bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of the dendritic tree of wild‐type cerebellar Purkinje cells in lurcher chimeric mice
Authors: Caddy Keith W. T. , Herrup Karl 
Published: January 2005

AbstractNaturally occurring mutations are valuable tools for the study of neural development, especially when used in conjunction with the techniques of chimeric mouse production. In this study we examine the response of Purkinje cell dendrites to the altered developmental environment found in the lurcher ↔ wild‐type chimera. Lurcher (+/Lc) is an autosomal dominant gene that causes the cell‐autonomous degeneration of all Purkinje cells of +/Lc genotype. Thus, in +/Lc → +/+ chimeras, only wild‐type Purkinje cells survive to maturity. The number of these survivors can vary from less than 10,000 to greater than 100,000, Previous work has shown that the final ratio of presynaptic granule cells to postsynaptic Purkinje cells is increased in lurcher chimeras. On average, therefore, one might expect that each remaining Purkinje cell would experience an increased supply of afferents, and our hypothesis was that dendritic growth and/or sprouting might occur as a result. This proved incorrect and, indeed, the Purkinje cells in the lurcher chimeras show changes of a predominantly atrophic nature. Unusual morphologies are found, including variable branching density, failure of the distal dendrite to reach the pial surface, loss of isoplanarity, and the frequent appearance of large caliber, primary or secondary dendritic branches ending abruptly in “stub ends.” Quantitative analysis of Golgi‐Cox impregnated material reveals that in lurcher chimeras the Purkinje cell dendritic arbor is reduced by more than 60% compared to wild‐type animals. We present possible explanations for this finding and consider several potential implications.
Vestibule‐ocular projections in the 11‐day chicken embryo: Pathway specificity
Authors: Pétursdóttir Gudrun 
Published: January 2005

AbstractThe organization of vestibulo‐ocular projections and their spatial relationship to vestibulo‐spinal projections were ascertained in the 11‐day chicken embryo through retrograde tracing experiments. An in vitro preparation of the brainstem facilitated precisely localized application of tracers. Unilateral labelling of the ascending medial longitudinal fascicle (MLF), just caudal to the trochlear nucleus, labelled coherent groups of vestibular neurons that had an asymmetrical distribution on the two sides of the brainstem. Axons originating from either side followed one of four trajectories, and the groups of neurons could therefore be identified on the basis of their position and their projection pathway. Labelling each side of the MLF with a different tracer showed that although neurons projecting in the ipsi‐ and contralateral MLF were intermingled in some areas, individual neurons projected on one side only.Labelling the ascending MLF and the high cervical spinal cord with different tracers showed that vestibulo‐ocular neurons had a wider rostro‐caudal distribution than vestibulospinal neurons. Some vestibulospinal and vestibulo‐ocular groups were spatially segregated, others were intermingled. Very few (in most preparations no) neurons were found to project to both targets.Together with our previous study on vestibulospinal projections in the 11‐day chicken embryo (Glover and Pétursdóttir, J. Comp. Neurol. 270: 25–38, '88) the results show that vestibular neurons in different regions project in characteristic subsets of the available pathways.
Interplexiform cells of the goldfish retina
Authors: Kalloniatis Michael , Marc Robert E. 
Published: January 2005

AbstractDopaminergic and glycinergic interplexiform cells (IPCs) in the goldfish retina were impregnated by using two new Golgi protocols. The two cell types have markedly different morphological characteristics: Dopaminergic IPCs have primary dendrites that descend into and stratify in the inner plexiform layer, where they give rise to processes that project to the outer plexiform layer. Conversely, glycinergic IPCs have primary dendrites that ascend to the outer plexiform layer and from this dendritic arbor, many processes then project into the inner plexiform layer. The apparent coverage of dopaminergic IPCs is almost four times that of glycinergic IPCs. Even so, the coverage of each glycinergic IPC in the outer plexiform layer allows it to provide an accurate copy of the S‐space to the inner plexiform layer. Considering the known GABAergic and glycinergic synaptologies in the inner plexiform layer, the glycinergic IPC must form a major element in the retinal circuitry of the goldfish.
Paraventricular organ of the lungfish Protopterus dolloi: Morphology and projections of CSF‐contacting neurons
Authors: von Bartheld Christopher S. , Meyer Dietrich L. 
Published: January 2005

AbstractThe morphology and projections of neurons in the paraventricular organ (PVO) were studied by means of silver impregnation after intraocular application of cobaltous lysine in the lungfish Protopterus dolloi. Cobalt‐labeled neurons were found exclusively in the PVO in the dorsal and infundibular hypothalamus. These bipolar neurons possess one CSF‐contacting process that protrudes into the ventricular lumen with a club‐shape ending and a thick, ramifying process directed into the hypothalamic neuropil; the ependymofugal processes form intra‐ and extrahypothalamic projections. Impregnated fibers from paraventricular neurons cross in infundibular and hypothalamic commissures, the commissure of the posterior tuberculum, the postoptic, the habenular, and the anterior commissures. Projections to the infundibulum and the median eminence are relatively sparse; no fibers are labeled in the pituitary gland. Ascending projections to the forebrain are extensive. Major targets include the dorsal hypothalamus, the periventricular preoptic nuclei, the habenula, the subhabenular region, the anterodorsal thalamus, and the medial telencephalic hemisphere (septum). Most ascending fibers follow the medial forebrain bundle; others course in the fasciculus retroflexus and terminate in rostral parts of the ipsilateral habenula. Descending fibers run caudally along the ventral floor of the brainstem. They terminate in the neuropil of the mesencephalic tegmentum, ventral tectum, isthmic region, ventral portions of the reticular formation throughout the rhombencephalon, and extend into the spinal cord.Intraocular application of cobaltous lyaine results in selective impregnation of neurons in the PVO and their ascending and descending projections, presumably via uptake of tracer from vascular circulation. These projections do not represent retinofugal or retinopetal projections. We provide conclusive evidence for the existence of a PVO in Protopterus. On the basis of PVO location and acetylcholinesterase histochemistry, we propose subdivisions of the infundibular hypothalamus corresponding to those in amphibians. Ascending PVO projections appear to be particularly well developed in lungfish compared with other species and may be related to specialized endocrine mechanisms in this group of vertebrates.
Developmental history of the transient subplate zone in the visual and somatosensory cortex of the macaque monkey and human brain
Authors: Kostovic Ivica , Rakic Pasko 
Published: January 2005

AbstractThe cytological organization and the timetable of emergence and dissolution of the transient subplate zone subjacent to the developing visual and somatosensory cortex were studied in a series of human and monkey fetal brains. Cerebral walls processed with Nissl, Golgi, electron‐microscopic, and histochemical methods show that this zone consists of migratory and postmigratory neurons, growth cones, loosely arranged axons, dendrites, synapses, and glial cells. In both species the subplate zone becomes visible at the beginning of the mid‐third of gestation as a cell‐poor/fiber‐rich layer situated between the intermediate zone and the developing cortical plate. The subplate zone appears earlier in the somatosensory than in the visual area and reaches maximal width at the beginning of the last third of gestation in both regions. At the peak of its size the ratio between the width of the subplate zone and cortical plate in the somatosensory cortex is 2:1 in monkey and 4:1 in man while in the occipital lobe these structures have about equal width in both species. The dissolution of the subplate zone begins during the last third of gestation with degeneration of some subplate neurons and the relocation of fiber terminals into the cortex. The subplate zone disappears faster in the visual than in the somatosensory area.The present results together with our previous findings support the hypothesis that the subplate zone may serve as a “waiting” compartment for transient cellular interactions and a substrate for competition, segregation, and growth of afferents originated sequentially from the brain stem, basal forebrain, thalamus, and from the ipsi‐ and contralateral cerebral hemisphere. After a variable and partially overlapping time period, these fibers enter the cortical plate while the subplate zone disappears leaving only a vestige of cells scattered throughout the subcortical white matter. A comparison between species indicates that the size and duration of the subplate zone increases during mammalian evolution and culminates in human fetuses concomitantly with an enlargement of cortico‐cortical fiber systems. The regional difference in the size, pattern, and resolution of the subplate zone correlates also with the pattern of cerebral convolutions. Our findings indicate that, contrary to prevailing notions, the subplate may not be a vestige of the phylogenetically old network but a transient embryonic structure that expanded during evolution to subserve the increasing number of its connections.
Explanation for the labeling of cervical motoneurons in young rats following the introduction of horseradish peroxidase into the calf
Authors: Haase Peter 
Published: January 2005

AbstractThis study was carried out to determine whether cervical motoneurons, labeled following the introduction of horseradish peroxidase into the rat hind leg, belong to the cutaneous trunci motoneuron pool. The cutaneous trunci is a superficial muscle that extends from the axilla, over the flank, and into the thigh. Its nerve supply is derived from the brachial plexus.In experimental animals, horseradish peroxidase was either injected directly into the right gastrocnemius muscles, or applied to gelfoam and implanted over the calf muscles in the right leg of 5‐, 10‐, 15‐day‐old and adult rats. In control animals the cutaneous trunci was denervated prior to the administration of horseradish peroxidase.Labeled cervical motoneurons were present in the 5‐, 10‐, and 15‐day‐old but not the adult experimental groups and were located within the predetermined confines of the cutaneous trunci motoneuron pool. No labeling of cervical motoneurons was observed in any of the control groups in which the cutaneous trunci muscle was denervated.The most likely explanation for the labeling of cervical motoneurons in young rats was the local diffusion of horseradish peroxidase from the calf to the thigh, where it entered the cutaneous trunci muscle and was taken up by some of its motoneurons. The absence of such labeling in adult rats was probably due to the presence of connective tissue barriers to diffusion and to the greater distance between the site of horseradish peroxidase application and the cutaneous trunci muscle, which prevented the tracer from reaching the cutaneous trunci muscle and labeling its motoneurons.
Thalamic midline cell populations projecting to the nucleus accumbens, amygdala, and hippocampus in the rat
Authors: Su Hong‐Sen , Bentivoglio Marina 
Published: January 2005

AbstractThe organization of the thalamic midline efferents to the amygdaloid complex, hippocampal formation, and nucleus accumbens was investigated in the rat by means of multiple retrograde fluorescent tracing. The present findings indicate that these connections derive from separate cell populations of the thalamic midline, with a low degree of divergent collateralization upon more than one of the targets examined.The neural populations projecting to the amygdala, hippocampus, or accumbens are highly intermingled throughout the thalamic midline, but display some topographical prevalence. Midline thalamo‐hippocampal cells are concentrated in the nucleus reuniens; thalamo‐accumbens neurons prevail in the ventral portion of the paraventricular nucleus, and in the central medial nucleus. Thalamo‐amygdaloid cells display a topographical prevalence in the rostral third of the thalamic midline and are concentrated in the dorsal part of the paraventricular nucleus and in the medial part of the nucleus reuniens. Both dorsally in the paraventricular nucleus and ventrally in the nucleus reuniens, thalamo‐amygdaloid cells are located closer to the ependymal lining than the neurons projecting to the hippocampus or nucleus accumbens. Further, thalamo‐amygdaloid cells, especially in the paraventricular nucleus, extend their dendritic processes in the vicinity of the ependymal lining, where they arborize profusely. These features indicate a close topographical relationship of neurons projecting to the amygdala with ependymal cells.The fairly discrete origin of midline outputs to the amygdala, hippocampus, and accumbens indicates that the flow of information is conveyed through separate channels from the thalamic midline to limbic and limbic‐related targets. Together with the literature on the limbic afferents to the thalamus, these findings emphasize the relationships between the thalamus and the limbic system subserved by parallel input‐output routes. However, because of the overlap of the projection cell populations, the thalamic midline may represent a locus of interaction among neurons connected with different parts of the limbic system.The functional implications of these findings are discussed in relation to the “nonspecific” thalamic system, as well as to the circuits involved in memory formation‐Key words: thalamus, limbic system, basal ganglia, parallel channels, memory processing.
Amygdaloid projections to the frontal cortex and the striatum in the rat
Authors: Kita H. , Kitai S. T. 
Published: January 2005

AbstractProjections from the basolateral nucleus of the amygdala (BLA) to the frontal cortex and the striatum were studied by using Phaseolus vulgaris‐leucoagglutinin (PHA‐L) anterograde tracing technique in the rat.PHA‐L injections into the rostral part of the BLA resulted in a dense labeling of fibers with boutons in the dorsal bank of the rhinal fissure and in the lateral and the medial agranular cortex. PHA‐L injections into the caudal part of the BLA produced a dense labeling of fibers in the medial surface of the frontal cortex. In most of the cortical regions, labeled fibers were predominantly distributed in two bands: one in the deep part of layers I and II and the other, heavier band, in layers V and VI.PHA‐L injections into the rostral BLA resulted in a dense labeling of fibers with boutons in the olfactory tubercle, the rostral and caudolateral portion of the nucleus accumbens, and a large region of the caudate–putamen. The labeled area of the caudate–putamen included the rostroventral area, the central area, and the area caudal to the anterior commissure and dorsal and lateral to the globus pallidus. PHA‐L injections into the caudal BLA produced fiber labeling in the most rostromedial area of the caudate–putamen facing the lateral ventricle, the medial portion of the nucleus accumbens, and the lateral septum. In the rostroventral striatum, PHA‐L‐labeled fibers selectively innervated the matrix compartment that contains abundant somatostatin‐immunoreactive fibers. Compartmental segregation was less clear in the caudo‐dorsolateral caudate–putamen and in the nucleus accumbens. Electron microscopy revealed that PHA‐L‐labeled boutons in the striatum contained abundant, small, round vesicles. These boutons formed asymmetrical synapses with dendritic spines of striatal neurons.
Requirement for olfactory axons in the induction and stabilization of olfactory glomeruli in an insect
Authors: Tolbert Leslie P. , Sirianni Peter A. 
Published: January 2005

AbstractThe role of antennal sensory axons in the induction and stabilization of olfactory glomeruli has been explored in the moth Manduca sexta. First, we asked the question: how many axons are necessary to induce glomerulus formation within the first‐order olfactory neuropil of the brain? Axons from as few as 10 of the normal 70–80 repeating antennal segments were sufficient to induce glomeruli. However, there was a dose dependence in the number of glomeruli that developed in partially innervated lobes. When only 11 segments of the antenna were allowed to provide innervation to the lobe, only 37 of the normal 59 ± 2 glomeruli developed; over 20 segments were necessary to induce the normal number of glomeruli. In a second set of experiments, we asked: for how long must antennal axons be present to stabilize newly formed glomeruli? We found that antennal axons must be intact for at least 2 to 4 stages (roughly equivalent to 2 to 4 days) for glomeruli to be stable even if the axons are subsequently severed. This finding, taken in the light of other recent findings in our laboratory, suggests that the formation of synapses may be a crucial element in the stabilization of glomerular structure. All together, the results of the present study indicate that induction and stabilization of glomeruli are separable events with different underlying cellular bases.
Demonstration of discrete place‐defined columns—segregates—in the cat SI
Authors: Favorov Oleg V. , Diamond Mathew E. 
Published: January 2005

AbstractThe SI forelimb area of cats was examined with receptive field (RF) mapping techniques. Arrays of closely spaced, near‐radial microelectrode penetrations were inserted into the crown of postsigmoid gyrus of ketamine anesthetized subjects and minimal RFs were obtained at several depths. The minimal RF was defined as the skin site providing the strongest input to each recorded cluster of neurons. Data analysis showed that all studied cortical territories contained groups of discrete cortical columns, 300–400 μm in diameter. The columns were regarded as topographic entities because no change in minimal RF location could be observed within their boundaries. The boundaries of columns were sharp and could be unequivocally distinguished because the minimal RFs sampled on opposite sides of a boundary occupied displaced, nonoverlapping positions.Pair‐wise comparison of single neuron maximal RFs (defined as the entire skin area providing input to the recorded neuron) further clarified the nature of the SI place‐defined columns: (1) no systematic differences in maximal RF position could be demonstrated for different parts of the same column (even though the maximal RFs in most columns varied extensively in size and skin areas covered), and (2) at the boundary between neighboring columns maximal RFs shifted en masse to center on a new skin locus. These minimal and maximal RF observations strongly support our recent proposal that body surface is represented in SI by a honeycomblike mosaic of discrete place‐defined cortical columns, segregates.
Morphology of sympathetic preganglionic neurons in the neonatal rat spinal cord: An intracellular horseradish peroxidase study
Authors: Forehand Cynthia J. 
Published: January 2005

AbstractUnderstanding the central neural control of autonomic functions requires a knowledge of the morphology of the preganglionic neurons, for the location of the dendritic arborizations of these neurons will indicate which central pathways may have access to them. In the present study, individual sympathetic preganglionic neurons in the neonatal rat spinal cord have been examined by the intracellular injection of horseradish peroxidase (HRP) in an in vitro preparation. Seventeen HRP‐labeled preganglionic neurons in thoracic segments T1–T3 were examined in detail; of these, 12 somata were located in the intermediolateral cell column (IML), one in the lateral funiculus (LF), two in the intercalated nucleus (IC), and two at the border between IML and IC.All of the neurons had extensive dendritic arborizations arising from an average of six primary dendrites; the average total dendritic length for these cells was 2,343 μm. The morphology of preganglionic neurons differed depending on the location of their cell bodies. Preganglionic neurons located in the IML were essentially two‐dimensional: the cells had some dendrites that coursed rostrocaudally for 300–500 μm within the IML and others that coursed mediolaterally, extending to the lateral surface of the cord and close to the central canal. Axons of these cells coursed ventrally from the cell body and exited from the spinal cord at the first ventral root caudal to the cell body. No intraspinal axon branches were observed. In contrast, preganglionic neurons with somata outside the IML had dendritic arborizations that radiated away from the cell body in three dimensions, extending into the IML, LF, and the dorsal and ventral horns of the spinal cord while traversing a rostrocaudal distance of about 400 μm. Two of these cells had axons that branched within the spinal gray.These results indicate that the dendrites of neonatal rat sympathetic preganglionic neurons extend outside the IML, where they may be contacted by inputs that do not terminate within IML. Moreover, the different dendritic arborizations of preganglionic neurons in different preganglionic nuclei may mean that the connectivity of preganglionic neurons varies according to cell body location. Finally, the intraspinal axon collaterals on some preganglionic neurons provide an anatomical substrate for local circuit interactions.
Distribution and projection pattern of motoneurons that innervate hindlimb muscles in the quail
Authors: Tyrrell Sophia , Schroeter Sally , Coulter Lynn , Tosney Kathryn W. 
Published: January 2005

AbstractWe characterized the motoneuron pool positions and projection patterns in the embryonic quail hindlimb and compared them to those in the chick to determine the degree of similarity and to form a baseline for future chimeric experiments. We find that the most similar parameters of pool position correlate with the major axonal pathway choices. First, the medial‐lateral pool position, which is highly conserved among birds and mammals, is identical in the quail and chick and correlates with the dorsal‐ventral pathway choice, the first and least plastic of the choices within the limb. Second, although quail pools were known to be compressed into seven rather than eight segments, we show that the map of pools is compressed about a central point (segment three) that preserves the spatial relationships between anterior pools and the crural plexus, and between posterior pools and the sciatic plexus. Access to guidance cues that are restricted to each plexus region is thus maintained between species. Third, pool position along the anterior‐posterior axis is the least similar parameter between species. In fact, the entire lumbosacral motor complex may shift by ± half a segment in individual quail. Despite the consequent differences in segmental projections, the specific projection pattern within each quail hindlimb is identical to that in the chick. There is no need to preserve the exact segmental pattern either phylogenetically or during development, because motoneurons accommodate to modest variations in their position along the anterior‐posterior axis by sorting out at the limb base. The contrast between variable segmental and constant limb projections also demonstrates that neither the specification nor the precise projection of motoneurons is dependent upon the specification or development of somites.