Hemodialysis using a Constant Potassium Gradient: Rationale of a Multicenter Study

1995 ◽  
Vol 18 (11) ◽  
pp. 731-734
Author(s):  
B. Redaelli ◽  
D. Limido ◽  
P. Beretta ◽  
M.R. Viganò
Keyword(s):  
Experimental Studies ◽  
Plasma Potassium ◽  
Resting Membrane Potential ◽  
Membrane Hyperpolarization ◽  
Kd Values ◽  
Clinical Consequences ◽  
K Concentration ◽  
The Impact ◽  
The Relationship ◽  
Potassium Gradient

The aim of this study is to evaluate the relationship between two different procedures for potassium removal during hemodialysis (HD) and cardiac arrhythmias. Cell excitability and the transmission of impulses may be influenced by variations of resting membrane potential (RMP). The rapid decrease of plasma potassium during the first two hours of standard HD causes a membrane hyperpolarization. A different K+ kinetic, with a gradual and constant elimination of K+ during HD, may reduce this further unphysiological aspect and its clinical consequences. This can be obtained keeping blood-dialysate K+ gradient as constant as possible with the use of a dialysate K+ concentration (Kd) decreasing during HD. Our experimental studies on various K+ intradialytic gradients seem to indicate as optimal to this purpose K+ gradients of 1.5 mEq/l at the beginning of dialysis, esponentially decreasing during treatment to Kd values of 2.5 mEq/l at the end of dialysis (variable Kd). Patients included in the trial will be submitted to two different methods of treatment with Kd 2 mEq/l and variable Kd, and to a 24 hours ECG the day of dialysis. We will compare the number of intra and interdialytic premature ventricular complexes to evaluate the impact of two different models of potassium removal on arrhythmias.

TRH-induced membrane hyperpolarization in rat clonal anterior pituitary cells

1985 ◽  
Vol 248 (1) ◽  
pp. E64-E69
Author(s):  
S. Ozawa
Keyword(s):  
Reversal Potential ◽  
Membrane Conductance ◽  
Gh3 Cells ◽  
Ionophore A23187 ◽  
Pituitary Cells ◽  
Bathing Medium ◽  
Membrane Hyperpolarization ◽  
K Concentration ◽  
The Relationship ◽  
Reversal Potentials

Thyrotropin-releasing hormone (TRH) induces biphasic membrane potential changes, a transient hyperpolarization followed by a prolonged enhancement of the generation of action potentials in the clonal GH3 pituitary cell. The nature of the TRH-induced hyperpolarization was studied in Cl--free solutions. Among various test substances, only TRH and its analogue, which stimulates the release of prolactin from the GH3 cells, were capable of inducing the transient membrane hyperpolarization. The Ca2+ ionophore A23187 also caused a transient hyperpolarization accompanied by an increase in the membrane conductance, although it failed to mimic the late facilitation of spike generation. The reversal potential of the TRH-induced hyperpolarization was identical with that induced by A23187. Reduction of the K+ concentration of the bathing medium caused a similar shift of both these reversal potentials toward a more hyperpolarized level. Injection of the Ca2+-chelator EGTA into the cell suppressed both TRH and Ca2+ ionophore-induced hyperpolarizations. These results suggest that TRH mobilizes the cellular-bound Ca, which in turn activates Ca2+-mediated K+ channels, thus causing the transient membrane hyperpolarization. The relationship between the membrane hyperpolarization and the TRH-stimulated hormone release is discussed.

The Growth of Vortices in the Vicinity of a Wall of Elastic Moving Airfoils

2013 ◽  
Author(s):  
Masaki Fuchiwaki ◽  
Tomoki Kurinami ◽  
Kazuhiro Tanaka
Keyword(s):  
Flow Field ◽  
Elastic Body ◽  
Elastic Deformation ◽  
Growth Process ◽  
Experimental Studies ◽  
Strain Component ◽  
Pitching Airfoil ◽  
The Impact ◽  
The Relationship ◽  
Significant Attention

There have been a number of studies on the flow field around a pitching airfoil and a heaving airfoil. Especially, the relationship between the wake structure and the characteristics of dynamic thrust has been clarified. Recently, the flow field around an elastic body has been attracted significant attention and the flow field is treated as a coupled problem between the fluid and structure. The flow field around an elastic body has been investigated primarily by numerical means, and there have been experimental studies. However, the details of the impact of elastic deformation effects on the growth process of vortices generated in the vicinity of the wall have not been clarified. In this study, we investigate the growth process of vortices generated in the vicinity of the wall of elastic moving airfoils experimentally. The elastic NACA0010 generates vortices in a large region of a wall and rolls up vortices, with the vortices growing gradually toward the trailing edge as a result of elastic deformation. The elastic NACA0010 has a characteristic whereby vortices having a rotational component that is stronger than the shear-strain component due to the vorticities in the vicinity of a wall of the elastic NACA0010 change not only spatial change of x- and y-components.

Stimulation of prolactin release by dopamine withdrawal: role of membrane hyperpolarization

1994 ◽  
Vol 267 (5) ◽  
pp. E781-E788 ◽  
Author(s):  
K. A. Gregerson ◽  
N. Golesorkhi ◽  
R. Chuknyiska
Keyword(s):  
Resting Membrane Potential ◽  
Prolactin Release ◽  
Membrane Hyperpolarization ◽  
Basal Release ◽  
K Concentration ◽  
Hypothalamic Dopamine ◽  
Ca2 Channels ◽  
Stimulation Of ◽  
External K

Hypothalamic dopamine (DA) tonically inhibits prolactin (PRL) release from the anterior pituitary gland, whereas removal of DA markedly augments its release to values exceeding pre-DA rates. We investigated whether electrical events induced by DA contribute to this secretory rebound. In primary cultured lactotropes, spontaneous Ca(2+)-dependent spiking activity was enhanced after recovery from DA-induced hyperpolarization. Voltage clamp studies showed a rapidly and a slowly inactivating Ca2+ current that were both augmented by a hyperpolarizing conditioning potential. We measured PRL release from perifused cells exposed to DA to correlate the electrical with the secretory responses. DA inhibited PRL release by 67%, whereas PRL secretion increased three- to fourfold over basal release after washout of DA. Valinomycin, used to directly hyperpolarize the cell membrane, mimicked the actions of DA, inhibiting PRL release (65%) and, upon washout, augmenting PRL secretion. Blocking the DA- or valinomycin-induced hyperpolarization by elevating external K+ concentration blocked both the inhibition and rebound of PRL release. These novel results demonstrate that hyperpolarization of the lactotrope membrane by DA is critical for the development of PRL rebound after DA withdrawal. We hypothesize the mechanism involves the removal of inactivation from a population of Ca2+ channels, leading to enhanced Ca2+ influx and PRL release upon recovery of the resting membrane potential after DA removal.

Parotid Clearance of Sodium and Potassium

1958 ◽  
Vol 195 (3) ◽  
pp. 693-696 ◽  
Author(s):  
L. L. Langley ◽  
C. H. Gunthorpe ◽  
W. A. Beall
Keyword(s):  
Precursor Solution ◽  
Plasma Potassium ◽  
Salivary Flow ◽  
Low Flow ◽  
Parotid Saliva ◽  
Flow Rates ◽  
K Concentration ◽  
Potassium Clearance ◽  
The Relationship ◽  
Sodium And Potassium

A current hypothesis suggests that the mechanism of salivary production involves the formulation of a precursor solution followed by reabsorption of sodium and water but not potassium. Since this is similar to kidney physiology, clearance techniques were used to test the hypothesis. At parotid flow rates below about 0.2 cc/min. the concentration of Na varies directly and that of K indirectly with the flow. At higher rates the K concentration is independent of the flow and closely approximates that of the plasma. Potassium clearance, then, is independent of flow only at very low flows. The concentration of Na in parotid saliva varies with that in the plasma. Extrapolation of the curve cuts the abscissa at a point indicating that if the plasma Na concentration were reduced below approximately 100 mEq/l. no Na would appear in the saliva. The relationship between plasma concentration and the saliva Na/plasma Na ratio is an ascending curve. As the plasma K concentration increases so does the concentration in the parotid saliva. Extrapolation of this curve approaches the origin. The saliva K/plasma K ratio is independent of the plasma K concentration. When K is infused salivary flow rate increases. The infusion of Na decreases flow. These results are consistent with the selective reabsorption theory at low flow rates but there must be another mechanism to explain the findings at higher flows. It is suggested that the influence of Na and K infusion on salivation may be, at least partially, indirect.

scholarly journals Features of technological processing of seeds with an electromagnetic field of microwave before sowing

2021 ◽  
Vol 845 (1) ◽  
pp. 012142
Author(s):  
S V Vendin
Keyword(s):  
Microwave Heating ◽  
Crop Production ◽  
Heating Temperature ◽  
Experimental Studies ◽  
Microwave Treatment ◽  
Microwave Exposure ◽  
Soil Preparation ◽  
Technological Processing ◽  
The Impact ◽  
The Relationship

Abstract To increase the efficiency of crop production in the arsenal of the agronomic service there is a number of techniques, methods and technologies that reveal the potential of agricultural plants for all stages of production, starting with soil preparation, selection and preparation of seeds for sowing, agrotechnological measures during the growing season, harvesting technologies, storage and processing of products. The article presents the results of experimental studies on the use of the energy of ultra-high frequency electromagnetic fields for pre-sowing treatment of lupine seeds in order to increase their germination. Revealed the relationship between the parameters of microwave exposure and seed germination. The areas of modes where microwave treatment allows to increase germination, as well as areas of modes in which the impact does not reach the planned effect, or has a negative (depressing) effect, have been determined. Recommendations are given for ensuring the optimal modes of microwave processing and ensuring control of the parameters of the technological process. Based on the results obtained, it can be reliably asserted that the region of microwave treatment of lupine seeds, with a result exceeding the control values, is observed at exposure in the range from 50 to 60 s and at a specific microwave power of exposure from 1.0 to 1.17 kW/kg. The best result of an increase in germination by 1.5% was obtained at 60 s and 1.17 kW/kg. When treating seeds, it is recommended to maintain an average microwave heating rate of 0.50 °C/s until an average microwave heating temperature of 51.5 °C is reached.

An Exploration of the Effects of Photograph Content, Photograph Source, and Price on Consumers’ Online Travel Booking Intentions

2018 ◽  
Vol 59 (1) ◽  
pp. 120-139 ◽  
Author(s):  
Yoojin Shin ◽  
Breffni M. Noone ◽  
Stephani K. A. Robson
Keyword(s):  
Experimental Studies ◽  
Cost Effective ◽  
Information Value ◽  
Consumer Reaction ◽  
Booking Intentions ◽  
Online Travel ◽  
Relationship Of ◽  
The Impact ◽  
The Relationship

This research employed two experimental studies to examine the relationship of photograph content with consumers’ online travel booking intentions, the role of photograph source in this relationship, and the impact of photograph content on consumer reaction to price. Study 1’s findings suggest that perceived information value mediates the effect of photograph content on consumers’ booking intentions, with product-focused photographs perceived as being higher in information value than experience-focused photographs. Further, perceived photograph credibility was found to influence consumer reaction to photograph content, with photograph source moderating the photograph content-perceived photograph credibility relationship. Study 2’s findings suggest that photograph content moderates the price–booking intentions relationship. When the price is higher than the average in the market, consumers are likely to rely more heavily on product-focused photographs than on experience-focused photographs to inform the booking decision. Together, the findings of these studies can guide travel marketers in developing cost-effective, photograph-based online content.

Mechanism of the Effect of Acetate on Frog Ventricular Muscle

1974 ◽  
Vol 52 (3) ◽  
pp. 404-423 ◽  
Author(s):  
Esther R. Anderson ◽  
J. G. Foulks
Keyword(s):  
Membrane Potential ◽  
Resting Membrane Potential ◽  
Acetate Solution ◽  
Tension Development ◽  
Electrogenic Transport ◽  
K Concentration ◽  
Reduced Rate ◽  
Induced Changes ◽  
The Relationship ◽  
Frog Ventricle

Substitution of acetate for external Cl produced a large persistent increase in the resting membrane potential (R.M.P.) of frog ventricle and a somewhat steeper relation between membrane potential (M.P.) and [K]o (external K concentration). An increased K conductance or reduced permeability to other ions could account for most of these results, but not for hyperpolarizations as great as −110 mV. Potentials of this size suggested a contribution from an active electrogenic transport system, but they were unaffected by several treatments including exposure to ouabain (10−7 M − 5 × 10−6 M), dinitrophenol (10−6 M, 10−5 M) or 30 mM tetraethylammonium.Acetate caused a prolongation of the action potential (A.P.) and a change in its configuration. Acetate also enhanced twitch tension and increased the rate of tension development. Similar changes are produced by removal of [K]o. The effects of both acetate and K removal on A.P. configuration were prevented by a reduced rate of stimulation.When acetate-induced hyperpolarization was reversed by raising [K]o to 10–15 mM, the configuration of the A.P. resembled that of controls and twitch tension did not increase. Thus, acetate-induced changes in the shape of the A.P. and in twitch tension appeared to be secondary to the increase in R.M.P. However, the relationship does not seem to be direct because these changes were temporary, whereas hyperpolarization was persistent.The character of the acetate-induced changes in A.P. configuration, and the dependence on stimulation rate and [Ca]o (external Ca concentration), suggested a raised [Ca]i (internal Ca concentration) and a possible increase in Ca influx. However, addition of Mn to the acetate solution did not prevent initial acetate-induced changes in the shape of the A.P. plateau and in twitch tension. Also in the absence of [Ca]o, disappearance of twitch tension was slowed by acetate. But acetate decreased the contracture tension produced in response to either increased [K]o or Na removal. Acetate may cause a redistribution of Ca within the cell.

scholarly journals Unified Theory for Flexural Strengthening of Masonry with Composites

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 680 ◽  
Author(s):  
Giancarlo Ramaglia ◽  
Francesco Fabbrocino ◽  
Gian Lignola ◽  
Andrea Prota
Keyword(s):  
Experimental Studies ◽  
Flexural Behavior ◽  
Strongly Correlated ◽  
General Validity ◽  
Flexural Strengthening ◽  
Strain Relationship ◽  
Low Efficiency ◽  
The Impact ◽  
The Relationship ◽  
Further Development

Recent calamitous events have shown the fragility of the existing masonry buildings. Many of them are heritage structures, such as churches and monumental buildings. Therefore, optimized strengthening strategies are necessary. Experimental studies performed on masonry elements strengthened with composite systems have shown the performance of these materials. However, further development is necessary to optimize the intervention strategies. In fact, due to the lack of general validity models, the design is usually based on prescriptive approaches according to manufacturers’ broad instructions, often producing systems with low efficiency and overestimations of the amount of reinforcement. In this paper a generalized approach is proposed to assess the flexural behavior of masonry sections strengthened with composites. The proposed theory has allowed performance of a sensitivity analysis assessing the impact both of the mechanical parameters of masonry and of the strengthening system. In particular, the impact of several constitutive relationships of composites (linear, bilinear, or trilinear) have been evaluated in terms of ultimate behavior of the strengthened masonry. For strengthening systems more compatible with the masonry substrate, the form of the stress–strain relationship becomes a key aspect. For such cases, the modeling of the reinforcement plays a fundamental role and the form of the relationship is strongly correlated to the type of reinforcement selected, e.g., organic versus inorganic matrix.

scholarly journals Microbiota and Immune-Mediated Skin Diseases—An Overview

2019 ◽  
Vol 7 (9) ◽  
pp. 279 ◽  
Author(s):  
Adrian Catinean ◽  
Maria Adriana Neag ◽  
Andrei Otto Mitre ◽  
Corina Ioana Bocsan ◽  
Anca Dana Buzoianu
Keyword(s):  
Autoimmune Diseases ◽  
Beneficial Effect ◽  
Skin Diseases ◽  
Experimental Studies ◽  
Immune Mediated ◽  
The Impact ◽  
The Relationship

In recent years, increased attention has been paid to the relationship between microbiota and various diseases, especially immune-mediated diseases. Because conventional therapy for many autoimmune diseases is limited both in efficacy and safety, there is an increased interest in identifying nutraceuticals, particularly probiotics, able to modulate the microbiota and ameliorate these diseases. In this review, we analyzed the research focused on the role of gut microbiota and skin in immunity, their role in immune-mediated skin diseases (IMSDs), and the beneficial effect of probiotics in patients with this pathology. We selected articles published between 2009 and 2019 in PubMed and ScienceDirect that provided information regarding microbiota, IMSDs and the role of probiotics in these diseases. We included results from different types of studies including observational and interventional clinical trials or in vivo and in vitro experimental studies. Our results showed that probiotics have a beneficial effect in changing the microbiota of patients with IMSDs; they also influence disease progression. Further studies are needed to better understand the impact of new therapies on intestinal microbiota. It is also important to determine whether the microbiota of patients with autoimmune diseases can be manipulated in order to restore homeostasis of the microbiota.

scholarly journals The Role of Secondary Brain Insults in Status Epilepticus: A Systematic Review

2020 ◽  
Vol 9 (8) ◽  
pp. 2521
Author(s):  
Candice Fontaine ◽  
Gwenaelle Jacq ◽  
François Perier ◽  
Mathilde Holleville ◽  
Stephane Legriel
Keyword(s):  
Systematic Review ◽  
Status Epilepticus ◽  
Experimental Studies ◽  
Temperature Management ◽  
Target Temperature Management ◽  
Numerous Experimental Data ◽  
Clinical Consequences ◽  
Brain Insults ◽  
The Impact

(1) Background: Little is known about the impact of pathophysiological mechanisms that underlie the enhancement of excitotoxicity and the neuronal consequences of status epilepticus (SE), as well as the clinical consequences of secondary brain insults (SBI) in patients with SE on outcome; (2) Methods: Electronic searches were conducted in May 2020 using Medline via PubMed, Embase, and Google Scholar (#CRD42019139092). Experimental studies of animals or randomized, observational, controlled trials of patients with SE in indexed journals were included. There were no language or date restrictions for the published literature included in this review. Information was extracted on study design, sample size, SBI characteristics, and primary and secondary outcomes, including the timing of evaluation; (3) Results: Among the 2209 articles responding to our inclusion criteria, 56 were included in this systematic review. There are numerous experimental data reporting the deleterious effects associated with each of the SBI in animals exposed to SE. In humans, only the effect of target temperature management in hypothermia (32–34 °C) has been explored. (4) Conclusions: There is little experimental evidence that favors the control of secondary brain insult after SE. Further studies are required to assess the neuroprotective interest of secondary brain insult control after SE in humans.

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