Biomedical subjects

Kazunori Takahashi

Publications and source records attributed to Kazunori Takahashi.

9 recordsLinked to original sources

PubMed2006

Prolonged ischemic conduction failure after reperfusion in diabetic nerve.

Diabetic nerve exhibits morphological vulnerability to ischemia and reperfusion, in contrast to its physiological resistance to ischemic conduction failure (RICF). To examine the sequence of ischemic conduction failure after reperfusion in diabetic nerve, we measured sciatic-tibial nerve conduction before and during 30-180 min of ischemia and after reperfusion for up to 1 week in streptozocin (STZ)-induced diabetic rats. RICF in diabetic rats was confirmed during ischemia. After reperfusion, control nerves showed an immediate recovery in amplitude of compound muscle action potential (CMAP) following ischemia for 120 min or less, and delayed recovery after 150 min of ischemia. In contrast, recovery in diabetic nerves was delayed even after 1 h of ischemia. Ischemia for 75 min in diabetic nerve resulted in either delayed or no recovery of the CMAP upon reperfusion. Following ischemia for 90 or 120 min, axonal degeneration was observed in diabetic nerve. Thus, severe ischemia for 60 or 75 min causes prolonged ischemic conduction failure in diabetic nerve, compared with 150 min in control nerve. In conclusion, diabetic nerve shows delayed recovery of ischemic conduction failure after brief ischemia, compared to controls, suggesting that patients with diabetic neuropathy have a worse prognosis when faced with nerve ischemia.

Animals↗

PubMed2006

[Degree of degraded proteoglycan in human vitreous and the influence of peroxidation].

PURPOSE: The degradation of hyaluronic acid induced by reactive oxygen species has been reported in vitro as a cause of vitreous liquefaction. In this study on in vivo human vitreous liquefaction, we examined the degree of degraded proteoglycan (PG) in human vitreous and the influence of peroxidation. SUBJECTS AND METHODS: In this study we examined the vitreous of 5 eyes with diabetic retinopathy, 12 eyes with retinal detachment, 2 eyes with retinal vein occlusion, and one eye with macular hole. The degree of degraded PG was determined by cellulose acetate membrane electrophoresis. To evaluate the influence of oxidation, copper ions, iron ions, hydrogen peroxide, lipid peroxide, L-ascorbic acid concentrations, and superoxide scavenging activity were measured. RESULTS: The electrophoretic patterns of PG were classified into the origin type (non-fragmented PG) in which only the origin was stained, and the mobile type (fragmented PG) showed other patterns. In the mobile type, the copper ion and hydrogen peroxide concentrations were higher, and the lipid peroxide concentrations were significantly higher, while the superoxide scavenging activity was lower. CONCLUSION: These results indicated that the degradation of PG and dissociation of glycosaminoglycan in human vitreous were associated with peroxidation.

Adolescent↗

PubMed2005

Synthesis and in vivo biodistribution of BPA-Gd-DTPA complex as a potential MRI contrast carrier for neutron capture therapy.

p-boronophenylalanine (BPA) conjugated Gd-DTPA complex (3) was synthesized from the active methyne compound 6, the allylic carbonate 7, and BPA by the palladium-catalyzed allylation reaction followed by the DCC coupling reaction. The in vivo biodistribution of complex 3 was evaluated by prompt gamma-ray analysis and alpha-autoradiography using the tumor-bearing rats. High accumulation of gadolinium was observed in the kidney and the %ID values were 0.17 and 0.088 at 20 and 60 min after injection of 3, respectively. The accumulation was also observed in the tumor and the %ID values were 0.010 and 0.0025 at 20 and 60 min after injection, respectively. The visualization experiment of boron distribution in the tumor-bearing rat by alpha-autoradiography indicates that boron was accumulated in the tumor and the intestines at 20 min after injection.

Animals↗

PubMed2004

Non-destructive on-chip cell sorting system with real-time microscopic image processing.

Studying cell functions for cellomics studies often requires the use of purified individual cells from mixtures of various kinds of cells. We have developed a new non-destructive on-chip cell sorting system for single cell based cultivation, by exploiting the advantage of microfluidics and electrostatic force. The system consists of the following two parts: a cell sorting chip made of poly-dimethylsiloxane (PDMS) on a 0.2-mm-thick glass slide, and an image analysis system with a phase-contrast/fluorescence microscope. The unique features of our system include (i) identification of a target from sample cells is achieved by comparison of the 0.2-microm-resolution phase-contrast and fluorescence images of cells in the microchannel every 1/30 s; (ii) non-destructive sorting of target cells in a laminar flow by application of electrostatic repulsion force for removing unrequited cells from the one laminar flow to the other; (iii) the use of agar gel for electrodes in order to minimize the effect on cells by electrochemical reactions of electrodes, and (iv) pre-filter, which was fabricated within the channel for removal of dust contained in a sample solution from tissue extracts. The sorting chip is capable of continuous operation and we have purified more than ten thousand cells for cultivation without damaging them. Our design has proved to be very efficient and suitable for the routine use in cell purification experiments.

Journal Article↗

PubMed2004

Separation of stereoisomers of some terpene derivatives by capillary gas chromatography-mass spectrometry and high-performance liquid chromatography using beta-cyclodextrin derivative columns.

Gas chromatographic separations of the stereoisomers of menthol derivatives, important intermediates in the synthesis of physiologically active natural products, were carried out on several substituted beta-cyclodextrin (CD) columns, including per-O-methyl-beta-cyclodextrin (PME-beta-CD), heptakis(2,3-di-O-acetyl-6-tert-butyldimethylsilyl)-beta-CD (DIAC-6-TBDS-beta-CD), and heptakis(2,3-di-O-methyl-6-tert-butyldimethylsilyl)-beta-CD (DIME-6-TBDS-beta-CD) as chiral stationary phases (CSPs). With the DIME-6-TBDS-beta-CD column, a separation of the Z- and E-isomers of methylidenementhol was accomplished; no separation was achieved with the other columns. The stereoisomers of methylidenementhol and the corresponding tert-butyldimethylsilyl (TBS) ether were separated on both the beta-CD and the heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TME-beta-CD) columns by high-performance liquid chromatography (HPLC) with a mobile phase involving acetonitrile and H(2)O. For the separation of the Z- and E-isomers of methylidenementhol, the TME-beta-CD column was superior. In contrast, the beta-CD column was preferable in the case of the corresponding TBS ether.

Chromatography, High Pressure Liquid↗

PubMed2003

Stereoselective construction of a beta-isopropenyl alcohol moiety at the C(2) and (3) of kallolide A and pinnatin a using a [2,3] Wittig rearrangement of cyclic furfuryl ethers.

A stereocontrolled synthesis of anti- and syn-beta-isopropenyl alcohol moieties at the C(2)-C(3) positions of kallolide A and pinnatin A was accomplished employing the [2,3] Wittig rearrangement of (E)-and (Z)-cyclic furfuryl ethers 8. Enantioselective Wittig rearrangement of (E)- and (Z)-furfuryl ethers 8 using butyllithium and a chiral bis(oxazoline) was also examined to provide (2R,3R)-homoallylic alcohol anti-9 in up to 61% ee and (2R,3S)-syn-9 in up to 93% ee, respectively.

Diterpenes↗

PubMed2003

Analyses of anandamide and endocannabinoid-like compounds using collision-induced dissociation in fast atom bombardment ionization-mass spectrometry and gas chromatography/chemical ionization-mass spectrometry.

The utility of the collision-induced dissociation (CID) of two different forms of precursor cations generated by the fast atom bombardment (FAB) ionization of N-arachidonylethanolamine (anandamide) and a series of endocannabinoid-like compounds, such as N-oleoylethanolamine, N-palmitoylethanolamine, N-stearoylethanolamine, N-linoleoylethanolamine, N-oleoylpropanolamine, and N-palmitoylpropanolamine, as a method of providing general information on their characterizations was examined. The CID spectra of lithium-adduct [M+Li]+ ions of the amines with unsaturated hydrocarbon chains were rich in structurally informative charge-site-remote (CSR) fragmentation patterns that provide information on the locations of double bonds in hydrocarbon chains. On the other hand, the CID reactions of [M+H]+ ions produced acylium ions that are derived from the cleavage of amide bonds, thus providing information on the size of the hydrocarbon chains, although CSR fragmentations were not observed. These compounds without derivatization were analyzed using gas chromatography/chemical ionization-mass spectrometry (GC/CI-MS) with a polyethylene glycol phased column with fused silica capillary pre-tubing. Identifiable molecular-related [M+H]+ ions were observed.

Arachidonic Acids↗

PubMed2002

Separation of stereoisomers of several furan derivatives by capillary gas chromatography-mass spectrometry, supercritical fluid chromatography, and liquid chromatography using chiral stationary phases.

The direct separation of several stereoisomers (enantiomers and geometrical isomers) of furan derivatives, important intermediates for the synthesis of physiologically active natural products, was achieved using capillary gas chromatography/mass spectrometry with a per-O-methyl-beta-cyclodextrin, supercritical fluid chromatography and high-performance liquid chromatography with a tris(3,5-dimethylphenylcarbamate) of cellulose or amylose for the chiral stational phases, respectively. The temperature dependence of the peak resolution (Rs) and the retention factor (k) over the range of 110-130 degrees was studied using crotyl furfuryl ether in gas chromatography. Successive increases in the Rs value and of the difference between the k value of the E-isomer and the k value of the Z-isomer were observed when the gradient temperature was decreased. The per-O-methyl-beta-cyclodextrin column was suitable for use with volatile furan ethers whose molecular masses are between 150 and 180. In conclusion, the separation of thermally unstable furan derivatives was accomplished using supercritical fluid chromatography and high-performance liquid chromatography.

Chromatography, High Pressure Liquid↗

PubMed2002

An agar-microchamber cell-cultivation system: flexible change of microchamber shapes during cultivation by photo-thermal etching.

A new type of cell-cultivation system based on photo-thermal etching has been developed for the on-chip cultivation of living cells using an agarose microchamber array. The method can be used to flexibly change the chamber structure by photo-thermal etching, even during the cultivation of cells, depending upon the progress in cell growth. We used an infrared (1064 nm) focused laser beam as a heat source to melt and remove agar gel at the heated spot on a thin chromium layer. The melting of the agar occurred just near the chromium thin layer, and the size of the photo-thermally etched area depended almost linearly on the power of the irradiated laser beam from 2 microm to 50 microm. Thus by using photo-thermal etching with adequate laser power we could easily fabricate narrow tunnel-shaped channels between the microchambers at the bottom of the agar-layer even during cell cultivation. After 48 h of cultivation of nerve cells, the nerve cells in two adjacent chambers made fiber connections through the fabricated narrow tunnel-shaped channels. These results suggest that photo-thermal etching occurred only in the area where an absorbing material was used, which means that it is possible to photo-thermally etch lines without damaging the cells in the microchambers. The results also suggest that the agar-microchamber cell cultivation system in combination with photo-thermal etching can potentially be used for the next stage of single cell cultivation including the real-time control of the interaction of cells during cell cultivation.

Journal Article↗