Effects of progesterone and estrogen on the histology of the oviduct of the garter snake, Thamnophis elegans

Seasonal steroid hormone levels and their relation to reproduction in the Western Diamond-backed Rattlesnake, Crotalus atrox (Serpentes: Viperidae)

“…However, the exact role of P, as well as interspecific variation in this role, is not well understood. The pregnancy maintenance properties of P in viviparous vertebrates include inhibition of follicular growth and oviductal contractility (Guillette et al, 1981) as well as maintenance of oviductal vascularity (Mead et al, 1981). Our results mimic those of a previous study (Bonnet et al, 2001) where P peaks early in gestation with a slow decline until parturition, suggesting that parturition may be stimulated by a drop in P levels.…”

Uterine morphology during the annual cycle inChalcides ocellatus tiligugu (Gmelin) (Squamata: Scincidae)

“…Yaron (1972) showed that progesterone reduced the stimulating effect of 17-␤ estradiol on the diameter of all the glands of the viviparous lizard Xantusia vigilis. In contrast, progesterone was not found to modify oviductal morphology in Thamnophis elegans (Mead et al, 1981).…”

“…We note morphological changes indicative of glandular modification during the annual cycle. In C. o. tiligugu, as in other reptiles (Mead et al, 1981;Uribe et al, 1988;Guillette et al, 1989), the endometrial glands grow rapidly in late preovulatory phase, filling with secretory granules. When the ovary contains vitellogenic follicles (Corso et al, 1978) and plasma estradiol concentrations are high (Angelini et al, 1986, the glands are fully developed.…”

Changes in oviducal vascularity during the reproductive cycle of three oviparous lizards (Eumeces obsoletus, Sceloporus undulatus and Crotaphytus collaris)

“…Exogenous administration of oestrogens to ovariectomized lizards in a manner similar to the natural reproductive cycle cause hypertrophy of the oviduct (Yaron, 1972: Christiansen, 1973Veith, 1974;Fawcett, 1975;Mead et al, 1981). Progesterone maintains the oviducts in some reptilian species (Veith, 1974), whereas it works synergistically with oestrogens in others (Fawcett, 1975;Mead et al, 1981).…”

“…Progesterone maintains the oviducts in some reptilian species (Veith, 1974), whereas it works synergistically with oestrogens in others (Fawcett, 1975;Mead et al, 1981).…”