Ampullary-isthmic Junction Research Articles

Accelerated ovum transport in rabbits induced by endotoxin II. Changes in oviductal smooth muscle activity

Oviductal motility, measured with open-ended perfused catheters in anesthetized animals injected with human Chorionic Gonadotropin (hCG), is depressed 2 h following endotoxin injection and returns to control levels by 3 h after endotoxin injection. This decrease in motility is prevented by indomethacin. Endotoxin did not affect spontaneous or phenylephrine (PE)-induced contractions of oviduct when it was added to the bathing medium of in vitro tissues. Oviductal segments removed 2 h after endotoxin (26 h after hCG) showed electrical activity confined to the ampullary-isthmic-junction (AIJ), where ova were located; the dose-response curve for PE was shifted to the right and the maximum contraction was depressed. Activity of tissues removed 4 h after endotoxin more closely resembled control tissues except that the maximum contraction to PE was depressed, ova had passed out of the oviduct and a proovarian bias in the isthmus was not present. The response of the oviduct to prostaglandins (PGs) in vivo is critically dependent on the previous exposure to PGs. In endotoxin-treated animals PGE then PGF levels increase and the decrease in motility coincides with increased PGE levels, but accelerated ovum transport with the return of motility and activation of the isthmus.

The role of cilia in fertility: An evaluation by selective microsurgical modification of the rabbit oviduct

Fertility, ovum transport, and ciliary activity were examined in 35 rabbits after either unilateral microsurgical reversal or double transection (surgical controls) of 1 cm. segments of distal, middle, or proximal ampulla. Fertility was also examined following similar segmental reversal at the level of the distal and proximal isthmus in eight additional rabbits. Reversal of 1 cm. segments of distal, middle, or proximal ampulla effectively prevented pregnancy. In contrast, control animals that underwent double transection without reversal experienced unaltered fertility. Reversal of 1 cm. segments of distal or proximal isthmus was also consistent with normal fertility. Ova placed on the fimbrial surface of oviducts that had undergone ampullary segmental reversal were arrested at the distal anastomosis of the reversed segment. When mechanically displaced into the reversed segment, such ova were transported toward the ovary and were again arrested at the distal anastomosis. Transampullary transport of ova was normal in doubly transected controls. Ova were transported across both anastomosis sites to the ampullary isthmic junction. Studies of ciliary activity confirmed that cilia within reversed segments of ampulla beat in the ovarian direction, counter to that in the rest of the oviduct. Direction of ciliary beat remained unaltered in surgical controls. These experiments demonstrate a critical role of tubal cilia in ovum transport through the rabbit ampulla. In contrast, other mechanisms control ovum transport into and through the tubal isthmus.

Fertility Following Microsurgical Removal of the Ampullary-Isthmic Junction in Rabbits

The role of the ampullary-isthmic junction (AIJ) in fertility was investigated in the rabbit by using microsurgical tuboplastic techniques. Microsurgical transection or resection of the AIJ failed to alter fertility significantly. Nine of ten rabbits which underwent unilateral transection of the AIJ became pregnant on the operated side and eight of the ten became pregnant on the unoperated control side. Of the ten rabbits which underwent unilateral AIJ resection, all became pregnant bilaterally. The results of this study indicate that the AIJ is not necessary for normal fertility in the rabbit.

A study of the time course of egg retention activity in the rabbit oviduct.

Changes in egg retention activity of the oviduct were assessed during the first 5 days after HCG-induced ovulation in rabbits. Dextran microspheres were used as ovum surrogates. They were injected into the peritoneal cavity at 0, 10, 32, 41, 50, 64, 72 and 80 h following HCG. The distribution of ova and surrogates in the genital tract was assessed 24 h following surrogate injection in all groups and at 8 h following surrogate injection in animals injected 50 h after HCG. The distribution of microspheres injected up to 50 h after HCG was similar to that of eggs. Surrogates were not retained at the ampullary-isthmic junction (AIJ) shortly after passage of ova through this region. Morever, spheres injected 38 h after ovulation reached the eggs at the proximal isthmus in 8 h or less. Surrogates injected at 64 h following HCG or later were retained at the AIJ, indicating resumption of retaining activity at this level. It is suggested that egg passage through the AIJ is associated with a temporary reduction of the retaining activity lasting for approximately 16 h. Retaining activity at the AIJ is regained before eggs pass from the proximal isthmus into the uterus.

A random walk model of ovum transport.

This paper discusses the random nature of ovum transport, and presents a Brownian Motion model of ovum transport in the ampulla and isthmus. A new explanation of the delay in transport at the ampullary-isthmic junction, based on widely differing diffusion coefficients for the ampulla and isthmus, is proposed.

Effect of Ovulation and Hormonal Treatment on the in Vitro Response of Rabbit Oviducts to Prostaglandins E1 and [formula omitted

Rabbit oviductal circular muscle isometric contractile response was measured in relation to treatment with prostaglandin E1 (PGE1) and prostaglandin F2alpha (PGF2alpha). PGE1 (1 mug/ml) inhibition of the contractile response of the rabbit oviduct to field stimulation was increased in the proximal isthmus after ovulation. Estrogen and progesteron, in doses known to alter ovum transport, did not affect the response of the oviduct to PGE1. In comparison to the response of estrous tissues, the stimulatory effect of PGF2alpha on the isthmus was decreased 24 hours after administration of human chorionic gonadotropin (HCG). Treatment with estrogen and progesterone did not affect these postovulatory changes. The response of the ampullary-isthmic junction to PGF2alpha was significantly reduced 72 hours after administration of HCG. Neither ovulation nor steroid treatment affected the response of the ampulla to PGF2alpha. Changes in the sensitivity of the oviduct to prostaglandins after ovulation may be necessary for successful ovum transport.

Temporal Relationships Critical to Estrogen-Induced Delay of Ovum Transport

Previous studies have shown that a pharmacologic dose of estradiol given at the time of injection of human chorionic gonadotropin (HCG) significantly delays the transport of ova through the rabbit oviduct and that the site of delay is located at the ampullary-isthmic junction. The current experiments investigated the effects of varying the timing of the estrogen injection on ovum transport rates. Fifty-eight rabbits received injections of either Depot-estradiol or crystalline estradiol at various times before or after the injection of HCG. "Tube-locking" resulted when estrogen was administered before or at the time of HCG administration, whereas acceleration occurred when estrogen was given 12 to 24 hours after HCG. The results demonstrate that pharmacologic doses of estrogen exert two effects on ovum transport in the rabbit: (1) delay at the ampullary-isthmic junction and (2) acceleration once that junction has been traversed. The possible application of these results to contraception is discussed.

Peripheral plasma progesterone during egg transport in the rabbit.

Peripheral plasma progesterone concentrations were measured in New Zealand rabbits every 6 hr beginning 12 hr before and continuing until 96 hr after either natural mating, hCG injection, or saline injection. The number of ovulation points in naturally mated animals (9.3 +/- 0.6, mean +/- SE) was not significantly different from that in hCG-injected animals (8.6 +/- 1.5). There was a surge in progesterone secretion following both mating and hCG injection. Plasma progesterone concentrations reached a peak prior to ovulation and then fell to basal levels at the time of ovulation. Beginning at approximately 30 hr after the ovulation-inducing stimulus, there was a progressive, significant (P less than 0.001) increase in plasma progesterone concentration, which continued for the duration of the sampling period. The initiation of the postovulatory increase in progesterone secretion corresponds temporally with the movement of eggs from the ampullary-isthmic junction into the isthmus. The progressive increase in plasma progesterone between 30 and 72 hr after the induction of ovulation corresponds with the gradual movement of eggs through the isthmus into the uterus. The data suggest that movement of eggs through the oviductal isthmus is influenced by the postovulatory secretion of progesterone.

Medicated intratubal silastic spheres do not prevent pregnancy in rabbits

Plastic or silastic spheres 1.2 – 1.3 mm in diameter were placed in the ampullae of oviducts of rabbits. Spheres remained at the ampullary-isthmic junction but failed to prevent pregnancy after artificial insemination.

Effects of Hormonal Treatments which Alter Ovum Transport on β-Adrenoceptors of the Rabbit Oviduct

Beta-Adrenoceptor activity of rabbit oviductal isthmus has been determined quantitatively in vitro in tissues isolated 24 and 72 hours after human chorionic gonadotropin injection and after two hormonal treatments known to accelerate (progesterone) and retard (estrogen) ovum transport. Under conditions in which ova are located at the ampullary-isthmic junction and distal isthmus, the isthmus demonstrates a low incidence of spontaneous activity in vitro, poor response to acetylcholine, low affinity of beta-adrenoceptors for isoproterenol, and low efficacy of isoproterenol to inhibit acetylcholine-induced contractions. Under conditions in which ova are passing into the uterus, the isthmus shows the converse of these parameters. These data support the hypotheses that the oviductal isthmus functions as an adrenergic sphincter and that the actions of progesterone and estrogen in altering ovum transport rates are at least partially mediated through changes in adrenoceptors.

Distribution patterns of rabbit embryos during preimplantation stage.

AbstractThe pattern of transport and distribution of rabbit embryos in the oviduct and uterus was studied 15 to 168 hours post coitum (p. c.). The reproductive tract was frozen in liquid nitrogen, thawed, and cleared in benzyl‐benzoate solution using Orsini's technique. The location of the eggs and the ampullary‐isthmic junction were identified using transmitted light from a dissecting microscope. Accumulation of the eggs in the oviduct occured in two phases. In the first phase the eggs were retained above the ampullaryisthmic junction, 3–12 hours after ovulation. In the second phase, the eggs were retained 36–60 hours after ovulation, above the uterotubal junction (at a distance approximately 12 % of the oviductal length). The rate of transport of individual eggs in the oviduct, and the time of the entry of eggs into the uterus were variable. Au 78 hours p. c. most blastocysts occupied the proximal half of the uterine horn, although some appeared very close to the internal os of the cervix. Spacing of blastocysts in the uterus, 114 to 120 hours p. c., involved movement of blastocysts away from the cervix. Unfertilized eggs remained in the uterus, along with developing blastocysts 168 hours p. c. Few eggs were retained in the oviduct at 108 and 115 hours p. c.

Effect of estrogen and progesterone on the time-course of tubal ovum transport in rabbits

Experiments were designed to establish the detailed time-course of ovum transport through the rabbit oviduct, as well as the sites at which estrogen and progesterone exert their effects on egg transport. Whole oviducts were cleared in benzyl benzoate, and the eggs located in situ. Histologic sections were cut distal and proximal to each egg or egg cluster, in order to locate the eggs anatomically (isthmus, ampulla, or ampullary-isthmic junction). The microscopic anatomy was then correlated with the per cent of the distance from the fimbria to the uterotubal junction traversed by the ova. The pause of ova at the ampullary-isthmic junction seen in the controls was prolonged by estrogen. Progesterone, in contrast, seemed to exert its influence at both the ampullary-isthmic junction and the proximal isthmus. Ova were never found in the 10 per cent of the oviduct closer to the uterotubal junction.

Electric and mechanical activity of the rabbit oviduct in vitro before and after ovulation.

Oviducts from 47 rabbits which had been mated or induced to ovulate were examined in vitro. Intraluminal pressure recorded without perfusion showed variable characteristics in the beginning of the study but was significantly lower than the perfusion pressure. Contractions were asynchronous and their frequency varied with time in respect to mating. Electric activity propagated in both directions on the oviduct. The relation of local bursts to propagating bursts and the relation of bursts propagating in the uterine direction to the bursts propagating in the ovarian direction varied with the site of the oviduct and with time in respect ot mating. In the ampullaryisthmic junction bias was strong in the ovarian direction at 17 hours after mating presumably resisting the movement of eggs from the ampulla to the Isthmus. There was no bias at 43 hours and a slight bias at 71 hours in the uterine direction. In the isthmus bias in the uterine direction increased from 17 to 71 hours probably increasing the probability of eggs being moved toward the uterus. Results emphasize the complexity of contractile activity of the oviduct.

The effects of adrenergic drugs on ovum transport through the rabbit oviduct.

Summary. The effect of adrenergic drugs on ovum transport through the oviduct was studied at 24, 36, 48, 60, 72 and 84 hr post coitum (p.c.) in 240 mature, female Dutch-belted rabbits. In untreated rabbits, ova were located in the area of the ampullaryisthmic junction at 24 hr p.c.; most ova entered the uterus between 72 and 84 hr p.c. Epinephrine increased (P<0·01) the rate of ovum transport at 60 and 72 hr p.c., and most of the ova were found in the uterus. Phenoxybenzamine (α-blocker) inhibited ovum transport at 48 hr p.c. (P<0·05), while propranolol (β-blocker) was ineffective in altering ovum transport in any of the time periods. Regulation of ovum transport through the rabbit oviduct appeared to be governed in part, by a neural-endocrine interrelationship; this relationship could be altered by adrenergic stimulants and blocking agents.

Utero-oviductal motility with emphasis on ova transport.

Utero-tubal motility in vivo has been observed in conscious animals by several methods. In women cyclic variations have been seen. As ovulation approaches the activity increases. In vitro motility was maximal in myometrial strips from estrous ewes intermediate in strips from ovariectomized ewes and least in strips taken during the luteal phase. It has been thought that estrogen stimulates and progesterone suppresses oviductal muscular contractility. This has been disproved. A relationship between the activity of the oviduct and of the uterus has not been shown in women. Experiments indicate that prostaglandins are involved in the regulation of the oviductal function and of the uterine musculature. Other possible effects of prostaglandins are thought to occur. In women oxytocin and vasopression exert their maximal responses in the utero-ovarian motility during the late luteal phase and during menstruation. Both epinephrine and norepinephrine have stimulatory effects on oviductal activity throughout the cycle but least during the luteal phase. The uterine musculature responds differently to the effects of epinephrine and norepinehprine being more relaxed under epinephrine. The pacemaker of oviductal contractions has been localized in a discrete area around the ampullary-isthmic junction. Uterine activity is myogenic. Myometrial pacemaker activity is not confined to a distinct anatomical area. Impulses are conducted through the uterine muscle in a wavelike pattern and are propagated equally in all directions. The mammalian oviduct is a dynamic structure. It is not a passive conduit for the gavetes. The progress of spermatozoa in 1 direction and the transport of ova in the opposite direction are primarily controlled by the coordinated action of peristaltic antiperistaltic and segmental waves of contraction. The stream of oviductal secretions and the rhythmic beat of cilia are also important. Oviductal and uterine smooth musculature are under the control of the secretions of the corpus luteum. The utero-tubal junction is a transitional zone. In women the intramural portion of the oviduct has a convoluted course and varies in length from 1 to 3.5 cm. It acts in concert with the uterus and the isthmic portion of the oviduct. The progressive movement of ova is temporarily arrested 1-2 cm from the uterus. Ova then pass rapidly through the utero-tubal junction. A timed delivery of the fertilized ovum is of critical significance for normal implantation. In some sterile dysmenorrheic women as isthmic spasm has been demonstrated and assumed to have caused the sterility. Contraceptive drugs profoundly affect the myometrial cycle by changing the regulatory system. IUDs have been shown to cause altered oviductal function.

Muscular activity in the rabbit oviduct: a combination of electric and mechanic recordings.

A method is described by which muscular activity of the rabbit oviduct can be recorded in detail. Spontaneous electric activity and intraluminal pressure were simultaneously recorded in vitro in the oviducts of five ovariectomized, estrogen-treated rabbits. Electric activity was examined by five suction electrodes placed on the surface of the oviduct. Intraluminal pressure of the isthmus was recorded during perfusion at constant flow rates of 1.4, 2.9, and 5.8 µl/min. Perfusion at these low rates did not increase the electric activity of the isthmus by stretch. The main pacemaker was localized on a discrete area around the ampullary-isthmic junction (AIJ). The mean frequency of electric discharges was 3.6 ± 1.6/mm (mean ± SD) in the AIJ and 1.6 ± 1.2/min in the ampulla. From the AIJ electric activity spread through the entire isthmus, at a velocity of 17 ± 2 mm/sec, and it always preceded the pressure cycles. The mean perfusion pressure was 4 ± 2 mm Hg, the amplitude of the pressure cycles 19 ± 2 mm Hg, their duration 6.2 ± 1.2 sec, and their maximum rate of rise 26 ± 7 mm Hg/sec, at the perfusion rate of 5.8 µl/min. The luminal diameter of the resting isthmus was calculated to be less than the diameter of eggs.

IV—REPRODUCTIVE ENDOCRINOLOGY

A review of reproductive endocrinology is presented. The testis and ovary have 2 functional components: 1) secreting hormones and 2) producing gametes. In the male the interstitial or Leydig cells produce testosterone; in the female the ovarian follicles secrete estrogen 17alpha hydroxide-progesterone and progesterone in varying amounts according to the time of the ovarian cycle. In the testis follicle stimulating hormone (FSH) promotes spermatogenesis and stimulates the metabolic activity of Sertoli cells. Both FSH and testosterone are necessary for normal spermatogenesis. The regulation of testis function depends entirely on the secretion of luteinizing hormone (LH) and FSH by the pituitary gland. In the ovary FSH initiates the development of a group of follicles 1 of which matures and becomes responsive to the ovulatory stimulus of LH. At ovulation the ovum and surrounding cumulus of cells is extruded. The granulosa layer of the follicle becomes vascularized and luteinized forming the yellow corpus luteum. After ovulation the ovum is captured by the fimbria of the fallopian tube and migrates quickly to the ampullary-isthmic junction where fertilization occurs a few hours later if spermatozoa have been recently deposited in the genital tract. After about 4 days the zygote enters the uterus. If this happens too early implantation does not occur and ova are rapidly lost from the uterus. The transport of ova down the fallopian tube is influenced considerably by estrogen. Ovulation can be induced in infertile women by treatment with human gonadotropin of pituitary or urinary origin or by stimulation of endogenous gonadotropin secretion with clomiphen. Oral estrogen-progestogen combinations provide the most effective method of fertility control apart from sperilization. Combined oral contraceptives act primarily by suppressing ovulation. The midcycle LH peak which stimulates ovulation and initiates luteinization is abolished by progestational compounds through feedback inhibition. FSH secretion is inhibited by the estrogenic component or oral contraceptives leading in turn to failure of follicular development and estradiol secretion. Other effects of steroidal contraceptives on cervical mucus and sperm activity have been described but clearly they act mainly on ovulation. Progestogens such as chlormadinone have given less effective fertility control than combined preparations. Progestogens cause changes in the cervical mucus and inhibit sperm penetration but they do not suppress ovulation.

Profile analysis of the oviductal wall in rabbits and cattle

AbstractTwelve nulliparous New Zealand White female rabbits, and eight nulliparous Hereford heifers were used for profile analysis of the oviductal layers after in vivo and in vitro fixation of the oviducts. The unstraightened oviducts were cut into eight segments of about 1 cm starting from the uterotubal junction. Using a projection microscope, the areas of the lumen, mucosa + submucosa, and musculature of cross sections from each segment were measured planimetrically. The lumen of segments 5 and 6 (from the fimbriae) had the smallest surface area at all reproductive stages in both species. At about 72 and 168 hours after ovulation, the surface area of the lumen at these two segments increased by two‐fold compared to the estrous stage. The ampullary‐isthmic junction (AIJ) is probably located at 6/10 to 7/10 of the oviductal length (segment 5 or 6) in both species. The widening of the lumen at the AIJ, 60–70 hours post ovulation, is sufficient to allow the trapped eggs to pass rapidly to the uterus. The whole isthmus and particularly the AIJ seems to function as a sphincter, the closure of which may be coordinated by neuro‐endocrine mechanisms.

Biochemical changes in different parts of the rabbit Fallopian tube during passage of ova

Biochemical changes in the ampulla, ampullary-isthmic junction, and the isthmus portions of the rabbit Fallopian tube have been investigated during passage of ova. An increase in acid phosphatase activity throughout the tube and elevation of lactic acid level in the individual parts dependent upon the physical presence of ova are particularly noteworthy. It is suggested that the enzyme plays a role in denudation of ova and removal of cumulus and corona cell debris. Lactic acid is possibly involved in development of ova.

A STUDY OF EGG TRANSPORT IN THE RABBIT USING A FREEZING--CLEARING TECHNIQUE

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.