bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphology of single, physiologically identified retinogeniculate Y‐cell axons in the cat following damage to visual cortex at birth
Authors: Weber A. J. , Kalil R. E. , Stanford L. R.
Published: January 2005

It has been reported previously that neurons in the dorsal lateral geniculate nucleus (LGN) of cats with neonatal damage to visual cortex (KVC cats) have receptive fields that are abnormally large and that the receptive fields of these neurons sometimes do not appear to conform to the normal retinotopic order in the LGN. A primary aim of this study was to determine if these physiological abnormalities are related to inappropriate patterns of retinogeniculate connections.

We therefore have analyzed the terminal arbors of retinogeniculate axons in adult cats that had received a lesion of visual cortex (areas 17, 18, and 19) on the day of birth. Single retinogeniculate axons were characterized physiologically and injected intracellularly with horseradish peroxidase. Consistent with earlier reports that neonatal removal of visual cortex results in a retrograde loss of retinal X‐cells, all of the retinogeniculate axons that we recorded were from Y‐cells. While the visual responses of these Y‐cell axons were normal, the morphology of their terminal arbors in the LGN was abnormal. Retinal Y‐cell axons in KVC cats have terminal fields in the A laminae of the LGN that are as large or larger than those of normal Y‐cells. However, since the LGN in KVC cats is severely degenerated, single Y‐cell arbors occupy a proportional volume of the LGN that is 12 times greater than normal. Thus an early lesion of visual cortex produces a severe mismatch between retinogeniculate axon arbor size and target size. Also, despite the normal size of retinogeniculate axon arbors in KVC cats, the number and density of terminal boutons are greatly decreased.

Thus our morphological results suggest that the unusually large receptive fields of LGN cells in KVC cats and the relative lack of retinotopic precision in the LGN are due, at least in part, to anomalies in the relative size and distribution of retinogeniculate axon arbors that develop after neonatal removal of visual cortex.
Anatomy of the auditory thalamocortical system of the guinea pig
Authors: Redies H. , Brandner S. , Creutzfeldt O. D.
Published: January 2005

We investigated the projection from the medial geniculate body (MG) to the tonotopic fields (the anterior field A, the dorsocaudal field DC, the small field S) and to the nontonotopic ventrocaudal belt in the auditory cortex of the guinea pig. The auditory fields were first delimited in electrophysiological experiments with microelectrode mapping techniques. Then, small quantities of horseradish peroxidase (HRP) and/or fluorescent retrograde tracers were injected into the sites of interest, and the thalamus was checked for labeled cells.

The anterior field A receives its main thalamic input from the ventral nucleus of the MG (MGv). The projection is topographically organized. Roughly, the caudal part of the MGv innervates the rostral part of field A and vice versa. After injection of tracer into low or medium best‐frequency sites in A, we also found a topographic gradient along the isofrequency contours: the dorsal (ventral) part of a cortical isofrequency strip receives afferents from the rostral (caudal) portions of the corresponding thalamic isofrequency band. However, it is not so obvious whether such a gradient exists also in the high‐frequency part of the projection. A second, weaker projection to field A originates in a magnocellular nucleus that is situated caudomedially in the MG and was therefore named the caudomedial nucleus.

The dorsocaudal field DC receives input from the same nuclei as the anterior field, but the location of the labeled cells in the MGv is different. This was demonstrated by injection of different tracers into sites with like best frequencies in fields A and DC, respectively. After injection of HRP into the 1‐2‐kHz isofrequency strip in field A and injection of Nuclear Yellow (NY) into the 1‐2‐kHz site in field DC, the labeled cells in the MGv form one continuous array that runs from caudal to rostral over the whole extent of the MGv. The anterior part of this array consists of NY‐labeled cells; i.e., it projects to field DC. The caudal part is formed by HRP‐labeled cells; i.e., it innervates field A. These findings indicate that there is only one continuous tonotopic map in the MGv. This map is split when projected onto the cortex so that two adjacent tonotopic fields (A and DC) result. The cortical maps are rotated relative to the thalamic map in that rostral portions of the MGv project to caudal parts of the tonotopic cortex and vice versa.

The small field S receives its main thalamic input from a region situated in the rostral half of the MG medial to the ventral nucleus (the rostromedial MG). After injection of tracer into the ventrocaudal belt, labeled cells were found dorsal, lateral, and ventral to the MGv. These cells form a continuous band that surrounds the MGv like a shell. A second population of labeled neurons was found in the caudomedial nucleus of the MG.

Similarities and differences between the auditory thalamocortical systems in the guinea pig and other mammalian species are discussed.
Light and electron microscopic study of galanin‐immunoreactive nerve fibers in the rat posterior thalamus
Authors: Blasco Isabel , Alvarez Francisco J. , Villalba Rosa M. , Solano Maria L. , Martínez‐Murillo Ricardo , Rodrigo José
Published: January 2005

Light and electron microscopic immunocytochemistry was used to study certain cell groups in the posteromedial thalamus which contain galanin‐immunoreactive (GAL‐IR) fibers. The nuclei subparafascicularis pars parvicellularis (SPFpc) and parafascicularis (PF) contain a dense network of GAL‐IR fibers which form basketlike structures around unstained cells. The periventricular area also contains numerous GAL‐IR fibers and these also occasionally form basketlike structures. The GAL‐IR terminal fields continue caudally in the mesodiencephalic junction and mege with other GAL‐IR fibers in the dorsal aspects of the substantia nigra and around the dorsolateral tip of the medial lemniscus.

Ultrastructural analysis of the GAL‐IR basketlike structures revealed that GAL‐IR terminals make numerous synapses with the cell bodies and proximal dendrites of SPFpc neurones. These results suggest that the activity of cells in the SPFpc and PF nuclei may be strongly influenced by galanincontaining nerve fibers probably originating in the spinal cord.
Degeneration and regeneration of peripheral nerve in the rat trigeminal system: III. Abnormal sensory reinnervation of rat guard hairs following nerve transection and crush
Authors: Munger Bryce L. , Renehan William E.
Published: January 2005

The present study was undertaken in an attempt to better understand the abnormalities of cutaneous sensibility that are present in patients following nerve injury with concomitant cutaneous denervation and subsequent reinnervation. Reinnervated intervibrissal pelage of the rat mystacial pad was studied in silver‐impregnated sections 3 and 5 months after transecting and 2 and 5 months after crushing the infraorbital nerve. The sensory terminals on guard and vellus hairs were analyzed in serial paraffin sections and in thick frozen sections. In normal rat mystacial skin, approximately nine/ten of innervated guard hairs have a typical piloneural complex consisting of a palisade of highly regular lanceolate terminals surrounded by circularly arranged Ruffini terminals and free nerve endings (FNEs). The remaining one of ten innervated guard hairs has only circularly arranged presumptive FNEs and Ruffini terminals. Vellus hairs, either singly or in clusters, typically have only circularly arranged terminals that in many cases are simple FNEs. We first recognized abnormalities in innervation of hairs following nerve transection and fully expected nerve terminals to be completely normal following nerve crush. Almost all reinnervated sensory nerve terminals associated with guard hairs were markedly abnormal following nerve transection and quantitatively abnormal following nerve crush. Following nerve transection, lanceolate terminals were almost completely absent, and they were remarkably reduced in number following nerve crush. Vellus hairs when reinnervated typically lacked the complex circular presumptive Ruffini terminals. These findings may be in part the basis for the abnormal cutaneous sensory perceptions (dysasthesias and paresthesias) noted in human subjects following damage to nerves with subsequent sensory reinnervation of the skin. Our findings are in accord with the reports of subtle physiologic abnormalities following nerve transection and crush. Morphologically abnormal reinnervated sensory terminals may retain modality specificity but in addition respond abnormally. These conclusions may be in part the basis for abnormal sensibilities that have been reported following crushing damage to peripheral nerves.
Two distinct visual pathways through the superficial pretectum in a percomorph teleost
Authors: Striedter Georg F. , Northcutt R. Glenn
Published: January 2005

The connections of the superficial pretectum and of nucleus isthmi were examined in a percomorph teleost, Lepomis cyanellus. Horseradish peroxidase was injected either with a pin into the parvicellular nucleus of the superficial pretectum or pressure injected into nucleus isthmi; the isthmal injections retrogradely labelled the neurons of the magnocellular nucleus of the superficial pretectum. Two main visual pathways can be recognized: The first projects from the retina to the parvicellular nucleus, and then to the intermediate nucleus of the superficial pretectum, the inferior raphe nucleus, and the trochlear nucleus. The second projects from the retina via the optic tectum to the magnocellular nucleus of the superficial pretectum, and from there to nucleus isthmi and the lateral thalamic nucleus; nucleus isthmi and the lateral thalamic nucleus project back to the optic tectum, and nucleus isthmi also projects back to the magnocellular nucleus. The two pathways are interconnected to some extent because both nucleus isthmi and the optic tectum project to the parvicellular nucleus; nevertheless, we suggest that they may be functionally and evolutionarily distinct. Compared to percomorphs, the first pathway appears reduced in cyprinid teleosts such as goldfish. Furthermore, the magnocellular nucleus of the second pathway is completely different in cyprinids, both in cellular architecture and in efferent connections. A phylogenetic analysis suggests that cyprinid ancestors went through a period of reduced vision and that the magnocellular nucleus of the superficial pretectum in modern cyprinids has been either extensively modified from the primitive condition or lost entirely and replaced by a superficially similar structure.
Auditory pathway and auditory activation of primary visual targets in the blind mole rat (Spalax ehrenbergi): I. 2‐deoxyglucose study of subcortical centers
Authors: Bronchti Gilles , Heil Peter , Scheich Henning , Wollberg Zvi
Published: January 2005

The blind mole rat Spalax ehrenbergi is a subterranean rodent that shows striking behavioral, structural, and physiological adaptations to fossorial life including highly degenerated eyes and optic nerves and a behavioral audiogram that indicates high specialization for low‐frequency hearing. A 2‐deoxyglucose functional mapping of acoustically activated structures, in conjunction with Nissl/Klüver‐Barrera‐stained material, revealed a typical mammalian auditory pathway with some indications for specialized low‐frequency hearing such as a poorly differentiated lateral nucleus and a well‐developed medial nucleus in the superior olive complex. The most striking finding was a marked 2‐deoxyglucose labeling of the dorsal lateral geniculate body and of cortical regions that correspond to visual areas in sighted rodents. The results render the blind mole rat a good model system for studying natural neural plasticity and intermodal compensation. In this report, we confine ourselves to the subcortical levels. The cortical level will be dealt comprehensively in a following paper.
Axon‐bearing amacrine cells of the macaque monkey retina
Authors: Dacey Dennis M.
Published: January 2005

A new and remarkable type of amacrine cell has been identified in the primate retina. Application of the vital dye acridine orange to macaque retinas maintained in vitro produced a stable fluorescence in the somata of apparently all retinal neurons in both the inner nuclear and ganglion cell layers. Large somata (∼15‐20 μm diam) were also consistently observed in the approximate center of the inner plexiform layer (IPL). Intracellular injections of horseradish peroxidase (HRP) made under direct microscopic control showed that the cells in the middle of the IPL constitute a single, morphologically distinct amacrine cell subpopulation. An unusual and characteristic feature of this cell type is the presence of multiple axons that arise from the dendritic tree and project beyond it to form a second, morphologically distinct arborization within the IPL; these cells have thus been referred to as axon‐bearing amacrine cells.

The dendritic tree of the axon‐bearing amacrine cell is highly branched (∼40‐50 terminal dendrites) and broadly stratified, spanning the central 50% of the IPL so that the soma is situated between the outermost and innermost branches. Dendritic field size increases from ∼200 μm in diameter within 2 mm of the fovea to ∼500 μm in the retinal periphery. HRP injections of groups of neighboring cells revealed a regular intercell spacing (∼200‐300 μm in the retinal periphery), suggesting that dendritic territories uniformly cover the retina.

One to four axons originate from the proximal dendrites as thin (<0.5 μm). smooth processes. The axons increase in diameter (∼1‐2 μm) as they course beyond the dendritic field and bifurcate once or twice into secondary branches. These branches give rise to a number of thin, bouton‐bearing collaterals that extend radially from the dendritic tree for1‐3 mm without much further branching. The result is a sparsely branched and widely spreading axonal tree that concentrically surrounds the smaller, more highly branched dendritic tree. The axonal tree is narrowly stratified over the central 0‐20% of the IPL; it is approximately ten times the diameter of the dendritic tree, resulting in a 100 times greater coverage factor.

The clear division of an amacrine cell's processes into distinct dendritic and axonal components has recently been observed in other, morphologically distinct amacrine cell types of the cat and monkey retina and therefore represents a property common to a number of functionally distinct cell types. It is hypothesized that the axon‐bearing amacrine cells, like classical neurons, use action potentials to transmit signals over long distances in the IPL and, on the basis of previous immunohistochemical results, contain the inhibitory neurotransmitter GABA.
Ongoing electrical activity of superior cervical ganglion cells in mammals of different size
Authors: Ivanov Alexander , Purves Dale
Published: January 2005

The ongoing synaptic activity of superior cervical ganglion cells in adult mammals was examined in situ by intracellular recording in anesthetized mice, hamsters, rats, guinea pigs, and rabbits. The proportion of neurons exhibiting subthreshold and suprathreshold synaptic activity during a standard period of observation was least in a small mammal like the mouse (30%), intermediate among neurons of mammals of intermediate size such as the hamster and rat (48% and 45%, respectively), and greatest in the largest animals in the series, the guinea pig (89%) and rabbit (91%). Ganglion cells in all species fell silent after transection of the cervical trunk. The average frequency of synaptic activity among tonically active cells also increased with animal size, being least in the mouse (1.0/second) and greatest in the rabbit (6.4/second). This variation of ongoing synaptic activity in sympathetic ganglion cells may reflect the demands of progressively larger peripheral targets on relatively fixed populations of autonomic neurons.
Distribution of GABAergic neurons and terminals in the auditory system of the barn owl
Authors: Carr C. E. , Fujita I. , Konishi M.
Published: January 2005

Antisera to GAD (glutamic acid decarboxylase) and GABA were used to determine the distribution of GABAergic cells and terminals in the brainstem and midbrain auditory nuclei of the barn owl. The owl processes time and intensity components of the auditory signal in separate pathways, and each pathway has a distinctive pattern of GAD‐ and GABA‐like immunoreactivity. In the time pathway, all the cells of the cochlear nucleus magnocellularis and nucleus laminaris receive perisomatic GABAergic terminals, and small numbers of GABAergic neurons surround both nuclei. The ventral nucleus of the lateral lemniscus (anterior division) contains both immunoreactive terminals and some GABAergic neurons. In the intensity pathway, dense immunoreactive terminals are distributed throughout the cochlear nucleus angularis, which also contains a small number of GABAergic neurons. The superior olive contains two GABAergic cell types and immunoreactive terminals distributed throughout the neuropil. All the neurons of the nucleus of the lateral lemniscus (ventral part) appear to be GABAergic, and this nucleus also contains a moderate number of immunoreactive terminals. Immunoreactive terminals are distributed throughout the neuropil of the ventral nucleus of the lateral lemniscus (posterior division), whereas multipolar and small fusiform GABAergic neurons predominate in the dorsal regions of the nucleus. The time and intensity pathways combine in the inferior colliculus. The central nucleus of the inferior colliculus contains a large number of fusiform and stellate GABAergic neurons and a dense plexus of immunoreactive terminals, whereas the external nucleus contains slightly fewer immunoreactive cells and terminals. The superficial nucleus contains dense, fine immunoreactive terminals and a small number of GABAergic neurons.
Intraspinal course of descending serotoninergic pathways innervating the rodent dorsal horn and lamina X
Authors: Bullitt E. , Light A. R.
Published: January 2005

Although numerous studies have discussed serotoninergic pathways projecting from the brainstem to the spinal cord, the intraspinal course of these descending axons remains a matter of debate. One of the difficulties with traditional immunohistochemical methods is that the interpretation of results has been subjective. We have therefore employed a computer‐assisted imageprocessing system to provide objective measurements of serotonin immunoreactivity within the rodent dorsal horn and lamina X caudal to unilateral thoracic cordotomy in order to establish the intraspinal course of descending serotoninergic fibers.

Lesion analysis combined with computer‐determined optical density measurements, high‐power microscopic examination, and camera lucida drawings demonstrated that the predominant serotoninergic pathway terminating within the dorsal horn courses unilaterally within the dorsal portion of the dorsolateral funiculus. The thoracic dorsal horn may receive a slightly greater contribution from the contralateral side than the lumbar dorsal horn. Lamina X receives serotoninergic innervation both from fibers descending within the ipsilateral dorsolateral funiculus and from more ventrally located ipsilateral pathways, and it also contains serotonin derived from other sources.
Origin of retinal astrocytes in the rat: Evidence of migration from the optic nerve
Authors: Ling Tailoi , Mitrofanis John , Stone Jonathan
Published: January 2005

To test recent ideas on the origin of retinal astrocytes, we have studied the spread of astrocytes in the developing retina of the albino rat. Astrocytes were identified with antibodies to their intermediate filaments, glial fibrillary acidic protein (GFAP). Astrocytes were first detected at E(embryonic day)18, forming a corona of processes around the optic disc. Over subsequent days, astrocytes extended over the retina, covering approximately 35% of the retina at birth (typically E21–22) and reaching the edge of the retina by P(postnatal day)8. As they spread, astrocytes were closely associated with the developing vasculature, spreading ahead of patent vessels by a small but distinct margin. The most peripheral astrocytes assumed a bipolar morphology and extended processes towards the margin of the retina. Astrocytes nearer the optic disc showed the stellate shape characteristic of mature cells. The appearance of astrocytes at the optic disc at E18, 2 days after the appearance of type‐1 astrocytes in the optic nerve (Miller et al.: Dev. Biol. 11135–41, '85), suggests that retinal astrocytes may be type‐1 astrocytes generated in the optic nerve. Watanabe and Raff (Nature 332:834–837, '88) have recently reported an independent study supporting the same conclusions.
Autoradiographic distribution of thyrotropin‐releasing hormone receptors in the african lungfish Protopterus annectens
Authors: Pack Alison M. , Caine S. Barak , Winokur Andrew , Manaker Scott , Fishman Alfred P.
Published: January 2005

We used quantitative autoradiography to examine the distribution of thyrotropin‐releasing hormone (TRH) receptors in the central nervous system (CNS) of the African lungfish Protopterus annectens. We found that the distribution of TRH receptors throughout the CNS of the lungfish was heterogeneous with the highest concentrations (500–800 fmol/mg protein) in the olfactory bulb and telencephalon, moderately high concentrations (200–500 fmol/mg protein) in the diencephalon, and moderate (50–200 fmol/mg protein) to low (<50 fmol/mg protein) concentrations in the brainstem and spinal cord. Except for the motor nuclei of the cranial nerves and spinal cord, TRH receptors were concentrated in the acellular regions. In the telencephalon and diencephalon, the receptor density was inversely related to cellular density. These results provide a neuroanatomic and neuropharmacologic basis for further investigations of TRH in the African lungfish.
Histochemical demonstration of zinc in the hippocampal region of the domestic pig: I. Entorhinal area, parasubiculum, and presubiculum
Authors: Holm Ida E. , Geneser Finn A.
Published: January 2005

A detailed description is given of the distribution of zinc in three areas of the domestic pig hippocampal region, viz., the entorhinal area, the parasubiculum, and the presubiculum. Zinc was demonstrated histochemically with use of the Neo‐Timm method, a recent modification of the sulphide silver procedure. Each of the studied areas showed a distinctly stratified staining pattern, which has been correlated in detail to fields and layers defined on the basis of cyto‐ and fibroarchitecture, providing a combined chemo‐ and cytoarchitectonic map. The staining was primarily confined to the neuropil, although stained nerve cell bodies were encountered in all three parts of the hippocampal region.

Two main subfields were identified in the entorhinal area that have been designated pars medialis and pars lateralis, in accordance with their topographical positions, but both the cytoarchitecture and Neo‐Timm staining pattern are indicative of further subdivision. In pars medialis, the deep half of layer I, the interstices between the stellate cell bodies in layer II, and layer III were medium to heavily stained, whereas layer IV stained weakly. Layers V‐VI were slightly darker than layer IV and were inseparable on the basis of the Neo‐Timm staining. The staining of pars lateralis differed in many respects from that of pars medialis, the most conspicuous feature being a much lighter layer III. In the parasubiculum, the deep half of layer I together with layers II‐III had the appearance of an intensely stained triangle wedged in between the entorhinal area and the presubiculum. The latter showed moderate staining of the inner half of layer I and posterior part of layer II, while layer IV was stained intensely. Layers III and V‐VI exhibited only weak staining.

The distribution of zinc in the pig was compared with that in the guinea pig and rat, described previously. Although many histochemical features are shared by the staining patterns of the three species, striking differences exist in the pig, the most notable being the virtually reverse staining of the entorhinal layer IV.

The possible functional implications of zinc in synaptic vesicles are considered.
Quantitation of catecholamine neurons in the locus coeruleus in human brains of normal young and older adults and in depression
Authors: Chan‐Palay V. , Asan E.
Published: January 2005

A quantitative study of the morphology and distribution of norepinephrinergic neurons in the human locus coeruleus (LC) is given for normal young and older adult brain. Norepinephrine (NE)‐producing neurons are identified by immunocytochemistry of two NE biosynethetic enzymes, tyrosine hydroxylase (TH) and dopamine‐β‐hydroxylase (DBH), visualized by the peroxidase‐antiperoxidase and immunogold‐silver‐staining methods. TH and DBH immunoreactions yield equivalent results. Both immunocytochemical visualization methods allow detailed analysis of neuronal morphology. The neurons of the human LC fall into four classes: large multipolar neurons with round or multiangular somata, large elliptical “bipolar” neurons, small multipolar neurons, and small ovoid “bipolar” neurons. Though most of the neurons contain neuromelanin pigment, some larger neurons lack pigmentation. Dendritic arborization of all neurons is extensive. Computer‐assisted quantitative measurements of the parameters somatic size, dendritic arbor length, surface area, and volume are given. Somatic areas of LC neurons of all four classes are decreased in older adult brain, but dendritic arborization is equally extensive as in the younger. The rostrocaudal length of the LC is approximately 15 mm, and no age‐dependent decrease is observed. Computer‐assisted mapping of immunoreactive neurons and three‐dimensional reconstruction allow division of the LC into rostral, middle, and caudal parts with characteristic distribution of neurons. Small neurons predominate in all parts, but the relative contribution of larger cells decreases in a rostrocaudal direction. A cell loss of 27–37% occurs in older adult brains and to 55% in the brain of a chronically depressed patient without dementia. Cell loss is highest in the rostral part, lower in the middle and absent in the caudal part, and more small cells are lost than larger ones.
Spectra of G ratio, myelin sheath thickness, and axon and fiber diameter in the guinea pig optic nerve
Authors: Guy John , Ellis E. Ann , Kelley Kay , Hope G. Marion
Published: January 2005

The spectra of fiber and axon diameter, myelin sheath thickness, fiber density, and g ratio of the optic nerve were analyzed for the strain‐13 guinea pig, an animal extensively utilized in the investigation of experimental disorders of demyelination. Our detailed analytical study of the normal guinea pig optic nerve provides the basis for comparison to disease states and the morphology of other species. As in the rat, mouse, and chipmunk, fiber diameters in the guinea pig were unimodal, but dissimilar to the trimodal fiber spectra of the cat and primate. The predominance of medium‐sized fibers (0.80–2.00 μm), common to most species, contributed to the larger mean fiber diameter (1.45 μm) of the guinea pig optic nerve, in which small fibers (0.50 μm or less) were infrequent and fibers larger than 5.00 μm in diameter, seen in the cat and primate, were absent. While myelin sheath thickness increased with axon diameter in the guinea pig, as in other species, a g ratio of 0.81 in the guinea pig was greater than in most mammals. Since conduction velocity is dependent on axon size, as well as myelin properties, the relatively larger mean axon diameter of the guinea pig optic nerve (1.18 μm) may compensate for the decrease in its myelination.
Immunohistochemical localization of GAP‐43 in the developing hamster retinofugal pathway
Authors: Moya Kenneth L. , Jhaveri Sonal , Schneider Gerald E. , Benowitz Larry I.
Published: January 2005

Metabolic labeling studies have shown that the developing hamster retinotectal pathway is marked by a high level of synthesis and axonal transport of the neuron‐specific phosphoprotein GAP‐43, which then decline sharply with synaptic maturation. To understand better the relationship of GAP‐43 to specific developmental events, we used a monospecific antibody to examine the location of this protein in the optic tract and retinal target areas at various stages. In late embryonic and in neonatal hamsters, dense GAP‐43 immunostaining was seen along the entire extent of the optic tract axons, including fascicles coursing over and through the lateral geniculate body (LGB) and within the upper layers of the superior colliculus (SC). The retinal origin of many of these fascicles was confirmed by their rapid disappearance after removal of the contralateral eye. During the first postnatal week, immunostaining in the fiber fascicles showed a marked decline, though the protein was still present throughout the neuropil of the LGB and SC. In the second postnatal week, the neuropil staining also diminished, and by 12 days after birth, both structures showed only light immunoreactivity. The high levels of GAP‐43 in embryonic and neonatal optic tract axons coincide temporally with axon elongation, initial target contact, and collateral formation by the retinofugal fibers, whereas subsequent concentration of the protein in the neuropil suggests its involvement in the elaboration of terminal arbors and synaptogenesis.
Immunoelectron‐microscopic localization of the 180 kD component of the neural cell adhesion molecule N‐CAM in postsynaptic membranes
Authors: Persohn Elke , Pollerberg G. Elisabeth , Schachner Melitta
Published: January 2005

In order to investigate the expression of cell adhesion molecules in synapses, we have studied the localization of the neural cell adhesion molecule N‐CAM in the cerebellum and hippocampus of adult mice by immunocytological and immunochemical methods. Of the three molecular components of N‐CAM with relative molecular masses (Mr) of 120, 140, and 180 kD, N‐CAM 120 is not detectable in synaptosomal membranes, whereas N‐CAM 140 is expressed on both pre‐ and postsynaptic membranes and N‐CAM 180 is restricted to postsynaptic sites, with localization of the N‐CAM 180‐specific epitope in postsynaptic densities. Specificity of immunoreactivity is indicated by the observation that antibodies to the neural cell adhesion molecule L1 do not label synaptic membranes, whereas antibodies to two major components of postsynaptic densities, actin and erythrocyte spectrin, react with synaptic structures. Interestingly, N‐CAM 180 is only detectable in subpopulations of synapses in the intact tissue. Isolated synaptosomes, opened for unimpeded accessibility of antibody by hypoosmotic treatment, also reveal a partial expression of N‐CAM 180 in that 67% are labeled by antibodies to N‐CAM 180, while antibodies to actin and erythrocyte spectrin react with 95% and 88% of all synaptosomes, respectively. N‐CAM 180 does not appear to be differentially expressed in synapses of a particular morphological type, but is detectable in all types of synapses in the cerebellum and hippocampus, except for mossy fiber synapses and synapses between basket and Purkinje cells, which are generally N‐CAM 180‐negative. Since N‐CAM 180 has been shown to be characteristic of stabilized or stabilizing cell contacts, possibly by its association with the cytoskeleton‐membrane linker protein spectrin (Pollerberg et al.: J. Cell Biol. 101: 1921–1929, '85; Nature 324: 462–465, '86; Cell Tissue Res. 250: 227–236, '87), we would like to suggest N‐CAM 180 plays an important role in determining the stability of contacts between pre‐ and postsynaptic membranes and state of synaptic activity.
Cholinergic and monoaminergic innervation of the cat's thalamus: Comparison of the lateral geniculate nucleus with other principal sensory nuclei
Authors: Fitzpatrick David , Diamond Irving T. , Raczkowski Denis
Published: January 2005

The cholinergic and monoaminergic innervation of the lateral geniculate nucleus (GL) and other thalamic nuclei in the cat was examined by using immunocytochemical and tract‐tracing techniques. Cholinergic fibers, identified with an antibody to choline acetyltransferase (ChAT), are present in all layers of the GL. They are fine in caliber and exhibit numerous swellings along their lengths. The A layers, the magnocellular C layer, and the medial interlaminar nucleus are rich in cholinergic fibers that give rise to prominent clusters of boutons, while the parvicellular C layers contain fewer fibers that are more uniformly distributed. The interlaminar zones are largely devoid of ChAT‐immunoreactive fibers. Double‐label experiments show that cholinergic projections to the GL originate from two sources, the pedunculopontine reticular formation (PPT) and the parabigeminal nucleus (Pbg). The PPT contributes cholinergic fibers to all layers, while Pbg projections are limited to the parvicellular C layers.

The lateral geniculate nucleus has a much greater density of cholinergic fibers than the other principal sensory nuclei: the density of fibers in the A layers is more than three times greater than that in the ventral posterior nucleus (VP) or the ventral division of the medial geniculate nucleus (GMv). In contrast, serotonin (5‐HT)‐immunoreactive fibers are distributed with equal density across the principal thalamic nuclei, while tyrosine hydroxylase (TH)‐immunoreactive fibers (presumed to contain norepinephrine) are noticeably less dense in the GL than in the others. Monoaminergic fibers also differ from cholinergic fibers in their laminar distribution within the GL: both TH‐ and 5HT‐immunoreactive fibers are distributed evenly across the layers and interlaminar zones and are slightly more abundant in the parvicellular C layers than in the other layers.

Other thalamic nuclei rich in cholinergic fibers include the pulvinar nucleus, the ventral lateral geniculate nucleus, the intermediate nucleus of the lateral group, the lateral medial and suprageniculate nuclei (Graybiel and Berson: Neuroscience 5: 1175–1238, '80), and the paracentral and central‐lateral components of the intralaminar nuclei. This pattern matches the distribution of projections from the PPT and is similar, but not identical, to the pattern of acetylcholinesterase staining. The fact that most of the nuclei rich in cholinergic fibers have been implicated in visual sensory or visual motor functions suggests that cholinergic projections from the reticular formation play an especially important role in visually guided behavior.
Development of glial cells in the cerebral wall of ferrets: Direct tracing of their transformation from radial glia into astrocytes
Authors: Voigt Thomas
Published: January 2005

Coronal sections of the cerebral wall from developing ferrets (newborn to adult) were double‐stained with antibodies to vimentin and glial fibrillary acidic protein (GFAP). At birth, the dominant glial population was radial glia and these cells labeled only for vimentin. A small population of immature astrocytes in the cortical plate was double labeled for GFAP and vimentin. In successive days, the number of vimentin‐positive radial glia gradually decreased and they disappeared entirely at about 21 days. During this same period, the double‐stained astrocytes increased in number and were distributed throughout the cortical plate and intermediate zone. After 6 weeks of age the astrocytes were mostly confined to the developing white matter. Around this time they gradually lost their vimentin staining, and in the adult no vimentin‐positive elements were seen except at the ependymal surface.

In newborn ferrets single radial glial cells were also visualized by applying the carbocyanine dye DiI onto the pial surface of fixed brains. While most radial glia extended from the ventricular zone to the pial surface, a substantial fraction of them had lost their contact to the ventricular zone. Their somata were displaced into the subventricular zone and lower portion of the intermdiate zone.

The possibility that radial glia transform into astrocytes was directly tested by injecting fluorescent dyes under the pial surface of newborn ferrets at a time when virtually no GFAP‐positive astrocytes are present. The tracer, which was taken up in the upper portion of the cortical plate, stained the radial glial cell somata in the ventricular zone in a similar way as the dye DiI did in the fixed brains. As the radial glial cells disappeared at successively longer survival times, the tracer was ultimately found within newly formed GFAP‐positive astrocytes. These results provide strong support for the hypothesis that radial glia cells are the immature form of astrocytes (Choi and Lapham: Brain Res. 148:295–311, ′78; Schmechel and Rakic: Anat. Embryol. (Berl.) 156:115–152, ′79), and also show that, at least in the ferret cortex, the transformation is accompanied by a change in the expression of intermediate filament protein.
Correlated light and electron microscopic study of dopaminergic neurons and their synaptic junctions with DARPP‐32‐containing cells in three‐dimensional reaggregate tissue culture
Authors: Won L. , Price S. , Wainer B. H. , Hoffmann P. C. , Bolam J. P. , Greengard P. , Heller A.
Published: January 2005

An antibody to tyrosine hydroxylase has been used in a correlated light and electron microscopic study to characterize dopaminergic neurons and synaptic junctions in three‐dimensional reaggregate cell culture. Dissociated fetal mesencephalic cells containing dopamine neurons were coaggregated with dissociated fetal striatal cells in rotatory culture for 21 days. Sections of the coaggregates were stained by the peroxidase anti‐peroxidase technique to reveal tyrosine hydroxylase‐immunoreactive structures. Clusters of immunoreactive perikarya as well as dendrites and axons were observed. Immunolabeled perikarya were round or oval and approximately 20 μm in diameter. Boutons immunoreactive for tyrosine hydroxylase formed symmetric synapses, primarily with unlabeled dendritic shafts. Symmetric membrane specializations were also observed between tyrosine hydroxylase‐positive boutons and unlabeled dendritic spines as well as with the perikaryon of an unlabeled medium‐size neuron possessing a slightly indented nucleus.

To characterize the neurochemical nature of the neurons postsynaptic to tyrosine hydroxylase‐positive boutons in the reaggregates, an antibody against DARPP‐32 (a dopamine and adenosine 3′:5′‐monophosphate‐regulated phosphoprotein) and an antibody against tyrosine hydroxylase were employed to visualize striatal dopaminoceptive neurons and dopaminergic structures, respectively, in the same section. Examination of reaggregate sections at the light microscopic level demonstrated that DARPP‐32‐immunoreactive cells were distributed into discrete clusters that were associated with patches of tyrosine hydroxylase‐positive axonal varicosities. Ultrastructural analysis of tyrosine hydroxylase‐positive boutons in such clusters revealed that dopaminergic axons synaptically contacted DARPP‐32‐immunoreactive neurons as well as unlabeled neuronal structures.

The results demonstrate that dopaminergic neurons in reaggregate cells in culture do form synaptic contacts and the DARPP‐32‐containing neurons are a subset of striatal cells that receive a dopaminergic innervation.
Compartmental organization of the ventral striatum of the rat: Immunohistochemical distribution of enkephalin, substance P, dopamine, and calcium‐binding protein
Authors: Voorn Pieter , Gerfen Charles R. , Groenewegen Henk J.
Published: January 2005

In the caudate‐putamen of the rat a patch/matrix organization can be recognized on the basis of the immunohistochemical distribution of several markers, which include enkephalin, substance P, dopamine, and calcium‐binding protein. In the present experiments the distributional relations of these markers were investigated in the nucleus accumbens. The distribution of enkephalin fibers shows different inhomogeneities according to their location in the nucleus. Rostrally, heavily labeled areas stand out against a moderately stained background, whereas caudally, in medial and ventral parts of the nucleus, lightly stained areas delineate regions in the moderately stained neuropil. In the distribution of substance P, areas with high staining intensity were observed in the medial and ventral parts of the nucleus accumbens. Inhomogeneities in the distribution of strong dopamine immunoreactivity consist of weakly immunoreactive areas throughout the rostrocaudal extent of the nucleus accumbens and extremely heavily labeled areas in the medial and ventral parts of the nucleus. Calcium‐binding protein immunoreactivity can only be detected in dorsal parts of the nucleus. The generally intense immunostaining for calcium‐binding protein is interspersed with “blanks” of weak immunoreactivity.

The heavily and moderately labeled enkephalin areas each maintain specific relations with inhomogeneities in the distribution of substance P, dopamine, and calcium‐binding protein. Rostrally, the heavily labeled enkephalin areas coincide with areas strongly immunostained for calcium‐binding protein and with lightly stained areas in the dopamine and substance P immunoreactivity patterns. In the same region lightly stained areas in the enkephalin distribution match heavily labeled substance P areas. Caudally, in the border region of the nucleus accumbens and the caudate‐putamen, the heavily labeled enkephalin areas are either related to “blanks” or to the intense staining regions in the calcium‐binding protein immunoreactivity distribution. The moderately labeled enkephalin areas caudomedially in the nucleus accumbens are in register with the heavily labeled regions in the distribution of substance P and with the extremely heavily labeled regions in the distribution of dopamine.

Relations with connectivity are discussed and the inhomogeneities are compared to those in the caudate‐putamen. It is concluded that in the ventral striatum either one patch and one matrix compartment exist with different immunohistochemical relationships or there are several compartments with different immunohistochemical characteristics and different input‐output relations.
Morphology of retinal ganglion cells in lungless salamanders (Fam. Plethodontidae): An HRP and Golgi study
Authors: Linke Rüdiger , Roth Gerhard
Published: January 2005

The family Plethodontidae consists of nearly two‐thirds of all living urodeles; most of them possess highly developed visual abilities. We investigated the morphology of retinal ganglion cells (RGCs) in four representative species by means of the horseradish peroxidase method in flatmounts and in transverse sections and with the Golgi method in transverse sections. In flatmount preparations, four classes of RGCs were found, differing in dendritic arborization, dendritic field size, and stratification pattern of dendrites in the inner plexiform layer (IPL). Class‐1 cells had small dendritic fields (29–44 μm2) and arborized throughout the entire depth of the IPL. Class‐2 cells had medium to large dendritic fields (75–206 μm2) and mostly arborized in two or three laminae or in a diffuse fashion in the IPL. Class‐3 cells had medium to large dendritic fields (72–200 μm2) but sparse dendritic arborization. They only arborized in the proximal lamina of the IPL. Class‐4 cells had large dendritic fields (273–626 μm2) and branched in the most sclerad stratum of the IPL. No large differences in intraspecific soma size of the different RGC classes were detected (although interspecific soma size varied to a considerable degree) and no “giant” cells typically found in other vertebrate retinas were present.

The results suggest that, with respect to the pattern of arborization and stratification of dendrites, lungless salamanders possess morphological classes of RGC similar to those found in frogs, but the morphology of RGCs in lungless salamanders seems to be simplified in comparison to frog RGCs. This simplification might be a consequence of paedomorphosis.
Carbohydrate components recognized by the cone‐specific monoclonal antibody CSA‐1 and by peanut agglutinin are associated with red and green‐sensitive cone photoreceptors
Authors: Röhlich Pál , Szél Ágoston , Johnson Lincoln V. , Hageman Gregory S.
Published: January 2005

Previous investigations have demonstrated that the monoclonal antibody CSA‐1 and peanut agglutinin label specifically cone photoreceptor cells. In the present study, we compared the binding of CSA‐1 and peanut agglutinin to that of the monoclonal antibodies COS‐1 and OS‐2, which have been shown to recognize the red/green‐ and blue‐sensitive cone visual pigments, respectively. Using lectin and immunocytochemistry on serial semithin sections of the pig retina, we have demonstrated in the present study that both CSA‐1 and peanut agglutinin label specifically the red‐, and green‐sensitive, but not the blue‐sensitive cone cell outer segments. Peanut agglutinin does bind, however, to the cone matrix sheaths associated with all three types of cones. These observations support the idea that red‐, and green‐sensitive cone cells share some common molecular epitopes and may represent a differentiation line of cones, considerably different from that of blue‐sensitive cones.
Distribution of β‐nerve growth factor receptors in the human basal forebrain
Authors: Allen Shelley J. , Dawbarn David , Spillantini Maria G. , Goedert Michel , Wilcock Gordon K. , Moss Timothy H. , Semenenko Frances M.
Published: January 2005

The distribution of neurons expressing the receptor for β‐nerve growth factor has been examined immunohistochemically in serial coronal sections of basal forebrain from aged normal human subjects. Neurons expressing the receptor were observed in the nucleus of the diagonal band of Broca and in the anterior, the intermediate, and the posterior portions of the nucleus basalis of Meynert. Neurons could also be seen in the medial septal nucleus and embedded in myelinated fibre tracts such as those of the external capsule, cingulum, medullary laminae of the globus pallidus, ansa penduncularis, ansa lenticularis, and anterior commissure. In situ hybridization with a 35S cDNA probe to the human β‐nerve growth factor receptor confirms a neuronal location as the site of synthesis of β‐nerve growth factor receptors in the nucleus basalis of Meynert in a fifth brain. A high percentage of Nissl‐stained hyperchromic magnocellular neurons expressed the receptor for β‐nerve growth factor, suggesting that most neurons in the human cholinergic magnocellular basal forebrain system express these receptors.

Recent data suggest that β‐nerve growth factor functions as a neurotrophic factor in basal forebrain cholinergic neurons. In Alzheimer's disease there is known to be a reduction in cholinergic function and an apparent loss of neurons in the cholinergic nucleus basalis of Meynert. For this reason we have examined the distribution of receptors for β‐nerve growth factor in the normal human basal forebrain in order to form a basis for comparison to those with Alzheimer's disease.