Biomedical subjects

Yoshihisa Kubota

Publications and source records attributed to Yoshihisa Kubota.

12 recordsLinked to original sources

PubMed2006

Multiple diffusion mechanisms due to nanostructuring in crowded environments.

One of the key questions regarding intracellular diffusion is how the environment affects molecular mobility. Mostly, intracellular diffusion has been described as hindered, and the physical reasons for this behavior are: immobile barriers, molecular crowding, and binding interactions with immobile or mobile molecules. Using results from multi-photon fluorescence correlation spectroscopy, we describe how immobile barriers and crowding agents affect translational mobility. To study the hindrance produced by immobile barriers, we used sol-gels (silica nanostructures) that consist of a continuous solid phase and aqueous phase in which fluorescently tagged molecules diffuse. In the case of molecular crowding, translational mobility was assessed in increasing concentrations of 500 kDa dextran solutions. Diffusion of fluorescent tracers in both sol-gels and dextran solutions shows clear evidence of anomalous subdiffusion. In addition, data from the autocorrelation function were analyzed using the maximum entropy method as adapted to fluorescence correlation spectroscopy data and compared with the standard model that incorporates anomalous diffusion. The maximum entropy method revealed evidence of different diffusion mechanisms that had not been revealed using the anomalous diffusion model. These mechanisms likely correspond to nanostructuring in crowded environments and to the relative dimensions of the crowding agent with respect to the tracer molecule. Analysis with the maximum entropy method also revealed information about the degree of heterogeneity in the environment as reported by the behavior of diffusive molecules.

Biophysics↗

PubMed2005

Radio-sensitivity of the cells from amyotrophic lateral sclerosis model mice transfected with human mutant SOD1.

In order to clarify the possible involvement of oxidative damage induced by ionizing radiation in the onset and/or progression of familial amyotrophic lateral sclerosis (ALS), we studied radio-sensitivity in primary cells derived from ALS model mice expressing human mutant SOD1. The primary mouse cells expressed both mouse and the mutant human SOD1. The cell survival of the transgenic mice (with mutant SOD1), determined by counting cell numbers at a scheduled time after X-irradiation, is very similar to that of cells from wild type animals. The induction and repair of DNA damage in the transgenic cells, measured by single cell gel electrophoresis and pulsed field gel electrophoresis, are also similar to those of wild type cells. These results indicate that the human mutant SOD1 gene does not seem to contribute to the alteration of radio-sensitivity, at least in the fibroblastic cells used here. Although it is necessary to consider the difference in cell types between fibroblastic and neuronal cells, the present results may suggest that ionizing radiation is not primarily responsible for the onset of familial ALS with the SOD1 mutation, and that the excess risks are probably not a concern for radiation diagnosis and therapy in familial ALS patients.

Amyotrophic Lateral Sclerosis↗

PubMed2004

Attenuation of biologic compensatory action of cardiac natriuretic peptide system with aging.

Although plasma B-type natriuretic peptide (BNP) levels increase with age, the mechanisms responsible for this increase are unknown. We investigated the predictors of elevated BNP in older subjects without cardiac systolic dysfunction and overt renal dysfunction. Furthermore, we analyzed the relations between BNP and its second messenger, cyclic guanosine monophosphate (cGMP), to aging. In 252 subjects (mean age 69 +/- 12 years) with left ventricular ejection fraction >/=50% and creatinine levels <==1.5 mg/dl, plasma levels of BNP, cGMP, blood urea nitrogen, creatinine, and beta2-microglobulin (an endogenous marker of renal function), estimated glomerular filtration rate, and echocardiographic data were prospectively evaluated. Plasma BNP levels increased with age (r = 0.4, p <0.0001). With use of multivariate analysis, predictors of elevated BNP levels were age, use of beta blockers, and serum beta2-microglobulin levels. The molar ratio of cGMP to BNP significantly decreased with aging (r = 0.55, p <0.0001). Elevated BNP in older subjects with normal cardiac systolic function may be due in part to renal impairment. With aging, biologic compensation of the cardiac natriuretic peptide system may be attenuated.

Adult↗

PubMed2004

Laparoscopy-assisted spleen-preserving distal pancreatectomy with conservation of the splenic artery and vein.

Herein, we report the successful performance of a laparoscopy-assisted spleen-preserving distal pancreatectomy with conservation of the splenic artery and vein for a patient with pancreatic cystadenoma, as a minimally invasive procedure with the preservation of function. The laparoscopy-assisted distal pancreatectomy procedure involved detaching the spleen and the distal pancreas from the retroperitoneum by a hand-assisted procedure, removing them from the peritoneal cavity through a small incision, and detaching the distal pancreas by ligating and transecting the short gastric artery and vein and the branches of the splenic artery and vein, while the spleen and main splenic artery and vein were preserved under direct view. The pancreatic parenchyma was transected with a stapling device (TL-30), and continuous suturing was added to the resected margin. The patient's postoperative course was uneventful; the patient started to eat and walk on postoperative day 2 and was discharged on day 8. It is considered that the combination of hand-assisted and laparoscopy-assisted distal pancreatectomy, with conservation of the splenic artery and vein, is a minimally invasive and clinically useful technique for treating tumors of cystic disease of the pancreas with low-grade malignant potential, or benign solitary neuroendocrine tumors.

Adult↗

PubMed2004

Significant contamination of superoxide dismutases and catalases with lipopolysaccharide-like substances.

Commercially available superoxide dismutase (SOD) and catalase induced remarkable morphological changes in cultured peritoneal resident macrophages (PRMs). The morphology resembled that of cells stimulated with various macrophage-activating substances such as bacterial lipopolysaccharides (LPS). PRMs treated with SOD and catalase for 24 h produced a significant amount of nitric oxide. Peritoneal thioglycollate-exudated macrophages (PEMs) that were induced to die by combined treatment with LPS and cycloheximide (protein synthesis inhibitor) were killed by the treatment with SOD and catalase in the presence of cycloheximide. The effect of SOD and catalase was heat-resistant and was not found in PEMs of the C3H/HeJ mouse, an LPS low responder strain. These results strongly indicated the presence of LPS-like substances in the sample of SOD and catalase used. An examination of commercially available SOD and catalase samples for the presence of LPS-like substances demonstrated that many were contaminated. The LPS contamination was directly confirmed by bacterial endotixins test. It is quite important to take into consideration that commercially available SODs and catalases may be contaminated with LPS and the contaminants may affect the results of studies.

Animals↗

PubMed2004

Radiation-induced apoptosis in peritoneal resident macrophages of C3H mice.

Gamma ray-radiation induced significant apoptosis in peritoneal resident macrophages (PRMs) of C3H/HeJ (C3H) mice, but not in other strains of mice. To investigate the role of DNA damage in the apoptosis, DNA damage was quantified in PRMs by use of the alkaline single-cell gel electrophoresis (Comet) assay. No significant difference was found between C3H and C57Black/6 mice in either radiation-induced DNA damage or repair. Radiation induced apoptosis at the same levels in PRMs of p53 knockout mice and atm knockout mice as those of wild-type C3H mice; however radiation-induced apoptosis was significantly less extensive in the thymocytes of these mutant mice than in those of wild-type mice. Apoptosis was also induced at the same level by an irradiation in PRMs of C3H scid mice as in those of wild-type C3H mice. Therefore it was suggested that radiation-induced DNA damage and TP53, ATM, or DNA-PK-mediated cellular responses occurring downstream thereof were not involved in the radiation-induced apoptotic cell death in C3H mouse PRMs.

Animals↗

PubMed2004

Experimental model for irradiating a restricted region of the rat brain using heavy-ion beams.

Heavy-ion beams have the feature to administer a large radiation dose in the vicinity of the endpoint in the beam range, its irradiation system and biophysical characteristics are different from ordinary irradiation instruments like X-rays or gamma-rays. In order to get clarify characteristic effects of heavy-ion beams on the brain, we have developed an experimental system for irradiating a restricted region of the rat brain using heavy-ion beams. The left cerebral hemispheres of the adult rat brain were irradiated at dose of 50 Gy charged carbon particles (290 MeV/nucleon; 5 mm spread-out Bragg peak). After irradiation, the characteristics of the heavy-ion beams and the animal model were studied. Histological examination and measurement showed that extensive necrosis was observed between 2.5 mm and 7.5 mm depth from the surface of the rat head, suggesting a relatively high dose and uniform dose was delivered among designed depths and the spread-out Bragg peak used here successfully and satisfactorily retained its high-dose localization in the defined region. We believe that our experimental model for irradiating a restricted region of the rat brain using heavy-ion beams is a good model for analyzing regional radiation susceptibility of the brain.

Animals↗

PubMed2003

Induction of DNA double strand breaks by arsenite: comparative studies with DNA breaks induced by X-rays.

Chinese hamster ovary (CHO-K1) cell line and two of its DNA double strand break (DSB) repair deficient mutant cell lines, xrs-5 (Ku80 mutant) and irs-20 (DNA-PKcs mutant), were treated with various concentrations of sodium arsenite for 2.5h, and the colony forming abilities were studied. The wild type cells showed the highest cell survival, while xrs-5 cells showed the lowest survival, and irs-20 cells had an intermediate survival. These results are very similar to the cell survival curves induced by X-rays in these three cell lines. Our data also show the dose dependent induction of DNA-DSBs in these cell lines exposed to arsenite. However, in order to obtain a similar cell survival in wild type cells, twice as many DNA-DSBs are necessary with arsenite exposure when compared with X-rays, suggesting that the types of DNA lesions leading to DSB induced by arsenite are different from those by X-rays. Based on these data, further mechanistic investigations including the involvement of DNA-DSB repair proteins are warranted in the recovery process from arsenic (As) exposure.

Animals↗

PubMed2003

Expression of neural cell adhesion molecule L1 in the brain of rats exposed to X-irradiation in utero.

To gain insight to the cellular and molecular mechanisms involved abnormal neuronal migration induced by irradiation, we investigated expression of neuronal cell adhesion molecule L1 and neuronal migration in the brains through comparison between rats prenatally exposed to X-ray and controls. To observe the pattern of neuronal migration, bromodeoxyuridine (BrdU) was chosen as a marker to label migrating cells. The results showed some of the labeled cells remained in the lower of the cortical plate in the irradiated rats, suggesting that neuronal migration was disrupted by X-ray. To study change of expressing neural cell molecule L1, rat brains were analyzed by SDS-PAGE after isolation of L1 by immunoaffinity chromatography. In the all brain membrane fraction, immunoaffinity purified L1 had bands at 200, 180, 140 and 80 kDa. However, the bands in the irradiated group were very weak when compared with the control. Taking these results into account, abnormal neuronal migration and reduction of expression L1 found in the irradiated brain indicated that migration of neural cells may be largely dependent on radial glial fiber as well as neural cell molecules like L1. A decrease in L1 expression may be one of reasons of abnormal neuronal migration.

Animals↗

PubMed2002

Inhibition of DNA-double strand break repair by antimony compounds.

DNA double strand breaks (DSBs), induced by gamma-irradiation in Chinese hamster ovary cells, were used to examine whether antimony compounds affect the repair of DNA damage. The cells were first incubated with antimony trichloride or antimony potassium tartrate (both Sb(III)) for 2 h, and then irradiated with gamma-rays at a dose of 40 Gy. The DNA DSB was quantified with pulsed field gel electrophoresis immediately after irradiation (non-repair group) as well as at 30 min post-irradiation (repair group). The degree of repair inhibition was determined by the differences in the amount of DNA DSB between non-repair and repair groups. Both antimony compounds inhibited repair of DNA DSB in a dose dependent manner. In trichloride, 0.2 mM antimony significantly inhibited the rejoining of DSB, while 0.4 mM was necessary in potassium antimony tartrate. The mean lethal doses, D(0), for the treatment with antimony trichloride and antimony potassium tartrate, were approximately 0.21 and 0.12 mM, respectively. This indicates that the repair inhibition by antimony trichloride occurred in the dose range near D(0), but the antimony potassium tartrate inhibited the repair at doses where most cells lost their proliferating ability. This is the first report to indicate that antimony compounds may inhibit the repair of radiation-induced DNA DSB.

Animals↗

PubMed2002

Histological and elemental changes in the rat brain after local irradiation with carbon ion beams.

The left cerebral hemispheres of adult Sprague-Dawley rat brains were irradiated at doses of 30, 50, or 100 Gy with charged carbon particles (290 MeV/nucleon; 5 mm spread-out Bragg peak). The spread-out Bragg peak used here successfully and satisfactorily retained its high-dose localization in the defined region. A histological examination showed that necrotic tissue damage, hemorrhage in the thalamus, and vasodilatations around the necrotic region were induced at 8 weeks after 100 Gy irradiation. The regions with tissue damage correlated well with those expected from the radiation-dose distribution, indicating an advantage of charged carbon particles for irradiating restricted brain regions. An X-ray fluorescent analysis demonstrated a decrease in the concentrations of K and P, and an increase in the concentrations of Cl, Fe, Zn in the damaged region at 8 weeks post-irradiation, though no significant changes were observed before 4 weeks of post-irradiation. This may indicate that even the very high radiation doses used here did not induce acute and immediate neuronal cell death, in contrast with ischemic brain injury where acute neuronal cell death occurred and the elemental concentrations changed within a day after the induction of ischemia.

Animals↗

PubMed2002

Types and three-dimensional distribution of neuronal ectopias in the brain of mice prenatally subjected to X-irradiation.

The types and three-dimensional distribution of neocortical ectopias following prenatal exposure to X-irradiation were studied by a histological examination and computer reconstruction techniques. Pregnant ICR mice were subjected to X-irradiation at a dose of 1.5 Gy on embryonic day 13. The brains from 30-day-old mice were serially sectioned on the frontal plane at 15 microns, stained with HE and observed with a microscope. The image data for the sections were input to a computer, and then reconstructed to three-dimensional brain structures using the Magellan 3.6 program. Sectional images were then drawn on a computer display at 240 microns intervals, and the positions of the different types of neocortical ectopias were marked using color coding. Three types of neocortical ectopias were recognized in the irradiated brains. Neocortical Lay I ectopias were identified as small patches in the caudal occipital cortex, and were located more laterally in the neocortex in caudal sections than in the rostral sections. Periventricular ectopias were located more rostrally than Lay I ectopias, and were found from the most caudal extent of the presumed motor cortex to the most caudal extent of the lateral ventricle. Hippocampal ectopias appeared as continuous linear bands, and were frequently associated with the anterior parts of the periventricular ectopias.

Animals↗