bluuebunny/crossref_metadata_2025 huggingface dataset:
The organization of motoneurons in the turtle lumbar spinal cord
Authors: Ruigrok T. J. H. , Crowe A.
Published: January 2005

The distribution of motoneurons in the lumbosacral spinal cord of the turtle Pseudemys scripta elegans was studied by using the technique of retrograde transport of horseradish peroxidase. A total of 19 different hindlimb muscles were injected with varying amounts of horseradish peroxidase. The resulting distribution of labeled motoneurons was studied in both longitudinal and transverse sections of spinal cord.

Motoneurons innervating a particular hindlimb muscle are clustered in longitudinally arranged motorpools. Motorpools of different muscles can show considerable overlap in both the rostrocaudal and transverse planes. The distribution of the various motorpools demonstrates a somatotopic organization of motoneurons within the lumbar spinal cord. Motoneurons innervating more distally positioned muscles are generally found in the more caudal segments, while motoneurons supplying proximal muscles are distributed throughout almost the whole lumbosacral intumescence. Motoneurons innervating anterodorsally positioned muscles are found in the ventrolateral part of area IX in the ventral horn, while more dorsomedially positioned motoneurons innervate the posteroventral muscles. These features are consistent with observations in other tetrapods, although the somatotopic representation of motoneurons is more evident in higher vertebrates such as chicken and cat.

The observed motorpool distribution is discussed in relation to the presumed ontogeny of the spinal cord and hindlimb muscles and also in relation to the functions of the investigated muscles.
Cortical connections of the middle temporal visual area (MT) and the superior temporal cortex in owl monkeys
Authors: Weller Rosalyn E. , Wall John T. , Kaas Jon H.
Published: January 2005

The connections of the middle temporal visual area (MT) and an adjoining superior temporal visual region (ST) were investigated with injections of 3H‐proline and horseradish peroxidase (HRP) in adult owl monkeys. Injections in MT revealed an extensive pattern of intrinsic connections that appeared to be organized in a series of bands across MT. MT was found to project ipsilaterally to an array of visual areas including the first (V I) and second (V II) visual areas, the dorsolateral visual area (DL), and the dorsomedial visual area (DM). When injection sites and projection zones were related to previously described retinotopic maps, it was apparent that the projections of MT to these fields were largely homotopic. Other projections were to posterior parietal cortex, the dorsointermediate visual area (DI), the ventral visual area (V), and possibly the medial visual area (M). In addition, dense projections to cortex on the rostral border of MT were used to define a new subdivision of visual cortex, the superior temporal visual region (ST), as the major projection zone of MT. Callosal connections of MT were mainly to MT, with some terminations in DL and ST.

Injections of 3H‐proline into ST revealed a diffuse projection to largely layer I of MT, and dense projections to posterior parietal cortex, cortex in more rostral parts of the superior temporal sulcus, ventromedial inferior temporal cortex, and the region of the frontal eye fields. Callosal projections were largely to ST cortex of the other cerebral hemisphere.

The results place MT and V II in distinctly different processing chains. While both MT and V II receive the major cortical outputs of V I, V II relays to DL and DL relays to subdivisions of inferior temporal cortex. In contrast, the most significant cortical target of MT appears to be to ST, which relays to posterior parietal cortex and other targets.
Projections to the frontal cortex from the posterior parietal region in the rhesus monkey
Authors: Petrides M. , Pandya D. N.
Published: January 2005

The projections to the frontal cortex from the various subdivisions of the posterior parietal region in the rhesus monkey were studied by means of autoradiographic technique. The rostral superior parietal lobule (area PE) projects to the dorsal areas 4 and 6 on the lateral surface of the frontal lobe as well as to the supplementary motor area (MII) on its medial surface. The caudal area PE sends its connections to dorsal area 6 and MII. The projections from the media parietal cortex (areas PEc and PGm) are similar to those of the superior parietal lobule but they tend to concentrate in the more rostral part of dorsal area 6, MII, and in the cingulate gyrus (area 24). The most caudal part of the medial parietal cortex also projects to area 8. The anteriormost part of the inferior parietal lobule (area PF) projects to the ventral area 6, including the caudal bank of the lower branch of the arcuate sulcus, to the ventral area 46 below the sulcus principalis, and to the frontal and pericentral opercular cortex. The middle inferior parietal lobule (areas PFG and PG) projects to the ventral part of area 46 and area 8, whilst the posteriormost inferior parietal lobule (caudal PG and area Opt) is connected with both dorsal and ventral area 46, dorsal area 8, as well as the anteriormost dorsal area 6, and the cingulate gyrus (area 24).
Serotoninergic axonal contacts on identified cat spinal dorsal horn neurons and their correlation with nucleus raphe magnus stimulation
Authors: Miletic V. , Hoffert M. J. , Ruda M. A. , Dubner Ronald , Shigenaga Y.
Published: January 2005

This study examined the distribution of serotoninergic (5‐HT) immunoreactive axonal contacts on spinal laminae I and II neurons by combining the intracellular horseradish peroxidase (HRP) method with immunocytochemistry. In addition, the 5‐HT distribution was correlated with effects produced by electrical stimulation within the nucleus raphe magnus (NRM). Responses of lamina I neurons and lamina II stalked cells to noxious stimulation were markedly suppressed during NRM stimulation. In contrast, responses of nociceptive lamina IIa islet or non‐nociceptive lamina IIb islet cells remained unchanged during nucleus raphe magnus stimulation. These inhibitory influences were positively correlated with the distribution of 5‐HT immunoreactive contacts on these neurons. Nociceptive lamina I neurons and lamina II stalked cells received a significantly greater number of contacts (average of 74 and 63, respectively) than either nociceptive lamina IIa islet or non‐nociceptive lamina lib islet cells (average of 25 and eight contacts, respectively). Irrespective of cell type, most 5‐HT contacts occurred on dendritic shafts rather than spines. These data reveal a differential distribution of 5‐HT contacts on neurons in spinal laminae I and II, and indicate that at least a portion of the NRM modulation of dorsal horn neuronal activity is serotoninergic and concentrated on the dendritic shafts of nociceptive lamina I neurons and lamina II stalked cells.
A monoclonal antibody against neurofilament protein specifically labels a subpopulation of rat sensory neurones
Authors: Lawson S. N. , Harper A. A. , Harper E. I. , Garson J. A. , Anderton B. H.
Published: January 2005

A monoclonal antibody (RT97) against neurofilament protein specifically and exclusively labelled n subpopulation of rat dorsal root ganglion (DRG) neurons. For seven ganglia (L4 and T13) studied quantitatively the frequency distribution histograms of the size of labelled cells could be fitted by a single normal distribution whose parameters were extremely close to those of the normally distributed large light cell population in that ganglion. On this basis and on the basis of a statistical analysis of the results it was suggested that this antibody can be used as a much needed specific label for the large light population of neurons in rat DRGs. The small dark neuron population was not labelled by this antibody. In one ganglion the subjective analysis of whether each neuron was labelled or not was directly compared with microdensitometric measurements of reaction product intensity. This analysis supported the above conclusion, and furthermore no subdivisions of the labelled population were apparent on the basis of neuronal size plotted against intensity of the reaction product.

Other neuronal cell bodies strongly labelled by this antibody were found in association with small unlabelled neurones not only in DRGs, but also in the trigeminal ganglion, the vagal ganglia, and the mesencephalic V nucleus, all of which are made up of primary afferent neurones and all of which are completely or partially derived from the neural crest.

Sympathetic and central nervous system neuronal cell bodies were unlabelled or occasionally very lightly labelled although immunoreactive fibers abound in the central nervous system.
Peripheral configuration and central projections of the lateral line system in Astronotus ocellatus (cichlidae): A nonelectroreceptive teleost
Authors: Meredith Gloria E.
Published: January 2005

The lateral line system of Astronotus ocellatus comprises one trunk canal, one tail canal, and three head canals. The sensory receptors on the head are innervated by rami of the dorsal anterior, ventral anterior, and posterior lateral line nerves, and those along the trunk and tail by rami of the posterior lateral line nerve. The peripheral configuration of lateral line canals and nerves was examined in whole mount preparations, the central connections of restricted groups of endorgans studied using HRP and degeneration methods, and the neuronal morphology and cytoarchitecture of the lateralis region invetitigated with Nissl, silver, and Golgi methods.

Neurons of the lateralis cell column are diffusely arrayed and of variable morphology. They are oriented primarily in the transverse plane and, with the exception of a dorsal lamina of large multipolar cells, are not organized into zones.

Lateralis fibers bifurcate on entering the brainstem, course in lateral tracts, and give off medially directed collaterals to terminate in the ipsilateral nucleus medialis and nucleus caudalis. In addition, fibers terminate in the eminentia granularis of the cerebellum, but only fibers supplying endorgans in the head canals penetrate the granule cell zone of the cerebellar corpus.

Fibers supplying sense organs in adjacent canals overlap in their central endings, whereas fibers of distantly separated receptors do not overlap. The rami supplying trunk and tail canal organs do not project as far rostrally in the central neuropil as do the other rami. Endings of posterior lateral line fibers lie dorsal to those of the anterior lateral line nerves, and some lateralis fibers terminate within the confines of the magnocellular, descending, and posterior nuclei of the octavus column. Although there is spatial order to the lateralis projections, there is no clear somatotopic organization in the lateralis region.
Cortical projections to the paramedian tegmental and basilar pons in the monkey
Authors: Leichnetz G. R. , Smith D. J. , Spencer R. F.
Published: January 2005

The efferent connections of the cerebral cortex to paramedial tegmental and basilar pons were studied in the monkey by using the retrograde and orthograde capabilities of the horseradish peroxidase (HRP) technique. Six capuchin monkeys (Cebus apella) received transcannular pontine HRP gel implants to retrogradely label the cells of origin of corticopontine projections. Four additional capuchin monkeys, one rhesus (Macaca mulatta), and one cynomolgus (Macaca fascicularis) monkey, received HRP gel implants in premotor (area 6), frontal eye field (FEF, area 8), superior (area 5), and inferior (area 7) parietal lobules to orthogradely label the course and termination of corticopontine projections, and thus to confirm the retrograde studies. The brains were processed according to the tetramethylbenzidine (TMB) protocol of Mesulam ('78) and studied with darkfield microscopy. Premotor (area 6) frontal cortex and FEF (area 8) were found to be the main sources of cortical inputs to the ipsilateral paramedian basilar pons, whereas FEF, dorsal prefrontal convexity, and dorsal medial prefrontal (granular frontal association) cortex, were the main sources of bilateral projections to the paramedian pontine tegmentum. The medial portion of the nucleus reticularis tegmenti pontis (NRTP), considered to be a tegmental extension of the basilar pontine gray, also received its principal cortical input from the frontal lobe. Parietal cortex, on the other hand, was observed to project to lateral NRTP and lateral basilar pons. Although the possibility exists of convergence of frontal and parietal eye field efferents in the NRTP, the frontal eye field and prefrontal cortex appear to be the principal source of cortical projections to the paramedian pontine tegmentum, which contains the physiologically defined PPRF (paramedian pontine reticular formation), an important preoculomotor center. The results are discussed primarily with regard to their significance for potential cortical influence on the oculomotor system.
Isofrequency labelling revealed by a combined [14C]‐2‐deoxyglucose, electrophysiological, and horseradish peroxidase study of the inferior colliculus of the cat
Authors: Servière Jacques , Webster William R. , Calford Michael B.
Published: January 2005

Tonotopic sequences of single units were recorded in the central nucleus (ICC) of the inferior colliculus of cats. The sites of units with a particular characteristic frequency (CF) were marked histologically. After injection with [14C]‐2‐deoxyglucose (2‐DG), each animal was stimulated with tone bursts, which corresponded to the CFs of the selected units. The position of a selected unit was found to correspond with the position of a band of discrete 2‐DG labelling. In some animals, multiple penetrations revealed that more than one unit with the same CF was located on the same band, indicating that the 2‐DG bands represent isofrequency contours. Single units were recorded in the pars lateralis (LV) of the medial geniculate body of cats and areas of consistent CF were found, which contained the same frequencies as some of those employed with 2‐DG. Horseradish peroxidase(HRP) Was Ejected into these selected areas and labelled cells were identified in ICC after retrograde transport. The labelled cells were found to lie in a band which had a similar orientation to the 2‐DG bands produced by the same frequencies. Both sets of data indicate that ICC is organized into three‐dimensional isofrequency sheets, the orientation of which do not match the concentric model of frequency organization inferred from some Golgi studies. The isofrequency sheets slope from medial to lateral throughout ICC with high‐frequency contours found more medially and caudally and low‐frequency contours more laterally and rostrally.

The organization of the isofrequency contours is largely in agreement with a recent Golgi model of the laminations in ICC put forward by Oliver and Morest ('84). The 2‐DG contours do not agree with the orientation of laminae in the lateral part of ICC as described by this model. The 2‐DG contours also extend further into the dorsal cortex than previous degeneration evidence would suggest.

The functional isofrequency contours are often quite narrow and could represent two or three overlapping cellular laminae. The results show clearly that there is only one tonotopic organization extending throughout ICC and the dorsal cortex.
Cell configurations in the olfactory tubercle of the rat
Authors: Millhouse O. E. , Heimer Lennart
Published: January 2005

The rat olfactory tubercle was studied with the rapid Golgi method. Several distinct cell types were identified mainly on the basis of the size of their somata and the structure of their dendrites. The commonest neuron type in the tubercle is the medium sized densely spined cell. The somata of these neurons occur chiefly in the dense cell and multiform layers. They also form the cell bridges that directly link the olfactory tubercle with the nucleus accumbens and caudate‐putamen. Their dendritic trees exhibit a variety of shapes; some of them are spherical, some are bipolar, and others are asymmetrical. The axons project dorsally, deep into the multiform layer. En route they give off numerous collaterals. A large version of this cell type is the crescent cell. Other medium‐sized neurons also have somata in the dense cell and multiform layers. They include the spindle cells, so named because of the shape of their cell bodies, and the medium‐sized spine‐poor neurons. Neither of these cell types has dendritic trees that are as highly branched as those of the medium‐sized densely spined cells.

There are three types of small cells; their somata occur primarily in the dense cell and molecular layers. The dwarf cells are near the pial surface, although their somata are included in the dense cell layer, and they have axons that resemble those of medium‐sized densely spined cells. The radiate cells have numerous, relatively short, spine‐free dendrites that extend out from the rounded somata in all directions. The small spine‐rich cells look like miniature versions of the medium‐sized densely spined neurons. They are frequently confined to the molecular layer.

Large spine‐poor neurons, with their cell bodies located in the dense cell and multiform layers, seem to be a heterogeneous cell group since there are subtle variations in the structure of their dendrites and the shape and extent of their dendritic trees. The large, moderately spined neurons are less common than the other large cells; their somata are found in all three layers.

The granule cells of the islands of Calleja make up the most homogeneous cell group. They have only a few dendrites, and these are quite thin.

Except for the medium‐sized densely spined and dwarf cells, the axons of the different cell types were not very well impregnated.

The different cell types in the tubercle are compared to cells in the nucleus accumbens, caudate‐putamen, and globus pallidus. The remarkable structural similarities that exist between certain cells in the tubercle and some in the basal ganglia and the direct structural continuity that occurs between these structures indicate that the olfactory tubercle, at least in part, represents a ventral extension of the caudate‐putamen and globus pallidus.
Non‐uniform postnatal growth of the cat retina
Authors: Mastronarde David N. , Thibeault Marcia A. , Dubin Mark W.
Published: January 2005

The distributions of alpha‐type ganglion cells in 3‐week‐old and adult cats were used to measure the increase in the distances between existing cells and thus the amount of growth in various regions of the retina. Growth shows two major non‐uniformities. (1) The area centralis is at the point of minimum growth; its area increases by only about 3% while regions near the retinal margin increase in area by about 80%. (2) The retina grows about half as much in linear extent as does the radius of the eye and thus comes to occupy a smaller fraction of the globe. Measurements of retinal dimensions indicate that both non‐uniformities also occur from birth to 3 weeks.

These non‐uniformities have the following implications. (1) They would tend to elongate dendritic fields radially, in the direction of the area centralis, in central retina but perpendicular to this direction in peripheral retina. However, these asymmetries are probably not the primary reason why ganglion cells throughout the retina tend to have radially oriented dendritic fields (Leventhal and Schall, '83). (2) Greater growth in the periphery could contribute to the gradient of increasing dendritic field size from central to peripheral retina if the dendritic fields of ganglion cells passively stretched as the retina expanded. Passive stretching is not the primary determinant of dendritic extent, however, because the dendritic fields of beta‐type ganglion cells were found to grow 70% more from 3 weeks to adulthood than can be accounted for by passive stretching. (3) Greater peripheral growth steepens the central‐to‐peripheral gradient of decreasing ganglion cell density; if this trend also occurs prenatally, it could be the major factor in producing the final adult gradient.
Retinal ganglion cells in two teleost species, Sebastiscus marmoratus and Navodon modestus
Authors: Ito Hironobu , Murakami Takeshi
Published: January 2005

Distribution patterns of ganglion cells in the retina were examined in Nissl‐stained retinal whole mounts of Sebastiscus and Navodon. The existence of area centralis in the temporal retina in both species suggests binocular vision. In Navodon, another high density area was found in the nasal retina, and a dense band of ganglion cells was observed along the horizontal axis between the two high‐density areas. There is an obvious trend for the ganglion cell size to increase as the density decreases. The total number of ganglion cells was estimated to be about 45 × 104 in Sebastiscus and 87 × 104 in Navodon, whereas the total number of optic nerve fibers was about 35 × 104 and 70 × 104, respectively.

The retinal ganglion cells labeled with HRP were classified into six types according to such morphological characteristics as size, shape, and location of the soma as well as dendritic arborization pattern. Type I cells have a small round or oval soma in the ganglion cell layer and a small dendritic field in the inner plexiform layer. Type II cells are similar to type I cells, but the dendrites arborize more closely to the ganglion cell layer in the innermost region of the inner plexiform layer. Type III cells have a medium‐sized round soma in the ganglion cell layer, and the dendrites extend in an extremely wide area in the inner plexiform layer with few branches. Type IV cells have a large soma which is located in the ganglion cell layer. Dendrites emanate from the soma in all directions, branching out several times within a rather small region in the innermost part of the inner plexiform layer. Type V cells have large somata of various shapes, usually dislocated to the inner plexiform or granular layer. The dendrites extend in every direction and occupy an extremely large area in the inner plexiform layer. Type VI cells have the largest somata, which are also dislocated to the inner plexiform or granular layer. Type VI cells have a characteristic triangular or fan‐shaped dendritic field.

Soma size and the axon diameter are intimately linked, that is, small somata of type I and II cells give off thin axons, and large somata of type V and VI give off thick axons. Medium‐sized somata of type III cells or large somata of type IV cells, which have rather small dendritic fields, give off medium‐sized axons. The histograms of the soma areas in the whole retina are quite similar to the histograms of the diameters of the optic nerve fibers.
Anterior thalamic afferents from the mamillary body and the limbic cortex in the rat
Authors: Seki Makoto , Zyo Katuya
Published: January 2005

Anterior thalamic afferents from the mamillary body and the limbic cortex were studied by using single and double retrograde transport methods in the rat. The medial mamillary nucleus was divided on the basis of the cytoarchitecture into four subnuclei: the pars medialis centralis, pars medialis dorsalis, pars lateralis, and pars basalis. Extensive connections were seen between each of these subdivisions of the mamillary body and the anterior thalamic nuclei, topographically organized so that the anteromedial thalamic nucleus receives projections exclusively from the pars medialis centralis, while the anteroventral thalamic nucleus receives projections from the pars medialis dorsalis and pars lateralis. Nuclei in the dorsal half of these two mamillary subdivisions project predominantly to the medial half of the anteroventral thalamic nucleus, and those in the ventral half to the lateral half of the nucleus. The pars basalis was found to have numerous projections to the magnocellular part of the anteroventral nucleus.

All limbic cortical areas send projections bilaterally to all regions of the anteromedial nucleus as well as to the parvicellular parts of the anteroventral thalamic nucleus, while the anterodorsal nucleus receives ipsilateral projections originating exclusively from the preagranular, anterior limbic, and cingular regions. The magnocellular part of the anteroventral nucleus, however, receives only ipsilateral projections from all of the limbic cortex. Some neurons in the infralimbic region also project bilaterally to all of the anterior thalamic nuclei except the anterodorsal nucleus. All of these cortical projections to the anterior thalamus originate in layers V and VI of the limbic cortex.
The effects of partial retinal lesions on activity and size of cells in the dorsal lateral geniculate nucleus
Authors: Eysel U. T. , Wolfhard U.
Published: January 2005

The nasal parts of the adult cat retina were photocoagulated. In the dorsal lateral geniculate nucleus (dLGN) the projection of the remaining innervation was shown by anterograde transport of 3H‐proline after eye injections. The neuronal activity was measured from single cells across the border region between innervated and deafferented parts of layer A of the dLGN contralateral to the lesions. A gradual decrease from normal light‐excitability to total inexcitability was observed over a range of 300 μm. The perikaryal cell sizes measured in the same part of the dLGN displayed a concomitant decrease. Blockage of the afferent impulses by chronic application of tetrodotoxin did not change the results, suggesting that it is the loss of connections, not the loss of activity, that produces the transneuronal atrophy in the adult cat dLGN.
Postnatal development of neurons containing choline acetyltransferase in rat spinal cord: An immunocytochemical study
Authors: Phelps P. E. , Barber R. P. , Houser C. R. , Crawford G. D. , Salvaterra P. M. , Vaughn J. E.
Published: January 2005

A monoclonal antibody to choline acetyltransferase (ChAT) has been used in an immunocytochemical study of the postnatal development of ChAT‐containing neurons in cervical and thoracic spinal cord. Specimens from rat pups ranging in age from 1 to 28 days postnatal (dpn) were studied and compared with adult specimens (Barber et al., '84). The development of established cholinergic neurons, the somatic motoneurons and sympathetic preganglionic cells, has been described as has that of previously unidentified ChAT‐positive neurons in the dorsal, intermediate, and central gray matter.

Cell bodies of somatic and visceral motoneurons contained moderate amounts of ChAT‐positive reaction product at birth that gradually increased in intensity until 14–21 dpn. The most intensely stained ChAT‐positive neurons in 1–5‐dpn specimens were named partition cells because this cell group extended from the central gray to an area dorsal to the lateral motoneurons, and thereby divided the spinal cord into dorsal and ventral halves. Partition cells were medium to large in size with 5–7 primary dendrites, and axons that, in fortuitous sections, could be traced into the ventrolateral motoneuron pools, the ventral funiculi, or the ventral commissure. Small ChAT‐positive cells clustered around the central canal and scattered in laminae III–VI of the dorsal horn were detectable at birth. These neurons were moderately immunoreactive at 11–14 dpn and intensely ChAT positive by 21 dpn. The band of ChAT‐positive terminal‐like structures demonstrated in lamina III of adult specimens (Barber et al., '84) was first visible in 11–14‐dpn specimens. By 28 dpn, both laminae I and III contained punctate bands that approximated the density of those observed in adult spinal cord.

This investigation has demonstrated ChAT within individual neurons of developing spinal cord, and has identified a group of neurons, the partition cells, that exhibit intense ChAT‐positive immunoreactivity earlier than any other putative cholinergic cells in spinal cord, including motoneurons. Another important observation has been that each ChAT‐positive neuronal type achieves adult levels of staining intensity at different times during development. A likely explanation for this differential staining is that various groups of neurons acquire their mature concentration of ChAT molecules at different developmental stages. In turn, this may correlate with the maturation of cholinergic synaptic activity manifest by individual cells or groups of neurons.
The central projections of intracellularly labeled auditory nerve fibers in cats
Authors: Fekete D. M. , Rouiller E. M. , Liberman M. C. , Ryugo D. K.
Published: January 2005

The central projections of physiologically characterized auditory nerve fibers were studied in the cochlear nuclei of adult cats after intracellular staining with horseradish peroxidase (HRP). This technique consistently labels only the type I spiral ganglion neurons which contact inner hair cells in the cochlea (Liberman and Oliver, '84). The central axon of each type I neuron bifurcates in the cochlear nucleus to form an ascending branch and a descending branch. The characteristic frequency (CF) of a fiber corresponds to the dorsoventral position of these major branches and their collateral ramifications within the nucleus. Fibers of low CFs are distributed ventrally, and fibers of increasing CF are distributed progressively more dorsally. In some cases, the collateral branches deviate from this tonotopic arrangement, particularly in (1) the octopus cell region of the posteroventral cochlear nucleus, (2) the zone of bifurcations of the auditory nerve fibers, and (3) the anterior, dorsal, and lateral margins of the ventral cochlear nucleus. Spontaneous discharge rate (SR) is related to the complexity of the axon arbor, especially along the ascending branch. Fibers of low and medium SR exhibit more axonal branch points and longer collateral lengths than do those with high SR. Six of 37 labeled fibers fail to innervate the dorsal cochlear nucleus, a feature apparently unrelated to CF or SR.
Distribution of somatic and visceral primary afferent fibres within the thoracic spinal cord of the cat
Authors: Cervero F. , Connell Lynne A.
Published: January 2005

Transport of horseradish peroxidase (HRP) through somatic and visceral nerve fibres was used to study the patterns of termination of somatic and visceral primary afferent fibres within the lower thoracic segments of the cat's spinal cord. A concentrated solution of HRP was applied for at least 5 hours to the central end of the right greater splanchnic nerve and of the left T9 intercostal nerve of adult cats. Some animals remained under chloralose anaesthesia for the duration of the HRP transport times (up to 53 hours) whereas longer HRP application and transport times (4–5 days) were allowed in animals that recovered from barbiturate anaesthesia.

Somatic afferent fibres and varicosities (presumed terminals) were found in laminae I, II, III, IV, and V of the ipsilateral dorsal horn and in the ipsilateral Clarke's column. The Density of the somatic projection was particularly high in the superficial dorsal horn. In parasagittal sections of the cord, bundles of somatic fibres were seen joining the dorsal horn from the dorsal roots via the dorsal columns and Lissauer's tract. A mediolateral somatotopic arrangement of somatic afferent terminations was observed, with afferent fibres from the ventral parts of the dermatome ending in the medial dorsal horn and afferent fibres from the dorsal parts of the dermatome ending in the lateral dorsal horn. The total rostro‐caudal extent of the somatic projection through a single spinal nerve was found to be of 2 and 2/3 segments, including the segment of entry, the entire segment rostral to it and two‐thirds of the segment caudal to it. A lateral to medial shift in the position of the somatic projection was observed in the rostro‐caudal axis of the cord.

Visceral afferent fibres and varicosities (presumed terminals) were seen in laminae I and V of the ipsilateral dorsal horn. The density of the visceral projection to the dorsal horn was substantially lower than that of the somatic projection. Visceral afferent fibres reached the dorsal horn via Lissauer's tract and joined a lateral bundle of fine fibres that run along the lateral edge of the dorsal horn. The substantia gelatinosa (lamina II) appeared free of visceral afferent fibres.

These results are discussed in relation to the mechanisms of viscerosomatic convergence onto sensory pathways in the thoracic spinal cord.
Ultrastructural localization of acetylcholinesterase in substantia nigra: A comparison between rat and guinea pig
Authors: Henderson Zaineb , Greenfield Susan A.
Published: January 2005

The distribution and ultrastructural localization of acetylcholinesterase (AChE) was examined in the substantia nigra of rat and guinea pig. Although the pars compacta, in both species, is clearly defined when stained with thionin, there is an apparent discrepancy in the distribution of AChE at the light microscope level. In the rat substantia nigra the enzyme appears to be concentrated mainly in the pars compacta, whereas in the guinea pig the AChE seems homogenous throughout the entire substantia nigra. Ultrastructural studies, however, reveal a close correspondence in the morphology of rat and guinea pig substantia nigra. The subcellular localization of AChE is also similar. The between‐species discrepancy seen with the light microscope was attributed to relative differences in level of intensity of staining for AChE. In both rat and guinea pig, the enzyme is localized in two types of neuron and in the extracellular space. The ultrastructural distribution of AChE is discussed with reference to neurochemical studies on its release from nigral neurons.
Connections of the auditory midbrain in a teleost fish, Cyprinus carpio
Authors: Echteler Stephen M.
Published: January 2005

Central auditory pathways were traced in Japanese carp, Cyprinus carpio, using electrophysiological mapping and HRP tract‐tracing methods. Multiunit recordings made from the carp torus semicircularis, the major midbrain area for processing octavolateralis information, revealed a mediolateral segregation of auditory and lateral line sensory modalities. Iontophoretic injections of HRP were made into the medial torus to trace afferent and efferent projections of the carp auditory midbrain.

Following unilateral HRP injections into the medial torus, retrogradely labeled neurons were observed within six nuclei of the carp medulla. Two octaval nuclei, the anterior octavus nucleus and descending octavus nucleus, contained HRP‐filled neurons. Labeled neurons were also observed within the ipsilateral superior olive, scattered among fibers of both lateral lemnisci, and bilaterally within the medullary reticular formation. In addition, bilateral retrograde cell labeling was found within a group of Purkinje‐like cells located adjacent to the IVth ventricle, just rostral to the level of the VIIIth nerve. Few labeled neurons were found within the nucleus medialis, a principal target for lateral line afferents within the medulla. At midbrain levels, retrogradely labeled neurons were observed within the contralateral torus semicircularis and the ipsilateral optic tectum. Three forebrain nuclei project to the carp auditory midbrain. Within the diencephalon, descending projections originate from the anterior tuberal nucleus, bilaterally, and from the ipsilateral central posterior thalamic nucleus. The ipsilateral caudal telencephalon also projects to the carp auditory midbrain via large multipolar neurons within area dorsalis pars centralis.

Anterograde labeling of fibers and terminals revealed efferent projections of the carp auditory midbrain to the following targets: the ipsilateral superior olive, the ipsilateral medullary reticular formation, the deep layers of the optic tectum, the contralateral torus semicircularis, the anterior tuberal nucleus, and the central posterior thalamic nucleus.

These results, together with recent studies of lateral line pathways in teleosts (Finger, '80, '82a), demonstrate that central auditory and lateral line pathways are anatomically distinct in the carp, at least from medullary to diencephalic levels. Furthermore, there are striking similarities in the organization of the central auditory pathways of the carp and those of amphibians and land vertebrates.
Organization of thalamic projections in the nucleus accumbens and the caudate nucleus in cats and its relation with hippocampal and other subcortical afferents
Authors: Jayaraman A.
Published: January 2005

The organization of thalamic projections in the nucleus accumbens (NA) and the caudate nucleus of cats and its relation to other subcortical striatal afferents Were studied with a retrograde tracing technique by use of lectin‐conjugated horseradish peroxidase.

The study showed that the paraventricular and medial parafascicular nuclei (PF) of the thalamus project to the medial NA and the parataenial and medial PF project to the lateral NA. The ventral tegmental area and substantia nigra pars dorsalis (SNpd) project to medial and lateral NA. The midline thalamic nuclei, rostral intralaminar nuclei, ventroanterior nucleus, medial and lateral PF, lateral posterior complex, and nucleus limitans project to medial caudate nucleus. The most medial substantia nigra pars compacta (SNpc) and rostral SNpd project to medial caudate nucleus. The center median, ventrolateral, and the central lateral nuclei of thalamus, SNpc, and SNpd project to lateral caudate nucleus.

These results suggest that the thalamic and subcortical nuclei known to connect with the limbic and frontal cortices project to NA and medial caudate nucleus. Those thalamic nuclei connected with the motor system project to lateral caudate nucleus. The hippocampus projects selectively to medial NA. The amygdala, raphe, and other mesencephalic nuclei project only to NA and medial caudate nucleus. The organization of hippocampal, amygdala, and other subcortical afferents suggests that NA and caudate nucleus can be separated into medial “limbic” and lateral nonlimbic “sensory‐motor” compartments, A brief review of the distribution pattern of some neurotransmitters, neuropeptides, and their receptors and behavior studies provides additional support to the concept that the striatum can be divided into several subcompartments.
Primary afferent projections of the major splanchnic nerve to the spinal cord and gracile nucleus of the cat
Authors: Kuo David C. , de Groat William C.
Published: January 2005

Splanchnic afferent projections to the spinal cord and gracile nucleus were labeled following the application of HRP to the central cut end of the major splanchnic nerve. Labeled afferent fibers were detected in the ipsilateral dorsal column, in Lissauer's tract (LT), in laminae 1, 5, 7, and 10, and in the dorsal gray commissure at T1–T13 levels of the spinal cord. Afferent projections were not identified in laminae 2–4. Collaterals from LT projected ventrally along the lateral and medial margins of the dorsal horn (called lateral and medial pathways, respectively). Afferents in the lateral pathway formed small bundles, spaced rostrocaudally at intervals of 300–1,000 μm, which passed medially at the base of the dorsal horn into laminae 5, 7, and 10 and to the cortralateral spinal cord. Some afferents in the lateral pathway projected to the intermediolateral nucleus where labeled sympathetic preganglionic neurons were located. Afferents in the medial pathway entered the lateral aspect of the dorsal column and projected as a group near the midline rostrally to the medulla. The dorsal column pathway terminated in the ventral gracile nucleus in four or five clusters, each occupying a region ranging in size from 0.01–0.1 mm3and separated in the rostrocaudal axis by distances of 400–800 μm. These clusters were concentrated in the middle and caudal portions of the nucleus below the obex.

A comparison of the present results with those from earlier experiments on the central projections of afferent fibers from the heart, kidney, and pelvic organs demonstrates a consistent pattern of visceral afferent termination in the thoracolumbar and sacral segments of the spinal cord. This is not unexpected, since visceral afferent pathways to different organs perform similar functions, such as the transmission of nociceptive information and the initiation of autonomic reflexes.
Quantitative electron microscopic observations on the non‐neuronal cells and lipid droplets in the posterior funiculus of the cat after dorsal rhizotomy
Authors: Franson Peter
Published: January 2005

Adult cats were subjected to unilateral dorsal L6, L7, and S1 rhizotomies. After survival times of 1–1,552 days the different glial cell types, the perivascular cells, and the lipid droplet content of each cell type were studied quantitatively at the ultrastructural level in sections from the posterior funiculus at the L1 level.

The number of astrocytes did not appear to change during the degeneration process. From 105 days postoperatively (p.o.), a marked reduction in the oligodendroglial cell population was observed. The number of microglial cells increased from 5 days p.o. onward. A large increase was observed particularly between 20 and 160 days p.o. The occurrence of pericytes was unchanged during the degeneration but the number of non‐pericytic perivascular cells/blood vessel was increased from 10 days p.o. onward.

The number of lipid droplets in the microglial cells increased early during the degeneration period. Subsequently an increase in lipid droplet number was observed in the astrocytes and somewhat later also in the non‐pericytic perivascular cells. These findings have been interpreted to reflect a redistribution of lipid droplet material from the degenerating white matter to cells in the perivascular space during the observed time period.
Number and distribution of stapedius motoneurons in cats
Authors: Joseph Michael P. , Guinan John J. , Fullerton Barbara C. , Norris Barbara E. , Kiang Nelson Y. S.
Published: January 2005

Cell bodies of stapedius motoneurons were identified by retrograde transport of horseradish peroxidase (HRP) following injections into the stapedius muscle. Large injections were made in an attempt to label all stapedius motoneurons. To control for labeling of non‐stapedial neurons resulting from spread of HRP, we determined the locations of brainstem neurons labeled by HRP applied to the facial nerve, the chorda tympani nerve, the auricular branch of the vagus nerve, the tensor tympani muscle, and the cochlea. In three cats analyzed in detail, 1,133–1,178 neurons projecting to the stapedius muscle were identified. Arguments are given which suggest that in these three cats all stapedius motoneurons were labeled. The labeled stapedius neurons may all be motoneurons because they all stain positively for acetylcholinesterase and have medium–coarse Nissl bodies. Most stapedius motoneurons were located around the motor nucleus of the facial nerve. Stapedius motoneurons were also found near the descending limb of the facial‐nerve root, in the peri‐olivary neuropil, and in the reticular formation with the ascending fibers of the facial‐nerve root.
Representation of whisker follicle intrinsic musculature in the facial motor nucleus of the rat
Authors: Klein Bradley G. , Rhoades Robert W.
Published: January 2005

Retrograde transport of wheatgerm‐agglutinin horseradish peroxidase (WGA‐HRP) and fluorescent tracers (true blue‐TB, nuclear yellow‐NY, and diamidino yellow‐DY) from isolated whisker follicles was used to define the somatotopic organization of the facial (VII) motoneurons which innervate the intrinsic follicle muscles. Motoneurons supplying these muscles were restricted almost completely to the lateral (Martin and Lodge, 1977) facial subnucleus and the motoneurons which innervated a given follicle were distributed over the entire length of this subnucleus. Cells projecting to dorsal (A‐row) follicles were located in the most lateral part of the lateral subnucleus, while those supplying ventral (E‐row) follicles were restricted to the medial part of the subnucleus. Injections of different tracers into rostral and caudal follicles within a given row revealed no somatotopic representation of the rostrocaudal axis of the whiskerpad. Additional control experiments demonstrated that some of the labelling obtained with WGA‐HRP resulted from spread of this tracer to extrinsic muscles. This was not the case with the fluorescent tracers. The results of the control experiments suggested further that a significant percentage of the motoneurons in the lateral facial subnucleus innervate only intrinsic follicle muscles.
Ontogeny of the visual system in the cuttlefish, sepiella japonica. II. Intramembrane particles, histofluorescence, and electrical responses in the developing retina
Authors: Yamamoto Masamichi , Takasu Nobuo , Uragami Itsuo
Published: January 2005

To study molecular and functional differentiation of photoreceptive membranes, the development of the retina in embryos of the cuttlefish, Sepiella japonica, was examined by the freeze‐fracture technique, by histofluorescence of retinal‐related protein, and by electrical responses to photic stimulation. P‐face particles in the microvillar plasma membrane of the receptor cell increased in density from about 2,000/μm2 to about 6,000/μm2 during the early stages of rhabdomere formation (from stage 31 to stage 36). The size distribution of P‐face particles in the microvillar and the cell body plasma membranes showed a similar monomodal pattern with a peak at 8 nm in diameter from stage 31 to 33. In the cell body plasma membrane, the size distribution pattern hardly changed throughout later stages, but in the microvillar membrane, the peak shifted progressively to 9 nm (stages 35 and 36) and then to 10 nm (stage 37). The histofluorescence of reduced rhodopsin was first visible at stage 36 in the layer of growing apical processes. The fluorescence of reduced retinochrome first appeared faintly at stage 40 on both sides of the basal lamina. Electroretinograms (ERGs) were first obtained at stage 34 when many microvilli appeared from the apical processes, increasing rapidly in amplitude with increase in regularity of the microvillar arrangement from stage 35 to 36. Early receptor potentials (ERPs) elicited by a bright light flash were first recorded at the earliest stage of the apical process formation (stage 30), increasing gradually in amplitude during development. The increase was correlated with an increase in the total number of P‐face particles in the microvillar membrane within the retina. These findings suggest that the P‐face particles in the microvillar membrane are associated with rhodopsin, that the receptor cells have a small amount of rhodopsin before rhabdomere formation, and that differentiation of the apical plasma membrane of the receptor cells into the functional photoreceptive membrane occurs in conjunction with its morphological differentiation into rhabdomeres.
The formation of the axonal pattern in the embryonic avian retina
Authors: Halfter Willi , Deiss Silvia , Schwarz Uli
Published: January 2005

Both the polarity of the axonal growth and the formation of the optic fiber pattern early in retinal morphogenesis were studied in silver stained whole mounts of embryonic chick, quail, and pigeon retinae. The surface area of the retina and of the optic fiber layer increases in size exponentially, the optic fiber layer expanding faster than the retina. The optic fiber layer covers the retinal surface at E5 in quail and at E6 in chick and pigeon. In all species studied, the retinal fiber layer does not expand homogeneously with the optic nerve head as the center. Instead, the retinal fiber layer enlarges with polarities in the dorsal to ventral and nasal to temporal direction. The very first axon bearing ganglion cells appear at stage 16 in the dorsal and central portion of the retina and grow ventrally to merge at the optic disk. From stage 23 on, the optic fiber layer expands faster in the temporal than in the nasal side. Measurements on the initial polarization of young axonal processes show that the axonal growth is directed toward the optic fissure and the optic nerve head. This growth polarization is found at the onset of growth cone formation and in axons far from the nearest ganglion cells or ganglion cell axons. Therefore axon‐axon interaction cannot be involved in the initial axon orientation early in retinal morphogenesis.