bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology and cellular interactions of growth cones in the developing corpus callosum
Authors: Norris Carolyn R. , Kalil Katherine 
Published: January 2005

AbstractPrevious studies of growth cones in invertebrates have shown that they become larger and more complex when changing direction in response to cellspecific contacts (Bentley and Caudy, '83; Raper et al., '83b; Caudy and Bentley, '86). In pathways of the vertebrate nervous system, analogous regions, termed “decision regions,” have been identified in which axons change direction and their growth cones become more elaborate than when tracking along straight trajectories (Tosney and Landmesser, '85a; Bovolenta and Mason, '87). In order to assess the generality of these principles to the mammalian CNS, we studied the morphology of growth cones and their interactions with the environment in the developing corpus callosum. Given the straight pathway that callosal axons could use to navigate across the callosum, one might predict that later arriving axons would extend on those growing out earlier and that therefore, by analogy with previous studies, many growth cones would have simple tapered morphologies. Surprisingly, however, virtually all growth cones in the callosal white matter, regardless of age or position, were complex with broad lamellipodial veils and/or numerous, often lengthy filopodia. Only growth cones entering the cortical target were consistently smaller. As seen in the EM, the predominant elements in the callosal pathway are other axons and growth cones; we found no evidence for specialized contacts. These results suggest that there is no specific decision region for the fiber population as a whole; rather it is possible that in this mammalian CNS pathway individual growth cones respond independently to molecular cues broadly distributed in the callosum.
Candidate cell populations for respiratory chemosensitive fields in the human infant medulla
Authors: Filiano James J. , Choi John C. , Kinney Hannah C. 
Published: January 2005

AbstractThe histology and location of human respiratory chemosensitive fields are not known. In contrast, the physiology of respiratory chemosensory areas in the ventral medulla of cats has been studied extensively, and their anatomy has been partially described. Using basic principles of comparative cytoarchitecture and computer‐aided reconstructions of serial‐sectioned medullae, we describe the histology and three‐dimensional distribution of putative respiratory chemosensors in the feline and human infant medulla. We found that ventrolateral neurons of the human nucleus conterminalis are homologous to neurons identified in the feline L chemosensitive field by Trouth and others, and that ventrolaterally situated neurons in the human arcuate nucleus correspond to neurons predominating in the feline S and M fields. In addition, there are foci of thickened marginal glia along the feline ventral medullary surface that colocalize with chemosensitive fields identified by physiologic studies reported by others; we identify similar foci in the infant medulla. Thickened marginal glia are intermixed with neuronal fibers, often adjacent to neurons of the feline chemosensitive fields and their human counterparts, suggesting that they constitute a chemosensory neuropil at the medullary surface. Computer‐aided reconstructions provide insight into the three‐dimensional topography of putative respiratory chemosensors and their relationships to other brainstem structures in ways not obvious in single or even multiple sections. This delineation of candidate human respiratory chemosensors is a first step toward their postmortem analysis in patients with central ventilatory control disorders where finding histological abnormalities in these sites would support their role in human ventilation.
Interspecific variation in the projection of primary afferents onto the electrosensory lateral line lobe of weakly electric teleosts: Different solutions to the same mapping problem
Authors: Lannoo Michael J. , Maler Leonard 
Published: January 2005

AbstractWe demonstrate that preterminal axons composing the primary afferent projection onto the four somatotopically organized electrosensory lateral line lobe (ELL) segments in weakly electric gymnotiform teleosts course in fundamentally different directions in the most commonly studied species. Afferents enter the deep fiber layer (dfl) of the ELL and course in variable, but speciesspecific, directions within a horizontal plane before turning dorsally to terminate within the deep neuropil layer of the ELL (dnl). Among the species considered here, apteronotids exhibit the tightest projection pattern. Afferents enter the rostral ELL from the anterior lateral line nerve ganglion (ALLNG) in a nonsomatotopic fashion. As they course horizontally, these fibers undergo a rostrocaudal somatotopic sorting along the ventrolateral border of the dfl, then turn within a horizontal plane to course medially across the ELL segments. These medially coursing horizontal fibers are sorted: they form sublaminae according to the nerve branch containing their peripheral axon. Horizontal axons then turn dorsally, form fascicles, and terminate within the dnl. Within the dorsal fascicles, axons run directly into the dnl with little deviation, and their terminal fields exhibit no appreciable spread.In sternopygids, dfl horizontal fibers course in directions orthogonal to those in apteronotids. Fibers enter the rostral ELL and course medially across segments before turning caudally within segments. Unlike apteronotids, sternopygid horizontal fibers do not sort tightly by nerve branch. As horizontal axons turn dorsally they also form tight fascicles. But rather than terminating directly and without spreading, as in apteronotids, sternopgid fibers disperse from these fascicles and become sorted horizontally a second time prior to terminating in the dnl. Gymnotids show a third pattern: their primary afferents course into the rostral ELL without an obvious organization, they form no tight laminae of horizontal fibers and no fascicles of dorsal fibers. Unlike the other gymnotiforms examined, afferents coursing to the gymnotid MS can take one of two routes, ventrally through the dfl in the manner of all other gymnotiforms, or, uniquely, dorsally through the plexiform layer of the ELL (pl), which is typically the location of ELL efferents. These afferents then turn ventrally to terminate.Variations in axonal trajectories do not appear to reflect major functional differences in the processing of electrosensory information, but instead may reflect the phylogenetic relationships of the developmental processes involved in guiding axons. We propose a simple model for the development of these different trajectories based on the assumption that among species similar guidance cues are expressed at different times as the projection develops.
Substance P‐, FMRFamide‐, and gastrin/cholecystokinin‐like immunoreactive neurons in the thoraco‐abdominal ganglia of the flies Drosophila and Calliphora
Authors: Lundquist Tomas , Nässel Dick R. 
Published: January 2005

AbstractImmunocytochemical analysis of the thoraco‐abdominal ganglia of the flies Drosophila melanogaster and Calliphora vomitoria revealed neurons displaying substance P‐ (SPLI), FMRFamide‐(FLI), and cholecystokinin‐like (CCKLI) immunoreactivity. It could be demonstrated that a number of neurons contain peptides reacting with antisera against all the three types of substances, others were either FLI or CCKLI alone. No neurons displayed only SPLI. Instead, the total number (about 30) of SPLI neurons constitute a subpopulation of the FLI/CCKLI neurons. Many of the identifiable immunoreactive neurons seem to be homologous in the two fly species. One set of six large neurons, termed ventral thoracic neurosecretory neurons (VTNCs), are among those that are SPLI, FLI, and CCKLI in both Drosophila and Calliphora. With the present immunocytochemical technique, the detailed morphology of the VTNCs could be resolved. These neurosecretory neurons supply the entire dorsal neural sheath of the thoraco‐abdominal ganglia with terminals, thus forming an extensive neurohaemal area. The VTNCs also have processes connecting the thoracic neuromeres to the cephalic suboesophageal ganglion, as well as extensive arborizations in the thoracic ganglia, suggesting an important role in integrating and/or regulating large portions of the central nervous system, in addition to their neurosecretory function. Most of the other SPLI, FLI, and CCKLI neurons in the thoraco‐abdominal ganglia seem to be interneurons. However, there are four FLI neurons that appear to be efferents innervating the hindgut and a few abdominal FLI and CCKLI neurons may be additional neurosecretory cells. From the present study it appears as if neuropeptides related to substance P, FMRFamide and CCK have roles as neurotransmitters/neuromodulators and circulating neurohormones in Drosophila and Calliphora.
Dendritic bundling in layer I of granular retrosplenial cortex: Intracellular labeling and selectivity of innervation
Authors: Michael J. Wyss , Van Groen Thomas , Sripanidkulchai Kittisak 
Published: January 2005

AbstractThe extrinsic projections to and from the retrosplenial cortex have been studied in detail, but the intrinsic circuitry within this region has been characterized less completely. To further define the internal connections, small injections of the retrograde, fluorescent tracer Fluorogold were made into the retrosplenial cortex of the rat. These injections label neurons in layers II‐V of the contralateral homotopic cortex. In layers III‐V, the labeled neurons are present over an area much larger than the injection site, but in layer II neurons are labeled in a very precise homotopic pattern. Following these injections, only the neurons in layer II display heavily labeled apical dendrites, and these labeled dendrites form tight bundles in layer Ic and Ib of the cortex and spread out in layer Ia. An examination of Golgi‐stained material demonstrates that most of the neurons in layer II are small pyramidal cells with 2–3 small basal dendrites and a single, large apical dendrite that arborizes extensively in layer Ia. To verify the structure of the layer II neurons, they were intracellularly filled with Lucifer yellow. Examination of these labeled cells confirms the observations from the Golgi‐stained material and demonstrates that many apical dendrites of the layer II cells angle acutely, apparently to join a bundle and/or avoid an interbundle space. Tract tracing experiments demonstrate that the anteroventral nucleus of the thalamus appears to project selectively to the region containing the dendritic bundles, whereas intracortical projections appear to terminate in layers Ib and Ic in the 30–200 μm spaces between the bundles. Furthermore, the areas containing the bundles display dense AChE staining, but the interbundle spaces are almost free of AChE staining. These findings demonstrate a form of dendritic bundling that is input and output specific and may play an important role in the regulation of thalamic inputs to the cingulate cortex.
Immunolocalization and quantitation of a novel nerve terminal protein in spinal cord development
Authors: Cabalka L. M. , Ritchie T. C. , Coulter J. D. 
Published: January 2005

AbstractIn the adult spinal cord, the neuron‐specific protein NT75 is located in nerve terminals synapsing in the superficial laminae of the dorsal horn. The present study examines the occurrence of NT75 in the developing rat spinal cord. NT75 immunoreactivity is detectable in primary afferent axons at the dorsal root entry zone on embryonic day 15. Subsequently, staining of presumptive nerve terminals appears in the deeper laminae of the dorsal horn, expanding into the superficial laminae during the first postnatal week. NT75 staining also appears in developing corticospinal tract axons in the brainstem at birth, and at lumbosacral levels by postnatal day 5. As NT75‐positive nerve terminals approach the adult distribution, staining of primary afferent and corticospinal axons decreases, becoming undetectable by postnatal day 30. Dense transient staining of presumed nerve terminals in the ventral horn is also apparent during early postnatal development. Quantitative analysis of developing spinal cord shows a low level of NT75 immunoreactivity at birth. NT75 activity then increases substantially, reaching values by the third and fourth postnatal weeks up to 2.5 times that seen in adults. The occurrence of NT75 immunoreactivity correlates with the reported time course of synaptic development in the spinal cord. In addition, the results suggest that NT75 immunoreactivity is maintained at high levels in the nerve terminals of certain neural pathways into adulthood, whereas in other systems NT75 immunoreactivity may be detectable only during development.
Central projections of cochlear nerve fibers in the alligator lizard
Authors: Szpir M. R. , Sento S. , Ryugo D. K. 
Published: January 2005

AbstractThe auditory (cochlear) ganglion cells of the alligator lizard (Gerrhonotus multicarinatus) give rise to two types of peripheral fibers: tectorial fibers, which contact hair cells covered by a tectoria membrane, and free‐standing fibers, which contact hair cells without a tectorial membrane. To determine the central projections of these fibers, we applied intracellular and extracellular injections of horseradish peroxidase (HRP) to the peripheral component of the cochlear nerve. After histological processing with diaminobenzidine, individual cochlear nerve fibers could be traced through serial sections with the aid of a light microscope and drawing tube. The projection patterns formed two morphologically distinct groups. Neurons whose peripheral processes contacted tectorial hair cells in the cochlea projected to three divisions of the cochlear nucleus: nucleus magnocellularis lateralis (NML), nucleus magnocellularis medialis (NMM), and nucleus angularis lateralis (NAL). Neurons whose peripheral processes contacted freestanding hair cells projected primarily to the nucleus angularis medialis (NAM), although some also sent a single, thin branch to the NML; these neurons never projected to NAL or NMM. Morphometric comparisons of tectorial and free‐standing fibers demonstrate that tectorial fibers have a larger axonal diameter, form a greater number of terminal swellings, and make proportionally more somatic contacts. By correlating the morphologically defined groups with previously reported physiologically defined groups, we conclude that different divisions of the cochlear nucleus are associated with separate frequency ranges and that stimuli in the different frequency ranges may be orocessed separately in the brain.
Radial glia and astrocytes in developing and adult telencephalon of the lizard Gallotia galloti as revealed by immunohistochemistry with anti‐GFAP and anti‐vimentin antibodies
Authors: Yanes C. , Monzon‐Mayor M. , Ghandour M. S. , De Barry J. , Gombos G. 
Published: January 2005

AbstractThe development of radial glia and astrocytes in the telencephalon of the lizard Gallotia galloti was studied by immunohistochemistry with anti‐vimentin and anti‐GFAP antibodies.Vimentin appears at embryonic stage 32 (E32) in the proliferative zone of the lateral ventricle and subpial end‐feet in the marginal zone. At E34‐35 the staining intensity for vimentin in all radial glia is maximal. It then decreases and disappears in most structures in adult animals.GFAP appears at E35 in the end‐feet in the marginal zone and its intensity increases until adulthood, particularly in radial and sinuous fibers and in fibers that originate from the sulci and invade the ventral striatum and the septum. In contrast, the reaction is weak in the cortex, in the anterior dorso‐ventricular ridge, and in the amygdala nuclei.Radial glia is still present in the adult, and the composition of its intermediate filaments changes during development from vimentin to GFAP.No GFA‐positive cell bodies except those of ependymal glia were deceted in telencephalon.
Neonatal capsaicin treatment induces invasion of the substantia gelatinosa by the terminal arborizations of hair follicle afferents in the rat dorsal horn
Authors: Shortland Peter , Molander Carl , Woolf Clifford J. , Fitzgerald Maria 
Published: January 2005

AbstractCapsaicin, administered on the day of birth, was found to alter laminar distribution, but not the receptive field properties or the morphology of the collateral arborizations of hair follicle afferents (HFAs) intra‐axonally injected with horseradish peroxidase (HRP). Of the 65 HFA terminal arbors in capsaicin treated rats, 46 (71 %) were found to enter the substantia gelatinosa (in control rats, 44/165, 27%). All of the collaterals projected to somatotopically normal areas of cord. Dorsal horn shrinkage (21%), as estimated by planimetric measurements of Nissl and acetylcholinesterase‐stained material, was only a partial explanation of this result. This idea was supported by the statistically significant increase (27%, P < 0.05) in the absolute dorsoventral length of collaterals.The results show that the destruction of unmyelinated fibres during the early postnatal period by capsaicin induces HFA invasion into the area that C fibres normally occupy. This invasion suggests that the laminar termination sites for different primary afferent fibres are not altogether specified and that intact neonatal primary afferents have the capacity to sprout into denervated regions of spinal cord.
GABA and tyrosine hydroxylase immunocytochemistry reveal different patterns of colocalization in retinal neurons of various vertebrates
Authors: Wulle I. , Wagner H.‐J. 
Published: January 2005

AbstractColocalization of GABA‐ and tyrosine hydroxylase‐like immunoreactivity was studied in the retinae of various vertebrate species in order to ascertain whether the presumed coexistence of GABA and dopamine, reported earlier for mammals (Kosaka et al.: Exp. Brain Res. 66:191–210, '87; Wässle and Chun: J. Neurosci. 8:3383–3394, '88) is a common phenomenon. GABA‐immunopositive cells constituted a separate population from tyrosine hydroxylase‐positive cells in fish and amphibians, whilst in higher–i.e., amniote–vertebrates, such as reptiles, birds, and mammals, all dopaminergic cells contained GABA‐like immunoreactivity. No clear correlation was found between the type of dopaminergic cell (amacrine/interplexiform) and the presence or absence of colocalization.
Expression of C‐fos‐like protein as a marker for neuronal activity following noxious stimulation in the rat
Authors: Bullitt Elizabeth 
Published: January 2005

AbstractC‐fos is a proto‐oncogene that is expressed within some neurons following depolarization. The protein product, c‐fos protein, can be identified by immunohistochemical techniques. Therefore, c‐fos expression might be used as a marker for neuronal activity throughout the neuraxis following peripheral stimulation. This study has analyzed patterns of c‐fos expression in both control and anesthetized animals and in anesthetized rats subjected to various forms of peripheral stimulation. Labeled cells were counted in the spinal cord, brainstem, hypothalamus, and thalamus. Little c‐fos immunoreactivity was found in control animals. Prolonged inhalational anesthesia increased the number of labeled cells at several brainstem sites. Noxious stimulation of anesthetized rats induced c‐fos within the neuraxis in patterns consistent with data obtained from electrophysiological studies and in additional locations for which few direct electrophysiological data are available, such as the ventrolateral medulla, the posterior hypothalamic nucleus, and the reuniens and paraventricular thalamic nuclei. Gentle mechanical stimulation was ineffective in inducing c‐fos‐like protein. The data suggest that c‐fos can be used as a transynaptic marker for neuronal activity following noxious stimulation. However, c‐fos is expressed only in some kinds of neurons following peripheral stimulation, and it therefore may be an incomplete marker for nociresponsive activity. In addition, at least a few neurons express c‐fos protein in the absence of noxious stimulation. Experiments analyzing c‐fos expression must be designed with care, as both extraneous stimuli and anesthetic depth influence the results.
Migration of neuroblasts by perikaryal translocation: Role of cellular elongation and axonal outgrowth in the acoustic nuclei of the chick embryo medulla
Authors: Book Kathryn J. , Morest D. Kent 
Published: January 2005

AbstractThe neuroblasts forming nucleus magnocellularis, the avian homologue of the mammalian ventral cochlear nucleus, migrate by growth and elongation of their leading processes and by perikaryal translocation through these processes from the matrix zone of the rhombic lip to the acoustico‐vestibular anlage. Golgi methods were used on staged chick embryos to reconstruct the morphogenetic phases of migration and early differentiation in situ. Fluorescence labeling of the living cells in vitro elucidated the role of axonal growth in the migratory process.In situ, branching cochlear nerve fibers, tipped with growth cones, enter the acoustico‐vestibular anlage at E4.5–5.5 before migration of the magnocellularis neuroblasts at E.5.5–6.5. The premigratory neuroblasts in the matrix zone of the rhombic lip resemble primitive epithelial cells, which extend branched, curving processes into a characteristic formation, the rhombic whorl. The leading process of the migrating magnocellularis neuroblasts gives rise to a bifurcating axon at the interface between the matrix and mantle zones. The lateral branch becomes the recurrent ipsilateral collateral; the medial branch crosses the midline, heading toward the contralateral target site in the region of the presumptive nucleus laminaris. The cell bodies of the migratory neuroblasts appear in intermediate locations along the migration route as they translocate radially through their leading processes past the axonal bifurcation and then tangentially and obliquely into the mantle zone. Neuroblasts destined for nucleus laminaris migrate coincidentally with magnocellularis neuroblasts. Nucleus angularis neuroblasts migrate later in development, after E6.5.In vitro, injections of a nontoxic fluorescent dye (diI) were made into explants of the medulla in the region of the contralateral target area at the time of neuroblast migration. DiI retrogradely labeled the cell bodies of premigratory magnocellularis neuroblasts in the matrix zone and of migratory neuroblasts in the mantle zone through their medial, crossing axonal branches. The morphology of the living neuroblasts in the explants resembled that in the Golgi impregnations at the corresponding stages of migration. Anterograde axonal transport also occurred.These results demonstrate migration by perikaryal translocation and early axon extension of a specific group of neuroblasts in the central nervous system. The morphology of the migrating neuroblasts is such that a simple radial arrangement of cellular guides, glial or otherwise, would not account for their configurations. The available evidence supports the proposition that cellular elongation and perikaryal translocation constitute the general mode of neuronal migration in the central nervous system. The early extension of axons into their target sites may play a critical role in migration and early development of specific types of neurons.