Showing papers by "Sophie Lumineau published in 1998"

Circadian rhythm of activity in Japanese quail in constant darkness: variability of clarity and possibility of selection.

Abstract: In conditions of constant darkness, interindividual variability in the clarity of circadian rhythmicity was observed in sexually immature young quail, with birds classified as more or less rhythmic or arrhythmic The relative clarity of this circadian rhythm was observed on the actograms by measurement of the autocorrelation coefficient ratio over 12 cycles Autocorrelation coefficients were calculated from sequential series of total activity over 12-minute periods Crosses of selected phenotypes with different clarities of rhythmicity were conducted in order to study the possibility of selection of this characteristic From a random population (N = 42, twice), pairs of the most rhythmic birds (3 families), and pairs of arrhythmic birds (4 families) were reared Autocorrelation coefficient ratios of Fl birds from rhythmic families (N = 54) were greater than those of Fl birds (N = 48) from arrhythmic families (t-test, p < 0001) These ratios in offspring were significantly correlated with that of the mean

Induction of Circadian Rhythm of Feeding Activity by Testosterone Implantations in Arrhythmic Japanese Quail Males

Abstract: Studies in vertebrates have shown that hormones can influence circadian rhythms of behavior. We investigated whether testosterone could induce rhythmicity in arrhythmic Japanese quail, kept in DD. The animals used were 3 1/2-week-old castrated males from a line of quail selected for the lack of the circadian rhythm of feeding activity. After 3 weeks in DD, 8 birds were implanted with an empty implant and 16 others with a testosterone implant. Two weeks later, the operation was repeated. After implantation, we noticed that 15 out of 16 testosterone-treated birds showed a circadian rhythm of feeding activity, in contrast to the control birds, which remained arrhythmic. The clarity of this rhythm increased significantly after each implantation. A positive correlation was found between the indexes of clarity of the rhythm (autocorrelation coefficient ratio and area of the peak of spectrum) and the plasma testosterone level. The period of the induced free-running rhythm was identical to the specific value of the endogenous circadian rhythm in immature quail. The circadian period showed a significant lengthening with the second implantation. This lengthening looks like the variation previously observed in maturing rhythmic or implanted quail. So, it would appear that testosterone can act on rhythmicity on at least two levels: by inducing the circadian rhythm and increasing its clarity and by modulating its period. To explain these results, several hypotheses can be considered. First, the observed arrhythmy may be the consequence of an internal desynchronization of oscillators, responsible for generating the circadian rhythm of feeding activity, and testosterone could play a role in the coupling of these oscillators. Alternatively, we suggest that testosterone could act on the transcription of genes implicated in the control of the rhythmicity or may regulate by rapid signals the cellular rhythmic activity. The possible functional values of the enhancing of circadian rhythmicity by testosterone at different stages of the bird's life were discussed.