Light Induces lnositol Trisphosphate Elevation in Blepharisma japonicum

Abstract— Photoinduced formation of inositol 1,4,5-trisphosphate (Ins[1,4,5]P₃) was examined using a specific radioimmu-noassay to investigate the molecular mechanisms of light signal transduction mediating photophobic responses in the ciliate Blepharisma japonicum. Application of light stimuli of moderate intensity to dark-adapted cells induced a rapid and significant increase in the basal level of Ins (1,4,5)P₃, with a peak at about 20 s. Thereafter, the level of Ins (1,4,5)P₃ declined to the resting value within the subsequent 100 s. Light stimuli of higher intensity raised the cell Ins (1,4,5)P₃ content to still higher levels within about 20 s, but the decaying time course was considerably prolonged. In ciliates incubated under dark conditions with agents interfering with the inositol signalling pathway, like neomycin and Li⁺ the basal levels of Ins (1,4,5)P₃ were lower than in control cells. A photoinduced rise of Ins (1,4,5)P₃, content in ciliates treated with neomycin or Li⁺ was significantly inhibited in a dose-dependent manner. Depolarizing ionic stimuli in dark-adapted ciliates induced no significant alterations of the resting Ins (1,4,5)P₃ level, indicating a lack of a contribution of this kind of stimulation to the inositol turnover. These studies are the first in vivo demonstration of a possible role for inositol trisphosphate as a second messenger in the light signal transduction process in the ciliate B. japonicum.     

Oxygen species adsorbed on CeX zeolites identified by ESR spectroscopy

Two kinds of paramagnetidc O^?₂ ions have been identified by contacting molecular oxygen with CeX zeolite heat treated at 200°C in vacuo. The first O^?₂ species corresponds to the usual O^?₂ ions adsorbed on cerium oxide with the following parameters: g₁ = g_? ≈ 2.035 ± 0.002, g₂ = g₃ = g_⊥ = 2.0095 ± 0.0005 and a hyperfine pattern of six and eleven lines centred about g₃ and split by about 78 Oe, the other two components being not resolved. The second paramagnetic species of much higher intensity (larger by 2 or 3 orders of magnitude) presents rather ESR parameters and hyperfine structure. One has: g₁ = 2.0242, g₂ = 2.0208 and g₃ = 2.0112 ± 0.0003; c₁ = 24 ± 3, c₂ = 66 ± and c₃ = 12 ± 3 Oe. The six and eleven hyperfine line pattern which has been observed shows that the unpaired spin is qually distributed between two oxygen nuclei. The g tensor values are interpreted in terms of almost complete averaging of g₁ and g₂ components due to rotational motion at ?196°C about axis (3 (χ_ξ). The species is attributed to O^?₂ ion formed according to the equilibrium:

. The Ce ions are located in cationic sites SII within the zeolite supercages and are only weakly bonded to the oxygen leading to rotational motion and to case of desorption, the species reversibly disappearing by outgassing at room temperature.     

An Improved Upper Bound to Maximum Deflections of Elastic-Plastic Structures at Shakedown

ABSTRACT

A method is presented providing an upper bound to the maximum shakedown deflections for elastic-perfectly plastic structures. The influence of plastic zones is taken into account. Residual stresses required by the Melan theorem can be expressed in terms of stresses due to ideal plastic hinges and of stresses due to the finite extent of plastic zones. Making use of this fact a bound on the total energy dissipated in a shakedown process as well as a bound to the permanent displacement have been derived. This bound permits an estimate of the deflections at shakedown. Application of the method is illustrated by means of two examples.