Studies of the mechanism of amniotic sac puncture-induced limb abnormalities in mice

The principal advantage of chorionic villus sampling (cvs) over amniocentesis for the determination of the genetic constitution of the embryo is that it may be undertaken earlier in pregnancy. If carried out too early in pregnancy, it has the risk of inducing craniofacial and limb abnormalities, a condition termed the oromandibulofacial limb hypogenesis (OMFL) syndrome in genetically normal infants. It is believed that the defects observed have a vascular origin, possibly due to anoxia of tissues due to fetal blood loss or thrombus formation at the site of biopsy with distal embolization. We believe that this does not adequately explain the findings from the experimental animal literature involving amniotic sac puncture (ASP). Based on these experimental findings, we have hypothesised that (i) the defects observed following cvs may result from the consequences of oligohydramnios following the inadvertent puncturing of the amniotic sac during this procedure, and (ii) that cleft palate and the postural limb defects observed (e.g., clubfoot and clubhand) are secondary to embryonic/fetal compression. Our experimental studies shed new light on the mechanism of induction of the limb defects seen, but particularly syndactyly. Evidence of hypoperfusion of the peripheral part of the developing limb bud is observed, which interferes with apoptosis that occurs in the digital interzones, or induces an abnormal degree of cellular proliferation and/or tissue regeneration in these sites, possibly because of over-expression of critical genes involved in limb pattern specification. Cleft palate, tail abnormalities and abnormalities of sternal ossification are also observed in our model.     

Subcellular effects of experimental oligohydramnios on the developing rat limb

In the rat, the development of the limb bud can be impaired by amniotic puncture. Selective haemorrhages are observed within 1 hour of the treatment. An ultrastructural analysis was undertaken to uncover the cytological changes associated with these haemorrhages. The earliest effect of oligohydramnios is the appearance of a periendothelial oedema which separates the mesodermal cellular processes from the endothelial basal lamina. The loosening of the latter and the distortion of the endothelial cells occur almost simultaneously. Subsequent damage of the mesodermal cells ensues, the ectoderm and the preskeletal condensations remaining unaffected. Only general damage of the embryo affecting all tissues will lead to the complete necrosis of the limb bud and even to foetal death. The great variability of skeletal defects observed in amniocentesis syndrome can be accounted for by the higher resistance of the differentiating cells to a decrease in blood supply.     

Amniotic Fluid Cells; Prenatal Sex Prediction and Culture

Sex chromatin studies were carried out on small amounts of amniotic fluid obtained by amniocentesis or from intact amniotic sacs removed at hysterotomy. Provided that satisfactory preparations were obtained the accuracy of fetal sexing was 87%. Nevertheless, in the management of a pregnancy in which there is a risk of a serious X-linked recessive disorder, repeat amniocentesis may be necessary to ensure satisfactory specimens.Of 90 samples of fluid cultured, satisfactory growth was obtained in 49; the success rate was not increased by the addition of stimulants to the culture medium. It is suggested that between the 13th and the 16th week of pregnancy is the optimum time for amniocentesis to obtain cells for culture, since sufficient cells are then present in a small volume of fluid and therapeutic abortion would still be possible once the results were available.     

The concurrence of ring constrictions in Adams-Oliver syndrome: additional evidence for vascular disruption as common pathogenetic mechanism.

We report on a girl with congenital scalp and acral reduction limb defects, consistent with the diagnosis of Adams-Oliver syndrome. The presence of constriction rings makes the limb anomalies in this case similar to those seen in the amniotic band disruption sequence. Vascular disruption--with or without secondary amniotic rupture--may be responsible for the observed anomalies. Therefore we believe that the present observation adds further evidence for the hypothesis that the Adams-Oliver syndrome is a vascular disruption sequence.     

Problems posed by prenatal diagnosis of abdominal wall malformations

The authors present 6 observations of in utero detected abdominal wall defect : 2 laparoschisis and 4 omphaloceles. In three cases the diagnosis have been done prior week 20, by systematic AFP assay for amniocentesis performed for cytogenetic or metabolic reasons; the pregnancy was terminated. In three other cases, the pregnancy was complicated by hydramnios after week 30; amniocentesis for AFP and echography were performed to detect fetal malformations after associated with hydramnios. The detected abdominal wall anomaly was not alone: two fetus had an abnormal caryotype (trisomy 18), three other presented a polymalformative syndrome, a Beckwith-Wiedemann syndrome was discussed for the last child. The in utero diagnosis of omphalocele or laparoschisis implicates difficulties for genetic counselling, particularly if the diagnosis is done prior week 20. These anomalies can be treated with surgical management, but frequency of associated malformations must be underlined. it is important for genetic counselling to know the family history, the amniotic fluid cells caryotype, and an ultrasound scanning performed to reveal any other malformations.     

Maternal cell contamination in amniotic fluid samples as a consequence of the sampling technique

Maternal cell contamination in amniotic fluid samples is easily detected by in situ hybridization if the karyotype of the fetus differs from the karyotype of the mother. One out of two amniotic fluid samples appears to contain more than 20% maternal cells. Bloody samples often contain even more than 50% maternal cells. Maternal cells can also be identified on the basis of their nuclear morphology. Maternal cell contamination is regularly observed in pregnancies with an anterior placenta, whereas it is rare in posterior placenta pregnancies. The maternal cells are therefore thought to be artificially introduced into the amniotic fluid sample, as a result of placental bleeding during amniocentesis. The implications of maternal cell contamination for prenatal diagnosis using uncultured amniotic fluid samples are discussed.     

Familial Down's syndrome.

A family is reported in which the same mother conceived two children with trisomy 21. The pregnancy with the second affected child was interrupted after diagnostic amniocentesis. Maternal chromosome analysis was normal. This family and those previously reported suggest that there is an increased recurrence risk of trisomy 21 after the birth of an affected individual, possibly caused by a genetic tendency for non-disjunction. After the birth of a child with Down's syndrome, amniocentesis and chromosome analysis of cultured amniotic fluid cells is indicated in each further pregnancy, irrespective of maternal age.     

Chromosome Analysis before Birth and its Value in Genetic Counselling

Chromosome analysis of amniotic cell cultures was achieved in 29 out of 30 consecutive patients who were referred for genetic counselling during pregnancy. Amniocentesis was performed without any apparent untoward maternal or fetal complication. The only pregnancy terminated was that of a carrier of X-linked granulomatous disease, in whom the amniotic cells showed that the fetus was male and also had Down''s syndrome (trisomy G). Chromosome analysis in the remaining 28 patients showed normal karyotypes. The interval between amniocentesis and a definitive karyotype varied from 7 to 31 (average 18·4) days.The reliability of chromosome analysis from amniotic cell culture and of fetal sex determination by means of the sex chromatin and Y-fluorescence techniques was studied further in amniotic fluid from cases of therapeutic abortion and of rhesus incompatibility. The fetal sex was correctly determined in all cases. It is concluded that antenatal diagnosis of genetic disease by amniocentesis now permits a more practical approach to genetic counselling.     

Prenatal diagnosis of Meckel syndrome

Summary The three main features of Meckel syndrome are encephalocele, polycystic kidneys, and polydactyly. Prenatal diagnosis of a fetus with Meckel syndrome was made in the 16th week of gestation by means of amniotic fluid alpha₁ fetoprotein estimation. The indication for amniocentesis was a previous child with an occipital meningocele and polycystic kidneys. Interpretation of the alpha₁-fetoprotein value (240 g/ml) was difficult due to fetal blood contamination. Prenatal diagnosis is indicated in any pregnancy following the birth of a child with only two major symptoms of Meckel syndrome.     

Amniotic Fluid Deficiency and Congenital Abnormalities both Influence Fluctuating Asymmetry in Developing Limbs of Human Deceased Fetuses

Fluctuating asymmetry (FA), as an indirect measure of developmental instability (DI), has been intensively studied for associations with stress and fitness. Patterns, however, appear heterogeneous and the underlying causes remain largely unknown. One aspect that has received relatively little attention in the literature is the consequence of direct mechanical effects on asymmetries. The crucial prerequisite for FA to reflect DI is that environmental conditions on both sides should be identical. This condition may be violated during early human development if amniotic fluid volume is deficient, as the resulting mechanical pressures may increase asymmetries. Indeed, we showed that limb bones of deceased human fetuses exhibited increased asymmetry, when there was not sufficient amniotic fluid (and, thus, space) in the uterine cavity. As amniotic fluid deficiency is known to cause substantial asymmetries and abnormal limb development, these subtle asymmetries are probably at least in part caused by the mechanical pressures. On the other hand, deficiencies in amniotic fluid volume are known to be associated with other congenital abnormalities that may disturb DI. More specifically, urogenital abnormalities can directly affect/reduce amniotic fluid volume. We disentangled the direct mechanical effects on FA from the indirect effects of urogenital abnormalities, the latter presumably representing DI. We discovered that both factors contributed significantly to the increase in FA. However, the direct mechanical effect of uterine pressure, albeit statistically significant, appeared less important than the effects of urogenital abnormalities, with an effect size only two-third as large. We, thus, conclude that correcting for the relevant direct factors allowed for a representative test of the association between DI and stress, and confirmed that fetuses form a suitable model system to increase our understanding in patterns of FA and symmetry development.     

Amniotic fluid cell morphology in early antenatal prediction of abortion and low birth weight.

The morphology of rapidly adherent (RA) amniotic fluid cells was examined in 201 pregnant women referred for amniocentesis because of two sequential high serum alpha-fetoprotein (AFP) concentrations. Out of 43 amniotic fluid samples containing increased amounts of AFP, 42 had neural or peritoneal cells predominating among the RA cells, the outcome being an infant with a neural-tube defect or exomphalos. In the other case with a raised amniotic fluid AFP concentration but only anterior placental cells the infant was normal. In 25 amniotic fluid samples containing normal amounts of AFP distinctive new patterns of RA cells were observed, termed fetal distress cells. These pregnancies resulted in five spontaneous abortions and 20 infants with birth weights under 2500 g. Fetal distress cells were not detected in any of the remaining 133 samples. One pregnancy was terminated because of a chromosomal abnormality, and there were seven twin pairs not recognised on ultrasonography before amniocentesis. The remaining 125 pregnancies went to term, resulting in infants with birth weights exceeding 2500 g. The results suggest that RA-cell morphology will prove to be of value in the early antenatal prediction of spontaneous abortion and low birth weight.     

Specificity and sensitivity of S100B levels in amniotic fluid for Down syndrome diagnosis

Down syndrome (DS) is the most common chromosomal abnormality and is associated with an extra copy of the chromosome 21. Although several markers are commonly used during pregnancy for the screening of DS, the definitive diagnosis is based on karyotype after amniocentesis, which is an expensive and laborious analysis. S100B is an astrocyte protein which had its gene mapped to the long arm of chromosome 21. Previous preliminary reports have found increased levels of this protein in the amniotic fluid of DS gestations. Aiming to achieve a simpler and cheaper test then karyotype to perform prenatal diagnosis of DS, here we have extended our previous studies and evaluated the real usefulness of amniotic S100B measurement for prenatal DS diagnosis. We have measured S100B in amniotic fluid of 96 pregnancies with DS and of 50 normal pregnancies. Pregnancies with DS presented significantly higher amniotic fluid S100B levels (M = 1.16 ng/mL; IQ = 0.83/1.78) than normal pregnancies (M = 0.51 ng/mL; IQ = 0.38/0.83) (p < 0.0001). A receiver operating characteristic (ROC) curve was performed to evaluate the sensitivity and specificity of S100B for DS diagnosis, and presented an area under the curve (AUC) of 0.82, indicating that S100B could be a reliable marker of DS. Moreover, values above 1.67 ng/mL were present only in DS fetuses, representing about 30% of affected pregnancies. However, as an overlap of values was observed between normal and DS gestations, we concluded that amniotic S100B alone is not a good test to discard DS diagnosis.     

Influence of Amniotic Fluid Volume on Lecithin Estimation in Prediction of Respiratory Distress

One hundred samples of amniotic fluid were obtained by amniocentesis from 82 patients at different stages of normal and abnormal pregnancies. The concentration of lecithin was estimated together with the volume of the amniotic fluid, using the dilution technique. Thus the total quantity of lecithin in any amniotic sac could be calculated. While confirming the findings of others that concentrations of lecithin below 3·5 mg/100 ml in the liquor immediately before delivery suggested that the baby was likely to develop respiratory distress syndrome, we found that in borderline cases the total amount of lecithin in the sac was of greater prognostic significance than the lecithin concentration.     

Contribution of amniocentesis to prenatal screening of neural tube closing defects: evaluation of 10 years of a center's experience

The authors report retrospective data on analysis of amniotic fluid DFTN markers (AFP and AChE) from 306 cases. Data were obtained from 261 amniocentesis done because there was a recurrence risk of DFTN and from 45 amniocentesis done because an anomaly as DFTN was diagnosed with ultrasonography. Results first show that the risk of recurrence is 3.03% in Rh?ne-Alpes area. In utero exposure to valproate appears as new indication for amniocentesis, in view of the possible association between Spina-Bifida and prenatal-valproate exposure (1/8 in the study). In contrast to anencephaly, Spina Bifida can be difficult to diagnose with ultrasonography before 20 weeks and require amniocentesis with AFP and AChE study.     

Ring chromosome 17. Case report and review of the literature.

A 46,XX,r(17) karyotype was observed in a 9-year-old infant with short stature, moderate mental retardation but without other physical abnormality. Eight cases with an r(17) have since been reported: 4 can be compared with our patient, one was detected by amniocentesis, and 3 have Miller-Dieker syndrome. Submicroscopic deletions in the subband p13.3 are probably the cause of Miller-Dieker syndrome. They are present in some cases of r(17) but, in others, this short arm region is entirely preserved.     

Antenatal diagnosis of glutaric acidemia

Two pregnancies at risk for glutaric acidemia were monitored. In one, in which the fetus was not affected, glutaric acid was not detected in the amniotic fluid at amniocentesis (15 weeks) and the glutaryl-CoA dehydrogenase activity of cultured amniotic cells was normal. In the other, a marked elevation of glutaric acid in the amniotic fluid, together with deficiency of glutaryl-CoA dehydrogenase in amniotic cells, prompted termination of the pregnancy, and studies on the abortus confirmed the diagnosis of glutaric acidemia. Glutaric acidemia, is, thus, another inborn error of metabolism which can be diagnosed in utero.     

Glycoproteins that distinguish different cell types found in amniotic fluid

Summary Two concanavalin A-binding glycoproteins of approximate Mw 150 K and 140 K are described, which enable two of the main cell types found in amniotic fluid samples obtained by amniocentesis, AF and F cells, to be reliably distinguished. Further, the Mw 150 K glycoprotein has been used to trace the developmental origin of the AF cell type. AF cells, which generally form the majority of amniotic fluid cells found in culture, appear to arise in the extra-embryonic membranes, specifically the amnion.     

Chorionic villi sampling: cytogenetic and clinical findings in 500 pregnancies.

The cytogenetic findings were analysed in a series of 500 pregnancies in which chorionic villi sampling was performed. In all cases a direct method was used, karyotyping being successful in 481 cases (96.2%). The main indication for sampling was maternal age over 36 (412 cases; 82.4%). Abnormal laboratory findings resulted in 24 terminations of pregnancy (4.8%); in addition five unexpected balanced chromosome rearrangements were detected. Twelve of 15 cytogenetic discrepancies were detected at amniocentesis, two after termination, and one at spontaneous abortion. Complete follow up data were available for the first 250 patients, among whom nine pregnancies (3.6%) ended in spontaneous abortion before the 20th week. There were no false negative findings. Seventy additional chromosome studies were performed because of failure of chorionic villi sampling or equivocal results, or for confirmation. Counselling before chorionic villi sampling should include the possibility that subsequent amniocentesis may be needed should mosaicism or other unexpected abnormalities be found. The success rate and accuracy of karyotyping chorionic villi samples by the direct method are acceptable but distinctly less than those of karyotyping cultured amniotic fluid cells.     

Catecholamines and DOPA in the amniotic fluid and amnion of the chick embryo

Identification and quantitative fluorimetric assay have been made on the content of DOPA, dopamine, noradrenaline and adrenaline in the amniotic fluid and amnion of the developing chick embryos. Significant increase in the content of DOPA, noradrenaline and adrenaline in the amniotic fluid was observed between the 6th and the 13th days of incubation; dopamine content sharply decreases at the 13th day. The content on amines in the amnion tissue remained essentially constant throughout the investigated period. The role of catecholamine in amniotic fluid in regulation of contractile activity of amniotic membrane in the developing chick embryo is discussed.     

Vascular endothelium: the battlefield of dengue viruses

Increased vascular permeability without morphological damage to the capillary endothelium is the cardinal feature of dengue haemorrhagic fever (DHF)/dengue shock syndrome (DSS). Extensive plasma leakage in various tissue spaces and serous cavities of the body, including the pleural, pericardial and peritoneal cavities in patients with DHF, may result in profound shock. Among various mechanisms that have been considered include immune complex disease, T-cell-mediated, antibodies cross-reacting with vascular endothelium, enhancing antibodies, complement and its products, various soluble mediators including cytokines, selection of virulent strains and virus virulence, but the most favoured are enhancing antibodies and memory T cells in a secondary infection resulting in cytokine tsunami. Whatever the mechanism, it ultimately targets vascular endothelium (making it a battlefield) leading to severe dengue disease. Extensive recent work has been done in vitro on endothelial cell monolayer models to understand the pathophysiology of vascular endothelium during dengue virus (DV) infection that may be translated to help understand the pathogenesis of DHF/DSS. The present review provides a broad overview of the effects of DV infection and the associated host responses contributing towards alterations in vascular endothelial cell physiology and damage that may be responsible for the DHF/DSS.