Dorsal-B, a splice variant of the Drosophila factor Dorsal, is a novel Rel/NF-kappaB transcriptional activator

The Drosophila transcription factor Dorsal, a member of the Rel/NF-kappaB family of proteins, plays a key role in the establishment of dorsoventral polarity in the early embryo and is also involved in the immune response. Here, we present evidence that the primary transcript of dorsal can be alternatively spliced, generating Dorsal-B, a new Rel/NF-kappaB family member. Dorsal and Dorsal-B are identical in the N-terminal region, which comprises both a DNA-binding domain and a dimerization domain. However, Dorsal-B lacks the nuclear localization signal located at the end of the Rel domain of Dorsal and is totally divergent in the C-terminal portion. Although Dorsal-B by itself is not able to induce the expression of a kappaB-controlled Luciferase reporter gene, we demonstrate that its C-terminal portion has transactivating properties. Analysis of the dorsal-B expression pattern indicates that the splicing is tissue-specific and excludes a putative role in early embryogenesis. However, dorsal-B synthesis is enhanced upon septic injury, and this challenge induces a nuclear accumulation of the protein in fat body cells suggesting that it may be involved in the immune response.

Potassium channel openers require ATP to bind to and act through sulfonylurea receptors

KATP channels are composed of a small inwardly rectifying K+ channel subunit, either KIR6.1 or KIR6.2, plus a sulfonylurea receptor, SUR1 or SUR2 (A or B), which belong to the ATP-binding cassette superfamily. SUR1/KIR6.2 reconstitute the neuronal/pancreatic beta-cell channel, whereas SUR2A/KIR6.2 and SUR2B/KIR6.1 (or KIR6.2) are proposed to reconstitute the cardiac and the vascular-smooth-muscle-type KATP channels, respectively. We report that potassium channel openers (KCOs) bind to and act through SURs and that binding to SUR1, SUR2A and SUR2B requires ATP. Non-hydrolysable ATP-analogues do not support binding, and Mg2+ or Mn2+ are required. Point mutations in the Walker A motifs or linker regions of both nucleotide-binding folds (NBFs) abolish or weaken [3H]P1075 binding to SUR2B, rendering reconstituted SUR2B/KIR6.2 channels insensitive towards KCOs. The C-terminus of SUR affects KCO affinity with SUR2B approximately SUR1 > SUR2A. KCOs belonging to different structural classes inhibited specific [3H]P1075 binding to SUR2B in a monophasic manner, with the exception of minoxidil sulfate, which induced a biphasic displacement. The affinities of KCO binding to SUR2B were 3.5-8-fold higher than their potencies for activation of SUR2B/KIR6.2 channels. The results establish that SURs are the KCO receptors of KATP channels and suggest that KCO binding requires a conformational change induced by ATP hydrolysis in both NBFs.

Fetal lung mRNA levels of Hox genes are differentially altered by maternal diabetes and butyrate in rats

Diabetes is known to be associated with delayed lung development in humans and in experimental animals. This includes delayed expression of surfactant apoproteins. An important component of the metabolic abnormalities in diabetes is elevated levels of analogs of butyric acid, and the effects of diabetes on surfactant apoproteins can be reproduced by exposure of fetal rat lung explants to butyrate. Dexamethasone has the opposite effects on lung development. In humans, antenatal exposure to dexamethasone results in a lower incidence of RDS, whereas in experimental animals, dexamethasone increases the expression of surfactant apoproteins. A subset of Hox genes are expressed in developing lung, and their level of expression decreases with advancing gestation. We hypothesized that: 1) lungs of fetuses of rats with streptozotocin-induced diabetes would have altered levels of expression of Hox genes, 2) the effect would be mediated in part through elevated levels of butyrate, and 3) dexamethasone would reverse the effect. We tested our hypotheses in vivo using fetuses from streptozotocin-treated rats and in vitro by treating lung explants from normal rats with sodium butyrate. Streptozotocin treatment increased expression of Hoxb-5 at 18 d of gestation, but did not affect Hoxa-5 expression. This was associated with a 20-fold increase in alpha-aminobutyrate levels. Dexamethasone tended to reverse this effect. In contrast, butyrate treatment of explants decreased the expression of Hoxa-5 and Hoxb-5. We conclude that diabetes alters expression of Hox genes, but that the effect of butyrate on lung development, and in particular on surfactant apoprotein expression, is independent of its effects on Hox genes.

N-Terminal extension of human immunodeficiency virus capsid protein converts the in vitro assembly phenotype from tubular to spherical particles

Expression of retroviral Gag polyproteins is sufficient for morphogenesis of virus-like particles with a spherical immature protein shell. Proteolytic cleavage of Gag into the matrix (MA), capsid (CA), nucleocapsid (NC), and p6 domains (in the case of human immunodeficiency virus [HIV]) leads to condensation to the mature cone-shaped core. We have analyzed the formation of spherical or cylindrical particles on in vitro assembly of purified HIV proteins or inside Escherichia coli cells. CA protein alone yielded cylindrical particles, while all N-terminal extensions of CA abolished cylinder formation. Spherical particles with heterogeneous diameters or amorphous protein aggregates were observed instead. Extending CA by 5 amino acids was sufficient to convert the assembly phenotype to spherical particles. Sequences C-terminal of CA were not required for sphere formation. Proteolytic cleavage of N-terminally extended CA proteins prior to in vitro assembly led to the formation of cylindrical particles, while proteolysis of in vitro assembly products caused disruption of spheres but not formation of cylinders. In vitro assembly of CA and extended CA proteins in the presence of cyclophilin A (CypA) at a CA-to-CypA molar ratio of 10:1 yielded significantly longer cylinders and heterogeneous spheres, while higher concentrations of CypA completely disrupted particle formation. We conclude that the spherical shape of immature HIV particles is determined by the presence of an N-terminal extension on the CA domain and that core condensation during virion maturation requires the liberation of the N terminus of CA.

In vitro assembly properties of purified bacterially expressed capsid proteins of human immunodeficiency virus

The Gag polyprotein of retroviruses is sufficient for assembly and budding of virus-like particles from the host cell. In the case of human immunodeficiency virus (HIV), Gag contains the domains matrix, capsid (CA), nucleocapsid (NC) and p6 which are separated by the viral proteinase inside the nascent virion, leading to morphological maturation to yield an infectious virus. In the mature virus, CA forms a capsid shell surrounding the ribonucleoprotein core consisting of NC and the genomic RNA. To define requirements for particle assembly and functional contributions of individual domains, we expressed domains of HIV Gag in Escherichia coli and purified the products to near homogeneity. In vitro assembly of CA, with or without the C-terminally adjacent spacer peptide, yielded tubular structures with a diameter of approximately 55 nm and heterogeneous length. Efficient particle formation required high protein concentration, high salt and neutral to alkaline pH. In contrast, in vitro assembly of CA-NC occurred at a 20-fold lower protein concentration and in low salt, but required addition of RNA. These results suggest that hydrophobic interactions of capsid proteins are sufficient for particle formation while the RNA-binding nucleocapsid domain may concentrate and align structural proteins on the viral genome.

Identification of endogenous Des-Arg9-[Hyp3]-bradykinin in human plasma with post-source-decay matrix-assisted laser desorption/ionization mass spectrometry

In the present study, the purification and sequence analysis of a peptide extracted from human plasma is described. After three chromatographic steps in one of the plasma fractions, a molecular mass of 920 Da was determined with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis. Further analysis with post-source-decay (PSD)-MALDI-MS revealed an amino acid sequence arg-pro(pro-gly+16)-phe-ser-pro-phe. With the data given from the spectrum, it was impossible to clarify the partial sequence (pro-gly+16). A comparison with a data base suggested that the sequence is very similar to des-arg9bradykinin (arg-pro-pro-gly-phe-ser-pro-phe). But many fragment masses, including the mass of the parent ion of the unknown peptide, are 16 Da larger than the corresponding fragment masses of des-arg9-bradykinin. The interpretation of the fragment pattern does not allow determination of the position of the amino acid that is 16 Da larger. With automated Edman sequence analysis of the fraction of interest, three more major component peptides in this fraction were observed, which were not detected with MALDI-MS. Nevertheless, with the help of the Edman sequence data it was possible to identify the unknown amino acid in the PSD-MALDI-MS sequence as hydroxyproline at the third position. In conclusion, the existence of des-arg9[hyp3]-bradykinin (arg-pro-hyp-gly-phe-ser-pro-phe) in human plasma is described. Furthermore, the study demonstrates that PSD-MALDI-MS and automated Edman sequence analysis complement each other if single unknown peptides from mixtures are to be sequenced.

Inhaled nitric oxide and persistent pulmonary hypertension of the newborn. The Inhaled Nitric Oxide Study Group

BACKGROUND

Persistent pulmonary hypertension of the newborn causes systemic arterial hypoxemia because of increased pulmonary vascular resistance and right-to-left shunting of deoxygenated blood. Inhaled nitric oxide decreases pulmonary vascular resistance in newborns. We studied whether inhaled nitric oxide decreases severe hypoxemia in infants with persistent pulmonary hypertension.

METHODS

In a prospective, multicenter study, 58 full-term infants with severe hypoxemia and persistent pulmonary hypertension were randomly assigned to breathe either a control gas (nitrogen) or nitric oxide (80 parts per million), mixed with oxygen from a ventilator. If oxygenation increased after 20 minutes and systemic blood pressure did not decrease, the treatment was considered successful and was continued at lower concentrations. Otherwise, it was discontinued and alternative therapies, including extracorporeal membrane oxygenation, were used.

RESULTS

Inhaled nitric oxide successfully doubled systemic oxygenation in 16 of 30 infants (53 percent), whereas conventional therapy without inhaled nitric oxide increased oxygenation in only 2 of 28 infants (7 percent). Long-term therapy with inhaled nitric oxide sustained systemic oxygenation in 75 percent of the infants who had initial improvement. Extracorporeal membrane oxygenation was required in 71 percent of the control group and 40 percent of the nitric oxide group (P=0.02). The number of deaths was similar in the two groups. Inhaled nitric oxide did not cause systemic hypotension or increase methemoglobin levels.

CONCLUSIONS

Inhaled nitric oxide improves systemic oxygenation in infants with persistent pulmonary hypertension and may reduce the need for more invasive treatments.

Retinoic acid increases surfactant protein mRNA in fetal rat lung in culture

Retinoic acid has both early or immediate (within hours) and late (after days) effects on gene expression. We studied the early effects of retinoic acid on the surfactant protein (SP) genes. Exposure of fetal rat lung explants to all trans-retinoic acid for 4 h resulted in a significant dose-dependent increase in SP-A, -B, and -C mRNA with markedly different dose-response characteristics. The maximal (2.5x) increase in SP-A mRNA was observed with 10(-10) M retinoic acid, whereas treatment with 10(-5) M resulted in a tendency to decreased levels. In contrast, maximal stimulation of SP-C (6x) was noted at 10(-5) M retinoic acid and that of SP-B (2x) at 10(-7) to 10(-5) M retinoic acid. Similar differences in the dose-response characteristics of SP-A and SP-C were observed with 9-cis-retinoic acid. A retinoic acid response element consensus sequence was identified in the rat SP-A gene; we hypothesize that retinoic acid-receptor complexes act directly on the SP-A gene via this response element.

Immune factor Gambif1, a new rel family member from the human malaria vector, Anopheles gambiae

A novel rel family member, Gambif1 (gambiae immune factor 1), has been cloned from the human malaria vector, Anopheles gambiae, and shown to be most similar to Drosophila Dorsal and Dif. Gambif1 protein is translocated to the nucleus in fat body cells in response to bacterial challenge, although the mRNA is present at low levels at all developmental stages and is not induced by infection. DNA binding activity to the kappaB-like sites in the A.gambiae Defensin and the Drosophila Diptericin and Cecropin promoters is also induced in larval nuclear extracts following infection. Gambif1 has the ability to bind to kappaB-like sites in vitro. Co-transfection assays in Drosophila mbn-2 cells show that Gambif1 can activate transcription by interacting with the Drosophila Diptericin regulatory elements, but is not functionally equivalent to Dorsal in this assay. Gambif1 protein translocation to the nucleus and the appearance of kappaB-like DNA binding activity can serve as molecular markers of activation of the immune system and open up the possibility of studying the role of defence reactions in determining mosquito susceptibility/refractoriness to malaria infection.

Drosophila immunity: a comparative analysis of the Rel proteins dorsal and Dif in the induction of the genes encoding diptericin and cecropin

In Drosophila, bacterial challenge induces the rapid transcription of several genes encoding potent antibacterial peptides. The upstream sequences of the diptericin and cecropin Al genes, which have been investigated in detail, contain two, respectively one sequence element homologous to the binding site of the mammalian nuclear factor kappaB. These elements have been shown to be mandatory for immune-induced transcription of both genes. Functional studies have shown that these kappaB-related elements can be the target for the Drosophila Rel proteins dorsal and Dif. Here we present a comparative analysis of the transactivating capacities of these proteins on reporter genes fused to either the diptericin or the cecropin kappaB-related motifs. We conclude from our results: (i) the kappaB motifs of the diptericin and cecropin genes are not functionally equivalent; (ii) the dorsal and Dif proteins have distinct DNA-binding characteristics; (iii) dorsal and Dif can heterodimerize in vitro; (iv) mutants containing no copies of dorsal and a single copy of Dif retain their full capacity to express the diptericin and cecropin genes in response to challenge.

Drosophila immunity. A sequence homologous to mammalian interferon consensus response element enhances the activity of the diptericin promoter

Bacterial challenge of larvae or adults of Drosophila induces the rapid transcription of several genes encoding antibacterial peptides with a large spectrum of activity. One of these peptides, the 82-residue anti-gram negative diptericin, is encoded by a single intronless gene and we are investigating the control of expression of this gene. Previous studies using both transgenic experiments and footprint analysis have highlighted the role in the induction of this gene of a 30 nucleotide region which contains three partially overlapping motifs with sequence homology to mammalian NF-kappa B and NF-IL6 response elements and to the GAAANN sequence present in the interferon consensus response elements of some mammalian interferon-induced genes. We now show that the latter sequence binds in immune responsive tissues (fat body, blood cells) of Drosophila a approximately 45 kDa polypeptide which cross-reacts with a polyserum directed against mammalian interferon Regulatory Factor-I. Using a transfection assay of Drosophila tumorous blood cells, we show that the GAAANN sequence positively regulates the activity of the diptericin promoter. We propose that this motif cooperatively interacts with the other response elements in the regulation of the diptericin gene expression.

Coenzyme A glutathione disulfide. A potent vasoconstrictor derived from the adrenal gland

The adrenal gland is involved in the regulation of vascular tone by secretion of vasoactive agents such as catecholamines, neuropeptide Y, or endogenous ouabain. A further potent vasoconstrictor is isolated from bovine adrenal glands and is identified by chromatography, mass spectrometry, UV spectroscopy, and enzymatic cleavage as coenzyme A glutathione disulfide (CoASSG). CoASSG is found in chromaffin granules of adrenal glands and is released from adrenal medulla slices by carbachol. At a concentration of 10(-12) mol/L CoASSG increases renal vascular resistance. Intra-aortic injection of 5 x 10(-10) mol CoASSG increases blood pressure in the intact animal. Besides its vasopressor properties, this substance potentiates the effects of angiotensin II on vascular tone. It is concluded that CoASSG could play a role in blood pressure regulation not only by direct effects but also by modulation of the action of angiotensin II.

Butyrate modulates surfactant protein mRNA in fetal rat lung by altering mRNA transcription and stability

We examined the effects of Na butyrate, a known regulator of gene expression, on surfactant protein mRNA concentration, transcription, and degradation. Exposure of explants of 18-day fetal rat lung to Na butyrate resulted in a decrease in surfactant protein A (SP-A) mRNA concentration to 7% of control after 6 h and to 18% of control after 24 h. The reduction in SP-A mRNA concentration was associated with decreased mRNA transcription and stability at both these times. The effects on SP-B mRNA were similar to those on SP-A, but quantitatively less. In contrast, butyrate had a biphasic effect on SP-C mRNA concentration. There was an initial decrease to 30% of control at 6 h, followed by an increase to control levels by 24 h. Transcription of SP-C was increased at both these times, whereas degradation was enhanced at 6 h, but not at 24 h. The level of surfactant protein mRNA after butyrate treatment therefore depends on the balance between induced changes in transcription and degradation. Butyrate had no effect on gamma-actin mRNA concentration in this system. Circulating levels of butyric acid analogues are elevated in the mothers and fetuses in diabetic pregnancies. Some of these fetuses have delayed lung maturation and decreased amniotic fluid SP-A levels. We speculate that butyric acid analogues partially mediate the changes in pulmonary maturation induced by maternal diabetes.

Identification of Hox genes in newborn lung and effects of gestational age and retinoic acid on their expression

Hox genes are sequence-specific DNA transcription factors, which are important in embryonic development and are expressed in a number of fetal tissues, including the lung. Additionally, retinoic acid (RA) has been shown to modulate Hox gene expression in a number of cell types. The specific aims of this study were to 1) identify those Hox genes expressed in newborn mouse lung using reverse transcription-polymerase chain reaction (RT-PCR), 2) study the ontogeny of Hox gene expression in fetal mouse and rat lung by Northern analysis using cDNAs for mouse Hox genes, and 3) study the effects of RA on whole lung Hox mRNA levels in cultured fetal rat lung explants. Our data show that 16 different homeobox genes are expressed in newborn mouse lung. This includes seven Hox genes not previously identified in lung, as well as the divergent homeobox gene Hex. Steady-state mRNA levels of Hox A5 (Hox 1.3), B5 (Hox 2.1), B6 (Hox 2.2), and B8 (Hox 2.4) decrease with advancing gestational age in mouse lungs (E14 to adult). Similarly, Hox A5, B5, and B6 follow the same decreasing pattern of expression with advancing gestational age in rat lungs (E15 to adult). RA treatment of E17 rat lung explants in culture resulted in a significant dose- and time-dependent increase in Hox A5, B5, and B6 mRNA levels. The highest mRNA levels were seen in explants treated with 1 x 10(-5) M RA for 4-16 h. We conclude that there are many homeobox genes expressed in developing rodent lung and that their mRNA levels are affected by both gestational age and RA.

Combined hormonal therapy for the prevention of respiratory distress syndrome and its consequences

In performing this meta-analysis, we have attempted to use comparable data, but there are limitations to the information that is available at present. Some studies reported results for all patients entered, whereas others reported only optimally treated patients (Table 2). Many of the trials have not yet been published in final form and subjected to peer review. In addition, all the studies reported here were conducted before the widespread use of surfactant therapy. It is unclear whether the benefit of antenatal TRH and steroid therapy on end points such as death or BPD would persist if surfactant was also used. (Surfactant has, however, little impact on the percentage of survivors with BPD, perhaps because sicker infants survive with this treatment and go on to develop BPD.) Studies comparing antenatal TRH plus steroid plus postnatal surfactant to antenatal steroid plus postnatal surfactant are clearly required, and are in progress in a number of centers around the world. Because of these limitations, the routine use of antenatal TRH plus steroid cannot be currently recommended. However, the apparent benefits of this therapy in terms of RDS, death, and CLD that have been reported here do suggest that it might be used in selected situations. An example is threatened delivery of a very premature infant with an immature amniotic fluid pulmonary maturation profile. These infants are at risk for RDS and CLD, even if antenatal steroid and postnatal surfactant therapy is used.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma thyroid hormones and prolactin in premature infants and their mothers after prenatal treatment with thyrotropin-releasing hormone

We assayed TSH, triiodothyronine, free thyroxine, and prolactin (PRL) in plasma of women and infants participating in a trial of prenatal thyrotropin-releasing hormone (TRH) treatment for prevention of newborn lung disease. Women in labor at 26-34 wk of gestation received 400 micrograms of TRH i.v. every 8 h (one to four doses) plus 12 mg betamethasone (one or two doses); controls received saline plus betamethasone. Mean cord concentrations in control infants were TSH 9.7 mU/L, triiodothyronine 0.6 nmol/L (40.2 ng/dL), free thyroxine 14.4 pmol/L (1.13 ng/dL), and PRL 67.6 micrograms/L. TRH increased maternal plasma TSH by 100% at 2-4 h after treatment and decreased levels by 28-34% at 5-36 h. In cord blood of treated infants delivered at 2-6 h, TSH, triiodothyronine, and PRL were all increased about 2-fold versus control, and free thyroxine was increased 19%; the response was similar after one, two, three, or four doses of TRH. In treated infants delivered at 13-36 h, cord TSH and triiodothyronine levels were decreased 62 and 54%, respectively, and all thyroid hormones were lower after birth at 2 h of age versus control. We conclude that prenatal TRH administration increases thyroid hormones and PRL in preterm fetuses to levels similar to those normally occurring at term. Pituitary-thyroid function is transiently suppressed after treatment to a greater extent in fetus than mother, and infants born during the early phase of suppression do not have the normal postnatal surge in thyroid hormones.

Surfactant protein C: hormonal control of SP-C mRNA levels in vitro

We have studied hormonal regulation of the surfactant protein C (SP-C) in fetal 18-dah rat lung explants. SP-C mRNA was detected in Northern blots with a specific rat SP-C cDNA probe and quantified by densitometry. Treatment of the explants with dexamethasone resulted in a dose-dependent increase of the SP-C mRNA level. Transcriptional assays have shown that the regulation of SP-C mRNA by dexamethasone involves a transcriptional step. Administration of the cAMP analogues, 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) or dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP), produced a dose-dependent increase of SP-C mRNA levels, with maximum stimulation observed at 200 microM. The thyroid hormone T3 had no effect on SP-C mRNA levels, whether administered alone or in combination with dexamethasone. Variation in the effects of the above hormones on three surfactant protein mRNAs, SP-A, SP-B and SP-C, indicates that the hormonal regulation of the surfactant proteins is a complex process and that each gene is, in part, differentially regulated.

Respiratory disease in very-low-birthweight infants after prenatal thyrotropin-releasing hormone and glucocorticoid. TRH Study Group

Although prenatal glucocorticoid treatment reduces neonatal respiratory morbidity, respiratory distress syndrome and chronic lung disease (CLD) develop in many very-low-birthweight infants despite therapy. To investigate the effect of additional prenatal treatment with thyrotropin-releasing hormone (TRH), we did a multicentre, blinded, randomised trial. 404 women with threatened preterm delivery at less than 32 weeks' gestation received betamethasone plus TRH (4 doses of 400 micrograms 8-hourly) or betamethasone plus placebo. 103 infants who were fully treated and of less than 1500 g birthweight were evaluated during the neonatal period. TRH treatment (55 infants) did not affect the total incidence of respiratory distress syndrome (47% vs 58% in controls) or of severe respiratory distress syndrome (13% vs 25% in controls, p = 0.11). CLD (defined as requirement for supplemental oxygen at 28 days after birth) developed in significantly fewer TRH-treated infants (18% vs 44% of controls, p less than 0.01). The unadjusted relative risk of CLD with TRH therapy was 0.40 (95% CI 0.26-0.80, p less than 0.05), and this was not materially changed after adjustment for potentially modifying variables. There were significantly fewer adverse outcomes, defined as death or continuing oxygen requirement, in the TRH group than in the steroid-alone group both at 28 days and when infants reached 36 weeks' postconceptional age. The incidence of other complications of prematurity was similar in the two groups. Prenatal TRH reduces the incidence of chronic lung disease among betamethasone-treated infants.

Comparison of the Maclura pomifera lectin-binding glycoprotein in late fetal and adult rat lung

The lectin, Maclura pomifera agglutinin (MPA), binds to alpha-galactose residues of glycoproteins on the apical surface of type II alveolar cells. It has recently been shown to bind to macrophages. We isolated the cell surface glycoprotein, which binds the MPA lectin, from fetal and adult rat whole lung to determine if changes in this glycoprotein occur during development from fetal to adult life. The glycoprotein was purified from whole lung cell membranes by lectin affinity chromatography that resulted in 10(5)-fold enrichment. The MPA binding glycoproteins from both fetal and adult lung had the same apparent molecular weight of 170 kD as determined by sodium dodecylsulfate-polyacrylamide gel electrophoresis. Amino acid analysis revealed similar composition of the fetal and adult proteins. Two-dimensional peptide maps of the 170 kD proteins isolated from fetal and adult lung were also similar. These data indicate that the glycoprotein that binds MPA to lung cell membranes does not change during this stage of development. Our method for the isolation of this glycoprotein can be used for the generation of antibodies or other molecular probes for further study of this protein.

Reduction of neonatal mortality after multiple doses of bovine surfactant in low birth weight neonates with respiratory distress syndrome

To determine if outcomes of low birth weight neonates with respiratory distress syndrome can be improved by the administration of multiple doses of bovine surfactant, we conducted two identical multicenter, controlled trials, and the results were combined for analysis. Seven hundred and ninety-eight neonates weighing 600 to 1750 g at birth who had developed respiratory distress syndrome within 6 hours of birth were assigned randomly to receive either 100 mg of phospholipid/kg of Survanta, a modified bovine surfactant (n = 402), or a sham dosing procedure (n = 396). Neonates whose respiratory distress persisted could be given up to three more doses, with all doses to be given in the first 48 hours after birth. Dosing was performed by investigators not involved in the clinical care of the neonates; nursery staff were kept blinded as to the treatment assignment. Fewer Survanta-treated neonates died of any cause (18.4% vs 27.3%, P = .002), died of respiratory distress syndrome (9.0% vs 20.3%, P less than .001), and either died or developed bronchopulmonary dysplasia due to respiratory distress syndrome (51.2% vs 64.6%, P less than .001). Neonates who received Survanta also had greater improvement in their oxygenation and ventilatory status from baseline to 72 hours than did control neonates. Survanta-treated neonates were at lowered risk for developing pulmonary interstitial emphysema (18.6% vs 39.3%, P less than .001) and other pulmonary air leaks (11.5% vs 25.9%, P less than .001). We conclude that multiple doses of Survanta given after diagnosis of respiratory distress syndrome reduce mortality and morbidity.

Hormonal effects on the surfactant protein B (SP-B) mRNA in cultured fetal rat lung

Glucocorticoids, triiodothyronine (T3), and cyclic adenosine monophosphate (cAMP) have been shown previously to modulate phosphatidylcholine and surfactant protein A (SP-A) synthesis in fetal rat lung explant cultures. In this report, we have examined the hormonal regulation of the rat surfactant protein B (SP-B) mRNA to determine whether SP-B expression is coordinately regulated with the surfactant phospholipids or with SP-A. Dexamethasone (1 to 200 nM) and cAMP (200 microM) had a stimulatory effect on SP-B mRNA levels, whereas T3 tended to inhibit the accumulation of SP-B mRNA. In combination experiments, treatment with dibutyryl-cAMP (200 microM) and dexamethasone (100 nM) resulted in about a 22-fold increase, whereas dexamethasone or dibutyryl-cAMP alone produced 18- and 2-fold increases, respectively. When the cAMP analogue 8-bromo-cAMP (200 microM) was used in combination with dexamethasone, there was no significant difference between the combined effect and that of dexamethasone alone. T3 treatment, however, resulted in a significant reduction of the dexamethasone-induced stimulation from about a 22-fold to a 14-fold increase. Tissue in situ hybridization showed that dexamethasone stimulated the levels of SP-B mRNA in cells from both the alveolar and bronchiolar epithelium. These data indicate that there are differences in the hormonal regulation of the components of surfactant, suggesting that they are independently regulated.

Regulation of fetal lung maturation

The recent identification of the genes for the surfactant proteins has greatly facilitated the study of the regulation of fetal lung alveolar epithelial cell development at the molecular level. In general, expression of the genes for the surfactant proteins is enhanced by the same hormones that stimulate phospholipid synthesis. There are, however, some notable differences that indicate that the genes for the different components of surfactant are independently regulated. Species differences in the response of the surfactant proteins to hormones such as glucocorticoids and adenosine 3',5'-cyclic monophosphate have also been demonstrated. This review focuses on current knowledge of the hormonal regulation of the surfactant proteins against a background of previous studies of lung development.

Regulation of surfactant protein A mRNA by hormones and butyrate in cultured fetal rat lung

We have previously shown that dexamethasone, triiodothyronine (T3) and dibutyryl adenosine 3',5'-cyclic monophosphate (cAMP) stimulate phosphatidylcholine (PC) synthesis in fetal rat lung explants in culture. There are also additive interactions between these agents with regard to PC synthesis. In this study we examined the regulation of surfactant protein A (SP-A) mRNA in fetal rat lung in culture. Dexamethasone increased SP-A mRNA in the explants in a dose-dependent fashion (1-200 nM), but T3 did not. Whereas 8-bromo-cAMP increased SP-A mRNA, a decrease was observed with dibutyryl cAMP. These findings support the view that at least some of the genes involved in the synthesis of the various components of surfactant are independently regulated. Since we observed differences in the effects of a cAMP analogue which contained butyrate and one that did not, explants were then cultured with Na butyrate, a known regulator of gene expression. A significant decrease in SP-A mRNA was observed at mM concentrations. Exposure of the explants to alpha-aminobutyric acid, a butyric acid analogue which is elevated in the blood of infants of diabetic mothers, resulted in a significant decrease in SP-A mRNA at a concentration 1/25 of that required for Na butyrate. This observation raises the question of whether the decreased SP-A levels reported in fetuses of diabetic mothers may, at least in part, be related to this metabolite.

Survival of infants with persistent pulmonary hypertension without extracorporeal membrane oxygenation

A retrospective evaluation was performed of the survival after conservative therapy of infants with persistent pulmonary hypertension who met the published criteria of Bartlett et al (Pediatrics. 1985;76:479-487) or Short et al (Clinics in Perinatology. 1987;14:737-748) for extracorporeal membrane oxygenation (ECMO) therapy. An 80% to 90% mortality rate can be predicted with these criteria, which are based on historical data, if ECMO is not used. The records of infants with the diagnosis of persistent pulmonary hypertension, weighing greater than 2 kg at birth and who were treated during two time periods, January 1980 to December 1981 [23 patients] and January 1986 to December 1988 [17 patients], were reviewed. During the earlier period, hyperventilation was the mainstay of our therapy, whereas during the later period, a more conservative approach (avoidance of hyperventilation) was adopted. In 1980 to 1981, 1 of the 6 patients (17%) who were eligible for ECMO by criteria of Bartlett et al survived, which is consistent with the published data. However, in 1986 to 1988, 9 of 10 ECMO-eligible patients (90%) survived (P less than .02). The corresponding survival figures using the alveolar-arterial oxygen difference criteria of Short et al were 0 of 5 survivors (0%) in 1980 to 1981 and 8 of 9 (89%) in 1986 to 1988 (P less than .006). These data indicate that approximately 90% of patients who are candidates for ECMO now survive in our institution without the use of that therapy.(ABSTRACT TRUNCATED AT 250 WORDS)