Spreading of a density front in the K\"untz-Lavall\'ee model of porous media

We analyze spreading of a density front in the K\"untz-Lavall\'ee model of porous media. In contrast to previous studies, where unusual properties of the front were attributed to anomalous diffusion, we find that the front evolution is controlled by normal diffusion and hydrodynamic flow, the latter being responsible for apparent enhancement of the front propagation speed. Our finding suggests that results of several recent experiments on porous media, where anomalous diffusion was reported based on the density front propagation analysis, should be reconsidered to verify the role of a fluid flow

Measurement of Volumetric Flow

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135278/1/jum200625101305.pd

Positional Plasticity in Regenerating \u3cem\u3eAmybstoma mexicanum\u3c/em\u3e Limbs is Associated with Cell Proliferation and Pathways of Cellular Differentiation

BACKGROUND: The endogenous ability to dedifferentiate, re-pattern, and re-differentiate adult cells to repair or replace damaged or missing structures is exclusive to only a few tetrapod species. The Mexican axolotl is one example of these species, having the capacity to regenerate multiple adult structures including their limbs by generating a group of progenitor cells, known as the blastema, which acquire pattern and differentiate into the missing tissues. The formation of a limb regenerate is dependent on cells in the connective tissues that retain memory of their original position in the limb, and use this information to generate the pattern of the missing structure. Observations from recent and historic studies suggest that blastema cells vary in their potential to pattern distal structures during the regeneration process; some cells are plastic and can be reprogrammed to obtain new positional information while others are stable. Our previous studies showed that positional information has temporal and spatial components of variation; early bud (EB) and apical late bud (LB) blastema cells are plastic while basal-LB cells are stable. To identify the potential cellular and molecular basis of this variation, we compared these three cell populations using histological and transcriptional approaches. RESULTS: Histologically, the basal-LB sample showed greater tissue organization than the EB and apical-LB samples. We also observed that cell proliferation was more abundant in EB and apical-LB tissue when compared to basal-LB and mature stump tissue. Lastly, we found that genes associated with cellular differentiation were expressed more highly in the basal-LB samples. CONCLUSIONS: Our results characterize histological and transcriptional differences between EB and apical-LB tissue compared to basal-LB tissue. Combined with our results from a previous study, we hypothesize that the stability of positional information is associated with tissue organization, cell proliferation, and pathways of cellular differentiation

Volumetric Blood Flow in Transjugular Intrahepatic Portosystemic Shunt Revision Using 3‐Dimensional Doppler Sonography

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135560/1/jum2015342257.pd

Mice with Infectious Colitis Exhibit Linear Growth Failure and Subsequent Catch-Up Growth Related to Systemic Inflammation and IGF-1

In developing communities, intestinal infection is associated with poor weight gain and linear-growth failure. Prior translational animal models have focused on weight gain investigations into key contributors to linear growth failure have been lacking. We hypothesized that murine intestinal infection with Citrobacter-rodentium would induce linear-growth failure associated with systemic inflammation and suppressed serum levels of insulin-like growth factor-1 (IGF-1). We evaluated 4 groups of mice infected or sham-infected on day-of-life 28: uninfected-controls, wild-type C.-rodentium-infected, partially-attenuated C. rodentium-infected (with deletion of 3 serine protease genes involved in colonization), and pair-fed (given the amount of daily food consumed by the wild-type C.-rodentium group). Relative to the uninfected group, mice infected with wild-type C.-rodentium exhibited temporal associations of lower food intake, weight loss, linear-growth failure, higher IL-6 and TNF-α and lower IGF-1. However, relative to the pair-fed group, the C.-rodentium-infected group only differed significantly by linear growth and systemic inflammatory cytokines. Between post-infection days 15–20, the infected group exhibited resolution of systemic inflammation. Between days 16–20, both wild-type C.-rodentium and pair-fed groups exhibited rapid linear-growth velocities exceeding the uninfected and mutant C.-rodentium groups; during this time levels of IGF-1 increased to match the uninfected group. We submit this as a model providing important opportunities to study mechanisms of catch-up growth related to intestinal inflammation. We conclude that in addition to known effects of weight loss, infection with C.-rodentium induces linear-growth failure potentially related to systemic inflammation and low levels of IGF-1, with catch-up of linear growth following resolution of inflammation

Expression, isolation, and characterization of an active site (serine 528----alanine) mutant of recombinant bovine prothrombin.

An active site mutant bovine prothrombin cDNA (Ser528----Ala) has been constructed, subcloned, and expressed in Chinese hamster ovary cells. The recombinant mutant prothrombin, expressed at the level of 1.5-2.0 micrograms/ml of cell medium, was fully carboxylated (9.9 +/- 0.4 mol of gamma-carboxyglutamic acid/mol of prothrombin). The mutant prothrombin could be activated to thrombin by Taipan snake venom and activated to meizothrombin by ecarin in a manner comparable to native bovine prothrombin or recombinant wild-type bovine prothrombin. The mutant meizothrombin thus formed was stable and did not autolyze. The initial rate of cleavage of mutant prothrombin catalyzed by the full prothrombinase was only 28% of the rate of cleavage of native prothrombin, while recombinant wild-type prothrombin was cleaved at the same rate as the native molecule. The mutant thrombin, obtained from the mutant prothrombin in situ by prothrombinase or Taipan snake venom activation, showed no enzymatic activity toward either fibrinogen or a synthetic chromogenic substrate, D-phenylalanyl-L-pipecolyl-L-arginine-p-nitroanilide dihydrochloride (S2238). The mutant thrombin also bound dansylarginine-N-(3-ethyl-1,5-pentanediyl)amide, a specific fluorescent inhibitor of the thrombin active site, with a weaker binding affinity (kd = 5.4 x 10(-8) M) than did native thrombin (kd = 1.7 x 10(-8) M). These results indicate that the mutant recombinant prothrombin described here is a useful tool for the study of meizothrombin or thrombin without the complications arising from the proteolytic activities of these molecules. Study of the activation of this mutant has already revealed a functional link between the site of initial cleavage by the prothrombinase and the conformation at the nascent active site of prothrombin

Control of the diffracted response of a metallic Wire Array with Double Period: Experimental Demonstration

In recent papers, it has been theoretically shown that by using dual-period wire gratings, it is possible to control the relative efficiencies of the diffracted orders, regardless of the wires’ material, incident polarization and wavelength. In this Letter, we experimentally demonstrate, for the first time, that by appropriately choosing the geometrical parameters of a nanometric periodic structure, it is possible to control the optical response in the visible range. We show examples of nanostructures designed to cancel out or to intensify a particular diffraction order. Such nanostructures allow a broad control over the directionality and the intensity of the diffracted light, which makes them useful for applications such as highly directional optical nanoantennas and photonic multiplexers

Control of the diffracted response of a metallic wire array with double period: experimental demonstration

In recent papers, it has been theoretically shown that by using dual-period wire gratings, it is possible to control the relative efficiencies of the diffracted orders, regardless of the wires’ material, incident polarization and wavelength. In this Letter, we experimentally demonstrate, for the first time, that by appropriately choosing the geometrical parameters of a nanometric periodic structure, it is possible to control the optical response in the visible range. We show examples of nanostructures designed to cancel out or to intensify a particular diffraction order. Such nanostructures allow a broad control over the directionality and the intensity of the diffracted light, which makes them useful for applications such as highly directional optical nanoantennas and photonic multiplexers.Centro de Investigaciones Óptica

Three‐Dimensional Sonographic Measurement of Blood Volume Flow in the Umbilical Cord

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135361/1/jum201231121927.pd

Distinct ligand preferences of Src homology 3 domains from Src, Yes, Abl, Cortactin, p53bp2, PLCgamma, Crk, and Grb2.

Src homology 3 (SH3) domains are conserved protein modules 50-70 amino acids long found in a variety of proteins with important roles in signal transduction. These domains have been shown to mediate protein-protein interactions by binding short proline-rich regions in ligand proteins. However, the ligand preferences of most SH3 domains and the role of these preferences in regulating SH3-mediated protein-protein interactions remain poorly defined. We have used a phage-displayed library of peptides of the form X6PXXPX6 to identify ligands for eight different SH3 domains. Using this approach, we have determined that each SH3 domain prefers peptide ligands with distinct sequence characteristics. Specifically, we have found that the Src SH3 domain selects peptides sharing the consensus motif LXXRPLPXpsiP, whereas Yes SH3 selects psiXXRPLPXLP, Abl SH3 selects PPXthetaXPPPpsiP, Cortactin SH3 selects +PPpsiPXKPXWL, p53bp2 SH3 selects RPXpsiPpsiR+SXP, PLCgamma SH3 selects PPVPPRPXXTL, Crk N-terminal SH3 selects psiPpsiLPpsiK, and Grb2 N-terminal SH3 selects +thetaDXPLPXLP (where psi, theta, and + represent aliphatic, aromatic, and basic residues, respectively). Furthermore, we have compared the binding of phage expressing peptides related to each consensus motif to a panel of 12 SH3 domains. Results from these experiments support the ligand preferences identified in the peptide library screen and evince the ability of SH3 domains to discern subtle differences in the primary structure of potential ligands. Finally, we have found that most known SH3-binding proteins contain proline-rich regions conforming to the ligand preferences of their respective SH3 targets