Spectroscopic constraints on CH3OH formation: CO mixed with CH3OH ices towards young stellar objects.

The prominent infrared absorption band of solid CO - commonly observed towards young stellar objects (YSOs) - consists of three empirically determined components. The broad 'red component' (2136 cm-1, 4.681 µm) is generally attributed to solid CO mixed in a hydrogen-bonded environment. Usually, CO embedded in the abundantly present water is considered. However, CO:H2O mixtures cannot reproduce the width and position of the observed red component without producing a shoulder at 2152 cm-1, which is not observed in astronomical spectra. Cuppen et al. showed that CO:CH3OH mixtures do not suffer from this problem. Here, this proposition is expanded by comparing literature laboratory spectra of different CO-containing ice mixtures to high-resolution (R = λ/Δλ = 25000) spectra of the massive YSO AFGL 7009S and of the low-mass YSOL1489 IRS. The previously unpublished spectrum of AFGL 7009S shows a wide band of solid 13CO, the first detection of 13CO ice in the polar phase. In this source, both the 12CO and 13CO ice bands are well fitted with CO:CH3OH mixtures, while respecting the profiles and depths of the methanol bands at other wavelengths, whereas mixtures with H2O cannot. The presence of a gradient in the CO:CH3OH mixing ratio in the grain mantles is also suggested. Towards L1489 IRS, the profile of the 12CO band is also better fitted with CH3OH-containing ices, although the CH3OH abundance needed is a factor of 2.4 above previous measurements. Overall, however, the results are reasonably consistent with models and experiments about formation of CH3OH by the hydrogenation of CO ices.

Processing of icy mantles in protostellar envelopes.

We have obtained CO absorption profiles of several young stellar objects (YSOs), spanning a range of mass and luminosity, in order to investigate their ice mantle composition. We present the first detection of CO toward the class I YSO L1489 IRS in the Taurus dark cloud. In general, the CO profiles for YSOs show evidence for both processed and pristine ices in the same line of sight, strong indirect evidence for CO, is suggested in R CrA IRS 7, L1489 IRS, Elias 18, and GL 961E. Toward other sources (R CrA IRS 1, IRS 2, W33A, NGC 7538 IRS 9, Mon R2 IRS 2) CO is present in (nearly) pure form. We propose an evolutionary scenario to explain the chemical diversity of the icy mantles toward these objects.

Dynamics of artificially immobilized Nitrosomonas europaea: Effect of biomass decay.

The dynamics of growth and death of immobilized Nitrosomonas europaea were studied. For this, the death rate of suspended cells was determined in the absence of ammonium or oxygen by following the loss of respiration activity and by fluorescein-diacetate (FDA)/lissamine-green staining techniques. The death rates obtained (1.06 x 10(-6) s(-1) or 4.97 x 10(-6) s(-1) in the absence of oxygen or ammonium, respectively) were incorporated in a dynamic growth model and the effects on the performance of the immobilized-cell process illustrated by model simulations.These model simulations and experimental validation show that if decay of biomass occurs the biomass concentration in the center of the bead decreases. As a result, the systems react slower to changes in substrate concentrations than if all cells remain viable.To show that cells in the center of the bead died, the FDA and lissamine-green staining techniques were adapted for immobilized cells. It was shown that biomass decay occurred, especially in the center of the bead; the amount of cells decreased there, and the remaining cells were all stained with lissamine green indicating cell death. After the substrate availability was decreased, also cells near the surface of the bead lost their viability. The number of viable cells increased again after increasing the substrate concentration as the result of cell multiplication. At low substrate concentrations and low hydraulic retention times, as for example in the treatment of domestic wastewater, the death rate of cells is thus an important parameter for the performance of the immobilized-cell system. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 630-641, 1997.

Resolution of hydrops in twin-twin transfusion syndrome: could steroids have a role?

A case of twin-twin transfusion is presented with hydrops occurring twice in the recipient twin and resolving. Polyhydramnios was treated with numerous volume-reducing amniocenteses (amnioreductions), which were performed prior to both occurrences of hydrops. Amnioreductions were only performed before the first resolution of hydrops, whereas betamethasone was given prior to both episodes of hydrops resolving. Steroids may be useful not just in case of premature delivery but also to help a compromised fetus cope in utero.

A cohort study of pregnancy outcome after amniocentesis in twin pregnancy.

We conducted a retrospective cohort study to assess the risk of amniocentesis in twin pregnancy for adverse outcomes. The study base consisted of women who had an amniocentesis performed during twin pregnancy and a comparison representative sample of women who carried a twin pregnancy, but did not have invasive prenatal diagnosis. The 227 women in each of the exposed and non-exposed groups were residents of the state of New South Wales, Australia, over the period 1980-92, and were matched on maternal age and period of the infant's birth. Nearly 10% of twin pregnancies among the women having an amniocentesis were affected by a stillbirth, and the stillbirth rate among exposed fetuses (5.3%) was nearly twice as high as among non-exposed fetuses (3.1%). After adjustment for confounding and excluding abnormalities, there was a non-significant elevated relative risk of stillbirth after exposure to amniocentesis. The analysis by type of amniocentesis (with and without methylene blue dye) was limited by small numbers, but the burden of risk was primarily among women who had dye exposure during amniocentesis (relative risk = 3.64, 95% confidence interval = 1.15, 11.48). This increase remained after adjusting for confounding, although the confidence interval was wide. In conclusion, we were unable to establish with certainty whether an increased risk of stillbirth could be ruled out among women who had any type of amniocentesis in twin pregnancy.

First trimester aneuploidy screening using nuchal translucency, free beta human chorionic gonadotrophin and maternal age.

Screening for aneuploidy using maternal age has a low detection rate and high false positive rate. Second trimester maternal serum screening increases trisomy 21 detection and decreases the false positive rate. First trimester screening would enable definitive diagnosis with chorionic villus sampling, and simple surgical termination of affected pregnancies would still be an option. Nuchal translucency (NT), free beta human chorionic gonadotrophin (f beta HCG) and maternal age were assessed in 302 patients before chorionic villus sampling. NT positively and f beta HCG negatively correlated with gestation, but neither correlated with maternal age nor with each other. Both NT and f beta HCG were increased in trisomy 21. NT was increased and f beta HCG was decreased in trisomy 18. Multivariate discriminant analysis enabled 87.5% detection of trisomy 21 in this high-risk population, for a 14% false positive rate. In a simulated normal population, using a risk cut-off of 1 in 250, 71% detection was achieved for a 7% false positive rate. The combination of NT, f beta HCG and maternal age is a simple, readily available and viable first trimester screening strategy.

New formula for estimating fetal weight below 1000 g: comparison with existing formulas.

Most estimated fetal weight formulas have been derived and tested with larger fetuses, yet accuracy in predicting birth weight is more critical at the limit of viability. Complete data from 142 pregnancies in which delivery took place within 7 days of an ultrasonographic examination were used to create an appropriate formula for fetuses less than 1000 g and compare it with 10 currently available formulas. Our formula (In [BW] = 0.66 x 1n [HC] + 1.04 x 1n [AC] + 0.985 x 1n [FL]) was significantly more accurate than all other formulas and also performed better on a prospective cohort of 27 fetuses with estimated fetal weight less than 1000 g. Of the existing formulas, the Hadlock formula (using head circumference, abdominal circumference, femur length) was the most accurate, being significantly more accurate than all but the Woo formula with all but the Woo formula.

Establishment and application of a normal range for nuchal translucency across the first trimester.

Before chorionic villus sampling at 10-13 weeks' gestation, 453 women had the crown-rump length and nuchal translucency (NT) measured with transabdominal ultrasound. There were 19 aneuploid pregnancies (ten cases of trisomy 21, six of trisomy 18, one of 47 + marker, one 47,XXX, and one 45,X mosaic). Average NT was 1.7 mm (range 0-5 mm), correlating with the crown-rump length, but not maternal age. A static cut-off of 2.5 mm gave a false-positive rate of 1.3 per cent for crown-rump length between 30 and 35 mm, rising to 13 per cent in fetuses with a crown-rump length between 50 and 65 mm. This gave an overall false-positive rate of 5.5 per cent for a detection rate of 30 per cent for trisomy 21. Applying a dynamic action limit (95th centile), the false-positive rate remained at 5 per cent irrespective of the crown-rump length, detecting 30 per cent of trisomy 21 and 36.8 per cent of all aneuploidies. Raising the action limit to the 97.5th centile halved the false-positive rate (2.5 per cent), with no change in trisomy 21 detection and only a slight decrease in aneuploidy detection (31.6 per cent). Aneuploid fetuses showed normal first-trimester growth. NT increases with gestational age, making a dynamic action limit necessary to decrease the false-positive rate, while maintaining aneuploidy detection rates. Aneuploidy does not cause significant first-trimester growth retardation, enabling normal ranges for NT with crown-rump length to apply.

Phage antibodies against an unstable hapten: oxygen sensitive reduced flavin.

It is difficult to raise antibodies against haptens and antigens that are unstable under the physiological conditions of the serum. Here we have used a phage antibody library to isolate antibody fragments against oxygen sensitive reduced flavin, by selection of the phage under anaerobic and reducing conditions at pH 5 and a pre-elution step with the oxidized flavin. The binding of the reduced hapten to one of the antibody fragments was characterised by time-resolved polarised fluorescence, and shown to be highly specific for the reduced flavin.

Fetal death after exposure to methylene blue dye during mid-trimester amniocentesis in twin pregnancy.

Methylene blue dye use during mid-trimester amniocentesis in twin pregnancy is associated with a high risk of small intestinal atresia. It is plausible that the effects of methylene blue as a fetotoxic agent may also lead to fetal death. We conducted a retrospective cohort study of all women who had an amniocentesis during twin pregnancy from 1980 through 1991 in New South Wales, Australia. Women who were exposed to methylene blue dye during the procedure were compared with women who had amniocentesis without dye exposure. Fetal death occurred in 31.8 per cent of pregnancies that had exposure to a high concentration of methylene blue, compared with 14.5 per cent of pregnancies exposed to a low concentration and 4.3 per cent of pregnancies with no exposure to dye. The unadjusted and adjusted risks and 95 per cent confidence intervals (CIs) for fetal death after any exposure to dye were 5.03 (2.12-11.91) and 8.52 (2.28-31.80), respectively. The adjusted odds ratio and 95 per cent CIs for the low and high concentration dye solutions were 4.63 (0.93-23.13) and 14.98 (3.40-66.08), respectively (chi-squared test for trend P < 0.001). Fetus papyraceous was significantly more likely among pregnancies exposed to a high concentration of methylene blue (P < 0.001) than among unexposed pregnancies. These results support the hypothesis that methylene blue dye use during mid-trimester amniocentesis in twin pregnancy increases the risk of fetal death.

Utility of fetal intraperitoneal saline infusion in the prenatal evaluation of diaphragmatic hernia.

The diagnosis of a diaphragmatic hernia at 18 weeks gestation by instillation of normal saline into the fetal peritoneal cavity under ultrasound guidance is described. The procedure established the diaphragmatic defect with certainty, outlined the contents of the hernia within the thorax, and demonstrated the degree of secondary lung compression.

Maternal serum screening and routine 18-week ultrasound in the detection of all chromosomal abnormalities.

Over a 15-month period, maternal serum screening (alpha fetoprotein, oestriol, chorionic gonadotrophin) and ultrasound were evaluated in the detection of all chromosomal abnormalities. Of the 981 screened, there were 8 chromosomally abnormal pregnancies. Six of these were considered to be at increased risk on serum screening, all of which were detected. Of the remaining 2, one was detected by ultrasound and the other resulted in a liveborn baby with trisomy 21. The positive and negative predictive values for serum screening for all chromosomal abnormalities was 7.8% and 99.9% respectively. The sensitivity and specificity was 87.5% and 91.5% respectively. Serum screening is useful in the detection of many chromosomal abnormalities, not just Down syndrome. The combination of maternal serum screening and ultrasound has a high negative predictive value and is valuable in providing reassurance of no underlying chromosomal abnormality. With a positive predictive value of 7.8% a chromosomal abnormality will be found once in every 13 amniocenteses performed.

Disappearing lung echogenicity in fetal bronchopulmonary malformations: a reassuring sign?

Congenital bronchopulmonary malformations detectable on prenatal ultrasound include cystic adenomatoid malformation (CAM), lobar sequestration, and upper airway atresia. We describe three fetuses with prenatally detected intrathoracic lesions in which the associated pulmonary hyperechogenicity disappeared before delivery. In the first case of pulmonary sequestration, the infant was asymptomatic after birth. However, in a case of CAM and another with laryngeal atresia, respiratory distress developed after delivery, despite recent scans showing apparently normal lung fields. This experience suggests that ultrasonic resolution of hyperechogenic lung lesions in utero does not necessarily indicate resolution of the underlying pathology.

Fetal ovarian cysts: diagnostic and therapeutic role for intrauterine aspiration.

Antenatal diagnoses of fetal ovarian cysts have not usually been confirmed until postnatal surgery. We describe 2 cases of hemorrhage into fetal ovarian cysts in which cyst aspiration in utero allowed both confirmation of the diagnosis prenatally and obviated the need for neonatal surgery. In both cases, cytology of the cyst aspirate demonstrated luteinized granulosa cells and biochemistry showed estradiol levels of > 10,000 pmol/l, indicating ovarian etiology. Hemorrhage, which had been suspected on ultrasound, was confirmed by cytology, showing hemosiderin-laden macrophages. There was no evidence of recurrence in either case following aspiration. The described association of fetal hypothyroidism was excluded by testing thyroid function in cord blood and/or cyst aspirate. We suggest that intrauterine aspiration contributes to the management of fetal ovarian cysts by confirming their ovarian origin, demonstrating the presence or absence of hemorrhage and facilitating preservation of ovarian function both by reducing the risk of torsion and the need for neonatal surgery.

Outcome of 1500 consecutive chorionic villus samplings.

OBJECTIVE: To evaluate the clinical complications and diagnostic problems of chorionic villus sampling. DESIGN: A pragmatic retrospective analysis. SETTING: Tertiary obstetric referrals mostly to private practice; sampling carried out at Royal Prince Alfred Hospital; diagnostic analysis usually at Oliver Latham Laboratory, or the Clinical Immunology Research Centre, Royal Prince Alfred Hospital, New South Wales. PATIENTS: 1500 women in the first trimester of pregnancy requesting prenatal diagnosis because of a risk of chromosomal or inherited genetic disorder in the fetus. INTERVENTIONS: Ultrasound-guided passage of a catheter into the chorion through the cervix. MAIN OUTCOME MEASURES: Incidence of unintended abortion, preterm births, low weight infants and discrepant karyotypes. RESULTS: There were 42 unintended abortions (3.0%), about 0.4% higher than the background abortion rate in women of similar age. Abortion did not occur more frequently in women with vaginal bleeding earlier in that pregnancy. Rates of preterm births and birth of low birthweight infants did not differ from the general population. A second diagnostic test was required in 68 women (4.5%). Mosaicism and tetraploidy were usually confined to the chorion. CONCLUSION: Chorionic villus sampling is an acceptable diagnostic test. Amniocentesis should be offered to patients who show mosaicism or tetraploidy.

False-negative amniotic fluid acetylcholinesterase in a case of meningo-encephalocele.

We describe a patient with a significantly elevated serum alphafetoprotein (AFP) concentration at 17 weeks of gestation, who showed only a marginally increased amniotic fluid AFP and lacked the second rapidly migrating band of acetylcholinesterase electrophoresis. Ultrasound examination revealed an encephalocele and ventriculomegaly. Autopsy showed that the encephalocele was not covered by skin.

The immediate effects of chorionic villus sampling on fetal movements.

The immediate effects of chorionic villus sampling on the fetus was studied by real-time ultrasound observation of fetal movements. Thirty-minute recordings, directly before and after chorionic villus sampling, were made in 10 women. No changes were observed in the incidence or distribution of the four movement patterns studied. This held true even in the two cases that ended in a spontaneous abortion. It is concluded that chorionic villus sampling does not stimulate movements or alter the intrauterine situation in such a way that fetal movements decrease.

DNA analysis for antenatal diagnosis of thalassaemia and haemophilia.

Two years' experience with DNA analysis for the antenatal diagnosis of thalassaemia and haemophilia is described. The advantages of DNA testing, including a first-trimester diagnosis and greater availability, must be considered in relation to the problems that are associated with this procedure. In particular, the risk of recombination in DNA polymorphism studies should be understood and explained fully to the patient.

Abnormal karyotype in the chorion, not confirmed in a subsequently aborted fetus.

An abnormal fetal karyotype, containing a del 16(q21-qter) as an extra chromosome, was diagnosed in all 14 metaphases examined in a sample of chorionic villous biopsy material. After elective abortion a mosaicism for this cell-line together with a normal one was detected in the chorionic tissue. Fibroblast cultures from several fetal skin biopsies all revealed a normal karyotype.