bluuebunny/crossref_metadata_2025 huggingface dataset:
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

A 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

Thrombospondin (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

Cholinergic 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

Secretoneurin 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

We 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

Olfactory 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

GABAergic 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

Most 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

The 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.
Polyneuronal innervation of spiny stellate neurons in cat visual cortex
Authors: Ahmed Bashir , Anderson John C. , Douglas Rodney J. , Martin Kevan A. C. , Nelson J. Charmaine
Published: January 2005

Our hypothesis was that spiny stellate neurons in layer 4 of cat visual cortex receive polyneuronal innervation. We characterised the synapses of four likely sources of innervation by three simple criteria: the type of synapse, the target (spine, dendritic shaft), and the area of the presynaptic bouton. The layer 6 pyramids had the smallest boutons and formed asymmetric synapses mainly with the dendritic shaft. The thalamic afferents had the largest boutons and formed asymmetric synapses mainly with spines. The spiny stellates had medium‐sized boutons and formed asymmetric synapses mainly with spines. We used these to make a “template” to match against the boutons forming synapses with the spiny stellate dendrite. Of the asymmetric synapses, 45% could have come from layer 6 pyramidal neurons, 28% from spiny stellate neurons, and 6% from thalamic afferents. The remaining 21% of asymmetric synapses could not be accounted for without assuming some additional selectivity of the presynaptic axons. Additional asymmetric synapses may come from a variety of sources, including other cortical neurons and subcortical nuclei such as the claustrum. Of the symmetric synapses, 84% could have been provided by clutch cells, which form large boutons. The remainder, formed by small boutons, probably come from other smooth neurons in layer 4, e.g., neurogliaform and bitufted neurons. Our analysis supports the hypothesis that the spiny stellate receives polyneuronal innervation, perhaps from all the sources of boutons in layer 4. Although layer 4 is the major recipient of thalamic afferents, our results show that they form only a few percent of the synapses of layer 4 spiny stellate neurons.
Direct and indirect retinohypothalamic projections to the supraoptic nucleus in the female albino rat
Authors: Levine Joel D. , Zhao Xi‐Shun , Miselis Richard R.
Published: January 2005

Earlier studies have shown that retinohypothalamic projections terminate extensively within the hypothalamus of the rat. Recently, we identified a light retinal projection to the supraoptic nucleus as well as a larger, well‐focused projection resulting in a peri‐supraoptic nucleus terminal field. In this study, we employed a double labeling method with cholera toxin conjugated to horseradish peroxidase (CT‐HRP) and pseudorabies virus, a transsynaptic neural tracer, to evaluate retinorecipient neurons in both the supraoptic nucleus and peri‐supraoptic nucleus terminal field. In addition, we looked for evidence that cells in the peri‐supraoptic nucleus terminal field project into the supraoptic nucleus. Three strains of pseudorabies virus were compared. A direct retinosupraoptic nucleus circuit was confirmed with all three strains. Retinorecipient neurons in the peri‐supraoptic nucleus terminal field were also confirmed. However, there was a strain‐based difference in the identification of these neurons. The wild‐type Becker strain labeled cells in the peri‐supraoptic nucleus terminal field in a manner paralleling the early, intermediate and late stages of infection of the suprachiasmatic nucleus. This parallel time course suggests that retinal ganglion cells terminate directly on cells in the peri‐supraoptic nucleus terminal field. Conversely, the Bartha and PRV‐91 strains showed appreciable labeling of peri‐supraoptic neurons only at long survival times. This longer time course suggests that these mutant strains label neurons in the peri‐supraoptic nucleus terminal field indirectly, after passing through additional neurons. In addition, experiments with monocular injection of CT‐HRP and posterior pituitary injection of pseudorabies virus showed retrogradely labeled second‐order cells in the peri‐supraoptic nucleus amidst the CT‐HRP labeled terminal field of the retinohypothalamic tract. These results demonstrate a direct projection from the retina to the supraoptic nucleus and provide evidence for an indirect circuit from the retina to the supraoptic nucleus via neurons located in the peri‐supraoptic nucleus terminal field. The strain‐based differences imply that those retinal ganglion cells that project to the peri‐supraoptic nucleus terminal field differ from those that project to the supra‐chiasmatic nucleus. In addition, these results suggest a neuroanatomic basis for photic effects on physiological mechanisms that are not mediated by the circadian timing system.
In situ hybridization detection of trka mRNA in brain: Distribution, colocalization with p75NGFR and up‐regulation by nerve growth factor
Authors: Gibbs Robert B. , Pfaff D. W.
Published: January 2005

In situ hybridization techniques were used to examine the distribution and the nerve growth factor (NGF) regulation of trkA mRNA in the adult rat brain in order to identify neurons in discrete regions of the brain that may be NGF responsive. In agreement with previous studies, trkA mRNA was detected within cells located in the medial septum (MS), diagonal band of Broca (DBB), and caudate. trkA mRNA was also detected in many other regions of the brain, including the nucleus basalis of Meynert, substantia innominata, paraventricular nucleus of the thalamus, interpeduncular nucleus, prepositus hypoglossal nucleus, vestibular nudei raphe obscuris, cochlear nucleus, sensory trigeminal nuclei, and gigantocellular as well as perigigantocellular neurons in the medullary reticular formation. By combining in situ hybridization detection of trkA mRNA with immunocytochemical detection ofp75NGFR, it was determined that the vast majority (> 90%) of the trkA mRNA‐containing cells detected in the MS and DBB also express p75NGFR. Likewise, the vast majority of p75NGFR‐IR cells detected in the MS and DBB expressed trkA mRNA. Intracerebroventricular infusions of NGF into the third ventricle adjacent to the preoptic area resulted in a 58% increase in relative cellular levels of trkA mRNA in the horizontal limb of the DBB. These data provide evidence that both p75NGFR and trkA are expressed by NGF‐responsive neurons in the MS and DBB. In addition, we note that areas that contained trkA mRNA and that also have been reported to contain p75NGFR are areas where high‐affinity NGF binding sites have been observed autoradio‐graphically, whereas areas that contain either trkA or p75NGFR alone are areas where no high‐affinity NGF binding has been reported. Together, these findings suggest that both trkA and p75NGFR play an important role in the formation of high‐affinity NGF receptors in brain and, furthermore, suggest that NGF may have physiological effects within many regions of the brain outside of the basal forebrain.
Regeneration of axons into the trochlear rootlet after anterior medullary lesions in the rat is specific for ipsilateral IVth nerve motoneurones
Authors: Derouiche Amin , Berry Martin , Sievers Jobst
Published: January 2005

The fibre projection from the IVth nerve nucleus to the superior oblique muscle was determined quantitatively in the normal rat by defining fibre numbers in transverse sections of the IVth nerve, and neurone numbers after retrograde labelling by horseradish peroxidase (HRP) injection into the muscle. There were 183 ± 27 (S.E.) labelled neurones in the nucleus contralateral to the injected muscle and only 2 ± 1 ipsilateral. The ipsilateral fibre number was 234 ± 7 and the cell/axon ratio 0.8 ± 0.1. Extensive analysis of all HRP retrogradely labelled material revealed no central fibre contribution to the IVth nerve other than from neurones resident in the trochlear nucleus.

The central portion of the trochlear nerve tract was severed at its point of decussation in the anterior medullary velum. Ninety days after lesion, 10 ± 4 (6% of control) neurones were labelled in the ipsilateral trochlear nucleus; none were labelled in the contralateral nucleus or in any other part of the midbrain, pons, medulla, or cerebellum. The number of myelinated fibres in the IVth nerve had decreased to 21 ± 5 (9% of control) so that the cell/axon ratio was 0.4 ± 0.2, thus suggesting that a single motoneurone has more fibres after lesion. In electron micrographs of the IVth nerve, larger than normal numbers of unmyelinated fibres were seen. Many myelinated fibres displayed signs of abnormal myelination.

After regeneration, the projection was exclusively ipsilateral and not crossed as in the normal. These findings establish that there is a high degree of specificity after regeneration since no myelinated central nervous system axons other than trochlear fibres select the IVth nerve root as a trajectory over which to regenerate.
Interconnections between the prefrontal cortex and the premotor areas in the frontal lobe
Authors: Lu Ming‐Teh , Preston James B. , Strick Peter L.
Published: January 2005

We examined interconnections between a portion of the prefrontal cortex and the premotor areas in the frontal lobe to provide insights into the routes by which the prefrontal cortex gains access to the primary motor cortex and the central control of movement. We placed multiple injections of one retrograde tracer in the arm area of the primary motor cortex to define the premotor areas in the frontal lobe. Then, in the same animal, we placed multiple injections of another retrograde tracer in and around the principal sulcus (Walker's area 46). This double labeling strategy enabled us to determine which premotor areas are interconnected with the prefrontal cortex.

There are three major results of this study. First, we found that five of the six premotor areas in the frontal lobe are interconnected with the dorsolateral prefrontal cortex. Second, the major site for interactions between the prefrontal cortex and the premotor areas is the ventral premotor area. Third, the prefrontal cortex is interconnected with only a portion of the arm representation in three premotor areas (supplementary motor area, the caudal cingulate motor area on the ventral bank of the cingulate sulcus, and the dorsal premotor area), whereas it is interconnected with the entire arm representation in the ventral premotor area and the rostral cingulate motor area. These observations indicate that the output of the prefrontal cortex targets specific premotor areas and even subregions within individual premotor areas.
Expression of the tight junction protein ZO‐1 in the olfactory system: Presence of ZO‐1 on olfactory sensory neurons and glial cells
Authors: Miragall Fernando , Krause Dorothee , De Vries Uwe , Dermietzel Rolf
Published: January 2005

The olfactory system is a unique part of the central nervous system since it retains neuronal turnover and regenerative capacities in adulthood. Thus it provides an ideal model to study plasticity of membrane moities involved in cell‐cell interactions. One structure particularly involved in cell‐cell interaction is the tight junction, which establishes polarization of epithelial cells and creates diffusion barriers to paracellular passages. ZO‐1 is a phosphoprotein peripherally associated with tight junctions. We have studied expression of ZO‐1 protein in the developing and adult olfactory system of the mouse in order to get information about the localization and developmental expression of this tight junction component. ZO‐1 expression has also been determined in cell cultures of olfactory bulbs.

ZO‐1 was present in the olfactory placode prior to formation of tight junctions. ZO‐1 was localized in the developing and mature olfactory epithelium at heterotypic contacts between supporting cells and olfactory neurons as well as at homotypic contacts between both these cell types. Confocal microscopy showed quantitative differences in the ZO‐1 expression among different olfactory dendrites. In the olfactory nerves ZO‐1 immunolabeling was detectable between olfactory ensheathing cells. From the seventh postnatal day ZO‐1 immunolabeling was detected at the mitral cell layer of the bulb on cells tentatively identified as oligodendrocytes. Myelinated tracts of the bulb were ZO‐1 negative. Cell cultures of olfactory bulbs showed ZO‐1 immunoreaction, mostly localized on glial fibrillary acidic protein (GFAP)‐positive cells.

Our results provide further evidence that ZO‐1 serves functions unrelated to the tight junction complex and indicate molecular heterogeneity of these cell‐cell contacts.
In vitro autoradiographic localization of calcitonin binding sites in human medulla oblongata
Authors: Sexton Patrick M. , Paxinos George , Huang Xu‐Feng , Mendelsohn Frederick A. O.
Published: January 2005

In this study we examined the distribution of calcitonin (CT) binding sites in the human medulla oblongata by in vitro autoradiography. In competition studies, the rank order of potency for calcitonins competing for 125I‐salmon CT binding was salmon CT > porcine CT > human CT, which is consistent with physiologically relevant CT receptors in other systems. For the determination of CT binding in the human medulla, 20‐μm cryostat sections were incubated with 125I‐salmon CT in the presence or absence of 10−6 M unlabelled salmon CT to map specific CT binding sites. Punctate binding was observed over discrete nuclei of the medulla. High binding densities were seen over subnuclei of the dorsal motor nucleus of the vagus, the nucleus of the solitary tract, the intermediate reticular zone, the gigantocellular and dorsal paragigantocellular nuclei, and the raphe obscurus nucleus. Moderate levels of binding were observed over the lateral paragigantocellular nucleus and the rostral extent of the epiolivary nucleus. The cuneate and gracile nuclei and the fiber tracts did not contain detectable binding, while the inferior olivary nucleus had moderate levels of nonspecific binding. The localization of calcitonin binding sites in the human presents similarities but also important differences to the distribution in rat and cat. The most notable difference is the extreme binding densities in the intermediate reticular zone of the human. The location of binding sites suggests involvement of calcitonin in regulation of autonomic function.
Immunohistochemical analysis of the relation between 5‐hydroxytryptamine‐ and neuropeptide‐immunoreactive elements in the spinal cord of an amphibian (Xenopus laevis)
Authors: Pieribone Vincent A. , Brodin Lennart , Hökfelt Tomas
Published: January 2005

In mammals, a large proportion of the bulbospinal 5‐hydroxytryptamine (5‐HT) neurons also contain neuropeptides, such as substance P (SP) and galanin (GAL). To examine whether a similar coexistence occurs in an amphibian, an immunofluorescence double‐labelling technique was employed on sections of the Xenopus laevis spinal cord. Antisera raised against SP, GAL, enkephalin (ENK), corticotropin‐releasing factor (CRF), calcitonin gene‐related peptide (CGRP), and cholecystokinin (CCK) produced a labelling of fibers at all rostrocaudal levels of the spinal cord, with the highest fiber densities for SP and ENK and intermediate densities for GAL, CCK, and CGRP, while CRF‐immunoreactive fibers were barely detectable in intact animals. 5‐HT‐immunoreactive fibers were widely distributed in the spinal cord, and they often occurred in the vicinity of different types of peptide‐immunoreactive fibers. However, no coexistence between 5‐HT and the different peptide immunoreactivities could be detected, although SP and GAL immunoreactivities were sometimes found to be colocalized in the same fiber. Similar negative results were obtained when 5‐HT + SP‐ and 5‐HT + GAL‐labelled sections were examined in single focal planes with a confocal microscope. After a spinal transection, (survival period 6 weeks to 4 months), almost all 5‐HT‐immunoreactive fibers below the lesion were lost, and a build‐up of immunoreactive material occurred in fibers just rostral to the cut. In contrast, no significant loss of peptide‐immunoreactive fibers occurred, although some swollen SP‐, GAL‐, ENK‐, CRF‐, and CCK‐immunoreactive fibers were present rostral to the cut. The distribution of swollen peptide‐immunoreactive fibers did not overlap with that of the swollen 5‐HT‐immunoreactive fibers. Although negative immunohistochemical data must be inter‐preted with caution, in conjunction with previous studies (Brodin et al. [1988] J. Comp. Neurol. 271:1‐18; Sakamoto and Atsumi [1991] Cell Tissue Res. 264:221‐230), the present results indicate that bulbospinal 5‐HT neurons in nonmammalian vertebrates cocontain neuropeptides to a lesser extent than in mammals.
Parvalbumin, calbindin D‐28k, and calretinin immunoreactivity in the ascending auditory pathway of horseshoe bats
Authors: Vater Marianne , Braun Katharina
Published: January 2005

In the subcortical auditory system of Rhinolophus rouxi, antibodies directed against the calcium‐binding proteins parvalbumin, calbindin D‐28k, and calretinin yield partly overlapping and partly complementary labeling patterns which are described in detail for each nucleus.

The most general features of the labeling patterns are that: (1) Parvalbumin is a potent marker for large and heterogenous populations of cells and puncta (presumed axon terminals) throughout the auditory pathway. (2) Immunostaining with the monoclonal calbindin‐antiserum was typically absent or sparse in most auditory brainstem centers, but prominent in auditory nerve fibers and in cells of the medial geniculate body (MGB). (3) Calretinin label is abundant but more restricted to subsets of auditory nuclei or subpopulations of cells than parvalbumin. (4) Calcium‐binding proteins are useful markers to define particular subregions or cell types in auditory nuclei: for example, (i) different labeling patterns are obtained within the nuclei of the lateral lemniscus and adjacent tegmental zones; (ii) in the inferior colliculus both calbindin‐ and calretinin‐antisera yield similar regional specific staining patterns, but label different cell types; (iii) subregions of the medial geniculate body have characteristic profiles of calcium‐binding proteins; and (iv) analyses of different nuclei showed that there is no simple common denominator for cells characterized by the expression of particular calcium‐binding proteins, nor does labeling correspond in a straightforward way with specific functional systems. (5) there are profound differences between the calbindin labeling patterns seen in Rhinolophus and those in other mammals.
Ventral root avulsion: An experimental model of death of adult motor neurons
Authors: Koliatsos Vassilis E. , Price William L. , Pardo Carlos A. , Price Donald L.
Published: January 2005

The present study proposes a reproducible model of experimental degeneration of adult motor neurons in the rat. Avulsion of ventral roots in the adult lumbar cord transects motor axons at the root exit and leads to retrograde cell death of 80% of motor neurons 2 weeks later; this result follows a series of retrograde changes, including chromatolysis, loss of transmitter phenotype, and accumulation of phosphorylated neurofilaments in perikarya. Glial cells recruited at the site of retrograde injury express both microglia‐specific epitopes (as exemplified by OX‐42 immunoreactivity) and macrophage‐specific markers (e.g., ED‐1 immunoreactivity). Macrophage‐specific markers become particularly intense 7 days postaxotomy and provide additional evidence of active phagocytosis of injured neurons. Ventral root avulsion is a very useful model for assessing mechanisms of motor neuron death and testing the ability of trophic factors and other agents to preserve the phenotype and promote the survival of adult motor neurons in vivo. © 1994 Wiley‐Liss, Inc.
Further characterization of the effects of brain‐derived neurotrophic factor and ciliary neurotrophic factor on axotomized neonatal and adult mammalian motor neurons
Authors: Clatterbuck Richard E. , Price Donald L. , Koliatsos Vassilis E.
Published: January 2005

Neurotrophins and neural cytokines are two broad classes of neurotrophic factors. It has been reported that ciliary neurotrophic factor (CNTF) and brain‐derived neurotrophic factor (BDNF) prevent the degeneration of axotomized neonatal motor neurons. In addition, BDNF is transported retrogradely to α‐motor neurons following injection into the muscle, and patterns of BDNF expressed in spinal cord and muscle suggest a physiological role for this factor in motor neurons. In the present study, we characterize the effects of BDNF on axotomized neonatal facial motor neurons and extend these observations to adult models of motor neuron injury (axotomy‐induced phenotypic injury of lumbar motor neurons). BDNF reduces axotomy‐induced degeneration of neonatal neurons by 55% as determined by Nissl staining (percentage of surviving neurons in vehicle‐treated cases, 25%; in BDNF‐treated cases, 80%). Rescued neurons have an intact organelle structure but appear smaller and slightly chromatolytic on electron microscopic analysis. As demonstrated by intense retrograde labeling with horseradish peroxidase (HRP) applied to the proximal stump of the facial nerve, neurons rescued by BDNF have intact mechanisms of fast axonal transport. CNTF did not appear to have significant effects on neonatal motor neurons, but the lack of efficacy of this factor may be caused by its rapid degradation at the application site. BDNF is not capable of reversing the axotomy‐induced reduction in transmitter markers [i.e., the acetylcholine‐synthesizing enzyme choline acetyl‐transferase (ChAT) or the degrading enzyme acetylcholinesterase (AChE)] in neonatal or adult animals or the axotomy‐induced up‐regulation of the low‐affinity neurotrophin receptor p75NGFR (nerve growth factor receptor) in adult motor neurons. However, BDNF appears to promote the expression of p75NGFR in injured neonatal motor neurons. In concert, the findings of the present study suggest that BDNF can significantly prevent cell death in injured motor neurons. However, this neurotrophin may not be a retrograde signal associated with the induction and/or maintenance of some mature features of motor neurons, particularly their transmitter phenotype. © 1994 Wiley‐Liss, Inc.
Morphology of parallel fibres in the cerebellar cortex of the rat: An experimental light and electron microscopic study with biocytin
Authors: Pichitpornchai C. , Rawson J. A. , Rees S.
Published: January 2005

Microinjections of biocytin have been made in the granular layer of the rat cerebellar cortex in order to label the axonal projections of a localised population of granule cells. Light microscopic techniques were used to determine the lengths of the parallel fibres and to measure the spacing and size of the fibre varicosities. Fibres were longest in the superficial one‐third of the molecular layer, where mean overall length was 4.7 mm, and mean length decreased to 4.2 mm in the lower one‐third of the molecular layer. We found no very short fibres but a small population deep in the molecular layer had a branch length of about one‐half the average. Mean intervaricosity interval and varicosity size varied with distance from proximal to distal along the fibres. Mean intervaricosity interval was 3.7 μm within 250 μm of the fibre bifurcation points and progressively increased towards the distal ends, where the mean interval was 7.4 μm. Mean varicosity size was 0.82 μm2 in this proximal region and decreased to 0.47 μm2 about 1.2 mm distally. Mean intervaricosity interval on the ascending axons of the granule cells was 4.0 μm. Electron microscopy revealed that a high proportion (89%) of the parallel fibre varicosities formed synaptic junctions. The majority of the synapses (91%) were formed on Purkinje cell dendritic spines. Some varicosities also formed simultaneous synaptic contacts or double synapses with two spines. These double synapses occurred more frequently in the proximal region of the fibres (11%) than on the distal ends (2%). The length of the postsynaptic density also differed according to the location of the varicosities and the mean length at the proximal parallel fibre synapses was 0.59 μm compared with 0.38 μm at the distal synapses. It is concluded that a beam or bundle of parallel fibres originating from cells in a focal region of the granular layer will exert a graded synaptic influence on its target Purkinje cells, with the most powerful influence occurring on cells located around the proximal region of the fibres where they bifurcate and the weakest action being exerted on cells located at the distal end of the fibres. © 1994 Wiley‐Liss, Inc.
Dorsal nucleus of the lateral lemniscus in the rat: Concentric organization and tonotopic projection to the inferior colliculus
Authors: Merchán Miguel A. , Saldaña Enrique , Plaza Ignacio
Published: January 2005

A basic principle of organization in auditory centers is the topographic‐tonotopic order. Whether this applies to the dorsal nucleus of the lateral lemniscus (DNLL), however, is still debated. To clarify this problem, we have utilized the neuroanatomical tracers horseradish peroxidase (HRP) and biotinylated dextran (BD) injected into different regions of the central nucleus of the inferior colliculus (CNIC) in the rat.

After large injections of HRP that included most of the CNIC, retrogradely labelled neurons were found all across the ipsi‐ and contralateral DNLL, showing that all parts of this nucleus innervate the CNIC bilaterally. More neurons were seen consistently on the side contralateral to the injection site. Labelled fibers, however, were abundant ipsilaterally, but scarce in the contralateral DNLL.

Single, small injections of HRP or BDinto the CNIC resulted in labelling in restricted areas of the ipsi‐ and contralateral DNLL. In coronal sections, the neurons and fibers labelled in the ipsilateral DNLL formed a well‐defined, ring‐shaped structure made of dendrites and axons oriented parallel to each other, which we termed “annular band.” The observation of serial sections revealed that the annular band seen in any individual section represents a slice through a more or less complete three‐dimensional, hollow, ovoid structure oriented rostrocau‐dally. The position and diameter of the annular band changed as the injection site was shifted along the tonotopic axis of the CNIC. Single injections placed in the ventromedial, high‐frequency region of the CNIC produced a large annular band along the periphery of the DNLL. After injections placed in progressively more dorsolateral, lower‐frequency regions of the CNIC, the annular band became smaller in diameter and occupied a successively more central position in the DNLL. Double injections along the tonotopic axis of the CNIC resulted in two roughly concentric annular bands. The labelled neurons and fibers in the contralateral DNLL systematically occupied a position symmetric to the annular band seen ipsilaterally.

These findings indicate that the rat DNLL is primarily composed of neurons with flattened dendritic arbors and flattened fields of terminal fibers. These two elements intermingle, forming concentric layers around the geometric center of the nucleus. The axons of neurons within corresponding layers on the two sides converge onto the CNIC of both sides in a strict topographic fashion: the peripheral layers project to the ventromedial, high‐frequency region of the CNIC, and the central layers project to the dorsolateral, low‐frequency region. These results suggest that the concentric arrangement of the DNLL is the substrate of its tonotopic organization. © 1994 Wiley‐Liss, Inc.
Immunocytochemical localization of immunoglobulins in the rat brain: Relationship to the blood‐brain barrier
Authors: Aihara Naoto , Tanno Hirokazu , Hall J. J. , Pitts Lawrence H. , Noble L. J.
Published: January 2005

The central nervous system has been traditionally regarded as an immunologically privileged area. This feature has been in part attributed to the blood‐brain barrier, which provides a restrictive interface to circulating immunoglobulins (IgG). Recent kinetic studies suggest that the barrier to immune proteins is not absolute, but rather may be regulated by a specific transfer mechanism. In this study, we confirm the presence of IgG in the central nervous system by immunocytochemistry and demonstrate a close anatomical relationship between the distribution of this protein and the blood‐brain barrier.

IgG was immunolocalized in the normal rat brain by using monoclonal and polyclonal antibodies to IgG and its subclasses. On the basis of an initial evaluation, the most appropriate antibodies and dilutions were selected for subsequent analyses. In the first study, IgG and albumin were immunolocalized in adjacent sections. In the second study, horseradish peroxidase (HRP) was given intravenously prior to sacrifice, in order to examine artifacts related to perfusion fixation. The distribution of HRP and IgG was then examined in adjacent sections. In the third study, IgG was immunolocalized in sections of brain after mild traumatic head injury.

A monoclonal antibody to IgG2a and a polyclonal antibody to IgG were selected on the basis of specificity and consistent, mutual localization. Distinct, patchy, perivascular staining, infrequently associated with labeled neurons, was noted throughout the brain. Electron microsocopy confirmed the perivascular localization; IgG was localized along the basal lamina of microvasculature and within the adjacent parenchyma. Albumin and HRP did not exhibit a similar pattern of perivascular immunostaining. After head injury, prominent immunostaining for IgG was observed in the injured hemisphere.

In summary, these data indicate that the normal rat brain contains IgG, which dramatically increases after head injury. The distinct perivascular distribution in the normal brain suggests local microvascular permeability. This permeability is selective for IgG, since albumin does not share a similar perivascular localization. The neuronal staining which is closely associated with perivascular label may reflect one intracellular route for extravasated IgG. © 1994 Wiley‐Liss, Inc.
Ultrastuctural studies of the primate lateral geniculate nucleus: Morphology and spatial relationships of axon terminals arising from the retina, visual cortex (area 17), superior colliculus, parabigminal nucleus, and pretectum of Galago crassicaudatus
Authors: Feig Sherry , Harting John K.
Published: January 2005

The electron microscopic autoradiographic tracing method has been used to examine the morphology and postsynaptic relationships of five projections (retina, cortical area 17, superior colliculus (tectal), parabigeminal nucleus, and pretectum) to the dorsal lateral geniculate nucleus of the greater bush baby galago crassicaudatus.

Retinal terminals have been examined in the contralaterally innervated layer of each of the three matched pairs [parvi‐(X‐cell), magno‐ (Y‐‐cell), and koniocellular (small, W‐cell)] of geniculate layers. These terminals are large and contain pale mitochondria and round vesicles (RLPs). RLPs are presynaptic to juxtasomatic regions of parvi‐and magnocellular neurons. In contrast, RLPs innervate more distal regions of konicellular neurons.

Labeled cortical, tectal, and parabigeminal terminals are relatively small and contain round vesicles na dark mitochondria. Cortical terminals in each of the three representative layers are presynaptic to small diameter dendrites. No convergence of cortical and retinal terminals has been seen in any layer. Labeled tectal and parabigminal terminals are found primarily in the koniocellular layers, but the latter are also seen in all other layers. Tectal and parabigeminal terminals have been observed converging with retinal terminals on dendrites of some koniocellular neurons.

Labeled pretectogeniculate terminals contain densely packed pleomorphic vesicles, dark mitochondria, and a dark cytoplasmic matric. These terminals, which are present in each of the representative layers, are presynaptic to conventional dendrites and profiles containing loosely despersed pleomorphic vesicles and a pale cytoplasmic matrix. © 1994 Wiley‐Liss, Inc.