Biomedical subjects

Akiko Hirai

Publications and source records attributed to Akiko Hirai.

5 recordsLinked to original sources

PubMed2006

Measurement of group refractive index wavelength dependence using a low-coherence tandem interferometer.

A technique for the measurement of the group refractive index wavelength dependence of optical materials using a low-coherence tandem interferometer and a spectrometer is proposed. Four channeled spectra resulting from interferences of light beams from different pairs of optical paths are used for the calculation of optical path differences. The group refractive index wavelength dependence is calculated from these optical path differences generated from the sample under measurement. No a priori information of the geometric thickness of a sample is required. The wavelength dependence of the group refractive index of the samples BK7 parallel plate of 5.200 and 10.025 mm from 675 to 850 nm is experimentally measured with an accuracy of the order of 10(-5) and a repeatability of the order of 10(-9).

Journal Article↗

PubMed2005

Prolyl-isomerase Pin1 accumulates in lewy bodies of parkinson disease and facilitates formation of alpha-synuclein inclusions.

Parkinson disease (PD) is a relatively common neurodegenerative disorder that is characterized by the loss of dopaminergic neurons and by the formation of Lewy bodies (LBs), which are cytoplasmic inclusions containing aggregates of alpha-synuclein. Although certain post-translational modifications of alpha-synuclein and its related proteins are implicated in the genesis of LBs, the specific molecular mechanisms that both regulate these processes and initiate subsequent inclusion body formation are not yet well understood. We demonstrate in our current study, however, that the prolyl-isomerase Pin1 localizes to the LBs in PD brain tissue and thereby enhances the formation of alpha-synuclein immunoreactive inclusions. Immunohistochemical analysis of brain tissue from PD patients revealed that Pin1 localizes to 50-60% of the LBs that show an intense halo pattern resembling that of alpha-synuclein. By utilizing a cellular model of alpha-synuclein aggregation, we also demonstrate that, whereas Pin1 overexpression facilitates the formation of alpha-synuclein inclusions, dominant-negative Pin1 expression significantly suppresses this process. Consistent with these observations, Pin1 overexpression enhances the protein half-life and insolubility of alpha-synuclein. Finally, we show that Pin1 binds synphilin-1, an alpha-synuclein partner, via its Ser-211-Pro and Ser-215-Pro motifs, and enhances its interaction with alpha-synuclein, thus likely facilitating the formation of alpha-synuclein inclusions. These results indicate that Pin1-mediated prolyl-isomerization plays a pivotal role in a post-translational modification pathway for alpha-synuclein aggregation and in the resultant Lewy body formations in PD.

Amino Acid Sequence↗

PubMed2005

[Anesthetic management of tracheobronchial stent insertion in patients who underwent laser resection, balloon dilatation and tracheostomy in advance].

BACKGROUND: We report successful management of tracheobronchial stent insertion under general anesthesia. METHODS: In thirty-two cases, tracheobronchial stent insertion was performed under general anesthesia. The technique for airway management was chosen depending on the type of stent or the constriction level of the airway portion. We employed tracheostomy in order to avoid repeated intubations during the insertion of Dumon or Dynamic stent. In case of severe airway stenosis, laser resection or balloon dilatation was performed before stent insertion. RESULTS: We had 32 successful cases in 36 trials. Four trials failed due to insufficient expansion in one, mismatches of stent angle in one and pneumomediastinum in one. There was no exacerbation of respiratory condition in failed cases. There was no case who needed percutaneous cardiopulmonary support system. CONCLUSIONS: We managed tracheobronchial stent insertion under general anesthesia. Both the airway expansion by laser resection or balloon dilatation before stent insertion and also the insertion of Dumon or Dynamic stent through a tracheostomy were helpful strategies. These techniques facilitated more definitive airway maintenance and stable anesthetic management.

Airway Obstruction↗

PubMed2003

Low-coherence tandem interferometer for measurement of group refractive index without knowledge of the thickness of the test sample.

A new low-coherence interferometric technique is proposed for measuring the group refractive indices of dispersive samples with high accuracy. A tandem configuration of interferometers is used to compensate for the asymmetrical distortion of interferograms that results from the broad spectrum of the light source. The group refractive index can be measured without knowledge of the geometrical thickness of the sample under test. The proposed technique can successfully measure even a thick sample. Computer calculations have shown the effectiveness of the proposed technique, which was verified by preliminary experiments; the difference between the experimental result and the catalog data was 7 x 10(-4).

Journal Article↗

PubMed2003

Broad-spectrum frequency comb generation and carrier-envelope offset frequency measurement by second-harmonic generation of a mode-locked fiber laser.

A frequency comb spanning more than one octave has been achieved by injecting the second-harmonic generation (780 nm) of a mode-locked fiber laser (1.56 microm) into a photonic crystal fiber. We propose and realize a novel interferometric scheme for observing the carrier-envelope offset frequency of the frequency comb. Frequency noise has been observed on the measured carrier-envelope offset frequency, which has been confirmed to be generated in the photonic crystal fiber by comparing the measured beat frequencies between cw lasers and frequency combs before and after the photonic crystal fiber. The mode-locked fiber laser is considered to be an important candidate for the light source used in realizing a compact optical frequency measurement system including applications in the telecommunication bands.

Journal Article↗