bluuebunny/crossref_metadata_2025_split huggingface dataset:
Organization of ascending hypothalamic projections to the rostral forebrain with special reference to the innervation of cholinergic projection neurons
Authors: Cullinan William E. , Záborszky László 
Published: January 2005

AbstractAxonal projections from hypothalamic nuclei to the basal forebrain, and their relation to cholinergic projection neurons in particular, were studied in the rat by using the anterograde tracer Phaseolus vulgaris‐leucoagglutinin (PHA‐L) in combination with choline acetyltransferase (ChAT) immunocytochemistry. Discrete iontophoretic PHA‐L injections were delivered to different portions of the caudal lateral hypothalamus, as well as to various medial hypothalamic areas, including the ventromedial, dorsomedial, and paraventricular nuclei, and anterior hypothalamic and medial preoptic areas. The simultaneous detection of PHA‐L‐labeled fibers/terminals and ChAT‐positive neurons was performed by using nickel‐enhanced diaminobenzidine (DAB) and nonenhanced DAB as chromogens. Selected cases were investigated at the electron microscopic level.Ascending hypothalamic projections maintained an orderly lateromedial arrangement within the different components of the medial forebrain bundle, as well as with respect to their terminal projection fields (e.g., within the bed nucleus of the stria terminalis and lateral septal nucleus). The distribution pattern of hypothalamic inputs to cholinergic projection neurons corresponded to the topography of ascending hypothalamic axons. Axons originating from neurons in the far‐lateral hypothalamus reached cholinergic neurons in a zone that extended from the dorsal part of the sublenticular substantia innominata (SI) caudolaterally, to the lateral portion of the bed nucleus of the stria terminalis rostromedially, encompassing a narrow band along the ventral part of the globus pallidus and medial portion of the internal capsule. Axons originating from cells in the medial portion of the lateral hypothalamus reached cholinergic cells primarily in more medial and ventral parts of the SI, and in the magnocellular preoptic nucleus and horizontal limb of the diagonal band nucleus (HDB). Axons from medial hypothalamic cells appeared to contact cholinergic neurons primarily in the medial part of the HDB, and in the medial septum/vertical limb of the diagonal band complex. Electron microscopic double‐labeling experiments confirmed contacts between labeled terminals and cholinergic cells in the HDB and SI. Individual hypothalamic axons established synapses with both cholinergic and noncholinergic neuronal elements in the same regions. These findings have important implications for our understanding of the organization of afferents to the basal forebrain cholinergic projection system.
Topographic distribution of connections from the primary motor cortex to the corpus striatum in Aotus trivirgatus
Authors: Whitworth Richard H. , Ledoux's M. S. , Gould Harry J. 
Published: January 2005

AbstractConnections between the primary motor cortex (MI) and the corpus striatum were studied in the owl monkey. Representations of specific body movements were elicited in MI by microstimulation techniques, and the efferent projections from these stimulation sites were labeled with wheat germ agglutinin‐horseradish peroxidase conjugate (WGA‐HRP).Dense projections were found in the putamen ipsilateral to the injection site and sparser projections occupied comparable areas in the contralateral putamen. Representations of hindpaw regions projected to the dorsomedial portion of the putamen with only slight extensions across cell bridges into the caudate nucleus. Representations of the forepaw and head projected to progressively more ventrolateral zones of the dorsal two‐thirds of the putamen. Projections from injections of cortex representing discrete body movements terminated in an irregular or patchy distribution over a relatively large portion of the putamen. Extensive projections from relatively discrete injections in MI are indicative of a large degree of divergence and provide evidence for possible overlap from representations of relatively disparate body parts. The results are consistent with observations reported in other species of primates, but different from those seen in carnivores. This difference is discussed with regard to possible general features of corticostriate organization.
Direct observations of synapses between GABA‐immunoreactive boutons and identified spinocervical tract neurons in the cat's spinal cord
Authors: Maxwell D. J. , Christie W. M. , Short A. D. , Brown A. G. 
Published: January 2005

AbstractThree spinocervical tract neurons in adult cats were physiologically characterized and intracellularly labelled with horseradish peroxidase. The neurons were reconstructed and examined with the light microscope and were prepared for postembedding immunochemical analysis by using an antiserum which specifically recognizes GABA in glutaraldehyde‐fixed tissue. Semithin sections were tested and examined with the light microscope. Somata, proximal, and distal dendrites of all three cells were associated with numerous punctate GABA‐immunoreactive structures. Immunoreactive perikarya of small neurons in the vicinity of spinocervical tract cells were also observed. Ultrastructural analysis, with the immunogold technique, revealed that somata and proximal dendrites of all three neurons received synaptic contacts (about 37% of total synapses) from GABA‐immunoreactive boutons and that distal dendrites were also associated with substantial numbers of immunoreactive structures (about 27% of synapses). Immunoreactive boutons were small (about 1 μm in diameter), contained irregularly shaped agranular vesicles, and formed symmetrical synaptic junctions with identified neurons. An additional group of immunoreactive boutons was observed to be associated with one of the cells only; these contained many large dense‐core vesicles in addition to small agranular vesicles. Boutons containing1 round agranular vesicles and flattened agranular vesicles were not observed to be immunoreactive.The evidence supports the idea that much of the postsynaptic inhibition observed in spinocervical tract neurons is mediated by GABA and that even the most distal dendrites of these neurons receive inhibitory inputs.
Relationship of retinotopic ordering of axons in the optic pathway to the formation of visual maps in central targets
Authors: Simon David K. , O'Leary Dennis D. M. 
Published: January 2005

AbstractWe examined in rats the relationship between the ordering of retinal axons in the optic pathway and the formation of a retinotopically organized projection to their primary target, the contralateral superior colliculus (SC). We have previously found that axons labeled by focal injections of 1, 1′‐dioctadecyl 3, 3, 3, ′3′ ‐tetramethylindocarbocyanine perchlorate (DiI) made in temporal or nasal retina of perinatal rats commonly mistarget along the medial‐lateral and rostral‐caudal axes of the SC. By postnatal day (P) 11–12, the retinocollicular projection attains an adult‐like topography. Incorrectly targeted axons or axon segments are removed; axons that persist terminate in the topographically appropriate part of the SC (Simon and O'Leary: Dev Biol 137:125, 1990).In the present study, we made similar DiI injections, covering less than 2% of the retinal area, in peripheral temporal, nasal, superior, or inferior retina, in rats of two age groups, embryonic day (E) 21 to P (postnatal day) 2 and P11‐P17. Whole mounts of retina, optic nerve and tract, and SC, and cross sections of the optic nerve, were examined. In E21‐P2 rats, retinal axons labeled from each retinal site are diffusely distributed in the SC, and poorly ordered in the optic pathway. In retina, labeled axons travel in fascicles directly from the injection site to the optic disc, but neighbor relationships begin to degrade as fascicles split and mix. Retinotopic order is virtually lost in the optic nerve; axons labeled from each injection site disperse throughout its cross‐sectional area, but the labeled axons tend to be concentrated toward a specific half of the nerve depending upon their retinal origin. This slight tendency toward retinotopic order increases in the optic tract, but axons are still poorly ordered as they leave the tract and enter the SC. Targeting errors along the medial‐lateral axis of the SC, but apparently not along its rostral‐caudal axis, are related to the positioning of axons across the width of the optic tract.In P11–P17 rats, axons labeled from each injection site arborize only in a small, topographically correct part of the SC. However, the distributions of labeled retinal axons observed in whole mounts of the retina and optic pathway have a degree of disorder similar to those in E21‐P2 rats. Further, the scatter of labeled axons in optic nerve cross sections is comparable in both age groups. Therefore, the emergence of topographic order in the retinocollicular projection is not accompanied by an emergence of a retinotopic ordering of axons in the optic nerve. This indicates that axons positioned anywhere within the optic nerve are equally likely to establish a correctly positioned arbor, and survive the phase of map remodeling. Thus, a retinotopic organization of the rat optic nerve at perinatal ages is neither essential nor important for the subsequent development of topographic order in retinal projections.
Disruption of developmental timing in the albino rat retina
Authors: Webster Maree J. , Rowe Michael H. 
Published: January 2005

AbstractWe have examined the spatial and temporal gradients of two developmental processes in albino and pigmented rats: outer plexiform layer (OPL) development, and rate of eel production. The OPL first appears as a thin, discontinuous break in the cytoblast layer that is frequently interrupted by the profiles of migrating neuro‐ and glioblasts. In both strains, this occurs in an area temporal to the optic disc that corresponds to the eventual site of peak ganglion cell density, but is not located along the line of nasotemporal division. The OPL is first evident at P5 in pigmented animals, but its appearance in albino animals is delayed approximately 30 hours, and its development appears Lo follow a flatter spatial gradient than in pigmented animals. In pigmented animals OPL formation is complete over most of the retina by P10, but in albino animals at this age it is yet to be completely formed at any retinal location.Reductions in mitotic activity are also first evident in temporal retina, but unlike OPL development, appear to follow the same temporal‐spatial gradient in both strains. Reductions in temporal retina are obvious by P4, and mitotic activity has ceased altogether in midtemporal retina by P6 and throughout most remaining retinal regions by P8. Thus, the initial reduction of mitotic activity precedes the onset of OPL formation in both strains, but OPL development lags behind the reduction of mitotic activity to a greater extent in albino than in pigmented animals.Some aspects of differentiation within the inner nuclear layer (INL) were also examined. Just prior to the time of the onset of OPL formation, three distinct sublaminae are apparent in the INL. Cells in the innermost sublamina appear to be in an early stage of differentiation. Cells in the middle sublamina appear to be postmigratory, but have not yet begun to differentiate. Cells in the outermost sublamina have the appearance of migrating neuroblasts. At least some of these outer cells appear to migrate across the developing OPL to the outer nuclear layer, since the outermost sublamina becomes thinner and eventually disappears at the same time that the OPL becomes a continuous, uninterrupted plexiform layer. Cells of the middle sublamina apparently begin differentiation at about the time that this migration is complete. Although this sequence is the same in both albino and pigmented strains, its onset is delayed in albino animals by the same amount as the onset of OPL formation. In the INL, as well as in the ganglion cell layer, the process of cell death, as judged by the presence of pyknotic profiles, also appears to be delayed in albino animals.These results illustrate that the temporal relationships between various developmental processes are not fixed, and are consistent with the idea that subtle changes in developmental timing can underlie the orderly evolution of complex neural systems.
Connectivity of glycine immunoreactive amacrine cells in the cat retina
Authors: Pourcho Roberta G. , Owczarzak Michael T. 
Published: January 2005

AbstractThe synaptic relationships of glycine immunoreactive amacrine cells in the cat retina were studied through the use of postembedding immunogold techniques. Glycine immunoreactive amacrine cells were found to synapse extensively with other amacrines and ganglion cells, particularly in strata 1–3 of the inner plexiform layer. This contrasts with GABA immunoreactive amacrine cells which provide major input to bipolar cells in strata 3–5. Glycine containing amacrine terminals exhibited diversity with respect to the morphology of their synaptic vesicles. The three types of terminals which could be distinguished were characterized by small pleomorphic (32–35 nm), medium‐sized flattened (38–45 nm), or larger rounded (48–55 nm) vesicles.Comparison of retinal sections processed for glycine immunoreactivity with adjacent sections stained for GABA reactivity revealed a colocalization of glycine and GABA in 3% of the cells in the amacrine layer and approximately 40% of the cells in the ganglion cell layer, The amacrine terminals in which glycine and GABA were colocalized typically contained the small pleomorphic type of vesicles.
Pudendal motor and premotor neurons in the male rat: A WGA transneuronal study
Authors: Collins William F. , Erichsen Jonathan T. , Rose Robert D. 
Published: January 2005

AbstractAnatomical studies using retrograde neuronal tracers were carried out to identify pudendal motoneurons and putative lumbosacral interneurons involved in the generation of penile reflexes in the adult male rat (Sprague‐Dawley). In agreement with previous studies, injection of the direct neuronal tracers, horseradish peroxidase or fluoro‐gold, into the left M. bulbospongiosus (dorsal division) resulted in direct retrograde labeling of motoneurons only in the ipsilateral dorsomedial (DM) nucleus. In contrast, similar injections of the transneuronal tracer, wheat germ agglutinin (WGA), resulted in direct retrograde labeling of ipsilateral DM motoneurons as well as transneuronal labeling of contralateral DM motoneurons and of bilaterally located putative spinal interneurons. The WGA‐labeling was determined to be transneuronal by a series of nerve cut experiments.The direct retrograde WGA‐labeling of ipsilateral DM motoneurons and the transneuronal WGA‐labeling of contralateral DM motoneurons and bilateral putative spinal interneurons occurred with different time courses. Direct retrograde labeling of ipsilateral DM motoneurons was seen at 20 hours survival and persisted up to 7 days survival. The shortest survival period for detecting transneuronal labeling of contralateral DM motoneurons and putative interneurons was 2 days. Transneuronal WGA‐labeling of contralateral DM motoneurons was transient in that the intensity of label increased from 2 to 3 days survival but was markedly reduced at 7 days survival. At the same time, the number of WGA‐labeled putative interneurons increased with longer survival times up to 7 days.WGA‐labeled putative interneurons were located primarily in regions receiving dendritic projections from WGA‐labeled DM motoneurons and, in particular, (1) the ventral gray matter between the DM and dorsolateral nuclei and (2) near the central canal and extending dorsally to the dorsal gray commissure. The rapid and extensive transneuronal transport between DM nuclei suggests that direct synaptic coupling may mediate coordinated, bilateral activation of DM motoneurons.
Two systems of branching axons in monkey's retina
Authors: Usai Cesare , Ratto Gian Michele , Bisti Silvia 
Published: January 2005

AbstractSeveral monkey retinae were stained, by using the reduced silver technique, in order to analyse long‐distance intraretinal connections. Long, bifurcating processes covering very large areas were identified. Morphological investigation of these processes suggests that they are members of two different systems of branching axons.The first population of these processes originates as axon collaterals from cells in the ganglion cell layer. These cells have a relatively large, elongated soma and straight, sparsely branching dendrites, stratified in the vitreal half of the inner plexiform layer. The main axon (0.6 μm average diameter) passes along the optic fibre bundles, disappearing into the optic disk, whilst its collaterals run mainly in the inner plexiform layer. A cell showing similar morphology has also been found in the ganglion cell layer of a cat retina.The second population of processes consists of very thick fibres (2.1 μm average diameter) apparently originating from the optic disk. The main branches run in the space between the optic fibre layer and the ganglion cell layer, with short, secondary processes crossing the ganglion cell layer orthogonally. Many higher‐order processes originate from the second‐order branches; these run almost horizontally in the inner plexiform layer.The ganglion cells generating axon collaterals may constitute an intraretinal firing synchronization system, or they may be a residual feature of retinal development. The centrifugal fibres may be related to the sensitivity control during retinal dark adaptation.
Phrenic motoneuron morphology in the neonatal rat
Authors: Lindsay Amy D. , Greer John J. , Feldman Jack L. 
Published: January 2005

AbstractThe morphology of neonatal rat phrenic motoneurons was studied following retrograde labeling with horseradish peroxidase, which resulted in Golgi‐like fills of phrenic motoneuron somata and dendrites. At birth, these neurons have well‐developed dendritic trees with many characteristics described for phrenic motoneurons in the adult rat. The dendrites form tightly fasciculated bundles that emerge from the phrenic nucleus primarily along four axes: ventromedial, ventrolateral, dorsolateral, and rostral/caudal, with smaller and more variable projections directly lateral and ventral. Although sparse, some dendritic appendages were also present, and in a few animals, somata clustering was apparent. The most significant difference between adult and neonatal rat phrenic motoneurons is in the extent to which medially and laterally projecting dendrites extend beyond the borders of the ipsilateral gray matter. In the neonate, unlike the adult, these dendrites project extensively past the gray/white border to the edge of the hemicord. Ventromedial dendrites occasionally cross to the contralateral ventral horn in the ventral white commissure and laterally projecting dendrites could be seen reaching the edge of the cord, turning and traveling rostrally or caudally for up to 100 μm. Phrenic motoneurons are not unique in having long dendrites at birth. A brief comparative study showed that neonatal cervical, thoracic, and lumbar motoneurons also have long dendrites that project to the medial and lateral borders of the hemicord.
From embryo to adult: Anatomy and development of a leg sensory organ in Phormia regina, Meigen (Insecta: Diptera). II. Development and persistence of sensory neurons
Authors: Lakes‐Harlan R. , Pollack G. S. , Merritt D. J. 
Published: January 2005

AbstractThe imaginal leg disc of Phormia regina contains eight neurons that arise during embryogenesis. Five of the neurons are associated with Keilin's organ, and of these five, two persist to the adult fly. Two new neurons arise at about the time of pupariation and flank each of these persisting neurons, forming two triplets of cells. Both triplets can be followed throughout metamorphosis; in the late pupa they are situated anteriorly and posteriorly at the tip of the fifth tarsomere. Two triplets of cuticular specializations are found at corresponding positions in the adult fly, each consisting of two campaniform sensilla and a trichoid hair. The central member of each set of sensilla, a campaniform sensillum, is associated with the persisting cell.
Organization of nucleoli and nuclear bodies in osmotically stimulated supraoptic neurons of the rat
Authors: Lafarga M. , Andres M. A. , Berciano M. T. , Maquiera E. 
Published: January 2005

AbstractThis study has analyzed variations in the number of nucleoli and nuclear bodies, as well as in their ultrastructural and cytochemical organization, after the osmotically induced activation of supraoptic nucleus (SON) neurons of the rat. The number of nucleoli and nuclear bodies and also the nucleolar size were determined on smear preparations of previously block‐impregnated SON. The mean number of nucleoli per cell was 1.35 ± 0.6 (mean ± SDM) in control rats. No significant variations in this value were registered either in dehydrated or rehydrated rats. The mean nucleolar volume and the total nucleolar volume per cell showed a significant increase in dehydrated rats with respect to the controls, whereas these two parameters tended to return to control values in rats rehydrated after dehydration. The mean number of nuclear bodies per cell increased significantly from 0.56 ± 0.50 (mean ± SDM) in control rats to 1.54 ± 1.1 after 6 days of dehydration. By electron microscopy, SON neurons displayed a reticulated nucleolar configuration. After the osmotically induced neuronal activation, there was an increase in the proportion of the total nucleolar area occupied by the granular component, and also a reduction in the mean fibrillar‐center area. The most characteristic nucleolar features in rehydrated rats were the tendency for the granular component to be segregated and the occurrence of intranucleolar vacuoles. Ultrastructural cytochemistry with a specific silver method revealed a selective silver reaction on the coiled threads of the nuclear bodies—identified as “coiled bodies”—and on the nucleolar fibrillar components in all animal groups studied. Since nucleoli play a major role in ribosome biogenesis, a relationship between these nucleolar changes and the level of cellular activity of SON neurons is proposed. Furthermore, the response of nuclear “coiled bodies” to neuronal activation suggests their participation in the processing and transport of rRNA precursors.
Distribution of neuropeptide Y (NPY) in the cerebral cortex of the lizards Psammodromus algirus and Podarcis hispanica: Co‐localization of NPY, somatostatin, and GABA
Authors: Dávila Joseé Carlos , de la Calle Adelaida , Gutiérrez Antonia , Megías Manuel , Andreu Manuel José , Guirado Salvador 
Published: January 2005

AbstractThe aim of the present study was to analyze the distribution and characteristics of NPY immunoreactive structures in the cerebral cortex of lizards and to investigate the degree of co‐existence of this neuropeptide with somatostatin and GABA. The immunoperoxidase method was applied to vibratome sections as well as to semithin sections.NPY neurons are multipolar or fusiform and were unevenly distributed throughout the brain cortex. Within the medial, dorsomedial and dorsal cortices, most NPY perikarya were located in the plexiform layers, especially in the deep one. This suggests that these cells could be regarded as interneurons. In the lateral cortex, NPY neurons were found throughout all layers. The dorsomedial cortex displayed the highest NPY cell density. Here, neuronal perikarya projected many immunoreactive processes toward two distinct zones: the deep plexiform layer of the medial cortex and the superpositio medialis. The NPY neurons of the dorsomedial cortex differed from the other NPY cortical immunoreactive cells in that the latter displayed very few immunoreactive processes.A high degree of co‐existence among NPY, somatostatin, and GABA (approx. 80%) was found. This co‐existence rate is very similar to that reported in mammals and suggests that co‐localization is a phylogenetically ancient phenomenon.