树鼩脑三维结构重建的研究 Ⅲ.脑外形立体结构的计算机辅助绘图

作者曾经详细介绍过树鼩脑切片二维结构重建的数据采集、计算机处理数据的算法及图形生成技术。在此基础上,本文介绍树鼩脑三维结构重建的数学模型及其自动生成三维图形的基本技术与计算机绘图的部分结果。     

脑空间信息学——连接脑科学与类脑人工智能的桥梁

提出脑空间信息学是示踪、测量、分析、处理和呈现跨层次多尺度脑空间信息数据的一门综合与集成的科学.讨论了脑空间信息学的研究内容、技术体系和关键科学问题,分析了其学科定位,展望了其应用前景.以显微光学切片断层成像为核心的全脑网络可视化技术体系的建立,标志着脑空间信息学这一新兴交叉学科日臻成熟.基于具有明确时空尺度和位置信息的神经元类型、神经环路和网络、血管网络等三维精细脑结构与功能大数据,提取跨层次、多尺度的脑连接时空特征,脑空间信息学将帮助科学家更好地破译脑功能与脑疾病,并推动类脑人工智能的发展.     

东亚飞蝗脑的形态学观察及三维重建

本文主要研究东亚飞蝗Locusta migratoria manilansis(Meyen)脑部的形态结构及其三维重建模型。采用石蜡包埋切片,在光镜下观察了东亚飞蝗脑部的形态结构,其由前脑、中脑和后脑3部分组成。为了获得整只蝗虫的连续、完整的图像数据集,采用冰冻切片技术将冰冻包埋剂(OCT)包埋的飞蝗成虫做连续切片。然后利用图像处理方法对飞蝗脑部的连续切片进行配准、分割,再用三维重建软件Image-Pro Plus(IPP)对分割后的脑部二维图像序列进行三维重建,构建出的飞蝗脑部三维结构模型可以任意旋转,能从不同角度观察。其结果为蝗虫生理和防蝗治蝗提供科学依据。     

中缅树鼩脑结构特征

树鼩脑的比较解剖学资料尚缺,它对树鼩的分类地位及其在神经科学研究上的应用都很有意义。本文对六例成年中缅树鼩,经10％福尔马林溶液灌流固定冰冻连续额状与矢状切片,改良美兰染色法制片,光镜观察,神经细胞构筑学分析并与猴相应脑结构进行对照。部分丘脑核团作了显微测量,用3/4πR~3公式计算了它们与丘脑的体积; 用πab公式计算了大脑与前额区型皮质的面积。发现下列特征:①大脑皮质属新皮质者占59％。可分为前额区型皮质;中央额区型皮质;顶区型皮质;颞区型皮质;枕区型皮质。额区型皮质占大脑皮质的     

脑网络：从脑结构到脑功能

人脑是自然界中最复杂的系统之一,不同的功能区域相互作用、互相协调,共同构成一个网络来发挥其功能。人脑是一个复杂的网络,具有高效的“小世界”拓扑属性。本文从脑结构到脑功能方面介绍了从不同模态影像学数据构造脑网络的主要进展,并探讨不同的脑疾病患者脑网络拓扑结构是否发生了异常,以及这些异常特征能否用来进行疾病分类,最后对本领域未来的研究做了简单的展望。     

大鼠脑内脑钠素mRNA分布的原位杂交

本工作以特异性的放射磷标记的鼠脑钠肽基因片段为探针,利用高灵敏度的原位杂交分析方法,对大鼠脑组织切片中脑钠肽的ｍＲＮＡ分布进行测定。结果表明,大鼠脑中存在脑钠肽基因的表达,其中下丘脑以及丘脑的边缘部分脑肽的ｍＲＮＡ浓度最高,杏仁核簇中浓度较高,嗅区其次,海马回和大脑皮层中浓度较低,小脑和延髓中几乎没有基因表达。     

β淀粉样蛋白斑块的高分辨全脑三维定量研究

中枢神经系统中β淀粉样蛋白斑块是阿尔兹海默症的主要病理特征之一,其负荷和数目的变化是病程发展的重要标志.已有研究主要是对局部脑组织进行二维切片成像,尚缺少在全脑三维空间对斑块进行高分辨率定量分析的研究方法.本文建立了适用于哺乳动物三维完整脑内β淀粉样蛋白斑块定量分析策略,包括全脑斑块快速荧光染色方法、基于荧光显微光学切片断层成像技术的高分辨全脑数据获取,以及斑块自动定位、统计数目等.与免疫组化染色比较,证明本方法对直径大于10μm的斑块检出率为97.71%±0.18%.并以0.32μm×0.32μm×2μm的成像分辨率,获取了5XFAD转基因小鼠全脑Aβ斑块分布数据集,首次以脑区/核团的三维轮廓划分出立体区域,定量统计了90个亚区内Aβ斑块的数量及分布密度.本文建立的快速、精准、价廉的方法将有助于全面高效地研究阿尔兹海默症致病机理和药效评估.     

编者按: 脑成像与脑网络

揭示脑的奥秘是人类面临的最大挑战之一。神经元是构成神经系统结构与功能的基本单位。神经元与神经元之间通过突触实现信息交互,并构成神经环路或神经网络。神经环路有局部的,也有跨脑区或长程的,甚至全脑尺度的。神经环路则是脑实现神经信息处理的基本单元。若干神经环路构成脑网络。脑网络研究已经成为脑功能与脑疾病研究领域的热点。 在国家自然科学基金委员会和科技部“973计划”等项目的支持下,我国科学家在这一领域已经开展了卓有成效的工作。2011年第393次香山科学会议“脑网络组及其临床应用的前沿科学问题”曾对此进行过比较深入的研讨。为促进对该领域现状及发展的了解,本期汇集了2篇述评和2篇研究论文,作为脑成像与脑网络专题发表,以飨读者。 利用9.4T功能磁共振成像(fMRI)获得轻度麻醉状态下大鼠静息状态及刺激激活的数据,通过互相关分析构建节点之间的相关系数矩阵并计算相应的网络参数,赖永秀等人报道了大鼠感觉运动系统静息态脑网络的研究成果,发现感觉运动系统在静息态时的脑网络具有小世界属性。 扩散磁共振成像(dMRI)的出现为大脑结构与功能研究提供了全新的检测手段,雷皓等报道了小动物高分辨扩散磁共振成像数据分析方法,为小动物脑dMRI研究提供了统一图像模板与完善的计算方法,对于检测神经纤维微观结构的变化,以及临床诊断,将具有极其重要的意义。 神经环路功能变化的实时在体监测是研究脑网络不可或缺的手段,曾绍群等评述了基于声光偏转器的快速无惯性随机扫描双光子显微成像技术的研究进展及发展趋势,指出该技术的进一步发展将为神经活动观测提供一种全新的方法,从而极大地推动脑科学研究的发展。 针对哺乳动物全脑的神经元网络成像,龚辉等从空间分辨率、探测范围、数据配准和成像速度等方面评述了光学显微水平全脑成像方法的研究进展,并讨论所面临的挑战。他们指出,要在全脑尺度获取突起水平分辨率的结构与功能数据,光学成像方法最为成熟。华中科技大学研制的MOST系统,率先获得了一系列高分辨率的完整大脑解剖数据集,该成果将在神经元网络的构建和脑功能与疾病研究中发挥重要作用。 我们期待更多、更好的有关脑成像与脑网络的论文发表,以更广泛和深入地促进我国脑科学研究领域的学术交流。     

辣根过氧化物酶标记与样品后染色联用在微观脑联结组学中的应用

三维电子显微成像(volume electron microscopy)是微观尺度脑联结组学(micro-brain connectomics)研究的主要研究手段.自动卷带式连续超薄切片-收片系统(automated tape-collecting ultramicrotome,ATUM)及扫描电镜序列成像系统的联合应用,是三维电镜成像中一种重要的技术手段.该方法利用卷带式收集超薄切片,形成完整的样品切片库,进而在后续成像中形成样品三维电镜成像数据库.根据ATUM系统镜外切片-收片、保留样本切片库等特点,对相应的生物样品制备方法进行改进,包括树脂配方及树脂渗透方式改良,神经元细胞膜辣根过氧化物酶(horseradish peroxidase,HRP)稀疏化标记与样本切片库后染色联用——从而很大程度上减少样品切片的褶皱率,并使得在整体高衬度的样品图像库中高效地识别神经元身份成为可能,最终获得符合脑联结组学所需的高质量成像数据.     

用计算机绘制脑图

圣地亚哥超级计算机中心的菲尔·默可利(Phil-Mercurio)首次制作出了一张彩色三维人脑图,他使用一个叫Wavefront的绘图包对一个正常人脑的数据进行处理。这些人脑的数据是由圣地亚哥的加州大学的神经科学家罗伯特·利文斯顿收集的,他把经过石蜡包埋并削成薄层的脑组织切片拍摄下来,然后把     

THE HYALURONIDASE OF BRAIN

Abstract— Hyaluronidase (hyaluronate glycanohydrolase, EC 3.2.1.35), with a pH optimum of 3.7, was detected in rat and bovine brain. It degraded hyaluronic acid and, at a slower rate, chondroitin sulphate to a mixture of higher oligosaccharides with N-acetylhexosamine at the reducing end. The enzyme was enriched 5- and 6-fold in a crude lysosomal fraction of rat brain or bovine cerebral cortex, and was further purified to a total enrichment of 9-fold by ammonium sulphate fractionation. The enzyme activity in grey matter was more than twice that found in white matter, and there was no significant change in enzyme activity as a function of increasing age from the neonatal to the adult rat brain. The level of hyaluronidase activity in rat brain is considerably greaterthan that required to account for the rate of catabolism of hyaluronic acid and chondroitin sulphate measured in vivo.     

THE METABOLISM OF TRITIATED DOPAMINE IN REGIONS OF THE RAT BRAIN IN VIVO—I

Abstract— A simple combination of acid- and base-exchange resin columns enabled a more complete separation of amine, acid and neutral metabolites of catecholamines from individual small brain samples to be made. Fractions containing individual catecholamines or metabolites were obtained in aqueous eluates suitable for fluorimetric or radioisotopic analysis. With consistent intraventricular injection and brain dissection techniques, this separation method enables a study of the metabolism of catecholamines in regions of the rat brain and the effects of drugs on this metabolism.     

THE NATURE OF THE INCREASED RATE OF DNA SYNTHESIS IN SCRAPIE-AFFECTED MOUSE BRAIN

—In vivo studies have been made of the incorporation of radioactive thymidine into acid insoluble components of control and scrapie-affected mouse brain. Experiments with hot trichloroacetic acid extracts of brain and with purified preparations of DNA have confirmed that there is an increased rate of DNA synthesis in scrapie brain which is entirely associated with nuclei. No increase was found in the rate of DNA synthesis in cytoplasmic fractions of scrapie brain. Hydroxyapatite chromatography of heat denatured and renatured DNA suggests that in scrapie brain there is a similar increase in the rates of synthesis of the poorly, moderately and highly reiterated (i.e. satellite) species of nuclear DNA. Experiments involving brain dissection indicate that the increased rate of DNA synthesis in scrapie does not take place exclusively in the subependymal layer of the lateral ventricles. From these and previously reported studies using radioautographic techniques it is concluded that the increased DNA synthesis in scrapie brain is not associated specifically with cells undergoing mitosis.     

THE MEASUREMENT OF TRIGLYCERIDE IN BRAIN AND THE METABOLISM OF BRAIN TRIGLYCERIDE IN VITRO

Abstract—

• 1 Triglyceride has been isolated from brain by thin-layer chromatography and determined by absorption of the carbonyl group at 1740 cm^?1. The means of yields from whole mouse brain, whole rat brain, rat brain grey matter, rat brain stem, and incubated slices of rat brain cortex were 0.15–0.17 μmole/g tissue.
• 2 The distribution of fatty esters varied from preparation to preparation. Palmitate, stearate and oleate usually occurred in greatest amounts. Hydrolysis of a preparation of triglyceride from whole rat brain with pancreatic lipase indicated that palmitate was equally distributed between the α and β esters.
• 3 [1-¹⁴C]Acetate was rapidly incorporated into triglyceride of slices of incubated rat brain cortex. When the resulting triglyceride was hydrolysed with pancreatic lipase the distribution of radioactivity amongst the hydrolysis products was consistent with both the α and β esters of the triglyceride having been radioactively labelled.

     

EFFECT OF TRANQUILIZERS ON REGIONAL DISTRIBUTION OF ASCORBIC ACID IN THE RAT BRAIN

—Studies were made of the effects of fluphenazine, chlorpromazine and triflupromazine on tissue concentration, liver synthesis of ascorbic acid and its distribution in different areas of the brain. All the three drugs were found to increase liver concentration and synthesis of the vitamin at 24 hr after administration of a single oral dose of the vitamin, but only fluphenazine was found to increase its concentration in the adrenals and brain; the increase in the latter case was found to vary in different regions of the brain, the olfactory lobes, hypothalamus and residual brain showing maximum increases, andthe basal ganglia, visual cortex and remaining dorsal cortex showing minimum increases. The effects were found to be reversed 72 hr after drug treatment.     

金丝猴(RHINOPITHECUS)脑的外部形态

本文是对三种金丝猴脑的外部形态的观察结果表明:金丝猴的大脑皮层除存在猴科固有的全部沟裂外,还较其他猴科动物具有更多的副沟。大脑的沟型与疣猴亚科的特征完全吻合,但是很多特点都较叶猴更近似于长臂猿。另外,除了蚓叶和蚓结节较小,四叠体的下丘较猕猴发达以外,金丝猴的小脑和脑干均与猴科的一般特征无明显差异。     

TRIPHOSPHOINOSITIDE PHOSPHODIESTERASE IN DEVELOPING BRAIN OF THE RAT AND IN SUBCELLULAR FRACTIONS OF BRAIN

Abstract— An assay system for the measurement of triphosphoinositide phosphodiesterase in homogenates of rat brain is described. With triphosphoinositide (TPI) as substrate, and in the presence of 0·1 m -KCI and saturating amounts of diethyl ether, the activity of phosphodiesterase in myelinated brain was 400–500 μmoles of TPI hydrolysed per g wet wt. per hr. One quarter of the adult level of the enzyme was present in rat brain one day after birth, with the remainder being added prior to and during the early stages of myelination. On subfractionation of brain homogenates, substantial activity of the enzyme was located in the soluble portion and in the paniculate fractions enriched in myelin and synaptosomes. The enzyme associated with the particulate fractions could not be detached from the membranes by any of several methods employed. There was a rough correlation between distribution of phosphodiesterase and that of 5'-nucleotidase, an enzyme associated with plasma membrane in a number of tissues. Some implications of the results are discussed.     

THE PENETRATION OF THE MEMBRANE OF BRAIN MITOCHONDRIA BY ANIONS

The permeability of the membrane of rat brain non-synaptosomal mitochondria, towards inorganic and substrate anions, was assessed by measuring the rate of swelling that occurred when mitochondria were suspended in an iso-osmotic solution of a permeant anion, in the presence of a permeant cation such as NH⁺₄ or K⁺ in the presence or absence of valinomycin. In NH⁺₄-phosphate swelling was higher than it was in KCI or K⁺-phosphate, which showed the prevalence of the mechanism of phosphate transport previously demonstrated in liver mitochondria. The entry of succinate and L-malate seemed to require the presence in the inner mitochondrial membrane of specific carriers. as previously postulated for liver mitochondria, but the rate of swelling of brain mitochondria was lower than that of liver organelles. In K⁺-succinate, in the presence of antimycin, added ATP induced swelling and this was attributable to the simultaneous permeation both of the anion and the cation. Fumarate did not penetrate into brain mitochondria. Practically no swelling was recorded in NH⁺₄ or K⁺-citrate, which indicated that this anion penetrated poorly into the isolated brain mitochondria even in the presence of malate. Swelling occurred in NH⁺₄-L-glutamate in the presence of rotenone, and the entry of this anion seemed to follow a gradient of concentration although the presence of a specific translocator in the inner mitochondrial membrane might be concerned. The entry of glutamate was independent of that of phosphate and N-ethylmaleimide appeared to be a specific inhibitor of this entry. Swelling in K⁺-L-glutamate, in the presence of rotenone, was enhanced by the addition of valinomycin or ATP but in the latter case when osmotic equilibrium was reached swelling was not reversed by oligomycin. In conclusion, the lesser extent of swelling of isolated brain mitochondria compared with liver mitochondria could be attributed to the heterogeneity of the populations of these organelles, each population possessing its own characteristics of membrane permeability. Observations of electron micrographs of brain mitochondria incubated in iso-osmotic substrate anions confirmed the heterogeneous rate of swelling of these particles.     

THE EFFECT OF DEVELOPMENT ON THE GANGLIOSIDES OF RAT AND PIG BRAIN

Abstract— The ganglioside content of the forebrain, brain stem and cerebellum have been studied, in the rat at various ages from 1 day to 27 months, and in the pig at various ages from 93 days gestation to 30 months. Each part of the brain was analysed for total ganglioside NANA and for four major gangliosides (G_Ml, G_D1a, G_Dlb and G_T1 in the nomenclature of S vennerholm , 1963). In the rat forebrain, the concentration of ganglioside NANA rose rapidly between 1 and 21 days after birth, fell to 3 months and subsequently rose to a mature value at 6 months. In the rat cerebellum, the peak concentration was reached at 2 months and the lower adult value at 9 months, whilst in the brain stern, the concentration rose more slowly and had a broad peak from 15 days to 2 months. Values are also given for the changes in the total amounts in each brain part. The changes in the concentrations and total amounts of ganglioside NANA, in the three parts of the pig brain were, on the whole, similar to those in rat brain except that the percentage distribution of the major gangliosides had almost attained the mature pattern at birth. In the forebrain of both species, the disialoganglioside, G_D1a, accounted for the highest percentage of the total gangliosides. The results are discussed with respect to their possible structural significance.     

THE MITOCHONDRIAL REDOX STATE OF RAT BRAIN

The use of the glutamate dehydrogenase (EC 1.4.1.3) and β-hydroxybutyrate dehydrogenase (EC 1.1.1.30) reactions for the calculation of the mitochondrial redox state of brain has been examined. To prevent post-mortem anoxic metabolism, brains were frozen in less than a second by using a new technique. Levels of ketone bodies in brain were so low relative to the contamination by blood and extracellular fluid that calculation of the mitochondrial redox state using the β-hydroxybutyrate dehydrogenase reaction was not practical. The concentrations of the non-nucleotide substrates of the glutamate dehydrogenase reaction could be accurately measured in brain and themitochondrial [NAD⁺]/[NADH] ratio calculated from the ratio [α-oxoglutarate] [NH₄⁺]/[glutamate]. The calculation is valid if the ratio [α-oxoglutarate] [NH₄⁺]/[glutamate] in mitochondria is the same as that measured in whole tissue. The evidence supporting this conclusion is the near-equilibrium of the aspartate aminotransferase (EC 2.6.1.l) reaction in brain and the observation by others that the distribution of label between α-oxoglutarate and glutamate in brain, after administration of labelled precursors, conforms to expectation. The alanine aminotransferase (EC 2.6.1.2) reaction was not near equilibrium in brain, probably because of the low in vivo activity of the enzyme.