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S Hawgood

Publications and source records attributed to S Hawgood.

68 records · Page 4Linked to original sources
PubMed1986

Regulation of pulmonary surfactant apoprotein SP 28-36 gene in fetal human lung.

Pulmonary surfactant stabilizes lung alveoli, preventing respiratory failure and hyaline membrane disease in premature infants. In addition to lipids, surfactant contains apoproteins that are thought to be critical for normal surfactant function. We have examined the ontogeny and regulation of the major surfactant-associated protein of molecular mass 28-36 kDa (SP 28-36) in human fetal lung. SP 28-36 was not detected in tissue from second trimester abortuses by either immunoblot analysis or enzyme-linked immunosorbent assay (less than 0.02 microgram per mg of DNA). Levels of mRNA for SP 28-36, assayed by cDNA hybridization, were low or undetectable in all preculture specimens. The concentration of saturated phosphatidylcholine in lung tissue was 30% of the adult value with no apparent increase between 15 and 24 weeks gestation. SP 28-36 content increased during explant culture in the absence of serum and hormones, exceeding adult levels (3.2 +/- 1.0 micrograms per mg of DNA) after 5 days. In cultures treated with triiodothyronine (2 nM) and dexamethasone (10 nM), hormones that regulate phosphatidylcholine synthesis, the increase in SP 28-36 was accelerated (treated/control ratio was 7.1 and 3.4 at 3 and 5 days, respectively). Levels of mRNA for SP 28-36 also increased during culture and were stimulated by hormones (treated/control = 8.6 and 1.9 at 3 and 5 days, respectively). SP 28-36 and its mRNA increased similarly in the presence of dexamethasone alone, whereas triiodothyronine alone had no apparent effect. The molecular weight and charge pattern was similar for SP 28-36 of adult and cultured fetal tissue. These findings indicate that expression of the SP 28-36 gene is low during the second trimester, increases during explant culture, and is accelerated by glucocorticoid treatment.

Apoproteins↗
PubMed1985

Effects of a surfactant-associated protein and calcium ions on the structure and surface activity of lung surfactant lipids.

Previous studies have demonstrated that lung-specific proteins are associated with surfactant lipids, particularly the highly surface active subfraction known as tubular myelin. We have isolated a surfactant-associated protein complex with molecular weight components of 36 000, 32 000, and 28 000 and reassembled it with protein-free lung surfactant lipids prepared as small unilamellar liposomes. The effects of divalent cations on the structure and surface activity of this protein-lipid mixture were investigated by following (1) the state of lipid dispersion by changes in turbidity and by electron microscopy and (2) the ability of the surfactant lipids to form a surface film from an aqueous subphase at 37 degrees C. The protein complex markedly increased the rate of Ca2+-induced surfactant-lipid aggregation. Electron microscopy demonstrated transformation of the small unilamellar liposomes (median diameter 440 A) into large aggregates. The threshold Ca2+ concentration required for rapid lipid aggregation was reduced from 13 to 0.5 mM by the protein complex. This protein-facilitated lipid aggregation did not occur if Mg2+ was the only divalent cation present. Similarly, 5 mM Ca2+ but not 5 mM Mg2+ improved the ability of the protein-lipid mixture to form a surface film at 37 degrees C. Extensive aggregation of the surfactant lipids without protein by 20 mM Ca2+ or 20 mM Mg2+ did not promote rapid surface film formation. These results add to the growing evidence that specific Ca2+-protein-lipid interactions are important in determining both the structure and function of extracellular lung surfactant fractions.

Animals↗
PubMed1985

Structure of canine pulmonary surfactant apoprotein: cDNA and complete amino acid sequence.

The apoproteins of pulmonary surfactant (PSAP) are thought to be critical for normal surfactant function. They bind to surfactant phospholipids and enhance their ability to form surface films in vitro. These acidic glycoproteins have monomeric molecular weights of 36,000, 32,000, and 28,000 (PSAP-36, -32, and -28). Each member of this family of proteins has a similar amino acid composition and their differences in electrophoretic mobility are due in part to glycosylation. We have derived the full amino acid sequence of PSAP-32 from the nucleotide sequence of PSAP cDNA. A cDNA library was prepared from canine lung poly(A)+ RNA and screened with oligonucleotide probes that were based on the NH2-terminal amino acids of PSAP-32 determined by Edman degradation. This protein has the striking feature of collagen-like and non-collagen-like sequences in the same polypeptide chain. There are 24 Gly-Xaa-Yaa triplets, where Yaa is often hydroxyproline. These repeats comprise one-third of PSAP near the NH2 terminus. The remaining two-thirds of PSAP is resistant to bacterial collagenase digestion and contains a possible N-glycosylation site near the carboxyl terminus. The NH2-terminal one-third of PSAP-32 probably contains the cysteine involved in interchain disulfide bonds.

Amino Acid Sequence↗
PubMed1985

Structural and functional aspects of protein: phospholipid interactions in surfactant.

Lung surfactant lipids require the presence of a specific protein and calcium ions in order to form surface films rapidly at air-water interfaces. Film formation is a necessary first step in maintenance of low surface tensions in the lung. We have studied some of the factors involved with the lipid-protein interactions in reassembled complexes as well as in isolated lung surfactant. For both of these systems, removal of apoprotein or calcium ions results in impaired surface spreading. Increasing the amounts of this apoprotein relative to phospholipid results in increased lipid-protein association, increased vesicle aggregation, and increased monolayer film formation at the air-water interface in the surface balance.

Animals↗
PubMed1984

An electrophoretic and immunochemical characterization of human surfactant-associated proteins.

We have prepared an antiserum against a serum-free extract of alveolar proteinosis lavage that recognizes the same proteins as an antiserum to human surfactant. Using one and two-dimensional gel electrophoresis, protein blotting and immunostaining we have found proteins with Mr of approx. 35 and 60 kDa to be present in every source of human surfactant we have examined. These proteins are immunologically related to those found in the lavage from alveolar proteinosis patients, have the same electrophoretic characteristics and are not found in serum. The 35 kDa protein is a group of at least eight isoforms ranging in relative molecular mass Mr from 32 to 36 kDa with isoelectric points between 4.8 and 5.5. Neuraminidase digestion studies have shown that at least part of this charge heterogeneity may be due to sialic acid residues. The less abundant form, with a Mr of about 60 kDa is also a sialoglycoprotein with similar isoelectric points.

Amniotic Fluid↗
PubMed1984

Intraventricular hemorrhage. Incidence and outcome in a population of very-low-birth-weight infants.

The incidence, extent, and outcome of germinal matrix hemorrhage-intraventricular hemorrhage (GMH-IVH) were determined with the use of ultrasound and autopsy findings in 100 consecutive infants, with a birth weight of less than 1,500 g. Serial ultrasound examinations once or twice weekly were performed with the use of a portable real-time linear-array scanner. The overall incidence of GMH-IVH was 46%. Twenty infants had grade 1 (GMH), 24 had grade 2 (IVH +/- GMH), and two had grade 3 (IVH +/- GMH with intracerebral hemorrhage) conditions. The mortality in infants with GMH-IVH was 35%, compared with 13% in infants without GMH-IVH. Although 11 (37%) of 30 survivors with GMH-IVH had ventricular dilatation, only two infants required ventriculoperitoneal shunts for progressive hydrocephalus. The incidence of GMH-IVH was increased in outborn infants, in those delivered vaginally, and in those who required mechanical ventilation, bicarbonate therapy, or volume expansion in the first 24 hours. The long-term prognostic significance of the ultrasound findings was unknown and will be determined by follow-up studies.

Cerebral Hemorrhage↗
PubMed1984

Role of apoprotein and calcium ions in surfactant function.

Pulmonary surfactant isolated in the presence of calcium ions contains substantial amounts of the morphologic structure, tubular myelin. Chelation of these calcium ions results in disruption of this structure and attendant loss of surface adsorption. Reassembly studies indicate that ability of the lipids to rapidly form surface films is dependent on the presence of a specific surfactant protein in addition to the calcium ions. The formation of this surface-active complex (apoprotein-lipid-calcium ions) is accompanied by aggregation of the lipid. This increase in aggregation may have important implications in the mechanism of surfactant function.

Adsorption↗
PubMed1983

Computerised nutritional data management in neonatal intensive care.

We report a minicomputer based recording, reporting, and research system for patient data management in the neonatal intensive care unit (NICU). It is moderately priced, transportable, and independent of a central computer. It requires only a desk top and standard power supply, and successfully meets the medical documentation, communication, and research needs of the NICU. The first phase of programme development has enabled us to process growth and nutritional data from infants on complex parenteral and enteral nutrition. The system is well suited to medical users and provides a practical interactive data management system with many potential applications in the NICU.

Australia↗
PubMed1981

Hospital referrals of home births in the intrapartum and postpartum periods.

Twenty home birth patients referred for hospital management were reviewed. Eleven mothers were referred in labour and nine infants in the first week after birth. The clinical presentation and neonatal outcome are described. The majority had antenatal factors suggesting increased perinatal risk. Careful patient selection, prompt detection and early referral of complications, and adequate facilities for infant resuscitation should minimise the risks of home birth. More research is required on the population requesting home birth and its outcome.

Adolescent↗
PubMed1979

Bee-sting anaphylaxis in childhood.

The syndrome of bee-sting anaphylaxis is described. Children who have suffered crescendo reactions to previous bee stings, especially children with a history of asthma, are significantly at risk. Desensitization is required in such cases; adrenaline should be kept in the home, and parents should be trained in its emergency use. The immunological mechanisms of bee-sting anaphylaxis are described. The striking seasonal incidence of anaphylaxis suggests that pollen or plant products which are incorporated in the venom may also be important in its genesis; it suggests also that antigens prepared from either whole-body or pure-venom extracts should be prepared from bees which are collected in late spring.

Aerosols↗
PubMedDate not supplied

Isolation and characterization of the human pulmonary surfactant apoprotein gene.

Pulmonary surfactant is a phospholipid-protein complex which serves to lower the surface tension at the air-liquid interface in the alveoli of the mammalian lung and is essential for normal respiration. Inadequate levels of surfactant at birth, a frequent situation in premature infants, results in respiratory failure. In all species examined, surfactant is composed primarily of dipalmitoylphosphatidylcholine and two major protein species of relative molecular mass (Mr) 32,000 (32K) and 10K (refs 2-5). Reconstitution in vitro of purified 32K pulmonary surfactant apoprotein (PSAP) with synthetic lipids forms a lipoprotein complex that lowers surface tension by spreading to create a thin interfacial film. Here we describe the cloning of the human PSAP gene and complementary DNA, and discuss features of the unusual encoded protein.

Amino Acid Sequence↗