Hiroshi Nakamura

Phosphatidylinositol 4-Phosphate 5-Kinase α Is a Downstream Effector of the Small G Protein ARF6 in Membrane Ruffle Formation

Synthesis of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2], a signaling phospholipid, is primarily carried out by phosphatidylinositol 4-phosphate 5-kinase [PI(4)P5K], which has been reported to be regulated by RhoA and Rac1. Unexpectedly, we find that the GTPgammaS-dependent activator of PI(4)P5Kalpha is the small G protein ADP-ribosylation factor (ARF) and that the activation strictly requires phosphatidic acid, the product of phospholipase D (PLD). In vivo, ARF6, but not ARF1 or ARF5, spatially coincides with PI(4)P5Kalpha. This colocalization occurs in ruffling membranes formed upon AIF4 and EGF stimulation and is blocked by dominant-negative ARF6. PLD2 similarly translocates to the ruffles, as does the PH domain of phospholipase Cdelta1, indicating locally elevated PI(4,5)P2. Thus, PI(4)P5Kalpha is a downstream effector of ARF6 and when ARF6 is activated by agonist stimulation, it triggers recruitment of a diverse but interactive set of signaling molecules into sites of active cytoskeletal and membrane rearrangement.

Electronic quenching and chemical reactions of SiH radicals in the gas phase

Abstract SiH radicals in the gas phase have been studied by LIF following the 193 and 248 nm photolysis of phenylsilane. The rate constants of electronic quenching by NO and O 2 of SiH A 2 Δ with a zero-pressure lifetime of 490±40 ns are determined to be (4.6±0.3) × 10 −10 and (1.3±0.2) × 10 −10 cm 3 molecule −1 s −1 , respectively. The reactions of SiH X 2 Π with NO, O 2 , SiH 4 , and phenylsilane proceed at rates of (2.5±0.3) × 10 −10 , (1.7±0.2) × 10 −10 , (2.8±0.6) × 10 −10 , and ≈ 3 × 10 −10 cm 3 molecule −1 s −1 , respectively. The quenching and reaction mechanisms are discussed in comparison with those of the isovalent CH radical.

Genetics of the Blue Light–Dependent Signal Cascade That Controls Phototaxis in the Cyanobacterium Synechocystis sp. PCC6803

The Synechocystis sp. PCC6803 can move on a solid surface in response to light, a phenomenon called phototaxis. Although many of the photoreceptors involved in phototaxis have been identified, the mechanisms that regulate directional motility of Synechocystis are not well understood. Previous studies showed that a mutant lacking the blue light-using flavin (BLUF) photoreceptor PixD exhibits negative phototaxis under conditions where the wild type responds positively. PixD interacts with the pseudo-response regulator-like protein PixE in a light-dependent manner, suggesting that this intermolecular interaction is important for phototaxis regulation, although genetic evidence has been lacking. To gain further insight into phototaxis regulation by PixD-PixE signaling, we constructed the deletion mutants ΔPixE and ΔPixD-ΔPixE, and characterized their phenotypes, which matched those of the wild type (positive phototaxis). Because ΔPixD exhibited negative phototaxis, PixE must function downstream of PixD. Under intense blue light (>100 μmol m-2 s-1; 470 nm) the wild type exhibited negative phototaxis, but ΔPixD-PixE exhibited positive phototaxis toward low-intensity blue light (∼0.8 μmol m-2 s-1; 470 nm). These results suggest that an unknown light-sensing system(s), that is necessary for directional cell movement, can be activated by low-intensity blue light; on the other hand, PixD needs high-intensity blue light to be activated. We also isolated spontaneous mutants that compensated for the pixE deletion. Genome-wide sequencing of the mutants revealed that the uncharacterized gene sll2003 regulates positive and negative phototaxis in response to light intensity.

Light Double Hyper Nuclei and Λ-Λ Interaction

The relation between the bound states of light double hyper nuclei with mass number 3, 4, 5, 6 and the A-A interaction is analysed by a simple variational method. It is strongly indicated that (i) unless the A-A force is very strong AAH3 and AAn3 do not exist because the N-A force is too weak in these systems, and that (ii) the well-depth parameter of the A-A interaction must be ;;::: 0.8 to allow the bound state AAH4. These conclusions have been obtained on the assumption of a central A-A interaction of a Yukawa shape with range parameter (2m,..)-1 (m,..: 7r-meson mass).

Connection of spinor fields

Abstract It is proved that the field introduced by the connection of γ-matrices can be eliminated by a suitable gauge transformation except in the case of the gravitational and electromagnetic fields. Discussions are given on related papers.

On a Model of Nucleon Structure and Meson-Nucleon Interaction. II

It is shown that Im Fi (t) (Fi: the iso-vector part of the form factors of r-nucleon vertex) have one or two additional zero points in general in our representation which did not appear in Frazer and Fulcos dynamical theory.sl Using this representation, the ratios of the p-nucleon coupling constants to the p-rr coupling constant are estimated from the experimental values of the form factors. The results suggest strongly the presence of Sakurais vector current J <rl. These results are also quite consistent with our· model. § l. Introduction The presence of two different types of resonance is well-known in nuclear physics. One of them arises from the attractive force between the incident particle and nucleus which can be described by optical potential and is observed as the resonances of broad width in general. The other arises through some unstable mediate state i.e. compound nucleus, and is observed as · sharp resonance. (Hereafter, we call the former the dynamical resonance and the latter kinematical resonance according to Chew and Mandelstam. 4l) These two types of resonance appear also in the problems of field theory. For example, the so-called (3, 3) resonance which was studied by Chew and Low6l is clearly a dynamical resonance, while the K-particle which decays into two or three pions is considered as a kinematical resonance (elementary particle) by the reason of its long life. But, with respect to the new resonances p, lll, K*, N**, N***, Y*, Y** which were discovered successively by Maglic et al., 6J the Broxad okhaven groups 7 l~BJ and other groups,9l it may be difficult to determine whether they are dynamical resonating states or new elementary particles (or composite particles), because the widths of these resonances are always narrower than the one calculated by dynamical description but not so narrow as to be accepted as elementary particles (composite particles) undoubtedly. By many authors, various attempts to deduce these resonances from dyxad namical theory have been proposed within recent two years. Especially, the case of S- and P-wave 7r-7r resonance was studied skillfully by Chew and Manxad delstam4l using dispersion relation theory and was applied to the problems of

The Mass Spectrum of the Exotic Meson with Strange Quark by the Diquark Cluster Model Calculation

The total quark number is nT = k + h where k is a number of quarks and h is a number of antiquarks. The mass for u and d quarks and the parameter of the harmonic oscillator are m = ω = 300 MeV. The mass of s quark is 476 MeV. and ω’= 238 MeV, respectively. The excitation energy of u or d quarks from 1s1/2 state to 1p1/2 state and to 1d3/2 state are M(1p1/2) = 150 MeV and M(1d3/2) = 375 MeV, respectively. In the case of s quark, M(1p1/2) = 178 Mev, M(1p3/2) = 268 MeV and M(1d3/2) = 387 MeV, respectively. The u or d quark-quark interaction in the s state diquark cluster for the spin 0 is Δ0 = a 3/4b, and for the spin 1 is Δ1= a + 1/4b, and a = 187 MeV, b = 195 MeV. The case of s and u or d quark interaction, a is the same but b is b’= (m/m’) b. The s-s quark-quark interaction case, b’’= (m/m’) b. The quark-quark interaction parameters for the p state in the diquark cluster are

The Mass Spectra of the Peculiar Hadrons

We calculated the mass spectrum for the hadron by the Diquark Cluster Model and the Two Center Quark Model.

An Application of SU3 Group to the Theory of Weak Interactions

A theory of strong and weak interactions is proposed. Strong interactions are assumed to be invariant under an SU3 group Gs and Gell-Manns scheme is adopted for baryons. Weak interactions are postulated to be invariant under an SU3 group (or an u~ group) Gw which is closely related to the group Gs. Invariance under the CR-conjugation is required for both strong and weak interactions. The vector and axial-vector part of baryon currents are then determined to be of F- and D-type, respectively. Consequently, i) the vector parts of baryon currents are conserved and ii) the coupling between pseudoscalar octet bosons and baryons is of D-type, if Goldberger-Treiman relation holds. It is shown that a special case of our theory is partly equivalent to a Cabibbos model. 1 ) The general theory of gauge transformation is applied to this model using a pair of spurions of an SU3 group and intermediary mesons. Accordingly, oS/oQ= -1 transitions do not exist. As a hopeful example, a nine-fold way of leptons is proposed where weak interactions are quite symmetrical in baryonic and leptonic multiplicities. This model requires the existence of four new leptons (two charged and two neutral) with non-zero mass and several intermediary mesons. The charged new leptons decay rapidly and, consequently, the detection of these new leptons is difficult at present time. The oS = 0 and oS /oQ = 1 interactions are of scalar couplxad ing and of vector coupling for the group Gw, respectively. It is shown that oSjoQ= -1 transitions can also be present in this model as an interaction of vector coupling for the group Gw.

Application of ρ-Meson Theory to 5 Bev π--p Data

The angular distribution of protons from pi- -p inelastic collisions at 5 Bev suggests a sharp tendency to forward scattering, and this fact is favorable for the existence of some isobaric states. Using rho-meson or (1,1) nucleoneum, a Feynman diagram was calculated and applied to the 5 Bev data. (N.W.R.)