bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isolated satellite cells of a peripheral nerve direct the growth of regenerating frog axons
Authors: Kuffler Damien P. 
Published: January 2005

AbstractFrog motor axons regenerate and grow back to reinnervate their targets, the original motor end plates, after a lesion. When the cutaneous pectoris muscle is cut away and a segment of peripheral nerve is placed in the vicinity of regenerating axons they turn and grow toward it. This is in marked contrast to the random pattern of axonal outgrowth seen in the absence of a target. The influence on the direction of axonal growth of motor neurons can be produced by a 1‐mm segment of nerve satellite cells over a distance of more than 8 mm.The nerve satellite cells have no influence on the direction of growth of the regenerating axons after all the cells in the nerve segment have been killed, leaving only the Schwann cell basal lamina tubes intact. These results show that the cells in the segment of the nerve trunk contain cues that actively direct the growth of motor neurons. Two possible explanations for this effect might be (1) that the cells act indirectly by influencing the organization of the substructure over which axons regenerate or (2) that the nerve satellite cells release a diffusible substance that acts directly on the regenerating axons.
Ultrastructural characterization of identified cholinergic neurons transplanted to the hippocampal formation of the rat
Authors: Anderson Kevin J. , Gibbs Robert B. , Salvaterra Paul M. , Cotman Carl W. 
Published: January 2005

AbstractThe ultrastructural features of cholinergic neurons transplanted to the rat hippocampal formation were studied by using a monoclonal antibody to choline acetyltransferase (ChAT). Septal cell suspensions were prepared from E‐18 rat embryos and injected into the hippocampus of host rats that had been previously subjected to a bilateral transection of the fimbria‐fornix. Rats with fimbria‐fornix lesions alone and unoperated rats served as controls and were examined to characterize the native hippocampal cholinergic system.Both unoperated controls and rats with fimbria‐fornix lesions showed a sparse population of intrinsic ChAT‐immunoreactive neurons that were most numerous in the subgranular zone, the hilus fascia dentata, and near the hippocampal fissure. ChAT‐positive terminals from controls formed synapses on dendritic structures that were primarily symmetrical. ChAT‐positive dendrites in controls received synaptic input from nonimmunoreactive axon terminals.In rats with septal transplants, ChAT‐immunoreactive transplant neurons were found that were either bipolar or multipolar. Axons of transplanted neurons were unmyelinated and arose either from the cell body or a primary dendritic process where they gave off numerous collaterals. Terminals from transplant neurons formed synapses with many nonimmunoreactive neurons. In transplant animals, two main targets of ChAT‐immunoreactive terminals were identified: (1) The great majority of synapses were symmetrical junctions with dendritic spines and shafts. (2) A number of terminals were found that appeared to be juxtaposed to nonimmunoreactive axon terminals, possibly forming symmetrical axo‐axonic connections. In contrast, such axo‐axonic contacts were not observed in the controls.It is concluded that transplanted cholinergic neurons may reinnervate the host hippocampus; however, this reinnervation is different from what is seen in the intact hippocampal formation.
Immunocytochemical studies on astroglia of the cat retina under normal and pathological conditions
Authors: Karschin Andreas , Wässle Heinz , Schnitzer Jutta 
Published: January 2005

AbstractThe cell density and morphology of astrocytes in whole‐mounted adult cat retinae have been studied by immunocytochemical localization of glial fibrillary acidic protein (GFAP). There was a peak density at the optic nerve head of about 2,000 astrocytes/mm2 dropping to approximately 200 astrocytes/mm2 in the far periphery. In the central area there was a local minimum of astrocyte density. Whereas the processes of astroglia in the outermost retinal periphery were radially arranged, thus giving the cells a characteristic star‐shaped appearance, the majority of astroglial processes in the central region of the retina were aligned in parallel with the ganglion cell axon bundles. To study the correlation between optic nerve fibres and astrocytes, ganglion cell axons were caused to degenerate following photocoagulation lesions close to the optic disc. Postlesion the processes of astrocytes in the central retina lost their directional preference and linearity, thus appearing to develop a star‐shaped morphology typical of astroglia in the far periphery of normal retinae. The density of astrocytes decreased by approximately 50% on the optic disc side of the lesions and by up to 80% on the peripheral side of the lesions. The results show that the morphology and number of astrocytes vary as a function of their proximity to optic nerve fibres and to the density of these fibres.
A second ascending visual pathway from the optic tectum to the telencephalon in the pigeon (Columba livia)
Authors: Gamlin Paul D. R. , Cohen David H. 
Published: January 2005

AbstractPrevious studies in the pigeon (Karten and Revzin: Brain Res. 2:368–377, '66; Karten and Hodos: J. Comp. Neurol. 140:35–52,'70) have described an ascending tectofugal visual pathway from the optic tectum to the ectostriatum by way of the nucleus rotundus of the thalamus. This present study used anterograde autoradiographic and retrograde horseradish peroxidase pathway‐tracing techniques to investigate another ascending tectofugal pathway in the pigeon. Injections of 3H‐proline/leucine confirmed a previous report that the optic tectum projects to the nucleus dorsolateralis posterior of the thalamus (DLP). This projection is predominantly ipsilateral and is confined to a large‐celled caudal region of the nucleus (DLPc); the rostral region of the nucleus (DLPr) is not tectorecipient. Injections of horseradish peroxidase in DLPc labeled cells predominantly ipsilaterally in layers 8–15 of the optic tectum. Injections of 3H‐proline/leucine placed in the DLPc labeled a discrete region of the ipsilateral telencephalon. Similar injections of DLPr labeled a contiguous, but more rostral, region of the neostriatum intermedium. Nissl‐ and silver‐stained material indicated that the region in which DLP terminates is cytoarchitecturally distinct from ventromedial ectostriatal core and belt. Injections of horseradish peroxidase at various locations in the neostriatal DLP terminal field demonstrated a rostrocaudal ordering of the DLP projection upon the neostriatum intermedium. Singleunit recording demonstrated that cells in DLPc respond to whole‐field illumination at the same latency as cells in the nucleus rotundus, indicating that the tecto‐DLPc‐neostriatal pathway transmits visual information to the telencephalon. We suggest that comparable pathways may exist in both reptiles and mammals.
Histochemical and architectonic differentiation of zones of pretectal and collicular inputs to the pulvinar and dorsal lateral geniculate nuclei in the macaque
Authors: Lysakowski Anna , Standage Gregg P. , Benevento Louis A. 
Published: January 2005

AbstractThe pattern of acetylcholinesterase (AChE) reactivity was studied in the pulvinar and dorsal lateral geniculate nucleus (DLG) of the adult macaque monkey. Discrete islands of AChE reactivity were found that correlated precisely in location with the pattern of projections from the superior colliculus and pretectum. Specifically, AChE overlies terminal fields of superior colliculus projections in the DLG, in four foci in the medial and lateral pulvinar, and in several foci in the inferior pulvinar. All of these tectal projection areas have very high AChE reactivity such that they are easily distinguished. In addition, the pretectum projects to a specific focus in the lateral pulvinar that also has a very dense AChE histochemical reaction. A number of these AChE foci could be further distinguished from other areas in the pulvinar by myeloarchitectonic characteristics. Some of the foci in the lateral and inferior pulvinars could also be distinguished by unique cytoarchitectonic features (as seen with both Nissl and Golgi stains). In an attempt to determine the possible origin of a cholinergic input to the pulvinar, horseradish peroxidase (HRP) injections and choline acetyltransferase immunohistochemistry were also done. The results of this experiment indicate that the AChE reactivity seen in the midbrain projection zones to the thalamus may be due to the precise overlap of terminal projections from the brainstem cholinergic cell groups, Ch5, Ch6, and Ch8. These results, taken together, imply that there are several anatomically and histochemically distinct zones related to extre ageniculate pathways located within classically defined thalamic boundaries.
Organization of immature intrahemispheric connections
Authors: Clarke Stephanie , Innocenti Giorgio M. 
Published: January 2005

AbstractIn the adult cat injections of retrograde fluorescent tracers near the border between areas 17 and 18 and extending to the underlying white matter label neurons in restricted parts of nine other ipsilateral visual areas. A very similar, restricted distribution of retrograde labeling is found in newborn kittens when injections near the 17/18 border are confined to the cortical gray matter. When, however, the neonatal 17/18 border injection reaches the underlying white matter, more visual areas and numerous nonvisual areas become labeled, each of them over nearly its whole tangential extent. Labeled nonvisual areas include the primary and secondary auditory areas, the auditory areas of the posterior ectosylvian gyrus, areas 7 and 5, the cingulate gyrus, and the primary and secondary somatosensory areas. The widespread labeling in kittens was not due to larger or differently placed injections, since the distribution and extent of retrograde labeling in the ipsilateral lateral geniculate nucleus were similar at all ages. The transitory projections from the auditory and somatosensory areas are not reciprocated by a projection from areas 17 or 18.In kittens injected around the end of the first postnatal month the distribution of labeled association neurons is similar to that found in the adult; i.e., many of the juvenile projections have been eliminated.Only a few of the transitory axons to areas 17 and 18 enter the gray matter; the others remain confined to the white matter. Some of these axons were anterogradely labeled with rhodamine‐B‐iso‐thiocyanate from the auditory cortex; they show bulbous endings, some of which are probably growth cones.Retrograde double‐labeling experiments showed that, in the newborn, some neurons on the lateral sulcus have at least two long collaterals, one running rostrally, the other caudally; such branching is not observed in adults.In conclusion, areas 17/18 receive at birth from a large, continuous territory including areas, or parts of areas, which will later eliminate these projections. Most of the transitory projections do not appear to enter the cortex to any great extent. The major reshaping of association projections occurs before end of the first postnatal month. The development of association projections resembles that of callosal projections.
Segmental homologies among reticulospinal neurons in the hindbrain of the zebrafish larva
Authors: Metcalfe Walter K. , Mendelson Bruce , Kimmel Charles B. 
Published: January 2005

AbstractWe have examined the morphology of identified reticulospinal neurons in larval zebrafish by retrogradely labeling them with horseradish peroxidase. We describe the morphology of 27 different types of reticulospinal neurons found in the hindbrain 5 days after fertilization. Nineteen of these types are present as single identified neurons on each side of the brain; the other are present as pairs or small groups of cells.The hindbrain reticulospinal neurons are present in seven bilateral clusters that are spaced periodically along the neuraxis. Each cluster contains two to five different types of reticulospinal neurons. Cells with similar morphological features are found in adjacent clusters. By considering cell position within the cluster and axon pathway, nearly all of the cells can be assigned to one of about seven serially repeated classes. Independent morphological features of the cells support the same classification.We propose that the clusters represent hindbrain segments and that the neurons of the same class that are present in the different clusters are segmental homologues. Assuming that this series evolved by successive duplications and divergence of the primitive segments, we have analyzed the changes that may have occurred during the evolution of each new segment. Changes between ipsilaterally and contralaterally projecting axons may have occurred several times during the evolution of the series. In addition, cells may have been added or deleted.
Light‐evoked and kainic‐acid‐induced disc shedding by rod photoreceptors: Differential sensitivity to extracellular calcium
Authors: Besharse Joseph C. , Spratt Gwendolyn , Forestner Donna M. 
Published: January 2005

AbstractIn order to study the light and Ca2+ dependence of disc shedding by rod photoreceptors, we have used eyecups prepared from adult Rana pipiens frogs that had been kept in constant light for 4 days. Disc shedding was initiated by a treatment involving 1 hour of darkness followed by exposure to light or by treatment with kainic acid. Maximal L‐evoked disc shedding occurred quickly (within 30–60 minutes) after light onset and could be triggered by brief (15 minutes) exposure to light. L‐evoked disc shedding was completely blocked by omission of Ca2+ from culture medium or by treatment with 3mM Co2+ or 12 mM Mg2+ in the presence of Ca2+ (2 mM). The response was also blocked by the organic Ca2+ antagonist nifedipine. Experiments designed to distinguish between Ca2+ dependence of the dark or light‐dependent processes necessary for shedding suggest that volage‐sensitive channels mediate a Ca2+‐dependent process involved in light‐triggering. Kainic acid caused a dose‐dependent stimulation of disc shedding under lighting conditions (continuous culture in light or darkness) that did not normally result in a significant response in the absence of the drug. Disc shedding induced by kainic acid was similar in time course and magnitude to that induced by light. However, kainic‐acid‐induced disc shedding was not inhibited by medium Ca2+ reduction or by the presence of Co2+. The latter observation suggests that kainic acid activates disc shedding directly, bypassing the Ca2+‐dependent process involved in the L‐evoked response. The Ca2+‐dependent process may involve release of an effector of disc shedding that is mimicked by kainic acid.
Morphology of retinogeniculate X and Y axon arbors in monocularly enucleated cats
Authors: Garraghty P. E. , Sur M. , Weller R. E. , Sherman S. M. 
Published: January 2005

AbstractWe examined the terminal arbors of single, physiologically identified retinogeniculate X and Y axons from the remaining retinas of adult cats raised from birth with monocular enucleation. These were compared with arbors of X and Y axons in normally reared cats. We used intra‐axonal injections of horseradish peroxidase to label each axon after recording its response properties. While the axons in monocularly enucleated cats exhibited normal response properties, both X and Y axons in these cats had abnormally large terminal arbors. Each of the hypertrophied X arbors appeared to be completely confined to the single geniculate lamina A or A1 appropriate to its eye of origin (i.e., lamina A for the contralateral retina and lamina A1 for the ipsilateral retina). In contrast, in addition to their normal terminations, most of the Y arbors seemed to extend well into laminae normally innervated only by the retina that was removed. Thus most or all of the translaminar sprouting previously reported for monocularly enucleated cats appears to reflect extensions of Y axon arbors. These data, in addition to earlier, analogous data from young kittens and cats reared with monocular lid suture, suggest the following sequelae during postnatal development: the retinogeniculate X arbors mature first and develop exuberant arbors that are later competitively pruned as the Y axons expand their innervation of the lateral geniculate nucleus; monocular lid suture prevents the Y axons from succeeding in this competition, so they fail to establish normal arbors and cannot reduce the exuberant X arbors; monocular enucleation offers a less resistant path in the denervated laminae for the rapidly growing Y arbors from the remaining eye, and the expansion of these arbors there reduces the competitive pressure on the exuberant X arbors. Thus, in monocularly enucleated cats, sprouting is limited to Y axons, either because only they possess the capacity to sprout or because they are in the midst of a period of relatively rapid growth at the time of the neonatal enucleation. The X axon arbors are also abnormally large within their appropriate laminae. This occurs presumably because they are able to maintain their immature exuberance, although we cannot rule out the possibility that they are pruned and later regrow to the final size seen in our experiments.
Callosal projections from area SII to SI in monkeys: Anatomical organization and comparison with association projections
Authors: Manzoni Tullio , Conti Fiorenzo , Fabri Mara 
Published: January 2005

AbstractThe present research was aimed at ascertaining in the macaque monkey the reciprocity of the heterotopical callosal connections between SI and SII, with particular regard to the connectivity of the hand representation, and at comparing the topographical and laminar pattern of these callosal connections with those of association connections entertained by these areas. Horseradish peroxidase (HRP) was unilaterally injected into area SI in five monkeys. The sites of HRP delivery included the trunk and the hand zones preliminarily identified by recording multi‐unit responses to peripheral stimulation by means of microelectrodes. Anterograde and retrograde labelling was studied in SII of both sides.The results showed the complete reciprocity of the heterotopical callosal connections between SI and SII. In the latter area both callosal axon terminals and neurones were found, which were labelled from either the trunk or the hand zone of contralateral SI. Labelling of callosal axon terminals occurred mainly in layer IV and in the lowermost part of layer III. Labelled callosal neurones were mainly in the lower half of layer III, whereas few occurred in infragranular layers. Topographically, the distribution of callosal terminals and cell bodies duplicated the distribution of association terminals and cell bodies labelled in SII on the side ipsilateral to HRP injection. The laminar pattern of termination of association fibres from SI was similar to that of callosal fibres. However, the distribution of association‐projecting neurones in SII showed a striking difference from that of callosal‐projecting neurones. Unlike the latter neurones, which were mainly located in supragranular layers, association cell bodies overwhelmingly dwelt in layers V and VI and were less numerous in layers II and III. This laminar pattern of association SII‐SI cells corresponds to the “feed‐backward” model and fits the laminar pattern of their axon terminations (Friedman: Brain Res. 273: 147–151, '83).The association and callosal inputs and outputs of area SII are discussed in relation to the function of the forward and backward type of reciprocal connections entertained with SI in the ipsilateral hemisphere and to the function of SII in the interhemispheric exchange of somatosensory information.
Cytoarchitecture and saccular innervation of nucleus Y in the mouse
Authors: Frederickson Christopher J. , Trune Dennis R. 
Published: January 2005

AbstractThe cytoarchitecture and saccular innervation of the mouse nucleus y were investigated by using Golgi, Nissl, and myelin stains and anterograde axonal transport of horseradish peroxidase. Nucleus y was found to be a compact group of cells in a small fiber‐free region dorsal to the restiform body. Qualitative and morphometric analyses showed that most (75%) of the nucleus y neurons could not be reliably subdivided into morphologic subgroups, but varied continuously in soma size (15–25 μm), shape (fusiform to stellate), and number of dendrites (two to four), and had sparsely branched dendrites with an average of 3 to 4 spines per 10 μm of length. Three groups of cells that were identified morphometrically accounted for 10% (type I: large stellate cells), 9% (type II: long‐dendrite cells), and 6% (type III: elongated soma cells) of the y neurons. Vestibular nerve axons transporting horseradish peroxidase after injury at their origin in the saccular neuroepithelium were found to form a dense terminal meshwork that was virtually co‐extensive with the cytoarchitectonic boundaries of nucleus y. Nucleus y was distinguished from the overlying infracerebellar nucleus on the basis of anatomical, cytoarchitectural, and hodological features.
Thalamic connectivity of the second somatosensory area and neighboring somatosensory fields of the lateral sulcus of the macaque
Authors: Friedman David P. , Murray Elisabeth A. 
Published: January 2005

AbstractThe thalamocortical relations of the somatic fields in and around the lateral sulcus of the macaque were studied following cortical injections of tritated amino acids and horseradish peroxidase (HRP). Special attention was paid to the second somatosensory area (S2), the connections of which were also studied by means of thalamic isotope injections and retrograde degeneration. S2 was shown to receive its major thalamic input from the ventroposterior inferior thalamic nucleus (VPI) and not, as previously reported, from the caudal division of the ventroposterior lateral nucleus (VPLc). Following small injections of isotope or HRP into the hand representation of S2, only VPI was labeled. Larger injections, which included the representations of more body parts, led to heavy label in VPI, with scattered label in VPLc, the central lateral nucleus (CL), and the posterior nucleus (Po). In addition, small isotope injections into VPLc did not result in label in S2 unless VPI was also involved in the injection site, and ablations of S2 led to cell loss in VPI. Comparison of injections involving different body parts in S2 suggested a somatotopic arrangement within VPI such that the trunk and lower limb representations are located posterolaterally and the hand and arm representations anteromedially. The location of the thalamic representations of the head, face, and intraoral structures that project to S2 may be in the ventroposterior medial nucleus (VPM).The granular (Ig) and dysgranular (Id) fields of the insula and the retroinsular field (Ri) each receive inputs from a variety of nuclei located at the posteroventral border of the thalamus. Ig receives its heaviest input from the suprageniculate‐limitans complex (SG‐Li), with additional inputs from Po, the magnocellular division of the medial geniculate n. (MGmc), VPI, and the medial pulvinar (Pulm). Id receives its heaviest input from the basal ventromedial n. (VMb), with additional inputs from VPI, Po, SG‐Li, MGmc, and Pulm. Ri receives its heaviest input from Po, with additional input from SG‐Li, MGmc, Pulm, and perhaps VPI. Area 7b receives its input from Pulm, the oral division of the pulvinar, the lateral posterior n., the medial dorsal n., and the caudal division of the ventrolateral n.These results indicate that the somatic cortical fields, except for those comprising the first somatosensory area, each receive inputs from an array of thalamic nuclei, rather than just one, and that individual thalamic somatosensory relay nuclei each project to more than one cortical field.