1992 — 1994 |
Mckinnon, David |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Autonomic Neurons and Cardiac Muscle @ State University New York Stony Brook
It is proposed to study the regulation of potassium channel gene expression in two cell types that contribute to cardiovascular function, sympathetic postganglionic neurons and cardiac myocytes. In the peripheral sympathetic nervous system, neurons in paravertebral ganglia have different firing properties compared with those in prevertebral ganglia and this is due in large part to differential expression of voltage-activated potassium channels. Specific Aims 1 and 3 are directed toward comparing the expression of potassium channel genes in sympathetic neurons in these two classes of ganglia to find which genes are differentially expressed and could therefore contribute to the differentiation of the electrophysiological phenotype. Specific Aims 2 and 3 will compare potassium channel expression in atrial and ventricular muscle. It is well established that the shape and duration of action potentials are markedly different in atrial and ventricular muscle cells, and much of this differentiation appears to be due to differential expression of voltage-gated potassium channels. We will determine which potassium channel genes are differentially expressed in atrial and ventricular muscle. These studies will provide a molecular framework for understanding how potassium channels contribute to the electrophysiological differentiation of adult tissues and could help develop strategies for finding new potassium channel antagonists with potential therapeutic value as class III anti-arrhythmics.
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1 |
1997 — 2000 |
Mckinnon, David |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Molecular Physiology--Cardiac Muscle @ State University New York Stony Brook
DESCRIPTION: The applicant has identified a new potassium channel gene (Kv4.3) that is expressed at high levels in canine and human ventricle. Based on mRNA expression studies and analysis of the functional properties of the transient outward current (Ito) in ventricular myocytes he has suggested that the Kv4.3 channel is the major channel underlying the Ito in canine and human myocytes. This channel is an important determinant of regional differences in the duration and shape of the cardiac action potential, which contribute to such fundamental phenomena as the configuration of the ST segment and the T wave in the electrocardiogram. It is also likely to be of considerable importance for understanding the actions and interactions of antiarrhythmic drugs. The applicant will intensively study the function and distribution of this channel in canine heart. He also will study the distribution of other potassium channel genes in canine heart with a view to gaining insight into which potassium channel genes contribute to the regional differentiation of the cardiac action potential. The specific aims are: 1) Compare the biophysical and pharmacological properties of the Kv4.3 channel with the native transient outward current (Ito) in canine heart to test the hypothesis that the Kv4.3 alpha subunit can, by itself, reproduce the function of the native current. 2) Examine the distribution of Kv4.3 channel protein expression in canine heart. 3) Examine potassium channel gene expression in different specialized regions of canine heart to determine the molecular basis for different action potential waveforms in these tissues.
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1 |
1998 — 2003 |
Mckinnon, David |
P01Activity Code Description: For the support of a broadly based, multidisciplinary, often long-term research program which has a specific major objective or a basic theme. A program project generally involves the organized efforts of relatively large groups, members of which are conducting research projects designed to elucidate the various aspects or components of this objective. Each research project is usually under the leadership of an established investigator. The grant can provide support for certain basic resources used by these groups in the program, including clinical components, the sharing of which facilitates the total research effort. A program project is directed toward a range of problems having a central research focus, in contrast to the usually narrower thrust of the traditional research project. Each project supported through this mechanism should contribute or be directly related to the common theme of the total research effort. These scientifically meritorious projects should demonstrate an essential element of unity and interdependence, i.e., a system of research activities and projects directed toward a well-defined research program goal. |
Molecular Physiology of Alpha1 Receptors and Potassium Channels @ Columbia University Health Sciences
Stimulation of alpha/1-adrenergic receptors increases the action potential duration and the force of contraction in cardiac myocytes via several modifications of cellular function. One important mechanism is the inhibition of potassium channels. Although the electrophysiological description of alpha-1-adrenergic inhibition of potassium channels was reported over a decade ago, further progress in understanding this system has lagged in comparison to our understanding of other neuromodulatory systems. In large part this limited progress has been due to the lack of suitable model systems in which a range of technical approaches can be combined to direct address this problem. We propose to study alpha/1-adrenergic modulation of two potassium channels that are expressed in cardiac myocytes: the inward rectifier channel (I/k1) and the transient outward channel (I/to). We will use two cell systems in which to analyze the mechanisms of inhibition: a heterologous expression system and a transfected cultured myocytes system. Most importantly, hypotheses concerning the nature of alpha/1-adrenergic modulation of potassium channels expressed in these cells will be studied using a combination of molecular, electrophysiological and protein chemistry approaches. It is currently uncertain how the alpha/1-adrenergic pathway modulates key effector molecules such as potassium channels in cardiac myocytes. This pathway in important in determining alpha-adrenergic effects on repolarization (affect heterogeneity of action potential duration and susceptibility to arrhythmias) and impulse initiation (important concerning arrhythmogenesis). Determination of the molecular mechanisms involved is essential to developing an understanding for how the sympathetic nervous system and its neurotransmitters can act to trigger cardiac arrhythmias.
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0.943 |
2000 |
Mckinnon, David |
S10Activity Code Description: To make available to institutions with a high concentration of NIH extramural research awards, research instruments which will be used on a shared basis. |
Acquisition of An Abi 377 Automatic Dna Sequence @ State University New York Stony Brook
This proposal requests funds for the purchase of a Perkin Elmer ABI DNA Sequencer 377 with upgrade to 96 lanes. The requested instrument package includes the automatic sequencing apparatus including gel electrophoresis unit, laser and fluorescence detection system as well as a computer (Macintosh) and sequence detection and analysis software. This system provides all the functionality required for the analysis of fluorescently labeled DNA sequences prepared by polymerase chain reaction (PCR). The instrument will be located in the State University of New York at Stony Brook (SUNY SB) DNA Sequencing Facility which is housed in the Department of Physiology and Biophysics. The sequencer will significantly promote the research objectives and laboratory productivity of fourteen distinguished scientists at SUNY SB who comprise the major users group. The sequencer will make available to these investigators the technology required for the rapid analysis of DNA sequences which is presently inadequately supported at SUNY SB and difficult to obtain from other organizations in the local area. Automatic DNA sequencing technology is far superior to manual sequencing, which most investigators have to rely upon in part or full, due to greatly increased throughput, read-length, accuracy, ease of use and the elimination of the requirement for radionucleotides. The automatic sequencer will not only facilitate currently active projects but will also open up new possibilities for investigators allowing them to tackle much larger sequencing projects than is currently feasible. The instrument will be operated and maintained by trained personnel at the SUNY SB DNA Sequencing Facility. The director of the facility will schedule daily operation and provide technical expertise for the users. An advisory committee will ensure access to the major users and other PHS- supported investigators and will be responsible for the long term operation of the instrument and the facility.
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1 |
2001 — 2004 |
Mckinnon, David |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Molecular Physiology--Control of Firing Properties @ State University New York Stony Brook
DESCRIPTION:(from applicant's abstract) The role that a neuron plays in a neural network is shaped by its intrinsic excitability, which is established developmentally to co-ordinate with its function within that network. We will study the control of neuronal firing properties in the rat peripheral sympathetic nervous system. There are two types of neurons in this system. Neurons in paravertebral ganglia have a simple wiring diagram and synaptic input to these cells is dominated by a large suprathreshold input from a single preganglionic motor neuron. These cells strongly accommodate in response to a sustained depolarizing current and are known as phasic neurons. In contrast, neurons in prevertebral ganglia integrate multiple small synaptic inputs from both sensory and motor neurons. These cells fire repetitively in response to a sustained depolarizing current and are known as tonic neurons. These different firing properties are determined by the differential expression of specific potassium currents. Phasic firing is produced by expression of a relatively large M-current. Tonic firing properties correlate with expression of an inward rectifier current and a low threshold, slowly inactivating current known as a D2 current. These two distinct electrophysiological phenotypes are determined during development by inductive events that affect transcriptional regulation of potassium channel genes. The overall aim of this proposal is to determine the molecular identity of those currents that control the switch in firing properties and to understand how the regulation of these channels is achieved. This work has relevance to the study of epilepsy since the regulation of intrinsic neuronal excitability is a key factor in determining the overall excitability of a neural network.
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1 |
2003 |
Mckinnon, David |
P01Activity Code Description: For the support of a broadly based, multidisciplinary, often long-term research program which has a specific major objective or a basic theme. A program project generally involves the organized efforts of relatively large groups, members of which are conducting research projects designed to elucidate the various aspects or components of this objective. Each research project is usually under the leadership of an established investigator. The grant can provide support for certain basic resources used by these groups in the program, including clinical components, the sharing of which facilitates the total research effort. A program project is directed toward a range of problems having a central research focus, in contrast to the usually narrower thrust of the traditional research project. Each project supported through this mechanism should contribute or be directly related to the common theme of the total research effort. These scientifically meritorious projects should demonstrate an essential element of unity and interdependence, i.e., a system of research activities and projects directed toward a well-defined research program goal. |
Molecular Basis of Ventricular Electrical Heterogeneity @ Columbia University Health Sciences
Ventricular myocytes show systematic variation in their electrical properties. There are consistent differences in action potential duration and in ion channel expression that depend upon the location of the myocyte within the ventricular walls. A major determinant of dispersion of repolarization is the non-uniform distribution of the transient outward current. This impacts on the determinants of repolarization in normal and abnormal hearts and is seen clinically in the ST segment and T wave of the ECG. We have previously described two genes encoding subunits of the transient outward channel that are differentially expressed in the ventricles. The KChlP2 gene is expressed in a large transmural gradient across the left ventricular free wall of large (canine and human) mammals and the Kv4.2 gene is expressed in a transmural gradient in rat. In both cases, differential regulation of these genes appears to be a primary determinant of the level of transient outward current expression and directly contributes to the electrical heterogeneity of ventricular myocytes. The overall aim of this proposal is to use molecular and biophysical techniques to further characterize the relationship between the differential expression of the KChlP2 and Kv4.2 genes and expression of the transient outward current, and to begin to determine the cellular and genetic mechanisms underlying the differential expression of these genes. The results of this study should permit a greater understanding of the mechanisms that determine repolarization in different species and, in collaboration with Project 1, at different ages. The understanding that evolves ultimately should be applicable to the modification of abnormal repoiarization in settings of cardiac disease.
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0.943 |