bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative analyses of postembryonic hair cell addition in the otolithic endorgans of the inner ear of the european hake, merluccius merluccius (gadiformes, teleostei)
Authors: Lombarte Antoni , Popper Arthur N.
Published: January 2005

Bony fishes add sensory hair cells to the saccule and lagena of the ear for at least several years after hatching. However, it is not known whether hair cell proliferation occurs for the whole lifetime of an animal, whether proliferation occurs in all endorgans of the ear, or whether the rate of proliferation is the same in all of the endorgans. To obtain answers to these questions, the extent of postembryonic hair‐cell proliferation was determined in the saccule, lagena, and utricle of the ear in the European hake, Merluccius merlaccius, for fish ranging from 7 to 75 cm in total length (6 months to 9 years of age). Results demonstrated that hair‐cell addition continued throughout this period in all three otic endorgans, although endorgan size was proportionally greatest in smaller animals. Of the three endorgans, cell addition was greatest in the saccule. Moreover, far more cells were added to the caudal end of the saccule than to the rostral end. Each saccule of the largest hake had over 900,000 hair cells. It is estimated that each saccule adds approximately 110,000 new hair cells each year (or 302 cells/day) over the life span of the fish studied. A significant number of small ciliary bundles, thought to represent newly proliferated hair cells, was found throughout each endorgan, and the number of such bundles declined as the rate of hair cell proliferation decreased. The results demonstrate that extensive proliferation occurs in all three otolithic endorgans of the ears in a fish and that such proliferation continues for virtually the whole life of the animal. The functional significance of this addition is not known. © 1994 Wiley‐Liss, Inc.
Dendritic development of dentate granule cells in the absence of their specific extrinsic afferents
Authors: Zafirov Silvana , Heimrich Bernd , Frotscher Michael
Published: January 2005

Dendrites and spines are postsynaptic structures that develop in association with presynaptic fibers. Recent studies have shown that granule cells of the fascia dentata survive in slice cultures and differentiate in a manner known from in situ studies. However, all extrinsic afferent fibers are absent under culture conditions. In the present study, we study whether dendrites and spines of granule cells in slice cultures differentiate normally, although they are not contacted by their normal layer‐specific afferents.

Slices of hippocampus were prepared from rat pups at the day of birth. After 5, 10, 15, and 20 days of incubation, granule cells in these cultures were Golgi impregnated. For comparison, perfusion‐fixed hippocampal sections of 5‐, 10‐, 15‐, and 20‐day‐old rats were impregnated the same way. Our results show that the total density of spines on granule cell dendrites in culture increased as in perfusion‐fixed animals. However, after 20 days of incubation, the absolute number of dendritic spine on cultured neurons was reduced because of a reduction of peripheral dendrites. This reduction was accompanied by an increase in the number of stem dendrites originating from the perikaryon. The density of spines on these proximal dendrites was larger in cultured granule cells than in controls.

Our results suggest that the lack of major extrinsic (entorhinal) afferents that normally terminate on peripheral granule cell dendrites causes retraction of these dendrites. At the same time, there is growth of paroximal dendritic portions. Proximal dendrites are targets of associational fibers, which are known to sprout under these culture conditions. © 1994 Wiley‐Liss, Inc.
Primate striatonigral projections: A comparison of the sensorimotor‐related striatum and the ventral striatum
Authors: Lynd‐Balta E. , Haber S. N.
Published: January 2005

The striatum receives topographic cortical inputs with the limbic lobe terminating in the ventral striatum and sensorimotor cortical regions terminating in the dorsolateral striatum. The organization of striatonigral projections originating from these different striatal territories was examined in primate by using several anterograde tracers.

The ventral striatum innervates a large area of the substantia nigra, including the medial pars reticulata and much of the pars compacta. Moreover, projections from separate areas of the ventral striatum overlap considerably in the substantia nigra. No mediolateral or rostrocaudal topographic order is apparent, and the area of the substantia nigra associated with the ventral striatum is extensive. In contrast, the sensorimotor‐related striatum innervates a limited region of the ventrolateral substantia nigra. Similar to ventral striatonigral projections, projections originating from different areas of the sensorimotor‐related striatum send converging inputs to the substantia nigra. Sensorimotor‐related striatonigral projections avoid the region of the dopaminergic neurons in the dorsal pars compacta. Striatonigral projections from the sensorimotor‐related and ventral striatum do not overlap in the substantia nigra. Examination of the outputs of discrete striatal loci indicates that the organization of striatonigral projections is more related to corticostriatal inputs than to a simple rostrocaudal, dorsoventral, or mediolateral tpography of the striatum.

Striatal projections that originate from different striatal territories are distinct and nonoverlapping, thus supporting the concept of segregated striatonigral circuits. However, areas of the striatum that receive common cortical inputs send converging inputs to the substantia nigra. This suggests that the substantia nigra is also an important link for integrating information between functionally related (sub)circuits. © 1994 Wiley‐Liss, Inc.
The development of GABA immunoreactivity in the retina of the zebrafish (brachydanio rerio)
Authors: Sandell Julie H. , Martin Stella C. , Heinrich Gerhard
Published: January 2005

The goal of this study was to determine the pattern of gamma‐aminobutyric acid (GABA) expression in the retina and optic nerve of the zebrafish (Brachydanio rerio) during embryonic development. Zebrafish embryos were fixed at intervals between 1 and 4 days postfertilization, and semithin plastic sections were prepared for postembedding immunocytochemistry with antisera, against GABA. Sections were also prepared from several adult zebrafish eyes for comparison. GABA immunoreactivity first appeared in the optic nerve at 2 days postfertilization, and by 2.5 days the inner nuclear layer (INL), inner plexiform layer (IPL), retinal ganglion cell layer, and optic nerve were all positive for GABA. The GABA expression in the retinal ganglion cell layer and optic nerve was transient, however, and these structures were largely unlabeled by 4 days postfertilization. The pattern of GABA immunoreactivity at 4 days resembled that seen in the adult zebrafish: A large population of presumptive amacrine cells was labeled at the base of the INL, and the IPL was positive for GABA, as were occasional cells in the ganglion cell layer. Horizontal cells, particularly at the retinal margins, were also GABA positive beginning at about 3 days postfertilization. The transient expression of GABA in retinal ganglion cells and their axons during the period when synaptic contacts are being established both within the retina and between the retina and central targets suggests that GABA may have a role in the development of this system, in addition to serving as a classical neurotransmitter. © 1994 Wiley‐Liss, Inc.
Proctolin and excitation of the crayfish swimmeret system
Authors: Acevedo Larisa D. , Hall Wendy M. , Mulloney Brian
Published: January 2005

The ventral nerve cord of crayfish contains axons of five pairs of excitatory interneurons, each of which can activate the swimmeret system. Perfusion of the ventral nerve cord with the neuropeptide proctolin also activates the swimmeret system. The experiments reported here were conducted to test the hypothesis that one or more of these excitatory interneurons uses proctolin as a transmitter.

Each of the five excitatory axons was located and stimulated separately in an individual crayfish, and similar motor activity was elicited by stimulating each of them. Quantitative comparison of spontaneous swimmeret motor patterns with activity caused by stimulating one of these excitatory axons, EC, or by perfusing with proctolin solutions showed that the motor patterns produced under these three conditions were not significantly different (P > 0.05).

By using a new, affinity‐purified proctolin antiserum, we labeled axons in the connective tissue between the last thoracic and first abdominal ganglion and compared the positions of labeled axons with the previously described positions of the excitatory axons. About 0.3% of the axons in these connective tissues showed proctolin‐like immunoreactivity, but heavily labeled pairs of axons did occur bilaterally in the regions of excitatory swimmeret axons. The projections of these labeled axons into the abdominal ganglia were traced in serial plastic sections. Labeled processes were abundant in the lateral neuropils, the loci of the swimmeret pattern‐generating circuitry.

From this evidence, we propose that three of these excitatory swimmeret interneurons use proctolin as a transmitter, but that a fourth does not. The evidence for the fifth axon is ambiguous. © 1994 Wiley‐Liss, Inc.
Single retinal ganglion cells projecting in bilaterally to the lateral geniculate nuclei or superior colliculi by way of axon collaterals in the cat
Authors: Kondo Yasuko , Takada Masahiko , Tokuno Hironobu , Mizuno Noboru
Published: January 2005

In most mammals with frontalized eyes, retinal ganglion cells in the nasal or temporal retina send their axons to the contralateral or ipsilateral half, respectively, of the brain. Previous studies in the cat, however, have indicated a retinal region of “nasotemporal overlap” from which arise the retinal projections to both the contralateral and ipsilateral halves of the brain. The present study thus examined in the cat whether any retinal ganglion cells give rise to bifurcating axons that innervate both halves of the brain.

By employing fluorescent retrograde double labeling, we investigated whether or not single retinal ganglion cells project bilaterally to the lateral geniculate nuclei or superior colliculi by way of axon collaterals. After Fast Blue was injected into the lateral geniculate nucleus on one side and Diamidino Yellow was injected contralaterally into the lateral geniculate nucleus, 100–200 ganglion cells in each retina were double labeled with both tracers. These double‐labeled cells were distributed primarily in the temporal retina, including the region around the vertical meridian and, additionally, in the nasal retina. About 60–80% of the double‐labeled cells had large cell bodies (more than 25 μm in diameter), and the others had medium‐sized ones (15–25 μm in diameter). The pattern of distribution of double‐labeled cells, which was observed after the combined injection into both superior colliculi, was similar to that seen after the combined injection into both lateral geniculate nuclei; more than 9% of double‐labeled cells, however, were large.

The results indicate that a certain population of ganglion cells in the cat retina send their axons bilaterally to the lateral geniculate nuclei or superior colliculi by way of axon collaterals. The bilaterally projecting ganglion cells are mostly large, corresponding probably to α cells (the morphological counterparts of Y cells). In comparison with the patterns of bilateral projections of single retinal ganglion cells in the rat and monkey, the pattern of the bilateral retinofugal projections in the cat could represent an intermediate between those in the rat and monkey. © 1994 Wiley‐Liss, Inc.
The neurons of the medial geniculate body in the mustached bat (Pteronotus parnellii)
Authors: Winer Jeffery A. , Wenstrup Jeffrey J.
Published: January 2005

The neurons in the medial geniculate body were studied in Golgi preparations from adult mustached bats (Pteronotus parnellii). Their somatic and dendritic configurations were compared with those of cells in other, nonecholocating mammals. A second goal was to use the thalamic nuclear subdivisions derived from Golgi material to integrate the findings in parallel studies of cytoarchitecture, immunocytochemistry, and tectothalamic connections.

Three primary divisions are defined. The ventral division is large and has a stereotyped neuronal organization. Medium‐sized perikarya (about 10 μm in diameter) represent tufted neurons; the fibrodendritic plexus forms laminae in the lateral part along which midbrain axons terminate. A smaller, possibly intrinsic, neuron with thin, sparse dendrites is rarely impregnated. Neurons in the larger, medial part, which represents frequencies of 60 kHz and higher, have more spherical dendritic fields; their branching pattern remains tufted, and the laminar organization was less evident. The dorsal division is about equal in size, and it has many nuclei and a corresponding neuronal diversity. These neurons are medium‐sized except in the suprageniculate nucleus, where many cells are larger. Four dorsal division nuclei are recognized. Each has neurons with radiate or weakly tufted dendritic arbors. Superficial dorsal nucleus neurons are oriented from medial to lateral, imparting a slightly laminated appearance to the neuropil. A few smaller, stellate neurons with modest dendritic domains are present. Suprageniculate nucleus neurons have radiating dendritic fields that project spherically; they have fewer branches than dorsal nucleus neurons. The posterior limitans nucleus is dorsomedial to the suprageniculate nucleus; it has small neurons with long, sparsely branched dendrites. The rostral pole nucleus, included in the dorsal division on cytoarchitectonic grounds, had too few neurons impregnated to reveal its neuronal architecture. The medial division, the smallest of the main parts, is one nucleus with at least six types of cells, including the magnocellular, bushy tufted, disc‐shaped, medium‐sized multipolar, elongated, and small stellate neurons. There is no laminar arrangement.

Many of the neurons resemble those in rodent, marsupial, carnivore, and primate auditory thalamic nuclei. Despite such morphological correspondences, functional differences, such as the evolution of combination sensitivity, suggest that structurally comparable auditory thalamic neurons may subserve diverse physiological representations. © 1994 Wiley‐Liss, Inc.
Projections of physiologically defined subdivisions of the inferior colliculus in the mustacbed bat: Targets in the medial geniculate body and extrathalamic nuclei
Authors: Wenstrup Jeffrey J. , Larue David T. , Winer Jeffery A.
Published: January 2005

This study examined the output of the central nucleus of the inferior colliculus to the medial geniculate body and other parts of the nervous system in the mustached bat (Pteronotus parnellii). Small deposits of anterograde tracers (horseradish peroxidase, [3H]leucine, Phaseolus vulgaris leucoagglutinin, wheat germ agglutinin conjugated to horseradish peroxidase, or biocytin) were made at physiologically defined sites in the central nucleus representing major components of the bat's echolocation signal. The topography, frequency specificity, and axonal morphology of these outputs were studied.

The medial geniculate body was a major target of inferior collicular neurons, with three distinct input patterns. The projection to the ventral division was tonotopically organized, but had a relatively sparse contribution from neurons representing frequency modulated components of the biosonar pulse. The second input was to the rostral medial geniculate body, in which projections from inferior collicular neurons representing constant frequency sonar components were separated from those representing frequency modulated components. A third input was to the suprageniculate nucleus, which received strong, topographically arranged projections. Inputs to the dorsal nucleus and medial division were also observed.

Extrathalamic regions receiving input included the pontine gray, external nucleus of the inferior colliculus, pericollicular tegmentum, nucleus of the brachium of the inferior colliculus, and pretectum. These central nucleus projections differed in organization and the structure of axon terminals, suggesting different physiological influences on their target nuclei. These results demonstrate that the central nucleus has divergent projections to various sensory and premotor nuclei, besides its well‐established projection to the medial geniculate body. © 1994 Wiley‐Liss, Inc.
The contralaterally projecting neurons of the isthmic nucleus in five anuran species: A retrograde tracing study with HRP and cobalt
Authors: Tóth Pál , Lázár Gyula , Wang Shu‐Rong , Li Tong‐Bin , Xu Jia , Pál Endre , Straznicky Charles
Published: January 2005

The morphology of projection neurons of the isthmic nucleus was studied in Rana esculenta, R. nigromaculata, Bufo marinus, B. bufo gargarizans, and Xenopus laevis from a comparative anatomical point of view. The main point of this work was to provide an anatomical basis for electrophysiological studies. Neurons projecting to the ipsilateral optic tectum were labeled by retrograde transport of horseradish peroxidase and cobaltous lysine complex injected into the optic tectum. Contralaterally projecting cells were filled by injecting the tracer substances into the crossed isthmotectal tract.

Cells of the anterior nonrim cortex and the rostral part of the medulla project to the ipsilateral tectum. A band of cells in the middle of the medulla, a few cells in the caudal part of the medulla, and most of the neurons in the rim cortex project to the contralateral tectum.

Five types of neurons were distinguished in the rim cortex of R. esculenta. Most of them have piriform perikarya and their dendrites arborize in the rim neuropil. In the medulla of the isthmic nucleus of R. escalenta, seven types of neurons were distinguished. Most of these neurons also exist in the other species. Medullary cells are piriform, fusiform, or multipolar, and are variable in size and in dendritic arborization. The isthmic neurons of the two Ranae and Bufo species are similar. The dominant cell types in Xenopus are multipolar with extensive dendritic arborization, which occupies more space in the nucleus than in the other species.

Neurons with narrow dendritic trees may represent a system of fine resolution, and those neurons with extensive dendritic arborization may belong to a coarser system. © 1994 Wiley‐Liss, Inc.
Descending propriospinal axons in the hindlimb enlargement of the red‐eared turle: Cells of origin and funicular courses
Authors: Berkowitz Ari , Stein Paul S. G.
Published: January 2005

Spinal neurons with descending axons are important components of spinal sensorimotor networks. We used an anatomical tracing technique to study the distribution of descending propriospinal axons and cell bodies in red‐eared turtles. We injected horseradish peroxidase into a portion of one funiculus in the middle of the hindlimb enlargement and examined six spinal segments rostral to the injection site (dorsal 3 through dorsal 8) for labeled neuronal cell bodies.

Injections into each region of the white matter labeled substantial numbers of descending propriospinal neurons. Each injection labeled cell bodies over most of the six spinal segments examined. Each injection also labeled cell bodies in the ipsilateral dorsal horn, intermediate zone, and ventral horn as well as the contralateral intermediate zone and ventral horn. Injections into each of four regions of the white matter, the dorsal funiculus, the medial part of the lateral funiculus, the lateral part of the lateral funiculus, and the ventral funiculus reliably gave rise to a distinct distribution of labeled cell bodies.

These experiments establish that descending propriospinal axons in red‐eared turtles are found in all regions of the spinal white matter. This finding contrasts with a popular contempopary view of the organization of descending propriospinal axons in mammals. These experiments also demonstrate that neurons in each region of the gray matter give rise to a different distribution of descending, funicular axons, although these distributions are widely overlapping. Different funicular axon distributions could be associated with different sets of synaptic contacts with the white‐matter dendrites of spinal neurons. © 1994 Wiley‐Liss, Inc.
Anatomical properties of brainstem trigeminal neurons that respond to electrical stimulation of dural blood vessels
Authors: Strassman Andrew M. , Potrebic Sonja , Maciewicz Raymond J.
Published: January 2005

Single unit recording studies in anesthetized cats have identified a population of neurons in the brainstem trigeminal complex that can be activated by stimulation of major dural blood vessels. Such dura‐responsive neurons exhibit response properties that are appropriate for a role in the mediation of vascular head pain in that they typically exhibit nociceptive facial receptive fields whose periorbital distribution is similar to the region of referred pain evoked by dural stimulation in humans. In the present study, intracellular labelling with horseradish peroxidase was used to examine the anatomical characteristics of brainstem trigeminal neurons that respond to dural stimulation.

A total of 17 neurons was labelled that responded to electrical stimulation of dural sites overlying the superior sagittal sinus or middle meningeal artery. Fourteen of these neurons also responded to electrical stimulation of the cornea. The neurons in this sample were located in the rostral two‐thirds of the trigeminal nucleus caudalis and the caudalmost part of the nucleus interpolaris. Within caudalis, the neurons were located in the deeper part of the nucleus, primarily lamina V, and were concentrated ventrolaterally. The dendritic arborizations of the dura‐responsive neurons typically exhibited a dorsolateral‐to‐ventromedial orientation and did not extend into the superficial laminae of caudalis. Dura‐responsive neurons had axonal collaterals and boutons in the nucleus caudalis, nucleus interpolaris, the infratrigeminal region ventral to nucleus interpolaris, the nucleus of the solitary tract, and the medullary reticular formation. The axonal boutons within the trigeminal complex exhibited a ventrolateral distribution which largely overlapped the distribution of the somata. The results are consistent with previous evidence that dura‐responsive brainstem trigeminal neurons may have a role in the mediation of dural vascular head pain and also indicate that such neurons may contribute to nociceptive processing within the dorsal horn. © 1994 Wiley‐Liss, Inc.
Architectonic subdivision of the orbital and medial prefrontal cortex in the macaque monkey
Authors: Carmichael S. T. , Price J. L.
Published: January 2005

The orbital and medial prefrontal cortex (OMPFC) of macaque monkeys is a large but little understood region of the cerebral cortex. In this study the architectonic structure of the OMPFC was analyzed with nine histochemical and immunohistochemical stains in 32 individuals of three macaque species. The stains included Nissl, myelin, acetylcholinesterase, Timm, and selenide stains and immunohistochemical stains for parvalbumin, calbindin, a nonphosphorylated neurofilament epitope (with the SMI‐32 antibody), and a membrane‐bound glycoprotein (with the 8b3 antibody). In addition to patterns of cell bodies and myelinated fibers, these techniques allow the visualization of markers related to metabolism, synapses, and neurotransmitters. A cortical area was defined as distinct if it was differentiated in at least three different stains and, as described in later papers, possessed a distinct set of connections. Twenty‐two areas were recognized in the OMPFC. Walker's areas 10, 11, 12, 13, and 14 [J. Comp. Neurol. (1940) 73:59–86] have been subdivided into areas 10m, 10o, 11m, 11l, 12r, 12l, 12m, 12o, 13m, 13l, 13a, 13b, 14r, and 14c. On the medial wall, areas 32, 25, and 24a, b, c have been delineated, in addition to area 10m. The agranular insula also has been recognized to extend onto the posterior orbital surface and has been subdivided into medial, intermediate, lateral, posteromedial, and posterolateral agranular insula areas. The OMPFC, therefore, resembles other areas of primate cortex, such as the posterior parietal and temporal cortices, where a large number of relatively small, structurally and connectionally distinct areas have been recognized. Just as the area‐specific neurophysiological properties of these parietotemporal areas underlie broader regional functions such as visuospatial analysis, it is likely that the many small areas of the OMPFC also make differential contributions to the general mnemonic, sensory, and affective functions of this region. © 1994 Wiley‐Liss, Inc.
Development of calretinin immunoreactivity in the mouse inner ear
Authors: Dechesne Claude J. , Rabejac Denis , Desmadryl Gilles
Published: January 2005

Calretinin is a calcium‐binding protein of the EF‐hand family. It has been previously identified in particular cell types of adult guinea pig, rat, and chinchilla inner ear. Development of calretinin immunoreactivity in the mouse inner ear was investigated from embryonic day 13 (E13) to the adult stage. In the adult mouse vestibule, calretinin immunoreactivity was present in the same structures as described for the rat and guinea pig: the population of afferent fibers forming calyx units and small number of ganglion neurons. The earliest immunoreactivity was found at E17 in vestibular hair cells (VHCs), then, at E19, in afferent fibers entering the sensory epithelia and in rare ganglion neurons. At postnatal day 4 (P4), a few vestibular nerve fibers and ganglion neurons were reactive. From this stage until P14, immunoreactivity developed in the calyx units and disappeared from VHCs. At P14, immunostaining was adult‐like. In the adult mouse cochlea, immunoreactivity was present in the same cell populations as described in the rat: the inner hair cells (IHCs) and most of Corti's ganglion neurons. Calretinin immunoreactivity appeared at E 19‐P0 in IHCs and ganglion neurons of the basal turn. At P1, outer hair cells (OHCs) of the basal turn were positive. Calretinin immunoreactivity then appeared in IHCs, OHCs, and ganglion neurons of the medial turn, then of the apical turn. At P4, all IHCs and OHCs and most of the ganglion neurons were immunostained. Immunoreactivity gradually disappeared from the OHCs starting at P10 and, at P22, only IHCs and ganglion neurons were positive. The sequences of appearance of calretini, n were specific to each cell type of the inner ear and paralleled their respective maturation. Calretinin was transiently expressed in VHCs and OHCs. © 1994 Wiley‐Liss, Inc.
Intrabulbar associational system in the rat olfactory bulb comprises cholecystokinin‐containing tufted cells that synapse onto the dendrites of GABAergic granule cells
Authors: Liu Wei‐Lin , Shipley Michael T.
Published: January 2005

The intrabulbar associational system (UAS) originates from tufted cells whose axons terminate in the internal plexiform layer (IPL) on the opposite side of the same olfactory bulb. The postsynaptic targets of the IAS are unknown. Subpopulations of tufted cells contain different neuropeptides and transmitters but it is not known if tufted cells forming the IAS are homogeneous with respect to neurotransmitters. Therefore, the goals of the present study were to identify thepostsynaptic targets of the IAS and to determine the major transmitter in this intrabulbar circuit.

Biocytin anterograde tracing revealed that the axons of superficially situated tufted cells coursed directly to the IPL where they turned abruptly to run ventrally and dorsally to terminate in the IPL on the opposite side of the olfactory bulb. WGAapoHRP‐Au retrograde tracing combined with immunohistochernistry for CCK revealed that all tufted cells retrogradely labeled by WGAapoHRP‐Au injection in the IPL were immunoreactive for CCK Anterograde transport of biocytin combined with postembedding immunocytochemical goldlabeling for GABA demonstrated that labeled IAS axons terminate predominantly, if not exclusively, on GABAergic granule cell dendrites in the IPL.

These results confirm that the IAS arises from tufted cells and is topographically organized. We further demonstrate that tufted cells forming the IAS use the neuropeptide CCK as a transmitter. In addition, we show that the postsynaptic targets of the CCKergic IAS are the dendrites of GABAergic granule cells coursing through the IPL toward the EPL. As CCK is generally an excitatory neuropeptide, we suggest that the IAS functions to excite topographically discrete populations of granule cells. This action may lead to inhibition of equally discrete populations of mitral/tufted cells. Thus, the IAS may be an intrabulbar inhibitory circuit that coordinates topographically organized neural networks in the olfactory bulb. © 1994 Wiley‐Liss, Inc.
Retinogeniculate projection fibers in the monkey optic chiasm: A demonstration of the fiber arrangement by means of wheat germ agglutinin conjugated to horseradish peroxidase
Authors: Naito Jumpei
Published: January 2005

The fiber arrangement of the retinogeniculate pathway was investigated in the chiasm of Japanese monkeys (Macaca fuscata) by an iontophoretic injection of wheat germ agglutinin conjugated to horseradish peroxidase into the lateral geniculate nucleus (LGN). It has been claimed that there is a distinct retinotopy in the monkey chiasm, despite lack of any clear anatomical evidence. However, the present data indicate a rather gross retinotopy or almost no discernible retinotopy. Fibers from the foveal‐to‐peripheral axis of the temporal retina show substantially no retinotopy owing to a marked overlap of fibers in the anterolateral and the posterocentral parts of the ipsilateral hemichiasm. In contrast, the foveal‐to‐peripheral axis of the nasal retina is re‐formed in a gross dorsoventral order in the chiasm. That is, nasal foveal‐parafoveal fibers which arise from small cells (which are Pβ mode) pass in the dorsal part of the chiasm adjacent to the brain. They widely overlap nasal perifoveal fibers which cross the chiasm more ventrally with very little contact with the brain. The nasal perifoveal fibers also widely overlap nasal peripheral fibers which cross the chiasm more ventrally. Furthermore, the nasal peripheral fibers overlap nasal far peripheral fibers which arise from large cells (including many of the Pα mode) which run near the pial surface. Fibers from the dorsal and ventral nasal retina cross the midline of the posterior and anterior parts of the chiasm, respectively, and are finally positioned in the medioventral and ventrocentral parts in the tract. Consequently, the dorsoventral retinal axis is re‐formed posteroanteriorly in the midline of the chiasm and in a roughly mediolateral direction in the tract. Furthermore, the present study shows that the nasal and temporal retinal fibers coming from the same eye are acutely segregated in the prechiasmal region and the anterior part of the hemichiasm. © 1994 Wiley‐Liss, Inc.
A reticuloreticular commissural pathway in the rat thalamus
Authors: Battaglia Giorgio , Lizier Carlotta , Colacitti Claudia , Princivalle Alessandra , Spreafico Roberto
Published: January 2005

To further characterize the communication between the thalami of the two hemispheres, a connection linking the rostral reticular nuclei of the two thalamic sides was investigated in the rat by retrograde and anterograde tracing. The rostral reticular nucleus can be divided into a medial region, with densely packed fusiform neurons, and a lateral region, with less densely packed, polymorphic neurons. After injections of Fluorogold (FG) in the medial region, retrogradely labeled, small fusiform neurons were found in the corresponding contralateral region. The retrograde labeling data were confirmed by the anterograde‐tracing experiments. Thin, beaded axons, anterogradely labeled after injection of biocytin or biotinylated dextranamine in the medial region, innervate the corresponding region in the contralateral reticular nucleus.

The present data suggest the existence of a commissural pathway specifically devoted to the crosstalk between the rostral reticular nuclei of the two thalamic sides. The commissural gamma aminobutyric acid (GABA)‐ergic input on the GABAergic neurons of the rostral reticular nucleus could modulate the generation of sleep spindles. The reticuloreticular pathway may, moreover, synchronize the diffuse modulatory effect of the rostral reticular nucleus on nonprimary cortical areas through the bilateral projections of the nucleus to the ventromedial, intralaminar, and anterior thalamic nuclei. © 1994 Wiley‐Liss, Inc.
Differential development of α‐bungarotoxin‐sensitive and α‐bungarotoxin‐insensitive nicotinic acetylcholine receptors in the chick retina
Authors: Hamassaki‐Britto D. E. , Gardino P. F. , Hokoç J. N. , Keyser K. T. , Karten H. J. , Lindstrom J. M. , Britto L. R. G.
Published: January 2005

The development of cells containing neuronal nicotinic receptors (nAChRs) in the chick retina was investigated by means of immunohistochemical techniques with antibodies directed against the α3 and α8 nAQhR subunits. The α3 subunit is one of the major α‐bungarotoxin‐insensitive nicotinic receptor subunits in the chick retina, whereas α8 appears to be the most common α‐bungarotoxin‐sensitive subunit in the same structure. α3‐like immunoreactivity (α3‐LI) was first detected in cells of the vitreal margin, on the embryonic day 4.5 (E4.5). α8‐LI was first detected in the same type of cell almost a day later. However, the processes of α8‐LI cells developed much faster than those of α3‐LI cells, generating visible stained laminae in the prospective inner plexiform, layer as early as E7. α3‐LI was only clearly seen in laminae of the inner plexiform layer by E12. By this date, both α3 and α8‐LI were seen in the same types of cells as in the adult retina, i. e., amacrines, displaced ganglion cells, and cells of the ganglion cell layer for α3‐LI; and amacrines, bipolar cells, and cells of the ganglion cell layer for α8‐LI, These results reveal different patterns of development of cells containing the α3 and α8 nAChR subunits in the chick retina and indicate that those nAChR subunits are expressed in the chick retina before choline acetyltransferase‐positive cells can be detected and well before synaptogenesis. These data also suggest that nAChRs may have a developmental function in the retina. © 1994 Wiley‐Liss, Inc.
Ultrastructural and immunocytochemical characterization of primary afferent terminals in the rat cuneate nucleus
Authors: De Biasi S. , Vitellaro‐Zuccarello L. , Bernardi P. , Valtschanoff J. G. , Weinberg R. J.
Published: January 2005

The cuneate nucleus is a relay center for somatosensory information by receiving tactile and proprioceptive inputs from primary afferent fibers that ascend in the dorsal funiculus. The morphology, synaptic contacts, and neurochemical content of primary afferent terminals in the cuneate nucleus of rats were investigated by combining anterograde transport of horseradish peroxidase conjugated to wheat‐germ agglutinin or to cholera toxin (injected in cervical dorsal root ganglia) with postembedding immunogold labeling for glutamate and GABA. Both tracers gave similar results. Two types of terminals were labeled: type I terminals were irregularly shaped, had a mean area of 4.0 μm2, synapsed on several dendrites, and were contacted by other terminals, some of which were GABA positive. Type II terminals were dome‐shaped, had a mean area of 2.18 μm2, and made synaptic contact on a single dendrite. All the anterogradely labeled terminals (interpreted as endings of primary afferents) were enriched in glutamate but not in GABA. The finding that identified primary afferent terminals are enriched in glutamate with respect to other tissue profiles strongly suggests a neurotransmitter role for glutamate in this afferent pathway to the rat cuneate nucleus. © 1994 Wiley‐Liss, Inc.
Ultrastructural and immunocytochemical analysis of the circuitry of two putative directionally selective ganglion cells in turtle retina
Authors: Guiloff Gloria D. , Kolb Helga
Published: January 2005

Two well‐stained, horseradish peroxidase‐filled varieties of putative ON‐OFF directionally selective ganglion cells, G14a and G15, that project to the dorsolateral optic tectum (Guiloff and Kolb [1992a] Vis. Neurosci. 8:295–313) were studied qualitatively and quantitatively. Both were bistratified ganglion cells with one tier of dendrites; in the OFF sublamina and the other in the ON sublamina of the inner plexiform layer (IPL). The cells were serially sectioned and examined for synaptic inputs by electron microscopy. Portions of the dendritic trees were also analyzed after postembedding immunocytochemistry for neurotransmitter candidates gamma aminobutyric acid (GABA), glycine, choline acetyltransferase (ChAT), and glutamate in presynaptic neurons.

Both G14a and G15 are dominated by amacrine cell inputs and have only minor bipolar cell involvement. Probably at least two different types of bipolar cell are presynaptic. Both ganglion cells receive some GABA‐Positive (GABA+) amacrine inputs and G14a receives ChAT+ amacrine inputs. Glycine+, and glutamate+ inputs could not be detected in either cell. The GABA+ inputs appeared to be regionally arranged in the dendritic trees. The general distribution of amacrine and bipolar inputs to the two tiers of dendrites in both cell types appeared to be asymmetrical, both along the radial extent of the dendritic trees and within the depth of the IPL.

Our data support some aspects of the current models for directional selectivity. We suggest candidate bipolar and amacrine cells that could have input to these ganglion cells. Since many of the putative presynaptic amacrine cells coincide with directionally selective types recorded and stained, by other authors, we propose that in turtle retina directional selectivity arises in neurons presynaptic to the ganglion cells. © 1994 Wiley‐Liss, Inc.
Spinal cord lamina V and lamina VII interneuronal projections to sympathetic preganglionic neurons
Authors: Cabot J. B. , Alessi V. , Carroll J. , Ligorio M.
Published: January 2005

This light and electron microscopic study sought to localize spinal cord interneurons that contribute to the normal and abnormal physiological regulation of spinal sympathetic preganglionic function. Sympathetic preganglionic neurons in caudal C8 through T4 of rat spinal cord were retrogradely labeled with wheat germ agglutinin (WGA) and/or cholera β subunit (CTβ) following injections into the superior cervical ganglion (SCG). With two exceptions, the observed locations of retrogradely VVGA‐ and CTβ‐labeled sympathetic preganglionic neurons were as expected from previous studies. The exceptions were restricted populations of cells in caudal C8 and rostral T1 spinal segments. These neurons were classified as ventrolateral (vlSPN) and ventromedial (vmSPN) sympathetic preganglionic neurons; their somata and dendrites encircled dorsolateral lamina IX motoneurons. Only WGA was transported transneuronally following the retrograde labeling of sympathetic preganglionic neurons. Transneuronally WGA‐labeled spinal interneurons were located principally in the reticulated division of lamina V and dorsolateral lamina VII. A strict segmental organization was observed. All transneuronally labeled interneurons were ipsilateral to, and coextensive with, retrogradely WGA‐labeled sympathetic preganglionic neurons. Electron microscopic observations suggested that retrograde transsynaptic passage of WGA occurred within the sympathetic preganglionic neuropil and showed further that similar classes of organelles were WGA immunoreactive in retrogradely labeled sympathetic preganglionic neurons and in transneuronally labeled lamina V and lamina VII neurons: (1) cisternae and vesicles at the trans face of the Golgi apparatus, (2) large endosomes/dense bodies, and (3) multivesicular bodies. The data are consistent with two hypotheses: (1) Somatic and visceral primary afferent inputs to thoracic spinal cord modify segmental sympathetic preganglionic function through activation of a disynaptic pathway involving lamina V and/or lamina VII interneurons, and (2) long‐loop propriospinal pathways access sympathetic preganglionic neurons through symmetrical, segmental interneuronal circuitry. © 1994 Wiley‐Liss, Inc.
Effects of denervation upon receptor cell survival and basal cell proliferation in tuberous electroreceptor organs of a weakly electric fish
Authors: Weisleder Pedro , Lu Ying , Zakon Harold H.
Published: January 2005

Weakly electric fish generate electric fields for the purposes of electrolocation and communication. These fields are detected by specialized receptor organs: the tuberous organs. In the present study we investigated the effects of denervation upon receptor cell survival and progenitor (basal) cell proliferation rate. The left, infraorbital, anterior lateral line nerve of brown ghosts (Apteronotus leptorhynchus) was sectioned, and the proximal stump was dipped in ricin to prevent regrowth. In groups of four, the animals were given two daily injections of the cell proliferation marker bromodeoxyuridine (BrdU) for 2 days at 1, 2, 3, or 4 weeks following denervation. At the completion of the BrdU injection schedule, a piece of cheek skin, rostroventral to the eye, was removed from the left (denervated) and the right (intact) sides and processed for light microscopy or immunocytochemistry. Our results show: (1) there is progressive receptor cell death and tuberous organ degeneration following denervation; (2) basal cell proliferation increases steadily with time after denervation and tuberous organ degeneration; and (3) despite denervation, some proliferating basal cells differentiate into receptor cells, but these new receptor cells eventually die. These results suggest that innervation is essential for tuberous electroreceptor cell survival and that the rate at which basal cells proliferate is regulated by receptor cell health, locally released factors, or both. © 1994 Wiley‐Liss, Inc.
Organization of projections from the ventromedial nucleus of the hypothalamus: A Phaseolus vulgaris‐Leucoagglutinin study in the rat
Authors: Canteras N. S. , Simerly R. B. , Swanson L. W.
Published: January 2005

The organization of projections from the four parts of the ventromedial nucleus (VMH) and a ventrolaterally adjacent region tentatively identified as the tuberal nucleus (TU) have been analyzed with small injections of the anterograde axonal tracer Phaseolus vulgaris‐leucoagglutinin (PHA‐L). Extrinsic and intranuclear projections of each part of the VMH display clear quantitative differences, whereas the overall patterns of outputs are qualitatively similar. Overall, the VMH establishes massive intrahypothalamic terminal fields in other parts of the medial zone, tending to avoid the periventricular and lateral zones. The ventrolateral VMH is more closely related to other parts of the hypothalamus that also express gonadal steroid hormone receptors, including the medial preoptic, tuberal, and ventral premamillary nuclei, whereas other parts of the VMH are more closely related to the anterior hypothalamic and dorsal premammillary nuclei. All parts of the VMH project to the zona incerta (including the A13 region) and parts of the midline thalamus, including the paraventricular and parataenial nuclei and nucleus reuniens. The densest inputs to the septum are to the bed nuclei of the stria terminalis, where the ventrolateral and central VMH innervate the anteroventral and anterodorsal areas and transverse and interfascicular nuclei, whereas the anterior and dorsomedial VMH innervate the latter two. The central, lateral, and medial amygdalar nuclei receive substantial inputs from various parts of the VMH. Other regions of the telencephalon, including the nucleus accurmbens and the piriform‐amygdaloid, infralimbic, prelimbic, anterior cingulate, agranular insular, piriform, perirhinal, entorhinal, and postpiriform transition areas, also receive sparse inputs. All parts of the VMH send a massive, topographically organized projection to the periaqueductal gray. Other brainstem terminal fields include the superior colliculus, peripeduncular area, locus coeruleus, Barrington's nucleus, parabrachial nucleus, nucleus of the solitary tract, and the mesencephalic, pontine, gigantocellular, paragigantocellular, and parvicellular reticular nuclei.

The projections of the TU are similar to, and a subset of, those from the VMH and are thus not nearly as widespread as those from adjacent parts of the lateral hypothalamic area. Because of these similarities, the TU may eventually come to be viewed most appropriately as the lateral component of the VMH itself. The functional implications of the present findings are discussed in view of evidence that the VMH plays a role in the expression of ingestive, affective, and copulatory behaviors. © 1994 Wiley‐Liss, Inc.
Postnatal development of parvalbumin immunoreactivity in the cerebral cortex of the cat
Authors: Alcántara Soledad , Ferrer Isidro
Published: January 2005

Parvalbumin immunoreactivity in the developing neocortex of the cat progresses following specific laminar, areal, and, in a particular area, roughly anteroposterior gradients. Parvalbumin immunoreactivity first occurs in basket cells and later in chandelier neurons. Pyramid‐like immunoreactive neurons are also transitorily observed from the second to the third week in layer V of the auditory association‐related areas. Parvalbumin‐immunoreactive neurons first appear in the primary somatosensory cortex and primary auditory and visual areas, followed by the primary motor and polysensory association areas and, finally, the auditory association areas and cortical areas related to the limbic system.

In addition to cortical neurons, three fiber systems are immunolabeled with antiparvalbumin antibodies: thalamocortical, callosal, and ipsilateral corticocortical. Parvalbumin‐immunoreactive thalamocortical fibers appear during the first month of postnatal life. Parvalbumin‐immunoreactive callosal and ipsilateral corticocortical fibers are seen from the fourth postnatal week onward. Because all parvalbumin‐immunoreactive cortical neurons in adulthood are nonpyramidal inhibitory cells, the present findings suggest that a number of ipsilateral corticocortical and callosal connections may be inhibitory. © 1994 Wiley‐Liss, Inc.