bluuebunny/crossref_metadata_2025 huggingface dataset:
Dreaming and Episodic Memory: A Functional Dissociation?
Authors: Fosse Magdalena J. , Fosse Roar , Hobson J. Allan , Stickgold Robert J.
Published: February 2003

The activity that takes place in memory systems during sleep is likely to be related to the role of sleep in memory consolidation and learning, as well as to the generation of dream hallucinations. This study addressed the often-stated hypothesis that replay of whole episodic memories contributes to the multimodal hallucinations of sleep. Over a period of 14 days, 29 subjects kept a log of daytime activities, events, and concerns, wrote down any recalled dreams, and scored the dreams for incorporation of any waking experiences. While 65% of a total of 299 sleep mentation reports were judged to reflect aspects of recent waking life experiences, the episodic replay of waking events was found in no more than 1–2% of the dream reports. This finding has implications for understanding the unique memory processing that takes place during the night and is consistent with evidence that sleep has no role in episodic memory consolidation.
Semantic Processing in the Left Inferior Prefrontal Cortex: A Combined Functional Magnetic Resonance Imaging and Transcranial Magnetic Stimulation Study
Authors: Devlin Joseph T. , Matthews Paul M. , Rushworth Matthew F. S.
Published: February 2003

The involvement of the left inferior prefrontal cortex (LIPC) in phonological processing is well established from both lesion-deficit studies with neurological patients and functional neuroimaging studies of normals. Its involvement in semantic processing, on the other hand, is less clear. Although many imaging studies have demonstrated LIPC activation during semantic tasks, this may be due to implicit phonological processing. This article presents two experiments investigating semantic functions in the LIPC. Results from a functional magnetic resonance imaging experiment demonstrated that both semantic and phonological processing activated a common set of areas within this region. In addition, there was a reliable increase in activation for semantic relative to phonological decisions in the anterior LIPC while the opposite comparison (phonological vs. semantic decisions) revealed an area of enhanced activation within the posterior LIPC. A second experiment used transcranial magnetic stimulation (TMS) to temporarily interfere with neural information processing in the anterior portion of the LIPC to determine whether this region was essential for normal semantic performance. Both repetitive and single pulse TMS significantly slowed subjects' reactions for the semantic but not for the perceptual control task. Our results clarify the functional anatomy of the LIPC by demonstrating that anterior and posterior regions contribute to both semantic and phonological processing, albeit to different extents. In addition, the findings go beyond simply establishing a correlation between semantic processing and activation in the LIPC and demonstrate that a transient disruption of processing selectively interfered with semantic processing.
COLLABORATIVE TACTICS FOR NESTSITE SELECTION BY PAIRS OF BLUE FOOTED BOOBIES
Authors: Stamps Judy , Calderón-De Anda Miriam , Perez Carmen , Drummond Hugh
Published: February 2003

The dual concern model suggests that pairs of animals can use four different behavioural strategies to resolve disputes that arise when making joint decisions. Based on their reproductive biology, we predicted that mated pairs of blue footed boobies would use one of these strategies, collaboration, when deciding on a location for their nest. Many of the behaviour tactics diagnostic of collaboration were observed in boobies. For instance, nestsite selection was accompanied by extensive exchanges of a specialized communication signal (nestpointing), rates of nestpointing at a given site were strongly related to the likelihood that a pair would select that site for their nest, couples in which the male and female 'disagreed' about the merits of an initial site went on to investigate additional sites together ('expanding the pie'), individuals pointed at maximal rates at a site only after their partner had already pointed at that same site ('feeling out procedures'), and both sexes appeared to have 'veto power' over potential nestsites, in the sense that a site was virtually never accepted for the nest if one of the two partners failed to point at that site prior to clutch initiation. These results support the hypothesis that mated pairs of blue footed boobies may use collaborative tactics when selecting a nestsite; descriptive accounts suggest that similar tactics may occur in other birds in which mated pairs jointly decide on the location for their nest.
'LAST WORD' EFFECTS OF MALE ADVERTISING CALLS ON FEMALE PREFERENCE IN LITTLE BLUE PENGUINS
Authors: Miyazaki Masamine , Waas Joseph
Published: February 2003

Playback experiments were conducted to investigate how advertising call overlap between male little blue penguins, Eudyptula minor, influenced other birds along shorelines in front of breeding colonies. We used a dual-speaker design in which calls from one speaker consistently overlapped those from the other speaker. Females approached overlapping advertising calls more than overlapped calls or a silent control speaker. At a proximate level, this might have occurred because 'masking effects' obscure information in overlapped calls that females require for mate choice. Alternatively, females may simply be able to locate overlapping calls (i.e. the last call they heard) more easily. Young birds and adult males did not distinguish between calling patterns. It is possible that call overlap is associated with dominance or other quality indicators; thus, females may approach overlappers more often because they represent higher quality mates.
INFLUENCE OF COLLECTIVE FEEDING ON WEIGHT GAIN AND SIZE VARIABILITY OF ANELOSIMUS JABAQUARA LEVI 1956 (ARANEAE: THERIDIIDAE)
Authors: De Oliveira Gonzaga Marcelo , Vasconcellos-Neto João
Published: February 2003

Differences in the size and weight of spiders within colonies may be an important factor for determining dispersion and food distribution among nestmates. In this study we report on the variation in size of spiders from 27 colonies of A. jabaquara, collected during one year. We also conducted an experiment under laboratory conditions to test if prey size, and consequently, collective or individual capture behaviours, influence the establishment of weight differences. Female size variation within colonies was high, increasing slightly from March to September. However, from November to January the variation was much lower, probably as a consequence of the emigration of large spiders during the reproductive period. Spiders that fed on large flies in the laboratory experiment grew more and collective feeding seemed to induce a larger variation in weight among individuals. These results indicate that collective feeding promotes an unequal distribution of food in A. jabaquara colonies.
Nebulization and anti-Pseudomonas aeruginosa activity of colistin
Authors: Diot P , Gagnadoux F , Martin C , Ellataoui H , Furet Y , Breteau M , Boissinot E , Lemarie E
Published: February 2003

Colistin aerosols are frequently administered to patients with cystic fibrosis. However, questions arise concerning the effect of both jet and ultrasonic nebulizers on the properties of the drug. The aim of this study was to characterize the anti-Pseudomonas aeruginosa (PA) activity of colistin after jet (Pari LL) and ultrasonic (DP100) nebulization. A bench study was performed by capturing the aerosols, determining the drug mass, and assessing its anti-PA activity. Because the inhaled mass of colistin had to be entirely recovered for the bacteriological study, it was assessed by isotopic methods, mixing the drug with a 99mTc-labelled tracer and demonstrating that 99mTc activity accurately predicted the mass of colistin. Colistin was extracted from the filters and its antibiotic activity was determined using the method employed for the study of the bacteriostatic and bactericidal power of serum on the ATCC 27853 PA strain. The postnebulization minimum inhibitory concentrations (MIC) were 1.9 micrograms.mL-1 with DP100 and 0.5 microgram.mL-1 with Pari LL. These values were less than two dilutions different from the 1 microgram.mL-1 MIC of non-nebulized colistin. We conclude that neither jet nebulization nor ultrasonic nebulization alter the antibiotic properties of colistin and that both systems can be used to nebulize colistin.
Sleep-related laryngospasm
Authors: Thurnheer R , Henz S , Knoblauch A
Published: February 2003

The term "sleep-related laryngospasm" refers to episodic, abrupt interruption of sleep accompanied by feelings of acute suffocation followed by stridor. The condition is included in the diagnostic and coding manual of the American Sleep Disorders Association (ASDA), but there are few references in the peer-reviewed literature. Our description of the distinct clinical picture associated with this condition is based on an analysis of the histories of a series of 10 patients. The patients and their families gave precise, uniform accounts of the dramatic attacks. Diagnostic work-up included pulmonary and gastroenterological assessment. All patients reported sudden awakening from sleep due to feelings of acute suffocation, accompanied by intense fear. Apnoea lasting 5-45 s was followed by stridor. Breathing returned to normal within minutes. Patients were left exhausted by the attacks. Nine of our 10 patients had evidence of gastro-oesophageal reflux and six responded to antireflux therapy. We conclude that the nocturnal choking attacks (and the occasional daytime attacks experienced by some of the patients) are caused by laryngospasm. The pathogenesis of the apparent underlying laryngeal irritability is unknown. The condition may be related to a gastro-oesophageal reflux.
Production of interleukin-8, RANTES and MCP-1 in intrinsic and extrinsic asthmatics
Authors: Folkard SG , Westwick J , Millar AB
Published: February 2003

The aim of this study was to determine the relative production of chemokines interleukin-8 (IL-8), regulated on activation, normal T-cell expressed and secreted (RANTES) and monocyte chemotactic protein-1 (MCP-1) by intrinsic and extrinsic asthmatics. Nine intrinsic asthmatics, 10 extrinsic asthmatics, five nonatopic and five atopic controls underwent bronchoalveolar lavage (BAL). Total BAL cells were cultured in the presence or absence of lipopolysaccharide. Chemokines were measured in BAL cell supernatants and in cell-free bronchoalveolar lavage fluid (BALF) by enzyme-linked immunoabsorbent assay (ELISA). BAL cell cytospins were stained immunohistochemically for chemokines. BAL cells from asthmatics produced more IL-8 than controls (statistically significant for extrinsic asthma). RANTES was elevated in the BAL cell supernatants of four out of nine intrinsic asthmatics as compared to nonatopic controls (not statistically significant). RANTES levels in the BAL cell supernatants of extrinsic asthmatics were all low. MCP-1 production by BAL cells was similar in all groups. Immunostaining of BAL cell cytospins showed the macrophage to be the predominant positive-staining cell type and correlated well with supernatant data. Measurement of chemokines in BALF showed significantly elevated IL-8 in intrinsic asthma compared to nonatopic controls, but no increase in extrinsic asthmatics relative to atopic control RANTES was elevated in three out of nine BALFs from intrinsic asthmatics compared with nonatopic controls (not statistically significant). MCP-1 was not elevated above control levels in BALF of either asthma group. These results suggest an up-regulation in the production of interleukin-8 and regulated on activation, normal T-cell expressed and secreted, but not monocyte chemotactic protein-1 (MCP-1), by macrophages in the bronchoalveolar lavage of asthmatic subjects. In addition, the data suggest that regulated on activation, normal T-cell, expressed and secreted, may be differentially produced by macrophages in atopic and nonatopic asthma.
Flow-dependent effect of formoterol dry-powder inhaled from the Aerolizer
Authors: Nielsen KG , Skov M , Klug B , Ifversen M , Bisgaard H
Published: February 2003

The output and size distribution of aerosols from dry powder inhalers are dependent on the flow rate through the device. Therefore, in an in vivo study, we examined the flow-dependency of the effect of formoterol when delivered from a dry powder inhaler, the Aerolizer, in a flow range relevant to schoolchildren. In a preliminary study comprising 126 asthmatic children aged 3-10 yrs, the relationship between age and peak inspiratory flow (PIF) rate through the Aerolizer was determined. Mean PIF was 104 L.min-1 and all children aged > 5 yrs performed a PIF > 60 L.min-1. Sixteen children aged 8-15 yrs with exercise-induced asthma (EIA) took part in the main trial comparing the protective effect of 12 micrograms formoterol inhaled at 60 and 120 L.min-1. The effect from high and low inspiratory flow was judged from the protective effect against EIA 12 h after drug administration. The decrease in forced expiratory volume in one second (FEV1) after exercise was 34% on the placebo day, but only 15% when formoterol was inhaled at the high flow rate. This difference was statistically significant. The decrease in FEV1 was 23% after treatment with formoterol inhaled at the low flow rate, that was not significantly different from placebo or from high-flow formoterol treatment. These clinical findings correspond with the in vitro findings of flow-dependent fine particle mass from the Aerolizer, and corroborate the relationship between fine particle mass of aerosol and clinical effect. The results indicate a flow-dependent effect of formoterol dry powder inhaled from the Aerolizer, within the range of inspiratory flow rate obtainable by school-children. This questions its applicability in children with asthma.
Airway deposition and airway effects of antiasthma drugs delivered from metered-dose inhalers
Authors: Pauwels R , Newman S , Borgstrom L
Published: February 2003

Many different metered-dose inhalation devices are becoming available for the treatment of airway diseases. Each of these inhalers differs in its delivery characteristics. An assessment of the efficacy of drug delivery by these inhalers is essential, in view of their therapeutic use. A review of the literature on the relationship between airway deposition and airway effects of drugs delivered from metered-dose inhalers is presented. Nebulizers or spacers are not discussed. The effect of an inhaler depends on the characteristics of the inhaler and the inhalation manoeuvre performed by the patient. This review focuses on the influence of inhaler characteristics on the airway deposition and airway effects. Data from several studies show that there is a significant relationship between the amount of drug deposited in the airways and the airway effects of the drug. Studies on the relationship between airway deposition and airway effect have been troubled by methodological problems, such as the absence of multiple dose comparisons and the difficulty in obtaining steep dose-response curves. The techniques for measuring airway deposition of inhaled drugs, namely the scintigraphic and the pharmacokinetic method, are discussed and compared. The appropriate use of these techniques can help to define and compare the drug delivery characteristics of different devices, thus enabling inhaled therapy to be optimized.
Migratory pulmonary infiltrates in a patient treated with sotalol
Authors: Faller M , Quoix E , Popin E , Gangi A , Gasser B , Mathelin C , Pauli G
Published: February 2003

Beta-blockers may induce several types of adverse respiratory reaction such as asthma, interstitial lung disease with or without pleural effusion, systemic lupus erythematosus or hypersensitivity pneumonitis. More recently, bronchiolitis obliterans with organizing pneumonia (BOOP) has been described. We report here on pulmonary migratory infiltrates with combined histopathological features of both BOOP and eosinophilic pneumonia in a woman treated with sotalol long-term. The patient improved only partially with steroids. Tapering off corticosteroid dosage resulted in relapse, and complete recovery was only obtained after sotalol was stopped.
Eosinophilic pneumonia as a presentation of occult chronic granulomatous disease
Authors: Trawick D , Kotch A , Matthay R , Homer RJ
Published: February 2003

We present a case of invasive pulmonary aspergillosis (IPA) in a previously healthy young woman who presented with what initially appeared to be an acute eosinophilic pneumonia. A second lung biopsy taken after treatment with steroids showed invasive Aspergillus with associated necrotizing granulomas, a pattern commonly found in chronic granulomatous disease (CGD). Both siblings, and by extrapolation, the patient, were actually found to have CGD. A review of the literature revealed other cases of presumed immunocompetent patients with IPA with presentations and lung histopathology similar to that of our patient. We conclude that chronic granulomatous disease presenting in the adult may be more common than previously assumed, and that patients previously presumed immunocompetent, but with granulomatous invasive pulmonary aspergillosis, may have chronic granulomatous disease. Furthermore, and most devastatingly in this case, the presentation may simulate a recently described steroid responsive acute lung disease, acute eosinophilic pneumonia.
Polarization of theC. eleganszygote proceeds via distinct establishment and maintenance phases
Authors: Cuenca Adrian A. , Schetter Aaron , Aceto Donato , Kemphues Kenneth , Seydoux Geraldine
Published: February 2003

Polarization of the C. elegans zygote along the anterior-posterior axis depends on cortically enriched (PAR) and cytoplasmic (MEX-5/6) proteins,which function together to localize determinants (e.g. PIE-1) in response to a polarizing cue associated with the sperm asters. Using time-lapse microscopy and GFP fusions, we have analyzed the localization dynamics of PAR-2, PAR-6,MEX-5, MEX-6 and PIE-1 in wild-type and mutant embryos. These studies reveal that polarization involves two genetically and temporally distinct phases. During the first phase (establishment), the sperm asters at one end of the embryo exclude the PAR-3/PAR-6/PKC3 complex from the nearby cortex, allowing the ring finger protein PAR-2 to accumulate in an expanding `posterior'domain. Onset of the establishment phase involves the non-muscle myosin NMY-2 and the 14-3-3 protein PAR-5. The kinase PAR-1 and the CCCH finger proteins MEX-5 and MEX-6 also function during the establishment phase in a feedback loop to regulate growth of the posterior domain. The second phase begins after pronuclear meeting, when the sperm asters begin to invade the anterior. During this phase (maintenance), PAR-2 maintains anterior-posterior polarity by excluding the PAR-3/PAR-6/PKC3 complex from the posterior. These findings provide a model for how PAR and MEX proteins convert a transient asymmetry into a stably polarized axis.
XOtx5b and XOtx2regulate photoreceptor and bipolar fates in theXenopusretina
Authors: Viczian Andrea S. , Vignali Robert , Zuber Michael E. , Barsacchi Giuseppina , Harris William A.
Published: February 2003

Photoreceptor and bipolar cells are molecularly related cell types in the vertebrate retina. XOtx5b is expressed in both photoreceptors and bipolars, while a closely related member of the same family of transcription factors, XOtx2, is expressed in bipolar cells only. Lipofection of retinal precursors with XOtx5b biases them toward photoreceptor fates whereas a similar experiment with XOtx2 promotes bipolar cell fates. Domain swap experiments show that the ability to specify different cell fates is largely contained in the divergent sequence C-terminal to the homeodomain,while the more homologous N-terminal and homeodomain regions of both genes,when fused to VP16 activators, promote only photoreceptor fates.XOtx5b is closely related to Crx and like Crx it drives expression from an opsin reporter in vivo. XOtx2 suppresses this XOtx5b-driven reporter activity providing a possible explanation for why bipolars do not express opsin. Similarly, co-lipofection ofXOtx2 with XOtx5b overrides the latter's ability to promote photoreceptor fates and the combination drives bipolar fates. The results suggest that the shared and divergent parts of these homologous genes may be involved in specifying the shared and distinct characters of related cell types in the vertebrate retina.
Tbx4-Fgf10system controls lung bud formation during chicken embryonic development
Authors: Sakiyama Jun-ichi , Yamagishi Atsushi , Kuroiwa Atsushi
Published: February 2003

The respiratory primordium is positioned and its territory is defined in the foregut. The visceral mesoderm of the respiratory primordium acquires the inducing potential that is necessary for endodermal budding morphogenesis and respiratory endoderm formation. Tbx4, a member of the T-box transcription factor gene family, was specifically expressed in the visceral mesoderm of the lung primordium. To analyze the function of Tbx4, we ectopically expressed Tbx4 in the visceral mesoderm of the foregut using in ovo electroporation. Ectopic Tbx4 induced ectopic bud formation in the esophagus by activating the expression of Fgf10. Conversely,interference of Tbx4 function resulted in repression of Fgf10expression and in failure of lung bud formation. In addition, ectopic Tbx4 or Fgf10 also induced ectopic expression of Nkx2.1, a marker gene specific for the respiratory endoderm, in the underlying esophagus endoderm. When the border of the Tbx4 expression domain, which demarcates the respiratory tract and the esophagus, was disturbed by misexpression ofTbx4, formation of the tracheo-esophageal septum failed. These results suggested that Tbx4 governs multiple processes during respiratory tract development; i.e. the initial endodermal bud formation,respiratory endoderm formation, and septation of the respiratory tract and the esophagus.
Genome-wide identification of in vivoDrosophilaEngrailed-binding DNA fragments and related target genes
Authors: Solano Pascal Jean , Mugat Bruno , Martin David , Girard Franck , Huibant Jean-Marc , Ferraz Conchita , Jacq Bernard , Demaille Jacques , Maschat Florence
Published: February 2003

Chromatin immunoprecipitation after UV crosslinking of DNA/protein interactions was used to construct a library enriched in genomic sequences that bind to the Engrailed transcription factor in Drosophilaembryos. Sequencing of the clones led to the identification of 203 Engrailed-binding fragments localized in intergenic or intronic regions. Genes lying near these fragments, which are considered as potential Engrailed target genes, are involved in different developmental pathways, such as anteroposterior patterning, muscle development, tracheal pathfinding or axon guidance. We validated this approach by in vitro and in vivo tests performed on a subset of Engrailed potential targets involved in these various pathways. Finally, we present strong evidence showing that an immunoprecipitated genomic DNA fragment corresponds to a promoter region involved in the direct regulation of frizzled2 expression by engrailed in vivo.
BDNF regulates spontaneous correlated activity at early developmental stages by increasing synaptogenesis and expression of the K+/Cl- co-transporter KCC2
Authors: Aguado Fernando , Carmona Maria A. , Pozas Esther , Aguiló Agustín , Martínez-Guijarro Francisco J. , Alcantara Soledad , Borrell Victor , Yuste Rafael , Ibañez Carlos F. , Soriano Eduardo
Published: February 2003

Spontaneous neural activity is a basic property of the developing brain,which regulates key developmental processes, including migration, neural differentiation and formation and refinement of connections. The mechanisms regulating spontaneous activity are not known. By using transgenic embryos that overexpress BDNF under the control of the nestin promoter, we show here that BDNF controls the emergence and robustness of spontaneous activity in embryonic hippocampal slices. Further, BDNF dramatically increases spontaneous co-active network activity, which is believed to synchronize gene expression and synaptogenesis in vast numbers of neurons. In fact, BDNF raises the spontaneous activity of E18 hippocampal neurons to levels that are typical of postnatal slices.

We also show that BDNF overexpression increases the number of synapses at much earlier stages (E18) than those reported previously. Most of these synapses were GABAergic, and GABAergic interneurons showed hypertrophy and a 3-fold increase in GAD expression. Interestingly, whereas BDNF does not alter the expression of GABA and glutamate ionotropic receptors, it does raise the expression of the recently cloned K+/Cl- KCC2 co-transporter, which is responsible for the conversion of GABA responses from depolarizing to inhibitory, through the control of the Cl-potential. Together, results indicate that both the presynaptic and postsynaptic machineries of GABAergic circuits may be essential targets of BDNF actions to control spontaneous activity. The data indicate that BDNF is a potent regulator of spontaneous activity and co-active networks, which is a new level of regulation of neurotrophins. Given that BDNF itself is regulated by neuronal activity, we suggest that BDNF acts as a homeostatic factor controlling the emergence, complexity and networking properties of spontaneous networks.
The p27cip/kip orthologdacapomaintains theDrosophilaoocyte in prophase of meiosis I
Authors: Hong Amy , Lee-Kong Steven , Iida Takako , Sugimura Isamu , Lilly Mary A.
Published: February 2003

Animal oocytes undergo a highly conserved developmental arrest in prophase of meiosis I. Often this marks a period of rapid growth for the oocyte and is necessary to coordinate meiotic progression with the developmental events of oogenesis. In Drosophila, the oocyte develops within a 16-cell germline cyst. Throughout much of oogenesis, the oocyte remains in prophase of meiosis I. By contrast, its 15 mitotic sisters enter the endocycle and become polyploid in preparation for their role as nurse cells. How germline cysts establish and maintain these two independent cell cycles is unknown. We demonstrate a role for the p21CIP/p27Kip1/p57Kip2-like cyclin-dependent kinase inhibitor (cki) dacapo in the maintenance of the meiotic cycle in Drosophila oocytes. Our data indicate that it is through the differential regulation of the cki Dacapo that two modes of cell-cycle regulation are independently maintained within the common cytoplasm of ovarian cysts.
Bicarbonate actions on flagellar and Ca2+-channel responses:initial events in sperm activation
Authors: Wennemuth Gunther , Carlson Anne E. , Harper Andrew J. , Babcock Donner F.
Published: February 2003

At mating, mammalian sperm are diluted in the male and female reproductive fluids, which brings contact with HCO3- and initiates several cellular responses. We have identified and studied two of the most rapid of these responses. Stop-motion imaging and flagellar waveform analysis show that for mouse epididymal sperm in vitro, the resting flagellar beat frequency is 2-3 Hz at 22-25°C. Local perfusion with HCO3- produces a robust, reversible acceleration to 7 Hz or more. At 15 mM the action of HCO3- begins within 5 seconds and is near-maximal by 30 seconds. The half-times of response are 8.8±0.2 seconds at 15 mM HCO3- and 17.5±0.4 seconds at 1 mM HCO3-. Removal of external HCO3- allows a slow return to basal beat frequency over ∼10 minutes. Increases in beat symmetry accompany the accelerating action of HCO3-. As in our past work,HCO3- also facilitates opening of voltagegated Ca2+ channels, increasing the depolarization-evoked rate of rise of intracellular Ca2+ concentration by more than fivefold. This action also is detectable at 1 mM HCO3- and occurs with an apparent halftime of ∼60 seconds at 15 mM HCO3-. The dual actions of HCO3- respond similarly to pharmacological intervention. Thus, the phosphodiesterase inhibitor IBMX promotes the actions of HCO3- on flagellar and channel function, and the protein kinase A inhibitor H89 blocks these actions. In addition, a 30 minute incubation with 60 μM cAMP acetoxylmethyl ester increases flagellar beat frequency to nearly 7 Hz and increases the evoked rates of rise of intracellular Ca2+ concentration from 17±4 to 41±6 nM second-1. However, treatment with several other analogs of cAMP produces only scant evidence of the expected mimicry or blockade of the actions of HCO3-, perhaps as a consequence of limited permeation. Our findings indicate a requirement for cAMP-mediated protein phosphorylation in the enhancement of flagellar and channel functions that HCO3- produces during sperm activation.
Dp1is required for extra-embryonic development
Authors: Kohn Matthew J. , Bronson Roderick T. , Harlow Ed , Dyson Nicholas J. , Yamasaki Lili
Published: February 2003

Release of E2F1/DP1 heterodimers from repression mediated by the retinoblastoma tumor suppressor (pRB) triggers cell cycle entry into S phase,suggesting that E2F1 and DP1 proteins must act in unison, either to facilitate or to suppress cell-cycle progression. In stark contrast to the milder phenotypes that result from inactivation of E2Fs, we report that loss ofDp1 leads to death in utero because of the failure of extra-embryonic development. Loss of Dp1 compromises the trophectoderm-derived tissues — specifically, the expansion of the ectoplacental cone and chorion, and endoreduplication in trophoblast giant cells. Inactivation ofp53 is unable to rescue the Dp1-deficient embryonic lethality. Thus, DP1 is absolutely required for extra-embryonic development and consequently embryonic survival, consistent with E2F/DP1 normally acting to promote growth in vivo.
Developing with lethal RA levels: genetic ablation ofRargcan restore the viability of mice lackingCyp26a1
Authors: Abu-Abed Suzan , Dollé Pascal , Metzger Daniel , Wood Caroline , MacLean Glenn , Chambon Pierre , Petkovich Martin
Published: February 2003

We have previously reported that the retinoic acid (RA) catabolizing enzyme CYP26A1 plays an important role in protecting tail bud tissues from inappropriate exposure to RA generated in the adjacent trunk tissues by RALDH2, and that Cyp26a1-null animals exhibit spina bifida and caudal agenesis. We now show that, in the absence of Cyp26a1, retinoic acid receptor gamma (RARγ) mediates ectopic RA-signaling in the tail bud. We also show that activated RARγ results in downregulation ofWnt3a and Fgf8, which integrate highly conserved signaling pathways known for their role in specifying caudal morphogenesis. Ablation of the gene for RARγ (Rarg) rescues Cyp26a1-null mutant animals from caudal regression and embryonic lethality, thus demonstrating that CYP26A1 suppresses the RA-mediated downregulation of WNT3A and FGF8 signaling pathways by eliminating ectopic RA in gastrulating tail bud mesoderm.
Quiescent center formation in maize roots is associated with an auxin-regulated oxidizing environment
Authors: Jiang Keni , Meng Yu Ling , Feldman Lewis J.
Published: February 2003

Embedded within the meristem of all Angiosperm roots is a population of slowly dividing cells designated the quiescent center (QC). In maize roots the QC can constitute upwards of 800-1200 cells, most of which spend an extended period of time (180-200 hours) in the G1 phase of the cell cycle. How the QC forms and is maintained is not known. Here we report that cells of the QC are characterized by their highly oxidized status. Glutathione and ascorbic acid occur predominately in the oxidized forms in the QC. This is contrasted with the status of these redox intermediates in adjacent, rapidly dividing cells in the root meristem, in which the reduced forms of these two species are favored. Using a redox sensitive fluorescent dye we were able to visualize an overall oxidizing environment in the QC, and we also made comparisons with the adjacent, rapidly dividing cells in the root meristem. Altering the distribution of auxin and the location of the auxin maximum in the root tip activates the QC, and cells leave G1 and enter mitosis. Commencement of relatively more rapid cell division in the QC is preceded by changes in the overall redox status of the QC, which becomes less oxidizing. We discuss how the position of the auxin maximum may influence the redox status of the QC and thereby modulate the cell cycle.
Hedgehog signalling is required for correct anteroposterior patterning of the zebrafish otic vesicle
Authors: Hammond Katherine L. , Loynes Helen E. , Folarin Amos A. , Smith Joanne , Whitfield Tanya T.
Published: February 2003

Currently, few factors have been identified that provide the inductive signals necessary to transform the simple otic placode into the complex asymmetric structure of the adult vertebrate inner ear. We provide evidence that Hedgehog signalling from ventral midline structures acts directly on the zebrafish otic vesicle to induce posterior otic identity. We demonstrate that two strong Hedgehog pathway mutants, chameleon(contf18b) and slow muscle omitted(smub641) exhibit a striking partial mirror image duplication of anterior otic structures, concomitant with a loss of posterior otic domains. These effects can be phenocopied by overexpression ofpatched1 mRNA to reduce Hedgehog signalling. Ectopic activation of the Hedgehog pathway, by injection of sonic hedgehog or dominant-negative protein kinase A RNA, has the reverse effect: ears lose anterior otic structures and show a mirror image duplication of posterior regions. By using double mutants and antisense morpholino analysis, we also show that both Sonic hedgehog and Tiggy-winkle hedgehog are involved in anteroposterior patterning of the zebrafish otic vesicle.
Rac promotes epithelial cell rearrangement during tracheal tubulogenesis inDrosophila
Authors: Chihara Takahiro , Kato Kagayaki , Taniguchi Misako , Ng Julian , Hayashi Shigeo
Published: February 2003

Cell rearrangement, accompanied by the rapid assembly and disassembly of cadherin-mediated cell adhesions, plays essential roles in epithelial morphogenesis. Various in vitro and cell culture studies on the small GTPase Rac have suggested it to be a key regulator of cell adhesion, but this notion needs to be verified in the context of embryonic development. We used the tracheal system of Drosophila to investigate the function of Rac in the epithelial cell rearrangement, with a special attention to its role in regulating epithelial cadherin activity. We found that a reduced Rac activity led to an expansion of cell junctions in the embryonic epidermis and tracheal epithelia, which was accompanied by an increase in the amount ofDrosophila E-Cadherin-Catenin complexes by a post-transcriptional mechanism. Reduced Rac activity inhibited dynamic epithelial cell rearrangement. Hyperactivation of Rac, on the other hand, inhibited assembly of newly synthesized E-Cadherin into cell junctions and caused loss of tracheal cell adhesion, resulting in cell detachment from the epithelia. Thus,in the context of Drosophila tracheal development, Rac activity must be maintained at a level necessary to balance the assembly and disassembly of E-Cadherin at cell junctions. Together with its role in cell motility, Rac regulates plasticity of cell adhesion and thus ensures smooth remodeling of epithelial sheets into tubules.
Delta-Notch signaling controls the generation of neurons/glia from neural stem cells in a stepwise process
Authors: Grandbarbe Luc , Bouissac Julien , Rand Matt , Hrabé de Angelis Martin , Artavanis-Tsakonas Spyros , Mohier Eliane
Published: February 2003

We examined the role of Notch signaling on the generation of neurons and glia from neural stem cells by using neurospheres that are clonally derived from neural stem cells. Neurospheres prepared fromDll1lacZ/lacZ mutant embryos segregate more neurons at the expense of both oligodendrocytes and astrocytes. This mutant phenotype could be rescued when Dll1lacZ/lacZ spheres were grown and/or differentiated in the presence of conditioned medium from wild-type neurospheres. Temporal modulation of Notch by soluble forms of ligands indicates that Notch signaling acts in two steps. Initially, it inhibits the neuronal fate while promoting the glial cell fate. In a second step, Notch promotes the differentiation of astrocytes, while inhibiting the differentiation of both neurons and oligodendrocytes.
Elastoplastic strain concentration factors in finite thickness plates
Authors: Livieri P , Nicoletto G
Published: February 2003

The paper presents a comparison of a detailed finite element modelling of elastoplastic strains at a notch root with experimental Moire interferometric data. The three-dimensional nature of the local constraint at a notch root for elastic or elastoplastic material behaviour is confirmed. The elastoplastic analysis shows that the stress concentration factor ratio from the mid-plane and the surface is practically insensitive to the actual σ—ε. relationship when the nominal stress achieves the yield stress.
Finite element analysis of calibration factors for the modified incremental strain method
Authors: Hwang B-W , Suh C-M , Kim S-H
Published: February 2003

To modify the incremental strain method used to evaluate non-uniform residual stress, a finite element analysis (FEA) of the reference model used to describe a hole-drilling test was conducted. The calibration factors for the x and y directions were obtained from the analysis and then their differences were compared under various loading conditions. A hole-drilling test using a steel plate as the reference specimen was introduced, and under the pure bending load, strain relaxation was measured at each hole-drilling step to determine the calibration factors. Although the calibration factors in the x and y directions varied with the boundary conditions used in the FEA, their differences were reduced to zero for all depths when the prescribed loads as the boundary conditions in the x and y directions became the same. In addition, it was analytically and experimentally confirmed that the calibration factors did not vary with the direction. Accordingly, by making the calibration factors equal in the x and y directions in the modified equation for the incremental strain method, no singularity is produced in the stress calculations.
Improved data reduction for the deep-hole method of residual stress measurement
Authors: DeWald A. T , Hill M. R
Published: February 2003

This paper describes an improved data reduction scheme for the deep-hole method of residual stress measurement. The deep-hole method uses the changes in diameter of a reference hole, drilled through the thickness of a component, to determine residual stress. The diameter changes result from the removal of a cylindrical core from the component, where the core is larger than and concentric with the reference hole. The new data reduction seeks to determine the unknown eigenstrain distribution that gives rise to the residual stress state and to the reference hole deformations; once the eigenstrain distribution is found, it is input to an elastic finite element analysis to provide the residual stress distribution in the original component. The new data reduction relies on expressing the unknown eigenstrain field in a polynomial basis, and finding the unknown basis function amplitudes from the measured reference hole diameter changes. The new data reduction is compared with the current technique, and it is shown that the proposed scheme offers several advantages to the current method of data reduction.
Desulfurization of Lignite and Coal Using Alkaline Solution from Biomass Ashes
Authors: Demirbaş Ayhan
Published: February 2003

This study has shown the technical potential of biomass ash to contribute to the desulfurization of problematic high sulfur lignites. The alkaline desulfurization is more effective in removing the pyritic sulfur from the coal, which is the less abundant form than the organic sulfur. Lignite and coal samples from Turkish resources were extracted with an aqueous alkaline solution obtained from the water-soluble fraction of biomass ash. By this method, high sulfur removal from lignites was possible. The effect of temperature, the amount of biomass ash used, extraction time, and stirring speed were studied in the range of 10–50 g, 350–550 K, 0.042–1.8 MPa, 15–60 min, and 300–600 rpm, respectively. The effect of pyritic and organic sulfur removal were investigated. This process removed 33.1, 35.3 and 37.2 % of total sulfur contents; 52.3, 53.6 and 60.7 % of pyritic sulfur contents; and 4.6, 22.1 and 18.0 % of organic sulfur contents from the lignite samples, respectively.
Modelling the Yaw Behaviour of a Small Wind Turbine
Authors: Bechly M. E. , Gutierrez H. , Streiner S. , Wood D. H.
Published: February 2003

This paper develops a mathematical model for a small wind turbine responding to changes in the wind direction. Here “small” implies that the turbine has a tail fin. Good yaw behaviour, in terms of tracking the changes in wind direction, is necessary to maximize power extraction. However large rates of change of yaw can lead to large stresses in the turbine components. The unsteady tail fin loads are more complex than implied by the “pseudo-static” assumption that the steady-state lift and drag act instantaneously. The aerodynamic model is applied first to data obtained from a 5 kW experimental turbine when it was not extracting power, because this almost removes the effect of the blades from the yaw behaviour. MATLAB's systems identification toolbox was used to optimise the fit of the model parameters to the data. The resulting values of a number of the parameters are shown to be in good agreement with earlier wind tunnel tests of the tail fin design. Some details of the comparisons, mainly in terms of the higher frequency components, suggest the need to characterise similarly the dynamics of wind vanes. When the turbine was extracting power, the flexible blades were deflected backwards by the aerodynamic loads. A blade element analysis suggests that the stabilizing moment due to this “coning” does not alter the form of the yaw response equation. The optimised fit of the model equations gave changes in the parameters broadly in agreement with the blade element analysis, but the quasi-steady analysis did not predict the measured increase in the damping associated with power extraction.
Global Optimum Design Method and Software for the Rotor Blades of Horizontal Axis Wind Turbines
Authors: Zhiquan Ye , Xiong Liu , Yan Chen
Published: February 2003

A global optimum design model for a HAWT rotor blade is presented in this paper. The model refers to the wind speed distribution function on the specific wind site, with the objective to satisfy the maximum annual energy output, using a complex method to carry on the global optimum searching. For obtaining more accurate performance data, strip theory is applied to calculate the aerodynamic performance. For obtaining aerodynamic data of the airfoil, an airfoil database is designed. Based on these factors, an aerodynamic performance and structure CAD software “BladeDesign for Windows” is setup. A 600kW wind turbine is designed and the results are compared with that of a 600kW commercial wind turbine. Satisfactory agreement is obtained.
Polyol‐Mediated Synthesis of Nanoscale Functional Materials
Authors: Feldmann C.
Published: February 2003

Nanoscale functional materials such as luminescent materials (ZnS:Ag+, Cl–; LaPO4:Ce3+,Tb3+; Y2O3:Eu3+), color pigments (CoAl2O4; Cr2O3; ZnCo2O4; (Ti0.85Ni0.05Nb0.10)O2; α‐Fe2O3; Cu(Fe,Cr)O4; TiO2), transparent conducting oxides (ZnO:In3+), and catalytically active oxides (CeO2; Mn3O4; V2O5) are prepared with the polyol method. All these materials are yielded as crystalline, spherical, and almost monodisperse particles, 30–200 nm in size. Characterization is carried out based on scanning electron microscopy (SEM), X‐ray powder diffraction (XRD), optical spectroscopy, and conductance measurements. The preparation via the polyol method is singled out due to its broad and easy applicability. The resulting material properties are similar to or better than nanoscale materials prepared by other measures. Some materials and their properties, e.g., ZnS:Ag+,Cl– as a phosphor, ZnCo2O4 and Cu(Fe,Cr)O4 as pigments, and ZnO:In3+ as transparent conductive oxide, are presented for the first time at the nanoscale.
Preparation and Characterization of Blue‐Luminescent Tris(8‐hydroxyquinoline)‐aluminum (Alq3)
Authors: Cölle M. , Gmeiner J. , Milius W. , Hillebrecht H. , Brütting W.
Published: February 2003

Using differential scanning calorimetry (DSC) measurements in combination with structural and optical characterization we have investigated the formation conditions of different phases of tris(8‐hydroxyquinoline)aluminum (Alq3). We have identified the δ‐phase as a high‐temperature phase of Alq3 being composed of the facial stereoisomer, and report an efficient method to obtain blue luminescent Alq3 by a simple annealing process. This allows the preparation of large amounts of pure δ‐Alq3 by choosing appropriate annealing conditions, which is necessary for further characterization of this blue‐luminescent phase, and offers the possibility of fabricating blue organic light‐emitting devices (OLEDs) from this material.
Magnetic Force Microscopy Images of a Nanometer‐Sized, Purely Organic High‐Spin Polyradical
Authors: Miyasaka M. , Saito Y. , Nishide H.
Published: February 2003

Magnetic force microscopy (MFM) was applied to study both the molecular image and the magnetic response of π‐conjugated, non‐Kekulé‐, and nondisjoint‐type poly(1,2‐phenylenevinylene) (nondisjoint refers to a molecule in which non‐bonding molecular orbitals share the same region in the molecule and a multiplet ground state is significantly stabilized) networks bearing 4‐substituted di‐tert‐butylphenoxyl moities. The polyphenoxyl radicals 1 with molecular weights of 2.6, 9.3, and 32 kDa have a substantial stability even at room temperature and in air, and molecular sizes in the nanometer range of 10, 20, and 35 nm, respectively, with a disk‐like shape. The MFM clearly shows a magnetic gradient response exactly on the position of the polyradical molecule dispersed on a graphite surface. The MFM molecular image of polyradical samples with different molecular weights and spin concentrations was examined as a nanoscale and single‐molecular‐based magnetic dot.
Organometallic Synthesis of Size‐Controlled Polycrystalline Ruthenium Nanoparticles in the Presence of Alcohols
Authors: Pelzer K. , Vidoni O. , Philippot K. , Chaudret B. , Collière V.
Published: February 2003

Ruthenium nanoparticles of controlled size have been prepared by decomposition of the organometallic precursor Ru(cod)(cot) (cod = 1,5‐cyclooctadiene, cot = 1,3,5‐cyclooctatriene) under an H2 atmosphere in either a pure alcohol or an alcohol/THF mixture as solvent and in the absence of further stabilizer. The particles were characterized by transmission electron microscopy (TEM), high‐resolution electron microscopy (HREM), X‐ray diffraction (XRD), wide‐angle X‐ray scattering (WAXS), and X‐ray photoelectron spectroscopy (XPS). The colloidal solutions are stable for long periods of time, in some cases longer than one year. TEM images reveal in most cases the presence of polycrystalline sponge‐like particles of regular spherical shape and homogeneous size or, in some cases, the presence of isolated and well‐dispersed monocrystalline particles, depending upon the alkyl chain length of the alcohol used. In all cases the size distributions are relatively narrow. WAXS and XRD analyses indicate the exclusive presence of hexagonal close‐packed (hcp) ruthenium in these materials. The size of the particles can be controlled by adjusting the reaction temperature or the composition of the solvent mixture. In case of MeOH/THF mixtures, a linear correlation was established between the solvent composition and the size of the particles in the range of 4–85 nm. In the absence of stirring, small individual monocrystalline Ru particles are formed inside superstructures that assemble in some cases into monolayers. Finally, these materials are promising in catalytic hydrogenation of arenes under mild conditions.