Potassium Permeability Research Articles

Inhibition of some multidrug-resistant bacteria using prepared essential oil Nanoemulsion formulas and their mode of action

Inhibition of some multidrug-resistant bacteria using prepared essential oil Nanoemulsion formulas and their mode of action

Ian Michael Glynn. 3 June 1928—7 July 2022

In the mid 1950s the convergence of crucial discoveries on nerve and muscle physiology brought to centre stage the question of how sodium and potassium concentration gradients needed for nerve conduction and muscle contraction are maintained. This was the subject Ian Glynn set out to investigate when he returned to Cambridge as a Trinity College graduate student in 1953. His initial results on the sodium and potassium permeabilities of the human red blood cell membrane, published in 1956–1967, established these cells as an ideal experimental system for studying the transport properties of the ‘sodium pump’ because of the ease with which the ionic composition of intra- and extracellular environments could be controlled, cell metabolism managed and ionic fluxes measured using isotopes. This work was followed by ground-breaking contributions from his research group over the next decades in a long series of brilliantly designed experiments, setting the foundations of our current understanding of the molecular mechanism of the sodium/potassium pump. Ian became a Trinity College fellow in 1960, advanced rapidly to a professorship in the Department of Physiology after being elected Fellow of the Royal Society in 1970, and was appointed head of department in 1986 until his retirement in 1995.

Impacts of multiple anthropogenic stressors on the transcriptional response of Gammarus fossarum in a mesocosm field experiment

Freshwaters are exposed to multiple anthropogenic stressors, leading to habitat degradation and biodiversity decline. In particular, agricultural stressors are known to result in decreased abundances and community shifts towards more tolerant taxa. However, the combined effects of stressors are difficult to predict as they can interact in complex ways, leading to enhanced (synergistic) or decreased (antagonistic) response patterns. Furthermore, stress responses may remain undetected if only the abundance changes in ecological experiments are considered, as organisms may have physiological protective pathways to counteract stressor effects. Therefore, we here used transcriptome-wide sequencing data to quantify single and combined effects of elevated fine sediment deposition, increased salinity and reduced flow velocity on the gene expression of the amphipod Gammarus fossarum in a mesocosm field experiment. Stressor exposure resulted in a strong transcriptional suppression of genes involved in metabolic and energy consuming cellular processes, indicating that G.fossarum responds to stressor exposure by directing energy to vitally essential processes. Treatments involving increased salinity induced by far the strongest transcriptional response, contrasting the observed abundance patterns where no effect was detected. Specifically, increased salinity induced the expression of detoxification enzymes and ion transporter genes, which control the membrane permeability of sodium, potassium or chloride. Stressor interactions at the physiological level were mainly antagonistic, such as the combined effect of increased fine sediment and reduced flow velocity. The compensation of the fine sediment induced effect by reduced flow velocity is in line with observations based on specimen abundance data. Our findings show that gene expression data provide new mechanistic insights in responses of freshwater organisms to multiple anthropogenic stressors. The assessment of stressor effects at the transcriptomic level and its integration with stressor effects at the level of specimen abundances significantly contribute to our understanding of multiple stressor effects in freshwater ecosystems.

The role of SH groups in the regulation of Gardos channels in glucose deficiency

Background. Disruption of the energy balance of erythrocytes under conditions of a decrease in the glycolysis level can cause a change in the ion permeability of their membrane. The aim. To study Ca2+-dependent potassium permeability of the erythrocytes membrane in the presence of SH group modifiers under conditions of glucose deficiency. Materials and methods. The study used precipitated erythrocytes obtained from the blood of 20 male Wistar rats. The change in the Ca2+-dependent potassium conductivity of the erythrocyte membrane was determined using the potentiometric method. The A23187-and redox-induced hyperpolarization responses of erythrocytes were evaluated. Results. Glucose deficiency in the medium, as well as the use of the glycolysis inhibitor 2-deoxyglucose, led to an increase in the amplitude of A23187-stimulated membrane hyperpolarization by the opening of the Gardos channels. At the same time, the redox-dependent hyperpolarization of the erythrocyte membrane turned out to be insensitive to a decrease in the glucose content in the medium and to the glycolysis inhibition. The effects of SH group modifiers in the normal incubation medium and under glucose deficiency turned out to be multidirectional and depended on the method of stimulation of Gardos channels. Conclusion. The results obtained indicate that metabolic disorders in erythrocytes under conditions of glucose deficiency lead to a change in the mechanisms of control of Gardos channels with the participation of SH groups of the proteins of these channels or their regulatory proteins.

Kv7.4 channels regulate potassium permeability in neuronal mitochondria

Mitochondrial K+ permeability regulates neuronal apoptosis, energy metabolism, autophagy, and protection against ischemia–reperfusion injury. Kv7.4 channels have been recently shown to regulate K+ permeability in cardiac mitochondria and exert cardioprotective effects. Here, the possible expression and functional role of Kv7.4 channels in regulating membrane potential, radical oxygen species (ROS) production, and Ca2+ uptake in neuronal mitochondria was investigated in both clonal (F11 cells) and native brain neurons.In coupled mitochondria isolated from F11 cells, K+-dependent changes of mitochondrial membrane potential (ΔΨ) were unaffected by the selective mitoBKCa channel blocker iberiotoxin and only partially inhibited by the mitoKATP blockers glyburide or ATP. Interestingly, K+-dependent ΔΨ decrease was significantly reduced by the Kv7 blocker XE991 and enhanced by the Kv7 activator retigabine. Among Kv7s, western blot experiments showed the expression of only Kv7.4 subunits in F11 mitochondrial fractions; immunocytochemistry experiments showed a strong overlap between the Kv7.4 fluorescent signal and that of the mitochondrial marker Mitotracker. Silencing of Kv7.4 expression significantly suppressed retigabine-dependent decrease in ΔΨ in intact F11 cells. Expression of Kv7.4 subunits was also detected by western blot in isolated mitochondria from total mouse brain and by immunofluorescence in mouse primary cortical neurons. Pharmacological experiments revealed a relevant functional role for Kv7.4 channels in regulating membrane potential and Ca2+ uptake in isolated neuronal mitochondria, as well as ΔΨ and ROS production in intact cortical neurons. In conclusion, these findings provide the first experimental evidence for the expression of Kv7.4 channels and their contribution in regulating K+ permeability of neuronal mitochondria.

Роль іонів калію у біосинтезі оксиду азоту в мітохондріях гладенького м’яза

The NO-synthase activity (mtNOS) in mitochondria of uterine smooth muscle was studied. The mitochondrial localization of NO synthesis in myocytes was proved using laser confocal microscopy method and specific fluorescent probes MitoTracker Orange (specific to mitochondria) and DAFFM (NO-sensitive fluorescent probe). It was demonstrated using flow cytometry that nitric oxide biosynthesis in isolated mytochondria decreased in the presence of a constitutive NOsynthase blocker 2-aminopyridine (100 μmol per l, 50% inhibition) and monoclonal antibodies (2.5 μg anti-Let m1 per 50 μg protein) against the H+-Ca2+-exchanger (Letm1 protein), but was’t sensitive to the mitochondrial permeability transition pore inhibitor cyclosporin A (5 μmol per l). A decrease of potassium ions concentration in the incubation medium and the presence of various types of potassium channel inhibitors significantly inhibited the NO-synthase reaction. We have concluded that potassium permeability of the inner mitochondrial membrane plays important role in the regulation of mtNOS activity.

STUDY OF IRRITANT AND SKIN-RESORPTIVE ACTION OF SODIUM-CONTAINING DRUG

Sodium-containing preparations have antimicrobial, anti-inflammatory and wound-healing activity, which determines their use in veterinary medicine. This effect is due to a wide range of physiological effects of sodium ions on animals metabolism. The article presents the results of experimental studies of the irritant effect of sodium-containing drugs: known – 2 % glycetinate, its analogues – 2 % ovocid, 3 % ovocid, 1.5 % potassium-sodium drug (Na / K, 1.5%). Studies of irritant and skin-resorptive action of drugs were performed by immersing the tail of animals in a test tube with the substance on white rats weighing 250–270 g. Four groups of rats were formed with 3 animals each: rats of I group (control) tails were immersed in test tubes with 2 % glycetinate, animals of II group – in test tubes with 2% oocide, III group – in test tubes with 3 % oocide, and in IV group rats – with Na / K, 1.5% drug. The exposure time was 4 hours. The animals were subjected to clinical observations, assessing their general condition and the reaction of the tail’s skin. The effect of drugs on the morphological and biochemical parameters of the rats blood was studied. The study of the local irritant effect of the studied drugs in rats from I, II and III groups showed a moderate local irritant reaction, as evidenced by the appearance of redness and thickening of the skin, and in group IV animals appeared only slight redness on the skin of the tails. This indicates a weaker local irritant effect of potassium-sodium-containing drug (1.5% K, Na), compared with other studied drugs.
 According to hematological studies, in the rats’s blood of groups III and IV, a reliable increase, within normal limits, the number of leukocytes and a decrease in hemoglobin content, compared with those of animals of group I. It was found that at 4 hours of the experiment under the action of the studied potassium-sodium drugs increases the permeability of Sodium and Potassium through the rats’s skin into the blood. In particular, in serum of animals from groups II and IV there was a reliable increase of Potassium content by 2.1 times, respectively, and a significant increase in Sodium content in the blood of animals from groups III and IV, compared with control group. In animals of groups II and IV there was a reliable increase of serum aspartate aminotransferase activity, and in rats of group III – increase of serum alanine aminotransferase, alkaline phosphatase activity and in triacylglycerol’s content, compared with rats of group I, which indicates the effect of 2 % glycecin analogues on metabolic processes in animals.

The Effects of Gasomediators on the Са2+-Dependent Potassium Permeability of the Erythrocyte Membrane

We investigated the effects of the H2S and CO gasomediators on Ca2+-dependent potassium channels and an anion exchanger, which participate in the induction of the hyperpolarization response of the erythrocyte membrane and play an important role in regulation of the volume and deformability of erythrocytes. We showed that in the presence of H2S and CO donors, the amplitude of the redox-stimulated membrane hyperpolarization decreased significantly due to a decrease in the activity of Ca2+-dependent potassium channels. It was found that H2S and CO eliminate the compression of erythrocytes observed during activation of Ca2+-dependent potassium channels or inhibition of the anion exchanger. It was shown that the H2S donor significantly increases the erythrocyte deformability.

Experimental estimation of the effects of exogenous carbon monoxide on blood cells

The aim of the study was to investigate the effect of the carbon monoxide (CO) donor on the Ca 2+ -activated potassium permeability of the erythrocyte membrane and platelet aggregation ability. Materials and methods. Healthy volunteers ( n = 27) and patients with chronic coronary heart disease (CHD) ( n = 32) of both sexes were examined. The material of the study was packed red blood cells and platelet-rich plasma obtained from patient’s venous blood. The change of Ca 2+ -dependent potassium conductivity of the erythrocyte membrane was evaluated by potentiometric method, and the platelet aggregation was studied by turbidimetric method. Carbon monoxide releasing molecule-2 ( CORM-2) was used as a CO donor. The amplitude of A23187- and redox-induced hyperpolarization response (HR) of erythrocytes, and the rate and degree of platelet aggregation were estimated. Results. It was shown that the addition of CORM-2 (10 and 100 μM) in the erythrocyte suspension caused a dose-dependent decrease in the amplitude of A23187- and redox-dependent HR in healthy donors, as well as in patients with chronic CHD. The maximum decrease was observed in the presence of 100 μM CORM-2. The effect of CORM-2 at concentrations of 10 and 100 μM on collagen-induced platelet aggregation led to a decrease in the degree and rate of aggregation in healthy donors. The maximum effect was shown at 100 μM of CO donor. However, such an unambiguous effect of CORM-2 on the aggregation parameters in patients with CHD was not observed. Conclusion . The results suggest that CO has a significant effect on the ion transport function of the erythrocyte membrane and platelet aggregation activity of both healthy donors and patients with CHD.

Measuring the passive cuticular membrane permeability of potassium with a parallel artificial membrane permeability assay and the implications for foliar nutrient formulations

A modified PAMPA (parallel artificial membrane permeability assay) is proposed for evaluating the passive cuticular membrane permeability of potassium in several foliar nutrient formulations. The modified PAMPA can measure the passive permeability of ionic nutrients under fully hydrated conditions through an artificial membrane designed to more closely resemble a plant cuticle, rather than the traditional phospholipid animal model. Foliar nutrient formulations, which in some cases contain a complex organic matter component, may be evaluated with the modified PAMPA in order to develop better structure activity relationships that can help guide rational formulation development. In addition, mechanistic insights may also be uncovered with the simplified system.

Calibration and characterization of intracellular Asante Potassium Green probes, APG‐2 and APG‐4

The response of fluorescent ion probes to ions is affected by intracellular environment. To properly calibrate them, intracellular concentration of the measured ion must be made equal to its extracellular concentration. In the first, computational, part of this work, we show, using the example of potassium, that the two requirements for ion equilibration are complete dissipation of membrane potential and high membrane permeability for both potassium and sodium. In the second part, we tested the ability of various ionophores to achieve potassium equilibration in Jurkat and U937 cells and found a combination of valinomycin, nigericin, gramicidin and ouabain to be the most effective. In the third part, we applied this protocol to two Asante Potassium Green probes, APG‐4 and APG‐2. APG‐4 shows good sensitivity to potassium but its fluorescence is sensitive to protein density; therefore, calibration buffer had to be supplemented with 50 mM sucrose to keep cell volume constant. With these precautions taken, the average potassium concentrations in U937 and Jurkat cells were measured as 132 mM and 118 mM, respectively. The other tested probe, APG‐2, is non‐selective for cations; this is, however, a potentially useful property because the sum [K+] + [Na+] determines the amount of intracellular water.Support or Funding InformationThe research was partly supported by the Kent State University Research Council (MM) and by the Russian Fedration grant 0124‐2018‐0003 (VY and AV)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Calibration and characterization of intracellular Asante Potassium Green probes, APG-2 and APG-4

The response of fluorescent ion probes to ions is affected by intracellular environment. To properly calibrate them, intracellular and extracellular concentrations of the measured ion must be made equal. In the first, computational, part of this work, we show, using the example of potassium, that the two requirements for ion equilibration are complete dissipation of membrane potential and high membrane permeability for both potassium and sodium. In the second part, we tested the ability of various ionophores to achieve potassium equilibration in Jurkat and U937 cells and found a combination of valinomycin, nigericin, gramicidin and ouabain to be the most effective. In the third part, we applied this protocol to two potassium probes, APG-4 and APG-2. APG-4 shows good sensitivity to potassium but its fluorescence is sensitive to cell volume. Because ionophores cause cell swelling, calibration buffers had to be supplemented with 50 mM sucrose to keep cell volume constant. With these precautions taken, the average potassium concentrations in U937 and Jurkat cells were measured at 132 mM and 118 mM, respectively. The other tested probe, APG-2, is nonselective for cations; this is, however, a potentially useful property because the sum [K+] + [Na+] determines the amount of intracellular water.

Apolipoprotein L1 confers pH-switchable ion permeability to phospholipid vesicles

Apolipoprotein L1 (ApoL1) is a human serum protein conferring resistance to African trypanosomes, and certain ApoL1 variants increase susceptibility to some progressive kidney diseases. ApoL1 has been hypothesized to function like a pore-forming colicin and has been reported to have permeability effects on both intracellular and plasma membranes. Here, to gain insight into how ApoL1 may function in vivo, we used vesicle-based ion permeability, direct membrane association, and intrinsic fluorescence to study the activities of purified recombinant ApoL1. We found that ApoL1 confers chloride-selective permeability to preformed phospholipid vesicles and that this selectivity is strongly pH-sensitive, with maximal activity at pH 5 and little activity above pH 7. When ApoL1 and lipid were allowed to interact at low pH and were then brought to neutral pH, chloride permeability was suppressed, and potassium permeability was activated. Both chloride and potassium permeability linearly correlated with the mass of ApoL1 in the reaction mixture, and both exhibited lipid selectivity, requiring the presence of negatively charged lipids for activity. Potassium, but not chloride, permease activity required the presence of calcium ions in both the association and activation steps. Direct assessment of ApoL1-lipid associations confirmed that ApoL1 stably associates with phospholipid vesicles, requiring low pH and the presence of negatively charged phospholipids for maximal binding. Intrinsic fluorescence of ApoL1 supported the presence of a significant structural transition when ApoL1 is mixed with lipids at low pH. This pH-switchable ion-selective permeability may explain the different effects of ApoL1 reported in intracellular and plasma membrane environments.

A high concentration of DMSO activates caspase-1 by increasing the cell membrane permeability of potassium.

Dimethyl sulfoxide (DMSO) is widely used in the laboratory and in clinical situations because it is soluble in both aqueous and organic media and can be used to treat many types of diseases. Thus, it is meaningful to assess the comprehensive and in-depth biological activities of DMSO. Here, we showed that a high concentration of DMSO induced pro-inflammatory cytokine interleukin-1β (IL-1β) secretion from the monocytic cell line THP-1. DMSO-induced IL-1β secretion was dependent on intracellular caspase-1 activation. Further study revealed that the activation of caspase-1 by DMSO relied on NLRP3 inflammasome formation. It is generally accepted that the NLRP3 inflammasome is activated by reactive oxygen species generation or potassium efflux; however, the common NLRP3 inflammasome trigger remains controversial. Here, we showed that although DMSO is a ROS scavenger, this chemical increases membrane permeability and potassium efflux, and the formation of the NLRP3 inflammasome reflects the increased membrane permeability and potassium efflux induced by DMSO. The present study reveals a new characteristic of DMSO, which should be considered when using this chemical in either the laboratory or the clinic.

Análise geológica e petrofísica de um bloco de travertino como análogo de reservatório de hidrocarbonetos

Os carbonatos de origem microbialítica vêm ganhando espaço na geologia do petróleo visto a existência de diversos reservatórios compostos por essas litologias nos campos produtores do Pré-Sal. Dentre as rochas propostas como análogas aos microbialitos estão os travertinos, os estromatólitos e as tufas calcárias. Neste trabalho foi realizado o estudo de parâmetros geológicos, petrofísicos e geofísicos de um bloco de travertino de dimensões 1,60 x 1,60 x 2,70m, de 21,2 toneladas e disponível no Centro de Estudos de Petróleo (CEPETRO) na Universidade Estadual de Campinas. O bloco de origem italiana, denominado T-block, corresponde ao volume elementar representativo da formação de origem e permitiu o estudo em uma escala intermediária entre a escala de afloramento e a amostra de mão. Foram realizados ensaios de permeabilidade, medições de espectrometria de raios gama e obtenção da porosidade superficial por meio de análise de imagens. Modelos foram gerados a partir dos dados obtidos e então associados à geologia descritiva do bloco. Foi registrado um padrão de redução de permeabilidade, porosidade e concentração dos elementos potássio (K), urânio (U) e tório (Th), seguindo um gradiente em direção ao topo do T-block que acompanha a redução do grau de desenvolvimento da fábrica da rocha.

Regulation of Contractile Responses of Vascular Smooth Muscle Cells under Conditions of Hypoxia-Reoxygenation.

We analyzed the effects of hypoxia and reoxygenation on changes in contractile activity in rat aortic smooth muscles. Both hypoxia and reoxygenation induced relaxation of smooth muscle cells precontracted with high-potassium Krebs solution (30 mM KCl) or α1-adrenoceptor agonist phenylephrine. Vasodilation resulted from enhancement of potassium permeability of smooth muscle cell membranes caused by activation of voltage-gated potassium channels (triggered by both precontracting agents) or by opening of ATP-sensitive potassium channels (phenylephrine). In isolated smooth muscle cells, both hypoxia and inhibition of Na+,K+-ATPase with ouabain led to depletion of intracellular store of macroergic substances, reduced potassium concentration, and elevated the content of sodium ions.

The Effect of Zinc Nutrition on Two Olive (Olea europaea L.) Cultivars Components and Alleviate Oxidative Damage in Salinity Conditions

The role of zinc (Zn) in enhancing defense capacity of several plants against salinity has been demonstrated but there is limited information on the impact of Zn nutrition on alleviating salinity-induced oxidative damage in olive. One-year-old seedlings of two varieties of olive (Olea europaea L. cvs. Frontoio and Conservolea) supplied with three Zn levels (0, 1 and 5 mM in the form of ZnSO4.7H2O) were exposed to four salinity levels (0, 40, 80 and 120 mM NaCl). The increase in plasma membrane permeability and elevated leakage of potassium (K) and Zn from the olive roots were considered as indices of oxidative damage caused by salinity on root cells. In contrast, root membrane permeability and leakage of Zn and K ions in plants supplied with Zn was less than those non-supplied with Zn. Addition of Zn resulted in higher activity of CAT and APX. Higher salt-tolerance of Frontoio cultivar was associated with higher concentration of sulfhydryl (-SH) groups and lower membrane permeability of its roots in comparison with Conservolea cultivar. Based on the results obtained, addition of Zn improved plant enzymatic defense system and partly alleviated oxidative injuries induced by salinity on the olive.

Mathematical Modeling in Neuroscience: Neuronal Activity and Its Modulation by Astrocytes.

Mathematical Modeling in Neuroscience: Neuronal Activity and Its Modulation by Astrocytes.

Guide to the Pharmacology of Mitochondrial Potassium Channels.

This chapter provides a critical overview of the available literature on the pharmacology of mitochondrial potassium channels. In the first part, the reader is introduced to the topic, and eight known protein contributors to the potassium permeability of the inner mitochondrial membrane are presented. The main part of this chapter describes the basic characteristics of each channel type mentioned in the introduction. However, the most important and valuable information included in this chapter concerns the pharmacology of mitochondrial potassium channels. Several available channel modulators are critically evaluated and rated by suitability for research use. The last figure of this chapter shows the results of this evaluation at a glance. Thus, this chapter can be very useful for beginners in this field. It is intended to be a time- and resource-saving guide for those searching for proper modulators of mitochondrial potassium channels.

Decrease in an Inwardly Rectifying Potassium Conductance in Mouse Mammary Secretory Cells after Forced Weaning.

Mammary glands are physiologically active in female mammals only during nursing. Immediately after weaning, most lactation-related genes are downregulated and milk production ceases. In our previous study, we have detected an inwardly rectifying potassium channel (Kir) 2.1-like current in mammary secretory (MS) cells freshly isolated from lactating mice. This current is highly sensitive to external Ba2+. The potassium permeability of the Kir channels may contribute to the secretion and/or preservation of ions in milk. We hypothesized that the functions of the Kir channels in MS cells are regulated after weaning. To test this hypothesis, we examined the effect of forced weaning on the Ba2+-sensitive Kir current and Kir2.1 expression in the mouse mammary glands. Twenty-four hours after weaning, the lumina of mammary acini were histologically enlarged by milk accumulation. The whole-cell patch-clamp analyses showed that the Ba2+-sensitive Kir current in the post-weaning MS cells was smaller than in the lactating MS cells. The inward conductances of the current in the lactating and post-weaning cells were 4.25 ± 0.77 and 0.93 ± 0.34 nS, respectively. Furthermore, real-time PCR and Western blot analyses showed that Kir2.1 mRNA and protein expression decreased in the post-weaning mammary gland (mRNA, 90% reduction; protein, 47% reduction). Moreover, the local milk accumulation caused by teat sealing decreased Kir conductance in MS cells (2.74 ± 0.45 and 0.36 ± 0.27 nS for control and sealed mammary glands, respectively). This was concomitant with the reduction in the Kir2.1 mRNA expression. Our results suggest that milk stasis after weaning immediately decreases the Kir conductance in MS cells. This decrease in the Kir conductance may be partly caused by the reduction in the Kir2.1 mRNA and protein expression. These alterations during the post-weaning period may be involved in the cessation of ion secretion and/or preservation in the milk.