scholarly journals An adaptive annual rhythm in the sex of first pigeon eggs

2010 ◽  
Vol 64 (9) ◽  
pp. 1393-1402 ◽  
Author(s):  
Cor Dijkstra ◽  
Bernd Riedstra ◽  
Arjan Dekker ◽  
Vivian C. Goerlich ◽  
Serge Daan ◽  
...  
Keyword(s):  
Annual Rhythm

Annual changes in 6-sulphatoxymelatonin excretion in man

1988 ◽  
Vol 117 (4) ◽  
pp. 470-476 ◽  
Author(s):  
Christopher J. Bojkowski ◽  
Josephine Arendt
Keyword(s):  
Intermediate Phase ◽  
Urine Samples ◽  
Plasma Samples ◽  
Annual Change ◽  
Melatonin Secretion ◽  
Normal Volunteers ◽  
Plasma Melatonin ◽  
Annual Rhythm ◽  
Major Urinary Metabolite ◽  
Annual Changes

Abstract: A recently developed RIA for 6-sulphatoxymelatonin, the major urinary metabolite of melatonin, has been used to investigate the annual change in melatonin secretion in humans. Twenty plasma samples were taken from 18 volunteers throughout a 24-h period and simultaneous 6-hourly urine samples were also collected. Plasma melatonin and urinary 6-sulphatoxymelatonin were measured by RIA. 6-Sulphatoxymelatonin assayed in the urine samples was shown to be a good index of the rhythmic characteristics of the plasma melatonin secretion. To study annual changes in excretion four sequential 6-hourly urine samples were collected at monthly intervals from 16 normal volunteers for 13 months. Cosinor curves were fitted to the 6-sulphatoxymelatonin excretion data and the 24-h rhythm was described by the cosinor parameters: amplitude, mesor and acrophase. Significant differences in the acrophase were found during the year. The summer acrophase was phase advanced relative to the winter acrophase by about 1.5 h while intermediate phase positions were observed in spring/autumn. The 24-h excretion of urinary 6-sulphatoxymelatonin was remarkably consistent and there was no annual rhythm. In contrast, the daytime 6-sulphatoxymelatonin excretion between 12.00–18.00 h showed a statistically significant seasonal rhythm, with peaks in December/January and in July.

Control of the annual rhythm of breeding in ewes: effect of an equatorial daylength with reversed thermal seasons

1967 ◽  
Vol 68 (1) ◽  
pp. 61-67 ◽  
Author(s):  
M. Wodzicka-Tomaszewska ◽  
J. C. D. Hutchinson ◽  
J. W. Bennett
Keyword(s):  
Annual Rhythm ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

1. Three groups of seven Southdown and seven medium wool Peppin Merino ewes were subjected, respectively, to seasons of daylength corresponding to a latitude of 60° S., reversed seasonal lighting (60° N.) and an equatorial daylength with reversed thermal seasons, for 2½ years. During the next 20 months group 1 continued as before. Group 2 had a 32-week photoperiodic year and group 3 had a 32-week thermal year with equatorial daylength.

Annual Rhythm of Human Reproduction: I. Biology, Sociology, or Both?

1990 ◽  
Vol 5 (3) ◽  
pp. 195-216 ◽  
Author(s):  
Till Roenneberg ◽  
Jürgen Aschof
Keyword(s):  
Human Reproduction ◽  
Annual Rhythm

Thyroxine levels in male and female white-tailed deer (Odocoileus virginianus)

1978 ◽  
Vol 56 (6) ◽  
pp. 945-949 ◽  
Author(s):  
G. A. Bubenik ◽  
A. B. Bubenik
Keyword(s):  
Population Structure ◽  
Odocoileus Virginianus ◽  
Wildlife Management ◽  
Mature Male ◽  
Male And Female ◽  
Annual Rhythm ◽  
Males And Females ◽  
Juvenile Males

Four major findings are described: (1) The episodic secretion of thyroxine in mature male white-tailed deer is most pronounced in the warmer months (June and September) and least demonstrated during the coldest months (November and January); (2) no clear annual rhythm of thyroxine was demonstrated in juvenile or mature male or mature barren female white-tailed deer. The monthly mean levels in mature males and females oscillate between 11 and 14 μg/100 ml throughout the year; (3) the seasonal levels of thyroxine in mature males are almost identical with the thyroxine levels of adult barren females; (4) the seasonal thyroxine levels of juvenile males are constantly higher than levels found in mature males. However, when these deer reach the age of 3 years, their thyroxine levels decrease to those of the adult.The collected data could serve as a tool of evaluation of population structure for wildlife management purposes.

CIRCANNUAL AND CIRCADIAN RHYTHMS IN PLASMA TESTOSTERONE IN FIVE HEALTHY YOUNG PARISIAN MALES

1975 ◽  
Vol 80 (4) ◽  
pp. 732-743 ◽  
Author(s):  
Alain Reinberg ◽  
Michel Lagoguey ◽  
Jean-Marc Chauffournier ◽  
François Cesselin
Keyword(s):  
Circadian Rhythm ◽  
Circadian Rhythms ◽  
Phase Shift ◽  
Statistical Analyses ◽  
Blood Sampling ◽  
Plasma Testosterone ◽  
Confidence Limits ◽  
Annual Rhythm ◽  
Fixed Times ◽  
Healthy Males

ABSTRACT Every other month, during the course of 14 months, the circadian rhythm in plasma testosterone (among others variables) of 5 healthy males (26 to 32 years) was documented. Subjects' synchronization: light-on at 7 ± 1 h; light-off at 23 ± 1.5 h during the whole year. Blood sampling 4-hourly, at fixed times during 28 h, for radioimmunological testosterone determinations. The cosinor method was used for statistical analyses. An annual rhythm in the testosterone 24-h mean is detected (P < 0.025) with a peak in October (from 16 July to 26 December, with 95% confidence limits). Annual mean (± 1 se) = 759 (± 26) ng/100 ml. Peaktrough difference = 197 ng/100 ml (from 106 to 290 with 95% confidence limits). The timing of the testosterone circadian peak, in the 24-h-scales also varies during the course of the year. The peak is found around 8 h in May and around 14 h in November, this phase-shift being statistically significant (P < 0.05).

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