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Day-6 rabbit blastocysts were able to accumulate [3H]quinuclidinyl benzilate (QNB) from their environment. This accumulation was reduced approximately 50% in the presence of 1.5 x 10(-4) M atropine (an accepted antagonist for ligands which bind to muscarinic cholinergic receptors). The accumulation of QNB was sensitive to temperature and was apparently saturable. In the presence of 2 nM QNB, Day-6 blastocysts accumulated 30.3 +/- 2.0 fmoles per blastocyst. When the cellular elements alone were examined, lesser amounts of specific binding were detected. Owing to the complexity of this multicompartmental system, Scatchard analysis did not provide meaningful results. This accumulation appears higher than that reported for other tissues such as rabbit heart homogenates or rabbit uterine endometrial cells. This muscarinic cholinergic accumulation may have some roll in blastocyst-maternal recognition.

Stromal cells and epithelial glands were separated after enzymic digestion of specimens obtained from 27 women at hysterectomy or endometrial biopsy during the luteal phase, and then cultured to confluence in vitro. PGE release into the culture medium (mean +/- s.e.m.: ng/mg protein/24 h) from gland cell cultures was not changed by oestradiol (17.6 +/- 1.3 for control and 25.5 +/- 2.8 for oestradiol, respectively). However, in the presence of oestradiol, PAF (5 ng/ml) significantly elevated PGE release to 44.2 +/- 5.8. No stimulation was observed in the presence of progesterone. Stromal cell medium had no effect on PGE release in gland cell cultures. PGE release was always much lower in stromal cell cultures than in glands (control: 4.7 +/- 0.6). PAF stimulated PGE release in the presence of oestradiol in these cells also; gland cell medium was without effect. In co-cultures of glandular and stromal cells, PGE release was more similar to that seen in gland cell cultures, with PAF being stimulatory under the influence of oestradiol. PGF release into the medium from the same gland cell cultures was significantly elevated by hormonal treatment, being greatest (62.0 +/- 11.3) with oestradiol alone, and was strongly inhibited in all wells by addition of PAF and stromal cell medium. In stromal cell cultures without hormonal addition, PGF levels (15.0 +/- 2.4) were similar to those seen in glands (18.1 +/- 3.1), and no stimulation was achieved by oestradiol (29.6 +/- 5.9). PAF was inhibitory on PGF release, while gland cell medium was without effect. Co-cultures gave PGF values generally similar to those of stromal cells; oestradiol was again stimulatory (55.0 +/- 9.3). PAF was significantly inhibitory in the presence of oestradiol. PAF (mean +/- s.e.m.: pmol/mg protein/24 h using a platelet serotonin release assay) in stromal cells was significantly increased from control [M199 alone] (0.31 +/- 0.12) by progesterone (1.00 +/- 0.17). Addition of PGE-2 (7.5 ng/ml) to progesterone-treated wells further increased PAF concentration (5.34 +/- 0.09), but was without effect in wells receiving oestradiol alone. Wells exposed to both hormones exhibited an intermediate response. Similar results were obtained with addition of gland cell culture medium, presumably due to its endogenous PGE content. In co-cultures, PAF concentrations were significantly elevated by progesterone alone (4.78 +/- 0.78) or when combined with oestradiol (2.38 +/- 0.51), but not by oestradiol alone. Treatment with PGE-2 caused no additional stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)

The effects of adrenergic drugs and prostaglandins (PCs) on rabbit oviductal isthmus motility were compared. Balloon-tipped fluid-filled catheters placed in the lumen of the isthmus were used to record muscular activity. The intravenous (iv) injection of E-series PGs and the �-adrenoceptor stimulator isoproterenol both caused a nearly complete suppression of spontaneous oviductal activity. Pretreatment with the �-adrenoceptor antagonist propranolol effectively blocked the response of the oviduct to isoproterenol but had no effect on the response to E- or F-series PGs. A maintained spasmodic contraction was induced by the iv injection of both norepinephrine, an a-adxenoceptor stimulator, and F-series PGs. Pretreatment with the n-adrenoceptor antagonist phenoxybenzamine blocked the response of the oviduct to norepinephrine without having any effect on the response to PGEs or PGFs. A mutual antagonism between the a-adrenoceptor stimulator and PGEs, and between the p-adrenoceptor stimulator and PGFs was also demonstrated. The relationship and similarity between adrenergic and PC responses indicate that both agents may be synergistically involved in the control of oviduct motility. The demonstration that adrenergic antagonists block the response of the oviduct to adrenergic stimulation, but have no effect on the response to PGs, suggests that adrenergic

Uteri from mature baboons at various stages of the menstrual cycle were collected at autopsy. Transverse slices of the uteri were incubated with [3H]prostaglandins in Tyrode's buffer. Bound and free ligands were separated by filtration. Prostaglandin (PG) accumulation by the tissue slices was evaluated as a function of incubation time, PG type and concentration, temperature, wet weight of tissue and stage of the menstrual cycle. There was no significant difference in PG accumulation in response to PG type (PGE2 or PGF2α) or stage of the menstrual cycle. These results from baboon uteri were compared with those using baboon oviducts and also rabbit uteri and oviducts. Unlike the rabbit tissues, the baboon oviducts and uterine tissues did not exhibit specific net accumulation of prostaglandins. J. Endocr. (1985) 106, 49–53

Membrane preparations (100 000 g pellet) of rabbit, baboon and tree shrew (Tupaia belangeri) uteri were studied for binding of [3H]prostaglandin E2 ([3H]PGE2). Unbound [3H]PGE2 was separated by filtration through Whatman GF/F filters. Nonspecific binding was determined by the amount of radioactivity associated with the filters in the presence of a 100-fold excess of radioinert PGE2. PGE2 bound to membranes could be displaced by some other prostaglandin (PG) molecules: PGE1, 16,16-dimethyl-PGE2, PGA1 and PGF2α, but not by 6-keto-PGF1α, PGD2 or arachidonic acid. No PGE2 binding was detected using either membrane ghosts from red blood cells or liposomes. Apparent equilibrium of the binding was reached by 60 min. There was no difference in dissociation constant (Kd) values between rabbits of different reproductive stages (mean range±s.e.m. was from 4·6±0·3 to 5·5 ± 1·0 nm), but pregnant baboons showed a significantly lower value (3·3±0·4 nm) than did cyclic animals (12·0 ± 2·0 nm). Binding capacity (Bmax) values, in contrast, were different only between oestrous rabbits and other reproductive stages. The small amounts of [ill] tissue only permitted estimates of the Kd and Bmax values to be made; these were 3·8 nm and 499 fmol/mg protein for oestrous animals and 5·4 nm and 674 fmol/mg protein for animals on day 7 of pregnancy, assuming only one class of sites. The present results demonstrate the presence of specific binding sites for PGE2 in uteri from several species.

Summary. Rats were treated with LH at 08 :00 h on the first day of dioestrus or on Days 1 and 2 of dioestrus. Peroxidase activity increased within 3 h in females injected with LH on Day 1 and was associated with a depletion of ascorbate that lasted until the afternoon of Day 1. Values of both substances then returned to basal values by the morning of Day 2. A second LH injection on Day 2 produced effects similar to those seen after LH on Day 1. Females treated with LH did not display greater \g=D\5-3\g=b\-HSD activity than did controls on Day 1 after one LH injection, but did on Day 2 after two LH injections. Nonetheless, the changes were only modest by comparison with those of peroxidase. The peroxidase\p=n-\ascorbatesystem appears to be involved in the mechanism responsible for the increased secretion of ovarian progesterone resulting from LH stimulation.

An increase in preload from 0.75 to 10 g caused an increase in the sensitivity of rabbit aortic strips to phenylephrine, serotonin, and KCl. Several eicosanoid synthesis inhibitors were utilized to determine whether production of endogenous eicosanoids contributed to the change in muscle sensitivity. Quinacrine (10 microM), indomethacin (10 and 50 micrograms/ml), meclofenamate (50 and 100 micrograms/ml), 5,8,11,14-eicosatetraynoic acid (ETA, 50 and 100 micrograms/ml), and nordihydroguaiaretic acid (NDGA, 10 microM) all shifted the concentration-response curves of various agonists to the right, indicating a decrease in the sensitivity of the muscle to these agents. Thromboxane synthesis inhibition by 1 microM (E)-3-[4-(1-imidazolylmethyl]phenyl-2-propenoate (OKY 046) exerted no effect on sensitivity. Indomethacin at both concentrations caused a parallel shift in the high and low preloaded strips but was unable to alter the influence of preload on sensitivity. A similar effect was observed with the lower concentrations of meclofenamate and ETA. NDGA and higher concentrations of meclofenamate and ETA not only shifted the sensitivity in both high and low preloaded strips but also eliminated the preload effect. These results indicate that cyclooxygenase and lipoxygenase metabolites both alter aortic smooth muscle sensitivity to contractile agents and suggest that lipoxygenase metabolites may play a role in the change in sensitivity seen with preload.

Arachidonic acid (AA) is often utilized in in vitro studies to label cellular pools of AA or to elicit cellular responses dependent on eicosanoid production. Because of the hydrophobic nature of AA, organic diluents such as ethanol or dimethyl sulfoxide are utilized in preparing concentrated solutions. The fate of AA when added to aqueous medium is not generally considered because of the dilution of the AA, although some investigators utilize bovine serum albumin (BSA) to solubilize as well as to trap AA and its hydrophobic metabolites. These experiments demonstrate a rapid and progressive decline in AA concentration when added to aqueous media in tissue baths and in glass test tubes. The extent of the decline was greater in the tissue baths than in the test tubes. The calcium ionophore A23187, which is used to stimulate AA metabolism, is also hydrophobic, and its concentration also decreased when added to aqueous media. The decline in the concentration of both AA and A23187 was due to adsorption to the container walls. The presence of 1% BSA in the aqueous solution attenuated and even eliminated the decline in the concentration, indicating binding of the two agents to the protein. However, the presence of BSA in culture medium inhibited the A23187-induced stimulation of AA metabolites in baboon aortic smooth muscle cells. These results underscore the complexities arising from the in vitro use of hydrophobic substances in biological systems.

Summary. Thirty-one virgin female rats in pro-oestrus were mated with fertile males (Day 0). Groups of four to six animals were dosed by mouth with Compound I.C.I. 33,828 (100 mg/kg) on 3 successive days starting, in different groups, on Days \p=m-\1,0, 1, 2, 3 and 4, respectively. Twelve control rats were given the vehicle only. In all groups treatment with I.C.I. 33,828 reduced the number of rats found pregnant at laparotomy, but in the treated animals found pregnant at laparotomy the mean number of implantation sites was not significantly different from that in the controls. In only one group, that dosed on Days 2 to 4, were no implantation swellings found in any animals. The results at autopsy showed that treatment resulted in heavy mortality of foetuses after implantation in those rats in which implantation occurred. In the control rats, 6\m=.\6%of the eggs shed were lost before and 6\m=.\6% after implantation. The corresponding figures for all the treated animals were 63\m=.\7and 30\m=.\2%respectively. Moreover, in the treated rats the development of the foetuses which survived to Day 19 was retarded, as judged by the size of the swellings on Day 8 or 11, and by the weight of the foetuses which at autopsy amounted on average to only two-thirds of that of the controls. In an experiment in which pseudopregnant rats were dosed with I.C.I. 33,828 either before or before and after one horn of the uterus had been traumatized, it was found that the compound prevented the occurrence of a full deciduomal reaction. The effect was more marked when it was administered on Days 2 to 4 than on Days 4 to 6 of pseudopregnancy. From these results it was deduced that the compound might produce its antifertility effects by inhibiting pituitary function, thus upsetting the endocrine balance necessary for the maintenance of pregnancy.

(0 A new technique is described in which 120-μ anionic resin spheres, impregnated with the radioactive gold isotope 198Au, are employed to simulate rabbit eggs. By their use, a study has been made of the pattern of egg transport in the Fallopian tube of the rabbit in vivo. (2) It has been shown that, in the first 8 hr after ovulation, the spheres have travelled 49% of the length of the tube. During the next 40 hr, movement down the tube is very slow until, at 48 hr after ovulation, the spheres are concentrated above the utero-tubal junction, 79% of the distance down the tube. (3) It has been possible to study the passage of the spheres into the uterus both at 56 and 64 hr after ovulation. Of the total number of spheres studied, 55% had passed into the uterus at the earlier and 90% at the later time. (4) Evidence is also included to show that the movement of the spheres reproduces the normal movement of eggs fairly closely. Their mean rate of progress is some 4% slower than the eggs, and this is due to a small proportion of the spheres lagging or

SUMMARY The technique of tracing the movement of 'artificial eggs' (radioactive spheres) by autoradiography was used to study the effects of progesterone and oestrogen either alone, or in combination, on egg movement through the reproductive tract of ovariectomized rabbits. Ovariectomy was performed 7 days before the transport experiments, except in one treatment group when it was done 35 days previously. The animals were autopsied at 8, 24, 48 or 56 hr. after insertion of the spheres into the ampullae of the Fallopian tubes. There were five or more animals in each group except one. The effects of various hormonal replacements were studied. It was found that removal of the ovaries, whether 7 or 35 days before the transport experiments commenced, caused extremely irregular movement of the spheres through the Fallopian tube. Marked differences were recorded between the behaviour of the spheres in animals ovariectomized for the shorter as compared with the longer period. None of the hormonal treatments produced normal movement of the spheres through the Fallopian tube. Progesterone delayed movement of the spheres through the ampulla very markedly, but if the spheres reached the isthmus they passed into the uterus on all occasions. Neither the isthmus nor the utero-tubal junction in animals so treated proved a barrier to the movement of the spheres into the uterus. Movement of the spheres through the uterus of these animals was inhibited, and most of the spheres recovered were found in the half of the uterus nearest to the utero-tubal junction. Oestradiol benzoate, in the dose administered, had an accelerating effect on the passage of the spheres through the tube, and also through the uterus. Some spheres were found to have entered the vagina in three out of the four time-groups studied. It was observed that despite the accelerating effect of oestrogen on the movement of the spheres through the Fallopian tube a certain percentage, even after the longest interval studied, was trapped at the junction of the ampulla and the isthmus. The two groups treated with oestrogen and progesterone in combination tended to produce results similar to those observed after treatment with either progesterone or oestrogen alone, depending on which hormone was dominant. It is concluded that the amount of oestrogen present is critical in ensuring rapid transport through the ampulla, but that a proper balance of oestrogen and progesterone must be maintained to ensure retention of the spheres or eggs in the isthmus until the correct time for entry into the uterus. It is clear that this pattern of egg movement through the Fallopian tube cannot be re-created by fixed daily doses of progesterone and oestrogen.

Studies of oviduct motility in rabbits have been made using indwelling balloon-ended fluid-ifiled catheters. Daily recordings were made on 12 rabbits for periods up to 21 days. Oviduct motility was characterized by bursts of activity which lasted for 2-3 mm followed by silent periods ranging up to 20 mm. In some cases contractile activity continued without intermission for many minutes. There was no correlation for bursts of activity in left and right oviducts of the same animal. Daily variations of muscular activity were seen in 10 of 12 rabbits, and in 6 of these 10 cyclical peaks of activity occurring every 4-7 days were observed. Each oviduct exhibited its own pattern of cyclical variation. In 4 of the 10 rabbits. exhibiting variations in muscular activity of the oviduct, ovulation was induced by an intravenous injection of 100 IU of human chorionic gonadotrophin. Following injection little increase in muscular activity of the oviduct was seen for 4 hr, by which time bursts of contraction occurred every 15 mm. There was then a rapid increase in the mean amplitude of contractions until 10 hr, followed by a further slower increase up to 24 hr after injection. At this latter time bursts of activity occurred every 5-8 mm. During the next 2 days there was a sharp fall in the amplitude of muscular contractions to preinjection levels.

Photomicrographs of the cytological changes of the sperm head and of the female chromatin in the rabbit egg, from the time of sperm penetration and activation of the second meiotic metaphase up to the formation of pronuclei and syngamy, are presented. During a study on factors affecting sperm penetration of rabbit eggs, some anomalous eggs were observed. One unfertilized egg possessed two second meiotic metaphases and associated first polar bodies, while another similar egg had two first and two second polar bodies, two sets of female chromatin, and one fertilizing sperm. In this latter egg fertilization was apparently proceeding normally. Two eggs within a single zona pellucida were also seen; one of these was a primary oocyte, while the other was a normally penetrated egg. Evidence is also presented which indicates that the incidence of polyspermy (usually dispermy) is increased, if eggs enter the oviduct at 14 hours or later after mating. This is thought to be due to more fully capacitated sperm present at the site of fertilization at these later times, and thus there is a greater chance of two or more sperm entering the vitellus at the same time.

Ten groups, five to ten animals per group were used in demonstrating that progesterone plus cortisol acetate can induce implantation and maintain embryonic growth in hamsters subjected to ovariectomy and adrenalectomy on Day 1 or on Day 4 of pregnancy, Fetal weights on Day 14 were, however, significantly lower than in sham-operated control animals, although they were not different from those in animals only ovariectomized and given progesterone. It is concluded, therefore, that it is unnecessary to invoke secretion of estrogen either from the ovaries or from the adrenals for induction of implantation in hamsters.

Administration of DHA (2.5, 5 or 10 mg/day sc) on days 2–5 interfered with pregnancy in rats. This effect could be produced in intact and adrenalectomized rats and was potentiated in partially hepatectomized ones, total failure of implantation being produced by daily doses of 10, 10 and 5 mg, respectively. Although doses of 2.5–10 mg/day of DHA greatly reduced the deciduomal response of the uterus to trauma in pseudopregnant rats, implantation failure was due not to this, but to expulsion of the eggs from the reproductive tract by day 5 of pregnancy. This effect was similar to that produced by administration of estrogens. Cortisol acetate did not influence the effect of DHA on pregnancy. In intact or adrenalectomized immature rats, the uterus responded to administration of DHA with a dose dependent increase in weight and histological changes similar to those produced by estradiol. In ovariectomized and ovariectomized-adrenalectomized animals smaller responses to similar doses of DHA were produced. In inta...

Ovariectomy of hamsters on day 1 or day 4 of pregnancy without steroid replacement resulted in complete failure of implantation. This was, however, induced by daily subcutaneous (s. c.) injection of either 1 or 2 mg progesterone. Although implantation could occur in the absence of oestrogen, greater numbers of eggs implanted in its presence after ovariectomy on day 1. Oestrogen administration (1 μg/hamster/day s. c. of oestrone) also increased the proportion of embryonic development to day 14 in the ovariectomized, progesterone-treated animal.

chorionic gonadotrophin, with iproniazid (25 mg/kg/day sc) or reserpine (0.25 or 1.0 mg/ kg/day sc). The animals were then killed at 26, 50 or 90 hr after insemination and the ovulating injection. The oviducts were divided into three portions-comprising the ampulla, distal and proximal isthmi. These portions and the uteri were flushed for recovery of eggs and then processed, along with the ovaries, for determination of the content and concentration of norepinephrine (NE). The levels of NE were substantially increased in all these tissues of all groups over those of untreated animals by the monoamine oxidase inhibitor and decreased to near zero by reserpine. The most significant changes in content and concentration of NE occurred in the distal isthmus, and to a lesser degree in the proximal isthmus. There was some indication of retarded egg transport associated with decreased NE in the isthmus of the reserpine-treated groups and accelerated transport with elevated NE in the isthmus of iproniazid-treated groups. These alterations in the speed of egg transport were, however, only marginal when compared to the effects of progesterone (accelerated) and estrogen treatment (retarded transport) in previous experiments. Furthermore, these hormonal treatments had both significantly elevated NE levels in the isthmus (Bodkhe and Harper, 1971). In the present experiments total NE in the tissue was measured, and no information on changes of NE free in the neurons was obtained. Thus egg transport through the oviduct may be controlled mainly by small changes in free NE or hormones may exert their effects in ways other than by changes in noradrenergic activity.

Newly ovulated eggs in cumulus, stained with toluidine blue, were transferred to the ampullae of the oviducts of (a) 5 rabbits at the time of ovulation, and thereafter at intervals of 24 hr for the 3 succeeding days, and (b) 21 does in estrus and at various times during induced pseudopregnancy. The mean times for the eggs to traverse the ampulla were 7.5 ± 0.7, 8.4±0.8 and 16.0±3.8 min in estrus, at ovulation, and on day 7 of pseudopregnancy, respectively. During this period the mean time of transport increased by 1.2 ± 0.28 min/day. This increase was highly significant. Owing to differences in oviduct lengths between rabbits, the rate of transport along the ampulla (mm/min) was felt to be a more valid measurement. The mean rates of transport were 11.4 ± 0.9, 8.9 ± 1.5 and 5.7 ± 0.8 mm/min in estrus, at ovulation and on day 2 1/2 of pseudopregnancy, respectively. During this period the mean rate of transport decreased by 2.36 ± 0.58 mm/min/day, a highly significant decrease. No further change was noted be...

SUMMARY By means of the technique of tracing the movement of 'artificial eggs' (radioactive spheres) by autoradiography (Harper, Bennett, Boursnell & Rowson, 1960) a study has been made of the effects of a decreasing oestrogen and various increasing progesterone doses on egg movement through the reproductive tract of ovariectomized rabbits. Five or more animals were autopsied at 8, 24, 48 and 56 hr. after insertion of the spheres into the ampulla of the Fallopian tube. It was hoped that such treatments would produce hormonal conditions similar to those in intact rabbits after ovulation, and that therefore normal tubal transport would occur. The treatments used produced normal movement of the spheres through the ampulla and the isthmus, and most of them were retained in the Fallopian tube up to 48 hr. after insertion. However, by 48 hr. one or more spheres were observed to have entered the vagina in all treatment groups. None of the treatments caused most of the spheres to enter the uterus between 48 and 56 hr. after insertion, as would be the case in intact animals at a similar time after ovulation. It was concluded, however, that such treatments could produce tubal transport normal up to 48 hr. in ovariectomized rabbits, and that the presence of oestrogen appeared to be the controlling factor.

Unfertilized eggs recovered fronu donor ral)bits shortly after ovulation induced by injection of HCG were transferred to the oviducts of mated recipients or recipients inseminated with 200 nuillion spermatozoa and injected with HCG at known times. It was found that although only 407r of such eggs were penetrated in 1.5 h following transfer to mated recipients at 9-9.75 h after mating, 58 and 66� were penetrated during the same period if transfers were delayed until 13.75-14.25 and 19.5-20.0 h after mating, respectively. By 24 h after nuating the percentage of eggs penetrated had fallen again to 43%. It was shown by ligation of the oviduct at the uterotubal junction that adequate sperm were in the oviduct by 9.25-9.75 h after inselllinatiOn to ensure this enhanced fertilization following transfer at 14 or 17 h hut not 20 lu after insemination. Tiuese results implied that although spernu continued to migrate from the utenis into the oviduct, more sperm in the oviduct at later times was not responsible for this plsenomellon. Further experiments in which ligation was done at the anipullar-isthmic junction or the middle of the isthnuls showed that sperm were retaiiued in the proxilnal isthmus just above the uterotuhal junction for several hours. When whole ovidncts were fixed and serially sectioned and the number .‘.nd distribution of sperm determined, it waS fnund that at 9 h after insemination few sperm were at the site of fertilization. In the oviducts of animals killed at 14 or 20 h after insemination, the spernu in tlue oviduct (irrespective of whether tile uterotubal junction luad been ligated or not) had become redistributed with many more found at the site of fertilization. It is concluded that more eggs are penetrated in a short period of time (1.5 h) followed late transfers because there is tile ilnmediate posSii)ility of egg and sperm Ineeting.

Hemi-ovariectomy on days 1, 2 and 3 after the appearance of leukocytes in vaginal smears in rats (made pseudopregnant by reserpine injections at estrus) caused a return of proestrus between 2 and 3 days after operation in all animals. There was compensatory ovulation at the first or second postoperative proestrus, as shown by counting healthy implantation sites at laparotomy following a successful mating. Progesterone replacement immediately after hemiovariectomy successfully maintained the persistent leukocytic vaginal smears of pseudopregnancy in all animals so treated. Sham operation was without effect. (Endocrinology 87:173,1970) THERE IS good evidence to indicate that the central nervous system chronically inhibits the secretion of prolactin in the rat (1–4). It has been postulated that the factor which stimulates luteotrophin secretion does so by suppressing this neural inhibition, and that, during pseudopregnancy, progesterone may maintain the secretion of luteotrophin by a positive feedback (3).

Platelet-activating factor (PAF) concentrations were low in the non-pregnant, oestrous uterus (mean +/- s.e.m.: 2.2 +/- 1.2 pmol/g, n = 3). However, uterine PAF increased dramatically during pregnancy to a maximum of 37.8 +/- 4.90 pmol/g (n = 7) on Day 5. By Day 7, PAF concentrations in the uteri of pregnant rabbits had returned to levels similar to those found at oestrus. In contrast, uterine PAF in pseudopregnant rabbits peaked at 30.6 +/- 2.8 pmol/g (n = 8) on Day 4, declined to 20.5 +/- 2.4 pmol/g (n = 8) on Day 5 and then remained at that concentration through Day 7. Uterine PAF co-migrated with synthetic PAF (1-O-hexadecyl-2-acetyl-sn-glycero-phosphocholine) in both thin-layer and normal-phase high-performance liquid chromatography. PAF activity in the uterus during pregnancy and pseudopregnancy was found almost exclusively in the endometrium; little or no PAF was found in myometrium, uterine flushings or blastocysts. While no PAF was detected in blastocysts on Days 5 and 6 of pregnancy, the presence of the embryo appears to modulate biosynthesis and/or degradation of PAF by the uterus, since PAF decreased significantly in uterine tissue apposed to the implanting embryo (but not in similar areas between such attachment sites). Increased concentrations of PAF in the preimplantation rabbit uterus followed by a dramatic decrease on the day of blastocyst attachment suggest that this potent inflammatory autacoid may play a vital role in implantation.

Endotoxin derived from Salmonella enteritidis (Boivin) completely interrupted pregnancy in the rabbit when given as a single dose (10 or 20 microgram/kg) intravenously on Day 4 or Day 8 of pregnancy. Indomethacin (2 or 10 mg/kg) was unable to prevent this effect.

Unfertilized eggs recovered from donor rabbits at known times after injection of HCG were transferred to the oviducts of mated recipients (prevented from ovulating by having their ovaries covered with nail polish) at specific times after mating. When newly ovulated eggs (11.25–13.5 hours after HCG injection) were left in the oviducts of the recipients for 1, 1.5, 2, 2.5 and 3 hours, 15, 30, 44, 59 and 75% respectively were penetrated by spermatozoa. If the unfertilized eggs were allowed to age in the oviducts of the donor before transfer then fertilizability decreased: only 41 and 25% of eggs 15–15.5 hours and 17–17.5 hours old at time of transfer respectively were penetrated during 2.5 hours in the recipients' oviducts compared to 59% of 13–13.5 hour eggs. No beneficial effect from maturation in the donor of the unfertilized egg and its membranes was observed. When eggs with cumulus cells removed were transferred to recipients at 9–9.5 hours after mating, then a decrease in the percentage of eggs penetrated during 2.5 hours in the recipients' oviducts was found. Removal of both cumulus and corona cells had no greater effect than removal of cumulus alone. However, when eggs similarly treated were transferred to recipients at 14 hours after mating, neither removal of cumulus nor of cumulus and corona cells had any effect on the percentage of eggs penetrated during 2.5 hours. It is concluded that when conditions for fertilization are not optimal the cumulus is important for ensuring meeting of sperm and egg, but that when conditions are optimal then presence of these cellular layers is not important. Whether the products of ovulation play a role in the final stages of capacitation of sperm was tested by transferring eggs into the oviducts of rabbits unilaterally ovariectomized (more than 3 weeks previously) at 13.5–14.75 hours after mating. No difference in percentage of eggs penetrated was observed between oviducts on the ovariectomized and intact sides. The contact of the sperm with the products of ovulation in the one oviduct did not give them an advantage over the sperm in the other oviduct without such contact. It was found that although only 30% of newly ovulated eggs were penetrated in 1.5 hours following transfer to recipients at 9–9.5 hours after mating, 57 and 66% were penetrated during the same period if the transfers of similar eggs were delayed until 13.75–14.0 hours and 19.5–20.0 hours after mating of recipients respectively. It is suggested that these increases in percentages of eggs penetrated are a reflection of the presence of more sperm or of more fully capacitated sperm in the oviduct at these later times.

Newly ovulated eggs in cumulus, stained with toluidine blue, were transferred to the ampullae of the oviducts of (a) 36 mature rabbits 7 days after bilateral ovariectomy, and (b) 13 intact mature rabbits. These rabbits received various doses of progesterone and/or estradiol benzoate (EB), dissolved in cotton seed oil and injected subcutaneously. The mean times (min) for the eggs to move from the base of the infundibulum to the junction of the ampulla and the isthmus were recorded, and subsequently converted in relation to the length of the ampulla to the mean rates of transport (mm/min). Ovariectomy decreased the mean rate of transport to 4.5 ± 0.8 mm/min, and this was not significantly further decreased (2.8 ± 0.4 mm/min) by daily treatment with 2 mg progesterone. Treatment with 2 and 4 /xg EB/day restored the rate of transport (8.4 ± 0.9 and 10.0 ±0.6 mm/min, respectively) to the levels seen in estrous animals. Progesterone injections (2 mg), which were given 13 hr before the observations on transport t...

The deciduomal response to uterine trauma in rats ovariectomized on day 2 or 4 of pseudopregnancy and given oestrone, 1 μg, progesterone, 2 mg, on various days thereafter has been compared with that in intact pseudopregnant controls. Trauma was effected by inserting a sterile silk thread into the lumen of one uterine horn of each animal on day 5 of pseudopregnancy and the response was evaluated at autopsy on day 9**. Significant differences in response were observed between rats ovariectomized on days 2 and 4, respectively, of pseudopregnancy. Progesterone whether given alone or with oestrone to rats ovariectomized on day 2 of pseudopregnancy produced an increase in weight of the traumatized horn not significantly smaller than that produced in intact controls. In animals given progesterone alone, however, the ratio of weight of the traumatized to untraumatized horns (T/U) was significantly smaller than control. In animals ovariectomized on day 4 of pseudopregnancy a different situation obtained. Progesterone alone from ovariectomy to autopsy produced only a moderate increase in the weight of the traumatized horn and a ratio T/U half that seen in control animals. Thus, in such animals both oestrone, given at least on day 4, and progesterone were needed to produce a deciduomal response not different from control.

A total of 251 mature female rabbits was used in this study. One hundred eight of these were divided into groups of 6 and orally dosed at 24, 48 and 72 hr after insemination and injection of human chorionic gonadotrophin (HCG), with graded doses of various estrogens [stilbestrol, estradiol cyclopentylpropionate (ECP), estrone, estradiol and ethinyl estradiol (EE) ], dissolved in 1 ml cottonseed oil. The eggs were recovered on day 6, and classified according to their development. EE was found to be the most effective estrogen in preventing normal blastocyst development. The ED50 (and its 95 % probability limits) was 0.012 (0.010–0.014) mg/ rabbit/day. EE was therefore used in the remainder of the study. Eighteen rabbits were given a single dose of 0.05 mg EE at 24, 48 or 72 hr after insemination and injection of HCG and no significant difference in the percentage of blastocyst development was found. This dose given at 24 hr was found to be as effective as a total dose of 0.048 mg EE given over 3 days in re...

Rats were given single doses of an orally-active estrogen by mouth on days 1–5 of pregnancy. Examination of uteri on day 8 for implantations revealed that the median effective doses for preventing 50% of the eggs shed from implanting were 0.047, 0.050, 0.035, 0.145 and 0.380 mg/kg for days 1, 2, 3, 4 and 5 respectively. It was found that failure of pregnancy after treatment with the minimal 100% effective dose (ED100) on days 1, 2 or 3 was due to expulsion of eggs from the reproductive tract by day 5. Treatment of rats with the ED100 on day 4 caused expulsion of some eggs from the tract by day 5, but also had effects on the uterus: the position of the blastocysts within the lumen was abnormal and their orientation relative to the mesometrial-anti-mesometrial axis disturbed. No decidual reaction was observed on day 6 in such rats or on day 9 in pseudopregnant rats treated similarly and subjected to uterine traumatization on day 5. Treatment with ED100 on day 5 had no effect on egg transport or on the positioning of blastocysts within the lumen on day 6. A decidual reaction was seen around the blastocyst on day 6, but in pseudopregnant rats treated similarly and subjected to uterine traumatization on day 5 no decidual reaction was found on day 9. The pontamine blue reaction was negative in nearly all rats dosed on day 4 and examined on days 6–8. In rats dosed on day 5, however, the blue reaction was negative on day 6, but positive on day 7, i.e., delayed by 24 hours compared to controls and appearing later than the decidual reaction. The blastocysts were unattached in these rats on day 6, but may have attached briefly on day 7 (suggested by the positive blue reaction) and subsequently failed to develop further owing to disappearance of the decidual tissue.

The amount and distribution of prenatal loss has been studied during the first pregnancy in albino rats of the random-bred, specific-pathogen-free colony maintained at Alderley Park. Out of a total of 196 virgin female rats mated and found to have spermatozoa in the vaginal smear on the following day (Day 1 of pregnancy), fourteen (7\m=.\1%)failed to become pregnant. In 145 rats which became pregnant, the mean number of eggs shed was 12\m=.\2\m=+-\0\m=.\19 and the mean number that implanted was 10\m=.\9\m=+-\0\m=.\19. In eighty rats in which pregnancy was allowed to continue to the 18th to 20th day, the mean number of viable foetuses found at autopsy was 10\m=.\1\m=+-\0\m=.\25.In various experimental groups, pre-implantation loss ranged from 9\m=.\8% to 13\m=.\9%of the eggs ovulated, the mean being 11\m=.\1%Post-implantation loss amounted to only 7\m=.\7%of the eggs ovulated, giving a total prenatal loss of 18\m=.\8%.It was found that the number of eggs ovulated

Movement of the Ovum in the Reproductive Tract: A Possible Explanation for the Failure of Non-Surgical Ovum Transfers in the Cow