Early ultrastructural changes in blood-brain barrier vessels of the rat embryo

The blood-brain barrier (BBB) in fetal rat brain has been shown by others to be more permeable to a variety of blood-borne solutes than the BBB in adults. We used ultrastructural morphometric methods to measured the density of putative vascular pores between the ages of embryonic day (E) 11 and birth to determine the structural basis for this relatively high permeability. We found that fenestrations, that are frequent at E11, declined rapidly and were last seen at E13 in intraparenchymal vessels and at E17 in pial vessels. Interendothelial junctions in fetal brain contained expanded clefts suggestive of paracellular channels at all ages examined, although they disappear after birth. Both of these features likely contribute to high fetal BBB permeability, but endothelial vesicles probably do not. The central nervous system is vascularized by ingrowth of capillary sprouts from the perineurial vascular plexus. Invading capillaries express BBB features in response to inductive signals from the surrounding neural tissue. We compared early ultrastructural changes in perineurial vessels, which are separated from neural tissue by a sizeable perivascular space, with those in intraneural vessels, which are totally enveloped by neural tissue, to determine whether the inductive interaction requires close cellular contact. For the most part, the perineurial and intraneural vessels matured in parallel. Furthermore, cerebellar vessels developed in parallel with cerebral vessels, even though they did not invade neural tissue until a comparatively late stage. These results suggest that intimate contact between neural tissue and vessel walls is not a requirement for BBB expression.

Cordocentesis for rapid karyotyping in fetuses with congenital anomalies or severe IUGR

The objective was to determine the role of percutaneous umbilical blood sampling (cordocentesis) as a rapid technique for chromosome analysis in a high risk obstetric population. Cordocentesis was attempted in 167 pregnant women (168 fetuses) with IUGR, a single anomaly or multiple anomalies. Gestational age ranged between 17 and 37 weeks. The procedure was successful in 152 (90%) fetuses with a blood sample withdrawan at first attempt in 80%. Neither technique was associated with any false negative or false positive findings. Postprocedural complications included one case of persistent fetal bradycardia, but no fetal death. In nine cases amniotic fluid was collected, resulting in 161 fetal blood or amniotic fluid samples for chromosome analysis. An abnormal chromosome pattern (n = 26) was established in 1/12 cases (8%) of severe IUGR, 6/88 cases (7%) with a single structural anomaly and 19/61 cases (31%) with multiple structural anomalies. In the presence of an abnormal chromosome pattern, the perinatal mortality rate was as high as 96%. There is a high association between multiple fetal anomalies and abnormal chromosome pattern.

Prenatal diagnosis of congenital diaphragmatic hernia: a retrospective analysis of 28 cases

In a retrospective analysis of 28 cases of fetal diaphragmatic hernia, overall mortality was 86 per cent, but fell to 70 per cent when multiple anomalies were excluded. Congenital heart disease constituted the majority of associated anomalies. The incidence of an abnormal karyotype was 10.5 per cent, but rose to 20 per cent when only fetuses with multiple anomalies were included. Polyhydramnios, which occurred in 75 per cent, was a poor predictor of fetal outcome. The same applied to the intrathoracic position of the fetal stomach. In all four survivors, diaphragmatic hernia was diagnosed beyond 32 weeks of gestation.

Ductus venosus flow velocity waveforms in relation to fetal behavioural states

OBJECTIVES

To establish the reproducibility of flow velocity waveforms in the human ductus venosus and to assess the influence of fetal behavioural states on these waveforms in normal term fetuses.

DESIGN

Reproducibility of Doppler waveform recording and analysis was studied in 10 normal pregnancies. The relation between ductus venosus flow velocities and behavioural states was investigated in 19 other term fetuses. Time-averaged, peak systolic, peak diastolic velocity, peak systolic/diastolic ratio and period time were calculated in both cross sectional studies.

SETTING

Outpatient clinic, department of obstetrics (prenatal diagnosis section), Academic Hospital, Rotterdam--Dijkzigt.

SUBJECTS

Twenty-nine women with normal singleton pregnancies at 36 to 39 weeks of gestation, resulting in uncomplicated births of healthy infants.

RESULTS

Within-patient coefficients of variation, ductus venosus waveform recordings were approximately 8 to 10% except for the peak systolic/diastolic ratio (4.3%). A decrease of approximately 30% was established for peak systolic, peak diastolic velocity and time-averaged velocity during behavioural state 1F (quiet sleep) as compared with state 2F (active sleep).

CONCLUSIONS

Flow velocity waveform recording in the ductus venosus demonstrates acceptable reproducibility. Fetal behavioural state-dependent changes were observed, suggesting a redistribution of umbilical venous blood through the ductus venosus shunt during the quiet sleep state.

Blood-eye barriers in the rat: correlation of ultrastructure with function

The function of different vascular beds in the rat eye and brain was evaluated by measuring the transfer of a vascular tracer, 14C-alpha-amino-isobutyric acid, from blood to tissue. The density of vascular pores was measured in electron micrographs of perfusion-fixed, age-matched tissue to determine whether the differences in tracer transfer were paralleled by differences in ultrastructure. Tracer transfer in retina was approximately four times that in brain of the same animal. The transfer constant was not changed by the inclusion of cold alpha-amino-isobutyric acid, showing that transport across retinal vessels is not saturable, and indicating that, as in brain, transport is due to passive diffusion. Ultrastructurally, retinal vessels have a higher density of interendothelial junctions and of endothelial vesicles, both of which suggest higher vascular permeability. However, pericytes, which contribute to a second line of defence in the blood-brain barrier, are approximately four times as numerous in retina as in brain, and we suggest that in the retina, they act to compensate for a more permeable endothelial barrier. Ciliary body vessels had a high transfer of tracer, probably as a consequence of the fenestrations in their walls. Iridial vessels had a relatively low transfer of tracer, similar to that in retina even though a proportion of the interendothelial junctions in iridial vessels had expanded junctional clefts suggestive of open paracellular channels. However, both iris and ciliary body may lose tracer to the anterior chamber fluid, leading us to underestimate the vascular permeability in these sites.

[A retrospective evaluation of exposure to dichloromethane by using a job-exposure matrix]

The impact of three features of a job-exposure matrix has been tested in a case-control study that evaluated the association of occupational exposure to dichloromethane and astrocytic brain cancer. These features were probability of exposure, an exposure assessment by decades, and the use of a more specific coding system of industries and occupations. The introduction of each feature had a striking effect on the estimate of relative risk. The odds ratio increased from 1.47 with none of these features, to 2.47 with high probability of exposure, to 4.15 with high probability of exposure and the specific coding system, to 6.08 with all features combined. These results indicate that job-exposure matrices efficacy in reducing the degree of exposure misclassification may be greatly improved by the introduction of these features.

Effects of three features of a job-exposure matrix on risk estimates

We tested the impact of three features of a job-exposure matrix on risk estimates in a case-control study that evaluated the association of methylene chloride and astrocytic brain cancer. These features were probability of use of the agent; the consideration of decade of predominant use of methylene chloride within each occupation; and the use of a more specific industrial-occupational coding system. We compared the risk estimates obtained with and without these features. The introduction of each feature had a striking effect on the estimate of relative risk. The odds ratio ranged from 1.47 with none of these features, to 2.47 with high probability of exposure within industry and occupation, to 4.15 with high probability of exposure and specific industrial-occupational coding, to 6.08 with the three features together. These results indicate that the degree of exposure misclassification can be reduced by the introduction of these features into the job-exposure matrix.

The relationship of astrocyte-like cells to the vessels that contribute to the blood-ocular barriers

Brain capillaries form a selective interface, the blood-brain barrier (BBB), between the neural parenchyma and the blood. The factors which regulate this interface are poorly understood. Both the iris and retina possess vascular beds that express some BBB characteristics; therefore, they provide attractive models to further our understanding of how blood-tissue interfaces are regulated. We have determined whether three BBB markers: the transferrin receptor, P-glycoprotein, and gamma-glutamyl transpeptidase (gamma-GTP), can be localized in the capillaries of the rat retina and iris. We have also compared, in retina and iris, the relationship which GFAP-positive cells have with the blood vessels to the expression of the three BBB markers by the vessels. Immunocytochemistry revealed that capillaries throughout the retina express P-glycoprotein and the transferrin receptor. Retinal vessels do not show detectable gamma-GTP activity. GFAP-positive cells ensheath capillaries in the nerve fibre layer of the retina. Of the three BBB characteristics we examined, iridial vessels expressed only one of them: P-glycoprotein. In the iris, GFAP-positive cells do not ensheath capillaries. From our results we conclude that all BBB characteristics do not have to be expressed and regulated in capillaries as a unit. Our results, in combination with those of earlier studies, suggest that the expression of some BBB features does not require intimate contact between capillaries and astrocytes or astrocyte-like cells. Barrier maintenance appears to be a complex process which involves the integration of several factors.

Barrier properties of testis microvessels

The blood-testis barrier is believed to be constituted by tight junctions between Sertoli cells in seminiferous tubules and possibly by myoid cells that encircle these tubules. We now show that testis microvessels are endowed with several markers of barrier properties of brain microvessels, such as the glucose transporter, P-glycoprotein, and gamma-glutamyl transpeptidase. Quantitative EM studies show that the endothelium in testis, as in brain, is continuous and has long junctional profiles and few vesicles. However, a small proportion of testis capillaries have expansions in their junctional clefts suggestive of patent paracellular channels, which may explain their higher permeability. Because barrier features are thought to be induced and/or maintained in brain microvessels by astrocytes, we assessed whether astrocyte-like cells exist in the testis. We found that the intertubular Leydig cells, adjacent to microvessels, express the astrocyte markers: glial fibrillary acidic protein, glutamine synthetase, and S-100 protein. We suggest that the testis endothelium contributes to the blood-testis barrier and that these endothelial barrier features are influenced by Leydig cells. We believe that the endothelial and the epithelial (Sertoli) components of the blood-testis barrier are "in series" and complement each other in achieving a stable milieu for spermatogenesis.

Maternal autoantibodies and congenital heart block: no evidence for the existence of a unique heart block-associated anti-Ro/SS-A autoantibody profile

One of the rare examples of the transfer of autoimmune disease from mother to (unborn) child is the neonatal lupus syndrome. This syndrome comprises the development of fetal heart disease (congenital heart block) or neonatal skin rash and is specifically associated with maternal anti-Ro/SS-A autoantibodies. Previous studies have suggested that especially maternal autoantibody reactivity against the 52 kDa protein of the Ro/SS-A antigen and/or against the La/SS-B antigen is responsible for the development of congenital heart block (CHB). To determine the CHB-associated antibody response in more detail, we analysed the presence of autoantibodies in sera from mothers of children with isolated heart block. All 14 mothers of children with congenital heart block were positive for anti-Ro/SS-A antibodies. Remarkably, their antibody profile, including recognition of different Ro/SS-A proteins and autoantibody levels against these proteins, did not differ from anti-Ro/SS-A positive mothers of healthy children. In contrast, all 8 anti-Ro/SS-A negative mothers had children with acquired heart block. We conclude from our data that maternal anti-Ro/SS-A antibodies are essential for CHB but that fine analysis of this autoantibody response does not predict the occurrence of CHB.

Doppler flow velocity waveforms in late first- and early second-trimester fetuses: reproducibility of waveform recordings

The objective of the study was to assess the reproducibility of Doppler flow measurements of the fetal umbilical vein and artery, descending and ascending aorta, mitral and tricuspid valve, pulmonary artery, inferior vena cava and ductus venosus in early pregnancy. In a cross-sectional study, Doppler measurements were obtained in a total of 54 women at 11-16 weeks of gestation, at 2-5 different vascular sites, on 3-5 different occasions, at 5-min time intervals. The total variance in the various flow velocity parameters was partitioned in a between-subject and within-subject component by analysis of variance, and, from these calculations, coefficients of variation in waveform recording were calculated. Flow velocity waveform recording was characterized by coefficients of variation in the range 2.2-5.7% except for the acceleration time (18.6-24.5%) and percentage reverse flow (8.8%). In conclusion, our data suggest that fetal flow velocity waveforms in early pregnancy demonstrate good reproducibility in the individual subject, while all parameters depict larger variabilities for between-subject values. Acceleration time turned out to be poorly reproducible. If a single flow velocity waveform measurement is used for the future evaluation of clinical conditions in early pregnancy, one has to consider that normal values will display a rather wide range.

Fetal renal artery flow velocity waveforms in the presence of congenital renal tract anomalies

Colour Doppler flow mapping of the renal arteries and subsequent pulsed Doppler measurement of impedance to flow in these vessels were attempted in 33 fetuses with postnatally confirmed renal pathology. The majority presented with unilateral or bilateral hydronephrosis (n = 21) and bilateral renal agenesis (n = 8). Renal artery blood flow could be visualized in all, except for the eight cases of bilateral renal agenesis. Bilateral flow velocity recordings were collected in six out of 12 cases of bilateral hydronephrosis and in five out of nine cases of unilateral hydronephrosis. The pulsatility index (PI), as a measure of downstream impedance, was in the normal range in 16 out of 18 kidneys (88 per cent) in bilateral hydronephrosis and in 12 out of 14 kidneys (85 per cent) in unilateral hydronephrosis. The PI was significantly higher in severe hydronephrosis compared with mild hydronephrosis. In four cases of unilateral multicystic kidney, the PI was always higher on the affected side. Colour Doppler flow mapping and pulsed Doppler evaluation may be helpful in our understanding of renal vascularization in renal pathology and in confirming the diagnosis of renal agenesis.

Fetal echocardiography and color Doppler flow imaging: the Rotterdam experience

The adjunctive role of Doppler color flow mapping in the evaluation of cardiac structures and function was studied in 440 normal fetuses between 17 and 22 weeks of gestation (median, 20 weeks) and in 73 fetuses with suspected congenital heart disease between 16 and 38 weeks of gestation (median, 28 weeks). Flow through atrioventricular and arterial valves was generally easy to identify and identification was successful in approximately 90% of the normal fetuses. Flow in the pulmonary veins and through the foramen ovale was visualized in approximately 60% of normal cases. In the group with suspected congenital heart disease, Doppler color flow imaging provided additional information on both cardiac structure and function in 34 fetuses, on function alone in 13 fetuses and on structure alone in 20 fetuses. No additional information was collected in six fetuses.

Re-evaluating the role of astrocytes in blood-brain barrier induction

Neural tissue induces brain capillary endothelial cells to express a diverse array of characteristics that allow them to regulate the passage of solutes between the blood and the brain; these features are collectively referred to as the blood-brain barrier (BBB). Because astrocytes are intimately associated with brain capillaries, they have been thought to be the cell type responsible for barrier induction. Widely accepted support of this hypothesis has been derived from experiments showing that astrocytes implanted into the anterior chamber of the rat eye, or onto the chorioallantoic membrane of the chicken embryo, remain unstained by circulating Evan's blue, while grafts of fibroblasts in these sites stain intensely. We have found several limitations associated with placing grafts in either site, leading us to believe that previously reported results are inconclusive. Astrocytes implanted into the anterior chamber form grafts that are poorly vascularized, whereas fibroblast grafts are richly vascularized by vessels which are often fenestrated. This likely accounts for apparent differences in vessel permeability reported by others. We have found that iridial vessels associated with astrocyte grafts do not change their ultrastructure to resemble brain capillaries. Grafting of cells to the chorioallantoic membrane elicits an extensive inflammatory response. Inflammation results in poor delivery of tracers to graft vasculature as well as altering vessel permeability. Treatment of hosts with steroidal anti-inflammatory agents in doses compatible with survival of the host does allow improved graft survival. Even after treatment with anti-inflammatory agents, however, astrocyte graft vasculature fails to express high levels of a barrier marker, the GLUT-1 isoform of the glucose transporter. Transplantation of avascular embryonic spinal cord, that induces robust vessel ingrowth and GLUT-1 expression in intra-embryonic vessels, was unable to elicit the ingrowth of more than a few vessels from the chorioallantoic membrane vasculature, and none of these expressed glucose transporter. We conclude that the anterior chamber and chorioallantoic membrane are not suitable sites for studying BBB induction, and that there is, at present, no conclusive evidence that mature astrocytes play a significant role in the initial expression of the BBB.

Validity of exposure in one job as a surrogate for exposure in a cohort study

Frequently, information pertaining to only one job is available or used to evaluate risk estimates of disease in occupational epidemiologic research. The amount of misclassification that such a practice could create has not, however, been examined. We used data from a mortality study of workers employed in 10 formaldehyde-producing or -using plants to address how closely several parameters of exposure based on the first, longest, or last job held in a company compared with those based on the worker's entire employment history at the plant. The best predictor for cumulative formaldehyde exposure at the plant was the longest job at that plant, with a correlation coefficient (r) of 0.70. The correlation with average exposure over the worker's employment was 0.77 for the first job and 0.74 for the longest and last jobs. Peak exposures and highest exposure levels experienced in the plant were more closely related to the first job (r = 0.72 and r = 0.74). The highest correlation with any of the measures was never with the last job. Variation between plants for each of these comparisons, however, was wide. These findings indicate that the use of a single job as a surrogate for exposure received at a particular worksite can result in different degrees of misclassification for different exposure measures. Even though the correlations were generally high, the associated misclassification of exposure could lead to a substantial underestimation of the relative risks in some situations. In this report two hypothetical examples show what effect the misclassification rates could have on estimates of disease risks.

Preterm delivery rate and fetal outcome in structurally affected twin pregnancies: a retrospective matched control study

Data from 23 twin pregnancies with one structurally affected fetus were compared with data from 23 twin pregnancies with proven absence of structural fetal anomalies and matched for maternal age, parity, and year of delivery. The preterm delivery rate (< 37 weeks) was high in both groups but not significantly different (57 vs. 48 per cent). Perinatal mortality was significantly higher in the structurally affected twin pregnancies (65 vs. 9 per cent). In the affected twins, birth weight of the anomalous fetus was significantly lower than that of the normal co-twin. Since there was no difference in the incidence of maternal disease (hypertensive disorders, diabetes), it was concluded that the higher perinatal mortality was determined mainly by the nature of the anomaly and not by the preterm delivery rate.

Evaluation of risks for non-Hodgkin's lymphoma by occupation and industry exposures from a case-control study

The etiology of non-Hodgkin's lymphoma (NHL) is not well understood. To develop hypotheses on causes of this tumor, data from a population-based case-control interview study of 1,867 white men (622 cases and 1,245 controls) in Iowa and Minnesota conducted during 1980-1983 were examined. Subjects, or their next of kin, were interviewed to obtain information on agricultural exposures, work history, medical conditions, and family history. This analysis focuses on risks of NHL by occupation, by industry, and by selected exposures. Although many comparisons were made, few significant associations were observed. Small numbers and limitations in exposure assessment, however, would tend to reduce opportunities to detect associations. The strongest finding was with various occupations that work in metals and metal products. The analysis by exposure estimates also uncovered a significant association with metals, but risks did not increase with estimated intensity of exposure. Slightly elevated risks were also noted among persons employed as painters and construction workers, agricultural and forestry workers, printers and typesetters, funeral directors and embalmers, and dry cleaners. Although the overall risks for benzene and other solvents were small, they increased slightly with level of assigned exposure. Although some associations may be due to chance, several of these occupations and industries have been linked to lymphoma in other investigations and deserve further attention.

Changes in inferior vena cava blood flow velocity and diameter during breathing movements in the human fetus

Breathing movements in the human fetus cause distinct changes in Doppler flow velocity measurements at arterial, venous and cardiac levels. In adults, breathing movements result in a momentary inspiratory collapse of the inferior vena cava vessel wall. The study objective was to quantify the inferior vena cava flow velocity modulation during fetal breathing movements and to evaluate possible inferior vena cava vessel diameter changes in normal third-trimester pregnancies. We studied 57 women after oral administration of dextrose (50 g). In 40 fetuses (n = 19, 27-32 weeks and n = 21, 36-39 weeks), fetal inferior vena cava waveforms were obtained during apnea and fetal breathing activity. In 30 fetuses (27-39 weeks) inferior vena cava vessel diameter changes were studied using the M-mode during apnea and breathing movements. Peak and time-averaged velocities of inferior vena cava flow velocity waveforms showed a gestational age-independent increase of 60-160% during breathing activity. A temporary inferior vena cava vessel wall collapse (range, 50-83%) was recorded, which was significantly different from vessel diameter changes during apnea (range, 11-19%). The marked increase of inferior vena cava flow velocities is due to a raised thoraco-abdominal pressure gradient, which may cause a reduction in vessel size and additional volume flow into the right atrium. The significance of the caval index for recognition of elevated right atrial pressure in abnormal human fetal development needs further investigation.

Doppler colour flow mapping of fetal intracerebral arteries in the presence of central nervous system anomalies

The adjunctive role of Doppler colour flow mapping in the evaluation of intracerebral morphology and arterial blood flow in the presence of normal and abnormal central nervous system morphology was determined. A total of 59 fetuses with suspected central nervous system pathology between 14 and 37 weeks of gestation was studied (median 31 weeks). One hundred and one fetuses with normal central nervous system anatomy between 14 and 37 weeks (median 19 weeks) served as controls. Visualisation of blood flow in one or more intracerebral arterial vessels was successful in more than 80% of normal fetuses. For the anterior, middle and posterior cerebral artery, the percentages were 63%, 89% and 45%, respectively, at 14-25 weeks and 74%, 100% and 55%, respectively, at 26-37 weeks of gestation. Intracerebral arterial flow identification was attempted in 52/59 (88%) affected fetuses. Identification of blood flow in one or more intracerebral arterial vessels was successful in 40/52 (77%) fetuses. End-diastolic flow velocities were present in at least one of the intracerebral arteries in 39/40 fetuses, absent in one case of hydrocephaly and raised in the presence of an intracerebral vascular tumour. Doppler colour flow mapping seems to provide only limited additional information on intracranial structural pathology.

Flow velocity waveforms in the ductus venosus, umbilical vein and inferior vena cava in normal human fetuses at 12-15 weeks of gestation

The objective was to determine the normal Doppler flow velocity waveform patterns in the human fetal ductus venosus, inferior vena cava and umbilical vein correlated with fetal heart rate, and to examine their reproducibility and their inter-relationship at 12 to 15 weeks of gestation. Cross-sectional recordings of 45 normal pregnant women were collected for a data reference range transvaginally and transabdominally depending on fetal size and position. Maximum flow velocity waveforms were obtained from the ductus venosus, the intra-abdominal part of the umbilical vein and inferior vena cava. Time-averaged velocities were calculated in all three vessels together with peak systolic, peak diastolic and time-averaged velocities in the ductus venosus and inferior vena cava. Doppler recordings in 21 other patients displayed good reproducibility. Continuous forward flow in the umbilical vein was associated with pulsatile systolic and diastolic forward flow in the ductus venosus. Retrograde flow was present only in the inferior vena cava. Mean time-averaged velocity (SD) in the ductus venosus was 28.8 (6.1) cm/s, in the umbilical vein 9.7 (2.9) cm/s and in the inferior vena cava 10.9 (2.5) cm/s. No correlation could be established between waveform parameters and fetal heart rate. Combined transvaginal and transabdominal Doppler ultrasound allows reproducible blood flow velocity recordings at venous level in early pregnancy. Relatively high velocities were observed in the ductus venosus compared with the umbilical vein and inferior vena cava. Differences in flow velocities in the ductus venosus and inferior vena cava suggest that little or no mixing of blood occurs, a situation well described in sheep.

Prenatal diagnosis of congenital cystic adenomatoid lung malformation: a report of seven cases

Six cases of macrocystic and one case of microcystic congenital adenomatoid lung malformation were diagnosed by ultrasound between 20 and 31 weeks of gestation. Combined polyhydramnios and fetal hydrops was present in three cases, polyhydramnios alone in one case, and isolated fetal hydrops also in one case. In the remaining two cases, both polyhydramnios and fetal hydrops were absent. Fetal outcome was poor, i.e., two terminations of pregnancy, three early neonatal deaths, and two survivors.

A morphometric study of the blood-brain barrier in Alzheimer's disease

BACKGROUND

Abnormalities in the human blood-brain barrier may contribute to the pathogenesis of Alzheimer disease (AD).

EXPERIMENTAL DESIGN

Morphometric parameters relevant to integrity of the blood-brain barrier (cerebral capillary endothelium) were assessed in brain biopsies from patients with AD and compared with values from age-matched nondemented controls.

RESULTS

Alzheimer patients showed diminished mitochondrial density and area within cerebral capillary endothelium, an increased number of capillary profiles containing pericytes (a possible second line of defense when the capillary endothelium fails), and features of inter-endothelial junctions that suggest 'leakiness' of the blood-brain barrier.

CONCLUSIONS

The data indicate subtle but definite abnormalities suggesting compromise of the blood-brain barrier in AD that may contribute to its pathogenesis, and support neuropharmacologic and morphologic studies that suggest that a form of denervation microangiopathy may occur in AD brain, possibly secondary to loss of neurons from the pontine locus ceruleus. The changes may also play a role in the deposition of A4 Alzheimer amyloid within cerebral microvessel walls.

Prenatal diagnosis of spina bifida aperta after first-trimester valproate exposure

In the context of a prospective study on the adverse effects of anti-epileptic drugs on fetal outcome, we evaluated our experience with prenatal diagnosis by ultrasonography and alpha-fetoprotein (AFP) determination in amniotic fluid. We compared these results with AFP values in maternal serum obtained prior to amniocentesis. From November 1985 to July 1990, amniocentesis at 16-18 weeks of gestation was performed in 267 pregnancies of 237 different women using anti-epileptic drugs. Among 92 pregnancies with maternal valproic acid use, five (including one concordantly affected monozygotic twin-pair) were terminated because of a spina bifida aperta, all prenatally diagnosed by AFP determination and acetylcholinesterase electrophoresis in amniotic fluid. The maternal serum AFP level was raised (> or = 2.5 multiples of the median (MOM) for singleton pregnancies and > or = 4.5 MOM for twin pregnancies) in only two of these five affected pregnancies. We emphasize that maternal serum AFP levels may be unreliable for prenatal screening for fetal neural tube defects in women taking valproate and recommend that amniocentesis and fetal ultrasound examination should be offered directly.