bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression of AMPA‐type glutamate receptor subunit (GluR2) in ON‐bipolar neurons in the rat retina
Authors: Kamphuis Willem , Klooster Jan , Dijk Frederike 
Published: December 2002

AbstractThe role of glutamate receptors (GluR) in the signal pathways of the retina is widely recognized. Photoreceptors make synaptic contact with functionally different classes of bipolar cells. The OFF‐type bipolar cells mediate light offset‐evoked responses and use ionotropic α‐amino‐3‐hydroxy‐5‐methyl‐isoxazole‐4‐propionate (AMPA)‐ or kainate‐type GluRs, whereas bipolars involved in the ON‐pathway use the metabotropic GluR6. This dichotomy predicts a defined expression pattern of AMPA‐type GluRs and mGluR6 in bipolar cell classes. This hypothesis was tested by performing immunocytochemical double labeling studies combining GluR‐specific antibodies with markers specific for the diverse bipolar cell populations in the rat retina. AMPA‐type receptors are composed of combinations of four types of subunits, GluR1–4. GluR1 is expressed by a few somata in the outer part of the inner nuclear layer (INL). Sparse colocalization with any of the bipolar markers used could be established. In contrast, GluR2 is expressed by many of the somata in the outer zone of the INL. At the transcript level, in situ hybridizations demonstrated abundant GluR2 expression over the complete width of the INL. In contrast to our expectations, approximately 70% of the somata labeled by the rod ON‐bipolar markers protein kinase C (PKC) or Goα, colocalized with GluR2. Approximately 90% of the OFF‐type bipolar cells, identified as recoverin‐positive, showed GluR2 immunoreactivity. At least 40% of the somata that were mGluR6‐immunoreactive, a both rod and cone ON‐type bipolar marker, were GluR2‐immunopositive. Ultrastructurally, examples were observed of GluR2 localization in bipolar processes with labeling outside the actual compartment associated with the synaptic complex of the rod terminal. No specific antibody was available against GluR3, but 74% of the PKC‐positive cells were GluR2/3‐positive. GluR4 did not show a somatic localization making double labeling impossible. On the basis of these results, we conclude that ionotropic GluRs are expressed by rod ON‐type bipolar cells (PKC‐ or Goα‐immunoreactive), and by cone ON‐ and OFF‐type bipolars based on a colocalization with nearly all of the present recoverin‐positive somata. Our observations show that the functional dichotomy in ON‐ and OFF‐type bipolars is not reflected in a matching expression pattern of ionotropic and metabotropic GluRs. This finding raises the intriguing possibility that the AMPA‐type GluRs are, in an as yet unclear manner, involved in the ON signaling pathways of rods and cones. J. Comp. Neurol. 455:172–186, 2003. © 2002 Wiley‐Liss, Inc.
Long‐term regeneration of abdominal vagus: Efferents fail while afferents succeed
Authors: Phillips Robert J. , Baronowsky Elizabeth A. , Powley Terry L. 
Published: December 2002

AbstractVagal afferents regenerate, by 18 weeks after subdiaphragmatic transection, to reinnervate the gut and to differentiate into the two types of terminals normally found in the smooth muscle wall of the gastrointestinal (GI) tract (Phillips et al. [2000] J Comp Neurol. 421:325–346). Regeneration, however, is neither complete nor entirely accurate by 18 weeks. Moreover, the capacity of the vagal efferents to reinnervate the GI tract under comparable conditions has not been evaluated. Therefore, to determine whether a more extended postaxotomy survival interval would (1) result in more extensive reinnervation of smooth muscle, (2) facilitate correction of the inaccuracies of the regenerated axons and terminals, and (3) yield motor as well as sensory reinnervation of GI targets, Sprague‐Dawley rats received either complete subdiaphragmatic vagotomies (n = 18) or sham surgeries (n = 12). Physiological endpoints that might normalize as vagal elements regenerated, including body weight, daily food intake, size of first daily meal, and metabolic efficiency, were monitored. At 45 weeks after the vagotomies, the animals were randomly assigned to afferent (wheat germ agglutinin–horseradish peroxidase) or efferent (cholera toxin subunit B–horseradish peroxidase) mapping conditions, and labeled axons and terminals in the stomach and first 8 cm of the small intestine were inventoried in whole‐mounts. Afferent regeneration was more extensive at 45 weeks than previously observed at 18 weeks after surgery; however, the amount of GI innervation was still not comparable to the intact pattern of the sham rats. Furthermore, abnormal patterns of sensory organization occurred throughout the reinnervated field, with small bundles of axons forming complex tangles and some individual axons terminating in ectopic locations. The presence of growth cone profiles suggested that vagal reorganization was ongoing even 45 weeks after surgery. In contrast to this relatively extensive, albeit incomplete, sensory reinnervation of the gut, motor fibers had failed to reinnervate the GI tract. Thus, dramatic differences exist in the regenerative capacities of the sensory and motor arms of the vagus under the same surgical and maintenance conditions. Furthermore, the functional measures of disordered energy regulation did not normalize over the 45 weeks during which afferent but not efferent innervation was restored. J. Comp. Neurol. 455:222–237, 2003. © 2002 Wiley‐Liss, Inc.
Expression of Ca2+‐activated BK channel mRNA and its splice variants in the rat cochlea
Authors: Langer Patricia , Gründer Stefan , Rüsch Alfons 
Published: December 2002

AbstractVoltage‐activated K+ channels are important for shaping the receptor potentials of cochlear hair cells. In particular, the functional maturation of inner hair cells in mice around the onset of hearing coincides with the expression of a large, fast K+ conductance, probably mediated by Ca2+‐activated K+ (BK) channels. In hearing organs of lower vertebrates, frequency tuning depends on BK‐type K+ channels with different kinetics. Kinetics are varied by alternative splicing of the channels' α subunits and combination with modulating β subunits. It is unclear whether similar mechanisms “fine tune” mammalian hair cells. We used various polymerase chain reaction (PCR) approaches to screen rat cochleae for splice variants of BK‐type α subunits. We isolated mainly minimal variants and only occasionally splice variants with additional inserts. We conclude that α subunits with different kinetics are not substantially used in the rat cochlea. However, we isolated six variants differing in their extreme C‐terminal sequences, which may be involved in the targeting of the channel protein. By using reverse transcriptase‐PCR, we demonstrated also the expression of transcripts for several β subunits. In situ hybridization experiments revealed strict coexpression of α with β1 transcripts. In inner hair cells, strong labeling emerged shortly before the onset of hearing. Labeling of outer hair cells appeared later and generally weaker. Thus, our molecular data confirm electrophysiological results that suggested that BK channels underlie the large K+ conductance in inner hair cells of mammals. Extensive splicing of BK channel transcripts, however, does not seem to be used in mammalian hair cells as is done in lower vertebrates. J. Comp. Neurol. 455:198–209, 2003. © 2002 Wiley‐Liss, Inc.
Topographical and laminar organization of subicular projections to the parahippocampal region of the rat
Authors: Kloosterman Fabian , Witter Menno P. , Van Haeften Theo 
Published: December 2002

AbstractIn this study, we analyzed in detail the topographic organization of the subiculoparahippocampal projection in the rat. The anterograde tracers Phaseolus vulgaris leucoagglutinin‐L and biotinylated dextran amine were injected into the subiculum at different septotemporal and transverse levels. Deep layers of the ento‐, peri‐, and postrhinal cortices are the main recipients of subicular projections, but in all cases we noted that a small fraction of the projections also terminates in the superficial layers II and III. Analysis of the fiber patterns in the parahippocampal region revealed a topographic organization, depending on the location of the cells of origin along both the transverse and the septotemporal axes of the subiculum. Projections originating from subicular cells close to CA1, i.e., proximal part of subiculum, terminate exclusively in the lateral entorhinal cortex and in the perirhinal cortex. In contrast, projections from cells closer to the subiculum‐presubiculum border, i.e., distal part of subiculum, terminate in the medial entorhinal cortex and in the postrhinal cortex. In addition, cells in septal portions of the subiculum project to a lateral band of entorhinal cortex parallel to the rhinal sulcus and to peri‐ or postrhinal cortices, whereas cells in more temporal portions project to more medial parts of the entorhinal cortex. These results indicate that subicular projections to the parahippocampal region precisely reciprocate the known inputs from this region to the hippocampal formation. We thus suggest that the reciprocal connectivity between the subiculum and the parahippocampal region is organized as parallel pathways that serve to segregate information flow and thus maintain the identity of processed information. Although this parallel organization is comparable to that of the CA1‐parahippocampal projections, differences exist with respect to the degree of collateralization. J. Comp. Neurol. 455:156–171, 2003. © 2002 Wiley‐Liss, Inc.
Calbindin and calretinin immunoreactivities identify different types of neurons in the adult lamprey spinal cord
Authors: Megías Manuel , Álvarez‐Otero Rosa , Pombal Manuel A. 
Published: December 2002

AbstractThe central pattern generator for locomotion in vertebrates is composed of different spinal neuronal populations that generate locomotor movement. In the lamprey spinal cord, several classes of interneurons have been identified based on morphologic and physiological criteria and integrated in the spinal cord circuits implicated in the generation of locomotion. However, the lack of histochemical markers for most of the interneurons makes it difficult to study whole populations along the spinal cord. We have investigated the immunoreactivity with antibodies raised against calbindin and calretinin. Several types of neurons could be classified: (1) strongly immunoreactive neurons located dorsomedially, (2) moderately immunoreactive neurons located laterally, (3) small weakly immunoreactive neurons, d) ventromedial neurons, (4) liquor contacting cells, and (5) motoneurons. The ventromedial group of calbindin‐immunoreactive neurons also is immunoreactive for serotonin and, therefore, represents the ventromedial group of dopamine/serotonin spinal neurons. Some of the lateral calbindin‐immunoreactive neurons may be CC‐type cells (cells with caudal‐crossed axons), because they are retrogradely labeled by tracer injections into the contralateral spinal cord. Other well‐characterized cell types, such as sensory dorsal cells, lateral interneurons, descending propriospinal edge cells, and spinobulbar giant interneurons are negative for both calbindin and calretinin. Therefore, calbindin and calretinin are useful markers for the study of cell populations that may be integrated in locomotor circuits. J. Comp. Neurol. 455:72–85, 2003. © 2002 Wiley‐Liss, Inc.
Ecological, evolutionary, and functional correlates of sensilla number and glomerular density in the olfactory system of decapod crustaceans
Authors: Beltz Barbara S. , Kordas Kashka , Lee Monaya M. , Long Jennifer B. , Benton Jeanne L. , Sandeman David C. 
Published: December 2002

AbstractOne of the features common among olfactory systems for vertebrate and invertebrate species is the division of the primary processing area into distinct clumps of synaptic neuropil, called glomeruli. The olfactory glomeruli appear to serve as functional units of olfaction and are the location of the primary processing between chemosensory afferents and second‐order neurons. Although glomeruli are found across all phyla, their numbers and size appear to be characteristic for each species, giving rise to the speculation that there is a relationship between glomerular number and function. It has been hypothesized, for example, that animals with more glomeruli may be able to resolve a wider range of odors. Crustacean species are distributed among freshwater, marine, and terrestrial habitats in arctic, temperate, and tropical climates. They also exhibit a variety of lifestyles and behaviors in which olfaction may play a dominant role. Feeding, for example, ranges from carnivorous, through subaquatic and terrestrial omnivorous scavenging, to filter feeding. Mating and territorial behaviors also are known to involve chemical signals. The current study examines glomerular numbers in the olfactory lobes of 17 crustacean species from six of the seven taxa now included in the reptantian decapods. Estimates of the glomerular numbers were obtained from the analysis of sectioned material treated immunocytochemically with an antibody against synapsin that labels proteins contained in neuronal terminals. The numbers of glomeruli found in the different species were then compared with the volume of the glomerular neuropil, numbers of olfactory sensilla, life styles, habitat, and phylogenetic affinities. The picture that emerges from these correlations is that the decapod crustaceans have exploited various strategies in the construction of their olfactory systems in which the problems of size, sensitivity, and selectivity have all interacted. We find a continuum across the groups ranging from those that favor a high convergence of receptor neurons onto a few glomeruli to those that share a small number of receptor neurons among many glomeruli. The potential functional consequences of these differences are discussed. J. Comp. Neurol. 455:260–269, 2003. © 2002 Wiley‐Liss, Inc.
Loss of calbindin‐D28k from aging human cholinergic basal forebrain: Relation to neuronal loss
Authors: Geula Changiz , Bu Jing , Nagykery Nicholas , Scinto Leonard F.M. , Chan Jennifer , Joseph Jeffrey , Parker Robert , Wu Chuang‐Kuo 
Published: December 2002

AbstractCholinergic neurons of the basal forebrain (BFCN) are selectively vulnerable in neurodegenerative disorders of the elderly, particularly in Alzheimer's disease (AD). We investigated age‐related changes in the BFCN that may serve as a substrate for this vulnerability. We report a substantial and selective age‐related loss of the calcium binding protein calbindin‐D28K (CB) from the human BFCN. Unbiased stereological estimation indicated that, in individuals under age 65 years, 72% of the choline acetyltransferase (ChAT)‐positive BFCN contained CB immunoreactivity. In individuals over age 65 years, only 28% of the BFCN contained CB immunoreactivity, a dramatic loss of 61%. Similar results were obtained using neuronal counts from matching single‐ or double‐stained sections in a larger cohort. The loss of CB immunoreactivity was neurochemically specific. No age‐related changes were observed in the number of ChAT‐ or low‐affinity nerve growth factor receptor (p75NTR)‐immunoreactive profiles. The loss of CB was greatest in very old individuals, in whom a small loss of BFCN was observed. Furthermore, the loss of CB displayed the same pattern as the loss of BFCN in AD and was more substantial in the posterior compared with the anterior BFCN sector, suggesting a role for CB in the selective vulnerability of BFCN in AD. The depletion of CB from the BFCN is likely to deprive these neurons of the capacity to buffer high levels of intracellular Ca2+ and thus to leave them vulnerable to pathological processes, such as those in neurodegenerative disorders, which can cause increased intracellular Ca2+, thus leading to their degeneration. J. Comp. Neurol. 455:249–259, 2003. © 2002 Wiley‐Liss, Inc.
Evidence that Sema3A and Sema3F regulate the migration of GABAergic neurons in the developing neocortex
Authors: Tamamaki Nobuaki , Fujimori Kazuhiro , Nojyo Yoshiaki , Kaneko Takeshi , Takauji Rumiko 
Published: December 2002

AbstractThe ganglionic eminence (GE) supplies neurons containing γ‐aminobutyric acid (GABA) to the pallium of the telencephalon. We investigated the molecular guidance mechanisms of GE cell migration in the neocortex and found neuropilin‐1 (Npn‐1) or neuropilin‐2 (Npn‐2) on the GE cells. Ectopic Sema3A or ‐3F expression by COS1 cell clusters placed on embryo neocortical slices reduced the cell migration but did not block it completely. However, the cell migration was almost completely blocked by COS1 cell clusters expressing both Sema3A and ‐3F. The direction of cell migration could be reversed by placing Sema3A‐ and ‐3F‐coexpressing COS1 cell clusters at the distal cut end of the neocortical slices. Further slice experiments revealed that migration of half of the GE cells in the neocortex was regulated by Sema3A and that migration of the other half of the GE cells in the neocortex was regulated by Sema3F. When the cells responding to Sema3A were diverted by ectopic Sema3A expression in vivo, Dlx2‐positive cells were found predominantly in the lower intermediate zone (IZ). When the cells responding to Sema3F were diverted by ectopic Sema3F expression in vivo, Dlx2‐positive cells were found predominantly in the upper IZ. It was speculated that the semaphorin–neuropilin interactions distribute the GABAergic GE cells evenly in the neocortex as well as guide the GE cells from the GE to the neocortex. The Sema3A expression site under the subplate extended dorsally as the embryo developed. The Sema3A expression seemed to block the Npn‐1‐positive GE cells in the neocortex from entering the cortical plate (CP) and guide them to the dorsal cortex and the hippocampus. Sema3F expression in the CP continued through the embryonic stages. The expression seemed to block Npn‐2‐positive GE cells in the neocortex from entering the CP and make them migrate into the lower IZ. Finally, the semaphorin–neuropilin interactions sorted GABAergic inteneurons into the CP and white matter neurons into the IZ. J. Comp. Neurol. 455:238–248, 2003. © 2002 Wiley‐Liss, Inc.
Inspiratory augmenting bulbospinal neurons express both glutamatergic and enkephalinergic phenotypes
Authors: Stornetta Ruth L. , Sevigny Charles P. , Guyenet Patrice G. 
Published: December 2002

AbstractMany of the inspiratory augmenting (I‐AUG) neurons of the rostral ventral respiratory group (rVRG) are premotor neurons that excite phrenic motor neurons during inspiration, probably by releasing glutamate. In the present study, we demonstrate that these neurons are indeed glutamatergic, in that their cell bodies contain vesicular glutamate transporter‐2 (VGLUT2) mRNA and spinal terminals from neurons in the region of the rVRG contain VGLUT2 protein. We also demonstrate by using parallel in situ hybridization and immunocytochemical evidence that most rVRG inspiratory premotor neurons are enkephalinergic. After iontophoretic deposits of biotinylated dextran amine (BDA) in the area of the rVRG, many BDA‐labeled terminals in the ventral horn of cervical spinal cord (C4–C5) were immunoreactive for enkephalin and VGLUT2. Injections of Fluoro‐Gold amidst phrenic motor neurons in C4–C5 labeled neurons in the area of the rVRG that contained both VGLUT2 mRNA and preproenkephalin (PPE) mRNA as revealed by double in situ hybridization. Thirty‐eight bulbospinal I‐AUG neurons were recorded in the rVRG and filled with biotinamide by using the juxtacellular labeling technique. Every biotinamide‐filled cell tested was positively labeled for VGLUT2 mRNA (n = 14), and most of the cells tested in a separate population exhibited PPE mRNA (16/18). We conclude that most of the phrenic inspiratory premotor neurons of the rVRG are glutamatergic neurons that may also release enkephalins. J. Comp. Neurol. 455:113–124, 2003. © 2002 Wiley‐Liss, Inc.
Olfactory‐enriched transcripts are cell‐specific markers in the lobster olfactory organ
Authors: Hollins Bettye , Hardin Debra , Gimelbrant Alexander A. , McClintock Timothy S. 
Published: December 2002

AbstractGenes expressed specifically in a tissue are often involved in the defining functions of that tissue. We used representational difference analysis of cDNA to amplify 20 cDNA fragments representing transcripts that were more abundant in the lobster olfactory organ than in brain, eye/eyestalk, dactyl, pereiopod, or second antenna. We then independently confirmed that the transcripts represented by these clones were enriched in the olfactory organ. The 20 cDNA fragments represent between 6 and 15 different genes. Six of the cDNAs contained sequences highly similar to known gene families. We performed in situ hybridization with these six and found that all were expressed in subsets of cells associated with the aesthetasc sensilla in the olfactory organ. Clones OET‐07, an ionotropic receptor, and OET‐10, an α tubulin, were specific to the olfactory receptor neurons. OET‐02, a monooxygenase, was expressed only in the outer auxiliary cells. OET‐03, a serine protease, was specific to the collar cells. OET‐11, an α2 macroglobulin, was expressed by the receptor neurons and the collar cells. OET‐17, a calcyphosine, was expressed in the receptor neurons, inner auxiliary cells, and collar cells. The identities and expression patterns of these six transcripts predict involvement in both known and novel properties of the lobster olfactory organ. J. Comp. Neurol. 455:125–138, 2003. © 2002 Wiley‐Liss, Inc.
Ultrastructural localization of serotonin 2A and N‐methyl‐D‐aspartate receptors in somata and dendrites of single neurons within rat dorsal motor nucleus of the vagus
Authors: Huang Jie , Pickel Virginia M. 
Published: December 2002

AbstractBoth glutamate and serotonin are potent modulators of autonomic functions involving the nucleus of the solitary tract (NTS) and the dorsal motor nucleus of the vagus (DMNV) at the level of the area postrema. Moreover, many of the dendrites in this NTS region express both N‐methyl‐D‐aspartate (NMDA) and serotonin (5HT) 2A receptors, and some of these dendrites may arise from the adjacent DMNV. Thus, single neurons in DMNV may also express both receptors. To test this hypothesis, we used electron microscopic immunocytochemistry for dual localization of the essential R1 subunit of the NMDA receptor (NR1) and the 5HT2A receptor in rat intermediate DMNV, a region serving mainly gastrointestinal functions. Gold particles representing NR1 and peroxidase reaction product for 5HT2A receptors were seen in the cytoplasm, as well as on distinct segments of the plasma membrane of many dendrites. Of the NR1‐labeled dendrites, 31% (254/814) also contained 5HT2A immunoreactivity; among the 5HT2A‐labeled dendrites, 52% (254/485) expressed NR1. The 5HT2A labeling was also present in numerous small unmyelinated axons, axon terminals, and glial processes. These profiles were largely without NR1 immunoreactivity, although NR1 was detected in some of the dendrites postsynaptic to 5HT2A‐labeled terminals. Our results suggest that calcium entry through NMDA channels and 5HT2A receptor activation may dramatically affect postsynaptic excitability of single neurons in the DMNV. In addition, the findings also indicate that the 5HT2A receptor is strategically positioned for involvement in modulation of the presynaptic release of neurotransmitters affecting the postsynaptic activity of DMNV neurons responsive to NMDA activation. J. Comp. Neurol. 455:270–280, 2003. © 2002 Wiley‐Liss, Inc.