bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations on the brainstem‐spinal descending systems of normal and reeler mutant mice by the retrograde HRP method
Authors: Terashima Toshio , Inoue Kaoru , Inoue Yoshiro , Mikoshiba Katsuhiko , Tsukada Yasuzo
Published: May 2005

Brainstem neurons which project to the lumbar spinal level were identified in both reeler mutant mice and normal controls (Balb/c mice) by the retrograde horseradish peroxidase (HRP) technique. In normal controls after HRP injection into the lumbar cord, retrogradely labelled neurons were observed in (1) the lateral vestibular nucleus, (2) the pontine and medullary reticular formations including the nucleus centralis caudalis pontis, nucleus gigantocellularis, nucleus paragigantocellularis, nucleus raphe magnus et pallidus, and nucleus centralis medullae oblongatae pars ventralis et dorsalis, and (3) the dorsal column nuclei, i.e., the nucleus gracilis and nucleus cuneatus medialis.

In reeler mutant mice, labelled neurons were again seen in the nuclei referred to above, and their cellular type and distribution patterns within the corresponding nuclei were similar to those of the normal controls. These observations suggest that (1) the brainstem nuclei of reeler mutant mice which project to the lumbar spinal cord are cytoarchitecturally normal, (2) the reeler genetic locus (rl) does not affect the nonlaminated structures in the brainstem, at least those referred to above, and (3) the motor dysfunctions observed in the reeler, such as action tremor, dystonic posture, and reeling ataxic gait, are not attributable to the brainstem–spinal descending systems.
Morphological alterations in rat CA1 hippocampal pyramidal cell dendrites resulting from chronic ethanol consumption and withdrawal
Authors: McMullen Patricia A. , Saint‐Cyr Jean A. , Carlen Peter L.
Published: May 2005

Hippocampal CA1 pyramidal cell dendrites were studied in rats after 5 months of consumption of an ethanol liquid diet and 5 months of ethanol diet followed by 2 months of withdrawal. Morphometric data were compared with those obtained from matched littermate, yoke‐fed control animals. Dendritic branching in Golgi–Cox‐stained tissues was assessed by standard and modified Sholl analysis techniques and basilar dendrites were analysed three‐dimensionally by computer.

Five months of chronic ethanol consumption caused a significant decrease in the number of second–order basilar dendrites, 60–90 μm from the apical border of the cell layer. No significant changes in the neuronal density of CA1 or CA3 cells were found; however, the thickness of the strata oriens and radiatum of the CA1 field was significantly decreased in the ethanol‐fed group.

After 5 months of chronic ethanol consumption and 2 months of withdrawal, the thickness of the strata returned to control sizes and the frequency of proximal basilar branching recovered. Evidence of lengthening and new branching of distal basilar dendrites occurred in the third‐, fourth‐, and fifth‐order segments when control animals 6 and 8 months of age were compared. During the 2–month period of withdrawal, the number and length of third‐, fourth‐, and fifth‐order segments of basilar dendrites increased when compared to the nonwithdrawn ethanol group while the number and length of second‐ and third‐order segments decreased. This is comparable to the changes seen during normal aging and suggests that withdrawal may interact with aging to produce enhanced dendritic growth in “compensation” for the developmental retardation induced by chronic ethanol intake.
Substance P in the interpeduncular nucleus of the rat: Normal distribution and the effects of deafferentation
Authors: Artymyshyn Roman , Murray Marion
Published: May 2005

The interpeduncular nucleus (IPN) is a midbrain structure that receives its major afferents from the medial habenulae via the fasciculi retroflexi. Among the axons projecting to the IPN is a population of substance P (SP)‐containing axons. The IPN has been subdivided into the central, dorsal, intermediate, rostral, and lateral subnuclei using cytoarchitectonic criteria. The distribution of SP among these subnuclei was determined by using Sternberger's ('79) peroxidase‐antiperoxidase technique. In the normal IPN the rostral subnucleus can be subdivided into two sectors on the basis of SP content. The ventral sector contains a moderate amount of SP and scattered SP positive perikarya. The dorsal cap of the rostral subnucleus contains denser SP than the ventral sector and it is continuous with the SP found in the dorsal subnucleus. The lateral subnuclei contain the densest SP found in the IPN and appear as laterally placed columns that expand in size caudally. The central and intermediate subnuclei contain very sparse SP.

The fasciculus retroflexus was destroyed in 30 animals unilaterally or bilaterally and animals were perfused 4 days to 3 months postoperatively. After unilateral fascicular lesion, the SP in the rostral part of the ipsilateral lateral subnucleus is almost abolished, but caudally the decrease is confined to its lateral aspect. There is no visible decrease contralateral to the lesion. SP in the rostral part of the cap of the rostral subnucleus is decreased ipsilaterally but no loss is seen contralaterally or caudally. Animals with bilateral lesions show a great decrease in staining in the dorsal cap of the rostral subnucleus and the lateral subnuclei, with no decrease seen in the central, dorsal, or intermediate subnuclei.

These results confirm that the origin of most of the SP in the IPN is fasciculus retroflexus fibers, but some of the SP arises from intrinsic SP perikarya located in the ventral sector of the rostral subnucleus and some may also arise from other sources. The areas of the IPN that receive bilateral SP projections from the fasciculus retroflexus (parts of the lateral and rostral subnuclei) show evidence for replacement of SP after lesion. This replacement implies sprouting or an increase in production of SP by remaining systems.
Cytoarchitectonics of substantia nigra grafts: A light and electron microscopic study of immunocytochemically identified dopaminergic neurons and fibrous astrocytes
Authors: Jaeger C. B.
Published: May 2005

Maturation of dopaminergic (DA) neurons and astroglia was studied in transplants of the substantia nigra grown for up to 7 months in the brain of rats. The investigation had three specific aims. The first was to observe effects of different transplant positions on the longevity of DA neurons. Second, the grafts were examined for changes of synaptic interactions and associations between DA neurons and astroglia. Third, an answer was sought to the question whether transplanted DA neurons migrate into the adjacent host brain. The grafts were taken from the ventral mesencephalon of rat embryos of different ages (day 14 to 18 of gestation) and placed into the cerebral cortex, tectum, cerebellum, or ventricles of newborn host animals. Following different times of survival the immunocytochemical localization of tyrosine hydroxylase (TH) and of glia filament protein (GFA) in the transplants were observed. In all of the transplantation sites, except for one, neurons of different morphologies that contained TH were found in the grafts. The cerebellar white matter of the host brain failed to support the long‐term survival of DA neurons. The overall structure of mature substantia nigra grafts had some resemblance to intact substantia nigra (SN). On the ultrastructural level, it was found that morphological expression of some immature features of DA neurons, such as glial sheaths, somatic spines, and lack of oligodendroglia, persisted in mature grafts. Specific associations of DA neurons and astroglia in the grafts suggested that the cytoarchitectonic appearance of a given brain region may be related to the existence of particular neuron glia relationships. In contrast to intact SN, transplants revealed deficiencies in unlabeled pleomorphic boutons and contained some TH‐immunoreactive terminals. Migration of DA neurons and their processes into the adjacent host brain was rarely observed.
Subclassification of neurons in the subthalamic nucleus of the lesser bushbaby (Galago senegalensis): A quantitative Golgi study using principal components analysis
Authors: Pearson J. C. , Norris J. R. , Phelps C. H.
Published: May 2005

The morphology of neurons in the subthalamic nucleus (STN) of the lesser bushbaby (Galago senegalensis) is described in coronal brain sections processed by Golgi‐ and Nissl‐staining techniques. Quantitative and statistical methods are used to evaluate (1) soma size and shape, (2) dendritic field size, shape, and branch frequency, (3) the number of dendritic and somatic spines per neuron, and (4) neuron location within the STN. Principal components analysis of these variables suggests that three classes of neurons are present. Two of these classes are considered to be projection cells, referred to as elongate‐fusiform and radiate neurons, respectively. Elongate fusiform neurons have somata and dendritic fields which are large in diameter, extremely fusiform in shape, and give rise to few appendages. Somata and dendritic fields of radiate neurons are smaller in diameter, more rounded in shape, and support more spines than the elongate‐fusiform neurons. The third class of cells in Galago STN is tentatively identified as consisting of interneurons on the basis of small soma and dendritic field size, thin and varicose dendritic morphology, and the presence of multilobulated dendritic appendages.
A comparative study of the intracellular lectin binding sites of neurons in culture with neurons in situ
Authors: Hart Clyde E. , Wood John G.
Published: May 2005

The cytochemical properties of intracellular membrane systems which are likely to be subcellular sites of glycoprotein oligosaccharide synthesis and trafficking have been compared in cultured neuroblastoma cells (as a potential model system) and in Purkinje neurons of rat cerebellum. In aldehyde‐fixed N18 cells, permeabilized with Triton X‐100, concanavalin A (Con A) binding sites were found in the somata, neurites, and growth cones. Con A binding sites in growth cones appeared as a fine, membranous network. Wheat germ agglutinin (WGA) binding sites were restricted to the perinuclear region of the soma and to the distal tips of growing neurites. As shown previously, Purkinje cell somata and presynaptic terminals also contain Con A binding sites. In this study, WGA and succinylated WGA binding sites were observed in the presynaptic terminals of Purkinje cells. Neuraminidase enzyme digestion prior to lectin labeling removed or greatly reduced WGA binding in the neuropil of the deep nucleus but not in presynaptic terminals of Purkinje cells. Succinylated WGA binding sites were not affected by neuraminidase digestion. Neuraminidase digestion also exposed Ricinis communis agglutinin I binding sites in the neuropil and in synaptic terminals of Purkinje cells. These results in combination with previous studies of intracellular lectin cytochemistry of neurons in the central nervous system demonstrate the similarity of these cells to neuroblastoma cells in their intracellular lectin binding characteristics. Results of the lectin cytochemical studies after neuraminidase digestion of presynaptic terminals support the possibility that neurons may use a post‐ or extra‐Golgi system for the addition of peripheral sugars to the oligosaccharides of certain glycoproteins destined for the cell surface.
The distribution of hypothalamic and extrahypothalamic vasotocinergic cells and fibers in the brain of a lizard, Gekko gecko: Presence of a sex difference
Authors: Stoll C. J. , Voorn P.
Published: May 2005

The distribution of vasotocin in the brain of the lizard Gekko gecko was studied with immunocytochemical methods. Vasotocinergic cells were found in the nucleus supraopticus, the nucleus paraventricularis, the bed nucleus of the stria terminalis, and in the rhombencephalon. Vasotocinergic fibers were found in the preoptic area, the lateral and ventral hypothalamus, and in many extrahypothalamic brain areas.

Furthermore, evidence was obtained of a conspicuous sex difference with regard to vasotocinergic innervation of the lateral septum, the ventrocaudal telencephalon (nucleus sphericus), and the periaqueductal gray; in these areas vastocinergic innervation is much denser in males than in females.

The results are discussed in relation to the sexually dimorphic vasopressinergic innervation of the rat brain. It is suggested that the vasotocinergic fiber system in the sexually dimorphic brain areas in Gekko gecko is related to the bed nucleus of the stria terminalis.
Development of the spinal‐medullary projection from the mouse barrel field
Authors: Crandall James E. , Whitcomb Julie M. , Caviness Verne S.
Published: May 2005

Neurons in layer V of the murine posteromedial barrel subfield (PMBSF) project to structures at or caudal to the spinal‐medullary junction. During postnatal development a reduction occurs in the density of the neurons which form this projection. In principle, three processes might be expected to contribute to this reduction: cell death, tissue growth, and axon pruning. Three different paradigms in which cells of origin of the projection are labeled retrogradely with True Blue, injected into the spinal‐medullary junction, taken together with an estimate of the relative growth of layer V, provide separate estimates of the magnitude and rate of reduction consequent to these different processes during the first 3 postnatal weeks. The density of neurons in an index sector of layer V of the PMBSF which contribute to the projection at varied ages is estimated by injections made at a range of ages from postnatal day 1 (P1) to P16, with a survival of 4 days in each instance. Overall reduction in density is 80%. The component due primarily to axon pruning is estimated to be 50% by injections delivered at graded ages from P1 to P16 with survival to P20 in each instance. The component of the reduction attributable to increase in volume is estimated at 30% by a series of injections delivered at P1 with graded survival times from P5 through P20. A reduction due to cell death is not identified. The reduction in density due to tissue growth is essentially linear through the interval P5–P11. At all ages, neuronal somata of origin of the spinal‐medullary projection are located within layer V. Subsequent to P15 they are confined to sublayer Vb; at earlier ages somata in Va and Vc also contribute axons to the projection. Although volume increase due to growth of the neuropil reduces the density of the population contributing to the projection equally in all three sublayers, final elimination of all contributions from Va and Vc depends upon axon pruning.
Spinal projections to the lateral reticular nucleus in the rat: A retrograde labelling study using horseradish peroxidase
Authors: Shokunbi M. T. , Hrycyshyn A. W. , Flumerfelt B. A.
Published: May 2005

The organization of the spinal projection to the lateral reticular nucleus (LRN) in the rat was investigated by means of a retrograde pathway tracing method in which horseradish peroxidase (HRP) served as an enzyme marker. Discrete placements of HRP into the LRN were achieved by a combination of dorsal (stereotaxic) and ventral (microsurgical) approaches. The extent and distribution of retrogradely labelled neurons in the spinal cord indicated a substantial and highly ordered projection to the LRN. All segments of the spinal cord contributed to the projection to the LRN. The limb enlargements were the richest sources of projection. The projection from the cervical spinal cord was bilateral with ipsilateral preponderance. The cervical neurons projecting to the ipsilateral LRN were located mainly in lamina VII of the spinal cord, while those projecting to the contralateral LRN were located mainly in lamina VIII. The lumbar spinal projection terminated in the contralateral LRN, and the neurons of the origin were located mainly in lamina VIII.

Most if not all parts of the LRN received afferents from the spinal cord. The projections terminated most abundantly in the caudomedial portions of the magnocellular LRN. The medial aspect of the LRN was the site of preferential termination of the cervical spinal projection. Lumbar spinal projections terminated preferentially in the rostrolateral region of the nucleus. These two imputs overlap in the central region of the nucleus.
Cholinergic innervation of the rat hippocampus as revealed by choline acetyltransferase immunocytochemistry: A combined light and electron microscopic study
Authors: Frotscher Michael , Léránth Csaba
Published: May 2005

The cholinergic innervation of the rat hippocampus proper and fascia dentata was investigated by using a monoclonal antibody against choline acetyltransferase (ChAT). At the light microscopic level, thin varicose ChAT‐immunoreactive fibers were observed mainly in the vicinity of the pyramidal and granular layers where they formed a fine network around proximal dendrites of pyramidal and granule cells. In addition, many ChAT‐immunoreactive fibers were found in the hilar region and in stratum oriens, radiatum, and lacunosum‐moleculare of all hippocampal sectors.

Electron microscopic analysis revealed ChAT immunoreactivity in thin unmyelinated varicose axons and terminals which established synaptic contacts. Asymmetric contacts of ChAT‐immunoreactive terminals were found on small spines in the dendritic layers of the hippocampus proper and in the molecular layer of the fascia dentata. Symmetric synaptic contacts were formed on the cell bodies of pyramidal and granule cells. Both symmetric and asymmetric synaptic contacts occurred on dendritic shafts. The analysis of serial thin sections, which allows identification of postsynaptic elements, suggests that pyramidal cells, granule cells, and nonpyramidal neurons of the hippocampus receive a cholinergic input.
Axonal projections from transplanted ectopic legs in an insect
Authors: Sivasubramanian P. , Nässel D. R.
Published: May 2005

Ectopic legs were produced in the fleshfly Sarcophaga bullata by transplantation of leg imaginal discs. Cobalt or horseradish peroxidase (HRP) fills from these supernumerary legs showed that their sensory axons invariably innervate the metathoracic leg neuropil via an abdominal nerve. This was so irrespective of whether they differentiated from pro‐, meso‐, or metathoracic leg disc. Implantation of left leg discs on the right side and vice versa revealed that the site of implantation determined which side (left or right) of the ganglion was innervated. In general, the same results were obtained when the implantation was made after removal of a leg disc from the host, except in a few instances in which the implanted leg directly innervated the deafferented leg neuropil. The results indicate that axonal pathfinding from the imaginal discs in this insect is via contact guidance along preexisting nerves or imaginal disc stalks.
Observations on the somatodendritic morphology and axonal trajectory of intracellularly HRP‐Labeled efferent neurons located in the deeper layers of the superior colliculus of the cat
Authors: Moschovakis A. K. , Karabelas A. B.
Published: May 2005

Efferent neurons of the deeper layers of the cat's superior colliculus were stained with horseradish peroxidase (HRP) to demonstrate patterns of somatodendritic morphology and axonal trajectory. A combination of somatodendritic and axonal features of the HRP‐labeled cells revealed the existence of three major groups of tectal efferent neurons (X, T, and I). X neurons are mostly large and multipolar and participate in the crossed descending and ipsilateral ventral ascending projections of the superior colliculus. The X group includes multipolar radiating (X1), tufted (X2), large vertical (X3), medium‐sized vertical (X4), and medium‐sized horizontal (X5) neurons. T neurons participate in one or two of the major tectofugal bundles (medial descending ipsilateral, lateral descending ipsilateral, medial dorsal ascending, crossed descending) besides providing a commissural branch. They also issue recurrent collaterals distributed within a more or less restricted area of the deeper layers. The T group includes medium‐sized, trapezoid, radiating (T1) and small or mediumsized, ovoid, vertical (T2) neurons. I neurons participate in the ipsilateral descending projection of the superior colliculus. They are small, triangular or ovoid, sparsely ramified cells that provide long, varicose collaterals irregularly distributed within the deeper layers. The majority of T neurons are located in the ventral stratum opticum or dorsal stratum griseum intermedialem, X3 and X5 neurons are situated immediately below in the dorsal stratum griseum intermediale, while X1, X2, X4, and I neurons are indiscriminately distributed within the deeper layers. The polythetic classification presented here provides a conceptual framework for the description of tectal efferent neurons. It is open‐ended and can thereby accomodate new cells types as indicated by the disclosure of a small horizontal (A) and a small radiating (unclassified) neuron. Moreover, it does not preclude the construction of alternate taxonomies. A dendro‐architectonic classification into four groups [vertical (X3, X4, T2, I), horizontal (X5, A), radiating (X1, T1, I), and tufted (X2)] can be made and would relate to the mode of integration of various tectopetal inputs. A classification based on the dorsoventral location of tectal efferent neurons is also possible and would relate to the dorsoventral distribution of neurons with specific response properties.
Distribution of cholecystokinin‐like immunoreactivity in the rat main olfactory bulb
Authors: Seroogy Kim B. , Brecha Nicholas , Gall Christine
Published: May 2005

The anatomical localization of cholecystokinin‐like immunoreactivity (CCK‐I) within the rat main olfactory bulb was analyzed by using the‐peroxidase‐antiperoxidase immunocytochemical technique. Neurons or neuronal processes containing CCK‐I were localized within all laminae of the olfactory bulb except the olfactory nerve fiber layer. A large population of CCK‐I neurons, with morphology, size, and distribution corresponding to that of the middle and external tufted cells, was observed within a zone extending from the deep periglomerular region through the superficial one‐half to one‐third of the external plexiform layer. A smaller number of immunoreactive perikarya were found in the deep external plexiform layer, the glomerular layer, and rarely within the inner plexiform layer. These CCK‐I neurons appeared to correspond to internal tufted cells, periglomerular cells, and deep short‐axon cells, respectively. Dense CCK‐I staining of fibers and terminals was present within the internal plexiform layer and, less densely, within the neuropil of the granule cell layer. In addition, terminal‐like CCK‐I was localized within layer 1A of the anterior olfactory nucleus, the olfactory tubercle, and the most rostral piriform cortex. This observation provides corroboration for the identification of the principal CCK‐I neuron in the rat olfactory bulb as the centrally projecting middle tufted cell. The present results, demonstrating the localization of CCK‐I to both local circuit and projection neurons of the olfactory bulb and to terminal‐like puncta in the internal plexiform and granule cell layers, suggest that CCK may be significantly involved in olfactory processing at several levels.
A callosal projection of area 17 upon the border region of area MT in the marmoset monkey, Callithrix jacchus
Authors: Kunz Birgit , Spatz W. B.
Published: May 2005

Injections of the retrograde tracer HRP into the border region of the temporal visual area MT and adjoining cortex in Callithrix labeled pyramidal neurons in area 17 of the contralateral hemisphere. Evidence is presented that this newly discovered heterotopic callosal projection of the monkey striate cortex connects regions of representation of the zero vertical meridian of the visual field in a retinotopic order.
The development of acetylcholinesterase activity in normal and transplanted superior colliculus in rats
Authors: Harvey A. R. , MacDonald A. M.
Published: May 2005

Histochemical techniques have been used to examine the development of the enzyme acetylcholinesterase (AChE) in normal and transplanted rat superior colliculus (SC). At birth (P0), relatively little AChE activity was found in SC in situ; however, there was a gradual increase in the intensity of AChE staining in the SC over the first 4 postnatal weeks. In the superficial layers, an increase in AChE activity was first seen in rostromedial SC at P6 and was found throughout the upper tectal layers by P10. An increase in AChE activity in the intermediate layers was apparent by P12 and the adult pattern, characterized by periodic bands of AChE staining, was established by P22.

In tectal grafts, the development of AChE activity followed a time course similar to that found in normal SC. Mature tectal grafts contained moderate AChE activity with AChE‐positive cells scattered throughout the neuropil. There were however, localized, often spherically shaped areas which displayed relatively intense AChE activity. These AChE‐dense areas had a characteristic appearance in adjacent sections stained for Nissl or neurofibrils. Significantly, host retinal input, where present, was always restricted to the AChE‐dense regions and it seems certain that these areas are homologous to the superficial layers of normal SC. AChE‐rich regions were also present, however, in grafts which received no retinal input and in general the pattern of AChE activity in tectal grafts was strikingly similar, irrespective of their location or connections with the host brain. It would appear, therefore, that much of the AChE activity in tectal transplants, and presumably in SC in situ, is intrinsic to that region and not derived from or dependent upon extrinsic innervation.
Spinal and trigeminal dorsal horn projections to the parabrachial nucleus in the rat
Authors: Cechetto David F. , Standaert David G. , Saper Clifford B.
Published: May 2005

We studied afferents to the parabrachial nucleus (PB) from the spinal cord and the spinal trigeminal nucleus pars caudalis (SNVc) in the rat by using the anterograde and retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP). Injections of WGA‐HRP into medial PB retrogradely labeled neurons in the promontorium and in lamina I of the dorsal rostral SNVc, while injections into lateral PB and the Kölliker‐Fuse nucleus retrogradely labeled neurons in these areas as well as in lamina I throughout the caudal SNVc and spinal dorsal horn. Injections of WGA‐HRP into the caudal SNVc and dorsal horn of the spinal cord resulted in terminal labeling in the dorsal, central, and external lateral subnuclei of PB and the Kölliker‐Fuse nucleus, all of which are known to receive cardiovascular and respiratory afferent information. Injections of WGA‐HRP into the promontorium and dorsal rostral SNVc resulted in terminal labeling in the same PB subnuclei, as well as in the medial and the ventral lateral PB subnuclei, which are sites of relay for gustatory information ascending from the medulla to the forebrain. The spinal and trigeminal projection to PB may mediate the convergence of pain, chemosensory, and temperature sensibilities with gustatory and cardiorespiratory systems in PB.
Topographic organization of facial motoneurons to individual pinna muscles in rat (Rattus rattus) and bat (Rousettus aegyptiacus)
Authors: Friauf Eckhard , Herbert Horst
Published: May 2005

The location and number of motoneurons to individual pinna muscles were determined by retrograde transport of horseradish peroxidase in rat and flying fox. The degree of ear mobility differs considerably between these species in that rats perform simpler ear movements while flying foxes move their pinnae in a sophisticated way. Five pinna muscles were investigated in each species. Motoneurons lay within the medial subdivision of the facial motor nucleus extending over its entire rostrocaudal length. They were topographically organized; however, a somatotopic order could not be observed. With one exception homologous pinna muscles were represented in corresponding areas in both species, supporting the idea of a common representation of ear muscles in mammals. In rat, motoneuron pools overlapped considerably, whereas in flying fox overlap was minute. A total of 1,110 and 1,646 motoneurons were labeled in rat and flying fox, respectively. We conclude that the higher number of pinna motoneurons in the latter species in addition to the more clear‐cut topography provide the structural substrates that underlie differences in the quality of ear movements as seen in bats vis‐a‐vis other mammals.
Primary sensory ganglion cells projecting to the principal trigeminal nucleus in the mallard, Anas platyrhynchos
Authors: Kishida Reiji , Dubbeldam Jacob L. , Goris Richard C.
Published: May 2005

The trigeminal and glossopharyngeal ganglia of the adult mallard were studied following HRP injections into the principal trigeminal nucleus (PrV). The PrV consists of the principal trigeminal nucleus proper (prV) and the principal glossopharyngeal nucleus (prIX). After an injection into the prV, the labeled cells were found in the ipsilateral trigeminal ganglion. After an injection into the prIX, labeled cells were found in the ipsilateral distal glossopharyngeal ganglion, but not in the proximal ganglion of the IX and X cranial nerve (pGIX + X).

In Nissl preparations, two types of ganglion cells in the trigeminal ganglion, pGIX + X, and distal ganglion of N IX could be distinguished: larger light cells and smaller dark cells. We could not determine whether the HRP‐labeled cells belonged to both types or to one of them; but because all the labeled cells were over 20 μm, we concluded that the smallest cells (10–19 μm) in the trigeminal ganglion and distal ganglion of N IX did not project to the PrV.

The labeling of the cells in the distal ganglion of N IX (average 34.5 μm) was uniformly moderate. In the trigeminal ganglion there were two types of labeled cells: heavily labeled cells (average 29.1 μm) and moderately labeled cells (average 35.1 μm). These two types of labeling (moderate and heavy) may reflect two types of primary sensory neurons: cells with ascending, nonbifurcating axons, and cells with bifurcating axons. We speculate that the former are proprioceptive neurons and the latter tactile neurons. Labeled bifurcating axons in the sensory trigeminal complex gave off collaterals to all parts of the descending trigeminal nucleus except to the caudalmost laminated spinal part.
Sensorimotor cortical projections to the primate cuneate nucleus
Authors: Cheema S. , Rustioni A. , Whitsel B. L.
Published: May 2005

The organization of the corticocuneate pathway was investigated in monkeys by using the anterograde and retrograde axonal transport of either horseradish peroxidase (HRP) or wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP).

Injection of either tracer into the precentral cortex (centered on area 4) results in heavy anterograde labeling in the tegmental region, which lies immediately ventrolateral to the cuneate nucleus, particularly at levels caudal to the obex. On the other hand, injections of the same tracers involving areas 3b, 1, and 2 cause anterograde labeling mainly within the core (pars rotunda of Ferraro and Barrera, '35, Arch. Neurol. Psychol. 33:262–75) of the cuneate nucleus. Anterograde labeling is also evident in the rostral parts of the cuneate nucleus, especially after injections involving areas 1 and 2. Injections restricted largely to area 3b cause anterograde labeling preferentially in the core of the cuneate nucleus.

After injection of HRP or WGA‐HRP into the dorsal medulla, retrogradely labeled neurons are present both in the pre‐ and postcentral gyrus, but their location depends upon the sites and extent of the injection site. When the tracer diffuses into the underlying tegmental area, many retrogradely labeled neurons appear in the precentral motor cortex, principally in area 4 although some of them also occur in area 6. With smaller injections, largely restricted within the cuneate nucleus, most labeled neurons are present in the postcentral gyrus, with the largest population in areas 1 and 2; a smaller number of small neurons in area 3b are best demonstrated with WGA‐HRP; and area 3a contains the smallest complement of retrogradely labeled neurons.

The data from these studies suggest a segregation of pre‐ and postcentral afferents in the ventral tegmental region and the cuneate nucleus, respectively. These findings pertaining to the corticocuneate projection in the monkey are discussed in relation to (1) the parallelism between monkeys and cats (2) possible physiological implications of the anatomical organization described, and (3) conflicting evidence in the neurophysiological observations obtained, by earlier investigators, by antidromic and orthodromic activation of this pathway.
An ultrastructural study of cat lumbosacral γ‐motoneurons after retrograde labelling with horseradish peroxidase
Authors: Lagerbäck Per‐Åke
Published: May 2005

Twelve retrogradely horseradish peroxidase (HRP)‐labelled triceps surae motoneurons of gamma size (mean cell body diameter<38 μm) were studied ultrastructurally. The contours of the cell bodies, as observed in the transverse midnucleolus plane, were elongated to rounded. The axons identified all originated from the cell body. The mean diameter of the stem dendrites was 4.5 μm.

A substantial part of the cell membrane was covered by glial extensions. The boutons and synaptic contacts apposing the γ‐motoneurons could be classified into two categories on the basis of the the type of synaptic vesicles: S‐type boutons with spherical synaptic vesicles and F‐type boutons with flattened vesicles. In each neuron, the values for mean length and mean area of apposition, percentage synaptic covering, and packing density of S‐type, F‐type, and S + F‐type boutons were estimated on the cell body and in two dendritic compartments. In comparison with α‐motoneurons and Renshaw cells, the cell bodies of the γ‐motoneurons were covered by smaller and strikingly fewer boutons of both the S‐ and F‐types. The values for percentage synaptic covering and packing density of boutons on the proximal dendrites were also lower for γ‐motoneurons than for both α‐motoneurons and Renshaw cells, although the differences were less pronounced than on the cell body. No boutons of the C‐, M‐, and T‐types described for α‐motoneurons were found on the γ‐motoneurons.
Thalamic projections to motor, prefrontal, and somatosensory cortex in the sheep studied by means of the horseradish peroxidase retrograde transport method
Authors: Dinopoulos A. , Karamanlidis A. N. , Papadopoulos G. , Antonopoulos J. , Michaloudi H.
Published: May 2005

In this study the motor, prefrontal, and somatosensory areas of the sheep cerebral cortex were defined on the basis of their thalamic afferents traced with the horseradish peroxidase method.

The motor area (areas 4 and 6) occupies the cruciate gyrus. It receives a substantial projection from the thalamic nuclei ventralis anterior, ventralis lateralis, medialis dorsalis, and centralis lateralis and a smaller one from the nuclei ventralis medialis, centralis medialis, paracentralis, lateralis dorsalis, lateralis posterior, centromedianus, parafascicularis, suprageniculatus, ventralis posterolateralis, and the midline nuclei. Area 4 receives afferents mainly from the nuclei ventralis anterior, ventralis lateralis, medialis dorsalis, and lateralis posterior, whereas area 6 receives afferents mainly from the nuclei ventralis anterior, medialis dorsalis, and lateralis posterior and fewer afferents from the nucleus ventralis medialis.

The prefrontal area occupies the gyrus proreus and receives numerous afferents from the nucleus medialis dorsalis and fewer from the nuclei lateralis posterior and ventralis medialis.

The area extending between the lateral fissure, the coronal sulcus, the presylvian sulcus, and the rostral branch of the lateral fissure is connected mainly with sensory thalamic nuclei. Thalamic afferents were found to emanate from the nuclei ventralis posteromedialis (its parvicellular part included), ventralis posterolateralis, ventralis medialis, paracentralis, lateralis posterior, medialis dorsalis, centromedianus, suprageniculatus, paraventricularis, the substantia nigra, and the ventral part of the lateral geniculate nucleus. The first somatosensory area (Johnson et al., '74, J. Comp. Neurol. 158:81–108) was found to extend between the coronal, the diagonal, and the anterior suprasylvian sulci and to receive afferents almost exclusively from the nucleus ventralis posteromedialis.
Localization of enkephalin‐like immunoreactive amacrine cells in the larval tiger salamander retina: A light and electron microscopic study
Authors: Watt Carl B. , Li Hai‐Biao , Fry Keith R. , Lam Dominic Man‐Kit
Published: May 2005

Immunohistochemistry was utilized to examine the light and electron microscopic localization of enkephalin‐like (enk) immunoreactive amacrine cells in the larval tiger salamander retina. The vast majority of enk‐immunoreactive cells were typical amacrine cells whose round or oval cell bodies (14–16 μm) were situated in the innermost cell row of the inner nuclear layer. A relatively small number of enk‐stained oval cell bodies (14–22 μm) were located in the ganglion cell layer and were designated as those of displaced amacrine cells. Enkephalin immunostaining was observed in the inner plexiform layer as a fine plexus in sublamina 1 and as a dense network of fibers in sublamina 5. In both the center and periphery of the retina the density of typical enk‐amacrine cells was determined to be 250 ± 16.36 cells per mm2 surface area of the retina.

At the ultrastructural level typical enk‐stained amacrine cells possessed a round, indented nuclear membrane. Enk‐immunoreactive processes sometimes contained dense‐core vesicles (60–115 nm) in addition to a rather homogeneous population of small, round, agranular synaptic vesicles (25–35 nm). In sublamina 1 the processes of enk‐amacrine cells were presynaptic to amacrine and bipolar cells. They also contacted processes devoid of synaptic vesicles which possibly arise from ganglion cells. As the postsynaptic element in sublamina 1, they received synaptic input from amacrine cells. In sublamina 5 the processes of enk‐amacrine cells were presynaptic to amacrine cells, bipolar cells, and the somas of cells situated in the ganglion cell layer. They also formed synaptic contacts onto processes devoid of synaptic vesicles, which may originate from ganglion cells. As the postsynaptic member in sublamina 5, the processes of enk‐amacrine cells received synapses from amacrine cells and bipolar cells.
Early vascularization of the embryonic cerebral cortex: Golgi and electron microscopic studies
Authors: Marin‐Padilla Miguel
Published: May 2005

Two developmental aspects in the establishment of the vasculature of the embryonic cerebral cortex have been analyzed: the vascular perforation of the external basal lamina and marginal glia by leptomeningeal capillaries and their early intracortical angiogenesis. Electron microscopic and rapid Golgi preparations have been used in this study. Four phases have been identified in the vascular perforation of the cortex. First, the leptomeningeal capillary approaches and establishes direct contact with the external basal lamina and marginal glia of the cerebral cortex. Second, the leading endothelium of the glia‐touching capillary undergoes considerable membrane activity forming many filopodia and pseudopodia. Some filopodia of this activated endothelium perforate the vascular and cortical basal laminae and penetrate into the neural tissue. This filopodial perforation is accompanied by swelling and disintegration of the subadjacent marginal glial endfeet. Third, the original perforation enlarges progressively and allows an entire endothelial cell (or cells) to penetrate into the neural tissue. Fourth, proliferation and progressive canalization of penetrated endothelial cells result in the formation of a new cortical capillary in situ. Its proximal wall becomes surrounded by perivascular glial processes which appear to replace the degenerated ones. Thus a vasculoglial barrier is formed around the growing capillary, isolating it from the neural tissue, while the filopodia at its leading edge are still growing among the neural elements without recognizable basal lamina. The formation of a shallow pial‐funnel at the capillary entrance can also be recognized at this time. This funnel contains the fine processes of leptomeningeal cells, a few collagen fibers, and the basal laminae of the penetrating vessel and of the perivascular glia. It represents an early stage in the formation of the Virchow‐Robin space. The intracortical embryonic vasculature is characterized by both capillary angiogenesis and regression and by the formation of anastomotic plexuses. While capillary angiogenesis and reabsorption are found everywhere and appear as random phenomena, the location of the anastomotic plexuses is specific and always associated with actively growing cortical regions.
Postnatal volumetric development of the prefrontal cortex in the rat
Authors: van Eden C. G. , Uylings H. B. M.
Published: May 2005

The medial and orbital parts of the prefrontal cortex (PFC) increase in volume during the first weeks of postnatal life. At the end of this period, however, the volumes of both parts of the PFC reach a significantly higher value than in adulthood. Subsequently the volumes decrease until the adult volume is attained. The three subareas of the medial PFC (i.e., the medial precentral area, the dorsal anterior cingulate, and the prelimbic area) reach a maximum volume around day 24, while the two orbital PFC subareas (i.e., the dorsal and ventral agranular insular areas) attain their maximum value around day 30. The differences found in the growth pattern of the five PFC subareas, which are innervated by specific subnuclei of the mediodorsal nucleus of the thalamus, suggest a role of these subnuclei in the PFC development.
Evidence for corticotropin‐releasing factor, neurotensin, and somatostatin in the neural pathway from the central nucleus of the amygdala to the parabrachial nucleus
Authors: Moga Margaret M. , Gray Thackery S.
Published: May 2005

The central nucleus of the amygdala (CNA) and the parabrachial nucleus of the pons (PBN) are included within a group of brain nuclei involved in autonomic responses. Previous studies have shown that the CNA sends a considerable projection to the PBN and that both nuclei contain neurons immunoreactive to many different peptides. In the present study, we used the combined retrograde fluorescence‐immunofluorescence method to determine whether the CNA projection to the PBN contains any of the following neuropeptides: corticotropin–releasing factor (CRF), neurotensin (NT), somatostatin (SS), and enkephalin (ENK). Following injections of fluorescent dye into the PBN, neurons within both lateral and medial subdivisions of the CNA were retrogradely labeled. A significant percentage of CRF (54–66%)–, NT (40–53%)–, and SS (31–50%)‐immunoreactive neurons were retrogradely labeled, predominantly within the lateral CNA. Enkephalin‐immunoreactive neurons were never retrogradely labeled, although they were often found adjacent to retrogradely labeled neurons. Our results show that the lateral CNA is a major source of CRF, NT, and SS terminals within the PBN. Neurons in the medial CNA also provide a significant contribution to the CNA‐PBN pathway, but their chemical nature remains to be determined. We conclude that CRF, NT, and SS are important putative neurotransmitters in the CNA's regulation of PBN function. This CNA‐PBN peptidergic pathway may participate in stress‐related cardiovascular and respiratory responses.
Corticocortical efferent systems in the monkey: A quantitative spatial analysis of the tangential distribution of cells of origin
Authors: Caminiti Roberto , Zeger Scott , Johnson Paul B. , Urbano Antonio , Georgopoulos Apostolos P.
Published: May 2005

The laminar and tangential distributions of association neurons projecting from areas 4 and 6 of the frontal lobe to area 5 of the superior parietal lobule were studied in macaque monkeys by using horseradish peroxidase histochemistry. In both areas 4 and 6 association neurons were medium‐large pyramidal cells of layers II and III, and pyramidal and fusiform cells of layers V‐VI. Tangentially, they were distributed unevenly over the cortical surface occupying only certain parts of areas 4 and 6, including the dorsomedial part of area 6, the proximal arm region of Woolsey's M1 map, parts of the postarcuate cortex, and the supplementary motor area. Within these projection zones, the number of projection cells waxed and waned in a periodic fashion.

Quantitative methods, including spectral analysis techniques, were used to characterize precisely spatial periodicities along the rostrocaudal dimension. The same quantitative analyses were used to determine the nature of the tangential distribution of corticocallosal cells of area 5 projecting to contralateral area 5. Both association and callosal spectra contained a strong component in the range of low spatial frequencies, corresponding to periods greater than 2 mm. Moreover, a consistent peak was observed in both spectra at spatial frequencies corresponding to periods ranging from 0.85 to 1.28 mm. This peak is in accord with the hypothesis of a modular organization of the cells of origin of these projection systems.
The origins of descending spinal projections in lepidosirenid lungfishes
Authors: Ronan Mark C. , Northcutt R. Glenn
Published: May 2005

The origins of descending spinal projections in the lepidosirenid lungfishes were identified by retrograde transport of horseradish peroxidase (HRP) introduced into the rostral spinal cords of juvenile African (Protopterus annectans and Protopterus amphibians) and South American (Lepidosiren paradoxa) lungfishes. Standard HRP histochemistry revealed retrogradely labeled neurons in the nucleus of the medial longitudinal fasciculus, midbrain tegmentum, red nucleus, optic tectum, mesencephalic trigeminal nucleus, granule cell layer of the cerebellum, superior, middle, and inferior medullary reticular nuclei, magnocellular and descending octaval nuclei, region of the descending trigeminal tract, solitary complex, and the margins of the spinal gray matter anterior to the spinal HRP implant. A small number of retrogradely labeled neurons were also present in the ventral thalamus of Protopterus. A descending spinal projection from the forebrain was not evident in either genus of lepidosirenid lungfishes. The presence of projections to the spinal cord from the diencephalon, medial reticular formation of the midbrain and medulla, octaval (vestibular) nuclei, solitary complex, and probable nucleus of the descendin trigeminal tract in lungfishes and their overall similarity to comparable projections in other vertebrates suggest that these pathways are among those representative of the primitive pattern of descending spinal projections in vertebrates.