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Proechimys (Rodentia: Echimyidae) is a neotropical rodent of the Amazon region that has been successfully colonized in the laboratory and used for experimental medicine. Preliminary studies indicated that Proechimys (casiragua) ro...
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Proechimys (Rodentia: Echimyidae) is a neotropical rodent of the Amazon region that has been successfully colonized in the laboratory and used for experimental medicine. Preliminary studies indicated that Proechimys (casiragua) rodents express an atypical resistance to developing a chronic epileptic condition in common models of temporal lobe epilepsy. Moreover, previous investigation of our laboratory described a remarkably different Proechimy's cytoarchitecture organization of the hippocampa! CA2 subfield. In the present study, we investigated the intrinsic neuronal properties and morphological characteristics of the Proechimys's hippocam-pal pyramidal neurons of the CA1 and CA2 areas. A comparative approach was performed using neurons recorded in Wistar rats. A striking finding in Proechimys rodents was the presence of iarge pyramidal-like neurons throughout the stratum oriens from CA2 to CA1 area. In order to confirm such distinctive feature of the Proechimys's hippocampus, we performed Nissl staining and immunohistochemistry for neurofilament protein SM311. CA2 pyramidal neurons in the stratum pyramidale of Proechimys exhibited a significantly higher input resistance and lower time constant when compared to corresponding cell groups in the same area of the Wistar rat's. This newly identified population of pyramidal-shaped neurons in stratum oriens of Proechimys exhibited distinct electrophysiological and morphological properties. This included larger capacitance, lower input resistance, larger rheobase, long latency to first action potential and slower firing frequency. In addition, the apical dendrites of these neurons were oriented in parallel to apical dendrites of regular pyramidal neurons in stratum pyramidale. Moreover, these neurons were immunoreactive to SM311 as the majority of the neurons of the pyramidal layer. The functional role of these hippocampal neurons of the rodent Proechimys deserves further investigation.
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Acetylcholine is considered to be an endogenous modulator of hippocampal neurotransmission and synaptic plasticity. The activation of muscarinic acetylcholine receptors (mAChRs) reportedly enhances hippocampal synaptic plasticity,...
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Acetylcholine is considered to be an endogenous modulator of hippocampal neurotransmission and synaptic plasticity. The activation of muscarinic acetylcholine receptors (mAChRs) reportedly enhances hippocampal synaptic plasticity, which plays an important role in memory function; however, the mechanism by which it enhances synaptic plasticity remains unclear. Here, we examined the involvement of the inhibition of Kv7/M K + channels, which are targets of mAChR modulation, during mAChR activation-induced enhancement of long-term potentiation (LTP) at rat hippocampal Schaffer collateral (SC)-CA1 synapses. When an electrical stimulus was applied to the stratum oriens before tetanic stimulation of the SCs, the magnitude of the induced SC-CA1 synapse LTP was enhanced as compared with that induced without stratum oriens stimulation. In the presence of the mAChR antagonist atropine, tetanic stimulation induced stable LTP, but the stratum oriens stimulation-evoked enhancement of LTP was abolished. The additional application of XE991, a selective blocker of Kv7/M K + channels, rescued the atropine-induced inhibition of LTP enhancement. The phospholipase C (PLC) inhibitor U-73122 inhibited the stratum oriens stimulation-evoked enhancement of LTP. Application of the T/R-type voltage-dependent Ca 2+channel (VDCC) blocker Ni 2+abolished the stratum oriens stimulation-evoked enhancement of LTP. In addition, tetanic stimulation with preceding stratum oriens stimulation was able to induce LTP during N-methyl-d-aspartate receptor blockade. We therefore propose that stratum oriens stimulation inhibits Kv7/M K + channels through mAChR activation-induced PLC activation, which leads to VDCC activation, and hence causes sufficient Ca 2+ influx to enhance LTP.
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Self‐assembly methods for colloidal crystals are widely developed by using the evaporative interface and capillary forces. Recently, a distinct phenomenon is discovered of macrospace partitioning by a po
Self‐assembly methods for colloidal crystals are widely developed by using the evaporative interface and capillary forces. Recently, a distinct phenomenon is discovered of macrospace partitioning by a polysaccharide membrane formed in a limited space by drying its aqueous liquid crystalline solution. Differing from typical fingering patterns, here, the viscous solution is in a nonequilibrium process between the polymer deposition and hydration during drying. By drying in limited space with a narrow gap, the nonequilibrium state causes accumulation of small depositions at several specific points and the deposited polymer bridging the substrates. Here, the split meniscus should make the area of the evaporative interface larger. To describe the correlation between the interfacial curve and the partitioning, the geometric effects of the evaporation front are discussed experimentally and numerically. By controlling the evaporation front three dimensionally, the necessary conditions for the vertical membrane formation are verified multilaterally. In future, this approach will help deposition control of not only the polysaccharides but also other biopolymers exhibiting microrod assembly.
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There is an expanding body of work characterizing dopaminergic modulation of synaptic plasticity in the hippocampus CA1 region, an area known to be involved in learning and memory. However, in vitro studies to date have focused al...
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There is an expanding body of work characterizing dopaminergic modulation of synaptic plasticity in the hippocampus CA1 region, an area known to be involved in learning and memory. However, in vitro studies to date have focused almost exclusively on the proximal and distal apical dendritic layers (strata radiatum and lacunosum moleculare, respectively). In this report, we establish that dopaminergic activity can enhance long-term potentiation (LTP) in the basal dendritic layer (stratum oriens) of CA1 in the rat hippocampal slice preparation. Application of the D_(1/5) agonist SKF38393 (20 μM) significantly increased the magnitude of basal LTP of the fEPSP response following high-frequency stimulation of the Schaffer collateral/commissural inputs in the stratum oriens layer. In addition, endogenous dopamine (DA) activity facilitated by the presence of cocaine (6 μM) was also capable of enhancing the magnitude of basal LTP. Prior application of the D_(1/5) antagonist SKF83566 (2 μM) prevented this effect of cocaine, indicating that endogenously released dopamine was exerting its LTP-enhancing effect in stratum oriens via activation of D_(1/5) receptors. This final result stands in contrast with the previously characterized effects of cocaine on apical LTP in the stratum radiatum, which instead have been shown to require D_3 receptor activation. These observations demonstrate that dopaminergic mechanisms resulting in the enhancement of hippocampal LTP are lamina specific at Schaffer collateral/commissural synapses in the CA1 region.
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The opportunity to compose this essay for the Eastern Association for the Surgery Trauma's Oriens Award has been the most terrific privilege of my training thus far. This award gave my passion a voice. It helped me better understa...
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The opportunity to compose this essay for the Eastern Association for the Surgery Trauma's Oriens Award has been the most terrific privilege of my training thus far. This award gave my passion a voice. It helped me better understand myself and my need to be a part of this world, this universe that selflessly dedicates every moment of themselves to the care of the critically ill and injured patient. I found every single past Oriens Essay and Keynote Address is a testament to the pure resilience, strength, and grit necessary to embody the calm and collected exterior of the internally screaming trauma surgeon. To me, this award, and all the previous essays, represents the genuine passion of this community and its continued support of each other. As I continue to process the honor of being selected for this prestigious award, I would like to thank my peers, mentors, and the entire trauma community for your perpetual inspiration and education. Your success and timeless dedication to the evolution of this field simply fascinates me. In preparing to join this society, it is my hope that some of these words may inspire, in an effort to reprise my mentors and truly thank you for selecting my essay for this year's award.
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Advent of foamed plastics, that allow materials to be reduced and also the mechanical proper ties to be maintained or even improved, would substantially extend the fields of applications as a resource saving material.In this paper...
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Advent of foamed plastics, that allow materials to be reduced and also the mechanical proper ties to be maintained or even improved, would substantially extend the fields of applications as a resource saving material.In this paper, on an assumption that the mechanical properties of foams are determined by the molecular orientations of cell walls associated with foaming, the study was made on how to enhance the strength of foams, which has revealed the following results.With very fine cell sizes, PS foams attain strengths that are higher than those estimated from the stress concentration and the foam magnification.This was assumed to be due to increase in the surface area of cell walls caused by foaming, as well as enhancement of molecular orientation of cell walls associated with foaming.
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Dravet syndrome (Dravet) is a rare, severe childhood-onset epilepsy, caused by heterozygous de novo mutations in the SCN1A gene, encoding for the alpha subunit of the voltage-gated sodium channel, NaV1.1. The neuronal basis of Dra...
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Dravet syndrome (Dravet) is a rare, severe childhood-onset epilepsy, caused by heterozygous de novo mutations in the SCN1A gene, encoding for the alpha subunit of the voltage-gated sodium channel, NaV1.1. The neuronal basis of Dravet is debated, with evidence favoring reduced function of inhibitory neurons, that might be transient, or enhanced activity of excitatory cells. Here, we utilized Dravet mice to trace developmental changes in the hippocampal CA1 circuit, examining the properties of CA1 horizontal stratum-oriens (SO) interneurons and pyramidal neurons, through the pre-epileptic, severe and stabilization stages of Dravet. Our data indicate that reduced function of SO interneurons persists from the pre-epileptic through the stabilization stages, with the greatest functional impairment observed during the severe stage. In contrast, opposing changes were detected in CA1 excitatory neurons, with a transient increase in their excitability during the pre-epileptic stage, followed by reduced excitability at the severe stage. Interestingly, alterations in the function of both inhibitory and excitatory neurons were more pronounced when the firing was evoked by synaptic stimulation, implying that loss of function of NaV1.1 may also affect somatodendritic functions. These results suggest a complex pathophysiological mechanism and indicate that the developmental trajectory of this disease is governed by reciprocal functional changes in both excitatory and inhibitory neurons.
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Functional studies indicate that the dopamine D5 receptor is involved in synaptic transmission in the hippocampus. However, previous anatomical studies have detected D5 receptor labelling primarily on the soma and main dendrites o...
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Functional studies indicate that the dopamine D5 receptor is involved in synaptic transmission in the hippocampus. However, previous anatomical studies have detected D5 receptor labelling primarily on the soma and main dendrites of CA1 pyramidal ceils and on dendritic spines in monkey but not in rats. In order to get a better understanding of putative dopamine function in the hippocampus, we quantified the D5 receptor immunoreactivity on the pyramidal cell somas and on spines and dendrites in stratum radiatum and stratum oriens in the hippocampal CA1 region of rats by quantitative immunofluorescence and immunogold electron microscopy. The quantitative immunogold results revealed a higher labelling density on dendritic spines, notably at their synaptic membranes, compared to pyramidal cell somas and dendrites. Hence, dopamine could have effects on spines as well as on somas and dendrites. The labelling density was similar on spines in stratum oriens and stratum radiatum, but the presence of labelling varied between the spines within each stratum, indicating that the effect of dopamine could be diverse between different spines.
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