bluuebunny/crossref_metadata_2025_split huggingface dataset:
δ13C and δ18O isotopic composition of CaCO3 measured by continuous flow isotope ratio mass spectrometry: statistical evaluation and verification by application to Devils Hole core DH‐11 calcite
Authors: Révész Kinga M. , Landwehr Jurate M. 
Published: November 2002

AbstractA new method was developed to analyze the stable carbon and oxygen isotope ratios of small samples (400 ± 20 µg) of calcium carbonate. This new method streamlines the classical phosphoric acid/calcium carbonate (H3PO4/CaCO3) reaction method by making use of a recently available Thermoquest‐Finnigan GasBench II preparation device and a Delta Plus XL continuous flow isotope ratio mass spectrometer. Conditions for which the H3PO4/CaCO3 reaction produced reproducible and accurate results with minimal error had to be determined. When the acid/carbonate reaction temperature was kept at 26 °C and the reaction time was between 24 and 54 h, the precision of the carbon and oxygen isotope ratios for pooled samples from three reference standard materials was ≤0.1 and ≤0.2 per mill or ‰, respectively, although later analysis showed that materials from one specific standard required reaction time between 34 and 54 h for δ18O to achieve this level of precision. Aliquot screening methods were shown to further minimize the total error. The accuracy and precision of the new method were analyzed and confirmed by statistical analysis. The utility of the method was verified by analyzing calcite from Devils Hole, Nevada, for which isotope‐ratio values had previously been obtained by the classical method. Devils Hole core DH‐11 recently had been re‐cut and re‐sampled, and isotope‐ratio values were obtained using the new method. The results were comparable with those obtained by the classical method with correlation = +0.96 for both isotope ratios. The consistency of the isotopic results is such that an alignment offset could be identified in the re‐sampled core material, and two cutting errors that occurred during re‐sampling then were confirmed independently. This result indicates that the new method is a viable alternative to the classical reaction method. In particular, the new method requires less sample material permitting finer resolution and allows automation of some processes resulting in considerable time savings. Published in 2002 by John Wiley & Sons, Ltd.
Identification of proteins in human cerebrospinal fluid using liquid‐phase isoelectric focusing as a prefractionation step followed by two‐dimensional gel electrophoresis and matrix‐assisted laser desorption/ionisation mass spectrometry
Authors: Davidsson P. , Folkesson S. , Christiansson M. , Lindbjer M. , Dellheden B. , Blennow K. , Westman‐Brinkmalm A. 
Published: November 2002

AbstractCerebrospinal fluid (CSF) is in close proximity to the brain and changes in the protein composition of CSF may be indicative of altered brain protein expression in neurodegenerative disorders. Analysis of brain‐specific proteins in CSF is complicated by the fact that most CSF proteins are derived from the plasma and tend to obscure less abundant proteins. By adopting a prefractionation step prior to two‐dimensional gel electrophoresis (2‐DE), less abundant proteins are enriched and can be detected in complex proteomes such as CSF. We have developed a method in which liquid‐phase isoelectric focusing (IEF) is used to prefractionate individual CSF samples; selected IEF fractions are then analysed on SYPRO‐Ruby‐stained 2‐D gels, with final protein identification by matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry (MALDI‐TOFMS). To optimise the focusing of the protein spots on the 2‐D gel, the ampholyte concentration in liquid‐phase IEF was minimised and the focusing time in the first dimension was increased. When comparing 2‐D gels from individual prefractionated and unfractionated CSF samples it is evident that individual protein spots are larger and contain more protein after prefractionation of CSF. Generally, more protein spots were also detected in the 2‐D gels from prefractionated CSF compared with direct 2‐DE separations of CSF. Several proteins, including cystatin C, IgM‐kappa, hemopexin, acetyl‐coenzyme A carboxylase‐α, and α‐1‐acid glycoprotein, were identified in prefractionated CSF but not in unfractionated CSF. Low abundant forms of posttranslationally modified proteins, e.g. α‐1‐acid glycoprotein and α‐2‐HS glycoprotein, can be enriched, thus better resolved and detected on the 2‐D gel. Liquid‐phase IEF, as a prefractionation step prior to 2‐DE, reduce sample complexity, facilitate detection of less abundant protein components, increases the protein loads and the protein amount in each gel spot for MALDI‐MS analysis. Copyright © 2002 John Wiley & Sons, Ltd.
Structural determination of hexadecanoic lysophosphatidylcholine regioisomers by fast atom bombardment tandem mass spectrometry
Authors: Hong Jongki , Kim Young Hwan , Gil Ji Hye , Cho Kun , Jung Jee H. , Han So‐Yeop 
Published: November 2002

AbstractThe structural determination of sn‐1 and sn‐2 hexadecanoic lysophosphatidylcholine (LPC) regioisomers was carried out using fast atom bombardment tandem mass spectrometry (FAB‐MS/MS). The collision‐induced dissociation (CID) of protonated and sodiated molecules produced diverse product ions due mainly to charge remote fragmentations. Based on the information obtained from the CID spectra of protonated and sodiated molecules, sn‐1 and sn‐2 hexadecanoic LPC isomers could be discriminated. Especially, the abundance ratio of the diagnostic ion pair [m/z 224/226] in the CID spectra of [M + H]+ ions was shown to be greatly different. Moreover, the CID‐MS/MS spectra of sodium‐adducted molecules for hexadecanoic LPC isomers showed characteristic product ions such as [M + Na − 103]+, [M + Na − 85]+, and [M + Na − 59]+, by which their regio‐specificity can be differentiated. Copyright © 2002 John Wiley & Sons, Ltd.
Investigation of cytolysin variants by peptide mapping: enhanced protein characterization using complementary ionization and mass spectrometric techniques
Authors: Stevens Stanley M. , Kem William R. , Prokai Laszlo 
Published: November 2002

AbstractMatrix‐assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) have been used in conjunction with time‐of‐flight (TOF) and quadrupole ion trap (IT) mass spectrometry, respectively, to analyze various cytolysin proteins isolated from the sea anemone Stichodactyla helianthus and digested by the protease trypsin. By employing different ionization methods, the subsequent changes in ionization selectivity for the peptides in the digested protein samples resulted in ion abundance variation reflected in the mass spectra. Upon investigation of this variation generated by the two ionization processes, it has been shown in this study that enhanced protein coverage (e.g., >95% for cytolysin III) can be achieved. Additionally, capillary and microbore reversed‐phase high‐performance liquid chromatography (RP‐HPLC) coupled with ESI mass spectrometry (MS) as well as flow injection analysis by nanoflow ESI‐MS afforded the necessary limit of detection (LOD) for detailed structural information of the cytolysin proteins by tandem mass spectrometry (MS/MS) methods. It can be concluded that cytolysins II and III correspond to sticholysins I and II, that “cytolysin I” is a mixture of modified forms of cytolysins II and III, and that “cytolysin IV” is an incompletely processed precursor of cytolysin III. Copyright © 2002 John Wiley & Sons, Ltd.
Structural characterisation of underivatised olive pulp xylo‐oligosaccharides by mass spectrometry using matrix‐assisted laser desorption/ionisation and electrospray ionisation
Authors: Reis Ana , Coimbra Manuel A. , Domingues P. , Ferrer‐Correia A. J. , Domingues M. Rosário M. 
Published: November 2002

AbstractPurified olive pulp glucuronoxylans, with a Xyl/GlcA ratio of 7:1, were subjected to mild acid hydrolysis and the mixture of oligosaccharides obtained was fractionated by size exclusion chromatography. One elution fraction representative of low molecular weight oligosaccharides was analysed by mass spectrometry using matrix‐assisted laser desorption/ionisation (MALDI) and electrospray ionisation (ESI) as ionisation methods, in the positive mode. Both types of spectra showed cationised molecules [M + Na]+ of xylo‐oligosaccharides in a range below m/z 1000. The xylo‐oligosaccharide structures identified were series of neutral oligosaccharides of xylose (Xyln, n = 3–7), of acidic oligosaccharides substituted by one glucuronic acid (XylnGlcA, n = 3–5) and by two glucuronic acid residues (XylnGlcA2, n = 2 and 3), and also of acidic oligosaccharides substituted with one 4‐O‐methylglucuronic acid residue (XylnmeGlcA, n = 2–4). The proposed structures were confirmed by tandem mass (MS/MS) spectra obtained using collision induced dissociation of the molecular ions. Fragmentation of cationised adducts of neutral Xyln yielded C‐ and A‐type fragments, while ammonium adducts mainly yielded B‐type fragments. The fragmentation of the sodium adducts of acidic oligosaccharides (XylnmeGlcA, XylnGlcA) resulted in the loss of the substituting residue (GlcA or meGlcA) as the predominant fragment, while the corresponding ammonium adducts yielded B‐type fragments. Copyright © 2002 John Wiley & Sons, Ltd.
Quantification of volatile compounds in the headspace of aqueous liquids using selected ion flow tube mass spectrometry
Authors: Španěl Patrik , Diskin Ann M. , Abbott Sian M. , Wang Tianshu , Smith David 
Published: November 2002

AbstractWe describe a method by which the concentrations of volatile compounds in the headspace of their dilute aqueous solutions in sealed containers can be determined using on‐line selected ion flow tube mass spectrometry (SIFT‐MS). Thus, the changing number density of the molecules of the volatile compound in the carrier gas of the SIFT‐MS instrument is described in terms of its changing flow rate as the pressure in the sealed container decreases during the sampling procedure. It is shown that the best analytical procedure is to determine the mean concentration of the trace gas in the liquid headspace over a given sampling time and relate this to the required concentration, which is the initial equilibrium concentration established before the pressure in the sealed container reduces significantly. To test the validity of this analytical approach, the headspace concentrations of acetaldehyde, ethanol and acetone above aqueous solutions of known concentrations have been determined. Hence, the Henry's Law constants for these compounds have been determined and found to agree with the published values. The confirmation of the quality of this sampling methodology combined with SIFT‐MS for the analysis of volatile compounds in liquid headspace paves the way for the rapid analyses of biological liquids such as urine and serum for clinical diagnosis and physiological monitoring. Copyright © 2002 John Wiley & Sons, Ltd.
DEVELOPMENT OF PERIODIC TENSION IN THE CONTRACTILE VACUOLE COMPLEX MEMBRANE OF PARAMECIUM GOVERNS ITS MEMBRANE DYNAMICS
Authors: Tani Tomomi , Tominaga Takashi , Allen Richard D. , Naitoh Yutaka 
Published: November 2002

AbstractThe contractile vacuole complex is a membrane‐bound osmoregulatory organelle of fresh water protozoa such as Paramecium. In Paramecium it consists of a central vacuole (the contractile vacuole) and 5–10 arms that radially extend from the vacuole into the cytosol (the radial arms). Excess cytosolic water, acquired osmotically, is segregated by the radial arms and enters the vacuole, so that the vacuole swells (the fluid‐filling phase). The vacuole then rounds (the rounding phase) and the radial arms sever from the vacuole. The vacuole membrane then fuses with the plasma membrane at the pore region and the pore opens. The vacuole shrinks as its fluid is discharged through the pore (the fluid‐discharging phase). The pore closes when the fluid has been discharged. The radial arms then reattach to the vacuole, so that the vacuole swells again as the fluid enters from the arms (the next fluid‐filling phase). We found that the vacuole continued to show rounding and slackening even after it together with a small amount of cytosol had been isolated from the cell. Using a microcantilever placed on the surface of the vacuole the tension of the in vitro vacuole increased to 5×10−3N m−1 as the vacuole rounds, and its lowest value was 1×10−4N m−1 during slackening. We propose a hypothesis that an increase in the spontaneous curvature of the organelle's membrane leads to an increase in membrane tension and thus to the vacuole's rounding, severing of the radial arms from the vacuole, and opening of the pore. Conversely, a decrease in the spontaneous curvature accompanied by a decrease in membrane tension could lead to the closing of the pore and reattachment of the radial arm at the start of the fluid‐filling phase.
TUBULAR‐VESICULAR TRANSFORMATION IN THE CONTRACTILE VACUOLE SYSTEM OF DICTYOSTELIUM
Authors: Gerisch Günther , Heuser John , Clarke Margaret 
Published: November 2002

AbstractThe contractile vacuole complex of Dictyostelium is the paradigm of a membrane system that undergoes tubular‐vesicular transitions during its regular cycle of activities. This system acts as an osmoregulatory organelle in freshwater amoebae and protozoa. It collects fluid in a network of tubules and cisternae, and pumps it out of the cell through transient pores in the plasma membrane. Tubules and vacuoles are interconvertible. The tubular channels are associated with the cortical actin network and are capable of moving and fusing. The contractile vacuole complex is separate from vesicles of the endosomal pathway and preserves its identity in a dispersed state during cell division. We outline techniques to visualize the contractile vacuole system by electron and light microscopy. Emphasis is placed on GFP‐fusion proteins that allow visualization of the dynamics of the contractile vacuole network in living cells. Proteins that control activities of this specialized organelle inDictyostelium have been conserved during evolution and also regulate membrane trafficking in man.
GIANT VACUOLES ARISING DURING ADH‐INDUCED TRANSCELLULAR BULK WATER FLOW ACROSS THE EPITHELIUM OF THE FROG URINARY BLADDER
Authors: Komissarchik Ya Yu , Snigirevskaya E. S. 
Published: November 2002

AbstractStructural changes of the cytoplasm of urinary bladder granular cells after an antidiuretic hormone (ADH) stimulation of water transport were studied using standard and cryogenic methods of electron microscopy. Numerous changes occurred in these cells, the cytoplasm of the granular cells becoming swollen, and the intercellular spaces enlarged. Most granules become fused with the apical membrane. Under maximal ADH action, giant vacuoles appear in the cytoplasm of granular cells, in association with microfilaments and microtubules. Analysis of ultrastructure of the granular cells has established the origin of giant vacuoles from the cis ‐cisterna of the Golgi complex. A hypothesis based on the morphofunctional homology of giant vacuoles in granular cells with the contractile vacuoles of Protozoa is proposed in which the giant vacuoles (‘contractile‐like’ vacuoles) are seen as operating a osmoregulatory role in these cells. It is also proposed that microtubules and microfilaments participate in giant vacuole migration through the cytoplasm.
VACUOLE FORMATION IN MAST CELLS RESPONDING TO OSMOTIC STRESS AND TO F‐ACTIN DISASSEMBLY
Authors: Koffer Anna , Williams Mark , Johansen Torben 
Published: November 2002

AbstractFluorescent probes were used to visualize the morphology of membranes and of F‐actin in rat peritoneal mast cells, exposed to hyperosmotic medium and consequently reversed to isotonicity. Hypertonicity induced cell shrinkage followed by a regulatory volume increase, and cell alkalinization that was sensitive to amiloride, an inhibitor of the Na+/H+ exchanger (NHE), but not to Latrunculin B, an inhibitor of actin polymerization. Using Bodipy‐Sphingomyelin, we have observed formation of vacuole‐like dilations (VLDs), primarily at or close to the adhesion plane, following the reversal from hyper‐ to isotonic medium. VLD formation was not inhibited by Latrunculin B or by amiloride. Phalloidin staining has shown that actin filaments do not surround the vacuoles and latrunculin‐induced depolymerization of actin has actually promoted vacuole formation, even in isotonic conditions. The results support the idea that a decrease in membrane tension promotes the internalization of the plasma membrane.
DYNAMIC VACUOLATION IN SKELETAL MUSCLE FIBRES AFTER FATIGUE
Authors: Lännergren Jan , Westerblad Håkan , Bruton Joseph D. 
Published: November 2002

AbstractVacuoles develop after fatiguing stimulation in frog skeletal muscle fibres. Experiments on isolatedXenopus muscle fibres show that this vacuolation is a dynamic process that reaches its maximum about 20min after the end of fatiguing stimulation and then recedes. Fatigue‐induced vacuoles originate from the t‐tubular system. Recent data indicate that vacuoles are formed because of lactate accumulation in the t‐tubules resulting in increased osmotic pressure and subsequent water influx. There is no obligatory connection between the presence of vacuoles and force depression, which is another common feature during the recovery from fatigue. Nevertheless, extensive vacuolation may exaggerate this force depression.
On the continuation of solutions for elliptic equations in two variables
Authors: Müller Frank 
Published: November 2002

We consider nonlinear elliptic differential equations of second order in two variables

F(x,y,z(x,y),z_x(x,y),\dots,z_{yy}(x,y))=0

,

(x,y)\in \Omega \subset \mathbb{R}^{2}

. Supposing analyticity of

F

, we prove analyticity of the real solution

z=z(x,y)

in the open set

\Omega

. Furthermore, we show that

z

may be continued as a real analytic solution for

F=0

across the real analytic boundary arc

\Gamma \subset \partial \Omega

, if

z

satisfies one of the boundary conditions

z=\varphi

or

z_{\bm{n}} = \psi (x,y,z,z_{\bm t})

on

\Gamma

with real analytic functions

\varphi

and

\psi

, respectively (

z_{\bm n}

denotes the derivative of

z

w.r.t. the outer normal

\bm n

on

\Gamma

and

z_{\bm t}

its derivative w.r.t. the tangent). The proof is based on ideas of H. Lewy combined with a uniformization method. Studying quasilinear equations, we get somewhat better results concerning the initial regularity of the given solution and a little more insight.

Résumé

Nous considérons les équations différentielles non-linéaires elliptiques d’ordre deuxième dépendant de deux variables

F(x,y,z(x,y),z_x(x,y),\dots,z_{yy}(x,y))=0

,

(x,y)\in \Omega \subset \mathbb{R}^{2}

. Supposent l’analyticité de

F

, nous démontrons l’analyticité de la solution réelle

z=z(x,y)

dans l’ensemble ouvert

\Omega

. En outre, nous démontrons qu’on peut prolonger

z

comme solution analytique réelle de

F=0

à travers la courbe

\Gamma \subset \partial \Omega

, si

z

vérifie une des conditions aux limites

z=\varphi

or

z_{\bm{n}} = \psi (x,y,z,z_{\bm t})

sur

\Gamma

avec des fonctions analytiques réelles

\varphi

et

\psi

(

z_{\bm n}

designe la dérivée de

z

par rapport à la normale extérieure

\bm n

sur

\Gamma

et

z_{\bm t}

la dérivée de

z

par rapport à la tangente). La démonstration est fondée sur des idées de H. Lewy, combinées avec une méthode d’uniformisation. En regardant des équations quasi-linéaires, nous réalisons des résultats améliorés en ce qui concerne la regularité initiale de la solution donnée et un peu plus de compréhension.
On the linearization of some singular, nonlinear elliptic problems and applications
Authors: Hernández Jesús , Mancebo Francisco J , Vega José M 
Published: November 2002

This paper deals with the spectrum of a linear, weighted eigenvalue problem associated with a singular, second order, elliptic operator in a bounded domain, with Dirichlet boundary data. In particular, we analyze the existence and uniqueness of principal eigenvalues. As an application, we extend the usual concepts of linearization and Frechet derivability, and the method of sub and supersolutions to some semilinear, singular elliptic problems.

Résumé
On étudie le spectre d’un problème à valeurs propres avec poids associé avec un opérateur elliptique singulier d’ordre deux sur un domaine borné avec condition au bord de Dirichlet. En particulier, on considère l’existence et l’unicité des valeurs propres principales. On donne comme application des extensions des notions de linéarisation et différentielle de Fréchet et de la méthode de sous et sursolutions à quelques problèmes elliptiques semilinéaires singuliers.
Convexity estimates for nonlinear elliptic equations and application to free boundary problems
Authors: Dolbeault Jean , Monneau Régis 
Published: November 2002

We prove the convexity of the set which is delimited by the free boundary corresponding to a quasi-linear elliptic equation in a 2-dimensional convex domain. The method relies on the study of the curvature of the level lines at the points which realize the maximum of the normal derivative at a given level, for analytic solutions of fully nonlinear elliptic equations. The method also provides an estimate of the gradient in terms of the minimum of the (signed) curvature of the boundary of the domain, which is not necessarily assumed to be convex.

Résumé
Nous démontrons la convexité de l’ensemble délimité par la frontière libre correspondant à une équation quasi-linéaire elliptique définie sur un domaine convexe en dimension 2. La méthode repose sur l’étude de la courbure des lignes de niveau aux points qui réalisent le maximum de la dérivée normale pour un niveau donné, pour des solutions analytiques d’équations elliptiques complètement non linéaires. La méthode donne aussi une estimation du gradient en fonction du minimum de la courbure (signée) du bord du domaine, qui n’est pas nécessairement supposé convexe.