scholarly journals Hyperpolarization-Activated Current, , in Mathematical Models of Rabbit Sinoatrial Node Pacemaker Cells

2013 ◽  
Vol 2013 ◽  
pp. 1-18 ◽  
Author(s):  
Arie O. Verkerk ◽  
Ronald Wilders
Keyword(s):  
Experimental Data ◽  
Computer Simulations ◽  
Rate Control ◽  
Ionic Current ◽  
Typical Feature ◽  
Pacemaker Activity ◽  
Pacemaker Cells ◽  
Personal View ◽  
Hyperpolarization Activated Current

A typical feature of sinoatrial (SA) node pacemaker cells is the presence of an ionic current that activates upon hyperpolarization. The role of this hyperpolarization-activated current, , which is also known as the “funny current” or “pacemaker current,” in the spontaneous pacemaker activity of SA nodal cells remains a matter of intense debate. Whereas some conclude that plays a fundamental role in the generation of pacemaker activity and its rate control, others conclude that the role of is limited to a modest contribution to rate control. The ongoing debate is often accompanied with arguments from computer simulations, either to support one's personal view or to invalidate that of the antagonist. In the present paper, we review the various mathematical descriptions of that have been used in computer simulations and compare their strikingly different characteristics with our experimental data. We identify caveats and propose a novel model for based on our experimental data.

scholarly journals Role of IP3 in modulation of spontaneous activity in pacemaker cells of rabbit urethra

2001 ◽  
Vol 280 (5) ◽  
pp. C1349-C1356 ◽  
Author(s):  
G. P. Sergeant ◽  
M. A. Hollywood ◽  
K. D. McCloskey ◽  
N. G. McHale ◽  
K. D. Thornbury
Keyword(s):  
Cyclopiazonic Acid ◽  
Pacemaker Activity ◽  
Pacemaker Cells ◽  
Outward Currents ◽  
Inositol 1,4,5 Trisphosphate ◽  
Inward Currents ◽  
Rabbit Urethra ◽  
Patch Technique ◽  
Spontaneous Transient Outward Currents

Isolated interstitial (“pacemaker”) cells from rabbit urethra were examined using the perforated-patch technique. Under voltage clamp at −60 mV, these cells fired large spontaneous transient inward currents (STICs), averaging −860 pA and >1 s in duration, which could account for urethral pacemaker activity. Spontaneous transient outward currents (STOCs) were also observed and fell into two categories, “fast” (<100 ms in duration) and “slow” (>1 s in duration). The latter were coupled to STICs, suggesting that they shared the same mechanism, while the former occurred independently at faster rates. All of these currents were abolished by cyclopiazonic acid, caffeine, or ryanodine, suggesting that they were activated by Ca2+ release. Whend- myo-inositol 1,4,5-trisphosphate (IP3)-sensitive stores were blocked with 2-aminoethoxydiphenyl borate, the STICs and slow STOCs were abolished, but the fast STOCs remained. In contrast, the fast STOCs were more nifedipine sensitive than the STICs or the slow STOCs. These results suggest that while fast STOCs are mediated by a mechanism similar to STOCs in smooth muscle, STICs and slow STOCs are driven by IP3. These results support the hypothesis that pacemaker activity in the urethra is driven by the IP3-sensitive store.

Conduction and Disorder in Y3NbO7 - Zr2Y2O7

2008 ◽  
Vol 1126 ◽  
Author(s):  
Dario Marrocchelli ◽  
Paul A. Madden ◽  
Stefan T. Norberg ◽  
Stephen Hull
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Detailed Analysis ◽  
Computer Simulations ◽  
Cation Sublattice ◽  
Static Disorder ◽  
Interaction Potentials ◽  
Experimental Trend

AbstractThe construction of interaction potentials for the Y0.5+0.25xNb0.25xZr0.5–0.5xO1.75 system, on a purely ab-initio basis, is described. These potentials accurately reproduce experimental data on both the structure and the dynamics of these systems; the computer simulations also reproduce the experimental trend of the conductivity, which decreases as x increases, and of the level of static disorder within the O2− sublattice, which increases with x. A detailed analysis of these phenomena shows that the static disorder in Y3NbO7 is caused by the high Nb5+ charge and that in this material the conduction is heterogeneous, i.e. some anions are completely immobile while some others are very mobile. The role of the cation sublattice is explained in detail.

Gut peristalsis is governed by a multitude of cooperating mechanisms

2009 ◽  
Vol 296 (1) ◽  
pp. G1-G8 ◽  
Author(s):  
Jan D. Huizinga ◽  
Wim J. E. P. Lammers
Keyword(s):  
Control Systems ◽  
Contractile Activity ◽  
Design Experiment ◽  
Pacemaker Activity ◽  
Control Mechanisms ◽  
Pacemaker Cells ◽  
Multiple Control ◽  
Control Activity ◽  
Cells Of Cajal

Peristaltic motor activity of the gut is an essential activity to sustain life. In each gut organ, a multitude of overlapping mechanisms has developed to acquire the ability of coordinated contractile activity under a variety of circumstances and in response to a variety of stimuli. The presence of several simultaneously operating control systems is a challenge for investigators who focus on the role of one particular control activity since it is often not possible to decipher which control systems are operating or dominant in a particular situation. A crucial advantage of multiple control systems is that gut motility control can withstand injury to one or more of its components. Our efforts to increase understanding of control mechanism are not helped by recent attempts to eliminate proven control systems such as interstitial cells of Cajal (ICC) as pacemaker cells, or intrinsic sensory neurons, nor does it help to view peristalsis as a simple reflex. This review focuses on the role of ICC as slow-wave pacemaker cells and places ICC into the context of other control mechanisms, including control systems intrinsic to smooth muscle cells. It also addresses some areas of controversy related to the origin and propagation of pacemaker activity. The urge to simplify may have its roots in the wish to see the gut as a consequence of a single perfect design experiment whereas in reality the control mechanisms of the gut are the messy result of adaptive changes over millions of years that have created complementary and overlapping control systems. All these systems together reliably perform the task of moving and mixing gut content to provide us with essential nutrients.

РОЛЬ ФИЗИЧЕСКОЙ РАЗМИНКИ В ПОДГОТОВКЕ К ТРЕНИРОВОЧНЫМ ЗАНЯТИЯМ И СОРЕВНОВАНИЯМ ШАХМАТИСТОВ БГУ

2019 ◽  
pp. 63-65
Author(s):  
Судоргин Е.П. ◽  
Карсакова И.Н.
Keyword(s):  
Experimental Data ◽  
Sport Performance ◽  
Warm Up ◽  
Physical Exercises ◽  
Methods Of Evaluation ◽  
Mental Fitness ◽  
Physical Preparation ◽  
Tools And Methods

Аннотация: О роли разминки перед тренировкой и соревнованиями написано много научных статьей и диссертаций. Ещё больше о значимости физической подготовки спортсменов, в том числе и шахматистов. В то же время авторы считают, что вопросу физической подготовки шахматистов и в частности разминке в научной и научно-методической литературе уделяется недостаточно внимания. В своей статье авторы приводят собственные экспериментальные данные о влиянии физических упражнений (разминки) на умственную работоспособность студентов-шахматистов БГУ и как следствие на спортивные результаты команды. Ключевые слова: Шахматы, разминка, умственная работоспособность, средства и методы разминки, методы оценки результатов. Аннотация: Машыгуунун жана мелдештердин алдында даярдоонун ролу жөнүндө көптөгөн илимий макала жана диссертация жазылган. Ошондой эле илимий жана илимий-методикалык адабияттарда шахматка даярдоого көп көңүл бурулбай жатат. Макаланын авторлору шахмат ойногон студенттерге физикалык көнүгүүлөрдүн тийгизген таасири жөнүндө өздөрүнүн эксперименталдык маалыматтарын көргөзүштү. Түйүндүү сөздөр: Шахмат, акыл-дарамет, курулуштар жана ыкмалар, баа берүү жыйынтыгы боюнча кабыл алынат. Abstract: on the role of warm-up before training and competitions written many scientific articles and theses. More about the significance of the physical preparation of athletes, including players. At the same time, the authors believe that the issue of fit- ness players and in particular workout in scientific and scientific-methodical literature neglected. In his article the authors cite their own experimental data on the influence of physical exercises (warm-up) on the mental fitness of students-BSU players and as a result the sport performance team. Keywords: chess, warm-up, mental fitness, workout tools and methods, methods of evaluation results.

scholarly journals Interpreting Locked Photographic Data: The Case of Apollo 17 Photo GPN-2000-00113

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 8
Author(s):  
Pyrrhon Amathes ◽  
Paul Christodoulides
Keyword(s):  
Experimental Data ◽  
Computer Simulations ◽  
The Moon ◽  
Geometrical Analysis ◽  
Apparent Position ◽  
Apollo Program ◽  
The Earth ◽  
Novel Approach ◽  
The World ◽  
The Moment

Photography can be used for pleasure and art but can also be used in many disciplines of science, because it captures the details of the moment and can serve as a proving tool due to the information it preserves. During the period of the Apollo program (1969 to 1972), the National Aeronautics and Space Administration (NASA) successfully landed humans on the Moon and showed hundreds of photos to the world presenting the travel and landings. This paper uses computer simulations and geometry to examine the authenticity of one such photo, namely Apollo 17 photo GPN-2000-00113. In addition, a novel approach is employed by creating an experimental scene to illustrate details and provide measurements. The crucial factors on which the geometrical analysis relies are locked in the photograph and are: (a) the apparent position of the Earth relative to the illustrated flag and (b) the point to which the shadow of the astronaut taking the photo reaches, in relation to the flagpole. The analysis and experimental data show geometrical and time mismatches, proving that the photo is a composite.

scholarly journals Oxidation of Terpenoids to Achieve High-Value Flavor and Fragrances—Questioning Microalgae Oxidative Capabilities in the Biotransformation of the Sesquiterpene Valencene and of Selected Natural Apocarotenoids

Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 821-830
Author(s):  
Davide De Simeis ◽  
Stefano Serra ◽  
Alessandro Di Fonzo ◽  
Francesco Secundo
Keyword(s):  
Experimental Data ◽  
Natural Products ◽  
Aqueous Medium ◽  
Photochemical Reaction ◽  
Substrate Oxidation ◽  
Market Size ◽  
Chlorella Sp ◽  
General Opinion ◽  
Natural Way

Natural flavor and fragrance market size is expected to grow steadily due to the rising consumer demand of natural ingredients. This market request is guided by the general opinion that the production of natural compounds leads to a reduction of pollution, with inherent advantages for the environment and people’s health. The biotransformation reactions have gained high relevance in the production of natural products. In this context, few pieces of research have described the role of microalgae in the oxidation of terpenoids. In this present study, we questioned the role of microalgal based oxidation in the synthesis of high-value flavors and fragrances. This study investigated the role of three different microalgae strains, Chlorella sp. (211.8b and 211.8p) and Chlorococcum sp. (JB3), in the oxidation of different terpenoid substrates: α-ionone, β-ionone, theaspirane and valencene. Unfortunately, the experimental data showed that the microalgal strains used are not responsible for the substrate oxidation. In fact, our experiments demonstrate that the transformation of the four starting compounds is a photochemical reaction that involves the oxygen as oxidant. Even though these findings cast a shadow on the use of these microorganisms for an industrial purpose, they open a new possible strategy to easily obtain nootkatone in a natural way by just using an aqueous medium, oxygen and light.

scholarly journals PROGNOSTIC ROLE OF ATRIAL FIBRILLATION AND HEART RATE CONTROL IN CHRONIC HEART FAILURE PATIENTS

2013 ◽  
Vol 61 (10) ◽  
pp. E735
Author(s):  
Savina Nodari ◽  
Marco Triggiani ◽  
Laura Lupi ◽  
Alessandra Manerba ◽  
Giuseppe Milesi ◽  
...  
Keyword(s):  
Heart Failure ◽  
Atrial Fibrillation ◽  
Heart Rate ◽  
Chronic Heart Failure ◽  
Rate Control ◽  
Heart Rate Control ◽  
Prognostic Role ◽  
Heart Failure Patients

scholarly journals Elucidating the Complex Interactions between Stress and Epileptogenic Pathways

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Aaron R. Friedman ◽  
Luisa P. Cacheaux ◽  
Sebastian Ivens ◽  
Daniela Kaufer
Keyword(s):  
Experimental Data ◽  
Blood Brain Barrier ◽  
Inflammatory Cytokine ◽  
Stress Hormones ◽  
Brain Barrier ◽  
Barrier Dysfunction ◽  
Complex Interactions ◽  
Narrow Focus ◽  
Analytical Tools

Clinical and experimental data suggest that stress contributes to the pathology of epilepsy. We review mechanisms by which stress, primarily via stress hormones, may exacerbate epilepsy, focusing on the intersection between stress-induced pathways and the progression of pathological events that occur before, during, and after the onset of epileptogenesis. In addition to this temporal nuance, we discuss other complexities in stress-epilepsy interactions, including the role of blood-brain barrier dysfunction, neuron-glia interactions, and inflammatory/cytokine pathways that may be protective or damaging depending on context. We advocate the use of global analytical tools, such as microarray, in support of a shift away from a narrow focus on seizures and towards profiling the complex, early process of epileptogenesis, in which multiple pathways may interact to dictate the ultimate onset of chronic, recurring seizures.

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