bluuebunny/crossref_metadata_2025 huggingface dataset:
Regenerating retinal axons of goldfish respond to a repellent guiding component on caudal tectal membranes of adult fish and embryonic chick
Authors: Vielmetter Jost , Walter Jochen , Stuermer Claudia A. O.
Published: January 2005

On a substrate of rostral/caudal tectal membrane stripes of adult fish, regenerating temporal retinal axons avoid the caudal membranes. Thus they behave like embryonic chick axons on chick E9 membranes. The caudal membranes of adult fish contain a repellent component that, as has previously been shown in the chick, is inactivated by the enzyme PI‐PLC. Fish axons respond not only to their own but also to the repellent component of embryonic chick membranes. Fish and more so chick E9 caudal membranes have an outgrowth reducing effect on fish axons that is also abolished by PI‐PLC treatment and is weaker on chick E16 membranes. Thus adult fish tecta express a guiding component for retinal axons related to that in the embryonic chick.
Nigropedunculopontine projection in the rat: An Anterograde tracing study with phaseolus vulgaris‐leucoagglutinin (PHA‐L)
Authors: Spann Bryan M. , Grofova Irena
Published: January 2005

The termination of the substantia nigra pars reticulata efferents in the nucleus tegmenti pedunculopontinus was studied in the rat by using the anterograde tracer Phaseolusvulgaris‐leucoagglutinin (PHA‐L). Both large and small injections of PHA‐L in various portions of the substantia nigra pars reticulata labeled varicose fibers in the ipsilateral and contralateral nucleus tegmenti pedunculopontinus, subnucleus dissipatus as well as in the ipsilateral nucleus tegmenti pedunculopontinus, subnucleus compactus. However, the bulk of the nigral fibers appeared to terminate in the medial two‐thirds of the ipsilateral subnucleus dissipatus of the pedunculopontine nucleus and exhibited a discrete dorsoventral topographical pattern. The terminal plexus displayed patches of uneven density, which was partly due to the numerous fiber bundles passing through the pedunculopontine nucleus, but also to an obvious preference of nigral fibers for some cells. Electron microscopic examination confirmed that nearly all of the varicosities observed in the light microscope contained synaptic vesicles and represented either terminal boutons or boutons en passant. The labeled boutons were elongated (average length: 1.5 μm) and consistently contained a prominent group of mitochondria.

The results suggest that the nigral input to the nucleus tegmenti pedunculopontinus may be directed toward specific subpopulation(s) of pedunculopontine neurons and may influence not only cells in the subnucleus dissipatus, but also in the subnucleus compactus.
Prefrontostriatal connections in relation to cortical architectonic organization in rhesus monkeys
Authors: Yeterian Edward H. , Pandya Deepak N.
Published: January 2005

Prefrontostriatal connections were investigated in rhesus monkeys using the autoradiographic technique to examine whether there are systematic relationships with regard to the architectonic organization of the prefrontal cortex. On the basis of progressive laminar elaboration, the different regions of the prefrontal cortex can be grouped into two architectonic trends. The dorsal trend, which begins in the medial proisocortical areas, can be followed through the dorsolateral prefrontal cortex, culminating in the dorsal arcuate region. The ventral trend, which originates in the orbital proisocortex, can be traced through the inferior prefrontal convexity to the ventral arcuate region. The results show that the main connections from the prefrontal cortex to the striatum are to the head and body of the caudate nucleus. These connections are topographically organized. Medial and dorsal prefrontal areas project predominantly to the dorsal and central portion of the head and body of the caudate nucleus, whereas orbital and inferior prefrontal areas are related mainly to the ventral and central portion. Moreover, prefrontostriatal connections have a medial‐lateral topography. Medial and orbital prefrontal areas project medially in the head and body of the caudate nucleus, whereas the dorsal and ventral arcuate regions project laterally, adjacent to the internal capsule. The prefrontal regions above and below the principal sulcus project mainly to the intermediate sector of the head and body of the nucleus. However, there appears to be some degree of overlap of corticostriatal projections from the dorsal and ventral prefrontal regions, as well as within each trend. Relatively minor projections are directed to the putamen as well as to the tail of the caudate nucleus from certain subregions of the prefrontal cortex. Thus the distribution of prefrontostriatal connections seems to reflect the architectonic organization of the prefrontal cortex. Possible functional aspects of prefrontostriatal connectivity are considered in the light of behavioral and physiological studies.
Sexual dimorphism of the anterior commissure and massa intermedia of the human brain
Authors: Allen Laura S. , Gorski Roger A.
Published: January 2005

Neuroanatomical sex differences were observed in the midsagittal area of both the anterior commissure and the massa intermedia on analysis of postmortem tissue from 100 age‐matched male and female individuals. The anterior commissure, a fiber tract whose axons in primates primarily connect the two temporal lobes, was an average of 12%, or 1.17 mm2 larger in females than in males. The massa intermedia, a structure that crosses the third ventricle between the two thalami, was present in 78% of the females and 68% of the males. Among subjects with a massa intermedia, the structure was an average of 53.3% or 17.5 mm2 larger in females than in males. Inclusive of subjects with and without a massa intermedia, this structure was a mean of 76% or 16.93 mm2 greater in females than in males. These sex differences were present despite the fact that the brains of males were larger than those of females. Since a majority of subjects were adults, it is unknown when sexual differentiation occurred. Anatomical sex differences in structures that connect the two cerebral hemispheres may, in part, underlie functional sex differences in cognitive function and cerebral lateralization.
Localization and characterization of angiotensin II receptor binding sites in the human basal ganglia, thalamus, midbrain pons, and cerebellum
Authors: Allen A. M. , Paxinos G. , McKinley M. J. , Chai S. Y. , Mendelsohn F. A. O.
Published: January 2005

Angiotensin II (Ang II) binding sites were localized in the thalamus, basal ganglia, midbrain, and pons of the human central nervous system by in vitro autoradiography, employing 125I‐[Sar1 Ile8]angiotensin II as the radioligand. High‐density binding occurs in the substantia nigra pars compacta, the interpeduncular nucleus and two of the raphe nuclei, the raphe magnus, and median raphe nucleus. Moderate densities occur in the caudate nucleus, putamen, bed nucleus of the stria terminalis, rostral linear nucleus, caudal linear nucleus, dorsal and paramedian raphe nuclei, locus coeruleus, and region of the subcoeruleus, oral dorsal paramedian nucleus, and A5/periolivary region. Low levels occur in the region between the subthalamic nucleus and the zona incerta, the mediodorsal thalamic nucleus, the central gray, the lateral and medial parabrachial nuclei, and the molecular layer of the cerebellum.

The high density of Ang II receptor binding in the substantia nigra occurs over pigmented, presumably dopaminergic, neurons. The binding in this site, and in the striatum, is not observed in any of the other species we have studied. It displays similar pharmacological characteristics to the Ang II receptor binding site in other regions of the human brain.

Overall we demonstrate a discrete pattern of Ang II receptor binding sites in the human brain, which shows a high correlation with the distribution observed in other mammalian species.
The rat's postero‐orbital sinus hair: I. Brainstem projections and the effect of infraorbital nerve section at different ages
Authors: Waite Phil M. E. , de Permentier Patrick
Published: January 2005

The central terminations, in the trigeminal nucleus, of afferents from the rat's postero‐orbital (PO) sinus hair have been investigated with transganglionic transport of horseradish peroxidase (HRP) and succinic dehydrogenase (SDH) histochemistry. The normal pattern of terminations has been compared with that found after section of an adjacent nerve, the infraorbital (IO) nerve, at three ages: neonatal, 1 week old, and adult.

The PO afferent fibres have three separate representations in the brainstem‐in trigeminal sensory nucleus principalis (Vp) and rostral subnucleus oralis (Vo), in trigeminal subnucleus interpolaris (Vi), and in caudal trigeminal subnucleus caudalis (Vc) and C1 dorsal horn. In coronal sections the areas of terminations were seen as oval patches lying ventrolaterally in Vp, Vo, and Vi and ventromedially in Vc and C1. Following neonatal IO nerve section the terminal areas were approximately doubled in Vp, Vo, and Vi but were unchanged in Vc and C1. IO nerve section at day 7 also caused a significant, though smaller (1.4× compared with 2.0×), increase in the terminal areas in the rostral three nuclei, without changing Vc and C1. However, no significant change in area occurred after adult IO nerve section. SDH histochemistry at 3 to 4 weeks of age showed patches of terminals on both normal and lesioned sides consistent with those seen after HRP.

Previous studies have reported increased functional representation of surrounding intact skin regions, including the PO sinus hairs, after neonatal but not adult, IO nerve section. The present results show that there are concomitant anatomical changes. Like the functional results, the extent of the anatomical changes are dependent on the maturity of the rat when lesioned.
Identity of cells produced by two stages of cytogenesis in the postnatal cat retina
Authors: Rapaport David H. , Vietri Andrew J.
Published: January 2005

Cytogenesis in the postnatal cat retina was studied with the aid of 3H‐thymidine autoradiography to identify the cell classes generated. Cell proliferate in two stages, Which are separate spatially and temporally. Previous studies have shown that during Stage 1, cytogenesis occurs at high density at the ventricular surface of the retina, whereas Stage 2 occurs at low density in the inner retinal layers. At the ages studied, the progeny of Stage 1 cytogenesis are distributed in an annulus toward the margin of the retina, and those of Stage 2 occur central to the annulus, indicating that Stage 2 follows Stage 1. Cell genesis in Stage 1 appears to cease by P16; genesis in Stage 2 persists until between P21 and P30. The same cell classes (amacrine cells, bipolar cells, Müller cells, and rod photoreceptors) are generated during both Stages 1 and 2, but there are significant changes in their proportions both within and between stages. The proportion of the Stage 1 mitoses that form bipolar cells increases from 31% at P0 to 62% at P14. A corresponding decrease is observed in the proportion of rods (from 60% at P0 to 32% at P14). The proportion of cells generated during Stage 2 that become rods increases from 39% at P0 to 70% at P21, whereas the proportion of bipolar cells decreases from 50% at P0 to 23% at P21. Müller cells form a relatively constant proportion (8 to 15%) of the cells generated during both Stage 1 and 2. Thus at the end of Stage 1, mostly bipolar cells are generated; at the end of Stage 2, mostly rods are generated.
Subpopulations of GABAergic neurons containing parvalbumin, calbindin D28k, and cholecystokinin in the rat hippocampus
Authors: Gulyás A. I. , Tóth K. , Dános P. , Freund T. F.
Published: January 2005

The possible coexistence of calbindin D28k with parvalbumin and of calbindin D28k with cholecystokinin was studied in nonpyramidal cells of the rat dorsal hippocampal formation. Neighbouring Vibratome sections were immunostained either for calbindin D28k and parvalbumin or for calbindin D28k and cholecystokinin. The cells, halved during sectioning, were identified in both sections immunostained for different antigens. The coexistence of calbindin D28k and parvalbumin in the same neuron was rare throughout the hippocampal formation with the exception of stratum oriens of the CA1 region, where 9.6% of the parvalbumin‐immunoreactive cells also contained calbindin D28k. In stratum radiatum of the CA3 region, calbindin D28k and cholecystokinin coexisted in 12.5% and 21.2% of the calbindin D28k and cholecystokinin‐immunoreactive cells, respectively. In other regions of the hippocampal formation, the two markers coexisted in less than 5% of the cells of either type. The present results demonstrate that calbindin D28k‐, parvalbumin‐ and cholecystokinin‐containing nonpyramidal cells represent largely nonoverlapping cell populations and may thus be involved in different inhibitory circuits.
Morphology and somatotopic organisation of the central projections of afferents from tactile hairs on the hind leg of the locust
Authors: Newland Philip L.
Published: January 2005

The morphology and organisation of the central projections of tactile hair afferents from the hind leg of the locust, Schistocerca gregaria, were examined by staining individual hair afferents. Each tactile hair on the femur, tibia, and tarsus is innervated by a single sensory afferent, which projects to the ipsilateral half of the metathoracic ganglion. Afferents arborize in the ventralmost and lateral ventral association centres (vVAC and lVAC). The projections are organised somatotopically in a map with three axes, according to the position of the hair on the leg. First, proximo‐distal: afferents from hairs on the proximal leg segments project more anteriorly than do those from hairs on distal leg segments. Moreover, on any given segment the afferents from the more proximal hairs project more anteriorly than do the afferents from the distal hairs. Second, antero‐posterior: afferents from hairs on the posterior surface of the leg project more medially than do afferents from anterior hairs. Third, dorso‐ventral: afferents from hairs on ventral parts of the leg project more ventrally than do afferents from the dorsal hairs. The afferents from posterior and anterior hairs project to an area between the central projections from dorsal hairs and ventral hairs The position of a projection within the map is dependent upon the location of the hair on the leg and not the peripheral routes taken by the axon of its afferent to reach the ganglion.
Distribution of acetylcholinesterase in the hippocampal region of the mouse: II. Subiculum and hippocampus
Authors: Slomianka L. , Geneser F. A.
Published: January 2005

The distribution of acetylcholinesterase (AChE) was examined in the subiculum and hippocampus of the adult mouse (Mus musculus domesticus). A distinctly stratified AChE pattern was observed in both areas and was compared in detail with the cytoarchitectural fields and layers.

In the subiculum, the lateral plexiform layer was lightly stained superficially and moderately stained at depth, where it abutted the lateral, moderately stained cell layer. Medially, a moderately stained deep plexiform layer separated the darkly stained superficial plexiform layer from the equally AChE‐intense cell layer. At depth, the subicular cell layer was delimited by a band of very high AChE activity. In regio superior of the hippocampus, AChE‐intense bands delimited the moderately stained strata moleculare, radiatum, and oriens toward the subjacent layers. In the stratum pyramidale, precipitate insinuated between the cell bodies gave a dark appearance to the deep part of the layer. The homologous strata of regio inferior appeared darker, but the relative staining intensities corresponded largely to those in regio superior. AChE activity in the layer of mossy fibers was almost absent septally but increased gradually to very high levels temporally.

The AChE staining pattern, in conjunction with cytochemical and morphological evidence, strongly suggests a division of the pyramidal cell layer of the mouse and rat into superficial and deep substrata and discourages the definition of a prosubiculum in rodents. A comparative analysis of the AChE pattern reveals that: (1) in the subiculum, differences between species are observed within a generalized pattern of medial darkly staining and lateral lightly staining portions; (2) in the hippocampus, a conservation of the AChE pattern is seen in strata associated with intrinsic hippocampal connections; while (3) numerous interspecific differences are found in the stratum moleculare.
A synaptic antigen (B16) is localized in retinal synaptic ribbons
Authors: Balkema Grant W.
Published: January 2005

This morphological and biochemical study examines the cytoplasmic synaptic determinant recognized by a monoclonal antibody (B16). This antibody was generated by using an immunosuppression protocol that generates antibodies to relatively rare antigens. The B16 antibody labels structures in the brain that are dot‐shaped and in the retina that resemble synaptic ribbons in their location, size, developmental emergence, and biochemical composition. The antigen is apparently conserved across species as it is found in retinas from lizards, frogs, fish, birds, mice, rats, rabbits, cats, and monkeys. This paper focuses on observations in the murine retina.

Labeling in the outer plexiform layer of the retina is confined to the margin between the outer plexiform layer (OPL) and the outer nuclear layer. The labeled structure resembles a semiellipse or an arc with the open end facing the OPL and the top facing the outer nuclear layer. Overall, the arc is approximately 1 μm in length and less than 0.5 μm thick. Approximately 10% of the labeled arcs occur in a proximal stratum of the OPL and form a planar cluster that resembles a flat plaque parallel to the OPL. Five to ten arcs are found in each plaque. The arcs found within the plaques are approximately 50% smaller than the larger isolated arcs. Counterstaining with peanut agglutinin (PNA), a lectin that recognizes cone photoreceptors and their associated processes, demonstrates that the plaques are associated with the cone pedicles. Animals that have a higher ratio of cones/rods than mice demonstrate a much higher ratio of plaques/isolated arcs in the OPL. The structure labeled in the inner plexiform layer resembles a short bar (0.8 μm long by < 0.5 μm wide) that is confined to the inner half of the inner plexiform layer in mice.

The relative mobility (Mr) of the B16 antigen obtained from mouse retinal and brain tissue is 88 kD, as determined by SDS‐PAGE followed by Western blotting. The mouse 88 kD protein is relatively soluble (precipitates at 70% ammonium sulphate) and elutes at a pH of 7.3 from an isoelectric focusing column. It appears that the determinant recognized by the B16 antibody is a previously undescribed synaptic protein that is associated with the synaptic ribbons in photoreceptor and bipolar terminals of most vertebrate retinas.
Distribution and morphology of human cone photoreceptors stained with anti‐blue opsin
Authors: Curcio Christine A. , Allen Kimberly A. , Sloan Kenneth R. , Lerea Connie L. , Hurley James B. , Klock Ingrid B. , Milam Ann H.
Published: January 2005

Primate cones maximally sensitive to short wavelength light (blue cones) have been previously identified by using indirect methods. We stained 7 wholemounted human retinas obtained from 6 female donors, using an affinity purified antibody to a 19 amino acid peptide sequence at the N‐terminus of blue opsin (Lerea et al., '89: Neuron 3:367–376), standard PAP immunocytochemistry, and controls. Cones were counted where all outer segments could be traced to inner segments and were measured where cells were well aligned vertically.

We find that: (1) 7% of cones within 4 mm of the foveal center are labeled by antiblue opsin; (2) compared to neighboring red/green cones, blue cone inner segments are 10% taller, have a larger cross‐sectional diameter near the junction with the outer segment, and a smaller diameter near the external limiting membrane, resulting in a more cylindrical shape, (3) foveal blue cones are sparse, irregularly spaced, and missing in a zone about 100 μm (0.35°) in diameter near the site of peak cone density, (4) the highest densities of blue cones (> 2,000 cells/mm2) are found in a ring at 0.1–0.3 mm eccentricity, and (5) the shortest distances between neighboring cones are between blue and red/green cones, and the blue and red/green mosaics are statistically independent.

These findings are consistent with psychophysical reports of foveal tritanopia and maximum sensitivity to blue light at 1° eccentricity. Blue cone spacing may limit resolution of the blue channel out to 20–30° eccentricity. The blue and red/green mosaics appear to be formed by separate processes.
Horizontal optokinetic nystagmus in unilaterally enucleated pigmented rats: Role of the pretectal commissural fibers
Authors: Reber Annie , Sarrau Jean Marie , Carnet Janick , Magnin Michel , Stelz Thérèse
Published: January 2005

Monocular enucleation reduces the asymmetry of horizontal optokinetic nystagmus (H‐OKN) in afoveate mammals by increasing responses to nasotemporal visual stimulation. The origin of these larger responses was investigated in adult pigmented rats monocularly enucleated as neonates or as adults by analyzing retinal and commissural projections to the deafferented nucleus of the optic tract (NOT) and the functional role of this nucleus before and after section of the posterior commissure.

Anatomically, monocular enucleation reduces the volume of the contralateral deafferented NOT. Anterograde tracers injected in the intact eye reveal a crossed projection of the retina to the NOT and to the dorsal (DTN) and medial (MTN) terminal nuclei of the accessory optic system as in normal rats. In addition, there is an uncrossed projection to the MTN in the rats enucleated as neonates. Retrograde tracer injected in the deafferented NOT confirms the absence of an uncrossed retinal projection but reveals connections between both NOT via the posterior commissure as in normal rats.

Electrophysiologically, the larger nasotemporal optokinetic responses in monocularly enucleated rats return to normal after posterior commissurotomy.

This study demonstrates that no anatomical remodelling takes place to increase nasotemporal responses in monocularly enucleated rats. The larger responses must then result from functional changes. The role of exclusive contralateral projections of the retina to the NOT and of the commissural connections in mediating the asymmetry of the optokinetic nystagmus in afoveate mammals is discussed.
Expression of a neurally related laminin binding protein by neural crest‐derived cells that colonize the gut: Relationship to the formation of enteric ganglia
Authors: Pomeranz Howard D. , Sherman Diane L. , Smalheiser Neil R. , Tennyson Virginia M. , Gershon Michael D.
Published: January 2005

In order to give rise to the enteric nervous system (ENS), cells migrating from the neural crest must find the bowel and cease migrating at appropriate locations within the gut. Previous studies of the development of the ENS in a mutant mouse have led to the hypothesis that laminin in the enteric mesenchyme may act as a signal to crest‐derived cells to cease migrating and extend neurites (or glial processes). Implied in this hypothesis is the idea that crest‐derived cells, as a prelude to their participation in ganglion formation, acquire a neurally related laminin receptor, which they do not express at pre‐enteric stages of migration. As a partial test of this hypothesis, single and double label immunocytochemistry at light and electron microscopic (EM) levels were used to study the expression of cell surface laminin binding proteins by crest‐derived cells in the process of migrating to or within the developing chick gut. Two antibodies (called 3070 and α‐110) raised against neuronal cell surface laminin binding proteins were employed for this purpose. Laminin binding protein immunoreactivity was found to be expressed within the bowel and ganglion of Remak by a subset of crest‐derived cells (identified immunocytochemically with NC‐1/HNK‐1 antibodies) and by all of those developing as neurons (identified immunocytochemically with antibodies to neurofilament‐associated proteins). Laminin binding protein immunoreactivity was also found to be expressed in fixed neural structures elsewhere in the embryos, including cranial and spinal roots, nerves, and ganglia. In contrast, laminin binding protein immunoreactivity was not expressed by migrating crest‐derived cells in the vicinity of the vagal or sacral regions of the neuraxis (from which the precursors of the ENS take origin); nor was it expressed by juxta‐pharyngeal vagal crest‐derived cells migrating to the foregut through the caudal branchial arches or by the caudal stream of sacral crest‐derived cells approaching the hindgut. EM immunocytochemistry confirmed that laminin binding protein immunoreactivity in the bowel was located on the surfaces of crest‐derived cells, and was exhibited both by those cells that could only be distinguished from their neighbors by their NC‐1/HNK‐1 immunoreactivity and by cells developing as neurons or glia. EM immunocytochemistry also revealed that the surfaces of crest‐derived cells migrating through the enteric mesenchyme were contacted by many small osmiophilic “puffs” of laminin‐immunoreactive extracellular material. These puffs coincided in location with membrane sites that expressed the immunoreactivity of the laminin binding protein. These observations are consistent with the hypothesis that laminin plays a role in the formation of enteric ganglia.
Projections of the tectospinal tract to the upper cervical spinal cord of the cat: A study with the anterograde tracer PHA‐L
Authors: Rose P. K. , MacDonald J. , Abrahams V. C.
Published: January 2005

The goal of the present experiments was to re‐examine the spinal projections of neurons in the superior colliculus (SC) of the cat by taking advantage of the high sensitivity of the anterograde tracer, phaseolus vulgaris leucoagglutinin (PHA‐L). In seven experiments, multiple injections of PHA‐L into different regions of the SC labelled a total of 172 axons in the predorsal bundle; yet only 11 tectospinal tract (TST) axons were found in the upper cervical spinal cord. Collaterals emerging from these axons were rare and arose exclusively from TST axons with a diameter of less than 1 μm. Individual collaterals had different termination zones: some terminated in the lateral part of lamina V and VI after taking a dorsolateral course through lamina VII and VIII; others terminated in the medial part of lamina VII. One collateral terminated within lamina IX and the ventral part of lamina VIII. The combined termination of all collaterals was densest in lamina VII and dorsal lamina VIII. A small number of boutons were also found in the lateral parts of laminae V and VI, and in lamina IX and immediately adjacent regions in lamina VIII. Compared to axons belonging to other spinal descending systems, individual TST axons give rise to much simpler intraspinal collaterals with relatively few boutons. This feature, together with the relative paucity of TST axons, suggests that direct connections from the SC to neurons in the upper cervical spinal cord are sparse. Furthermore, our results are consistent with electrophysiological studies that show that few, if any, neck motoneurons receive monosynaptic connections from TST neurons. Projections to neck motoneurons must therefore involve a relay, either through other descending pathways, such as the reticulospinal system, or via local segmental interneurons.
Differential immunochemical markers reveal the normal distribution of brain macrophages and microglia in the developing rat brain
Authors: Milligan Carolanne E. , Cunningham Timothy J. , Levitt Pat
Published: January 2005

Brain macrophages and microglia play important roles in central nervous system (CNS) development, especially during regressive events in which particular neuronal and glial constituents are eliminated. The purpose of this study is to provide a complete map of brain macrophage and microglia distribution in all regions of the neuraxis from birth to sexual maturity. We have utilized morphology and immunostaining with the specific antibodies OX‐42 and EDI to distinguish between brain macrophages and microglia. Brain macrophages are large, round cells, 10–15 μm in diameter, with few or no cytoplasmic processes; these cells are EDI‐ and OX‐42‐immunopositive. Microglia have small cell bodies with numerous, ramified cytoplasmic processes. These cells are OX‐42‐positive, and ED1‐negative. We found a specific pattern of distribution of brain macrophages, targeting specific cortical and subcortical areas transiently, including developing fiber tracts. These cells disappeared completely by the third postnatal week. In contrast, OX‐42‐positive microglia exhibited a gradual increase in number and were distributed uniformly throughout gray matter and within white matter tracts. These cells remain in the adult CNS, constituting the resident microglia population. We suggest that these two distinct phagocytic cell populations perform unique functions in the developing brain, including remodeling of restricted CNS areas by brain macrophages that is part of a normal morphological process.
Effects of hypothyroidism upon the granular layer of the dentate gyrus in male and female adult rats: A morphometric study
Authors: Madeira M. D. , Cadete‐Leite A. , Andrade J. P. , Paula‐Barbosa M. M.
Published: January 2005

The effects of hypothyroidism upon the structure of the central nervous system of adult rats are poorly understood in spite of evidence that the mature brain is vulnerable to this condition. Existing developmental studies show that the morphological changes induced by thyroid hormone deficiency are related to alterations in neurogenesis. We studied the granular layer of the dentate gyrus under different experimental conditions of hypothyroidism, because in rodents the neurogenesis of the granule cells continues during adulthood. The following groups of rats were analysed: (1) control; (2) hypothyroid from day 0 until day 180 (hypothyroid group); (3) hypothyroid until day 30 and thenceforth maintained euthyroid (recovery group); and (4) hypothyroid since day 30 (adult hypothyroid group). Groups of 6 male rats and 6 female rats were analysed separately. The volume of the dentate gyrus granular layer and the numerical density of its neurons were evaluated, so we were able to estimate the total number of granule cells.

Because in the experimental groups the volume of the granular layer and the numerical density of its neurons were reduced, the total number of granule cells was decreased. In the hypothyroid and recovery groups the alterations were identical and more striking than in the adult hypothyroid groups. The total number of granule cells displayed sexual differences in all groups studied except in the hypothyroid groups.

The present results support the view that thyroid hormone deficiency interferes with the process of cell acquisition by reducing neuronal proliferation and that it also leads to increased cell death. These events underlie the irreversible morphological changes observed in the brain of hypothyroid rats, either during development or at maturity. The referred structural alterations are probably related to the functional deficits observed in this condition.
Developmental expression of neural cell adhesion molecules in the mouse neocortex and olfactory bulb
Authors: Chung Wen‐Wei , Lagenaur Carl F. , Yan Yimin , Lund Jennifer S.
Published: January 2005

Polyclonal antibodies to N‐CAM and L1 and monoclonal antibodies to epitopes of N‐CAM (designated 12F11, 8A2, and 12F8) were used to investigate the spatial and temporal distribution of these neural cell adhesion molecules during the development of mouse cortex and olfactory bulb. The aim of the study was to correlate developmental events such as cell migration, dendritic and axonal outgrowth, and synaptogenesis with the appearance and disappearance of specific molecules involved in cell‐cell interactions. Western transfer studies indicated that 12F8 antibody recognized polysialic acid found on embryonic N‐CAM; 8A2 antibody primarily recognized the 140 kD component of N‐CAM while the 12F11 antibody recognized the 180 and the 140 kD forms. The study demonstrates a high degree of cell surface molecular specialization of different compartments in developing neocortex and olfactory bulb. L1 is found on a variety of unmyelinated fiber tracts including thalamocortical fibers, olfactory nerve, and inner plexiform layer of the olfactory bulb. In contrast, N‐CAM epitope recognized by 12F11 antibody is present on olfactory nerve fibers but appears later and is much weaker than L1 on thalamocortical fibers and is absent from the olfactory lobe inner plexiform layer. Dendritic regions are best labeled by 12F8 antibody; the epitope becomes faint in adult cortex but remains strongly expressed in olfactory bulb. This study reveals that widespread N‐CAM expression in the central nervous system is constituted by a diversity of local expression of different molecular forms of N‐CAM; their different anatomical distributions suggest they may each have unique roles.
The sensory epithelium and its innervation in the mole rat cochlea
Authors: Raphael Yehoash , Lenoir Marc , Wroblewski Romuald , Pujol Remy
Published: January 2005

The mole rat (Spalax ehrenbergi) burrows throughout its life in subterranean tunnels. Several structural and functional features which adapt the mole rat to its habitat have been discerned. The goal of this study was to elucidate the structural basis for adaptation of the auditory end‐organ to an environment where low‐frequency acoustical signals prevail. For this purpose, cochleae of adult mole rats were studied with light and electron microscopy. Inner hair cells throughout the cochlea, and outer hair cells in the basal (high‐frequency) portion of the cochlea, were similar in structure to those seen in other mammals. In contrast, outer hair cells in the apical (low‐frequency) portion displayed unique structural features. These features resembled the structure of inner hair cells or immature outer hair cells. The innervation of outer hair cells was most uncommon, in that classical medial efferent innervation was not found throughout the cochlear spiral.
Morphology of intracellularly labeled canine intracardiac ganglion cells
Authors: Xi X. , Randall W. C. , Wurster Robert D.
Published: January 2005

The purpose of this study was to determine the morphological organization and structure‐function correlation of mammalian intracardiac ganglion cells. Conventional intracellular microelectrode techniques were applied to the tissue whole mount preparation of canine intracardiac ganglia. Forty neurons were intracellularly recorded and labeled by means of horseradish peroxidase iontophoresis. Cell morphology was quantitatively analyzed by light microscopy and camera lucida technique. Somata were elongated (mean 62 × 40 μm) and had 2–12 primary dendrites restricted within the ganglion. Almost half of the neurons had either a short axon that was traced only within the ganglion or no axon distinguishable. These neurons may have perhaps been intraganglionically active neurons. The other cells had a long axon that either coursed out of the ganglion to peripheral cardiac tissue or exited the ganglion via interganglionic nerve to innervate more remote cardiac tissue or cells in other intracardiac ganglia. Interaction between neurons was suggested by the close proximity of processes from different neurons. Previously defined electrophysiological cell types (R‐, S‐, and N‐cells), which were significantly different in their passive and active membrane properties, had different morphological features of the somata but not the axonal or dendritic processes. Intra ganglionic or long axon neurons were not associated with a particular electrophysiological cell type. These findings provide the possibility of ganglionic modulation of vagal efferent activity in mammalian heart and also provide some morphological basis for the electrophysiological cell types.
Development of the projections from the dorsal lateral geniculate nucleus to the lateral suprasylvian visual area of cortex in the cat
Authors: Tong Lillian , Kalil Ronald E. , Spear Peter D.
Published: January 2005

In the study reported in the preceding paper, we used retrograde labeling methods to show that the enhanced projection from the thalamus to the posteromedial lateral suprasylvian (PMLS) visual area of cortex that is present in adult cats following neonatal visual cortex damage arises at least partly from surviving neurons in the dorsal lateral geniculate nucleus (LGN). In the C layers of the LGN, many more cells than normal are retrogradely labeled by horseradish peroxidase (HRP) injected into PMLS cortex ipsilateral to a visual cortex lesion. In addition, retrogradely labeled cells are found in the A layers, which normally have no projection to PMLS cortex in adult cats. The purpose of the present study was to investigate the mechanisms of this enhanced projection by examining the normal development of projections from the thalamus, especially the LGN, to PMLS cortex. Injections of HRP were made into PMLS cortex on the day of birth or at 1, 2, 4, or 8 weeks of age. Retrogradely labeled neurons were present in the lateral posterior nucleus, posterior nucleus of Rioch, pulvinar, and medial interlaminar nucleus, as well as in the LGN, at all ages studied. Within the LGN of the youngest kittens, a small number of retrogradely labeled cells was present in the interlaminar zones and among the cells in the A layers that border these zones. Such labeled cells were virtually absent by 8 weeks of age, and they are not found in normal adult cats. Sparse retrograde labeling of C‐layer neurons also was present in newborn kittens. The density of labeled C‐layer neurons increased 5‐ to 10‐fold between 1 day and 1 week of age and then increased further to adult values by 4 weeks of age. These results indicate that there is not an exuberant projection from the C layers of the LGN to the PMLS cortex in young kittens. This suggests, therefore, that the enhanced projection from the C layers to PMLS cortex after an early visual cortex lesion, described in the preceding paper, is due to new axonal growth. In contrast, at least part of the enhanced projection from the A layers after an early visual cortex lesion may result from the retention of an initially transient projection from the interlaminar zones and immediately adjacent cells in the A layers.
Immunocytochemical demonstration of salmon GnRH and chicken GnRH‐II in the brain of masu salmon, Oncorhynchus masou
Authors: Amano Masafumi , Oka Yoshitaka , Aida Katsumi , Okumoto Naoto , Kawashima Seiichiro , Hasegawa Yoshihisa
Published: January 2005

We have recently developed sensitive and specific radioimmunoassays (RIAs) for salmon gonadotropin‐releasing hormone (sGnRH) and chicken GnRH‐II (cGnRH‐II) and have measured the contents of both GnRHs in the rainbow trout brain. Our results showed that contents of the two GnRHs are variable among different brain regions. Therefore, in order to confirm the differential distribution of the two GnRHs by a different technique, we examined the distribution of immunoreactive sGnRH and cGnRH‐II in the brain of masu salmon by using immunocytochemical techniques.

sGnRH immunoreactive (ir) cell bodies were scattered in the transitional areas between the olfactory nerve and the olfactory bulb, the ventral olfactory bulb, between the olfactory bulb and the telencephalon, the ventral telencephalon, and the preoptic area. These sGnRH‐ir cell bodies were dispersed in a strip‐like region running rostrocaudally in the most ventral part of the ventral telencephalon. sGnRH‐ir fibers were distributed in the various brain regions from the olfactory bulb to the spinal cord. They were especially abundant in the olfactory bulb, ventral telencephalon, preoptic area, hypothalamus, deep layers of the optic tectum, and thalamus. sGnRH‐ir fibers also innervated the pituitary directly.

cGnRH‐II‐ir cell bodies were found in the nucleus of the medial longitudinal fasciculus (nMLF). The distribution of cGnRH‐II‐ir fibers was similar to that of sGnRH‐ir fibers, except that cGnRH‐II‐ir fibers were absent in the pituitary. The number of cGnRH‐II‐ir fibers was much fewer than that of sGnRH‐ir fibers.

The results of the present immunocytochemical study are in basic agreement with those of our previous RIA study. Thus, we suggest that in masu salmon, sGnRH not only regulates gonadotropin (GTH) release from the pituitary but also functions as a neuromodulator in the brain, whereas cGnRH‐II functions only as a neuromodulator.
Afferents to the medial nucleus of the trapezoid body and their collateral projections
Authors: Kuwabara N. , DiCaprio R. A. , Zook John M.
Published: January 2005

Cells and axons that supply direct afferent input to the medial nucleus of the trapezoid body are described. Afferents were intracellularly labeled in brainstem tissue slices of two rodent and two bat species. The main afferents are calyciferous axons from globular bushy cells of the ventral cochlear nucleus. Calyciferous axons were highly consistent across species, projecting directly from the cochlear nucleus, across the midline in the trapezoid body, to the contralateral medial nucleus of the trapezoid body. Within the target nucleus, a typical axon turned sharply away from horizontal to form a large ending, the calyx of Held, around the soma of a single principal cell. Three groups of calyciferous axons were classified based on the path taken from bend to calyx.

In subjects younger than four weeks, single axons often formed two calyces, each on a different cell. These calyx pairs were often found on adjacent or vertically aligned cells. In older animals, calyx pairs were more closely aligned, but fewer double calyx axons were seen.

A secondary focus of this study was the system of thin collateral branches that characterizes calyciferous axons in all species. The projection patterns of these collaterals suggest that calyciferous axons may provide ascending input to periolivary cell groups with descending projections.

In addition to calyciferous afferents, labeled cells that provide input to the medial nucleus of the trapezoid body from adjacent periolivary cell groups are described. Also described is a type of afferent that descends from the level of the lateral lemniscus to the medial nucleus of the trapezoid body.
Cerebellar nuclei and the nucleocortical projections in the rat: Retrograde tracing coupled to GABA and glutamate immunohistochemistry
Authors: Batini Cesira , Compoint Claude , Buisseret‐Delmas Catherine , Daniel Herve , Guegan Maryvonne
Published: January 2005

The amino acids GABA and glutamate (Glu) are thought to be the principal substances in the central nervous system responsible for neuronal inhibition and excitation. Their distributions among the different neurons in a defined pathway may thus be indicative of the contributions of the cells to pathway function. Examples of such neurons are those of the cerebellar nuclei which, while regulating output from the Purkinje cells of the cerebellar cortex, are also found to project back to the cerebellar cortex.

Immunohistochemical experiments were done to identify GABA and glutamate (Glu) containing cells in the adult rat cerebellar nuclei. Consecutive semithin and serial vibratome sections were incubated with antisera raised in rabbit against GABA and Glu. In semithin sections, only small neurons were intensely GABA immunoreactive (GABA‐IR) (31.7%), and the majority (80.5%) were Glu immunoreactive (Glu‐IR) of different sizes. Consistent with Glu being a metabolic precursor for GABA, 75.4% of the GABA‐IR population colocalized Glu. In vibratome sections GABA‐IR neurons showed some local differences in number, whereas the Glu‐IR were uniformly distributed in the three nuclei studied. Measured mean diameters for these neurons showed a distinct size difference for the GABA‐ and Glu‐IR with little overlap.

Cerebellar nuclei neurons projecting to the cortex (nucleocortical neurons, NCN) were identified by locally preinjecting the retrograde transported WGA‐apo HRP‐colloidal gold complex in the cerebellar cortex. Vibratome sections of these cerebella were silver intensified for the retrograde tracer and double labeled for GABA and Glu. Of the total number of identified NCN, 8.7% were GABA‐IR (10 animals) and 47.7% Glu‐IR (5 animals). Many retrograde labeled NCN in the core of the thick sections were immunonegative for both amino acids due to poor antibody penetration, thus underestimating the proportions of cells containing GABA and Glu. The size distributions for the GABA‐IR and Glu‐IR NCN were similar to those measured in non‐retrograde labeled nuclei in thick sections.

The conclusions reached are that GABA‐IR neurons of the cerebellar nuclei, including the NCN, use GABA as the presumed inhibitory neurotransmitter and that Glu‐IR neurons may use Glu or another excitatory neurotransmitter.
Dendritic sampling across processing streams in monkey striate cortex
Authors: Malach Rafael
Published: January 2005

Cytochrome oxidase (CO) dense blobs in primate striate cortex provide a striking example of parallel processing of visual information. The level of isolation of the blobs from the surrounding interblob tissue was investigated in the present study by combining CO staining with Golgi impregnation of dendritic arbors in the same tissue sections. The data are based on material from two marmoset and three squirrel monkeys. The analysis was conducted on two types of Golgi preparations. In the first preparation, dense networks of overlapping dendrites were impregnated over blob margins. The results of analyzing these networks with transmission and confocal microscopy revealed that dendritic arbors penetrate freely through blob margins. Statistical analysis revealed that the density of dendritic crossings at blob margins was similar to that found at blob and interblob centers. In the second type of Golgi preparation, single, isolated neurons were impregnated. Studies of such neurons revealed occasional examples of dendritic arbors that appeared to reflect back from blob margins, but counter examples were equally abundant. Bias index analysis indicated that dendritic arbors were generally unaffected by the presence of a nearby blob margin. Scanning a large number of impregnated arbors indicated that at least half of the population of blob‐related neurons had dendrites in both blob and interblob territory.

Under the conditions of free dendritic penetration of blob margins, the sole factor that determines the level of blob/interblob mixing appears to be the relationship between blob size and the dendritic spread of blob neurons. Interestingly, in both the marmoset and squirrel monkeys this size ratio is similar despite a large difference in their cortical surface area. Thus, it is hypothesized that blob size is optimally matched to the dendritic span so as to create a smooth transition of dendritic sampling from blob to interblob‐related processing streams.