Rao, Hartley, and Cochran’s Sampling Scheme: Application

This paper takes a look at the Rao, Hartley, and Cochran’s sampling scheme, when it is required to select sample of sizes 4, 6, 12, and 18 with probability proportional to size without replacement sampling (unequal probability sampling without replacement). This is done by using the data from the 2008 Nigeria Demographic and Health Survey (NDHS). We studied the distribution of women age 15 – 49 years employed in the 12 months preceding the survey by type of employer. Here, we considered self-employed women alone. It is shown how sample of sizes 4, 6, 12, and 18 could be randomly selected from the population of size 36.  Population total and variance were computed with confidence interval constructed for the population total. For the randomly selected states in this paper, we realized that as the sample size increases, the variance and standard error decreases. Keywords: Rao, Hartley, and Cochran’s sampling scheme, probability proportional to size without replacement, sample size four, six, twelve, eighteen

[Increase of potassium conductance and spontaneous electric activity in vitro: comparison of nicorandil and cicletanine].

Nicorandil (N) increases potassium conductance in vascular smooth muscle and so induces vasodilation; N also dose-dependently reduces action potential duration (APD). However, it is unclear whether increased potassium conductance, and concomitant APD shortening, might be arrhythmogenic, particularly when myocardial ischemia (where potassium efflux is increased) concurs. Data on the anti-arrhythmic effectiveness of N have also been published: N reduced the spontaneous discharge of sino-atrial node and so reduced heart rate, both in vitro and man. On the other hand, among other vasodilators, cicletanine (C) has been reported to increase potassium conductance, an effect which was advocated to explain its antiarrhythmic potency. In the present investigation the direct myocardial effects of N were compared to those following C in 63 experiments (from 13 Guinea-pigs), using atrial strips (containing sino-atrial node) superfused in 1-compartment bath with normal Tyrode's solution. Using glass microelectrodes, standard electrophysiologic variables were recorded (APA, RMP, APD50%, Vmax) in spontaneously beating atrial tissue, either in Tyrode, dimethyl-sulfoxide (DMSO 1:100, as solvent), C 10(-5) M (in DMSO 1:100), and N 10(-3) M (in DMSO 1:100), whose respective perfusion periods (15 min) were randomized, always following 15 min of washout with Tyrode. Only N was tested in experiments of both 15 and 30 min duration.(ABSTRACT TRUNCATED AT 250 WORDS

Effects of bimakalin on human cardiac action potentials: comparison with guinea. Pig and nicorandil and use dependent study

Electrophysiologic effects of K(ATP) channel openers (KCOs) are rarely studied for tissue and species specificity, and use-dependent investigations in human tissues are lacking. We therefore investigated in vitro the concentration-dependent effects of the KCO bimakalim [from 10 nM to 10 μM, at 1,000 ms of cycle length (CL) and 37°C] on human (atrium, n = 4, and ventricle, n = 6) and guinea pig (atrium, n = 7, and ventricle, n = 6) transmembrane action potential (AP). The frequency relation (from CL 1,600 to 300 ms, 31°C) of human atrial AP duration 90% (APD90) shortening (10 μM vs. baseline, n = 7) also was determined. A parallel study was performed with the KCO nicorandil (from 10 nM to 1 mM, n = 3) in human atrial APs, at 31 °C. Resting membrane potential and maximal upstroke velocity of AP were not modified by bimakalim at maximal concentration, whereas AP amplitude was decreased in both guinea pig preparations (p < 0.05); APD90 was shortened in all tissues (p < 0.01). Median effective concentration (EC50) for APD90 shortening at 37°C was 0.54 and 2.74 μM in atrial and ventricular human tissue, respectively, and 8.55 and 0.89 μM in atrial and ventricular guinea pig tissue, respectively. In human atrial tissue at 31°C, EC50 with bimakalim was 0.39 μM; a much higher value was seen with nicorandil (210 μM). Bimakalim (10 μM)-induced APD90 shortening as a function of stimulation rate was greatest at longest CL. Evidence is provided for (a) species (human vs. guinea pig) and tissue (atrium vs. ventricle) differential AP sensitivity to bimakalim; (b) an ≃500-fold higher efficacy of bimakalim versus nicorandil to shorten human atrial APD90; and (c) normal use- dependence of human atrial APD90 shortening with bimakalim at 10 μM