bluuebunny/crossref_metadata_2025 huggingface dataset:
Light and electron microscopic studies of the effects of p‐chloroamphetamine on the monoaminergic innervation of the rat spinal cord
Authors: Ridet Jean‐Luc , Geffard Michel , Privat Alain
Published: January 2005

A previous report has shown that small diameter serotoninergic (5‐HT) axons innervating the forebrain are selectively eliminated by treatment with an amphetamine derivative, (±)p‐chloroamphetamine (PCA; Mamounas et al., [1991] J. Comp. Neurol. 314:558—586). It is well known that the spinal cord is the target of numerous monoaminergic fibers of different types. We have previously shown that the dorsal and ventral horns and the intermediolateral cell column are innervated by numerous serotonin‐, noradrenaline‐ and dopamine‐containing axons, including both thin axons with small varicosities and beaded axons with large varicosities. In all these regions, the large majority of fine indolaminergic fibers do not establish synaptic contacts, contrasting with the beaded axons which mostly exhibit synapses. The present work was conducted to study the effect of PCA on the monoaminergic innervation of the adult rat spinal cord. Animals received two subcutaneous doses of PCA 24 hours apart and were perfused 3 weeks later. Immunocytochemistry was performed to detect 5‐HT, noradrenergic and dopaminergic fibers by using light and electron microscopy. Light microscopy revealed that PCA treatment caused a marked and selective elimination of the fine 5‐HT‐immunoreactive fibers, mainly found in the dorsal horn, but spared all other larger axons. This selective effect on the dorsal horn innervating thin 5‐HT fibers was confirmed with the electron microscope by calculating the synaptic incidence(s) of monoaminergic innervation. These results suggest that fine and beaded 5‐HT axons correspond to two anatomically, biochemistry and pharmacologically different types of fibers, which could arise from two subpopulations of brainstem neurons.In addition, this drug could be used to provide an experimental animal, devoid of 5‐HT nonsynaptic fibers, thereby facilitating a study on the role of dorsal horn nonsynaptic system in pain modulation. © 1994 Wiley‐Liss, Inc.
Neuroanatomy of the rhabdocoel flatworm Mesostoma ehrenbergii (focke, 1836). I. Neuronal diversity in the brain
Authors: Elvin Mark , Koopowitz Harold
Published: January 2005

We investigated the neuronal configurations of brain cells in the rhabdocoel flatworm Mesostoma ehrenbergiiand compared them to those of the polyclad Notoplan acticolato determine neuronal synapomorphies for these different flatworm clades. The fluorescent dye Lucifer yellow was used to fill and visualize cells in the brain of M.ehrenbergii. The predominant cell types for both animals were heteropolar bipolar and heteropolar multipolar cells. Isopolar bipolar and isopolar multipolar cells wer also found but in much lower numbers. Small amacrine‐type multipolar cells tht might be glial in nature were also found in an area of neuropil. A few unipolar cells were found that ranged from small amacrine‐type cells to typical invertebrate‐type unipolars. In addition, a number of morphologically identified cells found in different animals are described. © 1994 Wiley‐Liss, Inc.
Distribution and proportions of GABA‐Immunoreactive neurons in cat primary somatosensory cortex
Authors: Li Jianying , Schwark Harris D.
Published: January 2005

Certain receptive field properties of cortical neurons depend upon inhibitory, GABAergic inputs. In the somatosensory cortex, iontophoresis of bicuculline, a GABAA receptor blocker, results in enlargement of receptive fields. However, bicuculline's effectiveness in changing receptive field size varies with the neuron's adaptation characteristics, location within a particular submodality region, and laminar location. To test whether regional differences in the effectiveness of bicuculline are correlated with the distribution of cortical GABAergic neurons, we determined the number and proportion of GABA‐immunoreactive [GABA(+)] neuron, within cat primary somatosensory cortex. The laminar distribution of GABA(+) neurons was similar across all four cytoarchitechonic areas of primary somatosensory cortex, with layer II containing the highest areal density of GABA(+) neurons. Numerical proportions of GABA(+) neurons in the total neuron population were similar in areas 3b and 2 (29.8% and 22.6%, respectively). Laminar distributions of the proportions of GABA(+) neurons were also similar in these two areas; in both areas layer I contained the highest proportion of GABA(+) neurons. The laminar distribution of GABA(+) neuron density as well as GABA(+) neuron proportion differed from the reported laminar distribution of bicuculline effects on respective field size. Moreover, within area 3b, these measures showed no evident pattern that might correspond to rapidly adaptation and slowly adapting submodality regions. © 1994 Wiley‐Liss, Inc.
Horizontal cells and cone photoreceptors in human retina: A Golgi‐electron microscopic study of spectral connectivity
Authors: Ahnelt Peter , Kolb Helga
Published: January 2005

Connections of the three human horizontal cell (HC) types with overlying cone pedicles have been studied via electron microscopy (EM). Because blue cones (B‐cones) can be recognized on distinctive morphological criteria, we could determine their presence by light microscopy (LM) in the mosaic overlying HC dendritic trees. Then we could confirm the presence or absence of dendritic contacts to B‐cone pedicles by examining EM serial sections and making reconstructions of examples of the three HC types.

Three HI cells have been reconstructed. Their dendritic terminals ended as lateral elements of ribbon synapses in green and red cone pedicles (G‐ and R‐cones) primarily. B‐cones pedicles in HI cell dendritic fields received no more than one or two contacts. Six reconstructed HII cells were found to contact all the pedicles within their dendritic field. However, their dendritic reached especially for B‐cones pedicles and innervated them with disproportionately large number of terminals compared with G‐ and R‐cines. HII axons appeared to contact B‐cones exclusively. The four reconstructed HIII cells were found to avoid completely B‐cones in their dendritic fields.

Data have been collected on synaptic ribbon lengths at HII and HIII lateral elements in the B‐cone as compared with G‐ and R‐cone pedicles. HIII dendritic terminals end almost exclusively at the smaller ribbons and HI dendrites at the large ribbons. The number of dendritic terminals provided by the HCs to G‐and R‐cone pedicles as compared B‐cone pedicles has been more accurately quantitated than was possible in the LM analysis (accompanying paper).

New findings on the morphology of B‐cone pedicles in peripheral retina have revealed that 1) B‐cone pedicles end further vitread in the outer plexiform layer (OPL) than other cone pedicles, thereby forming a sublayer of the OPL neuropil, here named OPLb, in comparison to OPLa, where the G‐ and R‐cone pedicles end; 2) B‐cone pedicles have very few telodentrial connections; and 3) in peripheral retina (probably beyond 8 mm from the fovea to the ora serrata), they are bi‐ or trilobed, with each lobe containing separate synaptic invaginations. The vitread position and unique morphology of B‐cone pedicles appear to relate directly to the unique morphology and unusual connectivity patterns of both their B‐cone‐specific bipolar and B‐cone‐related horizontal cell, the HII cell. Taken together with the LM and quantitative data of our two preceding papers, these findings provide morphological evidence that a chromatically selective weighting pattern in HCs and could play a role in color‐opponent surround formation in the human retina. © 1994 Wiley‐Liss, Inc.
Pedunculopontine nucleus in the squirrel monkey: Distribution of cholinergic and monoaminergic neurons in the mesopontine tegmentum with evidence for the presence of glutamate in cholinergic neurons
Authors: Lavoie Brigitte , Parent André
Published: January 2005

The topographical relationships between cholinergic neurons, identified by their immuno‐reactivity for choline acetyltransferase (ChAT) or their staining for β‐nicotinamide ademine dinucleotide phosphate (NADPH)‐diaphorase, and dopaminergic, serotoninergic, Nonadrenergic, and glutamatergic neurons that occur in the mesopontine tegmentum, were studied in the squirrel monkey (Saimiri sciureus). The ChAT‐positive neurons in the pedunculopontine nucleus (PPN) form two distinct subpopulations, one that corresponds to PPN pars compacta(PPNc) and the other to PPN pars dissipata (PPNd). The ChAT‐positive neurons in PPNc are clustered along the dorsolateral border of the superior cerebellar peduncle (SP) at trochlear nucleus levels, whereas those in PPNd are scattered along the SP from midmesencephalic to midpontine levels. At levels caudal toe the trochlear nucleus, ChAT‐positive neurons corresponding to the laterodorsal tegmental nucleus (LDT) lie within the periaqueductal gray and extend caudally as far as locus coeruleus levels. All ChAT‐positive neurons in PPN and LDT stain for NADPH‐diaphorase; the majority of large neurons in PPN and LDT are cholinergic, but some large neurons devoid of NADPH‐diaphorase also occurnin these nuclei. Cholinergic neurons in the mesopontine tegmentum form clusters that are largely segregated from raphe serotonin immunoreactive neurons, as well as from nigral dopaminergic and coeruleal noradrenergic neurons, as revealed by tyrosine hydroxylase immunohistochemistry. Nevertheless, dendrites of cholinergic and noradrenergic neurons are clolinergic and noradrenergic neurons are closely intermingled, suggesting the possibility of dendrodendritic contacts. In addition, numerous large and medium‐sized glutamate‐immunoreactive neurons are intermingled among cholinergic neurons in PPN. Furthermore, at trochlear nucleus levels, about 40% of cholinergic neurons display glutamate immunoreactivity, whereas other neurons express glutamate or ChAT immunoreactivity only. This study demonstrates that (1) cholinergic neurons remain largely segregated from monoaminergic neurons throughout the mesopontine tegmentum and (2) PPN contains cholinergic and glutamatergic neurons as well as neurons coexpressing ChAT and Glutamate in primates. © 1994 Wiley‐Liss, Inc.
Development of specificity in corticospinal connections by axon collaterals branching selectively into appropriate spinal targets
Authors: Kuang Rong Zhen , Kalil Katherine
Published: January 2005

Corticospinal projections in adult rodents arise exlusively from layer V neurons in the sensorimotor cortex. These neurons are topographically organized in their connections to spinal cord targets. Previous studies in rodents have shown that the mature distribution pattern of corticospinal neurons develops during the first 2 weeks postnatal from an initial widespread pattern that includes the visual cortex to a distribution restricted to the sensorimotor cortex. To determine whether specificity in corticospinal connections also emerges from an intially diffuse set of projections, we have studied the outgrowth of corticospinal axons and the formation of terminal arbors in developing hamsters. The sensitive fluorescent tracer 1, 1′, dioctadecyl‐3, 3, 3′, 3′‐tetramethylindocarbocyanine perchlorat (DiI) was used to label corticospinal axons from the visual cortex or from small regions of the forelimb or hindlimb sensorimotor cortex in living animals at 4–17 days postnatal. Initially axon outgrowth was imprecise. Some visual cortical axons extended transiently beyond their permanent targets in the pontine nuclei, by growing through the pyramidal decussation and in some cases extending as far caudally as the lumbar enlargement. Forelimb sensorimotor axons also extended past their targets in the cervical enlargement, in many cases growing in the corticospinal tract to lumbar levels of the cord. By about 17 days postnatal these misdirected axons or axon segments were withdrawn from the tract. Despite these errors in axon trajectories within the corticospinal tract, terminal arbors branching into targets in the spinal gray matter were topographically appropriate from the earliest stages of innervation. Thus visula cortical axons never formed connections in the spinal cord, forelimb sensorimotor axons arborized only in the cervical enlargement, and hindlimb cortical axons terminated only in the lumbar cord at all stages of development examined. Corticospinal arbors formed from collaterals that extended at right angles from the shafts of primary axons, most likely by the process of interstitial branching after the primary growth cone had extended past the target. Once collaterals extended into the spinal gray matter, highly branched terminal arbors formed within 2–4 days, beginning at about 4 and 8 days postnatal for the cervical and lumbar enlargements, respectively. These results show that specificity in connectivity is achieved by selectivty growth of axon collaterals in to appropriate spinal targets from the beginning and not by the later remodeling of intially diffuse connections. In contrast, errors occur in the initial outgrowth of axons in the corticospinal tract, which are subsequently corrected. Copyright © 1994 Wiley‐Liss, Inc.
Morphology and spatial distribution of GABAergic neurons in cat primary auditory cortex (AI)
Authors: Prieto Jorge J. , Peterson Barbara A. , Winer Jeffery A.
Published: January 2005

This is a survey of the distribution, form, and proportion of neurons immunoreactive for gamma‐aminobutyric acid (GABA) or glutamic acid decarboxylase (GAD) in cat primary auditory cortex (AI). The cells were studied in adult animals and were classified with respect to their somatic size, shape, and laminar location, and with regard to the origins and branching pattern of their dendrites. These attributes were used to relate each of the GAD‐positive neuronal types to their counterparts in Golgi preparations.

Each layer had a particular set of GABAergic cell types that is unique to it. There were 10 different GABAergic cell types in AI. Some were specific to one layer, such as the horizontal cells in layer I or the extraverted multipolar cells in layer II, while other types, such as the small and medium‐sized multipolar cells, were found in every layer.

The number and proportion of GABAergic cells were determined by using postembedding immunocytochemistry. The proportion of GABAergic neurons was 24.6%. This was slightly higher than the values reported elsewhere in the neocortex. The laminer differences in density and proportion of GABAergic and non‐GABAergic neurons were also comparable (though somewhat higher) to those found in other cortical areas: thus, 94% of layer I cells were GABAergic, while the values in other layers ranged from 27% (layer V) to 16% (layer VI). Layer VI had the most heterogeneous population of GABAergic neurons.

The proportion of these cells across different regions within AI was studied. Since some receptive field properties such as sharpness of tuning and aurality are distributed non‐uniformly across AI, these might be reflected by regional differences across the cerebral cortex. There were significantly more GABAergic somata in layers III and IV in the central part of AI, along the dorsoventral axis, where physiological studies report that the neurons are tuned most sharply (Schreiner and Mendelson [1990] J. Neurophysiol. 64:1442–1459). Thus, there may be a structural basis for certain aspects of local inhibitory neuronal organization. © 1994 Wiley‐Liss, Inc.
Laminar distribution and neuronal targets of GABAergic axon terminals in cat primary auditory cortex (AI)
Authors: Prieto Jorge J. , Peterson Barbara A. , Winer Jeffery A.
Published: January 2005

The form, density, and neuronal targets of presumptive axon terminals (puncta) that were immunoreactive for gamma‐aminobutyric acid (GABA) or its synthesizing enzyme, glutamic acid decarboxylase (GAD), were studied in cat primary auditory cortex (AI) in the light microscope. High‐resolution, plastic‐embedded material and frozen sections were used. The chief results were: (1) There was a three‐tiered numerical distribution of puncta, with the highest density in layer Ia, an intermediate number in layers Ib–IVb, and the lowest concentration in layers V and VI, respectively. (2) Each layer had a particular arrangement: layer I puncta were fine and granular (less than 1 μm), and layer V and VI puncta were mixed in size and predominantly small. (3) The form and density of puncta in every layer were distinctive. (4) Immunonegative neurons received, in general, many more axosomatic puncta than immunopositive cells, with the exception of the large multipolar (presumptive basket) cells, which invariably had many puncta in layers II–VI. (5) The number of puncta on the perikarya of GABAergic neurons was sometines related to the number of puncta in the layer, and in other instances it was independent of the layer. Thus, while layer V had a proportion of GABAergic neurons similar to layer IV, it had only a fraction of the number of puncta: perhaps the intrinsic projections of supragranular GABAergic cells are directed toward layer IV, as those of infragranular GABAergic neurons may be.

Since puncta are believed to be the light microscopic correlate of synaptic terminals, they can suggest how inhibitory circuits are organized. Even within an area, the laminar puncta patterns may reflect different inhibitory arrangements. Thus, in layer I the fine, granular endings could contact preferentially the distal dendrites of pyramidal cells in deeper layers. The remoteness of such terminals from the spike initation zone contrasts with the many puncta on all pyramidal cell perikarya and the large globular endings on basket cell somata. Basket cells might receive feed‐forward disinhibition, pyramidal cells feed‐forward inhibition, and GABAergic non‐basket cells would be the target of only sparse inhibitory axosomatic input. Such arrangements imply that the actions of GABA on AI neurons are neither singular nor simple and that the architectonic locus, laminar position, and morphological identity of a particular neuron must be integrated for a more refined view of it role in cortical circuitry. © 1994 Wiley‐Liss, Inc.
Localization of nerve growth factor (NGF) and low‐affinity NGF receptors in touch domes and quantification of NGF mRNA in keratinocytes of adult rats
Authors: English Kathleen B. , Harper Sarah , Stayner Naida , Wang Zheng‐Ming , Davies Alun M.
Published: January 2005

Touch doems are clearly delineated mechanoreceptors that are visible on the depilated skin of mammals. These structures consist of a sharply circumscribed disk of thickened epithelium surmounting a group of Merkel cells that are innervated by type I sensory neurons. These characteristic cutaneous structures provide an ideal opportunity for investigating whether the localization of nerve growth factor (NGF) in the skin related to sites of sensory axon termination. For these reasons, we have used immunocytochemistry to study the distribution of NGF and the low‐affinity NGF receptor (p75NGFR) in the touch domes of adult rat skin. Intense NGF‐like immunoreactivity was sharply restricted to keratinocytes (excluding the stratum corneum) of the thickened epidermis of the touch domes. The epidermis immediately surrounding touch domes and the epidermis of the tylotrich hair follicle associated with touch domes were immunonegative for NGF but were immunopositive for p75NGFR as werer the type I nerve endings innervating these cells. Quantitative Northern blotting revealed that the level of NGF mRNA was substantially higher in keratinocytes isolated from the stratum granulosum and stratum spinosum than in keratinocytes isolated from the stratum germinativum. These findings indicate that NGF synthesis in mature skin has a highly restricted regional distribution that is primarily associated with the innervation of a specialized touch receptor. © 1994 Wiley‐Liss, Inc.
Structure of reticulospinal axon growth cones and their cellular environment during regeneration in the lamprey spinal cord
Authors: Lurie Diana I. , Pijak Donald S. , Selzer Michael E.
Published: January 2005

The large larval sea lamprey is a primitive vertebrate that recovers coordinated swimming following complete spinal transection. An ultrastructural study was performed in order to determine whether morphologic features of regenerating axons and their cellular environment would provide clues to their successful regeneration compared to their mammalian counterparts. Three larvel sea lampreys were studied at 3, 4 and 11 weeks following complete spinal transection and compared with an untransected control. Müller and Mauthner cells or their giant reticulospinal axons (GRAs) were impaled and injected with horseradish peroxidase (HRP). Alternating thick and thin sections were collected for light and electron microscopy. A total of 9 neurites were examined.

At all times, growth cones of GRAs differed from those of cultured mammalian neurons in being packed with neurofilaments and in lacking long filopodia, suggesting possible differences in the mechanisms of axon outgrowth. Morphometric analysis suggested that GRA growth cones contact glial fibers disproportionately compared to the representation of glial surface membranes in the immediate environment of these growth cones. No differences were found between glial cells in regenerating spinal cords and those of untransectred control animals with regard to the size of the cell body and nucleus and the packing density of their intermediate filaments. Glial fibers in control animals and glial fibers located far from a transection were oriented transversely. Glial cells adjacent to the transection site sent thickened, longitudinally oriented processes into the blood clot at the transection site. These longitudinal glial processes preceded the regenerating axons. Desmosomes were observed on glia adjacent to the lesion but were scarce in the lesion during the first four weeks post‐transection. These findings suggest that longitudinally oriented glial fibers may serve as a bridge along which axons can regenerate across the lesion. The presence of desmosomes might prevent migration of astrocytes near the transection, thus stabilizing the glial bridge. © 1994 Wiley‐Liss, Inc.
Redistribution of insoluble interphotoreceptor matrix components during photoreceptor differentiation in the mouse retina
Authors: Mieziewska Kristina , Szél Agoston , van Veen Theo , Aguirre Gustavo D. , Philp Nancy
Published: January 2005

The development of the nervous‐system is largely influenced by the extracellular matrix (ECM). In the neural retina, the photoreceptors are surrounded by a unique ECM, the interphotoreceptor matrix (IPM). The IPM plays a central and possibly crucial role in the development, maintenance and specific function of the photoreceptors. Therefore, the characterization of IPM components is necessary to understand the mechanisms regulating photoreceptor differentiation.

The IPM in the mouse retina was examined during photoreceptor morphogenesis with the monoclonal antibody (MAb) F22, which recognizes a 250 kDa component of the interphotoreceptor matrix. The binding pattern of MAb F22 revealed a striking redistribution in the expression of the 250 kDa F22 antigen in late stage of postnatal photoreceptor differentiation in the mouse retina.

The F22 staining was detectable in the IPM around the inner segments on the third postnatal day (P3). The MAb F22 initially labeled the region around inner segments, but as the outer segments elongated, the F22 distribution became concentrated to the matrix around the rod and cone outer segments until P16–17. At P17, the F22 label around rods began to disappear, while the label around cones became more defined. The shift in label distribution was largely completed by P20. Residual rod‐associated label disappeared within a few days. In the adult animal, the F22 antibody labeled the cone‐associated matrix only, and this labeling pattern remained stationary. The change in the distribution of MAb F22 demonstrated by immunolabeling was not accompanied by changes in the size of the molecule; F22 antigen isolated from the IPM of P13–15, and from adult IPM migrated with the same molecular weight on SDS gels.

The distribution of MAb F22 was compared to that of chondroitin sulfate proteoglycans which are abundant in the IPM. The labeling patterns of MAbs CS‐56, C6‐S and C4‐S were distinct from that of MAb F22. A general decrease of the label intensity was seen with two chondroitin sulfate MAbs (CS‐56 and C4‐S) between 16 days and 4 months, but a total loss of rod‐associated label was not observed. All three chondroitin sulfate MAbs labeled the retina at embryonic day (E) 11.5–13.5, a time of outgrowth of ganglion cell axons, but the F22 antigen was not detected in the retina at this stage of development. The results demonstrate that the F22 and the chondroitin sulfate antibodies are recognizing different molecules that have distinct roles in retinal morphogenesis. The expression of the F22 antigen was temporally correlated with photoreceptor outer segment differentiation. The redistribution of F22 label at P17–20 occurred at the end of the developmental period and suggests that the F22 antigen could have different roles, both in photoreceptor differentiation, and in the mature retina. © Wiley‐Liss, Inc.
Synaptic terminal coverage of primate triceps surae motoneurons
Authors: Starr Kathy A. , Wolpaw Jonathan R.
Published: January 2005

This study examined the synaptic terminal coverage of primate triceps surae (TS) motoneurons at the electron microscopic level. In three male pigtail macaques, motoneurons were labeled by retrograde transport of cholera toxin‐horseradish peroxidase that was injected into TS muscles bilaterally and visualized with tetramethylbenzidine stabilized with diamino‐benzidine. Somatic, proximal dendritic, and distal dendritic synaptic terminals were classified by standard criteria and measured. Overall and type‐specific synaptic terminal coverages and frequencies were determined.

Labeled cells were located in caudal L5 to rostral S1 ventral horn and ranged from 40 to 74 μm in diameter (average, 54 μm). The range and unimodal distribution of diameters, the label used, and the presence of C terminals on almost all cells indicated that the 15 cell bodies and associated proximal dendrites analyzed here probably belonged to α‐motoneurons.

Synaptic terminals covered 39% of the cell body membrane, 60% of the proximal dendritic membrane, and 40% of the distal dendritic membrane. At each of these three sites, F terminals (flattened or pleomorphic vesicles, usually symmetric active zones, average contact length 1.6 μm) were most common, averaging 52%, 56%, and 58% of total coverage and 56%, 57%, and 58% of total number on cell bodies, proximal dendrites, and distal dendrites respectively. S terminals (round vesicles, usually asymmetric active zones, average contact length 1.3 μm) averaged 24%, 29%, and 33% of coverage and 33%, 35%, and 36% of number at these three sites, respectively. Thus, S terminals were slightly more prominent relative to F terminals on distal dendrites, than on cell bodies. C terminals (spherical vesicles, subsynaptic cisterns associated with rough endoplasmic reticulum, average contact length 3.5 μm) constituted 24% and 11% of total terminal coverage on cell bodies and proximal dendrites, respectively, and averaged 11% and 6% of terminal number at these two locations. M terminals (spherical vesicles, postsynaptic Taxi bodies, some with presynaptic terminals, average contact length 2.7 μm) were absent on cell bodies and averaged 3% and 7% of total coverage and 2% and 5% of terminals on proximal and distal dendrites, respectively. Except for M terminals, which tended to be smaller distally, terminal contact length was not correlated with location. Total and type‐specific coverages and frequencies were not correlated with cell body diameter.

Primate TS motoneurons are similar to cat TS motoneurons in synaptic terminal morphology, frequency, and distribution. However, primate terminals appear to be smaller, so that the fraction of menitrane covered by them is lower. © 1994 Wiley‐Liss, Inc.
Changes in nerve growth factor immunoreactivity following entorhinal cortex lesions: Possible molecular mechanism regulating cholinergic sprouting
Authors: Conner J. M. , Fass‐Holmes B. , Varon S.
Published: January 2005

To assess the possible role of trophic factors in lesion‐induced plasticity, we have used a sensitive immunohistochemical technique to evaluate changes in nerve growth factor (NGF) staining in the hippocampal formation 3, 8, 16, and 30 days following entorhinal cortex lesions. Our results indicate that a band of NGF immunoreactivity appears in the outer molecular layer of the ipsilateral dentate gyrus following entorhinal ablation. The distribution of the NGF‐immunoreactive band exactly coincides with the distribution of sprouting cholinergic terminals revealed by acetylcholinesterase histochemistry or NGF‐receptor immunostaining. Increased NGF‐immunoreactivity is detectable at 3 days postlesion, is most intense at 8 days, and decreases to near control levels by 30 days. Lesion‐induced increases in NGF immunostaining also occur in animals in which septohippocampal fibers had been removed by prior destruction of the fimbria‐fornix. Increases in NGF‐immunoreactivity, however, are substantially reduced in animals receiving intraventricular injections of colchicine, which presumably blocks NGF release. These results indicate that (1) increases in NGF immunostaining, which occur following entorhinal lesions, precede any changes in cholinergic sprouting parameters and are greatest during the period of maximal cholinergic sprouting; (2) increased NGF‐immunoreactivity is not due to NGF binding by septohippocampal fibers; and (3) increased NGF‐immunoreactivity appears to depend on the release of NGF by neurons that produce it. We hypothesize that, following entorhinal lesions, NGF immunostaining within the hippocampal formation may represent NGF “anchored” within the tissue and that NGF accumulation by such a mechanism may direct the sprouting response of NGF‐sensitive cholinergic neurons. © 1994 Wiley‐Liss, Inc.
Distribution of synapses on two ascending interneurones carrying frequency‐specific information in the auditory system of the cricket: Evidence for gabaergic inputs
Authors: Hardt M. , Watson A. H. D.
Published: January 2005

Two identified cricket: auditory interneurones, AN1 and AN2, were intracellularly labelled with horseradish peroxidase following physiological characterisation. The neurones, which have some structural similarities, have their somata in the prothoracic ganglion and axons that project to the brain. Although both carry auditory information, they have different response properties and participate in different types of phonotactic behaviour. Ultrathin sections from selected regions of their Prothoracic arborisations were examined in the electron microscope after postembbdding immunostaining for the inhibitory transmitter GABA. In the prothoracic ganglion AN1 branches only in the medial ventral association centre (mVAC) contralateral to the soma, and receives only input synapses. Twenty‐seven percent of these were made by processes ‐immunoreactive for GABA. AN2 branches not only in mVAC on both sides of the ganglion but also in several other areas. It makes output synapses from large diameter neurites in mVAC on both sides of the ganglion as well as from neurites in more posterior regions of the neuropile. Most input synapses are received onto branches in the contralateral mVAC where about 19% were made from GABA‐immunoreactive processes. © 1994 Wiley‐Liss, Inc.
Early development of the somatotopic map and barrel patterning in rat somatosensory cortex
Authors: Schlaggar Bradley L. , O'Leary Dennis D. M.
Published: January 2005

Several lines of evidence implicate a crucial role for thalamic afferents from the ventroposterior nucleus (VP) in the development of barrels and their characteristic pattern in the primary somatosensory cortex (Sl) of rodents. We sought to determine the stage in development when VP thalamocortical afferents are first distributed in a periphery‐related pattern and the sequence of events that culminate in a mature pattern. Using acetylcholinesterase (AChE) histochemistry, an early marker for VP thalamocortical afferents, and the anterograde axon tracer DiI, we show that VP thalamocortical afferents become distributed into a peripheryrelated pattern earlier than was previously reported, including their parcellation into a barrel‐related pattern that mirrors the distribution of sensory hairs on the face. The earliest periphery‐related patterning observed is transiently present in the deep cortical layers prior to the emergence of layer 4, the layer in which barrels later develop. AChE histochemistry reveals a clear sequence of maturation of the barrel pattern in the distribution of VP afferents: An initially patternless distribution of AChE‐reactive afferents is followed by their distribution in a nascent trigeminal representation, from which rows subsequently emerge; barrel‐related clusters of afferents then emerge from the rows. This process begins before birth, and the transition from row‐related to barrel‐related distributions of VP afferents is evident during the first postnatal day (P0). This demonstration of a periphery‐related pattern in developing rat S1 precedes by about 2 days that revealed by any other marker reported to delineate barrels. These findings confirm that VP thalamocortical afferents are the first barrel component to have a periphery‐related pattern and support the hypothesis that thalamocortical afferents provide to immature S1 the patterning information that initiates the formation of barrels and their characteristic array. Furthermore because these findings show an earlier onset for barrel formation than was previously realized, they necessitate a reevaluation of conclusions drawn from experiments examining, developmental plasticity in barrel patterning. © 1994 Wiley‐Liss, Inc.
Cytoarchitecture of the medial geniculate body in the mustached bat (Pteronotus parnellii)
Authors: Winer Jeffery A. , Wenstrup Jefferey J.
Published: January 2005

The cytoarchitectonic organization of the medial geniculate body and adjoining thalamic nuclei was analyzed in the mustached bat (Pteronotus parnellii). These subdivisions provide a reference for structural, physiological, conncetional, and nurochemical work. Most nuclei recognized in other mammals exist in the mustached bat, although the relative volume of the three divisions was species specific. The ventral division contains medium‐sized neurons and a few smaller cells and is well developed. Neurons in the lateral part lie in regularly aligned rows corresponding to the laminae in Golgi material; in the medial part, these laminae are obscured by fibers. The dorsal dividion has at least four nuclei, each with a unique cytoarchitecture and myeloarchitectonic organization. The suprageniculate nucleus is prominent and has many large radiate neurons. Cells in the superficial dorsal nucleus have weakly laminated dendrites, while dorsal nucleus neurons have spherical dendritic fields. There is a wide range of neuropil patterns within the dorsal division. The suprageniculate nucleus has thick myelinated axons, while the fibers in the superficial and dorsal nuclei are much thinner. The rostral pole nucleus becomes prominent in the anterior one‐half of the auditory thalamus; its architectonic affiliation is equivocal, and connectional and immunocytochemical studies suggest that it may belong to the dorsal division. The medial division is one nucleus with many types of neurons, and it has coarse axons without laminar orientation. It is the smallest of the divisions and is present throughout the medial geniculate complex, except at the caudal tip and at the rostral pole.

Many features of medial geniculate body organization evident in other mammals are recognized in the mustached bat. These include a prominent ventral division, some of whose neurons have a laminar organization, and a comparatively small medial division that is devoid of fibrodendritic laminae. Other features, such as the presence of a large rostral pole nucleus, whose homologue in other species is uncertain, or the sparse number or small cells that may participate in local circuits, set it apart from carnivores and primates and suggest that there are species specific patterns of medial geniculate body organization. © 1994 Wiley‐Liss, Inc.
Amino acid immunocytochemistry of primary afferent terminals in the rat dorsal horn
Authors: Valtschanoff Juli G. , Phend Kris D. , Bernardi Patrizia S. , Weinberg Richard J. , Rustioni Aldo
Published: January 2005

We combined transganglionic tracing methods with postembedding electron microscopic immunocytochemistry to determine whether identified primary afferent fibers terminating in spinal laminae I‐IV may use glutamate and aspartate as neurotransmitters. Sciatic injections of wheat‐germ agglutinin conjugated to horseradish peroxidase labeled fine afferent fibers with terminals in laminae I‐II of the lumbar spinal cord, whereas injections of the B subunit of cholera toxin conjugated to horseradish peroxidase labeled primary afferent terminals in deeper laminae. Many labeled primary afferent terminals in superficial laminae were involved in glomerular synaptic arrangements; others established nonglomerular contacts. Most glomerular arrangements were clearly immunopositive for glutamate, compared with dendrites, astrocytes, or terminals immunopositive for γ‐aminobutyic acid (GABA). The degree of enrichment varied in labeled terminals of different morphological types. Aspartate was enriched, though to a lesser degree than glutamate, in labeled central terminals of glomeruli in superficial laminae. Labeled primary afferent terminals in laminae III‐IV were immunopositive for glutamate, though at lower levels than glomerular terminals in superficial laminae. Aspartate was not enriched in these terminals compared with dendrites, glia, and GABA‐positive terminals. These results support a neurotransmitter role for glutamate in primary afferents to the dorsal horn. Quantitative differences in the content of glutamate in identified primary afferent terminals may be related to functional differences. Enrichment of aspartate in terminals in superficial but not deep laminae is compatible with a role for this amino acid in sustained, NMDA‐mediated phenomena characteristic of activity in fine caliber afferents. © 1994 Wiley‐Liss, Inc.
Growth cones of regenerating retinal axons contact a variety of cellular profiles in the transected goldfish optic nerve
Authors: Strobel Gabrielle , Stuermer Claudia A. O.
Published: January 2005

Following optic nerve transection in goldfish, retinal axons regenerate. To determine what the growth cones use as a substrate for their growth, regenerating growth cones were labeled by horseradish peroxidase (HRP) application to the retina 5–6 days after intraorbital optic nerve section (ONS) and identified at 10–11 days after ONS in the brain sided (distal) portion of the optic nerve in thick and serial ultrathin sections. Leading growth cones (n = 5) were found in intimate contact with a variety of elements: with myelin fragments alone, with myelin fragments and glial cells, and with the basal lamina of the glia limitans and the surface of a fibroblast outside the boundary of previous fascicles.

In ultrathin sections of conventionally treated regenerating optic nerves, (unlabeled) axon profiles—in addition to myelin fragments—were seen to be in contact with an astrocyte and an oligodendrocyte, suggesting that the growth cones of these axons may have been associated with those cells. The data suggest that leading growth cones of regenerating axons may be capable of growing along myelin fragments and on a wide variety of cellular surfaces in the goldfish optic nerve. © 1994 Wiley‐Liss, Inc.
Neuropeptide Y immunoreactivity identifies a regularly arrayed group of amacrine cells within the cat retina
Authors: Hutsler Jeffrey J. , Chalupa Leo M.
Published: January 2005

Retinal amacrine cells can be divided into subgroups on the basis of morphological properties and chemical content. It is likely that these subgroups have specific connections and serve unique functional roles within the inner plexiform layer. In the present study we show that immunoreactivity to neuropeptide Y (NPY) identifies a group of amacrine cells (165,000–170,000) whithin the adult cat retina. This is the largest group of peptide‐containing amacrine cells identified to date in the cat retina. These neurons have small cell bodies and are regularly spaced at all regular spacing, suggests that these neurons form a specific subgroup of the amacrine cell class and are likely to serve a unique role in the transfer of visual information through the inner plexiform layer. © 1994 Wiley‐Liss, Inc.
Distribution of neuropeptide FF in porcine spinal cord in comparison with other neuropeptides and serotonin
Authors: Wasowicz K. , Panula P.
Published: January 2005

A large number of neurotransmitters and neuropeptides are concentrated in the dorsal horn of the spinal cord, Where they interact in a complex manner and modulate sensory mechanisms. Most studies are carried out in the rat, and little is known of other species. It is relevant to study mammals with a more complex central nervous system, because pain mechanisms are central in both human and veterinary medicine. Immunoreactivity for neuropeptide FF, an amidated octapeptide originally isolated from bovine brain, was found immunocytochemically at all levels of porcine spinal cord. In contrast to other species studied so far, the peptide immunoreactivity in porcine spinal cord was confined to the intermediolateral gray matter, especially to the intermediolateral cell column and lamina X of the gray matter. This distribution was remarkably different from that of substance P, proenkephalin A‐derived peptides, thyrotropin‐releasing hormone, serotonin, and neuropeptide Y. Pharmacologic administration of neuropeptide FF alters behavior in assays for analgesia. The distribution of neuropeptide FF immunoreactivity as revealed by this study suggests that there may be marked species differences in the distribution and function of the peptide. © 1994 Wiley‐Liss, Inc.
Tangential organization of callosal connectivity in the cat's visual cortex
Authors: Boyd Jamie , Matsubara Joanne
Published: January 2005

Cells and/or terminals of corticocortical pathways in mammalian visual cortex often have a discontinuous distribution across the surface of the cortex. A modular organization of cortical function has been shown to underlie the tangential segregation of many inputs and outputs. Here, we present evidence that the callosal pathway in the visual cortex of the cat follows these general principles. Large injections of wheat germ agglutinin‐horseradish peroxidase or biotinylated dextran amine were made in areas 17 and 18, and callosal labeling was analyzed in tangential sections. The band of callosal cells and terminals straddling the border of areas 17 and 18 was not uniform but varied in density in a complicated fashion. Fluctuations in density of callosal connections became more clear 2–3 mm lateral or medial to the 17/18 border, as the callosal labeling became less dense. Here, regular fluctuations with a periodicity of about 1 mm in area 17, and slightly greater than 1 mm in area 18 were apparent. Cytochrome oxidase staining in areas 17 and 18 showed a pattern of dense blobs with the same spacing as the callosal labeling in these areas, and the blobs were found to align with the patches of callosal labeling. Larger, more irregularly spaced stripes of callosal labeling extended from the lateral part of area 18 across area 19 and into more lateral visual areas. These results suggest that the callosal pathway in the cat's visual cortex has a patchy distribution similar to many ipsilateral corticocortical projections, and that the columnar system marked by cytochrome oxidase is important for the organization of (interhemispheric) corticocortical connectivity in cats. © 1994 Wiley‐Liss, Inc.
Lack of Purkinje cell loss in adult rat cerebellum following protracted axotomy: Degenerative changes and regenerative attempts of the severed axons
Authors: Dusart Isabelle , Sotelo Constantino
Published: January 2005

The cerebellar Purkinje cells, due to their geometrical disposition and their high calbindin content, offer an optimal system in which to test the adequacy of current opinions on axotomy effects. We have, therefore, analyzed with calbindin immunostaining the morphological changes of Purkinje cells from 1 day to 6 months after axonal section in the cerebellar white matter. This method allows us to study the morphological changes in their dendrites, cell bodies, and axons. We have also searched for simultaneous changes in glial cells and vascularization by using cell type‐specific markers. In addition, an ultrastructural study of Purkinje cells, 7 days after large electrolytic lesions affecting the white matter and the overlying granular layer, was carried out to determine whether amputation of the recurrent collateral system provokes a fast neuronal death.

Neither the Purkinje cells axotomized close to their cell bodies (electrolytic lesions) nor those axotomized in the white matter (cerebellar transection) degenerated. Thus, this study demonstrates that Purkinje cells are extremely resistant to axotomy; those severed in the white matter at distances varying from 100 μm to 3 mm remain alive for as long as 6 months. At all survival times studied, axotomized Purkinje cells exhibited few changes in their somata and dendrites, as well as in their glial microenvironment. The major changes occurred in the axonal compartment. Axonal alterations, namely the presence of torpedoes and hypertrophy of the recurrent collateral system, were early events already noticeable 24 hours after the lesion, although they later differed in their time course and spatial distribution. It is remarkable that the distal segments of the central stumps of the cut axons survived in large numbers without any apparent retraction, with their terminal varicosities apposed to the wall of the wound cavity even 6 months after the lesion. Nevertheless, these segments were thinner than normal Purkinje cell axons (axonal atrophy). Despite this apparent immutability, some regenerative attempts did occur in the severed axons, such as axonal sprouts penetrating the deeper region of the granular layer in zones close to the lesion, presence of arciform axons, and hypertrophy of the recurrent collateral system. However, the Purkinje cell axons did not regenerate, and these neurons remained separated from their targets by a cavity in virtually all cases. © 1994 Wiley‐Liss, Inc.