bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tectoreticular pathways in the turtle, Pseudemys scripta. I. Morphology of tectoreticular axons
Authors: Sereno Martin I. 
Published: January 2005

AbstractTectoreticular projections in turtles were examined by reconstructing from serial sections axons that were anterogradely filled with horseradish peroxidase after tectal injections. Three tectoreticular pathways each contain extensively collateralized axons. The crossed dorsal pathway (TBd) contains large and small caliber axons. After leaving the tectum, TBd axons emit collaterals into the ipsilateral profundus mesencephali rostralis and then give off a main rostral branch that bears secondary collaterals in the ipsilateral interstitial nucleus, of the medial longitudinal fasciculus and the suprapeduncular nucleus. The main trunks cross the midline and descend in the predorsal bundle, generating collaterals at regular intervals. These terminate mostly in the medial half of the reticular core from the midbrain to the caudal medulla. Axons in the uncrossed intermediate pathway also emit collaterals into a midbrain reticular nucleus (profundus mesencephali caudalis) and often have a thick rostral branch. The main caudal trunks, however, remain ipsilateral and travel in a diffuse, laterally placed tract, where each emits a long series of collaterals into the lateral half of the reticular core. The uncrossed ventral pathway (TBv) contains medium and small caliber axons. TBv axons often have collaterals within the tectum and apparently lack main rostral branches. Their caudal trunks run in the tegmental neuropile below the TBi where they collateralize less exuberantly than do TBd and TBi axons.The morphology of axons in all three pathways suggests that projections from disjunct tectal loci converge at many rostrocaudal levels within the reticular formation. This point was examined explicitly in experiments in which two disjunct injections were placed in one tectal lobe. Intermediate pathway axons traced from the two loci initially formed two distinct bundles but then intermingled in the reticular formation.
Tectoreticular pathways in the turtle, Pseudemys scripta. II. Morphology of tectoreticular cells
Authors: Sereno Martin I. , Ulinski Philip S. 
Published: January 2005

AbstractThe morphology of tectoreticular neurons in turtles was examined with serial section reconstructions of neurons retrogradely filled with HRP. Six classes of tectal neurons project into the three tectobulbar pathways characterized in the preceding paper (Sereno, '85). (1) Large multipolar neurons with somata in the central gray layers, and with moderately branched dendrites sometimes spanning over a millimeter, project into the dorsal tectobulbar pathway, TBd. Their dendrites are covered with fine spicules and tend to arborize in the lower third of the superficial gray layers. (2) Medium‐sized neurons with multiple radial dendrites and somata in the central white and upper periventricular layers probably project into the ipsilateral intermediate tectobulbar pathway, TBi. Their dendrites also bear fine spicules and usually reach the tectal surface. (3) Small radial cells in the periventricular layers, and (4) small bitufted radial cells in the superficial gray project into the small caliber component of the ipsilateral ventral tectobulbar pathway, TBv(sm). (5) Medium‐sized central gray neurons with stratified dendrites, and (6) medium‐sized central gray neurons with horizontal dendrites probably project into the medium caliber component of the ventral tectobulbar pathway, TBv(med). In contrast to TBd and TBi neurons, these last four classes emit a spray of long, filamentous dendritic appendages in the central gray and have dendritic arbors near the top of the superficial gray.The morphology of the neurons described in this and the preceding paper is briefly discussed in light of current ideas about tectally mediated sensorimotor transformations.
Rat medulla oblongata. IV. Topographical distribution of catecholaminergic neurons with quantitative three‐dimensional computer reconstruction
Authors: Kalia Madhu , Woodward Donald J. , Smith Wade K. , Fuxe Kjell 
Published: January 2005

AbstractWe examined serial 40 μm vibratome, immunoperoxidase‐stained sections of the medulla with tyrosine hydroxylase (TH), dopamine‐beta‐hydroxylase (DBH), and phenylethanolamine N‐methyltransferase (CPNMT) antisera followed by Nissl staining to locate catecholaminergic neurons in cytoarchitectonic regions followed by a three‐dimensional (3D) computer reconstruction of these cell groups to determine their spatial organization. Overlay drawings of low and high power photomicrographs showing cell bodies and nuclear boundaries were entered into a digital computer storage system. Every section in the series was plotted to yield an accurate representation of regional densities of cells and location of nuclei, as revealed by two‐dimensional plots of individual sections as well as three‐dimensional plots of groups of sections. Data files were scanned in a number of ways to obtain total cell counts of TH‐, DBH‐, and PNMT‐immunoreactive cells within a designated area or cell counts of only one type of immunoreactive cell. This combination of data manipulation produced the following results: (1) A1 group is a homogeneous population of noradrenergic neurons at levels caudal to the obex, and at the obex it is mixed with adrenergic cells. The dimensions of the A1 cell group are 1.3 × 2.7 mm, extending from −2.5 to +0.2. Part of this cell group lies in the lateral reticular nucleus. (2) A2 group is not purely noradrenergic as previously suspected. It is a very mixed cell group containing mainly dopaminergic neurons in the area postrema (periventricular region) and the dorsal motor nucleus of the vagus, mainly noradrenergic neurons in the medial subnucleus of the nucleus of the tractus solitarius (nTS), mainly adrenergic neurons in the dorsal strip and dorsal subnucleus of the nucleus of the tractus solitarius, and a mixture of all three catecholaminergic neurons in the other subnuclei of the nTS. The dimensions of this group are 0.4 × 3 mm extending from −2.7 to +0.3. (3) C1 group is a homogeneous population of adrenaline cells extending from +1 to +2.5 with dimensions of 1.5 × 1.5 mm and consisting of scattered neurons some of which occupy the gigantocellular reticular nucleus. (4) C2 group is a homogeneous population of adrenaline neurons extending from +1 to +3 with dimensions of 2.5 × 3 mm. Accurate visual imaging and quantitation of the spatial organization of medullary catecholaminergic neurons within the classical anatomical framework of cytoarchitecture provides an enhanced comprehension of the organization of this region of the central nervous system.
Immunocytochemical localization of choline acetyltransferase in rat cerebral cortex: A study of cholinergic neurons and synapses
Authors: Houser C. R. , Crawford G. D. , Salvaterra P. M. , Vaughn J. E. 
Published: January 2005

AbstractCholine acetyltransferase (ChAT), the acetylcholine‐synthesizing enzyme and a definitive marker for cholinergic neurons, was localized immunocytochemically in the motor and somatic sensory regions of rat cerebral cortex with monoclonal antibodies. ChAT‐positive (ChAT+) varicose fibers and terminal‐like structures were distributed in a loose network throughout the cortex. Some immunoreactive cortical fibers were continuous with those in the white matter underlying the cortex, and many of these fibers presumably originated from subcortical cholinergic neurons. ChAT+ fibers appeared to be rather evenly distributed throughout all layers of the motor cortex, but a subtle laminar pattern was evident in the somatic sensory cortex, where lower concentrations of fibers in layer IV contrasted with higher concentrations in layer V. Electron microscopy demonstrated that immunoreaction product was concentrated in synaptic vesicle‐filled profiles and that many of these structures formed synaptic contacts. ChAT+ synapses were present in all cortical layers, and the majority were of the symmetric type, although a few asymmetric ones were also observed. The most common postsynaptic elements were small to medium‐sized dendritic shafts of unidentified origin. In addition, ChAT + terminals formed synaptic contacts with apical and, probably, basilar dendrites of pyramidal neurons, as well as with the somata of ChAT‐negative nonpyramidal neurons.ChAT+ cell bodies were present throughout cortical layers II–VI, but were most concentrated in layers II–III. The somata were small in size, and the majority of ChAT + neurons were bipolar in form, displaying vertically oriented dendrites that often extended across several cortical layers. Electron microscopy confirmed the presence of immunoreaction product within the cytoplasm of small neurons and revealed that they received both symmetric and asymmetric synapses on their somata and proximal dendrites. These observations support an identification of ChAT + cells as nonpyramidal intrinsic neurons and thus indicate that there is an intrinsic source of cholinergic innervation of the rat cerebral cortex, as well as the previously described extrinsic sources.
Numbers of myelinated and unmyelinated axons in the dorsal, lateral, and ventral funiculi of the white matter of the S2 segment of cat spinal cord
Authors: Chung Kyungsoon , Sharma Jivesh , Coggeshall Richard E. 
Published: January 2005

AbstractThe present work determines the numbers of myelinated and unmyelinated axons in the dorsal, lateral, and ventral funiculi of the S2 segment of the cat spinal cord. The major finding is that unmyelinated axons are almost as numerous as myelinated axons in these pathways. The myelinated axons tend to be distributed uniformly, although there is a slight concentration of these fibers in the dorsal part of the lateral funiculus. By contrast, the unmyelinated fibers, although found in significant numbers in all parts of these funiculi, concentrate in the dorsal part of the lateral funiculus and in the dorsal funiculus. Of particular note are the unmyelinated fibers in the dorsal funiculus, because it is highly likely that some of these are sensory. The findings in this study will serve as a basis for experimental studies to determine the numbers, locations, and types of unmyelinated fibers in the white matter of the mammalian cord.
Possible target neurons of 5‐hydroxytryptamine fibers in the lamprey spinal cord: Immunohistochemistry combined with intracellular staining with lucifer yellow
Authors: Van Dongen Paul A. M. , Hökfelt Tomas , Grillner Sten , Verhofstad Albert A. J. , Steinbusch Harry W. M. 
Published: January 2005

AbstractIntracellular recordings were made from 76 neurons belonging to various cell types in the lamprey spinal cord, and these neurons were subsequently stained with Lucifer yellow. Sections were made of spinal cords containing Lucifer‐yellow‐filled neurons, and in the same sections 5‐hydroxytrytamine (5‐HT)‐containing neurons and fibers were made visible with immunohistochemical methods. Motoneurons and lateral cells appeared to send part of their dendrites into a dense ventromedial 5‐HT plexus, and these dendrites were adjacent to 5‐HT varicosities. No or few 5‐HT varicosities have been found adjacent to cell bodies or dendrites of sensory dorsal cells, giant interneurons, and edge cells. The combined application of intracellular staining and immunohistochemistry appeared, to be suited to screen for possible transmitter‐identified contacts on morphologically identified neurons.
GABA neurons in the superficial layers of the rat dorsal cochlear nucleus: Light and electron microscopic immunocytochemistry
Authors: Mugnaini Enrico 
Published: January 2005

AbstractThis article is an application of light and electron microscopic immunocytochemistry to the study of the neuronal circuit of the superficial layers in the rat dorsal cochlear nucleus (DCN). An antiserum against the intrinsic marker glutamate decarboxylase (GAD) is used to identify and map axon terminals and neurons that use gamma aminobutyric acid (GABA) as a neurotransmitter. It is demonstrated that layers 1 and 2 of the DCN contain a very high density of GABAergic boutons, matched only by the granule cell domains of the ventral cochlear nucleus, especially the superficial granule cell domain. These two layers also contain much higher concentrations of GABAergic cell bodies than all other magnocellular regions of the cochlear nuclear complex. Cartwheel and stellate neurons, and probably also Golgi cells, previously characterized in Golgi and electron microscopic investigations, appear immunostained and, therefore, are presumably inhibitory. The synaptic relations between parallel fibers, the axons of granule cells, and cartwheel and stellate neurons are confirmed. The present study also supports the conclusion that stellate cells are coupled to one another by gap junctions. Also scattered in layer 1 are large, GABAergic neurons that occur with irregular frequency and presumably represent displaced Purkinje cells, previously identified with a Purkinje‐cell‐specific marker. Granule neurons and pyramidal neurons remain unstained, even after topical injection of colchicine, which enhances immunostaining of the other glutamate‐decarboxylase‐positive cells, and therefore must use transmitters different from GABA.The possible analogies between the spiny cartwheel and the aspiny stellate cells of the DCN and the cerebellar Purkinje and stellate/basket cells are discussed in the light of data from Golgi, electon microscopy, and transmitter imunocytochemistry.
Fine structural survey of the rat's brainstem sensory trigeminal complex
Authors: Ide Linda S. , Killackey H. P. 
Published: January 2005

AbstractThe fine structural organization of the principal sensory trigeminal nucleus was compared with that of the spinal trigeminal nucleus (subnuclei oralis, interpolaris, and the deep layers of caudalis) in adult albino rats. Direct comparisons indicate similarities between all of the subdivisions of the brainstem trigeminal complex both in the major morphological classes of neurons present and in basic patterns of synaptic connections. Major differences between the several subdivisions occur in the relative numbers and distribution of the different cell types.The spinal trigeminal nucleus is distinguished by more numerous large (22–40 μm) polygonal neurons which give rise to long straight primary dendrites. Both the perikaryal surface and the thick primary dendrites of many of these cells are densely innervated by synaptic terminals. Especially large cells of this type are a prominent feature of subnucleus oralis. By contrast, the principal sensory nucleus is distinguished by its high density of small to medium‐sized (8–20 μm) round or ovoid neurons. These smaller neurons tend to receive a sparse axosomatic innervation. In addition to these differences the spinal trigeminal neuropil is distinguished by the striking manner in which it is broken up by large rostrocaudally oriented bundles of myelinated axons. Proximal dendrites of polygonal and fusiform neurons often wrap around these large axon bundles.Morphologically heterogeneous populations of synaptic terminals with round vesicles (R terminals) and terminals with predominantly flattened vesicles (F terminals) occur in all of the subdivisions of the trigeminal complex. Both types of terminal make primarily axodendritic synapses, but both also make axosomatic synapses, and axospinous synapses with somatic as well as dendritic spines. In addition, axoaxonic synaptic contacts from F terminals onto large R terminals are seen in all subdivisions. Convincing examples of presynaptic dendrites were not observed in any of the brainstem subdivisions.Synaptic glomeruli, characteristic groupings of dendrites and synaptic terminals, are found throughout the brainstem trigeminal complex. The dendritic elements in these glomeruli tend to be small‐diameter dendrites, spines, and large, spinelike appendages. Within the glomerulus these elements are postsynaptic to a single large R terminal and may also be postsynaptic to smaller F terminals. In addition, axoaxonic synaptic contacts from the F terminals onto the R terminal are a consistent feature of trigeminal synaptic glomeruli. Serial reconstructions of glomeruli indicate that both the R and the F terminals commonly occur as boutons en passant, with single axons innervating multiple glomeruli. Within the trigeminal complex synaptic glomeruli are often grouped together into clusters, which we have termed “glomerular nests.” We suggest that the peripherally related afferent segmentation characteristic of the rat's brainstem trigeminal complex is reflected in the distribution of these nests.
Developing pigeon retina: Light‐evoked responses and ultrastructure of outer segments and synapses
Authors: Bagnoli Paola , Porciatti Vittorio , Lanfranchi Alberto , Bedini Celina 
Published: January 2005

AbstractMorphological development of photoreceptor outer segments and synapses in the foveal region of the pigeon retina was studied by electron microscopy. In addition, the maturation of outer retina function was investigated by recording electroretinographic (ERG) responses to either flash or pattern stimuli. The first ERGs to unpatterned or patterned stimulation can be recorded at 4–6 days posthatching. These results are consistent with anatomical analysis of pigeon photoreceptor and synapse development. Indeed, photosensitive lamellae in the outer segments can be observed simultaneously with the appearance of the first retinal responses to light. A few synapses can already be seen in the outer plexiform layer at the time photoreceptor disks first appear. In contrast, numerous synapses are already present in the inner plexiform layer when photoreceptor lamellae have yet to appear. A comparable maturation pattern has been reported to occur in chicks toward the end of the incubation time.
Dark rearing prolongs physiological but not anatomical plasticity of the cat visual cortex
Authors: Mower George D. , Caplan Caren J. , Christen William G. , Duffy Frank H. 
Published: January 2005

AbstractRecent studies (Cynader and Mitchell, '80; Mower et al., '81) have shown that total dark rearing prolongs susceptibility to the physiological effects of monocular deprivation (MD) in visual cortex beyond the normal age limits. The present study addressed whether this delayed physiological plasticity is accompanied by delayed anatomical plasticity in the geniculocortical pathway.Ocular dominance (OD) columns as defined by transsynaptic autoradiography following injection of 3H proline into one eye were studied both qualitatively and quantitatively in 17 cats. Compared to normal rearing (N‐3), both binocular eyelid suture (N‐2) and total dark rearing (N‐3) resulted in incomplete segregation of OD columns in area 17. This apparent immaturity after binocular deprivation, however, did not reflect a delayed capacity for development and plasticity. Visual experience after dark rearing produced no marked changes. In cats who experienced MD after dark rearing, injection of either the nondeprived (N‐2) or deprived eye (N‐3) resulted in a nearly uniform distribution of label throughout layer IV of area 17. The same result occurred with binocular vision after dark rearing (N‐1). MD from birth, however, produced expansion of columns from the nondeprived eye (N‐1) and contraction of columns from the deprived eye (N‐1). MD imposed after 4 months of normal vision resulted in normal OD columns (N‐1).Electrophysiological studies revealed a high proportion of binocular cells within layer IV in cats who experienced monocular or binocular vision after dark rearing. Outside of layer IV there were clear environmental effects on OD of single cells in these cats. Measurements of cell sizes in the clateral geniculate nucleus showed shrinkage of cells innervated by the deprived eye when MD was initiated at birth (N‐3). MD after dark rearing (N‐4) produced no differences in cell sizes.It is concluded that (1) visual input is necessary for the formation of normal OD columns, (2) the critical period for formation and environmental modification of OD columns is limited to early life, and (3) the physiological effects of visual experience after dark rearing reflect changes occurring beyond the geniculocortical pathway.
Distribution of central cholinergic neurons in the baboon (papio papio). II. A topographic atlas correlated with catecholamine neurons
Authors: Satoh K. , Fibiger H. C. 
Published: January 2005

AbstractThe topographic distribution of central cholinergic and catecholaminergic neurons has been investigated in the baboon (Papio papio). The perikarya were mapped on an atlas through the brain and spinal cord employing sections processed for acetylcholinesterase (AChE) pharmacohistochemistry coupled with choline acetyltransferase (ChAT) immunohistochemistry or aqueous catecholamine‐fluorescence histochemistry. Compared with subprimates, there is a remarkable increase in the volume occupied by and the number of cholinergic cells contained in the nucleus basalis and nucleus tegmenti pedunculopontinus (subnucleus compacta). The elaboration of these parts of the cholinergic system is accompanied by a large extension of catecholaminergic cell groups in the midbrain (groups A8–A10), particularly the substantia nigra (pars compacta), and in the dorsolateral pontine tegmentum (A5–A7 complex). Although cholinergic and catecholaminergic soma generally occupy distinctly different regions of the brain, a close apposition of cholinergic and noradrenergic neurons occurs in the dorsolateral pontine tegmentum. In the peripeduncular region ChAT‐positive cells and green fluorescent neurons of the A6–A7 complex form parallel lines and do not intermingle as has previously been demonstrated in the cat. Two distribution patterns, aggregated or disseminated, are another common feature of central cholinergic and catecholaminergic perikarya. The cholinergic neurons in the nucleus tegmenti pedunculopontinus and the catecholaminergic neurons in A6–A7 complex display both patterns. This comparative study of three transmitter systems in the baboon suggests that the cholinergic as well as the catecholaminergic neurons that give rise to ascending telencephalic and dorsal diencephalic projections undergo phylogenetic development in terms of cell number and nuclear volume.