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Biomedical subjects

Y Furusawa

Publications and source records attributed to Y Furusawa.

At least 73 records · Page 4Linked to original sources
PubMed1997

Characterization and application of UV detector spore films: the sensitivity curve of a new detector system provides good similarity to the action spectrum for UV-induced erythema in human skin.

The UV action spectra of two different biologically weighting UV photofilms (spore films), produced with Bacillus subtilis spores (wild-type and DNA repair-deficient strains), were determined at the Okasaki large spectrograph (OLS) within the level of wavelength range 254-400 nm. The action spectrum of the mutant strain film was modified with a cut-off filter, yielding a sensitivity curve similar to the action spectrum for erythemal induction in human skin. The detector system was tested in a field study and in a study using lamps with different UV spectral compositions. The system demonstrated its applicability over the spectral region lambda = 290 nm to the visible light. The system could be calibrated to give the minimal erythemal dose.

Erythema↗
PubMed1997

Irradiation of mixed beam and design of spread-out Bragg peak for heavy-ion radiotherapy.

Data on cellular inactivation resulting from mixed irradiation with charged-particle beams of different linear energy transfer (LET) are needed to design a spread-out Bragg peak (SOBP) for heavy-ion radiotherapy. The present study was designed to study the relationship between the physical (LET) and biological (cell killing) properties by using different monoenergetic beams of 3He, 4He and 12C ions (12 and 18.5 MeV/nucleon) and to attempt to apply the experimental data in the design of the SOBP (3 cm width) with a 135 MeV/nucleon carbon beam. Experimental studies of the physical and biological measurements using sequentially combined irradiation were carried out to establish a close relationship between LET and cell inactivation. The results indicated that the dose-cell survival relationship for the combined high- and low-LET beams could be described by a linear-quadratic (LQ) model, in which new coefficients alpha and beta for the combined irradiation were obtained in terms of dose-averaged alpha and square root of beta for the single irradiation with monoenergetic beams. Based on the relationship obtained, the actual SOBP designed for giving a uniform biological effect at 3 cm depth was tested with the 135 MeV/nucleon carbon beam. The results of measurements of both physical (LET) and biological (90% level of cell killing, etc.) properties clearly demonstrated that the SOBP successfully and satisfactorily retained its high dose localization and uniform depth distribution of the biological effect. Based on the application of these results, more useful refinement and development can be expected for the heavy-ion radiotherapy currently under way at the National Institute of Radiological Sciences, Japan.

Animals↗
PubMed1997

Effects of reoxygenation on repair of potentially lethal radiation damage in cultured MG-63 osteosarcoma cells.

The effects of reoxygenation on repair of potentially lethal radiation damage were investigated using MG-63 human osteosarcoma cells in vitro. When exponentially growing MG-63 cells were cultured under hypoxic conditions for 24 h, cells stopped growing and remained at a low density. The hypoxic cells were then reoxygenated by exposure to air and irradiated with a single dose of 3 Gy X rays. The fraction of the reoxygenated cells surviving after 3 Gy increased by a factor of 20.6 when the colony assay was delayed for 24 h. In control cells which were cultured under aerobic conditions before receiving a single dose of 3 Gy, the surviving fraction increased by a factor of 2.5 when the assay was delayed for 24 h. The difference in the magnitude of the repair observed between reoxygenated and aerobic cells was less prominent in confluent cells plated at high density. The enhanced repair after reoxygenation was due mainly to a decrease in the alpha coefficient when the dose-survival curve was fitted to the linear-quadratic model, whereas the most significant change in the fit of the dose-survival curve for the aerobic cells was a decrease in the beta coefficient. The control aerobic cells accumulated at G2/M phase after irradiation, whereas the reoxygenated cells did not show such an accumulation. When the hypoxic cells were irradiated and then reoxygenated, repair of these cells irradiated under hypoxic conditions was also enhanced. This is the first report to show that reoxygenation could increase cell survival after tumor irradiation.

Aerobiosis↗
PubMed1997

Response of mouse intestine after single and fractionated irradiation with accelerated carbon ions with a spread-out Bragg peak.

The responses of mouse intestine were examined after irradiation with accelerated carbon ions with a spread-out Bragg peak. The carbon-ion beam (135 MeV/nucleon), accelerated by the RIKEN ring cyclotron facility, was modulated to have a spread-out Bragg peak (SOBP) 3 cm wide. In the SOBP the biological dose (relative physical dose x RBE) was designed in earlier studies to be flat at the 10% survival level of Chinese hamster V79 cells. The numbers of surviving crypt clonogenic cells after single and fractionated irradiation with the carbon-ion beam were obtained by a microcolony assay method. The composite single-dose survival curves for the crypt clonogenic cells were calculated and fitted by a linear-quadratic (LQ) model. An analysis with the LQ model for crypt clonogenic cells showed that the alpha coefficient increased along with increasing LET, and that the beta coefficient was relatively constant, even for high-LET radiations. The biological dose distributions for the crypt clonogenic cells at the 10% survival level were flat in the SOBP. The isoeffective design of the SOBP for the 135 MeV/nucleon carbonion beam, based on biological data from a mammalian in vitro cell system, appears to be applicable to the response of murine intestinal tissue in vivo.

Animals↗
PubMed1997

Dependence of induction of interphase death of Chinese hamster ovary cells exposed to accelerated heavy ions on linear energy transfer.

Induction of interphase death was examined in Chinese hamster ovary cells exposed to accelerated heavy ions (carbon, neon, argon and iron) of various linear energy transfers (LETs) (10-2000 keV/microm). The fraction of cells that underwent interphase death was determined by observing individual cells with time-lapse photography (direct method) as well as by counting cells undergoing interphase death made visible by the addition of caffeine (indirect method). After exposure to X rays, interphase death increased linearly with dose above a threshold of about 10 Gy, whereas it increased at a higher rate without a threshold after exposure to high-LET heavy ions. The relative biological effectiveness (RBE) compared to X rays, as determined at the 50% level of induction, increased with LET, reached a maximum at an LET of approximately 230 keV/microm and then decreased with further increase in LET. The range of LET values corresponding to the maximum RBE appears to be narrower for interphase death than for reproductive death (120-230 keV/microm), as assayed using loss of colony-forming ability as a criterion. The inactivation cross section for interphase cell death reached a plateau of 5-10 microm2. This means that the probability for the induction of interphase death by traversal of a single heavy-ion track through the nucleus (size: about 130 microm2) is about 0.04-0.08.

Animals↗
PubMed1996

The role of DNA repair on cell killing by charged particles.

It can be noted that it is not simple double strand breaks (dsb) but the non-reparable breaks that are associated with high biological effectiveness in the cell killing effect for high LET radiation. Here, we have examined the effectiveness of fast neutrons and low (initial energy = 12 MeV/u) or high (135 MeV/u) energy charged particles on cell death in 19 mammalian cell lines including radiosensitive mutants. Some of the radiosensitive lines were deficient in DNA dsb repair such as LX830, M10, V3, and L5178Y-S cells and showed lower values of relative biological effectiveness (RBE) for fast neutrons if compared with their parent cell lines. The other lines of human ataxia-telangiectasia fibroblasts, irs 1, irs 2, irs 3 and irs1SF cells, which were also radiosensitive but known as proficient in dsb repair, showed moderated RBEs. Dsb repair deficient mutants showed low RBE values for heavy ions. These experimental findings suggest that the DNA repair system does not play a major role against the attack of high linear energy transfer (LET) radiations. Therefore, we hypothesize that a main cause of cell death induced by high LET radiations is due to non-reparable dsb, which are produced at a higher rate compared to low LET radiations.

Animals↗
PubMed1996

Single- and double-strand breaks in pBR322 plasmid DNA by monochromatic X-rays on and off the K-absorption peak of phosphorus.

Using a synchrotron irradiation system pBR322 plasmid DNA was irradiated under vacuum by monochromatic X-rays having five specific photon energies (2.147, 2.153, 2.159, 2.168 and 2.199 keV) both on and off the K-absorption peak (2.153 keV) of phosphorus. The single- and double-strand breaks (ssb and dsb) were measured as conversions of the closed circular form of DNA (form I) to open circular (form II) and linear (form III) forms respectively. Exposures to induce one strand break per molecule were lowest at the peak (2.153 keV), and highest at 2.147 keV; the ratios were 2.7 for ssb and 3.0 for dsb. The exposures for dsb were 21-26 times higher than those for ssb. When the exposures were converted to absorbed doses in grays the absorbed doses per ssb were almost independent of photon energy. This result indicates that a certain absorbed dose was necessary to induce a ssb, regardless of whether photons were absorbed by the K-shell of phosphorus or by other shells, or by other atoms. However, the absorbed dose per dsb at 2.147 keV was 1.17 times higher than that averaged over four X-ray energies above 2-153 keV, indicating that the K-shell absorption, and the subsequent Auger event, efficiently induce dsb. The results are also discussed concerning the number of photo-absorptions of the constituent atoms per DNA strand break.

Animals↗
PubMed1996

Experimental correspondence between spore dosimetry and spectral photometry of solar ultraviolet radiation.

The biologically effective dose of solar UV radiation was estimated from the inactivation of UV-sensitive Bacillus subtilis spores. Two types of independent measurements were carried out concurrently at the Aerological Observatory in Tsukuba: one was the direct measurement of colony-forming survival that provided the inactivation dose per minute (ID/min) and the other was the measurement of the spectral irradiance by a Brewer spectrophotometer. To obtain the effective spectrum, the irradiance for each 1 nm wavelenght interval from 290 to 400 nm was multiplied with the efficiency for inactivation derived from the inactivation action spectrum of identically prepared spore samples. Integration of the effective spectrum provided the estimate for ID/min. The observed values of ID/min were closely concordant with the calculated values for the data obtained in four afternoons in 1993. The average ratio (+/- SD) between them was 1.24 (+/- 0.16) for 14 data points showing high inactivation rates (> 0.05 ID/min). Considering difficulties in the absolute dosimetry of UV radiation, the concordance was satisfactory and improved credibility of the two types of monitoring systems of biologically effective dose of solar UV radiation.

Bacillus subtilis↗
PubMed1996

Radiolytic products of bromodeoxyuridine in solids by 60Co gamma-rays and monoenergetic soft x-rays at the K-absorption edge of bromine.

In order to investigate DNA damage due to Auger cascades in bromodeoxyuridine (BrdU), BrdU mixed with other nucleosides, as a model of DNA, was irradiated in solids by gamma-rays and monoenergetic x-rays at around the K-absorption edge of bromine (13.47 keV). The main products of BrdU were deoxyuridine produced through debromination, and bromouracil produced through the decomposition of a sugar group. The rates of the debromination and the nucleobases release of additives were markedly increased in the mixed sample. This observation indicated that the additives surrounding BrdU efficiently supplied protons and then decomposed. The major products by x-rays were the same as those by gamma-rays, indicating that Auger cascades in bromine atoms did not produce specific products. The production rates for all products from the mixed sample were about 2.5 times higher at 13.51 (above the K-absorption edge) keV than at 13.43-keV x-rays.

Bromodeoxyuridine↗
PubMed1996

Lethal effect of K-shell absorption of intracellular phosphorus on wild-type and radiation sensitive mutants of Escherichia coli.

The present study was conducted to clarify the lethality of Auger cascades induced by the K-shell photoabsorption of phosphorus in Escherichia coli. Killing of wild-type and radiation-sensitive mutants of E. coli was examined. Three x-ray energies were chosen for irradiation; at 2.153 keV: the resonance peak of K-shell photoabsorption of phosphorus; at 2.146 and 2.160 keV: off-peak. Enhancement ratio, which was defined as the ratio of the killing sensitivity of 2.153 keV to that at 2.146 keV, were 1.32 to 1.54 for examined strains. Increment of absorbed energy calculated in entire cells for 2.153 keV radiation could not explain the degree of observed enhancement of killing. Lethality of Auger cascades depended on the killing sensitivity with x-rays which did not induce Auger cascades. The lethality for wild-type was lower than that for recombination repair-deficient mutants. It was concluded that one part of damages produced by Auger cascades was repaired in wild-type strains.

Absorption↗
PubMed1995

A comparison of biological effects of modulated carbon-ions and fast neutrons in human osteosarcoma cells.

PURPOSE: To compare the biological effects of a 135 MeV/u carbon-ion beam and 13 MeV fast neutron beam using human osteosarcoma cells. METHODS AND MATERIALS: We have studied the clonogenic cell survival, recovery of potentially lethal damage (PLD) in plateau phase cells, and spheroid cure in multicellular spheroid after irradiation at various positions in the plateau and spread out Bragg peak (SOBP) of a 135 MeV/u carbon-ion beam and with 13 MeV neutrons. The carbon beam had a 4-cm range in water and a range filter was used to produce a 3-cm extended-peak region. The reference radiation was 137Cs gamma-rays. RESULTS: The relative biological effectiveness (RBE) values for 10% survival level of plateau phase cells for carbon-ions at the position of plateau, proximal peak, midpeak, and distal peak within the SOBP, and neutrons were 1.71, 2.48, 2.63, 3.47, and 2.29, respectively. Corresponding RBE values at 1% level were 1.64, 1.93, 2.06, 2.49, and 2.05. The extent of recovery from PLD was reduced after carbon-ions at proximal peak, midpeak, and distal peak, and neutrons, although not substantially reduced after carbon-ions at plateau. The RBE values for 50% spheroid cure level of spheroids for carbon-ions at the position of plateau, proximal peak, midproximal peak, middistal peak, and distal peak within the SOBP, and neutrons were 1.69, 1.88, 1.87, 1.94, 2.03, and 1.90, respectively. CONCLUSIONS: The biological parameters measured all indicate an approximately comparable biological effectiveness between 75-80 KeV/microns carbon-ions of the SOBP and 13 MeV neutrons in the human tumor model studied in vitro.

Carbon↗
PubMed1995

[Coronary artery bypass grafting in cases with the atherosclerotic ascending aorta].

Among 172 cases of coronary artery bypass grafting, 9 cases (5%) revealed severely atherosclerotic ascending aorta. In 3 of the 9 cases, total aortic cross-clamping in the distal anastomoses of saphenous vein graft (SVG) and partial aortic clamp in the proximal anastomoses of SVG were performed. In 1 case with this technique, cerebral infarction was occurred. In 4 cases, total aortic cross-clamping in the distal and proximal anastomoses of SVG was performed. In 2 of these cases with this technique, cerebral infarctions were occurred. Hypothermic circulatory arrest was performed in 2 of the rest. In one case that was predicted to have atherosclerosis of ascending aorta prior to operation, the left internal thoracic artery was anastomosed to the left anterior descending, and SVG to the right coronary artery with hypothermia and ventricular fibrillation. And during the proximal anastomoses of SVG, hypothermic circulatory arrest without aortic clamping was initiated. In another case, atherosclerosis of ascending aorta was noted after aortic cross-clamping. Then the aorta was declamped, hypothermic circulatory arrest was established, the aorta was opened, the diseased segment was resected, and proximal anastomoses of SVG was performed to Dacron patch which was implanted for aortic wall. There were no cerebral infarction in last two patients.

Aged↗
PubMed1994

Quantitative RT-PCR assay detecting the transcriptional induction of vascular endothelial growth factor under hypoxia.

Quantitative reverse transcription-polymerase chain reaction (RT-PCR) assay was used to examine the induction of vascular endothelial growth factor (VEGF) transcript in human osteosarcoma cells, MG-63, under hypoxic culture condition. Using this assay system, the expression of VEGF mRNA was estimated eight-fold higher when cells were cultured under hypoxic condition. Transcription level of hypoxanthine phosphoribosyl transferase (HPRT) mRNA was also examined as an internal control. HPRT mRNA level under hypoxia was reduced to one fourteenth. Secretion of VEGF into the cell culture medium was implied by its stimulating activity on the growth of mouse vascular endothelial cultured cells in vitro.

Aerobiosis↗
PubMed1994

Single- and double-strand breaks in pBR322 DNA by vacuum-UV from 8.3 to 20.7 eV.

Solid pBR322 DNA was irradiated in a vacuum by monochromatic photons from 8.3 eV (150 nm) to 20.7 eV (60 nm), and the formation of single- and double-strand breaks (ssb and dsb) was determined using agarose gel electrophoresis. The action cross sections increased 20 times (ssb) and 43 times (dsb) from 8.3 eV to 20.7 eV; the quantum yields increased 5.4 times (ssb) and 12 times (dsb). The cross sections for dsb were 0.0059 at 8.3 eV and 0.013 at 20.7 eV of those of ssb; these values were smaller than about 0.04 for 2.1 keV photons, or about 0.18 for 60Co gamma-rays. Although vacuum UV photons were proved to induce dsb, they had a lower efficiency than when using soft X-rays or gamma-rays.

DNA↗
PubMed1993

Purification of blood-group substances in human hepatic bile (HHB) and immunological characterization of anti-HHB serum.

Blood-group substances (BGS) in human hepatic bile (HHB) of blood type A were purified 3657-7314-fold by ethanol sedimentation and column chromatography with DEAE Sephadex A-50 and Concanavalin A Sepharose 4B. An anti-HHB serum was raised by immunizing rabbits with the purified BGS in the HHB. Cross-reactions of the native anti-HHB serum with such human materials as type A blood cell, plasma, seminal fluid and saliva were eliminated by stepwise sequential absorptions with type A red blood cells, type O seminal fluid and type AB plasma. Precipitin titers of the native anti-HHB serum were x 320 and x 80 and those of the absorbed anti-HHB serum x 80 and x 20 against the immunogen and HHB, respectively. Organ and species specificity of the absorbed anti-HHB serum was checked by counter immunoelectrophoresis. It reacted specifically only with the immunogen and HHBs of various ABO blood types. No reactions with animal gallbladder biles were observed. In practical examinations, the specific anti-HHB serum identified 15 out of 20 (75%) HHB samples and 41 out of 46 (89%) human faeces samples. No reactions with animal gallbladder biles and animal faeces were observed.

ABO Blood-Group System↗
PubMed1993

Uracil-DNA glycosylase produces excess lethal damage induced by an Auger cascade in BrdU-labelled bacteriophage T1.

T1 phages with and without 5-bromo-2'-deoxyuridine (BrdU) labelling were irradiated in solids with monochromatic X-rays at 12.40 and 13.51 keV, below and just above the K-absorption edge of bromine (13.47 keV) in vacuum and wet states. Irradiated phages were assayed on uracil-DNA glycosylase (Udg) deficient (ung-1) and sufficient (ung+) host strains of Escherichia coli, in order to investigate the nature of the lethal damage induced by Auger cascade following X-ray absorption at the K-shell of bromine as a key atom. The results were: (1) An Auger-specific enhancement (1.15) was observed only when BrdU-labelled phages were irradiated in the wet state and assayed on ung+ host cells. (2) A Udg-specific enhancement was observed only for BrdU-labelled phages, not for unlabelled phages. (3) The sensitivities of BrdU-unlabelled phages were almost the same, despite the irradiation states and strains of the host cell, indicating that this sensitivity was a common fraction of the sensitivity under all conditions. (4) The lethal damage for the T1 phage was categorized into four fractions according to the sensitivities under different conditions: the general fraction was defined as being the sensitivity of unlabelled phages (G-fraction); BrdU-specific, but unrecognizable by Udg (B-fraction); Udg specific, but not Auger-specific (U-fraction); and Auger-specific (A-fraction). (5) Although the so-called indirect action of water radicals increased only the G-fraction by about three-fold, the B- and U-fractions were not affected by any change in the irradiation states, thus indicating that these two fractions were caused by the so-called direct action.

Affinity Labels↗
PubMed1993

[Studies on quantitative analysis of paraquat in whole blood--the evaluation of pre-treatments and analytical methods].

Paraquat and diquat are bipyridylium herbicide, which fatal poisoning cases have been reported in recent years. There are a number of methods for the pre-treatment and analysis of paraquat in body fluids and postmortem tissues. But the combined evaluation of these pre-treatments and analytical methods can be hardly found in literatures. We have carried out quantification of paraquat in whole blood with various combinations of pre-treatments and analytical methods, and evaluated those with respect to the sensitivity, recovery, time and cost. Non-treatment sample was a diluted solution of whole blood containing an aliquot of paraquat. The pre-treatments were achieved using two sorts of protein precipitants or Sep-Pak C18 cartridge. HPLC, second-derivative spectroscopy and ELISA were selected as analytical methods for quantification of paraquat. The most sensitive methods were combination of protein precipitants or Sep-Pak C18 and ELISA, but a combination of protein precipitant of sulfosalicylic acid and second-derivative spectroscopy was found to be more rapid and economical method. These methods would be applicable in forensic and clinical laboratories.

Chromatography, High Pressure Liquid↗