bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic influences on life span and survival among elderly African‐Americans, Caribbean Hispanics, and Caucasians
Authors: Lee Joseph H. , Flaquer Antonia , Costa Rosann , Andrews Howard , Cross Peter , Lantigua Rafael , Schupf Nicole , Tang Ming‐Xin , Mayeux Richard 
Published: May 2004

AbstractAn investigation of the genetic influences on life span and survival was conducted among elderly African‐Americans, Caribbean Hispanics, and Caucasians Medicare recipients (ages 65–104 years). Family history information on 13,161 parents and siblings was obtained. Heritability of life span varied by the age and by ethnic group being lowest for African‐Americans. We recalculated the heritability coefficients for life span including only probands and their siblings, but the differences across ethnic groups persisted. In contrast the heritability of survival was more similar across ethnic groups but was similar to that for life span. Heritability coefficients for survival in probands and their siblings revealed little difference between ethnic groups and suggested that as much as 35% of the variation in survival may be genetically influenced. These results indicate that life span and survival are genetically influenced. Comparisons across generations and ethnic groups indicate that changes in environmental hygiene, social welfare, and health care systems are significant contributors to life span and survival, but genetic influences are also important. Identifying the genes associated with life span and survival will provide insight into how the genes interact with environment to influence aging in humans. © 2004 Wiley‐Liss, Inc.
Suprafluide Heliumtröpfchen: außergewöhnlich kalte Nanomatrices für Moleküle und molekulare Komplexe
Authors: Toennies J. Peter , Vilesov Andrey F. 
Published: May 2004

AbstractDieser Aufsatz gibt einen Überblick über neuere Experimente zur Spektroskopie und zu chemischen Reaktionen von Molekülen und Komplexen in Heliumtröpfchen. Im Inneren solcher Matrices wird eine ähnlich hohe spektroskopische Auflösung wie in der Gasphase erzielt, und durch Verdampfungskühlung lässt sich eine isotherme Tieftemperaturumgebung von T=0.37 K (4He‐Tröpfchen) oder 0.15 K (3He‐Tröpfchen) aufrechterhalten – kälter als in den meisten Festkörpermatrices möglich ist. Die Heliumtröpfchentechnik kombiniert somit die Vorteile von Gasphasen‐ und klassischen Matrixisolationstechniken. Ein wichtiger Punkt ist, dass die suprafluide Heliumumgebung binäre Stöße erleichtert und die bei der Rekombination freigesetzte Bindungsenergie absorbiert. Die Tröpfchen lassen sich folglich als isotherme nanoskopische Reaktoren betrachten, in denen Einzelmoleküle, Cluster oder sogar einzelne reaktive Stöße bei ultratiefen Temperaturen isoliert werden können.
Titelbild: Ultrafast Electron Crystallography of Surface Structural Dynamics with Atomic‐Scale Resolution (Angew. Chem. 20/2004)
Authors: Vigliotti Franco , Chen Songye , Ruan Chong‐Yu , Lobastov Vladimir A. , Zewail Ahmed H. 
Published: May 2004

AbstractDie Dynamik von Oberflächenstrukturen wird mit präzedenzloser räumlicher und zeitlicher Auflösung durch ultraschnelle Elektronenkristallographie bestimmt. Die dynamischen Prozesse werden durch einen Femtosekunden‐Laserpuls ausgelöst, ein ultrakurzer Elektronenpuls bildet die kurzlebigen Oberflächenstrukturen ab. Momentaufnahmen der Beugungsmuster zu Verzögerungszeiten Δt ermöglichen die Beobachtung der Dynamik von Oberflächenstrukturen in Echtzeit mit atomarer Auflösung. Mehr dazu erfahren Sie in der Zuschrift von A. H. Zewail et al. auf S. 2759 ff.
Superfluid Helium Droplets: A Uniquely Cold Nanomatrix for Molecules and Molecular Complexes
Authors: Toennies J. Peter , Vilesov Andrey F. 
Published: May 2004

AbstractHerein, recent experiments on the spectroscopy and chemical reactions of molecules and complexes embedded in helium droplets are reviewed. In the droplets, a high spectroscopic resolution, which is comparable to the gas phase is achieved, while an isothermal low‐temperature environment is maintained by evaporative cooling at T=0.37 K (4He droplets) or 0.15 K (3He droplets), lower than possible in most solid matrices. Thus the helium‐droplet technique combines the benefits of both the gas phase and the classical matrix‐isolation techniques. Most important, the superfluid helium facilitates binary encounters, and absorbs the released binding energy upon recombination. Thus the droplet can be viewed as an isothermal nanoscopic reactor, which isolates single molecules, clusters, or even a single reactive encounter at ultralow temperatures.
Thymol and carvacrol binding to DNA: model for DRUG–DNA interaction
Authors: Nafisi Sh. , Hajiakhoondi A. , Yektadoost A. 
Published: May 2004

AbstractThymol and carvacrol can bind to major and minor grooves of B‐DNA. The aim of this study was to examine the interaction of calf thymus DNA with thymol and carvacrol in aqueous solution and physiological pH with thymol/DNA and carvacrol/DNA (phosphate) molar ratios of 1/20, 1/10, 1/5, and 1/1. Fourier transform infrared and UV‐visible difference spectroscopy were used to determine the thymol and carvacrol binding mode, binding constant, sequence selectivity, DNA secondary structure, and structural variations of thymol/DNA and carvacrol/DNA complexes in aqueous solution. Spectroscopic evidence showed that the thymol and carvacrol interaction occurred mainly through H‐bonding of the thymol and carvacrol OH group to the guanine N7, cytosine N3, and backbone phosphate group with overall binding constant of K(thymol–DNA) = 2.43 × 103M−1, K(carvacrol–DNA) = 1.55×103M−1. In thymol and carvacrol–DNA complexes, DNA remains in the B‐family structure. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
Immunosuppressory activity of ubiquitin fragments containing retro‐RGD sequence
Authors: Szewczuk Zbigniew , Stefanowicz Piotr , Wilczyński Andrzej , Staszewska Anna , Siemion Ignacy Z. , Zimecki Michał , Wieczorek Zbigniew 
Published: May 2004

AbstractA peptide fragment corresponding to the ubiquitin50–59 sequence (LEDGRTLSDY) (U50–59) possesses a very high immunosuppressory activity, comparable to that of cyclosporine, both in the cellular and humoral immune responses. We found that the pentapeptide DGRTL (U52–56) is the shortest, effective immunosuppressory fragment of ubiquitin, although its potency is weaker than that of U50–59. Replacement of each consecutive residue with alanine in U52–56 allowed identification of essential amino acids involved in the immunosuppression. We also evaluated the roles of its N‐ and C‐terminal groups by their acetylation and/or amidation, respectively. The active sequence is located in the external loop of the molecule and therefore it may serve as an important functional epitope for intermolecular binding. Based on the crystal structure of ubiquitin molecule, we designed and synthesized the cyclic analogue with a restricted conformation, cyclo(Glt–Gln–Leu–Glu–Asp–Gly–Arg–Thr–Leu–Ser–Asp–Lys)—NH2 (Glt = glutaryl) by reacting the C‐terminal Lys side chain with the glutarylated N‐terminus. The peptide was designed to mimic the ubiquitin48–59 loop, in order to obtain the ligand that may interact with hypothetical receptors of the loop. The cyclization product selectively but strongly suppresses the cellular immune response. The results indicate that the 48–59 loop may serve as an important functional epitope in the ubiquitin molecule for intermolecular binding. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
Simultaneous quantitation of zidovudine and zidovudine monophosphate from plasma, amniotic ﬂuid and tissues by micellar capillary electrophoresis
Authors: Alnouti Yazen , White Catherine A. , Bartlett Michael G. 
Published: May 2004

AbstractZidovudine (AZT) therapy given during pregnancy has been shown to reduce the vertical transmission of the human immunodeﬁciency virus (HIV) from mother to fetus. In order to investigate the efﬁcacy of AZT, it is important to know the concentration of its active phosphorylated metabolites. We have developed the ﬁrst CE method for the simultaneous quantitation of AZT and zidovudine monophosphate (AZT‐MP) from rat plasma, amniotic ﬂuid and fetal tissues. Sample extractions were performed by protein precipitation using acetonitrile for the plasma and amniotic ﬂuids, while in fetal tissues solid phase extraction using Waters Oasis™ HLB extraction cartridges was used. Recoveries ranged from 78 to 92% for AZT, AZT‐MP and 3′‐azidouridine (internal standard, AZDU), in the three matrices. The optimum separation conditions were achieved using a 40 mm sodium dodecylsulfate (SDS) in 50 mm phosphate buffer (pH 7) with a run voltage of 15 kV. The CE system consists of a 75 µm i.d., 50 cm effective length uncoated fused silica capillary. The method was validated over the range 0.5–100 µg/ml (µg/g for tissues). Intra‐day precision (RSD) and accuracy (%error) for AZT ranged from 0.13 to 11 and 0.68 to 11.1%, respectively, while for AZT‐MP it ranged from 2.05 to 11.1 and 4.22 to 11.7%. Inter‐day precision and accuracy for AZT ranged from 3.82 to 11.2 and 3.14 to 9.01%, while for AZT‐MP it ranged from 3.9 to 9.32 and 3.44 to 9.37%, respectively. We also report the enzymatic dephosphorylation of AZT‐MP in the placental tissue of rats. This new enzymatic pathway provides increased understanding of the mechanism of anti‐viral transport in the rat during pregnancy. Copyright © 2004 John Wiley & Sons, Ltd.
Study on the bioavailability of nateglinide–hydroxypropyl‐β‐cyclodextrin complex capsule in rabbits by liquid chromatographic–tandem mass spectrometry
Authors: He Zhonggui , Chen Xiaoyan , Zhong Dafang , Zhao Chunshun , Liu Xiaohong , Zhang Ruhua 
Published: May 2004

AbstractTo evaluate the bioavailability of nateglinide–hydroxypropyl‐β‐cyclodextrin (HPCD) complex, a rapid and speciﬁc liquid chromatographic–tandem mass spectrometric method was developed and validated to determine nateglinide in rabbit serum. The analyte was extracted from serum samples by liquid–liquid extraction, separated on a Zorbax C18 column and detected by tandem mass spectrometry with an atmospheric pressure chemical ionization interface. Daidzein was used as the internal standard. The method has a lower limit of quantitation of 0.25 mg/L using 200 µL serum. The intra‐ and inter‐day relative standard deviations calculated from quality control (QC) samples were below 4%. The inter‐day relative error was within 1%. Nateglinide serum concentrations in rabbits given nateglinide–hydroxypropyl‐β‐cyclodextrin complex were much higher than those given the free drug. Signiﬁcant difference was observed in main pharmacokinetic parameters of tmax and Cmax but not AUC0–t between the complex and free drug. It was concluded that the absorption rate of nateglinide–HPCD complex was enhanced, compared with that of nateglinide free drug. Copyright © 2004 John Wiley & Sons, Ltd.
Evaluation of experimental strategies for the development of chiral chromatographic methods based on diastereomer formation
Authors: Srinivas Nuggehally R. 
Published: May 2004

AbstractThe past two decades has seen explosive growth in the ﬁeld of chirality as illustrated by the rapid progress in the various facets of this intriguing ﬁeld. Firstly, it is the basic understanding of the importance of chirality and, secondly, the awareness of the therapeutic pitfalls due to failure to recognize chirality that have paved the way for a rejuvenated interest in the ﬁeld. Needless to say that the impetus for chiral separation advancement and enhancement has been found to be the highest in the past decade and still continues to be an area of high focus. In this regard, both direct and indirect separation approaches have been instrumental in placing into literature stereoselective pharmacokinetic and pharmacodynamic data of plethora of drug racemates. Also, today, the cloud of uncertainty associated with the development of a chiral molecule is a thing of the past because the ﬁeld is so evolved and numerous options are available for stereoselective analysis. However, the decision to advance either a single enantiomer or a racemate for development has to be made by a rational approach with adequate justiﬁcation.Although indirect method of chiral separation has been well established with numerous examples of well‐documented cases of stereoselective pharmacokinetic data, there is a growing need for a review that provides a strategic overview of considerations and key issues for developing chromatographic methods based on diastereomer formation. This review provides a general framework for the exploratory planning and a deﬁnitive game plan for the establishment of chiral methods based on diastereomer formation. Also, it provides an exhaustive list of applications of numerous chiral derivatization reagents that have been used in the generation of stereoselective pharmacokinetic data. Copyright © 2004 John Wiley & Sons, Ltd.
Comparative study on the inclusion behaviour of cyclodextrin derivatives with venoruton and rutin by thin layer chromatography
Authors: Guo Xiliang , Shuang Shaomin , Wang Xiaoping , Dong Chuan , Pan Jinghao , Aboul‐Enein Hassan Y. 
Published: May 2004

AbstractThe interaction of rutin and venoruton (troxerutin), with α‐, β‐ and γ‐cyclodextrin (CD), hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) and methyl‐β‐cyclodextrin (M‐β‐CD) was investigated by reversed‐phase thin layer chromatography on polyamide plates. A mobile phase consisted of NH4OH; NH4Cl buffer solution containing various CD concentrations (pH = 9.7, 20°C) was used as mobile phase. The equilibrium constants (Kf) and the retention factor (Rf) were determined and used to study the inclusion process. The inﬂuence of CDs on the solubility of rutin and venoruton was characterized by RM values and the increasing hydrophilicity of drugs. The results show that the inclusion capacity of cyclodextrins follows the order HP‐β‐CD > M‐β‐CD > β‐CD > γ‐CD, and rutin is more easily included by the studied cyclodextrins than venoruton. In addition, the thermodynamic parameters (ΔH, ΔS) for the formation of complexes were obtained from the van't Hoff equation, displaying the enthalpy–entropy compensation effect. Copyright © 2004 John Wiley & Sons, Ltd.
Platinum particles‐modiﬁed electrode for HPLC with pulsed amperometric detection of thiols in rat striatum
Authors: Cao Xu‐Ni , Li Jin‐Hua , Xu Hai‐Hong , Lin Li , Xian Yue‐Zhong , Yamamoto Katsunobu , Jin Li‐Tong 
Published: May 2004

AbstractA new chemically modiﬁed electrode based on the immobilization of Pt particles is fabricated and exhibits electrocatalytic oxidation for l‐cysteine (l‐Cys), glutathione (GSH) and penicillamine (PEN) with relatively high sensitivity. It is also adaptable to HPLC for pulsed amperometric detection (PAD) of these thiols. PAD largely improves the detection sensitivity because the alternated polarizations can effectively clean and reactivate the electrode surface. It is shown that the peak currents of l‐Cys, GSH and PEN are linear to their concentrations, with the calculated detection limit of 1.1 × 10−7, 1.8 × 10−7 and 3.8 × 10−7 mol L−1, respectively (S/N = 3). The method has been successfully applied to assess the contents of l‐Cys and GSH in rat striatal microdialysates. The average contents of the two analytes in rat striatum are 2.6 × 10−6 and 2.8 × 10−6 mol L−1, respectively. Copyright © 2004 John Wiley & Sons, Ltd.
Analysis of salivary peptides using HPLC–electrospray mass spectrometry
Authors: Vitorino Rui , Lobo M. João C. , Duarte José A. R. , Ferrer‐Correia A. J. , Domingues Pedro M. , Amado Francisco M. L. 
Published: May 2004

AbstractSalivary peptides are involved in a wide range of functions constituting the ﬁrst line of defence of oral cavity and precursors of dental pellicle formation. The presence of mucins in saliva makes difﬁcult the analysis of the proteic content. This is due mainly to aggregation phenomenon between mucins and other high molecular weight glycoproteins and salivary proteins. Considering the importance of salivary peptides in biological functions, we have evaluated the inﬂuence of four different extraction methodologies on the separation and identiﬁcation of these proteins by HPLC‐MS. Based on their molecular weight, we identiﬁed a total of 22 peptides when extraction was performed using a solution of guanidine (6 m), compared with 14 peptides identiﬁed when saliva is acidiﬁed with TFA, which is an often used procedure. Our results also show the presence of mucin bind peptides, which include statherin, PRP1, PRP3, Histatin 1 and Histatin 5. Copyright © 2004 John Wiley & Sons, Ltd.
HPLC method for determination of DRF‐4367 in rat plasma: validation and its application to pharmacokinetics in Wistar rats
Authors: Mullangi Ramesh , Kallem Raja Reddy , Bhamidipati Ravi Kanth , Mamidi Rao N. V. S. , Srinivas Nuggehally R. 
Published: May 2004

AbstractA speciﬁc, accurate, precise and reproducible high‐performance liquid chromatography (HPLC) method was developed for the estimation of DRF‐4367, a novel cyclooxygenase‐2 inhibitor in rat plasma. The assay procedure involved simple liquid/liquid extraction of DRF‐4367 and internal standard (IS, celecoxib) from plasma into dichloromethane. The organic layer was separated and evaporated under a gentle stream of nitrogen at 40°C. The residue was reconstituted in the mobile phase and injected onto a Kromasil KR 100‐5C18 column (4.6 × 250 mm, 5 µm). The mobile phase consisting of 0.01 m potassium dihydrogen ortho‐phosphate (pH 3.2) and acetonitrile (40:60, v/v) was used at a ﬂow rate of 1.0 mL/min. The eluate was monitored using an UV detector set at 247 nm. The ratio of peak area of analyte to IS was used for quantiﬁcation of plasma samples. Nominal retention times of DRF‐4367 and IS were 6.6 and 11.2 min, respectively. The standard curve for DRF‐4367 was linear (r2 > 0.999) in the concentration range 0.1–20 µg/mL. Absolute recovery was >86% from rat plasma for both analyte and IS. The lower limit of quantiﬁcation of DRF‐4367 was 0.1 µg/mL. The inter‐ and intra‐day precisions in the measurement of quality control samples, 0.1, 0.3, 8.0 and 15.0 µg/mL, were in the range 6.93–9.34% relative standard deviation (RSD) and 0.48–6.59% RSD, respectively. Accuracy in the measurement of QC samples was in the range 91.24–109.36% of the nominal values. Analyte and IS were stable in the battery of stability studies, viz. benchtop, autosampler and freeze–thaw cycles. Stability of DRF‐4367 was established for 1 month at −80°C. The application of the assay to a pharmacokinetic study in rats is described. Copyright © 2004 John Wiley & Sons, Ltd.
Continuous capillary electrophoresis with ﬂow injection and its application for determination of Ephedrine and Pseudo‐ephedrine in Chinese medicinal preparations
Authors: Pan Zhongwei , Chen Xingguo , Hu Zhide 
Published: May 2004

AbstractThis article presents a new, simple and rapid continuous separation method by combination of ﬂow injection with capillary electrophoresis designed for the analysis of basic traditional Chinese medicines. The device was produced using commercial capillary and components readily available in analytical laboratory. In double‐T conﬁguration, the designed horizontal separation channel was 25 µm i.d. × 146 mm length (an effective separation length of 93 mm) quartz capillary, with two vertical elicitation arms produced from 0.5 mm i.d. pump tubing. The capillary was embedded in a 40 × 20 × 3 mm organic glass base. Using the double‐T conﬁguration, continuous introduction of a series of samples was achieved. More than 3.00 resolution for ephedrine and pseudo‐ephedrine were obtained using 100 mm borate buffer (pH 9.80) within 8 min in 25 µm separation channel with an electrical ﬁeld strength of 137 V/cm (UV detection at 215 nm). The linear calibration range was 50–1500 µg/mL (ephedrine, r = 0.9982; pseudo‐ephedrine, r = 0.9990) for both analytes. The limits of detection were 2.65 µg/mL for ephedrine and 2.92 µg/mL for pseudo‐ephedrine. In this device, the contents of ephedrine and pseudo‐ephedrine in ﬁve Chinese medicinal preparations were determined with RSDs (n = 5) in range 1.16–4.51% and recoveries in range 90.4–114.6%. Copyright © 2004 John Wiley & Sons, Ltd.
Quality assessment for tramadol in pharmaceutical preparations with thin layer chromatography and densitometry
Authors: Krzek Jan , Starek Małgorzata 
Published: May 2004

AbstractResearch studies have been carried out to develop a chromatographic and densitometric method suitable for identiﬁcation and determination of tramadol and impurities. In addition, the stability of tramadol in solutions was investigated, including an effect of solution pH, temperature and incubation time. In the ﬁrst instance the conditions for identiﬁcation and quantitative determination of tramadol and impurities in pharmaceutical preparations were established. The separation was performed on silica gel‐coated chromatographic plates (HPTLC) using two mobile phases: (I) chloroform–methanol–glacial acetic acid (9:2:0.1, v/v/v); (II) chloroform–toluene–ethanol (9:8:1, v/v/v). The UV densitometry was carried out at λ = 270 nm. The developed method is of high sensitivity and low detection and determination limits ranging from 0.044 to 0.35 µg. For individual constituents the recovery ranges from 93.23 to 99.66%. The next step was to evaluate the stability of tramadol and determine a method of decomposition under various experimental conditions. It was found that tramadol decomposes in various ways in acidic and basic environments producing (1RS)‐[2‐(3‐methoxyphenyl)cyclohex‐2‐enyl]‐N,N‐dimethylmethanamine (imp. B) and (1RS, 2RS)‐2‐[(dimethylamino)methyl]‐1‐(3‐methoxyphenyl)cyclohexanol (imp. cis‐T) or imp. cis‐T, respectively. Copyright © 2004 John Wiley & Sons, Ltd.
Microemulsion electrokinetic chromatography with laser‐induced ﬂuorescence detection: as tested with amino acid derivatives
Authors: Jianping Xie , Jiyou Zhang , Huanxiang Liu , Jiaqin Liu , Jianniao Tian , Xingguo Chen , Zhide Hu 
Published: May 2004

AbstractOver a decade ago, microemulsion electrokinetic chromatography was introduced as a novel mode of capillary electrophoresis. However, there has not been publication on the combination of microemulsion electrokinetic chromatography with laser‐induced ﬂuorescence detection. In this paper, a preliminary method using microemulsion eletrokinetic chromatography combined with laser‐induced ﬂuorescence detection and second derivative electrophoregram was established as a sensitive and selective assay for separation and determination of nine amino acids after derivatization with 4‐chloro‐7‐nitrobenzo‐2‐oxa‐1, 3‐diazol. The derivatization and separation conditions were optimized. In the investigated concentration ranges correlation coefﬁcients were better than 0.995. The relative standard deviation (n = 5) of the migration times and peak heights were 0.56–0.76 and 2.21–7.15%, respectively. The detection limits (S/N = 3) were at a neaomolar level (0.32–2.20 nm). The method was applied for the analysis of compound amino acid injection and a Chinese traditional herbal medicine. The recoveries were 95.9–107.9%. Copyright © 2004 John Wiley & Sons, Ltd.