Foetal lung maturity

Black Film Method for Assessment of Foetal Lung Maturity... 

The creation of sensitive methods for assessment of foetal lung maturity are needed for prophylactics and neonate treatment of RDS. Numerous methods for prediction of lung... 

The results on formation and stability of black foam films, on the first place those on bilayer foam films (NBF) (see Sections 3.4.1.2 and 3.4.4) have promoted the development of methods which enable lung maturity evaluation. The research on stability of amphiphile bilayers and probability for their observation in the grey foam films laid the grounds of the method for assessment of foetal lung maturity created by Exerowa et al. [20,24]. Cordova et al. [25] named it Exerowa Black Film Method. It involves formation of films from amniotic fluid to which 47% ethanol and 7-10 2 mol dm 3 NaCl are added [20,24]. In the presence of alcohol the surface tension of the solution is 29 mN m 1 and the adsorption of proteins from the amniotic fluid at the solution/air interface is suppressed, while that of phospholipids predominates. On introducing alcohol, the CMC increases [26], so that the phospholipids are present also as monomers in the solution. The electrolyte reduces the electrostatic disjoining pressure thus providing formation of black foam lipid films (see Sections 3.4.1.2 and 3.4.4). 

The scope of the method for assessment of foetal lung maturity has been extended for evaluation of the risk for development of RDS of new-boms by testing AF with blood and mecomium, obtained from women with normal pregnancy [33]. An experimental study of corticosteroid action on lung surfactant [34] as well as the effect of betamethasone (Celestone) on foetal lung development in rats [35] has been also carried out. 

The experimental curves W(d) and W(C), shown in Fig. 11.6, are very informative with respect to formation of foam bilayers from amniotic fluid because these dependences are very steep. This fact allows precise determination of d, and C,. The clearly pronounced value of Cc (W = 0) practically coincides with the threshold concentration C, for observation of foam bilayer with W = 1, which was defined in the method for assessment of foetal lung maturity. 

The studies discussed expand the use of the method for assessment of foetal lung maturity with the aid of microscopic foam bilayers [20]. It is important to make a clear distinction between this method [20] and the foam test [5]. The disperse system foam is not a mere sum of single foam films. Up to this point in the book, it has been repeatedly shown that the different types of foam films (common thin, common black and bilayer films) play a role in the formation and stability of foams (see Chapter 7). The difference between thin and bilayer foam films [19,48] results from the transition from long- to short-range molecular interactions. The type of the foam film depends considerably also on the capillary pressure of the liquid phase of the foam. That is why the stability of a foam consisting of thin films, and a foam consisting of foam bilayers (NBF) is different and the physical parameters related to this stability are also different. Furthermore, if the structural properties (e.g. drainage, polydispersity) of the disperse system foam are accounted for it becomes clear that the foam and foam film are different physical objects and their stability is described by different physical parameters. 

Ishizuka, T. Ishikawa, K. Maseki, M. Tomoda, Y. Tsuda, T. Determination of phosphatidylglycerol in amniotic fluid for prediction of foetal lung maturity by microbore-column liquid chromatography, J.Chromatogr., 1986, 380, 43—53. 

Respiratory distress syndrome (RDS) is a common problem in premature infants. The immature lung fails to produce dipalmitoylleci-thin, which is a surfactant. RDS occurs when the alveoli collapse inwards after expiration and adhere under the prevailing surface tension (atelectasis). The function of dipahnitoyllecithin is to reduce the surface tension and permit expansion of the alveoli on inflation. Assessment of the maturity of foetal lung function can be made by measuring the ratio of lecithin to sphingomyelin (the L/S ratio) in amniotic fluid. 

In the foetal rabbit lung, pilocarpine administered subcutaneously to the mother (5 mg/kg) on days 24 through 27 of gestation, morphometry revealed a significant increase in the number of mature type II cells, both per unit area and per 1,000 lung cells of any kind (Smith et al. 1979). By electron microscopy, the alveolar epitheUum demonstrated mor-... 

In the preterm Macaca nemestrina (130-156 days of gestation), the number of alveolar macrophages is low and increases rapidly after birth (Jacobs et al. 1985). In foetal rabbits, macrophage appearance coincides with maturation of the lung near term and in the first days after birth (Zeligs et al. 1977, Sieger 1978). 

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