bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution of choline acetyltransferase immunoreactivity in the brain of the lizard Gallotia galloti
Authors: Medina Loreta , Smeets Wilhelmus J. A. J. , Hoogland Piet V. , Puelles Luis
Published: January 2005

The aim of the present study is to provide a complete description of the distribution of choline acetyltransferase (ChAT) immunoreactivity (i) in the brain of the lizard Gallotia galloti, on the basis of two different primary antisera: rat anti‐ChAT and rabbit anti‐chicken ChAT. Considering that the brain is a segmented structure, we have analysed our data with respect to transverse segmental domains (or neuromeres), which have been previously described by several authors in the brain of vertebrates.

In the telencephalon, ChATi neurons are seen in the cortex, anterior dorsal ventricular ridge, basal ganglia, diagonal band, and bed nucleus of the stria terminalis. Further caudally, ChATi cell bodies are located in the preoptic area, hypothalamus, habenula, isthmus, and all motor efferent centers of the brainstem and spinal cord.

Plexuses of ChATi fibers are observed in the areas containing cholinergic cell bodies. In addition, distinct plexuses are found in the cortex, the posterior dorsal ventricular ridge, the neuropiles of all primary visual centers of the diencephalon and mesencephalon, and several non‐visual nuclei of the brainstem.

The distribution of ChAT immunoreactivity in the brain of G. galloti resembles in many respects that of other vertebrates, and differences are mainly observed in the pretectum and midbrain tectum. Transverse segmental domains were identified in the brainstem and forebrain of Gallotia when the cranial nerve roots and fiber tracts were used as a reference, and most cranial motor nuclei were found to occupy the same segmental positions as have been reported in the chick. © 1993 Wiley‐Liss, Inc.
Interlaminar connections of the superior colliculus in the tree shrew. I. The superficial gray layer
Authors: Hall William C. , Lee Psyche
Published: January 2005

One of the most persistent problems in the study of the superior colliculus is the relationship between its superficial and deep layers. The superficial tier of layers is considered to be visuosensory in function, whereas the deep tier is multisensory and has premotor functions. This fundamental distinction is the primary basis for the view that a visually triggered shift in the direction of gaze depends on the transfer of information from sensory cells in the superficial tier to premotor cells in the deep tier. The goal of the present experiments was to examine the interalaminar projections of the superficial gray layer in the tree shrew Tupaia belangeri. We used biocytin as the marker for tracing the pathways. The tree shrew was chosen because its large and distinctly laminated superior colliculus facilitates the task of examining connections between the layers. Biocytin was used because of its sensitivity and because it allowed us to place very small injections restricted entirely to the superficial gray layer. The results demonstrated that a prominent pathway originates in the superficial gray layer and terminates in stratum opticum. In comparison, the projection from the superficial gray layer to the layers beneath stratum opticum is extremely sparse. The pathway from the superficial gray layer to stratum opticum has a columnar distribution, extending about 100 m̈m rostrally and caudally from the center of the injection site. There were no signs of more remote intracollicular connections, nor of patches or bands of terminals. The biocytin injection sites also labeled pathways to nuclei as distant from the superior colliculus as the diencephalon, including the dorsal and ventral lateral geniculate bodies, and the pulvinar. The results suggest that stratum opticum may serve as a link between the superficial gray layer and the deeper layers. © 1993 Wiley‐Liss, Inc.
Contact‐spacing among astrocytes is independent of neighbouring structures: In vivo and in vitro evidence
Authors: Tout Simon , Dreher Zofia , Chan‐ling Tailoi , Stone Jonathan
Published: January 2005

We have examined the morphology of astrocytes and the arrays they form in two situations, in retinas from which ganglion cells and blood vessels have been caused to degenerate, and in vitro. These observations were made to test whether the regularity of the spacing of astrocytes within normal central nervous tissue results from interaction among astrocytes, or from interaction between astrocytes and other elements of that tissue. Both in the partially degenerated cat retina, and in cultures of astrocytes from neonatal rat cortex, astrocytes make and maintain contact with neighbouring astrocytes, yet space their somas apart, giving regularity to the arrays. These results support the hypothesis that the regularity observed in arrays of astrocytes in intact tissue results from an interaction among astrocytes, independent of neighbouring structures, and lead us to suggest that the cell‐cell interactions involved in contact spacing serve to distribute astrocytes through the central nervous system, and may, in other tissues, underlie the formation of epithelia. © Wiley‐Liss, Inc.
Spatial distributions of chemically identified intrinsic neurons in relation to patch and matrix compartments of rat neostriatum
Authors: Kubota Yoshiyuki , Kawaguchi Yasuo
Published: January 2005

The spatial distributions and dendritic branching patterns of chemically identified subpopulations of striatal intrinsic neurons, defined by immunoreactivity for choline acetyltransferase (ChAT), neuropeptide Y or parvalbumin, were studied in relation to patch and matrix compartments of rat neostriatum. ChAT‐immunoreactive cells and fibers showed an uneven pattern of distribution in the striatum. ChAT immunoreactivity was higher in the dorsolateral part and lower in the ventromedial part of the striatum. This regional gradient pattern is the inverse of the overall pattern of calbindin D28k immunoreactivity. However, in small regions close to the lateral ventricle and globus pallidus, areas containing fewer ChAT‐immunoreactive cells and fibers coincided with those containing low calbindin D28k immunoreactivity. Neuropeptide Y immunoreactivity was uniform in the neostriatum. Certain neuropeptide Y cells (about 20%) were also immunoreactive for calbindin D28k, indicating that at least a small population of calbindin D28k‐immunoreactive cells are medium aspiny cells. Parvalbumin immunoreactivity was not uniform in the striatum. A higher density of parvalbumin immunoreactivity was found in the neuropil in lateral and caudal parts than in the medial part. Small regions with weaker parvalbumin‐immunoreactive neuropil partially corresponded to calbindin D28k poor patches. Larger cells immunoreactive for parvalbumin were preferentially located in lateral and caudal parts of the striatum.

Cells immunoreactive for ChAT, neuropeptide Y or parvalbumin showed basically similar distribution patterns in relation to the patch and matrix compartments. Most stained cells were located in the matrix, but some were located at the borders of patches and a few were inside patches. Most primary dendrites of stained cells in the matrix or patches remained confined to these compartments, but cells on the borders invariably extended dendrites into both compartments. The striatal intrinsic neurons form chemically differentiated neuronal circuits within the matrix, and the patches and those whose dendrites cross the borders may contribute to associational interconnections between the two compartments, unlike the spiny projection neurons whose dendrites are confined to one or the other compartment. © Wiley‐Liss, Inc.
Pre‐ and postnatal development of the primary visual cortex of the common marmoset. II. Formation, remodelling, and elimination of synapses as overlapping processes
Authors: Missler Markus , Wolff Annelies , Merker Hans‐Joachim , Wolff Joachim R.
Published: January 2005

During ontogenesis changes in the numerical density of synapses are usually assumed to depend essentially on variations in the formation of synapses. Only the final adjustment to adult synapse densities is thought to include the elimination of synapses in some brain regions of certain species. Here, we focus attention on quantitative aspects of synapse elimination throughout development of area 17 of marmoset monkeys (Callithrix jacchus). Mature synapses, various precursor forms, and indicators of lysosomal degradation of synapses were quantitatively analysed by electron microscopy and morphometric methods. A total number of about 135 × 109 synapses was calculated for area 17 in each adult hemisphere corresponding to a volume density of 600 × 106 synapses/mm3. At 3 months of age, the respective values were 508 × 109/area and 1,159 × 106/mm3, while at birth these values were 69 × 109/area and 328 × 106/mm3. Consequently, at least three out of four synapses are eliminated between 3 months and adulthood. However, the real number of synapses being eliminated during development is probably much larger if the time course of lysosomal degradation is additionally taken into account. The frequency of lysosomes in presynaptic endings is highest before net‐elimination of synapses occurs, i.e., between 1 and 3 months. This suggests that lysosomal degradation is not directly responsible for the majority of synapses removed during ontogenesis but apparently represents a second mechanism for synapse remodelling and elimination. Thus, it appears from this study that remodelling and elimination of synapses are quantitatively as important as their formation, and accompany synaptogenesis from its very onset onwards. © 1993 Wiley‐Liss, Inc.
A biphasic sequence of myelination in the developing optic nerve of the frog
Authors: Playford D. E. , Dunlop S. A.
Published: January 2005

We have examined the sequence of myelination along the optic nerve of the frog Litoria (Hyla) moorei from early tadpole life to adulthood. Myelinated axons were counted in electron micrographs of transverse sections taken from behind the eye, at the optic foramen and the chiasm. In tadpoles, myelinated axon numbers were significantly higher at the foramen than at the other levels. By metamorphic climax, numbers had risen at all three levels but more so behind the eye and at the chiasm to become approximately equal along the nerve. After metamorphosis, there was a dramatic increase in myelinated axon numbers, but another pattern was seen; in frogs of 5 cm and 7 cm body length, counts were significantly higher at the chiasm than at the foramen and lowest behind the eye. Thereafter, myelinated axon numbers stabilized at the chiasm but increased behind the eye and at the foramen so that in the most mature stage for this species, 9 cm adults, counts were again similar at the three levels. In addition, total axon numbers, that is, myelinated plus unmyelinated, were assessed from electron micrographs and increased from approximately 8,500 in early tadpoles to 0.65 million in fully mature adults. The proportion of axons that were myelinated showed two peaks, one before and the other after metamorphosis. Measurements of axon diameters from electron micrographs suggested that there was a critical diameter for myelination of 0.3 μm before, and of 0.5 μm after metamorphosis.

The data indicate that there is a biphasic sequence of myelination of optic axons, the first phase being pre‐metamorphic and the second post‐metamorphic. The first phase is initiated at the foramen, and then extends both towards the eye and chiasm and continues until metamorphic climax. During the second phase, myelination originates at the chiasm, spreads towards the eye, and is complete only in the most mature adults. The critical diameter for myelination is smaller in the first phase than in the second. © 1993 Wiley‐Liss, Inc.
Developmental expression of a synaptic ribbon antigen (B16) in mouse retina
Authors: Bachman Katherine M. , Balkema Grant W.
Published: January 2005

We investigated the developmental expression of the synaptic antigen B16 in the outer and inner plexiform layers in the retina. We compared the expression of this protein with published accounts of retinal ribbon synaptogenesis. The time course of B16 expression was found to be similar, if not identical, to the time course of synaptogenesis in the photoreceptor terminal, supporting our idea of the synaptic nature of the B16 protein. This study provides further evidence which suggests that the B16 antigen is a ribbon associated protein. The morphology, location, and developmental expression of this antigen is coincident with the structure and development of the ribbon synaptic elements located in both the photoreceptor and bipolar terminals.

The emergence of the B16 protein was also examined in retina from mice homozygous for the retinal degeneration (rd) mutation which affects photoreceptor synaptogenesis. The B16 expression in the rd retina paralles that in the wild‐type retina at early stages of development. However, significant changes in the morphology and staining pattern of the B16 antigen in the rd retina occurring at later postnatal stages are consistent with the degeneration observed in the photoreceptor terminals. © 1993 Wiley‐Liss, Inc.
Retinal degeneration in the nervous mutant mouse. II. Electron microscopic analysis
Authors: White Mary P. , Gorrin Gregg M. , Mullen Richard J. , LaVail Matthew M.
Published: January 2005

Nervous mutant mice (nr/nr) show a rapid loss of most of cerebellar Purkinje cells between the ages of 3 and 7 weeks, as well as a progressive photoreceptor cell degeneration that occurs most rapidly between postnatal days (P) 13 and 19, but with a much slower attrition during the subsequent months. We have carried out an electron microscopic analysis of nr/nr and littermate control mice at representative ages to characterize the subcellular cytopathological changes in this form of retinal degeneration, to gain insight into photoreceptor cell degeneration mechanisms by comparing these changes to those in other rodent forms of retinal degeneration, and to compare the photoreceptor changes with those of cerebellar Purkinje cells.

Ultrastructural observations were limited to rod photoreceptors, since the number of cones was limited in our micrographs. The retinas of nr/nr mutant mice can be distinguished from those of normal littermates as early as postnatal day (P) 6. At this time, some of the mitochondria in rod inner segments are larger and more rounded than normal. This represents the earliest cytopathological change thus far observed in this mutant. As early as P9 and thereafter, the volume and integrity of rod outer segment membranes are reduced from normal. In the inner segments of some rod photoreceptor cells, there is a reduction in the volume or number of polyribosomes as early as P11, a reduction in rough endoplasmic reticulum as early as P13, and reduced incidence and less organized Golgi membranes as early as P16. Qualitative evaluation and quantitative stereological analysis show that the enlarged mitochondria in rod inner segments never become normal in shape or size. No changes are seen in the inner retinal layers at any age. Despite similarities with inherited retinal dystrophy in the Royal College of Surgeons rat, as noted in the original description of retinal degeneration in nr/nr mice, ultrastructural features clearly distinguish these mutants. Moreover, nr/nr mice can be distinguished from all other murine forms of retinal degeneration by electron microscopy. © 1993 Wiley‐Liss, Inc.
Input organization of distal and proximal forelimb areas in the monkey primary motor cortex: A retrograde double labeling study
Authors: Tokuno Hironobu , Tanji Jun
Published: January 2005

The present double‐labeling study was designed to demonstrate the morphological framework for motor control in coordinated distal and proximal forelimb movements, which may partly, at least, depend on corticocortical and thalamocortical inputs to the forelimb area in the primary motor cortex. After intracortical microstimulation mapping of the forelimb area in the primary motor cortex of four macaque monkeys, a retrograde tracing study with fluorescent dyes was attempted to label simultaneously neurons in cortical and subcortical sites projecting to the distal forelimb representation area and those projecting to the proximal representation area of the primary motor cortex. Neurons projecting to distal and proximal forelimb parts of the primary motor cortex were largely separate in the following areas: the premotor area, primary somatosensory area, secondary somatosensory area, area 5, and thalamus. In contrast, there was no precise topographic organization of labeled projection neurons in the following areas: the supplementary motor area, cingulate motor area, primary motor cortex adjacent to the injection sites, claustrum, and basal nucleus of Meynert. The present study revealed that the forelimb area of the primary motor cortex receives both segregated and intermixed inputs from cortical and subcortical sources. In particular, the fact that the forelimb area of the primary motor cortex receives topographically organized inputs from the premotor area and nontopographically organized inputs from the supplementary motor area and cingulate motor area indicates possible different functional roles of frontal premotor areas in control of coordinated distal and proximal forelimb movements. © 1993 Wiley‐Liss, Inc.
Hippocampal regulation of the survival and morphological development of locus coeruleus neurons in dissociated cell culture
Authors: Robinson Lisa J. , Black Ira B. , Dreyfus Cheryl F.
Published: January 2005

The influence of traget structure on neural development, originally described for the peripheral nervous system, has more recently been investigated in the central nervous system. We sought to determine whether targets regulate the development of the locus coeruleus, with its diffuse and complex projections in marked contrast to the simpler neural circuits of the peripheral nervous system. Dissociated locus coerules cells were grown alone or with the hippocampus in serum‐free, chemically defined medium that minimized non‐neuronal growth. Coculture with the hippocampus resulted in a significant increase in locus coeruleus tyrosine hydroxylase activity. Elevated tyrosine hydroxylase activity was accompanied by a commensurate increase in the number of tyrosine hydroxylase‐immunoreactive cells, suggesting hippocampal enhancement of locus coeruleus survival. Furthermore, when hippocampal cells were added to locus coeruleus dissociates at zero time, or after two days, tyrosine hydroxylase‐positive cell number was increased only by hippocampal cells added initially, suggesting that the target does indeed foster survival. The apparent target enhancement of locus coeruleus survival seems to be selective since total protein and total neuron number, estimated with neuron‐specific enolase immunocytochemistry, were not affected by the hippocampus. Coculture with the hippocampus also increased the length and complexity of locus coeruleus cell processes. Neither the increase in tyrosine hydroxylase cell number nor the changes in morphology could be attributed to nonspecific effects of the increased cell density in cocultures. Our observations thus suggest that the target hippocampus influences the survival and neurite elaboration of afferent locus coeruleus neurons. © 1993 Wiley‐Liss, Inc.
Quantitative study of primary sensory neurone populations of three species of elasmobranch fish
Authors: Snow Peter J. , Plenderleith Mark B. , Wright Layne L.
Published: January 2005

In order to assess the ability of sharks and rays to sense pain, the proportion of myelinated versus unmyelinated sensory fibres in the dorsal roots and the diameter spectrum of cells in the dorsal root ganglia of three species of elasmobranch fish were ascertained. Electron micrographs were used to count the numbers of myelinated and unmyelinated fibres in montages of whole dorsal roots of the long‐tailed stingray (Himantura sp.), the shovelnose ray (Rhinobatus battilum), and small specimens of the black‐tip shark (Carcharhinus melanopterus). The diameters of dorsal root ganglion cells in each species were measured by using the light microscope. Less than 1% of the dorsal root axons in the long‐tailed stringray and a large specimen of the shovelnose were unmyelinated, whereas in smaller shovelnose rays and in the small black‐tipped sharks, from 14% to 38% of axons were unmyelinated. Unmyelinated fibres differed from those in mammalian nerves in that there was a one‐to‐one association of the fibre with a Schwann cell. We conclude from these observations that myelination was incomplete in the black‐tipped sharks and the smaller specimens of the shovelnose rays. The distribution of the diameter of cells of the dorsal root ganglia of these species was unimodal, resembling the diameter range that has been reported for the somata of myelinated fibres in the cat. We interpret these results as indications that sharks and rays lack the neural apparatus essential for the sensation of pain and we suggest that, to these life forms, the perception of pain might have little relevance to survival. © 1993 Wiley‐Liss, Inc.
Patterns of adrenergic and peptidergic innervation in human olfactory mucosa: Age‐related trends
Authors: Chen Ying , Getchell Thomas V. , Sparks D. Larry , Getchell Marilyn L.
Published: January 2005

The distribution and targets of nerves containing the adrenergic markers tyrosine hydroxylase, dopamine β‐hydroxylase, and neuropeptide Y in the human olfactory mucosa were investigated by immunohistochemistry. Tissue was obtained at autopsy from the nasal cleft of 16 adults ranging in age from 24 to 90 years, and from one spontaneously aborted 16‐week‐old fetus. The presence of olfactory receptor neurons in nasal mucosa was confirmed by staining with the antibody to olfactory marker protein. Targets of adrenergic innervation were blood vessels, including the vasa nervorum within the sheaths of olfactory nerve bundles, and Bowman's glands in the lamina propria. Adrenergic fibers penetrated the adventitia of blood vessels and terminated near the media, and were in close proximity to Bowman's glands but did not enter the acini. In the fetal tissue, the vasa nervorum were the major targets of adrenergic fibers. Age‐related differences in the pattern and statistically significant differences in the density of innervation of blood vessels were noted between adults under and over 60 years of age. In the younger group, plexuses of nerve fibers containing colocalized dopamine β‐hydroxylase and neuropeptide Y occurred adjacent to arterioles and large bundles of fibers adjacent to venules; in older individuals, few fiber plexuses occurred adjacent to arterioles and thin bundles of fibers adjacent to venules. The distribution of adrenergic innervation suggests that vasomotor tone and secretion are regulated by adrenergic nerves. The decrease in adrenergic innervation in older individuals, with resultant effects on perireceptor processes, may be associated with age‐related declines in olfactory function. © 1993 Wiley‐Liss, Inc.
Neuronal morphology and efferent projections of the dorsal nucleus of the lateral lemniscus in the rat
Authors: Bajo Victoria M. , Merchán Miguel A. , López Dolores E. , Rouiller Eric M.
Published: January 2005

The dorsal nucleus of the lateral leminsucs (DLL) is the main source of inhibitory influence in the auditory brainstem of mammals. The cytoarchitecture and connectional properties of DLL were established in the cat in contrast to the rat. The goal of the present study was to establish to what extent the anatomical properties of the rat DLL compare to those of the cat, thus providing a basis of interpretation for future functional studies in the rat, an animal model used more and more in the auditory system.

DLL of the rat contains four well‐differentiated neuronal types, as seen in Nissl‐stained material. Type I neurons are large and multipolar with abundant cytoplasm and darkly stained Nissl substance. Type II neurons are large, bipolar and darkly stained in Nissl material. Type III neurons are medium in size and their soma is round or ovoid. Type IV neurons are small and round with scant cytoplasm; they seem to be also the least common neuronal type of the DLL.

After Phaseolus vulgaris‐leucoagglutinin or biocytin injections in the DLL, fibers and terminals labeled by orthograde transport were observed in the corresponding region of the contralateral DLL and in the inferior colliculus, bilaterally. A few labeled fibers and terminal fields were seen in the deep layers of the superior colliculus bilaterally, as well as in the medial division of the medial geniculate body and, even more rostrally, in the posterior nucleus of the thalamus. Descending projections from DLL terminated in the periolivary regions of the ipsilateral superior olivary complex.

Retrograde tracing based on injections of horseradish peroxidase in the various targets of the DLL confirmed the connections established with orthograde labeling. © 1993 Wiley‐Liss, Inc.
Experimentally induced visual projections to the auditory thalamus in ferrets: Evidence for a W cell pathway
Authors: Roe Anna W. , Garraghty Preston E. , Esguerra Manuel , Sur Mriganka
Published: January 2005

We have previously reported that following specific neonatal brain lesions in ferrets, a retinal projection is induced into the auditory thalamus (Sur et al., Science 242:1437, '88). In these “rewired” ferrets, a novel visual pathway is established through auditory thalamus [the medial geniculate nucleus (MGN)] and primary auditory cortex (A1); cells in both MGN and A1 are visually responsive and exhibit properties similar to those of visual cells in the normal visual pathway.

In this paper, we use three approaches—physiological, anatomical, and developmental—to examine which of the retinal ganglion cells project to the MGN in these rewired ferrets. We find that: (1) physiological response properties of postsynaptic visual cells in the MGN are W‐like; (2) retinal ganglion cells back‐filled from the MGN are small and similar to soma sizes of subsets of the normal retinal W cell population; and (3) subpopulations of these small cells can be preferentially rerouted to the MGN in response to different surgical manipulations at birth, consistent with differential W cell projection patterns in normal animals. These data suggest that retinal W cells come to project to the MGN in rewired animals. These findings not only provide a basis on which to interpret functional properties of this novel visual pathway, but also provide important information about the developmental capabilities of specific retinal ganglion cell classes and the regulation of their projections by target structures in the brain during development. © 1993 Wiley‐Liss, Inc.
Immunohistochemical study of catecholamine enzymes and neuropeptide Y (NPY) in the rostral ventrolateral medulla and bulbospinal projection
Authors: Tseng Ching‐Jiunn , Lin Hui‐Ching , Wang Shwun‐De , Tung Che‐Se
Published: January 2005

The purpose of this study was to determine whether neuropeptide Y (NPY) terminals in the intermediolateral spinal cord originate from the rostral ventrolateral medulla (RVLM). Immunohistochemical staining of tyrosine hydroxylase (TH), dopamine‐β‐hydroxylase (DBH), phenylethanolamine‐N‐methyltransferase (PNMT), and NPY in the rat brainstem and spinal cord were performed in this study in order to examine consequences of lesions of the RVLM and of intracisternal injections of 6‐hydroxydopamine (6‐OHDA) on catecholamine and NPY immunoreactivity in the intermediolateral column (IML) of rats. In addition, ricin, a retrograde neurotoxin, was applied in the superior cervical ganglion (SCG) to determine its effect on catecholamine and NPY immunoreactivity in the IML. Computer‐aided image analysis was used to quantify the immunohistochemical changes in the RVLM and spinal cord. The results demosntrated that many catecholamine‐ and NPY‐containing neurons and/or fibers existed in the RVLM and their teminals were found in the IML. After administration of 6‐OHDA intracisternally, the catecholamine and NPY immunoreactivities were decreased both in the brainstem and IML of the spinal cord. Following unilateral microinjection of 6‐OHDA into the RVLM, the number of NPY‐ and catecholamine‐containing neurons decreased and there was a reduction in neuron terminals on the ipsilateral side. After injection of ricin into the SCG, the catecholamine and NPY neurons of the medulla were not affected, whereas their terminals in the IML decreased ipsilaterally. These results indicate that most of the catecholamine‐ and NPY‐immunoreactive terminals found in the IML originated in the RVLM. These terminals appear to project towards the superior cervical ganglia. © 1993 Wiley‐Liss, Inc.
Organization of the nucleus magnocellularis and the nucleus laminaris in the barn owl: Encoding and measuring interaural time differences
Authors: Carr C. E. , Boudreau R. E.
Published: January 2005

The circuit from the cochlear nucleus magnocellularis to the nucleus laminaris supports the encoding and measurement of interaural time differences in the auditory brainstem. Specialization for the encoding of temporal information include the few and/or short dendrites and thick axons of the magnocellular and laminaris neurons, and the high degree of convergence in the circuit.

Magnocellular cells have large cell bodies covered with somatic spines. The cells have few dendrites, and the number of dendrites decreases from low to high best frequency regions of the nucleus. Magnocellular neurons receive both auditory nerve terminals and GABAergic terminals with symmetric synapses and terminals filled with pleomorphic vesicles.

The axonal projections of magnocellular neurons to the nucleus laminaris form maps of interaural time difference. About 100 magnocellular afferents from each side converge on each laminaris neuron, and the terminals from each side do not occupy separate domains on the cell. These terminals form punctate asymmetric synapses on both the dendrites and the cell bodies of laminaris neurons. Laminaris neurons also receive GABAergic terminals which form symmetric synapses. Laminaris neurons have oval cell bodies covered with very short dendrites. The cells in the low best frequency region of the nucleus laminaris have longer dendrites. © 1993 Wiley‐Liss, Inc.
GABAergic innervation of the rat fascia dentata: A novel type of interneuron in the granule cell layer with extensive axonal arborization in the molecular layer
Authors: Soriano Eduardo , Frotscher Michael
Published: January 2005

By using the combined Golgi/electron microscopy (EM) technique and postembedding immunocytochemistry for gamma‐aminobutyric acid (GABA), we describe a novel type of local circuit neuron in the rat fascia dentata that gives rise to an axon profusely ramifying in the dentate molecular layer. The relatively small ovoid cell body (long axis 12–15 μm) is located directly underneath the granular layer. From both poles of the cell body dendritic processes emerge that enter the molecular layer and hilar region, respectively. The apical dendrites traverse the granular layer, invade the molecular layer, and branch in the same way as granule cell dendrites. Some branches reach the hippocampal fissure. Thus, the apical dendrites of these neurons may receive a similar input pattern as the granule cells. The dendrites are smooth, occasionally bearing varicosities. A few spines are regularly observed. The axon originates from the apical dendrite and traverses the molecular layer horizontally for up to 500 μm. It gives off numerous collaterals that are distributed throughout the entire width of the molecular layer and only rarely enter the granule cell layer. Electron microscopy of the cell body of gold‐toned neurons revealed the well‐known fine‐structural characteristics of nonpyramidal neurons, i.e., an indented nucleus with nuclear inclear inclusions and large aggregations of endoplasmic reticulum. Apical as well as basal dendrites are densely covered with presynaptic boutons, mainly forming asymmetric synapses. The axon terminals of these cells form symmetric synapses with dendritic shafts and, to a lesser extent, with spines. These symmetric synapses, together with the results of our GABA postembedding immunocytochemical study, suggest that this cell is a GABAergic inhibitory neuron that almost exclusively innervates the dentate molecular layer. Together with data from the literature on dentate axoaxonic cells (which innervate the axon initial segments of the granule cells) and GABAergic basket cells (which innervate the granule cell somata and proximal dendrites in the granular layer), the present results indicate that there is a lamination of the GABAergic innervation of the fascia dentata corresponding to the well‐known segregated termination of entorhinal and commissural afferents to this region. © 1993 Wiley‐Liss, Inc.
Sexual dimorphism in the volume of song control nuclei in European starlings: Assessment by a Nissl stain and autoradiography for muscarinic cholinergic receptors
Authors: Bernard Daniel J. , Casto Joseph M. , Ball Gregory F.
Published: January 2005

Previous studies have found that the volume of several song control nuclei is larger in male songbirds than in female songbirds. The degree of this volumetric sex difference within a given species appears to be systematically related to the degree of the behavioral sex difference. The largest volumetric differences have been reported in species in which the male sings and the female sings little, if at all, and the smallest sex differences in volume have been reported in species in which males and females both sing in nearly equal amounts. We compared the volume of three song control nuclei in male and female European starlings (Sturnus vulgaris), a species in which females are known to sing, though at a much lower rate than males. We investigated the volume of hyperstriatum ventrale, pars caudale, nucleus robustus archistriatalis, and area X of the lobus parolfactorius as defined with the use of a Nissl stain. In addition, we measured the volume of area X as defined by the density of muscarinic cholinergic receptors visualized by in vitro receptor autoradiographic methods. The volumes of all three of the song nuclei, as defined by Nissl staining, are significantly larger in males than in females. For area X, Nissl staining and receptor autoradiography indicate the same significant volumetric sex difference. The three nuclei are approximately one and one half to two times larger in males than in females, a degree of dimorphism that is intermediate to those reported for other species. Previous investigations of sex differences in the avian vocal control system have used only Nissl stains to define nuclear volumes. We demonstrate in this paper that receptor autoradiography can be used to assess dimorphisms in nuclear volume. Broad application of this approach to a number of neurotransmitter receptor systems will better characterize the dimorphisms in the song system, and therefore will provide greater insight into the neuroanatomical and neurochemical control of birdsong. © 1993 Wiley‐Liss, Inc.
The early development of thalamocortical and corticothalarnic projections
Authors: Miller Brad , Chou Larry , Finlay Barbara L.
Published: January 2005

The early development ofthalamocortical and corticothalarnic projections in hamsters was studied to compare the specificity and maturation of these pathways, and to identify potential sources of information for specification of cortical areas. The cells that constitute these projections are both generated prenatally in hamsters and they make reciprocal connections. Fluorescent dyes (Dil and DiA) were injected into the visual cortex or lateral geniculate nucleus in fixed brains of fetal and postnatal pups. Several issues in axonal development were examined, including timing of axon outgrowth and target invasion, projection specificity, the spatial relationship between the two pathways, and the connections of subplate cells. Thalarnic projections arrive in the visual cortex 2 days before birth and begin to invade the developing cortical plate by the next day. Few processes invade inappropriate cortical regions. By postnatal day 7 their laminar position is similar to mature animals. By contrast, visual cortical axons from subplate and layer 6 cells reach posterior thalamus at l day after birth in small numbers. By 3 days after birth many layer 5 cell projections reach the posterior thalamus. On postnatal day 7, there is a sudden increase in the number of layer 6 projections to the thalamus. Surprisingly, these layer 6 cells are precisely topographically mapped with colabeied thalarnic afferents on their first appearance. Subplate cells constitute'a very small component of the corticothalarnic projection at all ages. Double injections of Dil and DiA show that the corticofugal and thalamocortical pathways are physically separate during development. Corticofugal axons travel deep in the intermediate zone to the thalarnic axons and are separate through much of the internal capsule. Their tangential distribution is also distinct. The early appearance of the thalamocortical pathway is consistent with an organizational role in the specification of some features of cortical cytoarchitecture. The specific initial projection of thalamocortical axons strongly suggests the recognition of particular cortical regions. The physical Separation of these two pathways limits the possibility for exchange of information between these Systems except at their respeetive targets. © 1993 Wiley‐Liss, Inc.
Subcortical connections of inferior temporal areas TE and TEO in macaque monkeys
Authors: Webster Maree J. , Bachevalier Jocelyne , Ungerleider Leslie G.
Published: January 2005

To investigate the subcortical connections of inferior temporal cortex, we injected its anterior and posterior portions (Bonin and Bailey's cytoarchitectonic areas TE and TEO, respectively) in 6 rhesus monkeys with retrograde and anterograde tracers. The results indicate that both areas TE and TEO receive nonreciprocal inputs from several thalarnic nuclei, including paracentralis, ventralis anterior, centralis, and limitans, and that TE also receives input from reuniens. Additional nonreciprocal inputs to both areas arise from the hypothalamus, basal nucleus of Meynert, dorsal and median raphe, loeus coeruleus, and reticular formation. TE and TEO are reciprocally connected with the lateral, medial, and inferior nuclei of the pulvinar and with the ventral portion of the claustrum. The main subcortical nonreciprocal Output from TE and TEO is to the striatum and from TEO to the superior colliculus. TE also sends a vcry limited projection to nucleus medialis dorsalis magnocellularis of the thalamus. AK‐huugh the connections of areas TE and TEO are overlapping in most subcortical structures, they are partially segregated in the pulvinar, the reticular nucleus of the thalamus, and the striatum. Specifically, relative to those of TE, the projections of TEO are located more laterally in the medial, lateral, and inferior nuclei of the pulvinar, more ventrally in the reticular nucleus, and more caudally in both the ventral putamen and tail and head of the caudate nucleus. e 1993 Wile.v‐Liss. Inc.

This article is a US Government work and, as such, is in the public domain in the United State of America.
Topographical representation of shoulder motor nuclei in the cat spinal cord as revealed by retrograde fluorochrome tracers
Authors: Hörner Michael , Kümmel Heinrich
Published: January 2005

The present investigation demonstrates the morphological relationships among the main shoulder motor nuclei within the spinal cord of the cat. The intraspinal position of these nuclei has been revealed by retrograde labelling of spinal motor neurones via their peripheral nerves supplying anatomically identified shoulder muscles. Multiple pressure injection of up to four fluorescent tracers (Bisbenzimide, Fast Blue, Fluoro‐Gold, Rhodamine‐b‐isothiocyanate) in one experiment was used to show the longitudinal distribution and topographical relations of motor neurones projecting to muscles acting on the scapulo‐humerus joint. Tracer‐positive cells have been found from middle C5 to rostral Th2 in the cervical cord, forming coherent longitudinal cell clusters separated in medial and lateral projection fields in the ventral horn. The present data suggest that the anatomical organization of spinal shoulder motor neurones corresponds to the embryonic origin of their later target muscles. All medial motor nuclei project to muscles deriving from ventral embryonic origins, while those motor nuclei lying in lateral positions innervate muscles originating from dorsal muscle primordia. Therefore, the spinal topography of shoulder motor nuclei seems to be independent of both the position and the funciton of a given muscle in the adult animal. © 1993 Wiley‐Liss, Inc.
Relationship of descending inferior colliculus projections to olivocochlear neurons
Authors: Thompson Ann M. , Thompson Glenn C.
Published: January 2005

With the objective of defining the relationship of descending inferior colliculus projections to the olivocochlear system in the guinea pig, inferior colliculus neurons were anterogradely labeled with Phaseolus vulgaris‐leucoagglutinin and olivocochlear neurons were retrogradely labeled with horseradish peroxidase in the same brain sections. Inferior colliculus neurons were found to project to many nuclei and regions of the hindbrain where olivocochlear neurons reside. The most substantial of these descending projections was to the ipsilateral medioventral periolivary region. Fewer descending projections terminated in the ipsilateral ventral nucleus of the lateral lemniscus, superior paraolivary nucleus, and rostral periolivary region; and even fewer ipsilateral projections terminated in the area surrounding the lateral superior olive, caudal periolivary region, and the lateroventral periolivary region. Descending neurons of the inferior colliculus also project to the contralateral hindbrain first via the lateral lemniscus and then the trapezoid body, to terminate in the contralateral medioventral periolivary region, superior paraolivary nucleus, rostral periolivary region, and the ventral nucleus of the lateral lemniscus. In addition to the projections into these regions that contain olivocochlear neurons, there are varicosities of inferior colliculus neurons that appear to contact the olivocochlear neurons themselves, both ipsilaterally and contralaterally, especially, but not only, in the ipsilateral medioventral periolivary region. We therefore conclude that descending inferior colliculus neurons do provide input to olivocochlear neurons and that the input is not limited to olivocochlear neurons of the ipsilateral medioventral periolivary region. However, given the robust nature of the projection to the ipsilateral medioventral periolivary region and the paucity of contacts observed in that region, we also conclude that the olivocochlear neuron is not the major target of descending inferior colliculus projections. © 1993 Wiley‐Liss, Inc.
Cellular and subcellular distribution of HNK‐1 immunoreactivity in the neural tube of Xenopus
Authors: Nordlander Ruth H.
Published: January 2005

The HNK‐1 antigen, a carbohydrate moiety bound to many cell adhesion and recognition molecules, is implicated in cell‐cell and cell‐substrate interactions during neural development. HNK‐1 immunoreactivity (HNK1‐IR) appears on neurons of the Xenopus neural tube very early in their development (Nordlander, Devel. Brain Res., 50:147‐153, 1989). The distribution and onset of expression of the HNK‐1 epitope on and within individual neurons is examined in this study. HNK‐1 labels developing neurons and their processes, and focal areas of other structures which are directly contacted by neurons, such as neuroepithelial cell surfaces, basal lamina, and culture surfaces. HNK1‐IR first appears in the Golgi apparatus and subsequently on the cell surface and in streams of punctate material directed toward the site of axon initiation and into the developing axon and its growth cone. The entire neuron is coated with a thin (20‐30 nm) surface layer of HNK1‐IR. In addition, the surface is dotted with small (100‐250 nm) boluses of HNK1‐IR material. Such boluses also occur within cytoplasmic vesicles, and extracellularly on basal lamina and culture substrata in proximity to neurons or their processes. The subcellar distribution of HNK1‐IR in this tissue is compatible with a role for the HNK‐1 epitope in axonal outgrowth and guidance. © 1993 Wiley‐Liss, Inc.
Merkel‐like basal cells in Necturus taste buds contain serotonin
Authors: Delay R. J. , Taylor R. , Roper S. D.
Published: January 2005

Several types of cells have been identified in vertebrate taste buds, including dark cells, light cells, intermediate cells, type III cells, and basal cells. The physiological roles of these cell types are not well understood, especially those of basal cells. In this paper we show that there are two types of basal cells in taste buds from Necturus maculosus. One type of basal cell is an undifferentiated cell, presumably a stem cell. By combining light microscopic immunocytochemistry with electron microscopy, we show that the other type of basal cell is positive for serotonin‐like immunoreactivity and that these cells have ultrastructural features similar to those found in cutaneous Merkel cells. Based on these findings, and the fact that the Merkel‐like taste cells have been shown to make synaptic contacts with adjacent taste cells and with innervating nerve fibers, we conclude that these Merkel‐like basal taste cells are serotonergic interneurons. © 1993 Wiley‐Liss, Inc.
Immunocytochemical localization of the amino acid neurotransmitters in the chicken retina
Authors: Kalloniatis Michael , Fletcher Erica L.
Published: January 2005

Postembedding immunocytochemistry was used to determine the cellular localization of the amino acid neurotransmitters glutamate, aspartate, gamma‐aminobutyric acid (GABA), and glycine in the avian retina. The through retinal pathway was glutamatergic, with all photoreceptors, bipolar cells, and ganglion cells being immunoreactive for glutamate. Bipolar cells displayed the highest level of glutamate immunoreactivity, with the cell bodies terminating just below the middle of the inner nuclear layer. All lateral elements, horizontal cells, amacrine cells, and interplexiform cells were immunoreactive for glycine or GABA. The GABAergic neurons consisted of two classes of horizontal cells and amacrine cells located in the lower part of the inner nuclear layer. GABA was also localized in displaced amacrine cells in the ganglion cell layer, and a population of ganglion cells that co‐localize glutamate and GABA. Both the horizontal cells and GABAergic amacrine cells had high levels of glutamate immunoreactivity, which probably reflects a metabolic pool. At least two types of horizontal cells in the avian retina could be discriminated on the basis of the presence of aspartate immunoreactivity in the H2 horizontal cells. Glycine was contained in a subclass of amacrine cells, with their cell bodies located between the bipolar cells and GABAergic amacrine cells, two subclasses of bipolar cells, displaced amacrine cells in the ganglion cell layer, and ganglion cells that colocalize glutamate and glycine. Glycinergic amacrine cells had low levels of glutamate. We have also identified a new class of glycinergic interplexiform cell, with its stellate cell body located in the middle of the inner nuclear layer among the cell bodies of bipolar cells. Neurochemical signatures obtained by analyzing data from serial sections allowed the classification of subclasses of horizontal cells, bipolar cells, amacrine cells, and ganglion cells. © 1993 Wiley‐Liss, Inc.