Endogenous Circannual Rhythm in Lh Secretion: Insight from Signal Analysis Coupled with Mathematical Modelling

نویسنده

  • ALEXANDRE VIDAL
چکیده

In sheep as in many vertebrates, the seasonal pattern of reproduction is timed by the annual photoperiodic cycle, characterized by seasonal changes in the daylength. The photoperiodic information is translated into a circadian profile of melatonin secretion. After multiple neuronal relays (within the hypothalamus), melatonin impacts GnRH (gonadotrophin releasing hormone) secretion that in turn controls ovarian cyclicity. The pattern of GnRH secretion is mirrored into that of LH (luteinizing hormone) secretion, whose plasmatic level can be easily measured. We addressed the question of whether there exists an endogenous circannual rhythm in a tropical sheep (Black-belly) population that exhibits clear seasonal ovarian activity when ewes are subjected to temperate latitudes. We based our analysis on LH time series collected in the course of 3 years from ewes subjected to a constant photoperiodic regime. Due to intraand interanimal variability and unequal sampling times, the existence of an endogenous rhythm is not straightforward. We have used time-frequency signal processing methods, and especially the Smooth Pseudo-Wigner-Ville Distribution, to extract possible hidden rhythms from the data. To further investigate the LF (low frequency) and HF (high frequency) components of the signals, we have designed a simple mathematical model of LH plasmatic level accounting for the effect of experimental sampling times. The model enables us (i) to confirm the existence of an endogenous circannual rhythm as detected by the LF signal component, (ii) to investigate the action mechanism of photoperiod on the pulsatile pattern of LH secretion (control of the interpulse interval) and (iii) to conclude that the HF component is mainly due to the experimental sampling protocol.

برای دانلود رایگان متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Endogenous circannual rhythm in luteinizing hormone secretion: insight from signal analysis coupled with mathematical modelling.

In sheep, as in many vertebrates, the seasonal pattern of reproduction is timed by the annual photoperiodic cycle, characterized by seasonal changes in the day length. The photoperiodic information is translated into a circadian profile of melatonin secretion. After multiple neuronal relays (within the hypothalamus), melatonin affects gonadotrophin-releasing hormone (GnRH) secretion, which in t...

متن کامل

Circannual alterations in the circadian rhythm of melatonin secretion.

To determine if a circadian rhythm known to be functionally related to the reproductive axis varies on a circannual basis, we monitored the circadian secretion of melatonin at monthly intervals for 2 years in four ovariectomized, estradiol-implanted ewes held in a constant short-day photoperiod. Prior to the study, ewes had been housed in a short-day (8L:16D) photoperiod for 4 years and were ex...

متن کامل

The Effect of Geographic Location on Circannual Adrenocorticotropic Hormone Plasma Concentrations in Horses in Australia

BACKGROUND Longitudinal evaluation of plasma endogenous ACTH concentration in clinically normal horses has not been investigated in the Southern Hemisphere. OBJECTIVES To longitudinally determine monthly upper reference limits for plasma ACTH in 2 disparate Australian geographic locations and to examine whether location affected the circannual rhythm of endogenous ACTH in the 2 groups of hors...

متن کامل

Effects of time after ovariectomy, season and oestradiol on luteinizing hormone and follicle-stimulating hormone secretion in ovariectomized ewes.

During the breeding season, five groups of three ewes were implanted at ovariectomy with 0.36, 0.5, 1.0 and 6.0 cm oestradiol implants or implants containing no steroid. Eleven days after receiving implants, blood samples were taken every 10 min for 6 h; implants were then removed. Treatments were repeated three times during each of two consecutive breeding seasons and four times during the int...

متن کامل

Mathematical Modelling on Lamprey GnRH-III using Autoregressive Logistic Processes

In this paper a mathematical model is developed based on current biological concepts of the lamprey GnRH-III involved in LH and FSH concentration . The physiologic role played by GnRH-III on gonadotropin secretion in mammalian species is controversial. Although GnRH-III is a weak GnRH agonist, early research in mammalian species suggested that GnRH-III can selectively stimulate the secretion of...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2009