission span the modulation of neurotransmitter receptors, transporters, activation of intracellular cascades and alterations in gene expression. Whether and how zinc affects inhibitory synaptic signalling in the dentate gyrus remains largely unexplored. We found that mono- and di-synaptic GABAergic inputs onto dentate granule cells were reversibly depressed by exogenous zinc application and enhanced by zinc chelation. Blocking T-type Ca2+ channels prevented the effect of zinc chelation. When recording from dentate fast-spiking interneurones, zinc chelation facilitated T-type Ca2+ currents, increased action potential half-width and decreased spike threshold. It also increased the offset of the input–output relation in a manner consistent with enhanced excitability. In granule cells, chelation of zinc reduced the time window for the integration of glutamatergic inputs originating from perforant path synapses, resulting in reduced spike transfer. Thus, zinc-mediated modulation of dentate interneurone excitability and GABA release regulates information flow to local targets and hippocampal networks. PMID:24081159

  17. Enduring changes in tonic GABAA receptor signaling in dentate granule cells after controlled cortical impact brain injury in mice.

    PubMed

    Boychuk, Jeffery A; Butler, Corwin R; Halmos, Katalin Cs; Smith, Bret N

    2016-03-01

    Changes in functional GABAAR signaling in hippocampus have previously been evaluated using pre-clinical animal models of either diffuse brain injury or extreme focal brain injury that precludes measurement of cells located ipsilateral to injury. As a result, there is little information about the status of functional GABAAR signaling in dentate granule cells (DGCs) located ipsilateral to focal brain injury, where significant cellular changes have been documented. We used whole-cell patch-clamp recordings from hippocampal slices to measure changes in GABAARs in dentate granule cells (DGCs) at 1-2, 3-5, and 8-13 weeks after controlled cortical impact (CCI) brain injury. Synaptic and tonic GABAAR currents (ITonicGABA) were measured in DGCs at baseline conditions and during application of the GABAAR agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-3-ol hydrochloride (THIP) to assess in the function of δ subunit-containing GABAARs. DGCs ipsilateral to CCI exhibited no changes in the amplitude of resting ITonicGABA relative to DGCs after sham-injury or contralateral to CCI. In contrast, there was a significant reduction in the THIP-evoked ITonicGABA in DGCs ipsilateral to CCI at both time-points. Tonic GABAergic inhibition of DGCs ipsilateral to injury also exhibited reduced responsiveness to the neurosteroid THDOC. ITonicGABA in DGCs ipsilateral to CCI did not exhibit a change in sensitivity to L655,708, an inverse agonist with selectivity for α5 subunit-containing GABAARs, suggesting a lack of functional change in GABAARs containing this subunit. At the 8-13 week time-point, gene expression of GABAAR subunits expected to contribute to ITonicGABA (i.e., α4, α5 and δ) was not significantly altered by CCI injury in isolated dentate gyrus. Collectively, these results demonstrate enduring functional changes in ITonicGABA in DGCs ipsilateral to focal brain injury that occur independent of altered gene expression. PMID:26772635

  18. Cognitive Enhancing Treatment with a PPARγ Agonist Normalizes Dentate Granule Cell Presynaptic Function in Tg2576 APP Mice

    PubMed Central

    Nenov, Miroslav N.; Laezza, Fernanda; Haidacher, Sigmund J.; Zhao, Yingxin; Sadygov, Rovshan G.; Starkey, Jonathan M.; Spratt, Heidi; Luxon, Bruce A.; Dineley, Kelly T.

    2014-01-01

    Hippocampal network hyperexcitability is considered an early indicator of Alzheimer's disease (AD) memory impairment. Some AD mouse models exhibit similar network phenotypes. In this study we focused on dentate gyrus (DG) granule cell spontaneous and evoked properties in 9-month-old Tg2576 mice that model AD amyloidosis and cognitive deficits. Using whole-cell patch-clamp recordings, we found that Tg2576 DG granule cells exhibited spontaneous EPSCs that were higher in frequency but not amplitude compared with wild-type mice, suggesting hyperactivity of DG granule cells via a presynaptic mechanism. Further support of a presynaptic mechanism was revealed by increased I–O relationships and probability of release in Tg2576 DG granule cells. Since we and others have shown that activation of the peroxisome proliferator-activated receptor gamma (PPARγ) axis improves hippocampal cognition in mouse models for AD as well as benefitting memory performance in some humans with early AD, we investigated how PPARγ agonism affected synaptic activity in Tg2576 DG. We found that PPARγ agonism normalized the I–O relationship of evoked EPSCs, frequency of spontaneous EPSCs, and probability of release that, in turn, correlated with selective expression of DG proteins essential for presynaptic SNARE function that are altered in patients with AD. These findings provide evidence that DG principal cells may contribute to early AD hippocampal network hyperexcitability via a presynaptic mechanism, and that hippocampal cognitive enhancement via PPARγ activation occurs through regulation of presynaptic vesicular proteins critical for proper glutamatergic neurotransmitter release, synaptic transmission, and short-term plasticity. PMID:24431460

  19. Enhanced CREB phosphorylation in immature dentate gyrus granule cells precedes neurotrophin expression and indicates a specific role of CREB in granule cell differentiation

    PubMed Central

    Bender, R. A.; Lauterborn, J. C.; Gall, C. M.; Cariaga, W.; Baram, T. Z.

    2011-01-01

    Differentiation and maturation of dentate gyrus granule cells requires coordinated interactions of numerous processes. These must be regulated by protein factors capable of integrating signals mediated through diverse signalling pathways. Such integrators of inter and intracellular physiological stimuli include the cAMP-response element binding protein (CREB), a leucine-zipper class transcription factor that is activated through phosphorylation. Neuronal activity and neurotrophic factors, known to be involved in granule cell differentiation, are major physiologic regulators of CREB function. To examine whether CREB may play a role in governing coordinated gene transcription during granule cell differentiation, we determined the spatial and temporal profiles of phosphorylated (activated) CREB throughout postnatal development in immature rat hippocampus. We demonstrate that CREB activation is confined to discrete, early stages of granule cell differentiation. In addition, CREB phosphorylation occurs prior to expression of the neurotrophins BDNF and NT-3. These data indicate that in a signal transduction cascade connecting CREB and neurotrophins in the process of granule cell maturation, CREB is located upstream of neurotrophins. Importantly, CREB may be a critical component of the machinery regulating the coordinated transcription of genes contributing to the differentiation of granule cells and their integration into the dentate gyrus network. PMID:11207803

  20. Abnormal UP/DOWN Membrane Potential Dynamics Coupled with the Neocortical Slow Oscillation in Dentate Granule Cells during the Latent Phase of Temporal Lobe Epilepsy123

    PubMed Central

    Ouedraogo, David W.; Lenck-Santini, Pierre-Pascal; Marti, Geoffrey; Robbe, David; Crépel, Valérie

    2016-01-01

    The dentate gyrus, a major entry point to the hippocampus, gates (or filters) incoming information from the cortex. During sleep or anesthesia, the slow-wave oscillation (SWO) orchestrates hippocampus–neocortex communication, which is important for memory formation. The dentate gate is altered in temporal lobe epilepsy (TLE) early during epileptogenesis, which favors the propagation of pathological activities. Yet, whether the gating of physiological SWO by dentate granule cells (DGCs) is altered in TLE has remained unexplored. We combined intracellular recordings of membrane potential (Vm) of DGCs and local field potential recordings of the SWO in parietal cortex in anesthetized rats early during epileptogenesis [post-status epilepticus (SE) rats]. As expected, in control rats, the Vm of DGCs weakly and rarely oscillated in the SWO frequency range. In contrast, in post-SE rats, the Vm of DGCs displayed strong and long-lasting SWO. In these cells, clear UP and DOWN states, in phase with the neocortical SWO, led to a bimodal Vm distribution. In post-SE rats, the firing of DGCs was increased and more temporally modulated by the neocortical SWO. We conclude that UP/DOWN state dynamics dominate the Vm of DGCs and firing early during epileptogenesis. This abnormally strong neocortical influence on the dynamics of DGCs may profoundly modify the hippocampus–neocortex dialogue during sleep and associated cognitive functions. PMID:27257629

  1. The Possible Roles of the Dentate Granule Cell’s Leptin and Other Ciliary Receptors in Alzheimer’s Neuropathology

    PubMed Central

    Whitfield, James F.; Chiarini, Anna; Dal Prà, Ilaria; Armato, Ubaldo; Chakravarthy, Balu

    2015-01-01

    Dentate-gyral granule cells in the hippocampus plus dentate gyrus memory-recording/retrieving machine, unlike most other neurons in the brain, are continuously being generated in the adult brain with the important task of separating overlapping patterns of data streaming in from the outside world via the entorhinal cortex. This “adult neurogenesis” is driven by tools in the mature granule cell’s cilium. Here we report our discovery of leptin’s LepRb receptor in this cilium. In addition, we discuss how ciliary LepRb signaling might be involved with ciliary p75NTR and SSTR3 receptors in adult neurogenesis and memory formation as well as attenuation of Alzheimer’s neuropathology by reducing the production of its toxic amyloid-β-derived drivers. PMID:26184316

  2. Inhibition of Protease-Activated Receptor 1 Does not Affect Dendritic Homeostasis of Cultured Mouse Dentate Granule Cells

    PubMed Central

    Schuldt, Gerlind; Galanis, Christos; Strehl, Andreas; Hick, Meike; Schiener, Sabine; Lenz, Maximilian; Deller, Thomas; Maggio, Nicola; Vlachos, Andreas

    2016-01-01

    Protease-activated receptors (PARs) are widely expressed in the central nervous system (CNS). While a firm link between PAR1-activation and functional synaptic and intrinsic neuronal properties exists, studies on the role of PAR1 in neural structural plasticity are scarce. The physiological function of PAR1 in the brain remains not well understood. We here sought to determine whether prolonged pharmacologic PAR1-inhibition affects dendritic morphologies of hippocampal neurons. To address this question we employed live-cell microscopy of mouse dentate granule cell dendrites in 3-week old entorhino-hippocampal slice cultures prepared from Thy1-GFP mice. A subset of cultures were treated with the PAR1-inhibitor SCH79797 (1 μM; up to 3 weeks). No major effects of PAR1-inhibition on static and dynamic parameters of dentate granule cell dendrites were detected under control conditions. Granule cells of PAR1-deficient slice cultures showed unaltered dendritic morphologies, dendritic spine densities and excitatory synaptic strength. Furthermore, we report that PAR1-inhibition does not prevent dendritic retraction following partial deafferentation in vitro. Consistent with this finding, no major changes in PAR1-mRNA levels were detected in the denervated dentate gyrus (DG). We conclude that neural PAR1 is not involved in regulating the steady-state dynamics or deafferentation-induced adaptive changes of cultured dentate granule cell dendrites. These results indicate that drugs targeting neural PAR1-signals may not affect the stability and structural integrity of neuronal networks in healthy brain regions. PMID:27378862

  3. Inhibition of Protease-Activated Receptor 1 Does not Affect Dendritic Homeostasis of Cultured Mouse Dentate Granule Cells.

    PubMed

    Schuldt, Gerlind; Galanis, Christos; Strehl, Andreas; Hick, Meike; Schiener, Sabine; Lenz, Maximilian; Deller, Thomas; Maggio, Nicola; Vlachos, Andreas

    2016-01-01

    Protease-activated receptors (PARs) are widely expressed in the central nervous system (CNS). While a firm link between PAR1-activation and functional synaptic and intrinsic neuronal properties exists, studies on the role of PAR1 in neural structural plasticity are scarce. The physiological function of PAR1 in the brain remains not well understood. We here sought to determine whether prolonged pharmacologic PAR1-inhibition affects dendritic morphologies of hippocampal neurons. To address this question we employed live-cell microscopy of mouse dentate granule cell dendrites in 3-week old entorhino-hippocampal slice cultures prepared from Thy1-GFP mice. A subset of cultures were treated with the PAR1-inhibitor SCH79797 (1 μM; up to 3 weeks). No major effects of PAR1-inhibition on static and dynamic parameters of dentate granule cell dendrites were detected under control conditions. Granule cells of PAR1-deficient slice cultures showed unaltered dendritic morphologies, dendritic spine densities and excitatory synaptic strength. Furthermore, we report that PAR1-inhibition does not prevent dendritic retraction following partial deafferentation in vitro. Consistent with this finding, no major changes in PAR1-mRNA levels were detected in the denervated dentate gyrus (DG). We conclude that neural PAR1 is not involved in regulating the steady-state dynamics or deafferentation-induced adaptive changes of cultured dentate granule cell dendrites. These results indicate that drugs targeting neural PAR1-signals may not affect the stability and structural integrity of neuronal networks in healthy brain regions. PMID:27378862

  4. The type 1 Interleukin 1 receptor is not required for the death of murine hippocampal dentate granule cells and microglia activation

    PubMed Central

    Harry, G. Jean; Funk, Jason; Lefebvre d’Hellencourt, Christian; Aoyama, Mineyoshi

    2008-01-01

    Alterations in the inflammatory process, neuronal death, and glia response have been observed under manipulation of the interleukin-1 (IL-1) cytokine and subsequent signaling through the type 1 IL-1 receptor (IL-1R1). To investigate the influence of IL-1R1 activation in the pathophysiology of a chemical-induced injury to the murine hippocampus, we examined the level and pattern of neuronal death and neuroinflammation in 25-day-old male mice exposed to trimethyltin hydroxide (2.0 mg/kg, i.p.). In IL-1R1 null (IL-1R1−/−) mice, the pattern and severity of dentate granule cell death was similar as compared to wild type mice. In both groups of mice, mRNA levels for TNFα and MIP-1α were elevated and the early activation of microglia, including their ability to progress to a phagocytic phenotype, was maintained. Compared to WT mice, IL-1R1−/− mice displayed a limited glial fibrillary acidic protein (GFAP) astrocytic response, as well as a preferential induction in mRNA levels of Fas signaling components. Cumulatively, these results indicate that IL-1R1 activation is not necessary for TMT-induced death of dentate granule neurons or local activation of microglia; however, IL-1R1 signaling is involved in mediating the structural response of astrocytes to injury and may also regulate apoptotic mechanisms by influencing Fas signaling components. PMID:18191113

  5. Tonic Inhibitory Control of Dentate Gyrus Granule Cells by α5-Containing GABAA Receptors Reduces Memory Interference

    PubMed Central

    Zarnowska, Ewa D.; Benke, Dietmar; Tsvetkov, Evgeny; Sigal, Maksim; Keist, Ruth; Bolshakov, Vadim Y.; Pearce, Robert A.; Rudolph, Uwe

    2015-01-01

    Interference between similar or overlapping memories formed at different times poses an important challenge on the hippocampal declarative memory system. Difficulties in managing interference are at the core of disabling cognitive deficits in neuropsychiatric disorders. Computational models have suggested that, in the normal brain, the sparse activation of the dentate gyrus granule cells maintained by tonic inhibitory control enables pattern separation, an orthogonalization process that allows distinct representations of memories despite interference. To test this mechanistic hypothesis, we generated mice with significantly reduced expression of the α5-containing GABAA (α5-GABAARs) receptors selectively in the granule cells of the dentate gyrus (α5DGKO mice). α5DGKO mice had reduced tonic inhibition of the granule cells without any change in fast phasic inhibition and showed increased activation in the dentate gyrus when presented with novel stimuli. α5DGKO mice showed impairments in cognitive tasks characterized by high interference, without any deficiencies in low-interference tasks, suggesting specific impairment of pattern separation. Reduction of fast phasic inhibition in the dentate gyrus through granule cell-selective knock-out of α2-GABAARs or the knock-out of the α5-GABAARs in the downstream CA3 area did not detract from pattern separation abilities, which confirms the anatomical and molecular specificity of the findings. In addition to lending empirical support to computational hypotheses, our findings have implications for the treatment of interference-related cognitive symptoms in neuropsychiatric disorders, particularly considering the availability of pharmacological agents selectively targeting α5-GABAARs. SIGNIFICANCE STATEMENT Interference between similar memories poses a significant limitation on the hippocampal declarative memory system, and impaired interference management is a cognitive symptom in many disorders. Thus, understanding

  6. In vivo 7 Tesla imaging of the dentate granule cell layer in Schizophrenia

    PubMed Central

    Kirov, Ivan I.; Hardy, Caitlin J.; Matsuda, Kant; Messinger, Julie; Cankurtaran, Ceylan Z.; Warren, Melina; Wiggins, Graham C.; Perry, Nissa N.; Babb, James S.; Goetz, Raymond R.; George, Ajax; Malaspina, Dolores; Gonen, Oded

    2013-01-01

    PURPOSE The hippocampus is central to the pathophysiology of schizophrenia. Histology shows abnormalities in the dentate granule cell layer (DGCL), but its small size (~100 micron thickness) has precluded in vivo human studies. We used ultra high field magnetic resonance imaging (MRI) to compare DGCL morphology of schizophrenic patients to matched controls’. METHOD Bilateral hippocampi of 16 schizophrenia patients (10 male) 40.7±10.6 years old (mean ±standard deviation) were imaged at 7 Tesla MRI with heavily T2*-weighted gradient-echo sequence at 232 micron in-plane resolution (0.08 μL image voxels). Fifteen matched controls (8 male, 35.6±9.4 years old) and one ex vivo post mortem hippocampus (that also underwent histopathology) were scanned with same protocol. Three blinded neuroradiologists rated each DGCL on a qualitative scale of 1 to 6 (from “not discernible” to “easily visible, appearing dark gray or black”) and mean left and right DGCL scores were compared using a non-parametric Mann-Whitney test. RESULTS MRI identification of the DGCL was validated with histopathology. Mean right and left DGCL ratings in patients (3.2±1.0 and 3.5±1.2) were not statistically different from controls’ (3.9±1.1 and 3.8±0.8), but patients’ had a trend for lower right DGCL score (p=0.07), which was significantly associated with patient diagnosis (p=0.05). The optimal 48% sensitivity and 80% specificity for schizophrenia was achieved with a DGCL rating of ≤2. CONCLUSION Decreased contrast in the right DGCL in schizophrenia was predictive of schizophrenia diagnosis. Better utility of this metric as a schizophrenia biomarker may be achieved in future studies of patients with homogeneous disease subtypes and progression rates. PMID:23664589

  7. Entorhinal Denervation Induces Homeostatic Synaptic Scaling of Excitatory Postsynapses of Dentate Granule Cells in Mouse Organotypic Slice Cultures

    PubMed Central

    Vlachos, Andreas; Becker, Denise; Jedlicka, Peter; Winkels, Raphael; Roeper, Jochen; Deller, Thomas

    2012-01-01

    Denervation-induced changes in excitatory synaptic strength were studied following entorhinal deafferentation of hippocampal granule cells in mature (≥3 weeks old) mouse organotypic entorhino-hippocampal slice cultures. Whole-cell patch-clamp recordings revealed an increase in excitatory synaptic strength in response to denervation during the first week after denervation. By the end of the second week synaptic strength had returned to baseline. Because these adaptations occurred in response to the loss of excitatory afferents, they appeared to be in line with a homeostatic adjustment of excitatory synaptic strength. To test whether denervation-induced changes in synaptic strength exploit similar mechanisms as homeostatic synaptic scaling following pharmacological activity blockade, we treated denervated cultures at 2 days post lesion for 2 days with tetrodotoxin. In these cultures, the effects of denervation and activity blockade were not additive, suggesting that similar mechanisms are involved. Finally, we investigated whether entorhinal denervation, which removes afferents from the distal dendrites of granule cells while leaving the associational afferents to the proximal dendrites of granule cells intact, results in a global or a local up-scaling of granule cell synapses. By using computational modeling and local electrical stimulations in Strontium (Sr2+)-containing bath solution, we found evidence for a lamina-specific increase in excitatory synaptic strength in the denervated outer molecular layer at 3–4 days post lesion. Taken together, our data show that entorhinal denervation results in homeostatic functional changes of excitatory postsynapses of denervated dentate granule cells in vitro. PMID:22403720

  8. Differential effects of rapamycin treatment on tonic and phasic GABAergic inhibition in dentate granule cells after focal brain injury in mice.

    PubMed

    Butler, Corwin R; Boychuk, Jeffery A; Smith, Bret N

    2016-06-01

    The cascade of events leading to post-traumatic epilepsy (PTE) after traumatic brain injury (TBI) remains unclear. Altered inhibition in the hippocampal formation and dentate gyrus is a hallmark of several neurological disorders, including TBI and PTE. Inhibitory synaptic signaling in the hippocampus is predominately driven by γ-aminobutyric acid (GABA) neurotransmission, and is prominently mediated by postsynaptic type A GABA receptors (GABAAR's). Subsets of these receptors involved in tonic inhibition of neuronal membranes serve a fundamental role in maintenance of inhibitory state, and GABAAR-mediated tonic inhibition is altered functionally in animal models of both TBI and epilepsy. In this study, we assessed the effect of mTOR inhibition on hippocampal hilar inhibitory interneuron loss and synaptic and tonic GABAergic inhibition of dentate gyrus granule cells (DGCs) after controlled cortical impact (CCI) to determine if mTOR activation after TBI modulates GABAAR function. Hilar inhibitory interneuron density was significantly reduced 72h after CCI injury in the dorsal two-thirds of the hemisphere ipsilateral to injury compared with the contralateral hemisphere and sham controls. Rapamycin treatment did not alter this reduction in cell density. Synaptic and tonic current measurements made in DGCs at both 1-2 and 8-13weeks post-injury indicated reduced synaptic inhibition and THIP-induced tonic current density in DGCs ipsilateral to CCI injury at both time points post-injury, with no change in resting tonic GABAAR-mediated currents. Rapamycin treatment did not alter the reduced synaptic inhibition observed in ipsilateral DGCs 1-2weeks post-CCI injury, but further reduced synaptic inhibition of ipsilateral DGCs at 8-13weeks post-injury. The reduction in THIP-induced tonic current after injury, however, was prevented by rapamycin treatment at both time points. Rapamycin treatment thus differentially modifies CCI-induced changes in synaptic and tonic GABAAR

  9. The dynamics of synchronized neurotransmitter release determined from compound spontaneous IPSCs in rat dentate granule neurones in vitro

    PubMed Central

    Williams, Stephen R; Buhl, Eberhard H; Mody, Istvan

    1998-01-01

    The properties of GABAA receptor-mediated spontaneous IPSCs generated in hippocampal dentate granule neurones were analysed using whole-cell voltage-clamp techniques in order to explore the functional consequences of the low number (6–12) and close proximity of synaptic contacts made by single GABAergic interneurones. Spontaneous IPSCs (sIPSCs) occurred with a frequency of 14.0 ± 9.1 Hz (n = 31) and revealed a multi-modal positively skewed amplitude distribution (39.0 ± 19.8 pA, median values). The variance of 10–90 % rise times and decay kinetics between IPSCs decreased with increasing peak amplitude. Larger amplitude events had significantly faster rise times, consistent with their site of generation being proximal to the soma. The decay kinetics of sIPSCs did not significantly change with amplitude. Large amplitude sIPSCs occurred singularly or in discrete bursts, repeated regularly at low frequency. The rising phase of such sIPSCs were multi-phasic, composed of clear step-like inflections that were not a product of noise. The variability between the rising phase of individual sIPSCs was quantified by calculating their standard deviation, which produced fast rising (0.22 ± 0.05 ms time to peak, n = 16) functions with half-widths of 0.38 ± 0.10 ms, which declined to plateaux. Computer simulations demonstrated that IPSCs with properties similar to those recorded experimentally could be generated by the linear summation of groups of temporally dispersed component events. Standard deviation functions of the rising phase of simulated IPSCs accurately described distributions of the temporal dispersion of unitary components. The GABA uptake inhibitor (R)-N-[4,4-bis(3-methyl-2-thienyl)but-3-enl-yl] nipecotic acid (tiagabine) (10 μM, n = 12) significantly prolonged the decay of mIPSCs (6.5 ± 0.8 to 8.7 ± 1.0 ms, median values) and sIPSCs (6.2 ± 0.4 to 7.3 ± 1.2 ms, median values), but failed to alter the frequency of occurrence, 10–90 % rise times or peak

  10. Impaired firing properties of dentate granule neurons in an Alzheimer's disease animal model are rescued by PPARγ agonism

    PubMed Central

    Nenov, Miroslav N.; Denner, Larry; Dineley, Kelly T.

    2014-01-01

    Early cognitive impairment in Alzheimer's disease (AD) correlates with medial temporal lobe dysfunction, including two areas essential for memory formation: the entorhinal cortex and dentate gyrus (DG). In the Tg2576 animal model for AD amyloidosis, activation of the peroxisome proliferator-activated receptor-gamma (PPARγ) with rosiglitazone (RSG) ameliorates hippocampus-dependent cognitive impairment and restores aberrant synaptic activity at the entorhinal cortex to DG granule neuron inputs. It is unknown, however, whether intrinsic firing properties of DG granule neurons in these animals are affected by amyloid-β pathology and if they are sensitive to RSG treatment. Here, we report that granule neurons from 9-mo-old wild-type and Tg2576 animals can be segregated into two cell types with distinct firing properties and input resistance that correlate with less mature type I and more mature type II neurons. The DG type I cell population was greater than type II in wild-type littermates. In the Tg2576 animals, the type I and type II cell populations were nearly equal but could be restored to wild-type levels through cognitive enhancement with RSG. Furthermore, Tg2576 cell firing frequency and spike after depolarization were decreased in type I and increased in type II cells, both of which could also be restored to wild-type levels upon RSG treatment. That these parameters were restored by PPARγ activation emphasizes the therapeutic value of RSG against early AD cognitive impairment. PMID:25540218

  11. New insights into the role of hilar ectopic granule cells in the dentate gyrus based on quantitative anatomic analysis and three-dimensional reconstruction

    PubMed Central

    Scharfman, Helen E.; Pierce, Joseph P.

    2014-01-01

    SUMMARY The dentate gyrus is one of two main areas of the mammalian brain where neurons are born throughout adulthood, a phenomenon called postnatal neurogenesis. Most of the neurons that are generated are granule cells (GCs), the major principal cell type in the dentate gyrus. Some adult-born granule cells develop in ectopic locations, such as the dentate hilus. The generation of hilar ectopic granule cells (HEGCs) is greatly increased in several animal models of epilepsy and has also been demonstrated in surgical specimens from patients with intractable temporal lobe epilepsy (TLE). Herein we review the results of our quantitative neuroanatomic analysis of HEGCs that were filled with Neurobiotin following electrophysiologic characterization in hippocampal slices. The data suggest that two types of HEGCs exist, based on a proximal or distal location of the cell body relative to the granule cell layer, and based on the location of most of the dendrites, in the molecular layer or hilus. Three-dimensional reconstruction revealed that the dendrites of distal HEGCs can extend along the transverse and longitudinal axis of the hippocampus. Analysis of axons demonstrated that HEGCs have projections that contribute to the normal mossy fiber innervation of CA3 as well as the abnormal sprouted fibers in the inner molecular layer of epileptic rodents (mossy fiber sprouting). These data support the idea that HEGCs could function as a “hub” cell in the dentate gyrus and play a critical role in network excitability. PMID:22612815

  12. Chronic Fluoxetine Induces the Enlargement of Perforant Path-Granule Cell Synapses in the Mouse Dentate Gyrus

    PubMed Central

    Kitahara, Yosuke; Ohta, Keisuke; Hasuo, Hiroshi; Shuto, Takahide; Kuroiwa, Mahomi; Sotogaku, Naoki; Togo, Akinobu; Nakamura, Kei-ichiro; Nishi, Akinori

    2016-01-01

    A selective serotonin reuptake inhibitor is the most commonly prescribed antidepressant for the treatment of major depression. However, the mechanisms underlying the actions of selective serotonin reuptake inhibitors are not fully understood. In the dentate gyrus, chronic fluoxetine treatment induces increased excitability of mature granule cells (GCs) as well as neurogenesis. The major input to the dentate gyrus is the perforant path axons (boutons) from the entorhinal cortex (layer II). Through voltage-sensitive dye imaging, we found that the excitatory neurotransmission of the perforant path synapse onto the GCs in the middle molecular layer of the mouse dentate gyrus (perforant path-GC synapse) is enhanced after chronic fluoxetine treatment (15 mg/kg/day, 14 days). Therefore, we further examined whether chronic fluoxetine treatment affects the morphology of the perforant path-GC synapse, using FIB/SEM (focused ion beam/scanning electron microscopy). A three-dimensional reconstruction of dendritic spines revealed the appearance of extremely large-sized spines after chronic fluoxetine treatment. The large-sized spines had a postsynaptic density with a large volume. However, chronic fluoxetine treatment did not affect spine density. The presynaptic boutons that were in contact with the large-sized spines were large in volume, and the volumes of the mitochondria and synaptic vesicles inside the boutons were correlated with the size of the boutons. Thus, the large-sized perforant path-GC synapse induced by chronic fluoxetine treatment contains synaptic components that correlate with the synapse size and that may be involved in enhanced glutamatergic neurotransmission. PMID:26788851

  13. Chronic Fluoxetine Induces the Enlargement of Perforant Path-Granule Cell Synapses in the Mouse Dentate Gyrus.

    PubMed

    Kitahara, Yosuke; Ohta, Keisuke; Hasuo, Hiroshi; Shuto, Takahide; Kuroiwa, Mahomi; Sotogaku, Naoki; Togo, Akinobu; Nakamura, Kei-ichiro; Nishi, Akinori

    2016-01-01

    A selective serotonin reuptake inhibitor is the most commonly prescribed antidepressant for the treatment of major depression. However, the mechanisms underlying the actions of selective serotonin reuptake inhibitors are not fully understood. In the dentate gyrus, chronic fluoxetine treatment induces increased excitability of mature granule cells (GCs) as well as neurogenesis. The major input to the dentate gyrus is the perforant path axons (boutons) from the entorhinal cortex (layer II). Through voltage-sensitive dye imaging, we found that the excitatory neurotransmission of the perforant path synapse onto the GCs in the middle molecular layer of the mouse dentate gyrus (perforant path-GC synapse) is enhanced after chronic fluoxetine treatment (15 mg/kg/day, 14 days). Therefore, we further examined whether chronic fluoxetine treatment affects the morphology of the perforant path-GC synapse, using FIB/SEM (focused ion beam/scanning electron microscopy). A three-dimensional reconstruction of dendritic spines revealed the appearance of extremely large-sized spines after chronic fluoxetine treatment. The large-sized spines had a postsynaptic density with a large volume. However, chronic fluoxetine treatment did not affect spine density. The presynaptic boutons that were in contact with the large-sized spines were large in volume, and the volumes of the mitochondria and synaptic vesicles inside the boutons were correlated with the size of the boutons. Thus, the large-sized perforant path-GC synapse induced by chronic fluoxetine treatment contains synaptic components that correlate with the synapse size and that may be involved in enhanced glutamatergic neurotransmission. PMID:26788851

  14. Neurotensinergic Excitation of Dentate Gyrus Granule Cells via Gαq-Coupled Inhibition of TASK-3 Channels.

    PubMed

    Zhang, Haopeng; Dong, Hailong; Cilz, Nicholas I; Kurada, Lalitha; Hu, Binqi; Wada, Etsuko; Bayliss, Douglas A; Porter, James E; Lei, Saobo

    2016-03-01

    Neurotensin (NT) is a 13-amino acid peptide and serves as a neuromodulator in the brain. Whereas NT has been implicated in learning and memory, the underlying cellular and molecular mechanisms are ill-defined. Because the dentate gyrus receives profound innervation of fibers containing NT and expresses high density of NT receptors, we examined the effects of NT on the excitability of dentate gyrus granule cells (GCs). Our results showed that NT concentration dependently increased action potential (AP) firing frequency of the GCs by the activation of NTS1 receptors resulting in the depolarization of the GCs. NT-induced enhancement of AP firing frequency was not caused indirectly by releasing glutamate, GABA, acetylcholine, or dopamine, but due to the inhibition of TASK-3 K(+) channels. NT-mediated excitation of the GCs was G protein dependent, but independent of phospholipase C, intracellular Ca(2+) release, and protein kinase C. Immunoprecipitation experiment demonstrates that the activation of NTS1 receptors induced the association of Gαq/11 and TASK-3 channels suggesting a direct coupling of Gαq/11 to TASK-3 channels. Endogenously released NT facilitated the excitability of the GCs contributing to the induction of long-term potentiation at the perforant path-GC synapses. Our results provide a cellular mechanism that helps to explain the roles of NT in learning and memory. PMID:25405940

  15. Mosaic organization of the hippocampal neuroepithelium and the multiple germinal sources of dentate granule cells

    SciTech Connect

    Altman, J.; Bayer, S.A. )

    1990-11-15

    This study deals with the site of origin, migration, and settling of the principal cell constituents of the rat hippocampus during the embryonic period. The results indicate that the hippocampal neuroepithelium consists of three morphogenetically discrete components--the Ammonic neuroepithelium, the primary dentate neuroepithelium, and the fimbrial glioepithelium--and that these are discrete sources of the large neurons of Ammon's horn, the smaller granular neurons of the dentate gyrus, and the glial cells of the fimbria. The putative Ammonic neuroepithelium is marked in short-survival thymidine radiograms by a high level of proliferative activity and evidence of interkinetic nuclear migration from day E16 until day E19. On days E16 and E17 a diffuse band of unlabeled cells forms outside the Ammonic neuroepithelium. These postmitotic cells are considered to be stratum radiatum and stratum oriens neurons, which are produced in large numbers as early as day E15. A cell-dense layer, the incipient stratum pyramidale, begins to form on day E18 and spindle-shaped cells can be traced to it from the Ammonic neuroepithelium. This migratory band increases in size for several days, then declines, and finally disappears by day E22. It is inferred that this migration contains the pyramidal cells of Ammon's horn that are produced mostly on days E17 through E20. The putative primary dentate neuroepithelium is distinguished from the Ammonic neuroepithelium during the early phases of embryonic development by its location, shape, and cellular dynamics. It is located around a ventricular indentation, the dentate notch, contains fewer mitotic cells near the lumen of the ventricle than the Ammonic neuroepithelium, and shows a different labeling pattern both in short-survival and sequential-survival thymidine radiograms.

  16. Long-Term Treatment with Low Doses of Methamphetamine Promotes Neuronal Differentiation and Strengthens Long-Term Potentiation of Glutamatergic Synapses onto Dentate Granule Neurons.

    PubMed

    Baptista, Sofia; Lourenço, Joana; Milhazes, Nuno; Borges, Fernanda; Silva, Ana Paula; Bacci, Alberto

    2016-01-01

    Methamphetamine (METH) is a psychostimulant, affecting hippocampal function with disparate cognitive effects, which depends on the dose and time of administration, ranging from improvement to impairment of memory. Importantly, in the United States, METH is approved for the treatment of attention deficit hyperactivity disorder. Modifications of long-term plasticity of synapses originating from the entorhinal cortex onto dentate granule cells (DGCs) have been proposed to underlie cognitive alterations similar to those seen in METH users. However, the effects of METH on synaptic plasticity of the dentate gyrus are unknown. Here, we investigated the impact of long-term administration of METH (2 mg/kg/d) on neurogenesis and synaptic plasticity of immature and mature DGCs of juvenile mice. We used a mouse model of neurogenesis (the G42 line of GAD67-GFP), in which GFP is expressed by differentiating young DGCs. METH treatment enhanced the differentiation of GFP(+) cells, as it increased the fraction of GFP(+) cells expressing the neuronal marker NeuN, and decreased the amount of immature DGCs coexpressing doublecortin. Interestingly, METH did not change the magnitude of long-term potentiation (LTP) in more immature neurons, but facilitated LTP induction in more differentiated GFP(+) and strengthened plasticity in mature GFP(-) DGCs. The METH-induced facilitation of LTP in GFP(+) neurons was accompanied with spine enlargement. Our results reveal a specific action of long-term use of METH in the long-term plasticity of excitatory synapses onto differentiating DGCs and might have important implications toward the understanding of the synaptic basis of METH-induced cognitive alterations. PMID:27419216

  17. Long-Term Treatment with Low Doses of Methamphetamine Promotes Neuronal Differentiation and Strengthens Long-Term Potentiation of Glutamatergic Synapses onto Dentate Granule Neurons

    PubMed Central

    Milhazes, Nuno

    2016-01-01

    Abstract Methamphetamine (METH) is a psychostimulant, affecting hippocampal function with disparate cognitive effects, which depends on the dose and time of administration, ranging from improvement to impairment of memory. Importantly, in the United States, METH is approved for the treatment of attention deficit hyperactivity disorder. Modifications of long-term plasticity of synapses originating from the entorhinal cortex onto dentate granule cells (DGCs) have been proposed to underlie cognitive alterations similar to those seen in METH users. However, the effects of METH on synaptic plasticity of the dentate gyrus are unknown. Here, we investigated the impact of long-term administration of METH (2 mg/kg/d) on neurogenesis and synaptic plasticity of immature and mature DGCs of juvenile mice. We used a mouse model of neurogenesis (the G42 line of GAD67-GFP), in which GFP is expressed by differentiating young DGCs. METH treatment enhanced the differentiation of GFP+ cells, as it increased the fraction of GFP+ cells expressing the neuronal marker NeuN, and decreased the amount of immature DGCs coexpressing doublecortin. Interestingly, METH did not change the magnitude of long-term potentiation (LTP) in more immature neurons, but facilitated LTP induction in more differentiated GFP+ and strengthened plasticity in mature GFP− DGCs. The METH-induced facilitation of LTP in GFP+ neurons was accompanied with spine enlargement. Our results reveal a specific action of long-term use of METH in the long-term plasticity of excitatory synapses onto differentiating DGCs and might have important implications toward the understanding of the synaptic basis of METH-induced cognitive alterations. PMID:27419216

  18. Running rewires the neuronal network of adult-born dentate granule cells.

    PubMed

    Vivar, Carmen; Peterson, Benjamin D; van Praag, Henriette

    2016-05-01

    Exercise improves cognition in humans and animals. Running increases neurogenesis in the dentate gyrus of the hippocampus, a brain area important for learning and memory. It is unclear how running modifies the circuitry of new dentate gyrus neurons to support their role in memory function. Here we combine retroviral labeling with rabies virus mediated trans-synaptic retrograde tracing to define and quantify new neuron afferent inputs in young adult male C57Bl/6 mice, housed with or without a running wheel for one month. Exercise resulted in a shift in new neuron networks that may promote sparse encoding and pattern separation. Neurogenesis increased in the dorsal, but not the ventral, dentate gyrus by three-fold, whereas afferent traced cell labeling doubled in number. Regional analysis indicated that running differentially affected specific inputs. Within the hippocampus the ratio of innervation from inhibitory interneurons and glutamatergic mossy cells to new neurons was reduced. Distal traced cells were located in sub-cortical and cortical regions, including perirhinal, entorhinal and sensory cortices. Innervation from entorhinal cortex (EC) was augmented, in proportion to the running-induced enhancement of adult neurogenesis. Within EC afferent input and short-term synaptic plasticity from lateral entorhinal cortex, considered to convey contextual information to the hippocampus was increased. Furthermore, running upregulated innervation from regions important for spatial memory and theta rhythm generation, including caudo-medial entorhinal cortex and subcortical medial septum, supra- and medial mammillary nuclei. Altogether, running may facilitate contextual, spatial and temporal information encoding by increasing adult hippocampal neurogenesis and by reorganization of new neuron circuitry. PMID:26589333

  19. Changes in task demands alter the pattern of zif268 expression in the dentate gyrus.

    PubMed

    Satvat, Elham; Schmidt, Brandy; Argraves, Melissa; Marrone, Diano F; Markus, Etan J

    2011-05-11

    Granule cells of the dentate gyrus (DG) are thought to disambiguate similar experiences--a process termed pattern separation. Using zif268 as a marker of cellular activity, DG function was assessed in rats performing two tasks: a place task (go east) and a response task (turn right). As these tasks occurred within the same physical space (a plus maze) without any physical cue to indicate the correct strategy in a given trial, this scenario critically involves disambiguation of task demands and presumably pattern separation. Performance of the two tasks induced zif268 expression in distinct populations of granule cells within the suprapyramidal but not the infrapyramidal blade of the DG. Repeated performance of the same task (i.e., two response-task trials or two place-task trials), however, elicited zif268 expression within a single subset of the granule cell population. This differential transcription pattern shows that the retrieval of different behavioral strategies or mnemonic demands recruit distinct ensembles of granule cells, possibly to prevent interference between memories of events occurring within the same physical space to permit the selection of appropriate responses. PMID:21562279

  20. Effects of formaldehyde exposure on granule cell number and volume of dentate gyrus: a histopathological and stereological study.

    PubMed

    Aslan, Huseyin; Songur, Ahmet; Tunc, Ayten Turkkani; Ozen, Oguz Aslan; Bas, Orhan; Yagmurca, Murat; Turgut, Mehmet; Sarsilmaz, Mustafa; Kaplan, Suleyman

    2006-11-29

    The hippocampal formation is a complex region of the brain related to memory and learning. The purpose of the present study was to determine whether exposure of neonatal rats to formaldehyde (FA) had either early or delayed effects on the numbers of granule cells in the dentate gyrus (DG). After birth, the neonatal male Wistar rats were exposed throughout a 30-day period to various concentrations of FA: 0 (control group), 6 ppm (low concentration group) and 12 ppm (high concentration group). This was done by placing them for 6 h/day and 5 days per week in a glass chamber containing FA vapor. Then, five animals from each group were anesthetized and decapitated on postnatal day (PND) 30, and the remaining five animals were sacrificed on PND 90 by intracardiac perfusion using 10% neutral buffered FA solution. The Cavalieri principle of stereological approaches was used to determine the volume of the DG in these sections. The optical fractionator counting method was used to estimate the total number of granule cells in the DG. The appearance of granule cells was normal under light microscopy in all PND 30 and PND 90 groups. There were significant age-related reductions in the volume of the DG at PND 90 irrespective of which group was examined. Significant age-related neuron loss was also determined at PND 90 compared to that at PND 30. Rats treated with a high concentration FA were found to have fewer granule cells than either the animals treated with a low concentration FA or the control group (p<0.01 and p<0.01, respectively) at PND 90 but not at PND 30. These findings clearly indicate that granule cells in the DG may be vulnerable to stress and the concentration of FA to which they are exposed during early postnatal life, and also that a neurotoxic effect of high dose FA on cell number is only seen after a long time period. These results may explain why some disorders do not appear until later life. PMID:17011527

  1. Influence of ontogenetic age on the role of dentate granule neurons.

    PubMed

    Tronel, Sophie; Lemaire, Valérie; Charrier, Vanessa; Montaron, Marie-Françoise; Abrous, Djoher Nora

    2015-03-01

    New neurons are continuously produced in the adult dentate gyrus of the hippocampus, a key structure in learning and memory. It has been shown that adult neurogenesis is crucial for normal memory processing. However, it is not known whether neurons born during the developmental period and during adulthood support the same functions. Here, we demonstrate that neurons born in neonates (first postnatal week) are activated in different memory processes when they are mature compared to neurons born in adults. By imaging the activation of these two different neuron generations in the same rat and using the IEG Zif268 and Fos, we show that these neurons are involved in discriminating dissimilar contexts and spatial problem solving, respectively. These findings demonstrate that the ontogenetic stage during which neurons are generated is crucial for their function within the memory network. PMID:24510284

  2. Parallel Computational Subunits in Dentate Granule Cells Generate Multiple Place Fields

    PubMed Central

    Ujfalussy, Balázs; Kiss, Tamás; Érdi, Péter

    2009-01-01

    A fundamental question in understanding neuronal computations is how dendritic events influence the output of the neuron. Different forms of integration of neighbouring and distributed synaptic inputs, isolated dendritic spikes and local regulation of synaptic efficacy suggest that individual dendritic branches may function as independent computational subunits. In the present paper, we study how these local computations influence the output of the neuron. Using a simple cascade model, we demonstrate that triggering somatic firing by a relatively small dendritic branch requires the amplification of local events by dendritic spiking and synaptic plasticity. The moderately branching dendritic tree of granule cells seems optimal for this computation since larger dendritic trees favor local plasticity by isolating dendritic compartments, while reliable detection of individual dendritic spikes in the soma requires a low branch number. Finally, we demonstrate that these parallel dendritic computations could contribute to the generation of multiple independent place fields of hippocampal granule cells. PMID:19750211

  3. Beneficial effect of Boswellia serrata gum resin on spatial learning and the dendritic tree of dentate gyrus granule cells in aged rats

    PubMed Central

    Hosseini-Sharifabad, Mohammad; Kamali-Ardakani, Razieh; Hosseini-Sharifabad, Ali

    2016-01-01

    Objective: The hippocampal formation, particularly the dentate gyrus (DG), shows age-related morphological changes that could cause memory decline. It is indicated that Boswellia resins attenuates memory deficits and the major component of Boswellia serrata (Bs) gum resin, beta boswellic acid increased neurite outgrowth and branching in hippocampal neurons. This study was designed to investigate the effect of Boswellia treatment on spatial learning performance and the morphology of dentate granule cells in aged rats. Materials and Methods: Sixteen male Wistar rats (24 months old) were divided into experimental and control groups. Experimental group was intragastrically administered with the aqueous extract of Bs (100 mg/kg/d for 8 weeks) and control group received a similar volume of water. Spatial learning performance of rats was tested using Morris water maze task. At the end of experiment, the brain was removed and the right hippocampus was serially sectioned for morphometric analysis. The Cavalieri principle was employed to estimate the volume of the DG. A quantitative Golgi study was used to analyze the dendritic trees of dentate granule cells. Results: Chronic treatment with Bs improved spatial learning capability during the three acquisition days. Comparisons also revealed that Bs-treated aged rat had greater DG with increased dendritic complexity in the dentate granule cells than control rats. Hippocampal granule cells of Bs-treated aged rats had more dendritic segments, larger arbors, more numerical branching density and more dendritic spines in comparison to control animals. Conclusion: This study provided a neuro-anatomical basis for memory improvement due to chronic treatment with Bs. PMID:27222832

  4. Potential implications of a monosynaptic pathway from mossy cells to adult-born granule cells of the dentate gyrus

    PubMed Central

    Scharfman, Helen E.; Bernstein, Hannah L.

    2015-01-01

    The dentate gyrus (DG) is important to many aspects of hippocampal function, but there are many aspects of the DG that are incompletely understood. One example is the role of mossy cells (MCs), a major DG cell type that is glutamatergic and innervates the primary output cells of the DG, the granule cells (GCs). MCs innervate the GCs as well as local circuit neurons that make GABAergic synapses on GCs, so the net effect of MCs on GCs – and therefore the output of the DG – is unclear. Here we first review fundamental information about MCs and the current hypotheses for their role in the normal DG and in diseases that involve the DG. Then we review previously published data which suggest that MCs are a source of input to a subset of GCs that are born in adulthood (adult-born GCs). In addition, we discuss the evidence that adult-born GCs may support the normal inhibitory ‘gate’ functions of the DG, where the GCs are a filter or gate for information from the entorhinal cortical input to area CA3. The implications are then discussed in the context of seizures and temporal lobe epilepsy (TLE). In TLE, it has been suggested that the DG inhibitory gate is weak or broken and MC loss leads to insufficient activation of inhibitory neurons, causing hyperexcitability. That idea was called the “dormant basket cell hypothesis.” Recent data suggest that loss of normal adult-born GCs may also cause disinhibition, and seizure susceptibility. Therefore, we propose a reconsideration of the dormant basket cell hypothesis with an intervening adult-born GC between the MC and basket cell and call this hypothesis the “dormant immature granule cell hypothesis.” PMID:26347618

  5. Effects of spaced learning in the water maze on development of dentate granule cells generated in adult mice.

    PubMed

    Trinchero, Mariela F; Koehl, Muriel; Bechakra, Malik; Delage, Pauline; Charrier, Vanessa; Grosjean, Noelle; Ladeveze, Elodie; Schinder, Alejandro F; Abrous, D Nora

    2015-11-01

    New dentate granule cells (GCs) are generated in the hippocampus throughout life. These adult-born neurons are required for spatial learning in the Morris water maze (MWM). In rats, spatial learning shapes the network by regulating their number and dendritic development. Here, we explored whether such modulatory effects exist in mice. New GCs were tagged using thymidine analogs or a GFP-expressing retrovirus. Animals were exposed to a reference memory protocol for 10-14 days (spaced training) at different times after newborn cells labeling. Cell proliferation, cell survival, cell death, neuronal phenotype, and dendritic and spine development were examined using immunohistochemistry. Surprisingly, spatial learning did not modify any of the parameters under scrutiny including cell number and dendritic morphology. These results suggest that although new GCs are required in mice for spatial learning in the MWM, they are, at least for the developmental intervals analyzed here, refractory to behavioral stimuli generated in the course of learning in the MWM. PMID:25740272

  6. Naringin attenuates granule cell dispersion in the dentate gyrus in a mouse model of temporal lobe epilepsy.

    PubMed

    Jang, Hannah; Jeong, Kyoung Hoon; Kim, Sang Ryong

    2016-07-01

    Morphological abnormalities of the dentate gyrus (DG) are an important phenotype in the hippocampus of patients with temporal lobe epilepsy. We recently reported that naringin, a bioflavonoid in grapefruit and citrus fruits, exerts beneficial effects in the kainic acid (KA) mouse model of epilepsy. We found that naringin treatment reduced seizure activities and decreased autophagic stress and neuroinflammation in the hippocampus following in vivo lesion with KA. However, it remains unclear whether naringin may also attenuate seizure-induced morphological changes in the DG, collectively known as granule cell dispersion (GCD). To clarify whether naringin treatment reduces GCD, we evaluated the effects of intraperitoneal injection of naringin on GCD and activation of mammalian target of rapamycin complex 1 (mTORC1), an important regulator of GCD, following intrahippocampal injection of KA. Our results showed that naringin treatment significantly reduced KA-induced GCD and mTORC1 activation, which was confirmed by assessing the phosphorylated form of the mTORC1 substrate, 4E-BP1, in the hippocampus. These results suggest that naringin treatment may help prevent epilepsy-induced hippocampal injury by inhibiting mTORC1 activation and thereby reducing GCD in the hippocampus in vivo. PMID:27040812

  7. The GABAA antagonist DPP-4-PIOL selectively antagonises tonic over phasic GABAergic currents in dentate gyrus granule cells.

    PubMed

    Boddum, Kim; Frølund, Bente; Kristiansen, Uffe

    2014-11-01

    GABAA receptors mediate two different types of inhibitory currents: phasic inhibitory currents when rapid and brief presynaptic GABA release activates postsynaptic GABAA receptors and tonic inhibitory currents generated by low extrasynaptic GABA levels, persistently activating extrasynaptic GABAA receptors. The two inhibitory current types are mediated by different subpopulations of GABAA receptors with diverse pharmacological profiles. Selective antagonism of tonic currents is of special interest as excessive tonic inhibition post-stroke has severe pathological consequences. Here we demonstrate that phasic and tonic GABAA receptor currents can be selectively inhibited by the antagonists SR 95531 and the 4-PIOL derivative, 4-(3,3-diphenylpropyl)-5-(4-piperidyl)-3-isoxazolol hydrobromide (DPP-4-PIOL), respectively. In dentate gyrus granule cells, SR 95531 was found approximately 4 times as potent inhibiting phasic currents compared to tonic currents (IC50 values: 101 vs. 427 nM). Conversely, DPP-4-PIOL was estimated to be more than 20 times as potent inhibiting tonic current compared to phasic current (IC50 values: 0.87 vs. 21.3 nM). Consequently, we were able to impose a pronounced reduction in tonic GABA mediated current (>70 %) by concentrations of DPP-4-PIOL, at which no significant effect on the phasic current was seen. Our findings demonstrate that selective inhibition of GABA mediated tonic current is possible, when targeting a subpopulation of GABAA receptors located extrasynaptically using the antagonist, DPP-4-PIOL. PMID:25103229

  8. Selective silencing of individual dendritic branches by an mGlu2-activated potassium conductance in dentate gyrus granule cells

    PubMed Central

    Brunner, János; Ster, Jeanne; Van-Weert, Susan; Andrási, Tibor; Neubrandt, Máté; Corti, Corrado; Corsi, Mauro; Ferraguti, Francesco; Gerber, Urs; Szabadics, János

    2013-01-01

    Group II metabotropic glutamate receptors (mGlu-IIs) modulate hippocampal information processing through several presynaptic actions. We describe a novel postsynaptic inhibitory mechanism mediated by the mGlu2 subtype that activates an inwardly-rectifying potassium conductance in the dendrites of dentate gyrus granule cells (GCs) of rats and mice. Data from glutamate uncaging experiments and simulations indicate that the mGlu2-activated potassium conductance uniformly reduces the peak amplitude of synaptic inputs arriving in the distal two-thirds of dendrites with only minor effects on proximal inputs. This unique shunting profile is consistent with a peak expression of the mGlu2-activated conductance at the transition between the proximal and middle third of the dendrites. Further simulations under various physiologically relevant conditions show that when a shunting conductance is activated in the proximal third of a single dendrite it effectively modulates input to this specific branch while leaving inputs in neighboring dendrites relatively unaffected. Thus, the restricted expression of the mGlu2-activated potassium conductance in the proximal third of GC dendrites represents an optimal localization for achieving the opposing biophysical requirements for uniform yet selective modulation of individual dendritic branches. PMID:23616537

  9. Bidirectional modulation of GABAergic transmission by cholecystokinin in hippocampal dentate gyrus granule cells of juvenile rats

    PubMed Central

    Deng, Pan-Yue; Lei, Saobo

    2006-01-01

    Cholecystokinin (CCK) interacts with two types of G protein-coupled receptors in the brain: CCK-A and CCK-B receptors. Both CCK and CCK-B receptors are widely distributed in the hippocampal formation, but the functions of CCK there have been poorly understood. In the present study, we initially examined the effects of CCK on GABAA receptor-mediated synaptic transmission in the hippocampal formation and then explored the underlying cellular mechanisms by focusing on the dentate gyrus region, where the highest levels of CCK-binding sites have been detected. Our results indicate that activation of CCK-B receptors initially and transiently increased spontaneous IPSC (sIPSC) frequency, followed by a persistent reduction. The effects of CCK were more evident in juvenile rats, suggesting that they are developmentally regulated. Cholecystokinin failed to modulate the miniature IPSCs recorded in the presence of TTX and the amplitude of the evoked IPSCs, but produced a transient increase followed by a reduction in action potential firing frequency recorded from GABAergic interneurons, suggesting that CCK acts by modulating the excitability of the interneurons to regulate GABA release. Cholecystokinin reduced the amplitude of the after-hyperpolarization of the action potentials, and application of paxilline or charybdotoxin considerably reduced CCK-mediated modulation of sIPSC frequency, suggesting that the effects of CCK are related to the inhibition of Ca2+-activated K+ currents (IK(Ca)). The effects of CCK were independent of the functions of phospholipase C, intracellular Ca2+ release, protein kinase C or phospholipase A2, suggesting a direct coupling between the G proteins of CCK-B receptors and IK(Ca). Our results provide a novel mechanism underlying CCK-mediated modulation of GABA release. PMID:16455686

  10. Naringenin ameliorates kainic acid-induced morphological alterations in the dentate gyrus in a mouse model of temporal lobe epilepsy.

    PubMed

    Park, Jungha; Jeong, Kyoung Hoon; Shin, Won-Ho; Bae, Young-Seuk; Jung, Un Ju; Kim, Sang Ryong

    2016-10-19

    Granule cell dispersion (GCD) in the dentate gyrus (DG) of the hippocampus is a morphological alteration characteristic of temporal lobe epilepsy. Recently, we reported that treatment with naringin, a flavonoid found in grapefruit and citrus fruits, reduced spontaneous recurrent seizures by inhibiting kainic acid (KA)-induced GCD and neuronal cell death in mouse hippocampus, suggesting that naringin might have beneficial effects for preventing epileptic events in the adult brain. However, it is still unclear whether the beneficial effects of naringin treatment are mediated by the metabolism of naringin into naringenin in the KA-treated hippocampus. To investigate this possibility, we evaluated whether intraperitoneal injections of naringenin could mimic naringin-induced effects against GCD caused by intrahippocampal KA injections in mice. Our results showed that treatment with naringenin delayed the onset of KA-induced seizures and attenuated KA-induced GCD by inhibiting activation of the mammalian target of rapamycin complex 1 in both neurons and reactive astrocytes in the DG. In addition, its administration attenuated the production of proinflammatory cytokines such as tumor necrosis tumor necrosis factor-α (TNFα) and interleukin-1β (IL-1β) from microglial activation in the DG following KA treatment. These results suggest that naringenin may be an active metabolite of naringin and help prevent the progression of epileptic insults in the hippocampus in vivo; therefore, naringenin may be a beneficial metabolite of naringin for the treatment of epilepsy. PMID:27584687

  11. Interactions between Inhibitory Interneurons and Excitatory Associational Circuitry in Determining Spatio-Temporal Dynamics of Hippocampal Dentate Granule Cells: A Large-Scale Computational Study

    PubMed Central

    Hendrickson, Phillip J.; Yu, Gene J.; Song, Dong; Berger, Theodore W.

    2015-01-01

    This paper reports on findings from a million-cell granule cell model of the rat dentate gyrus that was used to explore the contributions of local interneuronal and associational circuits to network-level activity. The model contains experimentally derived morphological parameters for granule cells, which each contain approximately 200 compartments, and biophysical parameters for granule cells, basket cells, and mossy cells that were based both on electrophysiological data and previously published models. Synaptic input to cells in the model consisted of glutamatergic AMPA-like EPSPs and GABAergic-like IPSPs from excitatory and inhibitory neurons, respectively. The main source of input to the model was from layer II entorhinal cortical neurons. Network connectivity was constrained by the topography of the system, and was derived from axonal transport studies, which provided details about the spatial spread of axonal terminal fields, as well as how subregions of the medial and lateral entorhinal cortices project to subregions of the dentate gyrus. Results of this study show that strong feedback inhibition from the basket cell population can cause high-frequency rhythmicity in granule cells, while the strength of feedforward inhibition serves to scale the total amount of granule cell activity. Results furthermore show that the topography of local interneuronal circuits can have just as strong an impact on the development of spatio-temporal clusters in the granule cell population as the perforant path topography does, both sharpening existing clusters and introducing new ones with a greater spatial extent. Finally, results show that the interactions between the inhibitory and associational loops can cause high frequency oscillations that are modulated by a low-frequency oscillatory signal. These results serve to further illustrate the importance of topographical constraints on a global signal processing feature of a neural network, while also illustrating how rich

  12. Analysis of current fluctuations during after-hyperpolarization current in dentate granule neurones of the rat hippocampus.

    PubMed Central

    Valiante, T A; Abdul-Ghani, M A; Carlen, P L; Pennefather, P

    1997-01-01

    1. We have studied macroscopic current fluctuations associated with the after-hyperpolarization current (IAHP) that follows a 200 ms voltage-clamp step to 0 mV in dentate granule (DG) neurones of the rat hippocampus. This maximally effective stimulus produced a peak IAHP of 205 +/- 20 pA. Background noise was minimized by using the whole-cell single-electrode voltage-clamp configuration. 2. Conventional current-variance analysis was performed on IAHP to obtain estimates of the unitary AHP channel current (i) and the maximal attainable AHP current (Imax). A second approach, utilizing changes in the power spectrum of IAHP 'noise' during the decay of IAHP, was employed to yield an independent estimate of Imax as well as an estimate of the mean open-state duration of AHP channels. 3. Changes in the power spectrum during IAHP decay revealed that the mean channel open time is fixed at 6.9 +/- 0.5 ms and that the decay is due to changes in channel closed-state duration. The same analysis gave a value for Imax of 320 +/- 20 pA (n = 7). 4. Current-variance analysis suggests that channels responsible for generation of IAHP have a unitary current of 0.29 +/- 0.08 pA at -45 mV in 5 mM extracellular potassium and an Imax of 400 +/- 180 (n = 7). Thus, both methods indicate that about 1200 channels are available to generate IAHP in DG neurones and that about 60% are open at the peak of a maximal IAHP. 5. Computer simulations of IAHP currents in a model neurone show that dendritic current sources will result in an underestimation of i while Imax is underestimated to a lesser extent. Estimates of Imax obtained from power-spectrum analysis are more accurate and less affected by neuronal electrotonic structure than estimates of Imax based on current-variance analysis. PMID:9061644

  13. Profilin 1 Associates with Stress Granules and ALS-Linked Mutations Alter Stress Granule Dynamics

    PubMed Central

    Figley, Matthew D.; Bieri, Gregor; Kolaitis, Regina-Maria; Taylor, J. Paul

    2014-01-01

    Mutations in the PFN1 gene encoding profilin 1 are a rare cause of familial amyotrophic lateral sclerosis (ALS). Profilin 1 is a well studied actin-binding protein but how PFN1 mutations cause ALS is unknown. The budding yeast, Saccharomyces cerevisiae, has one PFN1 ortholog. We expressed the ALS-linked profilin 1 mutant proteins in yeast, demonstrating a loss of protein stability and failure to restore growth to profilin mutant cells, without exhibiting gain-of-function toxicity. This model provides for simple and rapid screening of novel ALS-linked PFN1 variants. To gain insight into potential novel roles for profilin 1, we performed an unbiased, genome-wide synthetic lethal screen with yeast cells lacking profilin (pfy1Δ). Unexpectedly, deletion of several stress granule and processing body genes, including pbp1Δ, were found to be synthetic lethal with pfy1Δ. Mutations in ATXN2, the human ortholog of PBP1, are a known ALS genetic risk factor and ataxin 2 is a stress granule component in mammalian cells. Given this genetic interaction and recent evidence linking stress granule dynamics to ALS pathogenesis, we hypothesized that profilin 1 might also associate with stress granules. Here we report that profilin 1 and related protein profilin 2 are novel stress granule-associated proteins in mouse primary cortical neurons and in human cell lines and that ALS-linked mutations in profilin 1 alter stress granule dynamics, providing further evidence for the potential role of stress granules in ALS pathogenesis. PMID:24920614

  14. Alterations in miRNA Levels in the Dentate Gyrus in Epileptic Rats

    PubMed Central

    Bot, Anna Maria; Dębski, Konrad Józef; Lukasiuk, Katarzyna

    2013-01-01

    The aim of this study was to characterize changes in miRNA expression in the epileptic dentate gyrus. Status epilepticus evoked by amygdala stimulation was used to induce epilepsy in rats. The dentate gyri were isolated at 7 d, 14 d, 30 d and 90 d after stimulation (n=5). Sham-operated time-matched controls were prepared for each time point (n=5). The miRNA expression was evaluated using Exiqon microarrays. Additionally, mRNA from the same animals was profiled using Affymetrix microarrays. We detected miRNA expression signatures that differentiate between control and epileptic animals. Significant changes in miRNA expression between stimulated and sham operated animals were observed at 7 and 30 d following stimulation. Moreover, we found that there are ensembles of miRNAs that change expression levels over time. Analysis of the mRNA expression from the same animals revealed that the expression of several mRNAs that are potential targets for miRNA with altered expression level is regulated in the expected direction. The functional characterization of miRNAs and their potential mRNA targets indicate that miRNA can participate in several molecular events that occur in epileptic tissue, including immune response and neuronal plasticity. This is the first report on changes in the expression of miRNA and the potential functional impact of these changes in the dentate gyrus of epileptic animals. Complex changes in the expression of miRNAs suggest an important role for miRNA in the molecular mechanisms of epilepsy. PMID:24146813

  15. Ectopic Expression of α6 and δ GABAA Receptor Subunits in Hilar Somatostatin Neurons Increases Tonic Inhibition and Alters Network Activity in the Dentate Gyrus

    PubMed Central

    Tong, Xiaoping; Peng, Zechun; Zhang, Nianhui; Cetina, Yliana; Huang, Christine S.; Wallner, Martin; Otis, Thomas S.

    2015-01-01

    The role of GABAA receptor (GABAAR)-mediated tonic inhibition in interneurons remains unclear and may vary among subgroups. Somatostatin (SOM) interneurons in the hilus of the dentate gyrus show negligible expression of nonsynaptic GABAAR subunits and very low tonic inhibition. To determine the effects of ectopic expression of tonic GABAAR subtypes in these neurons, Cre-dependent viral vectors were used to express GFP-tagged GABAAR subunits (α6 and δ) selectively in hilar SOM neurons in SOM-Cre mice. In single-transfected animals, immunohistochemistry demonstrated strong expression of either the α6 or δ subunit; in cotransfected animals, both subunits were consistently expressed in the same neurons. Electrophysiology revealed a robust increase of tonic current, with progressively larger increases following transfection of δ, α6, and α6/δ subunits, respectively, indicating formation of functional receptors in all conditions and likely coassembly of the subunits in the same receptor following cotransfection. An in vitro model of repetitive bursting was used to determine the effects of increased tonic inhibition in hilar SOM interneurons on circuit activity in the dentate gyrus. Upon cotransfection, the frequency of GABAAR-mediated bursting in granule cells was reduced, consistent with a reduction in synchronous firing among hilar SOM interneurons. Moreover, in vivo studies of Fos expression demonstrated reduced activation of α6/δ-cotransfected neurons following acute seizure induction by pentylenetetrazole. The findings demonstrate that increasing tonic inhibition in hilar SOM interneurons can alter dentate gyrus circuit activity during strong stimulation and suggest that tonic inhibition of interneurons could play a role in regulating excessive synchrony within the network. SIGNIFICANCE STATEMENT In contrast to many hippocampal interneurons, somatostatin (SOM) neurons in the hilus of the dentate gyrus have very low levels of nonsynaptic GABAARs and exhibit

  16. The expression of GABAA beta subunit isoforms in synaptic and extrasynaptic receptor populations of mouse dentate gyrus granule cells.

    PubMed

    Herd, Murray B; Haythornthwaite, Alison R; Rosahl, Thomas W; Wafford, Keith A; Homanics, Gregg E; Lambert, Jeremy J; Belelli, Delia

    2008-02-15

    The subunit composition of GABA(A) receptors influences their biophysical and pharmacological properties, dictates neuronal location and the interaction with associated proteins, and markedly influences the impact of intracellular biochemistry. The focus has been on alpha and gamma subunits, with little attention given to beta subunits. Dentate gyrus granule cells (DGGCs) express all three beta subunit isoforms and exhibit both synaptic and extrasynaptic receptors that mediate 'phasic' and 'tonic' transmission, respectively. To investigate the subcellular distribution of the beta subunits we have utilized the patch-clamp technique to compare the properties of 'tonic' and miniature inhibitory postsynaptic currents (mIPSCs) recorded from DGGCs of hippocampal slices of P20-26 wild-type (WT), beta(2)(-/-), beta(2N265S) (etomidate-insensitive), alpha(1)(-/-) and delta(-/-) mice. Deletion of either the beta(2) or the delta subunit produced a significant reduction of the tonic current and attenuated the increase of this current induced by the delta subunit-preferring agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP). By contrast, mIPSCs were not influenced by deletion of these genes. Enhancement of the tonic current by the beta(2/3) subunit-selective agent etomidate was significantly reduced for DGGCs derived from beta(2N265S) mice, whereas this manipulation had no effect on the prolongation of mIPSCs produced by this anaesthetic. Collectively, these observations, together with previous studies on alpha(4)(-/-) mice, identify a population of extrasynaptic alpha(4)beta(2)delta receptors, whereas synaptic GABA(A) receptors appear to primarily incorporate the beta(3) subunit. A component of the tonic current is diazepam sensitive and is mediated by extrasynaptic receptors incorporating alpha(5) and gamma(2) subunits. Deletion of the beta(2) subunit had no effect on the diazepam-induced current and therefore these extrasynaptic receptors do not contain this

  17. Quantitative and morphological analysis of dentate granule cells with recurrent basal dendrites from normal and epileptic rats.

    PubMed

    Dashtipour, Khashayar; Yan, Xiao-Xin; Dinh, Trinh T; Okazaki, Maxine M; Nadler, J Victor; Ribak, Charles E

    2002-01-01

    Granule cells with recurrent basal dendrites (RBDs) were previously reported in both control and epileptic rats. RBDs are dendrites that arise from the basal half of granule cell bodies and curve toward and extend into the molecular layer. They are increased in frequency in the pilocarpine model of epilepsy. The present study was undertaken to analyze the distribution and morphology of granule cells with RBDs and the synaptic connections of RBDs. Granule cells were labeled by retrograde transport of biocytin. Those with an RBD were found throughout the granule cell layer, but were most numerous at the hilar border. The morphology of these cells varied in the different depths of the granule cell layer; the angle of their cell body's long axis was mainly vertical at the hilar margin, and changed to virtually horizontal close to the molecular layer border. Quantitative data on the distribution of granule cells with RBDs and the angle of the cell body's long axis confirmed these descriptions. At the electron microscopic level, RBDs showed the typical features of dendrites and formed numerous axodendritic and axospinous synapses with labeled and unlabeled axon terminals. These results showed that RBDs of granule cells from epileptic rats are postsynaptic to axon terminals, including mossy fibers, and thus are involved in a similar synaptic circuitry as apical dendrites of granule cells from these animals. PMID:12000120

  18. Complementary functions of SK and Kv7/M potassium channels in excitability control and synaptic integration in rat hippocampal dentate granule cells

    PubMed Central

    Mateos-Aparicio, Pedro; Murphy, Ricardo; Storm, Johan F

    2014-01-01

    The dentate granule cells (DGCs) form the most numerous neuron population of the hippocampal memory system, and its gateway for cortical input. Yet, we have only limited knowledge of the intrinsic membrane properties that shape their responses. Since SK and Kv7/M potassium channels are key mechanisms of neuronal spiking and excitability control, afterhyperpolarizations (AHPs) and synaptic integration, we studied their functions in DGCs. The specific SK channel blockers apamin or scyllatoxin increased spike frequency (excitability), reduced early spike frequency adaptation, fully blocked the medium-duration AHP (mAHP) after a single spike or spike train, and increased postsynaptic EPSP summation after spiking, but had no effect on input resistance (Rinput) or spike threshold. In contrast, blockade of Kv7/M channels by XE991 increased Rinput, lowered the spike threshold, and increased excitability, postsynaptic EPSP summation, and EPSP–spike coupling, but only slightly reduced mAHP after spike trains (and not after single spikes). The SK and Kv7/M channel openers 1-EBIO and retigabine, respectively, had effects opposite to the blockers. Computational modelling reproduced many of these effects. We conclude that SK and Kv7/M channels have complementary roles in DGCs. These mechanisms may be important for the dentate network function, as CA3 neurons can be activated or inhibition recruited depending on DGC firing rate. PMID:24366266

  19. Reliable Genetic Labeling of Adult-Born Dentate Granule Cells Using Ascl1CreERT2 and GlastCreERT2 Murine Lines

    PubMed Central

    Yang, Sung M.; Alvarez, Diego D.

    2015-01-01

    Newly generated dentate granule cells (GCs) are relevant for input discrimination in the adult hippocampus. Yet, their precise contribution to information processing remains unclear. To address this question, it is essential to develop approaches to precisely label entire cohorts of adult-born GCs. In this work, we used genetically modified mice to allow conditional expression of tdTomato (Tom) in adult-born GCs and characterized their development and functional integration. Ascl1CreERT2;CAGfloxStopTom and GlastCreERT2;CAGfloxStopTom mice resulted in indelible expression of Tom in adult neural stem cells and their lineage upon tamoxifen induction. Whole-cell recordings were performed to measure intrinsic excitability, firing behavior, and afferent excitatory connectivity. Developing GCs were also staged by the expression of early and late neuronal markers. The slow development of adult-born GCs characterized here is consistent with previous reports using retroviral approaches that have revealed that a mature phenotype is typically achieved after 6–8 weeks. Our findings demonstrate that Ascl1CreERT2 and GlastCreERT2 mouse lines enable simple and reliable labeling of adult-born GC lineages within restricted time windows. Therefore, these mice greatly facilitate tagging new neurons and manipulating their activity, required for understanding adult neurogenesis in the context of network remodeling, learning, and behavior. SIGNIFICANCE STATEMENT Our study shows that Ascl1CreERT2 and GlastCreERT2 mice lines can be used to label large cohorts of adult-born dentate granule cells with excellent time resolution. Neurons labeled in this manner display developmental and functional profiles that are in full agreement with previous findings using thymidine analogs and retroviral labeling, thus providing an alternative approach to tackle fundamental questions on circuit remodeling. Because of the massive neuronal targeting and the simplicity of this method, genetic labeling will

  20. Acute effects of electro-acupuncture (EA) on hippocampal long term potentiation (LTP) of perforant path-dentate gyrus granule cells synapse related to memory.

    PubMed

    He, Xiaokuo; Yan, Tiebin; Chen, Rongfa; Ran, Dongzhi

    2012-01-01

    Acupuncture, a traditional Chinese therapeutic method, has been widely used in clinical practice to treat diseases such as stroke, Bell's palsy, Alzheimer disease, Parkinson diseases, dysmenorrhea and chronic pain. Mounting lab data had suggested that electro-acupuncture could alleviate dementia and restore long term potentiation of hippocampus in rat. Clinical data also indicated that electro-acupuncture could improve electrical activity of brain in vascular dementia patients. However, its biological basis and acute effects on hippocampal long term potentiation (LTP) remain not well understood. Therefore, we sought to investigate whether acute electro-acupuncture (acupoints: ST36 and SP6; continuous wave, 2 mV, 2Hz; lasted 20 min) could enhance LTP of perforant path-dentate gyrus granule cells in anesthetized rat and explore its underlying mechanisms. We found that electro-acupuncture could significantly increase PS2/PS 1 in pair pulse test (P <0.05, inter-pulse interval: 20ms and 90ms). When compared to control group, electro-acupuncture could significantly enhance LTP to about 234% which was about 143% of that in control group (P <0.05). It suggested that electro-acupuncture could modulate the function of interneurons in hippocampus hence increase LTP. PMID:23156202

  1. Isolation Rearing Reduces Neuronal Excitability in Dentate Gyrus Granule Cells of Adolescent C57BL/6J Mice: Role of GABAergic Tonic Currents and Neurosteroids.

    PubMed

    Talani, Giuseppe; Biggio, Francesca; Licheri, Valentina; Locci, Valentina; Biggio, Giovanni; Sanna, Enrico

    2016-01-01

    Early-life exposure to stress, by impacting on a brain still under development, is considered a critical factor for the increased vulnerability to psychiatric disorders and abuse of psychotropic substances during adulthood. As previously reported, rearing C57BL/6J weanling mice in social isolation (SI) from their peers for several weeks, a model of prolonged stress, is associated with a decreased plasma and brain levels of neuroactive steroids such as 3α,5α-THP, with a parallel up-regulation of extrasynaptic GABAA receptors (GABAAR) in dentate gyrus (DG) granule cells compared to group-housed (GH) mice. In the present study, together with the SI-induced decrease in plasma concentration of both progesterone and 3α,5α-THP, and an increase in THIP-stimulated GABAergic tonic currents, patch-clamp analysis of DG granule cells revealed a significant decrease in membrane input resistance and action potential (AP) firing rate, in SI compared to GH mice, suggesting that SI exerts an inhibitory action on neuronal excitability of these neurons. Voltage-clamp recordings of glutamatergic spontaneous excitatory postsynaptic currents (sEPSCs) revealed a SI-associated decrease in frequency as well as a shift from paired-pulse (PP) depression to PP facilitation (PPF) of evoked EPSCs, indicative of a reduced probability of glutamate release. Daily administration of progesterone during isolation reverted the changes in plasma 3α,5α-THP as well as in GABAergic tonic currents and neuronal excitability caused by SI, but it had only a limited effect on the changes in the probability of presynaptic glutamate release. Overall, the results obtained in this work, together with those previously published, indicate that exposure of mice to SI during adolescence reduces neuronal excitability of DG granule cells, an effect that may be linked to the increased GABAergic tonic currents as a consequence of the sustained decrease in plasma and hippocampal levels of neurosteroids. All these

  2. Isolation Rearing Reduces Neuronal Excitability in Dentate Gyrus Granule Cells of Adolescent C57BL/6J Mice: Role of GABAergic Tonic Currents and Neurosteroids

    PubMed Central

    Talani, Giuseppe; Biggio, Francesca; Licheri, Valentina; Locci, Valentina; Biggio, Giovanni; Sanna, Enrico

    2016-01-01

    Early-life exposure to stress, by impacting on a brain still under development, is considered a critical factor for the increased vulnerability to psychiatric disorders and abuse of psychotropic substances during adulthood. As previously reported, rearing C57BL/6J weanling mice in social isolation (SI) from their peers for several weeks, a model of prolonged stress, is associated with a decreased plasma and brain levels of neuroactive steroids such as 3α,5α-THP, with a parallel up-regulation of extrasynaptic GABAA receptors (GABAAR) in dentate gyrus (DG) granule cells compared to group-housed (GH) mice. In the present study, together with the SI-induced decrease in plasma concentration of both progesterone and 3α,5α-THP, and an increase in THIP-stimulated GABAergic tonic currents, patch-clamp analysis of DG granule cells revealed a significant decrease in membrane input resistance and action potential (AP) firing rate, in SI compared to GH mice, suggesting that SI exerts an inhibitory action on neuronal excitability of these neurons. Voltage-clamp recordings of glutamatergic spontaneous excitatory postsynaptic currents (sEPSCs) revealed a SI-associated decrease in frequency as well as a shift from paired-pulse (PP) depression to PP facilitation (PPF) of evoked EPSCs, indicative of a reduced probability of glutamate release. Daily administration of progesterone during isolation reverted the changes in plasma 3α,5α-THP as well as in GABAergic tonic currents and neuronal excitability caused by SI, but it had only a limited effect on the changes in the probability of presynaptic glutamate release. Overall, the results obtained in this work, together with those previously published, indicate that exposure of mice to SI during adolescence reduces neuronal excitability of DG granule cells, an effect that may be linked to the increased GABAergic tonic currents as a consequence of the sustained decrease in plasma and hippocampal levels of neurosteroids. All these

  3. Alteration of the langerin oligomerization state affects Birbeck granule formation.

    PubMed

    Chabrol, Eric; Thépaut, Michel; Dezutter-Dambuyant, Colette; Vivès, Corinne; Marcoux, Julien; Kahn, Richard; Valladeau-Guilemond, Jenny; Vachette, Patrice; Durand, Dominique; Fieschi, Franck

    2015-02-01

    Langerin, a trimeric C-type lectin specifically expressed in Langerhans cells, has been reported to be a pathogen receptor through the recognition of glycan motifs by its three carbohydrate recognition domains (CRD). In the context of HIV-1 (human immunodeficiency virus-1) transmission, Langerhans cells of genital mucosa play a protective role by internalizing virions in Birbeck Granules (BG) for elimination. Langerin (Lg) is directly involved in virion binding and BG formation through its CRDs. However, nothing is known regarding the mechanism of langerin assembly underlying BG formation. We investigated at the molecular level the impact of two CRD mutations, W264R and F241L, on langerin structure, function, and BG assembly using a combination of biochemical and biophysical approaches. Although the W264R mutation causes CRD global unfolding, the F241L mutation does not affect the overall structure and gp120 (surface HIV-1 glycoprotein of 120 kDa) binding capacities of isolated Lg-CRD. In contrast, this mutation induces major functional and structural alterations of the whole trimeric langerin extracellular domain (Lg-ECD). As demonstrated by small-angle x-ray scattering comparative analysis of wild-type and mutant forms, the F241L mutation perturbs the oligomerization state and the global architecture of Lg-ECD. Correlatively, despite conserved intrinsic lectin activity of the CRD, avidity property of Lg-ECD is affected as shown by a marked decrease of gp120 binding. Beyond the change of residue itself, the F241L mutation induces relocation of the K200 side chain also located within the interface between protomers of trimeric Lg-ECD, thereby explaining the defective oligomerization of mutant Lg. We conclude that not only functional CRDs but also their correct spatial presentation are critical for BG formation as well as gp120 binding. PMID:25650933

  4. Physical exercise prevents stress-induced activation of granule neurons and enhances local inhibitory mechanisms in the dentate gyrus.

    PubMed

    Schoenfeld, Timothy J; Rada, Pedro; Pieruzzini, Pedro R; Hsueh, Brian; Gould, Elizabeth

    2013-05-01

    Physical exercise is known to reduce anxiety. The ventral hippocampus has been linked to anxiety regulation but the effects of running on this subregion of the hippocampus have been incompletely explored. Here, we investigated the effects of cold water stress on the hippocampus of sedentary and runner mice and found that while stress increases expression of the protein products of the immediate early genes c-fos and arc in new and mature granule neurons in sedentary mice, it has no such effect in runners. We further showed that running enhances local inhibitory mechanisms in the hippocampus, including increases in stress-induced activation of hippocampal interneurons, expression of vesicular GABA transporter (vGAT), and extracellular GABA release during cold water swim stress. Finally, blocking GABAA receptors in the ventral hippocampus, but not the dorsal hippocampus, with the antagonist bicuculline, reverses the anxiolytic effect of running. Together, these results suggest that running improves anxiety regulation by engaging local inhibitory mechanisms in the ventral hippocampus. PMID:23637169

  5. The terpenoids Myrtenol and Verbenol act on δ subunit-containing GABAA receptors and enhance tonic inhibition in dentate gyrus granule cells.

    PubMed

    van Brederode, Johannes; Atak, Sinem; Kessler, Artur; Pischetsrieder, Monika; Villmann, Carmen; Alzheimer, Christian

    2016-08-15

    Sideritis plants and their extracts have been used in traditional medicine as sedatives, anxiolytics and anticonvulsant agents. Pinenes are the most prevalent of the volatile aroma components in Siderites extracts and the pinene metabolites myrtenol and verbenol have been identified as the most potent positive allosteric modulators of synaptic GABAA receptors composed of α1β2 and α1β2γ2 subunits. In view of their therapeutic spectrum, we wondered whether these two terpenoids would also augment tonic GABA currents mediated by extrasynaptic GABAA receptors containing the δ subunit. When we expressed α4β2δ receptors in HEK293 cells, we found that co-application of myrtenol or verbenol enhanced whole-cell current responses to GABA by up to 100%. Consistent with their effects on heterologous α1β2γ2 receptors, we found that myrtenol and verbenol, when co-applied with GABA via local perfusion, increased the amplitude and area of miniature inhibitory postsynaptic potentials (mIPSCs) recorded in whole-cell voltage-clamp recordings from granule cells in the dentate gyrus of mouse hippocampal brain slices. In addition, co-application of terpenoids with GABA was also able to enhance tonic GABA current, measured from the change in baseline current and current noise, compared to GABA perfusion alone. Our results suggest that myrtenol and verbenol act as positive allosteric modulators at synaptic and extrasynaptic GABAA receptors, thereby augmenting phasic and tonic GABAergic inhibition. Thus, our study reveals an important pharmacological and therapeutic target of bicyclic monoterpenoids. PMID:27312536

  6. Increased expression of axogenesis-related genes and mossy fibre length in dentate granule cells from adult HuD overexpressor mice.

    PubMed

    Perrone-Bizzozero, Nora I; Tanner, Daniel C; Mounce, Joanna; Bolognani, Federico

    2011-01-01

    The neuronal RNA-binding protein HuD plays a critical role in the post-transcriptional regulation of short-lived mRNAs during the initial establishment and remodelling of neural connections. We have generated transgenic mice overexpressing this protein (HuD-Tg) in adult DGCs (dentate granule cells) and shown that their mossy fibres contain high levels of GAP-43 (growth-associated protein 43) and exhibit distinct morphological and electrophysiological properties. To investigate the basis for these changes and identify other molecular targets of HuD, DGCs from HuD-Tg and control mice were collected by LCM (laser capture microscopy) and RNAs analysed using DNA microarrays. Results show that 216 known mRNAs transcripts and 63 ESTs (expressed sequence tags) are significantly up-regulated in DGCs from these transgenic mice. Analyses of the 3'-UTRs (3'-untranslated regions) of these transcripts revealed an increased number of HuD-binding sites and the presence of several known instability-conferring sequences. Among these, the mRNA for TTR (transthyretin) shows the highest level of up-regulation, as confirmed by qRT-PCR (quantitative reverse transcription-PCR) and ISH (in situ hybridization). GO (gene ontology) analyses of up-regulated transcripts revealed a large over-representation of genes associated with neural development and axogenesis. In correlation with these gene expression changes, we found an increased length of the infrapyramidal mossy fibre bundle in HuD-Tg mice. These results support the notion that HuD stabilizes a number of developmentally regulated mRNAs in DGCs, resulting in increased axonal elongation. PMID:22004431

  7. Calcium permeable AMPA receptor-dependent long lasting plasticity of intrinsic excitability in fast spiking interneurons of the dentate gyrus decreases inhibition in the granule cell layer.

    PubMed

    Dasgupta, Debanjan; Sikdar, Sujit Kumar

    2015-03-01

    The local fast-spiking interneurons (FSINs) are considered to be crucial for the generation, maintenance, and modulation of neuronal network oscillations especially in the gamma frequency band. Gamma frequency oscillations have been associated with different aspects of behavior. But the prolonged effects of gamma frequency synaptic activity on the FSINs remain elusive. Using whole cell current clamp patch recordings, we observed a sustained decrease of intrinsic excitability in the FSINs of the dentate gyrus (DG) following repetitive stimulations of the mossy fibers at 30 Hz (gamma bursts). Surprisingly, the granule cells (GCs) did not express intrinsic plastic changes upon similar synaptic excitation of their apical dendritic inputs. Interestingly, pairing the gamma bursts with membrane hyperpolarization accentuated the plasticity in FSINs following the induction protocol, while the plasticity attenuated following gamma bursts paired with membrane depolarization. Paired pulse ratio measurement of the synaptic responses did not show significant changes during the experiments. However, the induction protocols were accompanied with postsynaptic calcium rise in FSINs. Interestingly, the maximum and the minimum increase occurred during gamma bursts with membrane hyperpolarization and depolarization respectively. Including a selective blocker of calcium-permeable AMPA receptors (CP-AMPARs) in the bath; significantly attenuated the calcium rise and blocked the membrane potential dependence of the calcium rise in the FSINs, suggesting their involvement in the observed phenomenon. Chelation of intracellular calcium, blocking HCN channel conductance or blocking CP-AMPARs during the experiment forbade the long lasting expression of the plasticity. Simultaneous dual patch recordings from FSINs and synaptically connected putative GCs confirmed the decreased inhibition in the GCs accompanying the decreased intrinsic excitability in the FSINs. Experimentally constrained network

  8. Regulation of action potential delays via voltage-gated potassium Kv1.1 channels in dentate granule cells during hippocampal epilepsy

    PubMed Central

    Kirchheim, Florian; Tinnes, Stefanie; Haas, Carola A.; Stegen, Michael; Wolfart, Jakob

    2013-01-01

    Action potential (AP) responses of dentate gyrus granule (DG) cells have to be tightly regulated to maintain hippocampal function. However, which ion channels control the response delay of DG cells is not known. In some neuron types, spike latency is influenced by a dendrotoxin (DTX)-sensitive delay current (ID) mediated by unidentified combinations of voltage-gated K+ (Kv) channels of the Kv1 family Kv1.1–6. In DG cells, the ID has not been characterized and its molecular basis is unknown. The response phenotype of mature DG cells is usually considered homogenous but intrinsic plasticity likely occurs in particular in conditions of hyperexcitability, for example during temporal lobe epilepsy (TLE). In this study, we examined response delays of DG cells and underlying ion channel molecules by employing a combination of gramicidin-perforated patch-clamp recordings in acute brain slices and single-cell reverse transcriptase quantitative polymerase chain reaction (SC RT-qPCR) experiments. An in vivo mouse model of TLE consisting of intrahippocampal kainate (KA) injection was used to examine epilepsy-related plasticity. Response delays of DG cells were DTX-sensitive and strongly increased in KA-injected hippocampi; Kv1.1 mRNA was elevated 10-fold, and the response delays correlated with Kv1.1 mRNA abundance on the single cell level. Other Kv1 subunits did not show overt changes in mRNA levels. Kv1.1 immunolabeling was enhanced in KA DG cells. The biophysical properties of ID and a delay heterogeneity within the DG cell population was characterized. Using organotypic hippocampal slice cultures (OHCs), where KA incubation also induced ID upregulation, the homeostatic reversibility and neuroprotective potential for DG cells were tested. In summary, the AP timing of DG cells is effectively controlled via scaling of Kv1.1 subunit transcription. With this antiepileptic mechanism, DG cells delay their responses during hyperexcitation. PMID:24367293

  9. Housing Complexity Alters GFAP-Immunoreactive Astrocyte Morphology in the Rat Dentate Gyrus

    PubMed Central

    Salois, Garrick; Smith, Jeffrey S.

    2016-01-01

    Rats used in research are typically housed singly in cages with limited sensory stimulation. There is substantial evidence that housing rats in these conditions lead to numerous neuroanatomical and behavioral abnormalities. Alternatively, rats can be housed in an enriched environment in which rats are housed in groups and given room for exercise and exploration. Enriched environments result in considerable neuroplasticity in the rodent brain. In the dentate gyrus of the hippocampus, enriched environments evoke especially profound neural changes, including increases in the number of neurons and the number of dendritic spines. However, whether changes in astrocytes, a type of glia increasingly implicated in mediating neuroplasticity, are concurrent with these neural changes remains to be investigated. In order to assess morphological changes among astrocytes of the rat dentate gyrus, piSeeDB was used to optically clear 250 μm sections of tissue labeled using GFAP immunohistochemistry. Confocal imaging and image analysis were then used to measure astrocyte morphology. Astrocytes from animals housed in EE demonstrated a reduced distance between filament branch points. Furthermore, the most complex astrocytes were significantly more complex among animals housed in EE compared to standard environments. PMID:26989515

  10. Glutamate transporters alterations in the reorganizing dentate gyrus are associated with progressive seizure activity in chronic epileptic rats.

    PubMed

    Gorter, Jan A; Van Vliet, Erwin A; Proper, Evelien A; De Graan, Pierre N E; Ghijsen, Wim E J M; Lopes Da Silva, Fernando H; Aronica, Eleonora

    2002-01-21

    The expression of glial and neuronal glutamate transporter proteins was investigated in the hippocampal region at different time points after electrically induced status epilepticus (SE) in the rat. This experimental rat model for mesial temporal lobe epilepsy is characterized by cell loss, gliosis, synaptic reorganization, and chronic seizures after a latent period. Despite extensive gliosis, immunocytochemistry revealed only an up-regulation of both glial transporters localized at the outer aspect of the inner molecular layer (iml) in chronic epileptic rats. The neuronal EAAC1 transporter was increased in many somata of individual CA1-3 neurons and granule cells that had survived after SE; this up-regulation was still present in the chronic epileptic phase. In contrast, a permanent decrease of EAAC1 immunoreactivity was observed in the iml of the dentate gyrus. This permanent decrease in EAAC1 expression, which was only observed in rats that experienced progressive spontaneous seizure activity, could lead to abnormal glutamate levels in the iml once new abnormal glutamatergic synaptic contacts are formed by means of sprouted mossy fibers. Considering the steady growth of reorganizing mossy fibers in the iml, the absence of a glutamate reuptake mechanism in this region could contribute to progression of spontaneous seizure activity, which occurs with a similar time course. PMID:11793340

  11. Developmental neurotoxicity of 3,3’,4,4’-tetrachloroazobenzene with thyroxine deficit: Sensitivity of glia and dentate granule neurons in the absence of behavioral changes

    PubMed Central

    Harry, G. Jean; Hooth, Michelle J.; Vallant, Molly; Behl, Mamta; Travlos, Gregory S.; Howard, James L.; Price, Catherine J.; McBride, Sandra; Mervis, Ron; Mouton, Peter R.

    2015-01-01

    Thyroid hormones (TH) regulate biological processes implicated in neurodevelopmental disorders and can be altered with environmental exposures. Developmental exposure to the dioxin-like compound, 3,3’,4,4’-tetrachloroazobenzene (TCAB), induced a dose response deficit in serum T4 levels with no change in 3,5,3’- triiodothyronine or thyroid stimulating hormone. Female Sprague-Dawley rats were orally gavaged (corn oil, 0.1, 1.0, or 10 mg TCAB/kg/day) two weeks prior to cohabitation until post-partum day 3 and male offspring from post-natal day (PND)4-21. At PND21, the high dose showed a deficit in body weight gain. Conventional neuropathology detected no neuronal death, myelin disruption, or gliosis. Astrocytes displayed thinner and less complex processes at 1.0 and 10 mg/kg/day. At 10 mg/kg/day, microglia showed less complex processes, unbiased stereology detected fewer hippocampal CA1 pyramidal neurons and dentate granule neurons (GC) and Golgi staining of the cerebellum showed diminished Purkinje cell dendritic arbor. At PND150, normal maturation of GC number and Purkinje cell branching area was not observed in the 1.0 mg/kg/day dose group with a diminished number and branching suggestive of effects initiated during developmental exposure. No effects were observed on post-weaning behavioral assessments in control, 0.1 and 1.0mg/kg/day dose groups. The demonstrated sensitivity of hippocampal neurons and glial cells to TCAB and T4 deficit raises support for considering additional anatomical features of brain development in future DNT evaluations. PMID:26029700

  12. Reduction of the immunostainable length of the hippocampal dentate granule cells' primary cilia in 3xAD-transgenic mice producing human A{beta}{sub 1-42} and tau

    SciTech Connect

    Chakravarthy, Balu; Gaudet, Chantal; Menard, Michel; Brown, Leslie; Atkinson, Trevor; LaFerla, Frank M.; Ito, Shingo; Armato, Ubaldo; Dal Pra, Ilaria; Whitfield, James

    2012-10-12

    Highlights: Black-Right-Pointing-Pointer A{beta} and tau-induced neurofibrillary tangles play a key role in Alzheimer's disease. Black-Right-Pointing-Pointer A{beta}{sub 1-42} and mutant tau protein together reduce the primary cilium length. Black-Right-Pointing-Pointer This shortening likely reduces cilium-dependent neurogenesis and memory function. Black-Right-Pointing-Pointer This provides a model of an A{beta}/tau targeting of a neuronal signaling organelle. -- Abstract: The hippocampal dentate gyrus is one of the two sites of continuous neurogenesis in adult rodents and humans. Virtually all dentate granule cells have a single immobile cilium with a microtubule spine or axoneme covered with a specialized cell membrane loaded with receptors such as the somatostatin receptor 3 (SSTR3), and the p75 neurotrophin receptor (p75{sup NTR}). The signals from these receptors have been reported to stimulate neuroprogenitor proliferation and the post-mitotic maturation of newborn granule cells into functioning granule cells. We have found that in 6-24-months-old triple transgenic Alzheimer's disease model mice (3xTg-AD) producing both A{beta}{sub 1-42} and the mutant human tau protein tau{sub P301L,} the dentate granule cells still had immunostainable SSTR3- and p75{sup NTR}-bearing cilia but they were only half the length of the immunostained cilia in the corresponding wild-type mice. However, the immunostainable length of the granule cell cilia was not reduced either in 2xTg-AD mice accumulating large amounts of A{beta}{sub 1-42} or in mice accumulating only a mutant human tau protein. Thus it appears that a combination of A{beta}{sub 1-42} and tau protein accumulation affects the levels of functionally important receptors in 3xTg-AD mice. These observations raise the important possibility that structural and functional changes in granule cell cilia might have a role in AD.

  13. DEVELOPMENTAL HYPOTHYROIDISM ALTERS SYNAPTIC TRANSMISSION IN DENTATE GYRUS AND AREA CA1 OF HIPPOCAMPUS.

    EPA Science Inventory

    Hypothyroidism during critical periods of brain developmental leads to learning deficits and alterations in hippocampal structure. Neurophysiological properties of the hippocampus, however, have not been well characterized. The present study examined field potentials evoked in...

  14. Hippocampus-based contextual memory alters the morphological characteristics of astrocytes in the dentate gyrus.

    PubMed

    Choi, Moonseok; Ahn, Sangzin; Yang, Eun-Jeong; Kim, Hyunju; Chong, Young Hae; Kim, Hye-Sun

    2016-01-01

    Astrocytes have been reported to exist in two states, the resting and the reactive states. Morphological changes in the reactive state of astrocytes include an increase in thickness and number of processes, and an increase in the size of the cell body. Molecular changes also occur, such as an increase in the expression of glial fibrillary acidic protein (GFAP). However, the morphological and molecular changes during the process of learning and memory have not been elucidated. In the current study, we subjected Fvb/n mice to contextual fear conditioning, and checked for morphological and molecular changes in astrocytes. 1 h after fear conditioning, type II and type III astrocytes exhibited a unique status with an increased number of processes and decreased GFAP expression which differed from the typical resting or reactive state. In addition, the protein level of excitatory excitatory amino acid transporter 2 (EAAT2) was increased 1 h to 24 h after contextual fear conditioning while EAAT1 did not show any alterations. Connexin 43 (Cx43) protein was found to be increased at 24 h after fear conditioning. These data suggest that hippocampus-based contextual memory process induces changes in the status of astrocytes towards a novel status different from typical resting or reactive states. These morphological and molecular changes may be in line with functional changes. PMID:27460927

  15. Transcriptional Profiling of Newly Generated Dentate Granule Cells Using TU Tagging Reveals Pattern Shifts in Gene Expression during Circuit Integration1,2

    PubMed Central

    Chatzi, Christina; Shen, Rongkun; Goodman, Richard H.

    2016-01-01

    Abstract Despite representing only a small fraction of hippocampal granule cells, adult-generated newborn granule cells have been implicated in learning and memory (Aimone et al., 2011). Newborn granule cells undergo functional maturation and circuit integration over a period of weeks. However, it is difficult to assess the accompanying gene expression profiles in vivo with high spatial and temporal resolution using traditional methods. Here we used a novel method [“thiouracil (TU) tagging”] to map the profiles of nascent mRNAs in mouse immature newborn granule cells compared with mature granule cells. We targeted a nonmammalian uracil salvage enzyme, uracil phosphoribosyltransferase, to newborn neurons and mature granule cells using retroviral and lentiviral constructs, respectively. Subsequent injection of 4-TU tagged nascent RNAs for analysis by RNA sequencing. Several hundred genes were significantly enhanced in the retroviral dataset compared with the lentiviral dataset. We compared a selection of the enriched genes with steady-state levels of mRNAs using quantitative PCR. Ontology analysis revealed distinct patterns of nascent mRNA expression, with newly generated immature neurons showing enhanced expression for genes involved in synaptic function, and neural differentiation and development, as well as genes not previously associated with granule cell maturation. Surprisingly, the nascent mRNAs enriched in mature cells were related to energy homeostasis and metabolism, presumably indicative of the increased energy demands of synaptic transmission and their complex dendritic architecture. The high spatial and temporal resolution of our modified TU-tagging method provides a foundation for comparison with steady-state RNA analyses by traditional transcriptomic approaches in defining the functional roles of newborn neurons. PMID:27011954

  16. Sex Steroids and the Dentate Gyrus

    PubMed Central

    Hajszan, Tibor; Leranth, Csaba

    2006-01-01

    In the late 1980s, the finding that the dentate gyrus contains more granule cells in the male than in the female of certain mouse strains provided the first indication that the dentate gyrus is a significant target for the effects of sex steroids during development. Gonadal hormones also play a crucial role in shaping the function and morphology of the adult brain. Besides reproduction-related processes, sex steroids participate in higher brain operations such as cognition and mood, in which the hippocampus is a critical mediator. Being part of the hippocampal formation, the dentate gyrus is naturally involved in these mechanisms and as such, this structure is also a critical target for the activational effects of sex steroids. These activational effects are the results of three major types of steroid-mediated actions. Sex steroids modulate the function of dentate neurons under normal conditions. In addition, recent research suggests that hormone-induced cellular plasticity may play a larger role than previously thought, particularly in the dentate gyrus. Specifically, the regulation of dentate gyrus neurogenesis and synaptic remodeling by sex steroids received increasing attention lately. Finally, the dentate gyrus is influenced by gonadal hormones in the context of cellular injury, and the work in this area demonstrates that gonadal hormones have neuroprotective potential. The expression of estrogen, progestin and androgen receptors in the dentate gyrus suggests that sex steroids, which could be of gonadal origin and/or synthesized locally in the dentate gyrus, may act directly on dentate cells. In addition, gonadal hormones could also influence the dentate gyrus indirectly, by subcortical hormone-sensitive structures such as the cholinergic septohippocampal system. Importantly, these three sex steroid-related themes, functional effects in the normal dentate gyrus, mechanisms involving neurogenesis and synaptic remodeling, as well as neuroprotection, have

  17. In vivo evaluation of the dentate gate theory in epilepsy

    PubMed Central

    Krook-Magnuson, Esther; Armstrong, Caren; Bui, Anh; Lew, Sean; Oijala, Mikko; Soltesz, Ivan

    2015-01-01

    The dentate gyrus is a region subject to intense study in epilepsy because of its posited role as a ‘gate’, acting to inhibit overexcitation in the hippocampal circuitry through its unique synaptic, cellular and network properties that result in relatively low excitability. Numerous changes predicted to produce dentate hyperexcitability are seen in epileptic patients and animal models. However, recent findings question whether changes are causative or reactive, as well as the pathophysiological relevance of the dentate in epilepsy. Critically, direct in vivo modulation of dentate ‘gate’ function during spontaneous seizure activity has not been explored. Therefore, using a mouse model of temporal lobe epilepsy with hippocampal sclerosis, a closed-loop system and selective optogenetic manipulation of granule cells during seizures, we directly tested the dentate ‘gate’ hypothesis in vivo. Consistent with the dentate gate theory, optogenetic gate restoration through granule cell hyperpolarization efficiently stopped spontaneous seizures. By contrast, optogenetic activation of granule cells exacerbated spontaneous seizures. Furthermore, activating granule cells in non-epileptic animals evoked acute seizures of increasing severity. These data indicate that the dentate gyrus is a critical node in the temporal lobe seizure network, and provide the first in vivo support for the dentate ‘gate’ hypothesis. Key points A key mechanistic concept in epilepsy is the dentate gate hypothesis, which argues that the dentate gyrus protects hippocampal circuits from overexcitation and that a breakdown of this gate leads to epilepsy. Direct in vivo evidence for the dentate gate hypothesis is lacking and it is therefore unclear whether interventions selectively targeting the dentate gyrus would inhibit seizures. We demonstrate that on-demand optogenetic restoration of the dentate gate through selective inhibition of granule cells is sufficient to inhibit spontaneous

  18. Running per se stimulates the dendritic arbor of newborn dentate granule cells in mouse hippocampus in a duration-dependent manner.

    PubMed

    Dostes, Sandrine; Dubreucq, Sarah; Ladevèze, Elodie; Marsicano, Giovanni; Abrous, Djoher N; Chaouloff, Francis; Koehl, Muriel

    2016-03-01

    Laboratory rodents provided chronic unlimited access to running wheels display increased neurogenesis in the hippocampal dentate gyrus. In addition, recent studies indicate that such an access to wheels stimulates dendritic arborization in newly formed neurons. However, (i) the presence of the running wheel in the housing environment might also bear intrinsic influences on the number and shape of new neurons and (ii) the dendritic arborization of new neurons might be insensitive to moderate daily running activity (i.e., several hours). In keeping with these uncertainties, we have examined neurogenesis and dendritic arborization in newly formed granular cells in adult C57Bl/6N male mice housed for 3 weeks under standard conditions, with a locked wheel, with a running wheel set free 3 h/day, or with a running wheel set permanently free. The results indicate that the presence of a blocked wheel in the home cage increased cell proliferation, but not the number of new neurons while running increased in a duration-dependent manner the number of newborn neurons, as assessed by DCX labeling. Morphological analyses of the dendritic tree of newborn neurons, as identified by BrdU-DCX co-staining, revealed that although the presence of the wheel stimulated their dendritic architecture, the amplitude of this effect was lower than that elicited by running activity, and was found to be running duration-dependent. PMID:26606164

  19. Impaired long-term potentiation induction in dentate gyrus of calretinin-deficient mice

    PubMed Central

    Schurmans, Stéphane; Schiffmann, Serge N.; Gurden, Hirac; Lemaire, Martine; Lipp, Hans-Peter; Schwam, Valérie; Pochet, Roland; Imperato, Assunta; Böhme, Georg Andrees; Parmentier, Marc

    1997-01-01

    Calretinin (Cr) is a Ca2+ binding protein present in various populations of neurons distributed in the central and peripheral nervous systems. We have generated Cr-deficient (Cr−/−) mice by gene targeting and have investigated the associated phenotype. Cr−/− mice were viable, and a large number of morphological, biochemical, and behavioral parameters were found unaffected. In the normal mouse hippocampus, Cr is expressed in a widely distributed subset of GABAergic interneurons and in hilar mossy cells of the dentate gyrus. Because both types of cells are part of local pathways innervating dentate granule cells and/or pyramidal neurons, we have explored in Cr−/− mice the synaptic transmission between the perforant pathway and granule cells and at the Schaffer commissural input to CA1 pyramidal neurons. Cr−/− mice showed no alteration in basal synaptic transmission, but long-term potentiation (LTP) was impaired in the dentate gyrus. Normal LTP could be restored in the presence of the GABAA receptor antagonist bicuculline, suggesting that in Cr−/− dentate gyrus an excess of γ-aminobutyric acid (GABA) release interferes with LTP induction. Synaptic transmission and LTP were normal in CA1 area, which contains only few Cr-positive GABAergic interneurons. Cr−/− mice performed normally in spatial memory task. These results suggest that expression of Cr contributes to the control of synaptic plasticity in mouse dentate gyrus by indirectly regulating the activity of GABAergic interneurons, and that Cr−/− mice represent a useful tool to understand the role of dentate LTP in learning and memory. PMID:9294225

  20. a-Band Oscillations in Intracellular Membrane Potentials of Dentate Gyrus Neurons in Awake Rodents

    ERIC Educational Resources Information Center

    Anderson, Ross W.; Strowbridge, Ben W.

    2014-01-01

    The hippocampus and dentate gyrus play critical roles in processing declarative memories and spatial information. Dentate granule cells, the first relay in the trisynaptic circuit through the hippocampus, exhibit low spontaneous firing rates even during locomotion. Using intracellular recordings from dentate neurons in awake mice operating a…

  1. Enhanced corticosteroid signaling alters synaptic plasticity in the dentate gyrus in mice lacking the fragile X mental retardation protein.

    PubMed

    Ghilan, M; Hryciw, B N; Brocardo, P S; Bostrom, C A; Gil-Mohapel, J; Christie, B R

    2015-05-01

    The fragile X mental retardation protein (FMRP) is an important regulator of protein translation, and a lack of FMRP expression leads to a cognitive disorder known as fragile X syndrome (FXS). Clinical symptoms characterizing FXS include learning impairments and heightened anxiety in response to stressful situations. Here, we report that, in response to acute stress, mice lacking FMRP show a faster elevation of corticosterone and a more immediate impairment in N-methyl-d-aspartate receptor (NMDAR) dependent long-term potentiation (LTP) in the dentate gyrus (DG). These stress-induced LTP impairments were rescued by administering the glucocorticoid receptor (GR) antagonist RU38486. Administration of RU38486 also enhanced LTP in Fmr1(-/y) mice in the absence of acute stress to wild-type levels, and this enhancement was blocked by application of the NMDAR antagonist 2-amino-5-phosphonopentanoic acid. These results suggest that a loss of FMPR results in enhanced GR signaling that may adversely affect NMDAR dependent synaptic plasticity in the DG. PMID:25731748

  2. Polymeric tannins significantly alter properties and in vitro digestibility of partially gelatinized intact starch granule.

    PubMed

    Amoako, Derrick B; Awika, Joseph M

    2016-10-01

    Excess calorie intake is a growing global problem. This study investigated effect of complexing partially gelatinized starch with condensed tannins on in vitro starch digestibility. Extracts from tannin and non-tannin sorghum, and cellulose control, were reacted with normal and waxy maize starch in 30% (30E) and 50% ethanol (50E) solutions at 70°C/20min. More tannins complexed with the 30E than 50E starches (mean 6.2 vs 3.5mg/g, respectively). In the 30E treatments, tannins significantly increased crystallinity, pasting temperature, peak viscosity, and slow digesting starch (from 100 to 274mg/g) in normal, but not waxy starch, suggesting intragranular cross-linking with amylose. Tannins doubled resistant starch (RS) to approx. 300mg/g in both starches. In 50E treatments, tannins made both maize starches behave like raw potato starch (>90% RS), suggesting granule surface interactions dominated. Non-tannin treatments generally behaved similar to cellulose. Condensed tannins could be used to favorably alter starch digestion profile. PMID:27132818

  3. Role of the postnatal radial glial scaffold for the development of the dentate gyrus as revealed by Reelin signaling mutant mice

    PubMed Central

    Brunne, Bianka; Franco, Santos; Bouché, Elisabeth; Herz, Joachim; Howell, Brian W.; Pahle, Jasmine; Müller, Ulrich; May, Petra; Frotscher, Michael; Bock, Hans H.

    2014-01-01

    During dentate gyrus development the early embryonic radial glial scaffold is replaced by a secondary glial scaffold around birth. In contrast to neocortical and early dentate gyrus radial glial cells these postnatal glial cells are severely altered with regard to position and morphology in reeler mice lacking the secreted protein Reelin. In this study we focus on the functional impact of these defects. Most radial glial cells throughout the nervous system serve as scaffolds for migrating neurons and precursor cells for both neurogenesis and gliogenesis. Precursor cell function has been demonstrated for secondary radial glial cells but the exact function of these late glial cells in granule cell migration and positioning is not clear. No data exist concerning the interplay between granule neurons and late radial glial cells during dentate gyrus development. Here we show that despite the severe morphological defects in the reeler dentate gyrus the precursor function of secondary radial glial cells is not impaired during development in reeler mice. In addition, selective ablation of Disabled-1, an intracellular adaptor protein essential for Reelin signaling, in neurons but not in glial cells allowed us to distinguish effects of Reelin signaling on radial glial cells from possible secondary effects based on defective granule cells positioning. PMID:23828756

  4. Repeated stimulation of dopamine D1-like receptor and hyperactivation of mTOR signaling lead to generalized seizures, altered dentate gyrus plasticity, and memory deficits.

    PubMed

    Gangarossa, Giuseppe; Ceolin, Laura; Paucard, Alexia; Lerner-Natoli, Mireille; Perroy, Julie; Fagni, Laurent; Valjent, Emmanuel

    2014-12-01

    The acute activation of the dopamine D1-like receptors (D1R) is involved in a plethora of functions ranging from increased locomotor activity to the facilitation of consolidation, storage, and retrieval of memories. Although much less characterized, epileptiform activities, usually triggered by disruption of the glutamate and GABA balance, have also been reported to involve the dopaminergic transmission. Using a combination of biochemical, immunohistochemical, electrophysiological, and behavioral approaches we have investigated the consequences of repeated stimulation of D1R using the selective D1R-like agonist SKF81297. Here, we report that repeated systemic administration of SKF81297 induces kindled seizures in mice. These seizure episodes parallel the hyperactivation of the mTOR signaling in the hippocampus, leading to disrupted long-term potentiation (LTP) in the dentate gyrus (DG) and altered recognition memories. The mTOR inhibitor rapamycin delays the development of SKF81297-induced kindled seizures, and rescues LTP in the DG and object recognition. Our results show that repeated stimulation of D1R is sufficient to induce generalized seizures leading to the overactivation of mTOR signaling, disrupted hippocampal plasticity, and impaired long-term recognition memories. This work highlights the interest of mTOR inhibitors as therapeutic strategies to reverse plasticity and cognitive deficits. PMID:25044816

  5. Early postnatal exposure to methylphenidate alters stress reactivity and increases hippocampal ectopic granule cells in adult rats.

    PubMed

    Torres-Reveron, Annelyn; Gray, Jason D; Melton, Jay T; Punsoni, Michael; Tabori, Nora E; Ward, Mary J; Frys, Kelly; Iadecola, Costantino; Milner, Teresa A

    2009-03-16

    To mimic clinical treatment with methylphenidate (MPH; Ritalin) for attention deficit/hyperactivity disorder (ADHD), rat pups were injected with MPH (5 mg/kg, i.p.) or placebo twice daily during their nocturnal active phase from postnatal day (PND) 7-35. Thirty-nine days after the last MPH administration (PND 76), four litters of rats experienced stressful conditions during the 2003 New York City blackout. MPH-treated rats that endured the blackout lost more weight and regained it at a slower pace than controls (p<0.05; N=7-11 per group). Furthermore, MPH-treated rats had elevated systolic arterial blood pressure (from 115.6+/-1.2 to 126+/-1.8 mmHg; p<0.05), assessed on PND 130 by tail cuff plethysmography. Immunocytochemical studies of transmitter systems in the brain demonstrated rearrangements of catecholamine and neuropeptide Y fibers in select brain regions at PND 135, which did not differ between blackout and control groups. However, MPH-treated rats that endured the blackout had more ectopic granule cells in the hilus of the dorsal hippocampal dentate gyrus compared to controls at PND 135 (p<0.05; N=6 per group). These findings indicate that early postnatal exposure to high therapeutic doses of MPH can have long lasting effects on the plasticity of select brain regions and can induce changes in the reactivity to stress that persist into adulthood. PMID:19100815

  6. AMP Kinase Activation Alters Oxidant-Induced Stress Granule Assembly by Modulating Cell Signaling and Microtubule Organization.

    PubMed

    Mahboubi, Hicham; Koromilas, Antonis E; Stochaj, Ursula

    2016-10-01

    Eukaryotic cells assemble stress granules (SGs) when translation initiation is inhibited. Different cell signaling pathways regulate SG production. Particularly relevant to this process is 5'-AMP-activated protein kinase (AMPK), which functions as a stress sensor and is transiently activated by adverse physiologic conditions. Here, we dissected the role of AMPK for oxidant-induced SG formation. Our studies identified multiple steps of de novo SG assembly that are controlled by the kinase. Single-cell analyses demonstrated that pharmacological AMPK activation prior to stress exposure changed SG properties, because the granules became more abundant and smaller in size. These altered SG characteristics correlated with specific changes in cell survival, cell signaling, cytoskeletal organization, and the abundance of translation initiation factors. Specifically, AMPK activation increased stress-induced eukaryotic initiation factor (eIF) 2α phosphorylation and reduced the concentration of eIF4F complex subunits eIF4G and eIF4E. At the same time, the abundance of histone deacetylase 6 (HDAC6) was diminished. This loss of HDAC6 was accompanied by increased acetylation of α-tubulin on Lys40. Pharmacological studies further confirmed this novel AMPK-HDAC6 interplay and its importance for SG biology. Taken together, we provide mechanistic insights into the regulation of SG formation. We propose that AMPK activation stimulates oxidant-induced SG formation but limits their fusion into larger granules. PMID:27430620

  7. Effect of chronic stress and mifepristone treatment on voltage-dependent Ca2+ currents in rat hippocampal dentate gyrus.

    PubMed

    van Gemert, N G; Joëls, M

    2006-10-01

    Chronic unpredictable stress affects many properties in rat brain. In the dentate gyrus, among other things, increased mRNA expression of the Ca2+ channel alpha1C 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 alpha1C 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 alpha1C 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. PMID:16965291

  8. Adult neurogenesis in the mammalian hippocampus: Why the dentate gyrus?

    PubMed Central

    Drew, Liam J.; Fusi, Stefano; Hen, René

    2013-01-01

    In the adult mammalian brain, newly generated neurons are continuously incorporated into two networks: interneurons born in the subventricular zone migrate to the olfactory bulb, whereas the dentate gyrus (DG) of the hippocampus integrates locally born principal neurons. That the rest of the mammalian brain loses significant neurogenic capacity after the perinatal period suggests that unique aspects of the structure and function of DG and olfactory bulb circuits allow them to benefit from the adult generation of neurons. In this review, we consider the distinctive features of the DG that may account for it being able to profit from this singular form of neural plasticity. Approaches to the problem of neurogenesis are grouped as “bottom-up,” where the phenotype of adult-born granule cells is contrasted to that of mature developmentally born granule cells, and “top-down,” where the impact of altering the amount of neurogenesis on behavior is examined. We end by considering the primary implications of these two approaches and future directions. PMID:24255101

  9. Deficiency of Starch Synthase IIIa and IVb Alters Starch Granule Morphology from Polyhedral to Spherical in Rice Endosperm.

    PubMed

    Toyosawa, Yoshiko; Kawagoe, Yasushi; Matsushima, Ryo; Crofts, Naoko; Ogawa, Masahiro; Fukuda, Masako; Kumamaru, Toshihiro; Okazaki, Yozo; Kusano, Miyako; Saito, Kazuki; Toyooka, Kiminori; Sato, Mayuko; Ai, Yongfeng; Jane, Jay-Lin; Nakamura, Yasunori; Fujita, Naoko

    2016-03-01

    Starch granule morphology differs markedly among plant species. However, the mechanisms controlling starch granule morphology have not been elucidated. Rice (Oryza sativa) endosperm produces characteristic compound-type granules containing dozens of polyhedral starch granules within an amyloplast. Some other cereal species produce simple-type granules, in which only one starch granule is present per amyloplast. A double mutant rice deficient in the starch synthase (SS) genes SSIIIa and SSIVb (ss3a ss4b) produced spherical starch granules, whereas the parental single mutants produced polyhedral starch granules similar to the wild type. The ss3a ss4b amyloplasts contained compound-type starch granules during early developmental stages, and spherical granules were separated from each other during subsequent amyloplast development and seed dehydration. Analysis of glucan chain length distribution identified overlapping roles for SSIIIa and SSIVb in amylopectin chain synthesis, with a degree of polymerization of 42 or greater. Confocal fluorescence microscopy and immunoelectron microscopy of wild-type developing rice seeds revealed that the majority of SSIVb was localized between starch granules. Therefore, we propose that SSIIIa and SSIVb have crucial roles in determining starch granule morphology and in maintaining the amyloplast envelope structure. We present a model of spherical starch granule production. PMID:26747287

  10. HIV-1 Gag Blocks Selenite-Induced Stress Granule Assembly by Altering the mRNA Cap-Binding Complex

    PubMed Central

    Cinti, Alessandro; Le Sage, Valerie; Ghanem, Marwan

    2016-01-01

    ABSTRACT Stress granules (SGs) are dynamic accumulations of stalled preinitiation complexes and translational machinery that assemble under stressful conditions. Sodium selenite (Se) induces the assembly of noncanonical type II SGs that differ in morphology, composition, and mechanism of assembly from canonical SGs. Se inhibits translation initiation by altering the cap-binding activity of eukaryotic translation initiation factor 4E (eIF4E)-binding protein 1 (4EBP1). In this work, we show that human immunodeficiency virus type 1 (HIV-1) Gag is able to block the assembly of type II noncanonical SGs to facilitate continued Gag protein synthesis. We demonstrate that expression of Gag reduces the amount of hypophosphorylated 4EBP1 associated with the 5′ cap potentially through an interaction with its target, eIF4E. These results suggest that the assembly of SGs is an important host antiviral defense that HIV-1 has evolved for inhibition through several distinct mechanisms. PMID:27025252

  11. Effects of hypothyroidism upon the granular layer of the dentate gyrus in male and female adult rats: a morphometric study.

    PubMed

    Madeira, M D; Cadete-Leite, A; Andrade, J P; Paula-Barbosa, M M

    1991-12-01

    The effects of hypothyroidism upon the structure of the central nervous system of adult rats are poorly understood in spite of evidence that the mature brain is vulnerable to this condition. Existing developmental studies show that the morphological changes induced by thyroid hormone deficiency are related to alterations in neurogenesis. We studied the granular layer of the dentate gyrus under different experimental conditions of hypothyroidism, because in rodents the neurogenesis of the granule cells continues during adulthood. The following groups of rats were analysed: 1) control; 2) hypothyroid from day 0 until day 180 (hypothyroid group); 3) hypothyroid until day 30 and henceforth maintained euthyroid (recovery group); and 4) hypothyroid since day 30 (adult hypothyroid group). Groups of 6 male rats and 6 female rats were analysed separately. The volume of the dentate gyrus granular layer and the numerical density of its neurons were evaluated, so we were able to estimate the total number of granule cells. Because in the experimental groups the volume of the granular layer and the numerical density of its neurons were reduced, the total number of granule cells was decreased. In the hypothyroid and recovery groups the alterations were identical and more striking than in the adult hypothyroid groups. The total number of granule cells displayed sexual differences in all groups studied except in the hypothyroid groups. The present results support the view that thyroid hormone deficiency interferes with the process of cell acquisition by reducing neuronal proliferation and that it also leads to increased cell death. These events underlie the irreversible morphological changes observed in the brain of hypothyroid rats, either during development or at maturity. The referred structural alterations are probably related to the functional deficits observed in this condition. PMID:1797872

  12. Expansion of the dentate mossy fiber-CA3 projection in the BDNF-enriched mouse hippocampus

    PubMed Central

    Isgor, Ceylan; Pare, Christopher; McDole, Brittnee; Coombs, Paulette; Guthrie, Kathleen

    2015-01-01

    Structural changes that alter hippocampal functional circuitry are implicated in learning impairments, mood disorders and epilepsy. Reorganization of mossy fiber (MF) axons from dentate granule cells is one such form of plasticity. Increased neurotrophin signaling is proposed to underlie MF plasticity, and there is evidence to support a mechanistic role for brain-derived neurotrophic factor (BDNF) in this process. Transgenic mice overexpressing BDNF in forebrain under the α-calcium/calmodulin-dependent protein kinase II promoter (TgBDNF mice) exhibit spatial learning deficits at 2–3 months of age, followed by the emergence of spontaneous seizures at ~6 months. These behavioral changes suggest that chronic increases in BDNF progressively disrupt hippocampal functional organization. To determine if the dentate MF pathway is structurally altered in this strain, the present study employed Timm staining and design-based stereology to compare MF distribution and projection volumes in transgenic and wild-type mice at 2–3 months, and at 6–7 months. Mice in the latter age group were assessed for seizure vulnerability with a low dose of pilocarpine given 2 hrs before euthanasia. At 2–3 months, TgBDNF mice showed moderate expansion of CA3-projecting MFs (~20%), with increased volumes measured in the suprapyramidal (SP-MF) and intra/infrapyramidal (IIP-MF) compartments. At 6–7 months, a subset of transgenic mice exhibited increased seizure susceptibility, along with an increase in IIP-MF volume (~30%). No evidence of MF sprouting was seen in the inner molecular layer. Additional stereological analyses demonstrated significant increases in molecular layer (ML) volume in TgBDNF mice at both ages, as well as an increase in granule cell number by 8 months of age. Collectively, these results indicate that sustained increases in endogenous BDNF modify dentate structural organization over time, and may thereby contribute to the development of pro-epileptic circuitry. PMID

  13. Dentate Gyrus-Specific Knockdown of Adult Neurogenesis Impairs Spatial and Object Recognition Memory in Adult Rats

    ERIC Educational Resources Information Center

    Jessberger, Sebastian; Clark, Robert E.; Broadbent, Nicola J.; Clemenson, Gregory D., Jr.; Consiglio, Antonella; Lie, D. Chichung; Squire, Larry R.; Gage, Fred H.

    2009-01-01

    New granule cells are born throughout life in the dentate gyrus of the hippocampal formation. Given the fundamental role of the hippocampus in processes underlying certain forms of learning and memory, it has been speculated that newborn granule cells contribute to cognition. However, previous strategies aiming to causally link newborn neurons…

  14. Postnatal changes in glucose transporter 3 expression in the dentate gyrus of the C57BL/6 mouse model

    PubMed Central

    Jung, Hyo Young; Yim, Hee Sun; Yoo, Dae Young; Kim, Jong Whi; Chung, Jin Young; Seong, Je Kyung; Yoon, Yeo Sung; Kim, Dae Won

    2016-01-01

    In this study, we observed the ontogenetic changes in glucose transporter 3 (GLUT3) immunoreactivity, a major neuronal GLUT, in the dentate gyrus of mouse brains at various ages: postnatal day (P) 1, 7, 14, 28, and 56. At P1, cresyl violet staining showed abundant neurons in the dentate gyrus, whereas the granule cell layer was ill-defined. At P7, the granule cell layer was observed, and cresyl violet-positive cells were dispersed throughout the polymorphic layer. At P14, the granule cell layer was well-defined, and cresyl violet positive cells were detected abundantly in the polymorphic layer. At P28 and P56, cresyl violet-positive cells were observed in the granule cell layer, as well as in the polymorphic layer. At P1, GLUT3 immunoreactivity was detected in the dentate gyrus. At P7, GLUT3 immunoreactive cells were scattered in the polymorphic and molecular layer. However, at P14, GLUT3 immunoreactivity was observed in the polymorphic layer as well as subgranular zone of the dentate gyrus. At P28, GLUT3 immunoreactivity was detected in the polymorphic layer of the dentate gyrus. At P56, GLUT3 immunoreactivity was observed predominantly in the subgranular zone of the dentate gyrus. GLUT3 immunoreactive cells were mainly colocalized with doublecortin, which is a marker for differentiated neuroblasts, in the polymorphic layer and subgranular zone of dentate gyrus at P14 and P56. These results suggest that the expression of GLUT3 is closely associated with postnatal development of the dentate gyrus and adult neurogenesis. PMID:27051437

  15. Altering the Structure of Carbohydrate Storage Granules in the Cyanobacterium Synechocystis sp. Strain PCC 6803 through Branching-Enzyme Truncations

    PubMed Central

    Welkie, David G.; Lee, Byung-Hoo

    2015-01-01

    ABSTRACT Carbohydrate storage is an important element of metabolism in cyanobacteria and in the chloroplasts of plants. Understanding how to manipulate the metabolism and storage of carbohydrate is also an important factor toward harnessing cyanobacteria for energy production. While most cyanobacteria produce glycogen, some have been found to accumulate polysaccharides in the form of water-insoluble α-glucan similar to amylopectin. Notably, this alternative form, termed “semi-amylopectin,” forms in cyanobacterial species harboring three branching-enzyme (BE) homologs, designated BE1, BE2, and BE3. In this study, mutagenesis of the branching genes found in Synechocystis sp. strain PCC 6803 was performed in order to characterize their possible impact on polysaccharide storage granule morphology. N-terminal truncations were made to the native BE gene of Synechocystis sp. PCC 6803. In addition, one of the two native debranching enzyme genes was replaced with a heterologous debranching enzyme gene from a semi-amylopectin-forming strain. Growth and glycogen content of mutant strains did not significantly differ from those of the wild type, and ultrastructure analysis revealed only slight changes to granule morphology. However, analysis of chain length distribution by anion-exchange chromatography revealed modest changes to the branched-chain length profile. The resulting glycogen shared structure characteristics similar to that of granules isolated from semi-amylopectin-producing strains. IMPORTANCE This study is the first to investigate the impact of branching-enzyme truncations on the structure of storage carbohydrates in cyanobacteria. The results of this study are an important contribution toward understanding the relationship between the enzymatic repertoire of a cyanobacterial species and the morphology of its storage carbohydrates. PMID:26668264

  16. EARLY EFFECTS OF TRIMETHYLTIN ON THE DENTATE GYRUS BASKET CELLS: A MORPHOLOGICAL STUDY

    EPA Science Inventory

    Electrophysiological evidence for reduction of recurrent inhibition in the dentate gyrus in animals exposed to trimethyltin (TMT) suggested alterations in the inhibitory neurons (basket cells) by TMT. The present study was designed to investigate the morphology of basket cells af...

  17. Developmental cuprizone exposure impairs oligodendrocyte lineages differentially in cortical and white matter tissues and suppresses glutamatergic neurogenesis signals and synaptic plasticity in the hippocampal dentate gyrus of rats.

    PubMed

    Abe, Hajime; Saito, Fumiyo; Tanaka, Takeshi; Mizukami, Sayaka; Hasegawa-Baba, Yasuko; Imatanaka, Nobuya; Akahori, Yumi; Yoshida, Toshinori; Shibutani, Makoto

    2016-01-01

    Developmental cuprizone (CPZ) exposure impairs rat hippocampal neurogenesis. Here, we captured the developmental neurotoxicity profile of CPZ using a region-specific expression microarray analysis in the hippocampal dentate gyrus, corpus callosum, cerebral cortex and cerebellar vermis of rat offspring exposed to 0, 0.1, or 0.4% CPZ in the maternal diet from gestation day 6 to postnatal day (PND) 21. Transcripts of those genes identified as altered were subjected to immunohistochemical analysis on PNDs 21 and 77. Our results showed that transcripts for myelinogenesis-related genes, including Cnp, were selectively downregulated in the cerebral cortex by CPZ at ≥0.1% or 0.4% on PND 21. CPZ at 0.4% decreased immunostaining intensity for 2',3'-cyclic-nucleotide 3'-phosphodiesterase (CNPase) and CNPase(+) and OLIG2(+) oligodendrocyte densities in the cerebral cortex, whereas CNPase immunostaining intensity alone was decreased in the corpus callosum. By contrast, a striking transcript upregulation for Klotho gene and an increased density of Klotho(+) oligodendrocytes were detected in the corpus callosum at ≥0.1%. In the dentate gyrus, CPZ at ≥0.1% or 0.4% decreased the transcript levels for Gria1, Grin2a and Ptgs2, genes related to the synapse and synaptic transmission, and the number of GRIA1(+) and GRIN2A(+) hilar γ-aminobutyric acid (GABA)-ergic interneurons and cyclooxygenase-2(+) granule cells. All changes were reversed at PND 77. Thus, developmental CPZ exposure reversibly decreased mature oligodendrocytes in both cortical and white matter tissues, and Klotho protected white matter oligodendrocyte growth. CPZ also reversibly targeted glutamatergic signals of GABAergic interneuron to affect dentate gyrus neurogenesis and synaptic plasticity in granule cells. PMID:26577399

  18. Alterations in stress granule dynamics driven by TDP-43 and FUS: a link to pathological inclusions in ALS?

    PubMed Central

    Aulas, Anaïs; Vande Velde, Christine

    2015-01-01

    Stress granules (SGs) are RNA-containing cytoplasmic foci formed in response to stress exposure. Since their discovery in 1999, over 120 proteins have been described to be localized to these structures (in 154 publications). Most of these components are RNA binding proteins (RBPs) or are involved in RNA metabolism and translation. SGs have been linked to several pathologies including inflammatory diseases, cancer, viral infection, and neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). In ALS and FTD, the majority of cases have no known etiology and exposure to external stress is frequently proposed as a contributor to either disease initiation or the rate of disease progression. Of note, both ALS and FTD are characterized by pathological inclusions, where some well-known SG markers localize with the ALS related proteins TDP-43 and FUS. We propose that TDP-43 and FUS serve as an interface between genetic susceptibility and environmental stress exposure in disease pathogenesis. Here, we will discuss the role of TDP-43 and FUS in SG dynamics and how disease-linked mutations affect this process. PMID:26557057

  19. Microelastic mapping of the rat dentate gyrus

    PubMed Central

    Luque, Tomás; Schaffer, David V.; Kumar, Sanjay

    2016-01-01

    The lineage commitment of many cultured stem cells, including adult neural stem cells (NSCs), is strongly sensitive to the stiffness of the underlying extracellular matrix. However, it remains unclear how well the stiffness ranges explored in culture align with the microscale stiffness values stem cells actually encounter within their endogenous tissue niches. To address this question in the context of hippocampal NSCs, we used atomic force microscopy to spatially map the microscale elastic modulus (E) of specific anatomical substructures within living slices of rat dentate gyrus in which NSCs reside during lineage commitment in vivo. We measured depth-dependent apparent E-values at locations across the hilus (H), subgranular zone (SGZ) and granule cell layer (GCL) and found a two- to threefold increase in stiffness at 500 nm indentation from the H (49 ± 7 Pa) and SGZ (58 ± 8 Pa) to the GCL (115 ± 18 Pa), a fold change in stiffness we have previously found functionally relevant in culture. Additionally, E exhibits nonlinearity with depth, increasing significantly for indentations larger than 1 µm and most pronounced in the GCL. The methodological advances implemented for these measurements allow the quantification of the elastic properties of hippocampal NSC niche at unprecedented spatial resolution. PMID:27152213

  20. Anatomical gradients of adult neurogenesis and activity: young neurons in the ventral dentate gyrus are activated by water maze training

    PubMed Central

    Snyder, Jason S.; Radik, Ruvim; Wojtowicz, J. Martin; Cameron, Heather A.

    2009-01-01

    Hippocampal function varies in a subregion-specific fashion: spatial processing is thought to rely on the dorsal hippocampus, while anxiety-related behavior relies more on the ventral hippocampus. During development, neurogenesis in the dentate gyrus proceeds along ventral to dorsal as well as suprapyramidal to infrapyramidal gradients, but it is unclear whether regional differences in neurogenesis are maintained in adulthood. Moreover, it is unknown whether young neurons in the adult exhibit subregion-specific patterns of activation. We therefore examined the magnitude of neurogenesis and the activation of young and mature granule cells in dentate gyrus subregions in adult rats that learned a spatial water maze task, swam with no platform, or were left untouched. We found that both adult neurogenesis and granule cell activation, as defined by c-fos expression in the granule cell population as a whole, were higher in the dorsal than the ventral dentate gyrus. In contrast, c-fos expression in adult-born granule cells, identified by PSA-NCAM or location in the subgranular zone, occurred at a higher rate in the opposite subregion, the ventral dentate gyrus. Interestingly, c-fos expression in the entire granule cell population was equivalent in water maze-trained rats and swim control rats, but was increased in the young granule cells only in the learning condition. These results provide new evidence that hippocampally-relevant experience activates young and mature neurons in different dentate gyrus subregions and with different experiential specificity, and suggest that adult-born neurons may play a specific role in anxiety-related behavior or other non-spatial aspects of hippocampal function. PMID:19004012

  1. Adiponectin Exerts Neurotrophic Effects on Dendritic Arborization, Spinogenesis, and Neurogenesis of the Dentate Gyrus of Male Mice.

    PubMed

    Zhang, Di; Wang, Xuezhen; Lu, Xin-Yun

    2016-07-01

    The hippocampus, a brain region critical for learning, memory and emotional processing, maintains its capacity to undergo structural plasticity throughout life. Hippocampal structural plasticity can be modulated by a number of intrinsic and extrinsic factors. This study investigated the effects of adiponectin, an adipocyte-derived hormone, on dendritic growth, arborization, and spinogenesis in mature granule neurons of the hippocampal dentate gyrus generated during embryonic (early-born) or early postnatal (late-born) stages. We found that adiponectin deficiency reduced dendritic length, branching and spine density of granule neurons. The reduction was more evident in early-born granule neurons than in late-born granule neurons. Intracerebroventricular infusion of adiponectin for 1 week increased of dendritic spines and arbor complexity in late-born granule neurons. Moreover, adiponectin deficiency decreased the production of adult-born new granule neurons through suppressing neural progenitor cell proliferation and differentiation, whereas intracerebroventricular adiponectin infusion increased the proliferation of neural progenitor cells in adult dentate gyrus. These results suggest that adiponectin plays an important role in dendritic spine remodeling and neurogenesis in the dentate gyrus. PMID:27187175

  2. The ventral hippocampus is the embryonic origin for adult neural stem cells in the dentate gyrus

    PubMed Central

    Li, Guangnan; Fang, Li; Fernández, Gloria; Pleasure, Samuel J.

    2013-01-01

    SUMMARY Adult neurogenesis represents a unique form of plasticity in the dentate gyrus requiring the presence of long-lived neural stem cells (LL-NSCs). However, the embryonic origin of these LL-NSCs remains unclear. The prevailing model assumes that the dentate neuroepithelium throughout the longitudinal axis of the hippocampus generates both the LL-NSCs and embryonically produced granule neurons. Here we show that the NSCs initially originate from the ventral hippocampus during late gestation and then relocate into the dorsal hippocampus. The descendants of these cells are the source for the LL-NSCs in the subgranular zone (SGZ). Furthermore, we show that the origin of these cells and their maintenance in the dentate are controlled by distinct sources of Sonic Hedgehog (Shh). The revelation of the complexity of both the embryonic origin of hippocampal LL-NSCs and the sources of Shh has important implications for the functions of LL-NSCs in the adult hippocampus. PMID:23643936

  3. Effect of chronic stress on synaptic currents in rat hippocampal dentate gyrus neurons.

    PubMed

    Karst, Henk; Joëls, Marian

    2003-01-01

    We investigated the effect of chronic stress on synaptic responses of rat dentate granule cells to perforant path stimulation. Rats were subjected for 3 wk to unpredictable stressors twice daily or to control handling. One day after the last stressor, hippocampal slices were prepared and synaptic responses were determined with whole-cell recording. At that time, adrenal weight was found to be increased and thymus weight as well as gain in body weight were decreased in the stressed versus control animals, indicative of corticosterone hypersecretion during the stress period. In slices from rats with basal corticosteroid levels (at the circadian trough, under rest), no effect of prior stress exposure was observed on synaptic responses. However, synaptic responses of dentate granule cells from chronically stressed and control rats were differently affected by in vitro activation of glucocorticoid receptors, i.e., 1-4 h after administration of 100 nM corticosterone for 20 min. Thus the maximal response to synaptic activation of dentate cells at holding potential of -70 mV [when N-methyl-D-aspartate (NMDA) receptors are blocked by magnesium] was significantly enhanced after corticosterone administration in chronically stressed but not in control animals. In accordance, the amplitude of alpha-amino-3-hydroxy-5-methylisolazole-4-propionic acid (AMPA) but not of NMDA receptor-mediated currents was increased by corticosterone in stressed rats, over the entire voltage range. Corticosterone treatment also decreased the time to peak of AMPA currents, but this effect did not depend on prior stress exposure. The data indicate that following chronic stress exposure synaptic excitation of dentate granule cells may be enhanced when corticosterone levels rise. This enhanced synaptic flow could contribute to enhanced excitation of projection areas of the dentate gyrus, most notably the CA3 hippocampal region. PMID:12522207

  4. A million-plus neuron model of the hippocampal dentate gyrus: Dependency of spatio-temporal network dynamics on topography.

    PubMed

    Hendrickson, Phillip J; Yu, Gene J; Song, Dong; Berger, Theodore W

    2015-01-01

    This paper describes a million-plus granule cell compartmental model of the rat hippocampal dentate gyrus, including excitatory, perforant path input from the entorhinal cortex, and feedforward and feedback inhibitory input from dentate interneurons. The model includes experimentally determined morphological and biophysical properties of granule cells, together with glutamatergic AMPA-like EPSP and GABAergic GABAA-like IPSP synaptic excitatory and inhibitory inputs, respectively. Each granule cell was composed of approximately 200 compartments having passive and active conductances distributed throughout the somatic and dendritic regions. Modeling excitatory input from the entorhinal cortex was guided by axonal transport studies documenting the topographical organization of projections from subregions of the medial and lateral entorhinal cortex, plus other important details of the distribution of glutamatergic inputs to the dentate gyrus. Results showed that when medial and lateral entorhinal cortical neurons maintained Poisson random firing, dentate granule cells expressed, throughout the million-cell network, a robust, non-random pattern of spiking best described as spatiotemporal "clustering". To identify the network property or properties responsible for generating such firing "clusters", we progressively eliminated from the model key mechanisms such as feedforward and feedback inhibition, intrinsic membrane properties underlying rhythmic burst firing, and/or topographical organization of entorhinal afferents. Findings conclusively identified topographical organization of inputs as the key element responsible for generating a spatio-temporal distribution of clustered firing. These results uncover a functional organization of perforant path afferents to the dentate gyrus not previously recognized: topography-dependent clusters of granule cell activity as "functional units" that organize the processing of entorhinal signals. PMID:26737346

  5. A Million-Plus Neuron Model of the Hippocampal Dentate Gyrus: Dependency of Spatio-Temporal Network Dynamics on Topography

    PubMed Central

    Hendrickson, Phillip J.; Yu, Gene J.; Song, Dong; Berger, Theodore W.

    2016-01-01

    This paper describes a million-plus granule cell compartmental model of the rat hippocampal dentate gyrus, including excitatory, perforant path input from the entorhinal cortex, and feedforward and feedback inhibitory input from dentate interneurons. The model includes experimentally determined morphological and biophysical properties of granule cells, together with glutamatergic AMPA-like EPSP and GABAergic GABAA-like IPSP synaptic excitatory and inhibitory inputs, respectively. Each granule cell was composed of approximately 200 compartments having passive and active conductances distributed throughout the somatic and dendritic regions. Modeling excitatory input from the entorhinal cortex was guided by axonal transport studies documenting the topographical organization of projections from subregions of the medial and lateral entorhinal cortex, plus other important details of the distribution of glutamatergic inputs to the dentate gyrus. Results showed that when medial and lateral entorhinal cortical neurons maintained Poisson random firing, dentate granule cells expressed, throughout the million-cell network, a robust, non-random pattern of spiking best described as spatiotemporal “clustering”. To identify the network property or properties responsible for generating such firing “clusters”, we progressively eliminated from the model key mechanisms such as feedforward and feedback inhibition, intrinsic membrane properties underlying rhythmic burst firing, and/or topographical organization of entorhinal afferents. Findings conclusively identified topographical organization of inputs as the key element responsible for generating a spatio-temporal distribution of clustered firing. These results uncover a functional organization of perforant path afferents to the dentate gyrus not previously recognized: topography-dependent clusters of granule cell activity as “functional units” that organize the processing of entorhinal signals. PMID:26737346

  6. Antibodies to the RNA Binding Protein Heterogeneous Nuclear Ribonucleoprotein A1 Colocalize to Stress Granules Resulting in Altered RNA and Protein Levels in a Model of Neurodegeneration in Multiple Sclerosis

    PubMed Central

    Douglas, Joshua N.; Gardner, Lidia A.; Salapa, Hannah E; Levin, Michael C.

    2016-01-01

    Objective Multiple sclerosis (MS) is the most common demyelinating disorder of the central nervous system (CNS). Data suggest that antibodies to CNS targets contribute to the pathogenesis of MS. MS patients produce autoantibodies to heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1). hnRNP A1 is an RNA binding protein (RBP) overexpressed in neurons that functions in pre-mRNA splicing, mRNA trafficking, and translation. Previously, we showed that anti-hnRNP A1 antibodies entered neuronal cells (in vitro) via clathrin-mediated endocytosis, caused mislocalization of endogenous hnRNP A1 protein and increased markers of neurodegeneration including decreased ATP concentration and apoptosis. In this study, we hypothesized that anti-hnRNP A1 antibodies might cause stress granule formation and altered levels of RNAs and proteins that bind hnRNP A1. Methods Neuronal cell lines were exposed to anti-hnRNP A1 and isotype-matched control antibodies in vitro and examined for neuronal granule formation, including stress granules, P bodies and transport granules. In addition, RNAs that bound hnRNP A1 were determined. Levels of RNA and their translated proteins were measured upon exposure to the anti-hnRNP A1 antibodies. Results Anti-hnRNP A1 antibodies induced and localized to stress granules, a marker of neurodegeneration, within a neuronal cell line. The anti-hnRNP A1 antibodies did not induce P bodies or neuronal granules. Clinically relevant RNAs were found to bind hnRNP A1. In addition, the anti-hnRNP A1 antibodies caused reduced levels of RNA and protein of the spinal paraplegia genes (SPGs) 4 and 7, which when mutated mimic progressive MS. Conclusions Taken together, these data suggest potential mechanisms by which autoantibodies may contribute to neurodegeneration in MS. PMID:27375925

  7. Evolution of the mammalian dentate gyrus.

    PubMed

    Hevner, Robert F

    2016-02-15

    The dentate gyrus (DG), a part of the hippocampal formation, has important functions in learning, memory, and adult neurogenesis. Compared with homologous areas in sauropsids (birds and reptiles), the mammalian DG is larger and exhibits qualitatively different phenotypes: 1) folded (C- or V-shaped) granule neuron layer, concave toward the hilus and delimited by a hippocampal fissure; 2) nonperiventricular adult neurogenesis; and 3) prolonged ontogeny, involving extensive abventricular (basal) migration and proliferation of neural stem and progenitor cells (NSPCs). Although gaps remain, available data indicate that these DG traits are present in all orders of mammals, including monotremes and marsupials. The exception is Cetacea (whales, dolphins, and porpoises), in which DG size, convolution, and adult neurogenesis have undergone evolutionary regression. Parsimony suggests that increased growth and convolution of the DG arose in stem mammals concurrently with nonperiventricular adult hippocampal neurogenesis and basal migration of NSPCs during development. These traits could all result from an evolutionary change that enhanced radial migration of NSPCs out of the periventricular zones, possibly by epithelial-mesenchymal transition, to colonize and maintain nonperiventricular proliferative niches. In turn, increased NSPC migration and clonal expansion might be a consequence of growth in the cortical hem (medial patterning center), which produces morphogens such as Wnt3a, generates Cajal-Retzius neurons, and is regulated by Lhx2. Finally, correlations between DG convolution and neocortical gyrification (or capacity for gyrification) suggest that enhanced abventricular migration and proliferation of NSPCs played a transformative role in growth and folding of neocortex as well as archicortex. PMID:26179319

  8. Blockade of intracellular Zn2+ signaling in the dentate gyrus erases recognition memory via impairment of maintained LTP.

    PubMed

    Tamano, Haruna; Minamino, Tatsuya; Fujii, Hiroaki; Takada, Shunsuke; Nakamura, Masatoshi; Ando, Masaki; Takeda, Atsushi

    2015-08-01

    There is no evidence on the precise role of synaptic Zn2+ signaling on the retention and recall of recognition memory. On the basis of the findings that intracellular Zn2+ signaling in the dentate gyrus is required for object recognition, short-term memory, the present study deals with the effect of spatiotemporally blocking Zn2+ signaling in the dentate gyrus after LTP induction and learning. Three-day-maintained LTP was impaired 1 day after injection of clioquinol into the dentate gyrus, which transiently reduced intracellular Zn2+ signaling in the dentate gyrus. The irreversible impairment was rescued not only by co-injection of ZnCl2 , which ameliorated the loss of Zn2+ signaling, but also by pre-injection of Jasplakinolide, a stabilizer of F-actin, prior to clioquinol injection. Simultaneously, 3-day-old space recognition memory was impaired 1 day after injection of clioquinol into the dentate gyrus, but not by pre-injection of Jasplakinolide. Jasplakinolide also rescued both impairments of 3-day-maintained LTP and 3-day-old memory after injection of ZnAF-2DA into the dentate gyrus, which blocked intracellular Zn2+ signaling in the dentate gyrus. The present paper indicates that the blockade and/or loss of intracellular Zn2+ signaling in the dentate gyrus coincidently impair maintained LTP and recognition memory. The mechanism maintaining LTP via intracellular Zn2+ signaling in dentate granule cells, which may be involved in the formation of F-actin, may retain space recognition memory. PMID:25603776

  9. Dynorphin up-regulation in the dentate granule cell mossy fiber pathway following chronic inhibition of GluN2B-containing NMDAR is associated with increased CREB (Ser 133) phosphorylation, but is independent of BDNF/TrkB signaling pathways

    PubMed Central

    Rittase, W. Bradley; Dong, Yu; Barksdale, DaRel; Galdzicki, Zygmunt; Bausch, Suzanne B.

    2014-01-01

    Emerging evidence suggests that neuronal responses to N-methyl-d-aspartate (NMDAR) activation/inactivation are influenced by subunit composition. For example, activation of synaptic NMDAR (comprised of GluN2A > GluN2B) phosphorylates cAMP-response-element-binding protein (CREB) at Ser 133, induces BDNF expression and promotes neuronal survival. Activation of extrasynaptic NMDAR (comprised of GluN2B>GluN2), dephosphorylates CREB (Ser 133), reduces BDNF expression and triggers neuronal death. These results led us to hypothesize that chronic inhibition of GluN2B-containing NMDAR would increase CREB (Ser 133) phosphorylation, increase BDNF levels and subsequently alter downstream dynorphin (DYN) and neuropeptide Y (NPY) expression. We focused on DYN and NPY because these neuropeptides can decrease excitatory neurotransmission and seizure occurrence and we reported previously that seizure-like events are reduced following chronic treatment with GluN2B antagonists. Consistent with our hypothesis, chronic treatment (17-21 days) of hippocampal slice cultures with the GluN2B-selective antagonists ifenprodil or Ro25,6981 increased both CREB (Ser 133) phosphorylation and granule cell mossy fiber pathway DYN expression. Similar treatment with the non-subtype-selective NMDAR antagonists D-APV or memantine had no significant effect on either CREB (Ser 133) phosphorylation or DYN expression. In contrast to our hypothesis, BDNF levels were decreased following chronic treatment with Ro25,6981, but not ifenprodil, D-APV or memantine. Blockade of BDNF actions and TrkB activation did not significantly augment hilar DYN expression in vehicle-treated cultures and had no effect in Ro25,6981 treated cultures. These finding suggest that chronic exposure to GluN2B-selective NMDAR antagonists increased DYN expression through a putatively pCREB-dependent, but BDNF/TrkB-independent mechanism. PMID:24769103

  10. Microglia engulf viable newborn cells in the epileptic dentate gyrus.

    PubMed

    Luo, Cong; Koyama, Ryuta; Ikegaya, Yuji

    2016-09-01

    Microglia, which are the brain's resident immune cells, engulf dead neural progenitor cells during adult neurogenesis in the subgranular zone (SGZ) of the dentate gyrus (DG). The number of newborn cells in the SGZ increases significantly after status epilepticus (SE), but whether and how microglia regulate the number of newborn cells after SE remain unclear. Here, we show that microglia rapidly eliminate newborn cells after SE by primary phagocytosis, a process by which viable cells are engulfed, thereby regulating the number of newborn cells that are incorporated into the DG. The number of newborn cells in the DG was increased at 5 days after SE in the adult mouse brain but rapidly decreased to the control levels within a week. During this period, microglia in the DG were highly active and engulfed newborn cells. We found that the majority of engulfed newborn cells were caspase-negative viable cells. Finally, inactivation of microglia with minocycline maintained the increase in the number of newborn cells after SE. Furthermore, minocycline treatment after SE induced the emergence of hilar ectopic granule cells. Thus, our findings suggest that microglia may contribute to homeostasis of the dentate neurogenic niche by eliminating excess newborn cells after SE via primary phagocytosis. GLIA 2016;64:1508-1517. PMID:27301702

  11. Spatial firing correlates of physiologically distinct cell types of the rat dentate gyrus

    PubMed Central

    Neunuebel, Joshua P.; Knierim, James J.

    2012-01-01

    The dentate gyrus (DG) occupies a key position in information flow through the hippocampus. Its principal cell, the granule cell, has spatially selective place fields. However, the behavioral correlates of cells located in the hilus of the rat dentate gyrus are unknown. We report here that cells below the granule layer show spatially selective firing that consists of multiple subfields. Other cells recorded from the DG had single place fields. Compared to cells with multiple fields, cells with single fields fired at lower rates during sleep; were less bursty; and were more likely to be recorded simultaneously with large populations of neurons that were active during sleep and silent during behavior. We propose that cells with single fields are likely to be mature granule cells that use sparse encoding to potentially disambiguate input patterns. Furthermore, we hypothesize that cells with multiple fields might be cells of the hilus or newborn granule cells. These data are the first demonstration, based on physiological criteria, that single-field and multiple-field cells constitute at least two distinct cell classes in the DG. Because of the heterogeneity of firing correlates and cell types in the DG, understanding which cell types correspond to which firing patterns, and how these correlates change with behavioral state and between different environments, are critical questions for testing longstanding computational theories that the DG performs a pattern separation function using a very sparse coding strategy. PMID:22423105

  12. Shifts in excitatory/inhibitory balance by juvenile stress: A role for neuron-astrocyte interaction in the dentate gyrus.

    PubMed

    Albrecht, Anne; Ivens, Sebastian; Papageorgiou, Ismini E; Çalışkan, Gürsel; Saiepour, Nasrin; Brück, Wolfgang; Richter-Levin, Gal; Heinemann, Uwe; Stork, Oliver

    2016-06-01

    Childhood trauma is a well-described risk factor for the development of stress-related psychopathology such as posttraumatic stress disorder or depression later in life. Childhood adversity can be modeled in rodents by juvenile stress (JS) protocols, resulting in impaired coping with stressful challenges in adulthood. In the current study, we investigated the long-lasting impact of JS on the expression of molecular factors for glutamate and γ-aminobutyric acid (GABA) uptake and turnover in sublayers of the dentate gyrus (DG) using laser microdissection and quantitative real-time polymerase chain reaction. We observed reduced mRNA expression levels after JS for factors mediating astrocytic glutamate and GABA uptake and degradation. These alterations were prominently observed in the dorsal but not ventral DG granule cell layer, indicating a lasting change in astrocytic GABA and glutamate metabolism that may affect dorsal DG network activity. Indeed, we observed increased inhibition and a lack of facilitation in response to paired-pulse stimulation at short interstimulus intervals in the dorsal DG after JS, while no alterations were evident in basal synaptic transmission or forms of long-term plasticity. The shift in paired-pulse response was mimicked by pharmacologically blocking the astrocytic GABA transporter GAT-3 in naïve animals. Accordingly, reduced expression levels of GAT-3 were confirmed at the protein level in the dorsal granule cell layer of rats stressed in juvenility. Together, these data demonstrate a lasting shift in the excitatory/inhibitory balance of dorsal DG network activity by JS that appears to be mediated by decreased GABA uptake into astrocytes. GLIA 2016;64:911-922. PMID:26875694

  13. Kindled seizures selectively reduce a subpopulation of (/sup 3/H)quinuclidinyl benzilate binding sites in rat dentate gyrus

    SciTech Connect

    Savage, D.D.; McNamara, J.O.

    1982-09-01

    Amygdala-kindled seizures reduced significantly the total number of (/sup 3/H)quinuclidinyl benzilate binding sites in both dentate and hippocampal gyri compared to electrode implanted unstimulated controls. Both high and low affinity carbachol displaceable binding site populations were significantly reduced in hippocampal gyrus. By contrast, a selective decline of low affinity sites was found in dentate gyrus membranes. The selectivity of the decline in dentate but not hippocampus gyrus underscores the specificity of this molecular response to amygdala-kindled seizures. We suggest that these receptor alterations underlie adaptive mechanisms which antagonize kindled epileptogenesis.

  14. Impaired Survival of Neural Progenitor Cells in Dentate Gyrus of Adult Mice Lacking FMRP

    PubMed Central

    Lazarov, Orly; Demars, Michael P.; Zhao, Kai Da Tommy; Ali, Haroon M.; Grauzas, Vanessa; Kney, Adam; Larson, John

    2011-01-01

    Fragile X syndrome (FXS) is the most common form of inherited intellectual disability in humans. Individuals affected with the disorder exhibit a deficiency of the fragile X mental retardation protein (FMRP), due to transcriptional silencing of the Fmr1 gene. It is widely accepted that learning deficits in FXS result from impaired synaptic function and/or plasticity in the brain. Interestingly, recent evidence suggests that conditional knockout of Fmr1 in neural progenitor cells in mice impairs hippocampal neurogenesis, which in turn contributes to learning impairments. To examine the nature of the neurogenic impairments and determine whether they impact the morphology of the dentate gyrus, we assessed the extent of neural progenitor cell proliferation, survival, and differentiation in older adult Fmr1 knockout mice. Here we show that the number of fast- proliferating cells in the subgranule layer of the dentate gyrus, as well as the subsequent survival of these cells, are dramatically reduced in Fmr1 knockout mice. In addition, the number of mature neurons in the granule layer of the dentate gyrus of these mice is significantly smaller than in WT littermate controls, suggesting that impaired proliferation and survival of neural progenitor cells compromises the structure of the dentate gyrus. Impaired adult neurogenesis may underlie, at least in part, the learning deficits that characterize fragile X syndrome. PMID:22128095

  15. Mutation of the maize sbe1a and ae genes alters morphology and physical behavior of wx-type endosperm starch granules.

    PubMed

    Li, Ji-Hong; Guiltinan, Mark J; Thompson, Donald B

    2007-12-10

    In maize, three isoforms of starch-branching enzyme, SBEI, SBEIIa, and SBEIIb, are encoded by the Sbe1a, Sbe2a, and Amylose extender (Ae) genes, respectively. The objective of this research was to explore the effects of null mutations in the Sbe1a and Ae genes alone and in combination in wx background on kernel characteristics and on the morphology and physical behavior of endosperm starch granules. Differences in kernel morphology and weight, starch accumulation, starch granule size and size distribution, starch microstructure, and thermal properties were observed between the ae wx and sbe1a ae wx plants but not between the sbe1a wx mutants when compared to wx. Starch from sbe1a ae wx plants exhibited a larger granule size with a wider gelatinization temperature range and a lower endotherm enthalpy than ae wx. Microscopy shows weaker iodine staining in sbe1a ae wx starch granules. X-ray diffraction revealed A-type crystallinity in wx and sbe1a wx starches and B-type in sbe1a ae wx and ae wx. This study suggests that, while the SBEIIb isoform plays a dominant role in maize endosperm starch synthesis, SBEI also plays a role, which is only observable in the presence of the ae mutation. PMID:17765880

  16. Starch granule formation and protein deposition in wheat (Triticum aestivum L.) starchy endosperm cells is altered by high temperature during grain fill

    NASA Astrophysics Data System (ADS)

    Hurkman, William J.; Wood, Delilah F.

    2010-06-01

    High temperatures during wheat grain fill decrease starch and protein levels, adversely affecting wheat yield and flour quality. To determine the effect of high temperature on starchy endosperm cell development, grain (Triticum aestivum L. 'Butte 86') was produced under a 24/17°C or 37/28°C day/night regimen imposed from flowering to maturity and starch and protein deposition examined using scanning electron microscopy. The high temperature regimen shortened the duration of grain fill from 40 to 18 days. Under the 37/28°C regimen, A- and B-type starch granules decreased in size. A-type starch granules also exhibited pitting, suggesting enhanced action of starch degradative enzymes. Under both temperature regimens, protein bodies originated early in development and coalesced during mid to late development to form a continuous protein matrix surrounding the starch granules. Under the 37/28°C regimen, the proportion of protein matrix increased in endosperm cells of mature grain. Taken together, the changes in starch granule number and size and in protein matrix amount provide clues for understanding how high temperature during grain fill can affect end use properties of wheat flour.

  17. Dentate Gyrus Circuitry Features Improve Performance of Sparse Approximation Algorithms

    PubMed Central

    Petrantonakis, Panagiotis C.; Poirazi, Panayiota

    2015-01-01

    Memory-related activity in the Dentate Gyrus (DG) is characterized by sparsity. Memory representations are seen as activated neuronal populations of granule cells, the main encoding cells in DG, which are estimated to engage 2–4% of the total population. This sparsity is assumed to enhance the ability of DG to perform pattern separation, one of the most valuable contributions of DG during memory formation. In this work, we investigate how features of the DG such as its excitatory and inhibitory connectivity diagram can be used to develop theoretical algorithms performing Sparse Approximation, a widely used strategy in the Signal Processing field. Sparse approximation stands for the algorithmic identification of few components from a dictionary that approximate a certain signal. The ability of DG to achieve pattern separation by sparsifing its representations is exploited here to improve the performance of the state of the art sparse approximation algorithm “Iterative Soft Thresholding” (IST) by adding new algorithmic features inspired by the DG circuitry. Lateral inhibition of granule cells, either direct or indirect, via mossy cells, is shown to enhance the performance of the IST. Apart from revealing the potential of DG-inspired theoretical algorithms, this work presents new insights regarding the function of particular cell types in the pattern separation task of the DG. PMID:25635776

  18. Selective alterations of neurons and circuits related to early memory loss in Alzheimer’s disease

    PubMed Central

    Llorens-Martín, Maria; Blazquez-Llorca, Lidia; Benavides-Piccione, Ruth; Rabano, Alberto; Hernandez, Felix; Avila, Jesus; DeFelipe, Javier

    2014-01-01

    A progressive loss of episodic memory is a well-known clinical symptom that characterizes Alzheimer’s disease (AD). The beginning of this loss of memory has been associated with the very early, pathological accumulation of tau and neuronal degeneration observed in the entorhinal cortex (EC). Tau-related pathology is thought to then spread progressively to the hippocampal formation and other brain areas as the disease progresses. The major cortical afferent source of the hippocampus and dentate gyrus is the EC through the perforant pathway. At least two main circuits participate in the connection between EC and the hippocampus; one originating in layer II and the other in layer III of the EC giving rise to the classical trisynaptic (ECII → dentate gyrus → CA3 → CA1) and monosynaptic (ECIII → CA1) circuits. Thus, the study of the early pathological changes in these circuits is of great interest. In this review, we will discuss mainly the alterations of the granule cell neurons of the dentate gyrus and the atrophy of CA1 pyramidal neurons that occur in AD in relation to the possible differential alterations of these two main circuits. PMID:24904307

  19. Behavior modification after inactivation of cerebellar dentate nuclei.

    PubMed

    Peterson, Todd C; Villatoro, Lee; Arneson, Tom; Ahuja, Brittany; Voss, Stephanie; Swain, Rodney A

    2012-08-01

    Effort-based decision making occurs when subjects are given a choice between a reward available at a high response cost and a reward available at a low response cost and is altered in individuals with disorders such as autism or particular patterns of brain injury. The current study explored the relationship between effort-based decision making and reinforcement characteristics in the T maze. This was done using both normal animals and animals with bilateral inactivation of the cerebellar dentate nuclei. Rats chose between alternatives in which one arm contained high-density reinforcement (HR) and the other arm contained low-density reinforcement (LR). During training, the HR arm was obstructed and the point at which the animal no longer worked for reinforcement (breaking point) was determined. The cerebellar dentate nuclei were then transiently inactivated and once again breaking points were assessed. The results indicated that inactivation of the dentate nucleus disrupted effort-based decision making. Additionally, altering both the palatability and the magnitude of the reinforcement were assessed in an attempt to reestablish the original preinactivation breaking point. It was hypothesized that an increase in the strength or magnitude of the reinforcement would promote an increase in the breaking point of the animal even when the cerebellum was inactivated. The results indicated that with both strategies animals effectively reestablished original breaking points. The results of this study will inform the current literature regarding the modification of behavior after brain injury and further the understanding of the behavioral deficits associated with cerebellar dysfunction. PMID:22845704

  20. Cholinergic afferent stimulation induces axonal function plasticity in adult hippocampal granule cells.

    PubMed

    Martinello, Katiuscia; Huang, Zhuo; Lujan, Rafael; Tran, Baouyen; Watanabe, Masahiko; Cooper, Edward C; Brown, David A; Shah, Mala M

    2015-01-21

    Acetylcholine critically influences hippocampal-dependent learning. Cholinergic fibers innervate hippocampal neuron axons, dendrites, and somata. The effects of acetylcholine on axonal information processing, though, remain unknown. By stimulating cholinergic fibers and making electrophysiological recordings from hippocampal dentate gyrus granule cells, we show that synaptically released acetylcholine preferentially lowered the action potential threshold, enhancing intrinsic excitability and synaptic potential-spike coupling. These effects persisted for at least 30 min after the stimulation paradigm and were due to muscarinic receptor activation. This caused sustained elevation of axonal intracellular Ca(2+) via T-type Ca(2+) channels, as indicated by two-photon imaging. The enhanced Ca(2+) levels inhibited an axonal KV7/M current, decreasing the spike threshold. In support, immunohistochemistry revealed muscarinic M1 receptor, CaV3.2, and KV7.2/7.3 subunit localization in granule cell axons. Since alterations in axonal signaling affect neuronal firing patterns and neurotransmitter release, this is an unreported cellular mechanism by which acetylcholine might, at least partly, enhance cognitive processing. PMID:25578363

  1. Different subsets of newborn granule cells: a possible role in epileptogenesis?

    PubMed

    Bielefeld, Pascal; van Vliet, Erwin A; Gorter, Jan A; Lucassen, Paul J; Fitzsimons, Carlos P

    2014-01-01

    Several factors, including epileptic seizures, can strongly stimulate ongoing neurogenesis in the adult hippocampus. Although adult-born granule cells generated after seizure activity have different physiological properties from their normal counterparts, they integrate into the existing, mature network of the adult hippocampal dentate gyrus. However, the exact role of the neurogenic response during epilepsy and its possible involvement in epileptogenesis have remained elusive. Here, we discuss recent studies shedding new light on the interplay between epilepsy and neurogenesis, and try to explain discrepancies in this literature by proposing seizure severity-dependent induction of two subsets of newborn cells with different properties. We hypothesise that a low seizure intensity would stimulate neurogenesis to a 'physiological plasticity' level and have few pathological consequences. In contrast, a high initial seizure intensity may induce a specific subset of altered and/or ectopically located new granule cells with different electrophysiological properties that could initiate hyperexcitatory recurrent networks that could, in turn, contribute to chronic epilepsy. This hypothesis may clarify previously contradictory data in the literature, and could thereby aid in our understanding of the role of neurogenesis in epileptogenesis, and open up promising avenues for therapeutic intervention. PMID:24387591

  2. Neurons of the Dentate Molecular Layer in the Rabbit Hippocampus

    PubMed Central

    Sancho-Bielsa, Francisco J.; Navarro-López, Juan D.; Alonso-Llosa, Gregori; Molowny, Asunción; Ponsoda, Xavier; Yajeya, Javier; López-García, Carlos

    2012-01-01

    The molecular layer of the dentate gyrus appears as the main entrance gate for information into the hippocampus, i.e., where the perforant path axons from the entorhinal cortex synapse onto the spines and dendrites of granule cells. A few dispersed neuronal somata appear intermingled in between and probably control the flow of information in this area. In rabbits, the number of neurons in the molecular layer increases in the first week of postnatal life and then stabilizes to appear permanent and heterogeneous over the individuals’ life span, including old animals. By means of Golgi impregnations, NADPH histochemistry, immunocytochemical stainings and intracellular labelings (lucifer yellow and biocytin injections), eight neuronal morphological types have been detected in the molecular layer of developing adult and old rabbits. Six of them appear as interneurons displaying smooth dendrites and GABA immunoreactivity: those here called as globoid, vertical, small horizontal, large horizontal, inverted pyramidal and polymorphic. Additionally there are two GABA negative types: the sarmentous and ectopic granular neurons. The distribution of the somata and dendritic trees of these neurons shows preferences for a definite sublayer of the molecular layer: small horizontal, sarmentous and inverted pyramidal neurons are preferably found in the outer third of the molecular layer; vertical, globoid and polymorph neurons locate the intermediate third, while large horizontal and ectopic granular neurons occupy the inner third or the juxtagranular molecular layer. Our results reveal substantial differences in the morphology and electrophysiological behaviour between each neuronal archetype in the dentate molecular layer, allowing us to propose a new classification for this neural population. PMID:23144890

  3. Adult-born dentate neurons are recruited in both spatial memory encoding and retrieval.

    PubMed

    Tronel, Sophie; Charrier, Vanessa; Sage, Cyrille; Maitre, Marlene; Leste-Lasserre, Thierry; Abrous, Djoher N

    2015-11-01

    Adult neurogenesis occurs in the dentate gyrus (DG) of the hippocampus, which is a key structure in learning and memory. Adult-generated granule cells have been shown to play a role in spatial memory processes such as acquisition or retrieval, in particular during an immature stage when they exhibit a period of increased plasticity. Here, we demonstrate that immature and mature neurons born in the DG of adult rats are similarly activated in spatial memory processes. By imaging the activation of these two different neuron generations in the same rat and by using the immediate early gene Zif268, we show that these neurons are involved in both spatial memory acquisition and retrieval. These results demonstrate that adult-generated granule cells are involved in memory beyond their immaturity stage. PMID:25913775

  4. Sustained transcription of the immediate early gene Arc in the dentate gyrus after spatial exploration.

    PubMed

    Ramirez-Amaya, Victor; Angulo-Perkins, Arafat; Chawla, Monica K; Barnes, Carol A; Rosi, Susanna

    2013-01-23

    After spatial exploration in rats, Arc mRNA is expressed in ∼2% of dentate gyrus (DG) granule cells, and this proportion of Arc-positive neurons remains stable for ∼8 h. This long-term presence of Arc mRNA following behavior is not observed in hippocampal CA1 pyramidal cells. We report here that in rats ∼50% of granule cells with cytoplasmic Arc mRNA, induced some hours previously during exploration, also show Arc expression in the nucleus. This suggests that recent transcription can occur long after the exploration behavior that elicited it. To confirm that the delayed nuclear Arc expression was indeed recent transcription, Actinomycin D was administered immediately after exploration. This treatment resulted in inhibition of recent Arc expression both when evaluated shortly after exploratory behavior as well as after longer time intervals. Together, these data demonstrate a unique kinetic profile for Arc transcription in hippocampal granule neurons following behavior that is not observed in other cell types. Among a number of possibilities, this sustained transcription may provide a mechanism that ensures that the synaptic connection weights in the sparse population of granule cells recruited during a given behavioral event are able to be modified. PMID:23345235

  5. Granulation of fine powder

    DOEpatents

    Chen, Ching-Fong

    2016-08-09

    A mixture of fine powder including thorium oxide was converted to granulated powder by forming a first-green-body and heat treating the first-green-body at a high temperature to strengthen the first-green-body followed by granulation by crushing or milling the heat-treated first-green-body. The granulated powder was achieved by screening through a combination of sieves to achieve the desired granule size distribution. The granulated powder relies on the thermal bonding to maintain its shape and structure. The granulated powder contains no organic binder and can be stored in a radioactive or other extreme environment. The granulated powder was pressed and sintered to form a dense compact with a higher density and more uniform pore size distribution.

  6. The Ever-Changing Morphology of Hippocampal Granule Neurons in Physiology and Pathology

    PubMed Central

    Llorens-Martín, María; Rábano, Alberto; Ávila, Jesús

    2016-01-01

    Newborn neurons are continuously added to the hippocampal dentate gyrus throughout adulthood. In this review, we analyze the maturational stages that newborn granule neurons go through, with a focus on their unique morphological features during each stage under both physiological and pathological circumstances. In addition, the influence of deleterious (such as schizophrenia, stress, Alzheimer's disease, seizures, stroke, inflammation, dietary deficiencies, or the consumption of drugs of abuse or toxic substances) and neuroprotective (physical exercise and environmental enrichment) stimuli on the maturation of these cells will be examined. Finally, the regulation of this process by proteins involved in neurodegenerative and neurological disorders such as Glycogen synthase kinase 3β, Disrupted in Schizophrenia 1 (DISC-1), Glucocorticoid receptor, pro-inflammatory mediators, Presenilin-1, Amyloid precursor protein, Cyclin-dependent kinase 5 (CDK5), among others, will be evaluated. Given the recently acquired relevance of the dendritic branch as a functional synaptic unit required for memory storage, a full understanding of the morphological alterations observed in newborn neurons may have important consequences for the prevention and treatment of the cognitive and affective alterations that evolve in conjunction with impaired adult hippocampal neurogenesis. PMID:26834550

  7. Object/Context-Specific Memory Deficits Associated with Loss of Hippocampal Granule Cells after Adrenalectomy in Rats

    ERIC Educational Resources Information Center

    Spanswick, Simon C.; Sutherland, Robert J.

    2010-01-01

    Chronic adrenalectomy (ADX) causes a gradual and selective loss of granule cells in the dentate gyrus (DG) of the rat. Here, we administered replacement corticosterone to rats beginning 10 wk after ADX. We then tested them in three discrimination tasks based on object novelty, location, or object/context association. Only during testing of the…

  8. Assessment of the Role of MAP Kinase in Mediating Activity-Dependent Transcriptional Activation of the Immediate Early Gene "Arc/Arg3.1" in the Dentate Gyrus in Vivo

    ERIC Educational Resources Information Center

    Chotiner, Jennifer K.; Nielson, Jessica; Farris, Shannon; Lewandowski, Gail; Huang, Fen; Banos, Karla; de Leon, Ray; Steward, Oswald

    2010-01-01

    Different physiological and behavioral events activate transcription of "Arc/Arg3.1" in neurons in vivo, but the signal transduction pathways that mediate induction in particular situations remain to be defined. Here, we explore the relationships between induction of "Arc/Arg3.1" transcription in dentate granule cells in vivo and activation of…

  9. Competition from newborn granule cells does not drive axonal retraction of silenced old granule cells in the adult hippocampus

    PubMed Central

    Lopez, Carla M.; Pelkey, Kenneth A.; Chittajallu, Ramesh; Nakashiba, Toshiaki; Tóth, Katalin; Tonegawa, Susumu; McBain, Chris J.

    2012-01-01

    In the developing nervous system synaptic refinement, typified by the neuromuscular junction where supernumerary connections are eliminated by axon retraction leaving the postsynaptic target innervated by a single dominant input, critically regulates neuronal circuit formation. Whether such competition-based pruning continues in established circuits of mature animals remains unknown. This question is particularly relevant in the context of adult neurogenesis where newborn cells must integrate into preexisting circuits, and thus, potentially compete with functionally mature synapses to gain access to their postsynaptic targets. The hippocampus plays an important role in memory formation/retrieval and the dentate gyrus (DG) subfield exhibits continued neurogenesis into adulthood. Therefore, this region contains both mature granule cells (old GCs) and immature recently born GCs that are generated throughout adult life (young GCs), providing a neurogenic niche model to examine the role of competition in synaptic refinement. Recent work from an independent group in developing animals indicated that embryonically/early postnatal generated GCs placed at a competitive disadvantage by selective expression of tetanus toxin (TeTX) to prevent synaptic release rapidly retracted their axons, and that this retraction was driven by competition from newborn GCs lacking TeTX. In contrast, following 3–6 months of selective TeTX expression in old GCs of adult mice we did not observe any evidence of axon retraction. Indeed ultrastructural analyses indicated that the terminals of silenced GCs even maintained synaptic contact with their postsynaptic targets. Furthermore, we did not detect any significant differences in the electrophysiological properties between old GCs in control and TeTX conditions. Thus, our data demonstrate a remarkable stability in the face of a relatively prolonged period of altered synaptic competition between two populations of neurons within the adult brain

  10. Increased dentate neurogenesis after grafting of glial restricted progenitors or neural stem cells in the aging hippocampus.

    PubMed

    Hattiangady, Bharathi; Shuai, Bing; Cai, Jingli; Coksaygan, Turhan; Rao, Mahendra S; Shetty, Ashok K

    2007-08-01

    Neurogenesis in the dentate gyrus (DG) declines severely by middle age, potentially because of age-related changes in the DG microenvironment. We hypothesize that providing fresh glial restricted progenitors (GRPs) or neural stem cells (NSCs) to the aging hippocampus via grafting enriches the DG microenvironment and thereby stimulates the production of new granule cells from endogenous NSCs. The GRPs isolated from the spinal cords of embryonic day 13.5 transgenic F344 rats expressing human alkaline phosphatase gene and NSCs isolated from embryonic day 9 caudal neural tubes of Sox-2:EGFP transgenic mice were expanded in vitro and grafted into the hippocampi of middle-aged (12 months old) F344 rats. Both types of grafts survived well, and grafted NSCs in addition migrated to all layers of the hippocampus. Phenotypic characterization revealed that both GRPs and NSCs differentiated predominantly into astrocytes and oligodendrocytic progenitors. Neuronal differentiation of graft-derived cells was mostly absent except in the dentate subgranular zone (SGZ), where some of the migrated NSCs but not GRPs differentiated into neurons. Analyses of the numbers of newly born neurons in the DG using 5'-bromodeoxyuridine and/or doublecortin assays, however, demonstrated considerably increased dentate neurogenesis in animals receiving grafts of GRPs or NSCs in comparison with both naïve controls and animals receiving sham-grafting surgery. Thus, both GRPs and NSCs survive well, differentiate predominantly into glia, and stimulate the endogenous NSCs in the SGZ to produce more new dentate granule cells following grafting into the aging hippocampus. Grafting of GRPs or NSCs therefore provides an attractive approach for improving neurogenesis in the aging hippocampus. Disclosure of potential conflicts of interest is found at the end of this article. PMID:17510219

  11. Roles of granule size in over-granulation during high shear wet granulation.

    PubMed

    Shi, Limin; Feng, Yushi; Sun, Changquan Calvin

    2010-08-01

    A mechanistic understanding of the over-granulation problem during high shear wet granulation (HSWG) process can guide efficient development of robust formulation and manufacturing process. Using microcrystalline cellulose (MCC) as a model compound, we demonstrate that size enlargement is an important mechanism for over-granulation in HSWG. A higher granulation water level results in larger granules and lower tabletability. With increasing water, granules enlarge sharply when water level is higher than 65%. Granule tabletability deteriorates with increasing granule size and becomes over-granulated when more than 70% water is used. For a batch of over-granulated granule that is ground and sieved, tabletability of the sieved fractions decreases with increasing granule size. The tabletability of the finest fraction (45-90 microm) is nearly four times that of the largest fraction (300-425 microm). These results show that size reduction can be an effective strategy to address the problem of over-granulation. PMID:20232456

  12. Calcium channel blockade attenuates abnormal synaptic transmission in the dentate gyrus elicited by entorhinal amyloidopathy.

    PubMed

    Gholami Pourbadie, Hamid; Naderi, Nima; Janahmadi, Mahyar; Mehranfard, Nasrin; Motamedi, Fereshteh

    2016-10-01

    Entorhinal-hippocampal network is one of the earliest circuits which is affected by Alzheimer's disease (AD). There are numerous data providing the evidence of synaptic deficit in the dentate gyrus (DG) of AD animal model. However, there is little known about how entorhinal cortex (EC) amyloidophaty affects each excitatory and/or inhibitory transmission in the early stage of AD. On the other hand, it is believed that calcium dyshomeostasis has a critical role in the etiology of AD. Here, the effect of the EC amyloid pathogenesis on excitatory or inhibitory post synaptic currents (EPSC and IPSC, respectively) in the DG granule cells and then the possible neuroprotective action of L-type calcium channel blockers (CCBs), nimodipine and isradipine, were examined. The amyloid beta (Aβ) 1-42 was injected bilaterally into the EC of male rats and one week later, synaptic currents in the DG granule cells were assessed by whole cell patch clamp. EPSCs were evoked by stimulating the perforant pathway. Voltage clamp recording showed profound decrease of evoked EPSC amplitude and paired pulse facilitation in the DG granule cells of Aβ treated rats. Furthermore, AMPA/NMDA ratio was significantly decreased in the Aβ treated animals. On the other hand, amplitude of IPSC currents was significantly increased in the DG granule cells of these animals. These modifications of synaptic currents were partially reversed by daily intracerebroventricular administration of isradipine or nimodipine. In conclusion, our results suggest that Aβ in the EC triggers decreased excitatory transmission in the DG with substantial decrement in AMPA currents, leading to a prominent activity of inhibitory circuits and increased inhibition of granule cells which may contribute to the development of AD-related neurological deficits in AD and treatment by CCBs could preserve normal synaptic transmission against Aβ toxicity. PMID:27240164

  13. C9orf72 Hexanucleotide Expansions Are Associated with Altered Endoplasmic Reticulum Calcium Homeostasis and Stress Granule Formation in Induced Pluripotent Stem Cell-Derived Neurons from Patients with Amyotrophic Lateral Sclerosis and Frontotemporal Dementia.

    PubMed

    Dafinca, Ruxandra; Scaber, Jakub; Ababneh, Nida'a; Lalic, Tatjana; Weir, Gregory; Christian, Helen; Vowles, Jane; Douglas, Andrew G L; Fletcher-Jones, Alexandra; Browne, Cathy; Nakanishi, Mahito; Turner, Martin R; Wade-Martins, Richard; Cowley, Sally A; Talbot, Kevin

    2016-08-01

    An expanded hexanucleotide repeat in a noncoding region of the C9orf72 gene is a major cause of amyotrophic lateral sclerosis (ALS), accounting for up to 40% of familial cases and 7% of sporadic ALS in European populations. We have generated induced pluripotent stem cells (iPSCs) from fibroblasts of patients carrying C9orf72 hexanucleotide expansions, differentiated these to functional motor and cortical neurons, and performed an extensive phenotypic characterization. In C9orf72 iPSC-derived motor neurons, decreased cell survival is correlated with dysfunction in Ca(2+) homeostasis, reduced levels of the antiapoptotic protein Bcl-2, increased endoplasmic reticulum (ER) stress, and reduced mitochondrial membrane potential. Furthermore, C9orf72 motor neurons, and also cortical neurons, show evidence of abnormal protein aggregation and stress granule formation. This study is an extensive characterization of iPSC-derived motor neurons as cellular models of ALS carrying C9orf72 hexanucleotide repeats, which describes a novel pathogenic link between C9orf72 mutations, dysregulation of calcium signaling, and altered proteostasis and provides a potential pharmacological target for the treatment of ALS and the related neurodegenerative disease frontotemporal dementia. Stem Cells 2016;34:2063-2078. PMID:27097283

  14. C9orf72 Hexanucleotide Expansions Are Associated with Altered Endoplasmic Reticulum Calcium Homeostasis and Stress Granule Formation in Induced Pluripotent Stem Cell‐Derived Neurons from Patients with Amyotrophic Lateral Sclerosis and Frontotemporal Dementia

    PubMed Central

    Dafinca, Ruxandra; Scaber, Jakub; Ababneh, Nida'a; Lalic, Tatjana; Weir, Gregory; Christian, Helen; Vowles, Jane; Douglas, Andrew G.L.; Fletcher‐Jones, Alexandra; Browne, Cathy; Nakanishi, Mahito; Turner, Martin R.; Wade‐Martins, Richard

    2016-01-01

    Abstract An expanded hexanucleotide repeat in a noncoding region of the C9orf72 gene is a major cause of amyotrophic lateral sclerosis (ALS), accounting for up to 40% of familial cases and 7% of sporadic ALS in European populations. We have generated induced pluripotent stem cells (iPSCs) from fibroblasts of patients carrying C9orf72 hexanucleotide expansions, differentiated these to functional motor and cortical neurons, and performed an extensive phenotypic characterization. In C9orf72 iPSC‐derived motor neurons, decreased cell survival is correlated with dysfunction in Ca2+ homeostasis, reduced levels of the antiapoptotic protein Bcl‐2, increased endoplasmic reticulum (ER) stress, and reduced mitochondrial membrane potential. Furthermore, C9orf72 motor neurons, and also cortical neurons, show evidence of abnormal protein aggregation and stress granule formation. This study is an extensive characterization of iPSC‐derived motor neurons as cellular models of ALS carrying C9orf72 hexanucleotide repeats, which describes a novel pathogenic link between C9orf72 mutations, dysregulation of calcium signaling, and altered proteostasis and provides a potential pharmacological target for the treatment of ALS and the related neurodegenerative disease frontotemporal dementia. Stem Cells 2016;34:2063–2078 PMID:27097283

  15. Understanding size enlargement and hardening of granules on tabletability of unlubricated granules prepared by dry granulation.

    PubMed

    Patel, Sarsvatkumar; Dahiya, Sandeepkumar; Sun, Changquan Calvin; Bansal, Arvind Kumar

    2011-02-01

    The mechanism of loss of "reworkability" or tabletability of dry granulated microcrystalline cellulose (MCC) was investigated in relation to both granule size enlargement and granule hardness. Slugs of MCC were prepared under three pressures (12.5, 37.5, and 93.8 MPa) and tabletability (tensile strength vs. pressure) of respective granules (three different sizes) was determined. Nominal single granule fracture strength and granule friability were measured. The reduction in tabletability was profound for harder granules, which were obtained from higher slugging pressure. This is consistent with their ability to resist granule fragmentation during tableting. Variation in granule size exhibits negligible effect on tabletability for the lowest slugging pressure and only a small effect for the middle and highest slugging pressure. This observation is again related to different tendency to granule fragmentation during compaction. The results suggest that granule-hardening negatively affects tensile strength more than that of granule size enlargement for MCC. PMID:20803605

  16. Distinct stages in stress granule assembly and disassembly.

    PubMed

    Wheeler, Joshua R; Matheny, Tyler; Jain, Saumya; Abrisch, Robert; Parker, Roy

    2016-01-01

    Stress granules are non-membrane bound RNA-protein (RNP) assemblies that form when translation initiation is limited and contain a biphasic structure with stable core structures surrounded by a less concentrated shell. The order of assembly and disassembly of these two structures remains unknown. Time course analysis of granule assembly suggests that core formation is an early event in granule assembly. Stress granule disassembly is also a stepwise process with shell dissipation followed by core clearance. Perturbations that alter liquid-liquid phase separations (LLPS) driven by intrinsically disordered protein regions (IDR) of RNA binding proteins in vitro have the opposite effect on stress granule assembly in vivo. Taken together, these observations argue that stress granules assemble through a multistep process initiated by stable assembly of untranslated mRNPs into core structures, which could provide sufficient high local concentrations to allow for a localized LLPS driven by IDRs on RNA binding proteins. PMID:27602576

  17. Age-Dependent Labeling and Imaging of Insulin Secretory Granules

    PubMed Central

    Ivanova, Anna; Kalaidzidis, Yannis; Dirkx, Ronald; Sarov, Mihail; Gerlach, Michael; Schroth-Diez, Britta; Müller, Andreas; Liu, Yanmei; Andree, Cordula; Mulligan, Bernard; Münster, Carla; Kurth, Thomas; Bickle, Marc; Speier, Stephan; Anastassiadis, Konstantinos; Solimena, Michele

    2013-01-01

    Insulin is stored within the secretory granules of pancreatic β-cells, and impairment of its release is the hallmark of type 2 diabetes. Preferential exocytosis of newly synthesized insulin suggests that granule aging is a key factor influencing insulin secretion. Here, we illustrate a technology that enables the study of granule aging in insulinoma cells and β-cells of knock-in mice through the conditional and unequivocal labeling of insulin fused to the SNAP tag. This approach, which overcomes the limits encountered with previous strategies based on radiolabeling or fluorescence timer proteins, allowed us to formally demonstrate the preferential release of newly synthesized insulin and reveal that the motility of cortical granules significantly changes over time. Exploitation of this approach may enable the identification of molecular signatures associated with granule aging and unravel possible alterations of granule turnover in diabetic β-cells. Furthermore, the method is of general interest for the study of membrane traffic and aging. PMID:23929935

  18. Age-dependent labeling and imaging of insulin secretory granules.

    PubMed

    Ivanova, Anna; Kalaidzidis, Yannis; Dirkx, Ronald; Sarov, Mihail; Gerlach, Michael; Schroth-Diez, Britta; Müller, Andreas; Liu, Yanmei; Andree, Cordula; Mulligan, Bernard; Münster, Carla; Kurth, Thomas; Bickle, Marc; Speier, Stephan; Anastassiadis, Konstantinos; Solimena, Michele

    2013-11-01

    Insulin is stored within the secretory granules of pancreatic β-cells, and impairment of its release is the hallmark of type 2 diabetes. Preferential exocytosis of newly synthesized insulin suggests that granule aging is a key factor influencing insulin secretion. Here, we illustrate a technology that enables the study of granule aging in insulinoma cells and β-cells of knock-in mice through the conditional and unequivocal labeling of insulin fused to the SNAP tag. This approach, which overcomes the limits encountered with previous strategies based on radiolabeling or fluorescence timer proteins, allowed us to formally demonstrate the preferential release of newly synthesized insulin and reveal that the motility of cortical granules significantly changes over time. Exploitation of this approach may enable the identification of molecular signatures associated with granule aging and unravel possible alterations of granule turnover in diabetic β-cells. Furthermore, the method is of general interest for the study of membrane traffic and aging. PMID:23929935

  19. Second Harmonic Generation Mediated by Aligned Water in Starch Granules.

    PubMed

    Cisek, Richard; Tokarz, Danielle; Krouglov, Serguei; Steup, Martin; Emes, Michael J; Tetlow, Ian J; Barzda, Virginijus

    2014-12-26

    The origin of second harmonic generation (SHG) in starch granules was investigated using ab initio quantum mechanical modeling and experimentally examined using polarization-in, polarization-out (PIPO) second harmonic generation microscopy. Ab initio calculations revealed that the largest contribution to the SHG signal from A- and B-type allomorphs of starch originates from the anisotropic organization of hydroxide and hydrogen bonds mediated by aligned water found in the polymers. The hypothesis was experimentally tested by imaging maize starch granules under various hydration and heat treatment conditions that alter the hydrogen bond network. The highest SHG intensity was found in fully hydrated starch granules, and heat treatment diminished the SHG intensity. The PIPO SHG imaging showed that dried starch granules have a much higher nonlinear optical susceptibility component ratio than fully hydrated granules. In contrast, deuterated starch granules showed a smaller susceptibility component ratio demonstrating that SHG is highly sensitive to the organization of the hydroxyl and hydrogen bond network. The polarization SHG imaging results of potato starch granules, representing starch allomorph B, were compared to those of maize starch granules representing allomorph A. The results showed that the amount of aligned water was higher in the maize granules. Nonlinear microscopy of starch granules provides evidence that varying hydration conditions leads to significant changes in the nonlinear susceptibility ratio as well as the SHG intensity, supporting the hypothesis from ab initio calculations that the dominant contribution to SHG is due to the ordered hydroxide and hydrogen bond network. PMID:25427055

  20. Differential control of learning and anxiety along the dorso-ventral axis of the dentate gyrus

    PubMed Central

    Kheirbek, Mazen A.; Drew, Liam J.; Burghardt, Nesha S.; Costantini, Daniel O.; Tannenholz, Lindsay; Ahmari, Susanne E.; Zeng, Hongkui; Fenton, André A.; Hen, René

    2013-01-01

    The dentate gyrus (DG), in addition to its role in learning and memory, is increasingly implicated in the pathophysiology of anxiety disorders. Here, we show that, dependent on their position along the dorso-ventral axis of the hippocampus, DG granule cells (GCs) control specific features of anxiety and contextual learning. Using optogenetic techniques to either elevate or decrease GC activity, we demonstrate that GCs in the dorsal DG control exploratory drive and encoding, not retrieval, of contextual fear memories. In contrast, elevating the activity of GCs in the ventral DG has no effect on contextual learning but powerfully suppresses innate anxiety. These results suggest that strategies aimed at modulating the excitability of the ventral DG may be beneficial for the treatment of anxiety disorders. PMID:23473324

  1. Activation of local inhibitory circuits in the dentate gyrus by adult-born neurons.

    PubMed

    Drew, Liam J; Kheirbek, Mazen A; Luna, Victor M; Denny, Christine A; Cloidt, Megan A; Wu, Melody V; Jain, Swati; Scharfman, Helen E; Hen, René

    2016-06-01

    Robust incorporation of new principal cells into pre-existing circuitry in the adult mammalian brain is unique to the hippocampal dentate gyrus (DG). We asked if adult-born granule cells (GCs) might act to regulate processing within the DG by modulating the substantially more abundant mature GCs. Optogenetic stimulation of a cohort of young adult-born GCs (0 to 7 weeks post-mitosis) revealed that these cells activate local GABAergic interneurons to evoke strong inhibitory input to mature GCs. Natural manipulation of neurogenesis by aging-to decrease it-and housing in an enriched environment-to increase it-strongly affected the levels of inhibition. We also demonstrated that elevating activity in adult-born GCs in awake behaving animals reduced the overall number of mature GCs activated by exploration. These data suggest that inhibitory modulation of mature GCs may be an important function of adult-born hippocampal neurons. © 2015 Wiley Periodicals, Inc. PMID:26662922

  2. Maternal Forced Swimming Reduces Cell Proliferation in the Postnatal Dentate Gyrus of Mouse Offspring

    PubMed Central

    Wasinski, Frederick; Estrela, Gabriel R.; Arakaki, Aline M.; Bader, Michael; Alenina, Natalia; Klempin, Friederike; Araújo, Ronaldo C.

    2016-01-01

    Physical exercise positively affects the metabolism and induces proliferation of precursor cells in the adult brain. Maternal exercise likewise provokes adaptations early in the offspring. Using a high-intensity swimming protocol that comprises forced swim training before and during pregnancy, we determined the effect of maternal swimming on the mouse offspring's neurogenesis. Our data demonstrate decreased proliferation in sublayers of the postnatal dentate gyrus in offspring of swimming mother at postnatal day (P) 8 accompanied with decreased survival of newly generated cells 4 weeks later. The reduction in cell numbers was predominantly seen in the hilus and molecular layer. At P35, the reduced amount of cells was also reflected by a decrease in the population of newly generated immature and mature neurons of the granule cell layer. Our data suggest that forced maternal swimming at high-intensity has a negative effect on the neurogenic niche development in postnatal offspring. PMID:27621701

  3. Maternal Forced Swimming Reduces Cell Proliferation in the Postnatal Dentate Gyrus of Mouse Offspring.

    PubMed

    Wasinski, Frederick; Estrela, Gabriel R; Arakaki, Aline M; Bader, Michael; Alenina, Natalia; Klempin, Friederike; Araújo, Ronaldo C

    2016-01-01

    Physical exercise positively affects the metabolism and induces proliferation of precursor cells in the adult brain. Maternal exercise likewise provokes adaptations early in the offspring. Using a high-intensity swimming protocol that comprises forced swim training before and during pregnancy, we determined the effect of maternal swimming on the mouse offspring's neurogenesis. Our data demonstrate decreased proliferation in sublayers of the postnatal dentate gyrus in offspring of swimming mother at postnatal day (P) 8 accompanied with decreased survival of newly generated cells 4 weeks later. The reduction in cell numbers was predominantly seen in the hilus and molecular layer. At P35, the reduced amount of cells was also reflected by a decrease in the population of newly generated immature and mature neurons of the granule cell layer. Our data suggest that forced maternal swimming at high-intensity has a negative effect on the neurogenic niche development in postnatal offspring. PMID:27621701

  4. Experience-dependent remodeling of basket cell networks in the dentate gyrus

    PubMed Central

    Pieraut, Simon; Gounko, Natalia; Sando, Richard; Dang, Westley; Rebboah, Elisabeth; Panda, Satchidananda; Madisen, Linda; Zeng, Hongkui; Maximov, Anton

    2014-01-01

    SUMMARY The structural organization of neural circuits is strongly influenced by experience, but the underlying mechanisms are incompletely understood. We found that, in the developing dentate gyrus (DG), excitatory drive promotes the somatic innervation of principal granule cells (GCs) by parvalbumin (PV)-positive basket cells. By contrast, presynaptic differentiation of GCs and interneuron sub-types that inhibit GC dendrites is largely resistant to loss of glutamatergic neurotransmission. The networks of PV basket cells in the DG are regulated by vesicular release from projection entorhinal cortical neurons and, at least in part, by NMDA receptors in interneurons. Finally, we present evidence that glutamatergic inputs and NMDA receptors regulate these networks through a presynaptic mechanism that appears to control the branching of interneuron axons. Our results provide insights into how cortical activity tunes the inhibition in a subcortical circuit, and reveal new principles of interneuron plasticity. PMID:25277456

  5. Stereotactic injection of cerebrospinal fluid from anti-NMDA receptor encephalitis into rat dentate gyrus impairs NMDA receptor function.

    PubMed

    Würdemann, Till; Kersten, Maxi; Tokay, Tursonjan; Guli, Xiati; Kober, Maria; Rohde, Marco; Porath, Katrin; Sellmann, Tina; Bien, Christian G; Köhling, Rüdiger; Kirschstein, Timo

    2016-02-15

    Autoimmune encephalitis is increasingly recognized in patients with otherwise unexplained encephalopathy with epilepsy. Among these, patients with anti-N-methyl D-aspartate receptor (NMDAR) encephalitis present epileptic seizures, memory deficits, and psychiatric symptoms. However, the functional consequences of such autoantibodies are poorly understood. In order to investigate the pathophysiology of this disease, we stereotactically injected either cerebrospinal fluid (CSF) from three anti-NMDAR encephalitis patients or commercially available anti-NMDAR1 into the dentate gyrus of adult female rats. Control animals were injected with either CSF obtained from three epilepsy patients (ganglioglioma, posttraumatic epilepsy, focal cortical dysplasia) lacking anti-NMDAR or saline. Intracellular recordings from dentate gyrus granule cells showed a significant reduction of the NMDAR-evoked excitatory postsynaptic potentials (NMDAR-EPSPs) in animals treated with anti-NMDAR. As a consequence of this, action potential firing in these cells by NMDAR-EPSPs was significantly impaired. Long-term potentiation in the dentate gyrus was also significantly reduced in rats injected with anti-NMDAR as compared to control animals. This was accompanied by a significantly impaired learning performance in the Morris water maze hidden platform task when the animals had been injected with anti-NMDAR antibody-containing CSF. Our findings suggest that anti-NMDAR lead to reduced NMDAR function in vivo which could contribute to the memory impairment found in patients with anti-NMDAR encephalitis. PMID:26721688

  6. Persistent discharges in dentate gyrus perisoma-inhibiting interneurons require hyperpolarization-activated cyclic nucleotide-gated channel activation.

    PubMed

    Elgueta, Claudio; Köhler, Johannes; Bartos, Marlene

    2015-03-11

    Parvalbumin (PV)-expressing perisoma-inhibiting interneurons (PIIs) of the dentate gyrus integrate rapidly correlated synaptic inputs and generate short-duration action potentials that propagate along the axon to their output synapses, supporting fast inhibitory signaling onto their target cells. Here we show that PV-PIIs in rat and mouse dentate gyrus (DG) integrate their intrinsic activity over time and can turn into a persistent firing mode characterized by the ability to generate long-lasting trains of action potentials at ∼50 Hz in the absence of additional inputs. Persistent firing emerges in the axons remote from the axon initial segment and markedly depends on hyperpolarization-activated cyclic nucleotide-gated channel (HCNC) activation. Persistent firing properties are modulated by intracellular Ca(2+) levels and somatic membrane potential. Detailed computational single-cell PIIs models reveal that HCNC-mediated conductances can contribute to persistent firing during conditions of a shift in their voltage activation curve to more depolarized potentials. Paired recordings from PIIs and their target granule cells show that persistent firing supports strong inhibitory output signaling. Thus, persistent firing may emerge during conditions of intense activation of the network, thereby providing silencing to the circuitry and the maintenance of sparse activity in the dentate gyrus. PMID:25762660

  7. Modeling the Nonlinear Properties of the in vitro Hippocampal Perforant Path-Dentate System Using Multielectrode Array Technology

    PubMed Central

    Courellis, Spiros H.; Gholmieh, Ghassan I.; Marmarelis, Vasilis Z.; Berger, Theodore W.

    2009-01-01

    A modeling approach to characterize the nonlinear dynamic transformations of the dentate gyrus of the hippocampus is presented and experimentally validated. The dentate gyrus is the first region of the hippocampus which receives and integrates sensory information via the perforant path. The perforant path is composed of two distinct pathways: 1) the lateral path and 2) the medial perforant path. The proposed approach examines and captures the short-term dynamic characteristics of these two pathways using a nonparametric, third-order Poisson–Volterra model. The nonlinear characteristics of the two pathways are represented by Poisson–Volterra kernels, which are quantitative descriptors of the nonlinear dynamic transformations. The kernels were computed with experimental data from in vitro hippocampal slices. The electrophysiological activity was measured with custom-made multielectrode arrays, which allowed selective stimulation with random impulse trains and simultaneous recordings of extracellular field potential activity. The results demonstrate that this mathematically rigorous approach is suitable for the multipathway complexity of the hippocampus and yields interpretable models that have excellent predictive capabilities. The resulting models not only accurately predict previously reported electrophysiological descriptors, such as paired pulses, but more important, can be used to predict the electrophysiological activity of dentate granule cells to arbitrary stimulation patterns at the perforant path. PMID:18270006

  8. Epileptiform activity in the dentate gyrus during low-calcium perfusion and exposure to transient electric fields.

    PubMed

    Richardson, T L; O'Reilly, C N

    1995-07-01

    1. The dentate gyrus fails to develop epileptiform activity in many experimental models of epilepsy, including the in vitro low-Ca2+ model. Although manipulating the K+ concentration or osmolality of normal low-Ca2+ perfusion mediums can enhance the propensity of the dentate gyrus to develop seizure activity, the specific mechanisms contributing to this change are still under investigation. Identification of these mechanisms should improve our understanding of epileptogenesis and of the factors contributing to the propensity for seizure discharge in other tissues. 2. In the present experiments we used externally generated electric fields to depolarize the somata of large populations of dentate granule cells during exposure to a perfusion medium with no added Ca2+ (low-Ca2+ medium). Uniform electric fields were generated across an individual slice by passing current between two parallel AgCl-coated silver wires placed on the surface of the artificial cerebral spinal fluid. The wires were positioned to straddle the slice such that the current flow was parallel to the dendrosomatic axis of the cell population under investigation. 3. Under control conditions (low-Ca2+ medium, no applied field), stimulation of the dentate hilus evoked a single antidromic population spike in 89% of the slices studied (n = 27). During application of electric fields the same stimulus evoked epileptiform activity in all trials. Well-formed bursts first occurred at an average field intensity of +22.9 +/- 2.5 (SE) mV/mm (n = 24). The amplitude of individual spikes and the total number of spikes, within a burst increased in a graded fashion as the magnitude of the applied field was increased. 4. High field intensities evoked epileptiform activity in the absence of a synchronizing antidromic stimulus. These field-induced bursts occurred after a progressive buildup of rhythmic activity recorded in the extrasomatic space and could persist for the entire duration of an applied field, lasting for

  9. Developmental iodine deficiency delays the maturation of newborn granule neurons associated with downregulation of p35 in postnatal rat hippocampus.

    PubMed

    Yu, Fei; Wang, Yi; Xu, Hongde; Dong, Jing; Wei, Wei; Wang, Yuan; Shan, Zhongyan; Teng, Weiping; Xi, Qi; Chen, Jie

    2014-08-01

    We evaluated the role of p35 in the maturation of hippocampal granule neurons in offspring caused by developmental iodine deficiency. Two developmental rat models were established with either an iodine-deficient diet, or propylthiouracil-adulterated water (5 ppm) to impair thyroid function, in pregnant rats from gestational day 6 until postnatal day 28. The protein levels of p35, cyclin-dependent kinase 5, β-catenin, and N-cadherin were assessed on postnatal day 14, 21, and 28. Dendritic morphogenesis of newborn granule neurons in dentate gyrus was examined. Developmental hypothyroidism induced by iodine deficiency and PTU treatment delayed the maturation of hippocampal granule neurons in the offspring and decreased the percentage of Dcx-positive neurons that expressed β-catenin on postnatal day 21 and 28. In addition, downregulation of p35 was observed in dentate gyrus of hypothyroid groups. Developmental hypothyroidism induced by iodine deficiency and PTU treatment could delay the maturation of newborn granule neurons in dentate gyrus, and this deficit may be attributed to the downregulation of p35. PMID:22987596

  10. Generation and Characterization of an Nse-CreERT2 Transgenic Line Suitable for Inducible Gene Manipulation in Cerebellar Granule Cells

    PubMed Central

    Pohlkamp, Theresa; Steller, Laura; May, Petra; Günther, Thomas; Schüle, Roland; Frotscher, Michael

    2014-01-01

    We created an Nse-CreERT2 mouse line expressing the tamoxifen-inducible CreERT2 recombinase under the control of the neuron-specific enolase (Nse) promoter. By using Cre reporter lines we could show that this Nse-CreERT2 line has recombination activity in the granule cells of all cerebellar lobules as well as in postmitotic granule cell precursors in the external granular layer of the developing cerebellum. A few hippocampal dentate gyrus granule cells showed Cre-mediated recombination as well. Cre activity could be induced in both the developing and adult mouse brain. The established mouse line constitutes a valuable tool to study the function of genes expressed by cerebellar granule cells in the developing and adult brain. In combination with reporter lines it is a useful model to analyze the development and maintenance of the cerebellar architecture including granule cell distribution, migration, and the extension of granule cell fibers in vivo. PMID:24950299

  11. Dentate gyrus-specific knockdown of adult neurogenesis impairs spatial and object recognition memory in adult rats

    PubMed Central

    Jessberger, Sebastian; Clark, Robert E.; Broadbent, Nicola J.; Clemenson, Gregory D.; Consiglio, Antonella; Lie, D. Chichung; Squire, Larry R.; Gage, Fred H.

    2009-01-01

    New granule cells are born throughout life in the dentate gyrus of the hippocampal formation. Given the fundamental role of the hippocampus in processes underlying certain forms of learning and memory, it has been speculated that newborn granule cells contribute to cognition. However, previous strategies aiming to causally link newborn neurons with hippocampal function used ablation strategies that were not exclusive to the hippocampus or that were associated with substantial side effects, such as inflammation. We here used a lentiviral approach to specifically block neurogenesis in the dentate gyrus of adult male rats by inhibiting WNT signaling, which is critically involved in the generation of newborn neurons, using a dominant-negative WNT (dnWNT). We found a level-dependent effect of adult neurogenesis on the long-term retention of spatial memory in the water maze task, as rats with substantially reduced levels of newborn neurons showed less preference for the target zone in probe trials >2 wk after acquisition compared with control rats. Furthermore, animals with strongly reduced levels of neurogenesis were impaired in a hippocampus-dependent object recognition task. Social transmission of food preference, a behavioral test that also depends on hippocampal function, was not affected by knockdown of neurogenesis. Here we identified a role for newborn neurons in distinct aspects of hippocampal function that will set the ground to further elucidate, using experimental and computational strategies, the mechanism by which newborn neurons contribute to behavior. PMID:19181621

  12. Effects of Rapamycin Treatment on Neurogenesis and Synaptic Reorganization in the Dentate Gyrus after Controlled Cortical Impact Injury in Mice

    PubMed Central

    Butler, Corwin R.; Boychuk, Jeffery A.; Smith, Bret N.

    2015-01-01

    Post-traumatic epilepsy (PTE) is one consequence of traumatic brain injury (TBI). A prominent cell signaling pathway activated in animal models of both TBI and epilepsy is the mammalian target of rapamycin (mTOR). Inhibition of mTOR with rapamycin has shown promise as a potential modulator of epileptogenesis in several animal models of epilepsy, but cellular mechanisms linking mTOR expression and epileptogenesis are unclear. In this study, the role of mTOR in modifying functional hippocampal circuit reorganization after focal TBI induced by controlled cortical impact (CCI) was investigated. Rapamycin (3 or 10 mg/kg), an inhibitor of mTOR signaling, was administered by intraperitoneal injection beginning on the day of injury and continued daily until tissue collection. Relative to controls, rapamycin treatment reduced dentate granule cell area in the hemisphere ipsilateral to the injury two weeks post-injury. Brain injury resulted in a significant increase in doublecortin immunolabeling in the dentate gyrus ipsilateral to the injury, indicating increased neurogenesis shortly after TBI. Rapamycin treatment prevented the increase in doublecortin labeling, with no overall effect on Fluoro-Jade B staining in the ipsilateral hemisphere, suggesting that rapamycin treatment reduced posttraumatic neurogenesis but did not prevent cell loss after injury. At later times post-injury (8–13 weeks), evidence of mossy fiber sprouting and increased recurrent excitation of dentate granule cells was detected, which were attenuated by rapamycin treatment. Rapamycin treatment also diminished seizure prevalence relative to vehicle-treated controls after TBI. Collectively, these results support a role for adult neurogenesis in PTE development and suggest that suppression of epileptogenesis by mTOR inhibition includes effects on post-injury neurogenesis. PMID:26640431

  13. Physico-chemical and technological properties of sodium naproxen granules prepared in a high-shear mixer-granulator.

    PubMed

    Di Martino, Piera; Malaj, Ledjan; Censi, Roberta; Martelli, Sante

    2008-12-01

    In the present work, authors produced tablets of anhydrous sodium naproxen by wet granulation using a high-shear mixer-granulator. Drug hydrated to the tetrahydrated form, as observed by X-ray powder diffractometry. After wet granulation, authors then performed two different drying procedures, obtaining granules of different water content and crystallographic characteristics. The first procedure dried granules in the high-shear mixer-granulator by applying vacuum at room temperature (batch A), while the second employed the same apparatus and time, under vacuum at 40 degrees C (batch B). X-ray powder diffractometry revealed that the sodium naproxen (SN) contained in batch A granules was a mixture of dihydrated and tetrahydrated forms (as demonstrated by the coexistence of peaks typical of both hydrated forms), while that of batch B granules was a mixture of monohydrated and tetrahydrated forms. This means that differences in drying procedures could lead to products of different crystallographic properties. The behavior under compression was evaluated, revealing that batch A offered the best tabletability and compressibility. These results make it possible to conclude that differences in the crystallographic properties and water content of SN are such that different hydration/drying processes can alter the drug crystal form and thus the tabletability of the resulting granules. PMID:18398910

  14. Inferred properties of stellar granulation

    SciTech Connect

    Gray, D.F.; Toner, C.G.

    1985-06-01

    Apparent characteristics of stellar granulation in F and G main-sequence stars are inferred directly from observed spectral-line asymmetries and from comparisons of numerical simulations with the observations: (1) the apparent granulation velocity increases with effective temperature, (2) the dispersion of granule velocities about their mean velocity of rise increases with the apparent granulation velocity, (3) the mean velocity of rise of granules must be less than the total line broadening, (4) the apparent velocity difference between granules and dark lanes corresponds to the granulation velocity deduced from stellar line bisectors, (5) the dark lanes show velocities of fall approximately twice as large as the granule rise velocities, (6) the light contributed to the stellar flux by the granules is four to ten times more than the light from the dark lanes. Stellar rotation is predicted to produce distortions in the line bisectors which may give information on the absolute velocity displacements of the line bisectors. 37 references.

  15. Behavioral experience induces zif268 expression in mature granule cells but suppresses its expression in immature granule cells

    PubMed Central

    Huckleberry, Kylie A.; Kane, Gary A.; Mathis, Rita J.; Cook, Sarah G.; Clutton, Jonathan E.; Drew, Michael R.

    2015-01-01

    Thousands of neurons are born each day in the dentate gyrus (DG), but many of these cells die before reaching maturity. Both death and survival of adult-born neurons are regulated by neuronal activity in the DG. The immediate-early gene (IEG) zif268 appears to be an important mediator of these effects, as its expression can be induced by neural activity and knockout of zif268 impairs survival of adult-born neurons (Richardson et al., 1992; Veyrac et al., 2013). Despite the apparent importance of zif268 for adult neurogenesis, its behavior-induced expression has not been fully characterized in adult-born neurons. Here we characterize behavior-evoked expression of zif268 in mature and newborn dentate granule cells (DGCs). We first quantified zif268 expression in doublecortin-positive (DCX+) immature neurons and in the general granule cell population after brief exposure to a novel environment (NE). In the general granule cell population, zif268 expression peaked 1 h after NE exposure and returned to baseline by 8 h post-exposure. However, in the DCX+ cells, zif268 expression was suppressed relative to home cage for at least 8 h post-exposure. We next asked whether suppression of zif268 in DCX+ immature cells occurs in other behavioral paradigms that recruit the hippocampus. Exposure to Morris water maze (MWM) training, an enriched environment, or a NE caused approximately equal suppression of zif268 expression in DCX+ cells and approximately equal activation of zif268 expression among the general granule cell population. The same behavioral procedures activated zif268 expression in 6-week-old BrdU-labeled adult-born neurons, indicating that zif268 suppression is specific to immature neurons. Finally, we asked whether zif268 suppression varied as a function of age within the DCX+ population, which ranges in age from 0 to approximately 4 weeks. NE exposure had no significant effect on zif268 expression in 2- or 4-week-old BrdU-labeled neurons, but it significantly

  16. Delayed coupling to feedback inhibition during a critical period for the integration of adult-born granule cells.

    PubMed

    Temprana, Silvio G; Mongiat, Lucas A; Yang, Sung M; Trinchero, Mariela F; Alvarez, Diego D; Kropff, Emilio; Giacomini, Damiana; Beltramone, Natalia; Lanuza, Guillermo M; Schinder, Alejandro F

    2015-01-01

    Developing granule cells (GCs) of the adult dentate gyrus undergo a critical period of enhanced activity and synaptic plasticity before becoming mature. The impact of developing GCs on the activity of preexisting dentate circuits remains unknown. Here we combine optogenetics, acute slice electrophysiology, and in vivo chemogenetics to activate GCs at different stages of maturation to study the recruitment of local target networks. We show that immature (4-week-old) GCs can efficiently drive distal CA3 targets but poorly activate proximal interneurons responsible for feedback inhibition (FBI). As new GCs transition toward maturity, they reliably recruit GABAergic feedback loops that restrict spiking of neighbor GCs, a mechanism that would promote sparse coding. Such inhibitory loop impinges only weakly in new cohorts of young GCs. A computational model reveals that the delayed coupling of new GCs to FBI could be crucial to achieve a fine-grain representation of novel inputs in the dentate gyrus. PMID:25533485

  17. Enhanced nonsynaptic epileptiform activity in the dentate gyrus after kainate-induced status epilepticus.

    PubMed

    Nogueira, G S; Santos, L E C; Rodrigues, A M; Scorza, C A; Scorza, F A; Cavalheiro, E A; de Almeida, A-C G

    2015-09-10

    Understanding the mechanisms that influence brain excitability and synchronization provides hope that epileptic seizures can be controlled. In this scenario, non-synaptic mechanisms have a critical role in seizure activity. The contribution of ion transporters to the regulation of seizure-like activity has not been extensively studied. Here, we examined how non-synaptic epileptiform activity (NEA) in the CA1 and dentate gyrus (DG) regions of the hippocampal formation were affected by kainic acid (KA) administration. NEA enhancement in the DG and suppression in area CA1 were associated with increased NKCC1 expression in neurons and severe neuronal loss accompanied by marked glial proliferation, respectively. Twenty-four hours after KA, the DG exhibited intense microglial activation that was associated with reduced cell density in the infra-pyramidal lamina; however, cellular density recovered 7 days after KA. Intense Ki67 immunoreactivity was observed in the subgranular proliferative zone of the DG, which indicates new neuron incorporation into the granule layer. In addition, bumetanide, a selective inhibitor of neuronal Cl(-) uptake mediated by NKCC1, was used to confirm that the NKCC1 increase effectively contributed to NEA changes in the DG. Furthermore, 7 days after KA, prominent NKCC1 staining was identified in the axon initial segments of granule cells, at the exact site where action potentials are preferentially initiated, which endowed these neurons with increased excitability. Taken together, our data suggest a key role of NKCC1 in NEA in the DG. PMID:26141843

  18. Distinct dendritic morphology across the blades of the rodent dentate gyrus.

    PubMed

    Gallitano, Amelia L; Satvat, Elham; Gil, Mario; Marrone, Diano F

    2016-07-01

    The dentate gyrus (DG) is a hippocampal region that has long been characterized as a critical mediator of enduring memory formation and retrieval. As such, there is a wealth of studies investigating this area. Most of these studies have either treated the DG as a homogeneous structure, or examined differences in neurons along the septal-temporal axis. Recent data, however, have indicated that a functional distinction exists between the suprapyramidal and infrapyramidal blades of the DG, with the former showing more robust responses during spatial tasks. To date, few anatomical studies have addressed this functional gradient in rats, and no study has done so in the mouse. To address this, we investigated dendritic morphology and spine density in hippocampal granule cells of rats and mice using the Golgi-Cox technique. We find that granule cells from the suprapyramidal blade of the DG contain greater dendritic material in the region receiving spatial information from the medial perforant path. This provides a potential anatomical substrate for the asymmetric response of the DG to spatial input. Synapse 70:277-282, 2016. © 2016 Wiley Periodicals, Inc. PMID:26926290

  19. mRNP granules

    PubMed Central

    Buchan, J Ross

    2014-01-01

    Messenger ribonucleoprotein (mRNP) granules are dynamic, self-assembling structures that harbor non-translating mRNAs bound by various proteins that regulate mRNA translation, localization, and turnover. Their importance in gene expression regulation is far reaching, ranging from precise spatial-temporal control of mRNAs that drive developmental programs in oocytes and embryos, to similarly exquisite control of mRNAs in neurons that underpin synaptic plasticity, and thus, memory formation. Analysis of mRNP granules in their various contexts has revealed common themes of assembly, disassembly, and modes of mRNA regulation, yet new studies continue to reveal unexpected and important findings, such as links between aberrant mRNP granule assembly and neurodegenerative disease. Continued study of these enigmatic structures thus promises fascinating new insights into cellular function, and may also suggest novel therapeutic strategies in various disease states. PMID:25531407

  20. Somatostatin-immunoreactive interneurons contribute to lateral inhibitory circuits in the dentate gyrus of control and epileptic rats.

    PubMed

    Boyett, J M; Buckmaster, P S

    2001-01-01

    Lateral inhibition, a feature of neuronal circuitry that enhances signaling specificity, has been demonstrated in the rat dentate gyrus. However, neither the underlying neuronal circuits, nor the ways in which these circuits are altered in temporal lobe epilepsy, are completely understood. This study examines the potential contribution of one class of inhibitory interneurons to lateral inhibitory circuits in the dentate gyrus of both control and epileptic rats. The retrograde tracer wheat germ ag-glutinin-apo-horse radish peroxidase-gold (WGA-apo-HRP-gold) was injected into the septal dentate gyrus. Neurons double-labeled for glutamic acid decarboxylase (GAD) and the retrograde tracer are concentrated in the hilus and may contribute to lateral inhibition. Neurons double-labeled for somatostatin and the retrograde tracer account for at least 28% of GAD-positive neurons with axon projections appropriate for generating lateral inhibition in control rats. Despite an overall loss of somatostatin-expressing cells in epileptic animals, the number of somatostatin-positive interneurons with axon projections appropriate for generating lateral inhibition is similar to that seen in controls. These findings suggest that somatostatinergic interneurons participate in lateral inhibitory circuits in the dentate gyrus of both control and epileptic rats, and that surviving somatostatinergic interneurons might sprout new axon collaterals in epileptic animals. PMID:11530846

  1. Proteoglycan modifications by granulation tissue in culture.

    PubMed

    Quintner, M I; Kollar, E J; Rossomando, E F

    1982-01-01

    To study the process of tissue remodeling that occurs during wound healing, radioactive proteoglycan ([35S]-PGS) was used to assay for enzymatic activities present in the extracellular fluid of healing tissue. Mice, wounded by removal of a 2 x 1.5 cm patch of skin from the dorsal surface, were sacrificed after 3 days of healing. Granulation tissue (1 cm2) was removed, spread onto a sterile wire mesh support and placed in the center well of an organ culture dish. To each well was added 1 ml MCDB medium supplemented with 10% fetal calf serum and antibiotics and 5-20 microliters of [35S]-PGS (100,000 cpm/10 microliters). Medium, removed from the well by aspiration after 24 and 48 h of culture, was boiled 5 min at 100 degrees C and stored frozen at -20 degrees C. Alterations of the PGS were assayed with a Sepharose 4B column (1 x 50 cm) which had an excluded and included volume of 17 and 46 ml, respectively. PGS, incubated without cells or with tissues from unwounded animals, eluted at 26 ml. PGS, incubated with granulation tissue and cultured for either 24 or 48 h, eluted from the Sepharose 4B at 29 ml, a 10% increase in elution volume, suggesting that the size or shape of the PGS has been altered by enzymes secreted by the cells of the granulation tissue. In contrast, PGS incubated with tissues from unwounded animals or without granulation tissue showed no changes. These data suggest that enzymatic activities secreted by cells of granulation tissue may be involved in remodeling during healing. PMID:6749574

  2. Dendritic remodeling of hippocampal neurons is associated with altered NMDA receptor expression in alcohol dependent rats

    PubMed Central

    Staples, Miranda C.; Kim, Airee; Mandyam, Chitra D.

    2015-01-01

    Prolonged alcohol exposure has been previously shown to impair the structure and function of the hippocampus, although the underlying structural and biochemical alterations contributing to these deleterious effects are unclear. Also unclear is whether these changes persist into prolonged periods of abstinence. Previous work from our lab utilizing a clinically relevant rodent model of alcohol consumption demonstrated that alcohol dependence (induced by chronic intermittent ethanol vapor exposure or CIE) decreases proliferation and survival of neural stem cells in the hippocampal subgranular zone and hippocampal neurogenesis in the dentate gyrus, implicating this region of the cortex as particularly sensitive to the toxic effects of prolonged ethanol exposure. For this study, we investigated seven weeks of CIE-induced morphological changes (dendritic complexity and dendritic spine density) of dentate gyrus (DG) granule cell neurons, CA3, and CA1 pyramidal neurons and the associated alterations in biochemical markers of synaptic plasticity and toxicity (NMDA receptors and PSD-95) in the hippocampus in ethanol-experienced Wistar rats 3h (CIE) and 21 days (protracted abstinence) after the last ethanol vapor exposure. CIE reduced dendritic arborization of DG neurons and this effect persisted into protracted abstinence. CIE enhanced dendritic arborization of pyramidal neurons and this effect did not persist into protracted abstinence. The architectural changes in dendrites did not correlate with alterations in dendritic spine density, however, they were associated with increases in the expression of pNR2B, total NR2B, and total NR2A immediately following CIE with expression levels returning to control levels in prolonged abstinence. Overall, these data provide the evidence that CIE produces profound changes in hippocampal structural plasticity and in molecular tools that maintain hippocampal structural plasticity, and these alterations may underlie cognitive dysfunction

  3. Review: granulation and fluidized beds

    SciTech Connect

    Kono, H.

    1981-01-01

    The history of granulation techniques is very long; however, the systematic study of the granulation phenomenon began only after 1950. The first, distinguished paper treating the fundamental binding mechanism of granules was published by Rumpf in 1958. Although there are several binding forces, the discussion in this paper is confined to granulation involving the capillary energy of a liquid-particle system. This technique has been applied widely and successfully to various fields of powder technology because of its advantages of simplicity and economy (ref. 2). Granules with diameters larger than 5 mm can be prepared efficiently by rotating-type granulators, such as a pan or a trommel (ref. 3, 4, 5). On the other hand, the purpose of fluidized-bed granulators (hereafter abbreviated as FBG) is to produce small granules with diameters from 0.3 to 3 mm (ref. 6). Because it contains a small amount of liquid, a fluidized-bed granulator has a fluidization state differing significantly from that of an ordinary fluidized bed. The dispersion of liquid and powder in the bed plays an important role in the granulation mechanism. This mechanism is compared to that of pan granulators, and the differences in characteristics are discussed.

  4. Isolation of neuromelanin granules.

    PubMed

    Tribl, Florian

    2008-12-01

    Neuromelanin granules are pigmented organelles in the human midbrain that give name to a brain area, substantia nigra pars compacta, which macroscopically appears as a dark brown region in the midbrain due to the insoluble pigment neuromelanin. The substantia nigra pars compacta massively degenerates in Parkinson's disease and gives rise to severely disabling movement symptoms. It has been suggested that neuromelanin granules play an important role in the neurodegenerative events in Parkinson's disease: redox-active iron is bound to neuromelanin and thereby retained within this compartment, but in Parkinson's disease it is thought to be increasingly released into the cytosol, promoting oxidative stress. This unit includes a methodological workflow for the isolation of neuromelanin granules from the human midbrain. This top-down approach (describes an approach that reduces the complexity of the sample stepwise from the level of tissue to cell, and from cell to organelle) encompasses the organelle isolation by sequential density gradient centrifugation and the assessment of the isolation efficacy by western blotting. PMID:19085988

  5. Absence of BRINP1 in mice causes increase of hippocampal neurogenesis and behavioral alterations relevant to human psychiatric disorders

    PubMed Central

    2014-01-01

    Background We have previously identified BRINP (BMP/RA-inducible neural-specific protein-1, 2, 3) family genes that possess the ability to suppress cell cycle progression in neural stem cells. Of the three family members, BRINP1 is the most highly expressed in various brain regions, including the hippocampus, in adult mice and its expression in dentate gyrus (DG) is markedly induced by neural activity. In the present study, we generated BRINP1-deficient (KO) mice to clarify the physiological functions of BRINP1 in the nervous system. Results Neurogenesis in the subgranular zone of dentate gyrus was increased in BRINP1-KO mice creating a more immature neuronal population in granule cell layer. The number of parvalbumin expressing interneuron in hippocampal CA1 subregion was also increased in BRINP1-KO mice. Furthermore, BRINP1-KO mice showed abnormal behaviors with increase in locomotor activity, reduced anxiety-like behavior, poor social interaction, and slight impairment of working memory, all of which resemble symptoms of human psychiatric disorders such as schizophrenia and attention–deficit/hyperactivity disorder (ADHD). Conclusions Absence of BRINP1 causes deregulation of neurogenesis and impairments of neuronal differentiation in adult hippocampal circuitry. Abnormal behaviors comparable to those of human psychiatric disorders such as hyperactivity and poor social behavior were observed in BRINP1-KO mice. These abnormal behaviors could be caused by alteration of hippocampal circuitry as a consequence of the lack of BRINP1. PMID:24528488

  6. The enigmatic mossy cell of the dentate gyrus.

    PubMed

    Scharfman, Helen E

    2016-09-01

    Mossy cells comprise a large fraction of the cells in the hippocampal dentate gyrus, suggesting that their function in this region is important. They are vulnerable to ischaemia, traumatic brain injury and seizures, and their loss could contribute to dentate gyrus dysfunction in such conditions. Mossy cell function has been unclear because these cells innervate both glutamatergic and GABAergic neurons within the dentate gyrus, contributing to a complex circuitry. It has also been difficult to directly and selectively manipulate mossy cells to study their function. In light of the new data generated using methods to preferentially eliminate or activate mossy cells in mice, it is timely to ask whether mossy cells have become any less enigmatic than they were in the past. PMID:27466143

  7. Morphometric study of dentate nucleus of cerebellum in Bangladeshi cadaver.

    PubMed

    Haque, M A; Khalil, M; Sultana, S Z; Mannan, S; Uddin, M M; Hossain, M; Ara, A; Choudhury, S; Shammi, N J

    2015-01-01

    This cross sectional descriptive study was done by using nonprobability sampling technique and performed by examining 63 (sixty three) cerebellum. Out of them 40 postmortem human cerebellum collected from Bangladeshi cadavers of both sexes (male 25 and female 15) age ranging from 5 to 60 years and 23 cerebellums from caesarian section of intrauterine death cases of both sexes (male 14 and female 9) age ranging from 34 to 41 weeks of gestation. Specimens were collected from dead bodies autopsied on different dates from April' 2009 to September' 2009 at the autopsy laboratory of department of Forensic Medicine and prenatal cases from Gynaecology and Obstetrics Department of Mymensingh Medical College, Mymensingh. The collected specimens were grouped into three age groups like Group A (28 to 42 weeks of gestation), Group B (5 to 30 years) and Group C (31 to 60 years) and, two sex groups (male and female) and two sides (right and left). A transverse section was made at the level of horizontal fissure, and length and breadth of dentate nucleus were measured by divider and scale. The mean (±SD) length and breadth of dentate nucleus was 8.619±2.995mm and 14.770±3.604mm respectively and it was observed that length and breadth of dentate nucleus increased with age upto certain level then slightly decreased in the late age Group C. In this study, differences of the mean length of dentate nucleus on both right and left sides were statistically moderately significant between age Groups A&B. The differences of mean breadth of dentate nucleus on both right and left side were statistically highly significant between age Groups A&B and moderately significant between age Groups A&C on right side and only significant on left side. The differences between male & female were statistically insignificant in length and breadth of dentate nucleus. PMID:25725664

  8. Doublecortin (DCX) is not Essential for Survival and Differentiation of Newborn Neurons in the Adult Mouse Dentate Gyrus

    PubMed Central

    Dhaliwal, Jagroop; Xi, Yanwei; Bruel-Jungerman, Elodie; Germain, Johanne; Francis, Fiona; Lagace, Diane C.

    2016-01-01

    In the adult brain, expression of the microtubule-associated protein Doublecortin (DCX) is associated with neural progenitor cells (NPCs) that give rise to new neurons in the dentate gyrus. Many studies quantify the number of DCX-expressing cells as a proxy for the level of adult neurogenesis, yet no study has determined the effect of removing DCX from adult hippocampal NPCs. Here, we use a retroviral and inducible mouse transgenic approach to either knockdown or knockout DCX from adult NPCs in the dentate gyrus and examine how this affects cell survival and neuronal maturation. Our results demonstrate that shRNA-mediated knockdown of DCX or Cre-mediated recombination in floxed DCX mice does not alter hippocampal neurogenesis and does not change the neuronal fate of the NPCs. Together these findings show that the survival and maturation of adult-generated hippocampal neurons does not require DCX. PMID:26793044

  9. Granulation of increasingly hydrophobic formulations using a twin screw granulator.

    PubMed

    Yu, Shen; Reynolds, Gavin K; Huang, Zhenyu; de Matas, Marcel; Salman, Agba D

    2014-11-20

    The application of twin screw granulation in the pharmaceutical industry has generated increasing interest due to its suitability for continuous processing. However, an understanding of the impact of formulation properties such as hydrophobicity on intermediate and finished product quality has not yet been established. Hence, the current work investigated the granulation behaviour of three formulations containing increasing amounts of hydrophobic components using a Consigma™-1 twin screw granulator. Process conditions including powder feed rate, liquid to solid ratio, granulation liquid composition and screw configuration were also evaluated. The size of the wet granules was measured in order to enable exploration of granulation behaviour in isolation without confounding effects from downstream processes such as drying. The experimental observations indicated that the granulation process was not sensitive to the powder feed rate. The hydrophobicity led to heterogeneous liquid distribution and hence a relatively large proportion of un-wetted particles. Increasing numbers of kneading elements led to high shear and prolonged residence time, which acted to enhance the distribution of liquid and feeding materials. The bimodal size distributions considered to be characteristic of twin screw granulation were primarily ascribed to the breakage of relatively large granules by the kneading elements. PMID:25124058

  10. Treatment and maintenance of a dentate patient with 'radiation caries'.

    PubMed

    Craddock, H L

    2008-11-01

    Patients with xerostomia are presenting dental practitioners with challenges in caries control, long-term restoration and prosthodontic difficulties. In many cases, extraction may be the best option, but for younger, dentate patients, this may be inappropriate. This paper describes the management of a young partially dentate patient with severe xerostomia following irradiation of the salivary glands. Preventive and restorative management are discussed, together with treatment and healing of peri-radicular pathology. The case report demonstrates that long-term stabilization and management of caries and peri-radicular lesions are possible over a seven-year period for a patient with severe radiation caries. PMID:19322963

  11. Regulation of the ERK pathway in the dentate gyrus by in vivo dopamine D1 receptor stimulation requires glutamatergic transmission.

    PubMed

    Gangarossa, Giuseppe; Valjent, Emmanuel

    2012-11-01

    Acute systemic administration of the dopamine D1/D5 receptors (D1Rs) agonist, SKF81297, activates the extracellular signal-regulated protein kinases (ERK) pathway selectively in the granule cells of the dentate gyrus. In this study, we examined the mechanisms involved in this regulation and investigated the molecular components that could promote ERK-dependent transcription and translation. SKF81297 induced phosphorylation of ERK and histone H3 required intact glutamatergic transmission. Blockade of glutamate release achieved by the mGluR2/3 agonist, LY354740 or the selective adenosine A1R agonist, CCPA as well as neurotoxic lesions of lateral entorhinal cortex reduced the ability of SKF81297 to induce ERK activation in the dentate gyrus. This activation required the combined stimulation of NR2B-containing NMDARs, mGluR1 and mGluR5. SKF81297 evoked phosphorylation of the ribosomal protein S6 (rpS6) selectively at the Ser235/236 site while the Ser240/244 site remains unchanged. The SKF81297 induced increased phosphorylation of rpS6 was dependent on PKC and ERK/p90RSK activation. Surprisingly, administration of D1Rs agonist suppressed mTORC1/p70S6K pathway suggesting an mTOR-independent regulation of rpS6 phosphorylation. Taken together, our results show that intact glutamatergic transmission plays a major role in the regulation of ERK-dependent phosphorylation of histone H3 and rpS6 observed in the mouse dentate gyrus after systemic administration of SKF81297. PMID:22796106

  12. Age-related changes in dentate gyrus cell numbers, neurogenesis, and associations with cognitive impairments in the rhesus monkey

    PubMed Central

    Ngwenya, Laura B.; Heyworth, Nadine C.; Shwe, Yamin; Moore, Tara L.; Rosene, Douglas L.

    2015-01-01

    The generation of new neurons in the adult mammalian brain is well-established for the hippocampal dentate gyrus (DG). However, the role of neurogenesis in hippocampal function and cognition, how it changes in aging, and the mechanisms underlying this are yet to be elucidated in the monkey brain. To address this, we investigated adult neurogenesis in the DG of 42 rhesus monkeys (39 cognitively tested) ranging in age from young adult to the elderly. We report here that there is an age-related decline in proliferation and a delayed development of adult neuronal phenotype. Additionally, we show that many of the new neurons survive throughout the lifetime of the animal and may contribute to a modest increase in total neuron number in the granule cell layer of the DG over the adult life span. Lastly, we find that measures of decreased adult neurogenesis are only modestly predictive of age-related cognitive impairment. PMID:26236203

  13. Age-related changes in dentate gyrus cell numbers, neurogenesis, and associations with cognitive impairments in the rhesus monkey.

    PubMed

    Ngwenya, Laura B; Heyworth, Nadine C; Shwe, Yamin; Moore, Tara L; Rosene, Douglas L

    2015-01-01

    The generation of new neurons in the adult mammalian brain is well-established for the hippocampal dentate gyrus (DG). However, the role of neurogenesis in hippocampal function and cognition, how it changes in aging, and the mechanisms underlying this are yet to be elucidated in the monkey brain. To address this, we investigated adult neurogenesis in the DG of 42 rhesus monkeys (39 cognitively tested) ranging in age from young adult to the elderly. We report here that there is an age-related decline in proliferation and a delayed development of adult neuronal phenotype. Additionally, we show that many of the new neurons survive throughout the lifetime of the animal and may contribute to a modest increase in total neuron number in the granule cell layer of the DG over the adult life span. Lastly, we find that measures of decreased adult neurogenesis are only modestly predictive of age-related cognitive impairment. PMID:26236203

  14. RNA Granules in Germ Cells

    PubMed Central

    Voronina, Ekaterina; Seydoux, Geraldine; Sassone-Corsi, Paolo; Nagamori, Ippei

    2011-01-01

    “Germ granules” are cytoplasmic, nonmembrane-bound organelles unique to germline. Germ granules share components with the P bodies and stress granules of somatic cells, but also contain proteins and RNAs uniquely required for germ cell development. In this review, we focus on recent advances in our understanding of germ granule assembly, dynamics, and function. One hypothesis is that germ granules operate as hubs for the posttranscriptional control of gene expression, a function at the core of the germ cell differentiation program. PMID:21768607

  15. Enhanced acoustic startle responding in rats with radiation-induced hippocampal granule cell hypoplasia

    SciTech Connect

    Mickley, G.A.; Ferguson, J.L.

    1989-01-01

    Irradiation of the neonatal rat hippocampus reduces the proliferation of granule cells in the dentate gyrus and results in locomotor hyperactivity, behavioral preservation, and deficits on some learned tasks. In order to address the role of changes in stimulus salience and behavioral inhibition in animals with this type of brain damage, irradiated and normal rats were compared in their startle reactions to an acoustic stimulus. Irradiated rats startled with a consistently higher amplitude than control and were more likely to exhibit startle responses. These animals with hippocampal damage also failed to habituate to the startle stimulus and, under certain circumstances, showed potentiated startle responses after many tone presentations.

  16. Adult Neurogenesis in the Mammalian Hippocampus: Why the Dentate Gyrus?

    ERIC Educational Resources Information Center

    Drew, Liam J.; Fusi, Stefano; Hen, René

    2013-01-01

    In the adult mammalian brain, newly generated neurons are continuously incorporated into two networks: interneurons born in the subventricular zone migrate to the olfactory bulb, whereas the dentate gyrus (DG) of the hippocampus integrates locally born principal neurons. That the rest of the mammalian brain loses significant neurogenic capacity…

  17. Hippocampus and dentate area of the European hedgehog. Comparative histochemical study.

    PubMed

    Crutcher, K A; Danscher, G; Geneser, F A

    1988-01-01

    The hippocampal formation in the European hedgehog was examined with acetylcholinesterase (AChE) histochemistry and catecholamine histofluorescence in order to define the normal distribution of septohippocampal fibers and noradrenergic fibers, respectively, as well as to compare these inputs with the hippocampal cytoarchitecture as revealed with Nissl stain. In addition, alterations in the histochemical appearance following septohippocampal denervation were examined. Although the overall pattern of AChE-positive and noradrenergic fibers is similar to that observed in other mammals, some striking variations were observed, particularly within the dentate area. Thus, except for a heavily stained supragranular band, the AChE activity of the molecular layer is uniformly low without any obvious lamination, contrasting with the situation in most other mammalian species. The noradrenergic innervation of the dentate area showed the same density of fibers in the molecular layer and hilus, a pattern differing strikingly from the predominance of noradrenergic fibers in the hilus of other mammalian species. Such variations may reflect greater phylogenetic diversity in diffuse modulatory connections as compared with more precise topographical pathways. PMID:3233486

  18. Rapid Feedforward Inhibition and Asynchronous Excitation Regulate Granule Cell Activity in the Mammalian Main Olfactory Bulb

    PubMed Central

    Burton, Shawn D.

    2015-01-01

    Granule cell-mediated inhibition is critical to patterning principal neuron activity in the olfactory bulb, and perturbation of synaptic input to granule cells significantly alters olfactory-guided behavior. Despite the critical role of granule cells in olfaction, little is known about how sensory input recruits granule cells. Here, we combined whole-cell patch-clamp electrophysiology in acute mouse olfactory bulb slices with biophysical multicompartmental modeling to investigate the synaptic basis of granule cell recruitment. Physiological activation of sensory afferents within single glomeruli evoked diverse modes of granule cell activity, including subthreshold depolarization, spikelets, and suprathreshold responses with widely distributed spike latencies. The generation of these diverse activity modes depended, in part, on the asynchronous time course of synaptic excitation onto granule cells, which lasted several hundred milliseconds. In addition to asynchronous excitation, each granule cell also received synchronous feedforward inhibition. This inhibition targeted both proximal somatodendritic and distal apical dendritic domains of granule cells, was reliably recruited across sniff rhythms, and scaled in strength with excitation as more glomeruli were activated. Feedforward inhibition onto granule cells originated from deep short-axon cells, which responded to glomerular activation with highly reliable, short-latency firing consistent with tufted cell-mediated excitation. Simulations showed that feedforward inhibition interacts with asynchronous excitation to broaden granule cell spike latency distributions and significantly attenuates granule cell depolarization within local subcellular compartments. Collectively, our results thus identify feedforward inhibition onto granule cells as a core feature of olfactory bulb circuitry and establish asynchronous excitation and feedforward inhibition as critical regulators of granule cell activity. SIGNIFICANCE

  19. Granulation techniques and technologies: recent progresses.

    PubMed

    Shanmugam, Srinivasan

    2015-01-01

    Granulation, the process of particle enlargement by agglomeration technique, is one of the most significant unit operations in the production of pharmaceutical dosage forms, mostly tablets and capsules. Granulation process transforms fine powders into free-flowing, dust-free granules that are easy to compress. Nevertheless, granulation poses numerous challenges due to high quality requirement of the formed granules in terms of content uniformity and physicochemical properties such as granule size, bulk density, porosity, hardness, moisture, compressibility, etc. together with physical and chemical stability of the drug. Granulation process can be divided into two types: wet granulation that utilize a liquid in the process and dry granulation that requires no liquid. The type of process selection requires thorough knowledge of physicochemical properties of the drug, excipients, required flow and release properties, to name a few. Among currently available technologies, spray drying, roller compaction, high shear mixing, and fluid bed granulation are worth of note. Like any other scientific field, pharmaceutical granulation technology also continues to change, and arrival of novel and innovative technologies are inevitable. This review focuses on the recent progress in the granulation techniques and technologies such as pneumatic dry granulation, reverse wet granulation, steam granulation, moisture-activated dry granulation, thermal adhesion granulation, freeze granulation, and foamed binder or foam granulation. This review gives an overview of these with a short description about each development along with its significance and limitations. PMID:25901297

  20. Granulation techniques and technologies: recent progresses

    PubMed Central

    Shanmugam, Srinivasan

    2015-01-01

    Granulation, the process of particle enlargement by agglomeration technique, is one of the most significant unit operations in the production of pharmaceutical dosage forms, mostly tablets and capsules. Granulation process transforms fine powders into free-flowing, dust-free granules that are easy to compress. Nevertheless, granulation poses numerous challenges due to high quality requirement of the formed granules in terms of content uniformity and physicochemical properties such as granule size, bulk density, porosity, hardness, moisture, compressibility, etc. together with physical and chemical stability of the drug. Granulation process can be divided into two types: wet granulation that utilize a liquid in the process and dry granulation that requires no liquid. The type of process selection requires thorough knowledge of physicochemical properties of the drug, excipients, required flow and release properties, to name a few. Among currently available technologies, spray drying, roller compaction, high shear mixing, and fluid bed granulation are worth of note. Like any other scientific field, pharmaceutical granulation technology also continues to change, and arrival of novel and innovative technologies are inevitable. This review focuses on the recent progress in the granulation techniques and technologies such as pneumatic dry granulation, reverse wet granulation, steam granulation, moisture-activated dry granulation, thermal adhesion granulation, freeze granulation, and foamed binder or foam granulation. This review gives an overview of these with a short description about each development along with its significance and limitations. PMID:25901297

  1. Estradiol rapidly modulates spinogenesis in hippocampal dentate gyrus: Involvement of kinase networks.

    PubMed

    Hojo, Yasushi; Munetomo, Arisa; Mukai, Hideo; Ikeda, Muneki; Sato, Rei; Hatanaka, Yusuke; Murakami, Gen; Komatsuzaki, Yoshimasa; Kimoto, Tetsuya; Kawato, Suguru

    2015-08-01

    This article is part of a Special Issue "Estradiol and cognition". Estradiol (E2) is locally synthesized within the hippocampus and the gonads. Rapid modulation of hippocampal synaptic plasticity by E2 is essential for synaptic regulation. The molecular mechanisms of modulation through the synaptic estrogen receptor (ER) and its downstream signaling, however, are largely unknown in the dentate gyrus (DG). We investigated the E2-induced modulation of dendritic spines in male adult rat hippocampal slices by imaging Lucifer Yellow-injected DG granule cells. Treatments with 1 nM E2 increased the density of spines by approximately 1.4-fold within 2h. Spine head diameter analysis showed that the density of middle-head spines (0.4-0.5 μm) was significantly increased. The E2-induced spine density increase was suppressed by blocking Erk MAPK, PKA, PKC and LIMK. These suppressive effects by kinase inhibitors are not non-specific ones because the GSK-3β antagonist did not inhibit E2-induced spine increase. The ER antagonist ICI 182,780 also blocked the E2-induced spine increase. Taken together, these results suggest that E2 rapidly increases the density of spines through kinase networks that are driven by synaptic ER. PMID:26122288

  2. Differential Recruitment of Dentate Gyrus Interneuron Types by Commissural Versus Perforant Pathways.

    PubMed

    Hsu, Tsan-Ting; Lee, Cheng-Ta; Tai, Ming-Hong; Lien, Cheng-Chang

    2016-06-01

    Gamma-aminobutyric acidergic (GABAergic) interneurons (INs) in the dentate gyrus (DG) provide inhibitory control to granule cell (GC) activity and thus gate incoming signals to the hippocampus. However, how various IN subtypes inhibit GCs in response to different excitatory input pathways remains mostly unknown. By using electrophysiology and optogenetics, we investigated neurotransmission of the hilar commissural pathway (COM) and the medial perforant path (MPP) to the DG in acutely prepared mouse slices. We found that the short-term dynamics of excitatory COM-GC and MPP-GC synapses was similar, but that the dynamics of COM- and MPP-mediated inhibition measured in GCs was remarkably different, during theta-frequency stimulation. This resulted in the increased inhibition-excitation (I/E) ratios in single GCs for COM stimulation, but decreased I/E ratios for MPP stimulation. Further analysis of pathway-specific responses in identified INs revealed that basket cell-like INs, total molecular layer- and molecular layer-like cells, received greater excitation and were more reliably recruited by the COM than by the MPP inputs. In contrast, hilar perforant path-associated and hilar commissural-associational pathway-related-like cells were minimally activated by both inputs. These results demonstrate that distinct IN subtypes are preferentially recruited by different inputs to the DG, and reveal their relative contributions in COM-mediated feedforward inhibition. PMID:26045570

  3. Development of maize starch granules

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Maize kernels of self-pollinated inbred line B73 harvested on various days after pollination (DAP) were subjected for starch granule development studies. Starch in endosperms was first observed on 6 DAP. A small amount of starch granules (<2% of dry weight) was found in the endosperm on 12 DAP. S...

  4. [Research of aerobic granule characteristics with different granule age].

    PubMed

    Zhou, Man; Yang, Chang-Zhu; Pu, Wen-Hong; Luo, Ying-Dong; Gong, Jian-Yu

    2012-03-01

    In the SBR reactor, we studied the different style, physicochemical characteristic, pollutants removal and microbial activity between the short age and long age aerobic granule, respectively. The short age aerobic granule was cultivated from activated floccules sludge and the other was gotten from aerobic granular sludge which was operated stably more than one year. The results indicated that the wet density, the specific gravity and integrated coefficient (IC) of the short age aerobic granule were 1.066 g x cm(-1), 1.013 g x cm(-3) and 98.7%, respectively. And that of long age were 1.026 g x cm(-3), 1.010 g x cm(-3) and 98.4%, respectively. All of them were higher than the long age aerobic granule. The mean diameters of them were 1.9 mm and 2.2 mm, respectively. The settling velocity of short age and long age aerobic granule were 0.005-0.032 m x s(-1) and 0.003-0.028 m x s(-1), respectively, and two kinds of aerobic granule settling velocity increased with the diameter increased. SVI of the former was lower. The COD removal rates of two aerobic granules were above 90%, and the NH4(+) -N removal rates of them were about 85%. The results of the COD effluent concentration, NH4(+) -N effluent concentration and the pollutants concentration in a typical cycle indicated that the short age aerobic granule had better pollutants removal efficiency. The TP removal rates of them were between 40% -90% and 32% -85%, respectively. The TN removal rates of them were about 80%. The SOUR(H) SOUR(NH4) and SOUR(NO2) of the short age aerobic granule were 26.4, 14.8 and 11.2 mg x (h x g)(-1), respectively. And that of long age were 25.2, 14.4 and 8.4 mg x (h x g)(-1), respectively. In summary, the aerobic granule had significantly different physical and chemical characteristics because of different granule age, and the short age aerobic granule exhibited better pollutants removal ability, higher microbial activity and more stability than the long age aerobic granule. PMID:22624385

  5. Sustained Arc expression in adult-generated granule cells.

    PubMed

    Meconi, Alicia; Lui, Erika; Marrone, Diano F

    2015-08-31

    The dentate gyrus (DG) plays a critical role in memory formation and maintenance. Fitting this specialized role, the DG has many unique characteristics. In addition to being one of the few places in which new neurons are continually added in adulthood, the region also shows a unique long-term sustained transcriptional response of the immediate-early gene Arc to sensory input. Although we know that adult-generated granule cells are reliably recruited into behaviorally-driven neuronal network, it remains unknown whether they display robust late-phase sustained transcription in response to activity like their developmentally-generated counterparts. Since this late-phase of transcription is required for enduring plasticity, knowing if sustained transcription appears as soon as these cells are incorporated provides information on their potential for plasticity. To address this question, adult F344 rats were injected with BrdU (50mg/kg/day for 5 days) and 4 weeks later explored a novel environment. Arc expression in both BrdU- and BrdU+ neurons was determined 0.5h, 1h, 2h, 6h, 8h, 12h, or 24h following this behavior. Recently-generated granule cells showed a robust sustained Arc expression following a discrete behavioral experience. These data provide information on a potential mechanism to sculpt the representations of events occurring within hours of each other to create uncorrelated representations of episodes despite a highly excitable population of neurons. PMID:26219984

  6. Distinct stages in stress granule assembly and disassembly

    PubMed Central

    Wheeler, Joshua R; Matheny, Tyler; Jain, Saumya; Abrisch, Robert; Parker, Roy

    2016-01-01

    Stress granules are non-membrane bound RNA-protein (RNP) assemblies that form when translation initiation is limited and contain a biphasic structure with stable core structures surrounded by a less concentrated shell. The order of assembly and disassembly of these two structures remains unknown. Time course analysis of granule assembly suggests that core formation is an early event in granule assembly. Stress granule disassembly is also a stepwise process with shell dissipation followed by core clearance. Perturbations that alter liquid-liquid phase separations (LLPS) driven by intrinsically disordered protein regions (IDR) of RNA binding proteins in vitro have the opposite effect on stress granule assembly in vivo. Taken together, these observations argue that stress granules assemble through a multistep process initiated by stable assembly of untranslated mRNPs into core structures, which could provide sufficient high local concentrations to allow for a localized LLPS driven by IDRs on RNA binding proteins. DOI: http://dx.doi.org/10.7554/eLife.18413.001 PMID:27602576

  7. Inhibition of Cerebellar Granule Cell Turning by Alcohol

    PubMed Central

    Kumada, Tatsuro; Komuro, Yutaro; Li, Ying; Hu, Taofang; Wang, Zhe; Littner, Yoav; Komuro, Hitoshi

    2010-01-01

    Ectopic neurons are often found in the brains of fetal alcohol spectrum disorders (FASD) and fetal alcohol syndrome (FAS) patients, suggesting that alcohol exposure impairs neuronal cell migration. Although it has been reported that alcohol decreases the speed of neuronal cell migration, little is known about whether alcohol also affects the turning of neurons. Here we show that ethanol exposure inhibits the turning of cerebellar granule cells in vivo and in vitro. First, in vivo studies using P10 mice demonstrated that a single i.p. injection of ethanol not only reduces the number of turning granule cells but also alters the mode of turning at the EGL-ML border of the cerebellum. Second, in vitro analysis using microexplant cultures of P0-P3 mouse cerebella revealed that ethanol directly reduces the frequency of spontaneous granule cell turning in a dose-dependent manner. Third, the action of ethanol on the frequency of granule cell turning was significantly ameliorated by stimulating Ca2+ and cGMP signaling or by inhibiting cAMP signaling. Taken together, these results indicate that ethanol affects the frequency and mode of cerebellar granule cell turning through alteration of the Ca2+ and cyclic nucleotide signaling pathways, suggesting that the abnormal allocation of neurons found in the brains of FASD and FSA patients results, at least in part, from impaired turning of immature neurons by alcohol. PMID:20691765

  8. Dentate gyrus–CA3 glutamate release/NMDA transmission mediates behavioral despair and antidepressant-like responses to leptin

    PubMed Central

    Wang, Xuezhen; Zhang, Di; Lu, Xin-Yun

    2014-01-01

    Compelling evidence supports the important role of the glutamatergic system in the pathophysiology of major depression and also as a target for rapid-acting antidepressants. However, the functional role of glutamate release/transmission in behavioral processes related to depression and antidepressant efficacy remains to be elucidated. In this study, glutamate release and behavioral responses to tail suspension, a procedure commonly used for inducing behavioral despair, were simultaneously monitored in real time. The onset of tail suspension stress evoked a rapid increase in glutamate release in hippocampal field CA3, which declined gradually after its offset. Blockade of NMDA receptors by intra-CA3 infusion of MK-801, a non-competitive NMDA receptor antagonist, reversed behavioral despair. The CA3 was innervated by granule neurons expressing the leptin receptor (LepRb) in the dentate gyrus (DG), representing a subpopulation of granule neurons that were devoid of stress-induced activation. Leptin treatment dampened tail suspension-evoked glutamate release in CA3. On the other hand, intra-CA3 infusion of NMDA blocked the antidepressant-like effect of leptin in reversing behavioral despair in both the tail suspension and forced swim tests, which involved activation of Akt signaling in DG. Together, these results suggest that the DG-CA3 glutamatergic pathway is critical for mediating behavioral despair and antidepressant-like responses to leptin. PMID:25092243

  9. TESTOSTERONE AND SOCIAL ISOLATION INFLUENCE ADULT NEUROGENESIS IN THE DENTATE GYRUS OF MALE RATS

    PubMed Central

    Spritzer, Mark D.; Ibler, Erin; Inglis, William; Curtis, Molly G.

    2011-01-01

    Testosterone has been previously shown to enhance adult neurogenesis within the dentate gyrus of adult male rats, whereas social isolation has been shown to cause a decrease in adult neurogenesis under some conditions. The current study tested the combined effects of testosterone and social isolation upon adult neurogenesis using two experiments involving adult male rats. For both experiments, half of the subjects were pair-housed and half were housed individually for the duration of the experiments (34 days). For experiment 1, the subjects were divided into four groups (n=8/group): 1) sham/pair-housed, 2) sham/isolated, 3) castrate/pair-housed, and 4) castrate/isolated. Rats in the castrate groups were bilaterally castrated, and rats in the sham groups were sham castrated. For experiment 2, all rats were castrated and the effects of testosterone were tested using daily injections of testosterone propionate (0.500 mg/rat for 15 days) or the oil vehicle. Subjects were divided into four groups (n =8/group): 1) oil/pair-housed, 2) oil/isolated, 3) testosterone/pair-housed, and 4) testosterone/isolated. All rats were injected with 5-Bromo-2’-deoxyuridine (BrdU, 200 mg/kg body mass) and immunohistochemistry was used to determine levels of neurogenesis following a 16-day cell survival period. For experiment 1, castrated subjects had significantly fewer BrdU-labeled cells along the granule cell layer and sub-granular zone (GCL+SGZ) of the dentate gyrus than did intact subjects, and this effect was mainly due to low levels of neurogenesis in the castrate/isolated group. For experiment 2, social isolation caused a significant decrease in neurogenesis within the GCL+SGZ relative to the pair-housed groups. Testosterone injections did not buffer against this effect but instead tended to cause a decrease in neurogenesis. Thus, social isolation reduced hippocampal neurogenesis, but the effects of testosterone were inconsistent. This suggests that normal circulating levels of

  10. Testosterone and social isolation influence adult neurogenesis in the dentate gyrus of male rats.

    PubMed

    Spritzer, M D; Ibler, E; Inglis, W; Curtis, M G

    2011-11-10

    Testosterone has been previously shown to enhance adult neurogenesis within the dentate gyrus of adult male rats, whereas social isolation has been shown to cause a decrease in adult neurogenesis under some conditions. The current study tested the combined effects of testosterone and social isolation upon adult neurogenesis using two experiments involving adult male rats. For both experiments, half of the subjects were pair-housed and half were housed individually for the duration of the experiments (34 days). For experiment 1, the subjects were divided into four groups (n=8/group): (1) sham/pair-housed, (2) sham/isolated, (3) castrate/pair-housed, and (4) castrate/isolated. Rats in the castrate groups were bilaterally castrated, and rats in the sham groups were sham castrated. For experiment 2, all rats were castrated, and the effects of testosterone were tested using daily injections of testosterone propionate (0.500 mg/rat for 15 days) or the oil vehicle. Subjects were divided into four groups (n=8/group): (1) oil/pair-housed, (2) oil/isolated, (3) testosterone/pair-housed, and (4) testosterone/isolated. All rats were injected with 5-bromo-2'-deoxyuridine (BrdU, 200 mg/kg body mass), and immunohistochemistry was used to determine levels of neurogenesis following a 16-day cell survival period. For experiment 1, castrated subjects had significantly fewer BrdU-labeled cells along the granule cell layer and subgranular zone (GCL+SGZ) of the dentate gyrus than did intact subjects, and this effect was mainly due to low levels of neurogenesis in the castrate/isolated group. For experiment 2, social isolation caused a significant decrease in neurogenesis within the GCL+SGZ relative to the pair-housed groups. Testosterone injections did not buffer against this effect but instead tended to cause a decrease in neurogenesis. Thus, social isolation reduced hippocampal neurogenesis, but the effects of testosterone were inconsistent. This suggests that normal circulating

  11. Granule consolidation during compaction.

    PubMed

    Rubinstein, M H

    1976-03-01

    The deformation of small cylindrical aggregates of dibasic calcium phosphate was measured during compaction. An analogy between these aggregates and cylindrical granules was proposed. No change in the original shape of the aggregates occurred; the cylindrical shape was maintained even at high compaction pressures. Relaxation of the aggregates occurred at pressures higher than 420 MNm-2 (60.9 x 10(3) lb in.-2) when removed from the compacts, but no relaxation took place at pressures below this value. In addition, the aggregates relaxed by an increase in thickness only; there was no corresponding change in diameter. Up to a pressure of 200 MNm-2 (29.0 x 10(3) lb in.-2), an increase in aggregate diameter occurred, which was accompanied by a reduction in thickness. This change produced only a small reduction in volume, which was attributable to interparticulate slippage resulting in a closer packed arrangement. At a pressure of 200 MNm-2, the aggregate diameter no longer increased because solid bridges were formed between the particles and the die wall, preventing further spreading. From 200 to 420 MNm-2, failure of the material occurred by plastic deformation, which produced only a decrease in aggregate thickness. From 420 to 800 MNm-2 (116.0 x 10(3) lb in.-2), a structure was formed that could support the applied load without further reduction of thickness, and this structure was shown to behave elastically. PMID:1263085

  12. Granulopoiesis and granules of human neutrophils.

    PubMed

    Cowland, Jack B; Borregaard, Niels

    2016-09-01

    Granules are essential for the ability of neutrophils to fulfill their role in innate immunity. Granule membranes contain proteins that react to environmental cues directing neutrophils to sites of infection and initiate generation of bactericidal oxygen species. Granules are densely packed with proteins that contribute to microbial killing when liberated to the phagosome or extracellularly. Granules are, however, highly heterogeneous and are traditionally subdivided into azurophil granules, specific granules, and gelatinase granules in addition to secretory vesicles. This review will address issues pertinent to formation of granules, which is a process intimately connected to maturation of neutrophils from their precursors in the bone marrow. We further discuss possible mechanisms by which decisions are made regarding sorting of proteins to constitutive secretion or storage in granules and how degranulation of granule subsets is regulated. PMID:27558325

  13. Linking granulation performance with residence time and granulation liquid distributions in twin-screw granulation: An experimental investigation.

    PubMed

    Kumar, Ashish; Alakarjula, Maija; Vanhoorne, Valérie; Toiviainen, Maunu; De Leersnyder, Fien; Vercruysse, Jurgen; Juuti, Mikko; Ketolainen, Jarkko; Vervaet, Chris; Remon, Jean Paul; Gernaey, Krist V; De Beer, Thomas; Nopens, Ingmar

    2016-07-30

    Twin-screw granulation is a promising wet granulation technique for the continuous manufacturing of pharmaceutical solid dosage forms. A twin screw granulator displays a short residence time. Thus, the solid-liquid mixing must be achieved quickly by appropriate arrangement of transport and kneading elements in the granulator screw allowing the production of granules with a size distribution appropriate for tableting. The distribution of residence time and granulation liquid is governed by the field conditions (such as location and length of mixing zones) in the twin-screw granulator, thus contain interesting information on granulation time, mixing and resulting sub-processes such as wetting, aggregation and breakage. In this study, the impact of process (feed rate, screw speed and liquid-to-solid ratio) and equipment parameters (number of kneading discs and stagger angle) on the residence time (distribution), the granulation liquid-powder mixing and the resulting granule size distributions during twin-screw granulation were investigated. Residence time and axial mixing data was extracted from tracer maps and the solid-liquid mixing was quantified from moisture maps, obtained by monitoring the granules at the granulator outlet using near infra-red chemical imaging (NIR-CI). The granule size distribution was measured using the sieving method. An increasing screw speed dominantly reduced the mean residence time. Interaction of material throughput with the screw speed and with the number of kneading discs led to most variation in the studied responses including residence time and mixing capacity. At a high screw speed, granulation yield improved due to high axial mixing. However, increasing material throughput quickly lowers the yield due to insufficient mixing of liquid and powder. Moreover, increasing liquid-to-solid ratio resulted in more oversized granules, and the fraction of oversized granules further increased at higher throughput. Although an increasing number

  14. Synaptic commitment: developmentally regulated reciprocal changes in hippocampal granule cell NMDA and AMPA receptors over the lifespan.

    PubMed

    Yang, Zhiyong; Krause, Michael; Rao, Geeta; McNaughton, Bruce L; Barnes, C A

    2008-06-01

    Synaptic transmission in hippocampal field CA1 is largely N-methyl-d-aspartate receptor (NMDA(R)) dependent during the early postnatal period. It becomes increasingly mediated by alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionate (AMPA) receptors until an adult ratio of AMPA to NMDA receptors is achieved. It is shown here that increases in the AMPA receptor (AMPA(R))-mediated field potential response continue over the life span of the F-344 rat at the perforant path-granule cell synapse in the dentate gyrus. In contrast, the NMDA(R)-dependent component of the response decreases with age between 1 and 27 mo, leading to an increase of AMPA(R)/NMDA(R) ratio with age. One possible explanation of this age difference is that the AMPA(R)/NMDA(R) ratio can be modified by experience. To test the idea that the changed ratio is caused by the old rats' longer lives, an intensive 10-mo period of enrichment treatment was given to a group of animals, beginning at 3 mo of age. Compared with animals housed in standard cages, the enrichment treatment did not alter the glutamatergic response ratio measured with field potential recording methods. These data provide support for the conclusion that the observed change with age is developmentally regulated rather than experience dependent. Given the role of the NMDA(R) in synaptic plasticity, these changes suggest a progressive commitment of perforant path synapses to particular weights over the life span. One possible implication of this effect includes preservation of selected memories, ultimately at the expense of a reduced capacity to store new information. PMID:18417629

  15. Microtubule-dependent association of AKAP350A and CCAR1 with RNA stress granules

    PubMed Central

    Kolobova, Elena; Efimov, Andrey; Kaverina, Irina; Rishi, Arun K.; Schrader, John W.; Ham, Amy-Joan; Larocca, M. Cecilia; Goldenring, James R.

    2009-01-01

    Recent investigations have highlighted the importance of subcellular localization of mRNAs to cell function. While AKAP350A, a multifunctional scaffolding protein, localizes to the Golgi apparatus and centrosomes, we have now identified a cytosolic pool of AKAP350A. Analysis of AKAP350A scaffolded complexes revealed two novel interacting proteins, CCAR1 and caprin-1. CCAR1, caprin-1 and AKAP350A along with G3BP, a stress granule marker, relocate to RNA stress granules after arsenite treatment. Stress also caused loss of AKAP350 from the Golgi and fragmentation of the Golgi apparatus. Disruption of microtubules with nocodazole altered stress granule formation and changed their morphology by preventing fusion of stress granules. In the presence of nocodazole, arsenite induced smaller granules with the vast majority of AKAP350A and CCAR1 separated from G3BP-containing granules. Similar to nocodazole treatment, reduction of AKAP350A or CCAR1 expression also altered the size and number of G3BP-containing stress granules induced by arsenite treatment. A limited set of 69 mRNA transcripts was immunisolated with AKAP350A even in the absence of stress, suggesting the association of AKAP350A with mRNA transcripts. These results provide the first evidence for the microtubule dependent association of AKAP350A and CCAR1 with RNA stress granules. PMID:19073175

  16. TDP-43 is directed to stress granules by sorbitol, a novel physiological osmotic and oxidative stressor.

    PubMed

    Dewey, Colleen M; Cenik, Basar; Sephton, Chantelle F; Dries, Daniel R; Mayer, Paul; Good, Shannon K; Johnson, Brett A; Herz, Joachim; Yu, Gang

    2011-03-01

    TDP-43, or TAR DNA-binding protein 43, is a pathological marker of a spectrum of neurodegenerative disorders, including amyotrophic lateral sclerosis and frontotemporal lobar degeneration with ubiquitin-positive inclusions. TDP-43 is an RNA/DNA-binding protein implicated in transcriptional and posttranscriptional regulation. Recent work also suggests that TDP-43 associates with cytoplasmic stress granules, which are transient structures that form in response to stress. In this study, we establish sorbitol as a novel physiological stressor that directs TDP-43 to stress granules in Hek293T cells and primary cultured glia. We quantify the association of TDP-43 with stress granules over time and show that stress granule association and size are dependent on the glycine-rich region of TDP-43, which harbors the majority of pathogenic mutations. Moreover, we establish that cells harboring wild-type and mutant TDP-43 have distinct stress responses: mutant TDP-43 forms significantly larger stress granules, and is incorporated into stress granules earlier, than wild-type TDP-43; in striking contrast, wild-type TDP-43 forms more stress granules over time, but the granule size remains relatively unchanged. We propose that mutant TDP-43 alters stress granule dynamics, which may contribute to the progression of TDP-43 proteinopathies. PMID:21173160

  17. DNA Methylation Program in Developing Hippocampus and Its Alteration by Alcohol

    PubMed Central

    Chen, Yuanyuan; Ozturk, Nail Can; Zhou, Feng C.

    2013-01-01

    During hippocampal development, the Cornus Ammonis (CA) and the dentate gyrus (DG) undergo waves of neurogenesis and neuronal migration and maturation independently. This stage is widely known to be vulnerable to environmental stresses, but its underlying mechanism is unclear. Alcohol exposure has been shown to alter the expression of genes that regulate the fate, survival, migration and differentiation of pyramidal and granule cells. Undermining this process might compromise hippocampal development underlying the learning and memory deficits known in Fetal Alcohol Spectrum Disorders (FASD). We have previously demonstrated that DNA methylation was programmed along with neural tube development. Here, we demonstrated that DNA methylation program (DMP) proceeded along with hippocampal neuronal differentiation and maturation, and how this DMP was affected by fetal alcohol exposure. C57BL/6 mice were treated with 4% v/v ethanol through a liquid diet along with pair-fed and chow-fed controls from gestation day (E) 7 to E16. We found that a characteristic DMP, including 5-methylcytidine (5mC), 5-hydroxylmethylcytidine (5hmC) and their binding proteins, led the hippocampal neuronal differentiation and maturation spatiotemporally as indicated by their phenotypic marks in the CA and DG pre- and post-natally. Alcohol hindered the acquisition and progression of methylation marks, and altered the chromatin translocation of these marks in the nucleus, which was correlated with developmental retardation. PMID:23544149

  18. Conditional Disabled-1 Deletion in Mice Alters Hippocampal Neurogenesis and Reduces Seizure Threshold

    PubMed Central

    Korn, Matthew J.; Mandle, Quinton J.; Parent, Jack M.

    2016-01-01

    Many animal models of temporal lobe epilepsy (TLE) exhibit altered neurogenesis arising from progenitors within the dentate gyrus subgranular zone (SGZ). Aberrant integration of new neurons into the existing circuit is thought to contribute to epileptogenesis. In particular, adult-born neurons that exhibit ectopic migration and hilar basal dendrites (HBDs) are suggested to be pro-epileptogenic. Loss of reelin signaling may contribute to these morphological changes in patients with epilepsy. We previously demonstrated that conditional deletion of the reelin adaptor protein, disabled-1 (Dab1), from postnatal mouse SGZ progenitors generated dentate granule cells (DGCs) with abnormal dendritic development and ectopic placement. To determine whether the early postnatal loss of reelin signaling is epileptogenic, we conditionally deleted Dab1 in neural progenitors and their progeny on postnatal days 7–8 and performed chronic video-EEG recordings 8–10 weeks later. Dab1-deficient mice did not have spontaneous seizures but exhibited interictal epileptiform abnormalities and a significantly reduced latency to pilocarpine-induced status epilepticus. After chemoconvulsant treatment, over 90% of mice deficient for Dab1 developed generalized motor convulsions with tonic-clonic movements, rearing, and falling compared to <20% of wild-type mice. Recombination efficiency, measured by Cre reporter expression, inversely correlated with time to the first sustained seizure. These pro-epileptogenic changes were associated with decreased neurogenesis and increased numbers of hilar ectopic DGCs. Interestingly, neurons co-expressing the Cre reporter comprised a fraction of these hilar ectopic DGCs cells, suggesting a non-cell autonomous effect for the loss of reelin signaling. We also noted a dispersion of the CA1 pyramidal layer, likely due to hypomorphic effects of the conditional Dab1 allele, but this abnormality did not correlate with seizure susceptibility. These findings suggest

  19. Effects of developmental hyperserotonemia on the morphology of rat dentate nuclear neurons.

    PubMed

    Hough, L H; Segal, S

    2016-05-13

    Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by deficits in social cognition, disordered communication, restricted interests and repetitive behaviors. Furthermore, abnormalities in basic motor control, skilled motor gestures, and motor learning, are common in ASD. These characteristics have been attributed to a possible defect in the pre- and postnatal development of specific neural networks including the dentate-thalamo-cortical pathway, which is involved in motor learning, automaticity of movements, and higher cognitive functions. The current study utilized custom diolistic labeling and unbiased stereology to characterize morphological alterations in neurons of the dentate nucleus of the cerebellum in developing rat pups exposed to abnormally high levels of the serotonergic agonist 5-methyloxytryptamine (5-MT) pre-and postnatally. Occurring in as many as 30% of autistic subjects, developmental hyperserotonemia (DHS) is the most consistent neurochemical finding reported in autism and has been implicated in the pathophysiology of ASD. This exposure produced dramatic changes in dendritic architecture and synaptic features. We observed changes in the dendritic branching morphology which did not lead to significant differences (p>0.5) in total dendritic length. Instead, DHS groups presented with dendritic trees that display changes in arborescence, that appear to be short reaching with elaborately branched segments, presenting with significantly fewer (p>0.001) dendritic spines and a decrease in numeric density when compared to age-matched controls. These negative changes may be implicated in the neuropathological and functional/behavioral changes observed in ASD, such as delays in motor learning, difficulties in automaticity of movements, and deficits in higher cognitive functions. PMID:26892293

  20. A computational model of pattern separation efficiency in the dentate gyrus with implications in schizophrenia

    PubMed Central

    Faghihi, Faramarz; Moustafa, Ahmed A.

    2015-01-01

    Information processing in the hippocampus begins by transferring spiking activity of the entorhinal cortex (EC) into the dentate gyrus (DG). Activity pattern in the EC is separated by the DG such that it plays an important role in hippocampal functions including memory. The structural and physiological parameters of these neural networks enable the hippocampus to be efficient in encoding a large number of inputs that animals receive and process in their life time. The neural encoding capacity of the DG depends on its single neurons encoding and pattern separation efficiency. In this study, encoding by the DG is modeled such that single neurons and pattern separation efficiency are measured using simulations of different parameter values. For this purpose, a probabilistic model of single neurons efficiency is presented to study the role of structural and physiological parameters. Known neurons number of the EC and the DG is used to construct a neural network by electrophysiological features of granule cells of the DG. Separated inputs as activated neurons in the EC with different firing probabilities are presented into the DG. For different connectivity rates between the EC and DG, pattern separation efficiency of the DG is measured. The results show that in the absence of feedback inhibition on the DG neurons, the DG demonstrates low separation efficiency and high firing frequency. Feedback inhibition can increase separation efficiency while resulting in very low single neuron’s encoding efficiency in the DG and very low firing frequency of neurons in the DG (sparse spiking). This work presents a mechanistic explanation for experimental observations in the hippocampus, in combination with theoretical measures. Moreover, the model predicts a critical role for impaired inhibitory neurons in schizophrenia where deficiency in pattern separation of the DG has been observed. PMID:25859189

  1. Ketamine Affects the Neurogenesis of the Hippocampal Dentate Gyrus in 7-Day-Old Rats.

    PubMed

    Huang, He; Liu, Cun-Ming; Sun, Jie; Hao, Ting; Xu, Chun-Mei; Wang, Dan; Wu, Yu-Qing

    2016-08-01

    Ketamine has been reported to cause neonatal neurotoxicity via a neuronal apoptosis mechanism; however, no in vivo research has reported whether ketamine could affect postnatal neurogenesis in the hippocampal dentate gyrus (DG). A growing number of experiments suggest that postnatal hippocampal neurogenesis is the foundation of maintaining normal hippocampus function into adulthood. Therefore, this study investigated the effect of ketamine on hippocampal neurogenesis. Male Sprague-Dawley rats were divided into two groups: the control group (equal volume of normal saline), and the ketamine-anesthesia group (40 mg/kg ketamine in four injections at 1 h intervals). The S-phase marker 5-bromodeoxyuridine (BrdU) was administered after ketamine exposure to postnatal day 7 (PND-7) rats, and the neurogenesis in the hippocampal DG was assessed using single- or double-immunofluorescence staining. The expression of GFAP in the hippocampal DG was measured by western blot analysis. Spatial reference memory was tested by Morris water maze at 2 months after PND-7 rats exposed to ketamine treatment. The present results showed that neonatal ketamine exposure significantly inhibited neural stem cell (NSC) proliferation, decreased astrocytic differentiation, and markedly enhanced neuronal differentiation. The disruptive effect of ketamine on the proliferation and differentiation of NSCs lasted at least 1 week and disappeared by 2 weeks after ketamine exposure. Moreover, the migration of newborn neurons in the granule cell layer and the growth of astrocytes in the hippocampal DG were inhibited by ketamine on PND-37 and PND-44. Finally, ketamine caused a deficit in hippocampal-dependent spatial reference memory tasks at 2 months old. Our results suggested that ketamine may interfere with hippocampal neurogenesis and long-term neurocognitive function in PND-7 rats. These findings may provide a new perspective to explain the adult neurocognitive dysfunction induced by neonatal

  2. Segmental cable evaluation of somatic transients in hippocampal neurons (CA1, CA3, and dentate).

    PubMed Central

    Turner, D A

    1984-01-01

    This study describes a detailed cable model of neuronal structure, which can predict the effects of discrete transient inputs. Neurons in in vitro hippocampal slices (CA1 and CA3 pyramidal cells and dentate granule neurons; n = 4 each) were physiologically characterized and stained with horseradish peroxidase (HRP). The HRP morphology was approximated with numerous small segments. The cable model included both these segments and spatially dispersed dendritic spines. The transient response function at the soma of the segmental model was numerically derived, and charging responses to simulated current inputs were computed. These simulations were compared with the physiological charging responses from the somatic penetrations, using an analysis of the charging time constants (tau i) and intercepts. The time constant ratio (tau 0/tau 1) did not significantly differ between the observed and simulated responses. A second index of comparison was the equivalent cylinder electrotonic length (L), which was derived using only the tau i values and their intercepts. The L values also did not differ significantly between the observed and simulated transients and averaged 0.91 length constant. Thus, using criteria based only on analysis of charging responses, the segmental cable model recreated accurately the observed transients at the soma. The equivalent cylinder model (with a lumped soma) could also adequately simulate the observed somatic transients, using the same criteria. However, the hippocampal neurons (particularly the pyramidal cells) did not appear to satisfy the equivalent cylinder assumption anatomically. Thus, the analysis of somatic charging transients alone may not be sufficient to discriminate between the two models of hippocampal neurons. Anatomical evidence indicates that, particularly for discrete dendritic inputs, the detailed segmental model may be more appropriate than the equivalent cylinder model. PMID:6743759

  3. Functional Analysis of Neurovascular Adaptations to Exercise in the Dentate Gyrus of Young Adult Mice Associated With Cognitive Gain

    PubMed Central

    Clark, Peter J.; Brzezinska, Weronika J.; Puchalski, Emily K.; Krone, David A.; Rhodes, Justin S.

    2009-01-01

    The discovery that aerobic exercise increases adult hippocampal neurogenesis and can enhance cognitive performance holds promise as a model for regenerative medicine. This study adds two new pieces of information to the rapidly growing field. First, we tested whether exercise increases vascular density in the granular layer of the dentate gyrus, whole hippocampus, and striatum in C57BL/6J mice known to display procognitive effects of exercise. Second, we determined the extent to which new neurons from exercise participate in the acute neuronal response to high levels of running in B6D2F1/J (F1 hybrid of C57BL/6J female by DBA/2J male). Mice were housed with or without a running wheel for 50 days (runner vs. sedentary). The first 10 days, they received daily injections of BrdU to label dividing cells. The last 10 days, mice were tested for performance on the Morris water maze and rotarod and then euthanized to measure neurogenesis, c-Fos induction from running and vascular density. In C57BL/6J, exercise increased neurogenesis, density of blood vessels in the dentate gyrus and striatum (but not whole hippocampus), and enhanced performance on the water maze and rotarod. In B6D2F1/J, exercise also increased hippocampal neurogenesis but not vascular density in the granular layer. Improvement on the water maze from exercise was marginal, and no gain was seen for rotarod, possibly because of a ceiling effect. Running increased the number of c-Fos positive neurons in the granular layer by fivefold, and level of running was strongly correlated with c-Fos within 90 min before euthanasia. In runners, ~3.3% (±0.008 S.E.) of BrdU-positive neurons in the middle of the granule layer displayed c-Fos when compared with 0.8% (±0.001) of BrdU-negative neurons. Results suggest that procognitive effects of exercise are associated with increased vascular density in the dentate gyrus and striatum in C57BL/6J mice, and that new neurons from exercise preferentially function in the

  4. Persistent Hyperactivity of Hippocampal Dentate Interneurons After a Silent Period in the Rat Pilocarpine Model of Epilepsy

    PubMed Central

    Wang, Xiaochen; Song, Xinyu; Wu, Lin; Nadler, J. Victor; Zhan, Ren-Zhi

    2016-01-01

    Profile of GABAergic interneuron activity after pilocarpine-induced status epilepticus (SE) was examined in the rat hippocampal dentate gyrus by analyzing immediate early gene expression and recording spontaneous firing at near resting membrane potential (REM). SE for exact 2 h or more than 2 h was induced in the male Sprague-Dawley rats by an intraperitoneal injection of pilocarpine. Expression of immediate early genes (IEGs) was examined at 1 h, 1 week, 2 weeks or more than 10 weeks after SE. For animals to be examined at 1 h after SE, SE lasted for exact 2 h was terminated by an intraperitoneal injection of diazepam. Spontaneous firing at near the REM was recorded in interneurons located along the border between the granule cell layer and the hilus more than 10 weeks after SE. Results showed that both c-fos and activity-regulated cytoskeleton associated protein (Arc) in hilar GABAergic interneurons were up-regulated after SE in a biphasic manner; they were increased at 1 h and more than 2 weeks, but not at 1 week after SE. Ten weeks after SE, nearly 60% of hilar GABAergic cells expressed c-fos. With the exception of calretinin (CR)-positive cells, percentages of hilar neuronal nitric oxide synthase (nNOS)-, neuropeptide Y (NPY)-, parvalbumin (PV)-, and somatostatin (SOM)-positive cells with c-fos expression are significantly higher than those of controls more than 10 weeks after SE. Without the REM to be more depolarizing and changed threshold potential level in SE-induced rats, cell-attached recording revealed that nearly 90% of hilar interneurons fired spontaneously at near the REM while only 22% of the same cell population did so in the controls. In conclusion, pilocarpine-induced SE eventually leads to a state in which surviving dentate GABAergic interneurons become hyperactive with a subtype-dependent manner; this implies that a fragile balance between excitation and inhibition exists in the dentate gyrus and in addition, the activity-dependent up

  5. Hyperintense Dentate Nuclei on T1-Weighted MRI: Relation to Repeat Gadolinium Administration

    PubMed Central

    Adin, M.E.; Kleinberg, L.; Vaidya, D.; Zan, E.; Mirbagheri, S.; Yousem, D.M.

    2016-01-01

    BACKGROUND AND PURPOSE A hyperintense appearance of the dentate nucleus on T1-weighted MR images has been related to various clinical conditions, but the etiology remains indeterminate. We aimed to investigate the possible associations between a hyperintense appearance of the dentate nucleus on T1-weighted MR images in patients exposed to radiation and factors including, but not limited to, the cumulative number of contrast-enhanced MR images, amount of gadolinium administration, dosage of ionizing radiation, and patient demographics. MATERIALS AND METHODS The medical records of 706 consecutive patients who were treated with brain irradiation at The Johns Hopkins Medical Institutions between 1995 and 2010 were blindly reviewed by 2 readers. RESULTS One hundred eighty-four subjects were included for dentate nuclei analysis. Among the 184 subjects who cumulatively underwent 2677 MR imaging studies following intravenous gadolinium administration, 103 patients had hyperintense dentate nuclei on precontrast T1-weighted MR images. The average number of gadolinium-enhanced MR imaging studies performed in the group with normal dentate nuclei was significantly lower than that of the group with hyperintense dentate nuclei. The average follow-up time was 62.5 months. No significant difference was observed between hyperintense and normal dentate nuclei groups in terms of exposed radiation dose, serum creatinine and calcium/phosphate levels, patient demographics, history of chemotherapy, and strength of the scanner. No dentate nuclei abnormalities were found on the corresponding CT scans of patients with hyperintense dentate nuclei (n = 44). No dentate nuclei abnormalities were found in 53 healthy volunteers. CONCLUSIONS Repeat performance of gadolinium-enhanced studies likely contributes to a long-standing hyperintense appearance of dentate nuclei on precontrast T1-weighted-MR images. PMID:26294649

  6. Stress-induced gene expression and behavior are controlled by DNA methylation and methyl donor availability in the dentate gyrus.

    PubMed

    Saunderson, Emily A; Spiers, Helen; Mifsud, Karen R; Gutierrez-Mecinas, Maria; Trollope, Alexandra F; Shaikh, Abeera; Mill, Jonathan; Reul, Johannes M H M

    2016-04-26

    Stressful events evoke long-term changes in behavioral responses; however, the underlying mechanisms in the brain are not well understood. Previous work has shown that epigenetic changes and immediate-early gene (IEG) induction in stress-activated dentate gyrus (DG) granule neurons play a crucial role in these behavioral responses. Here, we show that an acute stressful challenge [i.e., forced swimming (FS)] results in DNA demethylation at specific CpG (5'-cytosine-phosphate-guanine-3') sites close to the c-Fos (FBJ murine osteosarcoma viral oncogene homolog) transcriptional start site and within the gene promoter region of Egr-1 (early growth response protein 1) specifically in the DG. Administration of the (endogenous) methyl donor S-adenosyl methionine (SAM) did not affect CpG methylation and IEG gene expression at baseline. However, administration of SAM before the FS challenge resulted in an enhanced CpG methylation at the IEG loci and suppression of IEG induction specifically in the DG and an impaired behavioral immobility response 24 h later. The stressor also specifically increased the expression of the de novo DNA methyltransferase Dnmt3a [DNA (cytosine-5-)-methyltransferase 3 alpha] in this hippocampus region. Moreover, stress resulted in an increased association of Dnmt3a enzyme with the affected CpG loci within the IEG genes. No effects of SAM were observed on stress-evoked histone modifications, including H3S10p-K14ac (histone H3, phosphorylated serine 10 and acetylated lysine-14), H3K4me3 (histone H3, trimethylated lysine-4), H3K9me3 (histone H3, trimethylated lysine-9), and H3K27me3 (histone H3, trimethylated lysine-27). We conclude that the DNA methylation status of IEGs plays a crucial role in FS-induced IEG induction in DG granule neurons and associated behavioral responses. In addition, the concentration of available methyl donor, possibly in conjunction with Dnmt3a, is critical for the responsiveness of dentate neurons to environmental stimuli in

  7. Smaller Dentate Gyrus and CA2 and CA3 Volumes Are Associated with Kynurenine Metabolites in Collegiate Football Athletes.

    PubMed

    Meier, Timothy B; Savitz, Jonathan; Singh, Rashmi; Teague, T Kent; Bellgowan, Patrick S F

    2016-07-15

    An imbalance in kynurenine pathway metabolism is hypothesized to be associated with dysregulated glutamatergic neurotransmission, which has been proposed as a mechanism underlying the hippocampal volume loss observed in a variety of neurological disorders. Pre-clinical models suggest that the CA2-3 and dentate gyrus hippocampal subfields are particularly susceptible to excitotoxicity after experimental traumatic brain injury. We tested the hypothesis that smaller hippocampal volumes in collegiate football athletes with (n = 25) and without (n = 24) a concussion history would be most evident in the dentate gyrus and CA2-3 subfields relative to nonfootball healthy controls (n = 27). Further, we investigated whether the concentration of peripheral levels of kynurenine metabolites are altered in football athletes. Football athletes with and without a self-reported concussion history had smaller dentate gyrus (p < 0.05, p < 0.10) and CA2-3 volumes (p's < 0.05) relative to healthy controls. Football athletes with and without a concussion history had a trend toward lower (p < 0.10) and significantly lower (p < 0.05) kynurenine levels compared with healthy controls, while athletes with a concussion history had greater levels of quinolinic acid compared with athletes without a concussion history (p < 0.05). Finally, plasma levels of 3-hydroxykynurenine inversely correlated with bilateral hippocampal volumes in football athletes with a concussion history (p < 0.01), and left hippocampal volume was correlated with the ratio of kynurenic acid to quinolinic acid in football athletes without a concussion history (p < 0.05). Our results raise the possibility that abnormalities of the kynurenine metabolic pathway constitute a mechanism for hippocampal volume differences in the context of sports-related brain injury. PMID:26493952

  8. A practical approach to diseases affecting dentate nuclei.

    PubMed

    Khadilkar, S; Jaggi, S; Patel, B; Yadav, R; Hanagandi, P; Faria do Amaral, L L

    2016-01-01

    A wide variety of diseases affect the dentate nuclei. When faced with the radiological demonstration of signal changes in the dentate nuclei, radiologists and clinical neurologists have to sieve through the many possibilities, which they do not encounter on a regular basis. This task can be challenging, and therefore, developing a clinical, radiological, and laboratory approach is important. Information on the topic is scattered and the subject has not yet been reviewed. In this review, a combined clinicoradiological approach is presented. The signal changes in T1, T2, fluid-attenuated inversion recovery (FLAIR), diffusion, susceptibility weighted, and gadolinium-enhanced images can give specific or highly suggestive patterns, which are illustrated. The role of computed tomography (CT) in the diagnostic process is discussed. Specific radiological patterns do not exist in a significant proportion of patients where the clinical and laboratory analysis becomes important. In this review, we group the clinical constellations to narrow down the differential diagnosis and highlight the diagnostic clinical signs, such as tendon xanthomas and Kayser-Fleischer rings. As will be seen, a number of these conditions are potentially reversible, and hence, their early diagnosis is desirable. Finally, key diagnostic tests and available therapies are outlined. The practical approach thus begins with the radiologist and winds its way through the clinician, towards carefully selected diagnostic tests defining the therapy options. PMID:26577296

  9. Early postischemic /sup 45/Ca accumulation in rat dentate hilus

    SciTech Connect

    Benveniste, H.; Diemer, N.H.

    1988-10-01

    Several studies have found postischemic regional accumulation of calcium to be time-dependent and coincident with the progression of ischemic cell change. In the most vulnerable cells in the hippocampus one would therefore expect to find a primary and specific early uptake of calcium after ischemia. Autoradiograms of /sup 45/Ca and /sup 3/H-inulin distribution were investigated before and 1 h after 20 min ischemia in the rat hippocampus. Two different methodological approaches were used for administration of /sup 45/Ca: (a) administration via microdialysis probes, (b) intraventricular injection. During control conditions the /sup 45/Ca autoradiograms showed variations in distribution volume in accordance with /sup 3/H-inulin determination of extracellular space size. One hour after ischemia a massive accumulation of /sup 45/Ca was found in the dentate hilus. No change in the distribution pattern of /sup 3/H-inulin could be demonstrated 1 h after ischemia. We suggest that /sup 45/Ca accumulation in dentate hilus 1 h after ischemia is a result of increased Ca/sup 2 +/ uptake before irreversible cell damage occurs and is not due to passive influx of calcium across a leaky plasma membrane.

  10. Multi-omics profile of the mouse dentate gyrus after kainic acid-induced status epilepticus

    PubMed Central

    Schouten, Marijn; Bielefeld, Pascal; Fratantoni, Silvina A.; Hubens, Chantal J.; Piersma, Sander R.; Pham, Thang V.; Voskuyl, Rob A.; Lucassen, Paul J.; Jimenez, Connie R.; Fitzsimons, Carlos P.

    2016-01-01

    Temporal lobe epilepsy (TLE) can develop from alterations in hippocampal structure and circuit characteristics, and can be modeled in mice by administration of kainic acid (KA). Adult neurogenesis in the dentate gyrus (DG) contributes to hippocampal functions and has been reported to contribute to the development of TLE. Some of the phenotypical changes include neural stem and precursor cells (NPSC) apoptosis, shortly after their birth, before they produce hippocampal neurons. Here we explored these early phenotypical changes in the DG 3 days after a systemic injection of KA inducing status epilepticus (KA-SE), in mice. We performed a multi-omics experimental setup and analyzed DG tissue samples using proteomics, transcriptomics and microRNA profiling techniques, detecting the expression of 2327 proteins, 13401 mRNAs and 311 microRNAs. We here present a description of how these data were obtained and make them available for further analysis and validation. Our data may help to further identify and characterize molecular mechanisms involved in the alterations induced shortly after KA-SE in the mouse DG. PMID:27529540

  11. Multi-omics profile of the mouse dentate gyrus after kainic acid-induced status epilepticus.

    PubMed

    Schouten, Marijn; Bielefeld, Pascal; Fratantoni, Silvina A; Hubens, Chantal J; Piersma, Sander R; Pham, Thang V; Voskuyl, Rob A; Lucassen, Paul J; Jimenez, Connie R; Fitzsimons, Carlos P

    2016-01-01

    Temporal lobe epilepsy (TLE) can develop from alterations in hippocampal structure and circuit characteristics, and can be modeled in mice by administration of kainic acid (KA). Adult neurogenesis in the dentate gyrus (DG) contributes to hippocampal functions and has been reported to contribute to the development of TLE. Some of the phenotypical changes include neural stem and precursor cells (NPSC) apoptosis, shortly after their birth, before they produce hippocampal neurons. Here we explored these early phenotypical changes in the DG 3 days after a systemic injection of KA inducing status epilepticus (KA-SE), in mice. We performed a multi-omics experimental setup and analyzed DG tissue samples using proteomics, transcriptomics and microRNA profiling techniques, detecting the expression of 2327 proteins, 13401 mRNAs and 311 microRNAs. We here present a description of how these data were obtained and make them available for further analysis and validation. Our data may help to further identify and characterize molecular mechanisms involved in the alterations induced shortly after KA-SE in the mouse DG. PMID:27529540

  12. Evaluating scale-up rules of a high-shear wet granulation process.

    PubMed

    Tao, Jing; Pandey, Preetanshu; Bindra, Dilbir S; Gao, Julia Z; Narang, Ajit S

    2015-07-01

    This work aimed to evaluate the commonly used scale-up rules for high-shear wet granulation process using a microcrystalline cellulose-lactose-based low drug loading formulation. Granule properties such as particle size, porosity, flow, and tabletability, and tablet dissolution were compared across scales using scale-up rules based on different impeller speed calculations or extended wet massing time. Constant tip speed rule was observed to produce slightly less granulated material at the larger scales. Longer wet massing time can be used to compensate for the lower shear experienced by the granules at the larger scales. Constant Froude number and constant empirical stress rules yielded granules that were more comparable across different scales in terms of compaction performance and tablet dissolution. Granule porosity was shown to correlate well with blend tabletability and tablet dissolution, indicating the importance of monitoring granule densification (porosity) during scale-up. It was shown that different routes can be chosen during scale-up to achieve comparable granule growth and densification by altering one of the three parameters: water amount, impeller speed, and wet massing time. PMID:26010137

  13. A Mathematical Model of Granule Cell Generation During Mouse Cerebellum Development.

    PubMed

    Leffler, Shoshana R; Legué, Emilie; Aristizábal, Orlando; Joyner, Alexandra L; Peskin, Charles S; Turnbull, Daniel H

    2016-05-01

    Determining the cellular basis of brain growth is an important problem in developmental neurobiology. In the mammalian brain, the cerebellum is particularly amenable to studies of growth because it contains only a few cell types, including the granule cells, which are the most numerous neuronal subtype. Furthermore, in the mouse cerebellum granule cells are generated from granule cell precursors (gcps) in the external granule layer (EGL), from 1 day before birth until about 2 weeks of age. The complexity of the underlying cellular processes (multiple cell behaviors, three spatial dimensions, time-dependent changes) requires a quantitative framework to be fully understood. In this paper, a differential equation-based model is presented, which can be used to estimate temporal changes in granule cell numbers in the EGL. The model includes the proliferation of gcps and their differentiation into granule cells, as well as the process by which granule cells leave the EGL. Parameters describing these biological processes were derived from fitting the model to histological data. This mathematical model should be useful for understanding altered gcp and granule cell behaviors in mouse mutants with abnormal cerebellar development and cerebellar cancers. PMID:27125657

  14. Rapid compensatory changes in the expression of EAAT-3 and GAT-1 transporters during seizures in cells of the CA1 and dentate gyrus

    PubMed Central

    2012-01-01

    Background Epilepsy is a neurological disorder produced by an imbalance between excitatory and inhibitory neurotransmission, in which transporters of both glutamate and GABA have been implicated. Hence, at different times after local administration of the convulsive drug 4-aminopyridine (4-AP) we analyzed the expression of EAAT-3 and GAT-1 transporter proteins in cells of the CA1 and dentate gyrus. Methods Dual immunofluorescence was used to detect the co-localization of transporters and a neuronal marker. In parallel, EEG recordings were performed and convulsive behavior was rated using a modified Racine Scale. Results By 60 min after 4-AP injection, EAAT-3/NeuN co-labelling had increased in dentate granule cells and decreased in CA1 pyramidal cells. In the latter, this decrease persisted for up to 180 min after 4-AP administration. In both the DG and CA1, the number of GAT-1 labeled cells increased 60 min after 4-AP administration, although by 180 min GAT-1 labeled cells decreased in the DG alone. The increase in EAAT-3/NeuN colabelling in DG was correlated with maximum epileptiform activity and convulsive behavior. Conclusions These findings suggest that a compensatory mechanism exists to protect against acute seizures induced by 4-AP, whereby EAAT-3/NeuN cells is rapidly up regulated in order to enhance the removal of glutamate from the extrasynaptic space, and attenuating seizure activity. PMID:22931236

  15. Oxytocin depolarizes fast-spiking hilar interneurons and induces GABA release onto mossy cells of the rat dentate gyrus.

    PubMed

    Harden, Scott W; Frazier, Charles J

    2016-09-01

    Delivery of exogenous oxytocin (OXT) to central oxytocin receptors (OXT-Rs) is currently being investigated as a potential treatment for conditions such as post-traumatic stress disorder (PTSD), depression, social anxiety, and autism spectrum disorder (ASD). Despite significant research implicating central OXT signaling in modulation of mood, affect, social behavior, and stress response, relatively little is known about the cellular and synaptic mechanisms underlying these complex actions, particularly in brain regions which express the OXT-R but lie outside of the hypothalamus (where OXT-synthesizing neurons reside). We report that bath application of low concentrations of the selective OXT-R agonist Thr4,Gly7-OXT (TGOT) reliably and robustly drives GABA release in the dentate gyrus in an action potential dependent manner. Additional experiments led to identification of a small subset of small hilar interneurons that are directly depolarized by acute application of TGOT. From a physiological perspective, TGOT-responsive hilar interneurons have high input resistance, rapid repolarization velocity during an action potential, and a robust afterhyperpolarization. Further, they fire irregularly (or stutter) in response to moderate depolarization, and fire quickly with minimal spike frequency accommodation in response to large current injections. From an anatomical perspective, TGOT responsive hilar interneurons have dense axonal arborizations in the hilus that were found in close proximity with mossy cell somata and/or proximal dendrites, and also invade the granule cell layer. Further, they have primary dendrites that always extend into the granule cell layer, and sometimes have clear arborizations in the molecular layer. Overall, these data reveal a novel site of action for OXT in an important limbic circuit, and represent a significant step towards better understanding how endogenous OXT may modulate flow of information in hippocampal networks. © 2016 Wiley

  16. A Role for Huntington Disease Protein in Dendritic RNA Granules*

    PubMed Central

    Savas, Jeffrey N.; Ma, Bin; Deinhardt, Katrin; Culver, Brady P.; Restituito, Sophie; Wu, Ligang; Belasco, Joel G.; Chao, Moses V.; Tanese, Naoko

    2010-01-01

    Regulated transport and local translation of mRNA in neurons are critical for modulating synaptic strength, maintaining proper neural circuitry, and establishing long term memory. Neuronal RNA granules are ribonucleoprotein particles that serve to transport mRNA along microtubules and control local protein synthesis in response to synaptic activity. Studies suggest that neuronal RNA granules share similar structures and functions with somatic P-bodies. We recently reported that the Huntington disease protein huntingtin (Htt) associates with Argonaute (Ago) and localizes to cytoplasmic P-bodies, which serve as sites of mRNA storage, degradation, and small RNA-mediated gene silencing. Here we report that wild-type Htt associates with Ago2 and components of neuronal granules and co-traffics with mRNA in dendrites. Htt was found to co-localize with RNA containing the 3′-untranslated region sequence of known dendritically targeted mRNAs. Knockdown of Htt in neurons caused altered localization of mRNA. When tethered to a reporter construct, Htt down-regulated reporter gene expression in a manner dependent on Ago2, suggesting that Htt may function to repress translation of mRNAs during transport in neuronal granules. PMID:20185826

  17. Process optimization for continuous extrusion wet granulation.

    PubMed

    Tan, Li; Carella, Anthony J; Ren, Yukun; Lo, Julian B

    2011-08-01

    Three granulating binders in high drug-load acetaminophen blends were evaluated using high shear granulation and extrusion granulation. A polymethacrylate binder enhanced tablet tensile strength with rapid disintegration in simulated gastric fluid, whereas polyvinylpyrrolidone and hydroxypropyl cellulose binders produced less desirable tablets. Using the polymethacrylate binder, the extrusion granulation process was studied regarding the effects of granulating liquid, injection rate and screw speed on granule properties. A full factorial experimental design was conducted to allow the statistical analysis of interactions between extrusion process parameters. Response variables considered in the study included extruder power consumption (screw loading), granule bulk/tapped density, particle size distribution, tablet hardness, friability, disintegration time and dissolution. PMID:20367553

  18. Drying and recovery of aerobic granules.

    PubMed

    Hu, Jianjun; Zhang, Quanguo; Chen, Yu-You; Lee, Duu-Jong

    2016-10-01

    To dehydrate aerobic granules to bone-dry form was proposed as a promising option for long-term storage of aerobic granules. This study cultivated aerobic granules with high proteins/polysaccharide ratio and then dried these granules using seven protocols: drying at 37°C, 60°C, 4°C, under sunlight, in dark, in a flowing air stream or in concentrated acetone solutions. All dried granules experienced volume shrinkage of over 80% without major structural breakdown. After three recovery batches, although with loss of part of the volatile suspended solids, all dried granules were restored most of their original size and organic matter degradation capabilities. The strains that can survive over the drying and storage periods were also identified. Once the granules were dried, they can be stored over long period of time, with minimal impact yielded by the applied drying protocols. PMID:27392096

  19. Selective sorting of alpha-granule proteins

    PubMed Central

    Italiano, J.E.; Battinelli, E. M.

    2010-01-01

    Summary One of the main functions of blood platelets is to secrete a variety of substances that can modify a developing thrombus, regulate the growth of the vasculature, promote wound repair, and contribute to cell-adhesive events. The majority of this vast array of secreted proteins is stored in alpha-granules. Until recently, it was assumed that platelets contained one homogeneous population of alpha-granules that undergo complete de-granulation during platelet activation. This review focuses on the mechanisms of alpha-granule biogenesis and secretion, with a particular emphasis on recent findings that clearly demonstrate that platelets contain distinct subpopulations of alpha-granules that undergo differential release during activation. We consider the implications of this new paradigm of platelet secretion, discuss mechanisms of alpha-granule biogenesis, and review the molecular basis of transport and delivery of alpha-granules to assembling platelets. PMID:19630794

  20. Usp9x-deficiency disrupts the morphological development of the postnatal hippocampal dentate gyrus.

    PubMed

    Oishi, Sabrina; Premarathne, Susitha; Harvey, Tracey J; Iyer, Swati; Dixon, Chantelle; Alexander, Suzanne; Burne, Thomas H J; Wood, Stephen A; Piper, Michael

    2016-01-01

    Within the adult mammalian brain, neurogenesis persists within two main discrete locations, the subventricular zone lining the lateral ventricles, and the hippocampal dentate gyrus. Neurogenesis within the adult dentate gyrus contributes to learning and memory, and deficiencies in neurogenesis have been linked to cognitive decline. Neural stem cells within the adult dentate gyrus reside within the subgranular zone (SGZ), and proteins intrinsic to stem cells, and factors within the niche microenvironment, are critical determinants for development and maintenance of this structure. Our understanding of the repertoire of these factors, however, remains limited. The deubiquitylating enzyme USP9X has recently emerged as a mediator of neural stem cell identity. Furthermore, mice lacking Usp9x exhibit a striking reduction in the overall size of the adult dentate gyrus. Here we reveal that the development of the postnatal SGZ is abnormal in mice lacking Usp9x. Usp9x conditional knockout mice exhibit a smaller hippocampus and shortened dentate gyrus blades from as early as P7. Moreover, the analysis of cellular populations within the dentate gyrus revealed reduced stem cell, neuroblast and neuronal numbers and abnormal neuroblast morphology. Collectively, these findings highlight the critical role played by USP9X in the normal morphological development of the postnatal dentate gyrus. PMID:27181636

  1. Usp9x-deficiency disrupts the morphological development of the postnatal hippocampal dentate gyrus

    PubMed Central

    Oishi, Sabrina; Premarathne, Susitha; Harvey, Tracey J.; Iyer, Swati; Dixon, Chantelle; Alexander, Suzanne; Burne, Thomas H. J.; Wood, Stephen A.; Piper, Michael

    2016-01-01

    Within the adult mammalian brain, neurogenesis persists within two main discrete locations, the subventricular zone lining the lateral ventricles, and the hippocampal dentate gyrus. Neurogenesis within the adult dentate gyrus contributes to learning and memory, and deficiencies in neurogenesis have been linked to cognitive decline. Neural stem cells within the adult dentate gyrus reside within the subgranular zone (SGZ), and proteins intrinsic to stem cells, and factors within the niche microenvironment, are critical determinants for development and maintenance of this structure. Our understanding of the repertoire of these factors, however, remains limited. The deubiquitylating enzyme USP9X has recently emerged as a mediator of neural stem cell identity. Furthermore, mice lacking Usp9x exhibit a striking reduction in the overall size of the adult dentate gyrus. Here we reveal that the development of the postnatal SGZ is abnormal in mice lacking Usp9x. Usp9x conditional knockout mice exhibit a smaller hippocampus and shortened dentate gyrus blades from as early as P7. Moreover, the analysis of cellular populations within the dentate gyrus revealed reduced stem cell, neuroblast and neuronal numbers and abnormal neuroblast morphology. Collectively, these findings highlight the critical role played by USP9X in the normal morphological development of the postnatal dentate gyrus. PMID:27181636

  2. [Hemocompatibility of various synthetic granulates].

    PubMed

    Jung, F; Mrowietz, C; Seyfert, U T; Franke, R P

    1997-06-01

    The adherence of platelets to different polymer granulates was examined in a perfusion chamber filled with platelet-rich plasma. The surface area of each of the granulates was of a standardised size. The results were compared with those found for a non-thrombogenic and a highly thrombogenic foreign-body surface. The three polymers examined-Cryolite, Styrolux and Zylar-must be considered non-thrombogenic. Platelet adherence to these substances is significantly less (3%) than that to a highly thrombogenic surface such as glass (95%). The three materials did not differ in terms of platelet adherence, and would appear to be suitable potential materials for use in cell separators. PMID:9312306

  3. Iron granules in plasma cells.

    PubMed Central

    Cook, M K; Madden, M

    1982-01-01

    The curious and unusual finding of coarse iron granules in marrow plasma cells is reported in 13 patients, in whom the finding was incidental. In 10 of these patients there was known alcohol abuse and serious medical complications of that abuse. Previous reports of the finding are reviewed. Haematological data of the 13 patients are presented. A hypothesis is outlined which may account for the finding. Images PMID:7068907

  4. A proposed aerobic granules size development scheme for aerobic granulation process.

    PubMed

    Dahalan, Farrah Aini; Abdullah, Norhayati; Yuzir, Ali; Olsson, Gustaf; Salmiati; Hamdzah, Myzairah; Din, Mohd Fadhil Mohd; Ahmad, Siti Aqlima; Khalil, Khalilah Abdul; Anuar, Aznah Nor; Noor, Zainura Zainon; Ujang, Zaini

    2015-04-01

    Aerobic granulation is increasingly used in wastewater treatment due to its unique physical properties and microbial functionalities. Granule size defines the physical properties of granules based on biomass accumulation. This study aims to determine the profile of size development under two physicochemical conditions. Two identical bioreactors namely Rnp and Rp were operated under non-phototrophic and phototrophic conditions, respectively. An illustrative scheme was developed to comprehend the mechanism of size development that delineates the granular size throughout the granulation. Observations on granules' size variation have shown that activated sludge revolutionised into the form of aerobic granules through the increase of biomass concentration in bioreactors which also determined the changes of granule size. Both reactors demonstrated that size transformed in a similar trend when tested with and without illumination. Thus, different types of aerobic granules may increase in size in the same way as recommended in the aerobic granule size development scheme. PMID:25661308

  5. The OM series of terminal field-specific monoclonal antibodies demonstrate reinnervation of the adult rat dentate gyrus by embryonic entorhinal transplants.

    PubMed

    Woodhams, P L; Kawano, H; Raisman, G

    1992-01-01

    Monoclonal antibodies OM-1 to OM-4 and IM-1 [Woodhams et al. (1991) Neuroscience 46, 57-69] have complementary immunostaining patterns in the molecular (dendritic) layer of the adult rat dentate gyrus, with OM-1 to OM-4 selectively recognizing the outer (distal) two-thirds (i.e. the entorhinal afferent zone), and IM-1 the inner (proximal) one-third (i.e. the hippocampal commissural/associational zone). Immunoblotting suggests that OM-1 recognizes a single glycoprotein antigen of mol. wt around 93,000, and OM-2, OM-3, and OM-4 all recognize a second glycoprotein antigen of mol. wt around 36,000. At four weeks after removal of the ipsilateral entorhinal cortex the background OM immunostaining of the entorhinal afferent zone is abolished and replaced by a network of densely stained granules, which we interpret as degenerating entorhinal afferent axons. At the same time, the proximal, IM immunoreactive zone expands by about 10 microns in width (while the distal deafferented zone shrinks by about 80 microns). Attempts were made to restore the OM immunoreactivity of the distal zone by grafting either small pieces or cell suspensions of embryonic day 18 entorhinal cortex directly into the dentate molecular layer of entorhinally deafferented adult hosts. About half (14/26) of the animals with successfully positioned grafts showed restoration of OM-2 to OM-4 immunostaining throughout the entire width of the outer two-thirds (entorhinal afferent zone) of the dentate molecular layer. Strikingly, however, in adjacent serial sections the restoration of OM-1 immunoreactivity was restricted to the "middle" molecular layer, i.e. the most proximal part of the distal (entorhinal) two-thirds of the dentate molecular layer. In no case did the OM-1 immunoreactivity extend to the outer margin of the molecular layer. This did not appear to be associated with incompleteness of the removal of the host entorhinal projection, since it occurred in grafted cases where the hippocampus had been

  6. Developmental hypothyroidism abolishes bilateral differences in sonic hedgehog gene control in the rat hippocampal dentate gyrus.

    PubMed

    Tanaka, Takeshi; Wang, Liyun; Kimura, Masayuki; Abe, Hajime; Mizukami, Sayaka; Yoshida, Toshinori; Shibutani, Makoto

    2015-03-01

    Both developmental and adult-stage hypothyroidism disrupt rat hippocampal neurogenesis. We previously showed that exposing mouse offspring to manganese permanently disrupts hippocampal neurogenesis and abolishes the asymmetric distribution of cells expressing Mid1, a molecule regulated by sonic hedgehog (Shh) signaling. The present study examined the involvement of Shh signaling on the disruption of hippocampal neurogenesis in rats with hypothyroidism. Pregnant rats were treated with methimazole (MMI) at 0 or 200 ppm in the drinking water from gestation day 10-21 days after delivery (developmental hypothyroidism). Adult male rats were treated with MMI in the same manner from postnatal day (PND) 46 to PND 77 (adult-stage hypothyroidism). Developmental hypothyroidism reduced the number of Mid1(+) cells within the subgranular zone of the dentate gyrus of offspring on PND 21, and consequently abolished the normal asymmetric predominance of Mid1(+) cells on the right side through the adult stage. In control animals, Shh was expressed in a subpopulation of hilar neurons, showing asymmetric distribution with left side predominance on PND 21; however, this asymmetry did not continue through the adult stage. Developmental hypothyroidism increased Shh(+) neurons bilaterally and abolished the asymmetric distribution pattern on PND 21. Adult hypothyroidism also disrupted the asymmetric distribution of Mid1(+) cells but did not affect the distribution of Shh(+) hilar neurons. The results suggest that the hippocampal neurogenesis disruption seen in hypothyroidism involves changes in asymmetric Shh(+) neuron distribution in developmental hypothyroidism and altered Mid1 expression in both developmental and adult-stage hypothyroidism. PMID:25539664

  7. Changes in protein synthesis accompanying long-term potentiation in the dentate gyrus in vivo.

    PubMed

    Fazeli, M S; Corbet, J; Dunn, M J; Dolphin, A C; Bliss, T V

    1993-04-01

    The possibility that the induction of long-term potentiation (LTP) is followed by changes in protein synthesis has been examined using high-resolution two-dimensional gel electrophoresis. 35S-methionine, infused into the third ventricle of anesthetized rats, was used to label hippocampal proteins. LTP was induced unilaterally in the dentate gyrus by tetanic stimulation of the perforant path, and followed either for 1 hr or for 3 hr. Two-dimensional gel autoradiographs were quantitatively analyzed using the PDQUEST system (Protein Databases Inc.). One hour after the unilateral induction of LTP, only one protein spot was found to be statistically different in intensity from corresponding spots in the contralateral control side. Three hours after LTP, however, 11 spots were found to have altered densities. Examination of basic proteins using the nonequilibrium pH gel electrophoresis system revealed changes in three proteins in the 3 hr group. Reductions as well as increases in spot intensities were observed. The results indicate that LTP is associated with a complex pattern of changes in protein synthesis. PMID:8463823

  8. Protein mobility within secretory granules.

    PubMed

    Weiss, Annita Ngatchou; Bittner, Mary A; Holz, Ronald W; Axelrod, Daniel

    2014-07-01

    We investigated the basis for previous observations that fluorescent-labeled neuropeptide Y (NPY) is usually released within 200 ms after fusion, whereas labeled tissue plasminogen activator (tPA) is often discharged over many seconds. We found that tPA and NPY are endogenously expressed in small and different subpopulations of bovine chromaffin cells in culture. We measured the mobility of these proteins (tagged with fluorophore) within the lumen of individual secretory granules in living chromaffin cells, and related their mobilities to postfusion release kinetics. A method was developed that is not limited by standard optical resolution, in which a bright flash of strongly decaying evanescent field (∼64 nm exponential decay constant) produced by total internal reflection (TIR) selectively bleaches cerulean-labeled protein proximal to the glass coverslip within individual granules. Fluorescence recovery occurred as unbleached protein from distal regions within the 300 nm granule diffused into the bleached proximal regions. The fractional bleaching of tPA-cerulean (tPA-cer) was greater when subsequently probed with TIR excitation than with epifluorescence, indicating that tPA-cer mobility was low. The almost equal NPY-cer bleaching when probed with TIR and epifluorescence indicated that NPY-cer equilibrated within the 300 ms bleach pulse, and therefore had a greater mobility than tPA-cer. TIR-fluorescence recovery after photobleaching revealed a significant recovery of tPA-cer (but not NPY-cer) fluorescence within several hundred milliseconds after bleaching. Numerical simulations, which take into account bleach duration, granule diameter, and the limited number of fluorophores in a granule, are consistent with tPA-cer being 100% mobile, with a diffusion coefficient of 2 × 10(-10) cm(2)/s (∼1/3000 of that for a protein of similar size in aqueous solution). However, the low diffusive mobility of tPA cannot alone explain its slow postfusion release. In the

  9. Internalized Tau sensitizes cells to stress by promoting formation and stability of stress granules

    PubMed Central

    Brunello, Cecilia A.; Yan, Xu; Huttunen, Henri J.

    2016-01-01

    Stress granules are membrane-less RNA- and RNA-binding protein-containing complexes that are transiently assembled in stressful conditions to promote cell survival. Several stress granule-associated RNA-binding proteins have been associated with neurodegenerative diseases. In addition, a close link was recently identified between the stress granule core-nucleating protein TIA-1 and Tau. Tau is a central pathological protein in Alzheimer’s disease and other tauopathies, and misfolded, aggregated Tau is capable of propagating pathology via cell-to-cell transmission. Here we show that following internalization hyperphosphorylated extracellular Tau associates with stress granules in a TIA-1 dependent manner. Cytosolic Tau normally only weakly interacts with TIA-1 but mutations mimicking abnormal phosphorylation promote this interaction. We show that internalized Tau significantly delays normal clearance of stress granules in the recipient cells sensitizing them to secondary stress. These results suggest that secreted Tau species may have properties, likely related to its hyperphosphorylation and oligomerization, which promote pathological association of internalized Tau with stress granules altering their dynamics and reducing cell viability. We suggest that stress granules and TIA-1 play a central role in the cell-to-cell transmission of Tau pathology. PMID:27460788

  10. GluN2A-/- Mice Lack Bidirectional Synaptic Plasticity in the Dentate Gyrus and Perform Poorly on Spatial Pattern Separation Tasks.

    PubMed

    Kannangara, Timal S; Eadie, Brennan D; Bostrom, Crystal A; Morch, Kristin; Brocardo, Patricia S; Christie, Brian R

    2015-08-01

    The different secondary subunits of the N-methyl-d-aspartate (NMDA) receptor each convey unique biophysical properties to the receptor complex, and may be key in determining the functional role played by NMDA receptors. In the hippocampus, the GluN2A and GluN2B subunits are particularly abundant; however, their exact roles in synaptic plasticity and behavior remain controversial. Here, we show that mice carrying a deletion for the GluN2A subunit (GluN2A(-/-)) demonstrate a severely compromised NMDA to AMPA receptor current ratio in granule cells from the dentate gyrus (DG), while granule cell morphology is unaltered. This deficit is accompanied by significant impairments in both LTP and LTD in the DG, whereas only minor impairments are observed in the CA1. In accordance with these hippocampal region-specific deficits, GluN2A(-/-) mice show impaired performance on the DG-associated task of spatial pattern separation. In contrast, GluN2A(-/-) mice show no deficit in temporal pattern separation, a process associated with CA1 functioning. Thus, our results establish the GluN2A subunit as a significant contributor to both bidirectional synaptic plasticity and spatial pattern separation in the DG. PMID:24554729

  11. Balloon-borne imagery of the solar granulation. II - The lifetime of solar granulation

    NASA Technical Reports Server (NTRS)

    Mehltretter, J. P.

    1978-01-01

    Phenomenological aspects of the temporal evolution of photospheric granulation are reported as derived from time series of granulation photographs obtained during a flight of a balloon-borne telescope. The distribution of granule lifetime probabilities is determined, and it is found that the data can be represented by an exponential decrease with a 'decay constant' of 5.9 min. The general properties of granular evolution are described along with the way individual granules evolve with time. The most common type of granule is shown to be a medium-sized or small fragment, and it is suggested that all granules are produced by fragmentation of preexisting granules. The relative frequencies of granule destruction by fragmentation, fading, and merging are determined to be 51%, 21%, and 28%, respectively. An average radial velocity of 0.8 km/s is computed for conglomerates with an average diameter of 2.25 arcsec.

  12. Calcium spatial distribution in aerobic granules and its effects on granule structure, strength and bioactivity.

    PubMed

    Ren, Ting-Ting; Liu, Li; Sheng, Guo-Ping; Liu, Xian-Wei; Yu, Han-Qing; Zhang, Ming-Chuan; Zhu, Jian-Rong

    2008-07-01

    Calcium-rich aerobic granules were cultivated after 3-month operation. The chemical form and spatial distribution of calcium in the granules and their physicochemical characteristics were explored. Examination with a scanning electron microscope combined energy dispersive X-ray detector (SEM-EDX) shows that Ca was mainly accumulated in the core of the granules. CaCO(3) was found to be the main calcium precipitate in the granules. The fluorescent in situ hybridization (FISH) analysis shows that the cells were crowded in the outer layer and gathered in clusters. Compared with the granules without Ca accumulation, the Ca-rich granules had more rigid structure and a higher strength. However, their specific oxygen uptake rate (SOUR) reduced after the Ca accumulation inside them. Comparison between the SOUR values of the granules with and without Ca accumulation suggests that Ca accumulated in the aerobic granules might have a negative effect on their bioactivity. PMID:18514253

  13. Carbon granule probe microphone for leak detection

    NASA Astrophysics Data System (ADS)

    Parthasarathy, S. P.

    1985-02-01

    A microphone which is not subject to corrosion is provided by employing carbon granules to sense sound waves. The granules are packed into a ceramic tube and no diaphragm is used. A pair of electrodes is located in the tube adjacent the carbon granules and are coupled to a sensing circuit. Sound waves cause pressure changes on the carbon granules which results in a change in resistance in the electrical path between the electrodes. This change in resistance is detected by the sensing circuit. The microphone is suitable for use as a leak detection probe in recovery boilers, where it provides reliable operation without corrosion problems associated with conventional microphones.

  14. Objective assessment of mastication predominance in healthy dentate subjects and patients with unilateral posterior missing teeth.

    PubMed

    Yamasaki, Y; Kuwatsuru, R; Tsukiyama, Y; Oki, K; Koyano, K

    2016-08-01

    We aimed to investigate mastication predominance in healthy dentate individuals and patients with unilateral posterior missing teeth using objective and subjective methods. The sample comprised 50 healthy dentate individuals (healthy dentate group) and 30 patients with unilateral posterior missing teeth (partially edentulous group). Subjects were asked to freely chew three kinds of test foods (peanuts, beef jerky and chewing gum). Electromyographic activity of the bilateral masseter muscles was recorded. The chewing side (right side or left side) was judged by the level of root mean square electromyographic amplitude. Mastication predominance was then objectively assessed using the mastication predominant score and the mastication predominant index. Self-awareness of mastication predominance was evaluated using a modified visual analogue scale. Mastication predominance scores of the healthy dentate and partially edentulous groups for each test food were analysed. There was a significant difference in the distribution of the mastication predominant index between the two groups (P < 0·05). The mastication predominant score was weakly correlated with self-awareness of mastication predominance in the healthy dentate group, whereas strong correlation was observed in the partially edentulous group (P < 0·05). The results suggest that the individuals with missing unilateral posterior teeth exhibited greater mastication predominance and were more aware of mastication predominance than healthy dentate individuals. Our findings suggest that an objective evaluation of mastication predominance is more precise than a subjective method. PMID:27121170

  15. Twin screw wet granulation: Binder delivery.

    PubMed

    Saleh, Mohammed F; Dhenge, Ranjit M; Cartwright, James J; Hounslow, Michael J; Salman, Agba D

    2015-06-20

    The effects of three ways of binder delivery into the twin screw granulator (TSG) on the residence time, torque, properties of granules (size, shape, strength) and binder distribution were studied. The binder distribution was visualised through the transparent barrel using high speed imaging as well as quantified using offline technique. Furthermore, the effect of binder delivery and the change of screw configuration (conveying elements only and conveying elements with kneading elements) on the surface velocity of granules across the screw channel were investigated using particle image velocimetry (PIV). The binder was delivered in three ways; all solid binder incorporated with powder mixture, 50% of solid binder mixed with powder mixture and 50% mixed with water, all the solid binder dissolved in water. Incorporation of all solid binder with powder mixture resulted in the relatively longer residence time and higher torque, narrower granule size distribution, more spherical granules, weaker big-sized granules, stronger small-sized granules and better binder distribution compared to that in other two ways. The surface velocity of granules showed variation from one screw to another as a result of uneven liquid distribution as well as shown a reduction while introducing the kneading elements into the screw configuration. PMID:25869451

  16. Ceramic granule strength variability and compaction behavior

    SciTech Connect

    Glass, S.J.; Ewsuk, K.G.; Readey, M.J.

    1995-08-01

    Diametral compression strength distributions and the compaction behavior and of irregular shape 150--200 {mu}m ceramic granules and uniform-size 210 {mu}m glass spheres were measured to determine how granule strength variability relates to compaction behavior of granular assemblies. High variability in strength, represented by low Weibull modulus values (m<3) was observed for ceramic granules having a distribution of sizes and shapes, and for uniform-size glass spheres. Compaction pressure data were also analyzed using a Weibull distribution function, and the results were very similar to those obtained from the diametral compression strength tests for the same material. This similarity suggests that it may be possible to model granule compaction using a weakest link theory, whereby an assemblage of granules is viewed as the links of a chain, and failure of the weakest granule (i.e., the weakest link) leads to rearrangement and compaction. Additionally, with the use of Weibull statistics, it appears to be possible to infer the variability in strength of individual granules from a simple pressure compaction test, circumventing the tedious task of testing individual granules.

  17. Castration and training in a spatial task alter the number of immature neurons in the hippocampus of male mice

    PubMed Central

    Benice, Ted S.; Raber, Jacob

    2010-01-01

    New neurons are generated in the granule cell layer of the dentate gyrus (GCL) throughout adulthood. This process is modulated by many environmental and neurochemical factors. We previously observed that castrated mice, compared to sham-operated mice, perform poorly in the delayed matching to place water-maze task (DMTP). In this study we quantified the number of doublecortin expressing (DCX+) immature neurons and Ki-67 expressing (Ki-67+) proliferating progenitors in mice previously tested in a spatial DMTP task, a non-spatial DMTP, or that received equivalent amounts of handling only. Regardless of DMTP training experience castration reduced immature neuron number in the GCL but had no effect on proliferating progenitors. Compared to handling only, visible DMTP training reduced the immature neuron number but hidden DMTP training had no effect. Castration did not alter these environmental effects. Finally, performance on the spatial DMTP task did not correlate with immature neuron number. In addition, while the number of immature neurons was strongly reduced following cranial irradiation with 137Cs, this treatment did not affect spatial DMTP performance. Thus, in mice, castration disrupts spatial memory and reduces immature neuron number, but there is no strong link between these effects. PMID:20233585

  18. Continuous twin screw granulation: influence of process variables on granule and tablet quality.

    PubMed

    Vercruysse, J; Córdoba Díaz, D; Peeters, E; Fonteyne, M; Delaet, U; Van Assche, I; De Beer, T; Remon, J P; Vervaet, C

    2012-09-01

    The aim of the current study was to screen theophylline (125 mg) tablets manufactured via twin screw granulation in order to improve process understanding and knowledge of process variables that determine granule and tablet quality. A premix of theophylline anhydrate, α-lactose monohydrate and PVP (ratio: 30/67.5/2.5,w/w) was granulated with demineralized water. Experiments were done using the high-shear wet granulation module (based on twin screw granulation) of the ConsiGma™-25 unit (a continuous tablet manufacturing system) for particle size enlargement. After drying, granules were compressed using a MODUL™ P tablet press (compression force: 10 kN, tablet diameter: 12 mm). Using a D-optimal experimental design, the effect of several process variables (throughput (10-25 kg/h), screw speed (600-950 rpm), screw configuration (number (2, 4, 6 and 12) and angle (30°, 60° and 90°) of kneading elements), barrel temperature (25-40°C) and method of binder addition (dry versus wet)) on the granulation process (torque and temperature increase in barrel wall), granule (particle size distribution, friability and flowability) and tablet (tensile strength, porosity, friability, disintegration time and dissolution) quality was evaluated. The results showed that the quality of granules and tablets can be optimized by adjusting specific process variables (number of kneading elements, barrel temperature and binder addition method) during a granulation process using a continuous twin screw granulator. PMID:22687571

  19. Mast cell secretory granules: armed for battle.

    PubMed

    Wernersson, Sara; Pejler, Gunnar

    2014-07-01

    Mast cells are important effector cells of the immune system and recent studies show that they have immunomodulatory roles in diverse processes in both health and disease. Mast cells are distinguished by their high content of electron-dense secretory granules, which are filled with large amounts of preformed and pre-activated immunomodulatory compounds. When appropriately activated, mast cells undergo degranulation, a process by which these preformed granule compounds are rapidly released into the surroundings. In many cases, the effects that mast cells have on an immune response are closely associated with the biological actions of the granule compounds that they release, as exemplified by the recent studies showing that mast cell granule proteases account for many of the protective and detrimental effects of mast cells in various inflammatory settings. In this Review, we discuss the current knowledge of mast cell secretory granules. PMID:24903914

  20. Electrochemical performance of granulated titania nanoparticles

    NASA Astrophysics Data System (ADS)

    Wilhelm, O.; Pratsinis, S. E.; de Chambrier, E.; Crouzet, M.; Exnar, I.

    The electrochemical performance of Li-ion insertion into electrodes made of various sizes of anatase titania nanoparticles embedded in larger granulated entities (1-10 μm) is investigated. The granules are formed by spray drying of a suspension containing titania nanoparticles made by hydrolyzing titanium tetraisopropoxide (TTIP). Depending on the three process steps, i.e. hydrolysis-condensation, hydrothermal processing and spray drying, different properties for the electrode made from these granules can be achieved in terms of phase composition, specific surface area (SSA) and specific charge capacity. Hydrothermally processed (HP) particles are more resistant to calcination than sol-gel precipitated (SGP) ones and have a higher SSA which leads to a better performance with respect to specific charge capacity. Electrodes made from granulated nanoparticles have superior specific charge capacity than from non-granulated ones as the former have more inter-particle contacts.

  1. [Correlation of dry granulation process parameters and granule quality based on multiple regression analysis].

    PubMed

    Cao, Han-Han; Du, Ruo-Fei; Yang, Jia-Ning; Feng, Yi

    2014-03-01

    In this paper, microcrystalline cellulose WJ101 was used as a model material to investigate the effect of various process parameters on granule yield and friability after dry granulation with a single factor and the effect of comprehensive inspection process parameters on the effect of granule yield and friability, then the correlation between process parameters and granule quality was established. The regress equation was established between process parameters and granule yield and friability by multiple regression analysis, the affecting the order of the size of the order of the process parameters on granule yield and friability was: rollers speed > rollers pressure > speed of horizontal feed. Granule yield was positively correlated with pressure and speed of horizontal feed and negatively correlated rollers speed, while friability was on the contrary. By comparison, fitted value and real value, fitted and real value are basically the same of no significant differences (P > 0.05) and with high precision and reliability. PMID:24961115

  2. Activation of the dentate nucleus in a verb generation task: A 7T MRI study.

    PubMed

    Thürling, M; Küper, M; Stefanescu, R; Maderwald, S; Gizewski, E R; Ladd, M E; Timmann, D

    2011-08-01

    There is increasing evidence of a topographic organization within the human cerebellar cortex for motor and non-motor functions. Likewise, a subdivision of the dentate nucleus in a more dorsal and rostral motor domain and a more ventral and caudal non-motor domain has been proposed by Dum and Strick (2003) based on anatomical studies in monkey. In humans, however, very little is known about topographic organization within the dentate nucleus. Activation of the dentate nucleus in a verb generation task was examined in young and healthy subjects using ultra-highfield 7T functional magnetic resonance imaging (fMRI) with its increase in signal-to-noise ratio. Data of 17 subjects were included in statistical analysis. Subjects were asked to (i) read words (nouns) aloud presented on a screen, (ii) silently read the same nouns, (iii) silently generate the appropriate verbs to the same nouns and (iv) to silently repeat the names of the months. A block design was used. For image processing, a recently developed region of interest (ROI) driven normalization method of the dentate nuclei was applied. Activation related to motor speech (contrast aloud reading minus silent reading) was strongest in the rostral parts of the dentate nucleus. Dorsorostral activations were present bilaterally. Activation related to verb generation (contrast verb generation minus silent reading) was found in the ventrocaudal parts of the dentate nucleus on the right. The present findings are in good accordance with the anatomical data in monkeys and suggest that the human dentate nucleus can be subdivided into a rostral and more dorsal motor domain and a ventrocaudal non-motor domain. PMID:21640191

  3. Influence of metronidazole particle properties on granules prepared in a high-shear mixer-granulator.

    PubMed

    Di Martino, Piera; Censi, Roberta; Malaj, Ledjan; Martelli, Sante; Joiris, Etienne; Barthélémy, Christine

    2007-02-01

    Metronidazole is a good example of high-dose drug substance with poor granulating and tableting properties. Tablets are generally produced by liquid granulation; however, the technological process failure is quite frequent. In order to verify how the metronidazole particle characteristics can influence granule properties, three metronidazole batches differing for crystal habit, mean particle size, BET surface area and wettability were selected, primarily designed according to their different elongation ratio: needle-shaped, stick-shaped, and isodimensional. In the presence of lactose monohydrate and pregelatinized maize starch, respectively as diluent and binder, they were included in a formula for wet granulation in a high-shear mixer-granulator. In order to render the process comparable as far as possible, all parameters and experimental conditions were maintained constant. Four granule batches were obtained: granules from placebo (G-placebo), granules from needle-shaped crystals (G-needle-shaped), granules from stick-shaped crystals (G-stick-shaped), and granules from isodimensional crystals (G-isodimensional). Different granule properties were considered, in particular concerning porosity, friability, loss on drying (LOD), and flowability. In order to study their tabletability and compressibility, the different granules obtained were then compressed in a rotary press. The best tabletability was obtained with the isodimensional batch, while the poorest was exhibited by the stick-shaped one. Differences in tabletability are in good accordance with compressibility results: to a better tabletability corresponds an important granule ability to undergo a volume reduction as a result of an applied pressure. In particular, it was proposed that the greatest compressibility of the G-isodimensional must be related to the greatest granule porosity percentage. PMID:17454043

  4. l-DOPA reverses the impairment of Dentate Gyrus LTD in experimental parkinsonism via β-adrenergic receptors.

    PubMed

    Pendolino, Valentina; Bagetta, Vincenza; Ghiglieri, Veronica; Sgobio, Carmelo; Morelli, Emanuela; Poggini, Silvia; Branchi, Igor; Latagliata, Emanuele C; Pascucci, Tiziana; Puglisi-Allegra, Stefano; Calabresi, Paolo; Picconi, Barbara

    2014-11-01

    Parkinson's disease (PD) patients exhibit motor and non-motor symptoms that severely affect quality of life. Cognitive alterations in PD subjects have been related to both structural and functional hippocampal changes. Here we investigated the effects of the 6-hydroxydopamine (6-OHDA) lesion in the Medial Forebrain Bundle (MFB) on the hippocampus focusing on the Dentate Gyrus (DG). In vivo microdialysis measurements revealed that the 6-OHDA injection disrupts both dopaminergic and noradrenergic transmission in rat DG. In vitro electrophysiological recordings showed that these neurochemical alterations were accompanied by impairment of long-term depression (LTD) at medial perforant path/DG synapses. Furthermore, this alteration was reversed by l-DOPA treatment. Notably, the therapeutic effect of l-DOPA on LTD was blocked by the antagonism of β-noradrenergic receptors, but not by dopamine D1 or D2 receptor antagonists. Thus, while the dopaminergic transmission does not seem to be implicated in this therapeutic effect of l-DOPA, the noradrenergic system plays a central role in the synaptic dysfunction of the DG in experimental PD. Our work provides new evidence on the role of catecholamines in DG synaptic plasticity and sheds light on the possible synaptic mechanisms underlying cognitive deficits in PD. Furthermore, our results indicate that l-DOPA exerts a therapeutic effect on the parkinsonian brain through different, coexistent, mechanisms. PMID:25058044

  5. NEDDylation promotes stress granule assembly

    PubMed Central

    Jayabalan, Aravinth Kumar; Sanchez, Anthony; Park, Ra Young; Yoon, Sang Pil; Kang, Gum-Yong; Baek, Je-Hyun; Anderson, Paul; Kee, Younghoon; Ohn, Takbum

    2016-01-01

    Stress granules (SGs) harbour translationally stalled messenger ribonucleoproteins and play important roles in regulating gene expression and cell fate. Here we show that neddylation promotes SG assembly in response to arsenite-induced oxidative stress. Inhibition or depletion of key components of the neddylation machinery concomitantly inhibits stress-induced polysome disassembly and SG assembly. Affinity purification and subsequent mass-spectrometric analysis of Nedd8-conjugated proteins from translationally stalled ribosomal fractions identified ribosomal proteins, translation factors and RNA-binding proteins (RBPs), including SRSF3, a previously known SG regulator. We show that SRSF3 is selectively neddylated at Lys85 in response to arsenite. A non-neddylatable SRSF3 (K85R) mutant do not prevent arsenite-induced polysome disassembly, but fails to support the SG assembly, suggesting that the neddylation pathway plays an important role in SG assembly. PMID:27381497

  6. Pattern separation of emotional information in hippocampal dentate and CA3.

    PubMed

    Leal, Stephanie L; Tighe, Sarah K; Jones, Craig K; Yassa, Michael A

    2014-09-01

    Emotional arousal, mediated by the amygdala, is known to modulate episodic memories stored by the hippocampus, a region involved in pattern separation (the process by which similar representations are independently stored). While emotional modulation and pattern separation have been examined independently, this study attempts to link the two areas of research to propose an alternative account for how emotion modulates episodic memory. We used an emotional discrimination task designed to tax pattern separation of emotional information by concurrently varying emotional valence and similarity of stimuli. To examine emotional modulation of memory at the level of hippocampal subfields, we used high-resolution fMRI (1.5 mm isotropic) of the medial temporal lobe. Consistent with prior reports, we observed engagement of the hippocampal dentate gyrus (DG) and CA3 during accurate discrimination of highly similar items (behavioral correlate of pattern separation). Furthermore, we observed an emotional modulation of this signal (negative > neutral) specific to trials on which participants accurately discriminated similar emotional items. The amygdala was also modulated by emotion, regardless of the accuracy of discrimination. Additionally, we found aberrant amygdala-hippocampal network activity in a sample of adults with depressive symptoms. In this sample, amygdala activation was enhanced and DG/CA3 activation was diminished during emotional discrimination compared to those without depressive symptoms. Depressive symptom severity was also negatively correlated with DG/CA3 activity. This study suggests a novel mechanistic account for how emotional information is processed by hippocampal subfields as well as how this network may be altered in mood disorders. PMID:24796287

  7. Alpha-CaMKII deficiency causes immature dentate gyrus, a novel candidate endophenotype of psychiatric disorders

    PubMed Central

    Yamasaki, Nobuyuki; Maekawa, Motoko; Kobayashi, Katsunori; Kajii, Yasushi; Maeda, Jun; Soma, Miho; Takao, Keizo; Tanda, Koichi; Ohira, Koji; Toyama, Keiko; Kanzaki, Kouji; Fukunaga, Kohji; Sudo, Yusuke; Ichinose, Hiroshi; Ikeda, Masashi; Iwata, Nakao; Ozaki, Norio; Suzuki, Hidenori; Higuchi, Makoto; Suhara, Tetsuya; Yuasa, Shigeki; Miyakawa, Tsuyoshi

    2008-01-01

    Elucidating the neural and genetic factors underlying psychiatric illness is hampered by current methods of clinical diagnosis. The identification and investigation of clinical endophenotypes may be one solution, but represents a considerable challenge in human subjects. Here we report that mice heterozygous for a null mutation of the alpha-isoform of calcium/calmodulin-dependent protein kinase II (alpha-CaMKII+/-) have profoundly dysregulated behaviours and impaired neuronal development in the dentate gyrus (DG). The behavioral abnormalities include a severe working memory deficit and an exaggerated infradian rhythm, which are similar to symptoms seen in schizophrenia, bipolar mood disorder and other psychiatric disorders. Transcriptome analysis of the hippocampus of these mutants revealed that the expression levels of more than 2000 genes were significantly changed. Strikingly, among the 20 most downregulated genes, 5 had highly selective expression in the DG. Whereas BrdU incorporated cells in the mutant mouse DG was increased by more than 50 percent, the number of mature neurons in the DG was dramatically decreased. Morphological and physiological features of the DG neurons in the mutants were strikingly similar to those of immature DG neurons in normal rodents. Moreover, c-Fos expression in the DG after electric footshock was almost completely and selectively abolished in the mutants. Statistical clustering of human post-mortem brains using 10 genes differentially-expressed in the mutant mice were used to classify individuals into two clusters, one of which contained 16 of 18 schizophrenic patients. Nearly half of the differentially-expressed probes in the schizophrenia-enriched cluster encoded genes that are involved in neurogenesis or in neuronal migration/maturation, including calbindin, a marker for mature DG neurons. Based on these results, we propose that an "immature DG" in adulthood might induce alterations in behavior and serve as a promising

  8. Involvement of over-expressed BMP4 in pentylenetetrazol kindling-induced cell proliferation in the dentate gyrus of adult rats

    SciTech Connect

    Yin Jinbo; Ma Yuxin; Yin Qing; Xu Haiwei . E-mail: haiweixu2001@yahoo.com.cn; An Ning; Liu Shiyong; Fan Xiaotang; Yang Hui . E-mail: huiyang64@yahoo.com

    2007-03-30

    The dentate gyrus (DG) of the hippocampus is one of a few regions in the adult mammalian brain characterized by ongoing neurogenesis. Proliferation of neural precursors in the granule cell layer of the DG has been identified in pentylenetetrazol (PTZ) kindling epilepsy model, however, little is known about the molecular mechanism. We previously reported that the expression pattern of bone morphogenetic proteins-4 (BMP4) mRNA in the hippocampus was developmentally regulated and mainly localized in the DG of the adult. To explore the role of BMP4 in epileptic activity, we detected BMP4 expression in the DG during PTZ kindling process and explore its correlation with cell proliferation combined with bromodeoxyuridine (BrdU) labeling technique. We found that dynamic changes in BMP4 level and BrdU labeled cells dependent on the kindling stage of PTZ induced seizure-prone state. The number of BMP4 mRNA-positive cells and BrdU labeled cells reached the top level 1 day after PTZ kindled, then declined to base level 2 months later. Furthermore, there was a significant correlation between increased BMP4 mRNA expression and increased number of BrdU labeled cells. After effectively blocked expression of BMP4 with antisense oligodeoxynucleotides(ASODN), the BrdU labeled cells in the dentate gyrus subgranular zone(DG-SGZ) and hilus were significantly decreased 16d after First PTZ injection and 1, 3, 7, 14d after kindled respectively. These findings suggest that increased proliferation in the DG of the hippocampus resulted from kindling epilepsy elicited by PTZ maybe be modulated by BMP4 over-expression.

  9. Early postnatal respiratory viral infection alters hippocampal neurogenesis, cell fate, and neuron morphology in the neonatal piglet.

    PubMed

    Conrad, Matthew S; Harasim, Samantha; Rhodes, Justin S; Van Alstine, William G; Johnson, Rodney W

    2015-02-01

    Respiratory viral infections are common during the neonatal period in humans, but little is known about how early-life infection impacts brain development. The current study used a neonatal piglet model as piglets have a gyrencephalic brain with growth and development similar to human infants. Piglets were inoculated with porcine reproductive and respiratory syndrome virus (PRRSV) to evaluate how chronic neuroinflammation affects hippocampal neurogenesis and neuron morphology. Piglets in the neurogenesis study received one bromodeoxyuridine injection on postnatal day (PD) 7 and then were inoculated with PRRSV. Piglets were sacrificed at PD 28 and the number of BrdU+ cells and cell fate were quantified in the dentate gyrus. PRRSV piglets showed a 24% reduction in the number of newly divided cells forming neurons. Approximately 15% of newly divided cells formed microglia, but this was not affected by sex or PRRSV. Additionally, there was a sexual dimorphism of new cell survival in the dentate gyrus where males had more cells than females, and PRRSV infection caused a decreased survival in males only. Golgi impregnation was used to characterize dentate granule cell morphology. Sholl analysis revealed that PRRSV caused a change in inner granule cell morphology where the first branch point was extended further from the cell body. Males had more complex dendritic arbors than females in the outer granule cell layer, but this was not affected by PRRSV. There were no changes to dendritic spine density or morphology distribution. These findings suggest that early-life viral infection can impact brain development. PMID:25176574

  10. Microinjection of histamine into the dentate gyrus produces antinociception in the formalin test in rats.

    PubMed

    Khalilzadeh, Emad; Tamaddonfard, Esmaeal; Farshid, Amir Abbas; Erfanparast, Amir

    2010-12-01

    The present study was aimed to investigate the effects of microinjection of histamine, chlorpheniramine (a histamine H(1) receptor antagonist), ranitidine (a histamine H(2) receptor antagonist) and thioperamide (a histamine H(3) receptor antagonist) into the dentate gyrus on the formalin-induced pain. A biphasic pattern (first phase: 0-5min and second phase: 15-60min) in nociceptive responses was induced after subcutaneous injection of formalin (50μl, 2.5%) into the ventral surface of the right hind paw. Microinjection of histamine (1 and 2μg) into the dentate gyrus decreased the intensity of nociceptive responses. Intra-dentate gyrus microinjection of chlorpheniramine and ranitidine at the same doses of 1 and 4μg had no effects, whereas thioperamide at a dose of 4μg suppressed both phases of formalin-induced pain. Pretreatments with chlorpheniramine and ranitidine at the same dose of 4μg prevented histamine (2μg)-induced antinociception, while thioperamide (4μg) increased histamine (2μg)-induced antinociception. These results indicated that activation of brain neuronal histamine at the levels of dentate gyrus produced antinociception. The post-synaptic H(1), H(2) receptors and pre-synaptic H(3) receptors of histamine may be involved in the histamine-induced antinociception at the level of the dentate gyrus. PMID:20826178