Effect of hysterectomy on the short life-cycle corpus luteum produced after GnRH-induced ovulation in the anoestrous ewe

Anoestrous Romney Marsh ewes were treated with small-dose (250 ng) multiple injections of GnRH. Ewes in Groups 1 and 3 were hysterectomized 2 weeks before treatment, while those in Groups 2 and 4 were intact controls. Groups 1 and 2 were primed with progesterone (+P) and treated with 2 h injections of GnRH (250 ng) for 36 h, while Groups 3 and 4 were not pretreated (-P) but were given 2 h injections of GnRH (250 ng) for 18 h. Both treatment regimens were terminated with a bolus injection of GnRH (125 micrograms), given to synchronize the timing of the LH surge and subsequent luteal progesterone production. The plasma progesterone profiles of 5/5 animals in Group 2 (+P controls) and 2/5 animals in Group 4 (-P controls) were indicative of normal luteal function, while the remaining 3/5 animals in Group 4 produced plasma progesterone profiles typical of abnormal luteal function. However, in all the hysterectomized animals (Groups 1 and 3) peripheral plasma progesterone concentrations rose to reach a mean peak value of 1.3 ng/ml plasma on Day 8 which was maintained in all animals irrespective of progesterone pretreatment. The absence of a fall in progesterone concentrations precluded the identification of any animal in Group 4 showing abnormal luteal function. It was also noted that, after hysterectomy, although the corpus luteum was maintained, it was with reduced secretory capacity. The prevention of the expected proportion (70%) of -P animals from displaying a decline in plasma progesterone concentration after hysterectomy provides firm evidence that the uterus is involved in the premature regression of the short-cycle corpus luteum.

Is oxytocin of conceptus origin involved in inhibition of luteal regression in early pregnancy in ewes?

This study describes the presence in and production by the ovine conceptus of an oxytocin-like peptide during the early stages of development. Oxytocin was measured by radioimmunoassay in ovine conceptuses from days 14 to 30 of pregnancy. Tissue concentrations of oxytocin increased from day 14 (24.8 +/- 5 pg/100 mg) until day 19 (122.9 +/- 52 pg/100 mg) and then decreased (3 +/- 1 pg/100 mg). Oxytocin was released into culture medium by day-15 ovine conceptuses at a rate of 262 +/- 55 pg/24 h. Reverse-phase high-performance liquid chromatography (HPLC) analysis of peptides extracted from a pool of ovine conceptuses was conducted using chromatographic conditions developed to separate oxytocin from other nonapeptides. Radioimmunoassay of HPLC fractions for oxytocin revealed an immunoactive conceptus peptide in a single fraction at the same retention time as chromatographed authentic oxytocin. Radioimmunoassay and chromatographic data therefore suggest that this oxytocin-like peptide is similar, if not identical, to authentic oxytocin. Concentrations of oxytocin in conceptus tissue were maximal during the period of inhibition of luteal regression (days 14-19). It is proposed that conceptus oxytocin is involved in the maintenance of luteal function in early pregnancy.

Effect of flushing of blastocysts on days 10-13 on the life-span of the corpora lutea in the pig

Blastocysts were flushed out of both uterine horns of gilts on Days 10, 11, 12 or 13. In mated non-pregnant gilts flushing had no effect on progesterone profile or cycle length (20.8 +/- 0.4 versus 20.6 +/- 0.6 days in the preflush cycle, N = 6, mean +/- s.e.m.). Flushing the blastocysts out of the uterine horns on Day 10 resulted in a cycle with a normal progesterone profile and a normal length (21.2 +/- 0.4 days, N = 5). Flushing on Days 11, 12 or 13 resulted in a normal cycle or in maintenance of the CL for 3-13 days as indicated by elevated progesterone concentrations and an increased interoestrous interval of, respectively, 22.0 +/- 1.2 versus 19.8 +/- 0.6 days (Day 11; N = 6), 24.8 +/- 1.4 versus 21.0 +/- 0.6 days (Day 12; N = 5; P less than 0.05) and 26.3 +/- 2.3 versus 20.5 +/- 0.4 days (Day 13; N = 6; P less than 0.05). There was a positive relationship between the change in interoestrous interval and the interval between the first observed standing oestrus and flushing of the blastocysts (rs = 0.350; n = 22; P less than 0.1). There was a large variation in the diameter of the blastocysts flushed on the same day. Only in those gilts in which the blastocysts were greater than or equal to 8 mm or filamentous were the CL maintained for 3 or more days. These results indicate that a first signal for maternal recognition of pregnancy is generated on Day 12 and that blastocysts greater than or equal to 8 mm are required for prolongation of CL function for 3 or more days. Since CL function is only extended for a maximum of 13 days (mean 7.4 +/- 1.0), a second signal seems necessary to maintain the CL for the whole period of pregnancy.

Modification of prostaglandin F-2 alpha synthesis and release in the ewe during the initial establishment of pregnancy

Pregnant (N = 10) and non-pregnant (N = 10) ewes were bled every 2 h from Days 12 to 17 after oestrus (oestrus = Day 0). Plasma concentrations of progesterone, 15-keto-13,14-dihydro-PGF-2 alpha and 11-ketotetranor-PGF metabolites were determined in all samples. The number of PGF-2 alpha pulses in non-pregnant ewes was 8.2 +/- 0.4 (mean +/- s.e.m.) with an interpulse interval of 10.7 +/- 0.7 h. Two or 3 pulses of low frequency (interpulse interval = 13.4 +/- 1.6 h) occurred in most non-pregnant ewes before the onset of luteolysis; the interpulse interval then decreased to 7.9 +/- 0.4 h for the 6.0 +/- 0.3 pulses temporally associated with luteolysis. In contrast, the number of PGF-2 alpha pulses in pregnant ewes was lower (2.5 +/- 0.7, 0-8) and the interpulse intervals longer (18.9 +/- 6.1 h). Most pulses occurred on Days 14 and 15 in the pregnant and non-pregnant ewes. The mean concentrations of both PGF-2 alpha metabolites in non-pregnant ewes were highest on Day 15 while basal levels of both metabolites remained constant at all times. In pregnant ewes, the mean concentrations of both metabolites were highest on Day 14; basal concentrations of both metabolites were also highest on Day 14. The mean concentrations of 15-keto-13,14-dihydro-PGF-2 alpha were higher in pregnant than in non-pregnant ewes on Days 13 and 14 (P less than 0.05) and higher in non-pregnant than pregnant ewes on Day 15 (P less than 0.05). The basal concentrations of the 15-keto metabolite were higher in pregnant than non-pregnant ewes at Days 13, 14, 15, 16 and 17 (P less than 0.05). Both the mean and the basal concentrations of 11-ketotetranor-PGF metabolites were higher in pregnant than in non-pregnant ewes on Day 14 (P less than 0.05). It is concluded that uterine production of PGF-2 alpha peaks at Days 14-15 after oestrus in pregnant and non-pregnant ewes. Patterns of release differ, however, in that non-pregnant ewes have a pulsatile PGF-2 alpha pattern superimposed on a constant baseline, while pregnant ewes have an increasing basal secretory pattern which is more nearly continuous, i.e. not pulsatile in form. Modification of pulsatile PGF-2 alpha synthesis and release is therefore a key aspect of prolongation of luteal function at the beginning of pregnancy in the ewe.

Characterization of plasma membrane lipids and luteinizing hormone receptors of ovine corpora lutea during luteolysis and early pregnancy

Lipid composition of plasma membranes from luteal cells was examined to determine whether changes in this organelle occur during regression and maintenance of the corpus luteum in nonpregnant (NP) and pregnant (P) ewes, respectively. Forty ewes were assigned to be killed on Day 13 or 15 of the estrous cycle (D13-NP and D15-NP) or pregnancy (D13-P and D15-P). Purification of luteal plasma membranes on discontinuous sucrose gradients yielded two fractions, designated F1 and F2, that exhibited the greatest enrichment of 5'-nucleotidase activity (five- and fourfold, respectively) over that of the homogenate. These fractions also yielded the lowest contamination by endoplasmic reticulum as represented by nicotinamide adenine dinucleotide phosphate (NADPH) cytochrome C reductase activity and mitochondrial membranes as indicated by succinate dehydrogenase activity. Predominant phospholipids identified in membranes obtained from all groups were phosphatidylcholine (PC, 48.9 +/- 0.6% of total phospholipid), phosphatidylethanolamine (PE, 33.3 +/- 0.4%), sphingomyelin (SPH, 9.7 +/- 0.3%), phosphatidylserine (PS, 3.5 +/- 0.2%), and phosphatidylinositol (PI, 4.0 +/- 0.5%). No changes in microgram phospholipid/mg membrane protein were observed for any luteal phospholipid on D13 and 15 of the estrous cycle or pregnancy. No significant changes in the relative percentages of major fatty acids present in PC (palmitic [16:0], oleic [18:1]), PE (stearic [18:0], 18:1 and arachidonic [20:4]), or PS (18:0, 18:1, docosatetraenoic [22:4]), nor in the ratios of unsaturated (U) to saturated (S) fatty acids in these phospholipids were observed. Significant differences in unsaturated fatty acids of chain length greater than 20 carbons present in minor quantities in PC, PE, and PS were detected between NP and P ewes as well as between days within reproductive stage. The profile of major fatty acids present in PI revealed decreases in 18:0 and 20:4 in D15-NP and increases in 22:4 and docosapentaenoic acid (22:5) in luteal membranes of both D13- and D15-NP ewes relative to the levels of these fatty acids in PI of corresponding groups of pregnant ewes. There was a general trend for 20:4 levels of PC and PI in membranes of D15-NP ewes to be inversely related to those of D15-P ewes. Collectively, these changes were reflected by an increased U:S fatty acid ratio in luteal membrane PI during the estrous cycle. Specific binding of [125I] iodo-human chorionic gonadotropin to luteal plasma membranes from NP and P ewes on D13 and 15 (6/group) revealed similar affinities and concentrations of unoccupied luteinizing hormone (LH) receptors.(ABSTRACT TRUNCATED AT 400 WORDS)

Steroidogenic capacity and ultrastructural morphology of cultured ovine luteal cells

Corpora lutea were surgically collected from superovulated ewes 36 h post-injection of human chorionic gonadotropin (hCG) (Day 2), dissociated (0.2% collagenase), plated, and maintained in culture Days 2-10 in Medium 199 supplemented with 5% calf serum. Accumulation of progesterone in the cultures did not decrease (p greater than 0.05) from Day 3 (17.5 +/- 5.1 nmol/10(6) cells) to Day 10 (4.8 +/- 1.7 nmol/10(6) cells). Calf serum (5%) in the medium supported greater (p less than 0.05) progesterone production than fetal calf serum (5%) or medium without added serum. Steroidogenic cells did not increase (Days 2-10) in numbers, but increased (p less than 0.01) in mean cell diameter (Day 2, 11.7 +/- 0.4 micron; Day 10, 24.5 +/- 1.6 micron). Steroidogenic capacity on Day 10 of cells cultured Days 2-10 (in vitro) was not different (p greater than 0.05) from that of cells collected from the ovary on Day 10 (in vivo); however, steroidogenic cells recovered from plates had greater (p less than 0.01) mean cell diameters (24.5 +/- 1.6 micron, in vitro, compared to 15.2 +/- 1.0 micron, in vivo). Transmission electron microscopy revealed that cultured cells (Days 5, 10) possessed less smooth endoplasmic reticulum but more lipid droplet inclusions, ribosomes, and rough endoplasmic reticulum than cells obtained in situ (Day 10). Electron-dense secretory granules were rarely seen. Although subcellular morphology of ovine luteal cells in culture was altered, these changes did not appear to significantly affect the ability of these cells to produce progesterone.

Neuroendocrine processes in the establishment of pregnancy and pseudopregnancy in rats

Rats, like mice, hamsters and other small rodents, have a short, incomplete estrous cycle. They lack a spontaneous luteal phase, and the corpora lutea (CL) of the estrous cycle are short-lived and nonfunctional. The activation of the luteal phase in these incompletely cycling females depends on the neuroendocrine reflex provided by the male at the time of mating. In this article we review our research on the cervix-brain-pituitary-ovary interaction at the endocrine, neuroendocrine, neurotransmitter and behavioural levels, dealing with the chain of events initiated by the male and necessary for the establishment of the progestational state.

Prolactin as an inhibitor of granulosa cell luteinization: implications for hyperprolactinemia-associated luteal phase dysfunction

Chronic and transient hyperprolactinemia have been associated with luteal phase dysfunction in both spontaneously cycling women and those subjected to ovarian hyperstimulation by exogenous gonadotropins. It is the objective of the in vitro and in vivo studies reported herein to examine the possibility that prolactin (PRL), a known constituent of ovarian follicular fluid, may account, at least in part, for the luteinization inhibitory (LI) activity exerted by follicular fluid (FF) under both physiologic and pathophysiologic circumstances. In vitro treatment with human PRL (100 ng/ml) reduced by 57% the specific binding of luteinizing hormone (LH) to follicle-stimulating hormone(FSH)-primed cultured rat granulosa cells, an effect associated with a 2.6-fold diminution of human chorionic gonadotropin (hCG; 10 ng/ml)-stimulated progesterone biosynthesis. Importantly, the ability of PRL to exert a direct inhibitory effect on FSH-supported LH binding was fully reproduced under in vivo conditions. Inasmuch as the acquisition of LH receptors and progesterone (P) biosynthetic capacity are acceptable as criteria of granulosa cell luteinization, the authors' findings indicate that PRL, acting at concentrations achievable in vivo within the ovarian FF, may account, if only in part, for physiologically encountered LI-like activity. Moreover, subject to limitations imposed by the rat model employed, consideration also must be given to the possibility that hyperprolactinemia-associated luteal phase dysfunction may not only reflect the suppressive effect(s) of PRL at the central level of the reproductive axis, but may also be due, at least in part, to the consequences of inappropriately elevated PRL at the level of the follicular microenvironment.

Persistent progesterone production associated with autoimmune oophoritis. A case report

A woman with autoimmune oophoritis was found to have luteal phase progesterone levels throughout a six-month period of amenorrhea. The common presentation of amenorrhea or metrorrhagia, despite the presence of a corpus luteum, in women with autoimmune oophoritis might result from this chronic progesterone production. A clinical picture consistent with a persistent corpus luteum may be a very early sign of autoimmune oophoritis.

Identification of bovine trophoblast protein-1, a secretory protein immunologically related to ovine trophoblast protein-1

This paper demonstrates that a group of proteins, representing a major secretory component of cattle conceptuses, is immunologically related to ovine trophoblast protein-1 (oTP-1), a principal product of culture Day 13 to 21 sheep conceptuses. Conceptuses from cows (Day 17-18) and ewes (Day 16-17) were cultured for 24 h in the presence of L-[3H]leucine. By using a rabbit antiserum to oTP-1 and Ouchterlony double-immunodiffusion analysis it was shown that material in the bovine conceptus culture medium was serologically related, but not identical, to oTP-1. A solid-phase radiobinding assay indicated that the cross-reacting bovine secretory component had an affinity for anti-oTP-1 antibody similar to that of oTP-1. Anti-oTP-1 antiserum specifically immunoprecipitated a group of 6-8 polypeptides from culture medium of cow conceptuses which, when analysed by two-dimensional gel electrophoresis, fell into two major molecular weight classes (22,000 and 24,000) with isoelectric points between 6.5 and 6.7. These immunoprecipitated polypeptides, defined as bTP-1, constituted the major secretory products of Day 16-25 cow conceptuses. They were larger and more basic than oTP-1 polypeptides (Mr about 18,000; pI 5.4-5.7). Anti-oTP-1 antiserum also recognized the major translation product of Day 17 bovine conceptus mRNA, a polypeptide significantly smaller (Mr approximately 18,000) than the secreted protein. It is suggested that oTP-1 and the homologous bovine protein may play similar roles in the phenomenon of maternal recognition of pregnancy in the two species.

Luteal phase insufficiency: clinical aspects

The author analyzes different controversial clinical aspects of luteal phase insufficiency (LPI) on the basis of his own data. Conceptual and diagnostic concerns include: (1) the lack of predictive value of midluteal plasma progesterone determination regarding the progestational transformation of the endometrium, and (2) the need for a minimum of two, and even three, endometrial biopsies for diagnosis of LPI. From an etiologic point of view, follicular phase determinants of LPI are emphasized. Primary therapeutic approaches of LPI and the effectiveness and significance of such therapy on fertility are discussed.

Measurement of glucuronometabolites of 17 beta-estradiol and progesterone in diluted overnight urine. An approach to the study of luteal insufficiency

The determination of the concentrations of estrone-3-glucuronide, pregnanediol-3-glucuronide and luteinizing hormone has been performed in early morning urine samples of 14 normal menstruating women using a timed and measured volume urine collection procedure. In order to investigate the variability of the urinary hormonal concentrations due to day-to-day differences in diuresis, the absolute hormonal concentrations have been corrected either for the urinary creatinine excretion or for the volume of urine voided during the night. The results demonstrate that both correction factors are able to reduce substantially the coefficient of variation values in comparison to the absolute hormonal concentrations. The urinary test of ovarian function has been performed in 11 infertile women affected by luteal insufficiency using the same procedure, and the hormonal profiles showed some alterations in both estrone-3-glucuronide and pregnanediol-3-glucuronide concentrations in comparison to the hormonal profiles of the normal subjects. Such alterations were significant in the single subject when integrated values of the hormonal data in defined time intervals were investigated.

Ovarian follicular development during early pregnancy in cattle

On the day of oestrus (Day 0), 23 cows were assigned randomly to 4 groups in a 2 X 2 factorial experiment. Main effects were cow status [pregnant (P) versus non-pregnant (NP; not mated)] and day (Day 17 versus Day 34) when cows were slaughtered and ovaries collected; i.e. Groups NP-17 (N = 6), NP-34 (N = 5), P-17 (N = 6) and P-34 (N = 6). To mimic CL maintenance associated with presence of a conceptus in Group P-34, cows assigned to Group NP-34 were hysterectomized between Days 4 and 6 after oestrus. Pregnancy in Groups P-17 and P-34 (recovery of conceptus) and CL maintenance between day of surgery and Day 34 in Group NP-34 were confirmed. In Group NP-17, all cows except one were slaughtered before luteolysis. CL-bearing ovaries were serially sectioned (10 microns) and follicles (greater than 0.15 mm) were counted and measured using routine histological techniques. For each size class of follicles, the percentages of follicles were similar (P greater than 0.1) on Days 17 and 34. The percentage of non-atretic follicles (less than 4 pycnotic bodies) was lower (P less than 0.002) in pregnant than non-pregnant groups in the smallest class of antral follicles (0.16-0.28 mm) but was higher (P less than 0.03) in larger classes (0.68-3.67 mm) for pregnant groups. Percentages of atretic follicles were 3.7 and 4.9 (P greater than 0.1) for follicles of 0.16-0.67 mm, 91.1 and 78.9 for follicles of 0.68-3.67 mm (P less than 0.04) and 5.1 and 16.1 (P less than 0.05) for follicles of 3.67-78.56 mm in pregnant and non-pregnant groups respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Bilateral maintenance of rabbit corpora lutea by the feto-placental unit

The present study was undertaken to determine whether the rabbit feto-placental unit maintains corpora lutea systematically and/or locally and the interrelationships between conceptus number, luteal weight, luteal progesterone concentrations and serum progesterone levels. Thirty-three does were divided into the following treatment groups: (I) bilaterally pregnant, two ovaries; (II) unilaterally pregnant, two ovaries; (III) bilaterally pregnant, one ovary; (IV) unilaterally pregnant, one ovary, contralateral and (V) unilaterally pregnant, one ovary, ipsilateral. Blood samples were obtained from all rabbits on days 6, 9, 12, 15, 18 and 21 post coitum. Does were killed on day 21, and the percentage of viable fetuses, fetal weights, and luteal weights recorded. Blood samples and corpora lutea were analysed for progesterone. Serum progesterone levels were similar for all groups until day 9 post coitum. Levels in groups III, IV and V declined significantly between days 9 and 12 following removal of one ovary at day 9. Fetal viability, fetal weights and luteal progesterone concentrations did not differ among any of the groups. Luteal weights did not differ among groups I, III, IV and V, but luteal weights of animals in group II were lower than those of group I (P less than 0.05). Ratios of viable fetuses to number of corpora lutea ranged from 1:11-10:5. No differences were observed in serum progesterone, luteal weights or luteal progesterone concentrations among animals with two conceptuses and those with seven or more, but serum progesterone levels in does with only one conceptus were lower than those in does with more (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Interrelationships between uterus and conceptus to maintain corpus luteum function in early pregnancy: sheep, cattle, pigs and horses

Processes associated with "Maternal Recognition of Pregnancy" are reviewed extensively from the ovine, bovine, porcine and equine species. Comparisons among these species indicate that CL maintenance is achieved primarily by a predominant antiluteolytic-anti PGF effect, and there is strong evidence for antiluteolytic-luteoprotective and luteotropic controls that complement this basic system. The nature of the chemical signals (steroids, prostaglandins and proteins) to regulate these processes among the species are described. Common to all of the species reviewed is a change in vascular dynamics to and from the uterus and ovary during early pregnancy. The dialogue between endometrial epithelium and trophectoderm of the developing conceptus is described. The consequence of these various physiological and biochemical responses of early pregnancy is maintenance of the CL to provide a sustained embryotrophic environment. Either in the absence of or death of a conceptus, an efficient and acute system is operational to terminate this progestational environment via regression of the CL through uterine production of PGF.

Prostaglandin concentrations in uterine fluid of cows with pyometra

Uterine fluid was obtained from eight clinical cases of pyometra with retained corpus luteum and nine additional samples of fluid were collected from animals slaughtered at an abattoir. These samples, along with uterine flushes from normal cows in their luteal phase were analyzed for prostaglandin of the F (PGF) and E (PGE) groups. Blood samples were also obtained from the clinical cases for analysis of 13,14-dihydro-15-keto PGF (PGFM) the major metabolite of PGF. Pyometrial exudate from clinical cases of abattoir samples had high concentrations of PGF (17.9 ng/mL) and PGE (33.2 ng/mL) and the total amount of PGF and PGE in the uterus was calculated to be several hundred times as great as in normal cows. Furthermore, clinical cases had elevated PGFM in their blood compared to that of controls, which suggests that at least some of the PGF was being absorbed from the uterus. These results are discussed in light of our current understanding of the maternal recognition of pregnancy in cattle.

Effect of partial stepwise luteectomy in pregnant gilts on maternal and fetal concentrations of progesterone

The number of corpora lutea (CL) in gilts was reduced to 8, 5, and 3 on Days 30, 40, and 50 of gestation, respectively. In a second group of gilts the number of CL was reduced to 5 by luteectomy by Day 50. Luteectomy did not affect concentrations of progesterone (P) in maternal uterine or fetal umbilical vessels sampled at Day 80. Concentration of P was higher in umbilical than uterine plasma in all treatments (P less than 0.01). The uterine arterial-venous (A/V) difference in concentrations of P was positive and the umbilical A/V difference was negative in all groups. The uterine and umbilical A/V differences at Day 80 decreased as the number of CL decreased. Fetal survival was reduced in luteectomized gilts. These results indicate that gradual reduction of numbers of CL does not result in placental secretion of P into the maternal circulation but does alter the uptake of P by the uterus and umbilical circulation.

Assessment of the cause of infertility

The different causes of infertility and evaluation of the infertile couple are reviewed in this paper. Forty to 50 percent of cases are due to male factors, and special emphasis is placed in describing techniques to diagnosis this type of infertility. Five to ten percent of infertile couples have infertility of unknown etiology even after a complete, appropriate evaluation. Special instruction in how to diagnose and treat these types of patients is described. A step by step evaluation of peritoneal factors, ovulation factors, and male and cervical mucus interaction is presented for the clinicians' use.

Unexplained infertility: a review

When investigations fail to reveal a cause for infertility, treatment must then be based on possible, but unproven, causes, and since there is a high spontaneous pregnancy rate in unexplained infertility the effect of any treatment is difficult to assess. Such treatment has included correction of anatomical variants such as uterine retroversion and the use of hormonal manipulation during the follicular and luteal phases of the menstrual cycle. Ovum entrapment, occult spontaneous abortion and faults in sperm fertilizing capacity have all been implicated, and it is likely that immunological factors play a substantial role in unexplained infertility. Evidence does not support the use of bromocriptine in the absence of hyperprolactinaemia. Successful treatment by intrauterine insemination is unlikely if there are circulating anti-sperm antibodies in the partner. Improving cervical mucus by treatment with oestrogens and clearing infections with antibiotics may have a modest place but it is very difficult to show that these treatments have more than a placebo effect. Endometriosis is often missed and the possibility of it having developed after initial investigation warrants repeat laparoscopy after 2 years. Three approaches are currently acceptable in the management of the couple with unexplained infertility: await spontaneous pregnancy, the empirical use of clomiphene and in-vitro fertilization.

Maternal recognition of pregnancy--a review of the literature

A review of the literature concerning the endocrinological changes around early pregnancy in the domestic animals is presented. During this period the presence of the blastocyst must be recognized by the mother ("Maternal Recognition of Pregnancy") leading to a rescue and maintenance of the corpus luteum function. Several hormones are involved in these processes and the initial hormonal changes are dependent on a viable blastocyst. The key event is its control of the prostaglandin synthetizing system.

Maternal recognition of pregnancy in cattle

Nature and potential functions of chemical signals involved in the process of pregnancy recognition in cattle are discussed. The array of prostaglandins, steroid metabolites, and proteins produced by the conceptus and endometrium are described and collated with histological and physiological responses of the uterus and ovary that lead toward maintenance of the corpus luteum. Advances during the last 10 yr partially have identified the conceptus-endometrial-ovarian signal sequence that is associated with maternal recognition of pregnancy in cattle. Final evaluation of the control system should permit investigators to improve embryo survival and augment further the impact of embryo manipulation to improve genetic merit of the cattle population.

Maintenance of the corpus luteum of early pregnancy in the ewe. III. Differences between pregnant and nonpregnant ewes in luteal responsiveness to prostaglandin F2 alpha

The effects of pregnancy and number of corpora lutea on luteal regression induced with prostaglandin F2 alpha (PGF2 alpha) were examined in 93 ewes. Bred and nonpregnant ewes were assigned randomly to receive a single im injection of PGF2 alpha: 0, 2, 4, 6, 8 or 10 mg/58 kg body weight. Injections were given on d 13 postestrus. The concentration of progesterone in serum 24 h after PGF2 alpha injection was affected by dose (P less than .001). The effect of pregnancy and the interaction of pregnancy with number of corpora lutea on levels of progesterone in serum were significant (P less than .05); therefore, data were partitioned according to pregnancy status and analyzed separately. There was an effect of number of corpora lutea on serum concentration of progesterone in pregnant (P less than .01) but not nonpregnant ewes (P greater than .10). Similar relationships among groups were observed for the concentration of progesterone in luteal tissue. In nonpregnant ewes the minimum dose of PGF2 alpha to produce a significant suppression of progesterone in serum (P less than .05) was 4 mg/58 kg body weight. In pregnant ewes with one or two corpora lutea, the minimum effective doses were 6 and 10 mg/58 kg body weight, respectively. The concentration of 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) in serum was related to the dose of PGF2 alpha injected. There were no differences in the concentration of PGFM in serum between pregnant and nonpregnant ewes either before or after injection. Corpora lutea of early pregnancy appear to be resistant to the luteolytic effect of PGF2 alpha.(ABSTRACT TRUNCATED AT 250 WORDS)

Rate of blood flow and growth of the corpora lutea of pregnancy and of previous cycles throughout pregnancy in the rat

The rate and distribution of ovarian blood flow was measured with radioactive microspheres in nulliparous rats at Days 4, 7, 10, 13, 16 and 22 of gestation; term is Day 23. Ovaries were dissected into large corpora lutea (or CL of pregnancy), small CL, assumed to be those of previous cycles, and the ovarian stroma which included follicles and additional small CL. Total ovarian blood flow was similar over Days 4-10, but then increased progressively to reach 916 +/- 69 microliter/min at Day 22. The main cause of this increase was a 786% rise in blood flow to the large CL over Days 10-22. Weight of the CL of previous cycles increased by 289% over Days 10-16 and their rate of blood flow and histological appearance were similar to those of the large CL. These results indicate that neither reduced blood flow nor vascular degeneration, as determined by light microscopic examination, initiates the reported fall in progesterone secretion near term. At least some of the CL of previous cycles are maintained and indeed grow during gestation and have a blood circulation and histological appearance characteristic of steroidogenic tissue.

Dissociation of copulation from ovulation in pregnant rabbits

Experiments were designed to determine why copulation in the pregnant rabbit does not terminate pregnancy while treatment with ovulatory doses of luteinizing hormone (LH) human chorionic gonadotropin (hCG) or luteinizing hormone-releasing hormone (LHRH) is known to do so. Pregnant rabbits (Day 8) were mated or were injected with hCG (25 IU/doe) or LHRH (1, 10 micrograms/kg). Serial blood samples were collected over the next 72 h and analyzed for content of LH, follicle-stimulating hormone (FSH) and progesterone. At sacrifice, uteri and ovaries from these animals were examined for viability of the embryos and for signs of recent ovulation. Injection of hCG or LHRH into pregnant animals led to ovulation and to patterns of LH, FSH and progesterone secretion like those which precede ovulation in estrous rabbits. However, mating the pregnant does did not lead to ovulation or to any changes in the circulating hormones. To investigate whether the elevated levels of progesterone during pregnancy were responsible for the dissociation of coitus from ovulation, nonpregnant rabbits were injected with progesterone (2 mg/kg) and then mated or injected with hCG or LHRH. In virtually every respect, the numbers of ovulations and the patterns of hormone secretion in the progesterone-treated, nonpregnant rabbits mimicked those observed in the 8-day pregnant animals; injection of hCG or LHRH caused ovulation and hormonal surges while hCG caused ovulation only. Mating did not lead to ovulation or any change in blood levels of LH, FSH or progesterone. Taken together, the results show that the elevated circulating levels of progesterone, characteristic of pregnancy, are probably responsible for the dissociation of copulation from gonadotropin release in pregnant rabbits.

Luteolytic influence of intrauterine dead embryos in the early pregnant rat

The present investigation was an endeavour to study if annihilation of embryos in the uterus of the rat before the establishment of placental luteotropic functions has any influence on corpus luteal function, and, if there is any, whether it is local or systemic. The responsibility of pregnancy maintenance was imposed on a single ovary by performing unilateral ovariectomy after implantation (on Day 5 postcoitum). The implantation sites in one uterine horn, either ipsilateral or contralateral to the remaining ovary, were selectively destroyed by injecting 0.1 ml of sterile normal saline to that particular horn only, and the peripheral progesterone level and viability of the embryos in the untreated horn, which depended on the functions of the remaining ovary, were examined. Selective killing of embryos in the uterine horn of the ovariectomized side did not exert any influence on the fetal viability in the untreated horn ( nonovariectomized side) and the peripheral progesterone level also remained statistically unaffected. On the contrary, induction of fetal resorptions in the uterine horn of the intact side produced a significant fall in the peripheral level of progesterone and induced resorption of embryos of the ovariectomized side also. The latter could significantly be prevented by simultaneous administration of exogenous progesterone, indicating luteolysis as the major, if not sole, factor responsible for fetal resorption in the untreated horn. The luteolytic effect was attributed neither to saline itself, nor to the distension of the uterine horn caused by saline injection. Luteolytic factors from the dead embryo-bearing horn which act locally on the adjacent ovary only, are discussed.