bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructural characterization of the synapses of the crossed temporodentate pathway in rats
Authors: Davis Lauren , Vinsant Sharon L. , Steward Oswald 
Published: January 2005

AbstractThe present, study was undertaken to define the ultrastructure of synapses of the crossed temporodentate pathway from the entorhinal cortex to the contralateral dentate gyrus and to compare the synapses of the sparse crossed pathway with those of the massive ipsilateral temporodentate pathway. The synapses of the crossed pathway were identified by using EM degeneration and EM autoradiographic techniques. For the degeneration studies, adult male Sprague‐Dawley rats were killed 1, 2, or 4 days following a unilateral entorhinal cortex lesion and prepared for electron microscopy. To identify the synapses by using autoradiographic techniques, four animals received injections of 3H‐proline into the entorhinal cortex, were allowed to survive for 3 days, and were prepared for EM autoradiography. Degenerating synapses of the crossed pathway that were found in the molecular layer of the dentate gyrus contralateral to a lesion formed asymmetric synapses on spines and possessed presynaptic organelles indistinguishable from synapses of the ipsilateral temporodentate pathway. The number of degenerating synapses was very low at all survival intervals (14.80 degenerating synapses/10,000μm2 at 1 day postlesion and 1.95 degenerating synapses/10,000μm2 at 2 days postlesion); no degenerating synapses were found at 4 days postlesion. Ninety‐eight percent of the degenerating synapses found at 1 day postlesion exhibited electron‐lucent degeneration. At 2 days postlesion 83% of the degenerating synapses in the dorsal blade and 18% of those in the ventral blade showed lucent degeneration; the remainder were electron dense. EM autoradiography confirmed the degeneration studies in terms of the type of terminals that were labeled and suggested that the density of the crossed pathway was higher than the degeneration results implied. We conclude that synapses of the crossed temporodentate pathway have a similar ultrastructure to synapses of the ipsilateral temporodentate pathway but exhibit a rapid form of degeneration such that they disappear very rapidly following the lesion.
Postnatal development of dendrites of relay neurons in the lateral geniculate nucleus of the marmoset (Callithrix jacchus): A quantitative Golgi study
Authors: Fritschy J. M. , Garey L. J. 
Published: January 2005

AbstractDendrites of multipolar relay neurons in the lateral geniculate nucleus of the marmoset (Callithrix jacchus), at various ages from birth to adulthood, were studied in rapid Golgi preparations. The dendrites were analyzed by means of three‐dimensional computer reconstructions and decomposed into intermediate and terminal segments, both of which were further classified according to their centrifugal order. Measurements were made of the number of segments per dendrite, the total length of dendrites, and the mean length of intermediate and terminal segments. In adult marmosets, there are four stem dendrites on average per neuron, and each dendrite divides into a mean of 14 segments. Between birth and 6 weeks of age, the mean dendritic length doubles, mainly because of changes in terminal segments. There is a significant decrease in dendritic length into adulthood. The total number of stem dendrites lose distal segments, after which there is a significant increase in the number of segments of orders 3 to 7. The mean length of intermediate segment does not change with age, nor with order, whereas the length of terminal segments increase from 50 to 120 μm from birth to 6 weeks of age, and then decrease to the adult value of 80μm. In conclusion, during the period of most rapid visual development, important morphological changes occur in geniculate relay‐cell dendrites, involving essentially terminal segments. These observations correlate well with changes of geniculate volume and neuronal density.
Demonstration of topographically organized projections from the hypothalamus to the pontine nuclei: An experimental anatomical study in the cat
Authors: Aas Jan‐Erik , Brodal Per 
Published: January 2005

AbstractIn 22 cats implantations and injections of horseradish peroxidase–wheat germ agglutinin (HRP‐WGA) or Fluoro‐Gold were placed in the pontine nuclei or the hypothalamus. The occurrence and distribution of labeled cells in the hypothalamus and of labeled terminal fibers in the pontine nuclei were mapped.Following implantations of HRP‐WGA ventromedially in rostral parts of the pontine nuclei, 22–44% of all labeled cells in the brainstem and diencephalon are found in the medial mamillary nucleus ipsilateral to the implantation. Some labeled cells are also found in the supramamillary, premamillary, anterior mamillary, and tuberomamillary nuclei. Thus, labeled cells in the hypothalamus make up 33–54% of all labeled cells in the brainstem and diencephalon in such cases. In contrast, implantations and injections in mediocaudal parts of the pontine nuclei result in labeling of cells mainly in the posterior, dorsal, and lateral hypothalamic areas (terminology of Bleier: The Hypothalamus of the Cat. Baltimore: Johns Hopkins Press, '61). In these cases the labeled cells in the hypothalamus make up 16–25% of all labeled cells in the brainstem and diencephalon. Implantations in more lateral parts of the pontine nuclei label only a few cells in the hypothalamus.Following implantations of HRP‐WGA in restricted parts of the hypothalamus, fibers from the medial mamillary nucleus were found to terminate ventromedially at all rostrocaudal levels of the pontine nuclei, ipsilateral to the implantation. In the rostralmost part of the pontine nuclei, the terminal labeling forms a dense, transversely oriented, c‐shaped band. Fibers from the posterior and dorsal hypothalamic areas terminate medially and dorsomedially in the caudal third of the pontine nuclei. Sparse terminal labeling is also seen in lateral parts of the pontine nuclei and medially at more rostral levels.In two cases with small implantations of HRP‐WGA ventromedially in rostral parts of the pontine nuclei, labeled cells are found both in the medial mamillary nucleus and the cingulate gyrus. Thus, it seems possible that fibers from the medial mamillary nucleus and the cingulate gyrus converge upon a restricted area ventromedially in rostral parts of the pontine nuclei.
Tonotopic projection from the dorsal to the anteroventral cochlear nucleus of mice
Authors: Wickesberg Robert E. , Oertel Donata 
Published: January 2005

AbstractTo understand how auditory information is processed in the cochlear nuclei, it is crucial to know what circuitry exists and how it functions. In slice preparations, horseradish peroxidase (HRP) injections into the anteroventral cochlear nucleus (AVCN) reveal two circuits: a connection between the dorsal cochlear nucleus (DCN) and AVCN and a local circuit confined to the AVCN. Extracellular injection in the AVCN labels a band of cells in the DCN. The labeled cells in the DCN lie within a band of auditory nerve fiber terminals that are labeled by the same injection, showing that the connection from the DCN to the AVCN is frequency specific. The injections into the AVCN also labeled a cluster of neurons in the AVCN dorsal to the injection site. These cells may be interneurons that relay information from areas encoding higher frequencies to areas encoding lower frequencies within the AVCN. In the parasagittal plane, the AVCN is organized along two orthogonal axes that are indicated with HRP labeling of fibers and cell bodies. The tonotopic axis runs approximately dorsoventrally; the isofrequency axis runs approximately rostrocaudally. The axons of labeled DCN neurons and the cluster lie along the tonotopic axis, whereas the labeled auditory nerve fibers define the isofrequency axis. Where they cross is where HRP is taken up by the fibers. The area of uptake is small and lies in the middle of the darkly stained injection site.
Projections of the retinorecipient pretectal nuclei in the pigeon (columba livia)
Authors: Gamlin Paul D. R. , Cohen David H. 
Published: January 2005

AbstractWe have used anterograde autoradiographic and retrograde HRP techniques to investigate the efferent connections of the retinorecipient pretectal nuclei in the pigeon. In the accompanying paper we identified these nuclei in the pigeon as the nucleus lentiformis mesencephali–pars lateralis and pars medialis, the tectal gray, the area pretectalis, and pretectalis diffusus. Although there are reports of a few of the projections of these nuclei, they had not previously been the subject of a detailed study.We found that different cell types in the lentiformis mesencephali, pars medialis and the lentiformis mesencephali, pars lateralis have descending projections to different targets. These targets include the inferior olive, the cerebellum, the lateral pontine nucleus, the nucleus papillioformis, the nucleus of the basal optic root, the nucleus mesencephalicus profundus, pars ventralis, the nucleus principalis precommissuralis, and the stratum cellulare externum. We found that a few cells in the lentiformis mesencephali project to the medial pontine nucleus, but that a much heavier projection arises from the nucleus laminaris precommissuralis, which is medial to the nucleus lentiformis mesencephali, pars medialis.The tectal gray has predominantly ascending projections to the diencephalon. The nuclei that it projects to are the nucleus intercalatus thalami, the nucleus of the ventral supraoptic decussation, the nucleus posteroventralis, the ventral lateral geniculate nucleus, the nucleus dorsolateralis medialis, and the nucleus dorsolateralis anterior. The tectal gray also projects topographically to layers 4 and 8–13 of the optic tectum.Area pretectalis has both ascending and descending projections. It has ipsilateral ascending projections to the nucleus dorsolateralis anterior, pars magnocellularis, the nucleus lateralis anterior, and the nucleus ventrolateralis thalami. It has ipsilateral descending projections to the central gray, the nucleus of the basal optic root, pars dorsalis, the lateral pontine nucleus, and the deep layers of the optic tectum. It has contralateral projections to the area pretectalis, the nucleus Campi Foreli, the interstitial nucleus of Cajal, the nucleus of Darkschewitsch, the cerebellum, and the Edinger‐Westphal nucleus.The efferent projections of pretectalis diffusus are limited. It projects contralaterally to the pretectalis diffusus, and ipsilaterally to the nucleus of the ventral supraoptic decussation, the lateral pons, and the cerebellum.Our results demonstrate that, by way of their ascending and descending projections, the retinorecipient pretectal nuclei can exert important influences on the range of visuomotor functions in which they participate. We know that area pretectalis mediates the pupillary light reflex (Gamlin et al., '84) and that the lentiformis mesencephali is involved in optokinetic nystagmus (McKenna and Wallman, '85). However, to our knowledge, other potential roles of the retinorecipient pretectal nuclei have not been identified.
Time of origin of cholinergic neurons in the rat basal forebrain
Authors: Semba Kazue , Fibiger Hans C. 
Published: January 2005

AbstractThe timing of the final mitotic division of basal forebrain cholinergic neurons was studied by injecting [3H]thymidine into timed pregnant rats and processing the brains of their progeny as young adults for immunohistochemistry with a monoclonal antibody to choline acetyltransferase (ChAT) followed by autoradiography. ChAT‐positive neurons located caudally in the basal forebrain were found to become postmitotic mostly on embryonic (E) days 12 and 13, whereas the peak final mitosis of more rostrally located ChAT‐positive neurons occurred increasingly later, with the most rostral ChAT‐immunoreactive neurons leaving their final mitotic cycles on E15 and E16. In all basal forebrain regions, cholinergic neurogenesis was complete by E17. These results indicate that the cholinergic neurons in the basal forebrain become postmitotic in a caudal‐to‐rostral gradient over about 5 days. The continuity of the gradient suggests that these cholinergic neurons may derive from the same germinal source.
Specificity of sensory projections to the spinal cord during development in bullfrogs
Authors: Smith Carolyn L. , Frank Eric 
Published: January 2005

AbstractSensory neurons in dorsal root ganglia of frogs project to areas of the spinal cord they do not normally innervate following removal of adjacent ganglia at tadpole stages (Frank and Westerfield, J. Physiol (Lond.) 324:495–505, '82b). A possible explanation of this phenomenon is that sensory neurons project to wider areas of the spinal cord in tadpoles than in adult frogs and that partial deafferentation causes the retention of these widespread projections. Therefore, the specificity of sensory projections to the spinal cord in tadpoles was assessed by staining individual dorsal roots with horseradish peroxidase. Thoracic sensory neurons project to thoracic segments of the spinal cord and to the brainstem in tadpoles, like thoracic sensory neurons in adult frogs. They rarely arborize in the brachial region even at stages when no other sensory fibers arborize at this level. Furthermore, their projections are restricted to the dorsal horn at all stages. Conversely, hypoglossal sensory neurons, which project into the intermediate gray matter in the adult, also project to this area in tadpoles. The finding that sensory neurons in tadpoles only project to areas of the spinal cord that they innervate in the adult suggests that the novel projections observed following partial deafferentation of the spinal cord are actually induced by the operation. An additional finding was that forelimb afferents, which project to an area extending from the obex to midthoracic levels in adult frogs, arborize at rostral spinal levels and at thoracic levels several stages before they form projections to the region around their own dorsal root. These differences in the stages at which projections to different levels of the spinal cord develop suggest that local properties of the spinal cord may control the timing of sensory fiber arborization.
Morphological diversity of displaced retinal ganglion cells in the rat: A lucifer yellow study
Authors: Buhl E. H. , Dann J. F. 
Published: January 2005

AbstractDisplaced retinal ganglion cells (DRGCs) were retrogradely labelled by injections of the fluorescent dye Fast Blue into the superior colliculi of pigmented rats. Following fixation these cells were intracellularly injected with Lucifer Yellow to determine their dendritic morphology and distribution.Graphic reconstruction of Lucifer Yellow‐filled prelabelled neurones revealed a heterogeneous population of DRGCs. Their stratification within the inner plexiform layer was diverse and cells were classified according to their dendritic morphology.The present sample consists largely of unistratifying neurones, the dendrites of which arborized within a narrow sublamina of the inner plexiform layer. They were characterized by a centrally located soma and densely branched dendritic network with little overlap within the branching pattern. In contrast, bistratifying DRGCs possessed a loose and sparsely branched dendritic structure, while diffusely stratifying neurones contained a high degree of dendritic crossing, culminating in a complex network, in which the soma position was biased toward the periphery.One type of DRGC bore a striking resemblance to type 1 neurones (Perry, 1979; Proc. R. Soc. Lond. [Biol.] 204:363–375) in the ganglion cell layer. They were characterized by a large soma (15.8 μm ± 2.2 μm s.d.) and a dendritic field diameter averaging 288 μm (s.d. ± 62 μm) and were on average larger than the rest of the displaced population but smaller than type 1 cells in the ganglion cell layer. Since the stratification patterns of the displaced and nondisplaced type 1 neurones were indistinguishable, it is reasonable to assume that the Lucifer Yellow‐filled cells in the present study represent the displaced counterpart of regular type 1 ganglion cells. Therefore, it appears that despite the aberrant location of the soma within the inner nuclear layer, the dendritic morphology of the cell develops unimpeded into a normal stratification pattern, although both soma and dendritic field size are reduced. If displacement is a developmental aberration, this size decrease may arise from overcrowding within the inner nuclear layer where the soma becomes lodged erroneously during its migration to the ganglion cell layer. This would also account for the heterogeneity of displaced cells found in the present study, since the randomness of a developmental error would ensure that a variety of ganglion cell types was included in the displaced population.
Relationship of the axonal and dendritic geometry of spiny projection neurons to the compartmental organization of the neostriatum
Authors: Penny G. R. , Wilson C. J. , Kitai S. T. 
Published: January 2005

AbstractIntracellular injection of HRP combined with immunocytochemistry for [Leu]enkephalin was used to demonstrate striatal spiny neuron dendritic and local axonal arborizations in the same section as enkephalin‐rich patches (striosomes). Cobalt intensification of the first DAB reaction prior to the immunoperoxidase steps resulted in good contrast between the black reaction product in the intracellularly labeled cells and the brown staining for [Leu]enkephalin. Serial reconstructions of the labeled cells and nearby boundaries between the enkephalin‐rich striosomes and enkephalin‐poor matrix allowed the relationship between the arborizations of the labeled cells and these boundaries to be established. It was also possible to examine the relationship to compartmental boundaries of a second neuronal class consisting of large, pallidallike neurons whose somatodendritic morphology was outlined by immunoperoxidase‐labeled terminals.We found that spiny projection neurons in both compartments have dendritic arbors and local axonal collaterals that are confined by compartmental boundaries. The termination or recurvature of dendrites at such boundaries suggests that the cellular basis of striatal compartmental organization is provided by this class of striatal neuron. On the other hand, large pallidumlike striatal neurons were found to have dendrites that extend across compartmental boundaries. These results support previous reports that striatal spiny projection neurons preserve the compartmental segregation of parallel striatal input‐output systems, whereas other classes of striatal neurons may serve to provide limited integration between compartments.
Medullary and spinal efferents of the pedunculopontine tegmental nucleus and adjacent mesopontine tegmentum in the rat
Authors: Rye David B. , Lee Henry J. , Saper Clifford B. , Wainer Bruce H. 
Published: January 2005

AbstractThe medullary and spinal efferents of the pedunculopontine tegmental nucleus and adjacent mesopontine tegmentum were investigated by employing (1) the anterograde autoradiographic methodology and (2) the retrograde transport of HRP and/or WGA‐HRP in combination with choline acetyltransferase immunohistochemistry.The anterograde experiments identified five descending pathways from the mesopontine tegmentum: (1) Probst's tract, which descends in the dorsolateral reticular formation in close relation to the nucleus of the solitary tract; (2) a ventrolateral branch of Probst's tract that extends ventrolaterally alongside the spinal trigeminal nucleus; (3) a ventromedial branch of Probst's tract that extends ventromedially through the gigantocellular field of the medulla; (4) the medial reticulospinal tract, which descends in parallel with the medial longitudinal fasciculus and turns ventrolaterally along the dorsal surface of the inferior olive to enter the ventrolateral funiculus of the spinal cord; and (5) a crossed ventromedial pathway, which descends in a ventral paramedian position through the magnocellular field of the medulla.The origins of these pathways reflected a rough lateral‐to‐medial topography of mesopontine tegmental cell groups. The parabrachial nucleus, situated furthest laterally, for example, projected primarily through Probst's tract and its ventrolateral branch. The pedunculopontine tegmental nucleus, midbrain extrapyramidal area, and the subceruleal region, situated more medially, projected descending axons largely through the ventromedial branch of Probst's tract. The pontine tegmental field, situated furthest medially and ventromedially, was the largest contributor to the medial reticulospinal tract.The retrograde transport experiments confirmed these general organizational features. The combination of retrograde transport with choline acetyltransferase immunohistochemistry established that the cholinergic pedunculopontine tegmental nucleus contributes a large portion to the mesopontine tegmental innervation of the medullary reticular formation. A much smaller number of cholinergic pedunculopontine neurons project as far as the spinal cord. Spinal projections from the mesopontine tegmentum originate largely from non‐cholinergic neurons of the midbrain extrapyramidal area, subceruleal region, Kölliker‐Fuse division of the parabrachial nucleus, and pontine tegmental field.
Topographical organization of cortical afferents to extrastriate visual area PO in the macaque: A dual tracer study
Authors: Colby C. L. , Gattass R. , Olson C. R. , Gross C. G. 
Published: January 2005

AbstractWe have examined the origin and topography of cortical projections to area PO, an extrastriate visual area located in the parieto‐occipital sulcus of the macaque. Distinguishable retrograde fluorescent tracers were injected into area PO at separate retinotopic loci identified by single‐neuron recording.The results indicate that area PO receives retinotopically organized inputs from visual areas V1, V2, V3, V4, and MT. In each of these areas the projection to PO arises from the representation of the periphery of the visual field. This finding is consistent with neurophysiological data indicating that the representation of the periphery is emphasized in PO. Additional projections arise from area MST, the frontal eye fields, and several divisions of parietal cortex, including four zones within the intraparietal sulcus and a region on the medial dorsal surface of the hemisphere (MDP).On the basis of the laminar distribution of labeled cells we conclude that area PO receives an ascending input from V1, V2, and V3 and receives descending or lateral inputs from all other areas. Thus, area PO is at approximately the same level in the hierarchy of visual areas as areas V4 and MT.Area PO is connected both directly and indirectly, via MT and MST, to parietal cortex. Within parietal cortex, area PO is linked to particular regions of the intraparietal sulcus including VIP and LIP and two newly recognized zones termed here MIP and PIP. The wealth of connections with parietal cortex suggests that area PO provides a relatively direct route over which information concerning the visual field periphery can be transmitted from striate and prestriate cortex to parietal cortex. In contrast, area PO has few links with areas projecting to inferior temporal cortex. The pattern of connections revealed in this study is consistent with the view that area PO is primarily involved in visuospatial functioning.