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Biomedical subjects

J Dai

Publications and source records attributed to J Dai.

At least 91 records · Page 5Linked to original sources
PubMed2000

Chronic alcohol ingestion induces osteoclastogenesis and bone loss through IL-6 in mice.

To investigate the role of IL-6 in alcohol-mediated osteoporosis, we measured a variety of bone remodeling parameters in wild-type (il6(+/+)) or IL-6 gene knockout (il6(-/-)) mice that were fed either control or ethanol liquid diets for 4 months. In the il6(+/+) mice, ethanol ingestion decreased bone mineral density, as determined by dual-energy densitometry; decreased cancellous bone volume and trabecular width and increased trabecular spacing and osteoclast surface, as determined by histomorphometry of the femur; increased urinary deoxypyridinolines, as determined by ELISA; and increased CFU-GM formation and osteoclastogenesis as determined ex vivo in bone marrow cell cultures. In contrast, ethanol ingestion did not alter any of these parameters in the il6(-/-) mice. Ethanol increased receptor activator of NF-kappaB ligand (RANKL) mRNA expression in the bone marrow of il6(+/+) but not il6(-/-) mice. Additionally, ethanol decreased several osteoblastic parameters including osteoblast perimeter and osteoblast culture calcium retention in both il6(+/+) and il6(-/-) mice. These findings demonstrate that ethanol induces bone loss through IL-6. Furthermore, they suggest that IL-6 achieves this effect by inducing RANKL and promoting CFU-GM formation and osteoclastogenesis.

Absorptiometry, Photon↗
PubMed2000

Neutral endopeptidase inhibits prostate cancer cell migration by blocking focal adhesion kinase signaling.

Neutral endopeptidase 24.11 (NEP, CD10) is a cell-surface enzyme expressed by prostatic epithelial cells that cleaves and inactivates neuropeptides implicated in the growth of androgen-independent prostate cancer (PC). NEP substrates such as bombesin and endothelin-1 induce cell migration. We investigated the mechanisms of NEP regulation of cell migration in PC cells, including regulation of phosphorylation on tyrosine of focal adhesion kinase (FAK). Western analyses and cell migration assays revealed an inverse correlation between NEP expression and the levels of FAK phosphorylation and cell migration in PC cell lines. Constitutively expressed NEP, recombinant NEP, and induced NEP expression using a tetracycline-repressive expression system inhibited bombesin- and endothelin-1-stimulated FAK phosphorylation and cell migration. This results from NEP-induced inhibition of neuropeptide-stimulated association of FAK with cSrc protein. Expression of a mutated catalytically inactive NEP protein also resulted in partial inhibition of FAK phosphorylation and cell migration. Coimmunoprecipitation experiments show that NEP associates with tyrosine-phosphorylated Lyn kinase, which then binds the p85 subunit of phosphatidylinositol 3-kinase (PI3-K) resulting in an NEP-Lyn-PI3-K protein complex. This complex competitively blocks FAK-PI3-K interaction, suggesting that NEP protein inhibits cell migration via a protein-protein interaction independent of its catalytic function. These experiments demonstrate that NEP can inhibit FAK phosphorylation on tyrosine and PC cell migration through multiple pathways and suggest that cell migration which contributes to invasion and metastases in PC cells can be regulated by NEP.

Animals↗
PubMed2000

Androgen-induced growth inhibition of androgen receptor expressing androgen-independent prostate cancer cells is mediated by increased levels of neutral endopeptidase.

Androgen-mediated growth repression of androgen-independent prostate cancer (AIPC) cells has been reported in androgen-independent PC-3 cells overexpressing the androgen receptor, and in androgen-independent derivatives of LNCaP cells that develop following prolonged culture in androgen-free media. Using two models of AIPC, PC3/AR cells and LNCaP-OM1 cells, a subclone of LNCaP cells derived by prolonged culturing in charcoal-stripped media, we investigated whether expression of neutral endopeptidase 24.11 (NEP), a cell-surface peptidase that cleaves and inactivates neuropeptides implicated in the growth of AIPC, is induced by androgen, and whether NEP contributes to the observed androgen-mediated growth repression. These cell lines each express high levels of androgen receptor. Culturing in dihyrotestosterone (DHT) resulted in a 30-56% (PC3) and 35-43% (LNCaP-OM1) decrease in cell number over 7 days concomitant with a significant increase in NEP enzyme specific activity. Northern analysis detected an increase in NEP transcripts following DHT treatment in PC3/AR cells. The addition of the NEP enzyme inhibitor phosphoramidon to PC3 and LNCaP-OM1 or the NEP competitive inhibitor CGS 24592 to LNCaP-OM1 blocked the increase in NEP enzyme activity and reversed the DHT-induced growth inhibition. Neither phosphoramidon or CGS 24592 alone inhibited cell growth. Furthermore, the reversal of growth inhibition in LNCaPOM1 cells was dose dependent on the concentration of CGS 24592. These data indicate that androgen-induced growth repression of AIPC cells PC3 and LNCaP-OM1 results in part from androgen-induced expression of NEP in these cells.

Androgens↗
PubMed2000

[CT diagnosis of fibrothecoma and fibroma of the ovary].

OBJECTIVE: To describe the CT characteristics and improve pre-operative diagnosis of fibrothecoma and fibroma of the ovary. METHODS: The clinical and CT image material of 14 postmenopausal patients with pathologically confirmed fibrothecoma or fibroma of the ovary were reviewed. RESULTS: Of the 14 cases, 7 had ascites. The tumor was solid in 10 cases, cystic or cystic-solid in 2 cases. It was round or elliptic in 9 cases, multilobular or irregular in shape in 5. In all cases, the tumors had clear border. On CT imaging, the solid tumor, the solid part of the cystic-solid tumor, and the cystic wall were similar in density to that of myometrium on precontrast scanning. There was no or slight uptake on postcontrast enhancement, the density of which was obviously lower than that of myometrium. In tumors heterogeneous in density, low density areas of light flakes or streaks were observed. In cystic or cystic-solid tumors, the demarcation between the cystic and solid portion was clear. Nodules on cystic wall were visible. CONCLUSION: CT is useful in the diagnosis of the fibrothecoma and fibroma of the ovary.

Adult↗
PubMed2000

Atypical antipsychotic effects of quetiapine fumarate in animal models.

AIM: To evaluate the effect of quetiapine fumarate in animal models of schizophrenia and its possibility to induce extrapyramidal side effects (EPSE). METHODS: The enhancement of immobility in a forced swimming test of mice induced by repeated treatment with phencyclidine and amphetamine swimming "normalization" test of mice were used as animal models of negative and positive symptoms of schizophrenia, respectively. The paw test of rats was used to evaluate the possibility by quetiapine fumarate to induce EPSE. RESULTS: After treatment with phencyclidine (10 mg.kg-1.d-1, s.c., 14 d), the immobility time in the forced swimming test of mice was increased (P < 0.01). Quetiapine fumarate (20, 40, and 80 mg.kg-1, ig) and clozapine (10 and 30 mg.kg-1, ig) attenuated the enhanced immobility in the forced swimming test induced by repeated treatment with phencyclidine (P < 0.01), whereas haloperidol (0.3 and 1 mg.kg-1, ig) had no effect. In amphetamine swimming "normalization" test, quetiapine fumarate ameliorated the disorder induced by amphetamine in a dose-dependent manner. In paw test, quetiapine fumarate was much less effective in increasing the forelimb retraction time (FRT) than the hindlimb retraction time (HRT). The minimal effective dose (MED) of HRT (MEDHRT) and FRT (MEDFRT) of quetiapine fumarate was 20 mg.kg-1 and 100 mg.kg-1, respectively, and the ratio of MEDFRT to MEDHRT was 5. CONCLUSION: The effects of quetiapine fumarate in these models indicated its clinical effect on schizophrenia with a reduced liability to produce EPSE.

Amphetamine↗
PubMed2000

[Expression of tumor metastasis gene MTA 1 in hepatocellular carcinoma: clinical implications].

OBJECTIVE: To evaluate the relevance of the expression of tumor metastasis gene metastasis-associated 1 (MTA 1) to HCC metastasis. METHODS: A fragment of MTA 1 cDNA was synthesized by reverse transcription (RT)-PCR. A DIG-labeled method of in situ hybridisation (ISH) was used to measure semiquantitatively MTA 1 mRNA in formalin-fixed, paraffin-embedded sections. RESULTS: Most of MTA 1 mRNA positive cells were located on the border of the tumor in some invasive HCC. High MTA 1 expression was found to correlate significantly with portal venous invasion, intrahepatic metastasis, tumor size or distant metastasis (P < 0.05), but not with gender, cirrhosis or AFP level. It also significantly predicted a shorter survival (P < 0.05). CONCLUSION: The overexpression of MTA 1 correlates closely with the invasion process of HCC.

Adult↗
PubMed2000

[Combined triple/multi-surgery of vitrectomy-lensectomy and posterior chamber intraocular lens implantation].

OBJECTIVE: To study the feasibility and safety of the combined triple/multi-surgery of vitrectomy-lensectomy and posterior chamber intraocular lens implantation. METHODS: Triple/multi-surgery was performed on 32 eyes of 32 cases, including 29 cases of serious eye injuries of traumatic cataract, lens luxation, vitreous hemorrhage (some cases with intraocular foreign body, iris damage or iridodialysis), 1 case with lens nucleus dislocated into the vitreous cavity during the senile cataract surgery and 2 cases with intraocular lens luxated into the vitreous cavity postoperatively. RESULTS: After follow up for 1 - 14 months (mean 5.6 months), 15 cases had the best corrected visual acuity (BCVA) >or= 0.5 (46.9%), 11 cases had BCVA of 0.1 - 0.4 (34.4%), and 6 cases had BCVA < 0.1 (18.8%). There was an average of 2.10 DC of astigmatism after surgery. Macular edema was found in 14 cases (43.8%). CONCLUSIONS: The results suggest that the triple/multi-surgery be safe and feasible. The major causes affecting the postoperative BCVA are astigmatism and macular edema. Proper selection of indication and skillful manipulation are the key points of the combined surgery.

Adolescent↗
PubMed2000

[Influence of hepatic stimulator substance on p21(ras) expression in human hepatic carcinoma cells BEL-7402].

The hepatic stimulator substance (HSS) was partially purified from schedule-lighted weanling rat livers. The effects of HSS on p21(ras) expression of human hepatic carcinoma cell BEL-7402 were examined. The results showed: (1) HSS was capable of promoting the proliferation of the cells, and its molecular weight was 14 20 kD; (2) the p21(ras) expression was increased under HSS effect time-dependently, and the effect of HSS appeared synergistic with EGF; (3) the p21(ras) expression induced by HSS manifested a dose-dependent manner, and the saturation effect of HSS occurred at the concentration of 100 microgram/ml. Considering together with our previous report about HSS regulation on EGF receptor, these results strongly suggest that the proliferatory effect of HSS on hepatic carcinoma cells is presumedly related with EGF receptor-mediated signal transduction.

Animals↗
PubMed2000

[Identification of Listeria species in 167 kinds of foods].

Through preliminary identification of isolation of Listeria species in six types foods, which consisted of 167 kinds of foods, we found both S-form and R-form colonies were suspected colonies of Listeria species, and some of them were catalase-negative, urease-positive, methyl red(MR) negative and Voges-Proskauer(VP) negative. The results showed that S-form, catalase-positive, urease-negative, MR-positive and VP-positive colony should not be used as the strict criteria for the identification of Listeria.

Animals↗
PubMed2000

[Screening for limonoid glucosides in Citrus grandis L. Osbeck by high performance liquid chromatography-electrospray ionization/mass spectrometry].

A screening method for limonoid glucosides in the peel of Citrus grandis L. Osbeck, utilizing high performance liquid chromatography (HPLC) with diode-array detection (DAD), interfaced to electrospray ionization-mass spectrometry (ESI-MS), has been developed. The methanol extract of citrus peel was preseparated with conventional polymer adsorption column and weak base anion ion-exchange column and then the eluate from the column was analysed by LC-ESI/MS. In this paper, the UV-Vis spectra and the mass spectra provide structural information without the necessity of isolating the individual compounds. Two major limonoid glucosides-obacunone glucoside (OG) and nomilin glucoside (NG) were identified in the methanol extract of the peel of Citrus grandis L. Osbeck. Then the two limonoid glucosides were taken as the target and isolated by means of preparative HPLC on a C18 reversed-phase column with an acidic acetonitrile-water mobile phase. The structures of OG and NG were further confirmed by NMR spectrometry. The results show that this method is rapid, convenient, sensitive and very useful for screening bioactive natural products.

Chromatography, High Pressure Liquid↗
PubMed2000

[Research on the separation of limonoid glucosides by reversed-phase preparative high performance liquid chromatography].

Obacunone-17-beta-D-glucopyranoside (OG) was isolated from the seeds of Citrus Sinensis Osbeck by using solvent extraction, classical polymer adsorption column separation and weak base anion ion-exchange separation, OG was finally purified by C18 reversed-phase preparative high performance liquid chromatography and was identified by thin-layer chromatography. The purity of OG was analyzed by analytical reversed-phase HPLC. At last the structure of OG was determined by 1H and 13C nuclear magnetic resonance spectrometry (NMR). In this work, the conditions of the reversed-phase preparative HPLC technique to purify limonoid glucosides was optimized. The reversed-phase preparative HPLC on a C18 column with a mobile phase of acidic acetonitrile-water (about 0.2% TFA, V/V) at pH 3 enabled the baseline separation of limonoid glucosides in the extract. The results show that OG is the predominant limonoid glucoside in the seeds of Citrus Sinensis Osbeck and nomilin glucoside is the second one. The results also show that the classical polymer adsorption column separation and weak base anion ion-exchange separation are effective for purifying limonoid glucosides.

Chromatography, High Pressure Liquid↗
PubMed1999

Arsenic trioxide selectively induces acute promyelocytic leukemia cell apoptosis via a hydrogen peroxide-dependent pathway.

Low concentrations of As(2)O(3) (</=1 micromol/L) induce long-lasting remission in patients with acute promyelocytic leukemia (APL) without significant myelosuppressive side effects. Several groups, including ours, have shown that 0.5 to 1 micromol/L As(2)O(3) induces apoptosis in APL-derived NB4 cells, whereas other leukemic cells are resistant to As(2)O(3) or undergo apoptosis only in response to greater than 2 micromol/L As(2)O(3). In this report, we show that the ability of As(2)O(3) to induce apoptosis in leukemic cells is dependent on the activity of the enzymes that regulate cellular H(2)O(2) content. Thus, NB4 cells have relatively low levels of glutathione peroxidase (GPx) and catalase and have a constitutively higher H(2)O(2) content than U937 monocytic leukemia cells. Glutathione-S-transferase pi (GSTpi), which is important for cellular efflux of As(2)O(3), is also low in NB4 cells. Moreover, As(2)O(3) further inhibits GPX activity and increases cellular H(2)O(2) content in NB4 but not in U937 cells. Selenite pretreatment of NB4 cells increases the activity of GPX, lowers cellular H(2)O(2) levels, and renders NB4 cells resistant to 1 micromol/L As(2)O(3). In contrast, concentrations of As(2)O(3) that alone are not capable of inducing apoptosis in NB4 cells induce apoptosis in the presence of the GPx inhibitor mercaptosuccinic acid. Similar effects are observed by modulating the activity of catalase with its inhibitor, aminotriazol. More important from a therapeutic point of view, U937 and HL-60 cells, which require high concentrations of As(2)O(3) to undergo apoptosis, become sensitive to low, clinically acceptable concentrations of As(2)O(3) when cotreated with these GPx and catalase inhibitors. The induction of apoptosis by As(2)O(3) involves an early decrease in cellular mitochondrial membrane potential and increase in H(2)O(2) content, followed by cytochrome c release, caspase 3 activation, DNA fragmentation, and the classic morphologic changes of apoptosis.

Amitrole↗
PubMed1999

Dynamic Surface Tension Measurement with a Dynamic Wilhelmy Plate Technique.

An experimental method called dynamic Wilhelmy plate technique (DWPT) for studying dynamic surface tension was designed in this study. A diffusion-controlled model corresponding to the initial and boundary conditions of this method was proposed. Dynamic surface tension of Triton X-100 and SDS was measured with this technique and analyzed with the proposed model. The calculated diffusion coefficients for the short- and long-time approximations are 3.7 x 10(-6) and 0.97 x 10(-6) cm(2)/s for Triton X-100 and 4.6 x 10(-6) and 0.79 x 10(-6) cm(2)/s for SDS, respectively. The predicted dynamic surface tension with these diffusion coefficients for the simultaneously generated aqueous/air interfaces is in good agreement with the drop mass technique. Another diffusion controlled model that considers the energy barrier at the aqueous/air interface was also proposed in this study. The calculated energy barriers are in the range of 4.1-5.7 RT for Triton X-100 and 6.5-8.0 RT for SDS. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Apoptosis and growth inhibition in malignant lymphocytes after treatment with arsenic trioxide at clinically achievable concentrations.

BACKGROUND: Arsenic trioxide (As2O3) can induce clinical remission in patients with acute promyelocytic leukemia via induction of differentiation and programmed cell death (apoptosis). We investigated the effects of As2O3 on a panel of malignant lymphocytes to determine whether growth-inhibitory and apoptotic effects of As2O3 can be observed in these cells at clinically achievable concentrations. METHODS: Eight malignant lymphocytic cell lines and primary cultures of lymphocytic leukemia and lymphoma cells were treated with As2O3, with or without dithiothreitol (DTT) or buthionine sulfoximine (BSO) (an inhibitor of glutathione synthesis). Apoptosis was assessed by cell morphology, flow cytometry, annexin V protein level, and terminal deoxynucleotidyl transferase labeling of DNA fragments. Cellular proliferation was determined by 5-bromo-2'-deoxyuridine incorporation into DNA and flow cytometry and by use of a mitotic arrest assay. Mitochondrial transmembrane potential (delta psi(m)) was measured by means of rhodamine 123 staining and flow cytometry. Protein expression was assessed by western blot analysis or immunofluorescence. RESULTS: Therapeutic concentrations of As2O3 (1-2 microM) had dual effects on malignant lymphocytes: 1) inhibition of growth through adenosine triphosphate (ATP) depletion and prolongation of cell cycle time and 2) induction of apoptosis. As2O3-induced apoptosis was preceded by delta psi(m) collapse. DTT antagonized and BSO enhanced As2O3-induced ATP depletion, delta psi(m) collapse, and apoptosis. Caspase-3 activation, usually resulting from delta psi(m) collapse, was not always associated with As2O3-induced apoptosis. As2O3 induced PML (promyelocytic leukemia) protein degradation but did not modulate expression of cell cycle-related proteins, including c-myc, retinoblastoma protein, cyclin-dependent kinase 4, cyclin D1, and p53, or expression of differentiation-related antigens. CONCLUSIONS: Substantial growth inhibition and apoptosis without evidence of differentiation were induced in most malignant lymphocytic cells treated with 1-2 microM As2O3. As2O3 may prove useful in the treatment of malignant lymphoproliferative disorders.

Adenosine Triphosphate↗
PubMed1999

Malignant cells can be sensitized to undergo growth inhibition and apoptosis by arsenic trioxide through modulation of the glutathione redox system.

Arsenic trioxide (As2O3) induces clinical remission in acute promyelocytic leukemia (APL) with minimal toxicity and apoptosis in APL-derived NB4 cells at low (1 to 2 micromol/L) concentration. We examined the basis for NB4 cell sensitivity to As2O3 to identify experimental conditions that would render other malignant cells responsive to low concentrations of As2O3. The intracellular glutathione (GSH) content had a decisive effect on As2O3-induced apoptosis. Highly sensitive NB4 cells had the lowest GSH and the sensitivity of other cell lines was inversely proportional to their GSH content. The t(14;18) B-cell lymphoma cell line had low GSH levels and sensitivity to As2O3 at levels slightly higher than in APL cells. Experimental upmodulation of GSH content decreased the sensitivity to As2O3. Ascorbic acid and buthionine sulfoxide (BSO) decreased GSH to a greater extent, and rendered malignant cells more sensitive to As2O3. As2O3-induced apoptosis was not enhanced by ascorbic acid in normal cells, suggesting that the combination of ascorbic acid and As2O3 may be selectively toxic to some malignant cells. Ascorbic acid enhanced the antilymphoma effect of As2O3 in vivo without additional toxicity. Thus, As2O3 alone or administered with ascorbic acid may provide a novel therapy for lymphoma.

Acetylcysteine↗
PubMed1999

Myosin I contributes to the generation of resting cortical tension.

The amoeboid myosin I's are required for cellular cortical functions such as pseudopod formation and macropinocytosis, as demonstrated by the finding that Dictyostelium cells overexpressing or lacking one or more of these actin-based motors are defective in these processes. Defects in these processes are concomitant with changes in the actin-filled cortex of various Dictyostelium myosin I mutants. Given that the amoeboid myosin I's possess both actin- and membrane-binding domains, the mutant phenotypes could be due to alterations in the generation and/or regulation of cell cortical tension. This has been directly tested by analyzing mutant Dictyostelium that either lacks or overexpresses various myosin I's, using micropipette aspiration techniques. Dictyostelium cells lacking only one myosin I have normal levels of cortical tension. However, myosin I double mutants have significantly reduced (50%) cortical tension, and those that mildly overexpress an amoeboid myosin I exhibit increased cortical tension. Treatment of either type of mutant with the lectin concanavalin A (ConA) that cross-links surface receptors results in significant increases in cortical tension, suggesting that the contractile activity of these myosin I's is not controlled by this stimulus. These results demonstrate that myosin I's work cooperatively to contribute substantially to the generation of resting cortical tension that is required for efficient cell migration and macropinocytosis.

Animals↗
PubMed1999

Membrane tether formation from blebbing cells.

Membrane tension has been proposed to be important in regulating cell functions such as endocytosis and cell motility. The apparent membrane tension has been calculated from tether forces measured with laser tweezers. Both membrane-cytoskeleton adhesion and membrane tension contribute to the tether force. Separation of the plasma membrane from the cytoskeleton occurs in membrane blebs, which could remove the membrane-cytoskeleton adhesion term. In renal epithelial cells, tether forces are significantly lower on blebs than on membranes that are supported by cytoskeleton. Furthermore, the tether forces are equal on apical and basolateral blebs. In contrast, tether forces from membranes supported by the cytoskeleton are greater in apical than in basolateral regions, which is consistent with the greater apparent cytoskeletal density in the apical region. We suggest that the tether force on blebs primarily contains only the membrane tension term and that the membrane tension may be uniform over the cell surface. Additional support for this hypothesis comes from observations of melanoma cells that spontaneously bleb. In melanoma cells, tether forces on blebs are proportional to the radius of the bleb, and as large blebs form, there are spikes in the tether force in other cell regions. We suggest that an internal osmotic pressure inflates the blebs, and the pressure calculated from the Law of Laplace is similar to independent measurements of intracellular pressures. When the membrane tension term is subtracted from the apparent membrane tension over the cytoskeleton, the membrane-cytoskeleton adhesion term can be estimated. In both cell systems, membrane-cytoskeleton adhesion was the major factor in generating the tether force.

Adhesiveness↗