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Biomedical subjects

O L Miakotina

Publications and source records attributed to O L Miakotina.

9 recordsLinked to original sources
PubMed1998

Insulin inhibits surfactant protein A and B gene expression in the H441 cell line.

Fetuses of mothers with uncontrolled gestational diabetes have an increased risk of developing neonatal respiratory distress syndrome and are frequently hyperinsulinemic, thus it has been proposed that high levels of insulin delay fetal lung maturation. We have shown previously that insulin inhibits the accumulation of mRNA for the surfactant-associated proteins A and B (SP-A and SP-B) in human fetal lung explants maintained in vitro. To test the hypothesis that the inhibitory effects of insulin on the surfactant proteins are the result of a direct action of insulin on the lung epithelial cell, we evaluated the effects of insulin in the H441 cell line, a human pulmonary adenocarcinoma cell line that expresses SP-A and SP-B mRNA. We observed that insulin treatment for 48 h decreased SP-A mRNA and protein levels in a concentration-dependent manner when compared to controls. The inhibitory effect of insulin on SP-A mRNA levels was apparent as early as after 4 h of exposure. SP-B mRNA levels were also significantly decreased by insulin in a concentration-dependent manner. Insulin, at 2.5 microg/ml, inhibited SP-A gene transcription by approx. 67%, and inhibited SP-B gene transcription by about 32%. There was no significant effect of insulin on SP-A or SP-B mRNA stability. Thus, we have observed a pattern of insulin inhibition of SP-A and SP-B gene expression in the H441 lung epithelial cell line similar to that previously observed in human fetal lung explants, which are comprised of both epithelial and mesenchymal cells. Our findings provide further evidence that insulin may delay fetal lung maturation by inhibiting SP-A and SP-B gene expression. Furthermore, our findings suggest that the inhibitory effects of insulin are, at least partially, the result of a direct action on the lung epithelial cell.

Adenocarcinoma↗
PubMed1998

Mechanism of all trans-retinoic acid and glucocorticoid regulation of surfactant protein mRNA.

The surfactant proteins (SPs) are required for the normal function of pulmonary surfactant, a lipoprotein substance that prevents alveolar collapse at end expiration. We characterized the effects of cortisol and all trans-retinoic acid (RA) on SP-A and SP-B gene expression in H441 cells, a human pulmonary adenocarcinoma cell line. Cortisol, at 10(-6) M, caused a significant inhibition of SP-A mRNA to levels that were 60-70% of controls and a five- to sixfold increase in the levels of SP-B mRNA. RA alone (10(-6) M) had no effect on SP-A mRNA levels and modestly reduced the inhibitory effect of cortisol. RA alone and the combination of cortisol and RA both significantly increased SP-B mRNA levels. RA had no effect on the rate of SP-A gene transcription or on SP-A mRNA stability. Cortisol alone and the combination of cortisol and RA significantly inhibited the rate of SP-A gene transcription but had no effect on SP-A mRNA half-life. RA at 10(-6) M had no effect on the rate of SP-B gene transcription but prolonged SP-B mRNA half-life. Cortisol alone and the combination of cortisol and RA caused a significant increase in the rate of SP-B gene transcription and also caused a significant increase in SP-B mRNA stability. We conclude that RA has no effect on SP-A gene expression and increases SP-B mRNA levels by an effect on SP-B mRNA stability and not on the rate of SP-B gene transcription. In addition, the effects of the combination of RA and cortisol were generally similar to those of cortisol alone.

Dose-Response Relationship, Drug↗
PubMedDate not supplied

[Change in neuronal membrane permeability exposed to adenosine-3',5'-cyclophosphate].

Ionic current induced by intracellular injection of cAMP was divided into constituent parts, and the dependence of these components on membrane potential and ionic composition of extracellular medium was demonstrated. The computation shows that practically all background neurone permeability for potassium ions is cAMP-dependent.

Animals↗
PubMedDate not supplied

[The effect of various protein kinase inhibitors on the response of snail neurons to the intracellular injection of cAMP].

Drugs preventing cAMP interaction with regulatory subunit of cAMP-dependent protein kinase, tolbutamide and db-cAMP injected into neurons of Helix lucorum decreased the cell response to cAMP, but H-8-a potent inhibitor of this enzyme catalytic subunit did not produce such effect. It is suggested that the neuron electric response to cAMP injection is not caused by protein phosphorylation.

Animals↗
PubMedDate not supplied

[Intraneuronal information processing. An increase in sodium and decrease in potassium permeability after injection of cyclic nucleotide and mechanical stimulation of the neuron].

In voltage clamp experiments the ionic permeability mechanism of the neuron soma evoked by the injection of cyclic nucleotides can be estimated only by studying the reversal potential. The value of this potential allows to conclude that permeability is mainly increased by opening potential independent sodium channels. A delay of ionic current evoked by cyclic nucleotides is tenfold less than the time of cAMP diffusion to the membrane. This leads to a hypothesis about the cyclic nucleotide dependent mechanical opening of sodium channels.

Action Potentials↗
PubMedDate not supplied

[The role of electro-mechanical and reaction-diffusion systems in the intra-neuron processing of information: effect of in-flow of calcium and intracellular calcium on cAMP activity].

Influx of calcium ions cannot control a generatory potential induced by the intraneuronal system because calcium ions enter the cell during impulses. These impulses are the result of problem solving and must not influence directly the generatory potential. Therefore cAMP and not calcium controls the permeability of sodium and potassium channels from the inside of the neuron. However the calcium ions and membrane potential of mitochondria affect the impact of cAMP injections. An increase in the intracellular concentration of free Ca2+ induced by the injection of Ca-EGTA buffer with 5.10(-7) M free Ca2+, electric excitation, uncouplers of oxidative phosphorylation or arsenate leads to an increase of cAMP-dependent depolarization and the inward current. The injection of Ca-EGTA buffer with 10(-5) M free Ca2+ and drop in [Ca2+]in by EGTA as well as generation of impulses after cAMP injection decrease the cAMP effect. As rise in [Ca2+]in activates phosphodiesterase and uncouples oxidative phosphorylation, and vanadate in contrast to arsenate suppresses the cAMP effect, a hypothesis is advanced that activating effect of calcium on cAMP action is associated with neuron deenergization.

Action Potentials↗
PubMedDate not supplied

[Intraneuronal information processing. Delay in the changes in membrane potential after administration of cyclic nucleotides].

Depolarization of the neuron membrane induced by cyclic adenosine monophosphate (cAMP) was shown both by ionophoresis and by injection with pressure. Swelling of the neuron during the injection of various substances with pressure causes membrane depolarization which is similar to that induced by cAMP. When applying pressure the cAMP effect can be distinguished by introducing small volumes of concentrated solutions. Similarity between the effects of cAMP and mechanical stimulation of the neuron suggests that in both cases the effect involves action of the electromechanical system consisting of microskeleton and micromuscles which regulate permeability of molecular channels. The delay of the effect after the moment of cAMP and cGMP introduction is small, which enables a conclusion concerning their direct interaction with the cytoskeleton.

Adenosine Triphosphate↗
PubMedDate not supplied

[Effect of oxidative phosphorylation inhibitors and uncoupling agents on cAMP activity].

Uncouplers of oxidative phosphorylation increased the speed of substrate oxidation and ATP hydrolysis and raised cAMP induced neuron membrane current. Different inhibitors decreased it. Both effects support the hypothesis that a signal of intracellular injected cAMP spreads to the neuron membrane as a mechanical signal. This signal propagated to the membrane along microtubules which according to this hypothesis serve as a sound generator with metabolic heat pumping.

Animals↗