Biomedical subjects

Akihiro Hori

Publications and source records attributed to Akihiro Hori.

6 recordsLinked to original sources

PubMed2005

Comparison of cough reflex sensitivity after an inhaled antigen challenge between actively and passively sensitized guinea pigs.

BACKGROUND: Late asthmatic response is observed following antigen challenge in actively, but not passively, sensitized guinea pigs. Although cough reflex sensitivity is increased after antigen challenge in actively sensitized guinea pigs, it is unknown whether the antigen-induced increase in cough reflex sensitivity develops in passively sensitized animals. The aim of this study was to compare the cough reflex sensitivity to inhaled capsaicin after an inhaled antigen challenge between actively and passively sensitized guinea pigs. METHODS: Measurement of number of coughs elicited by increasing concentrations of capsaicin (10(-6) and 10(-4) M) and bronchial responsiveness to ascending concentrations of methacholine, and analysis of bronchoalveolar lavage fluid (BALF) were separately performed 24 h after an antigen challenge in actively and passively sensitized guinea pigs. RESULTS: Percentage of eosinophils in BALF and bronchial responsiveness to methacholine were increased 24 h after the antigen challenge in both actively and passively sensitized animals compared with saline-challenged actively and passively sensitized animals, respectively. Absolute number of eosinophils in BALF from actively sensitized and antigen-challenged guinea pigs was significantly greater than that from passively sensitized and antigen-challenged animals. Cough response to capsaicin and concentration of substance P in BALF were increased 24 h after the antigen challenge in actively sensitized guinea pigs, but not in passively sensitized guinea pigs. Bronchial responsiveness, cough reflex sensitivity and substance P concentration and total cells in BALF were increased in actively sensitized and saline challenged guinea pigs compared with passively sensitized and saline challenged animals. CONCLUSION: The results suggest that active sensitization per se increases cough reflex sensitivity accompanied by increased inflammatory cells and substance P level in BALF, and antigen challenge further increases them, while simple IgE- and/or IgG-mediated allergic reaction per se or the low intensity of eosinophil infiltration in the airway itself may not affect cough reflex sensitivity in guinea pigs.

Journal Article↗

PubMed2004

Vortex tubes in turbulence velocity fields at Reynolds numbers Re lambda approximately equal to 300-1300.

The most elementary structures of turbulence, i.e., vortex tubes, are studied using velocity data obtained in a laboratory experiment for boundary layers with Reynolds numbers Re(lambda) =295-1258 . We conduct conditional averaging for enhancements of a small-scale velocity increment and obtain the typical velocity profile for vortex tubes. Their radii are of the order of the Kolmogorov length. Their circulation velocities are of the order of the root-mean-square velocity fluctuation. We also obtain the distribution of the interval between successive enhancements of the velocity increment as the measure of the spatial distribution of vortex tubes. They tend to cluster together below about the integral length and more significantly below about the Taylor microscale. These properties are independent of the Reynolds number and are hence expected to be universal.

Journal Article↗

PubMed2003

Probability density function of turbulent velocity fluctuations in a rough-wall boundary layer.

The probability density function of single-point velocity fluctuations in turbulence is studied systematically using Fourier coefficients in the energy-containing range. In ideal turbulence where energy-containing motions are random and independent, the Fourier coefficients tend to Gaussian and independent of each other. Velocity fluctuations accordingly tend to Gaussian. However, if energy-containing motions are intermittent or contaminated with bounded-amplitude motions such as wavy wakes, the Fourier coefficients tend to non-Gaussian and dependent of each other. Velocity fluctuations accordingly tend to non-Gaussian. These situations are found in our experiment of a rough-wall boundary layer.

Journal Article↗

PubMed2003

Vortex tubes in velocity fields of laboratory isotropic turbulence: dependence on the Reynolds number.

The streamwise and transverse velocities are measured simultaneously in isotropic grid turbulence at relatively high Reynolds numbers Re(lambda) approximately 110-330. Using a conditional averaging technique, we extract typical intermittency patterns that are consistent with velocity profiles of a model for a vortex tube, i.e., Burgers vortex. The radii of the vortex tubes are several of the Kolmogorov length, regardless of the Reynolds number. Using the distribution of an interval between successive enhancements of a small-scale velocity increment, we study the spatial distribution of vortex tubes. The vortex tubes tend to cluster together. This tendency is increasingly significant with the Reynolds number. Using statistics of velocity increments, we also study the energetical importance of vortex tubes as a function of the scale. The vortex tubes are important over the background flow at small scales especially below the Taylor microscale. At a fixed scale, the importance is increasingly significant with the Reynolds number.

Journal Article↗

PubMed2002

Probability density function of turbulent velocity fluctuations.

The probability density function (PDF) of velocity fluctuations is studied experimentally for grid turbulence in a systematical manner. At small distances from the grid, where the turbulence is still developing, the PDF is sub-Gaussian. At intermediate distances, where the turbulence is fully developed, the PDF is Gaussian. At large distances, where the turbulence has decayed, the PDF is hyper-Gaussian. The Fourier transforms of the velocity fluctuations always have Gaussian PDFs. At intermediate distances from the grid, the Fourier transforms are statistically independent of each other. This is the necessary and sufficient condition for Gaussianity of the velocity fluctuations. At small and large distances, the Fourier transforms are dependent.

Journal Article↗

PubMed2002

[Frequency of previous tuberculosis history in patients with and without active tuberculosis admitted to our hospital in 1980-83 and in 1997-99].

To study recurrence rate over a long period after recovery from previous tuberculosis history, we examined the frequency of previous tuberculosis history in patients who were admitted to our hospital in 1980-83 and in 1997-99 and the comparison was made between cases with and without culture-positive tuberculosis. The tuberculosis groups comprised of 297 patients in 1980-83 and 688 patients in 1997-99. The non-tuberculosis groups (control groups) comprised of 373 patients in 1980-83 and 1092 patients in 1997-99 with non-tuberculosis diseases other than the tuberculosis-related diseases such as non-tuberculosis mycobacteriosis, pulmonary aspergillosis, bronchiectasis, chronic bronchitis and tuberculosis sequelae. The patients with viral chronic hepatitis previously operated and transfused were also excluded as they might be operated because of pulmonary tuberculosis in the era of surgical treatment for tuberculosis. In both tuberculosis and control groups, they had previous tuberculosis history most frequently when they were twenties. In the control groups, the frequency of previous tuberculosis history among cases admitted in 1980-83 and were born in 1910-19, 20-29, 30-39, 40-49 were 15/84 (17.9%), 22/93 (23.7%), 11/77 (14.3%) and 3/43 (7.0%), respectively, and those admitted in 1997-99 were 11/70 (15.7%), 30/231 (13.0%), 28/288 (9.7%), and 10/230 (4.3%), respectively. In these 4 birth year groups, frequency of previous tuberculosis history among cases admitted in 1997-99 were significantly lower than that admitted in 1980-83 (p < 0.05, one-sided paired t-test), and the fact suggests that persons with tuberculosis history died earlier than those without it. In the tuberculosis groups, the frequencies of previous tuberculosis history among cases admitted in 1980-83 and were born in 1910-19, 20-29, 30-39 and 40-49 were 20/35 (57.1%), 31/58 (53.4%), 19/48 (39.6%), and 11/53 (20.8%), respectively, and those among cases admitted in 1997-99 were 30/99 (30.3%), 58/125 (46.4%), 22/102 (21.6%) and 17/136 (12.5%), respectively. The frequency of previous tuberculosis history among cases admitted in 1997-99 was significantly lower than that admitted in 1980-83 (p < 0.01) as was the case in the control groups. As recurrence within 5 years had occurred in only 4 out of 113 tuberculosis patients (3.5%) in the above-mentioned 4 birth year groups, almost all tuberculosis patients were assumed to have recovered completely from previous tuberculosis. Comparison between the recurrence rate from previous tuberculosis and the incidence rate from the remotely infected persons without previous tuberculosis history in the same birth year group can be done by calculating the prevalence of tuberculosis infection for each birth year group using a model of annual risk of tuberculosis infection appropriate for Japanese. The ratios between the recurrence rate from previous tuberculosis patients and the incidence rate from remotely infected persons without previous tuberculosis history were 4.71, 2.33, 1.78 and 1.11 in 1980-83 and 1.84, 3.99, 1.80 and 1.11 in 1997-99 for groups born in 1910-19, 20-29, 30-39 and 40-49, respectively. The ratio did not change systematically with time in these groups, indicating the recurrence rate did not change with time more than ten years after recovery from previous tuberculosis. The ratio was about 3 for groups born in 1910-19 and 20-29 and 1 for group born in 1940-49. Almost all patients born in 1940-49 could receive chemotherapy for tuberculosis in their twenties, while most of the patients born in 1910-29 could not. Therefore, the above-mentioned fact may reflect the recurrence rate of patients treated successfully with chemotherapy is almost the same as the incidence rate from remotely infected persons, while that the recurrence rate from previous tuberculosis patients spontaneously recovered is 3 times higher than the incidence rate from remotely infected persons.

Adolescent↗