bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pallidal neurons in the rat
Authors: Millhouse O. E. 
Published: January 2005

AbstractThe globus pallidus has been examined in rat brains with Golgi methods. Most of the impregnated cells, the typical pallidal neurons, have relatively large cell bodies and thick, infrequently branched dendrites that are several hundred microns long. Most dendrites have one or two spines, some of them are moderately spiny, and a few are quite spiny. Although the dendrites generally end by simply becoming thinner and beaded, they occasionally form special dendritic ramifications, which are similar to the complicated dendritic endings reported in primate brains. The variability in the size of the somata and in the structure of the dendrites is not sufficiently consistent to permit dividing the neurons into distinctive subsets. However, two forms of dendritic trees can be defined. The neurons in the center of the pallidum have radiate dendritic trees, whereas the cells along the borders have compressed dendritic trees. Two axonal patterns have been seen: ones with and ones without collaterals. All of the axons are beaded.Two other cell types were found. The special border cells along the external medullary lamina in caudal pallidum have dendrites that extend for some distance into the caudate‐putamen. They otherwise resemble typical pallidal neurons. Small neurons that were infrequently impregnated may be interneurons, but their axons were not visualized. Their dendrites are short, varicose, and have a few spines. The spherical dendritic trees have a radius of 150–170 μm.Two sorts of axons that are probably afferent fibers were observed. The more common ones are nonbeaded, thin axons that have several boutons en passant and collaterals spaced along their length. In comparison, the other afferent fiber has numerous swellings, boutons en passant, and collaterals that are crowded together. They appear to invest the dendrites closely.
The ipsilateral retinocollicular projection in the rabbit: An autoradiographic study of postnatal development and effects of unilateral enucleation
Authors: Ostrach Louis H. , Crabtree John W. , Chow Kao Liang 
Published: January 2005

AbstractThe postnatal development of the ipsilateral retinocollicular projection in the rabbit and the effects of unilateral enucleation (performed on the day of birth, day 0) on that development were studied by using the anterograde axonal transport of tritiated proline injected introcularly. Material from 1‐, 6‐, and 10‐day‐old (i.e., at days 1, 6, and 10) and adult animals was examined. On day 1, autoradiographically labelled optic fibers from the ipsilateral eye formed distinct patches and bands within the superior colliculus (SC), which were restricted primarily to the lateral one‐half and anterior one‐third to one‐half of the nucleus. At subsequent ages no major changes in the location of this projection were found for normal animals or animals enucleated on day 0 (0‐DE animals). From dorsal‐view reconstructions, the pattern of the ipsilateral projection appeared wedge‐shaped with a broad base aligned with the lateral SC border for all normal and 0‐DE animals at the various postnatal ages examined. In normal animals the surface area of this projection increased with age and maintained a constant proportion of the increasing surface area of the total SC. In 0‐De animals the surface area of the projection initially increased more rapidly than in normal animals. Thus, by day 6 the area was already within the normal adult range but did not exceed this range at later postnatal ages. The only obvious difference in the appearance of the ipsilateral retinocollicular projection between normal and 0‐DE animals at corresponding ages was an enhanced radial distribution of the projection across laminae in the 0‐De animals. Taken together these findings suggest that, in the rabbit, once topographically appropriate connections are established between the SC and the ipsilateral retinal projection, they are maintained regardless of substantial postnatal growth of the SC and removal of the contralateral retinal projection to the SC.
Pre‐ and postsynaptic correlates of interocular competition and segregation in the frog
Authors: Constantine‐Paton Martha , Ferrari‐Eastman P. 
Published: January 2005

AbstractSegregated zones of termination between converging inputs that arise from different presynaptic populations are a common property of topographically organized zones within the vertebrate central nervous system. Increasing evidence suggests that such segregation is at least in part established on the basis of competitive interactions that depend upon the activity patterns within each afferent population. However, the cellular mechanisms of these interactions are poorly understood.We have used a preparation in which a stereotyped interdigitating pattern of retina‐specific termination stripes are produced in frog tecta innervated by two retinas as a result of embryonic implantation of a third eye primordia. In these animals it has been possible to examine the relationship between the number of retinal ganglion cells in each of the retinas innervating a striped tectum, the volumetric changes in the tectum as a result of this double innervation, and the pattern of eye‐specific segregation that is produced. Counts of retinal ganglion cells in the retinas of the three‐eyed frogs with one completely striped tectal lobe revealed no significant differences between cell numbers in the doubly innervating retinas and the normal retinas of the same animals. The average increase in retinal ganglion cell innervation to the striped tecta of these animals was 100%. However the tecta only increased in total volume by 26%. This later increase consisted of a 25% increase in the volume of the deep lying and predominately cellular tectal laminae and a 37% increase in the superficial retinotectal synaptic zone.In many of these same animals HRP and 3H‐proline were used to differentially label the set of stripes from each retina and measurements of the extent of each projection were performed. We found that the volume of tectal neuropil occupied by a striped projection is relatively unrelated to the number of ganglion cells making up that projection.Observations of the striping pattern after HRP processing to visualize stripes in whole unsectioned tecta indicate that the periodicities and rostrocaudal orientation of stripes are robust over a wide range of relative innervation densities. When one projection is much smaller than the other, stripes appear to break down into a series of “puffs” or islands of retina‐specific termination zones. Nevertheless, these puffs still have a rostrocaudal alignment and the spacing of fully formed stripes.These observations suggest that the formation of exclusive termination zones may be a threshold phenomenon: so after a certain innervation density is reached one input can take over a unit of target neuropil in an all‐or‐none manner. The data are discussed in the context of how activity and functional circuits in the tectum may control the segregation pattern.
Postembryonic differentiation of serotonin‐immunoreactive neurons in fleshfly optic lobes developing in situ or cultured in vivo without eye discs
Authors: Näussel Dick R. , Ohlsson Lennart , Sivasubramanian Pakkirisamy 
Published: January 2005

AbstractThe differentiation of serotonin‐immunoreactive (5‐HTi) neurons in the optic lobes of fleshflies was studied during in situ development and in in vivo cultures. All 5‐HTi neurons with cell bodies in the imaginal optic lobes differentiate during postembryonic (pupal) development. These are local anaxonal neurons. In addition there are two large 5‐HTi bilateral neurons that connect all optic lobe neuropil regions on both sides of the brain and have their cell bodies in the midbrain proper.Deafferentation of optic lobes cultured in vivo leads to drastic reduction in optic lobe volume and increased cell death. All the 5‐HTi neurons differentiate after deafferentation but their morphology changes. The neuropil receiving the photoreceptor inputs, the lamina, degenerates but a disorganized “pseudolamina” is formed by the processes of the two large 5‐HTi neurons. The layering of the optic lobe neuropils cannot be distinguished and 5‐HTi processes form novel projectional patterns. Hence, the 5‐HTi neurons do not require afferent inputs from the retina for their differentiation and survival, but the effect on other optic lobe interneurons is reflected in the morphological plasticity of the 5‐HTi neurons.
Spinal and trigeminal projections to the nucleus of the solitary tract: A possible substrate for somatovisceral and viscerovisceral reflex activation
Authors: Menétrey D. , Basbaum A. I. 
Published: January 2005

AbstractThis study used the retrograde transport of a protein‐gold complex to examine the distribution of spinal cord and trigeminal nucleus caudalis neurons that project to the nucleus of the solitary tract (NST) in the rat.In the spinal grey matter, retrogradely labeled cells were common in the marginal zone (lamina I), in the lateral spinal nucleus of the dorsolateral funiculus, in the reticular part of the neck of the dorsal horn (lamina V), around the central canal (lamina X), and in the region of the thoracic and sacral autonomic cell columns. The pattern of labeling closely resembled that seen for the cells at the origin of the spinomesencephalic tract and shared some features with that of the spinoreticular and spinothalamic tracts. Labeled cells in lamina IV of the dorsal horn were only observed when injections spread dorsally, into the dorsal column nuclei, and are thus not considered to be at the origin of the spinosolitary tract. They are probably neurons of the postsynaptic fibers of the dorsal column.Retrogradely labeled cells were also numerous in the superficial laminae of the trigeminal nucleus caudalis, through its rostrocaudal extent. The pattern of marginal cell labeling appeared to be continuous with that of labeled neurons in the paratrigeminal nucleus, located in the descending tract of trigeminal nerve.Since the NST is an important relay for visceral afferents from both the glossopharyngeal and vagus nerves, we suggest that the spinal and trigeminal neurons that project to the NST may be part of a larger system that integrates somatic and visceral afferent inputs from wide areas of the body. The projections may underlie somatovisceral and/or viscerovisceral reflexes, perhaps with a significant afferent nociceptive component.
Ultrastructural studies of physiologically identified electrosensory afferent synapses in the gymnotiform fish, Eigenmannia
Authors: Mathieson William B. , Heiligenberg Walter , Maler Leonard 
Published: January 2005

AbstractEigenmannia is a weakly electric fish that emits a constant‐frequency electric organ discharge (EOD). Probability coder (P unit) and phase coder (T unit) electroreceptive afferents differentially encode changes in EOD amplitude and phase, respectively. physiologically identified T and P units were intracellularly labelled with HRP and their terminals were examined with electron microscopy to determine their postsynaptic targets. This technique reveals that phase and amplitude are relayed to first‐order electrosensory neurons by two parallel but not independent pathways. P‐type afferents terminate on granular interneurons, basilar pyramidals, and polymorphic cells, electrosensory lateral line lobe targets that monitor amplitude modulations, but P‐type afferents do not contact spherical cells. T‐type afferents relay phase information to spherical cells and thus form a separate afferent pathway. T unit terminals do not synapse directly on basilar pyramidal cells. Collateral branches from T‐type afferents, however, were also found to terminate on granule and polymorphic cells, thereby adding phase information into the amplitude channel. P‐ and T‐type afferents exhibit cellular specificity by forming synaptic junctions with different subsets of post synaptic targets in the deep neuropil. The afferent terminals make either asymmetric chemical or gap junction synapses depending on the identity of the post synaptic target.T units contacting granule cells or polymorphic cells had not been previously described. Two possible roles of adding phase to amplitude information are discussed in terms of electrolocation.
Development of synaptic connections between muscle sensory and motor neurons: Anatomical evidence that postsynaptic dendrites grow into a preformed sensory neuropil
Authors: Jackson Patrick C. , Frank Eric 
Published: January 2005

AbstractThe anatomical development of muscle sensory arbors and dendrites of brachial motoneurons in the spinal cord of the bullfrog was studied by labeling both types of cells with horseradish peroxidase. Sensory and motoneurons were labeled in tadpoles (stages XV‐XVIII) by backfilling the triceps nerve in vivo with HRP throughout the stages in development when functional monosynaptic connections between these cells are first being formed. Individual triceps motoneurons were injected with HRP in other tadpoles at the same developmental stages. By stage XV, triceps sensory afferents already projected to and arborized in the ventral sensory neuropil region of the spinal cord where sensory‐motor connections are made. In contrast, the dendrites of triceps motoneurons rarely were present in this region until stage XVI. By stage XVII, triceps dendrites in this region were common and they intermingled with the collaterals of muscle sensory axons. Thus, sensory axons supplying limb muscles grow into the future neuropil region well in advance of the arrival of motoneuronal dendrites.Electrophysiological studies have shown that the connections between triceps sensory and motor neurons are already specific at stage XVII, as soon as monosynaptic potentials between these cells can be detected (Frank and Westerfield: J. Physiol (Lond.) 343:593–610, '83). The present anatomical results demonstrate that the processes of sensory and motor cells are not in close anatomical proximity before this time; thus the selection of appropriate synaptic partners must occur from the outset.
Synapses of cone horizontal cell axons in goldfish retina
Authors: Marshak David W. , Dowling John E. 
Published: January 2005

AbstractThe axon terminals of cone horizontal cells in the goldfish retina form typical chemical synaptic contacts in the middle of the inner nuclear layer. Approximately 60% of the identified postsynaptic elements were perikarya, axons and dendrites of bipolar cells. The other identified postsynaptic elements were perikarya and processes of interplexiform cells. We propose that the horizontal cell axon terminals contribute to the antagonistic surround responses of the bipolar cells and that they modulate inputs to the outer plexiform layer conveyed by interplexiform cells. Output synapses from horizontal cell axons to unidentified neuronal processes as well as occasional input synapses to the axons from interplexiform cell processes and unidentified perikarya were also observed in the same region of the inner nuclear layer.
Ultrastructural organisation of the projection from the superior colliculus to the ventral lateral geniculate nucleus of the rat
Authors: Taylor Alison M. , Lieberman A. R. 
Published: January 2005

AbstractRetinorecipient regions of the ventral lateral geniculate nucleus of the thalamus and the superior colliculus of the midbrain are linked by reciprocal axonal projections. In this study we have investigated the ultrastructural characteristics, the distribution, and the postsynaptic targets of the terminals of axons projecting to the ventral lateral geniculate nucleus from the superior colliculus. Horseradish peroxidase was injected into the superior colliculi of adult albino rats, and the Hanker‐Yates method was used to visualize anterogradely and retrogradely transported peroxidase in the ventral lateral geniculate nuclei 24 hours following the injection.Labelled terminals were found in the lateral and ventrolateral parts of the external division of the ipsilateral ventral lateral geniculate nucleus. The labelled terminals were confined to areas of simple, nonglomerular neuropil. They were 0.45–1.5 m̈m in diameter; contained small, dark mitochondria and spherical synaptic vesicles; and established Gray type I (asymmetrical) synaptic contacts with the dendritic shafts, dendritic spines, and occasionally cell bodies of cells with the ultrastructural characteristics of projection cells. A few labelled terminals established synaptic contact with retrogradely labelled cells.Thus, in the rat, the projection from the superior colliculus gives rise to a uniform population of axon terminals in the nonglomerular neuropil of the lateral portion of the ventral lateral geniculate nucleus, which synapse with, and are probably excitatory to, geniculocollicular and other projection cells.
Structural features of the terminal loop region of frog retinal rod outer segment disk membranes: II. Organization of the terminal loop complex
Authors: Corless Joseph M. , Fetter Richard D. , Zampighi Olga B. , Costello M. Joseph , Wall‐Buford Deena L. 
Published: January 2005

AbstractIn addition to a lipid bilayer component (Corless, Fetter, and Costello:J. Comp. Neurol. 257:1–8, '87), the terminal loop region of frog rod outer segment (ROS) disks displays a clustering of discrete elements referred to as theterminal loop complex.It consists of (1) semicircular or crescentic densities within the terminal loop, (2) linear interdisk densities spanning the cytoplasm near terminal loops, and (3) distinctive freeze‐fracture particles associated with the terminal loop, located between 1 and 2.The linear interdisk densities are organized on a two‐dimensional lattice that appears to ensheath completely the lamellar domains of all ROS disks. Indirect evidence is presented for a net axial alignment of intraloop densities. We interpret the large freeze‐fracture particles of the terminal loop region to reflect transmembrane components that connect the interdisk and intraloop densities. Thus, we propose that the entire terminal loop (TL) complex is organized on a two‐dimensional net. We further infer that each TL complex is organized as a dimeric unit and that such dimers interact axially and laterally to generate the observed lattice structure. It is suggested that one component of the terminal loop complex is the high molecular weight protein localized along the disk perimeter by Papermaster, Schneider, Zorn, and Kraehenbuhl (J. Cell Biol 78:415–425, '78).
The gonadotropin‐releasing hormone containing ventral hypothalamic tract in the fetal rhesus monkey (Macaca mulatto)
Authors: Goldsmith Paul C. , Song Tianbao 
Published: January 2005

AbstractA well‐defined, gonadotropin‐releasing hormone (GnRH)‐containing fiber pathway, the ventral hypothalamic tract (VHT), is described by immunostaining in fetal rhesus macaques (109–156 days gestation). The VHT arises above the lateral aspects of the optic chiasm near the supraoptic nucleus, and courses ventromedially close to the ventral hypothalamic surface to terminate in the infundibulum and zona externa of the median eminence. It is formed by the confluence of GnRH‐immunopositive (GnRH +) axons from local neurons, from a few GnRH+ cells in the inferior thalamic peduncle, and probably from more anterior neurons in the septum and preoptic area. Bipolar GnRH 4‐ neurons contributing directly to the VHT are grouped at its origin dorsolateral to the optic chiasm, dorsal and medial to the optic tracts, at the infundibular lip, and within the pathway between. At the infundibular lip, GnRH+ perikarya are generally lateral or ventral to the infundibular (arcuate) nucleus, and are rarely within the nucleus itself. Cell bodies here are sometimes tripolar, but GnRH+ intercellular contacts are seldom seen. A few VHT fibers extend to the ventral surface of the brain just beneath the pia mater. Abundant capillaries in the subarachnoid space suggest a possible route for delivery of GnRH to the adenohypophysis in early gestation, before maturation of the hypophysial portal system occurs. Posterior to the infundibulum, a few VHT fibers are joined by descending periventricular fibers forming a dense fiber band beneath the premammillary recess of the third ventricle.Totals of GnRH+ cell bodies in the prosencephalon of the fetal rhesus macaque are estimated to be 5,600 in females (n=2) and 2,600 in males (n=3). More than 60% of VHT neurons are located in the medial basal hypothalamus, and the majority of basal hypothalamic GnRH+ neurons (86%) are associated with the VHT. Furthermore, reports of the autonomy of the medial basal hypothalamic‐hypophysial unit in control of gonadotropin secretion suggest that the VHT may be the most important GnRH system involved in primate reproduction. It is clear that fetal material may offer the best model to study the GnRH neuronal system in primates.
Thalamocortical and thalamo‐amygdaloid projections from the parvicellular division of the posteromedial ventral nucleus in the cat
Authors: Yasui Yukihiko , Itoh Kazuo , Sugimoto Tetsuo , Kaneko Takeshi , Mizuno Noboru 
Published: January 2005

AbstractProjections from the parvicellular division of the posteromedial ventral thalamic nucleus (VPMpc) of the cat were examined. After injection of horseradish peroxidase conjugated with wheat germ agglutinin (WGA‐HRP) into the VPMpc, both anterogradely labeled axon terminals and retrogradely labeled neuronal cell bodies were found ipsilaterally in three discrete regions of the cerebral cortex, i.e., in the orbital cortex, caudoventral part of the infralimbic cortex, and medial part of the fundus of the posterior rhinal sulcus (perirhinal area); in the subcortical regions, anterogradely labeled axon terminals were seen ipsilaterally in the rostrodorsal part of the lateral amygdaloid nucleus. Neuronal connections between these VPMpc‐recipient regions were further verified by injecting WGA‐HRP into each of the three cortical and the lateral amygdaloid regions. After injection of WGA‐HRP into each of the three cortical regions, labeled neuronal cell bodies and axon terminals were seen ipsilaterally in the VPMpc, especially in its medial part, and in the other two of the three VPMpc‐recipient cortical regions. In the rostrodorsal part of the lateral amygdaloid nucleus, both axon terminals and neuronal cell bodies were labeled after WGA‐HRP injection into the perirhinal area, and only axon terminals were labeled after WGA‐HRP injection into the orbital cortex, but no labeling was observed after WGA‐HRP injection into the infralimbic cortex. After injection of WGA‐HRP into the rostrodorsal portion of the lateral amygdaloid nucleus, both axon terminals and neuronal cell bodies were labeled ipsilaterally in the perirhinal area and the ectorhinal area, and only neuronal cell bodies were labeled ipsilaterally in the VPMpc (especially in its medial part) and orbital cortical region; no labeling was observed in the infralimbic cortex.The present results indicate that the VPMpc of the cat is connected reciprocally with the orbital, infralimbic, and perirhinal cortical regions on the ipsilateral side, that the three VPMpc‐recipient cortical regions are reciprocally connected with each other, that the VPMpc sends fibers ipsilaterally to the rostrodorsal part of the lateral amygdaloid nucleus, which may relay information from the VPMpc to the perirhinal cortical area, and that the VPMpc‐recipient area in the lateral amygdaloid nucleus receives cortical fibers from the orbital and perirhinal cortical regions.