Gonadotropin, Chorionic(Bristol Myers)

Summary. The utilization of a freezing\p=m-\clearingtechnique with rabbit oviducts produced data which differed from those obtained by tubal flushings or autoradiography. The current study indicated that the primary site for sphincteric activity was the tubo-uterine junction rather than the ampullary\p=m-\isthmicjunction. Previous studies have suggested that ova are retained in the ampullary portion of the oviduct before continuing through the isthmus (Burdick & Pincus, 1935; Aiden, 1942; Black & Asdell, 1958). Attempts by Greenwald (1961) to reveal the existence of a sphincter between the ampulla and isthmus have failed. In the earlier studies, ovum transport data were obtained by such techniques as tubai flushing (Greenwald, 1959) and autoradiography (Harper, Bennett, Boursnell & Rowson, 1960), both of which required manipulation of the oviduct. More recently, Hafez (1963) has suggested that tubai secretions may play a role in egg transport. If this is correct, it is possible that manipulation of the oviducts during flushing or autoradiography could result in the displace¬ ment of ova from their normal position. The purpose of this study was to reveal the position of eggs within the oviduct through the utilization of a technique that minimizes tubai manipulation. Sexually mature, New Zealand does were killed 15 to 65 hr after ovulation (induced by an intravenous injection of 75 i.u. hcg, Squibb, Follutein) by an overdose of Nembutal. Within 1 min, the animals were opened and liquid nitrogen was gently poured over both uterine horns and oviducts. Following gradual thawing, the entire oviducts with a 5-mm segment of the proximal uterine horn were dissected free of fat and subjected to a benzyl benzoate clearing technique described by Orsini (1962). The exact positions of the ova with respect to the ampullary-isthmic junction (AIJ) and the tubo-uterine junction (TUJ) were determined by microscopic examination. The length of the different tubai segments of seventy cleared oviducts was as follows: ampullary portion, 30 to 80 mm (average 58 mm) ; isthmic segment, 40 to 85 mm (average 54 mm) ; total oviduct length including the TUJ, 70 to 160 mm (average 112 mm). The position ofall AIJ was 40 to 65% (average52%) of the distance from the fimbria to the TUJ. Such variation was noted not only among animals but between oviducts in the same doe.