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Search Results: 1 - 10 of 180088 matches for " Daniel H?nggi "
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araneae: Spinnen Europas – Spiders of Europe: http://www.araneae.unibe.ch
Blick, Theo,Nentwig, Wolfgang,Gloor, Daniel,Hnggi, Ambros
Arachnologische Mitteilungen , 2011, DOI: 10.5431/aramit4107
Abstract: determination key for Europe
In Vitro Study of Cerebrospinal Fluid Dynamics in a Shaken Basal Cistern after Experimental Subarachnoid Hemorrhage
Ulrich Kertzscher, Torsten Schneider, Leonid Goubergrits, Klaus Affeld, Daniel Hnggi, Andreas Spuler
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0041677
Abstract: Background Cerebral arterial vasospasm leads to delayed cerebral ischemia and constitutes the major delayed complication following aneurysmal subarachnoid hemorrhage. Cerebral vasospasm can be reduced by increased blood clearance from the subarachnoid space. Clinical pilot studies allow the hypothesis that the clearance of subarachnoid blood is facilitated by means of head shaking. A major obstacle for meaningful clinical studies is the lack of data on appropriate parameters of head shaking. Our in vitro study aims to provide these essential parameters. Methodology/Principal Findings A model of the basal cerebral cistern was derived from human magnetic resonance imaging data. Subarachnoid hemorrhage was simulated by addition of dyed experimental blood to transparent experimental cerebrospinal fluid (CSF) filling the model of the basal cerebral cistern. Effects of various head positions and head motion settings (shaking angle amplitudes and shaking frequencies) on blood clearance were investigated using the quantitative dye washout method. Blood washout can be divided into two phases: Blood/CSF mixing and clearance. The major effect of shaking consists in better mixing of blood and CSF thereby increasing clearance rate. Without shaking, blood/CSF mixing and blood clearance in the basal cerebral cistern are hampered by differences in density and viscosity of blood and CSF. Blood clearance increases with decreased shaking frequency and with increased shaking angle amplitude. Head shaking facilitates clearance by varying the direction of gravitational force. Conclusions/Significance From this in vitro study can be inferred that patient or head shaking with large shaking angles at low frequency is a promising therapeutic strategy to increase blood clearance from the subarachnoid space.
Calcium and Potassium Channels in Experimental Subarachnoid Hemorrhage and Transient Global Ischemia
Marcel A. Kamp,Maxine Dibué,Toni Schneider,Hans-Jakob Steiger,Daniel Hnggi
Stroke Research and Treatment , 2012, DOI: 10.1155/2012/382146
Abstract: Healthy cerebrovascular myocytes express members of several different ion channel families which regulate resting membrane potential, vascular diameter, and vascular tone and are involved in cerebral autoregulation. In animal models, in response to subarachnoid blood, a dynamic transition of ion channel expression and function is initiated, with acute and long-term effects differing from each other. Initial hypoperfusion after exposure of cerebral vessels to oxyhemoglobin correlates with a suppression of voltage-gated potassium channel activity, whereas delayed cerebral vasospasm involves changes in other potassium channel and voltage-gated calcium channels expression and function. Furthermore, expression patterns and function of ion channels appear to differ between main and small peripheral vessels, which may be key in understanding mechanisms behind subarachnoid hemorrhage-induced vasospasm. Here, changes in calcium and potassium channel expression and function in animal models of subarachnoid hemorrhage and transient global ischemia are systematically reviewed and their clinical significance discussed. 1. Introduction Despite current treatment options, delayed cerebral ischemia following aneurismal subarachnoid hemorrhage (SAH) is still associated with a high morbidity and mortality [1]. The narrowing of cerebral blood vessels by vasospasm represents the main cause of delayed cerebral ischemia [2]. Because vasospastic smooth muscle cells are known to be depolarized compared to controls [3, 4], the expression and function of ion channels in these cells after SAH are of great interest. Furthermore, the inhibitor of L-type calcium channels nimodipine remains gold standard in treatment and prophylaxis of vasospasm after SAH. However, recent studies have revealed that several ion channels of different subfamilies are impacted by SAH and may contribute to delayed vasospasm. The goal of the present analysis is to review ion channel expression and function in healthy cerebral blood vessels as well as after SAH. 2. Ion Channels Healthy Cerebral Vessels 2.1. Expression and Function of Potassium Channels in Healthy Cerebral Vessels Membrane potential of cerebrovascular smooth muscle cells and thus dilation and constriction of cerebral arteries are directly dependent on potassium conductance [5, 6]. Members of four potassium superfamilies have been shown to be expressed in smooth muscle cells of healthy cerebral vessels: inwardly rectifying (Kir), ATP-dependent-(KATP), voltage-gated ( ), and large-conductance calcium-activated (BK) potassium channels. Kir2.1
The Impact of Experimental Preconditioning Using Vascular Endothelial Growth Factor in Stroke and Subarachnoid Hemorrhage
Sven Oliver Eicker,Moritz Hoppe,Nima Etminan,Stephan Macht,Jason Perrin,Hans-Jakob Steiger,Daniel Hnggi
Stroke Research and Treatment , 2013, DOI: 10.1155/2013/948783
Abstract: Vascular endothelial growth factor (VEGF) stimulating angiogenesis was shown to be a potential novel therapeutic approach for the treatment of ischemic vascular diseases. The goal of the present study was to examine whether transfection of VEGF before occurrence of major stroke (part I) and cerebral vasospasm after experimental subarachnoid hemorrhage (SAH; part II) develops neuroprotective qualities. A total of 25 (part I) and 26 (part II) brains were analyzed, respectively. In part one, a significant reduction of infarct volume in the VEGF-treated stroke animals (43% reduction, ) could be detected. In part two, significant vasospasm was induced in all hemorrhage groups . Analyzing microperfusion, a significant higher amount of perfused vessels could be detected , whereas no significant effect could be detected towards macroperfusion. Histologically, no infarctions were observed in the VEGF-treated SAH group and the sham-operated group. Minor infarction in terms of vasospasm-induced small lesions could be detected in the control vector transduced group and saline-treated group . The present study demonstrates the preconditioning impact of systemic intramuscular VEGF injection in animals after major stroke and induced severe vasospasm after SAH. 1. Introduction Cerebral vasospasm and delayed cerebral ischemia contribute the major part of secondary morbidity and mortality after severe subarachnoid hemorrhage (SAH) [1–5]. Despite the current treatment strategies, the rate of related permanent disability is estimated at 10% to 20% [6–9]. Vascular endothelial growth factor (VEGF) is involved in neurogenesis, inhibition of apoptosis, learning, and memory [10]. It can directly promote neuroprotection, but first of all VEGF is the main factor responsible for angiogenesis whereby an indirect neuroprotection is discussed. VEGF expression is increased during cerebral ischemia in humans and animals [11]. However, endogenous VEGF seems to be insufficient to protect the brain from ischemic injury completely. Interestingly, it could be shown that exogenous administrated VEGF induces angiogenic changes that result in a reduction of cerebral ischemic injury [12, 13]. For this reason VEGF was adopted as a potential novel therapeutic approach for the treatment of ischemic vascular disease, particularly in ischemic stroke [14–18]. The aim of the present experimental study was to examine the effect of systemic overexpression of VEGF prior to stroke and SAH with regard to cerebral infarction, vasospasm, and perfusion. 2. Material and Methods This study was carried out in
Schweizer Erfahrungen mit Livial basierend auf einer randomisierten Vergleichsstudie versus konventioneller HRT
Hnggi W
Journal für Menopause , 1999,
Abstract: In unserer randomisierten Kontrollstudie, die mittlerweile auszugsweise in mehreren namhaften internationalen Zeitschriften publiziert wurde, konnten wir uns von der effektiven Wirksamkeit und guten Vertr glichkeit von Tibolon im Vergleich zu klassisch konventionellen HRT-Schemata überzeugen. Tibolon zeigt sowohl bezüglich klimakterischem Syndrom als auch in der Erhaltung der Knochenmineraldichte dieselbe Effektivit t wie transdermales oder perorales strogen in zyklisch-sequentieller Kombination. Die oft als nachteilig hervorgestrichene Tatsache des HDL-Abfalles wird durch die Senkung des Lp(a) und durch den fehlenden Anstieg der Triglyzeride weitgehend kompensiert. Interessant ist auch die Tatsache, da Tibolon denselben Effekt auf die periphere kapill re Durchblutung und auf die Serumendothelinspiegel wie strogen aufweist. Zudem wurde von anderen Autoren nachgewiesen, da Tibolon zumindest im Tiermodell eine protektive, nicht lipidabh ngige, pr ventive Wirkung auf die Atherosklerose aufweist. Als wesentlicher Pluspunkt und für die Langzeit-Compliance u erst wichtig darf die fehlende Stimulation von Tibolon auf das Endometrium und die damit verbundene Blutungsfreiheit hervorgestrichen werden.
Klinische kardiovaskul re Effekte der Hormonsubstitutionstherapie
Hnggi W
Journal für Menopause , 2000,
Abstract: W hrend des letzten Jahrzehnts hat eine grosse Zahl epidemiologischer Studien deutliche Hinweise darauf ergeben, dass die Hormonsubstitutionstherapie bei postmenopausalen Frauen eine Schutzwirkung für das Herz hat und das Risiko der KHK um bis zu 50 % senken kann. Der infolge des erh hten Endometriumkarzinomrisikos heute unabdingbare Gestagen-Zusatz bei nichthysterektomierten Frauen schm lert diese positive Oestrogenwirkung, abh ngig vom gew hlten Gestagen, nur geringgradig. Vor allem die "natürlichen2 Gestagene Progesteron und Dydrogesteron (ein Retro-Progesteron) sowie einige Abk mmlinge des 17alpha-Hydroxyprogesterons zeichnen sich durch ein praktisch inertes Stoffwechselverhalten bezüglich der kardiovaskul ren Risikofaktoren aus. Die Applikationsroute der Oestrogene ist im Normalfalle für die kardioprotektive Wirkung von geringer Bedeutung und richtet sich vorwiegend nach der subjektiven Wahl der Patientin. Mit zunehmendem Alter nehmen auch das kardiovaskul re Risiko und die Verschlechterung der strogenabh ngigen Risikofaktoren zu. Es ist deshalb naheliegend, den Oestrogenschutz auch lteren Frauen nicht vorzuenthalten. Durch die Verabreichung von geringeren Oestrogendosen k nnen die unangenehmen Nebenwirkungen bei ann hernd gleichbleibender Wirkung auf Kreislauf und Knochen wesentlich reduziert werden. In den vorliegenden Daten zum Mammakarzinomrisiko wie auch zu denjenigen des thromboembolischen Risikos wurde ebenfalls eine Dosisabh ngigkeit von Oestrogen nachgewiesen, was auch hier für eine Reduktion der bisher üblichen Oestrogendosis sprechen dürfte. Insbesondere die fixe, kontinuierliche Kombination wird infolge Wegfalls der Abbruchblutungen zu einer Erh hung der Langzeit-Compliance führen.
Neue Behandlungsstrategien bei zerebralem Vasospasmus nach aneurysmatischer Subarachnoidalblutung
Hnggi D
Journal für Neurologie, Neurochirurgie und Psychiatrie , 2012,
Abstract: Der zerebrale Vasospasmus und die verz gerte zerebrale Isch mie sind auch heutzutage unter modernster Therapie die hauptverantwortlichen Faktoren für das Auftreten einer sekund ren Morbidit t und Mortalit t nach aneurysmatischer Subarachnoidalblutung. Neben den erw hnten evidenzbasierten Therapiestrategien ist die Rate einer konsekutiven permanenten Behinderung unver ndert hoch und das Bemühen um alternative Behandlungsstrategien wichtig. Das vorliegende Manuskript fasst die publizierten Studien zu den neuen alternativen Behandlungsstrategien zusammen und versucht anhand der Resultate, einen wissenschaftlichen Ausblick zu schaffen.
Von der Kontrazeption bis zum Endometriumschutz in der Postmenopause: Stellenwert des levonorgestrelhaltigen Intrauterinsystem Mirena
Hnggi W
Journal für Menopause , 2000,
Abstract: Mirena ist ein levonorgestrel-freisetzendes, intrauterines System, das zur Kontrazeption entwickelt wurde. Bei geringen systemischen Nebeneffekten zeichnet sich Mirena durch eine usserst niedrige, mit der definitiven Sterilisation vergleichbaren Versagerquote aus. Es bestehen Hinweise, dass Mirena auch vor Extrauteringravidit ten schützt. Durch die lokale Wirkung des freigesetzten Levonorgestrels kommt es zu einer Hemmung des proliferativen Effektes der Oestrogene am Endometrium. Dies führt einerseits zu einer massiven Senkung des Blutverlustes bei funktionell verursachten Menorrhagien. Anderseits wird eine Endometriumprotektion im hyperoestrogenen perimenopausalen Zyklus wie auch unter Oestrogensubstitution gew hrleistet. Mirena erfüllt somit in nahezu idealer Weise die Anforderungen, die an eine Gestagentherapie in der Perimenopause gestellt werden.
Device-independent quantum key distribution
Esther Hnggi
Computer Science , 2010,
Abstract: In this thesis, we study two approaches to achieve device-independent quantum key distribution: in the first approach, the adversary can distribute any system to the honest parties that cannot be used to communicate between the three of them, i.e., it must be non-signalling. In the second approach, we limit the adversary to strategies which can be implemented using quantum physics. For both approaches, we show how device-independent quantum key distribution can be achieved when imposing an additional condition. In the non-signalling case this additional requirement is that communication is impossible between all pairwise subsystems of the honest parties, while, in the quantum case, we demand that measurements on different subsystems must commute. We give a generic security proof for device-independent quantum key distribution in these cases and apply it to an existing quantum key distribution protocol, thus proving its security even in this setting. We also show that, without any additional such restriction there always exists a successful joint attack by a non-signalling adversary.
Fluctuation, Dissipation and the Arrow of Time
Michele Campisi,Peter Hnggi
Entropy , 2011, DOI: 10.3390/e13122024
Abstract: The recent development of the theory of fluctuation relations has led to new insights into the ever-lasting question of how irreversible behavior emerges from time-reversal symmetric microscopic dynamics. We provide an introduction to fluctuation relations, examine their relation to dissipation and discuss their impact on the arrow of time question.
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