弱电刺激大鼠迷走神经中枢端在海马CA1区产生周期性theta电振荡

目的：观察弱电刺激迷走神经中枢端对正常大鼠海马细胞放电及场电的影响。方法：雄性成年大鼠45只．分离其颈部左侧迷走神经,结扎外周端,弱电（10Hz,0．5ms,1.5～5.0V,15-20／chain）刺激,每5min一次,共20串：记录右侧海马CAI细胞放电及双侧海马CAI场电。结果：双侧场电出现周期性theta电振荡（38／45,84．4％）,伴有theta—on（n=30）和theta—off（n=5）两种形式的非簇状紧张性细胞放电.结论：弱电刺激迷走神经中枢端激活海马CAI区网络,并对网络内细胞放电有紧张性调制作用.     

麝香、麝香酮对体外培养大鼠视网膜神经细胞存活影响的比较研究

为比较麝香、麝香酮对大鼠视网膜神经细胞存活的影响,分别单独将麝香、麝香酮加入大鼠视网膜神经细胞混悬液中,用MTT法评价麝香、麝香酮对大鼠视网膜神经细胞存活的影响;另分别在麝香和麝香酮中加入定量的m-NGF,采用同法评价麝香(或麝香酮) m-NGF对大鼠视网膜神经细胞存活的影响。结果表明,单独应用麝香、麝香酮对体外培养大鼠视网膜神经细胞的存活无明显影响(P>0.05);在加入定量m-NGF的条件下,麝香、麝香酮分别在50～800μg/mL和100～800μg/mL的浓度范围明显促进大鼠视网膜神经细胞的存活,且呈一定的量效关系。说明麝香、麝香酮无直接促进视网膜神经细胞存活的作用;麝香、麝香酮均与NGF协同增进视网膜神经细胞的存活;麝香酮是麝香中增强NGF生物效应的有效成分之一。     

Cleavage of BNIP-2 and BNIP-XL by caspases

BNIP-2 and BNIP-XL are BCH domain-containing proteins that are implicated in programmed cell death. It has been reported that overexpression of BNIP-2 in neuroblastoma cell lines resulted in massive cell death, whereas BNIP-XL was upregulated during NGF-depletion-induced apoptosis in neuroblastoma and was involved in the regulation of differentiation, survival, and aggressiveness of tumor cells. Despite their importance in apoptosis, our understanding of BNIP-2 containing proteins is limited. In this communication, we demonstrate that both BNIP-2 and BNIP-XL are cleaved by caspases during apoptosis. Significantly, the caspase cleavage sites on BNIP-2 are located on its N-terminal EF-hand motif, while that on BNIP-XL is located upstream of the C-terminal BCH domain. Our results suggest that the caspase-mediated cleavage of BNIP-2 and BNIP-XL could result in the release of the BCH domain or smaller fragments that are crucial for their proapoptotic activities.     

Optimedin induces expression of N-cadherin and stimulates aggregation of NGF-stimulated PC12 cells

Optimedin, also known as olfactomedin 3, belongs to a family of olfactomedin domain-containing proteins. It is expressed in neural tissues and Pax6 is involved in the regulation of its promoter. To study possible effects of optimedin on the differentiation of neural cells, we produced stably transfected PC12 cell lines expressing optimedin under a tetracycline-inducible promoter. Cells expressing high levels of optimedin showed higher growth rates and stronger adhesion to the collagen extracellular matrix as compared with control PC12 cells. After stimulation with nerve growth factor (NGF), optimedin-expressing cells demonstrated elevated levels of N-cadherin, beta-catenin, alpha-catenin and occludin as compared with stimulated, control PC12 cells. Expression of optimedin induced Ca(2+)-dependent aggregation of NGF-stimulated PC12 cells and this aggregation was blocked by the expression of N-cadherin siRNA. Expression of optimedin also changed the organization of the actin cytoskeleton and inhibited neurite outgrowth in NGF-stimulated PC12 cells. We suggest that expression of optimedin stimulates the formation of adherent and tight junctions on the cell surface and this may play an important role in the differentiation of the brain and retina through the modulation of cytoskeleton organization, cell-cell adhesion and migration.     

生长抑素前体蛋白1和前脑啡肽原mRNA在鸡肠Remak神经中的分布

肠Remak神经(Intestinal nerve of Remak,INR)是禽类特有的一根自主神经节链,但INR中肽类递质的分布至今仍然存在许多疑问。本文应用RT-PCR方法从鸡脑组织提取的RNA中扩增生长抑素前体蛋白1(Somatostatin precursor1,PSS1)和前脑啡肽原(Preproenkephalin,PPE)基因片段,将其连接于pGM-Teasy质粒,经过转化大肠杆菌、挑取阳性克隆和测序鉴定,确定为目的片段。分别以线性化的SS1/pGM-Teasy和PPE/pGM-Teasy质粒为模板,用体外转录的方法合成正反义地高辛标记RNA探针。通过原位杂交方法将合成的探针用于探查PPE和PSS1 mRNA在鸡空回肠段和直肠段INR中的分布情况。结果表明:INR中大部分神经细胞中有PPE和PSS1的mRNA的转录,其中PPE探针杂交阳性细胞在空回肠段和直肠段INR分别占83.79%±7.96%和96.04%±4.53%,而PSS1探针在空回肠段和直肠段INR中的杂交阳性细胞分别占86.98%±7.93%和86.07%±6.11%;在整个INR中都可能有PPE和PSS1 mRNA共存于同一神经细胞的现象;原位杂交阳性神经细胞胞体呈有突起的梭形或椭圆形,其纵轴与INR延伸的方向平行;阳性神经细胞胞体在INR神经节中呈层状或成群分布,在节间束也有少量的阳性细胞分布。本文从基因水平证明INR中大量神经细胞进行PPE或PSS1的mRNA的转录,并可能作为外源性生长抑素1和脑啡肽能神经纤维支配到肠壁和输卵管     

Binding of a Naja naja venom acidic phospholipase A2 cognate complex to membrane-bound vimentin of rat L6 cells: Implications in cobra venom-induced cytotoxicity

An acidic phospholipase A₂ enzyme (NnPLA₂-I) interacts with three finger toxins (cytotoxin and neurotoxin) from Naja naja venom to form cognate complexes to enhance its cytotoxicity towards rat L6 myogenic cells. The cytotoxicity was further enhanced in presence of trace quantity of venom nerve growth factor. The purified rat myoblast cell membrane protein showing interaction with NnPLA₂-I was identified as vimentin by LC-MS/MS analysis. The ELISA, immunoblot and spectrofluorometric analyses showed greater binding of NnPLA₂-I cognate complex to vimentin as compared to the binding of individual NnPLA₂-I. The immunofluorescence and confocal microscopy studies evidenced the internalization of NnPLA₂-I to partially differentiated myoblasts post binding with vimentin in a time-dependent manner. Pre-incubation of polyvalent antivenom with NnPLA₂-I cognate complex demonstrated better neutralization of cytotoxicity towards L6 cells as compared to exogenous addition of polyvalent antivenom 60–240 min post treatment of L6 cells with cognate complex suggesting clinical advantage of early antivenom treatment to prevent cobra venom-induced cytotoxicity. The in silico analysis showed that 19–22 residues, inclusive of Asp48 residue, of NnPLA₂-I preferentially binds with the rod domain (99–189 and 261–335 regions) of vimentin with a predicted free binding energy (ΔG) and dissociation constant (K_D) values of ?12.86 kcal/mol and 3.67 × 10^?10 M, respectively; however, NnPLA₂-I cognate complex showed greater binding with the same regions of vimentin indicating the pathophysiological significance of cognate complex in cobra venom-induced cytotoxicity.     

Metformin relieves neuropathic pain after spinal nerve ligation via autophagy flux stimulation

Neuropathic pain is a well‐known type of chronic pain caused by damage to the nervous system. Autophagy is involved in the development and/or progression of many diseases, including neuropathic pain. Emerging evidence suggests that metformin relieves neuropathic pain in several neuropathic pain models; however, metformin's cellular and molecular mechanism for pain relief remains unknown. In this study, we investigated the therapeutic effects of metformin on pain relief after spinal nerve ligation (SNL) and its underlying mechanism of autophagy regulation. Behavioural analysis, histological assessment, expression of c‐Fos and molecular biological changes, as well as ultrastructural features, were investigated. Our findings showed that the number of autophagosomes and expression of autophagy markers, such as LC3 and beclin1, were increased, while the autophagy substrate protein p62, as well as the ubiquitinated proteins, were accumulated in the ipsilateral spinal cord. However, metformin enhanced the expression of autophagy markers, while it abrogated the abundance of p62 and ubiquitinated proteins. Blockage of autophagy flux by chloroquine partially abolished the apoptosis inhibition and analgesic effects of metformin on SNL. Taken together, these results illustrated that metformin relieved neuropathic pain through autophagy flux stimulation and provided a new direction for metformin drug development to treat neuropathic pain.     

Quantification of collagen fiber structure using second harmonic generation imaging and two‐dimensional discrete Fourier transform analysis: Application to the human optic nerve head

Second harmonic generation (SHG) microscopy is widely used to image collagen fiber microarchitecture due to its high spatial resolution, optical sectioning capabilities and relatively nondestructive sample preparation. Quantification of SHG images requires sensitive methods to capture fiber alignment. This article presents a two‐dimensional discrete Fourier transform (DFT)–based method for collagen fiber structure analysis from SHG images. The method includes integrated periodicity plus smooth image decomposition for correction of DFT edge discontinuity artefact, avoiding the loss of peripheral image data encountered with more commonly used windowing methods. Outputted parameters are as follows: the collagen fiber orientation distribution, aligned collagen content and the degree of collagen fiber dispersion along the principal orientation. We demonstrate its application to determine collagen microstructure in the human optic nerve head, showing its capability to accurately capture characteristic structural features including radial fiber alignment in the innermost layers of the bounding sclera and a circumferential collagen ring in the mid‐stromal tissue. Higher spatial resolution rendering of individual lamina cribrosa beams within the nerve head is also demonstrated. Validation of the method is provided in the form of correlative results from wide‐angle X‐ray scattering and application of the presented method to other fibrous tissues.      

Muscle LIM Protein Is Expressed in the Injured Adult CNS and Promotes Axon Regeneration

1. Download high-res image (193KB)
2. Download full-size image