bluuebunny/crossref_metadata_2025 huggingface dataset:
Afferent fibers in the substantia gelatinosa of the adult monkey (Macaca mulatta): A Golgi Study
Authors: Beal John A. , Fox Clement A.
Published: January 2005

In horizontally and sagittally sectioned Golgi preparations of the adult monkey spinal cord the afferent fibers in the substantia gelatinosa(laminae II and III of Rexed, '52) were studied with the hope of finding clues that would make it possible to correlate them with the afferent fibers that Ramón y Cajal ('09) traced from the white matter into the substantia gelatinosa in Golgi preparations of the newborn cat.

Throughout the substantia gelatinosa there are fibers with fine terminal branches, bearing small “bouton en passant” endings. These fine terminal branches and the collaterals of the axons of the neurons in the substantia gelatinosa are similar; hence, the fine terminal branches are interpreted as the terminals of the proprius bundles generated by the axons of the neurons in the substantia gelatinosa. Also, there are fibers in lamina II that can be followed for relatively long distances(900 microns) before they are cut off in section. They have collaterals bearing large irregular endings, which usually consist of several or more elongated swellings connected by constricted regions. Some of these endings have holes within them and their surfaces have prominent indentations.

The fibers with fine terminal branches and the fibers with large irregular endings are interpreted here as the two varieties of fine or superficial collaterals of the substance of Rolando described by Ramón y Cajal('09).

The most elaborate afferent formations in the present material are found in horizontal sections. They are designated “confined ansiform axonal complexes” and are confined to elongated, oblong blocks of substantia gelatinosa that approximate each other in length, width and depth. Their branches, running rostrally and caudally, loop back and forth, interweave in an intricate pattern and bear large synaptic endings. because these formations are elaborate and because their parent fibers and initial branches are thicker in lamina III than they are in lamina II, these complexes are interpreted here as the large or deep collaterals of the substance of Rolando described by Ramón y Cajal('09). Considering their shapes, sizes and surface contours, it is probable that the large endings on the ansiform axonal complexes and the large irregular endings on the long fibers in lamina II are the central terminals in the glomeruli of the substantia gelatinosa that have been revealed by electron microscopy.

Finally, there are fine collaterals from fibers in Lissauer's fasciculus which distribute exclusively to the marginal zone (lamina I) of the dorsal horn. Their endings are ovoid or bulbous and are almost uniformly approximately 2 microns in diameter. Undoubtedly, these collaterals are the marginal collaterals Ramón y Cajal ('09) demonstrated in Ehrlich's methylene blue preparations of the 8‐day old cat.
Regeneration of retinal axons into the goldfish optic tectum
Authors: Murray Marion
Published: January 2005

The growth of regenerating retinal axons into the central portion of the optic tectum of adult goldfish was examined with the light and electron microscopes. Optic tracts were cut and, two days to five months later, the animals were perfused and the tecta prepared for microscopy. Regenerating axons first reached central regions of the tectum seven to ten days postoperatively. Regenerating axons appear in very large numbers and travel in fascicles in the stratum opticum (SO) and in the adjacent neuropil, the stratum fibrosum et griseum superficiale (SFGS). In the SO, the fascicles are bordered by glial cells and degenerating debris. Within the SFGS, however, the fascicles do not seem to be similarly associated with glial cells and degenerating debris. The youngest regenerating axons are very slender processes, containing microtubules but few or no neurofilaments or dense granular material. By 10 to 14 days postoperatively, neurofilaments can be seen and, in addition, large numbers of vesicles with dense cores appear. The vesicles with dense cores increase in numbers until about 28 days postoperatively and then become quite rare. That vesicles with dense cores were seen in regenerating axons in both SO and SFGS during the period of growth into the tectum but were not seen in axon terminals at any time, suggests that they may be concerned with axon elongation. During the period one month to five months postoperatively, the regenerating axons gradually increase in diameter but do not reach preoperative sizes, suggesting that the regenerative changes may still be occurring. Remyelination is delayed and proceeds slowly. Many axons remain unmyelinated for as long as five months postoperatively.
Trigeminal projections in snakes possessing infrared sensitivity
Authors: Schroeder Dolores M. , Loop Michael S.
Published: January 2005

The first order projections of the trigeminal nerve were studied in four species of snakes, three of which are infrared sensitive, utilizing silver degeneration and cobalt iontophoresis techniques. The trigeminal nerve projected ipsilaterally to a main sensory nucleus, descending spinal nucleus, ventral trigeminal field and solitary nucleus with a contralateral projection to the base of the descending spinal nucleus in all four species. A major additional projection to the lateral nucleus of the trigeminal was present in all three infrared sensitive species but absent in the other. Iontophoresis of cobalt chloride into a trigeminal branch composed entirely of infrared sensitive fibers and into a trigeminal branch containing no infrared fibers indicated that the lateral nucleus of the trigeminal nerve was the sole first order target of the infrared system.
Projections of the globus pallidus and adjacent structures: An autoradiographic study in the monkey
Authors: Kim Ronald , Nakano Katsuma , Jayaraman A. , Carpenter Malcolm B.
Published: January 2005

Because the globus pallidus gives rise to the principal efferent system of the corpus striatum and is traversed by several fibers systems, attempts were made to study the projections of its cells by autoradiographic technics. Tritiated amino acids (L‐leucine, L‐proline and L‐lysine) were injected into: (1) the medial pallidal segment (MPS), (2) the MPS and the substantia innominata (SI), (3) portions of the MPS and the lateral pallidal segment (LPS) and (4) parts of the putamen.

Cells labeled by injections of the MPS transported isotope to thalamic nuclei (ventral anterior, VApc, ventral lateral, VLo and VLm, and the centromedian, CM), the pedunculopontine nucleus (PPN), and the lateral habenular nucleus (Hbl). Labeled cells of the MPS and SI transported isotope to: (1) thalamic nuclei (VLo, VLm and CM), (2) PPN, (3) Hbl, (4) lateral and posterior regions of the hypothalamus, and (5) extensive dorsal regions of the substantia nigra (SN). Comparisons of label transported from uptake of isotope by cells of the MPS, and cells of both pallidal segments, suggest that the LPS projects fibers only to the subthalamic nucleus (STN). Not all regions of the STN appear to receive fibers from the LPS. Selectively labeled neurons of the putamen transport isotope to broad regions of both pallidal segments and to the pars reticulata of the SN.

This study suggests that cells of the MPS project profusely and topographically to: (1) the rostral ventral tier thalamic nuclei (VApc, VLo and VLm), (2) lateral portions of CM, and (3) the PPN. Fibers of the lenticular fasciculus appear to terminate preferentially in VLo. Cells in sublenticular portions of SI, and those extending into the medullary laminae of the pallidum, appear to project to: (1) HBl via the stria medullaris, (2) the pars compacta of SN, (3) lateral and posterior regions of the hypothalamus, and (4) the so‐called nucleus of the ansa lenticularis. Some fibers from cells of SI appear to join the dorsal stria terminalis, but none enter the inferior thalamic peduncle and none project to any part of the dorsomedial nucleus of the thalamus.
Areal and laminar distribution of some pulvinar cortical efferents in rhesus monkey
Authors: Trojanowski John Q. , Jacobson Stanley
Published: January 2005

The areal and laminar distribution of the cortical efferents of the medial, lateral and inferior pulvinar nuclei (PM, PL and PI respectively) were determined in rhesus monkey using autoradiography and Horseradish Peroxidase (HRP). The autoradiographic data indicated that: areas 8a, 45 and 46 on the convexity and 11 and 12 on the orbital surface of the frontal lobe received projections from PM; areas 20, 21 and 22 in temporal lobe received projections from PM primarily with caudal‐medial parts of PM projecting to more rostral‐dorsal parts of temporal lobe and rostral‐lateral parts of PM projecting to more caudal‐ventral parts of temporal lobe but PL also sends some efferents to caudal temporal lobe; areas 5 and 7 in parietal lobe and 18 and 19 in occipital lobe received projections primarily from the region in pulvinar comprising PL and PI with the more ventral parts of this region projecting to the ventral‐lateral parts of occipital lobe and the more dorsal parts of this region projecting to the more dorsal‐lateral and medial parts of parieto‐occipital cortex and with PM contributing slightly to these projections rostrally.

The autoradiographic information on the pulvinar projections to frontal lobe and temporal pole was supplemented by data derived from cortical HRP injections. These indicated that although only PM of the pulvinar subnuclei projected to these regions, three other caudal thalamic structures, i.e., medial dorsal nucleus, nucleus limitans and suprageniculate nucleus also projected to these regions raising some questions about the identity of the densocellular part of the medial dorsal nucleus which has also been considered to be part of pulvinar.

The laminar distribution of pulvinar cortical efferents was uniformly similar regardless of the pulvinar recipient area examined. Elevated numbers of silver grains were observed over all cortical layers, but the silver grains were densest over the deep parts of layer III.

The thalamic reticular nucleus was the only diencephalic structure observed to receive projections from pulvinar and it did so from PM, PL and PI.

The pulvinar's efferents are to homotypical rather than heterotypical cortex and its connections are most extensive with cortex rather than with subcortical structures.
Growth of the adult goldfish eye. II. Increase in retinal cell number
Authors: Johns Pamela Raymond , Easter Stephen S.
Published: January 2005

The retinas of adult goldfish, one to four years of age, 4–23 cm in length, were examined with standard paraffin histology to determine if new cells were being added with growth. Retinal cell nuclei were counted and the area of the retina was measured. An analysis of cell densities in various regions throughout the retina showed that the cells are distributed nearly homogeneously. The density (No./mm2 of retinal surface) of ganglion cells, inner nuclear layer cells and cones decreases with growth, but the density of rods remains constant. Thus the rods account for a larger proportion of the cells in larger retinas. The total number of cells per retina increases: the ganglion cells from 60,000 to 350,000; the inner nuclear layer cells from 1,500,000 to 4,000,000; the cones from 250,000 to 1,400,000; the rods from 1,500,000 to 15,000,000. This increase in the number of retinal neurons implies the formation of even more new synapses, and suggests the adult goldfish retina as a model for both neuro‐ and synaptogenesis.
Subdivisions of the auditory cortex of the cat: The retrograde transport of horseradish peroxidase to the medial geniculate body and posterior thalamic nuclei
Authors: Winer Jeffery A. , Diamond I. T. , Raczkowski Denis
Published: January 2005

Each subdivision of auditory cortex was injected with horseradish peroxidase (HRP). The amount of HRP injected was varied with the result that in some cases the diffusion of HRP was restricted while in other cases, HRP diffused over an entire cortical subdivision and encroached on adjacent subdivisions. In the case of restricted diffusion only a relatively small number of thalamic cells were “labelled”; in the case of extensive diffusion many times that number of cells were labelled. Whether relatively few or many cells, the distribution of labelled cells fell into distinctive patterns. Each pattern consisted of a focus or concentration of labelled cells in one thalamic subdivision and a sparser population of labelled cells in other thalamic subdivisions. The most striking example of a pattern is produced by injecting AI. This injection resulted in a band in the ventral division of the medial geniculate body densely populated with labelled cells; but even after the smallest injection, labelled cells were also found outside the ventral division, in the magnocellular and dorsal divisions of the medial geniculate body, and in the posterior group. (The ventral extremity of the ventral division was always free of cells and this sector is likely a separate nucleus which projects to Ep.) Other patterns are produced by injecting HRP in other cortical subdivisions: temporal injections produced a concentration in the caudal division of the medial geniculate body; insular injections resulted in a concentration in the medial sector of the posterior group; AII injections led to a concentration in the magnocellular and deep dorsal divisions of the medial geniculate body; injections in ventral Ep led to a concentration of labelled cells in the dorsal division of the medial geniculate body; finally, dorsal Ep seems to be very different from the other divisions inasmuch as injections in it resulted in labelled cells in non‐auditory thalamus–the pulvinar and lateral nuclei, as well as the auditory thalamus.

These results lead to the following conclusions. The laminated and principal part of the ventral division of the medial geniculate body projects only to AI. Every other thalamic subdivision projects to two or more cortical subdivisions: the caudal division projects primarily to the temporal area with sparser projections to AII and Ep; the dorsal division projects primarily to Ep with sparser projections to AI, AII, and the temporal area; the medial sector of the posterior group projects primarily to the insular area and to the posterior ectosylvian gyrus; the magnocellular division of the medial geniculate body projects to every subdivision of auditory cortex, including AI and AII.
The projections of the entopeduncular nucleus and globus pallidus in rat as demonstrated by autoradiography and horseradish peroxidase histochemistry
Authors: Carter D. A. , Fibiger H. C.
Published: January 2005

The efferent projections of the globus pallidus (GP) and entopeduncular nucleus (EP) in the rat were studied using autoradiographic and horseradish peroxidase (HRP) histochemical techniques. Following stereotaxic injections of 3H‐leucine into EP, transported label was observed in the lateral part of the ventromedial nucleus (VM) of the thalamus, and more laterally, in the ventrolateral aspect of the ventral lateral‐ventral anterior thalamic complex (VALv). Selective accumulation of autoradiographic grains was also found in the parafascicular nucleus (Pf) and in the lateral habenular nucleus. HRP injections into the thalamus confirmed the entopeduncular projections to these nuclei. Comparison of grain distribution in the thalamus after 3H‐leucine injections into EP and the zona reticulata of the substantia nigra (Clavier et al., '76) indicates that there is considerable overlap between nigral and EP projections to both VM and Pf. The nigrothalamic and entopedunculothalamic projections to VM and VALv are discussed with reference to the possibility that in the rat these nuclei are homologous to specific nuclei within the ventral lateral‐ventral anterior complex in primates.

Injections of 3H‐leucine into GP resulted in major accumulations of autoradiographic grains in the medial part of the subthalamic nucleus and the substantia nigra. Light and diffuse labelling was also observed in the dorsal thalamus. However, a consistent feature of the GP injections was that they appeared to result in diffusion of isotope to the reticular nucleus of the thalamus, and in view of the widespread thalamic projections of this nucleus, the label in dorsal thalamus could not be positively attributed to pallidal efferents. HRP injections throughout the thalamus failed to produce reactive cells in the GP. These experiments provided no firm support therefore for a recent suggestion that there are extensive projections from the globus pallidus to the thalamus in rat.
Early stages of uptake and transport of horseradish‐peroxidase by cortical structures, and its use for the study of local neurons and their processes
Authors: Vanegas Horacio , Holländer Horstmar , Distel Hansjürgen
Published: January 2005

It is well known that, when horseradish‐peroxidase (HRP) is injected into the central nervous system, it is taken up by nerve terminals and retrogradely transported to their cells of origin. We have now injected HRP into the visual cortex of cats in order to study light‐microscopically the pattern of its spread, the neural structures that take it up locally, and the initial steps of its retrograde descent towards the dorsal lateral geniculate nucleus (LGNd). Special attention was given to post‐injection times of ten minutes to eight hours, but animals with up tofive days' survival were also analyzed.

It was found that the brown spot produced by the initial spread (primary diffusion) of HRP remains constant in size for about two hours and then spreads out (secondary diffusion) to involve neighboring visual cortical areas. Secondary diffusion, however, does not result in further retrograde labelling of LGNd neurons. Local nervous structures labelled during primary diffusion of HRP include a large number of infracortical axons, many of which show bifurcations directed towards the cortex. As HRP descends within these axons, fewer and deeper axonal branchings appear labelled, as though, after initial uptake, HRP were no longer taken up. The possible reasons for the lack of further HRP uptake, including observed local inflammatory reactions, are discussed. Intracortical labelled structures include neuron somata and processes. These resemble Golgi‐impregnated structures and, particularly at short survival times, show fine details such as dendritic spine necks, terminal bouton stalks, synaptic contacts, and a remarkable degree of axonal preterminal and terminal branching. Some of these structures were also examined electron‐microscopically.
Connections of the visual cortex in the hedgehog (Paraechinus hypomelas). I. Halamocorticalprojections
Authors: Gould Harry J. , Hall William C. , Ebner Ford F.
Published: January 2005

Visual thalamocortical projections were studied in the Pakistani hedgehog with anterograde degeneration techniques following large aspiration lesions and discrete electrolytic lesions of visual thalamic nuclei. After 3‐ to 9‐day survival periods, the brains were processed and stained with the Fink‐Heimer technique, and examined with the light microscope.

The resutls of these studies show that there are at least four separate thalamic nuclei that project to visual cortex in the hedgehog. First, the dorsal lateral geniculate nucleus projects with a topographic order to layer IV and the adjacent portion of layer III of striate cortex. Second, a thalamic transition zone, adjacent to the dorsal lateral geniculate nucleus, projects widely to layer VI throughout striate cortex and possibly to all laminae of striate cortex in the area lying just medial to the striate‐parastriate border. The laminar pattern of termination of this transition zone is similar to that of the lateral posterior nucleus. Third, the lateral posterior nucleus projecs with little discernible topographic localization to layer VI of both striate and parastriate cortex, and in addition, to the remaining laminae of parastriate cortex except the outer one‐half of layer I. Fourth, the anterior intralaminar region projects to the outer one‐third to one‐half of layer I in both striate and parastriate cortex. Evidence derived from ablations of the entire thalamus on one side suggests that there may be still another thalamic nucleus that projects to visual cortex in the hedgehog.
Catecholamine innervation of the basal forebrain. I. The septal area
Authors: Moore Robert Y.
Published: January 2005

The septal area of the rat is known to receive a rich innervation by axons of catecholamine (CA) neurons. In the present study this innervatic was studied using biochemical assay of CA content and fluorescence histochemical analysis of the distribution of CA‐producing axons to determine the nuclei origin of the septal CA innervation and the effects of lesions on these parameters. The autoradiographic tracing technique and the horseradish peroxidase (HRP)‐retrograde transport technique also were used for this purpose.

The norepinephrine (NE) content of the normal septal area is 1,162 ± 127 ng/g and the dopamine (DA) content is 522 ± 106 ng/g. Hemisection of the brainstem caudal to the locus coeruleus results in a 47% decrease in septal NE content and a unilateral locus coeruleus lesion produces a 48% decrease in septal NE content. These observations suggest that the NE innervation of the septal area arises approximately equally from the locus coeruleus and nuclei in the caudal brain stem. This is confirmed, at least in part, by the anterograde and retrograde transport studies. The DA innervation of the septal area is shown by all of the techniques employed to arise almost exclusively from cells of the ventral tegmental area.

NE axons arising from the locus coeruleus distribute in the septal area to the hippocampal rudiment, the nucleus of the diagonal band, the interstitial nucleus of the stria terminalis, the medial septal nucleus, the lateral septal nucleus and the nucleus septofimbrialis. In each area the innervation is sparse to moderate in density and has the plexiform organization typical of locus coeruleus innervation. The brainstem NE innervation is very dense in the interstitial nucleus of the stria terminalis, moderately dense in the lateral septal nucleus and sparse in the nucleus of the diagonal band.

The DA axons innervating the septum terminate in two distinct patterns. The first is identical to that seen in the neostriatum. Preterminal axons are very fine and non‐varicose. As they reach a terminal area they branch markedly and give rise to extremely numerous, closely‐packed, fine varicosities. This type of DA innervation is found in the medial part of the lateral septal nucleus in a dense band and about some scattered lateral septal nucleus neurons, in the nucleus accumbens and in the interstitial nucleus of the stria terminalis. The second pattern is for non‐varicose preterminal axons to branch and terminate in pericellular baskets about lateral septal nucleus neurons or simply terminate in the lateral septal nucleus neuropil. In each case the terminal branches give off distinct varicosities which are larger than those formed in the first pattern of DA innervation.

Thus, the septal area has a complex organization of CA innervation with NE axons arising from caudal brainstem nuclei and the locus coeruleus and DA axons arising from the ventral tegmental area.
Neurons associated with the dorsal longitudinal flight muscles ofDrosophila melanogaster
Authors: Coggshall John C.
Published: January 2005

The anatomy of the neurons associated with the six fibers formingthe dorsal longitudinal flight muscle (DLM) of Drosophila melanogaster has been investigated using a horseradish peroxidase label. The two dorsal‐most fibers are innervated by the same neuron whose cell body is in the dorsal, contralateral, mesothoracic region of the thoracic ganglion. The ventral‐most fourfibers are innervated by four neurons whose cell bodies are clusteredin the ventral, ipsilateral, prothoracic region. The processes ofallfive of these cells ramify extensively in the dorsal part of theipsilateral and contralateral mesothoracic neuromeres.

A large interneuron has been discovered which is associated with the DLM and whose cell body is located contralaterally.

Several neurons with small cell bodies on the ventral midline of the mesothoracic neuromere are also consistently labeled. A single fiber projects dorsally from a midline cell body, forms a Y‐branch near the top of the ganglion and apparently sends an axon into each posterior dorsal mesothoracic nerve (PDMN) subsequently innervating the DLM.
Organization of the mossy fiber system of the rat studied in extended hippocampi. II. Experimental analysis of fiber distribution with silver impregnation methods
Authors: Gaarskjaer Frank B.
Published: January 2005

The mossy fibers, a major intrinsic hippocampal pathway connecting the dentate granule cells with the pyramidal cells in CA4 and CA3, have been reexamined in rats using mainly Fink‐Heimer silver impregnation methods for demonstration of degenerating axons. By extending isolated hippocampi and cutting sections normal to the long axis, simple two‐dimensional reconstructions of both the lesions and the resultant degeneration could be made.

In the hilus, the zone with the greatest concentration of degenerating boutons was found between the lesioned granule cells and the CA3 pyramidal cells abutting on the hilus; outside this zone the concentration declines rather rapidly. Degenerating boutons were also observed in low concentration up to 200‐300 μm septal and temporal to the lesion.

The mossy fibers in CA3 nearest the hilus have an intrapyramidal course and display a lamellar organization with fibers from the granule cells of the medial blade lying deep to those from the dentate crest. These in turn lie deep to those from the granule cells of the lateral blade.

A mediolateral difference in the projection of the granule cells on the CA3 pyramidal cells was discovered: fibers from the medial granule cells descend about 600 μm in the temporal direction, whereas fibers from the lateral granule cells descend about 1,200 μm. This causes a divergence of the fibers from one single level, especially of the part of the fibers, being farthest away from the hilus. The degree of descent of the fibers from each mediolateral position of the granule cells was constant at all septotemporal levels examined.
Superior colliculus connections with the extraocular motor nuclei in the cat
Authors: Edwards Stephen B. , Henkel Craig K.
Published: January 2005

Direct and indirect projections from the cat superior colliculus to the extraocular motor nuclei were studied using the orthograde autoradiographic tracing method, the retrograde horseradish peroxidase technique, and Golgi methods.

The results show that the superior colliculus projects to the central gray matter directly overlying the oculomotor complex. This projection arises almost entirely from the rostral third of the colliculus, and it terminates most heavily over the rostral half of the oculomotor complex. Dendrites of oculomotor cells extend into this tectal termination zone, making direct tecto‐oculomotor contacts possible. Central gray cells within this termination zone project bilaterally to the abducens nuclei. It is proposed that the superior colliculus projection to the supraoculomotor central gray matter and the projection from the central gray matter to the abducens nuclei play a role in convergent eye movements.

The superior colliculus projects lightly to a cell group directly ventrolateral to the trochlear nucleus.

The superior colliculus sends a small direct projection to the contralateral abducenns nucleus and a substantial projection to wide regions of the reticular formation that have been shown previously to project, in turn, to the abducens nucleus. Colliculus cells projecting to the abducens nucleus and adjacent reticular formation are located only in the caudal three‐fourths of the colliculus, where they become increasingly concentrated at successively more caudal levels. It is proposed that the graded density of the cells of origin of this projection is the basic structural mechanism by the which the colliculus generates horizontal foveating saccades of different amplitudes.

Laminar analysis of the origin of all the superior colliculus projections to the extraocular motor regions described here revealed that they arise mostly from the stratum griseum intermedium.
The forms of non‐pyramidal neurons in the visual cortex of the rat
Authors: Feldman Martin L. , Peters Alan
Published: January 2005

Rapid Golgi preparations from area 17 of young adult rats have been studied to determine the morphology and distribution of non‐pyramidal neurons. Such cells were observed in all of the cellular laminae of the cortex, but were particularly prevalent in layers IV and V. Non‐pyramidal neurons were categorized according to two features: (1) dendritic projection pattern, and (2) abundance of dendritic spines. Dendritic patterns were classified as multipolar, bitufted, and bipolar, and spine patterns as spinous, sparsely spinous, and spine‐free. Spinous dendrites were associated only with multipolar neurons, while sparsely spinous and spine‐free dendrites were each associated with cells of all three non‐pyramidal dendritic patterns. The most frequently observed non‐pyramidal cell types were multipolar cells of the spine‐free and sparsely spinous varieties. All of the general cell types encountered have been described in the literature on non‐pyramidal neurons, indicating the lack of any unique forms in rat area 17. An analysis of the dendritic projections of individual non‐pyramidal neurons through particular cortical laminae made possible an evaluation of common sources of dendrites present in the neuropil of each layer. Non‐pyramidal cell axons were impregnated only in small numbers. Spinous multipolar axons invariably exhibited a descending main branch, while the axons of bipolar neurons were distributed in a narrow vertical field. Axonal patterns of remaining cell types, including Golgi type II arborizations, did not appear to correlate consistently with dendritic morphology. Axons of the basket cell type and “horsetail” axons associated with double bouquet cells of Cajal's original type were not impregnated.
The role of ependyma in regeneration of the spinal cord in the urodele amphibian tail
Authors: Nordlander Ruth H. , Singer Marcus
Published: January 2005

The new spinal cord formed during tail regeneration in te newt first develops as a caudal extension of the ependymal tube. Neuroblasts and neuroglia subsequently differentiate from cells of the ependymal tube in a proximal‐caudal sweep. Descending axons from the cord rostral to the lesion and from newly differentiating neurons travel in channels which are present prior to the ingrowth of axons. The present study confirms previous observations from our laboratory and presents details of the ultrastructural relations of axons and ependymal processes within the cord.

The ependymal cell surface facing channels typically forms numerous digitor sheet‐like protuberances which extend into the channel lumen. As axons enter the channels in increasing numbers these protuberances partially subdivide the axons into smaller groupings, even occasionally segregating individual axons.

At levels where fibers have not yet entered or have most recently entered the ependymal channels two specializations appear on the ependymal plasmalemma facing the channels and their axons: coated membranes and hemides‐mosome‐like structures. At more mature levels, where many fibers have already; entered the channels, axons in contact with ependymal processes sometimes show synapse‐like vesicle accumulations with associated membrane densities. Coated membranes and hemidesmosome‐like structures are lacking at these levels.

Our observations suggest that ependymal processes, in addition to providing substrate and direction for regenerating spinal cord axons, may also furnish or exchange more specific information at the morphologically identifiable specializations described above.
Serotonin neurons of the midbrain raphe: Ascending projections
Authors: Moore Robert Y. , Halaris Angelos E. , Jones Barbara E.
Published: January 2005

The ascending projections of serotonin neurons of the midbrain raphe were analyzed in the rat using the autoradiographic tracing method. Axons of raphe serotonin neurons ascend in the ventral tegmental area and enter the medial forebrain bundle. A number of fibers leave the major group to ascend along the fasciculus retroflexus. Some fibers enter the habenula but the majority turn rostrally in the internal medullary lamina of the thalamus to innervate dorsal thalamus. Two additional large projections leave the medial forebrain bundle in the hypothalamus; the ansa peduncularis‐ventral amygdaloid bundle system turns laterally through the internal capsule into the striatal complex, amygdala and the external capsule to reach lateral and posterior cortex, and another system of fibers turns medially to innervate medial hypothalamus and median eminence and form a contralateral projection via the supraoptic commissures. Rostrally the major group in the medial forebrain bundle divides into several components: fibers entering the stria medullaris to terminate in thalamus; fibers entering the stria terminalis to terminate in the amygdala; fibers traversing the fornix to the hippocampus; fibers running through septum to enter the cingulum and terminate in dorsal and medial cortex and in hippocampus; fibers entering the external capsule to innervate rostral and lateral cortex; and fibers continuing forward in the medial olfactory stria to terminate in the anterior olfactory nucleus and olfactory bulb.
Ascending connections to the forebrain in the tegu lizard
Authors: Lohman A. H. M. , van Woerden‐Verkley I.
Published: January 2005

The ascending connections to the striatum and the cortex of the Tegu lizard, Tupinambis Nigropunctatus, were studied by means of anterograde fiber degeneration and retrograde axonal transport. The striatum receives projections by way of the dorsal peduncle of the lateral forebrain bundle from four dorsal thalamic nuclei: nucleus rotundus, nucleus reuniens, the posterior part of the dorsal lateral geniculate nucleus and nucleus dorsomedialis. The former three nuclei project to circumscribed areas of the dorsal striatum, whereas nucleus dorsomedialis has a distribution to the whole dorsal striatum. Other sources of origin to the striatum are the mesencephalic reticular formation, substantia nigra and nucleus cerebelli lateralis. With the exception of the latter afferentation all these projections are ipsilateral.

The ascending connections to the pallium originate for the major part from nucleus dorsolateralis anterior of the dorsal thalamus. The fibers course in both the medial forebrain bundle and the dorsal peduncle of the lateral forebrain bundle and terminate ipsilaterally in the middle of the molecular layer of the small‐celled part of the mediodorsal cortex and bilaterally above the intermediate region of the dorsal cortex. The latter area is reached also by fibers from the septal area. The large‐celled part of the mediodorsal cortex receives projections from nucleus raphes superior and the corpus mammillare.
The central projections of the glossopharyngeal and vagus ganglia in the mallard, Anas platyrhynchos L.
Authors: Dubbeldam Jacob L. , Brus Ernst R. , Menken Steph B. J. , Zeilstra Schelte
Published: January 2005

The central projections of the glossopharyngeal and vagus nerves in the mallard have been studied with the Fink‐Heimer I method and are compared to those of the trigeminal and facial nerves. The N. vagus projects ipsilaterally and contralaterally upon the central nuclei of the solitary complex, except the most rostral part of it, upon the n. sulcalis dorsalis, the parasolitary nuclei and the n. commissuralis. The glossopharyngeal nerve contributes to the rostral pole of the n. centralis anterior and to the n. ventrolateralis anterior of the solitary complex, but it has also terminal fields in a cellgroup sIX of the principal sensory trigeminal nucleus, in a small cellgroup sIXd on the dorsum of the descending trigeminal tract, in the n. interpolaris of this tract and in nuclei of the cuneate complex. There is hardly any overlap of the respective terminal fields. The convergence of projections from N VII and N IX can be connected with the presence of tastebuds in upper and lower bill and in the soft palate. The converging projections from N V and N IX in “trigeminal” nuclei may reflect the functional coherence of the mechanoreceptors in bill and tongue. It is suggested that these nuclei play a role in the feeding behavior.
Variability of laminar patterns in the human lateral geniculate nucleus
Authors: Hickey T. L. , Guillery R. W.
Published: January 2005

The structure of the human lateral geniculate nucleus has been studied on serial Nissl stained sections from 57 human brains. Most of the brains were from neurologically normal individuals and were obtained during routine autopsy procedures. The laminar arrangement within the human nucleus is surprisingly variable. It is always possible to recognize a small segment with two layers (the monocular segment), one with four layers and one with six layers. Often an 8‐layered segment can also be seen. The posterior half of the nucleus, within which central vision is represented, is made up mainly of six layers, and is the least variable part of the nucleus. Here the layers lie roughly parallel to each other. In the anterior half of the nucleus the laminar arrangement is more variable, and the layers often form complex and irregular interdigitations with each other. The 8‐layered segment varies greatly in size and may be absent. It generally lies at the edge of the 4‐layered segment not, as might have been expected, within the borders of the 6‐layered segment.

In many parts of the nucleus nerve cells are organized in short rows that run perpendicular to the layers; also, individual nerve cells are elongated in this direction. This neuronal orientation follows the lines of projection that are defined by the borders of a zone of retrograde degeneration, and also corresponds to the orientation of a cellular discontinuity that probably is the geniculate representation of the blind spot. Thus, we conclude that the neuronal orientation indicates the lines of projection within the nucleus.
Branching of sensory axons in the dorsal root and evidence for the absence of dorsal root efferent fibers
Authors: Langford Lauren A. , Coggeshall Richard E.
Published: January 2005

The present study demonstrates that there are more dorsal root axons than dorsal root ganglion cells in the L6‐S1 dorsal roots of the rat. The excess fibers do not come from aberrant dorsal root ganglion cells and our control procedures indicate that there are no extraneous fibers in these dorsal roots. Accordingly many dorsal root axons must branch in the dorsal root.
Sources of subcortical projections to the superior colliculus in the cat
Authors: Edwards Stephen B. , Ginsburgh Charles L. , Henkel Craig K. , Stein Barry E.
Published: January 2005

A comprehensive search for subcortical projections to the cat superior colliculus was conducted using the retrograde horseradish peroxidase (HRP) method. Over 40 different subcortical structures project to the superior colliculus. The more notable among these are grouped under the following categories.

Visual structures: ventral lateral geniculate nucleus, parabigeminal nucleus, pretectal area (nucleus of the optic tract, posterior pretectal nucleus, nuclei of the posterior commissure).

Auditory structures: inferior colliculus (external and pericentral nuclei), dorsomedial periolivary nucleus, nuclei of the trapezoid body, ventral nucleus of the lateral lemniscus.

Somatosensory structures: sensory trigeminal complex (all divisions, but mainly the γ division of nucleus oralis), dorsal column nuclei (mostly cuneate nucleus), and the lateral cervical nucleus.

Catecholamine nuclei: locus coeruleus, raphe dorsalis, and the parabrachial nuclei.

Cerebellum: medial, interposed, and lateral nuclei, and the perihypoglossal nuclei.

Reticular areas: zona incerta, substantia nigra, midbrain tegmentum, nucleus paragigantocellularis lateralis, and the hypothalamus.

Evidence is presented that only the parabigeminal nucleus, the nucleus of the optic tract, and the posterior pretectal nucleus project to the superficial collicular layers (striatum griseum superficiale and stratum opticum), while all other afferents terminate in the deeper layers of the colliculus. Also presented is information concerning the rostrocaudal distribution of some of these afferent connections. These findings stress the multiplicity and diversity of inputs to the deeper collicular layers, and more specifically, identify multiple sources of the physiologically well‐known representations of the somatic and auditory modalities in the colliculus.
Tectal projections in the goldfish (Carassius auratus): A degeneration study
Authors: Grover B. G. , Sharma S. C.
Published: January 2005

Efferents revealed by degeneration staining following tectal lesions in goldfish are presented. Four major projections were found.

Ascending ipsilateral projections to pretectal‐diencephalic areas exit the tectum rostrally and laterally and terminate in the area pretectalis (AP), lateral geniculate (LGN), nucleus pretectalis (NP), and nucleus rotundus (NR). Ascending contralateral projections exit rostrally and possibly laterally, enter the posterior and postoptic commissures and terminate in the contralateral AP, LGN, NP, NR and rostral tectum. A medially directed projection enters the intertectal commissure, and some of these fibers may terminate sparsely in an area of the contralateral tectum homotopic to the lesion. A descending projection exits the tectum laterally and projects ipsilaterally to a dorsolateral tegmental nucleus (DLT) and the lateral reticular formation of the tegmentum and pons, and contralaterally to the medial reticular formation of the tegmentum and pons.
Synaptogenesis in the cervical cord of the human embryo: Sequence of synapse formation in a spinal reflex pathway
Authors: Okado Nobuo , Kakimi Shigeo , Kojima Tokuzo
Published: January 2005

Synaptogenesis in the cervical cord was studied by light and electron microscopy in human embryos ranging from four to seven weeks of ovulation age. The stage of embryonic development was estimated on the basis of external morphology of embryos and histology of the eye ball with reference to Streeter's horizon. No synapses were found in the cervical cord of the embryo at Streeter's horizon XIV (8 mm; estimated ovulation age, 28‐30 days). A small number of axodendritic synapses appear in the motor neuropil of the cervical cord at Streeter's horizon XVII (14 mm; estimated ovulation age, 34‐36 days). Since no primary afferents are demonstrated to reach the motor neuropil at this stage (the premotile period), these synapses are considered to be formed between interneurons and motor neurons. On the other hand, the formation of synapses outside the motor neuropil of the cervical cord was recognized at Streeter's horizon XX (22 mm; estimated ovulation age, 40‐42 days), which corresponded to the period of onset of the precocious reflex, but not by horizon XIX (18 mm; estimated ovulation age, 38‐40 days). The first axosomatic synapses were found in the motor neuropil at Streeter's horizon XVII (estimated ovulation age, 34‐36 days). The present study suggests that the formation of synapses between interneurons and dendrites of spinal motor neurons precedes that of synapses between interneurons and collaterals of primary afferents. This sequence of synaptogenesis is in agreement with that reported in earlier studies with silver stain methods.
The sensory component of the facial nerve of a reptile (Lacerta viridis)
Authors: Jacobs Virgil L.
Published: January 2005

The sensory fibers of the facial nerve in Lacerta viridis have been studied with a silver impregnation method to follow the course of axonal degeneration. Destruction of the geniculate ganglion demonstrated the degenerated sensory component of the facial nerve adjacent to the anterior vestibular root. Within the lateral vestibular area the facial sensory fibers consist of numerous rootlets separated by vestibular fibers and cells. These rootlets may join to form a main or paired sensory tract that passes through the vestibular nuclei to enter the tractus solitarius and divide into a small ascending prefacial component and a major descending prevagal division. A few fibers continue into the postvagal part of tractus solitarius and extend caudally to terminate in the nucleus commissura infima. Prefacial fibers terminate along the periventricular gray while prevagal fibers terminate within the tractus solitarius on the dendrites of cells of nucleus tractus solitarius and near the periphery of the dorsal motor nucleus of X. There was no noticeable degeneration in the descendens tractus trigemini. Terminal degeneration to descendens nucleus trigemini and motor nucleus of VII followed the tractus solitarius course. Most facial sensory fibers are probably related to taste and other visceral information.
Anatomical organization of the primary visual cortex (area 17) of the cat. A comparison with area 17 of the macaque monkey
Authors: Lund J. S. , Henry G. H. , Macqueen C. L. , Harvey A. R.
Published: January 2005

Golgi and axonal transport techniques have been used to examine the organization of neurons within primary visual cortex, area 17, of the cat. This organization has been compared to that of the primate cortical area 17 as described in previous studies and it is discussed in relationship to the distribution of afferents from the dorsal lateral geniculate nucleus (dLGN). The visual cortex of the cat and monkey show strong similarities in the laminar positions of neurons projecting extrinscially and also in the restriction of spiny stellate neurons to a central lamina (lamina 4) receiving input from the dLGN. However, lamina 4B in the monkey, which contains spiny stellate neurons but does not receive direct input from the dLGN, has no direct counterpart in cat area 17. Axon projections of spiny stellate neurons in the other divisions of lamina 4 differ in cat and monkey: the small, closely packed neurons in the lowermost division of lamina 4 (4B in the cat, 4Cß in the monkey) project chiefly within lamina 4 in the cat whereas in the monkey they have a strong projection to lamina 3. In the cat, spiny stellate neurons of lamina 4A project upon lamina 3 whereas in the monkey those in the apparently equivalent zone, 4Cα, project upon lamina 4B. Most non‐spiny stellate neurons examined have precisely organized interlaminar axonal projections which differ from the axon trajectories of neighboring spiny neurons.
Electron microscopic studies of serially sectioned cat spinal α‐motoneurons. I. Effects of microelectrode impalement and intracellular staining with the fluorescent dye “procion yellow”
Authors: Berthold C‐H. , Kellerth J‐O. , Conradi S.
Published: January 2005

Cat spinal α‐motoneurons were studied in the light and electron microscope after intracellular recording and staining with the fluorescent dye Procion Yellow. Generally, the ultrastructural preservation of the stained neurons improved when the amount of dye delivered was decreased, and when the duration of the microelectrode impalement of the neuron as well as the time between the intracellular staining and the tissue fixation was kept as short as possible. Utilizing the optimal experimental procedure finally arrived at, about one‐third of the stained neurons could be used for further quantitative morphometric analysis. With respect to synaptology and gross architecture these cells appeared to differ from control motoneurons mainly with regard to a focal disarrangement of the cell body periphery, probably a result of the microelectrode injury, and a certain degree of damage to some large boutons.