Changes in contractile proteins during differentiation of myeloid leukemia cells. II. Purification and characterization of actin

A myeloid leukemia cell line, M1, differentiates to macrophage and gains locomotive and phagocytic activity when incubated with conditioned medium (CM) from a fibroblast culture and bacterial endotoxin. To characterize the actin molecules before and after differentiation, the actin was purified through three sequential steps: DEAE-sephadex A- 50, polymerization/depolymerization, and sephadex G-150 chromatography. There were no essential differences between the inhibitory activity of actins from control M1 cells and CM-treated M1 cells on both DNase I and heavy meromyosin (HMMM) K(+)-EDTA-ATPase; the same dose response as with skeletal muscle actin took place. After the treatment with CM, however, the specific activity for the activation of HMMM Mg(2+)- ATPase by actin became two-fold that of untreated M1 actin, which was one third of the value for skeletal muscle actin. The V(max) for the control and the CM-treated M1 cell, as well as the skeletal muscle actins, proved to be the same. By contrast, the K(app) values for the control and CM-treated M1-cell actins were 3- and 1.5-fold the value for skeletal-muscle actin. This means that CM treatment of the M1 actin produced a twofold affinity for the Mg(2+)-ATPase of skeletal-muscle myosin. The critical concentrations for polymerization were compared under different salt concentrations and temperatures. Although no marked difference was found for the presence of 2 mM MgCl(2), 0.1 M KCl in place of MgCl(2) at 5 degrees C gave the following values: 0.1 mg/ml for skeletal-muscle actin, 0.7 mg/ml for control M1 actin, 0,5 mg/ml for CM- treated M1 actin, and 1.0 mg/ml for the D(-) subline that is insensitive to CM. Although the critical concentration of D(-) actin is extraordinarily high, this actin showed normal polymerization above the critical concentration. This together with the data presented in our previous paper, that the D(-) actin in the crude extract did not polymerize, suggests that an inhibitor for actin polymerization is present in the subline. The kinetics experiment at 0.1 M KCl and 25 degrees C revealed a slower polymerization of untreated M1- and D(-)-cell actins as compared with CM-treated M1 actin. This delayed polymerization was due to a delay during the nucleation stage, not during the elongation stage. By isoelectric focusing, the ratios of β- to γ-actin showed a marked difference depending on the states of cells: about 4.9 for control M1, 2.8 for CM-treated M1, and 7.6 for D(-)-subline actins. Tryptic peptide maps also revealed the presence of different peptides. Thus, the functional differences of actin before and after the differentiation was accompanied by some chemical changes in actin molecules

Lamb Wave Tomography Using Laser-Based Ultrasonics

Lamb waves are widely used for the nondestructive evaluation of plate structures. By using Lamb wave attenuation, velocity and mode conversion, information about the sizes and positions of existing defects can be obtained. Lamb waves have also been used for C-scan imaging of plates. In C-scan imaging, the measurement has to be performed at each point on the sample to characterize the material at that point. Recently, computed tomography techniques using Lamb waves and surface acoustic waves have been proposed and investigated [1–3]. The computed tomographic technique provides faster image reconstruction and the ability to image an area from outside the area. This is often desired when the defected area is not directly accessible

Wide-Field Infrared Imaging Polarimetry of the NGC 6334 Region: A Nest of Infrared Reflection Nebulae

We report the detection of eighteen infrared reflection nebulae (IRNe) in the $J$, $H$, & $Ks$ linear polarimetric observations of the NGC 6334 massive star-formation complex, of which 16 IRNe are new discoveries. Our images cover $\sim$180 square arcminutes, one of the widest near-infrared polarization data in star-formation regions so far. These IRNe are most likely associated with embedded young OB stars at different evolutionary phases, showing a variety of sizes, morphologies, and polarization properties, which can be divided into four categories. We argue the different nebula characteristics to be a possible evolutionary sequence of circumstellar structures around young massive stars.Comment: 4 pages, 1 figur

Exact Analysis of ESR Shift in the Spin-1/2 Heisenberg Antiferromagnetic Chain

A systematic perturbation theory is developed for the ESR shift and is applied to the spin-1/2 Heisenberg chain. Using the Bethe ansatz technique, we exactly analyze the resonance shift in the first order of perturbative expansion with respect to an anisotropic exchange interaction. Exact result for the whole range of temperature and magnetic field, as well as asymptotic behavior in the low-temperature limit are presented. The obtained g-shift strongly depends on magnetic fields at low temperature, showing a significant deviation from the previous classical result.Comment: 4 pages, 3 figures,to be published in Phys. Rev. Let

Magnetic response and quantum critical behavior in the doped two-leg extended Hubbard ladder

We have investigated quantum critical behavior in the doped two-leg extended Hubbard ladder, by using a weak-coupling bosonization method. In the ground state, the dominant fluctuation changes from the conventional d-wave-like superconducting (SCd) state into density-wave states, with increasing nearest-neighbor repulsions and/or decreasing doping rate. The competition between the SCd state and the charge-density-wave state coexisting with the p-density-wave state becomes noticeable on the critical point, at which the gap for magnetic excitations vanishes. Based on the Majorana-fermion description of the effective theory, we calculate the temperature dependence of the magnetic response such as the spin susceptibility and the NMR relaxation rate, which exhibit unusual properties due to two kinds of spin excitation modes. On the quantum critical point, the spin susceptibility shows paramagnetic behavior with logarithmic corrections and the NMR relaxation rate also exhibits anomalous power-law behavior. We discuss the commensurability effect due to the umklapp scattering and relevance to the two-leg ladder compounds Sr_{14-x}Ca_xCu_{24}O_{41}.Comment: 18 pages, 9 figures, accepted for publication in Phys. Rev.