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Biomedical subjects

N Yamauchi

Publications and source records attributed to N Yamauchi.

At least 127 records · Page 7Linked to original sources
PubMed1988

Antagonistic effect of somatostatin on corticotropin-releasing factor-induced anorexia in the rat.

The effect of somatostatin on corticotropin-releasing factor (CRF)-induced anorexia was examined in rats. Intracerebroventricular (icv) administration of 0.11 nmol and 0.21 nmol ovine CRF significantly suppressed food intake of 24 h-starved rats. Icv administration of 0.31 nmol somatostatin 14 and somatostatin 28 partially reversed suppression of food intake induced by icv injection of 0.21 nmol CRF in 24 h-starved rats. These results suggest that somatostatin may counteract the suppressive effect of CRF on food intake within the central nervous system.

Animals↗
PubMed1988

Sequential changes in serum thyroglobulin, triiodothyronine, and thyroxine following partial thyroidectomy for nontoxic nodular goiter.

The sequential changes in serum thyroglobulin (Tg), thyroxine (T4), free thyroxine (FT4), triiodothyronine (T3) and thyrotropin (TSH) were evaluated in ten patients on whom partial thyroidectomy for nontoxic nodular goiter had been performed. These changes were compared with those in ten patients who underwent upper abdominal surgery (cholecystectomy) under similar anesthesia, and whose calorie and fluid intake was similar until at least 48 hours after surgery. In agreement with previous reports, marked elevations in serum Tg that reached peak concentration (660 to 1350 ng/mL) at one or two hours after the thyroid incision (mean +/- SD; 787 +/- 304.0 ng/mL and 839 +/- 345.7 ng/mL, respectively) were observed. On the other hand, the significant but minimal increases in serum T4 and FT4 were observed at 24 hours (P less than .001 and P less than .001, respectively), 48 hours (P less than .01 and P less than .001, respectively), and 72 hours (P less than .01 and P less than .01, respectively) after the thyroid incision compared with the level just prior to the thyroid incision. Similarly, serum T3 also increased significantly at 6 to 168 hours after the thyroid incision (P less than .01, P less than .05, P less than .05, P less than .05, and P less than .05, respectively). These increases in serum T4, FT4 and T3 were not observed in the cholecystectomy patients. The mean serum TSH levels at 24 to 72 hours after thyroid incision and those at 6 to 48 hours after the abdominal incision were significantly decreased compared with those before thyroid and abdominal incision, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Self-induction of defense against tumor necrosis factor cytotoxicity in tumor cells and normal cells.

Investigation on the effect of TNF on RNA and protein synthesis by tumorigenic and normal cell lines showed their synthesis in tumor cells to be increased at 12 h and to peak at 24 h of incubation with TNF, while that in normal diploid fibroblast (HEL) cells was apparently unaffected by the presence of TNF. The increase correlated with cell susceptibility to cytotoxic effect by TNF. Artificial inhibition of either RNA or protein synthesis by L-M cells, by addition of actinomycin D or cycloheximide, increased the cytotoxic effect of TNF and thus suggested that the elevated RNA and protein synthesis is related not to the cytotoxic reaction itself but rather to a defense mechanism. Similar incubation of HEL cells with TNF in the presence of either inhibitor resulted in the occurrence of cytotoxicity not observed with TNF alone, thus suggesting the existence of a defense mechanism in normal, TNF-resistant cells which is absent or greatly weakened in tumor cells.

Animals↗
PubMed1988

Therapeutic effect of OK-432 induced endogenous TNF on tumor bearing mice and cancer patients.

The therapeutic effect of OK-432 induced endogenous TNF on tumor bearing mice and cancer patients was investigated. OK-432 (10 KE/mouse) was administered intraperitoneally to Balb/c mice 7 days prior to the transplantation of Meth A cells (1 x 10(6)/mouse) into the abdominal cavity. And at day 1 of tumor inoculation, 1 KE/mouse of OK-432 was administered intraperitoneally. The significant prolongation of life span was observed in these mice. On the basis of these observation, therapeutic effect of endogenous TNF on cancer patients was clinically evaluated. OK-432 was administered intraperitoneally or intrapleurally to cancer patients with peritonitis carcinomatosa or pleuritis carcinomatosa 4 times (10KE each) every other day and 50KE of OK-432 was readministered with the interval of 7 days. An appreciable activity of TNF was detected in peritoneal fluids or pleural effusion, and the significant decreasing of these fluids was observed. It is therefore concluded that these therapeutic approach may well be taken into account in treatment of cancer.

Aged↗
PubMed1988

Cytocidal mechanism of TNF: effects of lysosomal enzyme and hydroxyl radical inhibitors on cytotoxicity.

The participation of lysosomal enzymes, hydroxyl radicals, and mitochondrial respiration in the cytocidal effect of TNF on tumor cells was investigated. The cytotoxicity of TNF on L-M cells was clearly reduced by lysosomotropic agents, DMSO (hydroxyl radical scavenger), NDGA (lipoxygenase inhibitor), and sodium azide (mitochondrial respiration inhibitor). The results suggest that lysosomal enzyme and hydroxyl radicals play an important triggering role in the destruction of tumor cells by TNF, and that the process of destruction might require ATP.

Ammonium Chloride↗
PubMed1988

Synergistic cytotoxicity of recombinant human TNF and various anti-cancer drugs.

A synergistic increase in the cytotoxic effects of recombinant human tumor necrosis factor (rH-TNF) and anti-cancer drugs was demonstrated in vitro. The cytotoxicity of rH-TNF against L-M cells in combination with Mitomycin C (MMC), Adriamycin (ADM), Cytosine arabinoside (Ara-C), Actinomycin D (ACD), Daunomycin (DM), Cisplatin (CDDP), Vincristine (VCR), and 5-Fluorouracil (5FU), based on the concentration necessary for 50% inhibition of cell growth (IC50), was 4 to 347 times as high as that of rH-TNF alone. The results suggest that combination therapy including rH-TNF and anti-cancer drugs may be of value in the treatment of malignancy in human patients.

Antineoplastic Agents↗
PubMed1988

Antitumor synergism between recombinant human tumor necrosis factor and recombinant human interferon-r.

We studied the antitumor synergy of human recombinant tumor necrosis factor (TNF) in combination with recombinant interferon-r (IFN-r) both in vitro and in vivo. Synergistic cytotoxic effects were observed in all three of the human tumor cells lines examined. Binding assays of KB human nasopharynx carcinoma cell surface receptors for TNF revealed that IFN-r increased the number of receptors and suggest that this increase may play a key role in the synergism. Furthermore, a remarkable antitumor effect by TNF in combination with IFN-r was observed in nude mice implanted with KB cells. The results thus suggest that TNF and IFN-r in combination may provide the basis for a useful antitumor therapeutic regimen.

Animals↗
PubMed1988

[Continuous internalization of TNF receptors in a human myosarcoma cell line].

The cell dynamics of the receptor on tumor necrosis factor (TNF) were studied with the use of TNF-sensitive KYM cells derived from human myosarcoma. With receptor synthesis inhibited by cycloheximide, the half-life of the surface TNF receptor was 2h in the absence of TNF and 30min in its presence, suggesting that the TNF receptor was non-recycling and that its internalization was accelerated by TNF. During cell incubation with suppression of TNF receptor degradation by chloroquine, the number of surface TNF receptors remained approximately constants, but the total number of surface and internal TNF receptors increased gradually, at 3h reaching 1.5 times of the initial number, thus suggesting continuous synthesis, externalization, internalization, and degradation of the TNF receptor in the absence of cycloheximide. When the cells were incubated with 125I-TNF, the intracellular quantity of the pulse-labeled TNF-receptor complex promptly increased, reaching a maximum at 20 min, and then declining gradually. Thus, it was confirmed that the TNF receptor is internalized as a TNF-receptor complex in the presence of TNF. In incubation with suppression of protein synthesis by cycloheximide following surface TNF receptor digestion by trypsin, TNF receptors reappeared on the cell surface, increasing in the number to a peak level at 60 min and gradually decreasing. The cells previously exposed to cycloheximide with or without TNF showed no recurrence of surface TNF receptors, suggesting that the TNF receptor is non-recycling. The results thus suggest that the TNF receptor is continuously internalized and degraded intracellularly by lysosomes without being recycled regardless of the presence or absence of TNF, and further that its internalization is accelerated when it is part of the TNF-receptor complex.

Cell Line↗
PubMed1988

Analysis of the TNF receptor on KYM cells by binding assay and affinity cross-linking.

The existence of a tumor necrosis factor (TNF) receptor on KYM human myosarcoma cells was elucidated by Scatchard plot and cross-linking analysis. The average number of specific binding sites per cell was 15,300 and the apparent dissociation constant Kd was 4.0 X 10(-10) M. The estimated relative molecular mass of a TNF receptor on KYM cell was approximately 95,000.

Cell Line↗
PubMed1988

[Implication of hydroxyl radical production in the killing of tumor cells by recombinant human tumor necrosis factor].

We investigated the effect of recombinant human tumor necrosis factor (rhTNF) on hydroxyl radical production by established cell lines in vitro, and its implication in the killing of tumor cells by rhTNF. During incubation of TNF sensitive mouse tumorigenic fibroblast L-M cells in the presence of rhTNF, hydroxyl radical production detected by the evolution of methane gas from dimethyl sulfoxide increased gradually, at 18 hours reached 1.8 times of that in the absence of rhTNF. This increase of hydroxyl radical production was dependent on the concentration of rhTNF. The addition of iron chelator 2,2'-bipyridine which inhibits iron catalized Fenton reaction and inhibits hydroxyl radical generation, suppressed both the increase of hydroxyl radical production and the cytotoxicity induced by rhTNF. The increase of hydroxyl radical production stimulated by rhTNF was also detected in TNF sensitive human myosarcoma derived KYM cells as well as in L-M cells, but no change was detected in TNF insensitive human embryonic lung fibroblast HEL cells. These results suggest that rhTNF induced increase of hydroxyl radical production may play a significant role in the mechanism of tumor cell killing by rhTNF.

Cell Line↗
PubMed1988

[Anti-tumor effect of human recombinant TNF].

In this article, the clinical effects of rH-TNF on various cancer patients and the mechanism of self-induction of defense against rH-TNF cytotoxicity in tumor cells and the counter measures against this are reviewed. 1) Clinical effects of rH-TNF Intratumoral administration of rH-TNF was performed in 7 patients and clinical efficacy (PR + MR) was observed in 3/7 (42.9%). Also a reduction of leukemia cells in peripheral blood was observed in all 4 leukemia patients following intravenous (i.v.) administration of rH-TNF. Furthermore, in 2 multiple myeloma patients, the myeloma protein and plasma cells in bone marrow were reduced by i.v. administration of rH-TNF. 2) Self-induction of defense against rH-TNF cytotoxicity Investigation of the effect of TNF on RNA and protein synthesis by tumorigenic and normal cell lines showed that their synthesis in tumor cells was increased at 12 h and peaked at 24 h of incubation with TNF, while that in normal diploid fibroblast (HEL) cells was apparently unaffected by the presence of TNF. Artificial inhibition of either RNA or protein synthesis by L-M cells, upon addition of Act D or CHI increased the cytotoxic effect of TNF, thus suggesting that the elevated RNA and protein synthesis is related not to the cytotoxic reaction itself but rather to a defense mechanism. Similar incubation of HEL cells with TNF in the presence of either inhibitor resulted in the occurrence of cytotoxicity not observed with TNF alone, thus suggesting the existence of a defense mechanism in normal, TNF-resistant cells which is absent or greatly weakened in tumor cells. 3) Combination therapy of rH-TNF with various anticancer drugs. A synergistic increase in the cytotoxic effects of rH-TNF and anti-cancer drugs was demonstrated in vitro The cytotoxicity of rH-TNF against L-M cells in combination with MMC, ADM, Ara-C, ACD, DM, CDDP, VCR and 5-FU was 4 to 347 times as high as that of rH-TNF alone. These results suggest that combination therapy including rH-TNF and anti-cancer drugs may be of value in the treatment of malignancy in human patients.

Antineoplastic Agents↗
PubMed1987

Cell cycle specificity of tumor necrosis factor and its receptor.

Phase specificity in the TNF cytotoxic effect and the number of TNF binding receptors was investigated using L-M cells incubated synchronously from the S phase. TNF cytotoxicity was observed to occur at various levels during the cell cycle, with peak effect in the G2-M phase. Analysis with 125I-labeled TNF to determine the number of receptors binding TNF in the various cell phases shewed a phase specificity with the maximum number occurring in the G2-M phase, similar to the peak in cytotoxicity. The results suggest the existence of a cell cycle specificity in the cytotoxicity of TNF which is apparently related to changes in the number of receptors capable of binding TNF.

Animals↗
PubMed1987

Desensitization of rat pituitary somatotrophs to growth hormone-releasing factor occurs in vitro.

Desensitization of rat pituitary somatotrophs to human growth hormone-releasing factor (hGHRF) was investigated using cultured rat anterior pituitary cells. Growth hormone (GH) release decreased but the production of cAMP was still induced in response to subsequently added 10(-9) M hGHRF from cells pretreated with hGHRF at concentrations ranging from 10(-11) to 10(-7) M for 4 h. Desensitization to 10(-9) M hGHRF was also observed in cells pretreated with 10(-9) M hGHRF for 4 h in the presence of 2 mM EGTA, 10 ng/ml nifedipine or 10(-9) M somatostatin-28, which decreased GH release during pretreatment. Forskolin and A23187, at concentrations of 10(-6) M and 10(-4) M, respectively, stimulated GH release from cells pretreated with hGHRF to the same extent as that from the control cells. These results, therefore, suggest that desensitization to GHRF occurs regardless of the presence of releasable GH pool and that some changes such as uncoupling of GHRF receptors with adenylate cyclase and decreased sensitivity to cAMP of cAMP-dependent protein kinase of the secretory mechanism of GH, in addition to the decrease in releasable GH pool and down regulation of GHRF receptors, may be involved in the desensitization mechanism.

Animals↗
PubMed1987

[Analysis of the signalling pathway of TNF in normal cells and tumor cells].

The internalization process and intracellular distribution of 125I-labeled TNF, in L-M (murine tumorigenic fibroblasts, highly sensitive to TNF cytotoxicity) cells and in HEL (human embryonic lung cells, non-sensitive to TNF cytotoxicity) cells bearing TNF receptor, were elucidated by pulse-chasing and by Percoll density gradient centrifugation. Effect of TNF treatment on the RNA and protein synthesis of target cells was also studied using 3H-UDR and 35S-methionine incorporation. In both L-M and HEL cells, receptor-bound 125I-TNF was rapidly internalized and delivered to lysosomes within 15-30 min, followed by degradation and release into the culture medium. RNA synthesis and protein synthesis were not affected by TNF treatment in HEL cells, but marked stimulation (3.5 times and 4.2 times, respectively) was observed in L-M cells.

Animals↗
PubMed1987

[Anti-tumor effect and mechanism of action of the tumor necrosis factor (TNF)].

TNF is cytokine derived from macrophages and shows much promise for use in cancer therapy because of its marked antitumor effects and its high specificity to tumors. The clinical application (Phase I-II) of TNF has been started because human recombinant TNF (rH-TNF) can be produced on a large scale. In spite of notable antitumor effects, little is known concerning the mechanism of its cytotoxic action. In this article, the antitumor effects of rH-TNF against human and murine tumors, the mechanism of its action and the synergistic effects of rH-TNF in combination with IFN-gamma, various anticancer drugs or with hyperthermia are reviewed.

Cell Line↗
PubMed1987

[The mechanism of action of tumor necrosis factor (TNF) on tumor vascularity--study using a transparent chamber].

Effects of human recombinant TNF on the tumor blood vessels and on the thrombus formation were investigated in relation to its mode of antitumor action against Meth-A sarcoma transplanted in BALB/c mice. The extent of the blood vessel lesion was evaluated by using transparent chamber placed in the mouse skin. Bleeding, hyperemia and congestion were observed at 1-2h, 4-6h and 24h after TNF (1 X 10(4)U/mouse) administration, respectively. In contrast, no histological changes in the normal blood vessels were observed microscopically following TNF injection. Thrombus formation was evoked in the tumor vessels 4h after TNF injection. However, when thrombus formation was prevented by heparin, no difference was observed among antitumor action of TNF against Meth-A fibrosarcoma necrotic response and the rate of complete cure. These results suggest that the direct effects of TNF causing lesions in the tumor blood vessels plays an important role in its antitumor action.

Animals↗