Jesus Ramos - Academia.edu (original) (raw)

Papers by Jesus Ramos

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2009

Research on sexual steroids has usually focus on seasonal changes, but little attention has been ... more Research on sexual steroids has usually focus on seasonal changes, but little attention has been paid to the existence of daily rhythms. A better knowledge of such daily fluctuations is required to asses accurately their plasma concentrations. To this end, in this paper we described the monthly day/night concentrations and seasonal daily rhythms of plasma sexual steroids (17β-estradiol, E 2 and testosterone, T) in Senegal sole females, reared under natural photo-and thermo-period. In addition, the influence of the natural annual fluctuation of the water temperature on the plasma concentration of these steroids was investigated, using one group of Senegal sole under a natural photoperiod, but with an attenuated thermal cycle (around 17-20 ºC) for one year. No significant day/night differences were detected in monthly samplings, but the existence of an annual rhythm of E 2 and T (p<0.01) with an acrophase in February was revealed by COSINOR analysis. Maximum values were reached in 1 March for both steroids (6.1 ± 1.7 ng ml-1 at mid-dark, MD and 4.0 ± 0.6 ng ml-1 at mid-light, ML for E2 and 1.4 ± 0.4 ng ml-1 at MD and 0.8 ± 0.1 ng ml-1 at ML for T) in anticipation of the spawning season (May-June). As regards seasonal daily rhythms, at the spring solstice (21 st March) a daily rhythm was observed for both steroids (COSINOR, p<0.01), with an acrophase at 20:00 h (E 2) and at 21:08 h (T). When Senegal sole females were submitted to an attenuated annual thermal cycle, the steroid rhythm disappeared (there was no surge in spring, as in the control group) and these fish did not spawn, despite being subjected to natural photoperiod conditions. This result underlined the importance of the natural annual fluctuation of water temperature and photoperiod on the synchronization of the spawning season and on the onset of steroidogenesis.

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2009

Research on sexual steroids has usually focus on seasonal changes, but little attention has been ... more Research on sexual steroids has usually focus on seasonal changes, but little attention has been paid to the existence of daily rhythms. A better knowledge of such daily fluctuations is required to asses accurately their plasma concentrations. To this end, in this paper we described the monthly day/night concentrations and seasonal daily rhythms of plasma sexual steroids (17β-estradiol, E 2 and testosterone, T) in Senegal sole females, reared under natural photo-and thermo-period. In addition, the influence of the natural annual fluctuation of the water temperature on the plasma concentration of these steroids was investigated, using one group of Senegal sole under a natural photoperiod, but with an attenuated thermal cycle (around 17-20 ºC) for one year. No significant day/night differences were detected in monthly samplings, but the existence of an annual rhythm of E 2 and T (p<0.01) with an acrophase in February was revealed by COSINOR analysis. Maximum values were reached in 1 March for both steroids (6.1 ± 1.7 ng ml-1 at mid-dark, MD and 4.0 ± 0.6 ng ml-1 at mid-light, ML for E2 and 1.4 ± 0.4 ng ml-1 at MD and 0.8 ± 0.1 ng ml-1 at ML for T) in anticipation of the spawning season (May-June). As regards seasonal daily rhythms, at the spring solstice (21 st March) a daily rhythm was observed for both steroids (COSINOR, p<0.01), with an acrophase at 20:00 h (E 2) and at 21:08 h (T). When Senegal sole females were submitted to an attenuated annual thermal cycle, the steroid rhythm disappeared (there was no surge in spring, as in the control group) and these fish did not spawn, despite being subjected to natural photoperiod conditions. This result underlined the importance of the natural annual fluctuation of water temperature and photoperiod on the synchronization of the spawning season and on the onset of steroidogenesis.