bluuebunny/crossref_metadata_2025_split huggingface dataset:
A light and electron microscopic study of the development of the mauthner cell and vestibular nerve in the axolotl
Authors: Leber Steven M. , Model Pat G. 
Published: January 2005

AbstractVestibular axons form synapses on a restricted area of the lateral dendrite of the Mauthner cell, a large, identified brainstem neuron found in fish land amphibians. The differentiation of the vestibular nerve, medullary neuropil, and Mauthner cell of the axolotl (Ambystoma mexicanum) was studied to understand better the means by which this synaptic specificity arises. The Mauthner cell first extends a medial process and then a lateral dendrite. The latter initially elongates as a simple process and later sends out branches. As the lateral dendrite grows, vestibular axons enter the brainstem to form one of the earliest of several discrete axon fascicles that course longitudinally through the neuropil. The fascicles, many of which are identifiable on the basis of their location and axonal morphology, are the precursors of the longitudinal tracts of the mature salamander. The lateral dendrite grows dorsally over the orthogonally oriented fascicles, making contact with each at a characteristic time and place. The first afferents to form synapses do so on the soma and proximal lateral dendrite; subsequent afferent groups terminate more distally. Axons within a given fascicle form synapses with the Mauthner cell in a discrete and initially homogeneous domain. As dendritic branches form and the organization of the longitudinal fascicles becomes more complex, the homogeneity of axons terminating on a given region of the Mauthner cell surface is lost, but no major rearrangement or migration of terminals is apparent. These observations are consistent with both active recognition and passive spatiotemporal models of synaptic site specificity.
Effect of precocious and delayed afferent arrival on synapse localization on the amphibian mauthner cell
Authors: Leber Steven M. , Model Pat G. 
Published: January 2005

AbstractAfferents often form synapses on restricted regions of their target cells. The connections between vestibular axons and the Mauthner cell are an example of this sort of specificity. The Mauthner cells are a pair of identifiable central neurons in certain fish and amphibians. In the axolotl (Ambystoma mexicanum), the large vestibular axons form club endings on only one portion of one dendrite of the Mauthner cell. During development, this specific distribution might result from nothing more than when and where the growing axons and dendrite meet (spatiotemporal model). Alternatively, the distribution might reflect constraints on where the developing axons may grow (axon segregation model) or form synapses (active recognition model). As a test of the spatiotemporal model, ears and vestibular ganglia from older embryos (Harrison stage 33/34–) were unilaterally grafted in place of prospective ear/ganglion placodes of younger embryos (stage 23). Light and electron microscopic examination revealed that the axons precociously entered the brain and formed synapses on the Mauthner cell. Similarly, grafts from younger to older embryos resulted in a delay. In both situations, mapping the club endings on the mature Mauthner cells of 21–mm larvae revealed a distribution similar to that of the contralateral control cells. Thus precocious and delayed afferent arrival did not alter the eventual localization of the synapses. These results conflict with the spatiotemporal model and imply that the vestibular axons are either restricted to a certain region of the neuropil or capable of recognizing a specific region of the Mauthner cell surface.
Dendritic morphology and development in the ferret lateral superior olivary nucleus
Authors: Henkel Craig K. , Brunso‐Bechtold Judy K. 
Published: January 2005

AbstractThe dendritic morphology of cells in the lateral superior olivary nucleus was studied with the Golgi method in adult and postnatal ferrets. The lateral superior olivary nucleus in the adult ferret is a convoluted structure with an M‐shape in frontal sections. The major cell type appears to have disk‐shaped dendritic trees. Most dendritic trees appear to be approximately orthogonal to the curved medial‐lateral axis of the nucleus. Depending on their position in the limb and on the plane of section with respect to the dendritic tree, the disk‐shaped cells are either bipolar or radiate in orientation. One subclass of disk‐shaped cells has secondary dendritic branches that end as tufts of tendril‐like processes. In a second subclass of cells, the dendrites exhibit several orders of dichotomous branching and lack obvious tufts of terminal processes. Marginal cells are observed at the border of the nucleus and have dendrites restricted to the margins of the cell plate.The bipolar orientation of disk‐shaped cells orthogonal to the axis of the limbs is already apparent by the time of birth. Transient spines and other appendages are abundant on somata and dendrites during the first postnatal week. By the end of the first postnatal month only distal appendages are found. Tufts of fine tendril‐like processes appear at the ends of dendrites between postnatal days 28 and 56.
GABA‐like immunoreactive cells containing nicotinic acetylcholine receptors in the chick retina
Authors: Hamassaki‐Britto D. E. , Brzozowska‐Prechtl A. , Karten H. J. , Lindstrom J. M. , Keyser K. T. 
Published: January 2005

AbstractThe possibility that GABA‐like immunoreactive cells of the chick retina also contain neuronal nicotinic acetylcholine receptors was investigated by means of immunohistochemical techniques. Double‐labeled cell bodies containing GABA‐like immunoreactivity and nicotinic receptor‐like immunoreactivity were seen in the inner third of the inner nuclear layer and were presumably amacrine cells. Approximately 29–36% of the GABA‐positive cells in the inner nuclear layer contained nicotinic receptor immunoreactivity. Their soma sizes ranged from 5–12 μm. Some double‐labeled cells ranging from 7–21 μm were observed in the ganglion cell layer as well. Between 9–37% of the GABA‐positive cells in this layer contained nicotinic receptor‐like immunoreactivity. Following injection of a retrograde tracer into the optic tectum, some of the retrogradely labeled cells were also double labeled with antibodies against GABA and nicotinic receptors. This indicates that at least some of the GABA‐positive cells containing nicotinic acetylcholine receptors in the ganglion cell layer are indeed ganglion cells. The present data appear to represent the first demonstration of the presence of acetylcholine receptors in GABA‐containing cells in the retina, thus providing a basis for a possible influence of acetylcholine upon those presumptive GABAergic cells.
Ontogeny of steroid accumulation in spinal lumbar motoneurons of the rat: Implications for androgen's site of action during synapse elimination
Authors: Jordan Cynthia L. , Breedlove S. Marc , Arnold Arthur P. 
Published: January 2005

AbstractAndrogens influence the postnatal development of motoneurons in the spinal nucleus ofthe bulbocavernosus (SNB) by regulating neuromuscular synapse elimination, the process through which multiple axonal inputs are retracted from each muscle fiber until single innervation is established. In the rat levator ani (LA), one of the target muscles for SNB motoneurons, much of this loss of multiple innervation can be prevented by prepubertal androgen treatment. We used steroid autoradiography to measure the ontogeny of steroid accumulation in the SNB and the retrodorsolateral nucleus (RDLN), two motoneuronal groups thought to differ in their sensitivity to androgens. Spinal cord tissue was analyzed from castrated male rats at 7, 14,21, and 60 days of age after injection of radiolabelled testosterone. SNB and RDLN motoneurons differ in the ontogeny of androgen accumulation. Over 80% of SNB motoneurons develop the capacity to accumulate androgen during the second week after birth, during the period when androgen regulates synapse elimination in the LA. In contrast, androgen accumulation in RDLN motoneurons develops much later (after 21 days). These data suggest that androgen may act directly on SNB motoneurons to influence synapse elimination.
Comparison of dorsal and ventral spinal root regeneration through semipermeable guidance channels
Authors: McCormack M. L. , Goddard M. , Guéanard V. , Aebischer P. 
Published: January 2005

AbstractSemipermeable guidance channels have been shown to support nerve regeneration in the peripheral nervous system (PNS) possibly through interactions with the wound healing environment. This study quantitatively assesses the ability of such channels to support regeneration in the PNS segment of the spinal roots across a 4 mm gap and compares the resultant dorsal and ventral root regeneration. Acrylic copolymer guidance channels with a molecular weight (Mw) cutoff of 50,000 Da were used in a transected rat spinal root model. Cohorts of 23 animals (11 ventral, 12 dorsal) were examined at four weeks; 6 animals (3 ventral, 3 dorsal) at ten weeks; and 10 animals (5 ventral, 5 dorsal) at twenty‐four weeks post‐implantation. Both the dorsal and ventral roots were able to regenerate across the gap within the semipermeable channel. At all time periods, the regenerated dorsal roots contained fewer myelinated axons than found in the contralateral control root and consisted of an abundance of collagenous tissue. In contrast, by ten weeks the regenerated ventral roots contained twice the contralateral control number of myelinated axons and were composed predominantly of large, myelinated axons. At twenty‐four weeks the number of unmyelinated axons was also quantified, with the regenerated dorsal root containing only one‐fifth of the control number and the regenerated ventral root containing more than four times the control. Due to the proximity of the dorsal root lesion to the axonal cell bodies, the dorsal root ganglion (DRG) neuronal cell loss was investigated at four weeks post‐implantation. A comparison of the cell numbers on the experimental side to those on the contralateral control side yielded a mean E/C ratio of 1.07, suggesting that a significant cell loss is an unlikely causative factor in the impairment of regeneration in the dorsal root. This study reports a difference in the regenerative capacities of dorsal and ventral roots using semipermeable guidance channels. Future studies involving variations in the regenerative environment may help determine the factors responsible for the different regenerative capabilities of the spinal roots.
Central projections of Limulus photoreceptor cells revealed by a photoreceptor‐specific monoclonal antibody
Authors: Calman B. G. , Lauerman M. A. , Andrews A. W. , Schmidt M. , Battelle B.‐A. 
Published: January 2005

AbstractStudies of lateral, median, and ventral eyes of the chelicerate arthropod Limulus polyphemus (the common American horseshoe crab) are providing important basic information about mechanisms for information processing in the peripheral visual system and for the modulation of visual responses by light and circadian rhythms. The processing of visual information in Limulus brain is less well understood in part because the specific central projections of the various classes of visual neurons are not known.This study describes a mouse monoclonal antibody, 3C6A3, which binds to Limulus photoreceptor cell bodies, their axons, and terminals, but not to any other cell type in the central nervous system. This antibody, and intracellular injection of biocytin, are used to demonstrate the central projections of each type of photoreceptor.Our main conclusions are that: (1) the photoreceptors (retinular cells) of the lateral eye project only to the lamina; (2) the photoreceptors of the lateral rudimentary eye project to both the lamina and medulla; (3) the photoreceptors of the median ocellus project only to the ocellar ganglion; and (4) the photoreceptors of the rudimentary median (endoparietal) eye project to the ocellar ganglion and also into the optic tract.These results, along with previous studies, allow us to infer the projections of the secondary cells. The eccentric cells of the lateral eye project to the lamina, medulla, optic tract, and ocellar ganglion. The arhabdomeral cells of the median ocellus project through the ocellar ganglion and the optic tract to the medulla.
Reinnervation of developing rat muscle by non‐axotomized motoneurons
Authors: Ziskind‐Conhaim Lea , Presley Scarlett 
Published: January 2005

AbstractTo study the ability of developing motoneurons to reinnervate their denervated muscle, axotomized motoneurons in rat neonates and pups were retrogradely labeled with two fluorescent tracers. Fluorogold (FG), a long‐lasting fluorescent dye, was injected into intercostal muscle T9 to retrogradely label the motoneurons that innervated it. Two days later intercostal nerves T7–T9 were cut. The intercostal muscle denervated at birth was reinnervated within 10–20 days, as evidenced by nerve‐evoked muscle contraction. Three weeks following axotomy, tetramethylrhodamine isothiocyanate (TRITC) was injected into the same muscle to label the motoneurons that reinnervated it. The motoneurons double‐labeled with FG and TRITC were, therefore, axotomized motoneurons that regenerated to reinnervate T8.In neonates, axotomy resulted in a significant reduction in the number of FG‐labeled motoneurons, which suggests that axon transection at early postnatal days causes a massive motoneuron death. The percentage of double‐labeled motoneurons was significantly smaller than that in non‐axotomized rats. TRITC‐labeled motoneurons constituted the majority of stained motoneurons; these were located in different nuclei than the intercostal motoneurons. These findings suggest that muscle reinnervation is, at least in part, by motoneurons which originally did not innervate intercostal muscle T8.Unlike axotomy at birth, axotomy performed 2–3 weeks after birth did not result in a significant motoneuron loss. The number of stained motoneurons labeled with both FG and TRITC was significantly smaller, however, than in non‐axotomized spinal cords. Our data indicate that in pups only a small percentage of axotomized motoneurons reinnervated the denervated muscle.
The contributors to volume 1 (1891) of The Journal of Comparative Neurology: C.L. Herrick, C.H. Turner, H.R. Pemberton, B.G. Wilder, F.W. Langdon, C.J. Herrick, C. von Kupffer, O.S. Strong, T.B. Stowell
Authors: Haines D. E. 
Published: January 2005

AbstractThe concept of a truly innovative “neurology” journal germinated in the mind of Clarence Luther Herrick and then flowered, in March of 1891, as the first issue of Volume 1 of The Journal of Comparative Neurology. The other parts appeared in June, October, and December of the same year. The contributors to this volume, and their affiliations, were: C.L. Herrick (University of Cincinnati‐UC), C.H. Turner (UC), B.G. Wilder (Cornell), F.W. Langdon (Miami Medical College, Cincinnati), C.J. Herrick (UC) H.R. Pemberton (Princeton), T.B. Stowell (State Normal and Training School, Potsdam), and O.S. Strong of Columbia who translated a large paper by Carl von Kupffer, the famous German anatomist. In 1890–91 some of these scientists (e.g., Wilder, Langdon, Stowell, von Kupffer) were well known and had already made notable contributions in their chosen fields. However, several were students (e.g., Turner, C.J. Herrick, Pemberton, Strong), most of whom would make important contributions in later years. The founder of JCN, Clarence Luther Herrick, by 1891 had an excellent reputation in geology and natural science and had already established a successful scientific journal.Based on the totality of their contributions, the authors of the papers that made up Volume 1 of JCN were a unique group. Textbooks that went through several editions came from Wilder, C.J. Herrick, and Strong; the latter is currently going into its 9th edition. Structures were named in recognition of the original descriptions by von Kupffer and C.L. Herrick, a type of insect behavior recognized Turner's discovery, and after their deaths several had university buildings, one a scientific club, and one a research award, named in their honor.There were also interesting and important links between these nine men. Turner and C.J. Herrick were students of C.L. Herrick, and Stowell served as a member of the Association of American Anatomists nomenclature committee which was chaired by Wilder, C.J. Herrick became a student (for his Ph.D.) of Strong's, and Strong became an associate editor of JCN under C.J. Herrick. Of the nine, two practiced medicine; Langdon in an academic setting, Pemberton in private practice.The lives of the nine scientists whose work made up Volume 1 of JCN are reviewed. Many of these individuals were notable, not only for their work in the first volume of JCN, but for their larger and enduring contributions in the biomedical sciences.
Postlarval growth of the peripheral gustatory system in the channel catfish, Ictalurus punctatus
Authors: Finger Thomas E. , Drake Susan K. , Kotrschal Kurt , Womble Mary , Dockstader Karen C. 
Published: January 2005

AbstractThe phenomenon of postlarval cell addition to the peripheral nervous system offish has been reported for some sensory systems, but has yet to be characterized for the gustatory system. Many fishes, such as catfish, possess taste buds scattered across their body surface, and presumably, the number of taste buds increases during growth of the animal. The present study was undertaken in order to examine the process of growth in the peripheral gustatory system and to determine whether the degree of convergence of receptors onto primary sensory afferents changes during growth.The recurrent facial nerve of channel catfish was used for these studies since this nerve contains no general cutaneous components and innervates taste buds along the fish's body surface. Electron micrographs were made of cross sections of this nerve taken from individuals ranging in size from 5.1 to 39.5 cm standard length. In addition, estimates were made of the number of taste buds innervated by this nerve by determining taste bud density along selected regions of the flank and fins in large and small fish.As catfish get larger, the number of both myelinated and unmyelinated axon profiles in the recurrent facial nerve increases, but at a slower rate than the number of taste buds innervated by this nerve. Thus, on average, the number of taste buds innervated by each fiber increases as the fish enlarges; on average there are 2 taste buds per axon profile in small fish and nearly 14 taste buds per axon profile in large fish. The rate of addition of new axon profiles to the nerve is estimated at roughly 70 per day over the range of sizes studied. Although generation of new ganglion cells and axons may contribute to this increase, several lines of evidence indicate that axonal branching occurs.In addition, the mean axon diameter for both myelinated and unmyelinated axons increases during postlarval growth. The finest myelinated fibers (0.2 μm) in small animals are significantly smaller than the finest myelinated fibers (0.7 μm) in larger animals.
Cytoskeletal components and calibers in developing fish Mauthner axon (Salmo gairdneri Rich)
Authors: Alfei L. , Albani L. Medolago , Mosetti A. R. , Scarfo C. , Stefanelli A. 
Published: January 2005

AbstractIn developing axons of many vertebrates, microtubular density is inversely correlated with fiber caliber. It is suggested that microtubules are causally related to axonal caliber. For this reason, cytoskeletal analysis during development of the fish Mauthner axon, which displays a giant caliber, is of particular interest. The Mauthner axon originates from the Mauthner cell in the medulla and runs in the fasciculus longitudinalis medialis in the spinal cord.At embryonic, larval and postlarval stages in trout (Salmo gairdneri Rich.), the following parameters were measured on conventional electron micrographs of Mauthner axon cross sections: axonal caliber, number of microtubules per axons, and microtubular and neurofilament densities. Results at each stage point to an inverse correlation between axonal caliber (x) and microtubular density (y) expressed by the equation y = axb (R = 0.932).Furthermore, three periods of Mauthner axon development are identified on the basis of the cytoskeletal content: (1) embryonic; the Mauthner axon has small caliber with a high microtubule density, (2) elongation period (larval stages); the axon enlarges and a transient peak of microtubules, corresponding to the caliber increment, is observed, and (3) postlarval; the axon enlarges still further (<500 μm2) but has the lowest microtubular content. During this period neurofilaments are the main axonal component.
Spatio‐temporal patterns of retinal ganglion cell death during Xenopus development
Authors: Gaze R. M. , Grant P. 
Published: January 2005

AbstractDuring development of the retina in mammals and birds, most retinal ganglion cells (RGC) that are produced are eliminated later in development by cell death. In lower vertebrates, however, such massive cell death has not been observed; total ganglion cell number increases linearly during most of development. Using 3H‐thymidine or 5‐bromodeoxyuridine labeling of retinal cell nuclei, we have been able to identify postmitotic RGC populations in Xenopus central retina at different developmental stages and follow their fate during development to postmetamorphic stages. RGC populations that become postmitotic between embryonic stages 32 and 49, during the initial stages of retinal growth, lose 40–77% of their cells during metamorphosis (approximately 4,000–5,000 cells). Twenty percent of the RGC present at stage 54, which later disappear, represent the same population of dying RGC that were present at stage 49. This suggests that the ganglion cells that became postmitotic between stage 49 and 53/54 show no apparent decline in numbers during metamorphosis. Since thyroxine is known to stimulate an increase in RGC number as well as the extent of fiber projection on the tectum, we suggest that this reduction in RGC numbers is not due to thyroxine‐induced neuronal cell death. After stage 54, however, binocular vision develops in Xenopus (Keating, '74) and ipsilateral fibers begin to grow into thalamic visual neuropils (Hoskins and Grobstein, '85). We suggest, therefore, that as in mammals, in which RGC elimination correlates with binocular segregation of contralateral and ipsilateral retinal axons in visual centers, a similar process may occur in the frog among those RGC projecting to thalamic visual neuropils.