bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glutathione peroxidase isoforms as part of the local antioxidative defense system in normal and Barrett's esophagus
Authors: Mörk Hubert , Scheurlen Michael , Al‐Taie Oliver , Zierer Annette , Kraus Michael , Schöttker Katrin , Jakob Franz , Köhrle Josef 
Published: April 2003

AbstractThe development of an oesophageal adenocarcinoma arising in Barrett's mucosa is associated with a multistep process of genetic lesions that may be triggered by persistent oxidative damage. The glutathione peroxidase isoforms pGPx and GI‐GPx, which were identified recently in the mucosa of the esophagus, may play a role as defense factors to prevent such oxidative injury. To determine alterations of the expression of pGPx and GI‐GPx in Barrett's mucosa as compared to primary and regenerative squamous epithelium. Biopsy samples of oesophageal mucosa of patients with Barrett's esophagus (n = 12), patients with squamous restoration after thermal ablation (n = 10), and healthy controls (n = 5) were analyzed for pGPx and GI‐GPx mRNA expression by Northern blot and for glutathione peroxidase activity by enzymatic assay. Squamous regeneration was induced by argon plasma coagulation (APC) combined with proton pump inhibitor therapy. In Barrett's epithelium mRNA levels of pGPx (the secreted isoform) were significantly reduced and of GI‐GPx (the intracellular isoform) significantly increased as compared to normal squamous mucosa. In squamous mucosa that had regenerated after APC, no significant differences compared to the expression pattern of primary squamous mucosa were found. Compared to squamous mucosa, Barrett's metaplasia shows a different mRNA expression of pGPx and GI‐GPx that may be associated with increased susceptibility to oxidative damage. © 2003 Wiley‐Liss, Inc.
Preferential neurotrophic activity of fibroblast growth factor‐20 for dopaminergic neurons through fibroblast growth factor receptor‐1c
Authors: Ohmachi Shigeki , Mikami Tadahisa , Konishi Morichika , Miyake Ayumi , Itoh Nobuyuki 
Published: April 2003

AbstractDegeneration of dopaminergic neurons of the substantia nigra causes Parkinson's disease. Therefore, neurotrophic factors for dopaminergic neurons are of substantial clinical interest. Fibroblast growth factor (FGF)‐20 preferentially expressed in the substantia nigra pars compacta (SNPC) of the rat brain significantly enhanced the survival of midbrain dopaminergic neurons. Here we examined the mechanism of action of FGF‐20 on dopaminergic neurons. FGF‐20 slightly enhanced the survival of total neurons of the midbrain, indicating that it preferentially enhanced the survival of dopaminergic neurons. FGF receptor (FGFR)‐1c was found to be expressed abundantly in dopaminergic neurons in the SNPC but at much lower levels in neurons of other midbrain regions by in situ hybridization. FGF‐20 was also found to bind FGFR‐1c with high affinity with the BIAcore system. Furthermore, FGF‐20 activated the mitogen‐activated protein kinase (MAPK) pathway, which is the major intracellular signaling pathway of FGFs. Both the FGFR‐1 inhibitor SU5402 and the MAPK pathway inhibitor PD98059 also significantly inhibited the activation of the MAPK pathway by FGF‐20 and the neurotrophic activity of FGF‐20. The present findings indicate that the activation of the MAPK pathway by FGF‐20 signaling through FGFR‐1c plays important roles in the survival of dopaminergic neurons in the SNPC. © 2003 Wiley‐Liss, Inc.
Glycosylation of acetylcholinesterase and butyrylcholinesterase changes as a function of the duration of Alzheimer's disease
Authors: Sáez‐Valero J. , Fodero L.R. , Sjögren M. , Andreasen N. , Amici S. , Gallai V. , Vanderstichele H. , Vanmechelen E. , Parnetti L. , Blennow K. , Small D. H. 
Published: April 2003

AbstractThe identification of biochemical markers of Alzheimer's disease (AD) may help in the diagnosis of the disease. Previous studies have shown that Aβ1–42 is decreased, and tau and phospho‐tau are increased in AD cerebrospinal fluid (CSF). Our own studies have identified glycosylated isoforms of acetylcholinesterase (Glyc‐AChE) and butyrylcholinesterase (Glyc‐BuChE) that are increased in AD CSF. Glyc‐AChE is increased in APP (SW) Tg2576 transgenic mice prior to amyloid plaque deposition, which suggests that Glyc‐AChE may be an early marker of AD. The aim of this study was to determine whether Glyc‐AChE or Glyc‐BuChE is increased in CSF at early stages of AD and to compare the levels of these markers with those of Aβ1–42, tau and phospho‐tau. Lumbar CSF was obtained ante mortem from 106 non‐AD patients, including 15 patients with mild cognitive impairment (MCI), and 102 patients with probable AD. Glyc‐AChE, tau and phospho‐tau were significantly increased in the CSF of AD patients compared to non‐neurological disease (NND) controls. Aβ1–42 was lower in the AD patients than in NND controls. A positive correlation was found between the levels of Glyc‐AChE or Glyc‐BuChE and disease duration. However, there was no clear correlation between the levels of tau, phospho‐tau or Aβ1–42 and disease duration. The results suggest that Glyc‐AChE and Glyc‐BuChE are unlikely to be early markers of AD, although they may have value as markers of disease progression. © 2003 Wiley‐Liss, Inc.
Morphological and electrophysiological characterization of abnormal cell types in pediatric cortical dysplasia
Authors: Cepeda Carlos , Hurst Raymond S. , Flores‐Hernández Jorge , Hernández‐Echeagaray Elizabeth , Klapstein Gloria J. , Boylan Marea K. , Calvert Christopher R. , Jocoy Emily L. , Nguyen Oanh K. , André Véronique M. , Vinters Harry V. , Ariano Marjorie A. , Levine Michael S. , Mathern Gary W. 
Published: April 2003

AbstractThe mechanisms responsible for seizure generation in cortical dysplasia (CD) are unknown, but morphologically abnormal cells could contribute. We examined the passive and active membrane properties of cells from pediatric CD in vitro. Normal‐ and abnormal‐appearing cells were identified morphologically by using infrared videomicroscopy and biocytin in slices from children with mild to severe CD. Electrophysiological properties were assessed with patch clamp recordings. Four groups of abnormal‐appearing cells were observed. The first consisted of large, pyramidal cells probably corresponding to cytomegalic neurons. Under conditions that reduced the contribution of K+ conductances, these cells generated large Ca2+ currents and influx when depolarized. When these cells were acutely dissociated, peak Ca2+ currents and densities were greater in cytomegalic compared with normal‐appearing pyramidal neurons. The second group included large, nonpyramidal cells with atypical somatodendritic morphology that could correspond to “balloon” cells. These cells did not display active voltage‐ or ligand‐gated currents and did not appear to receive synaptic inputs. The third group included misoriented and dysmorphic pyramidal neurons, and the fourth group consisted of immature‐looking pyramidal neurons. Electrophysiologically, neurons in these latter two groups did not display significant abnormalities when compared with normal‐appearing pyramidal neurons. We conclude that there are cells with abnormal intrinsic membrane properties in pediatric CD. Among the four groups of cells, the most abnormal electrophysiological properties were displayed by cytomegalic neurons and large cells with atypical morphology. Cytomegalic neurons could play an important role in the generation of epileptic activity. © 2003 Wiley‐Liss, Inc.
Melatonin regulates neuronal plasticity in the hippocampus
Authors: El‐Sherif Y. , Tesoriero J. , Hogan M.V. , Wieraszko A. 
Published: April 2003

AbstractThe influence of melatonin on hippocampal evoked potentials initiated by low‐ and high‐frequency electrical stimulations and by two pulses applied in rapid succession was investigated. In confirmation of our previous studies, melatonin attenuated the population spike triggered by low‐frequency stimulation (0.03 Hz). High‐frequency stimulation (HFS; 100 Hz for 1 sec, three times every 10 sec), which in control slices permanently facilitated neuronal excitability (347% ± 32%), was also able to amplify the melatonin‐depressed potential (467.8% ± 59.6%). Because melatonin is a hydrophobic molecule, it was dissolved and applied in ethanol. Ethanol (0.4%) by itself reduced the magnitude of HFS‐induced potentiation (233.5% ± 16.8%). The slices stimulated with two pulses separated with a delay longer than 15 msec demonstrated a facilitation of the response to the second stimuli (paired‐pulse facilitation; PPF). The influence of melatonin (100 μM) on PPF was biphasic: Shortly after addition of melatonin, PPF was briefly (5–10 min) reversed to paired‐pulse inhibition (PPI), which gradually returned to a stable PPF. Ethanol (0.4%) applied without melatonin exerted only a marginal, facilitatory effect on PPF. The delay between two successively applied pulses, shorter than 13 msec, resulted in attenuation of the response to the second stimuli (PPI). Melatonin (100 μM) reversed the attenuation of the second potential within 15–20 min following its application. Ethanol applied by itself at the concentration of 0.4% temporarily (5–10 min), but significantly, depressed the second potential. These results demonstrate the ability of melatonin to modulate specific forms of plasticity in hippocampal pyramidal neurons. © 2003 Wiley‐Liss, Inc.
Normal nigrostriatal innervation but dopamine dysfunction in mice carrying hypomorphic tyrosine hydroxylase alleles
Authors: Althini Susanna , Bengtsson Henrik , Usoskin Dmitry , Söderström Stine , Kylberg Annika , Lindqvist Eva , Chuva de Sousa Lopes Susana , Olson Lars , Lindeberg Jonas , Ebendal Ted 
Published: April 2003

AbstractWe investigated the use of the mouse tyrosine hydroxylase (TH) gene to drive knock‐in constructs in catecholaminergic neurons. Two targeting constructs representing truncated forms of either of the BMP receptors ALK‐2 or BMPR‐II preceded by an internal ribosome entry site (IRES) were introduced into the 3′ untranslated region of TH. An frt‐flanked neomycin‐resistance (neor) cassette was placed in the 3′ end of the targeting constructs. Mice homozygous for the knock‐in alleles showed various degrees of hypokinetic behavior, depending mainly on whether the neor cassette was removed. In situ hybridization and immunohistochemistry showed that TH mRNA and protein were variously down‐regulated in these mouse strains. Reduced levels of dopamine and noradrenalin were found in several brain areas. However, number and morphology of neurons in substantia nigra and their projections to striatum appeared normal in the neor‐positive TH hypomorphic mice as examined by markers for L‐aromatic amino acid decarboxylase and the dopamine transporter. Elimination of the neor cassette from the knock‐in alleles partially restored TH and dopamine levels. The present neor‐positive TH hypomorphic mice show that nigrostriatal innervation develops independently of TH and should find use as a model for conditions of reduced catecholamine synthesis, as seen in, for example, L‐dihydroxyphenylalanine‐responsive dystonia/infantile parkinsonism. © 2003 Wiley‐Liss, Inc.
Analytical resolution of a parallel second‐order reaction mechanism
Authors: Croce A. E. , Mogni L. V. , Irrazábal C. Vicente 
Published: April 2003

AbstractThe competition among the three different elementary second‐order processes involving the radicals A and B,

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is frequently established in many combustion and atmospheric chemistry systems. The analytical resolution of the above mechanism for kAB = 2kAA and kAB = 2kBB, that is, for a cross‐combination ratio ϕ = kAB/(kAAkBB)1/2 = 2, is well‐known, but it has been claimed not to exist for ϕ ≠ 2.In the present paper an analytical resolution of the system (1)–(3), performed under the condition kAB ≠ 2kAA and kAB ≠ 2kBB, leads to

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The mathematical procedure leading to this equation and the equation itself are valid independently of the nature of the products of the reactions (1), (2) and (3), that is, recombination or disproportionation products, provided that the reactants and the order of the reactions remain the same.The comparison with numerical integration for exemplary cases is performed. The solutions for the particular cases kAB ≠ 2kBB or kAB ≠ 2kAA are also presented. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 246–251, 2003
Über das viskositätsverhalten von holzcellulosenitraten
Authors: Zapf von F. 
Published: April 2003

AbstractIn Fortführung der Untersuchungen über die Ursachen der anomal hohen Km‐Werte von Holzcellulosenitraten wurde durch quantitative Fraktionierung, durch vergleichende viskosimetrische und osmotische Messungen und durch Aufstellung der Verteilungskurven nachgewiesen, daß die Km‐Werte der unfraktionierten Nitrate um so höher sind, je uneinheitlicher der molekulare Verteilungszustand ist. Die Km‐Werte der einzelnen Fraktionen haben den normalen Wert von Baumwollcellulosenitraten.An der Massenverteilungskurve des polymeranalogen Nitrates einer schonend isolierten. Fichtencellulose wurden 3 Maxima festgestellt. Ein Zusammenhang zwischen der molekularen Uneinheitlichkeit und der Entstehung der Holzcellulose in verschiedenartigen Zellen (tracheale, Parenchym‐ und Sklerenchym‐Zellen) wird erwogen.Durch vorhergehendes Umfällen der Zellstoffe aus Schweizers Reagens mit Seignettesalzlösung werden die Km‐Werte der polymeranalogen Nitrate nur unbedeutend niedriger. Ein durch die Seignettesalzlösung nicht ausgefällter Anteil besteht aus Holzpolyosen, deren Entfernung die Fraktionierung der Zellstoffnitrate begünstigt.In die Cellulosemoleküle eingebaute Fremdgruppen oder geringe Beimengungen von nichtcellulosischen Bestandteilen sind für die Viskosität von verdünnten Cellulose‐nitratlösungen ohne wesentlichen Einfluß. Dagegen wirken sie sich infolge ihrer schlechten Löslichkeit bzw. ihrer heteropolaren Natur in konzentrierten Lösungen viskositätserhöhend aus. Durch Vergrößerung der Schubspannung wird dieser viskositätserhöhende Effekt wirkungslos.In Äther gelöstes Diazomethan baut Cellulosenitrate in Acetonlösung rasch ab. Der Chemismus des Abbaues ist noch unbekannt.
Über einige S,S′‐alkylenbiscysteine und deren isolierung aus chemisch modifizierter wolle
Authors: Zahn von H. , Wollemann B. 
Published: April 2003

Abstract

Die chemische Stabilisierung von Wolle durch Einwirkung bifunktioneller Halogen‐derivate auf reduzierte Wolle (Harrisverfahren) wurde präparativ‐chemisch studiert.
Die von Harris angenommenen Bisthioäther des Cysteins wurden aus l‐Cystein und aliphatischen α,ω‐Dihalogenverbindungen X(CH2)nX mit n = 1–6 dargestellt und durch Elementaranalyse und Papierchromatographie charaketerisiert.
Bei der präparativen Aufarbeitung von reduzierter und mit den genannten α,ω‐Dihalogenverbindungen umgesetzter Wolle wurden S,S′‐Polymethylenbiscysteine in guten Ausbeuten isoliert, welche mit den synthetischen Verbindungen identisch sind.
Der von Harris 1941 angegebene Reaktionsmechanismus für die chemische Modifizierung von Wolle konnte somit präparativ‐chemisch bestätigt werden.
Über die quellung resp. Inclusion der cellulose mit niederen fettsäuren
Authors: Staudinger von Hermann , Eicher Theo 
Published: April 2003

AbstractEs wird der Unterschied zwischen Quellung und Inclusion bei der Einwirkung von niederen Fettsäuren auf Linters gezeigt. Die Ameisensäure vermag die Wasserstoffbrücken zwischen den Cellulose ketten zu sprengen, also die Cellulose zu quellen und in einen reaktionsfähigen Zustand überzufübren. Die Propionsäure und Buttersäure dagegen sind dazu nicht befähigt, können aber zwischen die Celluloseketten nach Vorquellung mit Wasser includiert werden. Diese „Inclusionscellulosen”︁ zeigen die gleiche Reaktionsfähigkeit wie die mit Ameisensäure gequollenen Cellulosen. Die Essigsäure nimmt eine Mittelstellung ein, sie quillt in der Kälte nur langsam, bei erhöhter Temperatur rasch; ferner kann sie durch Vorbehandlung der Cellulose mit Wasser includiert werden. Die Reaktionsfähigkeit der trockenen und includierten Cellulosen wird durch die Acetylierungsgeschwindigkeit mit Essigsäureanhydrid in Benzol (Überchlorsäure als Katalysator) charakterisiert.
Multimerisation: Assoziation und aggregation. III. Einfluß der offenen assoziation auf die ungestörten dimensionen von polyäthylenglykolen
Authors: Elias Von Hans‐Georg 
Published: April 2003

AbstractDie STAUDINGER‐Indices [η] von Polyäthylenglykolen mit Molekulargewichten zwischen 62 und 38000 wurden bei 25°C in Wasser, Methanol, Dimethylformamied, Acetonitril, Dioxan, Tetrachlorkohlenstoff, Methylacetat und Benzylalkohol, und in Benzol bei 10 bzw. 37°C gemessen. Die Funktion [η]/M = f(M) durchläuft mit steigendem Viskositätsmittel des Molekulargewichtes Mv ein Minimum und steigt dann zuerst steil und später langsamer an. Die Extrapolation der Asymptoten bei hohen Molekulargewichten zu M → 0 ergibt unabhängig vom Assoziationszustand der Polyäthylenglykole in der verschiedenen Lösungsmitteln ein lim

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Die konventionelle Auswertung über den Molekulargewichtsbereich vom Minimum aufwärts führt zu KΘ‐Werten, die mit steigender Gleichgewichtskonstante der Assoziation abnehmen. Bei kleinen Molekulargewichten nähern sich die STADUINGER‐Indices einem Grenzwert [η]0. Für nicht assoziierende Lösungsmittel wurde [η]0 = 2,5 ml/g gefunden. Mit steigender Assoziationskonstante fällt [η]0 zu tieferen Werten ab. Die Befunde werden durch intermolekulare Wasserstoffbrücken von der Hydroxyl‐Endgruppen zu den mittelständigen Äthergruppierungen gedeutet.
NMR observations of drawn polymers VI. Poly (ethylene oxide)
Authors: Olf H. G. , Peterlin A. 
Published: April 2003

AbstractWide line NMR spectra of cold drawn poly(ethylene oxide) (PEO) were recorded at temperatures between −196°C. and 66°C. as a function of the alignment angle between the draw direction and the magnetic field. Line width, second moment, and mobile fraction were determined and are discussed in terms of segmental motion. In agreement with other authors two motional processes were found. (1) The β‐process, commencing at temperatures around −45°C., probably occurs in non‐crystalline regions and causes the emergence of a narrow NMR line in addition to the broad one. (2) The β‐process was observed between 0°C. and the melting point (66°C.) and led to a pronounced decrease of the width of the broad line and of the second moment. This decrease was anisotropic and was greatest at the alignment angle γ = 45°. As a consequence of this the dependence of the line width and of the second moment on γ is changed: whereas both these quantities show at low temperatures (<0°C.) a maximum at γ = 45° and an absolute minimum at γ = 0°, near the melting point, a minimum close to γ = 45° and an absolute maximum at γ = 0° were found. These changes are explained by oscillations of the helical molecules around their axes in crystalline regions.
The influence of temperature on the plastic deformation of polyethylene
Authors: Corneliussen R. , Peterlin A. 
Published: April 2003

AbstractTemperature influences the attainable draw ratio, the transparency of the drawn material, the long period and the intensity distribution in the small angle X‐ray diffraction pattern. Drawing at or below 80°C yields a first order small angle maximum with relatively large lateral width indicating a variation of lamellar surface orientation between 90° and 45° to the draw direction. Drawing above 80°C reduces the lateral width of the first order maximum and leads to the appearance of the second order. The thermal history of the starting material, quenched, slowly cooled, or annealed, affects the draw behavior. The long period, however, seems to be independent of the physical conditions of the initial sample. At 60°C, for instance, the drawing of polyethylene samples with a long period of 195, 250, 290, 310, and 380 Å yields a material with long periods between 170 and 180 Å.Annealing drawn samples produces observable changes even at 90°C. At temperatures below 120°C annealing for 100 min yields long periods slightly below those for samples drawn at the same temperature. At 120°C and above the drawing and annealing show nearly the same long period. Annealing also greatly increases the intensity of the X‐ray small angle reflections, but at temperatures below 120°C causes only minor changes in the lateral width of the same reflections.
Polymerization of itaconic acid under high pressure
Authors: Nakamoto Hideo , Ogo Yoshiaki , Imoto Tatsuya 
Published: April 2003

AbstractRadical polymerizations of itaconic acid were investigated under high pressure up to 5000 kg/cm2 in several different solvents.The critical pressures under which polymerization does not take place were determined in each solvent and the relation between the dielectric constant of the solvent and the critical pressure was found to be linear. The overall rate of polymerization increases markedly with pressure and the activation volume indicates fairly large absolute values compared with those of other vinyl compounds.The polymers obtained under high pressure are white and brittle having a somewhat hygroscopic property, are soluble in methanol, dimethylformamide and especially in water, and are insoluble in other organic solvents.
Linear conditions in chain systems with neighbour interaction. II. Application of structural conditions: Atactic polypropylene
Authors: Allegra Giuseppe 
Published: April 2003

AbstractIt is shown here how the theory proposed in the preceding paper may be applied to the conformational analysis of atactic polymers as well as of oligomers in solution. The calculation of the free mean‐square lengths of polypropylenes with various types and degrees of tacticity is discussed in detail. In particular, the chain distributions of d and I units, coresponding to the models taken into consideration, are closely represented by the MARKOFFian law. The agreement between our results and those obtained by FLORY et al. through Monte‐Carlo calculations is substantially good. The reasons why the configurational defects in nearly isotactic poly‐α‐olefins should be more closely represented by the (… dddlddd …) sequences than by the (… dddlll …) ones proposed by FLORY, avidenced.
Gitterstörungen in polyäthylen
Authors: Hosemann Von R. , Wilke W. 
Published: April 2003

AbstractEs wird gezeigt, wie aus Messungen der Winkelabhängigkeit der Linienbreite in Röntgenweitwinkeldiagrammen von Hochpolymeren die kristallitgröße und die Gitterstörungen bestimmt werden können. In lösungskristallisierten linearen Polyäthylenen treten rein parakristalline Gitterstörungen auf, die thermodynamisch stabil sind. Verzweigtes Polyäthylen zeigt mit dem Verzweigungsgrad anwachsende Gitterstörungen und abnehmende Kristallitgrößen. Im schmelzkristallitgrößen linearen Polyäthylen werden Spannungen beobachtet; die Werte der Kristallitgrößen sind teilweise erheblich höher als im lösungskristallisierten Material. In Kettenrichtung sind die Gitterstörungen wesentlich kleiner als senkrecht dazu. Kombination von Rötgenmessungen mit anderen Untersuchungsmethoden (ESR, NMR, Suszeptibilität, Reißfestigkeit) geben die Möglichkeit, genauere Einblicke in den Verstreck‐ und Reißvorgang zu gewinnen.
Thermal properties of ethylene‐propylene block copolymers
Authors: Clegg G. A. , Gee D. R. , Melia T. P. 
Published: April 2003

AbstractA precision, adiabatic, vacuum calorimeter and a differential scanning calorimeter have been used to measure the heat capacities of two ethylene‐propylene block copolymers containing 12 and 17 mole per cent ethylene, respectively, over the temperature range 80 to 500°K. An estimate has been made of heat capacity values below 80°K. Values of the heat capacity, entropy, enthalpy, and free energy are listed at lO°C intervals. Two first order transitions at 399 ± 3°K and 435 ± l°K were observed in both copolymers. These are attributed to the melting of ethylene and isotactic propylene blocks. Values for the heats of fusion of the copolymers are listed.