bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative HPTLC determination of prostaglandin E1
Authors: Luitjens K.‐D. , Funk W. , Rawer P. 
Published: May 2005

AbstractDirect in situ determination of PGE1 in dioxane/water (1:1) at concentrations between 50 μg/ml and 1 mg/ml is described. HPTLC of PGE1 was carried out on HPTLC Kieselgel 60 o.F. plates; application (200 nl) was with a Nano‐Appllcator and ethyl acetate/formic acid (400:5, v/v) served as mobile phase. The spots were located by dipping the plates into a 3% cupric acetate solution in 15% aqueous phosphoric acid, followed by heating at 120°C for 15 min. The plates were then evaluated directly at λ = 345 nm by chromatogram spectrometry. The coefficient of variation is 3.6%.
Fourier transform ion mobility spectrometry of barbiturates after capillary gas chromatography
Authors: Eatherton R. L. , Siems W. F. , Hill H. H. 
Published: May 2005

AbstractThis paper demonstrates a novel operating mode of an ion mobility detector (IMD) for obtaining both qualitative and quantitative data after capillary gas chromatographic separation of 5,5′‐disubstituted barbiturates. Using a recently developed time dispersive Fourier transform method for ion mobility spectrometry, complete ion mobility spectra could be obtained for each component in the chromatogram. This type of spectra can be used for providing qualitative information on unknown compounds or for selecting the proper detector conditions needed when operating in the continuous mobility monitoring mode.In this study each of the five barbiturates investigated produced a Fourier transformed ion mobility spectrum containing one major product ion. When drift times corresponding to those of the product ions measured in the FT mode were monitored continuously, selective chromatographic detection of the barbiturates was achieved. In one case even isomers could be differentiated based on mobility characteristics.
Capillary supercritical fluid chromatography with ultraviolet multichannel detection of some pesticides and herbicides
Authors: France J. E. , Voorhees K. J. 
Published: May 2005

AbstractThe useful combination of capillary supercritical fluid chromatography with ultraviolet multichannel detection is demonstrated by the analysis of selected pesticides and herbicides. In this application the advantages of compound identification by ultraviolet spectrometry are appended to the separating capability of capillary supercritical fluid chromatography. A pseudo oncolumn detection approach is used. Compromises from the theoretically ideal conditions for both capillary SFC and the multichannel UV detector are made to achieve a practical interfacing of the chromatographic and spectrophotometric techniques. Detection limits are at the low nanogram levels.
Determination of methylated dibenzothiophenes in environmental sarnples by on‐line HPLC‐CGC
Authors: Berthou F. , Dreano Y. 
Published: May 2005

AbstractConcurrent solvent evaporation with a loop‐type interface was used for on‐line HPLC‐CGC in the analysis of methylated dibenzothiophene (DBT) isomers in oil samples. The chromatographic behavior of 20 methyl DBT's was studied by HPLC on an aminopropylsilane DBTA phase and by GC on a selective methyl‐phenylsilicone phase. That provided a method for analyzing by GC‐flame photometric detection, the individual components of the DBT family, previously picked out of the crude oil matrix by HPLC. The GC oven temperature was shown to be critical during HPLC eluent introduction into the GC pre‐column. Too high a temperature induced a severe broadening of early eluted peaks whereas a temperature too close to the boiling point of the liquid at the inlet pressure induced double peaks. Optimized conditions were retained on this basis and may be used for the analysis of other families of polyaromatic hydrocarbons.
Computer‐aided selection and optimization of chromatographic columns and conditions for multicolumn analysis procedures
Authors: Villalobos Richard , Annino Raymond 
Published: May 2005

AbstractClearly, the usefulness of a computer‐aided column design program will depend on its ability to predict quickly and accurately, a design which will yield chromatograms closely approximating those obtained experimentally. Such a computer model for designing and specifying operating conditions for optimum performance of either single or serially coupled columns with different stationary phases is described herein. Tests have been performed in order to verify the accuracy of the model.In addition to single column optimization and the design of column combinations which can be used to achieve separations difficult or impossible on a single phase alone, the model has proven quite useful as an aid to the design and development of multicolumn analysis procedures that involve critical timing of valve‐switching sequences.
Quantitative determination of sulfur compounds in FCC gasolines by AED. A study of the effect of catalyst type and catalytic conditions on sulfur distribution
Authors: Albro Thomas G. , Dreifuss Peter A. , Wormsbecher Richard F. 
Published: May 2005

AbstractThe identification and quantification of sulfur‐containing compounds in gasoline has become an area of interest because of impending legislation regulating total sulfur levels in these fuels. To study the effects of catalyst type and catalytic conditions on gasoline sulfur distribution, a method has been developed employing both the compound‐independent and element‐specific response of the atomic emission detector (AED). Calibration and quantification can be accomplished even where standards are not available, owing to the nature of the AED response.Compounds were separated on a thick film polydimethylsiloxane column. An external calibration curve was applied to the area responses of individual sulfur components in the sulfur chromatogram, and the concentrations of each were calculated. Summation of these sulfur concentrations over the gasoline range yields the total sulfur content of the gasoline.The method is applicable to the determination of these compounds in raw crude oils, finished gasolines, fluid cracking catalyst (FCC) unit gasolines, and fluid catalytic cracking “model” compound studies. A prefractionating column was employed to remove heavy (>C13) materials; prefractionation is not, however, necessary for distilled or commercial gasoline samples. Detection limits, linearity, detector stability, and accuracy are discussed.
High resolution gas chromatographic method for determination of Robusta coffee in commercial blends
Authors: Frega Natale , Bocci Fabio , Lercker Giovanni 
Published: May 2005

AbstractThe unsaponifiable lipid fractions extracted from Arabica and Robusta coffee samples were analyzed by high resolution gas chromatography (HRGC) in a polar column with a thermally stable stationary phase (TAP, Chrompack). Certain characteristic ratios among diterpenic alcohols were found to permit measurement of the amount of Robusta blended with Arabica coffee, given a minimum content of 5–10%. Determination does not appear to be influenced by geographic origin of produce or even by decaffeination.
Isomeric composition of the ester fraction from epicuticular waxes of Festuca arundinacea Schreb
Authors: Tava Aldo , Cunico Cristina , Cremona Roberta , Piccinini Emiliana 
Published: May 2005

AbstractThe ester portion of epicuticular waxes of tall fescue (Festuca arundinacea Schreb.) is composed of mixtures of homologous series of fatty acids esterfied with fatty alcohols. GC analyses of natural esters gave rise to the separation of several compounds of different chain length. To identify and quantify individual components in the mixture, GC/MS analyses were carried out, and the mass spectra of each peak were recorded and analyzed for characteristic ions. This approach permitted a comparison with data obtained from classical methods using GC analysis of acid and alcohol moieties obtained by hydrolysis.
Reversed phase HPLC coupled on‐line to GC by the vaporizer/precolumn solvent split/gas discharge interface; analysis of phthalates in water
Authors: Hyötyläinen Tuulia , Grob Konrad , Biedermann Maurus , Riekkola Marja‐Lüsa 
Published: May 2005

AbstractReversed phase liquid chromatography (RPLC) was coupled on‐line to gas chromatography (GC) via the vaporizer chamber/preco‐lumn solvent split/gas discharge interface outlined recently. Water‐containing eluents were driven into a vaporizer chamber at 300°C by the LC pump. The Vapors were removed through an early vapor exist by the carrier gas. Solvent/solute separation occurred in hte retaining precolumn. Special attention was paid to the parame‐ters determining the losses of the most volatile compounds. The oven temperature during transfer was lowered close to the dew point of the eluent (the temperature at which recondensation occurs) in order to maximise the retention power of the retaining precolumn. The dew point depends on the transfer rate, the gas flow rate, and the gas inlet pressure. Sometimes even better retention of the vola‐tiles was observed at temperatures below the dew point, i.e. despite partial reconsideration. The method was applied to the analysis of phthalates in drinking and surface waters. The detection limits, using MS, were 5–10 ng/l.
Recombinant human secretory phospholipase A2: Purification and characterization of the enzyme for active site studies
Authors: Stadel J. M. , Jones C. , Livi G. P. , Hoyle K. , Kurdyla J. , Roshak A. , McLaughlin M. M. , Pfarr D. A. , Comer S. , Strickler J. , Bennett C. F. , Marshall L. 
Published: May 2005

AbstractA secreted form of phospholipase A2 (PLA2) is thought to play an important role in inflammatory diseases. To characterize this enzyme the cDNA encoding a low molecular weight PLA2 was cloned from a human placental cDNA library. The cDNA encoding the human PLA2 was subcloned into an expression vector and subsequently transfected into Chinese hamster ovary (CHO) cells. A stable CHO cell clone, secreting ca I mg/L of recombinant PLA2 into the medium, was scaled up in culture to 180L. The recombinant enzyme was purified from the cell supernatant to apparent homogeneity by a novel procedure combining adsorption to poly(vinylidene difluoride) membranes, ion exchange chromatography and size exclusion chromatography. The final recovery of PLA2 activity was 58%. A direct comparison between the purified recombinant human PLA2 and PLA2 purified from human synovial fluid, including molecular weight, antigenicity, ionic dependence, substrate specificity and sensitivity to know PLA2 inhibitors, indicated that the two enzymes exhibit identical biochemical properties. These results show that the recombinant PLA2 can be efficiently expressed and purified in sufficient quantities to characterize the enzyme active site, to aid in the rational development of PLA2 inhibitors as potential anti‐inflammatory drugs, and to investigate further the role of PLA2 in inflammatory disease.
Spectrofluorimetric study of the intermolecular complexation of monoclonal antibodies with the high potency sweetener N‐(p‐cyanophenyl)‐N′‐(diphenylmethyl)guanidineacetic acid
Authors: Droupadi P. R. , Anchin J. M. , Meyers E. A. , Linthicum D. S. 
Published: May 2005

AbstractMolecular complexation between a set of five monoclonal antibodies (MAbs) and a N,N′,N″‐trisubstituted guanidinium sweetner (TGS) was studies by monitoring the intrinsic fluorescence of the MAbs. Changes in the emission spectral properties of the MAbs were found to be related to the tryptophan residues in the antibody complementarity determining regions (CDRs). Two of the MAbs, NC10.10 and NC10.8, showed fluorescence quenching and hypsochromic (blue) shifts in the emission maxima upon complexation with the TGS ligand. Experiments with three other MAbs, NC6.8 and NC2.3, revealed only monotonic fluorescence quenching. The association constants obtained by spectroscopic techniques for the different MAb‐TGS complexes were found to be comparable with those determined using a conventional RIA. The thermodynamic parameters of the MAb‐TGS complexation were also examined. The intermolecular complexation was found to be exothermic for four of the five MAbs in this study. However, MAb NC2.3 was found to be an exception, in that it was associated with a small positive enthalpic change. This type of Spectrofluorimetric analysis can aid in the identification of interactive residues and molecular dynamics involved in TGS recognition by this set of MAb. Such information may prove useful in understanding the molecular recognition motifs responsible for the intense taste properties of high potency guanidine sweeteners.
Specific effect of corticoids on acetylcholine receptor expression in rat skeletal muscle cell cultures
Authors: Vilquin J.‐T. , Braun S. , Labouret P. , Zuber G. , Tranchant C. , Poindron P. , Warter J.‐M. 
Published: May 2005

AbstractThe potential effect of different classes of steroids on the expression of acetylcholine receptors (AChR) was studied in different primary cultures of newborn‐rat skeletal muscle cells. Comparison among three techniques for preparing newborn skeletal muscle cells showed that these systems were equivalent to study AChR expression. Only corticoids stimulated myogenesis as a twofold increase in AChR expression indicated. Among the corticoids, the glucocorticoids were the more potent, whereas the mineralocorticoid aldosterone had less marked effect. The sex hormones progesterone and testosterone partially blocked these effects, without inducing any significant effect when given alone. The steroids tested differed in efficacy in correlation with their different chemical structures. Among the glucocorticoids a clear structure‐activity relationship could be established. These results emphasize the specificity of corticoid action on muscle cells and suggest an explanation for the effects induced by glucocorticoids used in treating human muscular or neuromuscular diseases.
Origin of cells in contact with the growth cones of embryonal peripheral nerves and histochemical detection of nonspecific cholinesterase activity in quail‐chick and chick‐quail chimeras
Authors: Haninec P. , Dubový P. 
Published: May 2005

AbstractThe types of cells contacted by growth cones were examined in chick‐quail and vice versa chimeras. Simultaneously, the presence of nonspecific cholinesterase (nChE) was monitored in developing peripheral nerves of these embryos. In all the chimeras studied, the growth cones were in contact with both Schwann cell progenitors and mesenchymal cells of the limb bud. This observation implies that the growth cones may obtained guidance cues directly from the mesenchymal cells of the limb bud. Schwann cell progenitors as well as mesenchymal cells in contact with growth cones were capable to produce nChE molecules. The reaction product indicating nChE activity was localized on the outer surface of the plasma membrane of both types of cells in contact with growth cones. However, mesenchymal cells forming the “primitive perineurium” were devoid of the reaction product on their plasma membrane. We conclude that with exception of classic adhesive molecules the process of axonal guidance can be mediated by nChE molecules.
Miniature endplate potentials induced by ammonium chloride, hypertonic shock, and botulinum toxin
Authors: Vautrin J. 
Published: May 2005

AbstractIntracellular recordings were made at the neuromuscular junction (NMJ) of the mouse diaphragm to study alteration of miniature endplate potential (MEPP) amplitude and rise time after different treatments. Following either hyperosmotic shock or 3 to 5 min of incubation in 10 to 50 mM ammonium chloride (NH4Cl) (replacing NaCl, a treatment which is known to raise intracellular pH) MEPP frequencies increased and the amplitudes of. MEPPs decreased. These treatments as well as type A botulinum toxin (BoTx) gradually prolonged the rising phase of some MEPPs, which increased their time‐to‐peak (slow‐MEPPs; Vautrin and Kriebel: Neuroscience 41:71–88, 1991) and increased eventually their amplitude. Fasciculation after hyperosmotic shock or during NH4C1 challenge was blocked by D‐tubocurarine and was due to large slow‐MEPPs that reached threshold for the muscle fiber action potential. The development of fasciculation provided the time course for the development of giant‐MEPPs. Increased frequency of giant MEPP is accompanied by a block of the nerveevoked muscle contraction. Effects of BoTx on spontaneous release were functionally antagonized either by NH4C1 or hyperosmotic shock. NH4C1 delayed BoTx blockage of bell‐MEPPs. Data suggest that BoTx alters the formation of transmitter packets gradually but similarly to other treatments which increase incidence of skew‐MEPPs.
Nicotinic receptors of rat lymphocytes during adjuvant polyarthritis
Authors: Maslinski W. , Laskowska‐Bozek H. , Ryzewski J. 
Published: May 2005

AbstractResting rat lymphocytes and thymocytes express specific [3H]nicotine binding sites with Kd values 7.5 and 10 nM, respectively. Resting T lymphocytes express 5–7 times as many binding sites (1,500/cell) as do unfractionated thymocytes (250/cell), suggesting that only a subset of thymocytes express nicotinic binding sites. Neither macrophages nor B cells bear nicotinic receptors. [3H]nicotine binding to lymphocytes is competitively inhibited in the presence of the cholinergic agonist carbamylcholine with IC50=100 μM. The number of receptors expressed on draining lymph node lymphocytes is upregulated during the course of adjuvant induced polyarthritis: maximum of [3H]nicotine binding is observed at day 21 of the disease with a subsequent decline reaching basal level at day 36. These results show the presence of [3H]nicotine binding sites on T lymphocytes and suggest their involvement in the later immune phase of adjuvant induced polyarthritis.
GnRH‐Associated peptide (GAP) is present in the rat striatum and affects the synthesis and release of dopamine
Authors: Gobert A. , Guibert B. , Lenoir V. , Kerdelhue B. , Leviel V. 
Published: May 2005

AbstractA possible interference of the GnRH‐associated peptide (GAP) with the metabolism of dopamine in the rat striatum was investigated. The presence of the precursor of the peptide in this central region of dopaminergic terminals was first evidenced using specific RIA. The action of GAP on dopamine release was investigated in the caudate nucleus using the local superfusion with a push‐pull cannula supplied with an artificial CSF containing the Fitiated precursor of dopamine ([3H]tyrosine). Addition of GAP (1 μM) to the superfusing fluid resulted in an increase of the release of the newly synthesized dopamine without a significant modification of the total amine release. In situ neutralization of GAP by addition in the CSF of a rabbit serum containing antibodies directed against the GAP produced opposite effects evidencing a tonic function for this peptide. In addition to the increased specific activity of the dopamine released during GAP treatment, the alterations observed in the efflux (and the specific activity) of dihydroxyphenyl acetic acid and the activation of dopamine synthesis obtained in vitro in striatal slices in the presence of GAP led us to conclude that the GAP system could be considered as a positive control of dopamine synthesis.
Common sequence on distinct Vβ genes defines a protective idiotope in experimental encephalomyelitis
Authors: Vainiene M. , Gold D. P. , Celnik B. , Hashim G. A. , Vandenbark A. A. , Offner H. 
Published: May 2005

AbstractSynthetic TCR peptides expressed by encephalitogenic T cells can induce both cellular and humoral responses that protect against experimental encephalomyelitis. In the Lewis rat, encephalitogenic T cells predominantly express Vβ8.2, and a peptide in the CDR2 region representing residues 39–59 could both protect against and treat experimental autoimmune encephalitis (EAE). Similarly, the homologous and cross reactive 39–59 peptide from Vβ8.6 expressed by an EAE‐protective clone also had protective and therapeutic activity against EAE. The consensus sequence between the Vβ8.2 and Vβ8.6 peptides, which included residues 44–54, was postulated to contain the protective idiotope. In this report, we demonstrate that this peptide, designated Vβ8‐44–54, has comparable activity to the longer peptides for treating both active and passive EAE. Similar to the longer Vβ8.2‐39–59 peptide, the Vβ8‐44–54 peptide stimulates protective TCR peptide‐specific CD4 +, CD8dim T cells restricted by MHC I. We also report for the first time the recovery of Vβ8‐44–54 reactive T cells that express a variety of Vβ genes in their T‐cell receptor (TCR), including Vβ4, 8, 10, 12, 15, 17, 19, and 20. Taken together, these data establish that the Vβ8‐44–54 sequence constitutes an important autoregulatory idiotope in EAE. Moreover, the heterogeneity observed in the TCR expressed by anti‐Vβ8‐44–54 T cells suggests that the mechanism that produces biased V gene use in response to myelin basic protein (BP) is distinct from that which shapes the V gene repertoire of the regulatory T cells.
Transferrin receptor expression in myelin deficient (md)rats
Authors: Roskams A. J. , Connor J. R. 
Published: May 2005

AbstractThe question of iron regulation in the brain is the subject of increasing interest as the evidence continues to accumulate that a loss of brain iron homeostasis plays a significant role in some neurodegenerative diseases. Most cells acquire iron through a specific receptor mediated process involving transferrin, the iron mobilization protein. It appears that in the brain, endothelial cells, neurons, and oligodendrocytes express the transferrin receptor. This study uses a strain of rats (myelin deficient, md) in which oligodendrocytes fail to mature, and examines the consequences of this genetic defect on the expression of the transferrin receptor in the brain. The affinity of transferrin for its receptor is similar between the cerebral cortex and cerebellum in both the normal and myelin deficient rats (Kd = 7.8–10.6 nM). The transferrin receptor density is normally 2–3 times higher in the cerebellum than in the cerebral cortex. In the myelin deficient rat strain, the density of the transferrin receptor is decreased in both the cerebrum (56%) and cerebellum (70%) compared to the littermate control animals. Because oligodendrocytes are the only cell type affected in this mutant, the results suggest that these cells are responsible for a considerable amount of the transferrin receptors that are expressed in the brain (excluding the endothelial cell contributions). These observations are consistent with the existing literature stating that oligodendrocytes are responsible for the majority of transferrin and transferrin mRNA which is expressed in the brain, and support the working hypothesis that imbalances in brain iron homeostasis, particularly during development, are associated with myelin disorders.
Reactive microglia/macrophages phagocytose amyloid precursor protein produced by neurons following neural damage
Authors: Shigematsu K. , McGeer P. L. , Walker D. G. , Ishii T. , McGeer E. G. 
Published: May 2005

AbstractKainic acid lesions of rat striatum caused an elevation of amyloid precursor protein (APP) immunoreactivity in neurons and neurites, some of which were then phagocytosed by reactive microglia/macrophages. Immunoexpression of APP was observed in neurites and neurons 1 day after the kainic injection. Four days after lesioning, immunoreactivity was still concentrated in thick and distorted neurites, but it began to appear in microglia/macrophages and in the tissue matrix. The cells were identified as microglia/macrophages by the phenotypic markers Ia (OX6), leukocyte common antigen (OX1), C3bi receptor (OX42), and macrophage marker (EDI). They were negative for the astrocytic marker glial fibrillary acidic protein (GFAP). APP immunoreactivity in these phago‐cytic cells was most prominent between 1 week and 1 month postlesioning. No extracellular amyloid fibrils were detectable. These results suggest that APP production is rapidly upregulated in damaged neurons and accumulates in degenerating axons. However, phagocytosis of APP by reactive microglia/macrophages in this rat model does not result in production of Alzheimer type amyloid deposits.