Quantitative analysis of cereulide, an emetic toxin of Bacillus cereus, by using rat liver mitochondria

An emetic toxin cereulide, produced by Bacillus cereus, causes emetic food poisonings, but a method for quantitative measurement of cereulide has not been well established. A current detection method is a bioassay method using the HEp-2 cell vacuolation test, but it was unable to measure an accurate concentration. We established a quantitative assay for cereulide based on its mitochondrial respiratory uncoupling activity. The oxygen consumption in a reaction medium containing rat liver mitochondria was rapid in the presence of cereulide. Thus uncoupling effect of cereulide on mitochondrial respiration was similar to those of uncouplers 2,4-dinitrophenol (DNP), carbonylcyanide m-chlorophenylhydrazone (CCCP), and valinomycin. This method gave constant results over a wide range of cereulide concentrations, ranging from 0.05 to 100 microg/ml. The minimum cereulide concentration to detect uncoupled oxygen consumption was 50 ng/ml and increased dose-dependently to the maximum level. Semi-log relationship between the oxygen consumption rate and the cereulide concentration enables this method to quantify cereulide. The results of this method were highly reproducible as compared with the HEp-2 cell vacuolation test and were in good agreement with those of the HEp-2 cell vacuolation test. The enterotoxin of B. cereus or Staphylococcus aureus did not show any effect on the oxygen consumption, indicating this method is specific for the identification of cereulide as a causative agent of emetic food poisonings.     

Changes in Ucp1, D2 (Dio2) and Glut4 (Slc2a4) mRNA expression in response to short-term cold exposure in the house musk shrew (Suncus murinus).

The house musk shrew (Suncus murinus), or so-called suncus, is a cold-intolerant mammal, but it is unclear why it is susceptible to low temperatures. Cold-intolerance may be the result of lower thermogenic activity in brown adipose tissue (BAT). The early phase of severe cold exposure is a critical period for suncus. Therefore, we exposed suncus to mildly cold temperatures (10-12 degrees C) for 1 to 48 h to increase non-shivering thermogenesis without causing stress and measured changes in the expression of uncoupling protein 1 (Ucp1), type II iodothyronine 5'-deiodinase (Dio2=D2), and glucose transporter 4 (Slc2a4=Glut4) in BAT. These mRNAs play a major role in non-shivering thermogenesis and are mainly regulated by the sympathetic nervous system via direct beta-noradrenergic innervation of BAT. During cold exposure, Ucp1 expression in BAT increased steadily over time, albeit only slightly. Neither D2 nor Glut4 expression in BAT increased immediately; however, they had increased significantly after 24 h and 48 h of cold exposure. These findings suggest that the responsiveness of mRNA regulation is weak and thus may be involved in cold-intolerance in suncus.     

Msn2p/Msn4p-activation is essential for the recovery from freezing stress in yeast

Recent data suggest that the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptor subtype plays a pivotal role in the pathogenesis of effective disorders and in the action of antidepressant drugs. After chronic treatment with the antidepressants desipramine or paroxetine, we measured by immunoprecipitation and Western blotting, the changes in the interaction of AMPA receptor subunits with proteins involved in trafficking and/or stabilization of the subunits into synaptic membranes of the hippocampus. Both antidepressants increased the interaction of GluR1 subunit with stargazin and of GluR2/3 with NSF. Paroxetine increased the interaction of GluR1 with Rab4A, and desipramine markedly increased the interaction of GluR1 with SAP97. Paroxetine, but not desipramine, also increased membrane levels of CaMKII, autophosphorylated CaMKII and GluR1 phosphorylated at the CaMKII site. Interactions of GluR1 and GluR2/3 with proteins implicated in AMPA receptor trafficking and with scaffolding proteins appear to account for the enhanced membrane expression of AMPA receptors in the hippocampus after antidepressant treatment.     

Phytotoxic cis-cinnamoyl glucosides from Spiraea thunbergii

Spiraea thunbergii Sieb. was found to contain 1-O-cis-cinnamoyl-beta-D-glucopyranose and 6-O-(4'-hydroxy-2'-methylene-butyroyl)-1-O-cis-cinnamoyl-beta-D-glucopyranose as major plant growth inhibitory constituents along with related compounds of lower phytotoxicity including 6-O-(trans-cinnamoyl)-1-O-(4"-hydroxy-3"-methyl-furan-2"-one)-beta-D-glucopyranose, 6-O-(4'-hydroxy-2'-methylene-butyroyl)-1-O-trans-cinnamoyl-beta-D-glucopyranose, and 1-O-trans-cinnamoyl-beta-D-glucopyranose. The former three compounds were cinnamoyl glucosides.     

Serum concentrations of androstenediol and androstenediol sulfate, and their relation to cytokine production during and after normal pregnancy

Since it is known that androstenediol (ADIOL) has potent immunoregulatory effects, changes in ADIOL levels during and after pregnancy might affect the maternal immune system. We examined serum concentrations of ADIOL and androstenediol 3-sulfate (ADIOLS) together with IFN-gamma and IL-4 production levels during pregnancy and after delivery up to 10-11 months postpartum. The subjects were 73 normal pregnant, 76 normal postpartum, and 28 normal non-pregnant women. ADIOL and ADIOLS were measured using EIA and GC/MS, respectively. The cytokine levels in the supernatant of whole-blood cultures stimulated with phorbol 12-myristate 13-acetate and ionomycin were measured using ELISA. ADIOL levels significantly decreased compared to non-pregnant levels in the first trimester (P < 0.05) and were reversed in the third trimester (P < 0.05). After pregnancy, ADIOL levels gradually declined, and a significant decrease was observed at 10-11 months postpartum (P < 0.05). ADIOLS levels were significantly lower in the third trimester (P < 0.05) and significantly higher at the first month postpartum (P < 0.001) compared to non-pregnant women. IFN-gamma and IL-4 levels decreased during pregnancy and subsequently increased postpartum. On the other hand, we found significant negative correlations between ADIOL concentrations and production levels of IFN-gamma (P < 0.05) or IL-4 (P < 0.05). These findings suggest that ADIOL may be involved in modifying the maternal immune response during and after pregnancy.     

In vivo and in vitro characterization of Ser477X mutations in polyhydroxyalkanoate (PHA) synthase 1 from Pseudomonas sp. 61-3: effects of beneficial mutations on enzymatic activity, substrate specificity, and molecular weight of PHA

Evolutionary engineered polyhydroxyalkanoate (PHA) synthases from Pseudomonas sp. 61-3 enhance PHA accumulation and enable the monomer composition of PHAs to be regulated. We characterized a newly screened Ser477Arg (S477R) mutant of PHA synthase by in vivo analyses of P(3-hydroxybutyrate) [P(3HB)] homopolymer and P(3HB-co-3-hydroxyalkanoate) [P(3HB-co-3HA)] copolymer productions in the recombinants of Escherichia coli. The results indicated that the S477R mutation contributed to a shift in substrate specificity to smaller monomers containing a 3HB unit rather than to an enhancement in catalytic activity. Multiple mutations of S477R with other beneficial mutations, for example, Ser325Cys, exhibited synergistic effects on both an increase in PHA production (from 9 wt % to 21 wt %) and an alteration of substrate specificity. Furthermore, the effects of complete amino acid substitutions at position 477 were characterized in terms of in vivo PHA production and in vitro enzymatic activity. The five mutations, S477Ala(A)/Phe(F)/His(H)/Arg(R)/Tyr(Y), resulted in a shift in substrate specificity to smaller monomer units. The S477Gly(G) mutant greatly enhanced activity toward all different sizes of substrates with carbon numbers ranging from 4 to 12. These results indicated that the residue 477 contributes to both the catalytic activity and substrate specificity of PHA synthase. In recombinant E. coli, the S477A/F/G/H/R/Y mutations consistently led to increases (up to 6 times that of wild-type enzyme) in weight average molecular weights of P(3HB) homopolymers. On the basis of our studies, we created a structural feasibility accounting for the mutational effects on enzymatic activity and substrate specificity of PHA synthase.     

Nitrite is an alternative source of NO in vivo

In this study, we investigated whether orally administered nitrite is changed to NO and whether nitrite attenuates hypertension in a dose-dependent manner. We utilized a stable isotope of [15N]nitrite (15NO2-) as a source of nitrite to distinguish between endogenous nitrite and that exogenously administered and measured hemoglobin (Hb)-NO as an index of circulating NO in whole blood using electron paramagnetic resonance (EPR) spectroscopy. When 1 mg/kg Na15NO2 was orally administered to rats, an apparent EPR signal derived from Hb15NO (A(Z) = 23.4 gauss) appeared in the blood. The peak blood HbNO concentration occurred at the first measurement after intake (5 min) for treatment with 1 and 3 mg/kg (HbNO: 4.93 +/- 0.52 and 10.58 +/- 0.40 microM, respectively) and at 15 min with 10 mg/kg (HbNO: 38.27 +/- 9.23 microM). In addition, coadministration of nitrite (100 mg/l drinking water) with N(omega)-nitro-L-arginine methyl ester (L-NAME; 1 g/l) for 3 wk significantly attenuated the L-NAME-induced hypertension (149 +/- 10 mmHg) compared with L-NAME alone (170 +/- 13 mmHg). Furthermore, this phenomenon was associated with an increase in circulating HbNO. Our findings clearly indicate that orally ingested nitrite can be an alternative to L-arginine as a source of NO in vivo and may explain, at least in part, the mechanism of the nitrite/nitrate-rich Dietary Approaches to Stop Hypertension diet-induced hypotensive effects.