Biomedical subjects
M Gola
Publications and source records attributed to M Gola.
Two subtypes of C current in identified Helix neurons.
Ca-activated K currents (C currents) were identified in various Helix pomatia neurons under voltage-clamp conditions. This comparative study revealed the existence of two C currents: a fast-inactivating current and a non-inactivating current; both had identical gating and pharmacological properties. Inactivation of the C currents was induced by either cell depolarization or short Ca entry.
Occupational contact dermatitis in 2 dental technicians.
2 dental technicians, both with chronic hand eczema, reported worsening from the use of 2 products containing methyl methacrylate, employed in manufacturing acrylic prostheses. Patch tests in both patients gave positive reactions to methyl methacrylate, ethylene glycol dimethacrylate and products employed in manufacturing acrylic prostheses (2% and 5% pet.). On the basis of results subsequently obtained from patch tests carried out with pieces of glove interposed between the skin and the allergens (methyl methacrylate and products employed), we advised our patients still to use latex gloves during work. Follow-up after 1 year showed complete regression of the dermatitis in 1 case and considerable improvement in the other.
Ca2(+)-activated K+ current involvement in neuronal function revealed by in situ single-channel analysis in Helix neurones.
1. The properties of single calcium-activated potassium channels (or C-channels) were studied in cell-attached patches using the patch-clamp technique. Experiments were performed on identified Ca2(+)-dependent U cells in juvenile specimens (1-2 months old) of Helix aspersa. 2. The criteria used to identify C-channels were based on comparison between macroscopic C-currents and currents reconstructed from unitary recordings. Both currents had a slow activation rate at large positive potentials which turned into fast activation after large Ca2+ entries. Both currents were blocked by intracellularly injected EGTA. 3. The unitary conductance in normal (5 mM) or reduced (0.5 mM) [K+]o ranged from 24 to 65 pS (mean +/- S.D., 48 +/- 13; n = 64). With 85-110 mM [K+]o, which is approximately equal to the internal [K+], the conductance was 64 pS and the reversal potential was approximately 0 mV. 4. C-channels in U cells were distributed in clusters of three to ten channels (mean 5.05 channels in seventy-five patches). Calcium channels were present in patches containing clustered C-channels. C-channels within clusters behaved independently. 5. With patch electrode containing 8 mM-calcium, C-channels opened transiently upon patch depolarization. Reopenings in quiescent depolarized patches were induced by whole-cell spikes triggered by current pulses applied to an intracellular electrode. Apparent inactivation of C-channels in depolarized patches was in fact due to a decrease in [Ca2+]i resulting from inactivation of Ca2+ channels. 6. Calcium-free saline solutions in the patch electrodes prevented C-channels from opening upon patch depolarization. Entry of calcium through the surrounding membrane induced delayed openings in the patch. Peak opening probability Po occurred 330 +/- 30 ms after a brief Ca2+ entry with a lag period of 50-80 ms. With patch electrodes filled with Ca2(+)-containing saline solutions and under conditions which maximized C-channel opening, peak Po was reached in 20-50 ms. The same value was observed for the whole-cell C-current. 7. The peak Po at a given patch potential and in response to a whole-cell spike was not altered by a previous long-lasting patch depolarization, or by producing several successive Ca2+ entries. Thus, C-channels did not appear to be inactivated by depolarization or increase in [Ca2+]i. 8. C-channels were found to be relatively highly voltage dependent, with an e-fold increase in Po per 14.9 mV increase in potential.(ABSTRACT TRUNCATED AT 400 WORDS)
Voltage-dependent opening of single calcium-activated potassium channels in Helix neurons.
Single Ca-activated K channels (C channels) were identified in cell-attached patches in Helix neurons. The respective effects of membrane potential and calcium on the opening probability Po were separated by using Ca-free filled patch electrodes. C channels were found to be highly voltage-dependent, with an e-fold increase in Po per 15 mV increase in potential. The location of the Po(V) curve on the voltage axis was dependent on the intracellular Ca concentration. These data indicate that C channels provide the cell with a powerful repolarizing mechanism.
Involvement of calcium-activated K+ channels in the firing characteristics of molluscan neurones.
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Unusual occupational allergic contact dermatitis in a nurse.
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Contact sensitization to acyclovir.
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Allergic contact dermatitis in a pastry cook.
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Epidemiology of contact dermatitis.
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Forskolin interaction with voltage-dependent K channels in Helix is not mediated by cyclic nucleotides.
The effects of the adenylate cyclase activator forskolin upon voltage-activated K(V) currents were investigated in Helix nerve cells. Forskolin induced a fast concentration-dependent inactivation of K(V) currents without modifying the activation kinetics. The induced fast inactivation did not result from a speeding up of the voltage-controlled slow inactivation; it could not be mimicked by intracellular injection of cAMP and it was not potentiated by inhibition of the phosphodiesterase. The forskolin induced K current relaxation can be simulated by a model assuming that the drug binds reversibly to open K channels with a dissociation constant of 16.4 microM.
Decreased resting membrane conductance as the proximate cause of burst modulation by an identified interneuron in Helix.
The mechanism by which an identified interneuron modulates bursting activity was studied in the mollusc Helix pomatia. Firing of the interneuron was found to enhance endogenous bursting activity by causing a slow, persistent decrease in resting K-conductance, leading to a relative increase in the effectiveness of the burst-generating mechanism.
Tegobetaine in contact lens solutions.
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Time course of Ca and Ca-dependent K currents during molluscan nerve cell action potentials.
The time courses of Ca and Ca-dependent K currents during Ca-dependent action potentials were obtained by recording the membrane currents produced in response to spike-like voltage clamp pulses before and after selective blockade of channels. The Ca current had a biphasic waveform with a first surge and a late, large entry. The Ca-dependent K(Ca) current onset was relatively fast with a peak occurring at half spike repolarization. The fast activation of the K(Ca) current was consecutive to the first Ca entry. It is concluded that K(Ca) currents constitute a powerful spike repolarization mechanism in addition to the voltage-dependent K currents.
Occupational photocontact dermatitis from Olaquindox.
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Computer analysis of 3312 cases of contact dermatitis.
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D600 as a direct blocker of Ca-dependent K currents in Helix neurons.
The effects of D600 and inorganic Ca blockers on calcium and Ca-dependent potassium currents were investigated in Helix neurons under current and voltage-clamp conditions. At low concentrations (10-50 microM), D600 enlarged the Ca-dependent spike in U cells, which was blocked at higher concentrations. D600 130 and 17 microM reduced the Ca current ICa and the Ca-dependent K current IK(Ca) respectively by half. IK(Ca) blockade developed rapidly and was almost irreversible. ICa blockade had a slower time course and was easily reversible. Hyperpolarization unblocked part of the Ca channels but had no effect on the blocked K(Ca) channels. Both currents were simultaneously reduced by half with 22 microM cadmium. These data indicate that D600, verapamil and diltiazem, block K(Ca) channels directly whether or not they have a blocking effect on Ca channels. It is concluded on the basis of intracellular D600 injection that the site of action is located on the outer mouth of the K(Ca) channels.