Regulatory response to washout of amniotic fluid in sheep

To test the hypothesis that a substance present in the amniotic fluid could serve as a regulator of amniotic fluid volume, we drained and discarded amniotic fluid while replacing it with lactated Ringer solution that was isotonic to amniotic fluid. Seven ewes with singleton fetuses at 119 +/- 1 days of gestation (mean +/- SE) were instrumented with multiple indwelling catheters in the pedal artery, pedal vein, and amniotic cavity. During the exchange periods, an average of 3,019 +/- 171 ml/day of lactated Ringer solution was infused into the amniotic cavity while an equal amount of amniotic fluid was pumped out and discarded. During the control period, amniotic fluid composition and volume were not altered. Exchange and control periods started with the same amniotic fluid volume, lasted 3 or 4 days, and were randomized with regard to order. Amniotic fluid volume measured by vacuum drainage was 556 +/- 98 ml at the end of the control period and 986 +/- 209 ml (P = 0.03) at the end of the exchange period. Fetal arterial blood gases, hemodynamic parameters and the osmolality gradient between fetal plasma and amniotic fluid were not altered by the exchange process. A linear relationship between the control amniotic fluid volume and the volume at the end of the exchange period (P = 0.003) suggests that the animals with larger control volumes responded to isovolumic dilution with a larger volume increase. We conclude that amniotic fluid may contain a substance that regulates amniotic volume.     

Meconium-stained amniotic fluid activates polymorphonuclear leukocytes ultrastructural and enzyme-cytochemical evidence

The purpose of the present study was to demonstrate morphological evidence that meconium-stained amniotic fluid activates polymorphonuclear leukocytes. We used Boyden chamber techniques to determine the chemotactic activity of meconium-stained amniotic fluid for leukocytes, and ultrastructural enzyme-cytochemistry for peroxidase and alkaline phosphatase to characterize the leukocyte features induced by contact with meconium-stained amniotic fluid. Amniotic fluid with meconium staining enhanced migration of leukocytes. These leukocytes exhibited more numerous cytoplasmic processes and more prominent phagosomes compared to peripheral blood leukocytes. Peroxidase and alkaline phosphatase activity were evident on the phagosomal membranes. Our results indicate that meconium-stained amniotic fluid activates or stimulates polymorphonuclear leukocytes. Meconium-stained amniotic fluid induced leukocyte activation might play important roles in the pathophysiology of initiation of term labor or of the meconium aspiration syndrome.     

Soluble Leukocyte-Associated Ig-Like Receptor-1 in Amniotic Fluid Is of Fetal Origin and Positively Associates with Lung Compliance

The soluble form of the inhibitory immune receptor leukocyte-Associated Ig-like Receptor-1 (sLAIR-1) is present in plasma, urine and synovial fluid and correlates to inflammation. We and others previously showed inflammatory protein expression in normal amniotic fluid at term. We hypothesized that sLAIR-1 is present in amniotic fluid during term parturition and is related to fetal lung function development. sLAIR-1 was detectable in all amniotic fluid samples (n=355) collected during term spontaneous deliveries. First, potential intra-uterine origins of amniotic fluid sLAIR-1 were explored. Although LAIR-1 was expressed on the surface of amniotic fluid neutrophils, LAIR-1 was not secreted upon ex vivo neutrophil stimulation with LPS, or PMA/ionomycin. Cord blood concentrations of sLAIR-1 were fourfold lower than and not related to amniotic fluid concentrations and placentas showed no or only sporadic LAIR-1 positive cells. Similarly, in post-mortem lung tissue of term neonates that died of non-pulmonary disorders LAIR-1 positive cells were absent or only sporadically present. In fetal urine samples, however, sLAIR-1 levels were even higher than in amniotic fluid and correlated with amniotic fluid sLAIR-1 concentrations. Second, the potential relevance of amniotic fluid sLAIR-1 was studied. sLAIR-1 concentrations had low correlation to amniotic fluid cytokines. We measured neonatal lung function in a convenient subset of 152 infants, using the single occlusion technique, at a median age of 34 days (IQR 30-39). The amniotic fluid concentration of sLAIR-1 was independently correlated to airway compliance (ρ=0.29, P=.001). Taken together, we show the consistent presence of sLAIR-1 in amniotic fluid, which originates from fetal urine. Concentrations of sLAIR-1 in amniotic fluid during term deliveries are independent from levels of other soluble immune mediators. The positive association between concentrations of amniotic fluid sLAIR-1 and neonatal lung compliance suggests that amniotic fluid sLAIR-1 may be useful as a novel independent marker of neonatal lung maturation.     

Origin and developmental patterns of lactase and other glycosidases in sheep amniotic and allantoic fluid.

Intestinal lactase activity (with its associated cellobiase, 4-methylumbelliferyl-beta-galactosidase and -beta-glucosidase activities) was used as a specific intestinal marker enzyme to study the release of protein and enzymes of intestinal origin in sheep amniotic fluid during gestation. In amniotic fluid, intestinal lactase activity peaked at 66--85 days of gestation and then decreased with gestation. This enzyme activity was very low or absent in allantoic fluid throughout gestation suggesting that there is no important transfer of amniotic fluid lactase towards the allantoic cavity. Maltase and 4-methylumbelliferyl-alpha-glucosidase showed no statistically significant variation with gestation in both amniotic and allantoic fluid whereas alpha-galactosidase and N-acetyl-beta-hexosaminidase which were first higher in allantoic than in amniotic fluid increased in amniotic fluid to reach allantoic fluid levels near term. Such patterns are consistent with the suggestion that the fetal urine is a source of alpha-galactosidase and N-acety-beta-hexosaminidase activities and that sheep urine is first accumulated in the allantoic sac via the urachus up to 86--90 days of gestation and thereafter passes more and more into the amniotic sac.     

Comparison of the specific binding of cortisol in human amnion, amniotic fluid, and plasma

The purpose of this study was to compare the specific cortisol-binding protein found associated with human amnion with specific cortisol binding in human amniotic fluid and plasma. The electrophoretic mobility on polyacrylamide gels of the specific cortisol binding in amnion, amniotic fluid, and maternal plasma was identical. The influence of pH on cortisol binding activity was similar in all tissues and the cortisol binding was immunoprecipitable by a polyclonal antibody raised against human corticosteroid-binding globulin. The interaction of the cortisol binding protein with concanavalin A was studied in preterm amniotic fluid, term amniotic fluid, term amnion, and plasma from pregnant women at term and women under oral contraceptive treatment. Binding to concanavalin A was similar in term amnion and term amniotic fluid but was less than that found with both preterm amniotic fluid and term plasma. These results indicate that the cortisol binding protein associated with human amnion has similar characteristics to plasma corticosteroid-binding globulin, but that its state of glycosylation appears to be more like that of the cortisol binding protein in term amniotic fluid rather than in plasma.     

Proteolytic enzymes in human fetal membranes and amniotic fluid. A comparison of normal and premature ruptured membranes

The amniotic and chorionic membranes obtained at term and term amniotic fluid contain a soluble protease activity which cleaves [14C]-labeled globin at acid pH. In contrast, a salt extract of the pellet fraction obtained from the fetal membranes displays only negligible protease activities at the pH range of 4-8. Specific activities of the proteases in the soluble and salt-extractable fractions of fetal membranes which were intact before onset of labor were not significantly different from the respective activities in cases of premature rupture of fetal membranes (PROM). However, the protease activity of the amniotic fluid was found to increase with advancing gestational age and to reach maximal activity at term. A heat-sensitive and nondializable protease inhibitory activity was found in term amniotic fluid. This inhibitory activity acted on the cytosolic protease of amniotic membranes from control and PROM cases, but not on the soluble protease of chorionic membranes, and had a similar potency in fluids from PROM cases or fluids collected at term. These results do not support a role for fetal membrane proteases, amniotic fluid proteases, or amniotic fluid protease inhibitory activities in the etiology of PROM. However, the observed changes in amniotic fluid protease activity with fetal age suggest a physiological role for the enzyme in normal fetal development.     

Amniotic fluid testosterone and testosterone glucuronide levels in the determination of foetal sex

Unconjugated testosterone levels were assayed in 351 amniotic fluid samples obtained at 15-19 weeks gestation. The median values for unconjugated testosterone in the 166 female foetuses and 185 male foetuses were 137 and 712 pmol/l respectively. Sixteen amniotic fluid samples from male foetuses had unconjugated testosterone levels lower than the highest female unconjugated testosterone value (361 pmol/l). Testosterone glucuronide was measured in amniotic fluid from 48 female and 55 male foetuses. There was a significant sex difference in the median values of testosterone glucuronide between female (median 160 pmol/l, range 64-465 pmol/l) and male (median 817 pmol/l, range 68-3707 pmol/l) amniotic fluid specimens (P less than 0.001). Of the sixteen male foetuses with amniotic fluid unconjugated testosterone levels in the female range, 12 had amniotic fluid testosterone glucuronide levels within the male testosterone glucuronide range of values. Hence used in conjunction with unconjugated testosterone, testosterone glucuronide increased the predictive accuracy of foetal sexing from 95.4 to 98.9%. Testosterone sulphate was measured in 24 female and 25 male amniotic fluid samples. There was no Testosterone sulphate was measured in 24 female and 25 male amniotic fluid samples. There was no significant difference between female (median 2591 pmol/l) and male (median 2964 pmol/l) testosterone sulphate levels.     

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.     

Differences in amniotic fluid and maternal serum cytokine levels in early midtrimester women without evidence of infection

The amniotic fluid cytokine profile has been shown to be indicative of various disease states, and changes may be associated with preterm labor or infection. Anti-inflammatory cytokine profiles may be essential for successful normal pregnancy. However, there are currently few normative data on the concentration of cytokines in amniotic fluids during pregnancy. The aim of this study was to provide new amniotic fluid cytokine data for future comparative studies in disease states, notably in utero viral infections, and to compare these with maternal serum levels. Amniotic fluid was obtained from 100 pregnant women undergoing elective amniocentesis at the Royal Hospital for Women, Randwick. Concentrations of 27 cytokines were simultaneously measured in amniotic fluid and a subset of matching maternal sera (n=33) using a multiplex bead-based immunoassay system (Bio-Plex, Bio-Rad). To exclude infection, nested multiplex PCR targeting 17 known congenital infectious agents were performed on all amniotic fluid and maternal serum samples, and serological testing was also performed against some of these agents. Maternal serum concentration was positively correlated with amniotic fluid levels for MIP-1beta (r=0.39, P=0.027). IL-1ra was positively correlated to maternal age (r=0.210, P=0.036), and mean IL-5 levels were significantly higher in amniotic fluids from pregnancies with male fetuses than those with female fetuses (P=0.036). Normal amniotic fluid concentrations for five cytokines (IL-6, IL-8, IP-10, MCP-1, IL-1ra) were found to be significantly elevated over maternal serum concentrations in matched pairs (P<0.05). Concentrations of 12 cytokines (eotaxin, IFN-gamma, IL-9, IL-12, IL-15, IL-17, MIP-1alpha, MIP-1beta, RANTES, TNF-alpha, VEGF, PDGF bb) were significantly elevated in maternal serum compared to paired amniotic fluid at midtrimester (P<0.05). Amniotic fluid may be more representative of the fetal cytokine profile than cytokine analysis on antenatal sera as it represents predominantly fetal urinary and respiratory secretions. This study provides new normative data for multiple cytokine levels in amniotic fluid and maternal sera at 14-16 weeks gestation, and is a valuable tool for future diagnostic and comparative studies.     

Intestinal and renal origin of trehalase activity in rabbit amniotic fluid

To utilize specific fetal markers in amniotic fluid for prenatal detection of fetal anomalies, it is necessary to determine the precise tissue origin of these markers. In rabbit fetuses, we distinguished between intestinal and renal forms of trehalase (alpha,alpha'-trehalose-1-D-glucohydrolase, EC 3.2.1.28) in amniotic fluid on the basis of differences in net electric charges. Trehalase was solubilized from purified brush-border membranes of fetal rabbit kidney and intestine by Triton X-100 treatment, whereas the trehalase activity in amniotic fluid was soluble. The kinetic properties of trehalase from intestine, kidney and amniotic fluid were very similar. The Mr of the soluble amniotic fluid trehalase was between 72,600 and 66,300 from hydrodynamic parameters, depending on the amount of sugar bound to the enzyme, and 48,500 by radiation inactivation, a method which detects only the protein part of the enzyme. For membrane-bound trehalase from kidney and intestine in situ the radiation inactivation method also gave a molecular size of around 49,000. Isoelectric focusing of freshly solubilized membranes allowed us to distinguish between renal and intestinal forms of trehalase in rabbit fetuses on the basis of different isoelectric points. Each trehalase form was also present in the amniotic fluid but in varying proportions depending on the gestational age at which the amniotic fluid was collected. The results suggest that early in gestation amniotic fluid trehalase activity originates exclusively from the fetal kidney but that more and more intestinal enzyme is released into the amniotic cavity as the fetus develops. Similar results were also obtained when ion-exchange chromatography was used to separate the various trehalase forms. The development of trehalase activity in rabbit fetal kidney and intestine correlates well with its occurrence in the amniotic fluid; trehalase activity in the kidney develops early in gestation whereas the intestinal trehalase activity develops just before term.     

THE NATURE AND ORIGIN OF THE SOLUBLE PROTEIN IN HUMAN AMNIOTIC FLUID

1. Amniotic fluid surrounds the human fetus and is separated from the uterus by the amnion, chorion and placenta. The ability to obtain samples of amniotic fluid from women by a simple procedure has encouraged studies on the nature and origin of the fluid, and on its use for the diagnosis of a variety of clinical conditions. The fluid contains cells, which are of fetal origin, and can be grown in a tissue culture. Cyto-genetic and biochemical analyses can therefore be used to detect chromosomal aberrations and inborn errors of metabolism in the fetus. 2. The supernatant of amniotic fluid contains many of the solutes typical of extracellular fluid. In particular, it contains a wide range of proteins and those which are of fetal origin are likely to be of use in the prenatal diagnosis of fetal disease. This review examines the nature and origin of the soluble protein in amniotic fluid, and discusses the diagnostic uses of the proteins which are of fetal origin. 3. In other mammals, the arrangement of the fetal membranes is different from that in man, and these differences are reflected by changes in the nature of the amniotic fluid. Thus data from other animals have little applicability to man. 4. Electrophoresis and immunoelectrophoresis have established that the major proteins in amniotic fluid are also present in maternal and fetal sera. Their concentrations in the fluid are influenced by their molecular weight and proteins larger than about 2.5 times 10⁶ may be excluded. Towards term, phenotyping studies show that a number of serum proteins in amniotic fluid are of maternal origin. In the case of group-specific component (Gc) this has been shown to be so throughout pregnancy. Such proteins must enter the fluid by diffusing across either the chorion or the chorionic plate and then the amnion. 5. It has been previously claimed that various serum proteins in amniotic fluid are of fetal origin. For albumin and IgG there are data that strongly support a maternal origin. The evidence on the origin of insulin is inconclusive. The concentration of β₂-microglobulin in amniotic fluid exceeds that in maternal serum and is probably too high also for fetal serum to be its major source. It has a wide tissue distribution and probably enters the fluid from surrounding structures. 6. Alpha-fetoprotein in amniotic fluid is of fetal origin as it is present in maternal serum at far lower concentrations. It is found in fetal serum, urine and yolk sac, but it is not clear how it enters the amniotic fluid of normal fetuses. The concentrations of Gc and alpha-fetoprotein have been measured in amniotic fluid and in their sera of origin. The relative concentration of Gc in amniotic fluid was found to be much greater than that of alpha-fetoprotein and the concentration gradients of these marker proteins can be compared with data for other proteins. In this way further evidence has been obtained that the albumin, α₁,-antitrypsin and transferrin in amniotic fluid are mainly of maternal origin throughout pregnancy. 7. Immunological studies have shown that at least three proteins of non-serum origin are present in amniotic fluid and they have also been located in the amnion and uterine decidua. 8. The enzymes present in amniotic fluid are summarized. Many lysosomal enzymes are clearly of fetal origin since they show altered specific activities in the appropriate cases where the fetus is affected with an inborn error of metabolism. For other enzymes, analysis of specific activity gradients can help to decide the extent to which an enzyme is of serum origin, although this will not exclude the possibility of a maternal (uterine) contribution. The results of such analyses suggest that, relative to the serum protein in amniotic fluid, the greatest concentrations of the minor non-serum proteins in the fluid occurs between thirteen and eighteen weeks of pregnancy and also towards term. 9. Some inborn errors of metabolism may be diagnosed prenatally by measuring the specific activity of the respective enzyme in amniotic fluid. However, the presence of different enzymes with similar substrate specificities has prevented this in Pompe's disease. 10. In cases where the fetus is affected with anencephaly or spina bifida there is an increase in the concentration of alpha-fetoprotein in the amniotic fluid. This has provided a way of detecting these diseases early enough to allow termination of pregnancy. 11. The discovery of new proteins in fetal serum and in the tissues surrounding the amniotic cavity would seem to provide the best chance of extending the uses of amniotic fluid into the other areas of prenatal medicine.     

Biochemical characteristics of amniotic and allantoic fluid in late gestational mares

The purpose of this study was to determine certain clinically important parameters of amniotic and allantoic fluid. Amniocentesis was performed on 10 normal mares in late gestation (323.8±10.2 d) and fluid was collected from both amniotic and allantoic cavities. Compared to amniotic fluid, allantoic fluid had significantly higher values of specific gravity, sorbitol dehydrogenase, total bilirubin, gamma glutamyltransferase, creatinine, phosphorus, total protein, and globulin. However, allantoic fluid had significantly lower values for sodium, chloride and alkaline phosphatase than amniotic fluid.     

Stimulation of myometrial and decidual prostaglandin production by amniotic fluid from term,but not midtrimester pregnancies

The effect of amniotic fluid obtained from second trimester (16–20 wks) and term pregnancies (38–41 wks) on the production of PGE and F by human amnion, decidua and myometrium at term was determined using tissue slices incubated in vitro. Midpregnancy amniotic fluid neither inhibited nor stimulated the prostanoid production by any of the tissues. In contrast, term amniotic fluid obtained before as well as after the onset of labor markedly increased the production of both PGE and PGF in decidua and myometrium from levels in Krebs solution. The prostanoid production (PGE + PGF) in amnoin was not significantly increased but the proportion of PGF was raised during incubations in term amniotic fluid. In decidua and myometrium the increase in PGE and PGF production in term amniotic fluid was approximately 200 and 400 percent respectively, from control values in Krebs solution. We propose that the stimulatory activity in term amniotic fluid in responsible for the accelerated synthesis of prostaglandins after of membranes, which is reflected in raised PGF metabolite levels in maternal circulation. It may also be the reason for the rise in amniotic fluid prostaglandin levels around the 35th week of gestation, and perhaps for the onset of labor.     

Identification of phospholipid platelet-activating factor (1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine) in human amniotic fluid and urine

Human amniotic fluid and fetal urine were examined for the presence of phospholipid platelet-activating factor (PAF). PAF was detected in lipid extracts of some samples of amniotic fluid obtained from women in labor but it was undetectable in samples of amniotic fluid obtained before the onset of labor. PAF was identified by chromatographic mobility, platelet aggregation and chemical modifications. LysoPAF was also present in amniotic fluid at higher concentrations than those of PAF. Both PAF and lysoPAF were identified also in newborn and adult urine.     

Total cortisol and L/S-ratio in amniotic fluid in late pregnancies complicated by diabetes mellitus

68 samples of amniotic fluid from 47 women with varying severity of diabetes mellitus and 48 samples from 43 normal women were obtained in the 31st to 40th week of pregnancy before onset of labour. The concentration of total cortisol and the L/S-ratio in amniotic flud were determined and related to gestational age. There was a continous rise of total cortisol with advancing gestational age in the diabetic pregnancies similar to that found in normal pregnancy. Diabetic pregnancies were associated with slightly lower amniotic fluid cortisol levels without significant difference to values found in normal pregnancy. The severity of the disease did not affect the cortisol levels in amniotic fluid. There was no correlation between total cortisol levels and L/S-ratios in amniotic fluid. Determination of total cortisol in amniotic fluid can thus not replace measurements of L/S-ratios to predict fetal lung maturation.     

Acetylcholine increase in amniotic fluid of experimental rats for intrauterine growth retardation

Previous reports from this laboratory have demonstrated evidence for synthesis and release of acetylcholine (ACh) and catecholamines (CAs) by human amniotic epithelial cells (HAEC) and the presence of ACh and CAs in amniotic fluid. To study the physiological role of amniotic ACh, we used an experimental pregnant rat model for intrauterine growth retardation. Prior to this experiment, we confirmed the presence of choline acetyltransferase in the HAEC by immunocytochemical staining. Amniotic fluid was collected at 48 and 72 h after a transient ligation of the uterine vessels near the lower and upper ends of the right horn of the pregnant rat. The ACh concentration in the amniotic fluid from rats received intrauterine ischemia increased with time to a greater degree compared with the control rat, although the increase was not statistically significant. These results suggest that intrauterine hypoxic conditions cause a tendency to increase ACh concentrations in the amniotic fluid.     

Bovine amniotic and allantoic fluids for the culture of murine embryos

This study evaluated bovine amniotic and allantoic fluids as culture media for two-cell murine embryos to the hatched blastocyst stage. Amniotic and allantoic fluids were collected from four 70-d periods of pregnancy and pooled from at least five different animals. In Experiment 1 (n = 470) the fluids were frozen twice. Treatments consisted of twice frozen amniotic or allantoic fluid from each pregnancy period, Whitten's medium and fetal calf serum. The later two media were controls. Twice-frozen amniotic fluid <70 d pregnancy period, fetal calf serum and Whitten's medium supported the development of embryos to the hatched blastocyst stage. Whitten's medium was superior to twice-frozen amniotic fluid <70 d pregnancy period or fetal calf serum (P<0.01). Biochemical analysis showed lower glucose in amniotic and allantoic fluids than in Whitten's medium. Experiment 2 (n = 425) was performed to evaluate the effect of glucose supplementation to amniotic fluid. No benefit of glucose supplementation of the amniotic fluid was observed. In Experiment 3 (n = 432), the fluids were transported nonfrozen on ice. Treatments consisted of nonfrozen amniotic fluid <70 d pregnancy period; nonfrozen amniotic fluid <70 d pregnancy period + glucose), nonfrozen allantoic fluid <70 d pregnancy period; and Whitten's medium. The percentages of embryos developing to hatched blastocyst stage were 66.6, 56.5, 57.4 and 63.9% respectively, for each of the four treatments. No differences were found between any two treatments (P<0.05). In Experiment 4 (n = 231) the fluids were stored at -20 degrees C for 15 d. Whitten's medium was superior to amniotic or allantoic fluid <70 d pregnancy period in sustaining embryo development (P<0.05). In conclusion, these data indicate that nonfrozen bovine amniotic or allantoic fluid <70 d pregnancy period can support the development of murine embryos to the hatched blastocyst stage comparable to culture in Whitten's medium. Glucose supplementation of the amniotic fluid offered no advantage, and freezing of fluids had an adverse effect on in vitro embryo development.     

Prenatal diagnosis of congenital anomalies in an intrauterine growth retarded fetus

Summary Chromosome analysis of amniotic fluid cells and amniotic fluid alpha-fetoprotein determinations were used to investigate a fetus with severe intrauterine growth retardation in the third trimester. The karyotype was 47,XY,18+ and increased alpha-fetoprotein levels indicated the presence of congenital malformations. We suggest that when severe fetal growth retardation is detected early in the antepartum course, amniotic fluid alpha-fetoprotein and amniotic fluid cell chromosome studies be done to determine if congenital anomalies may be an etiological factor.     

羊水菌群的研究进展

传统观念认为胎儿在宫内发育的过程是无菌的。随着研究方法的快速发展,针对于微生物的研究方法从传统的培养到现代分子生物学检测的进步,研究者已经认识到胎盘、羊水中具有微生物的存在。目前的研究尚不能明确胎儿宫内胎盘、羊水的菌群来源及菌群转移的具体途径,但已有的研究提示羊水菌群最可能来源为母亲肠道、生殖道以及口腔。本文综述了研究者对羊水菌群认识的转变、羊水菌群的来源以及羊水菌群与早产的相关性。     

Alpha-fetoprotein and albumin in experimentally-induced exencephaly in the rat.

Alpha-fetoprotein and albumin were quantified in the sera and amniotic fluids from control, Vitamin A-treated non-exencephalic and Vitamin A-treated exencephalic rat fetuses. Exencephaly was associated with amniotic fluid alpha-fetoprotein concentrations which were significantly elevated over those of Vitamin A-treated non-exencephalic and of untreated fetuses. Amniotic fluid albumin concentrations also were higher in the exencephalic fetuses than in the non-exencephalic fetuses. Serum alpha-fetoprotein and albumin concentrations were lower in the exencephalic than in the non-exencephalic fetuses. The results are cosistent with simple diffusion across a defective barrier as the cause of elevated amniotic fluid alpha-fetoprotein concentrations in the presence of open neural tube defects. This experimental model of neural tube defects result in changes in amniotic fluid alpha-fetoprotein similar to those changes found in human amniotic fluid alpha-fetoprotein concentrations in the presence of neural tube defects.