bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of lesions of telencephalic visual structures on visual discriminative performance in turtles (Chrysemyspicta picta)
Authors: Reiner Anton , Powers Alice Schade 
Published: January 2005

AbstractAscending thalamotelencephalic visuaJ pathways that terminate in specific telencephalic regions have been described in all reptiles studied. Although the anatomical data suggests that such telencephalic regions may play a role in visual processing in reptiles, few behavioral data are available. In the present study, the effects of destruction of either the core nucleus (CN) of the dorsal ventricular ridge (telencephalic terminus of the tectothal‐amofugalpathway) or the dorsal cortex (telencephalic terminus of the retino‐thalamofugal pathway) on visual discriminative performance in the turtle were examined. Following extensive bilateral destruction of the CN, turtles were severely impaired in their performance of both a simultaneous pattern discrimination and a simultaneous visual intensity discrimination. The extent of the discriminative impairment was found to be specifically correlated with the amount of CN damage. In contrast to the effects of CN lesions, lesions of the dorsal cortex had no evident effect on the performance of either a simultaneous pattern discrimination or a simultaneous visual intensity discrimination. The present results suggest that, as in birds and mammals, telencephalic visual areas play an important role in visual functions in reptiles. As in at least some birds (such as pigeons), the telencephalic terminus of the tectothalamofugal visual pathway appears to play a larger, or at least more readily measurable, role in visual discrimination than does the telencephalic terminus of the retinothalamofugal pathway.
The termination of primary afferents within the rat dorsal horn: Evidence for rearrangement following capsaicin treatment
Authors: Nagy J. I. , Hunt S. P. 
Published: January 2005

AbstractThe mode of termination of primary afferent fibres within the superficial dorsal horn of the spinal cord was studied with anterograde tracing methods in normal rats and in animals which had been treated with capsaicin (50 mg/kg. s.c.) shortly after birth. In normal animals following injections of horseradish peroxidase (HRP) into lumbar dorsal root ganglia L4, L5, L6, a Golgi‐like filling of primary afferent fibres was seen consistently within laminae I, II, and III of the dorsal horn. Several types of lamina related arborisations were observed, depending upon the survival time after HRP injection. At the earliest survival time (1–2 days) a punctate granular labelling was found in laminae I and II inner (IIi). At 3 days survival a Golgi like labelling of primary afferent axons occurred and three tiers of arborisation were seen within laminae I, II outer (IIO), and II inner (IIi), respectively. By 7 days after injection this pattern was considerably reduced and there was coarser fibre labelling within laminae I, IIO, and III.When these tracing experiments were repeated in capsaicin‐treated rats in which up to 90%of unmyelinated fibres had been destroyed, evidence for a considerable loss of some inputs and rearrangement of the remaining fibres was found. At 3–5 days survival the axonal labelling within laminae I and IIi was severely depleted yet some input, particularly to lamina IIO, was present. At 7 days survival deep fibre labelling within lamina III now extended well into lamina II.Mapping of the primary afferent input following 3H‐proline injections into the dorsal root ganglion and subsequent autoradiographic processing confirmed that primary afferents terminated throughout the dorsal horn but most heavily in two bands within laminae I and IIi. These two dense layers of termination were not present in capsaicin‐treated animals, suggesting that they corresponded to areas of unmyelinated primary afferent fibre input.These data, taken together with histochemical observations on the distribution of substance P and fluoride‐resistant acid phosphatase (FRAP)‐containing primary afferents, suggests that the earliest‐labelled fibre systems (3days) were unmyelinated and replaced at 7 days by predominantly A6 myelinated fibres. It is further suggested that of the three tiers of C fibre terminations seen at 3 days, the most superficial corresponds in part to those primary afferents that can be stained for substance P within lamina I while the most ventral tier within lamina IIi are those primary afferents containing FRAP. The presence of the two temporally distinct fibre systems also suggests that laminae I and IIo, receive both C and A6 primary afferent input while lamina IIi, receives only C fibre input.
Distribution of GABA‐T‐Intensive neurons in the hat forebrain and midbrain
Authors: Nagai T. , McGeer P. L. , McGeer E. G. 
Published: January 2005

AbstractThe neuronal distribution of 7‐aminobutyric acid (GABA) transaminase (GABA‐T), the enzyne which metabolizes GABA, has been mapped in rat brain. The method involves staining for newly synthesized GABA‐T by the previously established nitro blue tetrazolium technique in animals killed 8–48 hours after administration of gabaculine, an irreversible inhibitor of GABA‐T. Neuronal staining is obscured by staining of other elements if initial suppression is inadequate or survival times postgabaculine are too long. With appropriate conditions, GABA‐T‐positive neuronal somata can be widely detected. The stained cells include neuronal groups previously reported to be GAB Aergic on the basis of glutamate decarboxylase (GAD)‐col‐chicine immunocytochemistry and other methods, i.e.: Purkinje, basket, Golgi, and stellate neurons of the cerebellum; basket and stellate neurons of the hippocampus; granule and periglomerular cells of the olfactory bulb; magnocellular neurons of the hypothalamus; and neurons of the striatum, pallidum, entopeduncular nucleus, cortex, medial septal area, diagonal band, substantia innominata, reticular nucleus of the thalamus, substantia nigra, and dorsal raphe. Other cells that stain intensely for GABA‐T and may be GABAergic include neurons in the midlateral septal area, accumbens, the central medial and basal. nucler of the amyugdala, zona in certa, the brainstem reticular formation, central gray, interstitial nucleus of Cajal, and various thalamic nuclei including the periventricular, intralami‐nar, rhomboid, and subparafascicular. Known non‐GABA neuronal groups are negative for GABA‐T staining under these conditions, reinforcing the hypothesis that GABA neurons are far more GABA‐T intensive than other neurons.
The secondary olfactory connections in two chondrichthians, the shark Scyliorhinus canicula and the ray Raja clavata
Authors: Smeets Wilhelmus J. A. J. 
Published: January 2005

AbstractThe secondary olfactory connections in the shark Scyliorhinus canicula and the ray Raja clavata have been studied with reduced silver techniques. After transction through the pedunculus olfactorus in Scyliorhinus degenerating fibers could be traced to the telencephalic hemisphere. On entering the henisphere these fibres subdivide into a small medial and a larger lateral olfactory tract. The medical olfactory tract also projects contralaterally to the submeningeal pallial zone via the commissural olfactoria inferior and to the stratum granulare bulbi olfactorii by way of the commissural olfactoria superio. The lateral olfactory tract distrubytes mainly to the pallium laterale. A striking difference between Scyliorhibnus and Raja is that in the latter no contralaterature for other cartilaginous fishes, it appears that the secondary olfactory connections of Sycliorhinus are more extensive than in other chondrichthians studied experimentally.In some cases of peduncle transction in Scyliorhinus the lateral part of the sttiatum was also involved in the lesion. In addition to the pattern of degeneration seen after olfactory peduncle lesions, degenerating fibres could be distinguished both in the stria medullaris and basal forebrain bundle. The former projects to hebenular nucleus, whereas the latter distributes to the hypothalamus, and brainstem tegmentum.
Thalamocortical projections in the reeler mutant mouse
Authors: Caviness Verne S. , Frost Douglas O. 
Published: January 2005

AbstractThe normal radial distribution of the different neocortical cell classes is inverted in the reeler mutant mouse. The organization of the thalamocortical projection in adult reelers has been investigated by using anterograde degeneration techniques. Thalarnocortical mons follow anomalous trajectories to their target cytoarchitectonic fields in the mutant. After leaving the internal capsule, the axons ascend in sigmoid‐shaped fascicles to enter a fiber stratum near the cortical surface. The axons course through this superficial stratum until they reach their target fields and then descend to terminate in deeper cortical planes. In the normal animal, by contrast, the mons course tangentially at the interface of the cortex with the subcortical white matter; upon reaching their target fields, they ascend to terminate more superficially in the cortex. Thus, in both genotypes the tangential portions of the axon trajectories pass through the polymorphic cell population.Both with respect to degree of divergence and the radial distribution of terminals within the different cytoarchitectonic fields, the thalamocortical projection in reeler, like that in the normal animal, appears to be composed of two distinct axon classes. The “class I” axons, the less‐divergent system which terminates densely in two or three tiers within the cortex, are the subject of the present analysis. The “class 1” projections form an orderly cortical representation of the thalamus: Despite distortions in the topography of the reeler thalamus and cortex, both the nucleus to field relationships and the detailed topologic organization of the projection appear to be normal.The terminals of class I projections are distributed in radially segregated tiers that resemble the tiered pattern of termination as in normal mice, and there are field‐specific variations in the tiers that, like those of normal mice, are systematically related to variations of cortical cytoarchitecture. Thus, similar mechanisms, which may depend in part on the interaction of ingrowing axons with specific postsynaptic cell surfaces, must determine the restricted radial distribution of thalamocortical projections in both genotypes. However, there is an abnormal mix of somata and dendrites at all radial levels of the mutant cortex, suggesting that the spatial domain of termination of thalamocortical axons may be governed to some extent by factors other than the distribution of specific prospective postsynaptic cell surfaces.The reeler mutation alters the radial but not the tangential structure of the neocortex, suggesting that these two aspects of cortical organization develop under the control of independent mechanisms. The present results suggest that despite the anomalies of radial position, normal relationships between thalamocortical afferents and distinct classes of postsynaptic elements with characteristic radial distributions are largely conserved in reeler. Certain types of aberrant connections are highly probable, however.
Plasticity of the corticospinal tract following midthoracic spinal injury in the postnatal rat
Authors: Bernstein Deborah R. , Stelzner Dennis J. 
Published: January 2005

AbstractRats received a midthoracic spinal cord “overhemisection” including right hemicord and left dorsal funiculus at birth (neonatal operates, N = 15) or 21 days of age (weanling operates, N = 14). In a second experiment neonatal (N = 6), 6‐day (N = 3), and 12‐day (N = 7) rats sustained a right sensorimotor cortex (SmI) ablation to destroy the left corticospinal tract (CST) at the same time as the spinal injury (double lesion operates). Later (3–12 months) injections of 3H‐proline and autoradiography were used to label the left or right CST. The results of the first experiment showed that most right CST axons failed to grow around the spinal lesion in neonatal operates (N = 9). There was an increase in the density of label, mainly to CST projection areas, in a 1‐mm zone rostral to the lesion. However, left CST axons bypassed the lesion by growing through the intact tissue in neonatal operates (N = 6). These displaced axons were consistently located within the dorsal portion of the lateral funiculus (dLF) and remained within that location caudal to the lesion, an area normally containing only a few CST axons. In spite of this abnormal position, these axons terminated bilaterally throughout the remainder of the cord in normal CST sites. In weanling operates, CST axons severed by the lesion did not regenerate around the lesion site. An increased density of label over the few spared axons within the left dLF and in CST projection zones immediately caudal to the lesion site suggested axonal sprouting by these axons. The results of the second experiment showed that the lack of growth of right CST axons around this injury in neonatal operates was, at least partially, due to an interaction with left CST axons. In neonatal double lesion operates, right CST axons grew around the spinal injury for a varying distance within the left dLF and distributed bilaterally to normal CST sites. The number of right CST axons bypassing the lesion was related to the configuration of the lesion site. A smaller number of right CST axons bypassed the lesion in 6‐day double lesion operates and most terminated within 2–3 mm of the lesion site. Right CST axons failed to grow around this injury in 12‐day double lesion operates. We conclude that the availability of intact spinal cord tissue allows uncut developing left CST axons to grow around a lesion when their primary pathway is destroyed. Differences in growth of left and right CST axons appear to be related to an interaction between left and right CST axons which limits the growth of right CST axons across the midline. The ability for CST axons to grow around this injury decreases at the time these axons are elongating through this region and ceases at the time synapses are being formed by these axons. However, further experiments are necessary to determine if these factors in the maturation of the CST, of if other factor in the maturation of the spinal cord, are critical in limiting CST groth after spinal injuryin the developing CNS.
Hyperplasia in the spinal sensory system of the frog. I. Plasticity in the most caudal dorsal root ganglion
Authors: Davis Miriam R. , Constantine‐Paton Martha 
Published: January 2005

AbstractIncreases in the amount of periphery available for innervation have been achieved by the unilateral removal of hindlimb dorsal root ganglion (DRGs) in Rana pipiens, a procedure which generally results in a compensatory cell number increase (hyperplasia) in the DRGs which remain. We have found that the hyperplastic response is extremely variable, and we have investigated various factors which might control its production. Our findings indicate, however, that the pattern of DRGs removed, the animal's age at the time of removal, and the survival period are not strictly related to the production of hyperplasia in hindlimb DRGs.Special emphasis has been placed on DRG 10, the caudalmost DRG which normally innervates the cloaca and sends a small projection to the hindlimb. This DRG displayed dramatic cell number increases of up to 564%. In addition, several unique features of the hyperplastic response have been observed in DRG 10. This DRG showed increases in cell number on both the operated and the unoperated sides. It showed hyperplasias in animals subjected to gangh'onectomy past metamorphosis as well as during larval development. Finally the production of DRG 10 hyperplasias exclusively occurred in male pre‐and postrnetamorphic animals. To account for these distinctive features of DRG 10 hyperplasia, baseline studies of the normal course of proliferation and cell death in DRG 10 were undertaken. They reveal no fundamental developmental differences between DRG 10 and other hindlimb DRGs. Other mechanisms responsible for these unusual features of developmental plasticity in DRG 10 are discussed.
Hyperplasia in the spinal sensory system of the frog. II. Central and peripheral connectivity patterns
Authors: Davis Miriam R. , Constantine‐Paton Martha 
Published: January 2005

AbstractCentral and peripheral connectivity patterns of hyperplastic dorsal root ganglia (DRGs) in Rana pipiens are examined in order to determine the relative roles of peripheral and central contacts in the production of DRG hyperplasias. The hyperplasias are produced in the intact hindlimb DRGs after the removal in tadpoles and young postmetamorphic frogs of neighboring DRGs (Davis and Const an tine‐Paton, '83). The peripheral target zones of the hyperplastic DRGs, determined by physiological recordings of sensory receptive fields, are found to undergo a significant degree of expansion relative to controls. Peripheral expansion is most pronounced in caudalmost DRG 10, and this effect occurs in experimental animals operated during larval and postmetamorphic stages. Further, anatomical labelling of peripheral sensory fibers coursing to the hindlimb reveals that the hyperplastic DRG 10 actually contains additional fibers projecting to the denervated regions. The central projection of the hyperplastic DRG 10 does not show corresponding increases in longitudinal arborization after the application of horseradish peroxidase to the appropriate dorsal roots. These observations are made on some of the same experimental animals in which peripheral fields are shown to have vastly expanded. We conclude that the peripheral processes of the hyperplastic DRGs are less rigidly specified than the central terminations, and that it is the periphery which plays the primary role in controlling the cell numbers increases.A second aim of this investigation is to identify whether sexually dimorphic connectivity patterns in normal frogs explain the production of DRG 10 hyperplasias exclusively in male experimental animals (Davis and Constantine‐Paton, '83). We apply the same techniques used in our connectivity studies of hyperplastic DRGs to the investigation of connectivity patterns of DRG 10s in normal males and females. No sex‐dependent differences in peripheral and central connectivity are found. Thus, since normal male and female frogs possess an equivalent amount of target space for DRG 10, the unique production of hyperplasias in male experimental animals cannot be explained solely on the basis of connectivity. We speculate on what other factors may be involved.
Topography of spinal, dorsal column nuclear, and spinal trigeminal projections to the pontine gray in rats
Authors: Swenson Rand S. , Kosinski Ross J. , Castro Anthony J. 
Published: January 2005

AbstractSeveral studies using a variety of animals have reported conflicting evidence concerning the distribution, laterality, and indeed the presence of ascending projections to the pontine nuclei. In an attempt to clarify this issue, projections to the pontine nuclei from the spinal cord, dorsal column nuclei, and spinal trigeminal nucleus were investigated with anterograde methods, i.e., the Fink‐Heimer technique and/or autoradiography, in Long‐Evans black‐hooded rats. Results revealed that dorsal column nuclear projections to the contralateral pontine gray terminate predominantly in two regions – one in the caudal aspect of the medial pontine subdivision and another overlapping the ventral and lateral subdivisions. Within the medial and ventrallateral nuclear regions, fibers from nucleus cuneatus primarily terminated more rostrally to afferents from the nucleus gracilis. Spinal trigeminal projections terminated most heavily within the contralateral pontine gray at midpontine levels. Similar to the dorsal column nuclear projections, trigeminal afferents were observed in the medial and ventrolateral subdivisions, although these terminations were rostral and dorsal to areas receiving cuneatus input. Additional projections from the spinal trigeminal nuclei to the contralateral ventral peduncular nucleus were also observed. In comparison to the above‐mentioned pontine afferents, both high cervical and midthoracic spinal cord lesions produced a similar pattern of axonal degeneration in the ipsilateral pontine gray which overlapped substantially with gracilis inputs. The observed topographic distribution pattern of ascending afferents to pontine gray confirm and extend previous findings which in general have only briefly described these pathways.
Light and electron microscopic studies of the basilar papilla in the duck, Anas platyrhynchos. II. Embryonic development
Authors: Chandler John P. 
Published: January 2005

AbstractThe intent of this study was to describe certain morphological aspects of cytodifferentiation of the basilar papilla in the duck, Anas platyrhynchos. The duck, with a longer incubation period than that of the chicken, has proven useful in identifying the earliest morphological changes during cytodifferentiation of the basilar papilla. Most of these changes occur first at the neural margin of the presumptive genu, at the site of initial contact by cochlear nerve fibers. A wave of differentiation of hair cells radiates abneurally, proximally, and distally, concurrent with the establishment of afferent innervation. Extracellular channels form in the papilla between cell bases just before the nerve fibers penetrate the basal lamina. Nerve fibers abut hair cell bases in the genu at the time the hair cells separate from the basal lamina on day 9. Hair cell bases contain granular vesicles and lie among the nuclei of supporting cells on day 10. Synaptic bodies are present opposite nerve endings on day 11. Efferent nerve endings appear on short hair cells in the genu on day 15 and on tall hair cells on day 17.
Synaptology of retinal terminals in the dorsal lateral geniculate nucleus of the cat
Authors: Rapisardi Salvatore C. , Miles Toni P. 
Published: January 2005

AbstractWe have made a fine structural investigation of the synaptic patterns made by axon terminals of retinal ganglion cells in the dorsal lateral geniculate nucleus of the cat. We compared the retinal input to dendritic processes that bear clusters of large appendages with the retinal input to relatively smooth dendritic segments that have only a few isolated spines. The study was restricted to the portion of laminae A and A1 that receive central visual field input. We were able to completely reconstruct 33 individual terminal boutons from long series of consecutive thin sections. Retinal terminals that were presynaptic to dendritic appendages tended to occupy the central position in the complex synaptic zones of geniculate fine structure called glomeruli. These terminals were surrounded by significantly more profiles than retinal terminals that were presynaptic to dendritic stems and averaged twice as many synaptic contacts per terminal bouton. The retinal input to dendritic appendages was heavily involved in a specific synaptic pattern called the triadic arrangement while retinal input to dendritic stems was only lightly involved in triads. Dendritic appendages in triads received greater synaptic input from profiles with flattened vesicles than did the dendritic stems that were found in triads.