bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of retinal lesions upon the distribution of nicotinic acetylcholine receptor subunits in the chick visual system
Authors: Britto L. R. G. , Torrao A. S. , Hamassaki‐Britto D. E. , Mpodozis J. , Keyser K. T. , Lindstrom J. M. , Karten H. J.
Published: January 2005

Immunohistochemistry was used in this study to evaluate the effects of retinal lesions upon the distribution of neuronal nicotinic acetylocholine receptor subunits in the chick visual system. Following unilateral retinal lesions, the neuropil staining with an antibody against the β2 receptor subunit, a major component of α‐bungarotoxin‐insensitive nicotinic receptors, was dramatically reduced or completely eliminated in all of the contralateral retinorecipient structures. On the other hand, neuropil staining with antibodies against two α‐bungarotoxinsensitive receptor subunits, α7 and α8, was only slightly affected after retinal lesions. Decreased neuropil staining for α7‐like immunoreactivity was only observed in the nucleus of the basal optic root and layers 2–4 and 7 of the optic tectum. For α8‐like immunoreactivity, slight reduction of neuropil staining could be observed in the ventral geniculate complex, griseum tecti, nucleus lateralis anterior, nucleus lentiformis mesencephali, layers 4 and 7 of the tectum, and nucleus suprachiasmaticus. Taken together with previous data on the localization of nicotinic receptors in the retina, the present results indicate that the β2 subunit is transported from retinal ganglion cells to their central targets, whereas the α7 and α8 subunit immunoreactivity appears to have a central origin. The source of these immunoreactivities could be, at least in part, the stained perikarya that were observed to contain α7 and α8 subunits in all retinoreceipient areas. In agreement with this hypothesis, the β2 subunit of the nicotinic acetylcholine receptors was not frequently found in perikarya of the same areas. © 1994 Wiley‐Liss, Inc.
Morphology of the release site of inhibitory synapses on the soma and dendrite of an identified neuron
Authors: Sur Cyrille , Triller Antoine , Korn Henri
Published: January 2005

Synapse are complex arrangements of pre‐and postsynaptic differentiations involved in neural communication. A key element in this synaptic transmission is the presynaptic active zone where the release of neurotransmitter occurs. Active zones can be visualized and analyzed after staining with ethanolic phosphotungstic acid (EPTA) on semithin (0.5μm) sections. This staining has been used in association with postembedding immunogold labeling for the neurotransmitters glycine or GABA, to investigate the organization of chemically defined inhibitory active zones, viewed in their full extent, on different regions of the goldfish Mauthner (M−) cell.

With this approach, a marked variability in size and shape was observed for the release sites contacting the different parts of the postsynaptic neuron. In the axon cap and on the soma, glycinergic afferent terminals have small presynaptic grids (0.066 ± 0.029 μm2, n = 30 and 0.076 ± 0.037 μm2, n = 46, respectively). These grids are quite circular and they include 12 to 13 presynaptic dense projections (PDPs). The situation is different on the lateral dendrite, where glycinergic and GABAergic active zones display a greater variability in their surface areas (mean = 0.147 ± 0.100 μm2, n =115 and 0.139 ± 0.080 μm2, n = 125, respectively), and their number of PDPs (mean = 19 ± 9) per individual grid. Similarly, the shape of the release sites over the dendrite is more complex (annular, horseshoe‐shaped) when compared to those on the soma. These differences of dendritic versus somatic release sites could represent a structural basis to maximize the shunting effect of glycinergic and GABAergic inhibitory junctions, i.e., close to excitatory inputs.

We also observed that the proportion of endings containing 1 or more active zones also varies. More precisely, 96% and 82% of glycinergic terminals in the axon cap and on the soma, respectively, display only one active zone. On the dendrite, their proportion falls to 65.5% for both glycine‐ and GABA‐containing boutons. The remaining inhibitory terminals contain 2 (30%) and 3 to 4 (4.5%) presynaptic grids. These results reveal a greater variability of morphology and organization of the inhibitory release sites at dendritic versus somatic locations. The functional significance of this observation for the synaptic transmission is discussed. © 1995 Willy‐Liss, Inc.
Organization of somatosensory cortex in monotremes: In search of the prototypical plan
Authors: Krubitzer Leah , Manger Paul , Pettigrew Jack , Calford Mike
Published: January 2005

The present investigation was designed to determine the number and internal organization of somatosensory fields in monotremes. Microelectrode mapping methods were used in conjunction with cytochrome oxidase and myelin staining to reveal subdivisions and topography of somatosensory cortex in the platypus and the short‐billed echidna. The neocortices of both monotremes were found to contain four representations of the body surface. A large area that contained neurons predominantly responsive to cutaneous stimulation of the contralateral body surface was identified as the primary somatosensory area (SI). Although the overall organization of SI was similar in both mammals, the platypus had a relatively larger representation of the bill. Furthermore, some of the neurons in the bill representation of SI were also responsive to low amplitude electrical stimulation. These neurons were spatially segregated from neurons responsive to pure mechanosensory stimulation. Another somatosensory field (R) was identified immediately rostral to SI. The topographic organization of R was similar to that found in SI; however, neurons in R responded most often to light pressure and taps to peripheral body parts. Neurons in cortex rostral to R were responsive to manipulation of joints and hard taps to the body. We termed this field the manipulation field (M). The mediolateral sequence of representation in M was similar to that of both SI and R, but was topographically less precise. Another somatosensory field, caudal to SI, was adjacent to SI laterally at the representation of the face, but medially was separated from SI by auditory cortex. Its position relative to SI and auditory cortex, and its topographic organization led us to hypothesize that this caudal field may be homologous to the parietal ventral area (PV) as described in other mammals. The evidence for the existence of four separate representations in somatosensory cortex in the two species of monotremes indicates that cortical organization is more complex in these mammals than was previously thought. Because the two monotreme families have been separate for at least 55 million years (Richardson, B. J. [1987] Aust. Mammal. 11:71–73), the present results suggest either that the original differentiation of fields occurred very early in mammalian evolution or that the potential for differentiation of somatosensory cortex into multiple fields is highly constrained in evolution, so that both species arrived at the same solution independently. © 1995 Willy‐Liss, Inc.
Multiterminal proprioceptors in Squilla mantis (stomatopoda, crustacea)
Authors: Wales B. , Ferrero E. A.
Published: January 2005

A series of morphologically simple multiterminal proprioceptors is described in the throacopods of the hoplocardian crustacean, Squilla mantis, which is a primitive offshoot of the main malacostracan evolutionary line. The description given here is primarily for the largest and most complex receptor that occurs in the second thoracopod, the raptorial limb. These stretch receptors, which lie distally in the coxopodite, consist of single multiterminal sensory neurones with widely branching dendrites innervating broad connective tissue strands. The single primary dendrite divides dichotomously or, occasionally, trichotomously to produce a large number of terminal dendrites. The terminal dendrites, which exhibit a beaded structure, run parallel to the connective tissue strands' longitudinal axis. Dendrites possess an elaborate connective tissue sheath consisting of a single inner glial layer and a multiple outer connective tissue layer. The presence of the beaded structure has been confirmed by transmission electron microscopy (EM), and, because microtubule density does not vary with dendrite diameter, the beads are not fixation artifacts. Beads have high numbers of mitochondria and glycogen deposits, which suggests that they have high metabolic activity. Dendritic tips are not associated with beads, arise from the terminals of smaller dendrites, and are embeded in the extracellular ground matrix of the connective tissue strand, where they lie parallel to and surround bundles of elastic fibrils. The different degree of development within the receptor series allows comparison between functionally different limbs, and comparison is made with other segmental receptor series. The evolution of multiterminal proprioceptors is discussed. © 1995 Willy‐Liss, Inc.
Convergence and divergence of ascending binaural and monaural pathways from the superior olives of the mustached bat
Authors: Vater Marianne , Casseday John H. , Covey Ellen
Published: January 2005

The lateral superior olive and medial superior olive give rise to pathways that terminate in the dorsal nucleus of the lateral lemniscus and central nucleus of the inferior colliculus. In most mammals, neurons in both the medial and lateral superior olives are binaural, but in the mustached bat most neurons in the medial superior olive are monaural. The aims of this study were to determine how the inputs to the medial superior olive contribute to its monaurality and to determine whether the ascending projections from the lateral and medial superior olives overlap or rema in segregated at their targets. Injections of two different tracers were placed in tonotopically matched areas of the lateral and medial superior olives in the same animal. Retrograde transport from injections in the medial superior olive labeled spherical cells in the contralateral anteroventral cochlear nucleus and principal cells in the ipsilateral medial nucleus of the trapezoid body. Few cells were labeled in ipsilateral cochlear nucleus. Anterograde transport resulted in tonotopically specific distributions of label with the same laterality as in nonecholocating mammals. In the dorsal nucleus of the lateral lemniscus, label from the lateral and medial superior olives largely overlapped. In the inferior colliculus, label from the two sources overlapped in the high and low frequency ranges, but in the frequency range around 60 kHz, label from the medial superior olive extended more dorsally than that from the lateral superior olive. These results indicate that projections of the lateral and medial superior olives overlap extensively at their targets. © 1995 Willy‐Liss, Inc.
Expression patterns and deprivation effects on GABAA receptor subunit and GAD mRNAs in monkey lateral geniculate nucleus
Authors: Huntsman M. M. , Leggio M. G. , Jones E. G.
Published: January 2005

The expression and regulation of seven GABAA receptor subunit gene transcripts were examined in the adult monkey lateral geniculate nucleus. In situ hybridization histochemistry was used to localize mRNAs of the genes encoding monkey‐specifical α1, α2, α4, α5, β1, β2, and γ2 subunits. The highest levels of expression in the nucleus were for α1, β2, and γ2 subunit transcripts. The levels were substantially higher in the magnocellular than in the parvocellular layers. Alpha‐2, α4, α5, and β1 subunit mRNAs were expressed at much lower levels, and magno‐ and parvocellular layers had approximately equal levels of expression.

Following 4‐ or 21‐day periods of monocular deprivation induced by intravitreal injections of tetrodotoxin, levels of the α1, α2, α4, α5, β1, and β2 mRNAs were decreased in the deprived geniculate laminae. Adjacent sections hybridized with probes specific for 67‐kDa glutamic acid decarboxylase (GAD) mRNA also showed decreased levels of expression in deprived laminae after the 21‐day deprivation period. Levels of γ2 receptor subunit mRNA were unaffected by monocular deprivation. In our previous studies, a clearly significant downregulation is observed for this subunit transcript in the visual cortex of monkeys deprived for equivalent times. The differential expression and responses to deprivation in the lateral geniculate nucleus suggest region‐specific regulation of GABAA receptor subunit genes. © 1995 Wiley‐Liss, Inc.
Expression of four immunoglobulin superfamily adhesion molecules (L1, Nr‐CAM/Bravo, neurofascin/ABGP, and N‐CAM)in the developing mouse spinal cord
Authors: Moscoso Lisa M. , Sanes Joshua R.
Published: January 2005

To identify cell adhesion molecules (CAMs) expressed by mammalian motoneurons, we applied the polymerase chain reaction to a murine motor neuron‐like cell line, NSC‐34. Using primers derived from a group of Ll‐related CAMs, we cloned two alternatively spliced forms of mouse L1, which differ by a 12‐base‐pair insert, plus putative murine orthologs of the chicken cell adhesion molecules Nr‐CAM/Bravo and neurofascin. All four mRNAs are expressed in NSC‐34 cells, but only neurofascin and the insert‐minus form of Ll are expressed in its neuroblastoma parent, N18TG2. Analysis of RNA in neonatal tissues reveals expression largely restricted to the brain and spinal cord. In situ hybridization histochemistry of spinal cord shows that motoneurons express L1, Nr‐CAM, and neurofascin as well as N‐CAM. Ll and N‐CAM RNAs are detected throughout the period studied (from embryonic day,[E]11 to postnatal day [P]28), whereas Nr‐CAM is expressed only at early ages (<E15) and neurofascin is predominantly expressed postnatally. Moreover, each CAM is expressed by distinct subsets of neighboring cells and at distinct times. For example, Nr‐CAM mRNA is present in floor plate cells of embryonic spinal cord, whereas neurofascin is expressed by a subset of glia postnatally. Finally, we show that each CAM has a distinct spatiotemporal pattern of expression in dorsal root ganglia. © 1995 Wiley‐Liss, Inc.
Neurofilament sidearm proteolysis is a prominent early effect of axotomy in lamprey giant central neurons
Authors: Hall Garth F. , Lee Virginia M.‐Y.
Published: January 2005

In the accompanying paper, it was shown that axotomy of lamprey spinal axons induces the rapid formation of condensed neurofilamentous masses in the proximal axon stump near the lesion. In this study, we used immunocytochemical and Western blot analysis to characterize these masses further and to determine the time course of their formation and dispersal. We show that monoclonal antibodies specific to the “rod” domain of lamprey neurofilament protein strongly stain such masses in tissue sections without staining other axonal neurofilaments. Antibodies specific for the neurofilament “sidearm” domain fail to recognize neurofilamentous masses but stain other axonal neurofilaments. Western blots of spinal cord segments from the lesion site were compared to unlesioned cord and to samples of cord distant from the lesion. We found that a neurofilament rodrspecific antibody identified breakdown products of the same size as the rod domain in samples from the lesion site, but not elsewhere. Other lesion‐specific neurofilament breakdown products were recognized by a sidearm‐specific antibody. This lesion‐specific pattern of neurofilament proteolysis was visible at 1 day postlesion and was still present 3 weeks later. Immunocytochemistry showed masses of rod‐staining neurofilaments in axon stumps by 12 hours postlesion that remained for 1–2 weeks postaxotomy; these dispersed with the onset of regeneration. Such neurofilament rod staining was also prominent in distal axon stumps undergoing Wallerian degeneration. We conclude that axotomy induces neurofilament sidearm proteolysis near the lesion, permitting antibody access to the rod domain. We suggest that sidearm loss causes the high packing density of neurofilaments within neurofilamentous masses near the lesion site and that neurofilament sidearm proteolysis can be used to distinguish degenerative from regenerative changes in lesioned lamprey axons. © 1995 Wiley‐Liss, Inc.
Neuronal and nonneuronal expression of neurotrophins and their receptors in sensory and sympathetic ganglia suggest new intercellular trophic interactions
Authors: Wetmore Cynthia , Olson Lars
Published: January 2005

Nerve growth factor promotes the survival of populations of sensory and sympathetic neurons. Although ganglia have been used for classical assays of neurotrophin action, knowledge is incomplete regarding the spatial arrangements through which neurotrophins are delivered to responsive cells within the ganglia and their attached nerve trunks. Whereas populations of ganglionic neurons may be capable of responding to a particular neurotrophin in vitro, the spectrum of receptor components and neurotrophins expressed by the various neuronal and nonneuronal cells comprising the ganglia in adult rats remains to be elucidated in vivo.

Brain‐derived neurotrophic factor (BDNF) mRNA was expressed by a population of small to medium sized neurons in all sensory ganglia except in the mesencephalic nucleus of the trigeminal nerve. Interestingly, BDNF immunoreactivity was detected in a more widespread population of neurons of these ganglia, as well as in scattered satellite cells of both sensory and sympathetic ganglia. These nonneuronal cells also expressed mRNA encoding a truncated form of the BDNF receptor, trkB trunc and full‐length transcripts of trkB appeared to be confined to neuronal populations. Several other components of neurotrophin receptors (low‐affinity neurotrophin receptor, trk, and trkC) were prominently expressed by different populations of neuronal cells in sympathetic and sensory ganglia, but they were not detected in nonneuronal cells. Neither nerve growth factor nor neurotrophin‐3 mRNAs were detected in these ganglia.

Unexpectedly, BDNF and trkB trunc expression was detected in oligodendrocytes myelinating the central processes of sensory neurons. Schwann cells did not express detectable quantities of either entity, thereby establishing a dramatic boundary delineated by neurotrophin/ neurotrophin receptor expression that coincided with the interface between the oligodendroglia of the central nervous system (CNS) and Schwann cells of the peripheral nervous system (PNS). Localization of BDNF expression to an additional population of nonneuronal cells—satellite cells within sensory and sympathetic ganglia—suggest a more extensive role for neurotrophic factors than originally encompassed by the target‐derived neurotrophic‐factorconcept paradigm. These data support the hypothesis of a possible autocrine or paracrine trophic interaction between populations of neuronal and nonneuronal cells in the peripheral nervous system. BDNF expression in oligodendrocytes but not in Schwann cells at the CNS/PNS junction may provide an additional means of maintaining cell‐appropriate connections in the nervous system. © 1995 Wiley‐Liss, Inc.
Evidence for a high density of secretoneurin‐like immunoreactivit in the extended amygdala of the rat
Authors: Marksteiner Josef , Lassnig Elisabeth , Telser Stefan , Kroesen Stefan , Kirchmair Rudolf , Fischer‐Colbrie Reiner , Miller Carl , Saria Alois
Published: January 2005

Secretoneurin is a novel 33‐amino‐acid neuropeptide produced by endoproteolytic processing from secretogranin II, which is a member of the chromogranin/secretogranin family. In this mmunocytochemical study, we compared the distribution pattern of secretoneurin immunoreactivity with that of tyrosine hydroxylase, calbindin, substance P, and Leu‐enkephalin in adjacent sections of rat forebrain. Secretoneurin appeared mainly in varicosities and fibers. Only a few cell bodies were stained. In the nucleus accumbens, a partial overlap of secretoneurin‐immunoreactive patches with enkephalin‐immunopositive areas was found. Secretoneurin displayed low to moderate levels of immunoreaction in calbindin‐rich as well as in calbindin‐immunonegative areas of the caudate‐putamen. In the globus pallidus, entopeduncular nucleus, and substantia nigra, secretoneurin immunoreactivity was oriented ventromedially preferentially in woolly fibers. The dense immunostaining in the medial nucleus accumbens was directly continuous with dense secretoneurin immunoreactivity in the bed nucleus of the stria terminalis. Two strongly secretoneurin‐immunopositive bands, one in the sublenticular portion and a smaller one along the posterior limb of the anterior commissure, interconnected the highly secretoneurin‐immunopositive centromedial amygdala with the bed nucleus of the stria terminalis. Thus, the distribution pattern of secretoneurin immunoreactivity provides a marker of the extended amygdala that forms a continuum between the centromedial amygdala and the bed nucleus of the stria terminalis. © 1995 Wiley‐Liss, Inc.
Distribution of gonadotropin‐releasinghormone immunoreactivity in the brain of the pacific hagfish, Eptatretus stouti (craniata: Myxinoidea)
Authors: Braun Christopher B. , Wicht Helmut , Northcutt R. Glenn
Published: January 2005

The distribution of gonadotropin‐releasing hormone (GnRH)‐like immunoreactivity in the brain of a myxinoid, the Pacific hagfish (Eptatretus stouti), was investigated via immunohistochemistry, including the use of six different antisera. In the diencephalon, immunoreactive cell bodies were found in two systems: the infundibular hypothalamus, a neuromodulatory nucleus with diffuse projections of varicose fibers to most areas of the brain, and a primarily preoptic system of putatively hypophysiotropic neurons that projects to the neurohypophysis. Some potential neurovascular and CSF contacts were also identified. These findings are consistent with those of similar studies in other craniates and suggest that a preoptic hypophysiotropic system may be present in all craniates. We therefore tentatively accept the homology of this system in hagfish and vertebrates. The homology of the distributed hypothalamic system is more dubious. It may be homologous to a caudal GnRH system of modulatory neurons found in many vertebrates. Antiserum PBL‐49 displays a differential affinity for the two systems, indicating that the two systems differ in the amount or identity of the immunoreactive substance. We suggest that the two systems have distinct functions in hagfish. The primitive function of GnRH‐like molecules in craniates may have thus been both neuromodulatory and hypophysiotropic. These findings also indicate that the brain‐pituitary axis of hagfish is more similar to that of vertebrates than has been previously suggested. © 1995 Wiley‐Liss, Inc.
Cervical primary afferent input to vestibulospinal neurons projecting to the cervical dorsal horn: An anterograde and retrograde tracing study in the cat
Authors: Bankoul S. , Goto T. , Yates B. , Wilson V. J.
Published: January 2005

Vestibulospinal neurons in the caudal half of the medial and descending vestibular nuclei terminate in the cervical spinal cord, not only in the ventral horn and intermediate zone but also in the dorsal horn. The purpose of the present study was to examine whether the areas containing these vestibulospinal neurons are reached by cervical primary afferents. In one group of experiments, wheat germ agglutinin‐horseradish peroxidase conjugate and horseradish peroxidase were pressure injected into spinal ganglia C2‐C8 and revealed anterogradely labeled fibers and boutons in the caudal part (caudal to the dorsal cochlear nucleus) of the ipsilateral medial and descending vestibular nuclei. This projection was verified in experiments in which wheat germ agglutinin‐horseradish peroxidase conjugate was microiontophoretically injected into the caudal half of either the medial or the descending vestibular nuclei and revealed retrogradely labeled cells only in ipsilateral spina ganglia C2‐C7, with a maximum of cells in C3. In another group of experiments, after microiontophoretic injections of Phaseolus vulgaris leucoagglutinin or Biocytin into either the medial or the descending vestibular nuclei, anterogradely labeled fibers and boutons were present in the cervical spinal cord, mainly bilaterally in the dorsal horn (laminae I–VI) but also, to a lesser extent, in the ventral horn and intermediate zone. The existence of a loop that relays cervical primary afferent information to vestibulospinal neurons projecting to the cervical spinal cord, in particular the dorsal horn, may have implications for vestibular control over local information processing in the cervical dorsal horn. © 1995 Wiley‐Liss, Inc.
Developmentally regulated expression of α‐ and β‐calcitonin gene‐related peptide mRNA and calcitonin gene‐related peptide immunoreactivity in the rat inferior olive
Authors: Morara Stefano , Sternini Catia , Provini Luciano , Rosina Anna
Published: January 2005

Immunohistochemical methods have revealed the transient neonatal expression of calcitonin gene‐related peptide (CGRP) in olivocerebellar compartments, and it has been hypothesized that this peptide plays a role in the development of olivocerebellar connectivity. Furthermore, the distribution of the CGRP binding sites in the cerebellar cortex also favors this hypothesis. In this study, the pattern of postnatal expression of α‐ and β‐CGRP mRNAs in the inferior olive (IO) complex was analyzed using in situ hybridization histochemistry with RNA probes complementary to specific sequences of α‐ and β‐CGRP mRNAs, and the results were compared with the pattern of CGRP immunoreactivity. High levels of α‐CGRP mRNA expression were found in specific subnuclei of the IO complex, i. e., the medial part of the dorsal fold of the dorsal accessory olive, the β nucleus, the dorsal cap, the caudal third of the medial accessory olive, and the rostral part of the dorso‐medial cell column; in the same subnuclei β‐CGRP mRNA was detected. The olivary distribution of the two CGRP mRNAs coincided with that of CGRP immunoreactivity. The expressions of α‐CGRP mRNA and CGRP immunoreactivity were restricted to the first 2 postnatal weeks, the peak being reached at the end of the first week; β‐CGRP mRNA was transiently expressed in the same olivary compartments, but only from postnatal day 6 to 9. In general, the α‐CGRP signal was also more intense than the β‐CGRP signal. The present findings indicate that the α‐ and β‐CGRP mRNA expression in the olivary complex is under developmental control and restricted to specific olivocerebellar compartments. The data provide a basis for the transient expression of a CGRP olivocerebellar compartment and further support the hypothesis of a role for CGRP in the complex postnatal cerebellar phenomena of connectivity reshaping and synapse stabilization. © 1995 Wiley‐Liss, Inc.
Organization of the avian “corticostriatal” projection system: A retrograde and anterograde pathway tracing study in pigeons
Authors: Veenman C. Leo , Wild J. Martin , Reiner Anton
Published: January 2005

Birds have well‐developed basal ganglia within the telencephalon, including a striatum consisting of the medially located lobus parolfactorius (LPO) and the laterally located paleostriatum augmentatum (PA), Relatively little is known, however, about the extent and organization of the telencephalic “cortical” input to the avian basal ganglia (i. e., the avian “corticostriatal” projection system). Using retrograde and anterograde neuroanatomical pathway tracers to address this issue, we found that a large continuous expanse of the outer pallium projects to the striatum of the basal ganglia in pigeons. This expanse includes the Wulst and archistriatum as well as the entire outer rind of the pallium intervening between Wulst and archistriatum, termed by us the pallium externum (PE). In addition, the caudolateral neostriatum (NCL), pyriform cortex, and hippocampal complex also give rise to striatal projections in pigeon. A restricted number of these pallial regions (such as the “limbic” NCL, pyriform cortex, and ventral/caudal parts of the archistriatum) project to such ventral striatal structures as the olfactory tubercle (TO), nucleus accumbens (Ac), and bed nucleus of the stria terminalis (BNST). Such “limbic” pallial areas also project to medialmost LPO and lateralmost PA, while the hyperstriatum accessorium portion of the Wulst, the PE, and the dorsal parts of the archistriatum were found to project primarily to the remainder of LPO (the lateral two‐thirds) and PA (the medial four‐fifths).

The available evidence indicates that the diverse pallial regions projecting to the striatum in birds, as in mammals, are parts of higher order sensory or motor systems. The extensive corticostriatal system in both birds and mammals appears to include two types of pallial neurons: (1) those that project to both striatum and brainstem (i. e., those in the Wulst and the archistriatum) and (2) those that project to striatum but not to brainstem (i. e., those in the PE). The lack of extensive corticostriatal projections from either type of neuron in anamniotes suggests that the anamniote‐amniote evolutionary transition was marked by the emergence of the corticostriatal projection system as a prominent source of sensory and motor information for the striatum, possibly facilitating the role of the basal ganglia in movement control. © 1995 Wiley‐Liss, Inc.
Origin of microglia in the quail retina: Central‐to‐peripheral and vitreal‐to‐scleral migration of microglial precursors during development
Authors: Navascués Julio , Moujahid Amale , Almendros Antonio , Marin‐Teva José L. , Cuadros Miguel A.
Published: January 2005

The origin, migration, and differentiation of microglial precursors in the avascular quail retina during embryonic and posthatching development were examined in this study. Microglial precursors and developing microglia were immunocytochemically labeled with QH1 antibody in retinal whole mounts and sections. The retina was free of QH1+ macrophages at embryonic day 5 (E5). Ameboid QH1+ macrophages from the pecten entered the retina from E7 on. These macrophages spread from central to peripheral areas in the retina by migrating on the endfeet of the Müller cells and reached the periphery of the retina at E12. While earlier macrophages were migrating along the inner limiting membrane, other macrophages continued to enter the retina from the pecten until hatching (E16). From E9 on, macrophages were seen to colonize progressively more scleral retinal layers as development advanced. Macrophages first appeared in the ganglion cell layer at E9, in the inner plexiform layer at E12, and in the outer plexiform layer at E 14. Therefore, it seems that macrophages first migrated tangentially along the inner retinal surface and then migrated from vitreal to scleral levels to gain access to the plexiform layers, where they differentiated into ramified microglia. Macrophages appeared to differentiate shortly after arrival in the plexiform layers, as poorly ramified QH1+ cells were seen as early as E12 in the inner plexiform layer and at E14 in the outer plexiform layer. Radial migration of macrophages toward the outer plexiform layer continued until posthatching day 3, after which retinal microglia showed an adult distribution pattern. We also observed numerous vitreal macrophages intimately adhered to the surface of the pecten during embryonic development, when macrophages migrated into the retina. These vitreal macrophages were not seen from hatching onwards, when no further macrophages entered the retina. © 1995 Wiley‐Liss, Inc.
Distribution and effects of tachykinin‐like peptides in the stomatogastric nervous system of the crab, Cancer borealis
Authors: Blitz Dawn M. , Christie Andrew E. , Marder Eve , Nusbaum Michael P.
Published: January 2005

The rhythmically active pyloric and gastric mill motor patterns in the stomatogastric ganglion of the crab, Cancer borealis, are influenced by modulatory projection neurons whose somata are located primarily in the other ganglia of the stomatogastric nervous system. One of these projection neurons exhibits substance P‐like immunolabeling. However, bath application of substance P does not influence these motor patterns. To determine whether a different peptide is responsible for the substance P‐like immunolabeling, we studied the presence and physiological effects of the locustatachykinins and the leucokinins, two families of tachykininlike peptides originally identified in insect nervous systems. Locustatachykinin‐hke immunolabeling has the same distribution in the stomatogastric nervous system as substance P‐like immunolabeling and colocalizes with it in the majority of immunopositive structures. Preincubation of locustatachykinin antibody with substance P, and preincubation of substance P antibody with locustatachykinin, blocks subsequent immunolabeling in the stomatogastric nervous system. In contrast, we found no leucokinin‐like immunolabeling in this system. Bath application to the stomatogastric ganglion of individual locustatachykinins or leucokinins excited the pyloric rhythm in a state‐dependent manner. Each peptide family had distinct effects on the pyloric rhythm. Thus, both of these tachykinin‐like peptide families are likely related to native neuropeptides that influence the pyloric rhythm. Furthermore, a member of the locustatachykinin family is likely to be the source of the previously identified substance P‐like immunoreactivity in the stomatogastric nervous system. © 1995 Wiley‐Liss, Inc.
Macrophages, microglia, and astrocytes are rapidly activated after crush injury of the goldfish optic nerve: A light electron microscopic analysis
Authors: Battisti W. P. , Wang J. , Bozek K. , Murray M.
Published: January 2005

Several matrix and adhesion molecules in fish optic nerve, which are constitutively expressed, are increased during axonal regeneration and are primarily associated with nonneuronal cells (W. P. Battisti, Y. Shinar, M. Schwartz, P. Levitt, and M. Murray [1992] J. Neurocytol. 21:557–573). The current study examines the reactions of specific cell types to optic nerve crush and axonal regeneration.

The goldfish optic nerve contains macroglia and microglia as well as a population of monocyte‐derived cells (granular macrophages) unique to goldfish. Two cell types were OX‐42 positive (granular macrophages and microglia), indicating monocyte lineage, each with a distinct morphology and distribution within the nerve. Within hours of the optic nerve crush, the number of OX‐42‐labeled cell profiles increased near the crush site, remained elevated during the time axons were elongating, and then declined. Microglia, but not granular macrophages, were phagocytically active. Astrocytes are readily identified in the normal optic nerve, but they exhibited marked morphologic changes within hours of injury, which is consistent with the contribution these cells make to the altered environment. Oligodendroglia could not be reliably identified in regenerating optic nerves until myelin was formed.

A comparison of the distribution of OX‐42‐labeled cells with that of transforming growth factor β‐1 (TGF‐β1) and tenascin suggests that these molecules are expressed by granular macrophages. Tenascin staining may be additionally associated with astrocytes and/or microglia. The rapid response of these nonneuronal cells to injury, their rapid phagocytic activity, and the secretion of growth‐promoting factors by these cells likely contributes to the environment that supports robust regeneration by optic axons in the goldfish. © 1995 Wiley‐Liss, Inc.
Early development of efferent projections from the chick tectum
Authors: Shepherd I. T. , Taylor J. S. H.
Published: January 2005

The early development of the uncrossed tectobulbar and the crossed tectospinal tracts was studied. These two projections arise from the same structure, the mesencephalon, and develop during the same time period, but follow divergent courses. We have traced the pathways followed by these projections and identified the positions at which axon guidance decisions are made. The first neurons differentiate either side of the entire rostrocaudal extent of the dorsal midline and initiate axons that extend dorsoventrally across the surface of the tectum. At the ventral edge of the tectum these axons turn abruptly and fasciculate to form a caudal descending projection to the hindbrain. These axons extend to the caudal hindbrain and do not project to the periphery along cranial nerve roots. We therefore consider this tract to be the teetobulbar, rather than the mesencephalic division of the trigeminal. While the tectobulbar projection is still developing, a second wave of axons is initiated, which arises from only the rostral part of the tectum. These axons grow beyond the tectobulbar turn point and continue toward the ventral midline, where they cross the floor plate, before turning caudally at the lateral edge of the main descending hindbrain tract, the ventrolateral tract. We discuss the development of these tracts with reference to possible guidance cues mediating their course. © 1995 Wiley‐Liss, Inc.
Projections of the lateral terminal accessory optic nucleus of the common marmoset (Callithrix jacchus)
Authors: Blanks Robert H. I. , Clarke Robert J. , Lui Fausta , Giolli Roland A. , Van Pham Sang , Torigoe Yasuhiro
Published: January 2005

The connections of the lateral terminal nucleus (LTN) of the accessory optic system (AOS) of the marmoset monkey were studied with anterograde 3H‐amino acid light autoradiography and horseradish peroxidase retrograde labeling techniques. Results show a first and largest LTN projection to the pretectal and AOS nuclei including the ipsilateral nucleus of the optic tract, dorsal terminal nucleus, and interstitial nucleus of the superior fasciculus (posterior fibers); smaller contralateral projections are to the olivary pretectal nucleus, dorsal terminal nucleus, and LTN. A second, mejor bundle produces moderate‐to‐heavy labeling in all ipsilateral, accessory oculornotor nuclei (nucleus of posterior commissure, interstitial nucleus of Cajal, nucleus of Darkschewitsch) and nucleus of Bechterew; some of the fibers are distributed above the caudal oculomotor complex within the supraoculornotor periaqueductal gray. A third projection is ipsilateral to the pontine and mesencephalic reticular formations, nucleus reticularis tegmenti pontis and basilar pontine complex (dorsolateral nucleus only), dorsal parts of the medial terminal accessory optic nucleus, ventral tegmental area of Tsai, and rostral interstitial nucleus of the medial longitudinal fasciculus. Lastly, there are two long descending bundles: (1) one travels within the medial longitudinal fasciculus to terminate in the dorsal cap (ipsilateral > > contralateral) and medial accessory olive (ipsilateral only) of the inferior olivary complex. (2) The second soon splits, sending axons within the ipsilateral and contralateral brachium conjunctivum and is distributed to the superior and medial vestibular nuclei.

The present findings are in general agreement with the documented connections of LTN with brainstem oculomotor centers in other species. In addition, there are unique connections in marmoset monkey that may have developed to serve the more complex oculomotor behavior of nonhuman primates. © 1995 Wiley‐Liss, Inc.
Effects of unilateral cochlea ablation on the distribution of calretinin mRNA and immunoreactivity in the guinea pig ventral cochlear nucleus
Authors: Winsky Lois , Jacobowitz David M.
Published: January 2005

The predominantly neuronal, calcium‐binding protein calretinin is highly expressed in the guinea pig auditory system. Within the ventral cochlear nucleus (VCN), calretinin‐positive auditory nerve fibers terminate on many calretinin‐containing bushy, octopus, and multipolar cells. The abundance of calretinin in the cochlear nucleus provides an ideal system for examining the effects of altered neuronal input on the expression of this calcium‐binding protein.

The present experiments examined the effects of unilateral cochlea ablation on calretinin immunoreactivity and mRNA levels in the VCN. Calretinin mRNA was labeled by in situ hybridization histochemistry using a radioactive oligonucleotide probe and was quantified by optical density measures on autoradiograms. Survival times of 1, 7, and 56 days postlesion were examined.

The results revealed a consistent increase in calretinin mRNA in the rostral portion of the ipsilateral anterior VCN 1 day postlesion but no effect on calretinin mRNA in this region at 7 and 56 days postlesion. The intensity of immunohistochemical label was also increased at 1 and 7 days after surgery. In contrast, calretinin mRNA was not affected 1 day postlesion in the ipsilateral posterior VCN but was decreased at both 7 and 56 days postlesion. The decrease in calretinin mRNA in the posterior VCN at longer survival times was accompanied by decreased immunolabeling of fibers projecting from VCN cells to the superior olivary complex. These results suggest that calretinin gene expression is regulated in part by auditory nerve activity in some cochlear neurons but that additional factors related to the unique cellular milieu also control calretinin expression. © 1995 Wiley‐Liss, Inc.
A histochemical study of iron‐positive cells in the developing rat brain
Authors: Connor James R. , Pavlick Geno , Karli David , Menzies Sharon L. , Palmer Charles
Published: January 2005

The establishment of normal iron levels in the neonatal brain is critical for normal neurological development. Studies have shown that both iron uptake and iron concentration in the brain are relatively high during neonatal development. This histochemical study was undertaken to determine the pattern of iron development at the cellular level in the rat forebrain. Iron‐stained cells were observed as early as postnatal day (PND) 3, which was the earliest time point examined. At PND 3, there were four major foci of iron‐containing cells: the subventricular zone and three areas within the subcortical white matter. These latter foci are associated with myelinogenic regions. The blood vessels were prominently stained for iron throughout the brain. At PND 7, as in PND 3, the majority of the iron‐containing cells were in white matter. However, there were also patches of iron staining located specifically in the layer IV of the somatosensory cortex. These cortical patches were no longer visible by PND 14. At PND 14, numerous iron‐stained cells were dispersed throughout White matter regions and the tanycytes aligning the third ventricle were prominently stained. The blood vessel staining was less prominent than at earlier time periods. By PND 28, the adult pattern of iron staining was emerging. Iron‐stained cells were aligned in rows in white matter and had an apparent preference for a location near blood vessels. This clustering of iron‐positive cells around blood vessels gave the white matter a “patchy” appearance. The pattern of development, cell distribution, and morphological appearance of the iron‐stained cells are consistent with that reported for oligodendrocytes. That iron‐positive cells in the neonate may be oligodendrocytes is consistent with the reports for iron staining in adult brains. The recent reports that oligodendrocytes are highly susceptible to oxidative damage would be consistent with the high iron levels found in these cells, These results indicate that oligodendrocytes play a major role in the development of iron homeostasis in the brain. The role of iron in oligodendrocytes may be associated with metabolic demands of myelinogenesis, including cholesterol and fatty acid synthesis. However, these cells may be a morphologically similar but functionally distinct subset of oligodendrocytes whose function is to regulate the availability of iron in the brain.
Two modes of hair cell loss from the vestibular sensory epithelia of the guinea pig inner ear
Authors: Li Lin , Nevill Graham , Forge Andy
Published: January 2005

In the vestibular and auditory neurosensory epithelia of poikilothermic vertebrates and of birds, damaged sensory “hair” cells are often deleted by extrusion from the apical surface. In contrast, in the adult mammalian auditory epithelium (the organ of Corti), the bodies of damaged hair cells degenerate within the epithelium. To determine whether this apparent difference is species related or is associated with the differing structural organisation of the epithelia, hair cell deletion in the mammalian vestibular end‐organs was examined. The structural organisation of these tissues is closer to that of the inner ear epithelia of lower vertebrates than to the organ of Corti. Hair cell loss was induced by chronic, systemic treatment of guinea pigs with the ototoxic aminoglycoside antibiotic gentamicin. The vestibular sensory epithelia were examined at various times after treatment via scanning electron microscopy, thin sectioning, and staining f‐actin with fluorescently labelled phalloidin. Two distinct modes of hair cell loss were identified: (1) degeneration of hair cells within the epithelium, which often showed morphological features consistent with those described for apoptosis, and (2) extrusion of intact cells from the apical surface. Neither process caused the formation of obvious lesions through the epithelial surfaces. Expansion of adjacent supporting cells during hair cell deletion resulted in repair that appeared to preserve permeability barriers. There was also no evidence of inflammation accompanying hair cell removal. Thus, with both modes of hair cell loss, it appeared that deletion of hair cells was achieved without disruption of tissue architecture or integrity. This may be important for subsequent repair and regeneration processes to operate.
Barreloids in adult rat thalamus: Three‐dimensional architecture and relationship to somatosensory cortical barrels
Authors: Land Peter W. , Buffer Sam A. , Yaskosky Jamie Dawn
Published: January 2005

Histochemical staining for cytochrome oxidase (CO) and axonal transport of horseradish peroxidase (HRP) were used to investigate thalamocortical connections in the vibrissa‐barrel system of adult rats. CO staining revealed that the medial division of the ventrobasal thalamic nucleus (VBm) consists of intensely stained rod‐like configurations, containing thalamocortical projection neurons and intervening neuropil, separated by lighter‐stained septa. CO‐dark rods span the thickness of VBm, are arranged in a pattern of rows and arcs that resembles the distribution of vibrissae on the mystacial pad, and are similar to the cytoarchitectonic structures termed “barreloids” in the mouse thalamus. Based upon the dimensions of CO‐dark structures and the numerical density of neurons in VBm we estimated that a barreloid in the rat may contain 250‐300 neurons.

HRP injections into lamina IV of the somatosensory cortex led to retrograde labeling of neurons within one or more barreloids. When injections were centered within the CO‐dark hollows of cortical barrels about 95% of retrogradely labeled neurons were located in the barreloid that is isomorphic to the injected barrel; up to 5% of labeled neurons were located within a single adjacent barreloid. Barrel hollow injections that also included a barrel side yielded a larger proportion of labeled neurons in non‐isomorphic barreloids. Interestingly, such extra‐barreloid labeling was topologically consistent in that HRP‐labeled neurons were distributed among barreloids that corresponded to cortical barrels nearest the injected barrel side. Injections into the septa between barrels similarly resulted in labeling within barreloids that corresponded to cortical barrels flanking the septal injection site.

Following lamina IV injections the density of labeled neurons tended to be highest in the ventrolateral one‐half to two‐thirds of VBm. Retrograde labeling of neurons in the dorsomedial one‐third to one‐half of VBm was more often observed after HRP injections at the lamina V/VI border. Thus, barreloid neurons may be heterogeneous with respect to their laminar pattern of terminations within the somatosensory cortex. Some HRP injections in the cortex resulted in orthograde labeling of corticothalamic axons in the barreloids. When observed, labeled corticothalamic axons arborized principally within the barreloid isomorphic to the injected barrel column. Indeed, terminal labeling was densest in the vicinity of neurons retrogradely labeled by the same injection.