Lung inflammation and simulated airway resistance in infants with cystic fibrosis

Cystic fibrosis (CF) is characterized by small airway disease; but central airways may also be affected. We hypothesized that airway resistance estimated from computational fluid dynamic (CFD) methodology in infants with CF was higher than controls and that early airway inflammation in infants with CF is associated with airway resistance. Central airway models with a median of 51 bronchial outlets per model (interquartile range 46,56) were created from chest computed tomography scans of 18 infants with CF and 7 controls. Steady state airflow into the trachea was simulated to estimate central airway resistance in each model. Airway resistance was increased in the full airway models of infants with CF versus controls and in models trimmed to 33 bronchi. Airway resistance was associated with markers of inflammation in bronchoalveolar lavage fluid obtained approximately 8 months earlier but not with markers obtained at the same time. In conclusion, airway resistance estimated by CFD modeling is increased in infants with CF compared to controls and may be related to early airway inflammation.

Cathepsin-G interferes with clearance of Pseudomonas aeruginosa from mouse lungs

The cystic fibrosis airway is susceptible to Pseudomonas aeruginosa infection, which stimulates an intense inflammatory response leading to airway obstruction and bronchiectasis. Neutrophils migrate into the airway, and once there, release high concentrations of neutral serine proteases during phagocytosis and in death. In particular, neutrophil elastase is central to progression of bronchiectasis by interfering with bacterial clearance and directly perpetuating the inflammatory response in the airway. Using a murine model of endobronchial inflammation, we found that a different neutrophil-derived serine protease, cathepsin G, inhibited the host's ability to clear Pseudomonas from the lung, based on a 1-log reduction in bacteria recovered from cathepsin G-deficient mice. Higher antibody concentrations were found in respiratory epithelial lining fluid from mice lacking cathepsin G, but there was no difference in other opsonins, such as surfactant proteins A and D. Chemokine levels measured in the lung correlated with bacterial burden and not the animal's genotype, indicating that airway inflammation was not affected by the presence (or absence) of specific serine proteases. These findings suggest that cathepsin G interferes with airway defenses, showing that proteases other than neutrophil elastase have roles in the pathogenesis of suppurative airway diseases.

Curved flight paths and sideways vision in peregrine falcons (Falco peregrinus)

When diving at prey straight ahead from great distances at high speeds, a peregrine has a conflict between vision and aerodynamics: it must turn its head approximately 40 degrees to one side to see the prey with maximum visual acuity at the deep fovea of one eye, but the head in this position increases aerodynamic drag and slows the falcon down. The falcon could resolve this conflict by holding its head straight and flying along a logarithmic spiral path that keeps the line of sight of the deep fovea pointed sideways at the prey. Wild peregrines, observed with binoculars, telescopes and a tracking device, did approach prey the size of American robins (Turdus migratorius) and smaller birds from distances of up to 1500 m by holding their heads straight and flying along curved paths that resembled the logarithmic spiral.

Sensitive assays for urinary retinol-binding protein and beta-2-glycoprotein-1 based on commercially available standards

Measurements of urinary retinol-binding protein (RBP) and beta-2-glycoprotein-1 (beta 2G1) provide sensitive indicators of proximal renal tubular malfunction. beta 2G1 is very stable in urine but RBP, which is much less stable, has been more extensively studied. We have designed two similar immunoassays allowing measurement of both proteins from one urine dilution. The assays both use widely available commercial standards and permit accurate measurement throughout most of the reference range. We measured both proteins in the urine of 70 healthy adults and 80 healthy children aged between three and 16 years, expressing the results as a ratio to creatinine concentration. Using the 98th centile as the upper reference limit, adults excreted up to 17 micrograms/mmol RBP (median 8) and up to 30 micrograms/mmol beta 2G1 (median 15) with no difference between the sexes. Children had different ranges to adults with excretion of up to 22 micrograms/mmol RBP (median 10) and up to 80 micrograms/mmol beta 2G1 (median 24).

Activation of gelatinase A (72-kDa type IV collagenase) induced by monensin in normal human fibroblasts

In monolayer culture, fibroblasts secrete all matrix metalloproteinases, including gelatinase A (72-kDa type IV collagenase), as inactive zymogens. Whereas limited proteolysis by plasmin or other matrix metalloproteinases (MMPs) can accomplish the extracellular activation of other proenzymes in this family, gelatinase A proenzyme is uniquely refractory to cleavage by such proteinases. Previously it has been shown that fibroblasts cultured in the presumably more physiologic culture milieu of a type I collagen lattice can be induced to secrete active gelatinase A. In monolayer culture, however, the plant lectin concanavalin A will induce gelatinase A activation. Here we show that in monolayer culture activation of gelatinase A by normal fibroblasts is also induced by the sodium ionophore monensin. The monensin response is dose-dependent, time-dependent, requires protein synthesis, and is specific to gelatinase A among the secreted matrix metalloproteinases. The activator appears to be associated with cell membranes and may be membrane-type matrix metalloproteinase 1(MT-MMP1). Both mRNA and immunodetectable protein of MT-MMP1 are increased with monensin treatment while message for the protein inhibitor of gelatinase A, TIMP-2, is unchanged. The monensin-induced signal transduction pathway leading to gelatinase activation in monolayer culture appears to be different from the integrin-mediated pathway operative in the collagen lattice system. The tyrosine kinase inhibitor genistein blocks monensin activation of gelatinase A in monolayer culture. In contrast, genistein has no effect on proenzyme activation in the collagen lattice. Likewise, the cyclooxygenase inhibitor indomethacin abrogates the monensin effect in monolayer culture and can be reversed by addition of exogenous prostaglandin E2 (PGE2). Neither indomethacin nor PGE2 affects activation of gelatinase A in the collagen lattice.

Comparison of cleavage site specificity of gelatinases A and B using collagenous peptides

The gelatinases (type IV collagenases) are members of the matrix metalloproteinase family that not only have a high degree of structural homology but are known to be nearly identical in their digestion profile against macromolecular substrates. We have shown previously that the preferred cleavage sites in the hydrolysis of type I gelatin, catalyzed by gelatinase A (72 kDa type IV collagenase), are bracketed by hydroxyproline in the P5 and P5' positions. In this report, a kinetic investigation using a series of collagenous dodecylpeptides in which the P5 and P5' hydroxyprolines were systematically varied and used as substrates for recombinant human gelatinase A, we show that replacement with either proline or alanine always resulted in increased Km. In contrast, substitution of the hydroxylated amino acids tyrosine and serine at P5 and P5' reduced the Km significantly, indicating that the hydroxyl moiety of the hydroxyproline is the functional group responsible for favorable enzyme-substrate affinity. This was shown by the kcat/Km ratio, which was doubled by the substitution of serine in that site. Cleavage of the same series of dodecylpeptides by recombinant human gelatinase B (92 kDa type IV collagenase) showed a very different kinetic profile for which no patterns were discernible. In subsequent comparisons of the two enzymes, it was found that gelatinase B cleaved the thiopeptolide substrate AcProLeuGly-S-LeuGly-OC2H5 at double the velocity of gelatinase A. In contrast, gelatinase A digested type I gelatin about 2.5-times faster than gelatinase B. SDS-PAGE analysis of gelatin cleavage products showed different patterns of product peptides for each enzyme. Further comparisons of the proteinases using synthetic peptide substrates with variations in size and in substituents at the P2' site again showed marked kinetic differences. Although these two matrix metalloproteinases seem similar in that they are both gelatinolytic and can degrade a nearly identical battery of macromolecular matrix components including type IV collagen, it is clear from these results that they are very different enzymatically. Since the regulatory portions of gelatinases A and B differ markedly, it has been assumed that the enzymes serve the same function, but respond to different stimuli. The differences in substrate specificity described herein suggest that their proposed physiological roles may require reevaluation.

Order-Disorder Transition in Polycrystalline C 60 Films

High-resolution Raman spectroscopy of polycrystalline films of C(60) deposited under ultrahigh-vacuum conditions show that the spectrum below 244 +/- 3 kelvin consists of a superposition of two components whose relative contributions are temperature-dependent. The spectrum of the more intense of the two components is similar to that obtained for air- or oxygen-exposed samples of C(60) at room temperature, whereas the spectrum above 244 +/- 3 kelvin corresponds to one previously reported for oxygen-free samples of C(60). The results may indicate an order-disorder phase transition involving the percolation of a cluster of C(60) molecules engaged in coherent Raman scattering.

Effect of BiTek agar on lysostaphin susceptibility of staphylococci

Staphylococci which were considered to be lysostaphin susceptible on P agar containing Bacto-Agar showed different degrees of resistance to lysostaphin when tested on P agar made with BiTek agar. As a result, lysostaphin-susceptible strains were misidentified as lysostaphin-resistant strains.

Comparison of methods for determining DNase and phosphatase activities of staphylococci

A greater percentage of DNase-positive strains was detected with DNase test agar than with DNase test agar containing 0.005% methyl green or 0.005% toluidine blue (P less than 0.01). No significant differences were obtained in the percentage of phosphatase-positive strains with the four methods compared. On the basis of ease of use, P agar containing para-nitrophenylphosphate disodium (0.495 mg/ml) would be the preferred method for determining phosphatase activity of staphylococci.

Use of Lysostaphin and Bacitracin Susceptibility for Routine Presumptive Identification of Staphylococci of Bovine Origin 1

A simple agar plate system based on susceptibility to lysostaphin and bacitracin to differentiate between staphylococci and micrococci is described. The system also uses susceptibility to novobiocin to aid in identification to species level of staphylococci. Growth from the agar plate can be used to prepare inocula for inoculation of rapid identification systems.

Identification of Staphylococcus species of bovine origin with the DMS Staph-Trac system

The DMS Staph-Trac system was evaluated as a means for identifying the species of bovine strains of staphylococci routinely isolated from quarter-milk samples. The species identity of 83 of 91 (91.2%) isolates of staphylococci was correctly determined by this method. One isolate could not be identified by this system. The Staph-Trac system was able to distinguish between Staphylococcus hyicus and Staphylococcus epidermidis. We obtained a higher percentage of correct identifications with the DMS Staph-Trac system (91.2%) than we did in a previous study with the API Staph-Ident system (45.1%), using the same isolates (Langlois et al., J. Clin. Microbiol. 18:1212-1219, 1983).

Identification of Staphylococcus species of bovine origin with the API Staph-Ident system

The API Staph-Ident system was evaluated as a means for identifying the species of bovine strains of staphylococci routinely isolated from quarter-milk samples. The species identity of 314 of 581 (54%) isolates of staphylococci was correctly determined by this method. The API Staph-Ident system was more accurate in correctly identifying Staphylococcus aureus (93.9%) than in correctly identifying non-S. aureus species (41.8%). False identifications of Staphylococcus epidermidis and Staphylococcus hominis were the main reasons for the incorrect identifications of the non-S. aureus species.