bluuebunny/crossref_metadata_2025 huggingface dataset:
Long descending projections of the hypothalamus in the pigeon, Columba livia
Authors: Berk Mitchell L. , Finkelstein Judith A.
Published: May 2005

An autoradiographic analysis was performed on the descending projections of nucleus periventricularis magnocellularis (PVM) of the hypothala‐mus in the pigeon. A PVM‐medullospinal pathway was observed coursing posteriorly through the lateral hypotlialamus, ventrolateral midbrain teg‐mentum, and into the spinal lemniscus (ls) in the ventrolateral pons and medulla. In the pons, some fibers course dorsomedially from ls and terminate at the lateral border of 1 he locus coeruleus. At medullary levels, fibers from ls sweep dorsomedially in the plexus of Horsley and project to certain regions of the nucleus of the solitary tract (NTS) and the dorsal motor nucleus of the vagus (NX). Specifically, PVM fibers project heavily into NTS subnuclei medialis superficialis, medialis ventralis, and lateralis (sulcalis) dorsalis as well as into the ventral parvocellular subnucleus of NX. Fibers in ls were traced caudally into the lateral funiculus as far as upper cervical levels of the spinal cord. Although autoradiographs of lower cervical or thoracic spinal cord sections were not available, PVM fibers do descend to thoracic spinal cord levels, as evidenced by the retrograde transport of horseradish peroxidase.

In addition to the medullospinal pathway, the autoradiographs demonstrated PVM projections to septum, diencephalon, and midbrain. Labeled PVM fibers are found in the lateral septal nucleus, nucleus of the anterior pallial commisure, dorsomedial thalamic nucleus, dorsolateral anterior tha‐lamic nucleus (pars ventralis), median eminence, medial and lateral hypo‐thalamus, medial mammillary area, and nucleus intercollicularis and central gray of the midbrain.

The projection of fibers to medullospinal regions and median eminence suggests that PVM is homologous to the mammalian par a ventricular nucleus. These projections to specific subnuclei of NTS and NX denote hypo‐thalamic control over certain autonomic functions.
Studies of the principal sensory and spinal trigeminal nuclei of the rat: Projections to the superior colliculus, inferior olive, and cerebellum
Authors: Huerta Michael F. , Frankfurter Anthony , Harting John K.
Published: May 2005

We have analyzed the connections between the sensory trigeminal nuclei and two major sensorimotor areas (i.e., the superior colliculus and crura I and II of the cerebellar cortex) in which tactile input from peri‐oral and other facial regions is a prominent feature. Following injections of horseradish peroxidase into the superior colliculus, retrogradely labeled cells occupy the ventral one chird of the contralateral principal sensory and spinal trigeminal nucleus; trigeminocollicular neurons are especially numerous within, the sub‐nucleus interpolaris (Svi). Injections of either 3H‐proline or horseradish per‐oxidase (HRP) into the Svi reveal that trigeminocollicular axons reach the rostral two‐thirds to three‐quarters of the contralateral superior colliculus, where they distribute in a nonuniform, patchy manner within layers IV‐VI.

In addition to demonstrating the trigeminocollicular projection, antero‐grade and retrograde transport studies of the Svi also reveal a trigeminooli‐vary projection which terminates primarily within the contralateral rostral dorsal accessory (DAO) and adjacent principal (PO) olives; some of the Svi neurons innervate both the superior colliculus and the DAO‐PO via axon collaterals.

Data from a final set of retrograde tracing experiments show that the trigeminorecipient zone of the DAO‐PO contains neurons which project to crura I and/or II of the cerebellar cortex. Of the various submodalities conveyed by the trigeminal system, it is likely that the trigeminal connections we have demonstrated are carrying tactile information. This is indicated by the fact that responses to tactile stimulation of the face have been reported for cells in (1) the deeper collicular layers, (2) the trigeminorecipient zone of the DAO‐PO, and (3) cerebellar targets of this zone, crura I and II.

All data are discussed in the context of the anatomical and physiological literature.
Contralateral termination of primary afferent axons in the sacral and caudal segments of the cat, as studied by anterograde transport of horseradish peroxidase
Authors: Matsushita Matsuo , Tanami Toshio
Published: May 2005

Contralateral termination of primary afferent axons in the sacral and caudal segments was studied with the anterograde horseradish peroxidase technique in the cat. The distribution of terminals and branching pattern of terminal fibers were examined on sections incubated in a diaminobenzidine‐cobalt chloride medium.

The crossed primary afferent axons passing in the dorsal commissure projected to (1) the dorsal gray commissure, (2) small, dorsomedial and ven‐trolateral parts of laminae III and IV, (3) lamina I, and (4) the Xth area (region dorsal to and around the central canal). In the dorsal gray commissure primary afferent axons formed a dense plexus after taking a tortuous course in mediolateral and rostrocaudal directions. Single axons terminated on both sides, but rarely did they extend outside of this region. The axons terminating in the dorsomedial and ventrolateral parts of laminae III and IV passed through the dorsal gray commissure without giving off collaterals. After reaching laminae III and IV they ascended and/or descended within these laminae and terminated at more rostral or caudal levels.

The crossed primary afferent axons passing in the ventral commissure terminated in lamina VIII of the Contralateral ventral horn. Some axons terminated in a region ventral to the central canal, and on both sides of lamina VIII.
Retinotopic patterns of connections of area 17 with visual areas V‐II and MT in macaque monkeys
Authors: Weller R. E. , Kaas J. H.
Published: May 2005

Patterns of connections of Area 17 with extrastriate visual areas V‐II and MT were studied in macaque monkeys by using 3H‐proline and HRP as anatomical tracers. The results support previous conclusions that V‐II is a split representation of the visual hemifield with most of the outer border formed by the zero horizontal meridian, and that MT is a topological representation of the visual hemifield. V‐II was estimated to be about 10–12 mm wide, 110 mm long along its shared border with V‐I, and 920 mm2in surface area, thereby almost equaling Area 17 in size. MT was judged to be 7 mm wide and 12 mm long, with a surface area of 68 mm2, or roughly 7% of the area of Area 17. In some cases, there was evidence for projections from Area 17 to a third area (or areas) of cortex of about 2 mm wide and of uncertain length on the outer boundary of V‐II. Terminationsin V‐II and MT werecon‐centrated in layer IV and extended into inner layer III. Cells projecting back to Area 17 were largely in layers III and V in V‐II and in layers III and VI in MT.
Enkephalin systems in diencephalon and brainstem of the rat
Authors: Khachaturian Henry , Lewis Michael E. , Watson Stanley J.
Published: May 2005

The immunocytochemical distribution of [Leu]enkephalin and an adrenal enkephalin precursor fragment (BAM‐22P) immunoreactivity was investigated in the diencephalon and brainstem of rats pretreated with relatively high doses of colchicine (300–400 μg/10 μl intracerebroventricularly). The higher ranges of colchicine pretreatment allowed the visualization of extensive enkephalin‐containing systems in these brain regions, some of which are reported for the first time. Immunoreactive perikarya were found in many hypothalamic and thalamic nuclei, interpeduncular nucleus, substan‐tia nigra, the colliculi, periaqueductal gray, parabrachial nuclei, trigeminal motor and spinal nuclei, nucleus raphe magnus and other raphe nuclei, nucleus reticularis paragigantocellularis, vestibular nuclei, several nor‐adrenergic cell groups, nucleus tractus solitarius, as well as in the spinal cord dorsal horn. In addition to the above regions, immunoreactive fibers were also noted in the habenular nuclei, trigeminal sensory nuclei, locus coeruleus, motor facial nucleus, cochlear nuclei, dorsal motor nucleus of the vagus, and hypoglossal nucleus. When adjacent sections to those stained for [Leu]enkephalin were processed for BAM‐22P immunoreactivity, it was found that these two immunoreactivities were distributed identically at almost all anatomical locations. B AM‐22P immunoreactivity was generally less pronounced and was preferentially localized to neuronal perikarya. The results of the present as well as the preceding studies (Khachaturian et ai., '83) strongly suggest substantial structural similarity between the adrenal proenkephalin precursor and that which occurs in the brain. Also discussed are some differences and parallels between the distribution of [Leu]enkeph‐alin and dynorphin immunoreactivities.
Tectal connections in Python reticulatus
Authors: Welker E. , Hoogland P. V. , Lohman A. H. M.
Published: May 2005

The origins of the axons terminating in the mesencephalic tectum in Python reticulatus were examined by unilateral tectal injections of horseradish peroxidase. Kutrogradely labeled cells were observed bilaterally throughout the spinal cord in all subdivisions of the trigeminal system, with the exception of nucleus principalis, which showed labeled cells only on the ipsilateral side. Labeling of the reticular formation occurred bilaterally in nucleus reticular is interiormagnocellularis, nucleus reticularis lateralis, nucleus reticularis medius and the mesencephalic reticular formation. The tectum also receives bilateral projections from the dorsal tegmentaJ field, the nucleus of the lateral lemniscus and nucleus isthmi, and ipsilateral projections from nucleus profundus mesencephali. A few labeled cells were found ipsilaterally in the locus coeruleus and in nuclei vestibulares ventrolateralis and centromedialis. In the diencephalon labeled cells were observed ipsilaterally in nucleus ventrolateralis thalami, nucleus ventromedialis thalami, nucleus suprapeduncularis, and in the dorsal and ventral lateral geniculate nuclei. Bilateral labeling was observed in nucleus periventricularis hypo‐thalami. Furthermore, labeling was ipsilaterally present in the ventral telen‐cephalic areas. The tectum in Python reticulatus receives a wide variety of afferent connections which confirm the role of the tectum as an integration center of visual and exteroceptive information.
Differentiation of cerebellar mossy fiber synapses in the rat: A quantitative electron microscope study
Authors: Hámori József , Somogyi József
Published: May 2005

The differentiation of cerebellar glomeruli was investigated by quantitative electron microscopy, starting with the period at which mossy fibers made their first appearance. Two developmental stages could be delineated in the maturation of the mossy fiber‐granule cell synapse.

A primary growth stage (postnatal days 6–15) characterized by the rapid enlargement of mossy rosettes and the intense proliferation of post‐synaplie dendrites. The synaptic perimeter of mossy terminals, i.e. percentage of membrane surface occupied by synaptic junctions, exhibited a simultaneous, rapid increase in that stage, reaching a peak at postnatal day 15.

Establishment and stabilization of differentiated glomeruli (15th‐45th day). Because the size of mossy rosettes did not change in this period, the increase of glomerular size was due exclusively to the continuing multi plication of postsynaptic dendrites. The characteristic feature of this stage was the massive elimination of synaptic junctions. The synaptic perimeter of 14.4% at day 15 decreased to 5.7% by day 30. Since the size of individual synaptic junctions and the size of mossy terminals did not decrease while the number of postsynaptic dendrites even increased during the same period, the elimination of synaptic junctions represents a net loss of the synaptic perimeter of mossy terminals.

The quantitative analysis suggests that the stabilization of the synaptic perimeter of mossy rosettes at about 6% is due to the elimination during the second developmental stage of immature synapticjunctions, produced in excess during the first growth phase. Also, the observation that synapse elimination and the subsequent stabilization of synaptic perimeter occurs in spite of a steady increase of available postsynaptic dendrites is indicative that the standard 6% value of synaptic perimeter is defined by the presynap‐tic mossy terminal itself.

On the basis of these observations, it is also proposed that elimination of synaptic junctions may well occur without the concomitant disappearance of presynaptic and/or postsynaptic neuronal processes.
Altered metabolic activity in the cerebral cortex of rats exposed to ketamine
Authors: Hammer Ronald P. , Herkenham Miles
Published: May 2005

Uptake of the metabolic marker, [3H]2‐deoxy‐D‐glucose(2DG) was compared in rats given subanesthetic (50–100 mg/kg, i.p.) or anesthetic (200 mg/kg, i.v.) doses of ketamine with that in normal, unanesthetized rats. All doses of ketamine caused a relative increase of 2DG labeling in limbic regions, including the hippocampus, dentate gyrus, and cingulate, piriform, and entorhinal cortices. Striking 2DG‐dense zones were confined to the molecular layer in the hippocampus, dentate gyrus, and entorhinal cortex. Sub‐anesthetic doses of ketamine produced a relative reduction of 2DG uptake in layers 1‐1V of granular somalosensory cortex while sparing up take in layer Va; therefore, the peak of dense uptake shifted from layer IV to layer Va. In regions of the somatosensory cortex which display a dysgranular layer IV, vertical columns of relatively dense 2DG uptake extended through all cortical layers. Columns of 2I) G label also occurred outside of S1, in visual and auditory areas. In the primary visual cortex, this dose of ketamine decreased 2DG uptake relative to secondary visual cortex.

Alteration of 2DG uptake in various cortical regions might be the consequence of a ketamine‐induced activation of specific neuronal pathways with special neurochemical features. During subanesthetic ketamine administration, peak 2DG uptake shifts from cortical layer IV, which receives specific thalamocortical input to layer Va which receives projections via intrinsic cortical circuits. The ketamine‐induced shift in the laminar focus of sensory cortical metabolism may reflect a functional disconnection from peripheral sensory input and/or enhanced internal (corticocortical) processing. These changes are more apparent during ketamine administration at doses too low to induce anesthesia and may, therefore, reflect the metabolic events that occur when ketamine and its analogues are taken as drugs of abuse.
Some afferent and efferent connections of the vestibular nuclear complex in the red‐eared turtle Pseudemys scripta elegans
Authors: Pangma G. C. , Donkelaar H. J. Ten
Published: May 2005

In the present study some afferent, commissural, and efferent connections of the vestibular nuclear complex in the turtle Pseudemys scripta elegans were demonstrated with the HRP tracing technique.

Afferent projections to the vestibular nuclei were found to arise in the nucleus of the basal optic root, the interstitial nucleus of the fasciculus longi‐tudina Jis medialis, the medial and lateral cerebellar nuclei, the perihypoglos‐sal nuclear complex, and the teticular formation. Distinct commissural projections appeared to arise in the dorsolateral, ventromedial, and descending vestibular nuclei. The commissural projection arising in the ventrolateral vestibular nucleus appeared to be only sparsely developed. Both ascending and descending efferent projections were demonstrated to arise from the vestibularnuclear complex. The ascending vestibulo‐oculomotorprojection was found to be organized in an ipsilateral pathway arising in the dorsolateral vestibular nucleus and in a contralateral pathway, arising mainly in the medial vestibular nucleus. These projections appeared to be directed to the interstitial nucleus of the fasciculus longitudinalis medialis, the oculomotor, trochlear, and abducens nuclei. Also the perihypoglossal nuclear complex appeared to be an important target of vestibular efferents. The origin and course in the brainstem of the descending vestibular projections, i.e., the lateral and medial vestibulospinal tracts, as demonstrated in previous anatomical and experimental studies in reptiles, were confirmed. However, in addition a direct projection of the vestibulospinal tracts to presumably neck motoneurons was found.

The organization of the vestibular connections observed in the turtle Pseudemys scripta elegans appeared to be basically comparable to the organization of the vestibular connections in birds and mammals.
The neuronal architecture of the dorsal division of the medial geniculate body of the cat. A study with the rapid Golgi method
Authors: Winer Jeffery A. , Morest D. Kent
Published: May 2005

The neurons in the nuclei of the dorsal division of the medial geniculate body were studied with the rapid Golgi method in kittens and young adult cats. The dorsal nuclei contain two principal cell types: a large stellate neuron with radiate dendrites and a bushy neuron with tufted dendrites, each with extensive dendritic fields. Two sizes of cells with locally arborizing axons (local circuit neurons) were found. The small and commonly observed one is stellate in shape, has a limited dendritic domain, and an axon with multiple, often profuse collaterals ending in the vicinity of the cell. A second, and much less common variety (large local circuit neuron) is somewhat larger and has fewer axon collaterals. Subtle, but distinct variations in these cell types distinguish the deep and superficial dorsal nuclei and also the anterior tier of naclei (deep dorsal and superficial). These functional differences may correlate with the relative morphological homogeneity of the ventral nucleus compared to the extremely heterogeneous medial division. The dorsal division should be regarded as part of the pulvinar‐lateralis posterior complex both structurally and functionally. In the suprageniculate nucleus, the principal neurons are stellate cells with large perikarya and numerous and extensive dendrites covered with appendages. The large axon is devoid of collaterals. A small local circuit cell with several axon collaterals, and sparse, restricted dendrites has also been observed. In the adjacent posterior limitans nucleus, the principal neuron has a medium‐sized, piriform or somewhat elongated Perikaryon, a few very long radiating dendrites, which may span the depth of the nucleus, and a long, poorly branched axon. Small neurons are also seen here.

A comparison of the structure, connections, and function of the medial geniculate body suggests that the dorsal division is predominantly, but probably not exclusively auditory, while the ventral nucleus is entirely auditory and relatively homogeneous, and the medial division, polymodal and heterogeneous with respect to input.
Selective lectin binding of the developing mouse retina
Authors: Blanks Janet C. , Johnson Lincoln V.
Published: May 2005

A battery of eight lectins with different carbohydrate specificities was used to study changes in glycoconjugate expression during cell differentiation in the mouse retina. The lectins tested included concanavalin A (Con A), wheat germ agglutinin (WGA), soybean agglutinin (SB A), peanut agglutinin (PNA), Ulex europaeus agglutinin (UEA), Ricinus communis agglutinin I (RCA), Dolichos biflorus agglutinin (DBA), and Limulus polyphemus agglutinin (LPA). Unfixed frozen sections of adult and early postnatal mouse retina were treated with fluorescein isothiocyanate‐conjugated lectins and examined by fluorescence microscopy.

The results showed selective lectin binding in both cellular and synaptic retinal layers of the adult mouse and throughout postnatal development. In general, an increase in intensity of fluorescent lectin staining during retinal development was observed for Con A, WGA, DBA, LPA, RCA, and PNA. This suggests an increase in the expression or accessibility of carbohydrate moieties during development. SBA and UEA showed little to no binding to adult or neonatal retina. Retinal vasculature was intensely stained by RCA, both during development and in the adult. All lectins binding to adult or neonatal retinal layers showed some degree of reactivity with the inner segment region of photoreceptor cells. However, only Con A, PNA and WGA bound to photoreceptor outer segments, suggesting significant differences in the glycosylated components of inner and outer segment membranes. PNA bound specifically to a subpopulation of photoreceptor cells and to discrete regions within the outer synaptic layer. The pattern of PNA binding suggests that this lectin binds preferentially to cone photoreceptor inner and outer segments and cone synaptic pedicles rather than to rod photoreceptor cells. This marked specificity of PNA binding suggests that it may provide a basis for the physical separation of cone and rod photoreceptor cells.
Kindled seizure‐induced reduction of muscarinic cholinergic receptors in rat hippocampal formation: Evidence for localization to dentate granule cells
Authors: Savage Daniel D. , Dasheiff Richard M. , McNamara James O.
Published: May 2005

The binding of [3H] quinuclidinyl benzilate ([3H] QNB) to muscarinic cholinergic receptors in dentate gyrus of rat hippocampal formation was analyzed by membrane binding assay and in vitro autoradiography. The destruction of dentate granule cells, either by neonatal irradiation or colchicine injection, resulted in nearly complete elimination of [3H] QNB binding sites in the molecular and granule cell layers. By contrast, neither perforant path transection nor destruction of the septal‐hippocampal cholinergic afferents caused a decline of [3H] QNB binding sites. Amygdala kindled seizures resulted in a 30% reduction of [3H] QNB binding sites which was distributed uniformly across the entire molecular and granule cell layers. Thus, most, if not all, of the muscarinic cholinergic receptors present in dentate gyrus appear to reside on the somata and dendritic trees of the dentate granule cells. We propose that this kindled seizure‐induced decline of muscarinic receptors represents an endogenous compensatory mechanism designed to stabilize granule cell excitability.
Accuracy of regeneration of vagal parasympathetic axons
Authors: Taylor Barbara , Finger Thomas E. , D'Arcy Genet , Roper Stephen D.
Published: May 2005

The degree of accuracy with which regenerating preganglionic parasympathetic fibers can restore their original connections was examined in the frog, Rana pipiens. The normal motor pool of the vagus nerve was determined by labeling the vagal cardiac branch fibers with horseradish peroxidase (HRP). Cardiac neurons form a relatively compact subgroup within the rostral half of the vagal motor column and represent less than 5% of the total vagal motor pool.

Five to 14 weeks after crushing the vagus nerve, HRP labeling revealed that a more extensive population of vagal motor neurons has reinnervated the cardiac branch. The regenerated cardiac motor neuron pool is about twice as numerous as normal but is still centered in the rostral half of the vagal motor column.

These experiments show that regeneration of the cardiac branch of the vagus nerve is neither a random process nor one which is completely accurate. Some degree of accuracy is maintained during regeneration following a crush lesion. Neurons nearer the original cardiac motor pool are more likely to reinnervate the cardiac branch than are vagal motor neurons located at some distance from the original cardiac pool.
Central neuronal projections and neuromuscular organization of the basal region of the shore crab leg
Authors: Bévengut M. , Simmers A. J. , Clarac F.
Published: May 2005

The musculature and associated skeleton, peripheral nervous system, and central projections of motor and sensory neurones of the two basal (thoracic and coxal) segments of the shore crab leg (fifth pereiopod, P5) were examined in vivo and with methylene blue or cobalt staining.

Each of the four main basal muscles, promotor/remotor, levator/depressor, controlling the thoracico‐coxal (T‐C) and coxo basal (C‐B) limb joints, respectively, comprises several more or less discrete fibre bundles (total 14), with little morphological segregation of different functional groups.

The innervation to the basal leg region is carried in two nerve roots arising from the thoracic ganglion. The anterior Th‐Cx root carries both sensory and motor axons, while the posterior Th‐Cx root is purely motor. Three previously undescribed sensory branches (two “epidermal” nerves and an “accessory” branch), in addition to that innervating the coxobasal chordotonal receptor, have been found in the distal part of the anterior Th‐Cx root. Two clusters of 10 to 15 multipolar somata (diam. 30–125 μm) are located proximally at the bifurcation of the accessory nerve and distally where the latter enters the basipodite.

The cell bodies (diameter 20–80 μm) of basal leg motoneurones (total ca. 30) lie in the dorsal cortex of the ganglion, with somata of functionally related motoneurones tending to form discrete structural groups. The morphology of individual motoneurones conforms to the general arthropod pattern. All are confined to the ipsilateral hemiganglion and their main neuropilar processes run parallel and in close apposition to each other with overlapping dendritic structures. Sensory projections arising from the CB chordotonal organ also ramify in the region of the neuropile invaded by motoneurones. The possible physiological significance of such structural associations within the CNS is discussed, as are the functional implications of basal limb anatomy in general.
A morphological analysis of vasoactive intestinal polypeptide (VIP)‐like immunoreactive neurons in the area dentata of the rat brain
Authors: Köhler Christer
Published: May 2005

The general distribution and morphology of vasoactive intestinal polypeptide‐like immunoreactive (VIP‐LI) neurons in the area dentata (AD) have been studied using immunohistochemical methods on thick (70–120 μm) sections from the rat brain. The long (≥ 72 hours) incubation of free‐floating sections in combination with a sensitive immunoperoxidase method resulted in extensive labeling of VIP‐positive cell bodies, along with their dendritic and axonal processes in the hippocampal formation, including the area dentata. The VIP‐positive cells are found in all parts of the area dentata, and plots of the distribution of individual cells showed that there is a preferential clustering of these neurons within, or in close proximity to, the granule cell layer, while the deep zones in the hilus are almost completely devoid of VIP‐LI immunoreactive neurons. Throughout the long axis of the AD the number and relative position of the VIP‐LI neurons remains rather constant. Analysis of the size and shape of the VIP‐positive neurons in the AD shows a remarkable morphological heterogeneity, with the soma ranging from small (long axis: ˜ 10 μm) ovoid or round, to large (long axis: ˜ 25 μm) stellate or multipolar; of these the small to medium sized cells predominate.

Comparisons between the morphology of neurons visualized with the VIP antibody and sections stained by the rapid Golgi method allow a rather conclusive classification of some of the VIP‐stained neurons, while the classification of a majority of the VIP nerons remains tentative, perhaps because of the selective visualization by the rapid Golgi method of only certain cell types in the AD. On the basis of this comparison, several displaced granule cells in the molecular layer, as well as granule cells, small ovoid cells, and pyramidal basket cells in the granule cell layer have been identified as VIP‐positive as determined by their somatic shape, dendritic branching pattern, and axonal projections. In addition, several VIP‐positive neurons have been identified with less certainty. These include the dentate basket cell of Cajal, certain small cells in the molecular layer, and fusiform cells in the polymorph layer. Taken together the present results demonstrate the usefulness of “Golgi‐like” immunoperoxidase staining for detailed classification of chemically defined neurons. Furthermore, these studies provide evidence for a morphological heterogeneity of VIP cells in the area dentata, and suggest that although some of the VIP cells may project out of the AD (the granule cells) a majority of the VIP neurons are interneurons that lack extrinsic projections.
Central projections of the brachial nerve in bullfrogs: Muscle and cutaneous afferents project to different regions of the spinal cord
Authors: Jhaveri Sonal , Frank Eric
Published: May 2005

The central projections of muscle and cutaneous sensory neurons in the bullfrog were labeled by filling their peripheral axons in the forelimb with horseradish peroxidase (HRP). Muscle afferent fibers were found to project exclusively to the ventral neuropil of the brachial spinal cord in the intermediate gray zone. Cutaneous afferent axons had their arbors limited to the dorsal neuropil. There is therefore a topography in the central representation of two classes of sensory modalities.
Radial organization of the hippocampal dentate gyrus: A Golgi, ultrastructural, and immunocytochemical analysis in the developing rhesus monkey
Authors: Eckenhoff Maryellen F. , Rakic Pasko
Published: May 2005

The cytoarchitectonic organization of the dentate gyrus was analyzed in the rhesus monkey at various embryonic (E) and postnatal (P) ages with the rapid Golgi method, transmission electron microscopy (EM), and immunocytochemical localization of glial fibrillary acidic protein (GFAP). From the earliest ages (stage I, E38‐E83), immature granule cells were arranged radially along elongated fibers that extend from the ventricular zone to the pial surface. The glial nature of these radial fibers was confirmed by the presence of GFAP antigen in their cytoplasm detected clearly by E70. EM analysis at this age showed that granule cells situated within the dentate plate, as well as many neurons still migrating from the ventricular zone, were closely apposed to fascicles of radial glial fibers. The radial organization of the dentate plate was even more evident during stage II (E83‐E165). Thus, in E97 and E125 specimens, radially oriented immunoreactive glial processes emerged from somas situated either in the ventricular or subgranular zones, penetrated between columns of neurons in the granular layer, branched upon entering the molecular layer, and finally terminated at the pial surface. Palisades of glial processes delineated ontogenetic radial units which consisted of stacks of granule cell bodies in different stages of maturation. In a given radial unit, more mature cells were located superficially (closer to the pial surface) and less mature cells were located at progressively deeper levels. This radial organization of the dentate gyrus was maintained during stage III (P0‐P60) and stage IV (2 months‐adult). Furthermore, the number of GFAP‐positive proliferating cells in the subgranular zone increased from 1 to 5 months. In the mature brain, the radial organization of the dentate gyrus was less apparent although many glial fibers still penetrated the granule cell layer. The present results indicate that the developing dentate gyrus in primates consists of a series of ontogenetic radial units that resemble those described in the fetal neocortex (Rakic, '72). They further suggest that the development and maintenance of this radial columnar organization may be imposed by the orientation of glial scaffolding during development.
Ascending somatosensory projections to the dorsal accessory olive: An anatomical study in cats
Authors: Molinari Helen H.
Published: May 2005

The cells in the gracile nucleus that project to the dorsal accessory olive were identified in cats with retrograde tracing techniques. In the same animals, the retrograde labeling patterns in the lateral cervical nucleus and the lumbosacral spinal cord were also examined. Small injections of wheat germ agglutinin complexed to horseradish peroxidase were made in the ventrolateral portion of the dorsal accessory olive without involving the medial accessory olive and without damaging the medial lemniscus. The tissue was processed with tetramethyl benzidine.

In each of the three relay nuclei, the neurons that project to the ventrolateral portion of the contralateral dorsal accessory olive are highly concentrated in small regions. In the gracile nucleus these cells are found almost exclusively in the transitional zone, just caudal to the obex and rostral to the clusters. In the lateral cervical nucleus they are concentrated in the dorsolateral tip. In the lumbosacral spinal cord in segments L5 and L6 the cells are found primarily in lamina V, while in segments L7 and S1 they are found along the ventromedial edge of the ventral horn. In the gracile and lateral cervical nuclei there is no segregation of neurons that project to the rostral and caudal portions of the dorsal accessory olive.

Comparison of these results with physiological data suggests that each of the three sources of ascending somatic input conveys some distinct aspect of sensory information from the hindlimb to the dorsal accessory olive.
Relation of target encounter and neuronal death to nerve growth factor responsiveness in the developing mouse trigeminal ganglion
Authors: Davies Alun , Lumsden Andrew
Published: May 2005

An aim of this study was to define precisely the period in the developmental history of primary sensory neurons during which nerve growth factor (NGF) exerts its growth‐promoting effect. The mouse trigeminal ganglion and its peripheral projection were studied at closely staged intervals throughout development using light and electron microscopy, and the influence of NGF and anti‐NGF antiserum on neurite outgrowth from ganglion explants was investigated at corresponding stages in culture. By embryonic day 9.5 (E9.5) peripheral fibers were first visible and increased in number until E13. Throughout this period in vitro neurites grew in the presence of anti‐NGF. Peripheral fibers initially contacted the epithelium of the mandibular process by E10.5 and the maxillary process by E11. This coincided with the stage in vitro during which the magnitude of neurite outgrowth was significantly increased by NGF. The development of this response was independent of target encounter since it occurred in neurons which had not contacted their targets prior to explantation. There was an approximate one‐to‐one relationship between the number of neurons in the ganglion and peripheral fibers throughout development. A peak of some 44,400 fibers and 42,600 neurons was reached by E13 and fell to 20,800 and 19,000, respectively, by birth. Neurite outgrowth was elicited by NGF throughout the period of neuronal death. It is argued that the time course of the influence of NGF is consistent with a role as a selective maintenance factor but not as an agent directing initial outgrowth.
Retinotectal terminals in the superior colliculus of the rabbit: A light and electron microscopic analysis
Authors: Schönitzer Klaus , Holländer Horstmar
Published: May 2005

The projection from the retina to the contralateral superior colliculus was studied light and electron microscopically by means of anterogradely transported horseradish peroxidase and tetramethylbenzidine histochemistry as well as light microscopically by experimental degeneration and [3H]‐leucine autoradiography.

Labeled boutons were found in stratum zonale (SZ) and in stratum griseum superficiale (SGS), but not in stratum opticum (SO). The number of boutons was maximal in a narrow zone in SZ about 25 to 100 μm below the surface. The labeled boutons contained numerous round vesicles and predominantly pale mitochondria. They usually formed asymmetrical synapses and contacted dendrites or boutons. Occasionally, labeled boutons were observed whose cytological features were different from those generally associated with retinotectal axons. In general, labled boutons in SZ contained fewer mitochondria than those from SGS.

Labeled myelinated axons were found throughout SGS, in the lowest part of SZ, and in SO. In upper and middle SGS they were small while in lower SGS and SO also large fibers were found.
Somatostatin in the caudal spinal cord: An immunohistochemical study of the spinal centers involved in the innervation of pelvic organs
Authors: Schrøder Henrik Daa
Published: May 2005

The distribution of somatostatin in the rat spinal cord was studied immunohistochemically with particular reference to the localization in the caudal centers that innervate the pelvic organs. For detailed studies of the laminar distribution of somatostatin the combination of immunohistochemistry and acetylcholinesterase enzyme histochemistry was employed.

Deafferentation experiments were carried out to shed light on the origin of the somatostatin‐containing axons. These experiments showed that the bulk of the spinal somatostatin has a spinal origin.

The structures showing somatostatin immunoreactivity formed a distinct and detailed pattern. The marginal layer and particularly the substantia gelatinosa contained a dense immunoreactivity in terminallike structures. Such structures were also found in the reticular nucleus, along the medial border of the dorsal horn, and in the nucleus of the dorsolateral funiculus. In all of these regions somatostatin‐positive cell bodies were also observed.

In the intermediate gray matter stained terminals were present around the central canal in a varying number. The most prominent stainability was found in the lumbosacral transition zone. Many terminals were also observed in the sacral parasympathetic intermediolateral nucleus. In contrast, very few appeared in the sympathetic nuclei. Immunoreactive somata were present in the surroundings of the central canal at all levels. Moreover, positive neurons were found in the intermediolateral nucleus of the sacral cord. By combined retrograde tracing and immunohistochemistry the existence of somatostatin‐containing parasympathetic visceromotoneurons was ascertained. Corresponding to this, somatostatin‐positive terminals were seen in the major pelvic ganglion.

The ventral horn generally contained few terminals, and the density was particularly low in the motoneuron neuropil. However, a dense somatostatin network was found in the sixth lumbar segment in relation to the neurons in Onuf's nucleus X complex, the nucleus that innervates the small pelvic muscles including the striated sphincters.

It is concluded that somatostatin, besides being involved in the processing of sensory input, serves an important motor task, that of taking part in the complex control of the pelvic organs and their associated striated muscles.
Axoaxonal synapse location and consequences for presynaptic inhibition in crustacean motor axon terminals
Authors: Atwood H. L. , Stevens J. K. , Marin L.
Published: May 2005

Serial sections were made of several excitatory nerve terminals in the stretcher muscle of the spider crab, Hyas areneus, to document locations of inhibitory axoaxonal synapses responsible for physiologically powerful presynaptic inhibition. The excitatory terminals are varicose, often with small side branches joined to the main terminal by thin bottlenecks. Axoaxonal synapses occur predominantly on the varicosities, both primary and secondary, with a smaller number on bottlenecks. The distribution is often clustered at specific locations of the excitatory terminal.

An electrical model was employed to ascertain the effectiveness of axoaxonal synapses at different locations on the terminal. The model plotted the potential distribution along the terminal with or without a synaptic conductance equivalent to one quantal unit of inhibitory transmitter action. It was assumed from recent work that terminal varicosities are not completely invaded by an action potential. The model predicts that large drops in potentials originating in the main axon occur in the terminals during inhibitory transmitter action, with the largest total drop produced by axoaxonal synapses on the terminal varicosities. The effectiveness of inhibitory action is critically dependent on the dimensions and internal resistance of the bottlenecks. Thus, the geometrical features of the excitatory terminal appear to play a key role in effectiveness of presynaptic inhibition.
Sizes, laminar and topographic origins of cortical projections to the major divisions of the red nucleus in the monkey
Authors: Humphrey D. R. , Gold R. , Reed D. J.
Published: May 2005

The retrograde transport of horseradish peroxidase was used to study the topographic and laminar origins of the cortical projections to the parvocellular and the magnocellular divisions of the red nucleus in Macaca mulatto and Macaca fascicularis. Approximately 90% of the corticorubral projection is directed to the parvocellular division of the nucleus. Corticoparvocellular division of the nucleus. Corticoparvocellular (CRp) neurons are pyramidally shaped, are smaller in size than corticospinal neurons, and are more numerous. They are found principally in sublamina Va of cytoarchitectonic areas 4 and 6, and in moderate quantities in sublamina Vb of posterior area 8 and area 5. In areas 4 and 6, the cells are grouped in clusters of three to 15 neurons each and are arranged in cellular bands of varying rostrocaudal thickness which course mediolaterally. With respect functionally define zones, CRp neurons are found through the supplementary motor area and the precentral motor cortex. In addition, they are found in parts of area 5, 6, and 24 that project to these cortical motor areas, and that are thought to have “premotor” or movement programmming functions.

The corticomagnocellular (CRm) projection arises principally from cells in sublamina Vb of the precentral arm and leg areas (area 4), and from adjacent parts of posterior area 6. CRm cells are pyramidally shaped and their size distribution is bimodal, with peaks that correspond, respectively, to the modal diameters of CRp and of corticospinal neurons.

These result and those of previous studies that CRm neurons are involved principally in the control of hand and foot movements, with little effect on proximal musculature. The massive CRp projection, however, is clearly part of a large cerebrocerebellar communications system, with motor and/or movement programming functions that have yet to be clearly defined.
Ontogeny and sexual dimorphism of the sonic motor nucleus in the oyster toadfish
Authors: Fine Michael L. , Economos Demetri , Radtke Richard , McClung J. Ross
Published: May 2005

Male oyster toadfish, Opsanus tau, produce a courtship boatwhistle call and have a larger sound‐producing organ than females, who do not boatwhistle. We investigated the possibility of sexual dimorphism in ontogeny of the sonic motor nucleus (SMN) of the toadfish. Brain weight increases for life though the increase decelerates with increasing fish weight. Neuron number, ranging from 760 to 2,888 in the SMN, increases rapidly to about 3 years, more slowly to about 8 years, and then levels off. There are no sexual differences in regressions of brain weight and SMN neuron number against fish size or age. Neuronal soma size in the SMN increases from 8 to 35 μm in average diameter and 67 to 916 μm2 in area over a period of at least 7 years. Males have larger neurons than females (P<.01). However, males can be separated by inspection into populations with large and small soma sizes. Neuron size is not different between females and males with small somas. Neurons in males with large somas are larger than neurons in females and neurons in males with, small somas. Such male dimorphism is reminiscent of other behavioral and morphological dimorphisms, which have led to characterization of males into territorial and satellite forms in certain mating systems.
Effects of unequal alternating monocular exposure on the sizes of cells in the cat's lateral geniculate nucleus
Authors: Tieman S. B. , Nickla D. L. , Gross K. , Hickey T. L. , Tumosa N.
Published: May 2005

In unequal alternating monocular exposure, each eye receives normal patterned input, but on alternate days and for unequal periods. This imbalance in stimulation produces a behavioral deficit for the less‐experienced eye and alters the ability of that eye to activate cortical cells. To determine whether unequal alternating exposure also affects the sizes of cells in the lateral geniculate nucleus (LGN), we measured the cross‐sectional areas of geniculate neurons in seven normally reared cats, 14 cats reared with equal alternating exposure, and 17 cats reared with unequal alternating exposure. We found that, in the LGNs of cats reared with unequal alternating monocular exposure, cells in layers that received their input from the less‐experienced eye were smaller than those in layers that received their input from the more‐experienced eye. This effect was restricted to the binocular segments of the nucleus, and the difference in cell size was a function of the imbalanced exposure, rather than the length of exposure per se. In control groups given balanced alternating exposure, cell size was not correlated with the length of daily exposure. In cats reared with unequal exposure, the change in cell size was greater in the nucleus ipsilateral to the less‐experienced eye. Further, the size of the effect was correlated with the size of the imbalance imposed during rearing: Cats reared with a moderate imbalance (8 hours/day vs. 4 hours/day) showed less change in cell size than cats reared with a large imbalance (8 hours/day vs. 1 hour/day). These results are consistent with those of behavorial and physiological studies and strongly suggest (1) that unequal alternating monocular exposure affects the sizes of cells in the LGN by altering the normal competitive balance between the retinogeniculocortical pathways from the left and right eyes, and (2) that the contralateral pathway has some inherent advantage in this competition. We also found a slight shrinkage of cells in the LGNs of cats reared with equal alternating monocular exposure. Since this effect was restricted to the binocular segments of the nucleus, and was not related to the length of exposure given, it was probably caused by the imbalanced binocular competition that occurred during each day's monocular exposure.
Central projections of the lateral line nerves in the shovelnose sturgeon
Authors: New John G. , Northcutt R. Glenn
Published: May 2005

Primary projections of the anterior (ALLN) and posterior (PLLN) lateral line nerves were traced in the shovelnose sturgeon by means of horseradish peroxidase (HRP) histochemistry and silver degeneration. The trunk of the ALLN divides into dorsal and ventral roots as it enters the medulla. Fibers of the dorsal root form ascending and descending branches that terminate within the ipsilateral dorsal octavolateralis nucleus and the dorsal granular component of the lateral eminentia granularis. Fibers of the ventral root of the ALLN, as well as fibers of the PLLN, enter the medulla ventral to the dorsal root of the ALLN where some of the fibers terminate among the dendrites of the magnocellular octaval nucleus. The bulk of the fibers form ascending and descending branches that terminate within the ipsilateral medial octavolateralis nucleus. A portion of the ascending fibers continue more rostrally land terminate in the ipsilateral eminentia granularis and bilaterally in the cerebellar corpus. Some fibers of the descending rami of both the ALLN and PLLN extend beyond the caudal limit of the medial octavolateralis nucleus to terminate in the caudal octavolateralis nucleus. The HRP cases also revealed retrogradely filled large neurons whose axons course peripherally in the lateral line nerve and are likely efferent to the lateral line organs.