Structural relationships of the major glycoproteins from human alveolar proteinosis surfactant.

Alveolar proteinosis is a disease characterized by accumulation of proteinaceous material in the alveolar space of the lung. Two major collagenase-sensitive polypeptides, alveolar proteinosis peptides of 34 kDa kilodaltons (APP-34) and of 62 kDa (APP-62), were isolated from bronchioalveolar lavage of patients with alveolar proteinosis. These proteins co-purified during fast-performance liquid chromatography (FPLC) chromatofocusing and were separated from each other by electroelution following SDS-polyacrylamide gel electrophoresis. Immunoblot analysis of these proteins demonstrated that both shared antigenic sites with the normal human surfactant-associated protein of Mr 34,000 (SAP-34) using both polyclonal and monoclonal antibodies generated against SAP-34. Removal of asparagine-linked oligosaccharides from the 34 kDa and 62 kDa alveolar proteinosis proteins with endoglycosidase F resulted in polypeptides of 28 kDa from APP-34 and 56 kDa from APP-62. Amino acid analysis and tryptic peptide maps of the electroeluted APP-34 and APP-62 proteins were essentially identical and similar to that previously reported for human SAP-34, supporting the likely relationship of APP-34 and APP-62 as monomer and dimer of the normal SAP-34. APP-34 and APP-62 were both sensitive to bacterial collagenase, yielding collagenase-resistant fragments of 21 kDa, similar in migration and amino acid composition to the fragment generated by collagenase digestion of normal human SAP-34. High molecular weight aggregates of APP-34 and APP-62 were the result of sulfhydryl-dependent and non-sulfhydryl-dependent cross-linking. A domain in the C-terminal non-collagenous portion of the molecules which forms sulfhydryl-dependent oligomers was identified. The two major polypeptides accumulating in the airway of patients with alveolar proteinosis are monomeric (34 kDa) and dimeric (62 kDa) forms of the major surfactant-associated glycoprotein, SAP-34.

The disposition of alfentanil in neonates with respiratory distress.

The disposition of continuous infusion alfentanil was evaluated in 13 mechanically ventilated neonates (gestational age 37.6 +/- 2.4 wks) with hyaline membrane disease (n = 7) or persistent pulmonary hypertension of the newborn (n = 6). Alfentanil was administered as a loading dose 8 micrograms/kg, followed by a variable-rate continuous infusion (maximum 10 micrograms/kg/hr; minimum 2.5 micrograms/kg/hr) for 27 hours. Serial plasma samples were obtained for pharmacokinetic analysis. Noncompartmental pharmacokinetic analysis of the data revealed the following estimates (mean +/- SD): total-body clearance 3.24 +/- 2.23 ml/kg/minute, volume of distribution 0.54 +/- 0.21 L/kg, and elimination half-life 4.14 +/- 2.58 hours. A significant effect of alfentanil plasma concentration on total-body clearance was found (r = -0.75; p = 0.02), suggesting nonlinear pharmacokinetics. No correlation was seen between total-body clearance and alfentanil dose (r = -0.37; p = 0.32). The results suggest that a larger dose-proportionality study is required to determine the linearity or nonlinearity of alfentanil pharmacokinetics in neonates.

Neonatal pharmacodynamics--basic principles. II: Drug action and elimination.

The concepts of pharmacokinetics and pharmacodynamics are summarized for the clinician who cares for the neonatal patient. Six important pharmacologic principles are simplified and presented in a fashion that should facilitate recall. In this article, the final three concepts are presented: (1) the mechanisms by which drugs exert their actions, (2) the essentials of drug elimination through biotransformation (metabolism) by the liver, and (3) the essentials of drug elimination by the kidney. Also discussed are elimination half-life, clearance, and what happens when these elimination mechanisms are overwhelmed, due to either an excess of the drug or immaturity of the newborn.

Neonatal pharmacodynamics--basic principles. I: Drug delivery.

The concepts of pharmacokinetics and pharmacodynamics are summarized for the clinician who cares for the neonatal patient. Six important pharmacologic principles are simplified and presented in a fashion that should facilitate recall. This article presents the first three concepts: (1) the various methods of drug administration and membrane transport, (2) the essentials of drug delivery to the site of action (pharmacokinetics), and (3) methods for maintaining drug at the site of action. The "body compartment" concept, utilized in pharmacokinetic modeling, is also defined and contrasted to real anatomic body compartments.

Continuous nasogastric administration of activated charcoal for the treatment of theophylline intoxication.

Two adolescents with serum theophylline concentrations in excess of 100 mg/L were treated with continuous nasogastric infusion of activated charcoal after an intentional overdose. In both cases, nasogastric boluses of 20 to 50 gm of charcoal resulted in prompt emesis of stomach contents despite the presence of a functional nasogastric tube. For nasogastric infusion, activated charcoal was diluted in 0.9% sodium chloride and infused at a rate of 0.25 to 0.5 gm/kg/hr up to a maximal rate of 50 gm/hr. Despite the high initial serum concentrations, the theophylline elimination half-lives during the first 20 hours after the start of charcoal were 7.7 and 13.5 hours. Subsequently, this decreased to 2.6 and 3.2 hours. No serious neurologic, cardiovascular, or metabolic derangements were observed. Continuous nasogastric infusions of activated charcoal may be safe and effective alternatives to charcoal hemoperfusion in patients with theophylline overdose.

Randomized, controlled trial of nasopharyngeal continuous positive airway pressure in the extubation of very low birth weight infants.

We conducted a prospective, randomized controlled trial to determine whether extubation of very low birth weight infants was facilitated by the use of nasopharyngeal continuous positive airway pressure (CPAP). Eligible infants included patients weighing 600 to 1500 gm at birth who required tracheal intubation within 48 hours of birth and who met specific predetermined criteria for extubation by day 14 of life. We also sought to determine whether varying the duration of nasopharyngeal CPAP influenced the likelihood of successful extubation. Infants underwent random assignment to receive nasopharyngeal CPAP until resolution of lung disease (n = 40), 6 hours of nasopharyngeal CPAP (n = 42), or oxygen supplementation delivered by hood (n = 42). Extubation failure was predefined as a requirement for > or = 80% oxygen, pH < or = 7.20, severe apnea, or predefined clinical deterioration, and extubation success was predefined as the ability to remain free of a requirement for mechanical ventilation for 7 days and a 66% reduction in the need for supplemental oxygen. Each group was similar with regard to race, sex, and birth weight. Extubation was successful in 62%, 61%, and 60% of infants. After stratification by birth weight, there were no significant differences in the rates of successful extubation among the treatment groups. We conclude that nasopharyngeal CPAP does not improve the likelihood of successful extubation of very low birth weight infants who are ready for extubation within the first 2 weeks of life.

Biophysical and biological activity of a synthetic 8.7-kDa hydrophobic pulmonary surfactant protein SP-B.

We have synthesized pulmonary surfactant apoprotein SP-B peptides by solid-phase chemistry and demonstrated their ability to enhance the surface-active properties of synthetic lipid mixtures. The synthetic peptides were reactive with antiserum generated against the native bovine surfactant peptide. Both peptides conferred surfactant-like properties to synthetic lipid mixtures as assessed by a Wilhelmy balance and pulsating bubble surfactometer. Likewise, mixtures of synthetic SP-B peptides and lipid restored compliance of isolated surfactant-deficient rat lungs. This work demonstrates the utility of SP-B as a functional component of pulmonary surfactant mixtures for treatment of respiratory distress syndrome or other disorders characterized by surfactant deficiency.

Hydrophobic surfactant-associated protein in whole lung surfactant and its importance for biophysical activity in lung surfactant extracts used for replacement therapy.

Hydrophobic protein of 6,000 and 14,000 daltons was isolated from mammalian pulmonary surfactant obtained from canine, human, and bovine alveolar lavage material. Low molecular weight, hydrophobic, surfactant-associated protein (SAP), herein referred to as SAP 6-14, was distinguished from SAP-35, the major glycoprotein in mammalian surfactants (the 35,000 dalton glycoprotein A or apolipoprotein A) by amino acid composition, peptide mapping, and by resistance of SAP 6-14 to digestion by endoglycosidase F, collagenase, trypsin, and other proteases. The amino acid composition of SAP 6-14 was found to be highly enriched in leucine and other hydrophobic amino acids. The characteristics of protein isolated from bovine replacement surfactant extracts utilized for the treatment of hyaline membrane disease in humans were also studied. SAP 6-14 isolated from calf lung surfactant replacement extracts (CLSE) and surfactant-TA were found to be identical to SAP 6-14 isolated from ether/ethanol extracts of various mammalian surfactants. By contrast, SAP-35, the major surfactant-associated glycoprotein of molecular weight = 35,000, and other higher molecular weight proteins were not detected in significant quantities in the CLSE or surfactant-TA replacement surfactants, either by highly sensitive silver stain analysis or by immunoblot using monospecific antisera generated against bovine SAP-35. Biophysical studies of the CLSE replacement surfactant containing only SAP 6-14 and native phospholipids demonstrated full surface activity compared to natural lung surfactant. Dynamic surface tension lowering and adsorption properties of CLSE were essentially identical to those of freshly isolated bovine whole surfactant. Thus, hydrophobic SAP 6-14 is the only protein detected in bovine lung extract surfactants with full biophysical activity.(ABSTRACT TRUNCATED AT 250 WORDS)