bluuebunny/crossref_metadata_2025 huggingface dataset:
Chondroitin sulfate proteoglycans in the developing cerebral cortex: The distribution of neurocan distinguishes forming afferent and efferent axonal pathways
Authors: Miller Brad , Sheppard Allan M. , Bicknese Alma R. , Pearlman Alan L.
Published: January 2005

The first thalamocortical axons to arrive in the developing cerebral cortex traverse a pathway that is separate from the adjacent intracortical pathway for early efferents, suggesting that different molecular signals guide their growth. We previously demonstrated that the intracortical pathway for thalamic axons is centered on the subplate (Bicknese et al. [1994] J. Neurosci. 14:3500‐3510), which is rich in chondroitin sulfate proteoglycans (CSPGs; Sheppard et al. [1991] J. Neurosci. 11:3928‐3942), whereas efferent axons cross the subplate to exit in a zone containing much less CSPG. To define the molecular composition of the subplate further, we used antibodies against CSPG core proteins and chondroitin sulfate disaccharides in an immunohistochemical analysis of their distribution in the developing neocortex of the rat. Immunolabeling for neurocan, a central nervous system‐specific CSPG (Rauch et al. [1992] J. Biol. Chem. 267:19537‐19547), and for chondroitin 6‐sulfate and unsulfated chondroitin becomes prominent in the subplate before the arrival of thalamic afferents. Immunolabeling is initially sparse in the cortical plate but appears later in maturing cortical layers. A postnatal decline in immunolabeling occurs uniformly for most proteoglycans, but, in the somatosensory cortex, labeling for neurocan, phosphacan, and chondroitin 4‐ and 6‐sulfate declines in the centers of the whisker barrels before the walls. In contrast to neurocan, immunolabeling for other proteoglycans is either uniformly distributed (syndecan‐1, N‐syndecan, 5F3, phosphacan, chondroitin 4‐sulfate), restricted to axons (PGM1), distributed exclusively on nonneuronal elements (2D6, NG2, and CD44), or undetectable (9. 2. 27, aggrecan, decorin). Thus, neurocan is a candidate molecule for delineating the intracortical pathway of thalamocortical axons and distinguishing it from that of cortical efferents.
Morphological classification of retinal ganglion cells in mice
Authors: Doi Motoaki , Uji Yukitaka , Yamamura Hideki
Published: January 2005

Mice have been used for extensive studies on optic nerves and retinal ganglion cells, but mouse retinal ganglion cells have not been classified morphologically. In the present study, normally placed retinal ganglion cells and displaced retinal ganglion cells in pigmented and albino mice were classified morphologically using horseradish peroxidase. These cells were classified into three types according to the sizes of the soma and the dendritic field: type I cells, large soma and large dendritic field; type II cells, small‐to‐medium soma and small dendritic field; and type III cells, small‐to‐medium soma and large dendritic field. Some ganglion cells had both symmetric and asymmetric cells. Each type was further subdivided according to the termination level of dendrites in the inner plexiform layer and the dendritic branching pattern. Except for type III displaced ganglion cells, dendrites of the normally placed ganglion cells and the displaced ganglion cells ramify in the outer two‐fifths of the inner plexiform layer (sublamina a) or the inner three‐fifths of the inner plexiform layer (sublamina b). Type III displaced ganglion cells ramify only in sublamina a. Dendrites of some normally placed type I ganglion cells ramify in both sublaminae. Displaced biplexiform cells were observed, the dendrites of which ramify in both the inner and the outer plexiform layers. All cell types were found in both mouse strains. © 1995 Wiley‐Liss, Inc.
Fine structure of the dorsal latreral geniculate nucleus of the turtle, Emys orbicularis: A Golgi, combined hrp tracing and GABA immunocytochemical study
Authors: Kenigfest N. B. , Repérant J. , Rio J.‐P. , Belekhova M. G. , Tumanova N. L. , Ward R. , Vesselkin N. P. , Herbin M. , Chkeidze D. D. , Ozirskaya E. V.
Published: January 2005

The afferent and efferent cortical projections of the dorsal lateral geniculate nucleus (GLD) of adult specimens of the turtle Emys orbicularis were investigated after intraocular or intracortical injections of horseradish peroxidase (HRP), and the distribution of gamma aminobutyric acid (GABA) immunoreactivity in the nucleus was carried out by immunocytochemical techniques, both techniques being combined with light and electron microscopy. In addition, some specimens were prepared for double‐labeling of HRP and GABA immunoreactivity, and additional samples impregnated by a rapid Golgi technique. On purely morphological grounds, four types of neurons can be distinguished by light microscopy: two types of large cells in the cell plate which project to the cortex, and two types of smaller cells in the neuropil and optic tract which do not. The small cells are consistently GABA‐immunoreactive, while the former are, with extremely rare exceptions, immunonegative for GABA. The supposition that the small neurons of the neuropil are interneurons is supported by electron microscopic observations; these strongly GABA‐immunoreactive cells have large plicated nuclei surrounded by a thin layer of cytoplasm poorly endowed with organelles. The dendrites of these cells may contain pleomorphic synaptic vesicles (DCSVs) and appear to be presynaptic to other dendritic profiles. These DCSVs are occasionally contacted by GABA‐immunoreactive axon terminals, and more frequently by retinal terminals consistently immunonegative for GABA. The latter, frequently organized in glomeruli, also make synaptic contacts with immunonegative dendrites arising from corticopetal neurons of the cell plate. Two major categories of GABA‐immunoreactive axon terminals can be distinguished, and we are led to the conclusion that one of these represents an intrinsic GABAergic innervation of the GLD, while the second is tentatively interpreted as an extrinsic source of GABA to the nucleus, possibly from ventral thalamic structures. The fine structure of the dorsal lateral geniculate nucleus of Emys orbicularis thus shows many similarities with that of mammals. © 1995 Wiley‐Liss, Inc.
Chick wing innervation. I. Time course of innervation and early differentiation of the peripheral nerve pattern
Authors: Hollyday Margaret
Published: January 2005

Anterograde transport of horseradish peroxidase was used to map the initial projection patterns of motor and sensory axons innervating the wing of the chick embryo. Injections which resulted in labeling large numbers of motor and sensory axons, separately or in combination, were used to define the time course of innervation and to visualize the progressive morphogenesis of the peripheral nerve pattern. Motor axons emerged from the spinal cord and accumulated near the ventromedial border of the myotome where they remained for up to 16 hours before growing into the plexus region and limb bud. Despite the known later time of sensory neuron production, the first sensory axons projected to the wing at the same time as motor axons. When axons first entered the wing bud, they were distributed in two loosely organized sheets of axon fascicles, one projecting to dorsal muscle mass, the other to ventral muscle mass. The width of the sheets was between one‐third to one‐half the width of the wing bud, and this distance was more than twice the diameter of the proximal nerve trunks measured at stage 28. In the proximal limb the basic pattern of peripheral nerves emerged gradually from stages 26 to 28. During these stages, the loosely organized sheets of axonal fascicles seen at younger stages were progressively transformed into several coherent nerve trunks and muscle nerves extended from common nerve trunks. The implication of these observations is that many outgrowing axons appear not to follow preformed pathways corresponding to the mature peripheral nerve branching pattern. This pattern may instead result from axonal recognition of cues within a largely undifferentiated limb bud, and from the subsequent bundling together of loosely organized axon fascicles. These events occur concurrently with limb growth and differentiation. © 1995 Wiley‐Liss, Inc.
Chick wing innervation. III. Formation of axon collaterals in developing peripheral nerves
Authors: Ferns Michael J. , Hollyday Margaret
Published: January 2005

Axon navigation during vertebrate limb innervation has been shown to be associated with position‐dependent changes in size and complexity of the axon growth cones, and sometimes with bifurcation of terminal growth cones and axon branching (Hollyday and Morgan‐Carr, companion paper). We have further examined axon branching and asked whether it extends to the projection of collaterals to different nerves. Injections of horseradish peroxidase or DiI were made into individual peripheral nerves in the wings of chick embryos at stages 28–35, and the trajectories of solidly labeled axons were traced proximally from the injection site in tissue sections. During stages when the peripheral nerves were first forming in the shoulder region, collaterals of retrogradely labeled axons were frequently observed to project into uninjected nerves proximal to the injection site. These two‐nerve collaterals were formed by a small percentage of axons in a high percentage of the embryos studied and could occur in both motor and sensory axons. Two‐nerve collateral projections were observed between nerves separated along both the proximodistal and anteroposterior axes of the limb, but they were limited in spatial extent to nerves supplying adjacent limb regions and were never seen between nerves projecting to widely disparate regions of the limb. Collaterals were not seen at the plexus projecting to both dorsal and ventral pathways. The apparent frequency of two‐nerve collaterals was found to decline progressively from stage 28–29 to stage 32; no two‐nerve collaterals were seen in the proximal wing at stage 33 and older. The mechanism of their elimination is presently unknown. These observations suggest that some axon branching seen during outgrowth is sufficiently divergent to result in axon collaterals which project to two different peripheral nerves. Presumably, two‐nerve collaterals reflect both the neuron's ability to branch and some imprecision in the axonal guidance mechanisms. Together these give rise to minor errors in projection which are subsequently removed. © 1995 Wiley‐Liss, Inc.
Glutamate is concentrated in and released from parallel fiber terminals in the dorsal cochlear nucleus: A quantitative immunocytochemical analysis in guinea pig
Authors: Osen Kirsten K. , Storm‐Mathisen Jon , Ottersen Ole Petter , Dihle Beate
Published: January 2005

The present paper addresses the identity of the neurotransmitter(s) of the parallel fibers in the molecular layer of the dorsal cochlear nucleus, A brainstem center in the pathway for sound perception. The distribution of putative neurotransmitter amino acids was studied by using postembedding single‐ and double‐immunolabeling procedures. Perfusion‐fixed brains and immersion‐fixed slices from in vitro release experiments were evaluated. Quantitative immunogold analyses revealed that the parallel fiber terminals were significantly enriched with glutamate immunoreactivity compared with other terminals, dendrites, and glial processes. Within the parallel fiber terminals, the gold particles signaling the presence of glutamate were concentrated over vesicle clusters relative to the axoplasmic matrix. Furthermore, the parallel fiber terminals, but not the parent granule cell bodies, could be depleted of glutamate immunoreactivity by exposure to depolarizing concentrations of K+ in vitro. This depletion was partly dependent on Ca2+In double‐labeled preparations, the glutamine:glutamate ratio was by far higher in glial processes than in other types of profile. Aspartate immunoreactivity was mainly concentrated in neuronal cell bodies and dendrites and was very low in fiber terminals, particularly in those of the parallel fibers.

These data indicate that parallel fiber terminals contain a glutamate pool that is associated with synaptic vesicles and that can be subject to release. The glial processes that are found in proximity to the terminals may provide them with the glutamine required for glutamate replenishment. No evidence was found for a neurotransmitter role of aspartate in the parallel fibers. © 1995 Wiley‐Liss, Inc.
Prenatal development of fibrous (white matter), protoplasmic (gray matter), and layer I astrocytes in the human cerebral cortex: A Golgi study
Authors: Marín‐padilla Miguel
Published: January 2005

The prenatal developmental histories of layer I, fibrous (white matter), and protoplasmic (gray matter) astrocytes have been studied in the human neocortex by the rapid Golgi method. The developmental route followed by each of these astrocytes is a distinct process which evolves from a specific precursor, occurs at a different time, and is linked to a specific event. The differentiation of layer I astrocytes is linked to the neocortex external glial limiting membrane (EGLM), that of fibrous astrocytes to the early white matter vascularization and maturation, and that of protoplasmic astrocytes to the late gray matter ascending vascularization and maturation. At the start of development, three glial precursors are established in the neocortex: 1) original radial neuroectodermal cells with nuclei above the primordial plexiform layer (PPL) by losing their ependymal and retaining their pial attachments become early astrocytes of layer I and EGLM components; 2) neuroectodermal cells with nuclei below the PPL that retain their pial and ependymal attachments become type I radial glial cells which are committed to the guidance of neurons and the early EGLM maintenance; and, 3) neuroectodermal cells that lose their pial but retain their ependymal attachment are transformed into type II radial glial precursors. By progressively losing their ependymal attachment, type II radial glia precursors become freely migrating cells, establish vascular contacts, and differentiate into fibrous astrocytes (and into oligodendrocytes?) throughout the subplate, developing white matter, and paraventricular regions. After the formation of the gray matter, additional layer I astrocytes are needed for the EGLM late prenatal and postnatal maintenance because type I radial glia cells start to regress and to reabsorb their EGLM endfeet. A late ependyma‐to‐pia migration of glial precursors progressively repopulates layer I with additional astrocytes and establishes the ephemeral subpial granular layer (SGL) of Ranke. From the 15th week of gestation to the time of birth, late astrocytes of layer I lose their EGLM attachments, migrate freely into the maturing gray matter, establish vascular contacts, and differentiate into protoplasmic astrocytes. The protoplasmic astrocytes of the gray matter evolve from transformation of layer I astrocytes rather than from radial glia cells as is generally believed. © 1995 Wiley‐Liss, Inc.
Brainstem afferents to the lateral mesencephalic tegmental region of the cat
Authors: Gerlach Irene , Thier Peter
Published: January 2005

The lateral mesencephalic tegmental region (LTR) is a part of the midbrain reticular formation characterized by the presence of neurons exhibiting head movement‐related discharge modulation. In addition, the LTR contains directionally selective visual units. Possible sources for these vestibular and visual signals were studied by retrograde axonal transport of horseradish peroxidase and three different fluorescent tracers (rhodamine, fast blue, and fluorogold) injected into various parts of the LTR.

All injections into the LTR traced afferents from the vestibular nuclei and from the nucleus prepositus hypoglossi. Predominant projections were derived from the ipsilateral nucleus prepositus hypoglossi and the ipsilateral medial vestibular nucleus, whereas the observed inputs from the inferior, lateral, and superior vestibular nuclei were much weaker. Further inputs to the LTR originated in the deep and intermediate layers of the ipsilateral superior colliculus and the ipsilateral periaqueductal gray, the contralateral LTR, and the contralateral marginal nucleus of the brachium conjunctivum. Tracer deposits in medial parts of the tegmentum neighboring the LTR never produced the pattern of afferents observed after injections into the LTR.

Our results suggest that afferents from the deeper layers of the superior colliculus are probably the source of visual signals in the LTR and that head movement‐related responses are likely to be derived from the nucleus prepositus hypoglossi and the medial vestibular nucleus. © 1995 Wiley‐Liss, Inc.
Laminar organization of receptive field properties in the dorsal lateral geniculate nucleus of the tree shrew (Tupaiaglis belangeri)
Authors: Holdefer Robert N. , Norton Thomas T.
Published: January 2005

A laminar analysis of the receptive field properties of relay cells in the binocular region of the tree shrew dorsal lateral geniculate nucleus (LGN) found three main subdivisions. Lamina 1 (receiving ipsilateral eye input) and lamina 2 (contralateral) comprise a pair of layers that contain only ON‐center neurons. Laminae 4 (contralateral) and 5 (ipsilateral) comprise a pair of layers with mostly OFF‐center cells (86%). Laminae 3 and 6 (both contralaterally innervated) also form a distinct pair, although lamina 3 contains a mixture of cells with ON‐centers (43%) or OFF‐centers (57%), and lamina 6 contains mostly cells with ON‐OFF centers and suppressive surrounds (81%). Cells located in the interlaminar zones resembled neurons in laminae 3 and 6. In comparison with the cells in the OFF‐center laminae 4 and 5, the ON‐center cells in laminae 1 and 2 had smaller, more elliptical receptive field centers with stronger responses to flashed visual stimuli. In addition, cells in the ipsilateral eye laminae 1 and 5 showed a greater change in center diameter, with eccentricity from the area centralis, than cells in the contralateral eye laminae 2 and 4. Principal components analysis using six receptive field properties (latency to optic chiasm stimulation, receptive field center diameter, maintained discharge rate, response onset latency, peak spike density, and phasic‐tonic index) suggested that the cells in laminae 3 and 6 and the interlaminar zones are W‐like. Principal components analysis of the same receptive field properties in laminae 1, 2, 4, and 5 did not reveal differences clearly related to X‐like (parvocellular) and Y‐like (magnocellular) categories. Ninety‐seven percent of the cells tested for linearity of spatial summation in laminae 1, 2, 4, and 5 were linear. We conclude that the dominant organizational features of the tree shrew LGN are the ON‐center, OFF‐mter, and W pairs of layers that project to different regions within the striate cortex. © 1995 Wiley‐Liss, Inc.
Neurons of the median neuroblast lineage of the grasshopper: A population study of the efferent DUM neurons
Authors: Campbell Holly R. , Thompson Karen J. , Siegler Melody V. S.
Published: January 2005

A group of lineally related neurons in the grasshopper was studied to determine the number of efferent neurons in the group and their morphological types. The neurons arise from the median neuroblast of the third thoracic neuromere and comprise what is commonly known as the DUM or dorsal unpaired median group. Of some 92 neurons in the group, about 20 are efferent neurons, the remainder being local or intersegmental interneurons. As part of our continuing developmental studies, we wished to identify the efferent neurons within the lineage and to determine their number. Ten efferent DUM neurons had been described in earlier studies, where neurons were stained individually through microelectrodes. The remaining unidentified neurons might be novel types, multiples of known types, or both, possibilities that would not be readily distinguished through further staining of neurons individually. Rather, we used methods of retrograde staining and axon tracing that allowed us to examine the entire group of efferent DUM neurons. Nineteen efferent neurons were identified, comprising two DUM1s, five DUM3s, six DUM3,4s, three DUM3,4,5s, and three DUM5s, neurons were named according to the lateral nerves containing their axons. The efferent neurons were further divided by type according to the distribution of axonal branches in lateral nerves, the course of the primary neurite within the deep or superficial DUM tract, and the diameter of the cell body. © 1995 Wiley‐Liss, Inc.
Hypothalamic Leu‐enkephalin‐immunoreactive fibers terminate on calbindin‐containing somatospiny cells in the lateral septal area of the rat
Authors: Szeidemann Zsolt , Shanabrough Marya , Leranth Csaba
Published: January 2005

Correlated light and electron microscopic double‐immunostaining experiments for Leuenkephalin and calbindin were employed to determine the postsynaptic targets in the septal complex of Leu‐enkephalin fibers. Chronic surgical isolation of the septal complex from its hypothalamic afferents and retrograde tracer studies using wheat germ agglutinin‐conjugated horseradish peroxidase, both followed by an immunostaining for Leu‐enkephalin, were performed to elucidate the location of the origin of these axon terminals. Furthermore, a colocalization study for glutamic acid decarboxylase and Leu‐enkephalin was carried out on hypothalamic sections to determine their possible coexistence in cells projecting to the lateral septum.

These studies revealed that (1) Leu‐enkephalin‐immunoreactive axons form pericellular baskets around a population of lateral septal area neurons; (2) they establish exclusively asymmetric synaptic contacts on their soma and initial dendritic segments; (3) 10% of the lateral septal area calbindin‐contatining cells, which are all of the γ‐aminobutyric acid (GABA)‐ergic somatospiny type, are innervated by Leu‐erikephalin‐immunoreactive baskets; (4) only 40% of the Leu‐enkephalin target neurons are calbindin immunopositive; 5) the septopetal Leuenkephalin fibers derive from neurons located in the ipsilateral perifornical area and anterior hypothalamus; and 6) none of their cells of origin cocontains the inhibitory transmitter GABA. These observations indicate that hypothalamic Leu‐enkephalin‐containing neurons are nonGABAergic excitatory cells. Hence, they can effectively stimulate a population of lateral septal area neurons, including the somatospiny cells, which are all GABAergic. Therefore, after stimulatory Leu‐enkephalin action, these neurons can inhibit their postsynaptic targets, including other projective lateral septal neurons. © 1995 Wiley‐Liss, Inc.
Evidence to support the distal vagal ganglion as the origin of C cells of the ultimobranchial gland in the chick
Authors: Kameda Yoko
Published: January 2005

Formation and development of the ultimobranchial anlage were studied in chicken embryos by immunohistochemistry with the antibodies to class III β‐tubulin, TuJ1, human leukemic cell‐line (HNK‐1), and protein gene product (PGP) 9.5, all of which recognized neurons. Medial to the fourth aortic arch, the ultimobranchial anlage was formed by the extension of the ventral portion of the fourth pharyngeal pouch at 4. 5 days of incubation. At 5 days of incubation, TuJ1—immunoreactive cells with long cell processes began to enter the ultimobranchial anlage, which displayed a follicle structure. At 6 days of incubation, numerous neuronal cells that were continuos with the distal vagal ganglion (nodose ganglion) and expressed immunoreactivity for TuJ1, HNK‐1, and PGP 9. 5 were found to be in direct contact with the peripheral portion of ultimobranchial anlage. The TuJ1 antibody reacted only with the neuronal cells, whereas the HNK‐1 and PGP 9. 5 antibodies reacted with both endodermal epithelial cells and the neuronal cells in the ultimobranchial anlage. Subsequently, the ultimobranchial anlage rapidly increased in size; the follicle wall was thickened and a central cavity disappeared. The TuJ1—immunoreactive cells were distributed throughout the ultimobranchial parenchyma in 7‐day‐old embryos. The neuronal cell streams from the distal vagal ganglion to the ultimobranchial anlage were still prominent at 8 days of incubation. Almost all parenchymal cells of the ultimobranchial glands were intensely immunoreactive for TuJ1, HNK‐1 and PGP 9. 5 between 10 and 16 days of incubation. These results indicate that the neuronal cells from the distal vagal ganglion enter into the ultimobranchial anlage and give rise to C cells, i.e., C cells differentiate along the neuronal lineage. During embryonic development, C cells of the chick ultimobranchial glands transiently express a number of neuronal properties. © 1995 Wiley‐Liss, Inc.
Presynaptic metabotropic glutamate receptors in adult and developing neurons: Autoexcitation in the olfactory bulb
Authors: van den Pol Anthony N.
Published: January 2005

The mitral cell of the olfactory bulb is the primary relay neuron that transmits information from the olfactory receptors to the rest of the brain. This excitatory neuron releases glutamate from presynaptic dendrites and axon terminals. All rat mitral cells studied showed strong, selective, and widespread metabotropic glutamate receptor mGluR1α immunoreactivity on the presynaptic membrane of dendrites, often at the synaptic vesicle release site, when examined with light and electron microscopy. The finding of glutamate receptors on mitral cell secondary dendrites supports the conclusion that not all dendritic membrane with glutarnate receptors necessarily have gray type I asymmetrical synaptic specializations. In contrast, the metabotropic glutamate receptor mGluR5 was not found in mitral cells but was expressed by granule cells and astrocytes around mitral dendrites.

Both mGluR1α and mGluR5 were expressed early in development, with strong immunostaining present by postnatal day 1. MGluR1α staining at birth mirrored the adult staining pattern. MGluR5 staining at birth showed different patterns of immunostaining than that found in the adult, particularly in the external plejdform layer. In vitro olfactory bulb neurons and their dendrites from embryonic day (E) 18 olfactory bulbs responded to t‐ACPD and quisqualate, selective and fionselective metabotropic glutamate receptor agonists, and to several ionotropic glutamatel agonists with increases in intracellular Ca2+ as studied with fura‐2 digital imaging. These data indicate that the receptors were functionally active at an early stage of development. Application of the glutarnate receptor blockers d‐2‐amino‐5‐phosphonovalerate (AP5) and 6‐cyano‐7‐nitroquinoxaline (CNQX) to E17 olfactory bulb neurons after only 4 days in vitro resulted in a dramatic decrease in Ca2+ levels in 70% of 128 cells tested, suggesting that embryonic neurons after a short time in vitro can actively secrete glutamate.

The presence of glutamate receptors on the long mitral cell dendrite suggests that it would be able to respond to release of its own excitatory transmitter, probably at an early stage of development. In the probable absence of other excitatory input to the secondary mitral dendrites, it would be the only excitatory “input.” This autoexcitatory response would be modulated by release of GABA from olfactory interneurons occurring milliseconds after glutamate release induced by olfactory nerve activation. This novel type of neuronal microcircuitry would potentially amplify signal transmission and current spread along the long mitral dendrites and could play an important role in lateral inhibition of olfactory neurons. © 1995 Wiley‐Liss, Inc.
Expression of glial fibrillary acidic protein and its relation to tract formation in embryonic zebrafish (Danio rerio)
Authors: Marcus Riva C. , Easter Stephen S.
Published: January 2005

To address possible roles of glial cells during axon outgrowth in the vertebrate central nervous system, we investigated the appearance and distribution of the glial‐specific intermediate filament, glial fibrillary acidic protein (GFAP), during early embryogenesis of the zebrafish (Danio rerio). Immunopositive cells first appear at 15 hours, which is at the time of, or slightly before, the first axon outgrowth in the brain. Immunopositive processes are not initially present in a pattern that prefigures the location of the first tracts but rather are distributed widely as endfeet adjacent to the pia, overlying most of the surface of the brain with the exception of the dorsal and ventral midline. The first evidence for a specific association of immunopositive cells with the developing tracts is observed at 24 hours in the hindbrain, where immunopositive processes border axons in the medial longitudinal fasciculus. By 48 hours, immunopositive processes have disappeared from most of the subpial lamina and are found exclusively in association with tracts and commissures in three forms: endfeet, radially oriented processes, and tangentially oriented processes parallel to axons. This last form is particularly prominent in the transverse plane of the hindbrain, where they define the boundaries between rhombomeres. These results suggest that glial cells contribute to the development and organization of the central nervous system by supporting early axon outgrowth in the subpial lamina and by forming boundaries around tracts and between neuromeres. The results are discussed in relation to previous results A neuron‐glia interactions and possible roles of glial cells in axonal guidance. © 1995 Wiley‐Liss, Inc.
Acute exposure to alcohol during early postnatal life causes a deficit in the total number of cerebellar Purkinje cells in the rat
Authors: Pauli J. , Wilce P. , Bedi K. S.
Published: January 2005

Alcohol taken regularly over a lengthy period of time has been claimed to cause to loss of neurons in both the adult and developing brain. However, it remains uncertain whether acute, as opposed to chronic, exposure to alcohol at specified periods can also cause disruption in the neuronal population of the developing brain. This question was investigated by exposing Wistar rat pups to 7.5 g/kg body weight of ethanol administered as a 10% solution via an intragastric cannula over an 8 hour period either on the 5th (PND5) or the 10th (PND10) postnatal day of age. Gastrostomy controls received a 5% sucrose solution substituted isocalorically for the ethanol. Another set of pups raised by their mothers was used as “suckle controls”. All surgical procedures were carried out under halothane vapour anaesthesia. After the artificial feeding regimes, all pups were returned to the lactating dams and weaned at 21 days of age. Between 52 and 54 days of age, the rats were anaesthetised with an intraperitoneal injection with Nembutal and killed by intracardiac perfusion with 3% glutaraldehyde in 0.1 M phosphate buffer. The relatively unbiased stereological procedure known as the “fractionator” method was used to estimate the total number of Purkinje cells in the cerebellum of each animal. The Purkinje cell nucleolus was used as the counting unit; it was assumed that each Purkinje cell contained only one nucleolus. PND10 ethanol‐treated rats and gastrostomy and suckle controls had between about 210,000‐232,000 Purkinje cells in the cerebellum. However, the PND5 ethanol‐treated rats had only about 137,000 Purkinje cells. Two‐way analysis of variance procedures revealed significant main effects of age at time of alcohol exposure and groups as well as a significant interaction between them. It is concluded that the Purkinje cell population numbers can be disrupted by acute exposure to alcohol on the 5th, but not the 10th, postnatal day of age. © 1995 Wiley‐Liss, Inc.
Distributions of the mRNAs for L‐2‐amino‐4‐phosphonobutyrate‐sensitive metabotropic glutamate receptors, mGluR4 and mGluR7, in the rat brain
Authors: Ohishi Hitoshi , Akazawa Chihiro , Shigemoto Ryuichi , Nakanishi Shigetada , Mizuno Noboru
Published: January 2005

The distribution of mRNAs for metabotropic glutamate receptors, mGluR4 and mGluR7, which are highly sensitive for L‐2‐amino‐4‐phosphonobutyrate (L‐AP4), was examined in the central nervous system of the rat by in situ hybridization. In general, the hybridization signals of mGluR7 mRNA were more widely distributed than those of mGluR4 inRNA, and differential expression of mGluR4 mRNA and mGluR7 mRNA was clearly indicated in some brain regions. Intense or moderate expression of mGluR4 mRNA was detected in the granule cells of the olfactory bulb and cerebellum, whereas no significant expression of mGluR7 mRNA was found in these cells. In other neurons or regions where mGluR7 mRNA was intensely or moderately expressed, no significant expression of mGluR4 mRNA was observed. Such were the mitral and tufted cells of the olfactory bulb; anterior olfactory nucleus; neocortical regions; cingulate cortex; retrosplenial cortex; piriform cortex; perirhinal cortex; CAl; CA3; granule cells of the dentate gyrus; superficial layers of the subicular cortex; deep layers of the entorhinal, parasubicular, and presubicular cortices; ventral part of the lateral septal nucleus; septohippo campal nucleus; triangular septal nucleus; nuclei of the diagonal band; bed nucleus of the stria terminalis; ventral pallidum; claustrum; amygdaloid nuclei other than the intercalated nuclei; preoptic region; hypothalamic nuclei other than the medial mammillary nucleus; ventral lateral geniculate nucleus; locus coeruleus; Purkinje cells; many nuclei of the lower brainstem other than the superior coUiculus, periaqueductal gray, interpeduncular nucleus, pontine nuclei, and dorsal cochlear nucleus; and dorsal horn of the spinal cord. Both mGluR4 mRNA and mGluR7 mRNA were moderately or intensely expressed in the olfactory tubercie, superficial layers of the entorhinal cortex, CA4, septofimbrial nucleus, intercalated nuclei of the amygdala, medial mammillary nucleus, many thalamic nuclei, and pontine nuclei. Intense expression of both mGluR4 mRNA and mGluR7 mRNA was further detected in the trigeminal ganglion and dorsal root ganglia, whereas no significant expression of them was found in the pterygopalatine ganglion and superior cervical ganglion. The results indicate differential roles of the L‐AP4‐sensitive metabotropic glutamate receptors in the glutarnatergic nervous system. © 1995 Wiley‐Liss, Inc.
Estrogen modulation of mRNA levels for the two forms of glutamic acid decarboxylase (GAD) in female rat brain
Authors: McCarthy M. M. , Kaufman L. C. , Brooks P. J. , Pfaff D. W. , Schwartz‐Giblin S.
Published: January 2005

Two separate forms of glutamic acid decarboxylase, now termed GAD65 and GAD67 are the rate limiting enzymes for synthesis of γ‐aminobutyric acid (GABA). Because of the significance of GABA to neuroendocrine processes, numerous attempts have been made to determine the impact of gonadal steroids on enzyme functioning with inconclusive results. Therefore, we attempted to determine the impact of estradiol on mRNA levels for each form of GAD by quantitative in situ hybridization histochemistry in various brain regions.

Ovariectomized rats were treated with estradiol benzoate or oil vehicle on 2 consecutive days and the brains collected on the third day. DNA probes specific for GAD65 or GAD67 were radiolabeled with CTP using asymmetric polymerase chain reaction. Results of in situ hybridizations for each probe on alternate sections from the same animals were analyzed for magnocellular preoptic area (McPOA), dorsal medial nucleus of the hypothalamus (DMN), zona incerta (ZI), and midbrain central gray (MCG). In the McPOA, estradiol exerted opposite effects on the frequency distribution of pixels per cell for the two GAD mRNA probes, significantly increasing GAD65 (P < .05) and decreasing GAD67 (P < .01; Kolmogorov‐Smirnov). In the DMN, estradiol treatment significantly increased GAD67 by 60% (P < .05; two‐way ANOVA) but decreased GAD65 mRNA by 73% (P < .01). Note the direction of effects are opposite between McPOA and DMN. In MCG, analysis showed no estradiol effect on GAD mRNA levels/cell, but the proportion of cells expressing detectable levels of GAD65 or GAD67 increased by 33–40% in estradiol‐treated rats (χ2, P < .001). © 1995 Wiley‐Liss, Inc.
Anatomical basis for interactions of enkephalins with other transmitters in the CNS of a snail
Authors: Dyakonova Varvara , Carlberg Mats , Sakharov Dmitri , Elofsson Rolf
Published: January 2005

Immunocytochemical techniques for double staining were employed to investigate the morphological basis for interactions between enkephalins and other neuroactive compounds in the behavior of the gastropod mollusc Cepaea nemoralis. Coexistence of each of the two enkephalins with FMRFamide, serotonin or GABA‐like immunoreactivity was found in certain neurons in cerebral, parietal, and pedal ganglia. Tyrosine hydroxylase‐immunoreactive neurons were occasionally seen in close apposition to, but never colocalized with, the enkephalins. A comparison between these anatomical observations and previous behavioral studies suggests that in gastropod molluscs cotransmission of enkephalins with classical transmitters may, at least partly, reflect synergism of these substances in the control of definite behavioral programs. © 1995 Wiley‐Liss, Inc.
Periventricular morphology in the diencephalon of antarctic notothenioid teleosts
Authors: Lannoo Michael J. , Eastman Joseph T.
Published: January 2005

We have examined the subependymal region of the diencephalic third ventricle in notothenioid perciforms and report a pattern of neuropil expansions that appears to be phyletically derived for notothenioids and their outgroups but that is otherwise unique among vertebrates. We recognize five types of expansions based on their composition (from less dense neuropil to sacs) and width or protrusion into the third ventricle. In the species with the most elaborate morphology,Trematomus bernacchii, bilateral subependymal expansions fuse along the midline to form a single sac within the ventricular cavity. The extent of these expansions loosely corresponds with phyletic position but also (and perhaps more importantly) is correlated with the habitation of cold water (r2= 0.48;P= 0.012). Furthermore, subependymal expansion type is positively correlated with the maximum size of the soma of neurons in two hypothalamic nuclei, the preopticus magnocellularis (r2= 0. 54;P= 0. 006) and the lateralis tuberis (r2= 0.40;P= 0.038). These nuclei project to the pituitary and contain cerebrospinal fluid‐contacting neurons. In considering the functional consequences of this morphology, we cannot dismiss the possibility that these structures form a specialized enteroceptive system tied to the monitoring of cerebrospinal and extracellular fluid components, including antifreeze glycopeptides and inorganic ions. © 1995 Wiley‐Liss, Inc.
Intrinsic connections of the rat amygdaloid complex: Projections originating in the basal nucleus
Authors: Savander Vesa , Go C.‐Genevieve , Ledoux Joseph E. , Pitkänen Asla
Published: January 2005

The amygdaloid complex is involved in associational processes, such as the formation of emotional memories about sensory stimuli. However, the anatomical connections through which the different amygdaloid nuclei process incoming information and communicate with the other amygdaloid nuclei, is poorly understood. As part of an ongoing project aimed at elucidating the intrinsic connections of the rat amygdaloid complex, we injected the antero grade tracer PHA‐L (Phaseolus vulgaris‐leucoagglutinin) into different rostrocaudal levels of the basal nucleus of the amygdala in 21 rats and analyzed the distribution of labeled fibers and terminals throughout the amygdaloid complex. The connectional analysis, together with cytoarchitectonic observations, suggested that contrary to previous notions the basal nucleus in the rat has three divisions: magnocellular, intermediate, and parvicellular. The magnocellular division has heavy reciprocal connections with the lateral portion of the parvicellular division and the intermediate division projects weakly to the parvicellular division, whereas the projection from the medial: portion of the parvicellular division to the intermediate division is heavy and the lateral and medial portions of the parvicellular division are only weakly interconnected, as are the magnocellular and intermediate divisions. The main intraamygdaloid targets of the basal nucleus projections are the nucleus of the lateral olfactory tract, the anterior amygdaloid area, the medial and capsular divisions of the central nucleus, the anterior cortical nucleus, and the amygdalohippocampal area. Our findings provide the most detailed understanding of the intra‐amygdala connections of the basal nucleus to date and show that the connections within the basal nucleus and between the basal nucleus and other amygdaloid areas are more widespread and topographically organized than previously recognized. © 1995 Wiley‐Liss, Inc.
Morphogenetic reorganization of the brain during embryogenesis in the grasshopper
Authors: Boyan George S. , Williams J. Leslie D. , Reichert Heinrich
Published: January 2005

We have studied the morphogenetic reorganization that occurs in the grasshopper brain during embryogenesis. We find that morphogenetic movements occur at three organizational levels during brain development. First, the entire developing brain changes its orientation with respect to the segmental chain of ventral ganglia. A 90° shift in the attitude of the brain neuraxis occurs during embryogenesis due to a gradual upward movement of the cerebral structures in the head. Second, the clusters of proliferating neuroblasts and progeny that generate the neuroarchitecture of the mature brain move relative to one another and to nonneural structures such as the stomodeum. This is especially pronounced for the pars intercerebralis and for the tritocerebrum, as shown by annulin and engrailed immunoreactivity. Third, individual neuroblasts within a given proliferative cluster undergo positional reorganization during embryogenesis. Identified neuroblasts of the tritocerebrum and the pars intercerebralis are displaced within the brain. We conclude that the transformation of the simple sheet‐like structure of the early embryonic brain into the highly differentiated structure of the mature brain involves a series of morphogenetic movements that occur in virtually all parts of the brain. © 1995 Wiley‐Liss, Inc.
Plasticity of mature sensory cerebrovascular axons following intracranial infusion of nerve growth factor
Authors: Isaacson Lori G. , Ondris D. , Crutcher K. A.
Published: January 2005

Mature perivascular sympathetic axons associated with the intradural segment of the internal carotid artery (ICA) of the adult rat respond by sprouting following a two week infusion of nerve growth factor (NGF) into the lateral ventricle of the brain. Because nonsympathetic axons such as those comprising the sensory and parasympathetic population have been shown to respond to NGF, the present study was carried out to determine whether mature sensory axons respond to in vivo NGF infusion and whether competitive interactions between the innervating populations might affect the responsiveness of these axons to NGF. Standard electron microscopic techniques as well as calcitonin‐gene‐related peptide (CGRP) immunohistochemistry at the light microscopic level were used to examine the effects of intracerebroventricular NGF infusion on mature perivascular fibers with and without prior sympathetic denervation (i. e., bilateral superior cervical ganglionectomy). Following NGF infusion, CGRPimmunoreactive fibers appeared thicker and more numerous in the longitudinal plane when compared with vehicle controls. However, at the ultrastructural level, a significant increase in the total number of axons was not observed, although there was an increase in the number of large granular vesicles, suggesting that the CGRP fibers responded to exogenous NGF with an increase in neurotransmitter content, but not by sprouting. Sympathetic denervation, on the other hand, resulted in a significant increase in the number of fibers passing in the circumferential plane. The most dramatic change in CGRP immunoreactivity was observed following combined sympathetic denervation and subsequent NGF infusion, where, in addition to the presence of thicker immunoreactive fibers, a significant increase in the perivascular density of immunoreactive fibers associated with the intradural blood vessels was observed. These findings suggest that exogenous NGF has different effects on mature sympathetic and nonsympathetic fibers that innervate intradural blood vessels. The former exhibit robust sprouting, whereas the latter do not sprout in response to NGF but show evidence for increased neuropeptide content. In addition, the heightened response by sensory axons following denervation and subsequent NGF infusion provides support for the idea that sensory and sympathetic axons normally compete for target space and/or target‐derived neurotrophic factors. © 1995 Wiley‐Liss, Inc.
Inositol 1,4,5‐trisphosphate receptor localization in the brain of a weakly electric fish (Apteronotus leptorhynchus) with emphasis on the electrosensory system
Authors: Berman Neil J. , Hincke Maxwell T. , Maler Leonard
Published: January 2005

Inositol 1, 4, 5‐trisphosphate is a widespread intracellular second messenger that mobilizes intracellular Ca2+ stores. The inositol 1, 4, 5‐trisphosphate receptor involved is associated with the endoplasmic reticulum in neurons. In mammalian brain, inositol 1, 4, 5‐trisphosphate receptor‐containing neurons are found in many diverse regions, with cerebellar Purkinje cells containing the highest density of these receptors.

We used immunohistochemical methods to identify the distribution of inositol 1,4,5‐trisphosphate receptor‐containing neurons in the brain of the weakly electric fish and Western blotting to confirm that a protein similar to the inositol 1,4,5‐trisphosphate receptor of mammalian brain was recognized in the fish brain.

In the telencephelon, the dorsal forebrain regions had low amounts of inositol 1,4,5‐trisphosphate receptor. In the diencephalon, only the nucleus tuberis posterior was moderately immunoreactive. In the mesencephalon, only the optic tectum contained cells with intense immunoreactivity, similar to our findings for the ryanodine receptor (G. K. H. Zupanc, J. A. Airey, L. Maler, J. Sutko, and M. H. Ellisman, 1992, J. Comp. Neurol. 325:135–151), which also mobilizes intracellular calcium. In the rhombencephalon, a subset of the pyramidal cells of the electrosensory lateral line lobe contained inositol 1, 4, 5‐trisphosphate receptor. These cells have been shown to contain ryanodine receptor (Zupanc et al., 1992). However, unlike the ryanodine receptor, the distribution of inositol 1,4,5‐trisphosphate receptor in these cells is constrained to the soma and proximal dendrites. This compartmentalization may indicate the limit of the range of second‐messenger action. Other regions containing immunoreactive cells were the nucleus praeminentialis dorsalis (multipolar and boundary cells), nucleus medialis and crista cerebellaris, and the cerebellum, whose Purkinje cells were the most intensely labeled. The functional implications of inositol 1,4,5‐trisphosphate receptor localization in the electrosensory lateral line lobe are discussed. © 1995 Wiley‐Liss, Inc.