Despite the central role of quantitative PCR (qPCR) in the quantification of mRNA transcripts, most analyses of qPCR data are still delegated to the software that comes with the qPCR apparatus. This is especially true for the handling of the fluorescence baseline. This article shows that baseline estimation errors are directly reflected in the observed PCR efficiency values and are thus propagated exponentially in the estimated starting concentrations as well as ‘fold-difference’ results. Because of the unknown origin and kinetics of the baseline fluorescence, the fluorescence values monitored in the initial cycles of the PCR reaction cannot be used to estimate a useful baseline value. An algorithm that estimates the baseline by reconstructing the log-linear phase downward from the early plateau phase of the PCR reaction was developed and shown to lead to very reproducible PCR efficiency values. PCR efficiency values were determined per sample by fitting a regression line to a subset of data points in the log-linear phase. The variability, as well as the bias, in qPCR results was significantly reduced when the mean of these PCR efficiencies per amplicon was used in the calculation of an estimate of the starting concentration per sample.
Background/Aims: Dietary potassium (K+) has beneficial effects on blood pressure and cardiovascular (CV) outcomes. Recently, several epidemiological studies have revealed an association between urinary K+ excretion (as proxy for dietary intake) and better renal outcomes in subjects with chronic kidney disease (CKD). To address causality, we designed the “K+ in CKD” study. Methods: The K+ in CKD study is a multicenter, randomized, double blind, placebo-controlled clinical trial aiming to include 399 patients with hypertension, CKD stage 3b or 4 (estimated glomerular filtration rate [eGFR] 15–44 mL/min/1.73 m2), and an average eGFR decline > 2 mL/min/1.73 m2/year. As safety measure, all included subjects will start with a 2-week open-label phase of 40 mmol potassium chloride daily. Patients who do not subsequently develop hyperkalemia (defined as serum K+ >5.5 mmol/L) will be randomized to receive potassium chloride, potassium citrate (both K+ 40 mmol/day), or placebo for 2 years. The primary end point is the difference in eGFR after 2 years of treatment. Secondary end points include other renal outcomes (> 30% decrease in eGFR, doubling of serum creatinine, end-stage renal disease, albuminuria), ambulatory blood pressure, CV events, all-cause mortality, and incidence of hyperkalemia. Several measurements will be performed to analyze the effects of potassium supplementation, including body composition monitoring, pulse wave velocity, plasma renin and aldosterone concentrations, urinary ammonium, and intracellular K+ concentrations. Conclusion: The K+ in CKD study will demonstrate if K+ supplementation has a renoprotective effect in progressive CKD, and whether alkali therapy has additional beneficial effects.
In the CAVB dog ventricular hypertrophy is not a prerequisite for electrical remodeling or drug-induced torsade de pointes, and the AT1-receptor has no dominant role in the completion of these remodeling processes.
PCT-guided therapy was non-inferior in terms of safety, but did not reduce prescription of antibiotic regimens in an ED population with fever. In this heterogeneous population, the accuracy of PCT in diagnosing bacterial infections was poor. TRIAL REGISTRATION IN NETHERLANDS TRIAL REGISTER: http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=4949.
Objectives: Electrical remodeling in cardiac hypertrophy often involves the downregulation of K + currents, including β-adrenergic (β-A)-sensitive I Ks . Temporal patterns of ion-channel downregulation are poorly resolved. In dogs with complete atrioventricular block (AVB), we examined (1) the time course of molecular alterations underlying I Ks downregulation from acute to chronic hypertrophy; and (2) concomitant changing responses of repolarization to β-adrenergic receptor (β-AR) stimulation. Methods and Results: Serial left-ventricular (LV) biopsies were collected from anesthetized dogs during sinus rhythm (SR; control) and at 3, 7 and 30 days of AVB. KCNQ1 mRNA and protein decreased within 3 days (protein expression 58 ± 10% of control), remaining low thereafter. β1-AR mRNA and protein decreased more gradually to 53 ± 8% at 7 days. In chronic-AVB LV myocytes, I Ks -tail density was reduced: 1.4 ± 0.3 pA/pF versus 2.6 ± 0.4 pA/pF in controls. β-A enhancement of I Ks was reduced. Isoproterenol shortened action-potential duration in control cells, while causing heterogeneous repolarization responses in chronic AVB. β-A early afterdepolarizations were induced in 4 of 13 chronic-AVB cells, but not in controls. In intact conscious dogs, isoproterenol shortened QT c at SR (by −8 ± 3% from 295 ms), left it unaltered at 3 days AVB (+1 ± 3% from 325 ms) and prolonged QT c at 30 days (+ 6 ± 3% from 365 ms). Conclusions: Profound decrease of KCNQ1 occurs within days after AVB induction and is followed by a more gradual decrease of β1-AR expression. Downregulation and blunted β-A activation of I Ks contribute to the loss of β-A-induced shortening of ventricular repolarization, favoring proarrhythmia. Provocation testing with isoproterenol identifies repolarization instability based on acquired channelopathy.
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