bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyamines Contribute to Ethanol Withdrawal‐Induced Neurotoxicity in Rat Hippocampal Slice Cultures Through Interactions With the NMDA Receptor
Authors: Gibson D. Alex , Harris Barton R. , Prendergast Mark A. , Hart Stewart R. , Blanchard John A. , Holley Robert C. , Pedigo Norman W. , Littleton John M. 
Published: August 2004

Background: Several reports demonstrate that withdrawal from long‐term ethanol exposure is associated with significant central nervous system neurotoxicity, produced at least in part by increased activity of N‐methyl‐d‐aspartate receptors (NMDARs). Recent evidence suggests that elevations in the synthesis and release of the polyamines spermidine and spermine, which are known modulators of NMDARs, contribute to the increased activity of the receptor during ethanol withdrawal. Therefore, the goal of this investigation was to examine what role, if any, spermidine and spermine have in the generation of ethanol withdrawal‐induced neurotoxicity.Methods: Neurotoxicity (measured as fluorescence of the cell death indicator propidium iodide, PI), glutamate release (measured by high‐performance liquid chromatography analysis), and polyamine concentrations (by high‐performance liquid chromatography) were measured in rat hippocampal slice cultures undergoing withdrawal from chronic (10 day) ethanol exposure (100 mM). In addition, the effects of the polyamine synthesis inhibitor di‐fluoro‐methyl‐ornithine (DFMO, 0.1–100 nM) and NMDAR polyamine‐site antagonists ifenprodil, arcaine, and agmatine (1 nM‐100 μM) on ethanol withdrawal‐ and NMDA‐induced neurotoxicity were measured.Results: Ethanol withdrawal significantly increased glutamate release (peaking at 18 hr with a 53% increase), increased concentrations of putrescine and spermidine (136% and 139% increases, respectively, at 18 hr), and produced significant cytotoxicity in the CA1 hippocampal region (56% increase in PI staining relative to controls) of the cultures. The cell death produced by ethanol withdrawal was significantly inhibited by ifenprodil (IC50= 14.9 nM), arcaine (IC50= 37.9 nM), agmatine (IC50= 41.5 nM), and DFMO (IC50= 0.6 nM). NMDA (5 μM) significantly increased PI staining in the CA1 region of the hippocampal cultures (365% relative to controls), but ifenprodil, arcaine, agmatine, and DFMO all failed to significantly affect this type of toxicity.Conclusions: These data implicate a role for polyamines in ethanol withdrawal‐induced neurotoxicity and suggest that inhibiting the actions of polyamines on NMDARs may be neuroprotective under these conditions.
Neurosteroid Modulation of Glutamate Release in Hippocampal Neurons: Lack of an Effect of a Chronic Prenatal Ethanol Exposure Paradigm
Authors: Carta Mario , Partridge L. Donald , Savage Daniel D. , Valenzuela C. Fernando 
Published: August 2004

Background: Pregnenolone sulfate (PREGS) is a promnesic neurosteroid that is abundantly expressed in the hippocampus of rodents. Studies have shown that the modulation of postsynaptic ligand‐gated ion channels by this neurosteroid is impaired in preparations from the brains of fetal ethanol‐exposed animals. In this study, we examined whether the presynaptic actions of PREGS also are affected by exposure to ethanol in utero.Methods: Rat dams were exposed to one of the following diets during pregnancy: (1) 5% ethanol liquid diet, (2) 0% ethanol liquid diet with pair‐feeding, and (3) ad libitum controls. We then studied the presynaptic actions of PREGS on (1) alpha‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate (AMPA) receptor‐mediated miniature excitatory postsynaptic currents (mEPSCs) recorded from cultured hippocampal neurons in the whole‐cell patch‐clamp configuration and (2) paired‐pulse facilitation of NMDA receptor‐dependent excitatory postsynaptic potentials that were intracellularly recorded from CA1 pyramidal neurons in hippocampal slices from adult rats.Results: Chronic prenatal ethanol exposure affected neither basal mEPSC frequency nor its potentiation by PREGS. Basal paired‐pulse facilitation (i.e., in the absence of PREGS) was unaffected by fetal ethanol exposure. Chronic prenatal ethanol exposure did not affect the PREGS‐induced potentiation of paired‐pulse facilitation.Conclusions: Chronic prenatal ethanol exposure does not affect the basal probability of glutamate release in immature or mature hippocampal neurons. Moreover, the presynaptic actions of the neurosteroid PREGS also are unaffected by this exposure. Given that modulation of glutamate release could have a role in the mechanism of the promnesic actions of this neurosteroid, future studies are warranted to determine whether PREGS can ameliorate learning and memory deficits in fetal ethanol‐exposed animals.
The Effect of Alcohol on Testosterone Concentrations in Alcohol‐Preferring and Non‐Preferring Rat Lines
Authors: Apter Susanna J. , Eriksson C. J. Peter 
Published: August 2004

Background: Previous studies have reported associations between human alcohol drinking and testosterone levels.Methods: In this study we investigated serum testosterone concentrations without and under the influence of alcohol in alcohol‐preferring (AA) and nonpreferring (ANA) rat lines. Animals were tested in both mornings and afternoons and the alcohol doses were 0.75 and 1.50 g/kg.Results: Higher basal serum testosterone levels were detected in the AA rats compared with the ANA rats in both mornings (152%, p= 0.028) and afternoons (75%, p= 0.035). The high alcohol dose decreased the testosterone concentrations of both the AA and the ANA rats (p= 0.001–0.01). The low dose, however, decreased testosterone concentrations only in the ANA line (line difference in the morning:p= 0.027; in the afternoon p= 0.000).Conclusion: The present results support previous indications of a positive association between testosterone and alcohol drinking. Furthermore, the present results, together with earlier reports on the AA and ANA rats, introduce the possibility of a connection between this association and the hypothalamic opiate system, which is also involved in the feedback regulation of testosterone synthesis.
Beyond cognitive and metacognitive tools: the use of the Internet as an ‘epistemological’ tool for instruction
Authors: Tsai Chin‐Chung 
Published: August 2004

AbstractThis paper argues that Internet‐based instruction should not be only perceived as a cognitive tool or a metacognitive tool; rather, it can be perceived and used as an epistemological tool. When the Internet is used as an epistemological tool for instruction, learners are encouraged to evaluate the merits of information and knowledge acquired from Internet‐based environments, and to explore the nature of learning and knowledge construction. This paper further asserts that Internet‐based instruction is perceived as a way to help learners develop advanced epistemologies. On the other hand, developmentally advanced epistemological beliefs can facilitate the practice of Internet‐based instruction.
Visions and realities of Internet use in schools: Canadian perspectives
Authors: Gibson Susan , Oberg Dianne 
Published: August 2004

AbstractTeachers in many countries are being expected to use the Internet in their work. Research on the Canadian experience of Internet implementation provides insights that may be valuable for researchers and educators in other countries. A three‐year study, using both quantitative and qualitative approaches, examined both the visions for Internet use and the realities of everyday practice related to Internet use in Canadian schools. Participants in the study included ministry of education officials, teacher association officials, classroom teachers, and school administrators. Findings of the study suggest that all four participant groups were positive about the visions of the Internet as a tool with the potential to contribute to the enhancement of teaching and the development of information literate students. The realities of Internet use, however, were quite different from the visions. All four participant groups reported that the Internet was being used mostly to increase access to information. Its potential as an innovative learning tool for students and for teachers was largely unrealised. Few respondents reported using the collaboration, creation, and dissemination capabilities of the Internet. This outcome appeared to be the result of limited infrastructure support, difficulties in infusing Internet use into curriculum, and lack of appropriate teacher professional development.
Teacher collegiality and electronic communication: A study of the collaborative uses of email by secondary school teachers in Uruguay
Authors: Grünberg Jorge , Armellini Alejandro 
Published: August 2004

AbstractTeacher collegiality has been consistently highlighted in recent years as a crucial factor in the success of processes of educational change and professional development. Consequently, there is considerable interest both from researchers and practitioners, in investigating strategies capable of supporting interactions and collaborations between teachers.Research, mostly carried out in industry, suggests that computer‐mediated communication (CMC) technologies may support collegiality in a diversity of contexts. Following the technological developments of the last few years, which have driven down the costs and complexity of computers and telecommunications, CMC technologies are becoming increasingly available to schools around the world. One of the more widespread of these new CMC technologies is electronic mail.The aim of this article is to discuss some of the results of a research project that investigated the potential of electronic mail for supporting the development of collegiality and professional exchange among secondary school teachers in Uruguay. At the time of this study, relatively little research had been carried out into the use of electronic mail for professional purposes by schoolteachers, especially in Latin America.The evidence suggests that email may support the formation of communities of highly committed users, where seeking and sharing professional resources are accepted behaviours.
Reduced incidence of upper gastrointestinal ulcer complications with the COX‐2 selective inhibitor, valdecoxib
Authors: Goldstein J. L. , Eisen G. M. , Agrawal N. , Stenson W. F. , Kent J. D. , Verburg K. M. 
Published: August 2004

SummaryAim : In a predefined analysis, data were pooled from eight blinded, randomized, controlled trials, and separately from three long‐term, open‐label trials to determine the rate of upper gastrointestinal ulcer complications with the cyclo‐oxygenase‐2 selective inhibitor, valdecoxib, vs. non‐selective non‐steroidal anti‐inflammatory drugs.Methods : In randomized, controlled trials, 7434 osteoarthritis and rheumatoid arthritis patients received placebo (n = 973), valdecoxib 5–80 mg daily (n =4362), or a non‐selective non‐steroidal anti‐inflammatory drug (naproxen, ibuprofen or diclofenac; n =2099) for 12–26 weeks. In long‐term, open‐label trials, 2871 patients received valdecoxib 10–80 mg daily for up to 1 year. All potential events were reviewed by a blinded, independent review committee based on a priori definitions of ulcer complications (perforations, obstructions, bleeds).Results : In randomized, controlled trials, 19 of 955 potential events were adjudicated to be ulcer complications. Valdecoxib was associated with a significantly lower ulcer complication rate than non‐selective non‐steroidal anti‐inflammatory drugs (0.68% vs. 1.96%, all patients; 0.29% vs. 2.08%, non‐aspirin users; P < 0.05). In long‐term, open‐label trials, seven of 310 potential events were adjudicated to be ulcer complications; the annualized incidence for valdecoxib was 0.39% (seven of 1791 patient‐years) for all patients and 0.2% (three of 1472 patient‐years) for non‐aspirin users.Conclusions : Valdecoxib, including above recommended doses, is associated with a significantly lower rate of upper gastrointestinal ulcer complications than therapeutic doses of non‐selective non‐steroidal anti‐inflammatory drugs.
Adjuvant biofeedback following anal sphincter repair: a randomized study
Authors: Davis K. J. , Kumar D. , Poloniecki J. 
Published: August 2004

SummaryAims : To evaluate the impact of adjuvant biofeedback following sphincter surgery.Methods : Thirty‐eight patients were randomized into sphincter repair or sphincter repair plus biofeedback groups. Outcome measures included a symptom questionnaire, patient's rating of satisfaction with continence function and improvement, change in continence score, quality of life and anorectal physiology. Endoanal ultrasonography was also performed pre‐ and post‐operatively.Results : Immediately following surgery, there was no statistically significant difference in any of the functional or physiological variables between the groups. Continence and patient satisfaction scores improved with a mean difference of −0.48 (95% CI: −3.30–2.33, P =0.73) and 1.03 (95% CI: −1.40–3.46, P = 0.39), respectively. Only the difference in embarrassment scores reached statistical significance (mean) 0.56 (95% CI: 0.12–0.99, P = 0.014). Resting and squeeze pressures also improved. Thirteen of 14 in the biofeedback and 11 of 17 (control) reported symptomatic improvement. In the biofeedback group, although not statistically significant continence and satisfaction scores improved and were sustained over time. In the control group, continence and satisfaction scores changed little between 3 and 12 months (P = NS). Quality of life measures improved within the biofeedback group but there was no statistical difference between the groups.Conclusion : Following surgery continence function improves in all patients but adjuvant biofeedback therapy improves quality of life and maintains symptomatic improvement over time.
Has disease outcome in Crohn's disease changed during the last four decades?
Authors: Wolters F. L. , Russel M. G. V. M. , Stockbrügger R. W. 
Published: August 2004

SummaryBackground : Disease outcome in Crohn's disease might have changed during the last four decades. Disease outcome measurement in Crohn's disease has methodological difficulties because of patient selection and lack of proper definition of diagnostic and outcome measurement criteria.Aim : To assess possible changes in disease outcome in Crohn's disease during the last four decades.Methods : A systematic literature search was performed using the MEDLINE search engine and major international conference libraries. Articles and abstracts were selected according to stringent inclusion criteria.Results : Forty articles and nine abstracts complied with the inclusion criteria. Seven studies with a median follow‐up time between 11.1 and 17 years showed standard mortality ratios in Crohn's disease ranging between 2.16 and 0.72 with a tendency of decline during the last four decades. One study with 11.4 years mean follow‐up time showed a statistically significant increased relative risk for colorectal cancer that was not confirmed by three others. Sixteen publications applied in the disease recurrence category. Probability of first resective surgery ranged between 38 and 96% during the first 15 years after diagnosis. The overall recurrence and surgical recurrence rates after first resective surgery ranged between 50 and 60, and 28 and 45% respectively during the following 15 years without an apparent time trend.Conclusion : This structured literature review provides no hard evidence for change in disease outcome in Crohn's disease during the last four decades.
The Molecular Basis for the Natural Resistance of the Cytochrome bc1 Complex from Strobilurin‐Producing Basidiomycetes to Center QP Inhibitors
Authors: Kraiczy Peter , Haase Uwe , Gencic Simonida , Flindt Sven , Anke Timm , Brandt Ulrich , Von Jagow Gebhard 
Published: August 2004

Mitochondria from the strobilurin A producing basidiomycetes Strobilurus tenacellus and Mycena galopoda exhibit natural resistance to (E)‐β‐methoxyacrylate inhibitors of the ubiquinol oxidation center (center Qp) of the cytochrome bc1 complex. Isolated cytochrome bc1 complex from S. tenacellus was found to be highly similar to that of Saccharomyces cerevisiae with respect to subunit composition, as well as spectral characteristics and midpoint potentials of the heme centers.To understand the molecular basis of natural resistance, we determined the exon/intron organization and deduced the sequences of cytochromes b from S. tenacellus, M. galopoda and a third basidiomycete, Mycena viridimarginata, which produces no strobilurin A. Comparative sequence analysis of two regions of cytochrome b known to contribute to the formation of center Qp suggested that the generally lower sensitivity of all three basidiomycetes was due to the replacement of a small amino acid residue in position 127 by isoleucine. For M. galopoda replacement of Gly143 by alanine and Gly153 by serine, for S. tenacellus replacement of a small residue in position 254 by glutamine and Asn261 by aspartate was found to be the likely causes for resistance to (E)‐β‐methoxyacrylates. The latler exchange is also found in Schizosaccharomyces pombe, which we found also to be naturally resistant to (E)‐β‐methoxyacrylates.
Influence of the Signal Sequence and Chaperone SecB on the Interaction between Precursor Protein prePhoE and Phospholipids
Authors: Van Raalte Anne L. J. , Demel Rudy A. , Verberkmoes Geerten , Breukink Eefjan , Keller Rob C. A. , De Kruijff Ben 
Published: August 2004

To investigate in a direct way the interaction between a precursor protein and phospholipids, monolayer studies were performed using the purified precursor of Escherichia coli outer‐membrane protein PhoE. It was demonstrated that prePhoE can insert efficiently into monolayers of dioleoylglycerophosphoglycerol (Ole2GroP Gro) and dioleoylglycerophosphoethanolamine (Ole2GroPEtn), this insertion was mainly driven by hydrophobic forces. Compared with previous results obtained with PhoE signal peptide, the full‐length precursor protein does not show the specific interaction with acidic lipids. PrePhoE inserted into a Ole2GroP Gro monolayer occupies an area of 28±30 nm2/molecule, which is approximately 10‐fold larger than the area occupied by the PhoE signal peptide. The purified mature PhoE protein has a lower capacity to insert into Ole2GroP Gro and Ole2GroPEtn monolayers and is, in contrast to prePhoE, fully accessible to proteinase K after interacting with a Ole2GroPGro monolayer. The results demonstrate that in the context of the precursor protein both the signal sequence and mature domain of prePhoE insert into lipid monolayers.It was found that PhoE, like prePhoE, can form in vitro a complex with the cytosolic chaperone SecB. Complexation with SecB increases the insertion of (pre)PhoE into acidic lipid monolayers. The high lipid affinity of prePhoE was also demonstrated by vesicle‐binding experiments which showed that SecB dissociates from the SecB‐prePhoE complex upon binding of the precursor to the bilayer. The implications of these findings for preprotein translocation are discussed and in addition some extrapolations to the insertion of PhoE into the outer membrane are made.
Muconolactone Isomerase of the 3‐Oxoadipate Pathway Catalyzes Dechlorination of 5‐Chloro‐Substituted Muconolactones
Authors: Prucha Matthias , Peterseim Anke , Timmis Kenneth Nigel , Pieper Dietmar Helmut 
Published: August 2004

An enzyme of Alcaligenes eutrophus JMP 134 which catalyzes dechlorination of (4R, 5R)‐and (4R, 5S)‐5‐chloro‐3‐methyl‐and (4R, 5S)‐5‐chloromuconolactone to principally 3‐methyl‐trans‐, 3‐methyl‐cis ‐dienelactone and cis ‐dienelactone, respectively, was purified to homogeneity. The enzyme was identified as muconolactone isomerase on the basis of its high activity with muconolactone and on its high degree of sequence similarity with previously described muconolactone isomerases.Molecular mass determinations of the highly hydrophobic and heat‐resistant enzyme indicated a decameric structure involving a single 10.100‐kDa subunit similar to that of muconolactone isomerase of Pseudomonas putida.Kinetic analysis showed cooperative effects between the subunits during conversion of (4R, 5S)‐5‐chloro‐3‐methylmuconolactone. (4R, 5S)‐5‐chloromuconolactone was the preferred substrate, over the natural substrate (4S)‐muconolactone. The (4S, 5S)‐structure was found to be an inhibitor of (4R, 5R)‐5‐chloro‐3‐methylmuconolactone transformation. Methylsubstitution of the substrate results in a higher affinity for the enzyme, but a drastically lower velocity, resulting in a lower specificity constant.
Isolation, Characterization and Electron Microscopy Analysis of A Hemidiscoidal Phycobilisome Type from the Cyanobacterium Anabaena sp. PCC 7120
Authors: Ducret Axel , Sidler Walter , Wehrli Ernst , Frank Gerhard , Zuber Herbert 
Published: August 2004

In this work we present the characterization of a hemidiscoidal phycobilisome type of the heterocyst‐forming cyanobacterium Anabaena sp. PCC 7120. The phycobilisome of this organism contains allophycocyanin, phycocyanin and phycoerythrocyanin, similar to the closely related thermophilic cyanobacterium Mastigocladus laminosus. Intact phycobilisomes exhibit an absorption maximum at 619 nm and two fluorescence maxima at 664 nm and 680 nm, corroborating the presence of a complete energy pathway along the antenna. Upon dissociation, the phycobiliproteins were released from the phycobilisome. One phycoerythrocyanin, one phycocyanin and three allophycocyanin complexes were isolated by ion‐exchange chromatography and characterized by absorption and fluorescence spectroscopy and by SDS/PAGE. The polypeptides contained in the phycobilisome of Anabaena sp. PCC 7120 were subjected to SDS/PAGE, blotted onto poly(vinylidendifluoride) membranes and identified by amino‐terminal sequence analysis. The amino‐terminal sequences of the polypeptides belonging to the phycoerythrocyanin and phycocyanin families were identical with the derived sequences of their corresponding genes. Partial amino‐terminal sequences of the polypeptides belonging to the allophycocyanin family are presented here. Our results show that the phycobiliproteins and linker polypeptides from Anabaena sp. PCC 7120 are similar to the phycobilisome components characterized in other cyanobacteria.The phycobilisome of Anabaena sp. PCC 7120 was extensively analyzed by electron microscopy. It differs from the common hemidiscoidal tricylindrical, six‐rod phycobilisome type by a core domain consisting of five core cylinders surrounded by up to eight rods radiating in a hemidiscoidal manner. One rod is linked to each basal core cylinder, whereas the remaining core cylinders bind two rods each. On the basis of the data presented in this work, a revised model for the hemidiscoidal pentacylindrical phycobilisome of Anabaena sp. PCC 7120, M. laminosus and Anabaena variabilis is proposed. This model accounts more accurately for the ‘grape’ pattern typically exhibited by these phycobilisomes in electron micrographs.