concanavalin-a and Neural-Tube-Defects

The current status and development of biochemical analyses on amniotic fluid in prenatal diagnosis of congenital malformations is shortly summarized. Based on reports on heterogeneity in the carbohydrate content of alphafetoprotein (AFP) a method for electrophoretic separation of heterogeneous fractions of AFP was developed. In principle the method was first described to predict the separation of glycoproteins on affinity chromatography columns. In the analysis AFP is first electrophoresed in an agarose gel containing free concanavalin A (con A). Thereby, AFP is separated into two fractions (with and without affinity to con A). By further electrophoresis--perpendicular to the first--into a gel containing monospecific antibody to AFP two precipitates are formed, where the relative size of the fraction without affinity to con A is determined (con A non-reactive AFP). To obtain the smallest possible analytical variation the method was modified by introduction of a line gel, which not only increased the precision, but also made the reading of the gels considerably easier. Also, casting of the antibody containing gel between two glass plates to obtain an equal thickness further reduced the variation. On each second dimension plate three patient samples and a control sample with a non-reactive fraction of AFP corresponding to the limit between samples from normal pregnancies and from pregnancies with fetal malformations were run. Using these modifications a constant coefficient of variation of 5 to 6% over a six-year period was obtained. The investigations showed that at least 50% of AFP from the fetal yolk sac (where the primary production takes place) consists of the non-reactive fraction, whereas only a few per cent of AFP from the fetal liver (where the secondary and major production takes place from 9-10 weeks) is of the non-reactive type. Correlated to the development of the fetal anatomy and physiology with advancing gestation it was expected that AFP in very early amniotic fluid mainly would be of the yolk sac type, but that a decrease in the non-reactive fraction could be expected by means of an elimination of the yolk sac AFP through the fetal gut and a partial replacement by fetal liver AFP (from the fetal liver) through fetal urine. In agreement with this theory a significant decrease in the fraction of AFP non-reactive with con A from high values (30-40%) in amniotic fluid samples from early pregnancy (8-12 weeks) to low values (0-3%) in amniotic f

Topics: alpha-Fetoproteins; Amniotic Fluid; Carbohydrate Conformation; Chemical Phenomena; Chemistry; Concanavalin A; Female; Gestational Age; Humans; Immunoelectrophoresis, Two-Dimensional; Infant, Newborn; Neural Tube Defects; Pregnancy; Prenatal Diagnosis; Receptors, Mitogen

Topics: Acetylcholinesterase; Acetylthiocholine; alpha-Fetoproteins; Amniotic Fluid; Benzenaminium, 4,4'-(3-oxo-1,5-pentanediyl)bis(N,N-dimethyl-N-2-propenyl-), Dibromide; Blood; Cholinesterase Inhibitors; Cholinesterases; Concanavalin A; Electrophoresis, Agar Gel; False Positive Reactions; Female; Gestational Age; Hernia, Umbilical; Humans; Neural Tube Defects; Phenothiazines; Pregnancy; Prenatal Diagnosis

Topics: Acetylcholinesterase; alpha-Fetoproteins; Amniotic Fluid; Cell Adhesion; Clinical Enzyme Tests; Concanavalin A; False Positive Reactions; Female; Gestational Age; Humans; Maternal-Fetal Exchange; Neural Tube Defects; Pregnancy; Prenatal Diagnosis; Prospective Studies; Radioimmunoassay

Alpha-fetoprotein (AFP) concanavallin-A-affinity molecular variant patterns were determined in amniotic fluid samples from 10 pregnancies complicated by anencephaly (6), spina bifida (1), Turner's syndrome (1), osteogenesis imperfecta congenita (1), and fetal death (1) and 20 normal pregnancies between 14.6 and 25.5 weeks of gestation. With the exception of one anencephalic pregnancy, the AFP concentrations in samples from women with a fetal abnormality were more than 5 SD above normal for gestational age. In every case, however, the proportion of total amniotic fluid AFP that was not reactive with concanavallin A was significantly smaller in the presence of a fetal abnormality (mean 2%) than when the fetus was normal (mean 20%). The results suggest that measuring the amount of concanavallin-A-non-reactive amniotic fluid AFP will be a valuable test for diagnosing fetal abnormality, especially when an increase in total amniotic fluid AFP concentration is equivocal or gestational age is uncertain.

Topics: alpha-Fetoproteins; Amniotic Fluid; Chromatography, Affinity; Clinical Trials as Topic; Concanavalin A; Double-Blind Method; Female; Gestational Age; Humans; Neural Tube Defects; Pregnancy; Prenatal Diagnosis; Retrospective Studies

Open neural tube defects developed in 12 of 122 alive chick embryos treated with exogenous lectin (concanavalin-A) at stages between 10 or 14 as defined by Hamburger and Hamilton. Embryos treated at stage 10, the time of anterior neuropore closure, developed exencephaly or extensive neural openings from the level of rhombencephalon to the thoracic spinal cord, while embryos treated at stages between 11 and 14, at posterior neuropore closure, developed only small myeloschisis in the thoracolumbar region. The failure of neural tube closure at a critical time is a major cause of neural tube defects.

Topics: Animals; Cell Adhesion; Chick Embryo; Concanavalin A; Ectoderm; Morphogenesis; Neural Tube Defects

During a 6-year period 19,647 consecutively received amniotic fluid samples were analyzed for the alpha-fetoprotein (AFP) concentration. In samples with an AFP concentration above the 95% upper normal limit the fraction of AFP non-reactive with concanavalin A (con A) was determined by crossed affinity immunoelectrophoresis. Of 436 samples from normal pregnancies with a moderate elevation of AFP (between the 95% limit and 2.5 times the median) the con A fraction was normal in 92 to 98% of the cases, depending on the gestational age. At significantly elevated AFP concentrations (above 2.5 times the median), the fractions were normal in 78% of the 50 cases with a normal outcome. In 80 of 89 cases of fetal malformations, abnormally low fractions were found, and in all 19 cases of abdominal wall defects and congenital nephrosis the fractions were low. No significant difference was found in the sensitivity for detection of fetal malformations by con A analysis compared to quantitative analysis for acetylcholinesterase (AChE). However, significantly more false positive results were found in normal pregnancies for the con A analysis compared to the AChE analysis. Both analyses performed significantly better than ultrasound scanning in terms of sensitivity. It is concluded that AChE is the test of choice in prenatal diagnosis of fetal neural tube defects. However, a sensitivity of 1.00 and a predictive value of a negative test of 1.00 were found for the con A analysis for fetal abdominal wall defects. The AchE analysis performed less well in this context.

Topics: Abdominal Muscles; Acetylcholinesterase; alpha-Fetoproteins; Amniotic Fluid; Concanavalin A; Female; Humans; Immunoelectrophoresis; Neural Tube Defects; Pregnancy; Prenatal Diagnosis; Ultrasonography

Topics: alpha-Fetoproteins; Amniotic Fluid; Concanavalin A; Electrophoresis; Female; Fetal Diseases; Humans; Neural Tube Defects; Pregnancy; Prenatal Diagnosis

From 1st March, 1980 and up to 29th February 1984 a multicenter serum alpha-fetoprotein (S-AFP) screening project was carried out for the detection of severe fetal malformations. S-AFP was determined by a radio-immunoassay in 28 062 pregnant women between the 16th and 20th week of gestation. Patients with elevated S-AFP values, e.g. above 95 percentile, were examined further with a second S-AFP and by ultrasound scan. 244 amniocenteses (0.9%) were carried out to detect 62 malformations (21 anencephalies, 14 spina bifidas, 2 encephaloceles, 7 omphaloceles, 5 gastroschises, 4 chromosome abnormalities and 9 other malformations). Fifteen of the 16 cases of spina bifida could not be verified by ultrasound scan, whereas all other malformations except chromosome abnormalities were confirmed by ultrasonography. Two cases of spina bifida and one case of skin-covered encephalocele had normal S-AFP concentrations and were therefore not detected. There were no definitive false-positives, e.g. therapeutic abortion of a normal fetus. Our conclusion is that a nationwide S-AFP screening should be recommended.

Topics: Abdominal Muscles; Adult; alpha-Fetoproteins; Amniotic Fluid; Concanavalin A; Congenital Abnormalities; Denmark; Female; Humans; Mass Screening; Neural Tube Defects; Pregnancy; Prenatal Diagnosis; Risk

Topics: alpha-Fetoproteins; Amniotic Fluid; Concanavalin A; Female; Humans; Neural Tube Defects; Pregnancy; Prenatal Diagnosis

Five biochemical tests, which have been proposed as possible adjuncts to the measurement of amniotic fluid alphafetoprotein for the identification of neural tube defects, have been measured in 49 normal and 46 neural tube defect affected pregnancies. One test, the alphafetoprotein component non-reactive with concanavalin A, was ineffective in differentiating normal and abnormal. The remaining four procedures, the activity of acetyl and total cholinesterase, the concentration of alpha 2 macroglobulin and the electrophoretic identification of acetyl cholinesterase effectively separated the normal and abnormal populations. The relative merits of these four latter tests in the evaluation of false positive and false negative amniotic fluid alphafetoprotein results, as well as in liquor samples with high alphafetoprotein levels associated with abnormalities not of neural origin, are discussed.

Topics: Abortion, Missed; Acetylcholinesterase; alpha-Fetoproteins; alpha-Macroglobulins; Amniotic Fluid; Cholinesterases; Concanavalin A; Female; Hernia, Umbilical; Humans; Neural Tube Defects; Pregnancy; Prenatal Diagnosis

Concanavalin A nonreactive alpha-fetoprotein was determined in samples of amniotic fluid from 16 abnormal pregnancies complicated by anencephaly (7), open spina bifida (6), intra-uterine death (1), anencephaly with exomphalos (1), or open spina bifida with exomphalos (1), and in amniotic fluid from 50 normal pregnancies with gestational age between 13 and 24 weeks. In all 16 cases with fetal malformations, the proportion of nonreactive alpha-fetoprotein was significantly decreased (median 5.3%) as compared with amniotic fluid from pregnancies with a normal outcome (median 39.7%). The results confirm that this measurement is useful in the diagnosis of neural tube defects, especially when the concentration of alpha-fetoprotein in amniotic fluid is normal or only slightly above normal and gestational age is uncertain.

Topics: alpha-Fetoproteins; Amniotic Fluid; Anencephaly; Concanavalin A; Female; Gestational Age; Humans; Infant, Newborn; Meningomyelocele; Neural Tube Defects; Pregnancy; Prenatal Diagnosis

The proportion of alphafetoprotein (AFP) not reacting with Concanavalin A(Con A) was determined by crossed line affinity immunoelectrophoresis (CLAIE) in amniotic fluid obtained from 16 pregnancies with open neural tube defects and other fetal abnormalities, and 25 pregnancies with normal outcome. The percentage of Con A non-reactive AFP was significantly lower in the presence of open neural tube defects (less than 3.9%, n = 13) compared with that in normal pregnancy (range 6.4-25.2%, n = 25). In this retrospective analysis, 2 pregnancies affected by open neural tube defect escaped diagnosis on the basis of an ambiguous total AFP estimation (+2SD less than x less than +5SD) in the amniotic fluid. These observations suggest that the elimination of false diagnose based on total AFP levels may be possible, if supplementary analysis by CLAIE is performed.

Topics: alpha-Fetoproteins; Amniotic Fluid; Concanavalin A; Female; Humans; Immunoelectrophoresis, Two-Dimensional; Neural Tube Defects; Pregnancy; Prenatal Diagnosis; Reference Values

We used concanavalin A crossed-line affinity immunoelectrophoresis to determine the percentage of concanavalin A nonreactive alpha-fetoprotein in amniotic fluid samples from pregnancies with normal and abnormal fetuses. In 167 samples from pregnancies with a normal outcome and normal values for total alpha-fetoprotein concentration in amniotic fluid the percentage decreased from a median value of 27.4% in the 13th week to 8.5% in the 21st week of gestation, and a statistically significant (p < 0.001) average decrease of 1.7% per week was found from the 14th to the 19th week. A similar average decrease (2.2%) was found in 22 pregnancies from which two or more samples were obtained. The clinical significance of this decrease is discussed. Of 108 samples from patients with above-normal values for total alpha-fetoprotein and a normal outcome, seven had a total alpha-fetoprotein above recommended cut-off values, and only one of these had a low percentage of concanavalin A nonreactive alpha-fetoprotein. In contrast, for all 27 samples from pregnancies with a severe fetal malformation this percentage was low, even in one case where the total alpha-fetoprotein concentration was below the recommended cut-off value.

Topics: alpha-Fetoproteins; Amniotic Fluid; Concanavalin A; Female; Gestational Age; Humans; Immunoelectrophoresis, Two-Dimensional; Neural Tube Defects; Pregnancy; Prenatal Diagnosis

The percentage of alpha-fetoprotein (AFP) not reacting with concanavalin A (con A) was determined by crossed line affino-immunoelectrophoresis in amniotic fluid from 25 pregnancies with neural tube defects (NTD) and other fetal abnormalities giving rise to elevated AFP levels, and from 128 pregnancies with normal outcome. The percentage of con A non-reactive AFP is significantly lower in the presence of fetal abnormalities (mean 3.4%, range: 0.0-6.3, n = 25), compared to the percentage found in normal pregnancies (mean 17.2%, range: 6.6-35.8%, n = 128). In amniotic fluid samples from normal pregnancies, the percentage of con A non-reactive AFP in 84 cases with total AFP levels lying within the 95% reference interval was not significantly different from the percentage found in 44 cases with levels above the 95% reference interval. The percentage of non-reactive AFP in fetal serum and cerebrospinal fluid was of the same magnitude as found in amniotic fluids of pregnancies with fetal abnormalities. It is concluded that analysis of the percentage of con A non-reactive AFP by crossed line affino-immunoelectrophoresis is a simple, reliable and apparently diagnostic test for NTD and other abnormalities with leakage of fetal serum or cerebrospinal fluid into the amniotic fluid. The test should therefore be used in all cases with only marginally elevated AFP levels, so false positives may be avoided.

Topics: alpha-Fetoproteins; Amniotic Fluid; Concanavalin A; Female; Fetal Blood; Gestational Age; Humans; Immunoelectrophoresis; Immunoelectrophoresis, Two-Dimensional; Neural Tube Defects; Pregnancy; Prenatal Diagnosis

We have extended our initial observations (Smith et al., 1979) on th use of determining the alpha-fetoprotein (AFP) concanavalin A-binding variant patterns in amniotic fluid for the detection of certain fetal malformations. We report here our complete series of amniotic fluids between 14 and 36 weeks of gestation from 52 normal pregnancies and 28 abnormal pregnancies including anencephaly, open spina bifida, Turner's syndrome, omphalocele, osteogenesis imperfecta congenita, meningomyelocele, meningocele, spinal cysts, spontaneous abortion and fetal death. The percentage of the total amniotic fluid AFP which was not reactive with concanavalin A was significantly lower in the presence of a communicating fetal abnormality (mean = 4.8%, P less than 0.001), one in which the fetal/amniotic fluid barrier is defective, than in the presence of a normal fetus (mean = 24.7%) (or of a noncommunicating fetal abnormality. We applied the concanavalin A-binding assay to two of the above amniotic fluids from pregnancies in progress and correctly classified the gestations as abnormal. Our results indicate that measurement of the percentage of concanavalin A-non-reactive amniotic fluid AFP is a valuable adjunct in the diagnosis of a communicating fetal abnormality, especially when the elevation of amniotic fluid AFP concentration is equivocal (between 2 and 5 S.D. above the mean), when gestational aging is uncertain or when the total amniotic fluid AFP concentration and ultrasonographic data are inconsistent.

Topics: alpha-Fetoproteins; Amniotic Fluid; Concanavalin A; Congenital Abnormalities; Female; Fetal Diseases; Humans; Neural Tube Defects; Pregnancy; Pregnancy Trimester, Second; Pregnancy Trimester, Third; Protein Binding

Topics: alpha-Fetoproteins; Amniotic Fluid; Concanavalin A; Female; Humans; Immunoelectrophoresis, Two-Dimensional; Neural Tube Defects; Pregnancy

Concanavalin A (con A) is teratogenic to rabbit embryos during gestational days 12--15. Intracoelomic injections of 40 microliter con A solution (4 microgram/microliter) were performed on rabbit embryos during gestational days 10--15. Control embryos received either 40 microliter of saline, sham injection or no treatment. Con A caused increased fetal resorptions on days 10 and 11, but malformation levels did not differ from controls. On days 12--15, con A produced craniofacial, trunk and limb anomalies. The highest percentage of malformation occurred on day 14. The defects were classified into four groups: (1) malformations of limbs including paw and digital dysplasias as well as fusions of the limbs to the head or body wall; (2) "closure" defects such as umbilical hernia, encephalocoele, exencephaly or ectopia cordis; (3) "contracture" defects such as club paws, extended knees, or clenched digits, which exhibited normal osseous and cartilaginous skeletons; and (4) miscellaneous, non-specific anomalies including fused or dysplastic sternebrae or ribs. Histologic analysis of selected 12-day embryos 4 to 18 hours post-injection was performed to ascertain potential sites of teratogenic action. At 12 hours ectodermal necrosis was observed in the limb buds adjacent to the apical ectodermal ridge. By 18 hours, the ectoderm had eroded, exposing the basal lamina to the amniotic fluid. Focal areas of mesenchymal necrosis were observed in association with the ectodermal erosion. The potential roles of amniocentesis and limb bud repair in the genesis of the malformations are discussed.

Topics: Abnormalities, Drug-Induced; Animals; Concanavalin A; Contracture; Ectoderm; Female; Fetal Resorption; Forelimb; Gestational Age; Hindlimb; Neural Tube Defects; Pregnancy; Rabbits