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Role of calcium and other trace elements in the gastrointestinal physiology

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World Journal of Gastroenterology 2006年第20期12卷 3229-3236页

作者： p Kirchhoff Jp geibel Department of Surgery Yale University School of Medicine 333 Cedar StreetNew HavenCT 06520United States

Calcium is an essential ion in both marine and terrestrial organisms, where it plays a crucial role in processes ranging from the formation and maintenance of the skeleton to the regulation of neuronal function. The Ca^2＋ balance is maintained by three organ systems, including the gastrointestinal tract, bone and kidney. Since first being cloned in 1993 the Ca^2＋-sensing receptor has been expressed along the entire gastrointestinal tract, until now the exact function is only partly elucidated. As of this date it still remains to be determined if the Ca^2＋-sensing receptor is involved in calcium handling by the gastrointestinal tract. However, there are few studies showing physiological effects of the Ca^2＋-sensing receptor on gastric acid secretion and fluid transport in the colon. In addition, polyamines and amino acids have been shown to activate the Ca^2＋-sensing receptor and also act as allosteric modifiers to signal nutrient availability to intestinal epithelial cells. Activation of the colonic Ca^2＋-sensing receptor can abrogate cyclic nucleotide-mediated fluid secretion suggesting a role of the receptor in modifying secretory diarrheas like cholera. For many cell types changes in extracellular Ca^2＋ concentration can switch the cellular behavior from proliferation to terminal differentiation or quiescence. As cancer remains predominantly a disease of disordered balance between proliferation, termination and apoptosis, disruption in the function of the Ca^2＋-sensing receptor may contribute to the progression of neoplastic disease. Loss of the growth suppressing effects of elevated extracellular Ca^2＋ have been demonstrated in colon carcinoma, and have been correlated with changes in the level of CaSR expression.

关键词： Calcium Trace elements Gastrointestinal physiology

Targeting TrkB–pSD-95 coupling to mitigate neurological disorders

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Neural Regeneration Research 2025年第3期20卷 715-724页

作者： Xin Yang Yu-Wen Alvin Huang john Marshall Department of Molecular Biology Cell Biology and BiochemistryBrown UniversityProvidenceRIUSA Department of Neurology Warren Alpert Medical School of Brown UniversityProvidenceRIUSA Center for Translational Neuroscience Robert J.and Nancy D.Carney Institute for Brain Science and Brown Institute for Translational ScienceBrown UniversityProvidenceRIUSA

Tropomyosin receptor kinase B(TrkB)signaling plays a pivotal role in dendritic growth and dendritic spine formation to promote learning and *** activity-dependent release of brain-derived neurotrophic factor at synapses binds to pre-or postsynaptic TrkB resulting in the strengthening of synapses,reflected by long-term ***,the association of postsynaptic density protein-95 with TrkB enhances phospholipase Cγ-Ca^(2+)/calmodulin-dependent protein kinaseⅡand phosphatidylinositol 3-kinase-mechanistic target of rapamycin signaling required for long-term *** this review,we discuss TrkB-postsynaptic density protein-95 coupling as a promising strategy to magnify brain-derived neurotrophic factor signaling towards the development of novel therapeutics for specific neurological disorders.A reduction of TrkB signaling has been observed in neurodegenerative disorders,such as Alzheimer's disease and Huntington's disease,and enhancement of postsynaptic density protein-95 association with TrkB signaling could mitigate the observed deficiency of neuronal connectivity in schizophrenia and *** with brain-derived neurotrophic factor is problematic,due to poor pharmacokinetics,low brain penetration,and side effects resulting from activation of the p75 neurotrophin receptor or the truncated TrkB.T1 *** TrkB agonists and antibodies that activate TrkB are being intensively investigated,they cannot distinguish the multiple human TrkB splicing isoforms or cell type-specific *** TrkB–postsynaptic density protein-95 coupling provides an alternative approach to specifically boost TrkB signaling at localized synaptic sites versus global stimulation that risks many adverse side effects.

关键词： Angelman syndrome autism brain-derived neurotrophic factor depression neurodegenerative disorder neurodevelopmental disorder postsynaptic density protein-95 synaptic plasticity TrkB

Surgical perspectives in gastrointestinal disease: From the editor

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World Journal of Gastroenterology 2006年第20期12卷 3138-3138页

作者： john geibel Walter Longo

In the following 20 articles we have attempted to give an update and overview of different aspects of gastrointestinal disease that are treated via a surgical intervention. In addition we have included topics related to advances and innovations in surgical instrumentation and training that are useful in treating gastrointestinal disease. Additional topics covered deal with the ethics of abdominal organ transplantation, inflammatory bowel disease in adolescents and children, and discussions of the quality of life following gastrointestinal cancer. We have also included a discussion of recent discoveries involving the calcium sensing receptor and how this receptor may be employed as both

关键词：手术治疗透视技术胃肠疾病病理机制

The theory of interaction between wave and basic flow

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Chinese physics B 2008年第3期17卷 1138-1146页

作者：冉令坤 john p.Boyd Laboratory of Cloud-precipitation physics and Severe Storms (LACS) Institute of Atmospheric PhysicsChinese Academy of Sciences Department of Atmospheric Oceanicand Space ScienceUniversity of MichiganAnn ArborMichiganUSA

This paper investigates the interaction between transient wave and non-stationary and non-conservative basic flow. An interaction equation is derived from the zonally symmetric and non-hydrostatic primitive equations in Cartesian coordinates by using the Momentum-Casimir method. In the derivation, it is assumed that the transient disturbances satisfy the linear perturbation equations and the basic states are non-conservative and slowly vary in time and space. The diabatic heating composed of basic-state heating and perturbation heating is also introduced. Since the theory of wave-flow interaction is constructed in non-hydrostatic and ageostrophic dynamical framework, it is applicable to diagnosing the interaction between the meso-scale convective system in front and the background flow. It follows from the local interaction equation that the local tendency of pseudomomentum wave-activity density depends on the combination of the perturbation flux divergence second-order in disturbance amplitude, the local change of basic-state pseudomomentum density, the basic-state flux divergence and the forcing effect of diabatic heating. Furthermore, the tendency of pseudomomentum wave-activity density is opposite to that of basic-state pseudomomentum density. The globally integrated basic-state pseudomomentum equation and wave-activity equation reveal that the global development of basic-state pseudomomentum is only dominated by the basic-state diabatic heating while it is the forcing effect of total diabatic heating from which the global evolution of pseudomomentum wave activity results. Therefore, the interaction between the transient wave and the non-stationary and non-conservative basic flow is realized in virtue of the basic-state diabatic heating.

关键词： wave flow interaction pseudomomentum wave activity diabatic heating Momentum Casimir method

Energy Gap Dependence on Mn Content in a Diluted Magnetic Quantum Dot

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Chinese physics Letters 2011年第4期28卷 201-204页

作者： p.Nalini A.john peter Department of physics Yadava College Govindarajan CampusThiruppalaiMadurai-625014India Department of physics Govt.Arts and Science CollegeMelur-625106MaduraiIndia

positively charged donor exciton binding energy is computed as a function of quantum-dot size within the single band effective mass approximation for different Mn contents in Cd_(1)−x_(𝑥in)Mn_(x𝑥in)Te/Cd_(1−xout)𝑥outMn_(xout)𝑥*** exciton bound polaron is computed for 0≤x𝑥≤0.08,on the Mn mole *** determine the energy gap using the mean field approximation and incorporate the exchange interaction between the carrier and the magnetic *** interband emission energy is studied with the height and radius of the cylindrical quantum ***-band anisotropy is included in our theoretical model using different hole masses in different spatial *** polaronic shifts as functions of quantum-dot radius and Mn concentration are estimated using the mean field *** is found that(i)the energy gap depends on the Mn mole fraction,(ii)it increases linearly with an increase in Mn content,and(iii)the effect is more pronounced for a narrow dot,showing the quantum size *** results are in good agreement with other recently published reports.

关键词： theory quantum radius

A Method of Characterizing Radio Signal Space for Wireless Device Localization

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Tsinghua Science and Technology 2015年第4期20卷 385-408页

作者： john-Austen Francisco Richard p.Martin Department of Computer Science Rutgers University

In this work we present a novel approach for describing radio signal spaces for localization algorithms. We first introduce a new metric, the Discretely Distributed Log-H61der Metric （DDLHM）. The DDLHM is designed to characterize the type and degree of signal distortion relative to Iognormal signal-to-distance path models. We first show how the DDLHM can describe and discriminate distortions in an exhaustive set of synthetic signal spaces. We then determine a reduced set of maximally diagnostic distortion parameters. Using only 4% of the maximal set of DDLHMs, we found the reduced set matches with an acceptable degree of error 95% of the time. Using the synthetic reduced set, we characterized a variety of wireless localization algorithms＇ behaviors to attenuation, bias, and multipath. We found algorithms made much different tradeoffs between best case and average case error. We then use the DDLHM to identify distortion types in three different physical environments using measured 802.11 signal strengths, and predict the positioning performance of several localization algorithms. Our approach predicts average localization error to within 2 meters of the observed average error.

关键词： radio propgation 802.11 WiFi

Chebyshev Spectral Methods and the Lane-Emden problem

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Numerical Mathematics(Theory,Methods and Applications) 2011年第2期4卷 142-157页

作者： john p.Boyd Department of Atmospheric Oceanic and Space ScienceUniversity of Michigan2455 Hayward AvenueAnn ArborMI 48109-2143USA

The three-dimensional spherical polytropic Lane-Emden problem is yr r+(2/r)y_(r)+y^(m)=0,y(0)=1,y_(r)(0)=0 where m∈[0,5]is a constant *** domain is r∈[0,ξ]whereξis the first root of y(r).We recast this as a nonlinear eigenproblem,with three boundary conditions andξas the eigenvalue allowing imposition of the extra boundary condition,by making the change of coordinate x≡r/ξ:y_(xx)+(2/x)y_(x)+ξ^(2) y^(m)=0,y(0)=1,y_(x)(0)=0,y(1)=*** find that a Newton-Kantorovich iteration always converges from an m-independent starting point y^((0))(x)=cos([π/2]x),ξ^((0))=*** apply a Chebyshev pseudospectral method to discretize *** Lane-Emden equation has branch point singularities at the endpoint x=1 whenever m is not an integer;we show that the Chebyshev coefficients are a_(n)∼constant/n^(2m+5) as n→∞.However,a Chebyshev truncation of N=100 always gives at least ten decimal places of accuracy—much more accuracy when m is an *** numerical algorithm is so simple that the complete code(in Maple)is given as a one page table.

关键词： Lane-Emden Chebyshev polynomial pseudospectral

A Fourier Companion Matrix (Multiplication Matrix) with Real-Valued Elements: Finding the Roots of a Trigonometric polynomial by Matrix Eigensolving

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Numerical Mathematics(Theory,Methods and Applications) 2013年第4期6卷 586-599页

作者： john p.Boyd Department of Atmospheric Oceanic&Space ScienceUniversity of Michigan2455 Hayward AvenueAnn Arbor MI 48109USA

We show that the zeros of a trigonometric polynomial of degree N with the usual(2N+1)terms can be calculated by computing the eigenvalues of a matrix of dimension 2N with real-valued elements M_(jk).This matrix M is a multiplication matrix in the sense that,after first defining a vector φwhose elements are the first 2N basis functions,Mφ=2cos(t)φ.This relationship is the eigenproblem;the zeros tk are the arccosine function of λ_(k)/2 where theλk are the eigenvalues of *** dub this the“Fourier Division Companion Matrix”,or FDCM for short,because it is derived using trigonometric polynomial *** show through examples that the algorithm computes both real and complex-valued roots,even double roots,to near machine precision accuracy.

关键词： Fourier series trigonometric polynomial rootfinding secular companion matrix

Hepatic tight junctions:From viral entry to cancer metastasis

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World Journal of Gastroenterology 2010年第3期16卷 289-295页

作者： Nikki p Lee john M Luk Department of Surgery Queen Mary Hospital Department of pharmacology and Department of Surgery National University Health SystemNational University of Singapore

The tight junction (TJ) is a critical cellular component for maintenance of tissue integrity, cellular interactions and cell-cell communications, and physiologically functions as the "great wall" against external agents and the surrounding hostile environment. During the host-pathogen evolution, viruses somehow found the key to unlock the gate for their entry into cells and to exploit and exhaust the host cells. In the liver, an array of TJ molecules is localized along the bile canaliculi forming the blood-biliary barrier, where they play pivotal roles in paracellular permeability, bile secretion, and cell polarity. In pathology, certain hepatic TJ molecules mediate virus entry causing hepatitis infection; deregulation and functional abnormality of the TJ have also been implicated in triggering liver cancer development and metastasis. All these findings shed new insights on the understanding of hepatic TJs in the development of liver disease and provide new clues for potential intervention.

关键词： Tight junctions Hepatocytes Blood-biliary barrier Bile canaliculi Hepatitis Liver steatosis Liver neoplasms