bluuebunny/crossref_metadata_2025_split huggingface dataset:
The earliest ultrastructural development of the tangential vestibular nucleus in the chick embryo
Authors: Petralia R. S. , Peusner K. D. 
Published: January 2005

AbstractThe tangential nucleus is a primary vestibular nucleus located where the vestibular fibers enter the medulla. It is composed of neurons that migrate between 5 and 8 days in the chick embryo. Although primary vestibular fibers enter the medulla at 3 days, the first synapses are formed at 5 days on the processes of neuron precursors by longitudinally coursing fibers. Since the major components, or their precursors, are present at 3 days within the presumptive nucleus, we are interested in determining what cellular interactions occur among these structures following their entry and during the time leading up to synapse formatio.At 2 days, prior to the appearance of VIIth and VIIIth nerve fibers in the medulla, the tangential nucleus anlage contained processes and endfeet of primitive epithelial cells, separated from each other by enlarged extracellular spaces. Longitudinal fibers first appeared within these spaces coincident with the appearance of root fibers, including some identified VIIth motor axons, associated with the primordial VII/VIIIth ganglia. By 3 days, some vestibular and VIIth nerve fibers could be identified by their ultrastructure and relative positions within the marginal zone and nerve roots. However, it was not until 4 days that the presumptive tangential nucleus acquired its orderly, characteristic organization. Although synapses were rare from 2 to 4 days, attachment plaques and coated pits were observed commonly between structures, especially between future synaptic structures. Thus, we confirm that synapse formation begins at 5 days. This represents the first detailed ultrastructural study of cranial sensory nerve ingrowth into the medull.
Organization of the histaminergic system in the brain of the teleost, Trachurus trachurus
Authors: Inagaki Naoyuki , Panula Pertti , Yamatodani Atsushi , Wada Hiroshi 
Published: January 2005

AbstractTo accumulate phylogenetic information on the central histaminergic system, we investigated the histaminergic system in the brain of a teleost, the jack mackerel (Trachurus trachurus), using the indirect immunofluorescent method with antiserum against histamine. A small number of histamine‐ immunoreactive cell bodies were observed in the posterior hypothalamus around the posterior recess. Histamine‐immunoreactive fibers innervated the telencephalon, diencephalon, tegmentum, and rostral part of the medulla oblongata. The immunoreactive fibers were very sparse or absent in the olfactory bulb, optic tectum, cerebellum, caudal part of the medulla oblongata, spinal cord, and hypophysis. Ascending fiber bundles were seen in the basal hypothalamus, supplying fiber collaterals to the telencephalon and diencephalon, whereas descending fibers were observed in the midline of the lower brainstem. These findings suggest that the central histaminergic system of the jack mackerel is homologous to those of mammals, reptiles, and amphibians, although poorly developed compared with them. The histamine‐immunoreactive neuronal cell bodies found in the border area between the mesencephalon and rhomb encephalon of the river lamprey were not detected in the brain of the jack mackere.
Connectional studies of the primate lateral geniculate nucleus: Distribution of axons arising from the thalamic reticular nucleus of Galago crassicaudatus
Authors: Harting John K. , van Lieshout David P. , Feig Sherry 
Published: January 2005

AbstractAnterograde and retrograde transport methods have been used to explore the interconnections between the thalamic reticular nucleus (TRN) and the dorsal lateral geniculate nucleus of Galago crassicaudatus. We first defined the region of the TRN, which is connected to the lateral geniculate nucleus, by examining the distribution of geniculo‐TRN axons, cortico‐TRN axons arising from area 17, and the location of TRN‐geniculate neurons. Following an intraocular injection of 3H‐proline/3 H‐leucine, trans‐synaptically transported protein is present bilaterally within the lateral portion of the caudal TRN. This same caudal and lateral region is also targeted by cortico‐TRN axons and contains neurons which project upon the lateral geniculate nucleu.Light microscopic anterograde transport methods were used to analyze the distribution of TRN‐geniculate axons. Our data reveal that all layers and interlaminar zones of the dorsal lateral geniculate nucleus contain TRN axon.Electron microscopic‐autoradiographic data support and extend our light microscopic findings by revealing labeled TRN terminals within all geniculate layers. These TRN profiles are the same size throughout the geniculate and exhibit morphological characteristics similar to Fl terminals described by others. That is, they possess predominantly pleomorphic vesicles, a dark cytoplasmic matrix, dark mitochondria, and symmetrical synaptic contacts. Two additional features of TRN terminals have been observed in some profiles. These include dense‐core vesicles and a dense, punctate cytoplasmic matrix, which is sometimes associated with the postsynaptic specialization. In addition to their morphology and size, the postsynaptic targets of TRN terminals are similar within the three sets (parvi‐, magno‐, and koniocellular) of geniculate layers. TRN profiles terminate upon dendrites of all sizes and somata. These findings suggest that the TRN modulates the retino‐geniculocortical pathway and that this modulation is occurring in all three streams.
Morphological differentiation of distinct neuronal classes in embryonic turtle cerebral cortex
Authors: Blanton Mark G. , Kriegstein Arnold R. 
Published: January 2005

AbstractAs a starting point for understanding the development of the cerebral cortex in reptiles and for determining how reptilian cortical development compares to that in other vertebrate classes, we studied the appearance and morphological differentiation of cerebral cortical neurons in embryonic turtles. 3H‐thymidine birthdate labeling and focal injections of horseradish peroxidase (HRP) in in vitro cortical slices revealed that replicating cells occupy the outer ventricular zone, and subsequently migrate to the ventricular surface where they divide. Postmitotic neurons begin differentiating and elaborating neurites while migrating back through the ventricular zone. On their arrival at the top of the ventricular zone, pyramidal and nonpyramidal neurons can be distinguished morphologically. Cells with multipolar apical dendritic tufts ascending in the marginal zone resemble immature pyramidal neurons. Neurons morphologically similar to these early pyramidal cells were retrogradely labeled by injections of the lipophilic tracer 1,1‐dioctadecyl‐3,3,3′,3′‐tetramethyl indocarbocyanine perchlorate (diI) in a known pyramidal cell target, the thalamus. Nonpyramidal neurons, resembling Cajal‐Retzius cells, had horizontally oriented long axons and dendrites coursing in the plexiform primordium, the future marginal zone. With further development morphological differences between cell types became accentuated, and pyramidal cell somata were segregated into a single cellular layer flanked by zones containing predominantly nonpyramidal cell.Axon elaboration occurred early in embryonic development, as pyramidal cells sent axonal branches to the septum, thalamus, and cortical targets soon after their generation, and the intracortical axonal plexus became increasingly dense during embryonic life. Over a similar time course the distribution of projecting neurons labeled by thalamic diI injections changed from an initial homogeneous distribution to a preferential location in the superficial half of the cellular laye.Results from this study demonstrate several features of cortical differentiation that are conserved in reptiles and mammals, including similar early morphological differentiation events, the early distinction of principal cell types, and the parallel development of pyramidal and nonpyramidal neurons. The context in which these similar developmental events occur, however, differs profoundly in reptiles and mammals, with differences in the timing and location of neurite elaboration and differences in the appearance and architectonic organization of the cortex. Comparison of cortical developmental patterns between reptiles and mammals shows that similar functional cortical circuits with balanced excitation and inhibition can emerge in diverse cortical structures.
Central course of digital axons within the median nerve of macaca mulatta
Authors: Brushart Thomas M. E. 
Published: January 2005

AbstractThe traditional view that axons are not functionally grouped within proximal human nerve is based on the interfascicular dissections of Sunderland ('45). However, microstimulation and microneurography (Schady et al., '83a; Hallin, '90) reveal proximal grouping of cutaneous sensory axons from small areas of skin. In the present studies, conjugates of horseradish peroxidase with wheat germ agglutinin (HRP‐WGA) were used to trace the course of digital nerve axons within the median nerve of Macaca mulatta. The electrophysiologic findings were confirmed, suggesting the potential for precise surgical realignment of functionally related axons even after proximal nerve transection.Radial digital nerves were labeled in the thumb (bilateral, 1 animal), the index finger (unilateral, 2 animals), and the middle finger (bilateral, 1 animal). Median nerve cross sections were cut at 1‐cm intervals, treated with tetramethyl benzidine to demonstrate HRP‐WGA within axons, and compiled to form maps of each digital nerve “territory” within the median nerve. These territories were limited to a single, densely labeled fascicle at the wrist level. They expanded somewhat in the forearm to encompass clusters of labeled axons within a matrix of unlabeled axon profiles. The clusters were more loosely packed in the arm, occupying ⅓ to ⅙ of the nerve cross section at the entrance to the brachial plexus. The three digital nerve territories studied were widely separated at the wrist level. In the proximal arm, there was moderate intermingling of axons from adjacent digits, but those to the middle finger and thumb remained segregated. Territory configuration differed widely overall, but was moderately constant for each digit. The location of territories within the nerve was often strikingly similar from right to left and from animal to animal, with occasional prominent variations reflecting isolated rotation of one nerve.
Morphology and mosaics of VIP‐like immunoreactive neurons in the retina of the rhesus monkey
Authors: Lammerding‐Köppel M. , Thier P. , Koehler W. 
Published: January 2005

AbstractVasoactive intestinal peptide (VIP) is a 28‐amino acid peptide that has been demonstrated to reside in cells (=VIP+ cells) of the retinae of various vertebrate species. In an attempt to study the morphology and distribution of VIP+ cells in the retina of the rhesus monkey in more detail, we subjected VIP+ cells observed in cryostat sections or wholemounts of rhesus monkey retinae to a quantitative analysis. VIP+ cells were found to reside in the innermost row of the inner nuclear layer (INL) and in the ganglion cell layer (GCL) in similar numbers (estimate: 50 cells/mm2 at 6–10 mm eccentricity each) and only on rare occasions (12% of all VIP+ cells) in varying positions within the inner plexiform layer (IPL). Somata of VIP+ cells were circular and had a mean diameter of 9.1 μm. They gave rise to 1–3 main dendrites, which were usually oriented toward the IPL. Main dendrites ramified widely into thin fibers (dendritic field diameter < = 1 mm), carrying varicose swellings. The fibers that contributed to one and the same plexus of VIP+ fibers preferred the middle third of the IPL, independent of the positions of the parent somata. A quantitative analysis of nearest‐neighbour distances in the retinal wholemount preparation suggested that VIP+ cells in the GCL and in the INL might be distributed according to 2 independent mosaics. A comparison with Golgi‐stained material leads to the tentative equation of VIP+ cells with the “spiny” A12 amacrine cell of Mariani ('90). Whereas the low density and large dendritic field size of VIP+ cells might suggest a more widespread function, the varicose dendritic morphology seems to be more compatible with functionally independent dendritic subunits mediating localized effects.
Access to gastric tissue promotes the survival of axotomized neurons in the dorsal motor nucleus of the vagus in neonatal rats
Authors: Rinaman Linda , Levitt Pat 
Published: January 2005

AbstractLesioning the vagus nerve in the neck (cervical vagotomy) results in a rapid and virtually complete loss of motoneurons in the dorsal motor nucleus of the vagus in neonatal rats. The present study sought to determine whether access to gastric target tissue will promote the survival of these motoneurons after axotomy. Quantitative analysis demonstrate that subdiaphragmatic vagotomy, which leaves the cut vagal axons in close proximity to their normal gastric targets, results in significantly less motoneuron loss than cervical vagotomy. Furthermore, the loss of motoneurons after cervical vagotomy can be significantly reduced by transplanting embryonic gastric tissue to the neck of vagotomized neonatal host rats, in the vicinity of the cut axons. The survival effect of transplanted gastric tissue appears specific because control‐transplants of embryonic bladder tissue fail to reduce motoneuron death after cervical vagotomy. Injections of the neural tracers Fluoro‐Gold and cholera toxin‐horseradish peroxidase into gastric transplants labeled surviving motoneurons in cervically vagotomized rats, whereas tracer injections into bladder transplants or into host cervical tissues did not. These results indicate that neonatal vagal motoneurons are capable of making the adjustments necessary to survive axotomy if they have access to gastric target cells. The apparent dependence of injured neonatal vagal motoneurons on gastric tissue offers a new system in which to examine in vivo the trophic interactions between neurons and their targets.
Generation and death of cells in the dorsal lateral geniculate nucleus and superior colliculus of the wallaby, setonix brachyurus (quokka)
Authors: Harman Alison M. 
Published: January 2005

AbstractTo study postnatal cell generation in primary visual centres of the quokka, tritiated thymidine was injected into pouch‐young aged postnatal day (P)1–P85. Brains were examined at P100, just before eye‐opening, when primary visual projections are essentially mature. Neurons in the dorsal lateral geniculate nucleus (dLGN) and superior colliculus (SC) were generated at P1–P10 and P1–P18 respectively. Peak numbers of labelled cells were seen at P3 and P5 in the dLGN and SC.Cell death was assessed in the dLGN and SC of young aged P10–P150. Low numbers of dying cells were seen in the dLGN throughout this period, with a small peak at P85. A more substantial peak of cell death was seen in the SC, also at P85. In the quokka, the time interval between the peaks of cell generation and of cell death in the dLGN and SC is 70–80 days, considerably longer than the interval of 40 days between birth and death of retinal cells.
Fibroblast growth factor receptor‐bearing neurons in the CNS: Identification by receptor‐mediated retrograde transport
Authors: Ferguson Ian A. , Johnson Eugene M. 
Published: January 2005

AbstractNeurons that internalize and retrogradely accumulate acidic (aFGF) or basic (bFGF) fibroblast growth factor were identified by autoradiography after injections of 125I‐aFGF or 125I‐bFGF into the adult rat central nervous system (CNS). Neuronal cell bodies within the lateral hypothalamus, pedunculpontine tegmental nucleus, laterodorsal tegmental nucleus, and the paracentral dorsal tegmental nucleus accumulated 125I‐aFGF. Neurons in the hippocampus, subiculum, the centrolateral, paracentral, central medial, and parafascicular thalamic nuclei, the supramammillary nucleus, and substantia nigra compacta accumulated 125I‐bFGF. The pattern of neuronal labeling with 125I‐bFGF in adult rats was similar to that observed in newborn guinea pigs. No 125I‐FGF labeling was observed in nerve growth factor (NGF) receptor‐bearing neurons, including the basal forebrain cholinergic neurons. Time‐course studies indicate that 125I‐FGF Was internalized at the terminals and retrogradely transported to the neuronal cell bodies. Neurons were retrogradely labeled either by injection of 125I‐bFGF into the lateral ventricle or by injection into innervated target tissues. Co‐injection of a 250‐fold excess of unlabeled FGF with the 125I‐FGF abolished the neuronal labeling. Co‐injection of wheat germ agglutinin (WGA), which nonspecifically blocks binding of 125I‐bFGF to its receptor, also prevented neuronal labeling. These studies demonstrate that specific neuronal populations within the CNS express functional receptors for aFGF and/or bFGF; in these neurons, aFGF and/or bFGF bind specifically to these receptors, are internalized and retrogradely transported to the neuronal soma in a manner analogous to NGF. The data indicate that FGF can provide trophic support to CNS neurons by both direct and indirect mechanisms.
Thalamic processing of vibrissal information in the rat: II. Morphological and functional properties of medial ventral posterior nucleus and posterior nucleus neurons
Authors: Chiaia Nicolas L. , Rhoades Robert W. , Fish Stephen E. , Killackey Herbert P. 
Published: January 2005

AbstractExtracellular recording, intracellular recording, intracellular horseradish peroxidase injection, and receptive field mapping techniques were employed to evaluate the physiological and morphological properties of medial ventral posterior nucleus (VPM) and posterior nucleus (POm) neurons in normal adult rats. Overall, we physiologically characterized 148 VPM and 121 POm neurons. Over 82% of the VPM cells were excited only by deflection of one or more mystacial vibrissae, 10% were activated by displacement of guard hairs, and the remainder were either excited by indentation of the skin or were unresponsive. Less than 40% of the POm cells were activated by vibrissa deflection, 18% were excited by displacement of guard hairs, and another 17% were unresponsive. Most of the rest of the POm cells were excited by stimulation of skin, mucosa, or activation of muscle‐related afferents. Small percentages of POm cells responded only to noxious stimulation, were classified as having a wide dynamic range, or were inhibited by peripheral stimulation. Electrical stimulation of either PrV or SpI activated most neurons in both VPM and POm. This excitation was almost invariably followed by a long‐lasting hyperpolarization which was generally strong enough to prevent responses to either electrical stimuli delivered in the brainstem or mechanical stimulation of the periphery. The receptive fields of vibrissa‐sensitive cells in POm were generally much larger than those of cells in VPM. Data obtained with extracellular recording indicated that VPM and POm cells responded to an average of 1.4 and 4.0 vibrissae, respectively. Intracellular recording from smaller samples of VPM and POm cells demonstrated the existence of inputs that were insufficient to produce spikes from the cell, but did yield epsp's. When both sub‐ and suprathreshold excitation were considered, the average number of vibrissa in the receptive field of a VPM cell was 2.7 and the value for POm cells became 7.8. HRP‐filled neurons recovered in POm (N = 20) generally had much larger dendritic arbors than neurons in VPM (N = 31). For the former cells, the size of the dendritic tree was significantly correlated with the number of vibrissa to which the cell responded; for the latter neurons, it was not.
Somatotopic organization of hindlimb skin sensory inputs to the dorsal horn of hatchling chicks (Gallus g. domesticus)
Authors: Woodbury C. Jeffery , Scott Sheryl A. 
Published: January 2005

AbstractThe somatotopic organization of skin sensory nerve projections to the lumbosacral dorsal horn of hatchling chickens was determined with the aid of transganglionic transport of horseradish peroxidase (HRP) processed with tetramethylbenzidine histochemistry, A total of eight hindlimb nerves were studied, five of which were purely cutaneous. When combined, the innervation fields of these nerves covered most of the hindlimb surface, allowing a nearly complete somatotopic map of the hindlimb to be generated.This report describes a novel pattern of cutaneous nerve projections to the dorsal horn. Unlike other vertebrates, cutaneous nerves of chickens formed two separate, somatotopically organized projections across the mediolateral axis of the dorsal horn; when serially reconstructed and superimposed, these projections produced two nonoverlapping somatotopic maps of the skin surface lying side by side. Each of these separate maps was nearly identical to the other in overall topology. These two separate maps appear to represent distinct modalities of sensory information, as projections composing the medial map were preferentially labeled by choleragenoid‐HRP, whereas those composing the lateral map were preferentially labeled by wheat germ agglutinin‐HRP. In mammals, these HRP ligands selectively label the central projections of myelinated and unmyelinated cutaneous afferents, respectively. The present study, therefore, strongly supports the cytoarchitectonic findings of Brinkman and Martin (Brain Res. 56:43–62, ′73) that lamina III lies medial, rather than ventral, to lamina II in the chicken dorsal horn. Further, the present studies also suggest that laminae II and III of chickens are homologous to the homonymous laminae in the dorsal horn of mammals.