Airway-parenchymal interdependence after airway contraction in rat lung explants

The constrictionof pulmonary airways is limited by the tethering effect exerted byparenchymal attachments. To characterize this tethering effect at thescale of intraparenchymal airways, we studied the pattern ofparenchymal distortion due to bronchoconstriction in a rat lung explantsystem. First, we measured the elastic modulus under tension for 2%(wt/vol) agarose alone (37.6 ± 1.5 kPa) and for agarose-filled lung(5.7 ± 1.3 kPa). The latter is similar to the elastic modulus ofair-filled lung at total lung capacity (4.5-6 kPa) (S. J. Lai-Fook, T. A. Wilson, R. E. Hyatt, and J. R. Rodarte.J. Appl. Physiol. 40: 508-513,1976), suggesting that explants can be used as a model of lung tissuedistortion. Subsequently, confocal microscopic images of fluorescentlylabeled 0.5-mm-thick explants prepared from agarose-filled rat lungsinflated to total lung capacity (48 ml/kg) were acquired. Images weretaken before and after airway constriction was induced by directapplication of 10 mM methacholine, and the pattern of parenchymaldistortion was measured from the displacement of tissue landmarksidentified in each image for 14 explants. The magnitude of the radialcomponent of tissue displacement was calculated as a function ofdistance from the airway wall and characterized by a parameter,b, describing the rate at which tissuemovement decreased with radial distance. The parameterb was 0.994 ± 0.19 (SE), which isclose to the prediction of b = 1 ofmicromechanical modeling (T. A. Wilson. J. Appl.Physiol. 33: 472-478, 1972). There was significantvariability in b, however, which wascorrelated with the fractional reduction in airway diameter (r = 0.496). Additionally, parenchymaldistortion showed significant torsion with respect to the radialdirection. This torsion was similar in concentric zones around theairway, suggesting that it originates from inhomogeneity in theparenchyma rather than inhomogeneous airway constriction. Our resultsdemonstrate the significance of the nonlinear mechanical properties ofalveolar walls and the anisotropy of the parenchyma in determining the nature of airway-parenchymal interdependence.

     

C-H activation by a terminal imidoiron(III) complex to form a cyclopentadienyliron(II) product

Imido complexes of the late transition metals have the ability to activate C-H bonds through the abstraction of hydrogen atoms from hydrocarbons. This paper describes the apparent hydrogen atom transfer from cyclopentadiene (CpH) to the isolable imidoiron(III) complex L^MeFeNAd (L^Me = 2,4-bis(2,6-diisopropylphenylimido)pent-3-yl; Ad = 1-adamantyl) in the presence of 4-tert-butylpyridine (^tBupy). The isolated product is not the amidoiron(II) complex, but instead it is L^MeFe(Cp)(^tBupy), the result of amido protonation by additional CpH. The crystal structures of both L^MeFeCp and L^MeFe(Cp)(^tBupy) are presented, and in the latter compound the Fe-C bonds are longer than in any previously characterized cyclopentadienyliron complex.     

Google search patterns suggest declining interest in the environment

Public interest in most aspects of the environment is sharply declining relative to other subjects, as measured by internet searches performed on Google. Changes in the search behavior by the public are closely tied to their interests, and those interests are critical to driving public policy. Google Insights for Search (GIFS) was a tool that provided access to search data but is now combined with another tool, Google Trends. We used GIFS to obtain data for 19 environment-related terms from 2001 to 2009. The only environment-related term with large positive slope was climate change. All other terms that we queried had strong negative slopes indicating that searches for these topics dropped over the last decade. Our results suggest that the public is growing less interested in the environment.     

Ultrastructural characterization of the pulmonary cellular defences in the lung of a bird,the rock dove,Columba livia

Free (surface) avian respiratory macrophages (FARMs) were harvested by lavage of the lung/air-sac system of the rock dove, Columba livia. The presence of FARMs in the atria and infundibula was confirmed by scanning electron microscopy. The respiratory system has developed several cellular defence lines that include surface macrophages, epithelial, subepithelial and interstitial phagocytes, and pulmonary intravascular macrophages (PIMs). Hence, C. livia appears to have a multiple pulmonary cellular protective armoury. Ultrastructurally, the FARMs and the PIMs were similar to the corresponding cells of mammals. The purported high susceptibility of birds to respiratory diseases, a state that has largely been deduced from morbidities and mortalities of commercial birds, and which has chiefly been attributed to paucity of the FARMs, is not supported by the present observations.