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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 9 (1986), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The catabolism of indole-3-acetic acid was investigated in chloroplast preparations and a crude enzyme fraction derived from chloroplasts of Pisum sativum seedlings. Data obtained with both systems indicate that indole-3-acetic acid undergoes decarboxylative oxidation in pea chloroplast preparations. An enhanced rate of decarboxylation of [1′-1C]indole-3-acetic acid was obtained when chloroplast preparations were incubated in the light rather than in darkness. Results from control experiments discounted the possibility of this being due to light-induced breakdown of indole-3-acetic acid. High performance liquid chromatography analysis of [2′-14C]indole-3-acetic acid-fed incubates showed that indole-3-methanol was the major catabolite in both the chloroplast and the crude enzyme preparations. The identification of this reaction product was confirmed by gas chromatography-mass spectrometry when [2H5]indole-3-methanol was detected in a purified extract derived from the incubation of an enzyme preparation with 32H5]indole-3-acetic acid.
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  • 2
    ISSN: 1432-2048
    Keywords: Deuterium ; Internal standard ; Isotope fraction ; High performance liquid chromatography ; Plant hormone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Deuterium-labelled indole-3-acetic acid, abscisic acid and phthalimido-1-aminocyclopropane-1-carboxylic acid were found to separate from the unlabelled compounds on reverse-phase high-performance liquid chromatography (HPLC). A similar separation was found for the methyl esters of these compounds on normal-phase HPLC. Such separations may lead to substantial errors when these compounds are used as internal standards for quantitation by gas chromatography-mass spectrometry/selective ion detection, unless the complete chromatographic peaks are collected.
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 380 (1996), S. 509-512 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Our methodology of two-dimensional (2D) EIT has been described in detail previously10'12'17. Electrodes are positioned with equal spacing around the body to be imaged, thus defining a plane through the object. Voltage profiles are collected for all drive and receive electrode-pair combinations, and ...
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 6 (1968), S. 375-386 
    ISSN: 1741-0444
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Description / Table of Contents: Sommaire Moyennant certaines hypothèses simplificatrices, on a pu déduire des relations entre l'amplitude et l'intervalle de temps séparant les crêtes positives et négatives des potentiels d'action des nerfs composés recueillis dans un conducteur, et la position relative des électrodes. Les calculs théoriques et les résultats expérimentaux donnés montrent la variation attendue de la forme suivant la taille de l'électrode détectrice. Les résultats indiquent une bonne concordance entre les résultats expérimentaux et la théorie simplifiée de l'effet de la position et de la taille de l'électrode sur la forme de l'onde: il est donc important d'en tenir compte pour l'analyse des formes.
    Abstract: Zusammenfassung Unter gewissen vereinfachenden Voraussetzungen werden Beziehungen zwischen Größe und Zeitintervall zwischen negativen und positiven Spitzen von Aktionspotentialen gemischter Nerven einerseits und der Lage der Ableitelektrode in Beziehung zum Nerven andererseits entwickelt. Die Potentiale wurden in einem Volumenkonduktor abgeleitet. Theoretische Rechnungen und experimentelle Ergebnisse werden mitgeteilt. Es zeigt sich die erwartete Wellenformänderung mit der Größe der Ableitelektrode. Die Ergebnisse geben gute Ubereinstimmung zwischen den experimentellen Ergebnissen und der vereinfachten Theorie der Wellenformabhängigkeit von Position und Größe oder Oberflächenelektrode. Bei Wellenformmessungen sollte daher immer der Einfluß der Elektrodenstellung berücksichtigt werden.
    Notes: Abstract Making certain simplifying assumptions, relationships are derived between the size and time interval between negative and positive peaks of compound nerve action potentials detected in a volume conductor, and the position of the recording electrode with respect to the nerve. Theoretical calculations and experimental results are also given showing the expected waveform change with the size of the detecting electrode. The results show good agreement between experimental results and simplified theory of waveform dependence on surface electrode position and size and suggest it is necessary to consider the effect of electrode placement whenever waveform measurements are being made.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 6 (1968), S. 493-502 
    ISSN: 1741-0444
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Description / Table of Contents: Sommaire Deux méthodes expérimentales ont été utilisées et comparées pour déterminer les spectres de fréquence des potentiels d’action des nerfs. Les deux méthodes se sont avérées capables d’évaluer de façon quantitative les petites différences entre les formes d’onde; ces méthodes sont appliquées à l’étude des variations des potentiels d’action des nerfs composés en fonction de la distance croissante entre stimulus et détecteur. Les résultats montrent une bonne concordance entre les résultats expérimentaux et les prévisions théoriques basées sur la dispersion des potentiels d’action des nerfs composés. Les spectres de fréquence obtenus suggèrent que les largeurs de bande de certains amplificateurs biologiques sont inutilement étendues.
    Abstract: Zusammenfassung Zwei experimentelle Methoden werden benutzt und hinsichtlich der Bestimmung von Frequenzspektra von Nervenaktionspotentialen verglichen. Beide Verfahren können kleine Unterschiede in der Wellenform quantitativ erfassen. Sie werden auf das Problem des Vergleichs zusammengesetzter Nervenaktionspotentiale angewandt, die bei wachsender Entfernung zwischen Reiz und Ableitung aufgenommen werden. Die Ergebnisse zeigen gute Übereinstimmung zwischen experimentellen Resultaten und theoretischen Voraussagen aufgrund der Dispersion des zusammengesetzten Nervenaktionspotentials. Frequenzspektra weisen darauf hin, daß die Bandbreite einiger biologischer Verstärker unnötig gro\ ist.
    Notes: Abstract Two experimental methods are used and compared for the determination of the frequency spectra of nerve action potentials. Both methods are shown capable of putting small differences between waveforms into quantitative form, and are applied to the problem of the comparison of compound nerve action potentials detected at increasing distance between stimulus and detector. The results show good agreement between experimental results and theoretical predictions based on the dispersion of the compound nerve action potential. Frequency spectra suggest that the bandwidth of some biological amplifiers are unnecessarily large.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 7 (1969), S. 255-255 
    ISSN: 1741-0444
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 9 (1971), S. 305-314 
    ISSN: 1741-0444
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Description / Table of Contents: Sommaire L'activité électrique du duodénum et de l'estomac humains a été analysée en utilisant les techniques vectorielles, de corrélation et d'histogrammes d'intervalles dans le but d'établir le sens de conduction de cette activité. Il est montré que l'activité électrique gastrique à une fréquence de 3/min est conduite le long de l'antrum pylorique, par l'anneau pylorique et à une certaine distance dans le duodénum. Alors que l'activité gastrique n'est conduite que dans le sens aboral, l'activité duodénale semble n'avoir aucun sens constant de transmission. La longueur de l'intestin grêle a été comparée par d'autres savants à une série d'oscillateurs lâchement reliés, fonctionnant à des fréquences qui diminuent avec la distance du duodénum. On montre que l'activié duodénale est semblable à celle d'un modèle qui consiste d'oscillateurs de relaxation fermement reliés qui ne sont pas vérouillés en phase alors qu'ils fonctionnent à une fréquence commune.
    Abstract: Zusammenfassung Die elektrische Aktivität des menschlichen Zwölffingerdarms und Magens ist mit Verwendung von Vektor, Korrelations- und Histogrammtechniken gemeinsamen Zwischenraums zu dem Zweck analysiert worden, die Richtung der Übertragung dieser Aktivität festzulegen. Es wird gezeigt, dass die gastrisch-elektrische Aktivität bei einer Frequenz von 3/min herunter über das pylorische Antrum, über den pylorischen Ring und diene kleine Strecke runter in den Zwölffingerdarm geleitet wird. Während die gastrische Aktivität nur in aborale Richtung geleitet wird, ergab sich, dass Aktivität des Zwölffingerdarms keine feststehende Sendungsrichtung hat. Die Länge des Dünndarms ist von früheren Bearbeitern mit einer Reihe lose verbundener Oszillatoren verglichen worden, die eine Frequenz haben, welche mit Entfernung vom Zwölffingerdarm abnimmt. Die Aktivität des Zwölffingerdarms zeigt sich im Einklang mit einem Modell, das aus eng verbundenen Kippgeneratoren besteht, welche mit gemeinsamer Frequenz schwingen, aber nicht zwangsweise in Phase sind.
    Notes: Abstract The electrical activity of the human duodenum and stomach has been analysed, using vector, correlation and joint interval histogram techniques, with a view to establishing the direction of conduction of this activity. It is shown that the gastric electrical activity at a frequency of 3/min is conducted down the pyloric antrum across the pyloric ring and some distance down the duodenum. Whilst the gastric activity is conducted only in the aboral direction the duodenal activity has been found to have no consistent direction of transmission. The length of small intestine has been likened by previous workers to a series of loosely linked oscillators running at frequencies which decrease with distance from the duodenum. The duodenal activity is shown to be consistent with a model consisting of tightly linked relaxation oscillators which, whilst oscillating at a common frequency, are not phase locked.
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  • 8
    ISSN: 1741-0444
    Keywords: Virtual biopsies ; Barrett's oesophagus ; Bio-electrical impedance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract It has previously been shown that it is possible to differentiate between squamous and columnar epithelia in rat and resected human tissues using an impedance probe to makein vitro measurements. This probe can be passed down an endoscope allowing measurements to be made in patients. However, the probe emerges parallel to the oesophageal wall, with little room to manoeuvre. The conditions of control required to give reliable readings have been investigated. The importance of pressure applied and the angle of approach to the oesophagus was assessed. Pressures in the range 26.6 Pa to 46.3 kPa and angles in the range 15–90 degrees were considered. Inin vitro studies it was observed that it was possible to obtain consistent readings with pressures greater than 2.9 kPa and with angles greater than 15 degrees between the probe and the oesophagus. These conditions can be achievedin vivo, and readings obtained from twelve patients are shown (45 readings on normal squamous, 34 on Barrett's oesophagus and 22 on stomach). At low frequencies (9.6–153.2 kHz), a Mann-Whitney test shows a significant difference (p〈0.001) when comparing the means from squamous and columnar, and also when readings from Barrett's and normal gastric epithelia are compared (p〈0.001).
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 11 (1973), S. 352-353 
    ISSN: 1741-0444
    Keywords: Impedance pneumograph ; tidal and minute-volume monitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 20 (1982), S. 512-516 
    ISSN: 1741-0444
    Keywords: Biological signals ; Companders
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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