bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ganglion cell arrangement and axonal trajectories in the anterior lateral line nerve of the weakly electric fish Apteronotus leptorhynchus (Gymnotiformes)
Authors: Lannoo Michael J. , Maler Leonard , Tinner Barbro 
Published: January 2005

AbstractTo determine the organizational principles underlying the peripheral electrosensory nervous system of weakly electric gymnotiform teleosts we labelled each of the four anterior lateral line nerve branches with HRP. We determined the position of labelled cell bodies within the ganglion and followed anterogradely filled fibers to their termination sites in one of the four somatotopic maps in the electroreceptive lateral line lobe (ELL). Within the ganglion, cell bodies exhibit a loose somatotopy based on nerve branch position: trunk electroreceptors have their cell bodies located in the caudal ganglion; cell bodies to the head receptors are rostral. Cell bodies to the head exhibit a rough dorsoventral polarity, supraorbital cells tend to be located dorsally, infraorbital cells centrally, and mandibular cells ventrally. Despite this general somatotopy there is substantial overlap (up to 30%) of cell bodies among regions. There appears to be no rostrocaudal topography within nerve branch regions. Iontophoretic WGA‐HRP injected into the medial segment of the ELL retrogradely labelled cell bodies that innervate ampullary organs. These cell bodies were dispersed throughout the ganglion, indicating that cell bodies do not cluster by receptor type. Peripherally directed axons from the ganglion appear to undergo an active reorganization in order to form the nerve branches. Within nerve branches, axons to a particular area of skin do not cluster together.Centrally from the ganglion, axons retain the position of their cell body until they reach the ELL border. Once in the ELL, fibers become sorted in the deep fiber layer according to receptor type and the map they terminate in. This reorganization involves rearrangement of fascicles and axons within fascicles. In toto, proceeding from peripheral to central, the electrosensory periphery loses at least a portion of its receptor topography in the distal nerve and ganglion and then acquires both a functional and somatotopic organization after reaching the ELL; conceptually it is torn down and rebuilt again. From an ontogenetic perspective, axonal growth occurs from the ganglion outward; the fact that ganglion cell bodies are not highly organized while the receptors they innervate and their central processes are suggests that active axonal guidance mechanisms are involved.
Immunocytochemical investigation of L‐glutamic acid decarboxylase in the rat hippocampal formation: The influence of transient cerebral ischemia
Authors: Johansen Flemming‐Fryd , Lin Chin‐Tarng , Schousboe Arne , Wu Jang‐Yen 
Published: January 2005

AbstractThe hippocampus is especially vulnerable to ischemic damage. Neurons in the CA3c region and dentate hilus demonstrate fast progressive damage while CA1 pyramidal cells demonstrate delayed neuronal damage. The delayed CA1 pyramidal cell loss could be caused by postischemic neuronal hyperactivity if hippocampal interneurons are lost after ischemia. Therefore we have counted the L‐glutamic acid decarboxylase (GAD)‐immunoreactive neurons in the hippocampus from control rats and rats surviving 4 or 11 days after 20 minutes of cerebral ischemia. All rats were injected intraventricularly with colchicine before they were killed.The hippocampal cell counts showed an increase in GAD‐immunoreactive somata visualized on the fourth postischemic day. Eleven days after ischemia, the number of GAD‐immunoreactive neurons visualized in the hippocampus CA1 and CA3c region decreased. GAD‐immunoreactive baskets were visualized in the pyramidal cell layer and the granule cell layer in controls and 4 days after ischemia, but not in the CA1 and CA3c pyramidal cell layer 11 days after ischemia.We suggest the number of GAD‐immunoreactive neurons visualized on the fourth postischemic day increases because somatal GAD accumulation increases and, therefore, ischemia may enhance GAD production. Our previous counts of CA1 interneurons 21 days after ischemia in toluidine‐stained semithin sections demonstrated no interneuron loss. Therefore we suggest that the decreased number of CA1 and CA3c GAD‐immunoreactive neurons visualized 11 days after ischemia is related to a decreased GAD production. It is possible at this stage after ischemia that the interneurons have decreased their GAD production because they have lost their input and/or target cells.We conclude that our counts of GAD‐immunoreactive neurons visualized after ischemia express changes in the content of somatal GAD rather than the actual number of GAD‐immunoreactive somata. Finally, we conclude that the delayed loss of CA1 pyramidal cells seen 4 days after ischemia is not preceded by loss of hippocampal GAD‐immunoreactive neurons.
Serotoninergic neurons in the mormyrid brain and their projection to the preelectromotor and primary electrosensory centers: Immunohistochemical study
Authors: Grant K. , Clausse S. , Libouban S. , Szabo T. 
Published: January 2005

AbstractSerotonin‐containing neurons in the brain of the weak‐electric fish Gnathonemus petersii (mormyridae, teleostei) were studied with the aid of immunohistochemical labeling. Study of the central serotoninergic innervation was focused on the structures subserving the command of the electric organ and the first central relay of the electrosensory system.In the midline raphe nuclei, serotoninergic neurons formed a column that stretched from the ventral caudal medulla to the dorsal midbrain, ending caudal to the cerebellar peduncle. In the dorsal tegmentum, serotoninergic neurons were found bilaterally at the anterior margin of the decussation of the lateral lemniscus. Labeled neurons were also present bilaterally immediately anterior to the cerebellar peduncle and also in the pretectal region. In the hypothalamus, many serotoninergic neurons were in contact with the ventricular wall, and a few were present in the preoptic area. This distribution of serotoninergic cell bodies showed many similarities to that in other fish and higher vertebrates but lacked the lateral spread of the serotoninergic raphe system found in the midbrain tegmentum in mammals.Labeled fibers were found in both the preelectromotor medullary relay nucleus and the electromotor command nucleus. These serotoninergic projections were traced to the posterior raphe. Serotoninergic fibers also formed a dense network in the cortex and in the nucleus of the electrosensory lobe, both of which receive primary input from electroreceptors.These results suggest that serotonin may have a role in the modulation of the intrinsic, rhythmic electromotor command and in the gating of electrosensory input.
Neurogenesis of glutamic acid decarboxylase immunoreactive cells in the hippocampus of the mouse. I: Regio superior and regio inferior
Authors: Soriano Eduardo , Cobas Alberto , Fairén Alfonso 
Published: January 2005

AbstractThe neurogenetic gradients of neurons showing glutamic acid decarboxylase (GAD) immunoreactivity were determined in the regio superior and in the regio inferior of the mouse hippocampus. Pregnant C57B1 mice received pulse injections of (3H)thymidine from E11 through E17 (E0 being the day of mating). Distributions of (3H)thymidine‐labeled, GAD‐positive neurons in the different strata of the hippocampus proper were recorded in adult animals. GAD‐positive neurons in this region are generated prenatally. Radial gradients of neurogenesis of GAD‐positive cells are characterized by two main features: (1) with the exception of the stratum lacunosum‐moleculare and its interface with the stratum radiatum, GAD‐positive neurons of the plexiform strata are generated before those destined for the pyramidal layer; (2) within the pyramidal layer, GAD‐positive cells are positioned according to an inside‐out sequence. In the transverse axis, neurogenesis of GAD‐positive cells follows a regio inferior to regio superior gradient. This gradient is due to prolonged neurogenesis of GAD‐positive cells for the pyramidal layer in the regio superior. Given the selective laminar disposition of the GABAergic interneurons in the hippocampus, the present authors explored whether or not the diverse types of these interneurons could have specific birth dates and concluded that no relationship exists between birth dates and adult phenotypes of GAD‐immunoreactive cells in the mouse hippocampus proper.
Structure‐function relationships in rat brainstem subnucleus interpolaris: III. Local circuit neurons
Authors: Jacquin Mark F. , Golden Judy , Rhoades Robert W. 
Published: January 2005

AbstractIntracellular recording, electrical stimulation, receptive field mapping, and intracellular injection of horseradish peroxidase were used to assess the response properties, collateral projections, and morphology of 44 local circuit (LC) neurons in the subnucleus interpolaris (SpVi) of the trigeminal brainstem complex of the rat. LC neurons were defined as those with axons restricted to brainstem areas receiving trigeminal primary afferent fibers. Thus, none were antidromically activated from the thalamus, tectum, or cerebellum, and their axons could be seen terminating exclusively within the trigeminal brainstem complex or reticular formation. All neurons sampled were discharged by innocuous or noxious mechanical stimulation of a restricted portion of the face or mouth. They were classified functionally as sensitive to vibrissae (N = 22), nociceptors (N = 9), guard hairs (N = 7), hairy skin (N = 3), or periodontia (N = 3). Fifty percent of the stained neurons were vibrissa sensitive. Twenty‐one of these 22 responded to deflection of only one vibrissa. The remaining functional groups also had small receptive fields.Intracellular staining revealed a consistency in vibrissa‐sensitive LC morphology. Somata were small to medium in size and multipolar. Their axons had an initial transverse trajectory and gave off recurrent collaterals which arborized extensively in the region of the soma. The parent axon then bifurcated. One branch traveled rostrally to subnucleus principalis while the other branch traveled caudally to subnucleus caudalis. The branches periodically sent collaterals into regions of the trigeminal complex corresponding to the transverse position of the soma. Dendrites extended 440 ± 140 μm rostrocaudally, forming a tree with a transverse perimeter of 459 ± 226 μm. Distal dendrites were thin and sinuous, had few spines, and extensively arborized adjacent to the soma. They ended in multiple swellings connected by slender processes.The stereotyped morphology of vibrissa‐sensitive LC neurons differed from the variable morphologies of LC neurons activated by nociceptors, guard hairs, hairy skin, or periodontia. Although no group of neurons in one of these categories displayed a distinguishing morphological characteristic, they collectively had features which distinguished them from the vibrissa‐sensitive neurons. Non‐vibrissa‐responsive neurons generally had more expansive, but less circular, dendritic and recurrent axonal arbors; dendrites had more spines, and axons often sent endings into the reticular formation. Some did not display rostrally and caudally directed axon bifurcation, while others branched more extensively than vibrissa LC cells. Nociceptors tended to be located in the V spinal tract, rostrally displaced substantia gelatinosa, or in the border regions between SpVi and the reticular formation.
Light microscopic study of degenerating cobalt‐filled optic axons in goldfish: Role of microglia and radial glia in debris removal
Authors: Springer Alan D. , Wilson Bryan R. 
Published: January 2005

AbstractLabeling severed axons with cobaltous‐lysine ultimately leads to the degeneration of their distal segments. The present study was designed to determine whether microglia and radial glia have comparable roles in the elimination of degenerating axons. Another purpose was to determine whether the cobalt could escape from degenerating axons and enter intact neuronal cells. Optic axons were filled with cobaltous‐lysine for 1 day and the retinal projections were examined from 1 to 106 days later. Optimal filling was obtained 1 day postlabeling. The number of filled axons in the optic tract was significantly reduced at the 2‐day time point, indicating that many axons had disintegrated. Many axons contained large swellings that resembled cells. However, transneuronally labeled neuronal cells were never observed. Labeled, rounded microglia appeared among the degenerating axons at the 3‐day time point, and the microglia changed shape at 5 days. They became elongated and manifested many processes. In addition, the microglia began to move toward, and entered, the ventricles and vasculature. Virtually all the labeled debris was removed between 17 and 28 days following the application of cobalt. The rapidity with which the axons were removed suggests that the cobalt accelerates the degenerative process either directly, or indirectly by accelerating the arrival of phagocytic cells.Radial glia appeared to play a smaller role in debris elimination. They took up labeled debris to a lesser degree than microglia and were briefly labeled. Interestingly, radial glia did not take up cobalt when it was injected intracranially and diffused through the brain. A previous claim of an axosomatic retinotectal projection to cells deep in the stratum periventriculare of a teleost fish is reinterpreted to represent cobalt within radial glia.
Subcortical projections to the pontine nuclei in the cat
Authors: Aas Jan‐Erik 
Published: January 2005

AbstractIn a systematic attempt to trace all projections from the brainstem and diencephalon to the pontine nuclei of the cat, implantations and injections of horseradish peroxidase‐‐wheat germ agglutinin (HRP‐WGA) or Fluoro‐Gold were placed in the pontine nuclei of 21 cats. In most of the cases there was no evidence of spread of tracer outside the pontine nuclei. Retrogradely labeled cells in the brainstem and diencephalon were carefully mapped and counted.The number of labeled cells in the brainstem and diencephalon ranged from 24 in cases with very small implantations to 3,490 in cases with large injections in the pontine nuclei (counts from every fifth section). The labeled cells are located bilaterally with an ipsilateral preponderance. After large injections, 25‐38% of the labeled cells were located in the brainstem reticular formation, 10‐16% in the pretectal nuclei, 10‐15% in the hypothalamus, 7‐9% in the zona incerta, 3‐9% in the fields of Forel, 4‐5% in the nucleus locus coeruleus, 3‐5% in the ventral lateral geniculate body, 2‐4% in the superior colliculus, 3% in the periaqueductal gray, and 14‐15% in other parts of the brainstem.Judging from cases with small tracer deposits entirely confined to the pontine nuclei, there appear to be two types of subcortical inputs: Projections from the reticular formation, the nucleus locus coeruleus, the periaqueductal gray, and the raphe nuclei are widespread, presumably reaching all parts of the pontine nuclei, while projections from a diversity of other sources are localized, reaching limited parts of the pontine nuclei only or predominantly.
Effects of intraocular tetrodotoxin on the development of the retinocollicular pathway in the syrian hamster
Authors: Thompson Lan , Holt Christine 
Published: January 2005

AbstractThe developing uncrossed retinocollicular projection in the Syrian hamster undergoes a characteristic set of changes during the first 2 postnatal weeks. The retinal fibres, which initially project across the whole superior colliculus, withdraw from the caudal part and their terminals become clustered into deep, discrete clumps rostrally. Coincident with these afferent changes, there is substantial retinal ganglion cell death. To examine whether neuronal activity plays a role in these changes, we made daily injections of the sodium channel blocker tetrodotoxin (TTX) into one or both eyes from postnatal day 2 or 4 up to day 12.Following TTX treatment, the uncrossed terminals retracted on schedule from the caudal and superficial parts of the superior colliculus and came to lie, as normal, in the deep layers rostrally. Within the rostral superior colliculus, however, the uncrossed terminals from TTX‐injected eyes lost their characteristic patchy distribution and were arranged diffusely. When only one eye received TTX injections, this inhibiting effect on terminal segregation was seen only in the projections from the TTX‐treated eye. The effect of TTX treatment on terminal segregation was much less severe than that of unilateral enucleation, after which uncrossed terminals persist throughout the entire superior colliculus.TTX injections appeared to have little effect on overall ganglion cell death since the total number of ganglion cells in the crossed projection from TTX‐treated eyes was similar to that in normal eyes. However, the relative distribution of uncrossed cells in temporal and nasal retina was altered. In eyes that received TTX injections, the proportion of uncrossed cells in nasal retina was about 1.6 times that in normal animals and was close to the proportion seen in unilaterally enucleated animals. This increase in the treated eye occurred whether one or both eyes were injected with TTX.We conclude that neuronal activity plays a role in the segregation of uncrossed terminals into discrete clumps in rostral colliculus and in the preferential elimination of uncrossed cells from the nasal retina. The inactive uncrossed projections from TTX‐treated eyes showed the greatest degree of disruption. The extent of the disruption was similar whether the crossed input from the other eye was active or inactive. This suggests that the activity‐driven interactions between ganglion cells within one eye are more significant than those between the two eyes in shaping the final form of the uncrossed retinocollicular projection.
Cytoarchitectural characteristic of the frontal eye fields in macaque monkeys
Authors: Stanton G. B. , Deng S.‐Y. , Goldberg E. M. , McMullen N. T. 
Published: January 2005

AbstractThe cytoarchitecture of the prearcuate gyrus, including the region of the physiologically defined frontal eye fields (FEF), was studied in four macaque monkeys (Macaca fascicularis, M. mulatta) to determine if the FEF could be anatomically identified. Brain sections were stained with standard Nissl and, in some cases, myelin stains.Two nonstandard planes of section were used: one tangential to the prearcuate gyrus and the second normal to the most posterior bend of the prearcuate gyrus. The first plane of section was advantageous for studying the location of the FEF with reference to the entire medial‐lateral extent of the gyrus and the second allowed good comparisons of the FEF to adjacent anterior and posterior cortical areas. Frontal plane sections through the prearcuate gyrus were also examined in 15 macaque monkeys for comparison with sections cut normal to the posterior bend of the gyrus and tangential to the gyrus.Intracortical microstimulation was performed in three monkeys. The FEF was defined as the area from which low‐threshold (≤50 μA) saccades could be evoked. The area extended about 10 mm along the anterior bank of the arcuate sulcus. Within the area, saccade amplitudes were represented in a mediolateral, large‐to‐small topography. No topography of saccade direction was noted within FEF but reversals of saccade direction for any given electrode pass were found. These results confirm the results from our earlier mapping study of FEF (Bruce et al.: J. Neurophysiol. 54:714‐734, '85).Cell bodies of large pyramidal cells in layers III and V of the prearcuate gyri from three hemispheres were measured with the aid of an image‐combining computer microscope. The distribution of cells of >22 μm diameter or cross‐sectional areas of <500 μm2 were plotted. In one monkey, marker lesions made at microstimulation sites within the FEF or in adjacent non‐FEF areas were also plotted. The location of the FEF appeared to coincide with the concentration of large layer V pyramidal cells in the prearcuate gyrus rather than with any previously mapped cytoarchitectonic area. The numbers of large pyramids in layer V were noticeably reduced along the lip of the prearcuate gyrus and at dorsomedial and ventrolateral locations which were outside the physiologically defined FEF.
Laminar and areal differences in the origin of the subcortical projection neurons of the rat somatosensory cortex
Authors: Killackey Herbert P. , Koralek Katherine‐Ann , Chiaia Nicholas L. , Rhoades Robert W. 
Published: January 2005

AbstractFluorescent retrograde tracing techniques were employed in a double‐labelling paradigm to determine the distribution of corticospinal, corticotectal, and corticotrigeminal projection neurons in layer Vb of the adult and neonatal rat somatosensory cortex. The double‐labelling paradigm allowed a direct comparison of the cortical distribution of neurons projecting to each target and identification of neurons projecting to more than one target.In the adult rat, each population of projection neurons was found to have a unique laminar and/or areal distribution. Corticospinal projection neurons were located throughout the width of layer Vb in the medial granular portion of somatosensory cortex, while corticotrigeminal projection neurons were distributed throughout the width of layer Vb in the more laterally located dysgranular portion of somatosensory cortex. Corticotectal projection neurons were located more superficially in layer Vb than either corticospinal or corticotrigeminal projection neurons and found scattered throughout both dysgranular and granular somatosensory cortex. Each combination of subcortical injections also resulted in double labelling a small percentage of uniquely distributed neurons. These distribution differences coupled with measurements of cell size allowed us to identify the parent population of the dual projection neurons. Subpopulations of corticotectal neurons also project to the brainstem trigeminal complex and to the spinal cord. Subpopulations of corticotrigeminal neurons also project to the spinal cord, and a proportion of corticotrigeminal neurons projects to at least two targets within the brainstem trigeminal complex (nucleus principalis and subnucleus interpolaris). In the adult rat, corticospinal neurons (as defined by either laminar position or somal size) did not appear to give off collaterals to either the superior colliculus or brainstem trigeminal complex.In the neonatal rat, double‐labelled neurons which project to both the spinal cord and the tectum are distributed throughout the full width of layer Vb, rather than restricted to the superficial portion of the layer as in the adult rat. Further, it appears as if the ontogenetic change in the laminar distribution of corticospinal and tectal projection neurons is achieved by mechanisms of selective process elimination rather than cell death.These results are discussed in terms of both the developmental factors which may contribute to the discrete distribution of cortical projection neurons found in the adult and the functional significance of bifurcating projection neurons.