Performance evaluation of a fluorescamine-HPLC method for determination of histamine in fish and fish products

A method for the quantification of histamine in fish and fish products using tandem solid-phase extraction and fluorescence derivatization with fluorescamine was previously developed. In this study, we improved this analytical method to develop an official test method for quantification of histamine in fish and fish products, and performed a single laboratory study to validate it. Recovery tests of histamine from fillet (Thunnus obesus), and two fish products (fish sauce and salted and dried whole big-eye sardine) that were spiked at the level of 25 and 50 μg/g for T. obesus, and 50 and 100 μg/g for the two fish products, were carried out. The recoveries of histamine from the three samples tested were 88.8-99.6% with good repeatability (1.3-2.1%) and reproducibility (2.1-4.7%). Therefore, this method is acceptable for the quantification of histamine in fish and fish products. Moreover, surveillance of histamine content in food on the market was conducted using this method, and high levels of histamine were detected in some fish products.     

A 20-ns 4-Mb CMOS SRAM with hierarchical word decoding architecture

A 20 ns 4-Mb CMOS SRAM operating at a single supply voltage of 3.3 V is described. The fast access time has been achieved by a newly proposed word-decoding architecture and a high-speed sense amplifier combined with the address transition detection (ATD) technique. The RAM has the fast address mode, which achieves quicker than 10-ns access, and the 16-b parallel test mode for the reduction of test time. A 0.6-μm process technology featuring quadruple-polysilicon and double-metal wiring is adopted to integrate more than 16 million transistors in a 8.35-mm×18.0-mm die     

Millimetre-wave radiation characteristics of a periodically plasma-induced semiconductor waveguide

A theoretical analysis is presented for the radiation characteristics of millimetre waves in a periodically plasma-induced semiconductor waveguide. The plasma is assumed to be generated by photoexcitation. The dependence of the phase and attenuation constants of TE-polarised waves on the plasma density is investigated numerically.     

A novel variant of translation elongation factor-1beta: isolation and characterization of the rice gene encoding EF-1beta2

A rice gene encoding a novel isoform of translation elongation factor-1beta subunit (termed EF-1beta2) was isolated and characterized. The gene comprises of eight exons, and encodes a 226-amino-acid protein. Expression of EF-1beta2 mRNA is abundant in seeds and cultured cells, but is considerably low in the tissues of the rice seedling. Antiserum raised against an EF-1beta2 synthetic peptide detected a protein with a relative molecular mass of about 32 kDa, indicating the EF-1beta2 gene is actually expressed in rice tissues. EF-1beta2 showed a close similarity to the cognate subunits from plant (beta and beta').     

Correlation between the differences in the free energy change and conformational energy in the folded state of hen lysozymes with Gly-Pro and Pro-Gly sequences introduced to the same site

We suggested for the introduction of a prolyl residue into a protein that if the N-terminus residue is glycine, an unfavorable interaction in the folded state caused by the introduction of the prolyl residue can be substantially avoided by use of mutant lysozymes in which Gly-Pro and Pro-Gly sequences are introduced to positions 101-102 in the loop region of the lysozymes [Ueda, T., Tamura, T., Maeda, Y., Hashimoto, Y., Miki, T., Yamada, H., and Imoto, T. (1993) Protein Eng. 6, 183-187]. In order to determine whether or not the information obtained is applicable to other regions, we prepared mutant lysozymes with Gly-Pro and Pro-Gly sequences at position 47, which is located in the beta-sheet, positions 70-71, which are located in the loop, positions 117-118, which are located in the beta-turn, and positions 121-122, which are located in the 3(10)-helix. The free energy changes of the native and mutant lysozymes for unfolding were determined at pH 5.5 and 35 degrees C. However, a mutant lysozyme with the Gly-Pro sequence was not always stabler than that with the Pro-Gly sequence at the same site. On the other hand, in order to determine whether or not strain caused by these sequences exists in the folded or unfolded state, the structures of these mutant lysozymes were determined by use of energy minimization. On comparison of the differences in the free energy change between the mutant lysozymes with Gly-Pro and Pro-Gly sequences at the same site with those in their total local conformational energies, it was found there is a good correlation between them. Therefore, it was suggested that the difference in total local conformational energy caused by the introduction of a Gly-Pro or Pro-Gly sequence could be estimated by use of the energy minimized structure. Moreover, the correlation indicated that the differences in the free energy change between Gly-Pro and Pro-Gly lysozymes may be reflected by the differences in the total local conformational energies in their folded state. It was suggested that the energy levels in the unfolded states of mutant lysozymes with Gly-Pro and Pro-Gly sequences at the same site in a Gdn-HCl solution were almost identical.     

Expression of a functional endothelin (ETA) receptor in human meningiomas

Endothelin (ET) receptor subtypes (ETA and ETB) in human meningiomas were characterized using quantitative receptor autoradiography. A single class of high-affinity 125I-ET-1 binding sites was localized in all meningioma tissue studied (dissociation constant: 2.4 +/- 0.3 nM, maximum binding capacity: 319 +/- 66 fmol/mg (mean +/- standard error of the mean for 13 tumors)). Unlabeled ET-1 showed a strong affinity for 125I-ET-1 binding to tissue sections of the tumors with a 50% inhibiting concentration (IC50) of 2.9 +/- 0.7 x 10(-9) M, whereas ET-3 showed a much lower affinity (IC50: 8.4 +/- 2.5 x 10(-6) M). Sarafotoxin S6c, a selective agonist for the ETB receptor, could not compete for 125I-ET-1 binding to meningiomas. Endothelin-1 significantly stimulated deoxyribonucleic acid (DNA) synthesis in a dose-dependent manner in cultured human meningioma cells. In contrast, no significant stimulation of DNA synthesis occurred with an S6c concentration up to 10(-7) M. Pretreatment of the meningioma cells with pertussis toxin, a bacterial toxin that adds adenosine 5'-diphosphate-ribose to the alpha subunit of guanine nucleotide binding (G) proteins such as Gi or G(o), induced a concentration-dependent reduction in ET-stimulated DNA synthesis in meningioma cells, but did not affect the epidermal growth factor-induced DNA synthesis. These observations suggest that the ETA receptor is predominantly expressed in human meningioma tissue and that ET may act as a growth factor on the meningioma cells by interacting with the ETA receptor and by pertussis toxin-sensitive mechanisms.     

Coronary endothelial dysfunction after Kawasaki disease: evaluation by intracoronary injection of acetylcholine

1. Caffeine (Cf) enhances the DNA cleavage induced by tert-butylhydroperoxide (tB-OOH) in U937 cells via a mechanism involving Ca2+-dependent mitochondrial formation of DNA-damaging species (Guidarelli et al., 1997b). Nitric oxide (NO) is not involved in this process since U937 cells do not express the constitutive nitric oxide synthase (cNOS). 2. Treatment with the NO donors S-nitroso-N-acetyl-penicillamine (SNAP, 10 microM), or S-nitrosoglutathione (GSNO, 300 microM), however, potentiated the DNA strand scission induced by 200 microM tB-OOH. The DNA lesions generated by tB-OOH alone, or combined with SNAP, were repaired with superimposable kinetics and were insensitive to anti-oxidants and peroxynitrite scavengers but suppressed by iron chelators. 3. SNAP or GSNO did not cause mitochondrial Ca2+ accumulation but their enhancing effects on the tB-OOH-induced DNA strand scission were prevented by ruthenium red, an inhibitor of the calcium uniporter of mitochondria. Furthermore, the enhancing effects of both SNAP and GSNO were identical to and not additive with those promoted by the Ca2+-mobilizing agents Cf or ATP. 4. The SNAP- or GSNO-mediated enhancement of the tB-OOH-induced DNA cleavage was abolished by the respiratory chain inhibitors rotenone and myxothiazol and was not apparent in respiration-deficient cells. 5. It is concluded that, in cells which do not express the enzyme cNOS, exogenous NO enhances the accumulation of DNA single strand breaks induced by tB-OOH via a mechanism involving inhibition of complex III.     

Synthesis of novel chiral poly(methacrylate)s bearing urethane and cinchona alkaloid moieties in side chain and their chiral recognition abilities

Two types of new chiral methacrylates, cinchoninyl(2-methacryloyloxyethyl)carbamate (CIMOC) and cinchonidinyl(2-methacryloyloxy-ethyl)carbamate (CDMOC) were synthesized from 2-methacryloyloxyethyl isocyanate (MOI) and cinchona alkaloid such as cinchonine and cinchonidine, respectively. Radical polymerizations of CIMOC and CDMOC were performed under several conditions to obtain the corresponding polymers whose specific optical rotations ([]₄₃₅²⁵) were 84.0–89.0° and 0.39–0.72°, respectively. From the results of radical copolymerizations of RMOC (CIMOC and CDMOC, M₁) with styrene (ST, M₂) or methyl methacrylate (MMA, M₂), monomer reactivity ratios (r₁, r₂) and Alfrey–Price Q–e were determined: r₁=0.18, r₂=0.48, Q₁=0.53, e₁=0.92 for the CIMOC–ST system; r₁=0.53, r₂=0.26, Q₁=4.91, e₁=1.80 for the CIMOC–MMA system r₁=0.59, r₂=0.47, Q₁=0.86, e₁=0.33 for the CDMOC–ST system; r₁=0.28, r₂=0.59, Q₁=2.15, e₁=1.74 for the CDMOC–MMA system. The chiroptical properties of the copolymers were strongly influenced by co-units. Poly(RMOC)-bonded-silica gel as chiral stationary phase (CSP) was prepared for high performance liquid chromatography (HPLC). The CSPs resolved some racemates such as mandelic acid and trans-2-dibenzyl-4,5-di(o-hydroxyphenyl)-1,3-dioxolane by HPLC. The chiral recognition ability of poly(RMOC) may be due to the interaction between some cinchona alkaloid units and the racemates and/or to secondary and higher-ordered structures of the polymer.