bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thalamocortical synapses involving identified neurons in mouse primary somatosensory cortex: A terminal degeneration and golgi/EM study
Authors: Hersch Steven M. , White Edward L. 
Published: January 2005

AbstractSynapses involving thalamocortical afferents and hitherto unexamined neuron types of the posteromedial barrel subfield (PMBSF) of the mouse have been identified using a combined degeneration and Golgi/EM technique (Peters et al., '77). Degeneration of thalamocortical axon terminals was produced with electrolytic lesions of the nucleus ventralis posterior, pars lateralis thalami, and the nucleus posterior thalami. Four days after receiving lesions, the animals were perfused, and blocks of cortex containing the PMBSF were processed by the Golgi method. The blocks were tissue‐chopped at 125 μm and examined with the light microscope. Sections containing neurons of interest were gold‐toned and deimpregnated in preparation for electron microscopy (Fairén et al., '77). Portions of selected neurons contained in layers III‐V were serially thin‐sectioned and examined with an electron microscope to determine if they were involved in synapses with degenerating thalamocortical axon terminals. Results showed thalamocortical synapses on the apical dendrites of five different sized pyramidal cells whose somata occurred in layers V and VI, and on dendrites of one spiny bitufted neuron and one non‐spiny multipolar neuron with somata in layer V. A non‐spiny bitufted neuron of layer IV which was not impregnated also received thalamocortical synapses.Although every neuron examined formed at least one thalamocortical synapse, some formed very few, whereas others formed many. Of the pyramidal cells, small layer V and VI pyramidal cells and a large deep layer V pyramidal cell were involved in small numbers of thalamocortical synapses, while a medium superficial layer V pyramidal cell and a large layer VI pyramidal cell each formed many. The spiny bitufted neuron formed a small number of thalamocortical synapses, while the non‐spiny bitufted neuron formed very many. The non‐spiny multipolar neuron was involved in a moderate number of thalamocortical synapses. The findings suggest that, whereas any type of neuron with a dendrite in layer IV likely receives some synaptic input from the thalamus, individual neurons were involved in very different quantities of thalamocortical synapses.
Displaced ganglion cells and the accessory optic system of pigeon
Authors: Fite Katherine V. , Brecha Nicholas , Karten Harvey J. , Hunt Stephen P. 
Published: January 2005

AbstractThe central projection and retinal distribution of displaced ganglion cells (DGC's) are described for the pigeon. Discrete, localized injections of horseradish peroxidase (HRP) into the nucleus of the basal optic root (nBOR) complex labeled as many as 4,800 DGC's in the contralateral retina. The greatest densities of DGC's were observed in the more peripheral regions of the middle and inferior temporal regions of the retina, with lowest densities occurring in the inferior nasal, red field, and foveal areas. Large HRP injections of the tectal lobes, which did not include the pretectal, accessory optic (nBOR), hypothalamic, or thalamic visual nuclei, labeled only ganglion cells within the ganglion cell layer. An HRP injection centered within the nucleus lentiformis mesencephali, also including portions of the optic tectum and optic tract, labeled only ganglion cells within the ganglion cell layer of the contralateral retina. DGC's thus appear to be the primary, if not exclusive, source of retinal afferents to the nBOR complex in pigeon. The observed retinal distribution of DGC's indicates that the areas of retina with the greatest density of cells in the receptor layer, inner nuclear layer, and ganglion cell layer are relatively devoid of DGC's. Since the nBOR complex projects directly upon the vestibulocerebellum and oculomotor nuclei, DGC's would thus appear to be involved in neural circuits that mediate oculomotor reflexes and visuomotor behavior.
Organization of corticospinal neurons in the monkey
Authors: Murray Elisabeth A. , Coulter Joe Dan 
Published: January 2005

AbstractThe retrograde axonal transport method has been employed to identify the cell bodies of cortical neurons projecting directly to the spinal cord in the monkey. The investigation has focused on aspects of the laminar, columnar, and somatotopic organization of corticospinal neurons within each of the cytoarchitectural and functional subdivisions of the sensorimotor cortex.The principle findings of these experiments are that: (i) cortical regions containing cell bodies of corticospinal neurons are the first motor cortex (area 4), the first somatic sensory cortex (areas 3a, 3b, 1, and 2), and part of the immediately adjacent posterior parietal cortex (area 5), the second somatic sensory cortex, the supplementary motor cortex (the medial aspect of area 6), and the medial part of the posterior parietal cortex in a region termed the supplementary sensory area; (ii) corticospinal neurons display a somatotopic organization within each of these functional subdivisions of the sensorimotor cortex; (iii) all corticospinal neurons arise from layer V of the cortex; and (iv) corticospinal neurons within the first motor and first somatic sensory cortex oftern occur in clusters, perhaps reflecting a columnar organization in the sensorimotor cortex.These findings demonstrate the origins of the corticospinal system to be more extensive than previously recognized and show that a number of common features characterize the organization of corticospinal neurons in all cortical areas. Across cortical subdivisions, however, major differences exist in the extent of spinal segmental representations, in the manner in which corticospinal neurons occur in groups, and in the numerical density and sizes of corticospinal neurons. These aspects of the organization of the corticospinal system presumably reflect specialization of the different cortical areas in spinal cord sensory and motor control.
Tectal projections of an infrared sensitive snake, Crotalus viridis
Authors: Schroeder Dolores M. 
Published: January 2005

AbstractCrotaline snakes have detectors for infrared radiation and this information is projected to the optic tectum in a spatiotopic manner. The tectal projections were examined in Crotalus viridis with the use of silver methods for degenerating fibers and the autoradiographic and horseradish peroxidase tracing methods. Large lesions included all of the tectal layers but not the underlying structures. Projections to the thalamus include a sparse input to the ipsilateral ventral and dorsal lateral geniculate nuclei, the ventromedial nucleus, and nucleus lentiformis thalami. Nucleus rotundus was not detected. The projections to the pretectal nuclei are primarily ipsilateral to the nucleus lentiformis mesencehali and pretectal nucleus. At the level of the mesencephalon, tectal efferents are bilateral to nucleus profundus mesencephali and the tegmentum. There is minimal input to the contralateral deep tectal layers. There are ispilateral terminations in a nucleus identified as the posterolateral tegmental nucleus. Descending fibers include the two major tracts—the ventral tectobulbar tract that terminates in the ipsilateral lateral reticular formation and the predorsal bundle that distributes throughout the contralateral medial reticular formation. Two small descending tracts were noted—the intermediate and dorsal tectobulbar tracts. All of these descending tracts appear to terminate by the time they reach the caudal medulla. After superficial lesions terminals could be found in the ventral lateral geniculate nucleus, the nucleus profundus mesencephali, and the posterolateral tegmental nucleus; the two major descending tracts contained degenerated fibers as well. The areas receiving tectal input in Crotalus were compared to those of other reptiles and discussed.
Thalamic connections with limbic cortex. I. Thalamocortical projections
Authors: Robertson Richard T. , Kaitz Suzan S. 
Published: January 2005

AbstractThe thalamocortical projections to limbic cortex in the cat have been studied with retrograde and anterograde axonal transport techniques. Five limbic cortical areas were identified on the basis of cytoarchitecture. The five areas are the anterior limbic area, the cingular area, the dorsal and ventral retrosplenial areas, and the presubiculum. Each of these cortical areas received small injections of horseradish peroxidase, and the afferent thalamic nuclei were identified by retrograde labelling of cells. The cortical projection of each of the anterior thalamic nuclei and the lateral dorsal nucleus was determined autoradiographically.Each of the anterior thalamic nuclei and the lateral dorsal nucleus projects to limbic cortex by two pathways. One group of fibers leaves the rostral thalamus by the fornix, pierces the corpus callosum, and joins the cingulate fasciculus to reach limbic cortex. The other group travels through the lateral thalamic peduncle and internal capsule. The anterior ventral nucleus projects primarily to the dorsal retroslenial area, particularly to layer I, the deep portion of layer II, and superficial portion of layer III. Sparse projections also exist to the ventral retrosplenial area, the cingular area, and the presubiculum. Very sparse projections to the anterior limbic area are seen. The anterior dorsal nucleus projects primarily to the ventral retrosplenial area, particularly layers I, the deep portion of layer II, and superficial layer III. Sparse projections exist to the dorsal retrosplenial area and presubiculum, but apparently no projections exist to the cingular or anterior limbic area. The anterior medial nucleus projects primarily to layers I and superficial III of the ventral retrosplenial area. Sparse projections exist to each of the other limbic cortical areas. The lateral dorsal nucleus projects extensively onto limbic cortex. Prominent projections occur to layer I, the external granular layer and lamina dessicans of the presubiculum, layers I and III‐IV of the dorsal retrosplenial area, and layers I, III, and IV of the cingular area. Sparse projections occur to the ventral retrosplenial area and the anterior limbic areas. Thalamocortical projections also originate in the midline and intralaminar nuclei including the central medial reuniens, rhomboid, paracentral, central lateral, and central dorsal nuclei.These data indicate that the anterior thalamic nuclei project upon limbic cortex in a complex manner. Further, the projections to limbic cortex from the anterior nuclei overlap with projections from the lateral dorsal nucleus. This overlap of thalamic projections onto limbic cortex suggests a convergence of information from nonprimary sensory systems with information from the classical limbic system.
Combined golgi and electron microscopic study on the synapses formed by double bouquet cells in the visual cortex of the cat and monkey
Authors: Somogyi P. , Cowey A. 
Published: January 2005

AbstractThe morphology of certain Golgi‐stained cells was examined in the striate and peristriate cortex of the cat and in the striate cortex of the rhesus monkey. Neurons in layer III were selected on the basis of their characteristic vertical axon bundles, which are 20–150 μ in diameter and traverse layers II–VSelected neurons were examined under the electron microscope to characterize their synapses and to establish their postsynaptic targets. It was found that double bouquet cells form symmetrical or type II synapses. In the cat the postsynaptic membrane specialization was more extensive than in the monkey. After removing the Golgi precipitate from boutons of two cells in the cat, small pleomorphic and flattened vesicles were found in the boutonsEarlier suggestions that double bouquet cells make synapses preferentially with spines of apical dendrites could not be confirmed. Out of 66 boutons in area 17 of the cat, 86.4% formed synapses with dendritic shafts, many of them belonging to nonpyramidal cells, 9% with perikarya of nonpyramidal cells, and only 4.6% with spines. Out of 19 synapses examined in area 18, 74% were contacting dendritic shafts and the rest contacted spines. In the monkey 60% of a total of 35 double bouquet cell synapses made synapses with dendritic shafts. A different type of double bouquet cell with densely spiny dendrites is also described in layer IV of the monkey striate cortex. This neuron formed asymmetrical synapsesIt is suggested that layer III double bouquet cells with vertical axon bundles are probably inhibitory and act on other nonpyramidal cells and certain parts of pyramidal cells.
Regional specialization of the chick retina as revealed by the size and density of neurons in the ganglion cell layer
Authors: Ehrlich David 
Published: January 2005

AbstractOn the basis of both morphological criteria and survival after ganglion cell axotomy, three populations of cells can be recognized in the ganglion cell layer of the chick retina. These are: (1) Irregularly shaped cells, which are not affected by axotomy and lack Nissl stain. They comprise about 5% of the total cell population and are probably glial cells. (2) Small cells which have a distinctive teardrop‐shaped perikarya, stain for Nissl substance, and are not affected by axotomy. They occur with a uniform density of about 4,000 cells/mm2 across the entire retina and comprise 30‐35% of the total number of cells in the ganglion cell layer. It is suggested that these cells are displaced amacrine cells. (3) Cells which stain strongly for Nissl substance and disappear after axotomy. These cells comprise 60‐65% of the population of cells in this layer. The density of the latter cells varies throughout the retina. A high‐density region in the central area extends into the superior‐temporal retina. This high‐density region corresponds to a position in the lateral visual field extending into the inferofrontal field. The total number of these cells agrees with the reported number of the optic nerve fibres in the chick, (Rager and Rager, '78); therefore they are presumably ganglion cells. The size distribution of the presumptive ganglion cells varies in different parts of the retinaThe only previous study of the distribution and size of cells in the ganglion cell layer of the avian retina did not distinguish between ganglion cells and displaced amacrine cells (Binggeli and Paule, 1969). The present results are therefore likely to be a more accurate description of the total number of ganglion cells, the regional variations in their density, and the characteristics of their size than previously reported.
Anatomical and neurochemical consequences of deafferentation in the development of the visual system of the moth manduca sexta
Authors: Maxwell Gerald D. , Hildebrand John G. 
Published: January 2005

AbstractThe primordium of the compound eye of the moth Manduca sexta was removed by surgery within 12 hours after the molt to the pupa. When the operated animals were examined as pharate adults just prior to emergence from the pupal cuticle, no eye tissue was present on the operated side. Histological examination of the brain at successive developmental stages showed that the volume of laminar neuropil on the operated side increased very little after deafferentation while the volume of the control‐side laminar neuropil increased more than 20‐fold. The impairment of development of the lamina was accompanied by a reduction in the synthesis and storage by the optic lobe of two neurotransmitter candidates, acetylcholine and 5‐hydroxytryptamine. The endogenous content of 5‐hydroxytryptamine was also reduced in these preparations. Excision of a section of the stemmatal nerve, which connects the primordium of the compound eye to the brain, also arrested the development of the lamina, but in this case the compound eye itself developed apparently normally without making contact with the brain. This finding supports the hypothesis that the centripetal growth of photoreceptor‐cell axons normally is contact‐guided. Results of neurochemical experiments on retinal tissue argue against the idea that acetylcholine, 5‐hydroxytryptamine, or gamma‐aminobutyric acid is a likely photoreceptor‐cell neurotransmitter. From these and our previous studies of the metamorphosing brain in Manduca we conclude that different classes of neurons in the same central nervous system can exhibit widely different degrees of dependency on their normal innervation for their survival and differentiation.
The organization of the claustroneocortical projections in the cat studied by means of the HRP retrograde axonal transport
Authors: Macchi G. , Bentivoglio M. , Minciacchi D. , Molinari M. 
Published: January 2005

AbstractThe projections from the claustrum to the cerebral cortex were examined in the cat by means of horseradish peroxidase (HRP) injections in various different areas of the lateral and medial surfaces of the neocortex. In all cases retrogradely labeled cells were observed in the ipsilateral claustrum insulare (ClI). In most of the cases some labeled cells were also observed in the contralateral ClI. The number of labeled cells was higher following large HRP injections in some cortical areas, such as the motor and visual cortex, than following large HRP injections in other areas, such as the second somatic sensory cortex. The patterns of distribution of labeled cells in the ClI following the different HRP injections evidenced a prevalent anteroposterior and dorsoventral topographical arrangement. However, some degree of overlapping was evident in the distribution of cells retrogradely labeled from injections in different cortical fieldsThe results of the present study indicate that: (a) in all likelihood the claustral projections are distributed upon the entire neocortex; (b) they are not uniformly distributed upon the neocortex from the quantitative point of view; (c) the arrangement of the claustrocortical projections is predominantly but not strictly topographicalThe widespread distribution of the claustral inputs suggests that they must be integrated in different models of cortical activity.
Normal postnatal development of medial superior olivary neurons in the albino rat: A Golgi and Nissl study
Authors: Rogowski Barbara A. , Feng Albert S. 
Published: January 2005

AbstractBipolar neurons in the medial superior olivary (MSO) nucleus of albino rats were studied at various ages (0–75 days) during development in order to elucidate normal neuronal growth patterns. Neurons, visualized in celloidin embedded Golgi/Nissl‐ and frozen Nissl‐stained sections, were analyzed quantitatively for cell size and extent of dendritic arborization. These parameters, from both sets of data, showed a consistent developmental trend with the existence of two major stages in the ontogenetic process: a rapid developmental and a stabilization stage. The first stage, encompassing postnatal days 0 through approximately 14, was characterized by a rapidly increasing cell size, as observed in frozen sections. At the peak of this rapid growth, Golgi‐stained neurons possessed thick dendrites with many appendages, growth cones, and filopodia. The peak in neuronal development coincided with the initiation of ear opening. Morphological features attained a more mature form in the second, stabilizing stage of development, which began at approximately postnatal day 14. This phase was distinguished by a decrement in cell size and dendritic branching. Also, dendrites possessed more regularly distributed varicosities and fewer appendages, growth cones, and filopodia in this period. It was observed that dendritic branching trends paralleled those of cell diameter growth.
Direct retinal projections to the hypothalamus, piriform cortex, and accessory optic nuclei in the golden hamster as demonstrated by a sensitive anterograde horseradish peroxidase technique
Authors: Pickard Gary E. , Silverman Ann‐Judith 
Published: January 2005

AbstractThe central projections of the retinal ganglion cells of the golden hamster were examined using horseradish peroxidase (HRP) as the anterograde tracer molecule. Following monocular injections of HRP into the vitreous, retinfugal fibers were histochemically demonstrated using the chromagen tetramethylbenzidine. This procedure, being more sensitive than the 3H‐amino acid radioautographic technique, provided a clear demonstration of previously controversial retinal projections, clearer definition of established projections, and the discovery of new retinal pathways.An inferior accessory optic system was shown to be unequivocally present in this species and to consist of both crossed and uncrossed components. A direct retinal projection to the suprachiasmatic nucleus (SCN) of the hypothalamus was confirmed in this study. But the distribution of terminals as seen by this procedure was substantially different than previously reported; both rostrocaudal and mediolateral asymmetries in the distribution of label between the ipsilateral and contralateral SCN were observed. Substantial differences in the retinal projection to the SCN in the hamster and the rat were also noted. It is suggested that these differences may reflect the different effects photic input has on the neuroendocrine‐gonadal axis in these two species. Finally, labeled retinal axons were followed leaving the optic tract and coursing anteriorly through the plexiform layer of the piriform cortex; other labeled fibers were seen to enter the septal region. The physiological significance of these previously undescribed retinal projections is not known.
Afferent connections of the interpeduncular nucleus and the topographic organization of the habenulo‐interpeduncular pathway: An HRP study in the rat
Authors: Contestabile R. A. , Flumerfelt B. A. 
Published: January 2005

AbstractThe HRP tracing method was employed to investigate the organization and afferent connections of the interpeduncular nucleus (IPN) in the rat. To study the topographical features of the different projections, a method was devised for obtaining HRP placements of limited size in different areas of the IPN.The main afferent connection of the IPN is a topographically organized projection from the medial habenula (Hb). This projection follows a reversed caudorostral pattern, terminating throughout all but the caudalmost part of the IPN. The dorsal part of the IPN receives a sparse innervation arising mainly from a narrow lateral and ventrolateral area of the medial Hb. The ventral two thirds of the IPN receives a much heavier projection, as follows: A large ventrolateral area of the medial Hb projects to the lateral part of the IPN in a completely bilateral way. An additional projection, which is predominantly ipsilateral, arises from the rostral half of the dorsolateral part of the medial Hb and terminates in the caudal IPN. The medial part of the medial Hb projects preferentially to central areas of the IPN.The projection from the lateral Hb is quantitatively much smaller but appears to be distributed to the entire length of the IPN, following a nonreversed caudorostral arrangement, with the ipsilateral projection predominating. The projections from the medial and lateral Hb to the IPN were confirmed by tracing anterogradely transported HRP as well. No reciprocal connection from the IPN to the Hb could be demonstrated.A sparse projection to the IPN with a strong ipsilateral predominance arises from the horizontal limbs of the nucleus of the diagonal band of Broca. This was the only projection observed from the septal region. Sparse projections from the premammillary and supramammillary nuclei were also demonstrated. Confirmatory data and some details of organization were also obtained for projections to the IPN from other areas, including the medial and dorsal raphe nuclei, the dorsal tegmental nucleus of Gudden, and the adjacent dorsolateral tegmental nucleus. Very small projections from the ventral tegmental nucleus and the locus coeruleus were also found.