bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immunocytochemical demonstration of early appearing astroglial structures that form boundaries and pathways along axon tracts in the fetal brain
Authors: Silver Jerry , Edwards Michael A. , Levitt Pat 
Published: January 2005

AbstractDuring normal development of the mammalian forebrain, the paired cerebral hemispheres are initially separated midsagittally by the connective tissue‐filled longitudinal fissure. During subsequent stages, the hemispheres fuse as basal lamina is remodeled and fibroblasts are eliminated from the fissure to create new central nervous system (CNS) territory in the midline. Two axon pathways, the corpus callosum and dorsal callosal stria, eventually use this region as part of their pathway. In order to assess the possible role of glial cells in the fusion process and in the guidance of axons in this and several other areas of the forebrain, we have analyzed the developing brain in timed cat and mouse embryos with immunohistochemical and morphological techniques. With the use of astroglial‐specific antibodies and electron microscopy, we have visualized two distinct, primitive astroglial structures associated with the cerebral midline, and seven more associated with other specific brain regions. The way in which one of these structures moves as a column along the hemispheric midline in synchrony with seam formation suggests the possibility that during morphogenesis of the telencephalon, astrocytes may aid in the fusion process. In addition, the compact assemblage, early appearance and location of this and the other glial structures in relation to well defined neuroanatomical landmarks or axon pathways suggest that they may transiently compartmentalize relatively large regions of the CNS and organize certain developing fiber systems by acting as guides or barriers at critical stages of ontogeny. © 1993 Wiley‐Liss, Inc.
Distributions of mRNAs for alpha‐2 adrenergic receptor subtypes in rat brain: An in situ hybridization study
Authors: Nicholas Anthony P. , Pieribone Vincent , Hökfelt Tomas 
Published: January 2005

AbstractSelective 35S‐labeled oligonucleotide probes were designed to sequences of the rat alpha‐2A (RG20), alpha‐2B (RNG), and alpha‐2C (RG10) adrenoreceptor mRNAs for use in in situ hybridization experiments on sections of unfixed rat brain, spinal cord and kidney. After hybridized sections were exposed to film or dipped in autoradiographic emulsion, specific and selective labeling patterns characteristic for each probe and region of the central nervous system were observed. Alpha‐2A mRNA labeling was most pronounced in neurons in layer six of the cerebral cortex, hypothalamic paraventricular nucleus, reticular thalamic nucleus, pontine nuclei, locus coeruleus, vestibular nuclei, trapezoid nuclei, deep cerebellar nuclei, nucleus tractus solitarii, ventrolateral medullary reticular formation, and the intermediolateral cell column of the thoracic spinal cord. In some of these locations, the receptor mRNA, in all probability, is present in noradrenaline and perhaps adrenaline neurons. The alpha‐2B probe, which primarily labels the kidney, gave only a very light signal in the thalamus in the central nervous system after extended exposure times. Alpha‐2C mRNA labeling was primarily observed in the olfactory bulb, cerebral cortex, islands of Calleja, striatum, hippocampal formation, cerebellar cortex, and dorsal root ganglia. Labeling patterns disappeared when excess unlabeled probes were added to their respective radiolabeled probes, or when sense probes were employed. When a hybrid antisense probe homologous to all three alpha‐2 probes was used, labeling patterns also disappeared. The present study therefore justifies the pharmacological subclassification of alpha‐2 receptors by providing anatomical evidence for specific and selective cell groups in the rat central nervous system containing mRNA for three alpha‐2 receptor subtypes. © 1993 Wiley‐Liss, Inc.
Histochemical localization of synaptic zinc in the developing cat visual cortex
Authors: Dyck Richard , Beaulieu Clermont , Cynader Max 
Published: January 2005

AbstractThe terminal boutons of many neurons in the telencephalon are known to contain a vesicle‐bound, chelatable pool of zinc (Zn2+) that can be selectively visualized with histochemical procedures. In this paper, the normal laminar, areal, and ultrastructural distribution of histochemically reactive zinc in the visual cortex of the adult cat as well as its development from birth are described. In the adult cat visual cortex, intense zinc staining was found in layers I, II, III, and V, with layer VI staining only lightly. The primary geniculostriate input zone, layer IV, was conspicuously distinguished by the relative absence of zinc. This distinct pattern was restricted only to areas 17 and 18 and differentiated them from adjacent cortical area 19 laterally and the subadjacent cingulate cortex. The earliest zinc‐positive staining in visual cortical areas 17 and 18 was first apparent by postnatal day 2 (P2) and was characterized by staining of a thin layer at the bottom of the cortical plate. By P10, and continuing through P20, synaptic zinc formed a trilaminar pattern of dense staining in areas 17 and 18, which included the top of layer I, and layers III and V. The laminar pattern of synaptic zinc in visual cortex appeared mature by P30, except that the distribution of zinc in layer IV was not uniform. This was most apparent around P50 in tangential sections through layer IV from opened and flattened cortex, where columnar patches of increased zinc staining were apparent in area 17. These columns were approximately 400 μm in diameter, with a centre‐to‐centre spacing of approximately 900 μm. The distribution of synaptic zinc apparently reflects the process of synaptic maturity of the cat visual cortex and appears to demarcate a particular form of columnar organization in visual cortex. © 1993 Wiley‐Liss, Inc.
The organization of the efferent projections from the pontine parabrachial area to the amygdaloid complex: Aphaseolus vulgarisleucoagglutinin (PHA‐L) study in the rat
Authors: Bernard Jean‐Françlois , Alden Marie , Besson Jean‐Marie 
Published: January 2005

AbstractThe organization of the efferent projections from the pontine parabrachial (pPB) area to the amygdala has been studied in the rat by using microinjections ofPhaseolus vulgarisleucoagglutinin (PHA‐L), a sensitive and selective anterograde axonal marker, into restricted subregions of the pPB area.The results confirmed that the pPB area primarily projected onto the ipsilateral nucleus centralis of the amygdala (Ce), and to a lesser extent onto the ipsilateral posterior basolateral (BLP), anterior basomedial (BMA), and amygdaloid cortical (ACo) nuclei of the amygdala. Substantial projections were also found in the substantia innominata dorsal/ventral portion of the globus pallidus (SId/GPv), substriatal (SStr), and fondus striatal (FStr) regions which continue the amygdala rostrally.The results demonstrated that the projections of the pPB area onto the Ce were topically organized: (1) The region of the pPB area mainly including the medial subnucleus (pPBm), the waist area (pPBwa), and a thin rostral lamina of the ventral lateral subnucleus (pPBvl) projects primarily to the medial portion of the Ce (CeM). Dense projections were also found in the BLP, BMA, and ACo nuclei of the amygdala, and in the SId/GPv, SStr, and FStr rostral areas. (2) The region of the pPB mainly including the rostral portion of the central lateral subnucleus (pPBcl) and the outer‐rostral protion of the external lateral subnucleus (pPBel) projects primarily to the lateral portion of the Ce (CeL). (3) The region of the pPB mainly including the dorsolateral subnucleus (pPBdl), the remaining pPBel, and the external medial (pPBem) subnuclei projects primarily to the lateral capsular protion of the Ce (CeLC) and bilaterally to its rostral portion. Dense projections were also found in the regions which extend the CeLC rostrally and in the SId/GPv, SStr, and FStr rostral areas.The possible role of each of the three parabrachio‐amygdaloid pathways described is discussed. It was suggested that the pPB‐CeM pathway is mainly implicated in gustatory processes; the pPB‐CeL pathway is mainly implicated in visceral and chemosensitive processes; and the pPB‐CeLC pathway is mainly implicated in respiratory, cardiovascular, and nociceptive processes. © 1993 Wiley‐Liss, Inc.
Coincidence of Schwann cell‐derived basal lamina development and loss of regenerative specificity of spinal motoneurons
Authors: Meeker Marianne L. , Farel Paul B. 
Published: January 2005

AbstractThe Schwann cell‐derived basal lamina forms a tube around single peripheral axons or small groups of axons that is continuous from the spinal cord to the target. In bullfrog tadpoles (Rana catesbeiana), motor axons transected at early developmental stages regenerate to the appropriate hindlimb region. In the present paper, we found that at these stages Schwann tubes are absent by morphological criteria, and individual axons are separated only by occasinal extensions of support cells. At stages when axons no longer regenerate to the correct hindlimb region, every axon is encased in a basal lamina tube. Schwann tubes persist in the distal stump after nerve transection, and regenerating axons grow within these tubes. These findings are consistent with previous results showing that the errors regenerating axons make in older animals are not random, but depend upon the course of the denervated Schwann tubes to which they ahve acces. In order to determine whether formation of the Schwann tube itself or interaction of its molecular constituents with growing axons was associated with loss of regenerative specificity, the expression during development of two major constituents of the basal lamina, laminin and heparan sulfate proteoglycan, was investigated. Immunoreactivity to both constituents was present both before and after the transition from specific to nonspecific regeneration, indicating that their expression per se was not sufficient to limit regnerative specificity. These data support the hypothesis that the physical constraint imposed by the Schwann cell‐derived basal lamina prevents regenerative specificity. © 1993 Wiley‐Liss, Inc.
Dendritic remodelling of retinal ganglion cells during development of the rat
Authors: Yamasaki Edna N. , Ramoa Ary S. 
Published: January 2005

AbstractInvestigation of the morphology of ganglion cells in the cat retina has shown that a remarkable reduction in the number of dendritic spines and branches occurs during development of the alpha and beta cell classes. To learn whether dendritic remodelling represents a generalized mechanism of mammalian retinal ganglion cell development, we have examined the morphology of ganglion cells in the retina of the developing rat. The present study has concentrated on type II cells, which retain a great number of dendritic spines and branches in the adult and comprise a large proportion of the population of rat retinal ganglion cells. To reveal fine dendritic and axonal processes, Lucifer yellow was injected intracellularly in living retinae maintained in vitro. Size and complexity of the dendritic trees were found to increase rapidly during an intial stage of development lasting from late fetal life until approximately postnatal day 12 (P12). Dendrites and axons of immature ganglion cells expressed several transient morphological features comprising an excessive number of dendritic branches and spine‐like processes, and short, delicate axonal sidebranches. The following developmental stage was characterized by a remarkable decrease in the morphological complexity of retinal ganglion cells and a slowed growth of their dendritic fields. The number of dendritic branches and spines of types I and II retinal ganglion cells declined after P12 to reach a mature level by the end of the first postnatal month. Thus, even cells that retain a highly complex dendritic tree into the adult state undergo extensive remodelling. These results suggest that regressive modifications at the level of the dendritic field constitute a generalized mechanism of maturation in mammalian retinal ganglion cells. © 1993 Wiley‐Liss, Inc.
Postnatal development and localization of an N‐acetylgalactosamine containing glycoconjugate associated with nonpyramidal neurons in cat visual cortex
Authors: Schweizer Michaela , Streit Wolfgang J. , Müller Christian M. 
Published: January 2005

AbstractWe have analyzed the appearance of N‐acetylgalactosamine containing glycogonjugates by staining sections of fixed cat visual cortex with the lectins from Vicia villosa (VVA) and Glycine max (SBA) conjugated to fluorescent labels, horseradish peroxidase, or biotin. The appearance of lectin staining during postnatal development followed an inside‐out gradient starting in the deep cortical layers at the fourth postnatal week, successively including more of the superficial layers during the first three postnatal months until labelled cells were present throughout layers II–VI at the seventh postnatal month. Staining was associated with the soma and proximal dendrites of bipolar and multipolar nonpyramidal neurons. Outside layer IV large neurons with basket cell and neurogliaform morphology predominated, whereas small multipolar cells were stained in layer IV. High power observation revealed a lattice‐like staining on neuronal surfaces. In the cortical white matter staining was found at the nodes of Ranvier.The ultrastructural localization of lectin binding sites was assessed by a pre‐embedding histochemical procedure with biotinylated lectin visualized with HRP‐conjugated avidin and diaminobenzidine as the chromogen. The reaction product was found exclusively in close association with synaptic terminals on somata and proximal dendrites of nonpyramidal neurons. There was no preference with respect to the morphology of the synaptic structure, i.e., symmetric synapses with ovoid or asymmetric synapses with round vesicles. In the vicinity of synaptic contacts the staining was associated with membranes of astrocytic processes ensheathing the synapses. In the cortical white matter astrocytic processes running along myelinated axons were strongly labelled at the nodes of Ranvier.Comparison of Western blots from 4‐week‐old and adult cat cortex membranes revealed one lectin‐positive protein band with an apparent molecular weight of about 24 kD in conjunction with the histochemical expression of perisynaptic staining in the adult tissue.It is concluded that the employed lectins selectively visualize distal astroglial processes ensheathing synapses on a subpopulation of cortical interneurons and nodes of Ranvier. On the basis of the developmental appearance and localization we consider and discuss the possibility that the N‐acetylgalactosamine containing glycoconjugate is involved in the stabilization of synaptic contacts on GABA‐ergic interneurons. © 1993 Wiley‐Liss, Inc.
Acetylcholinesterase staining differentiates functionally distinct auditory pathways in the barn owl
Authors: Adolphs R. 
Published: January 2005

AbstractThe aim of this study was to examine how the functional specialization of the barn owl's auditory brainstem might correlate with histochemical compartmentalizaiton. The barn owl uses interaural intensity and time differences to encode, respectively, the vertical and azimuthal positions of sound sources in space. These two auditory cues are processed in parallel ascending pathways that separate from each other at the level of the cochlear nuclei. Sections through the auditory brainstem were stained for acetylcholinesterase (AChE) to examine whether nuclei that process different auditory cues stain differentially for this enzyme. Of the two cochlear nuclei, angularis showed more intense staining than nucleus magnocellularis. Nucleus angularis projects to all of the nuclei and subdivisions of nuclei that belong to the intensity processing pathway. Acetylcholinesterase stained all regions that contain terminal fields of nucleus angularis and thus provided discrimination between the time and intensity pathways. Moreover, staining patterns with acetylcholinesterase were complementary to those prevously reported with an anti‐calbindin antibody, which stains terminal fields of nucleus laminaris, and thus stains all the nuclei and subdivisions of nuclei that belong to the time pathway. Some of the gross staining patterns observed with AChE were similar to those reported with antibodies to glutamate decarboxylase. However, AChE is a more convenient and definitive marker in discriminating between these pathways than is calbindin or glutamate decarboxylase. Acetylcholinesterase staining of the intensity pathway in the owl may be related to encoding of sound intensity by spike rate over large dynamic ranges. © 1993 Wiley‐Liss, Inc.
Differential regulation of substance P and somatostatin in martinotti cells of the developing cat visual cortex
Authors: Wahle Petra 
Published: January 2005

AbstractIn order to determine their morphological development and ontogenetic fate, Martinotti neurons immunoreactive for substance P and somatostatin have been analysed in the cat visual cortex. Martinotti neurons are located in layers V and VI. They are multipolar to bitufted, and most dendrites remain in layers V and VI. Their typical feature is the ascending axon, which emerges from an apical dendrite or from the upper pole of the soma. A number of collaterals branch off in layer V, forming a local terminal plexus. The axon then branches into 2–8 collaterals, which ascend as a bundle to layers III and II, where a second terminal plexus is formed. Some collaterals ascend to layer I where they adopt a horizontal course. Horizontal collaterals in the terminal layers V, III, II, and in layer I may reach up to 400 μm in length.Martinotti neurons begin to differentiate perinatally. The quantitative analysis reveals that the initial time course of differentiation of Martinotti cells is very similar in material stained for substance P and for somatostatin. Double immunofluorescence then confirms that the two peptides are colocalized in Martinotti cells of layers V and VI during the early postnatal period. Further, substance P is colocalized with GABA.Substance P expression in Martinotti cells can be observed only in the immature visual cortex. After postnatal day 15, the Martinotti neuron system becomes less and less detectable by substance P immunoreactivity. It declines to virtually undetectable levels after the third postnatal month. The adult visual cortex is almost devoid of substance P‐immunoreactive cell bodies, processes and axon terminals. In situ hybridization confirms this finding, revealing beta‐preprotachykinin mRNA‐expressing cell bodies in layers V and IV at postnatal day (P)6 and P12, but not in the adult cortex. This suggests a downregulation of the substance P expression at the transcriptional level.In contrast, somatostatin‐immunoreactive Martinotti cells, most of which have coexpressed substance P during early postnatal life, can still be observed in the adult cortex. Thus, the Martinotti neurons constitute a persisting cell type, although many individual neurons of this type disappear during the second postnatal month by degeneration and cell death.In summary, while somatostatin is permanently expressed in Martinotti neurons in the cat visual cortex, substance P peptide and mRNA are transiently expressed during an early postnatal period, and apparently are downregulated later in development. © 1993 Wiley‐Liss, Inc.
Embryonic development of rat sympathetic preganglionic neurons: Possible migratory substrates
Authors: Phelps Patricia E. , Barber Robert P. , Vaughn James E. 
Published: January 2005

AbstractSpinal somatic and autonomic (sympathetic preganglionic) motor neurons are generated synchronously and, subsequently, migrate from the ventricular zone together to form a common primitive motor column. However, these two subsets of motor neurons ultimately express several phenotypic differences, including somal size, peripheral targets, and spinal cord locations. While somatic motor neurons remain ventrally, autonomic motor neurons (AMNs) move both dorsally and medially between embryonic days 14 and 18, when they approximate their final locations in spinal cord. The goal of the present investigation was to determine the potential guidance substrates available to AMNs during these movements. The dorsal translocation was studied in developing upper thoracic spinal cord, because, at this level, the majority of AMNs are located dorsolaterally. Sections were double‐labeled by ChAT (choline acetyltransferase) and SNAP/TAG‐1 (stage‐specific neurite associated protein/transiently expressed axonal surface glycoprotein) immunocytochemistry to visualize motor neurons and the axons of early forming circumferential interneurons, respectively. Results showed that during the developmental stage when AMNs translocated dorsally, SNAP/TAG‐1 immunoreactive lateral circumferential axons were physically located along the borders of the AMN region, as well as among its constituent cells. These findings indicate that lateral circumferential axons, as well as the SNAP/TAG‐1 molecules contained upon their surfaces, are in the correct spatial and temporal position to serve as guidance substrates for AMNs. The medial translocation was studied in developing lower thoracic‐upper lumbar spinal cord, because, at this level, more than half of the AMNs are medially located. Sections were double‐labeled by ChAT and vimentin immunocytochemistry to visualize motor neurons and radial glial fibers, respectively. Observations on consecutive developmental days of the medial traslocation revealed that AMNs were aligned with parallel arrays of radial glial fibers. Thus, the glial processes could serve as guides for the AMN medial movement. Future experimental analyses will examine whether circumferential axons and redial glial fibers are in fact functioning as migratory guides during AMN development, and, if so, whether specific surface molecules on these guides trigger the subsequent differentiation of AMNs.