bluuebunny/crossref_metadata_2025 huggingface dataset:
Anterior cingulate error‐related activity is modulated by predicted reward
Authors: Amiez Céline , Joseph Jean‐Paul , Procyk Emmanuel
Published: July 2005

Learning abilities depend on detection and exploitation of errors. In primates, this function involves the anterior cingulate cortex. However, whether anterior cingulate error‐related activity indicates occurrence of inappropriate responses or results from other computations is debated. Here we have tested whether reward‐related parameters modulate error‐related activity of anterior cingulate neurons. Recordings in monkeys performing stimulus–reward associations and preliminary data obtained with a problem‐solving task revealed major properties of error‐related unit activity: (i) their amplitude varies with the amount of predicted reward or the proximity to reward delivery; (ii) they appear both after execution and performance errors; (iii) they do not indicate which error occurred or which correction to make; and (iv), importantly, the activity of these neurons also increases following an external signal indicating the necessity to shift response. Hence, we conclude that anterior cingulate ‘error’ activity might represent a negative deviation from a predicted goal, and does not only reflect error detection but signals events interrupting potentially rewarded actions.
Developmental downregulation of low‐voltage‐activated Ca2+ channels in Cajal‐Retzius cells of the mouse visual cortex
Authors: Kirmse Knut , Grantyn Rosemarie , Kirischuk Sergei
Published: July 2005

Cajal‐Retzius (CR) cells have been demonstrated to fulfil an important secretory function in the developing neocortex. On the other hand, the contribution of CR cell electrical activity during cortex development is still unclear. Using the whole‐cell patch‐clamp technique, we studied low‐voltage‐activated (LVA) Ca2+ channels in CR cells in the layer I of the mouse visual cortex. CR cells were found to display a transient Ca2+ current (IT) in response to a depolarization step from −100 mV to −40 mV. IT showed: (i) typical for LVA Ca2+ channels voltage dependence of activation (half‐activation at −55 mV) and inactivation (half‐inactivation at −76 mV); (ii) fast activation and inactivation kinetics, with time constants of 1.4 and 28 ms, respectively, at −40 mV; (iii) fast recovery from steady‐state inactivation (time constant: 290 ms); (iv) a complete block by 1 µm mibefradil; and (v) a partial block (to 55%) by 100 µm Ni2+. The density of IT dramatically decreased between postnatal day (P) 1 and P9. Immunostaining demonstrated the presence and postnatal downregulation of the α1G‐subunit of LVA Ca2+ channels in CR cells. Experiments performed in the current‐clamp mode revealed that mibefradil delayed an action potential generation in response to a suprathreshold depolarizing current at P1, but not at P8–9. We suggest that LVA Ca2+ channels might influence CR cell excitability during the first postnatal week and thereby contribute to the shaping of synaptic connectivity in the neocortical layer I.
Primary afferent nociceptor mechanisms mediating NGF‐induced mechanical hyperalgesia
Authors: Malik‐Hall Misbah , Dina Olayinka A. , Levine Jon D.
Published: July 2005

The underlying mechanism for nerve growth factor (NGF) evoked pain and long‐lasting mechanical hyperalgesia remains poorly understood. Using intrathecal antisense against the NGF receptor, receptor tyrosine kinase (TrkA), we found NGF to act at the primary afferent nociceptor directly in the Sprague–Dawley rat. Inhibitors of the three major pathways for TrkA receptor signalling, extracellular signal‐related kinase (ERK)/mitogen‐activated protein kinase kinase (MEK) (ERK/MEK), phosphatidylinositol 3‐kinase (PI3K), and phospholipase Cγ (PLCγ) all attenuate NGF‐induced hyperalgesia. Although inhibitors of kinases downstream of PI3K and PLCγ[glycogen synthetase kinase 3 (GSK3), calmodulin‐dependent protein kinase II (CAMII‐K) or protein kinase C (PKC)] do not reduce mechanical hyperalgesia, hyperalgesia induced by activation of PI3K was blocked by ERK/MEK inhibitors, suggesting cross‐talk from the PI3K to the ERK/MEK signalling pathway. As integrins have been shown to modulate epinephrine and prostaglandin E2‐induced hyperalgesia, we also evaluated a role for integrins in NGF‐induced mechanical hyperalgesia using β1‐integrin‐specific antisense or antibodies.
Prolongation and enhancement of γ‐aminobutyric acidA receptor mediated excitation by chronic treatment with estradiol in developing rat hippocampal neurons
Authors: Nuñez Joseph L. , Bambrick Linda L. , Krueger Bruce K. , McCarthy Margaret M.
Published: July 2005

GABAA receptor activation during brain development is a critical source of excitation. This is due to the positive equilibrium potential for chloride relative to resting membrane potential, resulting in membrane depolarization sufficient to open voltage sensitive calcium channels. The gonadal steroid estradiol has pronounced trophic effects on the developing hippocampus, promoting cell survival and synaptogenesis. In the current study, we investigated the effect of estradiol on GABAA receptor‐mediated calcium transients in cultured neonatal hippocampal neurons, from Sprague–Dawley rats, using the calcium sensitive dye, Fura‐2‐AM. Treatment of hippocampal neurons with physiological levels of estradiol significantly increased the peak amplitude of calcium transients, increased the number of cells responding to the GABAA agonist muscimol with membrane depolarization, and delayed the rate of clearance of free intracellular calcium. These effects were significantly attenuated by pretreatment with the oestrogen receptor antagonist ICI‐182,780. This suggests that estradiol, via its action on the oestrogen receptor, prolongs the developmental duration of depolarizing GABA. Estradiol likely maintains GABA‐mediated excitation by promoting increased protein levels of the active/phosphorylated form of the chloride cotransporter Na+K+2CL– and L‐type voltage sensitive calcium channels containing the α1C subunit. We propose that a component of the trophic effects of estradiol on hippocampal development results from enhanced calcium influx subsequent to GABAA receptor activation.
Distribution and regulation of L‐type calcium channels in deep dorsal horn neurons after sciatic nerve injury in rats
Authors: Dobremez E. , Bouali‐Benazzouz R. , Fossat P. , Monteils L. , Dulluc J. , Nagy F. , Landry M.
Published: July 2005

Deep dorsal horn neurons are involved in the processing of nociceptive information in the spinal cord. Previous studies revealed a role of the intrinsic bioelectrical properties (plateau potentials) of deep dorsal horn neuron in neuronal hyperexcitability, indicating their function in pain sensitization. These properties were considered to rely on L‐type calcium currents. Two different isotypes of L‐type calcium channel alpha 1 subunit have been cloned (CaV1.2 and CaV1.3). Both are known to be expressed in the spinal cord. However, no data were available on their subcellular localization. Moreover, possible changes in CaV1.2 and CaV1.3 expression had never been investigated in nerve injury models. Our study provides evidence for a differential expression of CaV1.2 and CaV1.3 subunits in the somato‐dendritic compartment of deep dorsal horn neurons. CaV1.2 immunoreactivity is restricted to the soma and proximal dendrites whereas CaV1.3 immunoreactivity is found in the whole somato‐dendritic compartment, up to distal dendritic segments. Moreover, these specific immunoreactive patterns are also found in electrophysiologically identified deep dorsal horn neurons expressing plateau potentials. After nerve injury, namely total axotomy or partial nerve ligation, CaV1.2 and CaV1.3 expression undergo differential changes, showing up‐ and down‐regulation, respectively, both at the protein and at the mRNA levels. Taken together, our data support the role of L‐type calcium channels in the control of intrinsic biolectrical regenerative properties. Furthermore, CaV1.2 and CaV1.3 subunits may have distinct and specific roles in sensory processing in the dorsal horn of the spinal cord, the former being most likely involved in long‐term changes after nerve injury.
Tetrodotoxin resets the clock
Authors: Noguchi Takako , Watanabe Kazuto
Published: July 2005

In mammals, circadian rhythms are driven by a pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus. We measured the rhythm of arginine vasopressin release in rat organotypic SCN slices following application of tetrodotoxin (TTX) or N‐methyl‐d‐aspartate (NMDA) at various times throughout the circadian cycle. TTX resets the clock in a manner similar to dark pulses. A 4‐h application of TTX starting in mid subjective day, at around circadian time (CT) 7.0, induced phase advances, while TTX treatment started in early subjective morning, at about CT 2.0, induced phase delays. On the other hand, NMDA resets the clock in a manner similar to a light pulse; that is, NMDA treatment in the early evening induced phase delays while treatment in the late night induced phase advances. The data indicate that deprivation of neuronal firing changes the circadian rhythm.
Food Stamp Benefits and Child Poverty
Authors: Jolliffe Dean , Gundersen Craig , Tiehen Laura , Winicki Joshua
Published: July 2005

In 2000, 8.8 million children lived in households participating in the Food Stamp Program, making this assistance program a crucial component of the social safety net. Despite its importance, little research has examined food stamps' effect on children's overall well‐being. Using the Current Population Survey from 1989 to 2001, we consider the impact of food stamps on three measures of poverty—the headcount, the poverty gap, and the squared poverty gap. We find that in comparison to the headcount measure, food stamp benefits lead to large reductions in the poverty gap and squared poverty gap measures.
Forecast Encompassing as the Necessary Condition to Reject Futures Market Efficiency: Fluid Milk Futures
Authors: Sanders Dwight R. , Manfredo Mark R.
Published: July 2005

The traditional necessary condition for futures market inefficiency is the existence of alternative forecasting methods that produce mean squared forecast errors smaller than the futures market. Here, a more exacting requirement for futures market efficiency is proposed—forecast encompassing. Using the procedure of Harvey and Newbold, multiple forecast encompassing is tested using Chicago Mercantile Exchange fluid milk futures. Time series models and USDA experts provide competing forecasts. Results suggest milk futures do not encompass the information contained in the USDA forecasts at a two‐quarter horizon. While the competing forecasts generate positive revenues, it is unlikely that returns exceed transaction costs in this relatively new market.
Genetically Modified Crops and Product Differentiation: Trade and Welfare Effects in the Soybean Complex
Authors: Sobolevsky Andrei , Moschini GianCarlo , Lapan Harvey
Published: July 2005

A partial equilibrium four‐region world trade model for the soybean complex is developed in which Roundup Ready (RR) products are weakly inferior substitutes to conventional ones, RR seeds are priced at a premium, and costly segregation is necessary to separate conventional and biotech products. Solution of the calibrated model illustrates how incomplete adoption of RR technology arises in equilibrium. The United States, Argentina, Brazil, and the Rest of the World (ROW) all gain from the introduction of RR soybeans, although some groups may lose. The impacts of RR production or import bans by the ROW or Brazil are analyzed. U.S. price support helps U.S. farmers, despite hurting the United States and has the potential to improve world efficiency.
The Significance and Insignificance of Demand Analysis in Evaluating Promotion Programs
Authors: Davis George C.
Published: July 2005

The estimated effects of promotion on demand are often small and insignificant. Yet, the estimated effects of promotion on industry profit are often positive and large. This puzzle is explained by demonstrating that (in)significance of promotion in a demand equation does not imply, and is not implied by, (in)significance of promotion in an industry profit equation. A Monte Carlo example is provided. The econometric modeling implications are discussed. The short‐run marginal effect of a dollar of generic beef promotion on slaughter cattle industry profit is estimated to be about $9.84 with a standard error of 3.77 for 1997.
Coupon Redemption and Its Effect on Household Cheese Purchases
Authors: Dong Diansheng , Kaiser Harry M.
Published: July 2005

By endogenizing unit value and coupon redemption, we estimate U.S. household cheese purchase, quality choice, and coupon redemption equations simultaneously. Zero purchases and missing values on coupons and unit values are taken into account in the model to correct for selectivity bias. Correlations among the three equations are found to be significant. Empirical findings show that high‐quality choice significantly decreases cheese purchases, while cheese coupon usage significantly increases purchases. We find that higher income households select higher quality cheese, while larger households choose lower quality cheese. For coupon redemption, we find that African‐American and Hispanic households redeem less, while Asian households have no significant difference compared to Caucasian households.
Somatostatin down‐regulates the expression and release of endozepines from cultured rat astrocytes via distinct receptor subtypes
Authors: Masmoudi Olfa , Gandolfo Pierrick , Tokay Tursonjan , Leprince Jérôme , Ravni Aurélia , Vaudry Hubert , Tonon Marie‐Christine
Published: July 2005

Endozepines, a family of regulatory peptides related to diazepam‐binding inhibitor (DBI), are synthesized and released by astroglial cells. Because rat astrocytes express various subtypes of somatostatin receptors (sst), we have investigated the effect of somatostatin on DBI mRNA level and endozepine secretion in rat astrocytes in secondary culture. Somatostatin reduced in a concentration‐dependent manner the level of DBI mRNA in cultured astrocytes. This inhibitory effect was mimicked by the selective sst4 receptor agonist L803‐087 but not by the selective sst1, sst2 and sst3 receptor agonists L779‐591, L779‐976 and L797‐778, respectively. Somatostatin was unable to further reduce DBI mRNA level in the presence of the MEK inhibitor U0126. Somatostatin and the sst1, sst2 and sst4 receptor agonists induced a concentration‐dependent inhibition of endozepine release. Somatostatin and the sst1, sst2 and sst4 receptor agonists also inhibited cAMP formation dose‐dependently. In addition, somatostatin reduced forskolin‐induced endozepine release. H89 mimicked the inhibitory effect of somatostatin on endozepine secretion. In contrast the PLC inhibitor U73122, the PKC activator PMA and the PKC inhibitor calphostin C had no effect on somatostatin‐induced inhibition of endozepine release. The present data demonstrate that somatostatin reduces DBI mRNA level mainly through activation of sst4 receptors negatively coupled to the MAPK pathway, and inhibits endozepine release through activation of sst1, sst2 and sst4 receptors negatively coupled to the adenylyl cyclase/PKA pathway.
Changes in calcineurin expression induced in the rat brain by the administration of antipsychotics
Authors: Rushlow W. J. , Seah Y. H. , Belliveau D. J. , Rajakumar N.
Published: July 2005

Calcineurin (CN) was recently identified as a susceptibility gene for schizophrenia as well as showing altered RNA expression levels in the post‐mortem brains of individuals with schizophrenia. CN knockout mice show a number of behaviours associated with schizophrenia, including deficits in sensorimotor gating, suggesting a link between CN and psychosis. Concurrently, we found, using genome screening techniques, that antipsychotics alter CN expression levels. Therefore, western blotting, in situ hybridization, immunocytochemistry and phosphatase assays were employed to determine what effect antipsychotics have on CN. The results indicate that clozapine, risperidone and haloperidol cause substantial reductions in the A subunit of CN but not CN B at both the RNA and protein levels in the striatum and prefrontal cortex. The changes could only be observed after repeated treatment with antipsychotics but not after acute administration. The alterations in CN protein levels were specific to antipsychotics and mediated by D2 dopamine receptor antagonism. However, despite reductions in CN protein levels, the phosphatase activity of CN was significantly elevated after treatment with antipsychotics. Collectively the results suggest that CN may be a common target for antipsychotics and that antipsychotic‐induced alterations in CN may represent one of the mechanisms by which antipsychotics alleviate psychosis.
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

Acetylcholinesterase (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

The 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

Synaptic 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

Huntington'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

The 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

The 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

The 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

Using 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

Although 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

In 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

We 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

The 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

Activation 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.
Human immunodeficiency virus type 1 envelope glycoprotein 120 induces cyclooxygenase‐2 expression in neuroblastoma cells through a nuclear factor‐κB and activating protein‐1 mediated mechanism
Authors: Álvarez Susana , Serramía Ma Jesús , Fresno Manuel , Muñoz‐Fernández MaÁngeles
Published: July 2005

Induction of cyclooxygenase‐2 (COX‐2) in the brain of people infected with human immunodeficiency virus type 1 (HIV‐1) has been proposed as a cause of cognitive impairment in AIDS dementia. Here, we have analyzed the molecular mechanism by which its induction takes place in neuroblastoma cells. The HIV‐1 envelope protein gp120 was able to induce COX‐2 mRNA and protein in several human neuroblastoma cell lines, which express CXCR4 and CCR5 but not CD4. Moreover, gp120 induces COX‐2 promoter transcription. Sequential deletions of the promoter show that deletion of a distal nuclear factor‐κB (NF‐κB) site abrogated gp120‐dependent transcription. More importantly, overexpression of NF‐κB inhibitory subunit, IκBα, completely abrogated gp120‐induced COX‐2 activity. However, transfection of p65/relA NF‐κB was not enough to induce COX‐2 transcription, suggesting that NF‐κB was necessary but not sufficient to control COX‐2 transcription induced by gp120. In addition to NF‐κB, activating protein‐1 (AP‐1) but not nuclear factor of activated T cells (NFAT)‐dependent transcription was induced by gp120. Transfection of a dominant negative mutant c‐Jun protein, TAM‐67, efficiently blocked the induction of COX‐2 promoter by gp120, confirming AP‐1 requirement. Moreover, gp120 rapidly activates the c‐Jun amino‐terminal kinase (JNK) and p38 mitogen‐activated protein kinase phosphorylation. The importance of NF‐κB and AP‐1 in COX‐2 promoter and protein induction was corroborated by using pharmacological NF‐κB, p38 and JNK inhibitors.
Distinct patterns of expression and regulation of GABAA receptors containing the δ subunit in cerebellar granule and hippocampal neurons
Authors: Follesa Paolo , Mostallino Maria Cristina , Biggio Francesca , Gorini Giorgio , Caria Stefania , Busonero Fabio , Murru Luca , Mura Maria Luisa , Sanna Enrico , Biggio Giovanni
Published: July 2005

Neuronal plasticity is achieved by regulation of the expression of genes for neurotransmitter receptors such as the type A receptor (GABAAR) for γ‐aminobutyric acid. We now show that two different rat neuronal populations in culture manifest distinct patterns of GABAAR plasticity in response to identical stimuli. Whereas prolonged exposure to ethanol had no effect on expression of the δ subunit of GABAARs at the mRNA or protein level in cerebellar granule neurons, it increased the abundance of δ subunit mRNA and protein in hippocampal neurons. Subsequent ethanol withdrawal transiently down‐regulated δ subunit expression in cerebellar granule neurons and gradually normalized that in hippocampal neurons. These effects of ethanol exposure and withdrawal were accompanied by corresponding functional changes in GABAARs. GABAARs containing the δ subunit were also distributed differentially in the cerebellar and hippocampal neurons. These findings reveal complex and distinct mechanisms of regulation of the expression of GABAARs that contain the δ subunit in different neuronal types.
The intracellular domain of p75NTR as a determinant of cellular reducing potential and response to oxidant stress
Authors: Tyurina Yulia Y. , Nylander Karen D. , Mirnics Zeljka Korade , Portugal Carmel , Yan Chaohua , Zaccaro Clara , Saragovi H. Uri , Kagan Valerian E. , Schor Nina F.
Published: July 2005

The low‐affinity neurotrophin receptor, p75NTR, has been found to be pro‐ or anti‐apoptotic depending upon the cell in which it is expressed. Reactive oxygen species play a major role in apoptosis induction and enactment. Using two polyclonal PC12 populations that, respectively, do or do not express p75NTR, this paper demonstrates that p75NTR expression confers resistance to oxidant stress upon PC12 cells maintained in serum‐containing medium. The effect of p75NTR on cell survival is mimicked in p75‐negative cells by expression of constructs that produce the p75NTR intracellular domain (ICD) or p75NTR with the extracellular domain deleted (ΔECD), suggesting that binding of an extracellular ligand to p75NTR is not required. Our studies further document that the differential sensitivity to oxidant stress is serum‐dependent and associated with differential oxidation of glutathione between p75‐positive and p75‐negative cells. These results suggest that the role of p75NTR in determining the consequences and treatment of age‐related disorders and conditions in which reactive oxygen species are involved may require neither the extracellular receptor domain nor, by inference, the cognate extracellular ligands of this neurotrophin receptor.
Correlations between physiology and lifespan – two widely ignored problems with comparative studies
Authors: Speakman John R.
Published: July 2005

Comparative differences between species provide a powerful source of information that may inform our understanding of the aging process. However, two problems regularly attend such analyses. The co‐variation of traits with body mass is frequently ignored, along with the lack of independence of the data due to a shared phylogenetic history. These problems undermine the use of simple correlations between various factors and maximum lifespan potential (MLSP) across different species as evidence that the factors in question have causal effects on aging. Both of these problems have been widely addressed by comparative biologists working in fields other than aging research, and statistical solutions to these issues are available. Using these statistical approaches, of making analyses of residual traits with the effects of body mass removed, and deriving phylogenetically independent contrasts, will allow analyses of the relationships between physiology and maximum lifespan potential to proceed unhindered by these difficulties, potentially leading to many useful insights into the aging process.
Empirical Bayes and Adjusted Estimates Approach to Estimating the Relation of Mortality to Exposure of PM10
Authors: Le Tertre Alain , Schwartz Joel , Touloumi Giota
Published: July 2005

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Retraction. Risk Analysis 25: 6, 1683

In the framework of the APHEIS program (Air Pollution and Health: A European Information System), a health impact assessment of air pollution in 26 European cities was performed for particles of an aerodynamic diameter less than or equal to 10 μm (PM10). For short‐term effects, it was based on overall estimates from the APHEA‐2 project (Air Pollution and Health: A European Approach). These city‐specific risk assessments require city‐specific concentration‐response functions, raising the question of which concentration‐response is most appropriate. Estimates from city‐specific models are more specific, but have greater uncertainty than those provided from multicity analyses. We compared several estimates derived from the city‐specific analyses in cities that were part of the APHEA‐2 project, as well as in a city that was not included in APHEA‐2 but was part of the APHEIS project. These estimates were: the estimates from a local regression model, the adjusted estimates based on two significant effect modifiers identified through meta‐regression models, and the city‐specific empirical Bayes (shrunken) estimates and their underlying distribution. The shrunken and adjusted estimates were used to improve the estimation of city‐specific concentration‐response function. From these different estimates, attributable numbers of deaths per year were calculated. The advantages and limits of the different approaches are discussed through real data and in a simulation study.
Priority Setting for the Distribution of Localized Hazard Protection
Authors: Lambert James H. , Turley Thomas
Published: July 2005

We address the problem of distributing safety‐enhancing devices across a region, where each identical device provides for only local protection of the population. The devices protect nonidentical sectors of the population. The sectors of population are exposed to nonidentical intensities of hazard. A method for the screening and prioritizing of needs for the protective devices is described. An approach of risk‐benefit‐cost analysis under uncertainty is recommended as follows. Measures of hazard intensity and population exposure are identified. Exogenous parameters that influence assessments of risks, benefits, and costs are identified. Uncertainties of the exogenous parameters are propagated by interval analysis. Several tiers of the plausibility of need for protection are identified. The tiers are useful in setting priorities for the distribution of the safety devices. The method is demonstrated in an engineering application to roadway lighting, but has implications for disaster preparedness, anti‐terrorism, transportation safety, and other arenas of public safety.