Ruth Ann Chapman

Learn More
Describing long-term dynamics in oak stands is hindered by a lack of archival data. In this study, archival data from the 1934 inventory of a 673-ha area within the Sylamore Experimental Forest were compared to a recent 2002 inventory to quantify changes in forest structure and species composition of this upland oak forest in the Ozark Mountains of(More)
1. Single Na+-activated K+ channels (K(Na)) were investigated by means of the inside-out patch clamp technique in ventricular myocytes isolated from the guinea-pig heart. 2. Na+-activated K+ channels were observed at very low density (< 9% of patches). In symmetrical (60/60 mM) K+ solutions, K(Na) channels had a mean slope conductance of 75 pS and in(More)
A chemical phosphatase, butanedione monoxime (BDM, at 12-20 mM), reduced open probability (P0) of single cardiac L-type Ca2+ channels in cell-attached patches from guinea-pig ventricular myocytes, without effect on the amplitude of single-channel current, the mean open time or the mean shorter closed time, but it increased mean longer closed time and caused(More)
1. In the presence of extracellular Na ions K contractures evoked from isolated frog atrial trabeculae show an initial phasic and a subsequent tonic contractile response. 2. The phasic response shows a steep dependence on membrane potential, persists in Na-free fluid, but is blocked by Mn ions, D600 and tetracaine. It has an indirect dependence on the [Ca]0(More)
The repetitive responses induced in squid giant axons by the application of sustained depolarizing currents under space clamp conditions are described. The relationships between membrane current, and a number of features of the repetitive response of the living axon are compared to computations made for the Hodgkin-Huxley equations. The comparison suggests(More)
A current generated by the Na-activated K channel has been identified in whole cell currents recorded from isolated guinea-pig ventricular myocytes. A partial activation of this current can be achieved near to the physiological range of intracellular sodium concentration [( Na+]i) when it contributes significantly to the global outward current. The decline(More)
1. Guinea-pig ventricular myocytes, isolated enzymatically without the aid of special media, show a similar sensitivity to the calcium paradox as Langendorff-perfused hearts. 2. Measurement of the intracellular activities of Na+ and Ca2+ ions, with a suction-type ion-sensitive microelectrode at rest, during calcium depletion and during inhibition of the Na+(More)
Sheep cardiac Purkinje fibers were exposed to solutions free of divalent cations for hour-long periods, while intracellular Na+ and K+ activities were measured using ion-sensitive microelectrodes. Intracellular Na+ activity (aiNa) increased to 50.1 +/- 8.1 mM, and intracellular K+ activity (aiK) decreased to 76.7 +/- 3.5 mM. These ionic changes could be(More)
A method for the manufacture of ion-sensitive micro-electrodes, which can be readily used with small single cells, is described in detail. A glass pipette with a tip size of 1 micron, essentially similar to those used as suction electrodes in whole-cell recording, when silanized and with its tip filled with a suitable ion-sensitive resin, produces an(More)
Twelve short-lived subconductance levels have been recognized in potassium channels activated by intracellular Na+ (KNa channels) in membrane patches excised from guinea-pig ventricular myocytes. When stable recording was achieved over a prolonged period (> 30 min), sojourns of opening to one of two stable subconductance levels (approximately 30 and 70% of(More)