Nafion

Project ID

2811

Category

PFAS

Added on

May 31, 2019, 6:09 a.m.

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2357 items found. Displaying 25 items on page 9 of 95.

PubMed
DOI WoS
Journal Article

Sequential measurement of aminotransferase activities by amperometric biosensors

Chang KS et al. 2007

Abstract  An l-glutamate biosensor modified by cation exchanger membrane on a palladium (Pd) electrode was designed for the purpose of preventing interferences and electrode fouling during the measurement of serum AST and ALT activities. The rate of signal increase obtained by our sensor for the determination of AST and ALT activity was 0.259 and 0.596 nA/min U(-1)l and the response of the sensor to AST and ALT activity were linear over the range of 8-200 and 8-250 Ul(-1), respectively. Both AST and ALT activities could be measured sequentially by injecting the serum into a solution containing l-aspartate and alpha-ketoglutarate. The rate of current increase was relative to AST activity. The activity of ALT was sequentially determined after addition of l-alanine into the solution. The change in the current increase rate after the addition of l-alanine was proportional to the ALT activity. By using the proposed biosensor, the interference of 1mM ascorbic acid was negligible on a dynamical aminotransferase determination when the dynamic data are taken after the steady state of an elevated baseline has been reached. The proposed l-glutamate biosensor provides adequate sensitivity for the measurement of AST and ALT and is expectable to be applied for rapid blood screening of AST and ALT activity in clinical sample.

PubMed
DOI WoS
Journal Article

CHARACTERISTICS OF CA2+-ACTIVATED K+ CHANNELS ISOLATED FROM THE LEFT-VENTRICLE OF A PATIENT WITH IDIOPATHIC LONG QT SYNDROME

Krause PC et al. 1993

Abstract  Early afterdepolarizations (EADs), possibly caused by reduced K+ conductance, have been hypothesized to cause the long QTU interval and ventricular tachyarrhythmias (VT) in patients with the long QT syndrome (LQTS). In a 26-year-old woman with aborted sudden death as a consequence of the idiopathic LQTS, we recorded with a contact electrode left ventricular endocardial EADs that were enhanced by epinephrine and phenylephrine. Because of uncertain efficacy and side effects achieved with beta-adrenoceptor blockade, the patient underwent left-sided cardiac sympathectomy, at which time we obtained left ventricular biopsy tissue. Crude membrane vesicles were prepared from this tissue and single-channel activity was studied after incorporation of the vesicles in an artificial lipid bilayer (phosphatidylserine, phosphatidylethanolamine, 4:5 weight ratio in decane) in the tip of a patch clamp pipette. Bath and pipette contained 100 mmol/L KCI and 25 mmol/L N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) at pH 7.4. We recorded K+ conducting channels with a mean slope conductance of 49.9 +/- 4.7 picosiemens (pS) (n = 5). Channel open probability was increased by the addition of 1 to 10 mumol/L Ca2+ to the experimental chamber. Addition of charybdotoxin (1-3 nmol/L), a known specific inhibitor of Ca(2+)-activated K+ channels, blocked channel activity. These results are the first to demonstrate Ca(2+)-activated K+ channels from a patient with idiopathic LQTS. These channels appear to show normal characteristics when studied in an artificial planar lipid bilayer.

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