bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of tissue transglutaminase on the solubility of proteins containing expanded polyglutamine repeats
Authors: Lai T.‐S. , Tucker T. , Burke J. R. , Strittmatter W. J. , Greenberg C. S.
Published: February 2004

The expansion of a polyglutamine (polyQ) domain in neuronal proteins is the molecular genetic cause of at least eight neurodegenerative diseases. Proteins with a polyQ domain that is greater than 40 Q (Q40) residues form insoluble intranuclear and cytoplasmic inclusions. Expanded polyQ proteins self‐associate by non‐covalent interactions and become insoluble. They can also be covalently cross‐linked by tissue transglutaminase (TTG), a calcium‐dependent enzyme present in cells throughout the nervous system. However, it remains unclear whether TTG cross‐linking directly contributes to the insolubility of the expanded polyQ proteins. Using an in vitro solubility assay, we found TTG cross‐linked Q62 monomers into high molecular weight soluble complexes in a calcium‐dependent reaction. Inhibition of TTG cross‐linking by primary amine substrates including putrescine and biotinylated pentylamine antagonized TTG's ability to form soluble complexes. In contrast, primary amines (histamine and lysine) that were less effective inhibitors of TTG cross‐linking did not inhibit Q62 from becoming insoluble. In summary, TTG can increase the solubility of expanded polyQ proteins by catalyzing intermolecular cross‐links. This demonstrates directly that TTG will reduce the ability of expanded polyQ proteins from becoming insoluble. Furthermore, the effectiveness of a primary amine substrate at inhibiting formation of insoluble inclusions may be related to their ability to inhibit intermolecular cross‐linking by TTG.
Mitochondrial calcium, oxidative stress and apoptosis in a neurodegenerative disease model induced by 3‐nitropropionic acid
Authors: Rosenstock T. R. , Carvalho A. C. P. , Jurkiewicz A. , Frussa‐Filho R. , Smaili S. S.
Published: February 2004

Intracellular calcium homeostasis is important for cell survival. However, increase in mitochondrial calcium (Ca2+m) induces opening of permeability transition pore (PTP), mitochondrial dysfunction and apoptosis. Since alterations of intracellular Ca2+ and reactive oxygen species (ROS) generation are involved in cell death, they might be involved in neurodegenerative processes such as Huntington's disease (HD). HD is characterized by the inhibition of complex II of respiratory chain and increase in ROS production. In this report, we studied the correlation between the inhibitor of the complex II, 3‐nitropropionic acid (3NP), Ca2+ metabolism, apoptosis and behavioural alterations. We showed that 3NP (1 mm) is able to release Ca2+m, as neither Thapsigargin (TAP, 2 µm) nor free‐calcium medium affected its effect. PTP inhibitors and antioxidants inhibited this process, suggesting an increase in ROS generation and PTP opening. In addition, 3NP (0.1 mm) also induces apoptotic cell death. Behavioural changes in animals treated with 3NP (20 mg/kg/day for 4 days) were also attenuated by pre‐ and co‐treatment with vitamin E (VE, 20 mg/kg/day). Taken together, our results show that complex II inhibition could involve Ca2+m release, oxidative stress and cell death that may precede motor alterations in neurodegenerative processes such as HD.
In vivo modulation of extracellular hippocampal glutamate and GABA levels and limbic seizures by group I and II metabotropic glutamate receptor ligands
Authors: Smolders Ilse , Lindekens Hilde , Clinckers Ralph , Meurs Alfred , O'Neill Michael J. , Lodge David , Ebinger Guy , Michotte Yvette
Published: February 2004

The effects of several metabotropic receptor (mGluR) ligands on baseline hippocampal glutamate and GABA overflow in conscious rats and the modulation of limbic seizure activity by these ligands were investigated. Intrahippocampal mGluR group I agonist perfusion via a microdialysis probe [1 mm (R,S)‐3,5‐dihydroxyphenylglycine] induced seizures and concomitant augmentations in amino acid dialysate levels. The mGlu1a receptor antagonist LY367385 (1 mm) decreased baseline glutamate but not GABA concentrations, suggesting that mGlu1a receptors, which regulate hippocampal glutamate levels, are tonically activated by endogenous glutamate. This decrease in glutamate may contribute to the reported LY367385‐mediated anticonvulsant effect. The mGlu5 receptor antagonist 2‐methyl‐6‐(phenylethynyl)‐pyridine (50 mg/kg) also clearly abolished pilocarpine‐induced seizures. Agonist‐mediated actions at mGlu2/3 receptors by LY379268 (100 µm, 10 mg/kg intraperitoneally) decreased basal hippocampal GABA but not glutamate levels. This may partly explain the increased excitation following systemic LY379268 administration and the lack of complete anticonvulsant protection within our epilepsy model with the mGlu2/3 receptor agonist. Group II selective mGluR receptor blockade with LY341495 (1–10 µm) did not alter the rats' behaviour or hippocampal amino acid levels. These data provide a neurochemical basis for the full anticonvulsant effects of mGlu1a and mGlu5 antagonists and the partial effects observed with mGlu2/3 agonists in vivo.
AICA riboside both activates AMP‐activated protein kinase and competes with adenosine for the nucleoside transporter in the CA1 region of the rat hippocampus
Authors: Gadalla Anne E. , Pearson Tim , Currie Ailsa J. , Dale Nicholas , Hawley Simon A. , Sheehan Mike , Hirst Warren , Michel Anton D. , Randall Andrew , Hardie D. Grahame , Frenguelli Bruno G.
Published: February 2004

5‐Aminoimidazole‐4‐carboxamide riboside (AICA riboside; Acadesine) activates AMP‐activated protein kinase (AMPK) in intact cells, and is reported to exert protective effects in the mammalian CNS. In rat cerebrocortical brain slices, AMPK was activated by metabolic stress (ischaemia > hypoxia > aglycaemia) and AICA riboside (0.1–10 mm). Activation of AMPK by AICA riboside was greatly attenuated by inhibitors of equilibrative nucleoside transport. AICA riboside also depressed excitatory synaptic transmission in area CA1 of the rat hippocampus, which was prevented by an adenosine A1 receptor antagonist and reversed by application of adenosine deaminase. However, AICA riboside was neither a substrate for adenosine deaminase nor an agonist at adenosine receptors. We conclude that metabolic stress and AICA riboside both stimulate AMPK activity in mammalian brain, but that AICA riboside has an additional effect, i.e. competition with adenosine for uptake by the nucleoside transporter. This results in an increase in extracellular adenosine and subsequent activation of adenosine receptors. Neuroprotection by AICA riboside could be mediated by this mechanism as well as, or instead of, by AMPK activation. Caution should therefore be exercised in ascribing an effect of AICA riboside to AMPK activation, especially in systems where inhibition of adenosine re‐uptake has physiological consequences.
Modulation ofnurr1gene expression in mesencephalic dopaminergic neurones
Authors: Volpicelli Floriana , Perrone‐Capano Carla , Da Pozzo Paola , Colucci‐D'Amato Luca , Di Porzio Umberto
Published: February 2004

The transcription factor/nuclear receptor Nurr1 is essential for the differentiation of midbrain dopaminergic neurones. Here we demonstrate that, during the ontogeny of rat ventral mesencephalon,nurr1gene expression is developmentally regulated and its levels show a sharp peak between embryonic day E13 and E15, when most dopaminergic neurones differentiate. In addition, in primary cultures from embryonic rat mesencephalon,nurr1gene follows a temporal pattern of expression comparable to that observedin vivo. We also report that exposure of embryonic mesencephalic cultures to depolarizing stimuli leads to a robust increase innurr1mRNA and protein. The depolarizing effect is also detected in mesencephalic cultures enriched in dopaminergic neurones by using a combination of bFGF and Sonic hedgehog. The latter further increases the number of dopaminergic neurones in these ‘expanded’ cultures, an effect abolished in the presence of anti‐Sonic hedgehog antibodies. Our data show thatnurr1gene is highly expressed in midbrain dopaminergic neurones in a sharp temporal window and that its expression is plastic, bothin vivoandin vitro. In addition we show that Sonic hedgehog can direct dopaminergic differentiation in proliferating dopaminergic neuroblastsin vitro.
Mutant superoxide dismutase 1 causes motor neuron degeneration independent of cyclin‐dependent kinase 5 activation by p35 or p25
Authors: Takahashi Satoru , Kulkarni Ashok B.
Published: February 2004

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by selective loss of motor neurons in the brain and spinal cord. Neurotoxicity mediated by glutamate is thought to play a role in the neuronal death through intracellular calcium‐dependent signaling cascades. Cyclin‐dependent kinase 5 (Cdk5) has been proposed as one of the calcium‐dependent mediators that may cause neuronal death observed in this disease. Cdk5 is activated in neurons by the association with its activators, p35 or p39. The calcium‐activated protease calpain cleaves p35 to its truncated product, p25, which eventually causes the cellular mislocalization and prolonged activation of Cdk5. This deregulated Cdk5 induces cytoskeletal disruption and apoptosis. To examine whether inhibition of the calpain‐mediated conversion of p35 to p25 can delay the disease progression of ALS, we generated double transgenic mice in which ALS‐linked mutant copper/zinc superoxide dismutase 1 (SOD1G93A) was expressed in a p35‐null background. The absence of p35 neither affected the onset and progression of motor neuron disease in the mutant SOD1 mice nor ameliorated the pathological lesions in these mice. Our results provide direct evidence that the pathogenesis of motor neuron disease in the mutant SOD1 mice is independent of the Cdk5 activation by p35 or p25.
The neurotrophic effect of oleic acid includes dendritic differentiation and the expression of the neuronal basic helix‐loop‐helix transcription factor NeuroD2
Authors: Rodríguez‐Rodríguez Rosa A. , Tabernero Arantxa , Velasco Ana , Lavado Eva M. , Medina José M.
Published: February 2004

We have shown recently that the presence of albumin in astrocytes triggers the synthesis and release of oleic acid, which behaves as a neurotrophic factor for neurons. Thus, oleic acid promotes axonal growth together with the expression of the axonal growth‐associated protein, GAP‐43. Here we attempted to elucidate whether the neurotrophic effect of oleic acid includes dendritic differentiation. Our results indicate that oleic acid induces the expression of microtubule associated protein‐2 (MAP‐2), a marker of dendritic differentiation. In addition, the presence of oleic acid promotes the translocation of MAP‐2 from the soma to the dendrites. The time course of MAP‐2 expression during brain development coincides with that of stearoyl‐CoA desaturase, the limiting enzyme of oleic acid synthesis, indicating that both phenomena coincide during development. The effect of oleic acid on MAP‐2 expression is most probably independent of autocrine factors synthesized by neurons because this effect was also observed at low cellular densities. As oleic acid is an activator of protein kinase C, the possible participation of this transduction pathway was studied. Our results indicate that added oleic acid or oleic acid endogenously synthesized by astrocytes exerts its neurotrophic effect through a protein kinase C‐dependent mechanism as the effect was inhibited by sphingosine or two myristoylated peptide inhibitors of protein kinase C. The transduction pathway by which oleic acid induces the expression of genes responsible for neuronal differentiation appears to be mediated by the transcription factor NeuroD2, a regulator of terminal neuronal differentiation.
Stimulus‐ and cell‐type‐specific release of purines in cultured rat forebrain astrocytes and neurons
Authors: Parkinson Fiona E. , Xiong Wei
Published: February 2004

Adenosine is formed during conditions that deplete ATP, such as ischemia. Adenosine deaminase converts adenosine into inosine, and both adenosine and inosine can be beneficial for postischemic recovery. This study investigated adenosine and inosine release from astrocytes and neurons during chemical hypoxia or oxygen–glucose deprivation. In both cell types, 2‐deoxyglucose was the most effective stimulus for depleting cellular ATP and for evoking inosine release; in contrast, oxygen–glucose deprivation evoked the greatest adenosine release. α,β‐Methylene ADP, an inhibitor of ecto‐5′nucleotidase, significantly reduced adenosine release from astrocytes but not neurons. Dipyridamole, an inhibitor of equilibrative nucleoside transporters, inhibited both adenosine and inosine release from neurons. Erythro‐9‐(2‐hydroxy‐3‐nonyl)adenine, an inhibitor of adenosine deaminase, reduced neuronal inosine release evoked by oxygen–glucose deprivation but not by 2‐deoxyglucose treatment. These data indicate that (1) astrocytes release adenine nucleotides that are hydrolyzed extracellularly to adenosine, whereas neurons release adenosine per se, (2) inosine is formed intracellularly and released via nucleoside transporters, and (3) inosine is formed by an adenosine deaminase‐dependent pathway during oxygen–glucose deprivation but not during 2‐deoxyglucose treatment. In summary, the metabolic pathways for adenosine formation and release were cell‐type dependent whereas the pathways for inosine formation were stimulus dependent.
Expression of glucose transporter isoform GLUT‐2 and glucokinase genes in human brain
Authors: Roncero Isabel , Alvarez Elvira , Chowen Julie A. , Sanz Carmen , Rábano Alberto , Vázquez Patricia , Blázquez Enrique
Published: February 2004

The glucose transporter isoform‐2 (GLUT‐2) and glucokinase are considered to be components of a glucose sensor system controlling several key processes, and hence may modulate feeding behaviour. We have found GLUT‐2 and glucokinase mRNAs in several brain regions, including the ventromedial and arcuate nuclei of the hypothalamus. GLUT‐2, glucokinase and glucokinase regulatory protein mRNAs and proteins were present in these areas as determined by biochemical approaches. In addition, glucose‐phosphorylating activity with a high apparent Km for glucose that displayed no product inhibition by glucose‐6‐phosphate was observed. Increased glycaemia after meals may be recognized by specific hypothalamic neurones due to the high Km of GLUT‐2 and glucokinase. This enzyme is considered to be the true glucose sensor because it catalyses the rate‐limiting step of glucose catabolism its activity being regulated by interaction with glucokinase regulatory protein, that functions as a metabolic sensor.
α7‐Nicotinic acetylcholine receptors mediate an Aβ1−42‐induced increase in the level of acetylcholinesterase in primary cortical neurones
Authors: Fodero L. R. , Mok S. S. , Losic D. , Martin L. L. , Aguilar M. I. , Barrow C. J. , Livett B. G. , Small D. H.
Published: February 2004

The β‐amyloid protein (Aβ) is the major protein component of amyloid plaques found in the Alzheimer brain. Although there is a loss of acetylcholinesterase (AChE) from both cholinergic and non‐cholinergic neurones in the brain of Alzheimer patients, the level of AChE is increased around amyloid plaques. Previous studies using P19 cells in culture and transgenic mice which overexpress human Aβ have suggested that this increase may be due to a direct action of Aβ on AChE expression in cells adjacent to amyloid plaques. The aim of the present study was to examine the mechanism by which Aβ increases levels of AChE in primary cortical neurones. Aβ1−42 was more potent than Aβ1−40 in its ability to increase AChE in primary cortical neurones. The increase in AChE was unrelated to the toxic effects of the Aβ peptides. The effect of Aβ1−42 on AChE was blocked by inhibitors of α7 nicotinic acetylcholine receptors (α7 nAChRs) as well as by inhibitors of L‐ or N‐type voltage‐dependent calcium channels (VDCCs), whereas agonists of α7 nAChRs (choline, nicotine) increased the level of AChE. The results demonstrate that the effect of Aβ1−42 on AChE is due to an agonist effect of Aβ1−42 on the α7 nAChR.
Testosterone amplifies excitotoxic damage of cultured oligodendrocytes
Authors: Caruso A. , Di Giorgi Gerevini V. , Castiglione M. , Marinelli F. , Tomassini V. , Pozzilli C. , Caricasole A. , Bruno V. , Caciagli F. , Moretti A. , Nicoletti F. , Melchiorri D.
Published: February 2004

An overactivation of α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate (AMPA)/kainate receptors has been implicated in the pathophysiology of oligodendrocyte damage in demyelinating disorders of the CNS. We decided to examine the effect of testosterone on excitotoxic death of oligodendrocytes because a gender difference exists in the incidence and disease course of multiple sclerosis. Short‐term pure cultures of oligodendrocytes (4 days in vitro) were exposed to a brief pulse with kainate or AMPA + cyclothiazide for the induction of excitotoxicity. Exposure to testosterone enantate was slightly toxic per se and amplified both AMPA and kainate toxicity. Testosterone treatment induced all gene targets of p53, and amplified the induction of these genes induced by kainate. The effect of testosterone was mediated by the activation of androgen receptors and was resistant to the aromatase inhibitors, dl‐aminoglutethimide and 4‐hydroxyandrost‐4‐ene‐3,17‐dione. Testosterone treatment also potentiated the stimulation of 45Ca2+ influx induced by AMPA + cyclothiazide or kainate without changing the expression of the glutamate receptor (GluR) 1, ‐2/3, and ‐4 subunits of AMPA receptors or the GluR6/7 subunits of kainate receptors. We conclude that testosterone amplifies excitotoxic damage of oligodendrocytes acting at an early step of the death cascade triggered by AMPA/kainate receptors.
Effect of Auxin Transport Inhibitors and Ethylene on the Wood Anatomy of Poplar
Authors: Junghans U. , Langenfeld‐Heyser R. , Polle A. , Teichmann T.
Published: February 2004

Abstract: The influence of the auxin transport inhibitors naphthylphthalamic acid (NPA) and methyl‐2‐chloro‐9‐hydroxyflurene‐9‐carboxylate (CF), as well as the gaseous hormone ethylene on cambial differentiation of poplar was determined. NPA treatment induced clustering of vessels and increased vessel length. CF caused a synchronized differentiation of cambial cells into either vessel elements or fibres. The vessels in CF‐treated wood were significantly smaller and fibre area was increased compared with controls. Under the influence of ethylene, the cambium produced more parenchyma, shorter fibres and shorter vessels than in controls. Since poplar is the model tree for molecular biology of wood formation, the modulation of the cambial differentiation of poplar towards specific cell types opens an avenue to study genes important for the development of vessels or fibres.
Poplar Genomics is Getting Popular: The Impact of the Poplar Genome Project on Tree Research
Authors: Tuskan G. A. , DiFazio S. P. , Teichmann T.
Published: February 2004

Abstract: Trees, due to their long life‐span, have characteristics that distinguish them from annual, herbaceous plants. It is likely that many of these properties are based on a tree‐specific genetic foundation. The U.S. Department of Energy initiated a genome‐sequencing project for Populus, a model perennial plant. Through international collaboration and input to the sequencing effort, the annotated whole genome sequence of Populus trichocarpa will be released to the public in early 2004. This genomic resource will, for the first time, allow comparison between a perennial and an annual plant on a whole genome basis and therefore provide clues for molecular research on tree‐specific questions like dormancy, development of a secondary cambium, juvenile‐mature phase change, or long‐term host‐pest interactions. The approximately 520 Mbp of annotated genomic sequence will complement and expand the knowledge provided so far by the 125 000 ESTs from poplar that are available in public databases. This article introduces the international poplar research programmes and points out the significance of the poplar genome project for plant research.
Induction of Poplar Leaf Nitrate Reductase: A Test of Extrachloroplastic Control of Isoprene Emission Rate
Authors: Rosenstiel T. N. , Ebbets A. L. , Khatri W. C. , Fall R. , Monson R. K.
Published: February 2004

Abstract: Several recent studies have suggested that control of isoprene emission rate is in part exerted by supply of extrachloroplastic phosphoenolpyruvate to the chloroplast. To test this hypothesis, we altered PEP supply by differential induction of cytosolic nitrate reductase (NR) and PEP carboxylase (PEPC) in plants of Populus deltoides grown with NO3− or NH4+ as the sole nitrogen source. Growth with 8 mM NH4+ produced a high leaf nitrogen concentration, compared with 8 mM NO3−, as well as slightly elevated rates of photosynthesis and significantly enhanced rates of isoprene emission and content of dimethylallyl diphosphate (DMAPP, a precursor to isoprene biosynthesis), chlorophyll (a+b) and carotenoids. Growth with 8 mM NO3− resulted in parallel reductions in both leaf isoprene emission rate and DMAPP. The differential effects of growth with NH4+ or NO3− were not observed when plants were grown with 4 mM nitrogen. The effects of reduced DMAPP availability were specific to isoprene emission and were not propagated to higher isoprenoids, as the correlations between nitrogen content and either leaf chlorophyll (a+b) or total carotenoids were unaffected by nitrogen source. Biochemical analysis revealed significantly higher levels of NR and PEPC activity in leaves of 8 mM NO3−‐grown plants, consistent with their fundamental roles in nitrate assimilation. Taken together, these results support the hypothesis that foliar assimilation of NO3− reduces isoprene emission rate by competing for carbon skeletons (mediated by PEPC) within the cytosol and possibly reductant within the chloroplast. Cytosolic competition for PEP is a major regulator of chloroplast DMAPP supply, and we offer a new “safety valve” hypothesis to explain why plants emit isoprene.
Expressed Sequence Tags from Poplar Wood Tissues ‐ A Comparative Analysis from Multiple Libraries
Authors: Déjardin A. , Leplé J.‐C. , Lesage‐Descauses M.‐C. , Costa G. , Pilate G.
Published: February 2004

Abstract: Xylogenesis involves successive developmental processes ‐ cambial division, cell expansion and differentiation, cell death ‐ each occurring along a gradient from the cambium to the pith of the stem. Taking advantage of the high level of organisation of wood tissues, we isolated cambial zone (CZ), differentiating xylem (DX) and mature xylem (MX) from both tension wood (TW) and opposite wood (OW) of bent poplars. Four different cDNA libraries were then constructed and used to generate 10 062 EST, reflecting the genes expressed in the different wood tissues. For the most abundant clusters, the EST distributions were compared between libraries in order to identify genes specific or over‐represented at some specific developmental stages. They clearly showed a developmental shift between CZ and DX, whereas there is a continuity of development between DX and MX. CZ was mainly characterized by clusters of genes involved in cell cycle, protein synthesis and fate. Interestingly, two clusters with no assigned function were found specific to the cambial zone. In DX and MX, clusters were mostly involved in methylation of lignin precursors and microtubule cytoskeleton. In addition, in DX, EST from TW and OW were compared: five clusters of arabinogalactan proteins, one for sucrose synthase and one for fructokinase were specific or over‐represented in TW. Moreover, a putative transcription factor and a cluster of unknown function were also identified in DX‐TW. The informative comparison of multiple libraries prepared from wood tissues led to the identification of genes ‐ some with still unknown functions ‐ putatively involved in xylogenesis and tension wood formation.
T‐DNA and Transposon Tagging in Aspen
Authors: Fladung M. , Deutsch F. , Hönicka H. , Kumar S.
Published: February 2004

Abstract: We have investigated the somatic activity of the maize Activator (Ac) element in haploid and diploid aspen with the objective of developing an efficient transposon‐based system for gene isolation in the model tree species Populus. It was shown that Ac is reinserted, frequently into or near coding regions in aspen, and therefore can be used for gene tagging studies. A number of phenotypic variants were also found following transformation of constructs harbouring the rolC gene. Comparative analyses of T‐DNA flanking regions of variants and wild type lines indicate that T‐DNA insertion has occurred in or near coding regions. However, the frequency of T‐DNA insertion into genes is about one half of the frequency of Ac insertion hitting coding sequences. The results obtained give a proof‐of‐concept for transposon tagging in a tree system. Given the long generation cycles in tree species, gene tagging strategies are practical only to obtain dominant gain‐of‐function mutants that do not require selfing or test crossing. In order to obtain recessive loss‐of‐function mutants, we have regenerated haploid lines from immature pollen. These lines were successfully transformed with a construct containing the rolC transgene from Agrobacterium rhizogenes and Ac element from maize. The results indicate that Ac is also active in haploid aspen and hence can be used in general for gene tagging in trees.
Liquid Phase Fluorescence in situ RT‐PCR Analysis for Gene Expression Analysis in Woody Stems
Authors: Gray‐Mitsumune M. , Abe H. , Takahashi J. , Sundberg B. , Mellerowicz E. J.
Published: February 2004

Abstract: We explore a rapid in situ RT‐PCR protocol for gene expression studies in woody stem tissues. In situ RT‐PCR was performed using fluorescent dye‐conjugated nucleic acid and the fluorescence signals derived from target RNAs were detected using confocal laser scanning microscopy. The signal to background ratio was greatly enhanced by performing two rounds of PCR reactions, first without the fluorescent dye and second with the dye. Using this protocol, we obtained strong gene‐specific signals in secondary stem tissues. The signals were PCR‐dependent, as shown by the lack of cytoplasmic signals in the tissue sections in which either DNA polymerase or primers were omitted from PCR reactions, and were RNA‐dependent, as shown by great reduction of cytoplasmic signals when sections were treated with RNase before RT reactions. To verify our protocol, transcript localization of the rbcS gene was examined in secondary stems of hybrid aspen (Populus tremula L. ×tremuloides Michx.) and compared to the chlorophyll autofluorescence signal. The in situ RT‐PCR signals form the rbcS gene and chlorophyll autofluorescence co‐localized in the same cell types. The signal was also confirmed by Northern blot analysis of isolated RNA from the cambium and developing xylem, thus confirming the validity of the protocol. Some difficulties of in situ transcript localization and the interpretation of the signal distribution in the secondary tissues are discussed.
Fluorescent Proteins in Poplar: A Useful Tool to Study Promoter Function and Protein Localization
Authors: Nowak K. , Luniak N. , Meyer S. , Schulze J. , Mendel R. R. , Hänsch R.
Published: February 2004

Abstract: The jellyfish (Aequorea victoria) green fluorescent protein (GFP) and its variants (CFP [cyan] and YFP [yellow]) were successfully used as a vital marker system for the transformation of hybrid poplar (Populus tremula×P. alba). Our results show that, in this woody plant, fluorescent proteins can be expressed: (i) transiently in protoplasts after PEG‐mediated transformation, as well as in leaf cells after particle bombardment, and (ii) stably in callus cells and plants after Agrobacterium‐mediated transformation. For these studies, we constructed vectors permitting easy recloning of any promoter fragments of interest. Confocal laser scanning microscopy was used both for visualization and differentiation between the different colours of the GFP variants and autofluorescence of chlorophyll and lignified xylem vessels. Peroxisomes were chosen as target organelles for GFP translocation via the peroxisomal targeting sequence PTS1 because this allowed us to concentrate the fluorochrome in the small volume of a few peroxisomes, giving a bright fluorescence over background noise.
Akuter Lumbago - ein funktioneller Ansatz
Authors: Debroux Jean-Jaques
Published: February 2004

Funktionelle und MLF-Techniken dienen der Homöostase. Zu ihnen zählen Strain-Counterstrain, Fazilitierter Positional Release, Sutherlands Gelenktechniken und die Faszientechniken. Als Erklärungsansatz für Letztere wird eine funktionelle Kontinuität zwischen den muskulären, faszialen und ligamentären Strukturen angenommen, die aber nicht bewiesen ist.
Der "Diagnostic Touch" von Rollin E. Becker
Authors: Seider Roger
Published: February 2004

Beckers Diagnostic Touch als Diagnostik des faszialen Systems baut auf den Begriff der Potenz als "Region der Stille" auf, deren Palpation erst erlernt werden muss, sowie auf den Begriff des Fulcrums als Unterstützungspunkt, mit dem die Potenz palpiert werden kann. Um den Diagnostic Touch zu entwickeln, sollte schrittweise vorgegangen werden.
Nonstationary behavior in a delayed feedback traveling wave tube folded waveguide oscillator
Authors: Ryskin N. M. , Titov V. N. , Han S. T. , So J. K. , Jang K. H. , Kang Y. B. , Park G. S.
Published: February 2004

Folded waveguide traveling-wave tubes (FW TWT) are among the most promising candidates for powerful compact amplifiers and oscillators in millimeter and submillimeter wave bands. In this paper, the nonstationary behavior of a FW TWT oscillator with delayed feedback is investigated. Starting conditions of the oscillations are derived analytically. Results of numerical simulation of single-frequency, self-modulation (multifrequency) and chaotic generation regimes are presented. Mode competition phenomena, multistability and hysteresis are discussed.
The electric double layer at a metal electrode in pure water
Authors: Brüesch Peter , Christen Thomas
Published: February 2004

Pure water is a weak electrolyte that dissociates into hydronium ions and hydroxide ions. In contact with a charged electrode a double layer forms for which neither experimental nor theoretical studies exist, in contrast to electrolytes containing extrinsic ions like acids, bases, and solute salts. Starting from a self-consistent solution of the one-dimensional modified Poisson–Boltzmann equation, which takes into account activity coefficients of point-like ions, we explore the properties of the electric double layer by successive incorporation of various correction terms like finite ion size, polarization, image charge, and field dissociation. We also discuss the effect of the usual approximation of an average potential as required for the one-dimensional Poisson–Boltzmann equation, and conclude that the one-dimensional approximation underestimates the ion density. We calculate the electric potential, the ion distributions, the pH-values, the ion-size corrected activity coefficients, and the dissociation constants close to the electric double layer and compare the results for the various model corrections.
Quartz capillary flow meter for gases
Authors: Berg Robert F.
Published: February 2004

This article describes an accurate meter for gas flow rates below 1000 μmol/s. (1 μmol/s≅1.3 cm3/min at 0 °C and 1 atm). Two gauges measure the input and output pressures as the gas flows through a flow element consisting of either a single quartz capillary or an array of parallel quartz capillaries. A hydrodynamic model determines the molar flow rate from the two pressures, the gas temperature, and the gas properties. Measurements with nitrogen demonstrated that three flow elements could span the flow range from 0.1 to 1000 μmol/s with a standard uncertainty of less than 0.03%. Additional measurements with helium, argon, propane, and sulfur hexafluoride demonstrated that, by using the capillary radius determined for nitrogen, the model could predict the flow rates of gases with widely varying properties.
Dust acoustic solitary waves and double layers in a dusty plasma with two-temperature trapped ions
Authors: El-Labany S. K. , El-Taibany W. F. , Mamun A. A. , Moslem Waleed M.
Published: February 2004

The combined effects of trapped ion distribution, two-ion-temperature, dust charge fluctuation, and dust fluid temperature are incorporated in the study of nonlinear dust acoustic waves in an unmagnetized dusty plasma. It is found that, owing to the departure from the Boltzmann ion distribution to the trapped ion distribution, the dynamics of small but finite amplitude dust acoustic waves is governed by a modified Korteweg–de Vries equation. The latter admits a stationary dust acoustic solitary wave solution, which has stronger nonlinearity, smaller amplitude, wider width, and higher propagation velocity than that involving adiabatic ions. The effect of two-ion-temperature is found to provide the possibility for the coexistence of rarefactive and compressive dust acoustic solitary structures and double layers. Although the dust fluid temperature increases the amplitude of the small but finite amplitude solitary waves, the dust charge fluctuation does the opposite effect. The present investigation should help us to understand the salient features of the nonlinear dust acoustic waves that have been observed in a recent numerical simulation study.
Third order nonlinear optical susceptibility of Cu:Al2O3 nanocomposites: From spherical nanoparticles to the percolation threshold
Authors: del Coso R. , Requejo-Isidro J. , Solis J. , Gonzalo J. , Afonso C. N.
Published: February 2004

The third order optical susceptibility of metal-dielectric nanocomposite films (Cu:Al2O3) has been determined by degenerate four wave mixing. The films have been synthesized by alternate pulsed laser deposition and consisted of Cu nanoparticles in an amorphous Al2O3 matrix. They have metal volume fractions, p, ranging from 0.07 to 0.45, and morphologies that range from spherical particles (diameter, φ∼2 nm) to a random network when close to the percolation threshold. In nanocomposites containing isolated oblate spheroids (p⩽0.17), the optical response at wavelengths close to that of the surface plasmon resonance (SPR) can be described in the frame of the Maxwell-Garnett effective medium theory. Above the particle coalescence threshold, in nanocomposites with higher Cu content (p⩾0.2), both the linear absorption in the near-infrared and the third order nonlinear optical susceptibility at the SPR are greatly enhanced, the latter achieving values as high as 1.8×10−7 esu. These results are discussed in terms of multipolar interactions among particles and giant local resonance effects that appear as a consequence of the particle coalescence and the increase in size of the nanocrystals.
Impulsive control for synchronization of a class of continuous systems
Authors: Wang Yan-Wu , Guan Zhi-Hong , Xiao Jiang-Wen
Published: February 2004

An impulsive control theory for synchronization of a class of continuous systems is developed. A sufficient condition for the impulsive control is derived. The proposed impulsive control scheme is illustrated by some continuous chaotic systems and the simulation results demonstrate the effectiveness of the method.
Shock to detonation transition in a plastic bonded explosive
Authors: Bourne N. K. , Milne A. M.
Published: February 2004

It is important to define a methodology to assess the safe handling conditions of explosive materials. Such a route must be simple enough to capture relevant mechanisms in order to construct a modeling capability. To this end, a series of plate impact experiments has been undertaken in order to characterize the unreacted Hugoniot of a research, castable, plastic-bonded explosive (PBX) RF-38-22. A second program, using embedded particle velocity sensors, has been undertaken to investigate the shock to detonation transition (SDT) in the PBX. The experimental facility is described, the techniques used are discussed, the material is introduced, and results obtained are reported. The data obtained have been used to calibrate a hydrocode model for SDT based on viscoplastic ignition and subsequent grain burning, with pressure-dependent kinetics. This model is described, and results of calculations are presented. This represents the program in the construction of the methodology. It is hoped that further work will increase its applicability.
Beryllium’s monocrystal and polycrystal elastic constants
Authors: Migliori Albert , Ledbetter Hassel , Thoma D. J. , Darling T. W.
Published: February 2004

Using resonant-ultrasound spectroscopy, we measured beryllium’s elastic constants for both a monocrystal and a polycrystal. Thus, we consider the monocrystal–polycrystal elastic-constant relationship for hexagonal symmetry. Beside the Cij, we report the Debye characteristic temperature Θ and the Grüneisen parameter γ. We comment on beryllium’s chemical bonding and its remarkably low Poisson ratio.
Metastable iron silicide phase formation by pulsed laser annealing
Authors: Comrie C. M. , Falepin A. , Richard O. , Bender H. , Vantomme A.
Published: February 2004

Thin films of ε-FeSi were grown by deposition of Fe on a Si〈111〉 substrate under ultrahigh vacuum conditions, followed by in situ annealing at 450 °C. These ε-FeSi films were subjected to irradiation from a pulsed excimer laser in the energy density range 0.30–0.90 J/cm2, in order to study the phase formation and crystallization processes of metastable [CsCl]Fe1−xSi phases. The samples were analyzed by Rutherford backscattering and channeling spectrometry and by cross-sectional transmission electron microscopy. Considerable diffusion of silicon into the silicide film was found to occur during the pulsed laser annealing, resulting in a film with nonstochiometric composition. In contrast to solid phase reaction, epitaxial ordering in the iron silicide film is observed during pulsed laser annealing when the film’s composition approaches that of FeSi2. Analysis by cross-sectional transmission electron microscopy confirmed that the phase which exhibits epitaxial ordering corresponds to the metastable [CsCl]Fe1−xSi phase. Upon annealing at 600 °C for 1 h, this metastable phase converts into the semiconducting β-FeSi2.
Optimal mixing in recirculation zones
Authors: Noack Bernd R. , Mezić Igor , Tadmor Gilead , Banaszuk Andrzej
Published: February 2004

Coarse-scale mixing in a recirculation zone is described with a simple vortex model. Time-dependent forcing is employed to change the vortex motion and mixing properties. An optimal mixing problem is defined in which the flux across the recirculation region shall be maximized under the side-constraints of bounded vortex motion and bounded actuation. Concepts of control theory and chaotic advection are used to achieve this goal. In particular, controllability is proven with a transformation into flat coordinates. Thus, a feedforward law for the optimal trajectory and a feedback law for its stabilization are derived. Observability of the vortex motion is indicated by a dynamic observer. Mixing in the optimized flow is studied using Poincaré maps. The low-frequency modulations to vortex motion are shown to substantially increase mixing in the average. Generalizations of the mathematical framework for mixing optimization are suggested for a larger class of models and flows.
Optical monitor for measuring the amplitude and phase of perturbations on the surface of a capillary jet in a high-speed cell sorter
Authors: Lansdorp Bob M. , Nelson Peter I. , Petersen Timothy W. , van den Engh Ger
Published: February 2004

High-speed jet-in-air cell sorters analyze and sort thousands of cells a second. The key to the accuracy and purity of their operation is the ability to maintain a stable location on the jet where the stream breaks into individual droplets. The physics of the instability of a capillary jet are well understood and date back to the 19th century. The time it takes for a jet of liquid to break into droplets depends exponentially on the amplitude of perturbations that develop on the surface of the jet. In this work, we describe a method to monitor the amplitude of these perturbations on the surface of a liquid jet using a novel detector. This detector may be combined with feedback mechanisms to actively stabilize the break off point in modern cell sorters. We also show that this detector can accurately monitor the phase of the perturbations with respect to the driving element, and this phase information, in turn, can be used to improve sort rates for high-throughput cell sorters.
Slotted-plate apparatus to measure yield stress of suspensions
Authors: Zhu L. , Papadopoulos K. D. , De Kee D.
Published: February 2004

A procedure is described to build a slotted-plate device to directly measure the static yield stress of a suspension. The technique involves a balance as well as a linear motion platform. A slotted plate is suspended from the balance and is vertically positioned in a suspension sample which stands on the platform. The yield stress is determined from the point where initially constant slope of the force versus platform travel distance changes. Wall effects associated with the original plate yield-stress instrument were minimized by opening a series of slots on the plates. Yield-stress values of both high-concentration (40, 50, 60, and 70 wt % TiO2) and low-concentration (2, 3, and 5 wt % bentonite) aqueous suspensions were measured. Very small yield-stress values (down to ∼10−4 Pa) could be determined with our slotted-plate device. Other methods, such as the popular vane technique, could not measure yield-stress values of the bentonite suspensions for concentrations less than 7 wt %, corresponding to a yield stress of 1.29 Pa.
Soft x-ray magnetic circular dichroism at 2 K: A tool in biological inorganic chemistry
Authors: Funk T. , Friedrich S. , Young A. T. , Arenholz E. , Delano R. , Cramer S. P.
Published: February 2004

X-ray magnetic circular dichroism (XMCD) is the asymmetric absorption of left- and right-handed circularly polarized x rays and can be used to measure element-specific spin and oxidation states and magnetic moments. We have built an end station for XMCD spectroscopy to study transition metals located in the active sites of proteins and inorganic model compounds. The instrument is equipped with a 6 T superconducting magnet and a liquid helium cooled sample stage designed for experiments at temperatures as low as 2.2 K and beyond 160 K. Sample heating by infrared radiation is minimized using a liquid helium cooled heat shield with 100-nm-thick Al windows. We demonstrate the capabilities of the apparatus in a total electron yield study on the model compound [(F8–TPP)Fe–O–Cu(TMPA)]+. We show that Fe and Cu are antiferromagnetically coupled by comparing the polarity of the XMCD signal at the respective L-edges. We discuss the capability of the instrument to study dilute (<1000 ppm) transition metals in proteins using partial fluorescence yield.
Control of synchrotron x-ray diffraction by means of standing acoustic waves
Authors: Zolotoyabko E. , Quintana J. P.
Published: February 2004

Synchrotron x-ray diffraction measurements in quartz crystals of different thickness excited by standing acoustic waves were carried out at the Advanced Photon Source of Argonne National Laboratory. We demonstrated the ability to significantly modify the quartz rocking curves for 20–25 keV x rays by changing the shear wave parameters in the frequency range between 15 and 105 MHz. Dynamic deformation introduced into the crystal lattice by acoustic waves resulted in a remarkable broadening of the rocking curves. The broadening effect strongly depends on the strength of the ultrasound, which can be easily regulated by changing the acoustic amplitude or frequency near the resonance. The maximum rocking curve broadening reached 17 times, which corresponds to the wavelength band, Δλ/λ=4×10−3, when used as a monochromator or analyzer for 20–25 keV x rays. The initial rocking curve shape is restored by sweeping the acoustic frequency within a 50–100 kHz range near the resonance. The tunable broadening effect allows effective manipulation of x-ray intensities in time domain. Time-resolved x-ray diffraction measurements under a 19.6 MHz acoustic wave excitation were performed by synchronizing the acoustic wave and x-ray burst periodicity. We used the fact that twice per period the standing wave produces a zero net deformation across the crystal thickness. By introducing an oscillating delay to the acoustic excitation, we were able to effectively change the phase of the acoustic wave relative to the x-ray burst periodicity. The x-ray diffraction intensity was strongly affected by tuning the timing of the x-ray arrivals to the minimum or maximum acoustic deformation. A deep modulation of x rays was observed in a wide frequency range between 0.1 Hz and 1 MHz, which certifies that acoustically excited quartz crystals can potentially be used as slow and fast x-ray modulators with high duty cycle.
New bioreactor for in situ simultaneous measurement of bioluminescence and cell density
Authors: Picart Pascal , Bendriaa Loubna , Daniel Philippe , Horry Habib , Durand Marie-José , Jouvanneau Laurent , Thouand Gérald
Published: February 2004

This article presents a new device devoted to the simultaneous measurement of bioluminescence and optical density of a bioluminescent bacterial culture. It features an optoelectronic bioreactor with a fully autoclavable module, in which the bioluminescent bacteria are cultivated, a modulated laser diode dedicated to optical density measurement, and a detection head for the acquisition of both bioluminescence and optical density signals. Light is detected through a bifurcated fiber bundle. This setup allows the simultaneous estimation of the bioluminescence and the cell density of the culture medium without any sampling. The bioluminescence is measured through a highly sensitive photomultiplier unit which has been photometrically calibrated to allow light flux measurements. This was achieved by considering the bioluminescence spectrum and the full optical transmission of the device. The instrument makes it possible to measure a very weak light flux of only a few pW. The optical density is determined through the laser diode and a photodiode using numerical synchronous detection which is based on the power spectrum density of the recorded signal. The detection was calibrated to measure optical density up to 2.5. The device was validated using the Vibrio fischeri bacterium which was cultivated under continuous culture conditions. A very good correlation between manual and automatic measurements processed with this instrument has been demonstrated. Furthermore, the optoelectronic bioreactor enables determination of the luminance of the bioluminescent bacteria which is estimated to be 6×10−5 W sr−1 m−2 for optical density=0.3. Experimental results are presented and discussed.