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Topic: K ion (physiology)

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	RU Newswire: Rockefeller University researchers decipher the shape of the sodium/potassium ion pump
		The sodium/potassium (Na/K) ion pump is one of the most prevalent: It occurs in every cell in the human body, and is a frequent target of heart-failure medications.
		Many of the residues in an ion pump have an electrical charge that works to either draw in or repel approaching ions, allowing only those with the correct charge to flow through to their destination.
		By altering the two residues it binds to and measuring the resulting change in the ion stream, the scientists were able to determine where those residues are located: in a wide opening near the mouth of the channel.
	newswire.rockefeller.edu /?page=engine&id=542 (609 words)

	LEARNING, MEMORY AND PLASTICITY
		(The calcium ion concentration in the extracellular space is over 10,000 times as great as it is in the presynaptic cytoplasm.) The calcium ions cause vesicles containing neurotransmitter to fuse with the presynaptic membrane and release neurotransmitter into the synaptic cleft.
		Indirectly-gated ion channels are not connected to receptors on the cell membrane, but are controlled through second messengers.
		The neurotransmitters GABA and glycine tend to have direct-gating receptors, whereas noradrenaline, dopamine and serotonin tend to have indirect-gating receptors.
	www.benbest.com /science/anatmind/anatmd3.html (5673 words)

	Published criticisms of AI Hypothesis and full rebuttals
		K+ mobility in healthy frog muscle cytoplasm is only 1/8 of that in free solution from 72 sets of experiments Ling and Ochsenfeld performed.
		Such variations are themselves at odds with the basic tenet of the membrane-pump theory, which requires all intracellular K+ activity measured in all living cells to be the same and equal to the K+ activity of that of a free water solution containing the same concentration of K+ as that in cells.
		Using Freedman's procedure rigorously, we were able to show that both the amount of K+ regained and Na+ extruded in the subsequent incubation of "resealed" ghosts in the presence of ATP quantitatively depends on the amount of residual proteins (mostly hemoglobin) in the ghosts in full agreement with the prediction of the association-induction hypothesis.
	www.gilbertling.org /lp7.htm (3079 words)

	Nutrition Courses, Diplomas, Training - registered clinicial nutritionists
		ION is a member of the Nutritional Therapy Council's (NTC) Schools Forum, has signed up to the NTC requirements and is now awaiting formal accreditation of the DipION from the NTC.
		The ION Science Access Courses are tailored specifically towards the NTDC, concentrating on those aspects of these subjects which are relevant to the course.
		This is an invaluable opportunity to explore your personal interests within the field of nutritional therapy and employ ION's and Luton's libraries and archives to research a particular area in which you may choose to specialise as a professional therapist.
	www.ion.ac.uk /ntdc.htm (2130 words)

	Plant Physiology Online: Potassium Channels
		The short selectivity filter is oriented in the outer portion of the 'teepee.' In a similar fashion with KcsA, the amide-carbonyl dipoles of the pore helices from AtCNGC2 are slanted in towards the pore axis from the outside orienting a partial negative charge inward towards the center of the pore.
		ion passes through the channel it is completely stripped of its hydration shell.
		Ketchum, K. A., and Slayman, C. (1996) Isolation of an ion channel gene from Arabidopsis thaliana using the H5 signature sequence from voltage-dependent K
	www.plantphys.net /article.php?ch=e&id=121 (2674 words)

	ion channels
		The cell membrane is permeable to a number of ions, the most important of which are Na, Ca and Cl These ions pass across the membrane through specific ion channels that can open (become activated) and close (become inactivated).
		For example, there are many different types of potassium channels that play an important role in resting membrane potential and in action potentials.
		It is the opening and closing of ion channels that alters specific ion conductances in a manner that determines resting potentials and generates action potentials.
	www.cvphysiology.com /Arrhythmias/A019.htm (364 words)

	Zhe Lu, MD, PhD
		Ion channels are a class of highly specialized membrane proteins that allow ions to flow across the cell membrane in a selective manner.
		Ionic currents through ion channels generate electrical voltage across the cell membrane which underlies the electrical impulses in neurons, muscle and hormone-secreting cells.
		With this combined approach of biophysics, biochemistry and molecular biology, we investigate both the molecular and the biophysical mechanisms underlying the various important biological functions of K+ channels, such as generating action potential, modulating the communications between neurons, controlling the rate of the cardiac pacemaker and coupling the blood glucose level to insulin secretion.
	www.med.upenn.edu /ins/faculty/lu.htm (603 words)

	Janos Lanyi
		Dr. Lanyi studies the physiology, biochemistry, and the molecular mechanisms of ion translocation across biological membranes.
		In bacteriorhodopsin, the reversible loss of a proton during the photocycle is thought to be the central event in the transport cycle.
		The kinetic and thermodynamic models for ion translocation, and the spectroscopic measurements, provide the framework for Dr. Lanyi's studies on the mechanistic aspects of transport in the two bacterial rhodopsins.
	www.ucihs.uci.edu /microbio/facultyResearch/faculty/lanyi.html (2333 words)

	GYGD pore motifs in neighbouring potassium channel subunits interact to determine ion selectivity -- Chapman et al. 530 ...
		Mutations of the GYGD motif in the rat drk1 (Kv2.1) K
		The ion selectivity and activation properties of the wild-type-wild-type dimer were indistinguishable from those of the wild-type subunit expressed as a homotetramer.
		ions are seen in the selectivity filter, which are co-ordinated by the backbone carbonyl oxygens of the amino acids V, G, Y and G. Functional channels are formed by assembly of four subunits.
	jp.physoc.org /cgi/content/full/530/1/21 (6827 words)

	Biophysical Journal: Noncontact dipole effects on channel permeation. VI. 5F- and 6F-Trp gramicidin channel currents (Site not responding. Last check: 2007-10-15)
		Ion transport in the gramicidin channel: free energy of the solvated right-handed dimer in a model membrane.
		Ion movements in gramicidin pores: an example of single-file transport.
		Ion binding constants for gramicidin A obtained from water permeability measurements.
	www.findarticles.com /p/articles/mi_qa3938/is_200210/ai_n9099564 (1053 words)

	Gerard Marriott, Department of Physiology, UW-Madison
		Optical switch conjugates of parvalbumin (PV) are being used as protein-based switches for calcium ions - PV binds very tightly to Ca (10 nM) and acts as a Ca buffer in cardiac muscle.
		The optical switch PV conjugate is designed to sequester Ca in the SP state but not the MC state; UV-pulsing of the SP-PV conjugate is being used to generate MC-PV, which release Ca while the high Ca affinity SP-PV conjugate is regenerated by irradiating MC-PV with green light, according to figure 1A.
		Miyata, H., Kinosita, K. and Marriott, G. Cooperative Association of Actin Monomers and Crosslinked Actin Oligomers in Filaments.
	www.physiology.wisc.edu /faculty/marriott.html (2260 words)

	Faculty::Physiology and Biophysics::WMC::Cornell University
		With this approach we can study the properties of individual ion channels-channel density, conductance, and open probability-in the living cell membrane.
		We are also using site-directed mutagenesis to investigate the parts of the proteins which determine channel conductivity, ion selectivity and gating.
		Our long-term goals are to understand at the molecular level how ions move across epithelial cell membranes, and how this movement is regulated to suit the needs of the organism.
	physiology.med.cornell.edu /faculty/palmer/palmer_research.html (322 words)

	Ion Channel Diseases
		Function: Forms ion pore; May be sufficient for funtional Na channel
		Physiology: Alteration in the whole-cell calcium current in Purkinje cells
		Brain CNG 1 and 2: Voltage gated K
	www.neuro.wustl.edu /neuromuscular/mother/chan.html (2213 words)

	K+ versus Na+ Ions in a K Channel Selectivity Filter: A Simulation Study -- Shrivastava et al. 83 (2): 633 -- ...
		A key property of all ion channels is their selective permeability; i.e., only certain species of ion may pass through a channel.
		ion, as is the case in the x-ray structure.
		The cavity and pore helices in the KcsA K
	www.biophysj.org /cgi/content/full/83/2/633 (7273 words)

	Ion permeation through the Na+,K+-ATPase : Abstract : Nature
		They provide a polar transmembrane pathway, to which access is strictly controlled by coupled gates that are constrained to open alternately, thereby enabling thermodynamically uphill ion transport (for example, see ref. 1).
		The distinct effects of differently charged reagents indicate that a wide outer vestibule penetrates deep into the Na -ATPase, where the pathway narrows and leads to a charge-selectivity filter.
		Acidic residues in this region, which are conserved to coordinate pumped ions, allow the approach of cations but exclude anions.
	www.nature.com /nature/journal/v443/n7110/abs/nature05129.html (337 words)

	Ion Channel--like Properties of the Na+/K+ Pump -- ARTIGAS and GADSBY 976 (1): 31 -- Annals of the New York Academy of ...
		Ion Channel--like Properties of the Na+/K+ Pump -- ARTIGAS and GADSBY 976 (1): 31 -- Annals of the New York Academy of Sciences
		Address for correspondence: David C. Gadsby, Laboratory of Cardiac/Membrane Physiology, The Rockefeller University, 1230 York Avenue, New York, NY 10021-6399.
		Ion pumps and exchangers are considered to be different from
	www.annalsnyas.org /cgi/content/abstract/976/1/31 (417 words)

	MCDB 3280 - Class Presentation Links
		The ion pair moves back and forth in a concerted manner between the 1,3 and 2,4 configurations [lower pathway] until a third ion enters on one side, causing the displacement of an ion on the opposite side [upper pathway].
		This keeps the K+ ion in a 'friendly' watery environment, even though it is actually in the 'middle' of the lipid membrane.
		Eight water molecules surround the K+ in the central cavity, as shown by this x-ray crystallographic density diagram, where red is water and green K+.
	mcdb.colorado.edu /courses/3280/lectures/class11.html (1663 words)

	The Ion Channel Web Ring
		The e.IP is an association of companies, research institutes and scientists with outstanding expertise in hard-, wet- and software development in modern electrophysiology.
		The basis of excitability is explored in terms of the operation of ion channels.
		Clinical and research efforts focused on disorders of ion channels and energy metabolism with an emphasis on childhood diseases
	s.webring.com /hub?ring=ionchannels (376 words)

	Lecture 5 (Site not responding. Last check: 2007-10-15)
		Each K+ ion carries away a unit of positive charge, and inside of cell thus becomes more negative, increasing probability that a K+ ion will reenter cell.
		Equilibrium established when ion moves across membrane and generates an electrical gradient strong enough to counter the diffusion gradient.
		Number of ions that must move is too small, in relative terms to significantly effect internal or external ion concentrations, only 1 in 860,000 ions must move out of cell
	soma.npa.uiuc.edu /courses/bio303/Ch4.html (1118 words)

	Faculty - Department of Physiology - The University of Texas Health Science Center at San Antonio (Site not responding. Last check: 2007-10-15)
		Current projects involve the roles of energy metabolism (especially carbohydrate metabolism) and voluntary exercise in aging and muscular dystrophy.
		These issues are studied in intact animals (rats, mice), isolated tissue (muscles of different anatomical locations) and cellular components (Na ion pumping, glucose transport and messenger RNA levels associated with these activities).
		Inhibitory effects of voluntary wheel exercise on apoptosis in splenic lymphocyte subsets of C57BL/6 mice.
	physiology.uthscsa.edu /Faculty/McCarter.html (381 words)

	MRC Group on Functional Regulation of Ion Channels and Transporters
		The native KATP channels is an octomeric complex of two types of subunits: inward rectifier K channel subunits that form the ion-conducting pore, and sulphonyl urea receptor subunits which modify functional and pharmacological properties of the channel.
		This device is being used to study the pattern(s) of normal depolarization and repolarization in mammalian hearts and to gain insights into the fundamental mechanisms of rhythm disturbances, as well as fibrillation and defibrillation.
		Calcium ion is an ubiquitous second messenger whose cytoplasmic concentration regulates a host of diverse biological events including muscle contraction, neurotransmitter secretion, hormone signaling, vesicle targeting and cell cycle control.
	www.ucalgary.ca /UofC/research/molbiol/pages/faculty.html (2177 words)

	Recent Publications (Site not responding. Last check: 2007-10-15)
		Bekar, L.K., Loewen, M.E., Cao, K., Sun, X., Leis, L., Wang, R., Forsyth, G.W. and Walz, W., (2005), "Complex expression and localization of inactivating Kv channels in cultured hippocampal astrocytes".
		Wang, K. and Walz, W., (2003), "Unusual topographical pattern of proximal astrogliosis around a cortical devascularizing lesion".
		Bekar, L.K. and Walz, W., (1999), "Evidence for chloride ions as intracellular messenger substances in astrocytes".
	duke.usask.ca /~walz/publications.htm (496 words)

	[No title]
		In this project, ion exchange activities assayed at the level of the intact tubule or in isolated plasma membrane vesicles are correlated with changes in abundance and/or post-translational processing of transporter proteins.
		We have established that active K absorption is the result of a K-H exchange energized by an apical membrane H,K-ATPase which is a member of a gene family of P-type ATPases.
		This structure is the basis for ongoing studies of the thermodynamics of RNA folding and the role of metal ions in RNA structure formation and catalysis.
	info.med.yale.edu /bbs/faculty/all.html (15597 words)

	Nelson Lecture 2 (Site not responding. Last check: 2007-10-15)
		Selectivity- most ion channels are selective for a particular ion, determined by size of central pore and electrical charges of chains of amino acids that dip into pore
		In every cycle three sodium ions (Na+) are moved out of cell, and two potassium (K+) ions are moved in, one ATP hydrolysed to ADP.
		Ion movements based on concentration and electrical gradients are passive, but require presence of ion channels.
	soma.npa.uiuc.edu /courses/physl341/Lec2_small.html (1534 words)

	APStracts 7:0476J, 2000. (Site not responding. Last check: 2007-10-15)
		A mathematical model is developed for simulation of action potential propagation through a single branch point of a myelinated nerve fiber with a parent branch bifurcating into two identical daughter branches.
		In this model, K ion concentration in the periaxonal space is dynamically linked to the activity of axonal fast K channels underneath the myelin in the paranodal region.
		Theoretical analysis showed that the cut- off frequency for transmission through the branch point is determined by temperature, local K ion accumulation, width of the periaxonal space, and internodal lengths at the vicinity of the branch point.
	www.uth.tmc.edu /apstracts/2000/jn/October/476j.html (299 words)

	Untitled
		Van Harreveld, A., T.M. Murphy and K. Nobel.
		A comparison of the effects of a fungal elicitor and ultraviolet radiation on ion transport and hydrogen peroxide synthesis by rose cells.
		Okubara, P.A., K. Pawlowski, T.M. Murphy and A.M. Berry.
	www-plb.ucdavis.edu /Labs/murphy/pubs.htm (2344 words)

	Physiology Online - Proceedings (Site not responding. Last check: 2007-10-15)
		Applied Physiology Research Group, School of Sport and Exercise Sciences, University of Birmingham B15 2TT, *Department of Clinical Neurophysiology, New Cross Hospital, Wolverhampton WV10 0QP and †Department of Clinical Pharmacology, Queen Elizabeth Hospital, Birmingham B15 2TH, UK Search Medline for articles by:
		The subject relaxed for a period of 45 minutes during which three control measurements of tremor were made and venous blood samples were taken.
		In these experiments there were a number of infusions of different drugs and placebos with each subject being infused on 5 occasions.
	www.physoc.org /publications/proceedings/archive/article.asp?ID=555PR1 (492 words)

	Houston CC: Anatomy & Physiology \| Chapter Quiz
		Na+ ions move with the concentration gradient to the outside of the cell.
		When the plasma membrane is at rest, activation gates of the voltage-gated Na+ ion channels are __________ and inactivation gates are __________.
		The absolute refractory period ends when the activation gates of voltage-gated Na+ ion channels are __________, and inactivation gates of voltage-gated Na+ ion channels are __________.
	highered.mcgraw-hill.com /sites/bb72351136/student_view0/chapter11/chapter_quiz.html (709 words)

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