Progestagen Concentrations Research Articles

Fetomaternal interactions and influences during equine pregnancy

The equine embryo takes 6 days to traverse the oviduct and, when it finally enters the uterus, it remains spherical in shape and moves continually throughout the uterine lumen until day 17 after ovulation to deliver its maternal recognition of pregnancy signal to the entire endometrium. Between day 25 and day 35 after ovulation, the trophoblast cells of a discrete annulate portion of the chorion multiply rapidly and acquire an invasive phenotype and, between day 36 and day 38, migrate deeply into the maternal endometrium to form the equine-unique endometrial protuberances known as endometrial cups. These cups secrete large quantities of a gonadotrophic hormone (eCG) into the maternal circulation which, in conjunction with pituitary FSH, stimulates the development of accessory luteal structures in the maternal ovaries to supplement the supply of progesterone to maintain the pregnancy until the placenta can assume this role at about day 100. The non-invasive allantochorion extends slowly to fill the uterus by days 80-85 and its microcotyledonary architecture, which provides both haemotrophic and histotrophic nutrition for the growing fetus, is not fully established until days 120-140. The fetoplacental unit synthesizes large quantities of steroid hormones during the second half of pregnancy, using fetal C-19 precursors secreted by the enlarged fetal gonads for the production of oestrogens and maternal C-21 precursors for the synthesis of progesterone and large quantities of 5alpha-reduced progestagens. Near term, additional pregnenelone is secreted by the fetal adrenal glands so that the mare exhibits the unusual phenomenon of foaling while maternal serum progestagen concentrations are increasing and oestrogen concentrations are decreasing.

Effects of maternally administered depot ACTH(1-24) on fetal maturation and the timing of parturition in the mare.

The aims of this study were to ascertain 1) whether fetal maturation could be induced precociously by maternal administration with adrenocorticotrophic hormone (ACTH) and 2) whether maturation could be achieved without significant risk to mare or fetus. Twenty-two mares received either 1 mg (low dose, LD, n = 6) or 4 or 5 mg (higher dose, HD, n = 16) synthetic Depot ACTH(1-24) at 300, 301 and 302 days gestation. Because, during the course of the study, ACTH appeared to have a greater influence on mares mated during the later part of the breeding season, the HD group were divided retrospectively into those mated before (HDE, n = 6), or after (HDL, n = 10), 1st July. All LD mares were mated before 1st July. Control injections were not performed but gestational data were compared retrospectively with 64 untreated, spontaneously foaling pony mares mated between May and October. Plasma progestagen and cortisol concentrations increased significantly (P<0.05) following ACTH administration in all groups, but progestagens were higher and cortisol elevated for longer in HD mares. ACTH stimulated mammary development and milk electrolyte changes in HD mares. Mean +/- s.e. gestation period (days) was significantly (P<0.01) shorter in HDL mares (318 +/- 1.8) compared with LD (335 +/- 3.7), HDE (340 +/- 4.3) and untreated mares mated after 1st July (327 +/- 1.3). All foals were mature except 2 HDL foals which were stillborn. HDL foals had a higher MCV and lower mean bodyweight, indicating they were delivered before full term. In conclusion, maternal ACTH administration appears to accelerate fetal maturation and delivery in pony mares given high doses and mated late in the breeding season. Further work is required to establish the optimal gestational age and dosage for maternal ACTH administration before clinical recommendations can be given for this therapy.

Effect of crestar ™ on estrus synchronization and the relationship between fecal and plasma concentrations of progestagens in buffalo cows

In buffaloes estrus synchronization provides an opportunity for enhanced use of AI; however, changes in hormone secretion during synchronization are poorly understood. The aim of this investigation was to determine if the concentration of progesterone metabolites in feces would correlate with the concentration of progesterone in blood and thus, could be used for noninvasive monitoring of the reproductive status in buffalo cows. Additionally, the influence of a norgestomet-estradiol treatment (CRESTAR ™-ear implant) was investigated. According to the clinical examination and the progesterone profile in blood samples during the three wks before the treatment, the 17 animals were allotted to 3 groups: 1) CL = presence of corpus luteum throughout the period of 3 wks before the treatment (n = 8); 2) CY = cyclic, corpus luteum present for less than 3 wks (n = 6); and 3) AE = anestrous, with inactive ovaries (n = 3). In the first group, 4 animals started an estrous cycle after implant withdrawal and conceived after natural mating. In the second group one of the cyclic cows showed estrus two d after implant withdrawal, the other 3 had a delayed estrus (12 to 16 d). The two cows which had had inactive ovaries at the beginning but were cyclic before the treatment started, remained cyclic after implant withdrawal but did not become pregnant. The 3 anestrous cows of the third group remained anestrous after the treatment. The progesterone concentration in blood clearly correlated with the concentration of the metabolites in feces. Therefore, this noninvasive method is a valuable tool for determining the luteal status, and such information may be useful for developing estrus synchronization regimens in buffalo cows.

Non-invasive monitoring of reproductive status in wild mongoose lemurs (Eulemur mongoz).

Endocrine profiles were investigated in wild and captive mongoose lemurs (Eulemur mongoz; Lemuridae) by analysing faecal progestagens and oestrogens. Oestrous cycle characterization was not possible, as most females appeared to conceive during the first oestrus of the breeding season. Conception was preceded by a pseudo-oestrus with no discernible luteal phase. Pseudo-oestrus and oestrus identification was possible by investigating the oestrogen:progestagen ratio. Pregnancy was reliably determined approximately 47 days after conception, when progestagen and oestrogen excretion increased above breeding season concentrations. Gestation was further characterized by high progestagen concentrations and a decline in oestrogen excretion 70-80 days after conception. Post partum, progestagens declined, but oestrogen excretion increased to exceed breeding season concentrations. In the wild group, a nulliparous daughter conceived while still a member of her natal group and aborted after 70-80 days of pregnancy at which time progestagens had declined but oestrogens remained high. Comparisons with other strepsirhine primates suggest that pseudo-oestrus followed by conception at first oestrus may be prevalent in lemurs. Gestational progesterone profiles vary between species, but a delayed increase in oestrogens during pregnancy could be common to all strepsirhines, although oestrogen levels during the final trimester of pregnancy differ between lemurs and lorises. Methodological investigations showed that prolonged storage of faeces in ethanol is viable and that the presence of undigested vegetable matter in the faecal pellets had no effect on the interpretation of hormone profiles.

Conservation Endocrinology: a Noninvasive Tool to Understand Relationships between Carnivore Colonization and Ecological Carrying Capacity

Abstract: Reproductive technology, especially the diagnosis of pregnancy by radioimmunoassay of fecal steroid metabolites, is an important component of captive propagation, but its role in our understanding of ecological interactions and in situ biological restoration has been more limited. Where large herbivores have been “released” from predation by the extirpation of carnivores, controversy often exists about possible detrimental effects at the ecosystem level. A related concern is that the reestablishment of large carnivores may decrease the availability of prey populations for human subsistence. We suggest that pregnancy assays can be a valuable tool to help distinguish between the roles of predation versus food‐imposed limitations on population size and their effects on juvenile recruitment in wild species. We explored this issue through analyses of fecal progestagen concentration ( FPC) levels to document pregnancy in moose (Alces alces) in the southern Greater Yellowstone Ecosystem, a site where wolves (Canis lupus) and grizzly bears ( Ursus arctos) are recolonizing former habitats after an absence of more than 60 years. Pregnancy was clearly discernible (mean FPC for pregnant and nonpregnant females, respectively: 10.60 vs. 2.57 μg/g; p &lt; 0.0001). Among the potential confounding variables that need to be considered if FPC is applied to ecological and demographic questions are whether baseline values are affected by handling, whether neonate survival has been assessed, and whether sampling efforts are directed at both pregnant and nonpregnant animals. With these issues accounted for, the local moose population experienced juvenile survival rates among the highest in North America. Pregnancy rates, however, dropped from 90% in 1966 to about 75% today, rendering them in the lowest fifteenth percentile among moose populations in North America. Our findings suggest that a relatively low frequency of juvenile moose is not the likely result of predation, and they illustrate how endocrinology can be applied to issues involving reproductive events within an ecological context. They also affirm that noninvasive and generally inexpensive endocrinological procedures will be applicable to understanding interactions between recolonizing predators and prey, an issue that will continue to arise because of global restoration efforts, and to the study of rare ungulates in remote systems where data on reproductive events are difficult to obtain.

Monitoring ovarian cycle and pregnancy in the giant anteater (Myrmecophaga tridactyla) by faecal progestagen and oestrogen analysis.

Oestrogen and progestagen metabolites were measured in the faeces of five female giant anteaters (Myrmecophaga tridactyla), to characterise the oestrous cycle and pregnancy. Faecal samples were collected twice weekly for a minimum of 6 months, and immunoreactive progestagens and oestrogens were analysed using enzyme immunoassays (EIA). For progestagens, two antibodies that cross-reacted with 20alpha-hydroxy- or 20-oxo-progestagens were used. Both assays effectively monitored ovarian cyclicity; however, the concentrations obtained using the antibody for 20alpha-hydroxy-progestagens were higher, and the hormonal changes were more pronounced. Regular ovarian cycles were identified in three of the five females. Average (+/-SEM) length of the oestrous cycle (n=10) was 51.4+/-5.6 days. Peak concentrations of 20alpha-hydroxy-progestagens ranged from 80-660 ng/g of faeces and those of oestrogens from 20-100 ng/g. Hormone concentrations were measured during parts of two pregnancies and during four post-partum periods. The length of one gestation (from oestrous oestrogen peak until parturition) was 184 days. In the second half of gestation, progestagen concentration started to increase above luteal phase values; in the week before parturition it was approximately 20 times higher than those during the luteal phase. Concentrations of excreted oestrogens began to increase after two thirds of gestation and exceeded that of the follicular phase by approximately 2.5-fold in the week before parturition. Onset of ovarian cyclicity after parturition varied from 4-11 weeks. In conclusion, the measurement of faecal immunoreactive progestagens and oestrogens in the giant anteater indicated an ovarian cycle of approximately 7 weeks in length and provided potentially useful data for successful breeding management.

The effect of dietary protein on reproduction in the mare. VII. Embryonic development, early embryonic death, foetal losses and their relationship with serum progestagen.

Sixty-four Thoroughbred and Anglo-Arab mares aged 6-12 years were randomly allocated to 4 dietary groups and fed diets that differed in the total protein content and quality (essential amino-acids). Forty mares were non-lactating and 24 lactating. Eight mares were withdrawn from the investigation owing to injuries or gynaecological pathology. An overall conception rate of 94.6% and a foaling rate of 80% was achieved. Five of 14 (35.7%) mares (Group 1) fed a low-quality protein diet suffered from early embryonic loss before 90 days of pregnancy compared to 3 of 41 (7.3%) mares in the remaining groups that received the higher-quality protein in their diets. Serum progestagen concentrations of mares in Group 1 that suffered foetal loss were indicative of luteal function insufficiency during the 1st 40 days post-ovulation. Non-lactating mares in all 4 groups gained on average approximately 30 kg in mass during the 90 days before the breeding period. Lactating mares in Group 1 (low-quality protein) lost on average 25 kg in mass during lactation, with no weight loss observed among the lactating mares in the other 3 groups. No difference in the diameter of the embryonic vesicle was found between dietary groups until Day 35 of pregnancy.

The effect of dietary protein on reproduction in the mare. VI. Serum progestagen concentrations during pregnancy.

Sixty-four Thoroughbred and Anglo-Arab mares aged 6-12 years were used, of which 40 were non-lactating and 24 lactating. Foals from these 24 mares were weaned at the age of 6 months. Non-lactating and lactating mares were divided into 4 dietary groups each. The total daily protein intake and the protein quality (essential amino-acid content) differed in the 4 groups of non-lactating and 4 groups of lactating mares. The mares were covered and the effect of the quantity and quality of dietary protein on serum progestagen concentrations during pregnancy was studied. A sharp decline in serum progestagen concentrations was recorded in all dietary groups from Days 18 to 40 of pregnancy, with some individual mares reaching values of less than 4 ng/ml. Serum progestagen concentrations recorded in some of the non-lactating mares on the low-quality protein diet increased to higher values (p < 0.05) than those of mares in the other 3 dietary groups at 35-140 days of pregnancy. A similar trend was observed for the lactating mares on a low-quality protein diet at 30-84 days of pregnancy. No such trends were observed in any of the other dietary groups. High-quality protein supplementation increased serum progestagen concentrations during the 1st 30 days of pregnancy. Lactation depressed serum progestagen concentrations until after the foals were weaned.

The effects of intrafetal ACTH administration on the outcome of pregnancy in the mare.

Enhanced adrenocortical activity in the fetus is related to the onset of parturition in many species. The aim of this study was to determine the effect of injection of fetal ACTH on gestational length and fetal viability in the horse. Pony mares (n=23) were studied from 300 days gestation. Seven control mares (Group 1) received three consecutive intrafetal injections of sterile water, while fetuses of a further 16 mares received Depot ACTH1-24. These mares were either allowed to foal spontaneously (Group 2, n=4) or delivery was induced within 3 days of the last fetal injection (Group 3, n=7); 5 mares aborted within 48 h of intrafetal ACTH injection. Maternal plasma progestagen concentrations increased significantly (P<0.05) in Groups 2 and 3 mares following intrafetal ACTH injection, compared with Group 1 mares. All Group 1 mares delivered live foals at a median gestational age of 327 days (interquartile range, 323 334), except one that aborted 16 days after the last fetal injection. Gestational length was significantly (P<0.05) shortened in Group 2 mares (median 314 [312-314]) days compared with controls. Group 1 and Group 2 foals showed normal postnatal adaptive responses and endocrine (plasma cortisol/progestagens) patterns. Group 3 mares delivered live foals at 306 (306-308) days gestation except one that aborted. Their foals were less mature compared with Groups 1 and 2 foals. Eight ACTH-injected fetuses were meconium-stained at delivery, including four that were aborted. Eight mares had thickened placentae, including three that aborted. The data show that both precocious maturation of the equine fetus and a significant reduction in gestational length compared with controls may be achieved in pony mares by intrafetal ACTH injections. This is probably mediated via adrenal regulation of fetal maturation and production of maternal progestagens.

Fecal Progestagen Concentration as an Indicator of the Estrous Cycle and Pregnancy in Moose

We established a noninvasive technique for monitoring the estrous cycle and pregnancy in moose (Alces alces). We collected fecal samples daily from nonpregnant yearling females (n = 3) for the duration of 3-4 estrous cycles, and weekly throughout gestation from 3 pregnant adult cows. We analyzed samples by radioimmunoassay (RIA) to quantify the concentration of progestagen metabolites. Peak luteal phase concentrations of progestagens were 4.5 ± 0.9 (SD) μg/g compared with 0.5 ± 0.1 μg/g during the follicular phase. Observed (n = 7) and suspected (n = 2) matings all occurred within ±2 days of the nadir in progestagen excretion. Fecal progestagens were above peak luteal phase concentrations by the eighth week of gestation (>7 μg/g of feces, P < 0.001), permitting accurate pregnancy detection by this time. Relative concentrations of fecal progestagens during the follicular phase, luteal phase, and pregnancy were 1:10:35, respectively. Monitoring fecal progestagen is a useful noninvasive technique for tracking ovarian activity and pregnancy in moose.

Plasma and fecal progestagen evaluations during and after the breeding season of the female vicuna ([formula omitted

Plasma and fecal progestagen patterns of female (n = 10) vicunas (Vicuna vicuna) were determined about 1 to 2 mo before and until 4 mo after breeding. The vicunas were caught wild and were penned at the Lauca National Park (Chile, 4470 m above sea level) for 7 mo (December to June). Plasma and fecal samples before and during the mating period (January to March) were collected 4 to 5 times weekly, and once or twice weekly thereafter. The samples were analyzed by enzymeimmunoassays (EIA) using antibodies against progesterone and 20α-dihydroprogesterone. High performance liquid chromatography (HPLC) separations confirmed that progesterone and 20α-dihydroprogesterone predominated in the plasma, whereas in the feces several unconjugated, immunoreactive progestagen metabolites containing either a 20-oxo- or a 20α-OH-group occurred. The coefficients of correlation (n = 409; P < 0.01) between matched plasma and fecal samples were 0.39 and 0.53 for 20-oxo- and 20α-progestagens, respectively. Elevated (5 to 6 d) plasma and corresponding fecal progestagens after mating indicated cyclic corpus luteum activity in 5 of the animals. After the mating period (23.2 ± 3.3 d), corpus luteum function in these 5 animals persisted, as it did in 3 other animals that were not observed to be mating. The persisting corpus luteum function was demonstrated by increased mean plasma and fecal progestagen concentrations (> 1 ng/ml and > 100 ng/g, respectively). Mean plasma 20α-dihydroprogesterone concentrations exceeded that of progesterone by about 1 ng/ml (P < 0.01). The results demonstrated that in addition to plasma progesterone, plasma 20α-dihydroprogesterone and noninvasive fecal progestagen evaluations are useful, valid tools for determining corpus luteum function in vicunas.

A retrospective study of increased plasma progestagen concentrations in compromised neonatal foals.

Plasma progestagen concentrations were measured daily by radioimmunoassay (RIA) in 35 sick foals for the duration of their illness. The foals were divided into three groups on the basis of time to stand after birth. Foals were given intensive care treatment according to the severity of their illness. Plasma and urine concentrations of pregnenolone (P5) and pregnenediol (P5 beta beta) were measured by gas chromatography--mass spectrometry; plasma cortisol concentrations were measured by RIA and the foals' renal and respiratory status were assessed by creatinine clearance ratios and arterial oxygen concentrations respectively. Five patterns of plasma progestagen concentrations were identified; in general, values increased when the foal's clinical condition deteriorated and decreased as the foal improved. Median progestagen concentrations decreased over the first three days post partum in Group 1 foals but remained elevated in foals from Groups 2 and 3. Similar changes were observed in plasma P5 and P5 beta beta concentrations. Plasma cortisol concentrations were highest in foals from Groups 2 and 3 (P < 0.01) compared with foals from Group 1. Regardless of foal group, mean cortisol concentrations were highest (P < 0.001) in those foals treated with adrenocorticotrophic hormone compared with those treated with dexamethasone or with neither drug. There was no relationship (r2 = 0.21) between plasma cortisol and progestagen concentrations. Results from renal clearance, steroid conjugation and respiratory status suggest that these factors did not play a significant role in elevating progestagen concentrations in sick foals. It is hypothesized that there may be a relationship between adrenal stimulation and an enzyme block resulting in overproduction of P5 and P5 beta beta in the sick neonatal foal.

Plasma Progestagen, Tri-lodothyronine, and Cortisol Concentrations in Postdate Gestation Foals Exposed In Utero to the Tall Fescue Endophyte Acremonium coenophialum 1

The effects of in utero exposure to the fescue endophyte Acremonium coenophialum on neonatal Cortisol, thyroid hormone, and progestagen concentrations were examined. Blood samples were collected at birth from 12 mares and foals exposed to the fescue endophyte A. coenophialum (E +; mean gestation, 358 days) and 6 mares and foals grazing endophyte-free (E −) fescue (mean gestation, 334 days). The plasma was assayed for tri-iodothyronine (T3), thyroxine (T4), reverse T3 (rT3), Cortisol, ACTH, and total progestagens by standard RIA. The maternal total progestagen concentration was significantly lower (p < 0.01; 4.7 ng/ml) in mares grazing E + fescue compared to mares grazing E − fescue (22.4 ng/ml). In the foals exposed in utero to endophyte, total progestagens, Cortisol, and T3 concentrations were significantly lower (p < 0.01; 6.7 ± 2.2 vs. 42.4 ± 8.5 ng/ml progestagens; 145.3 ± 23.1 vs. 360.0 ± 21.4 ng/ml T3; and 4.1 ± 2.1 vs. 59.5 ± 6.1 ng/ml Cortisol) than corresponding concentrations in foals not exposed to endophyte. ACTH concentrations in foals that died acutely after delivery were significantly lower at birth than values in foals that survived (37.6 ± 16.47 vs. 291.4 ± 69.8 ng/ml). Umbilical vein progestagen concentrations did not differ between treatment groups (19.7 ± 3.2 vs. 18.3 ± 2.7 ng/ml). In foals that survived the natal period, there was a significant increase in Cortisol, T3, and progestagens from birth to 12 h of age. In foals that succumbed within the first 24 h, no increase in progestagens, T3, or Cortisol was noted. These results demonstrate that exposure of pregnant mares to A. coenophialum-infected tall fescue results in altered neonatal adrenocortical and thyroid hormone production. Placental steroidogenesis as evidenced by umbilical vein progestagen concentrations appears unaffected. Therefore, we suggest that prolonged gestation and fetal dysmaturity in fescue toxicoses results from abnormal adrenal and thyroid hormone production by the late-term fetus.

Concentrations of faecal immunoreactive progestagen metabolites during the oestrous cycle and pregnancy in the black rhinoceros (Diceros bicornis michaeli).

The analysis of reproductive hormones in faecal samples is a possibility for non-invasive monitoring of reproductive status in free-ranging or intractable species. In the present study, faecal samples from three black rhinoceroses (Diceros bicornis michaeli) were collected at about weekly intervals during oestrous cycles and pregnancy. Daily samples were taken during the week after parturition. Total immunoreactive progestagens in faecal extracts were analysed with three different enzymeimmunoassays (EIA) that had considerable specificity for progestagens containing either a 20 alpha-hydroxyl or a 20-keto group. With each EIA it was possible to distinguish between the follicular and luteal phases of the oestrous cycle. Mating corresponded with low concentrations of faecal progestagens. Samples from five and six consecutive cycles were available from two rhinoceroses and cycle lengths of 24 and 26.5 days were calculated. All three animals became pregnant and the duration of gestation ranged from 440 to 470 days. After fertilization, the concentration of progestagens increased continuously, as in the luteal phase, reaching values 5-10 times higher between days 60 and 250. During the two weeks before parturition faecal progestagens declined and within 3-4 days post partum had reached follicular phase values. It was concluded that several immunoreactive progestagens are present in the faeces of black rhinoceroses and that their measurement with EIA enables non-invasive monitoring of the oestrous cycle and pregnancy.

Monitoring of corpus luteum function by measuring progestagens in faeces of non-pregnant mares ( Equus caballus) and Przewalski mares ( Equus przewalskii)

Faecal samples were collected daily from 12 Warmblood mares and five Przewalski mares for 4–7 weeks in spring. Blood samples from nine Warmblood mares were taken one to two times a week. In faecal samples the concentration of progestagens was determined using a radioimmunoassay (RIA) and an enzyme-immunoassay (EIA) for 20α-dihydroprogesterone (20α-G) and an EIA for 20β-dihydroprogesterone (20β-G). In seven Warmblood mares the concentrations of progesterone (P4) in plasma (RIA) and progestagens in faeces revealed a cyclic pattern. When comparisons were made for faecal steroids in samples corresponding to lower (less than 1 ng ml −1) and higher (more than 2 ng ml −1) plasma P4 concentrations, a significant difference ( P<0.05) for each progestagen assay was noted (20 α-G RIA: 58±23 ng g −1, 161±67 ng g −1; 20 α-G EIA: 90±64 ng g −1, 156±86 ng g −1; 20 β-G EIA: 145±98 ng g −1, 367±173 ng g −1 faeces respectively). The coefficients of correlation between plasma P4 and the faecal 20α-G RIA, 20α-G EIA and 20β-G EIA were 0.69, 0.47 and 0.59 respectively ( P<0.01). Four Przewalski mares showed concentrations of faecal progestagens, which were indicative of an oestrous cycle. The remaining mare showed a low concentration of faecal progestagens. The values of 20α-G in faeces were comparable, whereas concentrations of 20β-G were only half of those in Warmblood mares. Supporting evidence for the methodology used was obtained using high-performance liquid chromatography (HPLC) followed by RIA and EIA for extracts of selected samples. It was concluded that different assays for the determination of progestagens in faecal samples of equine species are suitable for non-invasive monitoring of the oestrous cycle.

Increase in plasma progestagen concentrations in the mare after foetal injection with CRH, ACTH or betamethasone in late gestation

Maternal plasma progestagen concentrations increase about 20 days before parturition. The major contributors to the increase are reduced metabolites (ie 5 alpha-pregnanes). Precocious increases (ie less than 310 days of gestation) in these metabolites may occur in abnormal pregnancies. The effects of CRH, ACTH or betamethasone administered to the foetus at gestational ages ranging from about 250 to 320 days were examined. Sixteen healthy pony mares were used for foetal injection employing aseptic techniques. Water or normal saline were used as controls. Maternal plasma progestagen concentrations were measured using a commercial radioimmunoassay (RIA) progesterone kit and results were confirmed using gas chromatography-mass spectrometry (GC-MS). Results demonstrated clearly that an increase in maternal plasma progestagen concentrations occurred after injection of ACTH, CRH or betamethasone to the foetus, irrespective of gestational age. A comparable increase was not observed in the control animals. Of the 16 mares in which the foetus was injected, 13 produced viable foals at gestational ages ranging from 307 to 339 days whereas 3 mares delivered non-viable foals at 284 to 306 days gestation. The results support the hypothesis that the pre-parturient rise in progestagens occurring in the mare is the result of foetal adrenocortical activity.

Repeatability of events during spontaneous and gonadotrophin-induced oestrus in bitches

Oestrus induction using equine chorionic gonadotrophin and human chorionic gonadotrophin was successful in five out of six bitches, although the first day of increased plasma progestagen concentration differed considerably between bitches. Induced oestrous periods differed from spontaneous cycles in the timing of vaginal epithelial cell cornification; plasma oestrogen concentrations were generally greater and progestogen concentrations were less in induced cycles. These results suggest that this schedule of oestrus induction would not be suitable for allowing mating on a predetermined day.

Flow and composition of ovarian lymph during pregnancy and luteolysis in the ewe

Ovarian lymph was collected continuously for periods of 65 to 648 h (mean 163 h) from 10 ewes cannulated at stages of pregnancy ranging from 61 to 123 days post coitum. During mid-pregnancy, ovarian lymph flowed with a rhythmic pattern characterized by periods of flow punctuated with short regular intervals of lymph stasis, while later in pregnancy the flow of lymph became more tonic in character. Lymph plasma samples were analyzed for progesterone, pregnenolone, pregnenolone sulphate, androstenedione, testosterone, oestrone, oestrone sulphate and oestradiol-17β. At all stages of pregnancy, luteal ovarian lymph contained high concentrations of progestagens and androgens while the levels of oestrogens in lymph were similar to those reported in blood plasma of pregnant ewes. When serial 10 min samples were collected over an 8-h period from one ewe on day 105 of pregnancy, the concentration and output of progesterone in ovarian lymph varied in a phasic manner, ranging from 3.3 to 7.1 μM and from 17.8 to 58.9 nmol/h, respectively. The intramuscular injection of 50 or 125 μg of the prostaglandin F 2α analogue cloprostenol into six cannulated ewes caused a severe perturbation to the vascular physiology of the luteal ovary. Ovarian lymph flow ceased completely within a few hours after injection (mean interval 4 h) and there was a reduced rate of protein filtration from blood to lymph within the luteal ovary.

Crystallization patterns in anterior vaginal fluid from bitches in oestrus.

Bitches exhibited a characteristic arborization pattern of the fluid from the anterior vagina during pro-oestrus and oestrus. These changes were monitored together with conventional vaginal cytology and plasma oestrogen and progestagen concentrations. A classical ferning pattern, similar to that seen in bovine cervical mucus at oestrus, occurred after the peak in plasma oestrogen concentrations. Ferning was most intense after the second peak of cornification of vaginal epithelial cells. It is suggested that a 'Ferning Index', when combined with conventional vaginal cytology, can be of use in determining the optimum mating time in the bitch.

Flow and composition of lymph from the ovary and uterus of cows during pregnancy.

Ovarian or uterine lymph was collected continuously for periods of up to 25 days from 16 cows cannulated at stages of pregnancy ranging from 96 to 278 days post coitum. Blood samples were taken acutely from the ovarian and uterine veins during surgery and periodically from the jugular vein during the course of lymph collection. The flow rate and cell content of lymph was measured and blood and lymph plasma samples were analysed for progesterone, pregnenolone, pregnenolone sulphate, androstenedione, testosterone, oestrone, oestrone sulphate, oestradiol-17 beta, prostaglandin (PG) F-2 alpha, total protein and albumin. There was a high flow rate of protein-rich lymph from luteal ovaries with rates up to 101.7 ml/h occurring in individual lymphatics over short periods. Peripheral ovarian and uterine lymph contained a low concentration of cells (mean less than 10(5) cells/ml) comprising about 82-87% lymphocytes, 11-14% macrophages and monocytes and 2-4% other cells. At all stages of pregnancy, the concentration of progestagens and androgens was higher in ovarian lymph than in uterine lymph or blood plasma. The differences were greatest for progesterone and androstenedione which occurred at 200-fold and 60-fold greater concentration respectively in ovarian lymph than in jugular plasma. When serial 10 min samples were collected over a 12-h period, the concentration and output of progesterone in ovarian lymph varied in a phasic manner, ranging from 3.5 to 7.6 microM and from 31.7 to 293.1 nmol/h respectively. There was a positive correlation between the output of progesterone in lymph and the progesterone concentration in jugular blood samples taken every 20 min. During most of pregnancy there was little difference between the concentration of oestrogens in ovarian lymph, ovarian venous plasma and jugular plasma but, during the 3-5 days before calving, these hormones occurred at slightly higher concentration in ovarian lymph. Apart from pregnenolone and androstenedione, all steroids occurred at lower concentrations in uterine lymph than in jugular plasma. Shortly before parturition there was an abrupt increase in the concentration of PGF-2 alpha in uterine lymph. Lymph reflects more accurately the milieu of tissue cells than efferent blood and further analysis of differences in the concentration of substances in lymph relative to the output in the ovarian and uterine arterial and venous blood may lead to the identification of factors important in local regulatory mechanisms in the reproductive tract.