bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neurons and synaptic patterns in the deep layers of the superior colliculus of the cat. A Golgi and electron microscopic study
Authors: Norita Masao 
Published: January 2005

AbstractGolgi and electron microscopic observations were made on the neurons in the deep layers (below the stratum opticum) of the cat superior colliculus. Large neurons, 35–60 μ in somal diameter, occur mainly in the lateral two‐thirds of the colliculus. They have numerous somatic and dendritic spines and receive a large number of axon terminals (bouton covering ratio: more than 70%). The medium‐sized neurons (20–30 μ), with a moderate number of dendritic spines, show a lower bouton covering ratio (25–30%). The ratio for small neurons (8–15 μ), with very few dendritic spines, is less than 10%. The medium‐sized and small neurons are distributed throughout the colliculus and show marked variability in the dendritic arrangement.Seven different types of axon terminals were distinguished: types I, II, V, and VII form asymmetrical and types III, IV, and VI symmetrical synapses. Type I terminals represent small boutons containing predominantly spherical vesicles, and are in contact mainly with small dendritic profiles. Type II terminals are medium‐sized and slender, contain a mixture of spherical and slightly oval vesicles, and make synaptic contacts with small to medium‐sized dendrites and somatic spines. This type of terminal is occasionally presynaptic to vesicle‐containing dendrites (type VIII). Type III terminals are small, contain flattened vesicles predominantly, and are presynaptic to a wide variety of neuronal elements in the deep layers of the superior colliculus. Type IV terminals are represented by medium to large‐sized boutons that contain pleomorphic vesicles and make synaptic contacts chiefly with the large neurons. Type V and VI terminals exhibit a quite dense axoplasmic matrix and mainly contact the large neurons. Type VII terminals are often in the form of boutons en passant and contain numerous large granular vesicles. Pleomorphic vesicle‐containing dendrites (type VIII terminals) are also observed to participate in the axodendrodendritic serial synapses.
Retinal ganglion cells projecting to the rabbit accessory optic system
Authors: Oyster Clyde W. , Simpson John I. , Takahashi Ellen S. , Soodak Robert E. 
Published: January 2005

AbstractRecent evidence from extracellular recording studies indicates that the medial terminal nucleus (MTN) of the rabbit accessory optic system receives inputs from a particular functional class of retinal ganglion cells—specifically, the on‐type direction‐selective cells. These ganglion cells have been selectively labeled by the retrograde transport of horseradish peroxidase (HRP) injected into the MTN. The number of labeled cells, their distribution over the retina, and their soma areas were determined. In one animal in which the HRP injection completely filled the nucleus, two thousand ganglion cells were labeled. This number agrees with previous estimates of the number of retinal axons terminating in the MTN. Unlike results in avians, none of the ganglion cells was displaced—i.e., they were not Dogiel cells. The density of labeled cells was highest in the visual streak and, overall, the distribution of labeled cells corresponded to the physiologically determined distribution of on‐type direction‐selective cells. Cells labeled by the HRP injection were among the 20% largest cells in the retina. This result, in conjunction with conclusions from other studies, leads to the prediction that on‐type direction‐selective cells can be characterized morphologically as cells with large cell bodies and a very extensive dendritic spread in which the dendrites ramify in the vitreal sublamina of the inner plexiform layer.
Early development of the brain and spinal cord in dysraphic mice: A transmission electron microscopic study
Authors: Wilson Doris B. , Finta Laurel A. 
Published: January 2005

AbstractThe hindbrain and spinal cord were studied by transmission electron microscopy with and without lanthanum nitrate treatment in nine‐day embryos of the loop‐tail (Lp) mutant mouse. Homozygous (Lp/Lp) individuals exhibit dysraphism from the hindbrain caudally throughout the embryo; in +/+ and Lp/+ individuals, the brains and spinal cords are normal. In contrast, the ventricular cells in the abnormal hindbrain and spinal cord showed increased amounts of intericellular space in an area intermediate between the luminal border and basal zone, and a flattening which occurs variably in their luminal surfaces. A most striking difference occurred in the frequency of gap junctional vesicles, circular structures bounded by a double membrane and containing ribosome‐like material. A quantitative analysis of the distribution of these organelles revealed that they are more numerous in the dysraphic hindbrain and lumbosacral spinal cord of the abnormal animals than in comparable regions of the normal; however, in the cervicothoracic spinal cord, the frequency of these vesicles is similar. In specimens treated with lanthanum, the tracer freely penetrated the luminal junctional complexes in both normal and abnormal animals, but was not present between the membranes of the gap junctional vesicles. The developmental significance of gap junctional vesicles frequently located in juxtaluminal regions of mitotic cells, but also found deeply in dividing cells, is not known; they may relate to cell‐to‐cell attachment and/or communication. In any event, furthe study of them may prove valuable in understanding normal and abnormal development of the neural tube.
Somatotopic and functional organization of the avian trigeminal ganglion: An HRP analysis in the hatchling chick
Authors: Noden Drew M. 
Published: January 2005

AbstractWhile the somatotopic organization of many central systems is well characterized, that of peripheral sensory neurons has not been adequately defined. This is especially true for the trigeminal ganglion. By applying HRP subcutaneously at each of 14 sites and also intramuscularly, it is possible to determine whether the location of sensory neurons within the ganglion reflects their peripheral projections.There is no discernible somatotopic organization of neurons in the ophthalmic lobe. However, the location of maxillary neurons in the maxillo‐mandibular lobe is organized with the most posterior cells projecting to sites closest to the ganglion and with neurons located more anteriorly projecting to progressively more distant sites. There is a less well defined organization in the superior‐inferior axis of the ganglion, and none along its proximal (root) to distal axis.Mandibular exteroceptive neurons are found primarily in the anterior region of the maxillo‐mandibular lobe, while mandibular proprioceptive cells are located in the proximo‐central part of this lobe. In most cases there is a considerable scattering of horseradish peroxidase (HRP)‐filled neurons. Projections to contralateral ganglia, the trigeminal motor nucleus, and the trigeminal motor nucleus, and the trigeminal mesencephalic nucleus were also examined.Cytologically, the hatchling trigeminal consists of two interspersed types of neurons: large, lightly staining and smaller, darkly staining cells. Previous experiments have proved that these two cell types do not correspond to each of the embryonic precursorsof trigeminal neurons, the neural crest and placodal cells. In this study HRP was found localized in both classes of neurons following injection at all sites, including jaw‐closing muscles. This indicates that the dual cytology is not correlated with either distribution of peripheral fibers or exteroceptive vs. proprioceptive functions. The possibilities that the two types of neurons may have different central projections and/or may be related to visceral vs. somatic afferent functions are discussed.
Disc morphogenesis in vertebrate photoreceptors
Authors: Steinberg Roy H. , Fisher Steven K. , Anderson Don H. 
Published: January 2005

AbstractElectron microscopic examination of the bases of adult rod and cone outer segments (rhesus monkey, ground squirrel, and grey squirrel) has led to a new model of disc morphogenesis. In this model the disc surfaces and disc rims develop by separate mechanisms and from separate regions of the membrane of the inner face of the cilium. This membrane is alternately specified into regions that will form either the disc surfaces or the disc rims. The disc surfaces develop by an evagination or outpouching of the ciliary membrane. The two surfaces of an evagination, scleral and vitreal, each form one of the surfaces of adjacent discs. The disc rim is initially specified as a region of ciliary membrane between adjacent disc‐surface evaginations. This region grows bilaterally around the circumferences of adjacent discs, zippering together the apposed surfaces to form the rim and completed disc. At the same time it seals the plasma‐membrane edges of the evaginations, which have become detached from the surfaces. Incisures form in rod discs by infolding of the rim and surfaces together, and they begin to form before the rim is completed around the disc perimeter. When a number of new discs are developing simultaneously the ciliary membrane at the base of an outer segment consists of a stack of rim forming and surface forming growth points. This model provides, in addition, for the continuous renewal of outer‐segment plasma membrane. It also establishes a developmental basis for the structural uniqueness of the disc rim. Finally, it indicates an evolutionary relationship between the discs of vertebrate visual cells and the membrane specializations of invertebrate visual cells.
Effects of indolic neurotoxins on enteric serotonergic neurons
Authors: Gershon Michael D. , Sherman Diane L. , Dreyfus Cheryl F. 
Published: January 2005

AbstractThe effects of the indolic neurotoxins 5,6‐ and 5,7‐dihydroxytryptamine (5,6‐DHT; 5,7‐DHT) on the enteric nervous system were examined. 5,6‐DHT, in moderate dosage, 40 mg/kg, decreased uptake of tritiated 5‐hydroxytryptamine (3H‐5‐HT) but not that of tritiated norepinephrine (3H‐NE). However, selectivity of the neurotoxins for enteric serotonergic rather than adrenergic axons was enhanced by pretreating animals with desmethylimipramine to inhibit the catecholamine uptake mechanism. When this was done, 5,7‐DHT was found to prevent the development of 5‐HT histofluorescence (following injection of L‐tryptophan) without affecting histofluorescence of NE. In contrast, 6‐hydroxydopamine virtually abolished NE histofluorescence and uptake of 3H‐NE without affecting development of 5‐HT histofluorescence or uptake of 3H‐5‐HT. Electron microscopy revealed that 5,7‐DHT induced dose‐dependent lesions of axonal varicosities in the enteric nervous system. Early lesions, 1–4 hours following injection, resembled cytolysosomes and consisted of membrane enclosed regions of opaque cytoplasm containing synaptic vesicles. Affected varicosities contained a mixed population of large dense cored (∼120nm) and small lucent vesicles (∼70nm) but none exhibited pre‐ or postsynaptic membrane specializations. After 24 hours terminals degenerated and were engulfed by surrounding supporting cells. It is concluded that peripheral serotonergic neurons resemble central serotonergic neurons in susceptibility to the toxic effects of indolic neurotoxins. These neurotoxins are useful anatomical markers of serotonergic terminal varicosities.
The nervus terminalis of the guinea pig: A new luteinizing hormone‐releasing hormone (LHRH) neuronal system
Authors: Schwanzel‐Fukuda M. , Silverman A. J. 
Published: January 2005

AbstractImmunoreactive LHRH‐like material has been found in the cells and fibers of the nervus terminalis in fetal and adult guinea pig brains. LHRH‐containing neurons and axons are seen in the nasal mucosa intermingled with fibers of the olfactory nerves, in ganglia along the ventromedial surfaces of the olfactory bulbs and forebrain, and in clusters surrounding perforating branches of the anterior cerebral artery in the regions of the septal nuclei and olfactory tubercle. Nonreactive neurons are found adjacent to the LHRH‐positive cells in all of the ganglia. LHRH‐immunoreactive cells and axons of the nervus terminalis are in intimate contact with cerebral blood vessels and the cerebrospinal fluid along the intracranial course of this nerve, deep to the meninges. The possible involvement of these structures in the neural mechanisms of sexual behavior and the neurohormonal regulation of reproductive function are discussed.
Time course and pattern of optic fiber regeneration following tectal lobe removal in the goldfish
Authors: Lo Raymond Y. S. , Levine Robert L. 
Published: January 2005

AbstractFollowing single tectal lobe removal in the adult goldfish, Carassius auratus, the pattern of regeneration of the optic fibers which had previously projected to that tectum was examined at 1, 2, 4, 6, 8, 10, and 12 weeks postoperative using 3H‐proline radioautography. We found that regenerating optic fibers grew across the midline through the transverse, minor, horizontal, and posterior commissures to innervate the remaining tectum. At early postoperative times innervation of the tectum was continuous, while later, the regenerating fibers segregated into discrete patches in the superficial layers of the tectum. In addition, regenerating fibers also grew into non‐optic centers/pathways such as the habenula, the fasciculus retroflexus, the forebrain, the torus semicircularis, the valvula and corpus cerebelli, the hypothalamus, and the medulla. While optic fibers were no longer apparent in the habenula and the fasciculus retroflexus after 2 weeks postoperative, all other structures were still occupied by the fibers at 12 weeks postoperative. Since most of the innervated pathways were either tectal efferent pathways, which should contain degenerating debris and proliferating glial cells after the tectal removal, or pathways closely associated with traumatized areas, we suggest that degenerating axonal debris and proliferating glia may play an important role in guiding regenerating fibers in this system.
The topographic organization of corticocollicular projections from physiologically identified loci in the AI, AII, and anterior auditory cortical fields of the cat
Authors: Andersen Richard A. , Snyder Russell L. , Merzenich Michael M. 
Published: January 2005

AbstractThe connections of the three auditory fields AI, AII, and the anterior auditory field (AAF) with the inferior colliculus (IC) were studied using anterograde tracing techniques. Microinjections of tracers were placed at physiologically identified loci after these fields had been functionally mapped using microelectrode recording techniques. This methodology ensured that the injections were well within the borders of each cortical field that was studied and enabled the elucidation of the topographies of the projections of AI and AAF onto the IC with respect to their cochleotopicorganizations.The projection of loci in AI to the caudal aspect of the IC was in the form of sheets of terminals in the dorsomedial division of the central nucleus bilaterally and the pericentral nucleus ipsilaterally. The topography of projection with respect to the cochleotopic organization of AI appeared to be in register with the described cochleotopic organization of the central nucleus and the pericentral nucleus.The sheets of labeled terminals in the dorsomedial division of the central nucleus that resulted from the projection of single loci in AI were of the proper orientation to be continuous with the morphological laminae described in the ventrolateral division of the central nucleus. These sheets of corticocollicular terminals also paralleled the dorsomedial aspect of the physiologically defined “isofrequency contours” of the central nucleus.Single injections placed in AAF produced autoradiographic label in the IC that was of the same basic pattern and systematic topography as the labeling recorded with AI injections; however, it was much weaker. The projection from AII was to the lateral (ipsilateral) and medial (bilateral) aspects of the pericentral nucleus.
Degeneration of hippocampal CA3 pyramidal cells induced by intraventricular kainic acid
Authors: Nadler J. Victor , Perry Bruce W. , Gentry Christine , Cotman Carl W. 
Published: January 2005

AbstractDegeneration of hippocampal CA3 pyramidal cells was investigated by light and electron microscopy after intraventricular injection of the potent convulsant, kainic acid. Electron microscopy revealed evidence of pyramidal cell degeneration within one hour. The earliest degenerative changes were confined to the cell body and proximal dendritic shafts. These included an increased incidence of lysosomal structures, deformation of the perikaryal and nuclear outlines, some increase in background electron density, and dilation of the cisternae of the endoplasmic reticulum accompanied by detachment of polyribosomes. Within the next few hours the pyramidal cells atrophied and became electron dense. Then these cells became electron lucent once more as ribosomes disappeared and their membranes and organelles broke up and disintegrated. Light microscopic changes correlated with these ultrastructural observations. The dendritic spines and the initial portion of the dendritic shaft became electron dense within four hours and degenerated rapidly, whereas the intermediate segment of the dendrites swelled moderately and became more electron lucent. No degenerative changes were evident in pyramidal cell axons and boutons until one day after kainic acid treatment.Less than one hour after kainic acid administration, astrocytes in the CA3 area swelled, initially in the vicinity of the cell body and mossy fiber layers. It is suggested that the paroxysmal discharges initiated in CA3 pyramidal cells by kainic acid served as the stimulus for this response. Phagocytosis commenced between one and three days after kainic acid administration, but remained incomplete at survival times of 6–8 weeks. Astrocytes, microglia, and probably oligodendroglia phagocytized the degenerating material.These results point to the pyramidal cell body and possibly also the dendritic spines as primary targets of kainic acid neurotoxicity. In conjunction with other data, they support the view that lesions made by intraventricular kainic acid can serve models of epileptic brain damage.
Single subthalamic nucleus neurons project to both the globus pallidus and substantia nigra in rat
Authors: Van Der Kooy Derek , Hattori T. 
Published: January 2005

AbstractThe organization of the major efferents of the rat subthalamic nucleus (STN) was investigated using a fluorescent retrograde double‐labeling technique. Red fluorcrescent Evans Blue was injected into the globus pallidus and blue fluorescent DAPI‐Primuline was injected into the substantia nigra. After retrograde axonal transport many double‐labeled neurons were seen throughout the STN. Occasional double‐labeled cells were seen in the lateral hypothalamus just medial to the STN and in a thin lateral strip of neurons extending laterally from the STN. Evidence for a mediolateral topography in both the STN‐pallidal and STN‐nigral pathways was obtained.The STN contains few, if any, local interneurons. Cell counts revealed that at least 94% of, and possibly all, STN neurons send axon collaterals to both the globus pallidus and substantia nigra.
Cells of origin of pathways descending to the spinal cord in some quadrupedal reptiles
Authors: Ten Donkelaar H. J. , Kusuma A. , De Boer‐Van Huizen R. 
Published: January 2005

AbstractThe cells of origin of pathways descending to the spinal cord have been determined in several quadrupedal reptiles, viz., the turtles Pseudemys scripta elegans and Testudo hermanni and the lizards Tupinambis nigropunctatus and Varanus exanthematicus, following a technique introduced by Kuypers and Maisky ('75). This technique was very effective in producing retrograde transport of HRP to a great many neurons in the hypothalamus and in the brain stem. Projections from the hypothalamus (the nucleus paraventricularis and the nucleus periventricularis hypothalami), the interstitial nucleus of the flm, the nucleus periventricularis hypothalami, the interstitial nucleus of the flm, the nucleus ruber, the nucleus of Edinger‐Westphal, the locus coeruleus, the subcoeruleus area, a conspicuous cell group comparable to Kuypers and Maisky's ('75, '77) lateral pontine area, the magnocellular reticular formation, the ventrolateral, ventromedial, and descending vestibular nuclei, the dorsal motor nucleus of the vagus, and the nucleus of the solitary tract, reach at least as far as far as the lumbar intumescence. Projections from two somatosensory nuclei, i.e., the nucleus descendens nervi trigemini and the nucleus funiculi dorsalis, as well as the laminar nucleus of the torus semicircularis, have been demonstrated to at least the ninth spinal segment. The two deep cerebellar nuclei, particularly the medial cerebellar nucleus, were found to project contralaterally to the spinal cord, in the lizard Varanus exanthematicus at least as far as the seventh segment; in the turtles studied so far, only projections as far caudal as the fourth spinal segment could be demonstrated.Data on the funicular trajectory of various descending pathways could also be obtained. It seems likely that in the reptiles studied, in addition to rubrospinal and reticulospinal pathways, projections from the hypothalamus, the nucleus of Edinger‐Westphal, the cell group comparable to the mammalian lateral pontine area, the locus coeruleus, and subcoeruleus area, and the nucleus of the solitary tract pass via the lateral funiculus.The pathways descending from the hypothalamus and brain stem to the spinal cord in the quadrupedal reptiles studied appear to show remarkable similarities to pathways in mammals as regards their cells of origin as well as their funicular trajectory. It seems likely that some of the projections demonstrated, viz., from the locus coeruleus, at least part of the cell group comparable to the lateral pontine area, as well as the cells in and around the dorsal motor nucleus of the vagus, are noradrenergic pathways.
Synapse‐to‐neuron ratios of the frontal and cerebellar cortex of 30‐day‐old and adult rats undernourished during early postnatal life
Authors: Bedi K. S. , Thomas Y. M. , Davies C. A. , Dobbing J. 
Published: January 2005

AbstractMale rats undernourished from birth to 30 days were nutritionally rehabilitated till 160 days of age. Quantitative stereological procedures at the light and electron microscopical levels were employed to estimate, among other things, the synapse‐to‐neuron ratios in the frontal cortex and granular layer of the cerebellum.In the frontal cortex, the 30‐day‐old undernourished rat had a mean ± SE of about 14,020 ± 1,540 synapses‐per‐neuron compared with 22,270 ± 3,250 for the controls. This was a deficit of 37% (p < 0.05). By 160 days of age the previously undernourished rats showed no statistically significant deficit in this ratio compared with controls (11,800 ± 690 and 13,360 ± 1,110 respectively, p > 0.1). This was due mainly to a fall in the synapse‐to‐neuron ratio with age. A much larger fall in the ratio occurred in the control than in the previously undernourished group.In the granular layer of the cerebellum the 30‐day‐old undernourished rats had 341 ± 17 synapses‐per‐neuron compared with 495 ± 25 for the controls. This was a deficit of 31% (p < 0.01). By 160 days of age the previously undernourished rats again showed no statistically significant deficit in this ratio compared with controls (627 ± 56 and 688 ± 38, respectively (p > 0.1).These results show that the previously undernourished rats are capable of at least some (if not complete) “catch‐up” with regard to the synapse‐to‐neuron ratio.