bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and functional properties distinguish two types of multipolar cells in the ventral cochlear nucleus
Authors: Smith Philip H. , Rhode William S. 
Published: January 2005

AbstractWe distinguish two types of large multipolar cells designated sustained (Cs) and onset (Oc) choppers in the anterior posteroventral cochlear nucleus (A‐PVCN)/nerve root region on the basis of certain anatomical and physiological features. Cs axons head into the trapezoid body, while Oc axons use the intermediate acoustic stria of Held. At the electron microscopic (EM) level, collateral terminals of Oc axons contain pleomorphic vesicles; Cs terminals contain small round vesicles. Cs dendritic trees tend to be distributed in a stellate fashion while Oc dendritic trees tend to be elongated. At the EM level the sustained chopper somata are sparsely innervated while the proximal dendritic tree receives considerably more input. The Oc somata are highly innervated and this heavy innervation continues out onto the proximal dendrites. Distally the dendritic innervation falls off considerably for both categories. Physiologically, members of the Oc population have wider dynamic ranges at the characteristic frequency (CF), wider response areas that are typically not flanked by inhibitory sidebands, and responses to short tones that do not show the same form of regularity expressed by sustained choppers. Intracellularly the sustained choppers exhibit sustained depolarization to short tones for the duration of the stimulus with resultant regular spiking at a rate that is stimulus level dependent. The response to swept tone shows this same level‐dependent regularity. In response to tones, the Oc cells also show a sustained depolarization whose amplitude is stimulus‐level dependent but whose range is much greater and whose onset is initiated more abruptly. Although the onset component of the Oc spike output is reliably initiated by these levels of depolarization, regular firing to the sustained depolarization is not initiated at levels of depolarization that would surely generate regular firing in sustained choppers. This regularity is also absent in the swept tone response despite marked levels of excitation.
Axonal redirection at the dorsoventral intraretinal boundary
Authors: Springer Alan D. , Morel Kimberly D. , Grobman Steven L. , Wilson Bryan R. 
Published: January 2005

AbstractCobaltous‐lysine applied to the goldfish optic nerve backfilled retinal ganglion cells and their axons. Confined to the ventronasal and ventrotemporal retina was a small population of retinal ganglion cells whose axons traveled dorsally and parallel to the retinal margin. On reaching the boundary between dorsal and ventral retina, the axons arched, joined radially oriented bundles of axons, and traveled toward the optic disk. Control studies showed that the axons came from retinal ganglion cells rather than from retinopetal cells. The somatic area of retinal ganglion cells (RGCs) with circumferential axons was 30–50 μm, and was similar to that of average ganglion cells. The axons of these cells coursed between the optic fiber and ganglion cell layers or between the ganglion cell and inner plexiform layers. Many somata were displaced slightly toward the inner plexiform layer, but were not really displaced ganglion cells. The aberrant axonal trajectory may be related to the slightly displaced location of the cell. However, ganglion cells that are displaced to the edge of the inner nuclear layer usually have radially coursing axons.We digitized the coordinates of the bending points and the dorsoventral retinal boundary. On average, the bending points occurred within 100 μm of the dorsoventral retinal border. These findings suggest that some molecular, rather than mechanical, factor at the dorsoventral retinal boundary alters the course of the circumferential axons. Furthermore, because there are cells with circumferential axons throughout the ventral retina, the data imply that at least ventral RGC axons avoid mingling with the axons from dorsal RGCs.
Pathfinding and target selection of goldfish retinal axons regenerating under TTX‐induced impulse blockade
Authors: Hartlieb Elke , Stuermer Claudia A. O. 
Published: January 2005

AbstractTo define the extent to which impulse blockade interferes with the morphological changes of regenerating retinal axons during their growth through the tectum, axons were deprived of activity by repeated intraocular injections of TTX. At intervals between 24 and 189 days after optic nerve section (ONS), a defined group of TTX‐silenced axons and of axons with normal activity (controls) were labeled by applications of HRP to the ventro‐ or dorsotemporal retina. The trajectories of these labeled axons were traced in DAB processed tectal wholemounts.As in controls, TTX‐blocked axons went through a phase of exploratory growth at early regeneration stages (24 to 80 days after ONS). Coursing in abnormal routes, the axons initially distributed their growing endings widely over the tectum. Axons with and without activity extended side branches with growth cones and filopodia over all regions of the tectum. These ramifications were of similar dimensions for the TTX‐blocked and control axons. Despite abnormal routes and branching over inappropriate territories, axons showed a preference for the rostral tectum. At late regeneration stages (120–189 days after ONS), axons had lost their side branches and their growth cones. Their preterminal segments exhibited striking bends, suggesting that they had undergone course corrections to achieve access to the retinotopic target. Axonal processes had disappeared from the caudal tectum, and the preferential accumulation of axons over the rostral tectum had increased. The majority of the TTX‐blocked and control axons ended in terminal arbors at retinotopic regions. The labeled arbors of the TTX‐group were no larger than those of the control group. The arbors of each group lay close together in a continuous cluster in the TTX‐group as well as in two‐thirds of the control group. In the other one‐third of the control group, however, terminal arbors were aggregated into separate patches. The clusters of the TTX‐blocked axons covered between 2.2 and 3.9% (mean 2.95%) of the tectal surface and the clusters and/or patches of active axons between 1.9 and 3.4% (mean 2.7%). Thus the terminal arbor clusters of the TTX‐silenced axons were not significantly larger than those of the active axons.These data show that retinal ganglion cell impulse activity is required for neither the extension of side branches in the early exploratory phase of regeneration nor for the withdrawal of these branches nor for the establishment of target‐directed routes and the deployment of normal‐size terminal arbors at retinotopic loci. Our data further suggest that the retinotopic map is refined considerably with time even in the absence of activity, a finding that is consistent with an abstract by Olsson and Meyer ('87).
Early expression of acetylcholinesterase activity in functionally distinct neurons of the zebrafish
Authors: Hanneman Eric , Westerfield Monte 
Published: January 2005

AbstractThe first expression and distribution of acetylcholinesterase (AChE) activity was studied among a distinct population of early neurons in embryonic zebrafish by using histochemical and retrograde labeling techniques. AChE first appeared in the nervous system in the primary motoneurons of the rostral spinal cord when the embryo had nine somites, approximately 14 hours postfertilization. Subsequent expression of AChE activity in the spinal cord proceeded in a rostral‐to‐caudal sequence. Cranial neurons expressed AChE activity shortly after it appeared in the rostral spinal cord. Several hours later, near the end of the first day, primary neurons in the hindbrain and spinal cord all contained AChE, including sensory neurons, reticulospinal interneurons, and primary motoneurons. AChE activity was also detected in the nucleus of the medial longitudinal fasciculus. Presumptive cranial ganglia transiently expressed AChE activity between 14 and 24 hours of development. These results, combined with previous observations that examined the time of origin and axogenesis of primary neurons, suggest that primary neurons in the embryonic zebrafish contain AChE before they sprout axons. The primary neurons appear to follow a common sequence of development consisting of a withdrawal from the cell division cycle, the expression of AChE, and axogenesis. Although this sequence is followed by all primary neurons, lack of a rostral‐to‐caudal sequence in the time of birth and variability in the time of axon outgrowth demonstrate that the relative timing of these three events is not rigidly programmed in individual neurons. Moreover, the very early expression of AChE in such diverse cell types suggests that it may have a developmental role in addition to its function in transmitter metabolism.
Duration of retinogenesis: Its relationship to retinal organization in two cricetine rodents
Authors: Wikler Kenneth C. , Perez G. , Finlay B. L. 
Published: January 2005

AbstractThe Mongolian gerbil (Meriones unguiculatus) has a prolonged period of development relative to other muroid rodents. We have explored the consequences of this relatively long period of maturation on retinal cell number and topography by comparing the duration and topography of neurogenesis in the gerbil retina with that of a closely related species which develops rapidly, the Syrian hamster (Mesocricetus auratus) (Sengelaub et al.: J. Comp. Neurol. 246:527–543, 1986). An analysis of thymidine‐labeled retinas indicate that cells destined for the gerbil retinal ganglion cell layer are generated for at least 12 embryonic days, twice the duration in the hamster. The period of cell loss in the gerbil retinal ganglion cell layer extends for at least 14 postnatal days, more than twice as long as in the hamster. The gerbil retina is generated in a center‐to‐periphery gradient for both retinal ganglion cells and displaced amacrine cells, while no such gradients are evident in the hamster retina. We conclude that the longer developmental period of the gerbil is associated with (1) a longer period of neurogenesis resulting in greater retinal cell number, (2) the expression of spatial gradients in neurogenesis, and (3) a larger eye at maturity. The last two factors, in part, may be related to the development of a highly differentiated area centralis and visual streak in the retina of this rodent.Unrelated to duration of growth, early differences in retinal shape between these two species contributes to the development of retinal topography. The gerbil, but not the hamster retina, is initially asymmetric, longer in its nasotemporal than its dorsoventral dimension. The gerbil retina then grows asymmetrically producing a spherical retina, and coincident in time, a nasotemporally extended visual streak.
Type B monoamine‐oxidase‐containing cells and fibers in the cat hypothalamus demonstrated by an improved enzyme histochemical method
Authors: Kitahama Kunio , Sallanon Marcelle , Lin Jian‐Sheng , Maeda Toshihiro , Jouvet Michel 
Published: January 2005

AbstractThe present study, using a diaminobenzidine (DAB)‐coupled peroxidation method, examined the distribution and morphological characteristics of neuronal structures containing type B monoamine oxidase (MAO‐B) in the cat hypothalamus. Large and intensely stained, distinctive MAO‐B‐positive cells, multipolar and with long dendritic arbors, were principally distributed in the ventral hypothalamus extending from A7 to A12.5 of the Horsley‐Clarke plane. These cells were located caudally in the ventral surface of the brain including the tuberomamillary nucleus (TM) and the region surrounding the mamillary nuclei. Rostrally, they were aggregated in the area surrounding the fornix, particularly in the lateral perifornical region, and dispersed in the anterior mamillary nucleus, lateral hypothalamic area (HLA), and the medial tip of the entopeduncular nucleus. The most rostral positive cell group was identified in a narrow space between the optic tract and the entopeduncular nucleus at the A12.5 level.In addition to these large cells, the present study disclosed the presence of “small” to “very small” MAO‐B‐positive cells in the area surrounding the mamillary recess and the lateral part of the caudal arcuate nucleus.Distinct MAO‐B‐stained fibers were identified in all regions of the hypothalamus. A large number of thick labeled fibers were observed in the ventral hypothalamus including the TM and premamillary nucleus and posterior and lateral hypothalamic areas. A dense network of MAO‐B‐positive terminal‐like fibers was observed in the dorsomedial nucleus where very small labeled cells were scattered. Many intensely stained thick and straight fibers were seen running ventrolaterally in the anterior part of the HLA and in the narrow space between the entopeduncular nucleus and optic tract. In the area of the tuber cinereum and the ventral part of the HLA, there were many positive fibers cut transversely, possibly projecting to the more anterior parts of the brain such as the diagonal band of Broca or septal nuclei.
Biochemical and immunocytochemical charaterization of olfactory marker protein in the rodent central nervous system
Authors: Baker Harriet , Grillo Mary , Margolis Frank L. 
Published: January 2005

AbstractOlfactory marker protein (OMP), previously thought to be expressed only by olfactory receptor neurons and their processes, was localized anatomically with immunocytochemical techniques to a number of brain regions in three rodent species, the mouse, rat, and hamster. In addition, the amount of antigen was quantified by radioimmunoassay (RIA) and characterized by an immunoblot procedure. In all three species the antigen could be detected immunocytochemically in the preoptic region and hypothalamus. The rat did not exhibit immunostaining in any other brain region. However, in the mouse neuronal labelling was observed throughout the neural axis, including cellular labelling in the bed nucleus of the anterior commissure, the median preoptic nucleus, the bed nucleus of the stria terminalis, the periventricular region, the anterior parvicellular subnucleus of the paraventricular nucleus, around the dorsomedial hypothalamic nucleus (pars compacta), the subincertal region, the arcuate nucleus, the anterior cortical nucleus of the amygdala, the suprageniculate nucleus, the lateral lemniscal nuclei, the lateraldorsal and lateralventral central gray, the posterior aspects of the commissural and marginal nuclei of the inferior colliculus, the paragenule nucleus, the A‐5 region, the area postrema, the ventromedial nucleus of the solitary tract, area X, the spinal trigeminal nucleus (pars zonale), and superficial laminae of the spinal cord. The hamster displayed a different pattern of labelling including cells in the periventricular gray, the pontine reticular tegmental nucleus, the A‐5 region, the medial vestibular complex, the prepositus hypoglossal nucleus, the parvicellular reticular nucleus, the lateral paragigantocellular nucleus, the raphe obscuras, the lateral reticular nucleus, and the lateral nucleus of the cerebellum. Immunostaining was seen in fibers within the red nucleus and within mossy fibers of the cerebellum. OMP levels could only be quantified by radioimmunoassay in the olfactory bulb of the three species and in the hamster cerebellum where they were 1/1,000 of those determined in the olfactory bulb. The authenticity of OMP measured in the RIA and detected immunocytochemically was verified by a double‐antibody immunoisolation/immunodetection procedure, which confirmed that the antigen being visualized had the molecular properties expected for OMP. In summary, these experiments demonstrate that authentic OMP exists in small groups of neurons in many areas of the central nervous system.
Comparative study of neuronal and glial gap‐junctions in crayfish nerve cords
Authors: Bosch Elizabeth 
Published: January 2005

AbstractElectrical synapses (neuronal gap‐junctions) and glial gap‐junctions were compared by using thin sectioning, freeze fracturing, and negative staining techniques. Neuronal and glial gap‐junctions differed in the length of the extracellular domains of the channels, in the presence of a cytoskeleton associated to neuronal gap‐junctions, and in their unit cell dimenstions. The difference in length of the channels and the fact that both glial and neuronal gap‐junctions had the same particle diameter suggest that the proteins forming glial and neuronal gap‐junctions might have different molecular weights.The cytoskeleton associated to neuronal gap‐junctions consisted of a beaded layer of densities located parallel to the membrane in the synaptic regions. Synaptic vesicles associated to neuronal gap‐junctions were attached to this cytoskeleton, which was in turn anchored to the synptic membrane through densities about 20 nm apart, a spacing similar to the neuronal unit cell dimension. These results suggest that the cytoskeleton might be responsible for the association of vesicles to neuronal gap‐junctions and for maintaining the crystalline appearance of neuronal gap‐junctions in situ.
Ultrastructural and neurochemical analysis of synaptic input to trigemino‐thalamic projection neurones in lamina I of the rat: A combined immunocytochemical and retrograde labelling study
Authors: Priestley John V. , Cuello A. Claudio 
Published: January 2005

AbstractThe synaptology of lamina I thalamic projection neurones in the spinal trigeminal nucleus of the rat was investigated by combining electron microscopic immunocytochemistry with the retrograde transport of horseradish peroxidase. Fifteen retrogradely labelled neurones were serially sectioned and their dendrites were traced for up to 160 μm in order to characterise the synaptic input to their cell bodies and proximal dendrites.Projection neurones receive synapses from dome‐shaped substance P and enkephalin immunoreactive terminals, which make simple axosomatic or axodendritic synapses. In addition, the cells receive synapses from numerous nonimmunoreactive terminals including a wide range of different domeshaped terminals and various scalloped or glomerular terminals. Domeshaped terminals synapse with small stubby spines in addition to cell bodies or dendritic shafts and they are probably derived from lamina II interneurones and from descending bulbospinal pathways. Glomerular terminals occur in two main classes: small type A terminals with dark axoplasm and larger type B terminals. Type B terminals participate in synaptic triads in which a peripheral terminal synapses both axoaxonically with the glomerular terminal and axodendritically with the projection neurone. Type A and type B terminals closely resemble the central terminals of spinal cord lamina II glomeruli and are probably derived from C and Aδ I° afferent fibers.The results indicate that lamina I projection neurones are under pre‐ and postsynaptic control from diverse sources. Their complex synaptic organisation highlights the key role that such cells play in the rostrad transmission of somatosensory information.
Connections of primary auditory cortex in the new world monkey, Saguinus
Authors: Luethke L. E. , Krubitzer L. A. , Kaas J. H. 
Published: January 2005

AbstractConnections of primary auditory cortex (A‐I) were investigated in the tamarin (Saguinus fuscicollis), a New World monkey. In each case, A‐I was defined by multiunit recordings, and best frequencies were determined for neurons at different recording sites. Microlesions were placed to mark recording sites for correlation with cortical architecture. Following mapping, separate injections of up to three different tracers (HRP‐WGA and fluorescent dyes) were placed into the representations of different frequencies within A‐I. The results support several conclusions: (1) high to low frequencies are represented in a dorsocaudal to ventrorostral sequence in A‐I, (2) intrinsic connections in A‐I are more pronounced along isofrequency contours, (3) the pattern of connections between A‐I and adjoining cortex suggests that this surrounding auditory cortex contains at least two tonotopically organized fields and possibly one or more additional auditory fields, (4) callosal connections of A‐I are largely between parts of A‐I matched for frequency representation, (5) thalamic connections of A‐I include topographic connections with the ventral division of the medial geniculate complex (MGv) and more diffuse connections with the medial (MGm) and dorsal (MGd) divisions of the medial geniculate complex and the suprageniculate nucleus (Sg), and (6) A‐I projects bilaterally to the dorsal cortex of the inferior colliculus.
Transient GABA immunoreactivity in cranial nerves of the chick embryo
Authors: von Bartheld Christopher S. , Rubel Edwin W. 
Published: January 2005

AbstractThe distribution and time course of γ‐aminobutyric acid (GABA) immunoreactivity was investigated in the cranium of the chick embryo from 2 to 16 days of incubation (E2–16). A fraction of nerve fibers transiently stains GABA‐positive in all cranial motor nerves and in the vestibular nerve. Cranial motor nerves stain GABA‐positive from E4 to E11, including neuromuscular junctions at E8–11; labeled fibers are most frequent in the motor trigeminal root (E6–9.5). Substantial GABA staining is present from E4 to E10 in a subpopulation (1–2%) of vestibular ganglion cells. Their peripheral processes are labeled in the vestibular endorgan, predominantly in the posterior crista. Some GABA‐positive fibers are present in the olfactory nerve (after E5) and in the optic nerve (after E9.5); their immunoreactivity persists throughout the period investigated. Transient GABA immunoreactivity follows “pioneer” fiber outgrowth and coincides with the formation of early synaptic contacts.GABA‐containing neurons may change their neuronal phenotype (loss of GABA expression) or they may be eliminated by embryological cell death. Periods of cell death were determined in cranial ganglia and motor nuclei by aggregations of pycnotic cells in the same embryonic material. The periods of embryonic cell death partly coincide with transient GABA immunoreactivity. The function(s) of transient GABA expression is unknown. Some lines of evidence suggest that GABA has neurotrophic functions in developing cranial nerves or their target tissue. In the developing neuromuscular junction, GABA may be involved in the regulation of acetylcholine receptors.