[Cessation of ovarian cycles in a young mouse while in parabiosis with an older one]

Female mice 3 and 22-24 months of age were jointed in heterochronic parabiosis. That led to permanent estrus in young mice and maintenance of intact anestrus in old mice. After 8-9 weeks of parabiosis there appeared morphological signs of accelerated ageing in the ovaries of young animals, while no changes in the ovaries of old mice were observed. Serum progesterone of young partners decreased to the levels of old animals and estradiol levels remained unchanged, while prolactin content in adenohypophysis was the same as in young single animals but exceeded the level noted in young mice in parabiosis with young partners. Hormone content in old parabionts remained unchanged, as compared to the control. An old organism is thought to be the source of unidentified factors suppressing the ovarian function in young animals.