scholarly journals The Role of Anisotropy in Distinguishing Domination of Néel or Brownian Relaxation Contribution to Magnetic Inductive Heating: Orientations for Biomedical Applications

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1875
Author(s):  
Luu Nguyen ◽  
Pham Phong ◽  
Pham Nam ◽  
Do Manh ◽  
Nguyen Thanh ◽  
...  
Keyword(s):  
Magnetic Nanoparticles ◽  
Heating Power ◽  
Inductive Heating ◽  
High K ◽  
Potential Applications ◽  
Viscous Media ◽  
Low K ◽  
Viscosity Dependence ◽  
Good Agreement

Magnetic inductive heating (MIH) has been a topic of great interest because of its potential applications, especially in biomedicine. In this paper, the parameters characteristic for magnetic inductive heating power including maximum specific loss power (SLPmax), optimal nanoparticle diameter (Dc) and its width (ΔDc) are considered as being dependent on magnetic nanoparticle anisotropy (K). The calculated results suggest 3 different Néel-domination (N), overlapped Néel/Brownian (NB), and Brownian-domination (B) regions. The transition from NB- to B-region changes abruptly around critical anisotropy Kc. For magnetic nanoparticles with low K (K < Kc), the feature of SLP peaks is determined by a high value of Dc and small ΔDc while those of the high K (K > Kc) are opposite. The decreases of the SLPmax when increasing polydispersity and viscosity are characterized by different rates of d(SLPmax)/dσ and d(SLPmax)/dη depending on each domination region. The critical anisotropy Kc varies with the frequency of an alternating magnetic field. A possibility to improve heating power via increasing anisotropy is analyzed and deduced for Fe3O4 magnetic nanoparticles. For MIH application, the monodispersity requirement for magnetic nanoparticles in the B-region is less stringent, while materials in the N- and/or NB-regions are much more favorable in high viscous media. Experimental results on viscosity dependence of SLP for CoFe2O4 and MnFe2O4 ferrofluids are in good agreement with the calculations. These results indicated that magnetic nanoparticles in the N- and/or NB-regions are in general better for application in elevated viscosity media.

scholarly journals Aldosterone-dependent and -independent regulation of Na+ and K+ excretion and ENaC in mouse kidneys

2020 ◽  
Vol 319 (2) ◽  
pp. F323-F334
Author(s):  
Lei Yang ◽  
Gustavo Frindt ◽  
Yuanyuan Xu ◽  
Shinichi Uchida ◽  
Lawrence G. Palmer
Keyword(s):  
Glomerular Filtration Rate ◽  
Western Blot ◽  
Filtration Rate ◽  
Ex Vivo ◽  
Western Blots ◽  
High K ◽  
Collecting Ducts ◽  
Low K ◽  
Clearance Methods

We investigated the regulation of Na+ and K+ excretion and the epithelial Na+ channel (ENaC) in mice lacking the gene for aldosterone synthase (AS) using clearance methods to assess excretion and electrophysiology and Western blot analysis to test for ENaC activity and processing. After 1 day of dietary Na+ restriction, AS−/− mice lost more Na+ in the urine than AS+/+ mice did. After 1 wk on this diet, both genotypes strongly reduced urinary Na+ excretion, but creatinine clearance decreased only in AS−/− mice. Only AS+/+ animals exhibited increased ENaC function, assessed as amiloride-sensitive whole cell currents in collecting ducts or cleavage of αENaC and γENaC in Western blots. To assess the role of aldosterone in the excretion of a K+ load, animals were fasted overnight and refed with high-K+ or low-K+ diets for 5 h. Both AS+/+ and AS−/− mice excreted a large amount of K+ during this period. In both phenotypes the excretion was benzamil sensitive, indicating increased K+ secretion coupled to ENaC-dependent Na+ reabsorption. However, the increase in plasma K+ under these conditions was much larger in AS−/− animals than in AS+/+ animals. In both groups, cleavage of αENaC and γENaC increased. However, Na+ current measured ex vivo in connecting tubules was enhanced only in AS+/+ mice. We conclude that in the absence of aldosterone, mice can conserve Na+ without ENaC activation but at the expense of diminished glomerular filtration rate. Excretion of a K+ load can be accomplished through aldosterone-independent upregulation of ENaC, but aldosterone is required to excrete the excess K+ without hyperkalemia.

scholarly journals MicroRNA-194 (miR-194) regulates ROMK channel activity by targeting intersectin 1

2014 ◽  
Vol 306 (1) ◽  
pp. F53-F60 ◽  
Author(s):  
Dao-Hong Lin ◽  
Peng Yue ◽  
Chengbiao Zhang ◽  
Wen-Hui Wang
Keyword(s):  
Collecting Duct ◽  
Luciferase Reporter ◽  
Pcr Analysis ◽  
Seed Sequence ◽  
Cortical Collecting Duct ◽  
Channel Activity ◽  
Luciferase Reporter Gene ◽  
High K ◽  
Low K

The aim of the study is to explore the role of miR-194 in mediating the effect of high-K (HK) intake on ROMK channel. Northern blot analysis showed that miR-194 was expressed in kidney and that HK intake increased while low-K intake decreased the expression of miR-194. Real-time PCR analysis further demonstrated that HK intake increased the miR-194 expression in the cortical collecting duct. HK intake decreased the expression of intersectin 1 (ITSN1) which enhanced With-No-Lysine Kinase (WNK)-induced endocytosis of ROMK. Expression of miR-194 mimic decreased luciferase reporter gene activity in HEK293 T cells transfected with ITSN-1–3′UTR containing the complementary seed sequence for miR-194. In contrast, transfection of miR-194 inhibitor increased the luciferase activity. This effect was absent in the cells transfected with mutated 3′UTR of ITSN1 in which the complimentary seed sequence was deleted. Moreover, the inhibition of miR-194 expression increased the protein level of endogenous ITSN1 in HEK293T cells. Expression of miR-194 mimic also decreased the translation of exogenous ITSN1 in the cells transfected with the ITSN1 containing 3′UTR but not with 3′UTR-free ITSN1. Expression of pre-miR-194 increased K currents and ROMK expression in the plasma membrane in ROMK-transfected cells. Coexpression of ITSN1 reversed the stimulatory effect of miR-194 on ROMK channels. This effect was reversed by coexpression of ITSN1. We conclude that miR-194 regulates ROMK channel activity by modulating ITSN1 expression thereby enhancing ITSN1/WNK-dependent endocytosis. It is possible that miR-194 is involved in mediating the effect of a HK intake on ROMK channel activity.

scholarly journals Dependence of mammalian putrescine and spermidine transport on plasma-membrane potential: identification of an amiloride binding site on the putrescine carrier

1998 ◽  
Vol 330 (3) ◽  
pp. 1283-1291 ◽  
Author(s):  
Richard POULIN ◽  
Chenqi ZHAO ◽  
Savita VERMA ◽  
René CHAREST-GAUDREAULT ◽  
Marie AUDETTE
Keyword(s):  
Plasma Membrane ◽  
Membrane Potential ◽  
Binding Site ◽  
Biochemical Properties ◽  
Mitochondrial Potential ◽  
Plasma Membrane Potential ◽  
High K ◽  
Polyamine Transport ◽  
Low K

The mechanism of mammalian polyamine transport is poorly understood. We have investigated the role of plasma-membrane potential (ΔΨpm) in putrescine and spermidine uptake in ZR-75-1 human breast cancer cells. The rate of [3H]putrescine and [3H]spermidine uptake was inversely correlated to extracellular [K+] ([K+]o) and to ΔΨpm, as determined by the accumulation of [3H]tetraphenylphosphonium bromide (TPP). Inward transport was unaffected by a selective decrease in mitochondrial potential (ΔΨmit) induced by valinomycin at low [K+]o, but was reduced by ≈ 60% by the rheogenic protonophore carbonylcyanide m-chlorophenylhydrazone (CCCP), which rapidly (≤ 15 min) collapsed both ΔΨpm and ΔΨmit. Plasma-membrane depolarization by high [K+]o or CCCP did not enhance putrescine efflux in cells pre-loaded with [3H]putrescine, suggesting that decreased uptake caused by these agents did not result from a higher excretion rate. On the other hand, the electroneutral K+/H+ exchanger nigericin (10 μM) co-operatively depressed [3H]TPP, [3H]putrescine and [3H]spermidine uptake in the presence of ouabain. Suppression of putrescine uptake by nigericin+ouabain was Na+-dependent, suggesting that plasma-membrane repolarization by the electrogenic Na+ pump was required upon acidification induced by nigericin, due to the activation of the Na+/H+ antiporter. The sole addition of 5-N,N-hexamethylene amiloride, a potent inhibitor of the Na+/H+ antiporter, strongly inhibited putrescine uptake in a competitive fashion [Ki 4.0±0.9 (S.D.) μM], while being a weaker antagonist of spermidine uptake. The potency of a series of amiloride analogues to inhibit putrescine uptake was clearly different from that of the Na+/H+ antiporter, and resembled that noted for Na+ co-transport proteins. These data demonstrate that putrescine and spermidine influx is mainly unidirectional and strictly depends on ΔΨpm, but not ΔΨmit. This report also provides first evidence for a high-affinity amiloride-binding site on the putrescine carrier, which provides new insight into the biochemical properties of this transporter.

Control of capillary hydraulic conductivity via membrane potential-dependent changes in Ca2+ influx

1992 ◽  
Vol 262 (1) ◽  
pp. H144-H148 ◽  
Author(s):  
R. S. Zhang ◽  
V. H. Huxley
Keyword(s):  
Membrane Potential ◽  
Repeated Measures ◽  
Chloride Concentration ◽  
Barrier Properties ◽  
Extracellular Potassium ◽  
High K ◽  
Important Regulator ◽  
Low K

Capillary permeability has been shown to be sensitive to the levels of intracellular calcium. We examined the role of membrane potential in the regulation of capillary water permeability by a Ca2+ leak mechanism. Repeated measures of Lp were taken in situ on individually perfused mesenteric capillaries of cerebrally pithed frogs (Rana pipiens). A rise in extracellular potassium ([K+]o) to 24 mM induced a 45% decrease in Lp (n = 20), whereas lowering [K+]o to 0.24 mM elevated Lp by twofold (n = 9). To investigate whether these changes in Lp were due specifically to changes in membrane potential and consequent changes in the driving force for Ca2+ influx, we performed the following experiments: 1) [K+]o was elevated while the product of [K+]o and extracellular chloride concentration [Cl-]o was kept constant, 2) [K+]o was elevated under nominally Ca(2+)-free conditions, 3) K+ leak was induced by addition of 10 microM valinomycin, and 4) Na(+)-K+ pump was blocked by 10 microM ouabain. A constant [K+]o [Cl-]o product did not prevent high K+ from lowering Lp. Nominally Ca(2+)-free conditions abolished the effect of high K+. Valinomycin mimicked the response to low K+, and ouabain failed to change Lp. The data from this study conform to the hypothesis that membrane potential is an important regulator of capillary barrier properties via changes in Ca2+ influx through leak channels.

scholarly journals Modulation of NCC activity by low and high K+ intake: insights into the signaling pathways involved

2014 ◽  
Vol 306 (12) ◽  
pp. F1507-F1519 ◽  
Author(s):  
María Castañeda-Bueno ◽  
Luz Graciela Cervantes-Perez ◽  
Lorena Rojas-Vega ◽  
Isidora Arroyo-Garza ◽  
Norma Vázquez ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Metabolic Alkalosis ◽  
Plasma Aldosterone ◽  
Ang Ii ◽  
High K ◽  
The Face ◽  
Low K ◽  
Positive Effect ◽  
Genetic Mouse Models

Modulation of Na+-Cl− cotransporter (NCC) activity is essential to adjust K+ excretion in the face of changes in dietary K+ intake. We used previously characterized genetic mouse models to assess the role of Ste20-related proline-alanine-rich kinase (SPAK) and with-no-lysine kinase (WNK)4 in the modulation of NCC by K+ diets. SPAK knockin and WNK4 knockout mice were placed on normal-, low-, or high-K+-citrate diets for 4 days. The low-K+ diet decreased and high-K+ diet increased plasma aldosterone levels, but both diets were associated with increased phosphorylation of NCC (phospho-NCC, Thr44/Thr48/Thr53) and phosphorylation of SPAK/oxidative stress responsive kinase 1 (phospho-SPAK/OSR1, Ser383/Ser325). The effect of the low-K+ diet on SPAK phosphorylation persisted in WNK4 knockout and SPAK knockin mice, whereas the effects of ANG II on NCC and SPAK were lost in both mouse colonies. This suggests that for NCC activation by ANG II, integrity of the WNK4/SPAK pathway is required, whereas for the low-K+ diet, SPAK phosphorylation occurred despite the absence of WNK4, suggesting the involvement of another WNK (WNK1 or WNK3). Additionally, because NCC activation also occurred in SPAK knockin mice, it is possible that loss of SPAK was compensated by OSR1. The positive effect of the high-K+ diet was observed when the accompanying anion was citrate, whereas the high-KCl diet reduced NCC phosphorylation. However, the effect of the high-K+-citrate diet was aldosterone dependent, and neither metabolic alkalosis induced by bicarbonate, nor citrate administration in the absence of K+ increased NCC phosphorylation, suggesting that it was not due to citrate-induced metabolic alkalosis. Thus, the accompanying anion might modulate the NCC response to the high-K+ diet.

scholarly journals The effect of sodium on the mineral balance of plants, using the example of root celery and stalk celery. Part I. The role of sodium and potassium in the process of accumulation and utilization of mineral elements

2013 ◽  
Vol 41 (2) ◽  
pp. 295-314
Author(s):  
Urszula Kruszelnicka
Keyword(s):  
Nutrient Medium ◽  
Mineral Elements ◽  
Antagonistic Effect ◽  
Apium Graveolens ◽  
Mineral Balance ◽  
High K ◽  
Mineral Components ◽  
Low K ◽  
Sodium And Potassium

In the years 1977 - 1980, studies were conducted on the effect of sodium used to supplement low (K = 800 mg/5 kg) and high (K = 1400 mg/5 kg) potassium doses on the content of mineral components, their accumulation in the yield and the percentage of their utilization. The study was carried out on root celery - <i>Apium graveolens</i> L. var. <i>rapaceum</i> (Mill.) and stalk celery - <i>Apium graveolens</i> L. var. <i>dulce</i> (Mill.). The results obtained in these experiments point to the following conclusions: it was found that potassium and sodium mutually limit each other's uptake. Sodium was more antagonistic towards the uptake of calcium than was potassium. However, no clearly antagonistic effect of these elements on the uptake of magnesium was determined. The accumulation of potassium and sodium by the experimental plants rose while the percentage of utilization of these elements decreased as their level in the nutrient medium increased. Sodium exerted a more distinct effect on the accumulation and utilization of other mineral elements than did potassium.

Modulatory role of endothelial calcium level in vascular tension of canine depolarized coronary arteries

1998 ◽  
Vol 274 (2) ◽  
pp. H494-H499 ◽  
Author(s):  
Kazuo Sato ◽  
Jun Yamazaki ◽  
Taku Nagao
Keyword(s):  
Smooth Muscle ◽  
Coronary Arteries ◽  
Muscle Tone ◽  
Typical Characteristic ◽  
Entry Pathway ◽  
High K ◽  
Intracellular Ca ◽  
The Relationship ◽  
Low K

The vascular tension in the coronary artery is modulated by factors released by endothelial cells. We investigated the relationship between the Ca2+ level in endothelium and endothelium-mediated changes in smooth muscle tone in high K+-depolarized canine coronary arteries by measuring intracellular Ca2+ concentration fluorimetrically with the Ca2+indicator fura 2. Addition of Ca2+(1 mM) caused an increase in endothelial Ca2+ and relaxed the 30 mM K+-depolarized arteries following inhibition of Ca2+ influx in the smooth muscle with diltiazem. This relaxation was inhibited by N G-monomethyl-l-arginine. As extracellular K+ concentration was decreased, increases of endothelial Ca2+ were augmented, whereas the relaxation was decreased. Basal muscle tone was found to be decreased in low K+ by measuring relaxation by sodium nitroprusside. These results suggest the importance of Ca2+ level in the endothelium in playing a modulatory role in coronary tension through the production of nitric oxide. The correlation of extracellular K+ to Ca2+ level in the endothelium indicates a typical characteristic of the passive Ca2+ entry pathway in the endothelium, whereas the resultant relaxation appears to be restricted by the basal muscle tone.

The contemporaneous emission of low-K and high-K trachybasalts and the role of the NE Rift during the 2002 eruptive event, Mt. Etna, Italy

2008 ◽  
Vol 71 (5) ◽  
pp. 575-587 ◽  
Author(s):  
C. Ferlito ◽  
M. Coltorti ◽  
R. Cristofolini ◽  
P. P. Giacomoni
Keyword(s):  
Eruptive Event ◽  
High K ◽  
Mt Etna ◽  
Low K ◽  
Ne Rift

ELECTRON SCATTERING IN BURIED InGaAs/HIGH-K MOS CHANNELS

2011 ◽  
Vol 20 (01) ◽  
pp. 95-103 ◽  
Author(s):  
S. OKTYABRSKY ◽  
P. NAGAIAH ◽  
V. TOKRANOV ◽  
M. YAKIMOV ◽  
R. KAMBHAMPATI ◽  
...  
Keyword(s):  
Dominant Role ◽  
Interface Layer ◽  
Barrier Thickness ◽  
Channel Mobility ◽  
High K ◽  
Amorphous Si ◽  
Inp Substrates ◽  
Low K

Hall electron mobility in buried QW InGaAs channels, grown on InP substrates with HfO 2 gate oxide, is analyzed experimentally and theoretically as a function of top barrier thickness and composition, carrier density, and temperature. Temperature slope α in μ ~Tα dependence is changing from α=-1.1 to +1 with the reduction of the top barrier thickness indicating the dominant role of remote Coulomb scattering (RCS) in interface-related contribution to mobility degradation. Insertion of low-k SiO x interface layer formed by oxidation of thin in-situ MBE grown amorphous Si passivation layer has been found to improve the channel mobility, but at the expense of increased EOT. This mobility improvement is also consistent with dominant role of RCS. We were able to a obtain a reasonable match between experiment and simple theory of the RCS assuming the density of charges at the high-k/barrier interface to be in the range of (2-4)×1013 cm-2.

Electron Probe Analysis of Vertebrate Smooth Muscle: Distribution of Ca and Ci

1976 ◽  
Vol 34 ◽  
pp. 334-335 ◽  
Author(s):  
Avril V. Somlyo ◽  
H. Shuman ◽  
A.P. Somlyo
Keyword(s):  
Smooth Muscle ◽  
Electron Probe ◽  
Preliminary Report ◽  
Cell Damage ◽  
Electron Probe Analysis ◽  
Perinuclear Space ◽  
Probe Analysis ◽  
High K ◽  
Low K ◽  
Initial Results

This is a preliminary report of electron probe analysis of rabbit portal-anterior mesenteric vein (PAMV) smooth muscle cryosectioned without fixation or cryoprotection. The instrumentation and method of electron probe quantitation used (1) and our initial results with cardiac (2) and skeletal (3) muscle have been presented elsewhere.In preparations depolarized with high K (K2SO4) solution, significant calcium peaks were detected over the sarcoplasmic reticulum (Fig 1 and 2) and the continuous perinuclear space. In some of the fibers there were also significant (up to 200 mM/kg dry wt) calcium peaks over the mitochondria. However, in smooth muscle that was not depolarized, high mitochondrial Ca was found in fibers that also contained elevated Na and low K (Fig 3). Therefore, the possibility that these Ca-loaded mitochondria are indicative of cell damage remains to be ruled out.

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