Trophoblast biology: Forum introduction

In mammals, a carefully orchestrated dialogue between the mother and conceptus (embryo/fetus and associate extraembryonic membranes) is initiated during the peri-implantation period of pregnancy as the trophoblast develops, functions to signal pregnancy recognition, and initiates implantation. The purpose of this Forum is to highlight comparative aspects of trophoblast morphogenesis and function in mammals

Conceptus signals for establishment and maintenance of pregnancy

Establishment and maintenance of pregnancy results from signaling by the conceptus (embryo/fetus and associated extraembryonic membranes) and requires progesterone produced by the corpus luteum (CL). In most mammals, hormones produced by the trophoblast maintain progesterone production by acting directly or indirectly to maintain the CL. In domestic animals (ruminants and pigs), hormones from the trophoblast are antiluteolytic in that they act on the endometrium to prevent uterine release of luteolytic prostaglandin F2 alpha (PGF). In cyclic and pregnant sheep, progesterone negatively autoregulates expression of the progesterone receptor (PR) gene in the endometrial luminal (LE) and superficial glandular epithelium (GE). Available evidence in cyclic sheep indicates that loss of the PR is closely followed by increases in epithelial estrogen receptors (ER) and then oxytocin receptors (OTR), allowing oxytocin to induce uterine release of luteolytic PGF pulses. In pregnant sheep, the conceptus trophoblast produces interferon tau (IFN tau) that acts on the endometrium to inhibit transcription of the ER alpha gene directly and the OTR gene indirectly to abrogate development of the endometrial luteolytic mechanism. Subsequently, sequential, overlapping actions of progesterone, IFN tau, placental lactogen (PL) and growth hormone (GH) comprise a hormonal servomechanism that regulates endometrial gland morphogenesis and terminal differentiated function to maintain pregnancy in sheep. In pigs, the conceptus trophoblast produces estrogen that alters the direction of PGF secretion from an endocrine to exocrine direction, thereby sequestering luteolytic PGF within the uterine lumen. Conceptus estrogen also increases expression of fibroblast growth factor 7 (FGF-7) in the endometrial LE that, in turn, stimulates proliferation and differentiated functions of the trophectoderm, which expresses the FGF-7 receptor. Strategic manipulation of these physiological mechanisms can offer therapeutic schemes to improve uterine capacity, conceptus survival and reproductive health

Recirculating flow in a basin with closed f/h contours

A general circulation model is used to study the time evolution of a rotating, weakly baroclinic fluid in a basin with sloping sidewalls. Contours of f/h, where f is the Coriolis parameter and h is the depth of the fluid, are closed in this model. The fluid is forced by a localized source of positive vorticity. The initial response is a narrow, recirculating cell that resembles a β-plume modified by bathymetry. Such cells have been found in previous studies and have been linked to the recirculation cells observed in the subpolar North Atlantic. However, this is not a steady solution in this basin with closed f/h contours, and the circulation evolves into a gyre that encircles the basin. The time at which this transition occurs depends on the Rossby number, with higher Rossby numbers transitioning earlier. Based on the budget of potential vorticity, an argument is made that the western boundary is not long enough to drain significant vorticity from the flow and therefore a bathymetric β-plume is not a steady solution. A similar argument suggests that the Labrador Sea cannot sustain steady, linear, barotropic recirculations either. We speculate that the observed recirculations depend on inertial separation at sharp bathymetric gradients to break the assumption of linearity, which leads to significant viscous dissipation

Amino acids in the uterine luminal fluid reflects the temporal changes in transporter expression in the endometrium and conceptus during early pregnancy in cattle

In cattle, conceptus-maternal interactions are critical for the establishment and maintenance of pregnancy. A major component of this early interaction involves the transport of nutrients and secretion of key molecules by uterine epithelial cells to help support conceptus development during the peri-implantation period of pregnancy. Objectives were to: 1) analyze temporal changes in the amino acid (AA) content of uterine luminal fluid (ULF) during the bovine estrous cycle; 2) understand conceptus-induced alterations in AA content; 3) determine expression of AA transporters in the endometrium and conceptus; and 4) determine how these transporters are modulated by (Progesterone) P4. Concentrations of aspartic acid, arginine, glutamine, histidine, lysine, isoleucine, leucine, phenylalanine and tyrosine decreased on Day 16 of the estrous cycle but increased on Day 19 in pregnant heifers (P < 0.05). Glutamic acid only increased in pregnant heifers on Day 19 (P,0.001). Asparagine concentrations were greater in ULF of cyclic compared to pregnant heifers on Day 7 (P < 0.05) while valine concentrations were higher in pregnant heifers on Day 16 (P < 0.05). Temporal changes in expression of the cationic AA transporters SLC7A1 SLC7A4 and SLC7A6 occurred in the endometrium during the estrous cycle/early pregnancy coordinate with changes in conceptus expression of SLC7A4, SLC7A2 and SLC7A1 (P < 0.05). Only one acidic AA transporter (SLC1A5) increased in the endometrium while conceptus expression of SLC1A4 increased (P < 0.05). The neutral AA transporters SLC38A2 and SLC7A5 increased in the endometrium in a temporal manner while conceptus expression of SLC38A7, SLC43A2, SLC38A11 and SLC7A8 also increased (P < 0.05). P4 modified the expression of SLC1A1, -1A4, -1A5, -38A2 , -38A4, -38A7, -43A2, -6A14, -7A1, -7A5 and -7A7 in the endometrium. Results demonstrate that temporal changes in AA in the ULF reflect changes in transporter expression in the endometrium and conceptus during early pregnancy in cattle, some of which are modified by P4. © 2014 Forde et al

Effects of the estrous cycle, pregnancy and interferon tau on expression of cyclooxygenase two (COX-2) in ovine endometrium

In sheep, the uterus produces luteolytic pulses of prostaglandin F(2α )(PGF) on Days 15 to 16 of estrous cycle to regress the corpus luteum (CL). These PGF pulses are produced by the endometrial lumenal epithelium (LE) and superficial ductal glandular epithelium (sGE) in response to binding of pituitary and/or luteal oxytocin to oxytocin receptors (OTR) and liberation of arachidonic acid, the precursor of PGF. Cyclooxygenase-one (COX-1) and COX-2 are rate-limiting enzymes in PGF synthesis, and COX-2 is the major form expressed in ovine endometrium. During pregnancy recognition, interferon tau (IFNτ), produced by the conceptus trophectoderm, acts in a paracrine manner to suppress development of the endometrial epithelial luteolytic mechanism by inhibiting transcription of estrogen receptor α (ERα) (directly) and OTR (indirectly) genes. Conflicting studies indicate that IFNτ increases, decreases or has no effect on COX-2 expression in bovine and ovine endometrial cells. In Study One, COX-2 mRNA and protein were detected solely in endometrial LE and sGE of both cyclic and pregnant ewes. During the estrous cycle, COX-2 expression increased from Days 10 to 12 and then decreased to Day 16. During early pregnancy, COX-2 expression increased from Days 10 to 12 and remained higher than in cyclic ewes. In Study Two, intrauterine infusion of recombinant ovine IFNτ in cyclic ewes from Days 11 to 16 post-estrus did not affect COX-2 expression in the endometrial epithelium. These results clearly indicate that IFNτ has no effect on expression of the COX-2 gene in the ovine endometrium. Therefore, antiluteolytic effects of IFNτ are to inhibit ERα and OTR gene transcription, thereby preventing endometrial production of luteolytic pulses of PGF. Indeed, expression of COX-2 in the endometrial epithelia as well as conceptus is likely to have a beneficial regulatory role in implantation and development of the conceptus

The Mare Reproductive Loss Syndrome and the Eastern Tent Caterpillar II: A Toxicokinetic/Clinical Evaluation and a Proposed Pathogenesis: Septic Penetrating Setae

Reviewing the mare reproductive loss syndrome (MRLS), it is proposed that the fundamental mechanism of this syndrome, which includes early fetal loss, late fetal loss, uveitis, pericarditis, and encephalitis, is tissue penetration by septic barbed setal fragments (septic penetrating setae) from Eastern tent caterpillars (Malacosoma americanum). Once ingested, these barbed setal fragments migrate through moving tissues, followed by rapid hematogenous spread of bacteria, bacterial emboli, and/or septic fragments of setae (septic penetrating setal emboli), collectively referred to as septic materials. Pathogenic bacteria, therefore, enter the horse as hitchhikers on or in the caterpillar setal fragments, and MRLS is caused by 1) the barbed setal fragments’ ability to penetrate moving tissues, including blood vessels, releasing septic materials, which rapidly distribute hematogenously; 2) the high sensitivity of the pregnant mare to bacteria from such septic materials introduced into the uterus, fetal membranes, or fetal fluids; 3) the unusually broad spectrum of bacterial pathogens carried on or in the setal fragments; and 4) the less effective antibacterial responses in certain susceptible extracellular fluids (e.g., fetal, ocular, pericardial, and cerebrospinal fluids). The driving force for MRLS pathology, including abortions, is septic material- induced bacterial proliferation, which provides a critical amplification step, enabling approximately 1-gram caterpillars to rapidly (32 hours) cause abortions in 680-kg (1,500- lb) mares. Calculations based on the unique eye data suggest that the actual number of distributing effective septic material quanta in field cases may be small—on the order of 10/horse/day—accounting for the lack of systemic clinical signs in affected horses. Therefore, it is proposed that MRLS starts with ingestion of Eastern tent caterpillars, followed by barbed setal fragments randomly penetrating intestinal tissues, including thinwalled venules and other blood vessels, with release of septic material that distributes hematogenously to all points in the body. Identification of abortigenic activity with the integument of the caterpillar and recent findings of large numbers of granulomatous lesions containing setal fragments in the intestines of pigs and rats directly supports the septic penetrating setal portion of the hypothesis. Analysis of the clinical syndromes and a toxicokinetic/ statistical analysis of MRLS suggest that setally-mediated introduction of septic material into blood vessels and other tissues may be key to understanding the very unusual toxicokinetics and pathogenesis of the unique group of syndromes that constitute MRLS. Like MRLS itself, this hypothesis is unique. The septic penetrating setal emboli portion is without precedent, is based on the unique clinical characteristics of MRLS, and appears well supported by ongoing experimental approaches

Multicenter Clinical Evaluation of the Xpert GBS LB Assay for Detection of Group B Streptococcus in Prenatal Screening Specimens

Neonatal infection with Streptococcus agalactiae (group B Streptococcus [GBS]) is a leading cause of sepsis and meningitis in newborns. Recent guidelines have recommended universal screening of all pregnant women to identify those colonized with GBS and administration of peripartum prophylaxis to those identified as carriers to reduce the risk of early-onset GBS disease in neonates. Enriched culture methods are the current standard for prenatal GBS screening; however, the implementation of more sensitive molecular diagnostic tests may be able to further reduce the risk of early-onset GBS infection. We report a clinical evaluation of the Xpert GBS LB assay, a molecular diagnostic test for the identification of GBS from broth-enriched vaginal/rectal specimens obtained during routine prenatal screening. A total of 826 specimens were collected from women undergoing prenatal screening (35 to 37 weeks' gestation) and tested at one of three clinical centers. Each swab specimen was tested directly prior to enrichment using the Xpert GBS assay. Following 18 to 24 h of broth enrichment, each specimen was tested using the Xpert GBS LB assay and the FDA-cleared Smart GBS assay as a molecular diagnostic comparator. Results obtained using all three molecular tests were compared to those for broth-enriched culture as the gold standard. The sensitivity and specificity of the Xpert GBS LB assay were 99.0% and 92.4%, respectively, compared to those for the gold standard culture. The Smart GBS molecular test demonstrated sensitivity and specificity of 96.8% and 95.5%, respectively. The sensitivities of the two broth-enriched molecular methods were superior to those for direct testing of specimens using the Xpert GBS assay, which demonstrated sensitivity and specificity of 85.7% and 96.2%, respectively

Insights into the Influence of Priors in Posterior Mapping of Discrete Morphological Characters: A Case Study in Annonaceae

Background - Posterior mapping is an increasingly popular hierarchical Bayesian based method used to infer character histories and reconstruct ancestral states at nodes of molecular phylogenies, notably of morphological characters. As for all Bayesian analyses specification of prior values is an integrative and important part of the analysis. He we provide an example of how alternative prior choices can seriously influence results and mislead interpretations. Methods/Principal Findings - For two contrasting discrete morphological characters, namely a slow and a fast evolving character found in the plant family Annonaceae, we specified a total of eight different prior distributions per character. We investigated how these prior settings affected important summary statistics. Our analyses showed that the different prior distributions had marked effects on the results in terms of average number of character state changes. These differences arise because priors play a crucial role in determining which areas of parameter space the values of the simulation will be drawn from, independent of the data at hand. However, priors seemed to fit the data better if they would result in a more even sampling of parameter space (normal posterior distribution), in which case alternative standard deviation values had little effect on the results. The most probable character history for each character was affected differently by the prior. For the slower evolving character, the same character history always had the highest posterior probability independent of the priors used. In contrast, the faster evolving character showed different most probable character histories depending on the prior. These differences could be related to the level of homoplasy exhibited by each character. Conclusions - Although our analyses were restricted to two morphological characters within a single family, our results underline the importance of carefully choosing prior values for posterior mapping. Prior specification will be of crucial importance when interpreting the results in a meaningful way. It is hard to suggest a statistically sound method for prior specification without more detailed studies. Meanwhile, we propose that the data could be used to estimate the prior value of the gamma distribution placed on the transformation rate in posterior mappin