Transcription factor E2F controls the reversible gamma delta T cell growth arrest mediated through WC1

IL-2-stimulated expansion of T cells requires continued and sequential passage of the dividing cells through a major cell cycle check point in the G1 phase. We have previously shown that a gamma delta T cell-specific surface receptor, WC1, induces G0/G1 growth arrest, reversible with Con A, in proliferating IL-2-dependent gamma delta T cells. We now show that this reversible WC1-induced cell cycle arrest is correlated with induction of the cyclin kinase inhibitor p27kip1 and an associated down-regulation in cyclins A, D2, and D3 expression, along with dephosphorylation of pocket proteins p107, p130, and pRb. Together with diminished pocket protein phosphorylation, p107 expression levels are significantly down-regulated in response to WC1 stimulation. This coordinated sequence of signaling events is focused on E2F regulation so that, downstream of the pocket proteins, WC1 stimulation results in a diminished DNA binding activity for free E2F as a consequence of reduced E2F1 expression, whereas E2F4 expression is unaffected. Consistent with this interpretation, overexpression of E2F1 overcomes the growth-arresting effects induced by WC1 stimulation. Finally, in accordance with our previous observations at both the cellular and molecular level, subsequent mitogen stimulation can reverse all the above changes induced by WC1. These results, focused on E2F regulation, therefore provide a first insight into the effects of both positive (mitogen) and negative (anti-WC1) stimuli on cell cycle control in IL-2-dependent gamma delta T cells.     

The utility of three-phase bone scintigraphy in the assessment of fractured carpal scaphoid

Thirty-seven joints in 36 patients with a fractured carpal scaphoid were evaluated by three-phase bone scintigraphy. They were classified into two groups according to their progress. Some were in good clinical condition and some in a non-union condition. Increased blood flow in the radial arteries and ample perfusion on and around the scaphoid bones on blood flow images suggested a good clinical course. The activity and the effectiveness of remodeling correlated well with the degree of scaphoid uptake on blood pool images taken more than seven days after the injury. Scaphoid uptake was more localized or there was almost none on blood pool images in cases with nearly complete recovery while it was amply visualized on static images. Blood pool images were indispensable for analyzing lesions and evaluating the clinical course. Two typical findings of scaphoid fractures were found on both blood pool and static images. One was diffusely increased scaphoid uptake seen in cases with a good clinical course, and the other was decreased uptake at proximal fragments seen in cases with non-union. It is concluded that three-phase bone scintigraphy provides useful information for evaluating the process of scaphoid fractures which cannot be obtained by means of conventional bone scintigraphy.     

Surgical therapy in a case of congenital mitral valve insufficiency]

Using sheep erythrocytes (SRBC) as the antigen, two subpopulations of spleen antigen-binding lymphocytes could be distinguished by a marked difference in the susceptibility of their receptors to trypsin. In unimmunized animals, 30% of the antigen-binding cells were trypsin-resistant, whereas at 5 days after immunization, 80-90% were trypsin-resistant, indicating an increase of about 50-fold in trypsin-resistant antigen-binding cells per spleen. In contrast, trypsin-sensitive cells per spleen were only 4-fold higher on day 5 than before immunization. The rise in % trypsin sensitivity preceded the increase in rosettes per spleen, implying that immunization produced a preferential increase in trypsin-resistant antigen binding cells partly by converting sensitive cells to resistant cells. After the 5th day, the trypsin sensitivity of antigen-binding cells slowly returned toward the unimmunized level, but a booster injection of SRBC restored trypsin resistance. Trypsin resistance was not lost in the presence of sodium azide or protein synthesis inhibitors. But a slightly increased trypsin susceptibility was conferred by 2-deoxyglucose, implying that glycolysis or the glycosylation of protein may be involved in maintaining trypsin resistance.     

Effect of 17 beta-estradiol on secretion of platelet-activating factor acetylhydrolase by HepG2 cells

Estrogen has been shown to decrease plasma platelet-activating factor (PAF) acetylhydrolase activity, but the precise mechanisms are not known. We examined the effect of estradiol on the secretion of PAF acetylhydrolase by HepG2 cells. In our previous study, we demonstrated the production of this enzyme by HepG2 cells, which we used as an experimental model of normal hepatocytes. 17 beta-Estradiol mildly but consistently inhibited the secretion of PAF acetylhydrolase by HepG2 cells in a concentration-dependent manner. Under basal conditions, HepG2 cells secreted 42.3 pmol/mg cell protein/min PAF acetylhydrolase in 24 hours (mean of 8 dishes), and the presence of 10(-7) mol/L 17 beta-estradiol decreased the secretion to 77% +/- 10.3% of control values (mean +/- SD, n = 8, P < .02). 17 beta-Estradiol treatment affected neither the secretion of apolipoprotein (apo) A-I nor cell-associated PAF acetylhydrolase activity. Electrophoretic separation of [35S]methionine-labeled PAF acetylhydrolase revealed a single band whose molecular weight was approximately 43,000 d. We conclude that estrogen decreases the secretion of PAF acetylhydrolase by the liver, and it may explain, at least in part, the effect of estrogen on plasma PAF acetylhydrolase.     

Dual control by divalent cations and mitogenic cytokines of alpha 4 beta 1 and alpha 5 beta 1 integrin avidity expressed by human hemopoietic cells

Beta-1 integrins have essential functions in hemopoietic and immune systems by controlling phenomenons such as cell homing and cell activation. The function alpha 4 beta 1 and alpha 5 beta 1 integrins is regulated by divalent cations and, as demonstrated more recently, by mitogenic cytokines which activate them by "inside-out" mechanisms. Using the adhesive interaction of a cytokine-dependent human hemopoietic cell line to immobilized fibronectin, we have analyzed the requirements in divalent cations Mn2+, Mg2+ and Ca2+ for alpha 4 beta 1 and alpha 5 beta 1 activation by "inside-out" mechanisms triggered by cytokines such as granulocyte-macrophage colony stimulating factor or KIT ligand, or by external conformational constraints with the function-activating anti-beta 1 integrin monoclonal antibody 8A2. The intrinsic difference between these two modes of beta 1 integrin activation was revealed by their different requirements in divalent cations. We found that in the absence of any divalent cations, alpha 4 beta 1 and alpha 5 beta 1 were non-functional even after further stimulation by cytokines or 8A2. However, whilst either Ca2+, Mg2+ or Mn2+ were able to restore adhesive functions of alpha 4 beta 1 and alpha 5 beta 1 when activated by 8A2, only Mg2+ and Mn2+ were able to support activation of alpha 4 beta 1 and alpha 5 beta 1 by cytokines. Furthermore, high concentrations of Ca2+ exceeding 20 mM dramatically inhibited cell adhesion to fibronectin induced by Mn2+ and cytokines but not by 8A2. On the contrary, in the presence of both Ca2+ and Mg2+, Mn2+ had an additive effect on the activation of alpha 4 beta 1 and alpha 5 beta 1 by mitogenic cytokines. The presence of the absence of these divalent cations did not inhibit early tyrosine phosphorylation induced by the binding of KIT ligand to its tyrosine-kinase receptor KIT. Therefore, we propose that in hemopoietic cells, Ca2+, Mg2+ and Mn2+ may modulate in vivo alpha 4 beta 1 and alpha 5 beta 1 regulation by mitogenic cytokines, a phenomenon involved in the regulation of hemopoietic progenitor cell homing within the bone marrow.     

Two-stage-type electrostatic precipitator re-entrainment phenomenaunder diesel flue gases

One of the applications of the electrostatic precipitator (ESP) is the cleaning of air to increase the visibility index in highway tunnels. Particles floating in air in highway tunnels are mainly carbon. Collection efficiency of a large particle diameter in an ESP often decreases when the ESP collects carbon particles which have low electric resistance. Collection efficiency often becomes negative in an experimental ESP. The negative collection efficiency means that the particle concentration flowing downstream is greater than that upstream in the ESP. This phenomenon is explained as the re-entrainment of particles. In this paper, experiments were carried out to investigate the cause of the decrease in efficiency of particle collection of the ESP. The time characteristic of the collection efficiency and the distribution of particle size on the collection electrodes were studied. Experimental results showed that the decrease in the collection efficiency was caused by re-entrainment of particles during the ESP operation. The effect of gas-flow velocity on the collection efficiency of the ESP was also investigated to study the cause of re-entrainment phenomena. The result showed that the re-entrainment phenomena depended on the gas-flow velocity     

Real-time imaging of two-photon-induced fluorescence with a microlens-array scanner and a regenerative amplifier

A real-time two-photon fluorescence microscope with a microlens-array scanner using a regenerative amplifier is presented. The regenerative amplifier generates pulsed laser lights with extremely high peak power and produces brighter two-photon-induced fluorescence compared with that produced without the amplifier. Experimental results obtained from the observation of some biological samples with the proposed microscope are given.     

Agglomeration of particles by ac corona discharge

Improving the collection efficiency for particles smaller than 1 μm on every precipitator is important. We sought to improve the collection of these particles on an ESP due to particle agglomeration. Particles are charged by ac corona discharge in a precharger and agglomerated by a dc electric field in an agglomerator downstream of the precharger. Diesel exhaust particles were used as particulate matter for the experiments. The distribution of particle size was measured using a particle counter and a scanning electron microscope. By these methods, particles as small as 0.01 μm could be counted. Results showed the agglomeration between particles at ac corona discharge operating mode. The concentration of particles smaller than approximately 0.35 μm decreases, and that of particles larger than approximately 0.35 μm increases in the agglomerator. The agglomeration rate increases with increasing applied voltage, then saturates. These results may be due to the size distribution and to decrease of concentration by agglomeration. © 1999 Scripta Technica, Electr Eng Jpn, 130(1): 30–37, 2000     

Index characterization of differential–algebraic equations in hybrid analysis for circuit simulation

Modern modeling approaches in circuit simulation naturally lead to differential–algebraic equations (DAEs). The index of a DAE is a measure of the degree of numerical difficulty. In general, the higher the index, the more difficult it is to solve the DAE. The modified nodal analysis (MNA) is known to yield a DAE with index at most two in a wide class of nonlinear time‐varying electric circuits. In this paper, we consider a broader class of analysis method called the hybrid analysis. For linear time‐invariant RLC circuits, we prove that the index of the DAE arising from the hybrid analysis is at most one, and give a structural characterization for the index of a DAE in the hybrid analysis. This yields an efficient algorithm for finding an optimal hybrid analysis in which the index of the DAE to be solved attains zero. Finally, for linear time‐invariant electric circuits that may contain dependent sources, we prove that the optimal hybrid analysis by no means results in a higher index DAE than MNA. Copyright © 2008 John Wiley & Sons, Ltd.     

Microstructure analysis of Ag films deposited by low-voltage sputtering

The microstructure of Ag films was investigated as a function of the cathode voltage during sputter deposition. It was found that the resistivity of the Ag films decreased when the Ag film was deposited at low cathode voltage using a magnetron cathode with high-magnetic flux density. X-ray diffraction measurement revealed that the Ag films deposited at low cathode voltages exhibited higher crystallization degree and larger crystallites. Besides, it was confirmed from glancing incident X-ray reflectivity measurement that the density of the Ag films increased with decreasing in the cathode voltage. It can be concluded from these results that the improvements in the resistivity and microstructure of Ag films result from the low-voltage sputtering. It can be concluded that the kinetic energy of the Ar gas particles decreased with decreasing the cathode voltage; as a result, the microstructure of Ag films should be improved.