bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ephrin‐A2 and ‐A5 influence patterning of normal and novel retinal projections to the thalamus: Conserved mapping mechanisms in visual and auditory thalamic targets
Authors: Ellsworth Charlene A. , Lyckman Alvin W. , Feldheim David A. , Flanagan John G. , Sur Mriganka 
Published: May 2005

AbstractSensory axons are targeted to modality‐specific nuclei in the thalamus. Retinal ganglion cell axons project retinotopically to their principal thalamic target, the dorsal lateral geniculate nucleus (LGd), in a pattern likely dictated by the expression of molecular gradients in the LGd. Deafferenting the auditory thalamus induces retinal axons to innervate the medial geniculate nucleus (MGN). These retino‐MGN projections also show retinotopic organization. Here we show that ephrin‐A2 and ‐A5, which are expressed in similar gradients in the MGN and LGd, can be used to pattern novel retinal projections in the MGN. As in the LGd, retinal axons from each eye terminate in discrete eye‐specific zones in the MGN of rewired wild‐type and ephrin‐A2/A5 knockout mice. However, ipsilateral eye axons, which arise from retinal regions of high EphA5 receptor expression and represent central visual field, terminate in markedly different ways in the two mice. In rewired wild‐type mice, ipsilateral axons specifically avoid areas of high ephrin expression in the MGN. In rewired ephrin knockout mice, ipsilateral projections shift in location and spread more broadly, leading to an expanded representation of the ipsilateral eye in the MGN. Similarly, ipsilateral projections to the LGd in ephrin knockout mice are shifted and are more widespread than in the LGd of wild‐type mice. In the MGN, as in the LGd, terminations from the two eyes show little overlap even in the knockout mice, suggesting that local interocular segregation occurs regardless of other patterning determinants. Our data demonstrate that graded topographic labels, such as the ephrins, can serve to shape multiple related aspects of afferent patterning, including topographic mapping and the extent and spread of eye‐specific projections. Furthermore, when mapping labels and other cues are expressed in multiple target zones, novel projections are patterned according to rules that operate in their canonical targets. J. Comp. Neurol. 488:140–151, 2005. © 2005 Wiley‐Liss, Inc.
Mechanisms of subventricular zone expansion after focal cortical ischemic injury
Authors: Gotts Jeffrey E. , Chesselet Marie‐Françoise 
Published: May 2005

AbstractThe rodent subventricular zone (SVZ) contains neural precursor cells that divide and then die in place or migrate to the olfactory bulb through the rostral migratory stream (RMS) to become new neurons. Despite the normally tight control in cell numbers in this region in adults, previous work from our laboratory and others has shown that SVZ cell number increases after a variety of brain injuries. The relative contribution of changes in rostral migration, cell proliferation, and cell death to increased cell number is poorly understood. We examined these parameters after focal cortical ischemic lesions distal from the SVZ in adult rats. Stereological analysis revealed that cell numbers remain constant in the SVZ and RMS until 5 days postinjury but then rapidly expanded by 150,000 cells by day 7 in each region. Rostral migration of SVZ cells was unaffected by the injury. Both cell death and proliferation increased in the SVZ as early as day 5. However, these two mechanisms became uncoupled when cell number increased, indicating that a distant brain injury expands the SVZ by disrupting the balance between cell death and proliferation in this adult neurogenic zone. J. Comp. Neurol. 488:201–214, 2005. © 2005 Wiley‐Liss, Inc.
Mixed intra‐ and extrafusal muscle fibers produced by temporary denervation in newborn rats
Authors: Werner Joan K. 
Published: May 2005

AbstractTemporary denervation of the medial head of gastrocnemius muscle in newborn rats has produced three major changes in muscle spindle development: (1) a modification of the spindles' components, (2) an increase or decrease in the number of spindles that developed in the experimental muscles and (3) an alteration in the location of spindles. The most striking change was observed in a total of 15 spindles from three of the experimental animals and consisted of a modification of the components. The abnormal, modified spindles usually contained only one muscle fiber, which had the morphological characteristics of an intrafusal fiber at one end and in the equatorial zone, and the morphological characteristics of an extrafusal fiber at the opposite end. These peculiar muscle fibers clearly represent a single cell which has differentiated along two distinctly different pathways and they show that the pattern of innervation can influence the course of differentiation of developing muscle cells to a significant extent.
Insular‐diencephalic connections in the Macaque
Authors: Wirth Fremont P. 
Published: May 2005

AbstractInsular‐diencephalic connections have been studied in five rhesus Macaques with both retrograde and anterograde degeneration techniques. Animals were prepared for study with bilateral symmetrical resections of temporal operculum or fronto‐parietal operculum or both, with or without excision of underlying insular cortex. The resections were staged such that the older was suitable for evaluation of retrograde cell change and myelin tract degeneration (cresyl violet and Loyez stain) and the more recent for anterograde fiber degeneration (Nauta). From the cresyl violet‐Loyez stained hemispheres evidence was obtained for sustaining fiber projections to the insula from n. ventralis caudalis parvocellularis. Nauta stains demonstrated projections from the insular cortex to n. ventralis caudalis, n. ventralis caudalis ventralis and n. ventralis caudalis parvocellularis. Connections were also demonstrated to n. centralis, n. parafascicularis, n. dorsalis oralis and the intralaminar nucleus. These connections closely resemble those of overlying fronto‐parietal operculum and suggest that insular cortex is an extension of sensory‐motor cortex as indicated by physiologic data. Projections from insula to the amygdala were also identified, indicating the association of insular cortex and the limbic system.
Anterograde degeneration study of the cortical projections of the lateral geniculate and pulvinar nuclei in the tree shrew (Tupaia glis)
Authors: Harting J. K. , Diamond I. T. , Hall W. C. 
Published: May 2005

AbstractSixty lesions were placed in the pulvinar nucleus or the lateral geniculate nucleus of the tree shrew, and degenerated axons and their terminals were traced to the cortex. In all but two of the animals the electrode approached the thalamic target through the cerebellum and midbrain, thus sparing the cortex and thalamic nuclei other than the target nuclei. The results show that the pulvinar nucleus projects in a topographic fashion to an extensive cortical zone that includes areas 18, 19 and several temporal areas below 19. While there are several architectonic areas in its cortical target, no corresponding subdivisions could be established within the pulvinar nucleus, and its projections are best explained in terms of a single topographic organization. Further, since the pulvinar nucleus receives fibers from the superficial layers of the superior colliculus, its extensive cortical target can be regarded as primary visual cortex. The lateral geniculate nucleus projects in a precisely topographic fashion to area 17. Further, our evidence suggests that each layer of the lateral geniculate nucleus projects to a horizontal strip within the fourth or granular layer of area striata. With respect to the question of the relation between ocular dominance and location in area 17, the pattern of projections from the lateral geniculate nucleus does not reveal ocular dominance columns in layer IV of the tree shrew. In contrast to our results Hubel and Wiesel ('68, '69) have shown that in the monkey there are vertical columns of cells in layer IV driven by either the homolateral or the contralateral eye. The case for the cat (Hubel and Wiesel, '62, '65) may be different from either of the other two species, thus posing the problem of discovering the mammalian plan and departures from the prototypical organization.
Cell proliferation in injured spinal cord. An electron microscopic study
Authors: Adrian Erle K. , Williams M. G. 
Published: May 2005

AbstractTo examine the fine structure of cells synthesizing DNA in the spinal cord in response to injury, mice were given a single injection of 3H‐thymidine two days after stab injury to the spinal cord and were sacrificed at either two hours or one, two, six or 14 days later. The most common type of labeled cell found at a distance from the wound at all the time intervals after 3H‐thymidine injection had an elongated or irregularly oval nucleus with clumps of condensed chromatin at the nuclear envelope and one or more nucleoli. The cytoplasm which was darker than adjacent axoplasm, contained dense bodies, scattered mitochondria, many free ribosomes, only a few rather long cisternae of granular endoplasmic reticulum, a prominent Golgi apparatus, and a few granules. These cells were similar in appearance to the cells that have been identified as microglia or multipotential glia by others. However, they also have many features in common with blood mononuclear cells. In the wound, in addition to the cells already described, the labeled cells at two hours after 3H‐thymidine injection included well developed macrophages, a few endothelial cells, and a large number of cells with large pale nuclei and cytoplasm containing abundant microtubules and granules. At the later time intervals, these cells apparently developed large numbers of cytoplasmic filaments. Although they bore some resemblance to reactive astrocytes, these labeled cells were not typical astrocytes, and their location, their apparent transformation from a cell without filaments, and their pseudopodia and surface vacuoles suggest the possibility that they may be derived from blood mononuclear cells.
Cytoarchitecture of nucleus sphericus in the common boa, Constrictor constrictor
Authors: Ulinski Philip S. , Kanarek David A. 
Published: May 2005

AbstractThe normal anatomy of nucleus sphericus in the common boa (Constrictor constrictor) is described here on the basis of routine light microscopic and Golgi material. Nucleus sphericus is a cup‐shaped aggregation of cells lying in the forebrain posterior to the anterior commissure and consisting of three concentric layers. The marginal layer is subependymal, is continuous rostrally with the anterior commissure, and contains fusiform cells with discoidal dendritic fields tangent to the mural layer, Marginal cell axons entwine mural cell dendrites. The mural layer forms the walls of the cup and appears as a closed ring of cells in transverse sections. Mural cell dendrites extend radially into the marginal and hilar layers and horizontally within the mural layer. All of these dendrites are profusely covered by dendritic spines with conical heads and slender stalks. Mural cell axons ascend to the marginal layer. The hilar layer forms the cup's cavity containing scattered cells whose dendrites extend in all directions and whose axons approach the cup's mouth. Afferent fibers in the nucleus run predominately at right angles to mural cell dendrites bearing varicosities at irregular intervals.
The tract of Lissauer in relation to sensory transmission in the dorsal horn of spinal cord in the macaque monkey
Authors: Denny‐Brown D. , Kirk E. J. , Yanagisawa N. 
Published: May 2005

AbstractThe classical method for study of the area of innervation of skin by one nerve root, isolated by section of three neighboring roots on either side, was used to study the contribution of neighboring segments of spinal cord to transmission at the first sensory synapse. The area from which response to pinscratch could be obtained in the conscious monkey was greatly increased if the spinal cord was sectioned just below the test segment, or hemisected above it, particularly if vascular infarction was avoided. The enlarged area was hypersensitive. The maximal area of skin innervated by any one nerve root was approximately twice as large as had been found by previous investigators. Each sensory point in the ventral parts of dermatomes must be innervated by at least five nerve roots. Work previously reported had shown that the area of test dermatome was reduced by sectioning neighboring roots medial to their ganglia after previous distal section of the same roots, or by section of more than three neighboring roots. These restrictions of area could be reversed by a subconvulsive dose of strychnine. The facilitatory and suppressive effects from neighboring nerve roots and spinal segments respectively were traced to the mechanism of Lissauer's tract, of which the medial division exerts a facilitatory effect and the lateral division a suppressor effect on transmission through the first synapse of the test root.These excitatory and inhibitory effects, thought to be derived from collaterals of nerve fibers of like and unlike function of all sizes entering the substantia gelatinosa of neighboring segments, must be transmitted by small cells with axons in the tract of Lissauer. The reversal of the inhibition by strychnine indicates a post‐synaptic mechanism at the first synapse. The prolongation of either tonic excitatory or tonic inhibitory influence for as long as five days after section of the corresponding input pathway represents a unique feature of the mass polysynaptic effects of the small interneurones making up the substantia gelatinosa, rather than the presence of a long‐lasting transmitter substance. There was evidence that both dorsal root ganglion cells and substantia gelatinosa continue to contribute to fringe effects after isolation from the periphery. The mechanism of the substantia gelatinosa could provide correlation for the type of sequential directional information such as is necessary for the spinal scratch reflex.
Neuroglial response to sciatic neurectomy. I. Light microscopy and autoradiography,
Authors: Kerns James M. , Hinsman Edward J. 
Published: May 2005

AbstractThe response of oligodendrocytes, astrocytes, microglia, and pericytes to sciatic neurectomy in young adult rats was studied from 1μ Epon sections for quantitative cell counts and autoradiography. Two hours after an IP injection of 3H‐thymidine animals were killed by aldehyde perfusion at survival periods of 2, 4, 7, and 14 days postoperative (dpo).At 2 dpo there was a marked increase in the number of labeled microglial cell nuclei and mitotic figures on the experimental side. This activation appeared to involve most of the “resting” microglia, which comprise about 6% of the total neuroglia in the normal ventral horn. A significant numerical increase (over fourfold) in perineuronal and total microglia was seen at 4 dpo followed by a gradual decline. Other findings include minimal chromatolysis in ventral horn neurons, contralateral effects, and a slight proliferative response in and around the central canal. A response was not apparent in the other neuroglia, pericytes, or mononuclear leukocytes. The relationship of the microglia to the multipotential glia of neuroectodermal origin is considered.
Distribution of transported proteins in the slow phase of axoplasmic flow. An electron microscopical autoradiographic study
Authors: Schonbach J. , Schonbach Ch. , Cuénod M. 
Published: May 2005

AbstractElectron microscopic autoradiography has been used to study the distribution of labeled proteins along the axons of the retinal ganglion cells in the pigeon, during the slow phase of axoplasmic flow. After intraocular injection silver grains were found over a small fraction of the axonal population at any given time and at any specific location. Where the slowly advancing wave of radioactivity was detectable, the grains were predominantly located over the axoplasm, microtubules, neurofilaments and mitochondria. When the peak of the radioactivity had passed, the grains were found mostly overlying the axolemma. A large amount of radioactivity was observed over the endings of the retinal ganglion cell axons in the tectum 14 days after the injection of the labeled aminoacid. The grains were for the most part located over the outer membranes of the synaptic processes and over synaptic vesicles. These data support the hypothesis that the slow phase of axoplasmic transport contributes to the continuing growth of the axon and is formed mainly of materials which are distributed to the axonal membrane and to its synaptic endings. In contrast, the fast phase of axoplasmic flow results in a distribution of silver grains over the axolemma and the agranular endoplasmic reticulum in the axons, and over mitochondria and synaptic vesicles in its terminals.
Sequence of developmental abnormalities leading to granule cell deficit in cerebellar cortex of weaver mutant mice
Authors: Rakic Pasko , Sidman Richard L. 
Published: May 2005

AbstractGolgi, electronmicroscopic and autoradiographic analyses of the developing cerebellar cortex were carried out in homozygous wild‐type (+/+), heterozygous (+/wv), and homozygous weaver (wv/wv) littermates. At 3 to 15 days after birth, when granule cells normally migrate from the external granular layer inward to their adult position, the somas of postmitotic granule cells in +/+ animals move along straight elongated Bergmann glial fibers which span the molecular layer. As early as postnatal day 3 and increasingly for about the next ten days, some Bergmann fibers in the +/wv cerebellum are enlarged, irregular in caliber, electronlucent and may contain dense bodies and vacuoles. Some granule cells contiguous with the altered Bergmann fibers have round rather than elongated somas, while some have lost contact with Bergmann fibers and appear to degenerate several days after their genesis. Most other granule cells migrate slowly but do eventually reach the granular layer, so that the pathology is less striking in adult than in developing heterozygotes. In wv/wv cerebella, radially‐aligned Bergmann fibers appear reduced in number during the developmental period, and few of them display normal cytological features. Few normally migrating granule cells were observed. Most granule cells fail to form axons and die in the external granular layer close to their site of genesis. While the primary genetic defect is unknown, the Bergmann glial disorder appears to precede the migration failure of granule cells and this in turn, along with impaired axon genesis, appears to be a factor leading to granule cell death.
Central projections of the trigeminal nerve in the bull frog (Rana catesbeiana)
Authors: Fuller Peter M. , Ebbesson Sven O. E. 
Published: May 2005

AbstractThe trigeminal nerve was unilaterally transected proximal to its ganglion in ten adult bull frogs. The course and termination of the axons were determined with the aid of Nauta and Fink‐Heimer techniques. The trigeminal primary afferents can be traced to five loci within the central nervous system, namely: the main sensory nucleus of the trigeminus, the descending nucleus of the trigeminus, a hitherto undescribed “ventral trigeminal field”, the rostral part of the nucleus of the solitary tract, and to the commissural nucleus of Cajal.
The neural organization of the lamina ganglionaris in the crayfish: A Golgi and EM study
Authors: Hafner G. S. 
Published: May 2005

AbstractThe lamina ganglionaris in the crayfish is composed of two cell layers and three acellular fibrous zones. The cells composing the layers above the acellular synaptic region (SR) show two distinct nuclear types in light microscopy and two cytoplasmic types with EM. Golgi impregnations of the lamina revealed three groups of elements which contribute processes to the SR; retinula axons from the retina, monopolar elements from the cell layers above the SR and horizontal elements whose perikaryal location is uncertain. Retinula elements terminate at various levels within the SR forming large irregular baglike terminals. Monopolar cells have a single axial fiber with numerous lateral processes which extend across the SR in a veriety of patterns. Horizontal elements have a more extensive lateral spead within the SR than monopolar processes. Electron microscopic data show the retinula terminal bags and monopolar processes to be organized into cartridge units at the superficial levels of the SR. Each cartridge consists of four enlarged terminals, three retinula axons and four to six central moncpolar processes. At deeper levels of the SR, the cartridge arrangement is not evident and the large terminals appear arranged in rows. Specialized synaptic contacts are found along the central borders of the retinula terminals.
The posterior lateral line lobe of a mormyrid fish — a golgi study
Authors: Maler L. 
Published: May 2005

AbstractThe posterior lateral line lobe is a rhombencephalic laminated structure. There is a topographic projection of anterior and posterior lateral line nerves upon the posterior lobe. The six separate lamina of the posterior lobe contain at least six cell types which can be distinguished on the basis of their dendritic trees. One lamina, the plexiform layer, contains the collateral plexus of the lamina of ganglion cells. There is an asymmetry in the dendritic fields and in the collateral plexus of neurons of the posterior lobe, such that their long axis runs in the sagittal plane.There is an extensive projection from granule cells of lobus caudalis to the posterior lobe molecular layer. This connection is organized in a fashion similar to that of the parallel fiber system of the cerebellum, i.e., the axons form an inverted T, the arms of which run parallel to the granule cell layer. This projection is confined to the upper part of the molecular layer, while the lower part of the molecular layer contains the axons arising in the posterior lobe granular layer.
Efferent connections of the red nucleus in the brainstem and spinal cord of the rhesus monkey
Authors: Miller Richard A. , Strominger Norman L. 
Published: May 2005

AbstractThree types of neuron with differences in Nissl pattern were found in the red nucleus of the rhesus monkey. Neurons with coarse Nissl bodies occurred only in the caudal third of the red nucleus except for a small number which extended rostrally a short distance along the dorsolateral margin. Neurons with fine Nissl bodies occupied the rostral two‐thirds of the nucleus. Neurons with slight cytoplasmic basophilia (achromatic) were smaller than the other types and distributed throughout the red nucleus. Perikaryal areas of the coarse and fine neurons, measured with a computer, had widely overlapping distributions.Electrolytic lesions were made unilaterally in the red nucleus of nine monkeys. Ascending axonal degeneration was studied in sections stained by the Fink‐Heimer method. Two separate descending tracts were followed. The rubrobulbo‐spinal tract took origin from coarse neurons, crossed completely in the ventral tegmental decussation, and terminated as follows: in parts of the superior sensory trigeminal, motor facial and lateral reticular nuclei; in the gracile and cuneate nuclei; in the nucleus medullae oblongata, subnucleus dorsalis; in Rexed's laminae V, VI, VII at all levels of the spinal cord. In contrast, the rubroreticulo‐olivary tract took origin from fine neurons, remained uncrossed, and terminated in some reticular nuclei (pedunculopontine, pontis oralis and caudalis, gigantocellularis) and in parts of the inferior olivary complex. Degeneration was profuse in the dorsal lamina of the main olive, abundant in the ventral lamina, particularly in its lateral side, sparse and inconstant in the medial accessory olive, and invariably absent in the dorsal accessory olive. Thus, nuclei which receive descending projections from the red nucleus may be grouped into those with connections to lower motor neurons, cerebellum, or thalamus.