Biomedical subjects

Yuta Shibamoto

Publications and source records attributed to Yuta Shibamoto.

39 records · Page 3Linked to original sources

PubMed2002

Effect of a hypoxic cell sensitizer doranidazole on the radiation-induced apoptosis of mouse L5178Y lymphoma cells.

We investigated the sensitizing effect of the 2-nitroimidazole analogue doranidazole, a new hypoxic radiosensitizer, on radiation-induced apoptosis in L5178Y cells. Apoptosis was assessed by checking DNA ladder formation, the presence of sub-G1 peaks in flow cytometry, and chromatin condensation. A radiosensitizing effect of doranidazole was also confirmed by a soft-agar colony assay of surviving cells. In the assay of DNA ladder formation, DNA fragmentation was observed following irradiation under an aerobic or hypoxic condition with or without doranidazole. The proportions of the cells at the sub-G1 peak in a flow cytometric measurement was not very different among the irradiations at 5 Gy under the aerobic condition, 15 Gy under hypoxia, and 10 Gy with 1 mM doranidazole under hypoxia. The fraction of cells with chromatin condensation was found to be significantly increased with doranidazole up to 3 mM when applied under hypoxic irradiation, but did not increase even at 10 mM. The sensitizer enhancement ratio was estimated to be about 1.7 with a concentration of 1 mM. This enhancement ratio was not different from that observed by assaying cell survivals. On the other hand, doranidazole showed no radiosensitizing effect under aerobic conditions with 1 mM. In conclusion, the radiation-induced apoptosis of L5178Y cells was enhanced by doranidazole under hypoxia.

Animals↗

PubMedDate not supplied

Multivariate analysis of dissemination relapse of medulloblastoma and estimation of its time parameter for craniospinal irradiation.

PURPOSE: To examine in retrospect prognostic factors influencing meningeal dissemination relapse of medulloblastoma (MB) and to estimate time parameter gamma/alpha of the biologically effective dose for fractionated craniospinal irradiation (CSI). MATERIALS AND METHODS: Fifty-eight patients with MB who had been treated at our six hospitals from 1980 to 1990, were analyzed by the proportional hazards model consisting of radiation factors of both CSI and local irradiation (LI), sequential CSI time-lag, and eight non-radiation factors (gender, age, performance status, T-stage, dissemination score, extent of resection, and use of chemotherapy and immunotherapy). The gamma/alpha for CSI was estimated by the profile likelihood method using the maximum value of conditionally calculated time-incorporated biologically effective dose, tBEDmax, of the field treated with the least dose. RESULTS: Dissemination relapse was seen in 23 (40%) patients. Nineteen disseminations occurred within four years, and the cumulative dissemination-free rate was 64% at five years. The site of initial dissemination relapse was both cranial and spinal in 13 patients (57%). Dissemination relapse was accompanied with local failure in 43% (10/23) of patients, and four of them were seen later than four years. In the multivariate analysis, significant prognostic factors were dissemination score (p=0.0008) and total dose of CSI (p=0.018). The estimate of gamma/alpha for CSI was about 0.2 Gy/day in BED units. In another multivariate analysis including the best-fitted tBEDmax, significant prognostic factors were dissemination score and the tBEDmax of both CSI (p=0.021) and LI (p=0.024). CONCLUSION: This analysis indicated that the dissemination score, total dose of CSI, and tBEDmax of both CSI and LI were significantly prognostic for dissemination relapse of MB. The estimate of gamma/alpha for CSI was smaller than that derived from our previous analysis for LI. However, in order to estimate the time factor for CSI more precisely, a larger group of patients treated with concurrent CSI is needed.

Adolescent↗

PubMedDate not supplied

Radiographic findings of aberrant right subclavian artery initially depicted on CT.

PURPOSE: To evaluate the radiographic findings of aberrant right subclavian artery (ARSCA) initially depicted on CT. METHODS: Twenty-five cases incidentally diagnosed during CT between June 1993 and May 2001, were examined. They included 13 men and 12 women aged from 29 to 84 years old (mean, 63 years). Three findings were evaluated on posteroanterior radiographs: 1) oblique edge, 2) vessel through the trachea, and 3) mass effect. On lateral radiographs, the following findings were evaluated: 1) posterior tracheal imprint, 2) retrotracheal opacity, and 3) aortic arch obscuration. RESULTS: On the posteroanterior radiographs, oblique edge, vessel through the trachea, and mass effect were observed in 32% (8/25), 44% (11/25), and 20% (5/25) of cases, respectively. On the lateral radiographs, posterior tracheal imprint, retrotracheal opacity, and aortic arch obscuration were observed in 95% (18/19), 58% (11/19), and 37% (7/19), respectively. On posteroanterior radiographs, normal cases were most frequent (40%). In contrast, lateral radiographs demonstrated at least one abnormality in all cases. As a variation of posterior tracheal imprint, the long-segment type of compression was observed in 32%. CONCLUSIONS: We consider detailed interpretation of the posterior tracheal edge on lateral radiographs to be important in diagnosing cases of mild ARSCA.

Female↗