bluuebunny/crossref_metadata_2025_split huggingface dataset:
Iron accumulation, iron‐mediated toxicity and altered levels of ferritin and transferrin receptor in cultured astrocytes during incubation with ferric ammonium citrate
Authors: Hoepken Hans H. , Korten Till , Robinson Stephen R. , Dringen Ralf 
Published: February 2004

AbstractThe cellular uptake and storage of iron have to be tightly regulated in order to provide iron for essential cellular functions while preventing the iron‐catalysed generation of reactive oxygen species (ROS). In contrast to cells in other organs, little is known about the regulation of iron metabolism in brain cells, particularly in astrocytes. To investigate the regulation of iron metabolism in astrocytes we have used primary astrocyte cultures from the brains of newborn rats. After application of ferric ammonium citrate (FAC), cultured astrocytes accumulated iron in a time‐ (0–48 h) and concentration‐dependent (0.01–1 mm) manner. This accumulation was prevented if FAC was applied in combination with the iron‐chelator deferoxamine (DFX). Application of FAC to astrocyte cultures caused a strong increase in the cellular content of the iron storage protein ferritin and a decrease in the amount of transferrin receptor (TfR), which is involved in the transferrin‐mediated uptake of iron into cells. In contrast, application of DFX strongly increased the level of TfR. Both up‐regulation of ferritin content by iron application and up‐regulation of TfR content by DFX were prevented by the protein synthesis inhibitor cycloheximide (CHX). During incubation of astrocytes with FAC, a mild and transient increase in the extracellular activity of the cytosolic enzyme lactate dehydrogenase and in the concentration of intracellular ROS was observed. In contrast, prevention of protein synthesis by CHX during incubation with FAC resulted in significantly more cell loss and a persistent and intense increase in the production of intracellular ROS. These results demonstrate that both iron accumulation and deprivation modulate the synthesis of ferritin and TfR in astrocytes and that protein synthesis is required to prevent iron‐mediated toxicity in astrocytes.
Massive accumulation of N‐acylethanolamines after stroke. Cell signalling in acute cerebral ischemia?
Authors: Berger Christian , Schmid Patricia C. , Schabitz Wolf‐Ruediger , Wolf Margit , Schwab Stefan , Schmid Harald H. O. 
Published: February 2004

AbstractWe investigated levels and compositions of N‐acylethanolamines (NAEs) and their precursors, N‐acyl phosphatidylethanolamines (N‐acyl PEs), in a rat stroke model applying striatal microdialysis for glutamate assay. Rats (n = 18) were treated with either intravenous saline (control), NMDA receptor antagonist MK801 (1 mg/kg), or CB1 receptor antagonist SR141716A (1 mg/kg) 30 min after permanent middle cerebral artery occlusion (MCAO). MK801 significantly attenuated the release of glutamate in the infarcted striatum (79 ± 22 μmol/L) as compared with controls (322 ± 104 μmol/L). The administration of CB1 antagonist SR141716A had no statistically significant effect on glutamate release (340 ± 89 μmol/L), but reduced infarct volume at 5 h after MCAO significantly by approximately 40%, whereas MK801 treatment resulted in a non‐significant (18%) reduction of infarct volume. In controls, striatal and cortical NAE concentrations were about 30‐fold higher in the infarcted than in the non‐infarcted hemisphere, whereas ipsilateral N‐acyl phosphatidylethanolamine (N‐acyl PE) levels exceeded contralateral levels by only a factor of two to three. Treatment with MK801 or SR141716A, or glutamate release in the infarcted tissue, had no significant effect on these levels. NAE accumulation during acute stroke may be due to increased synthesis as well as decreased degradation, possibly by inhibition of fatty acid amide hydrolase (FAAH).
Opposite modulatory roles for adenosine A1and A2Areceptors on glutamate and dopamine release in the shell of the nucleus accumbens. Effects of chronic caffeine exposure
Authors: Quarta Davide , Ferré Sergi , Solinas Marcello , You Zhi‐Bing , Hockemeyer Jörg , Popoli Patrizia , Goldberg Steven R. 
Published: February 2004

AbstractPrevious studies have demonstrated opposing roles for adenosine A1and A2Areceptors in the modulation of extracellular levels of glutamate and dopamine in the striatum. In the present study, acute systemic administration of motor‐activating doses of the A2Areceptor antagonist MSX‐3 significantly decreased extracellular levels of dopamine and glutamate in the shell of the rat nucleus accumbens (NAc) and counteracted both dopamine and glutamate release induced by systemic administration of motor‐activating doses of either the A1receptor antagonist CPT or caffeine. Furthermore, exposure to caffeine in the drinking water (1 mg/mL, 14 days) resulted in tolerance to the effects of systemic injection of CPT or caffeine, but not MSX‐3, on extracellular levels of dopamine and glutamate in the NAc shell. The present results show: first, the existence of opposite tonic effects of adenosine on extracellular levels of dopamine and glutamate in the shell of the NAc mediated by A1and A2Areceptors; second, that complete tolerance to caffeine's dopamine‐ and glutamate‐releasing effects which develops after chronic caffeine exposure is attributable to an A1receptor‐mediated mechanism. Development of tolerance to the dopamine‐releasing effects of caffeine in the shell of the NAc may explain its weak addictive properties and atypical psychostimulant profile.
Rat brain arachidonic acid metabolism is increased by a 6‐day intracerebral ventricular infusion of bacterial lipopolysaccharide
Authors: Rosenberger Thad A. , Villacreses Nelly E. , Hovda Jonathan T. , Bosetti Francesca , Weerasinghe Gayani , Wine Robert N. , Harry G. Jean , Rapoport Stanley I. 
Published: February 2004

AbstractIn a rat model of acute neuroinflammation, produced by a 6‐day intracerebral ventricular infusion of bacterial lipopolysaccharide (LPS), we measured brain activities and protein levels of three phospholipases A2 (PLA2) and of cyclo‐oxygenase‐1 and ‐2, and quantified other aspects of brain phospholipid and fatty acid metabolism. The 6‐day intracerebral ventricular infusion increased lectin‐reactive microglia in the cerebral ventricles, pia mater, and the glial membrane of the cortex and resulted in morphological changes of glial fibrillary acidic protein (GFAP)‐positive astrocytes in the cortical mantel and areas surrounding the cerebral ventricles. LPS infusion increased brain cytosolic and secretory PLA2 activities by 71% and 47%, respectively, as well as the brain concentrations of non‐esterified linoleic and arachidonic acids, and of prostaglandins E2 and D2. LPS infusion also increased rates of incorporation and turnover of arachidonic acid in phosphatidylethanolamine, plasmenylethanolamine, phosphatidylcholine, and plasmenylcholine by 1.5‐ to 2.8‐fold, without changing these rates in phosphatidylserine or phosphatidylinositol. These observations suggest that selective alterations in brain arachidonic acid metabolism involving cytosolic and secretory PLA2 contribute to early pathology in neuroinflammation.
Neuroprotection of immortalized hippocampal neurones by brain‐derived neurotrophic factor and Raf‐1 protein kinase: role of extracellular signal‐regulated protein kinase and phosphatidylinositol 3‐kinase
Authors: Rössler Oliver G. , Giehl Klaus M. , Thiel Gerald 
Published: February 2004

AbstractWe have investigated the molecular mechanisms of neurotrophin‐mediated cell survival in HT22 cells, a murine cell line of hippocampal origin, expressing the brain‐derived neurotrophic factor (BDNF) receptor TrkB as well as the TrkB.T1 splice variant. Stimulation with BDNF protected HT22‐TrkB cells, but not HT22‐TrkB.T1 cells, against programmed cell death induced by serum deprivation. BDNF did not, however, provide protection against oxidative glutamate toxicity, indicating that serum deprivation‐induced cell death differs substantially from glutamate‐induced cell death. Using a pharmacological strategy to block either the extracellular signal‐regulated protein kinase (ERK) or the phosphatidylinositol 3‐kinase (PI3) pathway, we show that activation of PI3 kinase is required for the neuroprotective activity of BDNF in HT22 cells. To further analyse the role of ERK in neuroprotection we expressed an inducible ΔRaf‐1:ER fusion protein in HT22 cells. Activation of this conditionally active form of Raf‐1 induced a sustained phosphorylation of ERK, and protected the cells from serum withdrawal‐induced cell death. Inhibition of ERK activation at different time points revealed that a prolonged activation of ERK is essential to protect HT22 cells from cell death triggered by the withdrawal of serum, indicating that the duration of ERK activation is of major importance for its neuroprotective biological function.
Transthyretin is involved in depression‐like behaviour and exploratory activity
Authors: Sousa João Carlos , Grandela Catarina , Fernández‐Ruiz Javier , De Miguel Rosário , De Sousa Liliana , Magalhães Ana Isabel , Saraiva Maria João , Sousa Nuno , Palha Joana Almeida 
Published: February 2004

AbstractTransthyretin (TTR), the major transporter of thyroid hormones and vitamin A in cerebrospinal fluid (CSF), binds the Alzheimer β‐peptide and thus might confer protection against neurodegeneration. In addition, altered TTR levels have been described in the CSF of patients with psychiatric disorders, yet its function in the CNS is far from understood. To determine the role of TTR in behaviour we evaluated the performance of TTR‐null mice in standardized tasks described to assess depression, exploratory activity and anxiety. We show that the absence of TTR is associated with increased exploratory activity and reduced signs of depressive‐like behaviour. In order to investigate the mechanism underlying these alterations, we measured the levels of cathecolamines. We found that the levels of noradrenaline were significantly increased in the limbic forebrain of TTR‐null mice. This report represents the first clear indication that TTR plays a role in behaviour, probably by modulation of the noradrenergic system.
Inhibiting Src family tyrosine kinase activity blocks glutamate signalling to ERK1/2 and Akt/PKB but not JNK in cultured striatal neurones
Authors: Crossthwaite Andrew J. , Valli Haseeb , Williams Robert J. 
Published: February 2004

AbstractGlutamate receptor activation of mitogen‐activated protein (MAP) kinase signalling cascades has been implicated in diverse neuronal functions such as synaptic plasticity, development and excitotoxicity. We have previously shown that Ca2+‐influx through NMDA receptors in cultured striatal neurones mediates the phosphorylation of extracellular signal‐regulated kinase 1/2 (ERK1/2) and Akt/protein kinase B (PKB) through a phosphatidylinositol 3‐kinase (PI 3‐kinase)‐dependent pathway. Exposing neurones to the Src family tyrosine kinase inhibitor PP2, but not the inactive analogue PP3, inhibited NMDA receptor‐induced phosphorylation of ERK1/2 and Akt/PKB in a concentration‐dependent manner, and reduced cAMP response element‐binding protein (CREB) phosphorylation. To establish a link between Src family tyrosine kinase‐mediated phosphorylation and PI 3‐kinase signalling, affinity precipitation experiments were performed with the SH2 domains of the PI 3‐kinase regulatory subunit p85. This revealed a Src‐dependent phosphorylation of a focal adhesion kinase (FAK)–p85 complex on glutamate stimulation. Demonstrating that PI3‐kinase is not ubiquitously involved in NMDA receptor signal transduction, the PI 3‐kinase inhibitors wortmannin and LY294002 did not prevent NMDA receptor Ca2+‐dependent phosphorylation of c‐Jun N‐terminal kinase 1/2 (JNK1/2). Further, inhibiting Src family kinases increased NMDA receptor‐dependent JNK1/2 phosphorylation, suggesting that Src family kinase‐dependent cascades may physiologically limit signalling to JNK. These results demonstrate that Src family tyrosine kinases and PI3‐kinase are pivotal regulators of NMDA receptor signalling to ERK/Akt and JNK in striatal neurones.
Mode of inheritance of the polymorphic esterases in Myzus persicae (Hemiptera: Aphididae) in Japan
Authors: Shigehara T. , Takada H. 
Published: February 2004

AbstractCrossing experiments were conducted with 43 different parental clones of Myzus persicae (Sulzer) to clarify the genetic bases of esterase variations detected by electrophoresis. A total of 468 F1 clones obtained were analysed for variants at six polymorphic esterase loci, including one associated with resistance to organophosphorus insecticides (RAE). In addition, the effect of six different host plants on the activity of esterases was examined. The inheritance of variants at two loci could be explained by two-allele models, and that at three other loci by three-allele models, while segregation ratios at the RAE locus suggested a cumulative effect of the multiple genes. An interdependent assortment was found between two loci. The activity of the esterases detected in the alimentary canal was affected by the host plant. By combining the variants at the six polymorphic esterase loci with those in body colour, a total of 2592 colour-esterase forms were distinguishable. Thus esterases could be useful as genetic markers to study the genotypic composition and its dynamics of M. persicaepopulations.
Habitat-related mtDNA polymorphism in the stored-bean pest Callosobruchus chinensis (Coleoptera: Bruchidae)
Authors: Tuda M. , Wasano N. , Kondo N. , Horng S.-B. , Chou L.-Y. , Tateishi Y. 
Published: February 2004

AbstractThe genetic diversity of populations of the azuki bean beetle, Callosobruchus chinensis (Linnaeus) from natural, pre-harvest and post-harvest sites, was investigated to understand population structure and gene flow. A 522-bp fragment of the mitochondrial gene COI was sequenced for eight populations of C. chinensisfrom Japan, Korea and Taiwan collected from different habitats. Six haplotypes were detected, one of which, U1, occurred most frequently and widely. The following hypotheses were tested as a cause of the wide distribution of haplotype U1; (i) topographical separation (by national boundaries), (ii) host plant species, and (iii) habitat type (natural, pre-harvest crop, or post-harvest storage). Categorization of collection sites by country or by host species did not yield differences in the occurrence of haplotype U1, but habitat type did. Populations utilizing cultivated post-harvest hosts that were mass stored were highly likely to be the common haplotype, whereas host plants in natural habitats away from agriculture were utilized by populations with locally characteristic haplotypes. Sampling of commercial beans for quarantine and export purposes indicated that gene flow in C. chinensis was largely unidirectional into Japan at the present time.
Seedling and adult plant resistance to Sitobion avenae (Hemiptera: Aphididae) in Triticum monococcum (Poaceae), an ancestor of wheat
Authors: Migui S.M. , Lamb R.J. 
Published: February 2004

AbstractCereal aphids are important pests of wheat, Triticum aestivum L. and Triticum durum Desf. Crop resistance is a desirable method for managing cereal aphids in central North America, where the dominant crop, spring-sown wheat, has a low value per unit area. A diploid ancestor of wheat, Triticum monococcum L., is reported to be partially resistant to Sitobion avenae (Fabricius), the most damaging cereal aphid in the region. To identify potential sources of resistance, 42 accessions of T. monococcum and three cultivated wheats were infested with aphids, seedlings for six days and adult plants for 21 days. Overall resistance was estimated by the biomass loss of foliage and spikes in relation to uninfested control plants. Antibiosis was estimated by the gain in biomass of aphids during infestation, and tolerance was estimated as a biomass conversion ratio, overall resistance divided by antibiosis. A few T. monococcum accessions exhibited partial resistance. No relationship was found between seedling and adult plant resistance: the former exhibited primarily antibiosis and the latter primarily tolerance. Two accessions with antibiosis reduced aphid biomass by 60% compared with commercial wheats. Tolerance was correlated with growth potential, and was useful only in accessions with high growth potential. Four accessions exhibited tolerance levels at least 30% greater than commercial wheats. Highly susceptible accessions also were identified, which would be useful for investigating the inheritance of antibiosis and tolerance.
Maturation feeding and reproductive development in adult pine weevil, Hylobius abietis (Coleoptera: Curculionidae)
Authors: Wainhouse D. , Boswell R. , Ashburner R. 
Published: February 2004

AbstractMaturation feeding on conifer bark by newly emerged Hylobius abietis(Linnaeus) is essential for reproductive development. When feeding occurs on young conifer transplants, this weevil causes significant economic damage. Between emergence and oviposition however, weevils feed on bark from different sources but of unknown nutritional ‘quality’. The factors influencing the rate of feeding by males and females and female reproductive development were determined in laboratory bioassays using two contrasting food sources – the bark on different species of seedling conifer and on logs of mature trees. The nutritional ‘quality’ of bark was characterized by the concentration of nitrogen, total sugars, total polyphenols and resin. Regression models were used to show that overall, the rate of feeding on the bark of both seedlings and logs increased with weevil size and was negatively related to nitrogen concentration. The nitrogen concentration in seedling bark (mean 1.1%) was about three times higher than that of logs (mean 0.4%). The rate of reproductive development increased with nitrogen intake during feeding and the preoviposition period for weevils feeding on seedlings and logs was ~ 13 days and 46 days, respectively. Analysis of weevil mortality and of the weight gain of surviving weevils suggests that a nitrogen content of around 0.3% may be limiting for H. abietis. The possibility that nutritionally adequate food resources may be limiting for H. abietis is briefly discussed.
Neotropical tadpoles influence stream benthos: evidence for the ecological consequences of decline in amphibian populations
Authors: Ranvestel Anthony W. , Lips Karen R. , Pringle Catherine M. , Whiles Matt R. , Bixby Rebecca J. 
Published: February 2004

Summary1. Few studies have assessed the role of tadpoles in tropical streams, although they are often abundant and conspicuous components of these systems. Moreover, amphibian populations are declining around the globe, particularly stream‐dwelling species in tropical uplands, and the ecological consequences of these losses are not understood.2. We chose a stream in the central Panamanian highlands, which has an intact fauna of stream‐breeding anurans, to examine the ecological consequences of amphibian losses. This site differs dramatically from sites in nearby western Panama and Costa Rica where anuran diversity and abundance have declined greatly in the last two decades.3. We used an underwater electric field to create tadpole exclosures in runs, so that we could evaluate their influence on sediment dynamics and the abundance and community structure of algae and aquatic insects. Tadpoles reduced total sediments and both organic and inorganic fractions on substrata. Tadpoles also reduced algal abundance on substrata by approximately 50% and decreased algal biovolume. Gut content analyses showed that tadpoles consumed algae and sediments and we could see that algae and sediments were also displaced through bioturbation.4. Atelopus zeteki, Rana warszewitschii, and Hyla spp. were the dominant larval anurans responsible for the effects observed. Visual surveys indicated that the densities of these taxa ranged from 23 (R. warszewitschii and Hyla spp. combined) to 43 m−2 (A. zeteki) in runs.5. The abundance of baetid mayflies was lower in tadpole exclosures compared with controls, and this was attributed to tadpoles facilitating mayfly feeding by removing sediments and exposing underlying periphyton.6. Tadpoles affect the abundance and diversity of basal resources and other primary consumers, and thus influence food web dynamics and energy flow in these tropical streams. Catastrophic decline in stream‐breeding anuran populations will influence the structure and function of neotropical stream ecosystems.
Simple traits do not predict grazing response in Australian dry shrublands and woodlands
Authors: Vesk Peter A. , Leishman Michelle R. , Westoby Mark 
Published: February 2004

Summary

Plant species composition and species response to grazing are fundamental to the management of grazing lands. Reliable prediction of grazing responses from species’ traits would be a major step forward in generalizing knowledge and management beyond the locality. Recently results have been presented showing that plant species’ responses to grazing in subhumid grasslands in Argentina and Israel could be predicted from simple traits: height, leaf size, life history and specific leaf area (SLA). This study assessed whether those relationships between traits and grazing responses hold for Australian semi‐arid and arid shrublands and woodlands.
Eleven lists of grazing responses from five published grazing studies were matched with a plant trait data set. Trait distributions were compared between response groups pooled across studies. Relationships between traits and grazing response were also assessed, both within and across studies, using meta‐analysis.
Overall there was little evidence for predictability of grazing responses with simple traits in the semi‐arid and arid shrublands and woodlands. There were relationships between grazing response and life history and growth form, and some weak evidence for grazing increasers having high SLA.
Synthesis and applications. It was concluded that prediction of grazing responses with simple traits is less clear in semi‐arid and arid rangelands, which are characterized by openness at ground level and high diversity of growth forms, compared with subhumid grasslands that have structurally simple, continuous swards. The finding that species’ traits may have differing predictive capacity for grazing responses in different situations means that we need more empirical studies in different situations. The most important contrasts between situations for investigation are likely to be on axes of rainfall/productivity and evolutionary history of grazing.