Mesencephalic dopaminergic cells exhibit increased density of neural cell adhesion molecule and polysialic acid during development

Polysialic acid in the rat brainstem and thoracolumbar spinal cord: Distribution, cellular location, and comparison with mouse

Polysialic acid (polySia), a homopolymer of α2,8-linked glycans, is a posttranslational modification on a few glycoproteins, most commonly in the brain, on the neural cell adhesion molecule. Most research in the adult central nervous system has focused on its expression in higher brain regions, where its distribution coincides with regions known to exhibit high levels of synaptic plasticity. In contrast, scant attention has been paid to the expression of polySia in the hindbrain. The main aims of the study were to examine the distribution of polySia immunoreactivity in the brainstem and thoracolumbar spinal cord, to compare the distribution of polySia revealed by two commercial antibodies commonly used for its investigation, and to compare labeling in the rat and mouse. We present a comprehensive atlas of polySia immunoreactivity: we report that polySia labeling is particularly dense in the dorsal tegmentum, medial vestibular nuclei and lateral parabrachial nucleus, and in brainstem regions associated with autonomic function, including the dorsal vagal complex, A5, rostral ventral medulla, A1, and midline raphe, as well as sympathetic preganglionic neurons in the spinal cord and central targets of primary sensory afferents (nucleus of the solitary tract, spinal trigeminal nucleus, and dorsal horn [DH]). Ultrastructural examination showed labeling was present predominantly on the plasma membrane/within the extracellular space/in or on astrocytes. Labeling throughout the brainstem and spinal cord were very similar for the two antibodies and was eliminated by the polySia-specific sialidase, Endo-NF. Similar patterns of distribution were found in rat and mouse brainstem with differences evident in DH.

A Comparative Study of Preparation Techniques for Improving the Viability of Nigral Grafts using Vital Stains, in Vitro Cultures, and in Vivo Grafts

The intracerebral transplantation of embryonic dopaminergic nigral neurons, although relatively successful, leads to a fairly low yield of surviving cells. Many factors may influence the viability of dopaminergic grafts and one of these is the preparation of the tissue prior to transplantation. We have investigated the effects of different steps during the preparation and storage of embryonic rat nigral cell suspensions on their subsequent survival at a variety of different time points using a combination of techniques and studies. For studies concerned with the first 24 h we employed vital stains, in the period covering the next 7 days we used in vitro cultures, and in the long term experiment we used in vivo grafts. The results suggest that nigral cell suspensions may remain sufficiently viable for grafting for much longer periods than previously reported. In addition a number of parameters which affect cell survival have been characterised, including the age of the embryonic donor tissue, the use of proteolytic enzymes and the trituration procedure used during the preparation of the suspension. The optimal preparation technique, therefore, uses E13-E14 embryos with the dissected ventral mesencephalon being incubated in purified 0.1% trypsin solutions for 60 min and triturated using a flame polished Pasteur pipette. This may have important implications in improving intracerebral transplantation for Parkinson's disease.

Effect of Cell Adhesion Molecules on the Neurite Outgrowth of Induced Pluripotent Stem Cell-Derived Dopaminergic Neurons

Intrastriatal transplantation of dopaminergic neurons has been shown to be a potentially very effective therapeutic approach for the treatment of Parkinson's disease (PD). With the detection of induced pluripotent stem cells (iPSCs), an unlimited source of autologous dopaminergic (DA) neurons became available. Although the iPSC-derived dopaminergic neurons exhibited most of the fundamental dopaminergic characteristics, detailed analysis and comparison with primary DA neurons have shown some aberrations in the expression of genes involved in neuronal development and neurite outgrowth. The limited outgrowth of the iPSC-derived DA neurons may hamper their potential application in cell transplantation therapy for PD. In the present study, we examined whether the forced expression of L1 cell adhesion molecule (L1CAM) and polysialylated neuronal cell adhesion molecule (PSA-NCAM), via gene transduction, can promote the neurite formation and outgrowth of iPSC-derived DA neurons. In cultures on astrocyte layers, both adhesion factors significantly increased neurite formation of the adhesion factor overexpressing iPSC-derived DA neurons in comparison to control iPSC-derived DA neurons. The same tendency was observed when the DA neurons were plated on postnatal organotypic striatal slices; however, this effect did not reach statistical significance. Next, we examined the neurite outgrowth of the L1CAM- or PSA-NCAM-overexpressing iPSC-derived DA neurons after implantation in the striatum of unilaterally 6-hydroxydopamine (6-OHDA)-lesioned rats, the animal model for PD. Like the outgrowth on the organotypic striatal slices, no significant L1CAM- and PSA-NCAM-enforced neurite outgrowth of the implanted DA neurons was observed. Apparently, induced expression of L1CAM or PSA-NCAM in the iPSC-derived DA neurons cannot completely restore the neurite outgrowth potential that was reduced in these DA neurons as a consequence of epigenetic aberrations resulting from the iPSC reprogramming process.

Mesencephalic GABA neuronal development: no more on the other side of oblivion

Midbrain GABA neurons, endowed with multiple morphological, physiological and molecular characteristics as well as projection patterns are key players interacting with diverse regions of the brain and capable of modulating several aspects of behavior. The diversity of these GABA neuronal populations based on their location and function in the dorsal, medial or ventral midbrain has challenged efforts to rapidly uncover their developmental regulation. Here we review recent developments that are beginning to illuminate transcriptional control of GABA neurons in the embryonic midbrain (mesencephalon) and discuss its implications for understanding and treatment of neurological and psychiatric illnesses.

Polysialic acid: biosynthesis, novel functions and applications

As an anti-adhesive, a reservoir for key biological molecules, and a modulator of signaling, polysialic acid (polySia) is critical for nervous system development and maintenance, promotes cancer metastasis, tissue regeneration and repair, and is implicated in psychiatric diseases. In this review, we focus on the biosynthesis and functions of mammalian polySia, and the use of polySia in therapeutic applications. PolySia modifies a small subset of mammalian glycoproteins, with the neural cell adhesion molecule, NCAM, serving as its major carrier. Studies show that mammalian polysialyltransferases employ a unique recognition mechanism to limit the addition of polySia to a select group of proteins. PolySia has long been considered an anti-adhesive molecule, and its impact on cell adhesion and signaling attributed directly to this property. However, recent studies have shown that polySia specifically binds neurotrophins, growth factors, and neurotransmitters and that this binding depends on chain length. This work highlights the importance of considering polySia quality and quantity, and not simply its presence or absence, as its various roles are explored. The capsular polySia of neuroinvasive bacteria allows these organisms to evade the host immune response. While this "stealth" characteristic has made meningitis vaccine development difficult, it has also made polySia a worthy replacement for polyetheylene glycol in the generation of therapeutic proteins with low immunogenicity and improved circulating half-lives. Bacterial polysialyltransferases are more promiscuous than the protein-specific mammalian enzymes, and new studies suggest that these enzymes have tremendous therapeutic potential, especially for strategies aimed at neural regeneration and tissue repair.

Ascending midbrain dopaminergic axons require descending GAD65 axon fascicles for normal pathfinding

The Nigrostriatal pathway (NSP) is formed by dopaminergic axons that project from the ventral midbrain to the dorsolateral striatum as part of the medial forebrain bundle. Previous studies have implicated chemotropic proteins in the formation of the NSP during development but little is known of the role of substrate-anchored signals in this process. We observed in mouse and rat embryos that midbrain dopaminergic axons ascend in close apposition to descending GAD65-positive axon bundles throughout their trajectory to the striatum. To test whether such interaction is important for dopaminergic axon pathfinding, we analyzed transgenic mouse embryos in which the GAD65 axon bundle was reduced by the conditional expression of the diphtheria toxin. In these embryos we observed dopaminergic misprojection into the hypothalamic region and abnormal projection in the striatum. In addition, analysis of Robo1/2 and Slit1/2 knockout embryos revealed that the previously described dopaminergic misprojection in these embryos is accompanied by severe alterations in the GAD65 axon scaffold. Additional studies with cultured dopaminergic neurons and whole embryos suggest that NCAM and Robo proteins are involved in the interaction of GAD65 and dopaminergic axons. These results indicate that the fasciculation between descending GAD65 axon bundles and ascending dopaminergic axons is required for the stereotypical NSP formation during brain development and that known guidance cues may determine this projection indirectly by instructing the pathfinding of the axons that are part of the GAD65 axon scaffold.

Atypical Parkinsonism in distal myopathy with rimmed vacuoles

A patient with distal myopathy with rimmed vacuoles (DMRV) exhibited Parkinsonism with a severe writing tremor that responded poorly to levodopa. Molecular genetic analysis revealed that the patient had the D176V/V572L compound heterozygous mutation in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene. Histopathological examination of a biopsied muscle specimen yielded findings compatible with those of DMRV, which is characterized by the presence of rimmed vacuoles without inflammatory cell infiltration in muscle fibers. The finding of normal cardiac meta-iodobenzylguanide uptake makes the possibility of incidental Parkinson's disease in this patient unlikely. These observations raise the possibility that atypical Parkinsonism is a rare complication of DMRV associated with GNE mutation.

How to make a mesodiencephalic dopaminergic neuron

Dopaminergic neurons located in the ventral mesodiencephalon are essential for the control of voluntary movement and the regulation of emotion, and are severely affected in neurodegenerative diseases such as Parkinson's disease. Recent advances in molecular biology and mouse genetics have helped to unravel the mechanisms involved in the development of mesodiencephalic dopaminergic (mdDA) neurons, including their specification, migration and differentiation, as well as the processes that govern axonal pathfinding and their specific patterns of connectivity and maintenance. Here, we follow the developmental path of these neurons with the goal of generating a molecular code that could be exploited in cell-replacement strategies to treat diseases such as Parkinson's disease.

Inhibition of proteoglycan synthesis affects neuronal outgrowth and astrocytic migration in organotypic cultures of fetal ventral mesencephalon

Grafting fetal ventral mesencephalon has been utilized to alleviate the symptoms of Parkinson's disease. One obstacle in using this approach is the limited outgrowth from the transplanted dopamine neurons. Thus, it is important to evaluate factors that promote outgrowth from fetal dopamine neurons. Proteoglycans (PGs) are extracellular matrix molecules that modulate neuritic growth. This study was performed to evaluate the role of PGs in dopamine nerve fiber formation in organotypic slice cultures of fetal ventral mesencephalon. Cultures were treated with the PG synthesis inhibitor methyl-umbelliferyl-beta-D-xyloside (beta-xyloside) and analyzed using antibodies against tyrosine hydroxylase (TH) to visualize dopamine neurons, S100beta to visualize astrocytes, and neurocan to detect PGs. Two growth patterns of TH-positive outgrowth were observed: nerve fibers formed in the presence of astrocytes and nerve fibers formed in the absence of astrocytes. Treatment with beta-xyloside significantly reduced the distance of glial-associated TH-positive nerve fiber outgrowth but did not affect the length of the non-glial-associated nerve fibers. The addition of beta-xyloside shifted the nerve fiber growth pattern from being mostly glial-guided to being non-glial-associated, whereas the total amount of TH protein was not affected. Further, astrocytic migration and proliferation were impaired after beta-xyloside treatment, and levels of non-intact PG increased. beta-Xyloside treatment changed the distribution of neurocan in astrocytes, from being localized in vesicles to being diffusely immunoreactive in the processes. To conclude, inhibition of PG synthesis affects glial-associated TH-positive nerve fiber formation in ventral mesencephalic cultures, which might be an indirect effect of impaired astrocytic migration.

Fibroblast growth factor-20 promotes the differentiation of Nurr1-overexpressing neural stem cells into tyrosine hydroxylase-positive neurons

Stem cells are currently considered as alternative cell resources for restorative transplantation strategies in Parkinson's disease. However, the mechanisms that induce differentiation of a stem cell toward the dopaminergic phenotype are still partly unknown thus hampering the production of dopaminergic neurons from stem cells. In the past, FGF-20 has been found to promote the survival of ventral mesencephalic (VM) dopaminergic (DA) neurons in culture. We hereby provide evidence that FGF-20, a growth factor of the FGF family, is expressed in the adult and 6-OHDA-lesioned striatum and substantia nigra, but is not expressed by VM glia or DA neurons, suggesting that FGF-20 may work on DA neurons in a paracrine- or target-derived manner. We also found that co-culture of Nurr1-NSCs with Schwann cells overexpressing FGF-20 induced the acquisition of a neuronal morphology by the NSCs and the expression of tyrosine hydroxylase (TH) as assessed by immunocytochemistry, cell ELISA, and Western blot analysis. RT-PCR showed, that both, Schwann cells and Nurr1-NSCs (differentiated or not), expressed the FGF-1 receptor suggesting that both direct and indirect actions of FGF-20 are possible. We show that differentiated Nurr1 cells retained both neuronal morphology and TH expression after transplantation into the striatum of 6-OHDA-lesioned postnatal or adult rats, but that neuritogenesis was only observed after postnatal grafts. Thus, our results suggest that FGF-20 promotes the differentiation of Nurr1-NSCs into TH-positive neurons and that additional factors are required for the efficient differentiation of DA neurons in the adult brain.

Adolescent exposure to cannabinoids induces long-lasting changes in the response to drugs of abuse of rat midbrain dopamine neurons

BACKGROUND

Recent studies have raised concerns about subtle long-lasting neurobiological changes that might be triggered by exposure to Cannabis derivatives, especially in a critical phase of brain maturation, such as puberty. The mesolimbic dopamine (DA) system, involved in the processing of drug-induced reward, is a locus of action of cannabinoids and endocannabinoids. Thus, we compared the effects of repeated cannabinoid administration in adolescent and adult rats on DA neuronal functions and responses to drugs of abuse.

METHODS

Single-unit extracellular recordings from antidromically identified mesoaccumbens DA neurons and from their target cells in the nucleus accumbens were carried out in urethane-anesthetized rats. Animals were pretreated during adolescence or adulthood, for 3 days, with the cannabinoid agonist WIN55212.2 (WIN) or vehicle and allowed a 2-week interval.

RESULTS

In cannabinoid-administered rats, DA neurons were significantly less responsive to the stimulating action of WIN, regardless of the age of pretreatment; however, in the adolescent group, but not in the adult, long-lasting cross-tolerance developed to morphine, cocaine, and amphetamine.

CONCLUSIONS

Our study suggests that an enduring form of neuronal adaptation occurs in DA neurons after subchronic cannabinoid intake at a young age, affecting subsequent responses to drugs of abuse.

Fetal lateral ganglionic eminence attracts one of two morphologically different types of tyrosine hydroxylase-positive nerve fibers formed by cultured ventral mesencephalon

The purpose of this study was to investigate the influence of fetal lateral ganglionic eminence (LGE) on nerve fiber outgrowth formed by fetal ventral mesencephalon (VM). Organotypic tissue cultures of fetal VM and LGE plated as single or cocultures were employed. Survival time was 3-21 days in vitro. Nerve fiber outgrowth and migration of astrocytes were analyzed using immunohistochemistry for tyrosine hydroxylase (TH) and S100. In addition, cultures were labeled with the TUNEL technique and with antibodies directed against neurofilament (NF) in order to study apoptosis and retraction of nerve fibers, respectively. The results revealed two morphologically different types of TH-positive outgrowth growing into the substrate. The initially formed TH-positive outgrowth radiated continuously without changing direction, while a second wave of TH-positive outgrowth became obvious when the initial growth already had reached a distance of approximately 1000 microm. The second wave of TH-positive outgrowth radiated from the tissue, but at a certain distance changed direction and formed a network surrounding the culture. The initially formed TH-positive growth was not associated with the presence of S100-positive astrocytes and avoided to grow into the LGE. At longer time points the first wave of TH-positive nerve fibers appeared dotted, with disrupted NF-immunoreactive fibers and in most cultures these long distance growing fibers had disappeared at 21 days in vitro. The second wave of TH-positive nerve fibers was growing onto a layer of glia and never reached the distance of the first wave. LGE became innervated by TH-positive fibers at the time point for when the second wave of TH-positive growth had been initiated, and the innervation appeared in TH-dense patches that also showed a high density of S100-positive astrocytes. Significantly increased TUNEL activity within LGE portion of cocultures was observed when TH-positive fibers entered the LGE and formed patches. In conclusion, two morphologically different types of TH-positive outgrowth were found and the initially formed fibers neither targeted the LGE nor were they guided by glial cells, but their potential to grow for long distances was high.

PSA-NCAM immunocytochemistry in the cerebral cortex and other telencephalic areas of the lizard Podarcis hispanica: differential expression during medial cortex neuronal regeneration

The lizard medial cortex, a region homologous to the mammalian dentate gyrus, shows postnatal neurogenesis and the surprising ability to replace its neurons after being lesioned specifically with the neurotoxin 3-acetylpyridine. As the polysialylated form of the neural cell adhesion molecule (PSA-NCAM) is expressed during neuronal migration and differentiation, we have studied its distribution in adult lizards and also during the lesion-regeneration process. In the medial cortex of control animals, many labeled fusiform somata, presumably corresponding to migratory neuroblasts, appeared in the inner plexiform layer. There were also scattered immunoreactive granule neurons in the cell layer. Double immunocytochemistry with 5'-bromodeoxyuridine revealed that some of the PSA-NCAM-expressing cells in the inner plexiform and cell layers were generated recently. PSA-NCAM immunoreactivity was also present in the dorsomedial, dorsal, and lateral cortices, as well as in the dorsal ventricular ridge, the nucleus accumbens, and the nucleus sphericus. Twelve hours after the injection of 3-acetylpyridine, some medial cortex granule neurons appeared degenerated, although some of them still expressed PSA-NCAM. One to 2 days after the injection, most granule neurons appeared degenerated and no PSA-NCAM immunoreactivity was detected in the medial cortex cell layer. Four to 7 days after treatment, abundant labeled fusiform cells populated the inner plexiform layer and some immunoreactive somata were seen in the cell layer. Fifteen to 30 days after the neurotoxin injection, the number of PSA-NCAM expressing granule neurons augmented considerably and the level was still above control levels in lizards that survived 42 days. Our results show for the first time the expression of PSA-NCAM in a reptile brain, where it appears to participate in the migration and differentiation of granule neurons during adult neurogenesis and regeneration.

Altered distribution of dopaminergic neurons in the brain of L1 null mice

Dopaminergic neurons of the mouse mesencephalon originate in the ventricular zone and migrate radially along radial glia then tangentially along nerve fibers that express the neural cell adhesion molecule L1 to form the substantia nigra (A9 group) and ventral tegmental area (VTA) (A10 group). The role of L1 in migration of dopaminergic neuronal precursors was investigated in L1 knockout mice by tyrosine hydroxylase (TH) immunostaining. An altered rostrocaudal distribution of dopaminergic neurons was observed within the substantia nigra and VTA of L1-minus mice. In L1-minus mice at postnatal day 0, TH-positive cells were present abnormally in the dorsomedial mesencephalon, suggesting impaired migration. Axons projecting from the substantia nigra to the caudate putamen also exhibited an abnormal targeting pattern. There was no evidence of dopaminergic cell loss in the mutant SN. Abnormal localization of dopaminergic neurons in L1-minus mice was also evident in the zona incerta of the thalamus (A13 group), and the arcuate (A12) and periventricular nucleus (A14) of the hypothalamus. Cell bodies and axons in the substantia nigra, VTA, and hypothalamus of wild type mouse embryos expressed L1. These results suggested that L1 plays an important developmental role in the organization of dopaminergic neuronal cell groups in the mesencephalon and diencephalon.

Cell surface molecules (NCAM and L1) in intrastriatal transplants of embryonic mesencephalon in rats

Cell surface molecules, NCAM and L1, reported to have a role in synaptogenesis, growth and fasciculation of the neurites in the brain, were traced in the embryonic nigral transplants in the host striatum of adult rats. Substantia nigra of five, 15 and 25 postnatal days were also examined for the same molecules. Tyrosine hydroxylase label was used as a marker to localize the nigral neurons and glial fibrillary acidic protein to detect if glial scar present. In the control as well as transplants large neurons had expressed tyrosine hydroxylase. By 15th postnatal day tyrosine hydroxylase neurons appeared mature and were scattered, suggesting a well-formed neuropil. NCAM and L1 reaction was seen as a peripheral rim in most of the cells on the fifth postnatal day. The reaction was mainly in relation to the large cells and more extensive on the 15th day. Thereafter on the 25th day, activity was negligible. Large neurons demonstrated strong reactivity for NCAM and L1 during early post-transplantation days. After 30 days only smaller cells were reactive, many of which could be identified as neurons. Strong reaction for these molecules was present only until 60 days, though faint reaction could be detected even on the 90th day. These observations indicate that the growth promoting molecules, the type seen in the neonatal period, can be detected normally only until the neurons mature. Prolonged expression of these molecules by the grafted neurons indicate delay in the maturation of these cells due to absence of adequate target sites for synaptic connections. Some of the smaller cells expressing these molecules after 30 days of transplantation could be astroglia, either proliferating or reactive.

Dynorphin-immunoreactive neurons in the rat nucleus accumbens: ultrastructure and synaptic input from terminals containing substance P and/or dynorphin

The endogenous opioid peptide dynorphin is enriched in neurons in the nucleus accumbens, for which coexistence and synaptic interactions with substance P have been postulated. We examined the immunogold-silver localization of dynorphin and immunoperoxidase labeling for substance P in single coronal sections through the core subregion of the nucleus accumbens of acrolein-fixed rat brain tissue. Dynorphin-immunoreactive somata were more prevalent than substance P-containing neurons throughout the region sampled for ultrastructural analysis. Dynorphin-labeled cells were spherical, contained unindented nuclei, and were closely apposed to other somata and dendrites, some of which also contained dynorphin immunoreactivity. The appositions were characterized by the absence of glial processes and contiguous contacts between the plasma membranes. Smooth endoplasmic reticulum and coated vesicles could also be identified in the cytoplasms on either side of the somatic or dendritic appositions. The dynorphin somata and dendrites received synaptic input from numerous unlabeled as well as dynorphin- and/or substance P-labeled axon terminals. Both types of terminals were morphologically similar in their content of small and large dense core vesicles and their formation of mainly symmetric synaptic specializations. In addition to dynorphin-immunoreactive targets, numerous dynorphin- and substance P-labeled terminals also formed synapses with unlabeled somata and dendrites. In some cases, terminals separately labeled for dynorphin and substance P converged on common targets with or without detectable dynorphin immunoreactivity. Terminals colocalizing both peptides were also found to synapse on unlabeled or dynorphin-labeled somata and dendrites. Additionally, presynaptic interactions were suggested by close appositions between dynorphin- and/or substance P-labeled terminals and other terminals that were unlabeled, dynorphin labeled, or substance P labeled. These results provide morphological data suggesting nonsynaptic communication between dynorphin-immunoreactive neurons and other neurons possibly mediated through receptive sites or second messengers associated with smooth endoplasmic reticulum in the nucleus accumbens. They also indicate that, in this region, 1) the activity of dynorphin neurons may be dependent on activation of autoreceptors for dynorphin as well as substance P and 2) additional neurons lacking dynorphin immunoreactivity are most likely inhibited (symmetric junctions) by terminals containing either one or both peptides. The findings may have implications for motor and analgesic responses to aversive tonic pain transmitted through dynorphin and substance P pathways within the nucleus accumbens.

Dopamine neoinnervation in the substantia nigra and hyperinnervation in the interpeduncular nucleus of adult rat following neonatal cerebroventricular administration of 6-hydroxydopamine

An aberrant network of dopamine axons was found to pervade the rat substantia nigra following neonatal destruction of its dopamine nerve cell bodies and dendrites by cerebroventricular administration of 6-hydroxydopamine. Light-microscopic immunocytochemistry with a primary monoclonal antibody directed against dopamine-glutaraldehyde-protein was used to investigate the time-course of development and the critical period of induction of this ectopic dopamine innervation (neoinnervation). In rats 6-hydroxydopamine-lesioned at postnatal day 3 (P3) and examined at P7, P10, P15, P30 or later, some dopamine fibers were already present in the substantia nigra at P7; their number increased sharply until P15 and only slightly thereafter, assuming a topographic distribution reminiscent of the missing dopamine nerve cell bodies and dendrites. A similar growth of dopamine fibers took place in the substantia nigra after lesions made at P6, P9 and P12, but was less pronounced after lesion at P15 and absent after lesion at P21 or later. Excessive innervation by dopamine axons (hyperinnervation) was concomitantly observed in the nearby interpeduncular nucleus. The sprouting of dopamine axons in both regions was therefore rapid and coincided in time and space with the developmental redistribution of mesencephalic dopamine neurons in normal rat. It is conceivable that these aberrant dopamine innervations play a role in the peculiar behavior and responsiveness to dopaminergic agents manifested by neonatally 6-hydroxydopamine-lesioned rats. It will be of particular interest to investigate the functional consequences of the dopamine neoinnervation in the substantia nigra, where an eventual axonal release might thus be replacing the normal somatodendritic release of this amine.

Thy-1 immunoreactivity distinguishes patches/striosomes from matrix in the early postnatal striatum of the rat

At P0, P2 and P3, islands of increased density of Thy-1-immunoreactive (Thy-1-IR) material, which coincided with the islands of dense dopaminergic axons, were noted in the striatum. By P5, the distribution of Thy-1-IR material was homogeneous throughout the developing striatum, but islands of dense dopaminergic axons persisted. The pattern of appearance of Thy-1, which is involved in extension of neurites and stabilization of synapses, suggests that it is involved in formation of connections between the substantia nigra and striatum in the developing rat brain.

Immunocytochemical demonstration of monoamine-containing cells in human fetal brain stem dissociated cultures

Primary dissociated cultures were prepared from the brain stems of 7- to 10-week-old human fetuses. Immunocytochemical detection of serotonin (5HT)-, dopamine (DA)-, noradrenaline (NA)- and tyrosine hydroxylase (TH)-containing cells was performed within 4 to 12 weeks in culture. We observed 5HT- and NA-stained neurons in the rhombencephalon. DA-stained cells were observed in the mesencephalon. TH-stained neurons were evidenced in both parts of the brain stem. Our in vitro system appears particularly appropriate for further investigation of grafts transplanted into the lesioned central nervous system (CNS).

Distribution and possible roles of the highly polysialylated neural cell adhesion molecule (NCAM-H) in the developing and adult central nervous system

The neural cell adhesion molecule (NCAM) is a cell surface glycoprotein which is thought to mediate cell adhesion and recognition. During developmental stages, NCAM is highly polysialylated (NCAM-H) by a unique alpha-2,8-linked polysialic acid chain (PSA), and this PSA portion of NCAM-H has been found to be closely associated with various developmental processes of the nervous system. Further, recent immunohistochemical investigations have revealed that even in the adult nervous system, a persistent PSA expression has been found confined to several regions: the olfactory bulb, the piriform cortex, the hippocampal dentate gyrus, the hypothalamus, some nuclei of the medulla and the dorsal horn of the spinal cord, which are related directly or indirectly to sensory systems. Moreover, in the dentate gyrus and olfactory bulb the expression is connected with adult neurogenesis that may add new neuronal circuits to the adult neural tissue. Therefore, the possible role of NCAM-H in the central nervous system may be associated not only with neural development, but also with adult functions, such as the processing system of sensory information and neuronal plasticity.

Degradation fragments of L1 antigen enhance tyrosine hydroxylase-immunoreactive neurite outgrowth in mesencephalic cell culture

The L1 antigen has been implicated in adhesion events controlling axonal elongation during formation of major fiber tracts, and promotes neurite outgrowth in culture. It is possible that injury of brain tissue causes neuronal surface molecules such as L1 antigen to be shed, and degradation fragments may therefore be present adjacent to the damage. These L1 fragments might then influence regeneration or injury-induced growth. We have evaluated neurite outgrowth from tyrosine hydroxylase-positive (TH +) E13 mesencephalic neurons grown in vitro on a substrate of mouse L1 antigen and on L1 degradation fragments separated by molecular weight. Mouse myelin-associated glycoprotein (MAG), laminin, poly-D-lysine, and fetal calf serum served as control substrates. L1 antibodies were added to one set of cultures (experimental), and compared to control cultures containing normal rabbit serum. After 3 days in vitro, the cultures were stained using an antibody against TH, and the length of the TH + neurites was measured by computer-assisted image analysis in a double-blind fashion. TH+ neurites were significantly longer when grown on L1 antigen, as well as on L1 degradation fragments, as compared to the control substrates. As compared to control normal rabbit serum, L1 antibodies eliminated the neurite-promoting effect of both the L1 substrate and the L1 degradation products. In addition, L1 substrates promoted clustering of TH + cells and the formation of loose bundles of TH + neurites. It is suggested that the L1 substrates influence TH-immunoreactive neurite outgrowth, at least partially, through indirect effects on glial cells.(ABSTRACT TRUNCATED AT 250 WORDS)