bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impairment of the ubiquitin‐proteasome system causes dopaminergic cell death and inclusion body formation in ventral mesencephalic cultures
Authors: McNaught Kevin St P. , Mytilineou Catherine , JnoBaptiste Ruth , Yabut Jocelyn , Shashidharan P. , Jenner Peter , Olanow C. Warren 
Published: May 2003

AbstractMutations in α‐synuclein, parkin and ubiquitin C‐terminal hydrolase L1, and defects in 26/20S proteasomes, cause or are associated with the development of familial and sporadic Parkinson's disease (PD). This suggests that failure of the ubiquitin–proteasome system (UPS) to degrade abnormal proteins may underlie nigral degeneration and Lewy body formation that occur in PD. To explore this concept, we studied the effects of lactacystin‐mediated inhibition of 26/20S proteasomal function and ubiquitin aldehyde (UbA)‐induced impairment of ubiquitin C‐terminal hydrolase (UCH) activity in fetal rat ventral mesencephalic cultures. We demonstrate that both lactacystin and UbA caused concentration‐dependent and preferential degeneration of dopaminergic neurons. Inhibition of 26/20S proteasomal function was accompanied by the accumulation of α‐synuclein and ubiquitin, and the formation of inclusions that were immunoreactive for these proteins, in the cytoplasm of VM neurons. Inhibition of UCH was associated with a loss of ubiquitin immunoreactivity in the cytoplasm of VM neurons, but there was a marked and localized increase in α‐synuclein staining which may represent the formation of inclusions bodies in VM neurons. These findings provide direct evidence that impaired protein clearance can induce dopaminergic cell death and the formation of proteinaceous inclusion bodies in VM neurons. This study supports the concept that defects in the UPS may underlie nigral pathology in familial and sporadic forms of PD.
Neurotensin regulates DARPP‐32 Thr34 phosphorylation in neostriatal neurons by activation of dopamine D1‐type receptors
Authors: Matsuyama Seiichiro , Higashi Hideho , Maeda Hisao , Greengard Paul , Nishi Akinori 
Published: May 2003

AbstractNeurotensin modulates dopaminergic transmission in the nigrostriatal system. DARPP‐32, a dopamine‐ and cAMP‐regulated phosphoprotein of Mr 32 kDa, is phosphorylated on Thr34 by cAMP‐dependent protein kinase, resulting in its conversion into a potent inhibitor of protein phosphatase‐1 (PP 1). Here, we examined the effect of neurotensin on DARPP‐32 Thr34 phosphorylation using mouse neostriatal slices. Neurotensin stimulated DARPP‐32 Thr34 phosphorylation by 4–7‐fold with a K0.5 of ∼50 nm. The effect of neurotensin was antagonized by a combined neurotensin receptor type‐1 (NTR1)/type‐2 (NTR2) antagonist, SR142948. It was not antagonized by a NTR1 antagonist, SR48692 or by a NTR2 antagonist, levocabastine; neither was it antagonized by the two combined. Pretreatment with TTX or cobalt abolished the effect of neurotensin. The effect of neurotensin was antagonized by a dopamine D1 antagonist, SCH23390, and by ionotropic glutamate receptor antagonists, MK801 and CNQX. These results indicate that neurotensin stimulates the release of dopamine from nigrostriatal presynaptic terminals in an NMDA receptor‐ and AMPA receptor‐dependent manner, leading to the increase in DARPP‐32 Thr34 phosphorylation. Neurotensin stimulated the phosphorylation of Ser845 of the AMPA receptor GluR1 subunit in wild‐type mice but not in DARPP‐32 knockout mice. Thus, neurotensin, by stimulating the release of dopamine, activates the dopamine D1‐receptor/cAMP/PKA/DARPP‐32/PP 1 cascade.
Cdk5 phosphorylates p53 and regulates its activity
Authors: Zhang Jianwen , Krishnamurthy Pavan K. , Johnson Gail V. W. 
Published: May 2003

AbstractCyclin dependent kinase 5 (Cdk5) is a proline‐direct protein kinase that is most active in the CNS, and has been implicated as a contributing factor in certain neurodegenerative diseases. Further, there is evidence to suggest that Cdk5 may facilitate the progression of apoptosis. However, the mechanisms involved have not been elucidated. The tumor suppressor protein p53, a transcription factor that is regulated by phosphorylation, increases the expression of genes that control growth arrest or cell death. To understand how Cdk5 could facilitate apoptosis, the effects of Cdk5 on p53 activity were examined. In the present study it is shown that in apoptotic PC12 cells the levels of p53 and Cdk5 increase concomitantly. Further, Cdk5/p25 effectively phosphorylates recombinant p53 in vitro. Transient transfection of Cdk5/p25 into cells results in an increase in p53 levels, as well as the expression of the p53‐responsive genes p21 and Bax. Furthermore, evidence is provided that increased Cdk5 activity increases p53 transcriptional activity significantly, suggesting that p53 is modulated in situ by Cdk5. This is the first demonstration that p53 is a substrate of Cdk5, and that Cdk5 can modulate p53 levels and activity.
Effect of GP120 on glutathione peroxidase activity in cortical cultures and the interaction with steroid hormones
Authors: Brooke Sheila M. , McLaughlin John R. , Cortopassi Karen M. , Sapolsky Robert M. 
Published: May 2003

AbstractGP120 (the protein component of the HIV viral coat) is neurotoxic and may contribute to the cell loss associated with AIDS‐related dementia. Previously, it has been shown in rat cortical mixed cultures that gp120 increased the accumulation of hydrogen peroxide and superoxide, two reactive oxygen species (ROS). We now demonstrate that gp120 increased activity of the key antioxidant glutathione peroxidase (GSPx), presumably as a defensive mechanism against the increased ROS load. Both estrogen and glucocorticoids (GCs), the adrenal steroid released during stress, blunted this gp120 effect on GSPx activity. The similar effects of estrogen and of GCs are superficially surprising, given prior demonstrations that GCs exacerbated and estrogens protected against gp120 neurotoxicity. We find that these similar effects of estrogen and GCs on GSPx regulation arose, in fact, from very different routes, which are commensurate with these prior reports. Specifically, estrogen has demonstrated antioxidant properties that may prevent the ROS increase (therefore acting as a neuroprotective agent) and rendered unnecessary the compensatory GSPx increased activity. To verify this we have added H2O2 to estrogen + gp120‐treated cells, and GSPx activity was increased. However, with addition of H2O2 to GCs + gp120‐treated cells there was no increase in activity. GCs appeared to decrease enzyme production and or activity and therefore under insult conditions ROS levels rose in the cell resulting in increased neurotoxicity. Overexpression of GSPx enzyme via herpes vector system reversed the GCs‐induced loss of enzyme and eliminated the GCs exacerbation of gp120 neurotoxicity.
Functional significance of a highly conserved glutamate residue of the human noradrenaline transporter
Authors: Sucic Sonja , Paczkowski Filip A. , Runkel Fabian , Bönisch Heinz , Bryan‐Lluka Lesley J. 
Published: May 2003

AbstractThe aim of the study was to investigate the role of glutamate residue 113 in transmembrane domain 2 of the human noradrenaline transporter in determining cell surface expression and functional activity. This residue is absolutely conserved in all members of the Na+‐ and Cl–‐dependent transporter family. Mutations to alanine (hE113A), aspartate (hE113D) and glutamine (hE113Q) were achieved by site‐directed mutagenesis and the mutants were expressed in transfected COS‐7 or HEK‐293 cells. Cell surface expression of hE113A and hE113D, but not hE113Q, was markedly reduced compared with wild type, and functional noradrenaline uptake was detected only for the hE113Q mutant. The pharmacological properties of the hE113Q mutant showed very little change compared with wild type, except for a decrease in Vmax values for noradrenaline and dopamine uptake of 2–3‐fold. However, the hE113D mutant showed very marked changes in its properties, compared with wild type, with 82–260‐fold decreases in the affinities of the substrates, noradrenaline, dopamine and MPP+, and increased Na+ affinity for stimulation of nisoxetine binding. The results of the study show that the size and not the charge of the 113 glutamate residue of the noradrenaline transporter seems to be the most critical factor for maintenance of transporter function and surface expression.
Oxygen and glucose deprivation induces mitochondrial dysfunction and oxidative stress in neurones but not in astrocytes in primary culture
Authors: Almeida Angeles , Delgado‐Esteban María , Bolaños Juan P. , Medina José M. 
Published: May 2003

AbstractIn order to investigate the potential neuroprotective role played by glucose metabolism during brain oxygen deprivation, the susceptibility of cultured neurones and astrocytes to 1 h of oxygen deprivation (hypoxia) or oxygen and glucose deprivation (OGD) was examined. OGD, but not hypoxia, promotes dihydrorhodamine 123 and glutathione oxidation in neurones but not in astrocytes reflecting free radical generation in the former cells. A specific loss of mitochondrial complex‐I activity, mitochondrial membrane potential collapse, ATP depletion and necrosis occurred in the OGD neurones, but not in the OGD astrocytes. Furthermore, superoxide anion but not nitric oxide formation was responsible for these effects. OGD decreased neuronal but not astrocytic NADPH concentrations; this was not observed in hypoxia and was independent of superoxide or nitric oxide formation. These results suggest that glucose metabolism would supply NADPH, through the pentose–phosphate pathway, aimed at preventing oxidative stress, mitochondrial damage and neurotoxicity during oxygen deprivation to neural cells.
Hypotension‐induced dopamine release in prefrontal cortex is mediated by local glutamatergic projections at the level of nerve terminals
Authors: Kawahara Yukie , Kawahara Hiroshi , Westerink Ben H. C. 
Published: May 2003

AbstractIn a previous study it was shown that nitroprusside‐induced hypotension strongly enhances the release of dopamine (DA) in the prefrontal cortex (PFC). In the present study we have further investigated the mechanism involved in this effect. Glutamate receptor antagonists were infused into the ventral tegmental area (VTA) or PFC, while DA release was measured in the ipsilateral PFC and hypotension was applied by intravenous infusion of nitroprusside. Infusion into the VTA of neither a NMDA receptor antagonist (CPP), nor a non‐NMDA antagonist (DNQX) affected the hypotension‐induced increase of DA in the PFC. Intracortical infusion of CPP also failed to affect significantly, whereas local infusion of DNQX inhibited the hypotension‐enhanced release of DA dose‐dependently. The stimulation of DA release was relatively small in the VTA as well as in the nucleus accumbens when compared with the response in the PFC. It is concluded that DA released from mesocortical neurons can be modulated by two different mechanisms: first, by glutamate afferents to the VTA that modify the nerve‐impulse flow of DA neurons; and, second, by glutamate afferents to the PFC that act at the level of the DA nerve terminals. The behaviour context (arousal or stress versus hypotension) determines which type of interaction predominates.
Trophic agents that prevent neuronal apoptosis activate calpain and down‐regulate CaMKIV
Authors: Tremper‐Wells Barbara , Mathur Anjili , Beaman‐Hall Carol M. , Vallano Mary Lou 
Published: May 2003

AbstractCaMKIV is enriched in neuronal nuclei and mediates Ca2+‐dependent survival via transcription factor phosphorylation. Cultured cerebellar granule neurons were used to examine whether distinct modes of Ca2+ signaling differentially modulate CaMKIV expression and function. For long‐term survival, these neurons require 25 mm KCl or NMDA, which stimulates Ca2+ entry through voltage‐sensitive Ca2+ channels or NMDA receptors (NRs). Lower levels of Ca2+ entry through NRs support survival of a neuronal subpopulation grown in 5 mm KCl media. Several effects were demonstrated: (i) sustained exposure to 25 mm KCl or 140 µm NMDA produced CaMKIV down‐regulation, compared to 5 mm KCl cultures; (ii) CaMKIV down‐regulation was attenuated by nifedipine, APV and CaM kinase inhibitors, indicating that it is Ca2+ dependent and reversible; (iii) down‐regulation was both selective for nuclear substrates and calpain‐mediated; (iv) proteolysis was exacerbated by leptomycin B, a nuclear export inhibitor. Although CaMKIV proteolysis by trophic agents seems paradoxical in light of evidence supporting its critical role in survival, the CaMKIV/CREB signal transduction pathway was preserved, as assessed by CaM kinase‐mediated CREB phosphorylation, and the ability of CaM kinase inhibitors to interfere with KCl‐mediated survival. We hypothesize that limited calpain‐mediated proteolysis of CaMKIV is a negative feedback response to the sustained activation of a Ca2+ and CaMKIV signaling pathway by these agents.
Peptidylarginine deiminase: a candidate factor in demyelinating disease
Authors: Moscarello M. A. , Pritzker L. , Mastronardi F. G. , Wood D. D. 
Published: May 2003

AbstractIn earlier studies we demonstrated that an increase in the relative amounts of citrullinated myelin basic protein (MBP) was found in multiple sclerosis (Moscarello et al. 1994). To determine the temporal relationship between the citrullinated MBP and peptidylarginine deiminase (PAD), the enzyme responsible for deiminating arginyl residues in proteins, we studied enzyme activity, enzyme protein, PAD mRNA in a spontaneously demyelinating transgenic mouse model and we correlated the amount of PAD with citrullinated MBP. Both PAD protein as measured in an immunoslot blot method and PAD RNA were elevated. In fractionation studies we showed that the increase in PAD enzyme was due to an increase in the PAD found in membrane fractions and not the soluble PAD (PADII). From our data we concluded that up‐regulation of myelin‐associated PAD was responsible for the increase in citrullinated MBP in our transgenic mice prior to onset of clinical or pathological signs of demyelination. We postulate that a similar mechanism may be responsible for the increase in citrullinated MBP in multiple sclerosis.
Neuroprotection by scatter factor/hepatocyte growth factor and FGF‐1 in cerebellar granule neurons is phosphatidylinositol 3‐kinase/Akt‐dependent and MAPK/CREB‐independent
Authors: Hossain Mir Ahamed , Russell Juliet C. , Gomes Raquel , Laterra John 
Published: May 2003

AbstractNeuroprotective actions of scatter factor/hepatocyte growth factor (SF/HGF) have not been described. We examined the effects of SF/HGF in comparison to acidic fibroblast growth factor‐1 (FGF‐1) on N‐methyl‐d‐aspartate (NMDA) and quinolinic acid (QUIN)‐induced excitotoxicity in primary cerebellar granule neurons. Exposure to NMDA or QUIN for 24 h resulted in concentration‐dependent cell death (p < 0.001) that was completely attenuated (p < 0.001) by pre‐treatment of cells with SF/HGF (50 ng/mL) or FGF‐1 (40 ng/mL). SF/HGF and FGF‐1 activated both Akt and MAP‐kinase > threefold (p < 0.001). Neither SF/HGF nor FGF‐1 activated cyclic AMP‐response element binding protein (CREB), a downstream target of MAP‐kinase, whereas brain‐derived neurotrophic factor (BDNF) activated both MAP‐kinase and CREB in granule neurons. Neuroprotection against NMDA or QUIN by SF/HGF and FGF‐1 was negated by the addition of LY294002 (10 µm) or wortmannin (100 nm), two distinct inhibitors of phosphatidylinositol 3‐kinase (PI3‐K), but not by the MAP‐kinase kinase (MEK) inhibitor PD98059 (33 µm). Likewise, expression of a dominant‐negative mutant of Akt (Akt‐kd) completely prevented the neuroprotective actions of SF/HGF and FGF‐1. Overexpression of a constitutively activated Akt (Akt‐myr) or wild‐type Akt (wtAkt) attenuated excitotoxic cell death. These data show that both SF/HGF and FGF‐1 protect cerebellar granule neurons against excitotoxicity with similar potency in a PI3‐K/Akt‐dependent and MAP‐kinase/CREB‐independent manner.
Instrumental role of Na+ in NMDA excitotoxicity in glucose‐deprived and depolarized cerebellar granule cells
Authors: Czyż Aneta , Baranauskas Gytis , Kiedrowski Lech 
Published: May 2003

AbstractIn glucose‐deprived cerebellar granule cells, substitution of extracellular Na+ with Li+ or Cs+ prevented N‐methyl‐d‐aspartate (NMDA)‐induced excitotoxicity. NMDA stimulated 45Ca2+ accumulation and ATP depletion in a Na‐dependent manner, and caused neuronal death, even if applied while Na,K‐ATPase was inhibited by 1 mm ouabain. The cells treated with NMDA in the presence of ouabain accumulated sizable 45Ca2+ load but most of them failed to elevate cytosolic [Ca2+] upon mitochondrial depolarization. Na/Ca exchange inhibitor, KB‐R7943, inhibited Na‐dependent and NMDA‐induced 45Ca2+ accumulation but only if Na,K‐ATPase activity was compromised by ouabain. In cells energized by glucose and exposed to NMDA without ouabain, KB‐R7943 reduced NMDA‐elicited ionic currents by 19% but failed to inhibit 45Ca2+ accumulation. It appears that a large part of NMDA‐induced Ca2+ influx in depolarized and glucose‐deprived cells is mediated by reverse Na/Ca exchange. A high level of reverse Na/Ca exchange operation is maintained by a sustained Na+ influx via NMDA channels and depolarization of the plasma membrane. In cells energized by glucose, however, most Ca2+ enters directly via NMDA channels because Na,K‐ATPase regenerating Na+ and K+ concentration gradients prevents Na/Ca exchange reversal. Since under these conditions Na/Ca exchange extrudes Ca2+, its inhibition destabilizes Ca2+ homeostasis.
Akt pathway mediates a cGMP‐dependent survival role of nitric oxide in cerebellar granule neurones
Authors: Ciani Elisabetta , Virgili Marco , Contestabile Antonio 
Published: May 2003

AbstractApoptotic death results from disrupting the balance between anti‐apoptotic and pro‐apoptotic cellular signals. The inter‐ and intracellular messenger nitric oxide is known to mediate either death or survival of neurones. In the present work, cerebellar granule cells were used as a model to assess the survival role of nitric oxide and to find novel signal transduction pathways related to this role. It is reported that sustained inhibition of nitric oxide production induces apoptosis in differentiated cerebellar granule neurones and that compounds that slowly release nitric oxide significantly revert this effect. Neuronal death was also reverted by a caspase‐3‐like inhibitor and by a cyclic GMP analogue, thus suggesting that nitric oxide‐induced activation of guanylate cyclase is essential for the survival of these neurones. We also report that the Akt/GSK‐3 kinase system is a transduction pathway related to the survival action of nitric oxide, as apoptosis caused by nitric oxide deprivation is accompanied by down‐regulation of this, but not of other, kinase systems. Conversely, treatments able to rescue neurones from apoptosis also counteracted this down‐regulation. Furthermore, in transfection experiments, overexpression of the Akt gene significantly decreased nitric oxide deprivation‐related apoptosis. These results are the first evidence for a mechanism where endogenous nitric oxide promotes neuronal survival via Akt/GSK‐3 pathway.
5‐Iodo‐A‐85380 binds to α‐conotoxin MII‐sensitive nicotinic acetylcholine receptors (nAChRs) as well as α4β2* subtypes
Authors: Kulak Jennifer M. , Sum Jocelyn , Musachio John L. , McIntosh J. Michael , Quik Maryka 
Published: May 2003

AbstractRecent work suggests that 5‐iodo‐A‐85380, a radioiodinated analog of the 3‐pyridyl ether A‐85380, represents a promising imaging agent for non‐invasive, in vivo studies of α4β2* nicotinic acetylcholine receptors (nAChRs; *denotes receptors containing the indicated subunits), because of its low non‐specific binding, low in vivo toxicity and high selectivity for α4β2* nAChRs. As an approach to elucidate nAChR subtypes expressed in striatum, we carried out competitive autoradiography in monkey and rat brain using 5‐[125I]iodo‐A‐85380 ([125I]A‐85380) and [125I]α‐conotoxin MII, a ligand that binds with high affinity to α6* and α3* nAChRs, but not to α4β2* nAChRs. Although A‐85380 is reported to be selective for α4β2* nAChRs, we observed that A‐85380 completely inhibited [125I]α‐conotoxin MII binding in rat striatum and that A‐85380 blocked > 90% of [125I]α‐conotoxin MII sites in monkey caudate and putamen. These results suggest that A‐85380 binds to non‐α4β2* nAChRs, including putative α6* nAChRs. Experiments to determine the percentage of [125I]A‐85380 sites that contain α‐conotoxin MII‐sensitive (α6β2*) nAChRs indicate that they represent about 10% of [125I]A‐85380 sites in rodent striatum and about 30% of sites in monkey caudate and putamen. These data are important for identifying alterations in nicotinic receptor subtypes in Parkinson's disease and other basal ganglia disorders both in in vitro and in in vivo imaging studies.
Plaque‐associated disruption of CSF and plasma amyloid‐β (Aβ) equilibrium in a mouse model of Alzheimer's disease
Authors: DeMattos Ronald B. , Bales Kelly R. , Parsadanian Maia , O'Dell Mark A. , Foss Eric M. , Paul Steven M. , Holtzman David M. 
Published: May 2003

AbstractTo better understand amyloid‐β (Aβ) metabolism in vivo, we assessed the concentration of Aβ in the CSF and plasma of APPV717F (PDAPP) transgenic mice, a model that develops age‐dependent Alzheimer's disease (AD)‐like pathology. In 3‐month‐old mice, prior to the development of Aβ deposition in the brain, there was a highly significant correlation between Aβ levels in CSF and plasma. In 9‐month‐old‐mice, an age at which some but not all mice have developed Aβ deposition, there was also a significant correlation between CSF and plasma Aβ; however, the correlation was not as strong as that present in young mice. In further exploring CSF and plasma Aβ levels in 9‐month‐old mice, levels of CSF Aβ were found to correlate highly with Aβ burden. Analysis of the CSF : plasma Aβ ratio revealed a selective two‐fold increase in plaque versus non‐plaque bearing mice, strongly suggesting a plaque‐mediated sequestration of soluble Aβ in brain. Interestingly, in 9‐month‐old mice, a significant correlation between CNS and plasma Aβ was limited to mice lacking Aβ deposition. These findings suggest that there is a dynamic equilibrium between CNS and plasma Aβ, and that plaques create a new equilibrium because soluble CNS Aβ not only enters the plasma but also deposits onto amyloid plaques in the CNS.
Exploring the perspectives of men who self‐harm
Authors: Taylor Ben 
Published: May 2003

AbstractSelf‐harm has become one of the great taboos of our time. In men it is even less acknowledged, accepted and understood than it is in women. This report looks at the almost invisible population of men who self‐harm. Using interviews with men who self‐harm, it explores their experiences and their perspectives on the support and services to which they have access. It draws on these perspectives to identify what professionals, service providers and commissioners can learn from men who self‐harm and proposes ways forward to better meet their needs.