I P Callard

Learn More
Adequate evidence exists to suggest the importance of temporal changes in steroid hormone ratios in the normal reproductive/vitellogenin cycle in oviparous and viviparous elasmobranchs and reptiles. In oviparous species, where the cycle is relatively short, secretion of gonadal hormones is synchronous; thus inhibitory actions of progesterone (P) on hepatic(More)
In non-mammals, estrogen-induced yolk precursors produced by the adult female liver are the main nutritional source for development. Evidence exists that progesterone exerts counter-regulatory effects on estrogen-induced vitellogenesis, and we have used the turtle model (Chrysemys picta) to study changes in hepatic progesterone receptor during the(More)
Significant changes in % free serum E2, T and P were observed during the annual cycle of the turtle. In contrast no significant changes in SHBG affinity constants (2.29-4.48 x 10(8) M-7) were found and binding capacity for estradiol 17B was between 3.47 and 3.96 x 10(-7) M except in preovulatory animals (2.00 +/- 0.25).
Anterior pituitary glands from ovulating Japanese quail (Coturnix coturnix) were used to investigate variation in sensitivity to chicken luteinizing hormone-releasing hormone (cLHRH I; Gln8-LHRH). Grouping the pituitaries by ovulatory stage provided preliminary evidence of changes in sensitivity to LHRH during the ovulatory cycle. Pituitaries taken from(More)
  • 1