bluuebunny/crossref_metadata_2025_split huggingface dataset:
The organization of the embronic and early postnatal murine hippocampus. II. Development of entorhinal, commissural, and septal connections studied with the lipophilic tracer DiI
Authors: Supèr Hans , Soriano Eduardo 
Published: January 2005

AbstractWe have analyzed the early development of the main hippocampal afferents in the mouse. Following injections of the lipophilic tracer 1–1′‐dioctadecyl‐3, 3, 3′, 3′‐tetramethylindocarbocyanine perchorate (DiI) in the entorhinal cortex, entorhinal axons were observed for the first time inthe hippocampus at E15, in the white matter, At E17, entorhinal fibers arborized within the stratum lacunosum‐moleculare. At subsequent stages entorhinal axons formed dense networks that were restricted to their appropriate termination zone in the lacunosum‐moleculare. The first axons invading the fascia dentata were noticed at E19, their density increasing at later stages. These axons were mainly present in the outer molecular layer. This onset of entorhinohippocampal projections was corroborated by retrograde labeling data after injections in the hippocampus. Commissural fibers first entered the contralateral hippocampus at E18, their number increasing at the following stages. Commissural axons arborized within the stratum oriens and radiatum in the hippocampus proper. In the fascia dentata, the earliest commissural fibers were seen at P2, terminating in the inner zone of the molecular layer and in the hilus. We conclude that developing entorhinal and commissural axons show a high degree of laminar specificity from the earliest stages of formation, which is compatible with the notion that distinct subsets of early maturing neurons populating the hippocampal plexiform layers may attract particular fiber systems.Hippocamposeptal fibers develop at E15, before the first septal fibers can be detected in the hippocampus. These early hippocamposeptal fibers originated from nonpyramidal neurons and terminated in the medial septal area, which is the main source of septal afferents to the hippocampus. In contrast, septohippocampal fibers were not seen in the hippocampus until E17. At perinatal stages, the hippocamposeptal connection reshapes, sending axons to the dorsolateral septal area as the innervation of the medial septum becomes less conspicuous. This sequence suggests that hippocampal neurons pioneer the formation of septohippocampal connections. © 1994 Wiley‐Liss, Inc.
Pedunculopontine nucleus in the squirrel monkey: Cholinergic and glutamatergic projections to the substantia nigra
Authors: Lavoie Brigitte , Parent André 
Published: January 2005

AbstractThe distribution and chemospecificity of the pedunculonigral neurons have been studied in squirrel monkeys (Saimiri sciureus)with cholera toxin subunit B (CTb) and fluorogold (FG) as retrograde tracers combined with immunohistochemistry for choline acetyltransferase (ChAT), glutamate, and the calcuium binding protein calbindin D‐28k. The injection of either CTb or FG into the substantia nigra produces prominent retrograde cell labeling in the mesopontine tegmentum. Labeled neurons are particularly numerous at the level of the decussation of the superior cerebellar peduncle, where they abound principally in the pars dissipata of the pedunculopontine nucleus (PPN). A significant proportion of retrogradely labeled neurons in the PPN display ChAT immunoreactivity. Whithin the entire PPN, approximately 25% of the retrogradley labeled neurons express ChAT immunoreactivity, but proportions of doubly labeled neurons are about 35%, 25% in the rostral, middle, and caudal thirds of the PPn, respectively. These doubly labeled neurons are scattered among numerous retrogradely labeled neurons that are ChAT‐negative and whose number increases along the rostrocaudal extent of the PPN. Several retrogradely labeled neurons in the PPN display glutamate immunoreactivity, but very few express calbindin. This study provides the first direct evedence for the involvement of cholinergic and glutamatergic neurons in the pedunculonigral projection in primates. Furthermore, the fact that some neurons of the PPN display bothe ChAT and glutamate immunoreactivity indicates that single neurons in the mesopontine tegmentum may exert a two‐fold effect upon dopaminergic neurons of the substantia nigra. This dual cholinergic and glutamatergic pedunculonigral projection may play a crucial role in the functional organization of primate basal ganglia. © 1994 Wiley‐Liss, Inc.
Catecholaminergic systems in the zebrafish. I. Number, morphology, and histochemical characteristics of neurons in the locus coeruleus
Authors: Ma Pokay M. 
Published: January 2005

AbstractThe locus coeruleus is a noradrenergic nucleus located in the isthmal tegmentum. In mammals, it contains several thousand neurons that have diverse projection patterns and contain various neuropentides. In fishes, this nucleus contains few neurons. This study attempts to define and quantify morphological types of locus coeruleus neurons, and search for neurochemical subpopulations in the zebrafish. In this fish, the locus coeruleus contains between 3 and 10neurons, and most nuclei contain between 5 and 8 cells. Nuclei in more inbred lines of fish have a narrower range of neurons. The difference in neuron number between the two sides of the same brain is small, but only 24% of the brains have identical numbers on both sides. These observations suggest that there is a two‐step control of neuron number: the genetic constitution of the fish determines the approximate number of cells, while epigenetic factors determine the final number. Based on dendritic orientation, three types of cells are identified: (1) V type, neurons with only ventrally projecting dendrites; (2) L types, neurons with only laterally projecting dendrites; and (3) VL type, neurons with both ventrally and laterally projecting dendrites. Over 65% of the neurons are of the V type; some nuclei have V type; some nuclei have V type cells only. There is a correlation between the total number of neurons and the ratio of each cell type. In nuclei with five cells or fewer, over 80% of the neurons are V type; higher percentages of the other two types are seen in nuclei with 6 or more neurons. The dendritic morphology and orientation suggest that various types of neurons may receive different inputs. Cholinesterases are not detectable in locus coeruleus neurons. Immunocytochemical staining for a number of neuropeptides also fails to demonstrate detectable levels. Neuropeptide Y is present in some cell abutting the locus coeruleus, but these are probably not catecholamine‐containing neurons. Some neurons contain choline‐acetyltransferase. These observations suggest that locus coeruleus neurons of the zebradish may be morphologically and neurochemically heterogeneous. © 1994 Wiley‐Liss, Inc.
Multiple striatal representation in primate substantia nigra
Authors: Parent André , Hazrati Lili‐Naz 
Published: January 2005

AbstractThe pattern of arborization of the striatonigral fibers in the squirrel monkey (Saimiri Sciureus) was studied with Phaseolus vulgaris‐leucoagglutinin (PHA‐L) and biocytin as anterograde tracers. Single, small injections of PHA‐L or biocytin in either the caudate nucleus or the putamen give rise to at least four distinct, nonoverlapping but interconnected fiber plexuses that are distributed throughout the rostrocaudal extent of the substantia nigra pars reticulata (SNr) according to a strikingly precise and constant sequence. These plexuses, which comprise numerous fibers that closely entwine unlabeled dendrites of SNr neurons (woolly fibers), often lie at the base of dopaminergic cell columns of the substantia nigra pars compacta (SNc). Long and varicose fibers emerge dorsally from SNr plexuses and climb along the ventrally oriented denarites of dopaminergic SNc neurons, as visualized with tyrosine hydroxylase immunohistochemistry. These fibers appear to contact en passant both dendrites and cell bodies of dopaminergic neurons belonging to the ventral tier of SNc. Anterograde double‐labeling experiments involving small deposits of PHA‐L and biocytin in adjacent areas of the caudate nucleus and the putamen reveal that neighboring striatonigral cell populations form two distinct sets of terminal plexuses that remain well segregated throughout SNr. Plexuses from the two sources interdigitate in some parts of SNr, but never intermix. Furthermore, the wooly fibers in these plexuses are composed exclusively of either PHA‐L‐or biocytin‐labeled elements; none of them display both types of labeling. These results reveal that the striatonigral projection in primates is highly divergent and that the striatum has multiple representations at nigral levels. They also indicate that striatal information is conveyed to the substantia nigra in a highly ordered fashion through multiple segregated channels. © 1994 Wiley‐Liss, Inc.
Cobalt accumulation in neurons expressing ionotropic excitatory amino acid receptors in young rat spinal cord: Morphology and distribution
Authors: Nagy István , Woolf Clifford J. , Dray Andy , Urbán László 
Published: January 2005

AbstractExcitatory amino acids (EAA) acting on N‐methyl‐D‐aspartate (NMDA), α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionic acid (AMPA) and kainate receptors play an important role in synaptic transmission in the spinal cord. Quantitative autordiography and physiological experiments suggest that NMDA receptors are localized mainly in lamina II while kainate and AMPA receptors are found on both dorsal and ventral horn neurons. However the cell types expressing EAA receptors and their laminar distribution is not known. We have used a cobalt uptake mentod to study the morphology and distribution of spinal cord neurons expressing AMPA, kainate, or NMDA excitatory amino acid receptors in the lumbar enlargement of the rat spinal cord. The technique involved superfusion of hemisected spinal cords of 14 day‐old rat pups in vitro with excitatory amino acid receptor ligands in the presence of CoCl2. Cobalt has been shown to enter cells through ligand‐gated ion channels in place of Ca2+. Cells which accumulated cobalt ions following activation by ionotropic excitatory amino acid receptors were visualised histochemically. The cobalt uptake generated receptors‐specific labeling of cells, as the NMDA receptor antagonist D‐(−)‐2‐amino‐(5)‐phosphonovaleric acid (D‐AP‐5) (20 μM) blocked the NMDA, but not kainte‐inducced cobalt uptake. The kainate‐induced cobalt labeling was reduced by the non‐selective excitatory amino acid receptor antagonist kynurenic acid (4 mM). Passive opening of the voltage‐gated Ca2+ ‐channel by KCI (50 mM) did not result in colbalt uptake, indicating that cobalt enters cells through ligand‐gated Ca2+ ‐channels.AMPA (500 μM), kainate (500 μM), or NMDA (500 μM) each induced cobalt uptake with characteristic patterns and distributions of neuronal staining. Overall, kainate induced cobalt uptake in the greatest number of neuronal perikarya while NMDA‐induced uptake was the lowest. AMPA and kainate, but not NMDA superfusion, resulted in cobalt labeling of glial cells.Our result show that the cobalt uptake technique is a useful way to study the morphology and distribution of cells expressing receptors with ligand‐gated Ca2+ channels. © 1994 Wiley‐Liss, Inc.
Early‐eye morphogenesis in the zebrafish, Brachydanio rerio
Authors: Schmitt Ellen A. , Dowling John E. 
Published: January 2005

AbstractEarly eye morphogenesis in the zebrafish between 12 and 36 hours postfertilization was studied by light‐ and scanning electron microscopy. Overall, early eye morphogenesis in the zebrafish is similar to that vertebrates even thought the optic primordia evaginate from the forebrain as solid masses of cells. After initial evagination 6–7 somite stage [SS], the optic primordia take on a wing‐like shape (8–9 SS). Subsequently, they bend ventrally and rotate slighlty in an anterior direction (10–12 SS). These changes serve to bring the primordia from a horizontal to a more Vertical orientation in relation to the embryonic neural axis. Invagination commences from the center of each primordium (14 SS) and progresses symmetrically out towards the periphery (14–20 SS). The choroid fissure forms by an involution along the anterior region of the eyecup (18–20 SS). By 24 hours postfertilization (pf), the eyecups are well formed. Between 24 and 36 hours pf, the eyes rotate further in relation to the axis of the embryo, and this repositions the choroid fissue to a typical ventral location by 36 hours pf. Because of the two rotations of the eye during early morphogenesis, particularly the later one, the anterior‐posterior orientation of the emerging optic primordium ultimately becomes the ventral‐dorsal axis of the completed eyecup. © 1994 Wiley‐Liss, Inc.
Long‐range horizontal connections between supragranular pyramidal cells in the extrastriate visual cortex of the rat
Authors: Lohmann H. , Rörig B. 
Published: January 2005

AbstractIn this study, we examined the morphological structure and synaptic physiology of long‐range axon projections among supragranular pyramidal cells in the extrastriate visual cortex of the rat. Intra‐and extracellular recordings form layer II/III pyramidal cells were performed in brain slices of area 18a following extracellular stimulation of either the underlying white matter or within layer II/III. Neurons were injected with biocytin for two‐dimensional reconstruction of their axon arborizations.The conduction velocity of afferent fibers (0.58 m/s) was twice as high as that of intracortical tangential fibers (0.28 m/s). Layer II/III cells were mainly di‐or polysynaptically driven by afferent activation, but predominantly monosynaptically driven from intracortical stimulation sites. The afferent as well as intracortically as well as intracortically evoked postsynaptic potentials showed a very similar time course and shape. From both stimulation sites, suprathreshold action potentials could be elicited. The current threshold for a postsynaptic response and the slope and width of excitatory postsynaptic potentials (EPSPS) increased with the distance of lateral stimulation. The morphological properties of layer II/III pyramidal cell axon collaterals colsely corresponded to the electrophysiological results. Long‐range intraareal axon collaterals could be followed up to 1 mm within the supragranular layers. Their length‐distance distribution showed an inverse relationship to the threshold currents of EPSPs. Pyramidal cells exhibited regularly spaced patches of horizontal axon collaterals with an interpatch distance of about 250 μm.We concluded that the supragranular horizontal network in the extrastriate visual cortex of the rat is qualitatively very similar to that of cats and monkeys. However, quantitative differences exist in its spatial extent and physiological characteristics. © 1994 Wiley‐Liss, Inc.
Distribution of TAG‐1/Axonin‐1 in fibre tracts and migratory streams of the developing mouse nervous system
Authors: Wolfer David P. , Henehan‐Beatty Anne , Stoeckli Esther T. , Sonderegger Peter , Lipp Hans‐Peter 
Published: January 2005

AbstractThe axonal cell adhesion molecule, TAG‐1/axonin‐1, stimulates axonal growth and supports neurite fasciculation in vitro. Using a polyclonal antiserum raised against chick axonin‐1, which shares 75% of its sequence with TAG‐1 of the rat, we have mapped the distribution of TAG‐1/axonin‐1 throughout the developing nervous system of the mouse.Although absent from proliferating neuroepithelia and from non‐neuronal cells, immunoreactivity for TAG‐1/axonin‐1 is expressed by stage‐specific subpopulations of differentiating neurons from embryonic day 10 to postnatal day 15. It stains their axons and the surface of their parent somata during the early phases of axogenesis. In agreement with a putative role of TAG‐1/axonin‐1 as an axon‐bound growth substrate, immunoreactivity is found in developing spinal and cranial nerves, in corticothalamic projections, as well as in subsets of fasciculating long projecting tracts of the central nervous system, such as the dorsal funiculi of the spinal cord, the lateral olfactory and optic tracts, the fasciculus retroflexus, and the predorsal bundle. High levels of immunoreactivity characterise the development of the cerebellar molecular layer, the corpus callosum, anterior and hippocampal commissure, and of crossed projections in the spinal cord and at several levels of the brainstem.Intense immunoreactivity in fine collaterals of cutaneous afferents, including their growth cones that are in contact with the embryonic skin, suggests a role of TAG‐1/axonin‐1 in target recognition. While staining is weak on the somata of radially migrating neurons such as cortical neurons and cerebellar granule cells, strong immunoreactivity is associated with neural somata and processes of the three tangential migrations that form the precerebellar nuclei, indicating a possible involvement of TAG‐1/axonin‐1 in contacts between these neurons and the processes they migrate upon. © 1994 Wiley‐Liss, Inc.
Cholinergic innervation in the human hippocampal formation including the entorhinal cortex
Authors: De Lacalle Sonsoles , Lim Chun , Sobreviela Teresa , Mufson Elliott J. , Hersh Louis B. , Saper Clifford B. 
Published: January 2005

AbstractThe cholinergic innervation of the hippocampal formation is thought to play an important role in memory processes, but its organization in humans has not been described in detail. We studied the cholinergic innervation of the human hippocampal formation by means of immunohistochemistry with polyclonal antisera directed against acetyleholinesterase (AChE), choline acetyltransferase (ChAT), and the low‐affinity (p75) nerve growth factor receptor (NGFR). The density of ChAT‐like immunoreactive (ChAT‐li) fibers differed substantially among the various regions, in general paralleling the pattern of AChE‐li staining. One notable exception was the presence of AChE‐li cell bodies. In contrast, ChAT immunoreactivity was associated only with fibers and terminals. NGFR‐li staining corresponded closely to the ChAT‐li fiber pattern.ChAT‐li fibers in the CA fields diffusely filled the stratum pyramidale and extended into the stratum oriens and radiatum as well. The highest density was consistently observed in CA4 and CA3 subfields. Staining decreased from CA4 to CA1 and was substantially less dense in the subicular complex. In the entorhinal cortex, the ChAT‐ and NGFR‐li fiber innervation displayed a laminar pattern, most intense over the nests of cells in layer II.There was a trend towards an age‐related reduction in the density of ChAT‐ and AChE‐li fibers and terminals. Nonetheless, we also found a surprisingly conserved NGFR‐li innervation and the presence of occasional NGFR‐li pyramidal cells, providing evidence of a plastic response in the brains of the elderly patients.© 1994 Wiley‐Liss, Inc.
Gamma‐aminobutyric acid in the nervous system of a planarian
Authors: Eriksson Krister S. , Panula Perm 
Published: January 2005

AbstractThe amino acid gamma‐aminobutyric acid (GABA) is an important inhibitory neurotransmitter in both vertebrates and invertebrates. Despite this, no reports of GABA in flatworms have to date been published. We have studied the presence of GABA in the planarian Dugesia tigrina with immunocytochemical methods and high‐pressure liquid chromatography. Fibers showing GABA‐like immunoreactivity (GABA‐IR) were present in abundance in the longitudinal nerve cords and lateral nerves. GABA‐IR was revealed in fibers forming commissures in the brain. The ventral part of the subepidermal plexus showed GABA‐IR. No cell somata containing GABA‐IR could be identified with certainty.The chromatographic analysis showed that the average GABA concentration in D. tigrina is 533.6 pmol/mg protein. This is substantially higher than the concentrations of dopamine (62.87 pmol/mg) and serotonin (233.20 pmol/mg). An enzyme assay confirmed the capacity for GABA‐synthesis in D. tigrina. The results indicate that GABA‐containing neurons appeared earlier in evolution than was previously thought and that GABA may serve an important role already in the flatworms. © 1994 Wiley‐Liss, Inc.
Coordination of gaze shifts in primates: Brainstem inputs to neck and extraocular motoneuron pools
Authors: Robinson Farrel R. , Phillips James O. , Fuchs Albert F. 
Published: January 2005

AbstractTo, determine whether there are brainstem regions that provide common input to the motoneurons that move both the head and the eyes, we injected wheat germ agglutinin‐horseradish peroxidase complex (WGA‐HRP) into neck motoneuron pools at spinal level C2 (N = 3) and extraocular motoneuron pools in the abducens (N = 1) and oculomotor/trochlear (N = 1) nuclei of rhesus and fascicularis macaques. We also injected WGA‐HRP into spinal level C5‐7 (N = 1) of a fascicularis macaque for comparison.After injections into C2, we observed retrogradely labeled cells in the ventral reticular formation (NRV), the gigantocellular‐reticular formation (NRG), and both the oral (NRPO) and the caudal (NRPC) divisions of the paramedian pontine reticular formation (PPRF). There was also a column of labeled cells in the cuneate reticular nucleus (NCUN) just lateral to the ipsilateral periaqueductal gray (PAG). This column extended rostrally into the central mesencephalic reticular formation (CMRF). In addition, there were labeled cells in the region ventral and caudal to the rostral interstitial nucleus of the MLF (riMLF), the area lateral to the interstitial nucleus of Cajal (INC), and the ventral part of the lateral vestibular nucleus (LVN) and lateral part of the medial vestibular nucleus (MVN). There were also a few labeled cells in the fastigial (FN) and interposed (IN) nuclei of the cerebellum but very few in the superior colliculus (SC). In contrast, the injection into C5‐7 labeled many cells in the lateral vestibular nucleus (LVN) and very few in FN or IN.Injecting WGA‐HRP into the abducens nucleus and the surrounding tissue labeled many cells in SC, PPRF, MVN, FN, and nucleus prepositus hypoglossi (NPH). Injecting into the oculomotor/trochlear nuclei and nearby tissue labeled cells in SC, INC, riMLF, FN, IN, MVN, and superior vestibular nucleus (SVN).Structures that project to both neck and eye motoneuron pools, and therefore probably participate in both head and eye movements, include the lateral part of the MVN and both NRPO and NRPC in the PPRF. Those that project primarily to neck motoneurons in C2 include the NRV, the NRG, and the NCUN‐CMRF column. Those projecting exclusively to extraocular nuclei include the NPH, INC, riMLF, NRPD, and SC. We use these data to propose a scheme for control of combined eye‐head movements in monkeys. © 1994 Wiley‐Liss, Inc.