bluuebunny/crossref_metadata_2025_split huggingface dataset:
The organization of trigeminotectal and trigeminothalamic neurons in rodents: A double‐labeling study with fluorescent dyes
Authors: Bruce Laura L. , McHaffie John G. , Stein Barry E. 
Published: January 2005

AbstractRetrogradely transported fluorescent dyes (fast blue and diamidinodihydrochloride yellow) were used to compare the distributions of trigeminofugal neurons that project to the superior colliculus and/or the thalamus in three rodent species. The objective was to determine what the projection and collateralization patterns of these trigeminofugal pathways are and whether they are similar among different species. In each anesthetized animal, one dye was injected into the superior colliculus and the other into the topographically congruent area of the thalamus. Counts of the numbers of yellow, blue, and double‐labeled neurons were made throughout the trigeminal complex: principalis, pars oralis, pars interpolaris, and pars caudalis.Trigeminothalamic projections were similar in each of the rodent species studied. The densest concentration of retrogradely labeled neurons was in principalis, with substantially fewer neurons in pars interpolaris, and fewer still in pars oralis and pars caudalis. These neurons were generally small and tended to have round or fusiform somata. A common pattern was also noted among the three species for trigeminotectal neurons. Most trigeminotectal projections originated from neurons in pars interpolaris, somewhat fewer from pars oralis, and the fewest from principalis and pars caudalis. These neurons tended to be the largest in each subdivision and were often multipolar.Following paired injections of the tracers, double‐labeled neurons were scattered throughout the sensory trigeminal complex and had morphologies characteristic of single‐labeled trigeminotectal neurons. Although comparatively few double‐labeled neurons were observed in any species, most of those seen were restricted to the ventrolateral portion of pars interpolaris, a position that corresponds to the representation of the vibrissae. These data indicate that, regardless of the rodent species, the vast majority of labeled trigeminal neurons project either to the superior colliculus or the thalamus, but not to both targets. This might be expected on the basis of the very different behavioral roles these structures play. On the other hand, a sub‐population of trigeminal neurons exists (mainly in pars interpolaris) that does project to both the superior colliculus and the thalamus, perhaps because both structures require some of the same somatosensory information to perform their behavioral functions.
Neuropeptide neuronal efferents from the bed nucleus of the stria terminalis and central amygdaloid nucleus to the dorsal vagal complex in the rat
Authors: Gray Thackery S. , Magnuson Debra J. 
Published: January 2005

AbstractThe lateral bed nucleus of the stria terminalis (BSTL) and central nucleus of the amygdala (Ce) are amygdaloid nuclei that have similar affer‐ent and efferent connections within the brain. Previous studies have demonstrated that both regions send axonal projections to the dorsal vagal complex (dorsal motor nucleus and nucleus tractus solitarii). The present study used the combined retrograde fluorescence‐immunofluorescence method to examine whether cells contributing to this pathway contained any of the following neuropeptides: corticotropin‐releasing factor, neurotensin, somatostatin, substance P, enkephalin, or galanin. The inputs to the dorsal vagal complex originated mainly from ventral BSTL and medial Ce, although a significant number of neurons within the dorsal BSTL and lateral Ce also contributed. Corticotropin‐releasing factor, neurotensin, and somatostatin neurons mainly located within the dorsal BSTL and the lateral Ce contained retrograde tracer after injections into the vagal complex. Substance P neurons in the ventral BSTL and medial Ce provide a sparse input to the dorsal vagal complex. Enkephalin and galanin neurons within the BSTL and Ce did not appear to project to the dorsal vagal complex. Corticotropin‐releasing factor and neurotensin neurons within the lateral hypothalamus also project to the dorsal vagal complex. Approximately 22% of the Ce and 15% of the BSTL retrogradely labeled neurons were peptide immunoreactive. Thus, it is concluded the Ce and BSTL are sources of a significant peptidergic pathway to the dorsal vagal complex. However, it is also apparent that the majority of putative transmitter types within the amygdaloid vagal projection still are unknown. The results suggest that the dorsal and ventral BSTL and the lateral and medial Ce, respectively, are homologous zones with regard to chemoarchitecture and connections. The data is discussed considering the possible function of peptides within descending amygdaloid pathways to the brainstem.
Developing neuronal populations of the cat retinal ganglion cell layer
Authors: Wong R. O. L. , Hughes A. 
Published: January 2005

AbstractAn improved flat‐mount procedure demonstrates that the developing ganglion cell layer of the cat retina contains two morphologically distinct populations of presumed neurons at all ages between embryonic day 36 (E36) and adulthood. One population resembles the adult “classical neurons” composing the ganglion cells and bar‐cells of Hughes, while the remaining cells, which are smaller and possess much less Nissl substance, presumably correspond to precursors of the adult microneurons.Although the total neuron population of the retinal ganglion cell layer remains quite constant at all studied ages, its component subpopulations alter significantly during prenatal development; some 50% of classical neurons disappear before birth and the microneuron population doubles during the same period. An obvious centroperipheral gradient exists for classical neurons by stage E47, but the microneuron density gradient only becomes apparent at birth. A 2:1 centroperipheral ratio for the total neuron population is also apparent at E47. Centroperipheral neuronal density gradients continue to increase during postnatal growth.Loss of classical neurons during prenatal life as a result of cell death or transformation into microneurons, has been postulated as a mechanism for determining neuron density gradients. Cell death does occur in the ganglion cell population but it is not yet established whether microneurons of the ganglion cell layer originate from ganglion cell transformation or migrate as a differentiated class from the ventricular layer. However, it can be concluded that not all microneurons originate from ganglion cell transformation, because the total loss of classical neurons is less than the increase in microneuron numbers during development.The population magnitudes of both neuronal classes in the ganglion cell layer stabilise after birth. However, it is during the postnatal period that the adult cruciate density topography is achieved by both populations. It is concluded that differential areal growth is the prime mechanism for postnatal cell redistribution.
Spatiotemporal gradients of kainate‐sensitivity in the developing chicken retina
Authors: Catsicas Stefano , Clarke Peter G. H. 
Published: January 2005

AbstractWe have studied the age‐dependence of the effects of kainate (KA) on the chick retina as a prelude to the accompanying paper on the effects of target‐removal on the isthmo‐optic nucleus. KA was injected into the eyes of chick embryos and chicks at different ages, and the retinas were fixed a few hours or several days later. The former group of retinas was scanned for pyknotic cells. The earliest age at which KA caused pyknosis was embryonic day 10 (E10), when pyknotic cells appeared in a ventrotemporal patch in the amacrine sublayer near the fundus. Over the next two days the sensitive region expanded tangentially, reaching the periphery first temporally, then nasally. Only after E12 did the KA cause pyknotic cells to occur also in the bipolar sublayer, where the sensitivity spread in the same spatiotemporal sequence as the initial wave, but two days later.Cell loss was examined in embryos that survived a week or more after the KA injection. Substantial cell depletion was found in both the inner nuclear and ganglion cell layers, but only when the injection had been made after E12. With progressively later injections, the depleted zone expanded in the same spatiotemporal sequence as described above, until at E15 the injections caused depletion throughout the entire extent of the retina. The reasons for the lack of cell depletion after KA injections made before E12 are discussed. Cell counts in the ganglion cell layer and studies of anterograde transport of intravitreally injected peroxidase along the retinofugal fibers showed that about half the ganglion cells (including the displaced ganglion cells) pass through a period of vulnerability to the KA injections, to which they subsequently become insensitive.
Immunocytochemical localization of γ‐aminobutyric acid in the hypoglossal nucleus of the macaque monkey, Macaca fuscata: A light and electron microscopic study
Authors: Takasu N. , Nakatani T. , Akikuni T. , Kimura H. 
Published: January 2005

AbstractThe hypoglossal nucleus of the macaque monkey Macaca fuscata was investigated with light and electron microscopic immunocytochemistry with an antibody directed against γ‐aminobutyric acid (GABA). At the light microscopic level, GABA immunoreactivity was present in small neurons, punctate structures, and thin, fiberlike structures. These GABA‐positive elements were distributed throughout the hypoglossal nucleus at rostrocaudal levels. There was no immunoreactivity in the hypoglossal motoneurons. The GABA‐positive small neurons, were fusiform or ovoid (15 × 9 μm) and extended a few proximal dendrites from both poles. At the ultrastructural level, there small neurons were characterized by a markedly invaginated nucleus and a scanty cytoplasm in which cisternae of rough endoplasmic reticulum were not organized into extensive lamellar arrays as seen in the motorneurons. The GABA‐positive punctate structures at the light microscopic level were identified as vesicle‐containing axon boutons at the electron microscopic level. These GABA‐positive axon terminals made synaptic contacts mainly with the dendrites of the motoneurons and infrequently with the somata. The majority of them made symmetric synapses and they contained pleomorphic synaptic vesicles. However, a small number of GABA‐positive terminals (7%) formed asymmetric synapses with the dendrites of motoneurons, and these contacts exhibited postsynaptic dense bars or Taxi bodies lying beneath the postsynaptic membranes. There were no GABA‐positive boutons that contacted the cell bodies of the small neurons. Although GABA‐positive myelinated and unmyelinated axons were seen as thin, fiberlike structures, these myelinated and unmyelinated axons rarely gave rise to boutons on the motoneurons.The present study suggests that GABAergic inhibition in the monkey hypoglossal nucleus occurs mainly on the dendrites of the motoneurons and to some extent on the somata.
Evidence for the existence of a lateral cervical nucleus in mice, guinea pigs, and rabbits
Authors: Giesler Glenn J. , Miller Lisa R. , Madsen Anne M. , Katter James T. 
Published: January 2005

AbstractThe lateral cervical nucleus of carnivores is large and is thought to play a prominent role in somatosensory processing. In contrast, early studies indicated that rats, mice, guinea pigs, and rabbits did not have a lateral cervical nucleus. However, we reported the existence of a lateral cervical nucleus in rats as a result of studies using retrograde transport techniques. In the present study, similar techniques were used to examine the possibility that early studies also overlooked the lateral cervical nucleus in mice, guinea pigs, and rabbits. In each of these species, a retrograde tracer was injected into the thalamus. These injections labeled a small number of neurons contralaterally in the dorsal part of the lateral funiculi of rostral cervical segments. Mice had the greatest number of neurons projecting from the lateral cervical nucleus to the thalamus, and rabbits had the fewest.
Spinocerebellar projections from the cervical enlargement in the cat, as studied by anterograde transport of wheat germ agglutinin–horseradish peroxidase
Authors: Matsushita Matsuo , Ikeda Michiko 
Published: January 2005

AbstractThe projection fields of spinocerebellar tracts arising from the cervical enlargement were studied by the anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) in the cat.Following injections of WGA‐HRP into the C5–C8 or T1 segments, labeled terminals were seen in lobule I to sublobule Vf of the anterior lobe, and lobule VI, sublobule VIIb, lobules VIII and IX, the simple lobule, crus II, and the paramedian lobule of the posterior lobe. In the sagittal plane of sublobules Ib–Vf and sublobules VIf and VId, the labeled terminals were distributed mainly in the superficial two thirds of the apicobasal extent. The labeled terminals in the anterior lobe accounted for about 70% of the total labeled terminals; the great majority were in lobule IV (17–20%) and lobule V (40%). The labeled terminals in the posterior lobe accounted for 30% of the total labeled terminals; the majority were in sublobules VIf (11–15%) and VId (6%). In the mediolateral extent, more than 50% of the total labeled terminals in each lobule were concentrated within 1.0 mm from the midline (the vermis) and 70–80% within 2.0 mm from the midline (the vermis and the medial part of the intermediate regions). A smaller number were also present in the intermediate region. Cases with lateral cordotomies revealed that the projections were bilateral but predominantly ipsilateral to the cells of origin and that the quantity of the ipsilateral projection was 66.5–75% of the total in each of sublobules IVb, Va, and VIf, The projection to the paramedian lobule was also predominantly ipsilateral.Projection fields in the horizontal plane were reconstructed from a series of transverse sections through each lobule. In sublobules Va–VIf labeled terminals were distributed in three areas; area 1 located within 0.25 mm from the midline in zone Al of Voogd; area 2 located between 0.5 and 0.75 mm lateral to the midline in zones Al and A2; and area 3, which appeared to be located between 0.75 and 1.5 mm lateral to the midline in zones A2‐B. These areas extended longitudinally in the apical two thirds of the lobules.From the present and previous retrograde HRP studies it was suggested that the neuronal groups in the cervical enlargement (the medial lamina VI group and the central lamina VII group) project to lobules I–V of the anterior lobe and lobule VI, sublobule VIIb, and lobule VIII of the posterior lobe. They have strong projections to caudal lobules of the anterior lobe (lobules III–Va) and lobules facing the primary fissure (sublobules Vd–Vf and sublobules VIf and VId).
VIP‐ and CCK‐like‐immunoreactive neurons in the hedgehog (Erinaceus europaeus) and Sheep (Ovis aries) brain
Authors: Antonopoulos J. , Papadopoulos G. C. , Karamanlidis A. N. , Parnavelas J. G. , Dinopoulos A. , Michaloudi H. 
Published: January 2005

AbstractThe distribution pattern and the morphology of vasoactive intestinal polypeptide (VIP)‐ and cholecystokinin (CCK)‐like‐immunoreactive neurons were studied in the brain of the hedgehog and the sheep by means of the peroxidase‐antiperoxidase immunocytochemical method. A total of 34 hedgehogs and 26 sheep of both sexes were used. Fourteen hedgehogs and 13 sheep received an intracerebroventricular injection of colchicine that enhanced the immunostaining and revealed “new” immunoreactive cell bodies. VIP‐immunoreactive bipolar and multipolar neurons were observed in both species in the cerebral cortex, hippocampal formation, amygdaloid complex, hypothalamus, and central gray substance of the midbrain. CCK‐immunoreactive bipolar, bitufted, and multipolar neurons displayed a broader distribution in both mammals than VIP neurons and were found in the cerebral cortex, the hippocampal formation, the amygdaloid complex, the hypothalamus, the mesencephalon, and the pons.In the cortex, in both the hedgehog and the sheep, VIP neurons were located in all layers but were concentrated in layers II and III, with the majority being typical bipolar. CCK neurons were more numerous in the superficial layers (I‐III) but were found in the deep layers as well. They were bipolar, bitufted, or multipolar in morphology. From these neurons a small percentage, which were located almost exclusively in layers II and III of the visual cortex, exhibited also VIP immunoreactivity. Perikarya of such double‐labeled cells were ovoid or round in shape with one or two main processes emanating from each pole of the cell body and oriented perpendicularly to the pia. The coexistence of the two peptides within individual neurons of the cortex has not been reported in other species and its physiological significance is discussed in relation to the GABAergic neurons of the cortex.
Role of the target in directing the outgrowth of retinal axons: Transplants reveal surface‐related and surface‐Independent cues
Authors: Hankin Mark H. , Lund Raymond D. 
Published: January 2005

AbstractIn the present investigation we have examined whether retinal axons can be directed to the superior colliculus via an alternate route when they do not have access to their normal substrates along the optic tract. To address this issue we transplanted embryonic mouse retinae into the mid‐brain parenchyma and to various positions around the outer surface of the midbrain of newborn rats and then examined the development of projections from the transplanted tissue. The projections from cortical grafts placed in the midbrain were studied to determine whether axons from different classes of neurons respond to the same cues for outgrowth.When retinae were placed within the midbrain close to the cerebral aqueduct, axons projected dorsally to the superficial layers of the superior colliculus. Directed outgrowth was seen from the earliest time a projection could be detected and was independent of whether the superior colliculus still received host optic afferents. In contrast, the major projection from similarly placed cortical transplants was directed toward the ventral part of the midbrain. Deafferentation of midbrain corticorecipient areas did not affect the projection patterns from either type of graft. Projections from retinae placed more ventrally in the midbrain tegmentum could not be detected. However, retinae placed on the surface of the midbrain, even as far ventral as the cerebral peduncle at the level of the inferior colliculus, always had a projection to the superior colliculus that ran along the brain‐stem surface.These observations, suggest that the superior colliculus exerts a positive influence on the growth of optic axons to the midbrain. However, while target cues appear to be able to support retinal axon growth through the midbrain parenchyma, their range appears to be limited, and at distances beyond the extent of their influence, optic fiber outgrowth occurs only over the surface of the brain. It is suggested, therefore, that there are both local surface‐related and target‐derived surface‐independent cues that guide optic axons to the tectum in developing mammals.
Factors guiding optic fibers in developing Xenopus retina
Authors: Bork Tracie , Schabtach Eric , Grant Philip 
Published: January 2005

AbstractWe have characterized, by electron microscopy, the growth of pioneering axons from the retina into the visual pathway during early development of Xenopus laevis. The subsequent development of following fibers from the growing retinal margin as they accumulated in the ganglion cell fiber layer (GCFL) of the retina was also studied.Extracellular channels bordered by neuroepithelial cells appear in the developing retina in a dorsal to ventral gradient before any pioneering axons are seen. Pioneering axons are subsequently observed in these channels, usually surrounded by neuroepithelial cell processes. Ruthenium red treatment of embryonic retinas reveals extracellular matrix (ECM) within these retinal channels, while extracellular spaces in the proximal optic stalk, just beyond the optic disc, lack this material. ECM is also seen in optic tectum wherever ingrowing retinal and nonretinal axons are found. The channels and the ECM contained within them may provide guidance cues for pioneering retinal axons. The early association of pioneering retinal axons with neuroepithelial cell processes (putative glia) appears to be important in further development of the GCFL.The so‐called following fibers of ganglion cells, arising later in development, fasciculate with pioneer axons in extracellular spaces and form fiber bundles of the GCFL on top of the layer of glial cell endfeet. It is not clear whether pioneering axons, glial cell surfaces, or both serve as guidance cues for following fiber migration.
Anatomical demonstration of ocular segregation in the retinogeniculocortical pathway of the new world capuchin monkey (Cebus apella)
Authors: Hess Douglas T. , Edwards Michael A. 
Published: January 2005

AbstractWe describe the architecture of the dorsal lateral geniculate nucleus and primary visual cortex (striate cortex; area 17) of the New World capuchin monkey (Cebus apella) on the basis of the distribution of cell bodies and cytochrome oxidase histochemistry. Changes in staining for cytochrome oxidase following unilateral enucleation served to indicate the organization of the representation of the two eyes in the retinogeniculocortical pathway.The number and disposition of eye‐specific layers within the lateral geniculate nucleus of Cebus are consistent with the common plan of geniculate organization in anthropoid primates, and the radial organization of area 17 fits the pattern common to New World squirrel and Old World macaque monkeys, including the presence of cytochrome‐oxidase‐rich zones in supragranular and deeper cortical layers (Horton: Philos. Trans. R. Soc. Lond. [Biol.]304: 199–253, '84).Our principal finding is that cytochrome oxidase histochemistry following unilateral eye removal unequivocally reveals ocular dominance columns in the striate cortex of Cebus. As in the macaque (Hubel: Nature 292: 762–764, '82), ocular dominance columns extend through the thickness of cortex and blobs are centered on columns, but the array of columns viewed tangentially is less orderly or more mosaic than in the macaque, and there is apparently significant overlap between columns.The presence of well‐defined ocular dominance columns in Cebus, as in Ateles (Florence, Conley, and Casagrande: J. Comp. Neurol. 243: 234–248, '86) but not in other New World monkeys examined previously, emphasizes the phylogenetic lability of binocular segregation in the primate visual cortex. In addition, the present results indicate significant differences with respect to the tangential organization of the ocular dominance domain between primate species in which ocular dominance columns are present.