Chemical Reaction Dynamics at Surfaces

Contains reports on three research projects.Joint Services Electronics Program (Contract DAAL03-86-K-0002)Joint Services Electronics Program (Contract DAAL03-89-C-0001)National Science Foundation (Grant CHE 85-08734)MIT Energy Laboratory - Synthetic Fuels CenterPetroleum Research Fund (Contract 19014-AC5

Chemical Reaction Dynamics at Surfaces

Contains reports on four research projects.National Science Foundation (Grant DMR81-19292)National Science Foundation (Grant CHE82-06422)Research CorporationCamille and Henry Dreyfus FoundationMonsant

Chemical Reaction Dynamics at Surfaces

Contains reports on four research projects.Center for Materials Science and EngineeringCamille and Henry Dreyfus FoundationNational Science Foundation (Grant CHE82-06422)Research CorporationNational Science Foundation (CHE85-08734)Synthetic Fuels Center of the Energy Laboratory at M.I.T.Center for Materials Science and EngineeringMonsant

Chemical Reaction Dynamics at Surfaces

Contains reports on six research projects.Joint Services Electronics Program Contract DAAL03-89-C-0001MIT Energy Laboratory - Synthetic Fuels CenterNational Science Foundation Grant CHE 85-08734Petroleum Research Fund Contract 19014-AC

The actin regulator zyxin reinforces airway smooth muscle and accumulates in airways of fatal asthmatics

Bronchospasm induced in non-asthmatic human subjects can be easily reversed by a deep inspiration (DI) whereas bronchospasm that occurs spontaneously in asthmatic subjects cannot. This physiological effect of a DI has been attributed to the manner in which a DI causes airway smooth muscle (ASM) cells to stretch, but underlying molecular mechanisms–and their failure in asthma–remain obscure. Using cells and tissues from wild type and zyxin-/- mice we report responses to a transient stretch of physiologic magnitude and duration. At the level of the cytoskeleton, zyxin facilitated repair at sites of stress fiber fragmentation. At the level of the isolated ASM cell, zyxin facilitated recovery of contractile force. Finally, at the level of the small airway embedded with a precision cut lung slice, zyxin slowed airway dilation. Thus, at each level zyxin stabilized ASM structure and contractile properties at current muscle length. Furthermore, when we examined tissue samples from humans who died as the result of an asthma attack, we found increased accumulation of zyxin compared with non-asthmatics and asthmatics who died of other causes. Together, these data suggest a biophysical role for zyxin in fatal asthma

Chemical Reaction Dynamics at Surfaces

Contains reports on four research projects.National Science Foundation (Grant CHE82-06422)Research CorporationCamille and Henry Dreyfus FoundationNational Science Foundation (Grant DMR81-19292)Monsant

Quantification of zyxin protein expression in the airways of asthmatic and non-asthmatic bronchi.

<p>A) Representative image of zyxin IHC staining. Black arrow indicates ASM bands and black star indicates epithelial layer. Scale bar is 100um. B) Comparison of the percent positivity for zyxin in the ASM layer of asthmatics and non-asthmatics expressed as a fraction of the positive control. C) Comparison of percent positivity for zyxin in the ASM of non-asthmatic controls (n = 27), non-fatal asthmatics (n = 21) and fatal asthmatics (n = 22) in the replication cohort expressed as a fraction of the positive control. p<0.05 denotes significance.</p

Subject characteristics for both initial discovery cohort and replication cohort. Age is expressed in years ± SD.

<p>Subject characteristics for both initial discovery cohort and replication cohort. Age is expressed in years ± SD.</p

Zyxin mediates post-fluidization resolidification in MASM.

<p>(A) Representative traction maps of wild type and zyxin^-/- primary ASM cells at baseline and 10, 50 and 300 seconds after a single transient isotropic stretch. Maps show colorized distribution of forces. The legend shows the color values in KPa. (B) Net contractile moment is similar in both zyxin^-/- and wild type primary MASM cells in isometric conditions. (C) Normalized changes in net contractile moment in wild type (n = 25) and zyxin^-/- (n = 26) primary MASM cells following a transient 5–10% stretch at time = 0 seconds. (D) Normalized changes in net contractile moment in wild type (n = 22) and zyxin^-/- (n = 23) primary ASM cells following a series of three transient 5–10% stretches at 0, 310 and 620 seconds.</p

Zyxin is recruited to sites of actin stress fiber strain following single isotropic stretch, and is responsible for decreasing the cytoskeleton remodeling rate.

<p>(A) Kymographic analysis of zyxin and actin on a representative stress fiber following a single isotropic stretch. The kymograph is a time lapse montage of images of an actin SF captured in a zyxin^-/- MEF rescued with zyxin-GFP and also expressing actin-mApple Zyxin localizes to sites of stress fiber fragmentation and facilitates stress fiber repair. (B) Quantification of actin and zyxin intensity on a representative stress fiber following a single isotropic stretch showing zyxin’s localization to a site of stress fiber fragmentation and the subsequent recovery of the stress fiber. Kymograph (C) and intensity analysis (D) of zyxin recruitment to an actin strain site in a HASM cells. (E) Mean square displacements (MSD) of microbeads adherent to the cytoskeleton in zyxin^-/- and GFP-zyxin-rescued MEFs. Zyxin^-/- cells have an increased rate of remodeling, as evidenced by the upward shift of the MSD curve. (F) qPCR shows successful knockdown of zyxin in HASM cells of approximately 90% by 48 hours. (G) Western blot shows large reduction in zyxin in HASM cells by 72 hours post-transfection. Two replicates of this knockdown are shown as the two lanes for each condition in the western blot. (H) Cytoskeletal remodeling rate in HASM cells is increased after zyxin knockdown as indicated by the upward shift of the MSD curve.</p