Taste preference and nerve response to 5'-inosine monophosphate are enhanced by glutathione in mice.

Previous human sensory evaluation studies have shown that glutathione (GSH) enhances deliciousness, accompanied by thickness, mouthfulness, and continuity feeling, which is known as "kokumi" in Japanese, in an umami solution containing monosodium glutamate and 5'-inosine monophosphate (IMP). We conducted behavioral and electrophysiological experiments to explore possible interactions of taste effectiveness between GSH and umami substances in mice. The 2-bottle preference test revealed that the mice preferred GSH at concentrations ranging from 1 to 10 mM. When GSH was added to IMP or a mixture of IMP and monopotassium glutamate (MPG), the mice showed increased preference for these solutions over the individual IMP or the binary mixture of IMP and MPG in both short-term and long-term tests. The addition of GSH to MPG, however, did not increase preference. Neural responses of the chorda tympani and glossopharyngeal nerves to the mixture of IMP and GSH showed synergism, whereas synergism was not observed in the mixture of MPG and GSH in either taste nerve. Another behavioral study with the use of the conditioned taste aversion paradigm showed that aversions to MPG generalized moderately to GSH, but aversions to GSH did not generalize to MPG. The present study suggests that GSH enhances preference for umami solutions containing 5'-ribonucleotide rather than glutamate. On the basis of these results, we discuss possible receptors involved for the action of GSH.

Basic study of susceptibility-weighted imaging at 1.5T.

With the aim of sequence optimization in susceptibility-weighted imaging (SWI), 2 image acquisition parameters (slice thickness and matrix size) and 2 image processing conditions (number of slices per minimum intensity projection (MIP) and Sliding Window) were investigated using a 1.5-T magnetic resonance imaging (MRI) system. The subjects were 12 healthy volunteers and the target region for scanning was the whole brain. Informed consent was obtained from all subjects. First, susceptibility-weighted images were acquired with various slice thicknesses from 1mm to 5mm and various matrix sizes from 256 x 256 to 512 x 512, and the images were assessed in terms of the contrast-to-noise ratio (CNR) and were also visually evaluated by three radiologists. Then, the number of slices per MIP and the usefulness of the Sliding Window were investigated. In the study of the optimal slice thickness and matrix size, the results of visual evaluation suggested that a slice thickness of 3mm and a matrix size of 448 x 448 are optimal, while the results of evaluation based on CNR were not significant. As regards the image processing conditions, the results suggested that the number of slices per MIP should be set to a minimum value of 2 and that the use of Sliding Window is effective. The present study provides useful reference data for optimizing SWI sequences.

Differences in glottal opening pattern between Tokyo and Osaka dialect speakers: factors contributing to vowel devoicing.

In Japanese, high vowels /i/ and /u/ are often devoiced when they are preceded and followed by voiceless consonants. The phenomenon is called vowel devoicing. The frequency of its occurrence is high in dialects of eastern Japan including standard (Tokyo) Japanese and low in dialects of western Japan including Osaka dialect. It has been claimed that consonants, but not vowels, are pronounced more carefully in eastern dialects compared to western dialects, which results in higher frequency of vowel devoicing. This paper examines whether the glottal opening gesture of voiceless consonants differs between those Tokyo speakers who consistently show vowel devoicing and Osaka speakers who do not show vowel devoicing. The results indicated that the duration of glottal opening for /k/ in voiced CV syllables was significantly longer for Tokyo speakers than for Osaka speakers. For Tokyo speakers, duration and maximum size of the glottal opening in devoiced /kite/ are significantly larger than /k/ in voiced syllables. This difference cannot be explained by the simple addition of the glottal gestures of [k] and [t]. Furthermore, the difference in vowel length between /i/ and /e/ was related, at least in part, to the difference in the amount of the airflow passing through the vocal tract about the time the stop closure was released.