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A E O'Connor

Publications and source records attributed to A E O'Connor.

16 recordsLinked to original sources
PubMed2006

A repository of ENU mutant mouse lines and their potential for male fertility research.

Many of the proteins and their encoding genes involved in spermatogenesis are unknown, making the specific diagnosis and treatment of infertility in males difficult and highlighting the importance of identifying new genes that are involved in spermatogenesis. Through genome-wide chemical mutagenesis using N-ethyl-N-nitrosourea (ENU) and a three-generation breeding scheme to isolate recessive mutations, we have identified mouse lines with a range of abnormalities relevant to human male fertility. Abnormal phenotypes included hypospermatogenesis, Sertoli cell-only (SCO) seminiferous tubules, germ-cell arrest and abnormal spermiogenesis and were accompanied, in some, with abnormal serum levels of reproductive hormones. In total, from 65 mouse lines, 14 showed a reproductive phenotype consistent with a recessive mutation. This study shows that it is feasible to use ENU mutagenesis as an effective and rapid means of generating mouse models relevant to furthering our understanding of human male infertility. Spermatozoa and genomic DNA from all mouse lines, including those with abnormal reproductive tract parameters, have been cryopreserved for the regeneration of lines as required. This repository will form a valuable resource for the identification and analysis of key regulators of multiple aspects of male fertility.

Activins↗
PubMed2006

Follistatin is a candidate endogenous negative regulator of activin A in experimental allergic asthma.

BACKGROUND: Activin A is a member of the transforming growth factor-beta superfamily which is directly implicated in airway structural change and inflammation in asthma. In vitro, the biological effects of activin A are neutralized by the soluble binding protein follistatin. OBJECTIVE: To determine the potential of endogenous follistatin to suppress activin A in vivo by analysing their relative tissue and kinetic compartmentalization during the effector phase of subchronic Th2-driven mucosal inflammation in a murine model of allergic asthma. METHODS: Eosinophilic mucosal inflammation was elicited by triggering Th2 recall responses by antigen challenge in ovalbumin-sensitized BALB/c mice. The kinetics and distribution of activin A and follistatin protein were assessed in lung tissue and bronchoalveolar lavage fluid and measured in relation to airway eosinophilia, goblet cell metaplasia and Th2 cytokine production in mediastinal lymph nodes. RESULTS: Follistatin was released concurrently with activin A suggesting it acts as an endogenous regulator: peak BAL concentrations coincided with maximal airway eosinophilia, and frequency of IL-4, IL-5 and IL-13 producing cells in mediastinal lymph nodes but induction lagged behind the onset of inflammation. Follistatin and activin A immunoreactivity were lost in airway epithelial cells in parallel with goblet cell metaplasia. Exogenous follistatin inhibited the allergen-specific Th2 immune response in mediastinal lymph nodes and mucus production in the lung. CONCLUSION: Follistatin is preformed in the normal lung and released in concert with activin A suggesting it serves as an endogenous regulator. Disturbance of the fine balance between activin A and its endogenous inhibitor follistatin may be a determinant of the severity of allergic inflammation or tissue phenotypic shift in asthma.

Activins↗
PubMed2006

Regulated production of activin A and inhibin B throughout the cycle of the seminiferous epithelium in the rat.

Production and regulation of activin A and inhibin B during the cycle of the seminiferous epithelium were investigated in adult rats. Immunohistochemistry localised the activin beta(A)-subunit to the Sertoli cell cytoplasm, with much weaker expression in spermatocytes and spermatids. Both activin A and inhibin B, measured by ELISA were secreted by, seminiferous tubule fragments over 72 h in culture. Activin A was secreted in a cyclic manner with peak secretion from tubules isolated at stage VIII. Tubules collected during stage VI produced the least activin A. Inhibin B secretion was highest from stage IX-I tubules and lowest from stage VII tubules. Addition of interleukin-1beta (IL-1beta) had relatively little effect on activin A or inhibin B secretion in culture. In contrast, the peak secretion of activin A by stage VIII tubules was blocked by co-incubation with an excess of human recombinant IL-1 receptor antagonist, whereas inhibin B secretion increased slightly. Dibutyryl cAMP stimulated activin A secretion by late stage VII and VIII tubules and stimulated inhibin B across all stages. These data indicate that activin A and inhibin B are cyclically regulated within the seminiferous epithelium, with endogenous IL-1 (presumably IL-1alpha produced by the Sertoli cells), responsible for a peak of activin A production subsequent to sperm release at stage VIII. These data provide direct evidence that production of activin A and inhibin B by the Sertoli cell is locally modulated by IL-1alpha , in addition to FSH/cAMP, under the influence of the developing spermatogenic cells.

Activins↗
PubMed2005

Effects of age and pregnancy on the circulatory activin response of sheep to acute inflammatory challenge by lipopolysaccharide.

The release of activin A in response to intravenous injection of the bacterial cell-wall component lipopolysaccharide (LPS) was investigated in an ovine model of acute inflammatory challenge in newborn and adult sheep, and in non-pregnant and pregnant ewes. Neonatal lambs (<20 days of age) showed a quantitatively similar response in terms of circulating concentrations of activin A, its binding protein follistatin and the cytokine interleukin-6 compared with adult ewes challenged with an equivalent dose (300 ng/kg bodyweight) of LPS. The fever response and plasma tumour necrosis factor-alpha release in response to LPS, however, were significantly (P < 0.01) less in lambs than in the adult group. Pregnant ewes in the last trimester of gestation had similar responses to LPS, in all aspects measured, compared with their non-pregnant counterparts, apart from an ablated fever response. Although the adult and neonatal sheep responded to LPS, a similar response was not apparent in the fetal circulation, possibly due to a protective effect of the placenta. A 10-fold increase in the dose of LPS (from 300 ng to 3 microg/kg bodyweight) given to neonatal lambs elicited an increase in several cytokine responses measured, with a significant (P< 0.05) increase in follistatin release. In contrast, the amount of activin released by the increased dose of LPS was similar to that invoked by the lower dose. The effect of tolerance to LPS was investigated by giving a second challenge of LPS 5 days after the initial injection. In all animals studied, there was an ablated (P < 0.05) response to the subsequent LPS injection, apart from a similar temperature-response profile. These data provide further evidence that activin A concentrations in the bloodstream are acutely responsive to inflammatory challenge in post-natal life and suggest that the response forms a significant component of the innate immune system.

Activins↗
PubMed2005

Reciprocal regulation of activin A and inhibin B by interleukin-1 (IL-1) and follicle-stimulating hormone (FSH) in rat Sertoli cells in vitro.

In several biological systems, the inhibin beta(A) homodimer activin A is stimulated by, and in turn, inhibits the action of interleukin (IL)-1 (both IL-1alpha and IL-1beta) and IL-6. The possibility that a similar regulatory relationship operates within the testis was investigated. Sertoli cells from immature (20-day-old) rats were cultured with human IL-1alpha or IL-1beta, human IL-6 and/or ovine FSH or dibutyryl cAMP. Activin A and the inhibin dimers, inhibin A and inhibin B, were measured by specific ELISA. Immunoreactive inhibin (ir-inhibin) was measured by RIA. Activin/inhibin subunit mRNA expression was measured by quantitative real-time PCR. Both IL-1 isoforms, but not IL-6, stimulated activin A secretion through increased synthesis of beta(A)-subunit mRNA. IL-1 also stimulated activin A secretion by testicular peritubular cells. In contrast to the effect on activin A, IL-1 suppressed inhibin beta(B)-subunit and, to a lesser extent, alpha-subunit mRNA expression, thereby reducing basal and FSH-stimulated inhibin B secretion by the Sertoli cells. Conversely, FSH inhibited basal activin A secretion and antagonised the stimulatory effects of IL-1. Dibutyryl cAMP partially inhibited the action of IL-1 on activin A secretion, but had no significant effect on basal activin A secretion. Secretion of inhibin A was low in all treatment groups. These data demonstrate that IL-1 and FSH/cAMP exert a reciprocal regulation of activin A and inhibin B synthesis and release by the Sertoli cell, and suggest a role for activin A as a potential feedback regulator of IL-1 and IL-6 activity in the testis during normal spermatogenesis and in inflammation.

Activins↗
PubMed2005

Regulation of activin A and inhibin B secretion by inflammatory mediators in adult rat Sertoli cell cultures.

The regulation of Sertoli cell activin A and inhibin B secretion during inflammation was investigated in vitro. Adult rat Sertoli cells were incubated with the inflammatory mediators, lipopolysaccharide (LPS), interleukin-1beta (IL-1beta), IL-6 and the IL-1 receptor antagonist (IL-1ra) over 48 h in culture. Activin A, inhibin B and IL-1alpha were measured in the culture medium by specific two-site ELISAs. Both IL-1beta- and LPS-stimulated activin A and inhibited inhibin B secretion. LPS also stimulated the production of IL-1alpha in the cultures. In contrast to IL-1beta, IL-6 had no effect on activin A, although it did have a significant inhibitory effect on inhibin B secretion. Ovine follicle-stimulating hormone (FSH) and the cAMP analogue dibutyryl cAMP opposed the actions of IL-1 and LPS by suppressing activin A and IL-1alpha secretion and by stimulating inhibin B. Blocking IL-1 activity in the cultures by addition of an excess of IL-1ra completely prevented the response of activin A to exogenous IL-1beta, and reduced the response to LPS by 50%. In the presence of IL-1ra, basal secretion of inhibin B was increased, but IL-1ra was unable to reverse the suppression of inhibin B by LPS. These data indicate the importance of both IL-1 isoforms in regulating secretion of activin A and inhibin B by mature Sertoli cells during inflammation. The data also establish that inflammation exerts its effects on activin A and inhibin B secretion via other pathways in addition to those mediated by IL-1, and that hormonal stimulation by FSH and cAMP moderates the Sertoli cell response to inflammation. Interference with the complex interactions between these cytokines and hormones may contribute to the disruption of reproductive function that can accompany infection and illness in men.

Activins↗
PubMed2004

The role of activin, follistatin and inhibin in testicular physiology.

The role of the inhibins, activins and follistatins in testicular function are being more clearly defined following studies describing the cellular localisation of these proteins to the testis and the availability of specific assay systems enabling measurement of these proteins. Taken together with the results of targetted gene inactivation experiments, several concepts emerge. Inhibin B is predominantly produced by the Sertoli cell in many adult male mammals whereas there is a perinatal peak of inhibin A in the rat. In contrast, activin A has its highest concentrations in the immediate post-natal period during which it is involved in the developmental regulation of both germ cells and Sertoli cells being modulated by follistatin. Activin A levels are considerably lower in the adult testis but Sertoli cell production is stimulated by interleukin-1 and inhibited by FSH. Little is known about the production of activin B due to the absence of a suitable assay but the beta(B) subunit mRNA is expressed in germ cells and Sertoli cells and is stage-dependent. This pattern of expression suggest that it may be involved in autocrine or paracrine actions within the seminiferous epithelium.

Activins↗
PubMed2004

Effect of graded hypoxia on activin A, prostaglandin E2 and cortisol levels in the late-pregnant sheep.

The aim of the present study was to determine whether activin A concentrations are dependent on feto-placental oxygen availability and to investigate the temporal relationship of activin A with prostaglandin (PG) E(2) and cortisol. Nine fetal sheep (six hypoxic and three control) were instrumented and catheterised at 0.8 gestation. Reduced uterine blood flow was used to achieve three levels of hypoxia (mild = fetal SaO(2) 40-50%; moderate = fetal SaO(2) 30-40%; severe = fetal SaO(2) 20-30%), for 4 h on 3 consecutive days. Activin A, PGE(2) and cortisol levels were determined in maternal and fetal blood and amniotic fluid. Moderate and severe hypoxia produced a significant (P < 0.05) increase in fetal plasma activin A concentrations. The amniotic fluid activin A concentrations were 15-fold higher than those in the fetal circulation, but were unchanged by hypoxia. The fetal PGE(2) response reflected the degree of hypoxia over the 3 days, with moderate and severe hypoxia producing a significant (P < 0.05) increase in PGE(2) concentrations. Fetal plasma cortisol concentrations were increased ( P < 0.05) during all levels of hypoxia. Fetal arterial activin A was increased in response to moderate and severe hypoxia, but levels were not maintained over the hypoxic period. The increases in activin A and cortisol concentrations preceded the increase in PGE(2).

Activins↗
PubMed2002

Follistatin concentrations in maternal and fetal fluids during the oestrous cycle, gestation and parturition in Merino sheep.

The aim of this study was to investigate the changes in follistatin, an activin binding protein, during the oestrous cycle, gestation and parturition in ewes using a radioimmunoassay for total follistatin, which uses dissociating reagents to remove the interference of activin. Follistatin concentrations remained unchanged (2.7 +/- 0.2 ng ml(-1)) during the oestrous cycle and decreased as pregnancy progressed. Follistatin concentrations in allantoic fluid also decreased during gestation, whereas in amniotic fluid follistatin concentrations reached a peak at day 75 of gestation (9.8 ng ml(-1)) and had decreased to 4.4 ng ml(-1) at day 140. Follistatin concentrations in fetal blood (7.0 +/- 0.5 ng ml(-1)) did not change from day 50 to day 140 of gestation but were significantly higher than in matched maternal samples (3.1 +/- 0.3 ng ml(-1)). Circulating follistatin in ewes was significantly increased on the day of parturition (5.6 +/- 0.6 ng ml(-1)) compared with the days before parturition (2.7 +/- 0.4 ng ml(-1)), but had decreased by day 2 after birth. Blood samples from newborn lambs showed that plasma follistatin concentration (13.4 +/- 2.3 ng ml(-1)) was significantly higher than that of the mothers and remained high for at least 7 days after birth. These data support previous studies of the human menstrual cycle indicating that follistatin is not an endocrine signal from the ovary; however, in contrast to human pregnancies, follistatin concentrations in sheep decreased and become high only after or during parturition. This difference observed between species may reflect different physiological effects of follistatin or may be the result of measurement of different isoforms.

Activins↗
PubMed2001

Do preformatted charts improve doctors' documentation in a rural hospital emergency department? A prospective trial.

AIM: To determine if the introduction of preformatted patient record charts improved documentation by doctors in a rural emergency department. METHODS: All medical records of patients who were discharged from the emergency department were collected and analysed for a period of two weeks (control). The preformatted patient charts were then introduced for a further two weeks, and analysed for the presence or absence of key content items RESULTS: After exclusions, 137 control charts and 96 preformatted charts were collected and analysed. It was found that, overall, there was a significant improvement in the number of the key items documented (p<0.005). There was a trend towards improvement in four parameters, but for three other key content items, there was a nonsignificant decline in documentation standards. CONCLUSION: A structured proforma does improve documentation. However, the improvement is small and further studies are required before use of preformatted patient records for the undifferentiated emergency department patients can be recommended.

Documentation↗
PubMed2000

Maternal serum inhibin A concentrations in early pregnancy after IVF and embryo transfer reflect the corpus luteum contribution and pregnancy outcome.

To compare maternal serum inhibin A concentrations in early pregnancy with pregnancy outcomes and treatment protocols, serum samples were collected from 237 women undergoing in-vitro fertilization (IVF) and embryo transfer cycles. Samples were collected on day 16 after oocyte retrieval for beta human chorionic gonadotrophin (HCG) pregnancy testing and inhibin A measurement. The samples were divided into non-pregnant (n = 128) and pregnant (n = 109) groups, the pregnancies were followed and outcomes determined. Inhibin A concentrations were significantly lower in non-pregnant women than in women with ongoing pregnancies (P: < 0.001) and those resulting in spontaneous abortions (P: < 0.001). In ongoing pregnancies, inhibin A concentrations were significantly lower in the absence of functioning ovaries (donor oocyte/embryo) (P: < 0.01) and in natural cycles (frozen-thawed embryo transfer) (P: < 0.01) compared with concentrations after ovarian stimulation. Further, since inhibin A concentrations were not significantly different between singleton and multiple pregnancies in the ovarian stimulation protocol, the size of the early trophoblast does not appear to influence the secretion of inhibin A. These data strongly support the concept that the corpus luteum is a major source of circulating inhibin A in early pregnancy. Additionally, low concentrations of serum inhibin A may be useful in predicting betaHCG-positive preclinical 'biochemical' pregnancies.

Abortion, Spontaneous↗
PubMed1999

Serum activin A and follistatin concentrations during human pregnancy: a cross-sectional and longitudinal study.

Activin A, a dimer of the betaA-subunit of inhibin, has been shown to have multiple biological activities and sites of production. Follistatin is a high-affinity binding protein for activin, which neutralizes its activity. This study provides the first data, using a cross-sectional design, on the measurement of both these proteins in the maternal circulation of a large cohort of women (6-39 weeks of gestation, n = 2-20 women/time point) during normal pregnancies, and confirms that similar patterns are seen in nine women studied longitudinally during pregnancy. The concentrations of total activin A were measured using a specific two-site enzyme-linked immunosorbent assay (ELISA), and a new radioimmunoassay for measuring total follistatin in serum utilizing dissociating reagents to eliminate the interference of activin is described. At 38-39 weeks gestation, both activin A and follistatin concentrations rose to a peak (4.59 +/- 0.54 ng/ml and 72.7 +/- 3.31 ng/ml, respectively). The activin A and follistatin concentrations were highly correlated both in the cross-sectional study (P <0.0001) and in individual women in the longitudinal study (P <0.05-0.0001). Concentrations of follistatin showed a greater increase in the second trimester of pregnancy relative to activin A concentrations. The parallel increase in the secretion of these two proteins throughout pregnancy probably reflects feto-placental secretion.

Activins↗
PubMed1999

Uterine milk protein, a novel activin-binding protein, is present in ovine allantoic fluid.

Activins are pluripotent growth factors that have recently been shown to be present in placental and fetal membrane preparations. Our previous studies have identified and purified activin A from ovine amniotic and allantoic fluids. In this study, ligand blots of side fractions from the isolation of activin A from allantoic fluid suggested the presence of activin-binding proteins other than follistatin. Further purification of one of these fractions involved two sequential reverse phase HPLC steps and a Superose 12HR fractionation. SDS-PAGE revealed a single protein band of 55 kDa, which was identified by NH2-terminal sequencing as ovine uterine milk protein (UTMP), a member of the serine protease inhibitor (serpin) superfamily of proteins. Further binding studies, using ligand blot techniques and Superose 12HR fractionation in the presence of [125I]activin, demonstrated UTMP to be an activin-binding protein with a lower affinity for activin than that of follistatin. A study of the specific binding behavior of UTMP to activin, using surface plasmon resonance, revealed an apparent equilibrium dissociation constant (Kd) of 49 +/- 25 nM, compared with the follistatin-activin Kd of 379 +/- 51 pM. Similar to another activin-binding protein, alpha2-macroglobulin, UTMP was unable to neutralize the bioactivity of activin in a bioassay based on the capacity of activin to inhibit the proliferation of an MPC-11 plasmacytoma cell line. The high concentrations of this protein in uterine fluid during pregnancy and its ability to bind activin suggest that UTMP may act as a low affinity, high capacity binding protein to sequester activin in the local uterine environment.

Activins↗
PubMed1994

Gonadotropin-suppressing activity of human recombinant inhibin in the male rat is age dependent.

We have examined the age-dependent effects of human recombinant inhibin A (hrI) on gonadotropin levels in intact male rats. A single s.c. injection of hrI in the dose range 6.25-100 ng/g BW resulted in a significant and consistent decrease (20-40%) in serum FSH measured 6 h later, at the higher (50 and 100 ng/g) doses, in animals 25-91 days of age. Administration of the same doses in animals < or = 20 days old had no significant effect on serum FSH levels. Similarly, no effect of hrI (100 ng/g) on serum FSH levels was observed in 15-day-old rats when FSH levels were monitored from 1 to 8 h. No effect of hrI was observed on serum LH levels except in 40-day-old rats, which exhibited a consistent and significant reduction at the higher (25-100 ng/g) doses of inhibin. Serum inhibin levels 6 h after the injection were not significantly altered at any dose in young animals (< or = 30 days); however, in older animals (40, 50, and 91 days) there was a significant elevation in circulating inhibin levels at the higher doses, strongly suggesting an age-related change in clearance. Testicular inhibin levels were not affected by administration of the exogenous material except at the highest dose (100 ng/g) in the oldest animals (91 days), when an approximately 30% reduction in both the concentration and the total content of inhibin was observed. The data clearly demonstrate that the effect of hrI on serum gonadotropins is age dependent and that changes in clearance may contribute to the period during which circulating inhibin levels are elevated postinjection.

Aging↗
PubMedDate not supplied

Kangaroo capers.

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Adult↗