bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology of single, physiologically identified retinogeniculate Y‐cell axons in the cat following damage to visual cortex at birth
Authors: Weber A. J. , Kalil R. E. , Stanford L. R. 
Published: January 2005

AbstractIt has been reported previously that neurons in the dorsal lateral geniculate nucleus (LGN) of cats with neonatal damage to visual cortex (KVC cats) have receptive fields that are abnormally large and that the receptive fields of these neurons sometimes do not appear to conform to the normal retinotopic order in the LGN. A primary aim of this study was to determine if these physiological abnormalities are related to inappropriate patterns of retinogeniculate connections.We therefore have analyzed the terminal arbors of retinogeniculate axons in adult cats that had received a lesion of visual cortex (areas 17, 18, and 19) on the day of birth. Single retinogeniculate axons were characterized physiologically and injected intracellularly with horseradish peroxidase. Consistent with earlier reports that neonatal removal of visual cortex results in a retrograde loss of retinal X‐cells, all of the retinogeniculate axons that we recorded were from Y‐cells. While the visual responses of these Y‐cell axons were normal, the morphology of their terminal arbors in the LGN was abnormal. Retinal Y‐cell axons in KVC cats have terminal fields in the A laminae of the LGN that are as large or larger than those of normal Y‐cells. However, since the LGN in KVC cats is severely degenerated, single Y‐cell arbors occupy a proportional volume of the LGN that is 12 times greater than normal. Thus an early lesion of visual cortex produces a severe mismatch between retinogeniculate axon arbor size and target size. Also, despite the normal size of retinogeniculate axon arbors in KVC cats, the number and density of terminal boutons are greatly decreased.Thus our morphological results suggest that the unusually large receptive fields of LGN cells in KVC cats and the relative lack of retinotopic precision in the LGN are due, at least in part, to anomalies in the relative size and distribution of retinogeniculate axon arbors that develop after neonatal removal of visual cortex.
Anatomy of the auditory thalamocortical system of the guinea pig
Authors: Redies H. , Brandner S. , Creutzfeldt O. D. 
Published: January 2005

AbstractWe investigated the projection from the medial geniculate body (MG) to the tonotopic fields (the anterior field A, the dorsocaudal field DC, the small field S) and to the nontonotopic ventrocaudal belt in the auditory cortex of the guinea pig. The auditory fields were first delimited in electrophysiological experiments with microelectrode mapping techniques. Then, small quantities of horseradish peroxidase (HRP) and/or fluorescent retrograde tracers were injected into the sites of interest, and the thalamus was checked for labeled cells.The anterior field A receives its main thalamic input from the ventral nucleus of the MG (MGv). The projection is topographically organized. Roughly, the caudal part of the MGv innervates the rostral part of field A and vice versa. After injection of tracer into low or medium best‐frequency sites in A, we also found a topographic gradient along the isofrequency contours: the dorsal (ventral) part of a cortical isofrequency strip receives afferents from the rostral (caudal) portions of the corresponding thalamic isofrequency band. However, it is not so obvious whether such a gradient exists also in the high‐frequency part of the projection. A second, weaker projection to field A originates in a magnocellular nucleus that is situated caudomedially in the MG and was therefore named the caudomedial nucleus.The dorsocaudal field DC receives input from the same nuclei as the anterior field, but the location of the labeled cells in the MGv is different. This was demonstrated by injection of different tracers into sites with like best frequencies in fields A and DC, respectively. After injection of HRP into the 1‐2‐kHz isofrequency strip in field A and injection of Nuclear Yellow (NY) into the 1‐2‐kHz site in field DC, the labeled cells in the MGv form one continuous array that runs from caudal to rostral over the whole extent of the MGv. The anterior part of this array consists of NY‐labeled cells; i.e., it projects to field DC. The caudal part is formed by HRP‐labeled cells; i.e., it innervates field A. These findings indicate that there is only one continuous tonotopic map in the MGv. This map is split when projected onto the cortex so that two adjacent tonotopic fields (A and DC) result. The cortical maps are rotated relative to the thalamic map in that rostral portions of the MGv project to caudal parts of the tonotopic cortex and vice versa.The small field S receives its main thalamic input from a region situated in the rostral half of the MG medial to the ventral nucleus (the rostromedial MG). After injection of tracer into the ventrocaudal belt, labeled cells were found dorsal, lateral, and ventral to the MGv. These cells form a continuous band that surrounds the MGv like a shell. A second population of labeled neurons was found in the caudomedial nucleus of the MG.Similarities and differences between the auditory thalamocortical systems in the guinea pig and other mammalian species are discussed.
Light and electron microscopic study of galanin‐immunoreactive nerve fibers in the rat posterior thalamus
Authors: Blasco Isabel , Alvarez Francisco J. , Villalba Rosa M. , Solano Maria L. , Martínez‐Murillo Ricardo , Rodrigo José 
Published: January 2005

AbstractLight and electron microscopic immunocytochemistry was used to study certain cell groups in the posteromedial thalamus which contain galanin‐immunoreactive (GAL‐IR) fibers. The nuclei subparafascicularis pars parvicellularis (SPFpc) and parafascicularis (PF) contain a dense network of GAL‐IR fibers which form basketlike structures around unstained cells. The periventricular area also contains numerous GAL‐IR fibers and these also occasionally form basketlike structures. The GAL‐IR terminal fields continue caudally in the mesodiencephalic junction and mege with other GAL‐IR fibers in the dorsal aspects of the substantia nigra and around the dorsolateral tip of the medial lemniscus.Ultrastructural analysis of the GAL‐IR basketlike structures revealed that GAL‐IR terminals make numerous synapses with the cell bodies and proximal dendrites of SPFpc neurones. These results suggest that the activity of cells in the SPFpc and PF nuclei may be strongly influenced by galanincontaining nerve fibers probably originating in the spinal cord.
Degeneration and regeneration of peripheral nerve in the rat trigeminal system: III. Abnormal sensory reinnervation of rat guard hairs following nerve transection and crush
Authors: Munger Bryce L. , Renehan William E. 
Published: January 2005

AbstractThe present study was undertaken in an attempt to better understand the abnormalities of cutaneous sensibility that are present in patients following nerve injury with concomitant cutaneous denervation and subsequent reinnervation. Reinnervated intervibrissal pelage of the rat mystacial pad was studied in silver‐impregnated sections 3 and 5 months after transecting and 2 and 5 months after crushing the infraorbital nerve. The sensory terminals on guard and vellus hairs were analyzed in serial paraffin sections and in thick frozen sections. In normal rat mystacial skin, approximately nine/ten of innervated guard hairs have a typical piloneural complex consisting of a palisade of highly regular lanceolate terminals surrounded by circularly arranged Ruffini terminals and free nerve endings (FNEs). The remaining one of ten innervated guard hairs has only circularly arranged presumptive FNEs and Ruffini terminals. Vellus hairs, either singly or in clusters, typically have only circularly arranged terminals that in many cases are simple FNEs. We first recognized abnormalities in innervation of hairs following nerve transection and fully expected nerve terminals to be completely normal following nerve crush. Almost all reinnervated sensory nerve terminals associated with guard hairs were markedly abnormal following nerve transection and quantitatively abnormal following nerve crush. Following nerve transection, lanceolate terminals were almost completely absent, and they were remarkably reduced in number following nerve crush. Vellus hairs when reinnervated typically lacked the complex circular presumptive Ruffini terminals. These findings may be in part the basis for the abnormal cutaneous sensory perceptions (dysasthesias and paresthesias) noted in human subjects following damage to nerves with subsequent sensory reinnervation of the skin. Our findings are in accord with the reports of subtle physiologic abnormalities following nerve transection and crush. Morphologically abnormal reinnervated sensory terminals may retain modality specificity but in addition respond abnormally. These conclusions may be in part the basis for abnormal sensibilities that have been reported following crushing damage to peripheral nerves.
Two distinct visual pathways through the superficial pretectum in a percomorph teleost
Authors: Striedter Georg F. , Northcutt R. Glenn 
Published: January 2005

AbstractThe connections of the superficial pretectum and of nucleus isthmi were examined in a percomorph teleost, Lepomis cyanellus. Horseradish peroxidase was injected either with a pin into the parvicellular nucleus of the superficial pretectum or pressure injected into nucleus isthmi; the isthmal injections retrogradely labelled the neurons of the magnocellular nucleus of the superficial pretectum. Two main visual pathways can be recognized: The first projects from the retina to the parvicellular nucleus, and then to the intermediate nucleus of the superficial pretectum, the inferior raphe nucleus, and the trochlear nucleus. The second projects from the retina via the optic tectum to the magnocellular nucleus of the superficial pretectum, and from there to nucleus isthmi and the lateral thalamic nucleus; nucleus isthmi and the lateral thalamic nucleus project back to the optic tectum, and nucleus isthmi also projects back to the magnocellular nucleus. The two pathways are interconnected to some extent because both nucleus isthmi and the optic tectum project to the parvicellular nucleus; nevertheless, we suggest that they may be functionally and evolutionarily distinct. Compared to percomorphs, the first pathway appears reduced in cyprinid teleosts such as goldfish. Furthermore, the magnocellular nucleus of the second pathway is completely different in cyprinids, both in cellular architecture and in efferent connections. A phylogenetic analysis suggests that cyprinid ancestors went through a period of reduced vision and that the magnocellular nucleus of the superficial pretectum in modern cyprinids has been either extensively modified from the primitive condition or lost entirely and replaced by a superficially similar structure.
Auditory pathway and auditory activation of primary visual targets in the blind mole rat (Spalax ehrenbergi): I. 2‐deoxyglucose study of subcortical centers
Authors: Bronchti Gilles , Heil Peter , Scheich Henning , Wollberg Zvi 
Published: January 2005

AbstractThe blind mole rat Spalax ehrenbergi is a subterranean rodent that shows striking behavioral, structural, and physiological adaptations to fossorial life including highly degenerated eyes and optic nerves and a behavioral audiogram that indicates high specialization for low‐frequency hearing. A 2‐deoxyglucose functional mapping of acoustically activated structures, in conjunction with Nissl/Klüver‐Barrera‐stained material, revealed a typical mammalian auditory pathway with some indications for specialized low‐frequency hearing such as a poorly differentiated lateral nucleus and a well‐developed medial nucleus in the superior olive complex. The most striking finding was a marked 2‐deoxyglucose labeling of the dorsal lateral geniculate body and of cortical regions that correspond to visual areas in sighted rodents. The results render the blind mole rat a good model system for studying natural neural plasticity and intermodal compensation. In this report, we confine ourselves to the subcortical levels. The cortical level will be dealt comprehensively in a following paper.
Axon‐bearing amacrine cells of the macaque monkey retina
Authors: Dacey Dennis M. 
Published: January 2005

AbstractA new and remarkable type of amacrine cell has been identified in the primate retina. Application of the vital dye acridine orange to macaque retinas maintained in vitro produced a stable fluorescence in the somata of apparently all retinal neurons in both the inner nuclear and ganglion cell layers. Large somata (∼15‐20 μm diam) were also consistently observed in the approximate center of the inner plexiform layer (IPL). Intracellular injections of horseradish peroxidase (HRP) made under direct microscopic control showed that the cells in the middle of the IPL constitute a single, morphologically distinct amacrine cell subpopulation. An unusual and characteristic feature of this cell type is the presence of multiple axons that arise from the dendritic tree and project beyond it to form a second, morphologically distinct arborization within the IPL; these cells have thus been referred to as axon‐bearing amacrine cells.The dendritic tree of the axon‐bearing amacrine cell is highly branched (∼40‐50 terminal dendrites) and broadly stratified, spanning the central 50% of the IPL so that the soma is situated between the outermost and innermost branches. Dendritic field size increases from ∼200 μm in diameter within 2 mm of the fovea to ∼500 μm in the retinal periphery. HRP injections of groups of neighboring cells revealed a regular intercell spacing (∼200‐300 μm in the retinal periphery), suggesting that dendritic territories uniformly cover the retina.One to four axons originate from the proximal dendrites as thin (<0.5 μm). smooth processes. The axons increase in diameter (∼1‐2 μm) as they course beyond the dendritic field and bifurcate once or twice into secondary branches. These branches give rise to a number of thin, bouton‐bearing collaterals that extend radially from the dendritic tree for1‐3 mm without much further branching. The result is a sparsely branched and widely spreading axonal tree that concentrically surrounds the smaller, more highly branched dendritic tree. The axonal tree is narrowly stratified over the central 0‐20% of the IPL; it is approximately ten times the diameter of the dendritic tree, resulting in a 100 times greater coverage factor.The clear division of an amacrine cell's processes into distinct dendritic and axonal components has recently been observed in other, morphologically distinct amacrine cell types of the cat and monkey retina and therefore represents a property common to a number of functionally distinct cell types. It is hypothesized that the axon‐bearing amacrine cells, like classical neurons, use action potentials to transmit signals over long distances in the IPL and, on the basis of previous immunohistochemical results, contain the inhibitory neurotransmitter GABA.
Ongoing electrical activity of superior cervical ganglion cells in mammals of different size
Authors: Ivanov Alexander , Purves Dale 
Published: January 2005

AbstractThe ongoing synaptic activity of superior cervical ganglion cells in adult mammals was examined in situ by intracellular recording in anesthetized mice, hamsters, rats, guinea pigs, and rabbits. The proportion of neurons exhibiting subthreshold and suprathreshold synaptic activity during a standard period of observation was least in a small mammal like the mouse (30%), intermediate among neurons of mammals of intermediate size such as the hamster and rat (48% and 45%, respectively), and greatest in the largest animals in the series, the guinea pig (89%) and rabbit (91%). Ganglion cells in all species fell silent after transection of the cervical trunk. The average frequency of synaptic activity among tonically active cells also increased with animal size, being least in the mouse (1.0/second) and greatest in the rabbit (6.4/second). This variation of ongoing synaptic activity in sympathetic ganglion cells may reflect the demands of progressively larger peripheral targets on relatively fixed populations of autonomic neurons.
Distribution of GABAergic neurons and terminals in the auditory system of the barn owl
Authors: Carr C. E. , Fujita I. , Konishi M. 
Published: January 2005

AbstractAntisera to GAD (glutamic acid decarboxylase) and GABA were used to determine the distribution of GABAergic cells and terminals in the brainstem and midbrain auditory nuclei of the barn owl. The owl processes time and intensity components of the auditory signal in separate pathways, and each pathway has a distinctive pattern of GAD‐ and GABA‐like immunoreactivity. In the time pathway, all the cells of the cochlear nucleus magnocellularis and nucleus laminaris receive perisomatic GABAergic terminals, and small numbers of GABAergic neurons surround both nuclei. The ventral nucleus of the lateral lemniscus (anterior division) contains both immunoreactive terminals and some GABAergic neurons. In the intensity pathway, dense immunoreactive terminals are distributed throughout the cochlear nucleus angularis, which also contains a small number of GABAergic neurons. The superior olive contains two GABAergic cell types and immunoreactive terminals distributed throughout the neuropil. All the neurons of the nucleus of the lateral lemniscus (ventral part) appear to be GABAergic, and this nucleus also contains a moderate number of immunoreactive terminals. Immunoreactive terminals are distributed throughout the neuropil of the ventral nucleus of the lateral lemniscus (posterior division), whereas multipolar and small fusiform GABAergic neurons predominate in the dorsal regions of the nucleus. The time and intensity pathways combine in the inferior colliculus. The central nucleus of the inferior colliculus contains a large number of fusiform and stellate GABAergic neurons and a dense plexus of immunoreactive terminals, whereas the external nucleus contains slightly fewer immunoreactive cells and terminals. The superficial nucleus contains dense, fine immunoreactive terminals and a small number of GABAergic neurons.
Intraspinal course of descending serotoninergic pathways innervating the rodent dorsal horn and lamina X
Authors: Bullitt E. , Light A. R. 
Published: January 2005

AbstractAlthough numerous studies have discussed serotoninergic pathways projecting from the brainstem to the spinal cord, the intraspinal course of these descending axons remains a matter of debate. One of the difficulties with traditional immunohistochemical methods is that the interpretation of results has been subjective. We have therefore employed a computer‐assisted imageprocessing system to provide objective measurements of serotonin immunoreactivity within the rodent dorsal horn and lamina X caudal to unilateral thoracic cordotomy in order to establish the intraspinal course of descending serotoninergic fibers.Lesion analysis combined with computer‐determined optical density measurements, high‐power microscopic examination, and camera lucida drawings demonstrated that the predominant serotoninergic pathway terminating within the dorsal horn courses unilaterally within the dorsal portion of the dorsolateral funiculus. The thoracic dorsal horn may receive a slightly greater contribution from the contralateral side than the lumbar dorsal horn. Lamina X receives serotoninergic innervation both from fibers descending within the ipsilateral dorsolateral funiculus and from more ventrally located ipsilateral pathways, and it also contains serotonin derived from other sources.
Origin of retinal astrocytes in the rat: Evidence of migration from the optic nerve
Authors: Ling Tailoi , Mitrofanis John , Stone Jonathan 
Published: January 2005

AbstractTo test recent ideas on the origin of retinal astrocytes, we have studied the spread of astrocytes in the developing retina of the albino rat. Astrocytes were identified with antibodies to their intermediate filaments, glial fibrillary acidic protein (GFAP). Astrocytes were first detected at E(embryonic day)18, forming a corona of processes around the optic disc. Over subsequent days, astrocytes extended over the retina, covering approximately 35% of the retina at birth (typically E21–22) and reaching the edge of the retina by P(postnatal day)8. As they spread, astrocytes were closely associated with the developing vasculature, spreading ahead of patent vessels by a small but distinct margin. The most peripheral astrocytes assumed a bipolar morphology and extended processes towards the margin of the retina. Astrocytes nearer the optic disc showed the stellate shape characteristic of mature cells. The appearance of astrocytes at the optic disc at E18, 2 days after the appearance of type‐1 astrocytes in the optic nerve (Miller et al.: Dev. Biol. 11135–41, '85), suggests that retinal astrocytes may be type‐1 astrocytes generated in the optic nerve. Watanabe and Raff (Nature 332:834–837, '88) have recently reported an independent study supporting the same conclusions.
Autoradiographic distribution of thyrotropin‐releasing hormone receptors in the african lungfish Protopterus annectens
Authors: Pack Alison M. , Caine S. Barak , Winokur Andrew , Manaker Scott , Fishman Alfred P. 
Published: January 2005

AbstractWe used quantitative autoradiography to examine the distribution of thyrotropin‐releasing hormone (TRH) receptors in the central nervous system (CNS) of the African lungfish Protopterus annectens. We found that the distribution of TRH receptors throughout the CNS of the lungfish was heterogeneous with the highest concentrations (500–800 fmol/mg protein) in the olfactory bulb and telencephalon, moderately high concentrations (200–500 fmol/mg protein) in the diencephalon, and moderate (50–200 fmol/mg protein) to low (<50 fmol/mg protein) concentrations in the brainstem and spinal cord. Except for the motor nuclei of the cranial nerves and spinal cord, TRH receptors were concentrated in the acellular regions. In the telencephalon and diencephalon, the receptor density was inversely related to cellular density. These results provide a neuroanatomic and neuropharmacologic basis for further investigations of TRH in the African lungfish.