Jutaro Takahashi

Development of photoreceptor cells in vitro: Influence and phagocytic activity of homo- and heterogenic pigment epithelium

Abstract Differentiation of photoreceptor cells and phagocytosis by the pigment epithelium were examined in vitro. Neural retina of postnatal 5- and 10-day-old mice was combined with the pigment epithelium and cultured for up to 15 days. Differentiation of the neural retina including lamellar membrane formation in the photoreceptor outer segments was normal for both 5- and 10-day-old albino mice (DD strain) in vitro. The retinas of dystrophic C3H mice when isolated to culture at postnatal day 5 underwent differentiation similar to that observed in the albino of the same age, but when isolated to culture at postnatal day 10, outer segments degenerated rapidly and were absent by 5 days in culture. When the albino 10-day pigment epithelium was cultured with dystrophic neural retina of the same age, or vice versa, photoreceptor outer segments were not formed in either case. However, the pigment epithelium in both cases could phagocytize the heterogenic outer segments. These results suggest, first, that the phagocytic function of the pigment epithelium of the dystrophic C3H mouse to outer segments was normal and second, that the outer segments of the dystrophic mouse were normal in so far as they were recognized and phagocytized by the pigment epithelium of the albino mouse.

Lysosomal behavior in the retina and choroid of spontaneously dystrophic rats

Abstract Lysosomal enzymes in spontaneously dystrophic rats (SDR) which were derived from spontaneously hypertensive rats were studied biochemically and histochemically. The total and free activities of cathepsin D and β-glucuronidase in the retina and choroid of 12-month-old SDR were about two-fold higher than in old Wistar rats. Acid phosphatase activity in the retinal pigment epithelium of SDR was histochemically abnormal in amount of reaction product and in distribution. The role of lysosomal enzymes on the pathology of retinal dystrophy in SDR was considered.

Dose-responsive effect of radiotherapy on the tumor uptake of L-[methyl-11C]methionine; feasibility for monitoring recurrence of tumor

The L-[methyl-11C]methionine [( 11C]Met) uptake by rat AH109A tumor was decreased irradiation-dose dependently from the control to 5, 10 and 20 Gy. After 10 Gy irradiation, the [11C]Met uptake decreased earlier than the tumor volume reduction, and later, it significantly increased earlier than the recurrent growth. Double tracer autoradiography with [14C]Met and 4-[18F]fluoroantipyrine showed a decrease in the [14C]Met tumor uptake without change of blood flow after irradiation. The [11C]Met uptake representing amino acid metabolism is a sensitive indicator for monitoring radiotherapeutic effect on tumor.

BNCT of Malignant Melanoma-Radiobiological Analysis and Data Comparison with Conventional Radiotherapy

Research on selective melanoma neutron capture therapy was initiated by Y. Mishima and his associates, consisting of physicists, chemists, pharmacologists, radiobiologists, and medical scientists. Following basic research of 13 years, this team started the first clinical. trial of melanoma BNCT using10B-paraboronophenylalanine (BPA) in 1987 and have treated 16 patients with various types of melanoma1−4.

A phase II study of cisplatin, oral administration of etoposide, OK-432 and radiation therapy for inoperable stage III non-small cell lung cancer

AbstractBackground. This study was designed to evaluate the feasibility and efficiency of giving cisplatin, etoposide, and OK432 concurrently with conventional radiotherapy (RTx) for patients with inoperable stage III, based on the TNM classification according to the International Union against Cancer staging system for lung cancer (1987) non-small cell lung cancer (NSCLC). Methods. From January 1992 to December 1994,31 patients with cytologically or histologically confirmed stage III NSCLC were treated with RTx, to a total dose of 56–64 Gy, with concurrent daily oral administration of etoposide (25mg) and cisplatin (20mg) for 5 days during the third or fourth week from the start of RTx. The subcutaneous injection of 1 or 2 KE of OK-432, three times a week, for the duration of radiotherapy also started from the beginning of RTx. Results. The number of eligible patients was 29 (26 men and 3 women). Their mean age was 66 years (range, 55–77 years). Six patients had an Eastern Cooperative Oncology Group performance status (PS) of 0; 15, 1; 8; 2. Three were stage IIIA, and 26, stage ITIB. Histologically, 2 had adenocarcinoma, 23, squamous cell carcinoma, and 4, large cell carcinoma. In 27 of the 29 patients, the RTx schedule was completed. There were no treatment-related deaths. Grade 4 toxicity (according to World Health Organisation criteria) leukopenia (700/μl was observed in 1 patient. The response rate was 79% and the median survival was 17 months. Survival rates at 1, 2 and 3 years were 62%, 31%, and 21%, respectively. The local failure rate was 51%. Conclusion. The combination of cisplatin, etoposide, and K-432, given concurrently with conventional RTx is feasible and effective for inoperable stage III NSCLC.

Assessment of Radiation Induced Damage of Mouse Brain Using 18F-2-Deoxy-D-Glucose and 99mTc-Hexamethylpropylene Amine Oxine

The most severe radiation-induced brain damage is brain necrosis. Clinically, it is difficult to differentiate between brain necrosis and recurrent brain tumor1. Radiation brain necrosis is a terminal stage of the brain damage. However, it is not well known the mechanisms underlying the process that produce the brain necrosis after irradiation: i.e. how glucose metabolism and blood flow distribution change after irradiation. We studied the uptake of 18F-2-deoxy-D-glucose (FDG) and 99mTc-hexamethylpropylene amine oxine (HMPAO) in the irradiated brain of the mouse regarding glucose and blood flow distribution, respectively. This study is a feasible for positron emission tomography.