Biomedical subjects

G E Rice

Publications and source records attributed to G E Rice.

At least 55 records · Page 3Linked to original sources

PubMed1998

Secretory phospholipases and membrane polishing.

Although secretory phospholipase A2 (PLA2) isozymes have been identified in human gestational tissues, their role in homeostasis and pathophysiology during pregnancy has yet to be clearly established. The aims of this brief commentary are: (1) to review recent data concerning the expression of secretory PLA2 isozymes in human gestational tissues; and (2) to present a case for their involvement in regulating the expression of glycerophospholipids in the exoplasmic monolayer of the cell membrane. Three secretory PLA2 isozymes and a secretory PLA2 cell-surface receptor have been identified in human term gestational tissues. In addition to their potential role in the formation of glycerophospholipid-derived metabolites (such as prostaglandins), these isozymes may function to regulate the expression of aminophospholipids on the cell surface. The exposure of aminophospholipids on the cell surface dramatically affects many aspects of cell function. Secreted PLA2 isozymes that display a substrate preference for the negatively charged aminophospholipids (e.g. phosphatidylserine or phosphatidylethanolamine) in the exoplasmic membrane may affect cell function and reactivity via a process of 'membrane polishing', that is, the preferentially removal of aminophospholipids from the exoplasmic leaflet of the cell membranes. By this process, secreted PLA2 isozymes may limit unsolicited cell-surface binding of exogenous proteins, membrane fusion events and recognition by cellular surveillance systems.

Cell Membrane↗

PubMed1998

Distribution of the phospholipase A2 receptor messenger RNA in human gestational tissues.

Recently, a model has been proposed for the involvement of secretory phospholipase A2 (sPLA2) in the onset of and/or progression of human labour via the metabolism of cell membrane glycerophospholipids to generate biologically active, phospholipid-derived mediators. The recent molecular cloning and characterization of a cell-surface receptor for sPLA2 raise the possibility that sPLA2 enzymes may also affect cell function in intrauterine tissues via a receptor-mediated pathway. The aim of this study was to determine the expression profile of the PLA2 receptor messenger RNA in human gestational tissues at term. Messenger RNA for the PLA2 receptor was detected in amnion, choriodecidua and placenta by RT-PCR and transcripts of similar size to the 6.5- and 5.4-kb transcripts previously reported in various other human tissues were detected in choriodecidua by Northern blot analysis. However, smaller transcripts of approximately 4, 2.3 and 1 kb were also detected in choriodecidua by Northern blot analysis and the 2.3-kb transcript and the 1-kb transcript were the only major transcripts detected in amnion and placenta, respectively. The presence of PLA2 receptor mRNA in human gestational tissues indicates that an alternative non-catalytic pathway may contribute to the regulatory effects of sPLA2 isozymes in these tissues. While the specificity and affinity of the various transcripts identified in this study have yet to be determined, PLA2 isozymes released from human gestational tissues during pregnancy and at the time of labour may function as paracrine or autocrine mediators to affect cell function.

Amnion↗

PubMed1998

Gene expression of plasminogen activation cascade components in human term gestational tissues with labour onset.

The plasminogen activation cascade is thought to play a critical role in labour-associated remodelling events, such as fetal membrane rupture and placental separation. The aim of this study was to quantify, by Northern analysis, the gene expression of urokinase plasminogen activator (UPA), urokinase receptor (UPAR) and plasminogen activator inhibitor type-2 (PAI-2) in human gestational tissues. Amnion, choriodecidua and placenta were collected from women before, during and after spontaneous-onset labour at term. The expression of UPAR mRNA was significantly (P < 0.05) increased in amnion tissue during and after labour and delivery, compared with the before-labour group. In contrast, UPAR gene expression in choriodecidua and placenta was not significantly altered in association with labour onset. PAI-2 mRNA expression was also significantly (P < 0.05) increased in amnion after labour. No statistically significant differences were observed in choriodecidua or placenta PAI-2 mRNA with labour onset. Neither was any significant effect of labour status on UPA mRNA identified in any of the tissues examined. This study is the first to describe a significant increase in UPAR and PAI-2 gene expression in human amnion tissue with labour. These data are consistent with the hypothesis that, during labour, up-regulation of UPAR expression in amnion serves to localize active UPA at the cell surface, thereby increasing proteolytic activity in fetal membranes. Increased PAI-2 in amnion after labour may provide a regulatory 'switch' to cease further proteolysis in this tissue type. In conclusion, the data obtained support the proposal that the plasminogen activation cascade contributes to the rupture of fetal membranes during active labour.

Amnion↗

PubMed1998

Immunolocalisation of interleukin-4 and interleukin-4 receptor in placenta and fetal membranes in association with pre-term labour and pre-eclampsia.

The aim of this study was to characterise the localisation and staining intensity of immunoreactive (ir) interleukin-4 (IL-4) and IL-4 receptor (IL-4R) in human placenta and fetal membranes in association with pre-term and term labour, and pre-eclampsia. The data obtained in this study establish the presence of irIL-4 and IL-4R in human placenta and fetal membranes obtained from women at 25-41 completed weeks of gestation. IL-4 and IL-4R immunohistochemical staining was principally localised in villous and chorionic trophoblast, and to amnion epithelial cells. The intensity of IL-4 and IL-4R immunohistochemical staining was not significantly affected by labour status at term or pre-term (p > 0. 05), with the exception of IL-4R in the amnion (p < 0.05). In term amnion, IL-4R was only detectable following labour onset. When data were stratified with respect to the presence or absence of pre-eclampsia, no statistical difference in immunohistochemical localisation or staining intensity for either IL-4 or IL-4R could be identified for any of the tissues studied. Co-localisation of IL-4 and IL-4R within gestational tissues may indicate auto- and/or paracrine mechanisms of action for this cytokine. Tissue-specific, labour-associated induction of IL-4R may contribute to the regulation of biological effects of IL-4 within the uteroplacental unit.

Amnion↗

PubMed1998

Parathyroid hormone-related protein (PTHrP) mRNA splicing and parathyroid hormone/PTHrP receptor mRNA expression in human placenta and fetal membranes.

During human pregnancy, parathyroid hormone-related protein (PTHrP) and parathyroid hormone (PTH)/PTHrP receptor are produced by the uterus, placenta, fetal membranes (amnion and chorion) and developing fetus. PTHrP alternative 3' mRNA splicing results in transcripts which encode three PTHrP isoforms and have been identified in amnion. Uteroplacental PTHrP expression is greatest in amnion and increases dramatically during late pregnancy. The aims of this study were to determine PTH/PTHrP receptor mRNA expression at preterm and term gestations and to determine 3' alternative splicing patterns in placenta, amnion and choriodecidua at preterm and term gestations. Using semiquantitative reverse transcription-polymerase chain reaction, PTHrP and PTH/PTHrP receptor transcripts were identified in preterm (n=5) and term (n=7) gestational tissues. PTH/PTHrP receptor mRNA expression did not differ between tissue types or change with advancing gestation. In contrast, PTHrP expression in the same tissues increased with advancing gestation and was significantly greater in amnion than in placenta and choriodecidua. Thus PTHrP, although produced predominantly in amnion, may act in amnion and other tissues including placenta, choriodecidua and myometrium. In amnion over placenta, transcripts encoding PTHrP 1-139 and 1-173 were detected in some preterm and all term samples and those encoding PTHrP 1-141 were detected in all samples. Similar results were obtained for reflected amnion. In placenta and choriodecidua, PTHrP 1-139 and 1-173 transcripts were undetectable or of low abundance. PTHrP 1-141 transcripts were detected in some placenta and choriodecidua samples. In summary, transcripts encoding PTHrP 1-141 appeared to be more abundantly expressed than those encoding PTHrP 1-139 or 1-173. However, the up-regulation of PTHrP expression in amnion at term may involve each of the alternative 3' mRNA splicing pathways since transcripts for each isoform appeared to be more consistently expressed at term.

Alternative Splicing↗

PubMed1998

Contribution of type II phospholipase A2 to in vitro phospholipase A2 enzymatic activity in human term placenta.

Although phospholipase A2 (PLA2) enzymatic activities have been implicated in the regulation of phospholipid metabolism and eicosanoid formation in human gestational tissues, the role and contribution made by individual PLA2 isozymes has not been established. The aim of this study, therefore, was to determine the contribution made by Type II PLA2 to PLA2 enzymatic activity present in human term placenta. The experimental paradigm used to establish the contribution made by Type II PLA2 to total in vitro PLA2 enzymatic activity present in placental extracts was to remove Type II PLA2 by immunoaffinity extraction and then to quantify residual PLA2 enzymatic activity. Before immunoaffinity extraction, Type II PLA2 immunoactivity and total PLA2 enzymatic activity present in placental extracts averaged 28.0 +/- 10.0 ng/mg protein and 1040 +/- 367 pmol/h per mg protein (n = 3) respectively. After solid-phase immunoaffinity batch extraction of placental extracts, immunoreactive Type II PLA2 was not detectable by ELISA, and PLA2 enzymatic activity was decreased by 82 +/- 1% (P < 0.001). Residual (i.e. non-Type II) PLA2 enzymatic activity was further characterised by Western blot analysis and enzyme activity assay. The data obtained are consistent with a contribution by both cytosolic PLA2 and other secretory PLA2 isozymes (i.e. non-Type II) to residual PLA2 enzymatic activity. The results obtained in this study support the conclusion that Type II PLA2 is quantitatively the primary PLA2 isozyme that contributes to in vitro PLA2 enzymatic activity present in extracts of human term placenta, accounting for at least 80% of total activity. These data further support the involvement of this extracellularly active isozyme in the regulation of placental phospholipid metabolism and eicosanoid formation during late gestation.

Blotting, Western↗

PubMed1998

Effects of dietary phytoestrogens in postmenopausal women.

The aim of this study was to test the hypothesis that increased dietary intake of phytoestrogens reduces the health impact of the menopause. To test this hypothesis, a double-blind, randomized, entry-exit, cross-over study was conducted to assess the effects of three dietary manipulations--soy and linseed diets (high in phytoestrogens) and a wheat diet (low in phytoestrogens). Postmenopausal women were recruited and randomly assigned to one of the three dietary regimens. Urinary phytoestrogen concentrations, hot flush rate, vaginal smears, bone mineral density and bone mineral content were assessed for two 12-week periods. Comparative analysis showed no significant differences, but, when analyzed separately, groups consuming high phytoestrogen diets had between 10 and 30 times higher urinary excretion of phytoestrogens compared to those consuming the low phytoestrogen diet (p < 0.01). Study participants consuming soy, linseed and wheat diets had a 22% (not significant, n.s.), 41% (p < 0.009) and 51% (p < 0.001) reduction in hot flush rate; a 103% (p < 0.04), 5.5% (n.s.) and 11% (n.s.) increase in vaginal cytology maturation index; and a 5.2% (p < 0.04), 5.2% (n.s.) and 3.8% (n.s.) increase in bone mineral content, respectively. No changes were detected in bone mineral density. The differential effects of high phytoestrogen dietary manipulations on outcomes may represent tissue-specific responses to isoflavones and lignans contained in soy and linseed, respectively. Whilst health outcome measures were not significantly different between groups, the data obtained from separate analysis suggest that phytoestrogens in soy and linseed may be of use in ameliorating some of the symptoms of menopause. Furthermore, the significant decrease in hot flush rate in the wheat group cannot be attributable to phytoestrogens measured in this study. Due to subject variability, larger studies are still needed to evaluate population benefit.

4-Butyrolactone↗

PubMed1997

Vascular effects of PTHrP (1-34) and PTH (1-34) in the human fetal-placental circulation.

The aim of this study was to examine the vasodilatory effects of parathyroid hormone-related protein (PTHrP) (1-34) and parathyroid hormone (PTH) (1-34) on the human fetal-placental circulation utilising an in vitro placental perfusion model. In all experiments, the vasculature of an isolated human placental cotyledon was pre-constricted with the thromboxane A2 mimetic U46619. A simple dose of PTHrP (1-34) or PTH (1-34) (1.7-300 nM) was then infused into the fetal-placental circulation of the cotyledon. In other experiments, cotyledons were repeatedly infused with PTHrP (1-34) or PTH (1-34) (51.3 nM). Vasodilatory responses were significantly reduced in response to repeated exposure to PTHrP (1-34) (P < 0.001), indicating that this peptide desensitizes the fetal-placental vasculature. PTHrP (1-34) and PTH (1-34) equipotently stimulated a significant vasodilation of the fetal-placental circulation (P < 0.0001). The PTHrP receptor antagonist [Asn10, Leu 11]PTHrP (7-34) (102 nM) was infused in U46619-constricted placentae in the presence and absence of PTHrP (1-34) (10.2 nM). The PTHrP antagonist alone had no significant effect in the fetal-placental circulation. The antagonist significantly attenuated the response to PTHrP (1-34) (P < 0.015). Based on the data obtained in this study it is suggested that locally produced PTHrP (1-34) may be involved in the regulation of normal human fetal-placental vascular tone in autocrine and/or paracrine fashion.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1997

The effect of monophosphoryl lipid A on lipopolysaccharide-induced prostaglandin E2 release in human choriodecidua.

The aim of this study was to determine the effect of an inhibitor of bacterial endotoxin, monophosphoryl lipid A (MLA), on lipopolysaccharide (LPS)-induced prostaglandin E2 (PGE2) formation by human choriodecidua explants incubated in vitro. LPS induced the release of PGE2 from explants in a time-and dose-dependent manner (P < 0.05, n = 5), thus establishing the efficacy of the experimental model. MLA at concentrations of 10 micrograms/ml also increased PGE2 release from explants when compared to vehicle controls (P < 0.05, n = 5). When used at a concentration that did not stimulate PGE2 release (1 microgram/ml), MLA pretreatment, coincubation or a combination of these protocols did not significantly affect LPS-induced PGE2 release. These data establish that MLA does not act by abrogating tissue LPS responsiveness. Under the conditions utilized in this study, MLA acts locally as a low potency 'LPS-like agent'. The previously reported in vivo efficacy of systemically administered MLA may involve the partial depletion or down regulation of LPS response pathways and the subsequent development of LPS tolerance.

Adjuvants, Immunologic↗

PubMed1997

Tumor necrosis factor-beta in human pregnancy and labor.

The aims of this study were to determine tumor necrosis factor-beta (TNF-beta) concentration profiles in peripheral venous plasma and amniotic fluid during pregnancy and at the time of labor and to characterise TNF-beta mRNA expression and TNF-beta release from human gestational tissues. In addition, we investigated the expression of TNF-beta binding protein, lymphotoxin-beta (LT-beta), in human gestational tissues. The mean (+/-S.E.M.) TNF-beta concentrations in maternal plasma (TIL, 78 +/- 12 pg/ml, n = 7 vs. TNIL, 304 +/- 88 pg/ml, n = 7) and amniotic fluid (TIL, 8 +/- 5 pg/ml, n = 6 vs. TNIL, 73 +/- 20 pg/ml, n = 20) were significantly (P < 0.05) decreased in association with term labor-onset (TIL) compared to term not-in-labor (TNIL). TNF-beta concentration in maternal plasma and amniotic fluid did not change significantly either with preterm labor (PIL), or during pregnancy. Group-matched comparison of maternal plasma and amniotic fluid TNF-beta concentrations demonstrated that amniotic fluid TNF-beta concentrations were 6-8 fold lower than maternal plasma TNF-beta concentrations. Furthermore, no detectable TNF-beta was secreted from cultured human amniotic, choriodecidual and placental explants. Although, TNF-beta mRNA was detected in amnion, choriodecidual and placenta, LT-beta was similarly expressed in these tissues, suggesting that TNF-beta may be cell membrane bound. These data demonstrate that TNF-beta is present at low levels within the intrauterine environment and may suggest that TNF-beta is specifically inhibited at the maternal-fetal interface.

Amniotic Fluid↗

PubMed1997

Differential expression of type II, IV and cytosolic PLA2 messenger RNA in human intrauterine tissues at term.

The involvement of phospholipase A2 (PLA2) enzymes in the formation of biologically-active phospholipid metabolites by human gestational tissues has principally been characterized by the use of enzyme activity assays. While such assays have established the presence of functional PLA2 activity, there is a paucity of information concerning the tissue distribution and relative contribution to net activity made by specific PLA2 isozymes. In particular, both secretory and cytosolic isozymes may be involved in gestational tissue phospholipid metabolism. Thus, the aim of this study was to test the hypothesis that phospholipase A2 mRNA transcripts encoding Type II, Type IV and cytosolic PLA2 are tissue-specifically expressed in human amnion, choriodecidua and placenta obtained at term. The relative expression of polyA+ mRNA encoding these PLA2 isozymes was determined by Northern blot analysis and laser densitometry. The data obtained confirm the tissue-specific expression of PLA2 mRNA in human intrauterine tissues. Cytosolic PLA2 mRNA was most abundantly expressed in amnion when compared to either choriodecidua (which was 5-fold less than amnion; P < 0.001) or placenta (72-fold less than amnion; P < 0.001). In contrast, the secretory PLA2 mRNA transcripts (i.e. Type II and Type IV) were most abundantly expressed in placenta. Type II PLA2 mRNA expression in choriodecidua and amnion was 30-fold less than that observed in placenta (both P < 0.001). Type IV PLA2 mRNA expression was 37-fold (P < 0.001) and 73-fold (P < 0.001) less in choriodecidua and amnion respectively. These data support the conclusion that cytosolic PLA2 is the principal PLA2 isozyme mediating phospholipid metabolism and the liberation of fatty acid substrate (i.e. arachidonic acid) in term amnion, while secretory PLA2 isozymes, and in particular, Type II PLA2 play a major role in phospholipid metabolism in term placenta.

Amnion↗

PubMed1997

Interleukin-8 release from human gestational tissue explants: the effects of lipopolysaccharide and cytokines.

Interleukin (IL)-8 is a chemotactic cytokine that has been implicated in the etiology of infection-induced and normal human labor. In particular, IL-8 has been implicated in the processes of cervical ripening and rupture of fetal membranes because of its role in neutrophil activation and release of cellular matrix remodeling enzymes. In this study, we tested the hypotheses that IL-8 is released locally in the intrauterine environment from human amnion, choriodecidua, and placenta, and that IL-8 release from these tissues is increased by bacterial endotoxin, lipopolysaccharides (LPS), and inflammatory cytokines. IL-8 was released from human amnion, choriodecidual, and placental explants, with choriodecidua demonstrating the most abundant release. IL-8 release was significantly (multiple analysis of variance, p < 0.05) increased by LPS in a time- and dose-dependent manner from both choriodecidual and placental explants, but not from amnion explants. In addition, IL-1alpha (0.28 nM) and tumor necrosis factor alpha (TNFalpha, 10 nM) significantly (Student's t-test, p < 0.05) increased IL-8 release from placental explants 2- to 3-fold. These studies establish that the amnion, choriodecidua, and placenta are a source of IL-8 and demonstrate tissue-specific and differential regulation of IL-8 release by LPS, IL-1alpha, and TNF-alpha. These data support a role for IL-8 in a cascade of inflammatory events initiated by an intrauterine infection and resulting in activation of the labor process.

Amnion↗

PubMed1997

Women who spontaneously quit smoking in early pregnancy.

Spontaneous quitters are prepregnancy smokers who quit by the time of their first antenatal visit. We recruited 192 self-declared spontaneous quitters and 407 smokers at their first visit to the antenatal clinic at the Royal Women's Hospital during April, 1994-May, 1995. Spontaneous quitters made up 23% of prepregnancy smokers. Information about self-declared quitters and smokers was collected by self-completed questionnaires. Urine samples collected at the first visit and in late pregnancy were assayed for cotinine to validate smoking status. A cut-off urinary concentration of > or = 653 nmol/L cotinine was used to determine active smoking. At the first visit, 20% of the self-declared spontaneous quitters were smoking and by late pregnancy, regardless of their initial biochemically verified status, 27% were smoking. Spontaneous quitters were different from women who said they were still smoking at their first antenatal visit, in a range of demographic variables and measures of addictive behaviour.

Adult↗

PubMed1997

Tissue-specific expression of the relaxed conformation of plasminogen activator inhibitor-2 and low-density lipoprotein receptor-related protein in human term gestational tissues.

The relaxed conformation of plasminogen activator inhibitor-2 (PAIr) is formed during inactivation of the matrix-degrading enzyme urokinase plasminogen activator (uPA). The presence of PAIr in tissues, therefore, indicates the in situ inhibition of uPA-mediated proteolysis. In addition, PAIr functions as a ligand for the clearance receptor low-density lipoprotein receptor-related protein (LRP), thereby promoting internalization of receptor-bound uPA-PAIr complexes from the cell surface. The rapid internalization of receptor-bound, inactivated uPA has been suggested to be characteristic of invasive cell phenotypes. The aims of this study were to characterize the immunohistochemical localization of PAIr in human term gestational tissues (amnion, choriodecidua, and placenta) and to establish its co-expression with other components of the uPA cascade. The results obtained indicate that PAIr immunoreactivity was exclusively localized to amnion epithelial cells, with only minimal staining in the underlying chorion. PAIr immunoreactivity was not detectable in any of the trophoblastic tissues examined (villous and extravillous). The tissue-specific expression of PAIr immunoreactivity was not significantly altered in association with labor onset. uPA and PAI-2 staining was localized predominantly to amnion epithelial cells, underlying chorion, and trophoblast cells of villous and extravillous tissue. Amnion and trophoblasts of extravillous and chorionic tissue showed uPAR immunoreactivity, whereas staining in placenta was absent. Immunoreactive LRP was confined to trophoblasts of the chorion, and the villous and extravillous tissue. For the first time, localization of PAIr at the tissue level has been identified. The data obtained are consistent with the hypothesis that cells of invasive phenotype, although expressing all components of the uPA cascade, do not accumulate immunoreactive PAIr, because it is rapidly internalized from the cell surface. Conversely, cells of noninvasive phenotype will accumulate PAIr immunoreactivity only in the absence of LRP expression. We propose that the presence of PAIr and the absence of LRP at the cell surface are putative markers of noninvasive phenotypes.

Amnion↗

PubMed1997

Release of Type II phospholipase A2 immunoreactivity and phospholipase A2 enzymatic activity from human placenta.

The aim of this study was to determine whether Type II phospholipase A2 (PLA2) is released from late pregnant human placental tissue. Placental explants were incubated in vitro and the release of immunoreactive (ir) Type II PLA2 and PLA2 enzymatic activity into the medium was determined. Both irType II PLA2 and PL2 enzymatic activity accumulated in the incubation medium in a time-dependent manner (P < 0.0001). This release was not associated with a loss of cell membrane integrity, as indicated by measurement of the intracellular enzyme, lactate dehydrogenase, in the incubation medium. The concentration of irType II PLA2 and PLA2 enzyme activity present in incubation medium were significantly correlated (P < 0.01). Consistent with the hypothesis that Type II PLA2 may be store in secretory granules within human placental tissue, incubation in the presence of a membrane depolarising concentration of KCI (60 mM) caused the release of irType II PLA2 2.0-fold (P < 0.001). PLA2 enzyme activity released into the incubation medium displays biochemical characteristics consistent with those previously reported for secretory PLA2 isozymes, that is, a requirement for millimolar concentrations of calcium for optimal enzyme activity, inhibited by reducing agents, such as dithiothreitol and insensitive to heat inactivation. The data obtained in this study establish that irType PLA2 is released from term placenta, when incubated in vitro. The release of this extracellularly-active PLA2 isozyme may contribute to gestational and labour-associated increases in glycerophospholipid metabolism and prostaglandin formation.

Female↗

PubMed1997

The expression of parathyroid hormone-related protein mRNA and immunoreactive protein in human amnion and choriodecidua is increased at term compared with preterm gestation.

Parathyroid hormone-related protein (PTHrP) gene expression and/or immunoreactive protein have previously been identified in the uterus and intrauterine gestational tissues. The putative roles of PTHrP during pregnancy include vasodilatation, regulation of placental calcium transfer, uterine smooth muscle relaxation and normal fetal development. The aims of this study were 1) to determine the tissue-specific and temporal expression of PTHrP mRNA and immunoreactive protein in human gestational tissues collected at preterm and term; and 2) to determine the effect of labour on PTHrP expression by collecting these tissues from women undergoing elective caesarean section (before labour), intra-partum caesarean section during spontaneous-onset labour (during labour), and women with spontaneous labour and normal vaginal delivery (after labour). Total RNA and protein were extracted from placenta, amnion (over placenta and reflected) and choriodecidua for analysis by Northern blot (using a specific human PTHrP cDNA probe), and by N-terminal PTHrP RIA respectively. In amnion over placenta, reflected amnion and choriodecidua both PTHrP mRNA relative abundance and immunoreactive protein were significantly elevated at term compared with preterm (P < 0.01). At term, both PTHrP and its mRNA were significantly greater in amnion than in placenta and choriodecidua (P < 0.05). Also, both PTHrP and its mRNA were significantly elevated in amnion over placenta compared with reflected amnion (P < 0.05). The expression of PTHrP and its mRNA did not change in association with term labour or rupture of the fetal membranes, therefore this study provides no evidence for a specific PTHrP role in the onset and/or maintenance of term labour. However, the significant up-regulation of PTHrP mRNA and protein in the fetal membranes at term compared with preterm suggests an important role in late human pregnancy.

Amnion↗

PubMed1996

Localization of type II phospholipase A2 messenger RNA and immunoactivity in human placenta and fetal membranes.

Although Type II phospholipase A2 (PLA2) immunoactivity has been identified in homogenates of human placenta and fetal membranes, there is a paucity of information concerning the sites of synthesis of this secreted PLA2 isozyme. The aim of this study, therefore, was to establish the cellular localization of Type II PLA2 messenger RNA (mRNA) in human term placental and fetal membranes by in situ hybridization. In addition, the co-localization of immunoreactive Type II PLA2 in gestational tissues was determined, and the effect of labour status and pre-eclampsia on immunolabelling intensity were established. Type II PLA2 mRNA was identified in all tissue sections examined and was localized principally in placental villous vasculature and mesenchymal elements of placenta, chorion and amnion. Within the vasculature, Type II PLA2 mRNA was associated with smooth muscle cells. Immunoreactive Type II PLA2 was identified in the fibroblast and spongy layers of the amnion, the fibroblast and reticular layer of the chorion, and in the mesenchymal core and trophoblasts of placental villi. Immunolabelling staining intensity was greater in placenta and chorion than that observed in amnion, however, staining intensity was unaffected by labour status. Pre-eclampsia was associated with increased immunolabelling for Type II PLA2 in placenta but not fetal membranes. The data obtained clearly established that Type II PLA2 is synthesized by multiple cell types within human gestational tissues and co-localization of Type II PLA2 mRNA and immunoreactive protein has been established. The role of Type II PLA2 in gestational tissue phospholipid metabolism and, in particular, in vascular and mesenchymal elements, has yet to be established. Possible roles for this isozyme may include, the provision of substrate for eicosanoid synthesis, maintaining cell membrane phospholipid asymmetry and prevention of clot formation within the placental vascular bed.

Amnion↗

PubMed1996

Characterisation of acyltransferase activity in ovine placental tissue during pregnancy and at the time of labour.

Although it is well established that the formation of eicosanoids by ovine intrauterine tissues increases during pregnancy and at the time of labour, the biochemical mechanisms involved remain to be clearly established. In this study, we tested the hypothesis that the gestational and labour-associated increases in eicosanoid formation are associated with a reduction in the activity of the reacylating enzyme, acyl Coenzyme A lysophosphatide acyltransferase (LAT). To evaluate this proposal, in vitro LAT activity was quantified in ovine placenta (cotyledons) obtained during pregnancy (85-147 days of gestation and at the time of labour). Ovine placental LAT increased from 1.81 +/- 0.06 nmol/min per mg protein at 85 days of gestation to 2.34 +/- 0.10 nmol/min per mg protein at 142 days of gestation (P < 0.005; n = 15). The apparent Km did not vary significantly between the 85- and 142-day groups. Vmax, however, was significantly greater in the late-gestation group (2.98 +/- 0.02 nmol/min per mg protein) than in the mid-gestation group (2.38 +/- 0.13 nmol/min per mg protein, P < 0.05). In association with labour, placental LAT activity decreased by 16% (1.96 +/- 0.13 nmol/min per mg protein) when compared with that observed in tissue obtained from the non-labouring ewe (P < 0.01). The data obtained are consistent with the hypothesis that changes in LAT activity in ovine placenta do not contribute to the gestational increase in prostaglandin formation, but a contribution to the labour-associated increase in non-esterified arachidonic acid availability and eicosanoid formation cannot be negated.

Acyltransferases↗