bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amino‐terminal region of secreted form of amyloid precursor protein stimulates proliferation of neural stem cells
Authors: Ohsawa Ikuroh , Takamura Chizuko , Morimoto Takako , Ishiguro Mariko , Kohsaka Shinichi 
Published: March 2003

Abstractβ‐Amyloid precursor protein (APP) has been reported to be expressed in the CNS from the early stages of development. However, the functional role of APP during early development remains unclear. In the present study, we found that the secreted form of APP (sAPP) significantly enhanced proliferation of neural stem cells. Cells were prepared from 13‐day embryonic rat neocortex, which was dissected with a Pasteur pipette to make cell clusters. After 12 h of cultivation in the medium without serum, cells around the centre of the cluster were still nestin‐positive proliferative cells, i.e. neural stem cells. To determine whether the proliferation of cells was regulated by sAPP, cultures were treated with recombinant sAPP695, the secreted form of human APP695 produced by yeast. Both DNA synthesis and expression of proliferating cell nuclear antigen markedly increased after 5 h of sAPP695 addition. The enhancement of DNA synthesis by sAPP695 stimulation was blocked by the 22C11 monoclonal antibody specific for the amino‐terminal region of sAPP. Then, we examined the effect of the amino‐terminal fragment of sAPP and the epitope peptide of 22C11 antibody, and found that both of them also promoted DNA synthesis, suggesting that the amino‐terminal region of sAPP is responsible for the biological activity. Our findings indicate the possibility that sAPP enhances proliferation of neural stem cells in vivo and plays an important role during the early CNS development.
Involvement of primary afferent C‐fibres in touch‐evoked pain (allodynia) induced by prostaglandin E2
Authors: Minami Toshiaki , Okuda‐Ashitaka Emiko , Hori Yuuichi , Sakuma Satoru , Sugimoto Tetsuo , Sakimura Kenji , Mishina Masayoshi , Ito Seiji 
Published: March 2003

AbstractNociceptive primary afferents have the capacity to induce a state of increased excitability in dorsal horn neurons of the spinal cord or central sensitization causing thermal hyperalgesia and touch‐evoked pain (allodynia). It is believed that primary afferent C‐fibres become hypersensitive and induce hyperalgesia and that low‐threshold Aβ‐fibres are responsible for induction of allodynia, the mechanisms of which remain elusive. We previously showed that intrathecal administration of prostaglandin E2 (PGE2) and prostaglandin F2α (PGF2α) induce allodynia in conscious mice. Here we demonstrated that selective elimination of C‐fibres by neonatal capsaicin treatment resulted in the disappearance of allodynia induced by PGE2, but not that by PGF2α. PGE2‐induced allodynia was not observed in N‐methyl‐D‐aspartate (NMDA) receptor ε1 subunit knockout mice and was sensitive to morphine. In contrast, PGF2α‐induced allodynia was not observed in NMDA ε4 subunit knockout mice and was insensitive to morphine. Furthermore, while PGF2α showed a capsaicin‐insensitive feeble facilitatory action on evoked excitatory postsynaptic currents in dorsal horn neurons, PGE2 induced a long‐lasting facilitation of evoked excitatory postsynaptic currents in a capsaicin‐sensitive manner. Taken together, the present study demonstrates that there are two pathways for induction of allodynia and that capsaicin‐sensitive C‐fibres may participate in PGE2‐induced allodynia.
Morphine injected into the paraventricular nucleus of the hypothalamus prevents noncontact penile erections and impairs copulation: involvement of nitric oxide
Authors: Melis Maria Rosaria , Succu Salvatora , Spano Maria Sabrina , Argiolas Antonio 
Published: March 2003

AbstractMale rats show four to six penile erection episodes when put in the presence of an inaccessible receptive female for 80 min. These noncontact erections occur concomitantly with an increase in nitric oxide production in the paraventricular nucleus of the hypothalamus. This is shown by the increases in the NO2– and NO3– concentrations in the paraventricular dialysate obtained from these males by in vivo microdialysis. The NO2– concentration increased from 0.75 ± 0.10 μm to 2.89 ± 0.39 μm and that of NO3– from 4.13 ± 0.58 μm to 9.5 ± 1.2 μm. Morphine (0.5, 1 and 5 μg), given unilaterally into the paraventricular nucleus 15 min before the introduction of the receptive female, prevented the NO2– and NO3– increases, and noncontact erections, dose‐dependently. In contrast, the κ opioid receptor agonist U‐69 593 (5 μg) was ineffective. The effects of morphine on NO2– and NO3–, and on noncontact erections, were prevented by the opiate receptor antagonist naloxone (10 μg) injected into the paraventricular nucleus 15 min before morphine. The NO2– and NO3– concentrations were also increased in the paraventricular dialysate of male rats during copulation, i.e. when in copula penile erections occurred. As found with noncontact erections, morphine, but not U‐69 593, injected into the paraventricular nucleus prevented the NO2– and NO3– increases and impaired copulatory behaviour, and naloxone prevented these responses when given before morphine. Although some diffusion of the opiate to surrounding brain areas cannot be completely ruled out, the present results suggest that morphine acts through μ receptors in the paraventricular nucleus to impair noncontact erections and copulation. These effects of morphine are apparently mediated by a prevention of the increased nitric oxide production that occurs in the paraventricular nucleus of the hypothalamus of male rats during sexual activity.
Presynaptic calcium‐channel currents in normal and csp mutant Drosophila peptidergic terminals
Authors: Morales Miguel , Ferrús Alberto , Martínez‐Padrón Manuel 
Published: March 2003

AbstractThe study of regulated vesicle exocytosis, which underlies neurotransmitter and neuropeptide release, has benefited from a convergence of several independent approaches. These include the use of genetically tractable organisms and model preparations that allow a direct characterization of presynaptic ionic currents. Aiming for a comprehensive analysis of release, we had already developed a Drosophila preparation in which electrophysiological recordings from peptidergic terminals are feasible. Here, we report on the characterization of the Ca2+‐channel currents present in these terminals. With Ba2+ as the charge carrier, the presynaptic membrane expresses a current type with high‐activation threshold and little inactivation. This current is blocked by verapamil and diltiazem at micromolar concentrations, it is relatively insensitive to nifedipine and completely resistant to non‐L‐type Ca2+‐channel antagonists. As a comparison, we also analysed the pharmacology of high‐threshold Ba+2 currents on muscle fibres. A high‐activation threshold Ca2+‐channel current is also present in muscle fibres, albeit with a distinct pharmacological profile. Thus, peptidergic terminals and muscle fibres exhibit different subtypes of voltage‐gated Ca2+ channels. The putative role of cysteine string protein (CSP) as a neuronal Ca2+‐channel modulator was tested by examining the peptidergic presynaptic current in csp null mutants. We show that CSP is expressed in peptidergic boutons and abolished in the mutant. Direct recordings, under conditions that inhibit calcium influx into glutamatergic terminals, show that Ca2+‐currents in peptidergic csp terminals are entirely normal. This result indicates that CSP is not a generic Ca2+‐channel modulator and it might perform different functions in fast versus slow forms of release.
In vitro electrophysiological properties of rat dorsal column nuclei neurons
Authors: Nuñez Angel , Buño Washington 
Published: March 2003

AbstractThe dorsal column nuclei include the gracile and cuneate nuclei, which receive somatosensory information from the periphery and project to the ventroposterior nucleus of the contralateral thalamus. The aim of this study was to determine the electrophysiological and morphological characteristics of the neurons of the dorsal column nuclei and to identify synaptic events evoked by electrical stimulation of the dorsal column, using an in vitro slice preparation. The results show two types of neurons, termed type I and II. A repolarizing sag distinguished type I cells during hyperpolarizing current injection, suggesting the activation of a Q‐current. Moreover, type I cells, but not type II cells, were capable of maintaining spontaneous rhythmic activity at 9–15 Hz. Both types of cells displayed a delay in their return to the resting membrane potential following hyperpolarizing current pulses, indicating the existence of an A‐current. Electrical stimuli applied to the dorsal column elicited brief EPSPs and IPSPs in both cell types. EPSPs were abolished by 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione, indicating that they were mediated through non‐NMDA receptors. IPSPs were blocked by picrotoxin, implying the activation of GABAA receptors. Intracellular staining with carboxyfluoresceine revealed that type I neurons had elongated somas and primary dendrites that extended radially. Type II cells were smaller and had round somas with few primary dendrites, most of them emerging from one pole of the soma. The axon of many type I neurons was stained and could be followed running ventrally and in rostral direction.
Intrinsic optical signal measurements reveal characteristic features during different forms of spontaneous neuronal hyperactivity associated with ECS shrinkage in vitro
Authors: Buchheim Katharina , Schuchmann Sebastian , Siegmund Herbert , Gabriel Hans Jürgen , Heinemann Uwe , Meierkord Hartmut 
Published: March 2003

AbstractWe induced three different forms of spontaneous synchronous hyperactivity in adult rat hippocampal–entorhinal cortex slices in order to investigate effects on the intrinsic optical signal and associated changes in the extracellular space (ECS) volume. Low‐Mg2+ artificial cerebrospinal fluid (ACSF) and the addition of 4‐aminopyridine induced synchronous hyperactivity resulting mainly from increased synaptic transmission, while low‐Ca2+ ACSF induced hyperactivity in the absence of evoked synaptic transmission. In the two models of enhanced synaptic transmission, spontaneous activity lead to an immediate increase of light transmission. In contrast, a decrease of light transmission took place during low‐Ca2+‐induced hyperactivity. All three forms of synchronous neuronal hyperactivity were associated with a shrinkage of the ECS volume, as revealed by the tetraethylammonium signal, measured with ion‐sensitive microelectrodes. This indicates that the change in the intrinsic optical signal is not simply related to a shrinkage in ECS volume. We conclude that different forms of spontaneous synchronous neuronal hyperactivity are associated with characteristic optical signals and that the direction of the change in intrinsic optical signal does not reflect ECS shrinkage alone.
Functional characteristics of skate connexin35, a member of the γ subfamily of connexins expressed in the vertebrate retina
Authors: White Thomas W. , Deans Michael R. , O'Brien John , Al‐Ubaidi Muayyad R. , Goodenough Daniel A. , Ripps Harris , Bruzzone Roberto 
Published: March 2003

AbstractRetinal neurons are coupled by electrical synapses that have been studied extensively in situ and in isolated cell pairs. Although many unique gating properties have been identified, the connexin composition of retinal gap junctions is not well defined. We have functionally characterized connexin35 (Cx35), a recently cloned connexin belonging to the γ subgroup expressed in the skate retina, and compared its biophysical properties with those obtained from electrically coupled retinal cells. Injection of Cx35 RNA into pairs of Xenopus oocytes induced intercellular conductances that were voltage‐gated at transjunctional potentials ≥ 60 mV, and that were also closed by intracellular acidification. In contrast, Cx35 was unable to functionally interact with rodent connexins from the α or β subfamilies. Voltage‐activated hemichannel currents were also observed in single oocytes expressing Cx35, and superfusing these oocytes with medium containing 100 μm quinine resulted in a 1.8‐fold increase in the magnitude of the outward currents, but did not change the threshold of voltage activation (membrane potential = +20 mV). Cx35 intercellular channels between paired oocytes were insensitive to quinine treatment. Both hemichannel activity and its modulation by quinine were seen previously in recordings from isolated skate horizontal cells. Voltage‐activated currents of Cx46 hemichannels were also enhanced 1.6‐fold following quinine treatment, whereas Cx43‐injected oocytes showed no hemichannel activity in the presence, or absence, of quinine. Although the cellular localization of Cx35 is unknown, the functional characteristics of Cx35 in Xenopus oocytes are consistent with the hemichannel and intercellular channel properties of skate horizontal cells.
Intramembranous structure of synaptic membranes with special reference to spinules in the rat sensorimotor cortex
Authors: Bozhilova‐Pastirova A. , Ovtscharoff W. 
Published: March 2003

AbstractThe intramembranous structure of the synaptic contact zone at presynaptic and postsynaptic membranes in the rat sensorimotor cortex was examined by means of the freeze‐etching technique. In axospinous synapses, the synaptic contact zone is characterized by perforated and nonperforated aggregates of intramembranous particles at the extracellular half or E‐face of the postsynaptic membrane. On some perforated synaptic contact zones, both synaptic membranes are marked by so called spinules. These invaginations of the postsynaptic membrane and the parallel presynaptic membrane into the axon terminal are situated at the particle free zones among the postsynaptic E‐face intramembranous particle aggregates or in close proximity to it. Intramembranous characteristics of the spinules at both freeze‐etched faces of presynaptic and postsynaptic membranes and their density of perforated axospinous synapses were analysed. The results are discussed in terms of plasticity at the synaptic contact zone of the axospinous synapses of the sensorimotor cortex in the rat.
Raf‐1 and B‐Raf proteins have similar regional distributions but differential subcellular localization in adult rat brain
Authors: Morice Cecile , Nothias Fatiha , König Sandra , Vernier Philippe , Baccarini Manuela , Vincent Jean‐Didier , Barnier Jean Vianney 
Published: March 2003

AbstractThe Raf kinases play an important and specific role in the activation of extracellular signal‐regulated kinases (ERK) cascade. Beside its role in the control of proliferation and differentiation, the ERK cascade has also been implicated in neuron‐specific functions. In order to gain clues on the function of Raf kinases in the adult central nervous system (CNS), we performed a comparative analysis of the distribution and subcellular localization of the different Raf kinases in rat brain with antibodies specific for the different Raf kinases. We show that B‐Raf and Raf‐1 proteins are present in most brain areas, whereas A‐Raf is not detected. Interestingly, the two Raf proteins have an approximately similar pattern of distribution with a rostro‐caudal decreasing gradient of expression. These two kinases are colocalized in neurons but they are differentially located in subcellular compartments. Raf‐1 is localized mainly in the cytosolic fraction around the nucleus, whereas B‐Raf is widely distributed in the cell bodies and in the neuritic processes. In addition, we demonstrated that numerous B‐Raf isoforms are present in the brain. These isoforms have a differential pattern of distribution, some of them being ubiquitously expressed whereas others are localized to specific brain areas. These isoforms also have a clear differential subcellular localization, specially in Triton‐insoluble fractions, but also in synaptosomal, membrane and cytosolic compartments. Altogether these results suggest that each Raf protein could have a distinct signalling regulatory function in the brain with regard to its subcellular localization.
Mint2/X11‐like colocalizes with the Alzheimer's disease amyloid precursor protein and is associated with neuritic plaques in Alzheimer's disease
Authors: McLoughlin Declan M. , Irving Nicholas G. , Brownlees Janet , Brion Jean‐Pierre , Leroy Karelle , Miller Christopher C. J. 
Published: March 2003

AbstractAberrant metabolism of the amyloid precursor protein (APP) is believed to be at least part of the pathogenic process in Alzheimer's disease. The carboxy‐terminus of APP has been shown to interact with the Mint/X11 family of phosphotyrosine binding (PTB) domain‐bearing proteins. It is via their PTB domains that the Mints/X11s bind to APP. Here we report the cloning of full‐length mouse Mint2 and demonstrate that in primary cortical neurons, Mint2 and APP share highly similar distributions. Mint2 also colocalizes with APP in transfected CHO cells. In Mint2/APP‐cotransfected cells, Mint2 reorganizes the subcellular distribution of APP and also increases the steady‐state levels of APP. Finally, we demonstrate that Mint2 is associated with the neuritic plaques found in Alzheimer's disease but not with neurofibrillary tangles. These results are consistent with a role for Mint2 in APP metabolism and trafficking, and suggest a possible role for the Mints/X11s in the pathogenesis of Alzheimer's disease.
Differential interaction of the tSXV motifs of the NR1 and NR2A NMDA receptor subunits with PSD‐95 and SAP97
Authors: Bassand Patrick , Bernard Anne , Rafiki Amina , Gayet Dimitri , Khrestchatisky Michel 
Published: March 2003

AbstractThe NR1 and NR2 subunits of the N‐methyl‐d‐aspartate (NMDA) receptor are encoded by distinct genes. In the rat brain, four C‐terminal variants of the NR1 subunit (NR1‐1 to NR1‐4) are encoded by a single gene, and are generated by alternative splicing of the C1 and C2 exon cassettes, while four different genes encode the NR2 subunits (NR2 A–D). Functional NMDA receptors result from the heteromultimeric assembly of NR1 variants with distinct NR2 subunits. The NR2B subunit interacts with post‐synaptic density protein 95 (PSD‐95), SAP97 and members of the membrane‐associated guanylate‐like kinase (MAGUK) family of proteins. This interaction occurs through the binding of the C‐terminal tSXV intracellular motif of the NR2B subunit to the N‐terminal PDZ (PSD‐95, discs‐large, ZO‐1) domains of the PSD‐95 and SAP97 proteins. Both NR1‐3 and NR1‐4 also display a consensus C‐terminal tSXV motif. Using the two‐hybrid genetic system in yeast and site‐directed mutagenesis, we compared the binding of the NR2A, NR1‐3 and NR1‐4 tSXV motifs with the PDZ domains of PSD‐95 and SAP97. The main conclusions of the present report are that: (i) while NR2A displays a strong interaction with PSD‐95 and SAP97, the NR1‐3 and NR1‐4 NMDA receptor subunits do not display any interaction despite the presence of tSXV motifs; (ii) the C‐terminal tSXV motif of the NR2A subunit is mandatory but not sufficient for efficient interaction with the PSD‐95 and SAP97 proteins; (iii) as yet unidentified upstream sequences of the receptor subunits determine whether the tSXV motifs will bind to the PSD‐95 and SAP97 PDZ domains; (iv) different tSXV motifs elicit interactions of variable strengths; and (v) residues in positions −3 and −4 modulate the binding affinity of the C‐terminal tSXV motifs. Using immunohistochemistry, we also compared the distribution of the PSD‐95, NR2A and SAP97 proteins in adult rat brain, and we show that in the cortex, hippocampus and cerebellum, there is evidence for colocalization of these proteins.
Muscarinic receptors regulate two different calcium‐dependent non‐selective cation currents in rat prefrontal cortex
Authors: Haj‐Dahmane Samir , Andrade Rodrigo 
Published: March 2003

AbstractPyramidal neurons of layer V in rat prefrontal cortex display a prominent fast afterdepolarization (fADP) and a muscarinic‐induced slow afterdepolarization (sADP). We have shown previously that both of these ADPs are produced by the activation of calcium‐dependent non‐selective cation currents. In the present report we examine whether they represent two distinct currents. In most pyramidal neurons recorded with caesium gluconate‐based intracellular solution, a calcium spike is followed by a fast decaying inward aftercurrent (IfADP). The decay of IfADP is monoexponential with a time constant (τ) of ≈ 35 ms. Administration of carbachol (10–30 μm) increases the time constant of this decay by ≈ 80% and induces the appearance of a much slower inward aftercurrent (IsADP). IfADP recorded in control conditions and in the presence of carbachol increases linearly with membrane hyperpolarization. In contrast, the carbachol‐induced IsADP decreases with membrane hyperpolarization. When the sodium driving force across the cell membrane was reduced, IfADP was found to reverse at around −40 mV whereas IsADP remain inward over the same voltage range tested. Finally, bath administration of flufenamic acid (100 μm–1 mm) selectively blocks the carbachol‐induced IsADP without a significant effect on the amplitude of IfADP. These differences in the electrical and pharmacological properties of IfADP and IsADP suggest that they were mediated by two distinct non‐selective cation currents.
Limbic P300s in temporal lobe epilepsy with and without Ammon's horn sclerosis
Authors: Grunwald T. , Beck H. , Lehnertz K , Blümcke I. , Pezer N. , Kutas M. , Kurthen M. , Karakas H. M. , Van Roost D. , Wiestler O. D. , Elger C. E. 
Published: March 2003

AbstractLimbic P300 potentials can be recorded within the mesial temporal lobes of patients with temporal lobe epilepsy (TLE). To delineate possible mechanisms of their generation and pathological alteration, we analysed limbic P300s in 55 TLE patients with and 29 without Ammon's horn sclerosis (AHS) and correlated their amplitudes with neuronal cell counts in 30 histopathological specimens. Limbic P300 amplitudes were reduced on the side of the epileptogenic focus only in patients with AHS. Moreover, in AHS patients, limbic P300 latencies were prolonged bilaterally; and in patients with left‐sided AHS, amplitudes were reduced bilaterally. Both findings suggest bilateral functional deficits in TLE with unilateral AHS. Limbic P300 areas correlated significantly with neuronal densities of dentate gyrus granule cells but not hippocampal pyramidal cells in the CA1–4 (cornu ammonis) subfields. This finding points to a potential mechanism for the bilateral effects of unilateral AHS as both dentate gyri exhibit strong reciprocal contralateral connectivity.