Glutamate recognition sites in human fetal brain

We used in vitro autoradiography with [3H]glutamate to examine the distribution of glutamate recognition sites in 18 and 21 week gestation human fetal brains. We found a wide distribution of [3H]glutamate binding in both specimens, in a pattern distinct from that reported in adult brain using the same autoradiographic methods. In fetal brain, prominent [3H]glutamate binding was evident in hippocampal formation, caudate-putamen, globus pallidus, subthalamic nucleus, reticular nucleus of thalamus and substantia innominata.     

Versican in human fetal skin development

 The extracellular matrix of human fetal skin differs substantially from that of adult skin. Fetal skin contains sparse amounts of fibrillar collagen enmeshed in a highly hydrated amorphous matrix composed of hyaluronan and sulfated proteoglycans. Both fetal and adult skin contain two major interstitial proteoglycans that are extracted by chaotrophic agents and detergents. These are the large chondroitin sulfate proteoglycan versican and the small dermatan sulfate proteoglycan decorin. For this study, proteoglycans extracted from fetal and adult skin were compared on Western blots to determine the relative amounts of versican. Decorin present in the same samples provided an internal standard for these studies. Fetal skin differed from adult skin in that it contained a significantly higher proportion of versican than did adult skin. Immunohistochemical studies compared early-fetal with mid-fetal skin and found that versican was a significant component of the interstitial extracellular matrix at both of these stages of skin development. However, by the mid-fetal period, interstitial versican became restricted to the upper half of the dermis, although versican also continued to be highly expressed around hair follicles, glands, and vasculature in the lower half of the dermis. Fetal skin extracts differed from an adult skin extract by the presence of a 66-kDa protein immunologically related to versican and by the absence of a 17-kDa core protein of a proteoglycan related to decorin. Both of these molecular species may represent degradation products of their respective proteoglycans. Monoclonal antibodies which detect epitopes in native chondroitin sulfate glycosaminoglycan chains recognized versican extracted from fetal skin. However, the tissue distribution of these antigens did not entirely conform to that for versican core protein, suggesting that versican in different regions of the skin may be substituted with glycosaminoglycan chains with different microchemistries. The results of these studies indicate that human fetal skin is structurally different from adult skin in terms of both the distribution and the composition of the large, aggregating chondroitin sulfate proteoglycan versican. Accepted: 13 July 1998     

Interactions of neurons and astrocytes during growth and development of human fetal brain in vitro

Morphologic details of interactions between neurons and astrocytes from human fetal cerebrum during the early phases of in vitro growth in dissociated cultures are described. There is an intimate relationship between these two cell types characterized by aggregation of neurons along the surface of the soma and processes of astrocytes and subsequent migration along astrocytic processes. Neurons form long processes that establish contact with other astrocytes. The occurrence of these features in dissociated cultures strengthens the significance of similar findings observed in the outgrowth of organotypic cultures. Dissociated cultures establish, furthermore, that the production and growth of neurites and survival of neurons during this early period in vitro are dependent upon the development of this close relationship with astrocytes. Another feature of this cellular interaction observed at the ultrastructural level in organotypic cultures is the development of an unusual type of junction between neurites and astrocytes, characterized by deposition of intermembranous electron-dense material. The findings suggest that the relationship between neurons and astrocytes is an important aspect of neural ontogenesis and lend further support to the thesis that astocytes play a role in neuronal migration and differentiation. The combined criteria for identification of neurons and astrocytes in culture based upon multiple procedures, including bright field stains, phase contrast microscopy, electron microscopy, and immunofluorescence are also reviewed in detail.     

Early fetal development of the human cerebellum

Early cerebellum development in humans is poorly understood. The present study histologically examined sections from 20 human embryos and fetuses at 6 weeks (12-16 mm crown-rump length (CRL); 4 specimens), 7-9 weeks (21-39 mm CRL; 8 specimens), 11-12 weeks (70-90 mm CRL; 4 specimens) and 15-16 weeks (110-130 mm CRL; 4 specimens). During 7-9 weeks (approximate CRL 28 mm), the rhombic lip (a pair of thickenings of the alar plate) protruded dorsally, bent laterally, extended ventrolaterally and fused with the medially located midbrain. During that process, the primitive choroid plexus appeared to become involved in the cerebellar hemisphere to form a centrally located eosinophilic matrix. At that stage, the inferior olive had already developed in the thick medulla. Thus, the term 'bulbo-pontine extension' may represent an erroneous labeling of a caudal part of the rhombic lip. The cerebellar vermis developed much later than the hemisphere possibly from a midline dark cell cluster near the aqueduct. In the midline area after 12 weeks (80 mm CRL), the growing bilateral hemispheres seem to provide mechanical stress such as rotation and shear that cause the development of several fissures much deeper than those on the hemisphere. The rapidly growing surface germinal layer may be a minor contributor to this vermian fissure formation. The vermian fissures seem to enable inside involvement of the surface germinal cells, and to induce cytodifferentiation of the vermis. Consequently, in the early stages, it appears that the cerebellar hemisphere and vermis develop independently of each other.     

Do oculomotor neuroblasts migrate across the midline in the fetal rat brain?

Summary Toluidine blue-stained semithin sections and Cajal-Castro preparations are used to study in rat fetuses whether oculomotor neuroblasts migrate across the midline at a certain period of development. In confirmation of previous studies, a group of oculomotor neuroblasts was detected which first grow cytoplasmic processes into the mesencephalic midline, and afterwards translocate their somata towards the midline, between the 12th and the 15th days of gestation. At this moment a midline mass of neuroblasts characterizes the meeting at this landmark of both left and right migrating neuroblastic groups. No crossing oculomotor axons yet are demonstrable with reduced silver techniques.In further stages of development the neuroblasts continue their migration until they arrive at the contralateral nucleus at the 16th and 17th day of gestation. At the midline the mass of neuroblasts disappears gradually and crossed oculomotor axons become visible.The electron microscope was then used to study ultrastructurally the migrating motoneurons. It was discovered that no preexisting structure guides their movement by contact. Their leading processes show no filopodial activity, and contain abundant microtubules and thick bundles of neurofilaments in eccentric position. The neuroblasts carry their axon across the midline as a trailing process.     

Associations between brain structure and sleep patterns across adolescent development

Study ObjectivesStructural brain maturation and sleep are complex processes that exhibit significant changes over adolescence and are linked to many physical and mental health outcomes. We investigated whether sleep–gray matter relationships are developmentally invariant (i.e. stable across age) or developmentally specific (i.e. only present during discrete time windows) from late childhood through young adulthood.MethodsWe constructed the Neuroimaging and Pediatric Sleep Databank from eight research studies conducted at the University of Pittsburgh (2009–2020). Participants completed a T1-weighted structural MRI scan (sMRI) and 5–7 days of wrist actigraphy to assess naturalistic sleep. The final analytic sample consisted of 225 participants without current psychiatric diagnoses (9–25 years). We extracted cortical thickness and subcortical volumes from sMRI. Sleep patterns (duration, timing, continuity, regularity) were estimated from wrist actigraphy. Using regularized regression, we examined cross-sectional associations between sMRI measures and sleep patterns, as well as the effects of age, sex, and their interaction with sMRI measures on sleep.ResultsShorter sleep duration, later sleep timing, and poorer sleep continuity were associated with thinner cortex and altered subcortical volumes in diverse brain regions across adolescence. In a discrete subset of regions (e.g. posterior cingulate), thinner cortex was associated with these sleep patterns from late childhood through early-to-mid adolescence but not in late adolescence and young adulthood.ConclusionsIn childhood and adolescence, developmentally invariant and developmentally specific associations exist between sleep patterns and gray matter structure, across brain regions linked to sensory, cognitive, and emotional processes. Sleep intervention during specific developmental periods could potentially promote healthier neurodevelopmental outcomes.     

波形蛋白阳性细胞在人胚脑中的分布

波形蛋白 (Ｖｉｍｅｎｔｉｎ)是中间丝蛋白的一种 ,其表达在神经系统发育过程中有一定的时间性 ,主要表达于尚未发生终末分化的细胞 ,即神经祖细胞 /前体细胞。神经祖细胞 /前体细胞是一类尚保留有分化潜能的细胞 ,是神经系统发育到一定阶段的细胞群体 ,具有有限的自我更新 (增殖 )和分化能力[1～ 3 ] 。该细胞移植后可以发生增殖和分化 ,为治疗神经系统退行性疾病开辟了一条新的途径[1] 。目前关于人胚胎神经干细胞 /祖细胞或前体细胞分布的研究尚少 ,本研究用2 7+ 2 周人胚脑 ,通过对Ｖｉｍｅｎｔｉｎ阳性细胞形态特征及其分布情况的研究 …     

胎脑与成年脑皮质组织的蛋白质组学分析

目的 应用蛋白质组技术研究成年和胚胎脑皮质蛋白质组表达差异,初步探索在胎脑与成年人中脑蛋白的变化情况.方法 收集成人无病变区正常脑皮质1份和水囊引产胎脑组织脑皮质2份(3月胎脑组织和5月胎脑组织),提取总蛋白,通过双相电泳分离蛋白,每组样品均重复电泳,使用PDQuest7.0图像分析软件分析电泳图谱,得到具有表达差异的蛋白质,分别选取在大脑发育过程中逐步降低和逐步升高的差异点及在胎脑成脑蛋白表达中差异两倍以上的蛋白点,应用胶内酶切和基质辅助激光解析电离飞行时间质谱(matrix-assisted laser desorption/ionization-time of flight-time of flight,MALDI-TOF-TOF)进行鉴定,得到肽指纹图谱,并查阅蛋白质数据库得到蛋白质的相关信息.结果 (1)成人脑组织、3月胎脑组织和5月胎脑组织的脑组织蛋白图谱分别测得642、511和527个点,图象匹配率达87%.成人脑蛋白图谱中碱性蛋白点明显多于胎脑的;(2)成人脑组织、3月胎脑组织和5月胎脑组织的脑组织单独特有蛋白分别为:172、171和152个;(3)与成人脑组织比较,3月胎脑组织和5月胎脑组织的差异蛋白质分别为131和115个;差异在2倍以上的蛋白点为60和40个,其中低表达的蛋白点分别有24和17个,高表达蛋白点为36和23个;(4)白蛋白、磷酸丙糖异构酶等8种蛋白表达均有不同的变化.脂肪酸结合蛋白7和未命名蛋白只在3月胎脑高表达,而5月胎脑和成人组均无表达;核酮糖1,5-二磷酸羧化酶/加氧酶和转导素只在成人脑中高表达,胎脑无表达.血清白蛋白却随着大脑发育逐渐降低.ATP合成酶、线粒体F0复合体亚基、磷酸丙糖异构酶随着大脑发育而逐渐升高.结论 人类从胚胎期到成人发育过程中脑部蛋白质可能会发生明显改变,这些差异蛋白的发现为研究脑发育机理提供了极其有益的线索.

Abstract：

Objective To study the differences of protein expression levels in the brain cortex of human fetus and adult with proteomics technique, and provide preliminary data on the change of proteins during brain development. Methods Proteins extracted from human temporal lobes in fetal (3 month and 5 month respectively) and adult (30 years old) brain were separated by two-dimensional gel electrophoresis (2DE).The proteins were then stained with colloidal Coomassie blue to produce a high-resolution map of the proteiome.The differential protein spots were analyzed by PDQuest 7.0 software and 8 spots,which were gradually reduced or gradually increased in brain development process and the protein spots of difference over two-fold in the brain,were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF/TOF).Results (1) On average, 642, 511 and 527 protein spots could be obtained in the temporal lobes of adult, 3 month and 5 month fetus. The matching rate of images was 87%. The basic proteins in adult brain were obviously much more than that in the fetus; (2) There were 172, 171 and 152 singular protein spots in temporal lobes of adult, 3 month and 5 month fetus respectively. (3) Compared with adult, there were 131 and 115 different protein spots in the 3 month and 5 month fetus respectively. There were 60 and 40 protein spots with more than 2 fold difference, among which 24 and 17 were down-regulated, and 36 and 23 were up-regulated respectively. (4) There was different expression in proteins such as serum albumin, triosephosphate isomerase, etc. in the 3 groups. Fatty acid binding protein 7 and unnamed proteins were only highly expressed in the 3 month brain;ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit and transducin beta-1 subunit were up-regulated in adult brain. Serum albumin decreases gradually with brain development. However, ATP synthase, mitochondrial F0 complex, and triosephosphate isomerase increase gradually with brain development. Conclusion The proteins of human brain cortex were obviously changed from embryonic stage to adult. The differentially displayed proteins may provide further insight into the understanding of development of human brain.     

Neural correlates of gesture processing across human development

Co-speech gesture facilitates learning to a greater degree in children than in adults, suggesting that the mechanisms underlying the processing of co-speech gesture differ as a function of development. We suggest that this may be partially due to children's lack of experience producing gesture, leading to differences in the recruitment of sensorimotor networks when comparing adults to children. Here, we investigated the neural substrates of gesture processing in a cross-sectional sample of 5-, 7.5-, and 10-year-old children and adults and focused on relative recruitment of a sensorimotor system that included the precentral gyrus (PCG) and the posterior middle temporal gyrus (pMTG). Children and adults were presented with videos in which communication occurred through different combinations of speech and gesture during a functional magnetic resonance imaging (fMRI) session. Results demonstrated that the PCG and pMTG were recruited to different extents in the two populations. We interpret these novel findings as supporting the idea that gesture perception (pMTG) is affected by a history of gesture production (PCG), revealing the importance of considering gesture processing as a sensorimotor process.     

Electrophysiological evaluation of human brain development

The complex development of the human brain during infancy can only be understood by convergent structural, functional, and behavioral measurements. The evaluation of event-related potentials (ERPs) is the most effective current way to look at infant brain function. ERP paradigms can be used to examine the simple transmission of sensory information to the cortex and the discrimination of this information within the cortex. The main developmental changes involve localization of function as the brain becomes tuned to the experienced world (related to synaptic pruning) and a speeding up of transmission as pathways become efficient (related to myelination). ERPs that occur in relation to different temporal aspects of a stimulus (onset-responses, offset-responses, sustained potentials and steady-state responses) and ERPs recorded at different stimulus rates may help track perceptual development from a temporal perspective. Particularly important in human development are the ERP changes that occur in the processing of speech sounds and human faces. At present, ERP studies can show differences between groups of subjects that can demonstrate developmental disorders or elucidate mechanisms of development. However, because of their variability, ERPs are less helpful in determining whether an individual infant is developing abnormally. Where possible, ERP measurements should be used in conjunction with behavioral tests so as to relate performance to mechanism, and with anatomical brain measurements to relate mechanism to structure.     

Evidence for differential human slow-wave activity regulation across the brain

The regulation of the timing of sleep is thought to be linked to the temporal dynamics of slow‐wave activity [SWA, electroencephalogram (EEG) spectral power in the ～0.75–4.5 Hz range] in the cortical non‐rapid eye movement (NREM) sleep EEG. In the two‐process model of sleep regulation, SWA was used as a direct indication of sleep debt, or Process S. Originally, estimation of the latter was performed in a gross way, by measuring average SWA across NREM–REM sleep cycles, fitting an exponential curve to the values thus obtained and estimating its time constant. In later studies, SWA was assumed to be proportional to the instantaneous decay rate of Process S, rather than taken as a direct reflection of S. Following up on this, we extended the existing model of SWA dynamics in which the effects of intrusions of REM sleep and wakefulness were incorporated. For each subject, a ‘gain constant’ can be estimated that quantifies the efficiency of SWA in dissipating S. As the course of SWA is variable across cortical locations, local differences are likely to exist in the rate of discharge of S, eventually leading to different levels of S in different cortical regions. In this study, we estimate the extent of local differences of SWA regulation on the basis of the extended model of SWA dynamics, for 26 locations on the scalp. We observed higher efficiency of SWA in dissipation of S in frontal EEG derivations, suggesting that SWA regulation has a clear local aspect. This result further suggests that the process involved in (local) SWA regulation cannot be identical to the Process S involved (with Process C) in effectual determination of sleep timing – a single behaviour that cannot vary between locations on the scalp. We therefore propose to distinguish these two representations and characterize the former, purely SWA‐related, as ‘Process Z’, which then is different for different locations on the scalp. To demonstrate those differences, we compare the gain constants derived for the medial EEG derivations (Fz, Cz, Pz, Oz) with each other and with the decay rate derived from SWA values per NREM–REM sleep cycle.     

Telencephalic origin of pulvinar neurons in the fetal human brain

Summary Our previous autoradiographic study of fetal human brain fragments exposed supravitally to thymidine-H³ had suggested that the primitive ependyma of the third ventricle ceases neuron production at a time when the pulvinar is only slightly developed. We sought a source of additional pulvinar neurons by examining serial horizontal sections through brains of 5- to 40-week fetuses. In the nearby telencephalon lies the ganglionic eminence, composed of germinal and immature cells coating the fetal corpus striatum and bulging into the lateral ventricle. It contains numerous proliferating cells to the end of gestation. Young cells appear to stream from it, cross beneath the sulcus terminalis to enter the diencephalon, and form a hitherto-undescribed layer, the corpus gangliothalamicus. This structure is found consistently just under the external surface of the developing pulvinar of fetuses from the 18th to the 34th weeks of gestation. A 22-week specimen freshly prepared by the rapid Golgi method shows a progression of cell forms from simple elongate bipolar cells in the part of the corpus gangliothalamicus closest to the telencephalon, through a series of gradations to multipolar young neurons in the most medial and deep parts of the structure, where it merges into the pulvinar proper. We conclude that many of the neurons of the pulvinar, a very large component of the human thalamus, arise in the telencephalon and migrate to the diencephalon during the fifth to eight lunar months of gestation.Supported by research grant 5 RO1-NB07053-02 from the National Institute of Neurological Diseases and Stroke, National Institutes of Health     

A new approach for exploring functional development of fetal brain pathways

Study of functional development of central pathways in fetuses is challenging due to the lack of methods available. In this article, we present a novel approach to test if and when central functional pathways are established by a combination of mapping with c‐fos and chronically cannulated fetuses in utero. This approach is based on brain structures such as circumventricular organs (CVOs) that lack the blood–brain barrier (BBB), but are rich in sensors to peripheral signals and contain projections to other brain regions. If signaling molecules in the blood that are too large to cross the BBB induced c‐fos expression in both the CVOs and other nuclei inside the fetal brain, this can be evidence that projections from the CVOs to those nuclei are established and functional. This is a useful real‐time method to explore the status of functional maturation of pathways between the CVOs and other brain areas in developing fetuses. Notably, at the moment, this is the first and only in vivo method that can detect functional projections in the fetal brain in vitro. © 2009 Wiley Periodicals, Inc. Dev Psychobiol 51: 384–388, 2009.     

Programmed demethylation in CpG islands during human fetal development

The mechanism for establishing the DNA methylation patterns observed in adult mammalian tissues is not well understood. To determine when adult patterns are established for housekeeping genes, we examined the clustered CpGs in genes on the human active X chromosome (PGK, G6PD, P3, GdX, HPRT) and the autosomal gene,DHFR. We find unique methylation patterns present at theP3 locus in all tissues analyzed from 6- to 9-week fetal specimens, and at theHPRT locus in adrenal gland DNA at this stage of development. Adult patterns are established subsequently by demethylating specific CpGs. Our results show that demethylating events affecting CpG islands are programmed during mammalian fetal development. They suggest that the process of de novo methylation in the fetus methylates at least some sites in the 3 region of the CpG islands in active genes and that adult patterns are established at 6–14 weeks developmental age by sequence-specific demethylation.     

Upper arm posture during human embryonic and fetal development

The upper extremity posture is characteristic of each Carnegie stage (CS), particularly between CS18 and CS23. Morphogenesis of the shoulder joint complex largely contributes to posture, although the exact position of the shoulder joints has not been described. In the present study, the position of the upper arm was first quantitatively measured, and the contribution of the position of the shoulder girdle, including the scapula and glenohumeral (GH) joint, was then evaluated. Twenty-nine human fetal specimens from the Kyoto Collection were used in this study. The morphogenesis and three-dimensional position of the shoulder girdle and humerus were analyzed using phase-contrast X-ray computed tomography and magnetic resonance imaging. Both abduction and flexion of the upper arm displayed a local maximum at CS20. Abduction gradually decreased until the middle fetal period, which was a prominent feature. Flexion was less than 90° at the local maximum, which was discrepant between appearance and measurement value in our study. The scapular body exhibited a unique position, being oriented internally and in the upward direction, with the glenoid cavity oriented cranially and ventrally. However, this unique scapular position had little effect on the upper arm posture because the angle of the scapula on the thorax was canceled as the angle of the GH joint had changed to a mirror image of that angle. Our present study suggested that measuring the angle of the scapula on the thorax and that of the GH joint using sonography leads to improved staging of the human embryo.     

Count and heterogeneity of human fetal blood lymphocytes in the course of fetal development

Blood specimens from 89 human embryos and fetuses were analyzed by immunological methods during gestation weeks 4–40. All formed elements circulate in fetal blood starting from week 13 of gestation. Lymphocytes predominate among blood leukocytes, because normally lymphocytosis is an inherent, feature of blood. T cells and their subpopulations: active T lymphocytes, Tγ lymphocytes, and theophylline-sensitive and risistant, cells are present. B lymphocytes are represented by cells with immunoglobulins M and G, zero cells, and large granular lymphocytes. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 126., No. 9, pp. 331–333, September, 1998     

Diversity of astroglial responses across human neurodegenerative disorders and brain aging

Astrogliopathy refers to alterations of astrocytes occurring in diseases of the nervous system, and it implies the involvement of astrocytes as key elements in the pathogenesis and pathology of diseases and injuries of the central nervous system. Reactive astrocytosis refers to the response of astrocytes to different insults to the nervous system, whereas astrocytopathy indicates hypertrophy, atrophy/degeneration and loss of function and pathological remodeling occurring as a primary cause of a disease or as a factor contributing to the development and progression of a particular disease. Reactive astrocytosis secondary to neuron loss and astrocytopathy due to intrinsic alterations of astrocytes occur in neurodegenerative diseases, overlap each other, and, together with astrocyte senescence, contribute to disease‐specific astrogliopathy in aging and neurodegenerative diseases with abnormal protein aggregates in old age. In addition to the well‐known increase in glial fibrillary acidic protein and other proteins in reactive astrocytes, astrocytopathy is evidenced by deposition of abnormal proteins such as β‐amyloid, hyper‐phosphorylated tau, abnormal α‐synuclein, mutated huntingtin, phosphorylated TDP‐43 and mutated SOD1, and PrP^res, in Alzheimer's disease, tauopathies, Lewy body diseases, Huntington's disease, amyotrophic lateral sclerosis and Creutzfeldt‐Jakob disease, respectively. Astrocytopathy in these diseases can also be manifested by impaired glutamate transport; abnormal metabolism and release of neurotransmitters; altered potassium, calcium and water channels resulting in abnormal ion and water homeostasis; abnormal glucose metabolism; abnormal lipid and, particularly, cholesterol metabolism; increased oxidative damage and altered oxidative stress responses; increased production of cytokines and mediators of the inflammatory response; altered expression of connexins with deterioration of cell‐to‐cell networks and transfer of gliotransmitters; and worsening function of the blood brain barrier, among others. Increased knowledge of these aspects will permit a better understanding of brain aging and neurodegenerative diseases in old age as complex disorders in which neurons are not the only players.