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Biomedical subjects

T Fu

Publications and source records attributed to T Fu.

At least 55 records · Page 3Linked to original sources
PubMed1993

The effect of epinephrine on the intracellular free calcium of parent and Ki-ras-transfected NIH3T3 cells.

Here we describe differences in the formation of the epinephrine-induced Ca2+ transients between parent and Ki-ras-transformed NIH3T3 fibroblasts. These transients proved to be the results of an efflux from both the thapsigargin-sensitive and -insensitive intracellular pools. While the epinephrine-induced detachment of the ras-transformed cells might be due to cytoskeletal and/or cell-matrix alterations.

3T3 Cells↗
PubMed1993

Inhibition of HIV infection by baicalin--a flavonoid compound purified from Chinese herbal medicine.

Baicalin (BA), (formulated as 7-D-glucuronic acid-5,6-dihydroxy-flavone), was purified from the plant Scutellaria Baicalensis Georgi. It has been used as a traditional Chinese herbal medicine. The inhibitory effect of BA against human immunodeficiency virus (HIV-1) infection and replication has been studied in vitro. The compound inhibits HIV-1 infection and replication as measured by: (1) a quantitative focal syncytium formation on CEM-ss monolayer cells; and (2) HIV-1 specific core antigen p24 expression and retroviral reverse transcriptase (RT) activity in the HIV-1-infected H9 cells. We have further demonstrated that the enzymatic activity of purified recombinant HIV-1/RT was inhibited by BA. In addition to lymphoid cell lines, the anti-HIV-1 activity of BA was also observed in cultures of primary human peripheral blood mononuclear cells infected with HIV-1 in vitro. Neither cytotoxic nor cytostatic effects on the indicator cells were found under the assay condition. This data suggests that BA may serve as a useful drug for the treatment and prevention of HIV infections.

Antiviral Agents↗
PubMed1992

Abolishment of bradykinin-induced calcium oscillations in ras-transformed fibroblasts by the expression of 80 kDa diacylglycerol kinase.

Our previous study showed bradykinin-induced periodic Ca2+ changes (Ca2+ oscillations) in v-Ki-ras-transformed NIH/3T3 (DT) cells in which protein kinase C (PKC) activity is partially down-regulated by a sustained high level of 1,2-diacylglycerol (DAG) [FEBS Lett. (1991) 281, 263-266]. In the present study, DAG kinase with 80 kDa mass (80K DGK) has been successfully transfected in DT cells, which exhibited enhanced cellular DAG kinase activities, decreased cellular DAG contents, and increased PKC activities compared to the control vector-transfected cells. Furthermore, these DGK-transfectants showed strong inhibition in bradykinin-induced Ca2+ oscillations. The results suggest that the sustained DAG increase down-regulates the PKC activity, thereby leading to the induction of Ca2+ oscillations in DT cells.

3T3 Cells↗
PubMed1992

Differential pathways (phospholipase C and phospholipase D) of bradykinin-induced biphasic 1,2-diacylglycerol formation in non-transformed and K-ras-transformed NIH-3T3 fibroblasts. Involvement of intracellular Ca2+ oscillations in phosphatidylcholine breakdown.

Bradykinin (BK) induced a biphasic increase in 1,2-diacylglycerol (DAG) in both K-ras-transformed fibroblasts (DT) and the parent NIH-3T3 cells. The first phase was coincident with the increase in Ins(1,4,5)P3 resulting from PtdIns(4,5)P2 hydrolysis, and the second, sustained, phase was derived from phosphatidylcholine (PtdCho) hydrolysis. In NIH-3T3 cells, stimulation by BK induced greater production of choline than phosphocholine in [3H]choline-labelled cells and appreciable phosphatidylethanol (PtdEtOH) formation in [3H]myristic acid-labelled cells, suggesting that PtdCho was hydrolysed mainly by a phospholipase D (PLD) activity. Pretreatment with propranolol, an inhibitor of phosphatidate phosphohydrolase, markedly diminished the second DAG accumulation, supporting the above notion. In DT cells, BK induced predominantly phosphocholine generation and little PtdEtOH formation, indicating that the PtdCho hydrolysis was due to a phospholipase C (PLC) activity. The BK-induced oscillations in intracellular Ca2+ concentration ([Ca2+]i) observed in single DT cells [Fu, Sugimoto, Oki, Murakami, Okano & Nozawa (1991) FEBS Lett. 281, 263-266] were detected as a sustained [Ca2+]i elevation when assayed in a cell suspension. A receptor-operated Ca2+ channel blocker, SK&F 96365, suppressed both the BK-induced phosphocholine generation and the sustained [Ca2+]i elevation in a similar dose-dependent manner. These results thus suggested that oscillations in [Ca2+]i are involved in the activation of PtdCho-specific PLC in DT cells.

3T3 Cells↗
PubMed1992

Thy-1 inhibits mitogen-induced Ca2+ oscillation in ras-transformed mouse fibroblasts.

Cell surface glycoprotein Thy-1 functions as a transformation suppressor in v-ras-transformed NIH/3T3 cells [Sugimoto et al., (1991) Cancer Res. 51, 99-104.]. In order to understand the mechanism of action of Thy-1, we examined the effect of Thy-1 expression on mitogen-induced Ca2+ oscillation which was correlated with v-ras-transformation [Fu et al., (1991) FEBS Lett. 281, 263-266.]. Forced expression of Thy-1 in v-ras-transformed cells inhibited mitogen-induced Ca2+ oscillation. Although v-Ras-free, Thy-1-positive NIH/3T3 cells (major population) did not show Ca2+ oscillation, whereas in Thy-1-negative NIH/3T3 cells (less than 1% of the population) Ca2+ oscillation was observed. Finally, replacement of the carboxyl-half of Thy-1 with that of CD4 abolished the inhibitory effect of Thy-1. These results suggest that Thy-1 directly or indirectly participates in the negative regulation of Ca2+ response by inhibiting Ca2+ oscillation.

3T3 Cells↗
PubMed1992

Clinical evaluation of radioimmunoimaging with 131I-C0C183B2 monoclonal antibody against ovarian carcinoma by intraperitoneal injection.

Forty-eight cases subjected to radioimmunoimaging (RII) by intraperitoneal injection with 131I-C0C183B2 monoclonal antibody (MAb) prepared in our laboratory were studied. Thirteen of 14 cases of proved primary ovarian carcinoma were positive. In 11 follow-up cases of ovarian carcinoma after initial surgery and chemotherapy, 5 recurrences were positive and 6 cases without recurrence were negative; all were confirmed histopathologically after a second operation. One false negative was ovarian mucinous adenocarcinoma, which also negatively stained with C0C183B2 by the peroxidase anti-peroxidase method. Twenty of 23 cases of nonepithelial or metastatic carcinoma of the ovary, benign tumors, and benign diseases were negative. The sensitivity and specificity were 94.7 and 89.7%, respectively. If patients had complications with ascites, the MAb which positively stained with the cancer cells in the ascites was chosen for RII. For follow-up cases PAP staining with the tumor tissue from the initial surgery and the MAb should be done before RII. These are the principal factors that increase the positive rate and accuracy of RII. The intraperitoneal route seems to be a valuable method for clinical staging and tumor localization as well as for follow-up use.

Adult↗
PubMed1992

Inhibition of human T cell leukemia virus by the plant flavonoid baicalin (7-glucuronic acid, 5,6-dihydroxyflavone).

The ability of baicalin (7-glucuronic acid, 5,6-dihydroxyflavone), a flavonoid compound purified from the Chinese medicinal herb, Scutellaria baicalensis georgi, to inhibit human T cell leukemia virus type I (HTLV-I) was examined. Baicalin produced concentration-dependent inhibition of HTLV-I replication in productively infected T and B cells. Moreover, baicalin treatment selectively reduced the detectable levels of HTLV-I p19 gag protein in infected cells by greater than 70% at concentrations that produced insignificant effects on total cellular protein and DNA synthesis with no loss in cell viability. Resistance to HTLV-I infection and virus-mediated transformation was noted in uninfected peripheral blood lymphocytes pretreated with baicalin before cocultivation with lethally irradiated chronically infected cells. Baicalin inhibited reverse transcriptase activity in HTLV-I-infected cells as well as the activity of purified reverse transcriptase from Moloney murine leukemia virus and Rous-associated virus type 2. These results suggest that baicalin may be a potential therapeutic agent against HTLV-I-associated T cell diseases.

Anti-Infective Agents↗
PubMed1992

Protective effects of dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylene dioxybiphenyl-2,2'-dicarboxylate on damages of isolated rat hepatocytes induced by carbon tetrachloride and D-galactosamine.

The protective effect of biphenyl dimethyl dicarboxylate (DDB) on chemically induced damages was studied in isolated suspended rat hepatocytes. The experimental results showed that DDB (200 micrograms/10(6) cells) efficiently protected the hepatocytes against carbon tetrachloride (CCl4 10 mmol.L-1) and D-galactosamine (1 mmol.L-1) induced damages. Membranal lipid peroxidation (malondialdehyde, MDA formation) and glutamic pyruvic transaminase (GPT) release from the hepatocytes were markedly decreased. The damage of the cell surfaces of the hepatocytes were also reduced as seen under a scanning electron microscope (SEM). Pretreatment with DDB (300 mg.kg-1) orally ameliorated the reduction of liver glycogen and blood glucose caused by ip injection of D-galactosamine (800 mg.kg-1) in mice. When normal rats were given DDB 300 mg.kg-1 once daily for 10 d, the free ribosomal protein and RNA in the liver increased significantly. These results indicate that DDB is of beneficial effects on both damaged and normal hepatocytes.

Alanine Transaminase↗
PubMed1992

Involvement of bradykinin-induced [Ca2+]i oscillations in phosphatidylcholine breakdown in K-ras-transformed fibroblasts.

Bradykinin (BK) induced a biphasic 1,2-diacylglycerol production in both K-ras-transformed (DT) cells and its parent NIH3T3 cells. The first phase was coincident with the transient phosphoinositide turnover and the second sustained phase was derived from hydrolysis of phosphatidylcholine (PC). In DT cells, the PC breakdown was considerably due to phospholipase C and dependent on intracellular calcium oscillations.

3T3 Cells↗
PubMed1991

Ba2+ current oscillation evoked by bradykinin in ras-transformed fibroblasts.

By voltage-clamp recording, we show a novel inward current which oscillates after activation with bradykinin or serum in v-Ki-ras-transformed NIH/3T3 cells. The current oscillation was infrequently observed in control NIH/3T3 fibroblasts. The same stimulation evokes Ca2+ oscillations in the ras-transformed cells but not in parental cells (Fu et al., FEBS Lett. 281, 263-266, 1991). The results suggest that the oscillatory currents are generated by influxes of divalent cations to maintain Ca2+ oscillations in ras-transformed NIH/3T3 cells.

Animals↗
PubMed1991

Calcium oscillation induced by bradykinin in polyoma middle T antigen-transformed NIH3T3 fibroblasts: evidence for dependence on protein kinase C.

Bradykinin (BK) triggered long lasting intracellular free calcium ([Ca2+]i) oscillation in polyoma middle T-transformed cell line MT3 cells but not in the parental NIH3T3 cells. This periodic [Ca2+]i fluctuation was extracellular Ca(2+)-dependent and blocked by pretreatments with Ca2+ channel blockers, SK&F 96365 or CdCl2, suggesting a crucial role of Ca2+ entry across the plasma membrane possibly through a receptor-operated Ca2+ channel. Brief pretreatment with phorbol myristate acetate (PMA) completely abolished the BK-induced [Ca2+]i oscillation, and a protein kinase C (PKC) inhibitor, H-7, reversed the effect of PMA, indicating involvement of PKC. On the other hand, in some cells, oscillatory changes in [Ca2+]i were seen without agonist stimulation. The spontaneous oscillation was also dependent on extracellular Ca2+, but neither treatment with PMA nor H-7 had any effect under the same conditions.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Calcium oscillation associated with reduced protein kinase C activities in ras-transformed NIH3T3 cells.

We show here novel intracellular Ca2+ oscillation in v-K-ras-transformed NIH3T3 cells induced by mitogenic peptide hormones, bradykinin and bombesin, as well as fetal calf serum. Induction of the Ca2+ oscillation is strongly correlated with the malignant properties and inversely with PKC activities in vitro and in vivo. These results suggest that the mitogen-induced Ca2+ oscillation is negatively regulated by PKC, which modulates Ca2+ influx in v-K-ras-transformed NIH3T3 cells.

Animals↗
PubMed1991

Diacylglycerol formation and DNA synthesis in endothelin-stimulated rat C6 glioma cells: the possible role of phosphatidylcholine breakdown.

Stimulation of C6 cells with endothelin-1 (ET) caused a biphasic sn-1,2-diacylglycerol (1,2-DG) generation, which occurred not only via phosphatidylinositol 4,5-P2 (PIP2) hydrolysis by specific phospholipase C action, but also through the breakdown of phosphatidylcholine (PC) induced by either PC phospholipase C or D. ET also stimulated DNA synthesis in serum-starved C6 cells. However, in the presence of 1-(5-isoquinolynylsulfonyl)-2-methylpiperazine (H-7), a protein kinase C (PKC) inhibitor, the [3H]thymidine incorporation was markedly inhibited, which was concurrent with the 1,2-DG formation: the second peak was reduced. These findings suggest that brain glial cells might be an important target for ET. In addition to other possible roles, ET may also mediate mitogenesis in the brain, presumably through a PKC-dependent activation of phospholipase C and/or D hydrolyzing PC.

Animals↗
PubMed1990

Receptor-linked early events induced by vasoactive intestinal contractor (VIC) on neuroblastoma and vascular smooth-muscle cells.

Vasoactive intestinal contractor (VIC) caused a series of biochemical events, including the temporal biphasic accumulation of 1,2-diacylglycerol (DAG), transient formation of Ins(1,4,5)P3, and increase in intracellular free Ca2+ [( Ca2+]i) in neuroblastoma NG108-15 cells. In these cellular responses, VIC was found to be much more potent in NG108-15 cells than in cultured rat vascular smooth-muscle cells. The single cell [Ca2+]i assay revealed that in the presence of nifedipine (1 microM) or EGTA (1 mM), the peak [Ca2+]i declined more rapidly to the resting level in VIC-stimulated NG108-15 cells, indicating that the receptor-mediated intracellular Ca2+ mobilization is followed by Ca2+ influx through the nifedipine-sensitive Ca2+ channel. Pretreatment with pertussis toxin only partially decreased Ins(1,4,5)P3 generation as well as the [Ca2+]i transient induced by VIC, whereas these events induced by endothelin-1 were not affected by the toxin, suggesting involvement of distinct GTP-binding proteins. The VIC-induced transient Ins(1,4,5)P3 formation coincident with the first early peak of DAG formation suggested that PtdIns(4,5)P2 is a principal source of the first DAG increase. Labelling studies with [3H]myristate, [14C]palmitate and [3H]choline indicated that in neuroblastoma cells phosphatidylcholine (PtdCho) was hydrolysed by a phospholipase C to cause the second sustained DAG increase. Down-regulation of protein kinase C (PKC) by prolonged pretreatment with phorbol ester markedly prevented the VIC-induced delayed DAG accumulation. Furthermore, chelation of intracellular CA2+ completely abolished the second sustained phase of DAG production. These findings suggest that PtdCho hydrolysis is responsible for the sustained production of DAG and is dependent on both Ca2+ and PKC.

Animals↗
PubMed1990

Endothelin-1 induces intracellular calcium rise and inositol 1,4,5-trisphosphate formation in cultured rat and human glioma cells.

The effects of endothelin-1 (ET) on the signal transduction in rat and human glioma cell line cells have been investigated. ET was found to initiate the increase of intracellular calcium ([Ca2+]i) levels in both C6 and A-172 cells, which was concurrent with the formation of inositol 1,4,5-trisphosphate (IP3(1,4,5)). In the presence of [ethylenebis(oxyethylenenitrilo)]tetraacetic acid (EGTA) in the incubation media, the duration of the intracellular calcium response was reduced, indicating that the ET-induced increase of intracellular calcium in glioma cells may be mediated by a dual mechanism, intracellular calcium mobilization and influx of extracellular calcium. These results suggest that ET may also act as a neuropeptide in the central nervous system.

Animals↗
PubMed1990

Bradykinin induces inositol 1,4,5-trisphosphate-dependent hyperpolarization in K+ M-current-deficient hybrid NL308 cells: comparison with NG108-15 neuroblastoma x glioma hybrid cells.

External application of bradykinin (BK) to mouse neuroblastoma X mouse fibroblast hybrid NL308 cells and mouse neuroblastoma X rat glioma hybrid NG108-15 cells produced a transient outward (hyperpolarizing) current. In NG108-15 cells, BK also induced an inward (depolarizing) current associated with a decrease in input membrane conductance, which results from the inhibition of a voltage-sensitive potassium current, the M-current. However, in NL308 cells, either no depolarization was elicited by BK or, even if the BK-induced depolarization was evoked, it was associated with an increased conductance. To explain the above difference, the intracellular second messenger system of NL308 cells was examined in detail. BK induced the rapid accumulation (three- to fivefold higher than the control level) of inositol 1,4,5-trisphosphate (InsP3) in NL308 cells. The cytosolic Ca2+ concentration was also elevated to 540 nM from 180 nM at a basal level. This seems to be enough to activate a voltage-independent and Ca2(+)-sensitive K+ current, resulting in the hyperpolarization. Intracellular injection of InsP3 replicated the hyperpolarization. NL308 cells possess protein kinase C (C-kinase), with specific activities of C-kinase in cytosolic and membrane fractions being 233 and 24 pmol/min/mg protein, respectively. The activity associated with particulates became higher after phorbol dibutyrate (PDBu) treatment. But NL308 cells did not show the characteristic inward relaxation by step hyperpolarizations and the outward rectification in the current-voltage relationship, indicating that the M current is deficient in NL308 cells. Therefore, application of PDBu failed to mimic the inward current. The results suggest the role of InsP3 and C-kinase in controlling two K+ currents.

Animals↗
PubMed1990

[Protective effects of biphenyl dimethyl dicarboxylate on damage in isolated rat hepatocytes induced by carbon tetrachloride and D-galactosamine].

The protective effect of DDB on chemically induced damages was studied in primary culture of rat hepatocytes. The experimental results showed that DDB (200 ug/10(6) cells) efficiently protected the hepatocytes against carbon tetrachloride (10 mM) and D-galactosamine (1 mM) induced damages. Membrane lipid peroxidation (malondialdehyde, MDA) formation and Glutamic Pyruvic Transaminase (GPT) released from the hepatocytes were markedly decreased. The damage of the cell surfaces of the hepatocytes were also reduced as seen under a scanning electron microscope (SEM). Pretreatment with DDB (300 mg/kg) orally could ameliorate the reduction of liver glycogen and blood glucose caused by injection of D-gal (800 mg/kg i. p) in mice. When normal rats received 300 mg/kg of DDB once daily for 10 days, free ribosomal protein and RNA in the liver increased significantly. These results indicated that DDB is of beneficial effects on damaged and normal hepatocytes.

Animals↗