bluuebunny/crossref_metadata_2025_split huggingface dataset:
Axonal projections and synaptogenesis by supraspinal descending neurons in the spinal cord of the chick embryo
Authors: Shiga Takashi , Künzi Ralf , Oppenheim Ronald W. 
Published: January 2005

AbstractFollowing the injection of horseradish peroxidase (HRP) into the brachial spinal cord of the chick on embryonic day (E)4.5, retrogradely labeled neurons can be found in the brainstem (Okado and Oppenheim: Journal of Comparative Neurology 232:143–161, 1985). By contrast, following high cervical spinal transection, functional (behavioral) deficits are not observed until E10 (Oppenheim: Journal of Comparative Neurology 160:37–50, 1975). To determine whether this temporal difference between projections and function reflects a delay in synaptogenesis, we looked for the presence of anterogradely HRP‐labeled pre‐synaptic terminals in brachial cord following injection of HRP into the boundary between brainstem and spinal cord at ages between E3.5 and E7. HRP‐labeled fibers were observed in the brachial cord by E4.5 and were diffusely distributed in the ventral and lateral marginal zones (presumptive ventral and lateral funiculi, respectively). Although some axo‐dendritic and axo‐somatic synapses were observed in the brachial cord prior to E6, the presynaptic profiles were always unlabeled by HRP and thus must originate from propriospinal sources. The first HRP‐labeled supraspinal synapses were found in the ventral and lateral funiculi on E6. They contained several clear spherical synaptic vesicles and were axo‐dendritic in nature. The cells of origin of the postsynaptic dendrites were determined by injecting HRP into the wing‐bud to label the brachial motoneurons retrogradely and the presynaptic component was identified as supraspinal by HRP injections into the brainstem/spinal cord boundary to orthogradely label the descending fibers. Several double‐labeled axo‐dendritic synapses were found in the ventral and lateral funiculi of E6 brachial cord. Therefore, at least some descending supraspinal fibers make synapses directly onto motoneuron dendrites. We conclude that (1) there is a delay of about 1.5 days between the arrival of supraspinal fibers and synapse formation in, the brachial cord, (2) the earliest synapses are axo‐dendritic in nature, (3) at least some supraspinal fibers make direct contact with motoneuron dendrites as early as E6, and 4) synaptogenesis from propriospinal sources precedes that from supraspinal descending axons. These observations provide evidence indicating that the temporal difference between the onset of projections of supraspinal descending fibers and the onset of their function may be partly owing to delayed synaptogenesis.
Serially homologous development of the peripheral nervous system in the mouthparts of the grasshopper
Authors: Meier Thomas , Reichert Heinrich 
Published: January 2005

AbstractSegmentally homologous neurogenesis and neuronal differentiation processes characterize the formation of the peripheral nervous system in the developing mouthparts of the grasshopper embryo. The peripherally located neurons derive from the ectoderm in each of the embryonic mouthparts. The major nerve branches serving the mandibles, maxillae, and labium are established by peripheral pioneer neurons, which project their axons into the central nervous system via a set of guidepost cells. The two secondary nerve branches in each appendage are established by fasciculation of peripheral afferent pioneers and central efferent pioneers or by efferent pioneers alone. Sensory cells differentiate and connect with the peripheral nerve branches after a basic peripheral nerve scaffold has been established. The serial homology of these developmental processes in the mouthparts and in the thoracic legs is striking and can be documented at the level of individual identified cells. Thus despite the enormous differences in gross structure and function among cephalic mouthparts and true thoracic legs, many aspects of neurogenesis and early neuronal differentiation are remarkably conserved in all of these appendages.
Origin of spinal projections to the anterior and posterior lobes of the rat cerebellum
Authors: Berretta Sabina , Perciavalle Vincenzo , Poppele Richard E. 
Published: January 2005

AbstractThe present study was carried out to analyze the topography of spinal projections to the anterior and posterior lobes of the cerebellum and to investigate whether projections to the two lobes come from different spinocerebellar neurons or from branching axons of the same cells. We used orthograde transport of horseradish peroxidase conjugated with wheat germ agglutinin (WGA‐HRP) to identify the cerebellar areas where spinocerebellar axons terminate and retrograde double‐labeling techniques to estimate the incidence of spinocerebellar neurons projecting to both anterior and posterior lobes via axon collaterals. Orthograde labeling confirmed that the rat, like other mammalian species, has spinocerebellar projections to two different regions of cerebellar cortex, i.e., lobules I–V of the anterior lobe and lobule VIII of the posterior lobe, with the highest incidence in lobules II, III, and VIII. We did not observe a clear difference in the distribution of afferents coming from different spinal segments to either of the two lobes. The double‐labeled cells were located primarily in the lower thoracic and upper lumbar segments, almost exclusively in Clarke's column and in the dorso‐lateral part of lamina 7 (in the region of the spinal border cells). It is likely that most or all of the spinocerebellar neurons in these structures project to both anterior and posterior lobes. Therefore, the two lobes of the cerebellum are likely to receive common information from these cells, but different information from the separate populations of spinocerebellar neurons that project only to one lobe or the other.
Vasoactive intestinal polypeptide‐containing cells in the rabbit retina: Immunohistochemical localization and quantitative analysis
Authors: Casini Giovanni , Brecha Nicholas C. 
Published: January 2005

AbstractVasoactive intestinal polypeptide (VIP) possesses neuroactive properties in the nervous system. In this study we characterized VIP immunoreactive neurons in the rabbit retina to provide a basis for a better understanding of the role of this peptide in retinal functions and to further define the morphology of wide‐field amacrine cells. VIP immunoreactivity was demonstrated in colchicine‐treated retinas. Immunolabeling was observed in amacrine cells located in the proximal inner nuclear layer and, occasionally, in the ganglion cell layer and inner plexiform layer (IPL). Varicose fibers were distributed in laminae 1, 3, and 5 of the IPL. The distribution of VIP immunoreactive cells showed a peak of ∼ 50 cells/mm2 in the visual streak and minimum values of ∼ 12 cells/mm2 in the peripheral retina. The total number of VIP immunopositive neurons was estimated to be about 11,000. Cell body diameters in the visual streak (8–9 μm) were slightly smaller than those measured in the dorsal or in the ventral retina (9–10 μm). The distribution of nearest neighbor distances (∼ 109 μm in the visual streak and ∼ 99 μm in the peripheral retina) showed that VIP immunoreactive neurons were nonrandomly spaced. Labeled neurons emitted one to three thick primary processes, arborizing in secondary processes and collaterals rich in varicosities; these processes often crossed among different IPL laminae. Arborization fields of individual cells overlapped extensively. In the dorsal retina, estimated areas of single arborization fields were larger and processes had lower branching frequency than in the visual streak and in the ventral retina. On the whole, VIP immunoreactive amacrine cells gave rise to a loose meshwork of fibers in the IPL. These characteristics indicate VIP is contained in a class of wide‐field amacrine cells and is likely to be involved in widespread regulatory or modulatory functions rather than in the direct transmission of visual information through the retina.
HVEM serial‐section analysis of rabbit foliate taste buds: I. Type III cells and their synapses
Authors: Royer Suzanne M. , Kinnamon John C. 
Published: January 2005

AbstractSerially sectioned rabbit foliate taste buds were examined with high voltage electron microscopy (HVEM) and computer‐assisted, three‐dimensional reconstruction. This report focuses on the ultrastructure of the type III cells and their synapses with sensory nerve fibers. Type III cells have previously been proposed to be the primary gustatory receptor cells in taste buds of rabbits and other mammals.Within rabbit foliate taste buds, type III cells constitute a well‐defined, easily recognizable class and are the only taste bud cells observed to form synapses with intragemmal nerve fibers. Among 18 type III cells reconstructed from serial sections, 11 formed from 1 to 6 synapses each with nerve fibers; 7 reconstructed type III cells formed no synapses. Examples of both convergence and divergence of synaptic input from type III cells onto nerve fibers were observed. The sizes of the active zones of the synapses and numbers of vesicles associated with the presynaptic membrane specializations were highly variable. Dense‐cored vesicles 80–140 nm in diameter were often found among the 40–60 nm clear vesicles clustered at presynaptic sites. At some synapses, these large dense‐cored vesicles appeared to be the predominant vesicle type. This observation suggests that there may be functionally different types of synapses in taste buds, distinguished by the prevalence of either clear or dense‐cored vesicles. Previous investigations have indicated that the dense‐cored vesicles in type III cells may be storage sites for biogenic amines.
Organization of the cerebellum in the pigeon (Columba livia): I. Corticonuclear and corticovestibular connections
Authors: Arends J. J. A. , Zeigler H. Philip 
Published: January 2005

AbstractThe projections of the cerebellar cortex upon the cerebellar nuclei and the vestibular complex of the pigeon have been delineated using WGA‐HRP as an anterograde and retrograde tracer. Injections into individual cortical lobules (II–IXa) produce a pattern of ipsilateral terminal labeling of both the cerebellar and vestibular nuclei. The pattern of corticonuclear projections indicates both a rostrocaudal and a mediolateral organization with respect to the lobules and is consistent with a division of the cerebellar nuclei into a medial (CbM) and a lateral (CbL) nucleus. The retrograde experiments indicate that these nuclei receive projections, respectively, from Purkinje cells within medial (A) and lateral (C) longitudinal zones, which alternate with longitudinal zones (B, E) projecting upon the vestibular complex.Purkinje cells in (vestibulocerebellar) lobules IXb–X show only limited projections upon the cerebellar nuclei, but do project extensively upon the cerebellovestibular process (PCV), as well as upon the medial, superior, and descending vestibular nuclei. As the injection site shifts from medial to lateral, there is a corresponding shift in focus of the. projection within PCV from areas bordering CbM to those abutting CbL.The topographic organization of corticovestibular projections is less clear‐cut than those of the corticonuclear projections. Lobules II–X project upon the lateral vestibular nucleus (anterior lobe) or the dorsolateral vestibular nucleus (posterior lobe). These projections originate from either side of the lateral (C) zone. Projections originating from the medialmost (B) zone are interrupted in lobules VI and VII. The anterior and posterior portions of the lateralmost (E) zone overlap along lobules VI and VII. In addition, the E zone of the anterior lobe is the source of projections upon the medial, the descending, and the superior vestibular nuclei. Projections from the auricle and adjacent lateral unfoliated cortex (F zone) focus upon the infracerebellar nucleus, the medial tangential nucleus, and the medial division of the superior vestibular nucleus.The data suggest that the cerebellar cortex of the pigeon, like that of mammals, may be subdivided into a mediolaterally oriented series of longitudinal zones, with Purkinje cells in each zone projecting ipsilaterally to specific cerebellar nuclei or vestibular regions. For cortical regions exclusive of the auricle and lateral unfoliated cortex, three such zones (A, B, and C) are defined that are comparable in their efferent targets with the A, B, and C zones of mammals. There does not appear to be a D zone in the pigeon. The results are discussed in relation to comparative data on amphibians, reptiles, and mammals.
SCPB‐ and FMRFamide‐like immunoreactivities in lobster neurons: Colocalization of distinct peptides or colabeling of the same peptide(s)?
Authors: Arbiser Zoya K. , Beltz Barbara S. 
Published: January 2005

AbstractVirtually all of the SCPB‐like immunoreactive neurons (ca. 60 cells) in the lobster Homarus americanus also contain FMRFamide‐like immunoreactivity. Control experiments reveal that SCPB‐and FMRFamide‐like immunoreactivities are successfully preadsorbed with their specific antigens, while the normal staining pattern is retained following preadsorption of each antibody with the alternate peptide. These experiments potentially lead to the conclusion that the anti‐SCPB and anti‐FMRFamide antibodies are labeling distinct compounds that are colocalized in lobster neurons.The lobster nervous system does not, however, contain authentic FMRFamide, but rather several FMRFamide‐like compounds (Trimmer et al., J. Comp. Neurol. 266:16–26, 1987). The most abundant of these is the octapeptide TNRNFLRFamide. Experiments demonstrate that SCPB‐like immunoreactivity is completely preadsorbed with synthetic TNRNFLRFamide, while there is a significant or complete loss of staining after preadsorption of the FMRFamide antibody with this molecule. Met‐enkephalin‐Arg‐Phe‐amide (YGGFMRFamide), an extended opioid peptide containing the FMRFamide sequence, also preadsorbs SCPB‐and FMRFamide‐like immunoreactivities, while Met‐enkephalin‐Arg‐Phe (YGGFMRF) has no effect on the staining properties of these antibodies. These results suggest that the SCPB antibody can bind to extended forms of FMRFamide‐like molecules, and that anti‐SCPB. and anti‐FMRFamide antibodies may be colabeling one or more FMRFamide‐like molecules in lobster neurons.
Nerve growth factor mRNA‐containing cells are distributed within regions of cholinergic neurons in the rat basal forebrain
Authors: Lauterborn Julie C. , Isackson Paul J. , Gall Christine M. 
Published: January 2005

AbstractIt has been proposed that nerve growth factor (NGF) provides critical trophic support for the cholinergic neurons of the basal forebrain and that it becomes available to these neurons by retrograde transport from distant forebrain targets. However, neurochemical studies have detected low levels of NGF mRNA within basal forebrain areas of normal and experimental animals, thus suggesting that some NGF synthesis may actually occur within the region of the responsive cholinergic cells. In the present study with in situ hybridization and immunohistochemical techniques, the distribution of cells containing NGF mRNA within basal forebrain was compared with the distribution of cholinergic perikarya. The localization of NGF mRNA was examined by using a 35S‐labeled RNA probe complementary to rat preproNGF mRNA and emulsion autoradiography. Hybridization of the NGF cRNA labeled a large number of cells within the anterior olfactory nucleus and the piriform cortex as well as neurons in a continuous zone spanning the lateral aspects of both the horizontal limb of the diagonal band of Broca and the magnocellular preoptic nucleus. In the latter regions, large autoradiographic grain clusters labeled relatively large Nissl‐pale nuclei; it did not appear that glial cells were autoradiographically labeled. Comparison of adjacent tissue sections processed for in situ hybridization to NGF mRNA and immunohistochemical localization of choline acetyltransferase (ChAT) demonstrated overlapping fields of cRNA‐labeled neurons and ChAT‐immunoreactive perikarya in both the horizontal limb of the diagonal band and magnocellular preoptic regions. However, no hybridization of the cRNA probe was observed in other principal cholinergic regions including the medial septum, the vertical limb of the diagonal band, or the nucleus basalis of Meynert. These results provide evidence for the synthesis of NGF mRNA by neurons within select fields of NGF‐responsive cholinergic cells and suggest that the generally accepted view of “distant” target‐derived neurotrophic support should be reconsidered and broadened.
Organization of midbrain catecholamine‐containing nuclei and their projections to the striatum in the North American opossum, Didelphis virginiana
Authors: Hazlett James C. , Ho Raymond H. , Martin George F. 
Published: January 2005

AbstractPresumptive catecholamine (CA) neurons in the opossum midbrain were identified by tyrosine hydroxylase immunohistochemistry. In the midline, small to moderate numbers of CA cells were present in the rostral third of the nucleus raphe dorsalis and throughout the nucleus linearis. Ventrolaterally, such cells were observed in the deep tegmental reticular formation, in all subnuclei of the ventral tegmental area, and in the three subdivisions of the substantia nigra. The CA cells in these areas conform to the dopamine cell groups, A8, A9, and A10 as described in the rat. In several areas there appeared to be no separation between the CA neurons belonging to cytoarchitecturally different nuclei. In order to determine which CA neurons gave rise to striatal projections, the neostriatum was injected with True Blue (TB), and sections through the midbrain were processed for tyrosine hydroxylase (TH) and visualized by immunofluoroscence. Neurons containing both TB and TH were observed in each of the CA cell groups mentioned above. The distribution of these cells confirmed organizational features that may be unique to the opossum's substantia nigra. In addition, different patterns of labeling resulted from caudate versus putamen injections, suggesting a rudimentary medial to lateral topography in the organization of nigrostriatal projections. Although our results suggest that the organization of midbrain CA neurons in the opossum is similar to that in placental mammals, it is clear that differences exist.
Mapping study of the parabrachial taste‐responsive area for the anterior tongue in the golden hamster
Authors: Halsell Christopher B. , Frank Marion E. 
Published: January 2005

AbstractThe locations of taste‐responsive areas within the brainstem parabrachial nucleus (PBN), an obligatory taste relay in the golden hamster (Mesocricetus auratus), were mapped in relation to cytoarchitectural boundaries. The PBN was systematically searched for multiunit neural activity in response to a taste mixture composed of 0.1 M sucrose, 0.03 M NaCl, and 0.1 MKCl applied to the anterior tongue. Taste responses were located exclusively in one of three subdivisions of the medial PBN, which is thought to be specialized for gustatory processing, and in one of six subdivisions of the lateral PBN, which is thought to be specialized for general visceral processing. Based on Nissl‐stained material, both the medial and lateral PBN subdivisions in the hamster were similar to those reported for the rat PBN. The largest group of taste‐responsive cells encompassed two‐thirds of the central medial subdivision, while a smaller group of taste cells was exclusively located within the ventral lateral subdivision. The two taste‐responsive subdivisions are separated by the superior cerebellar peduncle and contain diverse cell types. The finding that anterior tongue taste may be exclusively represented in circumscribed cy to architecturally defined parts of two PBN divisions suggests that taste information from the anterior tongue is required for both specific gustatory and general visceral functions.
Planar differences in nuclear area and orientation in the subventricular and intermediate zones of the rat embryonic neocortex
Authors: Bayer Shirley A. , Altman Joseph , Dai Xiaofeng , Humphreys Laura 
Published: January 2005

AbstractNuclear area and orientation in the subventricular and intermediate zones was studied quantitatively in coronal vs. sagittal sections of the dorsomedial neocortex. Nissl‐stained methacrylate‐embedded normal rat embryos were studied between embryonic days (E) 13 and E22. The area of nuclear profiles and the degrees their long axes (defined as a straight line through the two most distant points in the nuclear profile) deviated from the horizontal (denned as parallel to the pial membrane) were determined with a computer‐graphics program. Because the nucleus is the most clearly outlined structure in embryonic cells, the area and orientation of the nucleus was taken to reflect the overall size and orientation of the cell body. Nuclear area is larger in the coronal plane than it is in the sagittal plane, especially between E17 and E20. Cell body orientation in the subventricular and lower intermediate zones is predominantly horizontal in the coronal plane and predominantly vertical in the sagittal plane. In the upper intermediate zone, cell body orientation is predominantly vertical in both planes, but more so in the sagittal plane. These data indicate that the majority of cell bodies in the subventricular and lower intermediate zones have a horizontally oriented, flattened elliptical shape with their larger diameters lying within the coronal plane and their smaller diameters in the sagittal plane. Because of the flattening, the cell bodies falsely appear to be vertically oriented in the sagittal plane. Qualitative observations in horizontal sections confirmed the quantitative computer analysis. These results are related to other findings with [3H]thymidine autoradiography concerning cell migration and the sojourn of cells in the subventricular and intermediate zones.
Hypophysiotrophic TRH‐producing neurons identified by combining immunohistochemistry for pro‐TRH and retrograde tracing
Authors: Kawano Hitoshi , Tsuruo Yoshihiro , Bando Hiroshi , Daikoku Shigeo 
Published: January 2005

AbstractTo determine hypophysiotrophic thyrotropin‐releasing hormone (TRH)‐producing neurons in the rat hypothalamus, we employed a combination of the immunohistochemistry for TRH prohormone (pro‐TRH) and the retrograde tracing of neurons that project to the median eminence (ME) by injecting biotinylated wheat germ agglutinin (WGA) into the ME. In intact rats, immunoreactive pro‐TRH‐positive neurons occurred in the parvicellular paraventricular nucleus (parvi‐PVN), basal part of the anterior and lateral hypothalamus, perifornical area and dorsomedial nucleus, especially accumulating in the parvi‐PVN. Twenty‐four hours after injection of the WGA into the middle portion of the ME., we found neurons that incorporated the lectin in the anterior periventricular area, the PVN, and the arcuate nucleus. When we examined serial sections consecutively stained. with anti‐WGA, anti‐pro‐TRH, and anti‐WGA, most of the pro‐TRH‐labeled neurons in the medial parvi‐PVN and a part of the neurons in the anterior periventricular area and in the anterior, lateral, and dorsal parvi‐PVN appeared to incorporate WGA. These neurons may correspond with the hypophysiotrophic TRH‐synthesizing neurons in the rat hypothalamus.