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T Tsunenari

Publications and source records attributed to T Tsunenari.

27 records · Page 2Linked to original sources
PubMed1988

Parathyroid hormone control of free cytosolic Ca2+ in the kidney.

We have established a perifusion system to monitor free cytosolic calcium concentrations ([Ca2+]i) in mouse kidney slices, which presumably reflects in vivo status more accurately than renal cells in culture, by means of the fluorescent calcium indicators quin-2 and fura-2. An increase in the extracellular calcium concentrations from 0 (no added Ca2+) to 3.0 mM resulted in an increase in [Ca2+]i from 52 to 239 nM. Replacement of 118 mM of extracellular Na+ with choline, or the addition of ouabain, an inhibitor of Na+,K+-ATPase, at 10(-6) M in the perfusate caused an increase in [Ca2+]i from 161 +/- 13 to 873 +/- 78 nM (n = 10) and 161 +/- 13 to 395 +/- 68 nM (n = 4), respectively, suggesting the possible existence of a Na+,Ca2+ exchange mechanism in the kidney slice. We further examined the effects of PTH on [Ca2+]i mobilization in the kidney. Both human PTH-(1-34) and hPTH-(1-84) increased [Ca2+]i within 60 s at physiologic concentrations of 10(-11)-10(-9) M in a dose-dependent manner. On the other hand, an increase in intracellular cAMP in the slice was also detected above 3 X 10(-9) M hPTH-(1-34) [base 2.1 +/- 0.4 pmol/mg, 3.2 +/- 0.6 pmol/mg (p less than 0.05 versus control values) 5 minutes after the application of 3 X 10(-9) M hPTH-(1-34) and 17.3 +/- 4.3 pmol/mg (p less than 0.05 versus control values) 3 X 10(-8) M hPTH-(1-34), mean +/- SEM, n = 7, p less than 0.05 versus control values].(ABSTRACT TRUNCATED AT 250 WORDS)

Aminoquinolines↗
PubMed1986

Altered parathyroid hormone- or calcitonin-stimulated adenosine 3', 5'-monophosphate release by isolated perfused bone from glucocorticoid-treated rats.

The present studies were designed to examine in vivo effects of glucocorticoid on PTH-or calcitonin (CT)-stimulated adenosine 3',5'-monophosphate (cAMP) release from the isolated perfused bone of rat and to test whether the duration of glucocorticoid administration influenced such effects. We assessed the ability of acute (24 hour) or chronic (2 week) dexamethasone administration to modulate the cAMP response to 5 micrograms human PTH-(1-34) or 1 micrograms eel CT. Acute treatment with dexamethasone (1 mg/100 g body wt) increased the cAMP response to PTH, but decreased the response to CT. This enhanced effect on PTH-stimulated cAMP release was not apparent in the presence of phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine (IBMX, ImM). In contrast, chronic dexamethasone treatment (0.2 mg daily for 2 weeks) led to a decrease in both PTH- and CT-stimulated cAMP release. Such impaired response of the dexamethasone-treated bones to PTH was also found in rats that underwent parathyroidectomy 24 hours before sacrifice. These data indicate that 1) the duration of glucocorticoid administration may influence the effect of PTH on bone and 2) glucocorticoid may decrease cAMP-mediated CT function, regardless of the duration of treatment.

1-Methyl-3-isobutylxanthine↗
PubMed1986

Impaired parathyroid hormone-stimulated adenosine 3',5'-monophosphate release by isolated perfused bones obtained from vitamin D-deficient rats.

The present studies were designed to explore the mechanism underlying skeletal refractoriness to PTH in a vitamin D-deficient animal by assessment of PTH-stimulated cAMP release from isolated perfused bone. In vitamin D-deficient (-D) rats both basal and PTH-stimulated cAMP release were markedly diminished, compared with that in vitamin D-replete (+D) rats. Isolated perfused bones from -D rats that had undergone parathyroidectomy 2 days before death still showed reduced cAMP release in response to PTH, compared with +D bones. To investigate which factors in terms of Ca, endogenous PTH, or vitamin D might primarily be responsible for the impaired PTH-stimulated cAMP release from -D bones, some -D rats were switched to a diet identical to the vitamin D-deficient diet but with high Ca content (4%) for 2 or 5 weeks before death. This schedule maintained normocalcemia despite vitamin D deficiency. PTH-stimulated cAMP release in these rats was increased to a level intermediate between that in -D rats and +D rats, indicating partial restoration of the impaired response to PTH in -D rats. These data indicate that skeletal refractoriness to PTH in vitamin D-deficient animals might, in part, be due to the impaired activation of adenylate cyclase, which cannot be explained entirely by hypocalcemia or associated secondary hyperparathyroidism. Vitamin D deficiency per se, therefore, may play a key role in the impaired cAMP response to PTH.

Animals↗
PubMedDate not supplied

In vitro antitumor activity of a new platinum complex, DWA2114R against human tumor cell lines.

The in vitro antitumor activities of a new platinum complex, (-)-(R)-2-aminomethylpyrrolidine(1,1-cyclobutanedicarboxylato++ +)platinum(II) monohydrate (DWA2114R), against various human tumor lines (23 solid tumor lines and 6 hematopoietic malignant lines) were examined in comparison with those of cis-diammine (1,1-cyclobutanedicarboxylato) platinum(II) (CBDCA) and cis-diamminedichloroplatinum(II) (CDDP). The growth inhibitory activities of the compounds were estimated by MTT assay after the incubation of cells under continuous exposure to the drug. The mean concentrations (microM) of DWA2114R, CBDCA and CDDP needed to inhibit the proliferation of cells by 50% (IC50) were 64.0, 55.1 and 6.8 against solid tumor lines and 8.5, 7.4 and 1.7 against hematopoietic malignant lines, respectively. Comparing the drug sensitivity of the solid tumor lines by type, ovarian cancer was found to be the most susceptible to all three compounds. The susceptibilities of other tumors were in the order prostate, breast and colon cancers for DWA2114R and CBDCA but colon, prostate and breast cancers for CDDP. The correlations of the mean IC50 values for all three combinations of the two compounds were statistically evaluated. A significant correlation was shown between DWA2114R and CBDCA, or CBDCA and CDDP, but not between DWA2114R and CDDP. These results suggest that DWA2114R is almost equivalent in effect to CBDCA which is several times less potent than CDDP, but also that the in vitro cell line subpanel specificity of DWA2114R is in certain respects different from CDDP, in contrast with CBDCA.

Antineoplastic Agents↗
PubMedDate not supplied

Therapeutic potential of humanized anti-interleukin-6 receptor antibody: antitumor activity in xenograft model of multiple myeloma.

A xenograft model of human multiple myeloma (MM) was established in athymic nude mice using S6B45 cells whose growth is dependent on IL-6 in an autocrine fashion. S6B45 cells were inoculated s.c. into mice pretreated with 500 cGy X-ray and anti-asialo GM1 antibody. In more than 90% of the mice, a palpable tumor emerged within 30 days at the inoculation site. Histological observation of the tumor section revealed that the tumor mass was composed of two different phenotypes of myeloma cells, corresponding to plasmablasts and mature plasma cells. I.v. injection of more than 0.125 mg of mouse monoclonal antibody (PM1) against human IL-6R (hIL-6R) on days 1, 3 and 5 markedly delayed the time of tumor incidence. One mg of anti-hIL-6 antibody (MH166) also strongly inhibited the growth of S6B45, whereas control antibody (MOPC31C) and anti-hIL-6R antibody without neutralizing activity (AUK181-6) produced no significant effects. To reduce the antigenicity of PM1 in human, mouse-human chimeric PM1 (chPM1) with human IgG1 constant region and humanized PM1 (hPM1), human IgG1 with mouse complimentarity determining regions, were constructed and evaluated for their in vivo antitumor activity in our model. The in vivo efficacy of these recombinant antibodies (chPM1 and hPM1) was shown to be equivalent to that of the original PM1. These results indicate that the antitumor activity of PM1 is completely recreated in hPM1, and that blocking of the IL-6 signal by this humanized antibody could be a potent therapy for MM.

Animals↗
PubMedDate not supplied

Flat revertant inducers, styryl diphenylamine derivatives, inhibit growth and metastasis of murine tumor cells in vivo.

Previously, we reported that a novel styryl diphenylamine derivative, RX-465, reverts the transformed phenotype of human fibrosarcoma HT1080 cells in vitro. To determine whether agents inducing such phenotypic reversion show antitumor and/or antimetastatic effects in vivo, we assessed tumor growth and metastasis in mice inoculated with either murine B16-, B16BL6 melanoma or M5076 reticulosarcoma. These mice received orally our new derivatives of RX-465, namely RX-512 and RX-549. We found that these-derivatives inhibited B16 melanoma and M5076 reticulosarcoma growth by greater than 80% in vivo. RX-512 also inhibited the metastatic dissemination of B16BL6 melanoma into the lung and that of M5076 reticulosarcoma into the liver by 98% and 100% at doses of 60 and 40 mg/kg/day, respectively. These treatments did not cause significant decreases in body weight. Our data strongly demonstrate that styryl diphenylamine derivatives that revert transformed phenotype in vitro potentially inhibit tumor growth and metastasis in mice with negligible toxicity at effective doses.

Animals↗