Biomedical subjects

Takashi Kimoto

Publications and source records attributed to Takashi Kimoto.

9 recordsLinked to original sources

PubMed2006

Discrimination of ionic pollutants except condensation nuclei of acid fog using an ultrasonic humidifier.

Fog droplets in the atmosphere are first produced by the activation of cloud condensation nuclei (CCN), which are originally some ionic compound. Subsequently, the nuclei grow by vapor diffusion. Fog droplets are polluted through the activation process and successive diffusion growth and residence (post activation). We cannot distinguish the effects of the two pollution processes of natural fog water samples. We found that fog droplets can be produced artificially without CCN using an ultrasonic humidifier. Because the artificial fog droplets are not polluted by CCN, the movement of the fog droplets in natural air will take up some pollutants in the air. Consequently, the two pollution processes of fog (the activation of CCN and the post activation process) can be discriminated using data from field experiments. This sampling analytical method is extremely important for further research regarding fog, clouds and environmental chemistry.

Journal Article↗

PubMed2006

Verification of the silica deficiency hypothesis based on biogeochemical trends in the aquatic continuum of Lake Biwa-Yodo River-Seto Inland Sea, Japan.

The silica deficiency hypothesis holds that increases of still waters caused by hydraulic alterations and high nitrogen (N) and phosphorus (P) discharges enhance the growth of freshwater diatoms, which take up the dissolved silicate (DSi) supplied by natural weathering. The consequent decrease in the DSi supply to the sea is advantageous to flagellates (nonsiliceous and potentially harmful) but not to diatoms (siliceous and mostly benign) in coastal marine ecosystems. Verification of this hypothesis has been hampered by lack of relevant data, particularly in Asia. We investigated the aquatic continuum composed of Lake Biwa, the Yodo River, and the Seto Inland Sea, Japan, where the natural conditions make the silica deficiency less likely to emerge due to the inherently rich supply of DSi. The results showed that the silica was retained both in the lake and nearby the estuary. The relative dominance of diatom and flagellates could not be explained solely by the stoichiometric arguments but by the supportive discussion on the difference of their behavioral characteristics and the process nearby the estuary, where direct inputs of N and P and effluent Si enhanced diatom bloom, even though the Si/N ratio was lowered in the upstream reservoir. Thus the retention of DSi occurred in two places: in the lake and nearby the estuary, where the other N and P are loaded directly. The rate of DSi retention correlated with socio-economic changes, such as rapid economic growth in the 1960s and mitigations implemented after the 1980s. Sensitivity of this continuum to the Si processes suggests the global significance of this hypothesis.

Diatoms↗

PubMed2004

Product analysis of caffeic acid oxidation by on-line electrochemistry/electrospray ionization mass spectrometry.

On-line electrochemistry/electrospray ionization mass spectrometry (EC/ESI-MS) was developed using a microflow electrolytic cell. This technique was applied to electrochemical oxidation of caffeic acid (CAF) which is known to be a highly antioxidative agent. Effects of electrolytic potentials on ion intensities of product ions and on electrolytic currents were examined at different pHs. Dimer products were detected at electrolytic potentials of E = 0.7 V (vs. Ag/AgCl) and trimer products at 1.0 V at pH 9. Dimer products were distinguished from hydrogen-bonded complexes by MS/MS experiments. Hydrogen/deuterium exchange experiments determined the number of hydroxyl and carboxyl groups in the Dimers formed by electrolysis. The mechanism of oxidative polymerization of CAF is discussed with speculation as to the structure of the dimer product.

Antioxidants↗

PubMed2004

Peroxynitrite-induced apoptosis in photoreceptor cells.

PURPOSE: To study the mechanisms of peroxynitrite-induced photoreceptor cell damage, using retinal cultures and a peroxynitrite donor, 3-morpholinosydnonimine (SIN-1). METHODS: Retinal explants obtained from 20-day-old Lewis rat pups, were exposed to SIN-1 for varying lengths of time at varying concentrations. Apoptosis in the photoreceptor cells was detected using the TdT-mediated dUTP-biotin nick end labeling (TUNEL) method and a DNA fragmentation assay. Selected retinal samples were processed for an ultrastructural analysis to confirm apoptosis. The retinas exposed to SIN-1 were tested for the expression of caspase-3 by immunohistochemistry and a Western blot analysis. The retinas were also evaluated for the prevention of apoptosis in the presence of the caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-fmk). RESULTS: The retinal explants exposed to SIN-1 showed a significant increase in the presence of TUNEL-positive photoreceptor cells. Similarly lineal increases in TUNEL-positive cells were seen in the presence of increasing concentrations of SIN-1. DNA ladder formation was seen with the exposure of SIN-1. Ultrastructurally, SIN-1 exposed retinas revealed typical apoptotic changes in the photoreceptor cell nuclei. The retinas preincubated with urate for 6 hours and exposed to SIN-1 for 16 hours showed significantly fewer TUNEL-positive cells compared to the retinas exposed to SIN-1 alone (p < 0.05). Moreover, the retinas exposed to SIN-1 showed the expression of caspase-3. This expression, as well as the number of apoptotic photoreceptors, significantly decreased in the presence of Z-VAD-fmk. CONCLUSIONS: These results show that peroxynitrite induces apoptosis in photoreceptor cells and that such retinal damage appears to be mediated by caspase-3. The apoptotic process can be minimized by peroxynitrite scavenger urate, as well as by the caspase inhibitor Z-VAD-fmk.

Amino Acid Chloromethyl Ketones↗

PubMed2003

Direct analysis of lipids in single zooplankter individuals by matrix-assisted laser desorption/ionization mass spectrometry.

A highly sensitive method to analyze the intact lipids in a single zooplankter individual at the level of a few tenths of a microgram was developed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) combined with a direct sampling technique. The sampling procedure involved (1) putting a zooplankter individual sample onto the MALDI sample plate, (2) cutting the sample into a few pieces by means of tweezers, (3) depositing aliquots of matrix and cationization reagent solutions on the zooplankter sample, and (4) irradiating with a N2 laser to cause MALDI. By using this technique, the mass spectra of the single zooplankter samples showed a series of ions generated from phospholipids with 34 or 36 carbons in the acyl groups and neutral lipids such as triglycerides and diacylglyceryl ethers with 50-54 carbons in their acyl and alkenyl groups. Accordingly, this method enabled us to estimate the relative quantity between "structured lipids" (phospholipids) and "storage lipids" (neutral lipids) in an individual zooplankter, which should give us a good clue to elucidate the roles of each class of lipids in its growth.

Animals↗

PubMed2003

Highly selective inhibitor of inducible nitric oxide synthase enhances S-antigen-induced uveitis.

PURPOSE: Investigated the effect of N-3-aminomethylbenzylacetamidine (1400 W), a highly selective inhibitor of inducible nitric oxide synthase (iNOS), on the effector phase of EAU. METHODS: Sixteen Lewis rats were sensitized with bovine retinal S-antigen; ten of them injected subcutaneously with 1400 W (20 mg/kg) three times a day, from day 11 through day 13 following the injection of S-antigen. Five of the ten rats were also injected intraperitoneally with polyethylene-glycol-modified superoxide dismutase (SOD 1000 IU) twice a day from day 7 through day 13. Six rats received intraperitoneal and/or subcutaneous injections of normal saline from day 7 through day 13. The eyes were enucleated on day 14. The intensity of the inflammatory lesion was assessed by a histological score. The thickness of the choroidal and photoreceptor layers was measured. RESULTS: The histological score was higher in the 1400 W-treated rats (26 +/- 2.1) than in the saline- (20.5 +/- 8; p < 0.0001) or 1400 W/SOD-treated rats (20.5 +/- 4.9; p < 0.005). The choroid was thicker in the 1400 W-treated rats (60.7 +/- 16.8 microm) than in the saline- (19.2 +/- 9.4 microm, p < 0.0005) or the 1400 W/SOD-treated rats (29.6 +/- 19.3 microm, p < 0.05). The photoreceptor layer was thinner in the 1400 W-treated rats (8.4 +/- 32.1 microm) than in the saline- (40 +/- 26.7 microm; p < 0.05) or 1400 W/SOD-treated rats (60.8 +/- 38.1 microm; p < 0.05). CONCLUSIONS: The data suggests that 1400 W exacerbates choroidal inflammation and photoreceptor damage at the effector phase of S-antigen-induced uveitis. This implies that iNOS expressed in the outer retina may have a protective role in EAU.

Amidines↗

PubMed2003

Pathogenic role of retinal microglia in experimental uveoretinitis.

PURPOSE: To devise methods for unequivocal identification of activated retinal microglia in experimental autoimmune uveoretinitis (EAU) and to investigate their role in the development of EAU. METHODS: A group of Lewis rats underwent optic nerve axotomy with the application of N-4-(4-didecylaminostyryl)-N methylpyridinium iodide (4Di-10ASP) at the axotomy site. On days 3, 14, and 38 after axotomy, the rats were killed, the eyes were enucleated, and the retinas were stained for OX42. Another group of such axotomized rats were immunized with S-antigen peptide and were killed on days 7 through 12 after the injection with peptide. The enucleated eyes were stained for OX42 and examined by confocal microscope. After axotomy, bone marrow (Y-->X) chimeric rats were injected with S-antigen peptide and were killed on days 10 and 12 after injection. The retinas were evaluated by PCR with Y-specific primers. Finally, a group of axotomized rats was injected with the S-antigen peptide and killed on days 6, 8, 9, and 10 after injection. Their enucleated eyes were examined for microglial expression of TNFalpha and for generation of peroxynitrite. RESULTS: In the axotomized, non-EAU eyes, 4Di-10ASP-labeled ganglion cells were detectable on days 3 and 14, and 4Di-10ASP-containing OX42-positive cells (microglia) were found in the nerve fiber and other inner retinal layers on days 14 and 38. The S-antigen peptide-injected rats showed migration of the microglia (4Di-10ASP-positive and OX42-positive) to the photoreceptor cell layer on day 9, and these cells increased in number at this site on day 10. No macrophages (OX42-positive and 4Di-10ASP-negative) were present at this early stage of EAU, but such cells appeared in the retina on days 11 and 12. PCR of the chimeric EAU retinas showed an absence of the Y chromosome-amplified product on day 10, but the presence of this product was detected on day 12. The expression of TNFalpha and generation of peroxynitrite were noted in the migrated microglia at the photoreceptor cell layer on days 9 and 10 of EAU. CONCLUSIONS: In the early phase of EAU, the microglia migrate to the photoreceptor cell layer where they generate TNFalpha and peroxynitrite. Such microglial migration and activation take place before infiltration of the macrophages. These findings indicate a novel pathogenic mechanism of EAU, in which retinal microglia may initiate retinitis with subsequent recruitment of circulation-derived phagocytes, leading to the amplification of uveoretinitis.

Animals↗

PubMed2002

Complete electrolysis using a microflow cell with an oil/water interface.

A novel microflow cell with a nitrobenzene (NB)/water (W) interface was developed. A poly(tetrafluoroethylene) membrane filter was employed to prepare the NB/W interface which was formed over a thin channel (0.1 mm thick, 48 cm long) on a silver plate. The silver plate was electrolyzed in advance and served as an Ag/AgCl electrode for controlling the Galvani potential difference across the NB/W interface as well as detecting the current flowing through the interface. Using the microflow cell, complete electrolysis was accomplished for the interfacial transfer of a representative ion (i.e., tetramethylammonium ion). Thus, the present microflow cell was shown to be promising for coulometric (i.e., absolute quantitative) analysis of ions. Also, the microflow cell was shown to be useful for determination of the number of electrons for complicated charge-transfer processes at the oil/water interface.

Journal Article↗

PubMedDate not supplied

Effects of local administration of interferon-beta on proliferation of retinal pigment epithelium in rabbit after laser photocoagulation.

PURPOSE: To investigate whether local administration of interferon (IFN)-beta promotes proliferation of the retinal pigment epithelium (RPE) in vivo. METHODS: Following local injection of IFN-beta into the sub-Tenon space of rabbit eyes, the penetration of IFN-beta into various intraocular areas was determined by means of enzyme-linked immuno-adsorbent assay. Retinal lesions were produced by laser photocoagulation (PC), and IFN-beta (1 x 10(6) IU, 1 x 10(5) IU, or 1 x 10(4) IU) was administered into the sub-Tenon space. Physiological saline was substituted for IFN-beta in controls. The proliferation of RPE cells was inspected histopathologically. RESULTS: After IFN-beta administration, IFN-beta was found in all intraocular areas examined, with the highest concentration detected in the choroid. After PC, profuse proliferation of RPE cells began earlier in the rabbits that received the highest dose of IFN-beta than in the control rabbits; repair of the central part of the coagulated lesion in those rabbits was complete within 7 days after PC. In control rabbits, the histopathologic wound repair process proceeded more slowly and to a limited extent. Proliferation of RPE cells in the low and medium dose IFN-beta-treated rabbits was similar to that in the control rabbits. CONCLUSION: The present study demonstrates that repair of the PC-induced retinal lesions, particularly the proliferation of RPE cells, is promoted in vivo by local administration of IFN-beta.

Administration, Topical↗