bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regional variations in the outer retina of atherinomorpha (Beloniformes, Atheriniformes, Cyprinodontiformes: Teleostei): Photoreceptors, cone patterns, and cone densities
Authors: Reckel Frank , Melzer Roland R. 
Published: June 2003

AbstractThe outer retinae of adults of 13 atherinomorph species, representing nine different families, were examined by both light and electron microscopy. The retinae were investigated with respect to photoreceptor types, cone densities, and cone patterns. All data were composed to eye maps. This procedure allows an interspecific comparison of the regional differences within the outer retina among these shallow‐water fish. Furthermore, for a more detailed pattern analysis nitro‐blue tetrazolium chloride‐ (NBT)‐stainings in the retina of Melanotaenia maccullochi are presented. Apart from rods, eight morphologically different cone types could be identified: short, intermediate, and long single cones, double cones (equal and unequal), triple cones (triangular and linear), and in Ameca splendens one quadruple cone. Dimensions and occurrence of photoreceptors vary among the respective species and within the retinal regions. In the light‐adapted state, the cones are arranged in highly ordered mosaics. Five different cone tessellation types were found: row patterns, twisted row patterns, square patterns, pentagonal patterns, and, exclusively in Belone belone, a hexagonal pattern. In Melanotaenia maccullochi the different spectral photoreceptor classes correspond well with the distribution of morphological photoreceptor classes within the mosaic. Double cone density maxima together with a highly ordered cone arrangement usually occur in the nasal and/or ventral to ventrotemporal retina. In most of the species that were examined these high‐density regions are presumed to process visual stimuli from the assumed main directions of vision, which mainly depend on feeding behavior and predator pressure. Our findings are discussed with respect to the variable behavioral and visual ecology and phylogeny of the respective species. J. Morphol. 257:270–288, 2003. © 2003 Wiley‐Liss, Inc.
Placoderm fishes, pharyngeal denticles, and the vertebrate dentition
Authors: Johanson Zerina , Smith Moya M. 
Published: June 2003

AbstractThe correlation of the origin of teeth with jaws in vertebrate history has recently been challenged with an alternative to the canonical view of teeth deriving from separate skin denticles. This alternative proposes that organized denticle whorls on the pharyngeal (gill) arches in the fossil jawless fish Loganellia are precursors to tooth families developing from a dental lamina along the jaw, such as those occurring in sharks, acanthodians, and bony fishes. This not only indicates that homologs of tooth families were present, but also illustrates that they possessed the relevant developmental controls, prior to the evolution of jaws. However, in the Placodermi, a phylogenetically basal group of jawed fishes, the state of pharyngeal denticles is poorly known, tooth whorls are absent, and the presence of teeth homologous to those in extant jawed fishes (Chondrichthyes + Osteichthyes) is controversial. Thus, placoderms would seem to provide little evidence for the early evolution of dentitions, or of denticle whorls, or tooth families, at the base of the clade of jawed fishes. However, organized denticles do occur at the rear of the placoderm gill chamber, but are associated with the postbranchial lamina of the anterior trunkshield, assumed to be part of the dermal cover. Significantly, these denticles have a different organization and morphology relative to the external dermal trunkshield tubercles. We propose that they represent a denticulate part of the visceral skeleton, under the influence of pharyngeal patterning controls comparable to those for pharyngeal denticles in other jawed vertebrates and Loganellia. J. Morphol. 257:289–307, 2003. © 2003 Wiley‐Liss, Inc.
Neuroanatomy of the harbor porpoise (Phocoena phocoena) from magnetic resonance images
Authors: Marino Lori , Sudheimer Keith , Sarko Diana , Sirpenski Gayle , Johnson John I. 
Published: June 2003

AbstractCetacean (dolphin, whale, and porpoise) brains are among the least‐studied mammalian brains because of the formidability of collecting and histologically preparing such relatively rare and large specimens. Among cetaceans, there exist relatively few studies of the brain of the harbor porpoise (Phocoena phocoena). Magnetic resonance imaging (MRI) offers a means of observing the internal structure of the brain when traditional histological procedures are not practical. Therefore, MRI has become a critical tool in the study of the brain of cetaceans and other large species. This article represents the first MRI‐based anatomically labeled three‐dimensional description of the harbor porpoise brain. Coronal plane sections of the brain of a young harbor porpoise were originally acquired and used to produce virtual digital scans in the other two orthogonal spatial planes. A sequential set of images in all three planes has been anatomically labeled and displays the proportions and positions of major neuroanatomical features. These images allow for the visualizing of the distinctive features of the harbor porpoise brain from various orientations by preserving the gross morphological structure of the specimen. J. Morphol. 257:308–347, 2003. © 2003 Wiley‐Liss, Inc.
Case of unilateral wing formation in the female of the glowworm Lampyris noctiluca
Authors: Maas Ulrike , Dorn August 
Published: June 2003

AbstractOn July 27, 1999, the first author found a unilaterally winged adult glowworm in a park in the city of Mainz. Except for the wings on the left side, the specimen exhibited female characteristics that extended to external sexual appendages, the lantern and the gonads. The internal organization showed some remarkable differences between right (wingless) and left (winged) side. The right ovary contained three times more mature eggs than the left side and the volume of the corpus allatum of this side was about one‐third larger than that of the left side. This suggests that aptery and egg maturation are affected by corpus allatum activity, i.e., juvenile hormone production. The findings do not support the hypothesis of Naisse ([1966] Arch Biol Liège 77:139–201) that wing formation, as a secondary male characteristic, is controlled by an androgenic hormone from the testes in the glowworm. Thus, the observations on this exceptional specimen have implications for the current hypotheses concerning the control of sexual wing dimorphism in Lampyris noctiluca. J. Morphol. 257:254–258, 2003. © 2003 Wiley‐Liss, Inc.
Ventral neurons in the anterior nerve cord of amphioxus larvae. II. Further data on the pacemaker circuit
Authors: Lacalli Thurston C. 
Published: June 2003

AbstractPrevious serial EM studies of the anterior nerve cord of amphioxus larvae implicate the third pair of large paired neurons (LPN3s) as key components of the pacemaker responsible for oscillatory premotor output in somites 1 and 2. Here the synaptic relationship between the LPN3s and a fourth such pair (LPN4s), located in somite 3, is examined from a second series of sections. Because of limited overlap between the two series, fiber identity can only be inferred in most instances. To act as pacemakers, the LPN3s must inhibit each other; the current data show similar patterns of synaptic contact, presumably also inhibitory, with the LPN4s. The oscillatory signal appears therefore to be relayed from one LPN pair to the next. Despite their evident importance in the anterior cord, the role these cells play more caudally in signal propagation is not clear. J. Morphol. 257:212–218, 2003. © 2003 Wiley‐Liss, Inc.
Direct‐temperature mass spectrometric detection of volatile terpenoids and natural terpenoid polymersin fresh and artificially aged resins
Authors: Scalarone Dominique , van der Horst Jerre , Boon Jaap J. , Chiantore Oscar 
Published: June 2003

AbstractElectron impact (EI) ionization and ammonia chemical ionization (NH3/CI) direct‐temperature mass spectrometry (DTMS) was used to characterize five natural terpenoid resins: dammar, mastic, colophony, Manila copal and sandarac. Compositional differences were highlighted by the identification of low molecular mass compounds, ranging from di‐ to triterpenoids, and polymeric components, based on polycadinene and polycommunic acid. Photo‐ageing processes occurring under accelerated indoor and outdoor exposure conditions were also investigated. NH3/CI and tetramethylammonium hydroxide EI were applied to increase the sensitivity towards highly oxidized molecules. Oxidation and cross‐linking reactions were found to affect mostly triterpenoid resins and diterpenoid abietane and pimarane molecules. Oxidation proceeds through a radical mechanism, generally starting from conjugated double bonds. Oxygen atoms are incorporated in the terpenoid structures in the form of alcohols, ketones and carboxylic acids. Oxidized cadinene oligomers released by pyrolytic degradation of the polycadinene fraction of dammar were detected even in unaged samples. Evidence is given indicating the occurrence of cleavages in the cross‐linked polycommunic structure of aged sandarac and Manila copal. Bond scissions produce oligomeric fragments based on the communic acid structure and sufficiently volatile to be desorbed at low temperature in DTMS measurements. Copyright © 2003 John Wiley & Sons, Ltd.
Effect of buffer cations and of H3O+ on the charge states of native proteins. Significance to determinations of stability constants of protein complexes
Authors: Verkerk Udo H. , Peschke Michael , Kebarle Paul 
Published: June 2003

AbstractThe progressive reduction of charge in charge states of non‐denatured proteins (lysozyme, ubiquitin, and cytochrome c), observed with nanospray in the positive ion mode, when the buffer salt ammonium acetate is replaced by ethylammonium acetates (EtNH3Ac, Et2NH2Ac and Et3NHAc) is rationalized on the basis of the charge residue model (CRM). The charge states of the multiply protonated protein are shown to be controlled by the increasing gas‐phase basicities, GB(B), of the bases(B) NH3, EtNH2, Et2NH and Et3N. Charge states derived from evaluated apparent gas‐phase basicities GBapp of the basic side‐chains of the protein and the known GB(B) of the above bases are found to be in agreement with the experimentally observed charge states. This is a requirement of the CRM, because in this model the small positive ions (the buffer cations in the present case) at the surface of the electrospray droplets are the excess ions that provide the charge of the final small droplet that contains the protein molecule and on evaporation of the solvent transfer the charge to the protein. The observed charge states in the absence of buffer salts, i.e. pure water, are attributed to excess H3O+ ions produced by the electrolysis process that attends electrospray. A proposed extended mechanism provides predictions of factors that determine the sensitivity for detection of the multiply protonated proteins. Consideration of restraints imposed by the CRM lead to some simple predictions for conditions that should be present to obtain accurate determinations by electrospray and nanospray of stability constants for the protein–complex equilibrium in aqueous solution. Copyright © 2003 John Wiley & Sons, Ltd.
Esterification of borate with NAD+and NADH as studied by electrospray ionization mass spectrometry and11B NMR spectroscopy
Authors: Kim Danny H. , Marbois Beth N. , Faull Kym F. , Eckhert Curtis D. 
Published: June 2003

AbstractThis paper describes for the first time the direct measurement of boric acid (B(OH)3) and borate (B(OH)4−) adduction to NAD+and NADH by electrospray ionization mass spectrometry (ESI‐MS) and11B NMR spectroscopy. The analysis demonstrates that borate binds to bothcis‐2,3‐ribose diols on NAD+forming borate monoesters (1 : 1 addition), borate diesters (1 : 2 addition) and diborate esters (2 : 1 addition), whereas, only borate monoesters were formed with NADH. MS in the negative ion mode showed borate was bound to acis‐2,3‐ribose diol and not to the hydroxyl groups on the phosphate backbone of NAD+, and MS/MS showed that the 1 : 1 addition monoester contained borate bound to the adenosine ribose. Boron shifts of borate monoesters and diesters with NAD+were observed at 7.80 and 12.56 ppm at pH 7.0 to 9.0. The esterifications of borate with NAD+and NADH were pH dependent with maximum formation occurring under alkaline conditions with significant formation occurring at pH 7.0. Using ESI‐MS, the limit of detection was 50 µMfor NAD+and boric acid (1 : 1) to detect NAD+–borate monoester at pH 7.0. These results suggest esterification of borate with nicotinamide nucleotides could be of biological significance. Copyright © 2003 John Wiley & Sons, Ltd.
Assignment of acetyl groups to O‐2 and/or O‐3 of pectic oligogalacturonides using negative electrospray ionization ion trap mass spectrometry
Authors: Quéméner Bernard , Cabrera Pino Juan Carlos , Ralet Marie‐Christine , Bonnin Estelle , Thibault Jean‐François 
Published: June 2003

AbstractPartially acetylated and methylated oligogalacturonides produced by enzymatic hydrolysis of sugar beet pectin were analysed by negative electrospray ionization ion trap mass spectrometry (ESI‐ITMS). The 18O labelling of the oligomer reducing end allowed the precise assignment of the fragments resulting from glycosidic bond and cross‐ring cleavages. The collisional‐induced dissociation of the Ci and Zj fragment ions through sequential MSn experiments always displayed 0, 2A‐type cross‐ring cleavage ions which were related to C2H4O2 losses. These 0, 2A ions appeared to be highly diagnostic ions allowing the precise location of the acetyl groups to the O‐2 and/or O‐3 of the acetylated galacturonic acid residues. Copyright © 2003 John Wiley & Sons, Ltd.
Development of a liquid chromatographic/tandem mass spectrometric assay for a new endothelin receptor antagonist, and its application to dog plasma samples generated after simultaneous i.v. and p.o. administration of the unlabeled and deuterium‐labeled forms of this antagonist
Authors: Lausecker B. , Fischer G. 
Published: June 2003

AbstractAn assay was developed and applied to determine the bioavailability of a new endothelin receptor antagonist after simultaneous p.o. and i.v. administration of the drug and its stable isotope‐labeled analogue. The drug, its main metabolite and the stable isotope‐labeled analogues of the drug and the main metabolite were quantified in dog plasma samples using a structural analogue as internal standard. In addition to the calculation of the bioavailability, the formation of the metabolite after p.o. and i.v. administration could be followed independently. The assay covered the concentration range 0.25–1000 ng ml−1 using sample aliquots of only 50 µl. Plasma samples were processed after protein precipitation with on‐line solid‐phase extraction, narrow‐bore high‐performance liquid chromatography and subsequent tandem mass spectrometric detection. Detection was accomplished with ionspray in the positive ion selected reaction monitoring mode. The inter‐assay precision and accuracy of the assay were in the range 4.7–14.2% and 90.3–113.3%, respectively, and the intra‐assay precision and accuracy were in the range 1.4–11.5% and 88.4–112.5%, respectively. The fragmentation of the drug was investigated and showed an unexpected shift of a methyl group. Data from MSn, medium‐resolution exact mass tandem mass spectrometry and H–D exchange experiments were employed to clarify the mechanism. Copyright © 2003 John Wiley & Sons, Ltd.
Manipulating internal energy of protonated biomolecules in electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry
Authors: Guo Xinghua , Duursma Marc C. , Kistemaker Piet G. , Nibbering Nico M. M. , Vekey Karoly , Drahos Laszlo , Heeren Ron M. A. 
Published: June 2003

AbstractThe internal energy of protonated leucine enkephalin has been manipulated in electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry with two newly designed pump–probe experiments. Blackbody infrared radiation was applied to pump an ion population into a well‐defined internal energy distribution below the dissociation threshold. Following this pumping stage, the internal energy distribution was probed using on‐resonance collisional activation to dissociate the ions. These pump–probe experiments were carried out in two different ways: (a) using on‐resonance collisional activation with variable kinetic energies to dissociate the ions at a constant initial ion temperature (determining the precursor ion survival percentage as a function of kinetic energy) and (b) using on‐resonance collisional activation with a constant kinetic energy to dissociate the ions at variable initial ion temperatures (to investigate the ion survival yield–initial ion temperature dependence). Using this approach, a detailed study of the effects of the initial ion temperature, the probing kinetic energy and the internal energy loss rate on the effective conversion efficiency of (laboratory‐frame) kinetic energy to internal energy was conducted. This conversion efficiency was found to be dependent on the initial ion temperature. Depending on the experimental conditions the conversion efficiency (for collisions with argon) was estimated to be about 4.0 ± 1.7%, which agrees with that obtained from a theoretical modeling. Finally, the reconstructed curves of the ion survival yield versus the mode of the (final) total internal energy distribution of the activated ion population (after pump and probe events) at different pump–probe conditions reveal the internal energy content of the activated ions. Copyright © 2003 John Wiley & Sons, Ltd.
Collision‐induced dissociation of the negative ions of simvastatin hydroxy acid and related species
Authors: Qin Xue‐Zhi 
Published: June 2003

AbstractSimvastatin hydroxy acid (1) is a well‐known, potent HMG‐CoA reductase inhibitor for the treatment of hypercholesterolemia. Its lactone, simvastatin (commercial name Zocor) (a prodrug of 1), has been widely prescribed in the USA and throughout the world. In this work, collision‐induced dissociation (CID) of the negative ion of 1 (m/z 435), a carboxylic anion, was analyzed in detail. The major fragmentation pathway of this ion is a novel de‐esterification to form the negative product ions at m/z 319 and 115. The ion at m/z 319 undergoes further collision‐induced rearrangements to form the negative ions at m/z 215, 159 and 85. Possible mechanisms of the de‐esterification are discussed in terms of both charge‐initiated and charge‐remote fragmentations. The de‐esterification of the negative ion of 1 and the rearrangements of the ion at m/z 319 are rationalized by charge transfer and negative‐charge initiated fragmentation. This study deepens our understanding of collision‐induced fragmentations of carboxylic anions with multi‐functional groups. A comparison of the CID data for the negative ions of 1 and 5 (a major oxidation degradate of 1) indicates that the analysis of the CID data for 1 can serve as a basis for identification of oxidation degradation products or metabolites of 1. The analysis of the CID data for the negative ion of 1 also reveals the fundamental characteristics of the CID data for the negative ions of other statin hydroxy acids such as lovastatin (3) and pravastatin (4). Copyright © 2003 John Wiley & Sons, Ltd.
Screening for and validated quantification of amphetamines and of amphetamine‐ and piperazine‐derived designer drugs in human blood plasma by gas chromatography/mass spectrometry
Authors: Peters Frank T. , Schaefer Simone , Staack Roland F. , Kraemer Thomas , Maurer Hans H. 
Published: June 2003

AbstractThe classical stimulants amphetamine, methamphetamine, ethylamphetamine and the amphetamine‐derived designer drugs MDA, MDMA (‘ecstasy’), MDEA, BDB and MBDB have been widely abused for a relatively long time. In recent years, a number of newer designer drugs have entered the illicit drug market. 4‐Methylthioamphetamine (MTA), p‐methoxyamphetamine (PMA) and p‐methoxymethamphetamine (PMMA) are also derived from amphetamine. Other designer drugs are derived from piperazine, such as benzylpiperazine (BZP), methylenedioxybenzylpiperazine (MDBP), trifluoromethylphenylpiperazine (TFMPP), m‐chlorophenylpiperazine (mCPP) and p‐methoxyphenylpiperazine (MeOPP). A number of severe or even fatal intoxications involving these newer substances, especially PMA, have been reported. This paper describes a method for screening for and simultaneous quantification of the above‐mentioned compounds and the metabolites p‐hydroxyamphetamine and p‐hydroxymethamphetamine (pholedrine) in human blood plasma. The analytes were analyzed by gas chromatography/mass spectrometry in the selected‐ion monitoring mode after mixed‐mode solid‐phase extraction (HCX) and derivatization with heptafluorobutyric anhydride. The method was fully validated according to international guidelines. It was linear from 5 to 1000 µg l−1 for all analytes. Data for accuracy and precision were within required limits with the exception of those for MDBP. The limit of quantification was 5 µg l−1 for all analytes. The applicability of the assay was proven by analysis of authentic plasma samples and of a certified reference sample. This procedure should also be suitable for confirmation of immunoassay results positive for amphetamines and/or designer drugs of the ecstasy type. Copyright © 2003 John Wiley & Sons, Ltd.
Approximation by Gegenbauer polynomials in the study of a rectangular ridged waveguide. Application to the analysis of a waveguide septum polarizer
Authors: Boukli‐Hacene Noureddine , Sombrin Jacques , Papiernik Albert 
Published: June 2003

AbstractSeveral methods have been used for the study of a ridged waveguide. In this paper, we propose the use of Gegenbauer polynomials in the decomposition of the electromagnetic field near the edges of the septum, for the computation of cut‐off frequencies and electromagnetic TE and TM fields in the ridged waveguide sections. This study is applied to analyse a waveguide septum polarizer that was experimentally studied by M.H. CHEN and G.N. TSANDOULAS en 1972. The useful performances of the polarizer (ellipticity ratio, circular polarization ratio) are computed from the geometrical dimensions of the waveguide and the septum. The method is based on the computation of discontinuities between waveguides with different ridge height by mode matching and the cascading of scattering parameter matrices representing the discontinuities and the waveguide lengths, resulting in the global S matrix of the polarizer. The computed results are compared with those obtained by other methods and shown to be in good agreement which verify the theory. Plots of field distributions prove also the accuracy of the results. Copyright © 2003 John Wiley & Sons, Ltd.