Biomedical subjects

T Shirasaka

Publications and source records attributed to T Shirasaka.

At least 109 records · Page 6Linked to original sources

PubMed1991

Potential anti-AIDS drugs. Lipophilic, adenosine deaminase-activated prodrugs.

Selected acid-stable (2'-fluoro-2',3'-dideoxyarabinofuranosyl)adenine nucleosides containing methyl groups and other lipophilic functions at various positions in the adenine ring were prepared and evaluated as anti-HIV agents. The N6-methyl (1f), N6-benzoyl (1g), and 6-chloro (1i) analogues had modest activity, giving 30-50% protection to ATH8 cells infected with HIV. 2-Methyl (1d), 8-methyl (1h), and 2,N6-dimethyl (1e) substitution, as well as N1-oxide (21) formation, abolished the activity of the parent compound (1a). Several of these compounds, originally designed as agents for treating HIV in the central nervous system, were further investigated as substrates for adenosine deaminase (ADA). Kinetic experiments showed that ADA catalyzed the formation of the anti-HIV active inosine compound 1b from the N6-methyl analogue 1f in a quantitative manner. The anti-HIV activity of 1f and 1i was abolished when the ADA inhibitor, 2'-deoxycoformycin, was added to the test mixture. In contrast, the activity of 1f was significantly enhanced when ADA was added to the test system. These data indicate that 1f and 1i are prodrug forms of 1b in systems containing ADA.

Adenosine Deaminase↗

PubMed1991

Characterization and purification of an immunosuppressive factor produced by a small cell lung cancer cell line.

The present study was undertaken to determine whether small cell lung cancer (SCLC) cell lines produce immunosuppressive factors and, if they do, to characterize the factors. The supernatants of SCLC cell lines, H69 and N857, inhibited not only the blastogenic response of human peripheral blood lymphocytes (PBL) to phytohemagglutinin or concanavalin A, but also the cytotoxic activity of lymphokine-activated killer cells. Neither was inhibited by supernatants from non-SCLC cell lines PC9, QG56, and A549. The immunosuppressive activity of H69 supernatant was stable upon heating to 56 degrees C for 60 min, but labile when heated to 70 degrees C for 10 min. The activity was abolished after dialysis at pH 2.0 or pH 11.0, but not at pH 4.5 or pH 9.0. Digestion with trypsin or proteinase eliminated the immunosuppressive activity, whereas treatment with neuraminidase, mixed glycosidase, DNase or RNase had no effect, suggesting that the immunosuppressive activity in H69 supernatant is due to a protein factor. This H69-derived immunosuppressive factor was isolated by ion exchange chromatography using a gradient of 0.04 to 0.08 M NaCl solution. Gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed the factor to have molecular weights of 98 kD and 102 kD, respectively. These results suggest that SCLC cells produce a potent immunosuppressive factor which may account for the immune deficiency in SCLC patients.

Carcinoma, Small Cell↗

PubMed1991

Synthesis and structure-activity relationships of 2',3'-dideoxypurine nucleosides as potential antiretroviral agents.

In order to study the structure-activity relationships of 2',3'-dideoxypurine nucleosides as potential anti-retroviral agents, various purine derivatives have been synthesized and tested against rous sarcoma virus (RSV) in chick embryo fibroblast (CEF) cells, and against human immunodeficiency virus (HIV) in human CD4+ T cells (ATH8). Some of the new purine derivatives found to be significant antiretroviral activities. And the correlations of activity between anti-RSV and anti-HIV have shown fairly good values so far.

Animals↗

PubMed1991

[Mechanism for synergistic antitumor effect in the combination of 5-fluorouracil with cisplatin in vivo tumor models: from the view of biochemical modulation of 5-fluorouracil].

The mechanism for 5-fluorouracil (5-FU) and cisplatin (CDDP) synergism was investigated in experimental tumor models in rodents in vivo. The reduced folates such as 5, 10-methylenetetrahydrofolate (CH2FH4) and tetrahydrofolate (FH4) which play a significant role in the metabolism of 5-FU were increased about 2 to 3 fold 5 in P388 and Yoshida sarcoma cells of rodents at 24 hours following intraperitoneal administration of CDDP (5 mg/kg), and tritiated 2'-deoxyuridine incorporation into DNA fraction of the CDDP-treated cells was more strongly inhibited than that of non-treated cells after incubation with 5-FU, which indicated the increased formation of a tight ternary complex between thymidylate synthase, FdUMP derived from 5-FU and elevated CH2FH4. The combination of single intraperitoneal CDDP and 6 day-continuous infusion of 5-FU and/or 7 consecutive oral administration 5-FU derivative, BOF-A2, enhanced synergistically the antitumor activity against solid Yoshida sarcomas in rats as compared to each drug alone. These data suggest that CDDP play an important role as not only an effector but also a modulator in biochemical modulation of 5-FU in cellular methionine metabolism and by resultant elevation of intracellular reduced folates.

Animals↗

PubMed1990

Lipophilic halogenated congeners of 2',3'-dideoxypurine nucleosides active against human immunodeficiency virus in vitro.

Four 2-amino-6-halo- and four 6-halo-2',3'-dideoxypurine ribofuranosides (ddPs) were synthesized and tested for in vitro activity to suppress the infectivity, cytopathic effect, Gag protein expression, and DNA synthesis of human immunodeficiency virus (HIV). The comparative order of in vitro anti-HIV activity of the eight 6-halo-ddPs was as follows: 2-amino-6-fluoro, 2-amino-6-chloro, 6-fluoro greater than 2-amino-6-bromo greater than 2-amino-6-iodo, 6-chloro greater than 6-bromo greater than 6-iodo. 2-Amino-6-fluoro-, 2-amino-6-chloro-, and 6-fluoro-ddPs showed a potent activity against HIV comparable to that of 2',3'-dideoxyinosine (ddI) or 2',3'-dideoxyguanosine (ddG) and completely blocked the infectivity of HIV without affecting the growth of target cells. The lipophilicity order was as follows: 2-amino-6-iodo greater than 2-amino-6-bromo greater than 2-amino-6-chloro greater than 2-amino-6-fluoro much greater than ddG greater than ddI. All eight 6-halo-ddPs were substrates for adenosine deaminase (ADA; adenosine aminohydrolase, EC 3.5.4.4). The relative rates of hydrolysis by ADA were as follows: ddA, 2-amino-6-fluoro much greater than 2-amino-6-chloro, 2-amino-6-bromo greater than 2-amino-6-iodo. Taken together, these compounds may represent an additional class of lipophilic prodrugs for ddI and ddG and may also provide a strategy for endowing therapeutic purine nucleosides with desirable lipophilicity.

Antiviral Agents↗

PubMed1990

Synthesis and antiviral activities of carbocyclic oxetanocin analogues.

9-Cyclobutyladenine (4a), cis- and trans-9-[3- (hydroxymethyl)cyclobutyl]adenine (4b) and 9-[3,3-bis(hydroxymethyl)cyclobutyl]adenine(4d) were prepared from the corresponding cyclobutylamine derivatives (1a, 1b and 1d). Guanine congeners (9a, cis- and trans-9b and 9d) and carbocyclic oxetanocin G (1',2'-trans-9f) were also prepared. Carbocyclic oxetanocin A(1',2'-trans-4f), the preparation of which we have already published, and G were found to be active against herpes simplex virus (type 1 and 2) in vitro, while cis-4b and cis-9b showed an in vitro antiretroviral activity against human immunodeficiency virus (type 1).

Adenine↗

PubMed1990

Elevated levels of soluble interleukin-2 receptors in tuberculous pleural effusions.

The levels of soluble IL-2R were measured in pleural fluid from patients with tuberculosis pleurisy. There were significantly elevated soluble IL-2R values in tuberculous pleural fluid as compared with pleural fluid of nontuberculous etiology including malignant, bacterial and transudative pleural effusions. In patients with tuberculous pleurisy, the level of soluble IL-2R in pleural fluid was markedly greater than that in serum. Furthermore, a significant positive correlation was observed between soluble IL-2R levels and adenosine deaminase levels in tuberculous pleural fluid. These findings suggest that elevated levels of pleural fluid soluble IL-2R in tuberculous pleurisy could reflect the local proliferation of activated T-cells and may be clinically useful in the diagnostic procedures for patients with pleural tuberculosis.

Adenosine Deaminase↗

PubMed1990

[Metabolic characteristics and antitumor activity of BOF-A2, a new 5-fluorouracil derivative].

A new 5-fluorouracil (5-FU) derivative, BOF-A2 (3-[3-(6-benzoyloxy-3-cyano-2-pyridyloxycarbonyl)benzoyl]-1- ethoxymethyl- 5-fluorouracil), is consisted of EM-FU (1-ethoxymethyl-5-fluorouracil) which is specifically and gradually converted to 5-FU by the drug-metabolizing enzyme of liver microsomes and CNDP (3-cyano-2,6-dihydroxypyridine), a potent inhibitor of 5-FU degradation in the liver. When BOF-A2 was given orally, blood levels of the main metabolites, EM-FU and CNDP, were maintained for a longer time in the tumor-bearing rats, and eventually the blood 5-FU levels were maintained over 12 hours. Moreover, 5-FU levels in the tumor tissue tended to be maintained higher and longer time over 24 hrs. than those in the blood of rats. Antitumor activity of such characterized BOF-A2 was investigated with transplantable tumors in rodents and DMBA-induced breast carcinomas in rats. The ED 50 (the dose for 50% inhibition of tumor growth) value was about 15 to 25 mg/kg against the tumors tested. These result may suggest that BOF-A2 has potent antitumor activity in accordance to the long persistence of 5-FU level in the tumor tissue.

Animals↗

PubMed1990

[Elevated soluble interleukin-2 receptor and interleukin-2 receptor positive cells in carcinomatous pleural effusions].

Soluble interleukin-2 receptor (IL-2R) level and IL-2R positive (IL-2R+) cells were studied in twenty patients with carcinomatous pleural effusions. The mean value of soluble IL-2R level in carcinomatous pleural effusions was 2930 +/- 1722 U/ml and that in sera was 965 +/- 610 U/ml. Soluble IL-2R level in carcinomatous pleural effusions was found to be significantly higher (p less than 0.001) than that in sera of patients with carcinomatous pleural effusions and that in transudates. Serum soluble IL-2R level in patients with carcinomatous pleural effusions was found, to be significantly higher (p less than 0.001) than that in normal controls (264 +/- 70 U/ml). We also studied IL-2R+ cells in pleural fluids and peripheral blood of patients with carcinomatous pleural effusions. The mean percentage of IL-2R+ cells in carcinomatous pleural fluid lymphocytes was 22.8 +/- 17.8%, as compared with 3.0 +/- 2.2% in peripheral blood lymphocytes of normal controls (p less than 0.001). No significant differences were observed among the cell types of lung cancer examined (adenocarcinoma, squamous, small cell and large cell carcinoma) and no correlation among levels of soluble IL-2R and IL-2R+ cell in either pleural fluid or blood. Our results suggest that in patients with carcinomatous pleural effusions, T cell-mediated active immune mechanisms (IL-2/IL-2R system) against cancer cells are more active in pleural fluid than in peripheral blood.

Adult↗

PubMed1990

[Antitumor activity and metabolism of BOF-A2, a new 5-fluorouracil derivative, with human cancers xenografted in nude mice].

Antitumor activity of BOF-A2, a new 5-fluorouracil (5-FU) derivative, was evaluated with human gastric (H-111 and H-81), colorectal (H-143), pancreatic (H-48) and breast (H-31) cancers xenografted in nude mice. Twenty-five consecutive oral administration of BOF-A2 at 17.5 to 30 mg/kg over 4 weeks caused marked inhibition or regression (over 92% of inhibition rate) to the growth of H-81, H-143 and H-31 cancers. Moreover, BOF-A2 effected to both H-111 and H-48 which have low sensitivity to 5-FU and its known derivatives. Throughout the experiments, the mice seemed to tolerate the consecutive administration of BOF-A2 without severe toxicity. When BOF-A2 was given orally, 5-FU levels in the blood of mice was notably durative for a long time as compared to 5-FU and UFT. Furthermore, 5-FU levels in the tumor tissue tended to increase and persist much more than those in the blood. This maintenance and persistence of objective level of 5-FU in the blood would be concluded to produce a high antitumor effect of BOF-A2 against human cancers xenografted in nude mice.

Administration, Oral↗

PubMed1989

Induction of tumoricidal macrophages from bone marrow cells of normal mice or mice bearing a colony-stimulating-factor-producing tumor.

Nonadherent cells of the bone marrow of C3H/HeN mice were incubated for 3 days with the culture supernatant of an L-929 cell line containing macrophage-colony-stimulating factor. Approximately, 70% of the cells became phagocytic, adherent to plastic dishes and positive for nonspecific esterase staining. The adherent cells exhibited a weak tumoricidal activity against syngeneic mammary carcinoma cells, and the cytotoxicity was strongly augmented by the addition of bacterial lipopolysaccharide to the cytotoxicity assay. The cytotoxicity induced by lipopolysaccharide was also shown to be mediated by Thy1.2- and asialo-GM1+ cells, and was abrogated by the addition of carrageenan. Macrophage-colony-stimulating-factor-producing (D66) and nonproducing (A23) variants were separated from the MM48 tumor line in in vitro culture following limiting dilution. There was no difference between these two variants in either the in vitro growth rate or the susceptibility to macrophage-mediated cytotoxicity. C3H/HeN mice inoculated i.p. with D66 survived longer than did those inoculated i.p. with A23. C3H/HeN mice bearing D66 or A23 as an ascitic form were given i.p. injections of Nocardia rubra cell wall skeleton (N-CWS). N-CWS significantly prolonged the survival period of mice bearing D66, whereas it exhibited no apparent antitumor effect on mice bearing A23. The increase in the cell number of D66 in the peritoneal cavity was significantly retarded, compared with that of A23. In contrast, the number of peritoneal macrophages increased more in D66-bearing mice than in A23-bearing mice. The increase in the peritoneal macrophage number was further augmented by an i.p. injection of N-CWS. Peritoneal macrophages of D66-bearing mice exhibited apparent tumoricidal activity against MM48 tumor cells in the presence of lipopolysaccharide, and the cytotoxicity was significantly augmented by i.p. injection of N-CWS. On the other hand, the responsiveness of peritoneal macrophages to lipopolysaccharide was found to be poor in A23-bearing mice and the tumoricidal activity was only weakly augmented by N-CWS. These results strongly suggest that M-CSF plays an important role not only in the maturation of macrophage progenitors but also in the induction and the accumulation of activated macrophages.

Animals↗

PubMed1989

Augmentative effect of Nocardia rubra cell-wall skeleton on the induction of human lymphokine-activated killer (LAK) cells by the production of LAK cell helper factor(s).

Nocardia rubra cell wall skeleton (N-CWS) was found to synergistically augment lymphokine-activated killer (LAK) cell generation from human peripheral blood mononuclear cells (PBMC) in the presence of a suboptimal dose of recombinant interleukin-2 (rIL-2). N-CWS increased the number of PBMC expressing IL-2 receptor on their surfaces, and the presence of N-CWS at the early stage of the culture period was essential for the exertion of its augmentative activity on the LAK induction. The predominant phenotype of LAK precursor cells responding to N-CWS and rIL-2 was CD3- CD16+. Culture supernatant from N-CWS-stimulated PBMC was found to act as a substitute for N-CWS in the induction of LAK generation in the presence of rIL-2, suggesting that these cells produced a factor capable of augmenting LAK cell induction (LAK helper factor, LHF). LHF was found to have a molecular mass of 29 kDa by gel filtration, and could also function as a killer helper factor to augment allo-antigen-specific cytotoxic T lymphocyte generation from human peripheral blood T cells as well as murine thymocytes. LHF showed no species specificity, indicating that it is different from IL-4. The enhancing activity of LHF was not neutralized with anti-TNF alpha, anti-IL-1 alpha, or anti-IL-1 beta antibodies. Furthermore, no tumor necrosis factor-alpha (TNF alpha), TNF beta, IL-1 alpha, beta, IL-2, IL-5, IL-6 or interferon activity was detected in semi-purified LHF during enzyme-linked immunosorbant assay and biological assays. The present findings indicate that LHF produced from N-CWS-stimulated PBMC is a molecule distinct from TNF alpha, TNF beta, interferon, IL-1, -2, -4, -5, and -6, and suggest that LHF might be a novel lymphokine involved in LAK generation.

Adjuvants, Immunologic↗

PubMed1989

Pharmacokinetic modulation of plasma 5-fluorouracil concentrations to potentiate the antitumor activity of continuous venous infusion of 5-fluorouracil.

Methods for pharmacokinetic modulation of the plasma 5-fluorouracil (5-FU) level to increase antitumor activity during continuous venous infusion (CVI) of low doses of 5-FU were examined in Yoshida sarcoma-bearing rats. These methods were additional infusion of 5-FU for a short period (4 h) or oral administration of UFT or Tegafur during long-term CVI of 5-FU that alone gave a plasma 5-FU level of about 50 ng/ml. The antitumor effect on Yoshida sarcoma was markedly potentiated when an additive dose of 5-FU combined with 3-cyano-2,6-dihydroxypyridine (CNDP), a potent inhibitor of 5-FU degradation, giving a plasma level of about 500 ng/ml, was infused for 4 h. A similar increase in the antitumor effect was observed with oral administration of a conventional dose of UFT during CVI of 5-FU without CNDP, giving a plasma level of 30 to 60 ng/ml. These results suggest that the antitumor effect of CVI of 5-FU can be potentiated by pharmacokinetic modulation of the 5-FU concentration in the blood.

Animals↗

PubMed1989

Synergy of Nocardia rubra cell wall skeleton and interleukin 2 in the in vivo induction of murine lymphokine-activated killer cell activity.

Combination of an ip injection of Nocardia rubra cell wall skeleton (N-CWS) and 3 daily sc injections of human recombinant interleukin 2 (rIL 2) into C3H/HeN mice resulted not only in a significant increase in the number of peritoneal cells (PC) but also in a potent induction of their lymphokine-activated killer (LAK) activity, compared with results obtained with N-CWS or rIL 2 alone. The augmented LAK activity of PC was mediated by nonadherent, nonphagocytic, Thy-1.2+(-)- and asialo GM1+ cells. Nonadherent PC induced by an ip injection of N-CWS bound more 125I-labeled rIL 2 than did normal, nonadherent PC, and generated high LAK activity when cultured overnight with rIL 2. In contrast, normal, nonadherent PC responded only weakly to the overnight stimulation with rIL 2. The phenotype of N-CWS-induced PC with an elevated IL 2 responsiveness was Thy-1.2+(-)-, Lyt-1.1-, Lyt-2.1- and asialo GM1+, suggesting that the N-CWS-stimulated LAK precursors were derived mainly from the NK cell lineage. However, mature T cells may also be involved in this mechanism, because N-CWS failed to augment the IL 2 responsiveness of nonadherent PC in BALB/c nu/nu mice. Treatment of C57BL/6N mice bearing solid Lewis lung carcinoma (3LL) tumors with an intratumoral injection of N-CWS followed by 6 daily sc injections of rIL 2 resulted in the apparent suppression of tumor growth, while N-CWS or rIL 2 alone produced no such suppression. These results suggest that N-CWS augments the antitumor effect of rIL 2 by accumulating LAK precursors and elevating their responsiveness to rIL 2 at the injection site.

Adjuvants, Immunologic↗

PubMed1989

Augmentation of murine lymphokine-activated killer cell induction by a factor produced by Nocardia rubra cell wall skeleton-stimulated T cells.

Four-hour exposure of C3H/HeN mouse spleen cells to Nocardia rubra cell wall skeleton (N-CWS) before 4-day culture with a suboptimal dose of human recombinant interleukin 2 (rIL 2) augmented the induction of lymphokine-activated killer (LAK) cell activity, whereas the treatment with N-CWS alone induced no cytotoxicity. In accordance with this, the IL 2 binding activity of spleen cells was augmented by combined stimulation with N-CWS and rIL 2. The augmented cytotoxicity was mediated by Thy-1.2+, Lyt-1.1-, Lyt-2.1- and asialo GM1+ cells. Cell cultures in diffusion chambers revealed that N-CWS-treated spleen cells produced a LAK cell induction-helper factor (LAK-helper factor, LHF) when cultured with rIL 2. The LHF production required Thy-1.2+, Lyt-1.1+, Lyt-2.1+ and asialo GM1- cells, and the coexistence of unstimulated accessory cells was also essential for the LHF production. Cells responding to both LHF and rIL 2 to generate LAK activity were Thy-1.2-, Lyt-1.1-, Lyt-2.1- and asialo GM1+. The culture fluid of spleen cells stimulated with both N-CWS and rIL 2 contained no tumor necrosis factor (TNF) activity, and the additional stimulation with N-CWS caused no production of either IL 2 or interferon (IFN). Murine recombinant interleukin 1 alpha (Mu-rIL 1 alpha) could not replace the augmentative effect of N-CWS on LAK cell induction. These results suggest that in the presence of rIL 2, N-CWS stimulates murine T cells to produce LHF that is probably distinct from IL 1, IL 2, TNF and IFN.

Adjuvants, Immunologic↗

PubMed1989

Effects of the plasma concentration of 5-fluorouracil and the duration of continuous venous infusion of 5-fluorouracil with an inhibitor of 5-fluorouracil degradation on Yoshida sarcomas in rats.

The correlations of the 5-fluorouracil (5-FU) level in the plasma and the duration of continuous 5-FU infusion with the antitumor activity of 5-FU on Yoshida sarcomas in rats were examined. The circadian variation in the plasma level of 5-FU during continuous infusion was prevented by treatment with 3-cyano-2,6-dihydroxypyridine (CNDP), which strongly inhibits 5-FU degradation. On continuous venous infusion of 2 to 30 mg/kg of 5-FU over 24 h with CNDP at a molar ratio of 1:10 into normal rats, the 5-FU level in the blood was linearly proportional to the dose of 5-FU. The optimum schedule for antitumor activity on Yoshida sarcomas in rats was found to be infusion of 5-FU at 5 mg/kg over 24 h for 6 consecutive days, which gave a plasma 5-FU level of 176 ng/ml. Continuous infusion of 5-FU to give a plasma level of 300 ng/ml for 6 consecutive days from day 5 after implantation of tumor cells, when the tumors weighed about 1.0 g, resulted in complete regression of the tumors in all rats.

Animals↗

PubMed1989

Antitumor activity of BOF-A2, a new 5-fluorouracil derivative.

A compound containing both CNDP (3-cyano-2,6-dihydroxypyridine), an inhibitor of 5-fluorouracil (5-FU) degradation, and EM-FU (1-ethoxymethyl-5-fluorouracil), a masked form of 5-FU, was synthesized and named BOF-A2 (3-[3-(6-benzoyloxy-3-cyano-2-pyridyloxycarbonyl)benzoyl]-1-ethoxy methyl-5- fluorouracil). The antitumor activity of BOF-A2 was investigated in sarcoma-180-bearing mice and Yoshida sarcoma-bearing rats. The ED50 (the dose for 50% inhibition) values of BOF-A2 were 25 mg/kg against sarcoma-180 and 15 mg/kg against Yoshida sarcoma. In vitro studies showed that BOF-A2 was rapidly degraded to EM-FU and CNDP in homogenates of the liver and small intestine of mice and rats, and in sera of mice, rats and human, and the conversion of EM-FU to 5-FU occurred only in the microsomal fraction of rat liver in the presence of NADPH. After oral administration of BOF-A2 at 15 mg/kg to Yoshida sarcoma-bearing rats, BOF-A2 was hydrolyzed to EM-FU, CNDP and 5-FU, and their maximum concentrations in the blood were 2000 ng/ml, 300 ng/ml and 40 ng/ml, respectively. Moreover when BOF-A2 was given at the same dose to tumor-bearing mice and rats, the 5-FU levels in the tumor tissue increased much more than those in the blood and persisted for more than 8 h, whereas those in the blood decreased more rapidly. This accumulation and maintenance of a high level of 5-FU in the tumor tissue are concluded to be related to the high antitumor activity of BOF-A2.

Administration, Oral↗

PubMed1989

[Soluble interleukin-2 receptor levels in patients with pulmonary tuberculosis].

Utilizing an enzyme-linked immunosorbent assay, we detected markedly elevated serum levels of soluble interleukin-2 (IL-2) receptors in patients with untreated pulmonary tuberculosis. In these patients, we also found that serum levels of soluble IL-2 receptors were closely correlated with serum adenosine deaminase levels (r = 0.869, p less than 0.001). Therefore, serum soluble IL-2 receptors appear to reflect the existence of active cell-mediated immunity in pulmonary tuberculosis and may prove to be a useful immunological marker for pulmonary tuberculosis.

Adult↗