bluuebunny/crossref_metadata_2025_split huggingface dataset:
The readthrough variant of acetylcholinesterase remains very minor after heat shock, organophosphate inhibition and stress, in cell culture and in vivo
Authors: Perrier Noël A. , Salani Monica , Falasca Cinzia , Bon Suzanne , Augusti‐Tocco Gabriella , Massoulié Jean 
Published: July 2005

AbstractAcetylcholinesterase (AChE) exists in various molecular forms, depending on alternative splicing of its transcripts and association with structural proteins. Tetramers of the ‘tailed’ variant (AChET), which are anchored in the cell membrane of neurons by the PRiMA (Proline Rich Membrane Anchor) protein, constitute the main form of AChE in the mammalian brain. In the mouse brain, stress and anticholinesterase inhibitors have been reported to induce expression of the unspliced ‘readthrough’ variant (AChER) mRNA which produces a monomeric form. To generalize this observation, we attempted to quantify AChER and AChET after organophosphate intoxication in the mouse brain and compared the observed effects with those of stress induced by swimming or immobilization; we also analyzed the effects of heat shock and AChE inhibition on neuroblastoma cells. Active AChE molecular forms were characterized by sedimentation and non‐denaturing electrophoresis, and AChE transcripts were quantified by real‐time PCR. We observed a moderate increase of the AChER transcript in some cases, both in the mouse brain and in neuroblastoma cultures, but we did not detect any increase of the corresponding active enzyme.
Identification of synaptic plasma membrane proteins co‐precipitated with fibrillar β‐amyloid peptide
Authors: Verdier Yann , Huszár Emőke , Penke Botond , Penke Zsuzsa , Woffendin Gary , Scigelova Michaela , Fülöp Lívia , Szűcs Mária , Medzihradszky Katalin , Janáky Tamás 
Published: July 2005

AbstractThe β‐amyloid peptide that is overproduced in Alzheimer's disease rapidly forms fibrils, which are able to interact with various molecular partners. This study aimed to identify abundant synaptosomal proteins binding to the fibrillar β‐amyloid (fAβ) 1–42. Triton X‐100‐soluble proteins were extracted from the rat synaptic plasma membrane fraction. Interacting proteins were isolated by co‐precipitation with fAβ, or with fibrillar crystallin as a negative control. Protein identification was accomplished (1) by separating the tryptically digested peptides of the protein pellet by one‐dimensional reversed‐phase HPLC and analysing them using an ion‐trap mass spectrometer with electrospray ionization; and (2) by subjecting the precipitated proteins to gel electrophoretic fractionation, in‐gel tryptic digestion and to matrix‐assisted laser desorption/ionization time‐of‐flight mass measurements and post‐source decay analysis. Six different synaptosomal proteins co‐precipitated with fAβ were identified by both methods: vacuolar proton‐pump ATP synthase, glyceraldehyde‐3‐phosphate dehydrogenase, synapsins I and II, β‐tubulin and 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase. Most of these proteins have already been associated with Alzheimer's disease, and the biological and pathophysiological significance of their interaction with fAβ is discussed.
Negative regulation of neurotransmitter release by calpain: a possible involvement of specific SNAP‐25 cleavage
Authors: Ando Kosuke , Kudo Yoshihisa , Takahashi Masami 
Published: July 2005

AbstractSynaptic transmission is conducted by neurotransmitters released from presynaptic nerve terminals by means of Ca2+‐dependent exocytosis of synaptic vesicles. Formation of a complex of soluble N‐ethylmaleimide‐sensitive fusion protein receptor (SNARE) proteins, including vesicle‐associated membrane protein‐2 (VAMP‐2) in the synaptic vesicle membrane, and syntaxin 1 and synaptosomal‐associated protein of 25 kDa (SNAP‐25) in the plasma membrane, is essential for exocytosis. Ionomycin treatment of cultured rat cerebellar granule cells led to cleavage of SNAP‐25, but not syntaxin 1 and VAMP‐2, that was dependent on extracellular Ca2+. Cleavage was also induced by N‐methyl‐d‐aspartate (NMDA) treatment, but not by depolarization. The use of various site‐specific antibodies to SNAP‐25, suggested that the cleavage site was in the N‐terminal domain of SNAP‐25. Calpain inhibitors abolished the Ca2+‐dependent cleavage of SNAP‐25 and markedly facilitated Ca2+‐dependent glutamate (Glu) release from cerebellar granule cells. These results suggest that calpain may play an important role in the long‐lasting regulation of synaptic transmission by suppressing neurotransmitter release, possibly through the proteolytic cleavage of SNAP‐25.
Regional and subtype selective changes of neurotransmitter receptor density in a rat transgenic for the Huntington's disease mutation
Authors: Bauer Andreas , Zilles Karl , Matusch Andreas , Holzmann Carsten , Riess Olaf , Von Hörsten Stephan 
Published: July 2005

AbstractHuntington's disease (HD) is an autosomal dominantly inherited progressive neurodegenerative disorder caused by a CAG/polyglutamine repeat expansion in the gene encoding the huntingtin protein. We have recently generated a rat model transgenic for HD, which displays a slowly progressive phenotype resembling the human adult‐onset type of disease. In this study we systematically assessed the distribution and density of 17 transmitter receptors in the brains of 2‐year‐old rats using quantitative multi‐tracer autoradiography and high‐resolution positron emission tomography. Heterozygous animals expressed increased densities of M2 acetylcholine (increase of 148 ± 16% of controls; p > 0.001; n = 7), nicotine (increase of 149 ± 16% of controls; p > 0.01; n = 6), and α2 noradrenergic receptors (increase of 141 ± 15% of controls; p > 0.001; n = 6), respectively. Densities of these receptors were decreased in homozygous animals. Decreases of receptor density in both hetero‐ and homozygous animals were found for M1 acetylcholine, 5‐HT2A serotonin, A2A adenosine, D1 and D2 dopamine, and GABAA receptors, respectively. Other investigated receptor systems showed small changes or were not affected. The present data suggest that the moderate increase of CAG/polyglutamine repeat expansions in the present rat model of Huntington's disease is characterized by subtype‐selective and region‐specific changes of neuroreceptor densities. In particular, there is evidence for a contribution of predominantly presynaptically localized cholinergic and noradrenergic receptors in the response to Huntington's disease pathology.
The excitoprotective effect of N‐methyl‐d‐aspartate receptors is mediated by a brain‐derived neurotrophic factor autocrine loop in cultured hippocampal neurons
Authors: Jiang Xueying , Tian Feng , Mearow Karen , Okagaki Peter , Lipsky Robert H. , Ann M. Marini  
Published: July 2005

AbstractThe neuroprotective effect and molecular mechanisms underlying preconditioning with N‐methyl‐D‐aspartate (NMDA) in cultured hippocampal neurons have not been described. Pre‐incubation with subtoxic concentrations of the endogenous neurotransmitter glutamate protects vulnerable neurons against NMDA receptor‐mediated excitotoxicity. As a result of physiological preconditioning, NMDA significantly antagonizes the neurotoxicity resulting from subsequent exposure to an excitotoxic concentration of glutamate. The protective effect of glutamate or NMDA is time‐ and concentration‐dependent, suggesting that sufficient agonist and time are required to establish an intracellular neuroprotective state. In these cells, the TrkB ligand, brain‐derived neurotrophic factor (BDNF) attenuates glutamate toxicity. Therefore, we tested the hypothesis that NMDA protects neurons via a BDNF‐dependent mechanism. Exposure of hippocampal cultures to a neuroprotective concentration of NMDA (50 μm) evoked the release of BDNF within 2 min without attendant changes in BDNF protein or gene expression. The accumulated increase of BDNF in the medium is followed by an increase in the phosphorylation (activation) of TrkB receptors and a later increase in exon 4‐specific BDNF mRNA. The neuroprotective effect of NMDA was attenuated by pre‐incubation with a BDNF‐blocking antibody and TrkB‐IgG, a fusion protein known to inhibit the activity of extracellular BDNF, suggesting that BDNF plays a major role in NMDA‐mediated survival. These results demonstrate that low level stimulation of NMDA receptors protect neurons against glutamate excitotoxicity via a BDNF autocrine loop in hippocampal neurons and suggest that activation of neurotrophin signaling pathways plays a key role in the neuroprotection of NMDA.
Astrocyte‐ and hepatocyte‐specific expression of genes from the distal serpin subcluster at 14q32.1 associates with tissue‐specific chromatin structures
Authors: Gopalan Sunita , Kasza Aneta , Xu Weili , Kiss Daniel L. , Wilczynska Katarzyna M. , Rydel Russell E. , Kordula Tomasz 
Published: July 2005

AbstractThe distal serpin subcluster contains genes encoding α1‐antichymotrypsin (ACT), protein C inhibitor (PCI), kallistatin (KAL) and the KAL‐like protein, which are expressed in hepatocytes, but only the act gene is expressed in astrocytes. We show here that the tissue‐specific expression of these genes associates with astrocyte‐ and hepatocyte‐specific chromatin structures. In hepatocytes, we identified 12 Dnase I‐hypersensitive sites (DHSs) that were distributed throughout the entire subcluster, with the promoters of expressed genes accessible to restriction enzyme digestion. In astrocytes, only six DHSs were located exclusively in the 5′ flanking region of the act gene, with its promoter also accessible to restriction enzyme digestion. The acetylation of histone H3 and H4 was found throughout the subcluster in both cell types but this acetylation did not correlate with the expression pattern of these serpin genes. Analysis of histone modifications at the promoters of the act and pci genes revealed that methylation of histone H3 on lysine 4 correlated with their expression pattern in both cell types. In addition, inhibition of methyltransferase activity resulted in suppression of ACT and PCI mRNA expression. We propose that lysine 4 methylation of histone H3 correlates with the tissue‐specific expression pattern of these serpin genes.
A genetic screen inCaenorhabditis elegansfor dopamine neuron insensitivity to 6‐hydroxydopamine identifies dopamine transporter mutants impacting transporter biosynthesis and trafficking
Authors: Nass Richard , Hahn Maureen K. , Jessen Tammy , McDonald Paul W. , Carvelli Lucia , Blakely Randy D. 
Published: July 2005

AbstractThe presynaptic dopamine (DA) transporter (DAT) is a major determinant of synaptic DA inactivation, an important target for psychostimulants including cocaine and amphetamine, and a mediator of DA neuron vulnerability to the neurotoxins 6‐hydroxydopamine (6‐OHDA) and 1‐methyl‐4‐phenylpyridinium ion. To exploit genetic approaches for the study of DATs and neural degeneration, we exploited the visibility of green fluorescent protein (GFP)‐tagged DA neurons in transgenic nematodes to implement a forward genetic screen for suppressors of 6‐OHDA sensitivity. In our initial effort, we identified three noveldat‐1alleles conferring 6‐OHDA resistance. Two of thedat‐1alleles derive from point mutations in conserved glycine residues (G55, G90) in contiguous DAT‐1 transmembrane domains (TM1 and TM2, respectively), whereas the third allele results in altered translation of the transporter's COOH terminus. Our studies reveal biosynthetic, trafficking and functional defects in the DAT‐1 mutants, exhibited bothin vitroandin vivo.These studies validate a forward genetic approach to the isolation of DA neuron‐specific toxin suppressors and point to critical contributions of the mutated residues, as well as elements of the DAT‐1 COOH terminus, to functional expression of catecholamine transporters in neurons.
Functional assessment of glutamate clearance mechanisms in a chronic rat glaucoma model using retinal ganglion cell calcium imaging
Authors: Hartwick Andrew T. E. , Zhang Xiaowei , Chauhan Balwantray C. , Baldridge William H. 
Published: July 2005

AbstractUsing optical imaging of retinal ganglion cell (RGC) calcium dynamics in living intact retinal wholemount preparations, we tested whether RGCs in an experimental rat glaucoma model were more sensitive to exogenously applied glutamate as a result of deficient glutamate clearance mechanisms. In contrast to post‐natal rat RGCs in purified cultures, in which the calcium influx induced by 200 μmNMDA and 10 μmglutamate was approximately equivalent, application of up to 500 μmglutamate did not affect calcium levels in RGCs in retinal wholemounts, even though the RGCs responded to 200 μmNMDA. Glutamate (500 μm) did elicit a RGC calcium response in retinal wholemounts when glutamate transporters were inhibited pharmacologically with DL‐threo‐β‐benzyloxyaspartate, confirming the presence of glutamate clearance mechanisms in this intact retina preparation. The effect of glutamate was then assessed on retinas from rats with chronically elevated intraocular pressure in one eye, produced by the injection of hypertonic saline into an episcleral vein. Application of up to 500 μmglutamate had no effect on RGC calcium levels, while millimolar concentrations of glutamate induced a calcium signal in RGCs that was indistinguishable from that in fellow control retinas. Therefore, there was no evidence for a global defect in glutamate uptake in this rat model of experimental glaucoma. Imaging glutamatergic calcium dynamics of RGCs in retinal wholemounts represents a novel methodology to probe glutamate transporter function and dysfunction in an intact CNS tissue system.
Amyloid‐β peptide enhances tumor necrosis factor‐α‐induced iNOS through neutral sphingomyelinase/ceramide pathway in oligodendrocytes
Authors: Zeng C. , Lee J. T. , Chen H. , Chen S. , Hsu C. Y. , Xu J. 
Published: July 2005

AbstractAlthough accumulating evidence demonstrates that white matter degeneration contributes to pathology in Alzheimer's disease (AD), the underlying mechanisms are unknown. In order to study the roles of the amyloid‐β peptide in inducing oxidative stress damage in white matter of AD, we investigated the effects of amyloid‐β peptide 25–35 (Aβ) on proinflammatory cytokine tumor necrosis factor‐α (TNF‐α)‐induced inducible nitric oxide synthase (iNOS) in cultured oligodendrocytes (OLGs). Although Aβ 25–35 by itself had little effect on iNOS mRNA, protein, and nitrite production, it enhanced TNF‐α‐induced iNOS expression and nitrite generation in OLGs. Aβ, TNF‐α, or the combination of both, increased neutral sphingomyelinase (nSMase) activity, but not acidic sphingomyelinase (aSMase) activity, leading to ceramide accumulation. Cell permeable C2‐ceramide enhanced TNF‐α‐induced iNOS expression and nitrite generation. Moreover, the specific nSMase inhibitor, 3‐O‐methyl‐sphingomyelin (3‐OMS), inhibited iNOS expression and nitrite production induced by TNF‐α or by the combination of TNF‐α and Aβ. Overexpression of a truncated mutant of nSMase with a dominant negative function inhibited iNOS mRNA production. 3‐OMS also inhibited nuclear factor κB (NF‐κB) binding activity induced by TNF‐α or by the combination of TNF‐α and Aβ. These results suggest that neutral sphingomyelinase/ceramide pathway is required but may not be sufficient for iNOS expression induced by TNF‐α and the combination of TNF‐α and Aβ.
HPLC conditions are critical for the detection of GABA by microdialysis
Authors: Rea K. , Cremers T. I. F. H. , Westerink B. H. C. 
Published: July 2005

AbstractIn microdialysis studies, neither exocytotic release of γ‐aminobutyric acid (GABA), nor the presence of GABA type B (GABAB) autoreceptors, have been clearly established. It was investigated whether the chromatographic separation of GABA may have contributed to discrepancies in the literature. After extending the profile of the HPLC chromatogram to a retention time of 60 min, it was observed that various unknown compounds of biological origin co‐eluted near the GABA peak. The retention time of GABA appeared to be extremely sensitive to pH; even at a retention time of around 60 min there was only a small pH window (5.26 ± 0.01) where GABA was consistently well separated from co‐eluting compounds. GABA determined by the improved assay was sensitive to tetrodotoxin (TTX), calcium depletion and the GABAB autoreceptor agonist baclofen. The present results illustrate that if the proper analytical conditions are applied, extracellular GABA can be sampled and quantified by microdialysis in free‐moving animals. However, when the time‐curves are considered, there is a striking delay of about 15–30 min before the effects of TTX, calcium depletion or baclofen are observed, as compared to the reported response of neurotransmitters such as dopamine (less than 5 min). It is assumed that the glial cells serve as a buffer between the GABA synapse and the microdialysis probes. It is proposed that microdialysis samples measure synaptic GABA indirectly, through glial cells surrounding the synapses.
Inhibition of p38 mitogen‐activated protein kinase attenuates interleukin‐1β‐induced thermal hyperalgesia and inducible nitric oxide synthase expression in the spinal cord
Authors: Sung Chun‐Sung , Wen Zhi‐Hong , Chang Wen‐Kuei , Chan Kwok‐Hon , Ho Shung‐Tai , Tsai Shen‐Kou , Chang Yi‐Chen , Wong Chih‐Shung 
Published: July 2005

AbstractWe have reported recently that intrathecal (i.t.) injection of interleukin‐1β (IL‐1β), at a dose of 100 ng, induces inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production in the spinal cord and results in thermal hyperalgesia in rats. This study further examines the role of mitogen‐activated protein kinase (MAPK) in i.t. IL‐1β‐mediated iNOS–NO cascade in spinal nociceptive signal transduction. All rats were implanted with an i.t. catheter either with or without an additional microdialysis probe. Paw withdrawal latency to radiant heat is used to assess thermal hyperalgesia. The iNOS and MAPK protein expression in the spinal cord dorsal horn were examined by western blot. The [NO] in CSF dialysates were also measured. Intrathecal IL‐1β leads to a time‐dependent up‐regulation of phosphorylated p38 (p‐p38) MAPK protein expression in the spinal cord 30–240 min following IL‐1β injection (i.t.). However, neither the phosphorylated extracellular signal‐regulated kinase (p‐ERK) nor phosphorylated c‐Jun NH2‐terminal kinase (p‐JNK) was affected. The total amount of p38, ERK, and JNK MAPK proteins were not affected following IL‐1β injection. Intrathecal administration of either selective p38 MAPK, or JNK, or ERK inhibitor alone did not affect the thermal nociceptive threshold or iNOS protein expression in the spinal cord. However, pretreatment with a p38 MAPK inhibitor significantly reduced the IL‐1β‐induced p‐p38 MAPK expression by 38–49%, and nearly completely blocked the subsequent iNOS expression (reduction by 86.6%), NO production, and thermal hyperalgesia. In contrast, both ERK and JNK inhibitor pretreatments only partially (≈ 50%) inhibited the IL‐1β‐induced iNOS expression in the spinal cord. Our results suggest that p38 MAPK plays a pivotal role in i.t. IL‐1β‐induced spinal sensitization and nociceptive signal transduction.
Regional distribution and age‐dependent expression of N‐acylphosphatidylethanolamine‐hydrolyzing phospholipase D in rat brain
Authors: Morishita Jun , Okamoto Yasuo , Tsuboi Kazuhito , Ueno Masaki , Sakamoto Haruhiko , Maekawa Nobuhiro , Ueda Natsuo 
Published: July 2005

AbstractThe endocannabinoid anandamide (N‐arachidonoylethanolamine) and other bioactive long‐chain N‐acylethanolamines are thought to be formed from their corresponding N‐acylphosphatidylethanolamines by a specific phospholipase D (NAPE‐PLD) in the brain as well as other tissues. However, regional distribution of NAPE‐PLD in the brain has not been examined. In the present study, we investigated the expression levels of NAPE‐PLD in nine different regions of rat brain by enzyme assay, western blotting and real‐time PCR. The NAPE‐PLD activity was detected in all the tested brain regions with the highest activity in thalamus. Similar distribution patterns of NAPE‐PLD were observed at protein and mRNA levels. We also found a remarkable increase in the expression levels of protein and mRNA of the brain NAPE‐PLD with development, which was in good agreement with the increase in the activity. The age‐dependent increase was also seen with several brain regions and other NAPE‐PLD‐enriched organs (heart and testis). p‐Chloromercuribenzoic acid and cetyltrimethylammonium chloride, which inhibited recombinant NAPE‐PLD dose‐dependently, strongly inhibited the enzyme of all the brain regions. These results demonstrated wide distribution of NAPE‐PLD in various brain regions and its age‐dependent expression, suggesting the central role of this enzyme in the formation of anandamide and other N‐acylethanolamines in the brain.
Activation of NMDA receptors induces protein kinase A‐mediated phosphorylation and degradation of matrin 3. Blocking these effects prevents NMDA‐induced neuronal death
Authors: Giordano Gennaro , Sánchez‐Pérez Ana María , Montoliu Carmina , Berezney Ronald , Malyavantham Kishore , Costa Lucio G. , Calvete Juan José , Felipo Vicente 
Published: July 2005

AbstractActivation of NMDA receptors leads to activation of cAMP‐dependent protein kinase (PKA). The main substrates phosphorylated by PKA following NMDA receptor activation remain unidentified. The aim of this work was to identify a major substrate phosphorylated by PKA following NMDA receptor activation in cerebellar neurones in culture, and to assess whether this phosphorylation may be involved in neuronal death induced by excessive NMDA receptor activation. The main PKA substrate following NMDA receptor activation was identified by MALDI‐TOFF fingerprinting as the nuclear protein, matrin 3. PKA‐mediated phosphorylation of matrin 3 is followed by its degradation. NMDA receptor activation in rat brain in vivo by ammonia injection also induced PKA‐mediated matrin 3 phosphorylation and degradation in brain cell nuclei. Blocking NMDA receptors in brain in vivo with MK‐801 reduced basal phosphorylation of matrin 3, suggesting that it is modulated by NMDA receptors. Inhibition of PKA with H‐89 prevents NMDA‐induced phosphorylation and degradation of matrin 3 as well as neuronal death. These results suggest that PKA‐mediated phosphorylation of matrin 3 may serve as a rapid way of transferring information from synapses containing NMDA receptors to neuronal nuclei under physiological conditions, and may contribute to neuronal death under pathological conditions.