bluuebunny/crossref_metadata_2025_split huggingface dataset:
Histological and ultrastructural studies on the origin of caudal neural crest cells in mouse embryos
Authors: Schoenwolf Gary C. , Nichols David H. 
Published: January 2005

AbstractThe origin of neural crest cells was studied histologically and ultrastructurally in caudal regions of mouse embryos at 8.5–11 days of gestation (day of vaginal plug = day 0). The neural tube of caudal regions develops in two different phases, called primary and secondary neurulation. The primary (more cranial) portion of the neural tube originates from the ectodermal neural plate, whereas the secondary (most caudal) portion originates from the tail bud. We asked in this study: Do neural crest cells of caudal regions originate exclusively from the developing primary portion of the neural tube and, Subsequently, migrate into areas undergoing secondary neurulation; or do some of these cells originate from the tail bud, with the secondary portion of the neural tube, forming in situ in caudal areas? Most embryos were preserved with fixative containing cetylpyridinium chloride (CPC) to facilitate the identification of neural crest cells, which stain darkly after exposure to CPC during fixation. Our results suggest that there are two sources of neural crest cells in caudal regions: the neuroectoderm of the neural folds flanking the closing posterior neuropore, and the tail bud. Neural crest cells derived from the neuroectoderm are designated as the primary neural crest, because they form in conjunction with the primary portion of the neural tube during primary neurulation, whereas neural crest cells derived from the tail bud are designated as the secondary neural crest, because they form in conjunction with the secondary portion of the neural tube during secondary neurulation.
Experimental immunohistochemical studies on the substance P neuron system in the lateral habenular nucleus of the rat: Distribution and origins
Authors: Shinoda Koh , Inagaki Shinobu , Shiosaka Sadao , Kohno Jōji , Tohyama Masaya 
Published: January 2005

AbstractWe examined the distribution and afferent projections of substance P‐like immunoreactive (SPI) fibers in the lateral habenular nucleus of the rats by using the indirect immunofluorescence method.On the basis of the distribution, a dense plexus of SPI fibers in the lateral habenular nucleus (LHb) could be divided into two parts: medial (mLHb) and lateral (lLHb).The present study demonstrates that SPI fibers in the lLHb originate from SPI cells in the rostral entopeduncular nucleus (rEP) and the adjacent area, while those in the mLHb originate from SPI cells in the medial habenular nucleus. Moreover, we showed that the axons from SPI cells in the rEP reached the lLHB via the “pallidohabenular tract.”
The course of axons of retinal ganglion cells within the optic nerve and tract of the chick (Gallus gallus)
Authors: Ehrlich David , Mark Richard 
Published: January 2005

AbstractSmall laser lesions placed in the posthatch chicken retina resulted in axotomy and then death of all ganglion cells located in a sector peripheral to the primary damage. With the use of silver techniques, the patterns of degenerating retinal fibers in the optic nerve, chiasm, and optic tract were examined.In the proximal part of the optic nerve, radial retinal lesions resulted in a sheet of degenerating axons along the rostrocaudal extent of the nerve. The position of degenerating axons was related to the site of their entry in the optic nerve head with an overlapping distribution of degenerating fibers entering the optic nerve head from equivalent points from the temporal and nasal sides. In the optic chiasm, the distribution of fibers was similar to that seen in the proximal part of the optic nerve. In the optic tract there was a similar mixing of fibers from opposite sides of the retina. The ventral, nasal and temporal retinal fibers lay in the superficial part of the tract whereas the fibers from the nasal and temporal dorsal retina ran in the deeper, medial aspect of the tract. The central‐to‐peripheral axes of the retina were mapped along the rostrocaudal axis of the tract. As the tract approached the tectum degenerating fibers from single retinal lesions did not always remain together. In the case of a lesion in the ventral nasal retina, degenerating fibers split into two bundles located at opposite ends of the tract only to reunite at their terminal regional at the caudal pole of the tectum.We conclude that ordering is present throughout the primary optic pathways. The ordering is not faithfully retinotopic and may not contain sufficient cues to produce the retinotopic map on the tectum by fiber‐to‐fiber interactions alone.
Regional (14C) 2‐deoxyglucose uptake during forelimb movements evoked by rat motor cortex stimulation: Pons, cerebellum, medulla, spinal cord, muscle
Authors: Sharp Frank R. , Ryan Allen F. 
Published: January 2005

AbstractElectrical stimulation of the right forelimb motor (MI) sensory (SI) cortex in normal, adult rats produced repetitive left forelimb movements. Regions of increased (14C) 2‐deoxyglucose (2DG) uptake were mapped autoradiographically during these movements. MI stimulation activated the ipsilateral reticular tegmental pontine nucleus (RTF) and the middle (rostral‐caudal) third of the pontine nuclei including pyramidal (P), medial (POM), ventral (POV), and lateral (POL) pontine nuclei. The ipsilateral inferior olivary complex was activated including dorsal accessory olive (DAO), principal olive (PO), and medial accessory olive (MAO).The contralateral lateral reticular (LR) nucleus and nucleus cuneatus (CU) were activated. Lateral vermal, paravermal, and hemispheric portions of the contralateral cerebellum were also activated. Parts of vermian lobules IV, V, VI, VII, and VIII, and lobulus simplex, crus I, crus II, paramedian lobule, and copula pyramidis were activated. Granule cell layers were activated much more than molecular layers. Discrete microzones of high granule cell 2DG uptake alternated with zones of low uptake in left paramedian lobule and copula pyramidis and may correlate with the fractured cerebellar somatotopy described physiologically by Welker and his associates. Portions of the left lateral and interpositus nuclei were metabolically activated.Medial portions of laminae I‐VI were activated in the dorsal horn of cervical spinal cord. The 2DG uptake was either unchanged or decreased in the ventral horn. Thoracic and lumbar spinal cord were not activated. Monsynaptic MI and SI connections to P, POM, POV, POL, RTF, DAO, PO, MAO, LR, CU, and spinal cord could account for activation of those structures. However, there are no direct MI or SI connections to the deep cerebellar nuclei, the cerebellar hemisphere, or the muscles. Activation of these structures must be due to activation of polysynaptic pathways, sensory feedback from the moving forelimb, or both. The present experiments cannot distinguish these possibilities.Comparison of the regions activated during forelimb MI stimulation (FLMIS) to those activated during vibrissae MI stimulation (VMIS) suggests that the pontine nuclei, cerebellar hemisphere, and possibly the deep cerebellar nuclei are somatotopically organized. RTP, LR, CU, and spinal cord were activated during FLMIS but were not activated during VMIS. The failure to activate the ventral horn of cervical spinal cord may be due to known inhibition of alpha‐motor neurons during motor cortex stimulation.
Development of the transient ipsilateral retinotectal projection in the chick embryo: A numerical flourescence‐microscopic analysis
Authors: Thanos Solon , Bonhoeffer Friedrich 
Published: January 2005

AbstractThe ipsilateral retinotectal projection in the developing chick was examined by using rhodamine‐B‐isothiocyanate (RITC)as an anterograde and retrograde vital marker for the retinal ganglion cells and their axons. Staining of the entire retina following intravitreal RITC injection between incubation days 3 and 16 revealed a small number of anterogradely labeled fibers in the optic tract and the anterior half of the optic tectum ipsilateral to the injection site. The total number of ipsilaterally projecting fibers was estimated to be about 2,000 on developmental day 9. The ipsilateral projection totally disappeared after day 15. The arrangement of fibers within the ipsilateral projection was examined by local anterograde RITC staining of localized retinal regions between days 9 and 10. The projection was retinotopically organized along the dorsoventral axis such that fibers of dorsal retinal origin projected on the ventral tectal half, whereas fibers of ventral retinal orgin projected on the dorsal tectal half.The localization of ipsilaterally projecting ganglion cell bodies was examined by retrograde RITC staining during days 9 and 15. Ganglion cells of all four quadrants of the central retina contributed to the production of the ipsilateral projection. The ipsilaterally growing retinotectal fibers did not represent collaterals of contralaterally projecting retinotectal axons.We assume that the tendency of early growing retinotectal axons to grow straight, as well as the ability of axonal growth cones to “sample” the environment, lead to a crossing of axons to the contralateral side. Ipsilateral projections would therefore represent “pathfinding errors.” Explanations for the elimination of the ipsilateral retinotectal projection are discussed.
Asymmetric and symmetric synaptic junctions in the dorsal lateral geniculate nucleus of cat and monkey
Authors: Rapisardi Salvatore C. , Lipsenthal Lee 
Published: January 2005

AbstractWe have investigated the applicability of traditional classifications of synaptic junctions in the dorsal lateral geniculate nucleus (DLGN) of the cat and monkey. Our principal sample is restricted to synapses made by the retinal terminal (round vesicles) in DLGN and to synapses made by flattened vesicle processes that were postsynaptic to the retinal terminal. We inspected consecutive thin sections through 250 synaptic junctions that showed clear synaptic clefts in every section. The thickness of the membrane and postsynaptic density (PSD) was measured on each section and an average thickness was computed for each synaptic junction. In both species the frequency distribution for these measurements forms an uninterrupted progression from the absence of a continuous PSD through the presence of a heavy density with most synaptic contacts falling in the midrange. Twenty‐two of the round vesicle profiles and 40 of the flat vesicle profiles we studied had very modest densities (13–16 nm) and exhibited an continuous PSD on some sections, but only small puffs of a complete lack of density on others. We concluded that this group which constituted 25% of the synaptic contacts we studied could not be classified as asymmetric of symmetric.As a group the round vesicle synaptic junctions exhibited a heavier PSD than the flat vesicle contacts. The difference between the mean thickness the mean thickness in both species was statistically significant. However, we hesitate to describe the round vesicle contacts as symmetric because such a large proportion of the former made synaptic contacts with a PSD thickness within the range of the latter.
The morphology of dorsal column postsynaptic spinomedullary neurons in the cat
Authors: Bennett Gary J. , Nishikawa Nozomu , Lu Guo‐Wei , Hoffert Marvin Jay , Dubner Ronald 
Published: January 2005

AbstractDorsal column postsynaptic (DCPS) spinomedullary neurons from the cat's lumbosacral enlargement were identified by antidromic stimulation of the cervical dorsal columns and stained intracellularly with horseradish peroxidase. The cell bodies were located in laminae III‐IV. Their dendritic arbors were elongated rostrocaudally but narrow mediolaterally. On the average, the arbors were ×5 longer than they were wide. Most of the neurons had nearly all of their dendrites in laminae III‐IV and some of the neurons had, in addition, a considerable amount of dendritic surface area in lamina V. Only one neuron had more than a very small amount of dendritic surface area dorsal to lamina III. Seven of the neurons had unmyelinated axon collaterals that arborized extensively and issued varicosity‐bearing terminal branches in laminae III‐V, both within and beneath their dendritic territories. All of the neurons were excited by myelinated, low‐threshold mechanoreceptors. Since the rostrocaudally elongated and mediolaterally narrow dendritic arbors of DCPS neurons are in register with the laminae III‐IV terminal distributions of myelinated, low‐threshold mechanoreceptors, it is probable that this excitation arises from a monosynaptic and topographically discrete innervation. About one‐half of the DCPS neurons were also excited by noxious stimuli. It is probable that this excitation is accomplished by a polysynaptic distributions are largely or completely separate.
The lateral suprasylvian corticotectal projection in cats
Authors: Segal Richard L. , Beckstead Robert M. 
Published: January 2005

AbstractThe projection from the lateral suprasylvian visual areas to the superior colliculus was investigated in cats using both anterograde and retrograde tracing techniques. The retrograde transport of horseradish peroxidase (HRP) or wheat germ agglutinin‐HRP (WGA‐HRP) from their site of deposit in the superior colliculus indicates that all divisions of the lateral suprasylvian visual areas project to both the superficial and deep layers of the superior colliculus. However, following tracer deposits in the superior colliculus that are confined to the layers below the stratum opticum (deep layers), more neurons are labeled along the lateral bank than along the medial bank of the middle suprasylvian sulcus. Conversely, tracer deposits in the superior colliculus dorsal to and including the stratum opticum label more cells in the medial than the lateral bank. These retrograde experiments also confirm that the visual cortex along the lateral gyrus (areas 17 and 18) projects to the superficial, but apparently not to the deep layers. The visual area in the cortex surrounding the caudal two‐thirds of the anterior ectosylvian sulcus projects to the deep, but not to the superficial layers.The laminar and areal patterns of anterograde axon labeling in the superior colliculus were examined after single deposits of 3H‐amino acids (autoradiography), HRP, or WGA‐HRP in the lateral suprasylvian cortical regions, or combined isotope and WGA‐HRP deposits. Axon labeling in the superior colliculus is generally densest in the stratum opticum and extends either dorsally into the superficial layers or ventrally into the intermediate gray layer. Specifically, the anterior divisions of the lateral suprasylvian cortex project primarily to the lateral portion of the superior colliculus, with the projection from the medial bank biased toward the superficial layers and axons from the lateral bank aimed mainly at the intermediate gray layer with some axons even reaching the deepest gray layer of the superior colliculus. Both the posteromedial and posterolateral divisions of the lateral suprasylvian cortex project to more extensive portions of the mediolateral and rostrocaudal dimensions of the superior colliculus than the anterior divisions. However, the posterolateral division projects more heavily to the intermediate gray layer than the posteromedial division; from the latter, axons distribute more superficially in the superior colliculus. Finally, the cortex surrounding the posterior suprasylvian sulcus projects primarily to the medial part of the superficial layers of the superior colliculus.We conclude that regions along the lateral bank of the middle suprasylvian sulcus have quantitatively the greatest direct access to the deep layers, and may, therefore, have a profound influence on the sensorimotor functions attributed to the cells in the deep layers of the superior colliculus.
Serotonin‐immunoreactive neurons in the brain of the honeybee
Authors: Schürmann F. W. , Klemm N. 
Published: January 2005

AbstractThe distribution of serotonin‐immunoreactive neurons in the brain of the worker honey bee Apis mellifera was studied by means of immunocytochemical staining by using a well‐characterized antibody to serotonin (5‐HT). About 75 immunoreactive perikarya are grouped into clusters in the optic lobe and in the median and dorsal protocerebrum. Immunoreactive fibers were resolved in all areas of the brain. The optic lobe shows restricted layers of 5‐HT‐immunoreactive fibers in the lamina and medulla organized perpendicular to the retinotopic elements. Immunoreactive fibers in the lobula represent invasions of protocerebral giant wide‐field neurons. The nonglomerular neuropil of the brain exhibits a meshwork of immunoreactive fibres invading glomerular neuropil of the mushroom bodies, central body complex, and antennal lobes. Mushroom body stalks and lobes contain immunoreactive fibers arranged perpendicular to the Kenyon cell fibers and matching subcompartments of these corpora pedunculata areas. The calyces are devoid of immunofluorescence. Serotonin‐positive fibres in the central body complex are arranged in its subcompartments. No 5‐HT immunoreactivity was found in the pons. Antennal glomeruli contain immunoreactive fibers restricted around the margin of the glomeruli. The selective mapping of 5‐HT‐immunoreactive neurons complements studies on the distribution of monoamine‐containing neurons in the bee brain. Serotonin‐ and catecholamine‐containing neurons often occur together in the same brain areas and subcompartments. The immunohistochemical approach in chemoneuroanatomy gives new evidence for a more complicated architecture of the brain than could be deduced from the classical neuroanatomical studies.
An EM‐autoradiographic analysis of the projection from cortical areas 17, 18, and 19 to the superior colliculus in the cat
Authors: Behan Mary 
Published: January 2005

AbstractThe electron microscopic autoradiographic method was used to identify terminals of axons from cortical areas 17, 18, and 19 in the superficial layers of the superior colliculus. The results show that terminals of area 17 neurons contain round vesicles and made asymmetrical synaptic contacts predominantly onto one or more dendrites or dendritic appendages. Some profiles postsynaptic to labeled terminals contain vesicles and presumably are involved in serial synaptic arrangements.Terminals of area 18 and 19 neurons in the superficial collicular layers appear to comprise two populations, one similar in most respects to area 17 terminals, containing round vesicles and making asymmetrical contacts. The other contains pleomorphic vesicles and makes symmetrical contacts upon dendrites and dendritic appendages. These terminals rarely contact more than one postsynaptic profile, and rarely do the postsynaptic profiles contain vesicles. The two populations of area 18 and 19 terminals containing round and pleomorphic vesicles, respectively, are present in the ratio of approximately 3:1, although this ratio varies throughout the sublaminae of the superficial collicular layers.The presence of two distinct types of cortical terminals in the colliculus suggests that cortical modulation of collicular processing is more complex than was previously conceived.
Projections from the superior olivary complex to the cochlear nucleus in the tree shrew
Authors: Covey E. , Jones D. R. , Casseday J. H. 
Published: January 2005

AbstractThe origins and targets of projections from the superior olivary complex to the cochlear nuclei were studied in the tree shrew by placing small injections of horseradish peroxidase (HRP) in the cochlear nucleus and small injections of 3H‐leucine in the superior olivary complex. The results show that the descending pathways originate in periolivary cell groups surrounding the medial and lateral superior olives and that the periolivary nuclei differ from one another in their patterns of projections to the cochlear nucleus. For example, cell groups may project either ipsilaterally or bilaterally. Cells in the lateral nucleus of the trapezoid body project only to the ipsilateral cochlear nucleus. Other periolivary cell groups project bilaterally, although some of these may project more heavily to one side than the other. Some pathways have widespread targets in the cochlear nucleus whereas others have relatively specific targets. Diffuse projections to all divisions of the cochlear nucleus arise from the lateral nucleus of the trapezoid body ipsilaterally and from the medial perioliviary nucleus bilaterally. The targets of other descending pathways are more restricted. The anterolateral, dorsal, and dorsolateral periolivary nuclei project mainly to the anteroventral cochlear nucleus; the ventral nucleus of the trapezoid body and the posterior periolivary nucleus project mainly to the dorsal and posteroventral cochlear nuclei. All of these specific projections are bilateral. These results suggest that projections from the periolivary cell groups to the cochlear nucleus consist of multiple components with different degrees of specificity.
Retinal terminals in the goldfish optic tectum: Identification and characterization
Authors: Airhart Mark J. , Kriebel Richard M. 
Published: January 2005

AbstractRetinal terminal profiles in the goldfish optic tectum were identified electron microscopically after (1) labeling with horseradish peroxidase and (2) in the early stages of degeneration in short‐term eye enucleates. All labeled terminals shared certain common morphological characteristics which were identical to those of a population of terminals in normal tecta. Terminals of this type disappeared 30 days after enucleation of the contralateral eye.Retinal terminal presynaptic profiles were characterized by (1) round and oval synaptic vesicles; (2) mitochondria with irregular, randomly oriented cristae, large intracristal spaces, dilated membrane spaces, and primarily light matrices; (3) a wide range in profile area, 0.06–6.82 μm2; (4) large numbers of synaptic vesicles per profile area 168± 33 synaptic vesicles per μm2; (5) asymmetric synapses; and (6) multiple synaptic contacts (1.46 ± 0.73 per terminal profile). The postsynaptic elements included both dendritic and, less commonly, pleomorphic vesicle‐containing profiles. The majority of postsynaptic dendritic profiles were small (0.01–0.40 μm2). Serial synaptic contacts were occasionally seen.The combination of vesicular and mitochondrial morphology (1 and 2 above) was necessary and sufficient to establish the retinal origin of a terminal, but use of such criteria would underestimate the number of retinotectal terminals by omitting those which did not have a mitochondrion in the plane of section. The number of such terminals was calculated from independent measurements, and the total number of retinal terminal profiles per area of neuropil was estimated.