bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of Argininosuccinate Synthetase mRNA Level in Rat Foetal Hepatocytes
Authors: Bourgeois Patricia , Harlin Jean‐Christophe , Renouf Sylvie , Goutal Isabella , Fairand Alain , Husson Annie
Published: June 2004

Expression of the hepatic gene for argininosuccinate synthase (ASS), one of the key enzymes of the urea cycle, was analysed during the perinatal period in the rat. To this end, the amount of specific mRNA was measured in the liver at various stages of development and in cultured foetal hepatocytes maintained in different hormonal conditions. The ASS mRNA was first detected in 15.5‐day foetuses and its level increased concomitantly with a rise in the enzyme activity, suggesting that the appearance of the ASS activity reflects the turning on of specific gene transcription. This was demonstrated by run‐on assay which showed an enhanced rate of transcription of the ASS gene during the perinatal period. When foetal hepatocytes were cultured with dexamethasone, a dose‐dependent increase in ASS mRNA was measured, which was completely abolished by actinomycin D addition. The transcription rate of the gene was increased about twofold in the presence of the steroid, as measured by nuclear run‐on assay. This transcriptional action could additionally require a protein factor since it could be inhibited by the simultaneous addition of puromycin. Insulin or glucagon respectively repressed or enhanced the dexamethasone‐induced accumulation of ASS mRNA when added simultaneously with the steroid for 24 h. This developmental regulation of the ASS mRNA by glucocorticoids, insulin and glucagon could account for the modulation of the enzyme activity previously observed in vivo and in vitro in the foetal liver.
Helix Stability in Barstar Peptides
Authors: Soler‐González Andrés S. , Fersht Alan R.
Published: June 2004

The complex between the ribonuclease barnase and barstar, its intracellular inhibitor, is a very good model for studying protein folding and molecular recognition. We have studied the stability of different peptides that cover the barstar α‐helix2 involved in the binding to barnase. A linear correlation between the helical amphipathy of these peptides and their inhibitory ability was obtained: the more helically amphipathic, the more the affinity for barnase. We estimated the amount of helix of these peptides in water and in trifluoroethanol by circular dichroism. There is a moderate correlation between the helical amphipathy and the helical content in water, in agreement with previous results that have shown the importance of the hydrophobicity periodicity in the design of peptides. The helical content in trifluoroethanol is related to helical propensity and helical amphipathy, suggesting that the local sequence determines these maximum helicities. The predicted helicity of these peptides, obtained using the algorithm AGADIR [Mufioz, V. & Serrano, L. (1994) Nat. Struct. Biol. 1, 399–409], appears to correlate with their ability to inhibit the activity of barnase in water. The correlation of inhibition constants, helical content in water, and maximum content of helix in trifluoroethanol with helical amphipathy supports the very important role of hydrophobicity pattern in peptide stability.
Two‐Component Flavin‐dependent Pyrrole‐2‐carboxylate Monooxygenase from Rhodococcus Sp.
Authors: Becker Dorit , Schräder Thomas , Andreesen Jan R.
Published: June 2004

Pyrrole‐2‐carboxylate can serve as the sole source of carbon, nitrogen, and energy for a strain tentatively identified to belong to the genus Rhodococcus. An NADH‐dependent oxygenase activity was detected in cell extracts that initiated the degradation of the substrate. During purification of the enzyme, this activity was separated into two protein components which were both purified to apparent homogeneity. A small monomeric 18.7‐kDa protein designated as reductase, catalyzed in vitro the NADH and FAD‐dependent reduction of cytochrome c and had an NADH‐oxidase activity. The second component, a 54‐kDa protein with a trimeric native structure had no enzymatic activity by itself, but exhibited a pyrrole‐2‐carboxylate‐dependent oxygen consumption when it was complemented with the reductase component, FAD, and NADH. This indicated that the large protein referred to as oxygenase was responsible for the oxygen‐dependent hydroxylation of the substrate. The rate of an uncoupled NADH oxidation without hydroxylation of the substrate was found to be strongly dependent on the molar ratio of both components. The uncoupling was nearly completely suppressed by a 5–7‐fold molar excess of the oxygenase component. The small protein was N‐terminally blocked. It was thus proteolytically digested and four of the resulting peptides were sequenced comprising 47 amino acids. The sequences of these fragments were similar to the sequences reported for the small component of different two‐component flavin monooxygenases. Furthermore, the N‐terminus of the oxygenase component showed high sequence similarity to the second, usually large subunit of these enzymes and to two single‐component flavin monooxygenases. Thus, the enzyme from Rhodococcus sp. designated as pyrrole‐2‐carboxylate monooxygenase belongs to the recently discovered new class of two‐component flavin aromatic monooxygenases. Some of the basic properties of both components were determined and their interaction during catalysis was investigated.
Structural Analysis of the O‐antigenic Polysaccharide from Vibrio cholerae O10
Authors: Kjellberg Alexandra , Weintraub Andrej , Albert M. John , Widmalm Göran
Published: June 2004

The structure of the O‐antigenic polysaccharide part of the lipopolysaccharide isolated from Vibrio cholerae O10 has been determined. The main method used has been 1H‐ and 13C‐NMR spectroscopy. Sugar and methylation analyses were also applied to the polysaccharide. The tetrasaccharide repeating unit of the polysaccharide was found to have the following structure:

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Supramolecular Assemblies from Lysosomal Matrix Proteins and Complex Lipids
Authors: Jadot Michel , Dubois Franz , Wattiaux‐De Contnck Simone , Wattiaux Robert
Published: June 2004

Most lysosomal hydrolases are soluble enzymes. Lamp‐II (lysosome‐associated membrane protein‐II) is a major constituent of the lysosomal membrane. We studied the aggregation of a series of lysosomal molecules. The aggregation‐sensitive lysosomal marker enzymes were optimally aggregated at intralysosomal pH. A similar pH dependence was recorded for aggregation of Lamp‐II. The pH‐dependent loss of solubility of isolated Lamp‐II required components of the lysosome extract. Conditions of mild acid pH promoting aggregation triggered the formation of complexes with lipids of lysosomal origin. We fractionated a membrane‐free lysosome extract by gel‐filtration chromatography and could reconstitute assemblies in vitro from separated fractions. We found some selectivity in the lysosomal proteins binding to complex lipids, hosphatidylcholine, sphingomyelin, and phosphatidylethanolamine being most effective. We propose that the formation at pH 5.0 of such Supramolecular assemblies between lysosomal proteins and lipids occurs within the intralysosomal environment. Some possible consequences of such an intralysosomal matrix formation on organelle function are discussed.
Analysis of the Complex Formed by Erythrina variegata Chymotrypsin Inhibitor with Chymotrypsin and Properties of the Peptides Prepared from the Inhibitor by a Limited Proteolysis
Authors: Kimura Makoto , Harada Nao , Iwanaga Shiroh , Yamasaki Nobuyuki
Published: June 2004

The stoichiometry of Erythrina variegata chymotrypsin inhibitor (ECI) and chymotrypsin interaction was previously estimated to be 1:2 by a titration of inhibitory activity. In the present study, gel‐permeation chromatography and reverse‐phase HPLC (RP‐HPLC) were employed to analyze the complex formed by the inhibitor and enzyme. The results showed that ECI and chymotrypsin molecules undergo aggregation in the complex‐forming buffer simultaneously with a binary complex consisting of one ECI and one chymotrypsin molecules in a soluble form.

A mild lysylendopeptidase digestion of ECI produced two peptides in high yield, which were separated by RP‐HPLC and characterized in terms of their structures and inhibitory activities. The N‐terminal peptide, ECI‐(1–107)‐peptide, containing the primary reactive site retained a slight inhibitory activity, while the C‐terminal peptide, ECI‐(108–179)‐peptide, exhibited no inhibitory activity. The inhibitory potency of the ECI‐(1–107)‐peptide was enhanced by the presence of the ECI‐(108–179)‐peptide in reconstituted mixture. Recovery of the native‐like structure of the reconstituted complex was further indicated by fluorescence spectra, which showed strong conformational interaction between the two peptides; their dissociation constant Kd was calculated to be 209 nM. Taken together with the previous result obtained by chymotryptic digestion, it is suggested that the primary binding loop in ECI interacts with chymotrypsin not only by a standard mechanism but also by a non‐substrate‐like manner. Alternatively, ECI might have an additional binding segment in the N‐terminal region which interacts with chymotrypsin by a non‐substrate‐like manner. Further, it is shown that the C‐terminal region may support the native conformation of the binding loop(s) in the N‐terminal region as an intramolecular chaperone.
Use of Anti‐(β2 Microglobulin) mAb to Study Formation of Amyloid Fibrils
Authors: Stoppini Monica , Bellotti Vittorio , Mangione Palma , Merlini Giampaolo , Ferri Giuseppina
Published: June 2004

Three mAbs, IgG1k 1F11, 7B6 and 14H3, were raised against in vitro‐self‐aggregated β2‐microglobulin. They recognize the native and unfolded forms of the protein and bind its fibrillar form that is present in amyloid tissue. When assayed in fibrillogenesis tests in vitro, mAb 14H3 inhibited fibril formation from β2‐microglobulin. This mAb recognizes a sequential epitope corresponding to the C‐terminal octapeptide, residues 92–99, of β2‐microglobulin. By using synthetic peptides it has been found that the integrity of the sequence is essential for the formation of the immunocomplex: the binding affinity is lowered by one order of magnitude (KA from 10−7 M to 10−6 M) by removal of Met99 and completely abolished when both Asp98 and Met99 are lost or Arg98 is substituted with Lys. The other two mAbs, 1F11 and 7B6, which bind sequences 20–41 and 63–75, respectively, are without effect on β2‐microglobulin fibrillogenesis. These two mAbs recognize β2‐microglobulin bound to the heavy chain in the major histocompatibility complex of type I located in the cell membrane, a property which is not shared by mAb 14H3.
Characterization of Dopuin, a Polypeptide with Special Residue Distributions
Authors: Chen Zheng‐wang , Bergman Tomas , Östenson Claes‐Göran , Efendic Suad , Mutt Viktor , Jörnvall Hans
Published: June 2004

A 62‐residue polypeptide, dopuin, has been isolated from pig small intestine. It is distinguished by an N‐terminal part with a high content of proline (7 in a 26‐residue segment), a C‐terminal part with a high proportion of histidine (3 in a 9‐residue segment), and six half‐cystine residues in three intrachain disulphide bridges (connecting positions 22–25, 23–54 and 35–44). The Cys and Pro distributions suggest a tight and special conformation. In contrast to PEC‐60 and somatostatin, it has no established inhibitory effect on insulin secretion. At 10 nM concentration, a weak inhibitory tendency is less than half of that of the other two peptides. Like gastrointestinal trefoil peptides, dopuin has three disulphide bridges, Ala‐Pro segments, and many charged residues, but they are differently distributed and dopuin belongs to a separate, apparently novel family. However, dopuin is similar to a peptide corresponding to an expressed‐sequence‐tag cDNA of human fetal liver and spleen, establishing the nature of the mature form of the product of this cDNA, and showing a general tissue, age, and species distribution of this peptide. A truncated form of vimentin, composed of its C‐terminal 37 residues, vimentin‐C37, was also purified and structurally characterized. These two peptides increase the complexity of known intestinal polypeptides and at least dopuin has properties compatible with specific biofunctions.
Electron Transfer Towards the RCI‐Type Photosystem in the Green Sulphur Bacterium Chlorobium limicola Forma Thiosulphatophilum Studied by Time‐Resolved Optical Spectroscopy In Vivo
Authors: Albouy Delphine , Joliot Pierre , Robert Bruno , Nitschke Wolfgang
Published: June 2004

Flash‐induced spectral changes in the wavelength region of the α‐peaks of heme proteins and in the time domain from microseconds to seconds have been recorded on whole cells of the green sulphur bacterium Chlorobium limicola forma thiosulfatophilum.

Extensive flash‐excitation by trains of flashes resulted in oxidation of 7–8 c‐type heme molecules/photosynthetic reaction centre. The complement of heme species was found to be spectrally heterogeneous allowing the study of electron transfer events induced by an isolated single‐turnover flash. Under single‐flash conditions, a c553 heme was seen to become oxidised with τ= 30 μs, concommitant with the reduction of the primary donor of the reaction centre. Subsequently, the α‐peak of the photooxidised heme broadened and shifted towards longer wavelengths (τ= 70 μs) indicating equilibration of the positive charge over two differing heme species. In the time domain t > 1 ms, rereduction of c‐type hemes was seen to be paralleled by a blue shift and further broadening of the α‐peak. Concommitantly, b‐type hemes were observed to first become reduced (within a few milliseconds), then over‐oxidised (t > 200ms) and eventually rereduced to their redox state prior to the flash.

The results obtained are discussed with respect to the question of the identity of the immediate electron donor to the photosynthetic reaction centre and with respect to the involvement of a cytochrome be complex in photo‐induced electron transport of green sulphur bacteria.
Purification and Characterization of Tilapia (Oreochromis mossambicus) Deoxyribonuclease I
Authors: Hsiao Yi‐Min , Ho Heng‐Chien , Wang Wen‐Yi , Tam Ming F. , Liao Ta‐Hsiu
Published: June 2004

DNase I of tilapia (Oreochromis mossambicus) was purified to homogeneity. Tilapia DNase I is most active at pH 8.5 with Mg2+ as activator. The Ca2+/Mg2+ pair has a synergistic effect on activation. The enzyme is readily inactivated by heating above 55°C, but is not inactivated by trypsin or 2‐mercapto‐ethanol under alkaline conditions, with or without CaCl2. Its isoelectric point is 6.0. The 258‐amino‐acid sequence of tilapia DNase I was derived from overlapping sequences of tryptic, chymotryptic and CNBr peptides. The purified enzyme has two variants differing by a single Lys→Arg mutation at position 125. The polypeptide chain has one disulfide bridge and one carbohydrate side chain. By mass spectrometry, the purified enzyme shows many molecular mass forms differing by Lys/Arg substitution and sugar‐chain length. The major form has a molecular mass of 30914 Da. A 1061‐bp nucleotide sequence for the cDNA of tilapia DNase I, obtained by gene cloning and DNA sequencing, contains an ORF coding for a putative 26‐residue transmembrane peptide and the mature DNase I polypeptide.
Sertoli Cell Tumour in a Cat
Authors: Benazzi C. , Sarli G. , Brunetti B.
Published: June 2004

A Sertoli cell tumour occurred in a cryptorchid testis of a 1‐year‐old cat with no signs of feminization. The tumour showed intratubular growth without interstitial infiltration and the neoplastic cells appeared polymorphous and vacuolated. Mitotic figures were rare. The diagnosis was based on histopathological, ultrastructural and immunohistochemical features of the tumour cells.
Factors Affecting Somatic Cell Count in Cow Bulk Tank Milk – A Case Study from Poland
Authors: Skrzypek R. , Wójtowski J. , Fahr R.‐D.
Published: June 2004

The aim of this paper was a retrospective analysis of factors affecting the somatic cell count (SCC) in cow bulk tank milk. The investigations concerned the year 2000 and were conducted on 212 family dairy farms in the Wielkopolska region (Western Poland). The average herd size was 13.3 cows (ranging from 5 to 48), whereas the mean SCC was 269 000 in 1 cm3 of milk (ranging from 63 000 to 631 000). In the period from July to September a higher SCC (P ≤ 0.01) was found than in the other months. In herds of more than 15 cows, higher SCC values (P ≤ 0.05) were observed than in the smaller herds. The following management and technological factors significantly decreased SCC: a 7–8‐week dry period (versus shorter period), foremilking with the use of a forestripper, practicing manual udder massage before milking, individual rationing of feeds according to production, and the application of MgO and β‐carotene additives to the feed ration.
Pregnancy Rate Following Post‐insemination Intrauterine Treatment of Endometritis in Dairy Cattle
Authors: Shams‐Esfandabadi N. , Shirazi A. , Ghasemzadeh‐nava H.
Published: June 2004

Of 1500 examined Holstein cows in milk, there were 315 cows with mucopurulent discharges at the time of insemination (21%). Twenty‐four hours after insemination, the infected animals randomly received no treatment (group I, control,n = 93), intrauterine infusion of 1 g oxytetracycline (group II,n = 63) and intrauterine infusion of 5 million IU procain penicillin G sodium (group III,n = 159). First service conception rate following treatment was 48.3, 49.2 and 47.7% in groups I, II and III, respectively. In conclusion, treatment with either antibiotic had no advantage relative to the control on first service conception rate.
Monotonicity and the Roy Model
Authors: Chevalier Arnaud , Lanot Gauthier
Published: June 2004

In this note we study the implications on a bivariate normal Roy model of two sets of monotonicity hypotheses proposed recently by Manski and Pepper (Econometrica, Vol. 64 (2000), pp. 997–1011). In that simple context, we show that these hypotheses imply strong restrictions on the correlations structure between the decision and the rewards.
Progression of a solitary, malignant cutaneous plasma‐cell tumour to multiple myeloma in a cat
Authors: Radhakrishnan A. , Risbon R. E. , Patel R. T. , Ruiz B. , Clifford C. A.
Published: June 2004

An 11‐year‐old male domestic shorthair cat was examined because of a soft‐tissue mass on the left tarsus previously diagnosed as a malignant extramedullary plasmacytoma. Findings of further diagnostic tests carried out to evaluate the patient for multiple myeloma were negative. Five months later, the cat developed clinical evidence of multiple myeloma based on positive Bence Jones proteinuria, monoclonal gammopathy and circulating atypical plasma cells. This case represents an unusual presentation for this disease and documents progression of an extramedullary plasmacytoma to multiple myeloma in the cat.
The Resistance of Clamped Sandwich Beams to Shock Loading
Authors: Fleck N. A. , Deshpande V. S.
Published: June 2004

A systematic design procedure has been developed for analyzing the blast resistance of clamped sandwich beams. The structural response of the sandwich beam is split into three sequential steps: stage I is the one-dimensional fluid-structure interaction problem during the blast loading event, and results in a uniform velocity of the outer face sheet; during stage II the core crushes and the velocities of the faces and core become equalized by momentum sharing; stage III is the retardation phase over which the beam is brought to rest by plastic bending and stretching. The third-stage analytical procedure is used to obtain the dynamic response of a clamped sandwich beam to an imposed impulse. Performance charts for a wide range of sandwich core topologies are constructed for both air and water blast, with the monolithic beam taken as the reference case. These performance charts are used to determine the optimal geometry to maximize blast resistance for a given mass of sandwich beam. For the case of water blast, an order of magnitude improvement in blast resistance is achieved by employing sandwich construction, with the diamond-celled core providing the best blast performance. However, in air blast, sandwich construction gives only a moderate gain in blast resistance compared to monolithic construction.
Fracture of Brittle Microbeams
Authors: Ostoja-Starzewski M.
Published: June 2004

The random polycrystalline microstructure of microbeams necessitates a reexamination of the crack driving force G stemming from the Griffith fracture criterion. It is found that, in the case of dead-load conditions, G computed by straightforward averaging of the spatially random elastic modulus E is lower than that obtained by correct ensemble averaging of the stored elastic energy. This result holds for both Euler-Bernoulli and Timoshenko models of micro-beams. However, under fixed-grip conditions G is to be computed by a direct ensemble averaging of E. It turns out that these two cases provide bounds on G under mixed loading. Furthermore, crack stability is shown to involve a stochastic competition between potential and surface energies, whose weak randomness leads to a relatively stronger randomness of the critical crack length.
Role of Phonon Dispersion in Lattice Thermal Conductivity Modeling
Authors: Chung J. D. , McGaughey A. J. H. , Kaviany M.
Published: June 2004

The role of phonon dispersion in the prediction of the thermal conductivity of germanium between temperatures of 2 K and 1000 K is investigated using the Holland approach. If no dispersion is assumed, a large, nonphysical discontinuity is found in the transverse phonon relaxation time over the entire temperature range. However, this effect is masked in the final prediction of the thermal conductivity by the use of fitting parameters. As the treatment of the dispersion is refined, the magnitude of the discontinuity is reduced. At the same time, discrepancies between the high temperature predictions and experimental data become apparent, indicating that the assumed heat transfer mechanisms (i.e., the relaxation time models) are not sufficient to account for the expected thermal transport. Molecular dynamics simulations may be the most suitable tool available for addressing this issue.
Fabrication and Performance of a Pin Fin Micro Heat Exchanger
Authors: Marques Christophe , Kelly Kevin W.
Published: June 2004

Nickel micro pin fin heat exchangers can be electroplated directly onto planar or non-planar metal surfaces using a derivative of the LIGA micromachining process. These heat exchangers offer the potential to more effectively control the temperature of surfaces in high heat flux applications. Of particular interest is the temperature control of gas turbine engine components. The components in the gas turbine engine that require efficient, improved cooling schemes include the gas turbine blades, the stator vanes, the turbine disk, and the combustor liner. Efficient heating of component surfaces may also be required (i.e., surfaces near the compressor inlet to prevent deicing). In all cases, correlations providing the Nusselt number and the friction factor are needed for such micro pin fin heat exchangers. Heat transfer and pressure loss experimental results are reported for a flat parallel plate pin fin micro heat exchanger with a staggered pin fin array, with height-to-diameter ratios of 1.0, with spacing-to-diameter ratios of 2.5 and for Reynolds numbers (based on the hydraulic diameter of the channel) from 4000 to 20,000. The results are compared to studies of larger scale, but geometrically similar, pin fin heat exchangers. To motivate further research, an analytic model is described which uses the empirical results from the pin fin heat exchanger experiments to predict a cooling effectiveness exceeding 0.82 in a gas turbine blade cooling application. As a final point, the feasibility of fabricating a relatively complex micro heat exchanger on a simple airfoil (a cylinder) is demonstrated.
Axially Tapered Microchannels of High Aspect Ratio for Evaporative Cooling Devices
Authors: Nilson R. H. , Griffiths S. K. , Tchikanda S. W. , Martinez M. J.
Published: June 2004

Analytical solutions are derived for evaporating flow in open rectangular microchannels having a uniform depth and a width that decreases along the channel axis. The flow generally consists of two sequential domains, an entry domain where the meniscus is attached to the top corners of the channel followed by a recession domain where the meniscus retreats along the sidewalls toward the channel bottom. Analytical solutions applicable within each domain are matched at their interface. Results demonstrate that tapered channels provide substantially better cooling capacity than straight channels of rectangular or triangular cross section, particularly under opposing gravitational forces. A multiplicity of arbitrarily tapered channels can be microfabricated in metals using LIGA, a process involving electrodeposition into a lithographically patterned mold.
Heat Transfer Performance During Condensation Inside Spiralled Micro-Fin Tubes
Authors: Bukasa Jean-Pierre M. , Liebenberg Leon , Meyer Josua P.
Published: June 2004

The effect of the spiral angle on the heat transfer performance in micro-fin tube condensers has not yet been clearly established because other geometric parameters affecting the heat transfer performance were simultaneously varied in previous studies. This paper reports on the influence of the spiral angle on the heat transfer during condensation inside spiralled micro-fin tubes having all other geometric parameters constant. Tests were conducted for condensation of R-22, R-134a, and R-407C inside a smooth (9.52 mm outer diameter) and three micro-fin tubes with approximately the same diameter, having spiral angles of 10 deg, 18 deg, and 37 deg, respectively. Experimental results indicated a heat transfer augmentation with spiral angle increase. A new semi-empirical predictive correlation was developed for practical design of spiralled micro-fin tubes. The proposed new correlation predicted the majority of experimental results of the present study within a deviation zone of ±20%.
Reduction of NOx in a Regenerative Industrial Furnace With the Addition of Methanol in the Fuel
Authors: Jiang Q. , Zhang C. , Jiang J.
Published: June 2004

The analysis of the combustion process and NOx emission in a gas-fired regenerative industrial furnace has been carried out numerically. The effect of the additive, methanol CH3OH, to the fuel on the NOx emission is studied. A moment closure method with the assumed β Probability Density Function (PDF) for the mixture fraction is used to model the turbulent non-premixed combustion process in the furnace. The combustion model is based on the assumption of instantaneous full chemical equilibrium. The P-1 model is chosen as the radiation model, and the Weighted-Sum-of-Gray-Gases Model is used to calculate the absorption coefficient. The numerical results showed that the use of CH3OH is effective in the reduction of NOx in a regenerative industrial furnace. The mechanism of NOx reduction by the use of CH3OH is also discussed.
A Dynamic Model for the Design of Methanol to Hydrogen Steam Reformers for Transportation Applications
Authors: Ohl Gregory L. , Stein Jeffrey L. , Smith Gene E.
Published: June 2004

As an aid to improving the dynamic response of the steam reformer, a dynamic model is developed to provide preliminary characterizations of the major constraints that limit the ability of a reformer to respond to the varying output requirements occurring in vehicular applications. This model is a first principles model that identifies important physical parameters in the steam reformer. The model is then incorporated into a design optimization process, where minimum steam reformer response time is specified as the objective function. This tool is shown to have the potential to be a powerful means of determining the values of the steam reformer design parameters that yield the fastest response time to a step input in hydrogen demand for a given set of initial conditions. A more extensive application of this methodology, yielding steam reformer design recommendations, is contained in a related publication.
Elastic-Plastic Stress Distribution in a Plastically Anisotropic Rotating Disk
Authors: Alexandrova N. , Alexandrov S.
Published: June 2004

The plane state of stress in an elastic-plastic rotating anisotropic annular disk is studied. To incorporate the effect of anisotropy on the plastic flow, Hill’s quadratic orthotropic yield criterion and its associated flow rule are adopted. A semi-analytical solution is obtained. The solution is illustrated by numerical calculations showing various aspects of the influence of plastic anisotropy on the stress distribution in the rotating disk.
Numerical Stability Criteria for Localized Post-buckling Solutions in a Strut-on-Foundation Model
Authors: Wadee M. Khurram , Coman Ciprian D. , Bassom Andrew P.
Published: June 2004

Some stability results are established for localized buckling solutions of a strut-on-foundation model which has an initially unstable post-buckling path followed by a restabilizing property. These results are in stark contrast with those for models with non-restabilizing behavior for which all solutions are unstable under dead-loading conditions. By approximating solutions with a nonperiodic set of functions, the stability of these static solutions can be assessed by examining the nature of the equilibrium using total potential energy considerations.
Antibiotic Resistance Conferred by a Class I Integron and SXT Constin in
Vibrio cholerae
O1 Strains Isolated in Laos
Authors: Iwanaga Masaaki , Toma Claudia , Miyazato Tomoko , Insisiengmay Sithat , Nakasone Noboru , Ehara Masahiko
Published: June 2004

Changes in the drug susceptibility pattern were observed in
Vibrio cholerae
O1 isolated in the Lao People's Democratic Republic during 1993 to 2000. In this study, 50
V. cholerae
O1 strains were selected during this period for studying the presence of class I integron and SXT constin. Twenty-four streptomycin-resistant strains out of 26 isolated before 1997 contained a class I integron harboring the
aadA1
gene cassette. Twenty-four strains isolated after 1997 contained an SXT constin (a large conjugative element). Twenty of the strains were resistant to chloramphenicol, tetracycline, streptomycin, and trimethoprim-sulfamethoxazole, while four strains were susceptible to the antibiotic tested. The resistance genes included in the SXT constins were
floR
,
tetA
,
strAB
, and
sulII
, which encode resistance to chloramphenicol, tetracycline, streptomycin, and sulfamethoxazole, respectively. The antibiotic resistance gene cluster was found to be deleted in the four susceptible strains. SXT
LAOS
did not contain
dfrA1
or
dfr18
, which confer resistance to trimethoprim in SXT
ET
and SXT
MO10
, respectively. A hot spot region of SXT
LAOS
was sequenced, and we identified two novel open reading frames showing homology to
sO24
(exonuclease) and
sO23
(helicase) of the genomic island associated with the multidrug resistance region of
Salmonella enterica
serovar Typhimurium DT104. Analysis of SXT
LAOS
showed that there is a continuous flux of genes among
V. cholerae
SXT constins which should be carefully monitored.
Inhibition of
Mycobacterium tuberculosis
AhpD, an Element of the Peroxiredoxin Defense against Oxidative Stress
Authors: Koshkin Aleksey , Zhou Xiao-ti , Kraus Carl N. , Brenner Jason M. , Bandyopadhyay Pradipta , Kuntz Irwin D. , Barry Clifton E. , Ortiz de Montellano Paul R.
Published: June 2004

The resistance of
Mycobacterium tuberculosis
to isoniazid (INH) is largely linked to suppression of a catalase-peroxidase enzyme (KatG) that activates INH. In the absence of KatG, antioxidant protection is provided by enhanced expression of the peroxiredoxin AhpC, which is itself reduced by AhpD, a protein with low alkylhydroperoxidase activity of its own. Inhibition of AhpD might therefore impair the antioxidant protection afforded by AhpC and make KatG-negative strains more sensitive to oxidative stress. We report here that the 3(
E
),17-dioxime of testosterone is a potent competitive AhpD inhibitor, with a
K

i

of 50 ± 2 nM. The inhibitor is stereospecific, in that the 3(
E
) but not 3(
Z
) isomer is active. Computational studies provide support for a proposed AhpD substrate binding site. However, the inhibitor does not completely suppress the in vitro activity of AhpC/AhpD, because a low titer of AhpD suffices to maintain AhpC activity. This finding, and the low solubility of the inhibitor, explains its inability to suppress the growth of INH-resistant
M. tuberculosis
in infected mouse lungs.
Molecular Characterization of Benzimidazole Resistance in
Helicobacter pylori
Authors: Mills Scott D. , Yang Wei , MacCormack Kathleen
Published: June 2004

A family of benzimidazole derivatives (BI) was shown to possess potent and selective activity against
Helicobacter pylori
, although the precise cellular target of the BIs is unknown. Spontaneous
H. pylori
mutants were isolated as resistant to a representative BI (compound A). Genomic DNA was isolated from a BI-resistant mutant, transformed into a BI-sensitive strain, and found to be sufficient to confer BI resistance. The resistance determinant was localized to a 17-kb clone after screening a lambda-based genomic library constructed from the BI-resistant strain. Upon sequencing and mapping onto the
H. pylori
strain J99 genome, the 17-kb clone was shown to contain the entire
nuo
operon (NADH:ubiquinone oxidoreductase). Further subcloning and DNA sequencing revealed that a single point mutation in
nuoD
was responsible for BI resistance. The mutation resulted in a G398S amino acid change at the C terminus of NuoD. Thirty-three additional spontaneous BI-resistant mutants were characterized. Sequencing of
nuoD
from 32 isolated mutants revealed three classes of missense mutation resulting in amino acid changes in NuoD: G398S, F404S, and V407M. One BI-resistant isolate did not have a mutation in
nuoD
. Instead, a T27A amino acid change was identified in NuoB. MIC testing of the wild-type
H. pylori
strain and four classes of
nuo
mutants revealed that all NuoD mutant classes were hypersensitive to rotenone, a known inhibitor of complex I (NADH:ubiquinone oxidoreductase) suggested to bind to NuoD. Further, a
nuoD
knockout verified that it is essential in
H. pylori
and may be the target of the BI compounds.
Effects of Fluoroquinolones on the Migration of Human Phagocytes through
Chlamydia pneumoniae
-Infected and Tumor Necrosis Factor Alpha-Stimulated Endothelial Cells
Authors: Uriarte Silvia M. , Molestina Robert E. , Miller Richard D. , Bernabo Jorge , Farinati Alicia , Eiguchi Kumiko , Ramirez Julio A. , Summersgill James T.
Published: June 2004

The anti-inflammatory activities of three quinolones, levofloxacin, moxifloxacin, and gatifloxacin, were investigated with an in vitro model of transendothelial migration (TEM). Human umbilical vein endothelial cells (HUVEC) were seeded in Transwell inserts, treated with serial dilutions of antibiotics, infected with
Chlamydia pneumoniae
, or stimulated with tumor necrosis factor alpha (TNF-α). Neutrophils or monocytes were also preincubated with serial dilutions of each antibiotic. TEM was assessed by light microscopic examination of the underside of the polycarbonate membrane, and levels of interleukin-8 (IL-8) and monocyte chemotactic protein 1 (MCP-1) were measured by enzyme-linked immunosorbent assay. In HUVEC infected with
C. pneumoniae
or stimulated with TNF-α, all fluoroquinolones significantly decreased neutrophil and monocyte TEM, compared to antibiotic-free controls. Moxifloxacin and gatifloxacin produced a significant decrease in IL-8 in
C. pneumoniae
-infected and TNF-α-stimulated HUVEC; however, moxifloxacin was the only fluoroquinolone that produced a significant decrease in MCP-1 levels under both conditions. Results from this study indicate similarities in the anti-inflammatory activities of these fluoroquinolones, although no statistically significant decrease in chemokine secretion was observed when levofloxacin was used. Mechanisms of neutrophil and monocyte TEM inhibition by fluoroquinolone antibiotics are unknown but may be partially due to inhibition of IL-8 and MCP-1 production, respectively.
In Vitro and In Vivo Bacteriolytic Activities of
Escherichia coli
Phages: Implications for Phage Therapy
Authors: Chibani-Chennoufi Sandra , Sidoti Josette , Bruttin Anne , Kutter Elizabeth , Sarker Shafiq , Brüssow Harald
Published: June 2004

Four
T4-like coliphages with broad host ranges for diarrhea-associated
Escherichia coli
serotypes were isolated from stool
specimens from pediatric diarrhea patients and from environmental water
samples. All four phages showed a highly efficient gastrointestinal
passage in adult mice when added to drinking water. Viable phages were
recovered from the feces in a dose-dependent way. The minimal oral dose
for consistent fecal recovery was as low as 10
3
PFU of phage
per ml of drinking water. In conventional mice, the orally applied
phage remained restricted to the gut lumen, and as expected for a
noninvasive phage, no histopathological changes of the gut mucosa were
detected in the phage-exposed animals.
E. coli
strains
recently introduced into the intestines of conventional mice and traced
as ampicillin-resistant colonies were efficiently lysed in vivo by
phage added to the drinking water. Likewise, an in vitro
phage-susceptible
E. coli
strain freshly inoculated into
axenic mice was lysed in vivo by an orally applied phage, while an in
vitro-resistant
E. coli
strain was not lysed. In contrast, the
normal
E. coli
gut flora of conventional mice was only
minimally affected by oral phage application despite the fact that in
vitro the majority of the murine intestinal
E. coli
colonies
were susceptible to the given phage cocktail. Apparently, the resident
E. coli
gut flora is physically or physiologically protected
against phage
infection.
Inhibition of Severe Acute Respiratory Syndrome Coronavirus Replication by Niclosamide
Authors: Wu Chang-Jer , Jan Jia-Tsrong , Chen Chi-Min , Hsieh Hsing-Pang , Hwang Der-Ren , Liu Hwan-Wun , Liu Chiu-Yi , Huang Hui-Wen , Chen Su-Chin , Hong Cheng-Fong , Lin Ren-Kuo , Chao Yu-Sheng , Hsu John T. A.
Published: June 2004

Antiviral agents are urgently needed to fight severe acute respiratory syndrome (SARS). We showed that niclosamide, an existing antihelminthic drug, was able to inhibit replication of a newly discovered coronavirus, SARS-CoV; viral antigen synthesis was totally abolished at a niclosamide concentration of 1.56 μM, as revealed by immunoblot analysis. Thus, niclosamide represents a promising drug candidate for the effective treatment of SARS-CoV infection.
Sustained-Release Formulation of Doxycycline Hyclate for Prophylaxis of Tick Bite Infection in a Murine Model of Lyme Borreliosis
Authors: Zeidner N. S. , Brandt K. S. , Dadey E. , Dolan M. C. , Happ C. , Piesman J.
Published: June 2004

The prophylactic potential of a single injection of sustained-release doxycycline hyclate (Atridox) was compared to that of a single oral dose of doxycycline hyclate in a murine model of Lyme borreliosis. Prophylaxis, as measured by the lack of cultivable spirochetes and demonstrable pathology, was noted for 43% of orally treated mice; in contrast, the sustained-release doxycycline hyclate completely protected mice from infection and resultant pathology.
No Findings of Dental Defects in Children Treated with Minocycline
Authors: Cascio Antonio , Di Liberto Chiara , D'Angelo Matteo , Iaria Chiara , Scarlata Francesco , Titone Lucina , Campisi Giuseppina
Published: June 2004

Forty-one children <8 years of age treated for brucellosis with oral minocycline (2.5 mg/kg) twice daily for 3 weeks were recalled and examined to check for dental staining and defects. Dental staining and defects were found in 14 of 41 exposed children (34.1%) and in 30 of 82 matched controls (36.6%), respectively (
P
> 0.2).
In Vitro Activities of Iodonium Salts against Oral and Dental Anaerobes
Authors: Goldstein Ellie J. C. , Citron Diane M , Warren Yumi , Merriam C. Vreni , Tyrrell Kerin , Fernandez Helen , Radhakrishnan Ukkiramapandian , Stang Peter J. , Conrads Georg
Published: June 2004

The comparative in vitro activities of 11 iodonium salt compounds, 0.12% chlorhexidine, and four antimicrobial agents against 322 anaerobic and fastidious potential dental and periodontal bacterial pathogens were studied. Iodonium salts 3, 4, 5, 9, and 10 had in vitro activities comparable to that of chlorhexidine against most isolates. These compounds may be suitable for incorporation into an oral mouthwash.
COHERENT SYSTEMS OF GENUS 0
Authors: LANGE H. , NEWSTEAD P. E.
Published: June 2004

In this paper we begin the classification of coherent systems (E,V) on the projective line which are stable with respect to some value of a parameter α. In particular we show that the moduli spaces, if non-empty, are always smooth and irreducible of the expected dimension. We obtain necessary conditions for non-emptiness and, when dim V=1 or 2, we determine these conditions precisely. We also obtain partial results in some other cases.
THE NONCOMMUTATIVE CHERN–CONNES CHARACTER OF THE LOCALLY COMPACT QUANTUM NORMALIZER OF SU(1,1) IN ${\rm SL}(2,\mathbb C)$
Authors: DIEP DO NGOC
Published: June 2004

We observe that the von Neumann envelop of (i.e. the smallest von Neumann algebra that contains) the quantum algebra of functions on the normalizer of the group SU (1,1)≅ SL (2,ℝ) in [Formula: see text] via deformation quantization contains the von Neumann algebraic quantum normalizer of SU (1,1) in the frame work of Waronowicz–Korogodsky, see ([8, Introduction and Sec. 1, Definition 1]), i.e. the C*-envelop or von Neumann envelop (W*-envelop) [Formula: see text] of the algebraic Hopf algebra. We then use the technique of reduction to the maximal subgroup to compute the K-theory, the periodic cyclic homology and the corresponding Chern–Connes character.
Dexamethasone treatment causes resistance to insulin-stimulated cellular potassium uptake in the rat
Authors: Rhee Michael S. , Perianayagam Anjana , Chen Pei , Youn Jang H. , McDonough Alicia A.
Published: June 2004

Patients treated with glucocorticoids have elevated skeletal muscle ouabain binding sites. The major Na+-K+-ATPase (NKA) isoform proteins found in muscle, α2 and β1, are increased by 50% in rats treated for 14 days with the synthetic glucocorticoid dexamethasone (DEX). This study addressed whether the DEX-induced increase in the muscle NKA pool leads to increased insulin-stimulated cellular K+ uptake that could precipitate hypokalemia. Rats were treated with DEX or vehicle via osmotic minipumps at one of two doses: 0.02 mg·kg−1·day−1 for 14 days (low DEX; n = 5 pairs) or 0.1 mg·kg−1·day−1 for 7 days (high DEX; n = 6 pairs). Insulin was infused at a rate of 5 mU·kg−1·min−1 over 2.5 h in conscious rats. Insulin-stimulated cellular K+ and glucose uptake rates were assessed in vivo by measuring the exogenous K+ infusion ([Formula: see text]) and glucose infusion (Ginf) rates needed to maintain constant plasma K+ and glucose concentrations during insulin infusion. DEX at both doses decreased insulin-stimulated glucose uptake as previously reported. Ginf (in mmol·kg−1·h−1) was 10.2 ± 0.6 in vehicle-treated rats, 5.8 ± 0.8 in low-DEX-treated rats, and 5.2 ± 0.6 in high-DEX-treated rats. High DEX treatment also reduced insulin-stimulated K+ uptake. [Formula: see text](in mmol·kg−1·h−1) was 0.53 ± 0.08 in vehicle-treated rats, 0.49 ± 0.14 in low-DEX-treated rats, and 0.27 ± 0.08 in high-DEX-treated rats. DEX treatment did not alter urinary K+ excretion. NKA α2-isoform levels in the low-DEX-treated group, measured by immunoblotting, were unchanged, but they increased by 38 ± 15% (soleus) and by 67 ± 3% (gastrocnemius) in the high-DEX treatment group. The NKA α1-isoform level was unchanged. These results provide novel evidence for the insulin resistance of K+ clearance during chronic DEX treatment. Insulin-stimulated cellular K+ uptake was significantly depressed despite increased muscle sodium pump pool size.
Mechanical anisotropy of adherent cells probed by a three-dimensional magnetic twisting device
Authors: Hu Shaohua , Eberhard Luc , Chen Jianxin , Love J. Christopher , Butler James P. , Fredberg Jeffrey J. , Whitesides George M. , Wang Ning
Published: June 2004

We describe a three-dimensional magnetic twisting device that is useful in characterizing the mechanical properties of cells. With the use of three pairs of orthogonally aligned coils, oscillatory mechanical torque was applied to magnetic beads about any chosen axis. Frequencies up to 1 kHz could be attained. Cell deformation was measured in response to torque applied via an RGD-coated, surface-bound magnetic bead. In both unpatterned and micropatterned elongated cells on extracellular matrix, the mechanical stiffness transverse to the long axis of the cell was less than half that parallel to the long axis. Elongated cells on poly-l-lysine lost stress fibers and exhibited little mechanical anisotropy; disrupting the actin cytoskeleton or decreasing cytoskeletal tension substantially decreased the anisotropy. These results suggest that mechanical anisotropy originates from intrinsic cytoskeletal tension within the stress fibers. Deformation patterns of the cytoskeleton and the nucleolus were sensitive to loading direction, suggesting anisotropic mechanical signaling. This technology may be useful for elucidating the structural basis of mechanotransduction.
Prenatal Nicotine Exposure Alters the Types of Nicotinic Receptors That Facilitate Excitatory Inputs to Cardiac Vagal Neurons
Authors: Huang Zheng-Gui , Wang Xin , Evans Cory , Gold Allison , Bouairi Evguenia , Mendelowitz David
Published: June 2004

Nicotinic receptors play an important role in modulating the activity of parasympathetic cardiac vagal neurons in the medulla. Previous work has shown nicotine acts via at least three mechanisms to excite brain stem premotor cardiac vagal neurons. Nicotine evokes a direct increase in holding current and facilitates both the frequency and amplitude of glutamatergic neurotransmission to cardiac vagal neurons. This study tests whether these nicotinic receptor–mediated responses are endogenously active, whether α4β2 and α7 nicotinic receptors are involved, and whether prenatal exposure to nicotine alters the magnitude of these responses and the types of nicotinic receptors involved. Application of neostigmine (10 μM) significantly increased the holding current, amplitude, and frequency of miniature excitatory postsynaptic current (mEPSC) glutamatergic events in cardiac vagal neurons. In unexposed animals, the nicotine-evoked facilitation of mEPSC frequency, but not mEPSC amplitude or holding current, was blocked by α-bungarotoxin (100 nM). Prenatal nicotine exposure significantly exaggerated and altered the types of nicotinic receptors involved in these responses. In prenatal nicotine-exposed animals, α-bungarotoxin only partially reduced the increase in mEPSC frequency. In addition, in prenatal nicotine-exposed animals, the increase in holding current was partially dependent on α-7 subunit–containing nicotinic receptors, in contrast to unexposed animals in which α-bungarotoxin had no effect. These results indicate prenatal nicotine exposure, one of the highest risk factors for sudden infant death syndrome (SIDS), exaggerates the responses and changes the types of nicotinic receptors involved in exciting premotor cardiac vagal neurons. These alterations could be responsible for the pronounced bradycardia that occurs during apnea in SIDS victims.