Expression of synapsin III in nerve terminals and neurogenic regions of the adult brain

We have examined the distribution of synapsin III in the adult mouse brain. Expression of synapsin III was observed in puncta throughout the brain, but demonstrated greater regional variation than that of synapsins I or II. This punctate staining is typical for synaptic vesicle proteins located at nerve terminals. These findings are also consistent with the well-established role for synapsins in regulating neurotransmitter release. However, unexpectedly, synapsin III was also highly expressed in the cell body and processes of immature neurons in neurogenic regions of the adult brain, such as the hippocampal dentate gyrus, rostral migratory stream, and olfactory bulb. Many synapsin III-positive neurons also reacted with an antibody directed toward polysialylated-neuronal cell adhesion molecule, a marker of immature, migrating neurons. These results suggest that synapsin III may also play a role in adult neurogenesis.     

A possible effect of the methylxanthines caffeine,theophylline and aminophylline on postnatal myelination of the rat brain

In order to determine whether an amino acid may act as a neurotransmitter in the perforant pathway we examined the effect of lesion of rat entorhinal cortex on the concentrations of various amino acids in the hippocampus proper and fascia dentata. Only the aspartic acid content was found significantly decreased after the lesion. This decreases is not due to a loss from target cells of the perforant pathway, but rather to a loss from its degenerating terminals.     

Expression patterns of epidermal growth factor receptor and fibroblast growth factor receptor 1 mRNA in fetal human brain

Factors that interact with the epidermal growth factor and fibroblast growth factor receptors have numerous effects in the central nervous system (CNS), inducing the proliferation of CNS stem cells and astrocytes and the survival and differentiation of neurons. Both receptors are expressed in the embryonic rodent brain in proliferative and nonproliferative regions, suggesting roles in numerous developmental processes. However, the roles of these factors in human brain development are not known. In the current study, we examined the expression of human epidermal growth factor receptor (HEGFR) and human fibroblast growth factor receptor 1 (HFGFR1) mRNAs in the human fetal brain. The expression of both receptors is strikingly conserved relative to previously reported patterns in the rodent. In the germinal zones, the sites of cellular proliferation, HFGFR1 was expressed primarily in the ventricular zone, whereas HEGFR was expressed in the subventricular zone, suggesting different roles in CNS progenitor proliferation. Differential expression was also observed in other brain areas examined, including the hippocampus and the cerebellum. The current study suggests that HEGFR and HFGFR1 are likely to play different roles during human brain development, but that these roles will be similar to those observed in the rodent brain.     

Proliferation of progenitor cells in the adult rat brain correlates with the presence of vimentin-expressing astrocytes

It is well established that proliferation of progenitor cells persists within the hippocampal dentate gyrus (DG) and the subventricular zone of the lateral ventricle (SVZ) in the adult brain. The aim of the present study was to determine whether the rate of cell proliferation within these germinative zones could be correlated to the occurrence of a particular glial environment. The cell proliferation marker bromodeoxyuridine (BrdU) was administrated to rats under different physiological and experimental conditions known to modify the rate of progenitor cell proliferation. Within both germinative zones, BrdU-labeled nuclei were associated with cell bodies immunostained for the neuronal marker polysialylated neural cell adhesion molecule, but not for the glial markers glial fibrillary acidic protein (GFAP) or vimentin (VIM). In all the rats examined, however, proliferating (BrdU-labeled) cells always exhibited close relationships with immature-like astrocytes that expressed both GFAP and VIM. There was a dramatic decrease of cell proliferation in the DG from both the aged rats and the corticosterone-treated adult rats that was correlated with a decreased expression of vimentin by the astrocytes present in this region. In contrast, both cell proliferation and vimentin expression were only slightly affected in the SVZ from these two treatment groups. Conversely, after either adrenalectomy or a surgical lesion through the lateral hippocampus, the increase in cell proliferation observed in the DG was correlated to the occurrence of an increased number of GFAP and VIM double immunostained structures in these regions. All together, these data suggest that immature-like astrocytes present in the germinative zones may provide a microenvironment involved in sustaining the proliferation of progenitor cells.     

Differential expression patterns of mRNAs for members of the fibroblast growth factor receptor family,FGFR-1–FGFR-4, in rat brain

We have examined the region-specific expression of mRNAs for four members of rat FGF receptor family, FGFR-1, FGFR-2, FGFR-3, and FGFR-4, in rat brain by in situ hybridization. The FGFR-1, FGFR-2, and FGFR-3 mRNAs were expressed widely but differentially in the brain. However, the FGFR-4 mRNA was not expressed in the brain. The FGFR-1 mRNA was strongly expressed in several regions including the hippocampus, cerebellum, and pedunculoptine tegmental nucleus. The FGFR-2 mRNA expression was high in the choroid plexus, and moderate in the fiber-rich regions (the corpus callosum, external capsule, and internal capsule) and the olfactory bulb. The FGFR-3 mRNA was expressed diffusely in the brain. We have also examined the cellular localization of these mRNAs in the brain. Although the FGFR-1 mRNA was expressed preferentially in neurons, the FGFR-2 and FGFR-3 mRNAs were expressed preferentially in glial cells. The present findings that the FGFR-1, FGFR-2, and FGFR-3 mRNAs were expressed widely but with region-and cell-specificity in the brain indicate that these receptors have different roles in the brain. © 1994 Wiley-Liss, Inc.     

Neurogenesis in neonatal rat brain is regulated by peripheral injection of basic fibroblast growth factor (bFGF)

Many major diseases of human brain involve deficiencies of select neuronal populations. As one approach to repair, we examined regulation of neurogenesis directly in vivo, employing postnatal day 1 (P1) cerebellar cortex, which is composed primarily of granule neurons and dividing precursors. We focused on basic fibroblast growth factor (bFGF), which stimulates precursor mitosis in culture and which is highly expressed in cerebellum during neurogenesis. Subcutaneous injection of bFGF increased [³H]thymidine ([³H]dT) incorporation, a marker for DNA synthesis, by 50% in whole cerebellar homogenates, suggesting that peripherally administered factor altered ongoing neural proliferation. Further, assay of isolated granule precursors revealed a 4-fold increase in [³H]dT incorporation following in vivo bFGF treatment, indicating that granule neuroblasts were the major bFGF-responsive population. Morphologic analysis indicated that twice as many granule precursors were in S-phase of the mitotic cycle after peripheral bFGF. To determine whether other neurogenetic populations respond to peripheral bFGF, we examined additional brain regions in vivo. bFGF stimulated DNA synthesis by 68% in hippocampus, and by > 250% in pontine subventricular zone (SVZ). In contrast, incorporation was not altered in basal pons or cerebral cortex, regions in which neurogensis has already ceased. To define potential direct actions of peripherally administered factor, ¹²⁵I-bFGF was used to study distribution. Intact 18 kDa ¹²⁵I-bFGF was recovered from brain following peripheral injection, suggesting that the factor acted directly to stimulate mitosis in dividing neuroblasts. The stimulation of neuronal proliferation by exogenous bFGF suggests that the factor normally regulates neurogenesis, and provides new therapeutic approaches to promote functional recovery from nervous system diseases. © 1996 Wiley-Liss, Inc.     

Coordination of fibroblast growth factor receptor 1 (FGFR1) and fibroblast growth factor-2 (FGF-2) trafficking to nuclei of reactive astrocytes around cerebral lesions in adult rats

Traumatic injury to the adult central nervous system initiates a cascade of cellular and trophic events, culminating in the formation of a reactive gliotic scar through which transected axons fail to regenerate. Levels of fibroblast growth factor-2 (FGF-2), a potent gliogenic and neurotrophic factor, together with its full-length receptor, FGF receptor 1 (FGFR1) are coordinately and significantly increased postinjury in both nuclear and cytoplasmic fractions of extracted cerebral cortex biopsies after a penetrant injury. FGFR1 is colocalized with FGF-2 in the nuclei of reactive astrocytes, and here FGF-2 is associated with nuclear euchromatin. This study unequivocally demonstrates coordinate up-regulation and trafficking of FGF-2 and full-length FGFR1 to the nucleus of reactive astrocytes in an in vivo model of brain injury, thereby implicating a role in nuclear activity for these molecules. However, the precise contribution of nuclear FGF-2/FGFR1 to the pathophysiological response of astrocytes after injury is undetermined.     

Localization of insulin-like growth factor I (IGF-I)-like immunoreactivity in the developing and adult rat brain

The cellular distribution of insulin-like growth factor I (IGF-I) immunoreactivity was examined in the rat brain from embryonic day 15 to maturity. IGF-I immunoreactivity was found in the perikarya of neurons distributed along the entire extension of the neuronal tube in all the embryonic ages studied (E15, E17, E19 and E21). In E21 animals, the majority of immunoreactive neurons was located in the olfactory bulb, cerebral cortex, hippocampus, striatum, diencephalon, mesencephalic colliculi, trigeminal ganglion and in motoneurons of the brainstem. In 10- and 20-day-old rats, in addition to the above areas, IGF-I immunoreactivity was also observed in capillary walls, ependymal cells, choroid plexus, glial cells and most fiber paths. In postnatal ages, immunoreactivity in neuronal somas mainly restricted to the cell nuclei. However, IGF-I immunoreactivity in the neuron cytoplasm was observed in 20-day-old rats treated with colchicine while fiber paths and neuronal cell nuclei were negative in these animals. In the telencephalon of 20-day-old rats injected with colchicine, the most intense immunoreactive neurons were observed in the olfactory bulb, cerebral cortex, tenia tecta, hippocampus, islands of Calleja, septal nuclei, striatum, endopyriform nucleus and amygdala. Most diencephalic nuclei, the substantia nigra, the mesencephalic colliculi, Purkinje cells in the cerebellar cortex and several nuclei in mesencephalon, pons and medulla oblongata were also immunoreactive. In adult rats injected with colchicine, IGF-I immunoreactivity was located in the same areas as in 20-day-old rats. The number of immunoreactive cells and the intensity of the staining was reduced in adult rats as compared to that found in young postnatal animals. Glial cells were negative in adults. The distribution of IGF-I in the developing and mature rat brain supports the proposed roles of this peptide as a neuromodulator and neurotrophic factor.     

Alterations of NMDAR1 and NMDAR2A/B immunoreactivity in the hippocampus after perforant pathway lesion

Immunohistochemical techniques were employed to examine the changes in immunolabeling of the N‐methyl‐d ‐aspartate (NMDA) receptor subunits NMDAR1 and NMDAR2A/B within the hippocampus 1, 3, 7, 14 and 30 days after a unilateral perforant pathway lesion was made in a rat brain. At 1 day post‐lesion, we observed a decrease in NMDAR1 immunolabeling in the granule cells in the dentate gyrus as well as in the mossy cells in the polymorphic region ipsilateral to the lesion, while an increase in diffuse neuropil labeling was observed. At 3 days post‐lesion, we observed a marked increase in NMDAR1 immunolabeling in the outer molecular layer of the dentate gyrus as well as in the stratum moleculare in the CA fields ipsilateral to the lesion. Although this increase was less marked at 7 and 14 days post‐lesion, an increase in NMDAR1 immunolabeling was evident at 30 days post‐lesion. In contrast, although a transient increase in NMDAR2A/B immunolabeling was observed in the outer molecular layer at 3 days post‐lesion, no other changes were detectable at any of the time points examined. Our study suggests that each subunit of the NMDA receptor displays a different response to deafferentation of the perforant pathway. We have previously observed that changes in the immunoreactivity of the receptor subunits of another class of glutamate receptor, α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoaxolepropionate (AMPA), occur at 30 days post‐lesion but not after a relatively short survival time. NMDA receptor subunits demonstrate an earlier response to the loss of the perforant pathway fibers than do the AMPA receptor subunits.     

Laminins in the adult and aged brain

Only recently have we become aware of the diversity of laminins in adult brain. In vascular basement membranes, the expression of at least five laminin chains has been demonstrated, suggesting the presence of several laminin variants. Recent ultrastructural evidence for heterogeneity of laminin expression in vascular basement membranes is an exciting finding, and points to structural and functional diversity of the basement membranes around cerebral blood vessels. Neuronal laminin-like immunoreactivity in the adult brain is a consistent observation, but does not fit well in the current understanding of the physiology and biochemistry of heterotrimeric laminins. Nevertheless, the unique localization of putative neuronal laminins warrants their further characterization. The structure and function of laminins produced by reactive astrocytes in the lesioned adult brain and that seen in the brains of Alzheimer disease (AD) patients are not yet resolved. The possibility that these laminins play an important role in the CNS response to injury and pathophysiology of AD is expected to be a fruitful investigation. The next decade should see very significant advances in the characterization of brain laminins and, hopefully, in the elucidation of functional correlates to the structural diversity of laminins in brain.     

不同鼠龄大鼠成纤维细胞生长因子及相关基因在牵引成骨局部的表达

背景：成纤维细胞生长因子及相关基因表达在骨再生和修复过程中起着重要的作用。 目的：通过对不同鼠龄大鼠在同样条件下牵引成骨的比较，进一步验证成纤维细胞生长因子及相关基因在成骨局部的表达水平与年龄的关系，及其在大鼠胫骨牵引成骨过程中对新骨形成的影响。 设计、时间及地点：随机对照动物实验，于2007-01/03在中南大学附属三医院中心实验室完成。 材料：健康雄性SD大鼠20只，3月龄和12月龄各10只，分为青年组和老年组。 方法：所有大鼠接受左胫骨中上段低能截骨，安置体外延长固定架。第2天起开始每天进行胫骨延长，速率为0.2 mm， 2次/d，共14 d。第15天，处死大鼠，采集胫骨标本。 主要观察指标：以X射线片定量分析新骨密度和新骨面积；以组织学定量分析骨内膜成骨和骨膜成骨；以反转录-聚合酶链反应分析成纤维细胞生长因子及相关基因的表达。 结果：青年组大鼠牵引区的新生成骨面积和新生骨密度，以及骨内膜成骨和骨膜成骨百分比均显著高与老年组大鼠(P < 0.05或0.01)；成纤维细胞生长因子及相关基因在老年组大鼠的表达水平明显低于青年组。 结论：老年大鼠骨形成障碍可能与局部生长因子表达降低，从而导致成骨细胞功能低下密切相关。     

Localization of basic fibroblast growth factor,a mitogen and angiogenic factor,in human brain tumors

Summary Fibroblast growth factor (FGF) is a potent angiogenic factor and a mitogen for a variety of mesoderm-and neuroectoderm-derived cell types (e.g., fibroblasts, endothelial cells, astrocytes, oligodendrocytes). After application of a monospecific polyclonal antiserum, we localized basic FGF on frozen sections of 73 human brain tumors using immunohisto-chemistry. FGF was present in a variable number of tumor cells (16/16 astrocytomas, 5/5 ependymomas, 0/3 benign and 4/7 anaplastic oligodendrogliomas, 11/12 glioblastomas, 11/11 meningiomas, 6/6 neurilemmomas, 0/3 pituitary adenomas, 2/2 choroid plexus papillomas, 0/1 neurocytoma, 2/2 benign fibrous histiocytomas, 2/5 metastatic carcinomas). FGF was detected in vascular cells of 59 tumors and in fibroblasts of connective tissue stroma from all papillomas and metastases. These results tend to indicate FGF involvement in the malignant progression of gliomas due to an autocrine or paracrine action. Histopathological aspects of malignant gliomas (e.g., pseudopalisading or pathological vessels) could be related to FGF activity.     

Differential induction of nerve growth factor and basic fibroblast growth factor mRNA in neonatal and aged rat brain

Stimulation of glucocorticoid or β-adrenergic receptors (BAR) has been shown to increase nerve growth factor (NGF) biosynthesis in adult rat brain. Little is known about the role of these receptors in the regulation of NGF expression in neonatal and aged brain. We have examined the effect of the synthetic glucocorticoid dexamethasone (DEX) and the BAR agonist clenbuterol (CLE) on the levels of NGF mRNA in neonatal (8 day old), adult (3 month old) and aged (24 month old) rats. By 3 h, DEX (0.5 mg/kg, s.c.) evoked a comparable increase in NGF mRNA in the cerebral cortex and hippocampus in both 8-day and 3-month-old rats. In contrast, CLE (10 mg/kg, i.p.) failed to change NGF mRNA levels in neonatal rats, while increasing (2–3-fold) NGF mRNA levels in the cerebral cortex of adult rats. In 24-month-old rats, both DEX and CLE elicited only a modest increase in NGF mRNA. This increase was, however, anatomically and temporally similar to that observed in adult animals. The weak effect of DEX or CLE was not related to a down-regulation of receptor function because both DEX and CLE were able to elicit a comparable increase in the mRNA levels for basic fibroblast growth factor (FGF2) in neonatal, adult and aged rat brain. Our data demonstrate that induction of NGF expression by neurotransmitter/hormone receptor activation varies throughout life and suggest that pharmacological agents might be useful tools to enhance trophic support in aging.     

Expression of free fatty acid receptor GPR40 in the neurogenic niche of adult monkey hippocampus

Polyunsaturated free fatty acids (PUFAs) are known to play critical roles for the development, maintenance, and function of the brain. Recently, we reported that G-protein coupled receptor 40 (GPR40), one type of PUFA receptors, is expressed throughout the adult primate central nervous system including the hippocampus. This opens a possibility that PUFA might act as extracellular signaling molecules at the GPR40 receptor to regulate neuronal function. Here we studied protein expression of GPR40 in the neurogenic niche of the adult monkey hippocampus under normal and postischemic conditions. Confocal laser microscope analysis of immunostained sections revealed GPR40 immunoreactivity in neural progenitors, immature neurons, astrocytes and endothelial cells of the subgranular zone (SGZ) of the dentate gyrus (DG); a well-known neurogenic niche within the adult brain. Immunoblotting analysis showed that the GPR40 protein increased significantly in the second week after global cerebral ischemia as compared with the control. This was compatible with the postischemic increment of GPR40-positive cells in the SGZ as detected by immunofluorescence imaging. Taken together with our previous findings of the SGZ progenitor cell upregulation after ischemia, the present data suggest that PUFA such as docosahexaenoic acid may act via GPR40 to regulate adult hippocampal neurogenesis in primates.     

Retroviral lineage analysis of fibroblast growth factor receptor signaling in FGF2 inhibition of oligodendrocyte progenitor differentiation

Fibroblast growth factor 2 (FGF2) inhibits oligodendrocyte progenitor cell (OPC) differentiation during development and limits remyelination following chronic demyelination. The current study examines the mechanism underlying this effect of FGF2 expression on OPC differentiation. Retroviral lineage tracing demonstrates a direct in vivo effect of FGF receptor (FGFR) signaling on OPC differentiation. Retrovirus expressing a dominant negative FGFR construct (FGFRdn) and green fluorescent protein (GFP) was injected into the dorsal columns of postnatal day 7 (P7) mice followed by perfusion at P28. Among the GFP-labeled cells, FGFRdn retrovirus generated a higher proportion of oligodendrocytes than did control infections. This result from FGFRdn expression in OPCs was similar to the result obtained in our previous study using control retrovirus in FGF2 null mice. Further, in vitro retroviral siRNA expression distinguishes the function of specific FGFR isoforms in OPC responses to FGF2. FGF2 inhibition of OPC differentiation was effectively blocked by siRNA targeted to FGFR1, but not FGFR2 or FGFR3. We propose a model of direct FGF2 activation of FGFR1 leading to inhibition of OPC differentiation. This signaling pathway may be an important regulator of oligodendrocyte generation during myelination in development and may perturb OPC generation of remyelinating oligodendrocytes in demyelinating disease.     

Nerve growth factor receptor immunoreactivity in the rat septohippocampal pathway: a light and electron microscope investigation.

Nerve growth factor receptor immunoreactivity in the septohippocampal pathway of adult Fischer 344 rats was assessed at the light and electron microscope level. The medial septum possesses immunoreactive somata, dendrites, axons, and terminals. Immunostained somata are either bipolar or multipolar in appearance. Dendritic processes of immunoreactive septal neurons are categorized into two groups: proximal dendrites with smooth plasma membranes and distal dendrites with numerous swellings. Immunoreactive axons within the septum are long and slender and do not possess varicosities. At the electron microscope level, immunoreactivity is confined predominantly to the plasma membrane of cell bodies and dendrites of septal neurons, as well as to the plasma membrane of axons and terminals. Both immunoreactive and nonimmunoreactive terminals that contain clear, spherical vesicles are observed contacting immunoreactive dendrites and somata. Although accumulations of vesicles are evident within these terminals at sites of contact, distinct synaptic specializations are difficult to distinguish due to the localization of reaction product on the apposing plasma membranes. Axons possessing immunoreactivity are also observed in the fimbria-fornix pathway, a major source of afferent inputs to the hippocampus. Immunoreactive axons and terminals are topographically organized in the hippocampal dentate gyrus. The density of immunostained axons and terminals is highest immediately adjacent to the granular layer. In comparison, a moderate density of immunoreactive axons is found in the outer molecular layer and a weak density in the inner molecular, granular, and polymorphic layers. Immunoreactivity is found on the plasma membrane of small unmyelinated axons and terminals aggregated into clusters throughout the dentate gyrus. Definitive examples of axosomatic and axodendritic synapses possessing immunoreactivity presynaptically are not observed. Immunoreactive profiles within the medial septum and hippocampus also circumfuse a small number of intracerebral vessels. Ultrastructural examination reveals that immunoreactivity is present within a narrowed extension of the subarachnoid space and appears to be closely associated with the plasma membrane of leptomeningeal cell processes. The present study provides direct evidence for the cellular distribution of nerve growth factor receptor immunoreactivity in the medial septum and dentate gyrus in the adult rat and offers new insight into the ultrastructural localization of nerve growth factor receptor among septal cholinergic neurons and their efferent projections to the hippocampus.     

Increased basic fibroblast growth factor (bFGF) immunoreactivity at the site of focal brain wounds

Basic fibroblast growth factor (bFGF) is a polypeptide found within the CNS with potent effects on the survival and proliferation of CNS glia and endothelial cells, and on the survival and outgrowth of CNS neurons. Immunohistochemical methods were used to examine relative changes in the levels and distribution of bFGF following focal brain injury. Two monospecific antisera to bFGF were used to immunostain intact mature rat brain, and brain in which a focal mechanical lesion had been made in the dorsolateral cerebral cortex one week previously. In the intact brain, staining was localized primarily in neuronal cell bodies, especially in limbic structures. In injured brain, a marked increase of bFGF immunoreactivity was found at the borders of lesions, localized to the dense accumulation of cells, many of which resembled ‘reactive’ astroglia. Such increases in local bFGF concentrations may contribute to the cascade of cellular changes — including glial and capillary proliferation, and neural sprouting — that follows focal brain injury.     

Characterization of the Netrin/RGMa receptor neogenin in neurogenic regions of the mouse and human adult forebrain

In the adult rodent forebrain, astrocyte‐like neural stem cells reside within the subventricular zone (SVZ) and give rise to progenitors and neuroblasts, which then undergo chain migration along the rostral migratory stream (RMS) to the olfactory bulb, where they mature into fully functional interneurons. Neurogenesis also occurs in the adult human SVZ, where neural precursors similar to the rodent astrocyte‐like stem cell and neuroblast have been identified. A migratory pathway equivalent to the rodent RMS has also recently been described for the human forebrain. In the embryo, the guidance receptor neogenin and its ligands netrin‐1 and RGMa regulate important neurogenic processes, including differentiation and migration. We show in this study that neogenin is expressed on neural stem cells (B cells), progenitor cells (C cells), and neuroblasts (A cells) in the adult mouse SVZ and RMS. We also show that netrin‐1 and RGMa are ideally placed within the neurogenic niche to activate neogenin function. Moreover, we find that neogenin and RGMa are also present in the neurogenic regions of the human adult forebrain. We show that neogenin is localized to cells displaying stem cell (B cell)‐like characteristics within the adult human SVZ and RMS and that RGMa is expressed by the same or a closely apposed cell population. This study supports the hypothesis that, as in the embryo, neogenin regulates fundamental signalling pathways important for neurogenesis in the adult mouse and human forebrain. J. Comp. Neurol. 518:3237–3253, 2010. © 2010 Wiley‐Liss, Inc.