998 resultados para potassium-40
Resumo:
Measurement of glutathione (GSH) and glutathione disulfide (GSSG) is a crucial tool to assess cellular redox state. Herein we report a direct approach to determine intracellular GSH based on a rapid chromatographic separation coupled with acidic potassium permanganate chemiluminescence detection, which was extended to GSSG by incorporating thiol blocking and disulfide bond reduction. Importantly, this simple procedure avoids derivatisation of GSH (thus minimising auto-oxidation) and overcomes problems encountered when deriving the concentration of GSSG from ‘total GSH’. The linear range and limit of detection for both analytes were 7.5 × 10−7 to 1 × 10−5 M, and 5 × 10−7 M, respectively. GSH and GSSG were determined in cultured muscle cells treated for 24 h with glucose oxidase (0, 15, 30, 100, 250 and 500 mU mL−1), which exposed them to a continuous source of reactive oxygen species (ROS). Both analyte concentrations were greater in myotubes treated with 100 or 250 mU mL−1 glucose oxidase (compared to untreated controls), but were significantly lower in myotubes treated with 500 mU mL−1 (p < 0.05), which was rationalised by considering measurements of H2O2 and cell viability. However, the GSH/GSSG ratio in myotubes treated with 100, 250 and 500 mU mL−1 glucose oxidase exhibited a dose-dependent decrease that reflected the increase in intracellular ROS.
Chemiluminescence detection of cannabinoids and related compounds with acidic potassium permanganate
Resumo:
The purpose of this work was to improve the analytical usefulness of acidic potassium permanganate chemiluminescence for the determination of various analytical compounds. This thesis also examined the fundamental chemistry involved with these types of reactions.
Resumo:
Sixty-six English-speaking postgraduate distance-education medical students completed the Learning Styles Questionnaire (LSQ: 40-item version). This was completed while attending a residential workshop at the beginning of the semester, and 44 of these students completed the same LSQ questionnaire 5 months later at the completion of the semester. The psychometric properties of the LSQ were assessed using Cronbach’s alpha (internal consistency), test-retest, correlational analyses and factor analysis. The results indicated that the LSQ (40-item version) has poor reliability and validity, and therefore requires further development and psychometric evaluation.
Resumo:
Background:
Rapid intradialytic potassium shifts during haemodialysis have been associated with increased mortality and morbidity. Standardising dialysate potassium to 2 mmol/l may decrease the potassium shift.
To examine the effect of standardising dialysate potassium to 2 mmol/l for all chronic dialysis treatments.
Pre- and post-intervention comparison of monthly serum potassium.
Participants:
Ninety-seven individuals, of whom 56 patients could be matched across both data collection periods.
Methods:
Serum potassium data were categorised based on a target range 3.5–6.0 mmol/l. Overall pre- and postintervention mean scores were compared using a paired samples t-test. Data for patients routinely prescribed dialysate potassium 1 mmol/l pre-intervention (n ¼ 6) underwent paired samples t-test to compare their mean serum potassium pre and post-intervention.
Results:
There was no statistically significant change in serum potassium post- intervention. The majority of patients remained within the target range, including the subset of patients who had a history of high serum potassium during the pre- intervention period.
Conclusions:
A standard potassium dialysate of 2 mmol/l may reduce intradialytic serum potassium shifts and may assist in standardising safer work practices.
Resumo:
High-performance liquid chromatography with chemiluminescence detection based on the reaction with acidic potassium permanganate and formaldehyde was explored for the determination of neurotransmitters and their metabolites. The neurotransmitters norepinephrine and dopamine were quantified in the left and right hemispheres of rat hippocampus, nucleus accumbens and prefrontal cortex, and the metabolites vanillylmandelic acid, 3,4-dihydrophenylacetic acid, 5-hydroxyindole-3-acetic acid and homovanillic acid were identified in human urine. Under optimised chemiluminescence reagent conditions, the limits of detection for these analytes ranged from 2.5 × 10−8 to 2.5 × 10−7 M. For the determination of neurotransmitter metabolites in urine, a two-dimensional high-performance liquid chromatography (2D-HPLC) separation operated in heart-cutting mode was developed to overcome the peak capacity limitations of the one-dimensional separation. This approach provided the greater separation power of 2D-HPLC with analysis times comparable to conventional one-dimensional separations.
Resumo:
Peptide toxins found in a wide array of venoms block K+ channels, causing profound physiological and pathological effects. Here we describe the first functional K+ channel-blocking toxin domain in a mammalian protein. MMP23 (matrix metalloprotease 23) contains a domain (MMP23TxD) that is evolutionarily related to peptide toxins from sea anemones. MMP23TxD shows close structural similarity to the sea anemone toxins BgK and ShK. Moreover, this domain blocks K+ channels in the nanomolar to low micromolar range (Kv1.6 > Kv1.3 > Kv1.1 = Kv3.2 > Kv1.4, in decreasing order of potency) while sparing other K+ channels (Kv1.2, Kv1.5, Kv1.7, and KCa3.1). Full-length MMP23 suppresses K+ channels by co-localizing with and trapping MMP23TxD-sensitive channels in the ER. Our results provide clues to the structure and function of the vast family of proteins that contain domains related to sea anemone toxins. Evolutionary pressure to maintain a channel-modulatory function may contribute to the conservation of this domain throughout the plant and animal kingdoms.
