Differential Rate and Potassium-Dependent Effects of the Class III Agents d-Sotalol and Dofetilide on Guinea Pig Papillary Muscle

The class III agents d-sotalol and dofetilide have been shown to exhibit differential effects in large controlled clinical trials. The aim of this study was to investigate the basic electrophysiological properties of these two antiarrhythmia agents in an in vitro experimental model with regard to potential antiarrhythmic and proarrhythmic action. Using standard microelectrode techniques, we evaluated the electrophysiological effects of d-sotalol and dofetilide on action potential parameters recorded from guinea pig papillary muscle at 2.5 mM, 3.5 mM, and 5.6 mM extracellular potassium concentrations. The following parameters were recorded: resting membrane potential (RMP), action potential amplitude (APA), action potential duration at 90% repolarization (APD 90), and maximum upstroke velocity (Vmax). Under all conditions studied, both d-sotalol and dofetilide exhibited highly selective reverse rate-dependent class III action. In contrast to dofetilide, the class III activity of d-sotalol was markedly influenced by changes in extracellular potassium concentrations, predominantly at low pacing rates. Hypokalemia enhanced the action potential–prolonging effects of d-sotalol, whereas hyperkalemia diminished this effect. In addition, reverse rate dependence associated with dofetilide was significantly more pronounced than reverse rate dependence associated with d-sotalol. Our observations provide a potential electrophysiological basis for differential antiarrhythmic and proarrhythmic mechanisms associated with these two drugs.     

Age-associated accumulation of CMV-specific CD8+ T cells expressing the inhibitory killer cell lectin-like receptor G1 (KLRG1)

Large clonal expansions of peripheral CD8+ T cells carrying receptors for single epitopes of CMV and EBV are common in the elderly and may be associated with an immune risk phenotype predicting mortality. Here we show that the frequency of CD8+ T cells expressing the inhibitory killer cell lectin-like receptor G1 (KLRG1), a marker of cells unable to undergo further clonal expansion, was markedly elevated in CD8+ T cells from old donors. Moreover, tetramer staining revealed that the elevated frequency of CMV-specific CD8+ T cells in the elderly was due to an accumulation of cells bearing this dominant negative receptor. The fraction of CMV-specific T cells able to secrete interferon-gamma after specific antigenic stimulation was significantly lower in the elderly than in the young, although the total number of functional cells was comparable. Therefore, the majority of the clonally expanded virus-specific CD8+ cells in the elderly was dysfunctional. Thus, T cell responses are altered in the aged by an accumulation of replicatively senescent dysfunctional T cells carrying receptors for persistent herpes viruses. The presence of clonal expansions of such virus-specific cells may shrink the available repertoire for other antigens and contribute to the increased incidence of infectious disease in the elderly.     

Long-term fluvastatin reduces the hazardous effect of renal impairment on four-year atherosclerotic outcomes (a LIPS substudy)

Mild renal impairment is an important risk factor for late cardiovascular complications. This substudy of the Lescol Intervention Prevention Study (LIPS) assessed the effect of fluvastatin on outcome of patients who had renal dysfunction and those who did not. Complete data for creatinine clearance calculation (Cockcroft-Gault formula) were available for 1,558 patients (92.9% of the LIPS population). Patients were randomized to fluvastatin or placebo after successful completion of a first percutaneous coronary intervention. Follow-up time was 3 to 4 years. The effect of baseline creatinine clearance on coronary atherosclerotic events (cardiac death, nonfatal myocardial infarction, and coronary reinterventions not related to restenosis) was evaluated. Baseline creatinine clearance (logarithmic transformation) was inversely associated with an incidence of adverse events among patients who received placebo (hazard ratio 0.99, 95% confidence interval 0.982 to 0.998, p = 0.01). However, no association was noted between creatinine clearance and the incidence of adverse events among patients who received fluvastatin (hazard ratio 1.0, 95% confidence interval 0.99 to 1.0, p = 0.63). No further deterioration in creatinine clearance was observed during follow-up, regardless of baseline renal function or allocated treatment. Occurrence of adverse events was not related to changes in renal function during follow-up. Fluvastatin therapy markedly decreased the risk of coronary atherosclerotic events after percutaneous intervention in patients who had lower values of creatinine clearance at baseline. The benefit of fluvastatin was unrelated to any effect on renal function.     

Immunocytochemical detection of p21 ras expression in fresh human leukaemic cells and cell lines

Summary The expression of p21 ^ras proteins was investigated by immunocytochemistry in permanent cell lines and in fresh human leukaemic cells. While high and low levels of p21 ^ras could be detected in most of the cell lines, no significant p21 ^ras immunoreactivity was noted in cells of ten human acute and chronic leukaemias. Thus, notwithstanding its possible role in the initial transformation process in human leukaemias, p21 ^ras expression appears not to be an irrevocable requirement for the maintenance of the transformed state.     

Use of fractional flow reserve versus stress perfusion scintigraphy in stent restenosis

BackgroundFractional flow reserve (FFR) is a valid surrogate for hemodynamic significance in stenotic native coronary arteries. The aim of this study was to examine the value of FFR compared to stress perfusion myocardial scintigraphy (SPMS) in patients with coronary stent restenosis.MethodsWe studied 42 patients, aged 62 ± 10 years, with stent restenosis 5.3 ± 1.6 months after coronary stent implantation. All patients had a single coronary lesion of intermediate severity (diameter stenosis 40–70%). FFR measurement, SPMS, and quantitative angiography of the stent stenosis were performed in all patients.ResultsThe mean percentage in stent diameter stenosis was 53 ± 9%. FFR was 0.77 ± 0.15. In 20 patients FFR was below 0.75. Nineteen patients had reversible perfusion defects in SPMS. FFR showed good diagnostic accuracy for the detection of reversible perfusion defects in SPMS (AUROC 0.86, 95% CI 0.74–0.98). The percentage of agreement of SPMS and FFR was 88%, with the best cutoff value of 0.75 for FFR.ConclusionsA FFR value of 0.75 is not only valid for diagnosing significant native coronary stenosis, but also for stent restenosis. Thus, FFR measurement should be taken into account when making decisions regarding patients with stent restenosis.     

Prediction of neurological outcome after cardiopulmonary resuscitation by serial determination of serum neuron-specific enolase.

AIMS: Data on the diagnostic accuracy of neuron-specific enolase (NSE) as marker of hypoxic brain damage are conflicting. The purpose of this prospective observational cohort study was to explore the prognostic value of serum NSE after cardiopulmonary resuscitation (CPR) and to define the most sensitive cutoff value with a specificity of 100% for the prediction of persistent coma. METHODS AND RESULTS: Serum NSE concentrations were serially determined in 227 consecutive unconscious patients after CPR who were classified according to the best Glasgow-Pittsburgh cerebral performance categories (CPC, 1-4) achieved within 6 months follow-up. Sixteen patients were excluded due to incomplete NSE data and 34 due to death under analgesia sedation. The prevalence of poor neurological outcome (persistent coma, CPC 4) in our 177 analysed patients was 33%. At a specificity of 100%, a peak NSE concentration above 80 ng/mL predicted persistent coma with a sensitivity of 63%, a positive predictive value of 100%, a negative predictive value of 84%, and a predictive accuracy of 88%. CONCLUSION: A peak serum NSE concentration exceeding 80 ng/mL is a highly specific but only moderately sensitive marker for a poor neurological outcome after CPR.     

Comparative assessment of the inhibition of recombinant human CYP19 (aromatase) by azoles used in agriculture and as drugs for humans

Azoles (imidazoles and triazoles) are used as antifungal agents in agriculture and in medicine, and also for antiestrogen therapy, e.g., for breast cancer treatment. Antifungal activity is based on inhibition of fungal CYP51 (lanosterol 14alpha-demethylase), and estrogen biosynthesis reduction is due to azole inhibition of CYP19 (aromatase). Inhibition of aromatase by antifungal agents is usually an unwanted side effect and may cause endocrine disruption. A fluorimetric assay based on human recombinant CYP19 enzyme with dibenzylfluorescein as a substrate was used to compare the inhibitory potency of 22 azole compounds. Dose responses were established and duplicate datasets were analyzed with a nonlinear mixed-effects model with cumulative normal distribution for the logarithm of concentration. IC50 values (50% inhibitory concentration) of 13 fungicides used in agriculture ranged more than 700-fold, starting from 0.047 microM. The potency of seven human drugs spanned more than 7000-fold, starting from 0.019 microM. Most potent fungicides included prochloraz, flusilazole, and imazalil, and most potent medicinal antifungals were bifonazole, miconazole, and clotrimazole. These in vitro data indicate that the top-ranking azoles used as antifungal agents or drugs are as potent inhibitors of aromatase as are antiestrogen therapeutics used to treat breast cancer. These putative effects of azole agents and drugs on steroid biosynthesis and sex hormone balance should be considered when used in human subjects and also in wildlife exposed to azole fungicides used in agriculture.