Effect of the sampling process upon a LH level signal with constant amplitude and pulse frequency.

<p>In all panels, . Top panel: theoretical continuously measured LH blood level (green curve). Panels A, B, C, D: sampling points (blue stars) of the time series obtained from the top panel signal through the sampling protocol. Panel A: first sampling time at <i>r</i> = 1 min, without any variability in the sampling process. Panel B: first sampling time at <i>r</i> = 4 min, without any variability in the sampling process. Panel C: first sampling time at <i>r</i> = 4 min, with variability in the sampling times . Panel D: first sampling time at <i>r</i> = 4 min, with variability both in the sampling times and the assays . The histograms correspond to the distribution of the levels at the basal line and the distribution of the amplitudes of the LH pulses, measured from the four cases A to D. The A and B time series, that only differ in the first sampling time, display constant (yet different) pulse amplitude. Red bars stand for case A (<i>r</i> = 1 min) value of the pulse amplitude (2.425 ng/ml) and level at the basal line (0.107 ng/ml). Green bars stand for case B (<i>r</i> = 4 min) value of the pulse amplitude (2.188 ng/ml) and level at the basal line (0.096 ng/ml). Blue bars stand for distributions of levels at the basal line and pulse amplitudes in case C (<i>r</i> = 4 min; <i>f</i> = 1.5 min) and case D (<i>r</i> = 4 min; <i>f</i> = 1.5 min; <i>b</i> = 10%, i.e. a variability of in the LH assays). In case D, the distributions of basal line levels (between 0.082 and 0.108 ng/ml) and pulse amplitudes (between 1.940 and 2.486 ng/ml) are wider than in case C (levels at the basal line between 0.092 and 0.101 ng/ml; pulse amplitude between 2.092 and 2.266 ng/ml), due to combined variabilities in the sampling times and assays.