The use of albuterol in hospitalized infants with bronchiolitis

OBJECTIVES

To determine whether the use of albuterol by nebulization enhances physiologic or clinical recovery in hospitalized infants with moderate bronchiolitis.

METHODS

This prospective, double-blind, placebo-controlled, randomized clinical trial was performed from December 1995 to March 1996. A total of 52 patients <24 months of age with a diagnosis of moderately severe, acute viral bronchiolitis were enrolled and assigned to receive nebulized albuterol or normal saline placebo for 72 hours under a standardized protocol. Primary outcome measures included improvement in oxygen saturation (SaO2) during hospitalization and survival analysis to assess the time required to reach preestablished discharge criteria on three measures: SaO2, accessory muscle use, and wheezing. An additional secondary outcome measure was actual length of hospital stay. Adverse outcomes also were compared between treatment groups.

RESULTS

There was no significant difference in mean SaO2 between albuterol and placebo at baseline, 24 hours, or maximum SaO2 achieved during hospitalization. Both groups showed significant improvement in oxygen saturation over time, but there was no significant difference in improvement between the two groups. The study had a power of 90% to detect a difference in mean percentage point improvement of 2% SaO2. There was no difference in time to reach discharge criteria as defined by SaO2, accessory muscle use, or wheezing. There was no difference in length of hospital stay or in the frequency of adverse outcomes.

CONCLUSIONS

Nebulized albuterol therapy does not appear to enhance recovery or attenuate severity of illness in infants hospitalized with acute, moderate bronchiolitis, as evidenced by improvement in oxygen saturation, time to meet standardized discharge criteria, or length of hospital stay.

Isolation of a fibrin-binding fragment from blood coagulation factor XIII capable of cross-linking fibrin(ogen)

Purified platelet Factor XIII was radioiodinated and then partially degraded by thrombin or trypsin, and a fibrin-binding fragment was identified by autoradiography and immunoblotting following separation by SDS/polyacrylamide-gel electrophoresis. Limited proteolysis of 125I-Factor XIII by thrombin or trypsin produced an 125I-51 kDa fragment and an unlabelled 19 kDa fragment. The 51 kDa fragment was purified by h.p.l.c. on a TSK-125 gel-filtration column. Partial amino acid sequence analysis of the 51 kDa fragment indicated that it was similar in sequence to the Gly38-Lys513 segment in placental Factor XIII a-chain. More than 70% of the 51 kDa fragment bound to fibrin, whereas the 19 kDa fragment did not bind. The active site was localized to the 51 kDa fragment since this fragment expressed transglutaminase activity, cross-linked fibrin and fibrinogen and incorporated iodo[14C]acetamide into the active-site cysteine residue. Isolation of a fibrin-binding fragment expressing transglutaminase activity demonstrates that each a-chain of the dimeric Factor XIIIa could function independently to cross-link fibrin. The fibrin-binding site could play an important role in localizing Factor XIIIa to the fibrin clot.

Gly-Pro-Arg-Pro modifies the glutamine residues in the alpha- and gamma-chains of fibrinogen: inhibition of transglutaminase cross-linking

During blood clotting Factor XIIIa, a transglutaminase, catalyzes the formation of covalent bonds between the epsilon-amino group of lysine and the gamma-carboxamide group of peptide-bound glutamine residues between fibrin molecules. We report that glycyl-L-prolyl-L-arginyl-L-proline (GPRP), a tetrapeptide that binds to the fibrin polymerization sites (D-domain) in fibrin(ogen), inhibits transglutaminase cross-linking by modifying the glutamine residues in the alpha- and gamma-chains of fibrinogen. Purified platelet Factor XIIIa, and tissue transglutaminase from adult bovine aortic endothelial cells were used for the cross-linking studies. Gly-Pro (GP) and Gly-Pro-Gly-Gly (GPGG), peptides which do not bind to fibrinogen, had no effect on transglutaminase cross-linking. GPRP inhibited platelet Factor XIIIa-catalyzed cross-linking between the gamma-chains of the following fibrin(ogen) derivatives: fibrin monomers, fibrinogen and polymerized fibrin fibers. GPRP functioned as a reversible, noncompetitive inhibitor of Factor XIIIa-catalyzed incorporation of [3H]putrescine and [14C]methylamine into fibrinogen and Fragment D1. GPRP did not inhibit 125I-Factor XIIIa binding to polymerized fibrin, demonstrating that the Factor XIIIa binding sites on fibrin were not modified. GPRP also had no effect on Factor XIIIa cross-linking of [3H]putrescine to casein. This demonstrates that GPRP specifically modified the glutamine cross-linking sites in fibrinogen, and had no effect on either Factor XIIIa or the lysine residues in fibrinogen. GPRP also inhibited [14C]putrescine incorporation into the alpha- and gamma-chains of fibrinogen without inhibiting beta-chain incorporation, suggesting that the intermolecular cross-linking sites were selectively affected. Furthermore, GPRP inhibited tissue transglutaminase-catalyzed incorporation of [3H]putrescine into both fibrinogen and Fragment D1, without modifying [3H]putrescine incorporation into casein. GPRP also inhibited intermolecular alpha-alpha-chain cross-linking catalyzed by tissue transglutaminase. This demonstrates that the glutamine residues in the alpha-chains involved in intermolecular cross-linking are modified by GPRP. This is the first demonstration that a molecule binding to the fibrin polymerization sites on the D-domain of fibrinogen modifies the glutamine cross-linking sites on the alpha- and gamma-chains of fibrinogen.

Regulation of plasma factor XIII binding to fibrin in vitro

The binding of plasma factor XIII to fibrinogen or fibrin that has been chemically or enzymatically induced to polymerize was studied. Factor XIII binding was assayed using a 3H-putrescine incorporation assay and an 125I-plasma factor XIII binding assay. More than 80% of the native and radiolabeled plasma factor XIII was bound to fibrin I formed by reptilase in EDTA, citrate, or heparin anticoagulated plasma. Plasma factor XIII and 125I-factor XIII was bound (89.6% to 92.5%) to fibrin II formed by thrombin in either citrate or EDTA anticoagulated plasma. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of 125I-plasma factor XIII bound to fibrin I or fibrin II formed by reptilase or thrombin in the presence of EDTA demonstrated the b2-subunit remained bound to the a-chains or thrombin-cleaved a-chains. In the presence of calcium chloride and thrombin, the b2-subunit dissociated and factor XIIIa was bound. Protamine sulfate caused fibrinogen polymerization in the absence of divalent cations and reduced both plasma factor XIII and immunologic fibrinogen levels. Fibrinogen polymerized by protamine sulfate bound plasma factor XIII and the a2-subunit of 125I-platelet factor XIII. Plasma factor XIII was also bound to sonicated non-cross-linked fibrin II in either normal plasma or afibrinogenemic plasma. Plasma levels of several coagulation proteins were unchanged after the addition of reptilase, protamine sulfate, or sonicated fibrin to plasma. These results demonstrate that a specific binding site for the a2-subunit of plasma factor XIII is present on polymerized fibrinogen, fibrin I, and fibrin II. Furthermore, the presence of divalent cations, thrombin-cleavage of plasma factor XIII, and release of fibrinopeptides A or B are not required for plasma factor XIII binding to polymerized fibrinogen and fibrin.

A new method for the detection of hydrogen in breath and its application to acquired and inborn sugar malabsorption

An electrochemical device for the measurement of hydrogen in end-expired air is described and compared with an existing gas chromatographic method. The application of both these methods to subjects with acquired and inborn defects of sugar malabsorption is documented. Our simplified method of breath collection and the rapid estimation of hydrogen concentration provides a reliable, convenient and well-tolerated means of detecting sugar malabsorption.