Circulating steroids and the relationship between ovarian and placental secretion during early and mid pregnancy in the baboon.код для вставкиСкачать
American Journal of Primatology 7:357-366 (1984) Circulating Steroids and the Relationship Between Ovarian and Placental Secretion During Early and Mid Pregnancy in the Baboon f.K. HODGES', R. TARhRA2, AND C. WANGIJLA2 MRC/ARC Comparative Physiology Rcworch Group, The Tnstitute of Zoology, T / LZoologLc.al ~ Socrety of London, Regen't's Park, London, lrnited Kingdom a n d 21nstitute of Primate Research, National Museums ofKenyo, Nairobi, Kenya, Africa Ovarian and placental steroid secretion was examined a t intervals during early and mid-pregnancy in the olive baboon, Papio anubis. Progesterone, androstenedione, testosterone, estrone, and estradiol170 were measured after celite chromatography in samples from peripheral circulation and from utero-ovarian veins draining ovaries with and without corpora lutea at the following stages of pregnancy: days 8-9 (unconfirmed pregnant), 10-19,34-40, 60-66, and 104-106 after ovulation. The pattern of hormone levels in peripheral and utero-ovarian vein samples indicated the following: 1)The corpus luteum was the principal source of progesterone until at least day 19. Placental secretion was well advanced by days 3440 and provided the major contribution to circulating progesterone levels by day 60. 2) There was a significant elevation in peripheral concentrations of androstenedione and testosterone on days 10-19 and 34-40 of pregnancy; androgen levels in peripheral and uteroovarian vein samples declined to baseline values by day 60. 3) Estrogens were secreted by the corpus luteum on days 10-19 but not on days 34-40. Placental secretion of estradiol-17fi increased markedly after days 60-66, whereas little, if any, placental secretion of estrone was apparent a t this time. These results provide circumstantial evidence that progesterone secretion by the corpus luteum of early pregnancy extends beyond the time when estrogen secretion has declined and that the timing of the luteo-placental shift in the baboon is intermediate between that in rhesus monkeys and that in marmosets and humans. Increased secretion of androgens during the first 6 weeks of gestation may be useful in early pregnancy diagnosis in the baboon, although the physiological significance of this event is not clear. Key words: pregnancy, olive baboon, Pupio anribis, ovarian steroids, placental steroids, progesterone, androstenedione, testosterone, estrone, estradiol-176 Received March 29, 1984, revision accepted July 4, 1984 Address reprint requests to J K Hodges, MKC ARC Comparative Physiology Research Group, Institute of Zooloby, The Zoological Society of London, Rcgent's Park, London N W 1 4RY, Unlted Kingdom 0 1984 -41an R. Liss, Inc. 358 I Hodges, Tarara, and Wangula INTRODUCTION The baboon has been the subject of detailed morphological studies on implantation and embryonic development [eg, Hendrickx, 1971; Pope, et al, 1982a1 as well as proving a useful experimental primate in applied aspects of teratology and immunological inteiference with pregnancy [Hendrickx et al, 1975; Stevens, 1974, 19811. Surprisingly little attention, however, has been paid to the hormonal control of early pregnancy in the baboon and, in particular, the relationship between luteal and placental endocrine function is poorly understood. Considerable information exists on maternal and fetal endocrinology during mid to late gestation Leg, Townsley, 1974; Albrecht et al, 1980; Dawood & Fuchs, 19801, but there is only one report relating to the hormonal control of early pregnancy, which describes changes in peripheral plasma levels of total estrogens and progestins at intervals during the first 25 days [Shaikh et al, 19761. Studies in other nonhuman primates and humans have shown that the maintenance of early pregnancy depends upon a n initial and variable period of steroid secretion by the corpus luteum, after which the placenta becomes the major source of steroids and the corpus luteum is dispensible [Csapo & Pulkkinen 1978; Goodman & Hodgen, 19791. There are, however, few details in any primate on the onset of placental endocrine function and on the proportions of steroids secreted by the ovary and placenta during the transition period. [Walsh et al, 1979; Hodges et al, 1983b). The purpose of this study, therefore, was twofold: to determine changes in circulating levels of steroid hormones at intervals during the first 100 days of pregnancy in the olive baboon (Papio anubis) (gestation length 175-185 days); and to examine the relative contribution of the ovary and placenta t o circulating steroid concentrations during this period. MATERIALS AND METHODS Animals Adult female Olive baboons (Papio anubis), at least 5 years old and weighing 15-18 kg, were used in this study. Animals were maintained in sheltered outdoor cages a t the Institute of Primate Research, Nairobi, Kenya. They were fed twice daily with commercial primate cubes supplemented with fruit and vegetables and provided with water ad libitum. Animals used for the collection of samples up to day 19 of pregnancy were kept in single cases (n = 11);samples during subsequent stages of pregnancy were collected from different animals maintained in harem groups (two males and approximately 25 females) in large corral-type cages (n = 16). These animals were trained to enter smaller individual cages (attached to the side of the main cage), normally used for collection of urine, where they were sedated with ketamine-xylazine (see sample collection) before removal for sampling and surgery. Mating Schedule Female baboons in harem groups were in continuous contact with males and were allowed to mate freely. Females housed individually were transferred to the males cage for 6 hours daily for up to 5 days during the period of maximum sex skin swelling (turgescence). The timing of the first day of mating within the period of turgescence was based on the duration of maximum sex skin swelling in previous menstrual cycles (known to be relatively constant within individuals). A vaginal swab was taken a t the end of each 6-hour period and examined for the presence of sperm. Timing of Pregnancy Changes in sex skin swelling were carefully monitored each day in all females in the study. The day of ovulation was estimated to be two days before the end of Steroids and Raboon Pregnancy / 359 maximum turgescence (ie. onset of deturgescence), based on the findings of previous studies [Wildt et al, 1977; Shaikh, 19821. This was also designated day 0 of pregnancy. Animals were divided into five groups, according to the stage at which blood samples were collected. Group 1: day 8-9 (nonpregnant or unconfirmed pregnant, n=4). These animals were mated as normal and surgery scheduled for the period around implantation. However, blastocysts were not recovered after uterine flushing, and there was no evidence of a n implantation site. No other test for pregnancy was carried out. Group 2: 10-19 days pregnant (n=7). Pregnancy was indicated by the presence of a n embryo and implantation site, subsequently confirmed by histological examination (separate study). Samples were collected on day 10 (n = 11, day 11( n = l ) , day 13 (n=2), day 17 (n=1), and day 19 (n=2). Group 3: (34-40 days, n=6). Group 4: (60-66 days, n=5). Group 5 : (104-106 days, n=5); pregnancy was confirmed by the presence of an embryo or fetus. Blood sampling and laparotomy were performed once on each animal. Sample Collection Animals were anesthetised with a ketamine-xylazine mixture, 0.1 m l k g body weight, i.m. (ketamine 70 mg/ml; xylazine 6 mg/ml) before removal from their cages. Peripheral blood samples (10 ml) were taken by femoral venepuncture using a 21gauge needle and a nonheparinized syringe. Animals were then intubated and maintained on gaseous anaesthesia using halothane (1.5-3%), nitrous oxide (0.5 L/ min), and oxygen (1.5 L/min). Laparotomy was performed by midventral abdominal incision, and left and right utero-ovarian vein blood samples were collected using a 2-ml nonheparinized syringe fitted with a 25-gauge needle. Blood samples were allowed to clot a t 4°C for 4-6 hours. Serum was collected after centrifugation at 400 g for 20 minutes at 4°C and stored at -20°C. Samples were shipped to London by air and kept frozen with dry ice. Chromatography Steroids were separated by Celite chromatography [Anderson et al, 19761 before assay. Tracer amounts (1,000 cpm) of 3H progesterone, 'H androstenedione, and 'H testosterone, or 'H estrone and 3H estradiol-176 (Amersham International Ltd, Bucks, England) with specific activities of 87, 98, 107, 92, and 102 Ciimmol, respectively, were added to the samples before extraction with ten volumes of redistilled diethyl ether. Extraction for the measurement of estrogens was performed separately from that for the measurement of the other steroids. The extracts were evaporated to dryness under nitrogen and allowed to reconstitute overnight in 1.0 ml iso-octane. Estrone and estradiol-17P were eluted from ethylene glycol columns as described by Hodges et a1 [1983c]. Other steroids were eluted from propylene glycol: celite (1:2 viw) columns with 2.5 ml isoctane (progesterone), 4.0 ml 8% ethyl acetate in iso-octane (androstenedione), 3.0 ml 15%ethyl acetate in iso-octane (rinse), and 4.0 ml 24% ethyl acetate in iso-octane (testosterone), based on the method described by Nakakura et a1 . The fractions were dried under nitrogen and reconstituted in 1.0 ml assay buffer for assay and recovery determination. Assays Radioimmunoassay of steroids was carried out according to the World Health Organization procedure for matched reagents as described in detail by Hodges et a1 11983~1.The origins and cross-reactivities of the antiserum for estrone and estradiol176 have been reported by Hodges et a1 [1983c], and those for the antisera for progesterone and testosterone by Harlow et a1  and Hodges et a1 [1983a], respectively. Androstenendione was measured using an antiserum (Steranti Re- 360 Hodges, Tarara, and Wangula search Ltd, St Albans, Herts, England) raised in a rabbit against androstenedione11-(succinyl)bovine serum albumin. Measured cross reactivities included androsterone l%, testosterone 0.5%, 5cr dihydrotestosterone, and dehydroepiandrostenedione 0.05%, CI8 and CZl steroids tested 0.01%. Dilution of antiserum was adjusted to give approximately 30% binding in the absence of competing cold steroid. Procedural losses were monitored individually. Mean recovery values for individual steroids after extraction and celite chromatography were between 65 and 84%. Assay sensitivity, calculated as the mass of hormone required to suppress the binding of labelled hormone to 90% of the binding achieved in the absence of unlabelled hormone, was between 5 and 10 pgltube depending on the steroid being measured. The volume of serum taken for extraction varied according to the sample volume available and the approximate hormone concentration expected (determined previously in separate assays). Buffer blanks which were extracted and run through celite gave values less than the assay sensitivities. The intraassay precision, expressed as the coefficient of variation, was below 10%for each hormone assay. Values for the interassay coefficient of variation, based on repeated measurements of a pool of monkey plasma were 11.1,11.6, 8.5, 12.1, and 14.7 for the estrone, estradiol-l7P, progesterone, androstenedione, and testosterone assays, respectively. Validation of the measurement of each hormone was achieved by performing cochromatography on celite and comparing immunoreactivity and recovery of pure tritiated steroid across the appropriate fractions at 0.5-ml intervals [Hodges et al, 1983~1.The elution profiles of immunoreactivity and radioactivity were similar for individual hormones, indicating the absence of substantial contamination from cross-reacting substances. Statistical Analysis Data for peripheral and utero-ovarian vein samples (including ratios) were analysed separately using a one-way analysis of variance. Means were compared post hoc by the Duncan Multiple Range Test. RESULTS The data for mean steroid concentrations in peripheral blood and in matched samples from the utero-ovarian veins draining ovaries with and without a corpus luteum are shown in Figures 1-5. All animals possessed a single corpus luteum. Mean peripheral levels of progesterone rose significantly between days 10-19 and days 34-40 (p < 0.011, after which there was no further increase (Fig. 1). Similarly, progesterone concentrations in the utero-ovarian vein not associated with a corpus luteum also increased between days 10-19 and days 34-40 (p < 0.05), without further significant change. In contrast, there were no significant differences between progesterone levels in the utero-ovarian vein associated with a corpus luteum. The mean ratio of progesterone levels in utero-ovarian veins with and without a corpus luteum was significantly lower by day 60 and thereafter, compared with days 8-9 (p < 0.01) and 10-19 (p < 0.05). Mean concentrations of androstenedione in peripheral blood were significantly higher on days 10-19 and days 34-40 (p < 0.01) than at the other three stages (Fig. 2). The levels in utero-ovarian vein samples associated with a corpus luteum were also significantly higher between days 10 and 19 than levels a t other stages (p < 0.05, p < 0.01), while concentrations in the opposite utero-ovarian vein were significantly elevated on days 10-19 and 34-40 (p < 0.05) and were similar to each other. Although the mean ratio of utero-ovarian vein levels fell from 1.85 between days 10 and 19 to 0.9 between days 34 and 40, the overall changes throughout the study were not significant. Steroids and Raboon Pregnancy / 361 The pattern of testosterone in peripheral circulation was similar to that of androstenedione, although the absolute levels were lower (Fig. 3). Mean concentrations were significantly higher beween days 10-19 and 34-40 (p < 0.01) compared with the other three stages, which were not significantly different from each other. The apparent increase in testosterone in utero-ovarian vein samples over the same period was not significant. This, however, is probably due to the extremely high values in one animal in the 10-19-day group (utero-ovarian vein levels of 11.6 n g h l and 12.4 ng/ml), since if these data were omitted, the adjusted means for uteroovarian vein levels with and without a corpus luteum were 1.25 ng/ml and 1.22 ngl ml, respectively, and there was a significant elevation in testosterone levels in both utero-ovarian veins between days 34 and 40 (p < 0.05). "here was no significant change in the ratio of utero-ovarian vein testosterone levels over the period of study before or after removal of the outlying data points mentioned above. Mean peripheral levels of estrone (Fig. 4)rose between days 8-9 and 60-66 (p < 0.05) with a further marked increase by days 104-106 (p < 0.01). In contrast, there were no significant changes in mean levels of estrone in samples from either utero-ovarian vein. However, the ratio between estrone levels in utero-ovarian veins with and without a corpus luteum was significantly higher on days 10-19 compared with all other stages (p < 0.01). Estradiol-17P concentrations in peripheral blood increased progressively from days 8-9 to 60-66, although due to large individual variation in the data, the mean values were not significantly different (Fig. 5). There was, however, a highly significant increase after days 60-66 (p < 0,001). Similarly, the levels of estradiol-170 measured in samples from the utero-ovarian veins with and without a corpus luteum also increased significantly at this time (p < 0.05, p < 0.01, respectively). The mean ratio of estradiol-170 levels in utero-ovarian veins with and without a corpus luteum was four- to sixfold higher on days 10-19 than a t subsequent stages, but the values were not significantly different. DISCUSSION The present study examines the relationship between ovarian and placental steroid secretion during early pregnancy in the baboon. The ratio of progesterone levels in utero-ovarian veins draining ovaries with and without a corpus luteum suggests that the corpus luteum is the major source of circulating progesterone until a t least day 19 of pregnancy, whereas by day 60 placental progesterone secretion has taken over. Although the onset of placental progesterone secretion is not clear from the present data, the pattern of progesterone in utero-ovarian vein samples without a corpus luteum indicates that secretion by the placenta is already well advanced by the fifth week of pregnancy. Thus, the rise in peripheral progesterone levels between days 10-19 and 34-40 of pregnancy reflects increasing placental production rather than extended secretion by the corpus luteum. From the sampling frequency used in this study it is difficult to compare the precise timing of the shift from luteal to placental progesterone secretion in the baboon with that in other primate species. In humans and marmoset monkeys, placental progesterone secret,ion begins around week 4-5 of pregnancy, although luteal secretion is still evident at day 40 in marmosets [Hodges et al, 1983bl and, in humans, the corpus luteum is not completely dispensible until week 6 [Csapo & Pulkkinen, 19781. In rhesus monkeys, however, placental progesterone production begins as early as day 22 [Goodman & Hodgen, 19791, at a time when there is no longer a substantial contribution from the corpus luteum [Walsh et al, 1974; Sholl et al, 19771. Thus, from the limited information available, the timing of the luteo-placental shift with respect to progesterone secretion in baboons appears to be intermediate between that of hu- 362 I Hodges, Tarara, and Wanmila - 350 - 300 - . -P 250 200 P - 150 g 100 ? u 24 4 II P 7 . 20 - p - 16 - 0 12 - a V I V 0 P $ 0 0-9 10-19 34-40 60-66 Days after ovulation 104-106 3 P 4 c 4 I 1 8-9 10-19 34-40 60-66 104-106 Days after ovulation Fig. 1. Upper portion. Concentrations or progesterone in the peripheral circulation ( A 1 and in uteroovarian veins draining ovaries with (*) and without (01 corpora lutea during early and mid pregnancy in the bahoon. Samples in the day-8-9 group are from nonpregnant animals or animals in which pregnancy 4 (days 8-9) and 5-7 (all other slagesi. Lower portion. was unconlirmed. Values are mean i s.e.m.. n : Ratio of progesterone concentrations in utero-ovarian veins draining ovaries with and without corpora lutea twithlwithout). Values are mean i s.e.m., n = 4 (days 8-91 and 5-7 (all other staged. Fig. 2. Concentrations of androstenedione in peripheral and utero-ovarian vein blood and the ratio of concentrations in utero-ovarian veins draining ovaries with and without a corpus luteum. See legend to Figure 1for full details. mans and marmosets and that of rhesus monkeys. Species differences in overall gestation length should, however, be taken into consideration (baboon 185 days; human 280 days; marmoset 144 days; rhesus monkey 165 days). The fourfold elevation in mean androstenedione and testosterone levels in the 10-19-day group compared with levels a t days 8-9, in the absence of marked differences in the levels of other steroids, is of particular interest. Although the reproductive status (ie, pregnant or nonpregnant) of the animals in the 8-9-day fsroup is uncertain, the levels of both androgens a t this time were similar to those reported by Kling and Westfahl 119781 during the midluteal phase in Papzo cynocephah. Irrespective of the composition of the 8-9-day group, however, the present data clearly indicate a marked increase in the secretion of testosterone and androstenedione within the first 2-3 weeks of pregnancy. Sequential sampling during conception and noxiconception cycles would be needed to confirm this and to determine the time course and magnitude of increased androgen secretion over the initial period of gestation. Some support for the current observations is, however, provided in a preliminary communication on P. qnorephalus by Castracane , which reports increased levels of androstenedione and testosterone during the conception cycle, rising to maximum values around day 40; no data on hormone levels are given, however. Although the stimulus for increased androgen secretion is not known, the period of elevated levels approximates the time when chorionic gonadotrophin is detectable in peripheral blood (12-55 days of pregnancy, [Tuller, 1974; Pope et al, 1982bj. Indirect evidence that the increases in androgen secretion during early pregnancy Steroids and Raboon Pregnancy I 363 i I Ir i I I $ A 2 Ly],J, $ 3 0 8-9 10-19 *[ I .-C 34-40 60-66 104-106 Days after ovulation Days after ovulation Fig. 3. Concentrations of testostcrone in peripheral and utero-ovarian vein blood and the ratio of concentrations in utero-ovarian veins draining ovaries with and without a corpus lutcuni. See legend to Figure I for full details. Fig. 4. Concentrations of cstrone in peripheral and utero-ovarian vein blood and the ratio of concentrations in utero-ovarian veins draining ovaries with and without a corpus luteum. See legend to Figure 1 for full details. T I p, 2.g 4 8-9 10-19 34-40 60-66 104-106 Days after ovulation Fig. 5. Concentrations of estradiol-178 in peripheral and utero-ovarian vein hlood and the ratio of concentrations in utero-ovarian veins draining ovaries with and without corpus luteum, *, **, =**; mean s.e.m. values for pcripheral samples 0.032 i 0.009 n g h l , 0.07 ? 0.02 ng/ml, and 0.11 0.02 ngiml, respectively. See legend to Figure 1for full details. 364 I Hodges, Tarara, and Wangula may be related to the onset of CG production is provided by Castracane  who showed that hCG administration during the nonpregnant luteal phase results in a n increase in circulating levels of both testosterone and androstenedione. However, it is not clear why, in the present study, secretion of androgens increased in the absence of any marked change in the circulating levels of estrogens or progesterone. The data shown in Figures 2 and 3 provide circumstantial evidence for luteal secretion of androstenedione between days 10 and 19 and for nonluteal (possibly placental) secretion of both androgens between days 34 and 40. If placental secretion of androgens does occur at this time, it is difficult to explain why it is limited to the early stages of pregnancy, since by day 60 both peripheral and utero-ovarian vein levels have declined to nonpregnant values. One possible explanation, supported by the increase in estrone and estradiol-17P between days 3 4 4 0 and 60-66, might be a feedback mechanism whereby androgen secretion is regulated by estrogens. Alternatively, a n increase in placental aromatisation of androgens may occur a t this stage of pregnancy. Clearly, further studies are required to clarify the control and physiological importance of androgen secretion during early pregnancy in the baboon. Circulating levels of estrone and estradiol-17P on days 8-9 and 100-106 were comparable to those measured a t equivalent stages in other species of baboon [Kling & Westfahl, 1978; Albrecht & Townsley, 1978) but considerably lower at days 60-66 than those (3.5 ng/ml estradiol-17P 1 reported in I? papio by Albrecht and Townsley . This discrepancy is unlikely to be due to differences in assay methodology (levels a t day 100 were similar) but most probably reflects a species difference with respect to the onset of increased estradiol-17P secretion. The utero-ovarian vein estrone concentration ratios indicate that the corpus luteum secretes estrone between days 10 and 19 but not at other stages. Luteal secretion of estradiol-176 on days 8-9 and 10-19 may also be inferred from the elevated utero-ovarian vein ratios a t these times, although due to individual variation in the levels of estradiol-l7/3, this could not be demonstrated statistically. There was, however, no evidence of luteal secretion of either estrogen by days 34-40 of pregnancy. Since days 34-40 represent a transitional period between luteal and placental secretion of progesterone, the corpus luteum of early pregnancy in the baboon may continue to secrete progesterone beyond the time when estrogen secretion has declined, which is similar to recent findings in the marmoset monkey [Hodges et al, 1983131. The origin of circulating estrone after days 34-40 is unclear, since the marked increase in peripheral levels occured in the absence of a rise in utero-ovarian vein concentrations. This observation suggests that during midpregnancy in P anubis, circulating estrone may derive largely from peripheral conversion and that there is little, if any, direct secretion from the placenta. Further studies are, however, needed to support this interpretation which a t present is purely speculative. In contrast to estrone, the marked elevation in circulating estradiol-17P levels by day 104 pregnancy appears to be directly related to increased placental secretion as evidenced by the rise in estradiol-17p concentrations in both utero-ovarian veins. Estradiol production during late pregnancy in P: papio is known to occur principally in the placenta from dehydroepiandrosterone (DHEA) secreted by the maternal and fetal adrenal glands [Townsley & Pepe, 1977: Schut ct al, 19781. The elevation in circulating estradiol-17P between days 66 and 104 of pregnancy may therefore be related to changes in the secretion and/or placental utilization of DHEA at this time. Although this would not seem to be supported by the pattern of DHEA in peripheral circulation, which does not show a significant increase until after day 150 [Townsley & Pepe, 19771, increased availability of DHEA or its sulphate for placental conversion may not necessarily be reflected by changes in concentrations in the peripheral bloodstream. Steroids and Baboon Pregnancy / 365 CONCLUSIONS 1. Comparison of progesterone concentrations in peripheral and utero-ovarian vein samples indicated that the corpus luteum is the major source of progesterone until at least day 19 of pregnancy and that the onset of placental progesterone secretion occurs before day 34. 2. Peripheral concentrations of testosterone and androstenedione were significantly elevated on days 10-19 and 34-40 compared with other stages. The increase in androgen levels during the first 6 weeks of pregnancy appears to reflect ovarian and possibly early placental secretion which declines by day 60. Measurement of testosterone or androstenedione may be useful in early pregnancy diagnosis in the baboon. 3. The corpus luteum secretes estrogens until at least day 19 of pregnancy but not a t day 34. Circulating estradiol-17P concentrations rise sharply between days 60-66 and 104-106, reflecting increased placental secretion. In contrast, very little placental secretion of estrone was evident at any of the stages observed. ,4CKNOWLEDGMENTS We are grateful to the colony management staff of the Institute of Primate Research for care and maintenance of the animals; Dr. N. Gulemhusein for assistance with surgery; the World Health Organisation for standards and antisera for the testosterone and estradiol-17P assays; and to Dr. D.H. Abbott and Mr. D. Harris for advice on statistical analysis. The work was supported by the World Health Organisation Special Programme on Human Reproduction, a Medical Research Council (U.K.) Programme Grant to Professor J. Hearn, and a core support grant from the A.B.R.C. to the Institute of Zoology. REFERENCES Albrecht, E.D.; Townsley, J.D. Serum estradiol in mid and late gestation and estradioy progesterone ratio in baboons near parturition. BIOLOGY OF REPRODUCTION 18: 247-250,1978. Albrecht, E.D.; Haskins, A.L.; Pepe, G.J. The influence of fetectomy at midgestation upon the serum concentrations of progesterone, estrone and estradiol in baboons. ENDOCRINOLOGY 107:766-770, 1980. Anderson, D.C.; Hopper, B.R.; Lasley, B.L.; Yen, S.S.C. A simple method for the assay of eight steroids in small volumes of plasma. STEROIDS 28:179-196,1976. Castracane, V.D. Androgens in the pregnant baboon (Papio cyruicephalus), Abstr. 71. INTERNATIONAL JOURNAL OF PRIMATOLOGY 3:269,1982. Csapo, A.L.; Pulkkinen, M.O. Indispensibility of the human corpus luteum in the maintenance of early pregnancy: Lutectomy evidence. OBSTETRICS AND GYNECOLOGY SURVEY 3369-80,1978. Dawood, M.Y.; Fuchs, F. Estradiol and progesterone in the maternal and fetal circulation in the baboon. BIOLOGY OF REPRODUCTION 22:179-184,1980. Goodman, A.L.; Hodgen, G.D. Corpus lutcum conceptus - follicle relationships during the fertile cycle in rhesus monkeys: Pregnancy mainenance despite early luteal removal. JOURNAL OF CLINICAL ENUOCRINOLOGY AND METABOLISM 49:469-471, 1979. Harlow, C.R.; Hearn J.P.; Hodges, J.K. Ovulation in the marmoset monkey: Endocrinology, prediction and detection. JOURNAL OF ENDOCRINOLOGY, 103:17-24,1984. Hendrickx, A.G., ed. EMBRYOLOGY OF THE BABOON. Chicago, University of Chi cago Press, 1971. Hendrickx, A.G.; Sawyer, R.H.; Lasley, B.L.; Barnes, R.D. Comparison of dcvelopmental stages in primates with a note on the detection of ovulation. Pp 305-315 in BREEDING SIMIANS FOR DEVELOPMENTAL BIOLOGY. LABORATORY HANDBOOKS 6. F.T. Perkins and P.N. O’Donoghue, eds. London, Laboratory Animals Ltd. 1975. Hodges, J.K.; Eastman, S.A.K.; Jenkins, N. Sex steroids and their relationship to binding proteins in the serum of the marmoset monkey (Callithrix jacchus). JOURNAL OF ENDOCRINOLOGY 96:443-450,1983a. Hodges, J.K.; Henderson, C.; Hearn, J.P. Relationship between ovarian and placental steroid production during early pregnancy in the marmoset monkey (Callithrix jac- 366 I Hodges, Tarara, and Wangula Wolf, R.C. Placental and luteal steroidogechus). JOURNAL OF REPRODUCTION nesis in the pregnant rhesus monkey. STEAND FERTILITY 69:613-621,1983b. ROIDS 29249-259,1977. Hodges, J.K.; Brand, H.M.; Henderson, C.; Kelly, R.W. The levels of circulating and Stevens, V.C. Fertility control through active immunisation using placental proteins. Pp urinary oestrogens during pregnancy in the 357-375 in IMMUNOLOGICAL APmarmoset monkey (Callithrix jacchus). PROACHES TO FERTILITY CONTROL, E. JOURNAL OF REPRODUCTION AND Diczfalusy, ed. Stockholm, Karohriska InFERTILITY 67:73-82, 1983~. stitutet, 1974. Kling, O.R.; Westfahl, P.K. Steroid changes during the menstrual cycle of the baboon Stevens. V.C. Vaccines against pregnancy. Pp (Papio cynocephalus) and human. BIOL211-227 in RECENT ADVANCES IN FEROGY OF REPRODUCTION 18:392-400, TILITY REGULATION, SYMPOSIUM 1978. PROCEEDINGS, BEIJING. C.C. Fen; D. Nakakura, K.; Czekala, N.M.; Lasley, B.L.; Griffin; A. Woolman, eds. Geneva, Atar, S.A. Benirschke, K. Fetal maternal gradients of 1981. steroid hormones in the nine banded arma- Townsley, J.D. Estrogen excretion of the dillo (Uasypus novemcinctus). JOURNAL pregnant baboon (Papio pupio). ENDOCRIOF REPRODUCTION AND FERTILITY NOLOGY 951759-1761,1974. 66:635-643, 1982. Townsley, J.D.; Pepe, G.J. Serum dehydroePope, C.E.; Pope, V.Z.; Beck, L.R. Developpiandrosterone and dehydroepiandrosterment of baboon preimplantation embryos to one sulphate in baboon (Pupio p ~ p i ~ ) post implantation stages in vitro. BIOLpregnancy. ACTA ENDOCRTNOLOGICA OGY OF REPRODUCTION 271915-924, 85:415-421, 1977. 1982a. Tullner, W.W. Comparative aspects of priPope, V Z.; Pope, C E.; Beck, L.R. Gonadotromate chorionic gonadotrophins. CONTRIpin production by baboon embryos in uitro. BUTIONS TO PRIMATOLOGY, 3:325-257. Pp 129-134 in IN VITRO FERTILIZATION 1974. & EMBRYO TRANSFER. E.S.E. Hafcz, Ed., Walsh, S.W.; Wolf, R.C.; Meyer, R.K. ProgesLancastcr, England, MTP Press Ltd. 198213. terone, progestins and 17 hydroxpregn-4ene-3,30-dione in the utero-ovarian, uterine Schut, H.A.J.; Pope, G.J.; Chez, R.A.; Townand peripheral blood of the pregnant rhesus sley, J.D. Contribution of dehydroepiandrosterone and its sulfate to estradiol in baboon monkey. ENDOCRINOLOGY 9517041710, i974. pregnancy. AMERICAN JOURNAL OF PHYSIOLOGY 235:E78-E81.1978. Walsh. S.W.: Wolf. R.C.: Mever. R.K.: RobinShaikh, A.A.; Ceyala, C.L.; Gomez, I.; son, J.A. Estro&ns in thk itero-dvarian, uterine and peripheral plasma in pregnant Shaikh, S.A. Temporal relationships of hormonal peaks to ovulation and sex skin derhesus monkeys. BIOLOGY OF REPROturgescence in the baboon. PRIMATES DUCTION 20:606-610,1979. 23444-452, 1982. Wildt, D.E.; Doyle, L.L.; Stone, S.C.; HarriShaikh, A.A.; Allen-Rowlands, C.; Dozier, T.; son, R.M. Correlation of perineal swelling Kraemer, U.C.; Goldzieher, J.W. Diagnosis with serum ovarian hormone levels, vagiof early pregnancy in the baboon. CONnal cytology and ovarian follicular developTRACEPTION 14:391-402,1976. ment during the baboon reproductive cycle. Sholl, S.A.; Anderson, N.G.,; Colas, A.E.; PRIMATES 18:261-270,1977.