bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solvent‐Free Enzymatic Synthesis of 1,3‐Diconjugated Linoleoyl Glycerol Optimized by Response Surface Methodology
Authors: Guo Zheng , Sun Yan 
Published: April 2004

AbstractAn operation mode with N2 bubbling under vacuum was employed for the solvent‐free synthesis of 1,3‐diconjugated linoleoyl glycerol (1,3‐dCLG) from conjugated linoleic acid (CLA) catalyzed by Novozym 435. The response surface methodology (RSM) was adopted for the optimization of the reaction conditions with five major factors (incubation time, temperature, enzyme load, substrate mole ratio, and system vacuum) and three responses (CLA conversion, 1,3‐dCLG yield, and acyl migration). Two sets of optimal conditions were recommended. Validation of the RSM model was verified by the good agreement between the experimental and the predicted values of 1,3‐dCLG yield. Under the optimal conditions, the yield of 1,3‐dCLG up to 93% was obtained. The reaction was scaled up to a production level of 100 g of 1,3‐dCLG at a yield of 90.7%, indicating a promising feature of the technology in industrial applications.
Effect of Streptavidin RGD Mutant on the Adhesion of Endothelial Cells
Authors: Chan Bernard P. , Reichert William M. , Truskey George A. 
Published: April 2004

AbstractAdhesion of endothelial cells (EC) to surfaces can be enhanced by supplementing the integrin‐mediated adhesion with high‐affinity streptavidin (SA) that links a biotinylated EC to a biotinylated surface. Biotin pullout from the EC membrane limits the effectiveness of this treatment, leading to a predominance of EC detachment by cohesive failure. In this study we investigated whether a RGD‐SA mutant that links SA to EC integrin receptors, and eliminates EC biotinylation, improves EC adhesion. Suspended EC were incubated with the RGD‐SA mutant prior to cell seeding, primarily via attachment to the RGD binding site on αvβ3 integrin. RGD‐SA‐incubated EC were subsequently seeded onto a surface preadsorbed with a mixture of fibronectin (Fn) and biotinylated bovine serum albumin (b‐BSA). Results showed EC adhesion supplemented with the RGD‐SA‐biotin system significantly increased cell retention under flow, critical shear stresses for detachment, focal contact area, and force per bond relative to SA used with biotinylated EC. These increases were accompanied by significant reductions in membrane fragments left behind following EC detachment, which suggested cohesive failure via cell membrane rupture was significantly reduced, and enhanced phosphorylation of focal adhesion kinase, which suggested activation and clustering of integrin receptors. Together, these results show that the integrin‐independent augmentation of EC adhesion using SA‐biotin can be further improved through use of an RGD‐SA mutant.
Enzyme Encapsulation in Permeabilized Saccharomyces cerevisiae Cells
Authors: Chow Chi‐Kin , Palecek Sean P. 
Published: April 2004

AbstractThe Saccharomyces cerevisiae cell wall provides a semipermeable barrier that can retain intracellular proteins but still permits small molecules to pass through. When S. cerevisiae cells expressing E. coli lacZ are treated with detergent to extract the cell membrane, β‐galactosidase activity in the permeabilized cells is approximately 40% of the activity of the protein in cell extract. However, the permeabilized cells can easily be collected and reused over 15 times without appreciable loss in activity. Cell wall composition and thickness can be modified using different cell strains for enzyme expression or by mutating genes involved in cell wall biosynthesis or degradation. The Σ1278b strain cell wall is less permeable than the walls of BY4742 and W303 cells, and deleting EXG1, which encodes a 1,3‐β‐glucanase, can further reduce permeability. A short Zymolyase treatment can increase cell wall permeability without rupturing the cells. Encapsulating multiple enzymes in permeabilized cells can offer kinetic advantages over the same enzymes in solution. Regeneration of ATP from AMP by adenylate kinase and pyruvate kinase encapsulated in the same cell proceeded more rapidly than regeneration using a cell extract. Combining permeabilized cells containing adenylate kinase with permeabilized cells containing pyruvate kinase can also regenerate ATP from AMP, but the kinetics of this reaction are slower than regeneration using cell extract or permeabilized cells expressing both enzymes.
Reversible Immobilization of Glutaryl Acylase on Sepabeads Coated with Polyethyleneimine
Authors: Alonso‐Morales Noelia , López‐Gallego Fernando , Betancor Lorena , Hidalgo Aurelio , Mateo Cesar , Fernández‐Lafuente Roberto , Guisán Jose M. 
Published: April 2004

AbstractThe immobilizaton of the enzyme glutaryl‐7‐aminocephalosporanic acid acylase (GA) was performed via ionic adsorption onto several supports: a new anionic exchange resin, based on the coating of Sepabeads internal surfaces with polyethyleneimine (PEI) of different molecular weights, and conventional EC‐Q1A‐Sepabeads and DEAE‐agarose. Immobilization occurred very rapidly in all cases, but the adsorption strength was much higher in the case of PEI‐Sepabeads than in the other supports at pH 7 (e.g., at 150 mM NaCl, 90% of the enzyme was eluted from the DEAE agarose and 15% was eluted from the EC‐Q1A‐Sepabeads, whereas no desorption was detected with the best PEI‐Sepabeads). Interestingly, the adsorption strength of the GA was increased when it was immobilized on PEI‐Sepabeads with higher molecular weights. For instance, enzyme desorption was detected from 75 mM NaCl for the derivative prepared onto Sepabeads coated with PEI 700 Da, whereas in the derivative prepared with the highest molecular weight PEI (600 000 Da) no enzyme desorption was detected below 150 mM NaCl. Optimal PEI‐Sepabeads (prepared with PEI of 600 000 Da) was even much more thermostable than the covalent derivative prepared onto cyanogen bromide agarose. Moreover, this derivative presented a half‐life 26‐fold higher than that of the soluble enzyme at 45 °C, and the support could be reused 10 times after the full desorption of the enzyme without decreasing loading capacity.
A Dynamic Mathematical Model To Clarify Signaling Circuitry Underlying Programmed Cell Death Control in Arabidopsis Disease Resistance
Authors: Agrawal Vikas , Zhang Chu , Shapiro Allan D. , Dhurjati Prasad S. 
Published: April 2004

AbstractPlant cells undergo programmed cell death in response to invading pathogens. This cell death limits the spread of the infection and triggers whole plant antimicrobial and immune responses. The signaling network connecting molecular recognition of pathogens to these responses is a prime target for manipulation in genetic engineering strategies designed to improve crop plant disease resistance. Moreover, as alterations to metabolism can be misinterpreted as pathogen infection, successful plant metabolic engineering will ultimately depend on controlling these signaling pathways to avoid inadvertent activation of cell death. Programmed cell death resulting from infection of Arabidopsis thaliana with Pseudomonas syringae bacterial pathogens was chosen as a model system. Signaling circuitry hypotheses in this model system were tested by construction of a differential‐equations‐based mathematical model. Model‐based simulations of time evolution of signaling components matched experimental measurements of programmed cell death and associated signaling components obtained in a companion study. Simulation of systems‐level consequences of mutations used in laboratory studies led to two major improvements in understanding of signaling circuitry: (1) Simulations supported experimental evidence that a negative feedback loop in salicylic acid biosynthesis postulated by others does not exist. (2) Simulations showed that a second negative regulatory circuit for which there was strong experimental support did not affect one of two pathways leading to programmed cell death. Simulations also generated testable predictions to guide future experiments. Additional testable hypotheses were generated by results of individually varying each model parameter over 2 orders of magnitude that predicted biologically important changes to system dynamics. These predictions will be tested in future laboratory studies designed to further elucidate the signaling network control structure.
Bioprocess Parameters and Oxygen Transfer Characteristics in β‐Lactamase Production by Bacillus Species
Authors: Çelik Eda , Çalık Pınar 
Published: April 2004

AbstractAfter screening potential β‐lactamase producers in a medium containing penicillin G, an inducible ( Bacillus subtilis NRS 1125) and a constitutive ( Bacillus licheniformis 749/C ATCC 25972) β‐lactamase producer were selected. As the highest enzyme activity was obtained with B. licheniformis 749/C, the effects of the concentration of carbon sources, i.e., glucose, fructose, sucrose, citric acid, and glycerol, and nitrogen sources, i.e., (NH4)2HPO4, NH4Cl, yeast extract, casamino acids and peptone, pH, and temperature on β‐lactamase production were investigated with B. licheniformis 749/C in laboratory scale bioreactors. Among the investigated media, the highest volumetric activity was obtained as 270 U cm−3 in the medium containing 10.0 kg m−3 glucose, 1.18 kg m−3 (NH4)2HPO4, 8.0 kg m−3 yeast extract, and the salt solution at 32 °C and pH0 = 6.0. By using the designed medium, fermentation and oxygen transfer characteristics of the bioprocess were investigated at V = 3.0 dm3 bioreactor systems with a VR = 1.65 dm3 working volume at QO/ VR = 0.5 vvm and N = 500 min‐1. At the beginning of the process the Damköhler number was <1, indicating that the process was at biochemical reaction limited condition; at t = 2–5 h both mass‐transfer and biochemical reaction resistances were effective; and at t = 6–10 h ( Da ≫1) the bioprocess was at mass transfer limited condition. Overall oxygen transfer coefficients ( KLa) varied between 0.01 and 0.03 s−1, enhancement factor ( KLa/ KLaO) varied between 1.2 and 2.3, and volumetric oxygen uptake rate varied between 0.001 and 0.003 mol m−3 s−1 throughout the bioprocess. The specific oxygen uptake and the specific substrate consumption rates were the highest at t = 2 h and then decreased with the cultivation. The maximum yield of cells on substrate and the maximum yield of cells on oxygen values were obtained, respectively, as YX/S = 0.34 and YX/O = 1.40, at t = 5 h, whereas the highest yield of substrate on oxygen was obtained as YS/O = 6.94 at t = 3.5 h. The rate of oxygen consumption for maintenance and the rate of substrate consumption for maintenance values were found, respectively, as mO = 0.13 kg kg−1 h−1 and mS = 3.02 kg kg−1 h−1.
Oxidative Burst in Suspension Culture of Taxus cuspidataInduced by a Laminar Shear Stress in Short‐Term
Authors: Han Rong‐Bin , Yuan Ying‐Jin 
Published: April 2004

AbstractGeneration of active oxidative species induced by shear stress in suspension cultures of Taxus cuspidata was investigated in a Couette‐type shear reactor. It was found that T. cuspidata cells respond to a shear rate of 95 s−1 with oxidative bursts. Their triphasic characteristics in 6 h were similar in both intracellular H2O2 production and extracellular O2−• production. Additionally, inhibition studies with diphenylene iodonium and azide suggested that the key enzyme responsible for oxidative bursts under the shear rate of 95 s−1 is primarily NADPH oxidase and the contribution of peroxidase for oxidative bursts was less. Investigation of the relationship between active oxidative species and defense responses induced by the shear stress indicated that the O2−• burst may account for the change of membrane permeability, and the H2O2 burst plays an important role in inducing secondary metabolites such as the activation of phenylalanine ammonia lyase enzyme and phenolic accumulation. Furthermore, oxidative bursts elicited by the shear rate of 95 s−1 were suppressed by treatment with suramin, nifedipine, and neomycin prior to the shear stress treatment, suggesting that G‐protein, Ca2+ channel, and phospholipase C are involved in the signal pathway for oxidative bursts induced by the shear stress. A model is proposed to explain the oxidative burst in cultured T. cuspidata cells challenged with the shear stress.
Genetically Engineered Fluorescent Cell Marker for Labeling CD34+ Hematopoietic Stem Cells
Authors: Ye Kaiming , Jin Sha , Schultz Jerome S. 
Published: April 2004

AbstractTo address the challenge of labeling and tracking stem cells in vivo, we have engineered a fluorescent cell marker CD34EGFP by utilizing the mechanism of the cell‐specific activity of CD34 promoter in CD34+ stem cells. A retroviral vector derived from a murine stem cell virus was constructed to integrate the CD34EGFP gene into the genome of the cells for labeling. Our experiment demonstrates that the 454 bp segment upstream of the murine CD34 cDNA sequence has full function of promoter activity and can serve as a cell‐specific promoter for driving the expression of EGFP in CD34+ hematopoietic stem cells (HSC), providing a living color for labeling stem cells. The CD34EGFP marker was tested in various types of cells, including terminally differentiated cells, CD34+ mouse myeloid leukemia progenitor cells, CD34− hematopoietic cells, and CD34+ HSCs. We show that the engineered CD34EGFP cell marker is expressed in the CD34+ stem or progenitor cells but not in CD34− or terminally differentiated cells. RT‐PCR assay indicates that the transcription level of the CD34EGFP gene from CD34 promoter is almost the same as that from CMV promoter in CD34+ progenitor cells. The approach we present here offers a framework for genetic engineering of fluorescent cell markers for labeling and tracking stem cells in vivo. We anticipate that a variety of cell markers could be generated by coupling variants of fluorescent proteins with various cell‐specific promoters.
Combining Synthetic and Analytical Strategies for Preparative HPLC Enantioseparation of Monastrol Racemic Mixture
Authors: Cavazzini Alberto , Massi Alessandro , Bergamaschi Giovanni , Braga Stefano , Dondi Francesco , Dondoni Alessandro 
Published: April 2004

AbstractLarge‐scale resolution of racemic monastrol has been carried out by normal‐phase mode HPLC on an amylose‐based chiral stationary phase. Because monastrol solubility, in media of proper compositions for normal‐mode HPLC separations (in terms of retention factors and selectivity), was significantly low and impractical for preparative scopes, racemic monastrol was transformed into the corresponding O‐ tert‐butyldimethylsilyl derivative. The tert‐butyldimethylsilyl group was chosen as a suitable derivatizing agent because it induced approximatively a six‐times higher solubility and allowed for an almost quantitative recovery of pure monastrol from the derivatization‐deprotection sequence. The competitive isotherms of the O‐tert‐butyldimethylsilyl compounds, measured through frontal analysis, were fitted to competitive Langmuir and four‐parameter bi‐Langmuir models. The equilibrium dispersive model of chromatography was used for modeling the nonlinear separation of the racemate and to optimize the experimental conditions for collection of highly concentrated fractions of pure (R,S)‐O‐tert‐butyldimethylsilyl compounds, from which significant amounts of the corresponding enantiomers of monastrol (about 100 mg of each enantiomer with 30 runs on an analytical‐scale column) were obtained by quantitative back‐derivatization.
Modeling and Biokinetics in Anaerobic Acidogenesis of Starch‐Processing Wastewater to Acetic Acid
Authors: Ahn Johng‐Hwa , Lee Sangyoung , Hwang Seokhwan 
Published: April 2004

AbstractStarch‐processing wastewater was anaerobically treated to produce acetic acid in laboratory‐scale, continuously stirred tank reactors. The optimal conditions, in which the maximum acetic acid production occurred, were 0.56 d hydraulic retention time, pH 5.9, and 36.1 °C. Acetic acid production at the optimum conditions was 672 ± 20 mg total organic carbonequivalent L−1, which indicated a 75% conversion efficiency of influent total organic carbon into acetic acid. A fourth order Runge‐Kutta approximation was used to determine the Monod kinetics of the acidogens by using unsteady‐state data from continuous unsteady‐state experiments at the optimum conditions. The model outputs and experimental data fit together satisfactorily, suggesting that the unsteady‐state approach was appropriate for the evaluation of acidogenic biokinetics. These included μm, Ks, Y, and kd, which were evaluated as being 0.13 h−1, 25 mg total carbohydrate (TC) L−1, 0.38 mg volatile suspended solid mg−1 TC, and 0.002 h−1, respectively.
Reply [to “Comment on ‘Righting the balance: Gender diversity in the geosciences’”] by Floyd Herbert
Authors: Bell Robin , Kane Mark , Miller Roberta B. , Mutter John C. , Pfirman Stephanie , Kastens Kim 
Published: March 2004

In our article “On Gender Equity in the Geosciences,” we are not advocating a quota of 50% women in the geosciences, but rather, suggesting that the field would be strengthened if all the individuals with doctorates in the geosciences (including the 28% of all Ph.D.s who are women) were to remain active in these fields [National Science Board, 2002; Kastens, 2003].Currently, only about 13% of employed Ph.D.s in these fields are women, which means that there is a considerable loss of trained scientists in the Earth, atmospheric, and oceanographic sciences. Even the entry‐level hires at Ph.D.‐granting institutions are only 20% female [Holmes et al, 2003].
Ultrasound‐guided large needle core biopsy of the axilla
Authors: Abdsaleh S. , Azavedo E. , Lindgren P. G. 
Published: April 2004

Purpose: To study the diagnostic yield and safety aspects of large needle core biopsy of pathologic lesions in the axillary region using a semi‐automatic biopsy gun. Material and Methods: A series of 21 consecutive large needle core (14G, 2.1 mm) biopsies of the axilla was evaluated. The biopsies were performed under ultrasound guidance with one ( n=13) or two ( n=8) needle passes. The results were correlated to the clinical, mammographic, ultrasound and surgical histopathologic findings. Results: In 18 patients, specimens large enough for diagnosis were retrieved. In two patients the specimens were insufficient and non‐diagnostic. In one patient with a non‐malignant yield the result was false‐negative. No neural or vascular injury occurred. Conclusion: The procedure might be safely employed in the diagnosis of ultrasonographically demonstrable lesions of the axilla, whenever specimens larger than those obtainable with a fine needle are desired.
Complications associated with percutaneous nephrostomies. a retrospective study
Authors: Radecka E. , Magnusson A. 
Published: April 2004

Purpose: To determine the morbidity and mortality associated with radiologically guided percutaneous nephrostomy (PCN). Material and Methods: A retrospective analysis of 401 patients treated with 569 PCN over a 5‐year period was performed. Using the Seldinger technique, the catheters (6–10 F) were placed under fluoroscopic, ultrasonographic, or CT guidance. Data on underlying disease, complications, subsequent management, and long‐term management were collected. Results: PCN was successful in 558 of the 569 attempts (98%). There were 22 major complications (4%) in 569 procedures, including cardiac arrest, bleeding requiring transfusion or embolization, septicemia, hydrothorax or pneumothorax. There were 38% minor complications, including urinary tract infection, catheter dislodgement, catheter obstruction by debris, urinary leakage, and inflammation of the skin at the site of insertion of the percutaneous catheter. Seventy‐seven (14%) of the procedures were followed by urinary tract infection during the PCN treatment. Seventy‐nine (14%) catheters slipped out unintentionally. Conclusion: Percutaneous nephrostomy is a gentle procedure associated with high technical success and low morbidity. However, the risk of the procedure has to be weighed against the expected benefit.
Safety of heparin reversal with protamin and immediate sheath removal after coronary angioplasty
Authors: Lohne F. , Kløw N. E. , Stavnes S. , Brekke M. , Hoffmann P. , Stensæth K. H. , Søvik E. , Pettersen M. S. 
Published: April 2004

Purpose: To study the safety of giving protamin after coronary angioplasty to reverse heparin for immediate removal of the femoral sheath. Material and Methods: After successful angioplasty, 100 patients were randomized to receive protamin and immediate sheath removal or to the control group with sheath removal after 3 h. Patients were followed for 30 days so that groin complications and coronary events could be compared. After 6 months, target vessel revascularization and death were recorded. Results: The time to mobilization was significantly shorter in the protamin group compared to the control group; 6 versus 19 h. The protamin patients were more satisfied than the control patients, in particular during bed rest after compression. Puncture site complications were one (2%) and two (4%) pseudoaneurysms in the protamin group and the control group, respectively. Early angina and restenosis/reocclusion before 30 days were seen in 4 patients in the protamin group and in 1 in the control group. Adverse incidents between 30 days and 6 months were the same for both groups. Conclusion: Protamin reversal improved patient comfort and reduced immobilization time. The cardiac safety concern observed requires the antiplatelet agent clopidogrel to be given before the procedure.
Threshold selection in virtual bronchoscopy: phantom study and clinical implications
Authors: Maniatis P. N. , Triantopoulou C. C. , Tsalafoutas I. A. , Malagari K. S. , Siafas I. G. , Psatha E. A. , Koulentianos E. D. , Kelekis D. A. 
Published: April 2004

Purpose: To investigate the effect of the threshold selection on the apparent diameter of a virtual bronchus and the virtual wall morphology and to examine the parameters that can affect the selection of the appropriate threshold for virtual bronchoscopy with single slice computed tomography. Material and Methods: A bronchial phantom containing plastic tubes simulating the airways of the tracheobronchial tree was constructed. The diameters of the virtual images of these tubes were measured using various thresholds for two different materials surrounding the tubes: air and water. These measurements were correlated with the density in HU of the walls. Furthermore, data from 20 virtual bronchoscopies in patients were retrospectively analyzed in the same way. Results: The diameter of a virtual bronchus is strongly affected by the selected threshold. The appropriate threshold for accurate diameter representation depends on the density of the bronchial wall. Conclusion: Our results suggest that in clinical practice a single threshold value cannot be used for imaging all segments of the tracheobronchial tree. While a value of −520 is appropriate for the trachea and lobar segments, values down to −720 could be needed on the level of segmental and subsegmental bronchi. At these levels, a threshold value about 65 HU more negative than the value where the artificial holes appear on the virtual bronchial walls could be used.