bluuebunny/crossref_metadata_2025 huggingface dataset:
Displaced ganglion cells and the accessory optic system of pigeon
Authors: Fite Katherine V. , Brecha Nicholas , Karten Harvey J. , Hunt Stephen P.
Published: January 2005

The central projection and retinal distribution of displaced ganglion cells (DGC's) are described for the pigeon. Discrete, localized injections of horseradish peroxidase (HRP) into the nucleus of the basal optic root (nBOR) complex labeled as many as 4,800 DGC's in the contralateral retina. The greatest densities of DGC's were observed in the more peripheral regions of the middle and inferior temporal regions of the retina, with lowest densities occurring in the inferior nasal, red field, and foveal areas. Large HRP injections of the tectal lobes, which did not include the pretectal, accessory optic (nBOR), hypothalamic, or thalamic visual nuclei, labeled only ganglion cells within the ganglion cell layer. An HRP injection centered within the nucleus lentiformis mesencephali, also including portions of the optic tectum and optic tract, labeled only ganglion cells within the ganglion cell layer of the contralateral retina. DGC's thus appear to be the primary, if not exclusive, source of retinal afferents to the nBOR complex in pigeon. The observed retinal distribution of DGC's indicates that the areas of retina with the greatest density of cells in the receptor layer, inner nuclear layer, and ganglion cell layer are relatively devoid of DGC's. Since the nBOR complex projects directly upon the vestibulocerebellum and oculomotor nuclei, DGC's would thus appear to be involved in neural circuits that mediate oculomotor reflexes and visuomotor behavior.
Organization of corticospinal neurons in the monkey
Authors: Murray Elisabeth A. , Coulter Joe Dan
Published: January 2005

The retrograde axonal transport method has been employed to identify the cell bodies of cortical neurons projecting directly to the spinal cord in the monkey. The investigation has focused on aspects of the laminar, columnar, and somatotopic organization of corticospinal neurons within each of the cytoarchitectural and functional subdivisions of the sensorimotor cortex.

The principle findings of these experiments are that: (i) cortical regions containing cell bodies of corticospinal neurons are the first motor cortex (area 4), the first somatic sensory cortex (areas 3a, 3b, 1, and 2), and part of the immediately adjacent posterior parietal cortex (area 5), the second somatic sensory cortex, the supplementary motor cortex (the medial aspect of area 6), and the medial part of the posterior parietal cortex in a region termed the supplementary sensory area; (ii) corticospinal neurons display a somatotopic organization within each of these functional subdivisions of the sensorimotor cortex; (iii) all corticospinal neurons arise from layer V of the cortex; and (iv) corticospinal neurons within the first motor and first somatic sensory cortex oftern occur in clusters, perhaps reflecting a columnar organization in the sensorimotor cortex.

These findings demonstrate the origins of the corticospinal system to be more extensive than previously recognized and show that a number of common features characterize the organization of corticospinal neurons in all cortical areas. Across cortical subdivisions, however, major differences exist in the extent of spinal segmental representations, in the manner in which corticospinal neurons occur in groups, and in the numerical density and sizes of corticospinal neurons. These aspects of the organization of the corticospinal system presumably reflect specialization of the different cortical areas in spinal cord sensory and motor control.
Tectal projections of an infrared sensitive snake, Crotalus viridis
Authors: Schroeder Dolores M.
Published: January 2005

Crotaline snakes have detectors for infrared radiation and this information is projected to the optic tectum in a spatiotopic manner. The tectal projections were examined in Crotalus viridis with the use of silver methods for degenerating fibers and the autoradiographic and horseradish peroxidase tracing methods. Large lesions included all of the tectal layers but not the underlying structures. Projections to the thalamus include a sparse input to the ipsilateral ventral and dorsal lateral geniculate nuclei, the ventromedial nucleus, and nucleus lentiformis thalami. Nucleus rotundus was not detected. The projections to the pretectal nuclei are primarily ipsilateral to the nucleus lentiformis mesencehali and pretectal nucleus. At the level of the mesencephalon, tectal efferents are bilateral to nucleus profundus mesencephali and the tegmentum. There is minimal input to the contralateral deep tectal layers. There are ispilateral terminations in a nucleus identified as the posterolateral tegmental nucleus. Descending fibers include the two major tracts—the ventral tectobulbar tract that terminates in the ipsilateral lateral reticular formation and the predorsal bundle that distributes throughout the contralateral medial reticular formation. Two small descending tracts were noted—the intermediate and dorsal tectobulbar tracts. All of these descending tracts appear to terminate by the time they reach the caudal medulla. After superficial lesions terminals could be found in the ventral lateral geniculate nucleus, the nucleus profundus mesencephali, and the posterolateral tegmental nucleus; the two major descending tracts contained degenerated fibers as well. The areas receiving tectal input in Crotalus were compared to those of other reptiles and discussed.
Thalamic connections with limbic cortex. I. Thalamocortical projections
Authors: Robertson Richard T. , Kaitz Suzan S.
Published: January 2005

The thalamocortical projections to limbic cortex in the cat have been studied with retrograde and anterograde axonal transport techniques. Five limbic cortical areas were identified on the basis of cytoarchitecture. The five areas are the anterior limbic area, the cingular area, the dorsal and ventral retrosplenial areas, and the presubiculum. Each of these cortical areas received small injections of horseradish peroxidase, and the afferent thalamic nuclei were identified by retrograde labelling of cells. The cortical projection of each of the anterior thalamic nuclei and the lateral dorsal nucleus was determined autoradiographically.

Each of the anterior thalamic nuclei and the lateral dorsal nucleus projects to limbic cortex by two pathways. One group of fibers leaves the rostral thalamus by the fornix, pierces the corpus callosum, and joins the cingulate fasciculus to reach limbic cortex. The other group travels through the lateral thalamic peduncle and internal capsule. The anterior ventral nucleus projects primarily to the dorsal retroslenial area, particularly to layer I, the deep portion of layer II, and superficial portion of layer III. Sparse projections also exist to the ventral retrosplenial area, the cingular area, and the presubiculum. Very sparse projections to the anterior limbic area are seen. The anterior dorsal nucleus projects primarily to the ventral retrosplenial area, particularly layers I, the deep portion of layer II, and superficial layer III. Sparse projections exist to the dorsal retrosplenial area and presubiculum, but apparently no projections exist to the cingular or anterior limbic area. The anterior medial nucleus projects primarily to layers I and superficial III of the ventral retrosplenial area. Sparse projections exist to each of the other limbic cortical areas. The lateral dorsal nucleus projects extensively onto limbic cortex. Prominent projections occur to layer I, the external granular layer and lamina dessicans of the presubiculum, layers I and III‐IV of the dorsal retrosplenial area, and layers I, III, and IV of the cingular area. Sparse projections occur to the ventral retrosplenial area and the anterior limbic areas. Thalamocortical projections also originate in the midline and intralaminar nuclei including the central medial reuniens, rhomboid, paracentral, central lateral, and central dorsal nuclei.

These data indicate that the anterior thalamic nuclei project upon limbic cortex in a complex manner. Further, the projections to limbic cortex from the anterior nuclei overlap with projections from the lateral dorsal nucleus. This overlap of thalamic projections onto limbic cortex suggests a convergence of information from nonprimary sensory systems with information from the classical limbic system.
Combined golgi and electron microscopic study on the synapses formed by double bouquet cells in the visual cortex of the cat and monkey
Authors: Somogyi P. , Cowey A.
Published: January 2005

The morphology of certain Golgi‐stained cells was examined in the striate and peristriate cortex of the cat and in the striate cortex of the rhesus monkey. Neurons in layer III were selected on the basis of their characteristic vertical axon bundles, which are 20–150 μ in diameter and traverse layers II–V

Selected neurons were examined under the electron microscope to characterize their synapses and to establish their postsynaptic targets. It was found that double bouquet cells form symmetrical or type II synapses. In the cat the postsynaptic membrane specialization was more extensive than in the monkey. After removing the Golgi precipitate from boutons of two cells in the cat, small pleomorphic and flattened vesicles were found in the boutons

Earlier suggestions that double bouquet cells make synapses preferentially with spines of apical dendrites could not be confirmed. Out of 66 boutons in area 17 of the cat, 86.4% formed synapses with dendritic shafts, many of them belonging to nonpyramidal cells, 9% with perikarya of nonpyramidal cells, and only 4.6% with spines. Out of 19 synapses examined in area 18, 74% were contacting dendritic shafts and the rest contacted spines. In the monkey 60% of a total of 35 double bouquet cell synapses made synapses with dendritic shafts. A different type of double bouquet cell with densely spiny dendrites is also described in layer IV of the monkey striate cortex. This neuron formed asymmetrical synapses

It is suggested that layer III double bouquet cells with vertical axon bundles are probably inhibitory and act on other nonpyramidal cells and certain parts of pyramidal cells.
Regional specialization of the chick retina as revealed by the size and density of neurons in the ganglion cell layer
Authors: Ehrlich David
Published: January 2005

On the basis of both morphological criteria and survival after ganglion cell axotomy, three populations of cells can be recognized in the ganglion cell layer of the chick retina. These are: (1) Irregularly shaped cells, which are not affected by axotomy and lack Nissl stain. They comprise about 5% of the total cell population and are probably glial cells. (2) Small cells which have a distinctive teardrop‐shaped perikarya, stain for Nissl substance, and are not affected by axotomy. They occur with a uniform density of about 4,000 cells/mm2 across the entire retina and comprise 30‐35% of the total number of cells in the ganglion cell layer. It is suggested that these cells are displaced amacrine cells. (3) Cells which stain strongly for Nissl substance and disappear after axotomy. These cells comprise 60‐65% of the population of cells in this layer. The density of the latter cells varies throughout the retina. A high‐density region in the central area extends into the superior‐temporal retina. This high‐density region corresponds to a position in the lateral visual field extending into the inferofrontal field. The total number of these cells agrees with the reported number of the optic nerve fibres in the chick, (Rager and Rager, '78); therefore they are presumably ganglion cells. The size distribution of the presumptive ganglion cells varies in different parts of the retina

The only previous study of the distribution and size of cells in the ganglion cell layer of the avian retina did not distinguish between ganglion cells and displaced amacrine cells (Binggeli and Paule, 1969). The present results are therefore likely to be a more accurate description of the total number of ganglion cells, the regional variations in their density, and the characteristics of their size than previously reported.
Anatomical and neurochemical consequences of deafferentation in the development of the visual system of the moth manduca sexta
Authors: Maxwell Gerald D. , Hildebrand John G.
Published: January 2005

The primordium of the compound eye of the moth Manduca sexta was removed by surgery within 12 hours after the molt to the pupa. When the operated animals were examined as pharate adults just prior to emergence from the pupal cuticle, no eye tissue was present on the operated side. Histological examination of the brain at successive developmental stages showed that the volume of laminar neuropil on the operated side increased very little after deafferentation while the volume of the control‐side laminar neuropil increased more than 20‐fold. The impairment of development of the lamina was accompanied by a reduction in the synthesis and storage by the optic lobe of two neurotransmitter candidates, acetylcholine and 5‐hydroxytryptamine. The endogenous content of 5‐hydroxytryptamine was also reduced in these preparations. Excision of a section of the stemmatal nerve, which connects the primordium of the compound eye to the brain, also arrested the development of the lamina, but in this case the compound eye itself developed apparently normally without making contact with the brain. This finding supports the hypothesis that the centripetal growth of photoreceptor‐cell axons normally is contact‐guided. Results of neurochemical experiments on retinal tissue argue against the idea that acetylcholine, 5‐hydroxytryptamine, or gamma‐aminobutyric acid is a likely photoreceptor‐cell neurotransmitter. From these and our previous studies of the metamorphosing brain in Manduca we conclude that different classes of neurons in the same central nervous system can exhibit widely different degrees of dependency on their normal innervation for their survival and differentiation.
The organization of the claustroneocortical projections in the cat studied by means of the HRP retrograde axonal transport
Authors: Macchi G. , Bentivoglio M. , Minciacchi D. , Molinari M.
Published: January 2005

The projections from the claustrum to the cerebral cortex were examined in the cat by means of horseradish peroxidase (HRP) injections in various different areas of the lateral and medial surfaces of the neocortex. In all cases retrogradely labeled cells were observed in the ipsilateral claustrum insulare (ClI). In most of the cases some labeled cells were also observed in the contralateral ClI. The number of labeled cells was higher following large HRP injections in some cortical areas, such as the motor and visual cortex, than following large HRP injections in other areas, such as the second somatic sensory cortex. The patterns of distribution of labeled cells in the ClI following the different HRP injections evidenced a prevalent anteroposterior and dorsoventral topographical arrangement. However, some degree of overlapping was evident in the distribution of cells retrogradely labeled from injections in different cortical fields

The results of the present study indicate that: (a) in all likelihood the claustral projections are distributed upon the entire neocortex; (b) they are not uniformly distributed upon the neocortex from the quantitative point of view; (c) the arrangement of the claustrocortical projections is predominantly but not strictly topographical

The widespread distribution of the claustral inputs suggests that they must be integrated in different models of cortical activity.
Normal postnatal development of medial superior olivary neurons in the albino rat: A Golgi and Nissl study
Authors: Rogowski Barbara A. , Feng Albert S.
Published: January 2005

Bipolar neurons in the medial superior olivary (MSO) nucleus of albino rats were studied at various ages (0–75 days) during development in order to elucidate normal neuronal growth patterns. Neurons, visualized in celloidin embedded Golgi/Nissl‐ and frozen Nissl‐stained sections, were analyzed quantitatively for cell size and extent of dendritic arborization. These parameters, from both sets of data, showed a consistent developmental trend with the existence of two major stages in the ontogenetic process: a rapid developmental and a stabilization stage. The first stage, encompassing postnatal days 0 through approximately 14, was characterized by a rapidly increasing cell size, as observed in frozen sections. At the peak of this rapid growth, Golgi‐stained neurons possessed thick dendrites with many appendages, growth cones, and filopodia. The peak in neuronal development coincided with the initiation of ear opening. Morphological features attained a more mature form in the second, stabilizing stage of development, which began at approximately postnatal day 14. This phase was distinguished by a decrement in cell size and dendritic branching. Also, dendrites possessed more regularly distributed varicosities and fewer appendages, growth cones, and filopodia in this period. It was observed that dendritic branching trends paralleled those of cell diameter growth.
Direct retinal projections to the hypothalamus, piriform cortex, and accessory optic nuclei in the golden hamster as demonstrated by a sensitive anterograde horseradish peroxidase technique
Authors: Pickard Gary E. , Silverman Ann‐Judith
Published: January 2005

The central projections of the retinal ganglion cells of the golden hamster were examined using horseradish peroxidase (HRP) as the anterograde tracer molecule. Following monocular injections of HRP into the vitreous, retinfugal fibers were histochemically demonstrated using the chromagen tetramethylbenzidine. This procedure, being more sensitive than the 3H‐amino acid radioautographic technique, provided a clear demonstration of previously controversial retinal projections, clearer definition of established projections, and the discovery of new retinal pathways.

An inferior accessory optic system was shown to be unequivocally present in this species and to consist of both crossed and uncrossed components. A direct retinal projection to the suprachiasmatic nucleus (SCN) of the hypothalamus was confirmed in this study. But the distribution of terminals as seen by this procedure was substantially different than previously reported; both rostrocaudal and mediolateral asymmetries in the distribution of label between the ipsilateral and contralateral SCN were observed. Substantial differences in the retinal projection to the SCN in the hamster and the rat were also noted. It is suggested that these differences may reflect the different effects photic input has on the neuroendocrine‐gonadal axis in these two species. Finally, labeled retinal axons were followed leaving the optic tract and coursing anteriorly through the plexiform layer of the piriform cortex; other labeled fibers were seen to enter the septal region. The physiological significance of these previously undescribed retinal projections is not known.
Afferent connections of the interpeduncular nucleus and the topographic organization of the habenulo‐interpeduncular pathway: An HRP study in the rat
Authors: Contestabile R. A. , Flumerfelt B. A.
Published: January 2005

The HRP tracing method was employed to investigate the organization and afferent connections of the interpeduncular nucleus (IPN) in the rat. To study the topographical features of the different projections, a method was devised for obtaining HRP placements of limited size in different areas of the IPN.

The main afferent connection of the IPN is a topographically organized projection from the medial habenula (Hb). This projection follows a reversed caudorostral pattern, terminating throughout all but the caudalmost part of the IPN. The dorsal part of the IPN receives a sparse innervation arising mainly from a narrow lateral and ventrolateral area of the medial Hb. The ventral two thirds of the IPN receives a much heavier projection, as follows: A large ventrolateral area of the medial Hb projects to the lateral part of the IPN in a completely bilateral way. An additional projection, which is predominantly ipsilateral, arises from the rostral half of the dorsolateral part of the medial Hb and terminates in the caudal IPN. The medial part of the medial Hb projects preferentially to central areas of the IPN.

The projection from the lateral Hb is quantitatively much smaller but appears to be distributed to the entire length of the IPN, following a nonreversed caudorostral arrangement, with the ipsilateral projection predominating. The projections from the medial and lateral Hb to the IPN were confirmed by tracing anterogradely transported HRP as well. No reciprocal connection from the IPN to the Hb could be demonstrated.

A sparse projection to the IPN with a strong ipsilateral predominance arises from the horizontal limbs of the nucleus of the diagonal band of Broca. This was the only projection observed from the septal region. Sparse projections from the premammillary and supramammillary nuclei were also demonstrated. Confirmatory data and some details of organization were also obtained for projections to the IPN from other areas, including the medial and dorsal raphe nuclei, the dorsal tegmental nucleus of Gudden, and the adjacent dorsolateral tegmental nucleus. Very small projections from the ventral tegmental nucleus and the locus coeruleus were also found.
Dendritic plasticity in mouse barrel cortex following postnatal vibrissa follicle damage
Authors: Harris Roger M. , Woolsey Thomas A.
Published: January 2005

Neonatal damage to a row of mystacial vibrissae in the mouse causes cytoarchitectonic alterations in the contralateral SmI barrel cortex. The region for the appropriate row of barrels develops as a smaller homogeneous zone while barrels in adjacent rows are expanded. To investigate the effects of this pehnomenon on the morphology of individual neurons, adult mice in which Row‐C vibrissae (the middle row) had been cauterized on days 1–5 following birth were processed by the Golgi‐Cox method. All neurons in layer IV of the Row‐C zones, of the Row‐C barrels of a control hemisphere, and some neurons in the adjacent enlarged Row‐B barrels were measured with a computer‐assisted microscope. Their location with respect to cytoarchitectonic boundaries was determined from a Nissl counterstain. Data from 239 cells are presented. For each cell, measures of dendritic length and branching were obtained. The orientation of the dendritic trees with respect to the barrel sides was also measured.

The measures of dendritic lenghts and branching did not show any differences between control and experimental animals or between animals damaged on different days. Measures of orientation did show changes related to the age at the time of damage. In animals damaged on postnatal day (PND)‐3 or earlier, many cells in the Row‐C zone were observed with dendrites orienting toward the adjacent Rows‐B or ‐D. “Putative” Row‐C cells in the expanded parts of Rows‐B and ‐D were strongly oriented toward barrels in those rows. These results suggest that dendritic length and branching may be determined intrinsically but that the orientation of the dendritic trees appears to be strongly influenced by the pattern of extrinsic afferent inputs from the thalamus. In the case of the whisker‐damaged animals, the orientation of the Row‐C neuron dendritic trees toward the “functional” thalamocortical inputs in Rows‐B and ‐D contributes strongly to the resultant cytoarchitectonic changes. The implications of these results for normal developmental processes and their relationship to functional studies of the cortex are considered.
Immunocytochemical localization of catecholamine synthesizing enzymes and neuropeptides in area postrema and medial nucleus tractus solitarius of rat brain
Authors: Armstrong D. M. , Pickel V. M. , Joh T. H. , Reis D. J. , Miller R. J.
Published: January 2005

The catecholaminergic and peptidergic neurons in the area postrema and adjacent portion of the medial nucleus tractus solitarii (mNTS) were characterized by the immunocytochemical localization of the catecholamine synthesizing enzymes tyrosine hydroxylase (TH), dopamine‐beta‐hydroxylase (DBH) and phenylethanolamine‐N‐methyltransferase (PNMT) and two neuropeptides, substance P and (Leu5)‐enkephalin. The catecholamine synthesizing enzymes TH and DBH, found jointly only in noradrenergic and adrenergic neurons, were localized in cells having a similar morphology and topographical distribution. These cells were located throughout the rostrocaudal and dorsoventral extent of the area postrema, as well as in neurons within the mNTS. The processes showing TH and DBH immunoreactivity appear to form reciprocal connections between the area postrema and mNTS. Phenylethanolamine‐N‐methyltransferase, the enzymatic marker found only in adrenergic neurons, was detected immunocytochemically in terminals distributed throughout the area postrema and in neuronal perikarya and varicosities within the adjacent mNTS. Like the catecholamine synthesizing enzymes TH and DBH, enkephalin‐like immunoreactivity was localized to perikarya, proximal processes and varicose axon terminals within the area postrema and the adjacent mNTS. However, in contrast to the widespread distribution of the enzymes, the enkephalin‐like immunoreactivity was localized predominantly along the dorsal and ventrolateral margins of the area postrema. The distribution of substance P immunoreactivity, which was detected only in varicose processes, paralleled the distribution of enkephalin‐like immunoreactivity, being predominantly located along the dorsal and ventrolateral margins of the area postrema. Within the mNTS adjacent to the area postrema, substance P immunoreactivity was localized to neuronal perikarya, proximal processes and varicose axon terminals. Based upon the presence of appropriate biosynthetic enzyme markers and neuropeptide localization, these findings suggest that neurons within the area postrema contain noradrenalin and enkephalin and that the afferent axons contain substance P, adrenalin and, probably, noradrenalin.
Neurogenesis of the sexually dimorphic nucleus of the preoptic area in the rat
Authors: Jacobson Carol D. , Gorski Roger A.
Published: January 2005

The sexually dimorphic nucleus of the preoptic area (SDN‐POA) of Sprague‐Dawley rats is larger in volume in the male and hormone‐dependent early in postnatal life. In the present study, we compared for each sex the time course of neuroblast proliferation which forms SDN‐POA or adjacent medial preoptic area (MPOA) neurons. Additionally, we investigated whether there is a temporal gradient of production of neurons in relation to their final position within the SDN‐POA. On day 14, 15, 16, 17, or 18 postfertilization (pf) pregnant rats were given a single injection of 3H‐thymidine (*thy). At 30 postnatal days of age the pups were sacrificed and brain sections were prepared and processed for autoradiography. Three sections of the SDN‐POA and an adjacent area just lateral to it in the MPOA wer also analyzed. In the MPOA and the SDN‐POA the percentage (%) of labeled neurons decreases as the day of injection of *thy approaches the end of gestation, but the time period in which neuroblast divisions occurred is markedly different for the SDN‐POA as compared to that for the MPOA. DNA synthesis occurs as late as day 18pf for neurons which form the SDN‐POA but ceases on day 16pf for those destined for the MPOA. There is a sex difference in neuronal production on both day 14 and 17pf for neurons destined for the SDN‐POA. After injection on day 14pf the % labeled neurons is larger in the female than in the male but after injection on day 17pf this is reversed. There are also significant sex differences as well as a temporal gradient associated with the % labeled neurons in the SDN‐POA in relation to their final anterior‐posterior position. In addition, this study confirms our previous results which justify labeling the SDN‐POA a nucleus, since neuronal density in this region in the male and female is significantly greater than that in the surrounding MPOA. These data illustrate that the specific neurons which comprise the SDN‐POA in both the male and female are being produced as late as day 18pf, whereas neurons located in the MPOA but not in the SDN‐POA have all been born by day 16pf. Neuroblast division which produces the neurons of the SDN‐POA may begin earlier and terminate sooner in the female than in the male. These differences in neuronal production may partially account for the sexual dimorphism seen in the volume and neuronal number of the SDN‐POA of the adult rat.
Two visual pathways to the telencephalon in the nurse shark (Ginglymostoma cirratum). II. Ascending thalamo‐telencephalic connections
Authors: Luiten Paul G. M.
Published: January 2005

As part of a study on retino‐telecephalic pathways the ascending connections to the telencephalic central nucleus were investigated by retrograde transport of horseradish peroxidase. The central nucleus of the telencephalon, which is the main recipient for input from the brainstem, grossly can be divided into three rostrocaudal parts according to their afferent connections. The rostral third receives input mainly from the contralateral central thalamic nucleus and to a lesser degree from the lateral geniculate nucleus, periventricular gray, and a nucleus called the ventral mesencephalic tegmentum. The middle third of the central nucleus maintains an afferent connection with contralateral lateral geniculate, ventrolateral optic, and central thalamic nucleus, with the ventral mesencephalic tegmentum and periventricular gray bilaterally, and with a group of cells in the superior raphé nucleus. Caudal central nucleus injections of HRP resulted in labeling of cells in the contralateral lateral geniculate nucleus, ventral mesencephalic tegmentum, and central thalamic bilaterally, and in the superior raphé nucleus preoptic area and periventricular gray. From these results it can be concluded that visual information may reach the central telencephalic nucleus by two separate pathways: one pathway from retina via ventrolateral optic nucleus to the middle third of the central nucleus, and a second pathway from retina to optic tectum, which reportedly projects to the lateral geniculate nucleus, which in turn provides afferents to the caudal two‐thirds of the central nucleus. As such the nurse shark's visual system posesses structural features that are homologous to the two visual systems of higher vertebrate groups.
The distribution and sizes of ganglion cells in the retinas of five Australian marsupials
Authors: Tancred Elizabeth
Published: January 2005

Maps of ganglion‐cell distribution have been constructed from whole‐mounted retinas of five Australian marsupial species. The pademelon wallaby (Thylogale billiardieri), the scrub wallaby or tammar (Macropus eugenii), and the carnivorous Tasmanian devil (Sarcophilus harissi) have both a visual streak and an area centralis. The retina of the brown bandicoot (Isoodon obesulus) also shows both these features but they are less prominent than in the former three species, whereas the burrow‐dwelling, hairy‐nosed wombat (Lasiorhinus latifrons) possesses a well‐developed visual streak but seems to lack an area centralis.

A study of ganglion‐cell sizes comparing nasal and temporal retina, the visual streak, and/or the area centralis was undertaken in each species. Results show that as in the cat, small ganglion cells tend to concentrate in the visual streak. However, the temporal‐nasal differences in cell sizes described in the cat (Stone et al., '80) could be detected only in those marsupials in which an area centralis was clearly recognizable.
A brainstem atlas of catecholaminergic neurons in man, using melanin as a natural marker
Authors: Bogerts Bernhard
Published: January 2005

The present paper provides an atlas showing the distribution of melanin‐containing nerve cells in the human brainstem. It was found that neuromelanin, which can be viewed as a waste product of catecholamine metabolism, is suitable as a natural marker for catecholaminergic neurons in the medulla oblongata, pons, and the mesencephalon of the adult human brain. Within these areas of the brain, there is a striking similarity between the location of melanin and the catecholamine cell bodies described in various animals and in human fetuses, whereas no melanin was found in the diencephalic dopaminergic cell groups. Cell counts from the center of each area showed that the mean density of melanin‐containing perikarya varied considerably between the different areas.
Neuronal plasticity in the deafferented hypothalamic arcuate nucleus of adult female rats and its enhancement by treatment with estrogen
Authors: Matsumoto Akira , Arai Yasumasa
Published: January 2005

The hypothalamic arcuate nucleus (ARCN) was examined ultrastructurally 3 or 21 days after complete deafferentation of the medial basal hypothalamus (MBH) in ovariectomized adult female rats. Axodendritic shaft (SHS) and spine synapses (SPS) were counted in a field of 18,000 μm2 in the middle part of the ARCN in each brain. The mean numbers of SHS and SPS at 3 or 21 days after deafferentation were reduced to about half of those in intact control animals. When the ARCNs of the ovariectomized MBH‐island rats were examined 3 days after treatment with estradiol benzoate (EB, 2 μg/day), the numbers of SHS and SPS did not differ from those in ovariectomized MBH‐island rats without EB treatment. However, EB treatment for 21 days produced a marked increase in the number of both SHS and SPS in the ovariectomized MBH‐island females, with the number of SHS in these females being restored to almost 75% of the intact level; the incidence of SPS was also significantly greater than that in the intact control animals. In these EB‐treated, ovariectomized MBH‐island rats, double synapses (spine‐spine and spine‐shaft double synapses) were frequently observed. In ovariectomized females without MBH deafferentation, however, estrogen failed to increase the numbers of SHS, SPS, and double synapses, which were almost comparable to those in intact and ovariectomized controls.

These results suggest that estrogen has a facilitatory effect on SHS and SPS formation in the deafferented ARCN, presumably stimulating not only axonal sprouting but also dendritic spine formation by intact arcuate neurons in the MBH island.
The ratio of preganglionic axons to postganglionic cells in the sympathetic nervous system of the rat
Authors: Brooks‐Fournier Rebecca , Coggeshall Richard E.
Published: January 2005

Previously reported preganglionic‐postganglionic ratios for the sympathetic system are a major part of the evidence for the widely accepted idea that the sympathetic innervation of the viscera is diffuse. Unfortunately, the previous reports did not assess the non‐preganglionic fibers in the nerves examined, and the limitations of light microscopy precluded accurate unmyelinated fiber counts. Thus, a recalculation of these ratios is necessary.

The present study recalculates these ratios for the cervical sympathetic system of the rat. All fiber counts are done with the electron microscope which has the resolution necessary for accurately determining axon numbers. Selective surgical procedures establish that 84% of the axons in the cervical sympathetic trunk are preganglionic, 11% are postganglionic, and 5% are sensory. Thus, the numbers of preganglionic fibers can now be accurately assessed and compared to the number of postganglionic neurons in the superior cervical ganglion. When this is done, a preganglionic/postganglionic ratio of approximately 1:4 is obtained. This ratio differs considerably from those previously published.
Viscertopic localization of preganglionic parasympathetic cell bodies of origin of the anterior and posterior subdiaphragmatic vagus nerves
Authors: Dennison S. J. , O'Connor B. L. , Aprison M. H. , Merritt V. E. , Felten D. L.
Published: January 2005

Utilizing the retrograde HRP transport method, fibers from anterior and posterior subdiaphragmatic branches of the vagus nerve in the rat were traced to their cells of origin in the brainstem. Efferents to the gut supplied by the subdiaphragmatic vagus nerves derive from cell bodies organized in a viscerotopic, spindle‐shaped longitudinal cell column throughout the longitudinal extent of the classically described dorsal nucleus of the vagus (DNV) and in regions of nucleus commissuralis (NC), caudal to the DNV. This entire longitudinal group of cells is called the DNV cell column. In the caudal one third of the DNV cell column, the cell bodies were found in the midline and paramedian posterior portion of the NC, and in the anterior portion of the caudal DNV, in a horizontally oriented cluster of cells when viewed in cross section. In the middle one third of the DNV cell column, the cell bodies moved laterally, but still maintained their anterior position in the nucleus. In the rostral one third of the cell column, the cell bodies were located at the lateral margin of the DNV. A few scattered cell bodies extended caudally from the DNV cell column into the dorsal region of lamina X of spinal cord, and reached as far caudal as the C5‐C6 segments. The anterior subdiaphragmatic branch of the vagus contained axons whose cell bodies were mainly but not exclusively located in the ipsilateral (left) side of the medulla, while the posterior subdiaphragmatic branch of the vagus contained axons whose cell bodies were found bilaterally in the medulla, with a majority (approx. 60%) located on the ipsilateral (right) side, and approximately 40% located on the contralateral (left) side.
Distribution of dendrites from biventer cervicis and complexus motoneurons stained intracellularly with horseradish peroxidase in the adult cat
Authors: Rose P. K.
Published: January 2005

The three‐dimensional distribution of dendrites from the dorsal neck muscles biventer cervicis (BC) and complexus (CM) was examined in the adult cat using intracellular staining techniques. Motoneurons were electrophysiologically identified, stained with injection of horseradish peroxidase, and reconstructurcted from serial histological sections. The dendritic distributions of all motoneurons examined followed an orderly pattern. Many dendrites extended rostrally and caudally to form a complex parallel collection of dendrites in the ventromedial nucleus. Other dendrites projected dorsolaterally into the spinal accessory nucleus and lateral parts of lamina VII and VIII. Dorsomedial dendrites followed a path parallel to the medial border of the ventral horn and frequently terminated near the central canal. A few scattered dendrites were usually found directly dorsal to the soma in lamina VIII.

This pattern of dendritic distribution differed distinctly from the dendritic distribution of motoneurons in other spinal regions. However, in all spinal regions, including the upper cervical spinal cord where BC and CM motoneurons were found, the pattern of dendritic distribution from different motoneurons was similar if their somata were located in the same region.

For 15 motoneurons with well‐stained dendrites, the mean rostral‐caudal extent of the dendritic tree was 2,860 μm. The mean total dendritic length of three of these motoneurons measured 73,100 μm, almost four times larger than hindlimb motoneurons involved in planter reflexes. Despite the large size of the dendritic trees of BC and CM motoneurons, the surface areas of BC and CM cell bodies were smaller than most large hindlimb motoneurons. These quantitative differences in motoneuron dimensions may in turn be reflected by differences in the electrotonic properties of motoneurons in different motoneuron nuclei.
Spinocerebellar projections to lobules I and II of the anterior lobe in the cat, as studied by retrograde transport of horseradish peroxidase
Authors: Matsushita Matsuo , Okado Nobuo
Published: January 2005

Spinocerebellar tract (SCT) neurons projecting to lobules I and II of the cerebellar anterior lobe were identified by the retrograde horseradish peroxidase technique in the cat. Instead of a conventional stereotaxic approach, we removed ventral parts of the vermis of the posterior lobe and approached the posterior aspect of lobule I through the fourth ventricle. Under direct visual guidance, discrete injections were made into lobule I or lobule II with a glass micropipette.

Neurons projecting to lobule I were located mainly in the central cervical nucleus (CCN), the medial part of lamina VII of L6 to the caudal segments, and in lamina VIII of S2 to the caudal segments (with crossed ascending axons). The latter two groups correspond to the medial lamina VII group of the lumbar to the caudal segments and the ventral horn group of the sacral‐caudal segments of our previous studies. A small number of Clarke column neurons (with uncrossed ascending axons) also projected to lobule I. All of these neuronal groups projected to lobule II. In addition, large neurons in lamina V and in the border between laminae IV and V from S2 to the caudal segments projected to sublobule IIA, and more numerously to sublobule IIB (with crossed ascending axons). They belong to the dorsal horn group of the sacral‐caudal segments of our previous studies. Spinal border cells (with crossed ascending axons) projected to sublobule IIB, and a small number, to sublobule IIA. It was suggested that the CCN neurons project more densely to the median region whereas Clarke column neurons project to the lateral part of these lobules.
Short‐ and long‐term effects of neonatal and adult visual cortex lesions on the retinal projection to the pulvinar in cats
Authors: Labar Douglas R. , Berman Nancy E. , Murphy E. Hazel
Published: January 2005

An increased retinal projection to the pulvinar occurred in cats following neonatal ablation of visual cortical areas 17, 18, and 19. After unilateral lesions, the retinopulvinar projection visualized with autoradiography was larger and denser on the lesioned side than on the intact side. This increased projection was first recognized when the lesioned kittens were 1 week old, when increased labeling in the pulvinar was first detected. The retinopulvinar projection on the intact side of the brain decreased in size with age over the first 3 months of life. This decrease in size was not observed on the lesioned side of the brain. The absence of this decrease on the lesioned side may represent a failure of retraction of exuberant connections, but because of the active invasion by retinal fibers immediately after the lesion, observations of the normal retraction may simply be obscured. Severe cellular degeneration in the dorsal lateral geniculate occurred a few days before the changes in the retinopulvinar projection began; this loss of a postsynaptic target for many retinal axons may trigger the reorganization of input to the pulvinar retino‐recipient zone (pulvinar‐RRZ).

After adult visual cortex lesions, no reorganization of the retinopulvinar projection took place. The modification of the projection from the retina to the pulvinar that occurs after ablation of visual cortex in the newborn cat may contribute to the sparing of visual abilities seen after these lesions.
Regional differences in fiber size in the cochlear nerve
Authors: Romand R. , Romand M. R. , Marty R.
Published: January 2005

The topographical variations in fiber size in the cochlear nerve of cat were quantitatively studied by electron microscopy. Measurements of fiber size as they appeared at the outlet of the spiral lamina show that fibers originating from the basal part of the cochlea are larger than those from the apex. When the diameter of apical fibers and their axoplasms at two different levels are compared, a significant variation in size is observed. As they appear in the internal acoustic meatus the apical fibers are larger at the level of the nerve trunk compared with the same fibers near the ganglion cell bodies. There are significant differences in fiber diameter with regard to their length for fibers derived from the apical turn. These results are compared with previous findings.
Immunohistochemical analysis of magnocellular elements in rat hypothalamus: Distribution and numbers of cells containing neurophysin, oxytocin, and vasopressin
Authors: Rhodes C. H. , Morriell J. I. , Pfaff D. W.
Published: January 2005

A cell‐by‐cell analysis of the magnocellular elements in hypothalami of fifty Long‐Evans (normal) and Brattleboro (diabetes insipidis) rats was done using the unlabeled antibody enzyme technique (PAP) with primary antisera directed against oxytocin (OXY), vasopressin (ADH), and the neurophysins.

The magnocellular neurons of the hypothalamus were found in the supraoptic (SON), paraventricular (PVN), and anterior comissural (ACN) nuclei, a number of accessory nuclei, and as individual cells in the anterior hypothalamic area. SON was divided by the optic tract into the principal part and retrochiasmatic SON. In retrochiasmatic SON a majority of the cells contained vasopressin. Within the principal part of SON oxytocin‐producing cells tended to be found rostrally and dorsally, while the vasopressin cells were more common caudally and ventrally. PVN was divided into three subnuclei, the medial, lateral, and posterior subnuclei, on the basis of cellular morphology and peptide content. The magnocellular cells of the medial and lateral PVN were closely packed together and nearly round, while those of posterior PVN were more separated and fusiform in shape with their long axis running in a medio‐lateral direction. Medial PVN consisted primarily of oxytocin‐producing cells, while lateral PVN was formed by a core of vasopressin‐producing cells with a rim of oxytocin cells. Posterior PVN contained largely oxytocin‐producing cells. Both ADH and OXY cells were found in the accessory nuclei.

In the Long‐Evans rat the SON had, on the average, 1443 OXY and 3236 ADH cells; the PVN had 1174 OXY and 976 ADH cells; and the accessory magnocellular groups in the hypothalamus (including the ACN) had 1286 OXY and 552 ADH cells. The Brattleboro strain animal had similar numbers of cells in these nuclei. (The cells which contain ADH in normal animals were identified in the Brattleboro rat as large, neurophysin‐negative cells.) Thus, a large fraction of the magnocellular oxytocin‐ and vasopressin‐producing cells in the rat were located outside of the PVN and SON. One accessory cell group in particular, ACN, had 616 OXY cells, or about 50% as many as PVN. In each nucleus the sum of the numbers of OXY and ADH cells was approximately the number of neurophysin cells.
Organization of afferent connections of the feline lateral habenular nucleus
Authors: McBride Russell L.
Published: January 2005

The organization of afferent projections to the lateral habenular nucleus (LHB) was studied in adult cats. In autoradiographic experiments, tritiated leucine injections were made into regions shown in retrograde transport studies to project to LHB (lateral hypothalamus, preoptic region, entopeduncular nucleus, and midbrain raphe) to determine the locations of axonal trajectories and terminal zones.

The distribution of silver grains in the ipsilateral LHB differed according to the injection site. Entopeduncular nucleus projected to the ventrolateral part, raphe to the dorsomedial part, preoptic region to the central part, anterior hypothalamus to all but the ventrolateral part, and posterior hypothalamus to all but the dorsomedial part. The lateral hypothalamus, preoptic region, and anterior portion of the entopeduncular nucleus projected primarily through the inferior thalamic peduncle and stria medullaris, while the posterior portion of the entopeduncular nucleus projected more diffusely through thalamus to enter LHB from its ventral aspect. Raphe axons reached LHB through the fasciculus retroflexus.

Entopeduncular and lateral hypothalamic axons passed through the habenular commissure to the contralateral stria medullaris to reach the contralateral LHB. Silver grains in LHB were distributed similarly bilaterally, but were much less dense contralateral to the injection.

The major afferent projections to the feline LHB are therefore topographically organized. The significance of this organization in relation to the possible role of the LHB in integrating limbic and extrapyramidal motor systems is discussed.