ショクヒンチュウ ノ ダイチョウキン O157 ニ タイスル マイクロハ ショウシャ ノ エイキョウ

We examined the survival and acid resistance of enterohemorrhagic Escherichia coli O157 (EHEC O157) in foods irradiated by microwave (2.45 GHz, 700 W, 7 s) with a domestic microwave oven. When the microwave irradiated foods inoculated with the cells at the cell density of 3 x 106 cells/g, the living cell number decreased below 65%. The cells in curry showed the lowest survival ratio (2%) among those in foods examined. Acid resistance of the cells in foods irradiated by the microwave was also effectively reduced below 10% irrespective of foods surveyed. Microwave could prove useful for reducing the living cell number and acid resistance of EHEC O157 in foods

Rhamnan sulfate attenuates methylmercury cytotoxicity in rat thymic lymphocytes

Rhamnan sulfate, one of sulfated polysaccharides from seaweeds, is considered to have various characteristics such as antioxidant, anticoagulant, anti-inflammatory, antitumor, contraceptive, and antiviral activities, for the treatment of several diseases. We examined the effect of rhamnan sulfate on thymic lymphocytes treated simultaneously with methylmercury chloride, a toxic organometallic compound, using a flow-cytometric techniques with fluorescent probes, fluo-3-AM (an indicator for intracellular Ca2+) and propidium iodide (an indicator for dead cells). Rhamnan sulfate attenuated the methylmercury-induced increase in cell lethality. This effect of rhamnan sulfate is supposed to be due to the attenuation of methylmercury-induced elevation of intracellular Ca2+ levels. Rhamnan sulfate may be useful for the prevention of organometallic intoxication

Production of Human Type Glycosylated Tissue Plasminogen Activator and the Role of Its Carbohydrate Moiety

To begin the examination of the role of human type carbohydrate moiety of tissue plasminogen activator (t-PA) on the binding of the enzyme to fibrin，the naturally glycosylated enzyme was produced by microcarrier culture of human cells established from normal uterine muscle. The cells grown on microcarrers in Haunks' MEM supplemented with 10 % FBS (1.6 x 10 6 cells/ml) rapidly detached themselves from microcarrier in a serum-free medium (t-PA production medium) within 5 days, and it was difficult to produce t-PA for long time (t-PA production: an average of 3 IU/ml/day over 5 days). Addition of 0.5% beef extract to the serum-free medium suppressed their detaching from microcarriers. By regulating the pH (7.4) and dissolved oxygen(4 ppm) of the serum free medium，the cell density of microcarrier culture increased to 1.2 x10 7 cells/ml and t-PA was produced over 38 days (t-PA production: an average of 836 IU/ml/day over 38 days). Native t-PAs purified to homogeneity from the culture broth had the molecular weight of 63,000 and 65,000 containing 5.6 and 8.5 % carbohydrate，respectively (molecular mass of protein moiety was calculated to be 59,500). By enzymatic digestion of carbohydrate moiety in native t-PA，we obtained partially deglycosylated t-PA with molecular weights of 60,000 and 62,000. Completely deglycosylated t-PA was obtained by t-PA production in the presence of 10μg/ml tunicamycin (N-glycosylation inhibitor). This suggests that N-glycosylationof t-PA occurs while O-glycosylation is absent. The binding strength of these enzymes to fibrin increased with decrease of the carbohydrate content. The carbohydrate moiety of human type glycosylated t-PA probably modulates the binding strength of the enzyme to fibrin

Modification of cell vulnerability to oxidative stress by N-(3-oxododecanoyl)-L-homoserine-lactone, a quorum sensing molecule, in rat thymocytes

N-(3-oxododecanoyl)-L-homoserine-lactone (ODHL), a quorum sensing molecule, affects intracellular Zn2+ concentration ([Zn2+]i) and cellular levels of nonprotein thiols ([NPT]i) of rat thymic lymphocytes, both of which are assumed to affect cell vulnerability to oxidative stress. Therefore, it is interesting to examine the effects of ODHL on the cells under oxidative stress. ODHL augmented the cytotoxicity of H2O2, but not calcium ionophore A23187. ODHL potentiated the H2O2-induced elevation of [Zn2+]i, wherein, it greatly attenuated the H2O2-induced increase in intracellular Ca2+ concentration. ODHL did not affect [NPT]i in the presence of H2O2. Therefore, we conclude that the elevation of [Zn2+]i is involved in the ODHL-induced potentiation of H2O2 cytotoxicity. Our findings suggest that ODHL modifies cell vulnerability to oxidative stress in host cells

ペトリフィルム TM オ モチイル ショクヒンチュウ ノ ニュウサンキン ノ セイキンスウ ソクテイ

We examined the living cell number of lactic bacteria in foods by anaerobic culture with Petri-filmTM (PFAC). As the reference medium, the de Man, Rogosa and Sharpe agar medium (MRSA) and an agar medium supplemented with bromocresol purple (BCPA) were used. When we determined the living cell number of lactic bacteria in various products of pickled vegetables (29 products), kimuchi (10 products), meats (13 products), lactic fermenting beverages (24 products) and cultured milks (6 products), the cell numbers determined with PFAC showed high correlations with those determined with MRSA and BCPA

Adsorption of Shiga Toxin to Poly-γ-Glutamate Precipitated

We screened foods containing indigestible ingredients in the ability to adsorb Shiga toxin (Stx). When 5 mg of foods and dietary fibers such as dry vegetables and inulin were mixed and incubated with 0.5 mL of Stx solution (100 ng/mL) containing 0.5% bovine serum albumin, both Stx1 and Stx2 seemed to be adsorbed by only a fermented food, natto (a traditional Japanese food prepared from steamed soybeans by the biological action of Bacillus subtilis). We purified the Stx-adsorbing substance from natto by extraction with H 2 O, acid treatment, Proteinase K treatment, and an ion exchange chromatography. The purified substance showed an average molecular mass of about 600 kDa. We identified it as poly-γ -glutamate (PGA) by amino acid analysis of its hydrolysate and peptide analysis after its treatment with Proteinase K. Purified PGA (MW: molecular weight = about 600 kDa) was considered to adsorb both Stx1 and Stx2 when we separated adsorbed and unadsorbed Stxs (MW = about 72 kDa) by an ultrafiltration method with a centrifugal filter unit (MWCO: molecular weight cut-off = 100 K). However, PGA with the ability to adsorb Stx was an insoluble form precipitated in the filter unit during centrifugation. PGA precipitated beyond the saturated density was also confirmed to well adsorb both Stx1 and Stx2 by an equilibrated dialysis method. To the best of our knowledge, this is the 1st report on food-adsorbing Stx

Hyperpolarization by N-(3-oxododecanoyl)-L-homoserine-lactone, a quorum sensing molecule, in rat thymic lymphocytes

To study the adverse effects of N-(3-oxododecanoyl)-L-homoserine-lactone (ODHL), a quorum sensing molecule, on mammalian host cells, its effect on membrane potential was examined in rat thymic lymphocytes using flow cytometric techniques with a voltage-sensitive fluorescent probe. As 3–300 μM ODHL elicited hyperpolarization, it is likely that it increases membrane K+ permeability because hyperpolarization is directly linked to changing K+ gradient across membranes, but not Na+ and Cl- gradients. ODHL did not increase intracellular Ca2+ concentration. ODHL also produced a response in the presence of an intracellular Zn2+ chelator. Thus, it is unlikely that intracellular Ca2+ and Zn2+ are attributed to the response. Quinine, a non-specific K+ channel blocker, greatly reduced hyperpolarization. However, because charybdotoxin, tetraethylammonium chloride, 4-aminopyridine, and glibenclamide did not affect it, it is pharmacologically hypothesized that Ca2+-activated K+ channels, voltage-gated K+ channels, and ATP-sensitive K+ channels are not involved in ODHL-induced hyperpolarization. Although the K+ channels responsible for ODHL-induced hyperpolarization have not been identified, it is suggested that ODHL can elicit hyperpolarization in mammalian host cells, disturbing cellular functions

非微生物素材表面への大腸菌の初期付着を抑制する穀類抽出液の分析

We examined the initial attachment of E. coli to abiotic surfaces conditioned with cereal extracts. The extracts were water-soluble fractions prepared from flours of barley, quinoa, rice and wheat. Strains used were E. coli ATCC 8739, E. coli NBRC 3301, E. coli NBRC 3302, E. coli NBRC 13168, E. coli NBRC 13891, and E. coli O157:H7 sakai. When surfaces of glass and stainless steel were conditioned at 25°C for 30 min with 0.5% cereal extracts, significantly lower numbers of E. coli cells attached to the conditioned surfaces than unconditioned ones, irrespective of strains used. The highest activity in reduction of the number of E. coli cells attached to the abiotic surfaces was found in the wheat extract. The suppressive activity was stable after treatments of the extract by autoclave and enzymatic digestion with α-amylase and Proteinase K. We purified the active compound by ammonium sulfate fractionation and gel filtration with HiPrep 16/60 Sephacryl S-200 HR after the enzymatic treatments. The purified compound showed an average molecular mass of about 300 kDa by light-scattering measurements. Analyses of its components indicated that the active compound was arabinoxylan; the molar ratios were 1.0 (arabinose) to 2.46 (xylose). Commercially available arabinoxylan (average molecular mass: 370 kDa) also showed the similar activity. To our knowledge, this is the first report on a dietary fiber from cereals which suppresses the initial attachment of E. coli to abiotic surfaces