bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preferential regeneration of spinal axons through the scar in hemisected lamprey spinal cord
Authors: Lurie Diana I. , Selzer Michael E. 
Published: January 2005

AbstractAxons of lamprey spinal cord can regenerate across a complete spinal transection. Thus, unlike the scar of injured mammalian spinal cords, the scar in the lamprey is not an absolute impediment to regeneration. However, it is still not known whether the scar is a relative impediment or whether it provides a favorable environment for regeneration compared to the spinal cord parenchyma. In order to answer this question, the cords of 12 large arval sea lampreys (4–5 years old) were hemisected at the level of the third gill and the animals allowed to recover for 10 weeks. The large reticulospinal neurons (Müller and Mauthner cells) or their giant axons were injected intracellularly with HRP and their regenerating neurites visualized in central nervous system (CNS) wholemounts. Forty‐five of seventy‐one regenerating neurites (64%) grew beyond the level of the hemisection. Of these, 36 (82%) regenerated through the scar and remained on the same side of the cord as their parent axons, while only 8 (18%) crossed the midline and grew around the scar. Thus, regenerating neurites of giant reticulospinal axons tended to grow through the hemisection scar rather than around it. Once they passed the level of injury, they continued to elongate in their appropriate paths.It is possible that this tendency for axons to regenerate through the scar reflects the greater amount of empty spaces on the hemisected side. In order to rule this out, 13 animals received contralateral simultaneous hemisections at the level of the 3rd and 7th gills. This procedure created large numbers of degenerating axons and potential empty spaces both rostral and caudal to the scars within both hemicords; 92 of 158 neurites (58%) regenerated beyond the level of their respective hemisections. All of these grew through the scar and none crossed to the contralateral side. Distal to either hemisection, neurites remained on their correct side regardless of whether the contralateral cord contained normal CNS parenchyma or axonal debris and empty spaces produced by Wallerian degeneration. Moreover, in hemisected and double hemisected animals, as well as in completely transected control animals, neurites regenerating in their correct direction grew further than those that were misrouted.Because lamprey spinal axons grow preferentially through a scar rather than around it, the scar may play a positive role in supporting axonal regeneration.
Functional projections from striate cortex and superior temporal sulcus to the nucleus of the optic tract (NOT) and dorsal terminal nucleus of the accessory optic tract (DTN) of macaque monkeys
Authors: Hoffmann K.‐P. , Distler C. , Erickson R. 
Published: January 2005

AbstractThe nucleus of the optic tract (NOT) and the dorsal terminal nucleus of the accessory optic tract (DTN) have been recognized to be relevant structures for optokinetic and vestibuloocular reflexes. NOT‐DTN neurons relay visual information to the vestibular nuclei via the nucleus prepositus hypoglossi and to the flocculus via the dorsal cap of the inferior olive. It has been previously shown that in carnivores the NOT‐DTN receives information from primary visual cortical areas in addition to the direct retinal input. In this study we demonstrate the presence and some functional characteristics such as latency and evicacy of considerable cortical projections to the NOT‐DTN in macaque monkeys.In anaesthetized and paralyzed monkeys NOT‐DTN neurons were identified physiologically and tested for cortical input by electrical stimulation in various cortical areas. Successful sites of stimulation to activate NOT‐DTN neurons orthodromically lie in the primary visual cortex (V1) and in the motion‐processing areas in the superior temporal sulcus (STS). In contrast, electrical stimulation in area V4 and in parietal areas in most cases did not yield orthodromic responses. Overall latencies of action potentials elicited by stimulation in V1 were 0.5 ms longer than those elicited from STS. These short latency differences between V1 and STS stimulation suggest a direct projection from both V1 and STS to the NOT‐DTN.The physiological results were supported by the results of anatomical experiments by using horseradish peroxidase as anterograde tracer. Both injections into V1 and into the lower bank of STS resulted in anterogradely labelled fibers and terminals around the recording sites of direction‐specific NOT‐DTN neurons.This paper is a first step in clarifying the significance of corticofugal projections from individual areas involved in the analysis of visual motion for the optokinetic reflex.
Administration or deprivation of nerve growth factor during development permanently alters neuronal geometry
Authors: Ruit Kenneth G. , Snider William D. 
Published: January 2005

AbstractWe investigated whether the administration or deprivation of a neuronal growth factor during development can permanently alter the dendritic architecture of sensitive neurons. Nerve growth factor (NGF) or NGF antiserum treatment in the first 2–3 postnatal weeks markedly affected the survival, size, and dendritic arborization of mouse sympathetic ganglion cells acutely. Six months after the completion of treatment, the number of surviving neurons, cell body size, and higher order dendritic branching had changed considerably from their values at 3 weeks, suggesting that these parameters remain malleable throughout postnatal life. However, the number of primary dendrites, a fundamental determinant of organization within sympathetic ganglia, was permanently altered by the neonatal treatment protocol.The idea emerging from this study is that NGF influences the elaboration of primary dendrites by sympathetic ganglion cells only during a critical developmental period. In maturity, NGF acts as a “maintenance” factor necessary for normal neuronal function and survival, but neurons lose the capacity to respond with wholesale rearrangements of dendritic architecture.
Brain macrophages and microglia respond differently to lesions of the developing and adult visual system
Authors: Milligan Carolanne E. , Levitt Pat , Cunningham Timothy J. 
Published: January 2005

AbstractTraumatic injury in the brain usually results in rapid degeneration of neuronal elements and a response by peripherally derived macrophages (brain macrophages, BMOs) and resident microglia. One intriguing result of lesions performed in the developing brain as compared to lesions of the mature brain is the faster resolution of the cellular debris and the absence of significant scarring. The purpose of this study was to examine the response of BMOs to induced cell death distant to the lesion site and to investigate possible differences in the responding phagocytic populations (BMOs versus microglia) following lesions in neonates and adults. Ablation of the visual cortex at birth results in very rapid retrograde degeneration and removal of neurons of the dorsal lateral geniculate nucleus (dLGN) within a few days. Lesions to the visual cortex of adult rats also induce neurons within the dLGN to die, but these cells do so over a much more protracted time course. Utilizing differences in morphology and immunocytochemical staining with the monoclonal antibodies EDI and OX‐42 to distinguish between BMOs and microglia, we found that in the developing CNS, BMOs are signalled rapidly and specifically to the location of induced cell death. Microglia are not involved in this response. As might be expected, the temporal response in the adult is much more protracted. In contrast to the developing brain, microglia and not macrophages are the predominant responding cell class after the adult lesion. The data suggest that these are distinct populations of phagocytic cells that respond to brain damage during development and in the adult, which may be critical in modulating the resolution and growth response after injury.
Postnatal development of cholinergic markers in the rat olfactory bulb: A histochemical and immunocytochemical study
Authors: Le Jeune Hélène , Jourdan François 
Published: January 2005

AbstractThe present study has defined the developmental time course and the distribution patterns of neuronal fibers and cell bodies displaying acetylcholinesterase (AChE) activity or choline acetyltransferase (ChAT) immunoreactivity in the rat olfactory bulb. The results indicate that the deployment of centrifugal AChE‐containing fibers is essentially postnatal. The subset of atypical glomeruli, including the modified glomerular complex, is innervated as early as the first postnatal day while the normal ones are not reached by this type of afferent before postnatal day 6. The comparison of AChE labelling with ChAT immunoreactivity strongly supports the assumption that AChE‐containing fibers represent mainly, if not exclusively, the cholinergic bulbopetal innervation emanating from the basal forebrain. A quantitative study has confirmed that the density of labelled fibers increases gradually in the postnatal period and spreads heterogeneously among the bulbar layers. The selective precocious innervation of atypical glomeruli is in favor of their involvement in the early processing of olfactory information in the olfactory bulb. Acetylcholinesterase is also expressed within a subset of ChAT‐negative interneurons of the developing olfactory bulb. The number of neurons expressing AChE increases from birth to postnatal day 15 and then decreases to reach the adult value on about postnatal day 30. This neuronal population could constitute a cholinoceptive subset mediating the effects of cholinergic afferents on the bulbar neuronal network.
Appearance and distribution of the 275 kD hair‐cell antigen during development of the avian inner ear
Authors: Bartolami S. , Goodyear R. , Richardson G. 
Published: January 2005

AbstractThe 275 kD hair‐cell antigen (HCA) is a protein that was originally identified using immunological techniques in the inner ears of early hatchling and adult chickens. The HCA is specifically associated with the apical surface of sensory hair cells; in the vestibular system the antigen is distributed over the entire stereocilia bundle, but in the auditory system it only extends a short distance up the shafts of the stereocilia. The objectives of this study were to ascertain when the HCA is first expressed during inner ear development, to compare the temporal and spatial patterns of HCA expression with those of neurite ingrowth, and to determine how the distribution of the antigen observed in the auditory system arises during development. Serial sections of otocysts from embryonic day (ED) 4 to ED7.5 (stages 24 to 32) were stained with a monoclonal antibody to the HCA and polyclonal antibodies to the neuron–glial cell adhesion molecule in order to analyse patterns of HCA expression and neurite ingrowth. Nerve fibres are first observed in the anterior pole of the otocyst at ED4.5 (stage 24), and in the evaginating basilar papilla by EDS (stage 26). The HCA first appears within the vestibular system in the anterior pole of the otocyst at EDS (stage 26), and within the auditory system in the distal end of the basilar papilla at ED6.5 (stage 29). Serial section analysis indicates that expression of the HCA is always limited to areas of the epithelium where nerve fibres are found, although the delay between the onset of innervation and the onset of HCA expression varies from one region of the otocyst to another. The growth of stereocilia bundles in the auditory system was studied from ED10 to 2 days after hatching in sections from the medial to distal regions of the basilar papilla double labelled with rhodamine phalloidin and monoclonal anti‐HCA, At ED12 the stereocilia bundles are 1.7 μm high and the staining observed with both phalloidin and the antibody extend to the same maximum height above the apical surface of the hair cell. The maximum height that anti‐HCA staining extends up the stereocilia bundle remains almost constant between ED12 and postnatal day 2, but between ED15 and ED18 the stereocilia bundle grows rapidly in height, with a membrane domain lacking the HCA forming at the distal ends of the stereocilia. The restricted distribution of the HCA observed on the apical surface of mature auditory hair cells in the basilar papilla is therefore generated during the final growth phase of the stereocilia bundle by the accumulation of HCA‐free membrane at the distal ends of the stereocilia.
Altered expression of pp60c‐src induced by peripheral nerve injury
Authors: Ignelzi Michael A. , Padilla Stephanie S. , Warder Daryl E. , Maness Patricia F. 
Published: January 2005

AbstractThe normal src protein (pp60c‐src) is localized principally in the nerve growth cone of developing neurons and declines to low levels with synaptic maturation. To determine whether pp60c‐src is reexpressed in regenerating axons, its expression was studied by immunoblotting and immunocytochemical analyses in adult chicken sciatic nerve following nerve crush injury. pp60c‐src expression was found to increase during nerve repair with a temporal and spatial pattern consistent with a localization in regenerating axons. At the crush site, pp60c‐src increased to maximal levels 7 days postinjury, increasing fivefold relative to 0 day nerve. In the nerve segment distal to the injury, the maximal increase in pp60c‐src was sevenfold and occurred between 11 and 21 days postinjury. Immunoperoxidase staining revealed pp60c‐src in regenerating axons and certain nonneuronal cells at the site of nerve repair. pp60c‐src was induced in both motor and sensory neurons, as shown by increased pp60c‐src immunoreactivity in their cell bodies located in the spinal cord and dorsal root ganglion. Phosphotyrosine‐modified proteins that were potential targets of pp60c‐src increased following nerve crush, and were localized to outgrowing neurites as well as to nonneuronal cells. These results suggest that pp60c‐src is a common component of cellular mechanisms regulating growth cone migration in both regenerating and developing axons.
A morphological correlate of target recognition by regenerating motor axons in the cockroach
Authors: Denburg Jeffrey L. , Caldwell Robert T. 
Published: January 2005

AbstractA specific cell recognition process during regeneration of severed axons of identified cockroach motor neurons eventually leads to the reformation of the original innervation pattern of target muscles in the leg. This occurs even though, at early times after nerve crush, the multiple branches of each regenerating axon grow into both appropriate and inappropriate muscles. In this study, we sought to examine whether there are any structural differences between regenerating axon branches in appropriate and inappropriate muscles that could lead to an understanding of why only those in inappropriate muscles are eliminated. A neuron subset‐specific monoclonal antibody, NSS‐2A, which labels the inhibitory motor neurons, was used to make their axon branches visible at various times after nerve crush. In inappropriate muscles, these axons grow primarily parallel to the muscle fibers and are later eliminated. In the appropriate muscles, these axon branches initially also grow parallel to the muscle fibers, but subsequently grow many interstitial collaterals. The formation of the collateral branches is a morphological correlate of the specific interaction of a neuron with its appropriate muscle. The simultaneous occurrence of axonal elimination and collateral sprouting supports the idea that the two processes are causally related, as suggested by the sibling neurite bias hypothesis.
Structural and functional consequences of neonatal deafferentation in the superficial layers of the hamster's superior colliculus
Authors: Mooney Richard D. , Nikoletseas Michael M. , King Tod D. , Savage Steven V. , Weaver Michael T. , Rhoades Robert W. 
Published: January 2005

AbstractIntracellular recording and horseradish peroxidase (HRP) injection techniques were used to evaluate the effects of neonatal enucleation upon the structural and functional properties of cells in the superficial retinorecipient laminae of the hamster's superior colliculus (SC). The physiological recordings confirmed previous results that normally visual superficial layer neurons develop somatosensory receptive fields in the enucleated animals. This study further showed that all of the physiological subclasses of somatosensory neurons normally encountered in the deep layers were present in the superficial laminae. With the exception of marginal cells, all of the morphological classes of neurons in the superficial SC laminae of sighted hamsters (narrowfield vertical cells, widen eld vertical cells, stellate cells, horizontal cells, and giant stellate cells) were recovered from the blinded animals. Quantitative comparison of neurons within a given morphological class demonstrated only slight differences between cells from blind and sighted hamsters. However, there was a significant reduction in the percentage of neurons with dorsally directed dendrites in the neonatally enucleated animals. Additional experiments with the Golgi technique also demonstrated that neonatal enucleation altered the distribution of morphological cell types in the superficial SC laminae. These results suggest that enucleation in the hamster may result in relative reductions in specific cell types in the superficial SC laminae rather than dendritic changes in all of the cell classes present in these layers.
Sensory reinnervation after partial removal of the olfactory bulb
Authors: Monti‐Graziadei A. G. , Graziadei P. P. C. 
Published: January 2005

AbstractIn this study, in order to provide the anatomical basis for future behavioral and electrophysiological experiments, we describe the effects of unilateral bulbar lesion on the peripheral sensory neurons and the parameters of reinnervation of the damaged olfactory bulb. Neonatal mice and rats were subjected to removal of portions of the olfactory bulb. At survival times from 2 to 6 months, the animals were killed by transcardial perfusion and processed for light (histological, immunohistochemical, autoradiographic) and electron microscopic observations. As a result of this surgery, in the basal layer of the olfactory neuroepithelium the rate of mitotic activity increased while the number of mature olfactory neurons was greatly reduced. The regrowing olfactory axons, by forming ectopic glomerular structures in the damaged target, profoundly influenced its reorganization. The typical layered morphology of the olfactory bulb was often disrupted in the bulbar remnant; the large dendrites of the deafferented mitral cells bent toward the ectopically located glomerular structures establishing numerous synaptic contacts. The results from this study indicate that the olfactory input plays an important role in the reorganization of the damaged olfactory bulb. Behavioral experiments in partially bulbectomized animals should provide essential information about the importance of a topological map in the processing of olfactory cues.
Axonal sprouting and frank regeneration in the lizard tail spinal cord: Correlation between changes in synaptic circuitry and axonal growth
Authors: Duffy Mark T. , Liebich Diana R. , Garner Laurie K. , Hawrych Andrew , Simpson Sidney B. , Davis B. M. 
Published: January 2005

AbstractIn our previous studies, we found that the number of supraspinal neurons projecting to the level of tail spinal cord increases by 74% during tail regeneration and that the number of local spinal neurons with descending projections increases 233%. However, only a small fraction of the supraspinal axons (< 4%) and half of the local spinal axons actually enter the regenerated spinal cord. We suggested that this may be the result of “synaptic capture” in which regrowing axons make synapses on denervated targets rostral to the transection, aborting further regeneration. To examine this hypothesis, morphometric analysis of electron microscope (EM) photomontages was used to test for changes in synaptic distribution on ventral horn neurons rostral to regenerating tail spinal cord. In addition, 3H‐thymidine and retrograde markers were used to determine whether the regenerate axons arose from cut axons, neurogenesis, or sprouting from uninjured neurons.3H‐thymidine injections during regeneration, combined with retrograde HRP pathway tracing, did not reveal the production of new neurons in the tail spinal cord. To test whether cut axons regenerate, fluorescein isothiocyanate conjugated latex beads were applied to the exposed end of the tail spinal cord. After tail regeneration, HRP was applied to the new spinal cord in the regenerated tail. Examination of local spinal neurons (the primary source of axons that enter the regenerated tail spinal cord) revealed that 28% of the neurons contained both labels. This indicated that cut axons successfully regrew into the new tail spinal cord.The regenerated axons that fail to enter the new tail spinal cord can be found in the normal spinal cord immediately rostral to the regenerated tail. To determine whether these axons were making synaptic contacts, lamina IX ventral horn neurons were examined. EM photomontages of the spinal cord rostral to the regenerate tail revealed the following properties: (1) neurons rostral to regenerated tails are larger in area compare to non‐regenerates (mean increase = 112%); (2) axosomatic contacts cover a greater percentage of the neuronal soma following regeneration compared to normal (mean increase = 23%); and (3) this increased innervation is the result of an increase in the number of synaptic boutons rather than larger boutons. The number of synaptic contacts in regenerated lizards returned to normal following lumbar transection, indicating that supraspinal and/or long descending propriospinal afferents were the major source of the increased synaptic contacts. These results suggest that increased synaptogenic activity in the spinal cord immediately rostral to the junction of normal and regenerating spinal cord, could be an important mechanism for inhibiting CNS axonal regeneration.
Phenylethanolamine N‐methyltransferase (PNMT)‐expressing horizontal cells in the rat retina: A study employing double‐label immunohistochemistry
Authors: Hammang Joseph P. , Bohn Martha C. , Messing Albee 
Published: January 2005

AbstractPhenylethanolamine N‐methyltransferase (PNMT), the final enzyme in the catecholamine biosynthetic pathway that converts norepinephrine to epinephrine, has been detected in the retinas of various vertebrate species. The expression of PNMT has generally been thought to occur in amacrine cells of the ganglion cell and inner nuclear layers. By using immunohistochemical techniques, we have found a population of PNMT‐ and neurofilament‐positive neurons at the border of the inner nuclear layer and the outer plexiform layer in the rat retina. We have classified these cells as horizontal neurons based on their location adjacent to the outer plexiform layer, their morphology, and their expression of vimentin and neurofilaments.