Dysregulation of placental cystathionine-β-synthase impact on fetal growth restriction

INTRODUCTION: Fetal growth restriction (FGR), which causes perinatal morbidity and mortality, is characterized by birth weight and body mass being below 10th percentile for gestational age. FGR babies are prone to develop cardiovascular diseases later in life. Inadequate placental transfer of nutrients from mother to fetus due to placental insufficiency is considered the underlying cause of FGR. Recently, we demonstrated that blockade of cystathionine-γ-lyase (CSE) activity induces preeclampsia-like condition in pregnant mice. We hypothesized that defect in cystathionine-β-synthase (CBS) / H2S pathway may promote FGR. METHODS: Placental CBS expressions were determined in women with FGR (n=9) and normal controls (n=14) by Western blotting and real-time qPCR. ELISA was used to determine angiogenic factors levels in plasma and first-trimester (8–12 weeks gestation) human placental explants. Time pregnant mice were treated with CBS inhibitor, aminooxyacetic acid (AOA). Mean arterial blood pressure (MBP), histological assessments of placenta and embryos were performed. RESULTS: Placental CBS expressions were significantly reduced in women with FGR. Inhibition of CBS activity by AOA reduced PlGF production from first-trimester human placental explants, Administration of AOA to pregnant mice had no effects on blood pressure, but caused fetal growth restriction, which was associated with reduced placental PlGF production. Histological analysis revealed a reduction in the placental junction zone, within which trophoblast giant cells and glycogen cells were less prominent in CBS inhibitor-treated animals. Furthermore, H2S donor GYY4137 treatment restored fetal growth in pregnant mice exposed to high level of sFlt-1. CONCLUSIONS: These results imply that placental CBS is required for placental development and that dysregulation of CBS activity may contribute to the pathogenesis of FGR but not preeclampsia opening up the therapeutic potentials of H2S therapy in this condition.

Placental contribution to the origins of sexual dimorphism in health and diseases: sex chromosomes and epigenetics

Sex differences occur in most non-communicable diseases, including metabolic diseases, hypertension, cardiovascular disease, psychiatric and neurological disorders and cancer. In many cases, the susceptibility to these diseases begins early in development. The observed differences between the sexes may result from genetic and hormonal differences and from differences in responses to and interactions with environmental factors, including infection, diet, drugs and stress. The placenta plays a key role in fetal growth and development and, as such, affects the fetal programming underlying subsequent adult health and accounts, in part for the developmental origin of health and disease (DOHaD). There is accumulating evidence to demonstrate the sex-specific relationships between diverse environmental influences on placental functions and the risk of disease later in life. As one of the few tissues easily collectable in humans, this organ may therefore be seen as an ideal system for studying how male and female placenta sense nutritional and other stresses, such as endocrine disruptors. Sex-specific regulatory pathways controlling sexually dimorphic characteristics in the various organs and the consequences of lifelong differences in sex hormone expression largely account for such responses. However, sex-specific changes in epigenetic marks are generated early after fertilization, thus before adrenal and gonad differentiation in the absence of sex hormones and in response to environmental conditions. Given the abundance of X-linked genes involved in placentogenesis, and the early unequal gene expression by the sex chromosomes between males and females, the role of X- and Y-chromosome-linked genes, and especially those involved in the peculiar placenta-specific epigenetics processes, giving rise to the unusual placenta epigenetic landscapes deserve particular attention. However, even with recent developments in this field, we still know little about the mechanisms underlying the early sex-specific epigenetic marks resulting in sex-biased gene expression of pathways and networks. As a critical messenger between the maternal environment and the fetus, the placenta may play a key role not only in buffering environmental effects transmitted by the mother but also in expressing and modulating effects due to preconceptional exposure of both the mother and the father to stressful conditions.

Hematoma Cervical e Hemotórax Espontâneos no contexto de Neurofibromatose Tipo I

Introdução: A neurofibromatose tipo I (NF1), também designada doença de Von Recklinghausen, é causada por uma anormalidade no cromossoma 17, de transmissão autossómica dominante, responsável pela produção deficiente de neurofibromina. Caracteriza-se por displasia nos tecidos mesodérmicos e neuroectodérmicos, e tem uma incidência de um para 2.500-3.300 nascimentos. A presença de manchas café-au-lait, neurofibromas cutâneos e hamartomas da íris são sinais cardinais da doença. Primeiramente descrita por Ruebi em 1945, a patologia vascular é uma complicação subestimada e pouco reconhecida na NF1. A ocorrência de hemorragia fatal ou quase fatal está reportada ocasionalmente nas cavidades pleural, abdominal, retroperitoneu, tecidos moles do tronco e extremidades. Esta hemorragia massiva é causada pela rutura de vasos sanguíneos friáveis, característicos pelos níveis reduzidos de neurofibromina e consequente proliferação endotelial e de músculo liso nas artérias e veias. Uma das consequências clínicas mais sérias descritas na NF1 é a ocorrência de hemorragia severa e dificuldade em alcançar controlo hemostático. Objetivo: Exposição de caso clínico de extenso hematoma cervical e hemotórax espontâneos por rutura troncos venosos braquiocefálico, veia subclávia e junção subclávio-jugular em doente com NF1. Caso clínico: Relata-se caso clínico de mulher de 51 anos, com antecedentes conhecidos de NF1 e hipertensão arterial. Foi admitida no serviço de urgência em choque hipovolémico hemorrágico, no contexto de dor súbita no ombro direito e volumosa tumefação cervical direita. Em angioTC foi objetivado volumoso hematoma, envolvendo a região cervical direita, a região retrofaríngea-prevertebral, escavado supraclavicular direito, mediastino, associando a importante hemotórax direito. Procedeu-se a abordagem supraclavicular com drenagem do hematoma e identificação de fontes hemorrágicas, nomeadamente: tronco venoso braquicefálico, veia subclávia e confluência subclávio-jugular. Foi necessária secção da clavícula para controlo hemorrágico e realização de rafias dos troncos venosos com prolene. Intraoperatoriamente, foi evidente a fragilidade e friabilidade excessiva dos vasos sanguíneos. Após controlo hemorrágico, foi realizada videotoracoscopia para drenagem de hemotórax e evacuação de coágulos, confirmando-se a ausência de hemorragia ativa. No pós-operatório a doente recuperou estabilidade hemodinâmica, sem evidência analítica de queda de hemoglobina. Realizou-se angioTC, onde se confirmou franca melhoria do hematoma cervical direito e retrofaríngeo em critérios quantitativos, e ausência de extravasamento de contraste. Objetivou-se adicionalmente aneurismas acular da artéria vertebral direita, corrigido ulteriormente através de embolização com coils. Conclusão: A NF1 é uma doença genética que raramente se pode associar a hemorragia life- -threatening. A vasculopatia é uma complicação subestimada e pouco reconhecida na NF1. A existência de friabilidade vascular excessiva com consequente hemorragia espontânea na NF1 é rara e pode ser fatal, exigindo um diagnóstico rápido e tratamento atempado.

Imaging of activated complement using ultrasmall superparamagnetic iron oxide particles (USPIO) - conjugated vectors: an in vivo in utero non-invasive method to predict placental insufficiency and abnormal fetal brain development.

In the current study, we have developed a magnetic resonance imaging-based method for non-invasive detection of complement activation in placenta and foetal brain in vivo in utero. Using this method, we found that anti-complement C3-targeted ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles bind within the inflamed placenta and foetal brain cortical tissue, causing a shortening of the T2* relaxation time. We used two mouse models of pregnancy complications: a mouse model of obstetrics antiphospholipid syndrome (APS) and a mouse model of preterm birth (PTB). We found that detection of C3 deposition in the placenta in the APS model was associated with placental insufficiency characterised by increased oxidative stress, decreased vascular endothelial growth factor and placental growth factor levels and intrauterine growth restriction. We also found that foetal brain C3 deposition was associated with cortical axonal cytoarchitecture disruption and increased neurodegeneration in the mouse model of APS and in the PTB model. In the APS model, foetuses that showed increased C3 in their brains additionally expressed anxiety-related behaviour after birth. Importantly, USPIO did not affect pregnancy outcomes and liver function in the mother and the offspring, suggesting that this method may be useful for detecting complement activation in vivo in utero and predicting placental insufficiency and abnormal foetal neurodevelopment that leads to neuropsychiatric disorders.

Hematoma sublingual espontáneo secundario a terapia anticoagulante con warfarina

Abstract Hemorrhagic complications in oral anticoagulant therapy are frequent. Spontaneous sublingual hematomas secondary to anticoagulants are an extremely unusual complication that is potentially lethal. The study reports a case of a patient on anticoagulation therapy with warfarine who develops a massive, spontaneous sublingual hematoma with obstruction of the high airway and cardiac arrest, where emergency transtracheal catheter ventilation was used.

A decrease in dkk1, a Wnt inhibitor, contributes to placental and fetal lipid accumulation in an obesity-prone rat model

Placenta, as the sole transport mechanism between mother and fetus, links the maternal physical state and the immediate and life-long outcomes of the offspring. The present study examined the mechanisms behind the effect of maternal obesity on placental lipid accumulation and metabolism. Pregnant Obese Prone (OP) and Obese Resistant (OR) rat strains were fed a control diet throughout gestation. Placentas were collected on gestational d21 for analysis and frozen placental sections were analyzed for fat accumulation as well as β-Catenin and Dkk1 localization. Additionally, DKK1 was overexpressed in JEG3 trophoblast cells, followed by treatment with NEFA and Oil Red O stain quantification and mRNA analysis to determine the relationship between placental DKK1 and lipid accumulation. Maternal plasma and placental NEFA and TG were elevated in OP dams, and offspring of OP dams were smaller than OR. Placental Dkk1 mRNA content was 4-fold lower in OP placentas, and there was a significant increase in β-Catenin accumulation as well as mRNA content of fat transport and TG synthesis enzymes, including Ppar-delta, Fatp1, Fat/Cd36, Lipin1, and Lipin3. There was significant lipid accumulation within the decidual zones in OP but not OR placentas, and the thickness of the decidual and junctional zones was significantly smaller in OP than OR placentas. Overexpression of DKK1 in JEG3 cells decreased lipid accumulation and the mRNA content of PPAR-Delta, FATP1, FAT/CD36, LIPIN1, and LIPIN3. Our results indicate that Dkk1 may be regulating placental lipid metabolism through Wnt-mediated mechanisms. Additionally, recent studies have suggested that maternal obesity may also program early development of non-alcoholic fatty liver disease (NAFLD), rates of which have correlated with the increase in the obesity epidemic. In the current study, livers of OP offspring had significantly increased TG content (P<0.05) and lipid accumulation when compared to offspring of OR dams. Additionally, hepatic Dkk1 mRNA content was significantly decreased in OP livers when compared to OR (P<0.05), and treating H4IIECR rat hepatocyte cells with NEFA showed that Dkk1 mRNA was also decreased in NEFA-treated cells (P<0.05) that also had lipid accumulation. Chromatin Immunoprecipitation (ChIP) analysis of the Dkk1 promoter in fetal livers showed a pattern of histone modifications associated with decreased gene transcription in OP offspring, which agrees with our gene expression data. These results demonstrate that the hepatic Dkk1 gene is epigenetically regulated via histone modification in neonatal offspring in the current model of gestational obesity, and future studies will be needed to determine whether these changes contribute to excessive hepatic lipid accumulation in offspring of obese dams.

Placental site trophoblastic tumor: a case report and review of the literature

We present a case of a gravida 1 para 1 woman, who presented with an 11- month history of amenorrhea after cesarean delivery. The patient was taking birth control pills at the time of presentation. She was observed with a slight elevation of serum β-hCG level, an enlarged heterogeneous uterus and hematometra. A biopsy was performed, and the patient was diagnosed with placental site trophoblastic tumor; the patient then underwent surgery. Placental site trophoblastic tumor is the rarest form of gestational trophoblastic disease, derived from intermediate trophoblast cells. It does not have a pathognomonic appearance; therefore, correlation with medical history, as well as results of laboratory tests and pathological analysis is mandatory. It is a relatively chemoresistant tumor, posing considerable therapeutic challenges; patients with localized disease are managed with surgery and those with metastatic disease require additional chemotherapy. Herein, we review the main features of this entity and top differential diagnosis, as the rarity of this tumor is associated with imaging and pathological pitfalls, reinforcing the need for further experience in this field.

Hematoma postoperatorio en neurocirugía: Presentación de un caso y revisión

El hematoma postoperatorio es una de las complicaciones más graves en neuro-cirugía, con una mortalidad que varía entre un 18 y 32%, y una morbilidad significativa. Se han identificado factores de riesgo clínicos, perioperatorios y patológicos que aumentan la probabilidad de sufrir esta complicación. Los autores reportan el caso de un paciente que presentó un hematoma postoperatorio luego de la exéresis de una metástasis cerebral y analizan las posibles causas que llevaron a dicha complicación. Asimismo realizan una exhaustiva revisión no sistemática de la literatura referente a la hemorragia postoperatoria, sus factores de riesgo y manejo perioperatorio.

Zika virus damages the human placental barrier and presents marked fetal neurotropism

An unusually high incidence of microcephaly in newborns has recently been observed in Brazil. There is a temporal association between the increase in cases of microcephaly and the Zika virus (ZIKV) epidemic. Viral RNA has been detected in amniotic fluid samples, placental tissues and newborn and fetal brain tissues. However, much remains to be determined concerning the association between ZIKV infection and fetal malformations. In this study, we provide evidence of the transplacental transmission of ZIKV through the detection of viral proteins and viral RNA in placental tissue samples from expectant mothers infected at different stages of gestation. We observed chronic placentitis (TORCH type) with viral protein detection by immunohistochemistry in Hofbauer cells and some histiocytes in the intervillous spaces. We also demonstrated the neurotropism of the virus via the detection of viral proteins in glial cells and in some endothelial cells and the observation of scattered foci of microcalcifications in the brain tissues. Lesions were mainly located in the white matter. ZIKV RNA was also detected in these tissues by real-time-polymerase chain reaction. We believe that these findings will contribute to the body of knowledge of the mechanisms of ZIKV transmission, interactions between the virus and host cells and viral tropism.

The severity of chorioamnionitis in pregnant sheep is associated with in vivo variation of the surface-exposed multiple-banded antigen/gene of ureaplasma parvum

Ureaplasma species are the bacteria most frequently isolated from human amniotic fluid in asymptomatic pregnancies and placental infections. Ureaplasma parvum serovars 3 and 6 are the most prevalent serovars isolated from men and women. We hypothesized that the effects on the fetus and chorioamnion of chronic ureaplasma infection in amniotic fluid are dependent on the serovar, dose, and variation of the ureaplasma multiple banded antigen (MBA) and mba gene. We injected high- or low dose U. parvum serovar 3, serovar 6, or vehicle intra-amniotically into pregnant ewes at 55 days of gestation (term = 150 days) and examined the chorioamnion, amniotic fluid, and fetal lung tissue of animals delivered by cesarean section at 125 days of gestation. Variation of the multiple banded antigen/mba generated by serovar 3 and serovar 6 ureaplasmas in vivo were compared by PCR assay and Western blot. Ureaplasma inoculums demonstrated only one (serovar 3) or two (serovar 6) MBA variants in vitro, but numerous antigenic variants were generated in vivo: serovar 6 passage 1 amniotic fluid cultures contained more MBA size variants than serovar 3 (P = 0.005),and ureaplasma titers were inversely related to the number of variants (P = 0.025). The severity of chorioamnionitis varied between animals. Low numbers of mba size variants (five or fewer) within amniotic fluid were associated with severe inflammation, whereas the chorioamnion from animals with nine or more mba variants showed little or no inflammation. These differences in chorioamnion inflammation may explain why not all women with in utero Ureaplasma spp. experience adverse pregnancy outcomes.

Maternal administration of erythromycin fails to eradicate intrauterine ureaplasma infection in an ovine model

Erythromycin is the standard antibiotic used for treatment of Ureaplasma species during 3 pregnancy; however, maternally administered erythromycin may be ineffective at eliminating 4 intra-amniotic ureaplasma infections. We asked if erythromycin would eradicate intra-amniotic 5 ureaplasma infections in pregnant sheep. At 50 days of gestation (d, term=150d) pregnant ewes 6 received intra-amniotic injections of erythromycin-sensitive U. parvum serovar 3 (n=16) or 10B 7 medium (n=16). At 100d, amniocentesis was performed; five fetal losses (ureaplasma group: 8 n=4; 10B group: n=1) had occurred by this time. Remaining ewes were allocated into treatment 9 subgroups: medium only (M, n=7); medium and erythromycin (M/E, n=8); ureaplasma only (Up, 10 n=6) or ureaplasma and erythromycin (Up/E, n=6). Erythromycin was administered intra11 muscularly (500 mg), eight-hourly for four days (100d-104d). Amniotic fluid samples were 12 collected at 105d. At 125d preterm fetuses were surgically delivered and specimens were 13 collected for culture and histology. Erythromycin was quantified in amniotic fluid by liquid 14 chromatography-mass spectrometry. Ureaplasmas were isolated from the amniotic fluid, 15 chorioamnion and fetal lung of animals from the Up and Up/E groups, however, the numbers of 16 U. parvum recovered were not different between these groups. Inflammation in the 17 chorioamnion, cord and fetal lung was increased in ureaplasma-exposed animals compared to 18 controls, but was not different between the Up and Up/E groups. Erythromycin was detected in 19 amniotic fluid samples, although concentrations were low (<10-76 ng/mL). This study 20 demonstrates that maternally administered erythromycin does not eradicate chronic, intra- amniotic ureaplasma infections or improve fetal outcomes in an ovine model, potentially due to 22 the poor placental passage of erythromycin.

Mesenchymal stem cells

Cell based therapies as they apply to tissue engineering and regenerative medicine, require cells capable of self renewal and differentiation, and a prerequisite is to be able to prepare an effective dose of ex vivo expanded cells for autologous transplants. The in vivo identification of a source of physiologically relevant cell types suitable for cell therapies therefore figures as an integral part of tissue engineering. Stem cells serve as a reserve for biological repair, having the potential to differentiate into a number of specialised cell types within the body; they therefore represent the most useful candidates for cell based therapies. The primary goal of stem cell research is to produce cells that are both patient specific, as well as having properties suitable for the specific conditions for which they are intended to remedy. From a purely scientific perspective, stem cells allow scientists to gain a deeper understanding of developmental biology and regenerative therapies. Stem cells have acquired a number of uses for applications in regenerative medicine, immunotherapy, gene therapy, but it is in the area of tissue engineering that they generate most excitement, primarily as a result of their capacity for self-renewal and pluripotency. A unique feature of stem cells is their ability to maintain an uncommitted quiescent state in vivo and then, once triggered by conditions such as disease, injury or natural wear or tear, serve as a reservoir and natural support system to replenish lost cells. Although these cells retain the plasticity to differentiate into various tissues, being able to control this differentiation process is still one of the biggest challenges facing stem cell research. In an effort to harness the potential of these cells a number of studies have been conducted using both embryonic/foetal and adult stem cells. The use of embryonic stem cells (ESC) have been hampered by strong ethical and political concerns, this despite their perceived versatility due to their pluripotency. Ethical issues aside, other concerns raised with ESCs relates to the possibility of tumorigenesis, immune rejection and complications with immunosuppressive therapies, all of which adds layers of complications to the application ESC in research and which has led to the search for alternative sources for stem cells. The adult tissues in higher organisms harbours cells, termed adult stem cells, and these cells are reminiscent of unprogrammed stem cells. A number of sources of adult stem cells have been described. Bone marrow is by far the most accessible source of two potent populations of adult stem cells, namely haematopoietic stem cells (HSCs) and bone marrow mesenchymal stem cells (BMSCs). Autologously harvested adult stem cells can, in contrast to embryonic stem cells, readily be used in autografts, since immune rejection is not an issue; and their use in scientific research has not attracted the ethical concerns which have been the case with embryonic stem cells. The major limitation to their use, however, is the fact that adult stem cells are exceedingly rare in most tissues. This fact makes identifying and isolating these cells problematic; bone marrow being perhaps the only notable exception. Unlike the case of HSCs, there are as yet no rigorous criteria for characterizing MSCs. Changing acuity about the pluripotency of MSCs in recent studies has expanded their potential application; however, the underlying molecular pathways which impart the features distinctive to MSCs remain elusive. Furthermore, the sparse in vivo distribution of these cells imposes a clear limitation to their study in vitro. Also, when MSCs are cultured in vitro, there is a loss of the in vivo microenvironment, resulting in a progressive decline in proliferation potential and multipotentiality. This is further exacerbated with increased passage numbers in culture, characterized by the onset of senescence related changes. As a consequence, it is necessary to establish protocols for generating large numbers of MSCs but without affecting their differentiation potential. MSCs are capable of differentiating into mesenchymal tissue lineages, including bone, cartilage, fat, tendon, muscle, and marrow stroma. Recent findings indicate that adult bone marrow may also contain cells that can differentiate into the mature, nonhematopoietic cells of a number of tissues, including cells of the liver, kidney, lung, skin, gastrointestinal tract, and myocytes of heart and skeletal muscle. MSCs can readily be expanded in vitro and can be genetically modified by viral vectors and be induced to differentiate into specific cell lineages by changing the microenvironment–properties which makes these cells ideal vehicles for cellular gene therapy. MSCs can also exert profound immunosuppressive effects via modulation of both cellular and innate immune pathways, and this property allows them to overcome the issue of immune rejection. Despite the many attractive features associated with MSCs, there are still many hurdles to overcome before these cells are readily available for use in clinical applications. The main concern relates to in vivo characterization and identification of MSCs. The lack of a universal biomarker, sparse in vivo distribution, and a steady age related decline in their numbers, makes it an obvious need to decipher the reprogramming pathways and critical molecular players which govern the characteristics unique to MSCs. This book presents a comprehensive insight into the biology of adult stem cells and their utility in current regeneration therapies. The adult stem cell populations reviewed in this book include bone marrow derived MSCs, adipose derived stem cells (ASCs), umbilical cord blood stem cells, and placental stem cells. The features such as MSC circulation and trafficking, neuroprotective properties, and the nurturing roles and differentiation potential of multiple lineages have been discussed in details. In terms of therapeutic applications, the strengths of MSCs have been presented and their roles in disease treatments such as osteoarthritis, Huntington’s disease, periodontal regeneration, and pancreatic islet transplantation have been discussed. An analysis comparing osteoblast differentiation of umbilical cord blood stem cells and MSCs has been reviewed, as has a comparison of human placental stem cells and ASCs, in terms of isolation, identification and therapeutic applications of ASC in bone, cartilage regeneration, as well as myocardial regeneration. It is my sincere hope that this book will update the reader as to the research progress of MSC biology and potential use of these cells in clinical applications. It will be the best reward to all contributors of this book, if their efforts herein may in some way help the readers in any part of their study, research, and career development.

Mammalian phylogeny

Living mammals can be divided into three subclasses (monotremes, marsupials and placentals) and within these, about 27 orders. Final resolution of the relationships between the orders is only now being achieved with the increased availability of deoxyribonucleic acid (DNA) sequences. Highlights include the deep division of placental mammals into African (Afrotheria), South American (Xenarthra) and northern hemisphere (Boreoeutheria) super-orders, and the finding that the once considered primitive ‘Insectivora’ and ‘Edentata’ clades, in fact, have members distributed widely among these super-orders. Another surprise finding from DNA studies has been that whale origins lie among the even-toed ungulates (Artiodactyla). Our order, Primates is most closely related to the flying lemurs and next, the tree shrews. With the mammal phylogeny becoming well resolved, it is increasingly being used as a framework for inferring evolutionary and ecological processes, such as adaptive radiation.

Ureaplasma parvum : understanding the complexities of intra-amniotic infection in an ovine model

The human Ureaplasma species are the most frequently isolated bacteria from the upper genital tract of pregnant women and can cause clinically asymptomatic, intra-uterine infections, which are difficult to treat with antimicrobials. Ureaplasma infection of the upper genital tract during pregnancy has been associated with numerous adverse outcomes including preterm birth, chorioamnionitis and neonatal respiratory diseases. The mechanisms by which ureaplasmas are able to chronically colonise the amniotic fluid and avoid eradication by (i) the host immune response and (ii) maternally-administered antimicrobials, remain virtually unexplored. To address this gap within the literature, this study investigated potential mechanisms by which ureaplasmas are able to cause chronic, intra-amniotic infections in an established ovine model. In this PhD program of research the effectiveness of standard, maternal erythromycin for the treatment of chronic, intra-amniotic ureaplasma infections was evaluated. At 55 days of gestation pregnant ewes received an intra-amniotic injection of either: a clinical Ureaplasma parvum serovar 3 isolate that was sensitive to macrolide antibiotics (n = 16); or 10B medium (n = 16). At 100 days of gestation, ewes were then randomised to receive either maternal erythromycin treatment (30 mg/kg/day for four days) or no treatment. Ureaplasmas were isolated from amniotic fluid, chorioamnion, umbilical cord and fetal lung specimens, which were collected at the time of preterm delivery of the fetus (125 days of gestation). Surprisingly, the numbers of ureaplasmas colonising the amniotic fluid and fetal tissues were not different between experimentally-infected animals that received erythromycin treatment or infected animals that did not receive treatment (p > 0.05), nor were there any differences in fetal inflammation and histological chorioamnionitis between these groups (p > 0.05). These data demonstrate the inability of maternal erythromycin to eradicate intra-uterine ureaplasma infections. Erythromycin was detected in the amniotic fluid of animals that received antimicrobial treatment (but not in those that did not receive treatment) by liquid chromatography-mass spectrometry; however, the concentrations were below therapeutic levels (<10 – 76 ng/mL). These findings indicate that the ineffectiveness of standard, maternal erythromycin treatment of intra-amniotic ureaplasma infections may be due to the poor placental transfer of this drug. Subsequently, the phenotypic and genotypic characteristics of ureaplasmas isolated from the amniotic fluid and chorioamnion of pregnant sheep after chronic, intra-amniotic infection and low-level exposure to erythromycin were investigated. At 55 days of gestation twelve pregnant ewes received an intra-amniotic injection of a clinical U. parvum serovar 3 isolate, which was sensitive to macrolide antibiotics. At 100 days of gestation, ewes received standard maternal erythromycin treatment (30 mg/kg/day for four days, n = 6) or saline (n = 6). Preterm fetuses were surgically delivered at 125 days of gestation and ureaplasmas were cultured from the amniotic fluid and the chorioamnion. The minimum inhibitory concentrations (MICs) of erythromycin, azithromycin and roxithromycin were determined for cultured ureaplasma isolates, and antimicrobial susceptibilities were different between ureaplasmas isolated from the amniotic fluid (MIC range = 0.08 – 1.0 mg/L) and chorioamnion (MIC range = 0.06 – 5.33 mg/L). However, the increased resistance to macrolide antibiotics observed in chorioamnion ureaplasma isolates occurred independently of exposure to erythromycin in vivo. Remarkably, domain V of the 23S ribosomal RNA gene (which is the target site of macrolide antimicrobials) of chorioamnion ureaplasmas demonstrated significant variability (125 polymorphisms out of 422 sequenced nucleotides, 29.6%) when compared to the amniotic fluid ureaplasma isolates and the inoculum strain. This sequence variability did not occur as a consequence of exposure to erythromycin, as the nucleotide substitutions were identical between chorioamnion ureaplasmas isolated from different animals, including those that did not receive erythromycin treatment. We propose that these mosaic-like 23S ribosomal RNA gene sequences may represent gene fragments transferred via horizontal gene transfer. The significant differences observed in (i) susceptibility to macrolide antimicrobials and (ii) 23S ribosomal RNA sequences of ureaplasmas isolated from the amniotic fluid and chorioamnion suggests that the anatomical site from which they were isolated may exert selective pressures that alter the socio-microbiological structure of the bacterial population, by selecting for genetic changes and altered antimicrobial susceptibility profiles. The final experiment for this PhD examined antigenic size variation of the multiple banded antigen (MBA, a surface-exposed lipoprotein and predicted ureaplasmal virulence factor) in chronic, intra-amniotic ureaplasma infections. Previously defined ‘virulent-derived’ and ‘avirulent-derived’ clonal U. parvum serovar 6 isolates (each expressing a single MBA protein) were injected into the amniotic fluid of pregnant ewes (n = 20) at 55 days of gestation, and amniotic fluid was collected by amniocentesis every two weeks until the time of near-term delivery of the fetus (at 140 days of gestation). Both the avirulent and virulent clonal ureaplasma strains generated MBA size variants (ranging in size from 32 – 170 kDa) within the amniotic fluid of pregnant ewes. The mean number of MBA size variants produced within the amniotic fluid was not different between the virulent (mean = 4.2 MBA variants) and avirulent (mean = 4.6 MBA variants) ureaplasma strains (p = 0.87). Intra-amniotic infection with the virulent strain was significantly associated with the presence of meconium-stained amniotic fluid (p = 0.01), which is an indicator of fetal distress in utero. However, the severity of histological chorioamnionitis was not different between the avirulent and virulent groups. We demonstrated that ureaplasmas were able to persist within the amniotic fluid of pregnant sheep for 85 days, despite the host mounting an innate and adaptive immune response. Pro-inflammatory cytokines (interleukin (IL)-1â, IL-6 and IL-8) were elevated within the chorioamnion tissue of pregnant sheep from both the avirulent and virulent treatment groups, and this was significantly associated with the production of anti-ureaplasma IgG antibodies within maternal sera (p < 0.05). These findings suggested that the inability of the host immune response to eradicate ureaplasmas from the amniotic cavity may be due to continual size variation of MBA surface-exposed epitopes. Taken together, these data confirm that ureaplasmas are able to cause long-term in utero infections in a sheep model, despite standard antimicrobial treatment and the development of a host immune response. The overall findings of this PhD project suggest that ureaplasmas are able to cause chronic, intra-amniotic infections due to (i) the limited placental transfer of erythromycin, which prevents the accumulation of therapeutic concentrations within the amniotic fluid; (ii) the ability of ureaplasmas to undergo rapid selection and genetic variation in vivo, resulting in ureaplasma isolates with variable MICs to macrolide antimicrobials colonising the amniotic fluid and chorioamnion; and (iii) antigenic size variation of the MBA, which may prevent eradication of ureaplasmas by the host immune response and account for differences in neonatal outcomes. The outcomes of this program of study have improved our understanding of the biology and pathogenesis of this highly adapted microorganism.