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G Barkai

Publications and source records attributed to G Barkai.

At least 127 records · Page 7Linked to original sources
PubMed1986

Effect of blood contamination on the fluorescence polarization value of amniotic fluid lamellar bodies.

Estimation of fetal lung maturity by examination of amniotic fluid samples is unreliable in the presence of blood. Centrifugation of amniotic fluid at 10,000 X g separates the surfactant-containing lamellar bodies from contaminants, such as serum lipids. The influence of serum contamination of amniotic fluid was evaluated using the fluorescence polarization technique for determination of fetal lung maturity. Addition of serum changed the amniotic fluid P value of both the amniotic fluid and the lamellar body pellets in the direction of the P value of serum. After centrifugation at 10,000 X g, there was no significant difference in the P value of the pre- and postcontamination samples, demonstrating that centrifugation resulted in the removal of pulmonary nonrelevant lipids in contaminated amniotic fluid specimens. In 24 patients in whom the amniotic fluid sample was blood stained, the P value on the lamellar body pellet compared favorably to that obtained from noncontaminated samples.

Amniotic Fluid↗
PubMed1986

Impact of a protocol for external cephalic version under tocolysis at term.

We present our experience with 60 trials of external cephalic version under tocolysis (EVT) performed on 58 women with uncomplicated (low-risk) pregnancies at term (37 to 42 weeks) during a 10-month period. Version was successful in 67.2% of the subjects (70.7% of trials). Fetal well-being was monitored before, during and after the procedure by cardiotocography and real-time ultrasound (RTUS). No analgetic or anesthetic medication was administered. Transient fetal bradycardia was recorded in 18 women. No major complications were noted. Compared with the period preceding the protocol, the breech rate declined during the study period by 1.02% (P less than 0.02) with a parallel decline of 1.12% (P less than 0.001) in the low-risk breech group affected by the protocol. The cesarean section rate for low-risk breeches fell from 1.85 to 0.89% (P less than 0.001), while the overall cesarean section rate decreased from 10.15 to 9.1% (not significant). We conclude from our experience and previous studies that EVT/RTUS is a reasonable alternative in the management of pathological presentations near term, provided that only low-risk pregnancies are included, and analgesia or anesthesia for external version under tocolysis is avoided.

Breech Presentation↗
PubMed1986

Determination of fetal lung maturity by fluorescence polarization of the amniotic fluid lamellar bodies.

High-speed centrifugation of amniotic fluid enables separation of surfactant-containing lamellar bodies. Fifty-three amniotic fluid samples from pregnancies of 28 to 39 weeks' gestation were examined for fetal lung maturity by measuring fluorescence polarization (P). For each sample the P value was determined at 37C on both the whole amniotic fluid and on the surfactant-containing lamellar bodies obtained by centrifugation at 10,000 X g. A close linear correlation (r = 0.80) was found between the P value of the amniotic fluid samples and that of the lamellar bodies. There was no difference in the specificity for discrimination of hyaline membrane disease cases by both methods (93.5%) with 95% confidence limits of 82.1 to 98.6%. Because high-speed centrifugation enables the selective sedimentation of pulmonary surfactant, determination of the lamellar body P value may offer a practical solution for the estimation of fetal lung maturity in amniotic fluid samples contaminated with blood.

Amniotic Fluid↗
PubMed1985

The effect of pressure on the lipid microviscosity and phase transition of lung surfactant.

The effect of pressure on the lipid dynamics of the rat lung surfactant was studied in liposomes made of the natural lung surfactant of the rat and of model phospholipid mixture. The determined parameter was the lipid microviscosity, monitored by the fluorescence polarization of the probe 1,6-diphenyl-1,3,5-hexatriene. Osmotic pressure of up to 47 atm, as well as hydrostatic pressure of up to 1.4 kbar, were applied at a constant temperature. The effect of pressure was monitored by the change in the lipid microviscosity of the system. The maximal change achieved with osmotic pressure at a constant temperature was only 30%. This suggests that the conversion of melted lipid to its solid phase above the lipid critical temperature requires several hundred atmospheres. Similarly, measurements of lipid microviscosity under increased hydrostatic pressure revealed transitions which occurred at above 400 atm. Since such pressures are far beyond the physiological scale, it excludes the possibility that pressure alone can be responsible for a full phase transition of the lung surfactant during respiration. Upon decompression, microviscosity of the examined lipid system was found to return to its original values, confirming the reversibility of the process.

Animals↗
PubMed1985

Determination of amniotic fluid microviscosity at body temperature: a predictor of fetal lung maturity.

One of the most convenient ways to determine fetal lung maturity is by measuring the fluorescence polarization (P) of the amniotic fluid at room temperature. With sensitivity fixed on 100%, specificity is relatively unsatisfactory. The present study compared the predictive power of fluorescence polarization measured at temperatures 25C (P25), 37C (P37), and 40C (P40) among 195 consecutive samples tested at both 25C and 37C, with a subgroup of 86 samples tested also at 40C. A better separation between the results for fetuses with and without hyaline membrane disease is attained at P37, demonstrated by a greater mean standardized distance (distance between P values for those patients with and the mean P value for those patients without hyaline membrane disease in unit of standard deviation of the latter; 1.597 +/- 0.528 for P25 versus 2.332 +/- 0.591 for P37). Fixing the sensitivity at 100%, the specificity of P25 and P37, were 68.9 and 94.9%, respectively; a highly significant difference (P less than .001). The specificity of P40 was 90.5%, lower than that of P37. P37 is the best predictor and adding either P25 or P40 does not improve the prediction of lung maturity. It is concluded that P37 should replace P25 as the definite index for fetal lung maturity.

Amniotic Fluid↗
PubMed1983

Asymmetry of lipid organization in cholinergic synaptic vesicle membranes.

The lipid composition of purified Torpedo cholinergic synaptic vesicles was determined and their distribution between the inner and outer leaflets of the vesicular membrane was investigated. The vesicles contain cholesterol and phospholipids at a molar ratio of 0.63. The vesicular phospholipids are (mol% of total phospholipids): phosphatidylcholine (40.9); phosphatidylethanolamine (24.6); plasmenylethanolamine (11.5); sphingomyelin (12); phosphatidylserine (7.3); phosphatidylinositol (3.7). The asymmetry of the synaptic vesicle membranes was investigated by two independent approaches: (a) determining accessibility of the amino lipids to the chemical label trinitrobenzenesulphonic acid (TNBS); (b) determining accessibility of the vesicular glycerophospholipids to phospholipase C (Bacillus cereus). TNBS was found to render the vesicles leaky and thus cannot be used reliably to determine the asymmetry of Torpedo synaptic vesicle membranes. Incubation of the vesicles with phospholipase C (Bacillus cereus) results in biphasic hydrolysis of the vesicular glycerophospholipids. About 45% of the phospholipids are hydrolysed in less than 1 min, during which no vesicular acetylcholine is released. In the second phase, the hydrolysis of the phospholipids slows down markedly and is accompanied by loss of all the vesicular acetylcholine. These findings suggest that the lipids hydrolysed during the first phase are those comprising the outer leaflet. Analysis of the results thus obtained indicate that the vesicular membrane is asymmetric: all the phosphatidylinositol, 77% of the phosphatidylethanolamine, 47% of the plasmenylethanolamine and 58% of the phosphatidylcholine were found to reside in the outer leaflet. Since phosphatidylserine is a poor substrate for phospholipase C (B. cereus), its distribution between the two leaflets of the synaptic vesicle membrane is only suggestive.

Acetylcholine↗
PubMed1983

Amniotic fluid fluorescence polarization value at physiological temperature: a marked improvement in assessing fetal lung maturity.

Determination of fetal lung maturity by measurement of the fluorescence polarization (P) value of the amniotic fluid at room temperature has become the method of choice in an increasing number of perinatal units because of its simplicity and relatively high predictive value. Nevertheless, its power to discriminate between cases with and without hyaline membrane disease (HMD) needs improvement. To this end, we assessed the discriminative power of the P value at the physiological temperature of 37 degrees C (P37) as compared with the power at 25 degrees C (P25). The study group consisted of 288 consecutive cases at risk for preterm delivery. Samples from all 288 cases were measured at 25 degrees C and samples from 112 of these were measured concurrently at 37 degrees C as well. HMD occurred in 27 infants of the total group, nine of whom belonged to the subgroup tested at both temperatures. When sensitivity was fixed at 100% the specificity of P37 was 97% as compared to 79% for P25 (p less than 0.001). The percentage of cases with infants free of HMD who had borderline P values was also significantly smaller: 1% vs 21%, respectively (p less than 0.001). Although data on more HMD cases are needed to establish the precise threshold of lung maturity for P37, we conclude that P37 is a considerably better discriminator for fetal lung maturity determination than P25.

Amniotic Fluid↗
PubMed1982

Thrombotic thrombocytopenic purpura in pregnancy.

A 20 week primigravida with intrauterine fetal death and the rare occurrence of thrombotic thrombocytopenic purpura (TTP) in pregnancy is presented. Aprotinin has been used to overcome uterine inertia non-responsive to oxytocin stimulation. TTP was successfully treated with repeated plasmaphereses. The literature is briefly reviewed and the complexity and importance of the differential diagnosis specific to the pregnant patient is discussed.

Adult↗
PubMed1982

Determination of fetal lung maturity from amniotic fluid microviscosity in high-risk pregnancy.

During a 3-year period, 377 samples of amniotic fluid, free of blood and meconium and obtained from a total of 471 patients, were examined by the fluorescence polarization technique to estimate fetal lung maturity. Fluorescence polarization values of 287 samples from normal and abnormal pregnancies were correlated with gestational age. A total of 272 pregnancies comprising cases complicated by toxemia, placental insufficiency, placenta previa, premature contractions, and diabetes mellitus, and including a control group of 37, were studied to discern the effect of such pathologic conditions on the usual decline of fluorescence polarization (FP) values with increasing gestational age. No complicated pregnancy had values significantly different from those of the control group, except for pregnancies complicated by diabetes mellitus. The threshold of fetal lung maturity as related to respiratory distress syndrome (RDS) was determined in correlation with the lecithin: sphingomyelin (L:S) ratio. FP values of 0.311 +/- .005 corresponded to an L:S ratio of 2.0. An FP value of 0.316 +/- .005 is recommended as a practical threshold related to the clinical outcome of the newborn as regards RDS. The technique was found reliable, simple, and accurate and has been of great value in the antenatal diagnosis of fetal lung maturity.

Amniotic Fluid↗
PubMed1979

Intra-amniotic thyroxine (T4) absorption by the premature human foetus.

We reported previously on the beneficial influence of intra-amniotic T4 injection in accelerating human foetal lung maturity. Twenty-four h after T4 (250 microgram) intra-amniotic injection, the mean cord serum T4 concentration in 13 premature newborns was 17 +/- 2.1 microgram/100 ml, while the T4 concentration in a matched group was only 11.6 +/- 0.9 microgram/100 ml: in 5 of the infants who received intra-amniotic thyroxine T4 was measured 12 h post-partum and rose from 16.1 +/- 1.8 to 24.3 +/- 2.6 microgram/100 ml. No change in maternal T4 concentration was observed. The mean cord serum T4 concentration in premature newborns delivered more than 3 days following T4 intra-amniotic injection, however, was not significantly different from that of the controls. These data suggest that T4 (250 microgram) injected intraamniotically is absorbed by the premature human foetus. Furthermore, the hyperthyroxinaemia is only transient, and does not prevent the post-natal T4 surge.

Absorption↗
PubMed1978

Enhancement of fetal lung maturity by intra-amniotic administration of thyroid hormone.

Following preliminary results in animal studies demonstrating that thyroxine (T4) injected directly into the fetus or the amniotic sac is capable of enhancing fetal lung maturity, a trial of thyroxine treatment in mean was carried out. Two hundred micrograms of T4 were injected intra-amniotically in eight women with high-risk pregnancies in which premature delivery was inevitable or indicated. Fetal lung maturity was evaluated by a recently developed, accurate, and rapid method using the microviscosity value epsilon (this being the linear expression of the polarization value P) of the lipid assembly of the amniotic fluid as a parameter of the surfactant content. epsilon Values, which were very high before T4 injection, dropped steeply to below the value of 4.344, indicating fetal lung maturity. Eight newborn infants delivered, five by caesarean section, soon after the T4 injection did not develop respiratory distress syndrome, although they were born prematurely. Intra-amniotic injection of T4 appears to be of therapeutic value in enhancing fetal lung maturity.

Amnion↗
PubMed1976

A new method for assessment of fetal lung maturity.

A new method for evaluation of fetal lung maturity in utero is described. The method is based on the fluorescence polarization (P) of the lipids in the amniotic fluid after labelling with a special dye. Tests performed with 49 amniotic fluid samples drawn from 33 pregnancies clearly demonstrated a decrease in P during gestation which correlated with the increase in the lecithin/sphingomyelin ratio (L/S) in the fluid. During gestation the P value at 24 degrees C decreased steadily from about 0-4 to 0-2 and the value of P (24 degrees C) = 0-310 has been tentatively chosen as the threshold above which respiratory distress syndrome may develop. The described method, which requires a specially designed instrument, offers a series of important advantages over the presently available methods. It is simple, rapid, highly accurate and reproducible, and independent of amniotic fluid volume. The P value reflects the microviscosity in the whole lipid assembly of amniotic fluid and is not confined specifically to lecithin.

Amniotic Fluid↗
PubMedDate not supplied

Hematopoietic progenitor cells as targets for non-invasive prenatal diagnosis: detection of fetal CD34+ cells and assessment of post-delivery persistence in the maternal circulation.

Culture expansion of fetal cells from the maternal circulation will provide an increased number of cells for non-invasive prenatal diagnosis. Hematopoietic CD34+ cells are potential candidates for this application. More information is needed regarding the frequency of these cells and the phenomenon of post-delivery persistence in the maternal circulation. In this study we assessed the number of fetal CD34+ cells in the maternal circulation, the effect of culture expansion on the number of fetal cells and the persistence of fetal CD34+ cells from previous pregnancies. Fetal cells were identified by the presence of Y-chromosome sequences detected by FISH and nested PCR. Fetal CD34+ cells were detected in all samples from women carrying a male fetus. A low number of residual fetal cells from previous pregnancies was detected (1-3 XY cells in 20 ml blood) in less than 1/3 of the samples from both non-pregnant women and those pregnant with a female fetus. Culturing of CD34+ cells resulted in a significant increase in fetal cell numbers. However, the number of fetal cells persisting from previous pregnancies also increased after culture. It is proposed that information derived from CD34+ cells could potentially support data derived from other cell types for more accurate non-invasive prenatal diagnosis.

Antigens, CD34↗