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Biomedical subjects

K Kaila

Publications and source records attributed to K Kaila.

83 records · Page 5Linked to original sources
PubMed1984

Facilitation of transmission at the crayfish neuromuscular synapse by a convulsant phenol.

The effects of the convulsant drug 4-Cl phenol on synaptic transmission were studied in the opener muscle of the crayfish walking leg. 4-Cl phenol was found to increase the amplitude of the excitatory postsynaptic potential without affecting the resting potential or input resistance of the muscle fiber. The drug did not change the frequency of spontaneous miniature postsynaptic potentials in K+-depolarized fibers. The postsynaptic voltage response to bath-applied glutamate (the excitatory transmitter compound) was decreased while the Cl(-) -conductance increase related to the action of bath-applied gamma-aminobutyric acid (the inhibitory transmitter) was not affected. In the light of previous results obtained on crayfish axons it is concluded that convulsant phenols induce an increase in the evoked release of transmitter by increasing the duration of the presynaptic depolarization through a block of voltage-dependent potassium channels.

Action Potentials↗
PubMed1984

Free extracellular [Ca2+] at photoreceptor level equals that in vitreous in frog and carp eyes.

The extracellular Ca2+ concentration has a strong influence on the function of retinal photoreceptors. In the present study both single- and double-barrelled Ca2+-sensitive microelectrodes were used to measure the free calcium ion concentration in the extracellular fluid bathing the photoreceptors in opened excised eyes of frogs and carps. The electrode tip was localized electrophysiologically by voltage drops related to current pulses passed radially through the preparation, using the high-resistance pigment epithelium as a landmark. The measurements showed that the extracellular Ca2+ concentration is very close or identical to that prevailing in the vitreous humour, 1.0-1.1 mM in the frog retina and 1.2-1.4 mM in the carp.

Animals↗
PubMed1982

Interstimulus interval dependence of the auditory vertex response and its magnetic counterpart: implications for their neural generation.

Auditory vertex responses elicited by short tone bursts were compared with their magnetic counter parts. Special attention was paid to the behaviour of the N100 deflection of the response. Electrical responses were recorded from scalp locations Fp2, Fz, Cz, Pz, C4 and T4 and the magnetic responses half way between P4 and T6, at a point where the response has one of its amplitude extrema. Different ISIs (from 1 to 16 sec) were applied in order to differentiate specific and nonspecific evoked potential components from each other. The main results were as follows: (1) The scalp distsribution of the electical vertex response depends on the ISI used: with frequent stimulation there are no marked differences in the amplitudes of N100 between frontal and central areas but with long ISIs the amplitude maxima move to the vertex. (2) The magnetic responses also show a clear ISI dependence. The magnetic counterpart of N100 saturates at shorter ISIs than N100 recorded from the vertex. Independent of the ISI the magnetic counterpart of P200 is constantly very small. On the basis of the different sensitivities of the EEG and MEG to current sources of different orientations it is concluded that the auditory vertex response contains both modality specific and non-specific components. Experimental conditions, especially the ISI used, determine the relative contributions of these components to the potential recorded on the scalp.

Adult↗
PubMed1982

Calcium-dependent increase in the potassium permeability of human red blood cells by pentachlorophenol and 2,4,6-trinitrophenol.

The effects of four phenol derivatives on the Ca2+ and K+ permeability of human red cells were studied at 0 degree C using 45Ca2+ and 86Rb+. Pentachlorophenol (PCP) and 2,4,6-trinitrophenol (TNP), which are mainly ionized at physiological pH, produced a marked influx of Ca2+ that increased with increasing pH. The elevated intracellular Ca2+ concentration was completely (TNP 5-10 mM, PCP 0.5 mM) or partly (PCP 1.0 mM) responsible for a concomitant increase in potassium permeability. No effects were found in connection with the weakly ionized 4-CI and 4-CI-3,5-di-CH3 derivatives at 1.0-5.0 mM and 0.5-2.0 mM, respectively. The fact that ionized phenols are able to transfer Ca2+ from water to a hydrophobic phase suggests that they may act as weak Ca2+ ionophores in the red cell plasma membrane.

Calcium↗
PubMedDate not supplied

Postsynaptic fall in intracellular pH induced by GABA-activated bicarbonate conductance.

Synaptic inhibition mediated by gamma-aminobutyric acid (GABA) is known to involve opening of receptor-gated chloride channels. Recent evidence indicates that these channels also show a significant permeability to the physiologically important bicarbonate anion. In all the excitable cells studied to date, the intracellular pH (pHi) is higher than would be predicted from a passive distribution of H+ ions, and consequently there is an outwardly directed electrochemical driving force for HCO3-. In the presence of CO2/HCO3- therefore, activation of GABA-gated channels could give rise to a significant efflux of bicarbonate, leading to a fall in postsynaptic pHi. We have examined the influence of GABA on pHi in crayfish skeletal muscle and we find that in the presence of CO2, GABA induces a dramatic fall in pHi which is coupled to an alkalosis at the extracellular surface. This fall in pHi and the extracellular alkalosis are attributable to a GABA-activated, picrotoxin-sensitive HCO3--conductance. In view of the sensitivity of ion channels and intracellular ion concentrations to changes in pHi, a GABA-induced postsynaptic acidosis could prove to be important in the modulation of inhibitory transmission.

Animals↗