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PubMed1993

Endothelin levels in human amniotic fluid at mid-trimester and at term before and during spontaneous labor.

Endothelin (ET)-1 is synthesized in human amnion and immunoreactive (ir) ET is present in amniotic fluid in concentrations 10- to 100-times those found in plasma. ET-1 is a potent uterotonin; therefore, the possibility must be considered that ET-1, derived from amnion/amniotic fluid, serves to promote the uterine contractions of human labor. In term pregnancies, after labor begins, the amniotic fluid normally becomes divided into the upper and forebag compartments as the fetal presenting part is engaged in the maternal pelvis. The forebag tissues are exposed in the vagina because of cervical dilatation. Vaginal fluid contains microorganisms, bacterial toxins, and cytokines, e.g., interleukin-1 beta, that oblige an inflammatory reaction. Increased ET-1 formation in these tissues of the forebag would be indicative that the greater rate of ET-1 formation and entry into amniotic fluid was an aftereffect of labor, not a cause of parturition. The levels of irET in amniotic fluid during the midtrimester of human pregnancy, 93.3 +/- 7.4 pmol/L (mean +/- SEM, n = 38), were significantly greater than those in amniotic fluid at term before the onset of labor, 39.8 +/- 4.1 (n = 33, p < 0.01). The levels of irET in the upper compartment during labor, 45.5 +/- 3.5 pmol/L (n = 40), were not significantly different from those in amniotic fluid before labor, but were significantly less (p < 0.01) than those in amniotic fluid of the forebag, 82.1 +/- 5.2 pmol/L (n = 125). These findings are suggestive that increases in the concentration of ET in amniotic fluid at parturition are confined to the forebag and are the result of ET formation after labor begins. Inflammation of the tissues lining the forebag compartment of the amniotic fluid is a normal consequence of labor. Therefore, the entry of inflammatory response mediators, some of which are uterotonins, viz., ET and prostaglandins, into forebag amniotic fluid is an aftereffect of labor and not indicative of a role for these agents (in amniotic fluid) in the initiation of parturition. In a subset of the amniotic fluids from normal pregnancies at term, prostaglandin (PG) levels also were determined. There was a highly significant correlation between the levels of irET and PGE2 in the forebag compartment (p < 0.0001); there was no correlation between irET and PGE2 levels in the upper compartment or in amniotic fluid collected at term prior to labor onset.(ABSTRACT TRUNCATED AT 400 WORDS)

Amniotic Fluid↗
PubMed1980

Prenatal diagnosis of neural tube defects. V. The value of amniotic fluid cholinesterase studies.

Total cholinesterase activity in amniotic fluid obtained from 150 fetuses was measured. Elevated values were found in 94% of samples from fetuses known to have neural tube defects (spina bifida, anencephaly) when compared to nonbloody samples from normal fetuses. Contamination of amniotic fluid with blood was observed to elevate total cholinesterase activity in some, but not all, such specimens. Total cholinesterase activity did not vary with gestational age between 15 and 24 weeks. These data were compared to our large alpha-fetoprotein (AFP) assay experience used for the prenatal detection of neural tube defects. We concluded that the assay of total cholinesterase activity in amniotic fluid could be a useful adjunct to the AFP assay, especially in those samples contaminated with blood.

Amniotic Fluid↗
PubMed1990

Human fetal intestinal alkaline phosphatase: molecular heterogeneity and immunological detection in amniotic fluids.

Human fetal intestinal alkaline phosphatase (fIALP) is present in amniotic fluids as free dimers (Mr 140,000) or membrane-bound through phosphatidylinositol residues. Extraction of corresponding particulate material with Triton X-100, resulted in release of tetrameric high Mr fIALP forms (Mr 380,000). In individual amniotic fluids, as well as in meconeum, both dimeric and tetrameric fIALP are sialylated to various extents. When measured by a double sandwich-ELISA, up to 10-fold higher fIALP antigen levels were found in amniotic fluids than when determined by an enzyme antigen immunoassay, based upon fIALP enzyme activity measurements. Frequency analysis of fIALP antigen levels, showed a more symmetrical distribution than analysis of fIALP enzyme activities; likewise, the lower 95% confidence limit, calculated for the fIALP antigen distribution curve, overlapped less with the bulk of values. In cystic fibrosis amniotic fluids, measurements of fIALP antigen levels resulted in a lower false-negativity outcome than fIALP enzyme activity measurements, whereas in amniotic fluids of trisomy pregnancies fIALP enzyme activities and fIALP antigen levels were equally unpredictive.

Alkaline Phosphatase↗
PubMed1997

[Evaluation of the intrauterine fetus in hypertension--biochemical assessment of amniotic fluid. IV. Ions].

Sixty two samples of amniotic fluid, collected by ultrasound guided amniocentesis, were submitted to biochemical investigation including 31 samples from women with pregnancy complicated by hypertension (studied group) and 31 samples deriving from healthy pregnant women (control group with). Both investigated and control groups consisted of pregnant women with the same gestational age of 37 +/- 2 weeks (34-40 weeks). The following ions were measured: NH4+, K+, Na+, Cl-, Mg++, total Ca, Ca++ and inorganic phosphorus (Pi). The ionic composition of amniotic fluid deriving from women with pregnancy complicated by hypertension was normal. The regular concentration of NH4+ ions in amniotic fluids of a studied group may suggest kidneys of the fetuses in pregnancy complicated by hypertension were as mature as in the normal pregnancy within the same gestational age.

Adult↗
PubMed1997

The analgesia-enhancing component of ingested amniotic fluid does not affect nicotine-induced antinociception in naltrexone-treated rats.

Ingestion of amniotic fluid and placenta by rats has been shown to enhance opioid-mediated antinociception but not affect the nonopioid-mediated antinociception produced by aspirin, suggesting specificity for opioid-mediated processes. However, enhancement by the active substance(s) in amniotic fluid and placenta (POEF, for placental opioid-enhancing factor) of antinociception produced by other nonopioid mechanisms has yet to be examined. The present experiments tested whether ingestion of amniotic fluid enhances the antinociception produced by nicotine injection. In Experiment 1A, enhancement of morphine-mediated antinociception by ingestion of amniotic fluid was demonstrated in a hot-plate assay. In Experiment 1B, rats pretreated with naltrexone were given an orogastric infusion of amniotic fluid or control (0.25 ml), then injected with nicotine (0, 0.075, 0.125, or 0.225 mg/kg subcutaneously), then tested for antinociception in a hot-plate assay. Amniotic fluid ingestion did not enhance the antinociception produced by various doses of nicotine. In Experiment 2, rats pretreated with naltrexone were given an orogastric infusion of amniotic fluid (0, 0.125, 0.25, or 0.50 ml) and then injected with 0.125 mg/kg nicotine. None of the doses of amniotic fluid enhanced the nicotine-induced antinociception. The findings of these experiments lend support to our contention that the enhancement by POEF of antinociception is specific to opioid-mediated processes.

Amniotic Fluid↗
PubMed2006

Micelles of pulmonary surfactant in human amniotic fluid at term.

Studies using in vitro analysis have shown that the interaction between pulmonary surfactant and vernix caseosa could explain the appearance of amniotic fluid turbidity. That phenomenon is interpreted based on the "roll-up" hypothesis. We tested the roll-up hypothesis by examining the presence of micelles of pulmonary surfactant in human amniotic fluid at term. Amniotic fluid samples were collected from each of six healthy pregnant women at term and at 16 wk of gestation. These samples were stained negatively and analyzed using an electron microscope. Ultrastructures present in amniotic fluid were compared with the structure of micelles derived from suspended surfactant TA isolated from bovine lung. Surfactant TA formed spheroidal and rod-shaped micelles 10-70 nm in diameter above the critical micelle concentration. Identical micelle particles were described in human amniotic fluid at term. In addition, surfactant protein B was identified in the micelle fraction of amniotic fluid. However, no micelles were found in human amniotic fluid taken at 16 wk of gestation. Our results support the view that pulmonary surfactant could induce the detachment of vernix caseosa and increase the turbidity of the amniotic fluid.

Amniotic Fluid↗
PubMed1999

Meconium and amniotic fluid embolism: effects on coagulation in pregnant mini-pigs.

OBJECTIVE: A hallmark of amniotic fluid embolism is the induction of coagulation defects. Little is known about the nature of these defects or the causative agent or agents. The purpose of this study was to assess the effects of meconium containing (native) meconium-amniotic-fluid infusion (MAFI) and meconium-free (centrifuged) amniotic-fluid infusion (AFI) on the coagulation system in the mini-pig model. DESIGN: Laboratory study. SETTING: University institute animal laboratory. SUBJECTS: Near-term pregnant Göttingen bred mini-pigs in three groups (control, MAFI, AFI) of six animals each. INTERVENTIONS: After induction of anesthesia, amniotic fluid was collected by cesarean section in all animals. Depending on the group, animals received either Ringer's solution (control), native amniotic fluid (MAFI), or centrifuged amniotic fluid (AFI) via an ear vein. MEASUREMENTS AND MAIN RESULTS: Blood samples were taken from a central vein before infusion (baseline), immediately after infusion, every 10 mins until 90 mins after infusion, and finally, every 20 mins until 150 mins after infusion. The following parameters were measured: Platelets, partial thromboplastin time, prothrombin time, fibrinogen, factors V, VII, VIII, antithrombin III, and protein C. The values relative to baseline in the MAFI and AFI groups were compared with control by rank order test. A p<.05 was considered statistically significant. Compared with the control group, platelets were lower in the MAFI group (p<.005), PTT was prolonged in both the MAFI and AFI groups (p<.005), fibrinogen was lower in both the MAFI and AFI groups (p<.05), prothrombin index was lower (i.e., prothrombin time was prolonged) in the MAFI group (p<.05), and protein C was lower in the MAFI group (p<.005). CONCLUSIONS: Both MAFI and, to a much lesser extent, AFI cause an activation of coagulation in mini-pigs. The changes induced by meconium-free AFI are probably not sufficient to explain the high mortality of the condition.

Amniotic Fluid↗
PubMed1977

Composition of amniotic fluid with experimental jejuno-ileal atresia.

The possibility that the composition of amniotic fluid is significantly altered with fetal intestinal obstruction was examined in 15 normal, 15 sham operated and 15 ewes in which jejuno-ileal atresia was created by devascularizing a 15 cm intestinal segment in the fetus at 90--100 days gestation. Samples of amniotic fluid for osmolality, urea N, creatinine, electrolytes, amylase, lipase, bilirubin, and proteins were obtained at 100 days gestation and at C-section performed 5 days prior to the anticipated date of delivery. One sham operated and four operated fetuses aborted prior to term for an 83% overall fetal survival rate. All surviving operated animals had total intestinal obstruction with the classical appearance of jejuno-ileal atresia. The volume of amniotic fluid at term varied from gelatinous material to as much as 1.0 liter of clear yellow to dark orange fluid. Amniotic fluid composition in term animals was not significantly different from those at 100 days gestation when the creatinine was below 15 mg%. However, sodium and chloride were significantly elevated in all groups at term when the creatinine was above 15 mg%. The osmolality and urea N in the latter group was not significantly different from animals at 100 days gestation. The amylase, lipase, total proteins, albumin, total and direct, and bilirubin in control animals at term was not significantly different from sham operated and experimental subjects. This study suggests that routine amniocentesis in the "high risk" patient would not be diagnostic of fetal intestinal obstruction.

Amniotic Fluid↗
PubMed2000

[Fibronectin level in amniotic fluid as an index of unavoidable labor].

During uterus contractions detaching of amino-chorionic layer from uterus wall occurs and released fibronectin penetrates into amniotic fluid. The aim of this study was to estimate in a quantity mode the presence of fibronectin in amniotic fluid and to find the dependence between the fibronectin level in amniotic fluid and the period of time from collecting the sample to the labor. We wanted also to find the dependence between fibronectin level in amniotic fluid and duration of pregnancy, preterm rupture of amniotic membranes, patients' age, parity and number of deliveries. We analysed 86 pregnant women where we estimated the fibronectin level in specimens of amniotic fluid. During carrying out the experiment we noted that fibronectin is present in amniotic fluid and can be identified in a quantity mode. We have proved dependence between fibronectin level in amniotic fluid and the period of time from collecting the sample, up to the delivery. Fibronectin level in amniotic fluid in pregnancies uncomplicated with premature delivery was on the average 350 mg/ml. Increase of fibronectin in amniotic fluid above 700 mg/ml points at detaching of amino-chorionic layer and the occurrence of unavoidable preterm labor at the time no longer than 24 hours. Fibronectin level in amniotic fluid doesn't depend of pregnancy duration, preterm rupture of amniotic membranes.

Adult↗
PubMed1994

Low amniotic fluid glucose levels are a specific but not a sensitive marker for subclinical intrauterine infections in patients in preterm labor with intact membranes.

OBJECTIVE: The purpose of this study was to evaluate the ability of a low amniotic fluid glucose level, as defined by previously published thresholds, to identify a subclinical intrauterine infection in women in preterm labor with intact membranes. STUDY DESIGN: Amniotic fluid glucose levels, amniotic fluid cultures, and placental histologic characteristics were determined in women with preterm labor (n = 55) and in preterm controls (n = 58). These amniotic fluid glucose levels were compared between women with and without intrauterine infection using the Mann-Whitney U test. The sensitivity, specificity, and positive and negative predictive values for the identification of an intrauterine infection were determined with four different previously published amniotic fluid glucose threshold levels and the threshold from receiver-operator characteristic curve analysis of the study data. RESULTS: The median amniotic fluid glucose level was significantly lower in patients with positive amniotic fluid cultures (intraamniotic infection group) but was not lower in the group of patients with only histologic chorioamnionitis (extra-amniotic infection group), compared with noninfected controls. The sensitivity of a low amniotic fluid glucose level to detect both types of intrauterine infection ranged from 41% to 55%, depending on the threshold used. The specificity of a low amniotic fluid glucose level to detect an intrauterine infection ranged from 94% to 100%, the positive predictive value ranged from 86% to 100%, and the negative predictive value ranged from 70% to 80% with the same thresholds. CONCLUSION: Low amniotic fluid glucose levels are a specific but not a sensitive marker for either intraamniotic or extra-amniotic intrauterine infections in patients with preterm labor.

Amniotic Fluid↗
PubMed1984

Amniotic fluid volume and in vivo permeability of ovine fetal membranes.

Serial measurements of amniotic fluid volume were made using a tracer dilution technique in sheep during the last half of gestation. No consistent trends were observed in amniotic fluid volume changes over this period. Disappearance of tracer-labeled urea and water from the amniotic fluid was observed at various gestational ages during the last half of pregnancy. The rate of disappearance of urea from the amniotic fluid decreased with gestational age. The disappearance rate of water did not change. Relationships between disappearance rates and amniotic fluid volume suggest that the permeability of the fetal membranes may be important in determining amniotic fluid volume.

Amniotic Fluid↗
PubMed1998

Expression of N-linked sialyl Le(x) determinants and O-glycans in the carbohydrate moiety of human amniotic fluid transferrin during pregnancy.

Transferrin, a glycoprotein involved in iron transport in body fluids, was isolated from amniotic fluid of a hydramniospatient by sequential anion-exchange chromatography and gel filtration. The N-glycans of human amniotic fluid transferrin (hAFT) were enzymatically liberated by PNGase-F digestion, isolated by gel filtration and fractionated by (high-pH) anion-exchange chromatography. After alkaline borohydride treatment of native hAFT, the released O-glycans were isolated by gel filtration and fractionated by anion-exchange chroma-tography. Structure elucidation of 14 N- and 2 O-glycans was performed by 500 or 600 MHz1H-NMR spectroscopy. Besides conventional N-glycans established earlier for human serum transferrin (hST), new (alpha1-3)-fucosylated N-glycans were found, representing sialyl Le(x) elements. Furthermore, as compared to hST, a higher degree of (alpha1-6)-fucosylation and an increase in branching from di- to triantennary compounds has been detected. The presence of O-glycans is demonstrated for the first time in transferrin.

Amino Acids↗
PubMed1983

Quantitative enzyme antigen immunoassay of acetylcholinesterase in amniotic fluid.

An enzyme immunoassay for acetylcholinesterase in amniotic fluid is described. Rabbit antiserum (IgG fraction) against human erythrocyte membrane acetylcholinesterase is first attached to microtitre plates. Samples containing acetylcholinesterase are added and the enzyme activity is then measured, with acetylthiocholine as substrate and Ellman's reagent as coupling salt. Results are comparable with those by qualitative determination of the enzyme after polyacrylamide gel electrophoresis, except for blood-contaminated amniotic fluids. One person can perform 200 enzyme analyses per day. Intra- and interassay coefficients of variation are less than 5% at concentrations from 15 to 450 arb. units/L. The mean catalytic concentration in 400 amniotic fluid samples was 21 arb. units/L (range 5 to 70 arb. units/L) with 1000 arb. units/L for a human serum pool as standard. All 39 cases of neural tube defects and two-thirds of cases with omphalocele and gastroschisis had abnormally high values, exceeding 75 arb. units/L.

Acetylcholinesterase↗
PubMed1990

Epidermal growth factor (EGF) concentrations in amniotic fluid and maternal urine during pregnancy.

Epidermal growth factor (EGF) was measured in amniotic fluid and maternal urine from women undergoing amniocentesis for genetic studies (15-22 weeks' gestation, n = 36) and lung maturational studies (35-39 weeks' gestation, n = 20). Amniotic fluid EGF concentrations (mean +/- SD) were higher near term (87 +/- 71 pM) than mid-gestation (35 +/- 8 pM) (p less than 0.0001). Urinary EGF concentrations were higher near mid-gestation (53.9 +/- 30.8 micrograms EGF/g creatinine) than near term (33.4 +/- 14.1 micrograms EGF/g creatinine) (p less than 0.006). There was no correlation between individual amniotic fluid and urinary EGF concentrations. The amniotic fluid EGF concentrations correlated with gestational age. However, there was no relationship between EGF concentrations and pulmonary maturity studies or placental weight from the pregnancies studied near term. We conclude that the concentration of EGF in amniotic fluid increases towards term. The lack of correlation between amniotic fluid and maternal urinary EGF concentrations suggests that there probably is a different source of EGF in the two compartments and that EGF does not cross the placenta to any great extent.

Amniocentesis↗
PubMed1983

[Experimental studies on amniotic fluid embolism].

The circulatory state of the so-called experimental amniotic fluid embolism (AFE) was studied in 39 dogs. The repeated infusion of a large quantity of human amniotic fluid had not produced the symptoms of AFE. But the infusion of human meconium-stained amniotic fluid, meconium suspension, its supernatant or boiled meconium suspension, or canine bile had produced the various typical shock symptoms of AFE. In these cases the shock effects were especially strong in the infusion of meconium suspension and the meconium-stained amniotic fluid. In these shock symptoms, arterial pressure decreased quickly after the infusion. When sudden death was fortunately avoided, right ventricular pressure increased and increases in pulmonary arterial pressure and pulmonary vascular resistance were indicated. In most cases cardiac output decreased. Central venous pressure increased suddenly before death. These experiments suggested that the pulmonary vasoconstriction was produced by the chemical factors in the amniotic fluid and by vasoactive substances released from the embolized lung. It also seemed that this pulmonary vasoconstriction rather than mechanical obstruction of pulmonary arterioles was probably the major cause of the shock symptoms of AFE.

Animals↗
PubMed1997

Longitudinal measurement of amniotic fluid index in term pregnancies and its association with intrapartum fetal distress.

OBJECTIVE: The aim of the present study was to evaluate the dynamic changes in serially obtained amniotic fluid index values and to determine any association with intrapartum fetal distress in a term population. MATERIALS AND METHODS: All patients, > or = 40 weeks of gestational age, evaluated at the Institute of Obstetrics and Gynecology, 'G. Salesi' Hospital, University of Ancona, between January 1, 1994, and December 31, 1995, participated in this longitudinal study. Women with an amniotic fluid index of > 50 mm, who also demonstrated a reactive nonstress test, underwent semiweekly amniotic fluid assessment until spontaneous labor. After 42 gestational weeks, the patients underwent an elective induction of labor. All patients were managed with continuous electronic fetal heart rate monitoring throughout labor. The incidence of intrapartum fetal distress, and meconium staining of amniotic fluid were evaluated with respect to the amniotic fluid index. RESULTS: Of the 117 patients that were evaluated by ultrasound, 83 women had multiple amniotic fluid index measurements and were enrolled in the study. A serial decrease in amniotic fluid index was documented in 54 women; the mean decrease per week was 20.7 +/- 15.4%. An increase in amniotic fluid index was noted in 17, while 11 women showed no change in amniotic fluid index over time. The 14 patients who underwent cesarean section for fetal distress had a significantly lower amniotic fluid index (p < 0.001) at the last sonographic examination than the normal outcome group. Significant differences were also observed for a serial decrease in the amniotic fluid index within a week (p < 0.001). The sensitivity and specificity of the 30% serial decrease in the amniotic fluid index cutoff point, with respect to intrapartum fetal distress were 86 and 93%, respectively. CONCLUSION: Longitudinal measurement of the amniotic fluid index seems to be an effective method in predicting intrapartum fetal distress in a term population.

Amniotic Fluid↗
PubMed1976

[Immunoglobulins and antibody titre in amniotic fluid of Rh-isoimmunized pregnant women (author's transl)].

On 90 samples of amniotic fluid coming from 54 cases of Rh-isoimmunization submitted to amniocentesis one or more times, the following tests were done: 1.) Coombs indirect test; 2) immunoelectrophoresis; 3) quantitative determination of immunoglobulins. The results were related to the degree of immunization as determined by Coombs indirect test on the mothers' serum and spectrophotometric curve of the amniotic fluid. For reasons of comparison, quantitative determination of immunoglobulins were performed on samples of amniotic fluid from 39 pregnant non-immunized patients. It was found that there was a direct relationship between antibody titers in the mothers' serum and those in the amniotic fluid, with the latter values always being inferior. Moreover, it was found that the level of IgG in the amniotic fluid and the degree of maternal immunization were proportional, with higher titers in the more severe cases. In addition to the routine tests, the determination of anti-Rh antibodies and titers of IgG in amniotic fluid can be useful in further evaluating degree of immunization in Rh-incompatibility. Furthermore, small quantities of IgA were found in amniotic fluid: these IgA were probably of secretory type (SIgA) and of amniotic origin, and therefore independent of any active immunization. Finally, all determinations of IgM were negative.

Amniocentesis↗
PubMed1978

Amniotic fluid fibronectin. Characterization and synthesis by cells in culture.

A glycoprotein immunologically related to plasma cold-insoluble globulin (CIG) and fetal skin fibroblast fibronectin has been purified from second-trimester human amniotic fluid. This protein (amniotic fluid fibronectin) migrated more slowly than CIG on sodium dodecyl sulfate gel electrophoresis and showed greater polydispersity which could result, at least in part, from heterogeneity in glycosylation. Cloned human amniotic fluid epithelioid and fibroblastic cells synthesized and secreted a protein with similar properties into the culture medium. Fibronectin was shown to be associated with the pericellular and extracellular matrix of cultured amniotic fluid cells by immunofluorescence, lactoperoxidase-catalyzed iodination, and labeling with ferritin-conjugated antibodies. The kinetics of secretion of the protein were consistent with its role as a matrix protein. We anticipate that amniotic fluid fibronectin will prove to be the same protein which elsewhere in the body is incorporated into connective tissues and basement membranes. Amniotic fluid could, therefore, serve as a convenient source of in vivo synthesized fibronectin for biological and structural studies.

Amniotic Fluid↗