bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterisation of flexible baffles in an oscillatory baffled column
Authors: Fitch A W , Ni X , Stewart J
Published: August 2002

In our previous studies the volume‐averaged strain rates, of 2–22 s−1, were obtained in an oscillatory baffled column (OBC) based on velocity measurements over a half baffled cell for oscillatory Reynolds numbers of 1000–4030. These values are very low compared with those in a traditional stirred tank vessel (at least >100 s−1) for similar operational conditions and the same power consumption. It was also observed that the volume‐averaged strain rates in the OBC fluctuated with the phase of oscillation over any cycle, with high values coinciding with eddy generation, and low values with eddy cessation. The objective of this study is to show that such fluctuations can be attenuated by employing innovative flexible baffles, whose inside edges move with the fluid oscillation. In this paper experimental measurements of velocity vector maps and strain rate distributions using Digital Particle Image Velocimetry (DPIV) are presented for both conventional and flexible baffles in an OBC. Mixing characterisation, in terms of axial dispersion coefficients, are compared for both baffle designs. The results show that the flexible baffles can reduce the fluctuations and magnitudes of the volume‐averaged strain rates in the OBC without compromising the mixing performance. Low and uniform strain rate distributions in time and space are essential biochemical, biomedical and pharmaceutical applications where shear sensitive cultures are involved.

© 2001 Society of Chemical Industry
Solubilization of methanol and ethanol in palm oil stabilized by medium‐ and long‐chain alkanols
Authors: Dzulkefly K , Lim W H , Hamdan S , Norsilah K
Published: August 2002

Solubilization of methanol and ethanol in crude palm oil, refined, bleached and deodorized palm oil (RBD PO) and RBD palm olein (POL) was studied using medium‐ and long‐chain alkanols (C4–C12). Ternary phase diagrams were constructed to determine the solubilization (isotropic) region. The results showed that methanol and ethanol are solubilized to a greater extent in an unsaturated palm olein than the saturated CPO and RBD PO in the presence of long‐chain alkanols. The minima of the solubilization curves for dodecanol, decanol and octanol were 27%, 30% and 33% of alkanol respectively in the methanol system, whereas in the ethanol system, the minima for the same alkanols were found at 22%, 24% and 27%. The longer chain‐length alkanol (dodecanol) requires a lesser amount (21% and 32%) to achieve miscibility compared with 53% and 57% for butanol in mixtures containing 70:30 and 50:50 wt ratios respectively. The kinematic viscosity of the isotropic solutions increases with the chain‐length and percentage of alkanols. Solubilization using a POL/methanol/butanol system significantly reduced the kinematic viscosity of POL from 72.7 mm2 s−1 to the value allowable for No 2 diesel fuel (1.9–4.1 mm2 s−1) or about a 96% reduction from the initial kinematic viscosity of POL.

© 2002 Society of Chemical Industry
Fragile X syndrome, the Fragile X related proteins, and animal models
Authors: Hoogeveen André T. , Willemsen Rob , Oostra Ben A.
Published: August 2002

The Fragile X syndrome (FraX), which is characterized among other physical and neurologic impairments by mental retardation, is caused by the absence of the product of the FMR1 gene. The Fragile X Mental Retardation Protein (FMRP) is a member of a novel family of RNA‐binding proteins. The latter includes two other proteins highly homologous with FMRP: the fragile X related proteins 1 and 2 (FXRP1 and FXRP2). Characterization of FXRPs, including their interaction with FMRP, will provide critical information about the mechanisms of action of FMRP and the role of this group of proteins in FMRP‐deficient conditions such as FraX. Genetic manipulations of FMRP and the FXRPs should also provide valuable tools for investigating pathophysiology and gene therapies in FraX. The present review summarizes the strategies used for identifying the FXRPs, their chromosomal localization, molecular structure, and tissue distribution. It also reviews interactions between different members of this family of RNA‐binding proteins. Animal models, both knockout and transgenic, of FMRP and the FXRPs are discussed. Phenotypic features of the FMR1 knockout mouse, the FMR1 transgenic rescue mouse, and other novel strategies for manipulating and delivering FMRP and FXRPs to the brain and other tissues are described. Microsc. Res. Tech. 57:148–155, 2002. © 2002 Wiley‐Liss, Inc.
Regulation of adhesive interaction between podocytes and glomerular basement membrane
Authors: Kretzler Matthias
Published: August 2002

Glomerular filtration depends on well‐orchestrated cell–cell and cell–matrix contacts of glomerular podocytes. Over the last years critical constituents of these contacts have been identified via molecular approaches. Podocyte cell–matrix interactions have been shown to be mediated in part by α3β1‐integrin heterodimers. Disturbances of integrin matrix interaction lead to detachment of podocytes in vitro, corresponding to the critical event of foot process retraction and glomerular basement membrane (GBM) denudation in vivo. Further, dystroglycan‐mediated matrix attachment appears to play a critical role for podocyte foot process architecture. Downstream signaling events are currently elucidated concentrating mainly on integrin‐dependent cascades and their consequences for podocyte adhesion and proliferation. An activation of the integrin‐linked kinase in podocyte damage in vivo and in vitro makes this molecule a particularly interesting candidate for integrin‐mediated inside‐out and outside‐in signaling in podocytes. Podocyte cell–cell interaction has been characterized in a few studies in vitro, indicating the slit diaphragm to be a modified adherens junction. The structural link between the cell–matrix and cell–cell contacts is maintained by the actin cytoskeleton, which may also enable cross‐talk between these two cell contact sites. Examining podocyte function in tissue culture, animal models and human expression studies should allow further detailed dissection of the molecular pathways responsible for maintenance and failure of the glomerular filtration barrier. Microsc. Res. Tech. 57:247–253, 2002. © 2002 Wiley‐Liss, Inc.
Diabetic vascular dysfunction: Links to glucose‐induced reductive stress and VEGF
Authors: Tilton Ronald G.
Published: August 2002

A complete biochemical understanding of the mechanisms by which hyperglycemia causes vascular functional and structural changes associated with the diabetic milieu still eludes us. In recent years, the numerous biochemical and metabolic pathways postulated to have a causal role in the pathogenesis of diabetic vascular disease have been distilled into several unifying hypotheses. These involve either increased reductive or oxidative stress to the cell, or the activation of numerous protein kinase pathways, particularly protein kinase C and mitogen‐activated protein kinases. As detailed below, there is tremendous crosstalk between these competing hypotheses. We propose that increased tissue glucose levels alter cytosolic coenzyme balance by increased flux of glucose through the sorbitol pathway increasing free cytosolic NADH levels. Increased NADH levels can generate reactive oxygen species via numerous mechanisms, lead to the formation of intracellular advanced glycation end products, and induce growth factor expression via mechanisms involving protein kinase C activation. The elevation in growth factors, particularly vascular endothelial growth factor (VEGF), is responsible for the vascular dysfunction via numerous mechanisms reported here in detail. Microsc. Res. Tech. 57:390–407, 2002. © 2002 Wiley‐Liss, Inc.
Differential response of mature TrkA/p75NTR expressing human and pig oligodendrocytes: Aging, does it matter?
Authors: Althaus Hans H. , Mursch Kay , Klöppner Sabine
Published: August 2002

A differential morphological response of mature oligodendrocytes (OL) isolated from human and pig brains to the phorbol ester 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) and to the nerve growth factor (NGF) was observed. In both cases, OL regenerate their processes; however, the rate and the extension of the process formation of human OL were behind that of pig OL. Presumably, the advanced age of the human tissue in these experiments might have contributed to this decrease in process formation, an effect that was already observed for rat OL [Yong et al. (1991) J Neurosci Res 29:87–99]. The less effectivity of NGF via TrkA, which was immunocytochemically shown in human OL, and of TPA via the protein kinase C (PKC) pathway, may have its common focus on the mitogen‐activated protein kinase (MAPK) cascade. In this context, it was noted that only a few studies on aging of mature OL are available. It is conceivable that age‐related changes in the properties of OL could be an important factor for their cellular responsiveness during longer lasting demyelinating diseases such as multiple sclerosis. Hence, this review would like to provide a basis for future investigations on the aging of mature OL. The data presently available suggest a preliminary classification of mature OL into three categories. Microsc. Res. Tech. 52:689–699, 2001. © 2001 Wiley‐Liss, Inc.
Alveolar macrophage–T cell interactions during Th1‐type sarcoid inflammation
Authors: Agostini Carlo , Facco Monica , Chilosi Marco , Semenzato Gianpietro
Published: August 2002

Sarcoidosis is an immunomediated, multisystem disorder of unknown cause(s) characterized by a heightened Th1 immune response that leads to an uncontrolled granuloma formation at sites of disease activity. The past few years have seen outstanding advances in the understanding of immunological and molecular events involved in the pathogenesis of this disease. The idea is that several cytokines and chemokines, which are secreted at sites of disease activity, participate in granuloma formation. This paper describes recent data that have clarified some of the events that govern the development of the hypersensitivity reaction during sarcoidosis. In particular, we will review recent evidence indicating that a complex relationship exists between the macrophage/lymphocyte cellular axis and the tissue networks of cytokines. Microsc. Res. Tech. 53:278–287, 2001. © 2001 Wiley‐Liss, Inc.
Expression of SR‐BI (Scavenger Receptor Class B Type I) in turtle (Chrysemys picta) tissues and other nonmammalian vertebrates
Authors: Duggan Annemarie E. , Marie Ronald Ste. , Callard Ian P.
Published: August 2002

In this study, the tissue distribution of the expression of an HDL‐receptor (SR‐BI; Scavenger Receptor Class B Type I) was investigated in the turtle using an antiserum to murine SR‐BI. Several turtle tissues including liver, heart, small intestine, kidney, oviduct, ovary, and testis were shown to express an 82 kDa membrane protein. In addition, SR‐BI expression in livers of other nonmammalian species such as the chicken, frog, goldfish, shark, and skate is also reported. Ovarian SR‐BI expression varies seasonally in the turtle as do plasma levels of apoA‐I and cholesterol ester. It is possible that changing levels of SR‐BI, the receptor for apoA‐I, is physiologically relevant to the demands of the turtle ovarian cycle and cholesterol distribution. J. Exp. Zool. 292:430–434, 2002. © 2002 Wiley‐Liss, Inc.
High performance liquid chromatographic separation of steroids from ovarian follicles of fresh water perch Anabas testudineus: Identification and characterization of the maturation‐inducing hormone
Authors: Bhattacharyya Sanghamitra , Sen Utpal , Bhattacharyya Sachi Prasad , Mukherjee Dilip
Published: August 2002

Accurate separation and identification of steroids from the postvitellogenic ovarian follicles of Indian climbing perch Anabas testudineus was performed by high‐performance liquid chromatography (HPLC) and specific radioimmunoassay (RIA). The steroids from such follicles, incubated in Cortland’s saline with or without homologous fish pituitary extract (FPE), were extracted with dichloromethane and separated on a μBondapak C18 column. Identification of the HPLC fractions was further confirmed by thin layer chromatography. As HPLC peaks for 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (DHP) and testosterone (T) were close, clear separation of these steroids and accurate measurement of their quantities was achieved by RIA of HPLC fractions using specific antibodies. Altogether, nine eluted fractions in the FPE‐untreated and ten in FPE‐treated samples were obtained. Of these, six were identified as: 5β‐pregnan‐3α,17α,20β‐triol (5β‐3α,17α,20β‐P); DHP; T; 17α‐hydroxyprogesterone (17α‐P4); progesterone (P4); and androstenedione (AD). Three fractions from untreated and four from FPE‐treated samples, however, remained unidentified. Of all the HPLC fractions examined for their relative maturational inducing (MI) potency on full grown (postvitellogenic) ovarian follicles of perch, the fraction identified as DHP was found to be the most effective inducer of germinal vesicle breakdown (GVBD) both at low and high concentrations. Fractions identified as 5β‐3α,17α,20β‐P and 17α‐P4 could induce only 32% and 20% GVBD at their highest concentration, while none of the unidentified fractions showed any MI activity. FPE caused increased production of DHP, testosterone, and 5β‐3α,17α,20β‐P. The qualitative differences between the fractions obtained from FPE‐treated samples and those from FPE‐untreated samples were only the appearance of a new polar metabolite of unknown function. The present study showed that, as a single steroid, DHP was the most potent MIH for A. testudineus. J. Exp. Zool. 292:565–572, 2002. © 2002 Wiley‐Liss, Inc.
Sex determination in the chicken embryo
Authors: Smith Craig A. , Sinclair Andrew H.
Published: August 2002

The chicken embryo represents a suitable model for studying vertebrate sex determination and gonadal sex differentiation. While the basic mechanism of sex determination in birds is still unknown, gonadal morphogenesis is very similar to that in mammals, and most of the genes implicated in mammalian sex determination have avian homologues. However, in the chicken embryo, these genes show some interesting differences in structure or expression patterns to their mammalian counterparts, broadening our understanding of their functions. The novel candidate testis‐determining gene in mammals, DMRT1, is also present in the chicken, and is expressed specifically in the embryonic gonads. In chicken embryos, DMRT1 is more highly expressed in the gonads and Müllerian ducts of male embryos than in those of females. Meanwhile, expression of the orphan nuclear receptor, Steroidogenic Factor 1 (SF1) is up‐regulated during ovarian differentiation in the chicken embryo. This contrasts with the expression pattern of SF1 in mouse embryos, in which expression is down‐regulated during female differentiation. Another orphan receptor initially implicated in mammalian sex determination, DAX1, is poorly conserved in the chicken. A chicken DAX1 homologue isolated from a urogenital ridge library lacked the unusual DNA‐binding motif seen in mammals. Chicken DAX1 is autosomal, and is expressed in the embryonic gonads, showing somewhat higher expression in female compared to male gonads, as in mammals. However, expression is not down‐regulated at the onset of testicular differentiation in chicken embryos, as occurs in mice. These comparative data shed light on vertebrate sex determination in general. J. Exp. Zool. 290:691–699, 2001. © 2001 Wiley‐Liss, Inc.
Fractional chromatic numbers of cones over graphs
Authors: Tardif Claude
Published: August 2002

We introduce a construction called the cone over a graph. It is a natural generalisation of Mycielski's construction. We give a formula for the fractional chromatic numbers of all cones over graphs, which generalizes that given in 3 for Mycielski's construction. © 2001 John Wiley & Sons, Inc. J Graph Theory 38: 87–94, 2001
Effect of the rate of gadolinium injection on magnetic resonance pulmonary perfusion imaging
Authors: Matsuoka Shin , Uchiyama Katsuhiro , Shima Hideki , Terakoshi Hiroaki , Oishi Sonomi , Nojiri Yoko , Ogata Hitoshi
Published: August 2002

Purpose

To determine whether the injection rate of contrast agent affects the dynamics of enhancement of the pulmonary parenchyma on magnetic resonance (MR) pulmonary perfusion imaging.

Materials and Methods

Fifteen healthy volunteers underwent enhanced MR pulmonary perfusion imaging to evaluate the effects of different injection rates. Injection rates were 1, 3, or 5 mL/second. Regions of interest (ROIs) were chosen in the lung and aorta to analyze the change in signal intensity over time.

Results

As the injection rate increased, the peak enhancement occurred significantly earlier (P = 0.0012), but the peak enhancement signal‐to‐noise ratio (SNR) value was not affected (P = 0.25). With the 3‐ and 5‐mL/second injection rates, images of both the pulmonary circulation and systemic circulation were obtained separately. However, with 1 mL/second, higher enhancement of the aorta was overlapped with peak enhancement of the lung tissue.

Conclusion

The injection rate affects the enhancement profiles of the pulmonary parenchyma. J. Magn. Reson. Imaging 2002;15:108–113. © 2002 Wiley‐Liss, Inc.
MR‐guided percutaneous core biopsy of small breast lesions: First experience with a vertically open 0.5T scanner
Authors: Schneider Jens P. , Schulz Thomas , Horn Lars C. , Leinung Steffen , Schmidt Frank , Kahn Thomas
Published: August 2002

Purpose

The growing use of highly sensitive but only moderate specific breast MRI requires the development of both minimal‐invasive as well as precise biopsy systems. The aim of the study was to prove the accuracy and feasibility of a biopsy procedure carried out in prone position in a vertically opened MR imager.

Materials and Methods

The biopsies were carried out in 21 women with lesions visible on MRI alone using an open breast coil with an integrated biopsy device. A 14 G coaxial needle was placed under near real‐time MRI‐guidance. After the tip of this needle was verified in contact with the lesion, we used a non MR‐compatible, but MR‐safe biopsy gun with a 16 G canula to take four to eight cores.

Results

We found eight malignant and 12 benign lesions. In one patient the procedure was not successful. In case of malignancy, the operation confirmed the diagnosis in all cases. The 12/21 patients with benign lesions have been followed without evidence of lesions growth over eight to 28 months.

Conclusion

The described procedure allows MRI‐guided minimal invasive core biopsy of small breast lesions (five to 17 mm) with a high degree of accuracy. J. Magn. Reson. Imaging 2002;15:374‐385. © 2002 Wiley‐Liss, Inc.
MRI in France: The French paradox
Authors: Lavayssière Robert , Cabée Anne‐Elizabeth
Published: August 2002

Although France is a modern, developed country, which spends nearly 10% of the gross national product on healthcare and has a highly praised level of medicine, the number of modern imaging scanners, such as CT (595), MRI (182), and PET (5), is quite low when compared to other European countries. Politics and a long‐standing tradition of centralization are prominent among reasons for such an underdevelopment. This situation has resulted in another French paradox not linked to wine consumption. The French life expectancy is very high, but the number of imaging equipment is very low. J. Magn. Reson. Imaging 2001;13:528–533. © 2001 Wiley‐Liss, Inc.
Development of clinical MR imaging in Russia and other CIS countries
Authors: Sinitsyn Valentin E.
Published: August 2002

This paper summarizes the development of magnetic resonance imaging (MRI) in the health systems of the USSR and later in Russia and the neighboring countries. Nuclear magnetic resonance (NMR) has been used as a scientific tool in the USSR since the 1940s. In 1982 the first whole‐body MR imager was installed. By the end of 1999, 131 MR systems were operating in Russia. There are substantial regional differences in the number of units installed. Russia has a domestic production of low‐field MR units. There are also plans for domestic production of MR contrast agents. Other former USSR republics have much less MR equipment. Most of the MRI centers experience difficulties in maintaining equipment in working condition. Some positive changes in the national health service systems give reason to believe in an increase in the quantity of MR units and the quality of their clinical use. J. Magn. Reson. Imaging 2001;13:645–647. © 2001 Wiley‐Liss, Inc.
Fast spin echo and fast gradient echo MRI with low acoustic noise
Authors: Hennel Franciszek
Published: August 2002

It has been shown previously that a significant reduction of the acoustic noise in standard, slow magnetic resonance imaging (MRI) sequences is achieved when the gradient pulses have long sinusoidal ramps. An improvement of this method is now presented for fast gradient echo (FLASH) and fast spin echo (RARE) sequences. The new strategy consists of using a sinusoidal readout pulse with no plateau and extending the phase encoding pulses to the entire readout period. The distribution of k‐space samples is no longer equidistant, and images have to be reconstructed with gridding. A reduction of the acoustic noise by 20–40 dBA was obtained with respect to standard sequences installed by the scanner manufacturer, which is 10–20 dBA better than that with the previously proposed method of sinusoidal ramps. J. Magn. Reson. Imaging 2001;13:960–966. © 2001 Wiley‐Liss, Inc.
Impact of ion cloud densities on the measurement of relative ion abundances in Fourier transform ion cyclotron resonance mass spectrometry: experimental observations of coulombically induced cyclotron radius perturbations and ion cloud dephasing rates
Authors: Gordon Eric F. , Muddiman David C.
Published: August 2002

Fundamental research into the quantitative properties of Fourier transform ion cyclotron resonance mass spectrometry (FTICR‐MS) has yielded interesting observations, especially in terms of factors affecting the accuracy of relative ion abundances. However, most of the previous discussions have focused on theoretical systems, or systems of limited scope. In this paper, we document ion motion attributes of a 30 spectra (six samples, five replicates each) system previously established as linear over two orders of magnitude. Observed behaviors include the perturbation of one charged species (cyclosporin A, CsA) of low ion density to a cyclotron orbit of greater radius than that of an almost identical, but slightly mass‐separated species (CsG) with a higher ion density. This radial perturbation is attributed to the coulombic repulsion between the two ion clouds as they interact during the excitation process, as previously proposed by Uechi and Dunbar. Magnitudes of the perturbation were confirmed by making cyclotron radii determinations utilizing the ratio of the third‐to‐first harmonics for the charged species of interest. It was found that these radial differences can account for as much as a 55% signal bias in favor of CsA for a single sample and a >20% positive bias in the slope of the regressed data set. A second behavior noted that also contributes to the potential inaccuracy of relative ion abundance measurements is the difference in signal decay rates for CsA and CsG. Damping constants and initial time domain signal amplitudes were evaluated using segmented Fourier transforms. Discrepancies in decay rates were not expected from two species that have essentially identical collisional cross‐sections. However, it has been observed that the faster decay rates are observed by the species of lower ion cloud density. We have attributed this differential signal decay phenomenon to the rates of loss of phase coherence for the two ion clouds. Previously, others have reported that less dense ion clouds are more susceptible to shearing and other disruptive forces during the course of their excited cyclotron motion. Our experimental evidence supports that it is the loss of cloud coherence that accounts for the signal loss over time, with the less dense cloud de‐phasing more quickly. As the ion populations of the two investigated species near equivalence, so do their time constants. Copyright © 2001 John Wiley & Sons, Ltd.
Mass spectrometric studies on small open‐chain piperazine‐containing ligands and their transition metal complexes
Authors: Nuutinen Jari M. J. , Ratilainen Jari , Rissanen Kari , Vainiotalo Pirjo
Published: August 2002

Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry was used to characterize the complexes formed between open‐chain piperazine‐containing ligands and transition metal salts (Cobalt, Copper, Zinc, and Cadmium as chlorides, nitrates, and acetates). Only single‐charged complexes were observed, formed of one ligand (L) and mainly one metal ion (M). Since the net charge of the complexes was one, a counterion (X) was attached to some of the complexes, with formation of [L + M + X]+ complexes, and a proton was lost from others, as in [L − H + M]+ complexes. In most cases the composition of the complexes was more dependent on the ligand than the metal salt. Collision‐induced dissociation measurements showed that complexes with related composition often differed in structure, or that interactions between the ligand and the metal ion were not alike. The metal ion influenced considerably the fragmentation pathways of the ligands, so that the fragmentation products could be used to deduce the binding sites of the metal. The variations observed in fragmentation behavior of complexes possessing the same ligand but different metal ions can mostly be explained by the ionic radius and electronic configuration of the metal ion. The results indicated a preference of the piperazine ring of the coordinated ligand for the boat conformation. Copyright © 2001 John Wiley & Sons, Ltd.
Factors contributing to peak broadening and mass accuracy in the characterization of intact spores using matrix‐assisted laser desorption/ionization coupled with time‐of‐flight mass spectrometry
Authors: Ramirez Javier , Fenselau Catherine
Published: August 2002

Factors contributing to peak broadening, accuracy and precision in mass assignment in the matrix‐assisted laser desorption/ionization characterization of a lipopeptide desorbed from intact Bacillus spores were investigated. These spores were studied as an example of a thick, topologically irregular sample, which present a more difficult target than a pure peptide or protein. The type of matrix, matrix:sample ratio, laser fluence, and localized repetitive laser irradiation were all found to affect the full‐width at half maximum of the biomarker. Both in‐source and post‐source phenomena were shown to contribute. Sample thickness had less effect. Precision and accuracy of mass assignment were also affected by matrix:sample ratio and laser fluence. In general, this sample was responsive to the same experimental variables as pure peptides, and the use of an internal standard produced significant improvements in precision and accuracy. Copyright © 2001 John Wiley & Sons, Ltd.
Formation of cryptophanes from their precursors as viewed by liquid secondary ion mass spectrometry
Authors: Brotin Thierry , Darzac Magali , Forest Danièle , Becchi Michel , Dutasta Jean‐Pierre
Published: August 2002

The formation of cryptophane‐A (C1) and the deuterated cryptophanes C2–C6 from their respective precursors P1–P6 in a mass spectrometer ion‐source was evidenced by liquid secondary ion mass spectrometry (LSIMS). Mass‐analyzed ion kinetic energy experiments performed on the precursor molecular ions suggested that cryptophane formation occurred mainly in the liquid‐matrix before desorption rather than in the gas phase. In addition, we observed that the presence of cations, such as lithium or sodium ions, inhibited the formation of the cryptophane molecular ions. In the light of these results we used the LSIMS technique to investigate the formation of the new cryptophanes C7–C13. All the data collected support the idea that a direct comparison can be made between these experimental findings and chemistry in solution. Copyright © 2001 John Wiley & Sons, Ltd.
Matrix‐assisted laser desorption/ionization collision‐induced dissociation of linear single oligomers of nylon‐6
Authors: Murgasova Renata , Hercules David M.
Published: August 2002

Matrix‐assisted laser desorption/ionization, collision induced‐dissociation (MALDI‐CID) has been used to obtain structural information for linear single oligomers of nylon‐6. The effects of matrix and cationization agent in MALDI‐CID analysis have been investigated. Fragmentation mechanisms are proposed for the series of ions that are observed in the MALDI‐CID spectra of the hexamer, octamer and dodecamer. Fragmentation processes observed in the MALDI‐CID spectra include cleavage of the end groups followed by dissociation of the m/z 113 unit. Cleavage of the oligamide chain occurs at the amide linkage, as well as at adjacent bonds. For the four matrices and three cationization agents investigated, 2,5‐dihydroxybenzoic acid and sodium chloride showed the best performance for MALDI‐CID analysis of the dodecamer. In addition, yields of the fragment ions in MALDI‐CID spectra were found to be dependent on the chain length distribution. Copyright © 2001 John Wiley & Sons, Ltd.
Mapping the ion kinetic energy in a helium microwave plasma orthogonal acceleration time‐of‐flight mass spectrometer
Authors: Su Yongxuan , Jin Zhe , Duan Yixiang , Olivares José A.
Published: August 2002

The ion kinetic energy of a helium microwave plasma is studied using an orthogonal acceleration time‐of‐flight mass spectrometer. The ions produced in the plasma are extracted into the mass spectrometer in an ‘off‐cone’ mode (i.e. the helium plasma plume is off the sampler cone), and enter the repelling zone in the x‐direction, which is perpendicular to the flight tube. The information of ion initial kinetic energy was obtained from both theoretical calculations and experimental results. The potential influence of two x‐direction steering plates (X‐steering plates) on the ion energy and signal intensity was examined. The influence of gas composition on the ion kinetic energy was also investigated. The calculated results show that ions with different m/z have different velocity and kinetic energy when they enter the ion modulation zone, and lighter ions have higher velocity and lower kinetic energy. The experimental results obtained demonstrate that the ion signals of different m/z produced with an ‘off‐cone’ sampling helium microwave plasma show similar trends as calculated with the potential difference of the X‐steering plates, revealing their narrow kinetic energy distribution in the x‐direction. Under typical operating conditions, the x‐direction kinetic energy of ions detected mostly range from about 14.9 eV for 7Li+ to 16.8 eV for 208Pb+. Published in 2001 by John Wiley & Sons, Ltd.
Investigation of ion‐pair precipitates of selected alkoxylates and complex salts of specific metal cations by liquid secondary ion mass spectrometry
Authors: Frański Rafał , Szymański Andrzej , Gierczyk Błażej , Chlebicki Jan , Frańska Magdalena
Published: August 2002

Liquid secondary ion (LSI) mass spectra of ion‐pair precipitates obtained for Triton X‐100 with strontium, lead, cadmium and mercury tetraphenylborates and for selected butoxylene–ethoxylene monoalkyl ethers with barium tetraiodobismuthate(III) are discussed. On the basis of LSI mass spectra, recorded in both positive and negative modes, the formulae of the ion‐pair precipitates were determined. On the basis of B/E mass spectra, the fragmentation routes of [M − H + Ba]+ ions for butoxylene–ethoxylene monoalkyl ether complexes of barium and [M − H + Cd]+ ions for the Triton X‐100 complex of cadmium are proposed. Copyright © 2002 John Wiley & Sons, Ltd.
Influence of a ring substituent on the tendency to form H2O adducts to Ag+ complexes with phenylalanine analogues in an ion trap mass spectrometer
Authors: Perera B. A. , Gallardo A. L. , Barr J. M. , Tekarli S. M. , Anbalagan V. , Talaty E. R. , Van Stipdonk M. J.
Published: August 2002

In a previous report we showed that certain binary Ag+–amino acid complexes formed adduct ions by the attachment of a single water and methanol molecule when stored in an ion trap mass spectrometer: complexes with aliphatic amino acids and with 4‐fluorophenylalanine formed the adduct ions whereas complexes with phenylalanine and tryptophan did not. In this study we compared the tendency of the Ag+ complexes derived from phenylalanine, 4‐fluorophenylalanine, 4‐hydroxyphenylalanine (tyrosine), 4‐bromophenylalanine, 4‐nitrophenylalanine and aminocyclohexanepropionic acid to form water adducts when stored, without further activation, in the ion trap for times ranging from 1 to 500 ms. Because the donation of π electron density to the Ag+ ion is a likely determining factor in complex reactivity, our aim in the present study was to determine qualitatively the influence of para‐position substituents on the aromatic ring on the formation of the water adducts. Our results show that the reactivity of the complexes is influenced significantly by the presence of the various substituents. Decreases in [M + Ag]+ ion abundance, and increases in adduct ion abundance, both measured as a function of storage time, follow the trend —NO2 > —Br > —F > —OH > —H. The complex of Ag+ with 4‐nitrophenylalanine was nearly as reactive towards water as the Ag+ complex with aminocyclohexanepropionic acid, the last being an amino acid devoid of π character in the ring system. Collision induced dissociation of the [M + Ag]+ species derived from the amino acids produces, among other products, Ag+ complexes with a para‐substituted phenylacetaldehyde: complexes that also form adduct species when stored in the ion trap. The trends in adduct ion formation exhibited by the aldehyde–Ag+ complex ions were similar to those observed for the precursor complexes of Ag+ and the amino acids, confirming the influence of the ring substituent. Copyright © 2002 John Wiley & Sons, Ltd.
Circulation of enteroviruses and persistence of meningitis cases in the winter of 1999–2000
Authors: Chambon Martine , Archimbaud Christine , Bailly Jean‐Luc , Henquell Cécile , Regagnon Christel , Charbonné Françoise , Peigue‐Lafeuille Hélène
Published: August 2002

The seasonal incidence of enterovirus meningitis was analyzed in a prospective study of patients admitted for suspected meningitis from October 1, 1998 to April 30, 2000. In‐house reverse transcription‐polymerase chain reaction (RT‐PCR) in cerebrospinal fluid (CSF) was used irrespective of cytological results. Fifty‐two (45.2%) of the 115 patients had positive RT‐PCR in CSF, including 44/86 children (51.2%) and 8/29 adults (27.6%). Six of the 52 (11.5%) had no pleocytosis. The numbers of CSF specimens with a predominance of lymphocytes or a predominance of neutrophils were closely similar. In 33 of the positive patients, an enterovirus, mainly echoviruses type 6 (48%) and 30 (24%), was recovered in one or more specimens. Sixteen cases of enteroviral meningitis were observed between November 1999 and March 2000 as against 2 cases between November 1998 and March 1999, showing that the disease persisted through the winter months of 1999–2000. During the same period, 96 enterovirus isolates were recovered from clinical specimens from other patients. The number of isolates was higher in the winter of 1999–2000 (P < 0.01) than in the winter of 1998–1999, indicating that the risk of enterovirus infection increased significantly in winter 1999–2000. Sixteen patients had aseptic meningitis, made a rapid recovery and had an enterovirus in throat swabs and stools (9/16) or in one of the two (7/16). RT‐PCR was not requested. Nine patients were admitted during the cold months. The clinical management of both adult and child patients could be improved by year‐round use of enterovirus generic RT‐PCR. J. Med. Virol. 65:340–347, 2001. © 2001 Wiley‐Liss, Inc.
Enteroviral meningitis in Northern Jordan: Prevalence and association with clinical findings
Authors: Meqdam Mamdoh M. , Khalousi Mohamed M. , Al‐Shurman Abdullah
Published: August 2002

During the summer‐autumn of 1999, 390 specimens of cerebrospinal fluid were taken from infants and children younger than 15 years of age. They were suspected of having meningitis and were admitted to Princess Rahma Hospital, Northern Jordan. They were investigated for the presence of enteroviruses using shell vial culture and indirect immunofluorescence assays. Most cases (46.9%) occurred in children younger than 1 year of age in which males represented 71.9%. The common symptoms were fever, vomiting, and headache. Enteroviruses were isolated from 32 (8.2%) cases, coxsackievirus B types 2, 4, and 5 from 15 (46.9%) cases, and echovirus 9 (31.3%) was the most common identified serotype. The virus isolation rate was directly proportional to the number of leukocytes in the cerebrospinal fluid. However, enteroviral isolation was demonstrated in 4 (12.5%) of 32 cerebrospinal fluid specimens without pleocytosis. Leukocyte differential count revealed a predominance of polymorphonuclear cells in 71.4% of the cases. Hospitalization ranged from 1 day to 25 days with a mean of 7 days. The majority of enterovirus‐infected patients (88.9%) were treated with at least one type of antibiotic. These results emphasize the importance of shell vial culture assay for diagnosing enteroviruses, especially in laboratories that do not have access to advanced techniques such as polymerase chain reaction. J. Med. Virol. 66:224–228, 2002. © 2002 Wiley‐Liss, Inc.
Reduced number of functional glutamatergic synapses in hippocampal neurons overexpressing full‐length TrkB receptors
Authors: Klau Michele , Hartmann Matthias , Erdmann Kai S. , Heumann Rolf , Lessmann Volkmar
Published: August 2002

Brain‐derived neurotrophic factor (BDNF) acutely modulates the efficacy of central glutamatergic synapses via activation of the receptor tyrosine kinase TrkB. On a longer time scale, recent evidence suggests an additional role of TrkB signaling in the formation of excitatory synaptic connections. Here, we have overexpressed full‐length TrkB receptors (fl‐TrkB) in hippocampal neurons, to investigate the contribution of BDNF signaling to the maturation of glutamatergic synapses. Using patch clamp recordings, we show a three‐fold reduction in glutamatergic excitatory autaptic and synaptic current amplitudes in neurons overexpressing fl‐TrkB, and application of saturating concentrations of BDNF and NT‐4/5 completely reverses this effect. Compatible with these overexpression data, in untransfected neurons, scavenging of endogenous BDNF and NT‐4/5 by TrkB‐IgGs reduces excitatory autaptic current (EAC) amplitudes. By overexpression of truncated TrkB receptors (TrkB.T1, TrkB.T2) and a chimeric receptor containing only the intracellular domain of fl‐TrkB, we show that intra‐ and extracellular domains of fl‐TrkB are necessary to observe the EAC reduction. Labeling of presynaptic terminals with FM 4‐64 revealed, that the reduced EAC amplitudes in fl‐TrkB overexpressing neurons are accompanied by a two‐fold reduction in synapse number. These results suggest, that ligand‐independent signaling through fl‐TrkB receptors can decrease glutamatergic synaptic strength, if sufficient amounts of BDNF or NT‐4/5 are not available. J. Neurosci. Res. 66:327–336, 2001. © 2001 Wiley‐Liss, Inc.
Toxic effect of L‐2‐chloropropionate on cultured rat cerebellar granule cells is ameliorated after inhibition of reactive oxygen species formation
Authors: Myhre O. , Bjugan B. , Fonnum F.
Published: August 2002

Oral administration of rats to L‐2‐chloropropionate (L‐CPA) causes selective necrosis to the granule cell layer of the cerebellum in vivo and to cultured rat cerebellar granule cells in vitro. The present study was conducted to characterize the involvement of reactive oxygen species (ROS) in cell death of L‐CPA to rat cerebellar granule cells in vitro. Exposure to L‐CPA (0.625–10 mM) produced a concentration dependent increase in formation of 2,7‐dichlorofluorescein (DCF) as a measure of formation of ROS. The elevation of ROS was inhibited after incubation of the cells with the ERK‐type of MAP kinases inhibitor U0126, the mitochondrial permeability transition pore inhibitor cyclosporin A (CSA), the antioxidant vitamin E, and the spin trap N‐tert‐butyl‐α‐(2‐sulfophenyl)‐nitrone (S‐PBN). Measurements of nitrite (NO2) in the cell culture supernatant using the Griess reagent indicate generation of nitric oxide (NO) after exposure to L‐CPA. Incubation with L‐CPA (10 mM) for 48 hr lead to cell death (90%). When the granule cells were incubated with L‐CPA in combination with the inhibitors of free radical production, the cell death was ameliorated. The results show that L‐CPA is toxic to granular cells by production of ROS. © 2001 Wiley‐Liss, Inc.
Brain metabolism and brain disease: Is metabolic deficiency the proximate cause of Alzheimer dementia?
Authors: Blass John P.
Published: August 2002

The potential of impairments in oxidative/energy metabolism to cause diseases of the brain had been proposed even before the major pathways of oxidative/energy metabolism were described. Deficiencies associated with disease are known in all the pathways of oxidative/energy metabolism and are associated with some of the most common disorders of the nervous system, including Alzheimer's disease (AD) and Parkinson's disease. A common mechanism in these conditions appears to be a downward mitochondrial spiral, involving abnormalities in energy metabolism, calcium metabolism, and free radicals (reactive oxygen and nitrogen species). In AD, the spiral appears to interact with abnormalities in the metabolism of the Alzheimer amyloid precursor protein (APP) and its Aβ fragment. Several lines of evidence indicate that the mitochondrial spiral may be a proximate cause of the clinical disabilities in AD. Decreases in cerebral metabolic rate (CMR) characteristically occur in AD and in other dementias. Inducing decreases in CMR leads to clinical disabilities characteristically associated with AD and with analogous problems in experimental animals. Treatments directed toward normalizing CMR appear to help at least some patients. Further studies of this possibility and of treatments designed to ameliorate the mitochondrial spiral may prove useful for treating AD and perhaps some other dementing disorders. © 2001 Wiley‐Liss, Inc.
Nitric oxide synthase‐positive neurons in the rat superior colliculus: Colocalization of NOS with NMDAR1 glutamate receptor, GABA, and parvalbumin
Authors: Soares‐Mota Marcia , Henze Isabela , Mendez‐Otero Rosalia
Published: August 2002

We analyzed the potential input and output components of nitric oxide synthase (NOS)‐containing neurons in the rat superior colliculus (SC). To identify whether NOS‐positive neurons receive glutamatergic input we investigated the colocalization of NOS with NMDA receptor subunit R1 (NMDAR1). In addition, to examine whether putative nitric oxide synthesizing neurons represent a neurochemically specific or distinct subpopulation of cells in the SC we studied the colocalization of NOS with the neurotransmitter GABA, the calcium‐binding proteins parvalbumin, calbindin and calretinin and with neuropeptides such as somatostatin, substance P and neuropeptide Y. We found that 90% of NOS‐positive neurons in the superficial layers of the rat SC express NMDAR1. Nearly 20% of the population of nitridergic neurons also expresses GABA and 15% of them express parvalbumin. NOS‐positive neurons in the superior colliculus did not contain calretinin, calbindin or either of the neuropeptides tested. The results of this study show that the capacity for synthesizing NO in the SC is largely restricted to neurons that receive glutamatergic inputs and that some of these neurons express GABA or parvalbumin. J. Neurosci. Res. 64:501–507, 2001. © 2001 Wiley‐Liss, Inc.
Ice crystal number concentration versus temperature for climate studies
Authors: Gultepe I. , Isaac G.A. , Cober S.G.
Published: August 2002

Ice crystal number concentration (Ni) is an important parameter, having a strong influence on the calculation of cloud optical and microphysical parameters. Cloud and precipitation parameterizations within climate and weather forecasting models, affecting the heat and moisture budget of the atmosphere, cannot be determined accurately if Ni is not estimated correctly. Previous studies of ice crystal number concentration versus temperature (T) have shown that Ni–T relationships are not unique. The present study uses observations made in the glaciated regions of stratiform clouds from two Arctic and two mid‐latitude field projects to study the Ni versus temperature relationship. Scatter plots of Ni versus T at the ice particle measurement level do not show a good correlation with T for ice crystals at sizes less than 1000 µm. For a given temperature, the variation in Ni is found to be up to two to three orders of magnitude for ice crystals with sizes larger than approximately 100 µm. A significant Ni–T relationship is found for precipitation sized particles with sizes greater than 1000 µm. The ice particle concentration for sizes between 100 and 1000 µm varied from 0.1 to 100 L−1, independent of geographic location where the measurements were made. Based on this work, it is concluded that modelling studies should be tested for the possible variations in Ni versus T. Copyright © 2001 Royal Meteorological Society
A non-tetradecarboxylative synthesis of 2,7,12,17-tetraphenylporphycene
Authors: GAVALDA ANA , BORRELL JOSÉ I. , TEIXIDO JORDI , NONELL SANTIAGO , ARAD OFIR , GRAU ROSER , CAÑETE MAGDALENA , JUARRANZ ANGELES , VILLANUEVA ANGELES , STOCKERT JUAN C.
Published: August 2002

A new synthetic method for 2,7,12,17-tetraphenylporphycene (2e, TPPo) which avoids tetradecarboxylation by sublimation of the intermediate tetracarboxylic acid 8 is reported. Thus, the use of a pyrrol 13a bearing two orthogonal ester groups allows the synthesis of bipyrrol 12a, from which the benzyl ester groups are selectively removed to afford diester 11. The latter is transformed to dialdehyde 10 by using the McFayden–Stevens reaction, thus avoiding the unstable bipyrrol 9 formed during the tetradecarboxylation of 8.
Raman microscopy of formamide‐intercalated kaolinites treated by controlled‐rate thermal analysis technology
Authors: Frost Ray L. , Kristóf János , Horváth Erzsébet , Theo Kloprogge J.
Published: August 2002

Raman spectroscopy of formamide‐intercalated kaolinites treated using controlled‐rate thermal analysis technology (CRTA), allowing the separation of adsorbed formamide from intercalated formamide in formamide‐intercalated kaolinites, is reported. The Raman spectra of the CRTA‐treated formamide‐intercalated kaolinites are significantly different from those of the intercalated kaolinites, which display a combination of both intercalated and adsorbed formamide. An intense band is observed at 3629 cm−1, attributed to the inner surface hydroxyls hydrogen bonded to the formamide. Broad bands are observed at 3600 and 3639 cm−1, assigned to the inner surface hydroxyls, which are hydrogen bonded to the adsorbed water molecules. The hydroxyl‐stretching band of the inner hydroxyl is observed at 3621 cm−1 in the Raman spectra of the CRTA‐treated formamide‐intercalated kaolinites. The results of thermal analysis show that the amount of intercalated formamide between the kaolinite layers is independent of the presence of water. Significant differences are observed in the CO stretching region between the adsorbed and intercalated formamide. Copyright © 2001 John Wiley & Sons, Ltd.