bluuebunny/crossref_metadata_2025_split huggingface dataset:
Auditory brainstem of the ferret: Long survival following cochlear removal progressively changes projections from the cochlear nucleus to the inferior colliculus
Authors: Moore David R. 
Published: January 2005

AbstractSome effects on auditory brainstem connections of long (1–2.3 years) survival following unilateral cochlear removal in infant and adolescent ferrets were examined by making multiple injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) in either the left or the right inferior colliculus (IC). Previous studies have shown that, in normal adult ferrets, about 50 times as many cochlear nucleus (CN) neurons project to the contralateral as to the ipsilateral IC. Right cochlear removal at P25 increased, within 30 days, the number of retrogradely labeled left CN neurons projecting to the left ipsilateral IC by 17% (from n = 235 to n = 275), relative to normals. In this study, longer survival (3 months to 1 year) after right cochlear removal at P25 resulted in larger increases (38–47%; n ≈ 100) in the number of neurons labeled in the left CN after injections of WGA‐HRP in the left IC. No change occurred in the number of neurons labeled in the right CN. Taken together, the results of these experiments show that the ratio of the number of labeled neurons in the left CN to that in the right CN increases progressively with survival time out to the maximum time tested (1 year). In contrast to these results, we have previously reported that right cochlear removal at P90 did not change the number of neurons projecting from the left CN to the left IC after 90 days of survival. However, in this study, very long survival (2–3 years) following right cochlear removal at P90 resulted in an increased (51%, from n = 235 to n = 355) number of left CN neurons labeled by WGA‐HRP injections into the left IC, relative to normals. The increased number of labeled neurons included neurons throughout each division of the CN and all of the principal morphological types. In a separate series of experiments involving long survival (1‐2 years), right cochlear removal at P25 or P40 did not significantly change the number of neurons in either CN retrogradely labeled by injections of WGA‐HRP in the right IC, or the ratio between the number of neurons labeled in each CN. Long survival following cochlear removal at P25–P90 did not result in any loss of neurons in the ipsilateral CN or in any shrinkage of CN neurons further than the 10–20% seen at a shorter survival time (90 days). These results show that at least one pathway within the auditory brainstem continues to be changed in later life following either early or late cochlear removal. They provide a possible anatomical basis for long‐term changes seen in sensory systems following lesions of the sense organs of mature animals. © 1994 Wiley‐Liss, Inc.
Quantitative aspects of the GABA circuitry in the primary visual cortex of the adult rat
Authors: Beaulieu Clermont , Campistron Ghislaine , Crevier Claire 
Published: January 2005

AbstractThe number and size of synaptic contacts made by GABA‐immunoreactive axonal boutons were estimated in each layer of the primary visual cortex (area Oc1M) of adult rats by using the disector method. Immunoreactivity for GABA was detected with the postembedding immunogold technique on ultrathin sections. Targets of GABA synaptic contacts were also identified to predict the sites of GABA influence in the rat visual cortex.For the total cortical depth, 82 million out of an overall population of 666 million synaptic contacts per mm3 of tissue (or 1 in 8 contacts, 12%) were GABA. Layer IV averaged 62% more GABA contacts per unit volume than did any other cortical layer. Consequently, these represented a larger proportion (1 in 6, 17%) of the overall population of layer IV synaptic contacts. This higher number of GABA contacts was not due to a greater density of GABA boutons, but to an increased number of contacts made by each layer IV GABA bouton (mean of 1.4 contacts per bouton compared to 1.1 in other cortical layers).The total area occupied by the contacts on an average GABA bouton was similar in all layers; the higher number of contacts per GABA bouton in layer IV being compensated for by their smaller size. This observed constancy in the area of synaptic contacts suggests the presence of one or more regulatory mechanisms maintaining optimal numbers of the different macromolecules forming the synaptic contacts.The increased density of GABA contacts in layer IV compared to other cortical layers was due to their greater number targeting distal regions of the dendritic tree. Since layer IV receives the vast majority of thalamocortical terminals and since these axons preferentially target dendritic spines, the specific arrangement of GABA synaptic contacts in this layer could be designed to exert a precise inhibition near the site of the thalamic input and thus serve as the structural basis for the strong GABA‐related hyperpolarization that followed the excitatory response after physiological stimulations of the thalamocortical pathway. © 1994 Wiley‐Liss, Inc.
Identification and viuotopic organization of areas PO and POd in Cebus monkey
Authors: Neuenschwander Sergio , Gattass Ricardo , Sousa Aglai P. B. , Piñon Maria Carmen G. P. 
Published: January 2005

AbstractTwo visual areas of the anterior bank of the parietooccipital sulcus, areas PO and POd, were identified and their visual field representations were studied in six anesthetized and paralyzed Cebus monkeys. The definition of these areas was based on electrophysiological mapping and myeloarchitecture. PO is located in the ventral aspect of the anterior bank of the parietooccipital sulcus and ventral precuneate gyrus. It borders area V2 posteriorly and ventrally in the depth of the parietooccipital sulcus, area V3d laterally, and another undescribed visual area medially. POd was located dorsal to area PO and ventral to architectonic area PE. The representations of the visual field in areas PO and POd are complex. In each hemisphere, these areas have a virtually complete representation of the contralateral visual hemifield. Different from the previously described visual areas, in PO and POd there is a precise organization of isopolar lines and a complex organization of the isoeccentric ones. In PO, as well as in POd, the representation of the horizontal meridian runs dorsoventrally along the parietooccipital sulcus. The upper visual quadrant is represented medially and the lower visual quadrant laterally. A large and complex representation of the periphery, from 20° to 60° eccentricity is present at the lateral and medial portions of these areas. By contrast, the representation of the central 20° is very small in both PO and POd. The central visual field is represented ventrally in PO and dorsally in area POd. Area POd shows a more stratified myeloarchitectonic pattern than PO and both areas can be distinguished from other surrounding areas by their heavier myelinated pattern. © Wiley‐Liss, Inc.
Postnatal development of the hamster coclea. I. Growth of hair cells and the organ of Corti
Authors: Kaltenbach James A. , Falzarano Pamela R. 
Published: January 2005

AbstractA morphometric analysis of the developing organ of Corti and its component hair cells was carried out in an age‐graded series of Syrian golden hamsters with the aid of scanning electron microscopy. The purpose was to establish a quantitative framework that would provide insight into the rules and principles by which the mammalian cochlea attains its adult proportions. This study examined postnatal development at two day intervals from birth to 22 days after birth. Our analysis included measures of cochlear length and hair cell numbers as well as measures of hair cell sizes in each of five sectors along the cochlear spiral. Our results demonstrate several principles of cochlear development: (1) The full two and one‐fourths turns seen in the adult cochlea are already present at birth, but the cochlea continues to elongate for the next 10–12 days. (2) Development of hair cells in the apex generally lags behind that in the base. Whereas the stereocilia and apical margins of hair cells are clearly defined in the basal turn, they become well defined in the apex only postnatally. (3) Growth in cochlear length occurs mainly by increases in cell size rather than in cell numbers; although hair cells do increase in numbers during the first 4 days of cochlear growth, this increase involves addition of hair cells only to preexisting regions of the cochlear apex. Moreover, the full complement of hair cells is established 6 days before the full size of the cochlea is attained; in contrast, hair cell growth occurs at all positions along the cochlear spiral and spans the entire period of cochlear elongation. (4) The period of hair cell growth exceeds the period of organ of Corti growth and appears to be possible by decreases in intercellular spacing, primarily in the apical region of the cochlea; inner and outer hair cell growth was complete between 16 and 18 days after birth. (5) Inner and outer hair cell neighbors remain virtually constant at different ages indicating that the spatial relationships between the two hair cell populations is preserved as the cochlea grows. (6) Comparison with previous developmental studies of auditory function in the hamster reveals that the age of 16 days after birth, when hair cells attain their mature sizes, coincides with the onset of brainstem auditory evoked responses. Growth of hair cell somas alone, however, cannot explain either the subsequent maturation of evoked potential thresholds or changes in frequency representation in the developing cochlea. © Wiley‐Liss, Inc.
Expression of thrombospondin in the adult nervous system
Authors: Hoffman John R. , Dixit Vishva M. , O'Shea K. Sue 
Published: January 2005

AbstractThrombospondin (TSP) is an extracellular matrix molecule that has been previously associated with neural development and neurite outgrowth in vitro. Little is known, however, about the expression of TSP in the adult nervous system. In this study, TSP localization was examined in nervous tissue from adult mouse, goldfish, newt, and adult and juvenile Xenopus. TSP was associated with neurons in the brains of all species examined. TSP was present in central nerve tracts capable of regeneration, such as the goldfish, Xenopus, and newt optic nerves, but was absent from tracts not capable of regeneration, such as the mouse optic nerve. TSP was also present in the neuropil of goldfish and newt spinal cord, but was restricted to motor neurons in mice and adult Xenopus. In addition, TSP was observed in sciatic nerves of mice, Xenopus, and newt. These results indicate a correlation between the presence of TSP and the potential for successful nerve regeneration across a wide range of animal classes. © Wiley‐Liss, Inc.
Choline acetyltransferase‐immunoreactive cochlear efferent neurons in the chick auditory brainstem
Authors: Code R. A. , Carr C. E. 
Published: January 2005

AbstractCholinergic neurons in the chick auditory brainstem were studied with the aid of an antiserum to choline acetyltransferase (ChAT), the biosynthetic enzyme for acetylcholine. ChAT‐immunoreactive (ChAT‐I) neurons were found in a ventrolateral and a dorsomedial cell group. The ventrolateral group is a rostrocaudally directed column of cells that surround the superior olive (SO), are ventromedial to the ventral facial nucleus (VIIv), and are lateral to the nucleus pontis lateralis (PL) as far rostrally as the nucleus subceruleus ventralis. Cells in the dorsomedial group were found in the pontine reticular formation medial to the dorsal facial nucleus and lateral to the abducens nerve root. Occasionally, small ChAT‐I cells were found in the crossed dorsal cochlear tract and in the medial vestibular nucleus near the dorsal border of the caudal nucleus magnocellularis (NM). No ChAT‐I neurons or fibers were observed in NM, nucleus angularis, nucleus laminaris, in the nuclei of the lateral lemniscus, or in the nucleus mesencephalicus lateralis pars dorsalis.To determine which cholinergic neurons project to the cochlea, a double‐labeling technique was used combining ChAT‐I and the retrograde transport of biotinylated dextran amine (BDA) from the inner ear. Double‐labeled cells were found bilaterally in both the ventrolateral and dorsomedial cell groups, with the exception of large ChAT‐I cells dorsal to the SO, which do not appear to project to the cochlea. Cholinergic cells that project to the cochlea were classified into three morphological groups: multipolar, elongate, and round‐to‐oval. Both the ventrolateral and the dorsomedial cell groups appear to have a mixture of these different cell types. The average somal area of cholinergic cochlear efferents was 246 μm2. Only about 70% of the cochlear efferent neurons, however, are cholinergic. © Wiley‐Liss, Inc.
Distribution of secretoneurin immunoreactivity in the spinal cord and lower brainstem in comparison with that of substance P and calcitonin gene‐related peptide
Authors: Marksteiner Josef , Mahata Sushil K. , Pycha Roger , Mahata Manjula , Saria Alois , Fischer‐Colbrie Reiner , Winkler Hans 
Published: January 2005

AbstractSecretoneurin is a peptide of 33 amino acids generated in brain by proteolytic processing of secretogranin II. The distribution of this newly characterized peptide was investigated by means of immunocytochemistry and in situ hybridization in the spinal cord and lower brainstem of the rat. The staining pattern of secretoneurin immunoreactivity (IR) was compared to that of substance P (SP) and calcitonin gene‐related peptide (CGRP) in adjacent sections. A high density of secretoneurin‐IR fibers and terminals was found in lamina I and outer lamina II of the caudal trigeminal nucleus and of the spinal cord at all levels, around the central canal, and in the sympathetic and parasympathetic areas of the lateral cell columns. The ventral horn displayed a low to moderate density of secretoneurin‐IR. The highest number of secretogranin II mRNA‐containing cells was found in lamina II of the dorsal horn and in neurons of the dorsal root ganglia. In the white matter, secretoneurin‐IR was most prominent in the dorsolateral part of the lateral funiculus and in the tract of Lissauer. The distributions of secretoneurin‐IR and SP‐IR were strikingly similar. CGRP‐IR and secretoneurin‐IR overlapped in the outer laminae of the dorsal horn, in the lateral cell column, and probably in some motoneurons. This study establishes that, like SP and CGRP, secretoneurin is a peptide highly concentrated in the terminal field of primary afferents and in sympathetic and parasympathetic areas. Thus secretoneurin might be involved in the modulation of afferent transmission. © Wiley‐Liss, Inc.
Axon overproduction and elimination in the anterior commissure of the developing rhesus monkey
Authors: LaMantia Anthony S. , Rakic P. 
Published: January 2005

AbstractWe have analyzed axon overproduction and elimination in the anterior commissure (AC) of 16 fetal, neonatal, and juvenile rhesus monkeys. Axons are added to the AC at an average rate of 115,000/day during the last two‐thirds of gestation, and growth cones are present in a constant proportion to AC axons throughout this period. The peak number of approximately 11 million axons in the AC is reached at birth. Thereafter, axons are eliminated at a net rate of approximately 1 axon/sec during the first 3 postnatal months until the adult number of approximately 3.3 ± 0.5 million axons is reached. Although there is considerable variability in AC axon number during the period of axon loss, the adult number of AC axons is relatively invariant among the eight adult rhesus monkeys examined. Increase in axon diameter and myelination begins before the major phase of axon elimination and is completed long after the adult number of axons is reached. Apparently, myelinated axons are not eliminated from the AC. Quantitative differences in the magnitude and timing of axon overproduction and elimination of AC versus that in the corpus callosum (LaMantia and Rakic [1990] J. Neurosci. 10:2156) indicate specific modulation of the development of each commissure, perhaps reflecting differences in the developmental history and functional identity of the distinct cortical regions that give rise to them. This process of overproduction and elimination of AC axons during postnatal development in primates might contribute to individual variations in AC size correlated with a wide range of physical and behavioral differences. © Wiley‐Liss, Inc.
On the formation of neuromata in the primtary olfactory projection
Authors: Schwob James E. , Youngentob Steven L. , Meiri Karina F. 
Published: January 2005

AbstractOlfactory axons have been shown to grow aberrantly and form dense collections of axons, termed neuromas, in the olfactory epithelium of rats in which the olfactory bulb was ablated. Likewise, in human olfactory mucosa, collections of neurites have been noted in a variety of disease states, including Alzheimer's disease. We report here an immunohistochemical and electron microscopic analysis of aberrant axonal growth in the rat olfactory mucosa induced by experimental lesion. In particular, we have used the monoclonal antibody 2G12, which binds to the phosphorylated form of GAP‐43, as an extremely sensitive marker for neuromatous axons, because it does not label neuronal cell bodies. In unilaterally bulbectomized rats, neuromas form in posterior olfactory epithelium on the operated side. Several lines of evidence, including serial section reconstruction, indicate that olfactory axons are induced to grow back into the epithelium at a distance from their point of origin as a consequence of bulbectomy, and are accompanied by glial cells from the olfactory nerve. Avulsion of a part of the olfactory nerve has similar effects as destruction of the olfactory bulb. Intraepithelial neuromas also develop in the olfactory mucosa of rats simultaneously exposed to methyl bromide gas and injected with 3‐methyl indole; this treatment severely damages the olfactory epithelium directly. Exposure to methyl bromide alone causes milder damage, and the neuromas that form are transient. The evidence indicates that neuromas form after the epithelium is directly damaged because axons are trapped in the epithelium. Both of the mechanisms identified here should be taken into account when considering the findings in the human olfactory mucosa. © Wiley‐Liss, Inc.
Ultrastructural evidence for intra‐ and extranuclear projections of GABAergic neurons of the suprachiasmatic nucleus
Authors: Buijs Ruud M. , Hou Yang‐Xun , Shinn Susan , Renaud Leo P. 
Published: January 2005

AbstractGABAergic projections of the suprachiasmatic nucleus (SCN) were demonstrated in a double‐labelling ultrastructural study which visualised the efferents of the SCN by PHA‐L tracing, diaminobenzidine (DAB) immunocytochemistry, and GABA with immunogold postembedding staining. The results show a strong contralateral projections of the SCN that is partly GABA‐containing. In addition, ipsilateral SCN projections to the dorsomedial hypothalamus and periventricular part of the paraventricular nucleus and subparaventricular nucleus were shown to contain GABA. The present results indicate that the SCN may utilize this inhibitory neurotransmitter to regulate and organize its own circadian rhythm as well as using GABA to transmit its diurnal information to other regions of the brain. © Wiley‐Liss, Inc.
Morphology and birth dates of horizontal cells in the retina of a marsupial
Authors: Harman Alison M. , Ferguson Janet 
Published: January 2005

AbstractMost eutherian (placental) mammals have two horizontal cell types; however, one type only has been seen in rodents. In order to assess whether one type of horizontal cell or two is a basic mammalian feature, we have examined the morphology of horizontal cells in a marsupial, the quokka wallaby, by Golgi staining or horseradish peroxidase labelling. The birth dates of horizontal cells have also been determined by 3H‐thymidine/autoradiography. There are two types of horizontal cell in the wallaby retina. One type has no axon and corresponds to the axonless cell in eutherian species; the other has shorter dendrites, an axon, and an axonal arbor, corresponding to the eutherian short‐axon cell. As in eutherian mammals, the dendrites of each horizontal cell type lie in the outer plexiform layer (OPL) and contact cones and the axonal arbor of the short‐axon cell contacts rods. The dendrites of the axonless cells are long, with an average length of 250 μm, and each cell has one, sometimes two, short, stubby processes, which branch off a dendrite, traverse the inner nuclear layer, and reach the inner plexiform layer. The dendritic field of these cells is elongated, and dendrites show a preferential orientation at right angles to the trajectory of overlying ganglion cell axons. Short‐axon cells have a morphology similar to that seen in other species, although the axonal arbor is relatively small. Both types of horizontal cell are generated in the first phase of retinal cell generation. © Wiley‐Liss, Inc.
Blood‐eye barriers in the rat: Correlation of ultrastructure with function
Authors: Stewart P. A. , Tuor U. I. 
Published: January 2005

AbstractThe function of different vascular beds in the rat eye and brain was evaluated by measuring the transfer of a vascular tracer, 14C‐α‐amino‐isobutyric acid, from blood to tissue. The density of vascular pores was measured in electron micrographs of perfusion‐fixed, age‐matched tissue to determine whether the differences in tracer transfer were paralleled by differences in ultrastructure. Tracer transfer in retina was approximately four times that in brain of the same animal. The transfer constant was not changed by the inclusion of cold α‐amino‐isobutyric acid, showing that transport across retinal vessels is not saturable, and indicating that, as in brain, transport is due to passive diffusion. Ultrastructurally, retinal vessels have a higher density of interendothelial junctions and of endothelial vesicles, both of which suggest higher vascular permeability. However, pericytes, which contribute to a second line of defence in the blood‐brain barrier, are approximately four times as numerous in retina as in brain, and we suggest that in the retina, they act to compensate for a more permeable endothelial barrier. Ciliary body vessels had a high transfer of tracer, probably as a consequence of the fenestrations in their walls. Iridial vessels had a relatively low transfer of tracer, similar to that in retina even though a proportion of the interendothelial junctions in iridial vessels had expanded junctional clefts suggestive of open paracellular channels. However, both iris and ciliary body may lose tracer to the anterior chamber fluid, leading us to underestimate the vascular permeability in these sites. © Wiley‐Liss, Inc.