bluuebunny/crossref_metadata_2025_split huggingface dataset:
Patterns of cell proliferation in the retina of the clawed frog during development
Authors: Beach D. H. , Jacobson Marcus 
Published: January 2005

AbstractQuantitative assays of the spatial pattern of cell production in the developing retina of Xenopus have been made using 3H‐thymidine labelling and colcemid blockade of mitosis. Reconstructions were made from serial sections showing the position of every mitotic figure in the retina. After stage 54 the number of mitotic figures decreases at the dorsal margin of the retina and increases at the ventral margin. The ventral:dorsal ratio of mitoses reaches 10:1 by metamorphosis. Density of mitotic figures is maximum at the point of entry of the ophthalmic vessels at the ventral margin. In spite of asymmetrical production of retinal cells the cell density remains constant throughout the retina, probably as a result of displacement of retinal cells dorsally to compensate for the relatively greater proliferation ventrally. It is also proposed that the asymmetrical retinal growth serves to maintain the relationship between each point in visual space and corresponding points in the two retinae as the eyes are displaced dorsally on the head during metamorphosis.
The generation of neurons involved in an early reflex pathway of embryonic mouse spinal cord
Authors: Sims Terry J. , Vaughn James E. 
Published: January 2005

AbstractThe generation of lateral motor neurons (LMNs), interneurons and dorsal root ganglion (DRG) neurons of the cervical mouse spinal cord has been investigated by [3H]thymidine autoradiographic techniques. This investigation has two main objectives: (a) to determine on which embryonic days these three neuronal populations are born, and (b) to investigate the possibility that the neurons comprising early reflex circuits might be formed by a retrograde temporal sequencing of generation. LMNs are the first neurons generated in the cervical spinal cord. They arise between E8.8 and E11.5, and approximately 90% of these cells are born within a 36‐hour period between E9 and E10.5. The earliest time of origin for interneurons is on E9.5, and those cells which are generated between E9.5 and E10.5 cluster in two distinct regions of the adult spinal cord. One of these regions is the lateral portions of laminae IV through VI; this appears to be the location of many ipsilateral association neurons. DRG neurons begin to arise on E9.5 and their generation is completed by E14. There is a trend within the DRG population for large neurons to be born before small neurons. Those cells with diameters of 40 μm or greater reach their generation peak on E10.5, while those smaller than 40 μm arise in the greatest numbers on E12.The findings of other investigations have provided evidence for a retrograde sequence of synaptic closure in the formation of the early disynaptic forelimb reflex pathway. The temporal difference in synapse formation in the terminal fields of DRG and association neurons is discussed in terms of our observation that both of these populations appear to have similar generation times. We suggest that factors responsible for the delayed synaptic closure of DRG afferents include the greater distances and the degree of collateralization which these afferents must undergo in order to establish their terminal fields. Finally, we discuss the possibility that the temporal sequence of neuronal generation and factors involved with the growth of neurites combine to produce a retrograde sequence of synaptic closure in the early disynaptic forelimb reflex pathway of mouse spinal cord.
An autoradiographic examination of corticocortical and subcortical projections of the mediodorsal‐projection (prefrontal) cortex in the rat
Authors: Beckstead Robert M. 
Published: January 2005

AbstractThe efferent connections of the cortex projected upon by the mediodorsal thalamic nucleus (MD‐projection cortex) have been re‐examined autoradiographically in the rat following the microelectrophoretic injection of 3H‐proline‐leucine into different parts of the medial and sulcal MD‐projection cortex. Contrary to previous negative findings, the present experiments revealed a system of extensive corticocortical projections and indicated that different areas of the MD‐projection cortex have distinctive patterns in both their corticocortical and subcortical projections. Thus, cell of Brodmann's area 32 send axons to the retrosplenial cortex, area 29d, the peri‐ and entorhinal cortices, and the presubiculum. Both supragenual and more posterior regions of area 24 project to the retrosplenial cortex and area 29d, but only the posterior portion projects additionally to the entorhinal area and presubiculum. The cortical targets of axons from the sulcal MD‐projection cortex are mainly the anterior part of the piriform cortex and, for the posterolateral part of the sulcal cortex (insular area), the retrosplenial area, lateral entorhinal area, and presubiculum. While the medial and sulcal divisions of the MD‐projection cortex project upon one another, the medial‐to‐sulcal projection is in general denser than its reciprocal.Earlier findings of projections to subcortical structures affiliated with the limbic system such as midline thalamic nuclei, hypothalamus, and paramedian mesencephalic tegmentum are confirmed, and appear to originate primarily in area 32 and the insular part of the sulcal cortex. The corticothalamic projection to MD in general terms reciprocates the organization seen in the thalamocortical projection from the various subnuclei within MD. Previously undocumented projections are demonstrated mainly from area 32 of the medial cortex and the insular part of the sulcal cortex to the lateral and basal amygdaloid nuclei, the medial part of the lateral septal nucleus, the nucleus accumbens, and the deep layers of the olfactory tubercle; the medial part of the lateral habenular nucleus receives a projection from areas 32 and 24. Projections to the pretectal area and superior colliculus appear to originate from all parts of the medial MD‐projection cortex, but are markedly denser when the posterior part of area 24 is injected. The distribution of this corticotectal projection shows a highly characteristic configuration in which areas of high grain concentration surround areas of lower grain concentration.
An autoradiographic examination of the central distribution of the trigeminal, facial, glossopharyngeal, and vagal nerves in the monkey
Authors: Beckstead Robert M. , Norgren Ralph 
Published: January 2005

AbstractThe central distributions of primary afferent axons in cranial nerves V, VII, IX, and X have been re‐examined autoradiographically after 3H‐proline injections into their peripheral ganglia. Fiber‐labeling after subtotal injections of the trigeminal ganglion, besides confirming earlier classical descriptions, suggests that trigeminal fibers of the ophthalmic and mandibular (but not maxillary) branches enter the ventrolateral part of the nucleus of the solitary tract (NST). Injection of VII's geniculate ganglion labels fibers which both ascend and descend upon reaching NST. The ascending fibers distribute in a compact and circumscribed zone immediately dorsal to the spinal V nucleus as far rostral as the caudal pole of the principal trigeminal nucleus. The descending fibers distribute to the lateral NST rostral to the level at which X joins the solitary tract. For a short distance caudal to this level, sparse label is confined to a small part of lateral NST ventral to the solitary tract, which corresponds to the zone receiving direct trigeminal afferents. Fiber‐labeling after injections of the ganglia of nerves IX and X suggest the following. Although, upon reaching NST, a few fibers of either IX or X ascend as far rostrally as had those of VII, both have a much larger descending component which distributes to more caudal levels of NST. Most of IX's axons appear to end in the lateral NST; only a few travel as far as the obex. Fibers of X, on the other hand, are abundant in the medial and commissural parts of NST. Moreover, only X appears to have a crossed projection in the commissural nucleus and caudal portion of the contralateral NST. A few fibers of vagal origin also appear to enter the area postrema. Whereas fibers of X appear to constitute the solitary tract, few if any fibers of VII or IX travel within that fascicle. A significant descending components of labeled fibers appears in the spinal V tract when the superior ganglion of either IX or X is injected. These fibers distribute mainly in the pars caudalis of the spinal V nucleus and, to a lesser degree, the cuneate nucleus.
Abnormal retino‐geniculate and geniculo‐cortical pathways in several genetically distinct color phases of the mink (Mustela vison)
Authors: Guillery R. W. , Oberdorfer M. D. , Murphy E. H. 
Published: January 2005

AbstractSeveral genetically distinct color phases of mink, which all show an abnormal reduction of pigment in the retinal pigment epithelium and which also show abnormalities of the retinofugal pathways, have been studied. Autoradiographic methods have been used to demonstrate the retino‐geniculate pathways, and retrograde degeneration or the retrograde transport of horseradish peroxidase has been used for the geniculo‐cortical pathways.The retino‐geniculate abnormality is mild in some of the color phases and extremely severe in others, but within any one color phase the variability is relatively low. Although the severity of the abnormality varies between color phases, a rather specific pattern of abnormal geniculate innervation is recognizable for mink in general and this is distinct from that found in Siamese cats. In the abnormal mink the size of geniculate lamina A1 is reduced and there is an abnormal crossed input going to the intermediate sectors of this reduced layer. Layer C1 also receives an abnormal crossed input, but this is more variable than that going to A1 and there appears to be little correspondence, retinotopically, between the normal inputs to layers A1 and C1. In some of the abnormal mink there are interruptions within the cytoarchitectonically definable layer A1, and opposite these gaps reduplications of layer A are commonly seen, as though there is an intrinsic geniculate mechanism for generating the characteristic multilaminar geniculate structure. However, there are also numerous examples of fusions between layers receiving afferents from the same eye, and these demonstrate that the development of geniculate lamination must also be under the influence of the retinal inputs.The geniculo‐cortical pathway shows a normal topography in most of the mink. Abnormal geniculo‐cortical projections, comparable to the “Boston” pattern of Siamese cats are extremely rare, and their occurrence could not be correlated with the severity of the retino‐geniculate abnormality or with the laminar pattern in the lateral geniculate nucleus. We suggest that the development of one or the other pattern of geniculo‐cortical projection may depend upon the relative timing of the two mechanisms that produce the geniculate lamination.
Neuronal populations of the human periaqueductal gray, nucleus lateralis
Authors: Laemle Lois K. 
Published: January 2005

AbstractThe present communication is part of a study designed to explore the neuronal populations and the organization of the periaqueductal gray matter (PAG). The data presented here deals exclusively with the nucleus lateralis (PAGL) and is based upon Golgi studies of 14 human brainstems. In this investigation 400 cells were measured and classified. Axonal origin, axonal and dendritic ramifications, and spine population were studied. The data demonstrate that morphologically the PAGL is comprised of a heterogeneous population of small and medium sized neurons consisting of three major cell types: vertical cells, stellate cells, and horizontal cells. Observations of axonal pathways and dendritic ramifications describes an anatomical substrate for direct communication between the PAGL and the superior colliculus, which includes a system of axonal projections from the PAGL into the superior colliculus. The cells of origin of this pathway have been identified as being primarily vertical and stellate cells. It is anticipated that these data will provide the groundwork for further detailed study of PAGL neurons and for identifying specific neuronal populations with their functional roles.
Topographic organization of the projections of the retina to the pretectal region in the rat
Authors: Scalia Frank , Arango Victoria 
Published: January 2005

AbstractThe pattern of projection of the retina to the pretectal region and its retinotopic organization were investigated in the rat by autoradiographic and silver impregnation techniques for axonal pathways. The endings of retinal axons form three terminal fields in the pretectum in: 1, olivary pretectal nucleus (PO), bilaterally; 2, posterior pretectal nucleus (PP), bilaterally; and 3, nucleus of the optic tract (NTO), contralaterally. The following retinotopic pattern was observed in rats surviving peripheral retinal lesions and injections of 3H‐proline in the same eye, when the positions occupied by terminal degeneration in Fink‐Heimer stained sections were matched with the corresponding areas deficient in radiolable in adjacent autoradiographic sections showing the surviving parts of the terminal fields. The nasal periphery of the retina maps along the adjoining edges of PO and PP, both of which extend obliquely, in a posterolateral direction, through the entire extent of the pretectum. Both nuclei map the line of representation of the anterior midline (in the temporal retina) along their opposite edges (anterolaterally, in PO; posteromedially, in PP). This mirror‐image symmetry is completed by the representation of the ventral peripheral retina separately in the rostral poles and the dorsal peripheral retina separately in the caudal poles of both nuclei. The map in NTO is vertically oriented, with the temporal retina, dorsally, the nasal retina, ventrally, the ventral retina, rostrally, and the dorsal retina caudally represented. The binocular area of the terminal field in PO is subdivided by a terminal‐free zone into two parts that may process separately events in the central and lateral visual field.
Ruffed cell: A new type of neuron with a distinctive initial unmyelinated portion of the axon in the olfactory bulb of the goldfish (Carassius auratus). I. Golgi impregnation and serial thin sectioning studies
Authors: Kosaka Toshio , Hama Kiyoshi 
Published: January 2005

AbstractA new type of neuron was recognized in the olfactory bulb of the goldfish (Carassius auratus) by means of light and high voltage electron microscopy of Golgi‐impregnated material, combined Golgi‐electron microscopy, and electron microscopy of serial thin sections.The neuron is located in the layer between the olfactory nerve layer and the anterior olfactory nucleus. It has a spherical cell body, about 10–20 μm in diameter, and several dendrites which form a spherical dendritic field, about 70–100 μm in diameter, in the vicinity of the cell body.The most remarkable structural feature of this neuron is that its initial unmyelinated portion of the axon (IP) has elaborate protrusions with many synapses. The IP can be divided into three parts, parts 1, 2 and 3, based on its structural features.Part 1 is the initial part of the IP, about 20–40 μm in length. Many elaborate protrusions arise from the shaft and intermingle with one another to constitute a spherical field, about 20–40 μm in diameter, around the shaft. Part 2 is the middle part of the IP, about 10–20 μm in length. There are several collaterallike protrusions, which are scattered along the shaft and extend laterally about 5–15 μm. Part 3 is the last part of the IP, and is cylindrical without protrusions. The length of part 3 varies from 20 to more than 100 μm. The axon acquires a myelin sheath at a distance of 70–250 μm from its origin.Protrusions make synaptic contacts mainly with granule cell dendrites. Some of them are of the reciprocal type. Protrusions are presynaptic in asymmetrical synapses, and postsynaptic in symmetrical synapses with granule cell dendrites. The shaft of the IP also has synapses similar to those on protrusions.The neuron described is a new type of neuron in the vertebrate central nervous system. We propose for it the name “ruffed cell”.
Efferent connections of the habenular nuclei in the rat
Authors: Herkenham Miles , Nauta Walle J. H. 
Published: January 2005

AbstractThe efferent connections of the medial (MHb) and lateral (LHb) habenular nuclei in the rat were demonstrated autoradiographically following small injections of tritiated amino acids localized within various parts of the habenular complex. Comparison of individual cases led to the following conclusions.MHb efferents form the core portion of the fasciculus retroflexus and pass to the interpeduncular nucleus (IP) in which they terminate in a topographic pattern that reflects 90° rotations such that dorsal MHb projects to lateral IP, medial MHb to ventral, and lateral MHb to dorsal IP. Most MHb fibers cross in the interpeduncular nucleus in the “figure 8” pattern described by Cajal, and terminate throughout the width of IP with only moderate preference for the ipsilateral side. However, the most dorsal part of MHb projects almost exclusively to the most lateral IP zone in a cluster pattern that is particularly dense on the ipsilateral side. The MHb appears to have no other significant projections, but very sparse MHb fibers may pass to the supracommissural septum and to the median raphe nucleus.Except for some fibers passing ventrally into the mediodorsal nucleus, all of the LHb efferents enter the fasciculus retroflexus and compose the mantle portion of the bundle. No LHb projections follow the stria medullaris. In the ventral tegmental area LHb efferents become organized into groups that disperse in several directions: (a) Rostrally directed fibers follow the medial forebrain bundle to the lateral, posterior and dorsomedial hypothalamic nuclei, ventromedial thalamic nucleus, lateral preoptic area, substantia innominata and ventrolateral septum. (b) Fibers turning laterally distribute to the substantia nigra, pars compacta (SNC); a small number continue through SNC to adjacent tegmentum. (c) The largest contingent of LHb efferents passes dorsocaudally into paramedian midbrain regions including median and dorsal raphe nuclei, and to adjacent tegmental reticular formation. Sparse additional LHb projections pass to the pretectal area, superior colliculus, nucleus reticularis tegmenti pontis, parabrachial nuclei and locus coeruleus. No LHb projections appear to involve the interpeduncular nucleus. All of these connections are in varying degree bilateral, with decussations in the supramammillary region, ventral tegmental area and median raphe nucleus.On the basis of differential afferent and efferent connections, the LHb can be divided into a medial(M‐LHb) and a lateral (L‐LHb) portion. The M‐LHb, receiving most of its afferents from limbic regions and only few from globus pallidus, projects mainly to the raphe nuclei, while L‐LHb, afferented mainly by globus pallidus and in lesser degree by the limbic forebrain, projects predominantly to a large region of reticular formation alongside the median raphe nucleus. Both M‐LHb and L‐LHb, however, project to SNC. The reported data are discussed in correlation with recent histochemical findings.
The cytoarchitecture of the interfascicular nucleus and ventral tegmental area of tsai in the rat
Authors: Phillipson O. T. 
Published: January 2005

AbstractThe cytoarchitecture of the ventral tegmental area of Tsai (VTA) has been studied in detail in the rat with the aid of both conventional techniques and glyoxylic acid‐fluorescence histochemistry. Three main dopamine containing cells groups can be distinguished: nucleus paranigralis, nucleus parabrachialis pigmentosus lies dorsally, and nucleus paranigralis ventrally in the VTA, while nucleus linearis continues posteriorly and medially from VTA and extends dorsally in the midline up towards the dorsal raphe nucleus. Fluorescent neurons in these three groups correspond to the A10 group. In addition to these previously described findings, the present study shows evidence for a further small but cytoarchitecturally distinct dopaminergic group called the interfascicular nucleus. This lies anterorly and ventrally in the ventral tegmentum in the midline, dorsal to the rostral portion of the interpeduncular nucleus and interpeduncular fossa.The significance of these cytoarchitectural findings in discussed in relation to the known connections of the region.
The GABA Neurons and their axon terminals in rat corpus striatum as demonstrated by GAD immunocytochemistry
Authors: Ribak C. E. , Vaughn J. E. , Roberts E. 
Published: January 2005

AbstractGlutamic acid decarboxylase (GAD, EC 4.1.1.15), the enzyme which catalyzes the α‐decarboxylation of L‐glutamate to form the neurotransmitter γ‐aminobutyric acid (GABA), was localized immunocytochemically in neurons of rat neostriatum, pallidum and entopeduncular nucleus. A large amount of GAD‐positive reaction product was observed in both the pallidum and entopeduncular nucleus in light microscopic preparations and was localized ultrastructurally to axon terminals that surrounded dendrites and large somata. In the neostriatum the relative numbers of GAD‐positive axon terminals per unit area were substantially less than in the pallidum. GAD‐positive terminals predominantly formed symmetric synapses with somata, dendrites and spines, but a small number of them formed asymmetric synapses with either dendrites or spines. The presence of GAD within these terminals is consistent with results of other investigations which have indicated that the striatopallidal and striatoentopeduncular pathways as well as neostriatal local circuit neurons and/or collaterals from neostriatal projection neurons, use GABA as a neurotransmitter.GAD‐positive reaction product was also localized within the somata and dendrites of neostriatal and pallidal neurons in colchicine‐injected preparations. The GAD‐positive somata in the pallidum were medium‐sized neurons and since such cells project to the substantia nigra, our results are in agreement with those from other studies which demonstrate a GABAergic, pallidonigral pathway. In the neostriatum, GAD‐positive somata were identified light microscopically as medium‐sized neurons with either round or fusiform shapes. Electron microscopic examinations also showed GAD‐positive reaction product within the perikaryal and dendritic cytoplasm of these neurons, as well as in dendritic spines. These findings are in accord with the results of studies which have indicated that medium‐sized, spinous neurons of the neostriatum give rise to a GABAergic, striatonigral pathway. The significance of GAD localization within these neostriatal neurons is discussed in relation to recent findings which show that substance P is contained within this same class of striatonigral projection neuron.