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E Ohmura

Publications and source records attributed to E Ohmura.

At least 19 recordsLinked to original sources
PubMed1998

Regulation of cyclin D-dependent kinase activity in rat liver regeneration.

The regulation of cyclin D-dependent kinase activity in tissue regeneration in vivo has not been fully described. In young adult rat liver after 70% partial hepatectomy, the association of cyclin D1 with cdk4 was significantly promoted during G1 phase and was maximal at 18 hr, corresponding mainly to late G1. Cyclin D1-dependent kinase activity also strongly increased during G1 phase. The timing of the induction of cyclin D1 / cdk4 complex assembly correlated well with that of cyclin D1-dependent kinase activity. At 18 hr after partial hepatectomy, the amounts of CDK inhibitors p21(CIP1) and p27(KIP1) were also maximal, while only one-tenth of p21(CIP1) and of p27(KIP1) was associated with cyclin D1. These findings suggest that cyclin D1, cdk4 and their association act as promoting factors, and that both p21(CIP1) and p27(KIP1) may have physiological functions as adaptor proteins in additions to their roles as CDK inhibitors in rat liver regeneration.

Animals↗
PubMed1997

Abutiloside A, a 26-acylamino-3 beta, 16 alpha-dihydroxy-5 alpha-cholesta-22-one glycoside from Solanum abutiloides.

In addition to solamargine and proto-dioscin, three new steroid glycosides, abutilosides A-C, have been isolated from roots of the Solanaceae Solanum abutiloides. The structure of abutiloside A has been elucidated as 3 beta, 16 alpha-dihydroxy-26-isovalerylamino-5 alpha,25 xi H-cholestan-22-one 3-O-[O-beta-D-xylopyranosyl-(1-->2)-O-alpha-L- rhamnopyranosyl-(1-->4)-beta-D-glucopyranoside]. De-N-acylation of its aglycone yielded solafloridine by 22,N-cyclization. Therefore, 26-aminocholestan-22-one derivatives are considered to be crucial intermediates in steroid biosynthesis. The co-occurrence of the (25R)-steroids soladulcidine, solafloridine and diosgenin together with abutiloside A in roots of S. abutilosides suggests that the configuration of abutiloside A at C-25 will also be R.

Carbohydrate Conformation↗
PubMed1996

Cholestane glycosides from Solanum abutiloides.

From the roots of Solanum abutiloides, glycosides of 26-hydroxy- and 26-aminocholestane were obtained and their structures were characterized. Both of them were regarded as key intermediates in the biogenesis of steroidal alkaloids.

Carbohydrate Sequence↗
PubMed1995

Degradation of cell surface heparan sulfates decreases the high affinity binding of basic FGF to endothelial cells, but not to FRTL-5 rat thyroid cells.

The role of cell surface heparan sulfate proteoglycans in the effect of basic fibroblast growth factor (bFGF) on FRTL-5 rat thyroid cells was investigated and compared with that of endothelial cells. FRTL-5 cells were incubated for 2 h with heparitinase (0.5-5.0 mU/mL), which specifically degrades heparan sulfate proteolgycans, and then stimulated by bFGF. The mitogenic effect of bFGF was estimated by measuring [3H]thymidine incorporation. Although cell surface heparan sulfates have been believed to be necessary for bFGF binding to its high affinity receptors, the heparitinase treatment had no significant effect on the DNA synthesis of FRTL-5 cells stimulated by bFGF. The binding study revealed that heparitinase treatment decreased low affinity bindings of [125I]bFGF to FRTL-5 cells by only 50% and did not attenuate the high affinity binding, while the same treatment abolished the high and low affinity binding to bovine pulmonary artery endothelial (CPAE) cells. Analysis of trypsin accessible cell surface 35SO4-labeled materials by Q-sepharose anion-exchange column chromatography showed that heparan sulfate proteoglycans, peaked at 0.55 M NaCl elution, disappeared from the surface of FRTL-5 cells after treatment with 2.0 mU/mL of heparitinase, indicating that the heparitinase resistant low-affinity binding sites are not heparan sulfates. These results demonstrate that cell surface heparan sulfates are not required for the high affinity binding of bFGF to FRTL-5 rat thyroid cells, while proteoglycans are necessary for binding to endothelial cells, and suggest that the mechanism of the action of bFGF is different in rat thyroid cells compared with endothelial cells.

Animals↗
PubMed1995

Effects of transforming growth factor alpha (TGF-alpha) on DNA synthesis and thyrotropin-induced iodine metabolism in cultured porcine thyroid cells.

Transforming growth factor alpha (TGF-alpha) is a potent mitogen that is similar structurally to epidermal growth factor (EGF). As EGF is a potent growth stimulator and an inhibitor of iodine metabolism in cultured thyroid cells of several species, we studied whether TGF-alpha has similar effects using porcine thyroid cells in culture. Recombinant human TGF-alpha dose-dependently stimulated DNA synthesis of thyroid cells, with maximal stimulation (eight- to ninefold above basal) occurring at 2 nmol/l. The potency was approximately 50% that of mouse EGF and correlated with the ability to compete with EGF for receptor binding, suggesting that the action of TGF-alpha is mediated by interaction with EGF receptors. When thyroid cells were cultured for 3 days with thyrotropin (TSH) in the presence of TGF-alpha, TSH-induced iodide uptake was inhibited in a dose-dependent manner. The potency of TGF-alpha again was approximately 50% that of EGF. Transforming growth factor alpha did not inhibit TSH-stimulated cAMP production. Moreover, iodide uptake stimulated by either forskolin or 8-bromo-cAMP also was inhibited by TGF-alpha. Thus, we conclude that TGF-alpha inhibits TSH-induced iodine metabolism largely by acting at the steps distal to cAMP production. Northern blot analysis revealed expression of TGF-alpha mRNA in porcine thyroid cells. These observations suggest that TGF-alpha acts as an autocrine modulator of growth and differentiated functions in porcine thyroid cells.

Animals↗
PubMed1994

Mechanism of inhibitory actions of minocycline and doxycycline on ascitic fluid production induced by mouse fibrosarcoma cells.

Semisynthetic tetracyclines (TCNs) are used for the management of malignant pleural effusions as sclerosing agents. However, their precise mechanism of actions are uncertain. In the present study, the mechanism of inhibitory effects of minocycline (MINO) and doxycycline (DOXY), on the accumulation of ascitic fluid induced by mouse fibrosarcoma (Meth-A) cells were investigated using male mice. Meth-A cells inoculated intraperitoneally elicited 2.5-4 ml of bloody ascites 10 days after implantation. The production of ascitic fluid was suppressed in a dose-related manner by daily intraperitoneal injections of MINO or DOXY, whereas vehicle (normal saline with 0.01N HCl) did not exert a significant effect. The inhibitory activity of these two substances was quite similar; one mg/mouse of MINO or DOXY inhibited the accumulation of fluid by 87% and 84%, respectively. The survival rate of Meth-A-bearing mice treated with MINO or DOXY was higher than that of the controls. Macroscopic examination of the peritoneal cavity did not reveal any obvious effects, such as adhesions, in mice treated with either MINO or DOXY. In vitro studies showed that MINO and DOXY suppressed Meth-A cell growth with IC50s of 5 microM and 8 microM, respectively. Maximal suppression (95%) was achieved at MINO and DOXY concentrations of 25 microM. The above observations suggest that MINO and DOXY inhibit the accumulation of ascites by a direct effect on Meth-A cell growth. Therefore, it appears that TCNs injected into the pleural cavity to manage malignant effusions in man exert their activity, at least in part, by suppressing malignant cell growth.

Animals↗
PubMed1994

Basic fibroblast growth factor (FGF-2) in renal cell carcinoma, which is indistinguishable from that in normal kidney, is involved in renal cell carcinoma growth.

To investigate the role of basic fibroblast growth factor (FGF) in renal cell carcinoma growth, we have analyzed the expression of mRNA of basic FGF. In 7 of 15 cases, basic FGF mRNA level in renal cell carcinoma tissues was higher than that in corresponding normal tissues. However, the tumor-to-normal ratios of expression levels are chiefly less than 2.0 and, in 5 cases, are even less than 1.0. Furthermore, there was no correlation between the ratio and the clinical stage. In protein analysis, we could not find any difference between basic FGF extracted from renal cell carcinomas and that from normal kidney tissues in bioactivity, immunoreactivity, molecular weight and affinity to heparin. On the other hand, anti-basic FGF monoclonal antibody inhibited the growth of a renal cell carcinoma cell line, VMRC-RCW, and this inhibition was reversed by an extraphysiological amount of exogenous basic FGF (100 ng./ml.). These results suggest that basic FGF itself may have no pivotal role in renal cell carcinoma etiology but is involved in the growth of renal cell carcinomas in an autocrine manner.

Animals↗
PubMed1993

Effect of somatostatin and its analogue on proliferation of human epidermoid carcinoma cells in vitro.

Somatostatin (SS) and its analogue inhibit the growth of some human tumors in vivo. Surprisingly, we found that SS-14 and its analogue (SMS 201-995) exhibited unexpected proliferative effects on two lines of cells, A431 and KB human epidermoid carcinoma cells, in vitro. The level of intracellular cyclic AMP, an important second messenger that controls the growth of A431 cells, was unaffected in A431 cells by either SS-14 or SMS 201-995. In contrast, SS-14 (20 nM) and SMS 201-995 (10 nM) reduced the level of intracellular inositol 1,4,5-trisphosphate rapidly but transiently.

Binding, Competitive↗
PubMed1993

Transforming growth factor-alpha activity in effusions: comparison of radioimmunoassay and radioreceptorassay.

Transforming growth factor-alpha (TGF-alpha) in pleural and peritoneal effusions was assayed by homologous radioimmunoassay (RIA) and radioreceptor assay (RRA) using human placental membrane. Effusions were obtained from 24 patients with and 17 patients without cancer. Most of the effusions were found to contain TGF-alpha by RIA and RRA, but immunoreactive epidermal growth factor (EGF) was not detected. Effusions were chromatographed on Bio-Gel P-60 with several peaks of TGF-alpha activity by both RIA and RRA. A discrepancy in the chromatographic pattern of TGF-alpha between RIA and RRa suggested the existence of EGF-like substances capable of binding to EGF receptors which lack immunoreactivity for EGF or TGF-alpha. The TGF-alpha concentration of the acetic acid-extracted malignant effusions assayed by RRA significantly exceeded the value obtained from benign effusions (17.0 +/- 8.7 vs. 9.2 +/- 6.3 ng/ml; mean +/- SD: p < 0.02). However, the concentrations obtained by RIA did not differ.

Aged↗
PubMed1993

Inhibition of human pancreatic cancer cell (MIA PaCa-2) growth by cholera toxin and 8-chloro-cAMP in vitro.

The effects of cholera toxin (CT) and 8-chloro-cAMP (8-Cl-cAMP) on cell growth were investigated using two human pancreatic carcinoma cell lines (MIA PaCa-2, Panc-1). CT, which catalyses the ADP ribosylation of Gs, suppresses the proliferation of MIA PaCa-2(PC) cells. CT at the low dose of 0.1 pg ml-1 was inhibitory of PC cell growth, and the maximum suppression (70%) was achieved at a CT concentration of 100 pg ml-1. This phenomenon was reversible. The production of cAMP by CT (100 pg ml-1) in PC cells was enhanced 320-fold compared with the control. In addition, cAMP analogues (8-Cl-cAMP, 8-Br-cAMP) and forskolin decreased the growth rate of PC cells in a dose-dependent manner. These results support the view that CT suppresses PC cell growth by stimulating cAMP production. Conversely, Panc-1 cells were far less sensitive to CT in cell growth and cAMP production. 8-Cl-cAMP was also less effective on Panc-1 cell growth. The binding of an insulin-like growth factor (IGF)-I and transforming growth factor (TGF)-alpha, which has been shown to stimulate PC cell growth in an autocrine manner, to PC cells was not modified in cells treated with CT or 8-Cl-cAMP. The results suggest that the inhibitory actions of these substances do not occur at the level of the receptor for IGF-I or EGF/TGF-alpha. We have previously shown that phorbol esters, which decrease the binding of TGF-alpha to PC cells, has an anti-proliferative activity on these tumour cells. Inhibited cell growth by maximum suppressive dose of CT or 8-Cl-cAMP was further inhibited by TPA. In addition, an oncogene product of K-ras which is commonly activated in pancreatic cancer, was increased by CT and 8-Cl-cAMP. It is concluded that CT and 8-Cl-cAMP inhibit PC cell growth, presumably in a similar manner, and their mechanism(s) of action may be different from that of TPA. The anti-proliferative effect of CT or 8-Cl-cAMP was enhanced by TPA, implying that the combination of these substances results in increased inhibition of the PC cell growth.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1992

Autocrine role of insulin-like growth factor (IGF)-I in a human thyroid cancer cell line.

An established cell line (TC-cell, clone 78) derived from human thyroid papillary cancer cells was investigated for production of peptide growth factors. The cells had specific binding sites for insulin-like growth factor-I (IGF-I) and responded to this growth factor with increased proliferation. Culture medium conditioned by TC cells was found to contain insulin-like growth factor (IGF)-I and IGF-binding protein(s). Furthermore, reverse transcription-polymerase chain reaction revealed expression of IGF-I mRNA. When monoclonal antibody to IGF-I receptors (alpha IR3) was added, the growth of TC cells cultured in serum-free medium was significantly reduced. The growth rate of the cells was restored when the antibody was removed from the medium. These results strongly suggest that TC cells produce IGF-I, which is involved in the regulation of their own growth.

Carcinoma, Papillary↗
PubMed1991

Urinary excretion of parathyroid hormone-related protein fragments in patients with humoral hypercalcemia of malignancy and hypercalcemic tumor-bearing nude mice.

To investigate whether parathyroid hormone-related protein (PTHrP), a hypercalcemia-inducing factor responsible for malignancy-associated hypercalcemia (MAH), is excreted into urine of these patients, radioimmunoassay was established using antiserum specific for the C-terminal region of PTHrP-(127-141). Immunoreactive PTHrP (iPTHrP) was detected in the urine of all patients with MAH (n = 6) in whom nephrogenous cyclic AMP excretion was elevated. However, iPTHrP was not detected in the urine of normal subjects (n = 25) or hypercalcemic patients with primary hyperparathyroidism (n = 8). In normocalcemic patients with malignant disorders iPTHrP was not detected in the urine in most cases (24 of 25 patients) but was detectable in 1 of 25 patients. iPTHrP was also detected in the urine of hypercalcemic nude mice transplanted with PTHrP-producing tumors, but not in the urine of control and normocalcemic nude mice transplanted with PTHrP-nonproducing tumor. Furthermore, size-exclusion high-performance liquid chromatography revealed that the molecular weight of iPTHrP is about 2000-6000 daltons in the urine of patients as well as tumor-bearing nude mice. These data indicate that the fragments of the C-terminal region of PTHrP are excreted into the urine of patients with MAH and in a few normocalcemic patients with malignancies, suggesting that the measurement of iPTHrP in the urine is potentially useful in the differential diagnosis of hypercalcemia, particularly in differentiating humoral hypercalcemia of malignancy and primary hyperparathyroidism.

Adult↗
PubMed1991

Transforming growth factor (TGF)-alpha in human milk.

Transforming growth factor (TGF)-alpha and epidermal growth factor (EGF) were measured in human milk by means of homologous radioimmunoassay. As previously reported, EGF concentration in the colostrum was approximately 200 ng/ml and decreased to 50 ng/ml by day 7 postpartum. The value of immunoreactive (IR)-TGF-alpha was 2.2-7.2 ng/ml, much lower than that of EGF. In contrast to EGF, the concentration of IR-TGF-alpha was fairly stable during the 7 postpartum days. There was no relationship between the concentrations of IR-TGF-alpha and IR-EGF, suggesting that the regulatory mechanism in the release of the two growth factors is different. On gel-chromatography using a Sephadex G-50 column, IR-EGF appeared in the fraction corresponding to that of authentic human EGF, while 70%-80% of the IR-TGF-alpha was eluted as a species with a molecular weight greater than that of authentic human TGF-alpha. Although the physiological role of TGF-alpha in milk is not known, it is possible that it is involved in the development of the mammary gland and/or the growth of newborn infants.

Epidermal Growth Factor↗
PubMed1991

Phorbol ester, not growth hormone releasing factor, consistently stimulates growth hormone release from somatotroph adenomas in culture.

In order to study the mechanism of GH secretion from somatotroph adenoma cells, we have compared the effect of 12-O-tetradecanoyl phorbol-13-acetate (TPA) with that of growth hormone releasing factor (GRF) on GH secretion from human somatotroph adenoma cells cultured in monolayer. Pituitary adenoma cells were obtained from 13 patients with acromegaly undergoing surgery. On the 7th day of culture, the cells were exposed for 2 h to secretagogues. All 13 adenoma cell cultures (100%) responded to TPA (1.6-16.0 nmol/l) with a two- to six-fold increase in GH release (240 +/- 37% increase of control: mean +/- SE). The response was detectable within 10 min, and was maximal at 2 h. Phospholipase C (7.7 mmol/l) also stimulated a two- to ten-fold increase in GH release in all four adenomas examined (100%). GH release was stimulated by GRF (2.0 nmol/l) in eight out of 12 adenoma cells (67%), but the magnitude of the responses to GRF (60 +/- 18% increase of control: mean +/- SE) were much smaller than that of TPA. Five out of 13 adenomas secreted detectable amount of PRL into the medium and these five adenomas (100%) responded to TPA (16.0 nmol/l) with a two- to six-fold increase. These observations indicate that the activation of protein kinase C is the consistent stimulator in GH and PRL secretion in human somatotroph adenoma cells. However, it is not determined whether the protein kinase C is involved in the in-vivo production of GH in patients with acromegaly.

Adenoma↗
PubMed1991

Falsely elevated serum parathyroid hormone levels due to immunoglobulin G in a patient with idiopathic hypoparathyroidism.

A 73-yr-old patient with idiopathic hypoparathyroidism was admitted to our hospital in May 1981. The immunoreactive PTH (iPTH) level determined by RIA using antiserum specific for the C-terminal region of PTH-(65-69) was in the upper normal range (0.6 ng/mL) and over the next 7 yr increased gradually to 6 ng/mL. Since iPTH levels determined using other commercial RIA kits remained constantly decreased or in the undetectable range, we studied the mechanism of false elevation of iPTH in this patient. The patient's serum contained no binding protein to the tracer ([125I]) [Tyr45] human PTH-(46-84)), nor was any heterophilic antibody to the first [guinea pig immunoglobulin G (IgG)] or the second antibody (goat IgG) detected. Consistent with these findings, the dilution curve of the serum was parallel with that of standard bovine PTH-(1-84). Gel filtration analysis revealed that the iPTH-like substance was eluted in the void volume (apparent mol wt, greater than 70,000). Almost all of the iPTH-like substance was adsorbod by a protein-A-Sepharose column. When the IgG fraction purified by protein-A-Sepharose affinity chromatography was applied to an antihuman IgG lambda-Sepharose column, 72% of the iPTH-like substance was detected in the IgG lambda. These results suggest that the falsely elevated iPTH in the patient's serum was due to IgGs (mainly IgG lambda), which were cross-reactive with the antiserum highly specific for the C-terminal region of human PTH-(65-69).

Aged↗
PubMed1990

Epidermal growth factor and transforming growth factor alpha induce ascitic fluid in mice.

Recent studies have suggested that pleural or peritoneal effusion associated with metastatic tumors is induced by some mediators produced by the tumor cells. We studied the ability of well-characterized peptide growth factors to produce ascites in mice. Peritoneal administration of epidermal growth factor (EGF, 10 to 40 micrograms/mouse/wk) or transforming growth factor alpha (TGF-alpha, 10 to 40 micrograms/mouse/wk) via osmotic minipumps resulted in formation of bloody ascites. The amount of ascites produced was dependent on the dose of growth factors. Vehicle alone or insulin-like growth factor I (40 micrograms/mouse/wk) was without effect. Indomethacin, a blocker of prostaglandin synthesis, significantly reduced the ascites accumulation induced by EGF, suggesting that prostaglandins are involved in ascites formation induced by EGF. Dexamethasone was also effective in attenuating the effect of EGF. Thus, it is possible that peritoneal effusion associated with disseminated tumors is, at least in part, due to EGF-like materials (most likely TGF-alpha) produced by tumor cells. The mechanism by which these peptides induce bloody ascites is not known for certain, but it may be due to the reported activity for neovascularization or increased vascular permeability.

Animals↗