Effects of Ultraviolet Radiation on the Plasma Membranes of Chara corallina. I The Hyperpolarized State

1976 ◽  
Vol 3 (5) ◽  
pp. 677
Author(s):  
C.J Doughty ◽  
A.B Hope
Keyword(s):  
Membrane Potential ◽  
Ultraviolet Radiation ◽  
Ultraviolet Irradiation ◽  
Plasma Membranes ◽  
Membrane Conductance ◽  
Chara Corallina ◽  
Potential Difference ◽  
Electrogenic Pump ◽  
Chloride Permeability ◽  
Membrane Potential Difference

Effects of 254 nm ultraviolet irradiation on the plasmalemma potential difference and conductance in C, corallina have been further analysed. Following an increase in passive chloride permeability, revealed from previous studies, and which is manifested as a depolarization of membrane potential difference and an increase in membrane conductance, a secondary depolarization was prominent at pH 7 and is attributed to u.v.-induced inhibition of an electrogenic pump. The secondary depolarization was usually accompanied by a decrease in membrane conductance. For doses of u.v. of 1400 J m-2, these effects were almost reversible within about 1 h

The stimulant action of acetylcholine and catecholamines on the uterus

1973 ◽  
Vol 265 (867) ◽  
pp. 149-156 ◽  
Keyword(s):  
Membrane Potential ◽  
Cell Membrane ◽  
Guinea Pig ◽  
Membrane Conductance ◽  
Primary Effect ◽  
Force Of Contraction ◽  
Chloride Permeability ◽  
Duration Of Action ◽  
Spike Discharge ◽  
Calcium Permeability

The α action of catecholamines on oestrogen dominated guinea-pig uterus is stimulant. The cell membrane is depolarized, membrane conductance is increased, spike discharge is accelerated and tension develops. This action resembles that of acetylcholine though catecholamines are less potent, and, in equiactive concentrations, catecholamines have a longer latency and a longer duration of action. Evidence, obtained by modifications of the ionic environment, indicates that the depolarization by acetylcholine is due to an increase in sodium and calcium permeability and that acetylcholine can release calcium from intracellular stores. The depolarization by catecholamines is due to an increase in chloride permeability and, in addition, sodium is required for the ensuing increase of spike discharge. Catecholamines produce an increase in the force of contraction, long outlasting their immediate stimulation. Moreover, their effect on membrane potential and membrane conductance persists in the presence of lanthanum. These results suggest that Ca release from intracellular stores may be the primary effect produced by the α action of catecholamines and that the increase in the cytoplasmic Ca 2+ concentration may cause the changes at the cell membrane.

Relation of membrane potential to basolateral TEA transport in isolated snake proximal renal tubules

1995 ◽  
Vol 268 (6) ◽  
pp. R1539-R1545 ◽  
Author(s):  
Y. K. Kim ◽  
W. H. Dantzler
Keyword(s):  
Steady State ◽  
Membrane Potential ◽  
Potent Inhibitor ◽  
Basolateral Membrane ◽  
Potential Difference ◽  
Renal Tubules ◽  
K Concentration ◽  
Electrochemical Equilibrium ◽  
Membrane Potential Difference ◽  
Basolateral Membrane Potential

We measured the effects of changes in bath K+ concentration ([K+]) on basolateral membrane potential difference (PD) and [3H]tetraethylammonium (TEA) transport in isolated snake (Thamnophis) proximal renal tubules (25 degrees C; pH 7.4). Increasing bath [K+] from 3 to 65 mM decreased PD from -60 mV (inside of cells negative) to -20 mV and 2-min uptake of [3H]TEA by approximately 25%, indicating that PD influences TEA entry into the cells. Uptake of [3H]TEA was inhibited similarly at both K+ concentrations by unlabeled TEA, indicating that uptake is carrier mediated. Kt (approximately 18 microM) for 2-min uptake of [3H]TEA in 3 mM K+ increased significantly in 65 mM K+, suggesting that the decrease in PD or the increase in [K+] alters the affinity of the transporter for TEA. The steady-state cell-to-bath ratio for [3H]TEA with 3 mM K+ (-60 mV PD) was approximately 16, significantly above the ratio of 10 predicted for passive distribution at electrochemical equilibrium. With 65 mM K+ (-20 mV PD) this ratio decreased to approximately 6, again significantly above the predicted ratio of 2. These data suggest that the PD can account for much, but not all, of the steady-state uptake of TEA. Efflux of [3H]TEA across the basolateral membrane was identical with either 3 or 65 mM K+ in the bath but was almost completely inhibited in either case by tetrapentylammonium, a potent inhibitor of TEA uptake. These data indicate that virtually all TEA transport across the basolateral membrane is carrier mediated and that transport out of the cells is unaffected by PD.

Effects of Ultraviolet Radiation on the Plasma Membranes of Chara corallina. II* The Action Potential

1976 ◽  
Vol 3 (5) ◽  
pp. 687
Author(s):  
C.J Doughty ◽  
A.B Hope
Keyword(s):  
Action Potential ◽  
Ultraviolet Radiation ◽  
Membrane Permeability ◽  
Ultraviolet Light ◽  
Plasma Membranes ◽  
Peak Height ◽  
Chara Corallina ◽  
Membrane Properties ◽  
Resting Potential ◽  
Gating Mechanisms

When cells of C. corallina were irradiated with 254 nm ultraviolet light, the action potential across the plasmalemma was unaffected in its peak height, but its duration (measured at half-peak height) was increased, more so as the dose was varied between 1500 and 6000 J m-2. The action potential across the tonoplast was reduced in peak height and increased in duration by U.V. The effects were slowly reversible. The effect of 285 nm u.v., effective in depolarizing the resting potential difference, was to decrease the peak of the plasmalemma action potential while leaving the duration virtually unaffected. The results are interpreted as revealing differential effects on gating mechanisms determining the duration, and on transient membrane permeability to chloride (and possibly potassium) determining the peak, of the action potential. Because of the differential wavelength effects, these two membrane properties are postulated to be mediated by molecules which act as distinctive targets to the two wavelengths.

scholarly journals Effects of Temperature on Membrane Permeability to Ions

1970 ◽  
Vol 23 (4) ◽  
pp. 1047 ◽  
Author(s):  
AB Hope ◽  
PA Aschberger
Keyword(s):  
Membrane Potential ◽  
Fresh Water ◽  
Marine Alga ◽  
Single Cells ◽  
Potential Difference ◽  
Varied Temperature ◽  
Effects Of Temperature ◽  
Fresh Water Alga ◽  
Red Marine Alga ◽  
Membrane Potential Difference

The effects of varied temperature on membrane potential difference (p.d.) and resistance were measured in single cells of the green, fresh water alga Ohara oorallina and the red, marine alga Griffithsia pulvinata. The effects of varied temperature on membrane potential difference (p.d.) and resistance were measured in single cells of the green, fresh water alga Ohara oorallina and the red, marine alga Griffithsia pulvinata.

scholarly journals The Rapid Movement of the Bladder of Utricularia Sp

1973 ◽  
Vol 26 (5) ◽  
pp. 1115 ◽  
Author(s):  
PH Sydenham ◽  
GP Findlay
Keyword(s):  
Membrane Potential ◽  
Internal Pressure ◽  
Membrane Resistance ◽  
Potential Difference ◽  
Rapid Movement ◽  
Membrane Potential Difference

The changes which occur in the internal pressure, volume, membrane potential difference (p.d.), and membrane resistance during the firing of bladders of Utricularia sp. are described.

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