bluuebunny/crossref_metadata_2025_split huggingface dataset:
Topographically organized projections from the nucleus subceruleus to the hypoglossal nucleus in the rat: A light and electron microscopic study with complementary axonal transport techniques
Authors: Aldes Leonard D. 
Published: January 2005

AbstractProjections from the nucleus subceruleus (nSC) to the hypoglossal nucleus (XII) were investigated with complementary retrograde and anterograde axonal transport techniques at the light and electron microscopic level in the rat. Injections of WGA‐HRP into XII resulted in labeling of neurons in and around the nSC. Labeled nSC neurons were few in number (<4 per 40–60 μm sections) and variable in size and shape. Most labeled nSC neurons were medium‐sized (X̄ = 16.89 μm), fusiform, triangular, or oval, with 3–4 dendrites typically oriented dorsomedially and ventrolaterally. These neurons were found throughout the rostrocaudal extent of the nSC but were most numerous medial, dorsomedial, and ventromedial to the motor trigeminal nucleus. Others were observed rostral to the motor trigeminal nucleus and ventral to the parabrachial nuclear complex.Confirmation of retrograde results was obtained following injections of tritiated amino acids or WGA‐HRP into the nSC. This resulted in labeling throughout the rostrocaudal extent of XII mainly ipsilaterally. Labeled fibers descended the brainstem in the dorsolateral and, to a lesser extent, in the ventromedial component of Probst's tract. Fibers entered XII mainly rostrally along the lateral border of the nucleus. All regions of XII were recipients of nSC afferents, but the caudoventromedial quadrant contained the greatest density of terminal labeling.Electron microscopic evaluation confirmed that nSC afferents synapsed on motoneurons in XII. Axon terminals containing WGA‐HRP reaction product were found contacting dendrites and somata, but primarily the former (81.3% versus 10.6%). Axodendritic terminals synapsed mainly on medium‐to‐small sized dendrites (<3 μm in diameter). The majority of labeled axodendritic terminals (90.1%) contained small, round, and clear synaptic vesicles (S‐type: 20–50 nm) and were associated with an asymmetric (60.6%), symmetric (11.4%), or no (18%) postsynaptic specialization. By contrast, most axosomatic terminals contained flattened vesicles (F‐type) and formed a symmetric or no postsynaptic specialization (75%). Large dense core vesicles (55–90 nm) were observed within a small proportion of all labeled axon terminals (1.3%).The results from this study demonstrate that the nSC projects to XII, preferentially targets a specific subgrouping of protrusor motoneurons, and synapses on both somata and dendrites, although mainly on the latter. The implications of these data are discussed relative to tongue control.
Cochlear‐nucleus branches of thick (medial) olivocochlear fibers in the mouse: A cochaleotopic projection
Authors: Brown M. C. , Pierce S. , Berglund A. M. 
Published: January 2005

AbstractOlivocochlear neurons have somata in the superior olivary complex and provide an efferent innervation to the cochlea. One subgroup of olivocochlear neurons, medial olivocochlear neurons, sends fibers to innervate the cochlear outer hair cells. En route to the cochlea, medial olivocochlear fibers give off branches to the ventral cochlear nucleus, the first auditory center of the brain. This study examines the cochlear‐nucleus branches of medial olivocochlear fibers, comparing those from fibers that innervate the cochlear base with those from fibers that innervate the cochlear apex. Basal fibers give off dorsal branches to the granule cell lamina and ventral branches to the auditory nerve root. Apical fibers give off few dorsal branches but many ventral branches that terminate rostrally to the nerve root. This cochleotopic mapping of medial olivocochlear branches corresponds in a general way to that of afferent fibers. Unlike afferent fibers, however, the branches terminate primarily along the edges of the cochlear nucleus. In the mouse, the particular edges of termination are (1) the medial border of the ventral cochlear nucleus where it meets the underlying vestibular nerve root, and (2) the border between the ventral cochlear nucleus and the granule cell lamina. Neurons and dendrites of these border regions may thus integrate efferent and afferent information in a frequency‐specific manner.
Effects of cortical and thalamic lesions upon primary afferent terminations, distributions of projection neurons, and the cytochrome oxidase pattern in the trigeminal brainstem complex
Authors: Chiaia Nicolas L. , Bennett‐Clarke Carol A. , Rhoades Robert W. 
Published: January 2005

AbstractEarly postnatal lesions of the primary somatosensory cortex alter the vibrissa‐related cytochrome oxidase (CO) pattern in nucleus principlis (PrV) of the rat's trigeminal (V) brainstem complex (Erzurumlu and Ebner, '88: Dev. Brain Res. 44:302–308). At present, the reason for this change is not clear. It may be that the corticotrigeminal projection is necessary for the maintenance of vibrissa‐related patterns in PrV. However, it is also possible that the loss of the normal pattern of CO activity reflects a change in the organization of brainstem cells resulting from transneuronal retrograde degeneration. In order to address this question, we made lesions of either the primary somatosensory cortex (S‐I) or ventrobasal thalamus (VB) in newborn rats and directly assayed distributions of V primary afferents by transganglionic transport of horseradish peroxidase and V‐thalamic neurons by retrograde transport of either fluorogold or true blue. Neonatal cortical and thalamic lesions produced no qualitative change in the distribution of primary afferent terminals in either PrV or V subnucleus interpolaris (SpI) beyond that which could be attributed to shrinkage of the brainstem resulting from retrograde degeneration. Most importantly, the “patchy” pattern of terminations observed in normal rats remained apparent in the brain‐damaged animals. The normal distribution of V‐thalamic neurons in PrV wasdisrupted by both cortical and thalamic lesions. These cells are normally patterned in a way that matches the distribution of primary afferent terminals and thus that of the mystacial vibrissae. This was not the case in the neonatally brain‐damaged rats. Taken together, these results are consistent with the conclusion that neonatal cortical and thalamic lesions disrupt the normal CO pattern in PrV primarily because of their effects upon the patterning of brainstem cells. The present findings demonstrate further that clustering of primary afferents does not require a normal complement of postsynaptic neurons.
Patterns of synaptic input on corticocortical and corticothalamic cells in the cat visual cortex. I. The cell body
Authors: Fariñas Isabel , DeFelipe Javier 
Published: January 2005

AbstractImmunocytochemical and electron microscopic methods were used to examine the ultrastructure and synaptology of callosal and corticothalamic pyramidal cell somata in the cat visual cortex (area 17). Callosal and corticothalamic cells were labeled after injection of horseradish peroxidase (HRP) in the contralateral visual cortex or in the ipsilateral lateral geniculate nucleus. The synaptic relationship between each of the two populations of pyramidal cells and cells containing the inhibitory neurotransmitter γM‐aminobutyric acid (GABA) was examined at the light and electron microscope level using the combined techniques of retrograde transport of HRP and GABA immunocytochemistry. We found that callosal and corticothalamic cell somata have an ultrastructure and synaptology that distinguishes them from each other. Reconstructions from electron micrographs of serial sections revealed that the vast majority of synapses (89–96%) on the cell body of pyramidal cells were formed by GABAergic axon terminals, and that within each population of pyramidal cells there was variability in the number and density of axosomatic synapses. Callosal pyramidal cells received a greater number and higher density of axosomatic synapses than corticothalamic cells. These data suggest that callosal cells receive more inhibition than corticothalamic cells at the level of their somata.
Immunocytochemical localization of calretinin in the forebrain of the rat
Authors: Jacobowitz David M. , Winsky Lois 
Published: January 2005

AbstractThe distribution of the calcium binding protein calretinin (protein 10) was examined in the rat forebrain by immunohistochemistry. The main and accessory olfactory bulbs had immunoreactive label in granule, periglomerular, and mitral cells. Positive fibers were noted in the external plexiform and granule cell layers, glomeruli, and in the molecular layer of the anterior olfactory nucleus. The cerebral cortex contained calretinin label in nonpyramidal bipolar cells. Cells in the substantia nigra compacta and ventral tegmental area were also calretinin positive as were nigrostriatal and mesolimbic projections (caudate‐putamen, nucleus accumbens). In the hippocampus, interneurons were stained in all the subfields of the CA1‐CA4 regions. In the thalamus, many positive cells were observed in the periventricular, reticular, lateral habenula, and reunions nuclei. Calretinin immunoreactive cells were particularly abundant in the lateral mamillary and septofimbrial nuclei. Several fiber tracts were also revealed, i.e., the lateral olfactory tract, mamillothalamic tract, fasciculus retroflexus, optic tract, and stria medullaris. These results demonstrate a distinct distribution of calretinin within cell bodies and fibers.
Regional brain glucose metabolism is altered during rapid eye movement sleep in the cat: A preliminary study
Authors: Lydic R. , Baghdoyan H. A. , Hibbard L. , Bonyak E. V. , De Joseph M. R. , Hawkins R. A. 
Published: January 2005

AbstractGlucose utilization was measured in 74 brain regions of the cat during states of wakefulness or rapid eye movement (REM) sleep. These data were obtained from intact, unanesthetized animals which were instrumented for objectively measuring states of consciousness. Through a chronically implanted intravenous catheter, the cats received 250 μCi of [6−14C]glucose during REM sleep (N = 3) or during wakefulness (N = 3). After spending ≈8 min in REM sleep or in quiet wakefulness, the cats were administered a lethal dose of barbiturate and the brains were removed and processed for autoradiography. The results revealed site‐specific changes in glucose metabolism during REM sleep. Significant alterations in glucose use occurred in the thalamus, the limbic system, and specific regions of the pontine reticular formation. These data demonstrate for the first time that during states comprised entirely of REM sleep there are anatomically specific changes in cerebral glucose metabolism. The majority of brain regions exhibiting REM sleep‐dependent changes in glucose metabolism either overlapped with regions known to contain cholinergic cell bodies, or with areas that receive prominent cholinergic input.
Similarities in the ultrastructural distribution of nerve growth factor receptor‐like immunoreactivity in cerebellar Purkinje cells of the neonatal and colchicine‐treated adult rat
Authors: Pioro Erik P. , Ribeiro‐Da‐Silva Alfredo , Cuello A. Claudio 
Published: January 2005

AbstractThe intracellular distribution of nerve growth factor receptor immunoreactivity was examined by electron microscopy in the cerebellum of adult and postnatal day 12 rats. The very faint immunostaining in Purkinje cells of naive adult animals was greatly amplified after colchicine treatment. Neonatal cerebellum, in contrast, contained prominent immunoreactivity in both Purkinje cells and germinal cells of the external granular layer. Intracellular distribution of the nerve growth factor receptor reaction product was very similar in Purkinje cells of both neonatal and colchicine‐treated adult animals. It was consistently present along the perikaryal cell membrane, in segments of the rough endoplasmic reticulum and Golgi complex. Numerous membrane‐bound aggregates of immunoreactive vesicles resembling multivesicular bodies (secondary lysosomes) were scattered throughout the cell soma, although less frequently in neonatal rats. Bulbous expansions along the proximal axons of colchicine‐treated Purkinje cells were filled with such immunoreactive multivesicular bodies. These cells also displayed evidence of nerve growth factor receptor internalization in the form of immunoreactive coated vesicles situated near the cell membrane. In addition to the staining in Purkinje cells, neonatal cerebellum contained high amounts of nerve growth factor receptor reaction product along the cell membrane of germinal cells in the external granular layer. Although Purkinje cells of naive adult animals possessed little or no cell membrane‐related nerve growth factor receptor immunoreactivity, reaction product was sometimes seen in cisternae of the rough endoplasmic reticulum and Golgi apparatus. These findings provide electron microscopic immunocytochemical evidence of nerve growth factor receptor synthesis, internalization, and catabolism in noncholinergic neurons of the central nervous system.
Morphological assessment of neuronal aggregates in the striatum of the rat
Authors: Paskevich P. A. , Evans H. K. , Domesick V. B. 
Published: January 2005

AbstractRegional variations in cell‐packing density, culminating in the formation of cell clusters, is now a recognized morphological characteristic of the striatum that has been correlated, in some instances, with either regional histochemical variations or the distribution pattern of afferent fiber systems, or both. Within these cluster regions a further level of organization exists, in the form of discrete neuronal aggregates. The light microscopic morphology of these neurons and the nature of their intercellular contacts at the electron microscope level form the focus of this report. The neurons composing such aggregates are characterized by contiguous soma‐somatic or soma‐dendritic contact with extended regions of junctionlike symmetrical and consistent contacts where the distance between the cytoplasmic membranes of apposing neurons narrows to as close as 7 nm. Coated vesicles close to the contact areas are common. Three‐dimensional computer reconstructions of serial 1 μm sections through aggregates in either the caudatoputamen or nucleus accumbens reveal “chains” of contiguous cells that frequently involve as many as 60 neurons. These contiguous cell aggregates are discrete entities within the larger clusters or islands. It is postulated that the cellular aggregates may represent the fundamental level of striatal organization and may be local modules for intrinsic information processing, modifying extrinsic data processed through the biochemical compartmentalization of the striatum imparted by striosomes, neuropeptides, and dopaminergic, thalamic and cortical afferents.
Mitral cell‐to‐glomerulus connectivity: An HRP study of the orientation of mitral cell apical dendrites
Authors: Buonviso Nathalie , Chaput Michel A. , Scott John W. 
Published: January 2005

AbstractIt has been suggested that the principal output cells of the main olfactory bulb, the mitral cells, along with the glomerulus they enter, form an anatomical and functional column. To test the extent to which mitral cell somata lying close together in the mitral cell layer are connected to the same glomerulus, we reconstructed 267 mitral cells labeled by extracellular injections of horseradish peroxidase (HRP) in the external plexiform layer.Results show that apical dendrites tilt rostrally from the somata to the glomeruli and this tilt is gradually greater as the somata are located more and more rostrally in the olfactory bulb. The apical dendrites of most mitral cells in the same region of the bulb are parallel. We analyzed the degree to which dendrites were parallel by measuring the difference in angle of all pairs of apical dendrites in each section, with the restriction that no cells were separated by more than 500 μm. About half of these pairs of dendrites differed in angle by 20° or less and were therefore said to be parallel. The degree of parallelism did not vary with the cell pair location or with intercell distance. Study of glomerular connections of pairs of mitral cells as a function of intercell distance revealed that 96% of mitral cells connected to the same glomerulus were separated by less than 120 μm, while 72% of cells connected to adjacent glomeruli and only 29% of cells connected to distant, i.e., nonadjacent, glomeruli were separated by less than 120 μm.These results show that mitral cells whose somata lie close together in the mitral cell layer tend to connect the same glomerulus, thus forming anatomical columns. The fact that some mitral cell apical dendrites deviate greatly from this pattern (for example about 5% of mitral cells send their apical dendrite in an opposite direction from their neighbors) suggests at least two influences determining mitral cell‐glomerulus connections.
Quantitative study of the tectally projecting retinal ganglion cells in the adult frog. II. Cell survival and functional recovery after optic nerve transection
Authors: Singman Eric L. , Scalia Frank 
Published: January 2005

AbstractIt is known from previous work that ganglion cells disappear from the retina in significant numbers during optic nerve regeneration in the adult frog, In the present study, the population sine of surviving ganglion cells that have returned axon terminals to the correct tectal loci was estimated by counts of retrogradely labeled cells in retina‐flat‐mounts after tectal injections of HRP. Bilaterally symmetric injections were delivered to allow comparison of the normal and affected retinas. The frogs studied had regenerated the left optic nerve and had visually guided behaviors initiated by the recovered eye (see below). The proportion of tectally projecting ganglion cells in the normal retinas and in retinas of normal frogs studied in parallel ranged from 83–86% (Singman and Scalia: J. Comp. Neurol. 302: 792–809, 1991), In the affected retinas, the subpopulation of tectally projecting cells was reduced by 40–90% after regeneration, and the relative size of this subpopulation ranged from 67–86%.The optic tectum was injected unilaterally in one specimen, on the side ipsilateral to the regenerated (left) optic nerve. The HRP‐labeled ganglion cells in the ipsilateral (left) retina accounted for only 0.8% of the surviving ganglion cells in this animal, whereas it was previously found that the ipsilateral tectally projecting ganglion cells normally amount to 0.9–2.3% (Singman and Scalia, op. cit.)In frogs recovering from transection of the left optic nerve, the frequency, latency, and accuracy of the prey‐acquisition responses initiated by the recovering eye were compared with those initiated by the normal eye. Mealworms or lure dummies were used to stimulate prey acquisition. In one experiment, the stimuli were presented unilaterally in the monocular fields of frogs permitted to use both eyes. Prior to the fourteenth postoperative week, the affected eye initiated responses of abnormally long latency and low frequency. In contrast, responses initiated by the affected eye after 14 weeks appeared to be normal in all respects. In another experiment, the normal eye was sutured shut in some frogs recovering for at least 24 weeks and then the affected eye was retested. The affected eye was capable of consistently initiating brisk and accurate prey acquisition. In a final experiment, two stimuli were presented simultaneously in bilaterally symmetric regions of the monocular fields of frogs surviving at least 42 weeks. These fully recovered frogs showed no preference for using either the normal or the recovered eye. Despite severe loss of tectally projecting ganglion cells during optic nerve regeneration, frogs are capable of apparently normal visual responses in prey acquisition tests.
Reinnervation of cerebellar Purkinje cells by climbing fibres surviving a subtotal lesion of the inferior olive in the adult rat. I. Development of new collateral branches and terminal plexuses
Authors: Rossi F. , Wiklund L. , van der Want J. J. L. , Strata P. 
Published: January 2005

AbstractCerebellar climbing fibres react by collateral sprouting after subtotal lesions of the inferior olive, and the newly formed branches are able to reinnervate neighbouring denervated Purkinje cells. In the present paper, we used the Phaseolus vulgaris leucoagglutinin (PHA‐L) tracing technique to label the climbing fibres and study their plasticity in detail at the light microscopical level. The specific objectives were to study the time course and morphological aspects of their sprouting, to estimate their extent of growth, and to compare the newly formed terminal plexuses with normal climbing fibres.Intraperitoneal injection of 3‐acetylpyridine induced degeneration of the majority of the olivary neurones, which terminate as climbing fibres in the cerebellar cortex. Regularly, small numbers of neurones survived in the inferior olive. In the cerebellar cortex scattered surviving climbing fibres were found, which were devoid of any sign of injury. Already 3 days after the lesion, surviving climbing fibres had emitted collateral branches, which elongated for some distance through the molecular layer and ended with a number of varicosities and very fine branchlets. By 7 days, it was possible to recognize new developing arbours which grew in the molecular layer with the same orientation as normal climbing fibres. At longer survival times, extensive terminal arbours had developed and double labelling experiments confirmed that they terminated around the proximal dendrites of Purkinje cells. The newly formed terminal plexuses resembled, in all essential aspects, normal climbing fibres. In addition, from 1 month onward, it was evident that every surviving climbing fibre was able to form several new terminal plexuses reinnervating a number of neighbouring Purkinje cells. The result of this process was the formation of large clusters of newly formed plexuses around the parental arborization. Quantitative estimates indicated that the domain of innervation of single surviving climbing fibres could be increased by more than six times.It is concluded that climbing fibres surviving a subtotal olivary lesion are capable of extensive sprouting, axonal growth, and formation of new terminal plexuses, which resemble normal climbing fibres. Previous electrophysiological evidence indicates that this reinnervation is functional. The high specificity with which sprouting olivary axons reinnervate the proximal Purkinje cell dendrites suggests the existence of precise interactions between the growing fibres and their target. This example of “homotypic” collateral sprouting and reinnervation may thus provide a useful model for the study of nerve–target interactions.