bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential negative coupling of type 3 metabotropic glutamate receptor to cyclic GMP levels in neurons and astrocytes
Authors: Wroblewska Barbara , Wegorzewska Iga N. , Bzdega Tomasz , Olszewski Rafal T. , Neale Joseph H.
Published: January 2006

Metabotropic receptors may couple to different G proteins in different cells or perhaps even in different regions of the same cell. To date, direct studies of group II and group III metabotropic glutamate receptors' (mGluRs) relationships to second messenger cascades have reported negative coupling of these receptors to cyclic AMP (cAMP) levels in neurons, astrocytes and transfected cells. In the present study, we found that the peptide neurotransmitter N‐acetylaspartylglutamate (NAAG), an mGluR3‐selective agonist, decreased sodium nitroprusside (SNP)‐stimulated cyclic GMP (cGMP) levels in cerebellar granule cells and cerebellar astrocytes. The mGluR3 and group II agonists FN6 and LY354740 had similar effects on cGMP levels. The mGluR3 and group II antagonists β‐NAAG and LY341495 blocked these actions. Treatment with pertussis toxin inhibited the effects of NAAG on SNP‐stimulated cGMP levels in rat cerebellar astrocytes but not in cerebellar neurons. These data support the conclusion that mGluR3 is also coupled to cGMP levels and that this mGluR3‐induced reduction of cGMP levels is mediated by different G proteins in cerebellar astrocytes and neurons. We previously reported that this receptor is coupled to a cAMP cascade via a pertussis toxin‐sensitive G protein in cerebellar neurons, astrocytes and transfected cells. Taken together with the present data, we propose that mGluR3 is coupled to two different G proteins in granule cell neurons. These data greatly expand knowledge of the range of second messenger cascades induced by mGluR3, and have implications for clinical conditions affected by NAAG and other group II mGluR agonists.
Cell death and expression of heat‐shock protein Hsc70 in the hyperthermic rat brain
Authors: Belay Hiwote T. , Brown Ian R.
Published: January 2006

Stressful stimuli induce two distinct cellular reactions, the heat‐shock (stress) response and programmed cell death. This study utilizes a dual procedure involving immunocytochemistry for heat‐shock protein localization and the terminal deoxynucleotidyl transferase‐mediated deoxyuridine triphosphate nick‐end labeling (TUNEL) assay for localization of cell death at the cellular level. Whole‐body hyperthermia resulted in cell death in the adult rat thymus and testis with a robust signal seen in the testis. Distinct populations of constitutively expressed Hsc70‐positive cells and TUNEL‐positive cells were apparent. Cellular layers that exhibited high levels of Hsc70 were not triggered into cell death by the thermal stress. High expression of Hsc70 was observed in neuronal populations in the dentate gyrus, CA1 and CA2 region of the hippocampus and Purkinje neurons of the cerebellum. Hyperthermia‐induced cell death was not observed in these neuronal cell types, suggesting that neuronal expression of constitutive Hsc70 may play roles in preprotecting neurons from stressful stimuli.
Knocking‐down the NMDAR1 subunit in a limited amount of neurons in the rat hippocampus impairs learning
Authors: Cheli V. , Adrover M. , Blanco C. , Ferrari C. , Cornea A. , Pitossi F. , Epstein A. L. , Jerusalinsky D.
Published: January 2006

Amplicon vectors derived from herpes simplex virus type 1 were built to modify NMDA receptors by expressing antisense RNA for the essential NR1 subunit. Their ability to modify endogenous levels of NR1 was tested in cultures of rat embryo neocortical neurons. We studied behaviour and tested for expression in adult rats injected with those vectors into the dorsal hippocampus to find out which cells and how many appear involved in memory formation. Rats injected with vectors expressing NR1 antisense performed significantly worse than control rats in an inhibitory avoidance task. Immunohistochemistry was performed in brain slices from the same animals. The transduced cells represented 6–7% of pyramidal neurons in CA1, showing that a single gene knockdown of NR1 in a small number of neurons significantly impaired memory formation. Perhaps neurons undergoing synaptic plasticity are more susceptible to NR1 knockdown, and hence NMDAR are particularly required in those neurons undergoing synaptic plasticity during learning, or perhaps, and more likely, there is not a high level of redundancy in the hippocampal circuits involved, leading to the idea that a certain level of NR1 expression/availability appears necessary for memory formation in most of CA1 pyramidal neurons.
Characterization of the REST/NRSF‐interacting LIM domain protein (RILP): localization and interaction with REST/NRSF
Authors: Shimojo Masahito , Hersh Louis B.
Published: January 2006

We previously identified a nuclear envelope protein repressor element‐1 silencing transcription factor (REST)/neuron‐restrictive silencer factor (NRSF)‐interacting Lin‐11, Isl‐1 and Mec‐3 (LIM) domain protein (RILP) that we proposed functions in the nuclear translocation of the transcriptional repressor REST/NRSF. In this study we assessed the functionality of the prenylation motif, protein kinase A (PKA) phosphorylation sites and nuclear localization sequences (NLSs) of RILP. [3H]‐mevalonolactone labeled endogenous RILP, showing that RILP is indeed prenylated, while phosphorylation analysis showed that the two PKA sites are phosphorylated. Blocking RILP prenylation, mutating the NLSs or mutating the PKA phosphorylation sites caused RILP to mislocalize to the cytosol. Concurrent with this mislocalization of RILP, REST/NRSF and REST4, which are normally found in the nucleus, co‐localized in the cytosol with the RILP mutants. This provides additional evidence that RILP interacts with REST/NRSF and REST4 in vivo, and is involved in the nuclear localization of REST/NRSF and REST4. Reporter gene analysis using the promoter region of the human cholinergic gene locus revealed that these RILP mutants prevented repression of the reporter gene. By trapping REST/NRSF in the cytosol, the RILP mutants prevented translocation to the nucleus where REST/NRSF binds to an RE‐1/NRSE element to repress gene transcription. These results show that RILP is required for REST/NRSF nuclear targeting and function.
Methamphetamine‐induced spectrin proteolysis in the rat striatum
Authors: Staszewski Robert D. , Yamamoto Bryan K.
Published: January 2006

Methamphetamine (METH) is a widely abused psychostimulant. Multiple high doses of METH cause long‐term toxicity to dopamine (DA) and serotonin (5‐HT) nerve terminals in the brain, as evidenced by decreases in DA and 5‐HT content, decreases in tyrosine and tryptophan hydroxylase activities, decreases in DA and 5‐HT re‐uptake sites, and nerve terminal degeneration. Multiple high doses of METH are known to elicit a rapid increase in DA release and hyperthermia. Although METH also produces a delayed and sustained rise in glutamate, no studies have shown whether METH produces structural evidence of excitotoxicity in striatum, or identified the receptors that mediate this toxicity directly, independent of alterations in METH‐induced hyperthermia. These experiments investigated whether METH can cause excitotoxicity as evidenced by cytoskeletal protein breakdown in a glutamate receptor‐dependent manner. METH increased calpain‐mediated spectrin proteolysis in the rat striatum 5 and 7 days after METH administration without affecting caspase 3‐dependent spectrin breakdown. This effect was completely blocked with the α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptor antagonist, GYKI 52466, but not the NMDA receptor antagonist, MK‐801. However, AMPA or NMDA receptor antagonism did not attenuate the METH‐induced depletions of the dopamine transporter (DAT). Independent mechanisms involved in mediating spectrin proteolysis and DAT protein loss are discussed.
Modifications of the iron–neuromelanin system in Parkinson's disease
Authors: Fasano Mauro , Bergamasco Bruno , Lopiano Leonardo
Published: January 2006

Parkinson's disease is a common neurodegenerative disorder with a mainly sporadic aetiology, although a number of monogenic familiar forms are known. Most of the motor symptoms are due to selective depletion of dopaminergic, neuromelanin‐containing neurones of the substantia nigra pars compacta. Neuromelanin is the dark insoluble macromolecule that confers the black (substantia nigra) or grey (locus coeruleus) colour to monoaminergic basal ganglia. In particular, nigral neurones are pigmented because of the accumulation of by‐products of oxidative metabolism of the neurotransmitter dopamine. The occurrence of dopamine (and all the enzymatic machinery required for dopamine synthesis, re‐uptake and disposal) and neuromelanin, and a large amount of iron ions that interact with them, makes dopaminergic nigral neurones peculiarly susceptible to oxidative stress conditions that, in turn, may become amplified by the iron–neuromelanin system itself. In this mini‐review we describe biophysical evidence for iron–neuromelanin modifications that support this hypothesis. Furthermore, we discuss the formation of the covalent linkage between α‐synuclein and neuromelanin from the early stages of the disease.
Thermal evolution of the orogenic lower crust during exhumation within a thickened Moldanubian root of the Variscan belt of Central Europe
Authors: TAJČMANOVá L. , KONOPÁSEK J. , SCHULMANN K.
Published: January 2006

At the eastern margin of the Bohemian Massif (Variscan belt of Central Europe), large bodies of felsic granulite preserve mineral assemblages and structures developed during the early stages of exhumation of the orogenic lower continental crust within the Moldanubian orogenic root. The development of an early steep fabric is associated with east–west‐oriented compression and vertical extrusion of the high‐grade rocks into higher crustal levels. The high‐pressure mineral assemblage Grt‐Ky‐Kfs‐Pl‐Qtz‐Liq corresponds to metamorphic pressures of ∼18 kbar at ∼850 °C, which are minimum estimates, whereas crystallization of biotite occurred at 13 kbar and ∼790 °C during decompression with slight cooling. The late stages of the granulite exhumation were associated with lateral spreading of associated high‐grade rocks over a middle crustal unit at ∼4 kbar and ∼700 °C, as estimated from accompanying cordierite‐bearing gneisses. The internal structure of a contemporaneously intruded syenite is coherent with late structures developed in felsic granulites and surrounding gneisses, and the magma only locally explored the early subvertical fabric of the felsic granulite during emplacement. Consequently, the emplacement age of the syenite provides an independent constraint on the timing of the final stages of exhumation and allows calculation of exhumation and cooling rates, which for this part of the Variscan orogenic root are 2.9–3.5 mm yr−1 and 7–9.4 °C Myr−1, respectively. The final part of the temperature evolution shows very rapid cooling, which is interpreted as the result of juxtaposition of hot high‐grade rocks with a cold upper‐crustal lid.
Reviews: Diagnosis and Management of Insomnia in Dialysis Patients
Authors: Novak Marta , Shapiro Colin M. , Mendelssohn David , Mucsi Istvan
Published: January 2006

Sleep‐related complaints affect 50–80% of patients on dialysis. Sleep disorders impair quality of life significantly. Increasing evidence suggests that sleep disruption has a profound impact both on an individual and on a societal level. The etiology of sleep disorders is often multifactorial: biologicsocialand psychological factors play a role. This is especially true for insomniawhich is the most common sleep disorder in different populationsincluding patients on dialysis. Biochemical and metabolic changeslifestyle factorsdepressionanxietyand other underlying sleep disorders can all have an effect on the development and persistence of sleep disruptionleading to chronic insomnia. Insomnia is defined as difficulty initiating or maintaining sleepor having nonrestorative sleep. It is also associated with daytime consequencessuch as sleepiness and fatigueand impaired daytime functioning. In most casesthe diagnosis of insomnia is based on the patient's historybut in some patients objective assessment of sleep pattern may be necessary. Optimally the treatment of insomnia involves the combination of both pharmacologic and nonpharmacologic approaches. In some cases acute insomnia resolves spontaneouslybut if left untreatedit may lead to chronic sleep problems. The treatment of chronic insomnia is often challenging. There are only a few studies specifically addressing the management of this sleep disorder in patients with chronic renal disease. Considering the polypharmacy and altered metabolism in this patient populationtreatment trials are clearly needed. This article reviews the diagnosis of sleep disorders with a focus on insomnia in patients on dialysis.
Endocrinology and Dialysis Jean L. HolleySeries Editor: Lipid Abnormalities Associated with End‐Stage Renal Disease
Authors: Liu Jia , Rosner Mitchell H.
Published: January 2006

Patients undergoing chronic renal replacement therapy have a high incidence of dyslipidemia. In generalthere are increased concentrations of triglyceride‐rich apolipoprotein B‐containing particles. These elevations lead to increased levels of non‐high‐density lipoprotein (HDL) levels. This pattern is further modified by the method of dialysis (peritoneal versus hemodialysis) and comorbidities such as diabetes. End‐stage renal disease patients also demonstrate increased levels of lipoprotein(a) (Lp(a)) and oxidized low‐density lipoprotein (LDL)both of which are highly atherogenic. This review focuses on the pathogenesis of these lipid abnormalities and their role in the atherosclerotic process.
Dialyzer Reuse—Part I: Historical Perspective
Authors: Twardowski Zbylut J.
Published: January 2006

The first apparatus for hemodialysis in animalsmade painstakingly by Abel et al. in their laboratory at the beginning of 20th centurywas cleaned with acid‐pepsin to digest blooddisinfected with thymoland reused for up to 30 experiments for as long as 8 months. The obvious incentive was saving time. In the early years of hemodialysis in patientsdialyzers and lines were assembled and sterilized immediately before dialysis. Various methods of dry and moist heat sterilization and miscellaneous chemical agents were employed for disinfection. Significant time was required to assemble the dialyzersso there was an incentive to reuse previously assembled dialyzers to save timeespecially for home hemodialysis. Bleach to clean and formaldehyde to disinfect the membranes and lines was used for this purpose. Preassembled dialyzerscommercially introduced in the 1950swere the most expensive components of hemodialysis systemstherefore reprocessing of these dialyzers was the most effective way to save money. Refrigeration of coil dialyzers with bloodintroduced in the mid‐1960swas associated with frequent febrile reactions and was soon abandoned. Preassembled coil and plate dialyzers permitted almost complete return of blood after dialysis and led to the introduction of chemical disinfection for dialyzer reprocessing. A variety of disinfectants have been used. Formaldehyde was the most common disinfectant until the end of the 1970s. Sodium hypochlorite was used to clean the majority of dialyzers and to sterilize dialyzers with polyacrylonitrile membranes. In the early 1980speracetic acid and glutaraldehyde started to compete with formaldehyde. By the 1990sformaldehyde had become less popular than peracetic acid. In the mid‐1990sdisinfection and membrane cleaning with acetic acid and heat was introduced. Manual reprocessing was replaced by early reuse machines in the mid‐1970s and a more sophisticated second generation of automated hemodialyzer reprocessing machines followed in the late 1970s. Recently disinfection of dialyzers with moist heat has resumed. Saving both time for the patient and money for the provider were the main motivations for designing a new machine for daily home hemodialysis. The machinedeveloped in the 1990scleans and moist‐heat disinfects the dialyzer and lines in situ so they do not need to be changed for a month. In contrastthe reuse of dialyzers in home hemodialysis patients treated with other hemodialysis machines has become less popular and is almost extinct.
Leptin and Renal Disease
Authors: Briley Libbie P. , Szczech Lynda A.
Published: January 2006

Leptin is a mediator of metabolism and disease in a variety of organ systemsmost notably as an agent of energy stores. Howeverits role in renal disease as an inflammatory agent as well as its potential impact on the cachexia of uremia have sparked new interest in the molecule for nephrologists. This review elucidates the complex uremic statethe historical discovery of leptin and its physiologyand the potential interactions leptin has on both the progression of kidney disease as well as the morbidity and mortality of end‐stage renal disease.
Nitrogen homeostasis in a willow leaf beetle, Plagiodera versicolora, is independent of host plant quality
Authors: Kagata H. , Ohgushi T.
Published: January 2006

While foliar nitrogen (N) content of host plants depends on environmental conditions, N content of herbivorous insects may remain relatively constant due to homeostasis. However, it is unknown to what extent insects can maintain their body elemental composition against natural variation in host plant quality. The present study examined the performance and N content of a willow leaf beetle, Plagiodera versicolora Laicharting (Coleoptera: Chrysomelidae), when fed leaves of host willow, Salix eriocarpa Franchet et Savatier (Salicaceae), with varying nutritional status.

Water content, toughness, and N content of willow leaves varied seasonally, and they affected performance of the leaf beetle. The leaf beetle achieved high performance when fed young leaves. On the other hand, the N content of the leaf beetle changed little, and it was independent of that of willow leaves, indicating strong N homeostasis of the leaf beetle. We discussed the function of N homeostasis in herbivorous insects in tritrophic level interactions.
Writing About Defoe: What is a Critical Biography?
Authors: Richetti John
Published: January 2006

This essay considers traditional biographical approaches to literary figures and examines the validity of the connections that literary biography claims to make between life events and an author's writings. Proposing several exemplary instances of critical biographies of Samuel Johnson by Lipking and De Maria that focus instead on an author's writing, the essay compares their approaches to the assumptions that guide two biographies of Daniel Defoe by Novak and Backscheider. The essay examines Defoe's life and writings to explore just how his personal life can be clearly related to the writing, concluding that not enough is known about his life to warrant a purely biographical approach. Instead, the essay outlines a critical‐biographical method that focuses on Defoe's writing and its political and social circumstances.
Binding of the viral immunogenic octapeptide VSV8 to native glucose‐regulated protein Grp94 (gp96) and its inhibition by the physiological ligands ATP and Ca2+
Authors: Ying Ming , Flatmark Torgeir
Published: January 2006

The molecular chaperone Grp94 (gp96) of the endoplasmic reticulum (ER) lumen plays an essential role in the structural maturation and/or secretion of proteins destined for transport to the cell surface. Its proposed role in binding and transferring peptides for immune recognition is, however, controversial. Using SPR spectroscopy, we studied the interaction of native glycosylated Grp94 at neutral pH and 25 and 37 °C with the viral immunogenic octapeptide RGYVYQGL (VSV8), derived from vesicular stomatitis virus nucleoprotein (52–59). The peptide binds reversibly with low affinity ([A]0.5 ≈ 640 µm) and a hyperbolic binding isotherm, and the binding is partially inhibited by ATP and Ca2+ at concentrations that are present in the ER lumen, and the effects are explained by conformational changes in the native chaperone induced by these ligands. Our data present experimental support for the recent proposal that, under native conditions, VSV8 binds to Grp94 by an adsorptive, rather than a bioselective, mechanism, and thus further challenge the proposed in vivo peptide acceptor–donor function of the chaperone in the context of antigen‐presenting cell activation.
Comparative metal binding and genomic analysis of the avian (chicken) and mammalian metallothionein
Authors: Villarreal Laura , Tío Laura , Capdevila Mercè , Atrian Sílvia
Published: January 2006

Chicken metallothionein (ckMT) is the paradigm for the study of metallothioneins (MTs) in the Aves class of vertebrates. Available literature data depict ckMT as a one‐copy gene, encoding an MT protein highly similar to mammalian MT1. In contrast, the MT system in mammals consists of a four‐member family exhibiting functional differentiation. This scenario prompted us to analyse the apparently distinct evolutionary patterns followed by MTs in birds and mammals, at both the functional and structural levels. Thus, in this work, the ckMT metal binding abilities towards Zn(II), Cd(II) and Cu(I) have been thoroughly revisited and then compared with those of the mammalian MT1 and MT4 isoforms, identified as zinc‐ and copper‐thioneins, respectively. Interestingly, a new mechanism of MT dimerization is reported, on the basis of the coordinating capacity of the ckMT C‐terminal histidine. Furthermore, an evolutionary study has been performed by means of in silico analyses of avian MT genes and proteins. The joint consideration of the functional and genomic data obtained questions the two features until now defining the avian MT system. Overall, in vivo and in vitro metal‐binding results reveal that the Zn(II), Cd(II) and Cu(I) binding abilities of ckMT lay between those of mammalian MT1 and MT4, being closer to those of MT1 for the divalent metal ions but more similar to those of MT4 for Cu(I). This is consistent with a strong functional constraint operating on low‐copy number genes that must cope with differentiating functional limitation. Finally, a second MT gene has been identified in silico in the chicken genome, ckMT2, exhibiting all the features to be considered an active coding region. The results presented here allow a new insight into the metal binding abilities of warm blooded vertebrate MTs and their evolutionary relationships.
Replacement of helix 1′ enhances the lipid binding activity of apoE3 N‐terminal domain
Authors: Redmond Katherine A. , Murphy Conrad , Narayanaswami Vasanthy , Kiss Robert S. , Hauser Paul , Guigard Emmanuel , Kay Cyril M. , Ryan Robert O.
Published: January 2006

The N‐terminal domain of human apolipoprotein E (apoE‐NT) harbors residues critical for interaction with members of the low‐density lipoprotein receptor (LDLR) family. Whereas lipid free apoE‐NT adopts a stable four‐helix bundle conformation, a lipid binding induced conformational adaptation is required for manifestation of LDLR binding ability. To investigate the structural basis for this conformational change, the short helix connecting helix 1 and 2 in the four‐helix bundle was replaced by the sequence NPNG, introducing a β‐turn. Recombinant helix‐to‐turn (HT) variant apoE3‐NT was produced in Escherichia coli, isolated and characterized. Stability studies revealed a denaturation transition midpoint of 1.9 m guanidine hydrochloride for HT apoE3‐NT vs. 2.5 m for wild‐type apoE3‐NT. Wild‐type and HT apoE3‐NT form dimers in solution via an intermolecular disulfide bond. Native PAGE showed that reconstituted high‐density lipoprotein prepared with HT apoE3‐NT have a diameter in the range of 9 nm and possess binding activity for the LDLR on cultured human skin fibroblasts. In phospholipid vesicle solubilization assays, HT apoE3‐NT was more effective than wild‐type apoE3‐NT at inducing a time dependent decrease in dimyristoylphosphatidylglycerol vesicle light scattering intensity. In lipoprotein binding assays, HT apoE3‐NT protected human low‐density lipoprotein from phospholipase C induced aggregation to a greater extent that wild‐type apoE3‐NT. The results indicate that a mutation at one end of the apoE3‐NT four‐helix bundle markedly enhances the lipid binding activity of this protein. In the context of lipoprotein associated full‐length apoE, increased lipid binding affinity of the N‐terminal domain may alter the balance between receptor‐active and ‐inactive conformational states.
Modulation of oat arginine decarboxylase gene expression and genome organization in transgenic Trypanosoma cruzi epimastigotes
Authors: Serra María P. , Carrillo Carolina , González Nélida S. , Algranati Israel D.
Published: January 2006

We have previously demonstrated that wild‐type Trypanosoma cruzi epimastigotes lack arginine decarboxylase (ADC) enzymatic activity as well as its encoding gene. A foreign ADC has recently been expressed in T. cruzi after transformation with a recombinant plasmid containing the complete coding region of the oat ADC gene. In the present study, upon modulation of exogenous ADC expression, we found that ADC activity was detected early after transfection; subsequently it decreased to negligible levels between 2 and 3 weeks after electroporation and was again detected ≈ 4 weeks after electroporation. After this period, the ADC activity increased markedly and became expressed permanently. These changes of enzymatic activity showed a close correlation with the corresponding levels of ADC transcripts. To investigate whether the genome organization of the transgenic T. cruzi underwent any modification related to the expression of the heterologous gene, we performed PCR amplification assays, restriction mapping and pulse‐field gel electrophoresis with DNA samples or chromosomes obtained from parasites collected at different time‐points after transfection. The results indicated that the transforming plasmid remained as free episomes during the transient expression of the foreign gene. Afterwards, the free plasmid disappeared almost completely for several weeks and, finally, when the expression of the ADC gene became stable, two or more copies of the transforming plasmid arranged in tandem were integrated into a parasite chromosome (1.4 Mbp) bearing a ribosomal RNA locus. The sensitivity of transcription to α‐amanitin strongly suggests involvement of the protozoan RNA polymerase I in the transcription of the exogenous ADC gene.
Delineation of exoenzyme S residues that mediate the interaction with 14‐3‐3 and its biological activity
Authors: Yasmin Lubna , Jansson Anna L. , Panahandeh Tooba , Palmer Ruth H , Francis Matthew S. , Hallberg Bengt
Published: January 2006

14‐3‐3 proteins belong to a family of conserved molecules expressed in all eukaryotic cells, which play an important role in a multitude of signaling pathways. 14‐3‐3 proteins bind to phosphoserine/phosphothreonine motifs in a sequence‐specific manner. More than 200 14‐3‐3 binding partners have been found that are involved in cell cycle regulation, apoptosis, stress responses, cell metabolism and malignant transformation. A phosphorylation‐independent interaction has been reported to occur between 14‐3‐3 and a C‐terminal domain within exoenzyme S (ExoS), a bacterial ADP‐ribosyltransferase toxin from Pseudomonas aeruginosa. In this study, we have investigated the effect of amino acid mutations in this C‐terminal domain of ExoS on ADP‐ribosyltransferase activity and the 14‐3‐3 interaction. Our results suggest that leucine‐428 of ExoS is the most critical residue for ExoS enzymatic activity, as cytotoxicity analysis reveals that substitution of this leucine significantly weakens the ability of ExoS to mediate cell death. Leucine‐428 is also required for the ability of ExoS to modify the eukaryotic endogenous target Ras. Finally, single amino acid substitutions of positions 426–428 reduce the interaction potential of 14‐3‐3 with ExoS in vitro.
Mutagenesis of the central hydrophobic cluster in Aβ42 Alzheimer's peptide
Authors: de Groot Natalia Sánchez , Aviles Francesc X. , Vendrell Josep , Ventura Salvador
Published: January 2006

Protein misfolding and deposition underlie an increasing number of debilitating human disorders. Alzheimer's disease is pathologically characterized by the presence of numerous insoluble amyloid plaques in the brain, composed primarily of the 42 amino acid human β‐amyloid peptide (Aβ42). Disease‐linked mutations in Aβ42 occur in or near a central hydrophobic cluster comprising residues 17–21. We exploited the ability of green fluorescent protein to act as a reporter of the aggregation of upstream fused Aβ42 variants to characterize the effects of a large set of single‐point mutations at the central position of this hydrophobic sequence as well as substitutions linked to early onset of the disease located in or close to this region. The aggregational properties of the different protein variants clearly correlated with changes in the intrinsic physicochemical properties of the side chains at the point of mutation. Reduction in hydrophobicity and beta‐sheet propensity resulted in an increase of in vivo fluorescence indicating disruption of aggregation, as confirmed by the in vitro analysis of synthetic Aβ42 variants. The results confirm the key role played by the central hydrophobic stretch on Aβ42 deposition and support the hypothesis that sequence tunes the aggregation propensities of polypeptides.
Calcium, mitochondria and oxidative stress in neuronal pathology
Authors: Chinopoulos Christos , Adam‐Vizi Vera
Published: January 2006

The interplay among reactive oxygen species (ROS) formation, elevated intracellular calcium concentration and mitochondrial demise is a recurring theme in research focusing on brain pathology, both for acute and chronic neurodegenerative states. However, causality, extent of contribution or the sequence of these events prior to cell death is not yet firmly established. Here we review the role of the alpha‐ketoglutarate dehydrogenase complex as a newly identified source of mitochondrial ROS production. Furthermore, based on contemporary reports we examine novel concepts as potential mediators of neuronal injury connecting mitochondria, increased [Ca2+]cand ROS/reactive nitrogen species (RNS) formation; specifically: (a) the possibility that plasmalemmal nonselective cationic channels contribute to the latent [Ca2+]crise in the context of glutamate‐induced delayed calcium deregulation; (b) the likelihood of the involvement of the channels in the phenomenon of ‘Ca2+paradox’ that might be implicated in ischemia/reperfusion injury; and (c) how ROS/RNS and mitochondrial status could influence the activity of these channels leading to loss of ionic homeostasis and cell death.
A simple in vivo assay for measuring the efficiency of gene length‐dependent processes in yeast mRNA biogenesis
Authors: Morillo‐Huesca Macarena , Vanti Manuela , Chávez Sebastián
Published: January 2006

We have developed a simple reporter assay useful for detection and analysis of mutations and agents influencing mRNA biogenesis in a gene length‐dependent manner. We have shown that two transcription units sharing the same promoter, terminator and open reading frame, but differing in the length of their 3′‐untranslated regions, are differentially influenced by mutations affecting factors that play a role in transcription elongation or RNA processing all along the transcription units. In contrast, those mutations impairing the initial steps of transcription, but not affecting later steps of mRNA biogenesis, influence equally the expression of the reporters, independently of the length of their 3′‐untranslated regions. The ratio between the product levels of the two transcription units is an optimal parameter with which to estimate the efficiency of gene length‐dependent processes in mRNA biogenesis. The presence of a phosphatase‐encoding open reading frame in the two transcription units makes it very easy to calculate this ratio in any mutant or physiological condition. Interestingly, using this assay, we have shown that mutations in components of the SAGA complex affect the level of mRNA in a transcript length‐dependent fashion, suggesting a role for SAGA in transcription elongation. The use of this assay allows the identification and/or characterization of new mutants and drugs affecting transcription elongation and other related processes.
ANTIBIOTIC RESISTANCE OF CAMPYLOLOBACTER ISOLATED FROM AUTOMATED BROILER FARMS
Authors: DE MOURA OLIVEIRA KEILY ALVES , MENDONÇA REGINA CÉLIA SANTOS , DE OLIVEIRA GLAUCO VIEIRA , SODRÉ ARTHUR FREITAS
Published: January 2006

The use of the same antibiotics in animal food and conventional medicine can cause problems in the treatment of human diseases, because poultry frequently carry human pathogens. The aim of the present study was to determine the antibiotic resistances patterns of Campylobacter jejuni isolated from the rearing environment of broiler chickens – litter, drinking water, feed and the bird's cloaca. The results showed significant resistance to the following antibiotics: sulfonamide (77%), tetracycline (100%), erythromycin (80%) and penicillin G (100%). Intermediary resistance was present in bacitracin (90%), trimethoprim (100%), vancomycin (100%), chloramphenicol (97%), nalidixic acid (100%) and azithromycin (100%). However, new studies need to be carried out in Brazil to determine the resistance amplitude of this microorganism in other animals and humans. It is important to define some control strategies of the antibiotics used in animal production and human medicine.
PHILIPPINE FOODBORNE‐DISEASE OUTBREAKS (1995–2004)
Authors: AZANZA MA. PATRICIA V.
Published: January 2006

The study presented details about 60 reported Philippines foodborne outbreaks for the period of 1995–2004. It was established that meat‐containing dishes were the more common causes of the outbreaks evaluated, with spaghetti as the leading food vehicle. Common risk settings for the outbreaks were the food services of schools and workplaces. Salmonella and Vibrio spp. were cited as the primary causes of infections, while human intoxications involved staphylococcal enterotoxins, paralytic shellfish poisoning (PSP) toxins and histamine.
Carnot and the fields formulation of elementary thermodynamics
Authors: Hannay J. H.
Published: January 2006

Thermodynamics centers on the fact that work and heat are not functions of state. However, the natural formalism to capture this fact was not incorporated into thermodynamics because it was formulated before the development of vector field notation. One reason for reexamining this omission is provided by the work of Sadi Carnot that initiated thermodynamics. His results, which he derived from his grand principle, were not obtained by what is now called the 2nd law of thermodynamics or by the 1st law of thermodynamics. Instead they were obtained by a (co)vector formula, albeit expressed in words not symbols. Carnot’s formula allowed him to obtain several standard results of thermodynamics, including the Clausius-Clapeyron equation. The formula also implies the Maxwell relations.
Quantum mechanics of the 1∕x2 potential
Authors: Essin Andrew M. , Griffiths David J.
Published: January 2006

In quantum mechanics a localized attractive potential typically supports a (possibly infinite) set of bound states, characterized by a discrete spectrum of allowed energies, together with a continuum of scattering states, characterized (in one dimension) by an energy-dependent phase shift. The 1∕x2 potential on 0<x<∞ confounds all of our intuitions and expectations. Resolving its paradoxes requires sophisticated theoretical machinery: regularization, renormalization, anomalous symmetry-breaking, and self-adjoint extensions. Our goal is to introduce the essential ideas at a level accessible to advanced undergraduates.
STRUCTURAL AND ELECTRICAL PROPERTIES OF Nb5+ SUBSTITUTED PZT CERAMICS
Authors: THAKUR O. P. , PRAKASH CHANDRA
Published: January 2006

The effect of niobium doping on the structure and electrical properties with the following compositions Pb ( Zr 0.52 Ti 0.48)1-5X/4 Nb X O 3 with 0<x<0.025 was investigated. The materials were prepared by the usual ceramic technique using high purity raw materials. Disc-shaped samples of each compositions were sintered at 1250°C for 3 hours. The sample structure was determined by X-ray diffractometry. The average grain size, the maximum dielectric permittivity and the remnant polarization first increases up to x = 0.005 concentration of Nb 5+ and then decreases with higher concentration of niobium, while the coercive field does not show any variation. The transition temperature decreases with the increase in niobium concentration.
LIFT AND POWER REQUIREMENTS IN FLIGHT IN A DRAGONFLY
Authors: SUN MAO , WANG JI KANG
Published: January 2006

The lift and power requirements of a model dragonfly in forward flight are studied, using the method of numerically solving the Navier-Stokes equations. The graph of power against flight speed is U-shaped, suggesting that a dragonfly might have a preferred cruising speed. Considerable variation in the relative phase between fore- and hindwings results in only very small change in power requirement. This suggests theat the forewing-hingwing interaction is weak and furthermore, might explain why phase angles ranging from to are employed by dragonflies in hovering and forward flight.
NUMERICAL EXPERIMENTS OF THE SPECTRAL VOLUME METHOD FOR VISCOUS FLOWS
Authors: SUN YUZHI , WANG Z. J.
Published: January 2006

In this paper, the spectral volume (SV) method is experimented for the Navier-Stokes equations by treating the viscous terms with a mixed formulation named the local Discontinuous Galerkin approach. The formulation of the SV method for the two-dimensional compressible Navier-Stokes equations is described. The solver is used to solve several viscous flow problems to show its potential.
ADAPTIVE SOLUTION OF FLOW PAST TWO SIDE-BY-SIDE CIRCULAR CYLINDERS
Authors: DING H. , SHU C.
Published: January 2006

In this paper, a solution-adaptive finite difference method is presented for the simulation of flow past a pair of side-by-side circular cylinders. The method consists of an adaptive 5-point stencil algorithm, a central-difference spatial discretization and an immersed boundary representation of complex geometry. Numerical results indicate that the method is capable of solving the flow problems with complex geometry in a multilevel manner.
LES OF TURBULENT FLOW IN 3D SKEW BLADE PASSAGE OF A REACTING HYDRO TURBINE
Authors: ZHANG LIXIANG , WANG WENQUAN
Published: January 2006

The turbulent flow in a reacting hydro turbine was simulated with large eddy simulation (LES) to investigate the spatial and temporal distributions of the turbulence in a 3D skew blade passage. The simulations show that the intrinsic features are quite complicated. LES can capture the details of the structures, and the results are generally agreeable with those by direct numerical simulation.
SIMULATIONS OF TRANSONIC INVISCID FLOWS OVER AIRFOILS USING MESHFREE ADAPTIVE ALGORITHM
Authors: MA ZHIHUA , CHEN HONGQUAN
Published: January 2006

A new mesh free algorithm, which is both solution and geometry adaptive, is introduced and described in this paper to capture the physical features of inviscid flows modeled by the Euler equations. Only clouds of points instead of grids are distributed over the computational domain and the spatial derivatives of the Euler equations are estimated using a weighted least-square curve fit on local clouds of points. The adaptive approach is compared to traditional global refinement techniques using structured grids. In this procedure, unnecessary "grid" points in adjacent area are prevented from being generated by using mesh free local clouds refinement techniques. These techniques operate, in particular, in the vicinity of shock influencing regions and near large curvature regions including the boundary surface of the geometry. Several numerical experiments with Euler flow simulation around airfoils at transonic regimes will be presented to illustrate the potential of this methodology in terms of accuracy, efficiency and low computer memory requirement of the mesh free adaptive algorithm.
ON NONPARALLEL STABILITY OF THREE-DIMENSIONAL COMPRESSIBLE BOUNDARY LAYERS
Authors: LIU JIXUE , TANG DENGBIN , ZHU GUOXING
Published: January 2006

Nonparallel stability of the compressible boundary layers for three-dimensional configurations having large curvature variation on the surface is investigated by using the parabolic stability equations, which are derived from the Navier-Stokes equations in the curvilinear coordinate system. The difference schemes with fourth-order accuracy can be used in the entire computational regions. The global method is combined with the local method using a new iterative formula, thus more precise eigenvalues are obtained, and fast convergences are achieved. Computed curves of the amplification factor and shape functions of disturbances show clearly variable process of the flow stability, and agree well with other available results.
BEHAVIOR OF TVD LIMITERS ON THE SOLUTION OF NON-LINEAR HYPERBOLIC EQUATION
Authors: QURESHI K. R. , LEE C-H.
Published: January 2006

The main objective of the present work is to solve the non-linear inviscid Burger equation using the second-order TVD scheme with the different TVD limiters. These limiters include Non-MUSCL (monotone upwind scalar conservation laws) Harten-Yee upwind limiters, Roe-Sweby upwind limiters and Davis-Yee symmetric TVD limiters. These limiters are then used in conjunction with the explicit finite difference second order TVD scheme to model the flow in which discontinuity is present. Non-linear Burger equation was solved for this purpose to capture a one dimensional traveling discontinuity. Every limiter was individually tested for its ability to resolve the discontinuity in as few mesh point as possible. In addition, each limiter's capability to eliminate spurious oscillations associated with numerical computation of discontinuities was investigated. The results showed that all the TVD limiters were able to completely eliminate the spurious oscillations except Roe-Sweby limiter that caused the solution to diverge.
INFLUENCE OF STATIC AEROELASTIC DEFORMATION OF AN AIRPLANE ON THE AERODYNAMIC CHARACTERISTICS AND FLIGHTLOADS
Authors: DENG L. D. , WAN Z. Q. , YANG C.
Published: January 2006

The static aeroelastic characteristics of a flexible V-tail airplane were studied by the analyses of the variations of aerodynamic derivatives and flight loads versus flight dynamic pressure. The results show that the variation trends of aerodynamic derivatives and flight loads of the flexible airplane are different from those of the rigid airplane. Therefore, it is necessary to consider the static aeroelastic effects during the flexible airplane design.
A FICTITIOUS DOMAIN / DOMAIN DECOMPOSITION METHOD AND ITS APPLICATIONS
Authors: ZHOU CHUNHUA , YAO YONGFENG
Published: January 2006

In this article, the combination of fictitious domain and domain decomposition has been presented. First, we construct an equivalent variational formulation for the Dirichlet problem of linear elliptic operators and discuss the space approximation. Then the approach is applied to the incompressible Navier-Stokes equations, including construction of the variational formulation and time discretization by operator splitting. Finally, some numerical results are presented to validate our approach.
THE PHYSICAL ORIGIN OF SEVERE LOW-FREQUENCY PRESSURE FLUCTUATIONS IN GIANT FRANCIS TURBINES
Authors: ZHANG R.-K. , CAI Q.-D. , WU J.-Z. , WU Y.-L. , LIU S.-H. , ZHANG L.
Published: January 2006

The physical origin of severe low-frequency pressure fluctuation frequently observed in Francis hydraulic turbines under off-design conditions, which greatly damages the structural stability of turbines and even power stations, is analyzed based on the hydrodynamic stability theory and our Reynolds-averaged Navier-Stokes equation simulation (RANS) of the flow in the entire passage of a Francis turbine. We find that spontaneous unsteady vortex ropes, which induce severe pressure fluctuations, are formed due to the absolute instability of the swirling flow at the conical inlet of the turbine's draft tube.
THE THEORETICAL MODEL OF SHOCK WAVE ATTENUATION IN PMMA
Authors: YANG BO , CHEN XIAO , ZHAO RUI , SHEN ZHONG-HUA , LU JIAN , NI XIAO-WU
Published: January 2006

A new analytic model of the intense shock-wave decay is deduced in the paper based on self-consistent and well-defined assumptions. The shock wave attenuation in PMMA can be divided into two stages. In the initial decay, a spherical wave model is adopted because the dimension of the wave origin is too small to be neglected in comparison with the dimension of target. Due to overdamp at initial stage, the pressure gradient along the radial direction is expressed as dp/dr=f(∂p/∂t, du/dp) with the term (du/dp) deduced from the transient equation of wave front and the linear relation between the wave velocity and particle velocity at the wave rear. A temporal equicrural trapezoidal pressure profile applied to the target surface is used as the initial condition in order to obtain the pressure of ∂p/∂t. This pressure profile induces three stages of shock wave evolution: (1) The formation stage of "pressure increase"; (2) The plateau of "maximum pressure"; (3) The decay stage of "pressure decreases". According to the relation between the surge pressure of shock wave and laser power density, the character of laser-induced shock wave is described in detail. The above assumptions could not be applied in the final stage of propagation because the distorted "negative" pressure caused by the overdamp assumption would appear. In the final stage, the famous Taylor's equations of shock wave attenuation based on underdamp assumption are adopted. The theoretical model and the numerical results are in good agreement with the experiment.
TRUNCATION ERROR REDUCTION METHOD FOR POISSON EQUATION
Authors: XIA JIAN , LIU CHAOQUN
Published: January 2006

A new so-called truncation error reduction method (TERM) is developed in this work. This is an iterative process which initially uses a coarse grid (2h) to estimate the truncation error and then reduces the error on the original grid (h). The purpose of this method is to use multigrid technique to achieve high-order accuracy on simple stencils.
EFFECT OF SURFACE ROUGHNESS ON MASS TRANSFER IN A FLAT-PLATE MICROCHANNEL BIOREACTOR
Authors: ZENG Y. , LEE T. S. , YU P. , LOW H. T.
Published: January 2006

Surface roughness exists in most microfluidic devices due to the microfabrication technique or particle adhesion. In this study, a numerical model based on Finite Volume Method has been developed to simulate the mass transfer in a flat-plate microchannel bioreactor with semi-circular protrusions uniformly distributed on the bottom. The results show that the mass transfer in rough channel is enhanced, as shown by lower minimum species concentration in the rough channel compared with that in smooth channel. Non-dimensional parameters such as Peclet number (Pe), Damkohler number (Da) and the roughness size ratio (β) can influence the effect of roughness greatly. However, it is important to ensure that the minimum species concentration in the rough channel is adequate for cell growth. The results would provide guidance on the perfusion requirements to avoid solute depletion or toxicity during cell culture.
HIGH ORDER LOCALIZED ENO SCHEMES ON UNSTRUCTURED MESHES FOR CONSERVATION LAWS
Authors: ZHU JUN , ZHAO NING , ZHENG HUASHENG
Published: January 2006

We construct a localized finite volume method by applying ENO (essentially non-oscillatory) reconstruction to solve hyperbolic conservation laws following the partitions of the spectral volume methods. The main idea is as follows: Firstly, separate the calculating domain into intervals, named main-cells, then divide the intervals into subintervals, named sub-cells. Secondly, use ENO methodology to reconstruct conservative variables in the main-cells by using the cell averages of proper sub-cells. After that, use the TVD Runge-Kutta time discrete method to obtain fully discrete scheme. Several classic numerical tests show that this scheme has capabilities to capture discontinuities in high resolution and robustness.