[Studies on infection of Helicobacter pylori and their subtypes cagA+ and hspA+ in population living in the areas with high and low incidence of gastric cancer]

OBJECTIVE

To explore the difference in infection of Helicobacter pylori (Hp) and their subtypes cagA+ and hspA+ in the residents living in the areas with high and low incidence of gastric cancer.

METHODS

Immunoglobulin G and A antibodies against Hp and immunoglobulin G antibodies against cagA+ and hspA+ were detected for the residents in Linqu and Cangshan Counties of Shandong Province with enzyme-linked immunosorbent assay (ELISA).

RESULTS

Rate of infection with Hp in the residents in Linqu County, an area with high incidence of gastric cancer, was 73.8 percent, significantly higher than that in Cangshan County (59.9%), an area with low incidence. Rates of infection with Hp cagA+ and hspA+ in the residents in Linqu County were 50.9 and 17.0 percent, respectively, also significantly higher than those in Cangshan County (34.0% and 13.2%, respectively). Sensitivities and specificities of the methods for detecting antibodies against Hp, cagA+ and hspA+ were 92.3, 63.2 and 21.9 percent and 71.0, 80.6 and 95.2 percent, respectively, evaluated with 13C-urea breath teat (13C-UBT). Rate of infection with Hp, especially with Hp cagA+, correlated significantly with the high incidence of gastric cancer.

CONCLUSION

The methods for detecting antibodies against Hp and cagA+ subtype are more sensitive and can be used as better indicators in epidemiological studies on gastric cancer.

D,L-S-methyllipoic acid methyl ester, a kinetically viable model for S-protonated lipoic acid as the oxidizing agent in reductive acyl transfers catalyzed by the 2-oxoacid dehydrogenase multienzyme complexes

D,L-S(6,8)-Methyllipoic acid methyl ester triflate salt (D,L-S-methyllipoic acid methyl ester) was synthesized as a model for S-protonated lipoic acid, suggested to be the active form of lipoic acid in the reductive acylation catalyzed by the E1 and E2 enzymes of the 2-oxoacid dehydrogenase multienzyme complexes by a previous model [Chiu, C. C., Chung, A., Barletta, G., and Jordan, F. (1996) J. Am. Chem. Soc. 118, 11026-11029]. While in that earlier study lipoic acid could only trap only the enamine/C2 alpha-carbanion intermediate in an intramolecular model, and with the assistance of mercury compound to shift the equilibrium to the products, D,L-S-methyllipoic acid methyl ester could trap the enamine derived from 2-alpha-methoxybenzyl-3,4,5-trimethylthiazolium salt in an intermolecular reaction in the absence of a mercury compound, and with a rate constant of 6.6 x 10(4) M-1 S-1. A tetrahedral adduct at the C2 alpha-position formed between the enamine and D,L-S-methyllipoic acid methyl ester was isolated and characterized. The reaction likely takes place by two-electron nucleophilic attack, since no evidence was found for C2 alpha-linked homodimers, expected from a free-radical mechanism. The results suggest that, in the reductive acyl transfer, there is nucleophilic attack by the enamine at one of the sulfur atoms of the lipoic acid [probably at S8, according to Frey, P. A., Flournoy, D. S., Gruys, K., and Yang, Y. S. (1989) Ann. N.Y. Acad. Sci. 373, 21-35], while there is concomitant electrophilic catalysis by a proton juxtaposed at S6 via a general acid catalyst located on the E1 enzyme. Oxidation of the enamine derived from C2 alpha-hydroxybenzyl-3,4,5-trimethylthiazolium salt by D,L-S-methyllipoic acid methyl ester was also deduced on the basis of the formation of 2-benzoylthiazolium ion as a major product; however, the tetrahedral intermediate could not be detected. Oxidation of the enamine by D,L-S-methyllipoic acid methyl ester can take place with either an ether or an alcohol at the C2 alpha position of the enamine.

Preliminary crystallographic studies of a protein from Pachyrrhizus erosus

Crystals of a protein extracted from the seeds of Pachyrrhizus erosus have been obtained by vapor-phase diffusion. The crystal belongs to the space group P4(1)2(1)2 or P4(3)2(1)2 with cell parameters a = b = 62.52, c = 147.42 A. There is one protein molecule of 33 kDa in an asymmetric unit. A data set at 3.1 A has been collected on an area detector.

[Preliminary studies on microbe-mediated N-nitrosamide synthesis]

Chemical synthesis of N-nitrosamide and influences on it by bacteria and fungi isolated from human gastric juice were studied with trace analysis method to explore the pathway of its endogenous formation. Results showed in synthesis of N-methyl-N-nitrosourea (MNU) with precursors of methylurea (0.42 mmol/L) and sodium nitrite (25 mmol/L) in a condition simulating human stomach, pH of the reaction system played an important role in the synthesis, the amount of synthetic chemical maximized at a pH of 1-3 and almost no synthesis was found at pH of 5-7. A study on the ability to synthesize MNU catalyzed by bacteria isolated from the patients with stomach cancer living in a high-risk area showed its synthesis could be accelerated by Pseudomonas aeruginosa at pH of 6-7 with its catalyzing activity existed in heat liable component of living bacteria. This is the first report showing microorganisms to catalyze the formation of N-nitrosamide from its precursors.

Temperature-compensated fiber specklegram strain sensing with an adaptive joint transform correlator

A temperature-compensated fiber specklegram strain sensor with an adaptive joint transform correlator (JTC) is presented. By exploiting the dual-channel correlation of the fiber specklegram JTC, we can measure the temperature-compensated strain. Experimental results have shown that the strain sensitivity can be as high as 0.1 µstrain/1°C.

Dynamic fiber specklegram sensing

We introduce a concept of dynamic sensing that uses fiber speckle fields. By autonomously updating the fiber speckle patterns (i.e., using a moving reference to perform frame-to-frame comparison) on an electronically addressable spatial light modulator, we can exploit the dynamic fiber status. In other words, by joint transforming the rapidly changing speckle patterns from a sensing fiber, we can determine the dynamic aspects of the fiber status. For demonstration, dynamic displacement sensing is illustrated in which we have observed that the rate change and the trend of the fiber perturbation can indeed be detected. We note that the dynamic sensing technique can be applied to a variety of sensing parameters, e.g., strain, stress, temperature, and possibly seismic monitoring.

Structure of trichosanthin at 1.88 A resolution

Trichosanthin (TCS) is one of the single chain ribosome-inactivating proteins (RIPs). The crystals of the orthorhombic form of trichosanthin have been obtained from a citrate buffer (pH 5.4) with KCl as the precipitant. The crystal belongs to the space group P2(1)2(1)2(1) with a = 38.31, b = 76.22, c = 79.21 A. The structure was solved by molecular replacement method and refined using the programs XPLOR and PROLSQ to an R-factor of 0.191 for the reflections within the 6-1.88 A resolution range. The bond length and bond angle in the protein molecule have root-mean-square deviations from ideal value of 0.013 A and 3.3 degrees, respectively. The refined model includes 247 residues and 197 water molecules. The TCS molecule consists of two structural domains. The large domain contains six alpha-helices, a six-stranded sheet, and an antiparallel beta-sheet. The small domain has a largest alpha-helix, which shows a distinct bend. The possible active site of the molecule located on the cleft between two domains was proposed. In the active site Arg-163 and Glu-160, Glu-189 and Arg-122 form two ion pairs, Glu-189 and Gln-156 are hydrogen bonded to each other. Three water molecules are bonded to the residues in the active site region. The structures of TCS molecule and ricin A-chain (RTA) superimpose quite well, showing that the structures of the two protein molecules are homologous. Comparison of the structures of the TCS molecule in this orthorhombic crystal with that in the monoclinic crystal indicates that there are no essential differences of the structures between the two protein crystals.

Polychromatic target identification with a color liquid-crystal-TV-based joint-transform correlator

A real-time polychromatic target-detection technique that uses a computer-addressable color liquid-crystal- TV-based joint-transform correlator (JTC) is presented. One of the major features of the polychromatic JTC is that the spectra content of the object can be exploited. Since the liquid-crystal-TV panel is computer addressable, the JTC system can be made adaptive, by which the joint-transform power spectrum can be manipulated. Experimental demonstration of the proposed polychromatic JTC is provided, in which we show that the spatial and the spectral content of targets can be detected.

Multimode fiber sensing by using mean-absolute speckle-intensity variation

We present a fiber-sensing technique that detects the mean-absolute speckle-intensity variation between the updated and the reference speckle pattern for determining the environmental perturbation factor (e.g., displacement, temperature, pressure, acoustic wave). We show that the proposed technique is highly sensitive and simple. One of the major advantages of the proposed technique is that it can perform a fast-response measurement with off-the-shelf electronic hardware. Experimental data for submicrometer displacement as well as temperature measurement are provided. To extend the dynamic range of the proposed technique, one can use an updated reference speckle pattern.

Attentional distribution in the visual field during same-different judgments as assessed by response competition

Judgments of same and different on a comparison task have been found to be subject to response competition if an irrelevant stimulus is presented in the display along with the target stimuli. For example, the reaction time for judging two letters the same is markedly increased if a different but irrelevant letter is also present in the display (C. W. Eriksen, O'Hara, & B. [A.] Eriksen, 1982). We have made use of this competition effect to map the visual attentional field in two dimensions. In two experiments, we varied the size of the attended area by varying the separation of the comparison stimuli. The boundaries of the attended area were mapped by varying the location of a response-competitive irrelevant noise letter. On this task, the attended area was found to be elliptical in shape, with the location of the target stimuli defining the major axis. The minor axis of the ellipse increased in direct proportion to increases in the major axis. Rather than interpret these field effects in terms of areas of enhanced processing, we propose that instead they represent the limits or failures in inhibition of competing stimulation.

Attentional distribution in visual space

The horizontal extent of the visual attentive field was measured by the use of a two-choice-RT task and compatible and incompatible distractors. The target was a line that inclined either to the left or to the right. Whether or not the subject performed the choice RT was made contingent upon whether two other stimuli presented in the visual display matched or mismatched. The match-mismatch stimuli varied in locations so as to manipulate the relevant visual area (the attended area). The locations of the distractors were also varied. The increase in RT associated with incompatible distractors was found to vary inversely with their distance from the edge of the area attended to and independently of their distance from the target lines. The results were interpreted in terms of an inhibitory field that surrounds the area attended to.

Tachycardia and fibrillation detection by automatic implantable cardioverter-defibrillators: sequential testing in time domain

The automatic implantable cardioverter-defibrillator (AICD), a device that delivers a high-energy shock (10-30 J) directly to the heart when life-threatening arrhythmias are detected, must accurately detect ventricular fibrillation (VF) and ventricular tachycardia (VT) rhythms. The signal-processing problem is how to accurately distinguish normal sinus rhythm or supraventricular tachycardia from malignant VT and VF signals. An approach based on discriminating probability distributions of interbeat intervals in electrogram signals recorded from atrial and ventricular leads is described. A sequential hypothesis-testing algorithm that allows desired false positive and false negative rates and the time it takes to detect the arrhythmias to be preset is presented. A tradeoff between reliability and duration of test is noted; a decision can be reached in a shorter time if higher error rates are accepted as permissible. In an analysis of 85 cases of VF and 85 cases of VT, 53% of VF cases and 66% of VT cases were classified after 1 s, 97.6% of VF cases and 100% of VT cases were classified after 5 s, and within 7 s, all the remaining VF cases were classified.