bluuebunny/crossref_metadata_2025 huggingface dataset:
GABA‐like immunoreactivity in the pedal ganglia of Mytilus galloprovincialis: Light and electron microscopic study
Authors: Vitellaro‐Zuccarello L. , De Biasi S.
Published: January 2005

The distribution of gamma‐aminobutyric acid (GABA)‐like immunoreactivity was investigated in the pedal ganglia (PG) of Mytilus galloprovincialis (Mollusca, Bivalvia) with the aid of an antiserum raised against GABA coupled to bovine serum albumin. Examination of whole‐mount preparations and serial vibratome and semithin sections showed the presence of different types of immunoreactive neurons. Small unipolar neurons were the most numerous, and were located mainly in the lateral ganglion cortex. A few bipolar and small multipolar neurons were scattered in the cortex, and, more rarely, in the neuropile. Furthermore, two large symmetrical multipolar neurons, the processes of which extended over large fields in the ipsilateral and contralateral neuropile, were consistently observed in each ganglion.

Immunoreactive fibers formed networks in the neuropile and ran parallel in the commissure and in all nerves and connectives.

The morphology and distribution of neurons and fibers immunostained by the anti‐GABA serum were similar to these of GAD‐like immunoreactive elements, which indicates that the neurotransmitter and its biosynthetic enzyme are present in the same neurons.

Moreover, comparison of serial semithin sections alternatively incubated in postembedding with anti‐GABA and antiserotonin sera revealed that immunoreactivity for these two substances was present in different neuronal populations. However, close association between serotoninlike and GABA‐like immunoreactive elements was observed in a few PG areas.

GABA‐like immunoreactivity was demonstrated on ultrathin sections by using secondary antiserum coupled to colloidal gold particles. Labeling was found over somata, fibers, and varicosities containing a distinct type of small (63 nm), pleomorphic, dense‐cored vesicle.
Organization and efferent connections of transplanted suprachiasmatic nuclei
Authors: Wiegand Stanley J. , Gash Don M.
Published: January 2005

The hypothalamic suprachiasmatic nucleus (SCh) is the principal brain structure involved in the generation of circadian rhythms. In the present study, we have employed immunohistochemical techniques to evaluate the development of the fetal SCh following its transplantation to the brain of adult host animals. Donor hypothalami were obtained from normal Long‐Evans fetuses and transplanted to the lateral, third, or fourth ventricle of Brattleboro rats, Neuronal aggregations exhibiting the organotypic features of the SCh were present in over 90% of the grafts recovered at each transplantation site. Like the normal endogenous SCh, SCh‐like cell groups identified within the transplants contained a prominent population of parvicellular (9–13 μm), neurophysin‐containing neurons that were immunopositive for vasopressin (VP) but not oxytocin. These SCh‐like cell groups also invariably contained similar small neurons that were immunoreactive for vasoactive intestinal polypeptide (VIP). Typically, VP and VIP immunoreactive perikarya were concentrated in contiguous, complementary parts of the grafted SCh, but fibers immunoreactive for either peptide were distributed throughout the extent of the nucleus.

Because the brain of the Brattleboro rat is deficient in vasopressin, it was possible to evaluate the projection of the vasopressinergic component of the transplanted SCh to the host brain. Although SCh were identified in grafts recovered from each intraventricular transplantation site, an appreciable input to the host brain could be identified only when the fetal tissue was grafted to the third ventricle. Here, grafted SCh established efferent connections with periventricular diencephalic structures which ordinarily receive a projection from the in situ SCh. Specifically, VP immunoreactive fibers originating from transplanted SCh were identified in the medial preoptic area, the periventricular and dorsomedial hypothalamic nuclei, the paraventricular nuclei of the thalamus and hypothalamus, and in the retrochiasmatic area, arcuate nucleus, and suprachiasmatic nucleus of the host brain. These results demonstrate that the fetal SCh not only survives transplantation but also retains its distinguishing cytological features and the capacity to form an appropriately restricted set of efferent connections with the brain of adult host animals.
Anatomical connections of the prepositus and abducens nuclei in the squirrel monkey
Authors: Belknap Dianne B. , McCrea Robert A.
Published: January 2005

The primary goal of this investigation was to identify the areas of the brainstem and cerebellum that provide afferent projections to the nucleus prepositus hypoglossi in primates. After horseradish peroxidase conjugated to wheat germ agglutinin (WGA‐HRP) was injected into the prepositus in squirrel monkeys (Saimiri sciureus), the largest populations of retrogradely labeled neurons were found in the vestibular nuclei, the contralateral perihypoglossal nuclei, and the medullary and pontine reticular formation. Unlike the cat, the prepositus in Saimiri received substantial projections from the nucleus raphe dorsalis and the central mesencephalic reticular formation, whereas few or no labeled cells were found in the cerebellar cortex, the superior colliculus, or the nucleus reticularis tegmenti pontis. By comparing the afferents to the prepositus with those to the abducens nucleus, we found that all regions projecting to the abducens also projected to the prepositus, without exception. Anterogradely transported WGA‐HRP showed that the major brainstem recipients of prepositus efferents were the vestibular and perihypoglossal nuclei, the inferior olive, the medullary reticular formation, and the extraocular motor nuclei. In the cerebellar cortex, the prepositus projected to restricted regions of crura I and II as well as the caudal vermis and vestibulocerebellum. The many parts of the oculomotor system receiving input from the prepositus and the parallel innervation of the prepositus and the abducens by a large number of premotor centers lend support to the hypothesis that the prepositus may distribute an efference copy of motor activity, and may also play an important role in the process of neural integration.
Taurine‐like immunoreactivity in the brain of the honeybee
Authors: Schäfer Sabine , Bicker Gerd , Ottersen Ole P. , Storm‐Mathisen Jon
Published: January 2005

Taurine (2‐aminoethanesulfonic acid) is one of the most abundant free amino acids in the insect central nervous system. We have investigated the distribution of taurine‐like immunoreactivity in the brain of the honeybee with an antiserum recognizing fixed taurine. Taurine‐like immunoreactivity appeared within neuronal perikarya, neurites, and terminals, whereas glial cells were unlabelled. All photoreceptor cells of the compound eyes and the ocelli were stained. So were the fibers of the anterior superior optic tract, which connects the optic lobes to the mushroom bodies in the median protocerebrum. In the mushroom bodies the majority of intrinsic Kenyon cells showed high levels of taurine‐like immunoreactivity. The lateral antennoglomerular tract, which interconnects the mushroom bodies with the antennal lobes, was also intensely stained. In. the antennal lobes, strong labelling was observed within, a few fibers that invade a set of posterior glomeruli from the posterior margin. Sensory projections from the antennal nerve into the antennal lobes showed only intermediate levels of staining. Sensory projections into the dorsal lobe were devoid of taurine‐like immunoreactivity. Labral, mandibular, maxillary, and labial nerves, which innervate the various parts of the feeding apparatus, contain a set of five to eight heavily stained fibers. A comparison of taurine‐like immunoreactivity with glutamate‐ and GABA‐like immunoreactivities in the brain of the honeybee indicates that the three amino acids are enriched in distinct neuronal populations.
Remodeling of nerves during claw reversal in adult snapping shrimps
Authors: Govind C. K. , Pearce Joanne
Published: January 2005

Adult snapping shrimps, Alpheus heterochelis, undergo a reversal of their claw laterality following removal of the major claw, a process in which the existing minor claw transforms into a major and a new minor regenerates at the old major site. During such reversals the nerves to the ganglion are remodeled from one claw type to the other. Conversion of the nerves from the minor to the major type occurs within several days after removal of the contralateral major claw and involves the rapid addition of large numbers of sensory axons together with deletion of a few. Thus modeling of the nerves is essentially complete within the first intermolt in tandem with changes in the motoneurons but well ahead of changes in the muscle and external morphology. Conversion of the major nerves to the minor type is via massive degeneration of sensory axons during the first and second intermolts because of the loss of their peripherally located cell bodies. This is followed by proliferation of largely unmyelinated axons in the third intermolt, some of which become myelinated in the subsequent intermolts. Thus remodeling of the major nerves to minor, which is associated with the loss of a claw and the regeneration of a new minor claw, is a more traumatic and prolonged process compared to the remodeling of the minor nerves to major which is associated with the transformation of an existing claw.
Comparison of growth and reinnervation properties of cholinergic neurons from different brain regions grafted to the hippocampus
Authors: Nilsson Ola G. , Clarke Deborah J. , Brundin Patrik , Björklund Anders
Published: January 2005

Grafts of five different types of central cholinergic neurons, from the septal‐diagonal band region, the nucleus basalis magnocellularis region (NBM), the striatum, the pontomesencephalic tegmentum of the brainstem, and the spinal cord, were compared with respect to their ability to grow and to reinnervate the cholinergically denervated hippocampal formation of adult rats. The areas were dissected from 14 to 15–day‐old rat fetuses, and the same number of viable cells (35 × 104) from each of the different regions were stereotaxically injected as cell suspensions into the hippocampus of rats subjected to a transection of the intrinsic septo‐hippocampal cholinergic pathways. At 17–19 weeks after transplantation, the various graft types differed considerably in their volume, the total amount of acetylcholinesterase (AChE)‐positive fiber outgrowth, and the innervation pattern and morphology of the AChE‐positive fibers growing into the host hippocampus. On average the NBM and spinal cord grafts had grown to become three to four times larger than the septal and the brainstem grafts, and 15–20 times larger than the striatal grafts. By contrast, the total ingrowth score of AChE‐positive fibers in the host hippocampus from the septal grafts was about twice that of the NBM and brainstem grafts, about five times greater than the striatal grafts, and about six times greater than that of the spinal cord grafts. The large NBM grafts thus exhibited similar fiber outgrowth to the much smaller brainstem grafts, and the AChE‐positive neurons of the grafted spinal cord grew very poorly into the hippocampus despite the fact that they survived very well. The innervation pattern and morphological features of the ingrowing AChE‐positive fibers in the host hippocampus proper and in the dentate gyrus resembled those of normal rats in animals with grafts from any of the three forebrain regions (i.e., septum, NBM, or striatum), whereas ingrowth from the brainstem and spinal cord grafts were markedly abnormal with respect to both innervation pattern and fiber morphology.

These results provide further evidence that the overall survival, growth, and fiber outgrowth of intracerebral neural grafts depend on interactions with the surrounding host tissue. Since the ability to reinnervate the previously denervated host target was greatest for the neuron type normally innervating that area, i.e., the septal‐diagonal band neurons, we conclude that neuronal properties beyond the transmitter type are essential for the optimal performance of implanted neurons in intracerebral grafting experiments.
Response of endogenous glial cells to motor neuron degeneration induced by toxic ricin
Authors: Streit Wolfgang J. , Kreutzberg Georg W.
Published: January 2005

The injection of toxic lectin from Ricinus communis into the rat facial nerve resulted in suicide transport and rapid degeneration of facial motor neurons. The reaction of glial cells to neuronal death in comparison with nerve crush lesions was studied by using lectin‐HRP conjugates derived from Griffonia simplicifolia for the selective staining of microglial cells at both light and electron microscopic levels. In addition, the proliferative activity of microglia was assessed by quantification of 3H‐thymidine incorporation. The astrocytic response was evaluated by light microscopic immunocytochemistry for glial fibrilliary acidic protein.

In the degenerating facial nucleus local microglial cells responded by rapid proliferation and phagocytosis of neuronal debris. After nerve crush, no phagocytes were observed, but microglial proliferation and perineuronal satellitosis were prominent. The astrocytic expression of glial fibrillary acidic protein in response to nerve crush proceeded gradually over a period of several weeks after which it declined, contrasting with accelerated astrocytic hypertrophy and permanent glial scarring after neuronal degeneration.

These results show that the expression of glial fibrillary acidic protein by fibrous astrocytes is intensified after lethal neuronal injury compared to sublethal insults. In the absence of any observations indicating participation of hematogenous elements, it is proposed that local microglial cells transform into brain macrophages.
Structure and distribution of dorsal unpaired median (DUM) neurones in the abdominal nerve cord of male and female locusts
Authors: Pflüger H.‐J. , Watson A. H. D.
Published: January 2005

Dorsal unpaired median (DUM) neurones in insects have been shown to modulate the activity of both skeletal and visceral muscle. It has been suggested that as a population they carry out a role analogous to that of the sympathetic nervous system in vertebrates; however, the extent of their distribution throughout the ventral nerve cord has not been assessed. This paper aims to fill this gap by systematically describing the number and morphology of DUM neurones in each of the abdominal ganglia of male and female locusts. To achieve this, the lateral nerves of each abdominal ganglion were backfilled to reveal the position of the somata of DUM neurones. To confirm their identity and reveal their structure, DUM somata were then impaled with microelectrodes and, after physiological characterization, the neurones were stained by intracellular injection with cobalt ions. In each of the first six abdominal ganglia of both sexes, two DUM neurones, one with axons in the tergal nerve and one with axons in the sternal nerve, were found. In the seventh abdominal, and the terminal, ganglion (composed of the eighth to eleventh neuromeres), there was considerable sexual dimorphism in DUM neurone distribution, which was most marked in those associated with some of the nerves innervating the genitalia. In the male, four clusters of somata in the seventh, eighth, and tenth segments have axons in the genital nerve. In the female, which lacks a genital nerve, clusters of DUM neurones, absent in the male, have axons in the seventh and eighth sternal nerves and the cercal nerve.
Serotonin‐containing neurons in Drosophila melanogaster: Development and distribution
Authors: Vallés Ana María , White Kalpana
Published: January 2005

Antibodies made against serotonin (5HT) were used to identify the serotonin neuronal system in the developing and adult nervous system of Drosophila melanogaster. The 5HT neuronal pattern is composed of a small number of neurons, 84 in larvae and 106 in adults, distributed in clusters composed of one to five neurons in the CNS; 5HT immunoreactive (5HT‐IR) neurons appear to be predominantly intrasegmental interneurons; however, intersegmental 5HT‐IR fibers are observed and at least some neurons send peripheral fibers. Acquisition of 5HT immunoreactivity in the CNS occurs late in embryogenesis, by 16–18 hours, and most if not all the 5HT neurons appear to persist into adulthood. During early metamorphosis, the intensity of 5HT‐IR neuropil transiently decreases. Other changes in the CNS during this period are reflected in the appearance of two new 5HT clusters and 5HT‐IR neuropil in the developing optic lobes. Comparison of the 5HT‐IR pattern with other transmitter systems in Drosophila as well as comparison of the 5HT‐IR pattern within different insect species is presented.
Connections of the corpus cerebelli in the thornback guitarfish, Platyrhinoidis triseriata (Elasmobranchii): A study with WGA‐HRP and extracellular granule cell recording
Authors: Fiebig Eberhard
Published: January 2005

The neuronal connections of the cerebellar corpus in the guitarfish Platyrhinoidis triseriata were investigated by WGA‐HRP injections and extracellular recording of sensory evoked electrical activity. Injections of WGA‐HRP into the corpus resulted in retrograde labeling of the following cell groups bilaterally: pretectal and accessory optic nuclei, interstitial nucleus of Cajal, nucleus ruber, oculomotor and possibly trochlear nucleus, central (periaqueductal) gray, nucleus H, reticular formation of the midbrain, cerebellar nucleus, caudal part of nucleus R tentatively locus coeruleus and subcoeruleus field, octaval and trigeminal nuclei, intermediate octavolateralis nucleus, medial inferior reticular formation, lateral reticular nucleus, and spinal cord. Unilaterally labeled cells were seen in the contralateral inferior olive, which was found to project in. sagittal zones onto the molecular layer of the corpus. Terminal fields of efferent Purkinje cell axons were labeled over the ipsilateral cerebellar nucleus exclusively. Purkinje cells in different parts of the corpus project topographically onto subdivisions of the nucleus.

Mapping of evoked electrical multiple unit activity recorded from the granule cell layer of the corpus shows separate visual and tactile areas, mostly confined to the anterior and posterior lobes, respectively. Granule cells within the tactile area also responded to lateral line stimuli and, at two distinct medial locations in the caudal and rostral parts of the posterior lobe, to weak electric field stimulation in the bath. The body surface is somatotopically represented in the tactile area, but discontinuities in the map might indicate that the somatotopy is “fractured.”
Distributions of tyrosine hydroxylase‐, dopamine‐β‐hydroxylase‐, and phenylethanolamine‐N‐methyltransferase‐immunoreactive neurons in the brain of the hamster (Mesocricetus auratus)
Authors: Vincent Steven R.
Published: January 2005

Antibodies to the catecholamine synthetic enzymes tyrosine hydroxylase (TH), dopamine‐β‐hydroxylase (DBH), and phenylethanolamine‐N‐methyltransferase (PNMT) were used in an immunohistochemical analysis of the brain of the golden hamster. The distributions and morphological characteristics of neurons displaying immunoreactivity to these enzymes were examined in sets of adjacent sections. Various novel groups of TH‐immunoreactive neurons were found. A distinct feature observed in the hamster brain was the presence of a population of magnocellular multipolar neurons in the basal forebrain which displayed intense TH immunoreactivity. These cells were found predominantly in the vertical and horizontal limbs of the nucleus of the diagonal band of Broca and in the lateral preoptic area. Many small TH‐positive cells were also found scattered in the deeper layers of the cortex in the hamster. The pericentral divisions of the inferior colliculus contained a large number of TH‐immunoreactive neurons, and a few small bipolar cells in the lateral superior olive were also stained; A major cell group was found in the lateral parabrachial nucleus at the level of the locus ceruleus that displayed TH but not DBH immunoreactivity and was obviously separate from the TH‐ and DBH‐positive cells of the locus ceruleus. Additional TH‐positive cell groups were found along the seventh nerve, within the medial longitudinal fasiculus, in the nucleus raphe pallidus, and in the pars caudalis of the spinal trigeminal nucleus.

The various catecholamine cell groups described by many people in the rat by use of histochemical and immunohistochemical techniques were also present in the hamster brain. These included the noradrenergic, TH‐ and DBH‐immunoreactive cell groups of the pons and medulla. The hamster also displayed groups of medullary neurons displaying immunoreactivity to TH, DBH, and PNMT. These appeared similar in distribution and morphology to the adrenaline cell groups described in the rat. TH‐immunoreactive cell groups in the olfactory bulb, hypothalamus, substantia nigra, and ventral tegmental area of the hamster appeared to correspond to the dopaminergic cells groups described in the rat and other species. In addition, as in the rat and cat, numerous TH‐positive cells were found in the dorsal motor nucleus of the vagus, the nucleus of the solitary tract, and the area postrema.

These observations suggest that catechols may be present in neurons in the cortex, basal forebrain, auditory brainstem, and the parabrachial nucleus of the hamster. These studies also emphasize the need for caution in making‐ generalizations regarding transmitter distributions across species.
Distribution of catecholamine fibers in the cochlear nucleus of horseshoe bats and mustache bats
Authors: Kössl M. , Vater M. , Schweizer H.
Published: January 2005

The glyoxylic‐acid‐induced fluorescence technique was applied to demonstrate patterns of catecholaminergic innervation within the auditory brainstem of echolocating bats and the house mouse. In the cochlear nucleus of the rufous horseshoe bat (Rhinolophus rouxi) and the mustache bat (Pteronotus parnelli), species‐specific catecholaminergic innervation patterns are found that contrast with the relatively homogeneous innervation in the rodent.

In both bats the subnuclei of the cochlear nucleus receive a differentially dense supply of catecholaminergic fibers, and within the subnuclei, the catecholamine innervation densities can be correlated with the tonotopic frequency representation. The areas devoted to the high‐frequency echolocation calls are less densely innervated than those regions which are responsive to lower frequencies.

Apart from this common scheme, there are noteworthy distinctions between the two bats which correlate with specialized cytoarchitectural features of the cochlear nucleus. The marginal cell group, located medially to the anteroventral cochlear nucleus of Pteronotus, receives the densest supply of catecholaminergic fibers of all auditory nuclei. This plexus is formed by a morphologically distinct population of catecholaminergic fibers.
Cotransplantation of embryonic mouse retina with tectum, diencephalon, or cortex to neonatal rat cortex
Authors: Sefton Ann Jervie , Lund Raymond D.
Published: January 2005

Retinae from embryonic mice were transplanted to the occipital cortex of neonatal rats together with their normal target regions, tectum or diencephalon, from embryonic mice or rats. In control experiments, retinae were cotransplanted with embryonic rat occipital cortex. In over 80% of the experimental animals, both transplants differentiated and grew. Ganglion cells in the retinae cotransplanted close to tectum or diencephalon survived for at least 15 weeks. Their survival was associated with the development of a distinct optic fiber layer and outgrowth of axons from the transplanted mouse retina. Specific innervation of distinct patches within the cotransplanted rat tectum or diencephalon was demonstrated by the use of an anti‐mouse antibody. The innervated regions, which could be as far away as 1.3 mm from the retinae, were correlated with cytological features of the Co‐transplanted tectum or diencephalon. By contrast, the host cortex was never innervated by the transplanted retinae. In the control animals in which the retinae were cotransplanted with occipital cortex and in four animals in which the cotransplants lay more than 2.7 mm apart, no ganglion cells were identified and there was no evidence of an optic fiber layer, outgrowth of axons, or innervation. These results support the idea that in order to survive, retinal ganglion cells need to innervate an appropriate target region. Further, the specific innervation of regions within the cotransplanted tectum or diencephalon suggests that these target regions are able to exert a tropic influence on the axons of retinal ganglion cells, even in the absence of many of the normal structure cues.
Mudpuppy retinal ganglion cell morphology revealed by an hrp impregnation technique which provides golgi‐like staining
Authors: Arkin Martin S. , Miller Robert F.
Published: January 2005

A new technique of retrograde labeling of ganglion cells with horseradish peroxidase (HRP) has been developed, based on orbital injections of HRP combined with a detergent (lysolecithin). When injections are followed by an appropriate survival time, dense staining of a small number of widely scattered cells results in Golgi‐like filling of each neuron. This technique, as well as a variation which causes mass staining of ganglion cell somas, has been used to analyze the morphology of mudpuppy retinal ganglion cells. Morphological analysis has relied on computer reconstruction techniques for display, analysis of dendritic sublamination pattern, and morphometric analysis of the dendrites and soma.

Based on morphological criteria, the mudpuppy retina contains a rich variety of ganglion cell types which vary according to soma placement, dendritic field size, polar vs. non‐polar dendritic fields, dendritic branching pattern, and dendritic sublamination. The mudpuppy retina contains both conventional and displaced ganglion cells: the latter constitute about 15% of the total ganglion cell population. Both conventional and displaced ganglion cells show morphological diversity of dendritic sublamination branching pattern; cells from each group have a dendritic branching pattern confined to either distal or proximal divisions of the inner plexiform layer, whereas other cells have dendrites which branch in both sublaminae. Using morphological criteria, two subtypes of ganglion cells were identified, which have a distinctive branching pattern and dendritic tree size.

The size and distribution of ganglion cell somas were analyzed from retinas in which mass staining of ganglion cells was present. The total number of ganglion cells was estimated at approximately 14,500 cells per retina. There was a tendency for soma size and density to decrease near the optic disk. The somas of displaced ganglion cells are smaller than their conventional counterparts, at the same retinal eccentricity.

The somas of all HRP filled cells swell when compared to those of unstained fixed and freshly dissected retinas. The degree of swelling is proportional to the length of exposure to HRP. Cell swelling was evident for both retrograde labeling and intracellularly injected HRP. This artifact of HRP staining could influence the interpretation of studies in which quantitative differences in soma sizes are based on the use of HRP labeling.
Parasagittal organization of mossy fiber collaterals in the cerebellum of the mouse
Authors: Heckroth J. A. , Eisenman L. M.
Published: January 2005

We have observed that WGA‐HRP injections in lobule VIII of the mouse result in the labeling of mossy fiber terminals in the anterior lobe (lobules I‐V), which are distributed in five distinct parasagittal bands. Injections in the anterior lobe label mossy fiber terminations in lobules VIII and IX. We interpret these results as indicating that an extensive system of mossy fiber collaterals exists between the anterior lobe and lobule VIII (less so to IX), which terminates as discrete parasagittal bands in the anterior lobe. Intermediate bands are thus occupied by fibers that do not send collaterals to the posterior vermis (VII–IX).

In an attempt to identify the source(s) of this collateral system we have used double retrograde tracing techniques. Following injections of one tracer in the anterior lobe and another in lobule VIII we observe large numbers of double retrogradely labeled neurons in the lateral reticular nucleus, the basilar pontine nuclei, and the spinal cord. Thus, these mossy fiber sources are the most likely origins for the banded collateral system. Our studies do not allow us to distinguish whether one, or more than one, of these regions contribute to the system.
Central distribution of the efferent cells and the primary afferent fibers of the trigeminal nerve in Pleurodeles waltlii (Amphibia, urodela)
Authors: Gonzalez Agustín , Muñoz Margarita
Published: January 2005

As part of a study on the organization of the brainstem in a primitive group of vertebrates, the efferent cells and primary afferent fibers of the urodele amphibian Pleurodeles waltlii were examined by means of retrograde and anterograde axonal transport and anterograde degeneration. The trigeminal motor nucleus is located in the periventricular gray just medial to the sulcus limitans. Its rostral part is a band of pear‐shaped cells lying parallel to the wall of the ventricle, whereas its caudal part is a round mass consisting of polygonal cells. In addition, a small group of scattered neurons is situated ventral to the rostral part of the nucleus. The primary afferent fibers enter the brainstem in the dorsal two‐thirds of the trigeminal root. They diverge into a short ascending and a long descending tract. The former distributes its axons to the principal sensory trigeminal nucleus, which is an ill‐defined cell group located at the ventrolateral edge of the periventricular gray. In the descending tract, the fibers of the ophthalmic nerve are predominantly located ventromedially, and those of the maxillomandibular nerve dorsolaterally. A fascicle of the ophthalmic nerve leaves the descending tract and, apparently, makes contact with the accessory abducens nucleus. The descending tract extends caudally into the three upper cervical segments of the spinal cord. The mesencephalic trigeminal nucleus consists of conspicuous large cells, which are scattered through the tectum of the mesencephalon. The cells with peripheral branches in the ophthalmic nerve are mainly located in the caudal half of the tectum, and those with peripheral branches in the maxillomandibular nerve in the rostral half Collaterals of the central branches of the mesencephalic trigeminal system were traced to an area of the periventricular gray situated between the motor nucleus and the principal sensory nucleus of the trigeminus.
Morphometric study of the glomerular population in the mouse olfactory bulb: Numerical density and size distribution along the rostrocaudal axis
Authors: Royet J. P. , Souchier C. , Jourdan F. , Ploye H.
Published: January 2005

A morphometric study of the glomerular population in the olfactory bulb of the mouse has been carried out by using stereological methods. On the basis of the assumption that the glomerular population is a polydispersed system of spheres, glomerular profile distributions obtained from profile measurements were subjected to a mathematical unfolding procedure to obtain the actual glomerular size distribution. We used a distribution‐free method to account for the combined effects of overprojection due to section thickness and truncation (two missing profile mechanisms). Results proved better than those obtained directly from profile measurements without stereological analysis. Several new findings were obtained. First, significant variations of the glomerulus sizes were found along the rostrocaudal axis. The glomeruli are larger in the middle region of the olfactory bulb, whereas their numerical density decreases in the same region. Moreover, the profile density is homogeneous along the rostrocaudal axis. In other words, the relative surface occupied by the periglomerular cells in the glomerular layer is invariant. As a consequence, it may be concluded that the variations in size and numerical density are inversely correlated. Thus, since the glomeruli are larger in the middle region, their number per unit volume is logically smaller in this same area. Finally, the computerization of all these data has led us to estimate the number of glomeruli (1,810 ± 41) in the olfactory bulb of the mouse. In order to get a comparative idea of their advantages and disadvantages, other standard stereological methods were used in the present study to determine this number. Functional interpretations of the variations of the size and numerical density along the rostrocaudal axis of the olfactory bulb are discussed with respect to ontogenetic and morphofunctional data obtained elsewhere.
Collateral reinnervation of taste buds after chronic sensory denervation: A morphological study
Authors: Kinnman Erik , Aldskogius Hårkan
Published: January 2005

Peripheral transganglionic transport of horseradish peroxidase (HRP) was used to label afferent fibers in the taste buds and lingual epithelium 2–12 weeks after chronic chorda tympani or combined chorda tympani‐lingual nerve lotions, From 4–12 weeks after a chronic chorda tympani lesion, taste buds could be found. These were innervated by fibers from the ipsilateral lingual nerve. From 8–12 weeks after a. chronic chorda tympanivlingual nerve lesion, nerve fibers from the contralateral lingual nerve could be found in a few taste buds on the denervated side of the tongue. Thus, collateral sprouting took place over the midline in this instance. These findings indicate that intact gustatory axons do not sprout into denervated taste buds, but trigeminal fibers in the lingual nerve do have this ability.
A Golgi‐electron microscopic study of fusiform neurons in the hilar region of the dentate gyrus
Authors: Ribak Charles E. , Seress László
Published: January 2005

The fusiform cells of the dentate gyrus are located in a portion of the hilus within 100 μm of the granule cell layer. They have ovoid somata and bipolar dendrites that generally run parallel to the granule cell layer. The dendrites of these cells are either spiny or sparsely spiny. The spiny fusiform cell has numerous spines along its dendrites, which are contacted by terminals with the features of granule cell axon collaterals. This cell type also displays somal spines that are contacted by similar terminals. In contrast, the sparsely spiny fusiform cell displays only a few spines, which are contacted by multiple small axon terminals that synapse with both the stalk and end bulb of the spine. Most synaptic input for this cell type is made with the smooth surfaces of the soma and dendrites. A variety of terminals form synapses with the sparsely spiny fusiform cell, including terminals that resemble the fine axon collaterals of mossy fibers. The somata of these two cell types also display differences in the amount of Nissl bodies and the degree of nuclear infolding.

The results indicate that spiny fusiform cells are similar to mossy cells, another hilar cell type that receives its major synaptic input from axon collaterals of mossy fibers from granule cells. The distribution of the dendrites of spiny fusiform cells and the pattern of granule cell axon collaterals suggest a high degree of convergence from granule cells. In contrast, the variety of axodendritic synapses for sparsely spiny fusiform cells suggests that more diverse inputs affect this cell's activity. Therefore, the structure and circuitry of these two hilar cell types are probably different. This study adds further evidence to indicate that the hilus contains a large variety of cell types with different neuronal connections.
Representation of the forepaw in the feline cuneate nucleus: A transganglionic transport study
Authors: Nyberg Gunnar
Published: January 2005

The projection of forelimb nerves innervating the paw to the cuneate nucleus was studied in the cat by the transganglionic transport method. Exposure of a single digital nerve to the tracer (a conjugate of horseradish peroxidase to wheat‐germ agglutinin) resulted in a longitudinal sequence of labeled patches throughout the extent of the nucleus. In the middle region the labeled patches coincided with the location of the cell clusters that are characteristic of this part of the nucleus. A very precise somatotopic termination pattern was found in the middle region of the nucleus. Afferent fibers from the palm were represented superficially close to the dorsal rim. The digits were represented in a mediolateral sequence, with the first digit in the dorsolateral part of the nucleus and the fifth digit in the dorsomedial part. The ventral surfaces of the digits were represented superficial to the dorsal surfaces. The dorsum of the paw was represented close to the center of the nucleus. A similar somatotopic organization, but much less detailed, was found in the rostral and caudal regions of the cuneate nucleus. These dissimilarities in somatotopic detail between the different cytoarchitectonic regions of the cuneate nucleus probably reflect differences in function between these regions.
Origin of sympathetic and sensory innervation of the elbow joint in the rat: A retrograde axonal tracing study with wheat germ agglutinin conjugated horseradish peroxidase
Authors: Widenfalk B. , Elfvin L.‐G. , Wiberg M.
Published: January 2005

After injection of wheat germ agglutinin conjugated horseradish peroxidase (WGA‐HRP) into the elbow joint of adult rats, labeled neurons were found in the stellate and the T2‐T4 ganglia of the ipsilateral sympathetic trunk, and also in dorsal root ganglia at the C4–T4 levels. Most labeled sympathetic cells, 90% or more, were located in the stellate ganglion. The sensory innervation to the joint originated mainly from the dorsal root ganglia at the levels of C7–T1.
Studies of the early stages of optic axon regeneration in the goldfish
Authors: Lowenger E. , Levine R. L.
Published: January 2005

We have studied the early stages (4–14 days) of axonal regeneration following intraorbital optic nerve crush in the goldfish. We used 3H‐proline autoradiography to anterogradely label and visualize the growing axons and wheat germ agglutinin–conjugated horseradish peroxidase (WGA:HRP) for retrograde labeling to determine the cells of origin of the earliest projections.

The first retinal ganglion cells (RGCs) that could be retrogradely filled from the optic tract, following optic nerve crush, were in the central retina and were seen at 8 days postoperative. More peripheral cells were only labeled with longer postcrush survival periods. Thus, the first axons to regenerate past the lesion were from central RGCs. The axons of these cells extended into the cranial nerve stump between 4 and 5 days postcrush and entered the nerve as a fascicle, which travelled just beneath its surface. Studies of nerve cross sections from animals at 5–8 days postoperative demonstrated that initial outgrowth was not confined to any particular locale within the nerv although the early fibers appeared to avoid its temporal aspect. When the regenerating axons reached the optic tract they remained in fascicles but left the surface to run along the medial, deep portion of the tract, immediately adjacent to the diencephalon and pretectum.

The positions occupied by the earliest‐regenerating axons in the optic nerve were variable and not always appropriate for their central retinal origin. However, the abrupt change in growth trajectory as the fibers entered the optic tract brought them into the areas of the visual paths that are occupied by central axons in intact animals. We suggest that this change in position is related to both changes in the structural organization of the intracranial visual paths and to possible axon guidance signals in the region of the nerve‐tract juncture.
Patterns of angiogenesis in neural transplant models: II. Fetal neocortical transplants
Authors: Krum Janette M. , Rosenstein Jeffrey M.
Published: January 2005

Vascular integration between transplanted fetal CNS tissues and host brain is essential for long‐term transplant survival. This study compares the time course and mechanism of vascularization in allografts of fetal cerebral cortex inserted either into the fourth ventricle or directly into the parietal cortex or hippocampus of perinatal rats. Recipient animals were administered 3H‐thymidine after various postoperative time periods. The tissues were processed for light microscopic autoradiography to determine the temporal pattern of endothelial proliferation at the graft sites. Correlative electron microscopy depicted the morphological changes in transplant vasculature. Some recipients were prelabelled with 3H‐thymidine prior to transplantation to determine if host vessels invaded the grafts; conversely, some donor tissues were prelabelled in utero to ascertain if the intrinsic vascular anlagen survived.

Intraventricular transplants contained patent vessels, probably originating from the host pia mater, as early as 24 hours postoperative. Intraparenchymal transplants had patent vessels by 72 hours and a more complete network by 5 days. Prelabelling experiments and ultrastructural observations demonstrated that adjacent host pial vessels became incorporated into the perimeter of the intraventricular transplants and later grew centrally into the grafts. Intraparenchymal transplants also contained host vessels that exhibited a similar growth pattern. Intrinsic graft vessels remained viable and continued their development, and presumably anastomosed with the ingrowing host vasculature. Temporal labelling studies revealed that both vessel populations attained their highest proliferative rates within 72 hours after transplantation.

This study demonstrates that the vasculature which develops within both intraventricular and intraparenchymal fetal CNS transplants is chimeric, consisting of intrinsic fetal vasculature and proliferating host vessels. The mechanism of transplant vascularization may be significant with regard to astrocytic, immunological, or blood‐brain–barrier characteristics at these transplantation sites.
Quantified regional and laminar distribution of the noradrenaline innervation in the anterior half of the adult rat cerebral cortex
Authors: Audet Marie Andrée , Doucet Guy , Oleskevich Sharon , Descarries Laurent
Published: January 2005

The regional and laminar distribution of the noradrenaline (NA) innervation in the adult rat cerebral cortex was quantified in radioautographs of semithin sections from whole hemisphere slices incubated with tritiated catecholamines and a monoamine oxidase inhibitor. Uptake‐labeled axonal varicosities (aggregates of silver grains) were counted with the help of a computerized image analyzer in seven cytoarchitectonic areas of the rostral half of the cortex: Cg3, rostral AID, Cg2, Fr1, Par1, caudal AID, and Pir (prepiriform) according to Zilles's nomenclature. Both dopamine (DA) and NA terminals were detected after incubation with [3H]DA and citalopram or with [3H]NA alone. In the presence of desipramine (DMI), DA terminals alone were demonstrated; the number of NA terminals was then obtained by subtraction from counts in adjacent slices incubated with or without DMI. These counts suggested that DA and NA varicosities were fully visualized only after labeling with their respective tritiated amine. Similar numbers of labeled NA varicosities as inferred after [3H]NA incubation with or without DMI were observed after [3H]NA incubation in the presence of benztropine (BZ). This indicated that NA terminals were then maximally detected to the exclusion of the DA ones, and the latter approach was adopted for the acquisition of normative data. Since the average diameter of the labeled NA varicosities was known from earlier measurements in electron microscope radioautographs, the initial counts of labeled sites/mm2 of histological section could be expressed as numbers of varicosities/mm3 of tissue following a double correction for incomplete detection at the chosen duration of radioautographic exposure and section thickness. The overall density of NA innervation was thus estimated at 1.2 million varicosities/mm3 of tissue, with no statistically significant differences between the seven cortical areas examined. In every region, the number of NA terminals was the greatest in the molecular layer (1.5–2 times the density in the rest of cortex) and then progressively decreased in the underlying cortex, with a two‐ to threefold difference between upper and lower layers. These numerical data allowed an estimation to be made of the possible number of cortical NA varicosities per locus coeruleus nerve cell body of origin (at least 300,000), of their average number per cortical neuron (30–50), their actual incidence among all terminals in the cortex (1/1,000), their mean endogenous amine content per varicosity (0.22 fg), and the mean number of recognition sites for the uptake blocker DMI (4,500/varicosity). Further quantification of the cortical NA innervation in correlation with these and other measurable parameters of Na function under physiological or experimentally altered conditions should improve our understanding of the properties and role(s) of this monoamine in cerebral cortex.
Maturation of rat visual cortex: IV. The generation, migration, morphogenesis, and connectivity of atypically oriented pyramidal neurons
Authors: Miller Michael W.
Published: January 2005

The generation, migration, and morphogenesis of atypically oriented pyramidal neurons in the rat visual cortex were examined. In the mature cortex, these neurons were distributed through layers II–VI. Moreover, the atypically oriented pyramidal neurons in a particular layer tended to be oriented in a specific way; atypically oriented pyramidal neurons in layer II, layers III–VIa, and layer VIb were obliquely, radially, and obliquely oriented, respectively. Ultrastructurally, the somata of atypically oriented pyramidal neurons contained large euchromatic ovoid nuclei and cytoplasm that was replete with rough endoplasmic reticulum and Golgi apparatus. These somata formed only symmetric axosomatic synapses. Many atypically oriented pyramidal neurons projected axons into the white matter as demonstrated by a Golgi method and by a retrograde tract‐tracing technique; however, some of these pyramidal neurons in layers III–V had axons that ascended to layer I.

By using a technique which combined retrograde tract tracing with [3H]thymidine autoradiography, it was determined that most atypically oriented pyramidal neurons in layers V and VIa, layer IV, and layer II were generated on gestational days (GD) 15–17, GD 17–19, and GD 20–21, respectively. Atypically oriented pyramidal neurons were identified during the period from postnatal day 0 (day of birth) to day 30. On day 0, obliquely oriented pyramidal neurons were distributed in the deep cortical plate, i.e., immature layer VI. On day 3, the youngest atypically oriented pyramidal neurons were radially oriented and were located in layer IV. Some obliquely oriented pyramidal neurons were present in layer II on day 6, but the greatest number and the most severely canted pyramidal neurons in layer II were evident on day 9. The orientations of the cell body and the apical dendrite did not change appreciably after migration was complete, except for those in layers V and VI with obliquely oriented cell bodies and radially oriented apical dendrites. The second and third postnatal weeks were marked by substantial morphological differentiation of all pyramidal neurons as noted by the lengthening and branching of dendrites and by the appearance of dendritic spines. By the fourth postnatal week, atypically oriented pyramidal neurons achieved their mature morphology.

The generation, migration, and morphogenesis of atypically oriented pyramidal neurons proceed by an inside‐to‐outside sequence. This development is similar and concurrent with that of typically oriented pyramidal neurons.