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1.
Toxicol In Vitro ; 63: 104742, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31785328

RESUMO

An appropriate balance of excitatory and inhibitory synapse maintains the network stability of the central nervous system. Our recent work showed lead (Pb) exposure can inhibit synaptic transmission in cultured hippocampal neurons. However, it is not clear whether Pb exposure disrupt the balance of excitatory and inhibitory synaptic transmission. Here, primary cultured hippocampal neurons from Sprague-Dawley (SD) rats were exposed to Pb (0.2 µM, 1 µM, 5 µM, respectively) from Days in Vitro (DIV) 7 to DIV 12 for 5 days and the excitatory and inhibitory synaptic transmission was examined. Patch clamp recording results showed that distinct from exposures of 0.2 µM and 5 µM, 1 µM Pb exposure significantly increased the mIPSC frequency and decreased the mEPSC frequency, leading to a uniform inhibitory outcome. Further, the number of inhibitory presynaptic puncta was significantly increased after 1 µM Pb exposure, while the number of excitatory presynaptic terminals was decreased. In addition 1 µM Pb increased the glutamic acid decarboxylase (GAD65) expression and the surface GABAA receptor (GABAAR) clusters. This shift might potentiate the synthesis of GABA and enhance the surface distribution of postsynaptic GABAAR clusters in hippocampus neurons. Together, these data showed that Pb exposure disrupted the balance of excitatory and inhibitory synaptic transmission via abnormal GABAergic neurotransmission.

2.
Sci Adv ; 5(8): eaaw3415, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31497642

RESUMO

Topological surface states (TSSs) in a topological insulator are expected to be able to produce a spin-orbit torque that can switch a neighboring ferromagnet. This effect may be absent if the ferromagnet is conductive because it can completely suppress the TSSs, but it should be present if the ferromagnet is insulating. This study reports TSS-induced switching in a bilayer consisting of a topological insulator Bi2Se3 and an insulating ferromagnet BaFe12O19. A charge current in Bi2Se3 can switch the magnetization in BaFe12O19 up and down. When the magnetization is switched by a field, a current in Bi2Se3 can reduce the switching field by ~4000 Oe. The switching efficiency at 3 K is 300 times higher than at room temperature; it is ~30 times higher than in Pt/BaFe12O19. These strong effects originate from the presence of more pronounced TSSs at low temperatures due to enhanced surface conductivity and reduced bulk conductivity.

3.
Nat Nanotechnol ; 14(7): 691-697, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31011219

RESUMO

Spin waves may constitute key components of low-power spintronic devices. Antiferromagnetic-type spin waves are innately high-speed, stable and dual-polarized. So far, it has remained challenging to excite and manipulate antiferromagnetic-type propagating spin waves. Here, we investigate spin waves in periodic 100-nm-wide stripe domains with alternating upward and downward magnetization in La0.67Sr0.33MnO3 thin films. In addition to ordinary low-frequency modes, a high-frequency mode around 10 GHz is observed and propagates along the stripe domains with a spin-wave dispersion different from the low-frequency mode. Based on a theoretical model that considers two oppositely oriented coupled domains, this high-frequency mode is accounted for as an effective antiferromagnetic spin-wave mode. The spin waves exhibit group velocities of 2.6 km s-1 and propagate even at zero magnetic bias field. An electric current pulse with a density of only 105 A cm-2 can controllably modify the orientation of the stripe domains, which opens up perspectives for reconfigurable magnonic devices.

4.
Toxicol Lett ; 296: 125-131, 2018 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-30121340

RESUMO

Lead (Pb) exposure impairs the nervous system, of which the injury of cognitive development is obvious. But the mechanism of Pb induced disorders of neuro-transmission remain elusive. In this study, primary hippocampal neurons were exposed to Pb at the dosage of 5 µM from days in vitro (DIV) 3 to DIV14 and the electrophysiological recordings were performed at DIV14. Sprague-Dawley (SD) rat pups were exposed to Pb from parturition to weaning indirectly from their mothers whose drinking water containing 250 ppm Pb, then directly exposed to Pb at the dosage of 250 ppm from postnatal day (PND) 21 to PND30. The results showed that Pb significantly decreased the frequency of both miniature excitatory postsynaptic current (mEPSC) and miniature inhibitory postsynaptic current (mIPSC) in cultured hippocampal neurons. Paird-pulse facilitation (PPF) recordings showed there was significant increase in Pb-exposed group. The increase of the magnitude of PPF (the ratio of second to first response amplitude) further confirmed that Pb reduced presynaptic neuro-transmission. By transmission electron microscope, it found that Pb disarranged presynaptic vesicles distribution and decreased the density of presynaptic vesicles. Moreover, it was interestingly found that phosphorylation of Synapsin1, which was phosphorylated by CDK5, has been decreased upon Pb exposure. With the treatment of R-Roscovitine (Ro), an inhibitor of CDK5, it was detected that Pb induced mEPSC and mIPSC frequency reduction have been reversed. Together, our results suggested that Pb disrupted the distribution of synaptic vesicles and impaired the neurotransmitter release, which was dependent on the phosphorylation level of Synapsin 1 via CDK5. This study will help for elucidation of environmental Pb-induced neuronal disorders.


Assuntos
Quinase 5 Dependente de Ciclina/metabolismo , Hipocampo/metabolismo , Chumbo/toxicidade , Sinapsinas/metabolismo , Transmissão Sináptica/efeitos dos fármacos , Animais , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Masculino , Neurônios/efeitos dos fármacos , Fosforilação , Cultura Primária de Células , Ratos , Ratos Sprague-Dawley , Proteínas SNARE/metabolismo , Vesículas Sinápticas
5.
Toxicol Sci ; 165(1): 224-231, 2018 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-29939358

RESUMO

Homeostatic synaptic plasticity (HSP) helps to stabilize the neuronal network activity, which is essential for optimal information coding. Synaptic scaling is a form of homeostatic plasticity that stabilizes neuronal firing in response to activity blockade. Lead (Pb) is a ubiquitous environmental neuro-toxicant and can impair the input-specific Hebbian type synaptic plasticity, but whether Pb exerts effects in HSP remains unknown. We previously reported that blocking L-type calcium channel induces synaptic scaling, which stimulates the synthesis of all-trans retinoic acid (RA) and the expression of GluA2-lacking α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor. Given Pb is a potent blocker of calcium channel, we hypothesized Pb may participate in synaptic scaling accompanied by RA synthesis and AMPA receptor trafficking. In this study, cultured hippocampal neurons were treated with Pb (1 µM 5 min, 15 min, 4 h, 24 h, and 10 µM 24 h) alone or in combination with tetrodotoxin (TTX, 1 µM, 24 h). The results showed that Pb alone, either at 1 µM or 10 µM, cannot induce synaptic scaling. But Pb participated in synaptic scaling when concurrent with TTX (10 µM Pb + 1 µM TTX, 24 h). Further results showed that surface heteromeric GluA1 and GluA2 AMPA receptors were increased in TTX+ Pb-induced synaptic scaling. In addition, RA was proved not to participate in TTX+ Pb-mediated synaptic scaling. Taken together, our work supported that TTX+ Pb could induce synaptic scaling and enhance synaptic accumulation of AMPAR GluA1 and GluA2 during synaptic up scaling. Our study would help for elucidation of the Pb-induced neuronal network instability mechanism.


Assuntos
Hipocampo/efeitos dos fármacos , Homeostase/efeitos dos fármacos , Chumbo/toxicidade , Plasticidade Neuronal/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Receptores de AMPA/metabolismo , Animais , Células Cultivadas , Hipocampo/metabolismo , Neurônios/metabolismo , Transporte Proteico , Ratos Sprague-Dawley , Tetrodotoxina/toxicidade
6.
Sci Adv ; 3(4): e1601614, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28435873

RESUMO

The role of damping in the spin Seebeck effect (SSE) was studied experimentally for the first time. The experiments used Y3Fe5O12 (YIG)/Pt bilayered structures where the YIG films exhibit very similar structural and static magnetic properties but very different damping. The data show that a decrease in the damping gives rise to an increase in the SSE coefficient, which is qualitatively consistent with some of the theoretical models. This response also shows quasi-linear behavior, which was not predicted explicitly by previous studies. The data also indicate that the SSE coefficient shows no notable correlations with the enhanced damping due to spin pumping, which can be understood in the frame of two existing models.

7.
Sci Rep ; 6: 32492, 2016 08 31.
Artigo em Inglês | MEDLINE | ID: mdl-27578147

RESUMO

Bisphenol-A (BPA, 4, 4'-isopropylidene-2-diphenol), a synthetic xenoestrogen that widely used in the production of polycarbonate plastics, has been reported to impair hippocampal development and function. Our previous study has shown that BPA exposure impairs Sprague-Dawley (SD) male hippocampal dendritic spine outgrowth. In this study, the sex-effect of chronic BPA exposure on spatial memory in SD male and female rats and the related synaptic mechanism were further investigated. We found that chronic BPA exposure impaired spatial memory in both SD male and female rats, suggesting a dysfunction of hippocampus without gender-specific effect. Further investigation indicated that BPA exposure causes significant impairment of dendrite and spine structure, manifested as decreased dendritic complexity, dendritic spine density and percentage of mushroom shaped spines in hippocampal CA1 and dentate gyrus (DG) neurons. Furthermore, a significant reduction in Arc expression was detected upon BPA exposure. Strikingly, BPA exposure significantly increased the mIPSC amplitude without altering the mEPSC amplitude or frequency, accompanied by increased GABAARß2/3 on postsynaptic membrane in cultured CA1 neurons. In summary, our study indicated that Arc, together with the increased surface GABAARß2/3, contributed to BPA induced spatial memory deficits, providing a novel molecular basis for BPA achieved brain impairment.


Assuntos
Poluentes Ocupacionais do Ar/farmacologia , Compostos Benzidrílicos/farmacologia , Região CA1 Hipocampal/efeitos dos fármacos , Plasticidade Neuronal/efeitos dos fármacos , Fenóis/farmacologia , Células Piramidais/efeitos dos fármacos , Memória Espacial/efeitos dos fármacos , Administração Oral , Animais , Animais Recém-Nascidos , Região CA1 Hipocampal/metabolismo , Região CA1 Hipocampal/ultraestrutura , Proteínas do Citoesqueleto/genética , Proteínas do Citoesqueleto/metabolismo , Espinhas Dendríticas/efeitos dos fármacos , Espinhas Dendríticas/metabolismo , Espinhas Dendríticas/ultraestrutura , Giro Denteado/efeitos dos fármacos , Giro Denteado/metabolismo , Giro Denteado/ultraestrutura , Feminino , Regulação da Expressão Gênica , Masculino , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Cultura Primária de Células , Células Piramidais/metabolismo , Células Piramidais/ultraestrutura , Ratos , Ratos Sprague-Dawley , Receptores de GABA-A/genética , Receptores de GABA-A/metabolismo , Memória Espacial/fisiologia , Sinapses/efeitos dos fármacos , Sinapses/fisiologia , Potenciais Sinápticos/efeitos dos fármacos , Transmissão Sináptica/efeitos dos fármacos , Lobo Temporal/efeitos dos fármacos , Lobo Temporal/metabolismo , Lobo Temporal/ultraestrutura
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