Abstract:Measurement of the production of surfactant is the most direct means of prenatally assessing fetal pulmonary maturity. We review assays which have evolved for measuring surfactant, classifying them into two general categories: biochemical quantitation and biophysical measurements. Biochemical quantitation assays include the amniotic fluid lecithin/sphingomyelin ratio and quantitation of lecithin and other surfactant phospholipids. Biophysical measurements include measurement of surface-tension-lowering ability… Show more
“…In human medicine, several tests have been developed to assess the presence of surfactant in the amniotic fluid during pregnancy (Freer & Statland, ; Schlueter, Phibbs, Creasy, Clements, & Tooley, ). Among these tests, foam‐stability assays depend on the ability of the pulmonary surfactant to generate stable foam in the presence of ethanol.…”
The goal of this study was to evaluate the reliability of amniocentesis during late pregnancy to assess lung maturity in puppies using a bubble test as described by Gunston and Davey (South African Medical Journal, 54, 1978, 495). Thirty-five bitches from eight different breeds were followed during late pregnancy before undergoing elective Caesarean (C)-section on days 61-62 after ovulation. Bubble tests were performed the day before the C-section (n = 11 bitches) and before the administration of aglepristone on amniotic fluid samples obtained via amniocentesis and were repeated the day of the surgery on amniotic fluid samples collected via puncture of the amniotic bags before they were opened (n = 35 bitches). No complications were observed following amniocenteses and the C-sections. The mortality rate (2.3%) was similar to the result of other studies using the same protocol for an elective C-section. Of the non-contaminated samples collected the day of the C-section, 89.6% were positive in the bubble test, which was consistent with observations of clinical maturity the day of the surgery and on the following days. In contrast, 70% of the samples collected the day before the C-section (when progesterone concentrations were still high) were negative, suggesting that the puppies were still immature at this point in the pregnancy. Additionally, we observed a significant difference in the bubble test results before and 18 hr after the administration of aglepristone, suggesting that aglepristone may act as an inducer of the final maturation of the puppies by inactivating progesterone receptors and simulating a physiological decrease in progesterone. Finally, we confirmed the need to exclude all contaminated samples, which could lead to false-negative results.
“…In human medicine, several tests have been developed to assess the presence of surfactant in the amniotic fluid during pregnancy (Freer & Statland, ; Schlueter, Phibbs, Creasy, Clements, & Tooley, ). Among these tests, foam‐stability assays depend on the ability of the pulmonary surfactant to generate stable foam in the presence of ethanol.…”
The goal of this study was to evaluate the reliability of amniocentesis during late pregnancy to assess lung maturity in puppies using a bubble test as described by Gunston and Davey (South African Medical Journal, 54, 1978, 495). Thirty-five bitches from eight different breeds were followed during late pregnancy before undergoing elective Caesarean (C)-section on days 61-62 after ovulation. Bubble tests were performed the day before the C-section (n = 11 bitches) and before the administration of aglepristone on amniotic fluid samples obtained via amniocentesis and were repeated the day of the surgery on amniotic fluid samples collected via puncture of the amniotic bags before they were opened (n = 35 bitches). No complications were observed following amniocenteses and the C-sections. The mortality rate (2.3%) was similar to the result of other studies using the same protocol for an elective C-section. Of the non-contaminated samples collected the day of the C-section, 89.6% were positive in the bubble test, which was consistent with observations of clinical maturity the day of the surgery and on the following days. In contrast, 70% of the samples collected the day before the C-section (when progesterone concentrations were still high) were negative, suggesting that the puppies were still immature at this point in the pregnancy. Additionally, we observed a significant difference in the bubble test results before and 18 hr after the administration of aglepristone, suggesting that aglepristone may act as an inducer of the final maturation of the puppies by inactivating progesterone receptors and simulating a physiological decrease in progesterone. Finally, we confirmed the need to exclude all contaminated samples, which could lead to false-negative results.
“…From this extrapolation we obtain that at 37 °C C c = 19.9 μg cm -3 and d c = 1.47. This value of C c at 37 °C corresponds to the lower limit (found by independent methods, refs and ) of phosphatidylcholine concentration which permits us to define a sample of amniotic fluid as a mature one. The above value should be regarded as a tentative one as far as it is determined for foam bilayers obtained from a complex lipid−protein mixture and its accuracy is the one of determination of the threshold dilution for samples of both normal pregnancy and pathological cases. 3 Arrhenius dependence of the critical concentration C c for formation of AF foam bilayer ( C c in μg cm -3 ): ▪, experimental data for DPPC foam bilayers; ·, experimental data for AF foam bilayers; ○, C c value for AF foam bilayers at 37 °C, calculated by extrapolation according to eq 2 under assumption C c = C e ; curves, best fit of eq 2 to experimental data under assumption C c = C e (curve 1, DPPC liquid crystalline foam bilayers; curve 2, DPPC gel foam bilayers; curve 3, AF foam bilayers).…”
Section: Discussionmentioning
confidence: 73%
“…As is well-known, , phosphatidylcholines are of the highest content in AF, the main component being dipalmitoylphosphatidylcholine (DPPC). That is why it is important to compare the data for the temperature dependence of the critical concentration C c for formation of foam bilayer from AF and from DPPC .…”
Section: Discussionmentioning
confidence: 96%
“…The chemical composition of amniotic fluid has been studied by numerous authors in detail, e.g., refs and . Saturated and unsaturated phosphatidylcholines (about 80% of the total lipid content) and mostly dipalmitoylphosphatidylcholine predominate in amniotic fluid.…”
The temperature effect on the threshold dilution (e.g., threshold concentration) for formation of foam bilayers (Newton black films) from amniotic fluid is investigated. Samples of amniotic fluid are collected during the 39th gestation week. Microscopic foam films are formed from diluted amniotic fluid and studied interferometrically by the method of Scheludko and Exerowa within the temperature range 10-30°C. The threshold dilution is determined from the experimental dependence of the probability for observation of foam bilayer on the dilution for each sample at different temperatures. It is shown that the threshold dilution is inversely proportional to the threshold concentration for formation of foam bilayer. This parameter is crucial for assessment of the risk for respiratory distress syndrome in newborns. The binding energy Q of a lipid molecule in the foam bilayer is calculated from the Arrhenius dependence of the threshold dilution applying the hole-nucleation theory of bilayer stability. The so-obtained values of Q for the various samples are very close to each other and vary from 5.3 × 10 -20 to 9.4 × 10 -20 J (about 13-22 kT), which indicates that in all cases the foam bilayers are in the liquid-crystalline state. Comparison is made with the phase states of dipalmitoylphosphatidylcholine foam bilayers.
IntroductionRecently a new approach was introduced for clarification of amphiphile bilayer formation and stability. A holenucleation theory which explains the amphiphile bilayer stability and permeability on the basis of short-range molecular interactions was developed. 1-3 This theory was confirmed experimentally for foam 4-6 and emulsion bilayers. 7 The parameters (for example the critical concentration C c for formation of foam bilayer) and relations set up in the theory are convenient for investigation of the formation and phase state of foam bilayers from various synthetic and natural surfactants. They present a method of obtaining some molecular characteristics of foam bilayers such as the binding energy of a phospholipid molecule in the bilayer and the specific edge free energy of the nucleus hole for different phase states of the bilayers.This new approach was applied successfully for studying foam bilayers from amniotic fluid (AF), as well as from some of its components 8 in relation to the physicochemical clinical method for diagnostics of lung maturity of newborns, proposed by us. 9 This method includes the detection of the threshold bulk concentration of phosphatidylcholines necessary for foam bilayer formation. This threshold concentration is determined from the experimental dependence of the probability for observation of foam bilayer from AF on the concentration. 9 Numerous methods for prediction of lung maturity by examination of amniotic fluid 10-16 and lung surfactant 17,18 have been developed. The air/solution interface is essential in the methods related to monolayer, 17 bubble, 18 and foam. 11 Each of these methods exploits a certain surface parameter for determination of the prop...
“…The laboratory conference period is used to discuss additional methods used to assess fetal lung development. 5 In week 6, the students examine factors which influence the rate of enzyme-catalyzed reactions, using the turbidimetric assay method with Micrococcus cell-wall suspensions and hen egg-white lysozyme (Sigma). The assay method used is similar to that described in the laboratory manual by Rendina.…”
Section: Detailed Description Of the Coursementioning
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