bluuebunny/crossref_metadata_2025 huggingface dataset:
Neuroanatomical effects of neonatal transection of the corpus callosum in hamsters
Authors: Lent Roberto
Published: January 2005

Newborn hamsters were subjected to surgical transection of their corpora callosa under hypothermic anesthesia. After completion of their development, one group of animals had their brains prepared for cyto‐ and myeloarchitectonic analysis. Another group had a small pellet of polyacrylamide gel containing horseradish peroxidase (HRP) implanted in different cortical loci. All were perfused with fixatives and had their brains cut into serial sections. The operated brains showed the following anatomical features: (1) The corpus callosum was partially or totally absent; (2) an abnormal longitudinal bundle was present bilaterally underneath the white matter; and (3) except for the physical displacement of some medial structures, the general architecture of the brain appeared unchanged. Analysis of HRP material revealed that (1) the longitudinal bundle contains cortical fibers, of which at least some are commissural; (2) these cortical fibers display a topographic arrangement within the bundle. Results suggest that brain anatomy of “surgical” acallosal hamsters compares closely with that observed in mice with congenital defects of the corpus callosum, a spontaneous condition which also occurs in humans.
Adult testosterone levels influence the morphology of a sexually dimorphic area in the mongolian gerbil brain
Authors: Commins Deborah , Yahr Pauline
Published: January 2005

This research shows that the medial preoptic area‐anterior hypothalamus (MPOA‐AH) of the gerbil contains a sexually dimorphic area (SDA) whose morphology is influenced by adult gonadal steroids. The characteristics of the SDA were studied initally in gonadally intact males and females and later in males and females that had been gonadectomized or gonadectomized and given testosterone. Coronal sections through the MPOA‐AH were stained with thionin to visualize the SDA. In male gerbils, the SDA is a darkly staining, hook‐shaped structure on either side of the third ventricle, above the suprachiasmatic nuclei and below the anterior commissure. Within the male SDA lies a small, dense cluster of cells, the SDA pars compacta (SDApc). In female gerbils, the SDA is more ovoid and diffuse and the SDApc is absent. Camera lucida tracings and planimeter measurements of the SDA showed that the total volume of the SDA is similar in the two sexes, but the proportion of the SDA that stains darkly and/or stands out clearly from the surround (dark volume) is larger in males. Gonadectomy decreases both total and dark volume of the SDA in both sexes and decreases the volume of the SDApc in males. Testosterone treatment prevents these changes. This is the first report of changes in the gross morphology of the mammalian brain after steroid hormone manipulations in adulthood. The changes in the SDA may be related to testosterone activation of scent marking behavior.
Dorsal cochlear nucleus projections to the inferior colliculus in the cat: A light and electron microscopic study
Authors: Oliver Douglas L.
Published: January 2005

In the Present report retrograde and anterograde labeling techniques are used to study the Projections of the dorsal cochlear nucleus (DCN) to the inferior colliculus in the cat. Horseradish peroxidase (HRP) or wheat germ agglutinin (WGA‐HRP) injections into the inferior colliculus produce large numbers of labeled neurons in the DCN on the opposite side. Labeled cells with projections to the colliculus are identified as fusiform and giant cells and are organized into rostrocaudal bands. The axons of these DCN neurons are labeled by anterograde transport of 3H‐leucine and/or proline and studied in light and electron microscopic autoradiographs. Axons from the DCN terminate within the central nucleus of the inferior colliculus in densely labeled, rostrocaudally oriented bands. Less heavily labeled extensions of these bands are found in the deepest layer of the dorsal cortex, and light labeling is found adjacent to the bands in the central nucleus and in the ventrolateral nucleus. Cells in the dorsomedial DCN project to the most ventromedial part of the central nucleus while progressively more ventrolateral cells in the DCN project to more dorsolateral parts of the central nucleus. This present evidence suggests that the DCN sends afferents to only two of the four subdivisions of the central nucleus. Within these regions, the axons from the DCN form terminal boutons or boutons de passage characterized by medium‐sized, round synaptic vesicles. The labeled endings nearly always make asymmetric synaptic contacts on the dendrites of disc‐shaped and stellate cells in the central nucleus. A few axosomatic contacts are found on one particular cell type, possibly the stellate variety.

The results support the hypothesis that each subdivision of the central nucleus receives afferents from a different set of cell types in the auditory nuclei of the lower brainstem. The banding patterns of the efferent cells in the cochlear nucleus and the axons within the central nucleus suggest that these inputs are congruent to the fibrodendritic layers of the central nucleus and may contribute to tonotopic organization in the central nucleus. Finally, the results suggest that each of the two major classes of cells in the central nucleus receives different patterns of inputs from the DCN. These morphological differences could contribute to different electrophysiological responses to the sound stimuli by these cells.
The descending and intrinsic serotoninergic innervation of an elasmobranch spinal cord
Authors: Ritchie T. C. , Roos L. J. , Williams B. J. , Leonard R. B.
Published: January 2005

The descending and the intrinsic components of the Serotoninergic (5HT) innervation of the Atlantic stingray spinal cord were described by comparing the distributions of neuronal elements exhibiting 5HT‐like immunoreactivity (peroxidase‐antiperoxidase method) in sections caudal and rostral to spinal transections. The cells of origin of the descending 5HT system were located with a double labeling method for both retrogradely transported horseradish peroxidase (HRP) and 5HT staining.

The descending system provides virtually the entire 5HT innervation of the dorsal horn, the intermediate zone, and the dorsal and lateral portions of the ventral horn. Fibers of the descending 5HT system course in the lateral funiculus, the dorsal portion of the ventral funiculus, and in the submeningeal zones of the dorsal and lateral aspects of the spinal cord. This projection primarily originates from the 5HT cell groups of the caudal rhombencephalon (groups II and III; Ritchie et al., '83), with a minor contribution from group IV in the rostral rhombencephalon. The organization of the descending 5HT system in stingrays is remarkably similar to that of mammals.

The intrinsic spinal 5HT system consists of cells distributed in the ventromedial spinal cord that have processes extending longitudinally in a ventral submeningeal fiber network. Fibers were traced from the submeningeal system to the ventral horn, where varicose processes were restricted largely to the neuropil ventral to the somata of the fin motoneurons. The existence of a well‐defined intrinsic 5HT system in stingrays supports the hypothesis that such a system exists in the spinal cords of a variety of vertebrates.
Optic axons ignore denervated foreign territory in goldfish tectum
Authors: Marotte L. R.
Published: January 2005

Ultrastructural morphometry was used to test firstly, whether regenerating optic axons in goldfish tectum will form connections in adjacent denervated foreign territory and secondly, whether intact optic axons will collaterally sprout to innervate this territory. The stratum fibrosum marginale of the tectum was partially denervated by removing the torus longitudinalis and cutting the tectal commissure. Optic axons do not normally synapse in this layer. Thirty days after partial denervation and optic tract section the numbers of normal synapses in a μm2 column through the stratum fibrosum marginale reached a minimum and then started to increase so that by 159–173 days after the operation they had returned to control levels. Optic terminals, recognised by their degeneration after optic nerve section, did not contribute to these increasing numbers of synapses. Instead, optic axons preferentially reinnervated their normal tectal layers. Similarly, there was no evidence of collateral sprouting of intact optic axons into the partially denervated stratum fibrosum marginale and numbers of normal synapses in the layer also returned to control levels. These probably arose from collateral sprouting of terminals remaining after the partial denervation, raising the possibility that optic axons were prevented from synapsing there by the rapid occupation of vacant sites by other axons. However, delaying the partial denervation with respect to the tract section did not alter the result. These results support the idea of a specific affinity between optic axons and their postsynaptic targets.
Ultrastructure of the mouse leptomeninx
Authors: Oda Yoshio , Nakanishi Isao
Published: January 2005

An electron microscopic study was made of the mouse leptomeninx with special attention to the ultrastructure of the subarachnoid space. The arachnoid membrane was divided into outer and inner layers. The outer layer was composed of elongated cells in contact with one another with numerous tight junctions. The cells in the inner layer had intricate cytoprocesses, some of which embraced the connective tissue matrix containing collagen fibers. Beneath the arachnoid membrane, there were a loose meshwork of arachnoid cells and a single layer of pial cells. No arachnoid trabeculae were found. The intercellular space of the leptomeninx except in the outer layer of the arachnoid membrane was filled with Ruthenium Red‐positive flocculent material and particles, in which various amounts of the collagen fibers and microfibrils were embedded. Elastic fibers were not identified. The subarachnoid space, which is believed to be a specialized channel exclusively containing the cerebrospinal fluid, was not recognized. These observations indicate that the cerebrospinal fluid circulates through the broad intercellular space, which contains extracellular matrix, of the leptomeninx.
Distribution of local axon collaterals of mitral, displaced mitral, and tufted cells in the rabbit olfactory bulb
Authors: Kishi Kiyoshi , Mori Kensaku , Ojima Hisayuki
Published: January 2005

To determine the projection fields of intrabulbar axon collaterals, mitral, displaced mitral, and middle tufted cells in the rabbit olfactory bulb were stained by intracellular injection of HRP. The axon collaterals of mitral cells and displaced mitral cells were distributed exclusively within the granule cell layer (GrL). Those of middle tufted cells were distributed mostly in the GrL and on rare occasions in the mitral cell layer. None of these collaterals entered the external plexiform layer.

Axon collaterals of mitral cells, emitted at the depths of the GrL, were distributed widely from the deep portion to the most superficial portion of the GrL. Collaterals of displaced mitral cells were also emitted in the deep part, but they tended to be distributed more superficially in the GrL than mitral cells. Collaterals of middle tufted cells were released and distributed superficially in the GrL.

The axon collaterals of these principal cells typically extended for a longer distance than the secondary dendrites, and they sometimes formed bushlike terminal arborizations.

The results indicate that the projection fields of the axon collaterals of principal cells are spatially separated from the dendritic projection fields. This suggests that the output of these principal cells through the collaterals has a functionally different role from the output through the dendrites. The observation that the three types of principal cells differ in the distribution pattern of their axon collaterals in the GrL suggests that there is a functional separation of the sublayers in the GrL.
Localization of forebrain neurons which project directly to the medulla and spinal cord of the rat by retrograde tracing with wheat germ agglutinin
Authors: Schwanzel‐Fukuda Marlene , Morrell Joan I. , Pfaff Donald W.
Published: January 2005

Wheat germ agglutinin (WGA) in a slow‐release polyacrylamide gel pellet was implanted in the medulla or spinal cord of the rat. Large numbers of retrogradely labeled cells were visualized by immunocytochemical procedures in specific nuclei of the forebrain mainly ipsilateral to the implant site following implants as far caudal as the sacral segments of the spinal cord. Total average number of labeled forebrain cells (three brains per category; 100 μm per 150 μm of brain tissue were examined microscopically): medulla, 2,115; cervical, 1,878; lumbar, 1,017; sacral, 385.

After WGA‐gel implants in the medulla or cervical cord the majority of retrogradely labeled neurons were seen in the lateral hypothalamic area, the zona incerta, and in subdivisions, of the paraventricular nucleus. A continuum of labeled cells extended from the caudal part of the paraventricular nucleus into the posterior hypothalamus and into the central gray of the midbrain. Labeled cells were also seen in the medial basal hypothalamus and the rostral part of the bed nucleus of the stria terminalis. A few labeled cells were observed in the medial and lateral preoptic areas, the rostral part of the paraventricular nucleus, and in the arcuate nucleus.

Following WGA‐gel implants in the lumbar or sacral cord many retrogradely labeled cells were observed mainly in the paraventricular nucleus, the lateral hypothalamus, zona incerta, medial basal hypothalamus, and posterior hypothalamic area. The continuum of labeled cells described above was also seen following these implants.

Our data indicate that the lateral hypothalamus and zona incerta, as well as specific parts of the paraventricular nucleus, are major loci of neurons which project directly to the medulla and spinal cord of the rat. The consistency with which labeled cells were localized across all brains examined within categories of implant sites and the large numbers of labeled cells counted within these areas appeared to verify the sensitivity of our retrograde tracing method. Therefore, we interpret the paucity or absence of labeled cells in particular brain regions to indicate that cells of these regions do not project to the medulla or spinal cord.
Effects of permeability of midtectal barriers in goldfish on compression of the visuotectal projection rostrally and regenerative escape caudally
Authors: Edwards M. A. , Jacobson M.
Published: January 2005

Physiological mapping and anatomical methods were used to evaluate changes in the retinotectal projection of goldfish 16–200 days after insertion of permeable or impermeable barriers that bisected the tectum into rostral and caudal halves. The projection to rostral tectum was left intact. Barriers composed of Gelfilm or impermeable Nucleopore material induced within 2–3 months an orderly compression of the visual field representation in rostral tectum only slightly less complete than that observed in animals with caudal half‐tectal ablation. In contrast, Nucleopore filter barriers with 0.1‐μm or 8‐μm holes did not cause significant compression.

According to both mapping and autoradiographic tracing, reinnervation of tectum behind the barriers occurred among all groups within 1–2 months. Physiologically, the projection caudal to permeable barriers was typically complete and appropriate, whereas the caudal projection in fish with impermeable barriers eventually consisted of a greatly expanded representation of the extreme temporal visual field. Autoradiography, normal fiber impregnations, and the orthograde horseradish peroxidase method revealed that regeneration past the barriers involved the formation of large bundles passing vertically along the cut Loctal margin and through the underlying valvula cerebelli or lateral tegmentum.

The simultaneous rostral compression and caudal expansion in the visual representation formed when more impermeable barriers were used provides evidence that, in addition to the influence of position‐dependent properties, axonal competition for target territory contributes to the control of the distribution of optic arbors. Further research is required to determine why reinnervation of tectum caudal to the more permeable barriers was more complete with respect to visual representation.
Axonal projections of mechanosensory neurons in the connectives and peripheral nerves of the leech, Haemopis marmorata
Authors: Johansen Jørgen , Hockfield Susan , McKay Ronald D. G.
Published: January 2005

The axonal projections of the seven mechanosensory neurons in the connectives and peripheral nerves were examined by horseradish peroxidase (HRP) injections.

In the connective the closely functionally related mechanosensory neurons travel in two bilaterally symmetrical regions, which comprise less than 10% of the connective's cross‐sectional area. This grouping may reflect the similar functional properties and synaptic connections of the cells.

Serial sections through the neuropil‐connective junction zone showed that the organization of the axons is independent of glial fasciculation. Fascicles are not rigid structures; they were found to part and fuse in a seemingly random manner. The glial cell seems therefore to have only a supportive structural function and not to play any role in axonal guidance or to define any specific nerve fascicles in the leech.

The projections of the mechanosensory cells in the peripheral roots were not as stereotyped as in the connective. However, examination of the branching of the medial and lateral P cells in the posterior root showed that the roots are highly structured and that some axons may be confined to tracts which have specific positions related to the branching of the root. The possible role of the P cells in pioneering these tracts is discussed.
The neural substrate for the pupillary light reflex in the pigeon (Columba livia)
Authors: Gamlin Paul D. R. , Reiner Anton , Erichsen Jonathan T. , Karten Harvey J. , Cohen David H.
Published: January 2005

The neural substrate of the pupillary light reflex in the pigeon was investigated using anatomical, stimulation, and lesion techniques. In birds, as in mammals, the sphincter pupillae muscle (which constricts the iris) is innervated by cells in the ciliary ganglion (Pilar and Tuttle, '82). These cells are in turn innervated by cells in the Edinger‐Westphal nucleus (EW) (Cowan and Wenger, '68; Narayanan and Narayanan, '76; Lyman and Mugnaini, '80). The efferent link of the pupillary light reflex must therefore involve cells in EW. To study the central course of this reflex pathway, injections of horseradish peroxidase (HRP) were placed in EW. These injections labeled cells in a number of regions including a contralateral pretectal nucleus, area pretectalis (AP). Only a limited number of cells in AP project to EW. Injections of tritiated amino acids into AP labeled a discrete region of the contralateral EW. This projection is confined to a dorsolateral region of caudal EW and overlies the somata of approximately 100 cells. Tritiated proline was injected into the eye, and the results confirmed an earlier report (Reperant, '73) that AP receives retinal input from the contralateral eye. Immunohistochemical studies demonstrated fibers in AP that stained positively for Substance‐P‐like, enkephalin‐like and tyrosine‐hydroxylase‐like immunoreactivity. Injections of HRP were placed in AP to examine the retinal ganglion cells mediating the reflex. Cells with an average diameter of approximately 14 μm (5–25 μm range) were labeled and averaged approximately 6 μm greater in diameter than the retinal ganglion cells (mean = 7.3 μm) labeled by an optic chiasm injection. The cells labeled by AP injections were distributed unevenly throughout the retina with a higher concentration in the central and temporal retina and a paucity in the red field and fovea. Our results demonstrate that AP receives input from a distinct sub‐population of large retinal ganglion cells that comprises a very small percentage of the total population of retinal ganglion cells. Unilateral lesions of AP abolished the pupillary light reflex in the eye contralateral to the lesion; stimulation of AP elicited pupilloconstriction in the eye contralateral to the stimulation site.

These results delineate the central course of the pupillary light reflex pathway in the pigeon and identify the retinal ganglion cells that subserve this reflex. They show that, at every point in the pathway, only a few cells mediate this simple reflex. These studies have allowed us to compare the pupillary light reflex pathway in the pigeon and monkey, and based on recent anatomical studies in the monkey (Steiger and Buttner‐Ennever, '79; Magnuson et al., '80), we propose that the central course is similar in both species and that the projection from the pretectum to EW is entirely crossed.
Olivary projections from the mesodiencephalic structures in the cat studied by means of axonal transport of horseradish peroxidase and tritiated amino acids
Authors: Onodera Satoru
Published: January 2005

By means of horseradish peroxidase (HRP) and autoradiographic methods, olivary projections from mesodiencephalic structures were studied in the cat.

Following HRP injections in various parts of the inferior olive, many cells were labeled ipsilaterally in the nucleus of Darkschewitsch, the nucleus accessorius medialis of Bechterew, the nucleus of the fields of Forel, and the subnucleus dorsomedialis and ventrolateralis of the parvocellular red nucleus. Some labeled cells also occurred ipsilaterally in the suprarubral reticular formation and a few labeled cells in the interstitial nucleus of Cajal.

After injection of tritiated amino acids in different parts of the mesodiencephalic region mentioned above, labeled fibers were found in different parts of the inferior olive, presenting a high degree of the topographic correlation within the mesodiencephalo‐olivary projection, which was exclusively ipsilateral. That is, the nucleus of Darkschewitsch was found to project to the rostral half of the medial accessory olive and the dorsomedial cell column. There was mediolateral topographic relation in this projection. The nucleus accessorius medialis of Bechterew was found to project to the ventral lamella and the lateral part of the dorsal lamella as well as to a small rostromedial part of the caudal half of the medial accessory olive. The subnucleus dorsomedialis and ventrolateralis of the parvocellular red nucleus projected to the rostral and caudal halves, respectively, of the medial part of the dorsal lamella. The subnucleus ventrolateralis of the parvocellular red nucleus also sent fibers to the lateral part of the ventrolateral outgrowth. The nucleus of the fields of Forel, suprarubral reticular formation, and interstitial nucleus of Cajal appeared to project to the caudal half of the medial accessory olive, the medial part of the ventrolateral outgrowth, the rostral part of the dorsal cap, and the caudal part of the dorsal accessory olive.
Glycinergic neurons in the human retina
Authors: Frederick Jeanne M. , Rayborn Mary E. , Hollyfield Joe G.
Published: January 2005

Neurotransmitter‐specific properties of glycinergic neurons in the human retina were studied using 11 pairs of eyes from donors ranging from 21/2 to 54 years in age. A mean endogenous level of 10.3 nmoles glycine per mg protein was measured by amino acid analysis in retinas isolated within 1 hour postmortem. When retinas were incubated with 3H‐glycine (2 μM) and processed for autoradiography, label was found associated with neurons whose somata reside within the inner nuclear layer. Some heavily labeled neurons located at the vitread border of the inner nuclear layer were identified as amacrine cells based on ultrastructural verification of the conventional synaptic contacts made by their processes in distal regions of the inner plexiform layer. In proximal regions of the inner plexiform layer, dendrites of glycine‐accumulating amacrine cells were postsynaptic to both ribbon and conventional synaptic contacts, suggesting input from bipolar and other, nonglycinergic amacrine cells. Their density (30 ± 11 S.D. cells/mm linear retinal expanse) tended to be greater toward the central fundus. A second population of lightly labeled, probable bipolar cells was present in the middle of the inner nuclear layer; the density of this second set of glycine‐accumulating cells approximated that of the heavily labeled population from the fovea, centrally, to the ora serrata, peripherally. Release of either accumulated or endogenous glycine was elicited by K+‐depolarization in a Ca2+‐dependent manner. Tissue fragments exposed for 6 minutes to normal medium, 40 mM K+‐substituted medium, or K+‐substituted medium with Co2+ release endogenous glycine into each bathing solution in average amounts of 0.6, 2.6, and 0.7 nmoles per mg protein, respectively. Together these data strongly implicate glycine as a neurotransmitter in the human retina.
Distribution and projections of cholecystokinin‐immunoreactive neurons in the hypothalamic paraventricular nucleus of rat
Authors: Kiss J. Z. , Williams T. H. , Palkovits M.
Published: January 2005

Analysis of coronal sections from colchicine‐treated rat brains reveals that CCK‐immunoreactivity (CCK‐ir) is present in two distinguishable neuronal systems in the paraventricular nucleus (PVN). More than 60% of these cells were found to be typical parvicellular neurons; the remainder were magnocellular neurons. The magnocellular CCK‐ir neurons were concentrated in the medial magnocellular subdivision, while more caudally they formed a ring around a zone of unstained magnocellular neurons. Immunostained parvicellular neurons predominate in medial and periventricular parvicellular subdivisions.

The efferent projections of CCK‐ir neurons were investigated by looking for retrograde accumulation of CCK‐ir in cell bodies after selective knife cuts. A parasagittal cut of the lateral retrochiasmatic area as well as transection of the rostral median eminence resulted in an accumulation of CCK‐ir material in a large number of both parvi‐ and magnocellular neurons. After pituitary stalk lesions, however, increased staining was only seen in magnocellular neurons. It is inferred that the magnocellular (presumed oxytocin‐CCK) cells send their axons to the pituitary, whereas axons of CCK‐ir parvicellular neurons appear to terminate in the median eminence.

After transection of the medial forebrain bundle (MFB), immunostaining increased in a small number of scattered transected fibers proximal to the knife cut and in a few perikarya in the PVN, indicating that very few CCK cells may send descending fibers to the lower brainstem.
A Golgi analysis of the primate globus pallidus. I. Inconstant processes of large neurons, other neuronal types, and afferent axons
Authors: François Chantal , Percheron Gérard , Yelnik Jérôme , Heyner Simone
Published: January 2005

The present paper is a Golgi study, with high‐power lenses, of the primate globus pallidus. Two kinds of inconstant processes of large neurons are first described: complex endings and thin processes. Complex endings are thick apparatuses terminally located on dendrites having many appendages of various types. Contacts were observed not only between striatal axons and these complex endings but also between complex endings and the soma, dendritic stems, dendritic portions or complex endings of other large pallidal neurons. Thin processes were usually beaded, very thin, and arose from any part of the dendritic tree. Contacts were seen between them and soma or dendrites of other large neurons. These thin processes were very similar to initial axonal collaterals and together constitute a common pool of processes. Complex endings and thin processes were essentially observed in the lateral nucleus of the pallidum where they apparently are evenly distributed inside the nucleus but randomly distributed on individual neurons. Two neuronal types other than large pallidal neurons were isolated: the smallest were considered to be local circuit neurons, while intermediate‐sized neurons might be the origin of a particular efference. Many striatal axons gave no branches over long distances and collaterals were of two types and most frequently were short (less than 50 μm). Larger axonal arborizations were rarely encountered. In addition to parallel contacts, numerous very short ones were observed. All these contacts between striatal axons and dendrites of large pallidal neurons seem to be irregularly distributed.
The vestibular nuclei in the macaque monkey
Authors: Brodal A.
Published: January 2005

The topography and the main features of the cytoarchitecture of the vestibular nuclear complex in the macaque monkey have been studied in serially cut, Nissl‐stained, transverse, parasagittal and horizontal sections. In addition to the four main vestibular nuclei, the topographically closely related small cell groups (f, 1, x, y, and z), distinguished by Brodal and Pompeiano (1957) in the cat, have been considered and illustrated.

The vestibular nuclear complex in the macaque in general corresponds in topography and architecture to the situation described in some other mammals on which information is available, such as opossum, rabbit, cat,Galago, and man. Some dissimilarities in detail are found. For example, in man the lateral vestibular nucleus differs somewhat from the general pattern, especially in its position, and the small group f, fusing with the descending nucleus, appears to be indistinct; likewise the group y. The latter and the group z appear to be particularly well developed and easily distinguished in the macaque.

The question of whether cytoarchitectonic areal differences within the vestibular nuclear complex can be correlated with differences in connections is discussed. Also in this respect there appears to be a general similarity between observations in the macaque and in other mammals. A correlation is most evident in the superior vestibular nucleus, and is rather clear in the medial and lateral vestibular nuclei and for the groups f, x, y, and z, whereas no such correlation can be found in the descending (inferior) nucleus. For several reasons it is difficult to draw reliable conclusions about comparative anatomical trends in the phylogenesis of the vestibular nuclear complex.
6‐Hydroxydopamine induced ectopia of external granule cells in the subarachnoid space covering the cerebellum. II. Differentiation of granule cells: A scanning and transmission electron microscopic study
Authors: Mangold Ulrich , Sievers Jobst , Berry Martin
Published: January 2005

The present report describes the morphological differentiation of ectopic granule cells from external granule cells that have been induced to escape from the cerebellar cortex into the subarachnoid space by injecting neonatal rats with 100 μg 6‐hydroxydopamine (6‐OHDA) into the cisterna magna.

The following cell types were observed in the period between 5 and 25 days postinjection (dpi): (1) unipolar cells with one process bearing a growth cone at its tip; (2) bipolar cells with two thin beaded processes originating from opposite cell poles, bearing growth cones at their tips; (3) bipolar cells with a T‐like process at one pole and a short process lacking a terminal growth cone at the opposite pole; (4) multipolar cells with one thin beaded process and two or more short processes bearing growth cones of a different morphology at their tips; (5) intermediate stages. In the late second week p.i., cell aggregates were observed that continually increased in size up to 30 dpi. On the basis of our light, transmission, and scanning electron microscopic findings, we interpret these cell types to be equivalent to the individual stages of granule cell differentiation that characterize axon formation, migration, and aggregation.

In the period between 30 and 365 dpi, granule cells were almost exclusively organized into cell colonies of different sizes, but small cell clusters and single granule cells exhibited the scanning electron microscopic features of adult granule cells, i.e., a small spherical cell body, a single axon with parent axonal stem, T‐junction, and parallel fiber, and dendrites engaged in synaptic glomeruli. The parallel fibers ran in fasciculi of different sizes, often parallel to each other, but without preferential orientation over the cerebellar surface.

During migration and aggregation, the granule cells and their processes were associated with a substrate of glial sheets that in turn were connected to intracortical Bergmann glia fibers. Our findings indicate that (1) granule cells differentiate normally in an ectopic environment in the presence of glia, (2) ectopic Bergmann glia contain no directional information to guide aberrant migratory granule cells to their correct destination, (3) granule cells can survive outside the brain parenchyma for periods up to one year (the longest postinjection interval studied).
Hypomyelination in the peripheral nervous system of shiverer mice and in Shiverer ↔ Normal chimaera
Authors: Peterson A. C. , Bray G. M.
Published: January 2005

In shiverer mice, the P1 component of myelin basic protein (MBP) is deficient in both the central nervous system (CNS) and peripheral nervous system (PNS) but compact myelin is more grossly defective in the CNS. In the PNS, myelin exhibits a normal periodic structure, and although examples of subtle abnormalities of shiverer Schwann cell ultrastructure have been described previously, myelin thickness has been reported as unremarkable when observed by light microscopy.

We report, a quantitative investigation of the myelin sheath thickness of shiverer Schwann cells in which a mild but apparently consistent hypomyelination of axons ensheathed by shiverer Schwann cells was observed. This abnormality was expressed both in the peripheral nerves of a homozygous shiverer mouse and in the shiverer Schwann cells populating the mosaic nerves of a mature ↔ shiverer normal mouse chimaera. In addition, multiple interlamellar gaps was found to be a highly consistent feature of shiverer myelin.

These observations extend the description of the peripheral nerve defects expressed in shiverer mice and further define these abnormalities as direct consequences of the shiverer Schwann cells' intrinsic genotype. In light of these results, a significant role for P1 in the formation and/or maintenance of normal myelin in the PNS is suggested.
Luteinizing hormone releasing hormone containing synapses in the diagonal band and preoptic area of the guinea pig
Authors: Silverman Ann‐Judith
Published: January 2005

Light microscopic immunocytochemical processing of the region of the ventral diagonal band of Broca (vertical limb) and the medial preoptic area of the guinea pig for LHRH revealed complex axonal bundles. The axons were of several different shapes and widths and showed varicosities of varying form. When such tissue was embedded and processed for electron microscopic localization of immunoreaction product, numerous LHRH‐positive synapses were seen. The synapses were made by large varicosities. They were all axodendritic and showed a well‐defined synaptic cleft, as well as a clustering of immunoreactive large granules and immunonegative small, clear vesicles. Postsynaptic densities were either very small or absent. These data show that LHRH is present in direct synapses within the CNS and is, therefore, in a position to be released and act as a neurotransmitter/neuromodulator as well as a neurohormone.
Changes in the topographically organized connections between the nucleus isthmi and the optic tectum after partial tectal ablation in adult goldfish
Authors: Dunn‐Meynell A. A. , Sharma S. C.
Published: January 2005

The projection of the nucleus isthmi to the ipsilateral optic tectum was examined in normal goldfish. This was compared to the projection in animals in which the entire visual field had been induced to compress onto a rostral half tectum by caudal tectal ablation. The isthmo‐tectal projection was examined by making localized injections of horseradish peroxidase into the optic tecta and observing the patterns of labeled cells within the nucleus isthmi. The teleost nucleus isthmi consists of a cell sparse medulla covered by a cellular cortex, which is thick on the rostral, medial, and dorsal surfaces of the nucleus. Almost all isthmic cells projecting to the tectum were located in the area of thick cortex. In normal fish, rostral tectal injections labeled cells in the rostroventral portion of the thick cortex; injections midway in the rostrocaudal tectal axis labeled more caudodorsally located cells, and caudal tectal injections labeled cells a little further caudally in extreme dorsal cortex. The rostroventral to caudodorsal isthmic axis was therefore seen to project rostrocaudally along the tectum. This topography contrasts somewhat with the situation seen in amphibia where the rostrocaudal tectal axis receives projections from the rostrocaudal isthmic axis. In fish with half‐tectal ablations, injections near the caudal edge of the half tectum (at a site that had originally been midtectal) labeled cells that had previously projected to caudal tectum. Rostral tectal injections in fish with compression of the visual field gave a normal pattern of labeled isthmic cells. The results indicate that a topographically ordered isthmo‐tectal projection exists in goldfish that may be induced to compress onto a half tectum.
The distribution of enkephalinlike immunoreactivity in the telencephalon of the adult and developing domestic chicken
Authors: Reiner Anton , Davis Brian M. , Brecha Nicholas C. , Karten Harvey J.
Published: January 2005

Immunohistochemical techniques were used to determine the distribution of enkephalinlike immunoreactivity in the telencephalon of chicken. The densest accumulation of enkephalinergic neurons and fibers was observed within the paleostriatal complex, the avian equivalent of the mammalian basal ganglia. Numerous small enkephalinergic neurons were observed in both lobus parolfactorius (LPO) and the paleostriatum augmentatum (PA), the two components of the small‐celled portion of the paleostriatal complex. The enkephalinergic neurons of LPO‐PA appeared to give rise to a dense plexus of enkephalinergic fibers within the large‐celled zone of the paleostriatal complex, the paleostriatum primitivum (PP). The distribution of enkephalin within the avian paleostriatial complex, when compared to the distribution of enkephalin within the mammalian basal ganglia, supports previous proposals that PP is comparable to the mammalian globus pallidus and that PA‐LPO are comparable to the caudate‐putamen (Karten and Dubbeldam, '73; Kitt and Brauth, '81; Parent and Olivier, '70; Reiner et al., '83). Observations on the development of enkephalinlike immunoreactivity within the chicken paleostriatal complex also support the suggestion that the major component nuclei of the avian paleostriatal complex have correspondents within the mammalian basal ganglia.

Enkephalinlike immunoreactivity was also observed within cell bodies and fibers in other portions of the avian telencephalon. Within the ventrolateral telencephalon, the nucleus accumbens, nucleus of the diagonal band, and tuberculum olfactorium contained enkephalinergic cell bodies and fibers while only enkephalinergic fibers were observed in the portion of the avian telencephalon that has been termed the ventral paleostriatum (Kitt and Brauth, '81; Reiner et al., '83). Within the medial wall of the telencephalon, enkephalinergic fibers were observed in the lateral septal nucleus, while enkephalinergic cell bodies and fibers were observed in the parahippocampal area. Little enkephalinlike immunoreactivity was observed dorsal to the paleostriatal complex except in the hyperstriatum dorsale. Within the hyperstriatum dorsale, a band of enkephalinergic neurons appeared to give rise to an overlying parallel band of dense enkephalinergic fibers.

The distribution of enkephalinlike immunoreactivity within the avian telencephalon thus shows remarkable similarity to that seen in the mammalian telencephalon. The largest accumulation of enkephalinlike immunoreactivity within the telencephalon of both vertebrate classes appears to be found within the ventrolateral wall of the telencephalon, including the basal ganglia. In comparison, much less enkephalinlike immunoreactivity is observed in either the mammalian neocortex or in the avian correspondent of mammalian neocortex.
The glial reaction in the course of axon regeneration: A stereological study of the rat hypoglossal nucleus
Authors: Reisert I. , Wildemann G. , Grab D. , Pilgrim Ch.
Published: January 2005

Both hypoglossal nuclei were examined by electron microscope stereology after unilateral axotomy. The principal aim of this study was a quantitative assessment of the accompanying glial reaction. Volume densities (%) of neuronal and glial perikarya, as well as their processes, were evaluated in terms of volume plus surface densities (mm−1). In addition, specific surfaces (surface to volume ratio) of these neuronal and glial processes were assessed.

First, a temporary decrease of dendritic volume density was detected on the ipsilateral side only. Further, the astrocytic reaction displayed differences between stem and lamellar processes. One day after axotomy, a bilateral decrease of volume density, as well as surface density of stem processes, was observed, yet their normal dimensions soon were reestablished. However, a more severe lamellar process reaction was evident. During the first 4 days, a significant increase of volume density and surface density was apparent. In the contralateral hypoglossal nucleus, this glial reaction also occurred but disappeared by day 14, whereas the ipsilateral nucleus continued to display a severe reaction of lamellar processes, only returning to normal status at day 77. In addition, a transient, severe reaction of presumptive microglia was established by employing the volume density and surface density quantitation procedure. Nevertheless, in comparison with the volume and surface contribution of astrocytic processes, the presumed microglial component was minimal.

This study indicates a two‐step involvement of astrocytes in regenerative repair. Namely, the first phase seems to result in an increase of lamellar processes through reshaping of the stem process. Following this, apparently a shift to de novo synthesis of astrocytic cytoplasmic and membrane constituents could occur, hence inducing a transient astrogliosis. The present investigation clearly indicates an essential supportive role of astroglia in the time course of regenerative processes initiated by hypoglossal nerve axotomy. Given such isolation of regenerating neurons, the microglial contribution to this regeneration probably is negligible.
Localization of sympathetic postganglionic and parasympathetic preganglionic neurons which innervate different regions of the dog heart
Authors: Hopkins David A. , Armour J. Andrew
Published: January 2005

The locations of sympathetic postganglionic and parasympathetic preganglionic neurons projecting to the heart have not yet been clearly established. Therefore, aliquots of horseradish peroxidase (HRP) were injected into specific regions of the heart, intraventricular cavity, pericardial sac, aortic arch, and the skin in 27 dogs. Following injections into the heart, aorta, or pericardial sac, retrogradely labeled neurons were present in the greatest numbers in the middle cervical ganglia bilaterally. Labeled neurons were located in the cranial poles of the stellate ganglia bilaterally and occasionally in the superior cervical ganglia. Labeled cells were also found in small ganglia located along cardiopulmonary nerves. Injections of HRP into specific areas of the heart did not result in labeling of cells in specific loci of the thoracic or cervical sympathetic ganglia. When the ansae were cut on one side, no labeled cells were found in the ipsilateral stellate ganglion or upper thoracic chain. Following injections into the skin of the left elbow or left cranial nipple, labeled cells were found in the stellate ganglia and the sympathetic chain and in one case in the middle cervical ganglion as well. These data suggest that postganglionic sympathetic neurons which project efferent axons to a specific cardiac region are not located in a specific region of a sympathetic ganglion or a specific sympathetic ganglion. Rather, neurons in one region of a sympathetic ganglion project axons to widespread areas of the myocardium. Sympathetic postganglionic neurons in the stellate ganglion or sympathetic chain project their axons to the heart via the subclavian ansae or interganglionic nerves, not via nerves arising directly from the sympathetic chain.

Small numbers of labeled neurons were found in the medulla oblongata, thus indicating that in comparison to sympathetic postganglionic neurons relatively few preganglionic parasympathetic neurons project directly to the heart. When labeled cells were present in the medulla, the majority were located in the ventrolateral nucleus ambiguus.
Mapping the body representation in the SI cortex of anesthetized and awake rats
Authors: Chapin John K. , Lin Chia‐Sheng
Published: January 2005

We have used single unit recording techniques to map the representation of cutaneous and joint somatosensory modalities in the primary somatosensory (SI) cortex of both anesthetized and awake rats. The cytoarchitectonic zones within the rat SI were divided into the following main categories: (1) granular zones (GZs)–areas exhibiting koniocortical cytoarchitecture (i.e., containing dense aggregates of layer IV granule cells), (2) perigranular zones (PGZs)–narrow strips of less granular cortex surrounding the GZs, and (3) dysgranular zones (DZs)–large areas of dysgranular cortex enclosed within the SI. The narrow strip between the SI and the rostrally adjacent frontal agranular cortex was termed the “transitional zone” (TZ).

Initial computer‐based studies of the properties of cutaneous receptive fields (RFs) in SI showed that, although there were differences in reponse threshold, adaptability, frequency response, and overall RF size and shape of adjacent neurons, the size and location of the “centers” of the RFs were quite constant and were similar to those seen in multiple unit recordings. The same was true of RFs of single neurons recorded through different anesthetic states.

The body representation in SI was first mapped by determining single unit and unit cluster RFs within a total of 2,170 microelectrode penetrations in barbiturate‐anesthetized rats. Cutaneous RFs in the GZs were quite discrete. Thus, a single, finely detailed, continuous map of the cutaneous periphery was definable within the GZs themselves. Only the forepaw had a double representation. RFs in the PGZs were larger and more diffuse, but since they covered roughly the same skin areas as the RFs in the most closely adjacent GZs, they fit into the same body map. Neurons in the DZs were unresponsive to any sensory stimuli in the anesthetized animal.

In chronically implanted, freely moving, awake animals cutaneous RFs were larger and more volatile than in the anesthetized, but the accuracy of the map was clearly preserved by the fact that the locations of the RF centers (which often must be defined quantitatively) were unchanged. The PGZs and DZs in the awake animals exhibited a multimodal convergence of cutaneous and joint movement RFs within single vertical penetrations, or even on single neurons. Directionally specific and bilateral cutaneous RFs were also observed in the DZs. It was concluded the DZs are more associational or integrative areas within the SI, but they could not be shown to comprise a distinct and separate body representation. The rat SI cortex therefore appears to contain, within a single overall body map, both granular and dysgranular cytoarchitectonic zones. Not only are different sensory modalities subserved within this map, but also different levels of physiological complexity and anesthesia sensitivity.