PubMed Health⌕ Search

Biomedical subjects

Yasuhiko Kobayashi

Publications and source records attributed to Yasuhiko Kobayashi.

13 recordsLinked to original sources
PubMed2003

Bystander effect induced by counted high-LET particles in confluent human fibroblasts: a mechanistic study.

The possible mechanism of a radiation-induced bystander response was investigated by using a high-LET heavy particle microbeam, which allows selected cells to be individually hit with precise numbered particles. Even when only a single cell within the confluent culture was hit by one particle of 40Ar (approximately 1260 keV/microm) or 20Ne (approximately 380 keV/microm), a 1.4-fold increase of micronuclei (MN) was detected demonstrating a bystander response. When the number of targeted cells increased, the number of MN biphasically increased; however, the efficiency of MN induction per targeted cell markedly decreased. When 49 cells in the culture were individually hit by 1 to 4 particles, the production of MN in the irradiated cultures were approximately 2-fold higher than control levels but independent of the number and LET of the particles. MN induction in the irradiated-culture was partly reduced by treatment with DMSO, a scavenger of reactive oxygen species (ROS), and was almost fully suppressed by the mixture of DMSO and PMA, an inhibitor of gap junctional intercellular communication (GJIC). Accordingly, both ROS and GJIC contribute to the above-mentioned bystander response and GJIC may play an essential role by mediating the release of soluble biochemical factors from targeted cells.

Cell Communication↗
PubMed2003

Penetrating keratoplasty surgery combined with vitrectomy after failing previous corneal surgery.

PURPOSE: The preoperative and postoperative factors influencing visual outcome were analyzed in 15 eyes of 15 patients with graft opacity after keratoplasty associated with vitreoretinal disease who underwent combined surgery of fresh corneal retransplantation and vitrectomy. MATERIALS AND METHODS: The data obtained consisted of diagnosis, preoperative visual acuity, corneal and vitreoretinal findings at the time of surgery, interval between the first visit and surgery, intraocular pressure before surgery, gonioscopic findings, results of bacterial culture of surgical specimens, surgical procedure for vitrectomy, corneal and vitreous findings after surgery, visual acuity 6 months after surgery, intraocular pressure after surgery, and additional surgical techniques. RESULTS: The cause of corneal opacity was graft rejection in all patients, who had been treated with high-dose administrations of steroids and cyclosporin. The preoperative diagnosis was proliferative vitreoretinopathy (PVR) in eight eyes and fungal endophthalmitis in seven eyes. Corneal transparency was achieved in 7 eyes (46.6%) 6 months after surgery. Vitreoretinal findings improved in 9 eyes (60%) and PVR recurred in 6 eyes (40%). Visual acuity improved in 7 eyes (46.6%), did not change in 2 eyes (13.3%), and deteriorated in 6 eyes (40%). The six eyes with decreased visual acuity developed phthisis bulbi. Preoperative intraocular pressure was 2.1 mmHg on average in the phthisis bulbi group, significantly lower than in the group with superior prognosis. Goniosynechia was noted before surgery and did not improve after surgery in all six eyes. CONCLUSIONS: The outcome was poor in eyes with goniosynechia and ocular hypotony, and combined surgery is not indicated for either anatomic or visual preservation in such cases. Care should be taken not to overlook intraocular infection in patients undergoing immunosuppressive therapy against graft rejection. The early detection of retinal detachment is also important in eyes exhibiting hypotony after surgery.

Adult↗
PubMed2003

The relationship between cellular radiosensitivity and radiation-induced DNA damage measured by the comet assay.

The relationship between deoxyribonucleic acid (DNA) damage and the cell death induced by gamma-irradiation was examined in three kinds of cells, Chinese hamster ovary fibroblast CHO-K1, human melanoma HMV-II and mouse leukemia L5178Y. Cell survival was determined by a clonogenic assay. The induction and rejoining of DNA strand breaks induced by radiation were measured by the alkaline and neutral comet assays. L5178Y cells were the most radiosensitive, while CHO-K1 cells and HMV-II cells were radioresistant. There was an inverse relationship between the survival fraction at 2 Gy (SF2) and the yield of initial DNA strand breaks per unit dose under the alkaline condition for the comet assay, and also a relationship between SF2 and the residual DNA strand breaks (for 4 hr after irradiation) under the neutral condition for the comet assay, the latter being generally considered to be relative to cellular radiosensitivity. In the present analysis, it was considered that the alkaline condition for the comet assay was optimal for evaluating the initial DNA strand breaks, while the neutral condition was optimal for evaluating the residual DNA strand breaks. Since the comet assay is simpler and more rapid than other methods for detecting radiation-induced DNA damage, this assay appears to be a useful predictive assay for evaluating cellular clonogenic radiosensitivity of tumor cells.

Animals↗
PubMed2002

Applicability of radiosurgery with heavy ion beams to inactivate specific organs in living organisms.

It was the aim of the study to test the applicability of radiosurgery in inactivating a specific organ through local irradiation with heavy ion beams. Silkworms were exposed to whole-body or local irradiation with carbon ion beams ((12)C(5+), 18.3 MeV/u, range=1.1 mm). After irradiation at the wandering stage, no significant differences were observed regarding either survival or cocoon quality between locally irradiated larvae and controls. Only localized effects were seen, such as the deletion of wings and functional disorders of the reproduction primordium, depending on both irradiation dose and site. This observation was not true for whole-body irradiated larvae. After local irradiation of the hemopoietic organs at the 4th instar premolting stage, the hemocyte densities were clearly reduced and the hemopoietic organ capacity was disrupted. The change in hemocyte densities was accompanied by changes of hemolymph components. These results show that radiosurgery utilizing heavy ion beams can destroy a specific organ or tissue in a living organism.

Animals↗
PubMed2002

Positional effect of cell inactivation on root gravitropism using heavy-ion microbeams.

When primary root apical tissues of Arabidopsis thaliana were irradiated by heavy-ion microbeams with 120 microm diameter, strong inhibition of root elongation and curvature were observed at the root tip. Irradiation of the cells that become the lower part of the root cap after gravistimulation showed strong inhibition of root curvature, whereas irradiation of the cells that become the upper part of the root cap after gravistimulation did not show severe damage in either root curvature or root growth. Further analysis using smaller area microbeams with 40 microm diameter indicated that the greatest inhibition of curvature occurred at the root tip and the next greatest inhibition occurred in the cells in the lower part of the root cap. These results indicate not only that the root tip and columella cells are the most sensitive sites for root gravity, but also that signalling of root gravity would go through the lower part of the cap cells after perception.

Arabidopsis↗
PubMed2002

Effects of heavy-ion radiosurgery on the hemopoietic function of the silkworm Bombyx mori.

To study the effects of heavy-ion radiosurgery on the hemopoietic function of a silkworm, hemopoietic organs of larvae were locally irradiated with carbon-ion beams, and the changes in the hemocyte density and in the hemocyte function were investigated. When the larvae were irradiated by 50 Gy to 300 Gy carbon ions on the 3rd day of the 4th instar, the hemocyte densities did not change for a while, though they gradually increased at a later stage, but were finally still significantly lower than those of unirradiated controls. The hemocyte densities of the larvae irradiated at different developmental stages showed suppressed increments, and carbon-ion irradiation given to larvae at early stages compared to the later stages had a significant suppressive effect on the hemocyte densities. On unilateral irradiated larvae a hemocyte intermediate increment between those of bilateral irradiated larvae and unirradiated controls was observed. The percentage of dead hemocytes was obviously higher for irradiated larvae than unirradiated controls during the later 5th instar. Thus, it is evident that carbon-ion radiosurgery on hemopoietic organs of silkworm induced not only a quantitative change, but also a qualitative change in the hemocytes.

Animals↗
PubMed2002

Detection of DNA damage in individual cells induced by heavy-ion irradiation with an non-denaturing comet assay.

Investigating the biological effects of high-LET heavy-ion irradiation at low fluence is important to evaluate the risk of radiation in space. It is especially necessary to detect radiation damage induced by a precise number of heavy ions in individual cells. We thus compared the number of ions traversing a cell and the DNA damage produced by ion hits. We applied a comet assay to measure the DNA damage in individual cells. Cells attached on ion-track detector (CR-39) were irradiated with 17.3 MeV/u 12C, 15.7 MeV/u, 10.4 MeV/u 20Ne ion and 7.2 MeV/u 40Ar beams at TIARA, JAERI-Takasaki. After irradiation, CR-39 was covered with 1% agarose. The agarose was allowed to solidify on a glass slide, and then the electrophoresis was performed. Afterward, the CR-39 was taken off the glass slide. The agarose gel on the CR-39 was stained with ethidium bromide and the opposite side of the CR-39 was etched with a KOH-ethanol solution at 37 degrees C. We observed that heavy ions with higher LET values induced heavier DNA damage, even with the same number of ion hits within the irradiated cells. The result indicated that the amount of DNA damage induced by one particle depended on the LET value of the heavy ions.

Animals↗
PubMedDate not supplied

Synthetic human alpha-atrial natriuretic peptide infusion in management after open heart operations.

Cardiopulmonary bypass (CPB) induces water retention in the third space, and the mechanism is partially associated with the activation of the renin-angiotensin-aldosterone system (RAAS). Atrial natriuretic peptide (ANP) has a gradual but strong diuretic effect and suppresses the RAAS activation. We examined the efficacy of synthetic human alpha-ANP (hANP) infusion in the management of the postoperative water balance control. Thirty patients (male:female = 18:12, 65.2 +/- 9.5 years) undergoing elective open heart operations in 2001 were allocated into one of two groups. Group H (n = 14) received 0.025 microg/kg/minute of synthetic hANP (HANP; Suntory Inc., Zeria Pharmaceutical, Tokyo, Japan) from the termination of CPB; the dose was gradually reduced to 0 until the 72nd postoperative hour. Group C (n = 16) served as control subjects. Twenty-four hours after operation, the central venous pressure, mean pulmonary arterial pressure, and pulmonary capillary wedge pressure were significantly lower in group H than in group C, and the cardiac index was significantly higher in group H. Total volume of plasma solution infused during the initial 24 postoperative hours was significantly smaller in group H. The total dosages of furosemide and potassium-chloride added during the first 72 postoperative hours were significantly smaller in group H. On the first postoperative day, plasma levels of renin activity and aldosterone were significantly lower in group H. These results suggest that postoperative hANP infusion, which provides a sufficient diuretic effect and suppresses CPB induced RAAS activation, may simplify management after open heart operations.

Aged↗
PubMedDate not supplied

Multifunction vitreous forceps (maculorrhexis forceps).

We developed novel multifunction vitreous forceps to decrease the frequency of forceps insertion and enable the removal of the internal limiting membrane and other intravitreal membranes for better surgical results. The basic forceps were conventional continuous curvelinear capsulorrhexis (CCC) forceps. The size of the shaft is 23G and its pointed end measures 500 microm in diameter. Additionally, there is a platform in its tip. The pointed end with platform helps to hold the membrane because the outer sheath can be moved while the tip of the forceps is fixed in position, and its pen hold type grip helps to reduce hand movement. The most advantageous thing is that the sharp point enables us to make an initial flap easily and the desired area of internal limiting membrane can be peeled off by firmly holding the platform.

Capsulorhexis↗
PubMedDate not supplied

Efficacy of daunorubicin encapsulated in liposome for the treatment of proliferative vitreoretinopathy.

BACKGROUND AND OBJECTIVE: To investigate the efficacy of daunorubicin encapsulated in liposome as a drug delivery system to treat proliferative vitreoretinopathy (PVR). MATERIALS AND METHODS: An experimental PVR model was made in pigmented rabbits by injecting a suspension of conjunctival fibroblasts and platelet-rich plasma into the vitreous cavity. Daunorubicin was encapsulated in newly developed empty liposome by mixing the empty liposome with the drug solution. Studies were performed 24 hours, 1 week, and 1 month after injection of daunorubicin encapsulated in empty liposome in an experimental PVR model. RESULTS: Compared with the control PVR model, daunorubicin prevented the formation of PVR. Although pathologic changes were observed in the eyes injected with daunorubicin alone, there were no adverse effects observed in the eyes injected with daunorubicin encapsulated in empty liposome. CONCLUSIONS: Daunorubicin encapsulated in empty liposome seems to be effective in preventing PVR without causing any adverse effects to the retina.

Animals↗