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Jonas F Schiemer,Axel Heimann,Karin H Somerlik-Fuchs,Roman Ruff,Klaus-Peter Hoffmann,Jan Baumgart,Manfred Berres,Hauke Lang,Werner Kneist 대한소화기 기능성질환∙운동학회 2019 Journal of Neurogastroenterology and Motility (JNM Vol.25 No.3
Background/AimsMotility disorders are common and may affect the entire gastrointestinal (GI) tract but current treatment is limited. Multilocularsensing of GI electrical activity and variable electrical stimulation (ES) is a promising option. The aim of our study is to investigate theeffects of adjustable ES on poststimulatory spike activities in 5 GI segments. MethodsSix acute porcine experiments were performed with direct ES by 4 ES parameter sets (30 seconds, 25 mA, 500 microseconds or1000 microseconds, 30 Hz or 130 Hz) applied through subserosal electrodes in the stomach, duodenum, ileum, jejunum, and colon. Multi-channel electromyography of baseline and post-stimulatory GI electrical activity were recorded for 3 minutes with hook needleand hook-wire electrodes. Spike activities were algorithmically calculated, visualized in a heat map, and tested for significance byPoisson analysis. ResultsPost-stimulatory spike activities were markedly increased in the stomach (7 of 24 test results), duodenum (8 of 24), jejunum (23 of24), ileum (18 of 24), and colon (5 of 24). ES parameter analysis revealed that 80.0% of the GI parts (all but duodenum) required apulse width of 1000 microseconds, and 60.0% (all but jejunum and colon) required 130 Hz frequency for maximum spike activity. Fivereaction patterns were distinguished, with 30.0% earlier responses (type I), 42.5% later or mixed type responses (type II, III, and X),and 27.5% non-significant responses (type 0). ConclusionsMultilocular ES with variable ES parameters is feasible and may significantly modulate GI electrical activity. Automatedelectromyography analysis revealed complex reaction patterns in the 5 examined GI segments.
GENETIC ANALYSIS OF ABA-MEDIATED CONTROL OF PLANT GROWTH IN Arabidopsis
Monika Iten,Thomas Hoffmann,Gregor Benning,Axel Himmelbach,Erwin Grill Plant molecular biology and biotechnology research 1998 Proceedings the 2nd Korean-Germany joint symposium Vol.1998 No.-
The plant hormone abscisic acid (ABA) plays an essential role in a variety of physiological responses such as seed dormancy, regulation of stomatal closure and inhibition of plant growth. We used the inhibitory effect of ABA to isolate mutants of Arabidopsis that reveal ABA-insensitive root growth as a prelude to elucidate the molecular steps of ABA-signalling modulating the growth response of plants. The characterisation of the mutants identified 8 new loci that were subdivided into two classes: pleiotropic mutants including the well-characterised mutants abi1 and abi2 which are impaired in all three above mentioned responses, and mutants that are impaired specifically in the growth response. The cloning of the ABI1 and ABI2 loci and characterisation of its gene products revealed that two homologous protein-serine/threonine phosphatases are components of ABA-signalling. The protein-phosphatases belong to the class 2C and are highly regulated by the pH and magnesium ion concentration. A pH-shift from 7.2 to 7.5 reported to occur in guard cells prior stomatal closure results in a 2.5-fold activation of the protein phosphatase activity. The introduction of a single amino acid exchange in the abi1 as well as in the abi2 protein provides a dominant negative mutation associated with a strongly reduced enzyme activity and a high ABA-insensitivity.
Substrate-free Biosensing using Brownian Rotation of Bio-conjugated Magnetic Nanoparticles
Seok-Hwan Chung,Axel Hoffmann,Liaohai Chen,Shouheng Sun,Konstantin Guslienko,Marcos Grimsditch,Samuel D. Bader 한국자기학회 2006 Journal of Magnetics Vol.11 No.4
The recent development of bio-conjugated magnetic nanoparticles offers many opportunities for applications in the field of biomedicine. In particular, the use of magnetic nanoparticles for biosensing has generated widespread research efforts following the progress of various magnetic field sensors. Here we demonstrate substrate-free biosensing approaches based on the Brownian rotation of ferromagnetic nanoparticles suspended in liquids. The signal transduction is through the measurement of the magnetic ac susceptibility as a function of frequency, whose peak position changes due to the modification of the hydrodynamic radius of bio-conjugated magnetic nanoparticles upon binding to target bio-molecules. The advantage of this approach includes its relative simplicity and integrity compared to methods that use substrate-based stray-field detectors.