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Biomedical subjects

H W Taeusch

Publications and source records attributed to H W Taeusch.

At least 19 recordsLinked to original sources
PubMed1991

Surfactant protein B: lipid interactions of synthetic peptides representing the amino-terminal amphipathic domain.

The mechanisms by which pulmonary surfactant protein B (SP-B) affects the surface activity of surfactant lipids are unclear. We have studied the peptide/lipid interactions of the amino-terminal amphipathic domain of SP-B by comparing the secondary conformations and surface activities of a family of synthetic peptides based on the native human SP-B sequence, modified by site-specific amino acid substitutions. Circular dichroism measurements show an alpha-helical structure correlating with the ability of the peptides to interact with lipids and with the surface activity of peptide/lipid dispersions. Amino acid substitutions altering either the charge or the hydrophobicity of the residues lowered the helical content and reduced the association of the aminoterminal segment with lipid dispersions. Surface activity of peptide/lipid mixtures was maximally altered by reversal of charge in synthetic peptides. These observations indicate that electrostatic interactions and hydrophobicity are important factors in determining optimal structure and function of surfactant peptides in lipid dispersions.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1991

Inhibition of mixtures of surfactant lipids and synthetic sequences of surfactant proteins SP-B and SP-C.

The respiratory distress syndrome of premature infants is caused by both surfactant deficiency and surfactant inhibition by capillary-alveolar leakage of serum factors. Dispersions of a standard surfactant lipid mixture, with and without various synthetic peptides, modeled on human surfactant proteins SP-B (residues 1-25, 49-66, 1-78) and SP-C (residues 1-10), were evaluated for inhibition by serum and by plasma constituents using a pulsating bubble surfactometer. Inhibition was derived from the changes in surface properties of these mixtures after addition of human serum or plasma constituents. Modified bovine surfactant (TA) containing native SP-B and SP-C was used as a control. In the absence of serum inhibitors, mixtures with synthetic peptides gave results similar to surfactant TA. However, inhibition was more evident in the dispersions with synthetic peptides when compared with surfactant TA. The peptide/phospholipid mixture with the entire sequence of SP-B and the first 10 residues of SP-C were more resistant to inhibition than mixtures with synthetic peptides containing fewer domains. Addition of calcium reduced the inhibitory effects of serum both in mixtures containing synthetic peptides and in surfactant TA. Therefore, synthetic SP-B and SP-C peptides in surfactant lipids, in cooperation with calcium, permit resistance to inhibition by several plasma constituents that probably inactivate surfactant by a variety of different mechanisms.

Adult↗
PubMed1991

Antibodies against synthetic amphipathic helical sequences of surfactant protein SP-B detect a conformational change in the native protein.

Synthetic peptides based on the native human sequence of surfactant protein B have been used to generate polyclonal monospecific antibodies against specific segments of the native SP-B protein. Circular dichroism analysis of the synthetic peptides shows they have a dominant helical content in structure promoting environments and tensiometric measurements indicate these peptides lower surface tension at air-water interfaces implying that they contain amphipathic alpha helical motifs. Antibodies directed against the C-terminal segment of SP-B react with the native protein in the oxidized and reduced state. Antibodies directed against the N-terminal sequence of SP-B react with the native protein only in the reduced state suggesting that this domain has a conformation dependent on disulfide bond formation.

Amino Acid Sequence↗
PubMed1991

Radiographic findings associated with surfactant treatment.

Radiographs of the chest (CXR) were evaluated in 35 of 41 infants enrolled in a randomized controlled trial of modified bovine surfactant extract (Surfactant-TA Tokyo-Tanabe) treatment. Infants between birthweight 1000 and 1500 gm with respiratory distress syndrome requiring mechanical ventilation and an inspired oxygen concentration 0.4 or greater were randomly assigned to either a single intratracheal dose of saline or surfactant-TA prior to 8 hours of age. Radiographs obtained prior to treatment and 24 hours after treatment were reviewed by a radiologist (N.T.G.) without knowledge of treatment group. Evaluation consisted of a score including criteria for inflation of the lungs, density of the lungs, and extent of air bronchograms. Pneumothorax, pulmonary interstitial emphysema, and asymmetric parenchymal involvement were noted as well. No significant difference in CXR scores were noted in the two groups, before or after treatment. There was a greater incidence of pneumothorax and pulmonary interstitial emphysema in the control infants, which supports the role of surfactant in preventing barotrauma. Increased incidence of asymmetric parenchymal involvement was noted in the surfactant-treated infants. Further study of the possibility of drug maldistribution is warranted.

Female↗
PubMed1991

Surfactant proteins and anti-surfactant antibodies in sera from infants with respiratory distress syndrome with and without surfactant treatment.

The presence of surfactant protein antigenemia and of surfactant protein antibodies was determined in serum from surfactant-treated and control infants with respiratory distress syndrome who were enrolled in a prospective randomized clinical trial. The surfactant used for treatment (surfactant TA) contained surfactant proteins (SPs) B and C and no SP-A. Enzyme-linked immunosorbent assays (ELISAs) that identify surfactant-associated proteins and ELISAs that identify IgG or IgM directed against surfactant proteins were used to investigate sera from these infants obtained prior to treatment, at 1 week of age, and at 2 months of age. There were no significant differences between average values in the surfactant-treated and control groups at each time period. However, in the control group, averaged results from ELISAs that identify SP-A and that identify IgM antibodies to SP-A or to SP-B, C showed significant differences between pretreatment sera and sera obtained at 1 week of age. No significant differences were noted in averaged results for IgG. Positive ELISA values were more frequently found in the control group than in the surfactant-treated group with regard to SP-A, and IgM against SP-A and SP-B, C in sera from neonates at 1 week of age. No positive ELISA values were found in sera from infants at 2 months of age. It is concluded that some patients with severe respiratory distress syndrome presumably leak surfactant proteins into the circulation and that this induces transient low titers of IgM antibody. This occurrence is decreased with surfactant treatment. Surfactant treatment may reduce leak of surfactant proteins into the vascular space by reducing lung damage.

Animals↗
PubMed1990

Structure-function relationships of bovine pulmonary surfactant proteins: SP-B and SP-C.

Pulmonary surfactant contains at least three unique proteins: SP-A, SP-B and SP-C. SP-B and SP-C from bovine surfactant are markedly hydrophobic and have molecular masses between 3 and 26 kDa. We identify surfactant proteins under nonreducing conditions on polyacrylamide gels with approximate molecular mass of 5, 14, 26 kDa (SP-5, 14, 26) when organic solvent-soluble material is eluted from a Sephadex LH-20 size exclusion column followed by separation on a high-performance reverse-phase chromatography system. These bands correspond to monomeric SP-C, oligomeric SP-C and oligomeric SP-B, respectively. Computer analysis (Eisenberg-hydrophobic moment) of sequences for these proteins suggests that SP-B contains surface-seeking amphiphilic segments. In contrast, SP-C resembles a more hydrophobic transmembrane anchoring peptide. Dispersions containing dipalmitoylphosphatidylcholine, phosphatidylglycerol, palmitic acid and multimeric SP-B and SP-C duplicate the surface activity of natural surfactant when assayed in a pulsating bubble surfactometer. We speculate that oligomers of SP-B and monomers and oligomers of SP-C may act cooperatively in affecting surfactant function. An important function of SP-B and SP-C may be to affect the ordering of surfactant lipids so that rates of transport of surfactant lipids to the hypophase surface in the alveoli are enhanced.

Amino Acid Sequence↗
PubMed1990

Health and developmental outcomes of a surfactant controlled trial: follow-up at 2 years.

Several randomized clinical trials have shown that surfactant therapy improves the pulmonary status of infants with respiratory distress syndrome and has the potential to reduce morbidity and mortality in these infants. Relatively little is known, however, about the long-term consequences of surfactant treatment. In this report, the results of health and developmental assessment are described at 1 and 2 years of age of 32 survivors of an initial group of 41 infants enrolled in a randomized clinical trial of bovine surfactant therapy. The frequencies of abnormal findings were comparable in the two groups although there was a trend toward a greater frequency of allergic manifestations in the control group (6 of 16 (38%) vs 1 of 15 (7%), P = .08). Similarly, no differences were seen in the mental and motor scores of the Bayley Scales of Infant Development at either 1 or 2 years of age. This study and other recently published reports of follow-up studies of infants treated with surfactant provide encouraging evidence that major long-term side effects do not result from surfactant therapy.

Animals↗
PubMed1990

Defining quality of care indicators for neonatal intensive care units independent of maternal risk factors.

Observed and birthweight-specific neonatal mortality rates have been used for assessing quality of neonatal care, but these are crude and affected by risk characteristics of the population served. Even when neonatal mortality rate is corrected for four risk factors, race, sex, birthweight, and multiple births, (California Data Research Facility, Santa Barbara, CA) it is possible that the corrected neonatal mortality rate is not comparable among institutions because of population differences not corrected for, eg, prenatal care. To analyze whether our high neonatal mortality rate is primarily dependent on population risk or quality of neonatal care, we used contemporaneous data collection by senior physicians and a microcomputer database system to construct indices of quality of care that are based on diagnoses graded according to disease severity. For the 1987/1988 academic year, we found: neonatal intensive care unit nosocomial infection rate, 20%; severe intraventricular hemorrhage per 100 very low birthweight infants (1500 g), 20%; bronchopulmonary dysplasia per 100 cases of severe respiratory distress syndrome, 27%; necrotizing enterocolitis per 100 neonatal intensive care unit discharges, 5%; air leak per 100 cases of severe respiratory distress syndrome, 21%; and neonatal mortality rate per very low birthweight delivery rate, 0.4. We propose that microcomputer, hospital-based analyses will improve comparisons of neonatal intensive care unit quality of care if appropriate indices can be sufficiently well-defined and shared.

Black or African American↗
PubMed1979

Thymus size and its relationship to the respiratory distress syndrome.

Thymic size can be affected by both exogenous and endogenous glucocorticoids. The risk of respiratory distress syndrome is reduced after maternal steroid administration. To find whether fetal lung maturity correlates with size of the thymus, the cardiothymic:thoracic ratio was measured in 167 newborn infants with and without RDS. Mean CT/T was significantly greater (0.40 vs 0.35; P less than 0.001) in those babies with RDS. This relation was independent of gestational age, although an increase in CT/T with advancing gestational age was shown. Prepartum maternal steroid administration did not result in significant involution of the cardiothymic shadow when compared with control infants with and without RDS. The CT/T may be of use in predicting which premature babies are more likely to develop RDS.

Female↗
PubMed1979

Augmentation of pulmonary surfactant secretion by lung expansion at birth.

To study the effect of lung expansion at birth on surfactant secretion, we delivered by hysterotomy 11 litters of rabbit pups at 30 days of gestation and divided them into three groups that were killed: 1) after 30 min air-breathing, 2) after 30 min nitrogen-breathing, and 3) after 30 min tracheal occlusion. Each group was compared to a littermate group killed at birth. Groups 2) and 3) continued respiratory efforts for 30 min despite progressive asphyxia. Six additional litters were pretreated with atropine; at delivery one-half of each litter was killed, the remaining pups were subjected to 30 min of hypoxic gas breathing. After sacrifice, alveolar surfactant was recovered by saline lavage and estimated quantitatively on a surface-tension balance. Surfactant concentration at birth was 1.40 +/- 0.22 mg/g dry lung and increased to 1.86 +/- 0.19 (+/- SEM) after 30 min air-breathing (P less than 0.01). Also, surfactant was increased in the nitrogen-breathing pups (from 1.61 +/- 0.35 in littermate controls to 2.41 +/- 0.58; P less than 0.03), but not to a significant degree in the occluded group (1.34 +/- 0.33 vs. 1.41 +/- 0.28), or the atropine pretreated breathing pups (1.77 +/- 0.29 vs. 1.89 +/- 0.25).

Animals↗
PubMed1979

Risk of respiratory distress syndrome after prenatal dexamethasone treatment.

A prospective double-blind randomized clinical trial was carried out to determine whether glucocorticoid treatment reduces the risk of respiratory distress syndrome (RDS) in prematurely born infants. There were 127 infants born to 122 mothers who received either steroid (dexamethasone phosphate) or placebo. No differences between groups occurred in risk factors for RDS (eg, prepartum asphyxia, male sex, cesarean section). When those who received a full course of dexamethasone therapy were compared with those who received placebo, a significant reduction was found in risk, severity, and deaths due to RDS. An increased incidence of infection in mothers treated with steroid was evident, particularly after premature rupture of membranes. We conclude that steroids are effective in reducing risk of RDS, but safer and more efficacious approaches for the prevention of RDS should be sought.

Clinical Trials as Topic↗