Plasma Progesterone during the Luteal Phase and Pregnancy in Parturient and Barren Blue Fox Vixens

Abstract

The variation in progesterone secretion during the luteal phase and pregnancy in blue fox vixens was analyzed. Progesterone was measured in blood plasma once or twice a week using radioimmunoassay. The material was allocated into three groups; five mated, but barren, blue fox vixens, six mated vixens with implantation zonès in the uterus, but no cubs at parturition, and 26 normally parturient vixens. The progesterone profiles for the three different groups of females showed a steady increase in progesterone immediately after mating. Maximum values were observed on days 8–12 of pregnancy. Then the progesterone levels decreased gradually until delivery around day 52. The levels of progesterone were found to be significantly different (P<0.05) between non-pregnant and pregnant females from day 22 after mating. The plasma progesterone level seems to be affected by the presence of conceptuses.     

Mucus and hormonal traits in three gestation patterns (pre-, full- and post-term) of Egyptian Nubian (Zaraibi) crossbred doe goats

In the present study, 48 crossbred does (Nubian × Baladi) were used to investigate physiological (mucus and hormonal) traits as affected by gestation pattern (pre‐, full‐ and post‐term parturitions). The incidence of full‐term (does with a gestation length of 146–152 days) was the highest (54.5%), followed by pre‐term (does with a gestation length of 140–145 days; 36.9%) and post‐term (does with a gestation length of 153 days; 8.9%), respectively. Prediction of gestation pattern by using some body measurements was also studied. Cervical mucus samples were collected during estrus to determine spinnbarkeit (i.e. strength, viscosity or stretchability) and pH values of the mucus. Mucus was also collected pre‐parturition daily from day 140 of gestation until delivery, to evaluate the ferning arborization. Blood samples were collected on the day before mating (0 time), 1 (at mating), 30, 60, 90 and 145 days after mating. The results showed that spinnbarkeit and pH in cervical mucus at estrus, serum estradiol‐17α (E2) at day 5 before delivery, and progesterone (P4) levels differed insignificantly according to gestation pattern. The fern degree between day 140 of gestation and day of delivery was the highest in pre‐term does, while it was the lowest in post‐ and full‐term does. The gestation length was the highest in post‐term does (157.5 days), and the lowest in pre‐term does (141.5 days). During winter, the incidence of pre‐term deliveries was the highest (54.5%), but in spring, full‐term deliveries were the most common (58.3%). Most of the traits studied were insignificantly affected by season of birth. Post‐term delivery can be estimated by doe weight and wither height, while full‐term delivery can be anticipated using by hip height and abdomen girth. Pre‐term does can be detected by cervical mucus fern between day 140 of gestation and day of delivery. Post‐term does can be defined by doe weight and wither height, while full‐term deliveries can be defined by hip height and abdomen girth, during pregnancy.     

Sequential changes in plasma progesterone, total oestrogens and corticosteroids in the cow throughout pregnancy and around parturition

Blood samples were taken thrice weekly for 2 weeks from 33 pregnant cows in nine groups, 1 month apart, and twice daily for 8 days commencing 1 week before parturition from eight cows. Plasma progesterone and total oestrogens were quantified by validated radioimmunoassays and total corticosteroids by a competitive protein binding technique. During the first 3 months of pregnancy, no remarkable changes were observed for the three hormones studied. From the fourth month on, concentrations of progesterone and total corticosteroids decreased significantly (P less than 0.05) and remained fairly constant until the ninth month. Values of total oestrogens increased significantly (P less than 0.05) from the fourth to the sixth month and thereafter remained unchanged. In the periparturient cows, progesterone levels decreased linearly (P less than 0.01) during the 3 days preceding delivery. Concentrations of total oestrogens rose sharply from day -5 and peaked at calving. Values of total corticosteroids increased dramatically on the sixth day and also at 24 hours before parturition. These results suggest that, contrary to earlier studies, plasma corticosteroids could have a primary key role for triggering parturition in cows.     

15-ketodihydro-PGF2 alpha, progesterone and cortisol profiles in heifers after induction of parturition by injection of dexamethasone.

In order to study rapid changes in 15-ketodihydro-PGF2 alpha, cortisol and progesterone in the period preceding parturition in cattle, pre-term parturition was induced in 4 late pregnant heifers. Parturitions were induced by 2 intramuscular injections of 20 mg dexamethasone with a 24-h interval. The first injection was made on days 254, 258, 264 and 265 in gestation, respectively. Twenty-four h before the first injection an intravenous polyurethane cannula was inserted. Blood samples were collected at least every hour until 12 h after parturition and during the second stage of labour at least 6 times per hour. Plasma was analysed for 15-ketodihydro-PGF2 alpha and progesterone by radioimmunoassays, and for cortisol by an ELISA. The average time from injection to parturition was 7.7 (6.6-8.9) days (mean (range)). Two of the heifers had retained foetal membranes (RFM). At the start of the experiment the levels of PGF2 alpha metabolite were low (< 300 pmol/L) and increased slowly to levels between 1000 and 2000 pmol/L at one day before parturition. During the last day, however, the levels increased rapidly and the highest levels (> 10,000 pmol/L) were reached at the time of delivery. No pulsatile release was seen. Immediately after foetal expulsion the PG-metabolite levels decreased rapidly in all animals. In the 2 animals with RFM, however, this decline ceased within a few h. The PG-metabolite levels in these animals then started to increase and reached levels as high as during parturition. Luteolysis occurred between 1.6 and 0.4 days before parturition in all animals. The cortisol profile showed a distinct peak at the time of parturition in the RFM heifers. This peak was absent in the non-RFM heifers. This study shows that the PGF2 alpha release at prepartal luteolysis and parturition is not pulsatile in cattle and that cortisol profiles in heifers with retained foetal membranes might differ from the profiles in non-RFM heifers at the time of parturition.     

Prostaglandin F2 alpha and prolactin in experimental hypogalactia in sows

Peripheral plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F2alpha(PGFM), progesterone, prolactin and oestrone were determined in 20 sows for two days before and three weeks after parturition. Groups of four sows each received one of the following five treatments post partum: 30 ml sterile 0.9 per cent saline solution intrauterinely; ovariectomy and 30 ml saline solution intrauterinely; 10 ml Lugol's iodine plus 20 ml saline solution intrauterinely; ovariectomy and 10 ml Lugol's iodine plus 20 ml saline solution intrauterinely, or progesterone (0.5 mg [kg bodyweight]-1 intramuscularly). Saline solution and iodine were administered every 48 hours, starting immediately after parturition, for one week. Ovariectomy was performed within eight hours of delivery. Progesterone was given every third day for 12 days. Piglet weight gains were used as a reflection of milk yield. In all sows, oestrone values were elevated before parturition, but fell by the end of delivery and were very low during lactation. PGFM concentrations rose during the last two days of pregnancy to reach maximal values at the time of delivery. Plasma progesterone levels declined concomitantly with the rise in PGFM values before parturition. Basal values of progesterone were achieved within 24 hours after delivery in control sows receiving saline treatment. Progesterone values fell immediately after ovariectomy in sows receiving saline or iodine treatment but were slightly elevated for one week in sows that received only intrauterine iodine treatment, suggesting that complete regression of corpora lutea is prevented by suppression of post parturient uterine prostaglandin production. Sows injected with progesterone maintained plasma values of about 5 to 15 nmol litre-1.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma Levels of Progesterone and Oestradiol-17 β in Reindeer (Rangifer Tarandus Tarandus) During Pregnancy

The plasma concentrations of progesterone and oestradiol-17p during pregnancy and the first 20 days after parturition were estimated in reindeer. The concentration of progesterone in the period 75–25 days prior to parturition was significantly higher than in the period 200– 75 days prior to parturition (P < 0.001). During the last 25 days before parturition the concentration decreased significantly. The concentration of oestradiol-17β was in most cases below 70 pg/ml until 50 days prior to parturition. During the last 25 days of pregnancy there was a significant increase in oestradiol-17β and the ratio progesterone/ oestradiol-17β was markedly lower than in the period 75–25 days before calving.Key words: reindeer, gestation, plasma, progesterone, oestradiol-17β     

Excretion patterns of fecal progestagens, androgen and estrogens during pregnancy, parturition and postpartum in okapi (Okapia johnstoni)

The aim of the present study was to establish a simple method to monitor ovarian activity and non-invasively diagnose pregnancy in okapi (Okapia johnstoni). The feces of a female okapi were collected daily or every 3 days for 28 months. Steroids in lyophilized feces were extracted with 80% methanol, and the fecal levels of immunoreactive progestagens (progesterone and pregnanediol-glucuronide), androgen (testosterone), and estrogens (estradiol-17beta and estrone) were determined by enzyme immunoassays with commercially available antisera. Using the progesterone profiles, the durations of the luteal phase, follicular phase, and estrous cycle were determined to be 11.1 +/- 0.4, 5.3 +/- 0.6, and 16.5 +/- 0.7 days (n=22), respectively. Fecal levels of immunoreactive progesterone, pregnanediol glucuronide, and testosterone gradually increased from early pregnancy and peaked several months before parturition. More pregnanediol glucuronide was excreted in feces than progesterone during late pregnancy, but not during the estrous cycle. Although the fecal concentrations of immunoreactive estradiol-17beta and estrone change a little throughout pregnancy and non-pregnancy, they rose sharply and temporarily on the day following parturition. The present study indicates that fecal assays with commercial antisera for progesterone and pregnanediol glucuronide are useful for evaluating luteal activity and diagnosing pregnancy and indicates that estrogens might have some role as a trigger of parturition.     

Prostaglandin Release at Dexamethasone Induced Parturitions in Cows

Three cows of the Swedish Red and White Breed (SRB) were used in the experiment. Cow no. 1 pregnant for 247 days, was given 20 mg dexamethasone twice with an interval of 48 hrs. Cows nos. 2 and 3, each pregnant for 254 days, received 20 mg of dexamethasone twice with an interval of 24 hrs. The cows delivered normal living calves 153, 138 and 137 hrs., respectively, after the second injection of dexamethasone. Blood samples were drawn from the jugular vein every third hour during the experimental period and the samples were analyzed for estrone, progesterone and 15-keto-13,14-dihydroprostaglandin F₂α. Following the dexamethasone injections there was a continuous increase in the blood plasma levels of estrone followed by a sharp decrease in conjunction with parturition. The blood plasma level of progesterone showed a slow but continuous decrease until about 24 hrs. before delivery when a marked drop occurred. The levels of the prostaglandin metabolite increased gradually until about 24 hrs. prior to delivery. This was followed by an abrupt rise, and high levels of the prostaglandin metabolite were recorded for up to four days following parturition. It is concluded that the estrone increase preceded that of the prostaglandin metabolite and that the final drop in the progesterone was synchronous with the final rise of the prostaglandin metabolite level.     

Sequential changes in plasma progesterone, total oestrogens and corticosteroids in cow throughout pregnancy and around parturition

Blood samples were taken thrice a week for 2 weeks from 33 pregnant cows in 9 groups, 1 month apart. In addition, blood samples were collected twice daily 1 week from 8 cows before parturition. Plasma progesterone and total oestrogens were quantified by validated radioimmunoassays and total corticosteroids by a competitive protein binding technique. During the 1st 3 month of pregnancy, no remarkable changes were observed from the 3 hormones studied. From the 4th month on, concentrations of progesterone and total corticosteroids decreased significantly (P less than 0.05) and remained fairly constant until the 9th month. Values of total oestrogens increased significantly (P less than 0.05) from the 4th to 6th months and stayed unchanged afterwards. Progesterone levels in periparturient cows decreased linearly (P less than 0.01) during 3 days preceding delivery. Concentrations of total oestrogens rose sharply from day -5 and peaked at calving. Values of total corticosteroids increased dramatically on the 6th day and 24 hours before parturition. The results obtained suggest that in contrast to studies cited earlier plasma corticosteroids could play a key role for triggering parturition in cows.     

24-Hour Secretion Patterns of Plasma Oestradiol 17β in Pony Mares in Late Gestation

The mare exhibits nocturnal uterine contractions in the last 6 days of gestation. It is hypothesized that estradiol 17β (O17β) may be associated with the nightly increase in uterine contractions. The 24‐h secretion pattern of plasma O17β was measured in 3 pony mares in late gestation to identify changes in release as the mare neared parturition. Blood was collected weekly at 08:00 hours beginning on day 240 and every third day from day 330 until delivery. Serial blood samples were collected from each mare every 30‐min for 24‐h beginning on gestation day 310 and every sixth day thereafter until parturition. Concentrations of O17β were elevated at night with lowest concentrations occurring directly before sunset (p < 0.01). The natural log of the variance was increased at sunset (p < 0.01) and was decreased during the 6‐h period immediately after sunrise. This pattern was especially evident in the 6 days that preceded parturition. The contrast between nocturnal and daytime concentrations of O17β in the last 6 days of gestation may contribute to night‐time delivery in the mare.     

Factors Influencing the Frequency of Pregnancy Loss among Thoroughbred Mares in Hidaka,Japan

Pregnancy loss in mares is thought to be a main problem associated with reproductive efficiency. To clarify the situation of pregnancy loss in Thoroughbred mares in Japan, the occurrence of pregnancy loss before and after 35 days of gestation was investigated with 1,476 Thoroughbred mares in Hidaka, Japan, from 2007 to 2009. Pregnancy loss on days 17-35 was determined by ultrasound examination between 17 and 35 days after the last mating. Follow-up surveys were conducted between 35 days and foaling to determine pregnancy loss on day 35 until foaling in 843 of these mares. Using multiple logistic regression analysis, we assessed the influence of mare age, reproductive status, twin pregnancy reduction, body condition score (BCS), estrus type in foaling mares (foal heat or not), progesterone therapy, and endometrial cysts on pregnancy loss rates on days 17-35 and on day 35 until foaling in this population of mares. The pregnancy loss rates on days 17-35 and on day 35 until foaling were 5.8% and 8.7%, respectively. The overall pregnancy loss rate (day 17 until foaling, including parturient losses) was 14.7%. Risk factors for pregnancy loss included decrease in BCS between 17 and 35 days, <5 BCS at day 35, mating during foal heat, and endometrial cysts. In all, 14.7% of pregnancies were lost between day 17 and birth, contributing significantly to reduced reproductive efficiency in Thoroughbred mares in Japan. These observations indicate that mares should be maintained at high BCS and should be prevented from mating in foal heat to decrease the pregnancy loss rates.     

Correlations among body temperature,plasma progesterone,cortisol and prostaglandin F2alpha of the periparturient bitch

The results of this study suggest that, besides the irrelevant role of body temperature measurement to predict the impending parturition in the bitch, progesterone and 15-ketodihydroprostaglandin F2alpha plasma level records could be more suitable to detect the approaching whelping in this species. More interesting was the statistically significant substantial increase in body temperature beginning 12 h after the onset of parturition. Therefore, if any significant increase in body temperature is recorded at the end of pregnancy without the beginning of the expulsion of fetuses, it could indicate problems at parturition. In this study, cortisol levels increased significantly at the time of delivery and remained high 12 h after the beginning of parturition, decreasing within 36 h after the onset of whelping. 15-ketodihydro-prostaglandin F2alpha levels increased significantly 24 h before parturition and again at the onset of whelping. Progesterone levels decreased significantly, starting 24 h before the onset of whelping and remained low after delivery.     

Plasma concentrations of steroid hormones in sows infected experimentally with Leptospira pomona or porcine enterovirus strain T1 in late gestation

Plasma levels of progesterone, corticosteroids and oestrone were determined during the late stages of pregnancy in four sows experimentally infected with Leptospira pomona and in a group of three sows in which fetuses were inoculated in utero with a strain of porcine enterovirus. Only one of the seven infected sows farrowed at full term. All fetuses were dead and delivery was prolonged in litters infected with the virus. In the sows with leptospirosis almost all piglets were expelled dead or in a weak condition. The amounts of progesterone in plasma were within the normal range and showed a decrease shortly before abortion similar to that observed before parturition in normal animals. The elevation in plasma corticosteroids at normal parturtion was not seen at abortion. An irregular pattern with rising levels of plasma oestrone was found in most sows. Peak levels of oestrone were usually reached close to the time of delivery, but occured earlier in most sows which aborted well before term. In conclusion differences were noted between the endocrine patterns in normal parturition and in abortion caused by infectious agents in sows.     

Predictive utility of pre-partum temperature changes in the mare

Rectal temperature was recorded from 22 mares at 0700, 1500 and 2300 h daily for seven days pre-partum and one day post partum. A circadian variation in rectal temperature was present with the lowest temperature recorded at 0700 h. Because of this, the mares were divided into three groups based on time of parturition; those foaling between 0700 and 1500 h (n = 2); between 1500 and 2300 h (n = 13); and between 2300 and 0700 h (n = 7). On the day prior to delivery (Day -1) the circadian pattern was absent because the nocturnal increase did not occur. A significant decrease in temperature was recorded prior to parturition in the group foaling between 1500 and 2300 h. A distinct decrease in temperature occurred in the majority of mares in the other two groups but this was not statistically significant. After parturition, rectal temperature increased to supranormal levels before returning to normal.     

Observations on Ovarian Structure and Development of the Southern Giraffe,Giraffa Camelopardalis Giraffa

The occurrence of vesicular follicles and corpora lutea (CL), without evidence of ovulation, in late fetuses and during prepubertal life was confirmed in the southern giraffe. In this, and other respects, the pattern of ovarian development is similar in the southern giraffe to the northern subspecies. This early ovarian activity recedes during late prepubertal life. Numerous accessory CL were present in pregnant and non-pregnant giraffe but they did not attain the size of the true CL of pregnancy. The latter undergo an initial phase of rapid enlargement lasting about 100 days, followed by a period of recession till mid-pregnancy and a second growth phase which persists until term (457 days). The CL of pregnancy rapidly regresses after parturition. The accessory CL regress slowly and form normal looking corpora albicantia (CA). These CA are most abundant during early adult life as also are vesicular follicles.     

The secretory pattern and source of immunoreactive prolactin in pregnant African (Loxodonta africana) and Asian (Elephas maximus) elephants

The objective of the present study was to define the secretion of prolactin (PRL) in pregnant African and Asian elephants. Levels of immunoreactive (ir-) PRL in serum and placental homogenates were measured by a heterologous radioimmunoassay (RIA) based on an ovine and human RIA system, and the localization of ir-PRL in the placenta was detected by immunohistochemistry using anti-human PRL. Circulating ir-PRL clearly showed a biphasic pattern during pregnancy in African and Asian elephants. Serum levels of ir-PRL started to increase from the 4 - 6th month of gestation and reached the first peak level around the 11-14th month. A second peak of circulating ir-PRL levels was observed around the 18-20th month of gestation followed by an abrupt decline after parturition. In contrast, in a case of abortion of an African elephant, the second peak of ir-PRL was not observed, and the levels remained low for about four months until parturition. The weight of the fetus delivered at the 17th month of gestation was 23.5 kg, which was quite small compared with normal fetuses in previous reports. Ir-PRL was detected in placental homogenates, and immunolocalization was observed in trophoblasts in both the African and Asian elephants, indicating that the placenta is the source of ir-PRL during pregnancy in elephants. The present results clearly demonstrated that circulating ir-PRL shows a biphasic pattern during normal pregnancy and that the placenta appears to be an important source of circulating ir-PRL during pregnancy in both African and Asian elephants.     

Prolactin, estradiol, and progesterone changes in paretic and nonparetic cows during the periparturient period

We studied the relationship of serum prolactin, estradiol-17 beta, and progesterone concentrations to plasma calcium, phosphorus, and free hydroxyproline concentrations, as well as to dry matter intake, in 14 aged dairy cows (mean of 4.5 parities), 7 of which became paretic, from 28 days before to 4 days after calving. Plasma calcium and phosphorus concentrations and dry matter intake decreased more at parturition in paretic cows than in nonparetic cows. Prolactin concentrations were not different between paretic and nonparetic cows, but were variable. Concentrations of estradiol were higher in paretic cows from 15 to 5 days before parturition, whereas hydroxyproline concentration was lower in paretic cows on days 10 through 3 before parturition. Progesterone concentration was lower in paretic cows and decreased earlier at parturition, compared with that in nonparetic cows. The findings suggested that high estradiol concentrations in late pregnancy inhibit bone resorption and predispose aged cows to parturient paresis. The earlier decrease in progesterone concentration at parturition and lower concentrations throughout late pregnancy might have contributed to the greater inappetence in paretic cows at parturition. The importance of prolactin in the pathogenesis of parturient paresis is not clear.     

Plasma steroid hormone concentrations and their relationships in Suffolk ewes during gestation and parturition

In this study, we measured plasma concentrations of progesterone, pregnenolone, estradiol, estrone, estrone sulfate, and cortisol and analyzed the correlations between these hormones during gestation in 13 Suffolk ewes, the main breed in Japan. Progesterone increased during gestation and decreased a few days before parturition; however, this pattern was different in samples with high progesterone concentrations (P4 spike samples). This P4 spike was associated with a high pregnenolone concentration. Apart from the P4 spike, the progesterone change was similar to that in other sheep breeds. Pregnenolone increased during gestation and decreased after parturition. A significant correlation between progesterone and pregnenolone was observed a few days before parturition. Estrone sulfate and estradiol concentrations increased during gestation, but estrone did not. They increased shortly before parturition, and then decreased immediately after parturition. At parturition, the correlation between estrone and estrone sulfate was significantly stronger. Moreover, a strong correlation between estrone sulfate and estradiol was observed after parturition. Cortisol did not change during gestation and increased shortly before parturition. The results showed steroid hormone dynamics in normal pregnant Suffolk ewes, which were mostly in line with those of other sheep breeds. It should be noted that high progesterone concentrations altered the typical patterns.     

Fecal progestagens to detect and monitor pregnancy in captive female cheetahs (Acinonyx jubatus)

The purposes of the present study were to establish a noninvasive monitoring assay of fecal progestagen measurement to detect pregnancy and to identify the components of fecal progestagens in early, middle and late pregnancy in cheetahs. Feces were collected from 7 female cheetahs and analyzed from 30 days before the last copulation to parturition in 9 pregnancies. Blood was collected from one cheetah. Fecal progestagen and serum progesterone concentrations were determined by enzyme immunoassay (EIA). The profiles of the fecal progestagen concentrations were similar to the serum progesterone profile. Fecal progestagen and serum progesterone concentrations remained at the baseline until copulation. In the mean fecal progestagen profile during pregnancy (92.8 ± 0.4 days; from the last copulation to parturition), the concentrations increased 3-4 days after the last copulation and remained high until parturition. To investigate changes in the components of progestagen metabolites in the tripartite periods of gestation, fecal progestagens were analyzed by HPLC-EIA. Marked immunoreactive peaks consistent with 5α-pregnan-3α/β-ol-20-one and 5α-pregnan-3,20-dione and small peaks consistent with 5β-pregnan-3α/β-ol-20-one were detected. There were no distinct difference in the components of progestagens among the first, second and third trimesters of pregnancy. The hormone assay, as an indicator of fecal 5α-reduced pregnanes, is useful for detecting pregnancy and monitoring pregnant luteal activity in cheetahs.     

The effect of a bacterial endotoxin or cloprostenol on the clinical status and hormonal levels in 80-100 days pregnant gilts

An experiment was conducted to examine the effect of a lipopoly-saccharide (LPS) of Salmonella typhimurium on the luteal function in 80 days pregnant gilts. Four animals were i.v. injected with 2 μg LPS/kg body weight and 3 animals were i.m. injected with 500 μg cloprostenol (CP). Gilts which maintained pregnancy after the initial injection were reinjected with GP around day 100. Clinical observations were made and plasma levels of 15-keto-13,14-dihydro-PGF₂α, progesterone, oestradiol-17β and oestrone sulphate were analysed by radioimmunoassay.The LPS induced a characteristic clinical endotoxemia. All LPS treated gilts maintained pregnancy until day 100 when 1 gilt aborted, 1 was emergency slaughtered and 2 reinjected. The comparative injections of CP induced abortion! within 48 h in 2 of 3 gilts at 80 days and in all reinjected animals at 100 days of pregnancy. Progesterone decreased immediately after both LPS and CP injections. In non-aborting gilts, the progesterone decrease had a transient character. The PGF_2α metabolite levels responded to LPS by a dramatic surge of approximately 4 h duration. All abortions were accompanied by a massive release of PGF_2α reaching peak levels during expulsion of the foetuses. Oestradiol-17ß and oestrone sulphate followed an ascendent pattern between days 80 and 100. Occasional transient decreases in oestradiol-17ß or increases in oestrone sulphate levels after LPS and CP injections were observed in several animals. Abortions were followed by a sharp decrease of both oestrogens. Post-abortum reproductive disorders occurred frequently. Endocrine changes associated with post-abortum ovarian activity were relevant to the clinical and morphological observations. The relationship between the stage of pregnancy in the pig and its endocrine response to abortifacient agents as well as some foetopathic effects of the endotoxin are discussed.