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Biomedical subjects

Y Maehara

Publications and source records attributed to Y Maehara.

At least 325 records · Page 18Linked to original sources
PubMed1987

A systematic survey of repetitive sequences abundantly expressed in rat tumors.

A cDNA library made from poly(A)+ RNA of a rat ascites hepatoma cell line, AH60C, was screened with respect to transcribed repetitive sequences by probing with AH60C genomic DNA. Thirty clones, comprising 1.2% of the library, were found to contain repetitive elements. The sequences of 12 clones among them were abundantly expressed in poly(A)+ RNA of AH60C, yet sparse in that of rat normal liver. This differential expression was also noted in case of other tumors and normal tissues tested. These 12 clones could be divided into two classes, depending on whether their sequences were expressed in cytoplasmic poly(A)+ RNA (class I) or not (class II). Rat Alu-like type II (B2) repeats and an unknown repetitive sequence were found in the clones of class I. Adjacent to each of them, we detected two non-repeated sequences, the expressions of which were also activated. The presence of another unknown repetitive sequence was observed in the clones of class II. It is noted that more than one-third of the transcribed repetitive sequences were involved in the predominant expression in tumor cells, whereas the majority of overall transcripts have been found to be common to both transformed cells and their normal counterparts.

Animals↗
PubMed1987

The ATP assay is more sensitive than the succinate dehydrogenase inhibition test for predicting cell viability.

The succinate dehydrogenase inhibition (SDI) test and the adenosine triphosphate (ATP) assay, are both used for in vitro human tumor chemosensitivity testing. We exposed HeLa cells to various concentrations of mitomycin C for 1, 2 or 3 days and found that the decrease in number of viable cells correlated with that of succinate dehydrogenase (EC 1.3.99.1) activity and that of intracellular ATP level of the viable cells. In the dead cells, the ATP level was extensively decreased, but the succinate dehydrogenase activity remained at a level of 24% of that of mitomycin C-untreated viable cells, even on day 3. Thus, the ATP level better reflected the cell viability. In clinical situations, the succinate dehydrogenase activity and the ATP level are assayed in whole cells following exposure to anticancer drugs, therefore the activity remaining in the dead cells must be taken into consideration for the chemosensitive prediction with the SDI test, but not with the ATP assay. This higher sensitivity of the ATP assay will enable a more accurate prediction of cell viability.

Adenosine Triphosphate↗
PubMed1987

1-Hexylcarbamoyl-5-fluorouracil is more cytostatic than 5-fluorouracil against human tumors in vitro.

The sensitivity of HeLa cells and 15 human tumors, including eight gastric cancers, five colorectal cancers and two lung cancers to 1-hexylcarbamoyl-5-fluorouracil (HCFU) was compared with that to 5-fluorouracil (5-FU) in vitro. HeLa cells were doubly sensitive to HCFU, as compared to 5-FU. After the HeLa cells had been treated with 5-FU or HCFU at 77 microM for 1-5 h, the intracellular levels of 5-FU and HCFU were determined, using gas chromatographic-mass spectrometric methods. The level of HCFU plus 5-FU in the HCFU-treated cells was twice as high as the level of 5-FU in the 5-FU-treated cells. The sensitivity to HCFU in 15 tumor tissues varied with the tissue; however, all tissues tested were more sensitive to HCFU than to 5-FU, assessed using the succinate dehydrogenase inhibition test. These results suggest that the hexylcarbamoyl structure facilitates the rapid uptake of HCFU through the cell membrane. HCFU may prove to be more effective for treating each individual patient with a malignant lesion.

Antineoplastic Agents↗
PubMed1987

Comparison between succinate dehydrogenase inhibition test and subrenal capsule assay for chemosensitivity testing.

The chemosensitivity result of the succinate dehydrogenase inhibition (SDI) test was compared with that of the subrenal capsule (SRC) assay in 23 human tumor tissues exposed to adriamycin (ADM), mitomycin C (MMC), cisplatin (DDP) and 5-fluorouracil (5-FU). The chemosensitivity was considered as positive when the succinate dehydrogenase (SD) activity of the drug-exposed cells was decreased to below 50% of that of control cells on day 3 in the SDI test, and the tumor size on day 6 was decreased to below -10% of that on day 0 in the SRC assay. Correlation rates between the decrease of SD activity in the SDI test and the decrease of tumor size in the SRC assay, using 23 evaluable cases in both assays, were r = 0.717 for ADM, r = 0.699 for MMC, r = 0.796 for DDP and r = 0.735 for 5-FU. The correlations of the chemosensitivity results were 73.9% for ADM, 73.9% for MMC, 82.6% for DDP and 60.9% for 5-FU. A positive correlation was noted between the in vitro and in vivo chemosensitivity results. This SDI test can serve as an effective tool for chemosensitivity testing.

Animals↗
PubMed1987

Isolation and characterization of a conserved sequence highly expressed in tumors and growing cells.

We isolated a cDNA clone, pAH1005, originating from the 6.8-kilobases mRNA of the rat ascites hepatoma cell line, AH60C. The sequence was highly expressed in various tumor tissues and tumor lines in rats, mice and humans. In rats, the expression of the sequence was also observed in fetal liver of 7 and 10 days of gestation, to some extent in the regenerating liver, yet was sparse in normal adult tissues. Additionally, this expression was induced when adult rat hepatocytes in primary monolayer cultures proliferated by the addition of epidermal growth factor and insulin. Southern blot analysis showed no major gene amplification and rearrangement between DNAs from hepatoma and normal liver of the same species. In addition, in vitro nuclear transcription assay revealed that a genomic clone corresponding to the pAH1005 hybridized to the nascent RNA from isolated nuclei of AH60C but not from those of normal rat liver. All these observations suggest that the expression of the conserved sequence we isolated is closely associated with cell growth and is regulated at the transcriptional level.

Animals↗
PubMed1987

Carboquone alters the protein synthesis of Chinese hamster V79 cell.

The effect of carboquone (CQ) on protein synthesis in Chinese hamster V79 cells was determined. While the syntheses of higher molecular weight proteins decreased, the relative level of a 43-kilodalton (kd) protein increased following exposure to CQ at the concentration of 0.5 microgram/ml, in a time-related fashion, determined using one-dimensional gel electrophoresis. Using two-dimensional gel electrophoresis, the 43-kd protein may be actin protein, and the syntheses of another two proteins of 8.5/45 and 4.8/270 (designated isoelectric point/molecular weight, kd) were increased in the CQ-treated V79 cells. These changes of the proteins induced by CQ in V79 cells were noted in HeLa cells. Three CQ-induced proteins are candidates for the elucidation of the antineoplastic effect of CQ.

Animals↗
PubMed1987

Poorly differentiated human gastric carcinoma is more sensitive to antitumor drugs than is well differentiated carcinoma.

The chemosensitivities of 41 poorly differentiated gastric cancer tissues were compared with that of 16 well differentiated tissues, using the in vitro succinate dehydrogenase inhibition test. These human tissues obtained at the time of surgery were exposed to six different antitumor drugs: carboquone (CQ), adriamycin (ADM), mitomycin C (MMC), aclacinomycin A (ACR), cisplatin (DDP) and 5-fluorouracil (5-FU). The chemosensitivity was determined as positive when the succinate dehydrogenase (SD) activity of the drug exposed cells was decreased to below 50% of that of control cells, on day 3 of exposure. Decrease in SD activity was remarkable in the poorly differentiated tissues, compared to the well differentiated tissues, exposed to ADM, MMC, DDP and 5-FU. The sensitive rates were higher in the poorly differentiated tissues than in the well differentiated tissues, against all six antitumor drugs. Sixty-three per cent of the poorly differentiated tissues were sensitive to more than three antitumor drugs, in an identical tissue, but the rate was only 19% in the well differentiated tissues. The resistant rates to all drugs tested were 20% in the poorly differentiated and 31% in the well differentiated tissues. This would indicate that patients with a poorly differentiated gastric cancer will probably show a better response to antitumor drugs, compared to those with a well differentiated type.

Aclarubicin↗
PubMed1987

[Chemosensitivity testing for 5-FU and 5-FU derivatives using subrenal capsule assay].

An evaluation was made, using in vivo subrenal capsule (SRC) assay, of the chemosensitivity of 12 human neoplastic tissues including 7 gastric cancers, 2 colo-rectal cancers, 2 lung cancers and 1 breast cancer, exposed to 5-fluorouracil (5-FU) and the 5-FU derivatives: tegafur (FT), UFT and hexylcarbamoyl-5-FU (HCFU). The relative variation of tumor size (delta TS/TS0) was calculated as follows: delta TS/TS0 = (TS6-TS0)/TS0 X 100 (%), where TS6 was the tumor size on day 6 and TS0 that on day 0, and more than a 10% decrease of delta TS/TS0 in the treated group was considered as positive for chemosensitivity. Delta TS/TS0 was decreased to -10.9 +/- 11.3% (mean +/- standard deviation) for 5-FU, -13.0 +/- 16.4% for FT, -19.8 +/- 18.2% for UFT and -18.8 +/- 15.1% for HCFU, and the inhibition of tumor growth following exposure to 5-FU correlated well with that following exposure to 5-FU derivatives (5-FU vs. FT, r = 0.659; 5-FU vs. UFT, r = 0.864; 5-FU vs. HCFU, r = 0.729). However, the sensitivity of each tumor varied; for example, the chemosensitivity was positive for 5-FU derivatives, but negative for 5-FU, in some tissues. The SRC assay appears to be useful for selecting sensitive drugs from 5-FU and 5-FU derivatives for individual cancer patients.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1987

[Comparison between the succinate dehydrogenase inhibition test and ATP assay for in vitro chemosensitivity testing].

The predicted level of cell viability was compared between the succinate dehydrogenase inhibition (SDI) test and the adenosine triphosphate (ATP) assay, both of which are used for in vitro human tumor chemosensitivity testing. After HeLa cells had been exposed to various concentrations of 5-FU for 1, 2, 3 or 4 days, the decrease occurring in viable cell number correlated with that of succinate dehydrogenase (EC 1.3.99.1) activity and that of the intracellular ATP level of the viable cells. In dead cells, the ATP level was extensively decreased, but the succinate dehydrogenase activity remained at a level of 11% of that of 5-FU-untreated viable cells, even on day 4. The cell viability correlated well with the intracellular ATP level, as compared with the succinate dehydrogenase activity. The activity remaining in dead cells must thus be taken into consideration for the prediction of chemosensitivity in the SDI test, but not in the ATP assay.

Adenosine Triphosphate↗
PubMed1986

A new family of LTR-like sequences abundantly expressed in rat tumors.

We report the identification of two genome DNA fragments containing middle repetitive sequences abundantly expressed in various rat tumors but rarely in normal tissues. These fragments included homologous regions which belonged to a new family of long terminal repeat (LTR) like sequences, designated RAL elements; one displayed the solitary type and the other a provirus structure. The element was transcribed in a strand specific fashion and started from the presumptive cap site within the RAL element. The presumptive polyA addition site within the element was also utilized as evidence of the analysis of a cDNA clone containing the RAL element. This evidence suggested that transcriptional control signals within the element were functioning. Run on assay revealed that expression of the element was regulated at the transcriptional level.

Animals↗
PubMed1986

Partial hepatectomy alters sensitivity of rat hepatocytes to 5-fluorouracil.

The sensitivity to 5-fluorouracil (5-FU) and the metabolism of 5-FU in the regenerating rat liver were investigated in vitro. Determination of cell viability using the succinate dehydrogenase inhibition test showed that the hepatocytes of the partially hepatectomized liver were more sensitive to 5-FU, compared to findings in the case of normal liver. The activities of 5-FU phosphorylation of the 3 pathways were higher in the regenerating than in the intact liver and the peak increase was seen 36 h after partial hepatectomy. The activity of 5-FU degradation decreased to about 30% at 36 h and then gradually increased reaching the normal range at 72 h after partial hepatectomy. These results suggest that the metabolic changes of 5-FU may be one of the causes for increased 5-FU susceptibility in the regenerating liver.

Animals↗
PubMed1986

Clinical study of the radioprotective effects of Amifostine (YM-08310, WR-2721) on chronic radiation injury.

We have previously reported that Amifostine, a radioprotective agent, was effective in treating acute radiation mucositis in the head and neck region. We found that when a considerable amount of Amifostine accumulates in the salivary glands, it may be useful in preventing chronic disturbances of salivary secretion. We have observed an increase in the uptake of Ga-67-citrate to the salivary glands when they were irradiated. In this paper, the radioprotective effects of Amifostine, in treating chronic radiation injury of the salivary glands, were studied, using the cessation of an increase in uptake of Ga-67-citrate after radiotherapy as the criterion. The subjects were 105 patients, (280 salivary glands in Ga-scintigrams) with malignancy of the head and neck region treated by irradiation from 1978 to 1984. Ga-negative glands were recognized in 97%, that is, 36 out of 37 glands, before irradiation, and the figure decreased to 19%, seven out of 37, within 1 to 2 weeks (10Gy less than or equal to) after the start of radiotherapy. In patients who were irradiated with more than 30 Gy and in whom scintigraphy was performed at 6 months or more after radiotherapy, Ga-negative glands were recognized in 18 out of 41 glands, 44%, with Amifostine, compared with 13%, four out of 32 glands, without Amifostine. A difference was recognized between these two groups in the negative change in Ga-67 uptake after radiotherapy (p less than 0.05). These facts suggest that Amifostine may have a radioprotective effect on chronic radiation injury.

Amifostine↗
PubMed1986

Intratumoral injection of thymidine: enhancement of the antitumor activity and incorporation of 5-fluorouracil into tumor RNA in a murine tumor system.

Intratumoral injection of thymidine (dThd) into mice bearing an Ehrlich ascites solid tumor in combination with an ip injection of 5-fluorouracil (FUra) was performed to investigate the following: (a) whether intratumoral injection of dThd would increase both the incorporation of FUra into tumor RNA and the antitumor activity of FUra as effectively as ip injection of dThd, and (b) whether intratumoral injection of dThd would have a selective advantage for increasing the incorporation of FUra into the tumor RNA, relative to normal tissue RNA. Pulse-labeling with [3H]FUra at different times after dThd injection indicated that the most effective incorporation of FUra into the tumor RNA occurred with both intratumoral and ip injection of dThd, when FUra and dThd were given simultaneously. The amount of FUra-containing RNA [(FU)RNA] was dThd dose-dependent and reached a maximum at a dThd dose of 100 mg/kg, in the case of either intratumoral or ip injection. The maximal level with intratumoral injection of dThd was twofold higher than the level with ip injection and at least fivefold higher than the level achieved with FUra alone. In a time course study, the amount of (FU)RNA formed after intratumoral injection of dThd was comparable to the level obtained with ip injection, which was fourfold to sixfold greater than that seen with FUra alone. Furthermore, in the four normal organs (bone marrow, intestine, kidneys, and lungs) the amount of (FU)RNA formed after intratumoral injection of dThd was markedly lower than the level with ip injection. Assay of FUra degradation products revealed low levels of FUra catabolism in the tumor tissue compared to liver. In addition, therapy experiments showed that the antitumor activity of FUra was increased 17-fold by coadministration of dThd by either route.

Animals↗