Search PubMed⌕ Search

Biomedical subjects

K Sasai

Publications and source records attributed to K Sasai.

At least 181 records · Page 10Linked to original sources
PubMed1989

[Hypoxia and reoxygenation in experimental tumors].

Hypoxic fractions (HF) and reoxygenation of various murine tumors were studies using a paired survival assay. All irradiations were given to whole-body of mice without anesthesia or physical restraint, both of which can increase HF artificially. HF's of 4 different tumors of 1 cm in diameter were between 4.5% and 14%. Thus, variation of HF due to tumor type was quite small. HF was roughly correlated with tumor size and proportion of necrotic areas. Reoxygenation was examined in two tumor systems, and it occurred rapidly (within 1 hr after radiation) in one tumor but rather slowly in another.

Animals↗
PubMed1989

Combined effects of radiation and IUdR on experimental liver tumors and hepatocytes.

IUdR, a thymidine analogue, increased the radiosensitivity of SCC VII tumor cells. A decrease in Dq value of cell survival curve was more prominent compared with that in D0 value. However, in experimental liver tumors made by transplanting SCC VII tumors, the decrease in D0 value was apparent. Proportion of IUdR incorporated tumor cells in the liver increased with an increase in number of IUdR injections, and reached 52% after five administrations of the drug at an interval of twelve hours. However, few hepatocytes incorporated IUdR. The response of hepatocytes to radiation was evaluated by micronucleus appearance frequency. To accelerate the appearance of micronucleus in hepatocytes, partial hepatectomy was performed immediately after irradiations. No differences in micronucleus frequency were observed between the treated and untreated with IUdR.

Animals↗
PubMed1988

Peripheral blood monocyte/macrophages and serum tumor necrosis factor in Kawasaki disease.

We analyzed the populations of peripheral blood monocyte/macrophages in 27 patients using a fluorescence-activated cell sorter, and investigated the possibility, in another 30 patients, that tumor necrosis factor (TNF) might be detectable in serum during the acute phase of Kawasaki disease (KD). Percentages of peripheral blood monocyte/macrophages among mononuclear cells and serum TNF levels were both seen to increase during the acute phase of the illness in patients with KD. The percentage of TNF positive cases in KD patients with coronary involvement was higher than that of patients without coronary involvement. These results suggest the possibility that immunological activation, accompanied by the secretion of TNF from monocyte/macrophages, is an important predisposing condition for the exacerbation of vascular damage in KD.

Antigens, Differentiation↗
PubMed1988

[Developments in the experimental methods of evaluating hypoxic cell sensitizers].

Recent developments in the evaluation methods for hypoxic cell sensitizers were reported with emphasis on the following 3 points. (1) A new sensitizer-screening system consisting of the EMT 6 single cell, spheroid, and solid tumor was proposed by us and was found to be a useful, sophisticated system. (2) In the in vivo experiments, irradiation conditions for mice and the drug dose level influenced the hypoxic fraction of tumors significantly. Investigators must always take these facts into consideration when doing in vivo experiments. (3) Three new compounds recently developed in Japan proved to be superior to misonidazole.

Animals↗
PubMed1988

Organ culture of the chicken colon: morphological observations after 24 and 48 hours of culture.

Colons from chickens, four weeks old, can best be maintained for 48 hours in a serum-free organ culture system using Trowell T8 medium-agar sheet at 25 degrees C. As determined by light microscopy as well as scanning and transmission electron microscopies, mucosal architecture involving classical ultrastructure of chicken colonic mucosa was preserved. Based on the morphological findings, it became evident that this organ culture system using Trowell T8 medium at 25 degrees C can be successfully used as an in vitro experimental model for as long as 48 hours. The organ culture system could be a useful tool in investigating mucosal function and mucosal response to pathogens.

Animals↗
PubMed1988

Organ culture of chicken colon: physiological observations after 24 and 48 hours of culture.

Colon from chickens, four weeks old, can best be maintained for 24 hours in a serum-free organ culture system using Trowell T8 medium-agar sheet at 25 degrees C. From physiological observations of DNA and protein synthesis it was found that the protein content of colonic explants did not change in up to 48 hours of culture while the DNA content did not change in up to 24 hours but decreased significantly to two thirds of the controls in 48 hours of culture. The organ culture system can be maintained satisfactorily for 24 hours.

Animals↗
PubMed1987

Organ culture of chicken cecum: morphologic and physiologic observations after 24 and 48 h of culture.

Cecum from chickens, 4 wk old, can best be maintained for 24 h in a serum-free organ culture system using Trowell T8 medium agar sheet at 25 degrees C. As determined by light microscopy as well as scanning and transmission electron microscopy, mucosal architecture involving classic ultrastructure of chicken cecal mucosa was preserved. Protein content of cecal explants did not change up to 48 h of culture. DNA content of cecal explants did not change up to 24 h of culture but decreased significantly to two-thirds of control in 48 h of culture. Based on the morphologic and physiologic findings, it became evident that this organ culture system using Trowell T8 medium at 25 degrees C can be successfully used as an in vitro experimental model for as long as 24 h. The organ culture system could be a useful tool, from the structural integrity of ceca observed in this study, in investigating mucosal function and mucosal response to drugs, carcinogens, trophic factors, and pathogens.

Animals↗
PubMed1987

Application of computed tomography for diagnosis of alveolar bony defects.

This study was performed to evaluate the usefulness of computed tomography (CT) in analyzing the three-dimensional structure of alveolar bony defects. The result showed that differences between CT film and actual readings from the cusp ridge to the bone crest were negligible, and the reading on CT film was underestimated approximately 1 mm at the distance from the cusp ridge to the bottom of the bony defect. By reading a series of CT films, one can easily evaluate the type of bony defects. Therefore, application of CT maybe useful for analyzing three-dimensional structure and diagnosis of the alveolar bony defects.

Adult↗
PubMed1987

Evaluation of various types of new hypoxic cell sensitizers using the EMT6 single cell-spheroid-solid tumour system.

Eleven new hypoxic cell sensitizers representative of those developed in Japan between 1980 and 1985 were evaluated in vitro and in vivo in comparison with misonidazole (MISO), SR-2508, Ro 03-8799, and ANT (2-amino-5-nitrothiazole). The new compounds included 2-nitroimidazole nucleoside analogues, nitrotriazoles and other nitroaromatics, non-nitro compounds, and electron-affinic compounds that readily intercalate DNA. The sensitizing activity in the EMT6 single cells correlated not only with the reduction potential but, for some compounds, also with the reactivity with non-protein sulphydryls. The sensitizers were also tested using the EMT6 spheroids and solid tumours. The patterns of changes in sensitizer enhancement ratios (SERs) for single cells, spheroids, and solid tumours were classified into two types: (1) SERs for the three testing systems were similar; and (2) SERs decreased in the order of: single cells, spheroids, and solid tumours. Only nitroimidazole and nitrotriazole derivatives belonged to the former type. RK-28 and RK-29, 2-nitroimidazoles with sugar analogue components, had in vivo effects almost equal to those of MISO. Also 3- and 4-nitrotriazole derivatives had definite in vivo effects.

Animals↗
PubMed1987

[Present status of hypoxic cell sensitizers and PLDR inhibitors].

Clinical and basic studies in hypoxic cell radiosensitizers and potentially lethal damage (PLD) repair inhibitors were reviewed. Most clinical trails on misonidazole (MISO) show that the toxicity of MISO is a major reason for failure in the trials and an adequate selection of tumors is needed for the success. Phase III studies on SR-2508 and RO 03-8799, less toxic and more effective sensitizers, are in progress. AK-2123 and RK-28 developed in Japan are drugs with similar clinical applicability of MISO. Thiol depletion of tumors is one of the way to increase the radiosensitization. The measurement of intercapillary distance on histopathological microslide is a valuable method to select the tumors containing much hypoxic cell fractions. Stable and effective chemicals as MISO in hypoxic cell sensitization must be developed to investigate the clinical applicability of PLD repair inhibitors.

Animals↗