bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extrinsic and intrinsic fiber connections of the telencephalon in a teleost, Sebastiscus marmoratus
Authors: Murakami Takeshi , Morita Yasuhiro , Ito Hironobu 
Published: January 2005

AbstractExtrinsic and intrinsic fiber connections of the telencephalic subdivisions of Nieuwenhuys (1962) in a teleost, Sebastiscus marmoratus, were studied by means of horseradish peroxidase (HRP) and Fink‐Heimer methodsThe olfactory bulb projects bilaterally to area dorsalis pars posterior, area ventralis pars ventralis, pars lateralis, pars posterior, pars intermedia, and the nucleus posterior tuberis of Peter et al. (1975) and receives fibers from ipsilateral area dorsalis pars centralis, pars posterior, area ventralis pars dorsalis, and pars supracommissuralis. Area dorsalis pars posterior sends numerous fibers to the ipsilateral ventral region of area dorsalis pars medialis, from which fibers of the medial forebrain bundle arise and terminate in the inferior lobe and nucleus posterior tuberisArea dorsalis pars lateralis, pars dorsalis, and the dorsal region of pars medialis are the main targets of extratelencephalic ascending afferents. Area dorsalis pars lateralis receives fibers from the ipsilateral nucleus pre‐thalamicus of Meacler (1934), where tectal projections terminate massively. Area dorsalis pars dorsalis and the dorsal region of pars medialis receive afferents from the ipsilateral nucleus prcglomerulosus of Schnitzlein (1962), nucleus posterior tuberis, area preoptica pars medialis of Crosby and Showers (1969), and nucleus entopeduncularis of Sheldon (1912). Raphe nuclei and locus ceruleus project bilaterally to area dorsalis pars centralis, pars dorsalis, pars lateralis, and the dorsal region of pars medialis. Area dorsalis pars centralis, pars dorsalis, and the dorsal region of pars medialis are important sources of extrateiencephalic efferents. These subdivisions give rise to the lateral forebrain bundle and project to the ipsilateral nucleus prethalamicus, nucleus pregiomerulosus, inferior lobe, nucleus paracommissuralis of Ito et al. (1982), optic tectum, torus semicircularis, and the bilateral mesencephalic tegmentumWithin the telencephalon, most of the ventral subdivisions project to ipsilateral area dorsalis pars centralis, pars dorsalis, pars lateralis, and the dorsal region of pars medialis. Area dorsalis pars centralis has reciprocal connections with ipsilateral area dorsalis pars lateralis, pars dorsalis, pars posterior, and the dorsal region of pars medialis. A dorsal part of the anterior commissure is composed of axons of the ventral region of area dorsalis pars medialis destined to the contralateral ventral region of area dorsalis pars medialis. A ventral part of the anterior commissure contains axons of area dorsalis pars centralis destined to contralateral area dorsalis pars lateralis.
Comparative cytoarchitectonic study of gudden's tegmental nuclei in some mammals
Authors: Hayakawa Tetsu , Zyo Katuya 
Published: January 2005

AbstractThe structure and location of the dorsal and ventral tegmental nuclei of Gudden were studied in brains of 12 species of mammals. The ventral teg‐mental nucleus of Gudden is composed of oval or polygonal, medium‐sized, well‐stained cells, and includes the pars principalis situated ventral to the fasciculus longitudinalis medialis, and the pars suprafascicularis in the cen‐tral gray matter dorsal to the fasciculus longitudinalis medialis (in the golden hamster, mouse, vole, and house shrew).The dorsal tegmental nucleus of Gudden is situated within the central gray matter. This nucleus includes the pars ventralis, composed of oval or triangular cells, medium‐sized but smaller than those of the ventral tegmen‐tal nucleus of Gudden, and the pars dorsalis, composed of round, small, and lightly stained cells, and often encapsulated by fibers of the fasciculus longi‐tudinalis dorsalis.The isthmus between the dorsal and ventral tegmental nuclei of Gudden is distinct. In the cat, dog, rat, gerbil, and rabbit, the isthmus stands at the dorsal edge of the fasciculus longitudinalis medialis; in the golden hamster, mouse, vole, and house shrew, within the central gray matter; and in the guinea pig, at the ventral edge of the fasciculus longitudinalis medialis. In the green monkey and man, we could not find a ventral tegmental nucleus of Gudden, and in the house shrew and man, the pars ventralis and pars dor‐salis of the dorsal tegmental nucleus of Gudden could not be separated.
The laminar distribution of intracortical fibers originating in the olfactory cortex of the rat
Authors: Luskin Marla B. , Price Josephl. 
Published: January 2005

AbstractIn this study, the autoradiographic method for tracing axonal connections was used to identify the laminar distribution of intracortical fibers originating in the olfactory cortical areas of the rat. Most of the projections can be divided into two major fiber systems with different laminar patterns of termination. The first of these, termed the layer Ib fiber system, arises in the anterior olfactory nucleus, the anterior and posterior piriform cortex, and the lateral entorhinal cortex, and terminates predominantly in layer Ib and, in many cases, layer III of the entire olfactory cortex. The second system, termed the layer II‐deep Ib fiber system, originates in three relatively small olfactory cortical areas‐the dorsal peduncular cortex, the ventral tenia tecta, and the periamygdaloid cortex and terminates in and around the cells of layer II in most parts of the olfactory cortex. There is significant overlap in the laminar distribution of the two systems, although the distinction between them is readily apparent.Within the layer Ib fiber system there are relatively slight but consistent differences in the lamination of fibers from different areas. The fibers from the anterior olfactory nucleus are concentrated in the deep part of layer Ib while those from the anterior piriform cortex are concentrated in the superficial part of this layer. The fibers from the posterior piriform cortex tend to be densest in the middle of layer Ib. These differences are maintained in all areas of termination of each set of fibers, both ipsilaterally and contra‐laterally.In addition, intracortical fibers from the anterior cortical nucleus of the amygdala are distributed throughout layer I, including layer la and Ib. Fibers from the nucleus of the lateral olfactory tract terminate bilaterally around the cells of the islands of Callej a and the medial edge of the anterior piriform cortex.
Fine structure of nigral and pallidal afferents in the thalamus: An em autoradiography study in the cat
Authors: Kultas‐ilinsky K. , Ilinsky I. , Warton S. , Smith K. R. 
Published: January 2005

AbstractUltrastructural characteristics and distribution of nigral and pallidal axon terminals on thalamic neurons were studied after injections of tritiated leucine into substantia nigra and entopeduncular nucleus respectively.Adult cats received 0.1–0.2‐μl injections of 2, 3, 4, 5, 3H‐leucine in a concentration 60 μCi/μl and were allowed to survive for 4–5 days. The brain tissue was processed for electron (EM) and light microscopic (LM) autoradiography. EM samples were obtained from the ventral medial and ventral anterior thalamic nuclei. Ultrastructural features of labelled nigral and pallidal boutons were analyzed both qualitatively and quantitatively.Ultrastructural characteristics of nigral and pallidal boutons appeared similar. Their length along postsynaptic membrane ranged from 0.8 to 10 μm, with average length of apposition around 2 μm. Both types of bouton contained small clear vesicles of extremely variable shape and formed symmetrical type contacts. Mean diameter of synaptic vesicles profiles (n = 500) was 32.5 nm and 33.3 nm in nigral and pallidal terminal respectively, and mean vesicle profile areas were 846 nm2 in nigral terminals and 878m2 in pallidal. Both parameters showed normal distribution in percentage distribution histograms. The mean ratios of longest and shortest diameters was 1.6 for synaptic vesicles in both types of boutons.Thus, no significant differences in morphological parameters of nigral and pallidal axon terminals were discovered except that pallidal afferents often formed “en passant”‐type synapses while nigral did not. However, this feature alone is not sufficient for distinction between the two types of termi‐nals in unlabelled tissue.Analysis of distribution of synaptic sites showed that only pallidal bou‐tons formed axosomatic synapses on thalamocortical projection neurons (TCPN), which comprised 21% of total number of pallidal terminals studied. On primary dendritic trunks of TCPN the proportion of nigral boutons was larger (28.8%) as compared to pallidal (19%). The percentage of both types of bouton contacting secondary TCPN dendrites was similar (36% pallidal, 30.6% nigral), while the proportion of nigral terminals on tertiary TCPN den‐drites was larger (23.6% versus 13%). Both afferents revealed a tendency to synapse preferentially at the branching points of TCPN dendrites with sev‐eral boutons often found along the perimeter of the branching site. Small but equal proportions (8%) of both types of axon terminal were found to synapse on vesicle‐containing dendrites of local circuit neurons. Nigral boutons were also found in complex synaptic arrangements in glomeruli.It is concluded that the organizations of pallidal and nigral afferent in‐puts in the thalamus are rather similar. Both occupy strategic positions which would allow them to exert strong influence on the firing pattern of TCPN.
Differentiation of fly visual interneurons after laser ablation of their central targets early in development
Authors: Näaassel Dick R. , Geiger Gad , Seyan Harjit S. 
Published: January 2005

AbstractTo test the differentiation of visual interneurons that had their targets removed before axogenesis, we ablated neuronal precursors in brains of first instar fly larvae by using a laser microsurgery unit. We describe ablations that resulted in the elimination of the third neuropil region (the lobula complex) of the optic lobes. Neural differentiation in the more peripheral second and first neuropil regions (the medulla and the lamina) was thus studied in the absence of the lobula complex.It was found that the medulla neuropil differentiated with normal columnar and layered organization. The neuropil, however, folded along its central surface. The only connection between the medulla and more central neuropil (the midbrain) was via a bundle of axons (the Cuccati bundle) present also in the normal optic lobes. Some types of neurons that normally connect the medulla and the lobula complex could be identified. These appeared to end in a disorganized neuropil mass in the center of the folded medulla.The differentiation of the lamina neuropil also appeared normal in flies with the lobula complex eliminated and the medulla folded. Also, in optic lobes where the medulla was severely disorganized and/or reduced due to laser ablations, the lamina neuropil appeared more or less normal.The results suggest that lamina and medulla nerve cells can differentiate and develop normal neuropil patterns in absence of their appropriate targets.
The cerebeillopontine system in the rat. II. Electron microscopic studies
Authors: Watt Carl B. , Mihailoff Gregory A. 
Published: January 2005

AbstractCerebellopontine axonal boutons in the neuropil of the basilar pontine nuclei (BPN) were marked for ultrastructural identification by producing unilateral electrolytic lesions of the superior cerebellar peduncle (SCP) as it exited from the cerebellum and before its decussation in the caudal midbrain. Three varieties of degenerating boutons were distinguished on the basis of size, type of degeneration, and postsynaptic locus. A relatively large variety of bouton (2.5–6.0 μm) that exhibited filamentous degeneration throughout the range of survival times employed (1–14 days) was the most frequently observed type of degenerating Cerebellopontine bouton. Such boutons formed synaptic contacts with several small, dendritic, spinelike profiles as well as the shafts of intermediate or proximal dendrites. A second, far less numerous and somewhat smaller type of bouton (1.5–4.5 μm) was distinguished by the fact that it exhibited advanced dark degenerative changes after a 2‐day survival period, formed multiple spine contacts (but not shafts), and was no longer apparent in the neuropil after a postlesion survival time of 6 days. The third variety of degenerating bouton was small (0.8–2.0 μm), exhibited dark degeneration with a 2–6‐day survival period, contacted primarily shafts of small‐diameter dendrites, and was observed more frequently than the larger dark boutons but less often than the large filamentous boutons. All three types of degenerating boutons contained round, clear, synaptic vesicles and formed only asymmetric synaptic active sites. It is suggested that the three types of degenerating axon terminals arise from at least three varieties of neurons in the deep cerebellar nuclei. Further it is suggested that such boutons originate from cerebellar efferent axons which distribute in collateral fashion to the thalamus, red nucleus, and/or the inferior olive.
Motor neuron columns in the lumbar spinal cord of the rat
Authors: Nicolopoulos‐Stournaras Stavroula , Iles John F. 
Published: January 2005

AbstractThe location in the rat spinal cord of motor neurons innervating 23 muscles or muscle groups of the hind limb has been determined by using retrograde transport of horseradish peroxidase. The motor neurons supplying a single muscle form a discrete longitudinal column in the lateral ventral horn. The columns extend through up to three adjacent spinal segments and their longitudinal location varies by as much as one segment in different animals. The relative positions of the columns supplying different muscles and their transverse location in the spinal cord are very consistent between individuals and a stereotaxic map has been constructed. This is briefly compared with descriptions from other species. Counts of the numbers of motor axons in seven different muscle nerves have been made with the aid of acetylcholin‐esterase histochemistry to identify the motor component. The numbers of motor neuron somata labelled with horseradish peroxidase are on average 70% of the axon counts.
Retrograde and anterograde‐transneuronal degeneration in the parabigeminal nucleus following tectal lesions in developing rats
Authors: Linden Rafael , Perry V. Hugh 
Published: January 2005

AbstractDegenerative effects in the parabigeminal nucleus were studied in adult rats that had received lesions of the superior colliculus at different postnatal ages. Unilateral lesions lead to complete degeneration of the dorsal and ventral divisions of the parabigeminal nucleus, which connect reciprocally with the damaged tecturn, and produce effects on the middle division which receives afferents from the ipsilateral and projects to the contralateral tectum. On the side contralateral to the lesion there was a reduction in the cross‐sectional area of the division as a consequence of retrograde degeneration, except in rats operated on at birth or when adults; ipsilateral to the lesion there was a reduction in the cross‐sectional area of the division as a result of anterograde‐transneuronal degeneration, except in animals operated on when adults. The reduction in cross‐sectional area is partly due to a decrease in the number of neurones in the middle division. The maximal effects in both cases occurred in animals operated on at 10 days after birth, and the sensitivity to retrograde degeneration follows a U‐shaped curve. Bilateral tectal lesions performed at birth or 5 days after birth produce virtually complete degeneration of the whole parabigeminal nuclei. Anterograde radio‐autographic tracing showed that all parabigeminal divisions receive topographically organized projections from the ipsilateral superior colliculus. Ipsilateral projections from the dorsal and ventral divisions and crossed projections from the middle division were identified in the tectum of newborn rats with fluorescent retrograde tracers. Possible explanations for the cases in which tectal lesions failed to produce an effect on the architecture of the middle division include increased resistance to axonal damage and regulative processes over natural neuronal death. The results also indicate that the two forms of degeneration are additive with regard to the whole population of developing parabigeminal neurones.
The organization of the fibers in the optic nerve of normal and tectum‐less Rana pipiens
Authors: Reh Thomas A. , Pitts Eleanor , Constantine‐Paton Martha 
Published: January 2005

AbstractWe have examined the detailed order of retinal ganglion cell (RGC) axons in the optic nerve and tract of the frog, Ranapipiens. By using horseradish peroxidase (HRP) injections into small regions of theretina, the tectum, and at various points along the visual pathway, it hasbeen possible to follow labelled fibers throughout their course in the nerve and tract.Several surprising features in the order of fibers in the visual pathway were discovered in our investigation. The fascicular pattern of RGC axons in che retina is similar to that described in other vertebrates; however, immediately central to their entry into the optic nerve head, approximately half of the fibers from the nasal or temporal retina cross over to the opposite side of the nerve. Although the axons from the dorsal and ventral regions of the retina generally remain in the dorsal and ventral regions of the nerve, some fiber crossing occurs in those axons as well. The result of this seemingly complex rearrangement is that the optic nerve of Rana pipiens contains mirror symmetric representations of the retinal surface on either side of the dorsal ventral midline of the nerve. The fibers in each of these representation are arranged as semicircles representing the full circumference of the retina. This precise fiber order is preserved in the nerve until immediately periphearal to the optic chiasm, at which point age‐related axon from both side of the nerve bundle together. Consequently, when a small pellet of HRP is placed in the chiasmic region of the nerve, an annualus of retinal ganglion cells and a corresponding annulus of RGC terminals in the tectum are la belled. As the age‐related bundles of fibers emerge from the chiasm they split to form a medial bundle and a lateral bundle, which grow in the medial and lateral branches of the optic tract, respectively. Although the course followed by RGC axons in the visual pathv/ay is complex, we propose a model in which the organization of fibers in the nerve and tract can arise from a few rules of axon guidance.To determine whether the optic tecta, the primary retinal targets, play a role in the development and organization of the optic nerve and tract, we removed the tectal primordia in Rana embryos and examined the order in the nerve when the animals had reached larval stages. We found that the order in the nerve and tract was well preserved in tectumless frogs. Therefore, we propose that guidance factors independent of the target direct axon growth in the frog visual system.
Fast and slow motoneurons with unique forms and activity patterns in lobster claws
Authors: Hill R. H. , Govind C. K. 
Published: January 2005

AbstractThe form of the fast closer excitor (FCE) and the slow closer excitor (SCE) motoneurons to the closer muscle in the claw of the lobster Homarus americanus was determined by injecting cobalt chloride or Lucifer Yellow into their respective somata. Both neurons are monopolar with the single neurite rising vertically to the dorsal surface of the ganglion, then travelling along this surface to where it gives offits dendrites before entering the second nerve root as an axon. The FCE and SCE motoneurons, however, differ in their dendritic form in several respects. First, the FCE completely lacks an anterior dendritic field, which is well elaborated in the SCE. Second, the FCE has fewer large primary dendrites in its posterior field than the SCE. Third, the posterior dendritic field of the FCE is not as extensive as that of the SCE. Fourch, the axon of the FCE originates from one of the posterior primary dendrites while that of the SCE is an axial extension of its neurite. Thus the SCE has a more elaborate dendritic field than the FCE, which may account for its greater excitability. For instance, recordings from intact lobsters show that the SCE has a lower firing threshold and is active for longer periods of time and at higher frequencies than the FCE.
Antennal neuropile in the brain of the crayfish: Morphology of neurons
Authors: Tautz Jürgen , Muller‐Tautz Rosemarie 
Published: January 2005

AbstractThe cellular composition of the antennal neuropile of the crayfish is described. As a context for this work the distribution of neuronal cell bodies throughout the supraoesophageal ganglion (brain) is also described. The neuronal cell bodies in the brain are concentrated in 19 distinct clusters Three paired clusters are located on the dorsal side of the brain, four paired and one midline cluster bend around the brain laterally and frontally respectively. Fewer than ten somata lie outside of these clusters. The antennal neuropile is composed of primary afferent terminals, efferents, and projecting and local interneurons. The structures of individual neurons of all four types were determined by filling them with Lucifer yellow, and an overview of the neuropile structure was obtained with cobalt backfills of selected nerves The antennal afferents are concentrated in four main tracts that run medially in the outer layer of the antennal neuropile. Up to 11 orthogonal side branches occur at equal distances (25–35 μm) along the main branches and penetrate the neuropile. The efferents contribute very thin dendrites to the antennal neuropile. The majority of the neuronal mass of the antennal lobe consists of projecting and local interneurons. The branching pattern of the interneurons within the antennal neuropile also shows an orthogonal arrangement of main branches and higher‐order branches. Thus the antennal neuropile displays a strong geometrical regularity: Main processes of all four types of neurons run in bundles the length of the long axis of the neuropile (lateral to medial inside the brain) giving rise to orthogonal side branches at regular intervals. This branching pattern leads to a striped appearance of the antennal lobe.
Spatial‐Temporal progress of peripheral nerve regeneration within a silicone chamber: Parameters for a bioassay
Authors: Williams Lawrence R. , Longo Frank M. , Powell Henry C. , Lundborg Göran , Varon Silvio 
Published: January 2005

AbstractThe spatial‐temporal progress of peripheral nerve regeneration across a 10‐mmgap within a silicone chamber was examined with the light and electron microscope at 2‐mm intervals. A coaxial, fibrin matrix was observed at 1 week with a proximal‐distal narrowing that extended beyond the midpoint of the chamber. At 2 weeks, Schwann cells, fibroblasts, and endothelial cells had migrated into the matrix from both nerve stumps. There was a delay of 7–14 days after nerve transection and chamber implantation before regenerating axons appeared in the chamber. At 2 weeks, nonmyelinated axons were seen only in the proximal 1–5 mm of the chamber in association with Schwann cells. Axons reached the distal stump by 3 weeks and a proximal‐distal gradient of myelination was observed. These observations define the parameters of a morphologic assay for regeneration in this chamber model which can be used to investigate cellular and molecular mechanisms underlying the success of peripheral nerve regeneration.