Yoshishige Hayashi

CRF receptor antagonist attenuates stress-induced noradrenaline release in the medial prefrontal cortex of rats

Noradrenaline release in rat medial prefrontal cortex (PFC) was measured using a brain microdialysis technique. Immobilization stress increased noradrenaline release to a maximum level of 248.7 +/- 12.8% of the basal release, which was significantly attenuated by preinjection of alpha-helical CRF9-41 (50 micrograms/rat) into the lateral cerebroventricle. Intracerebroventricular injection of CRF also increased noradrenaline release in the medial PFC. These results suggest that immobilization-stress facilitates noradrenaline release in the medial PFC through activation of the CRF system in the brain.

Enzymatic activity of Chromobacterium viscosum lipase in an AOT/Tween 85 mixed reverse micellar system

To enhance the Chromobacterium viscosum lipase (glycerol-ester hydrolase; EC 3.1.1.3) activity for the reaction of water-insoluble substrates, the AOT/isooctane reverse micellar interface was modified by co-adsorption of a non-ionic surfactant. Polyoxyethylene sorbitan trioleate (Tween 85) was used as the non-ionic surfactant and olive oil as a water-insoluble substrate. An appreciable increase of lipase activity was observed and at higher Wo values (where Wo = molar ratio of water to total surfactants of the micellar system) there was no sharp fall of the enzyme activity such as a typical bell-shaped profile. The kinetic model for the lipase-catalysed hydrolysis of olive oil in AOT/isooctane reverse micellar system was applied to the enzymatic reaction in this mixed reverse micellar system. It was found that the predictions of the model agree well with the experimental kinetic results and that the adsorption equilibrium constant of olive oil molecules between the micellar phase and the bulk phase of the organic solvent is smaller in AOT/Tween 85 mixed reverse micellar systems than in simple AOT reverse micellar systems. © 1999 Society of Chemical Industry

Ultrasonication enhanced hydrolytic activity of lipase in water/isooctane two-phase systems

The hydrolysis of olive oil catalyzed by Chromobacterium viscosum lipase (EC 3.1.1.3) in a water/isooctane two-phase system was carried out both under ultrasound and conventional stirring. The maximum activity of lipase in the ultrasonicated system was 1.75 times higher than that in the stirred system. The lipase activity was dependent on ultrasonic power and volume ratio of isooctane to water. The optimum reaction temperature in both systems was around 25°C. The stability of lipase at 25°C in the ultrasonicated system decreased more rapidly than that in the stirred system. In the presence of exogenous oleic acid, however the half-life of lipase in the ultrasonicated system was improved to a value, which was respectively half and twice of that in stirred systems with and without oleic acid. The maximum reaction rate (Vmax) was increased by ultrasonication whereas the Michaelis constant (Km) remained unaltered.

Improvement in enzyme activity and stability by addition of low molecular weight polyethylene glycol to sodium bis(2-ethyl-L-hexyl)sulfosuccinate/ isooctane reverse micellar system

The activity and stability of Chromobacterium viscosum lipase (glycerolester hydrolase, EC 3.1.1.3)-catalyzed olive oil hydrolysis in sodium bis (2-ethyl-1-hexyl)sulfosuccinate (AOT)/isooctane reverse micelles is increased appreciably when low molecular weight polyethylene glycol (PEG 400) is added to the reverse micelles. To understand the effect of PEG 400 on the phase behavior of the reverse micellar system, the phase diagram of AOT/PEG 400/water/isooctane system was studied. The influences of relevant parameters on the catalytic activity in AOT/PEG 400 reverse micelles were investigated and compared with the results in the simple AOT reverse micelles. In the presence of PEG 400, the linear decreasing trend of the lipase activity with AOT concentration, which is observed in the simple AOT reverse micelles, disappeared. Enzyme entrapped in AOT/PEG reverse micelles was very stable, retaining>75% of its initial activity after 60 d, whereas the half-life in simple AOT reverse micelles was 38 d. The kinetics parameter maximum velocity (Vmax)exhibiting the temperature dependence and the activation energy obtained by Arrhenius plot was suppressed significantly by the addition of PEG 400.

The 5-HT1A receptor agonist, 8-OH-DPAT, attenuates stress-induced anorexia in conjunction with the suppression of hypothalamic serotonin release in rats

The effect of the selective 5-HT(1A) receptor agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) on stress-induced anorexia and serotonin (5-HT) release in the rat hypothalamus was studied with brain microdialysis. Subcutaneous injection of 8-OH-DPAT (1 mg/kg) significantly attenuated the immobilization-induced anorexia for 3 h, but had no effect during the following 9 h. Injection of 8-OH-DPAT itself had no effect on basal release of 5-HT, while it significantly blocked the immobilization-induced 5-HT release in the lateral hypothalamus. The results suggest that 8-OH-DPAT attenuated the stress-induced anorexia through the activation of 5-HT(1A) autoreceptors in dorsal raphe nucleus.

A kinetic model for enzymatic reactions in a reverse micellar system, involving water-insoluble substrate

A kinetic model was proposed for enzymatic reactions in a reverse micellar system, involving a water-insoluble substrate. Though surfactant is one of the main structural components of reverse micelles, an increase in the surfactant concentrations affects the enzyme activity remarkably. A relationship between the enzyme activity and the surfactant concentration is discussed. In this study it was assumed that free substrate in the organic phase was in adsorption equilibrium with the surface of the micellar surfactant, and that the adsorption coefficient and the true K m value (Michaelis constant) were independent of the surfactant concentration. The validity of this model was verified by data on the hydrolysis of olive oil, catalyzed by Chromobacterium viscosum lipase (Glycerolester hydrolase ; EC 3.1.1.3) in an AOT/isooctane reverse micellar system. The activity value predicted by the model equation agreed well with the experimental data.

Lipase-catalyzed esterification of fatty acid in DMSO (dimethyl sulfoxide) modified AOT reverse micellar systems

AOT reverse micellar system was modified with DMSO for improved esterification activity of Chromobacteriumviscosum lipase (glycerol–ester hydrolase, EC 3.1.1.3). The enzymatic activity was strongly affected by the concentration of DMSO, and maximum activity was obtained at 30–40 mM. The various relevant physical parameters such as w0 (molar ratio of water to AOT), pH and reaction temperature that influence the activity of lipase were studied in order to obtain the best value and compared with those in simple AOT reverse micelles. The apparent activation energy decreased in the presence of DMSO. The stability of lipase entrapped in modified AOT systems was excellent, and the half-life was about 3.25 times than that observed in simple AOT systems at 25°C. A simple first-order deactivation model was considered to determine the deactivation rate constant. The thermodynamic stability of lipase in reverse micelles was measured by the Gibbs free energy. A fluorescence study was performed to provide information on structural changes in AOT reverse micelles which was accompanied by the addition of DMSO.

Removal efficiency of heavy metals from laboratory wastewater containing ligands by an aluminium hydroxide co‐precipitation system

The aluminum co‐precipitation process is one of the usual methods to remove heavy metals from laboratory wastewater: however, ligands contained in the wastewater can interfere with the process. Hea...

Leakage of mercury from chelate resin columns by chelate detaching

Abstract It is known from experience that mercury leaks from chelate resin columns which are used for mercury wastewater treatment. In this paper, one of the reasons for the mercury leakage phenomena is discussed. After shaking the synthetic mercury wastewater with chelate resin, the supernatant became turbid. Using a highly sensitive mercury analysis, it was found that the results at lower mercury concentrations deviated from the Freundlich relation. From the results, it was presumed that the chelate component was detached by friction in the process of packing chelate resin into the column, and this chelate component adsorbed mercury while passing through the column.