7.0T Mn2+增强MRI追踪大鼠神经传导束

目的 探讨7.0T Mn~(2+)增强MRI(MEMRI)追踪活体大鼠神经传导束的作用.方法 SD大鼠9只,立体定位下向右侧运动皮层内注射1 mol/L MnCl_2溶液0.4 μl,分别于注药前、注药后24 h、48 h、72 h、7 d行7.0T micro-MR扫描,观察皮质脊髓束及相关神经传导束的走行.结果 MnCl2皮质内注射后分时间段进行MR扫描可以完整地显示活体大鼠皮质脊髓束从运动皮层、丘脑、大脑脚、脑桥的走行区结构,24～48 h显示最佳,部分Mn~(2+)通过胼胝体到达对侧运动皮层功能区.结论 7.0T Mn~(2+)增强MR能够清晰、动态地显示大鼠皮层内神经传导通路,Mn~(2+)增强后的皮质脊髓束的解剖定位与Paxinos等大鼠解剖图谱定位一致;MEMRI能够显示两侧大脑半球间的联系,对活体研究大脑功能及损伤后脑的神经可塑性有重要的作用.     

感染性多脏器功能衰竭与血清钙浓度：附95例临床分析

Ca~(2+)是机体细胞内参与正常机能调节的第二信使之一,细胞内Ca~(2+)稳态失衡可致细胞功能和结构的不可逆损害。本文通过95例感染性多脏衰患者血清Ca~(2+)浓度分析,结果表明:(1)感染性多脏衰多有低Ca~(2+)血症(70/95例),尤其合并休克及呼衰者更明显;且脏衰数目越多,病情越严重低Ca~(2+)比例越高,二者有密切关系。(2)血清Ca~(2+)水平与感染性多脏衰病死率呈负相关。这提示多脏衰治疗中应用Ca~(2+)拮抗剂及黄瞟呤氧化酶抑制剂,以减少自由基生成,保护细胞膜防止Ca~(2+)内流,将有助于提高多脏衰挽救成功率。     

锰离子增强磁共振成像在动物神经系统研究中的应用

以二价锰离子(Mn2 )为探针的锰离子增强磁共振成像(MEMRI)是近年来发展迅速的一种脑成像新技术。Mn2 作为强顺磁性钙离子竞争剂,可以通过钙离子通道进入神经细胞,并可通过轴突、突触运输,减少含Mn2 组织的T1值,从而增强区域T1加权MRI信号。目前,MEMRI主要用于三方面的研究:活动诱导观察脑的功能活动,在体、动态地追踪神经传导通路,并可以精细观察脑部形态学。MEMRI在多领域的研究结果表明它是探测生物体内的分子过程和大脑功能活动的重要工具和手段。本文综述了MEMRI的原理及其在动物中枢神经系统研究中的应用。     

高尔基体在氧化应激中促凋亡作用的研究进展

高尔基体是细胞内重要的细胞器,除参与细胞内蛋白加工修饰、脂类代谢及囊泡转运等生理活动外,在离子稳态、应激等方面也发挥着重要作用。在氧化应激中高尔基体发生应激反应,功能上出现Ca~(2+)/Mn~(2+)泵活性改变,Ca~(2+)/Mn~(2+)稳态失衡;结构上出现高尔基体碎裂,释放应激性碎裂产物,上述行为将启动高尔基体相关凋亡通路,介导细胞发生凋亡。p115是高尔基体应激相关蛋白,在氧化应激中p115裂解后产生的碎裂片段通过促p53磷酸化而发挥促凋亡作用。     

大黄对严重烫伤大鼠肠道平滑肌细胞内无机元素的影响研究

目的探讨严重烫伤大鼠肠道平滑肌内无机元素的变化规律及大黄促进肠道运动的作用。方法选取健康成年Wistar大鼠68只,其中8只设为健康对照组;另外60只建立30%烫伤大鼠模型,其中烫伤治疗组(30只)管饲大黄水提液,烫伤对照组(30只)管饲等量蒸馏水,测定伤后6、12、24、48及72h肠道平滑肌细胞内铜离子(Cu~(2+))、锌离子(Zn~(2+))、钙离子(Ca~(2+))、镁离子(Mg~(2+))浓度。结果烫伤对照组Cu~(2+)、Zn~(2+)、Ca~(2+)浓度均有降低,而Mg~(2+)浓度则先升高后降低,与健康对照组比较差异均有统计学意义(P0.05);烫伤治疗组大鼠在烫伤后12h各无机元素浓度基本恢复至正常水平,且各时间点与烫伤对照组比较差异均有统计学意义(P0.05)。结论严重烫伤后早期大鼠肠道平滑肌细胞内无机元素水平出现明显变化,早期给予大黄治疗可调节无机元素水平。     

钙所引起的缺血性心肌损伤

钙离子(Ca~(2+))在人体生理中作用的重要性,早在一世纪以前已有所了解。但目前对 Ca~(2+)的研究工作已深入至亚细胞的结构水平,对临床工作发生了重大的影响。Ca~(2+)不仅参与骨骼肌、平滑肌、心肌的     

钙通道阻滞剂的临床选择及应用评价

CEB与神经精神疾病 钙通道阻滞剂(CEB)通过以下作用对若干神经精神疾患产生有益影响:(1)在不降低体循环血压的情况下选择性地在扩张脑血管,解除脑血管痉挛,从而避免了罂粟碱、硝酸酯类等脑血管扩张药选择性差的弱点;(2)抑制血小板的活化和血小板物质的释放;(3)阻止Ca~(2+)进入细胞内,为恢复红细胞的变形能力提供帮助,降低血液粘稠度;(4)有抗组胺、5-羟色胺作用,阻滞Ca~(2+)内流,增高动物的癫痫发作阀。     

锰离子增强MRI在动物嗅觉神经系统研究中的应用

二价锰离子（Mn²⁺）具有顺磁性,可作为钙离子类似物利用细胞膜钙通道进入神经细胞内,并可通过轴突、跨突触运输;由于能缩短T1,Mn²⁺沉积在组织中,使之在MR T1WI中呈高信号。锰增强MRI（MEMRI）已被越来越多地用于神经系统的活体动物研究中。本文针对MEMRI在动物嗅觉神经系统研究中的应用进展进行综述。     

红细胞（Ca^2＋—Mg^2＋）—ATP酶和（Na^＋—K^＋）—ATP酶活性同步测定法

本文介绍一种简易、实用的同步测定红细胞(Ca~(2+)-Mg~(2+))-ATP酶和(Na~+-K~+)-ATP酶活性的方法,重复性试验CV分别为1.67%和8.66%。30名健康成人(Ca~(2+)-Mg~(2+))-ATP酶活性(±SD):142.22±13.50μmol Pi·gHb~(-1)·2h~(-1),(Na~+-K~+)-ATP酶活性为19.68±3.62μmol Pi·gHb~(-1)·2h~(-1);20名健康婴幼儿(Ca~(2+)-Mg~(2+))-ATP酶活性为137.44±12.50μmol PigHb~(-1)·2h~(-1),(Na~+-K~+)-ATP酶活性为18.07±3.72μmol Pi·gHb~(-1)·2h~(-1),两种酶活性在健康成人和婴幼儿之间均无统计学差异。     

星形胶质细胞和嗅鞘细胞之间的Panglial缝隙连接介导Ca~(2+)瞬变的传递和神经血管耦合

星形胶质细胞排列在有高度组织性的缝隙连接耦合网络中,通过Ca~(2+)波的传播进行通信。星形胶质细胞不仅与邻近的星形胶质细胞结合,而且还与少突胶质细胞偶联,形成panglial合胞体。但panglial合胞体中的神经胶质细胞是否通过Ca~(2+)信号传递信息尚不清楚。我们使用共聚焦Ca~(2+)成像来研究小鼠嗅球中星形胶质细胞和嗅鞘神经胶质细胞(OECs)之间的细胞间通讯。研究结果表明,通过"笼状" ATP和"笼状" tACPD的局部光解可引起的肾小球旁星形胶质细胞中的Ca~(2+)瞬变,导致OEC中随之而来的Ca~(2+)反应。这种从星形胶质细胞到OEC的Ca~(2+)反应的传递在神经元抑制的情况下持续存在,但是当用甘珀酸抑制缝隙连接偶联时消失。当通过DHPG的抽吸在OEC中直接诱发Ca~(2+)瞬变时,它们导致肾小球星形胶质细胞中的Ca~(2+)反应延迟,表明Ca~(2+)信号的panglial传递以双向方式发生。此外,从星形胶质细胞到OEC的Ca~(2+)信号的panglial传递导致嗅觉神经层中OEC相关血管的收缩。本研究结果证明了在缝隙连接耦合的panglial网络中,不同类别的神经胶质细胞之间通过Ca~(2+)进行信号传递,并借此调节嗅球中血管的直径。     

Tracing odor-induced activation in the olfactory bulbs of mice using manganese-enhanced magnetic resonance imaging

Ithas previously been demonstrated that it is possible to map active regions of the brain using MRI relying on the fact that Mn(2+) ion enters excitable cells through voltage-gated calcium channels and is an excellent relaxation agent. In addition, Mn(2+) has been shown to trace neuronal connections in the mouse olfactory and visual systems, enabling MRI neuronal tract tracing. The purpose of the present studies was to determine if these two properties could be combined to trace Mn(2+) from sites of activation in the olfactory epithelium to the olfactory bulb thereby localizing regions within the olfactory bulb that respond to a particular odor. Mice were exposed to an aerosolized solution containing either a high pheromone content odor (male mouse urine) or amyl acetate plus MnCl(2). In both cases the odors caused a localized T(1) MRI enhancement in the olfactory epithelium and bulb that was dependent upon the presence of Mn(2+). The high pheromone containing solution caused enhancement in the anatomically correct location of the accessory olfactory bulb. Amyl acetate also caused T(1)-weighted MRI enhancement in specific regions of the olfactory bulb. These areas showing activation agree well with previous 2-deoxyglucose and BOLD fMRI results in the rat. Using manganese-enhanced MRI (MEMRI) it should be possible to rapidly map a variety of odors. Furthermore, since the effects of activation are imaged after the activation protocol it should be possible to take the time to obtain very high resolution images and make MEMRI maps from awake behaving animals.     

Manganese enhanced MRI reveals functional circuitry in response to odorant stimuli

To investigate the circuitry involved in detecting odorants in the rodent brain, we developed a method using manganese-enhanced MRI (MEMRI) to map the flow of neural information from the olfactory sensory neurons (OSNs) to the central layers of the olfactory bulb. Studies have shown that Mn(2+) enters active neurons and is transported anterogradely to axon terminals where it can cross synapses to functionally trace neural networks. Thus, by delivering MnCl(2) directly into the nasal cavity of mice and then exposing them to defined odorants, Mn(2+) is preferentially taken up by activated OSNs. Using the time course of the MRI signal, we generated maps of Mn(2+) accumulation in the olfactory bulb for both glomerular and mitral cell layers. Results demonstrated that overlapping yet distinct enhancement patterns were produced by exposure to either octanal, acetophenone, or carvone. Notably, areas of Mn(2+) accumulation in the mitral cell layer were similar to those in the glomerular layer consistent with neural information that passes from specific OSNs to specific mitral cells. Finally, by correlating specific Mn(2+) signal peaks to genetically labeled glomeruli that are known to be activated by the odorant octanal, we show that MEMRI maps can be resolved at the level of individual glomeruli.     

In vivo visualization of reactive gliosis using manganese-enhanced magnetic resonance imaging

Reactive astrogliosis occurs after diverse central nervous system (CNS) insults. While astrogliosis provides protection against inflammation, it is also obstructive in the progress of neuranagenesis after CNS insults. Thus, a method that enables in vivo visualization and tissue characterization for gliosis would be invaluable for studies of CNS insults and corresponding treatments. Manganese has proven to be a useful MRI contrast agent that enters cells via Ca²⁺ channels and has been applied to manganese-enhanced MRI (MEMRI) for neuronal functional mapping. This study investigated whether MEMRI can detect astrogliosis after focal ischemia in vivo. Rats were divided into groups according to the number of days after either transient middle cerebral artery occlusion or a sham. Ring- or crescent-shaped enhancement of MEMRI corresponded to the GFAP-positive astroglia observed in the peripheral region of the ischemic core 11 days after middle cerebral artery occlusion. This indicates that MEMRI enhancement predominantly reflects reactive astrogliosis after stroke.     

Quantitative measurement of changes in calcium channel activity in vivo utilizing dynamic manganese-enhanced MRI (dMEMRI)

The ability of manganese ions (Mn(2+)) to enter cells through calcium ion (Ca(2+)) channels has been used for depolarization dependent brain functional imaging with manganese-enhanced MRI (MEMRI). The purpose of this study was to quantify changes to Mn(2+) uptake in rat brain using a dynamic manganese-enhanced MRI (dMEMRI) scanning protocol with the Patlak and Logan graphical analysis methods. The graphical analysis was based on a three-compartment model describing the tissue and plasma concentration of Mn. Mn(2+) uptake was characterized by the total distribution volume of manganese (Mn) inside tissue (V(T)) and the unidirectional influx constant of Mn(2+) from plasma to tissue (K(i)). The measurements were performed on the anterior (APit) and posterior (PPit) parts of the pituitary gland, a region with an incomplete blood brain barrier. Modulation of Ca(2+) channel activity was performed by administration of the stimulant glutamate and the inhibitor verapamil. It was found that the APit and PPit showed different Mn(2+) uptake characteristics. While the influx of Mn(2+) into the PPit was reversible, Mn(2+) was found to be irreversibly trapped in the APit during the course of the experiment. In the PPit, an increase of Mn(2+) uptake led to an increase in V(T) (from 2.8±0.3 ml/cm(3) to 4.6±1.2 ml/cm(3)) while a decrease of Mn(2+) uptake corresponded to a decrease in V(T) (from 2.8±0.3 ml/cm(3) to 1.4±0.3 ml/cm(3)). In the APit, an increase of Mn(2+) uptake led to an increase in K(i) (from 0.034±0.009 min(-1) to 0.049±0.012 min(-1)) while a decrease of Mn(2+) uptake corresponded to a decrease in K(i) (from 0.034±0.009 min(-1) to 0.019±0.003 min(-1)). This work demonstrates that graphical analysis applied to dMEMRI data can quantitatively measure changes to Mn(2+) uptake following modulation of neural activity.     

Using manganese-enhanced MRI to understand BOLD

The 1990s were designated "The Decade of the Brain" by U.S. Congress, perhaps in great anticipation of the impact that functional neuroimaging techniques would have on advancing our understanding of how the brain is functionally organized. While it is impossible to overestimate the impact of functional MRI in neuroscience, many aspects of the blood oxygenation level-dependent (BOLD) contrast remain poorly understood, in great part due to the complex relationship between neural activity and hemodynamic changes. To better understand such relationship, it is important to probe neural activity independently. Manganese-enhanced MRI (MEMRI), when used to monitor neural activity, is a technique that uses the divalent manganese ion, Mn(2+), as a surrogate measure of calcium influx. A major advantage of using Mn(2+) as a functional marker is that the contrast obtained is directly related to the accumulation of the ion in excitable cells in an activity dependent manner. As such, the contrast in MEMRI is more directly related to neural activity then hemodynamic-based fMRI techniques. In the present work, the early conceptualization of MEMRI is reviewed, and the comparative experiments that have helped provide a better understanding of the spatial specificity of BOLD signal changes in the cortex is discussed.     

Detection of cortical gray matter lesion in the late phase of mild hypoxic-ischemic injury by manganese-enhanced MRI

Noncystic periventricular leukomalacia (PVL) in premature infants is becoming a predominant lesion form. However, detection of the gray matter (GM) lesions involved in this disease, which closely relate to the later cognitive and behavioral deficits, is challenging because of their subtle and transient nature observed by conventional MRI. This study evaluated manganese-enhanced MRI (MEMRI) for detecting such GM lesions in 7-day-old rats with mild hypoxic-ischemic (H-I) insult, a characteristic model of noncystic PVL. Group 1 (n=6) and Group 2 (n=8) were administered intraperitoneally with MnCl(2) at hour 3 and day 7 after H-I insult, respectively. Control Group (n=6) received no MnCl(2). T1-, T2- and diffusion-weighted imaging (T1WI, T2WI and DWI, respectively) was performed. Animals were sacrificed for H&E staining, and immunohistochemical staining for glutamine synthetase (GS) and Mn-superoxide dismutase (Mn-SOD), which are two Mn-binding enzymes against glutamate toxicity and oxidative stress respectively in neurodegeneration. In Control Group, MRI appearance of H-I lesions normalized by day 7 after H-I insult. In Group 1, MEMRI provided the enhanced and prolonged GM lesion detection from day 3 up to day 21. In Group 2, similar Mn enhancement was observed, enabling day 8 detection of GM lesions that were invisible before Mn injection at day 7. These in vivo Mn-induced GM lesion enhancements were found to correlate with increased immunoactivities of GS and Mn-SOD. These findings suggest the potential utility of MEMRI in detecting the GM lesions that are otherwise undetectable using the conventional MRI techniques in late phase of mild H-I injury.     

Mn‐alginate gels as a novel system for controlled release of Mn2+ in manganese‐enhanced MRI

The aim of the present study was to test alginate gels of different compositions as a system for controlled release of manganese ions (Mn²⁺) for application in manganese‐enhanced MRI (MEMRI), in order to circumvent the challenge of achieving optimal MRI resolution without resorting to high, potentially cytotoxic doses of Mn²⁺. Elemental analysis and stability studies of Mn‐alginate revealed marked differences in ion binding capacity, rendering Mn/Ba‐alginate gels with high guluronic acid content most stable. The findings were corroborated by corresponding differences in the release rate of Mn²⁺ from alginate beads in vitro using T₁‐weighted MRI. Furthermore, intravitreal (ivit) injection of Mn‐alginate beads yielded significant enhancement of the rat retina and retinal ganglion cell (RGC) axons 24 h post‐injection. Subsequent compartmental modelling and simulation of ivit Mn²⁺ transport and concentration revealed that application of slow release contrast agents can achieve a significant reduction of ivit Mn²⁺ concentration compared with bolus injection. This is followed by a concomitant increase in the availability of ivit Mn²⁺ for uptake by RGC, corresponding to significantly increased time constants. Our results provide proof‐of‐concept for the applicability of Mn‐alginate gels as a system for controlled release of Mn²⁺ for optimized MEMRI application. Copyright © 2012 John Wiley & Sons, Ltd.