Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “AMNION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18Linked to original sources
PubMed1992

Catecholamines modulate epidermal growth factor-induced prostaglandin E2 production in amnion-like (WISH) cells by means of a cyclic adenosine monophosphate-dependent pathway.

OBJECTIVE: The purpose of this study was to test the hypothesis that catecholamines can modulate epidermal growth factor-induced prostaglandin E2 production in amnion-derived cells via a cyclic adenosine monophosphate-dependent pathway. STUDY DESIGN: Human amnion-derived WISH cells were used as the model system to study the regulation of prostaglandin E2 production. The concentrations of prostaglandin E2 and cyclic adenosine monophosphate were measured by radioimmunoassay. Statistical significance was determined with the Student t test. RESULTS: Preexposure of WISH cells to either epinephrine, norepinephrine, or dopamine inhibited epidermal growth factor-induced prostaglandin E2 production. In addition, propranolol blocked both the increase in cyclic adenosine monophosphate accumulation and the inhibition of prostaglandin E2 production caused by epinephrine. CONCLUSIONS: These results indicate that epidermal growth factor-induced prostaglandin E2 production can be attenuated by preexposure of amnion cells to catecholamines and that the inhibitory effect of catecholamines on epidermal growth factor response may be mediated via a beta-adrenergic receptor--coupled adenylate cyclase.

1-Methyl-3-isobutylxanthine↗
PubMed1993

Stimulation of cultured amnion cell prostaglandin endoperoxide H synthase activity by glucocorticoids and phorbol ester.

OBJECTIVE: The effects of a phorbol ester activator of protein kinase C and the glucocorticoids cortisol and dexamethasone on the enzyme activity of prostaglandin H synthase (cyclooxygenase) in confluent cultures of human amnion epithelial cells were tested. STUDY DESIGN: Amnion epithelial cells from spontaneously delivered placentas at term were isolated and grown in culture until confluent. The activity of the enzyme prostaglandin H synthase was determined in these cells with a well-characterized enzyme assay monitoring the conversion of arachidonic acid to prostaglandin E2. The Michaelis-Menten constant and maximum velocity were determined from the substrate velocity data by means of Lineweaver-Burk plots. RESULTS: Amnion cells lost most of their prostaglandin H synthase activity within 2 days of culturing. This activity could be restored when cells were treated with 12-O-tetradecanoyl phorbol-13-acetate, a phorbol ester activator of protein kinase C, or with the glucocorticoids cortisol and dexamethasone. Epidermal growth factor also increased the specific activity, whereas 17 beta-estradiol had no effect on the specific activity of the enzyme. There was a direct correlation between the specific activity of prostaglandin H synthase and the output of prostaglandin E2 by cells treated with these agonists. CONCLUSION: Our data support the view that increases in prostaglandin H synthase specific activity in intrauterine tissues can be caused by stimulation by specific agonists, and this in turn is responsible for enhanced prostaglandin output by these tissues.

Amnion↗
PubMed1983

The effects of polyamines and aminoglycosides on phosphatidylinositol-specific phospholipase C from human amnion.

The effects of polyvalent cations (polyamines and aminoglycoside antibiotics) on Ca2+-dependent phosphatidylinositol-specific phospholipase C activity of human amnion tissue were examined. In the presence of 1 mM Ca2+, the hydrolysis of phosphatidylinositol (2 mM) by phospholipase C was increased greatly (240-560% of control) by spermine (0.4 mM), spermidine (1 mM), neomycin (0.1 mM), gentamicin (0.2 mM), kanamycin (0.4 mM) and streptomycin (0.8 mM). Putrescine and cadaverine (0.1-2.0 mM), however, stimulated phospholipase C activity only slightly. The effects of spermidine, spermine and gentamicin on phospholipase C activity were characterized and found to be dependent upon the concentrations of phosphatidylinositol, Ca2+ and the particular polyvalent cation. At low concentrations of phosphatidylinositol and Ca2+ the predominant effect of polyamines and aminoglycosides was to inhibit phospholipase C activity. When the concentrations of phosphatidylinositol and Ca2+ were increased, spermidine, spermine and gentamicin stimulated phospholipase C activity. In the presence of 16 mM Ca2+, however, phospholipase C activity was maximal and was unaffected by either polyamines or aminoglycosides. At all concentrations of Ca2+ examined, the maximal stimulation of phospholipase C activity by a given polyvalent cation occurred at a fixed molar ratio of the particular polyvalent cation to phosphatidylinositol. Polyamines and aminoglycosides appeared to modulate the Ca2+ requirement for phospholipase C activity, but could not substitute completely for Ca2+. The activities of phospholipase A2, diacylglycerol lipase, monoacylglycerol lipase and diacylglycerol kinase in amnion tissue were unaffected by any of the polyvalent cations examined. It is proposed that any in vivo influences (stimulatory or inhibitory) of polyamines and aminoglycosides on amnion phospholipase C activity would depend upon the effective concentrations of Ca2+ and phosphatidylinositol.

Aminoglycosides↗
PubMed1988

Phorbol ester-induced stimulation of prostaglandin biosynthesis in human amnion cells.

Both phorbol 12-myristate 13-acetate (PMA) and phorbol 12,13-dibutyrate (10(-8)-10(-6) M) induced concentration-dependent increases in prostaglandin E2 (PGE2) production by human amnion cells, with maximum stimulations of 10.8-fold and 5.9-fold, respectively. 4 alpha-Phorbol 12,13-didecanoate, an inactive phorbol ester analogue, had little or no effect on PGE2 production by amnion cells. PMA and phorbol 12,13-dibutyrate (10(-7) M) induced a maximal increase in the rate of PGE2 biosynthesis within 15 min of treatment. These results suggest that there is an active protein kinase C present in amnion cells that is linked to arachidonic acid release and/or metabolism.

Amnion↗
PubMed1988

Paradoxical stimulation of both lipocortin and prostaglandin production in human amnion cells by dexamethasone.

Glucocorticoids inhibit prostaglandin biosynthesis by inducing the formation of lipocortins. In human amnion cells dexamethasone elicited a concentration-dependent increase in prostaglandin production and raised intracellular lipocortin 1 concentrations. Dexamethasone could also potentiate the epidermal growth factor (EGF)-induced stimulation of prostaglandin production. EGF alone or in combination with dexamethasone increased lipocortin 1 formation in amnion cells. Human amnion cells may provide a unique insight into interactions between glucocorticoids, lipocortin and eicosanoid biosynthesis.

Amnion↗
PubMed1989

The concentration of collagen and the collagenolytic activity in the amnion and the chorion.

Fetal membranes obtained from second-trimester abortions, elective Caesarean sections and after normal deliveries were studied. The hydrolytic activity against a DNP-peptide expressing the collagen turn-over was found to be very high in the second trimester and relatively high at term of pregnancy. The activity in the chorion was twice that in the amnion. The concentration of another collagen-degrading enzyme, leukocyte elastase, which is present during inflammatory reactions was high at the site of rupture. The collagen concentration given as micrograms hydroxyproline per mg dry weight was unchanged throughout pregnancy and labour in both fetal membranes. The concentration in amnion was twice that in the chorion. After delivery, the collagen content given as microgram/cm2 in the chorion was decreased at the rupture line. This was due to decreased thickness of the membrane, whereas the hydroxyproline concentration (microgram/mg dry weight) was unchanged. The amnion was thinner than the chorion, but the decreasing collagen content (micrograms/cm2) at the rupture line was less pronounced. The thinning of especially the chorionic membrane might be secondary to the mechanical stress of pregnancy and labour and/or, as our results suggest, due to enhanced catabolism.

Amnion↗
PubMed1990

Regulation of prostaglandin E2 synthesis in human amnion by protein kinase C.

A role for protein kinase C (PKC) in mediation of prostaglandin E2 synthesis in human amnion cells has been suggested. We have investigated the specificity of the stimulation of PGE2 synthesis by phorbol esters and employed putative PKC inhibitors to demonstrate the specificity of PKC stimulation. The three phorbol esters, tetradecanoyl phorbol-13-acetate, phorbol-12,13-dibutyrate and phorbol-12,13-didecanoate gave concentration-dependent (10(-10)-10(-7)M) increases in PGE2 synthesis when added to amnion cells in monolayer, however, no effect was seen with the structurally similar phorbols phorbol-12-13-diacetate, 4 alpha phorbol-12-13-didecanoate or phorbol base. The stimulatory effect of TPA (10(-8)M) on amnion PGE2 synthesis could be prevented by coincubation with the putative protein kinase C inhibitors 1-(5-isoquinoline sulphonyl) piperazine, 1-0-octadecyl-2-0-methyl-rac-glycero-3-phosphocholine, sphingosine and chlopromazine at concentrations of 10(-6)-10(-4)M. Addition of the transcription inhibitor actinomycin D at 10(-6)-10(-5)M prevented TPA (10(-8)M)-induced PGE2 synthesis. However, paradoxically, a further increase in PGE2 synthesis was seen when 10(-9)-10(-7)M actinomycin D was added together with TPA. The phospholipase A2 inhibitor quinacrine was able to prevent the TPA-induced increase in PGE2 synthesis even in the presence of exogenous arachidonic acid suggesting that phospholipase A2 may be a target for PKC action.

Amnion↗
PubMedDate not supplied

Epidermal growth factor receptors in rat placenta, amnion and yolk sac: characteristics of specific binding are dependent on gestational age.

Studies of [125I]-EGF binding to the rat placenta, amnion and yolk sac were carried out on days 14, 17 and 20 of gestation. In the placenta EGF binding was detectable on all 3 days; in the amnion EGF binding was undetectably low on day 14 but was present on days 17 and 20, while in the yolk sac EGF binding was undetectably low on all 3 days. Although Scatchard analysis of EGF binding to placental tissue raised the possibility of high and low affinity receptors, a statistical analysis of the ligand binding data was consistent with the presence of only one type of EGF receptor. The overall affinity of the receptors did not change with stage of gestation. However, the concentration of EGF receptors was lower in placental tissue on day 17 than on days 14 or 20 of gestation; the receptor concentrations were similar on days 14 and 20. It is suggested that EGF binding to the placenta, amnion, and yolk sac may reflect the levels of cell proliferation in those tissues in the latter part of gestation.

Amnion↗
PubMed1994

Neurotrophic effects of amnion explants co-cultured with rat mesencephalon.

We investigated amnion-derived neurotrophic effects on embryonic day 14 rat mesencephalic (E14M) explants in co-culture. E14M explants showed extensive neurite outgrowth directed toward amnion tissue. Tyrosine hydroxylase immunocytochemistry, western immunoblot and [3H]dopamine uptake studies revealed significant neurotrophic effects on E14M dopaminergic neurons over 14 days in culture. Thus, amnion tissue appears to have potent neurotrophic effects for embryonic mesencephalic dopaminergic neurons in vitro.

Amnion↗
PubMed1994

Type IV collagenases in human amniotic fluids and amnion epithelial cells.

Gelatin zymograms revealed in human second trimester amniotic fluids a constant M(r) 66,000 proteolytically active polypeptide that in immunoblotting was recognized by antiserum against the human fibroblast gelatinase/type IV collagenase. Isolated cultured human amnion epithelial cells produced the M(r) 66,000 proteinase and frequently a M(r) 92,000 one. The production of the former was enhanced by transforming growth factor-beta and that of the latter by tetradecanoyl phorbol acetate. Immunoprecipitation experiments indicated that the M(r) 66,000 amnion epithelial cell proteinase was identical with that found in the amniotic fluids and that the M(r) 92,000 one corresponded to the human macrophage/granulocyte gelatinase/type IV collagenase. Approximate quantifications of the M(r) 66,000 proteinase in amniotic fluids and sera from same individuals were assessed by comparison of dilution series of the samples and standard enzyme preparations in zymography. These measurements indicated that the amount of the proteinase in the amniotic fluids was about 5-10 micrograms/ml representing 0.1-0.2% of total proteins. In sera the corresponding figures were 30-40 micrograms/ml and 0.03-0.06%, respectively. Thus the relative concentration of the M(r) 66,000 proteinase in amniotic fluids was approx. 3-4-fold that in sera, suggesting local production of the protein. The proteinase may be produced by amnion epithelial cells that under so far unknown physiologic stimulus also may start secreting the M(r) 92,000 enzyme.

Amnion↗
PubMed1985

Amnion overlay meshed skin autograft.

Meshed skin autografts are conventionally dressed with fine petrolatum gauzes. Pain and haemorrhage are a frequent sequel to changing dressings in the early days after grafting. We have explored the use of amnion to overlay the meshed autograft (3:1) in addition to the fine petrolatum gauze. Eleven patients with 24 burn wounds were treated. The amnion provided good protection to the underlying meshed autograft and the neoepithelium. It did not block the re-epithelialization and may have promoted the healing process. Most of the grafts had healed completely by 7 days after application. Pain and haemorrhage were markedly reduced. The non-antigenic nature, adherent quality and inexpensive cost makes amnion a promising biological dressing for meshed autografts.

Adolescent↗
PubMed1990

Pathways of arachidonic acid metabolism in human amnion cells at term.

We have compared the metabolism of (3H) arachidonic acid by monolayers of human amnion, cells obtained prior to or following labor at term. Radiolabel was either added exogenously or previously incorporated into cellular phospholipid pools to compare metabolism of arachidonic acid from different substrate sources. Cells obtained both prior to and following labor synthesized metabolites co-chromatographing on HPLC with di- and mono-HETEs and also a metabolite with polarity corresponding to a epoxyeicosatrienoic acid. Both types of cells were able to synthesize PGE2 when (3H) arachidonic acid was added exogenously. However, only those cells obtained following labor synthesized PGE2 from (3H) arachidonic acid incorporated into intracellular pools. These findings suggest that the cyclooxygenase and PGE2 isomerase enzymes are present in amnion prior to delivery but that exogenous arachidonic acid would be required for PGE2 synthesis at that time as the enzymes do not appear to be linked to a source of endogenous arachidonic acid. At the time of parturition, there may be a switching on of an enzyme system to generate arachidonic acid from intracellular pools specifically for PGE2 synthesis or alternatively coupling of such a system to a cyclooxygenase-PGE2 isomerase system resulting in PGE2 synthesis. These findings raise intriguing new possibilities for the regulation of eicosanoid synthesis in amnion which may include membrane topography, substrate pool-enzyme linking and regulation of specific phospholipase enzymes.

Amnion↗
PubMed1991

Isolation of multiple substances in amniotic fluid that regulate amnion prostaglandin E2 production: the effects of gestational age and labor.

The present study was undertaken to evaluate the effects of whole amniotic fluid (AF) and fractions of AF on amnion cell prostaglandin E2 (PGE2) production. Amnion cells were grown to confluence and then incubated in the presence of AF, or fractions thereof, obtained at 17-19 weeks gestation (MID), at term prior to the onset of labor (NIL), and at term after spontaneous onset of labor (LABOR). All whole AFs were stimulatory to amnion cell PGE2 production (p less than 0.001) but the stimulation by NIL and LABOR AFs was significantly greater (p less than 0.001) than stimulation by the MID AF. Fractionation of the AFs from the three groups (n = 9-10 per group) revealed multiple discernable peaks of stimulatory activity in each group. The majority of peaks had retention times that were similar among the three groups, and peak stimulatory activities were greater in NIL and LABOR samples than in MID samples.

Amnion↗
PubMed1993

Actions of interleukin-2 on amnion prostaglandin biosynthesis.

Preterm labor is associated with increased intrauterine prostaglandin (PG) production. Intrauterine infections are frequently associated with preterm labor and increased cytokine production. The cytokine interleukin-2 (IL-2) is a potent T-cell growth factor necessary for effective cell-mediated immunity. In this study we evaluated the effects of IL-2 on PGE2 biosynthesis by human amnion cells. IL-2 alone modestly but significantly inhibited amnion PGE2 production. Moreover, IL-2 also attenuated, in a concentration-related fashion, the stimulatory actions of IL-1 beta on PGE2 production by amnion cells. These data suggest that IL-2 could potentially represent a negative regulatory element in the mechanisms of preterm labor in association with intrauterine infection.

Amnion↗
PubMed2004

In vitro lesion repair by human amnion epithelial and mesenchymal cells.

OBJECTIVE: The purpose of this study was to compare wound healing by human amnion epithelial and mesenchymal cells from preterm and term placenta with the use of an in vitro lesion repair assay. STUDY DESIGN: Lesions were created in confluent monolayers of amnion epithelial and mesenchymal cells from preterm and term placentas. The repair was monitored by the measurement of the lesion area and the response to potential stimulants (platelet-derived growth factor, tumor necrosis factor-alpha, fibrinogen, and phorbol myristate acetate). Cell proliferation was detected with 5-bromodeoxyuridine staining. RESULTS: Lesion repair was complete within 40 hours in control epithelial cultures from preterm and term placenta but incomplete in mesenchymal cultures (preterm cells, 80%; term cells, 40%). Platelet-derived growth factor, tumor necrosis factor-alpha, fibrinogen, and phorbol myristate acetate did not accelerate repair in either cell type. CONCLUSION: An in vitro lesion repair assay revealed the differences in lesion repair capacity between amnion epithelial and mesenchymal cells and between mesenchymal cells from preterm and term placenta.

Amnion↗
PubMed2005

In situ immunolabeling allows for detailed localization of prostaglandin synthesizing enzymes within amnion epithelium.

Detailed information regarding the subcellular distribution of proteins within amnion epithelial cells is a goal of numerous placental biologists. In this report, we describe a versatile technique for in situ immunolabeling in amnion that is as technically permissible as traditional immunolabeling of cultured cells and, when coupled with confocal laser scanning microscopy, is similarly capable of providing detailed information regarding subcellular protein distribution. Using antibodies directed against sequential enzymes of the prostaglandin E biosynthesis cascade, we compared this novel method with immunofluorescent labeling using amnion cells in primary culture and cryosections of reflected fetal membrane rolls. By several criteria, we observed morphological variation between the cells cultured in vitro and the tissue specimens. Despite general consistencies in immunostaining patterns between the cryosectioned specimens and those labeled in situ, morphological preservation was superior using the latter technique. Relative to the cryosectioned specimens, in situ immunostaining was advantageous in that it permitted improved sampling efficiency, and allowed regional variations in labeling to be observed in a more global context within the tissue. Our results demonstrate that in situ immunolabeling provides a useful adjunct or alternative to immunolabeling using membrane roll preparations.

Amnion↗
PubMed2006

PCB 50 stimulates release of arachidonic acid and prostaglandins from late gestation rat amnion fibroblast cells.

Amniotic phospholipase A2 activity contributes to elevated levels of arachidonic acid and prostaglandins observed during labor. Polychlorinated biphenyls (PCBs) activate PLA2 and have been associated with shortened gestation length. To determine if PCBs stimulate amniotic PLA2, cell cultures of rat amnion fibroblasts (RAF) were established from gestation day (gd) 20 rats and labeled with 0.5 micro Ci [3H]-arachidonic acid prior to a 0.5- or 4-h exposure to 0.1% DMSO (solvent control), PCB 50 (1-50 micro M) or TNFalpha (positive control). PCB 50 and TNFalpha induced significant release of [3H]-arachidonic acid from amnion fibroblast cells in time-dependent manners (p<0.001), an effect associated with a significant increase in iPLA2 expression (p<0.05). PCB 50 also stimulated prostaglandin production from RAF cells independent of changes in immunoreactive COX-2. These data suggest that amnion may serve as a target for PCB-induced release of arachidonic acid and uterotonic prostaglandins, with a potential for adverse pregnancy outcomes.

Amnion↗
PubMed1990

Morphologic study of changes of collagenous tissue in the amnion and cervix during prostaglandin-induced abortion and delivery.

Marked dissociation of the cervical collagenous tissue during prostaglandin-induced abortion is well recognized, but the response of collagenous tissue of the amnion to prostaglandin treatment is not known. A morphologic study of amniotic collagenous tissue was performed after prostaglandin-induced abortion and prostaglandin-induced term delivery. The collagenous fibers of the amnion were found to be closely packed with no ground substances and formed in a thick layer. Cervical collagenous tissue of the same patients showed a marked dissociation of fibers and abundant ground substance. The fetus was often delivered within a complete sac at midtrimester. These findings suggest differences in collagenous tissue responses to prostaglandin treatment between the amnion and cervix.

Abortion, Induced↗