bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laminar origin of cortical neurons which project upon the caudate nucleus: A horseradish peroxidase investigation in the cat
Authors: Royce G. James 
Published: January 2005

AbstractThe horseradish peroxidase method was used to study the cortical projections upon the caudate nucleus in the cat. The cells of origin of the corticostriatal projection arise from both the supragranular (II and III) and infragranular (V and VI) cortical layers, in contrast to all other known corticofugal pathways to subcortical structures, which appear to arise only from the infragranular layers. This finding has been verified in the present study by several novel surgical procedures, which include direct injections into the caudate nucleus, after the overlying tissues have been removed.The present study also shows that there is a truly widespread distribution of the cells contributing to the corticostriatal projection. Some portion of every neocortical gyrus contains labeled cells, though their relative numbers vary greatly. Also, simple topographical relationships are maintained, but there is much overlap. In addition, present findings show that the corticostriatal projection is strikingly bilateral and originates from regions which are homotopic to the ipsilateral projection.
Connections of the small bipolar cells with the photoreceptors in the turtle. An electron microscope study of Golgi‐impregnated, gold‐toned retinas
Authors: Dacheux Ramon F. 
Published: January 2005

AbstractThe connections between photoreceptors and the small bipolar cells with a Landolt club in the turtle retina (Pseudemys scripta elegans) were analyzed with the electron microscope after Golgi impregnation and gold toning. The dendritic tree of several bipolars was partially or completely reconstructed from continuous series of thin sections. All bipolar cells studied established both basal and invaginating junctions with cone pedicles; in invaginating junctions, their dendrites invariably ended as the central process of triads. Dendrites of this bipolar cell type make invaginating synapses, basal junctions, or a mixture of both. In turn, each pedicle found within the dendritic field of the bipolar cell contacts it with a mixture of invaginating and basal junctions; furthermore, each pedicle synapses with more than one dendrite from the same bipolar cell. All small bipolar cells examined also synapse with rod pedicles; the geometry of the connections and the types of synapses are the same for both rods and cones. The fact that small turtle bipolars can form both basal and invaginating contacts with a single cone indicates that the polarity of the postsynaptic response can not be predicted on the basis of the structure of the photoreceptor‐to‐bipolar cell synapse.
The afferent connections of the tectum mesencephali in two chondrichthyans, the shark Scyliorhinus canicula and the ray Raja clavata
Authors: Smeets Wilhelmus J. A. J. 
Published: January 2005

AbstractThe afferent connection of the tectum mesencephali were studied in the spotted dogfish Scyliorhinus canicula and the thornback ray Raja clavata by means of the horseradish peroxidase (HRP) technique. Following unilateral injections in the tectum, labeled neurons could be identified in all main divisions of the brain and in the cervical spinal cord. Telencephalic neurons which project to the tectum mesencephali were observed in the caudal part of the pallium. Diencephalic projections to the tectum originate from the thalamus dorsalis pars medialis, the thalamus ventralis pars lateralis, the nucleus medius infundibuli, and the pretectal area. In Scyliorhinus labeled neurons could also be found in the corpus geniculatum laterale. Mesencephalic cells of origin of tectal afferent pathways were identified in the stratum cellulare externum of the contralateral tectum, in the nucleus tegmentalis lateralis, in the ventrolateral tegmentum, and in the nucleus ruber. Rhombencephalic cells projecting to the tectum could be identified in the nucleus cerebelli (only in Scyliorhinus), the nucleus vestibularis superior, the reticular formation, the nucleus funiculi lateralis, the nucleus tractus descendens nervi trigemini, and the nucleus dorsalis and intermedius areae octavolateralis. In addition a number of small‐and medium‐sized cells of the reticular formation were found labeled. Diffusely scattered labeled cells could be observed in the dorsal part of the cervical spinal cord. It is concluded that the tectal afferent connections in the chondrichthyans studied in general resemble those of other vertebrates, but that some striking differences exist. In particular, tectal afferents originating from the nucleus medius infundibuli, the nucleus cerebelli, and the nucleus dorsalis and intermedius areae octavolateralis have not been reported in other vertebrates.
Retinal degeneration during clinical scrapie encephalopathy in hamsters
Authors: Buyukmihci Ned , Goehring‐Harmon Faye , Marsh Richard F. 
Published: January 2005

AbstractWeanling hamsters were inoculated intracerebrally with brain suspensions from normal or scrapie‐infected hamsters. A third group of uninoculated animals was fed cuprizone. Histologic and electron microscopic examination of the neural retinas and retinal pigment epithelium was done. At 50 days postinoculation, when scrapie‐infected animals began to show clinical signs of encephalopathy, there was a variable degree of photoreceptor degeneration. By the time animals were moribund, at 74 days postinoculation, photoreceptor degeneration was severe, as demonstrated by loss of most outer and inner segments and cell bodies. The outer plexiform, inner nuclear, and inner plexiform layers were reduced in thickness. Some retinal pigment epithelial cells contained lipoidal inclusions. The neural retinas and retinal pigment epithelium of noninfected and cuprizone‐treated animals were normal. We have previously shown that the scrapie agent accumulates in the retina; that together with our present work, we conclude that the scrapie agent is the cause of photoreceptor degeneration in experimentally inoculated hamsters.
Peripheral control of midbrain mitotic activity in the frog
Authors: Kollros Jerry J. 
Published: January 2005

AbstractEyes were removed unilaterally from stage 19–25 embryos and stage I larvae of Rana pipiens. Control and operated animals were fixed 2–27 days later, at stages I through V +. Midbrains were removed and sectioned, and complete counts of all mitoses in both tecta were made, to permit comparisons between tecta receiving optic nerve fibers and those lacking them. Differences between the two sides were insignificant in control animals and in those fixed at stages I and II. In the 39 stage III animals differences approached significance (P < 0.06), whereas for stages IV and V, with 20 animals in each group, significance was seen (P < 0.01). Rostral parts of the tectum, richly supplied by optic nerve fibers, showed much greater percentage differences in mitotic activity than did the caudal parts of the tectum, poorly supplied or lacking such fiber input. Overall, areas of ventricular surface in the affected tecta at stages IV and V were reduced very nearly to the same degree as was cell division. The role of the optic nerve fibers in maintaining division rates is made evident, particularly by the reduction of numbers of prospective ependymal cells. That the influence is seen so very early implies that production of prospective neurons, not just glia, has been affected.
A light and electron microscopic study of the interstitial nucleus of cajal in rat
Authors: Rutherford J. G. , Gwyn D. G. 
Published: January 2005

AbstractThe morphology of the interstitial nucleus of Cajal (INC) in the rat was studied with the light and electron microscope. The INC was mapped throughout its rostrocaudal extent from cresyl violet‐stained frozen sections cut transversely through the midbrain in the stereotaxic plane. Caudally, the INC consisted of a small number of scattered cells lying ventrolateral to the periaqueductal grey. In three of four cases studied, the caudal tip of the nucleus was located between 40 and 120 μm rostral to the rostral tip of the somatic cell columns of the oculomotor nucleus. Proceeding rostrally, the INC increased in size, reaching its maximal development just caudal to its most rostral extent. The INC was limited rostrally by the fibers of the fasciculus retroflexus. The mean rostrocaudal length of the INC was 1.12 mm.On the basis of light microscopic observations of cresyl violet‐stained paraffin sections, two groups of neurons could be distinguished in the INC. One group consisted of large, oval to multipolar cells with mean dimensions of 33 × 23 μm. The second group, which included by far the greatest number of cells, consisted of small to medium neurons, round, triangular, polygonal or fusiform in shape, with mean dimensions of 19 × 14 μm.Injection of horseradish peroxidase into lesions in the cervical spinal cord resulted in retrograde labeling of neurons of all sizes and shapes throughout the length of the INC. Labeled neurons were also found in the red nucleus, the mesencephalic reticular formation, and the nucleus of the posterior commissure.All the morphological varieties of neurons described with the light microscope could be identified in the electron microscope. Large neurons, and some cells of the small to medium group, contained well developed Nissl bodies, together with numerous cytoplasmic organelles. Many neurons in the small to medium group, however, did not contain conspicuous Nissl bodies, and had a poorly developed rough endoplasmic reticulum.Axon terminals containing either round or pleomorphic vesicles were seen in the INC. Axosomatic synapses were formed by both types of terminals. Such synapses were usually symmetrical, regardless of the shape of the vesicles within the terminal. In a number of neurons, the percentage of the surface of the neuronal somata in direct apposition to axon terminals was measured. The results of such measurements suggest that a greater percentage (more than 50%) of the surface of larger neurons is apposed by axon terminals than is the case with smaller neurons, which, on the average, were invested by axon terminals over 15% of their total surface in any given single plane of section. Axon terminals investing the surfaces of proximal dendrites were morphologically similar to those in apposition to neuronal somata.
Immunohistochemical evidence of indolamine neurons in monkey spinal cord
Authors: Lamotte Carole C. , Johns Donald R. , de Lanerolle Nihal C. 
Published: January 2005

AbstractIn this study, we have identified over 150 cells in the adult macaque spinal cord that are immunoreactive when stained with an antibody to 5‐HT by means of the PAP method. The staining was blocked by preabsorption of the primary antibody by the 5‐HT‐BSA conjugate (used to generate the antibody) and by 5‐HT, while BSA, dopamine, norepinephrine, 5‐methoxytryptamine and tryptamine preabsorption did not block staining. In addition, the Falck‐Hillarp histofluorescence technique was applied to the lumbosacral cord from one of the three monkeys studied; results confirm the presence of cells with yellow fluorescence and rapid fading to brown characteristic for serotoninergic cells.The neuronal identity of these immunoreactive cells is based on light and electron microscopic morphology and the presence of synaptic terminals in contact with labeled somata and dendrites. Most of these neurons were small (10–25 μm) and located ventral to the central canal in lamina X. Some processes of the cells extended into the intermediate gray and the ventromedial area of the ventral horn; other processes wrapped around large blood vessels in lamina X or around the wall of the central canal. Cells were most frequent in the cervical cord (approximately 6–7/mm length of cord) and less frequent in thoracic (1.5/mm), lumbar (3/mm), and sacral (2/mm) cord. A few cells were also found in the marginal and gelatinosa regions of the dorsal horn of the sacral cord.Examination of sections from the medulla‐spinal cord junction (obex level) indicates that the spinal cells may be an extension of cell groups located near the raphe obscurus in the gray region around the IVth ventricle. The indolamine spinal cells may act as interneurons in spinal circuits, control spinal blood flow through vessel innervation, or play a role in CSF composition through central canal innervation.
Chandelier cells in rat visual cortex
Authors: Peters Alan , Proskauer Charmian C. , Ribak Charles E. 
Published: January 2005

AbstractGolgi‐impregnated chandelier cells in rat visual cortex have been examined by both light and electron microscopy. All of the chandelier cells impregnated have their cell bodies within layer II/III and although they occur throughout area 17, there are increased numbers at the area 17/18a border and to a lesser extent at the area 17/18 border. Most of the chandelier cells are bitufted neurons, with groups of dendrites extending from the upper and lower poles of an elongate cell body, but some cells have a more multipolar configuration. The perikaryal cytoplasm is rich in rough endoplasmic reticulum and both the cell body and the sparsely spinous dendrites receive axon terminals forming symmetric and asymmetric synapses. The axons of these neurons arise from either the lower pole of the cell body or the base of one of the dendrites in the lower tuft, and the axons form laterally spread plexuses which terminate in vertical strings of boutons. The boutons in each string synapse with axon initial segments of layer II/III pyramidal cells, the uppermost bouton in each string being 7 to 14 μm distant from the pyramidal cell body. Some layer II/III pyramidal cells seem to receive boutons from more than one chandelier cell, others from a single chandelier cell, and still others appear to receive no chandelier cell terminals. The axon terminals of the chandelier cells are irregular in shape, contain pleomorphic synaptic vesicles, and form symmetric synapses. Evidence is presented to show that axon terminals exhibiting the same morphological features and site of synaptic termination as those of the chandelier cells contain glutamic acid decarboxylase (GAD), the enzyme which synthesizes GABA. Hence the chandelier cells are probably GABAergic, inhibitory neurons. Other GAD‐positive axon terminals synapse with the cell bodies, axon hillocks, and proximal portions of the axon initial segments of the layer II/III pyramidal cells, and these terminals are probably derived from the smooth and sparsely spinous stellate cells.
Quantitative electron microscopic analysis of the optic nerve of the turtle, Pseudemys
Authors: Geri George A. , Kimsey Randall A. , Dvorak Charles A. 
Published: January 2005

AbstractIt is estimated by means of electron microscopy that the optic nerve of the turtle Pseudemys scripta elegans contains 394,900 fibers of which approximately 80% are myelinated. The total fiber count agrees well withcounts obtained from electron microscopic studies on other turtle species. There are, however, differences among these species in the percentage of myelinated fibers in the optic nerve. The axon diameter distribution of the myelinated fibers (excluding myelin) has a mode at 0.87 μm while that of the unmyelinated fibers has a mode at 0.42 μm. Both distributions are unimodal and are of a similar form in all areas of the nerve sampled. The total fiber count reported here agrees well with previous reports of ganglion cell counts in Pseudemys and the characteristics of the fiber distributions are comparable to those reported for nonreptilian vertebrates.
Generation of new cerebral ganglion neurons in the snail Melampus: An ultrastructural study
Authors: Moffett Stacia , Austin Daniel R. 
Published: January 2005

AbstractReports in the literature have established that reconnection of central neural tracts occurs following commissurotomy and cerebral ganglion excision in the primitive pulmonate snail Melampus bidentatus and have suggested the possibility that long‐term regeneration might result in the appearance of new neurons in the ganglion bud. We have used electron microscopy to examine the ganglion buds that form by reconnection of cerebral nerves, commissure, and connectives following cerebral ganglion excision in adult Melampus. The buds were examined from 2.5 to 12 months postoperatively. By 2.5 months, ganglion buds consist of a mixture of axon tracts that travel through the bud region and some dendritic processes; a few synaptic contacts can be identified at this stage, scattered throughout the bud. By 5–6 months, some of the most advanced ganglia have undifferentiated cells that are distinct from glia. By 7 months, differentiated neurons with clear, small dense‐core or neurosecretory vesicles are present, although these cells are not all concentrated in a rind on the ganglion surface. Another cell type, the pigment‐sheath cell, is present by this stage. By 11–12 months, the most advanced regenerating ganglia have neurons which form a cell rind on the ganglion surface. The gross appearance of a regenerated ganglion at this stage is similar to that of the intact contralateral cerebral ganglion, although the regenerated ganglion is smaller. One 12‐month ganglion was found to possess fairly normal intraganglionic morphology, with lobes and cell types that were recognizable. Hence, nerve cell regeneration can occur in the absence of body part regeneration in adult members of one species of pulmonate snail.
The developmental morphology of Torpedo marmorata: Electric lobe‐electromotoneuron proliferation and cell death
Authors: Fox Geoffrey Q. , Richardson Guy P. 
Published: January 2005

AbstractElectromotoneuron proliferation and cell death have been quantitativelystudied in the electric lobe of Torpedo marmorata from an embryonic body‐length stage of 26‐mm to adult animals. These neurons project to the electric organ and form synapses with electrocytes which possess a remarkably large postsynaptic target surface. For this reason cell death would not be predicted to occur if synaptic competition were to be hypothesized as thecause. Isolated observations at the ultrastructural level suggested, however, that cell death was indeed taking place and therefore it seemed appropriate to examine this question in detail.Our findings show first that neuron production appears to be a continuous process throughout the period studied, generating totals of over 70,000 electromotoneurons per lobe by adulthood. Second, two waves of cell death were identified, one occurring early in embryogenesis (stage 30 mm), well before the onset of synaptogenesis, and a second coincident with the onset ofsynaptogenesis (stages 55‐74 mm). It is difficult to reconcile this latter wave with the hypothesis of synaptic competition as the postsynaptic surface at this time of development is largely devoid of synaptic contacts. We conclude that in the electromotor system of Torpedo, synaptic competition is probably not the mechanism of cell death.
Generation of motoneurons in the rabbit brainstem
Authors: Shaw Marjorie D. , Alley Keith E. 
Published: January 2005

AbstractAutoradiography of 3H‐thymidine incorporation was used to determine the time of origin of motoneurons in the rabbit brainstem. With the exception of the facial nucleus, neurons of the branchial motor column originated earlier (days 9 and 10) than somatic motor column neurons (day 11). Labeling was obtained as early as embryonic day 8 for many motor nuclei and the mesencephalic trigeminal nucleus. The significance of temporal patterns of neurogenesis is discussed.
Afferent connections of the cerebellum in various types of reptiles
Authors: Bangma G. C. , Donkelaar H. J. Ten 
Published: January 2005

AbstractThe origin of cerebellar afferents was studied in various types of reptiles, viz., the turtles Pseudemys scripta elegans and Testudo hermanni, the lizard Varanus exanthematicus, and the snake Python regius, with retrograde tracers (the enzyme horseradish peroxidase and the fluorescent tracer “Fast Blue”). Projections to the cerebellum were demonstrated from the nucleus of the basal optic root, the interstitial nucleus of the fasciculus longitudinalis medialis, the vestibular ganglion, and the vestibular nuclear complex, two somatosensory nuclei, viz., the descending nucleus of the trigeminal nerve and the nucleus of the dorsal funiculus, the nucleus of the solitary tract, the reticular formation, and throughout the spinal cord. A distinct bilateral projection to the cerebellum was found to arise in a nucleus previously called nucleus parvocellularis medialis (Ebbesson, ′67). In the present study this cell mass is termed the perihypoglossal nuclear complex, considering its comparable position and fiber connections to the perihypoglossal nuclei in mammals. In all reptilian species studied a contralateral cerebellar projection of a cell mass located in the caudal brainstem adjacent to the nucleus raphes inferior was observed. It seems likely that this cell mass represents the reptilian homologue of the mammalian inferior olive. Most of the spinocerebellar fibers appeared to arise in neurons located in area VII‐VIII of the gray matter. In this respect the origin of the spinocerebellar projection in reptiles resembles the origin of the rostral and ventral spinocerebellar tracts in mammals. No indications for the existence of a column of Clarke or a central cervical nucleus in the reptilian spinal cord were obtained.On comparison of the cerebellar afferents in reptiles with the known connections of the cerebellum in amphibians, birds, and mammals, a basic pattern of cerebellar afferent projections appears to exist in these vertebrateclasses, including retinal, vestibular, precerebellar, somatosensory, and spinal afferents.
Quantitative analysis of neuronal development in the lateral motor column of mouse spinal cord. I. Genetically associated variations in somal growth patterns
Authors: Holley John A. , Wimer Cynthia C. , Vaughn James E. 
Published: January 2005

AbstractThe relative somal and nuclear sizes of neurons in the lateral motor column (LMC) of adult and embryonic mouse brachial spinal cord were determined by light microscopic morphometry. Three genetically varying mouse strains, previously shown to differ in the development of a forelimb reflex pathway, were studied. In adults, the size distribution of somata, nuclei, and nucleoli were bimodal for each strain, indicating that there are two distinct size classes of LMC neurons. The size division between large and small LMC neurons differed among strains with more large LMC neurons occurring in strain CBA/CaJ than in either LP/J or C57BL/6J. In embryos, the growth of LMC cells was studied by determining the average area of nuclear profiles for specimens ranging in age from embryonic day 11 (E11) to 16. The average nuclear profile area increased significantly during this period in all three strains, and differences were found in the initial size and apparent rate of growth among strains. Early in development (E11‐12), strain differences in apparent cell size were: C57BL/6J>CBA/CaJ>LP/J, and this strain order corresponds to observed strain differences in the onset of reflexogenesis and synaptogenesis (Vaughn et al., ′75). Later in development (E16), strain differences in apparent cell size were: CBA/CaJ>LP/J≥C57BL/6J, and this relationship corresponds to a more rapid increase of presumptive afferent synapses in CBA/CaJ than in the other two strains between E15 and E16. Possible causal relationships among neuronal size, growth, and synaptogenesis are suggested by these strain differences.