George W. Brumley

Correlations of Mechanical Stability, Morphology, Pulmonary Surfactant, and Phospholipid Content in the Developing Lamb Lung*

Pressure-volume characteristics and surface tension measurements of the lamb of 120 to 130 days gestational age were typical of the mature lung in the upper lobes and the immature lung in the lower lobes. By term both upper and lower lobes had findings characteristic of the mature animal. Phospholipid concentration per milligram DNA and per cent saturated fatty acids on pulmonary phosphatidyl choline were relatively constant from 60 to 120 days gestational age; thereafter there was a significant increase in both measurements. These changes usually coincided with an increase in osmiophilic inclusion bodies in the large alveolar cell.A concentration of disaturated phosphatidyl choline per milligram DNA in excess of 0.170 mg per mg was associated with a minimal surface tension below 13 dynes per cm (p < 0.001). Newborn animal lungs contained over 3 times this critical concentration, whereas adult lungs contained 1.5 times this value. The excess disaturated phosphatidyl choline per milligram DNA may represent a reservoir of pulmonary surfactant.

A unique phosphatidylcholine exchange protein isolated from sheep lung

It has been established that disaturated phosphatidylchohne is the major surface-active agent in mammalian lung surfactant which lowers surface tension and prevents alveolar collapse at end-expiration [1,2]. Investigations of the synthesis, packaging and release of lung phosphatidylcholine (PC) have demonstrated that the endoplasmic reticulum of Type II pneumocytes is the major site of PC synthesis [3] and that lamellar bodies of these cells make up the primary intracellular storage organelle [4]. The mechanisms by which PC is transferred from the site of synthesis to the storage organelle or onto the alveolar surface are unknown. Phosphatidylcholine exchange proteins which catalyze the exchange of PC between membr~e structures in vitro [5,6], are widely distributed f7] and have been well characterized in bovine liver [8,9], heart [lO,ll] , brain [12] and in rat liver 113,141 andintestine [15]. We report here the purification of a novel phosphatidylcholine exchange protein from sheep lung with pI 7.1 and mol. wt 21 000 as determined by Sephadex G 75 chromatography and SDS-polyacrylamide gel electrophoresis. A second phosphatidylcholine exchange protein also was isolated from sheep lung which is very similar to that purified from bovine liver [S] ; pI 5.8, mol. wt 22 000. Both exchange proteins have been purified over 1 SO-fold.

Protein-catalyzed transfer of phosphatidyglycerol by sheep lung soluble fraction

It is generally agreed that the phospholipids oflung surfactant lower the surface tension at the alveolar air-water interface and allow the alveolus to remain open at end-expiration [ 11. While a monolayer of disaturated phosphatidylcholine is sufficient to adequately lower this surface tension [2], other phospholipids such as phosphatidyglycerol, the second most abundant surfactant phospholipid, may be required for monolayer formation under physiological conditions [3]. Phosphatidylglycerol is absent in the tracheal secretions of infants with Respiratory Distress Syndrome but appears during recovery from this disease [4]. Its dynamics are therefore of considerable interest. While a number of investigations have been concerned with the synthesis of phosphatidylglycerol [ 5,6], little is known about the mechanism by which it becomes a major constituent of lung surfactant. The presence of phospholipid exchange proteins has been demonstrated in the soluble fraction of lung [7-91 and they are known to catalyze the transfer of phosphatidylcholine between membrane fractions of the lung [9,10]. These proteins may be important in providing a mechanism for packaging specific phospholipids into lamellar bodies, but thus far the transfer of phosphatidylglycerol has not been reported. We provide evidence here of protein catalyzed phosphatidylglycerol transfer by sheep lung soluble fraction; this activity chromatographs on Sephadex G75 with an elution volume corresponding to the 30 000 MW range.

Lung phosphatidylcholine transfer in six vertebrate species: Correlations with surfactant parameters

We have examined phosphatidylcholine transfer activity in lung-soluble fractions from six vertebrate species. There is a significant correlation between the amount of phosphatidylcholine transfer activity and both the alveolar surface area and surface active material. This suggested that phosphatidylcholine exchange proteins have a role in the lung surfactant system.

Evaluation of serum immunoglobulin concentrations in the perinatal period by use of a standardized method of measurement

Concentrations of IgG, IgA, and IgM were quantitatively estimated by single radial diffusion in 133 maternal cord serum pairs and in 84 newborn sera. The antisera and reference standards were prepared in this laboratory and the IgM antibody-agar plates for cord and newborn sera contained the optimal amount of antiserum for IgM concentrations usually found at those ages. All data were converted to logarithms for statistical analyses. The ±2 standard deviation limits obtained for cord and newborn serum IgM concentrations were found to be sufficiently narrow to permit ready detection of deviations from the norm by standard statistical tests of significance.

Neonatal pneumonia associated with medium-chain triglyceride feeding supplement

The appearance of a similar pattern of multifocal pulmonary consolidation in four neonates receiving undiluted medium-chain triglyceride oil suggested a cause-and-effect relationship. This was supported by the demonstration in rabbits that the transtracheal injection of MCTO caused severe pneumonia. It is suggested that MCTO be mixed with formula before it is given to neonates.

Fetal lamb lung phosphatidylcholine: Response to asphyxia and recovery

Acute fetal asphyxia resulting from maternal blood loss and hypotension causes a reduction in the incorporation of precursors into disaturated phosphatidylcholine, the principal lipid in the pulmonary surfactant. Treatment of the maternal hypotension is associated with return of fetal lung DSPC synthesis to control levels by 72 hours.

Comparative incorporation of P32 into lung phosphatidyl choline in mammals with different metabolic and pulmonary morphologic characteristics.

Summary In the present study the incorporation of P32 into lung PC (cpm/mg DNA) was lowest in the sloth, was progressively higher in the cat, rabbit, and rat, and was highest in the mouse. It was 25 times greater in the adult mouse than in the sloth when expressed per gram fresh weight of lung tissue; it was 15 times greater when expressed as per mg DNA; and it was 11 times greater when expressed as specific activity. Lung PC specific activity from this study correlates well with alveolar surface area per unit lung volume, alveolar diameter, and oxygen consumption.

Fetal lamb lung lavage and its effect on lung phosphatidylcholine.

Summary: The lungs of intrauterine 135–136-day-old lambs were lavaged with amnionic fluid, with or without meconium, to determine the effect on lung phosphatidylcholine (PC) concentration, synthesis, and function. No differences were apparent between animals lavaged with amnionic fluid or amnionic fluid with meconium. When lavaged lungs were compared to nonlavaged controls, no detectable differences were observed in histology or the quantity of saturated (SPC) and unsaturated phosphatidylcholine (UPC). However, the lavaged lungs retained a larger fraction of maximal lung volume at 5 cm H2O distending pressure and the incorporation of (32P) orthophosphate into lung PC was significantly reduced. In addition, two lavaged animals who became acidotic (pH < 7.20) exhibited decreased incorporation of (14C) palmitate into whole lung unsaturated, and saturated phosphatidylcholine.Speculation: These data indicate that amnionic fluid can reduce lamb lung de novo synthesis of PC and may contribute to the alterations in lung PC found in neonatal syndromes of respiratory distress. Acidosis may accentuate this effect.

318 RISK: BENEFIT CONSIDERATIONS FOR THE SAFE USE OF ISOXSUPRINE IN THE TREATMENT OF PREMATURE LABOR

Seventy consecutive patients treated with isoxsuprine for premature labor were studied to determine pregnancy factors associated with tocolytic success, the extent of placental drug transfer, and time course of therapy in order to define conditions which would maximize success and minimize acute neonatal isoxsuprine toxicity. In patients with intact membranes, successful prolongation of pregnancy >7 days occurred in 77% of women with ≤50% cervical effacement and ≤3 cm dilatation at the initiation of therapy, and in none with >50% effacement and >3 cm dilatation. Cervical effacement was the primary factor in determining success. Cord isoxsuprine concentrations averaged 90% of maternal concentrations at delivery. Maternal and cord isoxsuprine concentrations at delivery were inversely correlated with the drug-free interval before delivery. An interval >5 hours was necessary to attain a cord concentration of <2 ng/ml, a level not associated with neonatal problems. Drug-free intervals ≤2 hours usually resulted in cord isoxsuprine values >10 ng/ml, levels associated with severe neonatal problems. Since 17 of the 22 infants with cord isoxsuprine concentrations >2 ng/ml and eight of nine with values >10 ng/ml were delivered of mothers with >3 cm dilatation or >50% effacement at the initiation or reinstitution of intravenous therapy, most severe neonatal drug-level related problems are preventable.