EFFECTS OF NAAG AND MPEP ON RAT CORTICAL SPREADING DEPRESSION

Cortical spreading depression(CSD)is a pathophysiological phenomenon.There are sufficient evidences to prove that CSD plays an important role in some neurological disorders.However,exact mechanisms of its initiation and propagation are still unclear.Previous studies showed that glutamate receptors could be concerned with CSD,but those studies were mostly performed oriented to ionotropic glutamate receptors(iGluRs).There is relatively little report about effects of metabotropic glutamate receptors(mGluRs)on CSD.Here,we applied optical intrinsic signal imaging(OISI)combined with direct current(DC)potential recording to examine influences of some mGluRs antagonist(or agonist)on CSD propagation in rat’s brain,to indirectly validate actions of some mGluRs on CSD.We found that N-acetyl-l-aspartyl-l-glutamate(NAAG,an agonist at mGluR3)inhibited the propagation of CSD,and the inhibition was gradually developed with time.However,6-methyl-2-phenylethynyl-pyridine(MPEP,an antagonist of mGluR5)did not produce any significant alterations with the CSD propagation.Our findings suggest that mGluR3 could play an important role in the CSD propagation,but the activity of mGluR5 was comparatively weak.These findings can help to understand the propagation mechanism of CSD,and consider the therapy of some neurological diseases involved with CSD.

Relationships between ionospheric parameters derived from ionosonde observations and characteristics of post-sunset GHz scintillation during high solar activities(2012−2013)at Sanya(18.3°N,109.6°E),China

In this study,we present characteristics of post-sunset GHz scintillation occurrence and their correlations with ionospheric parameters derived from ionosonde observations in high solar activity years(2012−2013)of solar cycle 24 at Sanya(18.3°N,109.6°E;dip lat.:12.8°N),China.The analyzed data include the F_(2)-layer’s critical frequency(foF_(2)),peak height(h_(m)F_(2)),and minimum virtual height(h’F),as well as the scale height around the F_(2)-layer peak(H_(m)),and virtual height(h’F_(5))and true height(hF_(5))measured at 5 MHz.We have investigated relationships between the equinoctial asymmetry of these scintillations and these ionospheric parameters.In addition,we calculate the growth rates of Rayleigh−Taylor instability on the basis of the ionosonde measurements and theoretical models,respectively.We find that the equinoctial asymmetry of scintillation onset time is associated with the scale length of the vertical electron density gradient(L),which has been shown to affect the growth of Rayleigh−Taylor instability at the bottom of the F-layer.The seasonal variations of foF_(2),H_(m)and scale length of vertical electron density gradient appear to cause the seasonal variations of scintillation occurrence;the equinoctial asymmetry of scintillation occurrence rate over low latitudes appears to be related to background electron density and vertical drifts in the F-layer around time of sunset.Further study is required to explain the observed correlational weakness in low latitudes between scintillation strength,represented by the daily maximum S4,and daily maximum values of foF_(2),h_(m)F_(2),h’F,H_(m),and also the drifts.

TWO-DIMENSIONAL VISUALIZATION OF THE PROPAGATION SPEED OF CORTICAL SPREADING DEPRESSION IN RAT CORTEX

Cortical spreading depression(CSD),which is a significant pathological phenomenon that correlates with migraines and cerebral ischemia,has been characterized by a wave of depolarization among neuronal cells and propagates across the cortex at a rate of 2–5mm/min.Although the propagation pattern of CSD was well-investigated using high-resolution optical imaging technique,the variation of propagation speed of CSD across different regions of cortex was not well-concerned,partially because of the lack of ideal approach to visualize two-dimensional distribution of propagation speed of CSD over the whole imaged cortex.Here,we have presented a method to compute automatically the propagation speed of CSD throughout every spots in the imaged cortex.In this method,temporal clustering analysis(TCA)and least square estimation(LSE)were first used to detect origin site where CSD was induced.Taking the origin site of CSD as the origin of coordinates,the data matrix of each image was transformed into the corresponding points based on the polar-coordinate representation.Then,two fixed-distance regions of interest(ROIs)are sliding along with the radial coordinate at each polar angle within the image for calculating the time lag with correlating algorithm.Finally,we could draw a twodimensional image,in which the value of each pixel represented the velocity of CSD when it spread through the corresponding area of the imaged cortex.The results demonstrated that the method can reveal the heterogeneity of propagation speed of CSD in the imaged cortex with high fidelity and intuition.

ACCURATELY DETERMINING PROPAGATION VELOCITY OF CORTICAL SPREADING DEPRESSION IN RATS BY OPTICAL INTRINSIC SIGNAL IMAGING

Cortical spreading depression(CSD)is a wave of neuronal and glial depolarization that propagates across the cortex at a rate of 2–5mm/min accompanied by reversible electroencephalogram(EEG)suppression,a negative shift of direct current(DC)potential,and change of optical intrinsic signals(OIS).Propagation velocity of CSD is an important parameter used to study this phenomenon.It is commonly determined in an electrophysiological way that measures the time required for a CSD wave to pass along two electrodes.Since the electrophysiology technique fails to reveal the spreading pattern of CSD,velocity calculated in this manner might be inaccurate.In this study,we combined the electrophysiological recording and OIS imaging(OISI)for detecting changes in DC potential and OIS during CSD simultaneously.An optical method based on OISI to determine the CSD velocity,which is measured by generating a series of regions of interest(ROI)perpendicular to the advancing wavefront along propagation direction of CSD at different time points and then dividing by the distance between ROIs over time,is presented.Comparison of the accuracy of the two approaches in determining the CSD velocity is made as well.The average rate of 33 CSDs is 3.52±0.87mm/min by use of the optical method and 4.36±1.65mm/min by use of the electrophysiological method.Because of the information about spreading pattern of CSD provided optically,the velocity determined by OISI is of smaller deviation and higher accuracy.

TRACING COLLATERAL CIRCULATION AFTER ISCHEMIA IN RAT CORTEX BY LASER SPECKLE IMAGING

The collateral circulation is crucial for the pathophysiology and outcome of acute cortical ischemia.Current understanding of collateral circulation still remains sparse,largely due to prior limitations of spatial or/and temporal resolution in methods to evaluate these diminutive redistributive routes of cerebral blood flow(CBF)especially in leptomeningeal anastomoses that connected cortical arteries.In the study,based on a mini-stroke model,laser speckle imaging with high spatiotemporal resolution was used to assess the dynamic evolution of the collateral circulation around a mini-ischemia in the rat cortex.We found that the blood flow and diameter in the intra-arterial anastomoses were enhanced immediately after the ligation of one branch of middle cerebral artery and recovered to baseline level as arterial recirculation was performed.Whereas the communicative flow-through of the posterior cerebral artery and the middle cerebral artery anastomoses was not significant enough to be determined.This is the evidence that intra-arterial anastomoses were the primary routes to restore blood flow into the ischemic territory during the acute phase of ischemia,and laser speckle imaging method was proven as a powerful tool to be potential for subserving further investigation of the collateral circulation.

Transient stability risk assessment of power systems incorporating wind farms

Large-scale wind farm integration has brought several aspects of challenges to the transient stability of power systems.This paper focuses on the research of the transient stability of power systems incorporating with wind farms by utilizing risk assessment methods.The detailed model of double fed induction generator has been established.Wind penetration variation and multiple stochastic factors of power systems have been considered.The process of transient stability risk assessment based on the Monte Carlo method has been described and a comprehensive risk indicator has been proposed.An investigation has been conducted into an improved 10-generator 39-bus system with a wind farm incorporated to verify the validity and feasibility of the risk assessment method proposed.

氰基苯乙烯基聚集诱导发光材料在光和pH调控下的多颜色和荧光转换

本文精心设计了一种具有聚集诱导发光增强特性的氰基苯乙烯基荧光团(Z-BDPA),由于其具有各种光化学反应和可逆的pH响应而呈现出多种可调节的颜色和荧光.在420 nm光照射下,Z-BDPA在四氢呋喃(THF)中发生Z→E异构化,其绿色荧光增强,该过程在365 nm光照射下可恢复;由于发生光二聚化过程,Z-BDPA在水含量(fw)为90%的THF/H_(2)O混合体系中的黄色荧光变为更强的黄绿色荧光.在酸性条件下,具有黄色荧光的Z-BDPA粉末通过质子化过程变为具有蓝色荧光的AIE荧光团Z-p-BDPA,该过程可通过在碱性条件下的去质子化作用恢复.在365 nm光照射下,Z-p-BDPA的蓝色荧光由于光异构化过程和随后的光环脱氢反应而蓝移且增强.基于其对于光化学反应和pH响应而呈现出的可调控的颜色和荧光,Z-BDPA可成功应用于光图案化和防伪.