Biomedical subjects

Takayuki Arai

Publications and source records attributed to Takayuki Arai.

3 recordsLinked to original sources

PubMed2006

Characteristic features of Japanese women's hair with aging and with progressing hair loss.

BACKGROUND: There have been few studies of the features of hair with aging and hair loss in Japanese women. OBJECTIVE: Features of Japanese women's hair with aging and with progressing hair loss were investigated. METHODS: Japanese women with hair loss (n=46) or with no or less hair loss (n=113), aged 14-68 years, were studied. Severity of hair loss was rated by visual comparison with six standard photographs. Hair density, hair growth rate, and hair diameter were analyzed by phototrichogram. Follicular units were deduced by a non-invasive method using tree-view analysis on scalp imaging. RESULTS: Hair loss in Japanese women is commonly characterized by a diffuse central pattern occurring after approximately 40 years of age. Hair density declines with age after the 40s. The reduction resulted from an increase in the number of one-haired follicular units and a reduction of three- and more-haired follicular units. Both the ratio and the growth rate of anagen hair also declined with age after the 40s. Mean hair diameter and the ratio of thick hairs increased with age from about 10 to 40 years, and decreased with progressing hair loss. There were few vellus-like hairs in women with hair loss, in comparison with male-pattern baldness. CONCLUSION: In Japanese middle-aged women, hair density declined with age without the appearance of hair loss. Hair loss appeared after approximately 40 years of age. The major causes might be reduction of hair density and the ratio of thick hairs, but not an increase of vellus-like hairs.

Adolescent↗

PubMed2006

In vitro study of the proteolytic degradation of Antheraea pernyi silk fibroin.

In this study, Antheraea pernyi silk fibroin (Ap-SF) films were incubated with Protease Type XXI from Streptomyces griseus, at 37 degrees C, to investigate the degradation behavior in an in vitro model system. The enzyme-resistant fractions of Ap-SF films and the soluble peptides formed by proteolytic degradation were collected at specified times, from 1 to 17 days, and analyzed by high performance liquid chromatography, differential scanning calorimetry, FT-Raman, and FT-IR spectroscopy. Proteolysis resulted in extensive weight loss and progressive fragmentation of films, especially at long degradation times. A range of soluble peptides was formed by proteolysis. By high performance-size exclusion chromatography it was found that their average molecular weight changed with the time of incubation. The chemical analysis of the enzyme-resistant fraction of Ap-SF films at different times of degradation indicated that the proteolytic attack preferentially occurred in the less ordered Gly rich sequences and that the contribution of the Ala rich crystalline regions to the composition of biodegraded films became progressively larger. Accordingly, DSC and spectroscopic results showed an enhancement of the crystalline character of the biodegraded films. From the behavior of the most important thermal transitions, it was deduced that the alpha-helix domains probably represent the most enzyme-resistant fraction. The in vitro approach used in the present study seems to be a valid tool for studying the rate and mechanism of degradation of Ap-SF films and of other biopolymers of potential biomedical utility.

Animals↗

PubMed2006

Improving syllable identification by a preprocessing method reducing overlap-masking in reverberant environments.

Overlap-masking degrades speech intelligibility in reverberation [R. H. Bolt and A. D. MacDonald, J. Acoust. Soc. Am. 21(6), 577-580 (1949)]. To reduce the effect of this degradation, steady-state suppression has been proposed as a preprocessing technique [Arai et al., Proc. Autumn Meet. Acoust. Soc. Jpn., 2001; Acoust. Sci. Tech. 23(8), 229-232 (2002)]. This technique automatically suppresses steady-state portions of speech that have more energy but are less crucial for speech perception. The present paper explores the effect of steady-state suppression on syllable identification preceded by /a/ under various reverberant conditions. In each of two perception experiments, stimuli were presented to 22 subjects with normal hearing. The stimuli consisted of mono-syllables in a carrier phrase with and without steady-state suppression and were presented under different reverberant conditions using artificial impulse responses. The results indicate that steady-state suppression statistically improves consonant identification for reverberation times of 0.7 to 1.2 s. Analysis of confusion matrices shows that identification of voiced consonants, stop and nasal consonants, and bilabial, alveolar, and velar consonants were especially improved by steady-state suppression. The steady-state suppression is demonstrated to be an effective preprocessing method for improving syllable identification by reducing the effect of overlap-masking under specific reverberant conditions.

Adolescent↗