A novel analgesic dipeptide from bovine brain is a possible Met-enkephalin releaser.

It is generally accepted that morphine exerts its analgesic effect by binding to specific opiate receptors in the brain and spinal cord. Since Hughes et al. isolated and identified two endogenous pentapeptides, Met- and Leu-enkephalin, from the brain and found that they acted as agonists at opiate receptors, alpha-, beta- and gamma-endorphins, larger peptides than enkephalins and having morphine-like activity, have been identified in either the brain or pituitary of various species. Several studies have demonstrated that enkephalins possess analgesic properties and that they are distributed in the pain-mediated pathways in the central nervous system. These findings suggest that enkephalins are important neurotransmitters or neuromodulators regulating pain transmission. We now report the isolation of a novel substance which has a Met-enkephalin releasing action. Our findings suggest the possibility of a regulating mechanism for the release of endogenous opioid peptides, especially Met-enkephalin.     

Met-enkephalin circulates in human plasma

The physiological roles of Met-enkephalin and Leu-enkephalin are still unknown. They may act as neurotransmitters in the central and peripheral nervous systems. Met-enkephalin has been detected in several species in a variety of tissues including brain, spinal cord and gut using bioassays, opiate receptor assays and radioimmunoassays (RIA). It has also been detected in human gut immunocytochemically and in human brain and cerebrospinal fluid by opiate receptor assay and RIA. However, all reported assays show some degree of cross-reaction with Leu-enkephalin and unequivocal differentiation between the two enkephalins and the larger endorphins has not always been possible. Thus the existence of Met-enkephalin in human tissues and fluids remains in doubt. Using a highly specific RIA, we have now obtained evidence that Met-enkephalin-like material circulates in the plasma of normal subjects and may be secreted by the adrenal gland. Chromatographically the material exists in plasma mainly as the intact pentapeptide and not as the biologically inactive degradation product Gly-Gly-Phe-Met as would be expected from metabolic studies.     

Downregulation of enkephalin-mediated inflammatory responses by CD10/neutral endopeptidase 24.11.

The antigen CD10 (common acute lymphoblastic leukaemia antigen), which is the zinc metalloprotease, neutral endopeptidase 24.11 (also known as NEP or 'enkephalinase'), is expressed by acute lymphoblastic leukaemias, normal lymphoid progenitors, mature polymorphonuclear leukocytes and certain nonhaematopoietic cells. CD10/NEP hydrolyses several naturally occurring peptides, including the endogenous opioid pentapeptides Met- and Leu-enkephalin. In invertebrate organisms such as the mollusc Mytilus edulis, Met-enkephalin triggers inflammatory responses by inducing morphological changes, directed migration and aggregation of haemocytes. We report here that a structure related to CD10/NEP is expressed by M. edulis haemocytes and that abrogation of CD10/NEP enzymatic activity reduces the amount of Met-enkephalin required for haemocyte activation by five orders of magnitude. Similar results are obtained with CD10+ human polymorphonuclear leukocytes, indicating that CD10/NEP related structures regulate enkephalin-mediated inflammatory responses in organisms whose ancestors diverged approximately 500 million years ago.     

Met-enkephalin-Arg6-Phe7, present in high amounts in brain of rat, cattle and man, is an opioid agonist

The enkephalins Met-enkephalin and Leu-enkephalin were first isolated from porcine brain by Hughes and co-workers. We have recently isolated from bovine adrenals another enkephalin with the structure Tyr-Gly-Gly-Phe-Met-Arg-Phe, or Met-enkephalin-Arg6-Phe7 (ref. 2). We report here that this new heptapeptide is found in human, rat and bovine striatum in concentrations comparable with or greater than that of Leu-enkephalin. This molecule should not be considered as a mere precursor of Met-enkephalin. A pharmacological study indicates that this naturally occurring enkephalin has similar properties to the two enkephalins characterized earlier.     

A dynorphinergic pathway of Leu-enkephalin production in rat substantia nigra

The amino acid sequence of the opioid peptide Leu-enkephalin is found within several larger peptides, which are generated from the precursors proenkephalin and prodynorphin. Proenkephalin contains four copies of the sequence of Met-enkephalin, a single copy of the sequence of Leu-enkephalin and one copy each of two extended Met-enkephalin sequences. Proenkephalin contains three peptides--alpha-neo-endorphin, dynorphin A and dynorphin B--the N-terminal sequences of which are identical to that of Leu-enkephalin. There is good evidence that the large amounts of Leu-enkephalin found in the adrenal medulla are generated from the precursor proenkephalin, but as yet prodynorphin has not been shown to be processed to yield Leu-enkephalin. We show here that the relatively high levels of Leu-enkephalin found in the rat substantia nigra are supplied by striatonigral axons and generated from the precursor prodynorphin.     

Evolutionary radiations and convergences in the structural organization of mammalian brains

The sizes of mammalian brain components seem to be mostly related to the sizes of the whole brain (and body), suggesting a one-dimensional scale of encephalization. Previous multivariate study of such data concludes that evolutionary selection for enlargement of any one brain part is constrained to selection for a concerted enlargement of the whole brain. However, interactions between structurally related pairs of brain parts confirm reports of differential change in brain nuclei, and imply mosaic rather than concerted evolution. Here we analyse a large number of variables simultaneously using multi-dimensional methods. We show that the relative proportions of different systems of functionally integrated brain structures vary independently between different mammalian orders, demonstrating separate evolutionary radiations in mammalian brain organization. Within each major order we identify clusters of unrelated species that occupy similar behavioural niches and have convergently evolved similar brain proportions. We conclude that within orders, mosaic brain organization is caused by selective adaptation, whereas between orders it suggests an interplay between selection and constraints.     

暗纹东方鲀、菊黄东方鲀和条纹东方鲀乳酸脱氢酶的比较研究

运用聚丙烯酰胺凝胶电泳的方法分析比较了暗纹东方鲀、菊黄东方鲀和条纹东方鲀的乳酸脱氢酶同工酶在不同组织中的电泳酶谱谱带的差异,结果表明:三种河鲀的心脏和肌肉组织都出现1条酶带,眼睛组织都有4条酶带,菊黄东方鲀和条纹东方鲀的大脑组织都出现4条酶带,而暗纹东方鲀的大脑组织却只有3条酶带;三种东方鲀的肝脏中都有5条LDH酶带,但酶带的分布却有着显著的差异,菊黄东方鲀和条纹东方鲀酶带分布比较相似.从LDH酶带迁移率可以看出,三种东方鲀眼睛和大脑组织中乳酸脱氢酶(LDH)酶带迁移率略显差异,但差异不显著(p＞005),在大脑中,菊黄东方鲀和条纹东方鲀比暗纹多出现一条酶带(该酶带的迁移率为0.118).上述结果表明淡水养殖的暗纹东方鲀与海水养殖的菊黄东方鲀和条纹东方鲀具有一定的差异性.     

鞭角华扁叶蜂预蛹神经内分泌系统的解剖

通过对鞭角华扁叶蜂预肾的解剖,明确屯其神经内分泌系统的构造及其分布。其中枢神经系统由脑、食管下神经节、腹神经索组成,前、中、后脑分化明显。腹神经索包括三对胸神经节、八对腹神经节及纵贯各神经节的神经索,其中各了的分布与叶蜂预肾体节相一致,位于各体节腹板的前缘中部。口道交感神经系统由位于脑前方食道背面的额神经节和位于脑后方的后头神经节组成的神经连锁构成。腹交感神经系统由位于腹神经索各神经节上的横神经组     

东方簇盾吸虫神经系统的研究

应用乙酰胆碱酯酶定位方法对东方簇盾吸虫(Lophotaspis orientalis Faust and Tang,1936)成虫的神经系统进行了研究.成虫的神经系统十分复杂,包括中枢神经结、脑神经联合、纵行的神经干、横向的神经连合.中枢神经结位于咽前部两侧,有1粗大的脑神经联合连接.在脑神经联合的下方有1个小的环形的结构.中枢神经结向前发出1对前背神经干和1对前侧神经干,这2对神经干向前的分支汇入围口腔的神经环.中枢神经结向后发出1对后背神经干和1对后腹神经干.后背神经干之间有横向的神经相连,在体末端与后腹神经干相汇合.后腹神经干最为粗大,并在虫体末端汇合,它在腹盘处有2对分支进入腹盘,前1对与腹盘边缘神经相连,后1对贯穿腹盘,其分支构成腹吸盘内复杂的神经网.腹吸盘的指状突起内也有神经分支.     

南方鲶脑和脑神经的观察

对南方鲶脑的外部形态和内部结构及脑神经特点进行了描述.与一般鲤科鱼类的脑比较其不同点在于:端脑发达,体积比视叶大;小脑特别发达,向前盖住中脑、间脑和部分端脑,后部向两侧扩展成耳状叶;间脑有明显的中间叶、球状核,视交叉紧靠间脑前方,脑下垂体在二下叶之间,远离视神经交叉.并具有特别的副侧线神经、侧线神经侧腹支及电觉初级中枢.靠味觉和嗅觉共同摄取食物.     

脑机接口技术研究方法

脑机接口（BCI）是一种基于脑电信号实现人脑与计算机或其他电子设备通讯和控制的系统，它不依赖人体的外周神经神经系统及肌肉组织，是一种新的人机接口方式，在康复医学和控制等领域有应用前景，近年来，脑机接口技术发展迅速。概述了采用事件相关电位P300、稳态视觉诱发电位（SSVEP）、事件相关同步或去同步9ERS／ERD）皮层慢电位（SCP）、自发EEG信号、植入电极等实现脑机接口技术的研究方法，讨论和比较了各种研究方法的特点和局限，介绍了脑机接口的发展现状和存在的问题，并对其应用前景进行了展望。     

Polymorphism and absence of Leu-enkephalin sequences in proenkephalin genes in Xenopus laevis

The structures of the genes coding for the opioid peptide precursors proopiomelanocortin, proenkephalin (proenkephalin A) and prodynorphin (proenkephalin B), are known for some mammalian species. To gain insight into the evolutionary history of these precursors, we have examined the proenkephalin gene in the South African clawed toad, Xenopus laevis, which diverged from the principal line of vertebrate evolution some 350 Myr ago. The human proenkephalin gene consists of four exons, of which the main exon (exon IV) contains all known biologically active peptides--six Met-enkephalin sequences and one Leu-enkephalin sequence. We report here the primary structures of the putative main exons of two proenkephalin genes in X. laevis, each of which codes for seven Met-enkephalin sequences but no Leu-enkephalin, indicating that Met-enkephalin preceded Leu-enkephalin in the evolution of the proenkephalin gene. The organization of the main exons of the toad genes is remarkably similar to that of the human gene and conserved regions provide evidence for functionally significant structures. We also detect a polymorphism in one of the toad proenkephalin genes, mapping 1.5 kilobases (kb) 5' of the main exon; it is caused by an insertion/deletion of a 1-kb repetitive sequence which has the characteristics of a transposable element.     

Genetics: relatedness among east African coelacanths

Coelacanths were discovered in the Comoros archipelago to the northwest of Madagascar in 1952. Since then, these rare, ancient fish have been found to the south off Mozambique, Madagascar and South Africa, and to the north off Kenya and Tanzania -- but it was unclear whether these are separate populations or even subspecies. Here we show that the genetic variation between individuals from these different locations is unexpectedly low. Combined with earlier results from submersible and oceanographic observations, our findings indicate that a separate African metapopulation is unlikely to have existed and that locations distant from the Comoros were probably inhabited relatively recently by either dead-end drifters or founders that originated in the Comoros.     

基于脑电的无创脑机接口研究进展

 脑机接口在脑与外部环境之间建立一种全新的不依赖于外周神经和肌肉的交流与控制通道，从而实现脑与外部设备的直接交互。脑电因具有非侵入式、易于使用及设备价格低廉等特点而被广泛应用于脑机接口。本文回顾了基于脑电的无创脑机接口的研究历史，从脑机接口的类型、应用及面临的挑战3个方面综述了脑机接口的研究现状，并展望了脑机接口的未来发展前景。     

Localization of nitric oxide synthase indicating a neural role for nitric oxide.

Nitric oxide (NO), apparently identical to endothelium-derived relaxing factor in blood vessels, is also formed by cytotoxic macrophages, in adrenal gland and in brain tissue, where it mediates the stimulation by glutamate of cyclic GMP formation in the cerebellum. Stimulation of intestinal or anococcygeal nerves liberates NO, and the resultant muscle relaxation is blocked by arginine derivatives that inhibit NO synthesis. It is, however, unclear whether in brain or intestine, NO released following nerve stimulation is formed in neurons, glia, fibroblasts, muscle or blood cells, all of which occur in proximity to neurons and so could account for effects of nerve stimulation on cGMP and muscle tone. We have now localized NO synthase protein immunohistochemically in the rat using antisera to the purified enzyme. We demonstrate NO synthase in the brain to be exclusively associated with discrete neuronal populations. NO synthase is also concentrated in the neural innervation of the posterior pituitary, in autonomic nerve fibres in the retina, in cell bodies and nerve fibres in the myenteric plexus of the intestine, in adrenal medulla, and in vascular endothelial cells. These prominent neural localizations provide the first conclusive evidence for a strong association of NO with neurons.     

2018年脑机接口研发热点回眸

 脑机接口提供了人脑与外部设备之间的直接通信通道,它的独特之处是不依赖于外周神经和肌肉组织。近年来,脑机接口领域发展迅速,脑机接口研究正在不断扩展,其应用范围也在不断扩大。本文综述了2018年脑机接口领域在系统应用与关键技术方面所取得的重要研究进展,展望了脑机接口智能化、移动化的发展新趋势,并提出脑机接口伦理风险的新思考。     

南方鲇口外味觉系统的外周神经分支和中枢神经系统的组织学研究

应用组织学切片和光镜观察的方法,对南方鲇口外味觉系统的外周神经分支和初级中枢结构的组织构筑进行研究,绘制出南方鲇口外味觉系统图谱,表明南方鲇的外周神经分支与初级中枢之间存在相互对应关系.作为鱼类味觉初级中枢的面叶,其组织结构的复杂性可能与食性及其对食物的好恶有关.     

Segmental patterns of neuronal development in the chick hindbrain

Identification of specific neuronal populations and their projections in the developing hindbrain reveals a segmental organization in which pairs of metameric epithelial units cooperate to generate the repeating sequence of cranial branchiomotor nerves. Neurogenesis also follows a two-segment repeat, suggesting parallels with insect pattern formation.     

A Survey of MRI-Based Brain Tumor Segmentation Methods

Brain tumor segmentation aims to separate the different tumor tissues such as active cells, necrotic core,and edema from normal brain tissues of White Matter（WM）, Gray Matter（GM）, and Cerebrospinal Fluid（CSF）. MRIbased brain tumor segmentation studies are attracting more and more attention in recent years due to non-invasive imaging and good soft tissue contrast of Magnetic Resonance Imaging（MRI） images. With the development of almost two decades, the innovative approaches applying computer-aided techniques for segmenting brain tumor are becoming more and more mature and coming closer to routine clinical applications. The purpose of this paper is to provide a comprehensive overview for MRI-based brain tumor segmentation methods. Firstly, a brief introduction to brain tumors and imaging modalities of brain tumors is given. Then, the preprocessing operations and the state of the art methods of MRI-based brain tumor segmentation are introduced. Moreover, the evaluation and validation of the results of MRI-based brain tumor segmentation are discussed. Finally, an objective assessment is presented and future developments and trends are addressed for MRI-based brain tumor segmentation methods.