6 research outputs found
The Effect of Stimulation Frequency on the Ionic Currents in Single Atrial Cells of the Rabbit
In single atrial cells isolated from rabbit hearts the calcium current and
[Caj-dependent transient outward current were recorded using the whole-cell clamp
technique and the effect of stimulation frequency on these currents was investigated.
Voltage dependent transient outward current, which contributes the initial, rapid
repolarization phase of the action potential and is frequency-dependent, was also
investigated. Increasing the stimulation frequency from O. 025 Hz to 1 Hz had no effect
on the calcium current and [Caj-dependent transient outward current and greatly
inhibited voltage-dependent transient outward current. The amplitude of voltage dependent
transient outward current increased as the membrane potential became
depolarized, its steady-state inactivation spans the voltage range -70 mV to -10 mVand
steady-state activation curve -30 mV to 30 mV. Within the range of the resting membrane
potential (at -70 mV), the voltage-dependent recovery time constant was 1. 3 s.
The reversal potential was about -50 mV. Voltage-dependent transient outward current
was inhibited by K-channel blockers and not inhibited by modulation of [Cali. From the
above findings, it is concluded that due to the amplitude and voltage-dependent recovery
time constant which were the basic mechanisms for frequency-dependency, the
voltage- dependent transient outward current contributes the initial, rapid repolarization
phase and changed the action potential configuration according to stimulation frequency
in the rabbit atrium
ReIationship of Plasma Potassium and Hydrogen Ion Concentrations in Acidosis-Induced HyperkaIemia and HyperkaIemia-Induced Acidosis
The relationship between the plasma potassium concentration and
blood pH was evaluated in acidosis-induced hyperkalemia and hyperkalemiainduced
acidosis in rabbits. In the first group of animals, metabolic acidosis was
induced by an intravenous infusion of 0.1 N hydrochloric acid, and in the second
group, hyperkalemia was induced by an intravenous infusion of 20 mM potassium
chloride solution. The third group of animals was infused with both hydrochloric
acid and potassium chloride. All three groups showed metabolic acidosis, hyperkalemia,
and compensatory respiratory alkalosis. The degree of alkalosis was
most extensive in HCl infused, and least in KCl infused animals. The simultaneous
infusion of HCl and KCl induced the most extensive change in the acid-base
status, and the hydrogen and potassium ion concentrations. However the quantitative
relationship between potassium and hydrogen ion concentrations was similar
in all three groups. It is, therefore, presumed that acidosis-induced hyperkalemia
and hyperkalemia-induced acidosis involve a common mechanism
์ธํฌ์ NA+๋๋ ๋ณํ๊ฐ ๊ธฐ๋ํผ๊ทธ ์ ํํ๊ทผ ์ํ์ ๋ฏธ์น๋ ์ํฅ
The characteristics of contractile and electrical responses to various concentrations
of extracel1ular sodium in the antrum of guinea-pig stomach were investigated in order
to elucidate the mechanisms generating and control1ing the slow wave which is known to be
responsible for the gastric motility. The results obtained were as fol1ows:
1) Tonic contraction increased as the concentration of extracel1ular sodium decreased.
However, phasic contraction gave a different response around 10 mM Na +.
2) In Na + -deficient solutions, prolongation in the second component and potentiation in
the spike component of the slow wave and membrane depolarization were observed, Those
changes became more marked with each decrement of Na + concentration.
3) In solutions below 10 mM Na +, small slow waves whose components could not be
clearly distinguished appeared at a faster frequency than it did in normal Tyrode solution.
4) In the presence of guanethidine and atropine the change described in 3) disappeared in
solutions of Na + concentration below 10 mM. Instead the same responses as described in 2)
were observable,
From the above results following conclusions can be made: As the concentration of extracel1ular
sodium decreases the configuration of the slow wave of the antral smooth muscle
in guinea-pig stomach changed markedly, showing prolongation in the second component,
potentiation in the spike component and depolarization in the membrane potential. These
results are direct effects of extracellular sodium on the smooth muscle cell membrane.
However, in low sodium concentration below about 10 mM, the influence of autonomic
nervous system on the slow wave becomes remarkable and above changes of the slow wave
cannot be found
๊ฒฐ์ฅ๋ด์ ์ ์ ๋ฌธ๋์์ K-์ ๊ฑฐ ๊ฒฝ์ถ์ ๋ํ ์ธํฌ๋ฐ Na์ ์ํฅ
To study the role of Na-Ca exchange mechanism which controls the intracellular
free Ca concentration, the changes in contractile force and membrane potential of G-I
smooth muscle were measured. Guinea-pig's taenia coli and gastric antrum were isolated,
and all experiments were performed in Tris-buffered Tyrode solution aerated with 100'10 O2
and kept 35"C. After application of K-free solution which is known to increase the intracellular
Na concentration due to inhibition of Na-K pump, Na-free or low Na solution were
applied. Contractions were recorded with force transducer, and membrane potentials were
measured by single sucrose-gap method. In the taenia coli, the extent of relaxation of K-free
contracture was inversely proportional to external Na concentration. As the external Na
concentration was decreased, the membrane potential was more hyperpolarized. In the gastric
antrum, the extent of relaxation of K-free contracture increased proportionately to the
decrease of external Na concentration. Membrane potential was maximally hyperpolarized at
Na-free solution. As extracellular Na concentration was increased, the degree of hyperpolarization
decreased, and at 125 mM Na the membrane potential was depolarized. When Ca
antagonist (verapamil) was applied, K-free contracture did not develop in the taenia coli. It is
concluded that Na-Ca exchange mechanism would play little role in the control of intracellular free Ca concentration in the taenia coli and gastric antrum. ; Na-Ca ๊ตํ ๊ธฐ์ ์ด ํํ๊ทผ์ ์ธํฌ๋ด ์นผ์ ์ด์จ ๋๋ ์กฐ์ ์ ๊ธฐ์ฌํ๋ ์ ๋๋ฅผ ์ฐ๊ตฌํ๊ธฐ ์ํ์ฌ ์์ฅ๊ด ํํ๊ทผ์ ์์ถ๊ณผ ์ธํฌ๋ง์ ์์ ๋ณํ๋ฅผ ๊ด์ฐฐํ์ฌ ๋ถ์ํ์๋ค.
auinea-pig์ ๊ฒฐ์ฅ๋ด์ ์ ์ ๋ฌธ๋์ ์ ์ถํ์ฌ 35โ์์ 100% ์ฐ์๋ก ํํ์ ์ด๋ฃฌ Tris-์์ถฉ Tyrode ์ฉ์ก์์ ์ด๋ค ์กฐ์ง์ด ์ผ์ ํ ๋น๋์ ํฌ๊ธฐ๋ก ์๋ฐ์ ์์ถ์ ํ๊ฒ ๋๋ฉด ์ธํฌ๋ด Nashd๋๋ฅผ ์ฆ๊ฐ์ํค๋ K-์ ๊ฑฐ ์ฉ์ก(K-free Tyrode solution)์ผ๋ก ์ ์ฒ์นํ์ฌ K-์ ๊ฑฐ ๊ฒฝ์ถ์ ์ ๋ฐ์ํค๊ณ ์ฌ๊ธฐ์ Na-์ ๊ฑฐ ์ฉ์ก๊ณผ ์ฌ๋ฌ ์์ค์ Na ๋๋ ์ฉ์ฝ์ ๊ด๋ฅ์์ผ ์์ถ๊ณก์ ์ ๋ณํ๋ฅผ ๊ธฐ๋กํ์๋ค. ๋จ์ผ ์๋น์ก ๊ฐ๊ทน๋ฒ(single sucrose-gap method)์ผ๋ก๋ ์ธํฌ๋ง์ ์ ๋ณํ๋ฅผ ๊ธฐ๋ก ๋ถ์ํ์ฌ ๋ค์๊ณผ ๊ฐ์ ๊ฒฐ๊ณผ๋ฅผ ์ป์๋ค.
1. ๊ฒฐ์ฅ๋ด์์ K-์ ๊ฑฐ ๊ฒฝ์ถ์ด ์ด์๋๋ ์ ๋๋ ์ธํฌ๋ฐ Na ๋๋์ ๋ฐ๋น๋กํ์๋ค.
2. ๊ฒฐ์ฅ๋ด์์ ์ธํฌ๋ฐ Na ๋๋๊ฐ ๋์์๋ก ๊ณผ๋ถ๊ทน๋๋ ์ ๋๊ฐ ์ ์๋ค.
3. ์ ๋ฌธ๋์์๋ ๊ฒฐ์ฅ๋ด์ฒ๋ผ K-์ ๊ฑฐ ๊ฒฝ์ถ์ด Na-์ ๊ฑฐ ์ฉ์ก์์ ์ด์๋์๊ณ , ์ธํฌ๋ฐ Na ๋๋๋ฅผ ์ฆ๊ฐ์ํค๋ฉด K-์ ๊ฑฐ ๊ฒฝ์ถ์ ์ด์์ํค๋ ์ ๋๊ฐ ์์์ก๊ณ , ์ธํฌ๋ง์ ์์ด ๊ณผ๋ถ๊ทน๋๋ ์ ๋๋ ์ธํฌ๋ฐ Na ๋๋๊ฐ ๋์์๋ก ์์๋ค.
4. Ca ์ต์ ์ ์ธ varapamil์ 1mg/l ์ ์ฒ์นํ๋ฉด K-์ ๊ฑฐ ๊ฒฝ์ถ์ด ๊ฑฐ์ ์๊ธฐ์ง ์์๋ค.
์ด์์ ๊ฒฐ๊ณผ๋ก ๋ณด์ ๊ฒฐ์ฅ๋ด์ ์ ์ ๋ฌธ๋์์๋ ์ธํฌ๋ด ์นผ์ ์ด์จ๋๋ ์กฐ์ ์ Na-Ca ๊ตํ ๊ธฐ์ ์ ์ญํ ์ด ์ค์ํ์ง ์๋ ๊ฒ์ผ๋ก ์๊ฐ๋๋ค
๋ฐฉ์ค๊ฒฐ์ ์ ์ธํฌ๋ง ์ด์จ์ ๋ฅ์ ๊ดํ ์ฐ๊ตฌ
The rabbit AV node was isolated and dissected into small strips of 0.3 mm
width to apply two microelectrode voltage clamp technique. Then, slow inward current (isJ,
hyperpolarization activated inward current (if) and pump current were recorded and their
kinetic properties were analysed.
The results obtained were as follows:
1. The isolated AV node continued to beat, but the rate was slower than that in the SA
node. The configuration of action potential showed regional difference. Small AV node
preparations also showed spontaneous action potentials whose configurations were similar to
those in the SA node. Resting membrane potential was about -40 mV.
2. On depolarization from the holding potential of -40 mV to various potential level, slow
inward current (isf) was recorded. It was disappeared by adding 2 mM Mn+ + and increased
remarkably by 10-6M adrenaline. Current-voltage relationship, steady-state inactivation and
recovery from inactivation were also studied and considered similar to those in other cardiac
tissues.
3. In response to hyperpolarizing voltage clamp pulse, the current if was activated. The
reversal potential was about -25 mV. 0.5 mM Cs" decreased if in a voltage-dependent
manner. 10-6M adrenaline showed little effect on if.
4. The activity of electrogenic Na+ pump was demonstrated by K+ -induced transient
outward current or transient hyperpolarization after pre-treatment with K+-free Tyrode solution.
The pump activity was affected by duration of pre-treatment, K+ concentration in
recovery solution and Ca + + concentration in K+ -free Tyrode solution
The Effect of Changes in the Separation Process for the Performance of Recycled Cement Powder: A Comparison with a Previous Study for Radioactive Waste Immobilization
Separation of hydrated cement paste from aggregate is a key technology to reduce the amount of radioactive concrete waste during the decommissioning process. If separated cement-paste portions can be recycled as a solidifying agent for other radioactive waste, the amount of radioactive concrete waste could be close to โzeroโ. A study was conducted to achieve circular economy in the area of concrete decommissioning and found it to be successfully used as a solidifying agent for immobilization of liquid radioactive waste. However, previous work used a process that requires large amounts of energy (heat treatment was applied to most of the concrete fraction) because the objective was to completely remove hydrated cement powder from the aggregate. In this work, the separation system was modified to increase energy efficiency (heat treatment was applied to separated powder only), but such a change decreased the surface area of the recycled cement powder due to a higher inclusion of aggregate powder. A relatively lower solution to binder ratio could have been achieved for the preparation of wasteform specimens, and as a result, a 28 day compressive strength of wasteform could have become higher, but the final leachability indices were lower than the results observed from previous work. The results from 28 day compressive strength, thermal cycling and 90 day leaching experiments met the acceptance criteria for wasteform, indicating that this modified system can also be used for immobilization of liquid radioactive waste to meet the โzeroโ production of concrete waste during the decommissioning of a nuclear power plant. It should be noted that accurate monitoring of aggregate content in recycled cement powder during production is important to maintain proper reactivity of recycled cement powder