bluuebunny/crossref_metadata_2025_split huggingface dataset:
Retinal projections to the superior colliculus and dorsal lateral geniculate nucleus in the tammar wallaby (Macropus eugenii): I. Normal topography
Authors: Flett D. L. , Marotte L. R. , Mark R. F. 
Published: January 2005

AbstractThe topography of retinal projections to the superior colliculus and dorsal lateral geniculate nucleus of a wallaby, the tammar (Macropus eugenii), was investigated by an anatomical method. Small laser lesions were made in the retinas of experimental animals, and the remaining retinal projections were visualized by means of horseradish‐peroxidase histochemistry. The position of each lesion was correlated with the position of the filling defects in the terminal label.The whole of the retina projects to the contralateral superior colliculus. The nasal retina is represented caudally, and the temporal retina rostrally. The ventral retina is represented medially, and the dorsal retina laterally. There is a projection to the ipsilateral superior colliculus, but it is patchy and its topography could not be determined by this method. The retinotopic map in the contralateral dorsal lateral geniculate nucleus has the nasal retina represented rostrally and the temporal retina caudally in the nucleus. The dorsal retina is represented ventrally, and the ventral retina is represented dorsally. It appears that the whole of the retina projects contralaterally, and in addition the temporal retina projects ipsilaterally. The maps of visual space through the two eyes were shown to be in topographic register in the binocular region by making a deposit of HRP in the visual cortex. This resulted in a column of retrogradely labeled cells in the nucleus. This column crossed the laminae, which are innervated by the ipsilateral and contralateral eye at right angles.
Retinal projections to the superior colliculus and dorsal lateral geniculate nucleus in the tammar wallaby (Macropus eugenii): II. Topography after rotation of an eye prior to retinal innervation of the brain
Authors: Marotte L. R. , Mark R. F. 
Published: January 2005

AbstractRetinal projections to visual centers in a marsupial mammal, the tammar wallaby (Macropus eugenii), have been investigated after an eye rotation prior to retinal innervation of the brain. Retinal topography to the superior colliculus and dorsal lateral geniculate nucleus was mapped by using laser lesions of the retina and horseradish peroxidase histochemistry. Despite the change in orientation of optic axon outgrowth from the developing eye after rotation, retinal ganglion cells made orderly connections in the colliculus and geniculate according to their original retinal position within the eye and not their rotated position. Axons must have corrected their pathways at some point between the back of the eye and their targets. The optic chiasm was one such site. Optic axons from the rotated eye took an abnormal course at the caudal end of the chiasm.Growth of optic axons through aberrant pathways in the brain did not preclude specific innervation of targets. When by chance optic axons entered through the oculomotor nerve root they specifically innervated their correct visual centers, albeit in reduced density, and did not innervate inappropriate targets. These results support the idea of specific interactions between growing axons, the pathways they grow along, and their targets.
Morphological identification of an interneuron in the hypoglossal nucleus of the rat: A combined Golgi‐electron microscopic study
Authors: Takasu Nobuo , Hashimoto Paulo H. 
Published: January 2005

AbstractHypoglossal small neurons of adult and juvenile (10–15‐day‐old) rats were examined by a combined Golgi–electron microscopic technique. In adult rats, Golgi‐impregnated neurons were fusiform or ovoid (17 × 12 μm) and emitted a few primary dendrites with few branches and few spines and an axon mainly from the proximal portion of the primary dendrite. At the ultrastructural level, the soma displayed an invaginated nucleus with a conspicuous nucleolus and a relatively scanty cytoplasm in which cisternae of rough endoplasmic reticulum were not organized into extensive lamellar arrays. A moderate number of axon terminals, which contained spherical clear or pleomorphic vesicles ∼ 25–40 nm in diameter, formed symmetric or asymmetric synapses on the soma, the dendrites, the axon hillock, and the initial segment. In a preparation from the juvenile rat, we could trace a full axon trajectory of the small neuron. In this sample, in which a small neuron and a motoneuron were simultaneously impregnated, the axon of the small neuron was found to receive an axoaxonic symmetric synapse with pleomorphic vesicles on a varicosity and to contact the motoneuron dendrites by means of another varicosity of the main axon and of two boutons from an axon collateral. The varicosity and the boutons contained pleomorphic synaptic vesicles and synapsed symmetrically with the motoneuron dendrites. We identified the small neuron in the rat hypoglossal nucleus morphologicaly as a Golgi type II interneuron. We discuss its function in relation to the GABAergic nature of small neurons (Takasu et al.: J. Comp. Neurol. 263:42–53, ′87).
Ultrastructure of synaptic remodeling in piriform cortex of adult rats after neonatal olfactory bulb removal: An immunocytochemical study
Authors: Westenbroek R. E. , Westrum L. E. , Hendrickson A. E. , Wu J.‐Y. 
Published: January 2005

AbstractThe purpose of this investigation was to study possible remodeling in synaptic structures of the piriform cortex (PC) of adult rats following neonatal deafferentation by removal of the olfactory bulb (OB) at birth. Emphasis was placed on possible qualitative changes in the ultrastructure and immunocytochemical localization of cholecystokinin (CCK, a possible excitatory neurotransmitter or modulator) and glutamic acid decarboxylase (GAD, precursor enzyme to the inhibitory transmitter GABA in axons, terminals, and synaptic complexes. Light microscopic results in normal adult material show that GAD‐positive terminals form a dense band subjacent to the lateral olfactory tract (LOT), become less dense in deeper Ib, and are rare in layer II. Following deafferentation, GAD‐positive terminals appear denser and more homogeneously distributed throughout layer I and are also more prevalent in layer II. Ultrastructural results of normals and controls indicate GAD‐positive terminals normally contain pleomorphic or flattened vesicles and form symmetric contacts onto dendritic shafts and branches throughout layer I. In deafferented layer I not only do there appear to be greater numbers of symmetric GAD‐positive contacts, but in contrast to normals, asymmetric contacts mainly onto spines are now present. Light microscopic results from deafferented material also show an apparent proliferation with spread or sprouting of CCK‐positive fibers or axonlike structures mainly into layer Ia, whereas these fibers are normally observed only in the LOT and are generally few in number. Also in normals the few CCK‐positive terminals in the area subjacent to the LOT contain flattened or pleomorphic vesicles and form symmetric contacts. Deafferentation results in CCK‐positive terminals throughout layer I with a greater frequency of synaptic contacts which now also include a few asymmetric contacts onto spines. The findings clearly show modifications in synaptic patterns of immunocyto‐chemical‐labeled terminals that might be compatible with the process of atypical reinnervation of deafferented postsynaptic sites and possible ingrowth of new axons.
Development of the rat thalamus: I. Mosaic organization of the thalamic neuroepithelium
Authors: Altman Joseph , Bayer Shirley A. 
Published: January 2005

AbstractShort‐survival, sequential, and long‐survival thymidine radiograms of rat embryos, fetuses and young pups were analyzed in order to delineate the boundaries of the proliferative thalamic neuroepithelium, describe its early transformations, identify its regional divisions, and, finally, attempt to relate its distinct neuroepithelial components to specific thalamic nuclei that they supply with neurons. On day E13 the thalamic neuroepithelium consists of two divisions, the rostral lobe and the caudal lobe, and interposed between the two is a small transient structure, the reticular protuberance. By day E14 the rostral lobe has become partitioned into the anterior lobule and the reticular lobule, and the caudal lobe into the intermediate lobule and the posterior lobule. By day E15 these four lobules have become further partitioned into sublobules, characterized as regional eversions and inversions (concavities and convexities) of the thalamic neuroepithelium. Several of these sublobules are still recognizable on day E16 but progressively disappear thereafter.In this introductory paper, some evidence is presented in support of the hypothesis that the identified thalamic sublobules represent putative cell lines committed to produce neurons for specific, early‐generated thalamic nuclei. Detailed documentation of the evidence on which the identifications are based is provided in subsequent papers of this series which deal with the early development of specific thalamic regions and nuclei. In our attempt to identify these putative cell lines, we sought to meet the following criteria: (1) a good match between the time course of mitotic activity in a neuroepithelial sublobule and the birth days of neurons in the nucleus that it is postulated to supply with neurons, (2) relative proximity between the putative neuroepithelial source and the thalamic target structure, and, where possible, (3) the tracing of migrating cells from the germinal source to its destination. Using these criteria we have made the following tentative identifications. The early derivatives of the anterior thalamic lobules are the sublobules (committed cell lines) of the anterior thalamic nuclei, and of the central lateral and mediodorsal nuclei. The early derivatives of the reticular lobule and reticular protuberance are the sublobules of the reticular nuclear complex. The early derivatives of the intermediate lobule are the sublobules of the ventrolateral and ventrobasal nuclei. Finally, the early derivatives of the posterior lobule are the sublobules of the dorsal geniculate, ventral geniculate, and medial geniculate nuclei. The proposed partitioning and mosaic organization of the thalamic neuroepithelium are discussed with reference to traditional descriptions.
Evidence of intracerebellar collateralization of nucleocortical cell processes in a prosimian primate (Galago): A fluorescence retrograde study
Authors: Haines D. E. 
Published: January 2005

AbstractThe distribution of single and/or double‐labeled neurons in the cerebellar nuclei was investigated in a prosimian primate (Galago) by means of fast blue (FB) and nuclear yellow (NY) as retrograde tracers. Injections were made into spatially separate regions of cerebellar cortex on one side (zones C1−C3 in lobules IV and V and in the paramedian lobule) and into the same zones of lobules IV and V on both sides. Following unilateral injections single‐ and double‐labeled somata were seen in the anterior (NIA) and posterior (NIP) interposed cerebellar nuclei on the same side. Single‐labeled cells were, in general, more concentrated in NIA from the lobule IV‐V injection and in NIP from the PML placement; double‐labeled somata were about evenly distributed between NIA and NIP. Cell labeling was sparse in the contralateral NIP. Large and small somata were filled with FB, NY, or FB+NY ipsilateral to the injection sites while the majority of labeled neurons on the contralateral side had small oval‐ or fusiform‐shaped somata. Subsequent to bilateral injections cells labeled with each tracer were concentrated in the NIA, moderate in number in the NIP, both on the ipsilateral side, and sparse in the contralateral NIP.The double labeling of cells in the present study indicates that these neurons project to spatially separated, yet possibly functionally related, areas of ipsilateral cortex. Since larger and small somata were double labeled it is possible that those cells with cerebellofugal processes to extracerebellar targets may simultaneously relay information to divergent cortical sites. In contrast, the few labeled cells seen in the contralateral NIP have small oval and fusiform somata. These neurons may be specifically involved in cerebelloolivary and olivocerebellar feedback loops.
Development of substance P‐containing neurons in the central nervous system in mice: An immunocytochemical study
Authors: Ni Li , Miller Jonakait G. 
Published: January 2005

AbstractThe embryonic development of substance P (SP) in the central nervous system (CNS) of mice has been studied with the use of peroxidase antiperoxidase (PAP) immunocytochemistry. Immature SP‐positive cells initially appear at embryonic day 12 (E12) in the epithalamus and in a column of cells extending from the myelencephalon throughout the length of the neural tube. By E13, SP‐positive cells appear in the amygdaloid nuclear complex, the bed nucleus of the stria terminalis, and in the caudal medulla. Fibers are first detected in the stria terminalis at this age. Over the next 48 hours, a plethora of SP‐positive cells appears throughout the CNS, notably in the septal area, diagonal band nucleus, piriform cortex, accumbens nucleus, hypothalamus, rostral striatum, superior and inferior colliculi, intercollicular nucleus, substantia nigra, interpeduncular nucleus, vestibular nuclei, spinal nucleus of the trigeminal, and the nucleus of the tractus solitarii. Subsequently, SP‐positive neurons and fibers increase in number and staining intensity except in the medullary raphe where the apparent number of SP‐positive neurons decreases after E16.Whereas the pattern of SP staining is quite similar in mice and rats, the time of initial detection of SP‐like immunoreactivity in specific nuclei is 1–4 days earlier in mice than that reported in rats with different antisera.
Neural control of leg movements in a metamorphic insect: Persistence of larval leg motor neurons to innervate the adult legs of Manduca sexta
Authors: Kent Karla S. , Levine Richard B. 
Published: January 2005

AbstractDuring metamorphosis of the hawkmoth Manduca sexta, the larval thoracic legs along with their associated sensory organs and muscles degenerate and new adult legs develop. The larval legs are small and relatively simple structures capable of lateral extension and medial flexion allowing them to grasp the substrate as the caterpillar crawls along. By contrast, the adult legs are used for walking with an alternating gait. They are much larger than the larval legs and articulate such that they are capable of movement in several directions. This change in form and function is accompanied by a reorganization of the neural circuits controlling leg movements. In a previous report (Kent and Levine: J. Comp. Neurol. 271:559–576, 88) we described motor neurons innervating the larval prothoracic legs, and here we describe motor neurons innervating the prothoracic legs of the adult. Using a combination of cobalt staining methods and the persistent fluorescent dye Fluoro‐Gold, we have found that some, if not all, larval leg motor neurons are retained and innervate the new adult leg muscles. Moreover, we have been able to discover the fate of individual larval leg motor neurons by marking a single larval neuron with Fluoro‐Gold and using a second fluorescent dye to double label the same neuron in the adult. Our results suggest that specific larval leg motor neurons innervate corresponding muscles in the adult stage, although their apparent function is significantly different. In addition, the motor neurons undergo significant remodeling of their dendritic branching patterns during metamorphosis, alterations which doubtless contribute to their new roles in adult behavior.
Two types of tyrosine hydroxylase‐immunoreactive amacrine cell in the rhesus monkey retina
Authors: Mariani Andrew P. , Hokoc Jan N. 
Published: January 2005

AbstractTwo types of amacrine cell immunoreactive for tyrosine hydroxylase (TH), the rate‐limiting enzyme in the catecholamine (CA)‐synthetic pathway, are described in the rhesus monkey retina with the indirect‐immunofluorescent method. These 2 types of neuron differ in soma size, plane of arborization in the inner plexiform layer, levels of the enzyme TH as quantified by microspectrofluorometry, and population density. Type 1 CA cells have comparatively large cell bodies almost exclusively in the innermost row of the inner nuclear layer; their processes arborize in the outermost stratum of the inner plexiform layer; they give rise to fine predominantly radially oriented fibers in the inner nuclear layer; and there are about 26 type 1 CA cells/mm2. Type 2 CA amacrine cells have relatively small cell bodies located in the inner nuclear layer (44.4%), the inner plexiform layer (35.6%) and the ganglion cell layer (20 %), and their processes arborize in the center of the inner plexiform layer. Although type 2 CA amacrine cells are more numerous (35 cells/mm2) than type 1 CA cells, type 1 CA amacrine cells are 3.5 X brighter than type 2 CA cells and therefore likely to contain 3.5 X more TH. Thus the primate retina contains 2 distinct catecholaminergic neuronal pathways that could have different functional roles in vision.
Microsurgical analyses of avian neurulation: Separation of medial and lateral tissues
Authors: Schoenwolf Gary C. 
Published: January 2005

AbstractNeurulation, formation of the neural tube, is a complex process involving shaping and bending of the neural plate and closure of the neural groove. We have used avian embryos as model systems to study this process. In the present investigation, blastoderms were cut parasagittally through their entire thickness, either unilaterally or bilaterally, at two mediolateral locations: (1) at the juncture between prospective neural plate and prospective surface epithelium, and (2) at the juncture between the midline strip of prospective neural plate and more lateral prospective neural plate. In the first experiment, shaping of the neural plate seemed normal, but elevation and convergence of the neural folds and closure of the neural groove were inhibited (except at the forebrain level). This result demonstrates that extrinsic forces generated by lateral tissues are required for neural plate bending and neural groove closure. In the second experiment, neuroepithelial cells within the isolated, midline strip became wedge shaped. This result indicates that neuroepithelial cell “wedging” is an active event occurring independently of forces generated by elevation of the neural folds. Additional studies are required to define the natures of neurulation forces and the mechanisms by which they are generated.
Neuronal architecture of the nucleus of the solitary tract in the hamster
Authors: Whitehead Mark C. 
Published: January 2005

AbstractThis study provides a scheme for subdividing the nucleus of the solitary tract of the hamster on the basis of cytoarchitectonic criteria, cell measurements, and neuronal cell types identified with the Golgi method. Reduced silver‐stained sections revealed the feltlike neuropil that characterizes the nucleus of the solitary tract and were used to define the boundaries of the nuclear complex. Adjacent sections stained for Nissl substance revealed ten subdivisions, each with a characteristic neuronal architecture based on cell sizes, shapes, and packing density. Some subdivisions, e.g., the ventral and medial subnuclei, were identified at all rostrocaudal levels of the nuclear complex, while other subdivisions, e.g., the caudally located dorsolateral and ventrolateral subnuclei, were restricted to particular levels. Golgi preparations were counterstained for Nissl substance, thus allowing dendro‐ and cytoarchitecture to be compared directly. This material permitted the identification of a number of functionally relevant features of the neuronal constituents of the subdivisions. This approach, employing three cytological methods, has permitted the assembly of a detailed atlas of the nucleus of the solitary tract. The subdivisions of the present atlas have been compared with their likely counterparts identified in previous investigations of the mammalian nucleus of the solitary tract. In order to relate cytoarchitecture with primary afferent termination sites and to define the gustatory‐recipient subdivisions, the differential relationships of the subdivisions with lingual afferent projections in the hamster are also described. The present parcellation scheme is intended to facilitate anatomical and physiological investigations of the types of circuits that compose the medullary gustatory and general visceral sensory systems.
Auditory receptor of the red‐eared turtle: II. Afferent and efferent synapses and innervation patterns
Authors: Sneary Michael G. 
Published: January 2005

AbstractInnervation patterns in the auditory receptor of the red‐eared turtle were reconstructed from serial ultrathin sections. Four locations were studied, including three on the basilar membrane and one on the basal limbus. In that area of the papilla located above the apical end of the basilar membrane most cells were innervated by single afferent fibers which, in turn, supplied as many as three cells. Although afferents in the midmembrane area of the papilla supplied fewer cells, the innervation pattern was similar in other respects to that in the apical area including an abundance of efferent synapses on afferents. In contrast, hair cells in the basal membrane area were contacted by two afferent fibers and had five times as many afferent synapses as observed previously. Here, each afferent made twice as many synapses as fibers in the previous two areas and supplied one or two hair cells but received no efferent synapses. In the basal limbus area, each hair cell was contacted by as many as eight afferents and each afferent supplied as many as seven hair cells. The significance of these innervation patterns is discussed in the light of structural information obtained from other vertebrate auditory receptors and in the light of available functional information derived from the turtle papilla.