bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physiological and biochemical response of freshwater cryptomonads (Cryptophyceae) to Fe deficiency
Authors: Li Xia , Xiaoming Qin , McKay R. Michael L. 
Published: May 2003

AbstractCryptomonads show strong seasonal distribution in lakes yet little is known of their nutrient requirements. In this study, we examined the role of Fe nutrition in the growth and photosynthetic properties of two freshwater cryptomonads (Cryptomonas sp. UTCC 337 and C. erosa UTCC 446). Cryptomonas sp. appeared more tolerant to Fe deprivation compared with C. erosa. Growth rates calculated for Cryptomonas sp. provided 100 nM and 1 000 nM Fe did not vary (0.55 d–1). Only cultures provided 10 nM Fe displayed significantly lower rates of growth (0.26 d–1) and lower cellular yields of chlorophyll. In contrast, cultures of C. erosa provided 10 nM Fe failed to grow, whereas cultures provided 100 nM Fe exhibited a reduced rate of growth (30% reduction) and lower yields of cellular chlorophyll (19% reduction) compared to high Fe (1 000 nM) cultures. Photochemical competency, assessed by measuring DCMU‐enhanced fluorescence, was high for cells of Cryptomonas sp. regardless of the level of Fe provided (Fv/Fm > 0.7). In contrast, photochemical competency was considerably reduced (Fv/Fm = 0.46) for C. erosa provided 100 nM Fe. Consistent with this, levels of the Fe‐containing electron transfer catalyst ferredoxin were reduced by 2.5 times in C. erosa provided 100 nM Fe compared to Fe‐replete cells. By comparison, ferredoxin levels varied only slightly in cells of Cryptomonas sp. provided either 100 nM or 1 000 nM Fe.
Diagnosis of Mycobacterium tuberculosis in cases of pulmonary infections from Jordanian hospitals
Authors: Saadoun Ismail , Nimri Laila , Amer Johnny 
Published: May 2003

AbstractThe aim of this study is to use the diagnostic utility of smear technique for the detection of Mycobacterium tuberculosis in clinical specimens obtained from patients suspected of having pulmonary tuberculosis. A total of 305 respiratory specimens (broncoalveolar lavage, sputum and pleural fluid) were collected from 298 patients having pulmonary infections as bronchitis, tuberculosis, pneumonia and other respiratory diseases. Results revealed that 25 specimens collected from 22 patients were positive (8.2%) by acid fast (AF) smear. Data indicated that the specificity and positive predictive value of the conventional smear assay were 100%, however, the sensitivity of the smear examination was 73.5%. Conventional smear technique actually detected M. tuberculosis in respiratory specimens and it could be applied for early and specific diagnosis of tuberculosis in such patients.
Protective role of certain chemicals against UV‐B‐induced damage in the nitrogen‐fixing cyanobacterium, Nostoc muscorum
Authors: Tyagi R. , Kumar A. , Tyagi M. B. , Jha P. N. , Kumar H. D. , Sinha R. P. , Häder D.P. 
Published: May 2003

AbstractThe protective effects of L‐cysteine, ascorbic acid, reduced glutathione, L‐tryptophan, and sodium pyruvate against UV‐B‐induced damages were studied in the nitrogen‐fixing cyanobacterium, Nostoc muscorum. When added to the culture suspension during UV‐B treatment, these chemicals caused a significant protective effect on survival and growth of the organism. Sodium pyruvate conferred the strongest protection whereas the weakest effect was elicited by tryptophan. A 20 min exposure of a culture suspension to UV‐B completely inactivated nitrogenase activity but the inactivation was strongly prevented by exogenous addition of ascorbic acid or reduced glutathione during UV‐B exposure, and weakly prevented by pyruvate, cysteine and tryptophan. In vivo nitrate reductase activity was not completely lost even after 80 min of UV‐B exposure, and addition of the test chemicals did not confer any significant protection to this enzyme. Whereas 14CO2 uptake was drastically inhibited (78% inhibition) by 30 min exposure to UV‐B in the absence of any test chemical, about 76% activity remained when the UV‐B exposure was given to cultures in the presence of ascorbic acid. These results suggest that the damaging effects of UV‐B are substantially minimized by certain reducing agents, the protective effect being particularly strong on the O2 sensitive enzyme, nitrogenase. Presence of these chemicals in their natural habitat or inside the cells of living organisms may partially protect/repair the damaging effects of UV‐B radiation.
Identification of deoxynivalenol, 3‐acetyldeoxynivalenol, and zearalenone in galactose oxidase‐producing isolates of Fusarium graminearum
Authors: Wilbert Fabricie Marcele , Kemmelmeier Carlos 
Published: May 2003

AbstractFusarium graminearum strains are well known for their role as plant pathogens and for their production of mycotoxins, and less known for their secretion of galactose oxidase, a well‐studied and useful enzyme. Three galactose oxidase‐producing isolates of F. graminearum were grown on rice to identify the production of zearalenone and trichothecenes through the use of thin layer chromatography and gas chromatography coupled to mass fragmentation. Detection and identification of deoxynivalenol, 3‐acetyldeoxynivalenol, and zearalenone were acomplished.
Bacillus thuringiensis associated with faeces of the Kerama‐jika, Cervus nippon keramae, a wild deer indigenous to the Ryukyus, Japan
Authors: Ohba Michio , Lee Dong–Hyun 
Published: May 2003

AbstractFaeces of the Kerama‐jika (Cervus nippon keramae), a wild shika deer indigenous to the Ryukyus, Japan, were examined for the natural occurrence of Bacillus thuringiensis. Of the ten faecal samples tested, seven contained this organism. The frequency of B. thuringiensis was 8.5% among 387 colonies of spore‐forming bacteria belonging to the Bacillus cereus/B. thuringiensis group. Of 33 B. thuringiensis isolates recovered, only one isolate, assigned to the serotype H3abc (serovar kurstaki), exhibited dual toxicity against larvae of the silkworm, Bombyx mori, and the mosquito, Aedes aegypti. All of 32 other isolates were serologically untypable or untestable, and were non‐toxic to larvae of the two insect species.
Isolation, identification and seasonal distrubution of airborne and waterborne fungi in Terkos Lake (Istanbul–Turkey)
Authors: Asan Ahmet , Kirgiz Timur , Sen Burhan , Camur–Elipek Belgin , Guner Utku , Guher Huseyin 
Published: May 2003

AbstractThis paper focuses on isolation and identification of airborne and waterborne fungi from different parts of Terkos Lake located in Istanbul (Turkey). The quantitative and qualitative fungal composition of the air and water of the Lake was surveyed monthly for a year (August 2000–July 2001). Water samples were taken at five different stations at Terkos Lake. Airborne fungal spore levels were estimated by exposing a petri dish containing Rose‐Bengal streptomycin agar medium to air for 15 minutes. A total of 2372 fungal colonies (1032 from air and 1340 water) was counted on 216 petri plates. We isolated twenty mould species belonging to 9 genera.Scopulariopsis brevicaulis, Penicillium expansumandCladosporium herbarumwere the most abundant species (22.0%, 13.4% and 12.9%, respectively).Cladosporium herbarumandsphaerospermumare very common in air samples (29.7% and 27.0%, respectively). Many of the species isolated are rarely in the atmospheric and water environment such asAspergillus nigerandCladosporium variabile. Statistical analysis revealed a positive correlation between total CFUs and a number of environmental factors.
Liquid flow in capillary (electro)chromatography: Generation and control of micro‐ and nanoliter volumes
Authors: Rapp Erdmann , Tallarek Ulrich 
Published: May 2003

AbstractWe describe and discuss instrumental developments in capillary (electro)chromatography which are of particular relevance for generating (and controlling) required volumetric flow rates in the micro‐ and nanoliter range through packed capillaries. Both isocratic and gradient elution are considered. For capillary HPLC this practically involves only commercial instrumentation, with systems based on syringe or piston pumps, but it also realizes the innovative concept of a high‐pressure electrokinetic pump. The numerous systems that have been used to generate electroosmotic flow through chromatographic beds are classified under the following headings: i) basically commercial capillary electrophoresis instruments (adapted for electrochromatography); ii) home‐built configurations; and iii) commercial capillary electrochromatography systems. Concerning the reviewed instrumentation, emphasis is placed on feasibility, automation, as well as system‐inherent delay times and dead volumes.
Onset of sample concentration effects on retention in field‐flow fractionation
Authors: Martin Michel , Feuillebois François 
Published: May 2003

AbstractIn field‐flow fractionation (FFF), when the sample amount is increased, a shift in retention occurs. Positive as well as negative deviations of the retention have been observed, depending on the type of sample and on the experimental conditions. Two concentration effects have been invoked to explain this retention shift: the viscosity effect (the velocity profile of the analyte suspension or solution is modified by the concentration dependence of the viscosity) and the mean distance effect (the mean distance of the analyte molecules or particles to the accumulation wall and the steady state cross‐sectional concentration profile of the analyte are affected by concentration‐dependent interactions between analyte molecules or particles). The general FFF retention equation has been solved in the case where the reciprocal of the viscosity and the FFF analyte‐field interaction parameter, λ, are linearly related to concentration. The two proportionality coefficients involved in these relationships are identified as the intrinsic viscosity and twice the second virial coefficient of the osmotic pressure, respectively. A general expression of the derivative of the analyte average relative velocity, R, with respect to the cross‐sectional average analyte concentration, 〈c〉, has been obtained as a function of these two coefficients, and of λo, the limit of λ for infinite dilution. A survey of retention effects reported in FFF literature for various sample types and FFF methods is presented.
AG+‐HPLC of conjugated linoleic acids on a silica‐based stationary phase. Part IV: A reference stationary phase and retention mechanisms
Authors: Cross Reginald F. , Zackari Henrik 
Published: May 2003

AbstractIn the previous paper on the Ag+‐HPLC of conjugated linoleic acids (CLAs) on a silica‐based stationary phase, we examined the relative retentions of the CLAs, their methyl esters (CLAMEs), and stearic acid. The retention of the CLAs far exceeds the sum of the retention of the CLAMEs and stearic acid. In this paper we isolate the interactions at the silica surface by determining the retentions of the same compounds on the NH4+ cation exchanger that is the precursor to the Ag+ column in the manufacturing process. On the NH4+ column, the CLAMEs are very weakly retained, but the sum of the retentions of the CLAMEs plus stearic acid is equal to that of the CLAs. It was determined that stearic acid is retained to the same degree on both the NH4+ and Ag+ stationary phases. By implication, the CLA carboxylic acid functionality does not interact with Ag+ and thus three‐centre complexes of the Ag+ with the CLA π bonds and carboxyl group do not occur. (Independent supporting evidence is also presented.) A model for CLA retention on the Ag+ stationary phase that explains the synergy of retention is presented. It involves a random arrangement of collapsed Ag+ alkyl sulphonate bonded phase on the silica surface. The nature of retention on the NH4+ stationary phase is also discussed. Partial separation of the CLAs on the NH4+ stationary phase shows that π bond interactions with the silica surface also contribute to the separations of the CLAs, the CLAMEs, and other unsaturated analytes. As was found on the Ag+ column in the absence acetonitrile, normal phase elution occurs and log k′ versus log (% strong solvent) plots for all analytes are linear on the NH4+ column. (Where the specific displacement mechanism of unsaturates from the Ag+ by ACN was present, the log‐linear plots were straight lines.)
Development of a liquid chromatography method for the assay and purity testing of josamycin propionate
Authors: Chepkwony Hezekiah Kibet , Rodriguez Evelio , Govaerts Cindy , Roets Eugène , Hoogmartens Jos 
Published: May 2003

AbstractA simple, robust, sensitive, and selective liquid chromatography method suitable for the determination of the semi‐synthetic antibiotic, josamycin propionate, and related substances is described. This method utilizes XTerra RP18 5 μm (25 cm×4.6 mm ID) as a stationary phase at 30°C and acetonitrile – 0.2 M ammonium acetate (pH 6.0) – water (51 : 3 : 46, v/v/v) as a mobile phase, delivered at 1.0 mL/min. UV detection is performed at 232 nm. Josamycin propionate is completely separated from the seven related substances of known identity and from at least seven unknown impurities, present in commercial samples. The robustness of the method was evaluated by a full‐factorial experimental design. The LOQ for josamycin propionate was 0.03% and the LOD was 0.01%. For most samples the analysis time is 90 min. Exceptionally, very strongly retained impurities may require an isocratic analysis time of 160 min. In that case, time can be saved by using gradient elution, which needs an analysis time of almost 100 min.
High‐performance liquid chromatography method for analysis of phenolic acids, phenolic aldehydes, and furanic derivatives in brandies. Development and validation
Authors: Canas Sara , Belchior A. Pedro , Spranger M. Isabel , Bruno‐de‐Sousa R. 
Published: May 2003

AbstractA simple and reproducible HPLC method permitting simultaneous determination of phenolic acids (gallic, vanillic, syringic, and ferulic), phenolic aldehydes (vanillin, syringaldehyde, coniferaldehyde, and sinapaldehyde), and furanic derivatives (furfural, 5‐hydroxymethylfurfural, and 5‐methylfurfural) in brandies was developed and validated. A considerable advantage of this method is the good separation and quantification of the compounds of interest without sample preparation. The method exhibited good linearity, high precision, high sensitivity, and suitable selectivity and specificity over a wide range of concentrations as well as low analytical limits. It can therefore be of a great interest either for scientific research or for routine analysis of brandies, namely in quality control. The analysis of four‐year‐aged brandies shows the real applicability of the method to distinguishing brandies according to the botanical species of the wooden barrel.
Evaluation of the use of microemulsions as eluents in high‐performance liquid chromatography
Authors: El‐Sherbiny Dina Tawfik Mohamed , El‐Ashry Saadia Mohamed , Mustafa Mohamed Ahmed , Abd‐El‐Rahman El‐Emam Ali , Hansen Steen Honoré 
Published: May 2003

AbstractAn overview of the use of microemulsions as eluents in HPLC is given. The separation mechanisms involved are discussed and the technique is compared to solvent modified micellar chromatography as well as to ordinary reversed‐phase HPLC in order to evaluate differences and similarities. The microemulsion systems have been used for the separation of a number of antihypertensives and non steroidal antiinflammatory drug substances as well as for the analysis of bumetanide and acebutolol in plasma and urine. The plasma samples may be injected directly onto the HPLC system after a simple dilution.
Analytical methods for the quantification of free melamine and cyanuric acid in Nylon 6/6,6 co‐polymer
Authors: Hamilton Deanna W. , O'Neal Patrick A. 
Published: May 2003

AbstractMelamine cyanurate is a salt of melamine and cyanuric acid, which is commonly used as a flame retardant in nylon polymer. Free cyanuric acid and/or melamine in nylon polymer can cause processing problems in molded applications, resulting in brittle parts with low ductility. Analytical methods have been developed to extract free cyanuric acid and melamine from nylon 6/6,6 co‐polymer using an octanesulfonic acid/isopropanol solution. An ion exclusion chromatography method with ultraviolet spectroscopic detection has been developed to quantify free cyanuric acid in the nylon extractant. Extraction efficiency of 88–133% and limit of detection of 0.4 ppm was obtained for free cyanuric acid in nylon polymer using this method. A liquid chromatography method with ultraviolet spectroscopic detection has been developed to quantify free melamine in the nylon extractant. Extraction efficiency of 76–90% and limit of detection of 2.8 ppm was realized for free melamine in nylon polymer using this method. These new analytical techniques have been successfully utilized to quantify free melamine and cyanuric acid in nylon 6/6,6 co‐polymer.
Application of naphthylcarbamate‐substituted β‐cyclodextrin bonded silica particles as stationary phase for high‐performance liquid chromatography
Authors: Gong Yinhan , Lee Hian Kee 
Published: May 2003

AbstractNaphthylcarbamate‐substituted (3‐(2‐O‐β‐cyclodextrin)‐2‐hydroxypropoxy)‐propylsilyl‐appended silica gel (NSCD‐HPS) has been synthesized via a convenient liquid‐solid phase reaction on a silica gel surface. The chromatographic behavior of NSCD‐HPS in high‐performance liquid chromatography (HPLC) was studied with several disubstituted benzenes and some chiral aromatic compounds under both normal and reversed‐phase conditions. The results show that NSCD‐HPS has excellent selectivity for the separation of positional isomers of disubstituted benzenes and enantiomers of chiral aromatic compounds.
Development of packed capillary columns using carbon dioxide slurries
Authors: Planeta Josef , Karásek Pavel , Vejrosta Jiří 
Published: May 2003

AbstractA modified procedure for the preparation of packed capillary columns by the use of supercritical or liquid carbon dioxide slurries is proposed. This technique removes the problems arising from sudden and rapid movement of sorbent suspension at the beginning of the filling process. The parameters influencing the packing process (temperature, pressure, and restrictor that controls the flow rate of CO2), have been optimized. The columns prepared under optimized conditions exhibit high efficiency (average value of the reduced plate height h′ ca. 2.2), and long term stability. An example of the SFC separation of polydimethylsiloxanes in silicone oil is presented.
Development of comprehensive two‐dimensional packed column supercritical fluid chromatography
Authors: Hirata Yukio , Hashiguchi Takashi , Kawata Etsushi 
Published: May 2003

AbstractA comprehensive two‐dimensional supercritical fluid chromatographic system with conventional packed columns was developed. The system used a computer‐controlled ten‐port valve, a capillary trap, and a restrictor. The mobile phase was pure carbon dioxide. The first dimension column was operated under constant pressure in the stopped‐flow mode, while the second dimension column was operated in the constant flow mode. The effluent of the first column was depressurized through the restrictor and solute was trapped within the capillary trap. Then the trapped solute was transferred into the second column by switching the valve. Since the solute transfer process is very rapid, the valve can be switched back after a short injection period in order to collect next fraction. This allowed the sampling time to be changed without changing any of the other conditions, such as the second dimension run time. The system was applied to the separation of triglycerides in fats and oils. Separations were performed using the same ODS packing materials for both columns, and the first column was operated under subcritical conditions and the second column under supercritical conditions.
Enantiomeric separation of aminoglutethimide by capillary electrophoresis using native cyclodextrins in single and dual systems
Authors: Abushoffa Adel M. , Fillet Marianne , Marini Roland D. , Hubert Philippe , Crommen Jacques 
Published: May 2003

AbstractAminoglutethimide (AGT) is one of the few examples of chiral drugs that can be enantioseparated by capillary electrophoresis using any of the three native cyclodextrins: α‐, β‐, or γ‐CD. A complete resolution of the enantiomers of this compound in cationic form could be achieved with each of the three CDs, using a pH 3 phosphoric acid‐triethanolamine buffer. Affinity constants for AGT enantiomers with the three native CDs were determined, confirming that the highest selectivity was given by γ‐CD while the strongest complexation was obtained with β‐CD. However, an opposite affinity pattern was observed with the latter. Selectivity was lower for AGT enantiomers in dual CD systems, compared to that obtained with a single selector at its optimal concentration, which confirms that dual systems are of more limited interest when the two selectors have a similar effect on the analyte mobility. These results are in good agreement with those predicted using recently developed mathematical models.
Analysis of gastrodin and tetramethylpyrazine in traditional Chinese preparations by micellar electrokinetic chromatography
Authors: Rongying Wang , Wanyun Ma , Dieyan Chen 
Published: May 2003

AbstractA simple, rapid, and accurate micellar electrokinetic chromatographic method has been developed for determination of gastrodin and tetramethylpyrazine in three traditional Chinese preparations: Zhennaoning jiaonang, Yangxue shengfa jiaonang, and Xiaoshuan zaizao wan. Running buffer comprising 50 mM sodium tetraborate and 15 M sodium dodecylsulfate (SDS), pH 9.50, was found to be most suitable for the separation. All experiments was performed with a 47 cm (40 cm effective length)×75 μm ID uncoated fused‐silica capillary and UV detection at 200 nm. The linear calibration ranges were 2.5–200 μg mL–1 (R = 0.999) for gastrodin and 5.0–200 μg mL–1 (R = 0.997) for tetramethylpyrazine; the detection limits were 0.5 μg mL–1 and 0.8 μg mL–1, respectively. Recoveries of the two analytes from the samples, calculated by use of a method described in detail in the text, were between 94.21 and 104.46%. The amounts of gastrodin and tetramethylpyrazine in the preparations were easily determined within 10 min.
Determination of dissociation constants of ten alkaloids by capillary zone electrophoresis
Authors: Gong Suxuan , Su Xiaodan , Bo Tao , Zhang Xu , Liu Huwei , Li Ke An 
Published: May 2003

AbstractThe dissociation constants of ten alkaloids, berbamine, (+)‐tetrandrine, thalifaretine, thalifaricine, northaltive, matrine, sophocarpine, sophoridine, oxymatrine, and oxysophocarpine isolated from herbal medicines Thalictrum and Sophora flavescens, were determined by capillary zone electrophoresis (CZE). The analysis time for each alkaloid was within 10 min under the following experimental conditions: acetate (pH 3.81–5.55) and phosphate buffer (pH 6.05–9.29) with ionic strength set at 0.03, applied voltage 30 kV, UV detection at 210 nm, capillary temperature 25°C. Effective mobility for each alkaloid and corresponding pH were fitted to an equilibrium expression by using nonlinear regression as well as linear regression, showing that the two models give comparable results for all studied alkaloids. The correlation coefficients were between 0.987 and 1.00 in the linear regression model, and between 0.978 and 1.00 in the nonlinear model. The measured pKa values for the ten alkaloids were from 5.7 to 7.8. The pKa values changed with the addition of organic additive to the buffer system.