| 1. |
- Hasselmo, Michael E., et al.
(författare)
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A phase code for memory could arise from circuit mechanisms in entorhinal cortex
- 2009
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Ingår i: Neural Networks. - : PERGAMON-ELSEVIER. - 0893-6080 .- 1879-2782. ; 22:8, s. 1129-1138
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Tidskriftsartikel (refereegranskat)abstract
- Neurophysiological data reveals intrinsic cellular properties that suggest how entorhinal cortical neurons could code memory by the phase of their firing. Potential cellular mechanisms for this phase coding in models of entorhinal function are reviewed. This mechanism for phase coding provides a substrate for modeling the responses of entorhinal grid cells, as well as the replay of neural spiking activity during waking and sleep. Efforts to implement these abstract models in more detailed biophysical compartmental simulations raise specific issues that could be addressed in larger scale population models incorporating mechanisms of inhibition.
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| 2. |
- Kamiie, Junichi, et al.
(författare)
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Amyloid-specific extraction using organic solvents
- 2020
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Ingår i: MethodsX. - : Elsevier BV. - 2215-0161. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Typing of amyloidosis by mass spectrometry (MS) based proteomic analysis contribute to the diagnosis of amyloidosis. For MS analysis, laser microdissection (LMD) is used for amyloid specific sampling. This study aimed to establish a method for selectively extracting amyloids from formalin-fixed, paraffin-embedded (FFPE) specimens by organic solvent instead of LMD. The extracts using dimethyl sulfoxide (DMSO), dimethylformamide (DMF), methanol, trifluoroethanol (TFE) or hexafluoro-2-propanol from FFPE brain of alzheimer's disease mouse model generated protein bands on SDS-PAGE, and Aβ was identified in the extract of DMF using mass spectrometry. The extract using DMSO from the kidney of a AA amyloidosis patient produced a protein band in SDS-PAGE. This protein band was identified to be serum amyloid A (SAA) by Western blotting and mass spectrometry. Circular dichroism spectrometry revealed that the secondary structures of Aβ and transthyretin were converted to α-helices from β-sheets in TFE. Our results suggest that organic solvents can extract amyloids from FFPE specimens by converting their secondary structure. This method could eliminate the LMD step and simplified amyloid typing by MS analysis. • DMSO, DMF, methanol, TFE and HFIP can extract Aβ specifically from the FFPE brain of a Alzheimer’ disease mouse model. • DMSO can extract SAA specifically from a FFPE section of AA amyloidosis. • Secondary structures of Aβ and transthyretin converted from β-sheet to α-helix in TFE.
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| 3. |
- Petersson, Marcus E., 1983-, et al.
(författare)
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Low-frequency summation of synaptically activated transient receptor potential channel-mediated depolarizations
- 2011
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Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 34:4, s. 578-593
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Tidskriftsartikel (refereegranskat)abstract
- Neurons sum their input by spatial and temporal integration. Temporally, presynaptic firing rates are converted to dendritic membrane depolarizations by postsynaptic receptors and ion channels. In several regions of the brain, including higher association areas, the majority of firing rates are low. For rates below 20 Hz, the ionotropic receptors alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor and N-methyl-d-aspartate (NMDA) receptor will not produce effective temporal summation. We hypothesized that depolarization mediated by transient receptor potential (TRP) channels activated by metabotropic glutamate receptors would be more effective, owing to their slow kinetics. On the basis of voltage-clamp and current-clamp recordings from a rat slice preparation, we constructed a computational model of the TRP channel and its intracellular activation pathway, including the metabotropic glutamate receptor. We show that synaptic input frequencies down to 3-4 Hz and inputs consisting of as few as three to five pulses can be effectively summed. We further show that the time constant of integration increases with increasing stimulation frequency and duration. We suggest that the temporal summation characteristics of TRP channels may be important at distal dendritic arbors, where spatial summation is limited by the number of concurrently active synapses. It may be particularly important in regions characterized by low and irregular rates.
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| 4. |
- Yoshida, Motoharu, et al.
(författare)
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mGluR-dependent persistent firing in entorhinal cortex layer III neurons
- 2008
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Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 28:6, s. 1116-1126
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Tidskriftsartikel (refereegranskat)abstract
- Persistent firing is believed to be a crucial mechanism for memory function including working memory. Recent in vivo and in vitro findings suggest an involvement of metabotropic glutamate receptors (mGluRs) in persistent firing. Using whole-cell patch-recording techniques in a rat entorhinal cortex (EC) slice preparation, we tested whether EC layer III neurons display persistent firing due to mGluR activation, independently of cholinergic activation. Stimulation of the angular bundle drove persistent firing in 90% of the cells in the absence of a cholinergic agonist. The persistent firing was typically stable for > 4.5 min at which point persistent firing was terminated by the experimenter. The average frequency of the persistent firing was 2.1 Hz, ranging from 0.4 to 5.5 Hz. This persistent firing was observed even in the presence of atropine (2 mu M), suggesting that the persistent firing can occur independent of cholinergic activation. Furthermore, ionotropic glutamate and GABAergic synaptic blockers (2 mm kynurenic acid, 100 mu M picrotoxin and 1 mu M CGP55845) did not block the persistent firing. On the other hand, blockers of group I mGluRs (100 mu M LY367385 and 20 mu M MPEP) completely blocked or suppressed the persistent firing. An agonist of group I mGluRs (20 mu M DHPG) greatly enhanced the persistent firing induced by current injection. These results indicate that persistent firing can be driven through group I mGluRs in entorhinal layer III neurons, suggesting that glutamatergic synaptic input alone could enable postsynaptic neurons to hold input signals in the form of persistent firing.
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