Using adult guinea-pigs, we have developed an experimental model in which alveolar surfactant phospholipids are removed by repeated lung lavage in vivo, and in which the short-term survival of the animals is ensured by artificial ventilation. Blood gases, parameters of lung mechanics, and histologic and electron microscopic findings indicate that the lavage procedure induces a condition similar to the adult respiratory distress syndrome. We propose that our technique might be used for evaluation of pharmacological agents and various forms of artificial ventilation which have been suggested for treatment of this disease.

No abstract

ABSTRACT. Objective. To determine whether early versus late treatment with porcine surfactant (Curosurf) reduces the requirement of mechanical ventilation in very preterm infants primarily supported by nasal continuous positive airway pressure (nasal CPAP).Design. Multicenter randomized, controlled trial.Patients. The study population comprised 60 infants <30 weeks' gestation with respiratory distress syndrome (RDS) who had an arterial to alveolar oxygen tension ratio (a/APO 2 ) of 0.35 to 0.22.The cohort from which the study population was generated comprised 397 infants.Results. The need for mechanical ventilation or death within 7 days of age was reduced from 63% in the latetreated infants to 21% in early-treated infants. Increasing numbers of antenatal steroid doses also improved the outcome, especially in the early-treated infants. Six hours after randomization mean a/APO 2 rose to 0.48 in the earlytreated infants compared with 0.36 in the late-treated. The need of mechanical ventilation before discharge was reduced from 68% in the late-treated to 25% in the earlytreated infants.Conclusions. Nasal CPAP in combination with early treatment with Curosurf significantly improves oxygenation and reduces the subsequent need for mechanical ventilation in infants <30 weeks' gestational age with RDS. Pediatrics 1999;103(2). URL: http://www.pediatrics. org/cgi/content/full/103/2/e24; respiratory distress syndrome, pulmonary surfactant, Curosurf, nasal continuous positive airway pressure.ABBREVIATIONS. RDS, respiratory distress syndrome; nasal CPAP, nasal continuous positive airway pressure; a/APo 2 , arterial to alveolar oxygen tension ratio; Fio 2 , fraction of inspired oxygen; TcPo 2 , transcutaneous partial pressure of oxygen; TcPco 2 , transcutaneous partial pressure of carbon dioxide; PDA, patent ductus arteriosus; NEC, necrotizing enterocolitis; BPD, bronchopulmonary dysplasia; IVH, intraventricular hemorrhage; PVL, periventricular leucomalacia; ROP, retinopathy of prematurity. I n a randomized, controlled study we have shown that a single dose of surfactant (Curosurf, Chiesi Farmateutici, Parma, Italy) given by short-lasting intubation reduces the need for mechanical ventilation and improves oxygenation in infants with moderate to severe respiratory distress syndrome (RDS) treated with early nasal continuous positive airway pressure (nasal CPAP).1 Very few pulmonary and extrapulmonary complications were observed in these infants. However, some of the surfactanttreated infants supported by nasal CPAP developed apnea despite good oxygenation and needed mechanical ventilation for that reason. In the same trial, there seemed to be a higher need for ventilation among infants randomized relatively late after birth and in infants with relatively low birth weight. From the literature we know that surfactant given prophylactically, 2-4 or as early treatment to infants requiring mechanical ventilation, 5 is more effective than late rescue treatment.The present study was designed to test the hypothesis that infants Ͻ30 we...

In babies with moderate-to-severe respiratory distress syndrome treated with nasal continuous positive airway pressure, a single dose of surfactant reduced the need for subsequent mechanical ventilation.

Hydrophobic low-molecular-mass proteins were isolated from minced pig lungs and separated into two fractions. Electrophoresis of protein fraction 1 showed two major bands. Calculations of molecular masses from the electrophoretic mobilities are unreliable because of the extreme hydrophobicity of the peptides. However, the two bands were at positions corresponding to apparent molecular masses of about 3 kDa and 14 kDa, while sequence degradation disclosed only one major structure. Electrophoretic separation of protein fraction 2 revealed one band, at an apparent molecular mass of about 6 kDa. Microheterogeneities at the N terminus of both fractions were observed. However, the two fractions had different N-terminal structures and amino acid compositions. Consequently they are concluded to represent different polypeptides without common segments. Bronchoalveolar lavage from humans also contains surfactant polypeptides and at least the fraction 2 peptide is highly similar in human and porcine surfactants.Artificial surfactant preparations, obtained by recombination of protein fraction 1 or 2 with a mixture of synthetic phospholipids, were evaluated with the pulsating bubble method and in experiments on artificially ventilated premature newborn rabbits. The addition of protein fraction 1 to the phospholipid mixture improved surface adsorption from more than 300 s to about 2 s and reduced minimum surface tension from more than 20 mN/m to nearly 0 as measured with a pulsating bubble. When this surfactant preparation was instilled into the airways of newborn rabbits, the tidal volumes at insufflation pressure 25 cm H 2 0 was increased about twentyfold compared to the volumes obtained in non-treated controls. Preparations based on protein fraction 1 had better in vitro and in vivo properties than those based on protein fraction 2. Both these protein-based preparations were decidedly more effective than phospholipids alone.

No abstract

Pulmonary surfactant contains two hydrophobic polypeptides, SP-B and SP-C, with known amino acid sequences and with truncated subforms lacking the N-terminal residues. Treatment of SP-C with KOH releases fatty acids (palmitic acid to more than 85%) in molar ratios of 1.8-2.0 relative to the polypeptide. Furthermore, plasma-desorption mass spectrometry shows native SP-C of both the intact and truncated types to be monomers with masses about 500 units higher than those expected for the polypeptide chains. After treatment with KOH, trimethylamine, or dithioerythritol, the polypeptide masses are obtained. These results prove that native SP-C is a lipopeptide with two palmitoyl groups covalently linked to the polypeptide chain. The deacylation conditions, the presence of two cysteine residues in the polypeptide, and the absence of other possible attachment sites establish that the palmitoyl groups are thioester-linked to the two adjacent cysteine residues. In contrast, the major form of porcine SP-B is a dimer without fatty acid components. That SP-C is a true lipopeptide with covalently bound palmitoyl groups suggests possibilities for functional interactions. It gives a direct physical link between SP-C and surfactant phospholipid components. Long-chain acylation may constitute a means for association of proteins with membranes and could conceivably modulate the stability and biological activity of surfactant fims.polypeptides in different subforms constituting N-terminally truncated molecules (20,21).Nevertheless, the primary structures of the polypeptides have been determined (18)(19)(20), showing SP-B to be a 79-residue polypeptide with a high content of cysteine residues, and SP-C to be a 35-residue polypeptide with two adjacent cysteine residues in a "palindromic" sequence (-Ile-Pro- Surfactant is essential for pulmonary function. It reduces the alveolar surface tension, preventing alveolar collapse, and is a prerequisite for normal respiration (1). The capacity for surfactant synthesis is limited in premature infants, and low amounts of surfactant are associated with neonatal respiratory distress syndrome. This serious disease can be treated effectively by replacement therapy through instillation of surfactant in the airways (2-7). Natural surfactant is composed of phospholipids and small amounts of specific polypeptides. In particular, two highly hydrophobic, low molecular weight polypeptides named SP-B and SP-C (8) appear to be essential components of surfactant preparations for replacement therapy (2, 3, 5-7). Both are derived from larger precursor polypeptides and have been structurally analyzed at the cDNA (9-16) and protein (17)(18)(19)(20) levels. Protein studies are essential for characterization ofthe mature polypeptides but are complicated by the extreme peptide hydrophobicities. SP-C in particular has essentially no aqueous solubility and is largely inert to conventional hydrolysis and other analytical steps. Furthermore, native preparations are heterogeneous, with the presence of the two M...

T Th he e p pr ro ot te ei in ns s o of f t th he e s su ur rf fa ac ct ta an nt t s sy ys st te em m SP-B is a 79-residue polypeptide that contains three intrachain disulphide bridges. It exists mainly as a homodimer, which is strongly positively charged and may selectively remove anionic and unsaturated lipid species from the alveolar surface film, thereby increasing surface pressure.SP-C is a mainly α-helical, extraordinarily hydrophobic polypeptide containing 35 amino acid residues and covalently linked palmitoyl groups. Its α-helical portion is inserted into surfactant lipid bilayers. SP-C accelerates the adsorption of lipid bilayers to an interfacial monolayer. In babies with respiratory distress syndrome, the clinical response to treatment with surfactant containing SP-B and SP-C is much faster than in babies treated with protein-free synthetic surfactant.We speculate that, in the near future, surfactant preparations based on recombinant hydrophobic proteins will be available for clinical use.