bluuebunny/crossref_metadata_2025_split huggingface dataset:
Activated JNK brings about accelerated apoptosis of Bcl‐2‐overexpressing C6 glioma cells on treatment with tamoxifen
Authors: Moodbidri Madhavi S. , Shirsat Neelam V. 
Published: March 2006

AbstractTamoxifen causes apoptosis of malignant glial cells at a concentration that does not kill normal astrocytes. C6 glioma cells were stably transfected with a vector expressing Bcl‐2 under the control of metallothionin promoter. Low leaky Bcl‐2 expression offered complete protection against tamoxifen‐induced apoptosis. High Bcl‐2 levels, on the other hand, accelerated the apoptosis, with Bcl‐2‐overexpressing clones dying within 48 h of tamoxifen treatment as compared to 6 days for parental C6 cells. Overexpressed Bcl‐2 is localized primarily in mitochondria and to a much lower extent in endoplasmic reticulum (ER). Only a minor fraction of the overexpressed Bcl‐2 gets phosphorylated in tamoxifen‐treated cells and the phosphorylation does not affect its binding to Bax. Tamoxifen treatment of Bcl‐2‐overexpressing clones was found to result in activation of c‐Jun N‐terminal kinase (JNK) and p38 kinase. Inhibition of JNK but not p38 kinase completely abrogated the accelerated apoptosis. Constitutively expressed endogenous c‐Jun was found to be phosphorylated, resulting in increased activator protein 1 (AP‐1) DNA‐binding activity. Expression of Fas ligand (FasL), an AP‐1 transcriptional target, increased during accelerated cell death. This presumably brought about activation of caspase 8, as inhibition of caspase 8 blocked the apoptosis. The JNK/c‐Jun/AP‐1/FasL pathway could be considered as a potential target for the therapy of gliomas.
Vlgr1 knockout mice show audiogenic seizure susceptibility
Authors: Yagi Hideshi , Takamura Yoshihiro , Yoneda Takunari , Konno Daijiro , Akagi Yoshio , Yoshida Kazunori , Sato Makoto 
Published: March 2006

AbstractSusceptibility to audiogenic seizures, which are reflex seizures provoked by loud noise, can be induced in rodents by acoustic priming (exposing animals to strong auditory stimuli at an early developmental stage). Some strains of mice and rats are susceptible to audiogenic seizures without priming and these have been used as good experimental models with which to study epilepsies. Here we identified Vlgr1d and Vlgr1e, novel alternatively‐spliced variants of Vlgr1b/MGR1, which, upon sequence analysis, were shown to be transcripts from a locus previously characterized as mass1. Vlgr1 (Vlgr1b, Vlgr1d and Vlgr1e) mRNA is expressed predominantly in the neuroepithelium of the developing mouse brain. Our protein‐tagged experiment suggested that Vlgr1d and Vlgr1e are secretory molecules, while Vlgr1b is a receptor. Knockout mice lacking exons 2–4 of Vlgr1 were susceptible to audiogenic seizures without priming, although there were no apparent histological abnormalities in their brains. Ninety‐five percent of these knockout mice exhibited wild running, a feature typical of the preconvulsive phase of audiogenic seizures triggered by loud noise (11 kHz, 105 dB), and 68% exhibited tonic convulsions at 3 weeks after birth. Our monogenic mice, which have a unique genetic background, serve as a useful tool for further studies on seizures.
Decreased calcium/calmodulin‐dependent protein kinase II and protein kinase C activities mediate impairment of hippocampal long‐term potentiation in the olfactory bulbectomized mice
Authors: Moriguchi Shigeki , Han Feng , Nakagawasai Osamu , Tadano Takeshi , Fukunaga Kohji 
Published: March 2006

AbstractOlfactory bulbectomized (OBX) mice showed significant impairment of learning and memory‐related behaviors 14 days after olfactory bulbectomy, as measured by passive avoidance and Y‐maze tasks. We here observed a large impairment of hippocampal long‐term potentiation (LTP) in the OBX mice. Concomitant with decreased acetylcholinesterase expression, protein kinase C (PKC)α autophosphorylation and NR1(Ser‐896) phosphorylation significantly decreased in the hippocampal CA1 region of OBX mice. Both PKCα and NR1(Ser‐896) phosphorylation significantly increased following LTP in the control mice, whereas increases were not observed in OBX mice. Like PKC activities, calcium/calmodulin‐dependent protein kinase II (CaMKII) autophosphorylation significantly decreased in the hippocampal CA1 region of OBX mice as compared with that of control mice. In addition, increased CaMKII autophosphorylation following LTP was not observed in OBX mice. Finally, the impairment of CaMKII autophosphorylation was closely associated with reduced pGluR1(Ser‐831) phosphorylation, without change in synapsin I (site 3) phosphorylation in the hippocampal CA1 region of OBX mice. Taken together, in OBX mice NMDA receptor hypofunction, possibly through decreased PKCα activity, underlies decreased CaMKII activity in the post‐synaptic regions, thereby impairing LTP induction in the hippocampal CA1 region. Both decreased PKC and CaMKII activities with concomitant LTP impairment account for the learning disability observed in OBX mice.
Simvastatin prevents oxygen and glucose deprivation/reoxygenation‐induced death of cortical neurons by reducing the production and toxicity of 4‐hydroxy‐2E‐nonenal
Authors: Lim Ji Hyae , Lee Jae‐Chul , Lee Yong Hyun , Choi In Young , Oh Yu‐Kyoung , Kim Hee‐Sun , Park Jin‐Sun , Kim Won‐Ki 
Published: March 2006

AbstractLipid membrane peroxidation is highly associated with neuronal death in various neurodegenerative diseases including cerebral stroke. Here, we report that simvastatin decreases oxygen and glucose deprivation (OGD)/reoxygenation‐evoked neuronal death by inhibiting the production and cytoxicity of 4‐hydroxy‐2E‐nonenal (HNE), the final product of lipid peroxidation. Simvastatin markedly decreased the OGD/reoxygenation‐evoked death of cortical neurons. OGD/reoxygenation increased the intracellular HNE level mostly in neuronal cells, not glial cells. Simvastatin decreased the intracellular level of HNE in neuronal cells exposed to OGD/reoxygenation. We further found that HNE induced the cytotoxicity in neuronal cells and synergistically increased the N‐methyl‐D‐aspartate (NMDA) receptor‐mediated excitotoxicity. Simvastatin largely blocked the NMDA neurotoxicity potentiated by HNE. However, simvastatin did not alter the NMDA‐evoked calcium influx in the absence or presence of HNE. HNE inhibited the activity of nuclear factor‐kappa B (NF‐κB), and the cytotoxicity of HNE was in good correlation with inactivation of NF‐κB. Simvastatin reversed the inhibition of NF‐κB activity induced by OGD/reoxygenation or HNE. The neuroprotection by simvastatin was significantly attenuated by various NF‐κB inhibitors, implying that simvastatin inhibits the cytotoxicity of HNE at least in part by maintaining the activity of NF‐κB. Further understanding of the neuroprotective mechanism of simvastatin may provide a therapeutic strategy for oxidative stress‐related neurodegenerative diseases.
Activation of ERK1/2 MAP kinases in Familial Amyloidotic Polyneuropathy
Authors: Monteiro F. A. , Sousa M. M. , Cardoso I. , do Amaral J. Barbas , Guimarães A. , Saraiva M. J. 
Published: March 2006

AbstractFamilial amyloidotic polyneuropathy (FAP) is a neurodegenerative disorder characterized by the extracellular deposition of transthyretin (TTR), especially in the PNS. Given the invasiveness of nerve biopsy, salivary glands (SG) from FAP patients were used previously in microarray analysis; mitogen‐activated protein (MAP) kinase phosphatase 1 (MKP‐1) was down‐regulated in FAP. Results were validated by RT‐PCR and immunohistochemistry both in SG and in nerve biopsies of different stages of disease progression. MKP‐3 was also down‐regulated in FAP SG biopsies. Given the relationship between MKPs and MAPKs, the latter were investigated. Only extracellular signal‐regulated kinases 1/2 (ERK1/2) displayed increased activation in FAP SG and nerves. ERK1/2 kinase (MEK1/2) activation was also up‐regulated in FAP nerves. In addition, an FAP transgenic mouse model revealed increased ERK1/2 activation in peripheral nerve affected with TTR deposition when compared to control animals. Cultured rat Schwannoma cell line treatment with TTR aggregates stimulated ERK1/2 activation, which was partially mediated by the receptor for advanced glycation end‐products (RAGE). Moreover, caspase‐3 activation triggered by TTR aggregates was abrogated by U0126, a MEK1/2 inhibitor, indicating that ERK1/2 activation is essential for TTR aggregates‐induced cytotoxicity. Taken together, these data suggest that abnormally sustained activation of ERK in FAP may represent an early signaling cascade leading to neurodegeneration.
Regulation of AMPA receptor trafficking by N‐cadherin
Authors: Nuriya Mutsuo , Huganir Richard L. 
Published: March 2006

AbstractDendritic spines are dynamically regulated, both morphologically and functionally, by neuronal activity. Morphological changes are mediated by a variety of synaptic proteins, whereas functional changes can be dramatically modulated by the regulation of α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate (AMPA) receptor trafficking. Although these two forms of plasticity appear to be highly coordinated, the connections between them are not fully understood. In this study the synaptic cell adhesion molecule N‐cadherin was found to associate with AMPA receptors and regulate AMPA receptor trafficking in neurons. N‐cadherin and β‐catenin formed a protein complex with AMPA receptors in vivo, and this association was regulated by extracellular Ca2+. In addition, these proteins co‐clustered at synapses in cultured neurons. In heterologous cells and in cultured neurons, overexpression of wild‐type N‐cadherin specifically increased the surface expression level of the AMPA receptor subunit glutamate receptor 1 (GluR1) and this effect was reversed by a dominant‐negative form of N‐cadherin. Finally, GluR1 increased the surface expression of N‐cadherin in heterologous cells. Importantly, recent studies suggest that N‐cadherin and β‐catenin play key roles in structural plasticity in neurons. Therefore, our data suggest that the association of N‐cadherin with AMPA receptors may serve as a biochemical link between structural and functional plasticity of synapses.
DOC2A and DOC2B are sensors for neuronal activity with unique calcium‐dependent and kinetic properties
Authors: Groffen Alexander J. A. , Friedrich Reut , Brian Elisabeth C. , Ashery Uri , Verhage Matthijs 
Published: March 2006

AbstractElevation of the intracellular calcium concentration ([Ca2+]i) to levels below 1 µm alters synaptic transmission and induces short‐term plasticity. To identify calcium sensors involved in this signalling, we investigated soluble C2 domain‐containing proteins and found that both DOC2A and DOC2B are modulated by submicromolar calcium levels. Fluorescent‐tagged DOC2A and DOC2B translocated to plasma membranes after [Ca2+]i elevation. DOC2B translocation preceded DOC2A translocation in cells co‐expressing both isoforms. Half‐maximal translocation occurred at 450 and 175 nm[Ca2+]i for DOC2A and DOC2B, respectively. This large difference in calcium sensitivity was accompanied by a modest kinetic difference (halftimes, respectively, 2.6 and 2.0 s). The calcium sensitivity of DOC2 isoforms can be explained by predicted topologies of their C2A domains. Consistently, neutralization of aspartates D218 and D220 in DOC2B changed its calcium affinity. In neurones, both DOC2 isoforms were reversibly recruited to the plasma membrane during trains of action potentials. Consistent with its higher calcium sensitivity, DOC2B translocated at lower depolarization frequencies. Styryl dye uptake experiments in hippocampal neurones suggest that the overexpression of mutated DOC2B alters the synaptic activity. We conclude that both DOC2A and DOC2B are regulated by neuronal activity, and hypothesize that their calcium‐dependent translocation may regulate synaptic activity.
The mechanism of 1,2,3,4‐tetrahydroisoquinolines neuroprotection: the importance of free radicals scavenging properties and inhibition of glutamate‐induced excitotoxicity
Authors: Antkiewicz‐Michaluk Lucyna , Lazarewicz Jerzy W. , Patsenka Antoni , Kajta Malgorzata , Zieminska Elzbieta , Salinska Elzbieta , Wasik Agnieszka , Golembiowska Krystyna , Vetulani Jerzy 
Published: March 2006

Abstract1‐Methyl‐1,2,3,4‐tetrahydroisoquinoline (1MeTIQ), unlike several other tetrahydroisoquinolines, displays neuroprotective properties. To elucidate this action we compared the effects of 1MeTIQ with 1,2,3,4‐tetrahydroisoquinoline (TIQ), a compound sharing many activities with 1MeTIQ (among them reducing free radicals formed during dopamine catabolism), but offering no clear neuroprotection. We found that the compounds similarly inhibit free‐radical generation in an abiotic system, as well as indices of neurotoxicity (caspase‐3 activity and lactate dehydrogenase release) induced by glutamate in mouse embryonic primary cell cultures (a preparation resistant to NMDA toxicity). However, in granular cell cultures obtained from 7‐day‐old rats, 1MeTIQ prevented the glutamate‐induced cell death and45Ca2+influx, whereas TIQ did not. This suggested a specific action of 1MeTIQ on NMDA receptors, which was confirmed by the inhibition of [3H]MK‐801 binding by 1MeTIQ. Finally, we demonstrated in anin vivomicrodialysis experiment that 1MeTIQ prevents kainate‐induced release of excitatory amino acids from the rat frontal cortex. Our results indicate that 1MeTIQ, in contrast to TIQ, offers a unique and complex mechanism of neuroprotection in which antagonism to the glutamatergic system may play a very important role. The results suggest the potential of 1MeTIQ as a therapeutic agent in various neurodegenarative illnesses of the central nervous system.
Fe(III) mineral formation and cell encrustation by the nitrate‐dependent Fe(II)‐oxidizer strain BoFeN1
Authors: KAPPLER A. , SCHINK B. , NEWMAN D. K. 
Published: March 2006

ABSTRACTUnderstanding the mechanisms of anaerobic microbial iron cycling is necessary for a full appreciation of present‐day biogeochemical cycling of iron and carbon and for drawing conclusions about these cycles on the ancient Earth. Towards that end, we isolated and characterized an anaerobic nitrate‐dependent Fe(II)‐oxidizing bacterium from a freshwater sediment. The 16SrRNA gene sequence of the isolated bacterium (strain BoFeN1) places it within the β‐Proteobacteria, with Acidovorax sp. strain G8B1 as the closest known relative. During mixotrophic growth with acetate plus Fe(II) and nitrate as electron acceptor, strain BoFeN1 forms Fe(III) mineral crusts around the cells. The amount of the organic cosubstrate acetate present seems to control the rate and extent of Fe(II) oxidation and the viability of the cells. The crystallinity of the mineral products is influenced by nucleation by Fe minerals that are already present in the inoculum.
The coupling of biological iron cycling and mineral weathering during saprolite formation, Luquillo Mountains, Puerto Rico
Authors: BUSS H. L. , BRUNS M. A. , SCHULTZ M. J. , MOORE J. , MATHUR C. F. , BRANTLEY S. L. 
Published: March 2006

ABSTRACTCorestones of quartz diorite bedrock in the Rio Icacos watershed in Puerto Rico weather spheroidally to form concentric sets of partially weathered rock layers (referred to here as rindlets) that slowly transform to saprolite. The rindlet zone (0.2–2 m thick) is overlain by saprolite (2–8 m) topped by soil (0.5–1 m). With the objective of understanding interactions between weathering, substrate availability, and resident micro‐organisms, we made geochemical and microbiological measurements as a function of depth in 5 m of regolith (soil + saprolite). We employed direct microscopic counting of total cell densities; enumeration of culturable aerobic heterotrophs; extraction of microbial DNA for yield calculations; and biochemical tests for iron‐oxidizing bacteria. Total cell densities, which ranged from 2.5 × 106 to 1.6 × 1010 g−1 regolith, were higher than 108 g−1 at three depths: in the upper 1 m, at 2.1 m, and between 3.7 and 4.9 m, just above the rindlet zone. High proportions of inactive or unculturable cells were indicated throughout the profile by very low percentages of culturable heterotrophs (0.0004% to 0.02% of total cell densities). The observed increases in total and culturable cells and DNA yields at lower depths were not correlated with organic carbon or total iron but were correlated with moisture and HCl‐extractable iron. Biochemical tests for aerobic iron‐oxidizers were also positive at 0.15–0.6 m, at 2.1–2.4 m, and at 4.9 m depths. To interpret microbial populations within the context of weathering reactions, we developed a model for estimating growth rates of lithoautotrophs and heterotrophs based on measured substrate fluxes. The calculations and observations are consistent with a model wherein electron donor flux driving bacterial growth at the saprolite–bedrock interface is dominated by Fe(II) and where autotrophic iron‐oxidizing bacteria support the heterotrophic population and contribute to bedrock disaggregation and saprolite formation.
On the energetics of chemolithotrophy in nonequilibrium systems: case studies of geothermal springs in Yellowstone National Park
Authors: INSKEEP W. P. , ACKERMAN G. G. , TAYLOR W. P. , KOZUBAL M. , KORF S. , MACUR R. E. 
Published: March 2006

ABSTRACTChemolithotrophic micro‐organisms are important primary producers in high‐temperature geothermal environments and may catalyse a number of different energetically favourable redox reactions as a primary energy source. Analysis of geochemical constituents followed by chemical speciation and subsequent calculation of reaction free energies (ΔGrxn) is a useful tool for evaluating the thermodynamic favourability and potential energy available for microbial metabolism. The primary goal of this study was to examine relationships among geochemical gradients and microbial population distribution, and to evaluate the utility of energetic approaches for predicting microbial metabolism from free‐energy calculations, utilizing as examples, several geothermal habitats in Yellowstone National Park where thorough geochemical and phylogenetic analyses have been performed. Acidic (pH ∼ 3) and near‐neutral (pH ∼ 6–7) geothermal springs were chosen for their range in geochemical properties. Aqueous and solid phase samples obtained from the source pools and the outflow channels of each spring were characterized for all major chemical constituents using laboratory and field methods to accurately measure the concentrations of predominant oxidized and reduced species. Reaction free energies (ΔGrxn) for 33 oxidation–reduction reactions potentially important to chemolithotrophic micro‐organisms were calculated at relevant spring temperatures after calculating ion activities using an aqueous equilibrium model. Free‐energy values exhibit significant variation among sites for reactions with pH dependence. For example, free‐energy values for reactions involving Fe3+ are especially variable across sites due in large part to the pH dependence of Fe3+ activity, and exhibit changes of up to 40 kJ mol−1 electron from acidic to near neutral geothermal springs. Many of the detected 16S rRNA gene sequences represent organisms whose metabolisms are consistent with exergonic processes. However, sensitivity analyses demonstrated that reaction free energies do not generally represent the steep gradients in local geochemical conditions resulting from air–water gas exchange and solid phase deposition that are important in defining microbial habitats and 16S rRNA gene sequence distribution within geothermal outflow channels.
Addition of U(VI) to a uranium mining waste sample and resulting changes in the indigenous bacterial community
Authors: GEISSLER A. , SELENSKA‐POBELL S. 
Published: March 2006

ABSTRACTBased on 16S rRNA gene sequence retrieval, changes in natural bacterial community structure induced by addition of uranyl or sodium nitrate to soil samples from a uranium mining waste pile were investigated. Our results demonstrate that both treatments cause drastic changes in the bacterial composition of the studied samples, resulting in strongly reducing the originally predominant Acidobacteria and Alphaproteobacteria. The addition of sodium nitrate induced a strong propagation of particular denitrifying and nitrate‐reducing populations belonging to Actinobacteria and Bacteroidetes. The treatment of the samples with uranyl nitrate demonstrated that most part of the mentioned Bacteroidetes and some of the actinobacterial populations do not tolerate high U(VI) concentrations. Instead, a strong propagation of Pseudomonas spp. from the Gammaproteobacteria occurred. At the initial stages of incubation (4 weeks after the addition of uranyl nitrate) U(VI)‐reducing Geobacter spp. appeared. However, at the later stages of incubation (14 weeks after the beginning of supplementation) no Geobacter populations were detected anymore. Interestingly, different U‐sensitive Bacteroidetes and alphaproteobacterial populations propagated in the U(VI)‐treated samples at these late stages of incubation. That indicated that the added U(VI) was no longer bioavailable.The drastic changes in bacterial community structure of the soil samples from the depleted uranium mining waste caused by the addition of uranyl nitrate indicate that most of the established indigenous bacterial populations do not tolerate U(VI). By the treatment with uranyl nitrate they are replaced by particular uranium resistant nitrate‐reducing and denitrifying populations that potentially interact with the added radionuclide. On the other hand, the large number of dead uranium‐sensitive bacteria likely liberates phosphate‐rich and other biopolymers capable of binding U(VI). On the basis of our results, we propose that bacteria along with the abiotic soil components such as minerals and humic acids may influence the behaviour of U(VI) in nature.
Microbial stratification in deeply buried marine sediment reflects changes in sulfate/methane profiles
Authors: BIDDLE J. F. , HOUSE C. H. , BRENCHLEY J. E. 
Published: March 2006

ABSTRACTWe examined sediments collected at Ocean Drilling Program (ODP) Leg 201 Site 1229 on the Peru Margin for microbial populations throughout the sediment column. Heterotrophic cultivation from these sediments yielded numerous colonies from various depths, including 49 bacterial isolates. At ODP Site 1229, there are significant interfaces of sulfate and methane, across which microbial cell numbers increase substantially. At these sulfate/methane transition zones (SMTZs), however, we observed a decrease in the success rate for the cultivation of bacterial colonies. Utilizing both direct plating and enrichment in different media, we cultivated isolates from the upper SMTZ around 30 m below seafloor (mbsf); however, similar attempts yielded no colonies from within the lower zone at 85 mbsf. The phylogenetic relationships of the 16S rRNA gene sequences for the isolates were determined and most were related to other organisms and sequences previously found in the subsurface belonging to the γ‐Proteobacteria, cytophaga–flavobacterium–bacteroides, high G + C Gram‐positives, and Firmicutes groups. The most diverse group of isolates from Site 1229 was found between the SMTZs at 50 mbsf. ODP Leg 201 Site 1228 was examined for comparison and yielded an additional 18 isolates from 16 to 179 mbsf that were similar to those found at Site 1229. Direct plating at Site 1228 also showed decreased colony formation in the area of sulfate/methane transition. Our results suggest that heterotrophic bacterial populations are affected by SMTZs in deeply buried sediment.