Biomaterial Database

Developmental changes in regulation of embryonic chick heart gap junctions. 1991

R D Veenstra

Department of Pharmacology, State University of New York/Health Science Center, Syracuse 13210.

Embryonic chick myocyte pairs were isolated from ventricular tissue of 4-day, 14-day, and 18-day heart for the purpose of examining the relationship between macroscopic junctional conductance and transjunctional voltage during cardiac development. The double whole-cell patch-clamp technique was employed to directly measure junctional conductance over a transjunctional voltage range of +/- 100 mV. At all ages, the instantaneous junctional current (or conductance = current/voltage) varied linearly with respect to transjunctional voltage. This initial response was followed by a time- and voltage-dependent decline in junctional current to new steady-state values. For every experiment, the steady-state junctional conductance was normalized to the instantaneous value obtained at each potential and the data was pooled according to developmental age. The mean steady-state junctional conductance-voltage relationship for each age group was fit using a two-state Boltzmann distribution described previously for other voltage-dependent gap junctions. From this model, it was revealed that half-inactivation voltage for the transjunctional voltage-sensitive conductance shifted towards larger potentials by 10 mV, the equivalent gating charge increased by approximately 1 electron, and the minimal voltage-insensitive conductance exactly doubled (increased from 18 to 36%) between 4 and 18 days of development. Decay time constants were similar at all ages examined as rate increased with increasing transjunctional potential. This data provides the first direct experimental evidence for developmental changes in the regulation of intercellular communication within a given tissue. This information is consistent with the hypothesis that developmental expression of multiple gap junction proteins (connexins) may confer different regulatory mechanisms on intercellular communication pathways within a given cell or tissue.

UI	MeSH Term	Description	Entries
D007365	Intercellular Junctions	Direct contact of a cell with a neighboring cell. Most such junctions are too small to be resolved by light microscopy, but they can be visualized by conventional or freeze-fracture electron microscopy, both of which show that the interacting CELL MEMBRANE and often the underlying CYTOPLASM and the intervening EXTRACELLULAR SPACE are highly specialized in these regions. (From Alberts et al., Molecular Biology of the Cell, 2d ed, p792)	Cell Junctions,Cell Junction,Intercellular Junction,Junction, Cell,Junction, Intercellular,Junctions, Cell,Junctions, Intercellular
D007473	Ion Channels	Gated, ion-selective glycoproteins that traverse membranes. The stimulus for ION CHANNEL GATING can be due to a variety of stimuli such as LIGANDS, a TRANSMEMBRANE POTENTIAL DIFFERENCE, mechanical deformation or through INTRACELLULAR SIGNALING PEPTIDES AND PROTEINS.	Membrane Channels,Ion Channel,Ionic Channel,Ionic Channels,Membrane Channel,Channel, Ion,Channel, Ionic,Channel, Membrane,Channels, Ion,Channels, Ionic,Channels, Membrane
D008433	Mathematics	The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Mathematic
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D009206	Myocardium	The muscle tissue of the HEART. It is composed of striated, involuntary muscle cells (MYOCYTES, CARDIAC) connected to form the contractile pump to generate blood flow.	Muscle, Cardiac,Muscle, Heart,Cardiac Muscle,Myocardia,Cardiac Muscles,Heart Muscle,Heart Muscles,Muscles, Cardiac,Muscles, Heart
D009210	Myofibrils	The long cylindrical contractile organelles of STRIATED MUSCLE cells composed of ACTIN FILAMENTS; MYOSIN filaments; and other proteins organized in arrays of repeating units called SARCOMERES .	Myofilaments,Myofibril,Myofilament
D002450	Cell Communication	Any of several ways in which living cells of an organism communicate with one another, whether by direct contact between cells or by means of chemical signals carried by neurotransmitter substances, hormones, and cyclic AMP.	Cell Interaction,Cell-to-Cell Interaction,Cell Communications,Cell Interactions,Cell to Cell Interaction,Cell-to-Cell Interactions,Communication, Cell,Communications, Cell,Interaction, Cell,Interaction, Cell-to-Cell,Interactions, Cell,Interactions, Cell-to-Cell
D002642	Chick Embryo	The developmental entity of a fertilized chicken egg (ZYGOTE). The developmental process begins about 24 h before the egg is laid at the BLASTODISC, a small whitish spot on the surface of the EGG YOLK. After 21 days of incubation, the embryo is fully developed before hatching.	Embryo, Chick,Chick Embryos,Embryos, Chick
D004553	Electric Conductivity	The ability of a substrate to allow the passage of ELECTRONS.	Electrical Conductivity,Conductivity, Electric,Conductivity, Electrical
D006321	Heart	The hollow, muscular organ that maintains the circulation of the blood.	Hearts