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At least 397 records · Page 22Linked to original sources
PubMed1975

[Studies of in vitro cultivated cells from the smooth muscle organs. 3. Effectiveness of some drugs on pulsation frequency of isolated smooth muscle cells of the chicken amnion].

The effects of some drugs on the beating frequency of isolated cells of the chick amnion cultivated on cover slips were investigated. Cholinergic and adrenergic agonists and antagonists, serotonine, antispasmodics, coronary dilatants and local anesthetics influenced the beating frequency significantly. The isolated chick amnion cells equal in their pharmacological behaviour the intact chick amnion and smooth muscle cells of mammals but differ from isolated beating heart cells.

Adrenergic beta-Antagonists↗
PubMed1978

Simian virus 40 (SV40) production from SV40-transformed human amnion cells of established lines.

Sixteen established cell lines of simian virus 40 (SV40)-transformed human amnion cells were examined for SV40 production. Many of these lines produced SV40 for extensive periods. Virus production had not ceased for 2 lines after 18 months, for 3 lines after 12 months, and for 3 lines at 3 months after recovery from "crisis". Three lines became virus-free in the first month, 1 line in the second month, 1 in the third month, and 1 in the fourth month, and 2 lines stopped virus production between 6 and 11 months after recovery. The virus titers were relatively low. Inclusion body-containing cells were infrequent. In contrast, in most cultures of SV40-transformed human fibroblasts rescued from crisis, no infectious virus was demonstrated, although exceptions have been reported. Virus was produced after heterokaryon formation of cells of the virus-free amnion lines with CV-1 cells in the presence of inactivated Sendai virus, as observed for SV40-transformed human fibroblasts. During the crisis period, some of the SV40-transformed amnion cells produced substantial amounts of virus. Titers decreased during the later periods of crisis. The most pronounced decrease in titers was in cultures from which established lines were recovered.

Amnion↗
PubMedDate not supplied

[The cholinergic reaction of the amnion in the chick embryo].

Studies have been made of the spontaneous contractions of the amnion and acetylcholine sensitivity of amniotic membrane in 8--14-day chick embryos. In 12--14-day embryos, the spontaneous rhythmic contractions were rather rare as compared to those in 8--9-day ones, their frequency being also lower. On the basis of kinetic analysis, it was concluded that both the dissociation constant (K) and the value of Pmax do not exhibit significant changes for tonotropic reaction from the 8th to the 14th day and for chronotropic reaction--from the 8th to the 10th day of incubation. After the 10th day of incubation, dose-effect chronotropic reaction not expressed. The spontaneous activity of the amnion and acetylcholine sensitivity of the amniotic membrane depend on the temperature being maximal at 38 degrees C. Possible regulatory mechanisms of contractile activity in chick amnion are discussed.

Amnion↗
PubMedDate not supplied

[Cholinesterase in the amnion of chick embryos].

Cholinesterase (ChE) activity in amnion was studied in developing chick embryos and the enzyme's substrate-inhibitory characteristics were established. The enzyme activity increased until the 8th day of incubation and then gradually decreased; on day 12-15 the activity is 40% only of the maximal one. On the basis of substrate-inhibitory analysis the enzyme was referred to propionyl-cholinesterases. Relations between age changes in ChE activity and morphological structure of smooth-muscle amnion tissue, its differentiation during development and functional activity of amnion are discussed.

Amnion↗
PubMed1989

[The microtexture of amnion and chorion connective tissue].

On microscopical, stereo-scan and TEM observations the microtexture of the connective tissue of amnion and chorion have been analysed. The "compact layer" of the amnion-connective tissue consists of single collagen fibrils, which are arranged felt-like in parallel layers. In the "fibroblast layer" the fibrils are mostly arranged in bundles, forming a network. Single fibrils and bundles of fibrils in both layers are arranged surface parallel. The superficial layer of the chorion's connective tissue is predominated by wave-like bundles of fibrils in parallel and latticed arrangements, which are consolidated by transversely and diagonally running fibres. In the inferior layer the fibres leave their formation, run diagonally in the direction of the trophoblast and interweave with each other to a mat of fibrils at the border to the trophoblast. The tensile strength of the amnion connective tissue is due to the felt-like fibril texture of the "compact-layer" and the special arrangement of surface-parallel collagen fibres and fibrils.

Amnion↗
PubMed1986

Release and lubricating properties of amniotic surfactants and the very hydrophobic surfaces of the amnion, chorion, and their interface.

Surface hydrophobicity of 17 fresh human chorioamniotic membranes was measured as the contact angle (theta) subtended when a drop of saline is placed upon any non-wettable surface. The contact angle averaged 75.5 +/- 4.2 degrees and 76.8 +/- 5.6 degrees on the epithelial surfaces of the amnion and chorion, respectively. The interface proved to be particularly hydrophobic, averaging 108.2 +/- 8.7 degrees on the amnionic side and 121.7 +/- 4.2 degrees on the chorionic side, especially when compared with 108 degrees for Teflon. High surface hydrophobicity implies good boundary (solid-to-solid) lubrication, good release from neighboring tissues, and water repellency, which is a possible factor enabling the chorioamniotic membrane to retain amniotic fluid. Good release (68 to 71%) and boundary lubrication (coefficient of kinetic friction = 0.24 +/- 0.072) were obtained from oriented monolayers of the phospholipid extracted from samples of human amniotic fluid obtained from term patients by amniocentesis. These results support the concept that the amnionic and chorionic membrane surfaces exhibit good release and boundary lubrication probably imparted by adsorbed surfactant.

Amnion↗
PubMed1985

[Comparison of the effects of taurine and magnesium on electrical characteristics of artificial and natural membranes. V. Study on the human amnion of the antagonism between magnesium, taurine and polluting metals].

The effects of metal pollutants (Pb, Cd, Hg, As) were studied on strips of human amnion isolated from the placental zone put in between two Ussing chambers with Hanks' solution at 37 degrees C and pH 7.4. The total conductance Gt through the human isolated amnion was decreased on the fetal side by Pb and As; on the maternal side by Cd, Hg and As. When Gt was decreased by metal pollutants, Mg or taurine (TA) were added in the external medium to induce an antagonism between Mg or TA and metal pollutants. The addition of Mg increased significantly the Gt reduced by Pb, Cd and Hg, but had no effect on the Gt reduced by As. The addition of taurine increased significantly the Gt reduced by Cd and Hg, but had no effect on the Gt reduced by Pb and As. Dixon's kinetics (Gt as a function of the Mg or TA concentration when the metal pollutant concentration increased) indicate that there is a competitive inhibition between Mg-Pb and Mg-Cd (the inhibition constant Ki is lower with Pb (= 2.5) than with Cd (= 11.4) and suggests a greater antagonism between Mg-Pb than between Mg-Cd). Moreover, there appears to be a noncompetitive inhibition between Mg-Hg, TA-Cd and TA-Hg. These results indicate that Mg and TA, on the fetal side, exert an action on the same sites and that, on the maternal side, their action takes place on the same sites and also on different ones. Also, TA can be considered as a partial magnesium agonist, at least in the human amnion.

Air Pollutants↗
PubMed1985

Cysteine proteinase procoagulant from amnion-chorion.

Various coagulation abnormalities are associated with pregnancy. Several investigators have suggested that there may be a unique procoagulant associated with amniotic tissue and fluid. We identified a cysteine proteinase from malignant tissue, cancer procoagulant, and had reason to believe a similar proteinase may be present in amniotic tissue. Amniotic fluid and extracts of amnion-chorion were purified by immunoaffinity chromatography with an antibody that was developed to cancer procoagulant antigen. The purified amnion-chorion procoagulant initiated clotting in normal and factor VII-deficient citrated human plasma and directly activated pure human factor X in a two-stage clotting assay. It was inhibited by 1 mmol/L of iodoacetamide and 0.1 mmol/L of HgCl2, and the procoagulant activity was activated by 10 mmol/L of KCN; these are classic properties of cysteine proteinases. The pure amnion-chorion procoagulant had the same mol wt and immunologic determinants as cancer procoagulant from rabbit V2 carcinoma, as determined by crossed immunodiffusion, suggesting that the same or very similar proteins were associated with both tissues. Thus, this procoagulant may be derived from both undifferentiated and dedifferentiated cells.

Amnion↗
PubMed1985

Monovalent cations transfer through isolated human amnion: a new pharmacological model.

Transfer of monovalent cation through the isolated human amnion consists of different factors: paracellular, coupling, ATPase dependent cellular transfer, leak cellular transfer. Understanding this transfer permits testing of the action of various substances. Physiological substances (Mg, taurine) increase ionic transfer and there is a vicarious effect between Mg and taurine. The tocolytic agents MgSO4 and ethanol do not exhibit a good effect on the transfer: decrease with ethanol; equality between entry and exit fluxes with MgSO4. On the other hand, amphotericin B increases mother-to-fetus transfer. Polluting metals (Pb, Cd, Hg, As) dramatically reduce exchanges and almost completely inhibit amnion permeability. Ingestion of ethanol also exhibits a dramatic effect on the exchange between mother and fetus through the amnion. Study of ionic transfer in vitro can be considered a pharmacological model to investigate the modifications of mother-fetus exchanges by various substances.

Amnion↗
PubMed1985

Cholesterol synthesizing enzymes in term human fetal amnion.

Based on the observations that human fetal membranes possess the ability to synthesize steroid hormones, we sought to investigate the precursor role of 2 - 14C acetate in cholesterol formation by term human fetal amnion. Concentrations of derivatized 14C cholesterol was measured by reverse-isotope dilution technique in incubations of 2 - 14C acetate with homogenates of term fetal amnion dissected from 5 human placentae (37-40 weeks gestation) delivered vaginally from uncomplicated pregnancies (age 22-29 years). Controls consisted of homogenates heated in a boiling water bath for 10 min. The data presented demonstrate incorporation of 2-14C acetate into 14C cholesterol by the viable tissue. The extent of enzymic conversion varied from 0.002% to 0.076%. The small but definite conversion indicates that the homogenates of term human fetal amnion contain the full complement of enzymes necessary to catalyse the transformation of acetate to cholesterol. The metabolic need for cholesterol supply during labor is discussed.

Adult↗
PubMed1983

Human thymus contains amnion epithelial antigens.

Antibodies produced in rabbits to detergent-solubilized human amnion were found to react with Hassall's corpuscles in human thymus. Following nomenclature for placental antigens, the immunogenic group responsible for these antibodies has been tentatively designated as amnion antigens 1 (AA1). The anti-AA1 antisera did not react with other thymic components, nor did they react with any other extra-embryonic tissues than amniotic epithelium. Some adult ectodermally derived tissues, such as breast ductal and corneal epithelium, reacted with anti-AA1, but others such as skin and vagina did not. These findings link an antigenic relationship between amniotic epithelium and certain ectodermal derivatives. Amnion exists long before these tissues are formed, raising the possibility that amniotic epithelium may play an inductive role in their development.

Amnion↗
PubMed1984

Type V collagen in human amnion is a 12 nm fibrillar component of the pericellular interstitium.

Immunoelectron microscopy was utilized to detect type V collagen in human amnion. Monospecific antibodies to type V collagen were detected with protein A-gold conjugates in tissue sections and epoxy-embedded sections of human amnion. Type V collagen was localized to the immediate vicinity of the basal lamina, but was distinct from laminin and type IV collagen, which localized only to the lamina lucida and lamina densa, respectively, of the basal lamina. At high magnification, 12 nm unbanded fibrils were seen to be labelled by anti-type V collagen antibody; these fibrils extended from the lamina densa of the basal lamina well into the interstitial matrix. In comparison, only the amorphous matrix of the lamina densa showed labelling with anti-type IV collagen antibodies. Anti-laminin antibodies labelled the lamina lucida. Quantitative analysis of grain distribution revealed the laminin labelling to be centered over the distal half of the lamina lucida (mean distance from the cell surface = 70 nm). In contrast, type IV collagen was centered over the lamina densa (mean = 115 nm). Both distributions were essentially Gaussian and distinct from the broad distribution of type V collagen. Type I collagen fibers with characteristic 67 nm periodicity were unlabelled with antibodies to type V collagen, although labelled type V fibrils were frequently enmeshed among the type I fibers. Antibodies to type I collagen labelled these fibers but not the type V fibrils. The results indicate that in human amnion, type V collagen is a 12 nm diameter, unbanded fibril which extends from the lamina densa of the basal lamina into the adjacent interstitial matrix. We hypothesize that type V collagen functions as a network of anchoring fibrils between the cell basal lamina and the extracellular matrix, especially type I collagen fibres. Type V collagen thus appears to be a unique interstitial collagen.

Amnion↗
PubMed1980

["Autodesmosomes", desmosomes formed between apposing surface membranes of the same cell, in the human chorion laeve and amnion (author's transl)].

An unusual desmosome formation in the human amnion and chorion laeve is described. The macula adherens, found at the cell surface, forms contact zones between different parts of one and the same cell: autodesmosomes. These zones appear to seal off and trap compartments of various sizes formed by invagination of the extracellular space. Furthermore they are indistinguishable morphologically from intracellular desmosomes. Epithelial cells of the chorion laeve display autodesmosomes along the whole cell surface, however the basal surfaces of these cells are particularly rich in these structures. Amnion epithelial cells exhibit autodesmosomes on their basal surface only. These surfaces are deeply indented and the foldings, in many cases, reach into the nuclear region. In this area semidesmosomes are found. It is suggested that autodemosomes are formed by semidesmosomes which have approached and become adjacent to each other. Moreover, the presence, and relationship of the autodesmosomes to the extracellular compartments, perhaps indicate a novel metabolic regulatory function of the chorionic and amnionic cells.

Amnion↗
PubMedDate not supplied

Arginine vasopressin antagonism of oxytocin-stimulated PGE2 release from rabbit amnion cells and the activities of thioanalogs of oxytocin and arginine vasopressin.

Using rabbit amnion membranes devoid of arginine vasopressin receptors, we have shown that arginine vasopressin acts as a partial agonist and oxytocin antagonist. We examined peptides with modifications in position 8 to determine the basis for partial agonism/antagonism. The 8-thioanalog of oxytocin had about 40% of oxytocin activity in eliciting PGE2 release by amnion cells and a corresponding 40% affinity for oxytocin binding sites on amnion membranes. Arginine vasotocin, which has arginine at the position 8 and about 90% homology with arginine vasopressin also acted as a full agonist. These results suggest that determination of the oxytocin antagonist activity of arginine vasopressin is largely dependent on the amino acid at position 3. We also synthesized the 8-thioanalog of arginine vasopressin, which had a very low affinity for arginine vasopressin binding sites in rat liver (V1 receptors) and rat kidney medulla (V2 receptors) membranes. These findings suggest that arginine vasopressin receptors are much more sensitive to modifications of the peptide bond between positions 8 and 9 than are oxytocin receptors.

Amino Acid Sequence↗
PubMed1994

[Effects of calcium antagonists on prostaglandin E2 production in cultured human amnion cells].

The purpose of this study was to determine the effects of calcium antagonists on the production of prostaglandin E2 (PGE2) in human amnion cells. Primary monolayer cultures of human amnion cells were stimulated by interleukin-1 beta (IL-1 beta), and PGE2 in the culture media was measured. Dihydropyridine calcium antagonists nifedipine, nicardipine and nilvadipine inhibited PGE2 production in a dose-dependent manner with maximal inhibition of 60, 80 and 80%, respectively observed at 100 microM. However, nondihydropyridine calcium antagonists verapamil and diltiazem did not inhibit PGE2 production. On the other hand, EGTA reduced PGE2 production only 32%. In addition, nifedipine, nicardipine and nilvadipine inhibited a cell-free preparation of phospholipase A2 (PLA2) activity in a dose-dependent manner, but verapamil and diltiazem failed to reduce PLA2 activity. In conclusion, the evidence suggests that dihydropyridines inhibit PGE2 production in amnion cells by directly inhibiting PLA2 rather than its actions on calcium channels.

Amnion↗
PubMed1996

Differentiation potential of rat amnion.

The differentiation potential of rat amnion was investigated by explantation to different extrauterine sites and by culturing in vitro. Amnion differentiated into full skin by a process that is morphologically indistinguishable from normal skin development (interactions of the surface embryonic ectoderm and underlying mesenchyme). This process is not dependent on the age of the amnion but is dependent on the culture conditions used. Possible implications of these findings are discussed.

Amnion↗
PubMed1979

The amnion regulates movement of fetally derived alpha-fetoprotein into maternal blood.

The present investigation documents that, under normal conditions, most fetally produced AFP reaches the maternal circulation via diffusion across the amnion from amniotic fluid. This has been determined by comparing maternal serum AFP levels with amniotic fluid albumin concentrations in paired samples. The proportionally demonstrated between them indicates a proportional, transamniotic exchange of the two proteins, each originating on opposite sides of the amnion. Albumin is known to reach amniotic fluid by transamniotic diffusion from maternal blood. All amnions restrict AFP movement into maternal serum, but some are distinctly more restrictive than others; in such cases, a relatively greater increase in amniotic fluid AFP concentration would likely have to occur from a fetal lesion before being reflected in maternal serum. Inconsistencies found in several paired samples identify that other variables may also influence passage of AFP to the mother.

Amnion↗
PubMedDate not supplied

Ceramide stimulates prostaglandin production by human amnion and decidual cells.

OBJECTIVE: To determine whether ceramide regulates prostaglandin (PG) production by cultured human amnion cells and decidual cells independently of interleukin-1 beta (IL-1 beta). METHODS: Cells were grown in monolayer culture and then incubated with varying concentrations of ceramide, IL-1 beta, ceramide in the presence and absence of IL-1, and control media. Production of PGE2 was determined using a specific radioimmunoassay. RESULTS: Ceramide induced a significant concentration-dependent increase in PGE2 production by amnion cells and decidual cells. However, PGE2 production induced by IL-1 beta was significantly more than with ceramide alone, and there was no potentiation of PGE2 production with coincubation of ceramide and IL-1 beta. CONCLUSION: We suggest that term human amnion cells and decidual cells are responsive to ceramide independent of IL-1 beta and that generation of these substances in response to an infection in the uterus may lead to increased PG production by human gestational tissues, indicating that there are several mechanisms leading to PG production by these cells.

Amnion↗