Non-parametric procedures for the determination of phase markers of circadian rhythms

The determination of empirical confidence intervals for the location of quantitative trait loci (QTLs) by interval mapping was investigated using simulation. Confidence intervals were created using a non-parametric (resampling method) and parametric (resimulation method) bootstrap for a backcross population derived from inbred lines. QTLs explaining 1%, 5% and 10% of the phenotypic variance were tested in populations of 200 or 500 individuals. Results from the two methods were compared at all locations along one half of the chromosome. The non-parametric bootstrap produced results close to expectation at all non-marker locations, but confidence intervals when the QTL was located at the marker were conservative. The parametric method performed poorly; results varied from conservative confidence intervals at the location of the marker, to anti-conservative intervals midway between markers. The results were shown to be influenced by a bias in the mapping procedure and by the accumulation of type 1 errors at the location of the markers. The parametric bootstrap is not a suitable method for constructing confidence intervals in QTL mapping. The confidence intervals from the non-parametric bootstrap are accurate and suitable for practical use.

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Circadian rhythms in plasma levels of cortisol, dehydroepiandrosterone, Δ4-androstenedione, testosterone and dihydrotestosterone of healthy young men

Acta Endocrinologica ◽

10.1530/acta.0.0940536 ◽

1980 ◽

Vol 94 (4) ◽

pp. 536-545 ◽

Cited By ~ 30

Author(s):

Michel M. Guignard ◽

Pierre C. Pesquies ◽

Bernard D. Serrurier ◽

Danielle B. Merino ◽

Alain E. Reinberg

Keyword(s):

Circadian Rhythms ◽

Ethyl Ether ◽

Plasma Levels ◽

Plasma Sample ◽

Young Men ◽

Venous Catheter ◽

Diurnal Activity ◽

Androgenic Steroids ◽

Healthy Males

Abstract. Three healthy males (18, 22 and 30 years of age; 85 kg/177 cm, 82 kg/181 cm and 75 kg/168 cm, respectively), synchronized with a diurnal activity (06.00 to 23.00 h) and nocturnal rest, volunteered for this study. Blood was sampled (venous catheter) hourly during a 24 h span. A radiocompetition method was used for cortisol determinations. Other steroids were first extracted (ethyl-ether) from each plasma sample, then chromatographed on a celite column to isolate 3 fractions: 1) Δ4-androstenedione (Δ-4); 2) dihydrotestosterone (DHT) and dehydroepiandrosteone (DHA); 3) testosterone (T). A radioimmunological assay was used thereafter for the determination of androgenic steroids. Statistically significant (both conventional and cosinor methods) circadian rhythms were detected (P < 0.005). Acrophases (peak times) occurred in the following order: cortisol (07.28), DHA (08.43), Δ-4 (09.54), T (11.15) and DHT (16.37). The respective circadian amplitudes of DHA and Δ-4 were smaller than those of cortisol while the amplitudes T and DHT did not show differences statistically significant from each other.

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