Quantification of pork, chicken and beef by using a novel reference molecule.

A standard plasmid was constructed as a novel reference molecule for use in real-time quantitative PCR assays to verify the identity of beef, pork, chicken, mutton, and horseflesh. The plasmid contained a target domain of the cytochrome b (cyt b) gene and an artificial DNA sequence. Primers CO-F and CO-R, and probe CO-P were specifically designed to detect the artificial sequence. The calculated R² values of the standard curves (10³-107 copies per reaction) for the five species ranged between 0.998 and 0.999 in the quantification analysis. The constructed plasmid provides a universal method for measuring the copy number of cyt b DNA in minced meat. This method would be a useful procedure for verifying food labels.

Specific detection of banana residue in processed foods using polymerase chain reaction.

Specific polymerase chain reaction (PCR) methods were developed for the detection of banana residue in processed foods. For high banana specificity, the primer set BAN-F/BAN-R was designed on the basis of the large subunit of ribulose-1,5-bisphosphate carboxylase (rbcL) genes of chloroplasts and used to obtain amplified products specific to banana by both conventional and real-time PCR. To confirm the specificity of these methods, genomic DNA samples from 31 other species were examined; no amplification products were detected. Subsequently, eight kinds of processed foods containing banana were investigated using these methods to confirm the presence of banana DNA. Conventional PCR had a detection limit of 1 ppm (w/w) banana DNA spiked in 50 ng of salmon testis DNA, whereas SYBR Green I real-time semiquantitative PCR had a detection limit as low as 10 ppm banana DNA. Thus, both methods show high sensitivity and may be applicable as specific tools for the detection of trace amounts of banana in commercial food products.

Brain activation during the spot the differences game.

Spot the Differences is a simple and popular game in which an observer compares a pair of similar pictures to detect the differences between them. Functional activation of the brain while playing this game has not been investigated. We used functional magnetic resonance imaging to investigate the main cortical regions involved in playing this game and compared the sites of cortical activation between a session of playing the game and a session of viewing 2 identical pictures. The right posterior parietal cortex showed more activation during game playing, and cortical activation volume correlated with game-playing accuracy. This cortical region may play an important role in awareness of differences between 2 similar pictures.

[Study of the normal database that affects 3D-SSP Z-score mapping].

The effects of image reconstruction conditions and devices used on 3D-SSP analysis (Z-score mapping) were investigated. Images of the 3D Hoffman brain phantom were taken with the IRIX device or E.CAM. Using two methods of image reconstruction (FBP and OSEM), several kinds of phantom normal databases (PNDB) and signal data, with or without correction for attenuation, were obtained at varying Butterworth filter cutoff frequencies. The results of 3D-SSP analyses were compared between combinations of PNDB and signal data obtained under the same conditions of image reconstruction and combinations obtained under different conditions. The results of PNDB obtained with different devices were also analyzed. For combinations of PNDB and signal data both obtained with OSEM, the Z-score of signals was high. When FBP was used to obtain both PNDB and signal data, the Z-score and signal size tended to become greater and the false-positive rate tended to decrease as the Butterworth filter cutoff frequency became lower. Whether or not correction for attenuation was incorporated did not affect the results of analysis when the same method was used to collect both PNDB and signal data. If the method for image reconstruction differed between PNDB and signal data, the false-positive rate was relatively high. Using a different device to obtain PNDB resulted in a relatively high false-positive rate. We therefore recommend that the conditions for image reconstruction from signal data should be matched to the conditions for image reconstruction from PNDB. It seems impossible to share the same NDB among different devices.