bluuebunny/crossref_metadata_2025_split huggingface dataset:
Axon morphology of mesencephalic trigeminal neurons in a snake, Thamnophis sirtalis
Authors: Dacey Dennis M. 
Published: May 2005

AbstractThe morphology of single axons of mesencephalic trigeminal neurons (Mes V) was studied in the eastern garter snake (Thamnophis sirtalis) by solid filling them with an extracellular horseradish peroxidase technique. Each Mes V axon can be divided into central, peripheral, and descending branches. The central branch descends from its soma of origin in the midbrain to the dorsal aspect of the motor nucleus of the trigeminal (Motor V) and the motor root, where it splits into peripheral and descending branches. The descending branch travels caudally from Motor V to the brainstemspinal cord junction. The peripheral branch passes dorsal to motor V and joins the motor root of V to exit the brainstem. All three branches issue a massive collateral system that distributes terminal swellings within the nuclear boundaries of Motor V. Single Mes V axons diverge to sparsely contact a large number of motoneurons throughout the nucleus, suggesting that single motoneurons receive a convergent input from many Mes V neurons. Since Motor V contains multiple, highly overlapping motor pools, single afferents are positioned to contact different motor pools. The descending branch is situated medial and adjacent to the spinal sensory nucleus of the trigeminal (Sensory V). It issues a collateral field to the entire length of Sensory V. The terminal swellings of these collaterals form rostrocaudally aligned sheets, flattened in the horizontal plane. Single terminal sheets have a divergent projection to a large field of sensory cells and single, fusiform sensory cells are positioned to receive a convergent projection from many terminal sheets.The results provide the first detailed description of Mes V axon morphology. The overall pattern of these axons closely resembles that recently described for spinal Ia afferent fibers in cat. There is evidence in both cases for divergence of single afferent terminal fields to a set of spatially overlapping motor pools and a convergence of input to single motoneurons from a large population of afferents. This anatomical pattern is consistent with the recently proposed role of sensory feedback in the activity of single motoneurons.
Topography, cytoarchitecture, and sulcal patterns in primary somatic sensory cortex (SmI) of the prosimian primate, Perodicticus potto
Authors: Fitzpatrick Kathleen A. , Carlson Mary , Charlton John 
Published: May 2005

AbstractThe topographic organization of the primary somatic sensory projection area (SmI) in relation to cytoarchitectural fields and sulcal patterns was examined in the prosimian primate Perodicticus potto. The area of cortex responding to low threshold (LT) cutaneous stimulation of the glabrous and hairy surfaces of the hand was determined by microelectrode mapping techniques, with standardized threshold stimuli for defining receptive fields. A single somatotopic projection of the two hand surfaces was found; the glabrous projection area is rostral to that of the hairy hand. Within both the glabrous and hairy areas, receptive fields on the distal digits are found anterior to those on the proximal hand. The glabrous hand projection area is coextensive with a dense granular area typical of koniocortex. The hairy hand area corresponds to a cytoarchitectural field which is less granular than the glabrous field. While koniocortex occupies the crown of the gyrus caudal to the coronally oriented sulcus, a large more rostral field, which contains both granule and large pyramidal cells, occupies the whole of the caudal bank of the sulcus. Force thresholds of many receptive fields (RFs) in Perodicticus were high both on the borders and within the LT area (perhaps because of the advanced age of these animals). However, the receptive field sizes for both the glabrous and hairy hand areas were of the same magnitude as those of Nycticebus (Carlson and FitzPatrick, '82). From the combined studies of three species of Lorisidae, Perodicticus, Galago (Carlson and Welt, '80), and Nycticebus (Carlson and FitzPatrick, '81), using similar mapping and stimulation techniques, both general and specific features of SmI hand area organization can be illustrated. A single projection of the glabrous and hairy hand is common to Perodicticus and Galago, but two glabrous projection areas are seen in Nycticebus. The projection area for the hand in Perodicticus is twice as large (relative to brain size) as in Galago and Perodicticus. The possible behavioral significance of increased differentiation of the hand area in Nycticebus and elaboration of the area in Perodicticus could be examined by study of hand use and tactile capacity in these same spcies.
Localization of neurons afferent to the optic tectum in longnose gars
Authors: Northcutt R. Glenn 
Published: May 2005

AbstractAfferent pathways to the optic tectum in the longnose gar were determined by unilateral tectal injections of HRP. Retrogradely labeled cells were observed in the ipsilateral caudal portion of the rostral entopeduncular nucleus and bilaterally in the rostral half of the lateral zone of area dorsalis of the telencephalon. The following diencephalic cell groups were also labeled following tectal injections: the ipsilateral anterior, ventrolateral, and ventromedial thalamic nuclei, the periventricular pretectal nucleus, and the central pretectal nucleus (bilaterally); the ventromedial thalamic and central pretectal nuclei revealed the largest number of labeled cells. At midbrain levels, retrogradely labeled cells were seen in the ipsilateral torus longitudinalis, nucleus isthmi, and accessory optic nucleus; cells were labeled bilaterally in the torus semicircularis and a rostral tegmental nucleus. Only a few cells were labeled in the contralateral optic tectum, suggesting that few of the fibers of the intertectal commissure are actually commissural to the tectum. At hindbrain levels, retrogradely labeled cells were seen bilaterally in the locus coeruleus, the superior, medial, and inferior reticular formations, the eurydendroid cells of the cerebellum, and the nucleus of the descending trigeminal tract; the contralateral dorsal funicular nucleus also exhibited labeling. Clearly, the tectum in gars receives a substantial number of nonvisual afferents from all major brain areas, most of which have been reported in other vertebrates. The functional significance of these afferent sources and their probable homologues in other vertebrate groups are discussed.
The location of cerebellar‐projecting neurons within the lumbosacral spinal cord in the cat. An anatomical study with HRP and retrograde chromatolysis
Authors: Grant G. , Wiksten B. , Berkley K. J. , Aldskogius H. 
Published: May 2005

AbstractThe locations of lumbosacral spinocerebellar neurons were examined by two anatomical methods in kittens. In one group of animals chromatolytic changes were provoked by cerebellar lesions. In another group horseradish peroxidase (HRP) was injected into the cerebellum. Projection laterality was investigated by making unilateral spinal lesions prior to the cerebellar HRP injections. Diaminobenzidine (DAB) or tetramethylbenzidine (TMB) was used as substrate for HRP. The morphological characteristics of HRP‐labeled neurons in the TMB‐processed material were examined.Neurons marked by the two methods were located within the same regions. A greater number of cells were marked with the HRP method, however, than with the retrograde chromatolysis method. Spinocerebellar neurons were found in laminae IV–IX with large differences with regard to specific locations depending on segmental level. Numerous marked neurons were found in the following areas: laminae IV–VI in L3–L7, the column of Clarke in L3–L4, the medial part of lamina VII in L6–L7, the lateral part of lamina VII in L3–L4, the dorsolateral nucleus of lamina IX in L3–L6, the ventrolateral nucleus of lamina IX in L4–L5, and the ventromedial nucleus of lamina IX in S3 (and Ca1). Dorsally located neurons were in general more likely to project ipsilaterally than ventrally located neurons. Marked structural differences were frequently observed between spinocerebellar neurons in different locations.These results provide additional information on the anatomical complexity of the spinocerebellar pathways from the lumbosacral region in the cat. Together with results from some other recent anatomical studies on spinocerebellar tracts, they also form a basis for further anatomical and physiological investigations which could contribute to a better understanding of the organization of the spinocerebellar tracts.
The midbrain periaqueductal gray in the rat, cat, and monkey: A Nissl, Weil, and Golgi analysis
Authors: Mantyh Patrick W. 
Published: May 2005

AbstractAnatomical staining methods including Nissl, Weil, Golgi, and horseradish peroxidase stain have been used to elucidate the cyto‐ and myeloarchitectural organization of the periaqueductal gray in monkey, cat, and rat. From these various staining methods it appears that the periaqueductal gray is composed of a tightly packed group of cells, which show a slight increase in soma size, dendritic diameter, and degree of myelinization from central to peripheral borders. This central gray region contains a wide variety of cell types including multipolar, fusiform, stellate, and pyramidal neurons. Clearly delineated subnuclei, distinguished on the basis of soma size, dendritic arborizations, pigmentation, or evidence of cytological individuality could not be discerned in this study. Together with the immunohistochemical and connectivity studies the present data suggest that the neuronal organization of the PAG could be described as a mosaic of clusters of functional related neurons rather than as three distinct subnuclei, each with its own unique cytoarchitecture and connectivity.
Synaptogenesis and its relation to growth of the postsynaptic cell: A quantitative study of the developing mauthner neuron of the axolotl
Authors: Jacoby Jean , Kimmel Charles B. 
Published: May 2005

AbstractWe describe the relation between growth and branching of an identified dendrite and the formation of synapses on its surface during a 3 1/2‐day period early in development. We studied the lateral dendrite and the adjacent lateral perikaryon of the Mauthner cell (M‐cell) during embryonic stages 39–43 in the axolotl Ambystoma mexicanum. Reconstructions from light micrographs of serial sections through the cell revealed that during this interval the dendrite elongates rapidly, and large numbers of ventrally directed branches are formed. Samples of the same material by electron microscopy showed that large numbers of synaptic contacts appear during the same interval. We quantitatively estimated changes in local synapse densities (the number of contacts/100 μm2 of M‐cell surface) and local surface areas of the M‐cell and found that synapses were most densely clustered, and accumulated most rapidly, on regions of the cell that were rapidly expanding. These data are in accord with previous evidence from work in this and in other systems that synaptic contacts induce local growth of dendrites. Furthermore, the data are consistent with a proposal that outgrowth of new dendritic branches is induced or stabilized by synapses in a concentration‐dependent fashion.
Localization of methionine‐enkephalin, substance P, and somatostatin immunoreactivities in the main olfactory bulb of the hamster
Authors: Davis Barry J. , Burd Gail D. , Macrides Foteos 
Published: May 2005

AbstractMethionine‐enkephalin, substance P, and somatostatin immunoreactivities are associated with different classes of neurons in the main olfactory bulb of the hamster. In the glomerular layer, methionine‐enkephalin immunoreactivity is observed in the somata and dendrites of periglomerular cells whereas substance P immunoreactivity is present in the somata and dendrites of external tufted cells. Substance P immunoreactivity may also be present in the superficial short axon cells. In the deeper layers, methionine‐enkephalin immunoreactivity is observed in a mixed population of neurons which appear to be primarily granule cells, whereas somatostatin immunoreactivity is present only in deep short axon cells. Methionine‐enkephalin‐, substance P‐, and somatostatin‐positive fibers of central origin are also observed in the main olfactory bulb.
Relation of medullary motor nuclei to nerves supplying the vocal tract of the budgerigar (Melopsittacus undulatus)
Authors: Manogue Kirk R. , Nottebohm Fernando 
Published: May 2005

AbstractThe locations of brainstem motor nuclei supplying efferents to organs of the vocal tract of the budgerigar (Melopsittacus undulatus) were determined as a first step in describing brain pathways for vocal control in this species. We identified four major nerves supplying the muscles of the syrinx, larynx, and tongue, and separately treated each of these with horseradish peroxidase. Nerves supplying efferents to the larynx and tongue arise from ipsilateral cells in the nucleus ambiguus and hypoglossal nucleus, respectively. Each right and left half of the syrinx is supplied by both right and left halves of the hypoglossal nucleus, via axons crossing in the common anastomosis of the tracheosyringeal nerves. This bilateral innervation of the syrinx will allow testing for central asymmetries of dominance for vocal control in the absence of any underlying anatomical laterality in the periphery.
Studies on cell migration and axon guidance in the developing distal auditory system of the mouse
Authors: Carney Paul R. , Silver Jerry 
Published: May 2005

AbstractThe events that take place along the potential route of distal auditory axons (future vestibular component) prior to and during their outgrowth were examined morphologically using timed mouse embryos. During embry‐onic (E) day 9.5 a discrete zone of cell death appears in the rostrolateral wall of the otic cup. Necrosis is accompanied by outward migration of epitheloid cells from the same region of the otic wall. Temporally and spatially corre‐lated with these two events is the widening of extracellular spaces between otic neuroepithelial cells and the breakdown of basement membrane. During E 10.5 migrating epitheloid cells condense to form a funnel‐shaped configu‐ration. This cellular “funnel” begins narrowly at the dorsorostrolateral wall of the otocyst and broadens as it reaches the auditory ganglion. During E 11.5 through E 12.5, “pioneer” distal auditory axons take a circuitous route and ascend from the auditory ganglion to enter the otocyst. Axons extend toward the otocyst moving along cells of the “funnel,” maintaining an orien‐tation similar to that of the cells that compose it. Axon growth cones enter the otocyst at sites devoid of basement membrane and invade the wall of the otocyst moving tangentially along radially arranged cells that bridge the otocyst and the “funnel.”These observations demonstrate that a preformed, funnel‐shaped tissue exists along the future route of the auditory fibers. We suggest that the “fun‐nel” may influence the growth and directionality of distal auditory axons as they extend from the auditory ganglion to the wall of the otocyst. At the otic wall, the transition provided by “bridge” epitheloid cells, together with the absence of basement membrane at specific sites of the otic wall, provide the auditory axons with a route into the otocyst.
Atlas of catecholamine perikarya, varicosities and pathways in the brainstem of the cat
Authors: Jones Barbara E. , Friedman Lee 
Published: May 2005

AbstractBy application of a modified glyoxylic acid‐paraformaldehyde histoflu‐orescence technique, catecholamine perikarya, varicosities, and pathways were delineated within the brainstem of kittens that were either untreated, pretreated pharmacologically, or injected intracerebrally with 6‐OHDA. Three principal catecholamine cell groups were identified within the medulla and pons: the dorsomedial medullary cell group, the dorsolateral pontine cell group, and a ventrolateral cell group extending from the medulla into the pons. Induced axonal accumulation of catecholamines with intracerebral 6‐6‐OHDA injections revealed a major longitudinal catecholamine bundle which courses in a dorsolateral position through the entire brainstem tegmentum. The dorsomedial medullary and dorsolateral pontine cell groups contribute ascending and descending fibers to this bundle. Axons of the ventrolateral pontomedullary cells also feed into the bundle at successive levels through radially coursing transverse fibers. Via this major dorsolateral conduit and its ventrally and medially coursing tributaries, catecholamine fibers and terminals are distributed to multiple nuclei through the brainstem. The regions of the catecholamine cell groups and the serotonin raphe nuclei all receive a dense catecholamine innervation. Varicosities are also dense in the visceral cranial nerve nuclei, moderately dense in most somatic spinal and cranial nerve motor nuclei, and moderate to light in sensory cranial nerve and relay nuclei. The lateral and ventromedial reticular formation are moderately innervated by varicose catecholamine fibers that traverse these regions. The longitudinal catecholamine bundle continues caudally into the lateral funiculus to descend into and innervate the spinal cord. Rostrally it continues into the tegmental fascicles of the midbrain to ascend into and innervate the diencephalon and there join the medial forebrain bundle to ascend into the telencephalon. Thus, the catecholamine neurons utilize this dorsolateral longitudinal bundle to distribute collaterals to mul‐tiple bulbar nuclei and to travel beyond the brainstem to innervate the spinal cord and forebrain.
Four types of amacrine in the cat retina that accumulate GABA
Authors: Freed Michael A. , Nakamura Yasuhisa , Sterling Peter 
Published: May 2005

AbstractRoughly one‐quarter of neurons in the amacrine cell layer accumulate exogenous γ‐aminobutyric acid (GABA). Some of these (8%) are interplexiform cells; the remainder are true amacrine cells. We partially reconstructed, from serial electron microscope autoradiograms, 25 GABA‐accumulating amacrines and distinguished four types based on cytoplasmic appearance, soma size and shape, and the form of primary and secondary processes. Type 1 had a large (609 ± 60 μm3), dark soma, and multiple, medium‐diameter (0.6 μm) processes splayed from the soma margins like the appendages from a crab. Type 2 had a medium (360 ± 40 μm3), helmet‐shaped, pale soma, and medium‐diameter (0.8 μm) processes that branched in sublamina α. Type 3 had a small (267 ± 44 μm3), dark, pyriform soma. The latter formed a single stout (3.0 μm) process that bifurcated in the middle of sublamina α. Type 4 had a very large, pale soma (860 μm3). This was pyriform, tapering into a stout (2.0 μm) process that descended into the middle of sublamina α where it emitted smaller tangential processes. It is to be expected that each of these amacrine cell types will have distinct functions in neurotransmitter retinal circuitry.
The relation of corpus callosum connections to architectonic fields and body surface maps in sensorimotor cortex of new and old world monkeys
Authors: Killackey H. P. , Gould H. J. , Cusick C. G. , Pons T. P. , Kaas J. H. 
Published: May 2005

AbstractCorpus callosum connections of parietal and motor cortex were studied in New World owl monkeys (Aotus trivirgatus)and Old World macaque monkeys (Macaca fascicnlaris) after multiple injections of 3H‐proline and horseradish peroxidase, HRP, into one cerebral hemisphere, and extensive microelectrode mapping of architectonic Areas 3b, 1, and 2 of the other hemisphere. Results were obtained both from parasagittal brain sections cut orthogonal to the brain surface and from sections from flattened brains cut parallel to the brain surface. Cortical fields varied in density of callosal connections, and the density of connections varied according to body part within sensory representations. Thus, Area 3b had few, Area 1 had more, and Area 2 had relatively dense callosal connections. Within each of these fields, connections were much less dense for the representations of the glabrous hand and foot and much more dense for the representations of the face and trunk. For the representation of the hand, retrogradely labeled cells were extremely sparse in Area 3b, moderately sparse in Area 1, and moderate in Area 2. There were less dense callosal connections in the hand representations of Areas 3b, 1, and 2 in macaque as compared to owl monkeys. Label in posterior parietal cortex was uneven with zones of extremely dense connections. A large region of very dense callosal connections was noted in motor cortex just medial to the probable location of the hand representation. In all regions, callosally projecting cells appeared to be more broadly distributed than callosal terminations. In no region was the discontinuous arrangement of callosal connections obviously organized into an extensive pattern of mediolateral or rostrocaudal bands or strips.
Investigations on the development and topographic order of retinotectal axons: Anterograde and retrograde staining of axons and perikarya with rhodamine in vivo
Authors: Thanos Solon , Bonhoeffer Friedrich 
Published: May 2005

AbstractRhodamine‐B‐isothiocyanate (RITC) is shown to be a convenient and advantageous fluorescence tracer both for anterograde staining of retinal ganglion cell axons on the tectum and for retrograde staining of ganglion cell bodies in the retina of chick embryos. After intravitreal injection the dye is taken up by ganglion cells of the retina from the extracellular space and is transported anterogradely at about 10 mm/day up to the axonal growth cones on the tectum. RITC can be taken up by growing axons on the tectum and it is transported retrogradely at about 5 mm/day to the cell bodies in the retina. Local staining can be achieved if RITC is applied in its crystalline form. RITC is nontoxic for the cells and their axons, is resistant to histologi‐cal fixation procedures, and allows quick observation in vivo and on dissected stained tissue.Local application of RITC to distinct retinal areas allows examination of the position of the corresponding stained fibers along the retinotectal pathway. Fibers which arise from the central temporal retina occupy deeper layers, whereas fibers from the peripheral temporal retina occupy more superficial layers in the optic tract and in the stratum opticum on the anterior tectum.The growth cones of early retinal fibers growing directly on the tectal surface show a different morphology to later growth cones growing on top of the stratum opticum on the tectum.